WO2019124039A1

WO2019124039A1 - Pulse wave detecting device

Info

Publication number: WO2019124039A1
Application number: PCT/JP2018/044441
Authority: WO
Inventors: 勇樹江戸; 足立　佳久; 莉絵子小川
Original assignee: シャープ株式会社
Priority date: 2017-12-20
Filing date: 2018-12-03
Publication date: 2019-06-27

Abstract

The present invention detects pulse waves more accurately than before. In a pulse wave detecting device (1), a light source unit (20) emits first light (L1) that has a first peak wavelength λ1 and second light (L2) that has a second peak wavelength λ2. A camera (30) receives first reflected light (Lr1) which is the first light (L1) reflected from a user (U) to generate a first image and receives second reflected light (Lr2) which is the second light (L2) reflected from the user (U) to generate a second image. An analysis unit (10) analyses the first image and the second image and detects a pulse wave of the user (U). λ1 and λ2 are λ1<λ2 and satisfy 520 nm≤λ1≤570 nm and 535 nm≤λ2≤590 nm.

Description

Pulse wave detection device

The following disclosure relates to a pulse wave detection device that detects a pulse wave of a living body.

For example,

Patent Documents

1 and 2 respectively disclose techniques aiming to improve detection (measurement) accuracy of a pulse wave of a living body.

Japanese Published Patent Publication "Tokukai 2016-521190" Japanese Patent Publication "Japanese Patent Application Laid-Open No. 2015-83101"

A pulse wave detection device according to an aspect of the present disclosure aims to detect a pulse wave with higher accuracy than conventional.

In order to solve the above-mentioned subject, a pulse wave detection device concerning one mode of this indication is a pulse wave detection device which detects a pulse wave of a living body, and the above-mentioned living body has the 1st light which has 1st peak wavelength λ1. The first light source emitting toward the second light source, the second light source emitting the second light having the second peak wavelength λ2 toward the living body, the imaging unit capturing an image of the living body, and the image analysis And an analysis unit that detects a pulse wave of the living body, and the imaging unit receives the first reflected light, which is light reflected from the living body by the first light, to thereby generate a first image. The second image is captured by receiving the second reflected light, which is the light reflected from the living body by the second light, and the analysis unit analyzes the first image and the second image. To detect the pulse wave of the living body, and λ 1 <λ 2, and Of the conditions (1-1) and (1-2),
520 nm ≦ λ1 ≦ 570 nm (1-1)
535 nm ≦ λ2 ≦ 590 nm (1-2)
Is satisfied.

In order to solve the above-mentioned subject, a pulse wave detection device concerning one mode of this indication is a pulse wave detection device which detects a pulse wave of a living body, and it is the 1st light which has 1st peak wavelength λ1. The first light source emitting toward the living body, the second light source emitting second light having the second peak wavelength λ2 toward the living body, and the third light emitting the third peak wavelength λ3 toward the living body A third light source, an imaging unit configured to capture an image of the living body, and an analysis unit configured to detect a pulse wave of the living body by analyzing the image, the imaging unit including the first light The first image is captured by receiving the first reflected light, which is light reflected from the living body, and the second reflected light, which is the light reflected from the living body, is received by the second light. A second image, and the third light is light reflected from the living body 3) The third image is captured by receiving the reflected light, and the analysis unit detects the pulse wave of the living body by analyzing the first image, the second image, and the third image. , Λ 1 <λ 2 <λ 3 and the following conditions (2-1), (2-2) and (2-3),
510 nm ≦ λ1 ≦ 560 nm (2-1)
525 nm ≦ λ2 ≦ 585 nm (2-2)
545 nm ≦ λ3 ≦ 590 nm (2-3)
Is satisfied.

Moreover, in order to solve the above-mentioned subject, the pulse wave detection device concerning one mode of this indication is a pulse wave detection device which detects the pulse wave of the living body concerned by analyzing the picture which imaged the living body, A first light source emitting first light having a first peak wavelength λ1 to the living body, a second light source emitting second light having a second peak wavelength λ2 to the living body, and a third peak wavelength λ3 A third light source for emitting the third light having the light toward the living body, a fourth light source for emitting the fourth light having the fourth peak wavelength λ4 to the living body, an imaging unit for capturing an image of the living body, And an analysis unit that detects a pulse wave of the living body by analyzing the image, and the imaging unit receives the first reflected light, which is the light reflected from the living body by the first light. To capture the first image, and the second light is the living body The second image is captured by receiving the second reflected light which is the reflected light, and the third image is received by receiving the third reflected light which is the light reflected from the living body by the third light. Is captured, and the fourth image is captured by receiving the fourth reflected light, which is the light reflected from the living body, and the analysis unit captures the fourth image, the second image, and the second image. The pulse wave of the living body is detected by analyzing the third image and the fourth image, and λ1 <λ2 <λ3 <λ4, and the following conditions (3-1), (3-2 ), (3-3), and (3-4),
510 nm ≦ λ1 ≦ 550 nm (3-1)
520 nm ≦ λ2 ≦ 570 nm (3-2)
530 nm ≦ λ3 ≦ 585 nm (3-3)
550 nm ≦ λ4 ≦ 590 nm (3-4)
Is satisfied.

According to the pulse wave detection device according to one aspect of the present disclosure, it is possible to detect the pulse wave with higher accuracy than in the related art.

FIG. 2 is a functional block diagram showing the configuration of the main part of the pulse wave detection device of the first embodiment. It is a figure which shows typically a mode that emitted light is irradiated to a user from a light source unit. It is a figure for demonstrating the structure of a camera. It is a figure which shows the relationship between the spectral characteristic of G filter, and the emission spectrum of 1st light and 2nd light. It is a figure which illustrates the flow of the pulse wave detection process in the pulse wave detection apparatus of FIG. It is a figure for demonstrating S1-S4 of FIG. It is a figure which shows the spectrum of the forehead at a certain time obtained by inventors' experiment. It is a figure which shows the time-sequential data of the output value in wavelength 560nm and each of 580 nm. It is a figure which shows the pulse wave calculated by the pulse wave calculation part. It is a figure which shows the power spectrum of the pulse wave of FIG. It is a figure which shows the relationship of the peak wavelength and SNR in each of Example 1 and a comparative example. It is a figure which showed the combination of (lambda) 1 and (lambda) 2 which the SNRs which SNR found over inventors found out to inventors. FIG. 7 is a functional block diagram showing a configuration of main parts of a pulse wave detection device of a second embodiment. FIG. 6 is a diagram showing combinations of λ1 to λ3 which can be obtained by the present inventors for achieving SNR exceeding SNR0. FIG. 6 is a diagram showing combinations of λ1 to λ3 which can be obtained by the present inventors for achieving SNR exceeding SNR0. FIG. 13 is a functional block diagram showing a configuration of main parts of a pulse wave detection device of a third embodiment. FIG. 6 is a diagram showing combinations of λ1 to λ4 at which SNR exceeding SNR0 is obtained by the inventors. FIG. 6 is a diagram showing combinations of λ1 to λ4 at which SNR exceeding SNR0 is obtained by the inventors. FIG. 6 is a diagram showing combinations of λ1 to λ4 at which SNR exceeding SNR0 is obtained by the inventors. It is a figure which shows the relationship between the number of peak wavelengths, and largest SNR.

