Annular Phase Filter for Focal Depth Extension
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Solution Overview
Problem
Existing phase filters with non-rotationally symmetric cubic phase distributions cause in-plane position shifts of image points due to defocus, leading to challenges in image processing and object measurement, and require complex and costly manufacturing processes for aspherical surfaces.
Innovation Solution
A phase filter with an annular structure rotationally symmetrical about the optical axis, featuring cross-sectional shapes of parabolas to uniformly extend incident rays and suppress in-plane position shifts, allowing for effective image processing and object measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a non-rotationally symmetric cubic phase distribution is used in the phase filter, then focal depth extension is achieved through WFC, but in-plane position shifts of image points occur due to defocus
Solution Approach 1:
The patent applies asymmetry principle by using a non-rotationally symmetric cubic phase distribution function W(x,y) = α(x³+y³) in the phase filter. This asymmetric phase distribution creates uniform blur for defocused points enabling WFC, while the patent acknowledges and compensates for the resulting lateral deviation through image processing techniques.
Solution Approach 2:
The patent changes the phase distribution parameters by using a cubic function with coefficient α that can be adjusted. By modifying the phase distribution parameters and applying deconvolution processing with appropriate point spread functions, the system achieves focal depth extension while managing position shifts through parameter optimization.
2Adaptability or versatility
If a non-rotationally symmetric phase distribution is used, then WFC image processing is enabled, but the manufacturing complexity and cost increase due to requiring complex aspherical surfaces
Solution Approach 1:
The patent uses a cubic phase distribution function W(x,y) = α(x³+y³) as a mathematical model or copy representation of the desired phase modulation. This analytical function serves as a simplified copy that can be implemented through various manufacturing methods including spatial light modulators or programmed deformable mirrors, avoiding the need for complex physical aspherical surfaces.
Solution Approach 2:
The patent replaces mechanical manufacturing of complex aspherical surfaces with computational methods. Instead of physically shaping glass or plastic into complex asymmetric forms, the system uses software-based phase modulation through spatial light modulators or digital processing to achieve the cubic phase distribution, substituting mechanical complexity with computational flexibility.
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 annular phase filter design suppresses in-plane position shifts during image processing, enabling accurate object measurement and reducing manufacturing costs by simplifying the production of rotationally symmetrical molds, while maintaining effective focal depth extension.
Implementation Method 1
a phase distribution given by a cubic function to a coordinate on the pupil plane
Implementation Method 2
uniforms blur of a point for defocus by providing a phase distribution
Data Source
AI summary
A phase filter 101 is configured to comprise an annular structure rotationally symmetrical about an optical axis, each annular zone including a cross-sectional shape of substantially parabola for uniformly extending incident rays of light on a focal plane and letting the rays overlap with each other.