Detectability of unresolved particles in off-axis digital holographic microscopy

Off-axis digital holographic microscopy (DHM) provides both amplitude and phase images, and so may be used for label-free 3D tracking of micro- and nano-sized particles of different compositions, including biological cells, strongly absorbing particles, and strongly scattering particles. Contrast is provided by differences in either the real or imaginary parts of the refractive index (phase contrast and absorption) and/or by scattering. While numerous studies have focused on phase contrast and improving resolution in DHM, particularly axial resolution, absent have been studies quantifying the limits of detection for unresolved particles. This limit has important implications for microbial detection, including in life-detection missions for space flight. Here we examine the limits of detection of nanosized particles as a function of particle optical properties, microscope optics (including camera well depth and substrate), and data processing techniques and find that DHM provides contras..., These datasets were collected using a common model digital holographic microscope as described in 
J. K. Wallace, S. Rider, E. Serabyn, J. Kuhn, K. Liewer, J. Deming, G. Showalter, C. Lindensmith, and J. Nadeau, Opt Express 23, 17367 (2015).
Sample chambers were either a coverslip on a microscope slide (\"flat\") or a coverslip on a slide separated by a silicone gasket of thickness 0.8 mm (\"thick\").
All wavelengths were 405 nm unless specified otherwise.
Frame rate was the maximum frame rate of the system and could be variable, use timestamps file for precision., , # Detectability of unresolved particles in off-axis digital holographic microscopy

## Description of the data and file structure

The datasets include a series of 2048x2048 pixel tiff files representing a DHM video at approximately 7 frames per second. The timestamps file provides exact timestamps for each image. The images are raw holograms taken with a \"common-mode\" off-axis DHM.

\"Flat\" indicates a sample chamber of a coverslip + slide

\"Thick\" indicates a 0.8 mm gasket between coverslip and slide.

Illumination wavelength was 405 nm unless specified to be 520 nm.

## Code/Software

The data were acquired using the software KOALA (LynceeTec).

Analysis may be performed using any holographic reconstruction software that reads tiff files. The package that we used for our published reconstructions is a Fiji plug-in available here:

The following are the datasets

 

**30 nm alumina**

Flat slide

2022.07.27 10-57

Thick chamber

2022.07.27 11-14

 

**100 nm alumina**

Flat slide

2...