Dynamic signal extension in optical detection systems

Patent metadata

Field	Value
Publication number	US-9347882-B2
Application number	US-201313737279-A
Country	US
Kind code	B2
Filing date	Jan 9, 2013
Priority date	Jun 22, 2011
Publication date	May 24, 2016
Grant date	May 24, 2016

Abstract

Systems and methods for measuring a target in a sample, the target being capable of generating an emitted light in response to an excitation light. In an example system, an excitation light source generates the excitation light along an excitation optical path. An attenuation filter arrangement selectively adds an attenuation filter to the excitation optical path. The attenuation filter attenuates the excitation light by a corresponding attenuation factor. The excitation light exits the attenuation filter arrangement along the excitation optical path to illuminate the sample. A light energy detector receives the emitted light generated in response to the excitation light, and outputs a measured signal level corresponding to an emitted light level. If the light energy detector indicates an overflow, signal measurement is repeated with attenuation filters of increasing attenuation factors until the measured signal level does not overflow.

First claim

What is claimed is:

1. A system for measuring a target in a sample, the target being capable of generating an emitted light in response to an excitation light, the system comprising:
an excitation light source configured to generate the excitation light along an excitation optical path;
an attenuation filter arrangement configured to selectively add an attenuation filter to the excitation optical path to attenuate the excitation light by a corresponding attenuation factor, where the excitation light exits the attenuation filter arrangement along the excitation optical path to illuminate the sample;
an emission monochromator disposed to receive the emitted light generated by the target in the sample in response to the excitation light, the emission monochromator configured to output the emitted light at a selected wavelength;
a photomultiplier tube (PMT) disposed to receive the emitted light from the emission monochromator, the PMT configured to measure an emitted light level and to output a measured signal level up to a maximum detector level;
a reference photodiode configured to measure a reference excitation light in the excitation optical path indicative of an excitation light level of the excitation light exiting the attenuation filter arrangement;
a reference beam splitter configured to reflect a part of the excitation light exiting the attenuation filter arrangement to the reference photodiode; and
a controller configured to:
receive the measured signal level and to execute a signal measurement function under program control, the signal measurement function configured to control the attenuation filter arrangement to add the attenuation filter to attenuate the excitation light if the measured signal level indicates an overflow condition in which the measured signal level is greater than the maximum detector level, to receive another measured signal level in response to an attenuated excitation light, and to process the measured signal level as a sample measurement value when the measured signal level does not indicate an overflow condition; and
correct the measured signal level by a factor of REF/SYSTEM REF, where:
REF=Reference excitation light level, and
SYSTEM REF=Maximum excitation light level.

2. The system of claim 1 , where the attenuation filter arrangement includes a plurality of attenuation filters each having a corresponding attenuation factor, and where the signal measurement function is configured to control the attenuation filter arrangement to add a first attenuation filter to attenuate the excitation light when the excitation light level indicates the overflow condition without attenuation, and to subsequently add attenuation filters with increasing attenuation factors after each measured signal level in response to an attenuated excitation light indicating an overflow condition.

3. The system of claim 1 , further comprising:
an excitation monochromator configured to receive the excitation light energy and emit the excitation light energy at a selected wavelength.

4. The system of claim 1 , where the controller is configured to set the PMT to a gain that remains constant during acquisition of measured signal levels for the sample.

5. The system of claim 1 , where the controller is configured to obtain N measured signal levels from the PMT, correct each of the N measured signal levels by the factor of REF/SYSTEM REF, and determine the sample measurement level as an average of the N measured signal levels.

6. The system of claim 1 , where the attenuation filter arrangement comprises:
a first attenuation filter having an attenuation factor of ˜10; and
a second attenuation filter having an attenuation factor of ˜100;
where the first attenuation filter is selected to attenuate the excitation light if the excitation light with no attenuation results in the overflow condition, and the second attenuation filter is selected to attenuate the excitation light if the excitation light attenuated by the first attenuation filter results in the overflow condition.

7. A method for analyzing a target in a sample, the target being capable of generating an emitted light in response to an excitation light, the method comprising:
generating an excitation light along an excitation light path to illuminate the sample, and to generate an emitted light from the sample;
passing the emitted light from the sample through an emission monochromator, and outputting the emitted light at a selected wavelength from the emission monochromator to a photomultiplier tube (PMT);
at the PMT, detecting a measured signal level from the emitted light;
if the measured signal level indicates an overflow condition in which the measured signal level is greater than a maximum detector level, performing the steps of:
adding an attenuation filter having a corresponding attenuation factor to the excitation light path to attenuate the excitation light by operating an attenuation filter arrangement, where the excitation light exits the attenuation filter arrangement along the excitation optical path; and
detecting a measured signal level from the emitted light in response to the attenuated excitation light;

processing the measured signal level as a sample measurement value when the measured signal level does not indicate an overflow condition,
where each step of detecting the measured signal level further comprises:
detecting a reference excitation light level in the excitation optical path indicative of an excitation light level of the excitation light exiting the attenuation filter arrangement, by reflecting a part of the excitation light exiting the attenuation filter arrangement to a reference photodiode; and
correcting the measured signal level for each sample by a factor of REF/SYSTEM REF, where:
REF=reference excitation light level, and
SYSTEM REF=Maximum excitation light level.

8. The method of claim 7 , further comprising:
before the step of detecting the measured signal level, setting a gain of the PMT.

9. The method of claim 7 , where the attenuation filter is a first attenuation filter in an attenuation filter arrangement that includes a second attenuation filter, the method further comprising:
after the step of detecting a measured signal level from the emitted light in response to the attenuated excitation light, performing the steps of:
adding the second attenuation filter having a corresponding attenuation factor greater than the attenuation factor of the first attenuation filter to the excitation light path to further attenuate the excitation light; and
detecting a measured signal level from the emitted light in response to the further attenuated excitation light.

10. The method of claim 7 , further comprising:
repeating the steps of detecting the measured signal level in response to the excitation light and detecting the measured signal level in response to the attenuated excitation light to generate N measured signal levels for the sample;
repeating the step of correcting the measured signal level to generate N corrected measured signal levels for the sample;
calculating an average of the N corrected measured signal levels to determine the sample measurement level.

11. The method of claim 7 , further comprising the step of:
selecting a wavelength for the excitation light;
enabling a wavelength selector to receive the excitation light and to transmit the excitation light at the selected wavelength.

12. The method of claim 7 , where the step of adding the attenuation filter comprises selecting a ˜10 attenuation filter having an attenuation factor of ˜10.

13. The method of claim 9 , where the step of adding the second attenua

Assignees

• Molecular Devices Llc

Inventors

• Atzler Josef J
• Schinwald Bernhard

Classifications

• G01N21/64 Primary

  Fluorescence; Phosphorescence · CPC title

• G01N21/645

  Specially adapted constructive features of fluorimeters · CPC title

• G01J3/0218

  using optical fibers · CPC title

• G01J3/10

  Arrangements of light sources specially adapted for spectrometry or colorimetry · CPC title

• G01J3/0235

  using means for replacing an element by another, for replacing a filter or a grating · CPC title