JP7637386B2 - SOUND VISUALIZATION SYSTEM, SOUND VISUALIZATION DEVICE, SOUND VISUALIZATION METHOD, AND PROGRAM - Google Patents

Description

The present invention relates to a technology for visualizing sound fields using light.

と表される。ただし、k_iは光の波数、n₀は定常状態の空気屈折率、p₀は定常状態の大気圧、γは空気の比熱比、pは音圧である。積分は光の伝搬経路に沿った線積分を表しており、ここでは光路をx軸と平行となるように定義した。k_i、n₀、p₀、γは計測条件から分かる定数である。ここで測定される量は空間内の一点の音圧ではなく、光路に沿った音圧の線積分値に比例する。 Direct observation of how sound propagates through space and how sound is emitted from a sound source is extremely important in understanding acoustic phenomena. Such sound visualization is generally performed using a microphone array, but arranging a large number of microphones spatially densely leads to an increase in the size and cost of the system, and there are issues with the very existence of the microphone array changing the sound field being measured. For this reason, a method using light has been proposed as a non-contact sound visualization method with high spatial resolution. First, we will explain a sound field observation method that utilizes the change in refractive index of a medium caused by sound, known as the acousto-optic effect. According to the acousto-optic effect, the phase change φ _s of light caused by sound is expressed as follows:

where k _i is the wave number of light, n ₀ is the refractive index of air in a steady state, p ₀ is the atmospheric pressure in a steady state, γ is the specific heat ratio of air, and p is the sound pressure. The integral represents the line integral along the propagation path of light, and here the light path is defined as being parallel to the x-axis. k _i , n ₀ , p ₀ , and γ are constants that can be determined from the measurement conditions. The quantity measured here is proportional to the line integral value of the sound pressure along the light path, not the sound pressure at a point in space.

Based on the above principles, Non-Patent Document 1 proposes an instantaneous two-dimensional sound field visualization method using parallel phase-shifting interferometry and a high-speed camera. Non-contact sound visualization is achieved by capturing the phase change of light caused by sound as an intensity change of interference light. Non-Patent Document 2 also achieves sound field visualization by using the principles of digital holography. Non-Patent Document 3 achieves similar sound measurement using a TV holography method that utilizes speckles.

Kenji Ishikawa, Kohei Yatabe, Nachanant Chitanont, Yusuke Ikeda, Yasuhiro Oikawa, Takashi Onuma, Hayato Niwa, and Minoru Yoshii, "High-speed imaging of sound using parallel phase-shifting interferometry", Opt. Express 24, 12922-12932, 2016. Osamu Matoba, Hiroki Inokuchi, Kouichi Nitta, and Yasuhiro Awatsuji, "Optical voice recorder by off-axis digital holography", Opt. Lett. 39, 6549-6552, 2014. OJ. Lokberg, "Sound in flight: measurement of sound fields by use of TV holography", Appl Opt., 33(13), 2574-2584, 1994.

One of the challenges with conventional optical sound field observation is the increase in the weight of the system as the observation range expands. With a typical lens, the thickness of the lens increases as the aperture becomes larger, so the weight increases significantly with larger apertures. Therefore, conventional optical systems for sound field observation have the challenge of significantly increasing weight as the aperture becomes larger. These challenges are particularly pronounced when building large-aperture visualization systems that observe ranges of tens of centimeters or more.

The present invention aims to provide a sound visualization system that has a lower overall system weight than conventional sound visualization systems.

In order to solve the above problem, according to one aspect of the present invention, the sound visualization system includes a laser that emits laser light, a first beam splitter that splits the optical path of the laser light into two, a magnifying lens system that includes at least one lens that includes at least one of a fine structure and a discontinuous shape and expands the beam diameter of the object light after passing through the first beam splitter, a reduction lens system that includes at least one lens that includes at least one of a fine structure and a discontinuous shape and reduces the beam diameter of the object light after passing through the magnifying lens system, a second beam splitter that combines the object light and the reference light, a phase distribution calculation unit that obtains a time-series phase distribution by calculation from the interference light obtained by combining the object light and the reference light, and a filtering unit that removes components other than sound contained in the time-series phase distribution and extracts sound information, and the sound to be visualized is generated between the magnifying lens system and the reduction lens system.

