Microlens Diffuser Layout for Low-Height VCSEL Illumination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing laser arrangements, particularly those using VCSEL arrays, face challenges in achieving a low building height and homogeneous illumination patterns due to the need for a large distance between the laser array and diffuser, leading to inhomogeneities and limitations in applications like smartphones where space is critical.
Innovation Solution
A laser arrangement with a regular pattern of lasers and optical elements, where each optical element provides a defined illumination pattern within a specific field-of-view, allowing for a closer placement of the diffuser to the laser array, reducing the overlap of emission cones and ensuring invariant emission characteristics even with lateral shifts, using conical lenses or free-form optics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a large distance is maintained between the laser array and diffuser, then homogeneous illumination pattern is achieved, but building height increases
Solution Approach 1:
The diffuser is segmented into multiple optical elements (microlenses) arranged in a regular pattern, where each microlens independently processes light from corresponding laser elements. This segmentation allows the system to achieve homogeneous illumination at shorter distances by distributing the optical processing across multiple discrete elements rather than relying on a single large-distance diffuser.
Solution Approach 2:
Each optical element (microlens) is designed with specific local optical properties and parameters tailored to its position in the array. The microlenses have different focal lengths, diameters, or shapes optimized for their local position, enabling each element to correct illumination non-uniformities in its specific region, thereby achieving overall homogeneous illumination at reduced building height.
2Length of stationary object
If the diffuser is placed close to the laser array, then building height is reduced, but emission cones overlap causing inhomogeneities
Solution Approach 1:
The optical system is divided into corresponding pairs of laser elements and microlenses, where each pair processes light independently. This segmentation prevents overlap-induced inhomogeneities by assigning specific spatial regions to specific microlens-laser pairs, maintaining illumination uniformity even at close distances where emission cones would otherwise overlap.
Solution Approach 2:
Each microlens is designed with position-specific optical parameters (focal length, diameter, curvature) that are locally optimized to handle the specific divergence angle and emission characteristics of its corresponding laser element. This local optimization ensures that even when emission cones overlap, each microlens correctly processes its designated light portion to maintain overall illumination homogeneity.
3Illumination intensity
If random microlens arrangements are used, then beam scattering is achieved, but manufacturing precision and alignment become difficult
Solution Approach 1:
Instead of using random microlens arrangements as in conventional approaches, this invention employs a regular, ordered pattern of microlenses that corresponds systematically to the laser element array. This inversion of the conventional random approach maintains the desired beam scattering and illumination homogeneity while dramatically improving manufacturability and alignment precision through predictable, repeatable positioning.
Solution Approach 2:
The invention changes the fundamental parameter of microlens arrangement from random to regular/ordered. This parameter change transforms the system from one requiring high-precision alignment of random elements to one where the regular pattern inherently provides alignment tolerance and simplifies manufacturing while maintaining optical performance.
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 enables a compact laser arrangement with reduced building height and invariant emission characteristics, simplifying mounting and maintaining homogeneous illumination patterns, suitable for applications like smartphones and time-of-flight cameras.
Implementation Method 1
Each optical element comprises a second optical axis. Each optical element is arranged to provide a defined illumination pattern along at least one first illumination axis in a reference plane in a defined field-of-view if laser light is received within a defined range of angles by each surface element of the respective optical element
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention describes laser arrangement (100) comprising a laser array and an optical arrangement, wherein the laser array comprises at a multitude of lasers (130) arranged in a first regular pattern, wherein each laser (130) is arranged to emit the same laser emission profile around a first optical axis with a divergence angle Θ/2 with respect to the first optical axis in at least one direction perpendicular to the first optical axis, wherein the optical arrangement comprises a diffusor (140), wherein the diffusor (140) comprises an array of optical elements (21) arranged in a second regular pattern, wherein each optical element (21) comprises a second optical axis, wherein each optical element (21) is arranged to provide a defined illumination pattern along at least one first illumination axis (33) in a reference plane in a defined field-of-view (160) if laser light (10) is received within a defined range of angles by each surface element of the respective optical element (21), wherein the defined range of angles is smaller than or equal to a range of angles between -θ and +θ, preferably between - θ/2 and + θ/2 with respect to the second optical axis, wherein the lasers (130) and the optical elements (21) are arranged relative to each other such that the diffusor (140) transforms laser light (10) received from the lasers (130) to transformed light (150), and wherein an emission characteristic of the transformed light (150) along the first illumination axis (33) in the reference plane in the defined field-of-view (160) is characterized by the same characteristics as the defined illumination pattern. The invention further describes a lighting device comprising such a laser arrangement (100) and a time of flight camera (200) comprising such a laser arrangement (100) or lighting device. The invention finally describes a method of manufacturing the laser arrangement (100).