JP5759868B2 - Observation device - Google Patents

Description

  The present invention relates to an apparatus for observing an image of an object.

  Conventionally, an apparatus for observing an object using a photoacoustic effect is known. For example, Patent Document 1 discloses an apparatus using photoacoustic tomography, which is based on a signal component derived from a homogeneous part separated from an inhomogeneous part inside a subject (object). An apparatus for determining an absorption coefficient is disclosed. Patent Document 2 discloses an irradiation unit that irradiates probe light from an arbitrary local surface portion of a measurement object, and an intensity of an acoustic signal generated inside the measurement object due to light irradiated through the irradiation unit. Disclosed is an apparatus for determining the object distribution of an object by photoacoustic tomography, comprising: a measuring means for measuring the amount of data; and a processing means for inputting and processing data measured by the measuring means to reproduce the substance distribution of the object to be measured Has been.

  Patent Document 3 discloses a method of irradiating a moving object such as red blood cells with light, detecting a sound wave generated by photoacoustic light with a microphone, and obtaining a fluid velocity from a Doppler shift amount of the detected sound wave. It is disclosed.

JP 2010-68885 A Japanese Patent No. 3456721 US Patent Application Publication No. 2009/0138215

  In the apparatus using the techniques described in Patent Documents 1 and 2, it is necessary that the object is stationary. Therefore, in order to obtain an intensity image / phase image of a moving object while improving SN with these devices, the object is stationary using a detector capable of high-speed measurement with a high frame rate. It is necessary to obtain a plurality of images in a period that can be regarded as being. However, there is a problem that a high-frequency circuit is required to detect the object multiple times within a time period that can be regarded as sufficiently stationary, and the circuit scale increases. Moreover, although the method of patent document 3 can obtain | require the velocity of a fluid, it cannot obtain the image of a target object.

  The present invention has been made to solve the above problems, and even when a detector with a low signal acquisition rate is used, an image of a moving object (acoustic impedance distribution, attenuation rate distribution, An object of the present invention is to provide an observation apparatus capable of obtaining a velocity distribution.

  The observation apparatus according to the present invention includes a signal generation unit that generates a signal having a predetermined frequency and a light source that generates light by inputting the signal having the predetermined frequency, and irradiates the moving object with light. A diffracted sound wave generator for generating a diffracted sound wave from the object by the photoacoustic effect, and a Doppler shift effect due to the movement of the object in the sound wave that reaches the predetermined plane among the diffracted sound waves generated by the light source by the light source Is a direction on a predetermined plane where the distance is constant, and a direction perpendicular to the moving direction of the object is defined as a first direction, and the direction on the predetermined plane orthogonal to the first direction is the moving direction of the object. When the parallel direction is the second direction, the data representing the sum in the second direction of the data that temporally changes at a frequency corresponding to the Doppler shift amount of the sound wave that has reached each position on the predetermined plane, For each position in the first direction For the detection unit that outputs at each time, and the data that has the position and time in the first direction on the predetermined plane output from the detection unit as variables, the one-dimensional Fourier transform for the time variable, the one-dimensional Fourier transform for the frequency, And an arithmetic unit that performs one-dimensional Fourier transformation in one direction and obtains data obtained by the one-dimensional Fourier transformation as an image of the object. Here, the first direction is a direction perpendicular to the moving direction of the object, and the second direction is a direction parallel to the moving direction of the object.

  In the observation apparatus of the present invention, a moving object is irradiated with light from a light source to generate a diffracted sound wave. The diffracted sound wave undergoes an amount of Doppler shift corresponding to the scattering direction. The diffracted sound wave is detected by the detection unit. A direction on the predetermined plane in which the Doppler shift effect due to the movement of the object is constant in the sound wave that has reached the predetermined plane is a direction perpendicular to the movement direction of the object as the first direction, A direction parallel to the direction of movement of the object is a second direction that is a direction on a predetermined plane orthogonal to each other. Data representing the sum in the second direction of data that temporally changes at a frequency corresponding to the Doppler shift amount of the sound wave that has reached each position on the predetermined plane is received from the detection unit at each time for each position in the first direction. Is output. In the calculation unit, the one-dimensional Fourier transform related to the time variable, the one-dimensional Fourier transform related to the frequency, and the one related to the first direction for the data whose variables are the position and time in the first direction on the predetermined plane output from the detection unit. Data obtained by performing the dimensional Fourier transform is obtained as an image of the object.

  In the observation apparatus of the present invention, the detection unit has a detection surface on a predetermined plane, and includes a plurality of microphones that receive sound waves on the detection surface and convert them into electric signals, and the plurality of microphones have a first direction and The microphones arranged in the second direction and connected in the second direction may be electrically connected on the output side.

