After a simple elaboration of the coordinates sent to the PC:
Overlaying the image taken by the webcam with the one reconstructed the result is:
Limits:
The system presents many limits, both physical and hardware:
the surface must be suitable: it has to be opaque enough to absorb the laser without spreading reflections
the lighting conditions are important: if the background is too bright the program can't find the laser
the picture rate is limited
the laser point is not very accurate
the hardware isn't very powerfull: 700 Mhz processor, 512 Mbit RAM
Improvements:
These measures can improve the performances:
using a better quality webcam
using a more accurate laser pointer
using a pen with a led instead of a laser pointer for better accuracy
using Linux on PC
Conclusions:
Although the
performances obtained with this project can't be compared with those of
a real graphic tablet, the result can still be considered acceptable
for the creation of doodles and rough drawings, expecially because of
the small cost of the components (30-40 €) and the reusability of
the Raspberry Pi. Of course, like in real drawings, the results
are greatly affected by the ability of the user: in the exemple above I
wasn't able to properly follow the word writted on the background, so
the result is not really great, but with more patience and a better
hand it could have been really good.
