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Thread: Review of ScanEco20 galvos from LaserShowParts.com

  1. #11
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    Smile

    Hi Aaron;

    Totally understand about hectic schedules man... Mine has been crazy these past few weeks. (Going back to nights now - ugh!)

    Yeah, you can roughly figure that point speed divided by 1000 is about equal to the minimum frame rate. That's not true for all cases, but it's rare that a frame has more than 1000 points in it. Of course, the number of points is usually changing from frame to frame, so the effective frame rate changes as well. Still, 20Kpps works out to around 20 frames per second. That doesn't mesh so well with a video camera running at 30 frames per second. (Even worse when it's changing up and down based on the number of points in each frame.) And when I digitize the video, I knock it down to 15 frames per second to make the file size more manageable, but that *really* plays havoc with the scanned images.

    It's sort of like trying to shoot video of a computer monitor. The frame rates don't quite sync up between the monitor and the camera, so you get a lot of flicker in the image. But in real life it looks nice and smooth, thanks to persistence of vision.

    Anyway, with regard to the 30K review, it's almost finished. You'll have your scanners back by next week, I promise! I tuned them up for the review, and they look great now. You'll be quite pleased with them.

    Adam

  2. #12
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    KVANT Australian projector sales
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  3. #13
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    Thumbs up Video finished for ScanEco-20 review

    Ok guys, I finally finished editing the video for the ScanEco-20 scanners that LaserShowParts.com sells. I'm uploading it to the FTP server right now. (ftp://ftp.ildaswap.net Login: ilda Pass: swap) The file name is 20Kgalvos.wmv

    It's about 35 megs or so, but it's worth it to grab the high-res version. It's a nice little demo reel that shows you just how awesome these bargain-priced scanners are. (Like all the other tests, this was done using a Pangolin QM-2000 intro board set at 20 Kpps.)

    If you'd like a smaller version, I've also uploaded a copy of the video to Google Video. Unfortunately, because of the compression they use, the video doesn't look nearly as good there.

    I should point out that the flicker that you see in the video is mostly due to the different frame rates between the projector, the camera, and the digitizer I used to get the video onto the computer. In real life the images were steady with barely any perceivable flicker.

    And before you ask, the music is "Above", by Blue Man Group. (Track # 1 on "The Complex")

    Adam

  4. #14
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    Hi guys I'm considering to buy this set. What kind of modulation is supported in the scaneco20? I'm sure i read TTL somewhere, but I can't find the source where I saw it

    Would this laser fit then: http://lasershowparts.com/store/inde...d&productId=33 ?

    I saw in the specs that it supports a TTL frequency between 1-10KHz (I figure this to be how fast it can turn on/off per sec, please correct me if I'm wrong), but what does this mean when scanning? Can the TTL frequency actually limit the complexity of the graphics shown (before the 20kpps threshold)?

  5. #15
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    I believe you're slightly confused; scanners don't support TTL or analog modulation - that's a function of the laser driver module. Scanners are rated for scan speed only, in thousands of points per second.

    Your second question makes a lot more sense: "Can the TTL frequency (of the laser's blanking circuit) actually limit the complexity of the graphics shown (before the 20kpps threshold)?" The short answer is yes. But as to how much it will affect it, well, that answer gets complicated...

    This is a very difficult question to answer because there is no standard for reporting the blanking speed of a laser. So when they say it is rated at 10Khz modulation, what do they mean? Can it turn on and back off at 10Khz with no loss of power (jellybeaning)? Or is it just a single transient (on or off) at that speed that is supported? Or, will it turn on and off at 10Khz, but with some loss in power? (How much loss) And what if you try to blank it faster than 10Khz? (See the problem?)

    However, in practice most lasers that say they are rated for 10Khz blanking will work just fine at 20Kpps scanning speed. (This is based upon my personal experience, and the experience of other laser hobbyists here on PhotonLexicon.) Likewise, a 20Khz laser will work just fine up to 30Kpps speed. Part of this is because it's very rare to have a single blanked point in-between two "lit" points. The other reason is that if you consider turning the laser on and off as a single cycle, that can actually be two points in a scanned image, so 10Khz (if it relates to a power on and a power off cycle) is really the same as 20Kpps...

    Bottom line: If you purchase the ScanEco20 scanners, they will probably work just fine with a 10Khz blanking laser.

    However, if you upgrade to the ScanPro30 scanners at some point in the future, you may notice some problems when scanning very complex patterns with that 10Khz blanking laser. (Problems like tails, blank spots, or dim areas of the pattern where the laser hasn't come back on at full power yet - a condition loosely termed "jellybeaning".) So at that point you'd want to upgrade the laser to one that supported 20Khz blanking.

    Adam

    PS: By the way - welcome to PhotonLexicon!

  6. #16
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    Hi Buffo and thanks for your thorough answer, I really appreciate it The reason why I asked if the scanner "supported" TTL or analog modulation, is because of the different voltages used, isn't there 0-1V with analog and 0-5V (standard voltages in digital circuits) for TTL?

  7. #17
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    Cool

    Not quite. TTL as it applies to lasers is not really true TTL as it would apply to other digital circuits. Likewise, analog isn't the same as it would normally be for something like a video signal, for example.

    Analog blanking for lasers is zero to +5 volts, with any value in-between being valid. TTL blanking is technically zero *OR* +5 volts, with *no* values in-between being valid. Thus, a laser that supports analog blanking will still function normally when connected to a TTL controller.

    In practice, most TTL lasers will turn on once you get around 2.5 volts on the blanking lead. (Some will turn on even lower than that) So that's not really true TTL. Likewise, most analog lasers need at *least* 1.2 volts on the blanking line before they turn on. Also, the power response of the laser is normally non-linear even once it's turned on. So again, that's not the same as a true analog color circuit.

    If you want to use a scanner for blanking (which is still common with large ion laser systems because of the high cost and peak power limits of a PCAOM), then you need a third scanner amp to drive it. You bounce the beam off the scanner mirror, off a retro-reflector, back off the scanner mirror again, and then to the galvos. Thus a small movement of the scanner mirror will mmove the beam off the X/Y galvo pair.

    Then you would wire the blanking amp in the same way as the X and Y amps (usinig differential signalling); except you use the intensity + and intensity - signals for the blanking scanner. Obviously this will give you TTL blanking only.

    Adam

  8. #18
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    Not to nit pick too much but you can do analog scanner blanking. It doesn't have to be TTL only. You just have to do some tweaking. I remember one of laser fantasy's top of the line systems used scanner blanking. They also used prism color mod. As well as a pcaom.

    Chad


    When the going gets weird, the weird turn pro.


  9. #19
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    Cool

    Yeah, I know. I didn't want to go into the details though, because they're *really* messy. Alignment is a bitch, and depending on the layout the beam path may actually shift a bit. And even so, it really doesn't work very well. (But arguably it's better than a TTL-only setup.)

    I've also seen a few creative things accomplished with neutral density filters; but again, this is old school stuff that hardly anyone uses anymore. Analog modulation of the laser driver is the way to go.

    Adam

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