Introduction to surveillance cameras
Surveillance cameras are distinguished by three main technologies:
- The analog cameras connected by cords to the video recorder (DVR), connected to the Internet
- The IP cameras , wifi option, connected directly to the Internet or via a digital recorder
- The GSM GPRS camera, Visio, 3G, autonomous, transmit video images thanks to a SIM card
- Webcams are not within this guide because they require a permanent connection PC
- The advantages and disadvantages cited correspond to customers appérications using conventional video surveillance systems
The analog camera is connected to a video surveillance system with coaxial video cable. The quality of the video image of analog cameras is determined by the number of image definition lines 330-700 lines, good value for the cameras 420 to 540 lines. The analog version wireless radio transmitter uses a 2.4GHz, this mode of transmission has a short range in practice (5-20 m) and not through walls.
- Advantages: robust and reliable cameras, low price of 100 to 400 euros
- Inconvenient: Requires a video surveillance system for the processing of the video image
Wired IP cameras, wifi or Plug and Play
The IP camera is connected to the video surveillance or Internet system via the network or directly via the Box ADSL Internet, according to securitypology. The quality of the IP camera video image is determined by the number of pixels of the image from 640×480 to 1600×1200 (megapixels). The megapixel cameras are used to images of very high resolution but require a broadband network. If a digital recorder is used, it must be compatible (driver).
The IP cameras plug and pla are préparamétrées for ADSL Internet Box and install without IT knowledge network.
- Advantages: autonomous network cameras, wireless wifi connection, remote quality control, price vary from 100 to 1400 euros related to corporate functions.Option wifi long distance 10m to 500m transmitter.
- Inconvenient: requires a dedicated computer network with many cameras with megapixel cameras, wifi recommended in industry
Visio cameras GSM GPRS 3G
The GSM camera GPR S transmits MMS or JPEG images, not video because of the low rate of this technology but with the advantage of an extensive network coverage and no Internet connection.Transmission over GSM phone or PC and PDA via email.
The camera with “VISIO call ” or “video call” transmits video only to phones with the “Video Call” or “video call”.
The 3G cameras transmit video to PC or 3G phone thanks to a 3G SIM card.
Note: the term 3G camera is commonly used for IP cameras, with Internet connection via ADSL Box, to receive video on a 3G phone.
Price: 250-700 euros
Indoor or outdoor surveillance camera
Indoor camera should only be used in a local or sensor will not be exposed to the sun , the majority of indoor cameras with no auto iris (automatic adjustment of the aperture) and no integrated UV filter, photosensor is rapidly destroyed by UV rays.
Outdoor cameras are designed to cope with high brightness, UV rays, rain (IP54 tightness, light splashing water, IP66, showers) and temperature variations from -10 to + 40 ° C. One optionthermostatically controlled box (heating and ventilation) can manage larger temperature variations (-20 to + 55 ° C) and quickly clears condensation from the lens when condensations (eg sunrise facing the camera) .
The CCD or CMOS sensors
The photosensitive sensor placed behind the lens converts the electromagnetic radiation into an electrical signal. The sensor is CMOS technology (Metal Oxide Semi-complmentary condiuctor) or CCD (Charge Coupled Device), these two technologies are currently equivalent to normal brightness but low-light CCD is preferable because more sensitive, the image is therefore better. The video quality is also linked to the quality of the lens and associated technologies: Gain Control (AGC), white peaking software (AWB), automaitque management cons days (WDR). The major manufacturers are SONY and SHARP.
IR illuminator (IR) and brightness
Brightness, or amount of light is measured in lux, 0 lux corresponding to total darkness, 1 lux at nightfall, 20,000 lux at a sunny lighting. The camera operating threshold is announced in the characteristics of each camera.
Infrared diodes or LEDs, integrated in the camera or in an infrared projector juxtaposed it possible toview video in total darkness thanks to non-visible infrared rays by the human eye. IR cameras and day / night cameras, automatically switch to night mode when lighting is poor and record black and white video. Traditional infrared range: 10 to 80 m
Lens surveillance cameras
Typical objectives have a size of 1.6 mm to 50 mm which corresponds to an opening angle of view of 130 ° to 5 ° . The larger the objective in mm, the greater the viewing angle is narrower and the areas to be monitored are filmed closely. Price from 20 to 200 euros.
- fixed targets 3.6mm (viewing angle of 70 °)
- varying objectives 4-9mm (viewing angle from 60 to 30 °) to adjust the area to be monitored accurately.
- variable targets of 5-50 mm (viewing angle 45-2 °) for areas of more than 20 m or for process monitoring.
Cases of surveillance cameras
Surveillance cameras have standard boxes to fit discreetly in an environment to be visible for deterrence:
- housing surveillance camera or Box: visible cubic box with external objective
- dome surveillance camera: hemispherical enclosure for integration ceiling
- motorized dome camera or PTZ (Pan Tilt Zoom) 3-axis moving target
- Spy Camera: mini box or hidden camera in an anonymous box (eg clock)
- vandal proof camera: box or dome shock resistant (eg projectile)
- Box metal or plastic option, with or without temperature control.