WO2006056577A1 - Trapezoid rectification in laser projection systems - Google Patents
Trapezoid rectification in laser projection systems Download PDFInfo
- Publication number
- WO2006056577A1 WO2006056577A1 PCT/EP2005/056171 EP2005056171W WO2006056577A1 WO 2006056577 A1 WO2006056577 A1 WO 2006056577A1 EP 2005056171 W EP2005056171 W EP 2005056171W WO 2006056577 A1 WO2006056577 A1 WO 2006056577A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- distortion
- line
- projection
- laser
- projection systems
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N9/00—Details of colour television systems
- H04N9/12—Picture reproducers
- H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
- H04N9/3129—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM] scanning a light beam on the display screen
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/0025—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical correction, e.g. distorsion, aberration
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N9/00—Details of colour television systems
- H04N9/12—Picture reproducers
- H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
- H04N9/3179—Video signal processing therefor
- H04N9/3185—Geometric adjustment, e.g. keystone or convergence
Definitions
- the invention relates to a method according to the preamble of patent claim 1.
- miniaturization of projection devices for their use in interaction with mobile telephones can be a way out of this contrast.
- a promising design of mini projectors is the projection with the aid of a laser beam deflected via a 2D micromirror.
- the laser beam scans the projection surface line by line, similar to the electron beam in a cathode ray tube.
- An image is created by modulating the image data onto the laser beam.
- a problem in the projection with mobile projection systems is that the angle between the projection direction, or between the center beam of the projection beam, and the normal of the projection surface can change during the projection. If this angle is not zero, image distortions occur, the so-called trapezoidal distortion or keystone distortion.
- the invention has for its object to provide a method for electronic equalization of the keystone distortion. This object is achieved by the features specified in patent claim 1 features.
- the compensation of the keystone distortion by means of a counter-distortion of the image content.
- This counterdistraction occurs in particular by a real-time adaptation of the laser modulation.
- Figure 1 is a basic concept of the method according to the invention
- Figure 2 is a schematic diagram for carrying out the inventive method
- FIGS 3 and 4 an application of the method according to the invention.
- the method according to the invention compensates for the trapezoidal drawing in that the image content is, so to speak, counter-distorted before the projection on electronic paths.
- the trapezoidal distortion resulting from the optical path is, for example, influenced by an oblique angle of incidence of the projection beam onto a projection surface, compensated by an electronically generated opposite distortion or distortion.
- an at least almost distortion-free projection image with parallel edges is formed as desired.
- the optical keystone distortion produces a comparatively wider image line at the upper edge of the image than at the lower edge.
- Such a distortion is caused, for example, by se by an obliquely upwardly directed projector on ei ⁇ nem table.
- the orientation between the projection axis and the projection surface is to be determined.
- methods for example via inclination sensors, or methods based on distance measurements. These methods are not the subject of the invention and are therefore not described in detail.
- the counter-distortion of the image content takes place by adaptation of the laser modulation.
- the pixels at the upper edge of the image are slightly compressed, for example by an algorithm, during the projection of a line. This results in narrower lines at the upper edge of the image projection and wider lines at the lower edge. This is done, as already stated in the principle description, in opposite relationship to the existing or on optical way resulting keystone distortion.
- the maximum line length in the example shown is the length of the line at the bottom of the screen.
- the line length t z thus also changes.
- the length of the delay time t D is linearly reduced from its maximum value in the uppermost row, for example, down to the value zero in the last row.
- the last, lowest line is a - largely - undistorted displayed line.
- the laser remains dark, ie no pixels are displayed on the projection surface.
- the delay time t D will increase from a value of zero to its maximum value or extreme value.
- the number of pixels per line is preferably constant throughout the image.
- the method according to the invention can be used in all laser projection devices in which the projection beam is deflected via micromirrors.
- One of the advantages is that no additional mechanical or optical components are needed, but only the activation of the laser is expanded.
- the method can be implemented, for example, as an electronic circuit, FPGA (ASIC) module or as software in a microcontroller or DSP.
- ASIC electronic circuit
- FIG 3 the method is illustrated by the example of a built-in a pen projection system. The details are the figure removed.
- the projection is designed in this example to an angle ⁇ of preferably 60 degrees between pin axis and projection surface. If, during use of the pen, this angle is changed by the hand position of the user, this change can be detected, for example, via an inclination sensor and corrected in real time by the method according to the invention.
- the method according to the invention is basically not only suitable for compensating a trapezoidal distortion in one direction, but can also compensate for distortions that arise due to the inclination of the projection unit in several directions or due to rotation.
Abstract
Description
Claims
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE102004056753 | 2004-11-24 | ||
DE102004056753.0 | 2004-11-24 |
Publications (1)
Publication Number | Publication Date |
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WO2006056577A1 true WO2006056577A1 (en) | 2006-06-01 |
Family
ID=35840499
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/EP2005/056171 WO2006056577A1 (en) | 2004-11-24 | 2005-11-23 | Trapezoid rectification in laser projection systems |
Country Status (1)
Country | Link |
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WO (1) | WO2006056577A1 (en) |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5465121A (en) * | 1993-03-31 | 1995-11-07 | International Business Machines Corporation | Method and system for compensating for image distortion caused by off-axis image projection |
EP0773679A2 (en) * | 1995-11-13 | 1997-05-14 | Daewoo Electronics Co., Ltd | Method for pre-compensating an asymmetrical picture in a projection system for displaying a picture |
US6191827B1 (en) * | 1998-12-01 | 2001-02-20 | Oplus Technologies Ltd. | Electronic keystone correction for electronic devices with a visual display |
US6493044B1 (en) * | 1998-06-01 | 2002-12-10 | Mustek Systems Inc. | Digital keystone modulation circuit |
US20040036844A1 (en) * | 2002-06-12 | 2004-02-26 | Wood John S. | Automatic keystone correction system and method |
-
2005
- 2005-11-23 WO PCT/EP2005/056171 patent/WO2006056577A1/en active Application Filing
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5465121A (en) * | 1993-03-31 | 1995-11-07 | International Business Machines Corporation | Method and system for compensating for image distortion caused by off-axis image projection |
EP0773679A2 (en) * | 1995-11-13 | 1997-05-14 | Daewoo Electronics Co., Ltd | Method for pre-compensating an asymmetrical picture in a projection system for displaying a picture |
US6493044B1 (en) * | 1998-06-01 | 2002-12-10 | Mustek Systems Inc. | Digital keystone modulation circuit |
US6191827B1 (en) * | 1998-12-01 | 2001-02-20 | Oplus Technologies Ltd. | Electronic keystone correction for electronic devices with a visual display |
US20040036844A1 (en) * | 2002-06-12 | 2004-02-26 | Wood John S. | Automatic keystone correction system and method |
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