Nonperiodic Optical Diffuser Surface for Uniform TOF Light Emission
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing diffusing filters for Time Of Flight (TOF) sensors, such as those using microlens arrays, suffer from light inefficiency, variability in light distribution, and interference due to periodic placement, leading to speckle phenomena and discontinuous light emission.
Innovation Solution
An optical element with concavity-and-convexity on its surface, featuring a singular closed curved diffusion range, non-periodic crests and valleys, and a frequency distribution of inclination angles proportional to cos−nθ (where 1≤n≤7), designed to minimize discontinuities and ensure efficient light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a microlens array is used for light diffusion, then light distribution control is achieved, but light efficiency deteriorates due to uncontrollable diffusion lights
Solution Approach 1:
The optical element divides the light diffusion function into multiple independent microlenses arranged in an array, where each microlens independently controls light diffusion in its local region. This segmentation allows precise control of light distribution while maintaining high efficiency, as each microlens operates autonomously without interfering with others.
Solution Approach 2:
Each microlens in the array is designed with specific local optical characteristics to control light diffusion in its designated region. The microlenses have different focal lengths and diameters optimized for their specific positions, creating localized light distribution patterns that collectively achieve uniform overall light emission.
2Ease of manufacture
If microlenses are placed periodically to match VCSEL arrangement, then manufacturing is simplified, but interfering bars are produced due to moire effect
Solution Approach 1:
The microlens array employs asymmetric design where microlenses have different diameters and focal lengths rather than being identical periodic structures. This asymmetry breaks the moire effect that occurs with periodic arrangements, eliminating interfering bars while maintaining manufacturing simplicity through the systematic variation of lens parameters.
Solution Approach 2:
The patent varies key parameters of the microlenses including diameter, focal length, and position to prevent periodic interference patterns. By changing these parameters across the array in a controlled manner, the design achieves uniform light distribution without moire effects, while still following a systematic placement pattern for easy manufacturing.
3Object-generated harmful factors
If microlens period is decreased to suppress interference, then moire effect is reduced, but speckle phenomenon increases due to light concentration
Solution Approach 1:
Each microlens is designed with optimized local parameters including specific diameter and focal length ratios that balance interference suppression and speckle reduction. The local optical characteristics are tuned to distribute light uniformly without creating concentration effects, achieving both moire effect suppression and speckle minimization simultaneously.
Solution Approach 2:
The optical element combines multiple microlenses with varying parameters in a composite array structure. This composite design integrates the advantages of different microlens configurations, where some lenses are optimized for interference suppression while others are optimized for uniform light distribution, achieving both goals through the composite system.
4Adaptability or versatility
If microlens array is placed at random to avoid VCSEL dependence, then optical characteristics are independent of placement, but discontinuous portions are produced reducing light efficiency
Solution Approach 1:
The optical element segments the light diffusion function across multiple independently controllable microlenses. This segmentation allows the system to maintain uniform light distribution regardless of the exact placement positions, as each microlens independently performs its diffusion function without requiring precise alignment with VCSEL positions.
Solution Approach 2:
The microlens array design provides universal light diffusion capability that works regardless of specific placement positions. The systematic variation in microlens parameters creates a robust system that maintains optimal optical characteristics whether the microlenses are placed regularly or irregularly, achieving both placement independence and high light efficiency.
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 optical element suppresses light inefficiency and variability in distribution, ensuring uniform light emission and high utilization efficiency without interference, suitable for wide-angle applications.
Implementation Method 1
a transparent body that includes concavity-and-convexity on at least one surface... the concavity-and-convexity includes a plurality of crests and valleys without a periodicity... a frequency distribution of an inclination angle θ of a surface of the concavity-and-convexity that diffuses the light
Implementation Method 2
a region of the concavity-and-convexity with the gradient that causes the incident light to be emitted and outgo to a region outside the diffusion range by Snell's law
Data Source
AI summary
an objective is to provide an optical element which has no discontinuous portion between adjacent lenses, and which suppresses a reduction of a light efficiency and also an occurrence of variability in light distribution due to diffusion, etc. An optical element capable of diffusing incident light to a predetermined diffusion range, and includes a transparent body including concavity-and-convexity on at least one surface. The diffusion range is defined as an internal side of a singular closed curved line on a predetermined plane. The concavity-and-convexity includes a plurality of crests and valleys without a periodicity. When it is defined that a wavelength of the light is λ, a refractive index of the transparent body is n1, and a refractive index of a medium around the transparent body is no, the concavity-and-convexity has no portion where a gradient of the concavity-and-convexity changes by 180 degrees within a range in which a width is λ/(n1−n0). A region of the concavity-and-convexity with the gradient causing the incident light to be emitted and outgo to a region outside the diffusion range by Snell's law is equal to or smaller than 5% of the entire region.