US5298973A — Phase difference controller and method for contro…

Claim 1

Independent Claim 216 words

A phase difference controller for controlling a phase difference δ 0 sin (ωt-Φ) between two linearly polarized components, which electrical vectors vibrate in direction perpendicular to each other, of light out of a photoelastic modulator which is forced to vibrate at angular frequency ω by an input voltage V 0 sin ω t, where δ 0 is amplitude of the phase difference, t is time, Φ is phase and V 0 is amplitude of the input voltage, comprising: a splitting polarizer (14A) for splitting incident linearly polarized monochromatic-light into main light (LM) and reference light (LR), said split main light and reference light passing through the photoelastic modulator, said main light being used as the phase-difference controlled light, said reference light being used for controlling the phase difference; an analyzer (42) for passing through said reference light from said photoelastic modulator; a photodetector (44) for detecting said reference light from said analyzer; and a photoelastic modulator control circuit (18A, 46-50) for outputting the voltage V 0 sin (ωt) to the photoelastic modulator and adjusting the amplitude V 0 so that a ratio of amplitude of ac component of angular frequency of 2ω to magnitude of dc component included in an output of said photodetector is maintained constant in order to make the amplitude δ 0 constant.

Claim 2

Dependent Claim 216 words

A phase difference controller for controlling a phase difference δ 0 sin (ωt-Φ) between two linearly polarized components, which electrical vectors vibrate in direction perpendicular to each other, of light out of a photoelastic modulator which is forced to vibrate at angular frequency ω by an input voltage V 0 sin ω t, where δ 0 is amplitude of the phase difference, t is time, Φ is phase and V 0 is amplitude of the input voltage, comprising: a splitting polarizer (14A) for splitting incident linearly polarized monochromatic-light into main light (LM) and reference light (LR), said split main light and reference light passing through the photoelastic modulator, said main light being used as the phase-difference controlled light, said reference light being used for controlling the phase difference; an analyzer (42) for passing through said reference light from said photoelastic modulator; a photodetector (44) for detecting said reference light from said analyzer; and a photoelastic modulator control circuit (18A, 46-50) for outputting the voltage V 0 sin (ωt) to the photoelastic modulator and adjusting the amplitude V 0 so that a ratio of amplitude of ac component of angular frequency of 2ω to magnitude of dc component included in an output of said photodetector is maintained constant in order to make the amplitude δ 0 constant.

Claim 3

Dependent Claim 129 words

A phase difference controller as defined in claim 1, wherein: said photodetector (44) is a photomultiplier (44); said photoelastic modulator control circuit comprises a dc amplifier (46) for ampligying said dc component included in said output of said photodetector; a sensitivity adjustment circuit (48) for adjusting sensitivity of said photomultiplier so that said magnitude of said dc component is maintained constant; a lock-in amplifier (5) which produces a signal proportional to said amplitude or square of said amplitude of said ac component of angular frequency of 2ω included in said output of said photodetector; and a photoelastic modulator driving circuit (18A) for outputting said voltage V sin (ω) to said photoelastic modulator and adjusting said amplitude V so that said signal produced by said lock-in amplifier is maintained constant.

Claim 4

Dependent Claim 47 words

A phase difference controller as defined in claim 2 wherein said splitting polarizer (14A) is a birefringence polarizer for splitting said incident light into ordinary light and extraordinary light one of which acts as said reference light and the other of which acts as said main light.

Claim 5

Dependent Claim 52 words

A phase difference controller as defined in claim 2 wherein said splitting polarizer comprises; a polarizer (14); a beam splitter (142) for splitting said incident light into transmitted light and reflected light which pass through said polarizer (14); and a reflector (143) for reflecting said transmitted light to pass through said polarizer.

Claim 6

Independent Claim 450 words

A method for adjusting phase difference of an apparatus including; a phase difference controller for controlling a phase difference δ 0 sin (ωt-Φ) between two linearly polarized components, which electrical vectors vibrate in directions perpendicular to each other, of light out of a photoelastic modulator which is forced to vibrate at angular frequency ω by an input voltage V 0 sin ω t, where δ 0 is amplitude of the phase difference, t is time, Φ is phase and V 0 is amplitude of the input voltage; a first analyzer (22) for passing through the phase-difference-controlled light from the photoelastic modulator; and a first photodetector (24) for detecting the phase-difference-controlled light from the first analyzer; wherein the phase difference controller including: a splitting polarizer (14A) for splitting incident linearly polarized monochromatic-light into main light (LM) and reference light (LR), the split main light and reference light passing through the photoelastic modulator, the main light being used as the phase-difference-controlled light, the reference light being used for controlling the phase difference; a second analyzer (42) for passing through the reference light from the photoelastic modulator; a second photodetector (44) for detecting the reference light from the second analyzer; and a photoelastic modulator control circuit (18A, 46-50) for outputting the voltage V 0 sin (ωt) to the photoelastic modulator and adjusting the amplitude V 0 so that a ratio of amplitude of ac component of angular frequency of 2ω to magnitude of dc component included in an output of the second photodetector is maintained constant in order to make the amplitude δ 0 constant; wherein the method comprising steps of; adjusting a direction of a transmission axis of the second analyzer (42) parallel to a direction of a transmission axis of the splitting polarizer (14A); adjusting a direction of a transmission axis of the first analyzer (22) parallel to a direction of the transmission axis of the splitting polarizer (14A); finding a first relation between the amplitude V 0 and an amplitude of ac component of angular frequency of 2ω included in an output of the first photodetector by varying the amplitude V 0 ; rotating the first analyzer around its optical axis by 90 degrees; finding a second relation between the amplitude V 0 and an amplitude of ac component of angular frequency of 2ω included in an output of the first photodetector by varying the amplitude V 0 ; setting the amplitude V 0 at a value such that the first relation is identical to the second relation so as to equal the Bessel function J 0 (δ 0 ) of the 0th order to 0; and starting the phase difference control by the phase difference controller after the setting.