Embodiment 1
Hereinafter, the pulse wave detection device 1 of the first embodiment will be described. For convenience of explanation, in each of the following embodiments, the same reference numerals will be appended to members having the same functions as the members described in the first embodiment, and the description thereof will not be repeated.

(Configuration of pulse wave detection device 1)
FIG. 1 is a functional block diagram showing the configuration of the main part of the pulse wave detection device 1. The pulse wave detection device 1 detects (calculates) a pulse wave of the user U by analyzing an image (a plurality of images) obtained by imaging the user U (living body). Although Embodiment 1 exemplifies a case where the living body is a person (user U), the living body is not necessarily limited to a person. The living body may be a non-human organism (eg, an animal such as a dog or a cat) whose pulse wave can be detected by image analysis.

The pulse wave detection device 1 includes an analysis unit 10, a light source unit 20, and a camera 30 (imaging unit). In the first embodiment, it is assumed that the analysis unit 10 also has a role as a control unit that controls each part of the pulse wave detection device 1 in an integrated manner. The analysis unit 10 includes a G pixel data calculation unit 11, a pulse wave calculation unit 12, and an SNR (Signal to Noise Ratio) calculation unit 13. The SNR may be referred to as the SN ratio. The operation of the analysis unit 10 will be described later.

The light source unit 20 includes (i) a first light source 21 that emits the first light L1 to the user U, and (ii) a second light source 22 that emits the second light L2 to the user U. The first light L1 and the second light L2 are both visible light. Hereinafter, the peak wavelength of the first light L1 is taken as λ1 (first peak wavelength). Further, the peak wavelength of the second light L2 is λ2 (second peak wavelength). The first light source 21 and the second light source 22 are, for example, LEDs (Light Emitting Diodes).

The first embodiment mainly illustrates the case where λ1 = 560 nm and λ2 = 580 nm (see FIG. 4). That is, the first light L1 and the second light L2 are both green light. λ1 and λ2 are different peak wavelengths. In the first embodiment, the case of λ1 <λ2 is mainly illustrated. The light emitted from the light source unit 20 toward the user U is referred to as outgoing light L. In the first embodiment, the outgoing light L generically represents the first light L1 and the second light L2.

FIG. 2 is a view schematically showing how the emitted light L is irradiated from the light source unit 20 to the user U. As shown in FIG. The light source unit 20 alternately emits the first light L1 and the second light L2 toward the predetermined site (measurement site UM) of the user U. FIG. 2 shows that the first light is emitted from the first light source 21 toward the measurement site UM.

The measurement site UM may be, for example, a predetermined site of the face of the user U. Examples of the measurement site UM include sites such as the forehead, cheeks, nose, and chin. Furthermore, the measurement site UM may not be limited to a predetermined site of the user U's face. The measurement site UM may be any predetermined site as long as a blood vessel is present.

The first light L1 incident on the measurement site UM is multiply scattered in the inside of the measurement site UM (inside the skin). Therefore, as shown in FIG. 2, the first light L1 is reflected by the skin of the user U (measurement site UM). Hereinafter, the first light L1 reflected by the user U will be referred to as a first reflected light Lr1.

Similarly, the second light L2 incident on the measurement site UM is reflected by the measurement site UM. Hereinafter, the second light L2 reflected by the user U will be referred to as a second reflected light Lr2. Further, the outgoing light L reflected by the user U is referred to as a reflected light Lr. In the first embodiment, the reflected light Lr generically represents the first reflected light Lr1 and the second reflected light Lr2.

The first reflected light Lr1 enters the camera 30. The camera 30 captures an image of the user U by receiving the first reflected light Lr1. Similarly, the second reflected light Lr2 enters the camera 30. The camera 30 captures an image of the user U by receiving the second reflected light Lr2.

Inside the measurement site UM, the optical path length passing through the hemoglobin in the blood vessel dynamically changes as the blood vessel contracts and dilates. Therefore, the temporal change of the luminance value of each pixel in the image obtained by the camera 30 can be used as an index of the pulse wave. Therefore, for example, the pulse wave can be calculated by analyzing a plurality of images captured at predetermined time intervals by the analysis unit 10.

FIG. 3 is a diagram for explaining the configuration of the camera 30. As shown in FIG. The camera 30 is, for example, a known RGB camera. The camera 30 includes an image sensor (not shown) including a plurality of light receiving elements (imaging elements). The camera 30 is provided with a filter (color filter) for selectively transmitting a predetermined wavelength component (in other words, a frequency component) of the reflected light Lr (each of the first reflected light Lr1 and the second reflected light Lr2). ing.

In the first embodiment, the camera 30 includes four filters: an R (Red, red) filter 310 R, a G (Green, green) filter 310 G, a B (Blue, blue) filter 310 B, and an IR (Infrared, near infrared) filter 310 IR. The case where the filter of is provided is illustrated.

As one example, the R filter 310R transmits red light of about 600 to 700 nm. The G filter 310 G transmits green light of about 450 to 650 nm (see FIG. 4). The B filter 310B transmits blue light of about 400 to 500 nm. The IR filter 310IR transmits near infrared light of about 805 nm or more. In the first embodiment, the G filter 310G transmits light (green light) in a wavelength range of 450 nm or more and 650 nm or less.

