Facebook | Display latency calibration for organic light emitting diode (OLED) display
Patent: Display latency calibration for organic light emitting diode (OLED) display
Publication Number: 10140955
Publication Date: 2018-11-27
Applicants: Facebook Technologies, LLC
Abstract
A system for calibrating an organic light emitting diode (OLED) display is presented. The calibration system includes a series of photodiodes coupled to at least a portion of illumination elements of the OLED display, a controller, and a driver circuit. The series of photodiodes is configured to measure, for one or more illumination elements, illumination latencies and time delays associated with different brightness levels. The controller obtains, for each illumination element, information about brightness levels associated with image light emitted from that illumination element for at least two consecutive video frames. Based on the measured latencies, the time delays and the information about brightness levels, the controller determines a driving signal for a driver circuit for each illumination element. The driver circuit applies the determined driving signal to that illumination element to calibrate the OLED display.
BACKGROUND
The present disclosure generally relates to calibration of an electronic display, and specifically relates to a display latency calibration for an organic light emitting diode (OLED) display.
An electronic display having illumination elements or pixels designed based on organic light emitting diodes can be referred to as an OLED display. During a frame of video content being displayed on the OLED display in a global illumination mode, data associated with the frame is loaded for all illumination elements of the OLED display during a scanning period. The global illumination of the OLED display occurs in a subsequent illumination period. A latency from execution of code causing the OLED display to occur and the illumination of the OLED display is increased when the OLED display is driven at lower than full brightness, as the illumination period is delayed and shortened at lower brightness levels. Moreover, a rising time of at least two frames is required for reaching the full brightness, and the rising time is even longer for reaching a partial brightness. Thus, both the latency of illumination and the rising time to achieve a desired brightness level vary based on an intensity of illuminated image light. The variable latency and rising time of the OLED display may cause visual discomfort especially when displaying moving objects with color differences relative to a background or other slower moving objects.
SUMMARY
Embodiments of the present disclosure support a system for calibrating an organic light emitting diode (OLED) display having a plurality of illumination elements that may be organized in a two-dimensional array. The calibration system includes one or more photodiodes coupled to at least a portion of the illumination elements, a controller and a driver circuit. The one or more photodiodes are configured to measure, for each illumination element in at least the portion of the illumination elements, a latency for that illumination element to illuminate image light of each brightness level of a plurality of brightness levels. The one or more photodiodes are further configured to measure, for each illumination element in at least the portion of the illumination elements, a time rise to reach each of the plurality of brightness levels. The controller coupled to the one or more photodiodes is configured to obtain, for each illumination element in at least the portion of the illumination elements, information about brightness levels associated with image light emitted from that illumination element for at least two consecutive video frames. The controller is further configured to determine, for each illumination element in at least the portion of the illumination elements, a driving signal based on the measured latency, the measured time rise and the information about brightness levels. The driver circuit coupled to the controller is configured to apply the determined driving signal to that illumination element.
The calibration system that includes the plurality of photodiodes, the controller and the driver circuit can be integrated into a head-mounted display (HMD). The HMD may be part of, e.g., a virtual reality (VR) system, an augmented reality (AR) system, a mixed reality (MR) system, or some combination thereof.
Embodiments of the present disclosure further support a method for calibrating an OLED display having a plurality of illumination elements. The calibration method includes measuring, for each illumination element in at least a portion of a plurality of illumination elements in an organic light emitting diode (OLED) display, a latency for that illumination element to illuminate image light of each brightness level of a plurality of brightness levels. The calibration method further includes measuring, for each illumination element in at least the portion of the illumination elements, a time rise to reach each of the plurality of brightness levels. The calibration method further includes obtaining, for each illumination element in at least the portion of the illumination elements, information about brightness levels associated with image light emitted from that illumination element for at least two consecutive video frames. The calibration method further includes determining, for each illumination element in at least the portion of the illumination elements, a driving signal based on the measured latency, the measured time rise and the information about brightness levels. The calibration method further includes applying the determined driving signal to that illumination element.
