Laser Diode Bias Control for Pulse Width Matching
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Solution Overview
Problem
Conventional image forming apparatuses face challenges in minimizing pulse width reduction during laser exposure due to variations in ambient temperature and limited adjustment ranges, leading to incomplete or inaccurate image formation.
Innovation Solution
An image forming apparatus with a driving circuit, current adjustment, pulse width expansion, and state detection mechanisms that adjust bias current and pulse width to match laser light emission with the pulse width of the image pulse signal, ensuring consistent and accurate light exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If bias current is increased to reduce oscillation delay time, then laser light emission responsiveness is improved, but the adjustment range becomes limited at low temperatures
Solution Approach 1:
The patent applies dynamics by making the bias current adjustable and adaptive rather than fixed. The control unit dynamically changes the bias current value based on detected oscillation delay time to optimize laser emission responsiveness under different operating conditions, particularly at low temperatures where the adjustment range is limited.
Solution Approach 2:
The patent implements feedback control by detecting the oscillation delay time and using this information to adjust the bias current. The control unit continuously monitors the laser diode's response characteristics and modifies the bias current accordingly, creating a closed-loop system that maintains optimal performance across varying temperature conditions.
2Ease of operation
If drive current is supplied starting at ON edge of pulse, then timing is simplified, but pulse width reduction occurs due to oscillation delay time
Solution Approach 1:
The patent applies preliminary action by supplying bias current before the actual drive current is applied. This preliminary bias current prepares the laser diode for faster response, reducing the oscillation delay time that would otherwise cause pulse width reduction. The bias current is established in advance of the main exposure pulse.
Solution Approach 2:
The patent changes the electrical parameters of the laser diode by applying a bias current that shifts the operating point. This parameter change reduces the time required for the laser diode to reach oscillation threshold when drive current is applied, thereby maintaining accurate pulse width despite the simplified timing approach.
3Duration of action of moving object
If conventional pulse width expansion is used, then laser light emission time is extended, but resolution is limited by control circuit clock
Solution Approach 1:
The patent replaces the mechanical/clock-based pulse width expansion method with an electrical solution. Instead of using control circuit clock cycles to extend pulse width, the patent uses bias current adjustment to reduce oscillation delay time, achieving effective pulse width compensation through electrical parameter modification rather than temporal extension.
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 effectively minimizes pulse width reduction, ensuring faithful laser exposure to the image pulse signal, regardless of ambient temperature variations, by combining pulse width expansion and bias current adjustments, thus improving image formation accuracy.
Implementation Method 1
When a laser diode (LD) used as a laser light source is supplied with drive current greater than oscillation threshold current, the LD emits laser light.
Data Source
AI summary
An image forming apparatus for performing laser exposure is provided. The image forming apparatus includes a driving circuit for supplying drive current to a laser light source in accordance with an image pulse signal; a pulse width expansion portion for expanding a pulse width of the image pulse signal supplied to the driving circuit; and an adjustment control portion for setting, based on state data indicating a state related to light emission start characteristics of the laser light source, a value of the bias current supplied as a part of the drive current to the laser light source and an amount of expansion of the pulse width in such a manner that laser light emission occurs in a period of time having a length equal to a length of a pulse width of each pulse in the image pulse signal.