CN115326637A - In-situ density measuring device and method based on diffuse reflection laser heterodyne coherence - Google Patents

Abstract

The present disclosure provides an in-situ density measurement device and method based on diffuse reflection laser heterodyne coherence, the device includes: a laser for generating a detection laser; the heterodyne coherent module is arranged behind the laser and is used for dividing the detection laser into measurement light and reference light, enabling the measurement light to penetrate through the transmission type diffuse reflection medium density measurement module to detect the medium to be detected, enabling the return light of the measurement light to interfere with the reference light to generate an interference light signal, demodulating the interference light signal and outputting the density of the medium to be detected; and the transmission type diffuse reflection medium density measurement module is arranged behind the heterodyne correlation module and used for coupling the measurement light with the medium to be measured and returning the return light of the measurement light to the heterodyne coherence module through the diffuse reflection object. The device and the method solve the problems of the existing interference measurement medium density by combining heterodyne and a diffuse reflection object as a method for detecting light reflection, and realize the in-situ measurement of the medium density under large dynamic range and high precision.

Description

In-situ density measuring device and method based on diffuse reflection laser heterodyne coherence

Technical Field

The disclosure relates to the technical field of optical density measurement, in particular to an in-situ density measurement device and method based on diffuse reflection laser heterodyne coherence.

Background

The density is an important characteristic and index of a substance, such as atmospheric density and ocean density, and is an important content for observing ecological environment, and the observation in the fields of ocean thermohaline circulation, climate change, biochemistry, ocean engineering, ecology and the like can be realized through the density.

In the prior art, the optical density measurement mainly comprises density detection based on laser deflection, but the sensitivity is not high, and the dynamic range is not high due to the limitation of the angle of a V-shaped groove and a detector, so that the gas-liquid two-phase compatible measurement cannot be realized; the surface plasma method is sensitive to the change of the refractive index of a medium through the metal surface, but a probe of the surface plasma method is a metal film and is easy to corrode, so that the surface plasma method cannot work underwater for a long time; the Mach-Zehnder interferometer with high sensitivity realizes density detection on a medium to be detected through a coherence principle, is a method with highest sensitivity at present, but adopts a mirror reflection or transmission mode, has larger angle difference of light transmission aiming at different media, has strict requirement on coherence angle of two beams of light, and cannot realize medium density measurement due to the fact that coherence cannot be realized when the difference of refractive indexes of the media is larger, so that the method has the problems of easiness in disturbance and small dynamic range.

Disclosure of Invention

In view of the above problems, the present invention provides an in-situ density measurement apparatus and method based on diffuse reflection laser heterodyne coherence, so as to solve the above technical problems.

One aspect of the present disclosure provides an in-situ density measurement device based on diffuse reflection laser heterodyne coherence, which includes:

a laser for generating a detection laser;

the heterodyne coherent module is arranged behind the laser and used for dividing the detection laser into measurement light and reference light, enabling the measurement light to penetrate through the transmission type diffuse reflection medium density measurement module to detect a medium to be detected, enabling return light of the measurement light to interfere with the reference light to generate an interference light signal, demodulating the interference light signal and outputting the density of the medium to be detected;

and the transmission type diffuse reflection medium density measurement module is arranged behind the heterodyne correlation module and is used for coupling the measurement light with the medium to be measured and returning a return light original path of the measurement light to the heterodyne correlation module through a diffuse reflection object.

Optionally, the heterodyne coherent module includes:

the first polarization beam splitter prism is used for splitting the detection laser into measurement light and reference light;

a beam splitter prism for making the return light of the measurement light coherent with the reference light;

and the demodulation system is used for demodulating the interference optical signal to obtain and output the density of the medium to be detected.

Optionally, the heterodyne coherent module further includes:

and the heterodyne modulator is arranged between the first polarization splitting prism and the splitting prism and is used for carrying out heterodyne modulation on the reference light.

Optionally, the heterodyne correlation module further includes:

the second polarization beam splitter prism is arranged between the first polarization beam splitter prism and the beam splitter prism and used for reflecting the return light of the measuring light to the beam splitter prism;

and the reflecting mirror is arranged between the heterodyne modulator and the light splitting prism and used for reflecting the reference light to the light splitting prism.

