JP2017003563A - Optical inspection method and optical inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical inspection device that can improve inspection accuracy.SOLUTION: An optical inspection method of a first embodiment inspecting a subject using an optical sensor including an irradiation system plurally containing a light source module LM, and a detection system plurally containing a detection module DM detecting an amount of light of light with which a measurement object is irradiated from the irradiation system and propagating in the measurement object includes the steps of: obtaining a first detection light-amount distribution serving as a detection light-amount (a light-amount distribution) for each of a plurality of optical models simulating the subject by a simulation virtually using the optical sensor; obtaining a second detection light-amount distribution serving as a detection light-amount (a light-amount distribution) of the subject using the optical sensor; and comparing the first detection light-amount distribution with the second detection light-amount distribution, and selecting the optical model suitable for the subject from the plurality of optical models.SELECTED DRAWING: Figure 16

Description

  The present invention relates to an optical inspection method and an optical inspection apparatus, and more particularly to an optical inspection method using an optical sensor and an optical inspection apparatus including the optical sensor.

  2. Description of the Related Art Conventionally, there is known a biological light measurement device that inspects a subject by irradiating the subject (living body) with light, detecting light propagated in the subject (see, for example, Patent Document 1).

  The living body optical measurement device disclosed in Patent Document 1 has room for improvement in inspection accuracy.

  The present invention includes an irradiation system including at least one light irradiator, and a detection system including at least one light detector that detects the amount of light irradiated from the irradiation system to the measurement object and propagated through the measurement object. An optical inspection method for inspecting a subject using an optical sensor comprising: a first detected light amount distribution that is a detected light amount distribution for each of a plurality of optical models simulating the subject; A plurality of steps based on the first and second detected light amount distributions, the step of obtaining by a simulation used for the first step, the step of obtaining a second detected light amount distribution that is a detected light amount distribution of the subject using the optical sensor; Selecting an optical model suitable for the subject from the optical model.

  According to the present invention, inspection accuracy can be improved.

It is FIG. (1) for demonstrating the correction | amendment by the conventional head external shape. It is FIG. (2) for demonstrating the correction | amendment by the conventional head external shape. It is FIG. (3) for demonstrating the correction | amendment by the conventional head external shape. It is FIG. (4) for demonstrating the correction | amendment by the conventional head external shape. It is a figure which shows the conventional probe arrangement | positioning and light quantity distribution. It is a figure which shows probe arrangement | positioning and light quantity distribution of 1st Embodiment. It is a figure which shows probe arrangement | positioning and light quantity distribution (when there exists a poor contact part) of 1st Embodiment. It is a figure for demonstrating schematic structure of the optical inspection apparatus which concerns on 1st Embodiment. It is a figure for demonstrating the water tank for phantoms. It is a figure for demonstrating the layout of a transparent window. FIG. 3 is a diagram (No. 1) for describing a schematic configuration of a light source module according to Embodiment 1; 2 is a diagram for explaining a schematic configuration of a detection module according to Embodiment 1. FIG. FIG. 3 is a second diagram illustrating a schematic configuration of the light source module according to the first embodiment. It is a figure for demonstrating the in-vivo propagation angle. It is a flowchart for demonstrating the method to measure the information in a subject. It is a flowchart for demonstrating the optical inspection method (absorber position estimation process) of 1st Embodiment. 1 is a diagram illustrating an optical model 1. FIG. It is a figure which shows the optical model. 2 is a diagram showing an optical model 3. FIG. It is a figure which shows the optical model. It is a figure which shows the optical model. It is a figure which shows the optical model. It is a figure which shows the optical model. 2 is a diagram showing an optical model 8. FIG. FIG. 3 is a first diagram illustrating a sensitivity distribution in a photodiode (PD). It is a figure (the 2) which shows the sensitivity distribution in PD. It is a figure for demonstrating the in-vivo propagation angle. It is a figure which shows the optical constant of each layer of an optical model. It is a figure which shows the characteristic of the optical models 1-8. It is a figure which shows the conventional probe arrangement | positioning and light quantity distribution. It is a figure which shows probe arrangement | positioning and light quantity distribution (when there exists a poor contact part) of 1st Embodiment. It is a figure which shows probe arrangement | positioning and light quantity distribution of 1st Embodiment. It is a figure for demonstrating the model selection process in the optical inspection method of 1st Embodiment. It is a figure for demonstrating the method of detecting the singular point of 4 directions of one LM, and the method of removing this singular point. It is a figure for demonstrating the method of detecting the singular point of 4 directions of one DM, and the method of removing this singular point. It is a figure for demonstrating the method to compare the detected light quantity in PointA in the square which makes two LM and two DM a vertex, and the method to correct | amend a detected light quantity. FIG. 37 (A) is a diagram showing the actual position of the light absorber, FIG. 37 (B) is a diagram showing the estimation result of the position of the light absorber, and FIG. 37 (C) is the light absorption in the comparative example. It is a figure which shows the detection result of the position of a body. FIG. 38 (A) is a diagram showing the actual position of the light absorber after movement, and FIG. 38 (B) is a diagram showing the estimation result of the position of the light absorber after movement, FIG. 38 (C). These are figures which show the detection result of the position of the light absorber in a comparative example. FIG. 10 is a diagram for explaining an arrangement of a plurality of light source modules and a plurality of detection modules in the optical sensor according to the second embodiment. FIG. 6 is a diagram for explaining a light source module LM (I type) according to a second embodiment. It is a figure for demonstrating the surface emitting laser array chip | tip of light source module LM (I type) of Example 2. FIG. FIG. 42A and FIG. 42B are views (No. 1 and No. 2) for explaining the light source module LM (II type) of Example 2, respectively. It is a figure for demonstrating the light source module LM (type III) of Example 2. FIG. It is a figure for demonstrating the positional relationship of the lens and surface emitting laser array chip | tip in light source module LM (type III) of Example 2. FIG. It is a figure for demonstrating the positional relationship of the lens in the light source module LM (type III) of Example 2, a surface emitting laser array chip | tip, and a prism. FIG. 6 is a diagram (No. 1) for describing an additional configuration of a light source module according to Embodiments 1 and 2. FIG. 6 is a second diagram illustrating an additional configuration of the light source modules according to the first and second embodiments. FIG. 10 is a third diagram illustrating an additional configuration of the light source modules according to the first and second embodiments. It is a ray diagram optically designed by an optical simulator. It is a figure which shows the result of the optical simulation in 1st Embodiment. It is a figure which shows the result of the optical simulation in a comparative example. FIG. 52A is a diagram for explaining the operation of the optical sensor of the comparative example, and FIG. 52B is a diagram for explaining the operation of the optical sensor of the first embodiment. It is a graph which shows the relationship between the incident angle from the air to a biological body, and the propagation angle in a biological body. It is a graph which shows the relationship between the incident angle from resin to a biological body, and the propagation angle in a biological body. FIG. 6 is a first diagram for explaining a schematic configuration of a detection module according to a second embodiment; FIG. 6 is a diagram (No. 2) for describing a schematic configuration of a detection module according to the second embodiment. FIG. 6 is a third diagram illustrating a schematic configuration of a detection module according to the second embodiment. 6 is a flowchart for explaining an optical characteristic detection method (position measurement method) according to the second embodiment. It is a figure which shows the estimation result of the inverse problem estimation in Example 2. FIG. It is a figure for demonstrating the effect | action of the optical sensor of 1st Embodiment. It is a flowchart for demonstrating the optical inspection method (measurement result correction | amendment process) of 2nd Embodiment. It is a graph which shows the light quantity change of a resting state and an activation state. It is a graph which shows the light quantity change of a resting state. It is a graph which shows the relationship between age and CSF (the thickness of a cerebrospinal fluid layer). It is a graph which shows the correlation of SCD (distance from the scalp surface to the brain surface) and the thickness of three layers. It is a graph which shows a light quantity correction image. It is a figure which shows the optical model reflecting cerebral blood flow. It is a figure which shows the correction coefficient for every optical model. It is a flowchart for demonstrating the optical characteristic detection method (position measurement method) of 2nd Embodiment. It is a figure which shows a light quantity correction image (depressed patient). It is a figure which shows a light quantity correction image (a healthy person). It is a figure for demonstrating arrangement | positioning of the several light source module and several detection module in the optical sensor of 3rd Embodiment. It is a figure for demonstrating the emission direction of each light source module and the detection direction of each detection module in the optical sensor of a comparative example. FIG. 74A is a diagram for explaining the emission directions of the four groups of the surface emitting laser array chip of the fourth embodiment, and FIG. 74B is the diagram of the four arrays of the PD array of the fourth embodiment. It is a figure for demonstrating the detection direction of PD. It is a figure for demonstrating the emission direction of each light source module and the detection direction of each detection module in the optical sensor of 4th Embodiment. It is a block diagram which shows the structure of a control part. It is a block diagram which shows the structure of a calculation part. FIG. 34 is a diagram (No. 1) for describing an additional process of the model selection process in FIG. 33; FIG. 34 is a diagram (No. 2) for explaining the additional processing of the model selection processing of FIG. It is a figure which shows arrangement | positioning with respect to the optical model of the light source module and detection module in 5th Embodiment. It is a figure for demonstrating the optical model of 5th Embodiment. It is a table | surface which shows the optical constant of each layer of the optical model of 5th Embodiment. It is a graph which shows the relationship of the light quantity ratio between a scattering coefficient and an incident direction. It is a graph which shows the relationship of the light quantity ratio between an absorption coefficient and an incident direction. It is a graph which shows the relationship between the sum of the thickness of a scalp and a skull, and the light quantity ratio between incident directions. It is a figure which shows the correlation of SCD (distance from the scalp surface to the brain surface) and the thickness of 3 layers. It is a figure for demonstrating the layout of the probe of a multi-distance system. It is a figure which shows the light propagation type of a multi-distance system. 89 is a graph showing the relationship between the scattering coefficient, the absorption coefficient, and the light amount ratio in the multi-distance method, and the lower diagram in FIG. 89 is a graph showing the relationship between the scattering coefficient, the absorption coefficient, and the light amount ratio in the multiple emission angle method. is there. The left diagram in FIG. 90 is a diagram illustrating light propagation when the scattering coefficient is small, and the right diagram in FIG. 90 is a diagram illustrating light propagation when the scattering coefficient is large.

  First, prior to the description of the first embodiment, the prior art will be described as an introduction.

  The conventional example shown in FIG. 1 (Non-Patent Document 1: NeuroImage85 (2014) 117-126) does not individually perform imaging by nuclear magnetic resonance imaging (hereinafter abbreviated as MRI (Magnetic Resonance Imaging)). A technique for detecting with high accuracy by using an MRI image of a standard brain (indicated as Atlas in the figure) and correcting the head outline as basic data is described.

  The error due to individual differences is eliminated by correcting the head profile. FIG. 1B shows a general human head shape called a standard brain, and the points in FIG. 1B show probe installation positions. Here, the “probe” means a light irradiator (also referred to as a light source module) or a light detector (also referred to as a detection module).

  The head shape of a person who actually measures is shown in FIG. 1-c, and the outer shape of the head is different. When the position of the probe is simply linearly expanded, it becomes as shown in FIG. 1-d, and there is a slight deviation. However, as shown in FIG. The probe position matches with accuracy.

  Accordingly, as shown in FIGS. 2 and 3, cerebral blood flow using f-MRI using the standard brain and using MRI image a or BOLD effect (decreasing deoxygenated hemoglobin). The image b (denoted as BOLD in FIGS. 2 and 3) substantially matches.

  However, as shown in FIG. 4, in the graph showing the temporal change in cerebral blood flow at a certain position, it can be seen that a nearly double error has occurred as an amount indicating the cerebral blood flow on the vertical axis. Thus, there is a possibility that the cerebral blood flow will be misread when the cerebral blood flow changes with time.

  Further, the conventional example of FIG. 1 employs a high-density probe method. This is because the amount of information obtained from the measurement object is increased by reducing the interval (13 mm) and increasing the number of probes compared to the general probe interval (30 mm), thereby realizing highly accurate detection. . However, since the probe density is high, the number of probes also increases, for example, nearly four times. When hair or the like is interposed between the probe and the scalp (if there is a contact failure), the amount of light is lost, but this amount of light loss varies depending on the probe. This light loss is a factor that increases the error. As the number of probes increases, errors occur. There is a trade-off between the number of probes and high-precision detection. In addition, since it becomes difficult to select an optical model that serves as a reference for measuring the position of the light absorber in the subject, which will be described later, an error occurs.

  A specific description will be given using the light quantity distribution of the conventional example shown in the right diagram of FIG. As shown in the left diagram of FIG. 5, when the incident direction of light from the light source module LM1 ′ to the measurement target (subject or optical model) is 1, it propagates through the measurement target and detects from the direction A. A detected light amount of light incident on DM1 ′ is shown, and this is a normalized light amount (1.0).

With this standardized light quantity as a reference, the incident directions of light from the three light source modules LM1 ′ to LM3 ′ to the subject are 1 to 3 and the incident directions of light to the three detection modules DM1 ′ to DM3 ′. 5 is a light amount distribution shown in the right diagram of FIG. In the left diagram of FIG. 5, since there are more (for example, six) probes than the number of beams to be irradiated (for example, three), the case where contact failure occurs between the probe and the measurement target is extremely There are many patterns. 5 when the probe is six as shown in the left figure, probe case a contact failure occurs between the measurement target, i.e. the case where a contact failure occurs in at least one probe, ₆ C ₁ + ₆ C _{2 + 6 C 3 + 6 C} 4 + 6 C 5 + 6 C 6 = the 64 combinations. In this case, 64 optical models to be created are also required. In this case, it becomes difficult to select an optical model.

<< First Embodiment >>
On the other hand, in the first embodiment, as shown in FIG. 6, light is incident from a plurality of directions (for example, three directions) to the same position of a measurement target from a light source module LM including a plurality of light emitting units. A plurality of (for example, three) lights propagating through the object are incident on the detection module DM from different directions. In the left diagram of FIG. 6, a case in which contact failure occurs between the probe and the measurement target because the number of beams to be irradiated (for example, the same number as three in FIG. 5) is smaller (for example, two). Is very limited.

  As shown in FIG. 7, the contact failure here has a single contact failure that affects the light emitting units of the light source module LM at substantially the same level. In other words, there are three cases in which contact failure occurs between the probe and the subject, that is, contact failure occurs in at least one probe when there are two probes as shown in the left figure of FIG. There are also three optical models to be used. Since there are few optical models, selection of an optical model becomes easy.

  FIG. 8 shows a schematic configuration of the optical inspection apparatus 100 according to the first embodiment.

  The optical inspection apparatus 100 is used for diffuse optical tomography (DOT) as an example. DOT is a technique for estimating optical characteristics inside a subject by irradiating the subject (scattering body) such as a living body with light and detecting the light propagated in the subject. In particular, by detecting blood flow in the brain, it is expected to be used as an auxiliary device for differential diagnosis and rehabilitation of depressive symptoms. In DOT, when the resolution is improved, the function of the brain can be understood in detail. Therefore, many research institutions are actively researching to improve the resolution.

  As shown in FIG. 8, the optical inspection apparatus 100 includes an optical sensor 10 including a light source module LM having a plurality of light emitting units and a detection module DM, a control unit, a display unit, a calculation unit, and the like. The control unit is configured as shown in the block diagram of FIG. In the control unit, the switch unit is controlled by the information from the central processing unit A-1, and the LM to emit light is selected. At this time, the current supplied to the LM via the switch unit is controlled to a desired value by the current control unit. The detection result (data) in DM is A / D converted, and an arithmetic process such as an averaging process is performed in the arithmetic unit (A-2). The calculation results in the calculation unit (A-2) are sequentially recorded in the recording unit (A-3).

  In the present specification, the light source module LM and the detection module DM are also referred to as probes when not distinguished from each other. In addition, in this specification, the words “pseudo living body”, “living body”, and “subject” are used as appropriate, but the pseudo living body and living body are still specific examples of the subject.

  The optical sensor 10 can be generally used as a sensor for detecting a light absorber in a subject, but the subject having the highest utility value is a living body. However, in general, it is not always easy to detect the position of the bloodstream (absorber) in a living body using an optical sensor. If the subject is a living body, it is difficult to confirm the effect (detection accuracy) of the optical sensor 10.

  Therefore, in this embodiment, a pseudo-living body (also referred to as a phantom) that is a cloudy liquid in a water tank is adopted as a subject that has versatility and allows easy detection accuracy.

  Hereinafter, Example 1 of the present embodiment will be described.

<Example 1>
In the first embodiment, a method is adopted in which light beams from the light emitting units are deflected by a prism so that the incident angle to the subject is different between the light beams.

  Here, as shown in FIG. 9, transparent windows made of a transparent acrylic plate are provided at eight locations on one side wall (+ Z side wall) of a water tank in which each wall is made of a black acrylic plate. The inside of the water tank is filled with an intrapid aqueous solution (intrapid 10% concentration diluted 10 times). That is, the simulated living body used in Example 1 is an intralipid aqueous solution.

  Black ink is dropped into the aqueous solution filled in the water tank so as to be about 20 ppm, so that the absorption coefficient and the scattering coefficient are almost the same as those of the living body. Then, a black light-absorbing body imitating blood flow is submerged in this cloudy intrapid aqueous solution. The light absorber is a sphere having a diameter of about 5 mm as black polyacetal. In order to control the position of the sphere, the sphere is fixed to a thin metal rod having a diameter of 1 mm connected to the automatic stage. The probe is accurately positioned and attached to each transparent window of the water tank.

  Here, the volume of the water tank is 140 mm × 140 mm × 60 mm. The thickness of the black acrylic plate is 4 mm. The eight transparent windows are composed of two types of circular transparent windows A and B (see FIG. 10). There are four transparent windows A and B. The diameter of the transparent window A is 9 mm, and the diameter of the transparent window B is 12 mm. The thickness of each of the transparent windows A and B is 1.5 mm.

  FIG. 10 shows the layout of eight transparent windows. The eight transparent windows are arranged in a lattice pattern at equal intervals in the X-axis direction and the Y-axis direction so that the transparent windows A and B are adjacent to each other. Here, a detection module DM is attached to each transparent window A, and a light source module LM is attached to each transparent window B (B1 to B4). The distance between the centers of two adjacent transparent windows is 30 mm.

  As shown in FIG. 11, the light source module LM includes a ceramic package (not shown) on which a lens, a prism, and a surface emitting laser array chip are mounted, and a flexible substrate (not shown) on which the ceramic package and analog electronic circuit are mounted. , Wiring connected to the flexible substrate, connector portion (not shown), a housing in which these are accommodated, a window member made of a transparent resin in contact with the subject, and the like. In the light source module LM, the light amount of the light emitting unit can be kept constant by controlling to an appropriate current value by a power source unit (not shown). The light source module LM is mounted in a state where the window member is in contact with the subject (transparent window B) from the + Z side.

  As shown in FIG. 12, the detection module DM includes a black resin casing, a contact member made of an elastic body attached to the front end (end on the −Z side) of the casing, and a diameter accommodated in the casing. It is configured to include a 3 mm hemispherical lens (divided lens) and a 4-divided PD array (in which four photodiodes (PD) are arranged in an array). An aperture (opening) is formed at the tip of the housing and the contact member. The detection module DM is mounted in a state where the contact member is in contact with the subject (transparent window A) from the + Z side. In FIG. 12, only two of the four PDs (light receiving units) are shown.

  The split lens is disposed in the vicinity of the + Z side of the aperture. Therefore, the light irradiated from the light source module LM to the subject and propagated through the subject enters the split lens through the aperture, and is refracted and emitted in a direction according to the incident position and the incident direction to the split lens. (See FIG. 12).

  The 4-division PD array is arranged on the + Z side of the division lens. Therefore, the light passing through the split lens is incident on one of the four light receiving portions (PD) of the quadrant PD array according to the traveling direction (the emission direction from the split lens). In this way, the detection module DM can classify the incident angles of the light incident from the subject into four angle ranges.

  The control unit detects the amount of light received by the four PDs (light receiving units) of the detection module DM mounted on each transparent window A (the total amount of light received by 16 PDs), converts it to a voltage using an operational amplifier, and records it. To record. The data is detected at a sampling rate of 1 msec, and the values measured for 20 sec are averaged. In one measurement, 16 PD data are acquired.

