Refractive Optical Element for Time-of-Flight Camera Irradiance Compensation
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Solution Overview
Problem
Existing camera systems face challenges in maintaining consistent irradiance of objects across the field of view, leading to inaccurate distance measurements in time-of-flight 3D cameras due to the dependence of irradiance on angular displacement from the optical axis.
Innovation Solution
An illumination system incorporating a refractive optical element, such as a refractive diffuser, structures light to compensate for the angular dependence of irradiance, ensuring objects at varying distances from the optical axis receive proportional illumination, thereby maintaining consistent irradiance across the field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional illumination system is used, then the system structure is simple, but the irradiance of objects varies with angular displacement from the optical axis, leading to measurement inaccuracies
Solution Approach 1:
A refractive optical element is introduced as an intermediary component between the light source and the field of view. This element modifies the light distribution pattern to compensate for angular displacement effects, ensuring uniform irradiance across the entire field of view without requiring complex multi-component illumination systems
Solution Approach 2:
The illumination system applies different light intensities to different regions of the field of view based on their angular displacement from the optical axis. Objects at larger angles receive proportionally higher illumination intensity to compensate for the cos^4(θ) irradiance reduction, achieving uniform measurement conditions across the entire field
2Measurement precision
If objects at different angular displacements are illuminated uniformly, then measurement accuracy improves, but the light distribution becomes inefficient as central regions receive excess light
Solution Approach 1:
The refractive optical element creates a non-uniform light distribution pattern where illumination intensity is locally adjusted according to angular displacement. Central regions receive baseline illumination while off-axis regions receive proportionally increased intensity, optimizing energy utilization across the entire field of view
Solution Approach 2:
The system changes the illumination parameter (intensity) as a function of angular displacement from the optical axis. By varying the light intensity parameter according to the cos^4(θ) compensation requirement, the system achieves uniform irradiance while maintaining energy efficiency
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 enhances the accuracy of distance measurements in time-of-flight 3D cameras by ensuring consistent irradiance, improving precision and reducing errors associated with angular displacement.
Implementation Method 1
An illumination system having a refractive optical element that compensates for dependence in irradiance of images of objects captured by a photosensor is provided. The refractive optical element receives light from the light source and structures the light to illuminate the field of view
Data Source
AI summary
An illumination system having a refractive optical element that compensates for dependence in irradiance of images of objects captured by a photosensor is provided. The refractive optical element may structure the light such that similar objects in the same spherical surface in the field of view of the camera have the same irradiance on the camera photosensor. The illumination system may have an image sensor, a light source, and a refractive optical element. The image sensor has a photosensor that captures images of objects in a field of view. The irradiance of images of objects having a given exitance that are captured by the photosensor may depend on angular displacement from an optical axis of the image sensor. The refractive optical structures light from the light source to illuminate the field of view to compensate for the dependence of irradiance on angular displacement from the optical axis.