Image pickup apparatus, control method, and non-transitory computer-readable storage medium with aberration and object information acquisition for correcting automatic focus detection

Patent metadata

Field	Value
Publication number	US-10122911-B2
Application number	US-201715413487-A
Country	US
Kind code	B2
Filing date	Jan 24, 2017
Priority date	Feb 9, 2016
Publication date	Nov 6, 2018
Grant date	Nov 6, 2018

Abstract

An image pickup apparatus is capable of executing automatic focus detection of an imaging optical system, and includes a first acquisition unit configured to acquire aberration information of the imaging optical system, a second acquisition unit configured to acquire object information of an object in a focus detecting area, a calculation unit configured to calculate, based on the aberration information of the imaging optical system and the object information, a correction value used to correct a difference between a focus state of a captured image and a result of the automatic focus detection, caused by the aberration of the imaging optical system, and a correction unit configured to correct the result of the automatic focus detection using the correction value.

First claim

What is claimed is:

1. An image pickup apparatus capable of executing automatic focus detection of an imaging optical system, the image pickup apparatus comprising:
a first acquisition unit configured to acquire aberration information of the imaging optical system;
a second acquisition unit configured to acquire object information of an object in a focus detecting area;
a determination unit configured to determine, based on the aberration information, whether it is necessary to obtain color information, angular information, and spatial frequency information of the object;
a calculation unit configured to calculate, based on the aberration information of the imaging optical system and the object information, a correction value used to correct a difference between a focus state of a captured image and a result of the automatic focus detection, caused by the aberration of the imaging optical system; and
a correction unit configured to correct the result of the automatic focus detection using the correction value.

2. The image pickup apparatus according to claim 1 , wherein the object information contains at least one of color information, angular information, and spatial frequency information of the object in the focus detecting area.

3. The image pickup apparatus according to claim 1 , wherein the aberration information of the imaging optical system contains information on at least one of an astigmatism, a chromatic aberration, and a spherical aberration.

4. The image pickup apparatus according to claim 1 , wherein the aberration information of the imaging optical system contains information on a plurality of imaging positions each of which corresponds to a maximum value of a modulation transfer function corresponding to one of a plurality of different spatial frequencies.

5. The image pickup apparatus according to claim 4 , wherein the calculation unit calculates the correction value based on a result of calculating an imaging position corresponding to a spatial frequency for a focus detection using information of an imaging position of the imaging optical system for each spatial frequency of the object, and a result of calculating an imaging position corresponding to a spatial frequency for the captured image using the information of the imaging position of the imaging optical system for each spatial frequency of the object.

6. The image pickup apparatus according to claim 5 , further comprising a setting unit configured to set a first weighting coefficient that depends on a first color, a second color, and a third color in color information of the object, a second weighting coefficient that depends on a first direction and a second direction orthogonal to the first direction in angular information the object, and a third weighting coefficient that depends on spatial frequency information of the object,
wherein the correction unit calculates the correction signal by weighting information of the imaging position of the imaging optical system for each spatial frequency of the object as set by the setting unit.

7. The image pickup apparatus according to claim 6 , wherein the correction unit performs a calculation using the aberration information, the first weighting coefficient, and the second weighting coefficient prior to a calculation using the aberration information and the third weighting coefficient.

8. The image pickup apparatus according to claim 1 ,
wherein the determination unit determines that it is unnecessary to obtain the color information when an amount of the chromatic aberration in the aberration information is smaller than a predetermined value.

9. The image pickup apparatus according to claim 1 ,
wherein the determination unit determines that it is unnecessary to obtain the angular information when an amount of the astigmatism in the aberration information is smaller than a predetermined value.

10. The image pickup apparatus according to claim 1 ,
wherein the determination unit determines that it is unnecessary to obtain the spatial frequency information when an amount of the spatial aberration in the aberration information is smaller than a predetermined value.

11. The image pickup apparatus according to claim 1 , wherein the determination unit further determines, based on the object information, whether it is necessary to calculate the correction value.

12. The image pickup apparatus according to claim 1 , wherein the determination unit further determines, based on the aberration information and the object information, that the correction value is to be calculated when at least one aberration among chromatic aberration, astigmatism, and spherical aberration of the object is larger than a predetermined value.

13. A control method for an image pickup apparatus capable of executing automatic focus detection of an imaging optical system, the control method comprising the steps of:
acquiring aberration information of the imaging optical system;
acquiring object information of an object in a focus detecting area;
determining, based on the aberration information, whether it is necessary to obtain color information, angular information, and spatial frequency information of the object;
calculating, based on the aberration information of the imaging optical system and the object information, a correction value used to correct a difference between a focus state of a captured image and a result of the automatic focus detection, caused by the aberration of the imaging optical system; and
correcting the result of the automatic focus detection using the correction value.

14. A non-transitory computer-readable storage medium storing a program that enables a computer to execute a method that includes the steps of:
executing automatic focus detection of an imaging optical system;
acquiring aberration information of the imaging optical system;
acquiring object information of an object in a focus detecting area;
determining, based on the aberration information, whether it is necessary to obtain color information, angular information, and spatial frequency information of the object;
calculating, based on the aberration information of the imaging optical system and the object information, a correction value used to correct a difference between a focus state of a captured image and a result of the automatic focus detection, caused by the aberration of the imaging optical system; and
correcting the result of the automatic focus detection using the correction value.

15. An image pickup apparatus capable of executing automatic focus detection of an imaging optical system, the image pickup apparatus comprising:
a first acquisition unit configured to acquire aberration information of the imaging optical system;
a second acquisition unit configured to acquire object information of an object in a focus detecting area;
a determination unit configured to determine, based on the aberration information, whether it is necessary to obtain color information of the object;
a calculation unit configured to calculate, based on the aberration information of the imaging optical system and the object information, a correction value used to correct a difference between a focus state of a captured image and a result of the automatic focus detection, caused by the aberration of the imaging optical system; and
a correction unit configured to correct the result of the automatic focus detection using the correction value,
wherein the determination unit determines that it is unnecessary to obtain the color information when an amount of the chromatic aberration in the aberration information is smaller than a predetermined va

Assignees

• Canon Kk

Inventors

• Takao Yumi

Classifications

• H04N23/672 Primary

  based on the phase difference signals · CPC title

• H04N25/61

  the noise originating only from the lens unit, e.g. flare, shading, vignetting or "cos4" · CPC title

• H04N23/667

  Camera operation mode switching, e.g. between still and video, sport and normal or high- and low-resolution modes · CPC title

• H04N25/704

  Pixels specially adapted for focusing, e.g. phase difference pixel sets · CPC title

• H04N25/445

  by skipping some contiguous pixels within the read portion of the array · CPC title