機(jī)械數(shù)控專業(yè)--外文資料及翻譯-數(shù)控設(shè)計(jì)(已修改)
2025-02-04 06:10 本頁(yè)面
【正文】 外文資料及譯文 原文： Television Video Signals Although over 50 years old , the standard television signal is still one of the most mon way to transmit an image. Figure shows how the television signal appears on an oscilloscope. This is called posite video, meaning that there are vertical and horizontal synchronization (sync) pulses mixed with the actual picture information. These pulses are used in the television receiver to synchronize the vertical and horizontal deflection circuits to match the video being displayed. Each second of standard video contains 30 plete images, monly called frames , A video engineer would say that each frame contains 525 lines, the television jargon for what programmers call rows. This number is a little deceptive because only 480 to 486 of these lines contain video information。 the remaining 39to 45 lines are reserved for sync pulses to keep the television’s circuits synchronized with the video signal. Standard television uses an interlaced format to reduce flicker in the displayed image. This means that all the odd lines of each frame are transmitted first, followed by the even lines. The group of odd lines is called the odd field, and the group of even lines is called the even field. Since each frame consists of two fields, the video signal transmits 60 fields per second. Each field starts with a plex series of vertical sync pulses lasting milliseconds. This is followed by either the even or odd lines of video. Each line lasts for microseconds, including a microsecond horizontal sync pulse, separating one line from the next. Within each line, the analog voltage corresponds to the gray
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