Scanning Exposure Device Beam Detection Timing Control
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Solution Overview
Problem
In scanning exposure devices, errors in beam detection by the BD sensor lead to variations in the second writing time, resulting in reduced accuracy of the writing position for the second beam on the second photosensitive member, making high-accuracy exposure challenging.
Innovation Solution
A scanning exposure device with a controller that stores reference surface identifiers and writing times for each reflecting surface of a polygon mirror, allowing for precise determination and storage of first and second writing times, as well as a reference time difference, enabling accurate correspondence between detection timings and exposure start times for each surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single BD sensor is used to detect the first beam for determining both first and second writing times, then the device complexity is reduced, but the manufacturing precision deteriorates due to detection errors affecting the second writing time accuracy
Solution Approach 1:
The patent divides the detection function into two separate optical sensors: one dedicated to detecting the first beam for determining the first writing time, and another dedicated to detecting the second beam for determining the second writing time. This segmentation eliminates the error propagation that occurs when a single sensor is used for both measurements, thereby resolving the contradiction between device simplicity and measurement accuracy.
Solution Approach 2:
The patent introduces a timing measurement unit that independently measures the detection timings of both beams, and a correspondence specification unit that establishes the relationship between the two sets of timing data. This intermediary mechanism allows for independent and accurate determination of both writing times without the errors that would result from using a single sensor for both purposes.
2Device complexity
If the second writing time is determined based on detection timing of the first beam only, then the device complexity is reduced, but the reliability deteriorates because detection errors cause variation in the second writing time
Solution Approach 1:
The patent segments the detection system into two independent detection paths: one for the first beam and another for the second beam. Each path uses its own optical sensor and timing measurement unit, ensuring that detection errors in one path do not affect the reliability of the other path's timing measurements. This independent segmentation guarantees consistent and reliable writing time determination.
Solution Approach 2:
The patent implements a feedback mechanism where the timing measurement unit continuously monitors the detection timings of both beams, and the correspondence specification unit adjusts the relationship between the two sets of timing data based on actual measurements. This feedback loop ensures that any variations in detection timing are accounted for, maintaining high reliability in the writing time determination.
3Manufacturing precision
If separate optical sensors are added for detecting both beams, then the manufacturing precision is improved, but the device complexity increases
Solution Approach 1:
The patent divides the optical detection system into specialized segments: a first optical sensor for the first beam and a second optical sensor for the second beam. Each sensor is optimized for its specific detection task, which improves measurement precision while keeping the overall system architecture modular and manageable, thus reducing the practical impact of increased complexity.
Solution Approach 2:
The patent designs the optical sensor system with universal functionality where each sensor serves its primary detection purpose while also contributing to the overall timing synchronization mechanism. The timing measurement unit and correspondence specification unit act as universal coordination mechanisms that manage both detection paths, reducing the need for separate complex control systems for each sensor.
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 ensures high-accuracy exposure by accurately setting the writing positions of both the first and second beams on their respective photosensitive members, improving the overall precision of the exposure process.
Implementation Method 1
a first optical sensor configured to detect the first beam reflected by the polygon mirror
Implementation Method 2
a second optical sensor configured to detect the second beam reflected by the polygon mirror
Implementation Method 3
a polygon mirror having N reflecting surfaces for reflecting the first beam and the second beam
Implementation Method 4
a first scanning optical system configured to focus the first beam, which is reflected by the polygon mirror, on a first image surface
Implementation Method 5
a second scanning optical system configured to focus the second beam, which is reflected by the polygon mirror, on a second image surface
Data Source
AI summary
A scanning exposure device including: a first and a second light sources emitting a first and second beam, respectively; a polygon mirror having reflecting surfaces; a first and a second optical sensors detecting the first and the second beam, respectively; and a controller storing first writing time until which an exposure by the first beam starts after the first beam is detected and second writing time until which an exposure by the second beam starts after the first beam is detected, for respective reference surface identifiers specifying the respective reflecting surfaces, and the controller acquires a first timing at which the first beam is detected and a second timing at which the second beam is detected for the respective reflecting surfaces identified by respective acquisition surface identifiers; and specifies a correspondence relation between the respective reference surface identifiers and the respective acquisition surface identifiers.