Reduction of Visual Artifacts in Laser Beam Scanning Displays

Area of Science:

• Optics and Photonics
• Display Technologies
• Micro-Electro-Mechanical Systems (MEMS)

Background:

• Laser beam scanning (LBS) projection systems using MEMS micromirrors are valuable for AR glasses and portable projectors due to their size and power efficiency.
• Raster scanning, a common LBS method, produces artifacts like dark bands and non-uniform line spacing, degrading image quality.
• Existing LBS systems lack methods to mitigate these scanning artifacts effectively.

Purpose of the Study:

• To address and eliminate scanning artifacts in MEMS-based LBS projection systems.
• To improve the scanning fill factor and uniformity of displayed images.
• To enhance the overall visual experience in LBS projection applications without hardware changes.

Main Methods:

• Introduced random variations to the slow-axis driving signal of MEMS micromirrors.
• Altered the vertical offset of scanning trajectories between successive scan cycles.
• Utilized the temporal integration effect of human vision for trajectory overlap and fill factor enhancement.

Main Results:

• Reduced the maximum non-uniform line spacing ratio from 7:1 to 1:1.
• Lowered the modulation of the scanned display image to 0.0006, below the human contrast threshold of 0.0039.
• Successfully eliminated dark bands and improved scanning trajectory distribution.

Conclusions:

• The proposed method effectively mitigates scanning display artifacts in LBS systems.
• Randomizing the slow-axis signal enhances the scanning fill factor and image uniformity.
• This technique offers a hardware-free solution for improving MEMS-based LBS projection quality.