Scanning Ring Illumination for Laser Processing
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
Laser processing is presently being performed at wavelengths well into the UV where there are few suitable optical materials and lenses. As a result, all-reflective optics are used, which have the additional advantage of freedom from chromatic aberration. There are commercially available reflective objectives, constructed with two mirrors as shown in Fig. 1. These objectives have a central obstruction, so that light directed toward their centers does not reach the image plane, as shown in Fig. 2. Thus, there is a reduction in power efficiency. In addition, light hitting the central portion of the mirror is scattered into the optical system, possibly causing detrimental effects. These difficulties can be eliminated in the manner shown in Figs. 3 and 4.