Digital focus detecting device

Claim 2

A digital focus detection system for detecting the focus condition of an objective lens, comprising: optical means for forming a plurality of images of an object, image signal generating means, having a plurality of sensors positioned to receive the plurality of images, for generating a plurality of digital image signals corresponding to the intensity distributions on the plurality of sensors, respectively; peak detecting means for detecting a peak of the plurality of image signals; comparing means for comparing the detected peak with a predetermined constant level; discriminating means for discriminating whether the focus detection is impossible when the detected peak is under the predetermined constant level; and defocus amount calculating means for calculating the amount of defocus of the objective lens in accordance with the plurality of image signals when the detected peak is over the predetermined constant level.

Claim 3

The digital focus detection system as claimed in claim 1, wherein said optical means includes means for forming displaced first and second images of an object, said image signal generating means has first and second sensors positioned to receive the first and second images and adapted to generate first and second digital image signals corresponding to the intensity distributions on the first and second sensors, respectively, and wherein said defocus amount calculating means includes means for calculating the amount of defocus of the objective lens on the basis of the first and second image signals.

Claim 4

A focus detection system for detecting the focus condition of an objective lens, comprising: optical means for forming a plurality of images of an object; image signal generating means for generating a plurality of image signals corresponding to the intensity distributions of the plurality of images; signal dividing means for dividing one of the plurality of image signals into a plurality of block image signals; contrast detecting means for detecting each of contrasts in accordance with each of the block image signals; level signal generating means for generating a plurality of level signals each corresponding to each of the block image signals; comparing means for comparing each of the detected contrasts with each of the corresponding level signals at each of the block image signals; discriminating means for discriminating that the focus detection by using a block image signal is impossible when the detected contrast is under the level signal with respect to that block image signal; and defocus amount calculating means for calculating the amount of defocus of the objective lens in accordance with the block image signal with respect to which the detected contrast is over the level signal.

Claim 5

A focus detection system for detecting the focus condition of an objective lens, comprising: optical means for forming a plurality of images of an object; image signal generating means for generating a plurality of image signals corresponding to the intensity distributions of the plurality of images; signal dividing means for dividing one of the plurality of image signals into a plurality of block image signals; contrast detecting means for detecting each of contrasts in accordance with each of the block image signals; level signal generating means for generating a plurality of level signals each corresponding to each of the block image signals; comparing means for comparing each of the detected contrasts with each of the corresponding level signals at each of the block image signals; discriminating means for discriminating that the focus detection by using a block image signal is impossible when the detected contrast is under the level signal with respect to that block image signal; and defocus amount calculating means for calculating the amount of defocus of the objective lens in accordance with the block image signal with respect to which the detected contrast is over the level signal.

Claim 6

The focus detection system as claimed in claim 3, wherein said optical means includes means for forming displaced first and second images of an object, said image signal generating means has first and second sensors positioned to receive the first and second images and adapted to generate first and second image signals corresponding to the intensity distributions on the first and second sensors, respectively, and wherein said signal dividing means includes means for dividing the first image signal into a plurality of block image signals.

Claim 7

The focus detection system as claimed in claim 4, wherein the size of each of a plurality of areas corresponding to each of the block image signals is different from each other.

Claim 8

A focus detection system for detecting the focus condition of an objective lens, comprising: optical means for forming a plurality of images of an object; image signal generating means for generating a plurality of image signals corresponding to the intensity distributions of the plurality of images; signal dividing means for dividing one of the plurality of image signals into a plurality of block image signals; reliability indicating signal producing means for producing, in accordance with the block image signals, a plurality of reliability indicating signals each indicating the reliability of focus detection at each of the block image signals; reliability level signal generating means for generating a plurality of reliability level signals at each of the block image signals; comparing means for comparing the reliability indicating signals with the reliability level signals at each of the block image signals to discriminate whether or not the focus detection is possible at each of the block image signals; and defocus amount calculating means for calculating the amount of defocus of the objective lens in accordance with the block image signal at which the focus detection is discriminated to be possible.

Claim 9

A focus detection system for detecting the focus condition of an objective lens, comprising: optical means for forming a plurality of images of an object; image signal generating means for generating a plurality of image signals corresponding to the intensity distributions of the plurality of images; signal dividing means for dividing one of the plurality of image signals into a plurality of block image signals; reliability indicating signal producing means for producing, in accordance with the block image signals, a plurality of reliability indicating signals each indicating the reliability of focus detection at each of the block image signals; reliability level signal generating means for generating a plurality of reliability level signals at each of the block image signals; comparing means for comparing the reliability indicating signals with the reliability level signals at each of the block image signals to discriminate whether or not the focus detection is possible at each of the block image signals; and defocus amount calculating means for calculating the amount of defocus of the objective lens in accordance with the block image signal at which the focus detection is discriminated to be possible.

Claim 10

The focus detection system as claimed in claim 6, wherein said optical means includes means for forming displaced first and second images of an object, said image signal generating means has first and second sensors positioned to receive the first and second images and adapted to generate first and second image signals corresponding to the intensity distributions on the first and second sensors, respectively, and wherein said signal dividing means includes means for dividing the first image signal into a plurality of block image signals.

Claim 11

A focus detection system for detecting the focus condition of an objective lens, comprising: optical means for forming a plurality of images of an object by receiving light coming from the object; image signal generating means for generating a plurality of image signals corresponding to the intensity distributions of the object images each formed by light transmitted through a plurality of areas of the optical means; reliability indicating signal producing means for producing, in accordance with the image signals, a plurality of reliability indicating signals each indicating the reliability of focus detection at each of the areas of the optical means; reliability level signal generating means for generating a plurality of reliability level signals; comparing means for comparing the reliability indicating signals with the reliability level signals at each of the areas to discriminate whether or not the focus detection is possible at each of the areas; and defocus amount calculating means for calculating the amount of defocus of the objective lens in accordance with the image signal corresponding to an area at which the focus detection is discriminated to be possible.

