Development of Small LiDAR System for Visualization of Breathing and Comprehensive Measurement of Particle Size and Velocity Distribution in Exhalation, and Inactivation of Coronavirus by light irradiation

Research and Development by


Corresponding Research Area

Indoor airflow simulation and visualization of droplets, which are necessary for improving the COVID-19 Infection Prevention Guidelines for each industrial sector

(1)Development of Small LiDAR system for Gas Measurement

We developed the small LiDAR system with an eye-safe laser that enable to visualize the atmospheric fluctuations by using the Schlieren method (of visualizing the difference in gas density).

System of Small LiDAR

(a) Measured Atmospheric Fluctuations

Succeeded in visualizing atmospheric fluctuations

Courtesy of RIKEN

→With the introduction of a large optical system and an eye-safe light source, a wide range of real-time visualization of the state of human exhalation has been achieved.

(2)Calibration for the Simulation of Droplet Scattering

It is necessary to measure particle size from small-diameter such as aerosols to large-diameter such as droplets by the same method. In this study, we examined the availability of a method to obtain the particle size from the interference fringes and the velocity from PIV/ PTV.

Particle size measurement method: Image of interference

Particle size can be estimated from the interference fringe spacing

Results: Image of interference


  • Glass beads with a diameter of 50um (reference sample)
  • Pre-experiment: Confirmed diameter by microscope. Variations of reference samples were 48-69um.

Results of interferometry

  • Could confirm the interference fringes.
  • Results of our method included 20-40 μm particle sizes.

Courtesy of RIKEN

→Going forward, we will try to improve the measurement accuracy by reviewing the setup and by comparing with other methods such as dependence of the response of Mie scattering on the particle size.

(3)Inactivation of Coronavirus by Light Irradiation

Examination of whether new coronavirus is inactivated by UV irradiation and photocatalyst.

Inactivation effect of new coronavirus by UV irradiation

  • Conditions: New coronavirus was irradiated with ultraviolet rays (UV-C) from 30 cm in distance for 0, 5, 15, 30 seconds in a moist environment.
  • Evaluation method: TCID50, qPCR

  • The virus decreased to 1/1000 after 15 seconds and to below the detection limit after 30 seconds of irradiation

Inactivation effect of new coronavirus by photocatalyst

  • Conditions: The new coronavirus floats in a chamber. The photocatalyst in the chamber was irradiated for 0, 5, 15 and 20 minutes.
  • Evaluation method: TCID50, qPCR

  • 99% of virus was inactivated in 13 minutes, and it was reduced to below detection limit in 20 minutes

Courtesy of RIKEN

  • UV irradiation may be able to efficiently inactivate viruses on clothing and walls.
  • Making curtains with light may prevent infections by virus in droplets and aerosol.
  • By using a photocatalyst, it may be possible to inactivate viruses in the air without adversely affecting the human body.