Light Projection Device Chromaticity Deviation Control
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Solution Overview
Problem
Conventional light projection devices experience chromaticity deviation and white balance loss due to the slow response time of liquid crystal elements in dimming attenuators, leading to inconsistent image color during image rendering.
Innovation Solution
A light projection device with a controller that adjusts the transmissivity of light sources based on predicted changes using feed-forward control, ensuring the chromaticity deviation is maintained within a specific range by acquiring light output characteristics and transmissivity information, and using sensors to detect actual transmissivity and temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the drive voltage is changed to adjust the transmissivity of the liquid crystal element, then the amount of projected light can be adjusted, but the transmissivity gradually changes during the response time, causing chromaticity deviation and white balance loss
Solution Approach 1:
The patent applies preliminary action by performing APC (auto power control) correction in advance during the blanking period before image rendering, rather than during the rendering period. The controller calculates corrected drive voltages for all light sources based on current transmissivity characteristics, and these corrected voltages are applied before the image frame is rendered. This ensures that the white balance is pre-corrected for the entire rendering duration, preventing chromaticity deviation even as transmissivity gradually changes during rendering.
Solution Approach 2:
The patent utilizes parameter changes by dynamically adjusting the drive voltages of light sources based on detected transmissivity characteristics of the liquid crystal element. The system measures the actual transmissivity at different wavelengths, calculates the deviation from target white balance, and computes corrected drive voltages that compensate for these changes. This allows the system to adapt to gradual transmissivity changes and maintain accurate white balance throughout the rendering period.
2Reliability
If APC is performed once every blanking period, then the white balance can be corrected between frames, but the correction is not updated during the rendering period, leading to chromaticity deviation
Solution Approach 1:
The patent performs APC correction in advance during the blanking period, utilizing the available time before rendering begins. By calculating and applying corrected drive voltages during this preliminary period, the system ensures that white balance correction is completed before any image rendering occurs, eliminating chromaticity deviation during the rendering period without requiring continuous updates.
Solution Approach 2:
The patent maintains continuous white balance accuracy by ensuring that the APC correction performed during the blanking period remains valid throughout the entire rendering period. The corrected drive voltages are applied in such a way that they compensate for transmissivity changes over the full rendering duration, providing continuous accurate color reproduction without interruption or additional corrections during rendering.
3Illumination intensity
If the transmissivity of the liquid crystal element is adjusted by changing drive voltage, then the brightness can be controlled, but the transmissivity changes differently for each wavelength, causing chromaticity deviation
Solution Approach 1:
The patent applies local quality by performing separate transmissivity measurements and corrections for each wavelength (RGB channels). The system measures the transmissivity of the liquid crystal element at different wavelengths independently, detects the specific chromaticity deviation for each color channel, and calculates individual corrected drive voltages for each light source. This wavelength-specific approach allows precise compensation for differential transmissivity changes, maintaining accurate white balance while controlling brightness.
Solution Approach 2:
The patent implements feedback by measuring the actual transmissivity of the liquid crystal element at different wavelengths, comparing it against target values, and using this information to calculate corrected drive voltages. The system continuously monitors transmissivity characteristics and adjusts light source output accordingly, creating a closed-loop control system that maintains accurate chromaticity despite variations in liquid crystal element performance.
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 prevents chromaticity deviation and maintains accurate white balance, allowing for precise adjustment of light output while ensuring consistent image color across frames.
Implementation Method 1
The transmission component has a liquid crystal element. The light outputted from the light sources is transmitted through the liquid crystal element at the transmissivity for each wavelength.
Implementation Method 2
the liquid crystal element is configured to change polarization angle of the light according to a drive voltage to adjust the transmissivity for each wavelength according to the drive voltage
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A light projection device includes a plurality of light sources, a transmission component, and a controller. The light sources are configured to output light of mutually different wavelengths. The transmission component is configured to transmit the light at a transmissivity of the light for each wavelength. The controller is configured to control amount of light of the light sources based on transmissivity information indicating a change in the transmissivity for each wavelength.