System and method for correcting multiple axis displacement distortion

• US 20030043303A1
• Filed: 06/12/2002
• Published: 03/06/2003
• Est. Priority Date: 06/12/2001
• Status: Active Grant

• Current Assignee: Geo Semiconductor Incorporated
• Original Assignee: Silicon Optix (Renesas Electronics Corporation)
• Inventors: Karuta, Bonaventure, Lee, Louie
• Granted Patent: US 7,352,913 B2
• Time in Patent Office: Days
• US Class Current: 348/744
• CPC Class Codes: G02B 27/0025 for optical correction, e.g. distorsion, aberration
• CPC Class Codes: G03B 27/68 Introducing or correcting distortion, e.g. in connection with oblique projection
• CPC Class Codes: G06T 2207/20021 Dividing image into blocks, subimages or windows
• CPC Class Codes: G06T 3/00 Geometric image transformations in the plane of the image
• CPC Class Codes: G06T 5/80 Geometric correction
• CPC Class Codes: H04N 5/74 Projection arrangements for image reproduction, e.g. using eidophor
• CPC Class Codes: H04N 9/3185 Geometric adjustment, e.g. keystone or convergence optical or mechanical adjustment of convergence H04N9/317; using scanning means H04N3/22; optical or mechanical adjustments of projectors not peculiar to the presence of an electronic spatial light modulator G03B21/14
• CPC Class Codes: H04N 9/3194 including sensor feedback

Abstract

A system and method for correcting distortion in projected images caused by the projection of an input image by a projector lens onto a projection screen having a surface that is not orthogonal to the projection axis of the projector. Projection parameters including the focal length of the projector lens and the angles that represent the pan, tilt and roll angle of the projector are obtained. Then the projected area and the best viewable rectangular area that fits within said projected area is determined. The distortion is then characterized by using a distortion transformation which corresponds to the transformation that exists between the vertices of the best viewable rectangular area and the corresponding vertices of the projected area. Finally, the distortion transformation is inverted and applied to input image to obtain a distortion free projected image.

Claims

1. A method for correcting distortion in projected images caused by the projection of an input image by a projector lens onto a projection screen having a surface that is not orthogonal to the projection axis of the projector, said projection screen being associated with assoiated with a display device, said method comprising the steps of:

(a) receiving projection parameters including the focal length of the projector lens, the aspect ratio of the input image relative to the aspect ratio of the display device, and the angles that represent the pan, tilt and roll angle of the projector;

(b) determining the projected area that results when distortion is present given the projection parameters from step (a) and then determining the vertices of a best viewable rectangular area that fits within said projected area such that the perimeter of said best viewable rectangular area is maximized;

(c) characterizing the distortion caused by projection using a distortion transformation which corresponds to the transformation that exists between the vertices of the best viewable rectangular area and the corresponding vertices of the projected area;

(d) inverting the distortion transformation to form a pre-distortion image transformation; and

(e) applying the pre-distortion image transformation to the input image to obtain a distortion free projected image.

2. The method of claim 1, wherein step (e) comprises applying the pre-distorted image transform as a 2D image transform.

3. The method of claim 1, wherein step (e) comprises applying the pre-distorted image transform as two separated 1D image transforms.

4. The method of claim 3, wherein step (e) comprises the steps of:

(i) separating the pre-distortion image transformation into a first pass transformation and a second pass transformation;

(ii) applying the first pass transformation using a first positional polynomial; and

(iii) applying the second pass transformation using a second positional polynomial.

5. The method of claim 1, wherein step (a) comprises receiving projection parameters for a range of angle sets, wherein each angle set contains angles that represent the pan, tilt and roll angle of the projector lens, wherein steps (b) to (d) are calculated for each angle set such that a pre-distortion image transform for a particular angle set can be dynamically obtained and applied to the input image.

6. The method of claim 1, wherein said method achieves correction of another distortion by executing step (b) such that the distorted image is the projected image that results from inclusion of said another distortion.

7. A system for correcting distortion in projected images caused by the projection of an input image by a projector lens onto a projection screen having a surface that is not orthogonal to the projection axis of the projector said projection screen being associated with a display device, said system comprising:

(a) a memory for storing projection parameters including the focal length of the projector lens, the aspect ratio of the input image relative to the aspect ratio of the display device, and the angles that represent the pan, tilt and roll angle of the projector;

(b) a processor coupled to said memory being adapted for determining the projected area that results when distortion is present given the projection parameters from step (a) and then determining the vertices of a best viewable rectangular area that fits within said projected area such that the perimeter of said best viewable rectangular area is maximized;

(c) said processor also being adapted to characterize the distortion caused by projection using a distortion transformation which corresponds to the transformation that exists between the vertices of the best viewable rectangular area and the corresponding vertices of the projected area;

(d) said processor also being adapted to invert the distortion transformation to form a pre-distortion image transformation; and

(e) said processor also being adapted to apply the pre-distortion image transformation to the input image to obtain a distortion free projected image.

8. The system of claim 7, wherein said processor is also adapted for applying the pre-distorted image transform as a 2D image transform.

9. The system of claim 7, wherein said processor is also adapted applying the pre-distorted image transform as two separated 1D image transforms.

10. The system of claim 9, wherein

(i) said processor is also adapted to separate the pre-distortion image transformation into a first pass transformation and a second pass transformation;

(ii) said processor is also adapted to apply the first pass transformation using a first positional polynomial; and

(iii) said processor is also adapted to apply the second pass transformation using a second positional polynomial.

11. The system of claim 7, wherein said processor is adapted to receive projection parameters for a range of angle sets, wherein each angle set contains angles that represent the pan, tilt and roll angle of the projector lens, and wherein said processor is adapted to calculate a pre-distortion image transform for each angle set such that a pre-distortion image transform for a particular angle set can be dynamically obtained and applied to the input image.

12. The system of claim 7, wherein said processor achieves correction of another distortion by determining the projected area that results when distortion and said another distortion is present given the projection parameters and then determining the vertices of a best viewable rectangular area that fits within said projected area such that the perimeter of said best viewable rectangular area is maximized.