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  • Continuous Diffuse Illumination Aids Package Inspection

Photonics Spectra
Feb 2003
Brent D. Johnson

Every year in the US, 770,000 medication errors are made, resulting in as many as 40,000 deaths -- more even than those from car accidents. Improved techniques for packaging, coding and inspection could significantly reduce these numbers, but the materials used in thermoform packaging pre-sent optical challenges that sometimes elude visual inspection regimes.

Thermoform machines often use platen printing to place product names, dosage, instructions and date/lot codes on the lid stock of tablets and capsules. Print issues such as low contrast and variations in quality can affect this information. These defects attract the attention of the Food and Drug Administration and reduce pharmacists' faith in the product, which can result in field complaints or even a recall.

A new inspection system from RVSI Acuity could reduce the number of drugs with labeling errors by resolving the issue of inspecting the printed material on reflective packaging.

The problem with inspecting thermoform packages is that they are covered with a shiny foil that acts like a mirror. In a typical inspection system, a light source is directed onto a tablet package, whereupon light from the sample reflects onto the detector, producing read errors.

A strobed Continuous Diffuse Illuminator enables the type on pharmaceutical foil packaging to be inspected without distortion.

To compensate for this reflection, RVSI Acuity integrated a strobed Continuous Diffuse Illuminator into its system. The patented device from Northeast Robotics of Weare, N.H., has two fiber optic bundles that provide Diffuse On-Axis Light and that illuminate an integrating sphere from a strobed xenon light source from PerkinElmer Optoelectronics of Fremont, Calif. The Diffuse On-Axis Light is bundled directly into the hole of the integrating sphere with a half-pass mirror. This fills in the hole and provides diffuse lighting for viewing the foil packaging.

The illuminator was the critical factor, said Jeffrey Snyder of RVSI Acuity. The "cloudy day" illumination allowed the system to read both paper and foil at the same time, a significant challenge With a machine speed of 35 indices per minute, four JAI CVM1 high-resolution CCD cameras and PC-based processing, it is possible to achieve 1300 x 1024 resolution with a 95 x 70-mm field of view. The system captures any defects, achieving 100 percent accuracy.

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