Laser Diode Light Control via Staged Reference Voltage Adjustment
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Solution Overview
Problem
Existing image forming apparatuses face challenges in accurately controlling the light emitted by a laser diode when print density changes, leading to potential overcurrent issues and reduced accuracy due to the need for complex structures and A/D conversion of detection voltages.
Innovation Solution
An image forming apparatus with a reference voltage control portion that adjusts the reference voltage in stages at a predetermined rate based on changed print density, using a light emitting unit, detecting unit, and emitted-light quantity control circuit to maintain accurate light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the reference voltage is changed during image forming operation to adjust print density, then the print density can be adjusted, but a potential difference between the CPU output voltage and the detection value becomes large, causing overcurrent to flow to the laser diode or insufficient current supply
Solution Approach 1:
The patent applies preliminary action by pre-adjusting the reference voltage in staged increments before the laser diode current reaches unsafe levels. The reference voltage generating portion increases the reference voltage by predetermined amounts (e.g., 0.1V steps) in advance, allowing the feedback control to gradually adjust the laser diode current without sudden large potential differences that would cause overcurrent or current supply failure.
2Ease of operation
If the detection voltage is subjected to A/D conversion in the CPU, then the detection value can be processed, but the structure becomes complex and the accuracy of light quantity control is lowered due to difficulty in setting dynamic range
Solution Approach 1:
The patent extracts the A/D conversion function from the CPU by introducing a dedicated analog-to-digital converter. The detection voltage from the photodiode is converted to a digital value by this separate A/D converter, which then outputs the digital signal to the CPU. This separation simplifies the CPU structure and improves measurement accuracy by allowing optimal dynamic range settings in the dedicated converter without constraining the CPU architecture.
3Adaptability or versatility
If the reference voltage is changed to adjust print density, then the density can be modified, but the accuracy of light emission control is reduced due to large potential difference
Solution Approach 1:
The patent applies preliminary action by pre-adjusting the reference voltage in staged increments before the laser diode current reaches unsafe levels. The reference voltage generating portion increases the reference voltage by predetermined amounts (e.g., 0.1V steps) in advance, allowing the feedback control to gradually adjust the laser diode current without sudden large potential differences that would cause overcurrent or current supply failure.
Solution Approach 2:
The patent applies dynamics by making the reference voltage adjustable and changeable during operation. The reference voltage generating portion dynamically modifies the reference voltage based on the desired print density, allowing the system to adapt to different printing requirements while maintaining control accuracy through staged adjustments rather than fixed reference voltage.
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 allows for precise control of light emission from the laser diode without increasing structural complexity, ensuring accurate light quantity adjustment with changing print density and preventing overcurrent issues.
Implementation Method 1
a light emitting unit that generates the light projected onto the surface of the photosensitive member
Implementation Method 2
a photodiode that detects the quantity of light emitted from the laser diode
Data Source
AI summary
An image forming apparatus includes an exposure unit, a developing unit and a transferring unit that transfers a visualized image of developer to an image recording medium. The exposure unit includes a light emitting unit, a detecting unit that detects a quantity of light, a reference voltage generating portion that generates a reference voltage set in accordance with a targeted value of the quantity of light, an emitted-light quantity control circuit that controls the quantity of light emitted from the light emitting unit so that a detection voltage becomes equal to a value of the reference voltage, and a reference voltage control portion that controls the reference voltage generating portion so as to change the reference voltage at a predetermined rate in stages. A new reference voltage is based on a density of the image of the developer obtained after being changed when the density is changed.