Printing Apparatus Exposure Controller Linear Tone Reproduction
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Solution Overview
Problem
Conventional printing apparatuses fail to achieve a linear tone reproduction curve due to shifts in exposed locations on the recording medium during exposure, leading to non-linear correspondence between image information and tone reproduction.
Innovation Solution
A printing apparatus that uses an electrostatic latent image carrier and an exposure controller to form electrostatic latent images with combinations of exposure amounts, optimizing the relative position of exposed locations to satisfy an index value condition, ensuring linear tone reproduction by adjusting exposure positions and energies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the exposure time is changed to change the exposure amount linearly, then the exposure amount varies linearly, but the exposed location shifts over time causing non-linear tone reproduction
Solution Approach 1:
The exposure time is divided into multiple time periods (e.g., 8 periods) with different exposure amounts e[0] to e[7]. By selectively enabling or disabling the exposing section for each time period based on image data, the patent achieves 256 patterns of cumulative exposure amounts. This segmentation allows precise control of exposure amounts while compensating for recording medium shifts, thereby achieving linear tone reproduction.
Solution Approach 2:
The patent dynamically adjusts the exposure amount for each time period based on the cumulative exposure amount required. The exposing section is selectively enabled or disabled for each time period according to image data, creating a dynamic exposure control system that adapts to the recording medium's movement and achieves linear tone reproduction.
2Manufacturing precision
If multiple exposure amounts are combined to form one pixel, then tone expression is improved, but the relative position of exposed locations must be optimized to maintain linearity
Solution Approach 1:
The patent uses an index value LNR (calculated from optical density od(n) and exposure parameters) as feedback to evaluate and optimize the combination of multiple exposure amounts. By calculating LNR for different exposure combinations and selecting the combination that minimizes LNR, the system achieves optimal linear tone reproduction while managing the complexity of multi-exposure control.
Solution Approach 2:
The patent changes multiple parameters simultaneously including exposure amounts e[0] to e[7], exposure times T[0] to T[7], and the combination patterns of exposing section activation. By optimizing these parameters together based on the LNR index, the system achieves linear tone reproduction despite the increased complexity of combining multiple exposure amounts.
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 enables the realization of an excellent linear tone reproduction curve by optimizing the interaction of exposure amounts, improving the correspondence between image information and tone reproduction, and adjusting exposure energies to maintain optical density consistency.
Implementation Method 1
an electrostatic latent image carrier for forming an electrostatic latent image, and an exposure controller for forming the electrostatic latent image corresponding to one pixel upon exposure of the electrostatic latent image carrier with a combination of a plurality of different exposure amounts
Data Source
AI summary
A printing apparatus for printing an image onto a recording medium based on input image data, comprises an electrostatic latent image carrier for forming an electrostatic latent image, and an exposure controller for forming the electrostatic latent image corresponding to one pixel upon exposure of the electrostatic latent image carrier with a combination of a plurality of different exposure amounts, wherein the exposure controller performs the exposure with the combination of the plurality of exposure amounts in a manner to satisfy a condition for an index value LNR expressed by a following general equation (1) using an optical density od (n) standardized on the condition of the maximum optical density equal to 1.0, identification information comb assigned to identify each combination of the plurality of exposure amounts, and the number of varieties m of a cumulative exposure amount used for modulation of the image data.LNR≤2/mLNR(comb)=∑n=0m-3[{(od(n+2)-od(n+1))-(od(n+1)-od(n))}2]/(m-2).(1)