JP2012061232A - Optical internal information measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal information measuring device whose measurement accuracy can be improved by increasing the depth resolution when detection internal information of a subject to be measured is retrieved and whose light intensity efficiency can be increased.SOLUTION: A jaundice meter as an optical internal information measuring device emits light from LED's 21 and 22 in a measurement head Hd in the direction inclined with respect to a normal NL to a measuring window WM whose surface to be brought into contact in parallel with the body surface of the subject to be measured is formed on a measurement reference surface FP. A plurality of reflected light beams which go out of the body through a long optical path LR and a short optical path SR in the body are individually detected by light receiving elements PD1 and PD2, and a bilirubin level of an intracorporal layer of fat PI is calculated. The depth distribution of the long optical path LR and the short optical path SR can be easily sharpened by oblique incidence and the depth resolution is improved. The light intensity efficiency can be increased by using the directivity of the incident light.

Description

  The present invention relates to an optical internal information measuring device used for a jaundice meter or the like.

  2. Description of the Related Art In recent years, development of technology for accurately measuring internal information of a target object by making light incident on the target object from the surface of the target object is progressing. In particular, regarding a technique for noninvasive measurement of in-vivo internal information, there is a great demand for high-precision measurement. As a method of obtaining information inside the living body, the light scattered and propagated inside the living body depends on the scattering coefficient and absorption coefficient of the living body, and the light scattered inside the living body is detected and analyzed. In general, a method of obtaining a scattering coefficient, an absorption coefficient, and the like and calculating values such as the concentration and absolute amount of a specific component inside the living body from these coefficients is generally used.

  For example, in a two-pass measurement type jaundice meter, light is radiated toward a living body, light emitted through different optical paths in the living body is detected from two locations, and the amount of light at a specific wavelength of the detected light is subcutaneously determined. It is known to calculate the bilirubin concentration in fat. Further, in the pulse oximeter, red light and infrared light are alternately emitted toward the living body, and the oxygen saturation is calculated from the respective light quantity ratios emitted through the living body.

  Patent Document 1 proposes a transcutaneous bilirubin concentration measuring apparatus that can measure the bilirubin concentration in subcutaneous fat in a non-contact manner using a measurement principle that applies the Law of Lambert Beer. In such a conventional apparatus, light is projected perpendicularly to the skin surface in order to obtain internal information of an arbitrary position range inside the living body using the two-light path measurement method.

JP 2000-279398 A

  However, in the device structure of Patent Technology 1, it cannot be said that sufficient measurement accuracy is obtained in the case of a person with a lot of melanin pigments on the skin surface, and therefore there is an increasing demand for obtaining more accurate internal information. Yes. The reason for the poor measurement accuracy is that it is necessary to extract the internal information of only the subcutaneous tissue part where the bilirubin in the blood is removed from the information on the skin surface such as the dermis and epidermis, but only the subcutaneous fat information is obtained with sufficient accuracy. It can be said that it has not been taken out. In addition, when the internal information such as the inside of the skin is not uniform, a depth resolution capable of accurately measuring the internal information of a layer of a predetermined depth is required. The distance relationship between the light emitting unit and the light detecting unit must be designed with high accuracy, and depth resolution cannot be obtained due to design errors, or internal information on the part to be obtained cannot be obtained. It can be said that was not obtained.

  Further, when measuring internal biological information, measurement with a low light amount that does not cause harm to the living body is desired, so it is important to efficiently secure the detected light amount. However, conventionally, in order to obtain information on the subcutaneous tissue portion, the incident optical axis of light to the living body and the optical axis of the light receiving element are set perpendicular to the living body, and the axis does not intersect in the subcutaneous tissue portion. It has a structure with high light loss. Specifically, in the case of skin that is a scattering medium, the mean free path is about 2 mm, and the amount of light decreases exponentially with distance. For this reason, even if light that does not affect the skin is incident, it is desirable to improve the accuracy in order to obtain a sufficient amount of light output in the light receiving element. However, the current technology is satisfactory in terms of the balance between the light amount and the accuracy. Not.

  The present invention has been made in view of such circumstances, and improves the measurement accuracy by improving the depth resolution when extracting the internal information, and the optical internal information that can increase the light quantity efficiency. It aims at providing a measuring device.

  In order to solve the above-mentioned problem, the invention of claim 1 makes light incident on the target body from the surface of the target object to be measured, detects the light emitted through the inside of the target object, and detects the target. An optical internal information measuring device that measures internal information of a body, and projects light toward the target from an angle with a predetermined angle with respect to a normal line of a measurement reference plane that is parallel to the surface of the target And a plurality of signals expressing the respective received light amounts are installed so as to receive light emitted through different paths inside the object through the measurement reference plane. It is characterized by comprising: a light receiving means; and a calculating means for calculating internal information of the object using the plurality of signals.

  According to a second aspect of the present invention, in the optical internal information measuring device according to the first aspect of the present invention, the optical internal information measuring device further includes a diaphragm means for restricting a light beam emitted from the light projecting means.

  According to a third aspect of the present invention, in the optical internal information measuring device according to the first or second aspect, the light receiving means detects the plurality of signals in parallel by a plurality of light receiving elements. And a plurality of signals obtained from the plurality of light receiving elements, respectively.

  According to a fourth aspect of the present invention, in the optical internal information measuring device according to the first or second aspect, the light receiving means has a plurality of positions at different distances from the light projecting means as respective light receiving ends. A plurality of light receiving elements that sequentially detect the plurality of signals in time order, and the plurality of signals are obtained from the plurality of light receiving elements, respectively.

  According to a fifth aspect of the present invention, in the optical internal information measuring device according to the first or second aspect, the light receiving means sequentially sets the light receiving positions at a plurality of positions having different distances from the light projecting means. And a sequential light detecting means for detecting the plurality of signals in a time sequential manner while being moved, wherein the plurality of signals are respectively obtained from the plurality of light receiving elements.

  Further, the invention of claim 6 is the optical internal information measuring device according to any one of claims 3 to 5, wherein the light projecting means is a fixed light projecting means for performing light projection in a fixed optical path; It is characterized by becoming.

  Further, the invention of claim 7 is the optical internal information measuring device according to any one of claims 3 to 5, wherein the light projecting means sets the light projecting path in a time sequential manner among a plurality of light projecting paths. And a light-projecting path switching means for switching to.

  According to an eighth aspect of the present invention, there is provided the optical internal information measuring device according to the seventh aspect, wherein the light projection path switching means switches the light projection position in time sequence among a plurality of light projection positions. Means.

  The invention according to claim 9 is the optical internal information measuring device according to claim 7, wherein the light projecting path switching means switches the light projecting direction in a time sequence between a plurality of light projecting directions. Means.

  The invention according to claim 10 is the optical internal information measuring device according to any one of claims 1 to 9, wherein the measurement reference surface is defined on an end face of a measuring head of the optical internal information measuring device. In addition, a measurement window is formed on the measurement reference plane, the light projecting unit includes a light emitting element disposed in a light projecting chamber formed in the measurement head, and the light receiving unit is configured to measure the measurement. A plurality of light receiving elements respectively disposed in a plurality of light receiving chambers formed in the head, and the plurality of light receiving chambers are disposed at different distances from the light projecting chamber along the measurement window. It is characterized by that.

  The invention of claim 11 is the optical internal information measuring device according to claim 10, wherein the measurement window is formed in each of the light projecting window formed in the light projecting chamber and the plurality of light receiving chambers. A plurality of unit light receiving windows formed in a single plane, and each unit light receiving window is formed in a long shape having a short axis in a direction from the unit window toward the light projecting window. It is characterized by.

  The invention according to claim 12 is the optical internal information measuring device according to any one of claims 1 to 11, wherein the light emitting means emits light of a plurality of wavelengths, and the light receiving means Receiving light emitted through the different paths for each of a plurality of wavelengths of light, the parameter calculation means, based on the plurality of signals obtained for each of the plurality of wavelengths of light, the internal information parameter Is calculated.

