Imaging apparatus and focus control method

Patent metadata

Field	Value
Publication number	US-9497410-B2
Application number	US-201514718258-A
Country	US
Kind code	B2
Filing date	May 21, 2015
Priority date	Nov 22, 2012
Publication date	Nov 15, 2016
Grant date	Nov 15, 2016

Abstract

It is intended to provide an imaging apparatus and a focus control method that can prevent AF speed reduction even at the occurrence of a flicker. A system control unit 11 of a digital camera having a solid-state imaging device 5 that shoots a subject via an imaging lens 1 including a focus lens selectively performs one of a first focus control for controlling the focus lens so as to move it to a focus position by a phase difference AF method and a second focus control for controlling the focus lens so as to move it to a focus position by a contrast AF method. The system control unit 11 selects and performs the first focus control in a state that a flicker detection unit 12 has detected a flicker.

First claim

The invention claimed is:

1. An imaging apparatus, comprising:
an imaging device that shoots a subject via an imaging optical system, the imaging optical system including a focus lens; and
at least one central processing unit (CPU) configured to
selectively perform one of a first focus control for controlling the focus lens so as to move the focus lens to a focus position by a phase difference AF method and a second focus control for controlling the focus lens so as to move the focus lens to a focus position by a contrast AF method; and
detect a flicker,
wherein the at least one central processing unit decides which of the first focus control and the second focus control should be performed selectively at least according to whether a flicker has been detected,
the imaging device comprises plural first phase difference pixels that receive one of a pair of light beams that pass through different portions of a pupil region of the imaging optical system and plural second phase difference detection pixels that receive other of the pair of light beams,
in a state that a flicker has been detected, the at least one central processing unit selects the first focus control if an exposure time of the imaging device that is necessary for the first focus control is shorter than or equal to a threshold value and selects the second focus control if the exposure time is longer than the threshold value, and
where the at least one central processing unit selects the second focus control method in the state that a flicker has been detected, the at least one central processing unit sets an exposure time of the imaging device of each of plural times of shooting necessary for the second focus control at a natural number multiple of a cycle of the detected flicker.

2. The imaging apparatus according to claim 1 , wherein the at least one central processing unit selects the first focus control until establishment of a state that a flicker can be detected.

Assignees

• Fujifilm Corp

Inventors

• Aoki Takashi

Classifications

• H04N23/673

  based on contrast or high frequency components of image signals, e.g. hill climbing method · CPC title

• H04N23/745

  Detection of flicker frequency or suppression of flicker wherein the flicker is caused by illumination, e.g. due to fluorescent tube illumination or pulsed LED illumination · CPC title

• H04N23/73

  by influencing the exposure time · CPC title

• H04N25/704

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

• G02B7/36 Primary

  using image sharpness techniques {, e.g. image processing techniques for generating autofocus signals (image data processing per se G06T; in cameras having a solid state image sensor H04N23/67)} · CPC title