Scattered light from PM2.5 particles is measured with a double-sided mirror design, which is said to collect about 1.8 times more scattered light than conventional single-sided designs. Mitsubishi says its shape-discrimination algorithm distinguishes between pollen and dust based on the respective differences in the optical characteristics of their scattered light.
PM2.5 is said to have caused air pollution and health-related issues in countries such as China, India and Japan. The trend has raised public concerns and increased the demand for high-precision air-quality sensors to detect PM2.5. At present, however, high-precision sensors for PM2.5 are large and expensive, limiting their applications to commercial use only.
Mitsubishi’s air-quality sensor prototype consists of a laser diode, aspheric lens, light-collecting mirror, photodetector and airflow controller. The prototype measures 67 x 49 x 35mm. The minimum size of a detectable particle is claimed to be 0.3µm.
