Patent Publication Number: US-2023133711-A1

Title: Detecting device and measuring device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is based on, and claims priority from JP Application Serial Number 2021-177280, filed Oct. 29, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a detecting device and a measuring device. 
     2. Related Art 
     Various measurement technologies for non-invasively measuring biological information such as heartbeats have been proposed in the related art. For example, JP-A-2012-194054 discloses a technology in which, in a detecting device including a light emitting portion that emits light to a living body and a light receiving portion that receives light that is incident thereon by being reflected by the living body after being emitted from the light emitting portion, a spectroscopic filter and an angle limiting filter are provided in the light receiving portion such that stray light transmitted through the spectroscopic filter is blocked by the angle limiting filter. 
     However, in the above detecting device, the amount of received light varies over the surface of the light receiving portion and thus it has been desired to provide a new technology capable of allowing light to be efficiently incident on the light receiving portion to further improve the detection accuracy. 
     SUMMARY 
     An aspect of the present disclosure provides a detecting device including a light emitting unit that emits a light, and a light receiving unit that includes: a sensor having a first light receiving region and a second light receiving region away from the light emitting unit than the first light receiving region, and an angle limiting having a first limiting region corresponding to the first light receiving region and a second limiting region corresponding to the second light receiving region, wherein a degree of angle limitation of the second limiting region is smaller than a degree of angle limitation of the first limiting region. 
     An aspect of the present disclosure provides a detecting device including a light emitting unit configured to emit light to a living body, a light receiving unit arranged in a first direction with respect to the light emitting unit and configured to receive light from the living body, and a plurality of light shielding walls arranged in the first direction and configured to limit an angle of incidence of light on the light receiving unit, wherein an interval between the light shielding walls in a region far from the light emitting unit is larger than an interval between the light shielding walls in a region close to the light emitting unit. 
     An aspect of the present disclosure provides a measuring device including the detecting device according to the above aspect and an information analysis unit configured to identify biological information from a detection signal indicating a detection result of the detecting device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a side view of a measuring device of a first embodiment. 
         FIG.  2    is a configuration diagram focusing on the functionality of the measuring device. 
         FIG.  3    is a plan view of a detecting device. 
         FIG.  4    is a cross-sectional view taken along line IV-IV in  FIG.  3   . 
         FIG.  5    is a diagram illustrating the behavior of light emitted from a light emitting unit. 
         FIG.  6    is a graph showing a transmission spectrum of a skin. 
         FIG.  7    is a cross-sectional view illustrating a configuration of a main part of the detecting device of the first embodiment. 
         FIG.  8    is a cross-sectional view illustrating a configuration of a main part of a detecting device of a second embodiment. 
         FIG.  9    is a graph showing simulation results of examples. 
         FIG.  10    is a graph showing simulation results of examples. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each of the following drawings, the scales and angles of members are made different from those of actual ones in order to make the members recognizable in size. 
     First Embodiment 
       FIG.  1    is a side view of a measuring device  100  of a first embodiment. The measuring device  100  of the present embodiment illustrated in  FIG.  1    is a biometric device that non-invasively measures biometric information of a subject (for example, a human) which is an example of a living body and is attached to a site (hereinafter referred to as a “measuring site”) M that is a measurement target on a body of the subject. The measuring device  100  of the present embodiment is a wristwatch-type portable device including a main body  1  and a belt  2  and can be worn on a wrist of the subject, which is an example of the measuring site (the living body) M, by winding the belt  2  in a band shape around the wrist. In the present embodiment, biological information is exemplified by a heartbeat (for example, a pulse rate) and an oxygen saturation (SpO2) of the subject. The heartbeat indicates the change of the internal volume of a blood vessel over time due to the pulsation of the heart. The oxygen saturation indicates the proportion (%) of hemoglobin bound to oxygen in hemoglobin in the blood of the subject and is an index for evaluating the respiratory function of the subject. 
       FIG.  2    is a configuration diagram focusing on the functionality of the measuring device  100 . As illustrated in  FIG.  2   , the measuring device  100  of the present embodiment includes a control device  5 , a storage device  6 , a display device  4 , and a detecting device  3 . The control device  5  and the storage device  6  are installed inside the main body  1 . As illustrated in  FIG.  1   , the display device  4  is installed on a surface of the main body  1  opposite to the measuring site M and displays various images including measurement results under the control of the control device  5 . The display device  4  is, for example, a liquid crystal display panel. 
     The detecting device  3  is an optical sensor module that generates detection signals S according to the state of the measuring site M. As illustrated in  FIG.  1   , the detecting device  3  is installed, for example, on a surface (hereinafter referred to as a detection surface)  16  of the main body  1  that faces the measuring site M. The detection surface  16  is a surface that comes into contact with the measuring site M. As illustrated in  FIG.  2   , the detecting device  3  of the present embodiment includes a light emitting unit (a light emitting portion)  11 , a light receiving unit (a light receiving portion)  12 , a drive circuit  13 , and an output circuit  14 . One or both of the drive circuit  13  and the output circuit  14  can also be installed as circuits external to the detecting device  3 . That is, the drive circuit  13  and the output circuit  14  may be omitted from the detecting device  3 . 
     The light emitting unit  11  includes a first light emitting element  50 , a second light emitting element  60 , and a third light emitting element  70 . The first light emitting element  50 , the second light emitting element  60 , and the third light emitting element  70  are elements that emit light having different wavelengths to the measuring site M. 
     The first light emitting element  50  emits green light (first light) LG having a green wavelength band of 500 nm to 550 nm toward the measuring site M. The green light LG of the present embodiment is, for example, light having a peak wavelength of 520 nm. 
     The second light emitting element  60  emits red light (second light) LR having, for example, a red wavelength band of 600 nm to 800 nm toward the measuring site M. The red light LR of the present embodiment is, for example, light having a peak wavelength of 660 nm. 
     The third light emitting element  70  emits near-infrared light (third light) LI having, for example, a near-infrared wavelength band of 800 nm to 1300 nm toward the measuring site M. The near-infrared light LI of the present embodiment is, for example, light having a peak wavelength of 905 nm. 
     For example, light emitting diodes (LED) of a bare chip or bullet type are preferably used as light emitting elements that constitute the first light emitting element  50 , the second light emitting element  60 , and the third light emitting element  70 . The wavelengths of light emitted by the light emitting elements are not limited to the above numerical ranges. Hereinafter, the first light emitting element  50 , the second light emitting element  60 , and the third light emitting element  70  are collectively referred to as “each of the light emitting elements  50 ,  60 , and  70 ” unless particularly specified. 
     The drive circuit  13  supplies a drive current to cause each of the light emitting elements  50 ,  60 , and  70  to emit light. The drive circuit  13  of the present embodiment periodically causes each of the light emitting elements  50 ,  60 , and  70  to emit light in a time division manner. Light emitted from the light emitting elements  50 ,  60 , and  70  is incident on the measuring site M and propagates in the measuring site M while being repeatedly reflected and scattered and then is emitted to the main body  1  side, reaching the light receiving unit  12 . That is, the detecting device  3  of the present embodiment is a reflection type optical sensor in which the light emitting unit  11  and the light receiving unit  12  are located on one side of the measuring site M. 
     The light receiving unit  12  receives light arriving from the measuring site M after being emitted by the light emitting unit  11 . The light receiving unit  12  of the present embodiment includes a first light receiving element  51  and a second light receiving element  61 . The first light receiving element  51  and the second light receiving element  61  generate detection signals according to the intensity of received light. Hereinafter, the first light receiving element  51  and the second light receiving element  61  are collectively referred to as “each of the light receiving elements  51  and  61 ” unless particularly specified. 
     The first light receiving element  51  receives green light LG that has propagated in the measuring site M after being emitted from the first light emitting element  50  and generates a detection signal according to the intensity of received light. The second light receiving element  61  receives red light LR that has propagated in the measuring site M after being emitted from the second light emitting element  60  or near-infrared light LI that has propagated in the measuring site M after being emitted from the third light emitting element  70  and generates detection signals according to the intensity of received light. 
     The output circuit  14  is configured to include, for example, an A/D converter that converts detection signals generated by the light receiving elements  51  and  61  from analog to digital and an amplifier circuit that amplifies the converted detection signals (both not illustrated) and generates a plurality of detection signals S (S 1 , S 2 , S 3 ) corresponding to different wavelengths. 
     The detection signal S 1  is a signal indicating the intensity of light received by the first light receiving element  51  when it has received green light LG emitted from the first light emitting element  50 . The detection signal S 2  is a signal indicating the intensity of light received by the second light receiving element  61  when it has received red light LR emitted from the second light emitting element  60 . The detection signal S 3  is a signal indicating the intensity of light received by the second light receiving element  61  when it has received near-infrared light LI emitted from the third light emitting element  70 . 
     Each detection signal S is a heartbeat signal including periodic fluctuations corresponding to pulsations (volume heartbeats) of the artery inside the measuring site M because the amounts of absorption by blood during dilation and contraction of blood vessels generally differ. 
     The drive circuit  13  and the output circuit  14  are mounted on a wiring board in the form of an IC chip together with the light emitting unit  11  and the light receiving unit  12 . The drive circuit  13  and the output circuit  14  can be installed outside the detecting device  3  as described above. 
