MEMS Mirror Control for Uniform Laser Scan Patterns
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Solution Overview
Problem
Laser scanning projectors using MEMS components face issues with non-uniform scan patterns and varying beam spot movement speed due to keystone angles, leading to inconsistent vertical spatial resolution and image brightness, which degrade image quality.
Innovation Solution
A processor generates and stores mechanical angle values for a slow-axis micro-mirror to maintain a uniform scan pattern by determining angles based on distances and times, ensuring constant beam spot speed across the target area, and generates driving signals to control the micro-mirror accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a linear scan is used with constant angular speed mirror actuation, then the scanning mechanism is simple, but the scan pattern becomes non-uniform and beam spot speed varies
Solution Approach 1:
The patent applies dynamics by transitioning from static constant angular speed actuation to dynamic variable angular speed actuation. The mirror actuation speed is continuously adjusted during the scan cycle to compensate for keystone effects, ensuring uniform scan pattern and constant beam spot speed across the entire scan area.
Solution Approach 2:
The patent changes the actuation parameter from constant angular speed to variable angular speed. By dynamically adjusting the mirror actuation speed parameter based on position, the system maintains uniform scan pattern and consistent image quality across different scan positions while keeping the mechanical structure simple.
2Area of stationary object
If keystone angle increases, then the projector can cover larger area, but vertical spatial resolution becomes non-constant
Solution Approach 1:
The patent dynamically adjusts the mirror actuation speed parameter as a function of scan position to compensate for keystone effects. This parameter change ensures that even when covering large areas with increased keystone angles, the vertical spatial resolution remains constant across the entire scan area.
3Ease of operation
If linear scan with constant speed is used, then the control is simple, but image brightness becomes uneven
Solution Approach 1:
The patent adjusts the mirror actuation speed parameter dynamically to maintain constant beam spot speed across the scan area. This ensures uniform illumination and consistent image brightness while preserving computational simplicity through pre-calculated lookup tables or analytical solutions.
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 solution achieves a uniform scan pattern with consistent vertical resolution and brightness, improving image quality by maintaining constant beam spot speed and uniformity across the scan area.
Implementation Method 1
directing the RGB laser beam to either a bi-axial mirror, or a set of two uni-axial mirrors working in tandem
Data Source
AI summary
Mirror control circuitry described herein is for controlling a first micro-mirror of a micro-mirror apparatus that scans across a target area in a scan pattern. The mirror control circuitry includes a processor that determines a mechanical angle of the first micro-mirror for a given instant in time during scanning of the first micro-mirror between upper and lower rotational limits, the mechanical angle being such to maintain the scan pattern as being uniform while the micro-mirror apparatus scans across the target area between the upper and lower rotational limits. The processor also generates a driving signal for the first micro-mirror as a function of the determined mechanical angle for the first micro-mirror at the given instant in time.