At the first try, we used a LDR panel for the alignment. But when proceeding we came across some issues with this method. When the distance between the transmitter and the receiver is increasing, all the LDRs get equal amount of light power due to scattering and dispersion effects. because of the issue we were not able to make the alignment between the transmitter and the receiver.

As a remedy we moved to use image processing techniques with the help of the same camera that we were using for the communication link.

Initially a blank image was captured and it was used as the reference image to find the centre of the image.

Then centre 4 LEDs were blinked and the image captured was processed and checked for the position of those LEDs related to the centre of the reference image.

The picture above depicts that the blinked LED positions are not at the centre of the receiver camera. In case the white patches are not at the centre. The arms of the receiver platform was programmed to move in x or y directions as required. This steps were repeated several times up until the receiver was aligned with the transmitter as shown in the last image.