1. Joint Service General Purpose Mask (JSGPM) Presented by: James R. LeBlanc Vice President Fosta-Tek Optics, Inc.

2. Optical Plastic Lens Design Introduction Optical Mechanics Military Specification Issues Quality Lens Design Issues

3. Optical Mechanics Distortion Resolution Prism Correction Optical Power

4. Distortion Problems : –Distortion affect lens resolution –Causes Eye Strain –May cause nausea Solutions : –Mold construction –Mold optical polishing –Processing conditions –Increases Resolution Non-uniform surfaces refract light away from the focal point.

5. Resolution The ability of an optical system to distinguish between closely spaced objects. –The higher the resolution of a lens the greater amount of detail the wearer can identify. Resolution is tested using standardized test targets. –Target consists of a series of graduated lines of various spacing.

6. Test for Resolution

7. Prism Correction Adjust image position Necessary for properly sighting a target Adjusts the perceived location of an image.

8. Optical Power Measured in Diopters: –Related to the focal length of a lens. Protective lenses are typically designed to have no power ( i.e. 0.0 diopters). –No interference with the wearer vision. Protective lenses are typically design to be worn over corrective lenses.

9. Military Lens Specifications Specification Issues: –Optics must be design at the start of the project. –Industry input regarding optical design issues. –Critical tolerances on optical power of the lens must be firmly established. –Drawing and specifications must coincide properly. Optical Zones: –Defining the critical area (Zone A). –Defining the non-critical area (Zone B).

10. Optical Zones Zone A: –Critical area of the lens. –Should encompass visual field of the eye. –Highest optical quality requirements. Zone B: –Non-Critical area of the lens. –Minor imperfection in optical quality acceptable.

11. Quality Lens Design Optical issues should be addressed at the start of the design process. Specifications should coincide with production drawings. Critical zone size and location established properly. Quality mold construction & optical polishing. Correct processing techniques for minimum distortion and highest resolution.