IMAGING APPARATUS AND MONITORING SYSTEM

• US 20200137293A1
• Filed: 10/25/2019
• Published: 04/30/2020
• Est. Priority Date: 10/26/2018
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Numata, Aihiko
• Granted Patent: US 11,399,126 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 7/36 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 Class Codes: G03B 13/32 Means for focusing
• CPC Class Codes: H04N 23/54 Mounting of pick-up tubes, electronic image sensors, deviation or focusing coils
• CPC Class Codes: H04N 23/58 Means for changing the camera field of view without moving the camera body, e.g. nutating or panning of optics or image sensors
• CPC Class Codes: H04N 23/67 Focus control based on electronic image sensor signals
• CPC Class Codes: H04N 23/673 based on contrast or high frequency components of image signals, e.g. hill climbing method
• CPC Class Codes: H04N 23/675 comprising setting of focusing regions
• CPC Class Codes: H04N 23/71 Circuitry for evaluating the brightness variation
• CPC Class Codes: H04N 25/70 SSIS architectures; Circuits associated therewith

Abstract

An imaging apparatus includes a focus controller, an image sensor, an angle controller configured to change an angle of an imaging plane of the image sensor, an evaluation value acquirer configured to acquire a contrast evaluation value in a first evaluation area of the image sensor during a focus control, and to acquire a contrast evaluation value in a second evaluation area different from the first evaluation area during an angle control, and an exposure controller configured to control an exposure condition of the image sensor. The exposure controller determines a first exposure condition so as to provide a correct exposure value to the first evaluation area during the focus control, and determines a second exposure condition different from the first exposure so as to provide a correct exposure value to the second evaluation area during the angle control.

Claims

1. An imaging apparatus comprising:

a focus controller configured to control a focus position of an imaging optical system;

an image sensor;

an angle controller configured to change an angle formed between a plane orthogonal to an optical axis of the imaging optical system and an imaging plane of the image sensor;

an evaluation value acquirer configured to acquire a contrast evaluation value in a first evaluation area of the image sensor during a focus control, and to acquire a contrast evaluation value in a second evaluation area different from the first evaluation area during an angle control; and

an exposure controller configured to control an exposure condition of the image sensor,

wherein the exposure controller determines a first exposure condition so as to provide a correct exposure value to the first evaluation area during the focus control, and determines a second exposure condition different from the first exposure so as to provide a correct exposure value to the second evaluation area during the angle control.

2. The imaging apparatus according to claim 1, wherein the exposure controller determines the first exposure condition during the focus control using a pixel signal of the first evaluation area, and determines the second exposure condition during the angle control using a pixel signal of the second evaluation area.

3. The imaging apparatus according to claim 1, wherein the first evaluation area is a central area of an effective pixel area of the image sensor, and the second evaluation area is a peripheral area of the effective pixel area of the image sensor.

4. The imaging apparatus according to claim 1, wherein the second evaluation area includes a first partial evaluation area, and a second partial evaluation area that has a distance from the imaging apparatus to the object surface longer than that of the first partial evaluation area, and

wherein the exposure controller

determines a variation amount in the contrast evaluation value during the angle control,

makes a weighting coefficient of the contrast evaluation value for the second partial evaluation area larger than that for the first partial evaluation area when the variation amount is larger than a first threshold, and

makes the weighting coefficient of the contrast evaluation value for the first partial evaluation area larger than that for the second partial evaluation area when the variation amount is smaller than the first threshold.

5. The imaging apparatus according to claim 1, wherein the second evaluation area includes a first partial evaluation area, and a second partial evaluation area that has a distance from the imaging apparatus to the object surface longer than that of the first partial evaluation area, and

wherein the exposure controller

determines a variation amount in the contrast evaluation value during the angle control,

uses the contrast evaluation value of the second partial evaluation area when the variation amount is larger than a first threshold, and

uses the contrast evaluation value of the first partial evaluation area when the variation amount is smaller than the first threshold.