In the camera 30, the light receiving elements are arranged in a matrix. Each light receiving element is provided with any one of the R filter 310R to the IR filter 310IR. Hereinafter, a pixel formed by the light receiving element provided with the G filter 310G is referred to as a G pixel (green pixel). In addition, (i) a pixel formed by a light receiving element provided with an R filter 310R is an R pixel (red pixel), and (ii) a pixel formed by a light receiving element provided with a B filter 310B is a B pixel (blue pixel And (iii) a pixel formed by the light receiving element provided with the IR filter 310IR is referred to as an IR pixel (near infrared pixel).

FIG. 4 shows emission spectra (wavelengths) of the spectral characteristics of the G filter 310G and the first light L1 (the light emitted from the first light source 21) and the second light L2 (the light emitted from the second light source 22) And the spectrum). In the graph of FIG. 4, the horizontal axis indicates the wavelength of light. The vertical axis indicates the transmittance (light transmittance) of the G filter 310G (color filter), and the light amount (emission intensity) of the first light L1 and the second light L2.

As shown in FIG. 4, the G filter 310G has a peak of transmittance at a wavelength of 550 nm. Further, the entire emission spectrum of the first light L1 and the second light L2 is included in the wavelength range in which the G filter 310G can suitably transmit light. Further, the first reflected light Lr1 and the second reflected light Lr2 respectively have the same emission spectrum as the first light L1 and the second light L2. Therefore, according to the G filter 310G, the first reflected light Lr1 and the second reflected light Lr2 can be selectively transmitted.

Therefore, the plurality of G pixels can receive the first reflected light Lr1 and the second reflected light Lr2, respectively. On the other hand, the first reflected light Lr1 and the second reflected light Lr2 are blocked by the R filter 310R, the B filter 310B, and the IR filter 310IR. Therefore, the first reflected light Lr1 and the second reflected light Lr2 can not be made incident on the pixels (R pixel, B pixel, and IR pixel) other than the G pixel.

As described above, the camera 30 of the pulse wave detection device 1 is configured to be suitable for imaging by G pixels. Hereinafter, an image captured by only G pixels is referred to as a G image. The analysis unit 10 can calculate a pulse wave by analyzing temporal changes in luminance values of a plurality of G pixels included in the G image.

Hereinafter, an image captured by the first reflected light Lr1 incident on the G pixel is referred to as a first G image (first image). In addition, an image captured by the second reflected light Lr2 entering the G pixel is referred to as a second G image (second image).

(An example of a flow of pulse wave detection processing in the pulse wave detection device 1)
FIG. 5 is a flowchart illustrating the flow of pulse wave detection processing in the pulse wave detection device 1. First, the pulse wave detection device 1 alternately turns on the first light source 21 and the second light source 22 over a predetermined time (light source lighting period) to capture a G image.

The pulse wave detection device 1 turns on the first light source 21 (S1), and radiates the first light L1 toward the user U. As described below, at the time of S1, the second light source 22 is turned off in advance. The camera 30 receives the first reflected light Lr1 and captures a first G image.

The G pixel data calculation unit 11 acquires a first G image from the camera 30. The G pixel data calculation unit 11 calculates an average value of luminance values of G pixels in the first G image (hereinafter, also referred to as G pixel luminance value average) (S2). Hereinafter, the G pixel luminance value average in the first G image is referred to as GD1. The G pixel data calculation unit 11 supplies GD 1 to the pulse wave calculation unit 12. At the time of S2, the pulse wave detection device 1 turns off the first light source 21.

Subsequently, the pulse wave detection device 1 turns on the second light source 22 (S3), and radiates the second light L2 toward the user U. In S3, the first light source 21 is turned off. The camera 30 receives the second reflected light Lr2 and captures a second G image.

The G pixel data calculation unit 11 acquires a second G image from the camera 30. The G pixel data calculation unit 11 calculates an average of G pixel luminance values (hereinafter, GD2) in the second G image (S4). The G pixel data calculation unit 11 supplies the GD 2 to the pulse wave calculation unit 12. At the time of S4, the pulse wave detection device 1 turns off the second light source 22.

The pulse wave detection device 1 refers to a timer (not shown) and determines whether the light source lighting period has ended (S5). If the light source lighting period has not ended, the process returns to S1. When the light source lighting period ends, the pulse wave calculation unit 12 calculates a pulse wave (S6).

As described later, the pulse wave calculation unit 12 calculates the temporal change of GD1 (that is, GD1 obtained in each of the following TM2) and the temporal change of GD2 (that is, GD2 obtained in each of the following TM4) Based on the pulse wave is calculated. The SNR calculating unit 13 calculates the SNR of the pulse wave using a known algorithm (S7).

(An example of lighting timing of each light source and acquisition timing of each image)
FIG. 6 is a graph (timing chart) for describing S1 to S4. In the graph of FIG. 6, the horizontal axis represents time, and the vertical axis represents the pixel average of the G pixel luminance value. First, in TM1 (first timing), the first light source 21 is turned on (corresponding to S1). Then, in TM2 (second timing), acquisition of the first G image (calculation of GD1) is performed (corresponding to S2).

Subsequently, at TM3 (third timing), the second light source 22 is turned on (corresponding to S3). Then, in TM4 (fourth timing), acquisition of the second G image (calculation of GD2) is performed (corresponding to S4). The processing of TM1 to TM4 is periodically performed in this order over the light source lighting period. By acquiring GD1 and GD2 a plurality of times in this way, it is possible to obtain the state of time change of each of GD1 and GD2.

As one example, the camera 30 captures a moving image composed of a plurality of continuous frames. In this case, for example, the first G image is an odd-numbered frame of the moving image (eg, first frame, third frame, fifth frame,...). The second G image is an even-numbered frame of the moving image (eg, the second frame, the fourth frame, the sixth frame,...).

In the example of FIG. 6, one frame time (time from TM2 to TM4 and time from TM4 to the next TM2) of the camera 30 is 0.1 to 100 ms (milliseconds). The one frame time is equal to the reciprocal of the frame rate of the moving image.

The time during which the first light source 21 is on (the time from TM1 to TM2) is referred to as the first exposure time. The time from TM4 (when the second G image is acquired) to the next TM1 (when the first light source 21 is lit) is referred to as a first spare time. The sum of the first exposure time and the first preliminary time is set smaller than one frame time. That is, both the first exposure time and the first preliminary time are set to fall within one frame time.

Similarly, the time during which the second light source 22 is on (time from TM3 to TM4) is referred to as a second exposure time. The time from TM2 (when the first G image is acquired) to TM3 (when the second light source 22 is turned on) is referred to as a second spare time. The sum of the second exposure time and the second preliminary time is set smaller than one frame time. That is, both the second exposure time and the second preliminary time are set to fall within one frame time.

