WHITE BALANCE FILTER IN AUTOMATIC COLOR TEMPERATURE SENSOR

PURPOSE:To relieve the change in object conditions and the displacement and quantity of the detected light and to enable detection in a high range with high accuracy by detecting information on a color temp. by a white balance filter which condenses various kinds of incident light and diffuses and mixes the incident light to make the light optically white. CONSTITUTION:A white balance filter 1 is formed of a transparent synthetic resin having excellent optical properties and is provided with a main body 11 consisting of a plate body. The rear surface 111 thereof is projected to one large spherical convex face to constitute a convex lens for condensing with about 30 deg. condensing angle. The front face 12 is formed to a rugged surface on which small spherical projections are distributed over the entire surface to constitute a diffusion plate. The filter is provided integrally with such condenser lens and the diffusion plate. The incident light is diffused by the front face 12 and is condensed by the rear face 111 and is supplied as optically white light to rear photodiodes 2, 3. A casing 5 is formed to a trumpet shape. The white balance filter 1 is attached to the front end of the casing and a printed wiring board 4 attached with the photodiodes 2, 3 is supported to the rear end thereby enclosing the photodiodes 2, 3.