|Surveyor Robotics Journal|
Wed, 18 Jul 2007
Simple (cheap) laser range finder
I recently located a very compact and cheap laser pointer to use as a range finder in conjunction with the SRV-1 camera. The laser is quite bright, but draws less than 45mA, is only 33mm long x 12 mm diameter (1.5" x 0.5"), and costs around $2 plus freight from Hong Kong.
Here's the ebay store that I purchased from ... Sure Electronics
It was really simple to add to the robot - I just replaced one of the IR LED's, and the existing interface electronics were exactly right for switching the laser on and off.
I used masking tape for a temporary mount, but it shouldn't be difficult to come up with a more permanent configuration.
Ideally, the laser should be mounted as far as possible from the camera to establish a long baseline that can be used to triangulate distances, but even with a baseline of only 2", it is possible to resolve distances of up to 6-8 feet with some accuracy at low camera resolution (160x128), with accuracy improving as objects get closer.
approx 10 ft
approx 6 ft
approx 3 ft
A nice configuration would be two or more lasers, with one or more looking forward, and one pointing downward to detect floor drop-offs. The beam can be focused or diffused to create a larger reflection, and the built-in SRV-1 image processing routines can be used to locate the bounced laser light, with the laser being switched on and off to confirm identity of the reflection.
We need to experiment with this approach and get some feedback from users, but given the lower cost and easy integration, we may consider replacing the SRV-1's IR components with these small lasers in future production.