Method and apparatus for measurement of light from illuminated specimen eliminating influence of background light

• US 6,597,439 B1
• Filed: 02/11/2000
• Issued: 07/22/2003
• Est. Priority Date: 02/12/1999
• Status: Expired due to Fees

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Hakamata, Kazuo
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): Punnoose, Roy M.
• Application Number:
  US09/502,579
• Time in Patent Office: 1,257 Days
• Field of Search: 356/73, 356/218, 356/445, 356/447, 356/432, 356/433
• US Class Current: 356/73
• CPC Class Codes: G01N 21/47 Scattering, i.e. diffuse reflection G01N21/25, G01N21/41 take precedence G01N21/55 takes precedence
• CPC Class Codes: G01N 21/64 Fluorescence; Phosphorescence

Abstract

A method and an apparatus for performing measurement of light from an illuminated specimen, under background light having intensity which varies cyclically with a period. A first measuring operation is performed for a certain length of time while illuminating the specimen. Then, a second measuring operation is performed for the same length of time as the first operation without the illumination of the specimen. A result of measurement unaffected by the background light is obtained by subtracting a result of the second measuring operation from a result of the first measuring operation. The difference between beginning times of the first and second measuring operations is made equal to an integer multiple of the above period. Alternatively, the above length of time of each of the first and second operations is made equal to an integer multiple of the above period.

Claims

1. An optical measurement method for performing measurement of first light, which has been emitted from or reflected by a specimen, or has penetrated through the specimen, under background light having intensity which varies cyclically with a period, said method comprising steps of:

(a) performing a first operation of measuring the first light for a first duration having a certain length and beginning at a first time, while illuminating the specimen with second light, to obtain a first measurement result;

(b) performing a second operation of measuring the first light for a second duration having the same length as the first duration and beginning at a second time which is different from said first time by an integer multiple of said period, while illumination of the specimen is stopped, to obtain a second measurement result; and

(c) subtracting said second measurement result from said first measurement result, to obtain a third measurement result which is not affected by said background light.

2. An optical measurement method according to claim 1, further comprising an additional step of obtaining said period by measuring the intensity of the background light.

3. An optical measurement apparatus for performing measurement of first light, which has been emitted from or reflected by a specimen, or has penetrated through the specimen, under background light having intensity which varies cyclically with a period, said apparatus comprising:

a first measurement unit which performs a first operation of measuring the first light while illuminating the specimen with second light, to obtain a first measurement result;

a second measurement unit which performs a second operation of measuring the first light while illumination of the specimen is stopped, to obtain a second measurement result;

a control unit which controls timing of the operations of the first and second measurement units so that said first operation is performed for a first duration having a certain length and beginning at a first time, and said second operation is performed for a second duration having the same length as the first duration and beginning at a second time which is different from said first time by an integer multiple of said period; and

a calculation unit which obtains a third measurement result, which is not affected by said background light, by subtracting said second measurement result from said first measurement result.

4. An optical measurement apparatus according to claim 3, further comprising an additional unit which obtains said period by measuring the intensity of the background light.

5. An optical measurement method for performing measurement of first light, which has been emitted from or reflected by a specimen, or has penetrated through the specimen, under background light having intensity which varies cyclically with a period, said method comprising steps of:

(a) performing a first operation of measuring the first light for a first duration having a length equal to an integer multiple of said period, while illuminating the specimen with second light, to obtain a first measurement result;

(b) performing a second operation of measuring the first light for a second duration having a length equal to the length of the first duration, while illumination of the specimen is stopped, to obtain a second measurement result; and

(c) subtracting said second measurement result from said first measurement result, to obtain a third measurement result which is not affected by said background light.

6. An optical measurement method according to claim 5, further comprising an additional step of obtaining said period by measuring the intensity of the background light.

