MEASUREMENT SENSITIVITY CALCULATION METHOD, MEASUREMENT SENSITIVITY CALCULATION DEVICE, MEASUREMENT SENSITIVITY CALCULATION PROGRAM, AND OPTICAL MEASUREMENT DEVICE

Abstract

In a measurement target model representing a measurement target, this measurement sensitivity calculation device uses, as measurement sensitivity, an optical path length difference between a first optical path length indicating the length of an optical path through which light emitted from a light emitter to the measurement target travels before being received by a first light receiver spaced apart by a first distance from the light emitter and a second optical path length indicating the length of an optical path through which light emitted from the light emitter travels before being received by a second light receiver spaced apart by a second distance from the light emitter, calculates the measurement sensitivity for each depth of the measurement target, and outputs the measurement sensitivity calculated for each depth of the measurement target.

Description

[Technical Field]

[0001] The present disclosure relates to a measurement sensitivity calculation method, a measurement sensitivity calculation device, a measurement sensitivity calculation program, and an optical measurement device. [Background technology]

[0002] In conventional hemodynamic measurements using near-infrared spectroscopy (NIRS), the following methods have been put into practical use: the continuous light method (a method of measuring changes in oxygen concentration using a pair of one light source and one light receiver), the spatial resolution method (a method of calculating the absolute value of oxygen concentration from the difference in spatial light intensity using a pair of one light source and two light receivers), the time resolution method, and the phase modulation method.

[0003] For example, Patent Documents 1 and 2 disclose measurement methods using a continuous light method. Non-Patent Document 1 discloses a measurement method using a spatial resolution method.

[0004] Regarding the question of measurement depth, i.e., how deep from the body surface can be measured for the object being measured, it is generally known that the measurement depth is about half the distance between the transmitter and receiver, based on the depth of the range known as the banana shape, which indicates the measurement range of the continuous light method.

[0005] Patent Document 1: International Publication No. 2014 / 34285 Pamphlet Patent Document 2: US Patent No. 5,902,235 Non-patent document 1: Masatsugu Niwayama, "Voxel-based measurement sensitivity of spatially resolved near-infrared spectroscopy in layered tissues", Biomedical Optics_2018.3: Summary of the Invention [Problem to be solved by the invention]

[0006] However, when it comes to the measurement depth in the spatially resolved method, if it is set to about half the distance between the transmitter and receiver, as is the case with NIRS using the continuous light method, there is a problem that the error becomes large and, in principle, it does not achieve true measurement sensitivity.

[0007] The present disclosure has been made in consideration of the above facts, and aims to provide a measurement sensitivity calculation method, a measurement sensitivity calculation device, a measurement sensitivity calculation program, and an optical measurement device that can accurately calculate the measurement sensitivity for each depth of the measurement object. [Means for solving the problem]

[0008] In order to achieve the above object, the measurement sensitivity calculation method according to the first aspect includes a step of performing processing in which a computer calculates the measurement sensitivity for each depth of the measurement object, using the difference in optical path length between a first optical path length representing the length of a first optical path from a light emitter to the measurement object until light is received by a first optical receiver spaced a first distance from the light emitter, and a second optical path length representing the length of a second optical path from the light emitter until light is received by a second optical receiver spaced a second distance from the light emitter, as the measurement sensitivity, and outputs the measurement sensitivity calculated for each depth of the measurement object.

[0009] In the measurement sensitivity calculation method according to the first aspect, the calculating step may include selecting multiple pairs of two photodetectors in which at least one of the first distance and the second distance is different, and calculating the measurement sensitivity for each depth of the object to be measured for the selected pairs of photodetectors.

[0010] In the measurement sensitivity calculation method according to the first aspect, the outputting step may output the first distance and the second distance for a pair of photoreceivers among the plurality of pairs of photoreceivers, the pair of photoreceivers in which the depth of the object to be measured is included in a depth range corresponding to a measurement sensitivity equal to or greater than a predetermined threshold value.

[0011] In the measurement sensitivity calculation method according to the first aspect, the measurement object model is a model that represents the measurement object using a plurality of voxels, and the calculating step may include calculating the first optical path length and the second optical path length for each of the plurality of voxels to calculate the measurement sensitivity, and accumulating the measurement sensitivities calculated for each voxel at each depth of the measurement object to calculate the measurement sensitivity for each depth of the measurement object.

[0012] The measurement sensitivity calculation device according to the second aspect includes a calculation unit that calculates the measurement sensitivity for each depth of the measurement object using the difference in optical path length between a first optical path length representing the length of the optical path from when light is emitted from a light emitter to when it is received by a first optical receiver that is a first distance away from the light emitter, and a second optical path length representing the length of the optical path from when light is emitted from the light emitter to when it is received by a second optical receiver that is a second distance away from the light emitter, as the measurement sensitivity, and an output unit that outputs the measurement sensitivity calculated for each depth of the measurement object.

[0013] The measurement sensitivity calculation program according to the third aspect causes a computer to execute processing including the steps of: calculating the measurement sensitivity for each depth of the measurement object, using the difference in optical path length between a first optical path length representing the length of a first optical path from a light emitter to the measurement object until light is received by a first light receiver spaced a first distance from the light emitter, and a second optical path length representing the length of a second optical path from the light emitter until light is received by a second light receiver spaced a second distance from the light emitter, as the measurement sensitivity; and outputting the measurement sensitivity calculated for each depth of the measurement object.

[0014] The optical measurement device according to the fourth aspect includes a light emitter that emits light toward a measurement object, three or more light receivers selected from a plurality of sets of light receivers selected by the measurement sensitivity calculation method according to the first aspect, a selection unit that selects two light receivers from the three or more light receivers, and a calculation unit that calculates the degree of light absorption based on the light intensity of the light received by the two light receivers.

[0015] The optical measurement device according to the fourth aspect may further include a measurement unit that measures the time of flight of light in the same positional relationship as that between the light emitter and two predetermined light receivers among the three or more light receivers, and an identification unit that identifies the measurement object corresponding to the absorption coefficient and scattering coefficient calculated based on the time of flight and a spatial gradient calculated based on the intensity of light received by the two light receivers by emitting light of multiple wavelengths from the light emitter, and the selection unit may select two light receivers from the three or more light receivers that correspond to the measurement object identified by the identification unit.

[0016] An optical measurement device according to a fifth aspect includes a light emitter that emits light toward a measurement object, three or more light receivers at different distances from the light emitter, a selection unit that selects two light receivers from the three or more light receivers, and a calculation unit that calculates the degree of light absorption based on the light intensity of the light received by the two light receivers.

