Messages

1

Video P*r*o*b*i*n*g / Re: video probe, tool or toy?

« on: September 09, 2009, 05:08:31 PM »

Hi Laurence,

You mean scanning a live human body or a cast made out of it?

I've been quite successfully scanning forms musical instruments - violins, violas and cellos. The resulting point cloud is processed to a g-code using software like VX Cad Cam or similar. I'm not reproducing my scanned instrument parts exactly as I prefer to do the final shaping myself, but I use my router as an "assistant" doing the rough work for me. The accuracy would be enough to make quite a finished product if that is what one desires... I've been using both Art's and Tom's video probe plug-in. With good adjustments and patience you can make a reasonably accurate scan with either of them, but after finding the proper setup Tom's probe is much more practical.
In the last month I haven't had time to go on with my experiments, but the last scans were already very good thanks to Tom's help.
Scanning a live human body would take quite a while. A cello back arching - an area of c. 450m x 760mm - with Y step 1mm and X step 60mm takes roughly an hour. And luckily for the accuracy, the cello back is a dead, immobile object...

For your purpose, I think this could be interesting: http://www.david-laserscanner.com/

Good luck,
Eero

2

Video P*r*o*b*i*n*g / Re: New 3d Video Probe

« on: August 04, 2009, 03:56:31 AM »

Hello Tom,

Attached the last calibration files and a snapshot of camera settings. The laser is at max brightness and I changed my pin point to a thinner one as well - diameter is now in the range of 1/3-1/4mm. As you can see the exposure is about 0.23 ms. I tuned the colour intensity (on the first page of camera settings) down by half. In the resulting scan the 255 max reading appears only 4 times for green and once for red. The scanning order is Y 1, X 2 and Z 3.
One question: After calibration scan, some calculations are done. Where is this resulting information stored? The properties window of scan3d.ini shows it not being changed since I stored the calibration settings BEFORE the calibration started. Is there some button that I'm missing to complete and store the data?

Eero

3

Video P*r*o*b*i*n*g / Re: New 3d Video Probe

« on: August 02, 2009, 06:26:36 PM »

Sorry - the attachment!

Eero

4

Video P*r*o*b*i*n*g / Re: New 3d Video Probe

« on: August 02, 2009, 06:20:27 PM »

Hello Tom,

With your advise  of using the Pause and Resume buttons, I got some snapshots of the screens. Here is again a zip-file with new calibration files and two pictures using the WatchportV3 (still 8mmF2.0 - I already thought of improving the setup so that it'd be quick to change the distance of camera and laser if needed - didn't have time to change it yet...)
This last calibration was done before I got your last reply - the values of green are still too high - even after reducing the exposure quite much and playing around with some of the other settings. The exposure is now less then 1/2 ms, but I had to increase the line brightness. The previous calibration files I sent were done with about 1/60 s. I don't know all the meanings/effects of the different adjustment possibilities of the Watchport screen...
With a 1/2 ms exposure there is a fluctuation of in the picture brightness that goes from a clean picture of the laserline to almost no line and the whole cycle takes something like 20-30 seconds. Specially close to the edges of the picture this gives trouble when trying to adjust the exposure and/or brightness of line right for a non saturated result on the graph. I don't know what causes this... (with a quite feeble line and longer - 1/60s -  exposure I didn't notice this). Increasing the Gamma (?) from one to 2.2 helped some , but I don't know what it means... Nor do I know if I should use the video compression, less or more colour... and white balance automatic or manual... ? Maybe you could send me a snapshot of your camera settings since you use basically the same camera?

The Watchport viewer shows the laser line quite a clean, straight - better then I remembered - or my settings have some way improved much. Even without any correction this should give quite a good scan - but the "bending" in my example last time was quite big. I'll try again tomorrow if I find a moment.

I'll keep an eye on the saturation levels of the colours, and try the axis order your way. (As my router is a X axis gantry type machine, I've just got to a habit of avoiding too much back and forth movement of the X-axis. That's the reason for the odd order of calibration.)

I'll send my email to your earthlink address.

Eero

5

Video P*r*o*b*i*n*g / Re: New 3d Video Probe

« on: July 30, 2009, 07:54:34 PM »

And here the zip files for the previous...

The object in the example scans is a flat steelbar of 8mm x 25mm x 100mm covered with thin masking tape to avoid too much reflection.

Ciao,
Eero

6

Video P*r*o*b*i*n*g / Re: New 3d Video Probe

« on: July 30, 2009, 07:44:20 PM »

Hi Tom,

Finally I got together some pictures, calibration files and a few scans, that you wished to see.

