Laser Power Switching for Scan Alignment in Printers
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Solution Overview
Problem
In laser printers, variations in laser beam intensity can lead to misalignment of forward and reverse scans due to inconsistent power levels when detected by the beam detect sensor, affecting image accuracy.
Innovation Solution
An apparatus with a laser driver and dual switches connected to holding capacitors maintains a constant laser beam intensity by switching between printing and beam detect power reference signals, ensuring proper power levels through regular adjustments during scan cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the laser power is changed to correspond with a selected pixel density, then the image quality is improved, but the beam detect sensor receives inconsistent power levels causing misalignment
Solution Approach 1:
The patent divides the laser power control into two separate segments: one for printing power control and another for beam detect power control. The first switch separates the printing power reference signal from the beam detect power reference signal, allowing independent optimization of each function without interference from the other.
Solution Approach 2:
The patent applies different power levels to different functional requirements: a first power level for printing operations and a second power level for beam detection. The second switch selectively connects different holding capacitors corresponding to different power reference levels, ensuring each operation receives the appropriate local power quality.
2Device complexity
If a single laser power level is used for both printing and beam detection, then the device complexity is reduced, but misalignment occurs between forward and reverse scans
Solution Approach 1:
The patent segments the power reference signals into separate pathways using the first switch, which selects between printing power reference and beam detect power reference. This segmentation allows independent optimization of power levels for each function while maintaining a relatively simple overall structure.
Solution Approach 2:
The holding capacitors store reference power levels in advance, and the switches pre-select the appropriate capacitor based on the current operation mode. This preliminary preparation of power reference levels eliminates the need for complex real-time power adjustment during scanning operations.
3Use of energy by moving object
If the laser power varies during scanning, then energy consumption is reduced, but the beam detect sensor cannot accurately determine beam position
Solution Approach 1:
The patent implements periodic switching between different power reference levels synchronized with the scanning cycles. The second switch alternates between holding capacitors at regular intervals (every other scan cycle), providing periodic calibration of the beam detect power reference to maintain detection accuracy while allowing power variation during normal operation.
Solution Approach 2:
The beam detect sensor provides feedback about beam position and the holding capacitors maintain reference power levels based on this feedback. The periodic switching and comparison of actual beam detect power with the stored reference power level enables continuous calibration and correction, ensuring accurate beam position detection.
Data Source
AI summary
An apparatus for switching and controlling the intensity of a laser beam directed toward a beam detect sensor for an image forming device. A printing power reference signal and a beam detect power reference signal is selectively connected to a laser driver through a first switch. A printing power reference holding capacitor and a beam detect power reference holding capacitor is selectively connected to the laser driver through a second switch that is controlled in tandem with the first switch. During each scan cycle, the output laser power is monitored and used to adjust one of the two holding capacitors based such that both the printing power and the beam detect power have a controlled reference.