FOCUS DETECTION APPARATUS, IMAGE PICKUP APPARATUS, IMAGE PICKUP SYSTEM, FOCUS DETECTION METHOD, AND NON-TRANSITORY COMPUTER-READABLE STORAGE MEDIUM

• US 20140146218A1
• Filed: 11/25/2013
• Published: 05/29/2014
• Est. Priority Date: 11/29/2012
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Kunieda, Shutaro, Ogawa, Takeshi
• Granted Patent: US 8,988,595 B2
• Time in Patent Office: Days
• US Class Current: 348/345
• CPC Class Codes: H04N 23/672 based on the phase difference signals
• CPC Class Codes: H04N 25/62 Detection or reduction of noise due to excess charges produced by the exposure, e.g. smear, blooming, ghost image, crosstalk or leakage between pixels
• CPC Class Codes: H04N 25/704 Pixels specially adapted for focusing, e.g. phase difference pixel sets

Abstract

A focus detection apparatus performs focus detection by a phase difference method using an image pickup element including first and second pixels, the focus detection apparatus includes a correlation data calculator which calculates correlation data between pixel data obtained from the first pixels and the second pixels in ranges of image data, a detector which detects a saturated pixel having a level of at least a predetermined value in each of the ranges, an adding processor which performs an addition processing of the correlation data calculated in each of the ranges based on a detection result, and a defocus amount calculator which calculates a defocus amount based on a result of the addition processing, and the adding processor performs the addition processing using correlation data obtained from a first range in which the number of the saturated pixels is less than a predetermined number.

Claims

1. A focus detection apparatus which performs focus detection by a phase difference method using an image pickup element including a plurality of first pixels and a plurality of second pixels, each pair of the first and second pixels sharing one microlens, the focus detection apparatus comprising:

a correlation data calculator configured to calculate correlation data between pixel data obtained from the plurality of first pixels and pixel data obtained from the plurality of second pixels in a plurality of ranges of image data obtained from the image pickup element;

a detector configured to detect a saturated pixel having a level of at least a predetermined value in each of the plurality of ranges;

an adding processor configured to perform an addition processing of the correlation data calculated in each of the plurality of ranges, based on a detection result of the saturated pixel by the detector; and

a defocus amount calculator configured to calculate a defocus amount based on a result of the addition processing,

wherein the adding processor performs the addition processing using correlation data obtained from a first range in which the number of the saturated pixels is less than a predetermined number.

2. The focus detection apparatus according to claim 1, wherein the adding processor uses the correlation data of the first pixels or the second pixels in a second range adjacent to the first range as the correlation data in the first range, for the first range in which the number of the saturated pixels among the first pixels or the second pixels is not less than the predetermined number.

3. The focus detection apparatus according to claim 2, wherein when the saturated pixel is included in the first pixels or the second pixels, the adding processor uses the correlation data in the second range adjacent to the first range as the correlation data in the first range, for a range in which the saturated pixel exists in the first range.

4. The focus detection apparatus according to claim 1, wherein when the saturated pixel is included in a first pixel array including the plurality of first pixels or a second pixel array including the plurality of second pixels, the adding processor performs the addition processing by multiplying a weight depending on she number of the saturated pixels by the correlation data in the first range.

5. An image pickup apparatus comprising the focus detection apparatus according to claim 1.

6. The image pickup apparatus according to claim 5,

wherein the first pixel and the second pixel receive light beams passing through different regions of an exit pupil different from each other in a pupil dividing direction so as to generate signals to be used to calculate the correlation data, and

wherein the adding processor adds the correlation data of each of the plurality of ranges in a direction orthogonal to the pupil dividing direction.

7. An image pickup system comprising:

an image pickup apparatus according to claim 5; and

a lens apparatus configured to be removably mounted on the image pickup apparatus,

wherein the image pickup apparatus performs a drive control of the lens apparatus based on a signal obtained from the focus detection apparatus.

8. A focus detection method of performing focus detection by a phase difference method using an image pickup element including a plurality of first pixels and a plurality of second pixels, each pair of the first and second pixels sharing one microlens, the focus detection method comprising the steps of:

calculating correlation data between pixel data obtained from the plurality of first pixels and pixel data obtained from the plurality of second pixels in a plurality of ranges of image data obtained from the image pickup element;

detecting a saturated pixel having a level of at least a predetermined value in each of the plurality of ranges;

performing an addition on processing of the correlation data calculated in each of the plurality of ranges, based on a detection result of the saturated pixel; and

calculating a defocus amount based on a result of the addition processing,

wherein the addition processing is performed using correlation data obtained from a range in which the number of the saturated pixels is less than a predetermined number.

9. A non-transitory computer-readable storage medium which stores a program to cause a computer to execute each step of the focus detection method according to claim 8.