How to generate a uniform rectangular laser beam 1m high

Hi everyone,

I want to make a rover that can home in on a laser beam.
the rover will have a 10cm horizontal line of LDRs to detect the laser beam.

I can detect the laser beam using an LDR, Ardrino and code, however as my laser is only a point source
the rover won't be able to see it unless it is exactly the same height as the laser beam.

I have tried using lasers used for DIY, which generate a vertical beam.
The problem with this is that the laser light spreads out more and more as you move away from the laser - and hence the laser light intensity decreases the further you go away from it making is hard to detect.

If the laser beam was spread into a rectangular shape say 0.5m vertical height,
that would solve the problem as the line would cut through my horizontal array of LDRs on the rover.
My idea is to use a stepper motor with a mirror mounted on it to generate a sweeping vertical triangle of laser light which could be picked up by the horizontal LDRs on the rover. But again the further from the laser, the less the laser light would be reaching the LDRs :frowning:

I hope I have been clear, and hope someone wiser than me can offer me some advice :slight_smile:

Kind regards

A laser beam is collimated; it does not spread out radially in the same way that light from a point source spreads.

Your idea of a rotating mirror might work, as that preserves the beam collimation, but LDRs are too slow to respond to a brief burst of intense light.

If you decide to go that route, you will need to use photodiodes for detectors. Also, you will want filters on the photodiodes to reduce interference from background light. However, sweeping a vertical triangle of light leaves you with the problem of that the horizontal component is still highly collimated.

Consider a completely different approach, using the Arduino compatible Pixy camera to home in on laser dot (not the source). That has been done before.

Thank you very much for your advice :slight_smile:

I'll look into that immediately,


My edit crossed your post. See that last line for a different suggestion.

You might look up "light sheet microscope" to see how vertical or horizontal sheets of light are generated in practice.