Extended Depth of Field Imaging via Longitudinal Chromatism
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Solution Overview
Problem
Conventional optical systems, such as digital cameras and FLIR systems, face limitations in depth of field and focus, making it difficult to capture crisp images of objects at varying distances without significant losses in light or resolution, and existing solutions are complex and costly.
Innovation Solution
The introduction of intentional longitudinal chromatism in the optics system, combined with deconvolution algorithms, allows for an extended depth of field by ensuring that radiation at different wavelengths is focused at specific points along the optical axis, enabling sharp image reconstruction across a broader range of distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If stopping down the optics is used to increase depth of field, then depth of field is improved, but light loss increases and resolution decreases
Solution Approach 1:
The patent changes the optical parameter by introducing intentional longitudinal chromatism, which deliberately introduces chromatic aberration to create different focal points for different wavelengths. This allows the system to achieve extended depth of field without stopping down the aperture, thereby avoiding light loss while still providing sharp focus across multiple distances through computational processing of the chromatically separated images
2Volume of moving object
If step-by-step focusing with multiple images is used to extend depth of field, then depth of field is improved, but device complexity increases and processing time increases
Solution Approach 1:
The patent segments the white light into different wavelength components using a diffractive optical element, creating spatially separated focal points for each wavelength. This segmentation allows all focal planes to be captured simultaneously in a single exposure, eliminating the need for mechanical refocusing and reducing device complexity while extending depth of field
Solution Approach 2:
The patent performs preliminary chromatic separation of light before detection using a diffractive optical element, so that different wavelengths are already focused at different positions when they reach the detector. This preliminary action eliminates the need for subsequent mechanical refocusing steps, reducing both device complexity and processing time while achieving extended depth of field
3Volume of moving object
If step-by-step focusing with multiple images is used to extend depth of field, then depth of field is improved, but processing time increases
Solution Approach 1:
The patent enables continuous capture of extended depth of field information in a single continuous exposure, rather than requiring discrete sequential focusing steps. The diffractive optical element continuously separates wavelengths spatially throughout the exposure, allowing all focal planes to be recorded simultaneously and processed more quickly, thus reducing processing time while maintaining extended depth of field
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 approach enables the capture of sharp images across an extended depth of field without significant loss of light or resolution, allowing for simultaneous focus on multiple objects at different distances, improving image clarity and recognition.
Implementation Method 1
The surface 227 is a diffractive optical surface (DOS)... The DOS is specifically designed so as to introduce intentional longitudinal chromatism into radiation passing through the optics 12
Implementation Method 2
The optics 12 are configured to distribute evenly along an optical axis the longitudinal chromatism for unequally-spaced wavelength nodes
Data Source
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AI summary
A method and apparatus involve using optics to direct radiation from a scene along an optical axis, the optics having a chromatic dispersion that is a function of a characteristic spectral signature for the scene so as to produce a chromatic blur that, for an extended depth-of-field region, is substantially spatially constant along the optical axis. A different method involves: identifying for a characteristic scene a spectral response curve; determining a plurality of different wavelength nodes dividing the area under the spectral response curve into a plurality of substantially equal segments; generating a mapping relationship that maps each of the wavelength nodes to a respective one of a plurality of focal points spaced substantially equally along the optical axis; and configuring the optical system as a function of the mapping relationship.