Imaging apparatus

• US 8,134,608 B2
• Filed: 10/27/2008
• Issued: 03/13/2012
• Est. Priority Date: 11/19/2007
• Status: Expired due to Fees

• Current Assignee: Alps Alpine Co., Ltd.
• Original Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Inventors: Yamashita, Tatsumaro, Kamata, Tomoya
• Primary Examiner(s): Ometz, David
• Assistant Examiner(s): Berhan, Ahmed A
• Application Number:
  US12/258,792
• Publication Number:
  US 20090128686A1
• Time in Patent Office: 1,233 Days
• Field of Search: 348/207.99, 348/222.1, 348/223.1, 348/148, 348/157, 348/159, 348/211.12, 348/221.1, 348/63, 348/255, 348/240.99, 348/240.1
• US Class Current: 348/222.1
• CPC Class Codes: B60R 1/26 to the rear of the vehicle
• CPC Class Codes: B60R 1/28 with an adjustable field of view
• CPC Class Codes: B60R 2300/108 using 'non-standard' camera systems, e.g. camera sensor used for additional purposes i.a. rain sensor, camera sensor split in multiple image areas
• CPC Class Codes: B60R 2300/30 characterised by the type of image processing
• CPC Class Codes: B60R 2300/306 using a re-scaling of images
• CPC Class Codes: G06T 3/047 Fisheye or wide-angle transformations
• CPC Class Codes: H04N 23/698 for achieving an enlarged field of view, e.g. panoramic image capture
• CPC Class Codes: H04N 5/2628 Alteration of picture size, shape, position or orientation, e.g. zooming, rotation, rolling, perspective, translation

Abstract

Disclosed is an imaging apparatus capable of enlarging a portion of an image captured by an imaging device of a fisheye camera and displaying the enlarged image on a display screen with little distortion. The imaging apparatus enlarges a section, which is a portion of an image captured by a fisheye camera, and displays the section on a display screen such that the enlargement ratios of points in the section are different from each other. An image processing method uses a change function that changes the enlargement ratio of a field angle depending on the place is used, and converts a portion of the captured image into a central projection image to generate a display image. The use of the change function makes it possible to generate a display image having high visibility.

Claims

1. an imaging apparatus comprising:

a lens;

an imaging device that detects light focused by the lens at a plurality of detection points;

and an image processing unit that generates image data for displaying an image on a display screen having a predetermined area, on the basis of image signals detected at the detection points of the imaging device,

wherein the image processing unit performs image processing to enlarge a section, which is a portion of the image captured by the imaging device, and displays the enlarged image on the display screen, and in the image processing, an enlargement ratio of a field angle varies depending on the place in the section,

wherein, in the image processing, the enlargement ratio of the field angle in an X-axis direction corresponding to a horizontal axis of the display screen, and the enlargement ratio of the field angle in a Y-axis direction that is orthogonal to the X-axis direction are changed on the basis of a predetermined change function, and

wherein, in the image processing, the following processes are performed on each pixel Pi of the display screen, and a process of making the pixels Pi correspond to image signals of the detection points of the imaging device is performed;

(1) a process of substituting the X-axis coordinate of the pixel Pi on the display screen into the change function to calculate a field angle α

x in the X-axis direction corresponding to the coordinate and substituting the Y-axis coordinate of the pixel Pi on the display screen into the change function to calculate a field angle (α

y in the Y-axis direction corresponding to the coordinate;

(2) a process of calculating the positions rx and ry of an image point of a display image on the basis of a focal length f corresponding to the enlargement ratio of the display image, the field angle α

x, and the field angle α

y;

(3) a process of calculating a zenith angle θ

i and an azimuth angle Φ

i of a spatial point to be projected onto the pixel Pi on the basis of the positions rx and ry;

(4) a process of making the pixel Pi correspond to the image signal detected at any one of the detection points of the imaging device on the basis of the zenith angle θ

i, the azimuth angle Φ

i, and a projection polynomial of the lens; and

(5) a process of performing the processes (1) to (4) on all the pixels of the display screen.

2. The imaging apparatus according to claim 1,

wherein, in the image processing, the enlargement ratio of a field angle varies depending on the place in the section, and a direction in which the field angle is enlarged is changed.

3. The imaging apparatus according to claim 1,

wherein, in the imaging process, as the distance from the optical axis of the lens is increased, the enlargement ratio of the field angle of the section is gradually changed.

4. The imaging apparatus according to claim 1,

wherein, in the imaging process, the field angle of an interest region of the image is enlarged, and the field angles of the other regions are reduced.

5. The imaging apparatus according to claim 1,

wherein the process (2) is performed by the equations given below:

rx=f·

tan(α

x), and

ry=f·

tan(α

y).

6. The imaging apparatus according to claim 1,

wherein, in the process (4), the coordinates (mx, my) of a detection point corresponding to the pixel Pi on the imaging device are calculated by equations given below:

r(θ

i)=k₁θ

i+k₂θ

i³+k₃θ

i⁵+k₄θ

i⁷+ . . . ,

mx=r(θ

i)·

cos(Φ

i), and

my=r(θ

i)·

sin(Φ

i)

(where r(θ

i) is calculated by an arbitrary order polynomial).

7. The imaging apparatus according to claim 1,

wherein one of the enlargement ratio in the X-axis direction and the enlargement ratio in the Y-axis direction is determined on the basis of a predetermined change function, and the other enlargement ratio is determined on the basis of a change function following a correction value of an aspect ratio.

8. The imaging apparatus according to claim 7,

wherein a correction function is obtained from a differential function of the one change function.

9. The imaging apparatus according to claim 1,

wherein, even when the enlargement ratio of the image captured by the imaging device is different from the enlargement ratio of a display image displayed on the display screen, a common change function is used.

10. The imaging apparatus according to claim 1,

wherein a display image is displayed on the display screen such that the enlargement ratio of the image captured by the imaging device and the enlargement ratio of the display image displayed on the display screen are changed.

11. The imaging apparatus according to claim 1,

wherein a display image is displayed on the display screen such that the enlargement ratio of the image captured by the imaging device and the enlargement ratio of the display image displayed on the display screen are changed, and

an adjustment angle for adjusting the central position of the field angle is added to the change function.