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Joint Service General Purpose Mask (JSGPM). Presented by: James R. LeBlanc Vice President Fosta-Tek Optics, Inc. Optical Plastic Lens Design. Introduction Optical Mechanics Military Specification Issues Quality Lens Design Issues. Optical Mechanics. Distortion Resolution
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Joint Service General Purpose Mask (JSGPM) Presented by: James R. LeBlanc Vice President Fosta-Tek Optics, Inc.
Optical Plastic Lens Design Introduction • Optical Mechanics • Military Specification Issues • Quality Lens Design Issues
Optical Mechanics • Distortion • Resolution • Prism Correction • Optical Power
Distortion Non-uniform surfaces refract light away from the focal point. • Problems: • Distortion affect lens resolution • Causes Eye Strain • May cause nausea • Solutions: • Mold construction • Mold optical polishing • Processing conditions • Increases Resolution
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.
Prism Correction Adjusts the perceived location of an image. • Adjust image position • Necessary for properly sighting a target
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.
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). Military Lens Specifications
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.
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.