Optionally, the transmissive diffuse reflection medium density measuring module includes:

the medium to be measured measuring area is used for setting the medium to be measured;

and the diffuse reflection object is used for uniformly reflecting the measuring light to form return light returning from the original path after the measuring light passes through the medium measuring area to be measured.

Optionally, the transmissive diffuse reflection medium density measurement module further includes:

and the first optical window and the second optical window are arranged on two sides of the medium measuring area to be measured.

Optionally, the diffuse reflecting object is provided on a vibration isolation gasket.

Another aspect of the present disclosure provides an in-situ density measurement method based on diffuse reflection laser heterodyne coherence, which is applied to the in-situ density measurement device based on diffuse reflection laser heterodyne coherence in the first aspect, and the method includes:

emitting detection laser;

dividing the detection laser into measurement light and reference light, enabling the measurement light to pass through a transmission type diffuse reflection medium density measurement module to be detected and coupled with a medium to be detected, enabling a return light original path of the measurement light to return to the heterodyne coherent module through a diffuse reflection object, and interfering with the reference light to generate an interference light signal;

demodulating the interference light signal and outputting a phase change signal of the measuring light caused by the medium to be measured;

and obtaining the density of the medium to be detected based on the phase change signal.

Optionally, the demodulating the interference light signal and outputting the phase change of the measurement light caused by the medium to be measured includes:

converting the interference light information into an electrical signal;

and demodulating the electric signal based on a heterodyne intermediate frequency signal demodulation algorithm to obtain a phase change signal of the medium to be detected.

Optionally, the obtaining the density of the medium to be measured based on the phase change includes:

obtaining the refractive index of the medium to be detected based on the mapping relation between the phase change signal and the refractive index of the medium to be detected;

and obtaining the density of the medium to be measured based on the mapping relation between the refractive index and the density of the medium to be measured.

The at least one technical scheme adopted in the embodiment of the disclosure can achieve the following beneficial effects:

the device and the method for measuring the in-situ density based on the heterodyne coherence of the diffuse reflection laser can realize the density measurement of a gaseous medium, a liquid medium and a gas-liquid medium under high precision and large dynamic range, and solve the problems of the existing interferometric medium density by combining the heterodyne with a diffuse reflection object as a method for detecting the light reflection on the basis of a Mach-Zehnder interferometer, thereby improving the coherent optical density measurement technology and realizing the in-situ measurement of the medium density under large dynamic range and high precision.

Drawings

For a more complete understanding of the present disclosure and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

fig. 1 schematically illustrates a schematic diagram of an in-situ density measurement device based on diffuse reflection laser heterodyne coherence according to an embodiment of the present disclosure;

fig. 2 schematically illustrates a schematic structural diagram of a heterodyne coherent module provided in an embodiment of the present disclosure;

FIG. 3 is a block diagram schematically illustrating a configuration of a transmissive diffuse reflection medium density measurement module according to an embodiment of the present disclosure;

fig. 4 schematically shows a flowchart of an in-situ density measurement method based on diffuse reflection laser heterodyne coherence, which is provided by an embodiment of the present disclosure.

Detailed Description

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood that the description is illustrative only and is not intended to limit the scope of the present disclosure. In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the disclosure. It may be evident, however, that one or more embodiments may be practiced without these specific details. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The terms "comprises," "comprising," and the like, as used herein, specify the presence of stated features, steps, operations, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.

All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. It is noted that the terms used herein should be interpreted as having a meaning that is consistent with the context of this specification and should not be interpreted in an idealized or overly formal sense.

Some block diagrams and/or flow diagrams are shown in the figures. It will be understood that some blocks of the block diagrams and/or flowchart illustrations, or combinations thereof, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the instructions, which execute via the processor, create means for implementing the functions/acts specified in the block diagrams and/or flowchart block or blocks.

Fig. 1 schematically illustrates a schematic diagram of an in-situ density measurement device based on diffuse reflection laser heterodyne coherence, provided by an embodiment of the present disclosure.

As shown in fig. 1, an in-situ density measurement device based on heterodyne coherence of diffuse reflection laser includes a laser, a heterodyne coherence module, and a transmission-type diffuse reflection medium density measurement module.

