Wavefront Coding for Imaging SNR and Depth of Field
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Solution Overview
Problem
Existing task-based imaging systems face challenges in achieving high signal-to-noise ratio (SNR) for biometric iris recognition and other tasks, particularly at longer standoff distances due to limitations in aperture size and depth of field, leading to low signal levels and resolution.
Innovation Solution
The implementation of a task-based imaging system that modifies the phase of electromagnetic energy using wavefront coding, enhancing the SNR by imaging a wavefront of electromagnetic energy to an intermediate image, modifying its phase, and detecting it over a range of spatial frequencies, thereby improving image data quality for tasks like biometric iris recognition and barcode reading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If small lens apertures are used for short standoff distances, then device complexity is reduced, but signal-to-noise ratio deteriorates
Solution Approach 1:
The patent applies wavefront coding to change the optical system parameters, specifically modifying the phase of light waves across the aperture to extend depth of field and improve signal-to-noise ratio at longer standoff distances without requiring larger physical apertures
Solution Approach 2:
The patent introduces wavefront coding as an intermediary technique between the lens aperture and the image sensor, using phase modulation to compensate for optical aberrations and extend the useful range of the imaging system
2Reliability
If larger lens apertures are used for longer standoff distances, then signal-to-noise ratio is improved, but depth of field deteriorates
Solution Approach 1:
Wavefront coding modifies the phase distribution across the wavefront to extend depth of field while maintaining large aperture benefits, effectively decoupling the relationship between aperture size and depth of field that normally exists in conventional optical systems
3Device complexity
If conventional imaging is used without phase modification, then device complexity is low, but image quality over range of spatial frequencies deteriorates
Solution Approach 1:
The patent modifies the phase parameter of the electromagnetic wavefront to improve image quality across a range of spatial frequencies, enabling better resolution and contrast for recognition tasks while managing the added system complexity
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 significantly enhances the SNR of the imaging system, enabling high-quality imaging over a range of optical aberrations and varying distances, effectively addressing the limitations of existing systems by maintaining or enhancing spatial frequencies of interest for recognition tasks.
Implementation Method 1
modifying phase of the wavefront... The optical element is configured for cooperating with the first detector so that the SNR of the task-based imaging system is greater than SNR of the task-based imaging system without phase modification of the wavefront
Data Source
AI summary
A task-based imaging system for obtaining data regarding a scene for use in a task includes an image data capturing arrangement for (a) imaging a wavefront of electromagnetic energy from the scene to an intermediate image over a range of spatial frequencies, (b) modifying phase of the wavefront, (c) detecting the intermediate image, and (d) generating image data over the range of spatial frequencies. The task-based imaging system also includes an image data processing arrangement for processing the image data and performing the task. The image data capturing and image data processing arrangements cooperate so that signal-to-noise ratio (SNR) of the task-based imaging system is greater than SNR of the task-based imaging system without phase modification of the wavefront over the range of spatial frequencies.