Raster Polygon 2D Scanning with Barrel Distortion Compensation
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Solution Overview
Problem
Laser-based image-generating systems using raster polygon mirrors produce curved and distorted scan lines due to asymmetrical rotation properties and distortion in optics, complicating image processing and timing.
Innovation Solution
A 2-D scanning system is designed with a raster-polygon and specially configured scan optics to minimize pin-cushion distortion by selecting an approach angle and tilt angle for the rotational axis, and using a scan and imaging lens to generate barrel distortion that compensates for pin-cushion distortion, resulting in straight and parallel scan lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a raster polygon mirror is used to perform 2-dimensional scanning of laser across an image-generating surface, then high-speed laser imaging is achieved, but the scan lines exhibit significant curvature and distortion
Solution Approach 1:
The patent applies asymmetry by intentionally introducing asymmetrical distortion through a cylindrical lens that compensates for the symmetrical pin-cushion distortion produced by the raster polygon mirror. This creates an asymmetrical optical path that corrects the scan line curvature, transforming the distorted arcs into straight lines while maintaining high-speed scanning capability
Solution Approach 2:
The patent changes optical parameters by selecting specific cylindrical lens characteristics (focal length, orientation, and position) to generate the required degree of asymmetrical distortion. By adjusting these parameters, the system compensates for the polygon mirror's distortion and achieves straight scan lines without sacrificing scanning speed
2Adaptability or versatility
If each reflective facet of the raster polygon mirror produces a different curvature, then 2-dimensional scanning is achieved, but noticeable and undesirable distortion of images is produced
Solution Approach 1:
The patent converts the harmful distortion effect into a beneficial correction by using a cylindrical lens to introduce asymmetrical distortion that precisely counteracts the pin-cushion distortion from the polygon mirror. The harmful curvature generated by each facet is transformed into a useful correction mechanism, eliminating visible distortion while preserving 2-D scanning functionality
3Ease of manufacture
If scan lines are curved rather than straight, then the raster polygon mirror can be used, but image processing and timing are greatly complicated
Solution Approach 1:
The patent applies preliminary action by correcting the scan line curvature optically before the image data is processed. The cylindrical lens pre-compensates for distortion in the optical domain, so that straight scan lines are delivered to the imaging surface without requiring complex software correction or timing adjustments, thereby simplifying overall 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 allows for ultrafast two-dimensional scanning with a single high-speed rotational element, producing straight and parallel scan lines that reduce visible distortion and enhance image quality.
Implementation Method 1
a scan and imaging lens is configured to generate barrel distortion of scan lines on the imaging surface to compensate for pin-cushion distortion
Implementation Method 2
scan optics are configured to produce straight scan lines on an imaging surface by generating asymmetrical distortion that compensates for pin-cushion distortion
Implementation Method 3
A laser beam incident on one of the reflective surfaces is directed to the image-generating surface, and as the polygon rotates, the incident laser beam sweeps across the image-generating surface
Data Source
AI summary
A 2-D scanning system uses a fast-rotating raster-polygon as a single scanning component to produce straight scan lines over a 2-D image surface. An approach angle of incident light beams to the raster-polygon is selected to minimize pin-cushion distortion of scan lines introduced by polygon scanning on the image surface, and a tilt angle of the rotational axis of the raster-polygon is selected to position said polygon-scanning distortion symmetrically on the image surface. In addition, scan optics are configured to generate a predetermined amount of barrel distortion of scan lines on the image surface to compensate for pin-cushion distortion introduced by polygon scanning.