<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Dear Daniel,<div class=""><br class=""></div><div class="">Shouldn’t it be in the range of some cm’s as it projects the screen in front of the eyes to far away/infinity? I thought a simple test for focal distance measurement is to project something with it that is far away, e.g. a lamp on a high ceiling or a window. The distance between the lens and the projection plane (e.g. table with white paper) is the focal distance. </div><div class=""><br class=""></div><div class="">I hope I am right and did not make an optical fool of myself in front of the vision list community ;)</div><div class=""><br class=""></div><div class="">Maarten Wijntjes</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><div><br class=""><blockquote type="cite" class=""><div class="">On 11 Oct 2021, at 13:50, Oberfeld-Twistel, Daniel <<a href="mailto:oberfeld@uni-mainz.de" class="">oberfeld@uni-mainz.de</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><meta charset="UTF-8" class=""><div class="WordSection1" style="page: WordSection1; caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><font size="2" face="Calibri" class=""><span style="font-size: 11pt;" class="">Dear list,<o:p class=""></o:p></span></font></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><font size="2" face="Calibri" class=""><span style="font-size: 11pt;" class=""><o:p class=""> </o:p></span></font></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><font size="2" face="Calibri" class=""><span lang="EN-US" style="font-size: 11pt;" class="">we’d like to determine the focal distance in the HTC Vive Pro headset, in order to use exactly this distance for tests of visual acuity before the actual VR experiment. An internet search produced a variation of estimates, ranging from 0.75 m to 2 m or even infinity. So we are wondering if someone here made optical measurements of the Fresnel lenses inside the Vive, to determine the effective focal distance of the display.<o:p class=""></o:p></span></font></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><font size="2" face="Calibri" class=""><span lang="EN-US" style="font-size: 11pt;" class=""><o:p class=""> </o:p></span></font></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><font size="2" face="Calibri" class=""><span style="font-size: 11pt;" class="">Best<o:p class=""></o:p></span></font></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><font size="2" face="Calibri" class=""><span style="font-size: 11pt;" class=""> <o:p class=""></o:p></span></font></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><font size="2" face="Calibri" class=""><span style="font-size: 11pt;" class="">Daniel<o:p class=""></o:p></span></font></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><font size="2" face="Calibri" class=""><span style="font-size: 11pt;" class=""> <o:p class=""></o:p></span></font></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><font size="2" face="Calibri" class=""><span style="font-size: 11pt;" class="">---------------------------------<o:p class=""></o:p></span></font></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><font size="2" face="Calibri" class=""><span style="font-size: 11pt;" class="">Prof. Dr. Daniel Oberfeld-Twistel<o:p class=""></o:p></span></font></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><font size="2" face="Calibri" class=""><span style="font-size: 11pt;" class="">Johannes Gutenberg - Universitaet Mainz, Experimental Psychology &<o:p class=""></o:p></span></font></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><font size="2" face="Calibri" class=""><span lang="FR" style="font-size: 11pt;" class="">Laboratoire ICube UMR7357 Université de Strasbourg<o:p class=""></o:p></span></font></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><font size="2" face="Calibri" class=""><span style="font-size: 11pt;" class="">Wallstrasse 3<o:p class=""></o:p></span></font></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><font size="2" face="Calibri" class=""><span style="font-size: 11pt;" class="">55122 Mainz<o:p class=""></o:p></span></font></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><font size="2" face="Calibri" class=""><span style="font-size: 11pt;" class="">Germany<o:p class=""></o:p></span></font></div><div style="margin: 0cm; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><font size="2" face="Calibri" class=""><span style="font-size: 11pt;" class=""><o:p class=""> </o:p></span></font></div></div><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; 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