Lens apparatus, image capturing apparatus, camera system, determination method of correction value and storage medium

Patent metadata

Field	Value
Publication number	US-10917554-B2
Application number	US-201916366011-A
Country	US
Kind code	B2
Filing date	Mar 27, 2019
Priority date	Apr 2, 2018
Publication date	Feb 9, 2021
Grant date	Feb 9, 2021

Abstract

A lens apparatus detachably attachable to an image capturing apparatus including a focus detection unit having a focus detection optical system and performing focus detection process, and a controller controlling driving of a focusing lens unit based on a result of the focus detection process, via an extender including an extender optical system, includes an image capturing optical system including the focusing lens unit, and a determination unit determining a first correction value used for correcting the result of the focus detection process. When the lens apparatus is attached to the image capturing apparatus via the extender, the determination unit determines the first correction value using first information regarding a diameter of a pupil of the focus detection optical system and second information regarding a diameter of a pupil of an optical system including the image capturing optical system and the extender optical system.

First claim

What is claimed is:

1. A lens apparatus detachably attachable to an image capturing apparatus, which includes a focus detection circuit having a focus detection optical system and configured to perform a focus detection process by a phase detection, and a controller configured to control driving of a focusing lens unit based on a result of the focus detection process by the focus detection circuit, via an extender including an extender optical system, the lens apparatus comprising:
an image capturing optical system including the focusing lens unit; and
a first determination circuit configured to determine a first correction value used when the controller corrects the result of the focus detection process,
wherein when the lens apparatus is attached to the image capturing apparatus via the extender, the first determination circuit determines the first correction value based on first information regarding a diameter of a pupil of the focus detection optical system and second information regarding a diameter of a pupil of an optical system including the image capturing optical system and the extender optical system.

2. The lens apparatus according to claim 1 , further comprising a memory configured to store a second correction value used when the controller corrects the result of the focus detection process where the lens apparatus is attached to the image capturing apparatus directly,
wherein the first determination circuit determines the first correction value based on the second correction value.

3. The lens apparatus according to claim 1 , further comprising a second determination circuit configured to determine a relationship between the diameter of the pupil of the focus detection optical system and the diameter of the pupil of the optical system including the image capturing optical system and the extender optical system,
wherein the first information is the diameter of the pupil of the focus detection optical system,
wherein the second information is the diameter of the pupil of the optical system including the image capturing optical system and the extender optical system, and
wherein the first determination circuit determines the first correction value based on a determination result by the second determination circuit.

4. The lens apparatus according to claim 3 , further comprising a memory configured to store a second correction value used when the controller corrects the result of the focus detection process where the lens apparatus is attached to the image capturing apparatus directly, and a third correction value in design used when the controller corrects the result of the focus detection process where the lens apparatus is attached to the image capturing apparatus via the extender, and
wherein where Φ af represents the diameter of the pupil of the focus detection optical system, Φ ext represents the diameter of the pupil of the optical system including the image capturing optical system and the extender optical system, BP ext represents the first correction value, BP tan represents the second correction value, b represents the third correction value, and α represents a coefficient,
in a case where the second determination circuit determines that a conditional expression of Φ af <Φ ext ×a (0.5≤a≤1.1) is satisfied, the first determination circuit calculates the first correction value using an expression of BP ext =b+α×BP tan (0<α), and
in a case where the second determination circuit determines that a conditional expression of Φ af >Φ ext ×a is satisfied, the first determination circuit calculates the first correction value using an expression of BP ext =b.

5. The lens apparatus according to claim 3 , further comprising a memory configured to store a second correction value used when the controller corrects the result of the focus detection process where the lens apparatus is attached to the image capturing apparatus directly, and a third correction value in design used when the controller corrects the result of the focus detection process where the lens apparatus is attached to the image capturing apparatus via the extender, and
wherein where Φ af represents the diameter of the pupil of the focus detection optical system, Φ ext represents the diameter of the pupil of the optical system including the image capturing optical system and the extender optical system, BP ext represents the first correction value, BP tan represents the second correction value, b represents the third correction value, and α 1 , α 2 (0<α 2 <α 1 ) represent coefficients,
in a case where the second determination circuit determines that a conditional expression of Φ af <Φ ext ×a (0.5≤a≤1.1) is satisfied, the first determination circuit calculates the first correction value using an expression of BP ext =b+α 1 ×BP tan , and
in a case where the second determination circuit determines that a conditional expression of Φ af >Φ ext ×a is satisfied, the first determination circuit calculates the first correction value using an expression of BP ext =b+α 2 ×BP tan .

6. The lens apparatus according to claim 2 ,
wherein the memory stores a third correction value in design used when the controller corrects the result of the focus detection process where the lens apparatus is attached to the image capturing apparatus via the extender, and
wherein when Φ af represents the diameter of the pupil of the focus detection optical system, Φ ext represents the diameter of the pupil of the optical system including the image capturing optical system and the extender optical system, BP ext represents the first correction value, BP tan represents the second correction value, b represents the third correction value, the first determination circuit calculates the first correction value using an expression of BP ext =b+(1−Φ af /Φ ext )×BP tan .

7. The lens apparatus according to claim 1 , further comprising a second determination circuit configured to determine a relationship between an F-number corresponding to the diameter of the pupil of the focus detection optical system and an F-number corresponding to the diameter of the pupil of the optical system including the image capturing optical system and the extender optical system,
wherein the first information is the F-number corresponding to the diameter of the pupil of the focus detection optical system,
wherein the second information is the F-number corresponding to the diameter of the pupil of the optical system including the image capturing optical system and the extender optical system, and
wherein the first determination circuit determines the first correction value based on a determination result by the second determination circuit.

8. The lens apparatus according to claim 7 , further comprising a memory configured to store a second correction value used when the controller corrects the result of the focus detection process where the lens apparatus is attached to the image capturing apparatus directly, and a third correction value in design used when the controller corrects the result of the focus detection process where the lens apparatus is attached to the image capturing apparatus via the extender,
wherein where F af represents the F-number corresponding to the diameter of the pupil of the focus detection optical system, F ext represents the F-number corresponding to the diameter of the pupil of the optical system including the image capturing optical system and the extender optical system, BP ext represents the first correction value, BP tan represents the second correction value, b represents the third correction value, and α represents a coefficient,
in a case where the second determination circuit determines that a conditional expression of F af >F ext ×a (0.9≤a≤2.0) is satisfied, the first determination ci

Assignees

• Canon Kk

Inventors

• Kosaka Yuichi

Classifications

• H04N23/67 Primary

  Focus control based on electronic image sensor signals · CPC title

• H04N23/672

  based on the phase difference signals · CPC title

• H04N23/663

  for controlling interchangeable camera parts based on electronic image sensor signals · CPC title

• H04N23/55

  Optical parts specially adapted for electronic image sensors; Mounting thereof · CPC title

• G02B7/28

  Systems for automatic generation of focusing signals · CPC title