GB1047603A - Illuminating apparatus - Google Patents

Abstract

1,047,603. Illuminating apparatus. S. H. HINE. June 24, 1965, No. 26809/65. Heading G2A. [Also in Division F4] An illuminating apparatus comprises a first light source, supported from a wall 10, which is a planar arrangement of annular fluorescent tubes 18, either in the form of separate concentric circles or a continuous spiral. The turns are closest together at the centre, where they surround an opening 12. Through this opening projects the lens system 36 of a camera 34. Also comprised is a second light source 44, projecting a beam of light 54A which is generally divergent after passing through a cross-over point 54. The divergent beam is partially reflected by a semi-relective mirror or beam-splitter 30, set at 45 degrees to the axis of the beam. The mirror 30 is set in a hermetically sealed, preferably evacuated, housing 24 secured to a flanged part 14 of wall 10 surrounding opening 12. The housing has a window 26 and two further windows 28. The optical geometry is such that the reflected beam 54A appears to originate at a virtual source 58 at the centre of the camera diaphragm 38. The beam falls on a retro-reflective screen 60, so that all the light is reflected back to the virtual source 58. At the same time, the screen is also illuminated by light from source 18. Thus any object, such as a ball 66, in front of the screen, is illuminated in such a way that its outline shows up on a photograph sharply and clearly, and free from penumbral shadows which would be produced by random reflections from the surface of the ball itself (Fig. 4a, not shown). If source 18 were extinguished, and source 44 used alone, the ball would show up on a photograph as a black circle having a sharp clear outline against a white background. A drawing which is to be reproduced may be made directly on the retro-reflective screen, or on a transparent overlay placed against it. The illuminating system of the invention is not considered as limited to the photographic application described.