Abstract: A novel device for use as an additive lamphouse in contact printing. White light is emitted by a source, collimated and then passed through a dispersion element to form a spectrum. The light is then selectively attenuated by wavelength to allow exact control of the color mixture of the light which falls on the negative and the positive contact. The use of a dispersion element rather than the dichroic principle of the prior art allows selective control of the color mixture of the light incident to the negative and thus to the contact by providing an improved control of the homogenuity of the color across the illuminated field. Also the problem of "color wedging" has been markedly reduced. The contact printer according to the present invention is more compact than those of the prior art and may be produced at a reduced cost.

Abstract: A teaching aid for demonstrating the component pure spectral colors of white light and the effect of selective recombination thereof. It utilizes the diffraction principle to produce a spectrum from white light and selectively filters the spectrum. By splitting the filtered light prior to recombination, it is possible to project an image of the selective filter and the recombined selectively filtered light adjacent to each other on a projection screen. Thus, the effects of the variation of the filter is shown directly by a variation in the color and intensity of the recombined light.