Laser Diode Driving Current Control for Luminance Uniformity
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Solution Overview
Problem
Laser diodes exhibit luminance unevenness in image display due to varying output light in response to current transitions, even with constant current application, leading to inconsistent image quality.
Innovation Solution
An image display device with a control unit that adjusts the driving current based on the time period for which a gradation value is set, to minimize luminance unevenness by compensating for the transient response characteristics of the laser diode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If voltage fluctuation compensation is applied to the laser diode driving power source, then luminance unevenness is reduced, but response characteristics variations cause luminance unevenness to persist
Solution Approach 1:
The control unit calculates a corrected current value in advance by adding a correction value to the initial current value corresponding to the second gradation value, before actually applying the current to the laser diode. This preliminary correction compensates for the transient response characteristics and accumulated error, ensuring accurate luminance output even when transitioning from different first gradation values held for different time periods.
2Stability of the object's composition
If constant current is applied to the laser diode, then voltage fluctuation is eliminated, but transient response characteristics cause luminance unevenness
Solution Approach 1:
The control unit dynamically adjusts the current parameter by adding a time-dependent correction value to the initial current value. This correction value changes based on the time period during which the first gradation value was held, allowing the system to compensate for transient response characteristics and accumulated error while maintaining overall current stability.
3Manufacturing precision
If the driving current is adjusted based on time period, then luminance unevenness is reduced, but control complexity increases
Solution Approach 1:
The control unit uses feedback from the time period information (how long the first gradation value was held) to calculate an appropriate correction value. This feedback mechanism allows the system to automatically adjust the driving current to compensate for transient response characteristics and accumulated error, reducing luminance unevenness without requiring complex manual control mechanisms.
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
The solution effectively reduces luminance unevenness in images by synchronizing the driving current with the time-dependent changes in the laser diode's output, ensuring consistent image quality across different gradation values.
Implementation Method 1
a light source (laser diode 32) that emits light in accordance with currents output from the control unit 31
Data Source
AI summary
An image display device includes: a light source configured to change the amount of light, depending on a driving current; and a control unit configured to, when a change is made from a first gradation value to a second gradation value, control the driving current at the second gradation value, depending on a time period for which the first gradation value is set.