7. An optical measurement apparatus for performing measurement of first light, which has been emitted from or reflected by a specimen, or has penetrated through the specimen, under background light having an intensity which varies cyclically with a period, said apparatus comprising:

a first measurement unit which performs a first operation of measuring the first light while illuminating the specimen with second light, to obtain a first measurement result;

a second measurement unit which performs a second operation of measuring the first light while illumination of the specimen is stopped, to obtain a second measurement result;

a control unit which controls timing of the operations of the first and second measurement units so that each of said first and second operations is performed for a duration having an identical length equal to an integer multiple of said period; and

a calculation unit which obtains a third measurement result, which is not affected by said background light, by subtracting said second measurement result from said first measurement result.

8. An optical measurement apparatus according to claim 7, further comprising an additional unit which obtains said period by measuring the intensity of the background light.

9. An optical measurement method for performing measurement of first light, which has been emitted from or reflected by a specimen, or has penetrated through the specimen, under a plurality of types of background light respectively having a plurality of different periods with which intensities of the plurality of types of background light vary cyclically, said method comprising steps of:

(a) performing a first operation of measuring the first light for a first duration having a length equal to an integer multiple of a least common multiple of said plurality of different periods, while illuminating the specimen with second light, to obtain a first measurement result;

(b) performing a second operation of measuring the first light for a second duration having a length equal to the length of the first duration, while illumination of the specimen is stopped, to obtain a second measurement result; and

(c) subtracting said second measurement result from said first measurement result, to obtain a third measurement result which is not affected by said plurality of types of background light.

10. An optical measurement apparatus for performing measurement of first light, which has been emitted from or reflected by a specimen, or has penetrated through the specimen, under a plurality of types of background light respectively having a plurality of different periods with which intensities of the plurality of types of background light vary cyclically, said apparatus comprising:

a first measurement unit which performs a first operation of measuring the first light while illuminating the specimen with second light, to obtain a first measurement result;

a second measurement unit which performs a second operation of measuring the first light while illumination of the specimen is stopped, to obtain a second measurement result;

a control unit which controls timing of the operations of the first and second measurement units so that each of said first and second operations is performed for a duration having an identical length equal to an integer multiple of a least common multiple of said plurality of different periods; and

a calculation unit which obtains a third measurement result, which is not affected by said plurality of types of background light, by subtracting said second measurement result from said first measurement result.

11. An optical measurement method for performing measurement of first light, which has been emitted from or reflected by a specimen, or has penetrated through the specimen, under a plurality of types of background light respectively having a plurality of different periods with which intensities of the plurality of types of background light vary cyclically, said method comprising steps of:

(a) performing a first operation of measuring the first light for a first duration having a certain length and beginning at a first time while illuminating the specimen with second light, to obtain a first measurement result;

(b) performing a second operation of measuring the first light for a second duration having the same length as the first duration and beginning at a second time which is different from said first time by an integer multiple of a least common multiple of said plurality of different periods, while illumination of the specimen is stopped, to obtain a second measurement result; and

(c) subtracting said second measurement result from said first measurement result, to obtain a third measurement result which is not affected by said plurality of types of background light.

12. An optical measurement method according to claim 11, wherein each of said first and second operations is performed a plurality of times.

13. An optical measurement method according to claim 11, wherein each of said first and second operations is performed in synchronization with one of the plurality of different periods of a selected one of the plurality of types of background light.

14. An optical measurement method according to claim 13, wherein each of said first and second operations is performed in the vicinity of a certain phase of said one of the plurality of different periods, where the intensity of the selected one of the plurality of types of background light is minimized in said certain phase.

15. An optical measurement method according to claim 13, wherein said one of the plurality of different periods is a minimum period of the plurality of different periods.

16. An optical measurement apparatus for performing measurement of first light, which has been emitted from or reflected by a specimen, or has penetrated through the specimen, under a plurality of types of background light respectively having a plurality of different periods with which intensities of the plurality of types of background light vary cyclically, said apparatus comprising:

a first measurement unit which performs a first operation of measuring the first light while illuminating the specimen with second light, to obtain a first measurement result;

a second measurement unit which performs a second operation of measuring the first light while illumination of the specimen is stopped, to obtain a second measurement result;

a control unit which controls timing of the operations of the first and second measurement units so that said first operation is performed for a first duration having a certain length and beginning at a first time, and said second operation is performed for a second duration having the same length as the first duration and beginning at a second time which is different from said first time by an integer multiple of a least common multiple of said plurality of different periods; and

a calculation unit which obtains a third measurement result, which is not affected by said plurality of types of background light, by subtracting said second measurement result from said first measurement result.

