Security camera: illumination and artificial lighting

Without light, we can't see anything, but to security cameras, they are slightly different, some high sensitive security cameras can capture clear monochrome images in starlight illumination condition, they also can see objects in complete darkness when using additional infrared lighting. In this article, we offer the basic knowledge about the natural lighting illumination, and the wide variety of artificial lighting.

Lux is a deprived unit based on lumen, and lumen is a deprived unit based on candela. The lumen (system: lm) is the SI unit of luminous flux, a measure of the power of light perceived by the human eye and the candela is the SI base unit of luminous intensity. One lux is equal to one lumen per square metre, where 4n lumens is the total luminous flux of a light source of one candela of luminous intensity.

When selecting an appropriate surveillance camera to install, be sure to consider the illumination condition in environment. Lux, it's the illumination level unit used to represent the designated area illumination. In good illumination area, user can choose to use a general performance security camera. However, the color system for environmental illumination is less than 2.0 Lux, monochrome illumination system for less than 0.2 Lux environment use the higher performance security camera (i.e. starlight security camera), it's very necessary. Using Lux meter can measure illumination level. If you don't have lux meter, you can refer to the following general illumination data table.

Indoor:

• Warehouse 20—75 Lux
• Emergency passway 30—75 Lux
• Corridor 75—200 Lux
• Shop 75—300 Lux
• Office 300—500 Lux
• Bank 200—1000 Lux
• Meeting Room 300—1000 Lux

Outdoor

• Sunny 10000—1000000 Lux
• Cloudy 100—10000 Lux
• Dawn Twilight 1—10 Lux
• Full moon over head 0.1—1 Lux
• Quarter moon 0.01—0.1 Lux
• Sunny Starlight 0.001—0.01 Lux
• Cloudy Starlight 0.0001—0.001 Lux

When security camera works in complete darkness environment (0 Lux), the camera image sensor will not be able to capture images. In this condition, the cameras have artificial lighting system such as infrared LEDs, white light LEDs, as well as laser emitters. These artificial lighting systems can help camera to capture clear monochrome or color images in low illumination or zero illumination environments. Recently, Hikvision and Sony launched day & night security cameras which utilize dual-lighting system.

Infrared illumination: utilizing infrared LEDs to emit invisible (to human) infrared lights. The infrared light wave length is 850nm, which allows camera to capture monochrome images. When using the IR illumination, the camera will encounter infrared-saturation problem cause the image loss details for objects located in central and short distance monitoring area. In order to solve this problem, IR-smart technology was introduced into many security cameras. IR-smart function can adjust camera's Infrared intensity according to the monitoring objects, avoid IR-saturation problem. Until now, the IR illumination can cover  0 - 200 meters distance.

White light illumination: utilizing white light LEDs to illuminate the monitoring area. The white light LED wavelength is 450 nm, which is belong to visible light. The white light illumination can enable camera capture color images in low illumination or zero illumination environments. Compared with infrared illumination, white light illumination can work in specific application such as license plate number recognition. Additionally, the white light illumination can be used to deter intruders/criminals. Sony dual-light IP camera can automatically turn on white light illumination, when people walk into monitoring area. The white light has much shorter illumination distance than infrared, its range is 0 - 50 meters.

Laser illumination: the latest cutting-edge technology that offers long distance illumination. Typically, laser emitter is equipped into PTZ camera which offers 30x optical zoom capability. The majority laser emitter utilizes 808 nm wavelength diodes, laser emitter has many advantages; long distance illumination, versatility, adapt to the environment, long lifespan, low risk. Laser illumination can help camera to capture clear images with high clarity.  Additionally, it enables camera to capture image within 1 kilometer or even 3 kilometers long distance. Recently, Hikvision launched 2.0 megapixel IP PTZ camera (DS-2DY9187-AIA) which supports 32x optical zoom, equipped with a laser emitter for long distance video surveillance at night.

Compared with conventional infrared technology, laser illumination technology has below advantages:

1. Suitable for long distance video surveillance applications. Laser illumination can be divided into short distance laser illumination (illumination distance range is 100 - 500 meters) and medium distance laser illumination (effective illumination distance range is 500 - 1000 meters), as well as long distance laser illumination (effective illumination distance range is 1000 - 3000 meters).
2. Support automatically adjust the lens focus, image clarity is greatly improved. Although infrared camera can see image at night, but can't see the details of human face. Additionally, conventional infrared technology has limited illumination distance. Some security cameras with laser illumination, can automatically adjust the illumination according to the moving object distance, speed.
3. Longer life expectancy, the lifespan of laser diode is three times longer than infrared LEDs. This lets laser illumination has outstanding advantage in 24-hours video surveillance application.
4. Eco-friendly, when conventional infrared illuminators work, they generate excessive heat and consume too much power. The heat will induce to camera core module cause the overheating problem, seriously affect the lifespan of the electronic components in the camera, laser emitter do not have this risk.