  Next, the light source module LM will be described in detail. As the light source of the light source module LM, a 40-channel surface-emitting laser array chip, that is, a surface-emitting laser array chip having 40 VCSELs (surface-emitting lasers) as light-emitting units is employed.

  On the optical path of the light from the surface emitting laser array chip, a lens having a diameter of 3 mm that makes the light substantially parallel is disposed (see FIG. 13). The distance between the emitting surface (light emitting surface) of the surface emitting laser array chip and the principal point of the lens (optical center of the lens) is set equal to the focal length f (for example, 9 mm) of the lens. That is, the surface emitting laser array chip is arranged so that the emission surface is located at the focal position of the lens. The “lens focal length” is the distance between the principal point of the lens and the focal point.

  Here, 40 channels are turned on simultaneously, and the total output is about 50 mW. The parallel light emitted from the VCSEL is deflected by the prism as shown in FIG.

  As the prism, an acrylic one having a refractive index equivalent to that of the acrylic water tank is employed. The reflecting surface of the prism is designed according to the diameter of the prism, and the angle of the reflecting surface is set so that light through the lens enters the acrylic water tank at an incident angle of about 50 °.

  The refractive index difference between the water tank and prism acrylic and the phantom (intrapid aqueous solution) is set so that the propagation angle in the phantom is about 60 ° (θ1 in FIG. 13) according to Snell's law. The surface emitting laser array chip, the lens, and the prism are attached to a rotation stage (not shown) that can rotate around a rotation axis extending in the Z direction. Here, the rotation axis of the rotary stage passes through the opening (window member) of the housing. Hereinafter, the rotation axis of the rotation stage is also simply referred to as “rotation axis”. A surface emitting laser array, a lens, and a prism are also collectively referred to as an “irradiation unit”. In FIG. 13, the window member is not shown.

  By rotating the rotary stage and the irradiation unit together, the incident angle and direction of light to the prism can be changed. Here, as shown in FIG. 14, measurement in four directions of + X, −X, + Y, and −Y is sequentially performed. That is, 16 measurements of 4 × 4 are performed in the positions of the four light source modules LM (four locations B1 to B4) and four directions. Between the prism and the water tank, a gel-like resin (not shown) having the same refractive index is filled. Thereby, refraction and reflection between the prism and the water tank can be prevented.

  Next, a method for measuring information in the subject (subject internal information) will be described with reference to the flowchart shown in FIG.

  First, a probe is set (step T1). The probe means the detection module DM and the light source module LM as described above. The probes to be set here are four detection modules DM and one light source module LM. The four detection modules DM are individually attached to four transparent windows A having a diameter of 9 mm shown in FIG. One light source module LM is mounted on the transparent window B1 shown in FIG.

  Next, the 40 channels (light emitting units) of the light source module LM are caused to emit light simultaneously (step T2). The current value is determined so that the emission intensity is about 50 mW in total. The light emission time is about 20 sec. During this period, the detection values of the PDs of the four detection modules DM are read (step T3), and several data (detection values) detected at 1 msec intervals are averaged. Then, the averaged detection value, that is, the average value of the detection values is stored in the recording unit (step T4).

  Next, the wavelength of the emitted light is switched and Steps T2 to T4 are performed again (Steps T5 and T6). Here, wavelengths of 780 nm and 900 nm can be selected. Specifically, two types of light source modules LM with different oscillation wavelengths (780 nm band and 900 nm band) are prepared in advance, and the wavelength of the emitted light can be switched by replacing the light source modules LM.

  Here, the measurement is performed in four directions of + X direction, + Y direction, -X direction, and -Y direction (steps T7 and T8). Specifically, steps T2 to T6 immediately after step T1 are performed with the prisms arranged in the + X direction. Next, the prism is rotated to the + Y direction. In this state, steps T2 to T6 are performed. Next, the prism is rotated to the −X direction. In this state, steps T2 to T6 are performed. Next, the prism is rotated to the −Y direction. In this state, steps T2 to T6 are performed.

  Next, the mounting position of the light source module LM is sequentially changed from the transparent window B1 to B2, B3, and B4, and the four directions are measured again (steps T9 and T10). Thereafter, the position of the light absorber is moved, and measurement is performed again at four mounting positions of the light source module LM in four directions (steps T11 and T12).

  The stored data is the light absorber, and the data without is the following r (s, i, n) (i = 1, 2, 3... M, n = 1, 2, 3... K). ), R (0, i, n) (i = 1, 2, 3... M, n = 1, 2, 3... K). i is a number assigned to each detection module DM. n is a number assigned to each group. Next, each difference Δr (i, n) is calculated.

  Hereinafter, a method for calculating the position of the light absorber (the optical characteristic of the pseudo living body) from the measurement result obtained by the measurement method based on the flowchart of FIG. 15 will be described. Here, an inverse problem estimation algorithm is used. When solving the inverse problem, first, measurement and simulation are performed, and a sensitivity distribution is created using the forward problem. Then, the next measured data is taken in and the inverse problem is estimated from the value.

  Hereinafter, the procedure of the optical inspection method of the first embodiment will be described with reference to the flowchart of FIG.

  In the first step S21, a Monte Carlo simulation is performed. The Monte Carlo simulation is performed by virtually using the optical sensor 10 for each of the eight types of optical models 1 to 8 shown in FIGS. Each optical model is a virtual model that imitates a subject (here, a human head). Here, each optical model is a five-layer model.

  Here, each optical model has a laminated structure in which a gray matter layer, a bone marrow fluid layer, a skull layer, a skin layer, and a hair layer are laminated in order from the deepest layer to the outermost layer. In particular, the optical model 1 is a model imitating the standard brain and is also called a standard model.

  Here, the light source module LM can irradiate four directions, and the detection module DM can detect four directions, and accordingly, a Monte Carlo simulation is performed.

  In the next step S22, the sensitivity distribution for each optical model is calculated based on the measurement result (virtual measurement result) by the Monte Carlo simulation.

  In the next step S23, measurement (actual measurement) is performed on the subject using the optical sensor 10 with the same probe arrangement as in the Monte Carlo simulation, and the sensitivity distribution of the subject is calculated.

  In the next step S24, an optical model is selected. Specifically, an optical model whose sensitivity distribution best matches (is most approximated to) the sensitivity distribution of the subject is selected.

  In the next step S25, inverse problem estimation is performed based on the sensitivity distribution of the selected optical model and the sensitivity distribution of the subject, and the position of the light absorber in the subject is estimated. This will be described below in order.

  FIG. 77 shows a block diagram of the calculation unit. Information such as the position of each module (probe) used in the previous Monte Carlo simulation, the refractive index, and the shape of the living body is recorded in the recording unit (B-1). Based on this information, the previous order problem is performed. For this calculation, a GPU (multi-graphics processor) capable of parallel calculation is used. By using this, the calculation can be made much faster than the conventional calculation speed. The sensitivity distribution obtained by the calculation is stored again in the recording unit (B-1). The calculation result and the measurement result stored in the recording unit (A-3) are input to the central processing unit (B-3), and inverse problem estimation is performed in the central processing unit (B-3). The estimation result is displayed on the display unit via the central processing unit (A-1) (see FIG. 76).

  By the way, conventionally, it has been considered that light is scattered almost isotropically in a scatterer such as a living body when calculating a forward problem. For this reason, simulations using diffusion equations with a small amount of calculation have been used. However, in recent academic societies and the like, it has been reported that light propagation in a living body has anisotropy in a fine area of mm. In order to perform a simulation reflecting this anisotropy, it is necessary to use a transport equation or perform a Monte Carlo simulation.

  In the present embodiment, since the light emitted from the light source is deflected and incident on the subject, the information on the incident angle cannot be reflected in the diffusion equation that is generally used. Although a method using a transport equation has been proposed, it is known that this calculation takes an enormous amount of time.

  Therefore, in this embodiment, Monte Carlo simulation is adopted. Monte Carlo simulation is a technique for stochastically expressing the conditions under which photons are scattered in a scattering medium using random variables and observing their macroscopic behavior. Specifically, each time a photon moves through a medium and travels a certain distance, it collides, and modeling is performed so that the directionality is changed by the collision. An average value of a certain distance at this time is an average free path, which is defined by a scattering coefficient, and a change in direction is defined by anisotropy g. Repeat this collision and record how it propagates within the defined area. The light behavior of the scattering medium can be simulated by calculating countless photons modeled in this way. The path through which one photon diffuses is recorded by Monte Carlo simulation.

The Monte Carlo simulation in the present embodiment, the number of photons is 10 ^9, the voxels as 1mm cubes, the calculation of three-dimensional area of 120mm × 120mm × 60mm. Here, the scattering coefficient of the scattering medium, the absorption coefficient, anisotropy, ^{7.8 mm} -1 refractive index respectively is almost equal numbers and the ^scalp, 0.019 mm -1, and 0.89,1.37. The above-described phantom (intralipid aqueous solution) is prepared so as to match this numerical value, and simulation is performed under the same conditions as the phantom, such as the light source module LM, the propagation angle, and the position of the detection module DM, and the sensitivity distribution is calculated.

At this time, the number of photons that have passed with respect to the position r of the voxel is φ ₀ (r). In particular, when the position of the light source module LM is rs, the number of photon passages at the voxel position r is φ ₀ (rs, r). Next, the light source module LM is arranged at the position where the detection module DM has been arranged, and the same number of photons is calculated again. When the detection module DM is installed at rd, the number of photons passing at the voxel position r is set to φ ₀ (r, rd).

Since the light path is reversible, this product is proportional to the number of photons that pass through the voxel position r, exit the light source module LM, and enter the detection module DM. The product obtained by normalizing this product with all the photon numbers φ ₀ (rs, rd) entering the detection module DM is the following sensitivity distribution A (r).

This sensitivity distribution A (r) indicates the degree of influence on the detection amount at the position r. When a light absorber is generated at the position r of the voxel, it indicates how much the detection value changes due to the generation.

  An example of the sensitivity distribution calculated as described above is shown in FIG. Here, the light source module LM and the detection module DM are arranged at (X, Y, Z) = (45, 60, 0) and (X, Y, Z) = (75, 60, 0), respectively. Since a voxel is a 1 mm cube, it is equivalent to a unit mm of these numerical values. The sensitivity of the voxel at each position is indicated by a logarithm (common logarithm) with a base of 10.

  Next, from FIG. 25, the result of extracting the line of Y = 60 and Z = 10 in voxel (x, y, z) and plotting the sensitivity as the vertical axis and the horizontal axis as the x position is shown in FIG. ing. At this time, as a propagation angle, the results when the angle with respect to the X axis on the plane with the Y axis as the normal line is set to + 60 ° and −60 ° are shown in FIG.

  As shown in FIG. 26, there is a difference in sensitivity distribution between +60 degrees and −60 degrees. This difference is a guideline for whether the resolution can be improved. That is, the difference in sensitivity distribution indicates that the propagation paths of light from the two light sources are different. If the propagation path is the same, even if the propagation angle is changed, the sensitivity distribution should be almost the same. Because the propagation paths of light from the two light sources are different, the light from the two light sources collects different information.

  This creates great value for the inverse problem estimation described later. As described above, the propagation of light is not simple isotropic scattering, but has a slight anisotropy in the order of several mm. This difference in the order of several millimeters is considered to be a factor for realizing the inverse problem estimation having a resolution of the order of several millimeters. This sensitivity distribution is performed under all conditions of propagation angle / detection angle with respect to all probe pairs (a pair of the light source module LM and the detection module DM) implemented in the phantom.

  The difference due to the angle shown in FIG. 27 cannot be seen in a simulation using a diffusion equation assuming isotropic propagation. This is the first result obtained using Monte Carlo simulation as in this embodiment. As a result, an increase in the amount of information using the difference due to the incident angle can be realized. In other words, inverse problem estimation can be realized with high accuracy by Monte Carlo simulation. Similarly, the correction using this can also be made highly accurate.

  As described above, the Monte Carlo simulation is performed for each of the eight optical models 1 to 8 shown in FIGS. However, only one light source module LM and one detection module DM are shown in FIGS. This is for ease of understanding, and is actually arranged in the same manner as the phantom in FIG.

  At this time, the optical constants shown in FIG. 28 are used as the optical constants of the five layers of the optical model and the poor contact portion. However, since the hair here is generally about 100 um thick, the absorption coefficient is adjusted in accordance with a 1 mm voxel for Monte Carlo simulation. Also, a plurality of optical models are made so that the position of the hair differs depending on the position of the hair, such as whether it is a voxel directly below or shifted by one relative to the light source module LM, the detection module DM, and the like.

  FIG. 29 shows details of the eight optical models 1 to 8 shown in FIGS. Here, the optical model 1 is a standard structure (standard model), and the other seven optical models 2 to 8 reflect the characteristics of the subject and the probe mounting state. In the Monte Carlo simulation, it is possible to create various optical models without being limited to these eight optical models 1 to 8, and it is also possible to create a plurality of stages for each parameter change.

  For example, the optical model 1 in FIG. 17 and the optical model 2 in FIG. 18 have different differences depending on the position of the hair. An optical sensor including a light source module LM that makes non-parallel light incident on the same position of a measurement target and a detection module DM that receives light that is irradiated from the light source module LM and propagates through the measurement target. No. 10 is advantageous in that the robustness to the hair position is high. In other words, information on light that is incident from the same position of the measurement target and has a different propagation path has an effect of reducing the influence of noise generated by the hair depending on the position of the hair. Light in all directions emitted from the light source module LM immediately above the hair is reduced in the same manner.

  On the other hand, in the conventional method of arranging probes at a high density, the propagation paths of a large number of light can be made different, so that the amount of information that can be acquired increases. The probability of being placed increases, and noise caused by hair increases. This is illustrated in FIG. 30 shows a case where hair is present directly under the detection module DM1 ′ and the light source module LM1 ′. In this case, the detected light amount (A) of DM1 ′ and the irradiated light amount (1) of LM ′ are smaller than the others. In this case, as shown in the matrix on the right side of FIG. 30, the numerical value of the matrix element (1, A) (hereinafter also referred to as “matrix value”) is less than the numerical value of the other matrix elements. Since this is unrelated to the cerebral blood flow, it is an error. As described above, when the light source module LM capable of irradiating a plurality of non-parallel lights and the detection module DM capable of dividing the incident angle are used, the hair is compared with the four-layer optical model not including the hair. By using a five-layer optical model including the detection accuracy, the detection accuracy is dramatically improved.

  In the above case, the error factor was poor contact with the hair, but it can be generalized as an error in the optical characteristics of each probe. However, an example that is likely to occur in an actual system is a phenomenon of poor contact.

  In this embodiment, hair is set as a parameter (layer configuration) of the optical model, but an absorption coefficient or a scattering coefficient may be added as a parameter deviating from the assumption.

  As shown in FIG. 31, even in this case, when a contact failure occurs, the influence is almost evenly applied to the entire light source module LM, so that all the irradiation light amounts 1 to 3 are reduced. In this case, since all the irradiation light amounts are reduced at substantially the same ratio, when normalized by (1, A), the distribution is almost the same as in the case of the standard structure (see FIG. 32). However, since the numerical value in the right diagram of FIG. 31 shows a standardized structure, the numerical value of (1, A) is 0.9. The numerical values of the other matrix elements are almost the same as those obtained by multiplying the numerical values in the right diagram of FIG. 32 by 0.9. That is, the light amount distribution in the matrix in the right diagram of FIG. 31 is similar to the light amount distribution in the matrix of the right diagram in FIG.

  When there are a plurality of contact failure portions as in the case of the conventional example of FIG. 30 described above, the light quantity changes only with the probe in which the contact failure occurs, resulting in an error. In other words, only when a plurality of non-parallel lights are incident on the same position of the measurement target, it is possible to remove the error due to the contact failure by modeling the contact failure and performing the simulation in advance. This makes it possible to correct the amount of light with high accuracy. Also, it is possible to estimate the inverse problem with high accuracy.

  If the occurrence of poor contact is modeled in the same manner as in the case of hair, it is easy to correct errors during model selection. In the light source module LM in which a plurality of non-parallel lights are incident on the same position of the measurement target, a decrease in the amount of light due to poor contact at the place where the light source module LM is installed (mounted) causes the plurality of lights from the light source module LM to be reduced. Therefore, it is not necessary to make many optical models that reflect the contact failure (hereinafter also referred to as “contact failure model”).

  In the case of the conventional example of FIG. 30, since there are a large number of contact points between a plurality of light source modules LM ′ that irradiate a single light and a measurement target, it is necessary to make a very large number of contact failure models. If the number of models increases in this way, a model selection error occurs during model selection. The smaller the number of models, the more accurate model selection and high-precision correction becomes possible.

  In the present embodiment, virtual measurement in simulation and actual measurement are performed for each optical model, and the sensitivity distribution for each optical model and the sensitivity distribution of the object are created based on the measurement result. By creating this sensitivity distribution, it is also possible to create a light quantity distribution without cerebral blood flow as shown in the right diagram of FIG. In the right side of FIG. 32, when the incident direction of light from the light source module LM to the optical model is 1, the detected light amount of light incident on the detection module DM in the incident direction A from the optical model is normalized to 1. Using this standardized light quantity as a reference, the detected light quantity for each of the incident directions 1 to 3 of light from the light source module LM to the optical model and the incident directions A to C of light from the optical model to the detection module DM are matrixed. This is the light amount distribution shown in the right side of FIG. With respect to this light amount distribution, all the eight optical models 1 to 8 shown in FIG. 29 can obtain different results.

  By comparing the first light quantity distribution obtained from the sensitivity distribution of each optical model and the second light quantity distribution obtained from the sensitivity distribution of the subject, the optical model most suitable for the subject is selected. . Here, an optical model having the best consistency between the first and second light quantity distributions is selected as a method of selection. At this time, calibration is performed before actual measurement. For the calibration, a black box in which a geracon resin is arranged and provided with a guide so that each probe can be arranged at an appropriate position is used. This calibration allows reproducibility with high accuracy. Here, the light distribution of each optical model is compared with the light distribution of the subject, and the optical model is selected based on the comparison result. Instead, the sensitivity distribution of each optical model and the subject are selected. The optical models may be selected based on the comparison results.

  As a selection method, a matrix value with the smallest error in actual measurement and virtual measurement is selected. Specifically, the difference between the matrix values of (1, A) at the time of actual measurement and (1, A) at the time of virtual measurement is taken. Next, the difference between the matrix values of (2, B) at the time of actual measurement and (2, B) at the time of virtual measurement is taken. This is repeated sequentially, the sum of the squares of the numerical differences of the corresponding matrix elements at the time of actual measurement and virtual measurement is taken, and the optical model having the smallest value is optimized.

  Various other methods can be used for selecting the optical model. For example, in addition to the selection method using the least square method of the matrix described above, there is a selection method in which selection is performed based on preconditions and correction or weighting is applied as described below.

  This selection method will be described with reference to the flowchart of FIG. Here, as a precondition, a method of removing a model in which poor contact occurs (for example, a model in which hair is interposed) was added. After that, correction was made so that there was almost no difference from the adjacent probe, and a method of weighting in consideration of the influence in the depth direction was adopted.

  First, virtual measurement results between adjacent probes are compared (steps S31 to S36). As shown in FIG. 34, the layout of the light source module LM and the detection module DM has four DMs adjacent to one LM. As described above, these four can be detected by dividing into four directions. Since the irradiation direction from the LM is also four azimuths, the previous matrix is 4 × 4.

  When this matrix is compared with four DMs (step S31), there is a case where the amount of light decreases specifically for only one DM, such as hair or poor contact. When determining the presence or absence of this singular point, the singular point is quantified and determined with a certain threshold (step S32). In the present embodiment, the DM having the weakest light quantity among the four DMs (here, DM (Min)) is determined based on how far it is from the average value of the other three DM matrices.

  In this case, as numerical values, the light amounts of (DM1, 3, A), (DM2, 4, B), (DM3, 1, C), and (DM4 2, D) in FIG. 34 are compared. These four numerical values are averaged, normalized by the average value, and when DM (min) is 0.9 or less when the average of the three DMs is 1, this is determined as a singular point.

  In this embodiment, since it is a phantom experiment, the threshold value γ of DM (min) is set to a high value of 0.9. The threshold value γ is appropriately selected by. The thickness of the skull on the forehead of the human body was assumed to be generally uniform in an area (60 mm square) within a quadrangle having four adjacent DMs as vertices. This is because the uniformity of cerebral blood flow is considered to be only a few mm or less. In the following, the degree of uniformity can be referred to as a sparse value β to give a physiological characteristic to the sparsity.

