Conferences and supporting programme
Understanding Imaging System Specifications for Pixel-Level Measurement of Displays
At the Society for Information Display (SID) 2017 Display Week, the call from keynote speaker Clay Bavor (VP, Virtual and Augmented Reality at Google) was simple: -We need more pixels. Way, way more pixels. - Producing lifelike visuals with greater contrast and color depth, improving sharpness of visual elements, and eliminating screen-door effects in immersive virtual reality environments (among other objectives) all require increasing display pixel density. In smart devices and wearables, displays become smaller in an effort to improve mobility and integration flexibility. Viewed at limited distances, these small-format displays must pack more pixels into limited spaces to achieve the visual qualities consumers desire—meaning, not only do displays contain -way, way more pixels,- but pixels are becoming much, much smaller. The performance of a display's pixels dictates the visual quality of a display. What's more, when color mixing is performed at the subpixel level in a display, the output luminance of each subpixel (typically producing red, green, and blue) determines the overall color of each pixel. If color mixing within a single pixel varies from adjacent pixels, this inconsistency can result in noticeable areas of non-uniformity or mura as viewed by a consumer. Measurement systems used for design and quality testing of increasingly small, pixel-dense displays aim at achieving pixel- and subpixel-level measurement that improves performance at each light-emitting element. Two-dimensional photometric measurement systems (imaging photometers or colorimeters) provide one display test option that is particularly efficient for measuring display defects. These systems can also be used to calculate discrepancies in luminance between subpixels, allowing manufacturers to apply corrections to emissive devices like LED or OLED displays to achieve pixel-to-pixel uniformity. For today’s displays, imaging systems that offer extremely high image quality and high resolution are required for providing accurate data not only from region to region in a display, but from pixel to pixel. A solid understanding of the specifications of an imaging measurement system is needed to evaluate the effectiveness of the device, especially where discrepancies in imaging data at the pixel level are a critical determinant for display qualification. Imaging performance can have a pivotal impact on the ability of the imaging system to collect and interpret photometric data from the display with precision and consistency. The proposed paper discusses the range of specifications available in today's high-resolution imaging technologies used for two-dimensional photometric display testing, and uses measurement examples from various systems to compare: - Sensor Type ----- A comparison of current CCD and CMOS sensors used in photometric imaging applications, such as display testing. ----- Resolution ----- The impact of resolution on pixel- and subpixel-level display measurement. ----- A comparison of available sensor resolutions and differences in accuracy based on sensor type (CCD or CMOS) and dynamic range (signal to noise ratio). - Sensor Pixel Size ----- The impact of CCD or CMOS pixel size on noise per pixel. - Signal to Noise Ratio (SNR) ----- A comparison of Photon Transfer Curves (PTC) output by different imaging systems'a key indicator of imaging system performance, especially at low gray levels.
--- Date: 27.02.2019 Time: 1:35 PM - 1:55 PM Location: Conference Counter NCC Ost