Optical measuring device having d.c. component elimination

• US 20030158486A1
• Filed: 02/10/2003
• Published: 08/21/2003
• Est. Priority Date: 02/15/2002
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Nakashima, Tetsuya, Kimura, Teiyuu, Inobe, Yasuji, Nagakusa, Seiji
• Granted Patent: US 6,922,577 B2
• Time in Patent Office: Days
• US Class Current: 600/481
• 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

Abstract

An optical measuring device includes a sensor which emits light flashes toward a subject of detection with a light emitting element which is supplied with electric power from a rechargeable battery for a certain duration at certain intervals and receives reflected light from the subject with a light sensitive element. A subtractor subtracts a d.c. component from a sensed signal provided by the light sensitive element, thereby extracting a variation component. The subtractor has its output signal amplified with an amplifier, with the output thereof being A/D-converted with an A/D converter.

Claims

1. An optical measuring device comprising:

a sensor having a light emitting element which emits light flashes to a subject of detection by being supplied with electric power from a battery for a prescribed duration at prescribed intervals and a light sensitive element which receives reflected light from the subject;

a subtractor which subtracts a d.c. component from a sensed signal provided by the light sensitive element, thereby extracting a variation component;

an amplifier which amplifies an output signal of the subtractor; and

an A/D converter which implements an A/D conversion for an output signal of the amplifier.

2. An optical measuring device according to claim 1 further comprising:

a d.c. component modifying means which modifies a d.c. component level based on a A/D-converted value provided by the A/D converter.

3. An optical measuring device according to claim 2, wherein the d.c. component modifying means operates to monitor a time-wise variation of the A/D-converted value provided by the A/D converter and modifies the d.c. component level based on the variation.

4. An optical measuring device according to claim 3, wherein the d.c. component modifying means raises the d.c. component level when the time-wise variation of the A/D-converted value has a trend of increase, and lowers the d.c. component level when the time-wise variation of the A/D-converted value has a trend of decrease.

5. An optical measuring device according to claim 1 further comprising:

a d.c. component modifying means which modifies a d.c. component level based on an A/D-converted value of the sensed signal provided by the light sensitive element.

6. An optical measuring device according to claim 5, wherein the d.c. component modifying means raises the d.c. component level when the A/D-converted value of the sensed signal provided by the light sensitive element becomes larger than a prescribed upper limit value, and lowers the d.c. component level when the A/D-converted value of the sensed signal provided by the light sensitive element becomes smaller than a prescribed lower limit value.

7. An optical measuring device according to claim 1, wherein data of a d.c. component of the sensed signal is delivered to a latter stage in addition to a data of A/D-converted value provided by the A/D converter.

8. An optical measuring device according to claim 1, wherein a light output of the light emitting element is adjusted based on at least an A/D-converted value provided by the A/D converter.

9. An optical measuring device according to claim 8, wherein the light output of the light emitting element is decreased when the A/D-converted value provided by the A/D converter is out of a prescribed range continuously.

10. An optical measuring device according to claim 8, wherein the light output of the light emitting element is increased when a time-wise variation of the A/D-converted value provided by the A/D converter is within a prescribed range.

11. An optical measuring device according to claim 1, wherein the sensor is used by being put on a part of a human body, with the light emitting element being adapted to emit the light flashes toward a blood vessel as a subject of detection.