ADNS 2620 Mouse Sensor and Lens?

MAIN QUESTION: What is a good simple way to hack together my own tiny lens that can go over a mouse sensor chip to allow it to focus about 10-20 cm away?

I bought a bunch of these mouse sensors (which are basically tiny cameras) right before I came down to panama I was hoping they could solve an ant-traffic monitoring problem I will be working on for the next few months. I basically need a really cheap device that I can point at part of a tree, and have it tell me whether or not an ant is walking by. Here’s a bigger description of the problem (with pictures!) (Main Pic

Anyway through some quick hacking (still don't have a resonator for it until next week), i managed to get the thing working.

So after lots of messing around, i got the first steps to it working going on! Based off this:

I modded an arduino sketch and a processing sketch to read the image, and display the image in processing:

Go into the examples folder and look for ADNScamera for the arduino, and the readmouseimage sketch for the corresponding one.

Things are STILL way hacky. The guy from has a nice pinlayout and schematic, but I didn’t have an oscillator, so I just put at jumper wire between the osc in and out. I’m sure this is bad, but it actually functions and responds! I also don’t have a lens for it.