  The invention according to claim 13 is the optical internal information measuring device according to claim 12, wherein the light receiving means separates light components of the plurality of wavelengths by wavelength filtering of the received light. To do.

  The invention of claim 14 is the optical internal information measuring device according to claim 12, wherein the light projecting means projects light of a plurality of wavelengths in a time division manner, and the light receiving means receives the received light. By separating the light of the plurality of wavelengths by time division.

  The invention of claim 15 is the optical internal information measuring device according to claim 12, wherein the light projecting means projects light while modulating light of a plurality of wavelengths at a plurality of modulation frequencies, respectively. The means is characterized in that the light components having the plurality of wavelengths are separated by demodulating the received light at the plurality of modulation frequencies.

  Further, the invention of claim 16 is the optical internal information measuring device according to any one of claims 1 to 15, wherein the object is a living body to be examined, and the internal information parameter is It is a parameter corresponding to a physiological or pathological examination value inside the living body.

  According to invention of Claim 1 thru | or 16, it measures by making this measurement reference plane parallel to a target object surface by comprising so that it may project lightly with respect to the normal line of a measurement reference plane. Accordingly, the measurement light is incident obliquely with respect to the normal of the object surface. As a result, the depth distribution of each of the different paths passing through the inside of the object to the light receiving means becomes sharp, and the depth resolution is improved. Depth resolution can be increased. For this reason, it becomes possible to obtain | require the internal information in the desired range of a target object accurately.

  In addition, by making the measurement light incident obliquely, the ratio of the optical path length in the depth direction of the measurement light (based on the optical path length) when the optical path length in the direction (lateral direction) along the surface of the object is used as a reference. (Aspect ratio) becomes smaller. As a result, the depth error amount with respect to the shift amount of the positions of the plurality of light receiving ends is reduced, and error tolerance is increased.

  In addition, by making the measurement light incident obliquely, it becomes easy to direct the incident optical axis to the measurement target region inside the object, and the use efficiency of the light amount can be improved as compared with the case where it is incident vertically.

  According to the second aspect of the present invention, the directivity can be enhanced by narrowing the luminous flux, and therefore the light quantity efficiency can be further increased.

  According to the invention of claim 5, since the light receiving means detects the plurality of signals sequentially in time while sequentially moving the light receiving position to a plurality of positions having different distances from the light projecting means, the number of light receiving elements is reduced. Can be reduced.

  According to the seventh to ninth aspects of the present invention, since the light projecting path switching means in the light projecting means realizes different paths by switching the light projecting position or the light projecting direction in time sequence, the number of light emitting elements is reduced. it can.

  According to the eleventh aspect of the present invention, each unit light receiving window is formed in a long shape whose short axis is the direction toward the light projecting window, so that the depth resolution can be improved while preventing a decrease in the detected light amount.

  According to the invention of claim 13, by separating the light components of the plurality of wavelengths by wavelength filtering of the received light, the light of the plurality of wavelengths can be simultaneously emitted without alternately emitting the light of the plurality of wavelengths. Since it becomes possible to enter the object, the time can be shortened.

  According to the invention of claim 15, light having a plurality of wavelengths is projected while being modulated with a plurality of modulation frequencies, and light having a plurality of wavelengths is demodulated by demodulating the received light respectively with the plurality of modulation frequencies. Since light of a plurality of wavelengths can be incident on the object at the same time without alternately emitting light, the time can be reduced.

It is a figure which shows the comparison with a prior art regarding a photon detection area | region. It is a figure which shows the comparison with a prior art regarding a photon detection area | region. It is a figure which shows the comparison with a prior art regarding depth resolution. It is a figure which shows the comparison with a prior art regarding depth resolution. It is a figure explaining the influence on the measurement result by the error of the mutual distance of two light receiving elements. It is a figure explaining the influence on the measurement result by the error of the mutual distance of two light receiving elements. It is a figure which shows the comparison with a prior art regarding light quantity efficiency. It is a figure which shows the comparison with a prior art regarding light quantity efficiency. It is a figure which shows the external appearance of the jaundice meter comprised using the optical internal information measuring device which concerns on this invention, (a) is a whole perspective view, (b) It is a bottom view of a measurement head, (c) is the longitudinal section FIG. It is a schematic diagram of the measurement head of the jaundice meter according to the present embodiment. It is a block diagram which shows the electrical component of the jaundice meter which concerns on this embodiment. It is a flowchart shown about the measurement operation | movement procedure of the jaundice meter which concerns on this embodiment. It is a figure which illustrates various combinations of a light projection means and a light reception means. It is a figure which shows the modification regarding light projection / reception of the light of a some wavelength. It is a figure which shows the modification regarding light projection / reception of the light of a some wavelength.

<1. Measurement Principle of Embodiment>
In the following, a jaundice meter is disclosed as an embodiment of the optical internal information measuring device of the present invention, but before entering into a detailed description of the jaundice meter, the measurement principle of the jaundice meter which is the premise of the present embodiment will be described. This will be explained in comparison with the measurement principle of the meter. Here, the conventional jaundice meter as an example is a jaundice meter in the bilirubin concentration measuring apparatus of Patent Document 1, and the degree of yellowness due to bilirubin present in the subcutaneous tissue of a newborn is expressed as 2 of blue wavelength and green wavelength. It is an apparatus that captures the optical density difference in the wavelength range.

  First, common points between the jaundice meter of this embodiment and the conventional measurement principle will be described.

  In general, Lambert-Beer Law is used to determine the concentration of an internal substance from the absorbance. If you want to measure the concentration of the substance to be measured contained in a sample, enter the sample with light of a wavelength that the substance absorbs significantly, detect the light reflected in the material, and identify the amount of light. The concentration of the substance to be measured can be obtained based on the distance (corresponding to the thickness) passing through the sample and the light absorption rate. The Lambert-Beer law equation is expressed as the following equation (1) using the absorption rate (absorbance) A, the absorption coefficient α, the thickness L, and the concentration C of the substance to be measured.

A = αLC (1)
From the above equation (1), it can be seen that the absorbance A is determined by the product of the molar absorption coefficient α, the molar concentration C, and the material thickness L of the substance to be measured.

  The jaundice meter can be configured as a device for determining the bilirubin concentration C from the measured absorbance A according to Lambert-Beer's law based on the known molar absorption coefficient α and substance thickness L of bilirubin.

  Incidentally, in order to obtain the light absorption coefficient α in the subcutaneous tissue portion, it is necessary to know the amount of light incident on the subcutaneous tissue portion and the amount of light reflected from the subcutaneous tissue portion. For this purpose, two basic information are used: light absorption in the first optical path passing through a specific subcutaneous tissue partial region (measurement region) and light absorption in the second optical path not passing through the measurement region. Based on these ratios, the light absorption coefficient α for only the region to be measured can be obtained. This is the basic idea of the two optical path measurement method.

  In addition, standardization is performed in which light having a wavelength that is not absorbed by bilirubin that is a substance to be measured is used as reference light, and the influence of light absorption by substances other than bilirubin on the optical path is removed.

  When blue light is used as the measurement light and green light is used as the reference light, the concentration calculation formula applying Lambert-Beer's law used in the jaundice meter in the two-path measurement method is the following formula (2) and It is expressed as (3).

εb (λb) × C × ΔL = Z (2)
Z = log {Ε1 (λg) / Ε1 (λb)} − log {Ε2 (λg) / Ε2 (λb)} (3)
However,
Εb (λb): the amount of detection light for the blue wavelength λb;
εb (λb): bilirubin extinction coefficient for blue wavelength λb;
C: bilirubin concentration;
ΔL: Effective optical path length difference = L1-L2;
L1: effective optical path length of the first optical path (long optical path);
L2: Effective optical path length of the second optical path (short optical path);
Ε1 (λb): Light quantity measurement data in the blue wavelength region in the first optical path;
Ε2 (λb): Light quantity measurement data in the blue wavelength region in the second optical path;
Ε1 (λg): Light quantity measurement data in the green wavelength region in the first optical path;
Ε2 (λg): Light quantity measurement data in the green wavelength region in the second optical path.

