Interlaced vs. Progressive Scanning of Industrial Camera
Industrial camera can be divided into interlaced scanning industrial cameras and progressive scanning industrial camera according to scanning mode.
Most displays and industrial cameras adopt the interlaced scanning, but it actually looks like a smooth image in human eyes. Industrial cameras usually get odd rows of images first, for CCIR standard, industrial cameras get the even rows after 1/50 seconds, but for EIA standard, the industrial cameras get the even rows after 1/60 seconds.
Most industrial cameras are interval transfer, namely interlaced scanning. When they are used for shooting moving objects, comb effect occurs. To eliminate this effect, half image can be collected (only odd rows or even rows). If a full resolution is required, the progressive scanning industrial camera shall be adopted.
Objects usually move very fast in the application of machine vision system. When using an interlaced scanning industrial camera, objects may move in two fields, as the result, a fuzzy image is produced, just like two exposure or a comb effect at the vertical edge. To solve this problem, the interlaced scanning industrial camera can be set for scanning only one field, so the vertical resolution will be reduced by half while the frame acquisition rate will be doubled. Such an operation of industrial cameras is called field mode, or non interlaced output, it’s quite useful for many machine vision system applications.
Field mode can also double the sensitivity, providing by the vertical pixel BINNING (pixel BINNING refers to a special readout mode of CCD sensor, the sensor binds 2 or more pixels together and lock, sum up charges accumulated from multiple pixels). Field mode can improve frame speed, sensitivity and signal-to-noise ratio, but it would reduce the resolution. Progressive scanning industrial camera shall be applied applications requiring full vertical resolution of fast moving objects.