Focus detection system and lighting device therefor

Abstract

A lighting device such as an electronic flash device attachable to a camera body includes first and second light projecting optical systems which project first and second light fluxes for illuminating an object to aid focus detection by a focus detection device. The second light flux spreads at a larger solid angle than the first light flux and illuminates a first distance zone which extends to a closer distance side while covering the whole of a second distance zone illuminated by the first light flux. An optical wedge disposed in the second light projecting optical system deflects a part of the second light flux towards the closer distance side of the first distance zone. Another lighting device includes a single light projecting optical system but it also includes an optical wedge for deflecting a part of a light flux projected by the light projecting optical system to widen a distance zone illuminated by the light flux towards a closer distance. The optical wedge also serves to produce a difference in intensity distribution of the light flux such that the light flux has higher intensity at a part thereof for illuminating a farther distance side of the distance zone than at a part thereof for illuminating a closer distance side of the distance zone. A light source of the light projecting optical system(s) is provided with a conical light reflecter surrounding a light emitting diode to reflect light emitted from side surfaces of the light emitting diode forward.