  Rewriting equation (3) yields the following equations (4A) to (4D). Equation (4A) is obtained by multiplying the attenuation factor (Kg) of green light caused by causes other than bilirubin by the optical attenuation factor F due to bilirubin, and the total attenuation factor (Kb) of blue light including bilirubin. The expression (4D) corresponds to an expression of the expression (2) as an exponential function.

Kb = Kg x F (4A)
Kb = E1 (λb) / Ε2 (λb) (4B)
Kg = Ε1 (λg) / Ε2 (λg) (4C)
F = exp {−εb (λb) × C × ΔL} (4D)
When measuring the face such as the forehead and cheeks of the human body with a jaundice meter, the epidermis is about 0.2 mm, the dermis is about 2.0 mm, and the subcutaneous tissue is about 2.0 mm. Is done. Jaundice meters are often used for the examination of newborn jaundice, but there is a strong demand for depth resolution accuracy especially when examining newborns.

  Next, of the principles of the jaundice meter according to the present embodiment, points that are different from the principles of the conventional jaundice meter will be described below.

  In the conventional jaundice meter, the light from the light source is vertically incident on the skin surface. However, in the jaundice meter according to the present embodiment, the light from the light source is configured to enter the skin surface in an oblique direction. Although a specific apparatus configuration will be described later, such oblique incidence is a main feature of this embodiment.

  First, the incident angle θ of light from the skin surface is defined as an angle measured from the normal direction of the skin surface.

  FIG. 1A is a diagram schematically showing a relationship (light path crossing relationship) between a light incident range and a detection light extraction range in the case of conventional vertical incidence (incidence angle θ = 0). FIG. 1B is a diagram illustrating an optical path crossing relationship in the case of oblique incidence according to the present embodiment (that is, the incident angle θ> 0). In each case, the position Pin on the skin surface T0 is a light projection position, and the two positions P1 and P2 are light detection positions. Further, the boundary surface T1 indicates the boundary between the epidermis region and the fat layer region. In addition, the conventional apparatus of FIG. 1A shows a type in which the detection optical axes Loso and Lolo are located on both sides of the incident optical axis Loin, and not only the incident optical axis but also the detection optical axis is substantially vertical. However, the following principle is the same in other cases.

  In the conventional apparatus shown in FIG. 1A, a cone-shaped area centering on the incident optical axis Loin perpendicular to the skin surface is the light incident range on the human body. Further, a cone-shaped region centering on the detection optical axis Lolo of the long optical path perpendicular to the skin surface is a light detectable range by the first light receiving element, and the detection light of the short optical path perpendicular to the skin surface. A conical region centered on the axis Loso is a light collection range by the second light receiving element. The reason why each region becomes a conical region is due to the directivity of both the light incident from the light source and the light detection by each light receiving element.

  Therefore, of the light from the light source, the light observed by the first light receiving element far from the light source at the position P1 is the light reflected by the region Sol where the light incident cone and the first light detection cone overlap. The light observed by the second light receiving element near P2 at the position P2 is light reflection in a region Sos where the light incident cone and the second light detection cone overlap. Here, “reflection” of light is used as a term including “scattering”. Since the amount of reflected light is complementary to the amount of absorbed light, this apparatus indirectly observes each of the light absorption in the two regions Sol and Sos.

  On the other hand, as shown in FIG. 1B, in the present embodiment, the incident optical axis Lnin is not zero with respect to the normal direction of the skin surface (generally, the direction perpendicular to the surface of the measurement object). The incident angle is a finite angle θ, and the inclined cone-shaped region centering on the incident optical axis Lnin is the light incident range on the human body. In this embodiment, the two detection optical axes Lnlo and Lnso in each of the long optical path and the short optical path are also finite angles (−φ1) and (−φ2) that are not zero with respect to the normal direction of the skin surface. So as to be inclined obliquely in the opposite direction to the incident optical axis Lnin. In addition, when the incident optical axis is set to be obliquely incident with respect to the normal direction of the skin surface, the two detection optical axes have an intersecting axis in the subcutaneous tissue portion even if zero with respect to the normal direction. Therefore, the same effect can be obtained. These angles may be φ1 = φ2 or may be different from each other.

  The inclined cone-shaped area centered on the incident optical axis Lnin is the light incident range on the human body, and the inclined cone-shaped areas centered on the detection optical axes Lnlo and Lnso are the first and second areas. It is each light collection range of a light receiving element. The reason why these regions are conical is that directivity is given to both the light incident from the light source and the light detection by each light receiving element.

  Therefore, the light observed by the first light receiving element of this embodiment is light reflected by the region Snl where the light incident cone and the first light detecting cone overlap, and the light observed by the second light receiving element is The light reflection in the region Sns where the light incident cone and the second light detection cone overlap. As a result, this apparatus indirectly observes each of light absorption in the two regions Snl and Sns.

  FIG. 1A is compared with FIG. In FIG. 1A, in order to improve the depth resolution, it is necessary to reduce the difference between the volume centroid of the measurement region Sos of the short optical path and the volume centroid of the measurement region Sol of the long optical path. However, for this purpose, it is necessary to reduce the distance between the two light receiving elements (the direction parallel to the skin surface), that is, the distance between the position P1 and the position P2, and then the two regions Sol and Sos overlap. The difference between the volume centroids of the non-applicable portions, that is, their intrinsic regions Rol and Ros (see FIG. 2A) is reduced, and the difference in the detected light amount of the two light receiving elements is reduced. Since there is an error in the light amount detection by the light receiving element, such a weak difference in the detected light amount cannot be accurately captured, and as a result, the depth resolution is not improved.

  Also in the embodiment of FIG. 1B, in order to improve the depth resolution, the difference between the volume centroid of the measurement region Sns of the short optical path and the volume centroid of the measurement region Snl of the long optical path is reduced to some extent. Therefore, the lateral distance between the two light receiving elements is also reduced. However, unlike the conventional apparatus, in the case of the embodiment, the portions where the two regions Snl and Sns do not overlap, that is, their intrinsic regions Rnl and Rns. The difference in the center of gravity in (see FIG. 2B) is not as small as that in the conventional apparatus in FIG. In FIG. 2A, since both of the intrinsic regions Rol and Ros are vertically long regions (regions that are long in the direction perpendicular to the skin surface), the volume centroid difference in the depth direction is small. On the other hand, in FIG. 2 (b), the shapes and positions of the eigenregions Rnl and Rns are considerably different from each other, the depth distribution of each is sharp, and the volume centroids in the depth direction. This is because a difference is likely to appear.

  As shown in FIG. 2, the difference (| Rol-Ros |, | Rnl-Rns |) of the detected light amount when the lateral distance between the two light receiving elements is reduced is | Rol-Ros | <| The relationship Rnl-Rns | always holds. This is because, in FIG. 2B, the geometric shapes of the eigenregions Rnl and Rns are considerably different from those of the eigenregions Rol and Ros in FIG. Therefore, since the difference in the detected light amount is larger in | Rnl-Rns | in FIG. 2B, the influence of the error is reduced, resulting in improved depth resolution.

  FIG. 3 shows this difference in terms of the depth of intersection between the incident optical axis and the detection optical axis. However, the conventional apparatus in FIG. 3 is of a type in which the light receiving positions P1 and P2 are arranged on one side of the light projecting position Pin and the detection optical axis is inclined in order to facilitate comparison with the embodiment. Illustrated. As shown in FIG. 3, the depth difference Dn between the intersections Qnl and Qns in the case of oblique incidence is smaller than the depth difference Do at the intersections Qol and Qos in the case of normal incidence (θ = 0). This shows that the depth resolution is higher in the case of oblique incidence (Dn <Do) even if the lateral distance between the two light receiving elements is the same.

