Laser Beam Detection Circuit for Image Forming Apparatus
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Solution Overview
Problem
Existing image forming apparatuses face complexity in circuit design and operation due to asynchronous relationships between image data and rotary polygonal mirror rotation, requiring complicated circuitry to accurately measure and synchronize laser beam detection signals for precise image writing.
Innovation Solution
An image forming apparatus with a high-speed clock and low-speed clock generation, a scanning unit for laser beam scanning, a detection unit for beam detection, a shift register unit for signal processing, and an output unit for synchronized detection timing, allowing for simple circuit arrangements and improved accuracy in image formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional method using a high-speed clock and N demultiplication is used to obtain beam detection signals, then the laser beam detection timing can be captured, but the circuit becomes complicated in both designing and operational aspects
Solution Approach 1:
The patent divides the clock system into two independent segments: a high-speed clock for the scanning unit (polygonal mirror rotation) and a low-speed clock for the detection unit (beam detection). This segmentation allows each unit to operate at its optimal speed without requiring complex clock multiplication and demultiplication circuits, thereby reducing circuit complexity while maintaining detection timing accuracy.
Solution Approach 2:
The patent introduces an intermediary mechanism (such as a delay circuit or buffer) between the high-speed scanning unit and the low-speed detection unit. This intermediary allows the beam detection signal to be captured and held until the next low-speed clock cycle, enabling accurate timing detection without requiring the detection circuit to operate at high speed, thus simplifying the overall circuit design.
2Adaptability or versatility
If the image data and rotary polygonal mirror rotation are in asynchronous relationship, then flexibility in data processing is improved, but accurate measurement of time required for laser beam travel becomes difficult
Solution Approach 1:
The patent implements preliminary action by pre-synchronizing the detection unit with the scanning unit using the respective clock signals. The detection unit is prepared to capture the beam detection signal at the precise moment it arrives, based on the predetermined relationship between the high-speed scanning clock and low-speed detection clock. This allows accurate measurement of laser beam travel time even though the overall system operates asynchronously, maintaining both flexibility and measurement precision.
3Device complexity
If a low-speed circuit is used for detection, then circuit complexity is reduced, but the speed of receiving laser beam detection signals decreases
Solution Approach 1:
The patent uses a copying mechanism where the high-speed scanning information is captured and transferred to the low-speed detection circuit through clock synchronization. The beam detection signal is effectively 'copied' from the high-speed domain to the low-speed domain, allowing the low-speed circuit to process the information accurately without losing the temporal precision of the original high-speed signal, thus maintaining detection speed accuracy while using simpler low-speed circuits.
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 solution enables speedy and accurate detection of laser beam signals with low-speed circuits, precise control of image writing start positions, and high-speed performance, enhancing image formation accuracy.
Implementation Method 1
form an electrostatic latent image on a surface of a photosensitive member with a laser beam scanning on the surface of the photosensitive member
Implementation Method 2
a detection unit configured to detect the laser beam during a scanning operation performed by the scanning unit
Data Source
AI summary
Image forming apparatus that forms an electrostatic latent image on a surface of a photosensitive member with a laser beam, including a generation unit configured to generate a high-speed clock and a low-speed clock mutually different in frequency, a scanning unit configured to perform scanning of the laser beam in a main scanning direction based on the low-speed clock, a detection unit configured to detect the laser beam during a scanning operation performed by the scanning unit, a first shift register unit configured to receive a detection signal from the detection unit according to the high-speed clock, and an output unit configured to receive a parallel output of the first shift register unit in synchronization with the low-speed clock and to output detection timing of the laser beam as a detection signal synchronized with the low-speed clock and a value corresponding to a shift number defined by the high-speed clock.