There are 4 things that limit the depth of field (the distance range from the camera where things are in focus): the accuracy of the lens, the size of the aperture (and consequently how bright is the object and how sensitive is the detection of that light), how long the exposure is (more time is more light), and the size of the object (small objects reflect less light). I want to film live rodents which challenges all aspects of depth of field: small, fast, cannot handle bright lights, and move in tight spaces that cannot handle big cameras or long distances from the camera. I am reading an article (link below) that proposes on page 24 that one solution is to have an array of lenses of different focal lengths positioned very close to each other and then use processing on the electronic chip that detects the images to determine the clear focus of all the different focal lengths. This adds a lot of complexity making such an idea impractical for something I might make myself. It is also not linear (a set number of focal lengths) and limited (you cannot go and change things for extreme situations). The idea I had at this point (and recording here before I forget) is to move a fine wire between the lens and the detection chip rapidly and possibly have two such wires moving 90 degrees apart and at different rates (to avoid a blind diagonal line where they cross). The dimming of the signal as the wire crosses the various rays can be used to calculate the exact angle of each ray to composite a 3-dimentional map of 2-dimetional image over all distances between lens and detection surface.