First, let's understand what Infrared Radiation (IR)? Infrared is a region of the electromagnetic radiation spectrum, where the wavelength is between 700 nm to 1 mm, which is more than the wavelength of visible light and less than radio waves. The frequency of IR is in the range of 300 GHz to 400 GHz, which is higher than the frequency of microwaves, but lower than that of visible light.

IR waves are not visible to human eye unlike visible light, but can be focused, reflected, and polarized just like visible light.

IR is mostly used in wireless communication, remote controls, sensors, thermal imaging, and night vision devices, but we will focus only on IR sensors in this chapter.

IR sensors are the devices that emit or/and detect IR radiation. The working principle of any IR sensor is governed by Plank's radiation law. As per Plank's radiation law, any object that has a temperature not equal to absolute zero (which is zero kelvin (0° K)) emits radiation.

In our case, we use IR sensors for obstacle or object detection, and for these applications the IR sensor module should consist of the following components:

• IR transmitter: An IR transmitter is a source of IR radiation for which IR LEDs and lasers are used.
• Transmission medium: For the transmission of IR waves, a medium such as a vacuum, atmosphere, or optical fibers is required.
• Optical component: Materials such as quartz are used to focus the infrared radiation in a particular area. Optical lenses such as quartz, germanium, and silicon are used to make optical components.
• IR receiver/detector: Photodiodes and LED are used as IR receivers and detectors respectively, which have good photo sensitivity for infrared radiations.
• A signal processing module: A signal processing module is used to amplify the signal received by the IR detector because the amplitude of the signal is very small.