In order to solve the above problem, according to another aspect of the present invention, the sound visualization system includes a laser that emits laser light, a first beam splitter that splits the optical path of the laser light into two, a magnifying lens system that includes at least one lens that includes at least one of a fine structure and a discontinuous shape and expands the beam diameter of the object light after passing through the first beam splitter, a reduction lens system that includes at least one lens that includes at least one of a fine structure and a discontinuous shape and reduces the beam diameter of the object light after passing through the magnifying lens system, a diffuser that converts the object light after passing through the reduction lens system into a speckle pattern, a second beam splitter that combines the speckle pattern and a reference light, a phase distribution calculation unit that obtains a time-series phase distribution by calculation from the interference light obtained by combining the speckle pattern and the reference light, and a filtering unit that removes components other than sound contained in the time-series phase distribution and extracts sound information, and the sound to be visualized is generated between the magnifying lens system and the reduction lens system.

The present invention has the effect of reducing the weight of the entire sound visualization system compared to conventional systems.

FIG. 1 is a functional block diagram of a sound visualization system according to a first embodiment. FIG. 2 is a diagram showing an example of a processing flow of the sound visualization system according to the first embodiment. 1A and 1B are diagrams showing examples of an interference image and a hologram. FIG. 13 is a diagram showing the effect of a spatiotemporal filter for extracting a sound field. FIG. 1 shows the frequency spectrum calculated from an unfiltered image. FIG. 11 is a functional block diagram of a sound visualization system according to a second embodiment. FIG. 11 is a diagram showing an example of a processing flow of the sound visualization system according to the second embodiment. 13A and 13B are diagrams showing absolute values of the difference between a speckle image generated by the optical system of the second embodiment and a speckle image obtained by tilting the reference light. FIG. 13 is a diagram showing an example of the configuration of a computer to which the present technique is applied.

The following describes an embodiment of the present invention. In the drawings used in the following description, components having the same functions and steps performing the same processing are denoted with the same reference numerals, and duplicate explanations will be omitted. In the following description, processing performed on an element-by-element basis of a vector or matrix is assumed to apply to all elements of that vector or matrix, unless otherwise specified.

<Key Points of the Invention>
Conventional optical systems for observing sound fields have the problem that the weight increases significantly as the aperture is increased, and the following problems are also considered. Conventional devices use precision interferometers or digital holography to measure sound. Lenses with smooth surfaces are used to observe the interference fringes caused by the interference of light waves. The smoother the lens surface, the less unevenness caused by the lens and the cleaner the interference fringes that can be obtained. The smoother the lens surface, the more precise the polishing required, so there is a problem that the more precise the lens, the higher the manufacturing costs.

The present invention uses a lens that includes at least one of a fine structure and discontinuous shape in a sound visualization system. As a lens that includes at least one of a fine structure and discontinuous shape, a Fresnel lens, a diffractive lens, a metalens, etc. can be used. By using such a lens, a light-weight, thin, and small sound visualization system can be constructed. In particular, by using a Fresnel lens, manufacturing costs can be reduced, so an example using a Fresnel lens will be described below. A Fresnel lens is a normal optical lens in which the curved surface is divided into concentric circles and replaced with grooves, and while being thin and lightweight, it functions as a lens that refracts light rays. Since it is easy to make it large and can be manufactured at low cost, it is mainly used for light-collecting applications and low-quality magnifying glass applications. On the other hand, since its performance as an imaging lens is low, it is rarely used for applications such as imaging and interferometers that require high quality. This is because the Fresnel lens has a concentric discontinuous shape due to its structure, which causes concentric lines due to the shape, a decrease in imaging performance due to light diffraction, and disturbance of the wavefront.

The present invention uses a Fresnel lens as part of the optical system to realize a large-diameter light-based sound visualization system that is lower cost and lighter than conventional technology. The present invention uses the physical characteristics of the sound field to be measured to eliminate the inconveniences caused by the use of a Fresnel lens. For example, the distortion pattern generated by a Fresnel lens is a quantity that does not vary over time, whereas the sound field is a quantity that varies over time and space. Therefore, by extracting only the components that vary through signal processing, it becomes possible to efficiently extract sound field information even from low-quality interference images.

