LED Light Emission Stability in Image Density Detection
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Solution Overview
Problem
Existing image forming apparatuses face challenges in precisely detecting image density due to variations in scattered and specularly reflected light, especially when the light emission amount from LEDs decreases over time due to heat generation, affecting the accuracy of optical sensors used for density correction.
Innovation Solution
The apparatus incorporates a controller that adjusts the current supply to LEDs based on temperature detection and output values from light receivers at different time periods, using LED correction coefficients to maintain a stable light emission amount, thereby compensating for temperature-induced changes in light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a constant current source is used to supply current to the LED, then the light emission amount can be maintained at a predetermined level, but the light emission amount still decreases over time due to heat generation from the LED
Solution Approach 1:
The patent implements a feedback control mechanism where the light receiver continuously monitors the light emission amount of the LED, and the controller adjusts the current supplied to the LED based on the detected light amount. This closed-loop feedback system compensates for temperature-induced light emission changes, maintaining stable detection accuracy despite LED heating over time.
Solution Approach 2:
The patent dynamically changes the operating parameters of the LED by adjusting the supplied current based on detected light emission levels. When the light emission amount decreases due to temperature rise, the controller increases the current to compensate, thereby maintaining the light emission amount within an acceptable range for accurate detection.
2Illumination intensity
If the light emission amount of the LED changes, then the amount of reflected light changes, but this variation hinders precise detection of image density
Solution Approach 1:
The light receiver monitors the actual light emission amount, and this information is fed back to the controller, which adjusts the LED current to maintain consistent illumination. This feedback mechanism ensures that variations in reflected light amount due to LED emission changes are compensated, preserving measurement precision.
Solution Approach 2:
The system uses the light receiver to monitor the LED's own emission amount and automatically adjusts the current through the controller. This self-service mechanism enables the system to self-correct for temperature-induced emission variations without external intervention, maintaining precise image density detection.
3Measurement precision
If the light receiver is used to monitor the light emission amount of the LED, then changes in light reception sensitivity of the light receiver can affect the accuracy of monitoring and correction
Solution Approach 1:
The light receiver monitors the light emission amount from the detection image, and this self-measured information is used by the controller to adjust the LED current. This self-service approach allows the system to use its own detection capability to compensate for sensitivity variations, improving overall monitoring accuracy without requiring external calibration.
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 precise and stable image density detection and correction by accurately controlling the light emission of LEDs, ensuring consistent image quality despite temperature fluctuations.
Implementation Method 1
For example, a light emitting diode (LED) is used as the light source
Implementation Method 2
The light receiver is configured to receive reflected light
Implementation Method 3
The LED generates heat after a lapse of time from start of lighting
Implementation Method 4
The temperature of the LED starts rising immediately after the start of lighting of the LED, and continues rising gradually
Data Source
AI summary
An image forming apparatus includes: an image forming unit configured to form an image on an image bearing member based on an image forming condition, an optical sensor including: a light emitter configured to irradiate the image bearing member with light based on a supplied current; and a light receiver configured to receive reflected light of the light emitted from the light emitter; a temperature detector configured to detect a temperature of the optical sensor; and a controller configured to: control the image forming unit to form a detection image on the image bearing member; control the optical sensor to detect reflected light from the detection image; and adjust the image forming condition based on a result of detecting the detection image by the optical sensor. The controller is configured to control the light emitter to emit light; and generate a correction condition.