Lensless, reflection-based dark-field microscopy (RDFM) on a CMOS chip

Meruyert Imanbekova, Ayyappasamy Sudalaiyadum Perumal, Sara Kheireddine, Dan V. Nicolau, Sebastian Wachsmann-Hogiu

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


We present for the first time a lens-free, oblique illumination imaging platform for on-sensor dark- field microscopy and shadow-based 3D object measurements. It consists of an LED point source that illuminates a 5-megapixel, 1.4 µm pixel size, back-illuminated CMOS sensor at angles between 0° and 90°. Analytes (polystyrene beads, microorganisms, and cells) were placed and imaged directly onto the sensor. The spatial resolution of this imaging system is limited by the pixel size (∼1.4 µm) over the whole area of the sensor (3.6×2.73 mm). We demonstrated two imaging modalities: (i) shadow imaging for estimation of 3D object dimensions (on polystyrene beads and microorganisms) when the illumination angle is between 0° and 85°, and (ii) dark-field imaging, at >85° illumination angles. In dark-field mode, a 3-4 times drop in background intensity and contrast reversal similar to traditional dark-field imaging was observed, due to larger reflection intensities at those angles. With this modality, we were able to detect and analyze morphological features of bacteria and single-celled algae clusters.

Original languageEnglish (US)
Pages (from-to)4942-4959
Number of pages18
JournalBiomedical Optics Express
Issue number9
StatePublished - Sep 1 2020
Externally publishedYes

ASJC Scopus subject areas

  • Biotechnology
  • Atomic and Molecular Physics, and Optics


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