MEASURING DEVICE INCLUDING LIGHT SOURCE THAT EMITS AT LEAST ONE LIGHT PULSE GROUP, PHOTODETECTOR, AND CONTROL CIRCUIT

• US 20190017932A1
• Filed: 06/24/2018
• Published: 01/17/2019
• Est. Priority Date: 07/12/2017
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Inventors: SHIONO, TERUHIRO, NAKAMURA, TATSUYA
• Granted Patent: US 10,352,853 B2
• Time in Patent Office: Days
• CPC Class Codes: A61B 2576/026 for the brain
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/0077 Devices for viewing the surface of the body, e.g. camera, magnifying lens
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/4064 Evaluating the brain A61B5/031, A61B5/369, A61B5/14553 take precedence
• CPC Class Codes: A61B 5/7485 Automatic selection of region of interest
• CPC Class Codes: G01N 2021/399 Diode laser
• CPC Class Codes: G01N 21/314 with comparison of measurements at specific and non-specific wavelengths dual wavelength spectrometry G01J3/427
• CPC Class Codes: G01N 21/39 using tunable lasers
• CPC Class Codes: G01N 21/474 Details of optical heads therefor, e.g. using optical fibres
• CPC Class Codes: G01N 2201/0697 Pulsed lasers
• CPC Class Codes: G01N 33/49 Blood chemical methods for determining blood cell populations G01N33/5094; chemical analysis of blood groups or blood types G01N33/80
• CPC Class Codes: G16H 30/40 for processing medical images, e.g. editing

Abstract

A measuring device includes: a light source that emits, toward a target part of an object, at least one light pulse group each including light pulses emitted sequentially, a photodetector that detects at least a part of at least one reflected light pulse group and including reflected light pulses sequentially returning from the target part, and a control circuit that controls the light source and the photodetector. The control circuit causes the light source to emit the at least one light pulse group within a first period, causes the photodetector to extract, within the first period, a first component that is a component of light included in at least a part of a leading reflected light pulse of the reflected light pulses, and causes the photodetector to output a first electric signal corresponding to the first component.

Claims

1. A measuring device comprising:

a light source that emits at least one light pulse group toward a target part of an object, the at least one light pulse group each including light pulses emitted sequentially;

a photodetector that detects at least a part of at least one reflected light pulse group, the at least one reflected light pulse group including reflected light pulses sequentially returning from the target part; and

a control circuit that controls the light source and the photodetector, wherein;

the control circuit causes the light source to emit the at least one light pulse group within a first period,

the control circuit causes the photodetector to extract a first component within the first period, the first component being a component of light included in at least a part of a leading reflected light pulse of the reflected light pulses, and

the control circuit causes the photodetector to output a first electric signal corresponding to the first component.

2. The measuring device according to claim 1, wherein:

the control circuit further causes the photodetector to extract a second component within the first period, the second component being a component of light included in a last reflected light pulse of the reflected light pulses during a falling period, the falling period being a period from a point in time at which the last reflected light pulse starts decreasing in light power to a point in time at which the last reflected light pulse finishes decreasing in light power, and

the control circuit causes the photodetector to output a second electric signal corresponding to the second component.

3. The measuring device according to claim 1, wherein:

the control circuit further causes the photodetector to extract a second component within a second period that is different from the first period, the second component being a component of light included in a last reflected light pulse of the reflected light pulses during a falling period, the falling period being a period from a point in time at which the last reflected light pulse starts decreasing in light power to a point in time at which the last reflected light pulse finishes decreasing in light power, and

the control circuit causes the photodetector to output a second electric signal corresponding to the second component.

4. The measuring device according to claim 1, wherein:

the at least one light pulse group includes a first light pulse group and a second light pulse group,

the at least one reflected light pulse group includes a first reflected light pulse group and a second reflected light pulse group,

the first reflected light pulse group includes first reflected light pulses,

the second reflected light pulse group includes second reflected light pulses,

the control circuit causes the light source to emit the first light pulse group and the second light pulse group within the first period,

the second light pulse group is emitted at a timing that is different from a timing at which the first light pulse group is emitted,

the first component is a component of light included in at least a part of a leading first reflected light pulse of the first reflected light pulses,

the control circuit further causes the photodetector to extract a second component within the first period, the second component being a component of light included in a last second reflected light pulse of the second reflected light pulses during a falling period, the falling period being a period from a point in time at which the last second reflected light pulse starts decreasing in light power to a point in time at which the last second reflected light pulse finishes decreasing in light power, and

the control circuit causes the photodetector to output a second electric signal corresponding to the second component.

