US3729261A — Stabilized multipass interferometer

Claim 1

Independent Claim 257 words

In combination: a Fabry-Perot interferometer utilizing a pair of spaced mirrors which can be angularly oriented with respect to each other, said interferometer providing an output signal in response to incident wave energy, said output signal having a level at any certain value of angular orientation of said mirrors, said level being a function of the absolute value of the difference between that certain value and a predetermined value thereof at which said output signal is a maximum, first means coupled to said mirrors for cyclically rotating said mirrors with respect to each other by a given incremental amount in one direction about an axis from a mean angular position during a first portion of each cycle and by substantially said given incremental amount in an opposite direction about said axis from said mean angular position during a second portion of each cycle, second means for measuring said output signal, third means including storage means coupled to said first and second means for comparing the measured output signal produced during the first portion of a cycle with the measured output signal produced during the second portion of that cycle to generate an error signal manifesting the algebraic difference between said compared signals, and fourth means coupled to said first and third means and responsive to said error signal for shifting the mean angular position of said mirrors in accordance with the error signal, which shifting tends to reduce the magnitude of said error signal, whereby the mean position of said mirrors is shifted toward said predetermined value.

Claim 2

Dependent Claim 257 words

In combination: a Fabry-Perot interferometer utilizing a pair of spaced mirrors which can be angularly oriented with respect to each other, said interferometer providing an output signal in response to incident wave energy, said output signal having a level at any certain value of angular orientation of said mirrors, said level being a function of the absolute value of the difference between that certain value and a predetermined value thereof at which said output signal is a maximum, first means coupled to said mirrors for cyclically rotating said mirrors with respect to each other by a given incremental amount in one direction about an axis from a mean angular position during a first portion of each cycle and by substantially said given incremental amount in an opposite direction about said axis from said mean angular position during a second portion of each cycle, second means for measuring said output signal, third means including storage means coupled to said first and second means for comparing the measured output signal produced during the first portion of a cycle with the measured output signal produced during the second portion of that cycle to generate an error signal manifesting the algebraic difference between said compared signals, and fourth means coupled to said first and third means and responsive to said error signal for shifting the mean angular position of said mirrors in accordance with the error signal, which shifting tends to reduce the magnitude of said error signal, whereby the mean position of said mirrors is shifted toward said predetermined value.

Claim 3

Dependent Claim 200 words

The circuit of claim 1 further including fifth means coupled to said mirrors for cyclically rotating said mirrors with respect to each other by a given incremental amount in one direction about another axis orthogonal to said first mentioned axis from another mean angular position during a third portion of each cycle and by substantially said last mentioned given incremental amount in an opposite direction about said other axis from said other mean angular position during a fourth portion of each cycle, said third means including said storage means further including means coupled to said second and fifth means for comparing the measured output signal produced during the third portion of a cycle with the measured output signal produced during the fourth portion of that cycle to generate another error signal manifesting the algebraic difference between said last mentioned compared signals, said fourth means being coupled to said fifth means and responsive to said other error signal for shifting the other mean angular position of said mirrors in accordance with said other error signal, which shifting tends to reduce the magnitude of said other error signal, whereby said other mean position of said mirrors is shifted toward said predetermined value.

Claim 4

Dependent Claim 100 words

The circuit of claim 2 wherein said third means includes A capacitor coupled to said second means and said comparing means for storing the measured output signal produced during one of said first and second cycle portions and including means for applying said stored output signal to said comparing means during the other of said first and second cycle portions for comparing the measured output signal produced during each of said first and second cycle portions, said third means further including discharge means coupled to said capacitor for discharging said stored signal at the end of said second cycle portion.

Claim 5

Dependent Claim 45 words

The circuit of claim 3 wherein said third means includes gating means coupled between said capacitor and said second means, said gating means being responsive to a control signal applied thereto for selectively passing only the measured output signal to be stored to said capacitor.

