Toplens Hangzhou [中文]
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Toplens Hangzhou Inc.
Bldg 7/1F, 1197 Bin'an Road,
Binjiang, Hangzhou, Zhejiang,
310052 China
TEL：+86 571 8777 4064
FAX：+86 571 8777 4033
info@toplens.cn
Free-form surface design (including progressive multifocal) is the soul of RX Labs. Freeform here is defined as lens surface with non-symmetrical optical power distribution that can be optimized to achieve a single or a plurality of the optical power, such as A-Toric surface, progressive multifocal surface or individual lens surface.
Solution to create such freeform with power distribution, has been evolved from high-order non-linear manner, finite element mesh of a smooth transition to the latest finite element integration and geometric optical ray tracing techniques.
Freeform surface design here actually contains two concepts: first, the design of the framework, such as the channel length, the shift amount, the area distribution and so on. This aspect is often defined differently among companies. The other concept is the maximum cylinder of astigmatism distortion area and the channel length within the same frame. In general, the further the maximum of cylinder spot in astigmatism distortion area is from effective optical power area, the more comfortable human eyes would feel.
Some parameters to judge design
The width of the channel
The bigger ADD value is, the narrower channels become. This is because the maximum cylinder of astigmatism increases with ADD value, which narrows the channel. If ADD value keeps constant, the width of the channel is directly related to the maximum cylinder value and the position where the astigmatism occurs. An evaluation on the design is to check whether maximum astigmatism will appear away from the effective center area (f40mm).
Effective Area
In effective area (f40mm), this value is generally greater than ADD value while a good design can make it less than ADD value. The following graph is the typical cylinder map of ADD2.0 freeform we designed.
Maximum astigmatism cylinder
In general, the larger the ADD value, the smaller the effective area ratio, the ratio of the area with a CYL <0.25D and 0.5D to the entire area. Please refer to the following figure.
The essence of designs with various purposes is to adjust the distribution ratio between far view and near view areas. Then there is interior design, the standard design, outdoor design, Office design and fatigue design with different purposes.