5. The measuring device according to claim 1, wherein:

the at least one light pulse group includes a first light pulse group and a second light pulse group,

the at least one reflected light pulse group includes a first reflected light pulse group and a second reflected light pulse group,

the first reflected light pulse group includes first reflected light pulses,

the second reflected light pulse group includes second reflected light pulses,

the control circuit causes the light source to emit the first light pulse group within the first period,

the first component is a component of light included in at least a part of a leading first reflected light pulse of the first reflected light pulses,

the control circuit further causes the light source to emit the second light pulse group within a second period that is different from the first period,

the control circuit causes the photodetector to extract a second component within the second period, the second component being a component of light included in a last second reflected light pulse of the second reflected light pulses during a falling period, the falling period being a period from a point in time at which the last second reflected light pulse starts decreasing in light power to a point in time at which the last second reflected light pulse finishes decreasing in light power, and

the control circuit causes the photodetector to output a second electric signal corresponding to the second component.

6. The measuring device according to claim 2, further comprising

a signal processing circuit that generates blood flow information on the target part through a computation based on the first electric signal and the second electric signal.

7. The measuring device according to claim 6, wherein:

the first electric signal includes blood flow information on a surface of the target part,

the second electric signal includes the blood flow information on the surface of the target part and blood flow information on an interior of the target part, and

the signal processing circuit generates the blood flow information on the interior of the target part.

8. The measuring device according to claim 6, wherein:

the photodetector is an image sensor including photodetection cells arrayed two-dimensionally, and

each of the photodetection cells

accumulates the first component as a first signal charge,

accumulates the second component as a second signal charge,

outputs, as the first electric signal, an electric signal corresponding to a total amount of the first signal charge, and

outputs, as the second electric signal, an electric signal corresponding to a total amount of the second signal charge.

9. The measuring device according to claim 8, wherein:

the control circuit causes the image sensor to output

a first image signal corresponding to a first two-dimensional distribution of the total amount of the first signal charge accumulated in the photodetection cells during a first period,

a second image signal corresponding to a second two-dimensional distribution of the total amount of the second signal charge accumulated in the photodetection cells during a second period that is identical to or different from the first period,

a third image signal corresponding to a third two-dimensional distribution of the total amount of the first signal charge accumulated in the photodetection cells during a third period preceding the first period, and

a fourth image signal corresponding to a fourth two-dimensional distribution of the total amount of the second signal charge accumulated in the photodetection cells during a fourth period preceding the second period, and

the signal processing circuit

receives the first to fourth image signals from the image sensor,

generates a first difference image corresponding to a difference between the first image signal and the third image signal, and

generates a second difference image corresponding to a difference between the second image signal and the fourth image signal.

10. The measuring device according to claim 9, wherein 0.1≤

M₁/M₂≤

10 is satisfied when

the first difference image includes first pixels each of which has a pixel value exceeding a first threshold, the first pixels forming a first region,

the second difference image includes second pixels each of which has a pixel value exceeding a second threshold, the second pixels forming a second region,

M₁ is an average pixel value in a part of the first region that overlaps the second region, and

M₂ is an average pixel value in a part of the second region that overlaps the first region.

11. The measuring device according to claim 1, wherein:

the at least one light pulse group includes a first light pulse group including light pulses having a wavelength of not shorter than 650 nm to shorter than 805 nm and a second light pulse group including light pulses having a wavelength of longer than 805 nm to not longer than 950 nm, and

the control circuit causes the light source to alternately emit the first light pulse group and the second light pulse group.

12. The measuring device according to claim 1, wherein

each of the light pulses has a length of time of not shorter than 0.5 nanosecond to shorter than 3.0 nanoseconds.

13. The measuring device according to claim 1, wherein

each of the light pulses has a length of time of not shorter than 0.5 nanosecond to shorter than 5.0 nanoseconds.

14. The measuring device according to claim 1, wherein:

the light source is a semiconductor laser, and

by supplying the light source with a driving current on which a high-frequency component has been superimposed, the control circuit causes the light source to emit the at least one light pulse group.

15. The measuring device according to claim 1, wherein

the light source is a self-oscillation laser.

16. A measuring device comprising:

a light source that emits at least one light pulse group and at least one second light pulse toward a target part of an object, the at least one light pulse group each including first light pulses emitted sequentially;

a photodetector that detects at least a part of at least one reflected light pulse group and at least a part of at least one second reflected light pulse returning from the target part, the at least one reflected light pulse group including first reflected light pulses sequentially returning from the target part; and

a control circuit that controls the light source and the photodetector, wherein;

the control circuit causes the light source to emit the at least one light pulse group within a first period,

the control circuit causes the photodetector to extract a first component within the first period, the first component being a component of light included in at least the part of the at least one reflected light pulse group,

the control circuit causes the photodetector to output a first electric signal corresponding to the first component,

the control circuit causes the light source to emit the at least one second light pulse at a timing within the first period or within a second period that is different from the first period, the timing being different from a timing at which the at least one light pulse group is emitted,

the control circuit causes the photodetector to extract a second component within the first period or within the second period, the second component being a component of light included in the at least one second reflected light pulse during a falling period, the falling period being a period from a point in time at which the at least one second reflected light pulse starts decreasing in light power to a point in time at which the at least one second reflected light pulse finishes decreasing in light power, and

the control circuit causes the photodetector to output a second electric signal corresponding to the second component.

17. The measuring device according to claim 16, wherein

a light power of the at least one second light pulse is greater than a light power of each of the first light pulses.