Closed Loop Focusing System for LED Print Bars
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Solution Overview
Problem
LED print bars in xerographic printing systems face imperfect imaging due to the limited depth of focus and light collection characteristics of SELFOC® lens arrays, leading to suboptimal print quality and requiring precise manual adjustments, which are costly and time-consuming.
Innovation Solution
A closed loop focusing system using piezopositioner actuators to adjust the positioning of LED print bars based on image sensor analysis of contrast and average density of halftone targets, optimizing focus across the full width of the print bar.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If manual focus adjustment with high-precision mounting hardware is used, then imaging precision is improved, but manufacturing cost and setup time increase
Solution Approach 1:
The patent implements dynamic focus adjustment through piezoelectric actuators that can modify the distance between the gradient index lens array and the photoreceptor surface in real-time. This replaces static high-precision mounting hardware with a dynamic system that achieves precision through active control rather than passive mechanical tolerancing.
Solution Approach 2:
The patent employs a closed-loop feedback system where an image sensor measures image quality metrics (such as contrast or sharpness) and feeds this information back to a controller that adjusts the piezoelectric actuators accordingly. This automatic feedback mechanism eliminates the need for costly manual setup and high-tolerance hardware by using measurement and adjustment cycles to achieve optimal focus.
2Manufacturing precision
If manual focus adjustment procedures are used, then focus precision is improved, but setup time and operational complexity increase
Solution Approach 1:
The patent implements a self-adjusting focus system where the device automatically performs focus optimization without requiring manual intervention. The image sensor continuously monitors image quality and the piezoelectric actuators automatically adjust the lens-to-photoreceptor distance to maintain optimal focus, making the system self-servicing rather than requiring operator expertise and time.
Solution Approach 2:
The patent replaces manual mechanical adjustment procedures with an automated electromechanical system. Instead of operators physically adjusting mounting hardware, the system uses piezoelectric actuators controlled by electronic feedback from image sensors, substituting mechanical manual operations with automated electro-optical control.
3Use of energy by moving object
If gradient index lens arrays are used for light focusing, then light collection efficiency is improved, but depth of focus is reduced
Solution Approach 1:
The patent compensates for the limited depth of focus of gradient index lens arrays by implementing dynamic positioning of the lens array relative to the photoreceptor surface. The piezoelectric actuators continuously adjust the lens-to-photoreceptor distance to maintain optimal focus, effectively extending the usable depth of focus range through active compensation rather than relying on passive optical design alone.
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
Automatically achieves the best possible image quality by iteratively adjusting the positioning elements to maximize contrast and ensure precise focus, eliminating the need for manual setup and high-tolerance hardware, thereby improving print quality and reducing manufacturing and service costs.
Implementation Method 1
A closed loop system used to focus light emanating from LED print bars in printers by adjusting positioning elements such as piezopositioner actuators
Implementation Method 2
SELFOC lens array 50 is arranged between multi-chip LED array assembly 52 and photoreceptor drum 54. LED light 56 from array assembly 52 is focused on drum 54 via lens array 50.
Data Source
AI summary
A system for focusing light including a gradient index lens array positioned at a first distance from a surface, and first and second positioning elements arranged to modify the first distance. The first and second positioning elements modify the first distance based on an analysis of an image formed on the surface across substantially a full width of a cross process direction of the surface.