Automatic focus controlling device

• Main Author: NUMATA; SABURO
• Format: Patent
• Language: English
• Published: 21.06.1983
• Subjects: DIAGNOSIS; GYROSCOPIC INSTRUMENTS; HUMAN NECESSITIES; HYGIENE; IDENTIFICATION; MEASURING; MEASURING ANGLES; MEASURING AREAS; MEASURING DISTANCES, LEVELS OR BEARINGS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS; MEASURING LENGTH, THICKNESS OR SIMILAR LINEARDIMENSIONS; MEDICAL OR VETERINARY SCIENCE; NAVIGATION; OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY; PHYSICS; SURGERY; SURVEYING; TESTING

In an optical instrument such as a photographic camera or an endoscope, the focus of an image of the object to be observed or photographed is automatically controlled based on the distance automatically measured. The distance of the object is automatically measured by use of a light source for illuminating the object, a photodetector, an image focusing optical system for focusing the image of the object on the photodetector, and an electric circuitry connected with the photodetector. The intensity of the illumination is periodically changed and the light reflected by the illuminated object received by the photodetector is measured. When the level of the output of the photodetector becomes equal to a predetermined level, a signal is generated to indicate that the brightness of the illuminated object has reached a predetermined level. Since the light intensity of the illumination at this point corresponds to the distance of the object, the distance is thus measured. According to the measured distance, a focusing lens is driven to automatically obtain a focused image.