In other words, the key point of this invention is that it focuses on the physical property that sound is a component that fluctuates in time and space, and makes it possible to observe sound field information using an optical system that uses low-quality Fresnel lenses that are usually unsuitable for interferometers. Even if a single image has a lot of distortion and noise and the measurement target is not clearly observed, the sound field can be visualized by applying filtering to the time-series images that takes into account the properties of the sound. Fresnel lenses, especially in the case of large diameters, are much lighter, thinner, and less expensive than lenses generally used in interferometers, making it possible to build a sound visualization system that is lower cost, lighter, thinner, and smaller than conventional systems.

In the first embodiment, a method using digital holography (see Non-Patent Document 2) is shown.

First Embodiment
FIG. 1 is a functional block diagram of a sound visualization system according to a first embodiment, and FIG. 2 shows an example of the processing flow thereof.

The sound visualization system includes a laser 110, a beam splitter 120, mirrors 131 and 132, a magnifying lens system 140 including a lens 141 and a Fresnel lens 143, a reducing lens system 150 including a Fresnel lens 153 and a lens 151, a beam splitter 160, a camera 170, a phase distribution calculation unit 180, a filtering unit 190, and a display unit 195.

Note that a device including the phase distribution calculation unit 180 and the filtering unit 190 is also referred to as a sound visualization device.

The sound visualization device is a special device configured by loading a special program into a publicly known or dedicated computer having, for example, a central processing unit (CPU), a main memory (RAM), etc. The sound visualization device executes each process under the control of the central processing unit, for example. Data input to the sound visualization device and data obtained in each process are stored in, for example, the main memory, and the data stored in the main memory is read out to the central processing unit as necessary and used for other processes. At least a part of each processing unit of the sound visualization device may be configured with hardware such as an integrated circuit. Each storage unit of the sound visualization device may be configured with, for example, a main storage device such as a RAM (Random Access Memory), or middleware such as a relational database or a key-value store. However, each storage unit does not necessarily have to be provided inside the sound visualization device, and may be configured with an auxiliary storage device configured with a semiconductor memory element such as a hard disk, optical disk, or flash memory, and may be configured to be provided outside the sound visualization device.

Each part is explained below.

<Optical system>
The laser 110 emits a laser beam (S110).

The beam splitter 120 splits the optical path of the laser light into two (S120). The laser 110, the beam splitter 120, the mirrors 131 and 132, the lens 141, the Fresnel lens 143, the Fresnel lens 153, the lens 151, the beam splitter 160, and the camera 170 are arranged so that one laser light is an object light and the object optical path passes through the sound field, and the other laser light is a reference light and the reference optical path does not pass through the sound field.

After passing through the beam splitter 120, the object light has its beam diameter expanded by the magnifying lens system 140 (S140).

The expanded light that passes through the sound field has its beam diameter reduced by the reduction lens system 150 (S150).

The beam splitter 160 combines the object light and the reference light (S160).

The image sensor of the camera 170 records the light combined by the beam splitter 160 as an interference image (S170). The interference image may be recorded in a memory in the camera 170, or in a memory provided inside the sound visualization device connected to the camera 170. An imaging lens system may be provided in front of the image sensor. The sound field to be measured is generated between the magnifying lens system 140 and the reducing lens system 150, and the magnified light passes through the sound field. Some or all of the lenses used in the magnifying lens system 140 and the reducing lens system 150 are Fresnel lenses. In the example of FIG. 1, the magnifying lens system 140 and the reducing lens system 150 use Fresnel lenses 143 and 153, respectively.

To remove higher-order diffracted light and unnecessary frequency components, an aperture may be placed on the Fourier transform plane of the reduction lens system 150. In this embodiment, a Mach-Zehnder interferometer is used as an example, but any interferometer such as a Michelson interferometer or a Fizeau interferometer may be used.

