Detector for focusing state

Abstract

Abstract PURPOSE:To prevent the flickering in display and the minute oscillation of a lens by applying hysteresis at the varying decision level of an evaluation value between the time when a focusing state changes from a non-focusing state and when the non-focusing state changes to the focusing state. CONSTITUTION:Part of the object light past a photographing lens 4 passes through the semitransparent part 1a of a movable mirror 1, is reflected on an auxiliary mirror 5 and is made incident to a photoelectric transducer 3. The analog voltage corresponding to the accumulated charge is subjected to A/D conversion with a converter 10, and an evaluation value Vn is calculated in a CPU11. The discriminated output is displayed via driving circuit 12 on display elements DA, DB, DC. Thresholds -X, X are determined with a focusing point O as a center, and the regions of front focus and rear focus are determined as A, C. Decision levels are provided above and below apart by (r) from the -X, X as centers. The value Vn is made the threshold -X +r of A B, the threshold X-r of C B, the threshold -X-r of B A, and the threshold X+r of B C.

Inventors

• 👤 Yukio Nakajima
• 👤 幸夫 中島

Bibliographic Details