| 摘要 |
<p>High performance optical spatial filters are produced photographically with an apparatus that directs a coherent beam of light (50) through or off a subject (66) and into a lens (68). The lens (68) focuses the diffracted and/or reflected light to define a Fourier transform of the subject information. A filter is produced by exposing a photographic plate at the Fourier transform plane (69), processing the plate, and repositioning it. A halogram (88) is recorded through the processed plate with the apparatus, which directs a reference beam (52) to a holographic recording plane. A second photographic plate is placed at the transform plane (69) and exposed with light directed through the hologram from a direction conjugate to the reference beam (52). The second plate is then processed. Successive generations of filters may also be produced. A method of using the filters of Isolating nonperiodic defects in IC photomasks and wafers is also disclosed.</p> |