     The control device  5  is an arithmetic processing unit such as a central processing unit (CPU) or a field-programmable gate array (FPGA) and controls the entirety of the measuring device  100 . The storage device  6  includes, for example, a non-volatile semiconductor memory and stores a program executed by the control device  5  and various data used by the control device  5 . It is also possible to adopt a configuration in which the functions of the control device  5  are distributed over a plurality of integrated circuits or a configuration in which some or all of the functions of the control device  5  are realized by a dedicated electronic circuit. Although the control device  5  and the storage device  6  are illustrated as separate elements in  FIG.  2   , a control device  5  including the storage device  6  can also be realized, for example, by an application specific integrated circuit (ASIC). 
     The control device  5  of the present embodiment identifies biological information of the subject from the plurality of detection signals S (S 1 , S 2 , S 3 ) generated by the detecting device  3  by executing the program stored in the storage device  6 . Specifically, the control device  5  can identify a pulse-to-pulse interval (PPI) of the subject from the detection signal S 1  indicating the intensity of green light LG received by the first light receiving element  51 . The control device  5  can also identify the oxygen saturation (SpO2) of the subject by analyzing the detection signal S 2  indicating the intensity of red light LR received by the second light receiving element  61  and the detection signal S 3  indicating the intensity of near-infrared light LI received by the second light receiving element  61 . 
     In the measuring device  100  of the present embodiment, the control device  5  functions as an information analysis unit that identifies biological information from the detection signals S indicating the detection results of the detecting device  3  as described above. The control device (information analysis unit)  5  causes the display device  4  to display the biological information identified from the detection signals S. It is also possible to notify the user of the measurement result by voice output. It is also preferable to adopt a configuration in which the user is notified of a warning (possibility of impaired physical function) when the pulse rate or oxygen saturation has fluctuated to values out of a predetermined range. 
       FIG.  3    is a plan view of the detecting device  3  of the present embodiment.  FIG.  4    is a cross-sectional view taken along a line IV-IV in  FIG.  3   . As illustrated in  FIGS.  3  and  4   , the detecting device  3  of the present embodiment includes a case  40  and a sealing layer  42  in addition to the light emitting unit  11  and the light receiving unit  12 . The drive circuit  13  and the output circuit  14  are not illustrated in  FIGS.  3  and  4   . 
     Hereinafter, the configuration of the detecting device  3  will be described using an XYZ coordinate system. The X-axis corresponds to an axis extending along a long side (one side) of the case  40  having a rectangular outer shape, the Y-axis corresponds to an axis that is orthogonal to the X-axis and extends along a short side (another side) of the case  40 , and the Z-axis corresponds to an axis that is orthogonal to the X and Y-axes and extends across the thickness of the case  40 . 
     As illustrated in  FIGS.  3  and  4   , the case  40  is a member that holds the elements of the detecting device  3  (the light emitting unit  11  and the light receiving unit  12 ). The case  40  is in the shape of a box including a bottom surface portion  40   a  in the shape of a rectangular flat plate, a frame plate portion  40   b  in the shape of a rectangular frame that projects to the +Z side from peripheral edges of the bottom surface portion  40   a , and a partition wall  41 . The case  40  is made of, for example, aluminum. An inner peripheral surface  40   b   1  of the frame plate portion  40   b  is colored black to have light blocking properties. This limits reflection on the inner peripheral surface  40   b   1  of the frame plate portion  40   b.    
     The material and manufacturing method of the case  40  are arbitrary. For example, the case  40  can be formed by injection molding of a resin material. It is also preferable to adopt a configuration in which the case  40  is integrally formed with the main body  1 . 
     The light emitting unit  11  and the light receiving unit  12  are installed on the bottom surface portion  40   a  of the case  40  while being mounted on a wiring board (not illustrated). In the case  40 , the light emitting unit  11  and the light receiving unit  12  are arranged in the X-axis direction (a first direction). 
     The partition wall  41  is a plate-shaped member that protrudes to the +Z side from the bottom surface portion  40   a  and extends in the Y-axis direction and separates the internal accommodation space of the case  40  into two parts in the X-axis direction. That is, the partition wall  41  is a member that separates the space accommodating the light emitting unit  11  and the light receiving unit  12  in a direction along the X axis. The partition wall  41  is a member having light blocking properties for blocking light emitted from the light emitting unit  11  such that it is not directly incident on the light receiving unit  12 . It can also be said that the partition wall  41  is a member that blocks a part of the green light LG, the red light LR, and the near-infrared light LI. 
     The sealing layer  42  is a light-transmitting resin material filled in a gap between the frame plate portion  40   b  and the light emitting and receiving units  11  and  12  accommodated in the case  40 . In the present embodiment, the sealing layer  42  seals the light emitting elements  50 ,  60 , and  70  and the light receiving elements  51  and  61 . The sealing layer  42  seals (molds) the light emitting and receiving units  11  and  12  in the case  40 . In the present embodiment, an upper surface of the sealing layer  42  is flush with upper surfaces of the frame plate portions  40   b  and  41  of the case  40 . The surface of the sealing layer  42  functions as the detection surface  16 . 
     The light emitting unit  11  is installed in the case  40  such that the light emitting surfaces of the light emitting elements  50 ,  60 , and  70  are parallel to the XY plane. That is, the light emitting elements  50 ,  60 , and  70  emit light toward the +Z side. 
     The light receiving unit  12  is installed in the case  40  such that the light receiving surfaces of the light receiving elements  51  and  61  are parallel to the XY plane. That is, the light receiving elements  51  and  61  receive light incident from the Z direction. 
     As illustrated in  FIG.  3   , the light emitting elements  50 ,  60 , and  70  are arranged side by side at intervals in the Y-axis direction (a second direction) orthogonal to (intersecting) the X-axis direction. Specifically, the second light emitting element  60  is arranged on the +Y side of the first light emitting element  50  and the third light emitting element  70  is arranged on the −Y side of the first light emitting element  50 . That is, the first light emitting element  50  is arranged between the second light emitting element  60  and the third light emitting element  70  in the direction along the Y axis. It can also be said that the first light emitting element  50  is located between the second light emitting element  60  and the third light emitting element  70 . 
     The light receiving elements  51  and  61  are arranged side by side at intervals in the X-axis direction intersecting (orthogonal to) the Y axis. Specifically, the first light receiving element  51  is arranged on the +X side of the light emitting unit  11  and the second light receiving element  61  is arranged on the +X side of the first light receiving element  51 . That is, the second light receiving element  61  is arranged on a side of the first light receiving element  51  opposite to the light emitting unit  11 . 
     Here, let D 1  be a distance from the first light emitting element  50  to the first light receiving element  51 , D 2  a distance from the second light emitting element  60  to the second light receiving element  61 , and D 3  a distance from the third light emitting element  70  to the second light receiving element  61 . The distance D 1  corresponds to the distance between central portions of the first light emitting element  50  and the first light receiving element  51  when viewed in plan in the Z-axis direction. The distance D 2  corresponds to the distance between central portions of the second light emitting element  60  and the second light receiving element  61  when viewed in plan in the Z-axis direction. The distance D 3  corresponds to the distance between central portions of the third light emitting element  70  and the second light receiving element  61  when viewed in plan in the Z-axis direction. 
     In the detecting device  3  of the present embodiment, the distance D 1  from the first light emitting element  50  to the first light receiving element  51  is shorter than the distance D 2  from the second light emitting element  60  to the second light receiving element  61 . The distance D 1  from the first light emitting element  50  to the first light receiving element  51  is also shorter than the distance D 3  from the third light emitting element  70  to the second light receiving element  61 . The distance D 2  and the distance D 3  are equal. 
     As described above, the detecting device  3  of the present embodiment adopts a configuration in which the first light receiving element  51  for receiving green light LG is arranged at a position closest to the first light emitting element  50  that emits the green light LG. That is, the first light receiving element  51  is provided closer to the light emitting unit  11  than the second light receiving element  61  is in the X-axis direction in which the light emitting unit  11  and the light receiving unit  12  are arranged. 
     As illustrated in  FIG.  4   , the first light receiving element  51  includes a sensor  20 , a first angle limiting filter (angle limiting member)  21 , and a bandpass filter  22 . 
     The sensor  20  includes, for example, a photodiode (PD). The first angle limiting filter  21  is provided to cover the entirety of a light receiving surface  20   a  of the sensor  20 . 
     The first angle limiting filter  21  has a property of transmitting light incident at an angle smaller than a predetermined incident angle and blocking light incident at an angle larger than the predetermined incident angle without transmitting the light. Thus, the first angle limiting filter  21  can limit the angle of incidence of light on the sensor  20 . 
     Specifically, the first angle limiting filter  21  transmits light which is incident at a predetermined incident angle (hereinafter referred to as an allowable incident angle) due to having propagated in the living body and guides it to the sensor  20  and blocks light which is incident at an angle larger than the allowable incident angle, such as external light such as sunlight or light which has not entered the living body, to prevent it from being incident on the sensor  20 . That is, the first angle limiting filter  21  is an angle limiting member that limits the angle of incidence of green light LG from the first light emitting element  50  with respect to the sensor  20 . Details of the configuration of the first angle limiting filter  21  will be described later. 
     The bandpass filter  22  has a property of selectively transmitting the wavelength band of green light LG and absorbing and blocking red light LR and near-infrared light LI which are light of other wavelength bands. The bandpass filter  22  is formed, for example, by alternately laminating low refractive index layers such as silicon oxide layers and high refractive index layers such as titanium oxide layers on the first angle limiting filter  21 . 
