JP2009047429A - Light measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform measurement, with relatively simple configuration and with relatively high accuracy, for specifying an optical path length and a depth of the optical path of scattered light in an object. <P>SOLUTION: A light measuring device 1 includes a low coherence light source 2 which emits a low coherence light; a branching section 3 which branches the low coherence light into a reference light and an irradiating light; an optical control section 4 which can vary the optical path length of the reference light; a first optical system 51 which irradidates an object 9 with the irradiating light; a second optical system 52 which condenses and guides a scattered light from the depths of the object 9 from a position different from an irradiating position of the irradiating light to the object 9 by the first optical system 51; a combining section 6 which combines the light guided by the second optical system 52 and the reference light; a light detecting section 7 which detects intensity of the light combined by the combining section 6; and a controlling section 8 (information processing section 81) which acquires information on depths of the object based on the optical path length of the reference light or iradiating light and the intensity of the light detected by the light detecting section. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical measurement device.

  For example, near-infrared light near 800 nm with high biological permeability was irradiated to the head to be measured, and was scattered by gray matter or white matter such as cerebral cortex located about 20 mm deep in the head. An optical topography method is known in which light is received by shifting the position from the irradiation position along the head surface, and information on the blood volume (hemoglobin concentration) is obtained from the intensity of the obtained light (for example, Patent Document 1). In this optical topography method, a map showing a change in blood flow in the head can be created.

  However, in a measuring apparatus employing a general optical topography method, the distance that the detected scattered light has propagated and the depth of the optical path of the scattered light in the measurement object are unclear.

In addition, for example, by irradiating an object to be measured with a short pulse laser emitted from a picosecond pulse laser device, and receiving scattered light from the object to be measured with a high-speed photodetector or the like, and performing time-resolved measurement A measuring device for specifying an optical path length is known (for example, Non-Patent Document 1).
Japanese Patent Laid-Open No. 9-19408 H. Edaetal., `` Multichannel time-resolved optical tomographic imaging system '', Review of Scientific Instruments, 1999, vol. 70, Issue 9, p. 3595-3602

  However, the measurement apparatus that specifies the optical path length by performing the time-resolved measurement requires a relatively expensive picosecond pulse laser apparatus and a high-speed photodetector, and it is necessary to configure them with relatively high accuracy.

  This invention makes it an example of a subject to cope with such a problem. In other words, it is possible to provide a light measurement device capable of performing optical measurement with a relatively simple configuration and with relatively high accuracy specifying the optical path length and the optical path depth of the scattered light in the object to be measured. It is an object of the present invention to provide a light measuring device and the like.

In order to achieve such an object, the present invention comprises at least the configurations according to the following independent claims.
An optical measurement device according to the present invention includes a low-coherence light source that emits low-coherence light, a demultiplexing unit that separates the low-coherence light emitted from the low-coherence light source into reference light and irradiation light, and an optical path of the reference light A light control unit that varies the length, a first optical system that irradiates the object to be measured with the irradiation light, and scattered light from a deep part of the object to be measured to the object to be measured by the first optical system. A second optical system that collects and guides light from a position different from the irradiation position of the irradiation light, and a combining unit that combines the light guided by the second optical system and the reference light And a light detection unit for detecting the intensity of the light combined by the multiplexing unit.

  Preferably, the light measurement device includes an information processing unit that acquires information on a deep portion of the measurement object based on the optical path length of the reference light and the intensity of light detected by the light detection unit. .

  In the light measurement device having the above configuration, the object to be measured is irradiated by the first optical system, and the scattered light from the deep part of the object to be measured is converted to the object to be measured by the first optical system by the second optical system. The light is guided from a position different from the irradiation position of the irradiation light. Then, the multiplexing unit of the light measurement device combines the light guided by the second optical system and the reference light, and detects the intensity of the light combined by the multiplexing unit by the light detection unit. Then, the information processing unit acquires information on the deep part of the measurement object based on the optical path length of the reference light and the intensity of the light detected by the light detection unit.

  An optical measurement device according to an embodiment of the present invention includes a low-coherence light source that emits low-coherence light, a demultiplexing unit that separates low-coherence light emitted from the low-coherence light source into reference light and irradiation light, and reference light A light control unit that varies the optical path length of the light source, a first optical system that irradiates the object to be measured with irradiation light, and irradiation of the scattered light from the deep part of the object to be measured to the object to be measured by the first optical system. A second optical system that condenses and guides light from a position different from the irradiation position of the light, a combining unit that combines the light guided by the second optical system and the reference light, and a combining unit A light detection unit that detects the intensity of the combined light, an information processing unit that acquires information about the depth of the object to be measured based on the optical path length of the reference light and the light intensity detected by the light detection unit Have

In the light measuring apparatus having the above configuration, the irradiation light is incident on the object to be measured by the first optical system, and the scattered light from the deep part of the object to be measured is measured by the first optical system by the second optical system. The light is guided from a position different from the incident position of the irradiation light to the object. Then, the multiplexing unit of the light measurement device combines the light guided by the second optical system and the reference light, detects the intensity of the light combined by the multiplexing unit by the light detection unit, The light control unit changes the optical path length of the reference light, and the information processing unit measures based on the optical path length of the reference light, the optical path length of the irradiation light, and the light intensity detected by the light detection unit. Get information about the depth of an object.
Examples of the measurement object include a living body, a substance having a relatively high water content, a substance containing a light scatterer, and the like.

