Optical system for periscopic sextant

Claim 1

AN OPTICAL SYSTEM FOR A PERISCOPIC SEXTANT USED IN CONJUNCTION WITH AN EXTERNAL AZIMUTH SCALE OF THE CHARACTER DESCRIBED COMPRISING A PERISCOPE TUBE, SAID AZIMUTH SCALE POSITIONED COAXIAL WITH SAID PERISCOPE TUBE AT THE UPPER END THEREOF, FIRST LENS MEANS ALONG SAID TUBE FOR DERIVING A BEAM FROM A CELESTIAL BODY, AN EYEPIECE SECTION TRANSVERSELY EXTENDING FROM THE LOWER END REGION OF SAID TUBE AND CONTAINING A COMMON FOCAL PLANE AND OCULAR LENSES FOCUSED AT SAID FOCAL PLANE, A SEMI-REFLECTIVE PELLICLE AT THE LOWER END REGION OF SAID TUBE BETWEEN SAID FOCAL PLANE AND SAID FORST LENS MEANS, SAID FIRST LENS MEANS PROJECTING THE CELESTIAL BEAM FIRST DOWNWARDLY TO REFLECTING MEANS AND THEN IN A TRANSVERSE DIRECTION THROUGH SAID PELLICLE TO SAID FOCAL PLANE, AND THEREBY CREATING A REAL IMAGE OF THE CELESTIAL BODY AT THE COMMON FOCAL PLANE, LAMP MEANS MOUNTED EXTERNAL OF SAID PERISCOPE TUBE; SECOND OPTICAL MEANS INCLUDING AN ILLUMINATING LENS FOR PROJECTING A LIGHT BEAM FROM SAID LAMP MEANS UPWARDLY UPON SAID AZIMUTH SCALE, SAID SECOND OPTICAL MEANS ALSO INCLUDING A LENSE ARRANGEMENT VERTICALLY EXTENDING ADJACENT SAID PERISCOPE TUBE AND SAID ILLUMINATING LENS TO FORM A REFLECTED IMAGE BEAM OF A PORTION OF THE SCALE ILLUMINATED BY SAID LAMP MEANS AND PROJECT IT DOWNWARDLY THROUGH AN OPENING EXTENDING INTO SAID PERSISCOPE TUBE, WITH SAID AZIMUTH SCALE BEAM INCIDENT ON SAID PELLICLE AND PASSING THERETHROUGH, A SMALL REFLECTOR POSITIONED BELOW SAID PELLICLE FOR THEN REFLECTING SAID AZIMUTH SCALE BEAM AGAINST THE OPPOSITE SIDE OF SAID PELLICLE, SAID PELLICLE POSITIONED TO TRANSVERSELY DIRECT SAID AZIMUTH SCALE BEAM AS A REAL IMAGE AT SAID COMMON FOCAL PLANE, A RETICLE EXTERNAL TO SAID PERISCOPE TUBE AND BELOW SAID LAMP MEANS FOR ILLUMINATION THEREBY, A PENDULOUSLY MOUNTED MIRROR POSITIONED BELOW SAID PELLICLE, THIRD OPTICAL MEANS ARRANGED TO DIRECT A BEAM OF SAID RETICLE ILLUMINATED BY SAID LAMP MEANS DOWNWARDLY INCIDENT ON THROUGH SAID PELLICLE TO SAID PENDULOUS MIRROR, SAID PENDULOUS MIRROR REFLECTING SAID RETICLE BEAM TO BE INCIDENT AGAINST THE OPPOSITE SIDE OF SAID PELLICLE, SAID PELLICLE POSITIONED TO TRANSVERSELY DEFLECT SAID RETICLE BEAM AND CREATE A REAL IMAGE OF SAID RETICLE AT SAID COMMON FOCAL PLANE, SAID SMALL REFLECTOR LATERALLY DISPLACED FROM THE PATH OF THE RETICLE BEAM AND OF SUFFICIENT DIMENSIONAL EXTENT TO REFLECT THE AZIMUTH BEAM WHILE AVOIDING INTERFERENCE WITH THE RETICLE BEAM, SAID PELLICLE REFLECTING BOTH SAID REFLECTED SCALE BEAM AND ILLUMINATED RETICLE BEAM INTO SAID FOCAL PLANE OF SAID EYEPIECE, WHEREBY SIMULTANEOUS OBSERVATION AT THE EYEPIECE IS AFFORDED OF REAL IMAGES OF THE CELESTIAL BODY, REFLECTED SCALE PORTION AND THE ILLUMINATED RETICLE.