     For example, a part of red light LR and near-infrared light LI emitted from the second and third light emitting elements  60  and  70  may pass through the living body and enter the first light receiving element  51 . In the case of the present embodiment, the first light receiving element  51  includes the bandpass filter  22  that selectively transmits green light LG. Therefore, the first light receiving element  51  can block red light LR and near-infrared light LI having wavelength bands different from that of green light LG. Thus, the first light receiving element  51  can efficiently receive green light LG emitted from the first light emitting element  50 . 
     The second light receiving element  61  includes a sensor  30  that receives red light LR or near-infrared light LI and a second angle limiting filter (angle limiting member)  31  that limits the angle of incidence of red light LR or near-infrared light LI that reaches the sensor  30 . That is, in the detecting device  3  of the present embodiment, the second light receiving element  61  differs from the first light receiving element  51  in that it does not include a bandpass filter that selectively transmits red light LR or near-infrared light LI. 
     The sensor  30  includes, for example, a photodiode. The second angle limiting filter  31  is provided to cover the entirety of a light receiving surface  30   a  of the sensor  30 . The second angle limiting filter  31  can limit the angle of incidence of red light LR or near-infrared light LI that reaches the sensor  30 . 
     For example, the second angle limiting filter  31  transmits red light LR or near-infrared light LI which is incident at an allowable incident angle after propagating in the living body and guides it to the sensor  30  and blocks light which is incident at an angle larger than the allowable incident angle, such as external light such as sunlight or red light LR or near-infrared light LI which has not passed through the living body, to prevent it from being incident on the sensor  30 . That is, the second angle limiting filter  31  is an angle limiting member that limits the angle of incidence, with respect to the sensor  30 , of red light LR or near-infrared light LI from the second light emitting element  60  or the third light emitting element  70 . Details of the configuration of the second angle limiting filter  31  will be described later. 
       FIG.  5    is a diagram illustrating the behavior of light emitted from the light emitting unit  11 . 
     As illustrated in  FIG.  5   , for example, a part of green light LG emitted from the first light emitting element  50  may be reflected by a surface layer of the living body (the measuring site M), such that it is directly incident on the first light receiving element  51  without reaching the blood vessel M 1  inside the living body. External light such as sunlight may also be directly incident on the first light receiving element  51  through a gap between the living body and the detection surface  16 . 
     Green light LG that is directed to the first light receiving element  51  without reaching the blood vessel M 1  is referred to as a “first stray light component SL 1 ” and external light that is directed directly to the first light receiving element  51  is referred to as a “second stray light component SL 2 ”. 
     Because the first stray light component SL 1  has a green wavelength band, it passes through the bandpass filter  22  and is incident on the first angle limiting filter  21  provided in a layer below the bandpass filter  22 . The first angle limiting filter  21  has a property of transmitting light incident at an angle smaller than the allowable incident angle and blocking light incident at an angle larger than the allowable incident angle as described above. 
     Because the first stray light component SL 1  is incident on the first light receiving element  51  without reaching the blood vessel M 1 , the angle of incidence of the first stray light component SL 1  with respect to the first light receiving element  51  is larger than the allowable incident angle of the first angle limiting filter  21 . That is, the first stray light component SL 1  is blocked by the first angle limiting filter  21 . Thus, the first light receiving element  51  can limit the incidence of the first stray light component SL 1  on the light receiving surface  20   a  of the sensor  20  through the first angle limiting filter  21 . 
     The second stray light component SL 2  is mostly blocked by the bandpass filter  22 , but a component having a green wavelength band included in the second stray light component SL 2  passes through the bandpass filter  22 . Here, the angle of incidence of the second stray light component SL 2  with respect to the first light receiving element  51  is larger than the allowable incident angle of the first angle limiting filter  21  because the second stray light component SL 2  is incident through the gap between the living body and the detection surface  16  as described above. Therefore, a part of the second stray light component SL 2  (a component having a green wavelength band) transmitted through the bandpass filter  22  is blocked by the first angle limiting filter  21 . Thus, the first light receiving element  51  can limit the incidence of the second stray light component SL 2  on the light receiving surface  20   a  of the sensor  20  through the first angle limiting filter  21 . 
     On the other hand, green light LG that has propagated in the blood vessel M 1  passes through the bandpass filter  22  and is incident on the first angle limiting filter  21  provided in the layer below the bandpass filter  22  at a predetermined angle. Because the green light LG that has propagated in the blood vessel M 1  is emitted from the inside of the living body, it is incident on the first light receiving element  51  at a smaller incident angle, that is, at an angle closer to the normal direction, compared to the first stray light component SL 1  reflected on the surface layer of the living body. 
     The allowable incident angle of the angle limiting filter is generally designed to be smaller than the angle of incidence of light that has propagated in the blood vessel with respect to the light receiving unit. The angle limiting filter is formed, for example, by embedding light shielding walls made of a light blocking material such as tungsten in a light-transmitting silicon oxide layer using a semiconductor process. In the related art, a general angle limiting filter has been configured by embedding light shielding walls arranged at equal intervals in a silicon oxide layer. 
     Based on simulations, the present inventor has found that light that has passed through the living body cannot be efficiently incident on the light receiving surface of the sensor of the light receiving unit when an angle limiting filter of the related art in which light-shielding walls are embedded in a silicon oxide layer at equal intervals is used. 
     In a light receiving element using an angle limiting filter in which light shielding walls are embedded at equal intervals as in the configuration of the related art, a light incident region in which green light LG is mostly incident is formed on the light receiving surface near the first light emitting element  50  and the amount of received green light LG incident on the light receiving surface decreases away from the first light emitting element  50 . That is, the amount of light received by the light receiving element varies over the surface when the angle limiting filter of the related art in which light shielding walls are embedded at equal intervals is used. 
       FIG.  6    is a graph showing a transmission spectrum of the skin. In  FIG.  6   , the horizontal axis represents the wavelength of light and the vertical axis represents the transmittance (in percentage).  FIG.  6    shows a transmission spectrum when the skin thickness is 0.43 mm as an example. 
     As shown in  FIG.  6   , the transmittance is about 30% when the wavelength band of green light LG (for example, 520 nm) is incident on the skin, about 50% to 60% when the wavelength band of red light LR (for example, 660 nm) is incident on the skin, and about 60% when the wavelength band of near-infrared light LI (for example, 905 nm) is incident on the skin. 
     The graph of  FIG.  6    shows that the distance that light can propagate in the living body differs depending on the wavelength of light. That is, according to the graph of  FIG.  6   , it can be seen that green light LG can propagate only a short distance in the living body, compared to red light LR or near-infrared light LI. That is, it can be said that red light LR and near-infrared light LI can propagate further in the living body than green light LG. Although  FIG.  6    illustrates the case where the skin thickness is 0.43 mm as an example, red light LR and near-infrared light LI can also propagate further in the living body with other skin thicknesses than green light LG. 
     The present inventor has found that green light LG is more likely to be attenuated when passing through a living body than red light LR and near-infrared light LI are as shown in the graph of  FIG.  6   . Thus, the present inventor has thought that, in a light receiving element using an angle limiting filter in which light shielding walls are embedded at equal intervals as in the related art, the likelihood that green light LG is attenuated in the living body before it is incident on the light receiving surface increases away from the first light emitting element  50 , and as a result, the amount of received light varies over the light receiving surface in the X-axis direction away from the first light emitting element  50 . 
     Therefore, the present inventor has focused on the structure of the angle limiting filter and completed the detecting device  3  of the present embodiment which can limit variations in the amount of received light over the light receiving element. 
       FIG.  7    is a cross-sectional view illustrating a configuration of a main part of the detecting device  3  of the present embodiment. 
     As illustrated in  FIG.  7   , the first light receiving element  51  has a plurality of light receiving regions. The plurality of light receiving regions include a first light receiving region IA 1 , a second light receiving region IB 1 , a third light receiving region IC 1 , and a fourth light receiving region ID 1 . Hereinafter, the first light receiving region IA 1 , the second light receiving region IB 1 , the third light receiving region IC 1 , and the fourth light receiving region ID 1  are collectively referred to as “each of the light receiving regions IA 1 , IB 1 , IC 1 , and ID 1 ” unless particularly specified. 
     The light receiving regions IA 1 , IB 1 , IC 1 , and ID 1  are provided on the light receiving surface  20   a  of the sensor  20  of the first light receiving element  51 . Specifically, the first light receiving region IA 1  is a region which is located closest to the light emitting unit  11  (located on the most −X side) in the light receiving surface  20   a  of the sensor  20 . The second light receiving region IB 1  is a region that is spaced further from the light emitting unit  11  to the +X side than the first light receiving region IA 1  is, the third light receiving region IC 1  is a region that is spaced further from the light emitting unit  11  to the +X side than the second light receiving region IB 1  is, and the fourth light receiving region ID 1  is a region that is spaced further from the light emitting unit  11  to the +X side than the third light receiving region IC 1  is. That is, the light receiving regions IA 1 , IB 1 , IC 1  and ID 1  are arranged on the light receiving surface  20   a  one by one on the +X side in this order. 
     The first angle limiting filter  21  includes a first limiting region  21 A, a second limiting region  21 B, a third limiting region  21 C, and a fourth limiting region  21 D. Hereinafter, the first limiting region  21 A, the second limiting region  21 B, the third limiting region  21 C, and the fourth limiting region  21 D are collectively referred to as “each of the limiting regions  21 A,  21 B,  21 C, and  21 D” unless particularly specified. 
