What are the pics called that have objects hidden in them?

Question

i cant remember the proper name of these pics, but in order to see the hidden image, you have to get right up close to it and slowly back away to adjust your eyes to see the pic...and when you do see the image its like im 3-d

Answer 1

I'm not sure exactly what they are called.

Is this similar to what you mean?

http://www.smart-kit.com/scategory/brain...

Answer 2

stereograms