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

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; a heterodyne coherence module, disposed after the laser, for dividing the detection laser into measurement light and reference light, allowing the measurement light to pass through a transmission-type diffuse reflection medium density measurement module to detect the medium to be measured, the return light of the measurement light interfering with the reference light to generate an interference light signal, demodulating the interference light signal, and outputting the density of the medium to be measured; a transmission-type diffuse reflection medium density measurement module, disposed after the heterodyne coherence module, 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 along its original path through a diffuse reflection object. By combining heterodyne and diffuse reflection objects as a method for detecting light reflection, the device and method solve the problems existing in existing interferometric measurement of medium density and achieve in-situ measurement of medium density with a large dynamic range and high precision.

Description

Technical Field

[0001] The present disclosure relates to the technical field of optical density measurement, and in particular to an in-situ density measurement device and method based on diffuse reflection laser heterodyne coherence. Background Art

[0002] Density is an important property and indicator of matter, such as atmospheric density and ocean density. It is an important part of ecological and environmental observation. Density can be used to observe areas such as ocean thermohaline circulation, climate change, biochemistry, marine engineering, and ecology.

[0003] The optical density measurement in the existing technology mainly includes density detection based on laser deflection, but its sensitivity is not high. Due to the limitations of the V-groove angle and the detector, its dynamic range is not high, and it cannot achieve compatible measurement of gas-liquid two-phases; the surface plasma method uses the metal surface's sensitivity to changes in the refractive index of the medium, but its detection head is a metal film, which is easily corroded and cannot work underwater for a long time; the high-sensitivity Mach-Zehnder interferometer uses the coherence principle to realize density detection of the medium to be measured. It is the most sensitive method at present, but due to the use of mirror reflection or transmission, the angles of light transmission for different media are quite different, and coherence has strict requirements on the coherence angles of the two beams of light. When the refractive index difference of the medium is large, coherence cannot be achieved, resulting in the inability to measure the medium density. Therefore, this method has the problems of easy disturbance and small dynamic range. Summary of the Invention

[0004] In view of the above problems, the present invention provides an in-situ density measurement device and method based on diffuse reflection laser heterodyne coherence to solve the above technical problems.

[0005] One aspect of the present disclosure provides an in-situ density measurement device based on diffuse reflection laser heterodyne coherence, characterized by comprising:

[0006] a laser for generating a detection laser;

[0007] a heterodyne coherent module, disposed after the laser, for dividing the detection laser into measurement light and reference light, allowing the measurement light to pass through a transmission-type diffuse reflection medium density measurement module to detect the medium to be measured, causing 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 measured;

[0008] The transmission diffuse reflection medium density measurement module is provided after the heterodyne correlation module, and is used to couple the measurement light with the medium to be measured, and to return the return light of the measurement light to the heterodyne coherence module along the original path through the diffuse reflection object.

[0009] Optionally, the heterodyne coherence module includes:

[0010] a first polarization beam splitter prism, configured to split the detection laser into measurement light and reference light;

[0011] A beam splitter prism, used to make the return light of the measuring light coherent with the reference light;

[0012] The demodulation system is used to demodulate the interference light signal to obtain and output the density of the medium to be measured.

[0013] Optionally, the heterodyne coherent module further includes:

[0014] The heterodyne modulator is provided between the first polarization beam splitter prism and the beam splitter prism, and is used for performing heterodyne modulation on the reference light.

[0015] Optionally, the heterodyne correlation module further includes:

[0016] a second polarization beam splitter prism, disposed between the first polarization beam splitter prism and the beam splitter prism, and configured to reflect the return light of the measurement light to the beam splitter prism;

[0017] A reflecting mirror is provided between the heterodyne modulator and the beam splitter prism, and is used for reflecting the reference light to the beam splitter prism.

[0018] Optionally, the transmission diffuse reflection medium density measurement module includes:

[0019] The medium to be measured measurement area is used to set the medium to be measured;

[0020] The diffuse reflection object is used to uniformly reflect the measuring light after the measuring light passes through the measuring area of ​​the medium to be measured to form return light that returns along the original path.

