Why Progressive Scan?

Quite simply, progressive scan means that the picture information is accumulated simultaneously and then output line-by-line or sequentially. The result is a non-interlace image with full vertical and horizontal resolution captured in a single rapid shutter event.

Traditional interlace CCD cameras are only capable of capturing one field, or half the vertical information, per shutter event because the scan function breaks the integration period into two sequential field scans. In dynamic image capture, by the time the second field of information is stored and scanned the subject already has moved. The result is a ghosting or blurring effect once the two scan periods are combined to create the whole, interlaced picture. Interlaced images of even static objects can introduce some noticeable "jitter". This is successfully eliminated with progressive scanning.

Full frame Electronic Shuttering

Images are electronically "shuttered" by scanning out just a portion of the total charge that has accumulated over one integration period. Specific shutter speeds are selected by varying the portion of the charge retained. Although interlace CCD cameras can and do employ electronic shuttering, only 50% of the vertical resolution, or half of a frame, is achieved per shutter event.

Cameras utilizing interline-transfer type progressive scan CCDs, such as the PULNiX cameras, are optimal for dynamic imaging. Frame-transfer type progressive scan cameras still require a mechanical shutter or strobe. Eliminating strobes or mechanical shutters can be extremely critical in applications such as airborne imaging. Electronic shuttering also permits very rugged cameras. With no moving (mechanical) parts, they are shock and vibration resistant, perfect for applications such as remotely piloted vehicles, high speed on-line inspection, and intelligent transportation systems.

"Non-TV" Format

Progressive scan cameras free users from the constraints of traditional television scanning systems, permitting full vertical frame electronic shuttering at very high resolutions. Normal TV scanning systems are not applicable in the 1024 x 1024 and higher pixel formats. In comparison to the 4:3 ratio format typical of TV format imagers, the square or nearly square pixel and aspect ratios characteristic of many non-TV format progressive scan imagers permit consistent dimensional analysis of an object despite its orientation to the camera. Most industrial and scientific imaging applications also use high speed PC-based image capture boards and VGA displays, therefore the restrictions of standard TV format outputs are not a concern.