Laser Diode APC Control for Stable Luminance and Stray Light Reduction
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Solution Overview
Problem
The existing laser scanning image drawing apparatus faces challenges in maintaining stable emission intensity due to temperature variations and aging of laser diodes, leading to inconsistent luminance and stray light influencing the projection image.
Innovation Solution
An image display apparatus with a light source unit, scanner, image processor, and sensor that adjusts the laser light output by measuring actual luminance and adjusting the current applied to the laser diodes, minimizing the emission period of adjustment laser light to reduce stray light impact, and dynamically setting the timing for luminance measurement based on emission conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If APC control is performed by outputting emission lines to the blanking area, then luminance stability is improved, but stray light influences the projection image
Solution Approach 1:
The patent extracts the APC emission line output from the blanking area and relocates it to a dedicated calibration period outside the normal scanning area. This separates the luminance stabilization function from the projection area, eliminating stray light contamination while maintaining APC effectiveness.
Solution Approach 2:
The patent performs APC calibration during a preliminary period before actual image projection begins. By completing the emission line output and luminance measurement in advance, the system establishes stable laser diode characteristics without introducing stray light during the projection phase.
2Measurement precision
If emission line output period is extended to ensure stable measurement, then measurement accuracy is improved, but energy consumption and stray light exposure increase
Solution Approach 1:
The patent dynamically adjusts the emission line output duration based on real-time luminance stabilization detection. The system continuously monitors whether the laser diode luminance has reached the target value and terminates the emission period immediately upon stabilization, optimizing the balance between measurement accuracy and energy efficiency.
Solution Approach 2:
The patent implements a feedback mechanism where the measured luminance value is continuously compared against the target value. Based on this feedback, the system adjusts the emission period duration and laser diode current to achieve stable luminance with minimal energy expenditure.
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 ensures stable and consistent luminance by dynamically adjusting the laser light output, minimizing the period of adjustment laser light emission and reducing stray light influence on the projection image, thereby improving the overall image quality.
Implementation Method 1
a sensor measures the actual luminance of the laser light that has been emitted as each emission line
Implementation Method 2
Each of RGB laser diodes outputs a laser light to an outside of a drawing area
Data Source
AI summary
An image drawing apparatus includes a light source unit that outputs a laser light, a sensor that measures an index regarding brightness of the laser light, a scanner that reflects and scans the laser light, and an image processor that controls the light source unit, outputs the laser light to a drawing area narrower than a scanning area of the scanner so that an image based on image data that has been input is drawn, outputting an adjustment laser light to adjust the brightness of the laser light to an outside of the drawing area, stops the output of the adjustment laser light when a period (e.g., variable) until the time the output of the adjustment laser light becomes stable is passed after the output of the adjustment laser light is started, and adjusts the laser light brightness based on the index regarding the adjustment laser light brightness.