When capturing a moving image with two light sources (the first light source 21 and the second light source 22), (i) a substantial frame rate of GD1 (a frame rate of a virtual moving image consisting of only the first G image); , (Ii) The substantial frame rate of GD 2 (the frame rate of a virtual moving image consisting only of the second G image) is half (1/2) of the frame rate of the moving image.

Preferably, the correspondence between the frame number of the moving image and the first G image / the second G image is set in advance. According to the configuration, after the moving image is captured, the above-described analysis (data processing) can be performed.

For example, a moving image stored in a storage device (not shown) is divided into frames. Then, each frame may be grouped into either the first G image or the second G image according to the frame number. Accordingly, in the pulse wave detection device 1, acquisition of moving images in real time and analysis processing are not essential. According to the pulse wave detection device 1, the pulse wave can also be detected using a moving image acquired in advance (for example, a moving image captured in the past).

The G pixel luminance value average may not necessarily be calculated for all G pixels of one image (first G image and second G image). The G pixel luminance value average may be calculated for G pixels in a specific area of one image (within a measurement area set in advance). As an example, the measurement area is an area in which the measurement site UM of the user U (for example, a predetermined site of the face) is represented in one image.

(Pulse wave calculation unit 12)
The pulse wave calculation unit 12 calculates the pulse wave using the independent component analysis. Hereinafter, an example of processing of the pulse wave calculation unit 12 will be described. First, the pulse wave calculation unit 12 performs trend removal on each of GD1 and GD2 to remove temporal variation of the G pixel luminance value average.

The pulse wave calculation unit 12 performs independent component analysis on GD1 and GD2 after trend removal has been performed. For example, the pulse wave calculation unit 12 appropriately weights and combines GD1 and GD2. After that, the pulse wave calculation unit 12 calculates two independent components (separated signals) from GD1 and GD2.

The pulse wave calculation unit 12 uses a digital band pass filter that selectively transmits a signal in the frequency band of 0.75 to 4.00 Hz for two independent components, and generates a low frequency component (less than 0.75 Hz). The frequency component) and the high frequency component (frequency component higher than 4.00 Hz) are respectively removed. Subsequently, the pulse wave calculation unit 12 performs FFT (Fast Fourier Transformation) on the two independent components from which the low frequency component and the high frequency component are removed, and the power spectrum (frequency spectrum) of each independent component Calculate

The pulse wave calculation unit 12 calculates one or more peak values of the power spectrum of each independent component in the range of 0.75 to 4.00 Hz. The pulse wave calculation unit 12 compares each peak value and specifies the peak (maximum peak) having the largest peak value. The pulse wave calculation unit 12 calculates (detects) an independent component having the largest peak as a pulse wave.

(Experimental example)
The inventors of the present application (hereinafter referred to as the inventors) conducted an experimental study on the conditions (numerical range) of λ1 and λ2 for improving the detection accuracy of the pulse wave in the pulse wave detection device 1. Hereinafter, an example of the result obtained by the said experiment is described.

The present inventors used adult spectrometers (FLAME-S-XR1-ES, GratingXR1, wavelength resolution 1.75 nm FWHM) manufactured by Ocean Optics and an integrating sphere with a halogen light source (ISP-REF) to forehead of an adult male. The spectrum of was obtained.

Specifically, the inventors acquired spectra for about 3 minutes at a sampling rate of about 100 milliseconds. The measurement wavelength was set in steps of 20 nm in the range of 400 to 900 nm (visible light to near red light). However, in the range of 500 to 600 nm, the measurement wavelength was set in 5 nm steps.

FIG. 7 is a graph showing the spectrum (wavelength spectrum) of the forehead at a certain time obtained by experiment. The vertical axis in the graph of FIG. 7 (and FIG. 8 described later) indicates the output value (arbitrary unit) of the spectrometer. The horizontal axis in the graph of FIG. 7 indicates the wavelength.

The inventors focused on two light wavelengths, 560 nm (i.e., λ1) and 580 nm (i.e., λ2), and conducted further studies. The inventors observed the time change at the output at the wavelengths of 560 nm and 580 nm, respectively.

FIG. 8 is a graph showing time-series data of output values (that is, an appearance of temporal change of output values) at wavelengths of 560 nm and 580 nm. The horizontal axis in the graph of FIG. 8 indicates time. In the example of FIG. 8, it was confirmed that light with a wavelength of 580 nm (corresponding to the second light L2) exhibits a higher output value than light with a wavelength of 560 nm (corresponding to the first light L1). The inventors used the two time series data of FIG. 8 as an input signal of independent component analysis. Then, the inventors calculated the pulse wave using the pulse wave calculation unit 12.

FIG. 9 is a graph showing the pulse wave calculated by the pulse wave calculation unit 12. In the graph of FIG. 9, the horizontal axis represents time, and the vertical axis represents the magnitude (amplitude) of the pulse wave. Subsequently, the inventors used the SNR calculator 13 to calculate the SNR of the pulse wave.

FIG. 10 is a graph showing the power spectrum of the pulse wave of FIG. The graph of FIG. 10 is obtained by frequency analysis of the pulse wave of FIG. 9 (eg, FFT is performed on the pulse wave of FIG. 9). The fundamental frequency of the pulse wave of a person at rest (user U) is known to be about 1 Hz. From this, in the power spectrum of FIG. 10, a component in a band of 0.95 to 1.05 Hz was regarded as a pulse wave component. Further, in the power spectrum, components in other bands (0.75 to 0.95 Hz and 1.05 to 4.00 Hz) were regarded as noise components.

The SNR calculating unit 13 performs an operation of adding (integrating) the power spectrum in the range of the pulse wave component band, and calculates the operation result as a Signal. The SNR calculating unit 13 performs an operation of adding (integrating) the power spectrum in the range of the noise component band, and calculates the operation result as Noise. The SNR calculator 13 calculates the SNR as SNR = Signal / Noise.

As the SNR is higher, it can be said that the power spectrum contains more pulse wave components than noise components. That is, it can be said that the detection accuracy of the pulse wave is higher as the SNR is higher. Thus, the SNR can be used as an index for evaluating the accuracy of the pulse wave detected by the pulse wave calculation unit 12.