     The limiting regions  21 A,  21 B,  21 C, and  21 D correspond respectively to the light receiving regions IA 1 , IB 1 , IC 1 , and ID 1 . 
     The first limiting region  21 A is arranged to overlap the first light receiving region IA 1  when viewed in plan from the +Z side and limits the angle of incidence of the green light LG with respect to the first light receiving region IA 1  of the first light receiving element  51 . 
     The second limiting region  21 B is arranged to overlap the second light receiving region IB 1  when viewed in plan from the +Z side and limits the angle of incidence of the green light LG with respect to the second light receiving region IB 1  of the first light receiving element  51 . 
     The third limiting region  21 C is arranged to overlap the third light receiving region IC 1  when viewed in plan from the +Z side and limits the angle of incidence of the green light LG with respect to the third light receiving region IC 1  of the first light receiving element  51 . 
     The fourth limiting region  21 D is arranged to overlap the fourth light receiving region ID 1  when viewed in plan from the +Z side and limits the angle of incidence of the green light LG with respect to the fourth light receiving region ID 1  of the first light receiving element  51 . 
     In the present embodiment, the degree of angle limitation of the second limiting region  21 B is smaller than the degree of angle limitation of the first limiting region  21 A. The degree of angle limitation of the third limiting region  21 C is smaller than the degree of angle limitation of the second limiting region  21 B. The degree of angle limitation of the fourth limiting region  21 D is smaller than the degree of angle limitation of the third limiting region  21 C. 
     That is, in the detecting device  3  of the present embodiment, the degree of angle limitation of each of the limiting regions  21 A,  21 B,  21 C, and  21 D progressively decreases away from the first light emitting element  50 . 
     Here, the degree of angle limitation being “small” indicates that light incident on the first light receiving element  51  at a large incident angle (a shallow angle] away from the vertical direction) can reach the light receiving surface  20   a  of the sensor  20 , i.e., that the allowable incident angle is large. 
     On the other hand, the degree of angle limitation being “large” indicates that light incident on the first light receiving element  51  at a small incident angle (a steep angle close to the vertical direction) can reach the light receiving surface  20   a  of the sensor  20 , i.e., that the allowable incident angle is small. 
     The first angle limiting filter  21  includes a silicon oxide layer  24  and a plurality of light shielding walls (first light shielding walls)  25  embedded in the silicon oxide layer  24 . Each of the light shielding walls  25  is formed in a plate shape extending to the +Z side from the light receiving surface  20   a  of the sensor  20 . Although omitted in  FIG.  7   , the plurality of light shielding walls  25  are arranged not only in the X-axis direction but also in the Y-axis direction such that they form a grid shape as a whole when viewed in plan from the +Z side. 
     The first angle limiting filter  21  is formed, for example, by embedding light shielding walls  25  made of conductive plugs having light absorptivity such as tungsten plugs in a silicon oxide layer  24  through a wiring forming process of a semiconductor process. The silicon oxide layer  24  forms an optical path for guiding light to the light receiving surface  20   a  of the sensor  20 . The light shielding walls  25  embedded in the silicon oxide layer  24  limit the angle of incidence of light passing through the optical path (the silicon oxide layer  24 ). That is, when light incident on the silicon oxide layer  24  is tilted more than a predetermined angle with respect to the optical path, the incident light hits a light shielding wall  25  and a part of the light is absorbed by the light shielding wall  25  while the rest is reflected. Because the intensity of the reflected light is weakened due to repeated reflections while the light passes through the optical path, light that can completely pass through the first angle limiting filter  21  is substantially limited to light whose inclination with respect to the optical path is within a predetermined limiting angle. 
     Based on such a configuration, the first angle limiting filter  21  functions as an angle limiting member that limits the angle of incidence of green light LG from the first light emitting element  50  with respect to the sensor  20 . 
     In the first angle limiting filter  21  of the present embodiment, the plurality of light shielding walls  25  are provided on the light receiving regions IA 1 , IB 1 , IC 1 , and ID 1  of the first light receiving element  51 . The plurality of light shielding walls  25  include light shielding walls  25   a ,  25   b ,  25   c ,  25   d , and  25   e.    
     The light shielding walls  25   a  and  25   b  define the first limiting region  21 A in the X-axis direction. The light shielding walls  25   b  and  25   c  define the second limiting region  21 B in the X-axis direction. The light shielding walls  25   c  and  25   d  define the third limiting region  21 C in the X-axis direction. The light shielding walls  25   d  and  25   e  define the fourth limiting region  21 D in the X-axis direction. 
     The degrees of angle limitation of the limiting regions  21 A,  21 B,  21 C, and  21 D are defined by the X-axis intervals between adjacent light shielding walls. 
     In the present embodiment, the plurality of light shielding walls that limit the angle of incidence of light on the light receiving unit  12  are arranged in the X-axis direction such that the interval between light shielding walls in a region far from the light emitting unit  11  is larger than the interval between light shielding walls in a region close to the light emitting unit  11 . Specifically, the X-axis interval between the adjacent light shielding walls  25   b  and  25   c  in the second limiting region  21 B among the plurality of light shielding walls  25  is larger than the X-axis interval between the adjacent light shielding walls  25   a  and  25   b  in the first limiting region  21 A among the plurality of light shielding walls  25 . 
     The X-axis interval between the adjacent light shielding walls  25   c  and  25   d  in the third limiting region  21 C among the plurality of light shielding walls  25  is larger than the X-axis interval between the adjacent light shielding walls  25   b  and  25   c  in the second limiting region  21 B among the plurality of light shielding walls  25 . 
     The X-axis interval between the adjacent light shielding walls  25   d  and  25   e  in the fourth limiting region  21 D among the plurality of light shielding walls  25  is larger than the X-axis interval between the adjacent light shielding walls  25   c  and  25   d  in the third limiting region  21 C among the plurality of light shielding walls  25 . 
     In the case of the present embodiment, for example, the interval between the light shielding walls  25   a  and  25   b  is set to 3 μm, the interval between the light shielding walls  25   b  and  25   c  is set to 4.5 μm, the interval between the light shielding walls  25   c  and  25   d  is set to 6 μm, and the interval between the light shielding walls  25   d  and  25   e  is set to 7.5 μm. The heights of the light shielding walls  25   a ,  25   b ,  25   c ,  25   d , and  25   e  are set to 5 μm. 
     The allowable incident angle of the second limiting region  21 B is larger than the allowable incident angle of the first limiting region  21 A because the second limiting region  21 B has a larger interval in the X-axis direction than the first limiting region  21 A as illustrated in  FIG.  7   . 
     In the first angle limiting filter  21  of the present embodiment, the X-axis intervals between adjacent light shielding walls are adjusted as described above such that the degree of angle limitation of the second limiting region  21 B is smaller than the degree of angle limitation of the first limiting region  21 A. 
     The allowable incident angle of the third limiting region  21 C is larger than the allowable incident angle of the second limiting region  21 B because the third limiting region  21 C has a larger interval in the X-axis direction than the second limiting region  21 B. 
     In the first angle limiting filter  21  of the present embodiment, the X-axis intervals between adjacent light shielding walls are adjusted as described above such that the degree of angle limitation of the third limiting region  21 C is smaller than the degree of angle limitation of the second limiting region  21 B. 
     The allowable incident angle of the fourth limiting region  21 D is larger than the allowable incident angle of the third limiting region  21 C because the fourth limiting region  21 D has a larger interval in the X-axis direction than the third limiting region  21 C. 
     In the first angle limiting filter  21  of the present embodiment, the X-axis intervals between adjacent light shielding walls are adjusted as described above such that the degree of angle limitation of the fourth limiting region  21 D is smaller than the degree of angle limitation of the third limiting region  21 C. 
     The first light receiving element  51  of the present embodiment is provided with the first angle limiting filter  21  such that the degree of angle limitation (the allowable incident angle) of the first light receiving element  51  decreases toward the +X side away from the first light emitting element  50  as described above. 
     Green light LG that has propagated in the blood vessel M 1  is emitted from the living body while being scattered as illustrated in  FIG.  5   . Therefore, green light LG that has propagated in the blood vessel M 1  has scattering components. A part of the scattering components includes scattering components LG 1  directed to the +X side of specular reflection components from the living body. 
     The scattering components LG 1  have a larger angle of incidence with respect to the first light receiving element  51  than the specular reflection components of green light LG that are emitted after propagating in the blood vessel M 1 . That is, the scattering components LG 1  have a larger inclination with respect to the normal direction of the light receiving surface  20   a  of the sensor  20 . 
     Therefore, in the case of an angle limiting filter in which light shielding walls are embedded at equal intervals, the degree of angle limitation is constant in the X-axis direction, such that the scattering components LG 1  having a larger angle of incidence than the specular reflection components of the green light LG are blocked by the light shielding walls and cannot be incident on the light receiving surface  20   a  of the sensor  20 . 
     On the other hand, in the first angle limiting filter  21  of the present embodiment, the degree of angle limitation of the first light receiving element  51  (the light receiving surface  20   a  of the sensor  20 ) decreases toward the +X side. That is, the first light receiving element  51  has a larger allowable incident angle on the +X side than on the −X side, such that it can transmit even the scattering components LG 1  having a large inclination with respect to the normal direction of the light receiving surface  20   a  of the sensor  20 . 
