Measurement of transparent container sidewall thickness

A method of measuring wall thickness of transparent cylindrical containers that comprises the steps of:

• (a) moving the containers transversely of its axis along a defined path and simultaneously rotating the containers about their central axes,
• (b) directing light energy onto each container traveling in said path, at an angle to the axis of the container such that a portion of the light energy is reflected from an outer surface of the container wall and a portion is refracted into the container wall and reflected from an inner wall surface,
• (c) directing into a light sensor portions of the light energy reflected from the outer and inner wall surfaces along a light paths coplanar with said axis, and
• (d) measuring wall thickness of each container as a function of separation at said sensor between said light portions reflected from the inner and outer wall surfaces of the container.

Apparatus for measuring wall thickness of a container, which comprises:

• a conveyor for moving the container transversely of its axis through an inspection station and simultaneously rotating the container about its axis,
• a light source and an illumination lens system for directing onto a wall of the container, as it passes through said inspection station, a line-shaped light beam having a long dimension perpendicular to the axis of the container and parallel to the direction of movement of the container through the inspection station,
• a light sensor and an imaging lens system for directing onto said sensor light energy reflected from portions of the outer and inner wall surfaces that are perpendicular to light energy directed onto the container as viewed from a direction parallel to the container axis, and
• an information processor responsive to light energy directed onto said light sensor by said imaging lens system for determining thickness of the container between said outer and inner wall surfaces.