Terms and Definitions

A

ActiveX - A set of technologies created by Microsoft that enables website technologies to interact with one another regardless of the language in which they were created. It is built on the Component Object Model (COM)

AGC - Automatic Gain Control. A circuit for automatically controlling amplifier gain in order to maintain a constant output voltage with a varying input voltage within a predetermined range of input-to-output variation.

Aperture - In television optics, it is the effective diameter of the lens that controls the amount of light reaching the photo-conductive or photo-emitting image pickup sensor.

Aperture Correction - Compensation for the loss in sharpness of detail because of the finite dimensions of the image elements or the dot-pitch of the monitor.

Aspect Ratio - The ratio of width to height for the frame of the televised picture. 4:3 for standard systems, 5:4 for 1K x 1K, and 16:9 for HDTV.

Attenuation - In general terms, a reduction in signal strength.

Auto Balance - A system for detecting errors in color balance in white and black areas of the picture and automatically adjusting the white and black levels of both the red and blue signals as needed for correction.

Automatic Brightness Control - In display devices, the self-acting mechanism which controls brightness of the device as a function of ambient light.

Automatic Gain Control - A process by which gain is automatically adjusted as a function of input or other specified parameter.

Automatic Iris Lens - A lens that automatically adjusts the amount of light reaching the imager.

Automatic Light Control - The process by which the illumination incident upon the face of a pickup device is automatically adjusted as a function of scene brightness.

B

Bandwidth - The number of cycles per second (Hertz) expressing the difference between the lower and upper limiting frequencies of a frequency band; also, the width of a band of frequencies.

Bounce - Sudden variations in picture presentation (brightness, size, etc.,) independent of scene illumination.

Brightness - The attribute of visual perception in accordance with which an area appear to emit more of less light. (Luminance is the recommended name for the photo-electric quantity which has also been called brightness.)

Broadband - In television system use, a device having a bandpass greater than the band of a single VHF television channel.

Burned-In-Image - Also called burn. An image which persists in a fixed position in the output signal of a camera tube after the camera has been turned to a different scene or, on a monitor screen.

C

CCD - See Charge Coupled Device

C Mount - A television camera lens mount of the 16 mm format, 1 inch in diameter with 32 threads per inch.

CCTV - Common abbreviation for Closed-Circuit Television.

Charge-Coupled Device - CCD. For imaging devices, a self-scanning semiconductor array that utilizes MOS technology, surface storage, and information transfer by shift register techniques.

CMOS (Complimentary Metal Oxide Semiconductor) - The CMOS image sensor offers integration of added circuitry on a single chip, lower power usage (up to ~1/10 the usage) and a more compact design at the expense of image quality and flexibility. As a result of this, CMOS image sensors are cheaper to manufacture and are usually sold at a lower cost. Also, the smaller system size allows for smaller cameras to be designed. In recent years the gap in image quality between CCD and CMOS image sensors has narrowed greatly. But, when the highest image quality is required, the CCD image sensor is still regarded as the preferred choice. CMOS image sensors are currently limited in low light conditions. With low light conditions the CMOS image sensor can produce either a very dark image or a very noisy image. CMOS image sensors are more susceptible to noise which can create interference or distortion in the image. CMOS image sensors should be used for high-volume, space-constrained applications where obtaining the highest image quality possible is not necessarily vital to the application.

Coaxial Cable - A particular type of cable capable of passing a wide range of frequencies with very low signal loss. Such a cable in its simplest form, consists of a hollow metallic shield with a single wire accurately placed along the center of the shield and isolated from the shield.

Color Burst - That portion of the composite color signal, comprising a few cycles of a sine wave of chrominance subcarrier frequency, which is used to establish a reference for demodulating the chrominance signal. Normally approximately 9 cycles of 3.579545 MHz.

Color Edging - Extraneous colors appearing at the edges of colored objects, and differing from the true colors in the object.

Color Encoder - A device which produces an NTSC color signal from separate R, G, and B video inputs.

Color Fringing - Spurious colors introduced into the picture by the change in position of the televised object from field to field.

Color Purity - The degree to which a color is free of white or any other color. In reference to the operation of a tri-color picture tube it refers to the production of pure red, green or blue illumination of the phosphor dot face plate.

Color Saturation - The degree to which a color is free of white light.

Color Sync Signal - A signal used to establish and to maintain the same color relationships that are transmitted.

Color Transmission - The transmission of a signal which represents both the brightness values and the color values in a picture.

Composite Video Signal - The combined picture signal, including vertical and horizontal blanking and synchronizing signals.

Compression - The reduction in gain at one level of a picture signal with respect to the gain at another level of the same signal.

