how do i make my own opaque projector?

Answer 1

With considerable difficulty. The old style requires a very bright light, a cooling system, a good large lens, a flat sheet of glass and a front surface mirror to change the direction so the book or paper can be laid flat and the image projected out. Then it is nothing more than a box to hold things in place. The focus distance is maintained by putting the glass at the bottom and pressing the paper or book up against it.
In theory, getting a lens from Edmund Optical or similar online company and using a bright projector bulb, it might be done for under $100. The requirements are less if you are not going to throw the image very far and can make the room very dark.
For a similar amount of money, you could use a color or B&W CCD camera and send the signal to a monitor or for a lot more money to a projector.