Optical measuring instrument

• US 6,611,698 B1
• Filed: 05/24/2001
• Issued: 08/26/2003
• Est. Priority Date: 10/13/1998
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd., Hitachi Medical Corporation (Hitachi, Ltd.)
• Inventors: Yamashita, Yuichi, Maki, Atsushi, Kawaguchi, Fumio
• Primary Examiner(s): Walberg, Teresa
• Assistant Examiner(s): FUQUA, SHAWNTINA T
• Application Number:
  US09/807,478
• Time in Patent Office: 824 Days
• Field of Search: 600/310, 600/322-324, 600/335-336, 600/407, 600/473, 600/476, 600/340-342, 600/319-320, 600/323, 600/337, 600/341
• US Class Current: 600/310
• CPC Class Codes: A61B 2562/02 Details of sensors specially adapted for in-vivo measurements
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 5/00 Measuring for diagnostic purposes radiation diagnosis A61B6/00; diagnosis by ultrasonic, sonic or infrasonic waves A61B8/00; Identification of persons
• CPC Class Codes: A61B 5/14553 specially adapted for cerebral tissue
• CPC Class Codes: G01N 21/49 within a body or fluid

Abstract

A highly reliable optical measuring instrument for multi-channel simultaneous measurement has an intensity of light emitted from a light source modulated at different frequencies and the light is applied to multiple positions of a test object. The light which is detected from the test object is converted into electric signals by a photodiode, and modulation signals are detected by a lock-in amplifier module. The signals are processed as information on the test object interior by a processing unit. Light is applied sequentially from a light source in a preparatory measurement step prior to final measuring, and the signal level of the detection light is measured for each light applied position. A control unit controls light intensity and detection signal level to ensure that the difference in detection light levels is kept within a specified range.

Claims

1. An optical measuring instrument wherein light is applied to multiple positions of the test object, and the light passing through said test object is detected and measured thereby;

said optical measuring instrument further characterized by comprising a measuring means to perform said measurement and a preparatory measuring means to prepare for final measurement;

where in said preparatory measuring means further comprises

a means to apply said light sequentially to said multiple positions and

a means to detect the light passing through said test object by said application of light and to generate detection signal for each of said light applied positions, thereby measuring said detection signal level.

4. An optical measuring instrument according to any one of claims 1, 2 and 3 further characterized in that said preparatory measurement means comprises a means to detect stray light when said light is not applied to said test object and to generate stray light signals, thereby measuring said stray light signal level.

5. An optical measuring instrument according to claim 4 characterized in that said preparatory measurement means comprises a means to increase the intensity of said applied light from the zero level to a specified level of intensity.

6. An optical measuring instrument according to claim 5 characterized in that said preparatory measurement means comprises a means to decrease said applied light intensity level to a specified intensity level if the reaction of said detection signal level when the intensity of said applied light is increased is non-linear.

2. An optical measuring instrument wherein light is applied to multiple positions of the test object, and the light including multiple signal components passing through said test object is detected and measured thereby;

said optical measuring instrument further characterized by comprising a measuring means to perform said measurement and a preparatory measuring means to prepare for final measurement;

wherein said preparatory measuring means further comprises

a means to apply said light including multiple signal components sequentially to said multiple positions and

a means to detect the light passing through said test object by said application of light and to generate detection signal for each of said light applied positions and for each of said signal components, thereby measuring said detection signal level.

3. An optical measuring instrument wherein light of multiple wavelengths is applied to multiple positions of the test object, and the light passing through said test object is detected and measured thereby;

said optical measuring instrument further characterized by comprising a measuring means to perform said measurement and a preparatory measuring means to prepare for final measurement;

wherein said preparatory measuring means further comprises

a means to apply said light sequentially for each of said light applied positions and for each of said wavelengths,

a means to detect the light passing through said test object by said application of light and to convert them into electric signals, and

a means to generate detection signals for each of said positions for light application and for each of said wavelengths based on said electric signals, thereby measuring said detection signal level.

7. An optical measuring instrument according to claim 3 wherein said final measuring means is characterized in that said light of multiple wavelengths is applied simultaneously to said multiple light applied positions.

