Focus detecting apparatus

• US 4,573,784 A
• Filed: 05/30/1985
• Issued: 03/04/1986
• Est. Priority Date: 12/11/1982
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Suzuki, Kenji
• Primary Examiner(s): ADAMS JR, RUSSELL E
• Application Number:
  US06/739,496
• Time in Patent Office: 278 Days
• Field of Search: 354/400, 354/402, 354/406, 354/407, 354/408
• US Class Current: 396/101
• CPC Class Codes: G02B 7/34 using different areas in a pupil plane

Abstract

This specification discloses a focus detecting apparatus having an optical system for forming a plurality of object images on the basis of object lights passed through different pupil areas of an objective lens, and a sensor for putting out a plurality of data signals for the respective object images, wherein the amount of relative deviation of the object images is detected by a predetermined operation based on the data signal to thereby discriminate the focus state of the objective lens and wherein in the data signals put out from the sensor, the number of the data signals used for an operation is varied in accordance with the focus state or other condition of the objective lens.

Claims

1. A focus detecting apparatus including:

(a) optical means;

(b) sensing means for sensing radiation distribution for forming an image formed by said optical means, said radiation distribution being formed from two image rays separated through different exit pupils of said optical means, and said sensing means comprising a first photosensitive array which forms electric signals corresponding to a radiation distribution formed by one of said image rays, and a second photo-sensitive array which forms electric signals corresponding to a radiation distribution formed by the other image ray; and

(c) discriminating means for effecting a detection operation of the focus state of said optical means, said discriminating means having;

(i) a first mode in which said discriminating means selects a smaller number of signals than the number of elements forming said first and second arrays, to detect the focus state on the basis of the selected signals from each array when the amount of defocus is over a predetermined value, said selected signals being output from elements from each of said first and second arrays; and

(ii) a second mode in which said discriminating means detects the focus state on the basis of the signals output from all the elements in said first and second arrays.

2. An apparatus according to claim 1, wherein said discriminating means has selecting means for selecting, in said first mode, only output signals from every other element in each of said first and second arrays.

3. An apparatus according to claim 1, wherein said discriminating means has selecting and calculating means for successively selecting a pair of adjacent elements in said first and second arrays and summing up the signals from the selected pairs to form said selected signals from each array in said first mode.

4. An apparatus according to claim 1, wherein said discriminating means has selecting and calculating means for successively selecting a pair of adjacent elements in said first and second arrays and averaging the signals from the selected pairs to form said selected signals from each array in said first mode.

5. A focus detecting apparatus comprising:

(a) optical means;

(b) sensing means for sensing a radiation distribution for forming an image formed by said optical means, said radiation distribution being formed from two image rays separated through different exit pupils of said optical means, and said sensing means comprising a first photosensitive array which forms electric signals corresponding to a radiation distribution formed by one of said image rays, and a second photo-sensitive array which forms electric signals corresponding to a radiation distribution formed by the other image ray;

(c) sample and output means for successively sampling signals output from each pair of photosensitive elements, wherein a predetermined operation is applied to the sampled signals from said first array to output third signals and wherein a predetermined operation is applied to the sampled signals from said second array to output fourth signals, when said optical means is in a defocus state; and

(d) means for detecting the focus state of said optical means, said detecting means detecting the correlation of image signals corresponding to the amount of defocus of said optical means on the basis of said third and fourth signals.

6. A focus detecting apparatus according to claim 5, wherein said sample and output means effects a summing operation of the outputs from each pair of said sensing elements which exist adjacent each other and each of the sums is used to effect autofocus operation.

7. A focus detecting apparatus according to claim 5, wherein said sample and output means calculates the average of outputs from each pair of said sensing elements which exist adjacent each other, and each average is used to effect autofocus operation.

8. A focus detecting apparatus according to claim 5, wherein said sample and output means selectively effects said operation by using all of the signals from each of said sensing means.

9. A focus detection apparatus including:

(a) optical means;

(b) a pair of sensing means each comprising an array of photo-sensitive elements, said two sensing means respectively receiving first and second radiation patterns of a detection scene formed by said optical means to form first data signals and second data signals respectively corresponding to said first and second radiation patterns; and

(c) discriminating means for effecting a detection operation of the focus state of said optical means on the basis of at least some of said first data signals and at least some of said second data signals, said discriminating means having a first mode in which said discriminating means selects some signals from each one of said first data signals and second data signals, said some signals being in a specific region of said radiation patterns and being output signals from a series of adjacent photo-sensitive elements, and a second mode in which said discriminating means selects some signals dispersedly existing over each one of said first and second radiation patterns, or some signals each of which is formed by calculating each pair of signals over each one of said first and second radiation patterns.

10. A focus detection apparatus according to claim 9, wherein the signals selected in said first mode are signals corresponding to the center area of said first and second radiation patterns.