  Here, the sparse value β is appropriately changed depending on the age and part of the subject. This is because the degree of uniformity can be guaranteed depending on the part to be measured. For example, the forehead is known to have a uniform structure such as a skull, and β was set to 60 mm.

  On the other hand, the structure of the skull is complicated in the part near the ear of the temporal region, and the uniformity is low in an area (60 mm square) in a quadrangle having four adjacent DMs as vertices. Therefore, the sparse value β of the portion near the temporal ear was set to 30 mm. In this part, the threshold value is appropriately determined such that the threshold value γ is set to 0.7. The relationship between the sparse value and the threshold value is determined by the Fermi function equation. By this Fermi function, a constant was determined to be 0.9 when the sparse value β exceeded 60 mm, and 0.7 when β was less than 30 mm.

  If there is a singular point, the matrix value is corrected (step S33). In the correction method, a coefficient is applied to all the matrix elements to be corrected so that the correction target matrix (light quantity distribution) becomes an average value of the other three matrices (light quantity distribution). When this correction is applied, the measured values of the four DMs are compared again to compare whether a singular point has occurred.

  Next, the same processing is performed by four LDs centered on one DM (steps S34 to S36, FIG. 35). Since this method is the same as above, it is omitted here.

  Next, after removing the singularity, light quantity comparison is performed between adjacent matrices, and correction is performed (steps S37 to S39). Comparison is performed in the area of Point A with the layout shown in FIG. The light propagation path most affected by the situation of this area is indicated by four arrows in FIG. These four propagation paths are (DM1 2 and LM1 B), (DM1 1 and LM2 A), (DM2 3 and LM1 C), (DM2 4 and LM2 D) in the matrix. Strongly related to light intensity. When the optical characteristics in each propagation path are the same, it is predicted from the simulation that the light amounts of the respective matrices match.

  However, in an actual system, an error ε occurs because the propagation paths are slightly different. In this embodiment, the distance of the position of the propagation path is 30 mm or less, but the optical characteristics of the area to be measured may change at the distance of 30 mm. Therefore, here too, by comparing with the sparse value β, it is determined whether or not the correction is performed depending on how much the error ε is accepted.

  If necessary, correction is performed in the same manner as in step S33 (step S39), and then an optical model is selected. In general, an optical model is affected by three types of skin color (skin thickness), skull thickness, and bone marrow fluid.

  Therefore, an optical model including the skin layer, skull layer, and bone marrow fluid layer was created. There are nine patterns of detection patterns based on combinations of this optical model and probe pairs (LM and DM pairs). The model most suitable for the area of the probe pair is selected from the nine patterns. As the selection, there is a matrix (similar to the right diagram in FIG. 7) created by the optical simulation results of nine patterns. It is sufficient to select a pattern with the smallest error between the numerical values of the nine matrix elements of the matrix and the corresponding nine matrix elements actually measured on the subject. .

  The skin layer, skull layer, and bone marrow fluid layer are arranged in a deep direction in order from the surface of the scalp. Therefore, weighting in the depth direction is performed (step S40). Specifically, if (1, A) and (3, C) are considered in the matrix of FIG. 7, (1, A) light propagates relatively on the surface, and (3, C) is Light propagates in a relatively deep part. In other words, (1, A) has a strong influence on the shallow part, so the skin color model of the shallow part is weighted. Since (3, C) has a strong influence in the deep part, the model of the bone marrow fluid in the deep part is weighted. For example, the weighting factor was determined as follows.

  For the selection of the skin model layer, the weighting factor was 2.0 for the matrix element (1, A), 1.5 for the matrix element (2, B), and 1.0 for the other matrix elements. In selecting the skull model layer, the weighting factor was set to 1.5 for the matrix element (2, B) and 1.0 for the other matrix elements. In selecting the bone marrow fluid model layer, the weighting factor was set to 2.0 for the matrix element (3, C) and 1.0 for the other matrix elements.

  After weighting in this way, model selection by the least square method is performed for each matrix element (step S41).

  When selecting a model, another sensor may be used in addition to the optical sensor. For example, there are an ultrasonic sensor for detecting bone density and a method for detecting and correcting disturbance light. Also, a method of removing an artifact by attaching an acceleration sensor or the like can be considered.

Next, inverse problem estimation is performed using the sensitivity distribution of the selected optical model and the sensitivity distribution of the subject.
Assuming that the change in absorption coefficient δμ _a (r) caused by the presence of the light absorber is sufficiently small, the following equation is established by approximation of Retov.

ν is the speed of light in the medium, S is the amount of light emitted from the light source module LM per unit time, rs is the position of the light source module LM, rd is the position of the detection module DM, and φ (rs, rd) is the light source module It represents the quantity of light emitted from the LM reaches the detection module DM, phi ₀ represents the intensity of light in the absence of light absorbing material. This equation means that if the light intensity φ _{0 in} the absence of the light absorber is given, the change in absorption coefficient δμ _a (r) caused by the presence of the light absorber and the observed value log φ (rs, rd) ) Can be linked to a linear relationship.

This can be simply described as:
Y = A (r) X
Here, Y is a change in the observed value due to the presence or absence of the light absorber, and X indicates a change in the absorption coefficient at the position r of the voxel. A (r) is a sensitivity distribution. In the above equation, it can be seen how the observed value Y changes by giving changes in the position and amount of the light absorber represented by X.

  In the inverse problem estimation, the reverse is performed, that is, the position X of the light absorber is estimated using the observed value Y. As described in the previous position measurement method, the change due to the presence or absence of the light absorber is measured as Δr (i, n). This Δr (i, n) becomes the observed value Y, and X is calculated from this.

  In general, an inverse problem estimation method called L2 norm regularization is used. In this method, X that minimizes the cost function C shown below is calculated.

Here, Y is an observed value, A is a sensitivity distribution, and λ is a regularization coefficient. Such a method is generally used for inverse problem estimation, but in this embodiment, inverse problem estimation is performed by Bayesian estimation that can also detect the depth direction. For the inverse problem estimation by Bayesian estimation, T. Shimokawa, T. Kosaka, O. Yamashita, N. Hiroe, T. Amita, Y. Inoue, and M. Sato, "Hierarchical Bayesian estimation improves Depth accuracy and spatial resolution of diffuse optical tomography, "Opt. Express * 20 *, 20427-20446 (2012). The results shown below are described in Japanese Patent Application No. 2014-230745 which is a prior application.

  As a result, an estimation result as shown in FIG. 37 can be derived. FIG. 37A shows the position of the light absorber. The grid in FIG. 37B is 3 mm, and it was found that the grid matches the actual position with an accuracy of 3 mm.

  As a comparative example, the result of detection using only one of the four directions is shown in FIG. This comparative example has almost the same configuration as a conventional NIRS (DOT) apparatus. In the comparative example, the detection in the depth direction is impossible, and the detection result is very wide. In Example 1, it is possible to detect the position and depth of the light absorber by the Bayesian estimation.

  In addition, FIG. 38B shows the result of estimation (estimation result) by changing the position of the light absorber (see FIG. 38A). Also in this case, it can be seen that the actual position of the light absorber can be accurately estimated. According to the method of Example 1, the position of the light absorber can be detected with high resolution. On the other hand, in the comparative example, as shown in FIG. 38C, the light absorber is considerably spread, and the position of the light absorber cannot be accurately detected.

  Hereinafter, Example 2 of this embodiment will be described. In the description of the second embodiment, a description related to the first embodiment will be given as appropriate.

Example 2
First, black ink is dropped to about 200 ppm in an aqueous solution of Intrapid injected into a transparent acrylic water tank (10% concentration of Intrapid is diluted 10 times). The scattering coefficient. A black light-absorbing body imitating blood flow is submerged in this cloudy intrapid aqueous solution. The light absorber is, for example, a black polyacetal sphere having a diameter of about 5 mm. The sphere is fixed to a thin metal rod having a diameter of 1 mm connected to an automatic stage so that the position of the sphere can be controlled. The side of this water tank, the position of the probe described later, is accurately determined and installed (mounted). Here, the acrylic water tank is a rectangular water tank having a volume of 140 mm × 140 mm × 60 mm and a wall thickness of 1 mm, for example.

  The optical sensor 10 includes an irradiation system including a plurality (for example, eight) of light source modules LM and a detection system including a plurality (for example, eight) of detection modules DM. The plurality of light source modules LM and the plurality of detection modules DM are respectively connected to the control unit via electrical wiring.

  The control unit controls the light emission timing of the light source in each light source module LM and the detection timing in each detection module DM, and transfers the obtained detection result to the recording unit. Further, the control unit performs control to read data recorded in the recording unit, perform calculation using the numerical value, and display the calculation result on the display unit.

  As shown in FIG. 39, the eight light source modules LM and the eight detection modules DM are, for example, a light source module LM with respect to the pseudo living body (not shown) in both the X direction and the Y direction orthogonal to each other. The detection modules DM are arranged in a matrix (two-dimensional lattice) at an equal pitch a in the X direction and the Y direction so as to be adjacent to each other. In FIG. 39, LM is indicated by a square mark, and DM is indicated by a circle mark.

  As shown in FIG. 40, the light source module LM (type I) of Example 2 includes, for example, an optical element such as a lens and a prism, a ceramic package (not shown) on which a plurality of surface emitting laser array chips are mounted, and the ceramic. A flexible substrate (not shown) on which a package or an analog electronic circuit is mounted, wiring connected to the flexible substrate, a connector part (not shown), a housing in which these are accommodated, and a transparent resin that contacts the subject Includes window members and the like.

  The light from each surface emitting laser array chip is refracted by the corresponding lens, deflected to a desired angle by a prism as a reflecting member formed inside the window member (reflected in a predetermined direction), and emitted outside the housing. Is done.

  As shown in FIG. 41, the surface emitting laser array chip has a square shape with a side of about 1 mm and includes a plurality of (for example, 20) surface emitting lasers arranged two-dimensionally.

  More specifically, each surface emitting laser array chip has five groups (ch groups) each including four surface emitting lasers. Here, the centers of four of the five groups are individually located at the four vertices of the square, and the centers of the remaining one group are located at the center of the square.

  The four channels of each group are mounted on the ceramic package as described above, and are connected to the same electrode pad (any one of the electrode pads 1 to 4) via bonding wires (wiring).

  The ceramic package is mounted on the wiring pattern of the flexible substrate by soldering. On the flexible substrate, a switching semiconductor and a current stabilizing semiconductor are arranged. Which channel of the surface emitting laser array chip emits light is controlled by the semiconductor for switching. The switching semiconductor causes the selected channel to emit light by an external serial signal. One end of the serial signal signal line and one end of the power supply line are connected to the flexible substrate, and the other end of the signal line and the other end of the power supply line are connected to the control unit.

  The amount of light emitted from each channel is set to be constant by calibration performed every predetermined period. In a normal usage method, five groups of light are emitted sequentially in short pulses. Such pulsed light emission is suitable for stabilizing the amount of emitted light because temperature rise due to heat generation is avoided. By detecting and averaging the detection values obtained by the detection module each time a short pulse is emitted, detection is strong against noise.

  By the way, the oscillation wavelength of the surface emitting laser (VCSEL) of each surface emitting laser array chip is 780 nm or 900 nm as an example. By using a plurality of surface emitting lasers having different oscillation wavelengths, a plurality of outgoing lights having different wavelengths can be obtained. Then, by irradiating a substantially identical position of a subject (for example, a living body) with a plurality of lights having different wavelengths, it becomes possible to recognize, for example, the state of hemoglobin (deoxygenated state or oxidized state). These wavelengths are selected because the absorption coefficient varies greatly depending on the oxygen concentration in the blood.

  In the light source module LM (II type) of the second embodiment shown in FIG. 42A, a surface emitting laser array chip 1 having an oscillation wavelength of 900 nm and a surface emitting laser array chip 2 having an oscillation wavelength of 780 nm are arranged in parallel. A lens 1 (individual optical element) is disposed in the vicinity of the emitting end of the surface emitting laser array chip 1, and a lens 2 (individual optical element) is disposed in the vicinity of the emitting end of the surface emitting laser array chip 2. A prism (common optical element) is commonly arranged on the optical path of the light. The surface emitting laser array chips 1 and 2 are arranged in the Y direction on the XY plane so that the emission direction is the Z-axis direction, and have substantially the same configuration (light emitting unit) except that the oscillation wavelengths are different from each other. Including the number and arrangement). The lenses 1 and 2 are substantially the same lens.

  Hereinafter, the surface emitting laser array chips 1 and 2 are also referred to as ch1 and ch2, and are collectively referred to as ch when not distinguished from each other.

  In LM (II type), the positional relationship between a plurality of light emitting units and the optical axis of the corresponding lens is the same between channels. Specifically, the center of each channel (array center) is on the optical axis of the corresponding lens.

  Here, attention is paid to three light emitting units arranged at equal intervals in the Y direction of each channel shown in FIG. Three light emitting units arranged at equal intervals M in the Y direction of ch1 are sequentially designated as a light emitting unit 1a, a light emitting unit 1b, and a light emitting unit 1c from the + Y side to the -Y side, and three light emitting units arranged at equal intervals M in the Y direction of ch2 In order from the + Y side to the -Y side are referred to as a light emitting unit 2a, a light emitting unit 2b, and a light emitting unit 2c. It is assumed that the light emitting unit 1b and the light emitting unit 2b are arranged on the optical axes of the corresponding lenses 1 and 2.

  As shown in FIG. 42A, the prism has a symmetric shape (axisymmetric shape) with respect to the central axis, and an incident surface IS orthogonal to the central axis and all of the surfaces inclined with respect to the central axis. The reflecting surfaces R1 and R2 and the exit surface OS orthogonal to the central axis are included.

  The incident surface IS is located on the optical path of light from the three light emitting portions 1a, 1b, and 1c of ch1 and on the optical path of light from the three light emitting portions 2a, 2b, and 2c of ch2.

  The total reflection surface R1 is emitted from the light emitting part 1a on the optical path of the light (light ray 1) via the lens 1 and the incident surface IS, and emitted from the light emitting part 2a via the lens 2 and the incident surface IS (light ray 2). Located on the optical path. The incident angle of the light rays 1 and 2 to the total reflection surface R1 is equal to or greater than the critical angle.

  The total reflection surface R2 is emitted from the light emitting portion 1c on the optical path of the light (light ray 3) via the lens 1 and the incident surface IS and emitted from the light emitting portion 2c of the ch2 light (light ray) via the lens 2 and the incident surface IS. 4) Located on the optical path. The incident angle of the light rays 3 and 4 to the total reflection surface R2 is equal to or greater than the critical angle.

  The exit surface OS is the light reflected by the total reflection surface R1 (light rays 1 and 2), the light reflected by the total reflection surface R2 (light rays 3 and 4), the light emitted from the light emitting portion 1b of ch1, the lens 1, the entrance surface Is positioned on the optical path of the light (ray 5) emitted from the light emitting portion 2b of ch2 and the light beam (ray 6) that has passed through (incidence) the lens 2 and the incident surface, and emits rays 1 to 5 ( Pass). Here, the emission surface OS is a contact surface that contacts the surface of the subject. Therefore, it is preferable that a transparent gel is interposed between the exit surface OS and the surface of the subject.

  In this case, the two lights having different wavelengths emitted from the two light emitting portions 1a and 2a and entering the lenses 1 and 2 are refracted by the lenses 1 and 2 and are substantially parallel to each other on the incident surface IS. Incident light is refracted by the incident surface IS and incident on the total reflection surface R1 in a substantially parallel state. Two lights having different wavelengths reflected by the total reflection surface R1 are incident on substantially the same position of the subject in a substantially parallel state. In this case, the incident positions of the two lights having different wavelengths on the subject are somewhat shifted (about the distance between the light emitting unit 1a and the light emitting unit 2a).

  Similarly, two lights having different wavelengths emitted from the light emitting portions 1c and 2c and entering the lenses 1 and 2 are refracted by the lenses 1 and 2 and enter the incident surface IS in a substantially parallel state. The light is refracted by the incident surface IS and is incident on the total reflection surface R2 in a substantially parallel state. Two lights having different wavelengths reflected by the total reflection surface R2 are incident on substantially the same position of the subject in a substantially parallel state. In this case, the incident positions of the two lights having different wavelengths on the subject are somewhat shifted (about the distance between the light emitting unit 1c and the light emitting unit 2c).

  In order to further improve the detection accuracy, it is desirable to make the incident positions of two lights having different wavelengths incident on the subject the same (as close as possible). One possible method is to make the optical paths of two lights having different wavelengths reflected by the total reflection surface of the prism substantially coincide.

  Therefore, it is conceivable to provide two reflecting surfaces separately on the optical paths of the two lights having different wavelengths from the two channels (see FIG. 40). It is difficult to substantially match the optical paths.

  In particular, it is possible to match the emission directions of two lights having different wavelengths from the two channels from the two lenses, but it is not possible to make the emission points (the positions of the light emitting portions) of the two channels the same. Is possible.

  The light source module LM (type III) of Example 2 shown in FIG. 43 will be described below. LM (type III) differs from LM (type II) shown in FIG. 42A in that the positional relationship between a plurality of light emitting units and the optical axis of the corresponding lens differs between channels. The configuration of is the same as that of LM (II type).

  In LM (type III), the center distance between two channels (the distance between the array centers) is about 1.4 mm. This is a positional relationship in which two channels are brought as close as possible in consideration of a pad portion when wire bonding is performed.

  By the way, each channel is 1 mm square, and the space (gap) between the two channels is mounted as close as several hundred um. Here, this proximity mounting is realized by devising the collet of the die bonder device.

  In addition, the light emitting portions (surface emitting lasers) of the two channels are manufactured by a semiconductor process using the same mask, and the position of the light emitting portion can be controlled with an accuracy of 0.5 μm or less.

  In the LM (III type), similarly to the LM (II type), the surface emitting laser array chip 1 (900 nm) and the surface emitting laser array chip 2 (780 nm) have the same layout with the same level of accuracy.

  In this way, two lights emitted from two channels whose centers are separated by about 1.4 mm and having different wavelengths via the corresponding lenses are reflected by the same total reflection surface of the prism and are incident on a subject (for example, a living body). To do.

  At this time, in the LM (type II) configuration, the light from ch1 and the light from ch2 that are in a corresponding relationship are maintained in a state of being parallel to each other at a substantially constant interval (about 1.4 mm) (for example, The incident position remains shifted by about 1.4 mm. Thus, when the deviation of the incident position is large, the resolution in fNIRS that detects cerebral blood flow by inverse problem estimation is lowered.

  Therefore, as a result of the present inventor's earnest study on a method for substantially matching the optical paths of two lights having different wavelengths and making the incident position the same without increasing the mounting cost, the center of the ch (array center), A method of shifting the optical axis of the corresponding lens by several um to several hundred um (preferably several tens of um) was devised, and this method was introduced into LM (type III).

  Details thereof will be described below with reference to FIG. Here, the center of each channel and the optical axis of the corresponding lens are shifted by about 20 μm. The amount to be shifted is not limited to 20 μm and can be changed as appropriate.

  Here, the lens corresponding to each channel is shifted without changing the center distance (positional relationship) between the two channels. The direction in which the lens is shifted with respect to ch may be arranged symmetrically (rotationally symmetric) with respect to the central axis of the prism that is a common optical element (see FIG. 45).

  That is, the two channels and the two lenses 1 and 2 may be arranged symmetrically with respect to the central axis of the prism (common optical element), and are not limited to the arrangement shown in FIG.

  Here, as an example, the two channels are arranged with the central axis in the Y direction so that the center is axially symmetric (point symmetric) with respect to the central axis of the prism. Each channel has five light emitting units (VCSEL), and the five light emitting units are individually arranged at the center of a square (array center) and four vertices whose one diagonal line is parallel to the Y direction.

  As an example, the center distance between the two channels is 1.4 mm, the effective diameter of each lens is 0.8 mmφ, and the focal length f of each lens is f = 600 μm. Here, the direction in which the lenses 1 and 2 are shifted with respect to the two channels 1 and 2 is such that the lenses 1 and 2 approach each other as shown in FIG. Here, the lens 1 is shifted by about 20 μm in the −Y direction from the state in which the optical axis of the lens 1 passes through the center of ch1, and the lens 2 is moved in the + Y direction by about 20 μm from the state in which the optical axis of the lens 2 passes through the center of ch2. Shift about. As a result, the center of ch1 and the optical axis of lens 1 are shifted by about 20 μm, and the center of ch2 and the optical axis of lens 2 are shifted by about 20 μm.

