Thin film characteristic measuring apparatus

A thin film characteristic measuring apparatus used for measuring a thickness or a width of a thin film of a subject, the thin film characteristic measuring apparatus comprising:

• a light source including a superluminescent diode (SLD);
• a first reflection mirror configured to reflect a ray irradiated from the light source;
• a first actuator configured to tilt the first reflection mirror in a predetermined angle range;
• and
• a lens assembly including a plurality of lenses, and in which the ray reflected by the first reflection mirror is incident and transmitted,
• wherein the lens assembly includes:
• a first lens that is a negative lens,
• a second lens disposed behind the first lens, the second lens being a positive lens,
• a third lens disposed in front of the first lens, the third lens being a positive lens,
• a fourth lens disposed between the third lens and the first lens, the fourth lens being a positive lens, and
• a fifth lens disposed between the third lens and the first lens, the fifth lens being a negative lens,
• wherein the plurality of lenses are configured to expand a diameter of the ray and reflect the ray towards the subject at different spots in a predetermined section of the subject,
• wherein the diameter of the ray is expanded while passing through the plurality of lenses, and the diameter of the ray is constant after exiting the plurality of lenses,
• wherein the lens assembly is configured so that an angle of a main ray of the ray transmitted through the lens assembly with respect to an optical axis is greater than or equal to an angel of the main ray of the ray incident on the lens assembly with respect to the optical axis, and
• wherein, after the ray exits the lens assembly, the ray is non-parallel to the optical axis.