[0017] In the optical measurement device according to the fifth aspect, the selection unit may select a plurality of pairs of two photoreceivers in which at least one of the first distance and the second distance is different, using the difference in optical path length in a measurement object model representing the measurement object as measurement sensitivity, where the difference is a first optical path length representing the length of a first optical path from when light emitted from a light emitter to the measurement object is received by a first photoreceiver spaced a first distance from the light emitter, and a second optical path length representing the length of a second optical path from when light emitted from the light emitter is received by a second photoreceiver spaced a second distance from the light emitter, and may select two photoreceivers corresponding to the measurement object based on the calculation results of the measurement sensitivity calculated for each depth of the measurement object for the plurality of selected pairs of photoreceivers.

[0018] In the optical measurement device according to the fifth aspect, the selection unit may select the second photoreceiver whose second distance is 14 mm or less when the measurement object is skin tissue and the depth of the measurement object is 1 mm or more and 3 mm or less.

[0019] In the optical measurement device of the fifth aspect, when the measurement object is skin tissue, the selection unit may select the first photoreceiver and the second photoreceiver corresponding to the first distance and the second distance that are closest to the first distance and the second distance that satisfy the condition that the first distance is 1 / 2 of the second distance and the depth of the skin tissue is 1 / 5 of the second distance.

[0020] In the optical measurement device according to the fifth aspect, the selection unit may select the first photodetector and the second photodetector based on a correspondence between the depth of the measurement object, the first distance, and the second distance derived based on a calculation result of the measurement sensitivity for each depth of the measurement object.

[0021] An optical measurement device according to a sixth aspect includes a light emitter that emits light toward a measurement object, two or more light receivers at different distances from the light emitter, and a measurement unit that measures the time of flight of light adjacent to at least one of the two or more light receivers.

[0022] The optical measurement device according to the sixth aspect may be configured to include a calculation unit that causes the light emitter to emit light of a plurality of wavelengths, and calculates information relating to at least one of an absorption coefficient and a scattering coefficient based on a spatial gradient calculated based on the intensities of the light received by the two or more light receivers, and the time of flight of light.

[0023] The optical measurement device according to the sixth aspect may be configured to include an identification unit that identifies the measurement object corresponding to at least one of the absorption coefficient and the scattering coefficient calculated by the calculation unit, and a selection unit that selects two or more photodetectors that correspond to the measurement object identified by the identification unit. [Effects of the Invention]

[0024] According to the present disclosure, it is possible to obtain an effect of accurately calculating the measurement sensitivity for each depth of the measurement target. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a diagram illustrating the configuration of a measurement sensitivity calculation device. [Figure 2] FIG. 2 is a functional block diagram of a measurement sensitivity calculation device. [Figure 3] FIG. 10 is a diagram illustrating an example of a measurement object model. [Figure 4] FIG. 10 is a diagram illustrating an example of a measurement object model. [Figure 5] 10 is a flowchart of a measurement sensitivity calculation process. [Figure 6] FIG. 10 is a diagram for explaining calculation of an optical path length. [Figure 7] FIG. 10 is a diagram illustrating an example of a measurement sensitivity distribution. [Figure 8] FIG. 10 is a diagram illustrating an example of a measurement sensitivity distribution. [Figure 9] FIG. 10 is a diagram illustrating an example of a measurement sensitivity distribution. [Figure 10] FIG. 10 is a diagram illustrating an example of a measurement sensitivity distribution. [Figure 11] 10 is a graph showing the relationship between measurement sensitivity and depth. [Figure 12] 10 is a graph showing the relationship between measurement sensitivity and depth. [Figure 13] 10 is a graph showing the relationship between measurement sensitivity and depth. [Figure 14] 10 is a graph showing the relationship between measurement sensitivity and depth. [Figure 15] FIG. 1 is a configuration diagram of an optical measurement device. [Figure 16] 10 is a flowchart of a measurement process. [Figure 17] FIG. 10 is a diagram showing the results of simulating measurement sensitivity for each measurement depth when the measurement target is skin tissue and the second distance D2 is 5 mm. [Figure 18] FIG. 10 is a diagram showing the results of simulating measurement sensitivity for each measurement depth when the measurement target is skin tissue and the second distance D2 is 8 mm. [Figure 19]FIG. 10 is a diagram showing the results of simulating measurement sensitivity for each measurement depth when the measurement target is skin tissue and the second distance D2 is 14 mm. [Figure 20] FIG. 10 is a diagram showing the results of simulating measurement sensitivity for each measurement depth when the measurement target is skin tissue and the second distance D2 is 30 mm. [Figure 21] FIG. 10 is a diagram showing the results of simulating measurement sensitivity for each measurement depth when the measurement target is gastrointestinal tissue and the second distance D2 is 5 mm. [Figure 22] FIG. 10 is a diagram showing the results of simulating measurement sensitivity for each measurement depth when the measurement target is gastrointestinal tissue and the second distance D2 is 8 mm. [Figure 23] FIG. 10 is a diagram showing the results of simulating measurement sensitivity for each measurement depth when the measurement target is gastrointestinal tissue and the second distance D2 is 14 mm. [Figure 24] FIG. 10 is a diagram showing the results of simulating measurement sensitivity for each measurement depth when the measurement target is gastrointestinal tissue and the second distance D2 is 30 mm. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0027] (First embodiment) 1 is a diagram showing the hardware configuration of a measurement sensitivity calculation device 50. The measurement sensitivity calculation device 50 is a device including a general computer.

[0028] 1, the measurement sensitivity calculation device 50 includes a controller 51. The controller 51 includes a CPU (Central Processing Unit) 51A, a ROM (Read Only Memory) 51B, a RAM (Random Access Memory) 51C, and an input / output interface (I / O) 51D. The CPU 51A, ROM 51B, RAM 51C, and I / O 51D are connected to each other via a system bus 51E. The system bus 51E includes a control bus, an address bus, and a data bus.

[0029] Furthermore, an operation unit 52, a display unit 53, a communication unit 54, and a storage unit 55 are connected to the I / O 51D.

[0030] The operation unit 52 includes, for example, a mouse and a keyboard.

[0031] The display unit 53 is configured with, for example, a liquid crystal display.

[0032] The communication unit 54 is an interface for performing data communication with an external device.

[0033] The storage unit 55 is configured with a non-volatile external storage device such as a hard disk, and stores a measurement sensitivity calculation program 55A, measurement object model data 55B, and measurement object depth information 55C, which will be described later. The CPU 51A loads the measurement sensitivity calculation program 55A stored in the storage unit 55 into the RAM 51C and executes it.