  In this case, the optical path from the lens 1 to the total reflection surface R1 of the light (light beam 1 ′) emitted from the light emission unit 1a of ch1 and incident on the total reflection surface R1 via the lens 1 and the incident surface IS, and the light emission unit of ch2 The optical path from the lens 2 to the total reflection surface R1 of the light (ray 2 ') emitted from the lens 2a and incident on the total reflection surface R1 through the lens 2 and the incident surface IS is non-parallel and closer to the total reflection surface R1. (See FIG. 43). In addition, when the incident angle of the light to the lens is the same, the refraction angle of the light increases as the incident position of the light to the lens moves away from the optical axis.

  Further, the optical path from the lens 1 to the total reflection surface R2 of the light (light ray 3 ') emitted from the ch1 light emission unit 1c and entering the total reflection surface R2 through the lens 1 and the incident surface IS, and the ch2 light emission unit 2c. The optical path from the lens 2 to the total reflection surface R2 of light (light ray 4 ') that is emitted from the lens 2 and enters the total reflection surface R2 via the incident surface IS is non-parallel and becomes closer as it approaches the total reflection surface R2. (See FIG. 43).

  Further, an optical path from the lens 1 to the exit surface OS of the light (light ray 5 ′) emitted from the ch1 light emitting unit 1b and incident on the exit surface OS via the lens 1 and the entrance surface IS, and the light emitted from the ch2 light emitting unit 2b. Then, the optical path from the lens 2 to the exit surface OS of the light (light ray 6 ') that enters the exit surface OS via the lens 2 and the entrance surface IS becomes closer as it approaches the exit surface OS (see FIG. 43).

  Then, the optical paths of two non-parallel lights (light rays 1 ′ and 2 ′) having different wavelengths reflected by the total reflection surface R1 intersect in the vicinity of the emission surface OS which is a contact surface with the subject. Further, the optical paths of two non-parallel light beams (light rays 3 ′ and 4 ′) having different wavelengths reflected by the total reflection surface R2 intersect in the vicinity of the emission surface OS which is a contact surface with the subject (see FIG. 43). .

  As a result, as shown in FIG. 43, the optical paths of two lights (light rays 1 ′ and 2 ′) having different wavelengths reflected by the total reflection surface R1 substantially coincide with each other, and the two lights enter the subject. The position is the same. In addition, the optical paths of two lights (light rays 3 ′ and 4 ′) having different wavelengths reflected by the total reflection surface R2 are substantially coincident, and the incident positions of the two lights on the subject are the same. In addition, the incident positions of the two lights (light rays 5 ′ and 6 ′) having different wavelengths from the incident surface IS toward the exit surface OS without passing through the total reflection surface are substantially the same.

  Further, the light beam including the light beams 1 ′ and 2 ′, the light beam including the light beams 3 ′ and 4 ′, and the light beam including the light beams 5 ′ and 6 ′ are non-parallel and are incident on substantially the same position of the subject. .

  The light from the two light emitting units other than the ch1 light emitting units 1a, 1b, and 1c and the light from the two light emitting units other than the ch2 light emitting units 2a, 2b, and 2c shown in FIG. It passes through the exit surface OS as it is and enters the subject at substantially the same position as the light beam of the subject.

  In the LM (type III) described above, the light paths of two lights having different wavelengths are substantially matched by a simple method of shifting the lens with respect to ch, and the incident positions of the two lights are made the same. Can do. By making the incident positions of two light beams having different wavelengths the same, it is possible to measure the cerebral blood flow position with high positional accuracy even in the NIRS apparatus that performs inverse problem estimation.

  On the other hand, if a member such as a half mirror is used instead of a lens shift in order to obtain the same effect as that of LM (type III), the number of new optical components that require highly accurate positioning increases, and the mounting cost increases. It ’s a mess.

  In LM (III type), the optical axes of the lenses 1 and 2 are shifted (shifted) from the positions passing through the centers of the corresponding ch1 and ch2, but this is not restrictive.

  For example, one optical axis of the lenses 1 and 2 may be shifted from a position passing through the center of the corresponding ch, and the other optical axis may be positioned at a position passing through the center of the corresponding ch.

  Further, instead of or in addition to shifting the lens with respect to the corresponding ch, the ch may be shifted with respect to the corresponding lens.

  In addition, the direction in which the lenses 1 and 2 are shifted with respect to the corresponding ch1 and ch2 can be changed as appropriate. For example, the lenses 1 and 2 may be shifted in the same direction, or may be shifted in opposite directions (directions toward each other or directions away from each other).

  Further, the shift amounts (shift amounts) for the ch1 and ch2 corresponding to the lenses 1 and 2 may be the same or different.

  In summary, in short, the positional relationship between the plurality of light emitting units and the optical axes of the corresponding lenses may be different between the channels so that the optical paths of the two lights having different wavelengths from ch1 and ch2 are substantially coincident.

  Specifically, the optical paths of two lights emitted from ch1 and ch2 and having different wavelengths via lenses 1 and 2 gradually approach each other, and the vicinity of the contact surface with the subject in LM (type III) (LM (type III) emission end) It is desirable that the positional relationship between the plurality of light emitting units and the optical axes of the corresponding lenses be different between the channels so that the optical paths of the two lights intersect in the vicinity.

  The reason why the surface emitting laser array chip is adopted as the light source of the optical sensor 10 will be described below. In the surface emitting laser array chip, a plurality of channels can be two-dimensionally arranged at close positions, and the light emission of each channel can be controlled independently. The traveling direction of the emitted light can be changed by installing a small lens near the ch.

  Further, in an optical sensor used for DOT, it is required to control the incident angle to the subject as accurately as possible. Since a general LED (light emitting diode) has a wide radiation angle, it is necessary to make the lens an aspherical surface in order to obtain highly accurate parallel light. In addition, a general LD (edge emitting laser) has an asymmetric radiation angle, and in order to produce highly accurate parallel light with a lens, it is necessary to combine two lenses or cylindrical lenses with different curvatures in length and width. Therefore, the configuration becomes complicated and high-precision mounting is required.

  On the other hand, the surface emitting laser has a substantially perfect far field pattern, and only one spherical lens may be arranged to produce parallel light. Further, when using coherent light emitted from the LD, speckle is generated in the subject (scattering body) where scattered light interferes with each other. This speckle pattern adversely affects measurement as noise.

  When the blood flow in the brain is viewed like DOT, the number of scattering is so large that there is no significant influence. However, the light reflected from the skin surface is affected by the return light that returns directly to the light source. The return light destabilizes the oscillation state inside the LD and prevents stable operation. Even in an optical disk or the like, when using coherent light stably, a wave plate or the like is used so that regular reflection light does not become return light. However, it is difficult to remove the return light of the reflected light from the scatterer.

  In the case of a surface emitting laser array chip, it is possible to simultaneously irradiate a minute area with a plurality of lights, and to reduce the return light interference (for example, refer to JP2012-127937A).

  In this embodiment (Examples 1 and 2), a convex lens (also simply referred to as “lens”) is disposed on the optical path of light from the surface emitting laser array chip (see FIG. 46).

  The diameter of the convex lens is 1 mm, and the effective diameter ε of the convex lens is 600 μm. The focal length f of the convex lens is 600 μm. The surface emitting laser array chip is a 1 mm square chip, and the distance dmax between the centers of the two most distant channels in the surface emitting laser array chip is 600 μm. Thus, by matching dmax and ε, the diameter of the convex lens can be minimized.

  Here, in the convex lens and the surface emitting laser array chip, the distance L in the optical axis direction of the convex lens between the principal point (optical center) of the convex lens and the light emitting surface (outgoing surface) of the surface emitting laser array chip is, for example, It is positioned to be 300 um. That is, f ≠ L.

  In this case, it is possible to avoid the phenomenon that light emitted from the surface emitting laser array chip and transmitted through the convex lens is regularly reflected by a prism or the like and condensed on the surface emitting laser array chip by the convex lens (return light phenomenon). it can. Thus, since no return light is generated, it is possible to stabilize the light emission quantity of each channel of the surface emitting laser array chip.

  However, when the influence of the return light is not taken into consideration (when high resolution is not required for NIRS), f = L may be used.

  Further, as shown in FIG. 47, the space between the convex lens and the surface emitting laser array chip is filled with a transparent resin so that no air layer is interposed. As the transparent resin, a resin having a refractive index equivalent to that of a convex lens (for example, a thermosetting epoxy resin) is used. That is, the refractive index does not change at each interface between the convex lens and the surface emitting laser array chip. The transparent resin may be molded with a mold before fixing the convex lens, or may be injected after fixing the convex lens.

  As described above, the space between the convex lens and the surface emitting laser array chip is filled with the transparent resin, so that the light emitted from the surface emitting laser array chip is reflected on the surface of the convex lens on the surface emitting laser array chip side. That is, generation of return light can be prevented. Since no return light is generated, the amount of light emitted from each channel can be stabilized. If the light quantity of each channel is stabilized, the S / N (signal / noise) ratio of the measurement system becomes good, and high-accuracy NIRS measurement and high resolution can be realized.

  As shown in FIG. 48, the convex lens is fixed to a package on which the surface emitting laser array chip is mounted via a submount. In the surface emitting laser array chip, an electrode (chip electrode) on the chip is electrically connected to a PKG electrode on the package by a wire. Since the wire has a height of about several tens of um, it is designed not to interfere with the submount. The fixed position L of the convex lens (the distance between the light emitting surface of the surface emitting laser array chip and the principal point of the convex lens) is restricted by the height of the wire. In other words, when a wire is used, it is necessary to have a structure that avoids the submount or to make the height of the wire 100 μm or less. That is, it is preferable that −100 μm <f−L <0. However, in FIG. 48, illustration of the transparent resin shown in FIG. 47 is omitted.

  The light emitted from the emission surface of the surface emitting laser is substantially circular, and its divergence angle is about 5 degrees in half width. Since a general LD beam is elliptical, it is necessary to consider an installation error in the rotation direction, but a surface emitting laser has an advantage that it is not necessary to consider it. Moreover, since it is circular, there is a merit that it is easy to perform approximation using symmetry for optical simulation used when solving an inverse problem.

  The beam emitted from the surface emitting laser is refracted by a convex lens disposed in the vicinity. The refraction angle is determined by the relative position between the surface emitting laser and the lens center (lens optical axis). Accordingly, a desired refraction angle can be obtained by appropriately setting the position of each group of the surface emitting laser array chip and the position of the lens.

  In Example 2, the relative position between ch and the optical axis of the convex lens is set so that the refraction angle is about 20 degrees. In the surface emitting laser array chip, since each channel can be controlled to emit light independently, the direction of light emitted from the light source module LM can be changed by selecting the channel to emit light.

  FIG. 49 shows an example of a ray diagram optically designed by an optical simulator. Here, three channels (light sources) imitating a surface emitting laser array chip, and a lens having a diameter of 1 mm and f = 600 μm are arranged in the vicinity of the three channels. One of the three channels is disposed on the optical axis of the lens, and the other two channels are individually disposed on one side and the other side of the optical axis of the lens. Light from ch other than ch on the optical axis is refracted by the lens, and the propagation direction (path) is bent. That is, two lights from two channels other than the ch on the optical axis are emitted in directions opposite to each other at an angle of about 20 degrees with respect to the optical axis of the lens.

  Here, the light source module LM is designed so that the incident angle of light on the subject is about 55 degrees. Specifically, as shown in FIG. 40, the light source module LM individually deflects a plurality of lights emitted from a convex lens in a direction inclined about 20 degrees with respect to the optical axis by a plurality of prisms. Therefore, the angle of each of the plurality of lights with respect to the optical axis of the lens is changed from about 20 degrees to about 55 degrees and is designed to be incident on the surface of the subject.

  Note that the prism is not limited as long as it reflects light, and for example, a glass substrate on which a metal film is formed may be used. Further, for example, a prism using a total reflection phenomenon caused by a difference in refractive index may be employed. As an example, FIG. 50 shows the result of optical simulation. The light beam emitted from the VCSEL is refracted by the convex lens and then enters the prism.

  Here, the material of the prism is BK7, but a general optical material may be used. The light incident on the prism is totally reflected on the side surface (reflecting surface) of the prism and is incident on the subject at an incident angle of about 55 °. That is, the light passing through the convex lens is deflected by the prism so that the incident angle of the light to the subject is about 55 °. At this time, a transparent gel is interposed between the prism and the subject in order to prevent light scattering at the interface between the prism and the subject. Here too, the plurality of lights from the surface emitting laser array chip are converted into a plurality of non-parallel lights by the convex lens, reflected by the prism, and incident on the subject. As a result, a plurality of non-parallel substantially parallel lights are incident on the same position of the subject (see FIG. 50).

  Due to Snell's law due to the refractive index difference between the prism and the subject, the propagation angle of the light beam in the subject changes from about 55 ° to about 60 °.

  In an optical system including a convex lens and a prism, the propagation angle of light in the subject can be set by utilizing the fact that the positions of the respective channels of the surface emitting laser array chip are different from each other. Here, by shifting the center of each ch (VCSEL) by about 200 μm from the optical axis of the convex lens, the propagation angle of the light emitted from the ch within the subject can be set to about 60 °. At this time, the plurality of lights emitted from the plurality of channels are emitted as a plurality of non-parallel substantially parallel lights from a plurality of positions having different exit surfaces of the convex lens.

  FIG. 51 shows, as a comparative example, the result of an optical simulation when the lens has a focal length f = 600 μm and the fixed position is L = 1.6 mm. If the difference between L and f is 1 mm or more, the beam will spread greatly as shown in FIG. When the beam spreads as described above, it is necessary to enlarge the incident surface of the subject. However, the practical size of NIRS is about φ2 mm. This restriction is that the interval between human hair roots is about 2 mm, and in an area larger than this, the hair becomes an obstacle in terms of optics, and high-resolution NIRS cannot be realized. In other words, the difference between f and L is preferably less than 1 mm.

  The lenses 1 and 2 shown in FIG. 40 are directly fixed to the ceramic package on which the surface emitting laser array chip is mounted so that the lenses 1 and 2 are accurately and stably arranged at the designed positions.

  In FIG. 49, the convex surface of the lens is directed to the surface emitting laser side, but the reverse is also possible. As shown in FIG. 49, it is possible to increase the distance between the surface emitting laser chip and the lens by arranging the convex surface of the lens to face the surface emitting laser and the plane portion of the lens to the subject side. it can. In the chip mounting process, it is preferable that the allowable distance is long to some extent in order to prevent interference between the arms for picking up the components and the components during mounting.

  The lens may be an optical component that refracts light, and a GRIN (Gradient Index) lens using a refractive index distribution of an optical fiber may be used. By using a GRIN lens, there is a merit that a spherical aberration is generally small, a lens having a small f value can be selected at a low cost, rather than using a spherical lens.

  In the second embodiment, it is desirable that the spherical aberration is small because light is also incident on the end of the lens.

  As can be seen from the above description, a plurality of non-parallel light beams are emitted from the light source module LM (type I, type II, type III) of the second embodiment (see FIGS. 40, 42, and 43). . Further, two light beams having different wavelengths are emitted from the light source module LM (I type and II type) in a state where the optical paths are substantially parallel and close to each other (see FIGS. 40 and 42). In addition, two light beams having different wavelengths are emitted from the light source module LM (type III) according to the second embodiment in a state where the optical paths are not parallel and substantially coincide with each other (see FIG. 43).

  A plurality of non-parallel light beams from the light source module LM (I type, II type, III type) are incident on substantially the same position of the subject (see FIGS. 40, 42, and 43). In addition, two light beams having different wavelengths with substantially the same optical path from the light source module LM (type III) are incident on the same position of the subject (see FIG. 43).

  The “substantially the same position” means, for example, the substantially same position with respect to 60 mm when the light source modules LM are arranged at an interval of about 60 mm. You can say "same position".

  Further, the above “same position” means higher identity than “substantially the same position”. However, not only strictly the same case but also a plurality of positions separated by 1 mm or less from each other can be referred to as “same position”. Absent.

  In addition, the above “optical path substantially coincides” means that an angle formed by two non-parallel optical paths is 10 ° or less. In order to enhance the coincidence of the optical paths as much as possible, the angle formed by the two non-parallel optical paths is more preferably 1 ° or less.

  An algorithm for solving the inverse problem will be described later. At that time, an optical simulation in which the position of the light source module LM is set is performed. When this optical simulation is performed, an error is not caused in the estimation of the inverse problem by accurately setting the deviation of the incident position on the subject.

  However, as in Patent Document 1, for example, in order to dispose the probe at a high density by shifting the probe position by 10 mm or more, it is necessary to dispose a plurality of light source modules independently. The operation of arranging the plurality of light source modules is a complicated mounting operation in which the hairs are separated one by one, and the number of the light source modules increases.

  In the present embodiment, as will be described in detail later, it is possible to obtain the same amount of information as when a plurality of light source modules are arranged, by simply arranging one light source module LM, without increasing complicated work. High-resolution detection realized by a high-density probe like Patent Document 1 is possible.

  In the comparative light source module shown in FIG. 52A, in which a plurality of lights parallel to each other are incident on the living body, a detection error occurs when there is an altered portion near the surface of the living body. The “deformed portion” means a portion having special optical characteristics, such as a hair root or colored skin. If there is such an altered portion, in the comparative example, the light from the light source 1 and the light source 2 is incident on different positions of the subject. For example, only the light from the light source 2 passes through the altered portion. To do. When the difference between the light source 1 and the light source 2 is calculated, this altered portion becomes noise.

  On the other hand, in this embodiment, as shown in FIG. 52B, the light from the light source 1 and the light source 2 passes through “substantially the same position” on the skin surface. When the light from one passes through the altered portion, the light from the other also passes through the altered portion. Further, when the light from one of the light source 1 and the light source 2 does not pass through the altered portion, the light from the other does not pass through the altered portion. More specifically, the light from the light source 1 and the light source 2 has the same optical path in the vicinity of the skin surface and passes through different optical paths in the depth direction. That is, although it is insensitive to the difference near the skin surface, the structure is sensitive to the difference near the brain tissue. The resolution is improved by reducing the noise near the skin surface. The meaning of “substantially the same position” allows a deviation of several millimeters as described above.

  In the second embodiment, a transparent gel is dropped on a window member provided in the housing, and a transparent gel is interposed between the window member and the subject surface to prevent air from entering.

  In the conventional light source module, light once emitted into the air propagates from the skin surface into the body. At this time, a refractive index difference occurs between the refractive index 1.0 in air and the refractive index 1.37 of the living body. Reflection and scattering occur due to the difference in refractive index. In addition, since the refractive index in the living body through which light propagates is smaller than in air outside the living body, the propagation angle in the living body (also referred to as the in-vivo propagation angle) is smaller than the incident angle. The refraction of light at the interface can be understood using the Snell equation. This Snell equation can be described only by the refractive index.

  FIG. 53 is a graph showing the refractive index, the relationship between the incident angle at the interface between 1.0 (air: incident side) and 1.37 (biological body: propagation side) and the in vivo propagation angle (light refraction). Has been. As can be seen from FIG. 53, even if the incident angle of light on the living body is 60 degrees, the propagation angle of light in the living body is as small as 40 degrees. For this reason, even if the propagation angle of light in the living body is required to be 60 degrees or more, it is understood that it cannot be realized by the incidence of light from the air. In other words, it is difficult to make a large propagation angle in the living body with the light once released into the air.

  Therefore, in Example 2, the refractive index of the transparent resin that is the material of the window member of the light source module LM is set to a refractive index (for example, 1.5 or more) that is higher than the refractive index of the living body 1.37 (FIG. 54). In this case, the propagation angle of light directly incident on the living body from the light source module LM at an incident angle of 60 degrees exceeds 70 degrees. When considering the design of the light source module LM, reducing the angle as much as possible has an advantage that the light source module LM can be reduced in size.

  In the light source module LM (I type) of the second embodiment, as shown in FIG. 40, the light emitted from the surface emitting laser in the direction parallel to the optical axis of the lens is refracted by the lens and is incident on the optical axis of the lens. It advances in a direction inclined about 20 ° with respect to the window member and enters the window member. This window member has a refractive index of about 1.5. The light that has passed through the lens is refracted when entering the window member, but it is not a large refraction because the incident angle is deep. The light incident on the window member is deflected by the reflecting surface of the prism and travels in a direction inclined about 55 ° with respect to the optical axis of the lens. The 55 ° angle is an angle in a window member having a refractive index of 1.5. As shown in FIG. 54, the propagation angle in a living body (refractive index of 1.37) is about 60 degrees. .

