Laser Scanning Jitter Error Compensation via Reference Image Feedback
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Solution Overview
Problem
Laser scanning systems, such as scanning laser ophthalmoscopes, suffer from jitter error due to imperfect timing of polygon facet position, random noise in the electronic triggering system, variations in facet cut depth, facet flatness, and rotational speed variations, leading to vertical shifts in scanned images, which affect image quality.
Innovation Solution
A method is introduced to reduce jitter error by using a reference object with periodic alternate black and white bands to calculate errors in the scanned image, allowing for adjustments in operating parameters of the laser scanning system to incorporate these errors as control variables, thereby reducing jitter. This involves processing the reference image to determine column shifts and adjusting capture times of scanning elements based on calculated errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a facet detector and polygon mirror are used to ensure accurate timing of polygon facet arrival, then line scan registration accuracy is improved, but jitter error is introduced causing vertical shifts in scanned images
Solution Approach 1:
The patent implements a feedback mechanism where the actual positions of scan lines are measured and used to adjust the timing of subsequent scan lines. A processor calculates timing adjustments based on measured deviations and applies these corrections to compensate for jitter errors, creating a closed-loop system that continuously refines scan line positioning accuracy.
Solution Approach 2:
The patent replaces the mechanical facet detector system with a software-based timing adjustment approach. Instead of using physical detectors to trigger scan lines, the system uses computational methods to calculate and apply timing corrections to the scan control signals, eliminating the mechanical sources of jitter while maintaining registration accuracy.
2Productivity
If the polygon rotational speed is increased to improve scanning productivity, then image acquisition speed is improved, but jitter error from rotational speed variations increases
Solution Approach 1:
The patent implements dynamic timing adjustments that adapt to real-time variations in polygon rotational speed. The system continuously monitors scan line positions and calculates timing corrections on-the-fly, allowing the system to maintain accurate registration even when the polygon rotates at varying speeds, thus enabling higher productivity without sacrificing stability.
Data Source
AI summary
A laser scanning system adapted to produce a scanned image including a number of lines of an object. A method includes the steps of providing a reference object arranged such that the scanned image produced by the laser scanning system includes a reference image of the reference object, processing the reference image to calculate an error arising from non-repeatable displacement of the lines of the reference image, and adjusting at least one operating parameter of the laser scanning system in response to the calculated error.