  In the observation apparatus of the present invention, the detection unit has a detection surface on a predetermined plane, and includes a plurality of microphones that receive sound waves on the detection surface and convert them into electric signals, and the plurality of microphones have a first direction and The calculation units may be provided in parallel in the second direction, and the calculation unit may include output summers that obtain the sum of the outputs of the microphones in the second direction.

  In the observation apparatus of the present invention, the detection unit includes a detection surface on a predetermined plane, and includes a microphone that receives a sound wave on the detection surface and converts the sound wave into an electric signal. The microphone vibrates due to the input sound wave. A plate, a fixed plate disposed with a predetermined distance from the diaphragm, a laser light source, a beam splitter, and a photocell for converting light intensity into an electrical signal, the photocell having a first direction and Data arranged in parallel in the second direction and representing the sum in the second direction may be output at each time for each position in the first direction.

  The observation apparatus of the present invention further includes a first reference sound wave generation unit that inputs a signal having a predetermined frequency from the signal generation unit and generates a first reference sound wave from the input signal, and the detection unit is provided on the detection surface. The diffracted sound wave generated in the object and the first reference sound wave may be heterodyne interfered.

  The observation apparatus according to the present invention further includes a first reference signal generation unit that inputs a signal having a predetermined frequency from the signal generation unit and generates a first reference signal from the input signal, and the detection unit has the second direction. The total sum of the microphone outputs and the first reference signal may be subjected to heterodyne interference.

  In the observation apparatus according to the present invention, among the diffracted sound waves generated in the object, the sound wave that appears at the center of the Franforfer diffraction image of the object is input, and after the input sound wave is converted into an electric signal, A second reference signal generation unit that generates a second reference signal from the signal may be further provided, and the detection unit may cause heterodyne interference between the sum of the outputs of the microphones in the second direction and the second reference signal.

  In the observation apparatus according to the present invention, among the diffracted sound waves generated in the object, the sound wave that appears at the center of the Franforfer diffraction image of the object is input, and after the input sound wave is converted into an electric signal, A second reference sound wave generation unit that generates a second reference sound wave from the signal may be further provided, and the detection unit may cause heterodyne interference between the diffracted sound wave generated by the object and the second reference sound wave on the detection surface.

  In the observation apparatus according to the present invention, the calculation unit uses the one-dimensional Fourier related to the frequency for the data including the maximum Doppler shift frequency around the predetermined frequency among the data obtained by the one-dimensional Fourier transform related to the time variable. Transformation and one-dimensional Fourier transformation related to the first direction may be performed.

  In the observation apparatus according to the present invention, the calculation unit increases or decreases the maximum Doppler shift frequency around the frequency of the signal obtained by modulating the signal of the predetermined frequency with a modulator among the data obtained by the one-dimensional Fourier transform relating to the time variable. The one-dimensional Fourier transform related to the frequency and the one-dimensional Fourier transform related to the first direction may be performed on the data in the region included in the.

  The observation apparatus of the present invention further includes a speed detection unit that detects the moving speed of the object, and the calculation unit calculates the speed of the object during the Fourier transform based on the speed of the object detected by the speed detection unit. It is good also as correcting about a change.

  In the observation apparatus of the present invention, the diffracted sound wave generator may include a light source that generates broadband light. In addition, the diffracted sound wave generator may include a light source that generates a pulse wave as light.

  According to the present invention, even when a detector with a low signal acquisition rate is used, an image of a moving object can be obtained.

It is a figure explaining the principle of acquisition of the image of the target object by the observation apparatus of this embodiment. It is a figure which shows the structure of the observation apparatus which concerns on 1st Embodiment. It is a figure which shows the calculator structure of the calculating part of the observation apparatus which concerns on 1st Embodiment. It is a figure which shows an example of the calculating unit structure of the calculating part of the observation apparatus which concerns on 2nd Embodiment. It is a figure which shows another example of the calculating unit structure of the calculating part of the observation apparatus which concerns on 2nd Embodiment. It is a figure which shows another example of the calculating unit structure of the calculating part of the observation apparatus which concerns on 2nd Embodiment. It is a figure which shows another example of the calculating unit structure of the calculating part of the observation apparatus which concerns on 2nd Embodiment. It is a figure which shows another example of the calculating unit structure of the calculating part of the observation apparatus which concerns on 2nd Embodiment. It is a figure which shows the structure of the observation apparatus which concerns on 3rd Embodiment. It is a figure which shows the structure of the observation apparatus which concerns on 4th Embodiment. It is a figure which shows the structure of the heterodyne detector using a multiplier. It is a figure which shows the structure of the observation apparatus which concerns on 5th Embodiment. It is a figure explaining the principle of an electrostatic microphone. It is a figure explaining the principle of an electrodynamic microphone. It is a figure explaining the principle of an optical microphone. It is a figure explaining the principle of an optical microphone. It is a figure explaining the principle of an optical microphone. It is a figure explaining the structure of the optical microphone used for the observation apparatus which concerns on 6th Embodiment. It is a figure which shows the calculator structure of the calculating part of the observation apparatus which concerns on 7th Embodiment. It is a figure which shows the calculator structure of the calculating part of the observation apparatus which concerns on 7th Embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  The observation apparatus of the present embodiment uses the Doppler shift effect generated in the diffracted sound wave generated from the moving object, and in particular, has a constant between the traveling direction of the diffracted sound wave generated in the object and the Doppler shift amount. An image of the object is acquired by utilizing the existence of the relationship. First, with reference to FIG. 1, a principle matter regarding acquisition of an image of an object by the observation apparatus of the present embodiment will be described.