  In order for light to propagate directly from the light source module LM into the simulated living body, it is necessary to remove the air layer that enters the interface between the simulated living body and the light source module LM. In order to remove this air layer, a transparent gel was used here. The transparent gel used here was a glycerin aqueous solution, and the one having good consistency with the simulated living body was selected. In addition, the transparency of the transparent gel is adjusted so that it does not evaporate during the inspection, that is, while the light source module LM is covered, and is adjusted so that it volatilizes or soaks into a simulated living body at an appropriate timing after the inspection is completed. . The optical properties of the transparent gel are transparent near the wavelength of 780 nm, and the refractive index is adjusted to be close to the surface of the pseudo living body. Here, it was blended so as to be about 1.37. With this blending, even if the surface of the simulated living body is uneven, there is no difference in the refractive index of the uneven surface, and there can be no reflection at all. As a result, reflection on the surface of the simulated living body could be almost eliminated. Moreover, even if the interface with the pseudo living body is physically uneven, there is no optical unevenness, so that scattering does not occur. As a result, it can be accurately propagated inside the pseudo living body in an appropriate propagation direction according to the light emission angle from the light source module LM. In general, propagation inside a pseudo-living body causes strong scattering, but the scattering on the skin surface is not small. Thereby, a large anisotropy of light can be secured. By making the anisotropy large, the incident angle of the plurality of lights from the light source module LM to the pseudo living body can be greatly changed, and the incident angles of the plurality of lights to the detection module DM are greatly changed as will be described later. Can do.

  As shown in FIG. 55, the detection module DM includes a flexible board (not shown) on which a housing, an optical element, a light receiving part, and an analog electronic circuit are mounted, wiring connected to the flexible board, and a connector part (not shown). ).

  In the detection module DM, as shown in FIG. 56, the light irradiated from the light source to the subject and propagated through the subject is divided into a plurality of lights and led to a plurality of light receiving units.

  In the conventional technology (see Japanese Patent Application Laid-Open No. 2011-179903), in a DOT using fluorescence, a light receiving unit is arranged corresponding to a plurality of lights emitted from a subject at multiple angles. However, in this arrangement of the light receiving unit, the light incident on the light receiving unit is light having all emission angles from the subject.

  On the other hand, the detection module DM of the present embodiment divides light from “substantially the same position” of the subject and individually detects the light. As described in the previous light source module LM, since it can be designed in the optical simulation, the accuracy of “substantially the same position” does not matter in the order of mm order.

  Hereinafter, the detection module DM will be described in detail. As shown in FIG. 57, the detection module DM includes a black resin casing, a contact member made of an elastic body attached to the tip of the casing, a transparent divided lens housed in the casing, and four light receiving sections. It is comprised including. An aperture (opening) is formed at the tip of the housing and the contact member.

  As the contact member, a black rubber member is used in order to improve the light shielding property. From the aperture of the contact member, the central portion (about φ1 mm) of the split lens protrudes outside the housing by about several hundred μm. Since this portion is in contact with the surface of the living body, Fresnel refraction and scattering are suppressed without optically containing air.

  Further, in the detection module DM, since the stability is further improved by using the above-described transparent gel, the transparent gel is used. The split lens is made of a transparent resin and has a refractive index of about 1.8. The split lens is fixed to the housing.

  The aperture is a circular hole of about 1 mm that penetrates the tip of the casing and the contact member, and has a function of limiting the position of light that propagates through the subject. The light emitted from this position is directed in different directions, the incident position is defined by the aperture, and then the incident light is divided into a plurality of lights by the dividing lens, and the plurality of lights are individually detected. Can do.

  It is realized by this aperture that the light from the subject described above is incident on the light receiving unit from “substantially the same position”.

  The light that has passed through the aperture is refracted in different directions by the split lens depending on the propagation direction of the light, and therefore the incident position on the light receiving unit is different.

  The split lens is a spherical lens having a diameter of about 3 mm and a focal length f of about 3 mm.

  The second embodiment uses a PD array (photodiode array) including four light receiving sections (PD: photodiodes) that are two-dimensionally arranged with the number of divisions of light at the dividing lens being four. In FIG. 57, only two light-receiving units 1 and 2 among the four light-receiving units (PD) are shown.

  Here, the PD array has a square shape with a side length of about 3 mm, and each PD has a square shape with a side length of 1.4 mm. An angle θ2 as shown in FIG. 57 was defined, and the distance between the PD array and the aperture was about 5 mm.

  One side of the lens is flat and only one side has a spherical surface. The plane is in contact with the simulated living body. Since the aperture position deviates from the focus position of the lens, parallel light cannot be produced, but has a function of limiting the light incident on the PD array.

  When a simple optical simulation is performed on this optical system, light of approximately −10 ° <θ2 <50 ° is incident on the light receiving unit 2, and light of approximately −50 ° <θ2 <10 ° is incident on the light receiving unit 1. I found out. That is, the light that propagates through the simulated living body and is emitted from the aperture is divided into a plurality of lights according to the emission angle, and each of the plurality of lights enters one of the four light receiving units.

  In the second embodiment, a spherical lens is used as the split lens, but it is also possible to detect a wider angle by using an aspheric lens. Since this division accuracy and the number of divisions are correlated with the estimation accuracy of the inverse problem described later, the necessary optical system is determined from the desired estimation accuracy. In this embodiment, a spherical lens and a division number of 4 are employed.

  Each PD is electrically wired and connected to an operational amplifier. A semiconductor operational amplifier is used as the amplifier, and a power supply voltage of 5 V is supplied. Since the amount of light detected is very small, the magnification of the operational amplifier is high and a two-stage amplifier configuration is adopted. Multiply about 5 digits in the first stage and about 3 digits in the second stage.

  In the second embodiment, a method for measuring the position of a light absorber existing in a simulated living body (a method for detecting an optical characteristic of a subject) will be described with reference to a flowchart shown in FIG.

  First, the probes (light source module LM and detection module DM) are set (mounted) on the simulated living body (step S1). At this time, a transparent gel is applied between the acrylic water tank and each probe, and the probe is carefully set to a position determined by the fixing member while checking each probe so that bubbles do not enter the transparent gel. .

  The probe has 16 light source modules LM and 8 detection modules DM in total, and the light source modules LM and the detection modules DM are alternately arranged in a lattice pattern at an equal pitch (see FIG. 39). The pitch of the lattice (interval between lattice points) is 30 mm, and the interval between the light source module LM and the detection module DM is 30 mm.

  In this state, the ch of any one light source module LM is caused to emit light (step S2). Light emission is performed for each group (4ch), and the current value is determined so that the light emission intensity is about 4 mW. The light emission time is about 10 msec. During this period, the detection values in all PDs are read and the data of several points detected at 1 msec intervals are averaged (step S3). Then, the averaged numerical value is stored in the recording unit (step S4). Similarly, the next group repeats light emission, measurement, and data storage for 10 msec (steps S5, S6, S2 to S4). In addition, in one light source module LM, the light emission of 4ch of the surface emitting laser array chip with an oscillation wavelength of 780 nm and the light emission of 4ch of the surface emitting laser array chip with an oscillation wavelength of 900 nm are sequentially performed in the same manner.

  However, in the following data processing, the two wavelengths are handled in substantially the same manner, and the measurement at the same position is simply performed twice each. When detecting a change in the original blood flow, the difference between the two wavelengths is used to detect oxyhemoglobin and reduced hemoglobin separately. In this embodiment, two surface emitting lasers having different oscillation wavelengths are used. By measuring once using the array chip, noise due to chip variation can be reduced.

  When the light emission and measurement of all the groups of one light source module LM are completed, the next light source module LM emits light (steps S7, S8, S2 to S6). Similarly, the light emission is sequentially performed for each group (4ch). When the light emission and measurement by all the light source modules LM are completed, the light absorber is set (steps S9 and S10). The light absorber is set using an optical stage so that the position can be accurately realized with good reproducibility. With this light absorber set, the numerical value of the PD is recorded again from the ch emission (steps S2 to S9).

  The stored data is the light absorber, and the data without is the following r (s, i, n) (i = 1, 2, 3... M, n = 1, 2, 3... K). ), R (0, i, n) (i = 1, 2, 3... M, n = 1, 2, 3... K). i is a number assigned to each detection module DM. n is a number assigned to each group. Next, each difference Δr (i, n) is calculated.

  The method of calculating the position of the light absorber (optical property of the pseudo living body) from the measurement result obtained by the position measurement method described above is based on the measurement result obtained by the measurement method based on the flowchart of FIG. Since this is the same as the method for calculating the optical characteristics of the simulated living body, the description thereof is omitted.

  As a result, an estimation result as shown in FIG. 59 can be derived. In FIG. 59, as a comparative example, only the central group (see FIG. 41) of the five groups of the surface emitting laser array chip is caused to emit light, and only the detection value of one PD among the four PDs of the PD array is obtained. The results detected using this are also shown. Other than that, numerical processing is performed in the same manner as in this embodiment. This comparative example has substantially the same configuration as a conventional NIRS (DOT) apparatus.

  In the present embodiment, it is possible to detect the position and depth of the light absorber by the Bayesian estimation. In the result shown in FIG. 59, a circle (circle) is displayed when the position of the light absorber can be detected. In the present embodiment, as the distance in the depth direction of the light absorber (here, the Z-axis direction in FIG. 25) increases, the distance from the light source module LM increases and the amount of light that can propagate decreases. For this reason, the detection becomes more difficult as the depth of the position of the light absorber increases. In this embodiment, detection was possible up to about 6 mm. The comparative example is a general NIRS (DOT) apparatus, and the depth direction cannot be detected even when Bayesian estimation is used. In order to detect the three-dimensional position of the light absorber including the depth with DOT with high accuracy, a high-density probe arrangement is generally required. In this embodiment, this can be realized with a low-density probe arrangement. .

  The optical sensor 10 of the present embodiment described above (Examples 1 and 2) includes an irradiation system including a plurality of light source modules LM (light irradiators) that irradiates light to a measurement target (subject), and the irradiation system. And a detection system for detecting the light that has been irradiated from and propagated through the measurement object. Each of the plurality of light source modules LM irradiates a plurality of non-parallel light beams to substantially the same position of the measurement target.

  In this case, a plurality of non-parallel light beams irradiated to substantially the same position of the measurement target (scattering body) have different incident angles on the measurement target and follow different propagation paths (see FIG. 60).

  As a result, the amount of information obtained with respect to the inside of the measurement object increases, and high resolution can be achieved. Further, by increasing the resolution, it is possible to reduce the probe density (the number of probes per unit area) for the same required resolution, and to improve the mountability.

  As a result, the optical sensor 10 can obtain high resolution without deteriorating the attachment property to the measurement target.

  Note that the plurality of light beams incident on substantially the same position of the measurement target are non-parallel means that the plurality of light beams form an angle. That is, the existence of angles formed by a plurality of light beams makes it possible to vary the propagation paths of the plurality of light beams in the subject. On the other hand, if a plurality of light beams incident on substantially the same position of the measurement target are parallel to each other (for example, parallel to the surface normal of the subject), the propagation paths of the plurality of light beams in the measurement target are the same. Become.

  In addition, the light source module LM of the present embodiment is disposed on a surface emitting laser array having a plurality of surface emitting lasers (light emitting units) and an optical path of a plurality of lights from the plurality of surface emitting lasers. Is a plurality of non-parallel convex lenses, and the distance between the principal point of the convex lenses and the surface emitting laser array does not match the focal length of the convex lenses.

  In this case, it is possible to prevent the return light from being focused on the surface emitting laser, and to prevent fluctuations in the output of the surface emitting laser. As a result, the amount of light emitted from the surface emitting laser can be stabilized, the detection accuracy of the optical sensor 10 can be improved, and the resolution of NIRS can be improved.

  On the other hand, when the surface emitting laser array is located at the focal position of the convex lens, the light reflected from the external reflecting surface is condensed on the surface emitting laser by the convex lens, and the laser oscillation becomes unstable. This is a phenomenon called return light or a self-mixing phenomenon. When a surface emitting laser array is used as a light source of an optical sensor, if this phenomenon occurs, the amount of emitted light becomes unstable and becomes a problem (detailed explanation is JP, 2011-114228, and JP 2012-132740).

  Further, the refractive index is filled with a transparent resin equivalent to the convex lens between the convex lens and the surface emitting laser array.

  In this case, since the refractive index does not change at the interface between the convex lens and the surface emitting laser array, the return light can be suppressed. As a result, the amount of light emitted from the surface emitting laser array can be stabilized, and the resolution of NIRS can be improved.

  Further, the detection system includes a plurality of detection modules DM including a plurality of light receiving units (PD) that individually receive a plurality of lights irradiated from the light source module LM to the measurement object and propagated through the measurement object.

  In this case, two pieces of information on two different propagation paths in the measurement target can be obtained individually.

  Further, the detection module DM is disposed between the measurement target and the plurality of light receiving units (PD), and the contact member and the housing provided with apertures that allow each of the plurality of lights propagated through the measurement target to pass therethrough. have.

  In this case, light can be taken into the housing from substantially the same position of the measurement target, that is, only light with a certain angle of incidence can be made incident from the measurement target into the housing, and light can be incident on a plurality of light receiving units. Can be made easier.

  The detection module DM has a split lens (light receiving lens) that individually guides a part of the plurality of light beams that have passed through the aperture to the plurality of light receiving units.

  In this case, a part of each of the plurality of lights that have passed through the aperture can be incident on the plurality of light receiving units individually with a stable light amount. That is, the detection module DM can individually detect a plurality of lights that have been irradiated from the light source module LM to the measurement target and propagated through the measurement target.

  Moreover, since the light source module LM has a window member made of a material (transparent resin) that is in contact with the measurement target and has a higher refractive index than the measurement target, the light source module LM is within the measurement target with respect to the incident angle to the measurement target. The propagation angle (refraction angle) can be increased. As a result, the propagation angle becomes large even at the same incident angle as compared with the case where light is incident on the measurement object from the air. Therefore, the difference in the propagation angle of the two lights in the measurement object becomes larger than the difference in the incident angles of the two lights incident at substantially the same position of the measurement object at different incidence angles, and the propagation path is greatly different. Can be made. As a result, further higher resolution can be achieved.

  The light source module LM includes a plurality of two-dimensionally arranged surface emitting lasers and an irradiation lens (lens) arranged on an optical path of light from the plurality of surface emitting lasers.

  In this case, the traveling direction of light from the plurality of surface emitting lasers can be changed to a desired direction (the direction in which the corresponding prism is disposed).

  The light source module LM includes a prism (reflecting member) that is disposed on the optical path of light through the irradiation lens and reflects the light in a predetermined direction.

  In this case, the traveling direction of the light from the irradiation lens can be further changed to a desired direction. That is, the incident angle on the measurement target can be set to a desired angle.

  As described above, the optical sensor 10 is an optical sensor that can achieve high resolution by effectively using light propagation anisotropy with a simple configuration, and is expected to be used in various fields such as DOT. The

  Further, the optical inspection apparatus 100 includes an optical sensor 10 and a control unit (optical characteristic calculation unit) that calculates an optical characteristic of a measurement target based on a detection result of the optical sensor 10.

  In this case, since the detection accuracy of the optical sensor 10 is high, the optical characteristics of the measurement target can be calculated with high accuracy.

  Further, the optical sensor 10 of the present embodiment (Examples 1 and 2) is irradiated with an irradiation system including a plurality of light source modules LM (light irradiators) that irradiate light to a measurement target (for example, a living body), and the irradiation system. The light source module LM can irradiate a plurality of lights having different wavelengths to substantially the same position of the measurement target.

  In this case, the information within the measurement target can be measured with high accuracy.

  Specifically, even in the NIRS device that performs inverse problem estimation, it is possible to measure the cerebral blood flow position with high positional accuracy.

  The light source module LM (type III) emits two lights having different wavelengths individually (the wavelengths of the emitted lights are different from each other) and two lights having different wavelengths from the two ch. Including two lenses 1 and 2 individually arranged on the optical path, and a prism commonly arranged on the optical paths of the two lights having different wavelengths via the two lenses, and the wavelength via the prism The optical paths of two lights having different values substantially coincide. Note that “the optical paths substantially coincide with each other” means that the angle formed by the optical paths of any two lights among a plurality of lights having different wavelengths via the prism is 10 ° or less.

  In this case, it is possible to irradiate the same position of the measurement target with two lights having different wavelengths with a simple configuration.

  In the LM (type III), the prism has reflection surfaces (total reflection surfaces R1 and R2) that reflect two lights having different wavelengths via the two lenses 1 and 2, and the two lenses 1 and 2 are used. The optical paths of two lights having different wavelengths from the reflecting surface to the reflecting surface are non-parallel.

  In this case, the configuration can be simplified and the cost can be reduced as compared with a configuration in which two light beams having different wavelengths are individually reflected by two reflection surfaces.

  Further, in LM (type III), the number of parts to be mounted is reduced and the mounting cost can be reduced as compared with the case of using a plurality of optical elements instead of the prism.

  In LM (type III), the optical paths of two light beams having different wavelengths from the two lenses 1 and 2 to the reflecting surface of the prism are closer to the reflecting surface of the prism. Can be reflected toward the measurement object with the optical path close to each other.

  In addition, in LM (III type), two lights having different wavelengths reflected by the reflecting surface of the prism intersect in the vicinity of the emission end of LM (III type), so that the two lights are surely placed at the same position on the measurement target. Can be made incident.

  In LM (type III), each of the two channels has a plurality of light emitting units arranged in an array, and the positional relationship between the plurality of light emitting units and the optical axes of the corresponding lenses is between the plurality of light sources. Since they are different, two lights having different wavelengths emitted from the two light emitting units in the correspondence relationship between the two channels can be emitted from the lenses 1 and 2 in a non-parallel state.

  Further, in LM (III type), since the center of each channel (array center) is at a position off the optical axis of the corresponding lens, when two light emitting units having a correspondence relationship between the two channels are paired In addition, the positional relationship with respect to the optical axis of all pairs of lenses can be varied.

  Further, the space between the two lenses 1 and 2 and the two channels may be filled with a transparent resin having a refractive index equivalent to that of the lenses 1 and 2 (see FIG. 47).

  The lenses 1 and 2 may have a shape that is convex toward the corresponding ch side (see FIG. 49).

  Further, the common optical element of LM (II type) and LM (III type) is not limited to a prism, and may be any member having at least one reflecting surface that reflects a plurality of lights having different wavelengths.

  The optical inspection method according to the first embodiment includes an irradiation system that irradiates a measurement target with light and includes a plurality of light source modules LM, and an amount of light that is irradiated from the irradiation system to the measurement target and propagates through the measurement target. An optical inspection method for inspecting a subject using an optical sensor 10 having a detection system including a plurality of detection modules DM for detection, and a detected light amount distribution (light amount distribution) for each of a plurality of optical models simulating the subject And a second detected light amount distribution that is a detected light amount distribution (light amount distribution) of the subject using the optical sensor 10. And comparing the first and second detected light quantity distributions and selecting an optical model suitable for the subject from a plurality of optical models.

  In this case, since the detected light amount distribution of the subject can be evaluated with reference to the detected light amount distribution of the optical model suitable for the subject, an examination with little error (for example, acquisition of information in the subject) can be performed.

  As a result, inspection accuracy can be improved.

  In addition, the optical inspection method of the first embodiment further includes a step of acquiring information in the subject using the first detected light amount distribution and the second detected light amount distribution of the selected optical model. Information can be acquired with high accuracy.

  Further, in the step of acquiring the information, since the position of the light absorber in the subject is estimated, the accuracy of estimating the position of the light absorber (here, the accuracy of the inverse problem estimation) can be improved.

  Further, since the simulation is a Monte Carlo simulation, the accuracy of inverse problem estimation can be further improved.

  Each optical model includes a virtual layer (for example, a hair layer) that can be interposed between the light source module LM and the detection module DM (generally referred to as a probe) and the surface of the subject. It is possible to suppress an error in the detected light amount due to poor contact with the subject surface.

  In addition, prior to the selecting step, the method further includes a step of correcting the first detected light quantity distribution, so that the accuracy of selecting the optical model can be improved.

