Let's start with an image of nothing.

Just a white noise...

Now, I managed to calibrate it better and run on the same surface to see if it gave me same (give or take) image.

My raster scan is not perfect as you can see this comb shape image.

Another problem I've noticed is that images are quite binary it each not touching (and getting 100-150) the surface or it does and goes to 240-250.

The yellow color is where fork touches something the blue/green is where nothing detected.

Contrast is another issue, it took me lots of trials to get a better contrast:

Last but not least is that I don't know what I see. I have only one sample of CD-RW surface which I have ripped off. Some places have information and others don't. I don't really have control over where I land in this nano world. 

Some claims to see atoms with STM, using similar piezoelectric discs, those structures are sub nano. Red laser, CD RW has 0.8micro size grooves and 1.6micro spaces between them. 

So, I've tried to change step sizes from 10 to 100. Still I don't seen the groves although I see some forms and they repeat until I restart the setup. 

I feel like this joke: the surgery was successful the patient died. 

I got working machine but the magnification so powerful I don't even know what to expect.