Abstract

In order to measure a measurement target on a PCB, height information of the PCB is acquired by using a first image photographed by illuminating a grating pattern light onto the PCB. Then, a first area protruding on the PCB by greater than a reference height is determined as the measurement target by using the height information. Thereafter, color information of the PCB is acquired by using a second image photographed by illuminating light onto the PCB. Then, the first color information of the first area determined as the measurement target out of the color information of the PCB is set as reference color information. Thereafter, the reference color information is compared with color information of an area except for the first area to judge whether the measurement target is formed in the area except for the first area. Thus, the measurement target may be accurately measured.