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Data Acquisition

Overview

In this section we will acquire image data using mobile devices.

We will honor the method devised by Antonie Leeuwenhoek in the 1600s. It is said that Leeuwenhoek performed some his earlier microscopy observations by using a drop of water as a powerful spherical lense.

This is decribed in more detail in this blog.

A drop of water typically will have a radius of about one or two millimeters, resulting in a large magnification power.

The magnification will be inversely proportional to the radius of the water drop. Therefore, it is desirable to make the drop as small as possible, while still keeping it well rounded. In this exercise we will place the water over a glass surface, therefore creating a half-spherical lense.

Hands-On

Acquisition Overview

Device

Use a mobile device

  • Cell phone
  • Tablet

Water

  • Get half a glass of water
  • Get a napkin

Slide Covers

  • Get cover slides from instructors
  • Be careful with the pieces of glass, they are very thin and can easily cut your skin.

Post-Its Notes

  • Get a block of post-its notes from instructors
  • This will be used to hold the cover slides
  • Distance to the camera will be adjusted by placing the cover slide in different 'pages' of the post-it block.

Camera selection

  • Identify if it has a forward facing camera, and if so, select this camera.
  • Verify that the camera and its surrounded area is covered in glass.
  • The camera area should not be vulnerable to water infiltration.

Acquisition

Water Drop

Water Drop

  1. Place the device on a flat surface.
  2. Immerse your finger in the glass of water as to draw a drop of water.
  3. Place the drop of water on top of the camera.
    • Make sure to place the water well centered on the camera.
    • Make the drop as small as possible, yet cover the sensor.

Object

Finger Focus

  1. Hold a small object or the tip of your finger in front of the water drop, without touching the drop.
  2. Monitor the image of the object in the screen of the mobile device.
  3. Once you get the object in focus, press the acquisition button.
    • Note that the object might only be in focus at the center of the image, this is a normal aberration for spherical lenses.
  4. Repeat until you master the process
  5. Note that some devices may allow you to use a timer to acquire an image.
    • For example, give a delay of three seconds between the time you press the button and the time the image is taken.
    • This may help to hold the sample at the right location for it to be in focus.
  6. Note that you could either acquire a still image or a video sequence.

Microscopy Samples

Cover Slide Position

  1. Take the microscopy samples distributed by instructors.
    • It typically will contain some microscopic organisms floating in a solution.
  2. Put a drop of the sample in a glass cover slide.
  3. Place the glass slide just above the water drop lens.
  4. Adjust the position until you see the sample in focus.
  5. Acquire the image.
    • Blocking any direct light with your hand may improve the illumination of the sample.

Examples

Examples of data acquisition can be seen at


http://www.kitware.com/blog/home/post/253


http://dx.doi.org/10.6084/m9.figshare.1051751


http://dx.doi.org/10.6084/m9.figshare.1058904

http://dx.doi.org/10.6084/m9.figshare.1058902

http://midas3.kitware.com/midas/folder/11394