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

1. A biological information detection device comprising:

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 reflected from the test portion and 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, wherein

the light detector is an image sensor,

the electrical signal includes an image signal obtained by the image sensor, and

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 device 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 device 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 device 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 device 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 device 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 device according to claim 6 , wherein

the calculation circuit, in operation,

predicts a intensity of the light emitted from the test portion or a rate of change of the intensity of the 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 light or the predicted rate of change of the intensity of the light is smaller than a first value, increases an intensity of the signal of the biological information.

8. The biological information detection device according to claim 7 , wherein when the predicted intensity of the light or the predicted rate of change of the intensity of the 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 device 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 device 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, 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 device 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 device 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 device according to claim 10 , wherein for each of one or more pixels contained in an image signal which is in the image signal obtained by the image sensor and which corresponds to the test portion, the calculation circuit, in operation, detects the distance, generates the signal of the biological information, and adjusts the intensity of the signal of the biological information.

14. The biological information detection device according to claim 10 , wherein the predetermined distance is the distance detected by the calculation circuit at a certain time.

15. The biological information detection device 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.

16. The biological information detection device according to claim 10 , wherein

the irradiation 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.

17. The biological information detection device 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.

18. The biological information detection device according to claim 1 , wherein the light contains a component with a wavelength of 650 nm or greater and 950 nm or less.

19. The biological information detection device 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.

20. A biological information detection device comprising:

a calculation circuit that, in operation, generates a signal of biological information related to a blood flow in a target area in a test portion of a subject based on an image signal received from a device including a light source that, in operation, emits irradiation light for irradiating the test portion, and an image sensor that, in operation, detects light reflected from the test portion and outputs the image signal of the test portion, wherein, in operation,

the calculation circuit 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.