System, method, and computer program for conducting optical transmission measurements and evaluating determined measuring variables

• US 20040260520A1
• Filed: 07/19/2004
• Published: 12/23/2004
• Est. Priority Date: 09/12/2001
• Status: Active Grant

• Current Assignee: Tecan Trading AG (Tecan Group AG)
• Original Assignee: Tecan Trading AG (Tecan Group AG)
• Inventors: Graeter, Matthias, Braendle, Hansjoerg, Nadler, Erich
• Granted Patent: US 7,473,897 B2
• Time in Patent Office: Days
• US Class Current: 702/189
• CPC Class Codes: G01F 23/2927 for several discrete levels, e.g. with more than one light-conducting sensing element
• CPC Class Codes: G01N 2035/1025 Fluid level sensing
• CPC Class Codes: G01N 21/3151 using two sources of radiation of different wavelengths G01N21/33 - G01N21/39 take precedence

Abstract

The invention relates to a device (40) for conducting a transmission measurement, comprising a system (42, 43, 44) for generating a light wave consisting of a first and a second wavelength fraction, in addition to an optical channel (1) guiding the light wave to a sample tube (45) with a sample, wherein the light wave permeates the sample tube (45) with a sample. The device (40) also has a motion unit for producing a relative movement of the light wave along the sample tube (45). A receiver (47) for receiving and separating the first and second wavelength fragments after the light wave has permeated the sample tube (45) with a sample is also provided. A converter (50) converts the first wavelength fraction into a first digital measuring value (X) describing the degree of transmission in the first wavelength and converts the second wavelength fraction into a second digital measuring value (Y) describing the degree of transmission in the second wavelength. Quotients are formed from the first digital measuring values (X) and the second digital measuring values (Y) by means of an evaluation system (41) and the first derivative of the quotients is calculated.

Claims

1. An apparatus for performing a transmission measurement, having:

a system for generating a light wave which includes a first and a second wavelength component,

an optical channel which guides the light wave to a sample container having a sample in such a way that the light wave penetrates the sample container having the sample,

a movement unit for generating a relative movement of the light wave along the sample container,

a receiver for receiving and separating the first and second wavelength components after the light wave has penetrated the sample container having the sample,

converters for converting the first wavelength component into first digital measurement values (X), which describe the degree of transmission at the first wavelength, and for converting the second wavelength component into second digital measurement values (Y), which describe the degree of transmission at the second wavelength,

an analysis system for producing a quotient from the first digital measurement values (X) and the second digital measurement values (Y), and for determining the first derivative of the quotient.

2. The apparatus according to claim 1, wherein the analysis system may determine the position of a boundary surface inside the sample in the sample container on the basis of the first derivative.

3. The apparatus according to claim 2, wherein the boundary surface may be determined by analyzing a first and a second zero crossing of the first derivative.

4. The apparatus according to claim 1, wherein the second derivative of the quotient may be determined by the analysis system.

5. The apparatus according to claim 4, wherein the filling level of the sample in the sample container may be determined by the analysis system on the basis of the second derivative.

6. The apparatus according to claim 5, wherein the filling level may be determined by analyzing the second derivative in order to determine the point of the first derivative at which the first derivative assumes an absolute minimum.

7. The apparatus according to claim 1, wherein the system for generating a light wave includes

a first light-emitting diode, which generates light having the first wavelength component,

a second light-emitting diode, which generates light having the second wavelength component, and

a modulator, which modulates the first wavelength component and the second wavelength component in order to generate the light wave.

8. The apparatus according to claim 7, wherein the light-emitting diodes emit light having near-infrared wavelengths.

9. The apparatus according to claim 1, wherein the receiver includes a pre-amplifier having an adjustable amplification factor, preferably with a connection to the analysis system, in order to be able to compensate for intensity variations of the light wave at the input of the receiver.

10. The apparatus claim 1, wherein the receiver has a lock-in amplifier for separating the first and second wavelength components using demodulation and/or for filtering.

11. The apparatus according to claim 1, wherein the analysis system includes a digital signal processor (DSP).

12. The apparatus according to claim 11, wherein the analysis system inputs, stores, and analyzes the first digital measurement values (X) and the second digital measurement values (Y).

13. The apparatus according to claim 11, wherein the analysis system includes a memory for storing the control code which is used to control the digital signal processor (DSP).

14. A method for performing a transmission measurement, having the following steps:

generating a light wave which includes a first and a second wavelength component,

illuminating a sample tube filled with the sample using the light wave while a relative movement of the light wave along the sample tube is performed;

receiving the first and second wavelength components after the light wave has penetrated through the sample tube having the sample,

separating the first and second wavelength components,

converting the first wavelength component into first digital measurement values (X), which describe the degree of transmission at the first wavelength,

converting the second wavelength component into second digital measurement values (Y), which describe the degree of transmission at the second wavelength,

producing the quotients of the first digital measurement values (X) and the second digital measurement values (Y), and

determining the first derivative of the quotients.

15. The method according to claim 14, wherein the following step is executed:

determining the position of a boundary surface in the sample container by producing the first derivative of the quotient.

16. The method according to claim 15, wherein the following step is executed:

determining the boundary surface by analyzing a first and a second zero crossing of the first derivative.

17. The method according to claim 14, wherein the following step is executed:

determining the first derivative of the quotients.

18. The method according to claim 17, wherein the following step is executed:

determining the filling level of the sample in the sample container by analyzing the second derivative.

19. The method according to claim 14, wherein a demodulation is performed to separate the first and second wavelength components.

20. The method according to claim 14, wherein two light-emitting diodes or laser diodes are activated using two square-wave signals to generate the light wave.

21. The method according to claim 14, wherein a pre-amplification step is executed before the separation of the first and second wavelength components, a dynamic adaptation of the pre-amplification preferably being performed in order to take intensity variations into consideration.

22. The method according to claim 14, wherein a search window is defined before the step to determine the first derivative, in order to exclude a part of the quotients from the determination of the first derivative.

23. A method for automatically determining a boundary surface inside a sample which is located in a sample container, wherein the method is performed according to claim 14 and the position of the boundary surface is output, preferably on a display screen or a printer.

24. A method for automatically determining the filling level of a sample which is located in a sample container, wherein the method is performed according to claim 18 and the position of the filling level is output, preferably on a display screen or a printer.

25. A control program for controlling the analysis of an optical transmission measurement using a computer or a digital signal processor (DSP), wherein the computer or the digital signal processor executes the following steps:

registering first digital measurement values (X), which describe the degree of transmission of a sample in the sample container at a first wavelength, and second digital measurement values (Y), which describe the degree of transmission of the sample of the sample container at a second wavelength,

producing the quotients of the first digital measurement values (X) and the second digital measurement values (Y), and

determining the first derivative of the quotients.

26. The control program according to claim 25, wherein the computer or the digital signal processor executes the following step:

determining the position of a boundary surface inside the sample in the sample container by producing the first derivative.

27. The control program according to claim 25, wherein the computer or the digital signal processor executes the following step:

determining the filling level of the sample in the sample container by producing the second derivative.

28. The control program according to claim 25, wherein the computer or the digital signal processor executes the following step:

controlling the sequence of the transmission measurement.

29. A computer program product which is loadable in an apparatus having a computer or digital signal processor, wherein the computer program includes the following modules:

a module for registering first digital measurement values (X), which describe the degree of transmission of a sample in the sample container at a first wavelength, and for registering second digital measurement values (Y), which describe the degree of transmission of the sample of the sample container at a second wavelength,

a module for producing the quotients of the first digital measurement values (X) and the second digital measurement values (Y), and

a module for determining the first derivative of the quotients.