Laser scanning using a distance-sensing laser

[normand blais]

Cut from this thread/post

...................
Got the link from MagWeb on
http://www.david-laserscanner.com/fo...ulptris#p12081 but that is another story...

[smreish]

David's Laser works well. I have done many instances of a video camera and laser pointer to create cloud point data. Fun.

Maker Faire or Make magazine is a great resource for this type of DIY laser imaging.

...back to the fun.

[Conrado_Navarro]

we also can put the scanner on the Mechmate, so besides a cnc router we can have a cnc scanner. I know it can be done, Just I have no time to do it.

[Gerald D]

If you want to mount a simple laser scanner on the MechMate, we can start another thread for that.
(there are some simple ideas that do work - simpler than the "David" style)

[normand blais]

I have seen some scanner technique on mach forum .but i dont have mach

http://www.machsupport.com/forum/ind...action=search2

[Gerald D]

Normand, your link doesn't work

I get the impression that the DIY folk interested in laser scanning are too fixed on the "projected_lines_plus_camera" methods like the "David" method. We folk with CNC tables (or lathes) already have systems for moving a probe to a very precise location. What we actually seek is a non-contact probe than can measure distance to a precise spot.....and lasers can do exactly that.

Imagine having a pin-point beam laser pointing straight down, mounted to our y-car, so that stays a fixed height above the table, movable in the x & y directions. But this is a special laser that has an electrical output of the distance it senses its focus dot to be away from itself. Actually, this concept is well known in devices like this.

So, we need to find a laser distance measuring unit that measures in the range of about 2" to 10", with a resolution of say 0.05", that gives an electrical output that we can log while our CNC motors move the laser across the surface of the object that we are probing. Once we find a cheap enough distance sensing laser, the only other part is the programming. There is a ShopBotter, who was a programmer in a previous life, who built himself a system like this, and now makes money off it. But he doesn't believe in sharing. . . . . .

I have assembled this thread in the hope that we can explore / develop this "spot-height" laser sense method. We need to:
a. find a low-cost laser "head" with output of distance
b. develop programming that works with Mach or EMC that will record the point cloud.

[liaoh75]

Gerald, does this shopBotter sell a product we could use?

[Gerald D]

No David, he doesn't. And he doesn't discuss his method either.

Here is a starting point of a commercially available system.

[Gerald D]

PS. I didn't check other forums before starting this thread.....we may be trying to re-invent the wheel. But I doubt that this stuff is available "open-source" for Mach and EMC yet.

[normand blais]

That mach link is the search page, try laser scanner and 3d scanner there are video scanning there too
I did the laser line scanning ,my laser been cheap and under power had poor result . I upgraded with a slide projector like they suggest cut a mirror the size of a slide and scratch a line with a razer blade .Nice bright line, thin much better than the laser I had.
The bulb burnt cause the fan stop.Cant find a replacement .So I might look for a super bright led to replace the bulb like in david forum. They even have structured light scanning with micro projector. The annoying thing with david scanner was the calibration pannel .They found a way to calibrate and replay the the line motion so the pannel are not nedded after (some with Mach )

Got the feeling this is the system he use http://www.scantech.dk/3d-laser-scan...-on-a-cnc.html

David he sell only to the military

[TheDave]

Love this idea!!

Preliminary find:
http://scientificsonline.com/product.asp_Q_pn_E_3095300

I think this does more than what we need and probably costs too much.

[Gerald D]

Dave, that laser does not have distance sensing.

Here is Baumer's range of distance sensing lasers.

Acuity range

It might also be possible to hack into one of these.

[D. van Randen]

Hi Guys , this topic has fascinated me for ages , I have never had the time to build but plenty of time to troll the internet.

Leica has hacked one already

Leica Disto D330i with Blue tooth, resolution is 1/32 or .03mm


there is a very good discussion thread on machsupport.com entitled video p*r*o*b*i*n*g. (yes it is spelled that way)

Another word to use when searching laser distance, is displacement. Keyence has several displacement models , but not cheap even if you go through ebay.

Then there is the alternate industrial method using video capture cards like those by Epix, but involves some programming of a camera and laser pointer to create the "blob" for tracking.

or do what this university student did.

http://sites.google.com/site/todddan...m_laser_ranger

[Gerald D]

I think the trick is to get the "camera" as close as possible to the line of the beam, so that one can probe deep profiles without the camera losing site of the spot. The closer the camera, the more difficult the triangulation. This is why I like the packaged sensors where the camera/detector is in the same housing as the laser emitter and it is already factory calibrated.

[hennie]

But they are so expencive

[normand blais]

Here is a compilation of 3d scanner info and link.http://www.simple3d.com/

[Gerald D]

Hennie, you can buy a Baumer distance sensor from RS components for R7000 [$1000], which IS expensive, but it is already focused and calibrated and it needs no fiddling around, compared to the David style dot/line/webcam/ DIY setup. And if RS has stuff like this for $1000, it probably means there are reasonable equivalents for much less. And realise that the distance sensor is the ONLY bit of hardware needed to make it work - the rest will be software, or macros for Mach3/EMC which already exist to some extent.

