Messages

71

Video P*r*o*b*i*n*g / Re: Just purchased a laser line pointer

« on: July 31, 2008, 11:14:04 AM »

I use lasers on my lathe/mill as home switches (shining onto detectors) but the cheapest laser I can get over here in the UK is from Maplin at £10 - 20$ - and it comes without any focusing. I have narrowed the beam by shining it down a 1mm dia hole about 1 inch long,

Are the lasers that you lads are getting - do they have any kind of focus device - so I could make my homing more accurate. I power mine from the 5 volt circuit for the rest of the home/limit switches. I could soon put another chip in to get down to 3.2v

Hello jimpinder,

I use modules by Aixiz. Below is a link to their ebay auction for a $12, 635nm, 5mw, 3.2vdc module with adjustable lens and optional line or cross generator lens. They list some modules for 3-5vdc usage but sent me 3.2vdc modules when I ordered. When I got my refund they told me that they figure we can just use 3.2vdc modules at 5vdc. No thanks.

However, they do sell some 5vdc modules directly. Same module diameter of 12mm but various lengths. These seem to be leftovers so you need to call to and find out what they have.

Warning: The modules that I have used have had hot cases. V+ is tied to the case. It is common for one power lead or the other to be tied to a laser diode case. The diodes appear to be press fit into the metal cylinder. So you may need to mount the cylinder so that it is electrically isolated. I have covered mine with clear half inch diameter heat shrink tube. I chose clear so I could read the label.

http://cgi.ebay.com/635nm-5mW-laser-module-3-2VDC-w-adjustable-lens-635-nm_W0QQitemZ360074182311QQcmdZViewItem?hash=item360074182311&_trkparms=72%3A552%7C39%3A1%7C66%3A2%7C65%3A12&_trksid=p3286.c0.m14.l1318

Tom Hubin
thubin@earthlink.net

72

Video P*r*o*b*i*n*g / Re: Photos of webcam scanner. ( no laughing.. :) )

« on: July 26, 2008, 02:10:22 AM »

Hello Gaston,

> I have found out what the problem is: I'm using "inch" system and MachCloud expect "mm" coordinates.
> I have brought my cloud file in Excel and multiplied each values by 25.4 and saved it.
> When opened in MachCloud now it can meshed and my parts are recognizable 

Can you post the cloud text file and a screenshot of the MachCloud meshed version?

Tom Hubin
thubin@earthlink.net

73

Video P*r*o*b*i*n*g / Re: Post your Point Clouds Here!

« on: July 24, 2008, 02:09:13 AM »

> Hi Tom
> Nice to see how good your scans are getting.

Thanx.

> I'm curious how we are going to get deeper profiles scanned. Can we step the
> Z down and take another slice then stitch the two meshes together or is getting
> a wider FOV setup the better way to go.

See my suggested volume scanning at http://www.machsupport.com/forum/index.php/topic,7084.msg46309.html#msg46309

Small FOV is preferred for any detail and for less distortion. Then as many overlapping passes as necessary to get the job done.

Art, or whoever is working on the 3d video probe plugin, needs to set that up to be user friendly. Otherwise, you have to do each pass separately then combine later with a spread sheet to get the offsets right.

Tom Hubin
thubin@earthlink.net

74

Video P*r*o*b*i*n*g / Re: Post your Point Clouds Here!

« on: July 24, 2008, 01:25:14 AM »

I was trashing some old pills and decided to try scanning bottles, caps and pills.

The closeup of the round pills shows impressed "I-2". I think these pills came from an Aleve bottle.

The closeup of the capsule shaped pill shows impressed "NUPRIN".

Text on the Nuprin bottle is readable because the camera exposure time was set so that the white areas produced a strong and usable signal while the dark areas produced a weak and unusable signal. The weak signals appear as gaps in the bottle's surface.

The video probe used has a PlaytStation 2 silver camera which has about 45 degree fov. The laser is 5mw, 5vdc red module from Aixiz directly (not ebay). USB cable provides power.

Attached are the point cloud TXT file and a GIF file of the Rhino screen showing the point cloud.

Tom Hubin
thubin@earthlink.net

75

Video P*r*o*b*i*n*g / Re: Post your Point Clouds Here!

