A through-the-lens method and system for focusing a projected image onto an imaging surface employs a confocal process and apparatus. Electromagnetic radiation projected through a subresolution aperture of origin located in an object plane passes through a confocal imaging device which forms an image of the aperture in the image plane. The radiation strikes the surface and is reflected back through the confocal imaging device to the aperture. The power of reflected radiation passing through the aperture is detected/measured. The distance between the imaging surface and the imaging device is then adjusted to maximize the detected power.