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I need to measure and detect a gap between two objects. I have an MB7062 (maxbotix) ultrasonic sonar sensor. Due to the wide beam of the sensor (FOV in distance of 2m is about 30cm from the center each side, that means totally 60cm,) the sensor cannot identify the gap. Is there any way to narrow its FOV so that it detects the gap?
This is the link to datasheet: http://www.warf.com/download/6439_4951_1.pdf
Sensor pin2 output:
The sensor operates at 42KHz. With speed of sound ~330m/s this gives a wavelength of around 8mm.
The Rayleigh Criterion allows us to approximate the imaging resolution of a system based on the diffraction limit. It is normally stated in terms of angular resolution, but a good approximation of the limit is
Resolution = Wavelength * Distance / Sensor Diameter
The source size appears to be about 25mm (based on physical dimensions in the datasheet), so at 2000mm distance, that sets a diffraction limit of ~80 wavelengths, or 640mm. This matches the observed behavior.
To get a resolution down to ~100mm @ 2m, would require a source of ~150mm in diameter. This might be possible to approximate with a custom elliptical horn (for focus at 2m), but I'm guessing this doesn't match you overall system requirements...