  As shown in FIG. 3, when the positions P1 and P2 of the light receiving elements and the light projecting position Pin are made the same as in the prior art and only the light incident axis is tilted, the measured depth differs from the conventional one. As shown in FIG. 4, by adjusting the angle on the light receiving side (specifically, by reducing the inclination of the light receiving axis), the intersection Qns of the short light path is positioned in the skin region, and the long light path Since the intersection point Qnl can be positioned in the fat layer, the problem of measurement depth does not occur. Alternatively, if the inclination of the light receiving axis of the light receiving element P1 is set as shown by the alternate long and short dash line in FIG. 4, the intersection Q'nl substantially matches the depth of the conventional one, and a better result can be obtained.

Further, in the arrangement of the embodiment, the influence on the measurement result due to the error in the mutual distance between the two light receiving elements is relatively small. The reason is described with reference to FIG. Consider a rectangle V0 in which the incident optical axis Sin of light is a diagonal line and the positions P1 and P2 of the two light receiving elements are two side positions. In this rectangle V0, the lateral distance r between the light receiving elements is shown in FIG.
tanθ = r / D (5A)
That is,
D = r / tan θ (5B)
Are in a relationship. However, the depth width D is a difference in the depth direction of the diagonal points of the rectangle.

From equation (5B), when an error Δr occurs in the position between the light receiving elements, the error ΔD generated in the depth width D is
ΔD = Δr / tan θ (6)
It becomes.

However, since the position error of each of the two light receiving elements is random, considering the position error ΔP of each light receiving element and considering the case where the error directions of the two light receiving elements are reversed, on average, The positional error Δr between the light receiving elements is
Δr = 0.5 × ΔP (7)
ΔD = 0.5 × ΔP / tan θ (8)
Can also be written. For simplicity, equation (6) is used below.

  When the tilt angle θ of the incident optical axis is large (FIG. 5), the value of tan θ also increases, so the reciprocal (1 / tan θ) becomes a small value, and the influence of the position error Δr on the depth width error ΔD is small.

  However, when the tilt angle θ of the incident optical axis is small (FIG. 6), the value of tan θ is small, so the reciprocal (1 / tan θ) is a large value, leading to the depth width error ΔD due to the position error Δr. The effect of. In the simple model considered here, when the angle θ is almost zero, (1 / tan θ) is infinite, but in reality, it is a finite value due to various other factors.

  This is the ratio of the optical path length in the depth direction of the measurement light (optical path length) when the measurement light is incident obliquely and the optical path length in the direction (lateral direction) along the surface of the object is used as a reference. Aspect ratio = ΔD / Δr) is reduced, and as a result, the depth error amount with respect to the shift amount of the positions of the plurality of light receiving ends is reduced. Therefore, the error tolerance is increased in the apparatus of the embodiment as compared with the conventional apparatus.

  Moreover, in the apparatus of the embodiment, the light amount loss of light to be used can be reduced. As shown in FIG. 7, since the incident optical axis Loin is vertical in the conventional apparatus, it corresponds to the intersection of the incident light cone centered on the incident optical axis Lo and the detection light cone centered on the detection optical axis Lo. The measured region TG to be measured is at a position away from the incident optical axis Loin. On the other hand, when the incident optical axis Loin is inclined as in the embodiment, the incident optical axis Loin can be directed to the measurement region TG.

  Generally, a light emitting element has the maximum light emission intensity in the direction of the light projecting axis, and the light emission intensity decreases as the distance from the light emitting element increases. Therefore, in the conventional apparatus, a non-maximum portion of the light amount distribution in the cross section of the incident light cone is used as shown in FIG. 8 as the light amount efficiency E0, but in the embodiment, as shown in FIG. 8 as the light amount efficiency En. The maximum part of the light quantity distribution in the cross section of the incident light cone can be used.

  As described above, in the embodiment, by providing the directivity toward the measurement region TG, the light distribution width W can be narrowed and the light amount loss can be suppressed.

  As described above, in the embodiment of the present invention, depth resolution and measurement accuracy can be improved by obliquely entering light. In addition, the light quantity efficiency can be increased by setting the directivity of the light emitting element so that the incident optical axis passes through the region to be measured.

  Hereinafter, a specific configuration and operation of the apparatus according to the embodiment will be described.

<2. Specific Configuration and Operation of Embodiment>
<2-1. Outline and configuration of jaundice meter>
Fig.9 (a) is a whole perspective view which shows the external appearance of the jaundice meter 10 which is embodiment of this invention. FIG. 9B is a bottom view of the measuring head Hd, and FIG. 9C is a longitudinal sectional view thereof.

  The jaundice meter 10 is a handy type jaundice meter as shown in FIG. 9 (a), and has a casing 11 that fits in the palm of a measurer (such as a doctor). Electrical components (see FIG. 11) described later are arranged. Further, a display unit 12 including a liquid crystal display that variably displays the measurement result, that is, the concentration of bilirubin deposited on the subcutaneous fat, is provided on the rear end side of the upper surface of the casing 11. Further, a power switch 11a is disposed on the rear side of the side surface of the casing 11, and a reset switch 45 (see FIG. 11) (not shown) is provided in FIG. 9 (a).

  Further, a rectangular parallelepiped measuring head Hd is provided at the front end side of the casing 11 so as to be able to move out and with respect to the casing 11 as indicated by an arrow AR. This measuring head Hd is urged in a protruding direction (AR side of the arrow) with respect to the casing 11 by urging means (not shown) such as a spring member, and the measurer is a part of the human body of the person to be measured, for example, When pressed against the forehead portion of the head and lightly pressed, the measuring head Hd is pushed into the casing 11 against the urging force of the urging means, and a first wavelength region light source (blue LED) 21 and a second wavelength region to be described later. The light source (green LED) 22 (see FIG. 9C) is configured to emit light.

  Then, when the measurement head Hd is pushed in and the blue LED 21 and the green LED 22 (see FIG. 9C and FIG. 10) emit light, the blue light and the green light from the blue LED 21 and the green LED 22 are shown in FIG. 9B. The light emitted from the light projection window W0 of the measuring head Hd in time order is incident on the forehead (measuring object) of the measurement subject and the light beam scattered in the body as described above is emitted from the measuring head Hd. The light enters the casing 11 through the light receiving windows W1, W2.

  As a specific structure of the measurement head Hd, as shown in FIGS. 9B and 9C, the measurement window WM is defined by a flat surface FP corresponding to the end face of the measurement head Hd. The measurement reference surface in this embodiment is the flat surface FP. The measurement window WM includes a light projecting window W0 serving as an outlet for light from the light projecting chamber R0 and unit light receiving windows W1 and W2 serving as light entrances to the two light receiving chambers R1 and R2, respectively. Each unit light receiving window W1, W2 has a short axis in the direction from the unit window W1, W2 to the light projecting window W0, and a long axis in the direction perpendicular to the unit window W1 (in the measurement reference plane FP). It is formed in a long shape. Specifically, the unit light receiving windows W1, W2 may be an ellipse, an ellipse, a rectangle, or the like. These light receiving chambers R1 and R2 are arranged at different distances from the light projecting chamber R0 along the measurement window WM.

  The light receiving windows W1 and W2 have a shape with the short axis in the direction toward the light projection window W0, thereby improving the geometric depth resolution by reducing the width in the direction toward the light projection window W0. On the other hand, by increasing the width in the direction orthogonal thereto, the decrease in the amount of received light can be suppressed and the S / N ratio of the signal can be maintained high.

  Further, as shown in FIG. 9C, the measurement head Hd has a plurality of light emitting elements arranged in a light projection chamber R0 formed in the measurement head Hd as a light projecting unit, that is, a first wavelength region. A blue LED 21 as a first light source that generates first light in a (blue wavelength region) and a green LED 22 as a second light source that generates second light in a second wavelength region (green wavelength region) are a plurality of light sources. As a parallel arrangement. The measurement head Hd further serves as a plurality of light receiving elements respectively disposed at substantially upper ends of the two light receiving chambers R1 and R2 formed in the measuring head Hd as light receiving means, that is, the first light receiving element PD1 (for short optical path). A photoelectric conversion element) and a second light receiving element PD2 (a photoelectric conversion element for a long optical path).