  Hereinafter, an optical measurement device according to an embodiment of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a configuration diagram of a light measurement apparatus 1 according to the first embodiment of the present invention. FIG. 2 is a diagram for explaining the optical path of scattered light in the deep part of the measurement object 9.

  The light measurement device 1 according to the first embodiment of the present invention includes a low coherence light source 2 and an interferometer. In this embodiment, a Michelson interferometer is employed. Specifically, as shown in FIG. 1, the light measurement apparatus 1 includes a low coherence light source 2, a demultiplexing unit 3, a light control unit 4, a first optical system 51, a second optical system 52, and a multiplexing unit 6. , A light detection unit 7, a control unit 8, and a display unit 85.

The low coherence light source 2 emits light having a relatively short coherence length, that is, so-called low coherence light. The low coherence light source 2 according to the present embodiment has, for example, a wavelength of 1347 nm and a coherence length of about 16 μm. In the present embodiment, when the low coherence light output from the low coherence light source 2 is demultiplexed into, for example, reference light and irradiation light, and then recombined, the low coherence light from the demultiplexed position to the combined position is obtained. The difference between the optical path of the reference light and the optical path of the irradiation light from the demultiplexed position to the combined position is detected as interfering light when it is within a short distance range of about 16 μm corresponding to the coherence length, It has a characteristic that it does not interfere when the optical path difference is larger than that.
As the low-coherence light source 2, for example, a light-emitting device that emits low-coherence light such as an LED (Light Emitting Diode) or an SLD (Super Luminescent Diode) can be used.

  The lens 201 is disposed between the low coherence light source 2 and the demultiplexing unit 3, converts the light output from the low coherence light source 2 into parallel light, and outputs the parallel light to the demultiplexing unit 3.

  The demultiplexing unit 3 separates the low-coherence light output from the low-coherence light source 2 through the lens 201 into reference light that is directed to the light control unit 4 and irradiation light that is irradiated to the measurement target 9 (power branching). ). The demultiplexing unit 3 according to this embodiment includes a beam splitter 301. As shown in FIG. 1, the beam splitter 301 demultiplexes the reference light toward the light control unit 4 arranged in the direction perpendicular to the low coherence light incident from the low coherence light source 2 and the irradiation light. For example, a half mirror can be adopted as the beam splitter.

  The light control unit 4 varies the optical path length of the reference light. Specifically, the light control unit 4 defines the optical path length of the reference light.

In the present embodiment, as shown in FIG. 1, the light control unit 4 changes the optical path length of the reference light from the demultiplexing unit 3 and outputs the reference light to the multiplexing unit 6. Specifically, the light control unit 4 includes a movable mirror (mirror) 41 and a drive unit 42 as shown in FIG.
The mirror 41 reflects the reference light from the demultiplexing unit 3 and makes it incident on the multiplexing unit 6. The mirror 41 according to the present embodiment reflects the reference light from the beam splitter 301 and outputs it to the multiplexing unit 6 via the beam splitter 301.
For example, the drive unit 42 receives a control signal output from the control unit 8 and moves the mirror 41 along the optical axis at a specified speed based on the control signal. The drive part 42 is comprised by drive devices, such as a drive motor and a piezoelectric element, for example.
For example, the drive unit 42 receives a control signal such as a triangular wave or a sawtooth wave output from the control unit 8 and translates the mirror 41 along the optical axis according to the signal level of the control signal.

  In the light control unit 4 configured as described above, since the mirror 41 moves along the optical axis at a specified speed with respect to the beam splitter 301, the frequency of the reference light shifts due to the Doppler effect of light. When the reference light whose frequency is shifted and the light scattered after the irradiation light enters the object to be measured are combined and received by the light detection unit 7, the light detection unit 7 responds to the frequency difference. An interference signal having a beat is obtained. By generating the interference signal in this way, the S / N ratio is increased, and the detection sensitivity of the signal by the scattered light in the deep part of the measurement object 9 is increased.

  The light control unit 4 is not limited to the above-described embodiment. For example, the light control unit 4 may change the optical path length of the reference light from the demultiplexing unit 3 using a piezo element, an optical fiber, or the like, and output the reference light to the multiplexing unit 6.

The first optical system 51 makes the irradiation light output from the demultiplexing unit 3 incident on the object to be measured 9. The first optical system 51 according to the present embodiment includes an optical lens 511 as shown in FIG. The optical lens 511 is disposed between the beam splitter 301 and the measurement object 9 and irradiates the specified position (incident position) of the measurement object 9 with the irradiation light output from the beam splitter 301.
The first optical system 51 is not limited to the above-described embodiment. For example, the reference light output from the demultiplexing unit 3 may be applied to the specified position of the measurement object 9 via a light guide such as an optical fiber.

  As shown in FIG. 2, when the irradiation light is irradiated onto the irradiation position (also referred to as an incident position) 9 </ b> A of the object 9 to be measured by the first optical system 51, the light is emitted according to the structure inside the object 9. Scattering or reflection occurs. Of the light scattered in the deep part of the measurement object 9, for example, the light scattered along the optical axis direction of the incident light is input to the multiplexing unit 6 via the optical lens 511 and the beam splitter 301. .

