Photometric optical system for external light injection system white balance device of video camera

Abstract

Abstract PURPOSE:To prevent a drop of the light quantity of a light beam which has been made incident on an image forming lens system, and to equalize an illuminance distribution on the surface of a photodetector, by constituting the titled system of the image forming lens system being different from a photographic lens, and a condenser lens for projecting an exit pupil of its image forming lens system, onto the surface of the photodetector positioned in the rear. CONSTITUTION:A light beam is made incident from the left, and an image of an object to be photographed is formed on a condenser lens 5 by an image forming lens 4. Subsequently, the condenser lens 5 projects an exit pupil of the image forming lens 4 onto the photodetecting surface of a photodetecting part 6 for detecting a color temperature, which is placed in the rear. In this way, the photodetecting part 6 receives the light beam, and based on its output, an automatic white balance is executed. That is to say, since a white diffusion plate and a lenticular lens are not used, the light beam reaches the surface of the photodetector without dropping the light quantity. Accordingly, with respect to an object to be photographed of a low illuminance, as well, the white balance can be executed. Also, since the light beam is diffused onto the surface of the photodetector by using the condenser lens, nonuniformity of a diffusion caused by a directivity of the diffusion plate does not occur.

Inventors

• 👤 Koji Iida
• 👤 幸司 飯田
• 👤 Akiyoshi Nakamura
• 👤 昭義 中村
• 👤 Hiroshi Otsuka
• 👤 博司 大塚

Bibliographic Details