VCSEL Array Illumination Module for Depth Camera Structured Light
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional depth cameras using collimated laser diodes for structured light illumination often face challenges with insufficient light intensity and limited pointing tolerance, which can affect the accuracy and reliability of depth image capture.
Innovation Solution
The use of a VCSEL array with projection optics and additional optical elements such as diffractive optical elements (DOEs) or beam splitters to enhance the structured light pattern, increasing the number of features and improving light distribution, thereby addressing the limitations of collimated laser diodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a collimated laser diode is used to produce structured light, then the light can be directed precisely, but the total light intensity is insufficient for adequate illumination
Solution Approach 1:
The patent divides the single laser source into multiple VCSELs (Vertical-Cavity Surface-Emitting Lasers) arranged in an array. Each VCSEL emits a beam that can be independently controlled, collectively providing both the directional precision of individual lasers and the combined intensity of multiple sources. This segmentation resolves the contradiction by distributing the lighting function across multiple elements.
Solution Approach 2:
The patent combines multiple VCSEL beams with a single collimated laser beam in terms of functional output. By using optical elements to merge the light paths and patterns, the system achieves the intensity of multiple sources while maintaining the directional control characteristic of laser illumination.
2Manufacturing precision
If a collimated laser diode is used for structured light illumination, then the beam can be focused tightly, but the pointing tolerance becomes too limited
Solution Approach 1:
By segmenting the light source into an array of VCSELs, the system can independently adjust the emission characteristics of each element. This allows the maintained tight focus of individual beams while the collective array provides broader pointing tolerance through distributed emission angles and positions.
Solution Approach 2:
The patent transitions from a single-point laser source to a two-dimensional array of VCSELs. This dimensional expansion allows the system to maintain precise focus in the optical dimension while gaining tolerance in the pointing dimension, as the array can accommodate variations in alignment across multiple emission points.
3Measurement precision
If the number of features in structured light is increased using optical elements downstream from projection optics, then depth image capture accuracy improves, but device complexity increases
Solution Approach 1:
The patent segments the feature generation function between the VCSEL array itself (which creates the initial pattern) and downstream optical elements (which multiply and distribute the features). This segmentation allows the system to achieve high feature counts for improved depth accuracy while managing complexity through functional division.
Solution Approach 2:
The patent uses optical elements such as DOEs (Diffractive Optical Elements) or beam splitters to create multiple copies of the light pattern from the VCSEL array. This copying mechanism increases the total number of features in the structured light without requiring a proportional increase in the number of VCSELs, thereby improving depth image accuracy while controlling device complexity.
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 enhances the light pattern's features, improving the depth image capture accuracy and reliability by increasing the number of features in the structured light output, which can lead to better depth perception and more precise tracking of objects in various applications.
Implementation Method 1
The VCSEL array includes a plurality of vertical cavity surface emitting lasers (VCSELs), each of which emits a separate beam of light
Implementation Method 2
The field lens receives the beams of light emitted by the VCSELs of the VCSEL array and converge the beams
Implementation Method 3
The objective lens receives the converged beams from the field lens and diverge the beams to produce the light pattern projected by the projection optics
Implementation Method 4
the illumination module can include diffractive optical element (DOE) configured to cause the total number of features included in the structured light output by the illumination module to be an integer multiple of the number of features included in the light pattern projected by the projection optics
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A depth camera includes an illumination module and an image detector module. The illumination module outputs structured light that illuminates a capture area. The image detector module captures an image of the structured light as reflected from object(s) within the capture area. The illumination module includes a VCSEL array and optical element(s), such as projection optics, an MLA or DOE, or combinations thereof. Projection optics receive a light pattern emitted by the VCSEL array and project the light pattern. An optical element, downstream from the projection optics, can cause a total number of features included in the structured light to be greater than the number of features included in the light pattern projected by the projection optics. In an embodiment, a pitch of an MLA is offset relative to a pitch of the VCSEL array. Various structures can include alignment elements to aid manufacture of the illumination module.