[0021] Optionally, the transmission-type diffuse reflection medium density measurement module further includes:

[0022] The first optical window and the second optical window are arranged on both sides of the measuring area of ​​the medium to be measured.

[0023] Optionally, the diffuse reflection object is arranged on a vibration isolation pad.

[0024] 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 described in the first aspect. The method comprises:

[0025] emitting a detection laser;

[0026] The detection laser is divided into a measurement light and a reference light, the measurement light is coupled with the medium to be measured by passing through a transmission-type diffuse reflection medium density measurement module, and the return light of the measurement light is returned to the heterodyne coherence module along the original path through a diffuse reflection object, thereby interfering with the reference light to generate an interference light signal;

[0027] Demodulating the interference light signal and outputting a phase change signal of the measuring light caused by the medium to be measured;

[0028] The density of the medium to be measured is obtained based on the phase change signal.

[0029] Optionally, the demodulating the interference light signal and outputting the phase change of the measuring light caused by the medium to be measured includes:

[0030] Converting the interference light information into an electrical signal;

[0031] The electrical signal is demodulated based on a heterodyne intermediate frequency signal demodulation algorithm to obtain a phase change signal of the medium to be measured.

[0032] Optionally, obtaining the density of the medium to be measured based on the phase change includes:

[0033] Obtaining the refractive index of the medium to be measured based on a mapping relationship between the phase change signal and the refractive index of the medium to be measured;

[0034] The density of the medium to be measured is obtained based on the mapping relationship between the refractive index and the density of the medium to be measured.

[0035] At least one of the above technical solutions adopted in the embodiments of the present disclosure can achieve the following beneficial effects:

[0036] The in-situ density measurement device and method based on diffuse reflection laser heterodyne coherence provided by the present invention can realize the density measurement of gaseous, liquid, and gas-liquid two-state media with high precision and a large dynamic range. On the basis of the Mach-Zehnder interferometer, by combining heterodyne with diffuse reflection objects as a method of detecting light reflection, the problems existing in the existing interference measurement of medium density are solved, thereby improving the coherent optical density measurement technology and realizing in-situ measurement of medium density with a large dynamic range and high precision. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] For a more complete understanding of the present disclosure and its advantages, reference will now be made to the following description taken in conjunction with the accompanying drawings, in which:

[0038] Figure 1 The following schematically shows 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;

[0039] Figure 2The following schematically shows a structural diagram of a heterodyne coherent module provided by an embodiment of the present disclosure;

[0040] Figure 3 The following schematically shows a structural block diagram of a transmission-type diffuse reflection medium density measurement module provided by an embodiment of the present disclosure;

[0041] Figure 4 A flowchart of an in-situ density measurement method based on diffuse laser heterodyne coherence provided by an embodiment of the present disclosure is schematically shown. DETAILED DESCRIPTION

[0042] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0043] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise," "include," etc. used herein indicate the presence of the features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0044] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0045] The accompanying drawings show some block diagrams and / or flow charts. It should be understood that some blocks in the block diagrams and / or flow charts, or combinations thereof, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that when these instructions are executed by the processor, they can create a device for implementing the functions / operations described in the block diagrams and / or flow charts.

[0046] Figure 1 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 is schematically shown.

[0047] like Figure 1As shown, an embodiment of the present disclosure provides an in-situ density measurement device based on diffuse reflection laser heterodyne coherence, which includes a laser, a heterodyne coherence module and a transmission diffuse reflection medium density measurement module.

[0048] The laser is used to generate a probe laser. The probe laser measures the density of the medium being measured, and density information is acquired through coupling between the probe laser and the medium being measured. In this embodiment, the probe laser is a narrow-linewidth laser with a wavelength range of 400 to 700 nm, which is used to carry density information of the medium being measured.