Normand, that is a long list....is there anything in there that helps us to put a Z-distance sensing laser onto an XY table and run it with Mach/EMC?

[hennie]

Never thought about it in detail,we are so used to plug and play.

[danielpower]

I wonder the price of distance-sensing laser.

[PEU]

what about his one: http://www.tormach.com/blog/?p=1038 not laser actually.

[Gerald D]

Sorry Pablo, that is 2D scanning only ...... you can call it "tracing", like using old-fashioned tracing paper.

[normand blais]

Gerald you right this is a long old link ,lots of missing link .I did not find anythyng . I never tough much about distance sensor scanner, to complicate or expensive for me . There is many type of scanner for many occasions.I am aiming more at scanning living been.dot scanning is too slow for that .Even line scanner like david is at the possible limit with the right equipment. Hacking electronic is to complicate for me I have to wait for some bright guy to guide me as to what to put together. On the local scene here Creaform bougnt Inspect.

[Gerald D]

There are distance sense lasers on e-bay for $100 at the moment, but they are the wrong spec. (long distance (low near resolution), big spots) Anybody know what the Leica Disto D330i costs?

[D. van Randen]

www.lascolaser.com 379.00 usd

Another scanning site , this idea could be quite good speed wise. www.grasp3d.com
They also supply lasers for scanning

The Grasp3d site is an offshoot of this site, www.intricad.com

[digger]

There is no price tag, but probably could be useful if the price is reasonable.

http://www.aculux.com/Index.htm

[riesvantwisk]

This method is very nice :
http://www.geeky-gadgets.com/proform...ra-23-11-2009/

However, I think this system would be bad for relieve scanning.

It seems like each scanning method has it's up's and downs, price, vs speed vs accuracy vs information captured.

[Gerald D]

Can I gently point out that the title of this thread is Laser scanning using a distance-sensing laser ?

[TheDave]

Everywhere I look, the Leica DISTO™ D330i sells for USD $379. I like the Bosch one you listed, about $100. Definitely worth hacking!

[Gerald D]

Before hacking a Bosch, or similar, there are a couple of things that must be checked:
- fairly small spot size
- a good resolution
- and a good speed of getting the data out.

Also realise that the laser/detector can be mounted fairly high up on the y-car, if needs be.

[riesvantwisk]

I have used the mentioned sensors.

I have been developing a system (with some colleagues, I did the software, must be 12 years ago) that could detect if there was cap correctly positioned on a oil drum (50 barrels)
if the cap was in a angle we could detect that, or if it was missing we could detect that.
The system consisted of a stepper motor that would move the laser sensor over the oil drum and measure distances. The output of that was just a single graph where we could see the slope of the top of the oildrum, including the cap, we did see a slope on the cap when it wasn't position right, or a big 'hole' when the cap was missing.

With scanning objects the problem here is that the datastream from the laser sensor needs to be well in sync with the position of the stepper motor, if you want to measure any object with decent speed, you don't want to have a system that goes like 'step->read->step->read', much like the touch probe systems.

With the measurements of the barrels we didn't care to much about this, because we knew the size of a barrel, and thus we could calculate and scale back pretty well, we even didn't care much about the speed of the sensor.
With scanning objects it's required that the software pulsing the stepper motor, and the software that reads the output of the laser distance sensor, must by well synced or else the object appears skewed or mis-formed in some way.

The sensors that RS components are selling (the square version) consist of a simple laser, and a single line CCD array, the CCD array is like found in a good old scanner, the CCD array simply 'detect' the laser dot on one or more of the arrays and based on the angle they know the distance. This is described well here : http://archives.sensorsmag.com/artic...laser/fig1.gif (http://www.eltrotec.com/db/pdf/LDS60e1.pdf)


A DIY version of this could be a single laser pen, and a webcam + red filter. The webcam can then detect the red dot on the object, the Mechmate will then move the camera + laser pen over the object. We simply point the laser down, the object (unless very shiny objects) will have enough diffuse reflection to get spotted by the camera.


Detecting a single dot on a camera image is very simple. You are only limited by scan speed because of the camera that has only (usually) 25 frames/second. The good part is, that a CCD camera has many lines instead of a single array, so you could potentially scan in one scan multiple lines at the same time.
For a better system, you might need two camera's along each side, for optimum laser point detection, may be even two laser in a angle, but that's just optimalisation.


With EMC you have a lot of control and you can add your own code to real time threads if you want to. If you use real distance sensors you then need to have a A/D converter and read that back over serial or parallel port. If you use EMC's real time treads for that then this can be perfectly synchronized so that steppers, position information and hight information can be accurately stored in one file.
If you use a camera stream then somehow this need to be stored on disk, and properly analyzed afterwards, I am not sure if there is enough CPU speed to handle that real time.


With Mach3 I am not sure how much control you have, and if you are allowed to write C code within the Mach3 kernel. if you can, then principles are the same as with EMC. If you cannot then there is not much you can do then step-measure-step-measure sort of system , like a touch probe.
Bottom line is, that if you cannot have your step-pulses synchronized with your read-outs from the sensor, then it's not going to work.