Method of detecting foreign material on upper surface of transparent substrate using polarized light

A method of detecting a foreign material on an upper surface of a transparent substrate using polarized light comprising:

• irradiating light having a predetermined incident angle to the transparent substrate;
• detecting a P-polarized component of the scattered light of foreign materials attached onto the transparent substrate by the irradiated light;
• detecting an S-polarized component of the scattered light of the foreign materials attached onto the transparent substrate by the irradiated light;
• comparing a brightness of the P-polarized component and a brightness of the S-polarized component with each other to distinguish the foreign material attached onto the upper surface of the transparent substrate and a foreign material attached onto a lower surface of the transparent substrate from each other;
• and
• removing the foreign material attached onto the lower surface of the transparent substrate,
• wherein in the case in which the brightness of the P-polarized component and the brightness of the S-polarized component are the same as each other, it is judged that the foreign material is the foreign material attached onto the upper surface of the transparent substrate, and in the case in which the brightness of the S-polarized component is darker than that of the P-polarized component, it is judged that the foreign material is the foreign material attached onto the lower surface of the transparent substrate.