关键词:
f-theta-lens
ghost images
glass machining
high power density
摘要:
At high power densities in excess of, say, 10(9) W/cm(2), such as may be created by focusing pulsed laser radiation of nanosecond pulse duration, optical glass is no longer transparent but absorbs the radiant power, resulting in stress and physical damage (cracks). While this is intended for certain techniques of machining glass and other normally transparent materials, secondary foci or 'ghost images ' inside the focusing optics may also exceed the threshold for absorption and thereby cause damage to lenses if such ghost images fall inside an optical element. When designing optics for laser machining of glass, it is therefore important to control the formation of ghost images and to ensure that they are located outside all lens elements. This dominates the design process for such optical systems.