LED Exposure Device Noise Reduction via Segmented Pulse Control
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Solution Overview
Problem
In electrophotographic image forming apparatuses using LEDs or organic EL elements, the simultaneous lighting of multiple light-emitting elements leads to significant switching noise due to the large number of simultaneous signal changes, which affects the quality of the latent image formation on the photoconductive drum.
Innovation Solution
The apparatus employs a configuration with two light-emitting element arrays disposed orthogonally to each other, where the exposure device generates distinct pulse signals for each array based on different delay times and pulse widths, ensuring that light emission starts and ends at specific timings relative to a line synchronizing signal, thereby reducing simultaneous changes and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple light-emitting elements are lit simultaneously to perform multiple exposure, then necessary light quantity is secured, but switching noise increases due to large number of simultaneous signal changes
Solution Approach 1:
The exposure device divides the light-emitting element array into multiple groups (first light-emitting element array and second light-emitting element array). Each group is controlled independently with different pulse signals, so that not all elements light up simultaneously. This segmentation reduces the number of simultaneous signal changes while still achieving multiple exposure through sequential lighting of different groups.
Solution Approach 2:
The patent implements periodic lighting control where different groups of light-emitting elements are activated in alternating periods. The first light-emitting element array lights up during one period, then the second array lights up in the next period, both synchronized with the line synchronizing signal. This periodic action ensures multiple exposure while reducing instantaneous switching noise.
2Illumination intensity
If multiple light-emitting element arrays are disposed in rotational direction to achieve multiple exposure, then light quantity is sufficient, but the complexity of control signals increases
Solution Approach 1:
The patent merges the control of multiple light-emitting element arrays by using a common line synchronizing signal as the basis for all pulse signals. While each array has its own pulse signal with different delay times and pulse widths, they all originate from the same synchronizing reference, simplifying the overall control architecture compared to completely independent control of each array.
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 configuration effectively minimizes switching noise and ensures consistent light exposure, improving the formation of latent images on the photoconductive drum by synchronizing the light emission of the arrays, thus enhancing image quality and reducing the impact of simultaneous signal changes.
Implementation Method 1
A publicly known electrophotographic image forming apparatus, such as a printer, includes an exposure device that includes LEDs or organic EL elements and exposes a photoconductive drum to form a latent image
Implementation Method 2
exposes a photoconductive drum to form a latent image
Data Source
AI summary
An image forming apparatus includes an exposure device configured to perform multiple exposure with a second light-emitting element array of a place exposed with a first light-emitting element array; and a controller configured to transmit a signal for controlling the exposure device. The exposure device sets a first pulse signal for light emission of the first light-emitting element array based on a first delay time and a first pulse width, sets a second pulse signal for light emission of the second light-emitting element array based on a second delay time, different from the first delay time, and a second pulse width, identical to the first pulse width, and starts and terminates light emission of each of the first light-emitting element array and the second light-emitting element array according to the set first pulse signal and second pulse signal.