[0034] Next, the functional configuration of the CPU 51A when the measurement sensitivity calculation device 50 executes the measurement sensitivity calculation program 55A will be described.

[0035] As shown in FIG. 2, the CPU 51A functionally includes a calculation unit 60 and an output unit 61.

[0036] The calculation unit 60 calculates the measurement depth for each depth of the measurement target using a measurement target model representing the measurement target. Examples of the measurement target include objects that absorb light, such as a living body, agricultural products, and wood. In the present embodiment, a case where a living body is the measurement target will be described as an example. However, the measurement sensitivity calculation device 50 is applicable not only to the medical device field but also to applications in the rehabilitation field, products and services in the sports science field, or quality control of various products such as agricultural products and wood.

[0037] The measurement target model is a simulation model in which the layer structure, light absorption coefficient, light scattering coefficient, etc. of the measurement target are defined.

[0038] FIG. 3 shows, as an example, a measurement target model M1 of gastrointestinal tissue as the measurement target. As shown in FIG. 3, the layer structure of the gastrointestinal tissue ST is a single-layer structure.

[0039] In this case, the calculation unit 60 calculates a first optical path length representing the length of the first optical path until the light emitted from the light emitter 24 to the gastrointestinal tissue is received by the first light receiver 26 separated from the light emitter 24 by a first distance D1 in the measurement target model M1 representing the gastrointestinal tissue as the measurement target. Further, the calculation unit 60 calculates the measurement sensitivity for each measurement target depth using the optical path length difference between the second optical path length representing the length of the second optical path until the light emitted from the light emitter 24 is received by the second light receiver 26 separated from the light emitter 24 by a second distance D2 as the measurement sensitivity. Note that D1 < D2, and D1 and D2 are set to, for example, 40 mm or less as an example.

[0040] Here, although the measurement target model M1 is not shown in FIG. 3, in the present embodiment, it is a model representing the measurement target by a plurality of voxels as an example. As the shape of the voxel, a case where a cube with a side length of 0.5 mm is used will be described as an example in the present embodiment, but the shape and size of the voxel are not limited to this.

[0041] In this case, the calculation unit 60 calculates the first optical path length and the second optical path length for each of multiple voxels to calculate the measurement sensitivity, and calculates the measurement sensitivity for each depth of the measurement object by accumulating the measurement sensitivity calculated for each voxel for each depth of the measurement object.

[0042] The output unit 61 outputs the measurement sensitivity calculated for each depth of the measurement object. Specifically, the output unit 61 displays the measurement sensitivity calculated for each depth of the measurement object on the display unit 53 and stores it in the memory unit 55.

[0043] Figure 4 shows a measurement object model M2 of thigh muscles as another example of a measurement object. The thigh muscles have a three-layer structure consisting of skin SK, fat FA, and muscle MU. It is also possible to identify measurement object models for various other human body parts, such as brain tissue and forearm muscles.

[0044] In the following description, when there is no need to distinguish between the measurement target models, they will be referred to as the measurement target model M.

[0045] Next, as an operation of this embodiment, the measurement sensitivity calculation process executed by the CPU 51A will be described with reference to the flowchart shown in FIG.

[0046] 5, in step S100, a selection screen for the user to select a measurement target is displayed on display unit 53, and the selection of the measurement target is accepted. Here, the user operates operation unit 52 to select a measurement target for which the measurement sensitivity is to be calculated from among multiple measurement targets.

[0047] In step S102, a selection screen for selecting a pair of light receivers 26 is displayed on the display unit 53, and the selection of the pair of light receivers 26 is accepted. Here, the user operates the operation unit 52 to select multiple pairs of two light receivers 26 in which at least one of the first distance D1 and the second distance D2 is different. In this embodiment, in order to simplify the calculation process, from among the multiple pairs of light receivers 26, pairs of light receivers 26 that are clearly considered to be ineligible are excluded, and the user is prompted to select multiple pairs of light receivers 26 that can be candidates in advance. Note that the process of step S102 may be omitted, and the processes of steps S104 to S114 may be performed for all of the multiple pairs of light receivers 26.

[0048] In step S104, a first optical path length is calculated for each of multiple voxels, representing the length of the first optical path from the light emitter 24 to the object to be measured until it is received by the first light receiver 26, which is spaced a first distance D1 from the light emitter 24.

[0049] Hereinafter, a method for calculating the optical path length in each voxel will be described with reference to FIG.

[0050] FIG. 6 shows a schematic diagram of the optical path that the light emitted from the light emitter 24 takes from the point where it is incident on the object to be measured until it is received by the light receiver 26. In FIG.

[0051] The i-th voxel V i The mean optical path length L of light passing through i The procedure for obtaining the above using the Monte Carlo method will be explained below.

[0052] It is assumed that N photon groups among the photon groups incident on the measurement object model M reach the photodetector 26, and Fig. 6 shows the movement of the nth photon group. The photon group has an intensity of 1 when it is incident, and this intensity attenuates according to the absorption coefficient of the medium in accordance with the Lambert-Beer law.

[0053] Furthermore, when a photon group changes direction due to scattering, the distance it takes to change direction (scattering distance) and the direction after scattering are determined using random numbers. If the scattering coefficient of the medium in which the photon group exists is μs and R is a uniform random number between 0 and 1, then the scattering distance is -ln(R) / μs.

[0054] The nth photon group scatters to voxel V i The optical path length when passing through the i,n The intensity of the photon group when it reaches the photodetector 26 is I n Then, voxel V i The average optical path length L of the photon group passing through i is expressed by the following equation:

[0055] JPEG0007813039000001.jpg6175 ···(1)

[0056] That is, the mean optical path length L i is the photon group in voxel V i The optical path length L when passing through i,n When the light reaches the receiver 26, the intensity I n and dividing it by the total amount of light of the photon group that has reached the photodetector 26. The average optical path length is also simply called the optical path length.

[0057] In step S104, all voxels V i Regarding the optical path length L of the first optical path, i Calculate.

[0058] In step S106, a first optical path length is calculated for each of the plurality of voxels, which represents the length of a first optical path along which light emitted from the light emitter 24 to the measurement object is received by the second light receiver 26 spaced a second distance D2 from the light emitter 24. Similarly, a second optical path length is calculated for each of the plurality of voxels, which represents the length of a second optical path along which light emitted from the light emitter 24 to the measurement object is received by the second light receiver 26 spaced a second distance D2 from the light emitter 24.

