Learn how industrial cameras scan

A machine vision system consists of three main parts: an industrial camera, a frame grabber, and a computer (or image processor) that stores and analyzes images to extract information. Image processors and frame grabbers are relatively easy electronic devices to choose, and their main parameters are storage capacity and processing speed. Industrial cameras are one of the most complex parts of these systems. Modern industrial analog and digital cameras use charge-coupled devices (CCDs) or complementary metal-oxide-semiconductor (CMOS) chips to capture images and generate electronic signals to send to a computer for processing.

Industrial cameras can be divided into interlaced industrial cameras and progressive scan industrial cameras according to the scanning method.

Most of these displays and industrial cameras are interlaced, but in reality it still looks like a smooth image to the human eye, and industrial cameras generally acquire odd lines of the image first, even lines after 1/50 of a second for CCIR standards, and even lines after 1/60 of a second for EIA standards. The vast majority of industrial cameras are spaced shift, i.e., interlaced, and when used to photograph moving objects, a comb effect occurs. To eliminate this effect, only half of the image can be captured (using only odd or even lines), and if full resolution is required, a progressive scan industrial camera must be utilized.

In machine vision system application, objects are typically move very fast. When an interlaced industrial camera is used, the object may move between two fields, resulting in a blurred image, like two exposures or a comb effect at vertical edges.To address this effect, the interlaced industrial camera can be set to scan only one field, so that the vertical resolution will be halved and the frame acquisition rate will be doubled. This operation of the industrial camera is called field mode, or non-interlaced output, and is useful for many machine vision system applications. Field mode can also provide the benefit of doubling sensitivity, which is obtained by vertical pixel BINNING (pixel BINNING is a special readout mode of CCD sensor, the sensor binds two or more pixels together and sums the charge accumulated from multiple pixels). Field mode can improve frame speed, sensitivity and signal-to-noise ratio, but can reduce resolution. In applications requiring full vertical resolution of fast moving objects, progressive scanning industrial cameras should be used.