Laser Illumination Apparatus Speckle Noise Reduction
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Solution Overview
Problem
Conventional illumination apparatuses using laser sources face challenges in achieving uniform surface illumination due to speckle noise caused by the temporal coherence of laser beams, which complicates image quality and noise reduction.
Innovation Solution
An illumination apparatus incorporating a two-dimensional diffraction optics and an optical guiding member with a changing part that alters the incident position of diffraction beams, either through a galvano mirror, reflective optics, or a diffuser plate, to reduce speckle noise and achieve uniform illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a laser source is used for illumination, then high brightness and coherence are achieved, but speckle noise is generated due to temporal coherence
Solution Approach 1:
The patent divides the laser beam into multiple diffraction orders using a two-dimensional diffraction grating. Each diffraction order acts as an independent light path, and their superposition on the object surface creates uniform illumination while reducing speckle noise through spatial diversity of the coherent beams
Solution Approach 2:
The patent transitions from one-dimensional to two-dimensional diffraction by using a two-dimensional diffraction grating with grating lines in both x and y directions. This creates a two-dimensional array of diffraction orders that provide spatial diversity in both dimensions, effectively reducing speckle noise while maintaining uniform illumination across the object surface
2Illumination intensity
If a uniformizing optical system (fly-eye lens or kaleidoscope) is used, then uniform surface illumination is achieved, but the system complexity and manufacturing difficulty increase
Solution Approach 1:
The patent merges the functions of beam splitting and uniformization into a single two-dimensional diffraction grating component. This eliminates the need for separate fly-eye lenses or kaleidoscope systems, reducing the number of optical components and simplifying the overall system configuration while achieving uniform illumination
Solution Approach 2:
The patent replaces complex mechanical uniformizing systems (fly-eye lenses, kaleidoscopes) with a static two-dimensional diffraction grating that achieves uniformization through optical diffraction and interference. This substitution eliminates moving parts and complex alignment requirements, reducing system complexity and improving reliability
3Illumination intensity
If a micro fly-eye lens is used for narrow field illumination, then uniform illumination is achieved, but manufacturing accuracy becomes difficult to ensure
Solution Approach 1:
The patent uses a two-dimensional diffraction grating that can be manufactured using standard photolithography and etching techniques on silicon or glass substrates. These gratings can be produced with high precision using semiconductor fabrication processes, making them more manufacturable and cost-effective than precision micro fly-eye lenses while achieving the same uniformization function
4Device complexity
If the optical system is simplified, then device complexity is reduced, but the ability to decrease speckle noise may be compromised
Solution Approach 1:
The two-dimensional diffraction grating performs multiple functions simultaneously: it splits the laser beam into multiple diffraction orders, uniformizes the illumination across the object surface, and reduces speckle noise through spatial diversity. This multi-functionality allows the system to be simplified without compromising speckle noise reduction capability
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 configuration effectively decreases speckle noise and achieves uniform illumination, improving image quality and resolution while simplifying the apparatus configuration and reducing component costs.
Implementation Method 1
a two dimensional diffraction optics on which laser beam from the laser source is made incident
Implementation Method 2
an optical guiding member on which diffraction beams from the two dimensional diffraction optics are made incident and through which incident beams travel while repeating total reflection
Data Source
AI summary
According to one aspect of the present invention, there is provided an illumination apparatus 110 including a laser source 11, a two dimensional diffraction optics 13 on which laser beam from the laser source is made incident, a rectangular rod 14 on which diffraction beams from the two dimensional diffraction optics 13 are made incident and through which incident beams travel while repeating total reflection, and a galvano mirror 12 changing an incident position of the diffraction beams from the two dimensional diffraction optics 13 in an incident end surface of the rectangular rod 14.