The second optical system 52 transmits the scattered light from the deep part of the measurement object 9 from the position 9B different from the incident position (position 9A) of the irradiation light to the measurement object 9 by the first optical system via the lens 521. Then, the light is condensed and guided, and output to the multiplexing unit 6.
Specifically, as shown in FIGS. 1 and 2, the second optical system 52 is configured to measure the object 9 with respect to the incident position (position 9 </ b> A) of the irradiation light on the object 9 to be measured by the first optical system. The light is condensed and guided from a position 9 </ b> B that is separated by a specified distance (for example, about 30 mm) along the surface, and is output to the multiplexing unit 6.

The combining unit 6 combines the light guided by the second optical system 52 and the reference light from the light control unit 4 and outputs the combined light to the light detection unit 7.
The multiplexing unit 6 according to the present embodiment includes a beam splitter 601 as shown in FIG. Specifically, as shown in FIG. 1, the beam splitter 601 is disposed at a position where the optical axis of the reference light from the light control unit 4 intersects the optical axis of the light of the second optical system 52. The beam splitter 601 combines the reference light from the light control unit 4 and the light from the second optical system 52 and outputs the combined light to the light detection unit 7.

  In addition, the beam splitter 601 according to the present embodiment combines the reference light input from the light control unit 4 via the beam splitter 301 and the light from the second optical system 52 to the light detection unit 7. Output. The light measurement device 1 has a structure in which the scattered light collected by the first optical system 51 is input to the beam splitter 601 via the beam splitter 301 and then output to the light detection unit 7. With the above configuration, the installation space of the light measurement device 1 is relatively small.

  The light detection unit 7 detects the intensity of the light combined by the combining unit 6. Specifically, the light detection unit 7 outputs an electric signal having a level corresponding to the intensity of the input light. As the light detection unit 7, for example, a light detection device such as a photodiode or a photomultiplier tube can be employed. Further, the light detection unit 7 outputs the detected signal to the control unit 8.

  The control unit 8 comprehensively controls each component of the light measurement device 1 to realize the function according to the present invention. The control unit 8 includes general computer components, and includes, for example, a CPU (Central Processing Unit), a storage unit, an operation input device such as a keyboard and a mouse, a display unit 85, and the like. The control part 8 implement | achieves the function which concerns on this invention by running the program memorize | stored in the memory | storage part, for example. Moreover, the control part 8 performs the process which displays the image which shows the information regarding the deep part of the to-be-measured object based on this invention on the display part 85. FIG.

As shown in FIG. 1, the control unit 8 according to the present embodiment includes an information processing unit 81, a drive system control unit 82, and the like.
The information processing unit 81 acquires information related to the deep part of the measurement object 9 based on the optical path length of the reference light and the intensity of the light detected by the light detection unit 7. More specifically, the control unit 8 acquires information about the deep part of the measurement object 9 based on the position information of the mirror 41 and the intensity of the light detected by the light detection unit 7.

Next, a specific example of the function of the information processing unit 81 will be described.
In the optical measurement device 1 according to the present embodiment, since measurement is performed with low coherence light, when the optical path length of the reference light from the demultiplexing unit 3 to the multiplexing unit 6 is defined, the demultiplexing unit 3 The optical path length of the irradiation light to the wave part 6 is defined. As shown in FIGS. 1 and 2, the optical path length of the irradiation light from the demultiplexing unit 3 to the multiplexing unit 6 is the optical path length from the beam splitter 301 to the incident position 9A on the surface of the measurement object 9 of the optical measurement device 1, This is the distance obtained by adding the optical path length of the scattered light inside the object to be measured 9 and the optical path length from the condensing position 9B on the surface of the object to be measured 9 to the beam splitter 601.

Further, the optical path length from the beam splitter 301 to the incident position 9A on the surface of the object 9 to be measured and the optical path length from the position 9B on the surface of the object 9 to the beam splitter 601 are, for example, the light measuring apparatus 1. Therefore, the optical path length of the scattered light in the object to be measured 9 can be calculated by subtracting these optical path lengths from the optical path length of the reference light.
Further, as described above, assuming that the optical path of the scattered light inside the object to be measured 9 is a substantially semicircular arc optical path as shown in FIG. 2, the depth of the optical path of the scattered light inside the object to be measured 9 ( Depth) can be calculated.

  Further, since the control unit 8 can move and drive the mirror 41, the optical path length of the reference light from the demultiplexing unit 3 to the multiplexing unit 6 can be defined as a predetermined optical path length. The desired optical path of the scattered light can be specified. In addition, the control unit 8 can detect the intensity of scattered light that has passed through a desired optical path in the measurement object 9.

  Further, the control unit 8, for example, the position of the mirror 41, the optical path length of the reference light, the optical path length of the scattered light in the measurement object 9, and the average depth (depth) of the optical path of the scattered light in the measurement object 9 ) And the like are stored in advance in the storage unit, and the control unit 8 uses the table, the position of the mirror 41, the drive signal, and the like in the optical path of the scattered light in the measurement object 9 during measurement. While specifying the length, the average depth of the optical path, and the like, the intensity of the scattered light passing through the desired optical path in the measurement target 9 may be detected.

