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Structured Light Experiments (LiDAR Attempt).

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LAN_403

Patrick

Tue Dec 11 2012, 10:30PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

iliasam wrote ...

Also there is another problem - DLIS-2k pixels a very small, so micron disalignment would case distance calculation error, so laser and image sensor holders must really solid and strong.

thats why i and the XV-11 use a vertical line generator, which light up the 4x32um pixels.

iliasam wrote ...

In my lidar I have found that the small pressure to one side of the lidar case error, and my sensor is only 128 pixel wide.
So now I am thinking about making lidar with stronger mechanics, and ELIS-1024 sensor.
ELIS-1024 can be switched to 128 pixels resolution, so the changes in microcontroller program will be small.

yes it must be ridgid. but with coarse pixels, youl loose range data... also my plan is to count dark pixels form close to far, then count lit pixels and divide by 2 then adding the dark pixel count. that would be one distance point.

Patrick

Wed Dec 12 2012, 05:28AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

New Work !

first visible light test arragement with red laser line generator.

12.7mm dia lens, with FL of 33mm. red laser light and its epoxied to a 1.5mm acrylic plate.

(the final version for IR will be epoxied to the 1.5mm thick filter.)

I shot the laser light in directly, so im not sure the beam width is accurate. beam length for the above test is 134 inches long, and in the pic its 0.140 wide...[thus 3.56mm wide @ 3.4m] and the thin beam is 0.033 " (or 0.8mm) wide.

EDIT: the O'great CAD gods are telling me that at 2.9m a 1.5mm beam will be 18um wide at the sensor plane, which is about 4 pixels wide.

iliasam

Wed Dec 12 2012, 08:55AM

Registered Member #8467 Joined: Mon Dec 03 2012, 05:36PM
Location: Moscow, Russia
Posts: 9

thats why i and the XV-11 use a vertical line generator, which light up the 4x32um pixels.

I wrote about horizontal misalignment, it does not depend on laser beam form.

Patrick

Wed Dec 12 2012, 09:00AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

iliasam wrote ...

thats why i and the XV-11 use a vertical line generator, which light up the 4x32um pixels.

I wrote about horizontal misalignment, it does not depend on laser beam form.

ok, i think for horizontal alignment, we just need the laser and detector to be ultra-stiff. and strong.

Iliasam, you should try with the ELS-1024, and ill try the DLIS-2k, that way well have good use of our efforts. then well evaluate the results and lessons learned. also want mine to be eye-safe.

edit: im thinking of using one of these RF 433MHz radios for the transmission of data.

Shrad

Mon Dec 17 2012, 01:52PM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780

Patrick,

While searchink for laser diode driver papers I stumbled upon this :

I think it is really close to what you are attempting and contacting them would raise a flag on several issues you could face, so more energy is spent polishing the design instead of bumping on obstacles

Patrick

Mon Jan 14 2013, 01:32AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

ok new work completed...

ive got two line generating lasers, one will be kep as a backup, in case i kill the other.

for 12 US$ i have a small barrel sized IR laser. I cut the case open to learn its made out of nickel-plated copper, which explians why its too dam heavy. having hack-sawed the case open ive found the back 80% of the tube filled with a dense populated circuit board, so thats a relief. the driver is fully integrated and working.

i wish i could figure out a way to rotate the beam and view port with out rotationg the sensor and laser, since moving brush contacts strike me as unreliable.

EDIT: i have removed half the wheight by means of cutting off the copper, but a thought occurs : that copper was the heatsink! DAM!

iliasam

Wed Jan 16 2013, 01:56PM

Registered Member #8467 Joined: Mon Dec 03 2012, 05:36PM
Location: Moscow, Russia
Posts: 9

i wish i could figure out a way to rotate the beam and view port with out rotationg the sensor and laser, since moving brush contacts strike me as unreliable.

As far as I know, SICK lidar have a special scanning mirror:
0 Aa317 A7f4c95e M

But I think that this scheme is not suitable for triangulation lidar.
Hokuyo lidar seems to have brush contacts: http://www.iheartrobotics.com/2010/03/under-hood-secrets-of-hokuyo-urg-04lx.html
Heato lidar have brush contacts.
Also i'm thinking that only brush contacts can give 360 scanning angle.
I have found this contact brush, it is looking interesting: http://www.adafruit.com/products/736

that copper was the heatsink!

I think that if your laser's power less then 5mw, laser and it's driver does not need heatsink.

Patrick

Wed Jan 16 2013, 06:32PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

yeah im already looking at carbon/graphite brushes, the geometry of a rotating viewport doesnt seem compatible with our trigonometry. i may start to etch boards soon.

Carbon_Rod

Thu Jan 17 2013, 08:56AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

...still standing firm like the Oak?

Have you considered blinking the laser off, and doing image background subtraction to recover your signal line?

Best of luck,
Rod

Patrick

Thu Jan 17 2013, 09:21PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Carbon_Rod wrote ...

...still standing firm like the Oak?

Have you considered blinking the laser off, and doing image background subtraction to recover your signal line?

Best of luck,
Rod

yes i am already implementing the blink rate into my design, and the DLIS-2k is compatible with image subtraction at high speed.

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