Pattern scanning device

A device for scanning the surface of a generally cylindrical object carrying a raised pattern thereon so as to detect that pattern, which device comprises:

• a. a transparent optical body having a substantially arcuate configuration about a first axis and having a convergent radial cross-section, and a channel parallel to and substantially co-axial with that axis, which channel presents a surface substantially parallel to the said axis, upon which the object whose surface is to be observed can be placed, and the underside of which channel surface serves as the optical base face to the convergent radial cross-section to the optical body;
• b. a source of incident light to be directed onto a light entry face of the convergent cross-section of the optical body, which source is an arcuate array of point light sources mounted with its longitudinal axis substantially co-incident with the longitudinal axis of the said optical body and adapted to direct a plurality of incident light beams onto the optical base face of said optical body, the configuration of the optical body being such that an incident light beam is adapted to strike the under-side of the said optical base face at substantially the angle of total internal reflection for the material from which the optical body is fabricated and to be reflected through a light exit face of the convergent cross-section of the optical body;
• and
• c. a means for observing the light reflected from the underside of the said optical base face through a light exit face of the convergent cross-section of the optical body and for providing a signal dependent upon the intensity of the light detected.

A transparent optical body suitable for use in scanning the surface of a generally cylindrical object carrying a raised pattern, the optical body comprising:

• a. a substantially central axial portion having a substantially circular or part circular radial cross-section;
• b. a second portion extending radially outward of the central portion and having a generally triangular radial cross-section to provide a light entry face to the optical body and a light exit face from the optical body;
• and
• c. an axial substantially circular or part circular cross-section recess having its longitudinal axis substantially co-incident with that of the said central portion, which recess presents an exposed surface substantially parallel to the said axis, the underside of which surface serves as the optical base face to the said second portion of the optical body, which recess is adapted to receive an object whose surface is to be scanned with at least part of the surface of the object in contact with the curved surface of the recess;
• the configuration of the optical body being such that an incident light beam shone onto one exposed face of the said second portion of the optical body is adapted to strike the under-side of the said optical base face of the recess at substantially the angle of total internal reflection for the material from which the optical body is fabricated and to be reflected through the same or another exposed face of the said second portion of the optical body, whereby light reflected at said surface of the recess can be detected by a light observing means.