can someone explain to me how free form progressive lenses are made?
can someone explain to me how free form progressive lenses are made?
The term Freeform has come to mean, a way of making a lens using machines that can cut almost any desired surface, not just spherical surfaces. This allows, in theory a lens to be made from a cube of plastic.
The Definity lens for example is made with the front surface produced with a portion of the add power on this surface the balance of the progressive is then placed on the back surface.
Some of the advantages to the freeform concept are being able to properly locate the distance vision optical center and the near distance optical center. Different PD's require slight changes in this relationship. The lens is made for the customer and the frame the customer chooses.
There are advantages to a total back side progressive. When worn the frame generally fits much better to the outer surface of the lens. The prescription is closer to the pupil is also a benefit.
Other benefits to Freeform technology is the accuracy of the surfacing when compared to traditional methods that require fining and polishing.
I hope this helps you better understand this process
I guess I still don't understand the actual process that free form takes to get to the finished product.
Freeform lenses can start as a single vision spherical blank lens. Then using x,y and z data point files a PAL (progressive lens) surface can be produced. These are special machines using CNC technology (Computer Numerically Controlled). A CNC machine can move and control the cuts that it makes so that that a surface similar to the front of a traditional cast progressive lens is actually produced on the back surface of a single vision semi finished lens blank.
Polishing is does not need to remove much material only to add luster to the surface. There are different approaches to this polishing process and many of these methods are confidential, other than those systems sold by optical machinary manufacturers such as Satis Loh, Schneider or Opto-Tech.
Does this better explain the process.
Is this a little clearer?
http://www.visionmonday.com/articles...s.asp?ID=14833Originally Posted by redsoxfanfewany
Here is a start. Schneider is the leader in the equipment used to produce free-form PALs. The machines can process all lenses, but it is their point-to-point accuracy that allows them to procude exceptional designs.
Varilux Ipseo
Varilux Physio 360
Hoya ID
Seiko Super Proceed Internal
SolaOne HD
AO Easy HD
Zeiss Individual
Ziess Short i
Essilor Definity
Rodenstock Multigressiv 2
Shamir Autograph
That's most of them, I believe. The Schneider machine can produce Rxs within a 100th or even a 1000th of a diopter.. Great machine, great designs, great PALs. The future of optics.
Adam
As a follow up comment to Cherry Opticals post, Schneider does make good equipment, but they are not the only equipment maker who can produce lenses with high degree of accuracy. I think you will find there are a number of machines that can produce lenses with similar accuracy. I have experience with machinary and have seen Schneider, Loh and Opto-Tech equipment running in the same lab in Europe and concluded like most equipment comparisions, this lab had features of each one they liked. What is most important with any equipment is to know that lens number 100,000 will be made to the same specifications as lens number 1. Keeping the tooling in alignment, replacing cutting tools when required etc.
We have developed special processes to produce wrap style prescription sunglass lenses and not all machines can cut the backside curves and have tool clearence to do this. With these processes the polishing of curves such as -14 are quite difficult. The production range of the equipment and the software are also very important to produce a quality freeform product.
in that artical posted by cherryoptical, there was the implication that practitioners (thats us) will in the future be able to modify specify and tweak the designs of PPL's. We would need a shed load more education before that, and we certainly would need to be un-programmed out of the "how wide" and "how shallow" mentality, before we started dabbling with lens designs
Progressive lens designs will still come from the manufactures (although I do know that there will be people/labs that will try to design their own progressive). The result is a "click fee" to that lens manufacturer/designer for every one that is cut. The custom designs or personal designs (Ipseo, Autograph...) will be dictated through special software programs from those lens manufacturers/designers based the patients Rx along with information (fitting ht's, vertex distance, eye/head ratio, right/left handed ...kidding!;) eventually who knows what else) from the Optician.
Free Form surfacing is not only dependent on the ability to cut complex curves, progressive / atoric..., but also polishing those surfaces. Those surfaces will be cut ready to polish (the polishing is not done on ridged tools or laps), polishing is done on an inflated bladder so as to conform to the complex surface that was cut.
Cutting curves with Free Form technology is not necessarily new. Progressive manufactures have been using Free Form for some time to cut the moulds used to cast their progressives.
The advantage this will bring to ophthalmic lenses is that it will take the lens design/accuracy, created from the manufacturer, straight to the lens surface where currently there are many steps from design to the cast semi-finish blank and each has its own set of tolerances.
Steve
Another thing to consider is that Free-Form lenses will may allow lens manufacturers to reduce their production. They will always have to produce 'standard' designs, but if they do not need to produce as many and can become more profitable by selling 'click-fees' they may have more money to stick into R&D.Originally Posted by Slug
Just another thought on the subject.
Adam
Originally Posted by Cherry Optical
Very True! Yet I beleive that aspect will be what holds up designs released to Labs from the major manufacturers (Essilor, Zeiss/Sola...) to be Free Formed due to their current investment in manufacturing. Bet they don't open up any more factories any time soon. Unless it is for Semi-Finished SV :D
Steve
Call your local lab. Ask them for a tour. It is simply amazing to go into one of the big labs and see the technology that is being used today; free form, ar coating, robotics and finishing.
It is also beneficial to see the amount of work that they do and they can still find your rush job for a status check.
