CN111060190B - Generalized orthogonal demodulation self-mixing vibration measurement method and device - Google Patents
Generalized orthogonal demodulation self-mixing vibration measurement method and device Download PDFInfo
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Abstract
The invention discloses a generalized orthogonal demodulation self-mixing vibration measurement method, which comprises the following steps: acquiring two paths of laser signals with preset phase difference; calculating to obtain phase difference estimated values of the two laser signals; and acquiring vibration information of the surface of the vibration body according to the phase difference estimated value. The invention also discloses a device applied to the generalized orthogonal demodulation self-mixing vibration measurement method. The generalized orthogonal demodulation self-mixing vibration measurement method can obtain two paths of laser signals in a light path, obtain a phase difference estimation value of the two paths of signals through calculation and demodulate vibration displacement information of the surface of the vibration body, so that the surface vibration information of the vibration body can be obtained; the generalized orthogonal demodulation self-mixing vibration measurement method can be applied to the field of self-mixing vibration measurement, and vibration information of the surface of a vibration body is measured under the condition of two paths of non-orthogonal signals, so that the universality of the method can be greatly improved.
Description
Technical Field
The invention relates to the technical field of laser measurement, in particular to a generalized orthogonal demodulation self-mixing vibration measurement method. The invention also relates to a device applied to the generalized orthogonal demodulation self-mixing vibration measurement method.
Background
The orthogonal demodulation is a demodulation method widely applied in the field of laser measurement, and the application condition of the orthogonal demodulation requires that two orthogonal signals are orthogonal, namely the phase difference of the two signals is 90 degrees on the optical phase; however, in practical applications, a large number of wave plates, coated optical elements, and the like often exist in a laser light path, and these elements cause that two signals are not orthogonal, that is, because factors such as the wave plates, the coated optical elements, and the like of the laser light path cause that the phase difference of the two signals is deviated from 90 degrees, especially when the wave plates rotate, the phases of the two signals are regulated by a rotation angle, so that the orthogonal demodulation method in the prior art cannot be applied under the condition that the two signals are not orthogonal.
Therefore, how to avoid the problem that the conventional quadrature demodulation method cannot be applied to two paths of non-orthogonal signals is a technical problem that needs to be solved by those skilled in the art at present.
Disclosure of Invention
The invention aims to provide a generalized orthogonal demodulation self-mixing vibration measurement method, which can obtain surface vibration information of a vibration body by utilizing two laser signals with phase difference in an optical path and adopting a generalized orthogonal demodulation algorithm. Another object of the present invention is to provide an apparatus applied to the above generalized quadrature demodulation self-mixing vibration measurement method.
In order to achieve the above object, the present invention provides a generalized quadrature demodulation self-mixing vibration measurement method, comprising:
acquiring two paths of laser signals with preset phase difference;
calculating to obtain phase difference estimated values of the two laser signals;
and acquiring vibration information of the surface of the vibration body according to the phase difference estimated value.
Optionally, the step of acquiring two laser signals with a preset phase difference includes:
detecting by a first detection unit to obtain a first feedback signal;
and detecting by a second detection unit to obtain a second feedback signal having a preset phase difference with the first feedback signal.
Optionally, the step of obtaining the phase difference estimated value of the two laser signals by computing includes:
according to Ia＝I0a+Aacos(fun(ωct)) obtaining a feedback current I of the first detection unitaWherein, I0aFeeding back a DC component of the current to the first detection unit, AaFeeding back the amplitude of the alternating current component of the current for the first detection unit;
according to Ib＝I0b+Abcos(fun(ωct) + δ) to obtain the feedback current I of the second detection unitbWherein, I0bFeeding back a DC component of the current to said second detection unit, AbFeeding back the amplitude of the alternating current component of the current for the second detection unit;
filtering and normalizing the direct current component of the feedback current of the first detection unit to obtain
Filtering and normalizing the direct current component of the feedback current of the second detection unit to obtain
According to
And calculating to obtain the estimated value of the phase difference, wherein arctan is an arc tangent function.
Optionally, the step of obtaining vibration information of the surface of the vibrating body according to the phase difference estimated value includes:
demodulating non-cooperative vibration displacement (x) by the phase difference estimation value;
according to
Obtaining vibration displacement information of the surface of the vibration body; where umwrap is the unwrapping function, λ is the center wavelength of the laser, and φ is the vibration displacement dependent phase component.