Claim 6

Dependent Claim 147 words

The circuit of claim 2 further including sixth means coupled to said mirrors to cyclically translate said mirrors with respect to each other in response to a scanning signal applied to said sixth means for scanning said incident wave energy to thereby produce an output signal of varying levels, each scanning cycle corresponding to a separate, different rotating cycle portion, said measured output signal varying proportionately with said varying levels, said third means including integrating means coupled to said storage means and said second means for integrating the varying measured output signal produced in each of said cycle portions, a separate integrated signal corresponding to a different cycle portion, said third means including means for comparing the integrated signals corresponding to the first and second cycle portions with each other and for comparing the integrated signals corresponding to the third and fourth cycle portions with each other.

Claim 7

Dependent Claim 39 words

The circuit of claim 5 wherein said third means includes gating means coupled between said integrating means and said second means for selectively passing said varying measured output signal produced during each cycle portion to separate respective integrating means.

Claim 8

Dependent Claim 73 words

The circuit of claim 6 wherein said third means includes discharge means coupled to said integrating means for discharging said integrating means at the end of said second and fourth cycle portions, said integrating means including different separate means for separately sequentially integrating the varying measured output signal produced in said first and third cycle portions, and for integrating the varying measured output signal produced in said second and fourth cycle portions, respectively.

Claim 9

Dependent Claim 173 words

The circuit of claim 7 wherein said integrating and storing means includes first and second capacitors, each capacitor having a pair of terminals, and said gating means includes first and second switches, each switch having an input terminal, an output terminal and a control terminal, said comparing means having a pair of input terminals and an output terminal, one terminal of said capacitors being connected to a reference potential, the other terminal of said first capacitor being connected to an output terminal of said first switch and an input terminal of said comparing means, the other terminal of said second capacitor being connected to an output terminal of said second switch and the other input terminal of said comparing means, the input terminals of said switches being coupled to said second means, the control terminal of said switches being coupled to a source of control signals for causing the selective passing of said varying measured signal to said integrating means, the output terminal of said comparing means being coupled to said fourth means.

Claim 10

Dependent Claim 63 words

The circuit of claim 8 wherein said discharge means includes a pair of unidirectional devices each device having a pair of terminals, one terminal of each device being connected to a different, separate one of said other capacitor terminals and being poled to flow current from said capacitors in response to a control signal applIed to the other respective terminals of said devices.

Claim 11

Dependent Claim 114 words

The circuit of claim 5 wherein said fourth means includes first and second storing means each coupled to a different one of said first and fifth means, and gating means coupled to said first and second storing means and to said comparing means, said gating means selectively passing a different one of said error signals to a separate different one of said storing means in response to a control signal applied to said gating means, the error signal produced by said first means being stored by the storing means coupled to said first means and the error signal produced by said fifth means being stored by the storing means coupled to said fifth means.

Claim 12

Dependent Claim 206 words

The circuit of claim 10 wherein said first storing means includes a first capacitor and said second storing means includes a second capacitor, each capacitor having a pair of terminals, said fourth means including a pair of difference amplifiers, each amplifier having two input terminals and an output terminal, a pair of transducers each having an input terminal, each transducer being coupled to one of said mirrors for angularly rotating said mirrors with respect to each other about a separate, different one of said axes in response to a signal applied to said transducer input terminal, said gating means including a pair of switches each switch having a control terminal, an input terminal and an output terminal, said switch input terminals being coupled to said comparing means, said switch output terminals each being coupled to said one input terminal of a different amplifier, the output terminal of each amplifier being respectively coupled to separate, different ones of said transducer input terminals, a terminal of one capacitor being coupled to said one input terminal of one amplifier and a terminal of the other capacitor being coupled to said one input terminal of the other amplifier, the other terminals of said capacitors being coupled to a reference potential.

Claim 13

Dependent Claim 72 words

The circuit of claim 2 wherein said first and fifth means each includes a pair of transducer means each having an input terminal and coupled to said mirrors, said transducer means each angularly displacing at least one of said mirrors with respect to the other mirror about a different respective one of said axis in response to a signal applied to the input terminal of that transducer corresponding to said one axis.

