Abstract: A compression type A/D converter for producing an output in the form of a digital value almost equal to the square root of the input analog value. For this purpose, the A/D converter is constructed as a dual-slope A/D converter in which the current signal for inverse integration increases as a function of a polynominal of order n (n=1) of the inverse integration period.

Abstract: In an in-focus state detection device for a camera for forming a plurality of images based on light fluxes transmitted through different areas of a pupil of an imaging lens and detecting the state of the imaging lens based on a relative positional relationship of the images, an optical system for forming the images and a sensor for sensing the images are constructed in a unit through two opposing mirrors to allow ready mounting of the optical system and the sensor, and the positions of the optical system and the sensor are adjusted through the unit member.

Abstract: This specification discloses an energizing control of a drive element for driving a motor or the like which drives a focusing lens. The energization is controlled on the basis of the detection of whether or not the position of the focusing lens is within the quasi-in-focus state, and when the continuation of the quasi-in-focus state for a predetermined time period or more is detected, energization of the driving element is stopped.

Abstract: An automatic focusing optical apparatus comprises an automatic focusing device which automatically controls the focal point of an optical system and is arranged to be operatable in such a manner that, once the optical system is focused on an object, the focal point of the optical system is fixed to be unvarying irrespectively of changes in the distance to the object; a display device which is capable of displaying the in-focus and defocus states of the optical system independently of the automatic focusing device; and control means for allowing the display device to display solely the in-focus state when the automatic focusing device fixes the focal point of the optical system to be unvarying irrespectively of changes in the distance to the object after the optical system is once focused on the object.