Multi-surface specular reflection inspector

An optical inspector, comprising:

• a time varying beam reflector;
• a radiating source that irradiates the time varying beam reflector;
• a telecentric scan lens configured to direct the radiation reflected by the time varying beam reflector onto a first surface of a transparent sample, wherein a portion of the radiation irradiates a second surface of the transparent sample;
• a first detector configured to receive at least a portion of top surface specular reflection and generate a first detector output signal, wherein the top surface specular reflection results from the irradiation of the first surface of the transparent sample;
• a second detector configured to receive at least a portion of the bottom surface specular reflection and generate a second detector output signal, wherein the bottom surface specular reflection results from the irradiation of the second surface of the transparent sample;
• and
• a processor that determines that a defect is present on the top surface or the bottom surface of the transparent sample using only two detector output signals:
• (i) the first detector output signal, and (ii) the second detector output signal.