A modified Michelson type of interferometer having a pair of substantially identical refractive prisms, each having a cross sectional shape of 1/2 of a hexagon, the division being along a line bisecting opposite sides of the hexagon, where each of the prisms has a side for beam input or output, a side that is coated to provide a mirror for beam reflection and a beamsplitter coating applied to one of the two surfaces along the line of division. Additionally, a collimating and/or focusing lens may be integral with the prism having the input or output side, such that linear, constant speed, relative scanning of the prisms in the direction of the line of division of the prisms enables the elimination of the mounting of all components, made a part of or attached to the prisms, to an optical bench.

A laser referencing system is disclosed which is used in a refractively scanning interferometer. The interferometer optics comprise a fixed wedge-shaped prism having a beamsplitter surface, a movable wedge-shaped prism, and two corner cube reflectors. A laser clocking beam enters the interferometer on a path below the infrared analytical beam, and leaves the interferometer on a path above the infrared beam. Quadrature control of the laser beams is used to control the ends of the scanning sweeps, eliminating the need for a third, "white light" interferometer beam. ZPD alignment is accomplished by horizontal adjustment of the fixed beamsplitter prism. The interferometer optics are supported three-dimensionally in a cast shell.

An interferometer/spectroradiometer that uses a beamsplitter means for dividing an input beam into two separate beams and presents the resultant beams to a rotary refractive window from symmetrically oriented optical elements such that the optical path differences through the refractive window as it rotates are additive and non-linearities are subtracted. The beams are returned through the refractive window to the beamsplitter for dividing the input beam, where fringes are generated for application to appropriate detectors. The detector output is applied to Fourier transform computer equipment for digitizing and processing for presentation on a spectrum display device.

A Michelson interferometer has a wedge-shaped beamsplitter (7) and compensator (9) plates of substantially identical wedge angle and thickness. The compensator plate is positioned to cancel out beam displacement and deviation introduced by the beamsplitter plate.

A double beam interferometer using the refractive scanning method is disclosed which includes a first fixed optical body having a pair of parallel principal surfaces, a second fixed optical body having a pair principal surfaces, one of which faces and is parallel to one principal surface of the first fixed optical body, and the other of which makes a predetermined angle with the one principal surface of the second fixed optical body, a movable optical body having a pair of principal surfaces, one of which faces and is parallel to the other principal surface of the second fixed optical body, and the other of which makes the predetermined angle with the one principal surface of the movable optical body in such a manner that the predetermined angle of the second fixed optical body and the predetermined angle of the movable optical body are formed on opposite sides, driving means for moving the movable optical body on a plane containing the one principal surface of the movable optical body, a semitransparent mirror provided on one of facing principal surfaces of the first and second fixed optical bodies for dividing light from a light source into transmitted light and reflected light, and first and second reflecting mirrors for reflecting the transmitted light and reflected light in a direction opposite to an incident direction, respectively.