Trapezoidal Distortion Correction Using Rotatable Range Finder

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Solution Overview

Problem

Existing projector technologies struggle to accurately correct trapezoidal distortion when the projector is mounted at an inclined angle, leading to image distortion and reduced image quality, especially in applications requiring high accuracy like CAD drawing display.

Innovation Solution

The method involves using a rotatable range finder to measure the trend of change in the distance between the projector and the projection plane, determining the correction included angle based on this trend, and then correcting the trapezoidal distortion accordingly. This approach allows for automatic and accurate trapezoidal distortion correction regardless of the projector's orientation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Shape

If digital trapezoidal distortion correction is applied, then trapezoidal image distortion is solved, but image quality is reduced with blurred lines and character edges

Engineering Contradiction:

Improveimage shape accuracyVSAvoidimage definition quality

Core Design Contradiction:

ShapeVSManufacturing precision

Solution Approach 1:

The patent replaces digital image processing correction with an optical correction system using a reflective mirror. The mirror physically adjusts the projection light path to pre-correct trapezoidal distortion before the image is formed, avoiding post-processing digital correction that degrades image quality. The mirror's angular adjustment mechanically compensates for the trapezoidal effect caused by inclined projection.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system performs preliminary optical correction of the projection light before the image is projected onto the screen. By adjusting the reflective mirror to pre-correct the light path geometry, the system prevents trapezoidal distortion from occurring in the first place, rather than correcting it digitally after the image is formed.

Inventive Principle:

Principle #10Preliminary action

2Extent of automation

If automatic vertical trapezoidal distortion correction is used with limited angle range, then correction is achievable within 0°-45°, but accurate correction cannot be realized when included angle exceeds 45°

Engineering Contradiction:

Improveautomatic correction capabilityVSAvoidprojection angle detection accuracy

Core Design Contradiction:

Extent of automationVSMeasurement precision

Solution Approach 1:

The system employs a movable reflective mirror that can dynamically adjust its angular position to accommodate various projection angles. The mirror's position is adjusted based on the detected projection angle, allowing the system to maintain accurate correction across a wide range of angles including those exceeding 45°, rather than being limited to a fixed angular range.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system uses a sensor to detect the projection angle and provides feedback to the control system. Based on this feedback, the reflective mirror's position is automatically adjusted to the appropriate angle for correction. This closed-loop feedback mechanism enables accurate detection and correction of projection angles beyond the limited 0°-45° range of conventional systems.

Inventive Principle:

Principle #23Feedback

3Area of stationary object

If projector is mounted at inclined angle to reach projection plane, then projection coverage is improved, but trapezoidal distortion occurs

Engineering Contradiction:

Improveprojection coverage areaVSAvoidprojection shape accuracy

Core Design Contradiction:

Area of stationary objectVSShape

Solution Approach 1:

The reflective mirror serves as an intermediary optical element between the projector and the projection screen. It receives the projection light from the inclined projector and redirects it at the appropriate angle to the screen, acting as a mediator that decouples the projector's inclined mounting position from the final projection geometry, thereby maintaining shape accuracy while allowing flexible positioning.

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution enables automatic and accurate trapezoidal distortion correction, improving image quality and ensuring precise projection even when the projector is mounted at inclined angles, thus addressing the limitations of existing technologies.

Implementation Method 1

measuring the distance between a projector and a projection plane by using the rotatable range finder

Methodology Applied

Scientific EffectLight reflection: Reflection

Data Source

PatentEP3306390B1Method and apparatus for realizing trapezoidal distortion correction of projection plane

Publication Date: 2025.05.28 ZTE CORP

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AI summary

Disclosed are a method and an apparatus for correcting trapezoidal distortion of a projection plane. The method includes: measuring a trend of change in a distance to a projection plane by using a rotatable range finder, and determining a correction included angle according to the trend of change; and correcting trapezoidal distortion according to the determined correction included angle.