外文翻譯---電視信號(存儲版)
【正文】 roup 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 scale of the image, with brighter values being in the direction away from the sync pulses. This place the sync beyond the black range. In video jargon, the sync pulses are said to be blacker than black.. The hardware used for analogtodigital conversion of video signals is called a frame grabber. This is usually in the form of an electronics card that plugs into a puter, and connects to a camera through a coaxial cable. Upon mand from software, the frame grabber waits for the beginning of the next frame, as indicated by the vertical sync pulses. During the following two fields,each line of video is sampled many times, typically 512,640 or 720 samples per line, at 8bits per sample. These samples are stored in memory as one row of the digital image. This way of acquiring a digital image results in an important difference between the vertical and horizontal directions. Each row in the digital image corresponds to one line in the video signal, and therefore to one row of wells in the CCD. Unfortunately, the columns are not so straightforward. In the CCD, each row contains between about 400 and 800 wells (columns)
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