Photographic contact or projection printers

摘要

694,154. Photographic contact and projection printing apparatus. POTTER, R. S. Dec. 7, 1951 [Oct. 9, 1951], No. 28731/51. Classes 98 (i) and 98 (ii). The light source of the apparatus comprises two fluorescent electric discharge tubes emitting light of different colours, and an adjustable shutter whereby the ratio of the intensities of the light emitted from the system by each tube may be controlled. Preferably, each tube is formed to provide a number of spaced lightemitting sections arranged side by side, sections of one tube alternating with sections of the other tube, a housing with a number of adjacent compartments all open on the same side, and shutter means to close the openings in alternate compartments and adjustable to vary the ratios of the intensities of the light emitted from the system by each tube. The apparatus is intended particularly for use with photographic sensitive material the contrast of which varies with the colour of the exposure light. As shown in Fig. 1, a housing 1 for the light source is divided by partitions 6. Fluorescent tubes 9, 10 emitting light of different colours both consist of U shaped portions 11 connected by straight portions 12. The portions 11 of tube 9 lie in alternate compartments 7 between partitions 6, and the portions 11 of tube 10 lie in the intermediate compartments. The portions 12, and if desired also the curved parts of portions 11, lie outside the compartments, and are either masked by opaque plates or coated with opaque material. A plate 15 is mounted, by means of studs 17 and slots 16, to slide on the front of the housing, and is formed with apertures of the same size as the openings of the compartments and intermediate opaque strips 19 of similar width. By sliding plate 15 by means of a handle 18, the strips may be moved from one position in which the portions 11 of tube 9 are covered by strips 19, to another position in which the portions 11 of tube 10 are covered, the intermediate positions of plate 15 giving light from both sources mixed in any required proportion when diffused as by a diffusing plate. The diffused light may, for example, illuminate a negative in a photographic enlarger; when the light sensitive material receiving the image is of the kind yielding a degree of contrast which varies with the colour of the exposure light, and when the colours and intensity of the light emitted by each tube is properly chosen, the degree of contrast obtained is continuously variable by moving plate 15, and can be indicated by a pointer on plate 15 and a scale on body 1. The tubes have fluorescent coatings having strong emission in a narrow spectral range, and may be coated with lacquer containing dyes to absorb unwanted emissions. Specifications 494,088, 547,060, 547,883 and 552,368 are referred to.