This is the view through the cat door. Below  is the view with the big door open. It's a wooden box with the hole on the far end just wide enough for Flo (and not wide enough for raccoons). To the right of the hole there is the light, to the left - the mirror, and inside the yellow plastic (hopefully waterproof) box is the digital camera, Kodak DVC323, connected to the computer via the USB port.

 The yellow box used to be a lantern, it has a glass window at the front. Through the mirror, the camera looks straight at the light.

This is what the camera sees normally.

And this is what it sees when Flo sticks her head in from the street. The image is captured as soon as the center of the picture becomes dark. At this point our software analyses the image to determine if Flo is carrying anything in her mouth.

This is how it looks if she does. The decision whether to unlatch the door has to be made within about a second - this is how long it typically takes Flo to reach the cat door from this position in front of the light.