Fabry-perot interferometer

A tandem Fabry-Perot interferometer comprising:

• a first pair of spaced plane mirrors forming a first Fabry-Perot interferometer radiating an output signal therefrom in response to an applied radiant input signal, said output signal comprising a series of equally spaced pass bands of radiant energy in a given wavelength range, each pass band having a mean wavelength which is a function of the spacing of said mirrors,
• a second pair of spaced plane mirrors forming a second Fabry-Perot interferometer,
• said first and second pairs of mirrors being oriented normal to an applied input signal beam,
• signal directing means for directing the output signal of said first interferometer as an input signal normal to the mirrors of said second interferometer,
• means for mounting the mirrors with the spacing between said second pair of mirrors sufficiently different from the spacing of said first pair of mirrors so that the pass bands of the two interferometers at one wavelength coincide and the pass bands adjacent to one wavelength of one of the interferometers are displaced in wavelength sufficiently from the pass bands adjacent the one wavelength of the other interferometer so that substantially only the one wavelength is passed by the second interferometer, and
• means for synchronously reciprocating one mirror of each said pair in the same direction so that said spacings are increased and decreased in magnitude synchronously, said mirrors being so placed such that the ratio of the incremental change of said spacings during said reciprocating is equal to the ratio of said spacings wherein essentially one pass band is passed in said range by said second interferometer during said reciprocating,
• said first pair of mirrors being positioned adjacent the second pair of mirrors with the planes of the pairs intersecting at an angle .theta., with the spacing between the first pair of mirrors being a distance L, and with the spacing between the second pair of mirrors being a distance L cos .theta., where .theta. is less than 90.degree..

A scanning Fabry-Perot interferometer comprising:

• a pair of spaced parallel plane mirrors,
• a base member on which is fixed one of said mirrors,
• support means on which is fixed the other of said mirrors, said support means including means movably mounting the support means to said base for translation in a direction parallel to the normal to said mirrors while maintaining the mirrors substantially interferometrically parallel, and
• support drive means for cyclically translating the support means with respect to said base member to thereby alter the spacing of said mirrors in a scanning mode,
• said support means being movable at least several orders of magnitude greater than the spacing of said mirrors in said scanning mode in said direction parallel to the normal,
• said support drive means including means for receiving a scan signal, transducer means responsive to said scan signal for displacing the support means with respect to said base to thereby alter the spacing of said mirrors, said transducer means tending to have a non-linear response to said scan signal, and linearity correcting means responsive to said displacement and received scan signal for generating a transducer drive signal which causes said transducer means to displace said mirrors linearly with respect to the valve of said scan signal.

A Fabry-Perot interferometer comprising:

• a base,
• a first plane mirror fixed to the base,
• a support member,
• a second plane mirror fixed to the support member parallel to said first mirror forming a Fabry-Perot optical resonant cavity therewith,
• an intermediate member between said support member and said base,
• first and second spaced flexible plane members fixed to said support and said intermediate members parallel to said mirrors,
• displacement means for cyclically displacing said support member with respect to said intermediate member in a direction normal to said mirrors to alter the spacing between said mirrors in response to an applied scan signal, said plane members being oriented to flex in response to said displacing without altering the parallelism of said mirrors, and
• means for displacing said intermediate member with respect to said base in a direction normal to said mirror.

A scanning Fabry-Perot interferometer comprising:

• a pair of spaced parallel plane mirrors forming a Fabry-Perot optical cavity,
• first displacement means for displacing one of said mirrors within a first scanning displacement range about a mean mirror spacing while maintaining said mirrors substantially interferometrically parallel, and
• second displacement means for setting said mean mirror spacing within a second range much greater than said first range for providing coarse adjustment of said mirror spacing while maintaining said mirrors substantially interferometrically parallel,
• said first displacement means including first mounting means to which one of said mirrors is fixed and second mounting means to which the other mirror is fixed, and means connected to both said mounting means arranged so that said mirrors remain interferometrically parallel when displaced in said first and second ranges,
• said first displacement means including piezoelectric transducer means connected between said first and second mounting means for displacing said mirrors within said first range,
• said second displacement means comprises third mounting means including roller bearing means connected to said first and second mounting means for displacing said mirrors within said second range.

An interferometer comprising, in combination:

• a first Fabry-Perot interferometer (FP) having a pair of plane mirrors spaced a distance L.sub.1 from one another, the mirrors being oriented normal to the input light signal beam,
• a second FP having a pair of plane mirrors spaced a distance L.sub.2 from one another, where L.sub.2 differs from L.sub.1,
• means during operation of said first and second FP's for applying the light signal produced as an output from said first FP as an input to said second FP, the mirrors of said second FP being oriented normal to the light signal beam from said first FP,
• means for concurrently adjusting the spacing between the pair of mirrors of the first FP and the pair of mirrors of the second FP by displacing one mirror with respect to the other mirror of each interferometer while maintaining the ratio L.sub.2 /L.sub.1 constant, and
• the plane of the mirrors of the first FP and the second FP intersecting at an angle .theta. less than 90.degree..

An interferometer comprising, in combination:

• a first Fabry-Perot interferometer (FP) having a pair of plane mirrors spaced a distance L.sub.1 from one another, the mirrors being oriented normal to the input light signal beam,
• a second FP having a pair of plane mirrors spaced a distance L.sub.2 from one another, where L.sub.2 differs from L.sub.1, the mirrors being oriented normal to the light signal beam from the first FP,
• means during operation of said first and second FP's for applying the light signal produced as an output from said first FP as an input to said second FP, and
• means for concurrently adjusting the spacing between the pair of mirrors of the first FP and the pair of mirrors of the second FP by displacing one mirror with respect to the other mirror of each interferometer while maintaining the ratio L.sub.2 /L.sub.1 constant,
• one mirror of each said FP being fixed to the same support, and said means for concurrently adjusting including means for moving the same support in a direction normal to the mirrors of said first FP.