Device for measuring light absorption characteristics of a biological tissue sample

• US 7,368,694 B2
• Filed: 08/20/2002
• Issued: 05/06/2008
• Est. Priority Date: 09/28/2001
• Status: Active Grant

• Current Assignee: Centre National De La Recherche Scientifique
• Original Assignee: Centre National De La Recherche Scientifique
• Inventors: Goulas, Yves, Moya, Ismael, Cerovic, Zoran
• Primary Examiner(s): Luu; Thanh X.
• Assistant Examiner(s): Yam; Stephen
• Application Number:
  US10/490,943
• Publication Number:
  US 20040233448A1
• Time in Patent Office: 2,086 Days
• Field of Search: 250/205, 356432-434, 356/436, 600/310
• US Class Current: 250/205
• CPC Class Codes: G01N 2021/8466 Investigation of vegetal material, e.g. leaves, plants, fruits
• CPC Class Codes: G01N 21/3151 using two sources of radiation of different wavelengths G01N21/33 - G01N21/39 take precedence

Abstract

A device includes an element (7) for illuminating the sample (1), alternately emitting first and second radiation beams; device (9) for receiving and analyzing radiation derived from the sample (1) which converts the output radiation into control signal (S0); monitoring and controlling device (31) emitting first (S1) and second (S2) signals controlling the illuminating means (7), and a measuring signal (Sm); and device for calculating absorption characteristics of the sample (1), on the basis of the measuring signal (Sm). The monitoring and control elements (31) are adapted so that, after at least one period (Tp) of variation of the radiation beams, the amplitude of the control signal (S0), sensed on emitting phases, is equal to the amplitude of the control signal (S0), sensed on emission phases of the other radiation, and the measuring signal (Sm) represents at least one of the control signals (S1, S2).

Claims

1. Device for measuring light absorption characteristics of a biological tissue sample comprising:

means for illumination (7;

307) of the sample (1) adapted to emit alternately at least one first and one second light radiation beam towards the sample, said radiation beams having respectively a first and a second wavelength which are different from one another;

means (9) for reception and analysis of the output light radiation emitted by the sample (1), said reception and analysis means (9) comprising means (23) for converting said output radiation into a monitoring signal (S₀);

monitoring and control means (31;

331) which receive the monitoring signal (S₀) as input and emit at the output at least first (S₁) and second (S₂) control signals for controlling the illuminating means (7;

307), corresponding to the first and second radiation beams respectively, and at least one measurement signal (S_m); and

means (33) for computing the absorption characteristics of the sample (1) which are adapted to receive said measurement signal (S_m) as input and to compute said characteristics as a function of said measurement signal (S_m),

characterised in that said monitoring and control means (31;

331) are adapted so that the light intensity (I_UV, I_R) of each of the radiation beams varies in a periodic manner, phase-shifted with respect to one another, and so as to regulate at least one of the control signals (S1, S₂) as a function of the monitoring signal (S₀) in such a way that, over an integration time period (T_i) of at least one period (T_p) of variation of said radiation beams, the amplitude of said monitoring signal (S₀) taken over the emission phases of one of the radiation beams is equal to the amplitude of the monitoring signal (S₀) taken over the emission phases of the other radiation beam,

and in that the measurement signal (S_m) represents at least one of said control signals (S₁, S₂) over the integration time period (T_i).

2. Measuring device as claimed in claim 1, characterised in that the monitoring and control means are adapted to deliver the first control signal (S₁) such that the amplitude of the light intensity (I_UV) of the first radiation beam is constant, whilst the amplitude of the second control signal (S₂) is regulated by said monitoring and control means (31).

3. Measuring device as claimed in claim 2, characterised in that said measurement signal (S_m) consists of said second signal (S₂) over the integration time period (T_i).

4. Measuring device as claimed in claim 1, characterised in that the illuminating means include first (11) and second (12) light sources which are adapted to emit the first and second radiation beams respectively and are supplied electrically by respective first (15) and second (16) electrical supply means, said supply means (15, 16) being controlled by the first and second control signals respectively.

5. Measuring device as claimed in claim 4, characterised in that at least one of the light sources (11, 12) is a light-emitting diode.

6. Measuring device as claimed in claim 4, characterised in that the first light source (11) emits the first radiation beam in a wavelength range corresponding to the ultraviolet range, particularly from 300 to 390 nm, particularly approximately 370 nm.

7. Measuring device as claimed in claim 4, characterised in that the second light source (12) emits the second radiation beam in a wavelength range corresponding to the red light range, particularly approximately 670 nm.

8. Measuring device as claimed in claim 4, characterised in that the illuminating means (7;

307) include at least one optical filter (19) adapted so as to filter the radiation beams from the light sources (11, 12) emitted towards the sample (1).

9. Measuring device as claimed in claim 1, characterised in that the monitoring and control means (31;

331) include synchronisation means (41) connected to the illuminating means (7), emitting at least one periodic synchronisation signal (S_s) towards said illuminating means (7) in such a way that the light intensity (I_UV, I_R) of each of the radiation beams varies in a periodic manner, phase-shifted with respect to one another.

10. Measuring device as claimed in claim 9, characterised in that the synchronisation means (41) are adapted so as to cause the light intensity (I_UV, I_R) of the first and second radiation beams to vary with a frequency greater than a minimum value substantially equal to 1 kHz.