Claim 14

Dependent Claim 131 words

The circuit of claim 12 wherein said first and fifth means includes means for applying a control signal at the input terminal of each of said transducer means, the control signal applied to one of said pair of transducer means causing said mirrors to cyclically rotate said first mentioned incremental amounts during said first and second cycle portions and for maintaining said mirrors at said first mentioned mean angular position during said third and fourth cycle portions about said first mentioned axis, the control signal applied to the other of said pair of transducer means causing said mirrors to cyclically rotate said second mentioned incremental amounts during said third and fourth cycle portions and for maintaining said mirrors at said other mean angular position during said first and second cycle portions.

Claim 15

Dependent Claim 187 words

A stabilized Fabry-Perot interferometer utilizing a pair of spaced mirrors which can be angularly oriented with respect to each other, said interferometer providing an output signal in response to incident wave energy impinging upon said mirrors at a given location thereon, said output having a level which is a function of any certain value of said orientation of said mirrors with respect to each other and any certain location on said mirrors at which said wave energy impinges, said interferometer comprising: an unstabilized single Fabry-Perot interferometer including at least one retroreflector coupled to said interferometer to obtain at least two passes of said incident wave energy on said mirrors, the incident wave energy of eacH pass being displaced from each other that distance by which the wave energy in each of said passes is processed by said interferometer substantially without interaction with the wave energy of the other pass, and stabilizing means coupled to said mirrors for stabilizing the angular orientation of said mirrors with respect to each other about a given degree of parallelism beyond which degree the level of said output signal is substantially reduced.

Claim 16

Dependent Claim 187 words

A stabilized Fabry-Perot interferometer utilizing a pair of spaced mirrors which can be angularly oriented with respect to each other, said interferometer providing an output signal in response to incident wave energy impinging upon said mirrors at a given location thereon, said output having a level which is a function of any certain value of said orientation of said mirrors with respect to each other and any certain location on said mirrors at which said wave energy impinges, said interferometer comprising: an unstabilized single Fabry-Perot interferometer including at least one retroreflector coupled to said interferometer to obtain at least two passes of said incident wave energy on said mirrors, the incident wave energy of eacH pass being displaced from each other that distance by which the wave energy in each of said passes is processed by said interferometer substantially without interaction with the wave energy of the other pass, and stabilizing means coupled to said mirrors for stabilizing the angular orientation of said mirrors with respect to each other about a given degree of parallelism beyond which degree the level of said output signal is substantially reduced.

Claim 17

Dependent Claim 25 words

The interferometer of claim 14 wherein said interferometer further includes means coupled to said mirrors for causing said mirrors to scan said incident wave energy.

Claim 18

Dependent Claim 57 words

The interferometer of claim 14 wherein said interferometer includes a pair of retroreflectors coupled to said mirrors, said retroreflectors being disposed in spaced relationship with respect to each other and said mirrors for obtaining at least five passes of said incident wave energy on said mirrors, each pass being displaced from the remaining passes by said distance.

Claim 19

Dependent Claim 46 words

The interferometer of claim 16 wherein said incident wave energy is formed of a beam of wave energy and undesirable stray wave energy, said interferometer further including means disposed between each of said retroreflectors and said mirrors for passing substantially only said beam of energy therebetween.

Claim 20

Dependent Claim 178 words

The interferometer of claim 14 wherein said stabilization means includes means coupled to said mirror for cyclically rotating said mirrors with respect to each other by a given incremental amount in one direction about an axis from a mean angular position during a first portion of each cycle and by substantially said given incremental amount in an opposite direction about said axis from said mean angular position during a second portion of each cycle, means for measuring said output signal, means including storage means coupled to said rotating means and said measuring means for comparing the measured output signal produced during the first portion of a cycle with the measured output signal produced during the second portion of that cycle to generate an error signal manifesting the algebraic difference between said compared signals, and means coupled to said rotating means and said error signal generating means and responsive to said error signal for shifting the mean angular position of said mirrors in accordance with the error signal, which shifting tends to reduce the magnitude of said error signal.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1976-04-23	1976-10-23	1977-04-24	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1980-04-23	1980-10-23	1981-04-24	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1984-04-23	1984-10-23	1985-04-24	$7700.00	Window Closed / Lapsed

Stabilized multipass interferometer

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