Polygonal Mirror Speed Control via Fixed Period Timing
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Solution Overview
Problem
Conventional image forming apparatuses face challenges in controlling the rotational speed of a rotatable polygonal mirror across a broad speed range due to limitations in measuring low-width times of synchronizing signals, particularly at slow rotational speeds, leading to complex acceleration control and potential deviations in printing positions.
Innovation Solution
A scanning optical device that emits laser light based on an image signal, using a detecting portion to output a detection signal and an outputting portion to generate a driving signal, where the output timing is adjusted with a fixed second period when the output period exceeds a first period, allowing for smooth speed control without increasing storage capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a counter operating with a high-speed clock and a time measuring memory are used to measure the low-width time of the synchronizing signal, then the low-width time can be measured with high precision, but the storing capacity of the time measuring memory is limited and cannot measure long low-width times
Solution Approach 1:
The patent divides the time measurement function into two separate components: a counter for high-precision timing and a flag memory for storing measurement status. The counter counts clock pulses during the low-width period with high precision, while the flag memory simply stores whether the measurement is complete or not. This segmentation allows the system to measure long low-width times without requiring large storage capacity, as the flag memory needs only store binary states rather than full time values.
2Speed
If the rotational speed of the rotatable polygonal mirror is slow, then the time from falling to rising of the synchronizing signal becomes long, but the low-width time cannot be measured due to memory capacity limits
Solution Approach 1:
The patent implements dynamic adaptation by making the measurement system's behavior dependent on the measured time duration. When the low-width time is within the measurable range, the system performs precise measurement and uses the actual measured value for control. When the low-width time exceeds the memory capacity, the system automatically switches to using a predetermined time value. This dynamic switching ensures continuous operational capability across all rotational speeds without being constrained by fixed memory limitations.
3Productivity
If predictive control with increased and decreased surface of the rotatable polygonal mirror is employed when low-width time cannot be measured, then speed control can be maintained, but the control becomes complicated and smooth acceleration control cannot be achieved
Solution Approach 1:
The patent extracts the complex predictive control logic and replaces it with a simple flag-based measurement system. By separating the measurement function into a dedicated counter and flag memory, the system eliminates the need for complicated predictive control algorithms. The controller simply checks the measurement completion flag and uses either the measured value or a predetermined value based on the flag state, achieving smooth acceleration control with minimal 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
Enables simple and efficient control of the rotatable polygonal mirror's speed from low to high without increasing storage capacity, stabilizing image formation even with variations in light quantity, ensuring precise rotational speed management.
Implementation Method 1
a rotatable polygonal mirror for deflecting the laser light emitted from the light source
Implementation Method 2
a detecting portion for outputting a detection signal on the basis of incidence of the laser light deflected by the rotatable polygonal mirror on a light receiving surface
Data Source
AI summary
A scanning optical device includes a light source for emitting laser light, a rotatable polygonal mirror for deflecting the laser light emitted from the light source, a detecting portion for outputting a detection signal on the basis of incidence of the laser light deflected by the rotatable polygonal mirror on a light receiving surface, and an outputting portion for outputting a driving signal for driving the light source on the basis of output timing of the detection signal and an output period in which the detection signal is outputted. The laser light is emitted depending on an image signal inputted at timing based on output timing of the driving signal. When the output period is longer than a first period, the outputting portion outputs the driving signal on the basis of the output timing of the detection signal and a fixed second period.