How to make a smartphone microscope from CD ROM

A microscope is an optical device used to magnify small objects. A smartphone or camera can record this image. Dimensions, angles or areas can then be measured in the images. This lens can't match professional microscopes, but it has enough magnification for simple observations.

We take out the lens from the old CD-ROM optical drive. Different drives, CD, DVD, RW have different types and sometimes multiple lenses. You need to try which one will be suitable for a specific smartphone.

We have to attach the lens to the smartphone camera somehow. It is best to drill a hole in a piece of plastic or print the holder on a 3D printer.

Insert the lens into the hole of the holder.

How to make a simple smartphone microscope and measure dimensions at the micrometer level

We attach the holder with the lens to the camera.

We cut out the backing and cover glass from the thin foil. The paper serves as a white background for scattering light.

Place the smartphone at the correct height so that the image is sharp.

smartphone microscope

The light comes from the bottom of the sample, or we will use a smartphone diode to light it up.

Accurate measurement of dimensions

Everyone has probably heard the phrase that an optical fiber is as thin as a human hair. But what is the actual size of the hair? I only trust the data I measured myself. To measure the dimensions in the pictures, we must first take a picture of a scale. For example, a classic ruler.

Ako zmerať presné rozmery z obrázku mikroskopu v programe ImageJ

In the picture there are two lines of a photographed ruler between which there is a distance of 1 millimeter, which is equivalent to 1000 μm (micrometers). We will use the free program ImageJ. Select the straight line icon from the toolbar. We draw a segment from the center of one line to the center of the other.

From the menu, select: Analyze > Set Scale. We enter the value 1000 for the known distance. In our case, we enter μm in the Unit of length field. The software automatically converts the number of pixels per micrometer. We will also check the Global item, which will make the setting apply to all other images as well.

How to measure hair thickness

Let's open a photo with hair. The photo must have the same resolution and zoom at which the ruler was taken. We draw at least 3 lines in different places that represent the thickness of the hair. After each drawing of a new segment, we press the keyboard shortcut CTRL+M. This will record the values in the Results window.

For evaluation, we select Results > Summarize, and this calculates the arithmetic mean of the measured values. The measured average hair thickness is therefore 53 micrometers.