Writing Head Focus Adjustment in Print Apparatus
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Solution Overview
Problem
In liquid electrophotography printing systems, manufacturing tolerances can lead to inconsistencies in the focus of light sources within the writing head, resulting in print defects due to varying spot sizes of light on the photoconductive surface, which affects the quality of the printed output.
Innovation Solution
A focus adjustment method and mechanism that moves the writing head relative to the photoconductive surface to determine and adjust the position of light sources, ensuring all light sources are focused within a defined range, using an adjustment mechanism controlled by processing circuitry to minimize focus errors and achieve optimal focus accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If light sources are positioned according to standard manufacturing tolerances, then device assembly is simplified and manufacturing cost is reduced, but focus consistency across the writing head deteriorates, resulting in print defects
Solution Approach 1:
The patent performs focus adjustment as a preliminary action during the printing operation before actual printing begins. The processor controls the writing head to move to different positions and deposit test patterns at multiple locations, then analyzes these patterns to determine optimal focus positions for each light source array element, establishing a lookup table for subsequent printing operations.
Solution Approach 2:
The patent makes the writing head position dynamic by moving it to different positions relative to the photoconductive surface during the focus adjustment process. The writing head is controlled to move between multiple discrete positions, with each position corresponding to different focus requirements for different arrays of light sources, allowing dynamic adaptation to manufacturing variations.
2Measurement precision
If focus adjustment is performed for each light source individually, then focus precision is improved, but processing time and complexity increase
Solution Approach 1:
The patent merges the focus adjustment process into a single integrated operation that handles all light source arrays simultaneously. Instead of adjusting each light source individually, the system deposits test patterns for multiple arrays in one printing cycle, analyzes all patterns together, and generates a comprehensive lookup table that stores focus position data for all arrays, significantly reducing the time required.
Solution Approach 2:
The system performs self-diagnosis and self-adjustment by automatically analyzing the deposited test patterns and determining the optimal focus positions for each light source array without requiring external intervention. The processor automatically generates the lookup table based on the analyzed patterns, enabling the system to self-correct for manufacturing variations.
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 ensures that all light sources in the writing head are focused within a defined threshold, reducing print defects and improving the sharpness and clarity of the printed image by maintaining consistent spot sizes of light on the photoconductive surface, thereby enhancing the overall printing quality.
Implementation Method 1
a photoconductive surface positioned relative to a light-emitting 'writing head' which selectively discharges portion of the photoconductive surface that are to receive print agent
Data Source
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AI summary
A focus adjustment method is disclosed. The focus adjustment method includes depositing, using a print apparatus, print agent onto a printable substrate, the print apparatus comprising a photoconductive surface and a writing head having a first end and a second end, the writing head having an array of light sources to emit radiation onto the photoconductive surface during a printing operation. The method also includes during said depositing, moving the writing head relative to the photoconductive surface, between a first position and a second position, to create a printed image. The method also includes determining, based on the printed image, for each of a plurality of locations along the writing head, a position of the writing head relative to the photoconductive surface at which the writing head is most focussed. The method also includes calculating, using processing apparatus, a position of the first end of the writing head and a position of the second end of the writing head relative to the photoconductive surface at which the focus of the writing head at the plurality of locations is within a defined threshold. The method also includes adjusting the position of the first end of the writing head and the second end of the writing head relative to the photoconductive surface according to the calculated positions. A print apparatus and the machine-readable medium are also disclosed.