TOF Depth Camera Illumination Light Shaping
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Solution Overview
Problem
Time-of-flight (TOF) depth cameras face challenges in uniformly illuminating large, non-circular image environments with coherent light, leading to inefficient light usage and variable signal-to-noise ratios due to random microlens distributions and non-uniform optical power distribution.
Innovation Solution
A TOF depth camera design featuring a light source generating coherent light, a periodic array of lens elements for light shaping, and a diffraction artifact reduction stage to form a desired illumination profile, transforming circular light into a rectangular or other shaped illumination envelope with controlled intensity and reduced diffraction artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If random arrangements of microlenses are used to achieve desired illumination light shape, then light distribution control is improved, but manufacturing precision and light profile consistency deteriorate
Solution Approach 1:
The illumination system is segmented into multiple independently controllable LED sources arranged in a grid pattern, each capable of being individually activated or deactivated. This segmentation allows precise control over the illumination profile shape while maintaining manufacturing consistency through standardized LED components and fixed geometric arrangement.
Solution Approach 2:
The system dynamically controls which LED segments are active based on the desired illumination profile, allowing the effective shape of illumination to be changed without physical reconfiguration. This dynamic control achieves shape flexibility while maintaining fixed, precise manufacturing geometry.
2Area of stationary object
If coherent light is projected into large, non-circular image environments, then illumination coverage is improved, but light usage efficiency deteriorates due to shape mismatch
Solution Approach 1:
Different regions of the LED array are selectively activated based on the local illumination requirements of the target environment. By controlling which specific LED segments are active, the system matches the illumination shape to the target area geometry, concentrating light energy where needed and eliminating waste in unused regions.
Solution Approach 2:
The system changes the effective illumination parameters (shape, size, distribution) by selectively activating different combinations of LED segments. This allows the illumination profile to be adapted to match various target geometries, improving light usage efficiency by minimizing energy waste in areas outside the desired illumination envelope.
3Area of stationary object
If imaging optics have large depth of field, then field-of-view coverage is improved, but illumination intensity uniformity deteriorates
Solution Approach 1:
Different LED segments are controlled with different intensity levels to compensate for the non-uniform illumination characteristics inherent in large depth-of-field optics. By adjusting the local emission intensity of each LED segment, the system achieves uniform overall illumination across the entire field of view despite the optical system's depth-of-field properties.
Solution Approach 2:
The system uses feedback from depth map data and scene geometry information to dynamically adjust LED segment intensities. This feedback mechanism allows real-time compensation for illumination non-uniformity across the field of view, maintaining consistent lighting levels throughout the entire imaging environment.
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 solution enables efficient, uniform illumination across large, non-circular image environments, reducing light waste and improving signal-to-noise ratios by reshaping the light profile and reducing diffraction interference, resulting in enhanced depth measurement precision and image quality.
Implementation Method 1
a light source configured to generate coherent light
Implementation Method 2
a first optical stage including an array of periodically-arranged lens elements positioned to receive at least a portion of the coherent light and adapted to diverge the coherent light to form divergent light
Implementation Method 3
a second optical stage positioned to receive at least a portion of the divergent light and adapted to reduce an intensity of one or more diffraction artifacts in the divergent light
Implementation Method 4
an image sensor configured to detect at least a portion of return illumination light reflected from the image environment
Data Source
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AI summary
Various embodiments of a time-of-flight (TOF) depth camera and methods for projecting illumination light into an image environment are disclosed. One example embodiment of a TOF depth camera includes a light source configured to generate coherent light; a first optical stage including an array of periodically-arranged lens elements positioned to receive at least a portion of the coherent light and to form divergent light; a second optical stage positioned to receive at least a portion of the divergent light and to reduce an intensity of one or more diffraction artifacts in the divergent light to form illumination light for projection into an illumination environment; and an image sensor configured to detect at least a portion of return illumination light reflected from the illumination environment.