[0059] That is, as in step S104, all voxels V i Regarding the optical path length L of the second optical path, i Calculate.

[0060] In step S108, voxel V i Measurement sensitivity S i Calculate the measurement sensitivity S i is the voxel V i The first optical path length is L i1 , the second optical path length is L i2 is expressed by the following equation:

[0061] S i =L i2 -L i1 ···(2)

[0062] That is, the measurement sensitivity S i Calculate the second optical path length L i2 and the first optical path length L i1 This is the difference between.

[0063] In step S110, each voxel V calculated in step S108 i Measurement sensitivity S i For example, for each voxel V i Measurement sensitivity S i This gives the measurement sensitivity for each depth. i Each voxel V i Measurement sensitivity S i may be integrated, and the measurement sensitivity S i The depth unit for accumulating the above can be set arbitrarily.

[0064] 7 to 10 show examples of measurement sensitivity distributions in contour maps. FIG. 7 shows the measurement sensitivity distribution for a pair of receivers with a first distance D1 of 3 mm and a second distance D2 of 5 mm. As shown in FIG. 7, the positive measurement sensitivity is 1×10 -1 (mm) ~ 1 × 10 -4 (mm) is shown as a contour line, and negative measurement sensitivity is -1×10 -1(mm), -1×10 -2 , -1×10 -4 The area of ​​negative measurement sensitivity is an area where accurate measurement is not possible. In Figures 7 to 10, the measurement sensitivity distribution is shown by contour lines for convenience, but the actual measurement sensitivity is calculated by dividing each voxel V by the i Measurement sensitivity S i This is done by integrating for each depth.

[0065] Similarly, FIG. 8 shows the measurement sensitivity distribution for a set of receivers with a first distance D1 of 5 mm and a second distance D2 of 7 mm.

[0066] FIG. 9 shows the measurement sensitivity distribution for a set of receivers with a first distance D1 of 9 mm and a second distance D2 of 14 mm.

[0067] FIG. 10 shows the measurement sensitivity distribution for a set of receivers with a first distance D1 of 20 mm and a second distance D2 of 30 mm.

[0068] 11 to 15 show graphs of measurement sensitivity corresponding to Figures 7 to 10, respectively. Figure 7 is a graph of measurement sensitivity corresponding to Figure 11, with the horizontal axis representing depth (mm) and the vertical axis representing measurement sensitivity.

[0069] As shown in Figure 11, for a photodetector pair with D1 = 3 mm and D2 = 5 mm, the depth at which the measurement sensitivity reaches its peak value P is approximately 1.5 mm. The depth range for the half-width W1 of the measurement sensitivity, i.e., the depth range at which the measurement sensitivity reaches 1 / 2 of the peak value, is 0.3 to 3.6 mm. The depth range for the 1 / 10 width W2, i.e., the depth range at which the measurement sensitivity reaches 1 / 10 of the peak value, is 0 to 6.2 mm.

[0070] 12, for a photodetector set with D1=5 mm and D2=7 mm, the depth at which the measurement sensitivity reaches its peak value P is approximately 3.4 mm. The depth range of the half-width W1 of the measurement sensitivity is 1.2 to 6.4 mm. The depth range of the 1 / 10 width W2 is 0.2 to 10.4 mm.

[0071] 13, for a photodetector pair with D1 = 9 mm and D2 = 14 mm, the depth at which the measurement sensitivity reaches its peak value P is approximately 5 mm. The depth range for the half-width W1 of the measurement sensitivity is 2.2 to 9 mm. The depth range for the 1 / 10 width W2 is 0.9 to 14 mm.

[0072] 14, for a photodetector set with D1 = 20 mm and D2 = 30 mm, the depth at which the measurement sensitivity reaches its peak value P is approximately 6 mm. The half-width W1 of the measurement sensitivity has a depth range of 2.6 to 10.5 mm. The depth range at which the 1 / 10 width W2 is reached is 0.8 to 14.5 mm.

[0073] As described above, it can be seen that the peak value of the measurement sensitivity varies depending on the first distance D1 and the second distance D2. Specifically, it can be seen that as the first distance D1 and the second distance D2 increase, the depth of the peak value of the measurement sensitivity gradually shifts to a deeper position.

[0074] In step S112, the depth of the predetermined sensitivity is output. That is, the depth of the predetermined sensitivity is displayed on the display unit 53 and stored in the memory unit 55. Here, the depth of the predetermined sensitivity may be, for example, the depth at which the measurement sensitivity is at its peak value, the depth in the range where the measurement sensitivity is at half-width, the depth in the range where the measurement sensitivity is at 1 / 10 width, etc., but a depth of the measurement sensitivity other than these may also be output.

[0075] In step S114, it is determined whether the processing of steps S104 to S112 has been executed for all pairs of photoreceivers selected in step S102, and if it has been executed for all pairs of photoreceivers, the process proceeds to step S116. On the other hand, if it has not been executed for all pairs of photoreceivers, the process proceeds to step S104, and the processing of steps S104 to S112 is executed for the pairs of photoreceivers that have not been executed.

[0076] In step S116, the first distance D1 and the second distance D2 for the pair of photoreceivers appropriate for the measurement object are output. Specifically, the measurement object depth information 55C is first referenced to obtain the depth of the measurement object selected in step S100. The measurement object depth information 55C is information on the depth of various types of measurement objects. Then, for example, among multiple pairs of photoreceivers 26, the first distance D1 and the second distance D2 for a pair of photoreceivers 26 whose depth of the measurement object falls within a depth range corresponding to a measurement sensitivity equal to or greater than a predetermined threshold are output. The threshold may be, for example, a measurement sensitivity slightly lower than the peak value (e.g., a measurement sensitivity several percent lower than the peak value), a measurement sensitivity of the half-width, i.e., 1 / 2 of the peak value, or, depending on the purpose of measurement, a measurement sensitivity of 1 / 10 of the width, i.e., 1 / 10 of the peak value. Specifically, for example, if the threshold value is set to 1 / 2 of the peak value and the depth of the measurement object is 10 mm, the pair of photoreceivers 26 in which the depth of 10 mm falls within the depth range corresponding to a measurement sensitivity of 1 / 2 or more of the peak value is the pair of D1 = 20 mm, D2 = 30 mm shown in Fig. 14. Therefore, this pair is selected as the pair of photoreceivers 26 suitable for the measurement object.

