Abstract Filtering apparatus is provided for isolating a very narrow optical frequency range in the order of a spectral line width. Features include a fixed geometry of a light input member relative to a barrier member as well as an appropriate selection of the media of these two members. The media of the input member can be any material that is more refractive than the barrier member and it has a flush interface with the barrier member disposed at such an angle that the interface angle of incidence is greater than the critical angle of the two members. Thus, all light wavelengths other than the wavelengths of particular concern, are internally reflected in the input member. To permit the desired optical frequency bank to pass, the barrier member is formed of a media having a capacity for absorbing input light in the immediate vicinity of a wavelength that falls within the narrow frequency pass band. The absorption produces an irregularity in the refractive dispersion curve for the barrier media. When the angle of incidence and the interface of the input and in barrier members is fixed sufficiently close to the critical angle for this interface, the irregularity varies the relative refractive index sufficiently to vary the relationship of the critical angle with the angle of incidence and permit the narrow band to pass into the barrier member and on into the output member.
Filtering apparatus for passing a narrow optical frequency band of input light received from a heterochromatic light beam source comprising: spaced light-transmissive input and output members, and a barrier member disposed between and in flush interface contact with said input and output members, said input member being formed of a more refractive media than said barrier member and the input member having its interface with said barrier member disposed at such an angle that the interface angle of incidence is greater than the critical angle of said interface whereby all light wavelengths of said source other than those included in said narrow band are internally reflected in said input member, said barrier member media being characterized by having the capacity to absorb light in the immediate vicinity of a wavelength within said narrow optical frequency band and said absorption producing an irregularity in the refractive dispersion curve for the barrier media, said angle of incidence at the interface of the input and barrier member being fixed sufficiently close to said critical angle that said irregularity resulting from said absorption varies the relationship of the critical angle with the angle of incidence sufficiently to permit said narrow band to pass from the input member into the barrier member, said barrier member being sized to pass a portion of said narrow band to said output member.
Claim 2
Dependent Claim
224 words
Filtering apparatus for passing a narrow optical frequency band of input light received from a heterochromatic light beam source comprising: spaced light-transmissive input and output members, and a barrier member disposed between and in flush interface contact with said input and output members, said input member being formed of a more refractive media than said barrier member and the input member having its interface with said barrier member disposed at such an angle that the interface angle of incidence is greater than the critical angle of said interface whereby all light wavelengths of said source other than those included in said narrow band are internally reflected in said input member, said barrier member media being characterized by having the capacity to absorb light in the immediate vicinity of a wavelength within said narrow optical frequency band and said absorption producing an irregularity in the refractive dispersion curve for the barrier media, said angle of incidence at the interface of the input and barrier member being fixed sufficiently close to said critical angle that said irregularity resulting from said absorption varies the relationship of the critical angle with the angle of incidence sufficiently to permit said narrow band to pass from the input member into the barrier member, said barrier member being sized to pass a portion of said narrow band to said output member.
Claim 3
Dependent Claim
14 words
The filtering apparatus of claim 1 wherein said barrier member media is a fluid.
Claim 4
Dependent Claim
14 words
The filtering apparatus of claim 2 wherein said barrier member media is a gas.
Claim 5
Dependent Claim
18 words
The filtering apparatus of claim 1 wherein said input and output members are formed of the same media.
Claim 6
Dependent Claim
26 words
The filtering apparatus of claim 4 wherein the interface angle of the output and barrier members parallel the interface angle of the input and barrier members.
Claim 7
Dependent Claim
21 words
The filtering apparatus of claim 5 wherein the narrow optical frequency baNd is in the order of a spectral line width.