Projector Screen Inclination Measurement via Modulated Light
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Solution Overview
Problem
Conventional projector systems face challenges in accurately measuring the inclination angle of a projection screen at longer distances, leading to insufficient measurement accuracy due to the limitations of phase difference sensors, which are difficult to miniaturize and require a specific lens configuration, making it hard to achieve distortion-free image projection.
Innovation Solution
A projector system that includes a projection unit, an optical modulator, a photoreception unit, and a distance measurement unit capable of detecting phase differences to measure distances and inclination angles using a matrix array of photodiodes, allowing for accurate calculation of screen inclination even at longer distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional phase difference sensor with lens is used to measure screen inclination, then the device can detect phase difference, but the measurement accuracy decreases as distance increases and the device size cannot be reduced further
Solution Approach 1:
The patent replaces the conventional mechanical/optical phase difference sensor system with a time difference measurement system. Instead of using a sensor that requires lens focusing and phase detection, the invention uses a light source that emits light modulated with identification information and a photodetector that measures the time difference between transmitted and reflected light. This substitution eliminates the lens and complex optical components, enabling accurate measurement at longer distances while reducing device size.
Solution Approach 2:
The patent changes the measurement parameter from phase difference to time difference. By modulating the light source with identification information and measuring the time delay of the reflected light, the system achieves accurate distance and inclination measurements at longer projection distances. This parameter change allows the measurement accuracy to be maintained even as the distance from projector to screen increases.
2Measurement precision
If a conventional phase difference sensor is used, then the device can measure inclination angle, but the device size cannot be reduced further due to lens requirements
Solution Approach 1:
The patent extracts and removes the lens component from the measurement system. By using a time difference measurement approach with modulated light, the invention eliminates the need for lens focusing, thereby removing the space requirement for the lens and reducing the overall device volume while maintaining inclination angle measurement capability.
Solution Approach 2:
The patent replaces the optical-mechanical phase difference sensor system with a temporal measurement system using modulated light and photodetection. This substitution eliminates the lens and associated optical components, significantly reducing the device size while preserving the ability to measure screen inclination angles accurately.
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
The system achieves high accuracy in measuring distances and inclination angles, enabling effective automatic keystone correction (AKC) for distortion-free image projection, even at longer distances, while also reducing the size of the projector components.
Implementation Method 1
a photoreception unit that receives a portion of the light reflected at a point on the projection screen; and a distance measurement unit that detects a phase difference at the photoreception unit between the light projected by the projection unit and the portion of the light reflected at the point on the screen
Data Source
AI summary
A light source 165 of a projection unit 16 AM modulates an electric current supplied to a built-in LED. The projection unit 16 projects the modulated light on a projection screen. A photoreceiver 171 receives, with a time lag, a reflected portion of the modulated light from the screen, which corresponds to a time required for the light to travel from its projection to its reception. A calculation unit 173 acquires a phase difference between the projected light and its reflection at a respective one of a plurality of points on the screen, acquires a distance from the projector to the respective one of the plurality of points on the screen, and then acquires an inclination angle of the screen. Because the distance from the projector to a respective one of the plurality of points on the screen is acquired based on the corresponding phase difference, the measurement accuracy is improved compared to the triangular distance measuring method. The projector requires no distance measurement-only light source, thereby reducing the size of the projector.