Narrowing the beam of Ultrasonic Sensors

Other Hardware Sensors
1

A major characteristic of ultrasonic sensors vs. optical distance sensors is their wide cone of "vision" which can be good and bad. In my usage, it is unfavorable. As to why I didn't get an IR sensor was because the problems from those were even less favorable. There are a couple of things that I thought might work

  1. Cover the transmitter/receiver/both and only leave a small hole
  2. Put the transmitter/receiver/both at the end of a tube
    Would either of these be plausible? Thanks.
2

Sound will propogate in the same cone soon as it leaves your tube. It's like trying to narrow the ripple of water when dropping a stone in a pond.
Whatever your problems were with the IR, they can be more easily overcome than what you're trying to do with ultrasonic.

Light gets more effective when you focus it. Sound gets wasted for the most part.

3

So what is it that you are trying to do, and why is IR not suitable?

4

For a single source, the wavelength of a wave and the defining aperture determine the beam spreading properties.

Compared to sound, light can be focused into narrow beams because the wavelength is so much smaller.

With a single sound emitter, you can use a large focusing dish to give a (relatively) nondivergent beam, but the beam will be roughly the diameter of the dish.

5

stormfalcon32:
A major characteristic of ultrasonic sensors vs. optical distance sensors is their wide cone of "vision" which can be good and bad. In my usage, it is unfavorable. As to why I didn't get an IR sensor was because the problems from those were even less favorable. There are a couple of things that I thought might work

  1. Cover the transmitter/receiver/both and only leave a small hole

Probably make the beam wider by diffraction

  1. Put the transmitter/receiver/both at the end of a tube

Probably get false triggering from reflection from tube end

Would either of these be plausible? Thanks.

You could try, but I fear the above problems might bite you.

Ideally you would focus the beam, but that requires either a large parabolic reflector, a gas-filled
balloon lens (again unwanted reflections would happen), or a phased array of transducers.

The wavelength of 40kHz sound is a mere 8mm, similar size to the transducers, so the beam must
spread out by basic physics. Any system to focus would need to be an order of magnitude larger than
the wavelength.