High-resolution image acquisition using a compact microlens-coupled detector

Daniel Unholtz; Ralf B. Schulz; Wolfhard Semmler; Jörg Peter

doi:10.1117/12.728465

Abstract

Recently, we have presented a thin optical detector assembly consisting of a microlens array (MLA) coupled to a large area CMOS sensor through a septum mask. The sensor is placed in the physical focal plane of the MLA. Each lens of the MLA forms a small image on the sensor surface, with individual images being separated from each other by the septum mask. The resulting sensor image thus shows a multitude of small sub-images. A low-resolution image can be attained by extracting only those pixels that are located on the optical axis of a microlens, as reported previously. Herein we describe an improved post-processing method to extract images of higher resolution (which can be focused to an arbitrary plane) from a single raw sensor image: Each lens of the MLA results in a mapping from points in object space to corresponding sensor pixels. By tracing back the light paths from sensor pixels through the lenses onto an arbitrary focal plane in object space this mapping can be inverted. Intensities captured on individual sensor pixels can be attributed to virtual pixels on that focal plane using the computed inverse mapping. As a result, from a single acquisition by the detector, images focused to any plane in object space can be calculated. In contrary to the approach of extracting focal point intensities, the spatial resolution is not limited by microlens pitch. We present experimental examples of extracted images at various object plane distances and studies determining the spatial resolution.

Citation Download Citation

Daniel Unholtz, Ralf B. Schulz, Wolfhard Semmler, Jörg Peter, "High-resolution image acquisition using a compact microlens-coupled detector", Proc. SPIE 6631, Novel Optical Instrumentation for Biomedical Applications III, 66311F (18 July 2007); doi: 10.1117/12.728465; https://doi.org/10.1117/12.728465

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