As described above, in the case where the first light L1 and the second light L2 are used as an example (example 1), the inventors (in other words, two light having different peak wavelengths (λ1, λ2) The SNR of the pulse wave obtained in the case of using

In addition, the inventors calculated the pulse wave using only the second light L2 (only one light having one peak wavelength (λ2)) as a comparative example. The comparative example corresponds to a conventional pulse wave detection device. Then, the inventors calculated the SNR of the pulse wave obtained in the comparative example.

FIG. 11 is a graph showing the relationship between peak wavelength and SNR in Example 1 and Comparative Example. We calculated the SNR for various λ1 and λ2. In the graph of FIG. 11, the horizontal axis indicates the wavelength, and the vertical axis indicates the SNR. The horizontal axis in the graph of FIG. 11 indicates λ2 in the case of the comparative example. On the other hand, in the case of the first embodiment, the horizontal axis in the graph of FIG. In the case of Example 1, λ2 was set to 580 nm (constant value). In the first embodiment, the SNR is also calculated for the case of λ1> λ2.

As shown in FIG. 11, in the comparative example (in the case of only λ2), when λ2 = 580 nm, the maximum value of SNR (maximum SNR) was obtained. The maximum SNR (hereinafter, SNR0) in the comparative example was 0.2300. The SNR 0 corresponds to the maximum SNR obtained in the conventional pulse wave detection device.

On the other hand, in Example 1 (when two peak wavelengths of λ1 and λ2 are used), it was confirmed that there are a plurality of combinations of λ1 and λ2 at which SNR exceeding SNR0 can be obtained. That is, the inventors found that by appropriately selecting λ1 and λ2 in the pulse wave detection device 1, it is possible to improve the detection accuracy of the pulse wave as compared to the prior art.

As shown in FIG. 11, when λ2 = 580 nm, SNRs exceeding SNR0 were obtained when λ1 = 520 nm, 530 nm, 545 nm, 550 nm, 560 nm, and 570 nm. Subsequently, in Example 1, we changed both λ1 and λ2, and calculated the SNR for each combination of λ1 and λ2.

FIG. 12 is a table (hereinafter, Table 1) showing combinations of λ1 and λ2 at which an SNR exceeding SNR0 is obtained, which the inventors found. In Table 1, in accordance with the magnitude of SNR, the experimental results are arranged in descending order for each row. The same applies to Tables 2 and 3 described below. In Table 1, λ1 <λ2. Hereinafter, this case is illustrated.

As shown in Table 1, for two peak wavelengths satisfying λ1 <λ2, the inventors change λ1 in the range of (i) 520 nm ≦ λ1 ≦ 570 nm, and (ii) 535 nm ≦ λ2 ≦ Λ2 was varied in the range of 590 nm. The inventors confirmed that in all combinations of λ1 and λ2 shown in Table 1, an SNR exceeding SNR0 can be obtained.

That is, the inventors set the following conditions (1-1) and (1-2) with respect to two peak wavelengths satisfying λ1 <λ2 in Example 1.
520 nm ≦ λ1 ≦ 570 nm (1-1)
535 nm ≦ λ2 ≦ 590 nm (1-2)
It has been confirmed that the pulse wave detection accuracy is improved more than before when the above were satisfied. Thus, by satisfying the conditions (1-1) to (1-2), the inventors can improve the pulse wave detection accuracy with the pulse wave detection device 1 as compared to the prior art. Found out.

As shown in the top row of Table 1, it was confirmed that the maximum SNR (hereinafter referred to as SNR1) in Example 1 was obtained when λ1 = 570 nm and λ2 = 580 nm. The SNR 1 was 0.2712.

(One consideration about the experimental result)
In general, it is known that the wavelength of light irradiated to a living body (e.g., a person) affects the detection accuracy of a pulse wave. It is because the light absorption property of the substance which comprises the skin of a living body, and the penetration depth of the light with respect to skin have wavelength dependence (reference: nonpatent literature 1).

Blood of a living body contains oxyhemoglobin (HbO ₂ ). Therefore, with regard to the wavelength dependency of the light absorption characteristics, it is considered that the pulse wave can be measured (detected) with high accuracy as the absorption coefficient of oxygenated hemoglobin (the substance contributing to the signal component of the pulse wave) is larger. Also, it is considered that the pulse wave can be measured with high accuracy as the light absorption coefficient of the substance that causes noise (eg, melanin) is smaller. In this regard, it is known that the absorption coefficient of oxyhemoglobin becomes larger at shorter wavelengths, and the absorption coefficient of melanin becomes smaller at longer wavelengths (see: Fig. 8 of Non-Patent Document 2).

Furthermore, the wavelength dependence of the penetration depth of the light arises along with the wavelength dependence of the light absorption characteristic. The longer the wavelength, the deeper the penetration depth, and the longer the optical path length, which is said to be suitable for pulse wave detection (see: Non-Patent Document 1).

Therefore, the combination of a plurality of peak wavelengths (for example, λ1 and λ2) effective for improving the detection accuracy of the pulse wave changes in a complicated manner depending on the composition of the measurement site UM, the position (depth) of the blood vessel, etc. It is thought that. Conditions (1-1) and (1-2) confirmed by the above experiment indicate numerical ranges of λ1 and λ2 considered to be effective even in consideration of such a complicated change. . This point is the same in the second and subsequent embodiments described later.

In the above-described experimental example, the forehead is taken as the measurement site UM. However, it is considered that similar experimental results can be obtained also when the other part of the face such as the cheek, nose, or chin is used as the measurement part UM. Since these parts are close to the forehead, the wavelength dependency of the light absorption characteristics and the penetration depth of light is considered to be similar to that of the forehead.

Therefore, according to the pulse wave detection device 1, various parts of the living body can be used as the measurement part UM. That is, while improving the detection accuracy of a pulse wave, the convenience of detection of a pulse wave can also be improved.

In the above-mentioned experimental example, light was dispersed by the diffraction grating of the spectroscope. Then, the light after dispersion was received by the silicon photodiode. On the other hand, in the pulse wave detection device 1, the filter of the camera 30 plays the role of dispersing light.

Here, in the pulse wave detection device 1, it is assumed that each of the first light L1 and the second light L2 is light having a narrow-band emission spectrum. Therefore, the main role of the filter in the camera 30 is to suppress ambient light (noise) having a wavelength band other than 450 to 650 nm.