In the embodiment described above, the optical path of the scattered light of the object 9 to be measured has a substantially semicircular arc shape as shown in FIG. 2, for example, but is not limited to this form.
For example, information such as the optical path of scattered light inside the object to be measured 9 and the depth of the optical path may be a result calculated by computer simulation such as the Monte Carlo method, or a short pulse laser beam may be applied to the object 9 to be measured. A result obtained by performing time-resolved measurement by irradiating and receiving scattered light from the object to be measured by a high-speed photodetector or the like may be used.

For example, the drive system control unit 82 outputs a control signal to the drive unit 42 of the light control unit 4 to control the movement of the mirror 41. In the present embodiment, the control unit 8 performs optical measurement while moving the mirror 41 and changing the optical path length.
The control unit 8 may acquire information related to the position of the mirror 41 by this control signal, or may acquire information related to the position of the mirror 41 by a sensor (not shown) that detects the position of the mirror 41.

  The second optical system 52 is provided with moving means 525 for moving the light collection position of the light reflected or scattered by the object 9 to be measured by a specified distance, and the drive system controller 82 causes the object 9 to be measured to move. Position control such as moving the light collection position of the light reflected or scattered by a predetermined distance may be performed. The drive system controller 82 corresponds to an embodiment of the position controller according to the present invention.

[Operation of Light Measuring Device 1]
Next, the operation of the light measuring apparatus 1 having the above configuration will be described with reference to the drawings.
First, low-coherence light is emitted from the low-coherence light source 2.
The light emitted from the low-coherence light source 2 is converted into parallel light by the lens 201 and then input to the beam splitter 301 of the demultiplexing unit 3 to be separated into reference light and irradiation light (power branching). One light (reference light) is reflected by the mirror 41 and is input again to the beam splitter 601 of the multiplexing unit 6 via the beam splitter 301. The other light (irradiation light) branched by the beam splitter 301 is collected by the optical lens 511 of the first optical system 51 and irradiated onto the object 9 to be measured.

  The light irradiated on the measurement object 9 is reflected or scattered in various directions. Among them, the light reflected or scattered in a direction substantially opposite to the incident direction passes through the optical lens 511. It is input to the beam splitter 301, combined with the reference light, and input to the beam splitter 601 of the multiplexing unit 6.

  As shown in FIG. 2, the light reflected by the measurement object 9 or the light scattered in the deep part of the measurement object 9 is irradiated with the irradiation position 9 </ b> A of the irradiation light to the measurement object 9 by the first optical system 51. Are condensed by the optical lens 521 from the position 9B different from the above and guided to the beam splitter 601 of the multiplexing unit 6. Then, in the beam splitter 601 of the multiplexing unit 6, the light guided by the second optical system 52 and the reference light are multiplexed.

  The optical lens 521 of the second optical system 52 receives, for example, scattered light that has propagated through the optical path as shown in FIG. Then, scattered light is input from the beam splitter 601 to the light detection unit 7, and the light detection unit 7 outputs an electrical signal having a level corresponding to the intensity of the input light.

  Further, the drive system control unit 82 of the control unit 8 outputs a control signal to the drive unit 42 to scan the mirror 41. When the mirror 41 scans, the frequency of the reference light is Doppler shifted, the optical path length of the reference light is changed, and the light detection unit 7 detects an interference signal. And the information processing part 81 of the control part 8 acquires the intensity | strength of scattered light by performing predetermined | prescribed detection processes, such as an envelope detection, for example to an interference signal. As this detection processing, a known technique of general OCT (Optical coherence tomography) may be used.

  As described above, the information processing unit 81 of the control unit 8 is an optical path through which the light reflected or scattered by the measurement object 9 propagates based on the position of the mirror 41 and the interference signal detected by the light detection unit 7. The measurement which specified length and the depth of the optical path of the scattered light in a to-be-measured object can be performed.

Further, the control unit 8 can generate a light intensity map at a specified depth in the measurement target 9 by scanning the mirror 41 and performing light measurement.
Further, the control unit 8 can generate a three-dimensional map of the light intensity in the measurement object 9 by performing the light measurement while shifting the condensing position of the second optical system 52. In addition, the control unit 8 can display the generated map on the display unit 85.

  In addition, the control unit 8 adjusts the optical path length of the optical path passing through the optical lens 511 and the optical path length of the optical path passing through the optical lens 521 (for example, adjusting these lengths differently), thereby The interference signal generated by the reflected / scattered light and the reference light collected by the optical lens 511 lens 2 of the optical system 51, and the reflected / scattered light and the reference light collected by the optical lens 521 of the second optical system 52. The resulting interference signal is separated with high accuracy.

  Moreover, the control part 8 can perform a more accurate optical measurement by prescribing | regulating an optical path length in consideration of the refractive index in a to-be-measured object.

[Second Embodiment]
FIG. 3 is a configuration diagram of an optical measurement device 1A according to the second embodiment of the present invention. FIG. 4 is a diagram for explaining the optical paths of the light irradiated by the light measurement device 1A shown in FIG. 3 and the scattered light in the deep part of the measurement object 9. In FIG. The description of the same configuration, effects, and the like as in the first and second embodiments is omitted.