6. The imaging apparatus according to claim 1, wherein the second evaluation area includes a first partial evaluation area, and a second partial evaluation area that has a distance from the imaging apparatus to the object surface longer than that of the first partial evaluation area, and

wherein the exposure controller

determines a variation amount in the contrast evaluation value during the angle control,

determines the second exposure condition using a pixel signal of the second partial evaluation area when the variation amount is larger than a first threshold, and

determines the second exposure condition using a pixel signal of the first partial evaluation area when the variation amount is smaller than the first threshold.

7. The imaging apparatus according to claim 1, further comprising:

a first illumination element; and

a second illumination element having an illumination range wider than that of the first illumination element,

wherein the exposure controller makes a ratio of a current passing through the second illumination element to the current passing through the first illumination element during the angle control larger than that during the focus control.

8. The imaging apparatus according to claim 7, wherein the exposure controller uses the first illumination element for the focus control and the second illumination element for the angle control.

9. The imaging apparatus according to claim 7, further comprising:

a third illumination element configured to illuminate an area corresponding to the first evaluation area; and

a fourth illumination element and a fifth illumination element each configured to illuminate an area corresponding to the second evaluation area,

wherein the exposure controller makes a ratio of a current passing through the third illumination element to an average value of a current passing through the fourth illumination element and a current passing through the fifth illumination element during the focus control larger than that during the angle control.

10. The imaging apparatus according to claim 9, wherein the second evaluation area includes a first partial evaluation area, and a second partial evaluation area that has a distance from the imaging apparatus to the object surface longer than that of the first partial evaluation area, and

wherein the exposure controller makes an illumination intensity of the fifth illumination element configured to illuminate the second partial evaluation area larger than that of the fourth illumination element configured to illuminate the first partial evaluation area during the angle control.

18. The imaging apparatus according to claim 1, wherein the exposure controller determines a variation amount in the contrast evaluation value during the focus control and during the angle control, and simultaneously performs the focus control and the angle control when the variation amount is smaller than a second threshold.

19. A monitoring system comprising the imaging apparatus according to claim 1.

11. An imaging apparatus comprising:

an imaging optical system;

a focus controller configured to control a focus position of the imaging optical system;

an image sensor configured to photoelectrically convert an optical image formed through the imaging optical system;

an angle controller configured to change an angle formed between a principal surface of the imaging optical system and the imaging plane of the image sensor;

an evaluation value acquirer configured to acquire a contrast evaluation value in a first evaluation area during a focus control and to acquire a contrast evaluation value in a second evaluation area different from the first evaluation area during an angle control; and

an exposure controller configured to control a read operation for reading a pixel signal from the image sensor,

wherein the exposure controller reads the pixel signal in a first read operation during the focus control, and reads the pixel signal in a second read operation different from the first read operation during the angle control.

12. The imaging apparatus according to claim 11, wherein the exposure controller reads the pixel signal in a first range including the first evaluation area during the focus control, and the pixel signal in a second range that includes the second evaluation area and is different from the first evaluation area during the angle control.

13. The imaging apparatus according to claim 11, wherein the second evaluation area includes a first partial evaluation area, and a second partial evaluation area that has a distance from the imaging apparatus to the object surface longer than that of the first partial evaluation area, and

wherein the exposure controller

determines a variation amount in the contrast evaluation value during the angle control,

reads the pixel signal in the second partial evaluation area when the variation amount is larger than a first threshold, and

reads the pixel signal in the first partial evaluation area when the variation amount is smaller than the first threshold.

14. The imaging apparatus according to claim 12, wherein a column direction of the image sensor coincides with a direction parallel to a tilt direction during the angle control.

15. The imaging apparatus according to claim 12, wherein during the focus control, a sampling pitch for reading the pixel signal from a third range other than the first range is larger than a sampling pitch for reading the pixel signal from the first range, and

wherein during the angle control, a sampling pitch for reading the pixel signal from a fourth range other than the second range is larger than a sampling pitch for reading the pixel signal from the second range.

16. The imaging apparatus according to claim 15, wherein the exposure controller changes the sampling pitch by thinning and reading the pixel signal from the image sensor.

17. The imaging apparatus according to claim 15, wherein the exposure controller changes the sampling pitch by adding and reading the pixel signal from the image sensor.

20. A monitoring system comprising the imaging apparatus according to claim 11.