Abstract: Apparatus for testing circular cylindrical or conical specularly reflective surfaces of pieces, e.g. optical elements or metal components, to be tested. A collimated light beam from a Fizeau interferometer is directed axially onto a specularly reflective conical surface of a member which reflects the light onto the surface to be tested. The surface to be tested, directly or indirectly, reflects the light onto the conical specularly reflective surface which, in turn, reflects it back towards the interferometer. Information on the trueness of the surface to be tested can be gained from inspection of the pattern of the interference between light projected by the interferometer and light reflected back to the interferometer.

Abstract: A vacuum document feeder which transports a document page in juxtaposition to an illumination platen of a reproduction apparatus where such page is illuminated for copying. The feeder includes a vacuum plenum having a reflective wall formed with a plurality of spaced ports overlying the exposure platen. A ported transport belt is moved in contact with the plenum wall to feed a document page to the platen for copying. The moving belt is positioned on the plenum wall so that the belt ports are maintained in spaced relation to the wall ports. Further, the wall ports and the belt ports are fluidically inter-connected so that vacuum within the plenum is effective to tack a document page to the moving belt for movement to the exposure platen. This structural arrangement prevents light trapping by the wall ports during illumination of such document page.