  The light measurement apparatus according to the present invention may include a plurality of optical systems that collect light reflected or scattered by the measurement object 9 from different positions and guide the light to the multiplexing unit 6.

  Specifically, as shown in FIGS. 3 and 4, the light measurement apparatus 1 </ b> A according to the present embodiment includes light that is reflected or scattered by the multiplexing unit 6 including the beam splitter 601 and the beam splitter 602, and the measurement target 9. Is collected from a condensing position 9C different from the incident position 9A of the first optical system 51 and guided to the multiplexing unit 6.

  The beam splitter 602 is disposed between the light detection unit 7 and the beam splitter 601. Specifically, the beam splitter 602 is disposed at a position where the optical detector 7, the optical axis of the beam splitter 601, and the optical axis of the third optical system 53 intersect.

The third optical system 53 includes an optical lens 531 that condenses the light reflected or scattered by the measurement target 9 from the condensing position 9C and enters the beam splitter 602 of the multiplexing unit 6. The condensing position 9C of the optical lens 531 is disposed at a position different from the condensing position 9B of the second optical system 52.
In this embodiment, as shown in FIGS. 3 and 4, the condensing position 9C of the optical lens 531, the condensing position 9B of the optical lens 521, and the irradiation position 9A of the irradiation light by the optical lens 511 are arranged linearly. Has been.

The operation of the light measuring apparatus 1A having the above configuration will be briefly described.
As shown in FIG. 4, light that has been reflected or scattered by the measurement object 9 and emerges from the surface of the measurement object 9 includes light that has reached various depths.

  As shown in FIG. 4, the light irradiated on the measurement object 9 is reflected or scattered in various directions, and the light reflected or scattered in a direction substantially opposite to the incident direction is optical. It is input to the beam splitter 301 via the lens 511, combined with the reference light, and input to the beam splitter 601 of the multiplexing unit 6.

  As shown in FIG. 4, the light reflected by the measurement object 9 or the light scattered at the deep part of the measurement object 9 is irradiated with the irradiation position 9 </ b> A of the irradiation light to the measurement object 9 by the first optical system 51. The light is condensed by the optical lens 521 from a position 9B different from the above and guided to the beam splitter 601 of the multiplexing unit 6. Then, in the beam splitter 601 of the multiplexing unit 6, the light guided by the second optical system 52 and the reference light are multiplexed.

  As shown in FIG. 4, the light reflected by the measurement object 9 or the light scattered at the deep part of the measurement object 9 is irradiated with the irradiation position 9 </ b> A of the irradiation light to the measurement object 9 by the first optical system 51. Are condensed by the optical lens 531 from the position 9C different from the above and guided to the beam splitter 602 of the multiplexing unit 6. Then, in the beam splitter 602 of the multiplexing unit 6, the light guided by the third optical system 53 and the reference light are multiplexed.

  Then, the light from the beam splitter 602 of the multiplexing unit 6 is input to the light detection unit 7, and the light detection unit 7 outputs an electric signal having a level corresponding to the intensity of the input light.

  At this time, the control unit 8 controls the light control unit 4 to define the optical path length of the reference light, and scatters from the positions 9A, 9B, and 9C on the surface of the measured object 9 via the desired optical path. Light can be detected.

  Further, as described above, by providing means for scanning the second optical system 52 of the light measurement apparatus 1 according to the first embodiment, it is possible to detect scattered light from a desired position on the surface of the measurement object 9. it can.

[Third Embodiment]
FIG. 5 is a configuration diagram of an optical measurement device 1B according to the third embodiment of the present invention. The description of the same configuration, effects, and the like in the first to third embodiments is omitted.
For example, the polarization characteristics of the light reflected or scattered by the measurement object 9 may change from the polarization characteristics of the reference light. When this reference light and irradiation light are combined and interfered by the combining unit 6, the intensity of the interference signal may be lowered. For this reason, the optical measurement device 1C according to the present embodiment relatively increases the level of the interference signal by controlling the polarization state of the scattered light.

Specifically, as shown in FIG. 5, the light measurement device 1 </ b> B according to the present embodiment includes a polarization controller 522 that controls the polarization angle of light reflected or scattered by the measurement object 9.
As shown in FIG. 5, the polarization controller 522 is disposed between the optical lens 521 and the beam splitter 601 of the multiplexing unit 6, and is reflected or scattered by the measured object 9 under the control of the control unit 8, for example. Adjust the polarization state of the light. As the polarization controller 522, for example, a ½ wavelength plate or a ¼ wavelength plate can be employed.
For example, the control unit 8 controls the polarization controller 522 so that the signal level of the interference signal detected by the light detection unit 7 is increased, thereby controlling the polarization state of the scattered light.

  In the optical measurement device 1B having the above-described configuration, the control unit 8 controls the polarization controller 522 so that the signal level of the interference signal detected by the light detection unit 7, for example, is maximized. Thus, the polarization state is controlled. The light detection unit 7 detects an interference signal having a relatively large signal level.

  As described above, since the optical measurement device 1B includes the polarization controller that controls the polarization state of the light reflected or scattered by the measurement object 9, the optical measurement device according to the first and second embodiments In comparison, an interference signal having a relatively large signal level can be obtained.

