Relay Optical Path for Polygon Mirror Cross-Track Error Reduction
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Solution Overview
Problem
Scanning mirrors, particularly rotary polygon mirrors, suffer from cross-scan errors due to machining imperfections and bearing imperfections, leading to uneven illumination and brightness banding in raster scans, which existing correction methods either fail to fully address or require size increases or precise timing.
Innovation Solution
An optical system with a scanning mirror and relay segments that invert reflection angles from one facet to the next, negating position errors and reducing cross-scan errors by relaying light through the same facet reflection, allowing for controlled illumination and improved scanning quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional scanning mirrors are used without relay segments, then the system structure is simple, but cross-scan errors occur due to machining and bearing imperfections
Solution Approach 1:
A relay optical system is introduced as an intermediary component between the scanning mirror and the target. This relay system includes optical elements (lenses or mirrors) that create an intermediate image plane, allowing the scanning errors to be corrected at this intermediate stage rather than directly at the target plane. The relay segment acts as a mediator that separates the scanning function from the imaging function, enabling error correction without fundamentally changing the scanning mirror itself.
Solution Approach 2:
The optical path is segmented into distinct functional sections: the scanning section (mirror facet), the relay section (optical elements creating intermediate images), and the target section. By dividing the optical system into these segments, the patent allows independent optimization of each section. The relay segment specifically addresses cross-scan errors by creating intermediate images at different positions for different facets, effectively separating the scanning motion from the imaging precision requirements.
2Manufacturing precision
If existing correction methods are used, then some error reduction is achieved, but the system size increases or precise timing is required
Solution Approach 1:
The relay optical system serves as an intermediary that corrects dynamic track errors through optical path management rather than mechanical adjustments. By introducing intermediate image planes and using optical elements to relay images, the system achieves error correction without adding significant mechanical complexity or size. The correction is achieved through the geometric arrangement of optical paths rather than active mechanical compensation mechanisms.
3Manufacturing precision
If tighter machining tolerances are applied to reduce manufacturing errors, then cross-scan error decreases, but manufacturing cost increases
Solution Approach 1:
Instead of requiring tighter machining tolerances on the scanning mirror facets, the patent introduces a relay optical system as an intermediary that corrects the errors optically. This approach shifts the precision requirement from the mechanical manufacturing of the mirror facets to the optical design and alignment of the relay system, which can achieve similar or better correction with more relaxed manufacturing tolerances and lower cost.
Solution Approach 2:
The patent converts the inherent imperfections of standard-machining facets into a correctable parameter through the relay optical system. Rather than viewing facet errors as unacceptable defects requiring expensive re-machining, the system accepts standard manufacturing tolerances and uses the relay optics to compensate for and correct these errors, effectively turning a potential disadvantage into a manageable parameter.
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 system effectively reduces cross-scan errors, enabling even illumination and improved scanning quality, suitable for applications like confocal microscopy with reduced system size and cost.
Implementation Method 1
providing once reflected light; one or more second optical elements defining a second beam path segment from the facet location and back to the facet location, to provide a second facet reflection of light from the light source
Data Source
AI summary
An optical system is provided which comprises a scanning mirror having a reflective facet, and a plurality of optical elements defining a light beam path from a first location to a second location via plural facet reflections on the facet comprising a relay segment from one facet reflection to a next facet reflection. A method is also provided comprising directing light from a light source along a light beam path from a first location to a second location via plural facet reflections on a rotary reflective facet of a scanning mirror, and relaying one facet reflection to a next facet reflection on the facet while rotating the facet.