<Phase distribution calculation unit 180>
Next, the phase distribution calculation unit 180 retrieves the interference image from the memory, and obtains the time-series phase distribution of the sound to be visualized by calculation (S180). For example, the phase distribution calculation unit 180 calculates a hologram or phase distribution of the object light modulated by the sound from the interference image, and obtains a time-series phase difference image that is the difference between an image of the phase distribution of the object light when there is no sound and a time-series image of the phase distribution of the object light when the sound is reproduced. This time-series phase difference image corresponds to the time-series phase distribution of the sound to be visualized.

In one embodiment, the object light and the reference light combined by the beam splitter 160 are superimposed off-axis (non-coaxial) with the optical axes slightly shifted. The phase distribution calculation unit 180 calculates the hologram or phase distribution of the object light from the interference fringes recorded in the interference image.

In another embodiment, multiple interference images are recorded in which the relative phase difference between the object light and the reference light contained in the interference light is shifted. The phase distribution calculation unit 180 calculates the hologram or phase distribution of the object light using a phase shift algorithm. The hologram of the object light is back-propagated by numerical calculation, object light information of a specific surface on the object light path is calculated, and the phase distribution at that surface is output as an image. Alternatively, the phase distribution at the imaging surface is output as an image.

The image sensor records multiple interference images, and the phase distribution calculation unit 180 obtains time-series images of the phase distribution of the object light by a similar procedure.

<Filtering Unit 190>
The filtering unit 190 performs filtering to extract sound information from the time-series phase difference images obtained by the phase distribution calculation unit 180 (S190). The filtering is performed for the purpose of removing components other than sound contained in the phase distribution. The properties of the filter are determined based on the properties of the sound to be measured. The components other than sound contained in the phase distribution include noise caused by a lens that has at least one of a fine structure and a discontinuous shape.

In one form, the filter treats the time series data of each pixel of the image as a time signal and applies an independent filter to each pixel. In this case, the frequency band of the sound field to be analyzed can be specified in advance, and a bandpass filter that passes the components of that band can be used. It is also possible to use a low-pass filter or high-pass filter that passes only low- or high-frequency components.

Alternatively, a spatial frequency filter can be used for each image. Similarly, the spatial frequency of the sound is defined and a filter is used accordingly.

Another approach is to apply three-dimensional spatio-temporal filtering. In this case, a single spatio-temporal filter can be used, or both a time filter and a spatial frequency filter can be used independently.

If the sound field being measured contains components whose frequency is equal to or greater than half the frame rate of the image sensor, the frequency of the sound will exceed the Nyquist frequency. Since the image sensor is not equipped with an anti-aliasing filter, components that exceed the Nyquist frequency will be recorded as frequency components that symmetrically fold back the Nyquist frequency. Therefore, in such cases, the filtering described above is performed on the folded back frequencies.

The filtering unit 190 outputs the filtered time-series image of the phase distribution as spatiotemporal sound visualization data and displays it on the display unit 195 (S195). The display unit 195 is, for example, a display or a touch panel.

<Measurement example>
Next, the results of an actual measurement example using the optical system of the first embodiment are shown. The measurement target was a 40 kHz sine wave sound field emitted by an ultrasonic transducer. The size of the captured image was 240 × 240 pixels, and 100 images were captured using a high-speed camera with a frame rate of 100,000 fps. Figure 3 shows the captured interference images sp1 and ap1, and holograms sp2, ap2, sp3, and ap3 obtained by performing back propagation calculation using off-axis Fresnel diffraction on the images. The interference images sp1 and ap1 are interference images recorded by the image sensor of the camera 170, and the phase difference image p4 is the output value of the phase distribution calculation unit 180. The upper row shows the interference image sp1 and holograms sp2 and sp3 when there is no sound, and the lower row shows the interference image ap1, holograms ap2, and ap3 of a certain frame when sound is reproduced. The rightmost phase difference image p4 shows the difference between the phases sp3 and ap3 of the holograms when sound is reproduced and when there is no sound. In the interference images sp1 and ap1, the unevenness of the light amount due to the Fresnel lens is clearly observed. In addition, high-frequency interference fringes are also captured. In the calculated holograms sp2, ap2, sp3, and ap3, the unevenness due to the Fresnel lens is also dominant, and the phase distribution has a complex pattern. In the phase difference image p4, a linear pattern due to phase discontinuity appears. Here, the sound field cannot be confirmed, because the amplitude of the sound field is small at about 0.01 rad, and the noise pattern is significantly larger. From this Figure 3, it can be seen that although a hologram can be obtained using an optical system including a Fresnel lens, the phase distribution has a large amount of noise as it is, and sound visualization cannot be achieved.