[0049] The heterodyne coherent module is arranged after the laser and is used to divide the detection laser into measurement light and reference light, so that the measurement light passes through the transmission diffuse reflection medium density measurement module to detect the medium to be measured, and the return light of the measurement light interferes with the reference light to generate an interference light signal, demodulate the interference light signal, and output the density of the medium to be measured.

[0050] The transmissive diffuse reflection medium density measurement module, located after the heterodyne correlation module, couples the measurement light to the medium being measured and, through a diffuse reflection object, directs the return light back along its original path to the heterodyne coherence module, eliminating light deflection and satisfying coherence requirements. This module enables real-time density measurement of gaseous, liquid, and gas-liquid mixtures, meeting the requirements for high-sensitivity and wide dynamic range density measurement.

[0051] Figure 2 The schematic diagram shows the structure of a heterodyne coherent module provided by an embodiment of the present disclosure.

[0052] like Figure 2 As shown, the heterodyne coherent module includes a first polarization beam splitter prism, a beam splitter prism and a demodulation system.

[0053] The first polarization beam splitter is used to split the detection laser into measurement light and reference light, and can adjust the transmission directions of the measurement light and the reference light. The optical paths of the measurement light and the reference light do not overlap.

[0054] The beam splitter prism is used to make the return light of the measuring light coherent with the reference light and refract the coherent light signal to the demodulation system.

[0055] The demodulation system is used to demodulate the interference light signal to obtain and output the density of the medium to be measured.

[0056] In this embodiment, a heterodyne modulator is further provided on the optical path of the reference light, specifically provided between the first polarization beam splitter prism and the beam splitter prism, for performing heterodyne modulation on the reference light.

[0057] In this embodiment, the heterodyne coherence module may further include a second polarization beam splitter prism and a reflector. The second polarization beam splitter prism is disposed between the first polarization beam splitter prism and the beam splitter prism and is configured to reflect the return light of the measurement light toward the beam splitter prism. The reflector is disposed between the heterodyne modulator and the beam splitter prism and is configured to adjust the direction of the reference light and reflect the reference light toward the beam splitter prism.

[0058] After the detection laser is split into two beams by a polarization beam splitter prism, one beam is used as the reference light and reaches the reflector after passing through a heterodyne modulator. The other measuring light passes through a polarization beam splitter prism and a lens, is reflected back by a diffuse reflecting object, reaches the beam splitter prism, and interferes with the reference light. The interference light signal is demodulated and output to realize the density measurement of the medium to be measured.

[0059] Figure 3 The structural block diagram of a transmission-type diffuse reflection medium density measurement module provided by an embodiment of the present disclosure is schematically shown.

[0060] like Figure 3 As shown, the transmission-type diffuse reflection medium density measurement module at least includes a measurement area for the medium to be measured and a diffuse reflection object.

[0061] The test medium measurement area is used to accommodate the test medium. The test medium can be gaseous, liquid, or both, and is transmissive. A first optical window and a second optical window can be positioned on either side of the test medium measurement area. The detection laser is reflected by a reflector, passes through the optical windows, reaches the detection area, passes through the optical windows to a diffusely reflecting object, passes through the diffusely reflecting object, passes through the optical window, passes through the test area, the optical window, and the reflector, and is then received by a lens in the heterodyne coherence module, achieving coherence.

[0062] The diffuse reflector is configured to uniformly reflect the measurement light after it passes through the measurement area of ​​the medium to be measured, forming return light that returns along its original path. The diffuse reflector is a Lambertian body with a surface capable of diffuse reflection, which uniformly reflects the probe beam in all directions. The lower end of the diffuse reflector is isolated from external environmental vibrations by a vibration isolation pad.

[0063] According to the in-situ density measurement device based on diffuse reflection laser heterodyne coherence provided by the embodiment of the present disclosure, it is possible to realize the density measurement of gaseous, liquid, and gas-liquid two-state media with high precision and a large dynamic range. On the basis of the Mach-Zehnder interferometer, by combining heterodyne with diffuse reflection objects as a method of detecting light reflection, the problems existing in the existing interference measurement of medium density are solved, thereby improving the coherent optical density measurement technology and realizing in-situ measurement of medium density with a large dynamic range and high precision.

