Who uses EMS 8000 Scanners?

[The_Doctor]

Concept of. I don't really know how it was supposed to work without, so without context I won't claim understanding.

Re WideMoves, just idle speculation. I have some. They take a beating, though I treat them well to prolong their life (barely use them for two years). They seem to have some magnet-liek tendency to halt in any axis that is stopping motion, as they should, but they do it early, and restart moving late. It's like some kind of magnetic detent. One reason I never bought more galvos since is that no-one ever told me for sure whether this was avoidable or not. Something Steve Roberts said makes sense, that if you're running close to the low levels in which noise or bearing irregularities begin to dominate, this can happen. But my instincts tell me it's happening on a larger scale than this. Besides, I never heard of any complaints about this from people with other scanners! So either very few people make patterns that reveal this, or it's not an issue with most other scanners. Slowly rotating simple regular polygons is a good way to reveal this if the problem exists. That would probably reveal it regardless of scan angle or scan speed. It looks like the drawn line sorts of skips a beat, warping a bit, trying to catch up with where it should be. I'm VERY keen to make sure that whatever I buy, it never shows me that crap again.

[The_Doctor]

my projector has dt40w's in it. they work pretty well. there's a little oscillation on some of the patterns, but it's totally acceptable.

check out my videos on youtube, if you're interested in seeing how they perform: https://www.youtube.com/user/swamidog

Oscillation? Can you name a specific video there that shows it clearly?

[JD3]

Concept of. I don't really know how it was supposed to work without, so without context I won't claim understanding.

Re WideMoves, just idle speculation. I have some. They take a beating, though I treat them well to prolong their life (barely use them for two years). They seem to have some magnet-liek tendency to halt in any axis that is stopping motion, as they should, but they do it early, and restart moving late. It's like some kind of magnetic detent. One reason I never bought more galvos since is that no-one ever told me for sure whether this was avoidable or not. Something Steve Roberts said makes sense, that if you're running close to the low levels in which noise or bearing irregularities begin to dominate, this can happen. But my instincts tell me it's happening on a larger scale than this. Besides, I never heard of any complaints about this from people with other scanners! So either very few people make patterns that reveal this, or it's not an issue with most other scanners. Slowly rotating simple regular polygons is a good way to reveal this if the problem exists. That would probably reveal it regardless of scan angle or scan speed. It looks like the drawn line sorts of skips a beat, warping a bit, trying to catch up with where it should be. I'm VERY keen to make sure that whatever I buy, it never shows me that crap again.

Well that sounds like something i would never want! haha

[swamidog]

it shows up as little sine wave like wiggles on some long diagonal lines.

here's a very old ilda 12k test pattern from the dt40w's fresh when i bought them (very early projector build)

Oscillation? Can you name a specific video there that shows it clearly?

[The_Doctor]

it shows up as little sine wave like wiggles on some long diagonal lines.

here's a very old ilda 12k test pattern from the dt40w's fresh when i bought them (very early projector build)

Hasn't got any long diagonals. But I think I can make it out on the long horizontal arrow. Looks like something that might iron out if scanned fast enough. I've seen somethign like it on WideMoves at some speeds, (might have been a hum loop one time anyway), but it's not as nasty as that stop-start problem I described.

Edit:
JD3, agreed, you wouldn't. But you can see it if you want now. Attached, one AVI file, XviD. It's a series of stills, one degree apart in rotation each time. Look for the warped shape in lines as they approach or leave either horizontal or vertical orientation. Regardless of the scan speed, or scan angle, a SLOW rotation of the resulting form will always show this error. This is why I'm keen to know about other scanners in this respect, before I buy. My assumption is that this is not normal, because if it were as unescpable as it is on my WideMoves, everyone would know about it.

[swamidog]

yeah... it's not bad. i see it less in LSX (there are more scanning optimization settings) than in pangolin. i consider dt40w's an excellent value for the money, but i'd never expect them to perform like CT's or EMS.

Hasn't got any long diagonals. But I think I can make it out on the long horizontal arrow. Looks like something that might iron out if scanned fast enough. I've seen somethign like it on WideMoves at some speeds, (might have been a hum loop one time anyway), but it's not as nasty as that stop-start problem I described.

[The_Doctor]

yeah... it's not bad. i see it less in LSX (there are more scanning optimization settings) than in pangolin. i consider dt40w's an excellent value for the money, but i'd never expect them to perform like CT's or EMS.

Sure. I imagine there's plenty I can live with. But whatever I get, it must not show the thing I show in the attached file on previous post. I'm not that fussy, especially if galvos are cheap, but that thing really got up my nose because it brutally interfered with the methods I was interested in coding for.

[JD3]

im guessing with all this said, it will be worth the $800 to upgrade

[mixedgas]

If you want to find irregularities in your scanners at small angles, project a 1000 foot throw onto a 150 foot by 450 building wall with no windows, using 7 watts of Argon.
That how when I found a way to see bearing and sensor noise without a oscilloscope.



Steve

[The_Doctor]

Ok, I think that might be hard for me to arrange. But whatever I see, I see it, and photographed it, and I'm guessing it's not a low-signal or noise problem. Whatever it is, if I can get some scanners that don't do it, I'll be happy enough. The conditions for that AVI file were about 7.5 feet to a scan 3.3 feet wide on the wall. This kind of scan angle seemed to be the sort of condition WideMoves were built for, which is why the effect is so galling. In an earlier post in this thread I tried to separate the apparent line separation from the bend in each line, and I'm not sure I should have. They look like aspects of one problem when I spend time looking at that small movie.

EDIT:
JD3, if you can verify that the EMS 8000's do not show the problem I showed, I'd say 'yes'. Go for it. 800 bucks is a lot of money, just for an upgrade (begs the question of total cost, and I bet it's slightly scary). The thing that makes this relevant is that WideMoves are apparently a clone or copy of earlier EMS scanners with many similarities inside and out. Until I know whether other scanners do the thing I want to avoid, I have no idea whether anything remotely similar in design might do it too.