CN111351585A - Phase measurement method using sawtooth wave phase modulation - Google Patents

Abstract

The invention discloses a phase measurement method using sawtooth wave phase modulation, which comprises the steps of firstly setting a phase to be measured as a signal carrying the phase, then carrying out phase modulation through periodic sawtooth waves, carrying out Fourier transform on the modulated signal in a period, and calculating a phase value. The invention adopts sawtooth wave to modulate phase, the modulation and demodulation process is convenient, the specific phase information can represent physical quantities such as length, optical path, refractive index and the like, the change information of the corresponding physical quantity can be obtained by measuring the phase change, and the invention can be widely applied to various measurement fields relating to phase.

Description

Phase measurement method using sawtooth wave phase modulation

Technical Field

The invention belongs to the technical field of phase measurement, and relates to a phase measurement method using sawtooth wave phase modulation.

Background

The phase measurement has the advantage of high resolution, and can measure micro phase change under one thousandth and one ten thousandth of wavelength. Currently, there are various phase measurement methods, which mainly include: heterodyne method, phase shift method, phase modulation method. The heterodyne method generates two paths of electric signals with a certain small frequency difference, namely electromagnetic waves or light waves, and the two paths of electric signals generate beat frequencies, wherein the phase of the beat frequency signals is phase information to be measured. The phase shift method is to use a phase shift device to generate several fixed phase shifts according to a certain step (such as pi/4), and to calculate the phase value by the signal under different phase shifts, which requires precise control of the phase shifter. The phase modulation method has the characteristics of low cost and simple design. The general phase modulation method is to make the phase periodically change according to the sine form, then extract the direct current signal (or double frequency signal) and single frequency signal in the modulation signal, these two paths of signals are mutually orthogonal, calculate the phase information from it, belong to indirect measurement, the work load is large.

Disclosure of Invention

Objects of the invention

The purpose of the invention is: the phase measurement method using sawtooth wave phase modulation is provided, phase modulation is performed by using sawtooth wave, phase information is obtained by directly demodulating by using a phase-locked amplifier, and the modulation and demodulation processes are convenient.

(II) technical scheme

In order to solve the above technical problems, the present invention provides a phase measurement method using sawtooth wave phase modulation, which includes the following processes:

first, the phase to be measured is set to

The signal carrying this phase is:

wherein A (t) and B (t) are amplitude and bias, respectively,

phase information to be extracted;

then, phase modulation is performed by a periodic sawtooth wave, where T is the modulation period and T is the modulation amplitude

Then the phase change over one complete cycle is:

the modulated signal becomes, within one period:

then, by fourier analysis, the X and Y signals were found to be:

x and Y are independent of signal bias B, X, Y the two signals are orthogonal to each other and have amplitude ratio of

Thus, there are:

wherein, in

In the case of (1):

(III) advantageous effects

The phase measurement method using sawtooth wave phase modulation provided by the technical scheme adopts sawtooth wave phase modulation, the modulation and demodulation processes are convenient, the specific phase information can represent physical quantities such as length, optical path, refractive index and the like, the change information of the corresponding physical quantity is obtained by measuring the phase change, and the phase measurement method can be widely applied to various measurement fields relating to phase.

Drawings

FIG. 1 is

Analog waveform in the case.

Detailed Description

In order to make the objects, contents, and advantages of the present invention clearer, the following detailed description of the embodiments of the present invention will be made in conjunction with the accompanying drawings and examples.

The phase measurement method using sawtooth wave phase modulation of the present invention includes the following processes:

first, the phase to be measured is set to

The signal carrying this phase is:

wherein, A (t) and B (t) are amplitude and bias respectively, which may change with time, and the phase information can be directly extracted by avoiding A and B through phase modulation

Then, phase modulation is performed by a periodic sawtooth wave, where T is the modulation period and T is the modulation amplitude

Then the phase change over one complete cycle is:

the modulated signal becomes during one period (the modulation period T is short, and the signal amplitude a and bias B can be considered constant during a short time):

then, by fourier analysis, the X and Y signals can be found as:

observing the above formula, the following characteristics are provided: x and Y are independent of signal bias B, X, Y the two signals are orthogonal to each other and have amplitude ratio of

Thus, there are:

in that

In particular cases of (a):

thus, only one phase-locked amplifier (or other methods) is used for demodulating X and Y signals, thereby calculating the phase information to be measured

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims (2)

1. A phase measurement method using sawtooth wave phase modulation, characterized by comprising the following processes:

first, the phase to be measured is set to

The signal carrying this phase is:

wherein A (t) and B (t) are amplitude and bias, respectively,

phase information to be extracted;

then, phase modulation is performed by a periodic sawtooth wave, where T is the modulation period and T is the modulation amplitude

Then the phase change over one complete cycle is:

the modulated signal becomes, within one period:

then, by fourier analysis, the X and Y signals were found to be:

x and Y are independent of signal bias B, X, Y the two signals are orthogonal to each other and have amplitude ratio of

Thus, there are:

2. the phase measurement method using sawtooth wave phase modulation according to claim 1, characterized in that

In the case of (1):

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