[0064] Figure 4A flowchart of an in-situ density measurement method based on diffuse laser heterodyne coherence provided by an embodiment of the present disclosure is schematically shown.

[0065] like Figure 4 As shown, the in-situ density measurement method based on diffuse reflection laser heterodyne coherence provided by the embodiment of the present disclosure includes S410 to S440.

[0066] S410, emitting a detection laser.

[0067] In this embodiment, the detection laser is a narrow linewidth laser with a wavelength range of 400 to 700 nm, which is used to carry density information of the medium to be measured.

[0068] S420, the detection laser is divided into measurement light and reference light, the measurement light is coupled with the medium to be measured through the transmission diffuse reflection medium density measurement module detection, and the return light of the measurement light is returned to the heterodyne coherence module along the original path through the diffuse reflection object, thereby interfering with the reference light to generate an interference light signal.

[0069] In this embodiment, after the probe laser is emitted, it passes through a heterodyne coherence module, which primarily splits the probe light into a reference beam. The reference beam undergoes heterodyne modulation, and the probe light is transmitted through optical components for directional transmission, thereby interfering with the reference beam. The transmissive diffuse reflection medium density measurement section primarily couples the probe light with the medium being measured. After coupling, the probe light reaches the diffusely reflective object, where it diffusely reflects and returns along its original path. Passing through the diffusely reflective object, the returned probe light maintains its original transmission path, ensuring the coherence of the two beams and preventing coherence degradation or failure due to probe light deflection.

[0070] S430: Demodulate the interference light signal and output a phase change signal of the measuring light caused by the medium to be measured.

[0071] S430 includes S431 to S432.

[0072] S431, converting the interference light information into an electrical signal.

[0073] S432: Demodulate the electrical signal based on a heterodyne intermediate frequency signal demodulation algorithm to obtain a phase change signal of the medium to be measured.

[0074] In this embodiment, a conventional heterodyne intermediate frequency signal demodulation algorithm is used to realize the phase output of the medium to be measured, wherein the signal carrying the phase information of the medium to be measured is:

[0075]

[0076] Among them, A is the DC signal caused by the intensity of the interference light, B is the magnitude of the interference light, and C is the radian of the heterodyne modulation. is the phase change caused by the medium to be measured, is the initial phase.

[0077] After demodulation, the phase signal output can be realized. The demodulated phase signal of the medium to be measured is:

[0078]

[0079] Where λ is the wavelength and L is the change in the optical path length of the detection laser.

[0080] S440: Obtain the density of the medium to be measured based on the phase change signal.

[0081] S440 includes S441 to S442.

[0082] S441 : Obtain the refractive index of the medium to be measured based on a mapping relationship between the phase change signal and the refractive index of the medium to be measured.

[0083] In this embodiment, the optical path and phase theory formula are combined:

[0084] L = n × s;

[0085] Where n is the refractive index of the medium to be measured, and s is the transmission distance, which is a constant here.

[0086] S442: Obtain the density of the medium to be measured based on a mapping relationship between the refractive index and the density of the medium to be measured.

[0087] In this embodiment, based on the Gladstone-Dale equation:

[0088] n=k ρ +1;

[0089] Where n is the refractive index of the medium to be measured, ρ is the density of the medium to be measured, and k is the Gladstone-Dyer constant of the detection laser wavelength of the test system.

[0090] Based on the above formula, the density calculation formula can be obtained:

[0091]

[0092] The present disclosure provides an in-situ density measurement method based on diffuse reflection laser heterodyne coherence. The method and device can achieve a large dynamic range and simultaneous measurement of gas and liquid densities, which makes up for the problem of small dynamic range of existing coherent density monitoring devices. The method can realize in-situ density measurement in marine environments with high accuracy and is not easily affected by the environment.

