LED Exposure Head Intensity Control Using Switched Resistances
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Solution Overview
Problem
Existing image forming apparatuses face limitations in adjusting light exposure amounts without changing the applied voltage to light emitting thyristors, particularly at increased image formation speeds, leading to restricted adjustable ranges and improper ON/OFF control.
Innovation Solution
A light emitting device with multiple resistance elements of varying resistance values and a switching circuit that adjusts the connection states to control light intensity without altering the applied voltage, using a light intensity controller to select appropriate resistance combinations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the light exposure period is reduced to increase image formation speed, then productivity is improved, but the adjustable range of light exposure amount becomes limited
Solution Approach 1:
The patent changes the parameter being controlled from light exposure period to light emission intensity. By adjusting the intensity parameter of the light emitting elements while maintaining a fixed exposure period, the system achieves both high image formation speed and wide adjustable range of light exposure amount.
2Illumination intensity
If the application voltage is adjusted to control light exposure amount, then light intensity is improved, but the adjustable range is limited by ON/OFF control requirements
Solution Approach 1:
The patent changes the control parameter from application voltage to light emission intensity. This allows independent adjustment of light exposure amount without affecting the ON/OFF control functionality, as intensity modulation can be achieved through other means such as pulse width modulation or current control while maintaining proper voltage levels for reliable switching.
3Device complexity
If a single light emitting element is used, then device complexity is reduced, but light intensity adjustment capability is insufficient
Solution Approach 1:
The patent segments the light emitting function into multiple light emitting elements that can be independently controlled. This segmentation enables fine-grained adjustment of total light emission intensity by selectively activating different numbers or combinations of elements, providing wide adjustment range while keeping each individual element simple.
Solution Approach 2:
The patent introduces dynamic control capability where the activation state of each light emitting element can be changed in real-time. This dynamic control allows flexible adjustment of light intensity by selectively turning on/off individual elements or groups of elements, achieving adaptability without increasing the complexity of each element itself.
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
Enables precise adjustment of light intensity per light emitting element, enhancing control over light exposure amounts and maintaining efficient ON/OFF operations even at higher speeds.
Implementation Method 1
an LED print head (LPH) including a light emitting element array in which a plurality of light emitting diodes (LEDs) serving as light emitting elements is arrayed
Implementation Method 2
a plurality of light emitting elements including anode terminals to which a reference potential is applied, and cathode terminals connected to first ends of the plurality of resistance elements in common
Implementation Method 3
a plurality of resistance elements having different resistance values; a switching circuit configured to switch connection states between second ends of the plurality of resistance elements and the turn-on potential applier
Data Source
AI summary
A light emitting device includes: plural resistance elements having different resistance values; plural light emitting elements including anode terminals to which a reference potential is applied, and cathode terminals connected to first ends of the plural resistance elements in common; a turn-on instructor configured to sequentially output turn-on instruction signals to the plural light emitting elements to sequentially turn ON the plural light emitting elements; a turn-on potential applier configured to apply a turn-on potential for turning ON the plural light emitting elements; and a switching circuit configured to switch connection states between second ends of the plural resistance elements and the turn-on potential applier.