Printer TRC Control via Electrostatic and Optical Sensor Fusion
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Solution Overview
Problem
Printers face challenges in accurately adjusting tone reproduction curves (TRC) due to low sensitivity of optical signals for solid and high-density halftone patches, leading to unpredictable solid densities influenced by variables like tribo charge and environmental conditions.
Innovation Solution
The integration of an electrostatic sensor, such as a non-contact electrostatic voltmeter (ESV), with an optical sensor to measure electrostatic voltage differences on a transfer surface, allowing for precise control of TRC settings by determining an ESV sensor response ratio between dense and less dense patches, enabling independent control across all patch densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical sensors are used to test solid and high-density halftone patches, then the printing system can adjust TRC settings, but the measurement precision is low due to low sensitivity of optical signals
Solution Approach 1:
The patent combines electrostatic sensing and optical sensing systems into a unified TRC adjustment mechanism. The electrostatic sensor measures toner patch density while the optical sensor provides complementary measurements, and their outputs are integrated to control the marking device, resolving the sensitivity limitation of optical sensors alone for solid and high-density halftone patches
Solution Approach 2:
The patent introduces electrostatic sensing as an intermediary measurement method between the toner patches and the control system. Instead of relying solely on optical sensors that struggle with solid patches, the electrostatic sensor acts as a mediator that provides reliable sensitivity measurements for solid and high-density halftone patches, which then informs TRC adjustments
2Productivity
If interpolation is used to determine solid patch settings from halftone patches, then the system can adjust TRC for halftones, but the manufacturing precision deteriorates due to out-of-control solid densities
Solution Approach 1:
The patent performs preliminary measurement of solid and high-density halftone patches using electrostatic sensing before final TRC determination. By measuring these patches directly with the electrostatic sensor rather than relying on interpolation from halftone data, the system establishes accurate baseline measurements that prevent out-of-control solid densities in final printing
Solution Approach 2:
The patent implements a feedback mechanism where electrostatic sensor measurements of solid and halftone patches are fed back to the control system to directly adjust TRC settings. This closed-loop feedback eliminates the need for interpolation and ensures solid densities remain controlled by providing real-time measurement data from actual solid patches
3Measurement precision
If multiple halftone patches are used to adjust TRC, then the system can control halftone densities, but the device complexity increases due to interpolation requirements
Solution Approach 1:
The patent extracts the measurement function for solid and high-density halftone patches from the optical sensing system and assigns it to the electrostatic sensing system. This separation allows the optical sensor to focus on halftone patches while the electrostatic sensor handles solid and high-density patches, eliminating the need for complex interpolation algorithms and reducing overall system complexity
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 provides high precision in controlling TRC settings, reducing variability and improving printing accuracy by using electrostatic sensors for solid patches and optical sensors for halftone patches, thereby addressing the limitations of optical sensors alone.
Implementation Method 1
The electrostatic sensor (which can be used alone or in combination with the optical sensor) is adjacent the transfer surface and measures electrostatic voltage of the transfer surface as the test patches on the transfer surface move past the electrostatic sensor
Implementation Method 2
These optical sensors, commonly called automatic density sensors (ADC), work by shining light on a toner patch on a photoreceptor or intermediate transfer belt (ITB) and recording the specular and diffuse reflections
Data Source
AI summary
Various methods and devices transfer test patches of marking material from a marking device of a printing apparatus to a transfer surface of the printing apparatus, optically measure the density of the test patches on the transfer surface using an optical sensor of the printing apparatus, and measure the electrostatic differences in charge of the transfer surface as the test patches on the transfer surface move by an electrostatic sensor of the printing apparatus. Such methods and devices adjust settings of the marking device based on output from the electrostatic sensor alone, or based on a combination of the output from the optical sensor and converted output from the electrostatic sensor.