[0093] Those skilled in the art will appreciate that the features described in the various embodiments and / or claims of this disclosure may be combined and / or coupled in various ways, even if such combinations and / or couplings are not explicitly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure may be combined and / or coupled in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or couplings are intended to fall within the scope of this disclosure.

[0094] Although the present 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 to the present disclosure without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents. Therefore, the scope of the present disclosure should not be limited to the above-described embodiments, but should be determined not only by the appended claims but also by the equivalents of the appended claims.

Claims

1. An in-situ density measurement device based on diffuse reflection laser heterodyne coherence, characterized in that: include: a laser for generating a detection laser; a heterodyne coherent module, disposed after the laser, for dividing the detection laser into measurement light and reference light, allowing the measurement light to pass through a transmission-type diffuse reflection medium density measurement module to detect the medium to be measured, causing 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 measured; Wherein, the heterodyne coherent module includes: a first polarization beam splitter prism, configured to split the detection laser into measurement light and reference light; A beam splitter prism, used to make the return light of the measuring light coherent with the reference light; A demodulation system, configured to demodulate the interference light signal to obtain and output the density of the medium to be measured; a heterodyne modulator, disposed between the first polarization beam splitter prism and the beam splitter prism, for performing heterodyne modulation on the reference light; a second polarization beam splitter prism, disposed between the first polarization beam splitter prism and the beam splitter prism, and configured to reflect the return light of the measurement light to the beam splitter prism; a reflecting mirror, disposed between the heterodyne modulator and the beam splitter prism, for reflecting the reference light to the beam splitter prism; A transmission-type diffuse reflection medium density measurement module, provided after the heterodyne coherence module, is used to couple the measurement light with the medium to be measured and to return the return light of the measurement light to the heterodyne coherence module along its original path through a diffuse reflection object; Wherein, the transmission diffuse reflection medium density measurement module includes: A medium measurement area for arranging the medium to be measured, wherein the medium to be measured includes a gaseous medium, a liquid medium, or a gas-liquid medium, and has transmissivity; The diffuse reflection object is used to uniformly reflect the measuring light after the measuring light passes through the measuring area of ​​the medium to be measured to form return light that returns along the original path.

2. The in-situ density measurement device based on diffuse reflection laser heterodyne coherence according to claim 1, characterized in that: The transmission-type diffuse reflection medium density measurement module further includes: The first optical window and the second optical window are arranged on both sides of the measuring area of ​​the medium to be measured.

3. The in-situ density measurement device based on diffuse reflection laser heterodyne coherence according to claim 1, characterized in that: The diffuse reflection object is arranged on the vibration isolation pad.

4. An in-situ density measurement method based on diffuse reflection laser heterodyne coherence, applied to the in-situ density measurement device based on diffuse reflection laser heterodyne coherence according to any one of claims 1 to 3, characterized in that: The method comprises: emitting a detection laser; The detection laser is divided into a measurement light and a reference light, the measurement light is coupled with the medium to be measured by passing through a transmission-type diffuse reflection medium density measurement module, and the return light of the measurement light is returned to the heterodyne coherence module along the original path through a diffuse reflection object, thereby 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; The density of the medium to be measured is obtained based on the phase change signal.

5. The in-situ density measurement method based on diffuse reflection laser heterodyne coherence according to claim 4, characterized in that: The demodulating the interference light signal and outputting the phase change of the measuring light caused by the medium to be measured includes: converting the interference light signal into an electrical signal; The electrical signal is demodulated based on a heterodyne intermediate frequency signal demodulation algorithm to obtain a phase change signal of the medium to be measured.

6. The in-situ density measurement method based on diffuse reflection laser heterodyne coherence according to claim 4, characterized in that: Obtaining the density of the medium to be measured based on the phase change includes: Obtaining the refractive index of the medium to be measured based on a mapping relationship between the phase change signal and the refractive index of the medium to be measured; The density of the medium to be measured is obtained based on the mapping relationship between the refractive index and the density of the medium to be measured.

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