[0077] For example, if the measurement target is the intestinal wall, a pair of photodetectors 26 with D1 = 3 mm and D2 = 5 mm is suitable. If the measurement target is the stomach or esophagus, a pair of photodetectors 26 with D1 = 5 mm and D2 = 7 mm is suitable. If the measurement target is muscle tissue, a pair of photodetectors 26 with D1 = 20 mm and D2 = 30 mm is suitable.

[0078] As described above, in this embodiment, a measurement object model representing the measurement object using multiple voxels is used to calculate the measurement sensitivity for each voxel, and the measurement sensitivity for each depth is calculated by integrating the measurement sensitivity for each depth. This allows the measurement sensitivity for each depth of the measurement object to be calculated with high accuracy, making it easy to identify a combination of photodetectors suitable for the measurement object. Furthermore, in this embodiment, the measurement sensitivity for each depth of the measurement object is calculated using the optical path length difference as the measurement sensitivity, thereby improving calculation efficiency. Note that the optical path length calculation method described in steps S104 and S106 of FIG. 5 is just one example. Because the absorption coefficient, scattering coefficient, etc. vary depending on the number of layers and medium of the measurement object model, it is preferable to calculate the optical path length using an optical path length calculation method appropriate for the measurement object model.

[0079] (Second embodiment)

[0080] Next, a second embodiment will be described.

[0081] Fig. 15 shows a schematic configuration of the optical measurement device 10. As shown in Fig. 15, the optical measurement device 10 includes a probe 12, a drive device 14, a control unit 16, an operation unit 18, a memory 20, and an output unit 22.

[0082] The probe 12 includes a light emitter 24, multiple light receivers 26, a ToF light emitter 40, and two ToF light receivers 42 mounted on, for example, a flexible, flat member 28 (e.g., a rubber member or the like). In this embodiment, the light emitter 24 is, for example, a light-emitting diode (LED), and the light receiver 26 is, for example, a photodiode. The probe 12 is attached to an endoscope used in surgery for esophageal cancer, stomach cancer, or the like, more specifically, to the tip of the forceps of the endoscope. In this case, the optical measurement device 10 measures the oxygen concentration and the like with the probe 12 applied to a measurement target 30 such as the esophageal tract or stomach wall. The measured oxygen concentration and the like are taken into consideration when determining how much of the esophageal tract or stomach wall to resect.

[0083] In this embodiment, the light emitter 24 is, for example, a light-emitting diode with two peak wavelengths, a first wavelength λ1 and a second wavelength λ2. The first wavelength λ1 and the second wavelength λ2 are set to wavelengths that are little absorbed by hemoglobin and water, specifically, two different wavelengths in the range of 700 nm to 900 nm. In this embodiment, for example, the first wavelength λ1 is 770 nm and the second wavelength λ2 is 830 nm.

[0084] The light emitter 24 and each light receiver 26 are arranged at different distances from each other, and three or more light receivers 26 are arranged in a row. These three or more light receivers 26 are selected as a set of light receivers suitable for the measurement object obtained by the measurement sensitivity calculation device 50 described in the first embodiment executing the measurement sensitivity calculation process of Figure 5. In other words, the distances between the light emitter 24 and the three or more light receivers 26 are distances suitable for the measurement object measured by the optical measurement device 10.

[0085] The ToF light emitter 40 emits pulsed light to measure the time of flight (ToF) of light. The ToF light emitter 40 is provided near the light emitter 24.

[0086] The two ToF photodetectors 42 receive light emitted from the ToF light emitter 40. The two ToF photodetectors 42 are respectively provided near two predetermined photodetectors 26 among the plurality of photodetectors 26. That is, the ToF light emitter 40 and the two ToF photodetectors 42 are arranged in the same positional relationship as the positional relationship between the light emitter 24 and the two photodetectors 26. The ToF light emitter 40 and the two ToF photodetectors 42 are an example of a measurement unit.

[0087] The driving device 14 includes an LED driver 32, a selection circuit 33, an IV converter 34, and an amplifier 36.

[0088] The LED driver 32, in response to an instruction from the control unit 16, causes the light emitter 24 to emit light at a predetermined wavelength and a predetermined light intensity.

[0089] The selection circuit 33 selects two photoreceivers 26 in response to an instruction from the control unit 16, and outputs the outputs from the selected two photoreceivers 26 to the IV converter .

[0090] The IV converter 34 converts the current obtained by photoelectrically converting the light received by the photodetector 26 selected by the selection circuit 33 into a voltage and outputs it to the amplifier 36 .

[0091] The amplifier 36 amplifies the voltage converted by the IV converter 34 to a voltage of a predetermined level, and outputs it to the control unit 16 as a signal indicating the light intensity.

[0092] The control unit 16 instructs the selection circuit 33 to select one of the two light receivers 26 and instructs the LED driver 32 to emit light from the light emitter 24, and calculates the hemoglobin concentration and the like based on the light intensity of the light received by the two selected light receivers 26. The calculation results are output to the output unit 22. The output unit 22 is composed of, for example, a display, a printer, etc., and outputs the calculation results by displaying or printing them.

[0093] The memory 20 stores in advance a program for a measurement processing routine, which will be described later, and data used in the processing, such as data relating to the results of a simulation that has been previously executed.

[0094] Next, as an operation of this embodiment, the measurement process executed by the control unit 16 will be described with reference to the flowchart shown in FIG.

[0095] When performing measurement, the subject brings probe 12 into contact with the measurement target and issues a command to start measurement by operating operation unit 18. This starts the processing shown in FIG.

[0096] In step S200, a method for selecting the measurement object is accepted. The user operates operation unit 18 to instruct whether the measurement object is to be selected automatically or manually.

[0097] In step S202, it is determined whether the selection method accepted in step S200 is automatic or not, and if it is manual, the process proceeds to step S204, and if it is automatic, the process proceeds to step S206.

[0098] In step S204, a measurement target is accepted. Here, the user manually indicates the measurement target to be measured by operating the operation unit 18. After the measurement target is accepted, the process proceeds to step S216.

[0099] In step S206, light of the first wavelength λ1 and light of the second wavelength λ2 are emitted sequentially from the light emitter 24, and the light intensities of the lights received by the two predetermined light receivers 26 are acquired, respectively.

[0100] In step S208, the spatial gradient in the spatial resolution method is calculated based on the light intensity acquired in step S206. The spatial gradient is calculated using a known method such as that described in Japanese Patent No. 5062698.

[0101] In step S210, the ToF light emitter 40 emits light, and the ToF until the emitted light is received by the ToF light receiver 42 is measured.

