3D vector from using a 2D camera

Hi,

Is it possible to measure the distance of an object to you using a camera and clever optics? We are allowed to take consecutive shots and object may be moving towards or away from us. Image can be distorted since we only want to know the distance, the beauty of the image is not a concern.

I guess I am trying to figure out the 3rd dimension motion vector when there is motion from a 2D camera and a special lens in front of it.

Thanks,
F.

Easiest way is to fire a laser when the image is captured, and use trigonometry (In the image, the dot will be in a position depending on how far the object is away).

May be difficult to hit the object with laser. I am hoping to find a totally passive solution.

I don't think it is possible, unless you are allowed to take the second image from a different position and hence use parallax/trig or something. Otherwise, you have no idea how large/small an object is, so not possible to figure out it's distance unless the microprocessor has some more knowledge of the scene that it is viewing (e.g. if it has beforehand knowledge of the distance of some other objects that it can see).
However, this is just a guess.. I'm no expert in this area : (