Semiconductor Laser Light Amount Control for Droop Correction
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Solution Overview
Problem
Existing electrophotographic image forming apparatuses fail to adequately correct light amount variations in semiconductor lasers due to temperature-dependent droop characteristics, leading to uneven image quality.
Innovation Solution
An image forming apparatus that includes a control unit to switch between electrostatic latent image forming and light amount control modes, using a light receiving unit to adjust the driving current and supply a correction current based on temperature data to maintain consistent light emission over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a constant current continues to be supplied to a semiconductor laser for a relatively long period, then the semiconductor laser operates continuously, but the light amount of the laser light is attenuated or increases due to self-heating, causing droop characteristic or inverse droop characteristic
Solution Approach 1:
The patent applies preliminary action by measuring the light amount at predetermined intervals before the droop characteristic fully develops, and storing correction data in advance. The correction data is prepared beforehand based on measured light amount variations, enabling compensation to be applied proactively rather than reactively when the droop occurs.
Solution Approach 2:
The patent implements feedback by measuring the actual light amount with a light receiving element, comparing it with the target light amount, and using the difference to generate correction data. This feedback loop continuously monitors and corrects light amount variations caused by self-heating, maintaining stable light emission during continuous operation.
2Device complexity
If the same correction data is used regardless of the temperature of the semiconductor laser, then the correction process is simple, but the droop characteristic or inverse droop characteristic cannot be sufficiently corrected when temperature varies
Solution Approach 1:
The patent applies parameter changes by organizing correction data according to temperature parameters. Multiple sets of correction data are stored, each corresponding to different temperature ranges of the semiconductor laser. The system selects and applies the appropriate correction data based on the current temperature, ensuring accurate correction across varying operating conditions.
3Measurement precision
If APC control is performed in each scanning cycle to control the laser light to the target light amount, then the light amount is controlled, but variations in light amount cause uneven potentials on the photosensitive member, leading to uneven toner adhesion and drop in image quality
Solution Approach 1:
The patent applies preliminary action by correcting the driving current waveform in advance to compensate for anticipated droop characteristics. By pre-adjusting the current based on stored correction data that accounts for self-heating effects, the system prevents light amount variations before they occur, ensuring uniform exposure and consistent image quality across the entire scanning period.
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
The solution effectively corrects light amount variations, ensuring consistent image quality by dynamically adjusting the driving current with temperature changes, thereby stabilizing the light emission and preventing attenuation or increase in light intensity over time.
Implementation Method 1
a light receiving element (photoelectric conversion element) receives laser light in each scanning cycle of the laser light
Implementation Method 2
a light source configured to emit a light beam for exposing the photosensitive member to light when supplied with a driving current
Data Source
AI summary
A droop characteristic or an inverse droop characteristic may fail to be sufficiently corrected depending on the temperature of a semiconductor laser. An image forming apparatus includes a droop correction unit configured to supply a correction current of which an attenuation tendency or a gradual increase tendency changes according to data about the temperature.