VCSEL Array with Wafer-Level Prismatic Optical Structure
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Solution Overview
Problem
Existing VCSEL arrays for infrared illumination in time-of-flight applications face limitations in providing a continuous and efficient illumination pattern due to the divergence of laser light, leading to optical losses and inefficient use of energy, especially when trying to integrate complex optical structures on a semiconductor substrate.
Innovation Solution
A VCSEL array with a common wafer-level integrated optical structure that includes a prismatic or Fresnel structure with steps of different heights, where each VCSEL is associated with a sub-surface to avoid illuminating steps and is coupled with an array of microlenses to collimate light, enhancing the illumination pattern's size and continuity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a common optical structure is integrated on wafer level to expand illumination pattern, then the illumination coverage and continuity are improved, but the manufacturing complexity and precision requirements increase
Solution Approach 1:
The common optical structure is segmented into multiple sub-surfaces, each associated with a specific VCSEL. This segmentation allows each VCSEL to illuminate only its designated sub-surface area, avoiding the steps between sub-surfaces and reducing optical losses while maintaining continuous illumination coverage across the entire pattern.
Solution Approach 2:
Different regions of the common optical structure are designed with different local properties - each sub-surface is optimized for its specific VCSEL's illumination characteristics. The distance between each VCSEL and its associated sub-surface is specifically arranged to ensure optimal illumination without hitting the steps, creating locally optimized optical paths throughout the structure.
2Area of stationary object
If VCSELs are arranged to illuminate sectors of expanded pattern, then the illumination coverage is improved, but the risk of illuminating steps and causing optical losses increases
Solution Approach 1:
The optical structure is divided into distinct sub-surfaces, each assigned to a specific VCSEL. This segmentation ensures that each VCSEL's light is confined to its designated sub-surface area, preventing light from spilling onto the steps between sub-surfaces and causing optical losses.
Solution Approach 2:
Each VCSEL is designed to illuminate only a partial area - specifically its associated sub-surface - rather than attempting to illuminate the entire common optical structure. This partial action approach ensures sufficient illumination coverage when all VCSELs work together while avoiding the harmful effect of light hitting the steps.
3Productivity
If microlenses are added to collimate light, then the illumination efficiency and pattern quality are improved, but the device complexity increases
Solution Approach 1:
The microlenses are integrated directly into the common optical structure, merging the collimation function with the illumination pattern formation. This integration approach provides the benefits of light collimation and improved illumination efficiency while avoiding the complexity of separate, discrete optical components.
Solution Approach 2:
The common optical structure serves multiple functions simultaneously - it expands the illumination pattern, segments the light paths for different VCSELs, and incorporates microlenses for collimation. This multi-functionality reduces the need for separate optical components and simplifies the overall device architecture.
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 a continuous and expanded illumination pattern with reduced optical losses, allowing for efficient use of energy and improved intensity distribution, suitable for applications like time-of-flight cameras and gesture recognition.
Implementation Method 1
The common optical structure is arranged to transform the laser light to transformed laser light such that a continuous illumination pattern can be provided in the reference plane
Implementation Method 2
the VCSEL array comprises an array of microlenses, wherein each VCSEL is associated with a microlens, wherein the microlens is arranged to collimate the laser light after traversing the common optical structure
Data Source
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AI summary
The invention describes a VCSEL array (100) comprising two, three, four or more VCSELs (130) arranged on a common semiconductor substrate (101), wherein the VCSEL array (100) further comprises one common optical structure (140) integrated on wafer level, wherein the common optical structure (140) is arranged to transform the laser light (10) to transformed laser light (150) such that a continuous illumination pattern (20) can be provided in the reference plane, wherein the common optical structure (140) is arranged to increase a size of the illumination pattern (20) in comparison to an untransformed illumination pattern which can be provided without the common optical structure (140), and wherein the common optical structure (140) is further arranged such that each VCSEL (130) is arranged to illuminate a sector (21) of the illumination pattern (20), wherein each sector (21) is smaller than the illumination pattern (20). The invention further describes a lighting device comprising such a VCSEL array (100), a time-of-flight camera (200) comprising such a lighting device and a method of manufacturing the VCSEL array (100).