Optionally, before the step of acquiring two laser signals with a preset phase difference, the method further includes:
emitting light by a laser with the built-in first detection unit;
one path of light is transmitted to the surface of the vibration body through the spectroscope, and the other path of light is reflected to the second detection unit.
The invention provides a generalized orthogonal demodulation self-mixing vibration measuring device, which is applied to any one of the generalized orthogonal demodulation self-mixing vibration measuring methods, and comprises the following steps:
the acquisition module is used for acquiring two paths of laser signals with preset phase difference;
the operation module is used for obtaining phase difference estimated values of the two laser signals through operation;
and the demodulation module is used for acquiring vibration information of the surface of the vibration body according to the phase difference estimated value.
Optionally, the obtaining module includes:
the first detection unit is used for detecting and obtaining a first feedback signal;
and the second detection unit is used for detecting and obtaining a second feedback signal with a preset phase difference with the first feedback signal.
Optionally, the operation module includes:
to be according to Ia＝I0a+Aacos(fun(ωct)) obtaining a feedback current I of the first detection unitaThe first arithmetic unit of (1);
to be according to Ib＝I0b+Abcos(fun(ωct) + δ) to obtain the feedback current I of the second detection unitbThe second arithmetic unit of (1);
the direct current component used for filtering and normalizing the feedback current of the first detection unit is obtained
The third arithmetic unit of (1);
the direct current component used for filtering and normalizing the feedback current of the second detection unit is obtained
The fourth arithmetic unit of (1);
to be based on
And a fifth arithmetic unit for calculating the estimated phase difference value.
Optionally, the demodulation module includes:
a first demodulation unit to demodulate non-cooperative vibration displacement (x) by the phase difference estimation value;
to be based on
And the second demodulation unit is used for acquiring vibration displacement information of the surface of the vibration body.
Compared with the background art, the invention designs a generalized orthogonal demodulation self-mixing vibration measurement method aiming at different requirements of laser measurement, and particularly the generalized orthogonal demodulation self-mixing vibration measurement method comprises the following steps: s1: acquiring two paths of laser signals with preset phase difference; s2: calculating to obtain phase difference estimated values of the two laser signals; s3: and acquiring vibration information of the surface of the vibration body according to the phase difference estimated value. Meanwhile, the application also provides a generalized orthogonal demodulation self-mixing vibration measuring device, which is applied to the generalized orthogonal demodulation self-mixing vibration measuring method and comprises an acquisition module, an operation module and a demodulation module, wherein the acquisition module is used for acquiring two paths of laser signals with preset phase differences; the operation module is used for calculating to obtain phase difference estimated values of the two laser signals; the demodulation module is used for acquiring vibration information of the surface of the vibration body according to the phase difference estimated value.
Therefore, the generalized orthogonal demodulation self-mixing vibration measurement method firstly obtains two laser signals with preset phase difference in a light path, then calculates to obtain the phase difference estimated value of the two laser signals, and finally demodulates the vibration displacement information of the surface of the vibration body by combining the obtained phase difference estimated value, so that the surface vibration information of the vibration body can be obtained. Compared with the traditional method that vibration information can be obtained through an orthogonal demodulation algorithm under the condition of two orthogonal signals, the generalized orthogonal demodulation self-mixing vibration measurement method provided by the application can be applied to the field of self-mixing vibration measurement, and the vibration information of the surface of a vibration body can be measured under the condition of two non-orthogonal signals, so that the universality of the method can be greatly improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a flowchart illustrating a generalized quadrature demodulation self-mixing vibration measurement method according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of an acquisition module in a generalized quadrature demodulation self-mixing vibration measurement apparatus according to an embodiment of the present invention.
Wherein:
the device comprises a vibration body 1, a wave plate 2, a fixed-focus lens 3, a spectroscope 4, a laser 5, a first detection unit 6 and a second detection unit 7.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The core of the invention is to provide a generalized orthogonal demodulation self-mixing vibration measurement method, which can obtain the surface vibration information of a vibration body by utilizing two laser signals with phase difference in a light path and adopting a generalized orthogonal demodulation algorithm. Another core of the present invention is to provide a device applied to the above generalized quadrature demodulation self-mixing vibration measurement method.
