Computer Vison geometry: distance estimation of moving object from single fixed camera

Question

I have a problem that I am still not sure if it's solvable. I have a system with a single fixed camera pointing to a fixed background (i.e., a wall). the distance between lens and background (at the image centroid) is known, as well as camera characteristics (H/V FOV, f, etc.). An object of unknown dimension is passing through the camera FOV with a certain unknown trajectory, and the camera is taking continuous pictures of it (i.e., from different angle), is there a way to estimate it's distance from the camera. Maybe it's an easy problem or maybe it's impossible. I am just quite new to it, and from my readings I cannot find so far a similar case. Thanks for feedbacks and help.