Patent ID: 6654061
Filing Date: 2003-11-25
Classification: H04N

Abstract:
A focus adjusting apparatus which performs focus adjustment by controlling an optical image formation system, comprising:a birefringent plate made of a uniaxial crystal which separates incoming light from an object into ordinary rays and extraordinary rays, the rays including all color components of the light, converging at different focal points from the birefringent plate in a direction of an optical axis; a polarizing plate, provided in front of the bireflingent plate, for controlling polarization direction of light wherein the light from the object is polarized by said polarizing plate and enters the bireflingent plate; an image sensor, provided behind said birefringent plate which senses said ordinary and extraordinary rays and converts them into an image signal and which is arranged so that the optical axis of the ordinary rays from said birefringent plate is normal to the photosensing surface of the image sensor, and whereby the ordinary rays converge to a point which is closer to the birefringent plate than a point to which the extraordinary rays converge; first filtering means for filtering a first signal component out of a luminance signal of the image signal obtained by said image sensor and outputting a first value corresponding to an amount of the first signal component; second filtering means for filtering a second signal component, having a frequency different from the first signal component, out of the luminance signal of the image signal obtained by said image sensor and outputting a second value corresponding to an amount of the second signal component; judging means for judging a focus condition of an image projected on said image sensor by comparing the first value with the second value, and control means for controlling the optical system to adjust the focus condition in accordance with a signal outputted from said judging means.