In order that those skilled in the art will better understand the disclosure, the invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
It should be noted that the following directional terms such as "upper end, lower end, left side, right side" and the like are defined based on the drawings of the specification.
Referring to fig. 1 and fig. 2, fig. 1 is a flowchart illustrating a generalized quadrature demodulation self-mixing vibration measurement method according to an embodiment of the present invention; fig. 2 is a schematic structural diagram of an acquisition module in a generalized quadrature demodulation self-mixing vibration measurement apparatus according to an embodiment of the present invention.
The generalized orthogonal demodulation self-mixing vibration measurement method provided by the embodiment of the invention comprises the following steps: s1: acquiring two paths of laser signals with preset phase difference; s2: calculating to obtain phase difference estimated values of the two laser signals; s3: and acquiring vibration information of the surface of the vibration body 1 according to the phase difference estimated value.
That is to say, the generalized orthogonal demodulation self-mixing vibration measurement method may first obtain two laser signals with a preset phase difference in a light path, then calculate a phase difference estimation value of the two laser signals, and finally demodulate vibration displacement information of the surface of the vibration body 1 by combining the obtained phase difference estimation value, so as to obtain surface vibration information of the vibration body 1.
It should be noted that the preset phase difference is a phase difference that may be 90 degrees or a phase difference other than 90 degrees, and is determined by the laser signal acquisition device, and the preset phase difference is an unknown quantity, and needs to be estimated by subsequent calculation.
Compared with the traditional method that vibration information can be obtained through an orthogonal demodulation algorithm under the condition of two orthogonal signals, the generalized orthogonal demodulation self-mixing vibration measurement method provided by the application can be applied to the field of self-mixing vibration measurement, and the vibration information of the surface of the vibration body 1 can be measured under the condition of two non-orthogonal signals, so that the universality of the method can be greatly improved.
Further, the step of acquiring two laser signals with a preset phase difference specifically includes:
firstly, a first feedback signal is obtained through detection of a first detection unit 6;
in the second step, a second feedback signal having a predetermined phase difference with the first feedback signal is detected by the second detection unit 7.
Of course, according to actual needs, before S1, that is, before the step of acquiring two laser signals with a preset phase difference, the method may further include:
firstly, emitting light by a laser 5 with a built-in first detection unit 6;
secondly, one path of light is transmitted to the surface of the vibration body 1 through the spectroscope 4, and the other path of light is reflected to the second detection unit 7.
Specifically, the laser emitted by the laser 5 is divided into two paths by the spectroscope 4, wherein one path is focused on the surface of the vibration body 1 by the fixed-focus lens 3, and the other path is reflected to the second detection unit 7, wherein the laser 5 and the first detection unit 6 can be packaged into a whole; meanwhile, a wave plate 2 may be disposed between the fixed focus lens 3 and the vibration body 1. Thus, according to the principle of laser self-mixing, two feedback signals with a certain phase relationship are generated on the first detection unit 6 and the second detection unit 7, and the optical phase difference of the two feedback signals can be generated by the thickness change of the external wave plate 2 or the rotation of the optical axis angle or the rotation angle of the spectroscope 4.
As will be described in detail below, first, for calibration of the system phase difference δ, it can be seen from the above that the phase difference generated by the thickness change of the external wave plate 2 or the rotation of the optical axis angle or the rotation angle of the spectroscope 4 is assumed to be δ, and the phase difference amount is an unknown amount.
The specific process of calculating to obtain the phase difference estimated values of the two laser signals can be set as follows:
first, the surface of the vibrating body 1 is subjected to a known frequency ωcTriangular or sinusoidal wave excitation of (a); omegacFor the vibrating body 1 with the vibrating calibration object as a sound box, the frequency omega thereofcThe function is assumed to be fun (ω) by taking 200 Hz and 300Hzct), the first feedback signal measured by the first detection unit 6 is:
Ia＝I0a+Aacos(fun(ωct)) (1)
the second feedback signal measured by the second detection unit 7 is:
Ib＝I0b+Abcos(fun(ωct)+δ) (2)
wherein, IaIs a feedback current of the first detection unit 6, I0aFor feeding back the direct component of the current, A, to the first detection unit 6aFor feeding back the amplitude of the alternating component of the current, I, of the first detection unit 6bIs a feedback current of the second detection unit 7, I0bFor feeding back the direct component of the current, A, to the second detection unit 7bThe amplitude of the alternating component of the current is fed back to the second detection unit 7.
