Trapezoidal Distortion Correction via Partial Pattern Projection
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Solution Overview
Problem
Existing image processing technologies face challenges in accurately detecting screen frames for trapezoidal distortion correction in projectors, as they often require a black image projection, which disrupts the user's view and complicates the detection of frame lines due to lens distortion.
Innovation Solution
An image processing device that superimposes a pattern with a nearly black area on the image, allowing for the detection of frame lines within a part of the projected surface without disturbing the user's view, and calculates a coordinate conversion factor to perform trapezoidal distortion correction based on the detected lines and their apexes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a black image is projected on the entire projection panel to detect screen frame lines, then the screen frame can be detected, but the user cannot confirm the image during the process and the view is disturbed
Solution Approach 1:
The projection panel is divided into a detection region (with nearly black area and pattern) and a display region. The detection region occupies only a portion of the projection panel, allowing screen frame line detection without requiring the entire panel to display black, thus maintaining user view of the remaining image content.
Solution Approach 2:
Only a specific local region of the projection panel is used for detection purposes, while other regions maintain normal image display quality. The nearly black area with pattern is localized to enable detection without affecting the overall viewing experience.
2Measurement precision
If the entire projection panel is used for pattern projection, then detection can be performed, but the processing load increases and user view is blocked
Solution Approach 1:
The projection panel is segmented into detection and display regions. Only the detection region contains the pattern and nearly black area, reducing the amount of processing required compared to using the entire panel, while still providing sufficient data for accurate frame line detection.
3Measurement precision
If lens distortion is present in the camera, then accurate detection of screen frame as four lines becomes difficult, but detection is still required for distortion correction
Solution Approach 1:
The system uses the detected screen frame lines and pattern positions to calculate coordinate conversion factors that compensate for lens distortion. The feedback loop continuously refines the detection accuracy by using the nearly black area and pattern as reference markers to correct for distortion effects.
Solution Approach 2:
The system changes the detection parameters by using a pattern with specific geometric features (lines and nearly black areas) that are more resistant to lens distortion effects. The coordinate conversion factors are adjusted based on detected line positions to compensate for distortion.
Data Source
AI summary
A measurement pattern having a predetermined shape and L-shaped black areas are superimposed and output to a liquid crystal panel, and a pattern is detected from a taken pattern image. Lines are detected based on an image of a screen frame in the pattern image, and coordinate conversion factors for conversion of camera coordinates in the taken image into panel coordinates are calculated based on panel coordinate values of the pattern and camera coordinate values of the pattern detected from the pattern image. Then, apexes of the screen frame in the panel coordinates are obtained based on the lines and the conversion coordinate factors detected with respect to each corner, correction values are calculated, and trapezoidal distortion correction is performed.