  FIG. 1 is a diagram for explaining the principle of acquisition of an image of an object by the observation apparatus of the present embodiment. In this figure, the ξη coordinate system and the uv coordinate system are shown. The ξ axis and the u axis are parallel to each other. The η axis and the v axis are parallel to each other. The object 2 to be observed exists on the ξη plane.

  It is assumed that the object 2 is moving in the -η direction on the ξη plane. It is assumed that the object 2 is irradiated with light L0 traveling in a direction perpendicular to the ξη plane. This light L0 is, for example, a plane wave. When the object 2 is irradiated with the light L <b> 0, thermal expansion occurs in the object 2 due to light absorption of the object 2, and as a result, sound waves are generated from the object 2. Such a phenomenon is called a photoacoustic effect. In the object 2, the diffracted sound waves L <b> 1 to L <b> 3 generated by the photoacoustic effect travel in various directions and undergo a Doppler shift due to the movement of the object 2. The diffracted sound wave L1 having the scattering direction vector component in the same direction as the moving direction of the object 2 has a high frequency. The frequency of the diffracted sound wave L2 having no scattering direction vector component in the moving direction of the object 2 does not change. The diffracted sound wave L3 having the scattering direction vector component in the direction opposite to the moving direction of the object 2 has a low frequency. These diffracted sound waves L1 to L3 reach the uv plane.

When the object 2 is irradiated with light having the modulation frequency ω ₀ , a sound wave having the frequency ω ₀ is generated from the object 2 by the photoacoustic effect. When the object 2 moving at the velocity vector V is irradiated with light having the modulation frequency ω ₀ , when the diffracted sound wave generated at the object 2 is observed at a stationary observation point, the diffraction with the Doppler shift frequency ω _d due to the Doppler effect is added The frequency of the sound wave is expressed by the following equation (1). In the equation (1), the incident unit vector to the object 2 is s _0, and the scattering unit vector indicating the scattering direction of the diffracted sound wave generated by the object 2 is s.

For example, consider a case where the light source is moving at a velocity V toward a stationary observer. In this case, since the light is emitted from the moving object itself, the incident vector s ₀ may be zero. Further, since the angle formed by the scattering unit vector s and the velocity vector V is 0 degree, the inner product of the scattering unit vector s and the velocity vector V is simply the speed | V |. Therefore, in this case, the equation (1) can be expressed by the equation (2), and the observer observes a frequency that is higher than the original frequency ω ₀ by (| V | / c) ω ₀ .

In the equation (1), when the speed | V | is sufficiently smaller than the velocity c of the sound wave, the equation (3) is derived. In equation (3), λ represents the wavelength of the sound wave. Expression (3) indicates that the Doppler shift amount ω _d is proportional to the inner product of (s−s ₀ ) and the velocity vector V of the moving object.

From equation (3), it can be seen that when the velocity V and the incident vector s ₀ are constant, the Doppler shift frequency of the diffracted sound wave observed at a certain position has a one-to-one correspondence with the scattering angle. Thus, the complex amplitude value of the wave at that Doppler shift frequency gives the complex amplitude value at that scattering angle of the diffracted sound wave. If the maximum detection angle of diffraction waves and theta _max, the maximum value of the resulting Doppler shift frequency is ± B _W. B _W is shown in equation (4).

  By the way, a diffracted sound wave pattern obtained when the detection surface of the diffracted sound wave is at infinity is obtained as an angle spectrum of the object. This can be confirmed by Equation (5) which is a first-order Born approximation at infinity.

In the above equation (5), f ₁ (s, s ₀ ) is a scattering amplitude, and F is a scattering potential. The vector K is 2π (s−s ₀ ) / λ. λ represents the wavelength of the sound wave. Equation (5) represents that the result of Fourier transform of the scattering potential F in the vector r space is the scattering intensity f ₁ in the K space. The K space is an angular spectrum or a spatial frequency K itself. In the case of a sound wave, if the sound speed outside the object is c ₀ and the sound speed distribution inside the object is c (r), the scattering potential F is expressed by the following equation (6).