Then, the direct current component of the feedback current of the first detection unit 6 and the direct current component of the feedback current of the second detection unit 7 are filtered and normalized respectively to obtain:
taking a series of deltai，δi∈{δ1Lδj,δj+1LδNJ ═ 1L N }, where δj+1＝δj+Δδ,ΔδTo meet the phase difference interval of the precision requirement, the estimated value of the phase difference is obtained by the following steps:
where arctan is the arctan function.
At S3, namely, the step of obtaining the vibration information of the surface of the vibrating body 1 according to the phase difference estimation value, may specifically be configured to include:
firstly, demodulating non-cooperative vibration displacement (x) through a phase difference estimation value;
a second step according to
Obtaining vibration displacement information of the surface of the vibration body 1; where umwrap is the unwrapping function, λ is the center wavelength of the laser 5, and φ is the vibration displacement dependent phase component.
Of course, according to actual needs, before demodulation, detection of non-cooperative vibration may also be included, and after filtering and normalization processing, signals measured by the first detection unit 6 and the second detection unit 7 may be expressed as:
after obtaining the estimated value of the phase difference, the estimated value of the phase difference can be combined
Demodulating the non-cooperative vibration displacement information displacement (x), wherein the generalized orthogonal demodulation algorithm is as follows:
that is to say that the first and second electrodes,
where umwrap is the unwrapping function.
Meanwhile, the invention also provides a generalized orthogonal demodulation self-mixing vibration measuring device, which is applied to the generalized orthogonal demodulation self-mixing vibration measuring method and comprises an acquisition module, an operation module and a demodulation module, wherein the acquisition module is used for acquiring two paths of laser signals with preset phase differences; the operation module is used for calculating to obtain phase difference estimated values of the two laser signals; the demodulation module is used for acquiring vibration information of the surface of the vibration body according to the phase difference estimated value.
Of course, according to actual needs, the acquiring module may specifically be configured to include: the device comprises a vibration body 1, a laser 5, a first detection unit 6, a second detection unit 7, a spectroscope 4 and a fixed-focus lens 3, wherein the laser 5 is used for emitting laser; the first detection unit 6 is used for detecting to obtain a first feedback signal; the second detection unit 7 is configured to detect a second feedback signal forming a preset phase difference with the first feedback signal; the spectroscope 4 is used for transmitting the light emitted by the laser 5 to the vibration body 1 in one path and reflecting the light to the second detection unit 7 in the other path; the fixed focus lens 3 is arranged between the spectroscope 4 and the vibration body 1, and the fixed focus lens 3 is used for focusing light rays to the surface of the vibration body 1.
Certainly, according to actual needs, a wave plate 2 may be further disposed between the fixed-focus lens 3 and the vibration body 1, the wave plate 2 is set at a preset thickness, and the wave plate 2 may adjust the phase difference of the two feedback signals according to the thickness of the wave plate 2; the vibrating body 1 may be provided as a sound box, and both the first detecting unit 6 and the second detecting unit 7 may be provided as detectors (photodiodes).
Furthermore, the first detection unit 6 may be embedded in the laser 5, and the laser 5 may be specifically configured as a semiconductor laser, that is, the first detection unit 6 and the laser 5 may be packaged together and independent of each other.
In order to optimize the above embodiment, the operation module may specifically be configured to include: a first arithmetic unit, a second arithmetic unit, a third arithmetic unit, a fourth arithmetic unit, and a fifth arithmetic unit, wherein:
the first arithmetic unit is used for calculating according to Ia＝I0a+Aacos(fun(ωct)) to obtain the feedback current I of the first detection unit 6a；
The second arithmetic unit is used for calculating according to Ib＝I0b+Abcos(fun(ωct) + δ) to obtain the feedback current I of the second detection unit 7b；
The third arithmetic unit is used for filtering and normalizing the direct current component of the feedback current of the first detection unit 6 to obtain
The fourth arithmetic unit is used for filtering and normalizing the direct current component of the feedback current of the second detection unit 7 to obtain
The fifth arithmetic unit is configured to operate in accordance with:
On the basis, the demodulation module may specifically include: a first demodulation unit and a second demodulation unit, wherein:
the first demodulation unit is used for demodulating the non-cooperative vibration displacement (x) through the phase difference estimation value;
the second demodulation unit is configured to demodulate the signal according to:
It is noted that, in this specification, relational terms such as first and second, and the like are used solely to distinguish one entity from another entity without necessarily requiring or implying any actual such relationship or order between such entities.
