Patent ID: 8716641

Claim:
A scanning imaging device, comprising: a first irradiation unit that irradiates a first spot light as a collimated light beam onto a target substrate for detection; a second irradiation unit that irradiates a second spot light as a collimated light beam onto the target substrate for detection; an optical system having a sensor array for receiving light from a target of detection existing at a focal position on a first plane in the target substrate for detection and the first spot light reflected at a second plane in the target substrate for detection and the second spot light reflected at a third plane in the target substrate for detection, the second and third planes being parallel to the first plane and displaced from the first plane in a thickness direction of the target substrate for detection; and a scanning unit for driving the optical system to scan the target substrate for detection at least in a main scanning direction, which is parallel to the first plane, wherein the first and second spot lights are irradiated onto respective positions each different from the focal position in the target substrate for detection, wherein the first and second spot lights reflected from the respective positions in the target substrate for detection are received to read out a signal from which a focusing signal is acquired, and wherein the first and second irradiation units are adapted for irradiating the first and second spot lights obliquely relative to the first plane.