Therefore, regardless of the filter configuration of the camera 30, if a light source (for example, a general visible LED) that emits light having a narrow emission spectrum with a half width of about 30 to 50 nm (see: Patent Document 2) is used. It is expected that the above experimental results can be applied. That is, the G filter 310 G can also be removed from the camera 30.

However, from the viewpoint of obtaining a G image (a higher quality G image) in which the influence of ambient light is reduced, it is preferable to provide the camera 30 with a G filter 310G. By providing the G filter 310G, it is possible to prevent a decrease in pulse wave detection accuracy.

In addition, as a light receiving element of the camera 30, a silicon-based semiconductor light receiving element is generally used. Therefore, the above experimental results can be expected to be applicable to general cameras. This is because a silicon-based semiconductor light receiving element has high light receiving sensitivity to light in a wavelength range of, for example, 500 to 600 nm (eg, 500 nm or more and 600 nm or less). By using a silicon-based semiconductor light receiving element, a G image can be appropriately captured. Therefore, the decrease in pulse wave detection accuracy can be prevented.

[Modification]
(1) In order to increase the light amount of the first light L1, a plurality of first light sources 21 may be provided. Similarly, a plurality of second light sources 22 may be provided to increase the light amount of the second light L2.

(2) The light amount of the first light L1 emitted from the first light source 21 may be adjusted according to the luminance value of the G pixel in the 1G image. Similarly, the light amount of the second light L2 emitted from the second light source 22 may be adjusted according to the luminance value of the G pixel in the second G image.

(3) In order to remove surface reflection in each of the light sources (the first light source 21 and the second light source 22) and the light receiving element, a polarizing element may be provided in each of the light source and the light receiving element. In particular, the surface reflection can be effectively removed by providing polarization elements different in polarization plane by 90 ° in each of the light sources and the light receiving elements.

The above (1) to (3) also apply to the pulse wave detection device 2 (more specifically, the third light source 23) and the pulse wave detection device 3 (more specifically, the fourth light source 24) described later. It is similar.

Second Embodiment
FIG. 13 is a functional block diagram showing the configuration of the main part of the pulse wave detection device 2 of the second embodiment. The light source unit of the pulse wave detection device 2 is referred to as a light source unit 20A. The light source unit 20A differs from the light source unit 20 in that the light source unit 20A further includes a third light source 23.

The third light source 23 emits the third light L3 toward the user U. The third light L3 is also green light, similarly to the first light and the second light. Hereinafter, the peak wavelength of the third light L3 is set to λ3 (third peak wavelength). λ3 is a peak wavelength different from λ1 and λ2. In the second embodiment, it is assumed that λ1 <λ2 <λ3. In the second embodiment, the emitted light L generically represents the first light L1 to the third light L3. The light in which the third light L3 is reflected by the user U is referred to as a third reflected light Lr3. In the second embodiment, the reflected light Lr generically represents the first reflected light Lr1 to the third reflected light Lr3.

In the pulse wave detection device 2, the camera 30 captures an image of the user U by further receiving the third reflected light Lr3. Hereinafter, an image captured by the third reflected light Lr3 entering the G pixel is referred to as a third G image (third image).

The G pixel data calculation unit 11 calculates the G pixel luminance value average (hereinafter, GD3) in the third G image. The pulse wave calculation unit 12 calculates three independent components from GD1 to GD3. Thereafter, as in the first embodiment, the pulse wave detection device 2 performs detection of the pulse wave and calculation of the SNR.

As another embodiment (Example 2), we use the SNRs of pulse waves obtained when the first light L1 to the third light L3 (that is, three peak wavelengths λ1 to λ3) are used. Calculated. Specifically, the inventors calculated the SNR for various λ1 to λ3.

FIG. 14 and FIG. 15 are tables (hereinafter, Table 2) showing combinations of λ1 to λ3 which can be obtained by the present inventors for obtaining an SNR exceeding SNR0. It should be noted that for convenience, the second table, which is one table, is represented in the two drawings (FIGS. 14-15).

As shown in Table 2, for three peak wavelengths satisfying λ1 <λ2 <λ3, the inventors changed (1) λ1 in the range of 510 nm ≦ λ1 ≦ 560 nm, and (ii) 525 nm ≦ λ2 ≦ Λ2 was changed in the range of 585 nm, and λ3 was changed in the range of (iii) 545 nm ≦ λ3 ≦ 590 nm. The inventors confirmed that in all combinations of λ1 to λ3 shown in Table 2, an SNR exceeding SNR0 can be obtained.

That is, in the second embodiment, the following conditions (2-1) to (2-3), regarding the three peak wavelengths satisfying λ1 <λ2 <λ3,
510 nm ≦ λ1 ≦ 560 nm (2-1)
525 nm ≦ λ2 ≦ 585 nm (2-2)
545 nm ≦ λ3 ≦ 590 nm (2-3)
It has been confirmed that the pulse wave detection accuracy is improved more than in the prior art when all the above are satisfied. As described above, by satisfying the conditions (2-1) to (2-3), the inventors can improve the detection accuracy of the pulse wave more than before by the pulse wave detection device 2 as well. I found out.

As shown in the top row of Table 2, it was confirmed that the maximum SNR (hereinafter referred to as SNR2) in Example 2 is obtained when λ1 = 550 nm, λ2 = 570 nm, and λ3 = 580 nm. The SNR2 was 0.2878.

Third Embodiment
FIG. 16 is a functional block diagram showing the configuration of the main part of the pulse wave detection device 3 of the third embodiment. The light source unit of the pulse wave detection device 3 is referred to as a light source unit 20B. The light source unit 20B is different from the light source unit 20A in that the light source unit 20B further includes a fourth light source 24.

The fourth light source 24 emits the fourth light L4 toward the user U. The fourth light L4 is also green light, similarly to the first to third lights. Hereinafter, the peak wavelength of the fourth light L4 is taken as λ4 (fourth peak wavelength). λ4 is a peak wavelength different from λ1 to λ3. In the third embodiment, it is assumed that λ1 <λ2 <λ3 <λ4. In the third embodiment, the emitted light L generically represents the first light L1 to the fourth light L4. The light in which the fourth light L4 is reflected by the user U is referred to as a fourth reflected light Lr4. In the third embodiment, the reflected light Lr generically represents the first reflected light Lr1 to the fourth reflected light Lr4.

