Optical rifle boresight alignment apparatus and method

An apparatus for aligning a riflescope on a rifle having a barrel with a barrel bore and a muzzle, the rifle having a mounted adjustable riflescope, the riflescope having an eyepiece end, a riflescope reticle, and an objective end, the apparatus comprising:

• an illumination multiplexer placed in proximity to, and aligned with, the eyepiece, the illumination multiplexer including a light source, or cooperating with an external light source, followed by a beam splitter, the illumination multiplexer constructed to supply an outgoing beam passing through the beam-splitter into the eyepiece, the outgoing beam passing through the riflescople reticle and along the barrel to an opto-mechanical module;
• the opto-mechanical module being attachable to the barrel between the objective end of the riflescope end the muzzle, the opto-mechanical module having a vee-clamp attachment member, the vee-clamp attachment member cooperating with the barrel rigidly to hold the opto-mechanical module to the barrel, and to align the opto-mechanical module with the barrel bore, the opto-mechanical module including an optical reference constructed to provide a return light beam aligned with the barrel bore;
• the return beam containing a first image, the first image being an image of the riflescope reticle, or an image of a target reticle, the return beam passing in a reverse direction through the objective end of the riflescope, the riflescope reticle and the eyepiece, to produce a composite return beam, the composite return beam containing superposition of the first image and a second image, the second image being a shadow image of the riflescope reticle, the composite return beam entering the beam splitter;
• the beam splitter being configured to provide a lateral reference image of the composite return beam containing both the first and second images;
• the apparatus being constructed so that when the riflescope is misaligned with the rifle bore, the first and second images are both visible and show two reticle images misaligned with one-another, and when the riflescope is aligned with the rifle bore, the first and second images align with one-another, and only one reticle image is seen.