Tessellated Optical Element for Wide-Angle Zero-Order Suppression
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Solution Overview
Problem
Current diffractive optical elements (DOEs) used for 3D scanning and gesture recognition are sensitive to deviations from design wavelength and fabrication errors, leading to eye-safety issues due to a stronger zero diffraction order and low efficiency, especially when producing wide-angle light patterns with small features.
Innovation Solution
An optical element with a surface featuring a plurality of regions arranged in a tessellation, each with a random spatial distribution of microstructures, such as saddle-shaped microstructures, which projects a target pattern with high efficiency and fixed speckle without a higher intensity in the zero diffraction order, using a coherent light source like a laser.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a DOE is designed with smaller features to cover a wider angular range, then the angular coverage is improved, but the manufacturing precision becomes more difficult to achieve and the zero diffraction order becomes stronger causing eye-safety issues
Solution Approach 1:
The optical element is divided into multiple regions (e.g., 3x3 grid) where each region contains a subset of the total microstructures. This segmentation allows each region to be manufactured with relaxed precision requirements while collectively achieving the desired wide angular coverage when all regions are illuminated together.
Solution Approach 2:
Different regions contain different subsets of microstructures with varying local diffraction characteristics. Each region is optimized for its specific local function, and the combination of all regions produces the overall wide-angle pattern with suppressed zero order through destructive interference.
2Adaptability or versatility
If a DOE is designed with smaller features to cover a wider angular range, then the angular coverage is improved, but the efficiency decreases due to energy loss to higher diffraction orders
Solution Approach 1:
The patent converts the harmful effect of higher diffraction orders (which normally represent energy loss) into a beneficial interference pattern. By carefully designing the phase profiles of microstructures across multiple regions, the higher diffraction orders from different regions interfere destructively in unwanted directions and constructively only in the desired output directions, thereby suppressing the zero order and redirecting energy efficiently.
3Object-affected harmful factors
If multiple DOEs are used to address the zero diffraction order, then the eye-safety is improved, but the device complexity increases and practical efficiency decreases
Solution Approach 1:
Multiple functional regions that would traditionally require separate DOE elements are merged into a single integrated optical element. Each region is etched with specific phase profiles on the same substrate, allowing the system to achieve zero-order suppression and wide-angle coverage through a single component rather than multiple stacked DOEs, thereby reducing complexity while maintaining safety.
4Loss of energy
If a grayscale DOE is fabricated with very small features for maximum efficiency, then the diffraction efficiency is improved, but the manufacturing difficulty increases significantly
Solution Approach 1:
The grayscale phase profile is segmented into discrete regions, each containing microstructures with specific phase depths. This allows the continuous grayscale profile to be approximated using discrete manufacturing steps (e.g., multi-level etching), making fabrication more feasible while maintaining high diffraction efficiency through precise control of phase differences between regions.
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 solution provides high-efficiency projection of a random spot distribution over a wide angular range, eliminating eye-safety concerns and maintaining speckle stability regardless of light source movement, suitable for 3D sensing applications.
Implementation Method 1
Diffractive optical elements (DOE's) are naturally suited to the task of producing light patterns, such as diffraction patterns. A DOE can be described as a thin surface structure, typically one wavelength of light, that can produce a light pattern by interference and/or diffraction.
Implementation Method 2
A DOE can be described as a thin surface structure, typically one wavelength of light, that can produce a light pattern by interference and/or diffraction.
Data Source
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AI summary
An optical element comprising a body having a surface, wherein the surface has a plurality of regions periodically arranged in a tessellation, and wherein each region of the plurality of regions has a random spatial distribution of microstructures is disclosed. An optical system comprises a light source; and the optical element is also disclosed. Methods of making and using the optical element and the optical system are also disclosed.