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US 4,289,403 AGranted
Optical phase modulation instruments
AssigneeIsco, Inc.
InventorRobert W. Allington
Life of this patent
Estimating the term…
Abstract
To obtain the refractive index of a fluid, each of two beams of light are transmitted at an angle through different ends of a vibrating quartz crystal to phase modulate the beams of light with respect to each other and then transmitted through two different flow cells before being combined at a point of nearly equal optical path length from the source of light, with the resulting interference pattern being transmitted onto a photocell to generate an electrical signal which varies periodically with the modulation of the two beams of light. The signal from the photocell and a signal representing the modulation of the crystal are compared in phase and a third signal indicates the refractive index of the effluent from the chromatographic column generated as a result of this comparison.
Claims69
A method of phase modulating two beams of light with respect to each other comprising the steps of:
- periodically modulating the phase between first and second beams of light with respect to each other in relationship to a modulating signal at one location;
- mixing said first beam of light with said second beam of light at a second location to create an interference pattern;
- deriving a second signal that has a time relationship to said interference pattern, whereby said second signal indicates said modulating signal at said second location;
- said step of phase modulating including the steps of transmitting said first beam of light through a material capable of passing light along a first path, transmitting said second beam of light through said material along a second path which enters and leaves said material at different locations than said first path and perturbing said material, whereby the differences between the two optical path lengths of said first and second beams of light is varied;
- and
- the step of phase modulating further including the step of phase modulating said first and second beams of light with respect to each other by passing at least one of said first and second beams of light through a cell in which the refractive index changes with time in addition to passing said beam of light through said material capable of passing light.
3 more elements
A method of phase modulating two beams of light with respect to each other comprising the steps of:
- phase modulating first and second beams of light with respect to each other in relationship to a modulating signal at one location;
- mixing said first and second beams of light at a second location to create an interference pattern;
- deriving a second signal that has a time relationship to said interference pattern, whereby said second signal indicates said modulating signal at said second location;
- said steps of phase modulating including the steps of transmitting said first beams of light through a material capable of passing light along a first path, transmitting said second beam of light through said material along a second path which enters and leaves said material at different locations than said first path and perturbing said material, whereby the difference between the two optical path lengths of said first and second beams of light is varied;
- said step of deriving a second signal includes the step of projecting said interference pattern on to a light sensor and deriving an electrical signal varying with the intensity of the interference pattern;
- said step of phase modulating first and second beams of light includes the step of phase modulating said first and second beams of light with respect to each other by passing at least one of said first and second beams of light through a cell in which the refractive index changes with time in addition to passing said beam of light through said material capable of passing light;
- and
- said step of perturbing said material includes the step of modulating a signal voltage and applying the signal voltage to a piezoelectric element.
5 more elements
An interferometric measuring method for measuring a characteristic of a test subject related to an optical path length comprising the steps of:
- generating a modulating signal;
- phase modulating first and second beams of light with respect to each other in relationship to said modulating signal;
- applying said first beam of light to said test subject;
- mixing said first beam of light with said second beam of light after it has been applied to said test subject to create an interference pattern;
- deriving a second signal that has a time relationship to said interference pattern;
- and
- comparing said modulating and second signals to obtain a third signal indicating the optical path length increase in said first beam of light caused by said test subject, whereby said characteristic may be determined.
4 more elements
Apparatus for phase modulating beams of light with respect to each other comprising:
- conductor means adapted to carry a modulating signal;
- an element capable of passing light;
- means for transmitting first and second beams of light along at least first and second predetermined paths respectively through said element with each of said beams entering said element at different locations and leaving said element at different locations;
- means for periodically modulating the phase between said first and second beams of light with respect to each other in accordance with said modulating signal;
- said means for periodically phase modulating including means for providing a variation in optical path length in one of said first and second paths with respect to each other;
- said means for providing a variation in optical path length comprising said element capable of passing light;
- said element capable of passing light being perturbed by said modulating signal;
- and
- means for comparing said first and second modulated beams of light to produce a result at a position remote from the position of said modulation, whereby said result may be interpreted;
- means, in addition to such means for periodic phase modulating, said first and second beams of light for further modulating at least one of said first and second beams of light by changing its optical path length in accordance with an information signal.
