Case Study: Testing Molded Plastic Lenses

Wells Research and Development (WRD) developed a special optical testing instrument for a manufacturer of inexpensive binoculars. The customer wanted to test the plastic double objective lenses but had a limited budget for equipment.

Before contacting WRD, the customer investigated, and eventually rejected, several conventional test strategies:

• Measuring the limiting resolution of the lenses (USAF chart) was easy to implement but did not correlate well with perceived image quality in the application.

• Full MTF testing correlated well but was rejected as too expensive.

• Interferometric testing was rejected because some of the surfaces were aspheres. In addition, interferograms were difficult to relate to image quality in the application.

WRD worked with this customer to select the final measurement strategy: image contrast (MTF) measured at a special spatial frequency. This test correlated well with perceived image quality and was within the manufacturer's budget. As an added benefit, the instrument could be reconfigured for afocal testing of finished binoculars.

If you have an optical testing problem that you would like to solve, without spending all of next year's budget too, contact Wells Research and Development, info@wellsresearch.com.