  In the jaundice meter 10, the measurement reference plane FP that defines the measurement window WM of the measurement head Hd is used while being in contact with the skin surface of the measurement subject in substantially parallel. For this reason, the normal line of the measurement reference plane FP that defines the measurement window WM and the normal line of the skin surface of the measurement subject substantially coincide. Hereinafter, this normal is referred to as “reference normal”.

  While the jaundice meter 10 is in use, the normal line of the measurement reference plane FP on which the measurement window W is formed and the normal line of the skin surface substantially coincide with each other. Since the directional relationship between the light emission direction and the skin surface cannot be specified when 10 is viewed alone, the normal line of the measurement reference plane FP that defines the measurement window W is the “reference normal line” as a configuration of the jaundice meter 10 itself. Defined. In general, the “measurement reference plane” in this invention is defined as a plane that is parallel to the surface of the object when performing measurement, but the measurement reference plane may be formed as a physical plane, It may be a surface that is supposedly intended.

  Further, the center of the projection window W0 is shifted laterally with respect to the installation positions of the blue LED 21 and the green LED 22. The blue LED 21 and the green LED 22 are attached to the ceiling surface of the light projecting chamber R0 so that their emission optical axes are inclined from the reference normal line.

  As a result, the optical axis of the light that enters the body of the subject from the measurement head Hd through the projection window W0 from the blue LED 21 and the green LED 22 is inclined from the reference normal line NL. That is, the light projecting optical axis is not only inclined from the normal line NL of the measurement window WM, but is also inclined from the normal line of the measurement subject's skin surface. This optical axis corresponds to the incident optical axis Lnin described in FIG. 1B and the like, and the incident angle θ is a finite value (for example, θ = 5 degrees or more) that is not zero. Naturally, the condition of θ <90 degrees is also satisfied.

  Further, the centers of the first light receiving element PD1 and the second light receiving element PD2 of the measuring head Hd are shifted laterally from the centers of the unit light receiving windows W1, W2. Accordingly, the optical axes of the two detection optical axes Lnlo and Lnso described in FIG. 1B are also inclined at finite angles (−φ1) and (−φ2) from the reference normal line NL. By these, the preferable optical arrangement described above is realized.

  The light projecting means is disposed in the light projecting window W0 and the light projecting window W0 as a diaphragm means for narrowing the light beam emitted from the LED 21 (first wavelength region light source) and the LED 22 (second wavelength region light source). And a Fresnel lens LC as a condensing optical element. In the case where the irradiation light beam in the subject's body is substantially parallel light, the Fresnel lens LC can also function as a collimator.

  Although not shown in FIG. 9, the unit light receiving windows W1 and W2 are preferably covered with dust-proof flat transparent glass. If it is desired to collect light with respect to the light receiving elements PD1 and PD2, a Fresnel lens may be provided instead of the flat glass covering the unit light receiving windows W1 and W2.

  FIG. 10 schematically shows the optical arrangement of the measuring head Hd. In FIG. 10, the light projecting chamber R0 and the light receiving chambers R1, R2 of the measuring head Hd are omitted. The Fresnel lens LC is conceptually depicted as an individual lens attached to each of the LEDs 21 and 22. As seen in FIG. 9, the center of the light projection window W0 of the light projection chamber R0 is shifted from the LEDs 21 and 22 in the lateral direction, and a Fresnel lens LC is further provided. The emission optical axes from the LEDs 21 and 22 are inclined from the reference normal line NL.

  As will be described later, each of the LEDs 21 and 22 emits light sequentially in time, but when attention is paid to the light emission period from any one of the LEDs, the first light receiving element PD1 detects the light emitted obliquely from the LED. The light passes through the short optical path SR, and the surface region PS of the subject's forehead, that is, the skin region, is used as the detection region DS.

  In summary, the jaundice meter 10 allows light to enter the target body from the surface (skin surface) of the target object (measurement subject) to be measured, and to emit light through different paths inside the target object. It is comprised as an optical internal information measuring device which detects the signal of (2) and measures the internal information (bilirubin density | concentration) of a target object.

  And this optical internal information measuring device (jaundice meter 10) is a flat surface on which a measurement reference surface (measurement window WM is formed) that is parallel to the surface (skin surface) of the object (measured person) when performing measurement. A light projecting means (a combination of the LEDs 21 and 22 and the light projecting chamber R0) that projects light obliquely toward the object at a predetermined angle θ with respect to the normal of the surface FP), and a measurement reference surface (flat surface FP) Light receiving means (first light receiving elements PD1 and PD2 and light receiving chambers R1 and R2) that receive light emitted through different paths from the inside of the target body and output a plurality of signals expressing the respective received light amounts. Combination).

  The light emitting means emits light of a plurality of wavelengths (blue light and green light), and the light receiving means receives light emitted through different paths for each of the plurality of wavelengths of light. ing.

  In this embodiment, since the horizontal positions of the first light receiving elements PD1 and PD2 and the light receiving chambers R1 and R2 do not change, the light projecting unit is a fixed light projecting unit that performs light projection in a fixed optical path. In the light receiving means, two light receiving elements (LEDs 21 and 22) having two light receiving ends (unit light receiving windows W1 and W2) at two positions having different distances from the light projecting means are sequentially arranged in time (that is, described later). In this manner, sequential light detection means for detecting (in time series) is provided.

<2-2. Electrical components of jaundice meter>
FIG. 11 is a block diagram showing electrical components of the jaundice meter 10 according to the present embodiment. The jaundice meter 10 includes a control unit 40 including a CPU, a light source driving unit 41 that drives the blue LED 21 and the green LED 22, and a measurement head Hd (see FIG. 9) against the urging force of the urging unit as described above. A measurement switch 42 that is automatically turned on when pushed into the casing 11 is provided. The jaundice meter 10 also includes A / D converters 541 and 542, a reset switch 45 for clearing the measurement result and returning to a state where the next measurement can be executed, a control program for the control unit 40, and a preset value. A ROM 46 that stores fixed data and the like and a RAM 47 that temporarily stores electrical signal data and the like are provided. This RAM (storage means) 47 is configured such that its memory contents are not erased by a built-in power supply (not shown). In addition, a rewritable nonvolatile memory such as an EEPROM may be provided as a storage means instead of the RAM 47 having a backup power source.

  The control unit 40 has a function as a light emission control unit, and is electrically connected to the light source driving unit 41. As described above, the measurement head Hd (see FIG. 9) against the biasing force of the biasing unit. Is pushed into the casing 11 to a predetermined position, the measurement switch 42 is automatically turned on, and accordingly, a light emission instruction signal is sent from the control unit 40 to the light source driving unit 41, and the light source driving unit 41 is connected to the blue LED 21 and The green LED 22 is caused to emit light sequentially in time.

  In the present embodiment, the blue LED 21 and the green LED 22 that are the light projecting means emit light sequentially in time, and light measurement at each wavelength is performed in time sequence. For this reason, in this embodiment, light emission of a plurality of different wavelengths and measurement based thereon are performed in a time division manner.

  The first light receiving element PD1 that receives the light beam that has passed through the short optical path SR (see FIG. 10) is electrically connected to the control unit 40 via the A / D converter 541, and from the first light receiving element PD1. The electric signals S1 (λb) and S1 (λg) having signal levels representing the received light amounts I1 (λb) and I1 (λg) are output to the control unit 40. The second light receiving element PD2 that receives the light beam that has passed through the long optical path LR (see FIG. 10) is electrically connected to the control unit 40 via the A / D converter 542, and the second light receiving element PD2 Electric signals S2 (λb) and S2 (λg) having signal levels representing the received light amounts I2 (λb) and I2 (λg) from the light are output to the controller 40.