That is, the spatial frequency K of the object appears on the Franforfer diffraction surface. The spatial frequency K is transformed into the Doppler shift frequency omega _d by the inner product of the velocity V. As described above, it can be seen from the two things that the spatial frequency spectrum of the object appears in the Doppler shift frequency spectrum.

(First embodiment)
The observation apparatus 1 according to the present embodiment acquires an image of the object 2 based on the principle described above. FIG. 2 is a diagram illustrating a configuration of the observation apparatus 1 according to the first embodiment. As shown in FIG. 2, the observation apparatus 1 of the present embodiment includes a signal generation unit SG, a diffracted sound wave generation unit 10, a detection unit 20, and a calculation unit 30.

The signal generator SG is a means for generating a signal for generating light, and outputs a sine wave sin (ω ₀ t) signal having a frequency ω ₀ to the diffracted sound wave generator 10.

The diffracted sound wave generator 10 is a means for generating a diffracted sound wave from the object 2 by photoacoustic effect by inputting a signal from the signal generator SG and irradiating light onto the moving object. The diffracted sound wave generator 10 includes a light source unit 12. The light source unit 12 receives a signal having a frequency ω ₀ from the signal generation unit SG, generates a laser beam having a modulation frequency ω ₀ , and irradiates the moving object with the laser beam. The laser light emitted from the light source unit 12 has a wavelength that is absorbed by the object 2. In this specification, the ξ-axis direction, u-axis direction, X-axis direction, and first direction are parallel to each other, and the η-axis direction, v-axis direction, Y-axis direction, and second direction are parallel to each other. The direction.

  The light source unit 12 irradiates the object 2 with this laser light. When the object 2 is irradiated with laser light, diffracted sound waves scattered in various directions in the object 2 are generated by the photoacoustic effect. The diffracted sound wave generated by the object 2 reaches the detection unit 20.

  Assuming that the object 2 is moving in the −η direction (−Y direction in FIG. 2) on the ξη plane, the Doppler shift frequency due to the movement of the object 2 is constant in the diffracted sound wave reaching the detection unit 20. The first direction is the u direction (X direction in FIG. 2) parallel to the ξ axis. The second direction orthogonal to the first direction is the v direction (Y direction in FIG. 2) parallel to the η axis. The detection unit 20 generates data representing the sum in the second direction (v direction) of data that temporally changes at a frequency corresponding to the Doppler shift amount of the sound wave that reaches each position on the detection surface in the first direction ( For each position in the u direction), it can be output at each time.

Detector 20 is constituted by the transducer d _n extending in a plurality of Y-direction. Transducer d _n is to reception waves reaching the detection unit 20 is means for converting into an electric signal. In the detection unit 20, N pieces of transducers _{d n (n = 1,2, ...} , N) toward the X direction is arranged. In FIG. 2, of which shows one transducer d _n. Each transducer is physically M microphones d _n which is arranged toward the Y-direction ^{(m) (m = 1,2,} ..., M) are constituted by. That is, the microphone _{d n} ^(m) is arranged in the first direction (X-direction) and second direction (Y-direction). Each microphone d _n ^(m) is converted into an electric signal by reception of acoustic waves. Each microphone d _n ^(m) corresponds to one pixel of the detection unit 20, and each microphone d _n ^(m) forms a detection surface. In the present embodiment, the detection surface of the detection unit 20 is disposed on the Fresnel diffraction image surface of the object 2 that is neither the Francophor diffraction image surface nor the imaging surface.

M microphones d _n which is arranged toward the Y-direction ^(m) are electrically connected on the output side. Each transducer d _n, the output signal i _n ^(m) multiplexes the electrical connection of the (t), the signal i which is the sum from 1 for the variable m for each time until M from each microphone d _{n ^(m) n} (t) is output. That is, in this embodiment, the microphone d is _n ^(m) are arranged in a two-dimensional, the electrical connection in the Y-axis direction of each microphone d _{n ^(m),} elongated in the Y-axis direction transducer d _n However, it has the same structure as the one-dimensional transducer arranged in parallel in the X-axis direction. The signal _i n (t) that is output at each transducer _{d n} shown in equation (7).

The calculation unit 30 performs a predetermined calculation on the signal i _n (t) output from the detection unit 20 to obtain an image of the object 2. The details of this calculation will be described below.

Calculating section 30 acquires a signal _i n outputted from each transducer _{d n} (t), as shown in equation (8), performs one-dimensional Fourier transform relates to the time variable t on this signal _i n (t) . In equation (8), ω is a variable representing a time frequency, and FT _t is a symbol representing a Fourier transform operation relating to the time variable t.

