Patent Publication Number: US-2022218245-A1

Title: Optical measurement device and probe holder set

Description:
TECHNICAL FIELD 
     The present invention relates to an optical measurement device and a probe holder set. In particular, the present invention relates to an optical measurement device in which a light-transmitting probe and a light-receiving probe are placed on a head of a subject, and also relates to a probe holder set for use in such an optical measurement device. 
     BACKGROUND OF THE INVENTION 
     Conventionally, in an optical measurement device, a configuration is known in which hairs of a subject are parted when placing a light-transmitting probe and a light-receiving probe on the head of the subject. Such a configuration is disclosed, for example, in Japanese Patent No. 5610065. 
     Japanese Patent No. 5610065 discloses a brain function measurement device provided with a photobiological measurement holder to be mounted on a head of a subject, a light-transmitting probe, a light-receiving probe, and a light-transmitting/light-receiving control unit. The photobiological measurement holder is provided with one straight trunk, four straight first branches, one straight second branch, and a band for securing the photobiological measurement holder to the head. The trunk extends in an X-direction. The first branch extends in a Y-direction perpendicular to the X-direction and includes one end connected to the trunk and the other end tapered for parting hairs. The first branches include two branches arranged on the right side and two branches arranged on the left side with respect to the center of the trunk. The second branch extends in the Y-direction perpendicular to the X-direction and includes one end connected to the trunk and the other end tapered to part hairs. The second branch is connected to the central portion of the trunk. A through-hole is formed in each first branch. A light-transmitting probe or a light-receiving probe is configured to be inserted into the through-hole. 
     When placing the light-transmitting probe and the light-receiving probe, first, a subject, a doctor, or the like inserts the light-transmitting probe and the light-receiving probe into the through-holes. Next, the subject, the doctor, or the like places the photobiological measurement holder on the head in such a manner as to move the holder from the front of the head toward the rear of the head while parting hairs. Then, the holder is fixed to the head. 
     PRIOR ART DOCUMENT 
     Patent Document 
     
         
         Patent Document 1: Japanese Patent No. 5610065 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     As disclosed in the above-described Japanese Patent No. 5,610,065, in order to perform accurate measurement when performing optical measurement (cerebral function measurement) of a head of a subject, it is crucial to bring the tip of the probe in close contact with the head surface such that hairs are not interposed between the probe and the head surface (scalp). 
     In the above-described Japanese Patent No. 5610065, a comb-shaped photobiological measurement holder having the first branches and the second branch is used such that the mounting of the photobiological measurement holder can be performed while parting hairs by the first branches and the second branch. However, even in the photobiological measurement holder having such a configuration, in some cases, hairs may be interposed between the probe and the head surface. 
     In a case where hairs are interposed therebetween, it is required for a doctor or the like to remove the probe once from the through-hole and reinsert the probe into the through-hole via the through-hole in a state in which the doctor or the like has parted hairs with a rod-shaped tool to expose the head surface. For this reason, conventionally, in addition to the subject, an assistant, such as, e.g., a doctor, is required to assist the attachment of the probe when performing the cerebral function measurement. Further, the operation for parting hairs is troublesome because it is required to be performed through each of the narrow through-holes by using a rod-shaped tool. 
     Under the circumstances, it has been desired that a probe can be placed such that hairs are not interposed between the probe and the head surface only by a subject without requiring an assistant and that the operation of parting hairs can be performed simply. 
     The present invention has been made to solve the above-described problems. One object of the present invention is to provide an optical measurement device and a probe holder set capable of arranging a probe such that hairs are not interposed between the probe and a head surface only by a subject in a simple operation. 
     Means for Solving the Problem 
     In order to achieve the above-described object, as a result of extensive studies by the present inventors, it has been found that the reason that hairs are interposed between the probe and the head surface by a conventional method is especially largely affected by the following two points. First, in a case where hairs extend along a head surface (i.e., hairs are laying) rather than a case where hairs extend upward from the head surface, a space is hardly formed between hairs and the head surface even if the hairs are parted. For this reason, it is difficult to form a space for bringing the probe in close contact with the head surface. Second, in some cases, it may not be effective to pair the hairs linearly in a particular direction because the direction in which hairs extend (the direction of hair orientation) differs depending on the measurement position of the head and/or the personal difference of a subject. For example, even if hairs are parted in a direction parallel to the hairs, the hairs cannot be paired so as to expose the region for arranging the probe. 
     Based on the above-described findings, the inventors of the present application have conceived the following invention. That is, an optical measurement device according to a first aspect of the present invention includes: 
     a device main body configured to irradiate a head surface of a subject with measurement light via a light-transmitting probe and detect the measurement light emitted from the head surface by way of an inside of a head via a light-receiving probe; 
     a holder configured to be attached to the head of the subject; and 
     a probe unit held by the holder, 
     wherein the probe unit includes: 
     a base member rotatably held by the holder about a central axis; 
     the light-transmitting probe protruding from the base member in a first direction toward the head surface; 
     the light-receiving probe protruding from the base member in the first direction; and 
     a plurality of pin members each protruding from the base member in the first direction for parting hairs of the head surface, 
     wherein the plurality of pin members is inclined obliquely at least either in a direction toward a central axis side of the base member or in a circumferential direction about the central axis. 
     A probe holder set for an optical measurement device configured to irradiate a head surface of a subject with measurement light via a light-transmitting probe and detect the measurement light emitted from the head surface by way of an inside of the head via a light-receiving prove, according to a second aspect of the present invention, the probe holder set includes: 
     a holder configured to be attached to the head of the subject; and 
     a probe unit held by the holder, 
     wherein the probe unit includes: 
     a base member rotatably held by the holder about a central axis: 
     the light-transmitting probe protruding from the base member in a first direction toward the head surface; 
     the light-receiving probe protruding from the base member in the first direction; and 
     a plurality of pin members each protruding from the base member in the first direction for parting hairs of the head surface, and 
     wherein the plurality of pin members is inclined obliquely at least either in a direction toward a central axis side of the base member or in a circumferential direction about the central axis. 
     Note that in this specification, the term “pin member” includes a broad concept meaning an elongated rod-shaped member and does not mean a member for fixing or sewing an object. 
     Effects of the Invention 
     According to the present invention, as described above, the probe unit includes a plurality of pin members protruding from the base member rotatably held by the holder about a central axis in the first direction for parting hairs of the head surface. Therefore, by simply placing the probe unit on the head surface and rotates it by the subject himself/herself, it is possible to rotate the pin members to part the hairs. At this time, the pin members are inclined obliquely at least either in a direction toward the central axis side or in a circumferential direction. For this reason, even in a case where hairs extend along the head surface, it is possible to lift the hairs along the slope of the pin member while parting the hairs. As a result, the parted hairs are raised, and therefore a space capable of arranging the probe without interposing hairs can be formed in the vicinity of the head surface. Further, the traveling path of the pin member is a closed circumference path about the central axis. Therefore, even if hairs extend in any orientation, the hairs can be parted by the pin members. As a result, according to the above-described configuration, it is possible to arrange the probe such that hairs are not interposed between the probe and the head surface by only a subject in a simple operation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic perspective view showing an optical measurement device and a probe holder set according to one embodiment. 
