Zoom Ratio Measurement via Offset Point Detection in Projection Systems
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Solution Overview
Problem
Current projection optical systems with zoom functions face challenges in accurately measuring and correcting for keystone distortion due to variations in focal distance caused by zoom ratio changes, leading to suboptimal image quality.
Innovation Solution
A method involving projecting a measuring image with a measurement point offset from the optical axis, detecting its position, and using pre-established correspondence to determine the zoom ratio, which is then applied to correct keystone distortion, ensuring the accuracy of zoom ratio measurement and image correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the focal distance of the projection optical system is used as an internal parameter in the correction process, then the correction accuracy should be improved, but the focal distance varies when controlling the zoom ratio, leading to measurement inaccuracy
Solution Approach 1:
The patent prepares correspondence between position information and zoom ratio in advance, before actual measurement is needed. This pre-established mapping relationship allows the system to determine zoom ratio directly from position measurements without needing to recalculate or measure focal distance during operation, thus resolving the contradiction between measurement accuracy and focal distance stability
Solution Approach 2:
The patent introduces position information of measurement points as an intermediary variable between the zoom ratio control and the correction process. Instead of directly using focal distance (which varies with zoom), the system uses stable position measurements that correlate with zoom ratio through pre-prepared correspondence, making the measurement process independent of focal distance variations
2Measurement precision
If a measurement point is positioned at an offset from the optical axis, then the zoom ratio can be determined through position detection, but the measurement system becomes more complex
Solution Approach 1:
The patent uses a single measurement point with offset from the optical axis that serves multiple functions: it detects both the zoom ratio through its position and can be used for keystone distortion correction. This multi-functional approach achieves accurate zoom measurement without requiring multiple specialized sensors or complex measurement arrangements
Solution Approach 2:
The measurement point itself provides the measurement information needed for zoom ratio determination through its detected position. The system uses the natural positional relationship between the offset measurement point and the optical axis without requiring additional active measurement components, making the measurement process self-contained and simple
Data Source
AI summary
A method of measuring a zoom ratio of a projection optical system adapted to project image light representing an original image on a projection screen, the method includes: (a) projecting and displaying a measuring image including a measurement point on the projection screen so that the measurement point is displayed at a position with an offset from an optical axis of the projection optical system; (b) detecting a projected measurement point, which is the measurement point projected and displayed on the projection screen, from a measurement point detection position having a fixed position relative to the projection optical system; and (c) determining the zoom ratio using position information of the detected projected measurement point and correspondence between the position information and the zoom ratio, the correspondence being prepared previously.