Each transducer d _n of the detector 20, the scattered waves having various frequencies are incident. Therefore, the sound wave detected by the detection unit 20 includes various frequency components. Here, when the signal i _n (t) is subjected to a one-dimensional Fourier transform with respect to the time variable t as shown in the equation (8), it is obtained when the detection surface of the detection unit 20 is arranged on the Fraunhofer diffraction image surface. A frequency distribution similar to the frequency distribution is obtained. That is, the irregular frequency distribution detected by the detection unit 20 arranged on the Fresnel surface is converted into a regular frequency distribution by the one-dimensional Fourier transform of the signal i _n (t) with respect to the time variable t.

Hereinafter, the signal I _n (ω) is expressed as I (n, ω). The variable n represents a first position of the transducer d _n. The signal I (n, ω) obtained by the equation (8) includes a Doppler spectrum centering on the frequency ω _{0 of} the sound wave generated from the object 2. The calculation unit 30 cuts out the frequency domain from the signal I (n, ω) so as to include the maximum Doppler shift frequency B _W (Equation (4)) around the time frequency ω ₀ (Equation (9)), position A Doppler shift frequency spectrum I (n, ω _d ) at n is obtained. Equation (9) represents an operation of cutting out I (n, ω−ω ₀ ) on the right side in a frequency range [−B _{W to} B _W ].

The Doppler shift frequency spectrum I (n, ω _d ) represents the spatial frequency spectrum of the object 2 in the Y direction. When the franc forfer diffraction image of the object 2 is expressed as G, the expression (9) can be expressed as the expression (10).

In equation (10), FT _n represents a Fourier transform with respect to the variable n. H (x) is a quadratic phase in the X direction. Here, x is a direction parallel to the first direction and represents coordinates on the Franforfer diffraction image plane. The secondary phase H is a value determined by the position where the detection unit 20 is arranged, and when the detection surface of the detection unit 20 is arranged on the Franforfer diffraction image plane (xy plane) of the object 2. The secondary phase H (x) is 1. In the present embodiment, the detection surface of the detection unit 20 is disposed at a position that is neither the Franforfer diffraction image plane nor the imaging plane. In this case, the blur of the image appears as this secondary phase H (x). This secondary phase H (x) is a value that can be obtained by measuring in advance before measuring the object 2.

Calculation unit 30, as shown in (11), by Fourier transform at the left side of (10) after dividing a secondary phase H (x), the position variable x, and the time-frequency variable omega _d A complex amplitude image g of the object 2 is obtained. In (11), _{FT (x, .omega.d)} represents the Fourier transform on the position variables x and the time-frequency variable omega _d.

FIG. 3 is a diagram illustrating a configuration of the calculation unit 30 in the present embodiment that performs the calculation processing as described above. The calculation unit 30 includes a first Fourier transform unit 31, a specific region extraction unit 34, a second Fourier transform unit 32, and a third Fourier transform unit 33. The first Fourier transform unit 31 performs a one-dimensional Fourier transform (the above equation (8)) on the time variable t for the signal i _n (t) having the position u on the uv plane and the time t as variables. The specific region cutout unit 34 includes the maximum Doppler shift frequency B _W (the above expression (4)) around the time frequency ω ₀ from the signal I (n, ω) obtained by the one-dimensional Fourier transform. The frequency domain is cut out (the above equation (9)). The second Fourier transform unit 32 performs this extracted data time-frequency omega _d 1-dimensional Fourier transform relates to ((11) Fourier transform with respect to time-frequency omega _d of expression). The third Fourier transform unit 33 includes a first fourth Fourier transform unit 33A, a secondary phase division unit 36, and a second fourth Fourier transform unit 33B. The first fourth Fourier transform unit 33A and the second fourth Fourier transform unit 33B perform Fourier transform related to the variable x (Fourier transform related to the variable x in equation (11) above) or inverse Fourier transform related to the variable x. The secondary phase division unit 36 divides the data output from the first fourth Fourier transform unit 33A by the secondary phase H (x) as shown in the equation (11). Focusing on the Fourier transform unit, in this embodiment, the arithmetic unit 30 performs a first Fourier transform unit 31 that performs a one-dimensional Fourier transform on a time variable, a second Fourier transform unit 32 that performs a one-dimensional Fourier transform on a frequency, A third Fourier transform unit 33 that performs one-dimensional Fourier transform in one direction. Note that the positions of the second Fourier transform unit 32, the first fourth Fourier transform unit 33A, and the second fourth Fourier transform unit 33B may be interchanged. The second Fourier transform unit 32 and the third Fourier transformer 33 constitutes a two-dimensional Fourier transform unit to time-frequency omega _d and variable x.

