How to Build a Simple Infrared Illuminator

What are Infrared Illuminators?

Infrared Illuminators are devices which emit light in infrared spectrum. They can be active devices which emit their own infrared light like various objects or passive devices which reflect the infra red light which falls on them. One of the major application is in night vision cameras.  The infrared illuminator incorporated in the night vision camera is actually an IR LED which emits light in infrared band. This infrared light is reflected by objects and is collected by the camera lens. Infrared imaging is not only useful of surveillance but also for applications like checking heat insulation of buildings, checking thermal pollution of water bodies etc.  The IR Illuminator can also be used in CCTV cameras.

3 Infrared Illuminating Devices: 

Let us have a detailed description of each Infrared Illuminating devices

1. Infrared LASERs: A LASER or Light Amplification by Stimulated emission of Radiation system works on the principle of amplification of generated light by constant stimulation by the generated photons. i.e. when a electron is illuminated with a photon, it gets energized and jumps to the higher level and while coming back to its original level, it emits another photon. This process continues and this is how a LASER emits light. LASERs emitting infrared light can be solid state LASERs made up of materials like Neodymium-Yag LASER which emits infrared light at 1064 nanometers. It can also be gas LASERs like CO2 LASERs which emit light in far infrared range and are used for cutting metals. LASERs emitting IR light are often considered to be dangerous and used mainly for military purposes.

2. Filtered Incandescent lamps: These devices consist of traditional Incandescent lamps which are covered with the infrared filter which allow only the infrared spectrum of the light produced, to pass through and block all other part of the spectrum. Mostly objects like vegetation, wild life, sand, etc which emit most of the heat are the objects which can be pictured using cameras with infrared filters.

3. IR LED: The IR illuminator mostly uses IR LED. An IR LED is a special  LED which emits infra red rays in the range of 760nm. They are mostly made up of Gallium Arsenide or Aluminum Gallium Arsenide. They operate at a voltage around 1.4V. They can either work in direct emission mode or reflected emission mode. Normally an array of such LEDs is incorporated in night vision cameras.

Night Vision Cameras and three ways to attain night vision

Night vision cameras are used in many applications like in spying robots and also for surveillance purpose. Like any normal camera, they too require illumination for their operation.. But for cameras used in surveillance purpose that are used mostly at night we cannot rely on visible light. In some cases this visible light can be amplified, but these cameras are not reliable and cannot be used at places where there is no light at all. For this purpose, another part of spectrum of light is used, that is the Infrared band. Some of the cameras makes use of the fact that all warm bodies radiate infrared light.

3 ways to attain night vision for these cameras.

• Low Light Imaging: These techniques involve the use of normal visible light and the basic principle involves amplifying the available visible light to increase its intensity. Some of the low imaging technique involves use of built in chips in cameras where the current generated due to light is constantly amplified.

• Thermal Imaging: These techniques are based on the fact that all the objects illuminate infrared light. The infrared radiation from all the objects is collected and an electronic image is formed.  Normally semiconductor devices involving Mercury Cadmium Telluride and Indium antimonite are used as infrared detectors. They can operate at low temperatures or at room temperature. These techniques basically use the thermal IR part of the Infrared spectrum which involves the wavelength range from 3 microns to 30 microns. They involve use of active illuminators, which emit infra red light on its own.

• Infrared Illumination: These techniques involve use of devices which can emit infrared light. An Infrared Illuminator works on the fact that all warm objects emit infrared radiation. Infra red band occupy a bandwidth besides the visible red band.

Approximate range of IR band is 430THz to 300GHz. Passive Illuminator is the one which produces IR light by reflection or refraction of IR rays from another source. These techniques use the near infrared part of the Infrared spectrum which involves wavelength range from 0.7 to 1.3 microns.

Advantages of IR illumination method for night vision cameras

1. They are not affected by surrounding light.
2. They are inexpensive.
3. The cameras using IR illuminators have good sensitivity
4. IR LEDs specifically have lower consumption rate and longer lifetime.
5. It is possible to take pictures at night time without disturbing the environment.

How to Build a Simple Infrared Illuminator?

You can make a Simple IR illuminator using Infrared LEDs. It is useful to give light for the Night vision Camera.

The circuit is too simple and can be constructed on a small piece of Common PCB. 18 Infrared LEDs are used with individual current limiting resistors R2 – R19. In order to increase current through the LEDs, low value ( 10 Ohms 1 Watt) resistors are used. Power to the circuit is obtained from a standard transformer power supply.

Simple Infrared Illuminator

A  6 volt 500 mA step down transformer is used. The full wave rectifier comprising D1 through D4 rectify the low volt AC to DC and the Smoothing capacitor C1 removes the ripples from the DC. The  pot VR1 can be used to adjust the brightness of the IR LEDs through controlling the voltage.

Basically The IR LEDS are powered using AC mains supply by converting the AC signal to DC signal using the bridge rectifier arrangement after which the pulsating DC signal is filtered using the electrolyte capacitor to remove the ac ripples. The voltage to the LEDs are changed using a variable resistor.

Since the IR ray is invisible, a trick can be used to check the circuit. Power the circuit and focus the Mobile phone camera or digital camera in front of the IR LEDs. A pink light will be visible which is the Infrared light. Enclose the IR LEDs in a reflective case so that the light will be further increased and focused.