Mariko Kawaguri

360° direction type human information sensor

Abstract The 360° direction type human information sensor has been developed using a pyroelectric infrared detector. This sensor attached to the ceiling can detect the number of occupants, their locations and movements. The sensor module consists of a one-dimensional array detector made of pyroelectric ceramics (PbTiO3), an infrared transparent lens, a 360° rotary scanning mechanism and a 3° chopping mechanism. Data on human conditions can be computed from the thermal distribution by the human detecting algorithm. The pyroelectric array detector fabricated by a new process has sufficient sensitivity for 20 Hz chopping frequency. The array detector rotating mechanism allows the sensor to have a wide view (10 m diameter). With the human detecting algorithm, data on humans such as the number of occupants and their locations can be detected with 73% accuracy in 389 samples (97% accuracy in case of allowing ±1 person). Human information obtained by this sensor can contribute to energy saving when applied to the control of air conditioners and lighting systems.

Characteristics of Pyroelectric Infrared Array Detector Made of PbTiO3 Ceramics

A one-dimensional pyroelectric array detector as a multi-element infrared sensor has been developed by using a new sheet forming method made of PbTiO3 bulk ceramics. This simple fabrication process is cost effective and enables us to control the film thickness accurately, thus decreasing the sensitivity variations that exist in one detector and among different detectors to within 10%. A pyroelectric detector responsivity of 2×104 V/W can be obtained at 10 Hz chopping frequency. A specific detectivity D* of 0.8×108 cm Hz1/2/W has been achieved. Furthermore, this detector has a sufficient sensitivity for performances at high chopping speeds up to 100 Hz. The time constant of this pyroelectric detector is about 8.6 ms, so the detector has a shorter response time compared with the commercially available conventional pyroelectric detector. The cross talk, which influences the output for the adjacent elements, is less than 10%. By using this high performance pyroelectric array detector, the thermal sources at lower temperatures than environmental conditions can be detected with high sensitivity, as much as the thermal sources at higher temperatures. The output voltage for the detector was gradually decreased as the atmospheric temperature increased.