  With the configuration described above, the observation apparatus 1 of the present embodiment can obtain an image of the moving object 2 with high sensitivity even when the detection unit 20 having a low signal acquisition rate is used. For example, an image of the moving object 2 can be obtained at a speed M times faster than a two-dimensional detector having M pixels in the Y direction and N pixels in the X direction. Moreover, in the observation apparatus 1 of this embodiment, even if the output sides of M microphones arranged in parallel in the Y direction are electrically connected, signals detected by the individual microphones can be separated. As a result, a two-dimensional diffraction image can be obtained without scanning the irradiated sound wave.

(Second Embodiment)
The observation device 1A of the second embodiment is different in the configuration of the detection unit and the calculation unit from the observation device 1 of the first embodiment. Other points are the same as those in the first embodiment.

The detection unit according to the present embodiment has a detection surface on a predetermined plane, and includes a plurality of microphones that receive sound waves on the detection surface and convert them into electric signals, and the plurality of microphones includes a first direction and a second direction. It is juxtaposed in the direction. Specifically, the detection unit, M number of microphones d _n ^(m) is formed aligned in the Y-direction (second direction). Arranged in the second direction m-th microphone d _n ^(m) outputs the detected data at each position in each time. In the detector according to the present embodiment, M-number of microphones d _n which is arranged toward the Y-direction ^(m) is not electrically connected on the output side.

In addition to the first Fourier transform unit 31, the specific region cutout unit 34, the second Fourier transform unit 32, and the third Fourier transform unit 33, the arithmetic unit 30A outputs the outputs of M detection units arranged in the Y direction. Are provided, and each output summing device 35 is a computing unit that outputs the sum of the outputs of the microphones dn ^(m) in the second direction from the first to the M- _th . Each output summer 35 can be arranged in various positions. An example of the calculator configuration of the calculator 30A is shown in FIG. As shown in FIG. 4, when each output summation device 35 is arranged in the preceding stage of the first Fourier transform unit 31, each output summation device 35 has M pieces of output from M microphones d _n ^(m) . Signals are acquired at predetermined time intervals, the sum of M signals is calculated at predetermined time intervals, and the result is output to the first Fourier transform unit 31. Since the subsequent stage has the same computing unit configuration as the computing unit 30 of the first embodiment, description thereof is omitted.

FIG. 5 and FIG. 6 show the arithmetic unit configuration of the arithmetic unit 30 </ b> A when each output summer 35 is arranged between the first Fourier transform unit 31 and the second Fourier transform unit 32. As shown in FIG. 5, when each output summer 35 is arranged between the first Fourier transform unit 31 and the specific region cutout unit 34, the computation unit 30 _</ b _{> A} receives from the M microphones dn ^(m) . M first Fourier transform units 311 to 31M that perform one-dimensional Fourier transform on the time variable t with respect to the output are arranged, and outputs of the outputs from the first Fourier transform units 311 to 31M are arranged after the first Fourier transform units 311 to 31M. Each output summer 35 that outputs the sum is arranged. Subsequent to the specific region cutout unit 34 arranged in the subsequent stage has the same arithmetic unit configuration as the arithmetic unit 30 of the first embodiment, and thus the description thereof is omitted.

  As shown in FIG. 6, when each output summer 35 is arranged between the specific region cutout unit 34 and the second Fourier transform unit 32, the arithmetic unit 30 </ b> A has M first Fourier transform units 311 to 31M. M specific area cutouts 341 to 34M that perform frequency cut-out on the output from the are output, and the sum of the outputs from the specific area cutouts 341 to 34M is output after the specific area cutouts 341 to 34M. Each output summer 35 is arranged. Since the second Fourier transform unit 32 and subsequent components arranged in the subsequent stage have the same arithmetic unit configuration as the arithmetic unit 30 of the first embodiment, description thereof will be omitted.

FIG. 7 and FIG. 8 show the arithmetic unit configuration of the arithmetic unit 30A in the case where each output summer 35 is arranged at the subsequent stage of the second Fourier transform unit 32. As shown in FIG. 7, when each output summer 35 is arranged between the second Fourier transform unit 32 and the third Fourier transform unit 33, the arithmetic unit 30 </ b> A has M specific region cutout units 341 to 34 </ b> M. the second Fourier transform unit of the M performing one-dimensional Fourier transform with respect to time-frequency omega _d for output from 321~32M is disposed from the second Fourier transform unit 321~32M downstream of the second Fourier transform unit 321~32M Each output summing device 35 for outputting the sum of the outputs is arranged. Since the 3rd Fourier-transform part 33 arrange | positioned in the latter stage becomes the same calculator structure as the calculating part 30 of 1st Embodiment, description is abbreviate | omitted.

  As shown in FIG. 8, when each output summer 35 is arranged at the subsequent stage of the third Fourier transform unit 33, the arithmetic unit 30 </ b> A has the third Fourier transform unit at the subsequent stage of the M third Fourier transform units 331 to 33 </ b> M. Each output sum total 35 which outputs the sum total of the output from 331-33M is arrange | positioned.

