arc light

**jimbobby** · 10-21-2002, 10:56 AM

Pete, I caught your seminar in Columbus on Oct.20th. At the seminar you mentioned using a special arc lamp when checking the backside surface of a lens. Could you expand on this thought: is it something special or can a 40watt clear filament bulb do as well? thanks

**Jim G** · 10-25-2002, 12:13 AM

Oh gad! Don't even consider an arc lamp. A 40w may be too strong...how about a 10w (just kidding)?

The arc lamp should only be used for process definition. We, as "experts" can find enough wrong with a lens without special equipment.

"As worn" should be the operative term. Seriously!

**chip anderson** · 10-25-2002, 06:24 AM

Origional device called a "Modern Arc" designed by Virgil Hancock and made by Modern Optics. I had my first job with them. Later there was a kick to inspect hard contacts with same. I remember you could not make a -6.00 contact that would pass same. Stronger and weaker could me made to pass.

Commercially I don't think anything other than well made glass lenses would pass things enough to be a saleable product. I know poly would be non exhistant if it had to pass.

Chip

**eyesguy** · 10-25-2002, 09:53 AM

Hi:

An Arc lamp is very critical inspection tool. You can simulate one buy going outside and focusing the sun through a lens you want to inspect onto a smooth white surface.

If you decide to buy one, I can give you the name of a company that makes them specifically for optical work. The price the last time I looked was about $1,500.

Regard,

eyesguy

**jimbobby** · 10-30-2002, 10:53 AM

Thanks for the response to my question about the arc lamp. Well, at $1,500 I would not consider one. I was wondering if anyone had considered starting a thread about best practices in surfacing different lens materials. As a lab rat my interest lies in developing and sharing ideas on getting the best backside surface possible. As with dispensing tips anyone have any surfacing tips?

**Pete Hanlin** · 10-30-2002, 02:52 PM

Pete, I caught your seminar in Columbus on Oct.20th. At the seminar you mentioned using a special arc lamp when checking the backside surface of a lens.
Nice to see someone was actually awake! Sorry I didn't see your question sooner (I've been travelling a bit lately and haven't been on OptiBoard too much).

Yes, the arc lamp costs around $1,500. I would argue that it is well worth the cost if you are in a wholesale surfacing environment...

Let me begin my case, however, by responding to Mr. G's comment: The arc lamp should only be used for process definition. We, as "experts" can find enough wrong with a lens without special equipment.

The arc lamp should NOT be used to final inspect the lens. As everyone has already mentioned here, it shows every tiny little defect in the lens and you'd reject a large percentage of your work. However, isn't the thought of getting a very detailed look at the true surface quality of your lenses worth something?

For example, you get a job that is just a bit fuzzy... looking through the arc lamp, you can tell if the defect is on the front or back side of the lens. Perhaps the manufacturer-applied scratch coat has waves in it- you can tell the waves are coming from the front of the lens because you mark them and then turn the lens to see if the shadow of the mark moves in relation to the shadow of the defect. If the shadows move in unison, the defect is on the surface you marked.

Maybe you are sending work out for AR coating and are experiencing poor results. An arc lamp will show you any defects on the surfaced side of the lens. For sure, you can see how well your polishing process is working (a lens that looks perfectly clear to the naked eye can show the swirls a less-than-ideal polishing leaves behind).

$1,500 is a lot of money. However, for a surfacing lab, it may be worth the expenditure if it shows you where your process is bad BEFORE you encounter spoilage. So many times, we have "mystery spoilage" that comes and goes without any pre-defined pattern. Perhaps the problem is rather constant, but simply rises to the level of causing a problem on a few jobs- the arc lamp tells all.

Without a doubt, I can say with confidence that the labs I managed could have improved their processes with the aid of an arc lamp. Plus, they make finding PAL markings a snap (they show up as plain as the type on this page under an arc lamp).

Anyway, that's my pitch for arc lamps (we don't manufacture them, so these are completely objective comments). Other than my B&L lensometer, my arc lamp is the most useful tool in my office!

PS- The idea of creating a thread for lab processing tips is a great one! I think my favorite tip is a quote made by someone at Gerber-Coburn (I believe)... "The quality of your lens surface will NEVER exceed the quality of your tool surface." How many of the tools in our labs have dents, gouges, or even swirl etchings from fining pins? All of these create a poor surface quality on the lens.

**John R** · 10-30-2002, 04:22 PM

Anyone got any tips on what would be needed to make one.. Or a link to a manufactures site...

**Pete Hanlin** · 10-30-2002, 04:43 PM

I've had a look on the search engines and wow! Finding an arc lamp isn't easy business! The one in my office is a Bulbtronics BT X75/LIS II (but its all nice and fancy and probably costs too much to be practical). We have some really simple ones downstairs (gathering dust) that don't look too hard to build.

From what I HAVE been able to find, the bulb for an arc lamp will probably set you back about $300. Perhaps I can tinker around and post directions on how to build your own.