Near infrared corresponds to wavelengths between 700 and 1000nm. We will use this feature of the camera to track the IFP signal. This is especially useful for us, as few things emit infrared signal, it reduces the background noise

The idea is to collect the spectrum up to near infrared wavelengths and then use a filter to eliminate the visible spectrum.

Light tracking

In order to view the light change in a chamber, we need to track the light intensity. For this part, we made a custom C++ code using OpenCV (you can find the entire code there https://github.com/arthurgiroux/igemtracking/).

You can find the result output here:

The most common color space used in programming is RGB, where the pixel color can be split into three components - Red, Green, Blue – each taking a value between 0 and 255.

However, there are many other color spaces, each adapted to a different application. In our case, we are interested in light intensity and not in colors. This made us choose another color space: the YcrCb.

In the YCrCb color space, each pixel is decomposed into three components:

• Y – the luma value (intensity)
• Cr – the red difference
• Cb – the blue difference

Lenses

The Raspberry Pi camera that we use has a fixed lens which is not adapted to what we want to do, as we cannot change the focus, the aperture or the zoom.

We searched for a different lens which would allow us more control, and found that the easiest way was to remove the initial Raspberry Pi lens, put a CS mount on it and attach a much bigger lens.

The first thing we did was to unplug the camera module from the PCB. Then, the lens was carefully removed by unscrewing it and the new lens was mounted.

You will then see the camera sensor (CMOS).

The CS mount was screwed on the board and the lens plugged in.

You can see here what the lens sees:

We can clearly see the chambers of the microfluidic chip.