         FIG. 2  is a schematic view for explaining optical measurement by a light-transmitting probe and a light-receiving probe. 
         FIG. 3  is a block diagram showing a configuration of an optical measurement device according to one embodiment. 
         FIG. 4  is a perspective view showing one example of a probe unit. 
         FIG. 5  is an exploded perspective view for explaining a configuration of a probe unit. 
         FIG. 6  is a cross-sectional view of a probe unit taken along the line  500 - 500  in  FIG. 8 . 
         FIG. 7  is a cross-sectional view of a probe unit taken along the line  600 - 600  in  FIG. 8 . 
         FIG. 8  is a bottom view of the probe unit shown in  FIG. 4 . 
         FIG. 9  is a schematic side view of a probe unit for explaining an arrangement operation of probes. 
         FIG. 10  is a schematic view showing a planar arrangement of pin members and probes for explaining the arrangement operation of the probes. 
         FIG. 11  is a schematic side view of a probe unit for explaining a lifting action of hairs by pin members. 
         FIG. 12  is a schematic side view of a probe unit showing a state in which tips of probes are in contact with a head surface. 
         FIG. 13  is a view showing a modification in which a plurality of pin members is obliquely inclined in a circumferential direction about a central axis of a base member. 
     
    
    
     EMBODIMENTS FOR CARRYING OUT THE INVENTION 
     Hereinafter, some embodiments in which the present invention is embodied will be described with reference to the attached drawings. 
     First, with reference to  FIGS. 1 to 8 , the entire configuration of an optical measurement device  100  according to one embodiment will be described. The optical measurement device  100  is configured to irradiate a head surface  91  of a subject  9  with measurement light and detect the measurement light emitted from the head surface  91  via the inside of the head. The optical measurement device  100  is a device configured to measure the change in the cerebral blood flow that reflects the brain activities of the subject  9 , based on the intensity (amount of the received light) of the detected measurement light. 
     The optical measurement device  100  is provided with a device main body  1  and a probe holder set  2 . The probe holder set  2  includes a holder  20  and a probe unit  30 . 
     Further, the optical measurement device  100  is provided with a plurality of measurement probes (light-transmitting probes  32  and light-receiving probes  33 ) connected to the device main body  1 . 
     The plurality of measurement probes each function as a light-transmitting probe  32  or a light-receiving probe  33 , and both the light-transmitting probe  32  and the light-receiving probe  33  have the same structure. The measurement probe means a probe to be brought into contact with or inserted into a sample for the purpose of measurement, experiments, etc. The measurement probe has one end connected to the device main body  1  and the other end to be brought into contact with the head surface  91  of the subject  9 . As shown in  FIG. 2 , the device main body  1  emits measurement light in the near-infrared range from the light-transmitting probe  32  arranged on the head surface  91  of the subject  9 . Then, the device main body  1  detects the measurement light incident from the light-receiving probe  33  arranged on the head surface  91 . The region serving as the path of the measurement light between one light-transmitting probe  32  and one light-receiving probe  33  configures one measurement point (measurement channel  5 ). The wavelength region of the near-infrared light is, for example, 700 nm or more and 900 nm or less. The near-infrared light is less absorptive in vivo, and therefore, the measurement light can reach the cerebral region in the head. 
     When the amount of hemoglobin in the blood in the brain increases at the activation site reflecting the brain activities of the subject  9 , the amount of measurement light absorbed by the hemoglobin increases. Thus, it is possible to acquire the change in the hemoglobin content associated with the cerebral activities based on the intensity of the acquired measurement light. Note that hemoglobin is classified into oxyhemoglobin bound to oxygen and deoxyhemoglobin not bound to oxygen. Oxyhemoglobin and deoxyhemoglobin have different absorption characteristics. For this reason, the optical measurement device  100  performs measurement using the measurement light of a plurality of wavelengths (e.g., three wavelengths of 780 nm, 805 nm, and 830 nm) considering the difference in the absorption characteristics. The temporal changes in the amounts of hemoglobin and the total amount thereof are calculated based on the intensities of measurement light of the respective acquired wavelengths. 
     As a result, based on the intensity (amount of the received light) of the measurement light incident on the light-receiving probe  33 , it is possible to acquire the change in the amount of hemoglobin associated with cerebral activities, i.e., the change in the blood flow rate or the activation state of oxygen metabolism in a non-invasive manner. The optical measurement device  100  is provided with a plurality of light-transmitting probes  32  and a plurality of light-receiving probes  33 . By measuring brain regions at a plurality of points (a plurality of measurement channels  5 ) using a plurality of light-transmitting probes  32  and a plurality of light-receiving probes  33 , it is possible to acquire the two-dimensional distribution of which regions of the brain are active and how. 
     Returning to  FIG. 1 , the probe unit  30  holds the light-transmitting probe  32  and the light-receiving probe  33  each connected to the device main body  1 . The probe unit  30  is arranged on the head surface  91  of the subject  9  and is configured to maintain the relative position between the light-transmitting probe  32  and light-receiving probe  33 , which constitute the measurement channel  5  by the measurement light, constant. 
     Specifically, the probe unit  30  includes a base member  31 , a light-transmitting probe  32 , a light-receiving probe  33 , and a plurality of pin members  34  for parting hairs on the head surface  91 . The light-transmitting probe  32 , the light-receiving probe  33 , and the plurality of pin members  34  are provided to the base member  31 . 
     The probe unit  30  is held by the holder  20 . The probe unit  30  is held in place on the head surface  91  of the subject  9  by the holder  20 . In this embodiment, the probe unit  30  is held by the holder  20  in such a manner as to be rotatable about the central axis. The probe unit  30  is configured such that the plurality of pin members  34  can part hairs by being rotated about the central axis with the probe unit  30  arranged on the head surface  91 . The detailed configuration of the probe unit  30  will be described later. 
     The holder  20  is mounted on the head of the subject  9 . The holder  20  is configured to hold one or a plurality of probe units  30 . The holder  20  has, for example, a socket (not shown) capable of removably mounting the probe unit  30  and removably and rotatably holds the probe unit  30  about the central axis. The holder  20  may, for example, hold the probe unit  30  in a rotatable manner but in a non-separably connected manner. 
     The holder  20  is not particularly limited in shape as long as it can be mounted immovably on the head of the subject  9 . The holder  20  may have a variety of shapes. For example, it is possible to adopt a holder shape, such as, e.g., a headband-like shape surrounding a head in a circumferential direction, a headphone shape to be mounted with both ears covered, a headgear-like shape that covers a part of a head, and a helmet-like shape that entirely covers a head. 
     In the example shown in  FIG. 1 , the holder  20  includes a band portion  21  that surrounds the head from the forehead to the back of the head in the circumferential direction and an arch portion  22  that extends laterally in the right-left direction from the left ear via the the upper portion of the head to the right ear. The band portion  21  includes, for example, a stretchable material and is secured to the head by the shrinkage force. The arch portion  22  is provided with a socket or a bracket having a through-hole and is configured to mount the probe unit  30  to the socket or the bracket. The holder  20  of the the example shown in  FIG. 1  is configured to hold the probe units  30  one on the left side and the other on the right side bordering the midline of the head. The holder  20  of the example shown in  FIG. 1  can hold, for example, two left probe units  30  and two right prove units  30  in the vicinity the positions of C3 and C4 according to the International  10 / 20  method. The number and the position for holding the probe units  30  by the holder  20  are not particularly limited and are not limited to those shown in  FIG. 1 . 
