Camera-Assisted Keystone Correction Using Structured Light
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing projector systems face challenges in effectively correcting two-dimensional keystone distortion, which occurs when the projector's optical axis is not perpendicular to the projection screen, requiring manual adjustments and iterative processes that can be cumbersome, especially for large screens or acute offset angles.
Innovation Solution
The implementation of a method using a digital camera attached to the projector to determine pitch and yaw offset angles through structured light patterns and statistical-geometric calibration techniques, creating look-up tables for automatic keystone correction, which does not rely on camera resolution or screen features and can be performed using existing microprocessor and memory in the projector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If manual keystone correction methods are used, then the projector can be adjusted to correct distortion, but the process becomes cumbersome and time-consuming
Solution Approach 1:
The system performs automatic self-calibration by capturing images of the projection screen with the attached camera, detecting geometric features automatically, and computing correction parameters without user intervention. The projector autonomously determines its offset angles and applies keystone correction, eliminating the need for manual adjustment procedures.
Solution Approach 2:
The attached camera provides visual feedback by capturing the projected image on the screen. The system processes this feedback information to automatically detect the projection geometry, calculate offset angles, and adjust keystone correction parameters, creating a closed-loop control system that eliminates manual intervention.
2Manufacturing precision
If iterative adjustment processes are used for keystone correction, then distortion can be corrected, but the correction speed is reduced
Solution Approach 1:
The system performs preliminary calibration by capturing a single image of the projection screen and pre-computing all necessary correction parameters including offset angles and keystone correction values. This preliminary action eliminates the need for iterative adjustments during actual operation, achieving both high accuracy and fast correction speed.
Solution Approach 2:
The patent replaces manual mechanical adjustment mechanisms with an automated vision-based system. The attached camera and processing algorithms substitute for manual positioning and iterative correction, directly computing the optimal projection parameters from a single geometric analysis.
3Measurement precision
If high-resolution cameras with advanced features are used for calibration, then measurement accuracy improves, but device complexity and cost increase
Solution Approach 1:
The system uses inexpensive, standard consumer cameras instead of specialized high-resolution industrial cameras. The calibration methodology is designed to work effectively with low-resolution sensors by focusing on geometric feature detection rather than pixel-level detail, making the system affordable and accessible.
Solution Approach 2:
The system creates a simplified geometric model (copy) of the projection geometry by detecting key features like screen corners and edges in the camera image. This abstract geometric representation is sufficient for calculating offset angles and correction parameters without requiring high-fidelity imaging capabilities.
Data Source
AI summary
A system and method for facilitating keystone correction in a given model of projector having an attached camera is disclosed. System calibration determines intrinsic and extrinsic parameters of the projector and camera; then control points are identified within a three-dimensional space in front of a screen. The three-dimensional space defines a throw range and maximum pitch and yaw offsets for the projector/screen combination. At each control point, the projector projects a group of structured light elements on the screen and the camera captures an image of the projected pattern. These images are used to create three-dimensional look-up tables that identify a relationship between each image and at least one of (i) pitch and yaw offset angles for the respective control point and (ii) a focal length and a principal point for the respective control point. The given model projectors use the tables in effectuating keystone correction.