Beam blocking method for optical characterization of surfaces

✍ Scribed by Moisés Cywiak; Janusz Murakowski; Glen Wade

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 120 KB
• Volume: 11
• Category: Article
• ISSN: 0899-9457
• DOI: 10.1002/1098-1098(2000)11:3<164::aid-ima1001>3.0.co;2-n

✦ Synopsis

A new method for measuring local topography of optical surfaces gives excellent lateral resolution. To obtain one-dimensional image information, the surface is mechanically scanned at a slow rate and vibrated sinusoidally in the direction of the scan. The motion lies in a plane perpendicular to an incident, focused, probing laser beam. The reflected laser beam, angularly modulated by the moving variations in the vibrating surface, is gathered by a lens and directed toward a knife-edge and photodiode combination. One half of the beam is blocked by the knife-edge, the orientation of which is at a right angle with respect to the angular motion of the beam. The detected signal from the photodiode is proportional to the derivative of the local slope convolved with a spread function stemming from the surface vibration and the beam profile. The operational characteristics of the proposed method are superior compared with available methods.