Abstract: The conventional two plates with beamsplitter of the Mirau interferometer are replaced with two achromatic ?/4 retarders. The upper surface of the second retarder is coated with a 50 percent reflecting film, so that it also functions as a beamsplitter. The objective is illuminated with a linearly polarized beam. As a result of this arrangement, the test and reference beam emerging from the Mirau interferometer are orthogonally polarized beams suitable for achromatic phase shifting, thereby facilitating the use of the Mirau interferometer for monochromatic to broadband phase-shifting interference microscopy. Alternatively, it can be used for equalization of beams intensity by placing a rotatable polarizer at the exit of the objective.

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.