Abstract: The present invention provides a method and apparatus for measuring both the linear displacement and angular displacement of an object using a linear interferometer system and an optical target comprising a lens, a reflective surface and a retroreflector. The lens, reflecting surface and retroreflector are specifically aligned and fixed in optical connection with one another, creating a single optical target which moves as a unit that provides multi-axis displacement information for the object with which it is associated. This displacement information is useful in many applications including machine tool control systems and laser tracker systems, among others.

Abstract: A wavelength division multiplex/demultiplexer (WDM) has a plurality of narrow-band zeroth order resonant grating filters (10a-10e) to multiplex or demultiplex multiple wavelengths that have very close channel spacing. In one embodiment, a plurality of these filters (10a14 10e) are assembled in a block (20) in parallel and at an angle to a propagation axis to reflect signals for a plurality of discrete frequency channels. The block spacing material (21) can be liquid or solid. In another embodiment, the angular orientation of the resonant grating filters (10f-10g) is varied slightly to provide reflected signals for the plurality of discrete frequency channels. Crosstalk between channels can be reduced by reflecting each signal three times. Individual filters can be of binary structure or a sinusoidal grating (16) and can be made using thin film techniques.

Abstract: A method is described for a systematic method of interpreting interference fringes obtained by using a corner cube retroreflector as an alignment aid when aigning a paraboloid to a spherical wavefront. This is applicable to any general case where such alignment is required, but is specifically applicable in the case of aligning an autocollimating test using a diverging beam wavefront. In addition, the method provides information which can be systematically interpreted such that independent information about pitch, yaw and focus errors can be obtained. Thus, the system lends itself readily to automation.