The generalized quadrature demodulation self-mixing vibration measurement method and device provided by the invention are described in detail above. The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
Claims (5)
1. A generalized quadrature demodulation self-mixing vibration measurement method, comprising:
acquiring two paths of laser signals with preset phase difference;
calculating to obtain phase difference estimated values of the two laser signals;
acquiring vibration information of the surface of the vibration body (1) according to the phase difference estimated value;
the step of acquiring two laser signals with preset phase difference comprises the following steps:
a first feedback signal is obtained through detection of a first detection unit (6);
a second feedback signal with a preset phase difference with the first feedback signal is obtained through detection of a second detection unit (7);
the step of calculating to obtain the phase difference estimated value of the two paths of laser signals comprises the following steps:
the first detection unit (6) detects to obtain a feedback current Ia，Ia＝I0a+Aacos(fun(ωct)), wherein I)0aFeeding back a direct current component of the current to the first detection unit (6), AaFeeding back the amplitude of the alternating component of the current to the first detection unit (6);
the feedback current I is obtained by the detection of the second detection unit (7)b，Ib＝I0b+Abcos(fun(ωct) + δ) in which I0bFeeding back a DC component of the current to the second detection unit (7), AbFeeding back the amplitude of the alternating component of the current to the second detection unit (7);
filtering and normalizing the direct current component of the feedback current of the first detection unit (6) to obtain
Filtering and normalizing the direct current component of the feedback current of the second detection unit (7) to obtain
According to
Calculating to obtain the estimated value of the phase difference, wherein arctan is an arc tangent function;
wherein, ω iscIs the angular velocity of vibration, t is the time, δ is the phase difference of the signals between the first detection unit (6) and the second detection unit (7).
2. The generalized quadrature demodulation self-mixing vibration measurement method according to claim 1, wherein said step of obtaining vibration information of the surface of the vibrating body (1) from said phase difference estimation value comprises:
demodulating non-cooperative vibration displacement (x) by the phase difference estimation value;
according to
Obtaining vibration displacement information of the surface of the vibration body (1); wherein umwrap is the unwrapping function, λ is the central wavelength of the laser (5), and φ is the phase component associated with the vibration displacement.
3. The generalized quadrature demodulation self-mixing vibration measurement method according to any one of claims 1 to 2, wherein before the step of obtaining two laser signals with a predetermined phase difference, the method further comprises:
emitting light by a laser (5) with the built-in first detection unit (6);
one path of light is transmitted to the surface of the vibration body (1) through the spectroscope (4), and the other path of light is reflected to the second detection unit (7).
4. A generalized quadrature demodulation self-mixing vibration measurement apparatus applied to the generalized quadrature demodulation self-mixing vibration measurement method according to any one of claims 1 to 3, comprising:
the acquisition module is used for acquiring two paths of laser signals with preset phase difference;
the operation module is used for obtaining phase difference estimated values of the two laser signals through operation;
the demodulation module is used for acquiring vibration information of the surface of the vibration body (1) according to the phase difference estimated value;
the acquisition module includes:
a first detection unit (6) for detecting a first feedback signal;
a second detection unit (7) for detecting a second feedback signal having a predetermined phase difference with the first feedback signal;
the operation module comprises:
the direct current component of the feedback current of the first detection unit (6) is filtered and normalized to obtain
The third arithmetic unit of (1);
the direct current component of the feedback current of the second detection unit (7) is filtered and normalized to obtain
The fourth arithmetic unit of (1);
to be based on
A fifth arithmetic unit for calculating the estimated phase difference value;
wherein, ω iscIs the angular velocity of vibration, t is the time, δ is the phase difference of the signals between the first detection unit (6) and the second detection unit (7).
5. The generalized quadrature demodulation self-mixing vibration measurement device as claimed in claim 4, wherein said demodulation module comprises:
a first demodulation unit to demodulate non-cooperative vibration displacement (x) by the phase difference estimation value;
to be based on
And the second demodulation unit is used for acquiring vibration displacement information of the surface of the vibration body (1), wherein umwrrap is a unwrapping function, lambda is the central wavelength of the laser (5), and phi is a phase component related to vibration displacement.
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