Diffractive Optical Element for Variable Magnification
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Solution Overview
Problem
Conventional image capturing devices face limitations in achieving high image quality due to complex mechanical systems, poor image quality from variable focal length lenses, and oversampling issues, particularly in portable devices where size and cost are concerns.
Innovation Solution
An image capturing device with an optical projection system that distorts the image by increasing magnification at the center and decreasing it at the borders, using a fixed focus system with fewer lenses, and a computing unit to process and correct the distorted image, ensuring optimal resolution utilization without moving parts or high costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a mechanical system with multiple lenses and moving parts is used to achieve optical zoom, then the magnification capability is improved, but the device complexity, size, weight, and cost increase significantly
Solution Approach 1:
The patent replaces the conventional mechanical lens system with a fixed focal length lens with a diffractive optical element (DOE) that uses diffraction to achieve variable magnification. The DOE modulates the wavefront of incident light to create different point spread functions, enabling optical zoom without any moving parts or mechanical adjustments.
Solution Approach 2:
The patent changes the optical parameters by using a diffractive optical element that can dynamically alter the point spread function width and shape through diffraction. By controlling the diffraction pattern, the system achieves variable magnification effects while maintaining a fixed physical lens structure, thus avoiding mechanical complexity.
2Adaptability or versatility
If variable focal length lenses are used to achieve optical zoom, then the magnification capability is improved, but the image quality deteriorates and the system becomes prone to fatigue and aging
Solution Approach 1:
The patent replaces variable focal length lenses with a fixed focal length lens combined with a diffractive optical element. This substitution eliminates the mechanical and material components that are prone to fatigue and aging, replacing them with a static optical system that uses diffraction patterns to achieve variable magnification, thereby improving reliability and image quality consistency.
3Area of stationary object
If the field of view is increased to capture more scene, then the coverage area is improved, but the resolution at the center of the image decreases
Solution Approach 1:
The patent applies local quality by creating different point spread function characteristics for different regions of the image sensor. The diffractive optical element is designed to produce a narrower PSF at the center region and a wider PSF at the border regions, allowing the center to achieve higher resolution while the borders maintain adequate coverage, thus optimizing both center resolution and overall field of view.
4Measurement precision
If the point spread function width is increased to improve resolution, then the resolution capability is improved, but the oversampling problem worsens at the border regions
Solution Approach 1:
The patent implements local quality by designing the diffractive optical element to produce position-dependent point spread functions. The PSF width is locally optimized: narrower at the center region to maximize resolution and wider at the border regions to match the pixel pitch, thereby eliminating oversampling at the borders while maintaining high resolution capability at the center.
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 solution provides improved image resolution at the center while maintaining overall resolution across the field of view, reducing oversampling and aberrations, and enabling cost-effective, compact image capturing devices with enhanced zoom capabilities.
Implementation Method 1
the projection system comprises a fixed focus lens and a diffractive optical element, the diffractive optical element being adapted to modulate a wavefront of incident light
Data Source
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AI summary
An image capturing device (1) is disclosed comprising an electronic image detector (17) having a detecting surface (15) , an optical projection system (5) for projecting an object within a field of view onto the detecting surface (15) , and, optionally, a computing unit (19) for manipulating electronic information obtained from the image detector (17) , wherein, the projection system (5) is adapted to project the object in a distorted way such that, when compared with a standard lens system, the projected image is expanded in a center region of the field of view and is compressed in a border region of the field of view. Preferably, the projection system (5) is adapted such that its point spread function in the border region of the field of view has a full width at half maximum corresponding essentially to the size of corresponding pixels of the image detector (17) .