In the pulse wave detection device 3, the camera 30 captures an image of the user U by further receiving the fourth reflected light Lr4. Hereinafter, an image captured by the fourth reflected light Lr4 entering the G pixel is referred to as a fourth G image (fourth image).

The G pixel data calculation unit 11 calculates the G pixel luminance value average (hereinafter, GD4) in the fourth G image. The pulse wave calculation unit 12 calculates four independent components from GD1 to GD4. Thereafter, as in the first embodiment, the pulse wave detection device 3 performs detection of the pulse wave and calculation of the SNR.

The inventors of the present invention have, as yet another example (example 3), SNR of pulse wave obtained when using the first light L1 to the fourth light L4 (that is, four peak wavelengths of λ1 to λ4). Was calculated. Specifically, the inventors calculated the SNR for various λ1 to λ4.

FIGS. 17 to 19 are tables (hereinafter, Table 3) showing combinations of λ1 to λ4 at which SNR exceeding SNR0 is obtained, which the inventors found. It should be noted that for convenience, one table, Table 3, is represented in the three drawings (FIGS. 17-19).

As shown in Table 3, for the four peak wavelengths satisfying λ 1 <λ 2 <λ 3 <λ 4
(I) change λ1 in the range of 510 nm ≦ λ1 ≦ 550 nm, (ii) change λ2 in the range of 520 nm ≦ λ2 ≦ 570 nm, and (iii) change λ3 in the range of 530 nm ≦ λ3 ≦ 585 nm, and (Iv) λ4 was changed in the range of 550 nm ≦ λ4 ≦ 590 nm. The inventors confirmed that in all combinations of λ1 to λ4 shown in Table 3, an SNR exceeding SNR0 can be obtained.

That is, in the third embodiment, the following conditions (3-1) to (3-4) for the four peak wavelengths satisfying λ1 <λ2 <λ3 <λ4:
510 nm ≦ λ1 ≦ 550 nm (3-1)
520 nm ≦ λ2 ≦ 570 nm (3-2)
530 nm ≦ λ3 ≦ 585 nm (3-3)
550 nm ≦ λ4 ≦ 590 nm (3-4)
It has been confirmed that the pulse wave detection accuracy is improved more than in the prior art when all the above are satisfied. As described above, by satisfying the conditions (3-1) to (3-4), the inventors can improve the detection accuracy of the pulse wave more than before by the pulse wave detection device 3 as well. I found out.

As shown in the top row of Table 3, it is confirmed that the maximum SNR (hereinafter referred to as SNR3) in Example 3 is obtained when λ1 = 520 nm, λ2 = 550 nm, λ3 = 560 nm, λ4 = 580 nm. It was done. The SNR 3 was 0.2960.

As described above, conditions (1-1) to (1-2), (2-1) to (2-3), and (3-1) The combinations are all newly discovered by the inventors.

(The relationship between the number of peak wavelengths and the maximum SNR)
FIG. 20 is a graph showing the relationship between the number of peak wavelengths and the maximum SNR. In the graph of FIG. 20, the horizontal axis is the number of peak wavelengths (hereinafter, N). Also, the vertical axis shows (i) maximum SNR (left side of graph) and (ii) simply improvement rate (right side of graph).

The case of N = 1 corresponds to the above-described comparative example. On the other hand, the case of N = 2 corresponds to the first embodiment, the case of N = 3 corresponds to the second embodiment, and the case of N = 4 corresponds to the third embodiment. As described above, it has been confirmed that the maximum SNR improves as N increases.

The improvement rate is an index indicating how much the maximum SNR improves (improves) as N is increased one by one. The improvement rate for N = 2 is represented as SNR1 / SNR0. In the case of N = 2, the improvement rate was 0.2712 / 0.2300 = 1.18.

On the other hand, the improvement rate in the case of N = 3 is represented as SNR2 / SNR1. In the case of N = 3, the improvement rate was 0.2878 / 0.2712 = 1.06. Further, the improvement rate in the case of N = 4 is represented as SNR3 / SNR2. In the case of N = 4, the improvement rate was 0.2960 / 0.2878 = 1.03.

Thus, it was confirmed that the improvement rate tends to decrease with the increase of N. From this, the inventors considered that even if N was increased to 5 or more, it would not be possible to achieve a significant increase in maximum SNR. Furthermore, when N is increased to 5 or more, with the increase in the number of light sources, (i) the cost of the pulse wave detection device increases, and (ii) the substantial value of each G pixel luminance value average. It is thought that problems such as a serious decrease in frame rate may occur.

From the above, the inventors considered that it is preferable to set N to 2 or more and 4 or less (2 ≦ N ≦ 4) in the pulse wave detection device according to one aspect of the present disclosure. By setting N to 2 or more and 4 or less, it is possible to provide a pulse wave detection device capable of detecting a pulse wave with high accuracy at low cost.

[Example of software implementation]
The control block (particularly the analysis unit 10) of the pulse wave detection devices 1 to 3 may be realized by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like, or may be realized by software .

In the latter case, the pulse wave detection devices 1 to 3 include a computer that executes instructions of a program that is software that implements each function. The computer includes, for example, at least one processor (control device) and at least one computer readable storage medium storing the program. Then, in the computer, the processor reads the program from the recording medium and executes the program to achieve the object of one aspect of the present disclosure. For example, a CPU (Central Processing Unit) can be used as the processor. As the above-mentioned recording medium, a tape, a disk, a card, a semiconductor memory, a programmable logic circuit or the like can be used besides “a non-temporary tangible medium”, for example, a ROM (Read Only Memory). In addition, a RAM (Random Access Memory) or the like for developing the program may be further provided. The program may be supplied to the computer via any transmission medium (communication network, broadcast wave, etc.) capable of transmitting the program. Note that one aspect of the present disclosure may also be realized in the form of a data signal embedded in a carrier wave in which the program is embodied by electronic transmission.

[Items to be added]
One aspect of the present disclosure is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the technical means disclosed in the different embodiments can be combined as appropriate. These embodiments are also included in the technical scope of one aspect of the present disclosure. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

[Other expressions of one embodiment of the present disclosure]
One aspect of the present disclosure can also be expressed as follows.