17. An optical measurement apparatus according to claim 16, wherein each of said first and second operations is performed a plurality of times.

18. An optical measurement apparatus according to claim 16, wherein each of said first and second operations is performed in synchronization with one of the plurality of different periods of a selected one of the plurality of types of background light.

19. An optical measurement apparatus according to claim 18, wherein each of said first and second operations is performed in the vicinity of a certain phase of said one of the plurality of different periods, where the intensity of the selected one of the plurality of types of background light is minimized in said certain phase.

20. An optical measurement apparatus according to claim 18, wherein said one of the plurality of different periods is a minimum period of the plurality of different periods.

21. An optical measurement method for performing measurement of first light, which has been emitted from or reflected by a specimen, or has penetrated through the specimen, under a plurality of types of background light respectively having a plurality of different periods with which intensities of the plurality of types of background light vary cyclically, said method comprising steps of:

(a) performing a first operation of measuring the first light for a first duration beginning at a first time and having a length equal to an integer multiple of a least common multiple of at least one period among said plurality of different periods, while illuminating the specimen with second light, to obtain a first measurement result;

(b) performing a second operation of measuring the first light for a second duration having the same length as the first duration and beginning at a second time which is different from said first time by an integer multiple of a least common multiple of said plurality of different periods other than said at least one period, while illumination of the specimen is stopped, to obtain a second measurement result; and

(c) subtracting said second measurement result from said first measurement result, to obtain a third measurement result which is not affected by said plurality of types of background light.

22. An optical measurement method according to claim 21, wherein each of said first and second operations is performed a plurality of times.

23. An optical measurement method according to claim 21, wherein each of said first and second operations is performed in synchronization with a selected one of said plurality of different periods other than said at least one period.

24. An optical measurement method according to claim 23, wherein each of said first and second operations is performed in the vicinity of a certain phase of said selected one of said plurality of different periods other than said at least one period, where the intensity of the selected one of the plurality of types of background light is minimized in said certain phase.

25. An optical measurement method according to claim 23, wherein said selected one of said plurality of different periods other than said at least one period is a minimum period of the plurality of different periods other than the at least one period.

26. An optical measurement apparatus for performing measurement of first light, which has been emitted from or reflected by a specimen, or has penetrated through the specimen, under a plurality of types of background light respectively having a plurality of different periods with which intensities of the plurality of types of background light vary cyclically, said apparatus comprising:

a first measurement unit which performs a first operation of measuring the first light while illuminating the specimen with second light, to obtain a first measurement result;

a second measurement unit which performs a second operation of measuring the first light while illumination of the specimen is stopped, to obtain a second measurement result;

a control unit which controls timing of the operations of the first and second measurement units so that said first operation is performed for a first duration beginning at a first time and having a length equal to an integer multiple of a least common multiple of at least one period among said plurality of different periods, and said second operation is performed for a second duration having the same length as the first duration and beginning at a second time which is different from said first time by an integer multiple of a least common multiple of said plurality of different periods other than said at least one period; and

a calculation unit which obtains a third measurement result, which is not affected by said plurality of types of background light, by subtracting said second measurement result from said first measurement result.

27. An optical measurement apparatus according to claim 26, wherein each of said first and second operations is performed a plurality of times.

28. An optical measurement apparatus according to claim 26, wherein each of said first and second operations is performed in synchronization with a selected one of said plurality of different periods other than said at least one period.

29. An optical measurement apparatus according to claim 28, wherein each of said first and second operations is performed in the vicinity of a certain phase of said selected one of said plurality of different periods other than said at least one period, where the intensity of the selected one of the plurality of types of background light is minimized in said certain phase.

30. An optical measurement apparatus according to claim 28, wherein said selected one of said plurality of different periods other than said at least one period is a minimum period of the plurality of different periods other than the at least one period.