« on: July 16, 2008, 02:53:29 PM »

Hello Gaston,

> > I see that the camera is shipped with a lens for 70 degree FOV. The lens is replaceable.
> > I suspect that the thread is M12-0.5mm. If so, you can get lenses on ebay.
> > Search for M12* and lens* in title and description...or I can point you to some I have seen listed.

> My search on Ebay was not very productive so I think I could use some pointers here.

Below is a link to an inexpensive assortment on ebay. This vendor has many M12-0.5mm thread lenses listed
on ebay and at his store. I have no affiliation with this vendor and have not purchased anything from him.

I would suggest that you choose the longer focal lengths since you probably already have the shortest one.
The longer focal lengths will give you a smaller FOV with greater magnification and detail.

http://cgi.ebay.com/Any-4-pcs-3-6-6-8-12-16mm-CCTV-board-Lens-set-dome_W0QQitemZ270255253150QQcmdZViewItem?hash=item270255253150&_trksid=p3286.m14.l1318

Tom Hubin
thubin@earthlink.net

76

Video P*r*o*b*i*n*g / Re: Post your Point Clouds Here!

« on: July 16, 2008, 12:27:17 AM »

Hello Gaston,

> > Neither the camera nor the lens should be pointed straight down. The camera and the lens need
> > to be pointed 90 degrees apart.
> > I have chosen to have the laser 30 degrees CW from the Z axis and the camera 60
> >  degrees CCW from the Z axis.

> As the same setup is used both for calibration and measurement why 90 deg be so important?
> I see that the amplitude of the deviation would be maximized with 90 deg but as I understand
> it the results would not be more valid.

If you were using a pinhole camera the geometry would not matter.

However, when you use a conventional camera with a lens which is parallel to the detector,
the optimal layout is with the object also parallel to the lens and the detector.

With the object (i.e. the laser plane) at 45 degrees to the camera lens, the image of the laser plane will NOT be parallel to the lens and therefore will not be superimposed on the detector. That means that you cannot get the entire laser plane in focus. That will hurt your accuracy.

The smaller your field of view the more of a problem you will have if the laser plane is not parallel to the lens and detector planes. It is possible that the accuracy using a 70 degree FOV is so bad already that the angle the camera makes with the laser does not make much difference.

There is a way to point the laser straight down the Z axis and set the camera at an oblique angle smaller than 90 degrees but this requires that the detector be mounted separately from the lens so that the detector can be tilted at the appropriate angle in accordance with the Scheimpflug condition.

For more detail on the normal arrangement and the Scheimpflug arrangement please read some of my posts in other threads in the Video Probing forum.

Tom Hubin
thubin@earthlink.net

77

Video P*r*o*b*i*n*g / Re: Post your Point Clouds Here!

« on: July 15, 2008, 03:18:45 AM »

Hello Gaston,

> I do not have the facility to set the exposure time, the camera is taking 29.970 frames/sec and that's it.

On the Video Probe screen, select Stop Video then select Source and/or Format to see if you have any exposure or resolution options. Then select Start Video to resume. Don't be surprised if Mach3 crashes when you try this.

You may find similar options with the camera vendor's software. Sometimes you can setup your camera options with the vendor's software and Mach3 will use that setup. I can send you stuff for other cameras that seems to be fairly generic.

> I have set the FOV to 70 which when calibrated with a 1" Styrofoam block give a distance approx right.
> The x-y dimensions seem also right.

I see that the camera is shipped with a lens for 70 degree FOV. The lens is replaceable. I suspect that the thread is M12-0.5mm. If so, you can get lenses on ebay. Search for M12* and lens* in title and description...or I can point you to some I have seen listed. I intend to get some of these M12-0.5mm threaded lenses from ebay but have not yet done so.

With a 70 degree field of view you will be able to look at large items in coarse detail. You will not get enough detail to pick out Lincoln's head on a penny. You will also have a good deal of distortion. You probably can determine by diameter that the coin is a penny, nickel, dime, quarter etc. To reproduce my results you will need a 12mm focal length lens or longer.

> > What camera are you using? Do you know the lens focal length? Do you know the field of view?

> http://www.supercircuits.com/Security-Cameras/Board-Cameras/PC302XS with a digitizer.
> The resulting image is 640x480 and black and white.

Black and white is good. Color info is not useful and results in larger data transfer that takes longer to transfer and process. Also, B&W cameras usually produce sharper images than color cameras. 

> I have found that the if I lower the voltage on the laser line generator I get a cleaner image of the line.