Contrast - The range of light to dark values in a picture or the ratio between the maximum and minimum brightness values.

Contrast Range - The ratio between the whitest and blackest portions of television image.

Crosstalk - An undesired signal from a different channel interfering with the desired signal.

D

dB - Basically, a measure of the power ratio of two signals. In system use, a measure of the voltage ratio of two signals, provided they are measured across a common impedance.

DDNS (Dynamic Domain Naming System) - Dynamic DNS is a service allowing users to alias their dynamic IP address to a static domain name. Most network cameras have DDNS as a configuration option. Once configured, the camera will update the static domain name with the current IP address of your Internet connection. This allows for easy access to your camera without needing to check your Dynamic IP address. This service is less expensive than having a static IP address and is more flexible.

Decoder - The circuitry in a color TV receiver which transforms the detected color signals into a form suitable to operate the color tube.

Definition - The fidelity of a television system to the original scene.

Depth of Field - The in-focus range of a lens or optical system. It is measured from the distance behind an object to the distance in front of the object when the viewing lens shows the object to be in focus.

Depth of Focus - The range of sensor-to-lens distance for which the image formed by the lens is clearly focused.

Digital Signal Processing - An algorithm within the camera that digitizes data (the image). Examples include automatic compensate for backlight interference, color balance variations and corrections related to aging of electrical components or lighting. Functions such as electronic pan and zoom, image annotation, compression of the video for network transmission, feature extraction and motion compensation can be easily and inexpensively added to the camera feature set.

Distortion - The deviation of the received signal waveform from that of the original transmitted waveform.

DVR - Digital Video Recorder

Dynamic Range - The difference between the maximum acceptable signal level and the minimum acceptable signal level.

E

EIA Sync - The signal used for the synchronizing of scanning specified in EIA Standards RS-170, RS-330, RS-343, or subsequent issues.

Equalizer - An electronic circuit that introduces compensation for frequency discriminative effects of elements within the television system, particularly long coaxial transmission systems.

F

Fiber Optics - Also called optical fibers or optical fiber bundles. An assemblage of transparent glass fibers all bundled together parallel to one another. The length of each fiber is much greater than its diameter. This bundle of fibers has the ability to transmit a picture from one of its surfaces to the other around curves and into otherwise inaccessible places with an extremely low loss of definition and light, by a process of total reflection.

Field of View - The maximum angle of view that can be seen through a lens or optical instrument.

Focal Length - Of a lens, the distance from the focal point to the principal point of the lens.

Focal Plane - A plane (through the focal point) at right angles to the principal point of the lens.

Focal Point - The point at which a lens or mirror will focus parallel incident radiation.

Frame - The total area, occupied by the television picture, which is scanned while the picture signal is not blanked.

Frame Frequency - The number of times per second that the frame is scanned. The U.S. standard is 30 frames per second.

Frame Transfer - A CCD imager where an entire matrix of pixels is read into storage before being output from the camera. Differs from Interline Transfer where lines of pixels are output

Frequency Response - The range of band of frequencies to which a unit of electronic equipment will offer essentially the same characteristics.

f/Stop - Also called F Number and F System. Refers to the speed or ability of a lens to pass light. It is calculated by dividing the focal length of the lens by its diameter.

G

Gain - An increase in voltage or power, usually expressed in dB.

Ghost - A spurious image resulting from an echo.

Gray Scale - Variations in value from white, through shades of gray, to black on a television screen. The gradations approximate the tonal values of the original image picked up by the TV camera.

H

Hue - Corresponds to colors such as red, blue, etcetera.

Hum - Electrical disturbance at the power supply frequency or harmonics thereof.

I

Image Intensifier - A device coupled by fiber optics to a TV image pickup sensor to increase sensitivity. Can be single or multi stage.

Image Plane - The plane at right angles to the optical axis at the image point.

Impedance (input or output) - The input or output characteristic of a system component that determines the type of transmission cable to be used. The cable used must have the same characteristic impedance as the component. Expressed in ohms. Video distribution has standardized on 75-ohm coaxial and 124-ohm balanced cable.

Incident Light - The light that falls directly on an object.

Interference - Extraneous energy which tends to interfere with the reception of the desired signals.

Interline Transfer - A technology of CCD design, where rows of pixels are output from the camera. The sensor's active pixel area and storage register are both contained within the active image area. This differs from "frame transfer" cameras that move all active pixels to a storage register outside of the active area.

Interlaced Scanning - A scanning process for reducing image flicker in which the distance from center to center of successively scanned lines is two or more times the nominal line width, and in which the adjacent lines belong to different fields.

IP - Internet Protocol

Iris - An adjustable aperture built into a camera lens to permit control of the amount of light passing through the lens.