VCSEL Optical Element for Uniform Dot Pattern Generation
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Solution Overview
Problem
Conventional diffusing filters with periodic micro lens arrays suffer from uneven light intensity due to diffraction, making them unsuitable for long-distance measurements in Time Of Flight (TOF) sensors, and require a collimate lens with a long focal distance, increasing device size.
Innovation Solution
An optical device with periodically arranged lenses and an emitting unit that satisfies specific distance and pitch conditions to achieve high light efficiency without a collimate lens, using a VCSEL light source and a DOE to create a dot pattern for uniform light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a collimate lens is used to produce collimated light from VCSEL, then light quality is improved, but device size increases due to long focal distance
Solution Approach 1:
The patent combines the collimation function and the optical element function into a single integrated optical element. The optical element includes both the microlens array for beam shaping and the diffraction optical element for dot pattern generation, eliminating the need for a separate collimate lens and reducing device size while maintaining light quality
Solution Approach 2:
The optical element is designed to perform multiple functions simultaneously: it collimates the divergent light from VCSEL, shapes the beam through the microlens array, and generates the dot pattern through the diffraction optical element. This multi-functional design replaces what would traditionally require multiple separate components
2Stability of the object's composition
If a micro lens array is arranged at random to suppress diffraction unevenness, then light uniformity is improved, but light intensity decreases making it unsuitable for long distance measurement
Solution Approach 1:
The patent applies different arrangement strategies to different regions of the microlens array. The optical element uses a periodic arrangement of lenses with specific pitch relationships to the VCSEL array, creating localized optimal conditions for each lens while maintaining overall uniformity. This allows preservation of both light uniformity and intensity
Solution Approach 2:
The patent optimizes specific parameters including the pitch ratio between VCSEL array and microlens array (set to integer ratio), the focal length of microlenses, and the distance between VCSEL array and optical element. These parameter optimizations enable the periodic arrangement to achieve both uniformity and high intensity
3Ease of manufacture
If a periodic micro lens array is used in diffusing filter, then manufacturing is simplified, but diffraction causes uneven light intensity
Solution Approach 1:
The patent converts the harmful diffraction effect into a beneficial one by using a diffraction optical element (DOE) designed to create a specific dot pattern. The periodic structure that causes unwanted diffraction in conventional filters is intentionally designed to produce the desired dot pattern projection, transforming the problem into a solution
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 enables high light efficiency and eliminates the need for a collimate lens, allowing for effective long-distance measurements with improved device compactness and light uniformity.
Implementation Method 1
a vertical resonance surface light emitting laser (VCSEL) that can easily make a two-dimensional array is adopted in many cases
Implementation Method 2
A DOE changes a phase difference by allowing such collimated light to pass through the concavo-convex pattern, and gives a predetermined light orientation distribution by the diffraction of those lights
Implementation Method 3
an optical element including a plurality of lenses arranged periodically, the lens allowing light with a wavelength λ to pass therethrough
Data Source
AI summary
An optical device is provided which does not need a collimate lens, and which has a high available efficiency of light. The optical device includes a light source unit 1 emitting light with a wavelength λ, and an optical element 2 with a concavo-convex structure including periodical lenses. When n is a natural number equal to or greater than 1, and the size of a k-th (where k is a natural number equal to or greater than 1) pitch from the smallest one among the pitches of the concavo-convex structure is Pk, a distance L1 between the light source unit and the optical element satisfies the following formula 1 for equal to or greater than any one pitch Pk.(n-0.1)Pk22λ≦L1≦(n+0.1)Pk22λ(1)