8. An optical measuring instrument according to claim 3 wherein said final measuring means is characterized by comprising

a means to apply said light of multiple wavelengths simultaneously to said multiple positions and

a means to detect the light passing through said test object by said application of light and to generate detection signal for each of said light applied positions and for each of said wavelengths;

wherein said final measuring means and said preparatory measurement means are further characterized in that the light passing through said test object is detected from multiple light detection positions of said test object.

9. An optical measuring instrument according to claim 8 wherein each of said final measuring means and said preparatory measurement means

comprises a means to give different modulation to said applied light for each of said light applied positions and for each of said wavelengths, and

generates detection signals for each of said light applied positions and for each of said wavelengths using a modulation detector.

10. An optical measuring instrument according to claim 9 further characterized in that said different modulation is given by an analog method using different frequency signals.

11. An optical measuring instrument according to claim 9 further characterized in that said different modulation is given by a digital method wherein light applied for each of said wavelengths and for each said light applied positions is flashed at different time intervals.

12. An optical measuring instrument according to any one of claims 9 to 11 further characterized in that each of said final measuring means and preparatory measuring means comprises a means to amplify said electric signal led into said modulation detector independently by means of each amplifier.

13. An optical measuring instrument according to any one of claims 9 to 11 further characterized in that said preparatory measurement means comprises a means to allow independent change in the intensity level of the light modulated for each said wavelength and for each said light applied position.

14. An optical measuring instrument according to any one of claims 9 to 11 further characterized in that said preparatory measurement means comprises a means to change the increase rate of said amplifier or the intensity level of said applied light so that the difference among said detection signal levels is kept within the specified range.

15. An optical measuring instrument according to any one of claims 9 to 11 further characterized in that said preparatory measurement means comprises a means to detect stray light when said light is not applied to said test object and to generate stray signal, and a means to change the following sums so that the total sum between the sum of said detection light levels for said light detection positions and the sum of said stray light signal levels is kept within the specified range.

16. An optical measuring instrument according to claim 15 further characterized in that said preparatory measurement means comprises a means to calculate the average of said detection light levels for all said light detection positions and to change the amplification factor of said amplifier so that each of said detection light levels will be virtually the same as said average value.

17. An optical measuring instrument according to claim 16 further characterized in that said preparatory measurement means comprises a means to determine if the product between said total sum and said amplification factor of the amplifier is kept within the specified range.

18. An optical measuring instrument according to claim 17 further characterized in that said preparatory measurement means

comprises a means to record said applied light intensity level and said amplification factor of amplifier when the product between said total sum and said amplification factor of amplifier is kept within the specified range.

19. An optical measuring instrument according to claim 17 further characterized in that said preparatory measurement is performed again if the product between said total sum and said amplification factor of the amplifier is not kept within the specified range.

20. An optical measuring instrument according to claim 18 further characterized in that said final measurement is performed when said recorded light intensity level and amplification factor are maintained.

21. An optical measuring instrument according to any one of claims 8 to 11 further characterized by comprising a means to calculate a balance indicator on said detection signal and to indicate the corresponding wavelength, light applied position and light detection position if said balance indicator has failed to reach the specified level.

22. An optical measuring instrument characterized by comprising a means to apply light of multiple wavelengths to multiple positions of test object, and a means to detect and measure the light passing through said test object by said application of light;

said optical measuring instrument further characterized in that

said light is applied sequentially to each of said positions for light application and for each of said wavelengths prior to the final measurement,

the light passing through said test object by said application of light is detected and is converted into electric signals,

detection signals are generated for each of said positions for light application and for each of said wavelengths based on said electric signals, and

a control unit is incorporated to control said light intensity level and said detection signal level so that the level differences of said detection signals are kept within the specified range.

23. An optical measuring instrument according to claim 22 further characterized in that said light applying means includes a light emitting diode or semiconductor laser for each of said light applied positions and for each of said wavelengths, and changes said light intensity level by adjusting the d. c. current or modulation current applied to said light emitting diode or semiconductor laser.

24. An optical measuring instrument according to claim 22 further characterized in that said light applying means comprises a dimming filter to change the intensity level of the light emitted therefrom for each of said light emitting diode or semiconductor laser.