The laser is used for generating detection laser. The detection laser medium to be measured density measurement medium realizes medium density information acquisition through the coupling effect of the detection laser and the medium to be measured. In this embodiment, the detection laser is a narrow linewidth laser, and the wavelength range of the detection laser is 400 to 700nm, which is used for carrying density information of the medium to be detected.

The heterodyne coherent module is arranged behind the laser and used for dividing the detection laser into measurement light and reference light, enabling the measurement light to penetrate through the transmission type diffuse reflection medium density measurement module to detect a medium to be detected, enabling return light of the measurement light to interfere with the reference light to generate an interference light signal, demodulating the interference light signal and outputting the density of the medium to be detected.

The transmission type diffuse reflection medium density measuring module is arranged behind the heterodyne correlation module and used for coupling the measuring light with the medium to be measured and enabling a return light original path of the measuring light to return to the heterodyne correlation module through a diffuse reflection object, light deflection does not occur, and the coherence condition is met. The module can realize real-time measurement of three media of gas state, liquid state and gas-liquid mixture, and meets the density measurement requirements of high sensitivity and large dynamic range.

Fig. 2 schematically illustrates a structural diagram of a heterodyne coherent module according to an embodiment of the present disclosure.

As shown in fig. 2, the heterodyne coherent module includes a first polarization splitting prism, a splitting prism, and a demodulation system.

The first polarization beam splitter prism is used for splitting the detection laser into measurement light and reference light, and the transmission directions of the measurement light and the reference light can be adjusted. There is no overlap in the optical paths of the measurement light and the reference light.

The beam splitting prism is used for making the return light of the measuring light and the reference light generate coherence and refracting a coherent light signal to a demodulation system.

And the demodulation system is used for demodulating the interference optical signal to obtain and output the density of the medium to be detected.

In this embodiment, a heterodyne modulator is further disposed on the light path of the reference light, and specifically disposed between the first polarization splitting prism and the splitting prism, and configured to perform heterodyne modulation on the reference light.

In this embodiment, the heterodyne coherent module may further include a second polarization splitting prism and a mirror. The second polarization beam splitter prism is arranged between the first polarization beam splitter prism and the beam splitter prism and used for reflecting the return light of the measuring light to the beam splitter prism; and the reflector is arranged between the heterodyne modulator and the light splitting prism and used for adjusting the direction of the reference light and reflecting the reference light to the light splitting prism.

The detection laser is divided into two beams by the polarization beam splitter prism, one beam serving as reference light reaches the reflector after passing through the heterodyne modulator, the other beam of measurement light is reflected back by the diffuse reflection object after passing through the polarization beam splitter prism and the lens, the two beams reach the beam splitter prism and interfere with the reference light coherently, and the interference light signal is output through signal demodulation to realize the density measurement of the medium to be measured.

Fig. 3 schematically shows a block diagram of a transmissive diffuse reflection medium density measurement module according to an embodiment of the present disclosure.

As shown in fig. 3, the transmission-type diffuse reflection medium density measurement module at least includes a medium measurement area to be measured and a diffuse reflection object.

The medium measuring area to be measured is used for setting the medium to be measured. The medium to be measured can be a gas medium, a liquid medium or a gas-liquid medium, and has transmissivity. A first optical window and a second optical window can be arranged on two sides of the medium measuring area to be measured. The detection laser is reflected by the reflector, reaches the detection area through the optical window, reaches the diffuse reflection object through the optical window, passes through the diffuse reflection object, passes through the optical window, is received by the lens in the heterodyne coherent module after passing through the area to be detected, the optical window and the reflector, and realizes coherence.

And the diffuse reflection object is used for uniformly reflecting the measuring light to form return light returning from the original path after the measuring light passes through the medium measuring area to be measured. The diffuse reflection object is a lambertian body of which the surface can realize diffuse reflection, and can realize uniform reflection in all directions on the detection light beam, wherein the lower end of the diffuse reflection object is isolated from the external environment through a vibration isolation gasket.

According to the in-situ density measuring device based on the diffuse reflection laser heterodyne coherence, the density measurement of a gaseous medium, a liquid medium and a gas-liquid medium under high precision and a large dynamic range can be realized, and on the basis of a Mach-Zehnder interferometer, the problem of the existing interferometric medium density is solved by combining heterodyne and a diffuse reflection object as a method for detecting light reflection, so that the coherent optical density measuring technology is improved, and the in-situ density measurement of the medium under the large dynamic range and the high precision is realized.

