Transcript Joint Service General Purpose Mask (JSGPM) - Fosta-Tek

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.
Test for Resolution
Telescope
Test Target
Sample Lens
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.
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).
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.