Compensating Filter for Multiple-Beam Raster Scanner
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Solution Overview
Problem
Multiple-beam scanning systems face issues such as banding, magnification errors, and rotation errors due to the complexity of filtering multiple beams, which existing technologies have not adequately addressed, leading to costly design complications and image quality defects.
Innovation Solution
A low-cost optical filtering method is introduced, where a compensating filter is placed in the Fourier plane of the scanning optical system, utilizing a spatial frequency filter with a specific autocorrelation to notch out problematic frequencies, ensuring all beams are filtered equally and minimizing image degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a spatial filter is positioned in the Fourier plane to compensate for imaging errors, then image quality defects such as banding and non-uniformity are reduced, but the device complexity increases due to the need for precise filter positioning and design
Solution Approach 1:
The patent uses a computer-generated hologram (CGH) that is a computational copy of the required filter pattern. Instead of manufacturing a complex physical filter, the system creates a digital holographic pattern that when optically reproduced provides the necessary spatial frequency filtering. This reduces manufacturing complexity while maintaining the precision needed for image quality compensation.
Solution Approach 2:
The patent replaces traditional mechanical optical filters with a holographic filtering approach. The spatial filtering function is achieved through holographic interference patterns rather than physical filter materials, eliminating the need for complex mechanical filter assemblies and positioning mechanisms while achieving the same image quality compensation.
2Productivity
If multiple beams are scanned to increase productivity, then imaging speed is improved, but banding and magnification errors increase due to the complexity of filtering multiple beams simultaneously
Solution Approach 1:
The patent combines multiple beam paths into a single unified filtering operation in the Fourier plane. By positioning the holographic filter at the common Fourier plane where all beam paths converge, the system filters all beams simultaneously through a single optical element rather than requiring separate filtering for each beam, thereby maintaining precision while preserving high productivity.
Solution Approach 2:
The holographic filter serves multiple functions simultaneously: it filters all beams in the array, compensates for magnification errors, corrects rotation errors, and maintains beam positioning accuracy. This multi-functional approach eliminates the need for separate error correction mechanisms for each beam, preserving the high imaging speed of multiple-beam systems.
3Measurement precision
If a compensating filter is designed to address specific errors like magnification and rotation, then imaging accuracy is improved, but the filter design and manufacturing cost increase
Solution Approach 1:
The patent uses computer-generated holograms that can be precisely designed through software algorithms and manufactured using standard photolithography techniques. The filter pattern is created as a digital copy that can be reproduced with high precision, reducing the cost and complexity of manufacturing compared to traditional custom optical filters. The holographic approach allows for precise error compensation while maintaining ease of manufacture through digital design and standard fabrication processes.
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 solution effectively reduces banding amplitude by approximately 39% while maintaining image quality, addressing unique errors in multiple-beam systems like magnification and rotation errors, and is applicable to both 1-D and 2-D arrays of beam generators.
Implementation Method 1
A collimator lens is positioned to receive the multiple beams
Implementation Method 2
an aperture stop is located where the multiple beams are spatially coincident with each other
Implementation Method 3
A scanning optical system is positioned to receive the beams from the aperture stop
Implementation Method 4
A filter is located where the multiple beams are spatially coincident with each other, whereby each of the multiple beams may be filtered by the supplied filter
Data Source
AI summary
A printing system includes a multiple-beam generator array configured to generate multiple beams. A collimator lens is positioned to receive the multiple beams, and an aperture stop is located where the multiple beams are spatially coincident with each other. A scanning optical system is positioned to receive the beams from the aperture stop, and a recording medium receives the beams from the scanning optical system. A filter is located where the multiple beams are spatially coincident with each other, whereby each of the multiple beams may be filtered by the supplied filter.