GB741127A - Improvements in and relating to optical light-projecting systems particularly for diascopic projection - Google Patents

Abstract

741,127. Optical systems. MARTIN H. Dec. 19, 1952 [Dec. 19, 1951]. No. 29775/51. Class 97 (1). An illuminating system for diascopic optical projection or for spot-lighting comprises a lamp 5, with a condenser system for producing a beam converging towards a point 3 near a lens 7 which images on to the object 10 a selected cross-section 8 of the converging beam, e.g. where it is uniform, a further condenser 9 concentrating the light transmitted by the object into a projection objective 11. In the form shown the lamp is disposed with its filament at the centre of a spherical reflector 6 and at the rear focus of one or more truncated ellipsoidal reflectors 1 surrounding a prismatic lens 4. When the system is used for spotlighting the object 10 is a mask shaped with the contour of the area to be lighted. A correcting member may be introduced if the light source is elongated and the shape of the object 10 is not, or vice versa. For this purpose a negative or positive cylindrical lens may be introduced between the lenses 7 and 9 or an inclined cylindrical mirror may reflect the beam through approximately 90 degrees. Where the source of light is a mercury arc an auxiliary lamp may be inserted in the system near the point 3 to project back to the main lamp to heat it and assist starting. This lamp may have a condensing system like the main lamp and the lens 7 may be movable to accommodate it. Specifications 327,129, (Class 97 (i)), 360,910, [Group XI], 567,154 and 573,700 are referred to.