     (Device Main Body) 
     As shown in  FIG. 3 , the device main body  1  is provided with a light output unit  11  and a light detection unit  12 . 
     The light output unit  11  outputs measurement light to the light-transmitting probes  32 . The light output unit  11  is provided with, for example, a semiconductor laser as a light source. To the light output unit  11 , a plurality of light-transmitting probes  32  can be connected. The light output unit  11  can individually output measurement light at any timing to each connected light-transmitting probe  32 . 
     The light detection unit  12  detects measurement light incident on the light-receiving probe  33 . The light detection unit  12  is provided with, for example, a photomultiplier tube or a photodiode as a detector. To the light detection unit  12 , a plurality of light-receiving probes  33  can be connected. The light detection unit  12  can individually detect the measurement light from each connected light-receiving probe  33 . 
     The device main body  1  can connect up to N pieces of the light-transmitting probes  32  and up to M pieces of the light-receiving probes  33 . The total number of the connectable probes is N+M, where N and M are each a natural number equal to or greater than 2. 
     Further, the device main body  1  is provided with a measurement control unit  13 , a main body control unit  14 , and a main storage unit  15 . The measurement control unit  13  performs the operation control of the light output unit  11  and the light detection unit  12 , such as, e.g., the timing control of the light output and the light detection. The measurement control unit  13  includes a driver circuit of the light output unit  11  and the light detection unit  12 . The main body control unit  14  executes various programs to control the entire device main body  1 . The main body control unit  14  is configured by a computer including a processor and a memory. The main storage unit  15  is configured to store various programs to be executed by the main body control unit  14  and measurement data obtained as a result of measurement. The main storage unit  15  is configured by a non-volatile memory, such as, e.g., a hard disk drive. Further, the optical measurement device  100  is provided with a display unit  16  and an operation input unit  17  connected to the device main body  1 . The display unit  16  is, for example, a liquid crystal display. The operation input unit  17  includes an input device, such as, e.g., a keyboard and a mouse. 
     The optical measurement is initiated by, for example, an input operation via the operation input unit  17 . The main body control unit  14  that has received the input operation performs the control for starting the measurement. When the measurement is started, the measurement control unit  13  controls the light output unit  11  in such a manner that each of the light-transmitting probes  32  outputs measurement light in order at a predetermined cycle. Then, in synchronization with the output of the measurement light, the measurement control unit  13  controls the light detection unit  12  to detect the measurement light from the light-receiving probe  33  that configures the measurement channel  5  together with the light-transmitting probe  32  from which the measurement light has been output. Based on the detected signal, the main body control unit  14  analyzes the change in the hemoglobin content associated with the cerebral activities and controls the display unit  16  to display the measurement result. 
     (Probe Unit) 
     Next, referring to  FIGS. 1 and 4 to 8 , the configuration of the probe unit  30  will be described. The probe unit  30  includes at least one light-transmitting probe  32  and at least one light-receiving probe  33 . 
     The base member  31  holds the light-transmitting probe  32  and the light-receiving probe  33  and a plurality of pin members  34 . Further, the base member  31  is held by a holder  20  rotatably about the central axis  80  (see  FIG. 4 ). In the example shown in  FIG. 1 , the base member  31  is detachably provided to the holder  20  and can be removed from the holder  20 . As shown in  FIG. 4 , the base member  31  is formed in, for example, a circular shape and is arranged to face the head surface  91 . The base member  31  is configured to hold the light-transmitting probe  32  and the light-receiving probe  33  at the outer peripheral portion thereof. The central axis  80  is an axis extending toward the surface  91 . 
     Hereinafter, with respect to the base member  31  held by the holder  20  (see  FIG. 1 ), the first direction toward the head surface  91  side (the direction approaching the head) is denoted as an X1-direction, and the second direction toward the other side (the direction away from the head) of the head surface  91  is denoted as an X2-direction. Both the X1-direction and the X2-direction are collectively referred to as an X-direction. The X1-direction is an example of the “first direction” recited in claims, and the X2-direction is an example of the “second direction” recited in claims. 
     &lt;Light-Transmitting Probe and Light-Receiving Probe&gt; 
     The light-transmitting probe  32  and the light-receiving probe  33  are each provided so as to protrude from the base member  31  in the X1-direction toward the head surface  91 . In the configuration example of  FIG. 4 , the light-transmitting probe  32  and the light-receiving probe  33  are each detachably mounted to the base member  31 . In the configuration example of  FIG. 4 , two light-transmitting probes  32  and two light-receiving probes  33  are mounted to the base member  31 . 
     As shown in  FIG. 5 , the light-transmitting probe  32  and the light-receiving probe  33  each have an optical fiber cable (hereinafter referred to as “optical fiber”)  41  and a fiber head  42  for holding the optical fiber  41 . The fiber head  42  has a tubular structure in which the optical fiber  41  can be inserted and is configured to hold and protect the tip portion of the optical fiber  41 . The optical fiber  41  is provided so as to pass through the inside of the fiber head  42  to be exposed from the tip portion of the fiber head  42 . The tip portion of the fiber head  42  from which the optical fiber  41  is exposed is served as the tip  35  of the light-transmitting probe  32  or that of the light-receiving probe  33 . With this, the light-transmitting probe  32  can emit measurement light from the tip  35 , and the light-receiving probe  33  can cause the measurement light to be incident on the inside of the optical fiber  41  from the tip  35 . 
     In  FIG. 5 , as an example, an L-shaped fiber head  42  in which the tip portion is bent substantially at a right angle is shown. The fiber head  42  has a hollow tubular structure and is attached to the base member  31  with the tip portion (i.e., the tip  35  of the probe) facing in the X1-direction. The fiber head  42  is a cylindrical member made of non-translucent resin or aluminum (aluminum or aluminum alloy). The example of the resin is exemplified by modified PPE (polyphenylene Ether), POM (polyoxymethylene), and the like. The optical fiber  41  is a light-transmitting cable in which a fiber wire constituting a light-transmitting path is covered with a covering material. 
     In the configuration example of  FIGS. 4 and 5 , the light-transmitting probe  32  and the light-receiving probe  33  are each provided so as to be movable in the X-direction with respect to the base member  31 . Specifically, the light-transmitting probe  32  and light-receiving probe  33  are each mounted to the base member  31  via a guide mechanism  36  one by one. The guide mechanism  36  includes a shaft  51  extending in the X-direction and a cylindrical guide tube  52  through which the shaft  51  is inserted. As shown in  FIG. 6 , the shaft  51  is connected to the end of the fiber head  42  in the X2-direction to hold the fiber head  42 . The guide tube  52  slidably holds the shaft  51  in the X-direction. When the shaft  51  is moved in the X-direction, the light-transmitting probe  32  or the light-receiving probe  33  held by the shaft  51  is moved in the X-direction. Note that a stopper member  57 , such as, e.g., a snap ring, is attached to the upper end portion of the shaft  51 . 
