Laser Light Intensity Control for Toner Density Detection
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Solution Overview
Problem
Image forming apparatuses face challenges in accurately forming toner patterns for density detection in the main scanning direction due to limitations in laser light intensity control, particularly when using optical scanning apparatuses without shading functions, leading to unclear boundary detection and difficulty in achieving target density levels under varying environmental conditions.
Innovation Solution
An image forming apparatus with a light source emitting light based on current value, a driving unit using PWM signals to control current, and a deflection unit to scan the light beam on a photoconductor, along with a control unit that adjusts pulse width to form toner images with different densities in parallel, and controls light amount based on scanning position, ensuring accurate light intensity control through a smoothing circuit and shading circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an optical scanning apparatus without a shading function is used to control laser light amount, then device complexity is reduced, but manufacturing precision of toner patterns for density detection deteriorates due to inability to control light intensity within one scanning period
Solution Approach 1:
The patent applies preliminary action by forming multiple toner patterns for density detection in the sub-scanning direction (parallel to each other) before reading them in the main scanning direction. This allows the use of a simpler optical scanning apparatus without shading function, as the light amount control is achieved through multiple sequential scans rather than within a single scan. The patterns are formed at different positions in the sub-scanning direction, enabling density detection without requiring precise light intensity control within one scanning period.
2Manufacturing precision
If a laser driving circuit with shading function is used to control light amount, then manufacturing precision of toner patterns improves, but device complexity increases due to low-pass filter requirements
Solution Approach 1:
The patent extracts the shading function from the laser driving circuit by removing the low-pass filter component. Instead of using a complex circuit with shading capability, the invention achieves light amount control through a simpler PWM signal approach where the duty ratio is adjusted to form toner patterns at different density levels. This extraction of the shading function allows using a simpler laser driving circuit while still achieving the required manufacturing precision for density detection patterns.
3Productivity
If multiple toner patterns for density detection are formed in the main scanning direction, then productivity improves by reducing sheet usage, but measurement precision deteriorates due to unclear boundary detection
Solution Approach 1:
The patent changes the spatial arrangement of toner patterns from the main scanning direction to the sub-scanning direction. Instead of placing patterns sequentially along the main scanning axis, multiple patterns are formed in parallel at different positions in the sub-scanning direction. This dimensional change allows all patterns to be formed on a single sheet while maintaining clear boundaries between them, as they are spatially separated perpendicular to the scanning direction. The sensor can then read these parallel patterns without boundary confusion, preserving measurement precision while improving productivity.
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 enables accurate formation of toner patterns for density detection in the main scanning direction and precise control of laser light intensity, improving the ability to achieve target density levels even under varying environmental conditions, enhancing image quality and efficiency.
Implementation Method 1
a light source configured to emit light beam in a light amount corresponding to a value of supplied current
Implementation Method 2
which includes a smoothing circuit that outputs a signal obtained by smoothing a second PWM signal input
Implementation Method 3
a deflection unit configured to deflect the light beam emitted from the light source such that the light beam scan the photoconductor
Implementation Method 4
an image forming unit including a photoconductor, a light source configured to emit light beam... the image forming unit develops, using toner, electrostatic latent image formed on the photoconductor by being scanned by the light beam
Implementation Method 5
the image forming unit develops, using toner, electrostatic latent image formed on the photoconductor by being scanned by the light beam
Data Source
AI summary
A CPU controls an image forming unit such that toner images for density detection are formed in parallel in a scanning direction of light beam under an image forming condition in which a period of time in which the light beam are emitted per unit time is changed and sets a target light amount of the light beam based on density information of the toner images for density detection formed by the image forming unit and relational data stored in a ROM.