  Here, in the present embodiment, the first light receiving element PD1 and the second light receiving element PD2 of the light receiving unit each time-divides the received light in accordance with the time division light emission of the light projecting unit, thereby changing the wavelength of each light. To separate the light components.

  The control unit 40 functions as parameter calculation means for calculating the bilirubin concentration as the internal information parameter of the subject using the plurality of signals S1 (λb), S1 (λg), S2 (λb), S2 (λg). The calculation result (calculation result) is displayed on the display unit 12. The display content may include diagnostic auxiliary information indicating whether or not the bilirubin concentration is in the normal (healthy) range together with or instead of the numerical value of the bilirubin concentration. Such bilirubin concentration information is an example of a parameter corresponding to a physiological or pathological test value inside the living body.

<2-3. Basic operation of jaundice meter>
Hereinafter, the measurement operation of the jaundice meter 10 will be described with reference to the flowchart of FIG. These operations are executed inside the control unit 40 or under the control of the control unit 40 in accordance with a control program stored in the control unit 40 except for the switch operation by the measurer.

  In step S1, the power switch 11a provided on the front side of the side surface of the casing 11 is switched from the off state to the on state by the measurer (see FIG. 9A).

  In step S2, the reset switch 45 is pressed to enable measurement, and the measurement head Hd of the jaundice meter 10 is pressed against a part of the person being measured, for example, the forehead part. Then, the measuring head Hd is pushed back into the casing 11 against the urging force of the urging means (see FIGS. 9A and 11).

  In step S3, the measurement is started when the measurement switch 42 is turned on and transmitted to the control unit 40 by being pushed in by a predetermined amount (see FIG. 11).

  In step S4, first, in response to a command from the control unit 40, the photoelectric driving unit 41 emits the blue LED (first wavelength region light source) 21 and emits the light from the projection window W0. As a result, the light beam in the blue wavelength region is irradiated into the body of the subject, and the scattered light scattered inside the skin of the subject enters from the light receiving window W1 and enters from the light receiving window W2 (FIGS. 9 and 11). reference).

  In step S5, incident light from the light receiving window W1 is received by the first light receiving element PD1, and an electric signal S1 (λb) representing the amount of received light is output to the control unit 40 via the A / D converter 541. Incident light from the light receiving window W2 is received by the second light receiving element PD2, and an electric signal S2 (λb) representing the amount of received light is output to the control unit 40 via the A / D converter 542, and is input to the RAM 47. Stored (see FIGS. 9 and 11). The blue LED 21 is turned off when this measurement is completed.

  In step S <b> 6, the photoelectric drive unit 41 emits a green LED (second wavelength region light source) 22 in response to a command from the control unit 40, and the subject's skin is irradiated with a luminous flux in the green wavelength region. Scattered light scattered inside the skin enters from the light receiving window W1 and enters from the light receiving window W2 (see FIGS. 9 and 11).

  In step S7, the incident light from the light receiving window W1 is received by the first light receiving element PD1, and an electric signal S1 (λg) representing the amount of received light is output to the control unit 40 via the A / D converter 541. Incident light from the light receiving window W2 is received by the second light receiving element PD2, and an electric signal S2 (λg) representing the amount of received light is output to the control unit 40 via the A / D converter 542, and is input to the RAM 47. Stored (see FIGS. 9 and 11). The green LED 22 is turned off when this measurement is completed.

  In step S8, it is determined whether or not the number n of light emission operations of the LEDs 21 and 22 has been performed for a preset number N, and if it has not been performed for the set number N yet (n <N: No in step S8). ), Returning to step S4, the loop from step S4 to step S7 is repeated. This repetition is for obtaining a more accurate measurement result by statistical processing (for example, averaging process) of a plurality of measurement results.

  On the other hand, if the number n of light emission operations of each LED 21 and 22 is performed a preset number N (n = N: Yes in step S8), the above-described average value of the data of the set number N is used. The calculation of bilirubin concentration calculation is performed according to the measurement principle (step S9), and the measurement result is displayed on the display unit 12 (step S10).

  In the measurement using the jaundice meter 10 described above, the measurement resolution in the depth direction is improved for the reasons already described, and therefore the measurement of the bilirubin concentration (and therefore the diagnosis of jaundice) can be performed accurately. In addition, since the measurement accuracy is high, it is not necessary to excessively increase the amount of light emitted from the light source.

  Furthermore, even when the time-lapse observation is performed using the jaundice meter 10, it is possible to detect the jaundice situation with higher accuracy than the conventional apparatus using the time change of the measurement subject's bilirubin concentration. For this reason, it becomes possible to perform follow-up observation more accurately.

<3. Modification>
As mentioned above, although embodiment of this invention has been described, this invention is not limited to the said embodiment, The following various deformation | transformation are possible. Although not described in detail in the following modification examples, in each modification example, a measurement reference plane is defined in the same manner as the above-described embodiment, and oblique incidence of light for measurement is determined from the normal line of the measurement reference plane. The incident is inclined.

<3-1. Modification regarding light projecting means and light receiving means>
In the embodiment of the present invention, the position of the light projecting unit is fixed, and the light receiving unit has been described to detect light of a plurality of wavelengths in time sequence. However, the present invention is not limited to this. Is possible. Here, the following type names are defined before describing the specific configuration examples. However, in the case of using a plurality of wavelengths of light (such as blue light and green light) as in the above-described embodiment, any light projection type or light reception type can be used properly for each wavelength light. In one apparatus, it is preferable to use the same light projecting / receiving type for light of a plurality of wavelengths.

First, the light projection means is classified into the following light projection types.
(1) Light projection type A (fixed):
Similar to the above-described embodiment, the light projecting unit includes a fixed light projecting unit that performs light projection on the fixed optical path.

(2) Light projection type B (variable position):
The LEDs 21 and 22 are configured to be movable in the horizontal direction, and a driving element or a driving mechanism for moving them is provided. Then, the long optical path and the short optical path are not realized at the same time (in parallel), but are realized in time sequence by the lateral movement of the LEDs 21 and 22.

  That is, the light projecting unit in this case includes a light projecting path switching unit that sequentially switches the light projecting path among the plurality of light projecting paths, and the light projecting path switching unit sets the “light projecting position” to a plurality of light projecting positions. It has a light projection position switching means for sequentially switching between the light projection positions.

(3) Light projection type C (variable direction):
In the light projection type C, the LEDs 21 and 22 are not moved in the horizontal direction, but the “light projection direction” from the LEDs 21 and 22 is changed in time order. In other words, the light projecting unit in this case includes a light projecting path switching unit that switches the light projecting path in time sequence between a plurality of light projecting paths. And the said light projection path | route switching means has a light projection direction switching means which switches a light projection direction in time sequence among several light projection directions.

(4) Projection type D (variable position direction):
The light projection type D is configured to move the LEDs 21 and 22 in the horizontal direction and to change the light projection direction. It can be said that this type D is a combination of type B and type C.

  Next, the light receiving means is classified into the following light receiving types.

(1) Light receiving type E (fixed):
Similarly to the above embodiment, the blue light from the blue LED 21 and the green light from the green LED 22 are detected in parallel by the light receiving elements PD1 and PD2. That is, the light receiving means in this case includes parallel light detection means for detecting each of the plurality of signals in parallel by the plurality of light receiving elements.

(2) Light receiving type F (variable):
By making the light-receiving element or the light-receiving guide that guides light to it move, light is received in series on different paths with a small number of light-receiving elements. In other words, the light detection means in this case includes sequential light detection means for detecting a plurality of signals in time sequence while sequentially moving the light receiving position.

  Based on the above definition, there are the following seven types of practical combinations of light projecting means and light receiving means.

