Patent ID: 6157783
Filing Date: 2000-12-05
Classification: G02B

Abstract:
An automatic focus adjusting device which forms two images of a subject and which measures a focus state of an objective lens or a distance to a subject based on light intensity distributions of said two images, said automatic focus adjusting device comprising:a photosensor on which said two images of a subject are formed;an assist light source which irradiates said subject with assist light;first focus detecting areas which are set up on said photosensor and which have a first predetermined defocus detecting range over which a first amount of defocus is detected;second focus detecting areas which are set up on said photosensor and which have a second predetermined defocus detecting range over which a second amount of defocus is detected, said second predetermined defocus detecting range being wider than said first predetermined defocus detecting range of said first focus detecting areas;a focus detecting area switch which selects between said first and second focus detecting areas; anda focus detector which performs focus detection based on one of said first and second focus detecting areas;wherein said focus area switch switches from said first focus detecting areas to said second focus detecting areas and said focus detector performs focus detection based on said second focus detecting areas when said subject is irradiated with assist light for focus detection.