Asian Journal of Physics Vol 32, Nos 5 – 8 (2023) 225-235

The Sheridan source:A novel coherent illumination source using a time varying
specklefield and a digital micro-mirror device

Damien P Kelly1 and Unnikrishnan Gopinathan2
1Institute for Lasertechnologies in Medicine and Metrology(ILM), Helmholtzstr.12,89081Ulm,Germany
2Instruments Research and Development Establishment, Raipur Road, Dehradun-248 008 (Uttarakhand), India.
Dedicated in memory of Prof John Sheridan

In this manuscript we propose and discuss a novel type of illumination source that consists of a (possibly but not necessarily) time-varying speckle field and Digital Micro-mirror Device (DMD) with associated combining optics. We assume that a paraxial optics regime is sufficiently accurate to model the optical systems described here. We, first conduct a brief review of general illumination modalities including Koehler and Critical illumination and where they find common application. We, then turn our attention to the spatial light modulator in the system which is an array of tiny micro-mirrors that can be rapidly (22KHz) turned ON and OFF. A detailed schematic of our proposed illumination system, which we refer to as a Sheridan source, is then discussed. The mathematical form of the resulting illumination field is derived and we examine some of its theoretical properties. Several different applications are proposed including how such a source could be used in new types of imaging systems within a computational optics frame work. © Anita Publications. All rights reserved.
Keywords: Speckle field, Digital Micro-mirror Device, Illumination optics, Coherence theory, Fourier optics, Structured illumination.

Peer Review Information
Method: Single- anonymous; Screened for Plagiarism? Yes
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