Diffractive Optical Element Asymmetric Arrangement
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Solution Overview
Problem
Existing three-dimensional measurement devices using diffractive optical elements face issues with unstable light intensity and roughness in light spot distribution, leading to decreased resolution and inability to obtain three-dimensional information in regions without light spots, due to interference between diffracted light and stray light.
Innovation Solution
A diffractive optical element configuration comprising a first and second diffractive element with basic units arranged in different directions and pitches, where the angle between their arrangement directions and the distance between light spots and stray light centers is optimized to prevent interference, ensuring stable light intensity and distinct light spots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single diffractive optical element is used to generate projection patterns, then the device structure is simple, but light spots of high intensity are formed in random positions causing roughness in the in-surface distribution and regions without light spots cannot obtain three-dimensional information
Solution Approach 1:
The single diffractive optical element is divided into multiple diffractive optical elements (first and second DOE). Each DOE generates a subset of the projection pattern, ensuring that light spots are distributed more uniformly across the measurement surface. This segmentation resolves the issue of random light spot positions and uncovered regions while maintaining manageable device complexity.
2Measurement precision
If multiple diffractive optical elements are used to improve light quantity distribution controllability, then the light distribution becomes more controllable, but stray light generated by the diffractive optical elements causes interference and unstable light intensity
Solution Approach 1:
The harmful stray light generated by the diffractive optical elements is extracted and separated from the useful diffracted light through spatial filtering. By positioning the DOE elements and detection plane appropriately, the stray light is directed to different spatial locations than the desired light spots, allowing it to be excluded from the measurement signal and preventing interference.
Solution Approach 2:
A spatial filter or aperture is introduced as an intermediary element between the diffractive optical elements and the measurement plane. This intermediary selectively transmits the useful diffracted light while blocking the harmful stray light, thereby stabilizing the light intensity and improving measurement reliability.
3Ease of manufacture
If the basic units of multiple diffractive elements are arranged in the same direction, then the manufacturing process is simplified, but the light spots and stray light coincide causing interference and unstable light intensity
Solution Approach 1:
The basic units of the multiple diffractive optical elements are arranged in asymmetric directions relative to each other. Specifically, the first DOE has its basic units arranged in one orientation while the second DOE has its basic units arranged in a different orientation. This asymmetric arrangement prevents the light spots and stray light from coinciding, eliminating interference patterns and stabilizing light intensity while maintaining manufacturability.
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 achieves stable light intensity and precise measurement by minimizing interference between diffracted light and stray light, allowing for uniform and stable light spot distribution, thereby enhancing the resolution of three-dimensional measurements.
Implementation Method 1
A diffractive optical element that diffracts at least a part of incident light is used in various optical devices
Implementation Method 2
a speckle pattern generated by a diffractive optical element is radiated as the projection pattern of light
Data Source
AI summary
A diffractive optical element includes: a first diffractive element in which a plurality of basic units are two-dimensionally arranged; and a second diffractive element in which a plurality of basic units are two-dimensionally arranged, wherein when a direction in which the basic units are arranged in the first diffractive element is a first direction, a direction in which the basic units are arranged in the second diffractive element is a second direction, an angle φ between the first direction and the second direction is such that −|φ1|<φ<|φ1|, and φ≠0, sin φ1=−α/Δx where a closest distance of zero-order light generated when the diffracted light generated by the first diffractive element is further incident on the second diffractive element is Δx and a closest distance of the diffracted light and stray light generated by the second diffractive element is α.