Scanning objective

US5608564A · kind A · utility

Assignee

• Siemens Aktiengesellschaft · DE

Inventor

• Anton Schick · Taufkirchen, DE

Key dates

• Filing date: Nov 23, 1994
• Grant date: Mar 4, 1997
• Expiry date: Nov 23, 2014

Classification

• Technology area (CPC G): Physics
• CPC primary: G02B21/0024
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

A high resolution with at the same time high testing speed is required of scanning objectives for the linewise or pointwise three-dimensional scanning of object surfaces. In order to be able to image as many image points as possible with high resolution, the scanning objective must exhibit a correspondingly large numerical aperture with, at the same time, a large image field. For this purpose, it is constructed of three lens groups (1; 2; 3). The first and second lens groups (1; 2) effect both a scan angle reduction and a pupil enlargement. The entrance pupil (61) is imaged into the entrance pupil (63) of the third lens group (3). The third lens group (3) has a large numerical aperture of, for example, 0.6. Furthermore, the real intermediate image (5) is imaged by the second lens group (2) with positive refractive power and greater focal length (f) than the first lens group (1), at infinity. With a beam diameter (D) at the entrance of the scanning objective of 7.5 mm, a scan angle (.theta.) of +/-16.degree. and a scan length S of 3.5 mm, it is possible to achieve, for example, a working spacing of 5 mm.