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Basic lensless imaging for low-cost microscopy

My attempt to build a microscope without the most expensive part.

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The cost of research-grade microscopes is largely determined by the quality of the optics. In particular, objective lenses can cost multiple thousands of dollars, a fact which prevents many people from having access to good microscopes for biological, medical, and hobbyist purposes.

Recent research in computational imaging has demonstrated that one may acquire high quality microscopic images using a cheap CMOS imager combined with computer code that models how light propagates through space. In this project, I will use these ideas to build my own lensless imaging system in an attempt to find cheap ways that make optics more "hackable."

Project Requirements

The goal of this project is to develop and implement a simple, low-cost system for lensless imaging of microscopic objects such as single-celled organisms, tissue, gels, and colloids. The main requirements of this system are as follows:

  1. The system should be affordable. By this I mean it should not be prohibitively expensive to implement by non-specialists such as hobbyists and students. USD 500 is an approximate upper limit on the cost of this imaging system.
  2. The system should be capable of video-rate imaging of microscopic objects. (The imaging need not necessarily be live.) Since this project is largely exploratory and a means for me to determine the capabilities of developing a low-cost imager, I am not placing strong requirements on the spatial or temporal resolutions of the system.
  3. The system should output images, i.e. two-dimensional arrays of numbers and metadata describing how they were produced.
  4. The system must use open-source software that is user-friendly and well-documented. Emphasis will be given to easy-to-use languages such as Python and well-established frameworks such as ImageJ to ensure portability and facilitate sharing of the system components.
  5. The system hardware must be easily acquired and user-friendly. Emphasis is given to platforms such as the Arduino and Raspberry Pi that are both affordable and for which a large online user base/community already exists.

Literature

  1. Ozcan and McLeod, Lensless Imaging and Sensing, 2016
  2. Görörcs and Ozcan, On-Chip Biomedical Imaging, 2013
  3. Latychevskaia and Fink, arXiv, 2016
  4. Aidukas, et al., bioRxiv 2018

Related Software

  1. Poppy - Physical optics simulations in Python
  2. HoloPy - Digital holography and light scattering tools in Python

Misc. Links

  1. Manoharan Lab at Harvard
  2. PLoS One Paper on Open-Source 3D Printed Optomechanics
  3. A Vision Solution with the USB 3.0 Board Level Camera
  4. Choosing the Right Camera Bus

LDD_v1.jpg

The very first prototype of the LM317T-based laser diode driver. This was just to make sure that I got the current and voltage calculations correct. It still needs a filter cap and transistor switch for the Raspberry Pi.

JPEG Image - 231.03 kB - 08/05/2017 at 15:57

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propagating_hologram_with_noise_poor.mp4

This is the same hologram as before but with severe sensor noise added. It demonstrates how realistic hologram simulations need to include noise from the camera and how this noise will look in the simulations.

MPEG-4 Video - 1.13 MB - 07/14/2017 at 06:23

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propagating_hologram.mp4

The propagation of a simulated hologram along the axial direction. The object is a circular, non-absorbing object 10 micrometers in diameter.

MPEG-4 Video - 284.00 kB - 04/29/2017 at 09:57

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