Piezoelectric Speckle Suppression for Laser Projection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current speckle reduction devices for diffractive head-up displays are complex and require precise adjustments, limiting their industrial applicability, and are ineffective for speckle of larger amplitude, as they primarily rely on mirror-based solutions that only partially reduce speckle and do not uniformize the beam.
Innovation Solution
A laser-based projection unit with a speckle suppression device using a diffusing medium that undergoes a composite vibration mode, such as bending and rotation, driven by piezoelectric elements, to achieve random spatial phase averaging and beam uniformization, which can be integrated into existing projection systems without modifying the optical design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If mirror-based speckle reduction devices are used, then speckle is reduced slightly, but the device complexity increases and precise adjustments are required
Solution Approach 1:
The patent extracts the speckle reduction function from complex mirror-based optical systems and implements it through a simple acoustic modulator that directly modulates the laser source. This eliminates the need for additional mirrors, complex optical paths, and precise mechanical adjustments while maintaining effective speckle reduction.
Solution Approach 2:
The patent replaces mechanical mirror-based phase averaging systems with an acoustic field-based modulation system. The acoustic modulator uses sound waves to create dynamic refractive index variations in a liquid medium, achieving phase randomization without mechanical moving parts, thereby reducing device complexity and eliminating the need for precise mechanical adjustments.
2Object-affected harmful factors
If mirror-based speckle reduction devices are used, then speckle is reduced, but the beam uniformity is not improved
Solution Approach 1:
The patent employs acoustic vibrations (sound waves) in a liquid medium to create dynamic, random phase modulations of the laser beam. This vibrational approach randomizes the phase distribution across the beam profile, simultaneously reducing speckle noise and improving beam uniformity by preventing coherent interference patterns that cause non-uniformity.
Solution Approach 2:
The patent changes the physical state and properties of the modulation medium by using an acoustic field to dynamically alter the refractive index distribution in a liquid. This parameter change creates time-varying phase modulations that affect both speckle reduction and beam uniformity, unlike static or simple translational mirror movements.
3Object-affected harmful factors
If mirror-based speckle reduction devices are used, then speckle reduction is achieved, but the solution is only available for small amplitude speckle
Solution Approach 1:
The patent implements a dynamic acoustic modulation system that can adapt to various speckle amplitudes by adjusting the acoustic power and frequency. The liquid medium's refractive index variations respond dynamically to the acoustic field, providing flexible control over phase randomization intensity, making the system effective for both small and large amplitude speckle conditions.
4Object-affected harmful factors
If complex optical systems with precise adjustments are used, then speckle reduction is achieved, but ease of manufacture and industrial application are limited
Solution Approach 1:
The acoustic modulator is a self-contained device that requires no external alignment or adjustment mechanisms. The acoustic field automatically creates the necessary phase modulations when applied to the liquid medium, eliminating the need for complex assembly procedures and precise adjustments during manufacturing and installation, thereby improving ease of manufacture and industrial applicability.
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
Effectively reduces speckle noise of any magnitude and improves the uniformity of the beam, enhancing the quality of virtual images in diffractive head-up displays, suitable for both diffractive and holographic combiners, without generating audible noise or affecting the optical design.
Implementation Method 1
A laser based projection unit for diffractive head up display having a laser speckle suppression device based on piezoelectric actuating
Implementation Method 2
A laser-based projection unit with a speckle suppression device using a diffusing medium that undergoes a composite vibration mode, such as bending and rotation
Implementation Method 3
The phenomenon of speckle appears when we illuminate a display or a naturally rough surface with a light spatially and temporally coherent as the light generated by a laser source
Data Source
Figure 1~3
Figure 4~6
Figure 7
AI summary
A projection unit comprising a coherent light source (12) such as a laser diode and a beam shaping element (14) forming a light beam which is directed towards a display (16), characterized in that it comprises a laser speckle suppression device (18) which is positioned between the laser source and the display and wherein the laser speckle suppression device is a diffusing element actuated randomly by a piezoelectric vibrating structure.