Depth Map Estimation Using Longitudinal Chromatic Aberration
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Solution Overview
Problem
Existing passive 3D imaging systems face challenges in determining image depth maps with extended depth of field, particularly due to uncorrected longitudinal chromatic aberration, which degrades color images and limits depth analysis to only three depth levels ('near', 'intermediate', and 'far') and requires multiple shots or complex processing.
Innovation Solution
A method that uses a longitudinal chromatic optical system to provide spectral images, which are then deconvolved and analyzed using a cost criterion to estimate a depth map from a single shot, employing a spectral image sensor with demosaicing and spectral estimation to reconstruct images with extended depth of field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a longitudinal chromatic optical system is used to capture spectral information, then depth map estimation becomes possible, but image quality deteriorates due to uncorrected longitudinal chromatic aberration
Solution Approach 1:
The patent converts the harmful longitudinal chromatic aberration into a beneficial spectral encoding mechanism. By deliberately using the wavelength-dependent focus shift to encode depth information in spectral images, the system transforms an optical defect into a useful signal for depth map estimation, while the deconvolution process recovers high-quality images.
Solution Approach 2:
The patent changes the optical parameter by intentionally leaving longitudinal chromatic aberration uncorrected in the optical system. This parameter change allows different wavelengths to focus at different depths, creating spectral images that encode depth information. The deconvolution step then reverses the blur to restore image quality.
2Measurement precision
If chromatism inversion is performed on three color channels, then depth information can be extracted, but only three depth levels ('near', 'intermediate', 'far') can be distinguished
Solution Approach 1:
The patent segments the spectral information into multiple wavelength bands beyond the three basic color channels. By capturing and processing spectral images across a broader wavelength range, the system divides the depth estimation problem into multiple spectral components, each contributing to a more granular depth map with continuous depth values rather than just three discrete levels.
3Measurement precision
If multiple shots with different coded apertures are used for depth from defocus, then depth map accuracy improves, but processing time and system complexity increase
Solution Approach 1:
The patent performs preliminary spectral estimation and deconvolution on the captured spectral images to obtain depth information and extended depth of field images in a single shot. This preliminary processing eliminates the need for multiple sequential shots with different coded apertures, significantly reducing processing time while maintaining depth map accuracy through the spectral encoding approach.
4Device complexity
If a passive single-sensor system is used, then system complexity is reduced, but the ability to capture full spectral information is limited
Solution Approach 1:
The patent makes the single sensor universal by equipping it with a spectral filter array that enables it to capture spectral information across multiple wavelengths. The sensor performs multiple functions: capturing spatial information, spectral information, and depth information simultaneously in a single shot, eliminating the need for multiple specialized sensors while preserving full spectral content.
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 the construction of image depth maps from a single shot with a passive single-sensor system, allowing real-time operation and overcoming limitations of prior systems by accurately estimating depths within a predetermined range.
Implementation Method 1
The optical system exhibits uncorrected longitudinal chromatism. The color images obtained are degraded by the longitudinal chromatism. Such an optical device focuses the blue, green and red components of these color images, for 'near', 'intermediate' and 'distant' objects respectively.
Implementation Method 2
determination of a set of spectral images from the image supplied by the longitudinal chromatic optical system
Data Source
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AI summary
The invention relates to a method for estimating the image depth map of a scene, characterised by comprising the following steps: providing (E1) an image, the focus of which depends on the depth and wavelength of the considered object points of the scene, using a longitudinal chromatic optical system; determining (E2) a set of spectral images from the image provided by the longitudinal chromatic optical system; deconvoluting (E3) the spectral images to provide estimated spectral images with field depth extension; and analysing (E4) a cost criterion depending on the estimated spectral images with field depth extension to provide an estimated depth map.