If you have access to the machine see the Screen_Capture module.
Which will give you the highest quality pixel image to work with and make things much easier.
If you cannot, include an image here in the forum and we can help you work through the issues ... taking pictures of screens is not an ideal way to go. You get a lot of noise and distortions but if you have no other recourse can be worked on.
Normally these feeds have XML, RSS, etc. digital feeds which you can access. Seems like that would be the best way to go. Using sensors like you mention will create more noise and potential for failure than a straight digital feed.