PROBLEM TO BE SOLVED: To accurately measure the volume of a liquid droplet discharged by an ink jet system.SOLUTION: A ring-shaped light source 12 and a camera 11 are provided above a liquid droplet L on a measurement substrate S so that a central axis of the ring-shaped light source and an optical axis of the camera 11 agree with each other and pass through an apex of the liquid droplet L and a radial direction of the ring-shaped light source 12 and a surface of the measurement substrate S are parallel to each other. A radius x of a ring of reflection of light with which the liquid droplet L is irradiated from the ring-shaped light source is determined on the basis of an image of the liquid droplet L captured by the camera 11 in the state of lighting the ring-shaped light source and a radius A of the liquid droplet L is determined on the basis of an image of the liquid droplet L captured by the camera 11 in the state of irradiating the liquid droplet L with light from the lower side of the measurement substrate S, so as to calculate the volume of the liquid droplet L using the radius x and the radius A.SELECTED DRAWING: Figure 1
展开▼
