Scanned Imaging Systems with Rotating Polygon Facets
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Solution Overview
Problem
Mechanically scanned imaging systems face inefficiencies due to dead time when incident light beams are stationary while facets rotate, particularly in systems operating with parallel or near-parallel radiation, limiting scanning efficiency to no better than 50%.
Innovation Solution
The system operates in image space with a rotating polygon having flat primary and secondary facets that focus an image of the scene near a facet, directing radiation from the primary facet to the secondary facet for reflection to the detector, ensuring the beam sweeps across the entire facet as it rotates, enhancing scanning efficiency while maintaining good radiometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a rotating polygon with parallel or near-parallel incident radiation is used, then the system operates in object space with a lens system, but scanning efficiency is limited to no better than 50% due to dead time between adjacent facets
Solution Approach 1:
The patent inverts the conventional object-space scanning approach by operating in image space. Instead of scanning parallel beams from the object, the system focuses diverging/converging beams from the image plane onto the rotating polygon facets, fundamentally changing the scanning geometry to eliminate dead time
Solution Approach 2:
The patent changes the key parameter of beam convergence by using an image-space lens system that focuses diverging or converging beams onto the facets, rather than using parallel beams. This parameter change in beam geometry enables continuous scanning without dead time between facets
2Productivity
If the beam is focussed to a point adjacent to a secondary facet and sweeps round with the primary facet, then scanning efficiency is improved, but the optical system complexity increases with primary and secondary facets
Solution Approach 1:
The patent merges the functions of the rotating polygon and the lens system by positioning them in close proximity in the image space, allowing the polygon facets to directly manipulate focused beams without requiring separate object-space and image-space optical paths
Solution Approach 2:
The patent transitions from two-dimensional parallel beam scanning in object space to three-dimensional diverging/converging beam manipulation in image space, utilizing the focal point dimension to achieve continuous beam coverage across facets
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 configuration significantly improves scanning efficiency by minimizing dead time and ensuring consistent beam alignment, achieving higher efficiency than traditional systems and maintaining optimal radiometry at the detector.
Implementation Method 1
an image space lens system for focussing an image of the scene to be scanned in the vicinity of a facet
Implementation Method 2
an optical system for directing radiation from a primary facet to its associated secondary facet for reflection to the detector
Data Source
AI summary
A scanned imaging system includes a lens system for directing radiation from a scene to be scanned onto external reflecting surfaces of a rotating polygon and onto a detector, the external reflecting surfaces including primary and secondary flat facets which rotate together on a common axis, the lens system including an image space lens system for focusing an image of the scene to be scanned in the vicinity of a primary facet, and further including an optical system for directing radiation from a primary facet to a focus at a point on or adjacent an associated secondary facet and to reflect the radiation from the secondary facet to the detector, the arrangement being such that a beam of radiation is incident on substantially the whole width of a primary facet and sweeps round with that facet as the polygon rotates.