[0102] In step S212, the absorption coefficient and scattering coefficient corresponding to the spatial gradient calculated in step S208 and the ToF measured in step S210 are calculated. For example, table data representing the correspondence between the spatial gradient and ToF and the absorption coefficient and scattering coefficient, which is calculated in advance from a theoretical analysis database or the like, is stored in advance in memory 20, and the absorption coefficient and scattering coefficient corresponding to the spatial gradient calculated in step S208 and the ToF measured in step S210 are calculated by referring to this table data.

[0103] In step S214, a measurement object corresponding to the absorption coefficient and scattering coefficient calculated in step S212 is identified. For example, table data showing the correspondence between the absorption coefficient and scattering coefficient and the measurement object is stored in advance in memory 20, and the measurement object corresponding to the absorption coefficient and scattering coefficient calculated in step S212 is identified by referring to this table data. This allows the measurement object to be automatically identified without the user having to manually specify the measurement object.

[0104] In step S216, a pair of photoreceivers corresponding to the measurement object identified in step S214 is selected. For example, table data showing the correspondence between measurement objects and pairs of photoreceivers is stored in advance in memory 20, and this table data is referenced to find a pair of photoreceivers corresponding to the measurement object identified in step S214, and selection circuit 33 is instructed to select photoreceivers 26 of the found pair.

[0105] In step S218, a measurement process is performed. That is, light of the first wavelength λ1 and the second wavelength λ2 is sequentially emitted from the light emitter 24, and the light intensities of the light received by the two light receivers 26 selected in step S216 are acquired. Then, the degree of light absorption is calculated based on the acquired light intensities. In addition, the hemoglobin concentration and the like are calculated based on the degree of light absorption. The degree of light absorption and the hemoglobin concentration and the like can be calculated using known methods, for example, as described in Japanese Patent No. 5062698.

[0106] In step S220, the measurement result of step S218 is output to the output unit 22.

[0107] In this way, the measurement target can be automatically identified, eliminating the need for the user to manually specify the measurement target. Also, the user can manually specify the measurement target, improving convenience.

[0108] In the second embodiment, the configuration in which two ToF light receivers 42 are provided in the vicinity of two predetermined light receivers 26 among the plurality of light receivers 26 has been described. However, a configuration in which one ToF light receiver 42 is provided may also be used. In this case, one ToF light receiver 42 is arranged at a position considering balance so as to be close to both of the two predetermined light receivers 26. Specifically, the ToF light receiver 42 may be provided at an intermediate position between the two predetermined light receivers 26. That is, the ToF light receiver 42 may be provided at a position where the distances from each of the two predetermined light receivers 26 are equal. This is preferable because an average scattering coefficient close to the scattering coefficients corresponding to the two optical paths from the light emitter 24 to the two predetermined light receivers 26 can be obtained. Also, in FIG. 15, a configuration in which only one ToF light receiver 42 adjacent to the light receiver 26 located in the center or one ToF light receiver 42 adjacent to the lowermost light receiver 26 is provided may also be used.

[0109] (Third Embodiment) Next, the third embodiment will be described. In the third embodiment, the simulation results of the measurement sensitivity in a plurality of combinations of the first distance D1 and the second distance D2 will be described.

[0110] FIG. 17 shows the results of simulating the measurement sensitivity (Sensitivity) for each measurement depth (Depth) by using a measurement target model of skin tissue (including subcutaneous tissue) as a measurement target, setting the second distance D2 to 5 mm, and making the first distance D1 variable within the range of 0 (mm) < D1 < 5 (mm). As shown in FIG. 17, the measurement sensitivity takes values in the range of -1.0 to 1.0, is color-coded into positive and negative sensitivities, and is displayed in gradation by changing the density according to the value.

[0111] As shown in FIG. 17, the region with a darker color within the region A1 surrounded by the broken line has the peak measurement sensitivity. Here, the peak measurement sensitivity is the measurement sensitivity at which the measurement sensitivity becomes 1 (mm). As shown in FIG. 17, it can be seen that the measurement sensitivity peaks in the range where the measurement depth is 1 (mm) or more and 2 (mm) or less.

[0112] In addition, in FIG. 17, there is no region with a negative measurement sensitivity. That is, there is no combination of the first distance D1 that results in a negative measurement sensitivity and the measurement sensitivity.

[0113] FIG. 18 shows the results of simulating the measurement sensitivity for each measurement depth under the same conditions as in FIG. 17, except that the second distance D2 is set to 8 mm and the first distance D1 is variable within the range of 0 (mm) < D1 < 8 (mm).

[0114] As shown in FIG. 18, the darker-colored region within the region A2 enclosed by the dashed line has the peak measurement sensitivity. As shown in FIG. 18, it can be seen that the measurement sensitivity peaks within the range where the measurement depth is 1.5 (mm) or more and 2.5 (mm) or less.

[0115] In addition, in FIG. 18, in the region B2 enclosed by the dashed line, the measurement sensitivity is negative.

[0116] FIG. 19 shows the results of simulating the measurement sensitivity for each measurement depth under the same conditions as in FIG. 17, except that the second distance D2 is set to 14 mm and the first distance D1 is variable within the range of 0 (mm) < D1 < 14 (mm).

[0117] As shown in FIG. 19, the darker-colored region within the region A3 enclosed by the dashed line has the peak measurement sensitivity. As shown in FIG. 19, it can be seen that the measurement sensitivity peaks within the range where the measurement depth is 2.0 (mm) or more and 4.0 (mm) or less.

[0118] In addition, in FIG. 19, in the region B3 enclosed by the dashed line, the measurement sensitivity is negative.

[0119] FIG. 20 shows the results of simulating the measurement sensitivity for each measurement depth under the same conditions as in FIG. 17, except that the second distance D2 is set to 30 mm and the first distance D1 is variable within the range of 0 (mm) < D1 < 30 (mm).

[0120] As shown in Fig. 20, the darker area within the area A4 surrounded by the dashed line represents the peak measurement sensitivity. As shown in Fig. 20, it can be seen that the measurement sensitivity peaks when the measurement depth is in the range of 3.0 mm or more and 6.5 mm or less.

[0121] In FIG. 20, the area B4 surrounded by the dashed line has a negative measurement sensitivity.

[0122] From the results of Figures 17 to 20, for example, in the measurement process in the optical measurement device 10 shown in Figure 15, when the measurement object is skin tissue and the depth of the measurement object is 1 mm or more and 3 mm or less, it is preferable to select the second photoreceiver 26 whose second distance D1 is 14 mm or less.