     The guide mechanism  36  is mounted to the base member  31  with the light-transmitting probe  32  or the light-receiving probe  33  movably held in the X-direction. As shown in  FIG. 5 , the guide tube  52  has a flange portion  53  protruding outward on the outer peripheral portion. The flange portion  53  is placed on the top surface of the base member  31  and is removably secured to the base member  31  by fastening members  54 , such as, e.g., bolts. 
     On the outer peripheral surface of the base member  31 , arrangement portions  55  each having a notched shape capable of arranging the light-transmitting probe  32  or the light-receiving probe  33  are formed. The inner surface of the arrangement portion  55  having a notched shape is configured as flat sliding surfaces  56  extending in a first direction and a second direction. The light-transmitting probe  32  or the light-receiving probe  33  is positioned inside the arrangement portion  55  and moves along the sliding surfaces  56 . The sliding surfaces  56  support the light-transmitting probe  32  or the light-receiving probe  33  against the external force applied in the circumferential direction (side surface side) when the base member  31  is rotated about the central axis  80 . 
     With this configuration, as shown in  FIG. 6 , each of the light-transmitting probe  32  and the light-receiving probe  33  is provided to the base member  31  so as to be movable to a first position  61  and a second position  62 . The first position  61  is a position away from the head surface  91  than the plurality of pin members  34 . The second position  62  is a position closer to the head surface  91  than the plurality of pin members  34 . The stroke amount  63  between the first position  61  and the second position  62  is equal to the length  64  between the stopper member  57  and the upper end of the guide tube  52  in  FIG. 6 . Note that the first position  61  and the second position  62  are the positions of the tip  35  of the probe. 
     &lt;Lock Mechanism and Biasing Member&gt; 
     In the configuration example of  FIG. 6 , the probe unit  30  includes a lock mechanism  37  and a biasing member  38 . 
     The lock mechanism  37  is configured to releasably hold each of the light-transmitting probe  32  and the light-receiving probe  33  at the first position  61 . The biasing member  38  is configured to bias each of the light-transmitting probe  32  and the light-receiving probe  33  toward the second position  62 . 
     As shown in  FIG. 5 , the lock mechanism  37  includes a spacer  58  provided between the stopper member  57  provided at the upper end of the shaft  51  and the upper end of the guide tube  52 . The spacer  58  has, for example, a C-shaped cross-section and is removably mounted to the shaft  51  (see  FIG. 6 ). The spacer  58  has a length substantially corresponding to the length  64  described above. As shown in  FIG. 6 , the spacer  58  is in contact with the stopper member  57  and the upper end of the guide tube  52  in a state in which the probe is in the first position  61  so as not to move the shaft  51  in the X1-direction. 
     The biasing member  38  is arranged inside the guide tube  52 . The biasing member  38  biases the fiber head  42  in the X1-direction. In the example of  FIG. 6 , the biasing member  38  is a compressed-coil spring in which the shaft  51  is provided. The upper end portion of the biasing member  38  is in contact with the locking portion  52   a  formed on the inner surface of the guide tube  52 , and the lower end portion of the biasing member  38  is in contact with the upper surface of the fiber head  42 . When the probe is positioned at the first position  61 , the biasing member  38  is in a state in which it is compressed more than its natural length to press the probe in the X1-direction. 
     When the spacer  58  is detached from the shaft  51 , the locking by the lock mechanism  37  is unlocked, which allows the shaft  51  to move in the X1-direction. Consequently, the biasing force of the biasing member  38  causes the probe (light-transmitting probe  32  and light-receiving probe  33 ) to move in the X1-direction toward the second position  62 . 
     (Pin Member) 
     As shown in  FIG. 4 , the plurality of pin members  34  is provided so as to protrude from the base member  31  in the X1-direction. The pin member  34  is configured to be moved in the circumferential direction in accordance with the rotational movement of the base member  31  (probe unit  30 ) about the central axis  80  to part the hairs of the head surface  91 . The pin member  34  is made of resin material (e.g., PP: polypropylene, etc.) formed in an elongated rod-shape (needle shape) suitable for parting hairs. The pin member  34  is provided so as to protrude from the lower surface of the base member  31  (X1-direction side surface) in the X1-direction. The pin member  34  is fixed to the base member  31 . The tip  34   a  of the pin member  34  (X1-direction side end) has a rounded smooth surface, such as, e.g., a spherical surface. 
     A plurality of pin members  34  is provided so as to be obliquely inclined at least either in a direction toward the central axis  80  of the base member  31  or the circumferential direction about the central axis  80 . In this embodiment, as shown in  FIGS. 7 and 8 , the plurality of pin members  34  is inclined obliquely in a direction toward the central axis  80  of the base member  31 . As shown in  FIG. 13 , the plurality of pin members  34  may be provided so as to be inclined obliquely in the circumferential direction about the central axis  80 . The plurality of pin members  34  may be inclined both in the direction toward the central axis  80  and in the circumferential direction about the central axis  80 . 
     In the example of  FIG. 7 , the inclination angle θ of the pin member  34  is, for example, 1 degree&lt;θ&lt;10 degrees, more specifically, 3 degrees&lt;θ&lt;8 degrees.  FIG. 7  shows an example of 0=5 degrees. The inclination angle θ is an angle formed by the centerline of the pin member  34  passing through the tip  34   a  with respect to the central axis  80  (X-direction). In contrast, the tip  35  of the light-transmitting probe  32  and that of the light-receiving probe  33  each extend from the lower surface of the base member  31  substantially in parallel to the central axis  80 . 
     In the example  FIG. 7 , the pin member  34  has a linear shape that is tapered toward the tip  34   a . The root portion of the pin member  34  is inserted in the mounting hole  31   a  extending diagonally. The mounting hole  31   a  is inclined in a direction approaching toward the central axis  80  of the base member  31 . Thus, the pin member  34  is mounted in a state of being inclined obliquely toward the central axis  80 . Note that it may be configured such that the mounting hole  31   a  is in parallel to the central axis  80  and the pin member  34  has a shape bent obliquely. 
     The tip  34   a  of the pin member  34  is arranged at the position of the protrusion length  65  in the X1-direction from the lower surface of the base member  31 . The tip  34   a  of the pin member  34  protrudes in the X1-direction than each of the tip  35  of the light-transmitting probe  32  and the tip  35  of the light-receiving probe  33  positioned at the first position  61 . As shown in  FIG. 6 , each of the tip  35  of the light-transmitting probe  32  and the tip  35  of the light-receiving probe  33  is movable to the second position  62  protruding from the tip  34   a  of the pin member  34  in the X1-direction. In a state in which the plurality of pin members  34  are in contact with the head surface  91 , the light-transmitting probe  32  and the light-receiving probe  33  are moved from the first position  61  toward the second position  62 . With this, at the position between the first position  61  and the second position  62 , each of the tip  35  of the light-transmitting probe  32  and the tip  35  of the light-receiving probe  33  comes into contact with the head surface  91 . 
