Reflector for varying illumination distribution

• US 4,323,952 A
• Filed: 05/30/1980
• Issued: 04/06/1982
• Est. Priority Date: 06/21/1979
• Status: Expired due to Term

• Current Assignee: Rollei Werke Franke and Heidecke KG
• Original Assignee: Rollei Werke Franke and Heidecke KG
• Inventors: Proske, Joachim
• Primary Examiner(s): Lechert, Jr., Stephen J.
• Application Number:
  US06/154,968
• Time in Patent Office: 676 Days
• Field of Search: 362/17, 362/18, 362/276, 362/280, 362/308, 362/318
• US Class Current: 362/17
• CPC Class Codes: G03B 15/05 Combinations of cameras with electronic flash apparatus; Electronic flash units
• CPC Class Codes: G03B 2215/0528 movable reflector, e.g. change of illumination angle or illumination direction

Abstract

The angular distribution of illumination passing through a selectively diffusing element can be varied by placing the diffusing element in a reflector unit so that the diffusing element is in the path between a light source and the object to be illuminated. A variable diffuser can comprise a liquid-crystal cell driven by a variable voltage to control the amount of diffusion by the reflector unit. The control voltage can be set in accordance with change in focal length in a zoom lens of a camera using the light source and reflector unit as a flash gun.

Claims

1. A camera and flash unit combination, said camera having a lens system with a variable focal length, and said flash unit comprising

a light source and a reflector mounted to effectively provide a front surface of said flash unit at which a selective portion of said light from said source is scattered, and

means for selectively controlling the relative angular distribution of the light that is transmitted through said front surface, by generating a control voltage and applying said control voltage to said at least one liquid-crystal cell to control the amount of said scattering, including at least one nematic liquid-crystal cell located in said transmitting surface of said flash unit and means for adjusting the magnitude of said control voltage in accordance with the focal length of said lens system to provide the corresponding relative angular distribution.

2. The flash unit of claim 1, said lens system including a zoom lens system, said means for selectively controlling the relative angular distribution comprising

a variable resistor and linkage means for changing the value of said variable resistor in correspondence to the focal length setting of said zoom lens system.

3. The flash unit of claim 2, said zoom lens system including means for adjusting said focal length by motion of one component of said zoom lens system along a predetermined direction,

said variable resistor comprising a movable center tap, and

said linkage means comprising a mechanical linkage between said movable component of said zoom lens and said movable center tap of said variable resistor.