Laser Scanning Video Projection Device Safety Luminance Control
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Solution Overview
Problem
Existing video projection devices using scanning-type lasers face a challenge in balancing safety and luminance, as the upper limit of laser output and screen brightness are determined by exposure levels at the end portions during reciprocating scans, making it difficult to ensure both safety and increased luminance simultaneously.
Innovation Solution
A video projection device and method that control the emission and scanning of a laser light source unit and laser scanning unit based on a video signal, varying the scanning angle and emission time between outgoing and return paths to reduce exposure levels at end portions, while maintaining or increasing luminance by adjusting the scanning cycle and emission periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the laser output is increased to improve screen luminance, then the brightness of the projected screen is improved, but the exposure level at end portions exceeds safety limits
Solution Approach 1:
The patent applies local quality by differentiating the laser emission control between different spatial regions. Specifically, the laser emission is stopped at end portions of the scanning range where exposure levels are highest, while maintaining emission during intermediate portions. This spatial differentiation allows the system to reduce peak exposure levels at critical locations without compromising overall screen luminance, as the majority of the scanning area continues to receive laser illumination.
Solution Approach 2:
The patent implements periodic action through pulse-width modulation of the laser emission. The laser is emitted in periodic pulses synchronized with the scanning motion, with the emission duration adjusted based on the scanning position. By controlling the emission to occur only during safe exposure windows and stopping emission at end portions, the system achieves periodic on-off cycles that maintain safety while preserving average luminance levels.
2Reliability
If the laser emission is stopped at end portions to reduce exposure levels, then safety is improved, but the luminance of the entire screen is reduced
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the laser emission parameters (on/off timing, pulse width) based on the scanning position. The control unit modifies the emission parameters in real-time, stopping emission when the scanning mirror approaches end portions and resuming emission during intermediate portions. This dynamic parameter adjustment allows the system to maintain safety compliance at end portions while preserving overall screen luminance through compensated emission during other regions.
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 approach allows for a guaranteed safety and improved luminance of the projected screen by reducing exposure levels at critical end portions, achieving a balance between safety and increased output.
Implementation Method 1
a scanning-type laser projector has been developed which draws video by varying the angle of laser light with a MEMS mirror or the like to perform scanning on a projected plane
Implementation Method 2
a laser light source unit which emits a laser
Data Source
AI summary
There are provided a video projection device and a video projection method which can realize both a guarantee of safety and an increase in luminance of a screen. The video projection device includes: a laser light source unit which emits a laser; a laser scanning unit which is provided with one or more scanning directions and project video by performing a reciprocating scan of the laser with respect to a scanning direction with the highest scanning frequency; and a control unit which controls operations of the laser light source unit and the laser scanning unit depending on a video signal so that a scanning angle when emission of the laser in an outgoing path is stopped is different from a scanning angle when emission of the laser in a return path is started with respect to the scanning direction along which the reciprocating scan is performed.