Danyang manufacture Semi finished SF cr39 1.49 bifocal round top eyeglasses optical lens blanks

I. Specification

II. Technical Data

• Round Top Bifocal Lenses

As people age, they may find that their eyes are not adjusting to distances as they used to. When people inch closer to forty, the lens of the eyes begin to lose flexibility. It becomes difficult to focus on close objects. This condition is called presbyopia. It can be managed to a large extent with the use of bifocals. Bifocal (also can be called Multifocal) eyeglass lenses contain two or more lens powers to help you see objects at all distances after you lose the ability to naturally change the focus of your eyes due to age.

• The definition of semi finished lens

Semi-finished lens is the raw blank used to produce the most individualized RX lens according to the patient's prescription. Different prescription powers request for different semi-finished lens types or base curves. 

• The process of semi finished lens

The starting point for freeform production is a semi-finished lens, also known as a puck due to its resemblance to an ice hockey puck. These are produced in a casting process that is also used to manufacture stock lenses. The semi-finished lenses are produced in a casting process. Here, liquid monomers are first poured into moulds. Various substances are added to the monomers, e.g. initiators and UV absorbers.

• What's the importance of a good semi-finished lens to RX production

a. High qualified rate in power accuracy and stability

b. High qualified rate in cosmetics quality
c. High optical features
d. Good tinting effects and hard-coating/AR coating results
e. Realize the maximum production capacity
f. Punctual delivery

Not just superficial quality, semi-finished lenses are more focus on the internal quality, such as precise and stable parameters, especially for the popular freeform lens.