The 2 Primary Types of IR Touchscreens
Infrared (IR) touchscreens are defined by their use of IR light to detect touch commands. They don't use conductive traces or contacts to detect touch commands. Rather, they use IR light.
IR touchscreens project light across the display interface that, when disrupted, allows the device to determine the location of a touch command. There are two primary types of IR touchscreens, however. While they both involve the use of IR technology, they use a different configuration.

#1) IR Grid
The most common type, IR grid is a type of touchscreen technology that uses an invisible grid of IR light to detect touch commands. IR grid touchscreens feature light-emitting diodes (LEDs) and sensors around the perimeter of the display interface. The LEDs project the IR light, whereas the sensors read the IR light.
IR grid touchscreens work by looking for disruptions in IR light. When you perform a touch command, you'll disrupt some of the IR light. The sensors will identify this disruption, and the IR grid touchscreen will respond by registering your touch command. IR grid touchscreens use a simple configuration, but they are highly effective at detecting and registering touch commands.
#2) IR Heat
Another common type of IR touchscreen is IR heat. IR heat touchscreens don't actually produce IR light. Instead, they use IR cameras to measure heat.
In IR heat touchscreens, there are IR cameras placed on the bottom that measure the temperature of the display interface. If you touch the display interface, the temperature will increase at the location of your touch command. The IR cameras will detect this heat signature, and the IR heat touchscreen will respond by registering your touch command.

