{"id":317,"date":"2015-08-25T14:35:00","date_gmt":"2015-08-25T14:35:00","guid":{"rendered":"http:\/\/machineryequipmentonline.com\/video-equipment\/uncategorized\/video-disc-technologyfields-tracks-and-modulation\/"},"modified":"2015-08-25T14:35:00","modified_gmt":"2015-08-25T14:35:00","slug":"video-disc-technologyfields-tracks-and-modulation","status":"publish","type":"post","link":"http:\/\/machineryequipmentonline.com\/video-equipment\/video-disc-technologyfields-tracks-and-modulation\/","title":{"rendered":"VIDEO DISC TECHNOLOGY:FIELDS, TRACKS AND MODULATION."},"content":{"rendered":"<div class=\"rbrii6a0dc930b155b\" ><script type=\"text\/javascript\">\n\tatOptions = {\n\t\t'key' : '61e5902552e2353963d8d2f1bd1f4a8f',\n\t\t'format' : 'iframe',\n\t\t'height' : 250,\n\t\t'width' : 300,\n\t\t'params' : {}\n\t};\n<\/script>\n<script type=\"text\/javascript\" src=\"\/\/www.highperformanceformat.com\/61e5902552e2353963d8d2f1bd1f4a8f\/invoke.js\"><\/script><\/div><style type=\"text\/css\">\r\n@media screen and (min-width: 1201px) {\r\n.rbrii6a0dc930b155b {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 993px) and (max-width: 1200px) {\r\n.rbrii6a0dc930b155b {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 769px) and (max-width: 992px) {\r\n.rbrii6a0dc930b155b {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 768px) and (max-width: 768px) {\r\n.rbrii6a0dc930b155b {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (max-width: 767px) {\r\n.rbrii6a0dc930b155b {\r\ndisplay: block;\r\n}\r\n}\r\n<\/style>\r\n<h3 align=\"justify\">FIELDS, TRACKS AND MODULATION<\/h3>\n<p align=\"justify\">There are two ways of arranging the television \ufb01elds on the surface of the disc, both illustrated in Fig. 20.1. At (a) is depicted the \u2018active\u2019 disc in which each TV \ufb01eld occupies one half of the disc\u2019s rotation, with all the \ufb01eld sync pulses lined up across a diameter of the disc. These play at a constant speed of 1500 r.p.m. and have the advantage of excellent trick-speed replay: the pick-up is \u2018skipped\u2019 sideways during the \ufb01eld blanking interval for still-frame or special-speed playback. This disc is a CAV (Constant Angular Velocity) type, and since the track-length for 1 \ufb01eld of 312^ lines varies greatly from the middle to the outside of the disc the pit-density is great at the beginning of play, but sparse at the end. CAV discs have 36 minutes\u2019 playing time per side.  <\/p>\n<p align=\"justify\">The alternative arrangement is the CLV (Constant Linear Velocity) disc shown at Fig. 20.1(b). Here the pit-density along the tracks is constant so that each TV \ufb01eld has the same track length. At replay start (disc centre) 2 \ufb01elds are read out per rev at 1500 r.p.m. As playback continues the disc slows down to maintain constant track- scanning speed until at the outer edge the pick-up is reading six fields  <\/p>\n<p align=\"justify\"><a href=\"http:\/\/lh3.googleusercontent.com\/-nbOqMVBmbCo\/Vdx9D6KSwUI\/AAAAAAAB1jI\/Oy00JE72CwQ\/s1600-h\/DIGITAL-CAMCORDERS-AND-VCRS-02402.jpg\"><img decoding=\"async\" loading=\"lazy\" style=\"background-image: none; border-right-width: 0px; margin: 0px auto; padding-left: 0px; padding-right: 0px; display: block; float: none; border-top-width: 0px; border-bottom-width: 0px; border-left-width: 0px; padding-top: 0px\" title=\"DIGITAL CAMCORDERS AND VCRS-0240\" border=\"0\" alt=\"DIGITAL CAMCORDERS AND VCRS-0240\" src=\"http:\/\/lh3.googleusercontent.com\/-STdpGnRoBQM\/Vdx9HNJPsYI\/AAAAAAAB1jQ\/AiE2uXLG274\/DIGITAL-CAMCORDERS-AND-VCRS-0240_thu.jpg?imgmax=800\" width=\"158\" height=\"244\" \/><\/a>  <\/p><div class=\"tdnsk6a0dc930b171a\" ><script async src=\"https:\/\/pagead2.googlesyndication.com\/pagead\/js\/adsbygoogle.js?client=ca-pub-0778475562755157\"\n     crossorigin=\"anonymous\"><\/script>\n<!