     (Arrangement of Pin Member and Probe) 
     As shown in  FIG. 8 , the plurality of pin members  34  are arranged side by side in the circumferential direction around the central axis  80  so as to surround the central axis  80  of the base member  31 . With this, the plurality of pin members  34  is configured to lift hairs in the center side region  66  surrounded by the plurality of pin member  34  in accordance with the rotation of probe unit  30 . 
     In the example of  FIG. 8 , the tips  34   a  of the plurality of pin members  34  are arranged side by side on the circumference  67  about the central axis  80  of the base member  31 . In the example of  FIG. 8 , the plurality of pin members  34  is provided in a row on the circumference  67 . In this embodiment, each of the tip  35  of the light-transmitting probe  32  and the tip  35  of the light-receiving probe  33  is positioned at the position on the circumference  67  or at the outer position proximate to the circumference  67 . In the example of  FIG. 8 , an example is shown in which each of the tip  35  of the light-transmitting probe  32  and the tip  35  of the light-receiving probe  33  is arranged at the position on the circumference  67 . Each of the tip  35  of the light-transmitting probe  32  and the tip  35  of the light-receiving probe  33  may be arranged at an outer position (e.g., see  FIG. 13 ) proximate to the circumference  67 . 
     Thus, in the example of  FIG. 8 , the tips  34   a  of the plurality of pin members  34 , and each of the tip  35  of the light-transmitting probe  32  and the tip  35  of the light-receiving probe  33  are arranged so as to be aligned on the circumference  67 . Then, in the circumferential direction about the central axis  80  of the base member  31 , at least one of the plurality of pin members  34  is arranged between the adjacent light-transmitting probe  32  and light-receiving probe  33 . 
     In the example of  FIG. 8 , the tips  35  of the two light-transmitting probes  32  and the tips  35  of the two light-receiving probes  33  are arranged at intervals of 90 degrees. The light-transmitting probe  32  and the light-receiving probe  33  are arranged alternately in the circumferential direction. In other words, the two light-transmitting probes  32  are arranged so as to face each other across the central axis  80 , and the two light-receiving probes  33  are arranged so as to face each other across the central axis  80  in a direction perpendicular to a direction facing the two light-transmitting probe  32 . With this, in the example of  FIG. 8 , between the light-transmitting probe  32  and the light-receiving probe  33  adjacent in the circumferential direction, four measurement channels  5  (measurement points) in total are formed. 
     Between the light-transmitting probe  32  and the light-receiving probe  33  adjacent in the circumferential direction, three pin members  34  are arranged. Twelve pin members  34  in total are provided such that three pin members  34  are arranged between adjacent probes of the four probes, respectively. In the example of  FIG. 8 , the tips  35  of the two light-transmitting probes  32 , the tips  35  of the two light-receiving probes  33 , and the tips  34   a  of the twelve pin members  34  are arranged at equal angular intervals on the circumference  67 . 
     Thus, in the embodiment of  FIG. 8 , the light-transmitting probes  32 , the light-receiving probes  33 , and the pin members  34  are arranged at intervals in the circumferential direction. The hairs parted by the pin members  34  are moved into the area of the interval. 
     With such a configuration, the plurality of pin members  34  moves in the circumferential direction about the central axis  80  in accordance with the rotational movement of the base member  31  about the central axis  80 . The moving path of the pin member  34  matches the circumference  67 . As the pin member  34  is moved in the circumferential direction, the hairs of the head surface  91  are parted and lifted along the inclined surface of the pin member  34 . 
     (Grip Portion) 
     As shown in  FIG. 4 , the probe unit  30  includes a grip portion  39  protruding from the base member  31  in the X2-direction opposite to the X1-direction. As shown in  FIGS. 6 and 7 , the light-transmitting probes  32 , the light-receiving probes  33 , the plurality of pin members  34 , and the grip portion  39  are provided to the base member  31  so as to be rotated integrally with the base member  31 . With this configuration, a subject  9  can rotate the entire probe unit  30  including the plurality of pin members  34  about the central axis  80  by gripping and rotating the grip portion  39  when performing the hair parting operation. 
     The grip portion  39  is arranged on the central axis  80  of the base member  31 . At the center of the base member  31 , a support column  39   a  extending in the X2-direction is provided. The grip portion  39  is fixed to the end of the support column  39   a  in the X2-direction. The grip portion  39  is formed in a circular shape and can be gripped and twisted (i.e., pivoted) by the subject  9 . The grip portion  39  is positioned at the highest position protruding in the X2-direction in the probe unit  30 . 
     (Probe Arrangement Procedures) 
     Referring now to  FIGS. 9 to 12 , the operation procedure for placing the light-transmitting probes  32  and the light-receiving probes  33  on the head surface  91  of the subject  9  will be described. All of the following operations can be performed by the subject  9  himself/herself and do not require the intervention of an assistant, such as, e.g., a doctor. Note that  FIG. 9 ,  FIG. 11 , and  FIG. 12  are schematic diagrams showing the probe unit  30  in a simplified manner and omit the illustration of the arrangement portion  55 , the fiber head  42 , etc. 
     First, the subject  9  (see  FIG. 1 ) attaches the probe unit  30  to the holder  20 . And the subject  9  attaches the holder  20  to the head. When the holder  20  is attached to the head, as shown in  FIG. 9 , the pin members  34  of the probe unit  30  come into contact with the head surface  91 . At this time, it is acceptable that hairs are interposed between the tip  34   a  of the pin member  34  and the head surface  91 . In  FIG. 9 , the hairs  92  of the subject  9  are schematically illustrated. The light-transmitting probes  32  and the light-receiving probes  33  are held at the first position  61  by the lock mechanisms  37  (see  FIG. 6 ) and are positioned away from the head surface  91 . 
     Next, the subject  9  rotates the probe unit  30  (base member  31 ) about the central axis  80  by gripping and rotating the grip portion  39  (see  FIG. 4 ) of the probe unit  30 . In accordance with the rotation of the probe unit  30 , the plurality of pin members  34  is moved in the circumferential direction about the central axis  80  while contacting the head surface  91 . As a result, as shown in  FIG. 10 , the pin members  34  move along the circumference  67  to part the hairs  92  inwardly and outwardly relative to the circumference  67 . With the rotational movement about the central axis  80 , the moving paths of the plurality of pin members  34  become closed circumference paths. Therefore, regardless of the direction in which the hairs  92  of the head surface  91  are orientated in  FIG. 10 , the hairs  92  are parted so as to be divided into the center side region  66  (hatched region) and the outer side region of the circumference  67 . 
     As shown in  FIG. 11 , since the pin members  34  are inclined with respect to the head surface  91 , the hairs  92  to be parted by the pin members  34  are lifted along the inclined pin members  34  after contacting the pin members  34 . In practice, a plurality of hairs  92  is overlapped and generates frictional resistance to each other, and therefore hairs not in direct contact with the pin member  34  are also lifted. For this reason, the hairs  92  in the center side region  66  shown in  FIG. 10  are entirely raised as a bundle. Due to the friction between the pin members  34  and the hairs  92  and the friction between the hairs  92 , the hairs  92  in the center side region  66  remains lifted even if the subject  9  stops the rotation of the probe unit  30 . When the hairs  92  are lifted up, the root portions thereof near the head surface  91  are raised. Therefore, a space suitable for placing the tip  35  of the probe is formed on the head surface  91  near the circumference  67  of the parted hairs. 