  In the above simulation, the plurality of light source modules LM and the plurality of detection modules DM are virtually mounted on the optical model so that at least two detection modules DM are adjacent to each light source module LM, and the first detected light amount distribution. In the step of correcting the light amount, the amount of light detected by at least two detection modules DM adjacent to the light source module LM of the light that has been transmitted from the light source module LM to the optical model in the simulation and propagated through the optical model is compared. Based on the result, it is possible to correct at least one detected light amount among the detected light amounts of at least two photodetectors.

  In this case, in the simulation, it is possible to suppress an error in the amount of light detected by the plurality of detection modules DM of the light that has been applied to the optical model from each light source module LM and propagated through the optical model. That is, errors due to poor contact between the detection module DM and the measurement target surface in the simulation can be suppressed.

  In the above simulation, the plurality of light source modules LM and the plurality of detection modules DM are virtually mounted on the optical model so that at least two light source modules LM are adjacent to each detection module DM, and the first detected light quantity distribution. In the step of correcting the detected light amount of the detection module DM of the light irradiated to the optical model from the at least two light source modules LM adjacent to each detection module DM and propagated in the optical model in the simulation, and the comparison Based on the result, it is possible to correct the amount of light detected by the detection module DM of light from at least one light irradiator out of at least two light source modules LM.

  In this case, in the simulation, it is possible to suppress an error in the amount of light detected by each of the detection modules DM of the plurality of lights that are irradiated to the optical model from the plurality of light source modules LM and propagated through the optical model. In other words, errors due to poor contact between the light source module LM and the optical model surface in the simulation can be suppressed.

  In the simulation, the plurality of light source modules LM and the plurality of detection modules DM are virtually connected to the optical model so that the light source module LM and the detection module DM are adjacent to each other in both the first and second directions intersecting each other. The two light source modules LM that are mounted on the optical model and are adjacent to each other on the optical model are first and second light source modules LM, and two detections that are adjacent to each other and adjacent to the first and second light source modules LM Assuming that the module DM is the first and second detection modules, in the step of correcting the first detected light amount distribution, in the simulation, the optical model irradiated with light from the first light source module LM and propagated through the optical model Detection light amounts 1 and 2 of the first and second detection modules DM, and a second light source module The detected light amounts 3 and 4 of the first and second detection modules DM of the light irradiated from M to the optical model and propagated in the optical model are compared, and the detected light amounts 1, 2, 3, 4 are compared based on the comparison result. At least one of the above can be corrected.

  In this case, an error in the detected light amount due to the difference in the installation state of the four adjacent probes in the simulation can be suppressed.

  The optical inspection apparatus 100 according to the first embodiment is an optical inspection apparatus for inspecting a subject. The irradiation system includes a plurality of light source modules LM that irradiates a measurement target with light, and the measurement is performed from the irradiation system. An optical sensor 10 including a detection system including a plurality of detection modules DM that detects the amount of light that has been irradiated on the target and propagated through the measurement target, and a control unit that controls the irradiation system and acquires the detected light amount of the detection system A first control light amount distribution that is a detected light amount distribution of the subject using the optical sensor 10, and the control system is obtained by simulation using the optical sensor 10 virtually. The second detected light amount distribution, which is the detected light amount distribution for each of a plurality of optical models simulating the subject, is compared with the first detected light amount distribution, and an optical model suitable for the subject is selected from the plurality of optical models. .

  In this case, since the detected light amount distribution of the subject can be evaluated with reference to the detected light amount distribution of the optical model suitable for the subject, an examination with little error (for example, acquisition of information in the subject) can be performed.

  As a result, inspection accuracy can be improved.

  Further, since the control system acquires information in the subject using the second detected light amount distribution and the first detected light amount distribution of the selected optical model, the information in the subject can be acquired with high accuracy.

  In addition, since the control system estimates the position of the light absorber in the subject, it is possible to improve the accuracy of estimating the position of the light absorber (in this case, the accuracy of inverse problem estimation).

  In addition, the control system uses the detected light amount distribution (second detected light amount distribution) of at least one optical model including the selected optical model among the plurality of optical models (first detection light distribution). Since the light amount distribution) is corrected, the accuracy of selecting the optical model can be improved.

  As a result, in the first embodiment, it is possible to reduce an error at the contact portion by causing a plurality of lights to enter the same position of the measurement target, and internal information (for example, cerebral blood flow) of the measurement target can be reduced. It can be detected accurately. In addition, the position where the plurality of lights are irradiated is the same position as the measurement target, and for example, the number of optical models simulating contact failure can be reduced, and the selection accuracy is improved. Since selection errors are suppressed, highly accurate internal information (for example, cerebral blood flow) can be detected.

  The optical inspection method according to the first embodiment is “an optical inspection method for inspecting an object using an optical sensor, and a first detection light amount distribution for each of a plurality of optical models simulating the object. A step of obtaining a light amount distribution by simulation using the optical sensor 10 virtually, a step of obtaining a second detected light amount distribution which is a detected light amount distribution of the subject using the optical sensor 10, and a first and a second detection An optical inspection method including a step of comparing light quantity distributions and selecting an optical model suitable for a subject from a plurality of optical models ”.

<< Second Embodiment >>
Next, a second embodiment of the present invention will be described. In the present embodiment, a method for adapting the probe described in the first embodiment to an actual human body will be described. Here, the subject is changed from the phantom (water tank containing cloudy water) in the above embodiment to the head of the human body, and the light absorber is used as the blood flow in the brain.

  The purpose of this embodiment is to accurately estimate the distribution of blood flow in the brain. In general, a subject (subject) is measured, a shape is modeled based on the data, and a Monte Carlo simulation is performed. The head shape of the subject is measured using nuclear magnetic resonance imaging (hereinafter abbreviated as MRI (Magnetic Resonance Imaging)). The shape of the four parts of the scalp, skull, cerebrospinal fluid, and cerebral cortex is measured from the image.

  However, in the present embodiment, this three-dimensional data is necessary for high-precision detection, but a plurality of standard-shaped brain models (optical models) are prepared and appropriately selected. It is possible to substitute it. Each part has a general scattering coefficient, anisotropy, and absorption coefficient, and the numerical values are used. The probe is fixed to the head accurately with a fixing jig, and the installed position is also measured accurately. An optical simulation is performed using each accurate shape, arrangement, and numerical value of each part. Thus, if measurement can be performed with high accuracy without an MRI image, there is an advantage that the inspection cost can be reduced.

  In the present embodiment, the measurement result is corrected according to the procedure shown in the flowchart of FIG.

  Also in the present embodiment, an optical simulation is performed on a plurality of optical models as in the first embodiment (step S51). Again, the above-described Monte Carlo simulation is performed. Four light source modules LM and four detection modules DM are fixed to the forehead of the head via a holder. The light source module LM has 5 directions and the detection module has 4 directions. The conditions such as the angle are the same as above. The optical simulation is performed for all probe pairs (light source module LM / detection module DM pair) under all propagation angle / detection angle conditions.

  The Monte Carlo simulation is performed on the eight optical models shown in FIGS. At this time, the optical constant shown in FIG. 28 is used. However, since the hair here is generally about 100 um thick, the absorption coefficient is adjusted in accordance with a 1 mm voxel for this simulation. In addition, a plurality of optical models are made so that the position of the hair also differs depending on the position of the hair, such as whether it is a grid directly below or shifted by one with respect to the light source module LM, the detection module DM, and the like. FIG. 29 shows details of eight optical models. Seven optical models 2 to 8 are shown with the optical model 1 as a standard. This simulation is not limited to this, and it is desirable to create various models.

  By performing the simulation, it is also possible to create a light amount distribution as shown in the right diagram of FIG. This indicates the detected light quantity of light incident from the optical model into the detection module DM in the incident direction A when the incident direction from the light source module LM to the optical model is 1, and this is normalized to 1. An example of the light amount distribution shown in the right diagram of FIG. 32 is obtained by detecting each matrix with the normalized light amount as a reference. However, although the 3 × 3 matrix is shown in the right side of FIG. 32, in this embodiment, the detection module DM is 4 probes in 4 directions, the light source module LM is 4 probes in 5 directions, and the matrix is 16 ×. There are 20 matrices. This light quantity distribution can be obtained in the eight optical models 1 to 8 shown in FIG. 29, all of which are different from the result of the optical simulation. By comparing the light quantity distribution of each optical model with the light quantity distribution obtained by measurement on the subject, that is, actual measurement (step S52), the optical model most suitable for the subject is selected. As a selection method, a method having the best consistency of the light amount distribution is selected here. At this time, calibration is performed before actual measurement. The calibration is performed using a black box in which a geracon resin is arranged and provided with a guide that can arrange each probe at an appropriate position. This calibration allows reproducibility with high accuracy.

  The measurement (step S52) for the subject is preferably performed for 20 seconds or longer. The graph shown in FIG. 62 shows the detection result with the probe installed (mounted) on the frontal lobe (forehead). The vertical axis represents the voltage value after detection by a light amount photodiode and current-voltage conversion. The horizontal axis indicates time, and during this time, the language fluency test is conducted from 1.5 minutes to 3.5 minutes after the start of measurement.

  During this language fluency test, brain activity in the frontal lobe is active and active. In this activated state, cerebral blood flow is generated, and the amount of light in this section is reduced. That is, the amount of transmitted light is reduced by the cerebral blood flow generated in the light propagation path, and the amount of detected light is reduced. At this time, the amount of light in the forehead portion has changed from 9 mV to 14 mV. Further, when attention is paid after 3.5 minutes at rest, it can be seen that the amount of light vibrates in the range from 12.7 mV to 13.5 mV.

  FIG. 63 shows an enlarged view of this portion. The horizontal axis is converted to seconds. The period of this vibration is about 20 seconds. It is known that such vibration generally measures cerebral blood flow like pulsation in a resting state (resting mode) of brain activity. In order to correct the fluctuation of the resting mode, it is necessary to measure for 20 seconds or more. Measurement accuracy improves by measuring for 20 seconds.

  In the present embodiment, a value having the largest light amount within the 20 seconds is employed. The largest amount of light can be considered as having almost no cerebral blood flow. Since the previous optical model assumes this state without cerebral blood flow, this state is closest to the optical model. By adopting a numerical value with the largest amount of light within 20 seconds, consistency with the optical model is enhanced and high-precision correction is possible.

  Next, selection of an optical model (step S54) will be described. As a selection method, a matrix value having the smallest error is selected. Specifically, the difference between the matrix values of (1, A) at the time of actual measurement and (1, A) at the time of virtual measurement is taken. Next, the difference between the matrix values of (2, B) at the time of actual measurement and (2, B) at the time of virtual measurement is taken. This is repeated sequentially, and the sum of the squares of the numerical differences of the corresponding matrix elements at the time of actual measurement and virtual measurement is taken, and the optical model with the smallest value is optimized.

  In the present embodiment, when selecting a model, information having a large correction effect is selected and its numerical value is input (step S53). “Information with a large correction effect” (hereinafter also referred to as “input information”) is, for example, the sex, age, height, weight, head circumference, hair thickness, hair density, skin color of the subject. Etc. By entering this condition, the model selection from the eight optical models 1 to 8 shown in FIG. 29 is made highly accurate.

  For example, FIG. 64 shows an example in which the age and the thickness of the cerebral spinal fluid layer (bone marrow fluid layer) are correlated. By inputting the age, the thickness of the cerebrospinal fluid layer can be predicted to some extent. In this embodiment, for example, in the case of 50 years old, it can be seen from the approximate straight line shown in the graph that the thickness of the cerebrospinal fluid layer is about 4 mm. Based on this, in the model, the cerebrospinal fluid layer is penalized with a 4 mm pattern and a 5 mm pattern to improve the selection accuracy. Specifically, at the age of 50, the cerebrospinal fluid layer thickness is “1” for 4 mm models, “1.2” for 5 mm models, “1.4” for 6 mm models, and 3 mm models. Set the value “1.2”. This set value is added to a numerical value when the error between the light amount distribution of the subject by actual measurement and the light amount distribution of the optical model by simulation described in the first embodiment is selected by the least square method. Thereby, in the case of 50 years old, it becomes easy to select a model with a cerebrospinal fluid thickness of 4 mm.

  The above penalty is applied to several optical models.

  Next, an example of a method for correcting the measurement result with the value of the outer circumference of the head will be described. Before carrying out this measurement, the head circumference is measured using a measure or the like, and the numerical value is input. From this outer periphery, the head is substantially circular, and the radius of curvature is calculated from the outer periphery of the head. For example, when the head has an outer periphery of 57 cm, the radius of curvature is about 9 cm.

  There is a method of adding a penalty only with this radius of curvature, but in this embodiment, a method of calculating the shape of the skull, skin, and bone marrow fluid from this outer periphery is adopted.

  In general, a person with a large head periphery tends to have a thick skull. This simply means that a person with a large body (a person with a large outer periphery of the head) has a thickened bone in order to keep the body. In other words, it is considered that there is a correlation between the radius of curvature and the thickness of the skull.

  In this embodiment, specifically, when the radius of curvature is 8 cm, the thickness of the skull is 5 mm, and when the radius of curvature is 10 cm, the linear transformation is performed so that the thickness of the skull is 6 mm. An optical model was adopted.

  For the four layers (four layers obtained by removing the hair model layer from the five-layer model), the data shown in FIG. FIG. 65 uses the fact that when the distance from the skin surface to the brain surface is determined from about 30 MRI images, there is a correlation with the thickness of the skin, the thickness of the skull, the thickness of the cerebrospinal fluid, and the like. ing.

  From the above, a model that is considered optimal from the outer periphery of the head and a model that deviates therefrom can be considered. This optimal model was treated in the same way as the penalty imposed on the cerebrospinal fluid thickness model by age. Thus, it becomes possible to improve the selection accuracy of the optimum model by correlating the input information with the model. By using the input information, correction with high accuracy is possible. By balancing the correction of bone marrow fluid thickness according to the previous age and the correction of this method, correction based on age and body size has been achieved.

  After selecting the optical model, the detection value (measurement result) is corrected (step S55). FIG. 66 shows a correction image of the detected value. In FIG. 66, the vertical axis is the estimated amount of cerebral blood flow, and the horizontal axis is the time axis. This indicates, for example, a detection value by 1ch of the detection module DM installed in the forehead. That is, this detection value is a detection value in a state where 1 ch light is emitted from the nearest channel of the detection module DM in the light source (surface emitting laser array) of the light source module LM.

  “Before correction” in FIG. 66 indicates the amount of light detected by the detection module DM. The fluctuation in the vertical axis direction has almost the same meaning as in FIG. 62 described above, but in order to make the vertical axis the same as the amount of cerebral blood flow, On the other hand, the vertical axis is inverted. Further, the maximum light quantity value is corrected to 0 in the initial 20 seconds. The time zone showing the maximum value of this graph is the time zone shown when a large amount of cerebral blood flow occurs in the forehead. This maximum value is determined by the optical characteristics of the subject. Here, a correction coefficient α is defined, and a process of simply applying a change in the amount of light by this α is performed. As a result, as shown in FIG. 66, the shape of the plot is similar and the time change is the same, but its size is corrected.

  Since an optical model suitable for the subject is selected by the method described above, a correction coefficient is determined for each optical model.

  The correction coefficient determines a certain standard and makes it possible to make a relative evaluation of the cerebral blood flow in the light of the standard.

  Also in this embodiment, the optical model 1 shown in FIG. 17 is set as the “standard structure”. On the other hand, assume that the selected model is, for example, the case of the optical model 2 shown in FIG. The optical model 2 is set when the hair is located directly under the LM and DM. In addition, you may add separately the optical model set when the hair is located only under one of the probe pair (LM and DM).

  In the optical model 2, the amount of light actually obtained is small in the first place because the irradiation light is absorbed by the hair. Therefore, it is expected that the change in the amount of light when cerebral blood flow occurs is small.

  Such a model can perform optical simulation assuming cerebral blood flow as shown in FIG. This optical simulation assuming cerebral blood flow is performed for all optical models 1-8. At this time, it is possible to calculate how much the value detected by the detection module DM changes with respect to the “standard structure”. By determining this change as a correction value and selecting an optical model, the correction value can be determined.

  By performing the correction, a relative evaluation of the cerebral blood flow with respect to the “standard structure” can be performed. This relative evaluation can compare the amount of cerebral blood flow for any subject. This is shown in FIG. 68 as a simple example. For each optical model, the correction coefficient is shown based on 1. For example, when hair is mixed as in the optical model 2, the correction coefficient is set larger than 1. Conversely, in the case of a person with white skin like the optical model 3, the correction coefficient is made smaller than 1.

  Hereinafter, a method for measuring blood flow in the brain will be described with reference to a flowchart shown in FIG. First, the subject is allowed to rest (step T31), and the probe (detection module DM and light source module LM) is set on the head (step T32). At this time, it is set (installed) carefully using a fixing member while confirming each probe so that hair or the like is not pinched between the probe and the scalp. In this state, ch is emitted (step T33). Light emission (pulse light emission) is performed for each group, and the current value is determined so that the intensity is about 4 mW. The light emission time is several msec, during which the detection values of all PDs are read and averaged (step T34). The averaged numerical value is stored in the recording medium (step T35).

  Similarly, the next group repeats light emission, measurement, and data storage for several milliseconds (steps T36, T37, T33 to T35). When the light emission and measurement of all the light source modules LM are completed, the subject is asked to perform a task (steps T38 to T41). Here, it was a general language fluency task. The language fluency problem is described in detail in Japanese Patent Application Laid-Open No. 2012-080975.

  Below, the case where this technique is applied about an actual optical topography inspection is described. Due to the revision of medical fees in April 2014, “differential diagnosis assistance for depression using optical topography test” has been covered by insurance.

  As shown in FIG. 70, even if the cerebral blood flow during a task (such as a language fluency test) seems to be large before correction, the estimated value of cerebral blood flow can be obtained by correcting the “standard structure”. May be smaller.

  This depends on what model is selected. For example, when the hair in the case of FIG. 18 is present in the vicinity of the detection module, when the skin color is white as in FIG. 19, or when the bone marrow fluid layer is thin as in FIG. In the case of a younger person, such a correction is applied. If the estimated value of cerebral blood flow does not reach a certain threshold, there is a possibility of depression.

  On the other hand, for example, when the skin color is black as in the case of FIG. 20 or when the body is large and the skull is thick as in FIG. However, by correcting with the “standard structure”, there is a possibility that it is determined that the person is healthy by exceeding the threshold. That is, it can be expected that the accuracy of depression diagnosis is improved by performing the above correction (see FIG. 71).

  When the subject performs a task (for example, a language fluency task), the brain is activated, and cerebral blood flow is generated only at the location where the activity has occurred. The bloodstream contains oxyhemoglobin and reduced hemoglobin, and light absorption occurs by the bloodstream. In the present embodiment, the amount of cerebral blood flow at each location is simply used as an index to determine the presence or absence of a disease as a comparison with the “standard structure”. However, when determining a disease, there is also a demand for knowing in detail how much cerebral blood flow occurs in which part and the position of the cerebral blood flow.

  The optical inspection method of the second embodiment described above irradiates the measurement target with light, includes an irradiation system including a plurality of light source modules LM, and the amount of light that is irradiated from the irradiation system to the measurement target and propagates through the measurement target. Is an optical inspection method for inspecting a subject using an optical sensor 10 including a detection system including a plurality of detection modules DM, and a detected light amount distribution (light amount distribution) for each of a plurality of optical models simulating the subject. And a second detected light amount distribution that is a detected light amount distribution (light amount distribution) of the subject using the optical sensor 10. And a step of comparing the first and second detected light quantity distributions and selecting an optical model suitable for the subject from the plurality of optical models, wherein the subject is selected from the plurality of optical models. Further comprising the step of correcting the first detected light intensity distributions second detection light amount distribution with the at least one optical model including an optical model (at least optical model 1) was.

  In this case, the second detected light amount distribution reflecting information (optical characteristics) in the subject can be corrected with high accuracy.

  Further, in the step of correcting the second detected light quantity distribution, a correction coefficient α is calculated from the first detected light quantity distribution of the at least one optical model, and the second detected light quantity distribution is corrected using the correction coefficient α. Therefore, the second detected light amount distribution can be corrected by a simple method.

  Further, in the step of correcting the second detected light amount distribution, at least one information among the sex, age, height, weight, head circumference, hair thickness, hair density, and skin color of the subject is used. In this case, the second detected light amount distribution can be corrected with higher accuracy.