Figure 4 shows the effect of the spatio-temporal filter to extract the sound field. The top row shows the phase difference image itself without applying a filter (examples of output values of the phase distribution calculation unit 180) nf0, nf10, nf20, the middle row shows the results of applying a 6th order IIR bandpass filter with a center frequency of 40 kHz and a bandwidth of 1 kHz to each pixel (examples of output values of the filtering unit 190 (time domain filter)) tf0, tf10, tf20, and the bottom row shows the results of applying a 2D Gaussian smoothing filter with a standard deviation of 16 pixels to the results in the middle row (examples of output values of the filtering unit 190 (time domain filter + spatial filter)) sf0, sf10, sf20. Note that the dashed lines in the figure are auxiliary lines to indicate the position of the sound wavefront. It is difficult to recognize the sound wavefront with the results without a filter, nf0, nf10, nf20. On the other hand, in the results of applying the time domain filter, tf0, tf10, and tf20, a wavefront can be seen progressing from right to left in the image between the three frames, but a spatially fine noise pattern caused by a Fresnel lens is superimposed on the sound wavefront. In the results of applying the spatial filter, sf0, sf10, and sf20, it can be seen that the sound wavefront is preserved while the fine noise pattern has been removed. To confirm that this wavefront is a sound wave, the frequency spectrum calculated from the central 100 pixels of the unfiltered images nf0, nf10, and nf20 in the upper row is shown in Figure 5. A clear peak appears at 40 kHz, which coincides with the frequency of sound, confirming that the visualization result is sound.

＜Effects＞
With the above configuration, the weight of the entire sound visualization system can be reduced compared to conventional systems.

By using a Fresnel lens, it becomes possible to construct a large-aperture sound visualization system, which has not been very practical in the past due to the cost and weight of the system. For example, in order to observe the state of sound propagation throughout a room, it is desirable to visualize a range of several tens of centimeters to several meters. If such a large-aperture interferometer is to be realized using a conventional optical system, the cost is very high and the lens is very heavy, making it very difficult to actually build it. In contrast, by using the method of the present invention, a low-cost, lightweight, thin, and small-sized sound visualization system with a large aperture can be constructed using inexpensive and lightweight lenses. Such a sound visualization system can visualize various sound fields, such as noise emitted from large musical instruments, electroacoustic equipment, automobiles, and machines, and is effective in elucidating acoustic phenomena and improving and promoting the quality of sound products.
<Other Modifications>
In this embodiment, the phase distribution calculation unit 180 obtains the time series phase distribution from the interference image, but it is not necessarily an interference image, and the time series phase distribution may be obtained from the interference light. As in this embodiment, an interference image may be obtained from the interference light, and the time series phase distribution may be obtained from the interference image, or the time series phase distribution may be obtained from other "information obtained from the interference light" other than the interference image. For example, a set of time waveforms for each channel may be obtained from the interference light, and the time series phase distribution may be obtained from the set of time waveforms.

Second Embodiment
The following description will focus on the differences from the first embodiment.

In the second embodiment, a method using an off-axis speckle interferometer (see Non-Patent Document 3) is shown.

Figure 6 shows a functional block diagram of the sound visualization system according to the second embodiment, and Figure 7 shows an example of the processing flow.

The sound visualization system includes a laser 110, a beam splitter 120, mirrors 131 and 132, a magnifying lens system 140 including a lens 141 and a Fresnel lens 143, a reducing lens system 150 including a Fresnel lens 153 and a lens 151, a diffuser 255, an aperture 256, a lens 257, a beam splitter 160, a camera 170, a phase distribution calculation unit 280, a filtering unit 290, and a display unit 195.

Note that a device including the phase distribution calculation unit 280 and the filtering unit 290 is also referred to as a sound visualization device.

<Diffuser 255, aperture 256, and lens 257>
In this embodiment, a diffuser 255 is installed behind the reduction lens system 150. The diffuser 255 converts the object light into a speckle pattern (S255).