That is, the pulse wave detection device according to an aspect of the present disclosure is a pulse wave detection device that detects a pulse wave of the living body by analyzing an image obtained by imaging the living body, and in a wavelength band included in visible light. A light source unit having a peak wavelength, and an imaging unit receiving light reflected from the living body by having light receiving sensitivity in a wavelength band included in visible light, the light source unit comprising a first light source unit having a peak wavelength λ1 A light source and a second light source having a peak wavelength λ2 are provided, wherein λ1 and λ2 satisfy 520 nm ≦ λ1 ≦ 570 nm and 535 nm ≦ λ2 ≦ 590 nm.

Further, a pulse wave detection device according to an aspect of the present disclosure is a pulse wave detection device that detects a pulse wave of the living body by analyzing an image obtained by imaging the living body, and in a wavelength band included in visible light. A light source unit having a peak wavelength, and an imaging unit receiving light reflected from the living body by having light receiving sensitivity in a wavelength band included in visible light, the light source unit comprising a first light source unit having a peak wavelength λ1 A light source and a second light source having a peak wavelength λ2 and a third light source having a peak wavelength λ3, wherein λ1, λ2, and λ3 are 510 nm ≦ λ1 ≦ 560 nm, 525 nm ≦ λ2 ≦ 585 nm, and 545 nm ≦ λ3 ≦ 590 nm I meet.

Further, a pulse wave detection device according to an aspect of the present disclosure is a pulse wave detection device that detects a pulse wave of the living body by analyzing an image obtained by imaging the living body, and in a wavelength band included in visible light. A light source unit having a peak wavelength, and an imaging unit receiving light reflected from the living body by having light reception sensitivity in a wavelength band included in visible light, the light source unit comprising a first light source having a peak wavelength λ1 And a second light source having a peak wavelength λ2 and a third light source having a peak wavelength λ3 and a fourth light source having a peak wavelength λ4, wherein λ1, λ2, λ3, and λ4 are 510 nm ≦ λ1 ≦ 550 nm, 520 nm ≦ λ2 ≦ 570 nm, 530 nm ≦ λ3 ≦ 585 nm, and 550 nm ≦ λ4 ≦ 590 nm are satisfied.

(Cross-reference to related applications)
This application claims the benefit of priority to Japanese Patent Application filed on Dec. 20, 2017: Japanese Patent Application No. 2017-243980, the entire contents of which are hereby incorporated by reference. Included in this book.

1, 2, 3 pulse wave detection device 10

analysis unit

20, 20A, 20B light source unit 21 first light source 22 second light source 23 third light source 24 fourth light source 30 camera (imaging unit)
310G G filter (color filter)
L1 first light L2 second light L3 third light L4 fourth light Lr1 first reflected light Lr2 second reflected light Lr3 third reflected light Lr4 fourth reflected light U user (living body)
λ1 first peak wavelength λ2 second peak wavelength λ3 third peak wavelength λ4 fourth peak wavelength

Claims

A pulse wave detection device for detecting a pulse wave of a living body, comprising:
A first light source for emitting first light having a first peak wavelength λ1 toward the living body;
A second light source that emits second light having a second peak wavelength λ2 toward the living body;
An imaging unit configured to capture an image of the living body;
And an analysis unit that detects a pulse wave of the living body by analyzing the image.
The imaging unit is
The first image is captured by receiving the first reflected light, which is the light reflected from the living body by the first light.
A second image is captured by receiving the second reflected light, which is the light reflected from the living body by the second light,
The analysis unit detects a pulse wave of the living body by analyzing the first image and the second image;
λ1 <λ2, and
The following conditions (1-1) and (1-2),
520 nm ≦ λ1 ≦ 570 nm (1-1)
535 nm ≦ λ2 ≦ 590 nm (1-2)
The pulse wave detection device characterized in that
A pulse wave detection device for detecting a pulse wave of a living body, comprising:
A first light source for emitting first light having a first peak wavelength λ1 toward the living body;
A second light source that emits second light having a second peak wavelength λ2 toward the living body;
A third light source for emitting third light having a third peak wavelength λ3 toward the living body;
An imaging unit configured to capture an image of the living body;
And an analysis unit that detects a pulse wave of the living body by analyzing the image.
The imaging unit is
The first image is captured by receiving the first reflected light, which is the light reflected from the living body by the first light.
A second image is captured by receiving the second reflected light, which is the light reflected from the living body by the second light,
The third image is captured by receiving the third reflected light in which the third light is the light reflected from the living body,
The analysis unit detects a pulse wave of the living body by analyzing the first image, the second image, and the third image.
λ1 <λ2 <λ3 and
The following conditions (2-1), (2-2) and (2-3),
510 nm ≦ λ1 ≦ 560 nm (2-1)
525 nm ≦ λ2 ≦ 585 nm (2-2)
545 nm ≦ λ3 ≦ 590 nm (2-3)
The pulse wave detection device characterized in that
A pulse wave detection device that detects a pulse wave of a living body by analyzing an image obtained by imaging the living body,
A first light source for emitting first light having a first peak wavelength λ1 toward the living body;
A second light source that emits second light having a second peak wavelength λ2 toward the living body;
A third light source for emitting third light having a third peak wavelength λ3 toward the living body;
A fourth light source that emits fourth light having a fourth peak wavelength λ4 toward the living body;
An imaging unit configured to capture an image of the living body;
And an analysis unit that detects a pulse wave of the living body by analyzing the image.
The imaging unit is
The first image is captured by receiving the first reflected light, which is the light reflected from the living body by the first light.
A second image is captured by receiving the second reflected light, which is the light reflected from the living body by the second light,
The third image is captured by receiving the third reflected light in which the third light is the light reflected from the living body,
The fourth image is captured by receiving the fourth reflected light, which is the light reflected from the living body, by the fourth light.
The analysis unit detects a pulse wave of the living body by analyzing the first image, the second image, the third image, and the fourth image.
λ1 <λ2 <λ3 <λ4, and
The following conditions (3-1), (3-2), (3-3), and (3-4),
510 nm ≦ λ1 ≦ 550 nm (3-1)
520 nm ≦ λ2 ≦ 570 nm (3-2)
530 nm ≦ λ3 ≦ 585 nm (3-3)
550 nm ≦ λ4 ≦ 590 nm (3-4)
The pulse wave detection device characterized in that
The pulse wave detection device according to any one of claims 1 to 3, wherein the imaging unit includes a color filter that transmits light in a wavelength range of 450 nm to 650 nm.
The pulse wave detection device according to any one of claims 1 to 4, wherein the imaging unit includes an imaging element having a light receiving sensitivity to light in a wavelength range of 500 nm to 600 nm. .