HUD Laser Scanning Phase Shift to Reduce Moire Interference
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Solution Overview
Problem
Current heads-up display (HUD) systems with microlens arrays in laser scanning systems suffer from interference patterns like moire and diffraction, which degrade image quality and viewability due to the relationship between scanning lines and microlens arrays, limiting the improvement of image quality and virtual image visibility.
Innovation Solution
The HUD system performs two-dimensional scanning twice in both the main and sub-scanning directions with different phases, starting points, and amplitude centers shifted in the sub-scanning direction, using a MEMS mirror and microlens array to generate an intermediate image, controlling the driving voltage to prevent moire development and enhance image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a microlens array is used in a laser scanning system to generate an intermediate image, then the image contrast is improved, but interference patterns such as moire and diffraction patterns occur, degrading image quality and viewability
Solution Approach 1:
The patent segments the scanning process into multiple passes, performing two-dimensional scanning twice with different phases. The first scanning performs main scanning and sub-scanning in a normal sequence, while the second scanning performs main scanning and sub-scanning in a reversed sequence. This segmentation of the scanning process prevents the formation of moire patterns by ensuring that scanning lines from different passes do not align to create interference patterns.
Solution Approach 2:
The patent implements periodic action by performing two-dimensional scanning twice to generate one frame of intermediate image. The first and second scans are conducted with different phases, where the second scanning reverses the sequence of main and sub-scanning compared to the first scan. This periodic repetition with phase variation eliminates moire interference while maintaining image quality.
2Manufacturing precision
If the pitches of microlenses or scanning lines are adjusted to improve image quality, then the occurrence of moire is reduced, but the device complexity increases due to additional control requirements
Solution Approach 1:
The patent applies dynamics by making the scanning sequence flexible and adaptive. Instead of using a fixed scanning pattern that may cause moire, the system dynamically adjusts the scanning sequence by performing the second two-dimensional scanning in a reversed order compared to the first scan. This dynamic approach allows the system to maintain consistent scanning line density while preventing moire interference, without requiring complex hardware modifications.
Solution Approach 2:
The patent changes the phase relationship between scanning lines by performing two-dimensional scanning twice with different phases. The first scanning uses a normal sequence while the second scanning uses a reversed sequence, effectively changing the temporal and spatial parameters of the scanning process. This parameter change ensures that scanning lines from different passes do not align to create moire patterns, while maintaining consistent scanning line density for high image quality.
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 effectively reduces moire interference and improves the visibility and quality of the virtual image displayed to the driver, enhancing the overall performance of the HUD system by ensuring consistent scanning line density and preventing moire occurrence.
Implementation Method 1
an optical deflector to deflect the laser beam two-dimensionally
Implementation Method 2
a microlens array (MLA) may be used to generate an intermediate image. A microlens array is an optical element on which a plurality of minute lenses (microlenses) are arranged at regular intervals
Implementation Method 3
a light source unit to emit a laser beam
Data Source
AI summary
An image display apparatus and a vehicle provided with the image display apparatus. The image display apparatus includes a light source to emit a laser beam, an optical deflector to deflect the laser beam two-dimensionally, and an intermediate image generator to perform two-dimensional scanning twice in a main scanning direction and a sub-scanning direction with the laser beam deflected by the optical deflector to generate an intermediate image of one frame, where the laser beam deflected by the optical deflector draws two scanning lines. In the image display apparatus, the two scanning lines have two different phases for the two-dimensional scanning for a first time and the two-dimensional scanning for a second time, respectively.