Thanks to - Precision Optical Laboratory

A full service optical lab 7148 Midlothian Turnpike

Richmond, VA 23225For Information Call 804-745-0171

Fax at 804-745-5817

Surfacing Overview In Pictures

Also Called: Generating, GrindingThe creation of lens power

through the grinding of curvesDL = D1 + D2

Surfacing Is --- 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= D1 + D2

DL = The power of a lens in diopters

D1 = The front curve or power D2 = The back curve or power DL = D1 is +8.00 D2 is -7.00 + 8.00 + -7.00 = +1.00 DL = +1.00

DL= D1 + D2

If the front base curve is a convex shape with positive or +8.00 power

And the desired Rx is +1.00 I will need to grind a concave

minus -7.00 curve on the back of the lens

Surfacing Is A 3 Step Process

Grinding (surfacing, generating) Removes material from back of lens

Fining Brings backside of lens to almost clear

Polishing Brings backside of lens to perfect

smooth clear finish that you can see through

Job Order FormsIt 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 BlanksA lab will stock thousands of them!

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

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

Protecting Lens BlankPlastic 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 blockThe block holds the lens in place through entire surfacing process

Lens blank is held to bock with alloy Block assures

proper alignment in grinder

Alloy creates bond with the lens & tape

Alloy is melted and reused

Lens blank attached to block

Note the various openings that hold block in the correct position

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

Surfacing Layout ScreenProvides all the information that the generator needs to complete the job

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 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 GeneratorNote Faint Red Axis LineLens back side is now an opaque smooth white with defined curves

Fining

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 TraySurfaced LensesLap 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.

FiningPerformed on a “cylinder machine”

Fining process

Lens Ready For Polishing

Note how thin the lens is now

Polishing Uses same

technique as fining but uses a soft pad and mild abrasive slurry instead.

Lens After Surface, Fine and PolishReady for de-blocking and finishing

Also See PowerPoint Presentation On Finishing

Finishing is the cutting of the surfaced lens to fit a frame

Labs Also 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!