Linear Printhead Pulse Timing Function for Exposure Consistency
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Solution Overview
Problem
In electrographic printing, linear printheads with arrays of LED light sources face challenges in maintaining consistent exposure levels due to variations in optical power over time, leading to streak artifacts in printed images, which requires an efficient method for determining and updating pulse timing functions to ensure accurate aim exposures.
Innovation Solution
A method is developed to control the printhead by providing an aim exposure function, determining an initial pulse timing function, updating it based on light output and aim exposure functions, and iterating until a predefined criterion is met, using the updated pulse timing function to activate light sources for specific pixel code values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pulse width of exposure clock pulses is adjusted to control exposure time, then the aim exposure level can be achieved, but the optical power varies with pulse width changes making the determination process complex
Solution Approach 1:
The patent applies dynamics by creating an iterative process that adapts the pulse timing function based on measured light output characteristics. The system dynamically adjusts pulse widths through multiple iterations, where each iteration refines the timing function based on actual measurements, transforming a static calibration into a dynamic adaptation process that resolves the complexity of determining accurate exposure levels.
Solution Approach 2:
The patent implements feedback by measuring the actual light output of the printhead and using this measurement to update the pulse timing function. The measured light output feeds back into the system to refine the relationship between pulse counts and exposure times, creating a closed-loop calibration process that achieves accurate aim exposure levels despite variations in optical power characteristics.
2Manufacturing precision
If factory calibration is performed to equalize light source power, then initial exposure uniformity is achieved, but residual streak artifacts remain and characteristics change over time
Solution Approach 1:
The patent applies preliminary action by performing an iterative calibration process before actual printing operations. The system pre-determines the accurate pulse timing function through multiple measurement and adjustment iterations, storing this calibrated timing function for use during normal operation. This preliminary calibration ensures both exposure uniformity and long-term reliability by establishing accurate timing parameters before the printhead is put into service.
Solution Approach 2:
The patent implements parameter changes by modifying the pulse timing function parameters based on measured light output characteristics. The system changes the relationship between pulse counts and exposure times to compensate for variations in optical power, adjusting the timing parameters iteratively until accurate aim exposure levels are achieved. This parameter adaptation maintains exposure consistency over time despite aging or environmental changes.
3Adaptability or versatility
If the aim exposure function is updated in the field during printer calibration, then the pulse timing function must be updated accordingly, but this requires an efficient field implementation method
Solution Approach 1:
The patent applies self-service by enabling the printhead calibration to be performed autonomously in the field without requiring specialized factory equipment or complex external measurement systems. The system uses its own printing capability to create test patterns, measures its own light output through the imaging process, and automatically updates its pulse timing function based on these self-generated measurements, making field calibration practical and efficient.
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 allows for the determination of a pulse timing function that maintains specified aim exposures despite variations in light output, effectively reducing streak artifacts and ensuring consistent image quality across different print modes.
Implementation Method 1
a linear printhead including an array of LED light sources is used to form the electrostatic latent image
Implementation Method 2
an electrostatic latent image is formed on a photoreceptor by uniformly charging the photoreceptor and then discharging selected areas
Implementation Method 3
charged toner particles are brought into the vicinity of the photoreceptor and are attracted to the latent image to develop the latent image into a toner image
Implementation Method 4
A suitable electric field is applied to transfer the toner particles of the toner image to the receiver to form the desired print image on the receiver
Data Source
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AI summary
A method is described for controlling a printhead including an array of light sources. An aim exposure function is provided which gives an aim exposure as a function of an integer pulse count. An initial pulse timing function is also provided which defines an exposure time as a function of pulse count. A light output function for the light sources is determined responsive to the pulse timing function, wherein the light output function gives a light output of the light sources as a function of exposure time. The pulse timing function is updated responsive to the light output function and the aim exposure function. The process is repeated until a predefined iteration termination criterion is satisfied. The determined pulse timing function is used to control the printhead, wherein each light source is activated for a pulse count corresponding to a pixel code value of an associated image pixel.