<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div>Deborah,</div><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div apple-content-edited="true" class=""><div class="" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div class=""><br class=""></div><div class="">Below is a section of a displays standards document that Louis Silverstein and I wrote about LED displays.</div><div class="">I hope it is helpful.</div><div class=""><br class=""></div><div class="">OLED displays may well be useful in psychophysics, though I have not tried them yet myself.</div><div class="">I believe they are used in some off-the-shelf adaptive optics systems from Imagine Eyes (<a href="http://www.imagine-eyes.com/">http://www.imagine-eyes.com/</a>).</div><div class=""><br class=""></div><div class="">Andrew B. Watson</div><div class="">Senior Scientist for Vision Research</div><div class="">NASA Ames Research Center</div><div class="">Moffett Field, CA 94035-1000</div><div class="">(650) 604-5419</div><div class=""><br class=""></div></div></div><br class=""><div class=""><h4><span style="font-family: 'Trebuchet MS'; "><span>1.1.1.1<span style="font: normal normal normal 7pt/normal 'Times New Roman'; "> </span></span></span>Light-Emitting Diodes (LEDs) and Organic Light-Emitting Diodes (OLEDs)<o:p></o:p></h4><p align="" class="hidhbody">The LED is a semiconductor device consisting of a single p-n junction;<span> </span>light is emitted when the junction is forward biased by the application of a suitable voltage. The first commercially available LEDs were introduced into the marketplace in 1968 and quickly became an important technology for indicator lamps and small segmented alphanumeric displays.<span> </span><o:p></o:p></p><p align="" class="hidhbody"><span> </span>LEDs are now capable of producing a full spectrum of colors with very high color saturation and good luminous efficiency.<span> </span>Nevertheless, relatively high cost, interconnect complexity and manufacturing limitations in building high-density arrays of full-color LEDs have restricted their usage primarily to very large displays for digital signage and electronic billboard applications.<span> </span><o:p></o:p></p><p align="" class="hidhbody">Organic LEDs (OLEDs) and polymer LEDs (PLEDs) are LEDs whose emissive electroluminescent layer consists of a film of organic compounds (Bulovic, 2005; King, 1994).<span> </span>These films emit light when subjected to an electric current. The SPD of the emitted light depends on the type of organic molecule in the emissive layer.<span> </span>Full-color OLEDs are generally achieved by either spatial patterning of R, G and B emissive materials or by use of a broad-band emissive material in conjunction with a spatial pattern of R, G, and B color selection filters.<span> </span>The intensity of the emitted light depends on the amount of electrical current applied.<span> </span>The nonlinear relationship between voltage and current provides OLEDs with a nonlinear transfer function which is well characterized by a power function.<o:p></o:p></p><p align="" class="hidhbody"><span> </span>Claimed advantages for OLEDs include:<span> </span>simplified manufacturing structure; compatibility with flexible substrates; lower manufacturing costs than LCDs or PDPs; high contrast with true black level; high luminance with good luminous efficiency; low power consumption; fast temporal response; wide viewing angle; and excellent grayscale performance (Bulovic, 2005; Ghosh & Hack, 2004).<span> </span>The principal disadvantages include limited lifetime of OLED and PLED emissive materials, lack of a stable short-wavelength emissive material with good lifetime, differential aging of emissive materials with different SPDs and susceptibility to contamination and damage from moisture.<span> </span>In addition, reflections from metal cathodes and other metallic structures within these devices can result in high levels of internal specular reflection under ambient illumination with commensurate degradations of ambient contrast.<span> </span>Circular polarizers may be used to mitigate these reflections, but their use dramatically reduces the luminous efficiency of the display.<o:p></o:p></p><p align="" class="hidhbody">OLED and PLED display technologies remain in a very active state of development with a great deal of ongoing research on OLED / PLED materials, display system architectures and manufacturing processes. <span> </span>To date only a few small, mobile display products using OLEDs and PLEDs have appeared and stayed on the market.