The speckle pattern on the surface of the diffuser 255 is imaged on the image sensor of the camera 170 by the lens 257. In this embodiment, the amount of light is adjusted by the aperture 256. As in the first embodiment, the speckle patterns of the reference light and the object light are combined by the beam splitter 160, and an interference image is recorded by the camera 170. In addition to the configuration in FIG. 6, a diffuser, aperture, and lens may also be installed on the reference light side, and an interference image of the object light speckle pattern and the reference light speckle pattern may be captured.

In this embodiment, the interference fringes are captured using off-axis speckle interferometry. First, an interference image of the object light and reference light is recorded in a soundless state. Next, the angle of incidence of the reference light is slightly tilted to generate a sound field to be measured in the measurement area, and the interference image is measured.

<Phase distribution calculation unit 280>
The phase distribution calculation unit 280 retrieves the interference image from the memory, and obtains a time-series phase distribution from the interference image by calculation (S280). For example, the phase distribution calculation unit 280 obtains an off-axis speckle interference image by calculating the difference between an image measured during sound field reproduction and an image in an initial state. This off-axis speckle interference image contains the phase difference between the light wave during sound field reproduction and the light wave in the initial state as an interference fringe. That is, an interference image is obtained in which the interference fringe of the spatial frequency according to the angle change of the reference light and the phase fluctuation component of the light due to the sound are superimposed. Here, the phase distribution of the object light is calculated from this interference image using a Fourier fringe analysis method or the like. By performing this process for each frame, a time-series image of the phase distribution of the object light is obtained.

<Filtering Unit 290>
Since this time-series image contains noise components due to speckle in addition to phase fluctuations due to sound, the filtering unit 290 performs filtering (S290) similar to that of the first embodiment to remove components other than sound contained in the phase distribution, together with the noise components due to speckle, and obtains space-time sound visualization data.

In this embodiment, even if the light wavefront is disturbed by the Fresnel lens, the diffuser generates random speckles, so that speckles with uniform properties are generated across the entire image sensor. Therefore, by tilting the reference light, it is possible to generate interference fringes with high contrast. Figure 8 shows the absolute value of the difference between the speckle image generated by the optical system of the second embodiment and the speckle image with the reference light tilted. Image A on the left of Figure 8 shows the initial speckle pattern, image B in the center shows the speckle pattern with the reference light tilted, and image C on the right shows the absolute value of the difference between the initial speckle pattern and the speckle pattern with the reference light tilted.

It can be seen that by tilting the angle of incidence of the reference light, speckle interference fringes can be observed even when a Fresnel lens is used. In such a speckle interferometer, sound fluctuations and random speckle patterns are measured in a superimposed manner, but by utilizing the difference between sound and noise components, it is possible to efficiently remove the speckle pattern by filtering. In particular, when the size of the speckle pattern is sufficiently small compared to the sound wavelength, the speckle component can be removed by a low-pass filter.

＜Effects＞
With this configuration, it is possible to obtain the same effects as in the first embodiment.

<Other Modifications>
The present invention is not limited to the above-mentioned embodiment and modified examples. For example, the above-mentioned various processes may be executed not only in chronological order as described, but also in parallel or individually depending on the processing capacity of the device executing the processes or as necessary. In addition, appropriate modifications are possible within the scope of the present invention.

<Program and recording medium>
The processing of the above-described sound visualization device can be implemented by loading a program for executing each step of the above-described method into the storage unit 2020 of the computer shown in FIG. 9 , and operating the control unit 2010, input unit 2030, output unit 2040, etc.

The program describing this processing can be recorded on a computer-readable recording medium. Examples of computer-readable recording media include magnetic recording devices, optical disks, magneto-optical recording media, and semiconductor memories.

The program may be distributed, for example, by selling, transferring, or lending portable recording media such as DVDs or CD-ROMs on which the program is recorded. Furthermore, the program may be stored in a storage device of a server computer, and the program may be distributed by transferring the program from the server computer to other computers via a network.

