Interlace monitor and progressive monitor concepts

Interlaced and progressive mainly refer to the scanning method of the monitor picture tube. The image of the monitor is a two-dimensional image, and its reproduction process is to convert the two-dimensional input image into a one-bit pixel string. The horizontal scanning process is used to achieve a uniform movement of the picture from the left to the right; vertical scanning will be horizontal The scanning line moves from the vertical direction at a uniform speed. Interlaced scanning refers to dividing an image into two fields for scanning. The first field (odd field) scans odd lines such as 1, 3, 5 and the second field (even field) scans even lines such as 2, 4, 6 etc. Together to form a complete image (ie a frame). Therefore, for the PAL system, scanning 50 fields per second, the field frequency is 50HZ, and the frame frequency is 25HZ; for NTSC, the field frequency is 60HZ, and the frame frequency is 30HZ, although the screen is reproduced in human vision It is a continuous image, but even-numbered field switching will cause screen flicker and obvious line spacing lines due to odd-numbered occasions.

Progressive scanning refers to the way in which the scanning lines are scanned line by line in order. Interlace monitors have the disadvantages of poor image quality, low resolution, large noise and severe image flicker. Progressive scan monitors are designed to eliminate the defects of interlaced scanning, convert analog video signals to digital signals, use digital color decoding, and use digital signal storage and control technology to realize the repeated use of one or one field of signal (i.e. low-speed reading, High-speed readout) 50HZ progressive scan mode, or increase the frame rate to achieve 60HZ, 75HZ and even 85HZ progressive scan mode. Progressive scan technology, because the input signal is converted into a digital video signal by A / D conversion and then processed by digital decoding and digital image processing circuits, the channel bandwidth is greatly improved (up to 10MHZ-20MHZ) The noise is greatly reduced, and the line-by-line display eliminates line spacing and inter-line flicker, while the increase in frame rate (such as 60HZ-85HZ) reduces or eliminates large area image flicker. Therefore, once the line-by-line monitor came out, it was very popular with users. Of course, since the progressive monitor uses one line or one field for repeated use, the line frequency is doubled compared to interlace, from 15625HZ to 31250HZ, and the 75Hz progressive line frequency is 46875Hz. After the line frequency is increased, the stability and reliability of the line output stage will be severely tested. The design and manufacturing costs of the whole machine are greatly increased, so the price of the whole machine is also higher.