Hey all, I am thinking about a device for optical distance measurement, and wondering why it hasn't been done already/ if it could work. Basically it works like this:
You have an emitter, perhaps a laser diode.
A reflector. Not a retroreflector, they have their uses but in this case I am thinking a ball bearing. This way the reflection occurs from exactly a known point on the surface of a sphere, which has many advantages.
a receiver, a photodiode of the type used in telecom, for instance, so capable of fast response.
An oscillator, whose output is to the laser diode, and whose input is the photodiode.
The goal here is to make a circuit which oscillates at a frequency that is a precisely known function of the optical path.
Thus, the changes in the distance from a reference point on the emitter/reciever thing, perhaps the center of the emitter, and the center of the ball bearing can be calculated easily, from the frequency at which the circuit oscillates This is interesting because while time periods are hard to measure, frequencies are easy and cheap to measure to very high accuracies. If the frequency can be converted with a precisely known function to a length, and vice versa, that opens very important doors for measurement from one point to another. The application I have in mind is CNC machinery.
I know it wouldn't be trivial to make this work, filtering, perhaps frequency filtering, might be in order. A phase locked loop that locks to the resonant frequency could be part of it, you can see. My main concern would be signal to noise ratio, there is not much light returned by the reflector. I can think of some means of improving that, such as a shade and a filter for the laser light.
I don't see why it would not work though? Precise point to point distance measurement would have major implications for the cnc machinery industry. Currently, optical distance measurement is very expensive and labor intensive because it is not point to point, and is complicated and expensive in other ways.
You have an emitter, perhaps a laser diode.
A reflector. Not a retroreflector, they have their uses but in this case I am thinking a ball bearing. This way the reflection occurs from exactly a known point on the surface of a sphere, which has many advantages.
a receiver, a photodiode of the type used in telecom, for instance, so capable of fast response.
An oscillator, whose output is to the laser diode, and whose input is the photodiode.
The goal here is to make a circuit which oscillates at a frequency that is a precisely known function of the optical path.
Thus, the changes in the distance from a reference point on the emitter/reciever thing, perhaps the center of the emitter, and the center of the ball bearing can be calculated easily, from the frequency at which the circuit oscillates This is interesting because while time periods are hard to measure, frequencies are easy and cheap to measure to very high accuracies. If the frequency can be converted with a precisely known function to a length, and vice versa, that opens very important doors for measurement from one point to another. The application I have in mind is CNC machinery.
I know it wouldn't be trivial to make this work, filtering, perhaps frequency filtering, might be in order. A phase locked loop that locks to the resonant frequency could be part of it, you can see. My main concern would be signal to noise ratio, there is not much light returned by the reflector. I can think of some means of improving that, such as a shade and a filter for the laser light.
I don't see why it would not work though? Precise point to point distance measurement would have major implications for the cnc machinery industry. Currently, optical distance measurement is very expensive and labor intensive because it is not point to point, and is complicated and expensive in other ways.