US6985183B2
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for exploring viewpoint and focal length of camera
Assignee: Appro Technology Inc
•
Filing: 2001-10-19
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Granted: 2006-01-10
•
Expires: 2021-10-19
Abstract
Abstract The present invention is a method for exploring the viewpoint and focal length of a fisheye lens camera (FELC). It employs the characteristic of the central symmetry of the distortion of the fisheye lens (FEL) to set its optic axis by means of a calibration target with a plurality of symmetrically homocentric figures. Once the optic axis is fixed, further disclose the viewpoint (VP) of the FELC along the optic axis through a trail-and-error procedure and calculate its effective focal length and classify it to the primitive projection mode. Because the invention is capable of finding out both the internal and external parameters of the FELC and the calibration method is easy, low-cost, suitable to any projection model, and has greater sensitivity corresponding to an increasing in image distortion, the distortive images can be transformed easily to normal ones which fit in with a central perspective mechanism. Furthermore, the invention is also practicable and excellent in its applications in the fields of quality identification of the FEL and wide-view 3-D metering.
Inventors
- 👤 Gwo-Jen Jan
- 👤 Chuang-Jan Chang
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 18:36
CPC Classifications
H; H04; H04N; H04N17/00; H04N17/002; H04N23/00; H04N23/80; H04N23/81
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
99 words
A method for exploring viewpoint and focal length of camera that has an axis-symmetrical nonlinear-distortive lens, the method comprises: providing a calibration target with a test pattern composed of at least one geometric figure; aiming the center of the test pattern at an optic axis of a lens in the camera; and searching a pinpoint along the optic axis to enable at least one image height on an image plane which is related to the geometric figure and the corresponding zenithal angle between the incident rays of light and the optic axis both fit in with a projection model.
Claim 2
Independent Claim
99 words
A method for exploring viewpoint and focal length of camera that has an axis-symmetrical nonlinear-distortive lens, the method comprises: providing a calibration target with a test pattern composed of at least one geometric figure; aiming the center of the test pattern at an optic axis of a lens in the camera; and searching a pinpoint along the optic axis to enable at least one image height on an image plane which is related to the geometric figure and the corresponding zenithal angle between the incident rays of light and the optic axis both fit in with a projection model.
Claim 3
Dependent Claim
26 words
The method according to claim 1 , wherein the geometric figure is selected from the group comprising a circle, a rectangle, a triangle and a polygon.
Claim 4
Dependent Claim
27 words
The method according to claim 1 , wherein there is a plurality of the geometric figures composed of concentric circles, concentric rectangles, concentric triangles or concentric polygons.
Claim 5
Dependent Claim
77 words
The method according to claim 1 , wherein the optic axis is further located by the steps comprise: placing the calibration target in the field of view of the camera to let the test pattern form a corresponding image on the image plane; and changing the position of the calibration target to make the image similar to the test pattern, then connecting both the centers of the calibration target and the image to locate the optic axis.
Claim 6
Dependent Claim
17 words
The method according to claim 1 , wherein the lens in the camera is a fisheye lens.
Claim 7
Dependent Claim
19 words
The method according to claim 1 , wherein the lens is a nonlinear lens with a given projection model.
Claim 8
Dependent Claim
27 words
The method according to claim 1 , wherein the projection model is selected from the group comprising an equidistant projection, an orthographic projection and a stereographic projection.
Claim 9
Dependent Claim
19 words
The method according to claim 1 , wherein the pinpoint is the viewpoint of the lens in the camera.
Claim 10
Dependent Claim
22 words
The method according to claim 1 , wherein the calibration target has at least one flat plane to provide the test pattern.
Claim 11
Dependent Claim
30 words
The method according to claim 8 , wherein the periphery of the flat plane further vertically extends a surface to turn the calibration target into a hollow and one-side-open shape.
Claim 12
Dependent Claim
31 words
The method according to claim 1 , wherein the camera is selected from the group comprising a CCD camera, a CMOS camera, a digital camera and a traditional camera with film.
Claim 13
Independent Claim
140 words
A method for exploring viewpoint and focal length of camera that has an axis-symmetrical nonlinear-distortive lens, the method comprises: providing a calibration target with a test pattern composed of at least one geometric figure; placing the calibration target in the field of view of the camera to let the test pattern form a corresponding image on an image plane; changing the position of the calibration target to make the image similar to the test pattern, then connecting both the centers of the calibration target and the image to locate an optic axis; and searching a pinpoint along the optic axis to enable at least one image height on the image plane which is related to the geometric figure and the corresponding zenithal angle between the incident rays of light and the optic axis both fit in with a projection model.
Claim 14
Independent Claim
140 words
A method for exploring viewpoint and focal length of camera that has an axis-symmetrical nonlinear-distortive lens, the method comprises: providing a calibration target with a test pattern composed of at least one geometric figure; placing the calibration target in the field of view of the camera to let the test pattern form a corresponding image on an image plane; changing the position of the calibration target to make the image similar to the test pattern, then connecting both the centers of the calibration target and the image to locate an optic axis; and searching a pinpoint along the optic axis to enable at least one image height on the image plane which is related to the geometric figure and the corresponding zenithal angle between the incident rays of light and the optic axis both fit in with a projection model.
Claim 15
Dependent Claim
28 words
The method according to claim 12 , wherein the geometric figure is selected from the group comprising a circle, a rectangle, a square, a triangle and a polygon.
Claim 16
Dependent Claim
27 words
The method according to claim 12 , wherein there is a plurality of the geometric figures composed of concentric circles, concentric rectangles, concentric triangle or concentric polygons.
Claim 17
Dependent Claim
17 words
The method according to claim 12 , wherein the lens in the camera is a fisheye lens.
Claim 18
Dependent Claim
19 words
The method according to claim 12 , wherein the lens is a nonlinear lens with a given projection model.
Claim 19
Dependent Claim
27 words
The method according to claim 12 , wherein the projection model is selected from the group comprising an equidistant projection, an orthographic projection and a stereographic projection.
Claim 20
Dependent Claim
19 words
The method according to claim 12 , wherein the pinpoint is the viewpoint of the lens in the camera.
Claim 21
Dependent Claim
22 words
The method according to claim 12 , wherein the calibration target has at least one flat plane to provide the test pattern.
Claim 22
Dependent Claim
31 words
The method according to claim 12 , wherein the periphery of the flat plane further vertically extends a surrounding surface to turn the calibration target into a hollow and one-side-open shape.
Claim 23
Dependent Claim
31 words
The method according to claim 12 , wherein the camera is selected from the group comprising a CCD camera, a CMOS camera, a digital camera and a traditional camera with film.
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