  Further, in the step of obtaining the second detected light amount distribution, when the detection is performed for 20 seconds or more and the second detected light amount distribution is obtained using the maximum value of the detected light amount, the second detected light amount distribution is accurately determined. You can ask well.

<< Third Embodiment >>
Next, a third embodiment of the present invention will be described. In the third embodiment, the light source module LM and the detection module DM similar to those in the first embodiment are used for the probe, and the arrangement thereof is elaborated. Except for the arrangement of the probes, the second embodiment is the same as the first embodiment, and the description thereof is omitted here.

  Incidentally, in Example 2 of the first embodiment, as shown in FIG. 39, the two detection modules DM and the two light source modules LM are arranged so as to be positioned at the apex of a substantially square. However, in this arrangement, the light path between the light source module LM and the detection module DM becomes long at the point indicated by x in FIG. For this reason, a sufficient amount of light cannot be obtained by the detection module DM, and noise at this point may be large and the detection accuracy may be reduced.

  Accordingly, the inventors have intensively studied the probe arrangement and found that the arrangement shown in FIG. 72 is optimal. 72, in the plurality of light source modules LM and the plurality of detection modules DM, two of the light source module LM and the detection module DM are individually positioned at two vertices of an equilateral triangle with respect to the subject, and the other 1 Are arranged at one remaining vertex of the equilateral triangle.

  Here, as a simple example, a place where the distance between the light source module LM and the detection module DM is the longest will be considered. However, the interval (pitch) between the detection module DM and the light source module LM is assumed to be a. In the position of x in FIG. 39, the distance of the broken line is √2a (about 1.414a). On the other hand, in the position of x in FIG. 72, the distance of the broken line is (1 + √3) a / 2 (about 1.366a) <√2a. That is, comparing the probe arrangement of FIG. 39 and FIG. 72 at the longest distance, it can be seen that the probe arrangement of FIG. 72 is shorter and preferable.

  As a result of estimating the inverse problem with this arrangement in the same manner as in the first embodiment, it was found that the detectable area was expanded by the probe arrangement of this embodiment.

<< 4th Embodiment >>
Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, the arrangement of the plurality of light source modules LM and the plurality of detection modules DM shown in the first embodiment is used, and the arrangement of the ch of the light source module LM and the arrangement of the PD of the detection module DM are elaborated. ing. Except for the arrangement of ch and PD, the second embodiment is the same as the first embodiment, and the description thereof is omitted here.

  In Example 2 of the first embodiment, as shown in FIG. 39, in the plurality of light source modules LM and the plurality of detection modules DM, the light source module LM and the detection module DM are orthogonal to each other with respect to the subject. They are arranged adjacent to each other in both the X direction and the Y direction.

  However, as described above, in this arrangement, the light path between the light source module LM and the detection module DM becomes long at the point indicated by x. For this reason, a sufficient amount of light cannot be obtained by the detection module DM, noise at this point increases, and the detection accuracy may be reduced.

  In the comparative example shown in FIG. 73, the plurality of light source modules and the plurality of detection modules are arranged so that the light source module and the detection module are adjacent to each other in the X direction and the Y direction perpendicular to each other. In addition, both the emission direction and the detection direction (light incident direction on the light receiving unit) are parallel to the X direction or the Y direction. Since the lens installed in the vicinity of the surface emitting laser has point-symmetric optical characteristics, the emission direction is determined by the position of the surface emitting laser and the group position. The detection direction is also determined by the division layout of the PD array because the lens has point-symmetric optical characteristics.

  Therefore, when the surface emitting laser array chip is arranged as shown in FIG. 74A, the emission direction is inclined with respect to the X direction and the Y direction in plan view (viewed from the + Z direction). This is because the center position of each group is inclined with respect to the lens center. Similarly, in the detection module DM, the center of the lens is arranged at the center of the four-divided PD array array chip (photodiode array chip), so that the detection direction (light incident direction to the light receiving unit) is as shown in FIG. ) As shown. The detection direction and the emission direction are shown in FIG. 75 together with the probe arrangement. It can be seen that the emission direction and the detection direction are oblique with respect to the X direction and the Y direction in plan view (viewed from the + Z direction).

  In this case, since the light has anisotropy as in the sensitivity distribution described above, it can be expected to have more sensitivity at the position of x in FIG.

  As a result of estimating the inverse problem in the same manner as in the first embodiment with the arrangement shown in FIGS. 74A and 74B, it was found that the detectable area is widened.

<< 5th Embodiment >>
Next, a fifth embodiment of the present invention will be described. FIG. 80 shows a state in which the light source module LM and the detection module DM are virtually mounted on the optical model (virtual model) in the fifth embodiment. Here, the optical model is a rectangular parallelepiped optical model (for example, a standard model) imitating the brain of a living body.

  Hereinafter, description will be made by appropriately using the XYZ three-dimensional orthogonal coordinate system shown in FIG. In the optical model, the surface on which the probe is virtually mounted is parallel to the XY plane.

  As shown in FIG. 80, the light source module LM and the detection module DM are arranged side by side in the X direction. The incident angles of the non-parallel plural (for example, three) lights from the light source module LM to the optical model are set to about 45 °. Here, the incident angle is determined in consideration of Snell's law based on the refractive index of the optical model.

  More specifically, of the three lights from the light source module LM (hereinafter referred to as “first to third lights”), the incident direction of the first light to the optical model is + Z direction and −X in the XZ plane. It is a direction that forms an angle of approximately 45 ° with respect to the direction, and the direction of the orthogonal projection vector onto the XY plane in the incident direction is the −X direction.

  The incident direction of the second light to the optical model is a direction that forms an angle of approximately 45 ° with respect to the + Z direction and the + X direction in the XZ plane, and the direction of the orthogonal projection vector on the XY plane in the incident direction is + X Direction.

  The incident direction of the third light to the optical model is a direction that forms an angle of approximately 45 ° with respect to the + Z direction and the + Y direction in the YZ plane, and the direction of the orthogonal projection vector on the XY plane in the incident direction is + Y Direction.

  Therefore, for the sake of convenience, the following description will be made assuming that the incident direction of the first light is the −X direction, the incident direction of the second light is the + X direction, and the incident direction of the third light is the + Y direction.

  In the fifth embodiment, the same calculation as in the Monte Carlo simulation described above was performed. As shown in FIG. 81, the optical model is composed of four layers: a scalp layer (skalp), a skull layer (skall), a cerebrospinal fluid layer (CSF), and a gray matter layer (Gray Matter). Optical constants are set for each layer (see FIG. 82). The sum of the thickness of the scalp layer and the skull layer is d1, and the thickness of the cerebrospinal fluid layer is d2 (see FIG. 81).

  For this optical model, the number of photons 1E9 is calculated, and the number of photons (light quantity) entering the detection module DM is detected. At this time, calculation is performed for each incident direction of the first to third lights, and the ratio of the number of photons for each incident direction is plotted. Here, the number of photons (light amount) of the first light is −X, the number of photons (light amount) of the second light is + X, and the number of photons (light amount) of the third light is + Y.

  In FIG. 83, for example, −X / + X and + Y / + X when the scattering coefficient of the laminate composed of the scalp layer and the skull layer is changed with respect to the reference value (17.5) shown in FIG. Is plotted. FIG. 83 shows that −X / + X changes from about 0.62 to about 0.81 when the scattering coefficient is changed from 0.5 times to 1.5 times the reference value. Here, d1 = 9 mm and d2 = 3 mm. When the scattering coefficient of the cerebrospinal fluid layer or gray matter layer is changed, a tendency similar to that in FIG. 83 is shown.

  The absorption coefficient is the same as the scattering coefficient, and the result is shown in FIG. Again, d1 = 9 mm and d2 = 3 mm.

  Further, it is known that -X / + X and + Y / + X change even when the thickness d1 and the thickness d2 change (see FIG. 85).

  As is clear from the above description, -X / + X and + Y / + X change due to the change in the parameters of each layer of the optical model, and the range of the change is about 0.6 to 0.95. .

  Therefore, by using the detected values of -X / + X and + Y / + X, the parameters of each layer of the optical model are corrected to values that are more suitable for the living body (values that match or approximate the values unique to the living body). Will be possible.

  However, since there are four variables (parameters) (thickness d1, thickness d2, scattering coefficient, absorption coefficient), the detected values are two variables -X / + X and + Y / + X. ing. This is a defect problem, and simple estimation is possible using inverse problem estimation.

  However, there is a high possibility that an error will occur in the inverse problem estimation. Therefore, we examined a method that can increase the detection value and determine the variable. For example, as a simple method, there is a method of measuring the head circumference of a subject and detecting the thickness d1 of a laminate composed of a scalp and a skull.

  For example, the paper in FIG. 86 proposes a method of acquiring a lot of data and calculating the thickness of the skull from the head circumference.

  Moreover, the thickness of the skull can be detected by using an ultrasonic sensor. In addition, the thickness of each part of the skull can be detected by using an MRI image or CT scan.

  As described above, in addition to using the optical sensor 10, there is a method for detecting parameters of the optical model, and there is a means for detecting the thicknesses d1 and d2 with high accuracy. If d1 and d2 can be determined, the rest will be the scattering coefficient and the absorption coefficient.

  In this case, the variable is two parameters (scattering coefficient and absorption coefficient), and there are two detection values, -X / + X and Y / + X, but these detection values are not mutually independent. Therefore, another independent detection value is required.

  Therefore, in the optical sensor 10 including the plurality of light source modules LM and the plurality of detection modules DM, in addition to the multiple emission angle method (method for irradiating a plurality of non-parallel lights to the same position of the measurement target), the light source module LM It is preferable to use a multi-distance method in which a plurality of distances between the detection modules DM are provided.

  This multi-distance method is described in, for example, Japanese Patent No. 5202636. The optical constants of the multi-distance method are, for example, values unique to the subject, such as bone density and skin color, and have low head region dependency. In other words, if only one part of the head is detected and corrected, the function can be generally satisfied as the correction.

  Here, when the multiple emission angle method and the multi-distance method are used in combination, for example, the multiple emission angle method light source module LM and the detection module DM are alternately arranged in a grid pattern at a predetermined interval (for example, 30 mm). The detection module DM may be additionally arranged at a predetermined interval (for example, 5 mm) with respect to the light source module LM, or the light source module LM may be additionally arranged at a predetermined interval (for example, 5 mm) with respect to the arranged detection module DM. You may arrange | position (refer FIG. 87).

  Thereby, a plurality of intervals (distances) between the light source module LM and the detection module DM can be provided, and the multiple emission angle method and the multi-distance method can be used in combination.

  In the case of the multi-distance system, the multi-distance system light propagation formula shown in FIG. 88 is used. Here, φ (rs, rd) indicates the amount of light propagating from rs (light source) to rd (photodetector). μs ′ is a scattering coefficient converted to anisotropy, μa is an absorption coefficient, rs is a position of a light source, rd is a position of a photodetector, and D, S, and υ are coefficients. In the light propagation equation of FIG. 88, the result of plotting the light amount ratio with μs ′ as a variable is shown in FIG.

  89 shows the value of the multi-distance method, and the light amount ratio of the lower diagram of FIG. 89 shows the value of the multiple emission angle method (−X / + X). Note that the value of the multi-distance method is that the total received light amount of DM with a distance of 5 mm from the LM (total detected value: sum of a plurality of detected values) and the total received light amount of DM with a distance of 30 mm from the LM (total detected value). Value: the sum of a plurality of detected values).

  FIG. 89 shows a case where, for example, three candidates (0.50, 1.00, 1.50) are given as the absorption coefficient μa.

  In the upper diagram of FIG. 89, the light quantity ratio, which is a value of the multi-distance method, is a graph that rises to the right with respect to an increase in the scattering coefficient μs ′ in any absorption coefficient μa. Here, when the light quantity ratio which is a value of this multi-distance method is 80, for example, the scattering coefficient μs ′ is a value (0.65) indicated by the arrow (1) and a value (1. 00) and the value (1.45) indicated by the arrow (3).

  On the other hand, in the lower diagram of FIG. 89, the light quantity ratio, which is the value of the multiple emission angle method (−X / + X), is a graph with a downward slope for any absorption coefficient μa with respect to the increase of the scattering coefficient μs ′. It becomes.

  Therefore, the scattering coefficient μs ′ at which the light amount ratio is 80 in the upper diagram of FIG. 89 and 65, for example, is 65 in the lower diagram of FIG. 89, is approximately the arrow (2) among the arrows (1) to (3). It can be estimated that the displayed value, that is, 1.00 (equal to the reference value). That is, if the value of the multi-distance method and the value of the multiple emission angle method are known, the scattering coefficient μs ′ can be obtained.

  As described above, the multi-distance method and the multiple emission angle method can be used as independent variables because the tendency of the change in the light amount ratio with respect to the change in the scattering coefficient is different. This is considered to be due to the fact that the emission position (irradiation position) appears to shift more greatly as the scattering coefficient μs ′ decreases in the multiple emission angle method.

  FIG. 90 shows this physical phenomenon as an example. When the scattering coefficient μs ′ is small as shown in the left diagram of FIG. 90, two non-parallel light beams emitted from the LM and incident on the same position of the optical model (incident directions are −X direction light and + X direction light beams). Since the light enters the deep part of the optical model, the maximum arrival position in the optical model is greatly separated, and -X / + X (light quantity ratio) increases.

  On the other hand, when the scattering coefficient μs ′ is large as shown in the right diagram of FIG. 90, two non-parallel light beams emitted from the LM and incident on the same position of the optical model (light beams having an incident direction of −X direction). And light in the + X direction) are scattered in the shallow part of the optical model, the maximum arrival position in the optical model is not so far away, and -X / + X (light quantity ratio) is small.

  That is, the smaller the scattering coefficient μs ′, the larger the maximum arrival position in the optical model of the two non-parallel lights, and the larger −X / + X (light quantity ratio).

  This is a finding obtained by the inventors for the first time in the multiple emission angle system. It is not easy for others in the industry to assume that this phenomenon will occur. Further, the scattering coefficient dependency of the multiple emission angle method tends to be opposite to that of the multi-distance method.

  Therefore, as shown in FIG. 89, the value of the multi-distance method and the value of the multiple emission method can be used as independent variables.

  In the case of the absorption coefficient as well, the smaller the smaller the maximum arrival position in the optical model of the two non-parallel light, the greater the distance between them, so as in the case of the scattering coefficient (the horizontal axis in FIG. 89 is the absorption coefficient). It is possible to obtain (by plotting the light quantity ratio at a plurality of scattering coefficients).

  Therefore, as in the case of the optical model described above, the scattering coefficient and the absorption coefficient of the subject can be obtained by using both the multiple emission angle method and the multi-distance method for the subject (for example, a living body).

  In particular, the light intensity ratio of -X / + X, + Y / + X, etc. takes a substantially constant value regardless of the probe mounting state on the subject (including the presence of foreign matter between the subject and the probe). Since the detection error can be reduced, the scattering coefficient and the absorption coefficient can be obtained with high accuracy.

  That is, since the value of the multiple emission angle method and the value of the multi-distance method are independent, the scattering coefficient and the absorption coefficient, which are two important parameters as the optical characteristics of the subject, can be obtained with high accuracy. Then, by replacing the scattering coefficient and absorption coefficient of the reference optical model (for example, standard model) with the obtained scattering coefficient and absorption coefficient, respectively, the optical model can be corrected to an optical model more suitable for the subject. . By using the corrected optical model, individual differences can be corrected, and the amount of cerebral blood flow can be accurately quantified. By determining this amount, an accurate diagnosis can be made.

  The optical inspection method according to the fifth embodiment described above includes an irradiation system including at least one LM (light irradiator) that irradiates a plurality of non-parallel lights to the same position of the measurement target, and the irradiation system to the measurement target. An optical inspection method for inspecting a subject using an optical sensor 10 including a detection system including at least one DM (photodetector) that individually detects the amount of light that has been irradiated and propagated through the measurement target. Then, using the optical sensor 10 to obtain a first detected light amount distribution that is a detected light amount distribution of the subject, and using a ratio of a plurality of detected values of DM included in the first detected light amount distribution, Correcting an optical model simulating the specimen.

  In this case, the error can be reduced by using a ratio of a plurality of detection values. The cause of the error in the detection value is dust or hair existing at the interface between the probe tip and the subject. For this reason, the error in the detection value varies greatly depending on the contact state between the probe and the subject. On the other hand, the “ratio” value of the two detection values obtained in the same contact state between the subject and the probe is substantially constant regardless of the detection value error due to the contact state. That is, the contact error factor can be removed. The change in the “ratio” is correlated with the change in the parameter (for example, scattering coefficient or absorption coefficient) of the subject. Specifically, this “ratio” decreases as the scattering coefficient and the absorption coefficient increase (see the lower diagram in FIG. 89).

  As a result, it is possible to narrow down the values of the parameters (for example, the scattering coefficient and the absorption coefficient) of the subject with high accuracy. That is, powerful information for correcting the optical model can be obtained.

  In addition, when the plurality of non-parallel lights include two lights in which the directions of the orthogonal projection vectors to the subject in the direction of incidence on the subject are opposite, the optical path to the DM of the two lights The difference in length can be made as long as possible. As a result, the difference between the detected values of the two lights in the DM can be made as large as possible, and the detection accuracy can be improved.

  Further, the detection system includes a plurality of DMs, and the step of obtaining the first detected light amount distribution is performed such that the distances between the plurality of DMs and the light irradiator LM are different from each other at least two DMs among the plurality of DMs. In the step of correcting the optical model, including a sub-process arranged on the subject, a ratio of a sum of a plurality of detected values of one DM and a sum of a plurality of detected values of another DM of the at least two DMs Is preferably used to correct the optical model.

  In addition, the irradiation system includes a plurality of LMs, and the step of obtaining the first detected light amount distribution that is the detected light amount distribution of the subject includes a plurality of LMs and DMs, and each of at least two LMs of the plurality of LMs and each DM. In the step of correcting the optical model, including a sub-step of arranging on the subject so that the distances are different from each other, the DM emits a plurality of lights irradiated from one of the at least two LMs and propagated in the subject. A sum of a plurality of detection values when individually detected and a plurality of detection values when the DM individually detects a plurality of lights irradiated from other LMs among the at least two LMs and propagated in the subject. It is preferable to further correct the optical model using the sum ratio.

  In these cases, a change in the “ratio” of the sum of a plurality of detection values of one DM and a sum of a plurality of detection values of another DM is correlated with a change in an object parameter (for example, a scattering coefficient or an absorption coefficient). is there. Specifically, this “ratio” increases as the scattering coefficient and the absorption coefficient increase (see the upper diagram of FIG. 89).

  Therefore, the most suitable value for the subject can be determined among the narrowed values of the subject parameters (for example, the scattering coefficient and the absorption coefficient).

  In this case, the optical model can be corrected to an optical model suitable for the subject.

  As a result, inspection accuracy can be improved.

  The optical inspection method according to the fifth embodiment includes a step of obtaining a second detected light amount distribution, which is a detected light amount distribution of the corrected optical model, by simulation using the optical sensor 10 virtually, and the first and second steps. It is preferable to further include a step of acquiring (estimating) information (for example, the position of the light absorber) in the subject using the detected light amount distribution.

  In this case, information in the subject can be obtained with high accuracy.

  It should be noted that, for example, an optical system more suitable for a subject from a plurality of optical models can be obtained by applying a multiple emission angle method and a multi-distance method to the first and second embodiments as in the fifth embodiment. A model can be selected.

  That is, the optical inspection method according to the modification includes an irradiation system including at least one LM (light irradiator), and a DM that detects the amount of light irradiated from the irradiation system to the measurement target and propagated through the measurement target. An optical inspection method for inspecting a subject using an optical sensor 10 including a detection system including at least one detection system, wherein a first detected light amount distribution that is a detected light amount distribution for each of a plurality of optical models simulating the subject is obtained. The step of obtaining by the simulation using the optical sensor 10 virtually, the step of obtaining the second detected light amount distribution which is the detected light amount distribution of the subject using the optical sensor 10, and the first and second detected light amount distributions. And a step of selecting an optical model suitable for the subject from a plurality of optical models.

  Further, in the optical inspection method of the modified example, the step of obtaining the second detected light amount distribution that is the detected light amount distribution of the subject includes a sub-step of irradiating the same position of the subject with a plurality of non-parallel lights from the LM, A sub-process for individually detecting the light amounts of a plurality of lights propagating in the subject with DM, and in the selecting step, a plurality of detection values of DM in the sub-process to be detected are used, An optical model suitable for the subject is selected from the optical model.