Fig. 4 schematically shows a flowchart of an in-situ density measurement method based on diffuse reflection laser heterodyne coherence, which is provided by an embodiment of the present disclosure.

As shown in fig. 4, the in-situ density measurement method based on the diffuse reflection laser heterodyne coherence includes steps S410 to S440.

And S410, emitting detection laser.

In this embodiment, the detection laser is a narrow linewidth laser, and the wavelength range of the detection laser is 400 to 700nm, which is used for carrying density information of the medium to be detected.

And S420, dividing the detection laser into measurement light and reference light, enabling the measurement light to pass through a transmission type diffuse reflection medium density measurement module to be detected and coupled with the medium to be detected, enabling a return light original path of the measurement light to return to the heterodyne coherent module through a diffuse reflection object, and interfering with the reference light to generate an interference light signal.

In this embodiment, after the detection laser is emitted, the detection laser passes through the heterodyne coherent module, which mainly splits the detection light and the reference light, wherein the reference light is heterodyne modulated, and the detection light realizes directional transmission of a light path via an optical element and realizes interference with the reference light; the transmission type diffuse reflection medium density measuring area mainly realizes the coupling effect between the detection light and the medium to be measured, the detection light reaches a diffuse reflection object after coupling, and the detection light returns in the original path after diffuse reflection. The transmission path of the returned detection light is unchanged through the diffuse reflection object, so that the coherence of the two beams of light is ensured, and the problem of reduced coherence or failure caused by the deflection of the detection light is avoided.

S430, demodulating the interference light signal and outputting a phase change signal of the measuring light caused by the medium to be measured.

S430 includes S431 to S432.

And S431, converting the interference light information into an electric signal.

S432, demodulating the electric signal based on a heterodyne intermediate frequency signal demodulation algorithm to obtain a phase change signal of the medium to be detected.

In this embodiment, a traditional heterodyne intermediate frequency signal demodulation algorithm is adopted to implement phase output of a medium to be measured, where a signal carrying phase information of the medium to be measured is:

wherein A is a direct current signal caused by the intensity of the interference light, B is the intensity of the interference light, C is a heterodyne modulation radian,

for the phase change caused by the medium to be measured,

is the initial phase.

Through demodulation, phase signal output can be realized, and the demodulated phase signal of the medium to be detected is as follows:

wherein, λ is wavelength, and L is detection laser transmission optical path change.

And S440, obtaining the density of the medium to be measured based on the phase change signal.

S440 includes S441 to S442.

S441, obtaining the refractive index of the medium to be measured based on the mapping relation between the phase change signal and the refractive index of the medium to be measured.

In this embodiment, the optical path and phase theory formula is combined:

L＝n×s；

wherein n is the refractive index of the medium to be measured, and s is the transmission path, and is a constant here.

And S442, obtaining the density of the medium to be measured based on the mapping relation between the refractive index and the density of the medium to be measured.

In this example, based on the Gladstone-Dale equation:

n＝k _ρ +1；

wherein n is the refractive index of the medium to be tested, rho is the density of the medium to be tested, and k is the Grasston-Deler constant of the detection laser wavelength of the test system.

Based on the above formula, a density calculation formula can be obtained:

the invention provides an in-situ density measurement method based on diffuse reflection laser heterodyne coherence, which can realize simultaneous measurement of density in a large dynamic range and a gas-liquid two-state, and solves the problem of small dynamic range of the existing coherent density monitoring device; the method can realize in-situ density measurement in the marine environment, has high precision and is not easily influenced by the environment.

Those skilled in the art will appreciate that various combinations and/or combinations of features recited in the various embodiments and/or claims of the present disclosure can be made, even if such combinations or combinations are not expressly recited in the present disclosure. In particular, various combinations and/or combinations of the features recited in the various embodiments and/or claims of the present disclosure may be made without departing from the spirit or teaching of the present disclosure. All such combinations and/or associations are within the scope of the present disclosure.

While the disclosure has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents. Accordingly, the scope of the present disclosure should not be limited to the above-described embodiments, but should be defined not only by the appended claims, but also by equivalents thereof.