[Fourth Embodiment]
FIG. 6 is a configuration diagram of an optical measurement device 1C according to the fourth embodiment of the present invention. The description of the same configuration, effects, and the like in the first to fourth embodiments is omitted.
The light measurement apparatus 1C according to the present embodiment measures a change in the intensity of reflected or scattered light due to a difference in wavelength by using, for example, a plurality of low coherence light sources having different center wavelengths. For example, if a low coherence light source 2A having a central wavelength of 780 nm and a low coherence light source 2B having a central wavelength of 830 nm are used, changes in oxygenated hemoglobin concentration, reduced hemoglobin concentration, and total hemoglobin concentration can be measured.

In detail, for example, the human head, from the outside to the inside, the scalp (including the fat layer), the skull, the dura mater, the subarachnoid space filled with cerebrospinal fluid, the buffy coat, the cerebral cortex (gray white) Quality) and white matter.
Near-infrared light irradiated from above the scalp reaches a depth of about 20 mm in the adult head, and is scattered by white matter or gray matter (cerebral cortex) and then emitted outside the scalp. For example, the scattered light is collected from a surface position 9B that is a predetermined distance, for example, about 30 mm away from the irradiation position 9A, and the blood volume (hemoglobin concentration) associated with the brain activity in the cerebral cortex from the detected intensity change of the scattered light. Capture changes. Hemoglobin includes oxygenated hemoglobin and reduced hemoglobin, and the oxygenated hemoglobin and the reduced hemoglobin have different absorption spectra. The molecular absorption coefficient at a wavelength of 780 nm is larger for reduced hemoglobin, and the molecular absorption coefficient at a wavelength of 830 nm is larger for oxygenated hemoglobin.

  The optical measurement device 1C according to the present embodiment measures changes in the oxygenated hemoglobin concentration, the reduced hemoglobin concentration, and the total hemoglobin concentration based on the above-described absorption spectrum characteristics.

  Specifically, as illustrated in FIG. 6, the light measurement device 1 </ b> C according to the present embodiment includes a low-coherence light source 2, light sources 2 </ b> A and 2 </ b> B that emit a plurality of low-coherence lights having different central wavelengths, and a lens 201. , 202, a wavelength synthesizing unit (dichroic mirror 203) for combining the light output from the plurality of light sources 2A, 2B according to the difference in wavelength, and a demultiplexing unit 3 (beam) for branching the light from the light sources 2A, 2B. A splitter 301), a movable mirror 41 that reflects the reference light branched by the demultiplexing unit 3, a drive unit 42 that moves the mirror 41 to change the optical path length, and a reference light branched by the beam splitter 301. A first optical system 51 that irradiates the measurement object 9 and guides the light reflected or scattered by the measurement object 9, and a second optical device that guides only the light reflected or scattered by the measurement object 9 52, a combining unit 6 (beam splitter 601) for combining the reference light reflected by the mirror 41 and the light guided by the second optical system 52, and branching the combined light according to the wavelength A wavelength branching unit (dichroic mirror 603) that receives light, a plurality of photodetectors 71 and 72 that receive the wavelength-branched light, and a control unit 8 that detects an interference signal according to the detection results of the photodetectors 71 and 72; Have

  The dichroic mirrors 203 and 603 have characteristics of reflecting light of a specific wavelength and transmitting light of other wavelengths.

The operation of the light measuring apparatus 1C having the above configuration will be briefly described.
For example, light emitted from the low-coherence light sources 2A and 2B is multiplexed by the dichroic mirror 203 via the lenses 201 and 202 and output to the demultiplexing unit 3. The combined light is input to the beam splitter 301 of the demultiplexing unit 3 and separated into reference light and irradiation light. The reference light is reflected by the mirror 41 and is input to the beam splitter 601 of the multiplexing unit 6 via the beam splitter 301 again. The other light (irradiation light) branched by the beam splitter 301 is collected by the optical lens 511 of the first optical system 51 and irradiated onto the object 9 to be measured.

  The light irradiated to the measurement object 9 is reflected or scattered in various directions according to the wavelength of the irradiated light, but the light reflected or scattered in the direction substantially opposite to the incident direction is The light is input to the beam splitter 301 via the optical lens 511, combined with the reference light, and input to the beam splitter 601 of the combining unit 6.

  As shown in FIG. 2, the light reflected by the measurement object 9 or the light scattered in the deep part of the measurement object 9 is irradiated with the irradiation position 9 </ b> A of the irradiation light to the measurement object 9 by the first optical system 51. The light is condensed by the optical lens 521 from a position 9B different from the above and guided to the beam splitter 601 of the multiplexing unit 6. Then, in the beam splitter 601 of the multiplexing unit 6, the light guided by the second optical system 52 and the reference light are multiplexed.

  The light output from the beam splitter 601 is reflected or transmitted by the dichroic mirror 603 according to the wavelength of the light, and is output to the light detection units 71 and 72. Specifically, for example, light having a wavelength of about 780 nm is reflected by the dichroic mirror 603 and output to the photodetector 72, and light of other wavelengths (for example, light having a wavelength of about 830 nm) is transmitted to the light detection unit 71. Is output.

  The control unit 8 detects an interference signal based on the results detected by the plurality of photodetectors 71 and 72. Then, the control unit 8 performs the light measurement while scanning the mirror 41.