A computer that executes such a program, for example, first stores in its own storage device the program recorded on a portable recording medium or the program transferred from a server computer. Then, when executing a process, the computer reads the program stored in its own recording medium and executes the process according to the read program. As another execution form of this program, the computer may read the program directly from the portable recording medium and execute the process according to the program, or may execute the process according to the received program each time a program is transferred from the server computer to this computer. Alternatively, the server computer may not transfer the program to this computer, but may execute the above-mentioned process by a so-called ASP (Application Service Provider) type service that realizes the processing function only by issuing an execution instruction and obtaining the results. Note that the program in this form includes information used for processing by an electronic computer that is equivalent to a program (such as data that is not a direct command to the computer but has properties that specify the processing of the computer).

In addition, in this embodiment, the device is configured by executing a specific program on a computer, but at least a portion of the processing may be realized by hardware.

Claims (6)

A laser that emits laser light;
a first beam splitter that splits the optical path of the laser light into two;
a magnifying lens system including at least one lens having a microstructure and/or a discontinuity in shape, and configured to magnify a beam diameter of the object light after passing through the first beam splitter;
a reduction lens system including at least a lens having at least one of a microstructure and a discontinuity in shape, the reduction lens system reducing a beam diameter of the object light after passing through the magnification lens system;
a second beam splitter for combining the object beam and the reference beam after passing through the reduction lens system ;
a camera for recording the light combined by the second beam splitter as an interference image;
a phase distribution calculation unit that obtains a time series phase distribution from the interference image by calculation;
A filtering unit that removes components other than sound included in the time-series phase distribution and extracts sound information.
Sound visualization system. A laser that emits laser light;
a first beam splitter that splits the optical path of the laser light into two;
a magnifying lens system including at least one lens having a microstructure and/or a discontinuity in shape, and configured to magnify a beam diameter of the object light after passing through the first beam splitter;
a reduction lens system including at least a lens having at least one of a microstructure and a discontinuity in shape, the reduction lens system reducing a beam diameter of the object light after passing through the magnification lens system;
a diffuser that converts the object light after passing through the reduction lens system into an object light having a speckle pattern;
a second beam splitter for combining the speckle pattern and a reference beam;
a camera for recording the light combined by the second beam splitter as an interference image;
a phase distribution calculation unit that obtains a time series phase distribution from the interference image by calculation;
A filtering unit that removes components other than sound included in the time-series phase distribution and extracts sound information.
Sound visualization system. A sound visualization device comprising the phase distribution calculation unit and a filtering unit according to claim 1 or 2,
The non-sound components included in the phase distribution include noise caused by a lens having at least one of a fine structure and a discontinuity in shape.
Sound visualization device. a laser emitting laser light;
A first beam splitter splits the optical path of the laser light into two;
A magnifying lens system including at least a lens having at least one of a microstructure and a discontinuity in shape expands a beam diameter of the object light after passing through the first beam splitter;
A reduction lens system including at least a lens having at least one of a microstructure and a discontinuity in shape, reducing a beam diameter of the object light after passing through the magnification lens system;
a second beam splitter combining the object beam and the reference beam after passing through the reduction lens system ;
a sound to be visualized is generated between the magnifying lens system and the reducing lens system, and a camera records the light combined by the second beam splitter as an interference image;
a phase distribution calculation step of obtaining a time series phase distribution from the interference image by calculation;
A filtering step of removing components other than sound included in the time series phase distribution and extracting sound information.
Sound visualization methods. a laser emitting laser light;
A first beam splitter splits the optical path of the laser light into two;
A magnifying lens system including at least a lens having at least one of a microstructure and a discontinuity in shape expands a beam diameter of the object light after passing through the first beam splitter;
A reduction lens system including at least a lens having at least one of a microstructure and a discontinuity in shape, reducing a beam diameter of the object light after passing through the magnification lens system;
a diffuser converting the object beam after passing through the reduction lens system into an object beam having a speckle pattern;
a second beam splitter combining the speckle pattern and a reference beam;
a sound to be visualized is generated between the magnifying lens system and the reducing lens system, and a camera records the light combined by the second beam splitter as an interference image;
a phase distribution calculation step of obtaining a time series phase distribution from the interference image by calculation;
A filtering step of removing components other than sound included in the time series phase distribution and extracting sound information.
Sound visualization methods. A program for causing a computer to function as the sound visualization device of claim 3.

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