     The first angle limiting filter  21  can allow the scattering components LG 1  to be incident on the light receiving surface  20   a  of the sensor  20 , for example, via the third limiting region  21 C or the fourth limiting region  21 D having a relatively large allowable incident angle. 
     According to the first light receiving element  51  of the present embodiment, the first angle limiting filter  21  whose degree of angle limitation decreases toward the +X side away from the first light emitting element  50  is provided, such that it is possible to inject the scattering components LG 1 , which are blocked by the angle limiting filter of the related art, into the sensor  20 . Thus, the first light receiving element  51  reduces variations in the amount of received light over the light receiving surface  20   a  of the sensor  20  and efficiently injects green light LG emitted from the light emitting unit  11  into the sensor  20 , thus achieving high detection accuracy. 
     Here, in the detecting device  3  of the present embodiment, a part of the red light LR emitted from the second light emitting element  60  or a part of the near-infrared light LI emitted from the third light emitting element  70  may be directly incident on the second light receiving element  61  without passing through the living body as illustrated in  FIG.  5   . External light such as sunlight may also be directly incident on the second light receiving element  61  through the gap between the living body and the detection surface  16 . Hereinafter, red light LR or near-infrared light LI that is directed directly to the second light receiving element  61  without passing through the living body is collectively referred to as a “third stray light component SL 3 ” and external light that is directed directly to the second light receiving element  61  is referred to as a “fourth stray light component SL 4 ”. 
     Because the third stray light component SL 3  is incident on the second angle limiting filter  31  without passing through the living body, the angle of incidence of the third stray light component SL 3  with respect to the second light receiving element  61  is larger than the allowable incident angle of the second angle limiting filter  31 . Because the fourth stray light component SL 4  is incident through the gap between the living body and the detection surface  16 , the angle of incidence of the fourth stray light component SL 4  with respect to the second light receiving element  61  is larger than the allowable incident angle of the second angle limiting filter  31 . 
     Therefore, the third stray light component SL 3  and the fourth stray light component SL 4  are satisfactorily blocked by the second angle limiting filter  31 . Thus, the second light receiving element  61  can limit the incidence of the third stray light component SL 3  and the fourth stray light component SL 4  on the light receiving surface  30   a  of the sensor  30  through the second angle limiting filter  31 . 
     The second light receiving element  61  is configured similar to the first light receiving element  51 . 
     The second light receiving element  61  has a plurality of light receiving regions including a first light receiving region IA 2 , a second light receiving region IB 2 , and a third light receiving region IC 2 . Hereinafter, the first light receiving region IA 2 , the second light receiving region IB 2 , and the third light receiving region IC 2  are collectively referred to as “each of the light receiving regions IA 2 , IB 2 , and IC 2 ” unless particularly specified. 
     Each of the light receiving regions IA 2 , IB 2 , and IC 2  corresponds to a part of the light receiving surface  30   a  of the sensor  30  of the second light receiving element  61 . The light receiving regions IA 2 , IB 2 , and IC 2  are arranged on the light receiving surface  30   a  one by one on the +X side in this order. 
     In the present embodiment, the number (3) of light receiving regions of the second light receiving element  61  differs from the number (4) of light receiving regions of the first light receiving element  51 . 
     The second angle limiting filter  31  is configured similar to the first angle limiting filter  21 . The second angle limiting filter  31  includes a first limiting region  31 A, a second limiting region  31 B, and a third limiting region  31 C. Hereinafter, the first limiting region  31 A, the second limiting region  31 B, and the third limiting region  31 C are collectively referred to as “each of the limiting regions  31 A,  31 B, and  31 C” unless particularly specified. 
     The limiting regions  31 A,  31 B, and  31 C correspond respectively to the light receiving regions IA 2 , IB 2 , and IC 2 . 
     The first limiting region  31 A is arranged to overlap the first light receiving region IA 2  when viewed in plan from the +Z side and limits the angle of incidence of the red light LR or the near-infrared light LI with respect to the first light receiving region IA 2  of the second light receiving element  61 . 
     The second limiting region  31 B is arranged to overlap the second light receiving region IB 2  when viewed in plan from the +Z side and limits the angle of incidence of the red light LR or the near-infrared light LI with respect to the second light receiving region IB 2  of the second light receiving element  61 . 
     The third limiting region  31 C is arranged to overlap the third light receiving region IC 2  when viewed in plan from the +Z side and limits the angle of incidence of the red light LR or the near-infrared light LI with respect to the third light receiving region IC 2  of the second light receiving element  61 . 
     In the detecting device  3  of the present embodiment, the degree of angle limitation of each of the limiting regions  31 A,  31 B, and  31 C progressively decreases away from the light emitting elements  60  and  70 . 
     The second angle limiting filter  31  includes a silicon oxide layer  34  and a plurality of light shielding walls (second light shielding walls)  35  embedded in the silicon oxide layer  34 . Each light shielding wall  35  is formed in a plate shape extending to the +Z side from the light receiving surface  30   a  of the sensor  30 . Although omitted in  FIG.  7   , the plurality of light shielding walls  35  are arranged not only in the X-axis direction but also in the Y-axis direction such that they form a grid shape as a whole when viewed in plan from the +Z side. 
     The second angle limiting filter  31  is formed through a wiring forming process of a semiconductor process similar to that of the first angle limiting filter  21 . 
     The plurality of light shielding walls  35  include light shielding walls  35   a ,  35   b ,  35   c , and  35   d.    
     The light shielding walls  35   a  and  35   b  define the first limiting region  31 A in the X-axis direction. The light shielding walls  35   b  and  35   c  define the second limiting region  31 B in the X-axis direction. The light shielding walls  35   c  and  35   d  define the third limiting region  31 C in the X-axis direction. The degrees of angle limitation of the limiting regions  31 A,  31 B, and  31 C are defined by the X-axis intervals between adjacent light shielding walls. 
     In the present embodiment, the X-axis interval between the adjacent light shielding walls  35   b  and  35   c  in the second limiting region  31 B among the plurality of light shielding walls  35  is larger than the X-axis interval between the adjacent light shielding walls  35   a  and  35   b  in the first limiting region  31 A among the plurality of light shielding walls  35 . 
     The X-axis interval between the adjacent light shielding walls  35   c  and  35   d  in the third limiting region  31 C among the plurality of light shielding walls  35  is larger than the X-axis interval between the adjacent light shielding walls  35   b  and  35   c  in the second limiting region  31 B among the plurality of light shielding walls  35 . 
     In the case of the present embodiment, for example, the interval between the light shielding walls  35   a  and  35   b  is set to 4.5 μm, the interval between the light shielding walls  35   b  and  35   c  is set to 6 μm, and the interval between the light shielding walls  35   c  and  35   d  is set to 7.5 μm. The heights of the light shielding walls  35   a ,  35   b ,  35   c , and  35   d  are set to 5 μm. 
     The second light receiving element  61  of the present embodiment is provided with the second angle limiting filter  31  such that the degree of angle limitation (the allowable incident angle) of the second light receiving element  61  decreases toward the +X side away from the light emitting elements  60  and  70  as illustrated in  FIG.  7   . 
     Here, the light emitting elements  50 ,  60 , and  70  (the light emitting unit  11 ) that emit green light LG, red light LR, and near-infrared light LI are arranged at the same position in the X-axis direction, while the second light receiving element  61  that receives red light LR or near-infrared light LI is arranged at a position spaced to the +X side further than the first light receiving element  51  that receives green light LG is as illustrated in  FIG.  5   . 
     Thus, the second light receiving element  61  is arranged at a position spaced further from the light emitting unit  11  in the X-axis direction than the first light receiving element  51  is, such that the angle of incidence of red light LR or near-infrared light LI with respect to the second light receiving element  61  is larger than the angle of incidence of green light LG with respect to the first light receiving element  51 . 
     In the case of the present embodiment, the degree of angle limitation of the first limiting region  31 A in the second angle limiting filter  31  is smaller than the degree of angle limitation of the first limiting region  21 A in the first angle limiting filter  21 . Specifically, the X-axis interval between the adjacent light shielding walls  35   a  and  35   b  in the first limiting region  31 A is larger than the X-axis interval between the adjacent light shielding walls  25   a  and  25   b  in the first limiting region  21 A. 
     That is, the allowable incident angle of the first limiting region  31 A in the second angle limiting filter  31  is larger than the allowable incident angle of the first limiting region  21 A in the first angle limiting filter  21 . Making the allowable incident angle of the first limiting region  31 A located on the light emitting unit  11  side in the second angle limiting filter  31  larger relative to that of the first limiting region  21 A in the first angle limiting filter  21  in this manner ensures that red light LR or near-infrared light LI that is incident at a larger angle with respect to the second light receiving element  61  can be incident on the light receiving surface  30   a  of the sensor  30  without being blocked as described above. 
     Because red light LR or near-infrared light LI that have propagated in the blood vessel M 1  is emitted from the living body while being scattered as illustrated in  FIG.  5   , the red light LR or near-infrared light LI has scattering components. A part of the scattering components includes scattering components LR 1  and LI 1  directed to the +X side of specular reflection components from the living body. 
     The scattering components LR 1  and LI 1  have a larger incident angle with respect to the second light receiving element  61  than the specular reflection components of red light LR or near-infrared light LI that are emitted after propagating in the blood vessel M 1 . 
