Reflective Display Hierarchical Dimming for Low-Light Artifacts
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Solution Overview
Problem
Designing electronic devices with displays that maintain high-quality image contrast and minimize visible artifacts across various usage contexts, particularly in environments with varying light conditions, is challenging due to light leakage and optics non-idealities.
Innovation Solution
The electronic device employs a reflective display panel and a waveguide system that adjusts image light brightness through processor-controlled bit plane modulation and dimming, using hierarchical brightness adjustment techniques to mitigate postcard artifacts in dark environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If brightness is reduced to minimize postcard artifacts in dark environments, then image quality is improved, but visibility and user experience deteriorate
Solution Approach 1:
The system dynamically adjusts bit plane duration based on ambient light conditions. In dark environments, the duration of bit plane sequences is reduced to lower overall brightness and minimize postcard artifacts, while in bright environments, the duration is increased to maintain visibility. This dynamic temporal modulation allows the display to adapt its brightness characteristics to environmental conditions.
Solution Approach 2:
The display employs periodic bit plane modulation sequences where individual bit planes are activated in alternating time slots. By controlling the duration and frequency of these periodic bit plane sequences, the system can reduce the effective brightness and duty cycle of light emission, thereby minimizing postcard artifacts while maintaining image information transmission.
2Illumination intensity
If bit plane duration is reduced to dim image light, then brightness is improved, but image data transmission completeness may deteriorate
Solution Approach 1:
The image data is segmented into multiple bit planes that are transmitted sequentially in time-divided slots. Each bit plane carries a portion of the image information, and by transmitting all bit planes over a complete modulation sequence, the full image data is reconstructed. This segmentation allows the system to control the duration of each bit plane individually, dimming the overall brightness while ensuring complete image data transmission through the cumulative effect of all bit planes.
3Illumination intensity
If drive current is increased to improve image light output, then brightness is improved, but power consumption increases
Solution Approach 1:
Instead of continuously driving the light source at high current, the system uses periodic bit plane modulation where the light source is activated only during specific time slots corresponding to active bit planes. This pulsed periodic operation significantly reduces the average power consumption compared to continuous high-current driving, while still delivering sufficient image light output during the active periods to maintain visibility.
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 reduces brightness to minimize postcard artifacts and maintain image quality by smoothly transitioning between brightness levels, enhancing user experience and power efficiency.
Implementation Method 1
a reflective display panel configured to receive image data and configured to generate image light by reflecting the illumination light based on the image data
Implementation Method 2
a waveguide configured to direct the image light towards an eye box
Data Source
AI summary
An electronic device having a display is provided. The device may include a projector that provides image light to a waveguide for display at an eye box. The projector may include light sources that provide illumination light to a reflective display panel. The panel may generate the image light by modulating image data onto the illumination light. To mitigate postcard artifacts at the eye box during low light conditions, the projector may perform hierarchical dimming that includes analog dimming, modulation-based dimming, and digital dimming as luminance decreases. The modulation-based dimming may include reducing a bit depth of a display modulation sequence in the image data and compressing the display modulation sequence over time. A display modulation sequence may be time-stretched to match the brightness of a preceding display modulation sequence to prevent flicker.