Anamorphic Optics for MEMS Spatial Light Modulator Contrast
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Solution Overview
Problem
Existing systems face challenges in achieving high power and improved contrast in spatial light modulators (SLMs) without the need for costly illumination sources with small numerical apertures (NAs), particularly in applications like additive manufacturing (AM), selective laser sintering (SLS), and computer-to-plate (CTP), where high power NIR laser sources are used, leading to reduced contrast due to the use of multiple emitters with low coherence and high NA optics.
Innovation Solution
A system comprising an array of modulators with anamorphic optics that provide a smaller vertical NA and a larger horizontal NA, utilizing high power diode lasers and anamorphic illumination and imaging optics to focus light effectively, allowing for improved contrast by separating 0th order and 1st order diffraction beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high power laser sources with large NA optics are used, then power handling capability is improved, but contrast between pixels is reduced
Solution Approach 1:
The patent segments the numerical aperture control into two independent dimensions: vertical NA is kept small to maintain pixel contrast, while horizontal NA is increased to improve power handling capability. This is achieved through anamorphic optics that independently control illumination angles in orthogonal directions, allowing the system to overcome the traditional trade-off between contrast and power.
Solution Approach 2:
The patent employs asymmetric illumination by using anamorphic optics to create different numerical apertures in the vertical and horizontal directions. The vertical NA is constrained to be smaller than half the diffraction angle to preserve contrast, while the horizontal NA is enlarged to accommodate high power laser sources, creating an asymmetric illumination profile that resolves the contradiction.
2Power
If multiple semiconductor diode lasers are used to achieve high power, then power output is improved, but coherence is reduced leading to lower contrast
Solution Approach 1:
The patent transitions from isotropic illumination to anisotropic illumination by introducing dimensional asymmetry through anamorphic optics. This allows the system to accommodate multiple diode lasers arranged in a linear array along the horizontal axis while maintaining vertical coherence for contrast, effectively using dimensional separation to resolve the contradiction between power output and 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
The system achieves high power handling and improved contrast by using inexpensive diode lasers and anamorphic optics, enhancing productivity in applications like 3D printing and CTP systems without the need for expensive optics, while maintaining adequate contrast ratios.
Implementation Method 1
a diffraction grating in which light is reflected by a plurality of modulators into the 0TH order non-diffraction mode or state, and plus and/or minus 1st order diffraction modes
Implementation Method 2
The illumination source includes a laser and anamorphic optics for focusing light from the laser onto the array
Data Source
Figure 1A~1B
Figure 1C
Figure 2
AI summary
A system including two dimensional, microelectromechanical system (MEMS) based spatial light modulators and anamorphic optics for improved contrast is provided. Generally, the system comprises an array of modulators having a plurality of pixels along a longitudinal axis, each pixel comprising a plurality of modulators along a transverse axis of the array. An illumination source including a laser and anamorphic optics for focuses light from the laser onto the array, and imaging optics focus modulated light from the array onto an image plane. The anamorphic optics are configured to provide a transverse numerical aperture (NA) along the transverse axis of the array that is smaller than a diffraction angle of the modulated light reflected from the array along a transverse axis of the image plane, and a longitudinal NA along the longitudinal axis of the array that is greater than the transverse NA. Other embodiments are also provided.