(1) First type: Light emission A (fixed) + Light reception E (fixed)
(2) Second type: Light emission A (fixed) + light reception F (variable)
(3) Third type: Light emission B (position change) + light reception E (fixed)
(4) Fourth type: Light emission C (direction change) + light reception E (fixed)
(5) Fifth type: Light emission D (change in position and direction) + light reception E (fixed)
(6) Sixth type: Light emission B (position change) + light reception F (variable)
(7) 7th type: Light emission C (direction change) + light reception F (variable)
FIG. 13 shows various arrangements corresponding to each of these types, which are described below in the order shown.

[Arrangement of FIG. 13A]
-Example of arrangement (a1):
This arrangement is an element arrangement close to the above-described embodiment, and belongs to the first type. However, the light receiving optical axes of the first light receiving element PD1 and the second light receiving element PD2 are substantially parallel to the reference normal line. This is an arrangement realized by arranging the center positions of the unit light receiving windows W1 and W2 in FIG. 9 so as to face the light receiving elements PD1 and PD2.

  Since the semiconductor light receiving elements of the light receiving elements PD1 and PD2 themselves do not have directivity, by providing a light receiving lens (not shown) and an aperture stop to provide directivity, the light receiving elements PD1 and PD2 have a directivity. The overlap of the light receiving range is reduced, and the depth resolution is improved.

[Arrangement of FIG. 13B]
Arrangement example (b1):
In this arrangement, only one light receiving element PD1 (or PD2) is provided in the light receiving means, and the position of the light receiving end is fixed. On the other hand, two LEDs 21 and 22 and two LEDs 21 ′ and 22 ′ are provided as the light projecting means, and a pair of LEDs 21 and 22 (or LEDs 21 ′ and 22 ′) are arranged at different positions in the horizontal direction. Each one is fixed. This arrangement belongs to the first type.

Arrangement example (b2):
On the other hand, only a pair of LEDs 21 and 22 (or LEDs 21 'and 22') are provided, and the pair of LEDs 21 and 22 (or LEDs 21 'and 22') are horizontally moved by a small motor or piezoelectric actuator along a horizontally extending guide. By doing so, a short optical path and a long optical path can be realized in time sequence. The arrangement in this case belongs to the third type.

[Arrangement of FIG. 13 (c)]
Arrangement example (c1):
This arrangement is the same as that shown in FIG. 13B on the light receiving side, but the light projecting direction and the light projecting position are variable, and belongs to the fifth type. The LED 21, 22 and the pair of LED 21 ', 22' are pivotably supported and driven by a small motor or a piezoelectric actuator to change the light projecting direction, and the LED 21, 22 and A mechanism for translating the pair of LEDs 21 ′ and 22 ′ also in the horizontal direction is provided to change the light projection position. The horizontal movement direction and the inclination change direction of the pair of the LEDs 21 and 22 and the LEDs 21 ′ and 22 ′ are determined when the inclination angles of the optical axes of the LEDs 21 and 22 and the LEDs 21 ′ and 22 ′ become large. It is determined to perform horizontal movement in the direction of widening the horizontal interval between the LEDs 21 'and 22' and the light receiving element PD1 (PD2). Thereby, even if each of the horizontal movement and the change in the tilt angle is small, a desired change in the detection depth can be ensured. Therefore, the measuring head Hd can be configured compactly.

  In this case, the projection direction from the LEDs 21 and 22 (or LEDs 21 ′ and 22 ′) is changed by attaching a lens to each of the LEDs 21 and 22 (or LEDs 21 ′ and 22 ′) as in FIG. Even so, it is preferable that the condensing function by the lens is not changed by the change in direction of the LEDs 21 and 22 (or LEDs 21 ′ and 22 ′).

[Arrangement of FIG. 13D]
Arrangement example (d1):
In this arrangement, the arrangement on the light projecting side is an arrangement in which the light projecting direction is variable as in FIG. 13C. On the light receiving side, the two light receiving elements PD1 and PD2 are shared by the ceiling surface of one common light receiving chamber (box) BX. Are spaced apart from each other in the horizontal direction. This arrangement therefore belongs to the fourth type. When the light projecting direction from the light receiving element PD1 (or PD2) is greatly inclined from the reference normal direction, the light passing through the shallow detection region DS corresponding to the skin region is received through a single window on the lower surface of the light receiving chamber BX. Detected by element PD1.

  On the other hand, when the inclination of the light projecting direction from the light receiving element PD1 (or PD2) is small, the light passing through the deep light detection region DP corresponding to the subcutaneous fat layer is a single window on the lower surface of the light receiving chamber BX. Is detected by the light receiving element PD2.

  In order to further improve the directivity, it is preferable to provide a condensing optical means such as a Fresnel lens in the single window.

[Arrangement of FIG. 13 (e)]
Arrangement example (e1):
In this arrangement, the lenses 21 and 22 are fixedly attached so that their light emission directions are horizontal, and the lens is arranged. A reflecting plate that moves in the horizontal direction is provided, and the reflecting plate is moved in the horizontal direction between the first reflecting plate position RF1 and the second reflecting plate position RF2. By reflecting the light from the LEDs 21 and 22 with the reflector when the reflectors are at such different reflector positions RF1 and RF2, the light of the short optical path SR and the long optical path LR can be obtained sequentially in time. . This reflecting plate functions as an optical axis horizontal conversion means for moving the optical axis of the light from the LEDs 21 and 22 in the horizontal direction.

  The light receiving means can receive light sequentially in time using a single fixed light receiving element PD1 (or PD2). That is, the light of the short optical path SR is detected in the first period and the light of the long optical path LR is detected by the single light receiving element in the second period. When a plurality of signals having different wavelengths are used, it is possible to detect each wavelength by assigning one light receiving element for each wavelength and arranging them adjacent to each other in the direction penetrating the paper surface of the figure. The arrangement in this case is the third type.

Arrangement example (e2):
By providing a mechanism for horizontally moving the light receiving element PD1 (PD2) in synchronization with the movement of the reflecting plate, the light in the short optical path SR and the long optical path LR can be obtained sequentially in different horizontal positions. Measurement accuracy can be increased by averaging. However, the moving speed of the reflecting plate and the moving speed of the light receiving element PD1 (PD2) are made different from each other. By adopting such a mode, measurement can be performed by changing the depth of the detection region DS of the short optical path SR and the depth of the detection region DP of the long optical path LR. The arrangement in this case is the sixth type.

Arrangement example (e3):
It is also possible to provide a mechanism for horizontally moving the light receiving element PD1 (PD2) while fixing the LEDs 21 and 22 and the reflecting plate. The arrangement in this case is the second type.

[Arrangement of FIG. 13 (f)]
Arrangement example (f1):
In this arrangement, the light projecting direction is variable. That is, by providing a shutter ST below the LEDs 21 and 22 and moving the shutter ST as indicated by an arrow OC by the driving means to selectively open and close, the light projection angles can be sequentially changed.

  The light receiving means can receive light sequentially in time using a single fixed light receiving element PD1 (or PD2). The arrangement in this case is the fourth type.

Arrangement example (f2):
By providing a mechanism for horizontally moving the light receiving element PD1 (PD2) in the direction of the arrow mv in synchronization with the opening and closing of the shutter ST, light in the short optical path SR and the long optical path LR can be obtained sequentially in time at different horizontal positions. Therefore, the measurement accuracy can be increased by averaging them. The arrangement in this case is the seventh type.

<3-2. Modified example of light emitting / receiving of light of plural wavelengths>
In the light projecting means and the light receiving means in the embodiment of the present invention, the light projecting / receiving of the light having a plurality of wavelengths is performed in parallel or in time division. However, the present invention is not limited to this. An apparatus for separating light components may be used.

  As a first method, the light receiving unit can separate light components having a plurality of wavelengths by performing wavelength filtering of the received light. That is, instead of using a plurality of types of light sources having different wavelength regions as shown in FIG. 14 showing only one of the long optical path and the short optical path, as shown in FIG. Light is incident in an oblique direction, and the detected light is applied to a plurality of filters (generally wavelength selection means) that transmit only different wavelength regions using a light guide element (such as an optical fiber or a mirror). The detection light having a plurality of wavelengths separated from each other by these filters may be detected by the light receiving element. Dichroic mirrors can also be used. The other of the long optical path and the short optical path can be configured similarly.

