Observation device and focus detection method comprising a controller to execute an imaging operation and to detect focus position based on an evaluation value

Abstract

An observation device, comprising an AF detection circuit that calculates an evaluation value showing a larger value as degree of focus increases, based on an image signal, and a controller that detects focus position where focus is achieved based on the evaluation value, wherein the controller, when peaks of the evaluation value have been detected for different focus positions, detects a minimum of the evaluation value between focus positions of the plurality of peaks, and in the event that a first difference between a first peak, among the plurality of peaks, and a focus position of the minimum, and a second difference between the minimum and a focus position of a second peak, among the plurality of peaks, are within respective specified ranges, detects a focus position where focus is achieved based on the focus position of the minimum.