Claim 7

Independent Claim 450 words

A method for adjusting phase difference of an apparatus including; a phase difference controller for controlling a phase difference δ 0 sin (ωt-Φ) between two linearly polarized components, which electrical vectors vibrate in directions perpendicular to each other, of light out of a photoelastic modulator which is forced to vibrate at angular frequency ω by an input voltage V 0 sin ω t, where δ 0 is amplitude of the phase difference, t is time, Φ is phase and V 0 is amplitude of the input voltage; a first analyzer (22) for passing through the phase-difference-controlled light from the photoelastic modulator; and a first photodetector (24) for detecting the phase-difference-controlled light from the first analyzer; wherein the phase difference controller including: a splitting polarizer (14A) for splitting incident linearly polarized monochromatic-light into main light (LM) and reference light (LR), the split main light and reference light passing through the photoelastic modulator, the main light being used as the phase-difference-controlled light, the reference light being used for controlling the phase difference; a second analyzer (42) for passing through the reference light from the photoelastic modulator; a second photodetector (44) for detecting the reference light from the second analyzer; and a photoelastic modulator control circuit (18A, 46-50) for outputting the voltage V 0 sin (ωt) to the photoelastic modulator and adjusting the amplitude V 0 so that a ratio of amplitude of ac component of angular frequency of 2ω to magnitude of dc component included in an output of the second photodetector is maintained constant in order to make the amplitude δ 0 constant; wherein the method comprising steps of; adjusting a direction of a transmission axis of the second analyzer (42) parallel to a direction of a transmission axis of the splitting polarizer (14A); adjusting a direction of a transmission axis of the first analyzer (22) parallel to a direction of the transmission axis of the splitting polarizer (14A); finding a first relation between the amplitude V 0 and an amplitude of ac component of angular frequency of 2ω included in an output of the first photodetector by varying the amplitude V 0 ; rotating the first analyzer around its optical axis by 90 degrees; finding a second relation between the amplitude V 0 and an amplitude of ac component of angular frequency of 2ω included in an output of the first photodetector by varying the amplitude V 0 ; setting the amplitude V 0 at a value such that the first relation is identical to the second relation so as to equal the Bessel function J 0 (δ 0 ) of the 0th order to 0; and starting the phase difference control by the phase difference controller after the setting.

Claim 8

Dependent Claim 129 words

A method as defined in claim 5, wherein said photodetector (44) is a photomultiplier (44); said photoelastic modulator control circuit comprises a dc amplifier (46) for amplifying said dc component included in said output of said photodetector; a sensitivity adjustment circuit (48) for adjusting sensitivity of said photomultiplier so that said magnitude of said dc component is maintained constant; a lock-in amplifier (5) which produces a signal proportional to said amplitude or square of said amplitude of said ac component of angular frequency of 2ω included in said output of said photodetector; and a photoelastic modulator driving circuit (18A) for outputting said voltage V 0 sin (ω) to said photoelastic modulator and adjusting said amplitude V 0 so that said signal produced by said lock-in amplifier is maintained constant.

Claim 9

Dependent Claim 45 words

A method as defined in claim 5, wherein said splitting polarizer (14A) is a birefringence polarizer for splitting said incident light into ordinary light and extraordinary light one of which acts as said reference light and the other of which acts as said main light.

Claim 10

Dependent Claim 50 words

A method as defined in claim 5, wherein said splitting polarizer comprises; a polarizer (14); a beam splitter (142) for splitting said incident light into transmitted light and reflected light which pass through said polarizer (14); and a reflector (143) for reflecting said transmitted light to pass through said polarizer.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1997-03-28	1997-09-27	1998-03-29	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2001-03-28	2001-09-27	2002-03-29	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2005-03-28	2005-09-27	2006-03-29	$7700.00	Window Closed / Lapsed

Phase difference controller and method for controlling phase difference

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