  In this case, it is possible to narrow down the values of the parameters of the subject (for example, the scattering coefficient and the absorption coefficient) with high accuracy.

  As a result, inspection accuracy can be improved.

  Further, in the optical inspection method according to the modified example, when the plurality of non-parallel lights include two lights whose orthogonal projection vectors to the subject in the direction of incidence on the subject are opposite directions, the two The difference in the optical path length of light to DM can be made as long as possible. As a result, the difference between the detected values of the two lights in the DM can be made as large as possible, and the detection accuracy can be improved.

  In the optical inspection method according to the modified example, the detection system includes a plurality of DMs, and the step of obtaining the second detected light amount distribution that is the detected light amount distribution of the subject includes a plurality of DMs and LMs prior to the irradiation sub-process. Are further arranged on the subject such that the distance between each of at least two DMs of the plurality of DMs and the LM is different from each other. In the selecting step, one of the at least two photodetectors is selected. It is preferable to select an optical model suitable for the subject from a plurality of optical models by further using a ratio of the sum of the plurality of detection values of the photodetector to the sum of the plurality of detection values of the other photodetectors.

  In addition, the irradiation system includes a plurality of LMs, and the step of obtaining the second detected light amount distribution that is the detected light amount distribution of the subject includes a plurality of LMs and DMs at least of the plurality of LMs prior to the irradiation sub-step. The method further includes a sub-process of arranging on the subject such that the distance between each of the two LMs and the DM is different from each other. In the selecting step, the LM is irradiated from one of the at least two LMs and propagates through the subject. Sum of a plurality of detection values when a plurality of lights are individually detected by the DM, and when the DM individually detects a plurality of lights irradiated from other LMs among the at least two LMs and propagated in the subject. It is preferable to select an optical model suitable for the subject from the plurality of optical models by further using the ratio of the sum of the plurality of detection values.

  In these cases, a change in the “ratio” of the sum of a plurality of detection values of one DM and a sum of a plurality of detection values of another DM is correlated with a change in an object parameter (for example, a scattering coefficient or an absorption coefficient). is there. Specifically, this “ratio” increases as the scattering coefficient and the absorption coefficient increase (see the upper diagram of FIG. 89).

  Therefore, the most suitable value for the subject can be determined among the narrowed values of the subject parameters (for example, the scattering coefficient and the absorption coefficient).

  In this case, an optical model more suitable for the subject can be selected from a plurality of optical models.

  As a result, inspection accuracy can be improved.

  Further, the optical inspection method of the modified example acquires (estimates) information (for example, the position of the light absorber) in the subject using the first detected light amount distribution and the second detected light amount distribution of the selected optical model. It is preferable to further include a step.

  In this case, information in the subject can be obtained with high accuracy.

  In the fifth embodiment and the modification, the multi-distance method is realized by using the LM and DM of the multi-emission angle method, but instead of or in addition to this, a light irradiator dedicated to the multi-distance method or A photodetector may be used. The light irradiator dedicated to the multi-distance method may be any device that can irradiate the measurement target with at least one light. The photodetector for exclusive use of the multi-distance method may be any detector that can detect at least one light propagated through the measurement target.

  Moreover, in the said 1st, 2nd and 5th embodiment and the modification, although the position of a light absorber is estimated, it is good also as estimating the magnitude | size of a light absorber instead of or in addition to this. Examples of the “light absorber” include those that absorb light such as cancer cells and polyps in addition to blood.

  Moreover, in the said 1st and 2nd embodiment and a modification, although eight optical models are used, seven or less may be sufficient and nine or more may be sufficient. In any case, it is desirable that a parameter affecting the optical characteristics, which represents the characteristics of the subject in the absence or presence of cerebral blood flow, be the characteristics of the optical model.

  Moreover, in the said 1st and 2nd embodiment and the modification, the layer structure (the number of lamination | stacking) of each optical model is 5 layers, However, 4 layers or less may be sufficient and 6 layers or more may be sufficient. In this case, it is preferable to include at least one layer that causes an error such as a hair model layer in the layer configuration.

  Further, in the optical inspection method according to the first embodiment and the modified example, prior to the step of acquiring information in the subject (for example, the absorber position estimation process), a plurality of opticals are provided as in the second embodiment. A step of correcting the second detected light amount distribution using the first detected light amount distribution of at least one optical model (at least the optical model 1) including an optical model suitable for the subject among the models (optical models 1 to 8). (See steps S42 to S44 in FIG. 78).

  In this case, the second detected light amount distribution reflecting the information (optical characteristics) in the subject can be corrected with high accuracy, and the accuracy of estimating the position of the light absorber can be further improved.

  Furthermore, in the optical inspection methods of the first embodiment and the modified example, model selection may be performed again after the step of correcting the second detected light amount distribution (see step S45 in FIG. 79). In this case, the selection accuracy of the optical model can be further improved.

  Further, in the optical inspection method of the first embodiment and the modified example, as in the optical inspection method of the second embodiment, in the step of correcting the second detected light amount distribution, the first of the at least one optical model is corrected. A correction coefficient may be calculated from the detected light quantity distribution, and the second detected light quantity distribution may be corrected using the correction coefficient. In this case, the second detected light amount distribution can be corrected by a simple method.

  Further, in the optical inspection method of the first embodiment and the modified example, in the step of correcting the second detected light amount distribution, as in the optical inspection method of the second embodiment, the gender, age, height, and weight of the subject are corrected. When at least one piece of information is used among the head outer circumference length, the hair thickness, the hair density, and the skin color, the second detected light amount distribution can be corrected with higher accuracy.

  Further, in the optical inspection method of the first embodiment and the modified example, similarly to the optical inspection method of the second embodiment, in the step of obtaining the second detected light amount distribution, detection is performed for 20 seconds or more, and the detected light amount When the second detected light quantity distribution is obtained using the maximum value of the second detected light quantity distribution, the second detected light quantity distribution can be obtained with high accuracy.

  Further, the optical inspection method of the second embodiment and the modified example includes a step of correcting the first detected light amount distribution prior to the step of selecting the optical model, similarly to the optical inspection method of the first embodiment. Further, it may be included. Also in this case, the accuracy of selecting the optical model can be improved.

  Further, in the optical inspection method of the second embodiment and the modified example, in the same manner as the optical inspection method of the first embodiment, in the step of correcting the first detected light amount distribution, each light source module LM is optically connected in the simulation. The detected light quantity of at least two detection modules DM adjacent to the light source module LM of the light irradiated to the model and propagated through the optical model is compared, and based on the comparison result, the detected light quantity of the at least two detection modules DM It may be possible to correct at least one detected light quantity (see steps S31 to S33 in FIG. 33).

  Also in this case, it is possible to suppress errors in the amounts of light detected by the plurality of detection modules DM of light that has been irradiated onto the optical model from each light source module LM and propagated through the optical model in the simulation. That is, errors due to poor contact between the detection module DM and the optical model surface in the simulation can be suppressed.

  Further, in the optical inspection method of the second embodiment and the modified example, as in the optical inspection method of the first embodiment, in the step of correcting the first detected light amount distribution, adjacent to each detection module DM in the simulation. The detected light amount of the detection module DM of the light that has been applied to the optical model from the at least two light source modules LM and propagated through the optical model is compared, and at least one of the at least two light source modules LM is compared based on the comparison result It may be possible to correct the amount of light detected by the detection module DM of the light from the light source module LM (see steps S34 to S36 in FIG. 33).

  Also in this case, it is possible to suppress an error in the amount of light detected by each detection module DM of the plurality of lights that are irradiated to the optical model from the plurality of light source modules LM and propagated in the optical model in the simulation. In other words, errors due to poor contact between the light source module LM and the optical model surface in the simulation can be suppressed.

  Further, in the optical inspection method according to the second embodiment and the modified example, similarly to the optical inspection method according to the first embodiment, in the simulation, the two light source modules LM adjacent to each other are replaced with the first and second light source modules. A process of correcting the first detected light amount distribution, assuming that two detection modules DM that are adjacent to each other and are adjacent to each other are the first and second detection modules DM. Then, in the above simulation, from the first and second light source modules LM, the detected light amounts 1 and 2 of the first and second detection modules DM of the light that has been applied to the optical model from the first light source module LM and propagated through the optical model. A ratio of the detected light amounts 3 and 4 of the first and second detection modules DM of the light irradiated to the optical model and propagated through the optical model is compared. And it may be capable of correcting at least one of the detected light 1,2,3,4 based on the comparison result (see step S37 to S39).

  In this case, it is possible to suppress errors due to the difference in the installation state of the four adjacent probes in the simulation.

  In the optical inspection methods of the second embodiment and the modified example, weighting in the depth direction (see step S40 in FIG. 33) may be performed in the step of correcting the first and second detected light amount distributions.

  Further, in the first and second embodiments and modifications, when acquiring the detected light amount distribution of the subject, a series of steps S31 to S33, a series of steps S34 to S36 in the flowchart of FIG. You may acquire by performing at least 1 of a series of processes of step S37-S39, and step S40. In this case, the detected light amount distribution of the subject can be acquired with high accuracy.

  Further, in each of the above embodiments and modifications, the number of light source modules LM in the irradiation system and the number of detection modules in the detection system can be changed as appropriate. In short, the irradiation system only needs to have at least one light source module LM. The detection system may have at least one detection module DM. The plurality of probes are preferably arranged so that the light source module LM and the detection module DM are adjacent (adjacent) in any of two directions intersecting each other.

  Moreover, in each said embodiment and modification, the structure of light source module LM (light irradiation device) can be changed suitably. For example, the number and arrangement of the surface emitting laser array chips of the light irradiator can be appropriately changed. The type, shape, size, number, etc. of the lenses can be changed as appropriate.

  In each of the above embodiments and modifications, a surface emitting laser is used as the light source of the light irradiator. For example, other than an edge emitting laser (LD), a light emitting diode (LED), an organic EL element, and a semiconductor laser. Alternatively, a laser or the like may be used.

  Moreover, in each said embodiment and modification, although the prism is used as a reflection member of a light irradiation device, another mirror etc. may be provided.

  Moreover, the number and arrangement of groups in the surface emitting laser array chip of Example 2 and the number and arrangement of ch in each group can be changed as appropriate.

  The configuration of the detection module DM (photodetector) can be changed as appropriate. For example, the aperture does not necessarily have to be provided. Further, for example, the split lens is not necessarily provided.

  Needless to say, the shapes, materials, numbers, dimensions, and numerical values described in the above description are merely examples, and can be changed as appropriate.

  In addition, at least one part of the configuration of the optical inspection apparatus and the optical sensor described in each of the above embodiments and modifications and at least one step in the optical inspection method is between the embodiments, between the embodiments and the modifications, and between the examples. Needless to say, they can be used interchangeably.

  DESCRIPTION OF SYMBOLS 10 ... Optical sensor, 100 ... Optical inspection apparatus, LM ... Light source module (light irradiation device), DM ... Detection module (light detector).

Japanese Patent No. 3779134

Claims (27)

An optical sensor comprising: an irradiation system including at least one light irradiator; and a detection system including at least one light detector that detects the amount of light emitted from the irradiation system to the measurement object and propagated through the measurement object. An optical inspection method for inspecting a subject using
Obtaining a first detected light amount distribution, which is a detected light amount distribution for each of a plurality of optical models simulating the subject, by simulation using the optical sensor virtually;
Obtaining a second detected light amount distribution which is a detected light amount distribution of the subject using the optical sensor;
Selecting an optical model suitable for the subject from the plurality of optical models based on the first and second detected light quantity distributions. The step of obtaining the second detected light amount distribution includes:
A sub-step of irradiating the same position of the subject with a plurality of non-parallel lights from the light irradiator;
A sub-step of individually detecting the light amounts of a plurality of lights propagated in the subject with the photodetector,
In the selecting step, an optical model suitable for the subject is selected from the plurality of optical models using a ratio of a plurality of detection values of the photodetector in the detecting sub-step. The optical inspection method according to claim 1.   3. The optical inspection method according to claim 2, wherein the plurality of non-parallel lights include two lights whose orthogonal projection vectors to the subject in a direction of incidence on the subject are opposite to each other. The detection system includes a plurality of the photodetectors,
In the step of obtaining the second detected light amount distribution, prior to the irradiating sub-step, the plurality of photodetectors and the light irradiator are respectively connected to at least two photodetectors of the plurality of photodetectors. Further including a sub-step of disposing on the subject such that the distance from the light irradiator is different from each other,
In the selecting step, the ratio of the sum of the plurality of detection values of one of the at least two photodetectors and the sum of the plurality of detection values of another photodetector is further used, The optical inspection method according to claim 2, wherein an optical model suitable for the subject is selected from the optical model. The irradiation system includes a plurality of the light irradiators,
In the step of obtaining the second detected light amount distribution, prior to the irradiating sub-step, the plurality of light irradiators and the light detectors are respectively connected to at least two of the plurality of light irradiators. A sub-step of disposing on the subject such that the distance from the photodetector is different from each other;
In the selecting step, a plurality of detection values when the light detector individually detects a plurality of lights irradiated from one of the at least two light irradiators and propagated in the subject. The ratio of the sum and the sum of a plurality of detection values when the light detector individually detects a plurality of lights irradiated from another light irradiator of the at least two light irradiators and propagated in the subject. The optical inspection method according to claim 2, further comprising: selecting an optical model suitable for the subject from the plurality of optical models.   6. The method according to claim 1, further comprising a step of acquiring information in the subject using the first detected light quantity distribution and the second detected light quantity distribution of the selected optical model. The optical inspection method according to claim 1. An irradiation system that includes at least one light irradiator that irradiates the same position of the measurement target with a plurality of non-parallel light beams, and individual light quantities of the plurality of lights that are irradiated from the irradiation system to the measurement target and propagated through the measurement target An optical inspection method for inspecting a subject using an optical sensor including a detection system including at least one photodetector for detecting the object,
Obtaining a first detected light amount distribution that is a detected light amount distribution of the subject using the optical sensor;
Correcting an optical model simulating the subject using a ratio of a plurality of detection values of the photodetector included in the first detected light amount distribution.   The optical inspection method according to claim 7, wherein the plurality of non-parallel lights include two lights whose orthogonal projection vectors to the subject in a direction of incidence on the subject are opposite to each other. The detection system includes a plurality of the photodetectors,
In the step of obtaining the first detected light amount distribution, the plurality of photodetectors and the light irradiators are arranged such that the distance between each of the light detectors and at least two of the plurality of photodetectors is the same. Including a sub-step of disposing differently on the subject,
In the correcting step, the optical model is further used by further using a ratio of a sum of a plurality of detection values of one of the at least two photodetectors and a sum of a plurality of detection values of another photodetector. The optical inspection method according to claim 7, wherein the optical inspection method is corrected. The irradiation system includes a plurality of the light irradiators,
In the step of obtaining the first detected light amount distribution, the plurality of light irradiators and the light detectors are separated from each other by a distance between at least two of the plurality of light irradiators and the light detector. Including a sub-step of disposing differently on the subject,
In the correcting step, a plurality of detection values when the photodetector individually detects a plurality of lights irradiated from one of the at least two light irradiators and propagated in the subject. The ratio of the sum and the sum of a plurality of detection values when the light detector individually detects a plurality of lights irradiated from another light irradiator of the at least two light irradiators and propagated in the subject. The optical inspection method according to claim 7, wherein the optical model is corrected by further using the method. Obtaining a second detected light amount distribution which is a corrected detected light amount distribution of the optical model by simulation using the optical sensor virtually;
The optical inspection method according to any one of claims 7 to 10, further comprising a step of acquiring information in the subject using the first and second detected light amount distributions.   The method further comprises a step of correcting the second detected light amount distribution based on the first detected light amount distribution of at least one optical model including the selected optical model among the plurality of optical models. Item 7. The optical inspection method according to any one of Items 1 to 6.   In the step of correcting the second detected light amount distribution, the second detected light amount distribution is corrected using a correction coefficient obtained from the first detected light amount distribution of the at least one optical model. The optical inspection method according to claim 12.   Prior to the step of acquiring the information, the second detected light amount distribution is corrected based on the first detected light amount distribution of at least one optical model including the selected optical model among the plurality of optical models. The optical inspection method according to claim 6, further comprising a step.   In the step of correcting the second detected light amount distribution, the second detected light amount distribution is corrected using a correction coefficient obtained from the first detected light amount distribution of the at least one optical model. The optical inspection method according to claim 14.   In the step of correcting the second detected light amount distribution, at least one information among the sex, age, height, weight, head circumference, hair thickness, hair density, and skin color of the subject is used. The optical inspection method according to any one of claims 12 to 15, wherein:   The optical model includes a virtual layer that can be interposed between the light irradiator and the photodetector and the surface of the subject. The optical inspection method described.   In the step of obtaining the second detected light amount distribution, detection is performed for 20 seconds or more, and the second detected light amount distribution is obtained using a maximum value of the detected light amount. The optical inspection method according to any one of 17.   The optical inspection method according to any one of claims 1 to 6, and 12 to 18, further comprising a step of correcting the first detected light amount distribution prior to the selecting step. The at least one photodetector is a plurality of photodetectors;
In the simulation, the light irradiator and the plurality of light detectors are virtually mounted on the optical model such that at least two light detectors are adjacent to the light irradiator,
In the step of correcting the first detected light amount distribution, the at least two photodetectors adjacent to the light irradiator of the light irradiated from the light irradiator to the optical model and propagated through the optical model in the simulation. 20. The optical inspection method according to claim 19, wherein the detected light amounts can be compared, and at least one of the detected light amounts of the at least two photodetectors can be corrected based on the comparison result. The at least one light irradiator is a plurality of light irradiators;
In the simulation, the plurality of light irradiators and the light detectors are virtually mounted on the optical model such that at least two of the light irradiators are adjacent to the light detectors,
In the step of correcting the first detected light amount distribution, in the simulation, the photodetector of light that has been applied to the optical model from the at least two light irradiators adjacent to the photodetector and propagated through the optical model The detected light amount of the light detector of the light from at least one of the at least two light irradiators can be corrected based on the comparison result. The optical inspection method according to 19 or 20. The at least one light irradiator is a plurality of light irradiators;
The at least one photodetector is a plurality of photodetectors;
In the simulation, the plurality of light irradiators and the plurality of light detectors are arranged so that the light irradiators and the light detectors are adjacent to each other in both the first and second directions intersecting each other. Is virtually attached to the
On the optical model, the two light irradiators adjacent to each other are defined as first and second light irradiators, the two adjacent to the first and second light irradiators and adjacent to each other. When the photodetectors are the first and second photodetectors,
In the step of correcting the first detected light amount distribution, in the simulation, the first and second photodetectors of light that has been applied to the optical model from the first light irradiator and propagated through the optical model. Are compared with the detected light amounts 3 and 4 of the first and second light detectors of the light that has been applied to the optical model from the second light irradiator and propagated through the optical model. The optical inspection method according to any one of claims 19 to 21, wherein at least one of the detected light amounts 1, 2, 3, and 4 can be corrected based on the comparison result.   The optical inspection method according to any one of claims 1 to 6, 11, and 12 to 22, wherein the simulation is Monte Carlo simulation. An optical inspection apparatus for inspecting a subject,
An optical sensor comprising: an irradiation system including at least one light irradiator; and a detection system including at least one light detector for detecting the amount of light irradiated from the irradiation system to the measurement object and propagated through the measurement object. When,
A control system for controlling the irradiation system and acquiring a detection light amount of the detection system,
The control system obtains a first detected light quantity distribution that is a detected light quantity distribution of the subject using the optical sensor, and a plurality of the specimens obtained by simulation using the optical sensor virtually An optical inspection apparatus that selects an optical model suitable for the subject from the plurality of optical models based on a second detected light quantity distribution that is a detected light quantity distribution for each optical model and the first detected light quantity distribution.   The said control system acquires the information in the said test object using the said 2nd detected light quantity distribution and the said 1st detected light quantity distribution of the selected said optical model, The said subject is characterized by the above-mentioned. Optical inspection device.   The control system corrects the first detected light amount distribution using the second detected light amount distribution of at least one optical model including an optical model selected from the plurality of optical models. The optical inspection apparatus according to claim 24 or 25. 27. The optical inspection apparatus according to claim 24, wherein the control system corrects the second detected light amount distribution prior to selection of the optical model.