Displacement measurement device and defect detection device

A displacement measurement device comprising:

• a laser light source configured to emit laser light to a measurement area on a surface of a measurement target object;
• a focusing optical system having a front focal point in the measurement area and a rear focal point on a predetermined imaging surface;
• a non-focusing optical system having a front focal point in front or rear of the measurement area and a rear focal point on the imaging surface;
• and
• a photodetector configured to detect light intensity on the imaging surface for each point.

A defect detection device comprising:

• an excitation unit configured to excite an elastic wave to a measurement target object;
• a laser light source configured to emit laser light to a measurement area on a surface of the measurement target object;
• a focusing optical system having a front focal point in the measurement area and a rear focal point on a predetermined imaging surface;
• a non-focusing optical system in which light from a surrounding range of a correspondence point in the measurement area corresponding to each point on the imaging surface with respect to the focusing optical system is incident on the point of the imaging surface;
• and
• a photodetector configured to detect light intensity on the imaging surface for each point.

A defect detection device comprising:

• an excitation unit configured to excite an elastic wave to a measurement target object;
• a laser light source configured to emit laser light to a measurement area on a surface of the measurement target object;
• a focusing optical system having a front focal point in the measurement area and a rear focal point on a predetermined imaging surface;
• a non-focusing optical system having a front focal point in front or rear of the measurement area and a rear focal point on the imaging surface;
• and
• a photodetector configured to detect light intensity on the imaging surface for each point.