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Thread: Laser guided surfacing using CC segs

  1. #1
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    Laser guided surfacing using CC segs

    Greetings,


    I am writing to get a response to the subject of returning to CC Segs (ground in plus Clylinder) with laser surfacing.

    It is true that with FT's and round segs the line would be less noticable facing the wearer face on. However, many labs are promoting that CC segs provide better acuity. Many years ago, we dispensed (no pun intended) with the glass CC segs, such as the CC ultex series, the barium and Flint CC round segs, etc., to provide the cylinder ground on the back surface. The reasoning then was to put the cyl. closer to the natural point of correction and thus providing better vision. Using the laser technology is fine - especially if, unlike normal surfacing where there is a + or - .25D variation in the power one always recieves pin point accuracy. If one orders a -6.00, they will get EXACTLY a -6.00. But, if the Cylinder is moved to the front surface, particularly in higher powers, are we not taking a step backward?

    Your thoughts,

    Sincerely,
    Brian L. Schnirel

  2. #2
    Allen Weatherby
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    Laser surfacing of a lens

    I am not familiar with laser surfacing. I know you can cut plastic with a laser however to use a laser as a surface removal device would require a very complex long cycle time from what I know of laser technologies.

    Is there a particular laser surfacing system you are familiar with?

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    DAC lathe digital surfacing system

    Hello,

    The tool used in processing the CC segs and other jobs is a DAC lathe.

    One company that uses this is a lab in Pittsburgh, Pa. I would provide the name but I wouldn't want to break Optiboard forum rules if it would be considered advertising.

    Sincerely,
    Brian L. Schnirel

  4. #4
    Allen Weatherby
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    Digital surfacing NOT Laser surfacing

    Thanks for the explaination. I assumed you were talking about a method of laser surfacing that I was not familiar with. Our facility ICE-TECH offers a backside dual zone product as well as backside individualized PALs and great wrap around fashion and sunlenses using digital surfacing.

    This technology uses precision cutting tools to process unque shapes. All machines will not all produce the same lenses. It depends on the lens design software available to the specific machine.

    If you would like more information about our digital surfacing produccts or digitally surfaced products in general please contact me via e-mail or via private message on this board.

  5. #5
    Master OptiBoarder Darryl Meister's Avatar
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    Free-form generators are not really capable of producing crisp bifocal segment or slab-off lines, because of the nature of single-point diamond-turning. It is extremely difficult to produce discontinuities in the surface, since the lens must spin very rapidly against the cutting tool in order to produce a sufficiently smooth surface. The soft lap polishing process will further smooth out any abrupt changes in surface features. Consequently, bifocal segments made using a free-form generator will always appear "blended." You can advertise this as a "feature" of the free-form process, but it's just as much a limitation, since a blending region is unavoidable.

    Also, there is no guarantee that the power of a free-form lens will be any more accurate than a traditionally surfaced lens. This will depend a lot on a given free-form laboratory's investment in process engineering and quality control. After all, both free-form and traditionally surfaced lenses are held to the same ANSI tolerances (+/-0.13 D). While free-form surfacing is arguably more precise, at least in the sense that it is generally not subject to the rounding error of traditional hard lap tools, lap tools are often cut in at least 1/8th (if not 1/10th) diopter increments. This puts the inherent rounding error of a traditional surfacing process at only 0.05 or 0.06 D.
    Darryl J. Meister, ABOM

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    Original subject question

    Hello,

    I also disagreed with the advertisement of precise power received. The process was described to me as laser induced. Obviously, that was incorrect.

    The main focus of this subject was the return to CC segs with the promotion of providing 'better vision'. I was hoping to get more response to this topic.

    Thanks.
    Sincerely,
    Brian L. Schnirel

  7. #7
    Master OptiBoarder Darryl Meister's Avatar
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    I don't know that you're going to get "better" reading vision by using a bifocal segment on the back surface. You might get a slightly wider field of view, but bifocals already provide a rather generous field in the first place. You will also get slightly less magnification, though this isn't necessarily considered a "good" thing for near vision. I suspect that the shape of the segment would also have to be carefully controlled in order to prevent becoming distorted (e.g., oblong) in the presence of high cylinder.
    Darryl J. Meister, ABOM

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    I know the lab thats in Pittsburgh. I just received another job from them yesterday. This was a +8.25 wrap sunglass. They did a very nice round blended seg, polycarb, with a anti-reflective coating. The power was not super high, so cosmetically it looked very nice. Patient liked it way better than the supposed "compensated lens blank" progressive that we had previously put in this frame. I have also gotten crsip, defined, round segs in transitions polycarb +8.25 wrap jobs. They do a very nice job. I am unsure of your question. I do not think that they / or anybody are promoting returning to plus cylinders ground on the front service.

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    Question concerning CC segs

    Hello,

    On Ft and RD Segs, This is what they said the design was (a CC seg for "better cosmetics and optics").

    Sincerely,
    Brian

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    addendum to CC seg Question

    If a CC seg is used, a plus Cylinder grinding form would have to used. A minus Cylinder grind would grind off the CC seg (if that is what they are using).

    Sincerely,
    Brian

  11. #11
    Objection! OptiBoard Gold Supporter shanbaum's Avatar
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    Quote Originally Posted by Brian L. Schnirel View Post
    If a CC seg is used, a plus Cylinder grinding form would have to used. A minus Cylinder grind would grind off the CC seg (if that is what they are using).

    Sincerely,
    Brian
    Not true; the new "direct surfacing" systems are capable of producing complex surfaces, combining a "seg," or a progressive addition field, with a toric (or other) surface.

    Current practice in this area usually employs a semi-finished blank having a spherical front, with a complex back.

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