Next, the output of each output summer 35 will be described. When each output summation device 35 is between the first Fourier transform unit 31 and the second Fourier transform unit 32, each output summation device 35 has a time frequency ω (= ω ₀ + ω _{d as} shown in the equation (12). ) To obtain the sum of the outputs from the M preceding arithmetic units. Here, I _n ^(m) (ω) represents the output data i _n ^(m) (t) of the microphone d _n ^(m) arranged m-th in the Y direction of the first Fourier transform unit 31 with respect to the time variable t. The output signal of the first Fourier transform unit 31 subjected to Fourier transform is shown. Since the Fourier operator FT _{t in the} middle side of the equation (12) can be exchanged with the summation operator Σ due to the linearity of the Fourier transform, the rightmost side of the equation (12) is obtained.

In the expression (12), the term on which the one-dimensional Fourier transform operator FT _t acts on the time variable t on the rightmost side is 1 of the waveform i _n ^(m) (t) output from the M microphones d _n ^(m). Represents the sum i _n (t) from ~ M. In other words, each output summer 35 provided in the arithmetic unit 30A outputs a signal obtained by Fourier transforming the signal output from the detection unit 20 in the first embodiment with respect to the time variable t. Therefore, it can be said that 2nd Embodiment is a structure which includes a part of the detection part 20 which outputs the sum total of a Y direction shown in 1st Embodiment in each time in 30 A of arithmetic parts.

On the other hand, when each output summation device 35 is in the subsequent stage from the second Fourier transform unit 32, each output summation device 35 outputs the output from the M preceding operation units at each time as shown in the equation (13). Get the sum. Here, i _n ^(m) (t) represents the output of the m-th second Fourier transform unit 32m. Further, the one-dimensional Fourier transform relating to the time variable t of i _n ^(m) (t) is expressed as I _n ^(m) (ω _d ). The term on which the one-dimensional Fourier transform operator FT _ω ^{−1 on} the right side of the equation (13) acts is the output of the second Fourier transform unit 32m. Therefore, the input of the specific region cutout unit 34 is a signal I _n ^(m) (ω ₀ + ω _d ) shifted by the frequency ω ₀ shown on the left side of the equation (14). Further, the rightmost side of the equation (14) represents the sum of the waveforms i _n ^(m) (t) output from the M detection units for each time from 1 to M. That is, since the output of each output summer 35 provided in the calculation unit 30A matches the signal output from the detection unit 20 in the first embodiment, the second embodiment is the second direction of the first embodiment. It can be said that the calculation unit 30A includes a part of the detection unit 20 that outputs data representing the sum at each time.

Further, when each output summation device 35 is in the preceding stage of the first Fourier transform unit 31, as shown in the equation (15), the sum of the outputs from the M preceding detection units 20A is obtained for each time. Here, i _n ^(m) (t) represents the m-th order output in the Y direction among the M detection units 20A arranged in the Y direction. The right side of the equation (15) represents the sum of 1 to M of the waveforms i _n ^(m) (t) output by the M detection units. That is, since the output of each output summation device 35 provided in the arithmetic unit 30A matches the signal output from the detection unit 20 in the first embodiment, the second embodiment uses the sum in the Y direction of the first embodiment. It can be said that the calculation unit 30A includes a part of the detection unit 20 that outputs data to be represented at each time.

(Third embodiment)

  In the first and second embodiments, the configuration in which the diffracted sound wave generated in the object 2 is detected directly by the detection units 20 and 20A is shown. 3rd Embodiment demonstrates the structure which detects the diffracted sound wave produced in the target object 2 using heterodyne measurement. The heterodyne measurement is a method of detecting a signal obtained by multiplying a diffracted sound wave including information on the object 2 by a known reference wave by a multiplier. In particular, the difference frequency component included in the output after multiplication is often used. The difference frequency component is a frequency component of the difference between the object wave and the reference wave. By using such a difference frequency component, calculation can be performed in a low frequency region, so that there is an advantage that signal processing becomes easy both analogly and digitally. Heterodyne measurement is a measurement method that has the effect of emphasizing only the modulation component due to the object because it obtains the difference signal between the object wave and the reference wave, and is also used for detection of minute signal changes.

  FIG. 9 shows the configuration of the observation apparatus 1B of the third embodiment. The observation apparatus 1B includes a signal generation unit SG, a diffracted sound wave generation unit 10, a detection unit 20B, a calculation unit 30B, and a reference sound wave generation unit 40 (first reference sound wave generation unit). The signal generator SG and the diffracted sound wave generator 10 have the same configurations as those described in the first or second embodiment.