[0123] The inventor also performed simulations similar to those shown in Figures 17 to 20 for various second distances D2 other than those shown in Figures 17 to 20. From the simulation results shown in Figures 17 to 20 and simulation results other than those shown in Figures 17 to 20, it was found that the measurement depth increases as the first distance D1 and the second distance D2 increase.

[0124] In addition, it was found that the following equation holds true, assuming that the measurement depth is Dp. Dp≒D2 / 5 (3) However, D1≒D2 / 2

[0125] That is, when the first distance D1 is approximately half of the second distance D2, the measurement depth Dp is approximated by 1 / 5 of the second distance D2. Specifically, as a result of performing a regression analysis, it was found that the correspondence relationship between the measurement depth Dp1, the first distance D1, and the second distance D2 is expressed by the following equation. Dp1=0.090×D1+0.079×D2+0.85 (4)

[0126] Therefore, for example, in the measurement process of the optical measurement device 10 shown in FIG. 15, when the measurement object is skin tissue, the first distance D1 is 1 / 2 of the second distance D2, and the depth of the skin tissue to be measured satisfies the condition of being 1 / 5 of the second distance D2. The first light receiver 26 and the second light receiver 26 corresponding to the first distance D1 and the second distance D2 closest to the first distance D1 and the second distance D2 may be selected.

[0127] Also, for example, in the measurement process of the optical measurement device 10 shown in FIG. 15, based on the correspondence relationship of the depth of the measurement object, the first distance, and the second distance derived based on the calculation result of calculating the measurement sensitivity for each depth of the measurement object, the first light receiver 26 and the second light receiver 26 may be selected. For example, based on the above formula (4), the first light receiver 26 and the second light receiver 26 may be selected.

[0128] FIG. 21 shows the results of simulating the measurement sensitivity for each measurement depth under the same conditions as FIG. 17, except that the measurement object model of gastrointestinal tissue as the measurement object is used, the second distance D2 is set to 5 mm, and the first distance D1 is variable within the range of 0 (mm) < D1 < 5 (mm).

[0129] As shown in FIG. 21, in the region A5 surrounded by the broken line, the darker region has the peak measurement sensitivity. As shown in FIG. 21, it can be seen that the measurement sensitivity peaks in the range where the measurement depth is 0.5 (mm) or more and 1.5 (mm) or less. In FIG. 21, there is no region with negative measurement sensitivity.

[0130] FIG. 22 shows the results of simulating the measurement sensitivity for each measurement depth under the same conditions as FIG. 21, except that the second distance D2 is set to 8 mm and the first distance D1 is variable within the range of 0 (mm) < D1 < 8 (mm).

[0131] As shown in FIG. 22, the dark-colored region within the region A6 surrounded by the dashed line has the peak measurement sensitivity. As shown in FIG. 22, it can be seen that the measurement sensitivity peaks within the range where the measurement depth is 1.0 (mm) or more and 2.0 (mm) or less. Note that in FIG. 22, there is no region with a negative measurement sensitivity.

[0132] FIG. 23 shows the results of simulating the measurement sensitivity for each measurement depth under the same conditions as in FIG. 21, except that the second distance D2 is set to 14 mm and the first distance D1 is variable within the range of 0 (mm) < D1 < 14 (mm).

[0133] As shown in FIG. 23, the dark-colored region within the region A7 surrounded by the dashed line has the peak measurement sensitivity. As shown in FIG. 23, it can be seen that the measurement sensitivity peaks within the range where the measurement depth is 2.5 (mm) or more and 4.0 (mm) or less.

[0134] Note that in FIG. 23, in the region B7 surrounded by the dashed line, the measurement sensitivity is negative.

[0135] FIG. 24 shows the results of simulating the measurement sensitivity for each measurement depth under the same conditions as in FIG. 21, except that the second distance D2 is set to 30 mm and the first distance D1 is variable within the range of 0 (mm) < D1 < 30 (mm).

[0136] As shown in FIG. 24, the dark-colored region within the region A8 surrounded by the dashed line has the peak measurement sensitivity. As shown in FIG. 20, it can be seen that the measurement sensitivity peaks within the range where the measurement depth is 3.0 (mm) or more and 5.5 (mm) or less.

[0137] Note that in FIG. 24, in the region B8 surrounded by the dashed line, the measurement sensitivity is negative.

[0138] The inventors performed simulations similar to those shown in Figures 21 to 24 for various second distances D2 other than those shown in Figures 21 to 24. From the simulation results shown in Figures 21 to 24 and the simulation results other than those shown in Figures 21 to 24, it was found that when the first distance D1 and the second distance D2 are the same, the measurement depth at which the measurement sensitivity reaches its peak is slightly shallower than when the measurement target is skin tissue.

[0139] Furthermore, as a result of performing a regression analysis, it was found that the relationship between the measurement depth Dp2, the first distance D1, and the second distance D2 is expressed by the following equation. Dp2=0.041×D1+0.073×D2+0.76 (5)

[0140] From the above simulation results, it was found that when the second distance D2 is 10 mm or less, the difference between the measurement depth Dp1 of the skin tissue and the measurement depth Dp2 of the gastrointestinal tissue is in the range of 10% or more and 20% or less, and the measurement sensitivity distributions of the two tissues can be calculated using the same measurement sensitivity calculation device.

[0141] It was also found that the measurement depth can be changed within a range of 1 to 5 mm by appropriately selecting the first distance D1 and the second distance D2 depending on the depth and type of tissue of the measurement target.

[0142] It should be noted that the present embodiment does not limit the invention as claimed, and not all of the combinations of features described in the embodiment are necessarily essential to the solution of the invention. The above-described embodiment includes inventions at various stages, and various inventions can be extracted by combining the multiple disclosed constituent elements. Even if some constituent elements are deleted from all the constituent elements shown in the embodiment, as long as the effect can be obtained, the configuration from which these constituent elements are deleted can be extracted as an invention.

[0143] In the above embodiment, the measurement sensitivity calculation program 55A is pre-installed in the storage unit 55, but the present invention is not limited to this. For example, the measurement sensitivity calculation program 55A may be provided by being stored in a storage medium such as a CD-ROM (Compact Disc Read Only Memory), or may be provided via a network.

[0144] Furthermore, in the above embodiment, the measurement sensitivity calculation process is described as being realized by a software configuration using a computer by executing a program, but this is not limited to this. For example, the measurement sensitivity calculation process may be realized by a hardware configuration or a combination of a hardware configuration and a software configuration.