Claims (10)

1. An in-situ density measurement device based on diffuse reflection laser heterodyne coherence is characterized by comprising:

a laser for generating a detection laser;

the heterodyne coherent module is arranged behind the laser and used for dividing the detection laser into measurement light and reference light, enabling the measurement light to penetrate through the transmission type diffuse reflection medium density measurement module to detect a medium to be detected, enabling return light of the measurement light to interfere with the reference light to generate an interference light signal, demodulating the interference light signal and outputting the density of the medium to be detected;

and the transmission type diffuse reflection medium density measurement module is arranged behind the heterodyne correlation module and is used for coupling the measurement light with the medium to be measured and returning a return light original path of the measurement light to the heterodyne correlation module through a diffuse reflection object.

2. The in-situ density measurement device based on diffuse reflection laser heterodyne coherence as claimed in claim 1, wherein the heterodyne coherence module comprises:

the first polarization beam splitter prism is used for dividing the detection laser into measurement light and reference light;

a beam splitter prism for making the return light of the measurement light coherent with the reference light;

and the demodulation system is used for demodulating the interference optical signal to obtain and output the density of the medium to be detected.

3. The in-situ density measurement device based on diffuse reflection laser heterodyne coherence as claimed in claim 2, wherein the heterodyne coherence module further comprises:

and the heterodyne modulator is arranged between the first polarization splitting prism and the splitting prism and is used for carrying out heterodyne modulation on the reference light.

4. The in-situ density measurement device based on diffuse reflection laser heterodyne coherence of claim 3, wherein the heterodyne correlation module further comprises:

the second polarization beam splitter prism is arranged between the first polarization beam splitter prism and the beam splitter prism and used for reflecting the return light of the measuring light to the beam splitter prism;

and the reflecting mirror is arranged between the heterodyne modulator and the light splitting prism and used for reflecting the reference light to the light splitting prism.

5. The in-situ density measurement device based on diffuse reflection laser heterodyne coherence as claimed in claim 1, wherein the transmissive diffuse reflection medium density measurement module comprises:

the medium to be measured measuring area is used for setting the medium to be measured;

and the diffuse reflection object is used for uniformly reflecting the measuring light to form return light returning from the original path after the measuring light passes through the medium measuring area to be measured.

6. The in-situ density measurement device based on diffuse reflection laser heterodyne coherence as claimed in claim 5, wherein the transmissive diffuse reflection medium density measurement module further comprises:

and the first optical window and the second optical window are arranged on two sides of the medium measuring area to be measured.

7. The in-situ density measurement device based on diffuse reflection laser heterodyne coherence as claimed in claim 5, wherein the diffuse reflection object is disposed on a vibration isolation pad.

8. An in-situ density measurement method based on diffuse reflection laser heterodyne coherence, which is applied to the in-situ density measurement device based on diffuse reflection laser heterodyne coherence in claims 1-7, and is characterized in that the method comprises the following steps:

emitting detection laser;

dividing the detection laser into measurement light and reference light, enabling the measurement light to pass through a transmission type diffuse reflection medium density measurement module to be detected and coupled with a medium to be detected, enabling a return light original path of the measurement light to return to the heterodyne coherent module through a diffuse reflection object, and enabling the return light original path of the measurement light to interfere with the reference light to generate an interference light signal;

demodulating the interference light signal and outputting a phase change signal of the measuring light caused by the medium to be measured;

and obtaining the density of the medium to be detected based on the phase change signal.

9. The in-situ density measurement device based on diffuse reflection laser heterodyne coherence as claimed in claim 8, wherein the demodulating the interference light signal and outputting the phase change of the measurement light caused by the medium to be measured includes:

converting the interference light information into an electrical signal;

and demodulating the electric signal based on a heterodyne intermediate frequency signal demodulation algorithm to obtain a phase change signal of the medium to be detected.

10. The in-situ density measurement device based on diffuse reflection laser heterodyne coherence as claimed in claim 8, wherein the obtaining the density of the medium to be measured based on the phase change includes:

obtaining the refractive index of the medium to be detected based on the mapping relation between the phase change signal and the refractive index of the medium to be detected;

and obtaining the density of the medium to be measured based on the mapping relation between the refractive index and the density of the medium to be measured.

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