Thanks to Precision Optical Laboratory A full service

Thanks to - Precision Optical Laboratory A full service optical lab 7148 Midlothian Turnpike Richmond, VA 23225 For Information Call 804 -745 -0171 Fax at 804 -745 -5817

Surfacing Overview In Pictures Also Called: Generating, Grinding The creation of lens power through the grinding of curves DL = D 1 + D 2

Surfacing Is --n n How a lens is created Lens begins as a chunk of plastic (or glass) that is finished on the front but is just raw plastic (or glass) on the back The back side is ground away with great precision with specific curves to match the curve on the front This creates the necessary power or prescription

The Nominal Lens Formula DL= D 1 + D 2 n n n DL = The power of a lens in diopters D 1 = The front curve or power D 2 = The back curve or power DL = D 1 is +8. 00 D 2 is -7. 00 + 8. 00 + -7. 00 = +1. 00 DL = +1. 00

DL= D 1 + D 2 If the front base curve is a convex shape with positive or +8. 00 power n And the desired Rx is +1. 00 n I will need to grind a concave minus -7. 00 curve on the back of the lens n

Surfacing Is A 3 Step Process n Grinding (surfacing, generating) n n Fining n n Removes material from back of lens Brings backside of lens to almost clear Polishing n Brings backside of lens to perfect smooth clear finish that you can see through

Job Order Forms It takes thousands of individual calculations to determine what curves will be ground.

Lens blanks come from the factory finished on the front but just raw plastic on the back

Lens Blanks A lab will stock thousands of them!

Lens Blank Stock S/V, Lined, Progressive, Transition, Polarized, Occupational, CR-39, Poly, Glass, Hi-Index…

Preparing Lens Blank For all sphero-cylinder lenses axis position must be marked before blocking the lens

Protecting Lens Blank Plastic film placed over the front of the lens protects it from heat and scratching

Lens Is “Blocked” Alloy or wax is used to hold the lens blank to the surfacing block The block holds the lens in place through entire surfacing process

Lens blank is held to bock with alloy n n n Block assures proper alignment in grinder Alloy creates bond with the lens & tape Alloy is melted and reused

Lens blank attached to block n Note the various openings that hold block in the correct position

Job Ready for Surfacing Job ticket for grinding parameters, lenses attached to blocks

Surfacing Layout Screen Provides all the information that the generator needs to complete the job n n n n Job number Base curve Cross curve Center thickness Crib diameter Pin Bevel Layout Axis Prism Front curve Back curve Edge thickness Diameter Material Block Tool Aren’t you glad we have computers!

Generator Cutting Wheel and Chuck Chamber n n n The orange nozzle sprays water on the lens and tool for cooling The tool seen on the right has diamond blades that will cut away the back of the lens The lens is seen on the left

Lens Off Generator Note Faint Red Axis Line Lens back side is now an opaque smooth white with defined curves

Fining n n n Lens is chucked in machine Lens is sandwiched between block and a mild abrasive pad Water or lubricant is sprayed on pad while pad oscillates over a tool that matches the backside curves with near perfect precision

Job Tray Surfaced Lenses Lap Tools With Fining Pads

A lab must stock thousands of tools to match the nearly infinite number of prescription curves

Tools may be for spheres or sphero-cylinder prescriptions

Machine holds lens in place using the block and pushes it against the tool which is covered with an abrasive pad.

Fining Performed on a “cylinder machine”

Fining process

Lens Ready For Polishing Note how thin the lens is now

Polishing n Uses same technique as fining but uses a soft pad and mild abrasive slurry instead.

Lens After Surface, Fine and Polish Ready for de-blocking and finishing

Also See Power. Point Presentation On Finishing is the cutting of the surfaced lens to fit a frame

Labs Also n n n n Stock single vision un-cut lenses Tint lenses Drill lenses Assemble complete pairs Add decorative touches to lenses Some stock frames Some apply anti-reflective coatings in house Labs can be as small as a few hundred square feet or as large as a factory

TAKE A TOUR! Contact your nearest optical lab and ask for a detailed tour. Ask Questions! Spend the day! LEARN!