11. Measuring device as claimed in claim 9, characterised in that the monitoring and control means (31;

331) include a monitoring and control device (43) connected to the synchronisation means (41) in such a way as to receive the synchronisation signal (S_s), receiving the monitoring signal (S₀) as input.

12. Measuring device as claimed in claim 11, characterised in that said monitoring and control device includes a high-pass filter (51) adapted so as to filter the monitoring signal (S₀) at the input.

13. Measuring device as claimed in claim 11, characterised in that said monitoring and control device (43) includes a demultiplexer device (53) which receives as input, on the one hand, a signal representing the monitoring signal (S₀) and, on the other hand, the synchronisation signal (S_s), said demultiplexer device being adapted so as to supply as output a first elementary signal (S_e1) representing the level of intensity of the output radiation (I_F) during an emission phase of the first radiation beam and a second elementary signal (S_e2) representing the level of intensity of the output radiation during an emission phase of the second radiation beam.

14. Measuring device as claimed in claim 13, characterised in that the demultiplexer device (53) includes at least two switch means (57, 58) controlled alternately for opening and closing by the synchronisation signal (S_s), and a memory means (60) associated with each of said switch means (57, 58).

15. Measuring device as claimed in claim 13, wherein the monitoring and control device includes a high-pass filter (51) adapted so as to filter the monitoring signal (S₀) at the input, and

wherein the signal representing the monitoring signal (S₀) is the monitoring signal filtered by said highpass filter (51).

16. Measuring device as claimed in claim 13, characterised in that the monitoring and control device (43) includes a differential amplifier (55) of which the inverting input receives the first elementary signal (S_e1) and the non-inverting input receives the second elementary signal (S_e2).

17. Measuring device as claimed in claim 16, characterised in that the monitoring and control device (43) includes an integrating circuit (61) which is supplied as input with the output signal from said differential amplifier (55) and is adapted so as to emit an integrated signal over at least one period of the synchronisation signal (S_s).

18. Measuring device as claimed in claim 17, characterised in that said integrated signal constitutes the measurement signal (S_m).

19. Measuring device as claimed in claim 1, characterised in that the converter means (23) include a photodetector (25) which converts an optical signal into an electrical signal and a preamplifier (27) of the electrical signal emitted by said photodetector (25).

20. Measuring device as claimed in claim 1, characterised in that the reception and analysis means (9) include an optical filter (21) interposed between the sample (1) and the converter means (23).

21. Measuring device as claimed in claim 1, characterised in that the computing means (33) are connected at the output to at least one peripheral (35), particularly a display screen and/or a data storage device.

22. Measuring device as claimed in claim 1, characterised in that the illumination means (307) are adapted so as to emit alternately three radiation beams of different wavelengths, the monitoring and control means (331) being adapted to deliver three corresponding control signals (S₁, S₂, S₃), the first control signal (S₁) being such that the amplitude of the light intensity of the first radiation beam is constant, whilst the respective amplitudes of the second control signal (S₂) and third (S₃) control signal are regulated by said monitoring and control means (331).

23. Measuring device as claimed in claim 1, characterised in that it has a pincer structure (100) comprising two arms (101, 102) articulated on one another in such a way as to be able to grip a sample, the first arm (101) being provided with the illumination means (7) and the second arm (102) being provided with the reception and analysis means (9).

24. Measuring device as claimed in claim 1, characterised in that it includes a bundle of optical fibres (201) through which the radiation beam emitted by the illumination means (7) and the radiation beam emitted by the sample (1) pass, this latter radiation beam being a reflected radiation beam.

25. Method of measuring the light absorption characteristics of a biological tissue sample, in which the following operations are carried out:

the sample (1) is illuminated by illumination means (7;

307) alternately by first and second radiation beams of different wavelengths and periodic intensities (I_UV, I_R);

the radiation emitted by the sample (1) is detected and said radiation is analysed;

said illumination means (7;

307) are controlled as a function of said detected radiation,

characterised in that said control is carried out in the following manner;

the intensity of the first and second radiation beams (I_UV, I_R) is regulated such that, over an integration time period (T_i) of at least one period (T_p) of variation of said radiation beams, the intensity (I_F) of the output radiation taken over the emission phases of one of the first and second radiation beams is equal to the intensity (I_F) of the output radiation taken over the emission phases of the other one of the first and second radiation beams; and

the light absorption characteristics of the sample are calculated as a function of the desired intensity of one (I_R) of said first and second radiation beams taken over a measurement time interval (T_m).

26. Method as claimed in claim 25, characterised in that the amplitude of the intensity (I_UV) of one of said first and second radiation beams is kept constant, whilst the amplitude of intensity (I_R) of the other one of said radiation beams is regulated.

27. Method as claimed in claim 25, characterised in that the radiation emitted by the sample (1) is filtered before it is analysed.

28. The method as claimed in claim 25, wherein the method is performed to measure the light absorption characteristics of a plant leaf, in particular in order to carry out the measurement of the concentration of compounds of the family of phenols or phenylpropanoids in the epidermis of a leaf.

29. The method as claimed in claim 25, wherein the method is performed in order to estimate the nutritional needs, particularly in terms of nitrogen, of a culture.

30. The method as claimed in claim 25, wherein the method is performed in order to measure the light absorption characteristics of an animal or human tissue containing hemoglobin derivatives.

31. The method as claimed in claim 25, wherein the method is performed to carry out a medical or veterinary diagnosis.