7 more elements
Apparatus for phase modulating beams of light with respect to each other comprising:
- conductor means adapted to carry a modulating signal;
- an element capable of passing light;
- means for transmitting first and second beams of light along at least first and second predetermined paths respectively through said element with each of said beams entering said element at different locations and leaving said element at different locations;
- means for phase modulating said first and second beams of light with respect to each other in accordance with said modulating signal;
- said means for phase modulating including means for providing a variation in optical path length in one of said first and second paths with respect to each other;
- said means for providing a variation in optical path length comprising said element capable of passing light;
- said element capable of passing light being perturbed by said modulating signal;
- means for comparing said first and second modulated beams of light to produce a result at a position remote from the position of said modulation, whereby said result may be interpreted;
- said conductor means includes means for generating an alternating current modulating signal having a sine wave form and said means for phase modulating said first and second beams of light with respect to each other includes means for modulating said first and second beams of light with said sine wave form and for modulating at least one of said first and second beams of light by changing its optical path length in accordance with an information signal;
- said means for phase modulating includes a piezoelectric element.
7 more elements
An interferometer for determining differences in effective optical path length comprising:
- conductor means adapted to carry a modulating signal;
- means for transmitting first and second beams of light along at least first and second predetermined paths respectively;
- means for phase modulating said first and second beams of light with respect to each other in accordance with said modulating signal;
- said means for phase modulating including means for providing a variation in optical path length in one of said first and second paths with respect to the other;
- means for combining said first and second beams of light after one of said first and second beams of light has had its optical path length varied to obtain an interference pattern;
- means for generating an interference pattern signal that has a time relationship to said interference pattern;
- and
- means for comparing said interference pattern signal with said modulating signal to obtain a comparison signal.
5 more elements
An interferometer for determining differences in effective optical path length comprising:
- conductor means adapted to carry a modulating signal;
- means for transmitting first and second beams of light along at least first and second predetermined paths respectively;
- means for phase modulating said first and second beams of light with respect to each other in accordance with said modulating signal;
- said means for phase modulating including means for providing a variation in optical path length in one of said first and second paths with respect to the other;
- means for combining said first and second beams of light after one of said first and second beams of light has had its optical path length varied to obtain an interference pattern;
- means for generating an interference pattern signal corresponding to changes in the intensity of light in said interference pattern;
- means for comparing said interference pattern signal with said modulating signal to obtain a comparison signal;
- said means for phase modulating includes a signal transparent element positioned at a location in the path of said first and second beams whereby said first and second beams enter it at two different locations and exit it at two different locations;
- means for perturbing said transparent element by said modulating signal;
- said means for comparing said interference pattern signal with said modulating signal further includes a photocell and a comparison circuit connected to the output of the photocell;
- said means for providing a variation includes means for transmitting said first beam through a substance, whereby said means for comparing obtains an indication of the refractive index of said substance;
- said conductor means for carrying a modulating signal includes means for generating an alternating electrical current modulating signal having a sine wave form;
- and
- said means for phase modulating includes a piezoelectric element.
11 more elements
An interferometer for determining differences in effective optical path length comprising:
- conductor means adapted to carry a modulating signal;
- means for transmitting first and second beams of light along at least first and second predetermined paths respectively;
- means for phase modulating said first and second beams of light with respect to each other in accordance with said modulating signal;
- said means for phase modulating including means for providing a variation in optical path length in one of said first and second paths with respect to the other;
- means for combining said first and second beams of light after one of said first and second beams of light has had its optical path length varied to obtain an interference pattern;
- means for generating an interference pattern signal corresponding to changes in the intensity of light in said interference pattern;
- means for comparing said interference pattern signal with said modulating signal to obtain a comparison signal;
- said means for modulating said two beams of light includes:
- a piezoelectric element;
- said piezoelectric element including at least a first portion capable of passing light;
- said piezoelectric element being positioned with respect to said first and second beams of light to permit said first and second beams of light to pass through said portion capable of passing light;
- p1 electrode means connected to said piezoelectric element for causing said piezoelectric element to vibrate in the direction of said beams of light;
- and
- said means for carrying said modulating potential being electrically connected to said electrode means.
