As some of you already know, DZ has recently agreed to be the US distributor for Jian's Dragon Tiger Scanners. You can read more about this on his website at www.dzelaser.com Also, Jian has just released some new scanners to compliment the existing DT-40 Pro's. The new scanners are the DT-25's.
David decided to send me a couple sets for me to review. This review is for the standard DT-25 set with the normal size mirrors. (A later review will cover the upgraded DT-25 set with the larger mirrors attached.)
David admitted that the scanners had already been tuned by him before he boxed them up and sent them to me. He also stated that, at least for now, *all* the scanners that he sells will be tuned by him before they are shipped to customers. Evidently when they come from China, the tuning is pretty far off. (One set actually started oscillating when David first tested them!) But if David is going to tune each set before they ship, then your results should be similar to mine below.
The new DT-25 scanners look very much like the DT-40 units. They have the same plastic end connection on the top, and the body looks just like virtually every other Chinese copy of the Cambridge 6800 scanners you've seen. The come already mounted in a hefty aluminum scanner mount. All cables and connectors are included of course.
The scanner amps are slightly different, however. The two amps are combined on a single board. There are separate power LED's for X and Y, but both amps power up and down in unison. Unlike the latest version of the DT-40 Pro amp, this combo amp retains the high frequency damping potentiometers for X and Y. Some people don't like this, as it makes tuning more complicated. However, I think having the pot makes for a better image - assuming you take the time to tune properly.
And I have to say that David's tuning was spot-on. I didn't even bother trying to re-tune them. They were already dialed in nice and tight. (Of course, given David's experience, I should have expected this!)
One thing to keep in mind, however, is your beam path. The scanners come from China with the X galvo placed on top in the scanner mount and the Y galvo on the bottom. This means the beam would enter from the left (if you were standing in front of the projector facing the aperture), then bounce down first, then out towards the audience.
However, my test rig is designed to have the beam enter the scanners from the right and bounce up first, and then out towards the audience. This means that the galvo on the bottom is now the X galvo, but it's still labeled Y.
Of course, so long as the galvo is connected to the matching side of the scanner amp, it doesn't matter which signal (X or Y) it's actually receiving. So you make your changes on the input connector to the amp. Just be mindful of this when you're setting them up and you'll be fine. (In my case, the Y galvo was still connected to the Y amp, but I had the X signal from the controller connected to that side's input.)
Normally this isn't an issue, because you usually have to mount the galvos in the scanner block yourself. But since in this case they're already mounted for you, it's easy to get things confused. Just be sure to go slow and you'll be fine.
The performance of these new scanners was impressive. I brought up the ILDA test pattern (scanning at 25Kpps), and was able to view it at just over 8 degrees optical scan angle. (The center circle started to pull away from the square at around 9 degrees.) The test pattern looked great!
http://www.photonlexicon.com/gallery...2/100_1919.JPG
Likewise, the LaserMedia test pattern showed no difference on the retrace lines. And the grid test pattern was amazing! It looked as clean as a set of standard 30K galvos! (Albeit with a little more flicker...)
After letting the scanners grind away on the test pattern for an hour or so, I took some temperature readings. The baseplate was 79 degrees F. The body of the Y scannner was 83 degrees, and the body of the X scanner was 86 degrees. The backplane on the scanner amp was 106 degrees. These numbers are quite low, suggesting that passive cooling may be all that will ever be needed for these units. (Assuming you've got a decent baseplate, that is.)
The mirrors on these new scanners are slightly thicker than the ones I had on my old DT-40 pro units. And the coating efficiency has improved as well. I measured a 4% power loss across the scanner block, so that's 2% per mirror. And indeed, the mirrors are spec'd for 98% reflectivity. (These measurements were taken at 532 nm with the galvos centered.) Contrast that with the 4 to 5 percent loss PER MIRROR that I experienced with my older DT-40's, and you can see that the mirror performance has really been improved.
I then ran several shows on the scanners, just to see how they looked on some of the old standards, and I have to say that they looked just great. I wasn't able to increase the scan angle quite as wide as I had hoped, but they did perform quite well nonetheless. I was particularly impressed by the relative lack of flicker in most of the images. Even though they were running nearly 20% slower than a standard set of 30K galvos, it was often difficult to tell from the scanned image. They're also very quiet. Even when scanning complex abstracts, I could barely hear them running.
Overall, I'd have to say that these scanners would probably be ideal for someone that is more interested in graphics shows, but can't afford a faster set of scanners. The increased flicker vs a true 30K set isn't all that noticeable, and the images are otherwise very clean. Also, I believe that the lack of a wide scan angle is not nearly as big of a drawback for graphics as it would be for beams.
Note: I did not try to de-tune the scanners to a slower speed. I would expect that you could pick up more scan angle if you tuned them for 20K, though you'd have more flicker in the image.
As for this specific set of scanners, they've only got about 3 or 4 hours of run time on them, and they're *really* tuned well. David has offered to donate them as a door prize for the upcoming Florida Laser Enthusiast's Meeting on November 8th in Orlando. So I'll be bringing them with me to give away. (WOOT!) Hopefully we'll soon see some pictures (or video even) of these scanners humming along in someone's projector!;)
In the mean time, have a look at the demo reel I posted on Google video which shows these scanners in operation. (There is a higher-resolution version on Cruch's FTP server as well. File name is DT25DemoReel.)
Adam
