Laser Blanking Apparatus for Projection Display Stray Light Control
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Solution Overview
Problem
Linear spatial light modulators in projection systems face inefficiencies due to scanning sequence limitations, such as light output reduction during mirror reset and charge build-up, leading to stray light and degraded contrast, particularly when using laser illumination.
Innovation Solution
Implementing laser blanking synchronized with the scan sequence to minimize stray light, and using an electro-optical modulation device like an LC shutter to control illumination dynamically, which can also flip the substrate to eliminate hysteresis and enhance contrast by adjusting attenuation levels based on image content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If laser illumination is used with linear spatial light modulators, then light efficiency is improved, but stray light increases during mirror reset causing degraded contrast
Solution Approach 1:
The patent applies preliminary anti-action by detecting the mirror reset state and preemptively blanking the laser illumination before stray light can reach the screen. The control system monitors mirror position and interrupts the laser beam during reset periods, preventing the harmful stray light effect before it occurs.
Solution Approach 2:
The patent introduces an intermediary control system that includes a mirror position sensor and a laser blanking mechanism. This intermediary detects the mirror reset condition and mediates between the laser source and the spatial light modulator, inserting a blanking action that blocks stray light during critical reset periods.
2Object-generated harmful factors
If mechanical iris is controlled in real time to reduce light from off-state devices, then contrast ratio is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the mechanical iris control system with an optical blanking approach. Instead of using a mechanically complex real-time iris controller, the system uses laser blanking controlled by mirror position detection, substituting mechanical complexity with a simpler optical interruption mechanism.
Solution Approach 2:
The patent extracts the contrast improvement function from the complex mechanical iris system and implements it separately through laser blanking. By removing the need for real-time iris control, the system achieves contrast ratio improvement through a simpler, dedicated blanking mechanism triggered by mirror reset detection.
3Object-generated harmful factors
If light-shielding member reflects stray light away from projection path, then some stray light is reduced, but reflected light may still reach screen causing contrast degradation
Solution Approach 1:
The patent converts the potential harm of stray light into a detectable signal. By using mirror position sensors to detect when the mirror is in reset position, the system identifies the exact moments when stray light would occur and uses this information to trigger precise laser blanking, turning the stray light problem into a controlled timing signal.
Solution Approach 2:
The patent takes preliminary action by detecting mirror position and blanking the laser before stray light can be generated. The control system continuously monitors mirror position and preemptively interrupts the laser beam during reset periods, preventing stray light formation rather than attempting to shield or block it afterward.
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 significantly improves contrast by reducing stray light and maintaining high light efficiency, allowing for better image reproduction and matching high-end commercial projection equipment standards.
Implementation Method 1
using an electro-optical modulation device like an LC shutter to control illumination dynamically
Implementation Method 2
LC shutter
Implementation Method 3
Implementing laser blanking synchronized with the scan sequence to minimize stray light
Data Source
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AI summary
A display apparatus (10) has at least one color channel providing a modulated light for each of a plurality of image frames (92). One or more laser sources that provide an illumination beam having a first polarization transmission axis. An imaging modulator (854, 85g, 85b) in the path of the illumination beam is actuable to direct the modulated light toward a projection lens. A laser blanking apparatus in the path of the modulated light is disposed to block transient light between image frames and has at least one analyzer (66) having a second polarization transmission axis that is orthogonal to the first polarization transmission axis and at least one light polarization modulator that is synchronously timed to rotate polarization of transient light during an interval between frames.