TIPS NO: 207
Revision:
Date: August 2000

 

 

1.56 EvoClear™ Single Vision Aspheric Lens

Purpose: The following information is intended to provide basic processing information for the 1.56 EvoClear Single Vision Aspheric lens. (Based on a 1.530 Tooling index.)

Single Vision Aspheric Lens
Characteristics & Dimensions

Characteristics

1.56 EvoClear Lens

Refractive Index

1.557

Dispersion Value (Abbe)

36.0

Density

1.240

Visible Light

91%

Rear Surface Coating

Recommended

UV Transmission Cutoff

392 nm

Chemical Resistance

Excellent

Machinability

Excellent

Blank Size:          74mm diameter
Base Curves:     0.50, 1.50, 2.50, 3.50, 4.50, 5.50, 6.50, 7.50, 8.50, 9.75
Power range:     -10.00 to +9.50

Nominal Base Curve

Actual Base Curve

Radius m/m

Sphere 50 mm SAG

** Aspheric 35 mm SAG

** Aspheric 60 mm SAG

Concave Curve

Edge Thickness

Center Thickness

0.50

0.54

981.481

0.32

0.18

0.57

3.00

15.7

12.6

1.50

1.44

368.056

0.85

0.44

1.39

3.00

15.7

13.8

2.50

2.28

232.456

1.35

0.68

2.07

3.00

15.7

14.9

3.50

3.51

150.997

2.08

1.02

3.04

6.00

15.6

12.2

4.50

4.51

117.517

2.69

1.30

3.84

6.00

15.4

13.2

5.50

5.49

96.539

3.29

1.57

4.56

6.00

13.6

12.5

6.50

6.49

81.664

3.92

1.86

5.41

6.00

13.8

13.9

7.50

7.50

70.667

4.57

2.16

6.36

6.00

11.7

13.2

8.50

8.58

61.772

5.29

2.49

7.41

6.00

10.1

13.4

9.75

9.56

55.439

5.96

2.78

8.34

6.00

9.9

14.7


 ** Aspheric sags are the actual (measured) sag values of the front surface.
These values are used to calculate the lens thickness. Use the Sphere Sag for calculating back curves.

General: These high index lenses have a refractive index of 1.557. Standard pads and polish materials used for surfacing CR-39® lenses can be applied to the 1.56 EvoClear Single Vision Aspheric lenses. If you have questions, please contact Technical Services at (800) 759-0075.

Abrasion Resistance Coatings: The front surface has the superior protection of the RLXPlusÒ non-tintable coating. The uncoated rear surface of the lens provides adequate durability for normal use. The application of a backside coating is an option that can be used if the lens will be worn in a highly abrasive environment. Using a backside coating after surfacing is always recommended when the lens will be anti-reflection coated. Either a tintable or non-tintable coating can be used. However, be sure to verify the impact resistance is maintained, particularly when using a non-tintable coating. Please call Technical Services for the latest test results with various backside coatings.

Tinting and Neutralizing: When using a tintable backside coating, the tinting performance and compatibility with specific neutralizers is coating dependent. We recommend against tinting prior to using a non-tintable coating. Coating applications can change the color or density of tinted surfaces. Special care must be taken when clamping 1.56 EvoClear Single Vision Aspheric lenses. The combination of edge pressure and high temperatures will cause warpage. You should position the clamp with only enough pressure to keep the lens from falling out. If the lens does warp during the tinting process, remove the warpage by setting the lens on a flat tray and bake in an oven at 175-200ºF for five minutes.

AR Coating: The compatibility of AR coatings with the backside coating should be confirmed. This should include impact testing. Using a backside coating after surfacing is always recommended when the lens will be anti-reflective coated. Please call Technical Services for the latest test results with various AR coatings. We recommend a minimum center thickness of 1.6 mm when a lens is AR coated.

Computer Calculation of Rx: The easiest and most efficient method to calculate and process values for an Rx is to use an existing computer software package that contains our 1.56 EvoClear aspheric design data. If your software company has not included our data in its package, our Technical Services group will be happy to provide your software vendor with the necessary specifications. Please forward us a contact name and phone number of your software vendor. If you do not have a software system for processing KODAK lenses, Signet Armorlite has developed the KODAK Lens Software Calculation Program. This program is available through Signet Armorlite's Technical Services Department.

Semi-Visible Markings: No semi-visible product codes are included on the 1.56 EvoClear Single Vision Aspheric lens.

Thermal Stability: The EvoClear lens material has a similar level of heat sensitivity as other high index materials. The lens can flex if heated while under pressure. To prevent warpage, avoid heating the lens over 130º F while it is under pressure from frame or clamping. Warpage can cause a plastic lens to fit loosely in the frame. If the lens should become warped, heat without pressure and allow the lens to return to its original shape.

Base Curve Selection: We have provided two base curve selection charts. The STANDARD version should be used by labs using 3-axis generators that can process very flat back curves for higher plus powers. The MODIFIED version should be used by labs with generators (Diamond wheel generators) that are limited to a minimum concave curve of 2.75 diopters.

CR-39 is a registered trademark of PPG.
RLXPlus and EvoClear are registered trademarks of Signet Armorlite, Inc