We would need a shed load more education before that, and we certainly would need to be un-programmed out of the "how wide" and "how shallow" mentality, before we started dabbling with lens designs.
You have restored my faith in the ophthalmic community- thank you for such an accurate assessment of the current thinking regarding PAL design (seriously, the "how wide, how short" mentality truly does need to go the way of the Dodo bird!).
Just a note regarding the direct surfacing of progression onto a lens blank. The technology has come a long way- and, as noted, equipment has been developed by various manufacturers (Schneider, LOH, DAC, etc.). However, direct surfacing (aka "freeform") is still an emerging technology. Can manufacturers produce high quality lenses using the existing equipment? Sure. Is there significant development still necessary to improve efficiency (and thus increase throughput and decrease costs)? Absolutely.
I like to compare it to the VHS vs. Betamax situation in 1979. In all likelihood, someone will really "crack the code" on how to best process direct surfaced lenses- but the eventual format is still undecided. Until then, labs investing in this technology risk purchasing 1.) equipment that will become obsolete rather quickly, or 2.) paying an extremely high premium for equipment which will soon drop significantly in price.
To the original question (i.e., how are these lenses created), the process has been laid out fairly completely in the previous posts.
In the future, direct surfaced lenses are likely to fall into one of three categories: Personalized to specific requirements of the wearer (e.g., Varilux Ipseo), Optimized to remove abberations (e.g., SolaOne in 1.67), or Customized to the particular activities of the wearer (e.g., Seiko Super Proceed 1 Internal- I believe there is a questionairre and the dispenser can order one of 6 different design types).
Pete Hanlin, ABOM
Vice President Professional Services
Essilor of America
http://linkedin.com/in/pete-hanlin-72a3a74
Well how would the opthalmic community, (especially such a novice optician as myself!) get out of that how wide and how shallow mentality when it comes to progressive design? Where would we get educated and informed about the specific science of progressives. I certaintly am eager to try and learn but have fallen short on avenues of where to obtain more knowledge!!!
rolandclaur
The need to know about all aspects of the lens design is not necessary by a despensing optician in my opinon. Just like a family doctor does not need to know every aspect of every heart surgery, but they do know to when to tell you to see a heart specialist. All doctors rely on their prescription drug reps for information. Yes every company has a reason to push their product but they also have a tremendous amount of knowledge in their field.Where would we get educated and informed about the specific science of progressives. I certaintly am eager to try and learn but have fallen short on avenues of where to obtain more knowledge!!!
What you need to know to dispense quality freeform lenses is the basics and like everything else in life. The low bidder is not necessarily the best deal. Know who you are dealing with and what sort of guarantee they offer.
Once you dispense freeform lenses as advised by the manufacturer it will come second nature to you. The accuracy available is much better than standard cast pre made semi finished PALs. They can be fit to the patient and to the frame the patient selects without some of the compromises placed on traditional cast PAL lenses.
When you are ready to start dispensing the manufacture for there guidence. Hopefully they will know and understand how to education opticans to this new technology.
Last edited by AWTECH; 12-15-2005 at 01:57 AM.
i think that we ought to learn about single vision lenses first. Untill we are all absoloutley fluent in all aspects of single vision lens design, we dont stand a chance in understanding bifocal or PPL lens designsOriginally Posted by rolandclaur
Single vision design looks inherently simple - nope
here is a list of some the things that we ought to understand AS A MINIMUM, before we dare design a single vision lens, Im sure there are a lot of other things that ought to be on the list
once we have learnt the aspects of single vision lens design, we have a slim chance of understanding PPL design
- the difference between real world thick lenses, and 2 theoretical thin lens surfaces
- all nuances of best form lenses, the whys, and hows
- what happens to the design when it leaves the best form?
- physiological effects and tollerances of the major and minor groups of lens distortions
- the physical surfacing qualities of the material
- asphericity - all types, the why's and how's
- efffects on lenses on binocular visual field
- entrance pupil optics
I come to the LA area once a year to call on an account in Long Beach. I would be more than willing to do a one-hour Free-Form training for you and your staff.Originally Posted by rolandclaur
Contact information is on my profile.
Adam
For anyone interested, I now have a reprint of an article I wrote on free-form technology earlier this year for Refractive Eyecare for Ophthalmologists available at: Free-Form Technology article.
Darryl J. Meister, ABOM
Good point......................but above all this is a very interesting thread full of positive and good comments.Originally Posted by QDO1
Darryl:Originally Posted by Darryl Meister
Great article. I just printed it for our entire staff to read.
Adam
What seems ironic to me is that free form technology can produce a lens to 1/100th of a diopter of tolerance and the soft wear takes the Rx and computes 3000 points on the lens for the best result and yet the practice of refraction has not changed in the last 80 years
Surely nobody dare tell the OO's and Optoms that *they* are going to have to change their ways.Originally Posted by ken@foothills
I agree completely.Originally Posted by QDO
Yeah, but we're getting better at actually realizing that refraction in a spectacle lens -- especially progressive lenses.Originally Posted by Ken
Thanks, Adam.Originally Posted by Cherry Optical
Darryl J. Meister, ABOM
What about single vision individual lenses, like ZEISS single vision individual? It is still a semi-finished blank with atoric surfaces at the back of the lenses in two major meridians. If yes, atoric lenses haven't been produced for quite a few years now? What is the new technology here? Is it just that they are made using free form generators?
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