外文翻譯---電視信號-展示頁
2025-05-27 09:02本頁面
【正文】 wo 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), depending on the particular device used. When a row of wells is read from the CCD, the resulting line of video is filtered into a smooth analog signal, such as in Figure . In other words, the video signal does not depend on how many columns are present in the CCD. The resolution in the horizontal direction is limited by how rapidly the analog signal is allowed to change. This is usually set at MHz for color television, resulting in a rise time of about 100 nanoseconds, , about 1/500th of the microsecond video line. When the video signal is digitized in the frame grabber, it is converted back into columns, However, these columns in the digitized image have no relation to the columns in the CCD. The number of columns in the digital image depends solely on how many times the frame grabber samples each line of video. For example, a CCD might have 800 wells per row, while the digitized image might only have 512 pixels ( , columns) per row. The number of columns in the digitized image is also important for another reason. The standard television image has an aspect ratio
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