Project "Free" "LIDAR"

[Adrenalynn]

Hi Dr Robotnik,

First and foremost - welcome to the TRC!

I really appreciate your thoughts - let me describe what I'm observing from this nearly-failed experiment...

An advantage to a laser system such as this is that it doesn't need a second imager. It is inherently stereoscopic and massively more accurate. It can tell you to a fraction of a millimeter where any visible point in space is, and it can take those samples in a fraction of a second - but that's also its failing for a navigational system. Imagine that when you looked at a tree your brain computed the exact dimensions of every leaf and its exact distance from you and from every other leaf. Your brain would end up leaving a very messy misty grayish pink coating over everything surrounding you. Too much data. POP!

Every time this system samples its environment it has to deal with a point cloud representing more than a million pieces of information. As implemented, it has the exact distance of about 1.3 million points in space and their relation to each other. Data overload. Deciding how to optimize that data in a lossy fashion is a non-trivial problem. How do you really know what can be safely thrown away or ignored without processing all that data first? And every fraction of a second you need to make those decisions again. In the short space between those, you need to decide how to act upon that datastream.

I believe a worthwhile avenue for exploration in navigation is to simplify this system by sampling less data. If we just simply scan a laser line across the scene, look for breaks in the line (where objects start and stop) and then measure the simple angle to each obvious obstacle, we have a system with millimeter accuracy [or better] that doesn't get swamped with data overload.

I "over-solved" navigation, but as Metaform3D points out, it probably has application in problems such as object recogniton with variable orientation. That's a great problem too, but not what I was trying to solve.

Again, thanks and Welcome!

[LinuxGuy]

Originally Posted by milw

@Linuxguy, what 3d software do you use? I'm heavily into Cinema4D and can use Maya, trying to learn SolidWorks too. C4d is not really intended for CAD tho, more for Pixar type character animation, but I may use it to simulate my mech!

I'm using Alibre Design.

8-Dale

[rudi]

Here are some links that may be of interest:

http://www.pages.drexel.edu/~twd25/webcam_laser_ranger.html
http://www.seattlerobotics.org/encod...110/vision.htm
http://www.ugcs.caltech.edu/~dstaff/distance.html
http://ashishrd.blogspot.com/2006/11...ebcam-and.html
http://ashishrd.blogspot.com/2007/03/autonomous-rc-car-ii-with-wireless.html

[Adrenalynn]

Hi Rudi, welcome to the TRC!

Addressing your links:

- Dot-based. Same idea as my first. Too low of fidelity and speed for my use, or to really be thought of as a "lidar"
- I saw that page - that gentleman's a crazy hacker with some cooool stuff. Alas that bill of materials starts to look like a real SICK price-wise.
- Hadn't seen that page, thanks! Looks similar to #1 - low fidelity dot based.
- Same
- Same

The project I describe here is very different, but alas suffers from the problem of being too high fidelity. What I want to work on at this point is something like #2 above, only PC-webcam based rather than embedded hardware based.

Thanks for digging these up! And again, welcome to the TRC!

[robot maker]

seattle robotics encoder has lot of good info on the site and i saw the same link and wanted to make something close to that design using mostly a webcam ,and cpu

Adrenalynn have you tried different lasers ,like different colors and straight line,and crosshair type
at my job ii so great i can get samples of what i need or company can buy them
and have a project on counting gold rings in a special sensor tube for detecting freon,so will need a laser for it

Originally Posted by Adrenalynn

Hi Rudi, welcome to the TRC!

Addressing your links:

- Dot-based. Same idea as my first. Too low of fidelity and speed for my use, or to really be thought of as a "lidar"
- I saw that page - that gentleman's a crazy hacker with some cooool stuff. Alas that bill of materials starts to look like a real SICK price-wise.
- Hadn't seen that page, thanks! Looks similar to #1 - low fidelity dot based.
- Same
- Same

The project I describe here is very different, but alas suffers from the problem of being too high fidelity. What I want to work on at this point is something like #2 above, only PC-webcam based rather than embedded hardware based.

Thanks for digging these up! And again, welcome to the TRC!

[Adrenalynn]

Yes. It's not so much the laser color as requiring a line. An inexpensive line level from Harbor Freight ($20) , one of the larger survey-style ones, is ideal.

The larger project to get the "perfect" amount of detail is *very* quickly looking at the line breaks and the parallax in between each break to determine distance. This ideally should be done at least ten times a second.

[robot maker]

i thought you are using a dot laser or are you using a line laser
we use single dot laser in a infrared thermometer and have alot of them ,plus a few line lasers

Originally Posted by Adrenalynn

Yes. It's not so much the laser color as requiring a line. An inexpensive line level from Harbor Freight ($20) , one of the larger survey-style ones, is ideal.

The larger project to get the "perfect" amount of detail is *very* quickly looking at the line breaks and the parallax in between each break to determine distance. This ideally should be done at least ten times a second.

[rudi]

Thank you for the warm welcome and response.

I got some line lasers for < $4 each here: http://search.ebay.com.au/_W0QQsassZff77hh

[Adrenalynn]

Without many many hours of scanning, it would be all but impossible for a point laser to make a 3D image like the ones I was showing. The first was a line generated through homemade optics (bubble level). Second was a line from a cheap line level.

I'm sure those IR thermometers are great, but once you convert them to a line, how wide is it, and what does it look like through a cheap camera? Because if the line is not very bright, very thin, and very visible in the camera, it's utterly worthless.

Hi Rudi, those are pretty cool, but the shipping will eatcha alive (at least to the US here).

[robot maker]

will have to try them
so the one from harbor freight is the one you are using
will look into get one to compare to ones i have,what class is the one you are using and power

my favorate place for optics is edmund scientific and optic bench is scientificsonline same company just low cost items optics and alot more,looking into buying a fiber optic system for my robot hand,something like a borescope,for beer-bot hand for finding a beer can or bottle using roborealm

Originally Posted by Adrenalynn

Without many many hours of scanning, it would be all but impossible for a point laser to make a 3D image like the ones I was showing. The first was a line generated through homemade optics (bubble level). Second was a line from a cheap line level.

I'm sure those IR thermometers are great, but once you convert them to a line, how wide is it, and what does it look like through a cheap camera? Because if the line is not very bright, very thin, and very visible in the camera, it's utterly worthless.

Hi Rudi, those are pretty cool, but the shipping will eatcha alive (at least to the US here).