Abstract: An electro-optic distance or profile measuring device focusses an energy beam into a line (4) which intersects a surface (5) under examination at at least one point. The energy scattered by the surface (5) is imaged onto a detector (6) whereby analysis of the image intensity distribution provides a measure of the distance from a reference point to the intersection point. The focussing means may be an astigmatic confocal microscope (3) which is confocal in one dimension. The energy beam may be light, other electromagnetic radiation, particle beams or a acoustic waves.

Abstract: Transmission holograms which produce a multicolor image when illuminated by white light are prepared by making the hologram as a number of superimposed component holograms of images of a subject. The images are formed either by an optical imaging system of by separate primary holograms of the subject. Each primary hologram is formed using coherent light of one wavelength to be seen when viewing the final transmission hologram, and the primary hologram is illuminated with coherent light of that wavelength when providing its image for the component hologram. The use of a sandwich of two photosensitive media, each containing at least one component hologram, to form the product transmission hologram is also described.