[0145] Furthermore, the processing flow of the measurement sensitivity calculation program described in the above embodiment (see Figure 5) is also an example, and it goes without saying that unnecessary steps may be deleted, new steps may be added, or the processing order may be rearranged within the scope of the present disclosure.

[0146] The disclosure of Japanese Patent Application No. 2020-161401 is incorporated herein by reference in its entirety. In addition, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually indicated to be incorporated by reference. [Explanation of symbols]

[0147] 10 Optical measuring device 12 probes 14 Drive unit 16 Control Unit 24 Light-emitting organ 26 Receiver 33 Selection circuit 40 ToF light emitter 42 ToF receiver 50 Measurement sensitivity calculation device 51 Controller 55 Storage section 55A Measurement Sensitivity Calculation Program 55B Measurement target model data 55C Measurement target depth information 60 Calculation Unit 61 Output section D1 First distance D2 Second distance M Measurement target model

Claims

1. a calculation unit that calculates, in a measurement object model that represents a measurement object using a plurality of voxels, a measurement sensitivity that is a difference between a first optical path length that represents the length of a first optical path from which light emitted from a light emitter to the measurement object is received by a first light receiver that is spaced a first distance from the light emitter, and a second optical path length that represents the length of a second optical path from which light emitted from the light emitter is received by a second light receiver that is spaced a second distance from the light emitter; and an output unit that outputs the measurement sensitivity calculated for each depth of the measurement object; Equipped with The calculation unit calculates the first optical path length by dividing a value obtained by weighting and adding optical path lengths when the photon group passes through the voxel with the intensity when it reaches the first optical receiver, by the sum of the light amounts of the photon group that reaches the first optical receiver, and calculates the second optical path length by dividing a value obtained by weighting and adding optical path lengths when the photon group passes through the voxel with the intensity when it reaches the second optical receiver, by the sum of the light amounts of the photon group that reaches the second optical receiver. Measurement sensitivity calculation device.

2. The calculation unit selects a plurality of pairs of two light receivers in which at least one of the first distance and the second distance is different, and calculates the measurement sensitivity for each of the selected pairs of light receivers for each depth of the measurement object.

2. The measurement sensitivity calculation device according to claim 1.

3. The output unit outputs the first distance and the second distance for a pair of light receivers among the plurality of pairs of light receivers, the pair of light receivers having a depth of the measurement object included in a depth range corresponding to a measurement sensitivity equal to or greater than a predetermined threshold.

3. The measurement sensitivity calculation device according to claim 2.

4. The calculation unit calculates the measurement sensitivity by calculating the first optical path length and the second optical path length for each of the plurality of voxels, and calculates the measurement sensitivity for each depth of the measurement object by accumulating the measurement sensitivity calculated for each voxel for each depth of the measurement object. The measurement sensitivity calculation device according to any one of claims 1 to 3.

5. a step of calculating a measurement sensitivity for each depth of the measurement object, using a difference in optical path length between a first optical path length representing the length of an optical path from a light emitter to the measurement object until the light is received by a first optical receiver spaced a first distance from the light emitter, and a second optical path length representing the length of an optical path from the light emitter until the light is received by a second optical receiver spaced a second distance from the light emitter, as a measurement sensitivity; outputting the measurement sensitivity calculated for each depth of the measurement object; A measurement sensitivity calculation method comprising:

6. On the computer, a step of calculating a measurement sensitivity for each depth of the measurement object, using a difference in optical path length between a first optical path length representing the length of a first optical path along which light emitted from a light emitter to the measurement object is received by a first light receiver spaced a first distance from the light emitter, and a second optical path length representing the length of a second optical path along which light emitted from the light emitter is received by a second light receiver spaced a second distance from the light emitter, in a measurement object model in which the measurement object is represented by a plurality of voxels; outputting the measurement sensitivity calculated for each depth of the measurement object; A measurement sensitivity calculation program that executes a process including: The calculating step calculates the first optical path length by weighting and adding the optical path lengths when the photon group passes through the voxel with the intensity when it reaches the first optical receiver, and dividing the resultant value by the sum of the light amounts of the photon group that reaches the first optical receiver; and calculates the second optical path length by weighting and adding the optical path lengths when the photon group passes through the voxel with the intensity when it reaches the second optical receiver, and dividing the resultant value by the sum of the light amounts of the photon group that reaches the second optical receiver. Measurement sensitivity calculation program.

7. a light emitter that emits light toward the measurement target; three or more light receivers at different distances from the light emitter; a selection unit that selects two light receivers selected from the three or more light receivers; a calculation unit that calculates a degree of light absorption based on the light intensities of the light received by the two light receivers; Equipped with The selection unit selects a plurality of pairs of two light-receivers in which at least one of the first distance and the second distance is different, using a difference in optical path length between a first optical path length representing the length of a first optical path from which light emitted from a light emitter to the measurement object until it is received by a first light-receiver spaced a first distance from the light emitter and a second optical path length representing the length of a second optical path from which light emitted from the light emitter until it is received by a second light-receiver spaced a second distance from the light emitter as measurement sensitivity in a measurement object model in which the measurement object is represented by a plurality of voxels, and selects two light-receivers corresponding to the measurement object based on a calculation result obtained by calculating the measurement sensitivity for each depth of the measurement object for the plurality of selected pairs of light-receivers.

1. An optical measurement device, comprising: The first optical path length is calculated by weighting and adding the optical path lengths when the photon group passes through the voxel with the intensity when it reaches the first optical receiver, and dividing the resultant value by the total amount of light of the photon group that reaches the first optical receiver. The second optical path length is calculated by weighting and adding the optical path lengths when the photon group passes through the voxel with the intensity when it reaches the second optical receiver, and dividing the resultant value by the total amount of light of the photon group that reaches the second optical receiver. Optical measuring device.

8. When the measurement target is skin tissue and the depth of the measurement target is 1 mm or more and 3 mm or less, the selection unit selects the second light receiver whose second distance is 14 mm or less.

8. The optical measurement device according to claim 7.

9. When the measurement target is skin tissue, the selection unit selects the first light receiver and the second light receiver corresponding to the first distance and the second distance that are closest to the first distance and the second distance, which satisfy the condition that the first distance is 1 / 2 of the second distance and the depth of the skin tissue is 1 / 5 of the second distance.

8. The optical measurement device according to claim 7.

10. The selection unit selects the first light receiver and the second light receiver based on a correspondence relationship between the depth of the measurement object, the first distance, and the second distance, which is derived based on a calculation result of the measurement sensitivity for each depth of the measurement object.

8. The optical measurement device according to claim 7.

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