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 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 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 telescope system has an intelligent motor controller for accurately controlling telescope position to facilitate location of celestial objects and to precisely control the speed at which the telescope moves to facilitate tracking of celestial objects. An optical encoder utilizes two photodetectors to provide enhanced servo control of the telescope positioning motors, a calibration circuit eliminates a need to test LED's during assembly of the optical encoder and a brushless mount provides electrical communication to an altitude drive motor located in a fork thereof in a manner which mitigates problems due to undesirable wrapping of an electrical cable around the mount as the mount rotates in azimuth.