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Angle of View
The scene angle that a video camera lens can show on the monitor, like Diagonal Angle, Horizontal Angle and Venrtical Angle, usually described in degree.
Focal Length(FL)is the ditance from the center of a lens to the focal point(CCD sensor chip).FL, as well as the CCD chip’s format, is the major factor to determine the angle of view of the a lens. For example, a 6.0mm FL lense on 1/3” sensor format has 56.8 degree of digonal angle of view and a 5.0mm FL lens on 1/3” sensor format has 66.9 degree. But, the same 6.0mm FL lens can see 75.5 degree on 1/2” sensor format. The angle of view varies a little depending on the manufacturer of the lens.
For 1/3” CCD chip camera, the following formula is a simple way to determine the focal length of a lens needed.(Distance to subject/ Width of subject) x 4.5mm=Focal length.For example, if you want to watch a subject of 5.5ft width at 10ft distance with a 1/3” CCD camera, you will need a 8.0mm FL lens. That is 10ft/5.5ft x 4.5mm=8.18mm. A 8.0mm FL lens mounted on 1/3” CCD camera will cover the subject you want to watch.
Direct Current Power, can be derived from an AC adapter or from a battery. Among DC voltages of 6,9,12,24,and 28, 12VDC is most common in the backup camera industry.
Most board cameras, mini cameras and about one third of the orofessional cameras work with 12V DC, 100mA to 200mA for B/W cameras and 150mA to 300mA for color ones. These cameras usually have DC jacks to accept DC power plugs. You should be careful about the polarity(positive and negative) for this power source. 12VDC power can be supplied with AC Adapter or battery pack. You may veven use a ”power cord” plugged to the cigarette lighter in a car.
Invisible light beyond the 750 nanometers(red end of the visible lights).
CCD(charge coupled device) consists of several hundred thousand individual picture elements(pixels) on a tiny 1/2”,1/3”, or 1/4” chip. Each pixel responds to light falling on it by storing a tiny charge of electricity. The pixel are arranged on a precise grid, with vertical and horizontal transfer registers carrying the signals to the camera’s video processing circuitry. This transfer of signals occurs sixty times per second. The 1/3” CCD chip is the most widely used sensor format these days; its size is 5.5mm(diagonal),4.4mm(horizontal) and 3.3mm(vertical). The 1/4” sensor format, recently being used in color cameras, is 4mm(diagonal), 3.2mm(horizontal) and 2.4mm(vertical).
CMOS (Complementary-Metal Oxide Semiconductor) chip, also a video image sensor.CMOS chips use transistors at each pixel to move the charge through traditional wires. This offers flexibility because each pixel is treated individually.Nowadays,CMOS chips also produce great video image and widely applied with camera industry.
The Radio Corporation of America; conveniently used to describe phono jack and plug, one of the audio/ video connectors.
TVL is defined as the maximum number of alternating light and dark vertical lines that can be resolved per picture height.A resolution of 400 TVL means that 200 distinct dark vertical lines and 200 distinct white vertical lines can be counted over a horizontal span equal to the height of the picture.The higher the number, the better the image quality.
PAL is a color television system, which is used in Europe, Australia, part of Africa and the Middle East. It has 625 horizontal scan lines and 25 frames per second. (Frame: A whole video image; is composed of two interlaced fields. A CCD chip produces 30 frames per second at NTSC system and 25 frames at PAL.)
NTSC formulates standards for American color system. NTSC system has 525 horizontal scan lines and 30 frames per second.