In this thesis work, a new indoor people counting algorithm is created by using Omron D-6T thermal sensor and Raspberry Pi. The sensor periodically generate thermal map of heat emitted in its field of view which is a one dimension array and pass the array to Raspberry for further processing. The people counting algorithm is created in Raspberry Pi by processing thermal map generated by D6T. After processing the number of people indoor is obtained. This chapter presents the hardware structure used including D6T thermal sensor and Raspberry Pi, moreover the people counting algorithm is discussed in detail.
D6T thermal sensor
D6T is a new product which is designed by Omron and released in 2012. By using Omro-n’s unique MEMS and ASIC technologies, it achieves a high SNR which leads to a digital output with superior noise immunity. While standard thermal sensors are only able to measure temperature at one certain contact point, the D6T can measure the temperature of an entire area without contact. As the figure shows, the D6T series sensors consist of a cap with silicon lens, MEMS thermopile sensor chips and dedicated analog circuit and a logic circuit for digital temperature value generation.
Figure 1. Omron D6T thermal sensor structure
Until now D6T has only 2 types which are D6T-44L-06 and D6T-8L-06. The main differences are D6T-44L-06 has 16 pixel elements while D6T-8L-06 has only 8 pixel elements which means they also have different field of view. In this thesis work, we use D6T-44L-06 for thermal map generation.
Figure 2. Types of D6T thermal sensors
Operating Principle and features
The radiated heat emitted from an object is collected by thermopile sensor through the silicon lens. Then the radiated heat will produce an electromotive force on the thermopile sensor. Afterwards, the analog circuit calculates the temperature of an object by using the electromotive force value and