     In the state of  FIG. 11 , the subject  9  unlocks each of the four lock mechanisms  37  (see  FIG. 6 ). That is, the subject  9  removes the spacer  58  from the shaft  51 . Consequently, due to the biasing force of the biasing member  38  (see  FIG. 6 ), as shown in  FIG. 12 , each of the tip  35  of the light-transmitting probe  32  and the tip  35  of the light-receiving probe  33  is moved from the first position  61  in the X1-direction and is brought into contact with the exposed head surface  91  on the circumference  67 . In the state in which each of the tip  35  of the light-transmitting probe  32  and the tip  35  of the light-receiving probe  33  is in contact with the head surface  91 , the biasing member  38  applies the pressing force toward the head surface  91  with respect to the probe to maintain the contact condition. 
     Consequently, the light-transmitting probe  32  and the light-receiving probe  33  are in close contact with the head surface  91 . Thus, the preparation for measurement by the optical measurement device  100  is completed. Thereafter, when the operation input to start the measurement to the optical measurement device  100  is performed, the optical measurement device  100  starts the measurement of the cerebral function. 
     Note that the hardness of hairs  92  and the direction of hairs  92  (direction of the hair orientation) greatly differ depending on the individual difference of the subject  9  and the position at which the probe unit  30  is to be placed. In a case where hairs  92  are relatively hard and the roots of the hairs  92  are raised from the head surface  91 , the head surface  91  is relatively easily exposed simply by parting the hairs  92 . On the other hand, as shown in  FIG. 9 , in a case where the hairs  92  are relatively soft and the root portions of the hairs  92  are along the head surface  91  (hairs  92  is laying), it is difficult to part the hairs  92 . In this case, the hairs  92  are likely to be interposed between the tip  35  of the probe and the head surface  91 . The action of lifting the hairs  92  by the pin members  34  inclined as described above can lift the hairs  92  to raise the root portions of the hairs  92  in a case where the hairs  92  are along the head surface  91 . Therefore, it is particularly effective. 
     Effects of this Embodiment 
     In this embodiment, the following effects can be obtained. 
     As described above, the optical measurement device  100  and the probe holder set  2  according to this embodiment is provided with the holder  20  to be mounted on the head of the subject  9  and the probe unit  30  held by the holder  20 . The probe unit  30  includes the base member  31 , the light-receiving probes  33 , and the plurality of pin members  34 . The base member  31  is held by the holder  20  in such a manner as to be rotatable about the central axis  80 . The light-transmitting probe  32  protrudes from the base member  31  in the X1-direction toward the head surface  91 . The light-receiving probe  33  protrudes from the base member  31  in the X1-direction. The plurality of pin members  34  protrude from the base member  31  in the X1-direction and parts the hairs  92  of the head surface  91 . The plurality of pin members  34  is obliquely inclined at least either a direction toward the central axis  80  of the base member  31  or the circumferential direction about the central axis  80 . 
     In this embodiment, by the above-described configuration, by simply arranging the probe unit  30  on the head surface  91  and rotating it by the subject  8  himself/herself, it is possible to rotate the pin members  34  to part the hairs  90 . At this time, the pin members  34  are obliquely inclined toward at least either a direction toward the central axis  80  or the circumferential direction. Therefore, by rotating the base member  31  in a state in which the pin members  34  are in contact with the head surface  91 , it is possible to lift the hairs  92  along the slope of the pin member  34  while parting the hairs  92  even in a case where the hairs  92  extend along the head surface  91 . As a result, the parted hairs  92  are raised so that a space in which the probe can be arranged without interposing the hairs  92  can be formed in the vicinity of the head surface  91 . Also, the moving path of the pin member  34  is a closed circumference path about the central axis  80 . Therefore, even in a case where the hairs  92  extend in any direction, it is possible to part the hairs  92  by the pin members  34 . As a result, according to the optical measurement device and the probe holder set  2  of this embodiment, it is possible only by the subject to arrange the probe such that the hairs  92  are not interposed between the probe and the head surface  91  with a simple operation. 
     Further, in the above-described embodiment, with the above-described configuration, the following configuration can be obtained. 
     That is, in this embodiment, as described above, the plurality of pin members  34  is arranged side by side in the circumferential direction about the central axis  80  of the base member  31  so as to surround the central axis  80 . The rotation of the probe unit  30  lifts the hairs  92  in the center side region  66  surrounded by the plurality of pin members  34 . With this configuration, it is possible to lift the hairs  92  on the circumference trajectory along which the plurality of pin members  34  arranged in the circumferential direction moves and the hairs  92  inside the trajectory to thereby effectively raise the root portions of the hairs  92  in the center side region  66 . Consequently, it is possible to expose the scalp surface covered by the hairs  92  to thereby more assuredly bring the tip of the probe (the light-transmitting probe  32 , and the light-receiving probe  33 ) into close contact with the scalp surface. 
     In this embodiment, as described above, the tips  34   a  of the plurality of pin members  34  are arranged side by side on the circumference  67  about the central axis  80  of the base member  31 . Each of the tip  35  of the light-transmitting probe  32  and the tip  35  of the light-receiving probe  33  is positioned at a position on the circumference  67  or at an outer position proximate to the circumference  67 . With this configuration, the tips  34   a  of the plurality of pin members  34  move above the same circumference  67  in accordance with the rotation of the base member  31 . Accordingly, it is possible to effectively obtain the action of parting the hairs  92  to the inside and the outside of the circumference  67  and the action of lifting the hairs  92  in the center side region  66  of the circumference  67 , respectively. Then, each of the tip  35  of the light-transmitting probe  32  and the tip  35  of the light-receiving probe  33  is arranged on the circumference  67  or just outside the circumference  67 . Therefore, it is possible to more effectively suppress the tip of the probe (the light-transmitting probe  32 , the light-receiving probe  33 ) from pinching the hairs  92  in the vicinity of the outer peripheral edge of the bundle of the parted and lifted hairs  92 . 
     Further, in this embodiment, as described above, each of the light-transmitting probe  32  and the light-receiving probe  33  is provided to the base member  31  so as to be movable to the first position  61  and the second position  62 . The first position  61  is a position away from the head surface  91  than the plurality of pin members  34 . The second position  62  is a position closer to the head surface  91  than the plurality of pin members  34 . With this configuration, when the rotational operation for parting the hairs  92  by the plurality of pin members  34  is performed, each of the light-transmitting probe  32  and the light-receiving probe  33  is arranged at the first position  61 . Therefore, it is possible to suppress the hairs  92  from being interposed between the tip of the probe and the scalp surface during the parting. It is possible to bring each of the light-transmitting probe  32  and the light-receiving probe  33  into close contact with the scalp surface by moving each of the light-transmitting probe  32  and the light-receiving probe  33  to the second position  62  after the scalp surface is exposed by the rotating operation of parting the hairs  92 . 
