Imaging apparatus and focus control method

Patent metadata

Field	Value
Publication number	US-10564392-B2
Application number	US-201816138578-A
Country	US
Kind code	B2
Filing date	Sep 21, 2018
Priority date	Mar 30, 2016
Publication date	Feb 18, 2020
Grant date	Feb 18, 2020

Abstract

An imaging apparatus includes: a distance measurement unit that measures distance values of a plurality of points in a first area which has a focus point as a reference point; a statistical unit that calculates statistics indicating a variation in the measured distance values of the plurality of points in the first area; a size determination unit that determines the size of a second area which has the focus point as a reference point, on the basis of the calculated statistics; a contrast evaluation value calculation unit that calculates a contrast evaluation value on the basis of an image of the second area; and a focusing unit that moves a focus lens to a lens position determined on the basis of the calculated contrast evaluation value.

First claim

What is claimed is:

1. An imaging apparatus comprising:
an imaging unit that captures an image of an object through an optical system including a focus lens;
a distance measurement unit that measures distance values of a plurality of points in a first area which is in the captured image and has a focus point as a reference point;
a statistical unit that calculates statistics indicating a variation in the measured distance values of the plurality of points in the first area;
a size determination unit that determines a size of a second area which is used to calculate a contrast evaluation value in the image and has the focus point as a reference point, on the basis of the calculated statistics;
a contrast evaluation value calculation unit that calculates the contrast evaluation value at each of a plurality of lens positions, on the basis of an image of the second area in an image captured by moving the focus lens to each of the plurality of lens positions; and
a focusing unit that moves the focus lens to a lens position determined on the basis of the calculated contrast evaluation value.

2. The imaging apparatus according to claim 1 ,
wherein the size determination unit reduces the size of the second area as the variation indicated by the statistics increases.

3. The imaging apparatus according to claim 1 ,
wherein the size determination unit increases the size of the second area as the variation indicated by the statistics is reduced.

4. The imaging apparatus according to claim 1 ,
wherein the statistical unit calculates, as the statistics, a variance or standard deviation of the distance values of the plurality of points in the first area.

5. The imaging apparatus according to claim 4 ,
wherein the statistical unit calculates the statistics on the basis of any one of a mean of the distance values in the first area, a mode of the distance values in the first area, and a distance value of a flat surface in the first area among the distance values of the plurality of points.

6. The imaging apparatus according to claim 1 ,
wherein the contrast evaluation value calculation unit evaluates contrast in the second area that has a focus point corresponding to an input command or the vicinity of the focus point as a center.

7. The imaging apparatus according to claim 1 , further comprising:
an area determination unit that determines an exclusion area to be excluded from the second area in the first area on the basis of the distance values of the plurality of points in the first area.

8. The imaging apparatus according to claim 1 , further comprising:
an imaging direction control unit that controls an imaging direction of the imaging unit to at least one of a pan direction, a tilt direction, or a roll direction,
wherein the imaging direction control unit controls the imaging direction of the imaging unit on the basis of the focus point.

9. The imaging apparatus according to claim 1 ,
wherein the distance measurement unit is a stereo camera that performs distance measurement using a stereo image or an optical distance measurement device that performs distance measurement using light.

10. The imaging apparatus according to claim 1 ,
wherein the imaging unit captures an image of a structure to be inspected, and
an input command indicating a main inspection portion of the structure to be inspected as the focus point is received.

11. A focus control method comprising:
a step of measuring distance values of a plurality of points in a first area which is in an image of an object captured by an imaging unit through an optical system including a focus lens and has a focus point as a reference point;
a step of calculating statistics indicating a variation in the measured distance values of the plurality of points in the first area;
a step of determining a size of a second area which is used to calculate a contrast evaluation value in the image and has the focus point as a reference point, on the basis of the calculated statistics;
a step of calculating the contrast evaluation value at each of a plurality of lens positions, on the basis of an image of the second area in an image captured by moving the focus lens to each of the plurality of lens positions; and
a step of moving the focus lens to a lens position determined on the basis of the calculated contrast evaluation value.

Assignees

• Fujifilm Corp

Inventors

• Watanabe Mikio

Classifications

• G03B17/00

  Details of cameras or camera bodies; Accessories therefor (lens hoods or caps G03B11/04) · 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

• G02B7/38

  measured at different points on the optical axis {, e.g. focussing on two or more planes and comparing image data} · CPC title

• G02B7/40

  using time delay of the reflected waves, e.g. of ultrasonic waves · CPC title

• G03B15/006

  Apparatus mounted on flying objects · CPC title