Keystone Correction Using Complementary Line Segments
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Solution Overview
Problem
Existing projection display systems face challenges in properly correcting keystone distortion when detecting incomplete frame sides of a screen, leading to incomplete keystone correction.
Innovation Solution
A projection display apparatus that includes an image capturing unit, an angle calculator, a straight line detector, and a line segment complementing section to calculate and set complementary line segments based on the relative angle between the projection plane and the projector, ensuring a rectangular area on the projection plane for accurate keystone correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If keystone correction is performed based on detected frame sides only, then correction accuracy is improved when all frame sides are detected, but correction cannot be performed when some frame sides are not detected
Solution Approach 1:
The system performs preliminary detection of the projection plane angle and vanishing points before attempting frame side detection. This preliminary information is used to guide the detection process and provide fallback mechanisms when frame sides are not fully detected, ensuring correction can proceed in more situations.
Solution Approach 2:
Vanishing points serve as intermediary elements between the detected frame sides and the keystone correction process. When frame sides are not fully detected, the vanishing points derived from the projection angle serve as substitute reference points, enabling correction to proceed with partial information.
2Adaptability or versatility
If frame side detection is made more sensitive to detect partial frame sides, then adaptability of keystone correction is improved, but detection precision of actual frame sides deteriorates
Solution Approach 1:
The frame detection process is segmented into multiple stages: initial detection of frame sides, detection of vanishing points from projection angle, and complementary detection using geometric relationships. This segmentation allows the system to use different detection strategies for different parts of the frame, maintaining precision while improving adaptability.
Solution Approach 2:
The system uses feedback from the detected projection angle and initial frame side positions to adjust the detection process. When frame sides are not fully detected, the system feeds back the vanishing point information and geometric constraints to guide complementary detection, ensuring that adaptability improvements do not compromise precision.
3Adaptability or versatility
If complementary line segments are added to compensate for undetected frame sides, then versatility of keystone correction is improved, but complexity of the correction process increases
Solution Approach 1:
The angle calculator and vanishing point calculator are designed to serve multiple functions: they provide information for both initial frame side detection and complementary line segment generation. This multi-functionality reduces overall system complexity while improving versatility, as the same computational components handle both detection scenarios.
Solution Approach 2:
The system dynamically changes parameters based on detection results. When all frame sides are detected, the system uses standard correction parameters. When frame sides are incomplete, it changes to use vanishing point-based parameters and geometric constraints, allowing the same system to handle both cases without requiring entirely separate correction pathways.
Data Source
AI summary
A projection display apparatus for displaying an image on a projection plane by projection, includes: an image capturing unit capturing an image; an angle calculator calculating an angle of the projection plane relative to the projection display apparatus; a straight line detector detecting at least one reference line segment in the captured image; a line segment complementing section setting at least one complementary line segment in the captured image on the basis of the calculated angle so that an area on the projection plane corresponding to an area defined by the reference line segment and the complementary line segment is rectangular; and a keystone corrector correcting a keystone distortion of an image displayed on the projection plane on the basis of the reference line segment and the complementary line segment.