Imaging Device Speckle Reduction via Temporal Attenuation
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Solution Overview
Problem
The use of laser-type light sources in head-up displays results in a speckle phenomenon due to coherence, which existing technologies have not effectively addressed, leading to suboptimal image quality.
Innovation Solution
An image forming device with a liquid crystal cell and polarization element that applies a variable voltage to control light beam attenuation, ensuring slightly different attenuation between frames to mitigate speckle, while maintaining a constant attenuation setpoint, using a movable mirror to scan a diffuser and project the image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If laser-type light sources are used to illuminate the diffuser, then the luminance and brightness of the displayed image are improved, but the speckle phenomenon occurs due to the coherence of the laser light
Solution Approach 1:
The patent applies dynamics by making the attenuation variable over time rather than static. The control module varies the attenuation from one frame to the next while maintaining an almost identical attenuation level, creating temporal variation that disrupts the speckle pattern without significantly changing the overall luminance. This temporal dynamics resolves the contradiction by allowing laser illumination while mitigating speckle through controlled variation.
Solution Approach 2:
The patent changes the attenuation parameter slightly between frames. The control module determines attenuation values that are almost identical but not exactly the same for successive frames. This parameter change approach allows the system to maintain high luminance from laser sources while introducing sufficient variation to reduce the speckle phenomenon, thereby resolving the technical contradiction.
2Stability of the object's composition
If the attenuation is kept constant to maintain stable image luminance, then the luminance stability is improved, but the speckle phenomenon persists
Solution Approach 1:
The patent introduces temporal dynamics to the attenuation parameter, making it vary slightly from frame to frame rather than remaining completely constant. This dynamic approach maintains luminance stability at the macro level while introducing micro-level variations that disrupt speckle patterns, thereby resolving the contradiction between stability and speckle reduction.
Solution Approach 2:
The patent implements periodic variation in attenuation across frames. The control module systematically varies the attenuation parameter in a periodic manner while maintaining an almost identical average level. This periodic action creates temporal modulation that reduces speckle while preserving overall luminance stability, resolving the technical contradiction.
3Object-generated harmful factors
If the attenuation is varied significantly from one frame to the next to reduce speckle, then the speckle phenomenon is reduced, but the luminance stability deteriorates
Solution Approach 1:
The patent applies parameter changes at a controlled, subtle level. The control module varies the attenuation parameter enough to reduce speckle but keeps the changes almost identical from frame to frame, avoiding significant luminance fluctuations. This controlled parameter change approach resolves the contradiction by finding the optimal variation level that reduces speckle while maintaining luminance stability.
Solution Approach 2:
The patent applies partial action by making small, subtle variations in attenuation rather than large changes. The control module introduces just enough variation to reduce speckle phenonmenon while avoiding excessive changes that would compromise luminance stability. This partial action approach resolves the technical contradiction effectively.
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 effectively reduces the speckle effect in head-up displays by varying the light beam attenuation between frames, improving image quality and extending the lifespan of the liquid crystal cell.
Implementation Method 1
The means for attenuating the light beam comprise a liquid crystal cell capable of imparting to the light beam a variable polarization as a function of a voltage applied to said cell; the attenuation means comprise a polarization element having a given direction of polarization
Implementation Method 2
a diffuser illuminated by the attenuated light beam so as to form an image
Data Source
Figure 1~5
AI summary
An imaging device (2) comprising a beam-forming module (12) configured to generate a light beam, light beam attenuating means (14), a diffuser (18) illuminated by the attenuated light beam so as to form an image, and a control module (10) configured to control the attenuation of the light beam by the attenuating means (14). The control module (10) is configured to control a first attenuation value for a given pixel of a first frame and a second attenuation value for the given pixel of a second frame temporally following the first frame. The second value is different from the first value but corresponds to a substantially identical attenuation. The invention also relates to a head-up display comprising a device of this type.