Open Source Laser Range Sensor Converts the Speed of Light into the Speed of Sound.

Open Source Laser Range Sensor Converts the Speed of Light into the Speed of Sound

Press Release, February 2014:

In a direct attack on both the laser rangefinder market and the ultrasonic rangefinder market, LightWare Optoelectronics (Pty) Ltd, a South African based manufacturer of laser rangefinders, has begun production of an open source laser sensor (OSLRF-01) that can convert signals traveling at the speed of light into signals traveling at the speed of sound. This sensor has all the benefits of a laser rangefinder, like direct aiming, long range, immunity to noise and wind and high accuracy but non of the headaches associated with the super high speed circuitry normally found inside laser products. Instead, the OSLRF-01 outputs analog signals that look just like those found on an ultrasonic sensor. These speed-of-sound signals can easily interface directly with the ADCs of a microcontroller where conventional ultrasonic signal processing and timing algorithms can be applied to the data.

If the speed of sound is too slow for you, there is a control input on the OSLRF-01 that lets you select what Mach number you want to work with, anywhere from Mach 0.1 up to Mach 5. Running at higher Mach numbers means that the analog signals get faster and the time it takes for the laser/ultrasonic pulse to make a round trip gets shorter. So if your processor can handle the additional speed, you can have a quicker response time.

The OSLRF-01 can be used as the "bare metal" front end in a complete laser or ultrasonic rangefinder, or it can become a conventional distance sensor connected directly to the host processor on small robots, UAVs or UGVs. All the components on the OSLRF-01 circuit board are readily available from the large electronics components suppliers and there is no electronic trickery hidden inside ASICs or FPGAs. The OSLRF-01 doesn't even have a processor, so there's no fancy software to worry about either.

A brief technical description and circuit diagram can be found here: OSLRF-01 description. With input from the open source community, the OSLRF-01 could one day become the foundation of many other sensing devices such as scanning LIDARs, proximity sensors, depth/width/height gauges, obstacle detectors and altimeters.

LightWare is currently selling the OSLRF-01 at US$100.00 excluding shipping and local taxes. For sales enquiries visit: LightWare Optoelectronics (Pty) Ltd

Hey Doug, there are quite a few differences between the SF02/F and the OSLRF-01. The most obvious being that the SF02/F has a 32 bit, Arm processor and FPGA to control the LRF functions. Other component differences include the optical filter, APD detector and the timing system.

In the SF02/F, the optical filter has a very narrow passband band that's matched to the laser and it gives the SF02/F better performance in bright sunlight. The APD detects the return signal and it's about 100 times more sensitive than a regular photodiode, hence the longer range. Both the optical filter and the APD are very expensive components but are critical to the performance of the SF02/F.

The timer on the SF02/F is an interesting system. It's based on something I saw at McDonald Observatory in Texas quite a few years back. The guys running the LLR program (Lunar Laser Ranging) were discussing how to improve the accuracy of the timing system they were using to measure to the Apollo reflectors on the moon, and I was stunned to see that their existing system used an analog ramp interlaced between digital clock cycles. I've always wanted to have a go at designing something similar, and when they shut down the LLR a few years ago, I started working on the timing system that you now have in the SF02/F - a small tribute to the awesome work that the people running the very last Apollo project had done.

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Comments

LightWare - Laser Developer February 18, 2014 at 12:43am

I've had a few enquiries from people who want to use the OSLRF-01 in bright sunlight. Whilst the unit will still operate, sunlight injects unwanted photons into the detector and this creates electrical noise which can make it harder to find small return signals. The best way to cut out this noise is the use a narrow band, optical filter that has a pass-band which matches the color of the laser. These filters appear opaque to sunlight and block out all but a very small portion of the solar spectrum (see picture below).

The OSLRF-01 has been designed to accept one of our standard optical filters (905nm) and if you want a unit with a filter then order the OSLRF-01 and filter separately and we will instal the filter for you at no charge.
LightWare - Laser Developer February 6, 2014 at 2:38pm

Hey Doug, there are quite a few differences between the SF02/F and the OSLRF-01. The most obvious being that the SF02/F has a 32 bit, Arm processor and FPGA to control the LRF functions. Other component differences include the optical filter, APD detector and the timing system.

In the SF02/F, the optical filter has a very narrow passband band that's matched to the laser and it gives the SF02/F better performance in bright sunlight. The APD detects the return signal and it's about 100 times more sensitive than a regular photodiode, hence the longer range. Both the optical filter and the APD are very expensive components but are critical to the performance of the SF02/F.

The timer on the SF02/F is an interesting system. It's based on something I saw at McDonald Observatory in Texas quite a few years back. The guys running the LLR program (Lunar Laser Ranging) were discussing how to improve the accuracy of the timing system they were using to measure to the Apollo reflectors on the moon, and I was stunned to see that their existing system used an analog ramp interlaced between digital clock cycles. I've always wanted to have a go at designing something similar, and when they shut down the LLR a few years ago, I started working on the timing system that you now have in the SF02/F - a small tribute to the awesome work that the people running the very last Apollo project had done.
Developer

Doug Weibel February 6, 2014 at 2:13pm

@Ranaud - No. If you want plug and play, look at the SF02. The SF02 is more money, but also 4x the range.

@Laser Developer - I have also been testing the SF02 and have been really happy with it thus far. A cursory read of the OSLRF-01 data sheet makes it appear that it has the same laser. Is the reduced range purely a function of the higher update rate and is there any ability to change that?
renaud barbier February 3, 2014 at 9:16am

so... how to interface this one on our apm or pixhawk? does it simply replace sonar as a plug and play?
Phill Scott February 3, 2014 at 7:49am

I have to say, I'm talking about the products these OEM type sensors might be found in. My mistake for not making it clearer.
Gisela & Joe Noci February 3, 2014 at 7:46am

Well, at least we can access the Lightware webpage - more than can be said for the 'sick' SICK.com page....
Dan Neault February 3, 2014 at 5:30am

I have to disagree with that, given SICK was at my office last week, and what they showed me :)
Phill Scott February 3, 2014 at 5:30am

Hi Laser Developer,

I don't know if you're the same person I've had a couple of conversations with over email, but I just wanted to say how pleased I am that you guys are bringing this to us. Looking at similar products, the prices are crazy, so I'm really happy to have the ability to take your kit and include it in my designs for future products!

Cheers,

Phill

Thanks again!
LightWare - Laser Developer February 3, 2014 at 5:26am

Dan, the main advantage of this technology is that you can push the range a lot further than most of the TOF camera devices and right now it is cheaper. However, we acknowledge that specialized TOF chips will be the wave of the future and, since we like riding this kind of wave, we will be releasing 1D, 2D and 3D TOF cameras based on these chip sets in the future as part of our regular product lines.
Dan Neault February 3, 2014 at 3:57am

Great stuff, but TOF CMOS arrays are cheap now, and getting cheaper everyday. Don't think this or other tech will match the results vs cost of TOF arrays.

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