  As described above, the optical measurement device 1C according to the present embodiment measures changes in the intensity of reflected or scattered light due to wavelength differences by using, for example, a plurality of low-coherence light sources having different center wavelengths. Can do. For example, if a low coherence light source 2A having a central wavelength of 780 nm and a low coherence light source 2B having a central wavelength of 830 nm are used, changes in oxygenated hemoglobin concentration, reduced hemoglobin concentration, and total hemoglobin concentration can be measured.

[Fifth Embodiment]
FIG. 7 is a configuration diagram of an optical measurement device 1D according to the fifth embodiment of the present invention. The description of the same configuration, effects, and the like in the first to fourth embodiments is omitted. The light measurement device 1D according to the present embodiment can detect a change in the polarization state of the light reflected or scattered by the object 9 to be measured.

  Specifically, as illustrated in FIG. 7, the light measurement device 1D includes a low coherence light source 2, a linear polarization conversion unit (polarizer 204) that converts light output from the low coherence light source 2 into linear polarization, A demultiplexing unit 3 (beam splitter 301) that branches the coherence light, a movable mirror 41 that reflects the reference light branched by the demultiplexing unit 3, and a demultiplexing unit 3 and a mirror 41 are installed, Means for changing the polarization state of light (for example, a quarter-wave plate 43), a drive unit 42 for moving the mirror 41 to change the optical path length, and the reference light branched by the beam splitter 301 to the object 9 to be measured A first optical system 51 that irradiates and guides the light reflected or scattered by the measurement object 9; a second optical system 52 that guides only the light reflected or scattered by the measurement object 9; Participation reflected by mirror 41 The combining unit 6 (beam splitter 601) that combines the light and the light guided by the second optical system 52, and the light combined by the combining unit 6 into light having polarization components orthogonal to each other. An optical element to be separated (polarization beam splitter 605), a plurality of photodetectors 71 and 72 that receive the separated light, and a control unit 8 that detects an interference signal according to the detection results of the photodetectors 71 and 72; Have

The operation of the optical measurement apparatus 1D having the above configuration will be briefly described.
The light output from the low coherence light source 2 is converted into linearly polarized light via the lens 201 and the polarizer 204 and then input to the beam splitter 301. The beam splitter 301 branches the input light into reference light and irradiation light.
One light (reference light) is input again to the beam splitter 301 via the quarter-wave plate 43 and the movable mirror 41.

  At this time, the ¼ wavelength plate 43 is arranged with a declination angle of 22.5 ° with respect to the plane of polarization of linearly polarized light. By doing so, the polarization plane of the light input again from the mirror 41 through the quarter wavelength plate 43 to the beam splitter 301 becomes linearly polarized light that has been subjected to 45 ° rotation conversion.

  The other light (irradiation light) is applied to the object 9 via the optical lens 511. Of the light reflected or scattered by the measurement object 9, the light reflected or scattered in a direction substantially opposite to the incident direction is collected by the optical lens 511 and combined with the reference light by the beam splitter 301.

Further, part of the light reflected or scattered by the measurement object 9 is collected by the optical lens 521 and combined with the reference light by the beam splitter 601.
The light output from the beam splitter 601 is separated into two orthogonal polarization components by the polarization beam splitter 605 and then input to the photodetectors 71 and 72, respectively. Detected.
The control unit 8 scans the position of the mirror 41 of the light control unit 4 and performs the measurement process.

As described above, in the optical measurement device 1D according to the present embodiment, the low coherence light source 2, the linear polarization conversion unit (polarizer 204) that converts the light output from the low coherence light source 2 into linearly polarized light, The light that is installed between the demultiplexing unit 3 and the mirror 41 and shifts the polarization angle of the reference light with respect to the irradiation light, and the light combined by the combining unit 6 Depending on the detection results of the optical elements (polarization beam splitter 605) for separating light having polarized components orthogonal to each other, a plurality of photodetectors 71 and 72 for receiving the separated light, and the photodetectors 71 and 72 Since the control unit 8 for detecting the interference signal is provided, a change in the polarization state of the light reflected or scattered by the measurement object 9 can be detected relatively easily.
Moreover, since two orthogonal linearly polarized light components are detected, even if the polarization state of the light reflected or scattered by the measurement object 9 changes, an interference signal independent of the change in the polarization state can be obtained. Can do.

  FIG. 8 is a diagram for explaining a modification of the optical measurement device 1D according to the fifth embodiment of the present invention. The description of the same configuration, effects, and the like as in the fifth embodiment is omitted.

When it is desired to change the polarization state of the light irradiated to the measurement object 9, for example, as shown in FIG. 8, a wave plate 512 for changing the polarization angle of the light is provided between the beam splitter 301 and the optical lens 511. Furthermore, a wave plate 521 that changes the polarization angle of light is provided between the beam splitter 601 and the optical lens 521.
Specifically, for example, in order to change the angle of the polarization plane of the linearly polarized light to be irradiated, half-wave plates may be inserted as the wave plates 512 and 521.
In addition, when the light to be irradiated is set to circularly polarized light, quarter wave plates may be inserted as the wave plates 512 and 521.