     In the second angle limiting filter  31  of the present embodiment, the degree of angle limitation of the second light receiving element  61  (the light receiving surface  30   a  of the sensor  30 ) decreases toward the +X side, such that the allowable incident angle on the +X side is larger than the allowable incident angle on the −X side. 
     Thus, the second angle limiting filter  31  can allow the scattering components LR 1  and LI 1  to be incident on the light receiving surface  30   a  of the sensor  30 , for example, via the second limiting region  31 B or the third limiting region  31 C which is located on the +X side and has a relatively large allowable incident angle. 
     According to the second light receiving element  61  of the present embodiment, the second angle limiting filter  31  whose degree of angle limitation decreases toward the +X side away from the light emitting elements  60  and  70  is provided, such that it is possible to inject the scattering components LR 1  and LI 1 , which are blocked by the angle limiting filter of the related art, into the sensor  30 . 
     Thus, the second light receiving element  61  reduces variations in the amount of received light over the light receiving surface  30   a  of the sensor  30 , such that red light LR or near-infrared light LI emitted from the light emitting unit  11  is efficiently injected into the sensor  30 , thus achieving high detection accuracy. 
     Further, in the detecting device  3  of the present embodiment, the distance D 1  between the first light emitting element  50  and the first light receiving element  51  is smaller than the distance between the second light emitting element  60  or the third light emitting element  70  and the second light receiving element  61  (the distance D 2  or D 3 ). 
     In the case of the present embodiment, the first light receiving element  51  is arranged at a position closest to the first light emitting element  50 , such that it can efficiently receive green light LG that is incident on the first light receiving element  51  after propagating in the living body. Red light LR and near-infrared light LI can propagate further in the living body than the green light LG as described above. Therefore, the second light receiving element  61  can efficiently receive the red light LR and the near-infrared light LI that have propagated a longer distance in the living body than the green light LG. 
     Thus, the detecting device  3  of the present embodiment can accurately detect green light LG, red light LR, and near-infrared light LI that have propagated in the living body through the light receiving unit  12 . 
     In the detecting device  3  of the present embodiment, the distance that the red light LR and the near-infrared light LI propagates in the living body until they are incident on the second light receiving element  61  is larger than the distance that the green light LG propagates in the living body until it is incident on the first light receiving element  51 . 
     The green light LG can propagate only a short distance in the living body, compared to the red light LR or the near-infrared light LI as described above. Therefore, if the green light LG propagates in the living body such that it can reach the second light receiving element  61 , the green light LG is sufficiently attenuated while passing through the living body. Thus, the green light LG cannot be incident on the second light receiving element  61 . 
     On the other hand, the red light LR and the near-infrared light LI can propagate further in the living body than the green light LG. Therefore, even when the red light LR and the near-infrared light LI have propagated a longer distance in the living body than the green light LG, a sufficient amount of the red light LR and the near-infrared light LI can be incident on the second light receiving element  61  spaced further from the light emitting unit  11 . 
     In the case of the present embodiment, only the red light LR and the near-infrared light LI are incident on the second light receiving element  61 , such that it is not necessary to provide the second light receiving element  61  with a band pass filter that selectively transmits the red light LR and the near-infrared light LI and blocks the green light LG. That is, the detecting device  3  of the present embodiment can adopt the above configuration in which only the first light receiving element  51  includes the bandpass filter  22  while the second light receiving element  61  does not include a bandpass filter. Thus, the detecting device  3  of the present embodiment can omit a bandpass filter for the second light receiving element  61 , reducing the cost. 
     The first light receiving element  51  of the present embodiment can make it difficult for the first stray light component SL 1  and the second stray light component SL 2  to be incident on the light receiving surface  20   a  of the sensor  20 . Thus, the first light receiving element  51  can limit the incidence of the first stray light component SL 1  and the second stray light component SL 2 , which are noise components, achieving a high S/N ratio. 
     The second light receiving element  61  of the present embodiment can also make it difficult for the third stray light component SL 3  and the fourth stray light component SL 4  to be incident on the light receiving surface  30   a  of the sensor  30 . Thus, the second light receiving element  61  can limit the incidence of the third stray light component SL 3  and the fourth stray light component SL 4 , which are noise components, achieving a high S/N ratio. 
     The detecting device  3  of the present embodiment can greatly improve the detection accuracy of the light receiving unit  12  by increasing the amount of received light while increasing the S/N ratio as described above. Thus, the detecting device  3  of the present embodiment enables highly accurate light reception by the light receiving elements  51  and  61 , such that it is possible to reduce power consumption of the light emitting unit  11  by limiting the amount of light emission from the light emitting elements  50 ,  60  and  70 . 
     The measuring device  100  of the present embodiment includes the above detecting device  3  and thus can provide a biometric measuring device capable of highly accurate detection while reducing power consumption. 
     Second Embodiment 
     Subsequently, a detecting device of a second embodiment will be described. The detecting device of the present embodiment differs from that of the first embodiment in the configurations of the first and second angle limiting filters which are angle limiting members. Hereinafter, the same reference numerals will be used for the components and members common with the first embodiment and reference numerals will be omitted for details. 
       FIG.  8    is a cross-sectional view illustrating a configuration of a main part of a detecting device  103  of the present embodiment. 
     As illustrated in  FIG.  8   , the detecting device  103  of the present embodiment includes a light emitting unit  11 , a light receiving unit  112 , a case  40 , and a sealing layer  42 . The light receiving unit  112  of the present embodiment includes a first light receiving element  151  and a second light receiving element  161 . 
     The first light receiving element  151  includes a sensor  20 , a first angle limiting filter (angle limiting member)  81 , and a bandpass filter  22 . The second light receiving element  161  includes a sensor  30  and a second angle limiting filter (angle limiting member)  91 . 
     In the detecting device  103  of the present embodiment, the first light receiving element  151  includes a first light receiving region IA 11 , a second light receiving region IB 11 , and a third light receiving region IC 11 . Hereinafter, the first light receiving region IA 11 , the second light receiving region IB 11 , and the third light receiving region IC 11  are collectively referred to as “each of the light receiving regions IA 11 , IB 11 , and IC 11 ” unless particularly specified. 
     Each of the light receiving regions IA 11 , IB 11 , and IC 11  corresponds to a part of the light receiving surface  20   a  of the sensor  20  of the first light receiving element  151 . The light receiving regions IA 11 , IB 11 , and IC 11  are arranged on the light receiving surface  20   a  of the sensor  20  one by one on the +X side in this order. 
     The first angle limiting filter  81  includes a first limiting region  81 A, a second limiting region  81 B, and a third limiting region  81 C. Hereinafter, the first limiting region  81 A, the second limiting region  81 B, and the third limiting region  81 C are collectively referred to as “each of the limiting regions  81 A,  81 B, and  81 C” unless particularly specified. 
     The limiting regions  81 A,  81 B, and  81 C correspond respectively to the light receiving regions IA 11 , IB 11 , and IC 11 . In the detecting device  103  of the present embodiment, the degree of angle limitation of each of the limiting regions  81 A,  81 B, and  81 C progressively decreases away from the first light emitting element  50 . 
     The first angle limiting filter  81  includes a silicon oxide layer  84  and a plurality of light shielding walls (first light shielding walls)  85  embedded in the silicon oxide layer  84 . In the first angle limiting filter  81 , the plurality of light shielding walls  85  are provided on the light receiving regions IA 11 , IB 11 , and IC 11  of the first light receiving element  151 . The plurality of light shielding walls  85  include light shielding walls  85   a ,  85   b ,  85   c ,  85   d ,  85   e ,  85   f , and  85   g.    
     The light shielding wall  85   a  and the light shielding wall  85   b  are arranged in the X-axis direction in the first limiting region  81 A. In the case of the present embodiment, the heights of the light shielding walls  85   a  and  85   b  are set to, for example, 5 μm. 
     The light shielding wall  85   c  and the light shielding wall  85   d  are arranged in the X-axis direction in the second limiting region  81 B. In the case of the present embodiment, the heights of the light shielding walls  85   c  and  85   d  are set to, for example, 4 μm. 
     The light shielding wall  85   e , the light shielding wall  85   f , and the light shielding wall  85   g  are arranged in the X-axis direction in the third limiting region  81 C. In the case of the present embodiment, the heights of the light shielding walls  85   e ,  85   f , and  85   g  are set to, for example, 3 μm. 
     The X-axis intervals between adjacent ones of the light shielding walls  85   a ,  85   b ,  85   c ,  85   d ,  85   e ,  85   f , and  85   g  are set to, for example, 3 μm. 
     The first angle limiting filter  81  of the present embodiment can be formed, for example, by providing portions in which conductive plugs such as tungsten plugs having light absorptivity are embedded and portions in which no conductive plugs are embedded through multiple steps into which a wiring forming process of a semiconductor process is divided, such that a plurality of light shielding walls  85  with different heights are embedded in the silicon oxide layer  24 . 
     In the case of the present embodiment, the degrees of angle limitation of the limiting regions  81 A,  81 B, and  81 C are defined by the heights of light shielding walls arranged in the X-axis direction. 
     In the present embodiment, the height of the light shielding walls  85   c  and  85   d  arranged in the X-axis direction in the second limiting region  81 B among the plurality of light shielding walls  85  is less than the height of the light shielding walls  85   a  and  85   b  arranged in the X-axis direction in the first limiting region  81 A among the plurality of light shielding walls  85 . 