  As the second method, as shown in FIG. 15, the light projecting means amplitude-modulates light of a plurality of wavelengths at a plurality of different modulation frequencies, synthesizes them by a synthesizer, and guides the synthesized light. Emits light from the element. The light receiving means can separate the light components of the plurality of wavelengths by guiding the received light from the light guide element to the plurality of demodulators and demodulating the light at the plurality of modulation frequencies. That is, it is also possible to detect a plurality of wavelength components by demodulating each wavelength light with a predetermined frequency component using the spatial frequency modulation method and making it incident simultaneously. The same applies to the other of the long optical path and the short optical path.

  By adopting these methods, it is possible to simultaneously enter light having a plurality of different wavelengths into the target body without sequentially measuring different wavelength region light sources, leading to a reduction in measurement time. Specifically, in the example of the present embodiment, after the first wavelength region light source 21 emits light, the second wavelength region light source 22 emits light (step S4 to step S7 in FIG. 12). Although it was necessary to sequentially emit the wavelength region light sources, in the apparatus adopting the first method, only the light emission of a single wide wavelength width light source is required, and in the apparatus adopting the second method, The first and second wavelength region light sources 21 and 22 can emit light simultaneously. Therefore, the time required for one loop from step S4 to step S7 is also halved, and the time required to repeat until reaching the set number N of step S8 is also halved.

<3-3. Other variations>
* In the embodiment of the present invention, the incident angle θ is adopted as a value larger than at least 5 degrees, but the incident angle θ is preferably in the range of 1 degree ≦ θ ≦ 45 degrees, and in particular, 5 degrees ≦ θ ≦ 30. A range of degrees is preferred.

  * In the embodiment of the present invention, a combination of a projection window and a condensing optical element is used as a diaphragm means for narrowing the light beam emitted from the light source. However, if the light source has sufficient directivity, the light beam is used. There is no need to squeeze.

  * In the embodiment of the present invention, the jaundice meter used for bilirubin concentration measurement has been described. However, the internal measurement range can be changed by changing the wavelength range of the light source, the interval between the light receiving elements (photosensors), and the calculation method. It is possible to measure various internal information of living bodies by changing measurement materials. For example, the present invention can be applied to a reflection type pulse oximeter using red light and infrared light.

  When applied to a medical examination instrument, the internal information parameter corresponds to a parameter corresponding to a physiological or pathological examination value inside the living body, such as the above-mentioned bilirubin concentration or oxygen saturation concentration.

  Furthermore, the measurement target is not limited to a living body, and can be used for internal information measurement in a wide range of fields, such as optically detecting ingredients contained in foodstuffs in containers.

  * In the embodiment, two optical paths, a short optical path and a long optical path, are used. However, by setting three or more optical paths and detecting light in these three or more optical paths, inspection values at a plurality of depths can be obtained. It is also possible to obtain.

  The wavelength to be used may be three or more wavelengths, and may be only one wavelength in applications that do not require a reference wavelength.

10 Jaundice meter 21 Blue LED (first wavelength region light source)
22 Green LED (second wavelength region light source)
40 Control Unit FP Measurement Reference Surface NL Reference Normal PD1 First Light Receiving Element PD2 Second Light Receiving Element WM Measurement Window W0 Light Projection Window W1, W2 Unit Light Receiving Window

Claims (16)

An optical internal information measuring device that measures the internal information of the object by detecting light emitted from the surface of the object to be measured and entering the object and detecting the light emitted through the object. There,
A light projecting means for projecting toward the target object from an oblique direction with a predetermined angle with respect to a normal line of a measurement reference plane parallel to the surface of the target object;
A light receiving means installed to receive light emitted through different paths inside the object through the measurement reference plane, and outputting a plurality of signals representing the respective received light amounts;
Calculating means for calculating internal information of the object using the plurality of signals;
An optical internal information measuring device comprising: In the optical internal information measuring device according to claim 1,
An optical internal information measuring device, further comprising a diaphragm means for narrowing a light beam emitted from the light projecting means. In the optical internal information measuring device according to claim 1 or 2,
The light receiving means is
A parallel light detection means for detecting the plurality of signals in parallel by a plurality of light receiving elements;
With
The optical internal information measuring device, wherein the plurality of signals are respectively obtained from the plurality of light receiving elements. In the optical internal information measuring device according to claim 1 or 2,
The light receiving means is
Sequential light detection means for detecting the plurality of signals in time sequence by a plurality of light receiving elements each having a plurality of positions at different distances from the light projecting means;
With
The optical internal information measuring device, wherein the plurality of signals are respectively obtained from the plurality of light receiving elements. In the optical internal information measuring device according to claim 1 or 2,
The light receiving means is
Sequential light detection means for detecting the plurality of signals in time sequence while sequentially moving the light receiving position to a plurality of positions having different distances from the light projecting means;
With
The optical internal information measuring device, wherein the plurality of signals are respectively obtained from the plurality of light receiving elements. In the optical internal information measuring device according to any one of claims 3 to 5,
The light projecting means
Fixed light projecting means for performing light projection in a fixed light path;
An optical internal information measuring device, characterized in that In the optical internal information measuring device according to any one of claims 3 to 5,
The light projecting means
Projection path switching means for switching the projection path between a plurality of projection paths in time sequence,
An optical internal information measuring device comprising: In the optical internal information measuring device according to claim 7,
The light projecting path switching means switches the light projecting position between a plurality of light projecting positions in time sequence,
An optical internal information measuring device comprising: In the optical internal information measuring device according to claim 7,
A light projection direction switching means for switching the light projection direction in time sequence between a plurality of light projection directions;
An optical internal information measuring device comprising: In the optical internal information measuring device according to any one of claims 1 to 9,
The measurement reference plane is defined on an end face of a measurement head of the optical internal information measurement device, and a measurement window is formed on the measurement reference plane.
A light emitting device in which the light projecting means is disposed in a light projecting chamber formed in the measurement head;
And having
A plurality of light receiving elements respectively disposed in a plurality of light receiving chambers formed in the measuring head;
Have
The optical internal information measuring device, wherein the plurality of light receiving chambers are arranged at different distances from the light projecting chamber along the measurement window. In the optical internal information measuring device according to claim 10,
The measurement window is
A light projection window formed in the light projection chamber;
A plurality of unit light receiving windows formed in each of the plurality of light receiving chambers;
In a single plane,
Each of the unit light receiving windows is formed in an elongated shape having a short axis in a direction from the unit window toward the light projecting window. In the optical internal information measuring device according to any one of claims 1 to 11,
The light emitting means emits light of a plurality of wavelengths,
The light receiving means receives light emitted through the different paths for each of the light of the plurality of wavelengths,
The optical internal information measuring device, wherein the parameter calculating means calculates the internal information parameter based on the plurality of signals obtained for each of the light of the plurality of wavelengths. In the optical internal information measuring device according to claim 12,
The optical internal information measuring device, wherein the light receiving means separates light components of the plurality of wavelengths by wavelength filtering of received light. In the optical internal information measuring device according to claim 12,
The light projecting means projects light of a plurality of wavelengths in a time division manner,
The optical internal information measuring device, wherein the light receiving means separates light of the plurality of wavelengths by time-sharing received light. In the optical internal information measuring device according to claim 12,
The light projecting means projects light while modulating light of a plurality of wavelengths at a plurality of modulation frequencies,
The optical internal information measuring device, wherein the light receiving means separates light components having the plurality of wavelengths by demodulating received light at the plurality of modulation frequencies. In the optical internal information measuring device according to any one of claims 1 to 15,
The object is a living body to be examined,
The optical internal information measuring apparatus, wherein the internal information parameter is a parameter corresponding to a physiological or pathological examination value inside the living body.

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