The hardware:

In addition to the original WatchportV3  4.9mm lens, I got a set of four 3.6 - 6 - 8 and 12mm on eBay
http://cgi.ebay.com/Any-4-pcs-3-6-6-8-12-16mm-CCTV-board-Lens-set-dome_W0QQitemZ370158397420QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item562f28e7ec&_trksid=p3286.c0.m14

In my setup I prefer the 8mm to the 12 mm lens because I need to have the FOV cover a Z variation of about 28 mm in one frame.

The adjustable focus 5mV green line laser comes from
http://shop.david-vision-systems.de/index.php/language/en

I made a small current regulator for controlling the brightness of the line. This way one can get a very nice and sharp line specially on a light coloured surface.

The calibration setup:

In the following photos you can see the needle fixed on a black velvet to get rid of all unwanted light or reflections that could disturb the calibration. The needle is about 40mm long and 0.8mm thick, painted matt black and touched on the point with white chalk, that lights up like a small LED when hit by the laser. In Scan3D intensities graph it gives a very clean and lonely peak. In the room there is no light and I even turn off the computer screen for the duration of the process. - And as "scanner" moves to the starting point of the calibration scan, I get out of the workshop myself. Not much fun to stay in the dark for hours...

As you guessed all the values I use are in mm.

The orientation for Watchport is 180 and for QuickCam 0 degrees.

And some questions:

My second question in the last post wasn't very clear. Sorry.
The camera-laser setup is fixed. This system has two planes: the laser plane and one perpendicular to it following the lens axis. If the laser line is parallel to X-axis this second plane is normally following the Y-Z plane. This is only very difficult or impossible to set precisely. Does it matter?  If I understand this needle point process right - any deviation of this would be corrected by the calibration, wouldn't it ?

Could you tell me what are the values of Elevation and Azimuth correspond to?

Attachments:
For some reason, as long as I have the camera connected, I can't get any of my computers to get a complete "Print Screen" from your Scan3D window - I only get the leftmost "camera view" window. To show the intensity graph of my calibration "needle point" I had to take a photo of my screen.

I send you two sets of zip files - one for each camera. They include: scan3d.ini, Scan3dCal.pts and an example Scan3dCloud.xyz - plus three photos: lower part of the Scan3DWindow and two pictures of the example PointCloud showing the distortion mentioned in my previous post.

- Too many attachments... You'll find the zip files in the following post below.

All the best,
Eero

7

Video P*r*o*b*i*n*g / Re: New 3d Video Probe

« on: July 29, 2009, 04:33:07 AM »

Hello Tom,

I've been trying your new Scan3D plugin and have some questions about the calibration.

I used Art's video probe with some success earlier, but as your Scan3D has more possibilities in the setup of camera and laser - and in the end a better scan - I'm trying to figure out how to make it work.

If I understand right the direction of the laserline can be chosen according to ones own needs. For me this would be parallel to X-axis ( I tried parallel to Y-axis as well, problems are the same). I have both the camera and the laser pointing down at 45 degrees so the camera is looking perpendicularly at the line (in the middle of its vertical field of view).

I have a nice focusable line laser and Watchport V3 camera with a set of different lenses (tried 8mm F2.0 and 12mm F2.0). I have as well a Logitech QuickCam Pro. The Watchport has a problem of a bigger distortion of the picture (a straight line seen as slightly bent). The QuickCam has a zoom that demands a calibration every time you plug it in after having disconnected it for milling work.

With Art's videoprobe the quickCam gave ok results but took always a lot of time setting up - the Watchport was useless. With your Scan3D I understood the calibration should take care of - at least some of - the distortion. And what's nice no calibration needed every time before a scan.

The problems:

1) I can't get the calibration process - done as you describe in the short manual - to correct the "bending". This is easy to see by scanning a flat surface with two parallel passes resulting to two "trays" with edges not meeting.

2)As I understand the calibration should automatically correct any slight deviation in the direction of the camera in relation to the laserline. I still get  the edges of two adjacent passes not meeting but as two slightly inclined bands. (This is easier to see using the QuickCam as the scan is not "bent")

3)The whole of these problems may be a result of some of the calibration process missing... In the Scan3D window after calibration the fields for FOWs, Elevation and Azimuth all show "1". ?

Hope you can make give me some advice how to solve this since your Plugin is a big step from the previuos one.

Thanks a lot.
Eero