     The height of the light shielding walls  85   e ,  85   f , and  85   g  arranged in the X-axis direction in the third limiting region  81 C among the plurality of light shielding walls  85  is also less than the height of the light shielding walls  85   c  and  85   d  arranged in the X-axis direction in the second limiting region  81 B among the plurality of light shielding walls  85 . 
     The allowable incident angle of the second limiting region  81 B is larger than the allowable incident angle of the first limiting region  81 A because the height of the light shielding walls of the second limiting region  81 B is less than that of the first limiting region  81 A as illustrated in  FIG.  8   . 
     In the first angle limiting filter  81  of the present embodiment, the heights of light shielding walls arranged in the X-axis direction are adjusted as described above such that the degree of angle limitation of the second limiting region  81 B is smaller than the degree of angle limitation of the first limiting region  81 A. 
     The allowable incident angle of the third limiting region  81 C is larger than the allowable incident angle of the second limiting region  81 B because the height of the light shielding walls of the third limiting region  81 C is less than that of the second limiting region  81 B. 
     In the first angle limiting filter  81  of the present embodiment, the heights of light shielding walls arranged in the X-axis direction are adjusted as described above such that the degree of angle limitation of the third limiting region  81 C is smaller than the degree of angle limitation of the second limiting region  81 B. 
     The first light receiving element  151  of the present embodiment is provided with the first angle limiting filter  81  such that the degree of angle limitation (the allowable incident angle) of the first light receiving element  151  decreases toward the +X side away from the first light emitting element  50  as described above. 
     The first angle limiting filter  81  of the present embodiment can allow the scattering components LG 1  to be incident on the light receiving surface  20   a  of the sensor  20 , for example, via the second limiting region  81 B or the third limiting region  81 C having a relatively large allowable incident angle. 
     According to the first light receiving element  151  of the present embodiment, the first angle limiting filter  81  whose degree of angle limitation decreases toward the +X side away from the first light emitting element  50  is provided, such that it is possible to inject the scattering components LG 1 , which are blocked by the angle limiting filter of the related art, into the sensor  20 . Thus, the first light receiving element  151  reduces variations in the amount of received light over the light receiving surface  20   a  of the sensor  20  to efficiently inject green light LG emitted from the light emitting unit  11  into the sensor  20 , thus achieving high detection accuracy. 
     The second light receiving element  161  is configured similar to the first light receiving element  151 . 
     The second light receiving element  161  has a plurality of light receiving regions including a first light receiving region IA 21 , a second light receiving region IB 21 , and a third light receiving region IC 21 . Hereinafter, the first light receiving region IA 21 , the second light receiving region IB 21 , and the third light receiving region IC 21  are collectively referred to as “each of the light receiving regions IA 21 , IB 21 , and IC 21 ” unless particularly specified. 
     Each of the light receiving regions IA 21 , IB 21 , and IC 21  corresponds to a part of the light receiving surface  30   a  of the sensor  30  of the second light receiving element  161 . The light receiving regions IA 21 , IB 21 , and IC 21  are arranged on the light receiving surface  30   a  of the sensor  30  one by one on the +X side in this order. 
     The second angle limiting filter  91  is configured similar to the first angle limiting filter  81 . The second angle limiting filter  91  includes a first limiting region  91 A, a second limiting region  91 B, and a third limiting region  91 C. Hereinafter, the first limiting region  91 A, the second limiting region  91 B, and the third limiting region  91 C are collectively referred to as “each of the limiting regions  91 A,  91 B, and  91 C” unless particularly specified. 
     The limiting regions  91 A,  91 B, and  91 C correspond respectively to the light receiving regions IA 21 , IB 21 , and IC 21 . In the detecting device  103  of the present embodiment, the degree of angle limitation of each of the limiting regions  91 A,  91 B, and  91 C progressively decreases away from the light emitting elements  60  and  70 . 
     The second angle limiting filter  91  includes a silicon oxide layer  94  and a plurality of light shielding walls (second light shielding walls)  95  embedded in the silicon oxide layer  94 . In the second angle limiting filter  91 , the plurality of light shielding walls  95  are provided on the light receiving regions IA 21 , IB 21 , and IC 21  of the second light receiving element  161 . The plurality of light shielding walls  95  include light shielding walls  95   a ,  95   b ,  95   c ,  95   d ,  95   e ,  95   f , and  95   g . The second angle limiting filter  91  is formed by embedding a plurality of light shielding walls  95  with different heights in the silicon oxide layer  24  through multiple steps into which a wiring forming process of a semiconductor process is divided, similar to the first angle limiting filter  81 . 
     The light shielding wall  95   a  and the light shielding wall  95   b  are arranged in the X-axis direction in the first limiting region  91 A. In the case of the present embodiment, the heights of the light shielding walls  95   a  and  95   b  are set to, for example, 4 μm. 
     The light shielding wall  95   c  and the light shielding wall  95   d  are arranged in the X-axis direction in the second limiting region  91 B. In the case of the present embodiment, the heights of the light shielding walls  95   c  and  95   d  are set to, for example, 3 μm. 
     The light shielding wall  95   e , the light shielding wall  95   f , and the light shielding wall  95   g  are arranged in the X-axis direction in the third limiting region  91 C. In the case of the present embodiment, the heights of the light shielding walls  95   e ,  95   f , and  95   g  are set to, for example, 2 μm. 
     The X-axis intervals between adjacent ones of the light shielding walls  95   a ,  95   b ,  95   c ,  95   d ,  95   e ,  95   f , and  95   g  are set to, for example, 3 μm. 
     In the case of the present embodiment, the degrees of angle limitation of the limiting regions  91 A,  91 B, and  91 C are defined by the heights of light shielding walls arranged in the X-axis direction. 
     In the present embodiment, the height of the light shielding walls  95   c  and  95   d  arranged in the X-axis direction in the second limiting region  91 B among the plurality of light shielding walls  95  is less than the height of the light shielding walls  95   a  and  95   b  arranged in the X-axis direction in the first limiting region  91 A among the plurality of light shielding walls  95 . 
     The height of the light shielding walls  95   e ,  95   f , and  95   g  arranged in the X-axis direction in the third limiting region  91 C among the plurality of light shielding walls  95  is also less than the height of the light shielding walls  95   c  and  95   d  arranged in the X-axis direction in the second limiting region  91 B among the plurality of light shielding walls  95 . 
     In the second angle limiting filter  91  of the present embodiment, the heights of light shielding walls arranged in the X-axis direction are adjusted as described above such that the degree of angle limitation (the allowable incident angle) of the second light receiving element  161  decreases toward the +X side away from the light emitting elements  60  and  70  as illustrated in  FIG.  8   . 
     In the case of the present embodiment, the degree of angle limitation of the first limiting region  91 A in the second angle limiting filter  91  is smaller than the degree of angle limitation of the first limiting region  81 A in the first angle limiting filter  81 . Specifically, the height of the light shielding walls  95   a  and  95   b  arranged in the X-axis direction in the first limiting region  91 A of the second light receiving element  161  is less than the height of the light shielding walls  85   a  and  85   b  arranged in the X-axis direction in the first limiting region  81 A of the first light receiving element  151 . 
     That is, the allowable incident angle of the first limiting region  91 A in the second angle limiting filter  91  is larger than the allowable incident angle of the first limiting region  81 A in the first angle limiting filter  81 . Making the allowable incident angle of the first limiting region  91 A located on the light emitting unit  11  side (the −X side) in the second angle limiting filter  91  larger relative to that of the first limiting region  81 A in the first angle limiting filter  81  in this manner ensures that red light LR or near-infrared light LI that is incident at a larger angle with respect to the second light receiving element  161  can be incident on the light receiving surface  30   a  of the sensor  30  without being blocked. 
     According to the second light receiving element  161  of the present embodiment, the second angle limiting filter  91  whose degree of angle limitation decreases toward the +X side away from the light emitting elements  60  and  70  is provided, such that it is possible to inject the scattering components LR 1  and LI 1 , which are blocked by the angle limiting filter of the related art, into the sensor  30 . 
     Thus, the second light receiving element  161  reduces variations in the amount of received light over the light receiving surface  30   a  of the sensor  30  to efficiently inject red light LR or near-infrared light LI emitted from the light emitting unit  11  into the sensor  30 , thus achieving high detection accuracy. 
     Similar to the detecting device  3  of the above embodiments, the detecting device  103  of the present embodiment can improve the detection accuracy of the light receiving unit  112  by increasing the amount of received light while increasing the S/N ratio as described above. Thus, the measuring device using the detecting device  103  according to the present embodiment can provide a biometric measuring device capable of highly accurate detection while reducing power consumption. 
     EXAMPLES 
     In order to demonstrate the effects of the detecting devices  3  and  103  of the above embodiments, the present inventor has simulated both the amount of light received by the light receiving element according to the distance from the light emitting unit and the light receiving rate of the light receiving element for a first example, a second example, and a comparative example that will be described below. 
     Specifically, the detecting device  3  of the first embodiment was used as the first example, the detecting device  103  of the second embodiment was used as the second example, and a detecting device using an angle limiting filter in which light shielding walls are embedded at equal intervals was used as the comparative example. 
     In the angle limiting filter of the detecting device of the comparative example, for example, the intervals between adjacent light shielding walls were set to 3 μm and the heights of the light shielding walls were set to 5 μm. 
