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US 5,510,837 AGranted
Automatic exposure control device performing weighted light measurement
AssigneeCanon Kabushiki Kaisha
InventorHirofumi Takei
Life of this patent
Estimating the term…
Abstract
An automatic exposure control device comprising a light measuring circuit for performing a weighted light measurement for a light measuring area set in a predetermined position within an image sensing plane, a discrimination circuit for detecting and evaluating the level of a luminance component in a video signal in each of a plurality of detecting areas set within the image sensing plane and for discriminating a photographic state while tracking a subject, and a compensation circuit for compensating a light measurement control signal produced by the light measuring circuit in accordance with a discriminating result made by the discriminating circuit.
Claims26
An exposure control device comprising:
- (a) light measuring means arranged to divide an image sensing plane into a plurality of blocks and to detect a luminance level of each block;
- (b) first detecting means for detecting a first light measurement value from luminance levels of the respective ones of n blocks constituting a central area including a central part of the image sensing plane from among said plurality of blocks;
- (c) second detecting means for detecting a second light measurement value from the luminance levels of the respective ones of m blocks of surrounding part of said central area of the image sensing plane;
- and
- (d) correction means arranged to discriminate a photographing state on the basis of a difference and a ratio of said first measurement value and said second measurement value.
2 more elements
An automatic exposure control device comprising:
- (a) light measuring means for performing a weighted light measurement for a light measuring area set in a predetermined position within an image sensing plane;
- (b) discriminating means for discriminating a photographic state by evaluating the distribution of luminance signal levels in each of a plurality of blocks set on the image sensing plane, said discriminating means being arranged to discriminate the photographing state on the basis of the difference and the ratio of a representative light measurement value of a central area in the image sensing plane and a representative light measurement value of an outside area of the central area;
- and
- (c) compensating means for compensating a light measurement control signal produced by said light measuring means in accordance with a discrimination result made by said discriminating means, wherein said compensating means is arranged such that a condition for transition to a compensation mode of compensating said light measurement control signal and a condition of releasing said compensation mode differ from each other.
1 more element
An exposure control device, comprising:
- (a) exposure control means for effecting exposure control on the basis of an image pickup signal outputted from image pickup means;
- (b) detecting means arranged to divide an image sensing plane into a plurality of blocks and to detect a luminance level of each block;
- (c) first computing means for computing representative light measurement value of an object from luminance level informations of each of the n blocks at the central part of the image sensing plane among said plurality of blocks, according to a first computing algorithm;
- (d) second computing means for computing a representative light measurement value of an outside part of the central part from the luminance level informations of each of n blocks located in the outside part according to a second computing algorithm which is different from said first computing algorithm;
- (e) discriminating means for discriminating a photographing state on the basis of a ratio of outputs of said first and second computing means;
- and
- (f) correction means for correcting said exposure control means on the basis of a result of discrimination effected by said discriminating means.
4 more elements
An exposure control device, comprising:
- (a) detection means for detecting an image signal level in a plurality of areas in an image sensing plane;
- (b) mode setting means, having a plurality of exposure control modes, for detecting a photographic state corresponding to an output of the detection means and for selecting an exposure control mode corresponding to the detected photographic state;
- (c) control means for controlling the mode setting means for making different a switch-over condition for switch-over from a first exposure mode to a second exposure mode from a restoring condition for restoring from the second exposure mode to the first exposure mode by the mode setting means.
An exposure control device for controlling exposure according to an image signal level, comprising:
- (a) exposure control means for performing exposure control so as to cause the image signal level to reach a predetermined value;
- (b) detection means for detecting image signal levels in a plurality of areas on an image sensing plane;
- (c) discrimination means for discriminating a predetermined photographic state on the basis of an output of the detection means,
- (d) correction means for correcting an operation of the exposure control means when the predetermined photographic state is discriminated by the discrimination means, and
- (e) control means for making an operation condition for an execution of a correction operation of the correction means different from a condition for an execution of a release of the correction operation of the correction means.
2 more elements
Dependencies are inferred from the claim text.