Claim 12

A focus detection system for detecting the focus condition of an objective lens, comprising: optical means for forming a plurality of images of an object by receiving light coming from the object; image signal generating means for generating a plurality of image signals corresponding to the intensity distributions of the object images each formed by light transmitted through a plurality of areas of the optical means; reliability indicating signal producing means for producing, in accordance with the image signals, a plurality of reliability indicating signals each indicating the reliability of focus detection at each of the areas of the optical means; reliability level signal generating means for generating a plurality of reliability level signals; comparing means for comparing the reliability indicating signals with the reliability level signals at each of the areas to discriminate whether or not the focus detection is possible at each of the areas; and defocus amount calculating means for calculating the amount of defocus of the objective lens in accordance with the image signal corresponding to an area at which the focus detection is discriminated to be possible.

Claim 13

The focus detection system as claimed in claim 8, wherein the reliability indicating signal producing means includes contrast detecting means for detecting contrast of each of the images formed by the light transmitted through the plurality of areas of the objective lens, the reliability level signal generating means includes contrast level signal generating means for generating a plurality of contrast level signals each corresponding to each of the areas, and comparing means includes contrast comparing means for comparing the detected contrasts with the contrast level signals at each of the areas.

Claim 14

The focus detection system as claimed in claim 9, wherein the size of each of the areas in the image is different from each other.

Claim 15

A focus detection system for detecting the focus condition of an objective lens, comprising: optical means for forming a plurality of images of an object; image signal generating means, having a plurality of sensors positioned to receive the plurality of images, for generating a plurality of image signals corresponding to the light intensity distributions of the images formed on the plurality of sensors, respectively; reliability indicating signal producing means for producing, in accordance with the image signals, a reliability indicating signal indicating reliability of focus detection; reliability level signal generating means for generating a reliability level signal; comparing means for comparing the reliability indicating signal with the reliability level signal to discriminate whether or not the focus detection is possible; defocus detecting means for detecting defocus state of the objective lens in accordance with the plurality of image signals; and level signal control means for controlling the reliability level signal in accordance with the last result of the defocus detection.

Claim 16

A focus detection system for detecting the focus condition of an objective lens, comprising: optical means for forming a plurality of images of an object; image signal generating means, having a plurality of sensors positioned to receive the plurality of images, for generating a plurality of image signals corresponding to the light intensity distributions of the images formed on the plurality of sensors, respectively; reliability indicating signal producing means for producing, in accordance with the image signals, a reliability indicating signal indicating reliability of focus detection; reliability level signal generating means for generating a reliability level signal; comparing means for comparing the reliability indicating signal with the reliability level signal to discriminate whether or not the focus detection is possible; defocus detecting means for detecting defocus state of the objective lens in accordance with the plurality of image signals; and level signal control means for controlling the reliability level signal in accordance with the last result of the defocus detection.

Claim 17

The focus detection system as claimed in claim 11, wherein said optical means includes means for forming displaced first and second images of an object, said image signal generating means has first and second sensors positioned to receive the first and second images and adapted to generate first and second image signals corresponding to the intensity distributions on the first and second sensors, respectively.

Claim 18

The focus detection system as claimed in claim 12, further comprising means for cyclically operating the focus detection operation by the optical means, the image signal generating means, the reliability indicating signal producing means, the reliability level signal generating means, the comparing means and the defocus detecting means, and wherein the level signal control means includes means for controlling the reliability level signal in accordance with the result of the focus detection of the former cycle.

Claim 19

The focus detection system as claimed in claim 13, wherein the level signal control means includes means for controlling the reliability level signal so that the reliability level signal used when the result of the focus detection of the former cycle indicates that the focus detection is impossible is higher than that used when the result indicates that the focus detection is possible.

Claim 20

The focus detection system as claimed in claim 12, further comprising means for cyclically operating the focus detection operation by the optical means, the image signal generating means, the reliability indicating signal producing means, the reliability level signal generating means, the comparing means and the defocus detecting means, and wherein the level signal control means includes means for controlling the reliability level signal in accordance with the reliability of a predetermined kind of data used in the focus detection operation of the present cycle.

Claim 21

The focus detection system as claimed in claim 15, wherein the level signal control means includes means for controlling the reliability level signal, so that the reliability level signal, used when the reliability of the predetermined kind of data in the focus detection of the present cycle is lower than a predetermined level, is lower than that used when the reliability of the predetermined kind of data in the focus detection of the present cycle is higher than a predetermined level.

Claim 22

The focus detection system as claimed in claim 15, wherein the level signal control means includes contrast detecting means for detecting contrast of at least one of the images on the plurality of sensors and means for controlling the reliability level signal in accordance with the detected contrast.

Claim 23

The focus detection system as claimed in claim 15, wherein the level signal control means includes peak detecting means for detecting a peak of the plurality of image signals and means for controlling the reliability level signal in accordance with the detected peak.

Claim 24

The focus detection system as claimed in claim 12, further comprising correlating calculating means for calculating correlations between the first and second image signals while repeatedly shifting the second image signal relative to the first image signal by a given pitch to provide a set of correlations, the number of which is identical with the number of the shifts, best correlation finding means for finding a best correlation having a minimum value among the plurality of calculated correlations, contrast detecting means for detecting the contrast of at least one of the object images on the first and second sensors, normalizing means for normalizing the correlation of the minimum value by dividing the same by the detected contrast.