     A graph of  FIG.  9    shows the results of simulating the amount of light received by the light receiving element according to the distance from the light emitting unit for the detecting devices of the first example, the second example, and the comparative example. In  FIG.  9   , the horizontal axis of the graph represents the distance from the light emitting unit in the direction in which the light emitting unit and the light receiving unit are arranged (for example, the X-axis direction in  FIG.  5   ) and the vertical axis of the graph represents the amount of light received by the light receiving element. 
     As shown in  FIG.  9   , it was confirmed that the amount of light received by the light receiving element increased as the distance from the light emitting unit increased in the detecting devices of the first and second examples, relative to the detecting device of the comparative example. That is, it was confirmed that the detecting devices of the first and second examples can make the amount of received light uniform over the surface of the light receiving element by decreasing the degree of angle limitation of the angle limiting filter as the distance from the light emitting unit increases. 
     A graph of  FIG.  10    shows the results of simulating the light receiving rate of the light receiving element for the detecting devices of the first example, the second example, and the comparative example.  FIG.  10    shows the amount of received light for each of the detecting devices of the first and second examples when the amount of light received by the light receiving element of the detecting device of the comparative example is set to 1.0. 
     As shown in  FIG.  10   , it was confirmed that the detecting devices of the first and second examples can increase the amount of light received by the light receiving element to 1.36 or 1.27 relative to the detecting device of the comparative example. 
     From the results shown in  FIGS.  9  and  10   , it was confirmed that the detecting device of the first example has a higher effect of increasing the amount of light received by the light receiving element compared to the detecting device of the second example. 
     From the above, it has been demonstrated that the detecting devices  3  and  103  of the above embodiments can increase the amount of light received by each light receiving element, compared to the detecting device of the comparative example. 
     Although the present disclosure has been described above based on the above embodiments, the present disclosure is not limited to the above embodiments and can be implemented in various modes without departing from the spirit of the disclosure. 
     For example, although a living body is exemplified by a human in the above embodiments, the present disclosure can also be applied to measurement of the biological information (for example, pulse) of other animals. 
     Although the measuring device  100  of the first embodiment has been described with respect to the case where the detecting device  3  is provided in the main body  1  as an example, the installation location of the detecting device  3  is not limited to this, and for example, the detecting device  3  may be embedded in the back side of the belt. 
     Although the measuring device  100  of the first embodiment has been described with respect to a configuration in which it is of a wristwatch type as an example, the present disclosure can also be applied to, for example, a configuration in which it is worn on the subject&#39;s neck as a necklace type or a configuration in which it is attached to the subject&#39;s body as a sealed type, or a configuration in which it is attached to the subject&#39;s head as a head-mounted display type. 
     Although the detecting device  3  of the first embodiment has been described with respect to the case where the sensor  20  of the first light receiving element  51  includes four light receiving regions as an example, the number of light receiving regions is not limited to this. For example, the sensor  20  only needs to include at least two light receiving regions (the first light receiving region IA 1  and the second light receiving region IB 1 ) and may also include five or more light receiving regions. Similarly, the sensor  30  of the second light receiving element  61  only needs to include at least two light receiving regions (the first light receiving region IA 2  and the second light receiving region IB 2 ) and may also include five or more light receiving regions. 
     Although the detecting device  103  of the second embodiment has been described with respect to the case where the sensor  20  of the first light receiving element  151  includes three light receiving regions as an example, the sensor  20  of the first light receiving element  151  only needs to include at least two light receiving regions (the first light receiving region IA 11  and the second light receiving region IB 11 ) and may also include five or more light receiving regions. Similarly, the sensor  30  of the second light receiving element  161  only needs to include at least two light receiving regions (the first light receiving region IA 21  and the second light receiving region IB 21 ) and may also include five or more light receiving regions. 
     Although the detecting device  3  of the first embodiment has been described with respect to the case where each of the light emitting elements  50 ,  60 , and  70  is caused to emit light in a time division manner as an example, the first light emitting element  50  may be constantly lit rather than being lit in a time division manner because the first light receiving element  51  corresponding to green light LG of the first light emitting element  50  is individually provided. Similarly, the first light emitting element  50  in the second embodiment may be constantly lit rather than being lit in a time division manner. 
     A detecting device of an aspect of the present disclosure may be configured as follows. 
     The detecting device of the aspect of the present disclosure includes a light emitting portion that emits light and a light receiving portion including an angle limiting member that limits an angle of incidence of light from the light emitting portion, wherein the light receiving portion has a first light receiving region and a second light receiving region that is spaced further from the light emitting portion than the first light receiving region is, the angle limiting member includes a first limiting region corresponding to the first light receiving region and a second limiting region corresponding to the second light receiving region, and a degree of angle limitation of the second limiting region is smaller than a degree of angle limitation of the first limiting region. 
     The detecting device of the aspect of the present disclosure may be configured such that, when a direction in which the light emitting portion and the light receiving portion are arranged is defined as a first direction, the angle limiting member includes a plurality of light shielding walls provided in the light receiving portion, and an interval in the first direction between adjacent light shielding walls in the second limiting region among the plurality of light shielding walls is larger than an interval in the first direction between adjacent light shielding walls in the first limiting region among the plurality of light shielding walls. 
     The detecting device of the aspect of the present disclosure may be configured such that the light emitting portion includes a first light emitting element configured to emit first light having a green wavelength band and a second light emitting element provided in a second direction intersecting the first direction with respect to the first light emitting element and configured to emit second light having a wavelength band longer than those of the green wavelength band, the light receiving portion includes a first light receiving element configured to receive the first light from the first light emitting element and a second light receiving element configured to receive the second light from the second light emitting element, and the first light receiving element is provided closer to the light emitting portion in the first direction than the second light receiving element is. 
     The detecting device of the aspect of the present disclosure may be configured such that the angle limiting member includes a first angle limiting filter configured to limit an angle of incidence of the first light with respect to the first light receiving element and a second angle limiting filter configured to limit an angle of incidence of the second light with respect to the second light receiving element, and a degree of angle limitation of the first limiting region in the second angle limiting filter is smaller than a degree of angle limitation of the first limiting region in the first angle limiting filter. 
     The detecting device of the aspect of the present disclosure may be configured such that the first angle limiting filter includes a plurality of first light shielding walls provided in the first light receiving element, the second angle limiting filter includes a plurality of second light shielding walls provided in the second light receiving element, and an interval in the first direction between adjacent ones of the second light shielding walls in the first limiting region of the second light receiving element is larger than an interval in the first direction between adjacent ones of the first light shielding walls in the first limiting region of the first light receiving element. 
     The detecting device of the aspect of the present disclosure may be configured such that, when a direction in which the light emitting portion and the light receiving portion are arranged is defined as a first direction, the angle limiting member includes a plurality of light shielding walls provided in the light receiving portion, and a height of the light shielding walls arranged in the first direction in the second limiting region is less than a height of the light shielding walls arranged in the first direction in the first limiting region. 
     The detecting device of the aspect of the present disclosure may be configured such that the light emitting portion includes a first light emitting element configured to emit first light having a green wavelength band and a second light emitting element provided in a second direction intersecting the first direction with respect to the first light emitting element and configured to emit second light having a wavelength band longer than those of the green wavelength band, the light receiving portion includes a first light receiving element configured to receive the first light from the first light emitting element and a second light receiving element configured to receive the second light from the second light emitting element, and the first light receiving element is provided closer to the light emitting portion in the first direction than the second light receiving element is. 
     The detecting device of the aspect of the present disclosure may be configured such that the angle limiting member includes a first angle limiting filter configured to limit an angle of incidence of the first light with respect to the first light receiving element and a second angle limiting filter configured to limit an angle of incidence of the second light with respect to the second light receiving element, and a degree of angle limitation of the first limiting region in the second angle limiting filter is smaller than a degree of angle limitation of the first limiting region in the first angle limiting filter. 
     The detecting device of the aspect of the present disclosure may be configured such that the first angle limiting filter includes a plurality of first light shielding walls provided in the first light receiving element, the second angle limiting filter includes a plurality of second light shielding walls provided in the second light receiving element, and a height of the second light shielding walls arranged in the first direction in the first limiting region of the second light receiving element is less than a height of the first light shielding walls arranged in the first direction in the first limiting region of the first light receiving element. 
     The detecting device of the aspect of the present disclosure may be configured such that the light receiving portion further includes a third light receiving region that is spaced further from the light emitting portion than the second light receiving region is, and the angle limiting member further includes a third limiting region corresponding to the third light receiving region and having a smaller degree of angle limitation than the second limiting region. 
     A detecting device of an aspect of the present disclosure may be configured as follows. 
     The detecting device of the aspect of the present disclosure includes a light emitting portion configured to emit light to a living body, a light receiving portion arranged in a first direction with respect to the light emitting portion and configured to receive light from the living body, and a plurality of light shielding walls arranged in the first direction and configured to limit an angle of incidence of light on the light receiving portion, wherein an interval between the light shielding walls in a region far from the light emitting portion is larger than an interval between the light shielding walls in a region close to the light emitting portion. 
     A measuring device of an aspect of the present disclosure may be configured as follows. 
     The measuring device of the aspect of the present disclosure includes the detecting device according to the above aspect and an information analysis unit configured to identify biological information from a detection signal indicating a detection result of the detecting device.