Low-Persistence Display Brightness Control for Variable Refresh
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Solution Overview
Problem
Variable refresh rate technologies cause flickering in low-persistence displays due to varying brightness, which is unsuitable for VR systems, as they pulse the backlight on-and-off at the display's refresh rate, leading to a brightening and dimming effect for users.
Innovation Solution
Dynamically adjust the light output of low-persistence, variable refresh rate displays by controlling the magnitude and duration of light pulses based on the time difference between sequential frames to maintain constant brightness, using techniques such as re-projection to compensate for pose inaccuracies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If variable refresh rate is used with low-persistence display, then refresh rate can be synchronized with frame rate, but display brightness varies causing flickering
Solution Approach 1:
The system preemptively adjusts the light output parameter before displaying each frame to counteract the brightness variation that would otherwise occur. By calculating the required light output adjustment based on the refresh rate and frame rate relationship in advance, the system prevents flickering before it happens, maintaining constant perceived brightness while allowing variable refresh rates.
2Productivity
If light pulses occur closer together at higher refresh rates, then image refresh is more frequent, but display appears brighter causing flickering
Solution Approach 1:
The system dynamically changes the light output parameter based on the refresh rate. When refresh rate increases and light pulses occur closer together, the light output parameter is reduced to maintain constant brightness. Conversely, when refresh rate decreases, the light output parameter is increased. This parameter adjustment compensates for the frequency changes and eliminates flickering.
3Use of energy by moving object
If light pulses occur farther apart at lower refresh rates, then image refresh is less frequent, but display appears dimmer causing flickering
Solution Approach 1:
The system dynamically adjusts the light output parameter in response to refresh rate changes. When refresh rate is low and light pulses are farther apart, the light output parameter is increased to compensate for the reduced frequency, maintaining constant perceived brightness. This ensures energy efficient operation at lower refresh rates while preventing flickering.
Data Source
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AI summary
Light output of a display can be dynamically adjusted on-the-fly. When implemented on a low-persistence display that supports a variable refresh rate, this adjustment maintains a constant brightness over a series of frames to eliminate flickering of the display. When pixel data of a given frame is output to a frame buffer for presenting an image on the display, a time difference between an illumination of the display's light emitting elements for a preceding frame and an upcoming illumination of the light emitting elements for the given frame may be determined, and this time difference is used to determine a value of a light output parameter. During presentation of the image, the light emitting elements can be illuminated in accordance with the value of the light output parameter. This determination iterates over a series of frames to dynamically adjust the display's light output.