As described above, the light measurement apparatus 1 according to the present invention includes a low-coherence light source 2 that emits low-coherence light, and a component that separates the low-coherence light emitted from the low-coherence light source 2 into reference light and irradiation light. The wave control unit 4, the light control unit 4 that changes the optical path length of the reference light, the first optical system 51 that irradiates the measurement object 9 with the irradiation light, and the scattered light from the deep part of the measurement target 9 A second optical system 52 that collects and guides light from a position different from the irradiation position of the irradiation light to the object 9 to be measured by the first optical system 51, and the light guided by the second optical system 52 A multiplexing unit 6 that combines the light, a light detection unit 7 that detects the intensity of the light combined by the multiplexing unit 6, the optical path length of the reference light, and the intensity of the light detected by the light detection unit And a control unit 8 (information processing unit 81) that acquires information on the deep part of the object to be measured. Since a relatively simple configuration, it is possible to measure identifying the depth of the optical path of the scattered light optical path length and the object to be measured to a relatively high accuracy.
In addition, since a relatively expensive device such as a picosecond pulse laser device or a high-speed photodetector is not used, the light measurement device 1 according to the present invention is relatively inexpensive.

  The present invention is not limited to the embodiment described above. For example, the present invention may be realized by combining the above-described embodiments.

In the above-described embodiment, the light control unit 4 is configured by the mirror 41 and the drive unit 42, but is not limited to this mode. For example, the light control unit 4 may change the optical path length by a piezo element.
In the above-described embodiment, the beam splitter 301 is employed as the demultiplexing unit 3, but the present invention is not limited to this form. For example, the demultiplexing unit 3 may be configured with an optical fiber, an optical coupler, or the like. The multiplexing unit may be configured with an optical fiber, an optical coupler, or the like.

1 is a configuration diagram of a light measurement apparatus 1 according to a first embodiment of the present invention. It is a figure for demonstrating the optical path of the scattered light of the deep part of the to-be-measured object. It is a block diagram of the optical measurement apparatus 1A which concerns on 2nd Embodiment of this invention. It is a figure for demonstrating the optical path of the irradiation light by the light measuring device 1A shown in FIG. 3, and the scattered light of the deep part of the to-be-measured object 9. FIG. It is a block diagram of the optical measurement apparatus 1B which concerns on 3rd Embodiment of this invention. It is a block diagram of the optical measurement apparatus 1C which concerns on 4th Embodiment of this invention. It is a block diagram of optical measurement apparatus 1D which concerns on 5th Embodiment of this invention. It is a figure for demonstrating the modification of optical measurement apparatus 1D which concerns on 5th Embodiment of this invention.

Explanation of symbols

1, 1A, 1B, 1C, 1D Optical measurement device 2 Low coherence light source 3 Demultiplexing unit 4 Optical control unit 6 Multiplexing unit 7 Optical detection unit 8 Control unit 9 Object to be measured (sample)
31 Beam splitter 41 Mirror (movable mirror)
42 driving unit 43 wave plate 51 first optical system 52 second optical system 71 photodetector 81 information processing unit 82 driving system control unit 85 display unit 201 lens 203 dichroic mirror 204 polarizer 511 optical lens 521 optical lens

Claims (9)

A low coherence light source that emits low coherence light;
A demultiplexing unit that separates low-coherence light emitted from the low-coherence light source into reference light and irradiation light;
A light control unit that varies an optical path length of the reference light;
A first optical system for irradiating the object to be measured with the irradiation light;
A second optical system for collecting and guiding the scattered light from the deep part of the object to be measured from a position different from the irradiation position of the irradiation light to the object to be measured by the first optical system;
A multiplexing unit that combines the light guided by the second optical system and the reference light;
And a light detection unit that detects the intensity of the light combined by the multiplexing unit.   The optical measurement apparatus according to claim 1, further comprising: an information processing unit that acquires information related to a deep portion of the measurement target based on an optical path length of the reference light and an intensity of light detected by the light detection unit.   The light measurement apparatus according to claim 1, further comprising: a plurality of optical systems that collect light reflected or scattered by the measurement object from different positions and guide the light to the multiplexing unit.   The light measurement apparatus according to claim 1, further comprising a position control unit that controls a light collection position of light reflected or scattered by the object to be measured.   The optical measurement apparatus according to claim 1, further comprising a polarization controller that controls a polarization state of light reflected or scattered by the object to be measured. The low-coherence light source includes a plurality of light sources that emit a plurality of low-coherence lights each having a different center wavelength,
A wavelength synthesizing unit that combines low-coherence lights having different center wavelengths output from the plurality of light sources and outputs the multiplexed light to the demultiplexing unit;
A wavelength branching unit that branches the light combined by the combining unit according to the wavelength;
The light measurement device according to claim 1, further comprising: a plurality of light detection units that receive each of the lights branched by the wavelength branching unit. A linear polarization converter that converts low coherence light emitted from the low coherence light source into linearly polarized light;
Means for changing the polarization state of the reference light;
An optical element that separates the light combined by the multiplexing unit into light having polarization components orthogonal to each other;
The light measurement device according to claim 1, further comprising: a plurality of light detection units that receive each of the lights separated by the optical element.   The light measurement device according to claim 7, wherein a wavelength plate is provided in the first optical system or the second optical system.   The light measurement device according to claim 1, wherein the light control unit includes a movable mirror that reflects the reference light from the demultiplexing unit and causes the light to enter the multiplexing unit.

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