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I'm badly visually impared in one eye and find judging distances while walking downhill hard. My goal is to create a real time range finder than can display the distance of the next step(s) while at normal walking pace. for example: walking down a 4 in 1 hill on an uneven forrest path.

First step is to choose a method of range finding that is lightweight, low power, accurate to within 5cm and returns distances in real time. The range of the device needs to be 50cm to 500cm. The target area for measurement needs to be about 10cm square.

This is my first attempt at this kind of device and know nothing of what types of sensors even exist, so even research suggestions would be useful.

So, what types of sensors exist that could return a realtime distance measurement?

Michael Karas
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Luke Douglas
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EDIT: The answer that I originally referenced got deleted, so I will edit to incorporate info from both...

One common approach for distance finding is to use an IR sensor for example, the SHARP one found here (https://www.sparkfun.com/products/8958). Basically, this is a IR LED and a 1-D image sensor combined with some onboard DSP. The 1-D image sensor picks up the reflected light at an angle which depends on the distance the object is to the sensor, as shown here: enter image description here AFAIK, the IR distance sensors are only available with analog voltage ouput, so you will need a free A/D pin on your microcontroller.

Another alternative is an ultrasonic sensor. There are cheaper alternatives, but one that my students have had success with is this: https://www.sparkfun.com/products/9495.

This particular device is convenient because it has 3 different read out methods. You can use either an analog voltage (which you can digitize using an A/D converter on a microcontroller), or read serial data directly. You can also have it output a PWM, which might be useful if you are driving some servo motors directly (not sure if it is actually servo compatible).

There are some advantages and disadvantages of using ultrasound vs. infrared. Ultrasound is more robust to different surfaces, and the beam width can be varied by choosing a particular sensor (so you can have it pick up obstacles in a wider or narrower area). On the other hand, having multiple sensors might cause interference, although there are ways to get around this. Also, ultrasonic sensors tend to be more expensive than the IR sensors previously mentioned.

Also, the Maxbotix ultrasonic sensors feature Jesus (look carefully on the PCB). This could be an advantage or disadvantage depending on your application.

Zuofu
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As suggested ultrasonic sensors are cheap and gives usable readouts, but it depends on the beam width which tends to spread in wider radius when used on longer distance. Also if used on porous/spongy ground, beam will be dampen.

I would not rely only on ultrasonic sensor. I would combine it with IR and returns the mean value of both outputs.

Gossamer
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