That is probably due to saturation of the CCD array. The fix is to reduce the exposure time or sensitivity of the camera. When you reduce the laser power you also reduce the CCD saturation, so that helps, but this does not reduce background noise like reducing exposure time does.

> I have to work on my setup so I can change the distance between the camera and the laser easily.
> Right now the laser is pointing straight down and the camera is at ~45deg.

Neither the camera nor the lens should be pointed straight down. The camera and the lens need to be pointed 90 degrees apart. I have chosen to have the laser 30 degrees CW from the Z axis and the camera 60 degrees CCW from the Z axis, as shown here: http://www.machsupport.com/forum/index.php/topic,5023.msg42913.html#msg42913 .

> As for meshing in Machloud:
> I do not understand what the Delauney Set is used for
> BallPivot mesh seems to works ok with the Prop.txt supplied by Art but I have not so far succeed to pick winning values > for the Ball Diameter, shortest Edge and Max Angle to produce the same kind of results on anything I have scan so far. I > am using inches dimensions. I wish somebody could explain how to set those parameters?

Sorry but I am also clueless there.

Tom Hubin
thubin@earthlink.net
 

78

Video P*r*o*b*i*n*g / Re: Post your Point Clouds Here!

« on: July 13, 2008, 06:17:49 PM »

Hello Gaston,

> 1. I would love to see a print screen of the 3DVideoProbe panel to make the scan of the penny.
> Could you please post it ?

I have posted a scan setup from today. The video shows a single line through the center of the penny. Exposure time was set at 1/3840 seconds and the resolution was 640x480. Mirror (left to right) and Flip (top to bottom) were selected since the camera is upside down.

I think that only the FOV is different. I changed it from 18.1 degrees to 15.4 degrees and got better proportions on the penny. This is about right for the +12mm focal length lens that I use on the Digi Watchport/V2 camera.

> 2. I have loaded the file thubin080712CloudPenny03.txt in MachCloud but when I go to mesh it the cloud disappears and no mesh is being done.
> Have you mesh that cloud? If yes what settings do you make on the BallPivot mesh panel?

I have had very little success with any of MachCloud's features. I have been using the free evaluation version of Rhino but have done little with it other than display and measure pointclouds.
I have figured out how to delete points from the cloud in Rhino. Never could get that to work right in MachCloud.

I could not get meshing or any of that kind of stuff working in MachCloud.  I have not tried that in Rhino.

What camera are you using? Do you know the lens focal length? Do you know the field of view?

Tom Hubin
thubin@earthlink.net

79

Video P*r*o*b*i*n*g / Re: Post your Point Clouds Here!

« on: July 12, 2008, 02:59:27 PM »

Hello,

Here is a single pass scan of a penny. yStep is 0.010 inches. Speed is 5ipm.

The penny is 0.75 inch diameter. This appears to be correct in the Y direction but more like 0.87 shown in the X direction.
I was guessing at the camera FOV. I will try to get the scaling right another time.

Camera is a Digi Watchport/V2 640x480 CCD webcam with exposure control set at about 1ms.
Exposure range is anywhere from 1/30000 sec to 1/4 sec.

Laser is a 5vdc, red (I forget which wavelength) module from Aixiz.
The laser module is getting power from a second USB port. 
I did not get this on ebay since Aixiz does not list their 5vdc modules with adjustable lenses.

Computer is 800MHz Dell Inspiron 8000 laptop.

Attached Txt file is the point cloud produced by Mach3.
Attached Gif file was produced by Rhino.

Tom Hubin
thubin@earthlink.net

80

Video P*r*o*b*i*n*g / Re: Post your Point Clouds Here!

« on: July 04, 2008, 02:31:28 AM »

Hello,

Here is a single pass scan of a boxend wrench. yStep is 0.010 inches. Speed is 5ipm.

The wrench measures about 5.5 inches but shows up in Rhino as closer to 5.0 inches.

Camera is a PlayStation 2 (silver color housing, not the black version) with exposure control set at 1.
Higherst exposure setting would be 130 and lowest setting would be zero.

Laser is a 5vdc, red (I forget which wavelength) module from Aixiz. The laser module is gettting power from a second USB port. 
I did not get this on ebay since Aixiz does not list their 5vdc modules with adjustable lenses.

Computer is 800MHz Dell Inspiron 8000 laptop.

Tom Hubin
thubin@earthlink.nety