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LED
Published in Tim Kuschel, The Live Event Video Technician, 2023
LED panels begin with their namesake, LEDs. There are several types of LED arrangements that have been used. Discrete LED means that there is a separate diode for each color: red, green, and blue. Because of the physical size of the diodes, the clusters cannot be placed that close together. In fact, discrete LED was used primarily for outdoor rated LED screens with a pixel pitch of 10–12 mm. Pixel pitch refers to the physical distance between LED diode clusters. Discrete LEDs were also able to produce high brightness levels for outdoor displays to compete with daylight. The brightness of LED is measured in nits (a measurement of direct light) versus lumens (a measurement of reflected light). Outdoor panels can be rated up to 10,000 nits, while indoor panels are around 1200 nits.
Photon-Counting Detectors for X-ray Imaging
Published in Paolo Russo, Handbook of X-ray Imaging, 2017
The XPAD3 chip represented a major redesign, abandoning the obsolete AMS-0.8 μm CMOS process in favor of the more modern IBM-0.25 μm. The pixel pitch was smaller than the one used in its predecessors (130 μm over a pixel matrix of 120 × 80), to provide higher spatial resolution (Pangaud et al. 2008). Two versions were designed: one that could accept positive carriers (XPAD-S), from Si or GaAs for example, and another for electron collection (XPAD3-C). The energy range at which those two chips work is also different: from 5 up to 25 keV for XPAD3-S, and across a 60 keV window for XPAD3-C (Berar et al. 2009), with the lower limit being set by the electronics noise (<140 e−) and the higher limit set by the absorption efficiency of the sensor. For example, for a 500 μm thick Si sensor, the thickness chosen for XPAD3-S, the detection efficiency at 25 keV, is only 25%. The input charge is amplified by a sensitive preamplifier and, subsequently, integrated in an operational transconductance amplifier (OTA) that converts the voltage into a current, which is then passed to the current mode discriminator.
Three-dimensional display systems
Published in John P. Dakin, Robert G. W. Brown, Handbook of Optoelectronics, 2017
Typically, the pixel pitch i is set by the choice of two-dimensional display and the minimum focal length, f, determined in large part by the substrate thickness on the front of the display. The viewing distance can again be derived from similar triangles:if=ez−f
The off-axis moiré effect in double-layered cylinder
Published in Journal of Modern Optics, 2023
The display size was 28 inch x 16.6 inch (71 cm x 42 cm), the pixel pitch 0.18 mm. During the experiments, the grating with the period of 5 or 6 pixels (i.e. 0.91 or 1.08 mm) was continually shown. The printed gratings had a period of 1 mm. The moiré effect in the monitor was observed in areas, where the printed grating was overlapped with the displayed grating.