Laser Exposure Control for Image Density Stability
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Solution Overview
Problem
Existing image forming apparatuses face challenges in maintaining precise control over high density ranges due to limitations in determining charging and developing biases, leading to instability in image density and tone reproduction, especially with existing methods requiring long adjustment times and imprecise corrections.
Innovation Solution
A method that forms latent images at multiple density levels using a laser spot larger than a unit pixel, allowing for precise control of charging and developing units by measuring potentials and controlling light and emission time, thereby obtaining correlations between density patches and development contrasts without altering charging or developing biases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the charging bias and developing bias are determined from the density of one patch, then the control process is simple, but it is hard to perform precise correction
Solution Approach 1:
The patent divides the image bearing member into multiple patches with different density levels (e.g., multiple cyan patches with different densities). By measuring potentials at multiple density levels rather than a single patch, the system achieves more precise correction while maintaining a manageable control process through systematic segmentation of measurement points.
Solution Approach 2:
The patent transitions from one-dimensional single-point measurement to multi-dimensional measurement by incorporating multiple density levels and multiple patches. This dimensional expansion allows for more comprehensive characterization of the charging and developing characteristics, enabling precise correction without excessive complexity.
2Measurement precision
If the charging bias and developing bias are changed to obtain correlation data, then precise control can be performed, but it takes long time to perform adjustment
Solution Approach 1:
The patent performs preliminary measurement of potentials at multiple density levels using fixed charging and developing biases. This preliminary action captures the inherent correlation between potential and density without requiring time-consuming bias adjustments, enabling precise control to be achieved rapidly through smart measurement rather than iterative adjustment.
Solution Approach 2:
The patent replaces the mechanical approach of adjusting biases to obtain correlation data with an electrical measurement approach. By measuring potentials directly at multiple density levels using fixed biases, the system substitutes time-consuming mechanical bias adjustments with rapid electrical measurements, achieving precise control without the time penalty.
3Manufacturing precision
If a laser spot smaller than unit pixel is used, then the resolution is high, but it is difficult to obtain accurate potential-density correlation
Solution Approach 1:
The patent applies local quality by using a laser spot size that is optimally matched to the patch size rather than simply using the smallest possible spot. This localized optimization ensures that the laser energy is sufficiently distributed across the measurement area to produce reliable potential-density correlation, while still maintaining adequate resolution for the application.
Solution Approach 2:
The patent changes the laser spot diameter parameter to be larger than a unit pixel, optimizing it for the specific purpose of measuring potential-density correlation. This parameter change trades some resolution for improved measurement accuracy, as the larger spot provides better signal-to-noise ratio and more reliable potential measurements across the density patches.
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
Enables precise control of high density ranges with improved stability and reduced adjustment time, allowing for faithful representation of developing characteristics and appropriate bias settings.
Implementation Method 1
a charging unit that charges an image bearing member
Implementation Method 2
an exposure unit that forms an electrostatic latent image on the charged image bearing member
Implementation Method 3
a developing unit that develops the electrostatic latent image
Data Source
AI summary
An electrostatic latent image is formed by controlling the amount of light, the emission time, and the like, considering the spot diameters of a laser, without changing the charging bias, the developing bias, and the like so as to obtain a plurality of correlations between density patches and development contrasts faithfully representing the developing characteristics of an image forming apparatus in a short time.