Abstract: A substantially neutral filter across the white-light spectrum is obtained by minimizing the wavelength-dependent effects of filtering components and of reflective coatings on surfaces. The incoming light is captured by a first prism and directed toward the interface formed by the optical contact of a second prism with a face of the first prism, where the light is partially reflected internally and partially transmitted into the second prism. The reflected light is further reflected internally and directed toward the image surface out of the first prism. The fraction of light transmitted into the second prism is reflected back and redirected out of the system toward the incoming beam. The amount of energy directed toward the image plane is controlled by the judicious selection of the refractive indices in the two materials at the contacting interface of the first and second prisms.

Abstract: A substantially neutral filter across the white-light spectrum is obtained by minimizing the wavelength-dependent effects of filtering components and of reflective coatings on surfaces. The incoming light is captured by a first prism and directed toward the interface formed by the optical contact of a second prism with a face of the first prism, where the light is partially reflected internally and partially transmitted into the second prism. The reflected light is further reflected internally and directed toward the image surface out of the first prism. The fraction of light transmitted into the second prism is reflected back and redirected out of the system toward the incoming beam. The amount of energy directed toward the image plane is controlled by the judicious selection of the refractive indices in the two materials at the contacting interface of the first and second prisms.

Abstract: A substantially neutral filter across the white-light spectrum is obtained by minimizing the wavelength-dependent effects of filtering components and of reflective coatings on surfaces. The incoming light is captured by a first prism and directed toward the interface formed by the optical contact of a second prism with a face of the first prism, where the light is partially reflected internally and partially transmitted into the second prism. The reflected light is further reflected internally and directed toward the image surface out of the first prism. The fraction of light transmitted into the second prism is reflected back and redirected out of the system toward the incoming beam. The amount of energy directed toward the image plane is controlled by the judicious selection of the refractive indices in the two materials at the contacting interface of the first and second prisms.

Abstract: A temperature-stable and temperature-tunable composite etalon with an increased field of view is constructed by partially filling the cavity with a transmissive parallel-plate filler. The coefficient of thermal expansion and the index of refraction of the filler material are selected so as to produce the desired rate of change of the optical length of the cavity as a function of temperature. The filler plate is preferably chosen to be significantly thicker than the remaining air gap in the etalon cavity. As a result, the fact that the filler plate occupies a large part of the cavity space increases the acceptance angle of the etalon of the invention in comparison with corresponding conventional air-spaced etalons.

Abstract: A compressive force is applied to a conventional air-spaced etalon filter to fine tune the thickness of the spacers to a precise and uniform optical length. The etalon is coupled to a housing device capable of adjusting the thickness of each spacer, thereby tuning the etalon to the desired filter wavelength. The resulting assembly is permanently set to the desired parameters for direct use in optical applications.

Abstract: A temperature-stable and temperature-tunable composite etalon with an increased field of view is constructed by partially filling the cavity with a transmissive parallel-plate filler. The coefficient of thermal expansion and the index of refraction of the filler material are selected so as to produce the desired rate of change of the optical length of the cavity as a function of temperature. The filler plate is preferably chosen to be significantly thicker than the remaining air gap in the etalon cavity. As a result, the fact that the filler plate occupies a large part of the cavity space increases the acceptance angle of the etalon of the invention in comparison with corresponding conventional air-spaced etalons.

Abstract: Two reflective surfaces disposed in a predetermined angular orientation inside the optical tube assembly of a telescope intercept the optical beam and deliver it from the objective to the eye-piece. By translating these surfaces simultaneously along the axis bisecting the angle between them, the separation between the focal points of the objective and the eye-piece is adjusted as required to re-focus the telescope in a continuous and reversible fashion without changing its overall dimensions.

Abstract: A targeting unit is incorporated into the main body of a solar telescope. The targeting image is provided by an aperture facing the sun in the housing of the telescope through which sunlight is received and directed to a transmissive viewing screen placed in the housing on the same side of the telescope's eyepiece. All parts of the targeting system are fixed to the housing of the telescope and removed from accidental contact by personnel operating the telescope, thereby minimizing the chance for events that might cause misalignments. In addition, this configuration makes it possible to easily position both the viewing screen and the eyepiece on the same side of the telescope following any degree of folding of the objective beam.

Abstract: A solar filter assembly combines a high-precision Fabry-Perot etalon with a variety of conditioning filters judiciously selected to effectively block completely all radiation except for the spectral line of interest. In addition, a tuning mechanism is provided to precisely control the peak frequency of the filter's output by varying the optical length of the etalon's cavity.

Abstract: A multi-layer thin-film narrow-band filter is fabricated by a process wherein each half of a symmetric stack is deposited under exact conditions, either successively or contemporaneously. The two halves of the filter structure are then combined and bonded together using a wet bonding process that remains reversible for a period of time sufficient for testing the filter and, if necessary, for separating the two halves to regain access to the spacer layer. Accordingly, the spacer layer may be adjusted to shift the peak wavelength, if necessary, to the precise design specifications for a particular application. After correction, the components of the symmetric filter are bonded again using the same wet process.

Abstract: A temperature-stable and temperature-tunable composite etalon with an increased field of view is constructed by partially filling the cavity with a transmissive parallel-plate filler. The coefficient of thermal expansion and the index of refraction of the filler material are selected so as to produce the desired rate of change of the optical length of the cavity as a function of temperature. The filler plate is preferably chosen to be significantly thicker than the remaining air gap in the etalon cavity. As a result, the fact that the filler plate occupies a large part of the cavity space increases the acceptance angle of the etalon of the invention in comparison with corresponding conventional air-spaced etalons.

Abstract: A compressive force is applied to a conventional air-spaced etalon filter to fine tune the thickness of the spacers to a precise and uniform optical length. The etalon is coupled to a housing device capable of adjusting the thickness of each spacer, thereby tuning the etalon to the desired filter wavelength. The resulting assembly is permanently set to the desired parameters for direct use in optical applications.

Abstract: A substantially neutral filter across the white-light spectrum is obtained by minimizing the wavelength-dependent effects of filtering components and of reflective coatings on surfaces. The incoming light is captured by a first prism and directed toward the interface formed by the optical contact of a second prism with a face of the first prism, where the light is partially reflected internally and partially transmitted into the second prism. The reflected light is further reflected internally and directed toward the image surface out of the first prism. The fraction of light transmitted into the second prism is reflected back and redirected out of the system toward the incoming beam. The amount of energy directed toward the image plane is controlled by the judicious selection of the refractive indices in the two materials at the contacting interface of the first and second prisms.