     Further, in this embodiment, as described above, the probe unit  30  further includes the lock mechanism  37  and the biasing member  38  for each of the light-transmitting probe  32  and the light-receiving probe  33 . The lock mechanism  37  releasably holds the probe at the first position  61 . The biasing member  38  biases each of the light-transmitting probe  32  and the light-receiving probe  33  toward the second position  62 . With this configuration, when the rotation operation for parting the hairs  92  is performed, each of the light-transmitting probe  32  and the light-receiving probe  33  can be held at the first position  61 . Thus, after parting the hairs, it is possible to move each of the light-transmitting probe  32  and the light-receiving probe  33  to the second position  62  by simply unlocking the lock mechanism. Therefore, the operation for arranging the probe can be further simplified. 
     Further, in this embodiment, as described above, the probe unit  30  further includes the grip portion  39  protruding from the base member  31  in the X2-direction opposite to the X1-direction. The light-transmitting probes  32 , the light-receiving probes  33 , the plurality of pin members  34 , and the grip portion  39  are provided to the base member  31  so as to be rotated integrally with the base member  31 . With this configuration, it is possible to perform the parting of the hairs  92  by rotating the entire probe unit  30  with an extremely simple operation in which the subject  9  only grasps and rotates the grip portion  39 . Further, for example, it is possible to avoid providing a complicated mechanism, such as, e.g., a mechanism in which only a plurality of pin members  34  is connected to the grip portion  39  to be rotatably moved with respect to the base member  31 . Therefore, the configuration of the probe unit  30  can be simplified. As a result, the probe unit  30  can be miniaturized such that it can be easily mounted to the head of the subject  9 . 
     Further, in this embodiment, as described above, at least one of the plurality of pin members  34  is arranged between the adjacent light-transmitting probe  32  and light-receiving probe  33  in the circumferential direction about the central axis  80  of the base member  31 . With this configuration, the pin member  34  is arranged between the light-transmitting probe  32  and the light-receiving probe  33 . For this reason, it is possible to reduce the rotation angle of the base member  31  to part the hairs  92  at the arrangement positions of the light-transmitting probe  32  and the light-receiving probe  33  by the pin members  34 . For example, without rotating the base member  31  by one revolution, the base member  31  is rotated by at least the angular interval between the light-transmitting probe  32  and the light-receiving probe  33 . With this, it is possible to part the hairs  92  at the arrangement position of the light-transmitting probe  32  and the light-receiving probe  33  by the pin members  34 . 
     Further, in this embodiment, as described above, the light-transmitting probe  32  and the light-receiving probe  33  are detachably attached to the base member  31 . With this configuration, it is possible to simplify the maintenance of the light-transmitting probe  32  and the light-receiving probe  33 . Further, even in the case of replacing the light-transmitting probe  32  or the light-receiving probe  33  due to aging degradation, it is possible to replace only the probe without replacing the entire probe unit  30 . 
     Modified Embodiments 
     It should be understood that the embodiments disclosed here are examples in all respects and are not restrictive. The scope of the present invention is indicated by claims rather than by the above-described described descriptions of the embodiment and includes all modifications within the meanings and ranges equivalent to the claims. 
     For example, in the above-described embodiment, an example is shown in which the plurality of pin members  34  is arranged in the circumferential direction about the central axis  80  of the base member  31  so as to surround the central axis  80 , but the present invention is not limited thereto. In the present invention, the plurality of pin members  34  may be arranged at radially displaced positions so as not to be aligned in the circumferential direction at the base member  31 . 
     Further, in the above-described embodiment, an example is shown in which the tips  34   a  of the plurality of pin members  34  are arranged side by side on the circumference  67 , but the present invention is not limited thereto. In the present invention, it is not required that all of the tips  34   a  of the plurality of pin members  34  are arranged on the circumference  67 . Some of the tips  34   a  of the plurality of pin members  34  may be arranged at positions deviated from the circumference  67 . 
     In the above-described embodiment, an example is shown in which the tips  34   a  of the plurality of pin members  34  are arranged in a line on the circumference  67 , but the present invention is not limited thereto. In the present invention, the tips  34   a  of the plurality of pin members  34  may be arranged concentrically to form a plurality of rows. 
     Further, in the above-described embodiment, an example is shown in which each of the tip  35  of the light-transmitting probe  32  and the tip  35  of the light-receiving probe  33  is arranged at a position on the circumference  67 , but the present invention is not limited thereto. As described above, each of the tip  35  of the light-transmitting probe  32  and the tip  35  of the light-receiving probe  33  may be arranged at an outer position proximate to the circumference  67 . Other than the above, each tip  35  of the light-transmitting probe  32  and the light-receiving probe  33  may be arranged at an inner position proximate to the circumference  67 . Each of the tip  35  of the light-transmitting probe  32  and the tip  35  of the light-receiving probe  33  is preferably provided in the vicinity of the path along which the pin member  34  moves in accordance with the rotation of the base member  31 . 
     In the above-described embodiment, an example is shown in which each of the light-transmitting probe  32  and the light-receiving probe  33  is configured to be movable to the first position  61  and the second position  62 , but the present invention is not limited thereto. In the present invention, each of the light-transmitting probe  32  and the light-receiving probe  33  may be fixed so as not to move in the X-direction with respect to the base member  31 . In this instance, the plurality of pin members  34  may be configured to move in the X-direction. Further, the light-transmitting probes  32 , the light-receiving probes  33 , and the plurality of pin members  34  may be fixed so as not to move in the X-direction. In that case, each of the tip  35  of the light-transmitting probe  32  and the tip  35  of the light-receiving probe  33  may be provided so as to have the same protrusion amount as the tip  34   a  of the pin member  34 . 
     Further, in the above-described embodiment, an example is shown in which the probe unit  30  is provided with the lock mechanism  37  and the biasing member  38 , but the present invention is not limited thereto. In the present invention, it may be configured such that the subject  9  manually moves each probe without providing the lock mechanism  37  and the biasing member  38 . Further, it may be configured to adapt the structure in which the holder  20  biases the probe unit  30  toward the head surface  91 , instead of providing the biasing member  38 . 
     Further, in the case of providing the lock mechanism  37 , the lock mechanism  37  may be configured to releasably hold the probe by a structure other than the spacer  58 . For example, the lock mechanism  37  includes a key member that engages a key groove formed in the shaft  51 . For example, the lock mechanism  37  includes a ball plunger that releasably engages an engagement recess formed on the outer peripheral surface of the shaft  51 . Thus, the configuration in which the lock mechanism releasably holds the probe is not limited to the one shown in the figure. 
     Further, in the above-described embodiment, an example is shown in which the grip portion  39  is provided to the probe unit  30 , but the present invention is not limited thereto. In the present invention, the grip portion  39  may not be provided to the probe unit  30 . The subject  9  may grasp and rotate any portion of the probe unit  30 , and a dedicated grip portion for grasping may not be provided. However, considering that the subject  9  himself/herself operates the probe unit  30  mounted on the head, it is difficult to perform the operation of visually recognizing the probe unit  30  or adjusting the gripping position, and therefore, the operability can be remarkably improved by providing the grip portion  39 . 
