Method and apparatus for measuring the phase shift iduced in a light signal by a sample
First Claim
1. Apparatus for measuring a phase shift induced in a light signal by a sample, the apparatus comprising:
- a first light source to emit a light signal along a measurement optical path, wherein the measurement optical path includes a sample location;
a second light source to emit a light signal along a dummy measurement optical path;
a measurement electronic circuit to receive the light signals from the measurement and dummy measurement optical paths, the measurement electronic circuit being arranged to provide outputs which are respectively indicative of the phase of the light signals received from each of the measurement and dummy measurement optical paths, wherein in use a phase shift is induced in light in the measurement optical path by a sample in said sample location;
a reference electronic circuit to receive a signal indicative of the phase of the light signals emitted by the first and second light sources;
circuitry to compare the phase of light indicated by the output of the measurement electronic circuit responsive to the first light source with the phase of light indicated by the reference electronic circuit to provide an output indicative of a first measured phase difference and an output indicative of a second measured phase difference, andcircuitry to apply a correction to the first measured phase difference on the basis of the second measured phase difference to correct for errors in said first measured phase difference due to phase changes induced by said measurement and reference electronic circuits so as to obtain an improved measurement of the shift in phase induced in the light of the first light source by the sample.
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Accused Products
Abstract
A first light source emits a light signal along a measurement optical path that includes a sample and a second light source emits a light signal along a dummy measurement optical path. A measurement circuit receives the light signals and provides outputs separated in time which are indicative of the phase of the respective light signals. A phase shift is induced in light in the measurement optical path by the sample. A reference circuit receives a signal indicative of the phase of the light signals emitted by the first and second light sources. Circuitry compares the phases of light output from the two circuits to provide output indicative of a first measured phase difference during operation of the first light source. Correction is applied to this measurement by taking a similar phase difference measurement during operation of the second light source and comparing the two phase differences.
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Citations
20 Claims
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1. Apparatus for measuring a phase shift induced in a light signal by a sample, the apparatus comprising:
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a first light source to emit a light signal along a measurement optical path, wherein the measurement optical path includes a sample location; a second light source to emit a light signal along a dummy measurement optical path; a measurement electronic circuit to receive the light signals from the measurement and dummy measurement optical paths, the measurement electronic circuit being arranged to provide outputs which are respectively indicative of the phase of the light signals received from each of the measurement and dummy measurement optical paths, wherein in use a phase shift is induced in light in the measurement optical path by a sample in said sample location; a reference electronic circuit to receive a signal indicative of the phase of the light signals emitted by the first and second light sources; circuitry to compare the phase of light indicated by the output of the measurement electronic circuit responsive to the first light source with the phase of light indicated by the reference electronic circuit to provide an output indicative of a first measured phase difference and an output indicative of a second measured phase difference, and circuitry to apply a correction to the first measured phase difference on the basis of the second measured phase difference to correct for errors in said first measured phase difference due to phase changes induced by said measurement and reference electronic circuits so as to obtain an improved measurement of the shift in phase induced in the light of the first light source by the sample. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of measuring a phase shift induced in a light signal by a sample, comprising the steps of:
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emitting a first light signal along a measurement optical path, wherein the measurement optical path includes a sample location; emitting a second light signal along a dummy-measurement optical path; receiving light signals from the measurement and dummy-measurement optical paths in a measurement electronic circuit; providing outputs from the measurement electronic circuit, wherein the outputs are respectively indicative of the phase of the light signals received from each measurement and dummy-measurement optical path; receiving a signal indicative of the phase of the first and second light signals in a reference electronic circuit; comparing the phase of light indicated by the output of the measurement electronic circuit and responsive to the first light signal with the phase of light indicated by the reference electronic circuit; providing an output indicative of the first measured phase difference; comparing the phase of light indicated by the output of the measurement electronic circuit in response to the second light signal with the phase of light indicated by the reference electronic circuit; providing an output indicative of a second measured phase difference; applying a correction to the first measured phase difference on the basis of the second measured phase difference to correct errors in said first measured phase difference due to phase changes induced by said measurement and reference electronic circuit so as to obtain an improved measurement of the shifting phase induced in the light of the first light source by the sample. - View Dependent Claims (15, 16, 17, 18, 19)
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20. Apparatus for measuring a phase shift induced in a light signal by a sample, comprising:
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a first light source to emit a light signal along a measurement optical path that includes a sample; and a second light source to emit a light signal along a dummy measurement optical path; a measurement circuit to receive the light signals and to provide output indicative of the phase of the respective light signals, wherein a phase shift is induced in light in the measurement optical path by the sample; a reference circuit to receive a signal indicative of the phase of the light signals emitted by the first and second light sources; circuitry to i) compare the phases of light output from the two circuits, ii) provide output indicative of a first measured phase difference during operation of the first light source, and iii) apply correction to this measurement by taking a similar phase difference measurement during operation of the second light source and comparing the two phase differences.
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Specification