SVSi | Scientific Vision Systems

Scientific Vision Systems (SVSi) is the leading supplier of scientific professional medical imaging equipment including medical printers, medical cameras, medical display monitors, & medical recorders for Endoscopy & Ultrasound, from top brand names as Sony, Hitachi, Panasonic, Tatung, Mitsubishi, National Displays, Double Black Imaging, and hard to find items. Also featuring the most complete glossary of medical digital imaging video electronic terms.

F Stop, F Number: Calibrated measure of lens iris aperture. Common F stops are F1.4, F2, F2.8, F4, F5.6, F8, F11, F16, F22. The higher the number, the smaller the iris aperture and the less light falling on the imager.

Field: Half of a TV picture consisting of only the odd or only the even lines. NTSC/EIA features 60 fields of 262.5 lines/second. PAL/CCIR features 50 fields of 312.5 lines/second. Odd/even field pairs recombine on screen as frames due to picture tube and human eye memory.

Field/frame integration: Two different pixel readout techniques in CCDs designed for interlaced output. Refers to the total integration time, field duration (16.6 ms NTSC/EIA or 20 ms PAL/CCIR) or frame duration (33.3 ms NTSC/EIA or 40 ms PAL/CCIR). Both modes give the same sensitivity.

Focal length: Distance between the optical center of a lens and the image focal point. Fixes the magnification and the angle of view of a lens. Vari-focal and zoom lenses have a variable focal length.

Frame: One complete TV picture consisting of two sequential interlaced scanned fields. NTSC/EIA has 30 frames and 525 lines per second. PAL/CCIR has 25 frames of 625 lines per second.