Laser range finder - how small

Does anyone know how small a laser range finder could be made without resorting to high cost
or exotic components?
I've been looking around the various manufacturers but they all seem to be oriented towards
high end applications.
I'm looking for a low cost small (hand held) device - it doesnt need to be very accurate or
work over long distances - say about 4 meters max.

What sort of accuracy?

Keith

hi kieth

the best I can get but thats not helpful so say about + or - 5cm (10cm total) does that sound do-able
under my conditions? presumably it would be pulse repetition frequency and width that affects that? (I've only just started
learning about practical laser use - I have worked with radar so the concepts aren't too alien from that point of view)

At that sort of range you could possibly use triangulation which is simpler. A fixed laser and linear sensor, either analogue or digital for sensing. Otherwise, I would suggest phase shift method - it is better at short range than pulsed. There is complete project on AVRfreaks for a laser rangefinder like one of the Bosch ones. Given your short range you could get away with fewer frequencies (and lower frequencies). In fact, a single frequency of maybe 10MHz would do. Be careful of eye safety.

There is no reason why it needs to be "large" - it depends on what you need. The biggest parts are often the optics. With 25mm diameter optics it is going to be 50mm wide unless you are going to use one set of optics for both transmit & receive.

Keith.

Thanks keith - lots to think about there.
I'll go away and start reading.

Unless it needs a small spot size, don't ignore LEDs. I have a thesis somewhere written by someone who made a rangefinder for mapping out a room using an LED as a light source.

Keith

Probably not what I need this time but I'm always interested in anything new if you happen to come across it keith.

"A time of Flight Optical Range Sensor for Mobile Robot Navigation" by Michael James Brownlow. Department of Engineering Science, University of Oxford, Trinity Term 1993.

Keith

I'll check it out - thanks keith.