JPH0222613A - Focal point detecting device - Google Patents

Abstract

PURPOSE:To improve the effect of projection of auxiliary light by providing an auxiliary light projecter, and arranging in such a way that a continuous striped pattern formed of light reflected from an object plane is made incident on plural accumulative photoelectric converting element trains on which an image is formed by a photographing lens. CONSTITUTION:In the auxiliary light projecter for detecting a focal point, an illuminating light source LED unit 121, a pattern chart 122 having an oblong and striped density pattern, and a projecting lens 123 are disposed on an optical axis 131; since the pattern chart 122 is placed in the vicinity of the focal point of the projecting lens 123, the pattern chart 122 is image-formed onto the plane of the object in the distance. With such a fill-in light illuminator, an auxiliary light pattern covering three focal point detection areas in the focal length of all photographing lenses is obtained in the range equal to or less than the ceiling of the prescribed angle of view. Thus, a satisfactory auxiliary illuminating light is always obtained irrespective of the focal length of a projecting lens.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an auxiliary light for a focus detection device having a plurality of distance measuring points over a wide range within a photographic screen.

[Conventional technology]

Conventionally, as a type of focus adjustment device for cameras, the exit pupil of the photographic lens is divided into two by an optical system for focus detection, and the two subject images formed by the light flux passing through each pupil area are captured using a photoelectric element. A method is known in which light is received by an array (for example, a CCD sensor array), the focal state of the photographic lens is detected from the output, and the photographic lens is driven based on the detection result. Furthermore, a method has been proposed in which a plurality of such focus detection devices are installed together and focus detection is performed based on subject images at different positions within the photographic screen.

To briefly explain the conventionally known basic method of focus detection, in FIG.
A lower field lens FLD is arranged on the same optical axis as S. Behind it, two secondary imaging lenses FCLA and FCLB are arranged at symmetrical positions with respect to the optical axis. Further behind that is the sensor row SAA.

SAB is placed. Secondary imaging lenses FCLA, FCL
Apertures DIA and DIB are provided near B. The field lens FLD forms an exit pupil of the photographic lens LNS into two secondary images approximately on the pupil planes of the lenses FCLA and FCLB. As a result, the light beams incident on the secondary imaging lenses FCLA and FCLB are emitted from regions of equal area that do not overlap with each other and correspond to the respective secondary imaging lenses FCLA and FCLB on the exit pupil plane of the photographing lens LNS. It becomes what is given. When the aerial image formed in the vicinity of the field lens FLD is re-imaged onto the surfaces of the sensor arrays SAA and SAB by the secondary imaging lenses FCLA and FCLB, based on the displacement of the aerial image position in the optical axis direction, , sensor array SAA
, the two images on the SAB will change their positions. Therefore, by detecting the amount of displacement (shift) in the relative positions of the two images on the sensor array, it is possible to know the focal state of the imaging lens LNS.

FIG. 11 shows an example of photoelectric conversion outputs of two images formed on the sensor arrays SAA and SAB. The output of SAA is A(i),
Let the output of SAB be B (i). Note that the number of pixels of the sensor is required to be at least five, and preferably several dozen or more.

Claims (2)

[Claims] (1) In a focus detection device having a plurality of accumulation-type photoelectric conversion element arrays that receive light at different positions within a shooting screen, and an auxiliary light projector that measures the subject and emits light at least in low brightness, the plurality of The photoelectric conversion element arrays have sampling directions in the same first direction, and the auxiliary light projector is arranged in the first direction.
A striped pattern whose longitudinal direction is a second direction substantially perpendicular to the direction of is projected, and the light reflected by the subject of one continuous striped light pattern is imaged by an objective lens, A focus detection device characterized in that the focus detection device is configured to be incident on the plurality of storage type photoelectric conversion element arrays. (2) Upon receiving focal length information of the objective lens to be used, when the focal length of the objective lens is shorter than a predetermined value, auxiliary light is projected onto a specific portion of the plurality of storage type photoelectric conversion element arrays. 2. The focus detection device according to claim 1, further comprising means for disabling light output.