-- 300x600 television-and-video -->\n<ins class=\"adsbygoogle\"\n     style=\"display:inline-block;width:300px;height:600px\"\n     data-ad-client=\"ca-pub-0778475562755157\"\n     data-ad-slot=\"6549443290\"><\/ins>\n<script>\n     (adsbygoogle = window.adsbygoogle || []).push({});\n<\/script><\/div><style type=\"text\/css\">\r\n@media screen and (min-width: 1201px) {\r\n.tdnsk6a0dc930b171a {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 993px) and (max-width: 1200px) {\r\n.tdnsk6a0dc930b171a {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 769px) and (max-width: 992px) {\r\n.tdnsk6a0dc930b171a {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 768px) and (max-width: 768px) {\r\n.tdnsk6a0dc930b171a {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (max-width: 767px) {\r\n.tdnsk6a0dc930b171a {\r\ndisplay: block;\r\n}\r\n}\r\n<\/style>\r\n<div class=\"pyhfp6a0dc930b164c\" ><script type=\"text\/javascript\">\n\tatOptions = {\n\t\t'key' : '0c1eb4c533eaedb7b996f49a5a4983a9',\n\t\t'format' : 'iframe',\n\t\t'height' : 300,\n\t\t'width' : 160,\n\t\t'params' : {}\n\t};\n<\/script>\n<script type=\"text\/javascript\" src=\"\/\/www.highperformanceformat.com\/0c1eb4c533eaedb7b996f49a5a4983a9\/invoke.js\"><\/script><\/div><style type=\"text\/css\">\r\n@media screen and (min-width: 1201px) {\r\n.pyhfp6a0dc930b164c {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 993px) and (max-width: 1200px) {\r\n.pyhfp6a0dc930b164c {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 769px) and (max-width: 992px) {\r\n.pyhfp6a0dc930b164c {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 768px) and (max-width: 768px) {\r\n.pyhfp6a0dc930b164c {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (max-width: 767px) {\r\n.pyhfp6a0dc930b164c {\r\ndisplay: block;\r\n}\r\n}\r\n<\/style>\r\n\n<p align=\"justify\">per rev at about 550 r.p.m. This disc is capable of 54 minutes playing time per side, but no trick-replay is possible.  <\/p>\n<p align=\"justify\">The pit-track pattern is shown in Fig. 20.1(c). The track pitch is 1.6 micron, the pit width is 0.4 micron and pit depth 0.1 micron. The surface of the disc is scanned by a very \ufb01ne (0.9 micron) spot of light from a laser, and the information is read out by a photodiode which discriminates between the re\ufb02ected light level during the presence or absence of a pit. In the absence of a pit most of the light is re\ufb02ected onto the pick-up diode which passes high current; when a pit is present most of the light is scattered and little returns to the photo- diode, whose current is now low as a result. The diode output contains all the video, colour and sound information.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>FIELDS, TRACKS AND MODULATION There are two ways of arranging the television \ufb01elds on the surface of the disc, both illustrated in Fig. 20.1. At (a) is depicted the \u2018active\u2019 disc in which each TV \ufb01eld occupies one half of the disc\u2019s rotation, with all the \ufb01eld sync pulses lined up across a diameter of [&hellip;]<br \/><a href=\"http:\/\/machineryequipmentonline.com\/video-equipment\/video-disc-technologyfields-tracks-and-modulation\/\" class=\"more-link\" >Continue reading&#8230;<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"aioseo_notices":[],"views":708,"_links":{"self":[{"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/posts\/317"}],"collection":[{"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/comments?post=317"}],"version-history":[{"count":0,"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/posts\/317\/revisions"}],"wp:attachment":[{"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/media?parent=317"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/categories?post=317"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/tags?post=317"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}