     Further, in the above-described embodiment, an example is shown in which the light-transmitting probes  32 , the light-receiving probes  33 , the plurality of pin members  34 , and the grip portion  39  are provided to the base member  31  so as to be rotated integrally with the base member  31 , but the present invention is not limited thereto. For example, it may be configured such that the portion of the base member  31  that holds the plurality of pin members  34  is relatively rotatable with respect to the portion that holds the light-transmitting probe  32  and the light-receiving probe  33 . The probe unit  30  may be configured such that the plurality of pin members  34  rotates about the central axis  80  in a state in which the light-transmitting probe  32  and the light-receiving probe  33  are fixed. 
     Further, in the above-described embodiment, an example is shown in which three pin members  34  are arranged between the adjacent light-transmitting probe  32  and light-receiving probe  33  in the circumferential direction about the central axis  80  of the base member  31 , but the present invention is not limited thereto. In the present invention, one, two, or four or more pin members  34  may be arranged between adjacent light-transmitting probe  32  and light-receiving probe  33 . Further, as shown in  FIG. 8 , in a case where a plurality of pairs of the adjacent light-transmitting probe  32  and light-receiving probe  33  is provided, it may be configured such that a pin member  34  is not arranged between any one pair and that a pin member  34  is arranged between the other pair. 
     Further, in the above-described embodiment, an example is shown in which a total of twelve pin members  34  is provided to the base member  31 , but the present invention is not limited thereto. The number of pin members  34  may be any number as long as it is plural. It is enough to provide a suitable number of pin members  34  to achieve an action of lifting the hairs  92  while parting the hairs  92  of the subject  9 . 
     In the above-described embodiment, an example is shown in which two light-transmitting probes  32  and two light-receiving probes  33  are provided to the base member  31 , but the present invention is not limited thereto. Any number of the light-transmitting probe  32  and the light-receiving probe  33  may be provided as long as at least one is provided. The number of the light-transmitting probes  32  and the number of the light-receiving probes  33  need not be the same, but may be different. 
     In the above-described embodiment, an example is shown in which the light-transmitting probe  32  and the light-receiving probe  33  are detachably attached to the base member  31 , but the present invention is not limited thereto. In the present invention, the light-transmitting probe  32  and the light-receiving probe  33  may be provided inseparably with respect to the base member  31 . 
     In the above-described embodiment, an example is shown in which the light-transmitting probe  32  and the light-receiving probe  33  have the L-shaped fiber head  42  and are attached to the notch arrangement portion  55  of the base member  31  from the side, but the present invention is not limited thereto. In the present invention, a straight fiber head may be provided instead of the L-shaped fiber head  42 . In this instance, instead of the shaft  51  of the guide mechanism  36 , a structure may be adopted in which a straight fiber head is inserted and mounted. The base member  31  may be provided with a through-hole through which, instead of the notch arrangement portion  55 , a straight fiber head passes. 
     [Aspects] 
     It will be understood by those skilled in the art that the above-described exemplary embodiments are concrete examples of the following aspects. 
     (Item 1) 
     An optical measurement device comprising: 
     a device main body configured to irradiate a head surface of a subject with measurement light via a light-transmitting probe and detect the measurement light emitted from the head surface by way of an inside of a head via a light-receiving probe; 
     a holder configured to be attached to the head of the subject; and 
     a probe unit held by the holder, 
     wherein the probe unit includes: 
     a base member rotatably held by the holder about a central axis; 
     the light-transmitting probe protruding from the base member in a first direction toward the head surface; 
     the light-receiving probe protruding from the base member in the first direction; and 
     a plurality of pin members each protruding from the base member in the first direction for parting hairs of the head surface, 
     wherein the plurality of pin members is inclined obliquely at least either in a direction toward a central axis side of the base member or in a circumferential direction about the central axis. 
     (Item 2) 
     The optical measurement device as recited in the above-described Item 1, 
     wherein the plurality of pin members is arranged side by side in the circumferential direction about the central axis of the base member so as to surround the central axis and is configured to lift the hairs in a center side region surrounded by the plurality of pin members in accordance with rotation of the probe unit. 
     (Item 3) 
     The optical measurement device as recited in the above-described Item 2, 
     wherein tips of the plurality of pin members are arranged side by side on a circumference about the central axis of the base member, and 
     wherein each of a tip of the light-transmitting probe and a tip of the light-receiving probe is arranged at a position on the circumference or at an outer position close to the circumference. 
     (Item 4) 
     The optical measurement device as recited in the above-described Item 1, 
     wherein each of the light-transmitting probe and the light-receiving probe is provided to the base member so as to be movable between a first position away from the head surface than the plurality of pin members and a second position closer to the head surface than the plurality of pin members. 
     (Item 5) 
     The optical measurement device as recited in the above-described Item 4, 
     wherein the probe unit further includes: 
     a lock mechanism configured to releasably hold each of the light-transmitting probe and the light-receiving probe at the first position; and 
     a biasing member configured to bias each of the light-transmitting probe and the light-receiving probe toward the second position. 
     (Item 6) 
     The optical measurement device as recited in the above-described Item 1, 
     wherein the probe unit further includes a grip portion protruding from the base member in a second direction opposite to the first direction, and 
     wherein the light-transmitting probe, the light-receiving probe, the plurality of pin members, and the grip portion are provided to the base member so as to be rotated integrally with the base member. 
     (Item 7) 
     The optical measurement device as recited in the above-described Item 1, 
     wherein in the circumferential direction about the central axis of the base member, at least one of the plurality of pin members is arranged between the light-transmitting probe and the light-receiving probe arranged adjacently. 
     (Item 8) 
     The optical measurement device as recited in the above-described Item 1, 
     wherein the light-transmitting probe and the light-receiving probe are each detachably attached to the base member. 
     (Item 9) 
     A probe holder set for an optical measurement device configured to irradiate a head surface of a subject with measurement light via a light-transmitting probe and detect the measurement light emitted from the head surface by way of an inside of a head via a light-receiving probe, the probe holder set comprising: 
     a holder configured to be attached to the head of the subject; and 
     a probe unit held by the holder, 
     wherein the probe unit includes: 
     a base member rotatably held by the holder about a central axis: 
     the light-transmitting probe protruding from the base member in a first direction toward the head surface; 
     the light-receiving probe protruding from the base member in the first direction; and 
     a plurality of pin members each protruding from the base member in the first direction for parting hairs of the head surface, and 
     wherein the plurality of pin members is inclined obliquely at least either in a direction toward a central axis side of the base member or in a circumferential direction about the central axis. 
     DESCRIPTION OF SYMBOLS 
     
         
           1 : Device main body 
           2 : Probe holder set 
           9 : Subject 
           20 : Holder 
           30 : Probe unit 
           31 : Base member 
           32 : Light-transmitting probe 
           33 : Light-receiving probe 
           34 : Pin member 
           34   a : Tip (tip of the pin member) 
           35 : Tip (tip of the light-transmitting probe and the light-receiving probe) 
           37 : Lock mechanism 
           38 : Biasing member 
           39 : Grip portion 
           61 : First position 
           62 : Second position 
           66 : Center side region 
           67 : Circumference 
           80 : Central axis 
           91 : Head surface 
           92 : Hairs 
           100 : Optical measurement device 
         X1: Direction from a base member toward a head surface (first direction) 
         X2: Direction opposite to an X1-direction (second direction)