Inspection periscope

Claim 1

An inspection lens for viewing a circumferentially disposed region within an internal, confined area of a structure of the type having inner and outer coaxial surfaces that form a narrow cylindrical passage, said lens comprising: an optically transparent tubular hollow cylinder having a central aperture therethrough surrounded by an inner sidewall, an outer sidewall, and first and second generally annular end surfaces; said cylinder being elongate in the direction parallel to said inner sidewall and said outer sidewall; said cylinder having a tapered outer wall to provide a thinning towards the end of the cylinder having said first annular end surface to permit a portion of said hollow cylinder having said first annular end surface to fit to varying depths between the inner and outer surfaces of said structure while a further portion of said hollow cylinder having said second annular end surface projects beyond said cylinder passage; said first annular end surface providing a focusing and magnifying function, said first annular end surface comprising a lens having in cross-section a curved, sloping optical surface extending between the inner and outer sidewalls for reflecting and focusing an image of said circumferentially disposed region at a predetermined distance from said first annular end surface through said transparent hollow cylinder toward said second annular surface; said second annular surface including an optical surface permitting focused viewing of said reflected image therethrough.