ToF Lens Assembly Spherical Design Light Collection
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Solution Overview
Problem
Time of flight (ToF) sensor systems face challenges in accurately measuring distances due to low intensity reflected light from large surfaces, requiring efficient light collection and homogeneous illumination, which is not adequately addressed by existing lens designs.
Innovation Solution
A lens assembly with specific design characteristics, including a fast f-number, low telecentricity, and the use of spherical lenses, optimized for infrared light sources, to enhance light collection and maintain performance across a wide temperature range, ensuring consistent illumination and accurate distance calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional lens design is used, then the structure is simple, but the light collection efficiency is insufficient and illumination homogeneity is poor
Solution Approach 1:
The lens is divided into multiple segments or zones with different optical properties. Specifically, the lens includes a central region and peripheral regions with different refractive indices or curvatures, allowing each zone to contribute differently to light collection and focusing, thereby improving overall light collection efficiency while maintaining a manageable structural complexity
Solution Approach 2:
Different regions of the lens are designed with locally optimized properties. The central region focuses on collecting on-axis light, while peripheral regions are optimized for off-axis light collection. This local differentiation improves illumination homogeneity across the sensor without requiring an excessively complex overall structure
2Area of stationary object
If the lens focuses light from large surfaces, then the illumination area increases, but the reflected light intensity becomes too low
Solution Approach 1:
The lens employs specifically designed curved surfaces with optimized radii of curvature. These spherical or aspherical surfaces are configured to efficiently collect and focus divergent reflected light from large surfaces onto the sensor, concentrating the dispersed light energy to maintain adequate intensity levels across the illumination area
Solution Approach 2:
The lens design combines multiple optical functions into a single integrated element. It simultaneously performs light collection, focusing, and field-of-view control in one component, maximizing the utilization of available reflected light from large surfaces while maintaining sufficient intensity for accurate ToF measurements
3Manufacturing precision
If the lens has high telecentricity, then the image quality is improved, but the magnification varies with object distance
Solution Approach 1:
The lens design incorporates dynamic optical characteristics that adapt to different object distances. By optimizing the lens curvature and position, the system maintains acceptable image quality across a range of distances while minimizing magnification variation, achieving a balance between image quality and distance adaptability for ToF applications
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 proposed lens assembly improves the accuracy and reliability of ToF sensor systems by efficiently collecting reflected light and providing homogeneous illumination, suitable for applications in autonomous vehicles and other environments.
Implementation Method 1
Optical elements such as lenses may be used in the light transmission and reception paths to focus light
Data Source
AI summary
Various lens designs for use in Time of Flight (ToF) sensor systems are discussed. Improvements to a ToF sensor system may be realized by, for example, incorporating a lens having particular features, such as a relatively short track length, fast lens speed (e.g., low f-number), low telecentricity, relatively flat field illumination, and fairly low cost. In some examples, such a lens of a ToF sensor system may be a lens assembly having a fixed focal length and that avoids use of lenses having aspheric surfaces so as to achieve relatively low cost.