Distance measurement apparatus and optical system using the same

Abstract

A CPU causes a Xe tube to emit light by charging a charging capacitor through an emission control circuit. Flash light from the Xe tube is projected toward an object to be measured through a mask, a visible light cutting filter, and a projection lens. Light reflected by the object is incident on a light-receiving element through a light-receiving lens and the visible light cutting filter. An output from the light-receiving element is input to a light position detection circuit. The CPU then calculates the distance to the object in accordance with an output from the light position detection circuit. A camera which can be used in water includes an electronic flash section capable of controlling its light amount. An underwater detection section detects whether the camera is used in water, and sends the detection result to a CPU. A distance measurement section projects a distance measurement light beam onto an object to be photographed, and measures the amount of light reflected by the object. The CPU estimates a light attenuation ratio in the environment where the camera is used on the basis of the detection result and the reflected light amount measurement result, and sets the amount of light to be emitted from the electronic flash section. With this operation, the electronic flash section is caused to emit light, and exposure in the camera is controlled by an exposure control section.