Jiangsu Aogang Optical Glasses Co., Ltd.
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1.56 Flat-top Bifocal AR Coating Semi Finished Lens Blanks For Near And Far Vision
I. Technical Data:
| 1.56 Semi Finished Flat Top Bifocal Lens Blanks | |
| Material: 1.56 Index NK55 Resin(Ne=1.549, Abbe=38, Specific Gravity=1.28) Segment Placement: 5mm down -5mm in Add Power: +1.00 to +3.50 in 0.25D steps Segment Size: 28mm | |
| CONVEX SURFACE | CONCAVE SURFACE | ||||||||
| Mominal Curve | True Curve | Sag(sagitta: 40mm) | Sag(sagitta: 50mm) | Radius | Radius | CT(mm) | ET(mm) | Dia(mm) | |
| 1.549 | 1.530 | ||||||||
| 4.25 | 4.18 | 4.04 | 1.51 | 2.37 | 131.29 | 132.50 | 8.7 | 11.7 | 70 |
| 6.25 | 6.25 | 6.03 | 2.27 | 3.57 | 87.87 | 88.80 | 11.3 | 8.8 | |
II. Flat top bifocal lens:
----Segment Widths
Bifocal lenses are available with one segment widths: 28 mm. The number after the "CT" in the product name indicates the segment width in millimeters. The diameter 28 mm provides correspondingly wider fields of view.
----Flat Top 28 Bifocal Lenses
A flat top 28 bifocal lens is offers correction for both near and far distances. It is a multifocal lens commonly prescribed for those suffering from both presbyopia and hypermetropia, a condition whereby, with age, the eye exhibits a progressively diminished ability to focus on near and far objects. The flat top lens includes a segment at the lower half of the lens with a prescription for reading (near distance). The width of the flat top 28 bifocal is 28mm wide at the top of the bifocal and looks like the Letter D turned 90 degrees.
Because the flat top bifocal is one of the easiest multifocal lenses to adapt to, it is one of the most popular bifocal lenses in the world. It's distinct "jump" from distance to near vision gives wearers two well-demarcated areas of their glasses to use, depending upon the task at hand. The line is obvious because the change in powers is immediate with the advantage being it gives you the widest reading area without having to look too far down the lens. It is also easy to teach someone how to utilize the bifocal in that you simply use the top for distance and the bottom for reading.
III. Compared with CR39 1.499 flat top bifocals:
| Production | flat top bifocal lens | |
| Index | 1.499 | 1.56 |
| Monomer | CR39 | NK55 |
| Diameter/Segment | 70/28mm | 70/28mm |
| Abbe value | 56 | 38 |
| Specific Gravity | 1.33 | 1.28 |
| Thickness | Index 1.56 lenses will be thinner than Index 1.499 lenses in the same diopters. As the increase in diopters, the difference will be bigger. | |
| Weight | As the same prescription, the thickness is thinner, the lenses will be lighter. | |
| Transmittance | 1.499 lens has the highest transmittance as compared with 1.56 lens. | |
| ABBE value | According to ABBE value, 56 is higher than 38, that means 1.499 biocal lens can provide the more comfortable visual experience. | |
IV. Production Process:
V. Packing:
1. Envelope:
a) standard white envelope
b) color envelope with customer design (Weight: 157g, Size: 9*9*9cm)
2. Outer Box
a) standard export paper carton (Size: 38*48*35cm, 0.064CBMS)
b) Include about 500 pairs of finished lens (Weight: about 21kg) or include about 100 pairs of 100 semi finished lens (Weight: about 15kg)
VI. Shipping:
1. Samples:
a) Delivery time: 3-7 days (by Fedex, DHL, UPS, TNT etc.)
b) Sample is free, but accroding to our company rule, the shipping cost need to be assumed by customers.
2. Batch Goods:
a) Delivery time: 10-30 days (depend on your quantity, by air, sea or express)
b) Carrier: We can choose for you or offer us your cooperative company