Rotating Polygonal Mirror Phase Detection Using BD and FG Signals
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Solution Overview
Problem
The existing methods for determining the phase of a rotating polygonal mirror in image forming apparatuses suffer from reduced accuracy due to machining errors and jitter in the FG signal, leading to incorrect specification of reflective faces, which complicates the assembly process and affects image quality.
Innovation Solution
An image forming apparatus is designed with a rotating polygonal mirror, a motor, a first detection unit for the light beam, a second detection unit for magnetic flux changes, and a specifying unit that determines the phase relationship between the signals to accurately specify the reflective face using setting information to choose between rising and falling edges of the FG signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the phase difference between BD signal and FG signal is detected to specify reflective faces, then face specification can be achieved, but the jitter of FG signal reduces detection accuracy
Solution Approach 1:
The patent introduces a light receiving element as an intermediary to generate the BD signal, which serves as a more reliable reference signal compared to the jitter-prone FG signal. By using the BD signal (generated from actual light reflection) as the primary reference and the FG signal only as a supplementary indicator, the system achieves accurate face specification without being adversely affected by FG signal jitter.
2Measurement precision
If the rotating polygonal mirror is fixed to the motor while checking phase alignment, then face specification accuracy improves, but the assembly process becomes complicated and labor-intensive
Solution Approach 1:
The patent enables the system to automatically determine face specification accuracy through signal analysis without requiring manual phase alignment during assembly. The control unit automatically compares the BD signal and FG signal to identify the specific reflective face, eliminating the need for workers to manually check and adjust phase alignment, thereby simplifying the assembly process while maintaining high accuracy.
Solution Approach 2:
The patent changes the approach from mechanical phase alignment to electrical signal comparison. By analyzing the temporal relationship between BD signal and FG signal parameters (phase difference, timing coincidence), the system determines face specification automatically, converting a mechanical alignment task into an electrical measurement and control task.
3Ease of operation
If rising edge of FG signal is used for phase detection, then face specification can be performed, but jitter causes inconsistent detection results
Solution Approach 1:
The patent implements a feedback mechanism where the control unit continuously monitors the relationship between BD signal and FG signal, and automatically adjusts the face specification determination based on the actual signal characteristics. When jitter causes the FG signal rising edge to coincidentally align with BD signal, the control unit uses feedback logic to verify whether this alignment is genuine or spurious, thereby maintaining consistent and accurate face specification.
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 improves the accuracy of phase detection for the rotating polygonal mirror while simplifying the assembly process, reducing the impact of jitter and ensuring precise specification of reflective faces, thereby enhancing image quality.
Implementation Method 1
a laser beam is deflected by a rotating polygonal mirror, and thereby scans the photosensitive member
Implementation Method 2
A second detection unit is configured to output a second signal whose period is different from a period of the first signal, by detecting magnetic flux change caused by rotation of a magnet attached to the rotor of the motor
Data Source
AI summary
A rotating polygonal mirror has deflection faces for deflecting a light beam. A motor drives the polygonal mirror. A first detection unit outputs a first signal by detecting a light beam. A second detection unit outputs a second signal whose period is different from a period of the first signal, by detecting magnetic flux change. A specifying unit obtains a phase relationship between the first signal and the second signal, and specifies a deflection face. A storage unit stores setting information for setting whether to use rising or falling of the second signal to specify the phase relationship. The specifying unit determines whether to use rising or falling of the second signal in order to obtain the phase relationship.