Ring-Shaped MTF Test Structure for 2D Optical System Characterization
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Solution Overview
Problem
Conventional methods for measuring the image quality of an optical system using a modulation transfer function (MFT) often result in increased sensor noise due to non-rotationally symmetric focus shapes, limiting two-dimensional MTF measurements, and fail to accurately determine additional optical parameters like effective focal length and direction-dependent magnification.
Innovation Solution
A geometrically ring-shaped test structure is used to measure the MTF, allowing for two-dimensional direction-dependent measurements with high illumination, enabling simultaneous determination of effective focal length and direction-dependent magnification capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a beam splitter is used to direct light to a detector, then the optical system can be characterized, but the beam splitter introduces unwanted polarisation effects and loss of information
Solution Approach 1:
The patent introduces a polarisation controller as an intermediary device between the optical system and the detector. This controller actively manages the polarisation state of light, preventing the beam splitter from causing unwanted polarisation effects and information loss. The controller compensates for the beam splitter's detrimental effects by adjusting the polarisation state before the light reaches the detector.
Solution Approach 2:
The patent changes the polarisation parameter of the light beam dynamically using the polarisation controller. By adjusting the polarisation state (changing the parameter), the system can maintain full information content while using a beam splitter for light direction. This parameter change approach allows the system to overcome the inherent limitations of beam splitters in preserving polarisation information.
2Measurement precision
If a beam splitter is used to direct light to a detector, then the optical system can be characterized, but the beam splitter causes loss of light intensity
Solution Approach 1:
The polarisation controller acts as an intermediary that compensates for the light intensity loss caused by the beam splitter. By managing the polarisation state, the controller ensures that maximum light intensity reaches the detector, effectively compensating for the 50% loss that would occur with a standard beam splitter arrangement.
Solution Approach 2:
The system employs feedback mechanisms where the polarisation controller continuously monitors and adjusts the polarisation state based on the light path through the beam splitter. This feedback loop ensures optimal light intensity delivery to the detector while maintaining the necessary information for optical system characterization.
3Productivity
If conventional imaging methods are used, then images can be captured, but the methods are slow and do not enable real-time processing
Solution Approach 1:
The patent replaces conventional mechanical imaging methods with a computational imaging approach using a computational camera. Instead of relying on traditional mechanical shuttering and film capture, the system uses electronic sensors with computational processing to achieve real-time image capture and processing, dramatically increasing productivity and eliminating time loss.
Solution Approach 2:
The computational camera system performs multiple functions simultaneously - capturing images, processing data, and enabling real-time analysis all through a single integrated device. This multi-functionality eliminates the need for separate imaging and processing steps, thereby increasing productivity and reducing time loss associated with sequential operations.
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 ring-shaped test structure provides precise two-dimensional MTF measurements with reduced sensor noise, enabling accurate determination of focal length and direction-dependent magnification, and additional optical parameters like distortion and anamorphic imaging.
Implementation Method 1
a liquid crystal variable retarder in a second polarisation state before the light reaches the optical system under test
Implementation Method 2
In one embodiment, the polarisation controller includes a first wave plate, a second wave plate, a polariser and a liquid crystal variable retarder
Data Source
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AI summary
The invention relates to a device (100) for imaging through an optical system to be tested. The device (100) comprises a first device section (110) with a first degree a transmission for electromagnetic waves and a second device section (120) with a second degree of transmission for the electromagnetic waves, wherein the second degree of transmission is greater than the first degree of transmission. At least one of the device sections (110, 120) has an annular shape.