<span> </span><o:p></o:p></p><p align="" class="MsoNormal"><o:p> </o:p></p><table class="MsoNormalTable" border="1" cellspacing="0" cellpadding="0" style="border-collapse: collapse; border-top-style: none; border-right-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; "><tbody><tr><td width="137" valign="top" style="width: 136.65pt; border-top-style: solid; border-right-style: solid; border-bottom-style: solid; border-top-color: black; border-right-color: black; border-bottom-color: black; border-top-width: 1pt; border-right-width: 1pt; border-bottom-width: 1pt; border-left-style: solid; border-left-color: black; border-left-width: 1.5pt; background-image: initial; background-repeat: initial; background-attachment: initial; -webkit-background-clip: initial; -webkit-background-origin: initial; background-color: rgb(254, 254, 187); padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; background-position: initial initial; "><p align="" class="hidhtable">Display Technology Attributes<o:p></o:p></p></td><td width="83" valign="top" style="width: 82.85pt; border-top-style: solid; border-right-style: solid; border-bottom-style: solid; border-top-color: black; border-right-color: black; border-bottom-color: black; border-top-width: 1pt; border-right-width: 1pt; border-bottom-width: 1pt; border-left-style: none; border-left-width: initial; border-left-color: initial; background-image: initial; background-repeat: initial; background-attachment: initial; -webkit-background-clip: initial; -webkit-background-origin: initial; background-color: rgb(254, 254, 187); padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; background-position: initial initial; "><p align="" class="hidhtable">General Rating<o:p></o:p></p></td><td width="259" valign="top" style="width: 259.3pt; border-top-style: solid; border-top-color: black; border-top-width: 1pt; border-left-style: none; border-left-width: initial; border-left-color: initial; border-bottom-style: solid; border-bottom-color: black; border-bottom-width: 1pt; border-right-style: solid; border-right-color: black; border-right-width: 1.5pt; background-image: initial; background-repeat: initial; background-attachment: initial; -webkit-background-clip: initial; -webkit-background-origin: initial; background-color: rgb(254, 254, 187); padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; background-position: initial initial; "><p align="" class="hidhtable">Comments<o:p></o:p></p></td></tr><tr><td width="137" valign="top" style="width: 136.65pt; border-top-style: none; border-top-width: initial; border-top-color: initial; border-left-style: solid; border-left-color: black; border-left-width: 1.5pt; border-bottom-style: none; border-bottom-width: initial; border-bottom-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">Spatial Addressability<o:p></o:p></p><p align="" class="hidhtable">Spatial Resolution<o:p></o:p></p></td><td width="83" valign="top" style="width: 82.85pt; border-top-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">High<o:p></o:p></p><p align="" class="hidhtable">High<o:p></o:p></p></td><td width="259" valign="top" style="width: 259.3pt; border-top-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1.5pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">-Spatial resolution can be enhanced by vertically stacked color pixel structure<o:p></o:p></p></td></tr><tr><td width="137" valign="top" style="width: 136.65pt; border-top-style: none; border-top-width: initial; border-top-color: initial; border-left-style: solid; border-left-color: black; border-left-width: 1.5pt; border-bottom-style: none; border-bottom-width: initial; border-bottom-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">Temporal Response<o:p></o:p></p></td><td width="83" valign="top" style="width: 82.85pt; border-top-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">Medium to High<o:p></o:p></p></td><td width="259" valign="top" style="width: 259.3pt; border-top-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1.5pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">-Native response in sub-millisecond range<o:p></o:p></p><p align="" class="hidhtable">-Temporal aperture extended by sample-and-hold mode of operation in active-matrix configurations<o:p></o:p></p></td></tr><tr><td width="137" valign="top" style="width: 136.65pt; border-top-style: none; border-top-width: initial; border-top-color: initial; border-left-style: solid; border-left-color: black; border-left-width: 1.5pt; border-bottom-style: none; border-bottom-width: initial; border-bottom-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">Luminance<o:p></o:p></p></td><td width="83" valign="top" style="width: 82.85pt; border-top-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">Medium to High<o:p></o:p></p><p align="" class="hidhtable"><o:p> </o:p></p></td><td width="259" valign="top" style="width: 259.3pt; border-top-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1.5pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">-Material dependent<o:p></o:p></p><p align="" class="hidhtable">-Use of circular polarizer to enhance ambient contrast reduces luminance<o:p></o:p></p></td></tr><tr><td width="137" valign="top" style="width: 136.65pt; border-top-style: none; border-top-width: initial; border-top-color: initial; border-left-style: solid; border-left-color: black; border-left-width: 1.5pt; border-bottom-style: none; border-bottom-width: initial; border-bottom-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">Contrast<o:p></o:p></p><p align="" class="hidhtable">Ambient Contrast<o:p></o:p></p></td><td width="83" valign="top" style="width: 82.85pt; border-top-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">High<o:p></o:p></p><p align="" class="hidhtable">Low to Medium<o:p></o:p></p></td><td width="259" valign="top" style="width: 259.3pt; border-top-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1.5pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">-Excellent black levels<o:p></o:p></p><p align="" class="hidhtable">-Specular reflectance from metal cathode limits ambient contrast<o:p></o:p></p><p align="" class="hidhtable">-Circular polarizer can be used to enhance ambient contrast<o:p></o:p></p></td></tr><tr><td width="137" valign="top" style="width: 136.65pt; border-top-style: none; border-top-width: initial; border-top-color: initial; border-left-style: solid; border-left-color: black; border-left-width: 1.5pt; border-bottom-style: none; border-bottom-width: initial; border-bottom-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">Grayscale Performance<o:p></o:p></p></td><td width="83" valign="top" style="width: 82.85pt; border-top-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">Very High<o:p></o:p></p></td><td width="259" valign="top" style="width: 259.3pt; border-top-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1.5pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">-Continuous analog grayscale capability<o:p></o:p></p><p align="" class="hidhtable">-transfer function a true power function<o:p></o:p></p></td></tr><tr><td width="137" valign="top" style="width: 136.65pt; border-top-style: none; border-top-width: initial; border-top-color: initial; border-left-style: solid; border-left-color: black; border-left-width: 1.5pt; border-bottom-style: none; border-bottom-width: initial; border-bottom-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">Viewing Angle<o:p></o:p></p></td><td width="83" valign="top" style="width: 82.85pt; border-top-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">Very High<o:p></o:p></p><p align="" class="hidhtable"><o:p> </o:p></p></td><td width="259" valign="top" style="width: 259.3pt; border-top-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1.5pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">-Effectively Lambertian viewing<o:p></o:p></p><p align="" class="hidhtable">-Contrast enhancement filters can attenuate luminance off axis<o:p></o:p></p></td></tr><tr><td width="137" valign="top" style="width: 136.65pt; border-top-style: none; border-top-width: initial; border-top-color: initial; border-left-style: solid; border-left-color: black; border-left-width: 1.5pt; border-bottom-style: none; border-bottom-width: initial; border-bottom-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">Color Gamut<o:p></o:p></p><p align="" class="hidhtable">Ambient Color Gamut<o:p></o:p></p></td><td width="83" valign="top" style="width: 82.85pt; border-top-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">High<o:p></o:p></p><p align="" class="hidhtable">Low to Medium<o:p></o:p></p></td><td width="259" valign="top" style="width: 259.3pt; border-top-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1.5pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">-Color gamut defined by OLED / PLED materials<o:p></o:p></p><p align="" class="hidhtable">-Specular reflections from metal cathode reduces color gamut under ambient<o:p></o:p></p><p align="" class="hidhtable">-Circular polarizer can be used to enhance ambient color gamut<o:p></o:p></p></td></tr><tr><td width="137" valign="top" style="width: 136.65pt; border-top-style: none; border-top-width: initial; border-top-color: initial; border-left-style: solid; border-left-color: black; border-left-width: 1.5pt; border-bottom-style: none; border-bottom-width: initial; border-bottom-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">Physical Package<o:p></o:p></p></td><td width="83" valign="top" style="width: 82.85pt; border-top-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">Very High<o:p></o:p></p></td><td width="259" valign="top" style="width: 259.3pt; border-top-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1.5pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">-Very small footprint & light weight<o:p></o:p></p><p align="" class="hidhtable">-Very small depth required<o:p></o:p></p></td></tr><tr><td width="137" valign="top" style="width: 136.65pt; border-top-style: none; border-top-width: initial; border-top-color: initial; border-left-style: solid; border-left-color: black; border-left-width: 1.5pt; border-bottom-style: none; border-bottom-width: initial; border-bottom-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">Application Flexibility<o:p></o:p></p></td><td width="83" valign="top" style="width: 82.85pt; border-top-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">Very high<o:p></o:p></p></td><td width="259" valign="top" style="width: 259.3pt; border-top-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-right-style: solid; border-right-color: black; border-right-width: 1.5pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; "><p align="" class="hidhtable">-Very amenable to portable or battery-powered applications<o:p></o:p></p><p align="" class="hidhtable">-Great flexibility in screen sizes<o:p></o:p></p></td></tr><tr style="height: 26.5pt; "><td width="137" valign="top" style="width: 136.65pt; border-top-style: none; border-top-width: initial; border-top-color: initial; border-left-style: solid; border-left-color: black; border-left-width: 1.5pt; border-bottom-style: solid; border-bottom-color: black; border-bottom-width: 1pt; border-right-style: solid; border-right-color: black; border-right-width: 1pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; height: 26.5pt; "><p align="" class="hidhtable">Other<o:p></o:p></p></td><td width="83" valign="top" style="width: 82.85pt; border-top-style: none; border-top-width: initial; border-top-color: initial; border-left-style: none; border-left-width: initial; border-left-color: initial; border-bottom-style: solid; border-bottom-color: black; border-bottom-width: 1pt; border-right-style: solid; border-right-color: black; border-right-width: 1pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; height: 26.5pt; "><p align="" class="hidhtable"><o:p> </o:p></p></td><td width="259" valign="top" style="width: 259.3pt; border-top-style: none; border-top-width: initial; border-top-color: initial; border-left-style: none; border-left-width: initial; border-left-color: initial; border-bottom-style: solid; border-bottom-color: black; border-bottom-width: 1pt; border-right-style: solid; border-right-color: black; border-right-width: 1.5pt; padding-top: 0in; padding-right: 5.4pt; padding-bottom: 0in; padding-left: 5.4pt; height: 26.5pt; "><p align="" class="hidhtable">-Prone to internal specular reflections under ambient<o:p></o:p></p><p align="" class="hidhtable">-Circular polarizer reduces luminance<o:p></o:p></p><p align="" class="hidhtable">-Differential aging of color materials can cause color shifts over time<o:p></o:p></p><p align="" class="hidhtable">-Active-matrix configurations prone to motion blur with dynamic imagery<o:p></o:p></p></td></tr></tbody></table><p align="" class="hidhcaption">Table <span>6</span>. OLED / PLED Technology Attribute Ratings and Comments</p></div></div><div><div>On Feb 18, 2009, at 5:36 PM, Deborah Apthorp wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div>Hi,<br><br>Does anyone know anything about the use of LED (NOT LCD) monitors for psychophysics? I am not sure if there are any available yet with a high enough refresh rate, but it seems as if potentially these could be very useful for vision research. I can't find much about them via Google so I wondered if anyone else in the vision community is exploring these possibilities.<br><br>Thanks,<br><br>Deborah Apthorp<br><br>(University of Sydney, Australia)<br>_______________________________________________<br>visionlist mailing list<br><a href="mailto:visionlist@visionscience.com">visionlist@visionscience.com</a><br>http://visionscience.com/mailman/listinfo/visionlist<br></div></blockquote></div><br></body></html>