11 more elements
A phase modulator comprising:
- A piezoelectric element having at least one portion capable of passing light;
- light path means for transmitting a first beam of light through the one portion entering said element at one location and leaving at a second location and for transmitting a second beam of light through said piezoelectric element not passing through the said one location and not passing through the second location;
- means for vibrating the one portion of said element in substantially the direction of said first beam of light, whereby said beams of light are phase modulated with respect to each other;
- and
- means for further modulating at least one of said first and second beams of light by changing its optical path length in accordance with an information signal.
2 more elements
A phase modulator comprising:
- a piezoelectric element having at least one portion capable of passing light;
- light path means for transmitting a first beam of light through the one portion entering said element at one location and leaving at another location and a second beam of light not passing through the said one location and not passing through the second location;
- means for vibrating the one portion of said element in substantially the direction of said first beam of light, whereby said beams of light are phase modulated with respect to each other;
- said one portion is offset from the center of the piezoelectric element and wherein the element is cut to flex.
1 more element
A phase modulator comprising:
- a piezoelectric element having at least one portion capable of passing light;
- light path means for transmitting a first beam of light through the one portion entering said element at one location and leaving at another location and a second location beam of light not passing through the said one location and not passing through the second location;
- means for vibrating the one portion of said element in substantially the direction of said first beam of light, whereby said beams of light are phase modulated with respect to each other;
- said light path means includes a source of light and a beam splitter means for forming two beams of light from the light emitted by said source of light;
- said piezoelectric element is a quartz crystal of the Y-cut family and said means for vibrating said crystal includes means for vibrating said crystal in the first-order flexural mode by applying second-order shear mode strain st the same frequency.
2 more elements
A phase modulator comprising:
- a piezoelectric element having at least one portion capable of passing light;
- light path means for transmitting a first beam of light through the one portion entering said element at one location and leaving at another location and a second beam of light not passing through the said one location and not passing through the second location;
- means for vibrating the one portion of said element in substantially the direction of said first beam of light, whereby said beams of light are phase modulated with respect to each other;
- said piezoelectric element is a quartz crystal of the Y-cut family and said means for vibrating said crystal includes means for vibrating said crystal in the first-order flexural mode by applying second-order shear mode strain at the same frequency.
1 more element
A differential phase modulator comprising:
- first and second phase modulation elements;
- means for generating first and second light beams;
- one of said first and second phase modulation elements being positioned in one of said first and second light beams and the other of said first and second modulation elements being positioned in the other of said first and second light beams;
- each of said phase modulation elements including means for phase modulating said beams according to a nonlinear but even function of applied electrical signals so that one element causes an increase in effective optical path length at the same time the other element causes a decrease in effective optical path length;
- and
- means for biasing said elements in such a way that the differential phase modulation is a linear function of the signal.
3 more elements
A differential phase modulator comprising:
- first and second phase modulation elements;
- means for generating first and second light beams;
- one of said first and second phase modulation elements being positioned in one of said first and second light beams and the other of said first and second modulation elements being positioned in the other of said first and second light beams;
- and
- means for causing one of said phase modulation elements to change the effective optical path length of one of said beams in one direction at the same time the other element causes a change in the effective path length of the other of said beams in the opposite direction by increasing the angle of said one element with respect to said one beam while the angle of said other element with respect to the other beam decreases and decreasing the angle of said one element with respect to said one beam while the angle of said other element with respect to the other beam increases.
2 more elements
Dependencies are inferred from the claim text.