AUTOMATIC FOCUS ADJUSTOR

• Main Author: KAYANO YASUAKI
• Format: Patent
• Language: English
• Published: 30.08.1988
• Subjects: ACCESSORIES THEREFOR; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USINGWAVES OTHER THAN OPTICAL WAVES; APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FORPROJECTING OR VIEWING THEM; CINEMATOGRAPHY; ELECTROGRAPHY; GYROSCOPIC INSTRUMENTS; HOLOGRAPHY; MEASURING; MEASURING DISTANCES, LEVELS OR BEARINGS; NAVIGATION; OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY; PHOTOGRAPHY; PHYSICS; SURVEYING; TESTING

PURPOSE:To accurately and stably decide focusing by switching an integration circuit to constant integration when one integral value reaches the threshold value of a comparator. CONSTITUTION:The signal of an infrared-ray photodetection sensor 1 is integrat ed by the integration circuit 3 and then inputted to the comparator 4. When the integral value of one of integration circuit 3 and 3 reached the threshold value of the comparator 4, the both enter constant integration. Consequently, the comparator 4 raises its output pulse and inputs it to terminals (a) and (b) of a microcomputer 10 when a larger integral value reaches the threshold value and when a smaller integral value reaches the threshold value after the switching to the constant integration. The microcomputer 10 controls the speed of an AF motor 12 according to the time difference between the signals inputted to its terminals (a) and (b). Consequently, factors of the difference in the distance of a subject and the reflection factor of the subject are not used to decide time difference, so focus decision making is accurately and stably performed.