Abstract
A major challenge encountered in digital holography applications is the need to synthesize computer-generated holograms (CGHs) that are realizable as phase-only elements while also delivering high quality reconstruction. This trade-off is particularly acute in high-precision applications such as photolithography where contrast typically must exceed 0.6. A seeded-phase point method is proposed to address this challenge, whereby patterns composed of fine lines that intersect and form closed shapes are reconstructed with high contrast while maintaining a phase-only CGH. The method achieves superior contrast to that obtained by uniform or random seeded-phase methods while maintaining computational efficiency for large area exposures. It is also shown that binary phase modulation achieves similar contrast performance with benefits for the fabrication of simpler diffractive optical elements.
Highlights
Computer-generated holograms (CGHs) are finding use in many applications where conventional imaging systems are not able to provide the required performance
The results suggest that binary phase computer-generated holograms (CGHs) compare favorably with their multiphase level counterparts, and that, diffraction efficiency is reduced for binary phase modulation, the fabrication of CGH in the form of diffractive optical elements is simplified considerably
We demonstrate the resulting image quality achieved by experimental photolithography exposure
Summary
Computer-generated holograms (CGHs) are finding use in many applications where conventional imaging systems are not able to provide the required performance. Examples include optical data storage, beam shaping of high power laser beams, three-dimensional optical tweezers for microscopy, displays, and photolithography Each of these exploits one or more capabilities offered by CGH imaging. A major challenge in the deployment of digital holography is the need to quantize the CGH distribution into a discrete set of amplitude and/or phase values, driven by the fact that complex modulation is not practical using currently available photomasks and spatial light modulator (SLM) devices. This modification introduces noise into the reconstructed image and results in poor image contrast
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