Light Source Drive Circuit for Linear Luminance Control
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Solution Overview
Problem
Existing image display systems face challenges in maintaining consistent luminance levels when adjusting drive current, leading to non-linear changes in luminance and reduced reproducibility of images.
Innovation Solution
An image display system that includes a processing unit and a driving unit with shaping circuits and D/A converters, which determine digital signal values based on instruction values to output drive currents to light sources, ensuring a linear relationship between luminance changes and instruction values, thereby improving image reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the drive current is increased in accordance with the picture signal to increase luminance, then the luminance output is improved, but the luminance changes drastically and reproducibility decreases
Solution Approach 1:
The patent applies parameter changes by modifying the drive current characteristics through gamma correction. The system changes the relationship between the input signal level and the actual drive current supplied to the laser, using a gamma correction circuit to transform the linear input signal into a non-linear drive current that compensates for the laser's exponential luminance response. This resolves the contradiction by adjusting the electrical parameter (drive current) to achieve linear luminance output.
2Measurement precision
If the drive current is adjusted to match the instruction value of luminance, then the control accuracy is improved, but the actual luminance changes non-linearly
Solution Approach 1:
The patent introduces an intermediary element - the gamma correction circuit - that sits between the input signal and the drive current generation. This intermediary transforms the linear input signal into a corrected signal that accounts for the laser's non-linear characteristics. The gamma correction circuit acts as a mediator that reconciles the linear control signal with the non-linear luminance response, maintaining both control accuracy and luminance linearity.
3Device complexity
If a simple drive circuit is used to control the light source, then the device complexity is reduced, but the luminance reproducibility deteriorates
Solution Approach 1:
The patent segments the drive circuit into distinct functional blocks: a gamma correction circuit and a drive current generation circuit. This segmentation allows each block to perform its specific function - the gamma correction block handles the non-linear compensation, while the drive current block supplies the corrected current to the laser. By dividing the circuit into specialized segments, the system achieves improved luminance reproducibility without excessive overall complexity.
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 system effectively adjusts actual luminance in response to instruction values, achieving a linear relationship and enhancing image reproducibility by using D/A converters to compute and output drive currents to light sources.
Implementation Method 1
The plurality of D/A converters are each configured to, in response to input of a digital signal, output an analog signal corresponding to a value of the digital signal
Implementation Method 2
an image display system for forming an image by use of light from a light source of a luminaire
Data Source
AI summary
The image display system includes a processing unit and a driving unit. The processing unit is configured to receive an image signal indicative of an instruction value of luminance of a light source. The driving unit is configured to supply a drive current to the light source in accordance with the instruction value indicated by the image signal received by the processing unit. The driving unit includes a shaping circuit and an adjusting unit. The shaping circuit includes a plurality of D/A converters and an arithmetic unit. The arithmetic unit is configured to output the drive current to the light source based on a computation result of analog signals outputted from the plurality of D/A converters. The adjusting unit is configured to determine values of digital signals inputted into the plurality of D/A converters of the shaping circuit in accordance with the instruction value.