What are inner progressives and outer progressives?


Outer Progressives

The outer progressive lens is also called the front surface design progressive lens, that is the power gradient area is placed on the front surface of the lens, farther away from the eyes.


Inner Progressives

Inner progressive is also known as back surface design progressive lens, this kind of progressive lens refers to the use of free form surface technology and lathe processing equipment to place the degree gradient design (functional surface) on the rear surface, relatively close to the eyes.


The manufacturing difference between inner progressive and outer progressive

Outer progressive lenses are manufactured using a combination of two processing methods.

1. First processing

The ADD and corridor length of the outer surface are designed in the front surface mold of the lens, and the mold on the rear surface of the lens has no change in photometric curvature. The lens substrate with ADD is produced by two molds using an assembly line, which is dedicated to progressive lenses. Substrate, not for use in the production of other types of lenses. Usually the production of such substrates needs to correspond to each ADD, so the storage inventory of substrates is quite large. 


2. Secondary processing

From the stock of lenses produced by the first processing, find out the UC lenses with the required ADD, and machine it on the back surface of the lens to achieve the distant power. After these two processing steps, a pair of progressive lenses is completed.


Inner progressive, its gradient surface is located on the inner surface of the lens, and its center is also located on the inner surface of the lens. Its outer surface adopts the same spherical or aspheric design as ordinary single vision lenses.

Different from the traditional processing technology, the free-form internal progressive lens can be designed according to the setting of the computer program, and adopt the integrated molding design. With the help of the "soft polishing" processing technology, the high-quality digital turning process of the rear surface of the lens can be completely preserved. The original progressive design.


Post time: Jun-08-2023