Laser Display Brightness Control Using Voltage-Drop Feedback
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Solution Overview
Problem
The generation of white light using lasers is challenging due to the unpredictable behavior of laser devices caused by temperature fluctuations, which affect the characteristic curves and color output, making precise control difficult.
Innovation Solution
A method is proposed to compensate for temperature-induced changes by measuring the current-voltage characteristics of laser devices, using a detector circuit to detect voltage drops during reverse operation, and adjusting supply currents based on these measurements to maintain desired brightness and color locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If laser devices are operated at high brightness levels, then the desired color space and white light can be displayed, but temperature increases cause characteristic curve shifts and color instability
Solution Approach 1:
The patent implements a feedback mechanism where the actual color output of the laser device is continuously measured by a color sensor, compared to the target color, and the drive current is adjusted accordingly to compensate for temperature-induced characteristic curve shifts, maintaining stable color output at high brightness levels
Solution Approach 2:
The patent dynamically adjusts the drive current parameter of the laser device based on measured temperature or characteristic curve changes, modifying the electrical input to compensate for thermal effects and maintain consistent color output across varying brightness levels
2Manufacturing precision
If the characteristic curve of the laser is made stable, then precise control of color and brightness is achieved, but the system becomes more complex due to temperature compensation requirements
Solution Approach 1:
The patent employs a self-service approach where the system automatically measures its own output characteristics and adjusts its drive parameters without external intervention, using an integrated color sensor and control algorithm that autonomously compensates for drift, reducing the need for complex external calibration equipment
Solution Approach 2:
The patent replaces complex mechanical temperature control systems with an electrical compensation approach, using software-based characteristic curve storage and lookup tables that dynamically adjust drive currents based on measured conditions, substituting physical thermal management with computational correction
3Temperature
If ambient temperature is compensated using temperature sensors, then slow temperature changes can be corrected, but dynamic self-heating effects cannot be measured or compensated
Solution Approach 1:
The patent uses the laser device's own optical output as an intermediary to indirectly measure its internal state, where the color and intensity of the emitted light serve as a proxy for temperature and characteristic curve position, allowing inference of internal conditions without direct temperature sensors inside the laser
4Adaptability or versatility
If multiple laser devices are used to generate white light through additive mixing, then the widest color space can be displayed, but the system requires precise control of multiple devices with different characteristic curves
Solution Approach 1:
The patent segments the color control task by assigning specific control algorithms and characteristic curve compensation to each individual laser device, allowing each device to be independently optimized and controlled, simplifying the overall system control while maintaining wide color space coverage through additive mixing
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 approach allows for precise control of laser devices, ensuring consistent color and brightness output by predicting future temperature effects, reducing optical artifacts, and enabling high-color accuracy in applications like data glasses and augmented reality.
Implementation Method 1
detecting, with a detector circuit coupled to the first laser device, a voltage drop across the first laser device
Implementation Method 2
a first and at least one second laser device, which are designed to generate laser light for illuminating the pixels in a pulsed mode
Data Source
AI summary
A method is described for operating at least two laser devices for generating a display, in which the at least two laser devices generate a sequence of light points. In a first step, a first one of the sequence of light spots is generated during a first period of time by at least one of the at least two laser devices and a voltage drop across the at least one of the at least two laser devices is detected within the first period of time. A target brightness is then determined for a second of the sequence of light points for at least one of the at least two laser devices. Subsequently, a supply current and/or a turn-on time is determined during a second time period for generating the target brightness for the at least one of the at least two laser devices.