Passive 3D Image Depth Sensing via Chromatic Focal Differentiation
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Solution Overview
Problem
Conventional active techniques for 3D image sensing in portable devices, such as smartphones, face limitations due to power consumption, spatial constraints, and difficulties in dynamic calibration, especially in varying ambient lighting conditions and object reflectivity.
Innovation Solution
A passive 3D image sensing system utilizing chromatic focal differentiation, where a lens assembly focuses light of different wavelengths to distinct focal planes, and an image sensor with photodetector elements computes magnitude ratios of chromatic responses to determine object distance without active illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If active techniques (time-of-flight, triangulation) are used for 3D sensing, then depth measurement capability is achieved, but power consumption increases and spatial requirements are not met for portable devices
Solution Approach 1:
The patent replaces active mechanical/electronic ranging systems (time-of-flight lasers, structured light projectors) with a passive optical system that uses chromatic aberration of a standard lens. The lens naturally separates wavelengths to different focal planes, eliminating the need for active illumination and complex depth calculation algorithms, thereby reducing power consumption while maintaining depth measurement capability
Solution Approach 2:
The system utilizes the inherent chromatic aberration property of the lens itself to perform depth sensing. Instead of requiring external active components, the lens's optical characteristic (different focal lengths for different wavelengths) is exploited directly to encode depth information in the chromatic responses captured by the image sensor
2Measurement precision
If active techniques with separate optical systems are used, then depth sensing is achieved, but device size and spatial constraints are violated
Solution Approach 1:
The patent merges the depth sensing function with the existing imaging function by using the same lens and image sensor for both purposes. The chromatic responses are extracted from the standard image capture process, eliminating the need for separate depth sensing optics and reducing the overall device footprint while maintaining depth sensing capability
Solution Approach 2:
The standard lens and image sensor serve dual functions: capturing both the image data and the chromatic depth information simultaneously. This multi-functionality approach allows the system to perform both imaging and 3D sensing with a single optical path, minimizing spatial requirements for portable devices
3Measurement precision
If conventional active techniques are used, then depth information is captured, but calibration reliability deteriorates in varying ambient lighting and object reflectivity conditions
Solution Approach 1:
The patent exploits chromatic aberration by capturing responses at different wavelengths (colors) from the same optical path. Since the chromatic ratio is derived from light that has traversed the identical optical path, variations in ambient lighting and object reflectivity affect all wavelengths equally and cancel out in the ratio calculation, thereby maintaining calibration reliability across varying conditions
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
Enables accurate and efficient 3D image sensing in portable devices by passively detecting object distance through chromatic focal differentiation, reducing power consumption and spatial requirements while improving calibration robustness.
Implementation Method 1
Light components of different wavelengths tends to be focused through the lens to different focal lengths
Implementation Method 2
an image sensor in optical communication with the lens assembly and comprising a plurality of photodetector elements
Data Source
AI summary
Techniques are described for passive three-dimensional (3D) image sensing based on chromatic differentiation for use in object verification. For example, multiple sub-images correspond to 3D feature regions of an object. The sub-images can be analyzed to obtain respective sets of feature depth measurements (e.g., depth, textural signatures, etc.) based on multiple differentiated chromatic components of raw image sensor data captured from the object. A verification signal can be output as a function of comparing the respective sets of feature depth measurements from the plurality of characteristic sub-images to previously stored feature depth expectations, such that the verification signal indicates whether an identity of the object is verified and/or whether the object is a spoof.