Biological information detection device including calculation circuit that generates signal of biological information

Abstract

A biological information detection device including: a light source that, in operation, emits irradiation light for irradiating a test portion of a subject; a light detector that, in operation, detects light reached from the test portion and that outputs an electrical signal corresponding to the light; and a calculation circuit that, in operation, generates a signal of biological information related to a blood flow in a target area in the test portion based on the electrical signal. The light detector is an image sensor. The electrical signal includes an image signal obtained by the image sensor. The calculation circuit, in operation, detects a magnitude of an inclination of an orientation of the test portion with respect to a reference orientation by image recognition based on the image signal, and determines the target area according to the magnitude of the inclination of the orientation of the test portion.

What is claimed is: 
     
         1 . A biological information detection system comprising:
 a light source that, in operation, emits light for irradiating a test portion of a subject;   a light detector that, in operation, detects return light which is returned from the test portion and outputs an electrical signal corresponding to the return light;   an image sensor that, in operation, obtains an image signal of the test portion; and   a calculation circuit that, in operation, generates a signal of biological information related to a blood flow in a target area in the test portion based on the electrical signal, wherein   the calculation circuit, in operation, detects a magnitude of an inclination of an orientation of the test portion with respect to a reference orientation by image recognition based on the image signal, and determines the target area according to the magnitude of the inclination of the orientation of the test portion.   
     
     
         2 . The biological information detection system according to  claim 1 , wherein, in operation, the calculation circuit determines at least one selected from the group consisting of a shape of the target area, and a position of the target area in the test portion. 
     
     
         3 . The biological information detection system according to  claim 1 ,
 wherein, in operation, the calculation circuit further determines whether or not the magnitude of the inclination of the orientation of the test portion has changed, and when it is determined that the magnitude of the inclination of the orientation of the test portion has changed, the calculation circuit changes a shape of the target area according to the magnitude of the inclination of the orientation of the test portion after the change.   
     
     
         4 . The biological information detection system according to  claim 1 ,
 wherein, in operation, the calculation circuit further determines whether or not the magnitude of the inclination of the orientation of the test portion has changed, and when it is determined that the magnitude of the inclination of the orientation of the test portion has changed, the calculation circuit changes a position of the target area in the test portion according to the magnitude of the inclination of the orientation of the test portion after the change.   
     
     
         5 . The biological information detection system according to  claim 1 , wherein the subject includes feature points, and
 the calculation circuit, in operation,   extracts the feature points from the image signal, and   detects the magnitude of the inclination of the orientation of the test portion based on positions of the feature points in the image signal.   
     
     
         6 . The biological information detection system according to  claim 5 , wherein
 the calculation circuit, in operation,   predicts a propagation path of the light inside the test portion based on the magnitude of the inclination of the orientation of the test portion, and   determines the target area based on the predicted propagation path.   
     
     
         7 . The biological information detection system according to  claim 6 , wherein
 the calculation circuit, in operation,   predicts a intensity of the return light returned from the test portion or a rate of change of the intensity of the return light with respect to a reference value based on at least one selected from the group consisting of the magnitude of the inclination of the orientation of the test portion and the predicted propagation path, and   when the predicted intensity of the return light or the predicted rate of change of the intensity of the return light is smaller than a first value, increases an intensity of the signal of the biological information.   
     
     
         8 . The biological information detection system according to  claim 7 ,
 wherein when the predicted intensity of the return light or the predicted rate of change of the intensity of the return light is larger than a second value, the calculation circuit decreases the intensity of the signal of the biological information.   
     
     
         9 . The biological information detection system according to  claim 1 , wherein
 the light detector, in operation, outputs the electrical signal at a plurality of times, and   the calculation circuit, in operation, generates the signal of the biological information over time based on the electrical signal outputted from the light detector at the plurality of times.   
     
     
         10 . The biological information detection system according to  claim 1 , wherein
 the calculation circuit, in operation, further detects a distance between the test portion and the light detector based on the electrical signal or the image signal, and   when the distance is longer than a predetermined distance, the calculation circuit increases an intensity of the signal of the biological information.   
     
     
         11 . The biological information detection system according to  claim 10 ,
 wherein when the distance is shorter than the predetermined distance, the calculation circuit decreases the intensity of the signal of the biological information.   
     
     
         12 . The biological information detection system according to  claim 10 ,
 wherein the calculation circuit, in operation, further determines whether or not the distance has changed, and when it is determined that the distance has changed, the calculation circuit changes the intensity of the signal the biological information to a value which is larger as the distance after the change is larger.   
     
     
         13 . The biological information detection system according to  claim 10 ,
 wherein the predetermined distance is the distance detected by the calculation circuit at a certain time.   
     
     
         14 . The biological information detection system according to  claim 10 ,
 wherein the predetermined distance is the distance detected by the calculation circuit when the generation of the signal of the biological information is started.   
     
     
         15 . The biological information detection system according to  claim 10 , wherein
 the light is pulsed light, and   the calculation circuit, in operation, detects the distance based on a time from when the light source emits the pulsed light to when the light detector detects the pulsed light.   
     
     
         16 . The biological information detection system according to  claim 10 , further comprising:
 a range sensor that detects a distance to the test portion,   wherein, in operation, the calculation circuit adjusts the intensity of the signal of the biological information based on the distance detected by the range sensor.   
     
     
         17 . The biological information detection system according to  claim 1 ,
 wherein the light contains a component with a wavelength of 650 nm or greater and 950 nm or less.   
     
     
         18 . The biological information detection system according to  claim 1 , wherein
 the test portion is a forehead of the subject, and   the biological information is information related to a blood flow in a cerebral cortex of the subject.   
     
     
         19 . A control method for a biological information detection system including:
 a light source that emits light for irradiating a test portion of a subject;   a light detector that detects return light which is returned from the test portion and outputs an electrical signal corresponding to the return light;   an image sensor that obtains an image signal of the test portion; and   a calculation circuit that generates a signal of biological information related to a blood flow in a target area in the test portion based on the electrical signal, the control method comprising:   causing the light source to emit the light to the test portion;   causing the light detector to detect the return light, and to output the electrical signal;   causing the image sensor to obtain the image signal; and   causing the calculation circuit to detect a magnitude of an inclination of an orientation of the test portion with respect to a reference orientation by image recognition based on the image signal, to determine the target area according to the magnitude of the inclination of the orientation of the test portion, and to output the biological information related to the blood flow information in the target area based on the electrical signal.   
     
     
         20 . A non-transitory computer-readable recording medium storing therein a program for controlling a biological information detection system including:
 a light source that emits light for irradiating a test portion of a subject;   a light detector that detects return light which is returned from the test portion and outputs an electrical signal corresponding to the return light;   an image sensor that obtains an image signal of the test portion; and   a calculation circuit that generates a signal of biological information related to a blood flow in a target area in the test portion based on the electrical signal,   wherein the program, when executed by a computer, causes the computer to execute:   causing the light source to emit the light to the test portion;   causing the light detector to detect the return light, and to output the electrical signal;   causing the image sensor to obtain the image signal; and   causing the calculation circuit to detect a magnitude of an inclination of an orientation of the test portion with respect to a reference orientation by image recognition based on the image signal, to determine the target area according to the magnitude of the inclination of the orientation of the test portion, and to output the biological information related to the blood flow information in the target area based on the electrical signal.