Detecting unit 20B, in addition to the transducer d _n extending in a plurality of Y-direction, and a square law detector 21 and a low pass filter 22. The configuration of the arithmetic unit 30B has substantially the same configuration as the arithmetic unit 30 described in the first embodiment, calculated in terms center frequency which a particular region cutout unit 34 cuts out a Ω rather than omega ₀ Different from part 30.

The reference sound wave generation unit 40 receives a signal having a predetermined frequency from the signal generation unit SG, modulates the input signal with a modulator, and then generates a reference sound wave (first reference sound wave) from the modulated signal. To do. The reference sound wave generator 40 acquires a sine wave output from the signal generator SG as a signal r (t). The reference sound wave generator 40 includes a frequency shifter 41 and a transducer 42. Frequency shifter 41 shifts the sine wave of frequency ω ₀ to the frequency ω _{0 +} Ω.

The transducer 42 acquires a sine wave having a frequency ω ₀ + Ω output from the frequency shifter 41 and generates a sound wave. The transducer 42 is composed of a plurality of speakers, and the phase relationship of the input signals to each speaker is kept at a predetermined amount so that a plane wave is incident on the object 2. In this embodiment, a sine wave having the same phase is input to each speaker. For this reason, the sound wave output from the transducer 42 becomes a plane wave. In addition, when the phase difference of the signal input to each speaker is a fixed amount, a plane wave having an angle corresponding to the amount of the phase difference with respect to the Z axis is emitted.

In the observation apparatus 1 </ b> B configured as described above, the detection unit 20 </ b> B receives the diffracted sound wave generated from the object 2 in the diffracted sound wave generator 10 and the reference sound wave from the reference sound wave generator 40. Due to the influence of the Doppler effect, the diffracted sound wave transits by the Doppler shift frequency ω _d and has a frequency ω ₀ + ω _d . The signal of the diffracted sound wave is sin (ω ₀ + ω _d ) t. This is called the first wave. On the other hand, the sound wave emitted from the reference sound wave generator 40 has a frequency ω ₀ + Ω. This reference sound wave signal is defined as sin (ω ₀ + Ω) t. This is called the second wave. By this first wave and a second wave is input to the detection unit 20B, signal superposition of these waves are output from the transducer d _n of the detection unit 20B.

A square law detector 21 downstream of the transducer d _n of the detection unit 20B, a low-pass filter 22 is provided. The square detector 21 squares the sum of the first wave and the second wave and outputs it, as shown in equation (16). The third term on the right side of equation (16) can be decomposed as in equation (17). Therefore, the output of the square detector 21 is decomposed into terms including the sum frequency difference 2ω ₀ + Ω + ω _d of the first wave and the second wave and the difference frequency Ω−ω _d of the first wave and the second wave. can do. The low-pass filter 22 extracts only the difference frequency component from the output of the square detector 21 and outputs it to the calculation unit 30B. The signal i _n (t) output from the low-pass filter 22 includes a Doppler shift frequency ω _d around the frequency Ω. In this way, the detection unit 20B causes heterodyne interference between the diffracted sound wave generated by the object 2 and the reference sound wave on the detection surface.

The calculation unit 30B obtains an image of the object 2 by performing a predetermined calculation on the output of the detection unit 20B. That is, the calculation unit 30B performs Fourier transform on the time waveform i _n (t) with respect to the time variable t by the first Fourier transform unit 31 and outputs I _n (ω). The specific region cutout unit 34 cuts out a frequency region including the maximum Doppler shift frequency B _W (the above expression (4)) before and after the frequency Ω. When this processing is expressed mathematically, it becomes as shown in equation (18).

  The calculations performed at the subsequent stage of the specific area cutout unit 34 and the calculator configuration are the same as those in the first and second embodiments, and thus the description thereof is omitted. By performing the above calculation, an image of the object 2 can be obtained.

In the present embodiment, the transducer d _n of the detection unit 20B, were the same as in the first embodiment. That is, the detection unit 20B has been described as comprising a one-dimensional transducer the transducer d _n extending in the Y direction are arranged in parallel in the X-axis direction. However, the detection unit 20B is not limited to such a configuration. For example, the transducer d _n of the detection unit 20B, a second embodiment M microphones described in d _n ^(m) is formed side by side in the Y-direction (second direction), it is arranged towards the Y direction M microphones d _n ^(m) may be one which is not electrically connected on the output side. In this case, the calculation unit 30B needs to include each output summation device 35 that obtains the sum of 1 to M, like the calculation unit 30A (FIGS. 4 to 8) described in the second embodiment.

(Fourth embodiment)
In the third embodiment, the reference sound wave generated by the reference sound wave generation unit 40 is input to the detection unit 20B as the second wave. In the present embodiment, a wave different from a sound wave is input to the detection unit.

FIG. 10 shows a configuration of an observation apparatus 1C according to the fourth embodiment. An observation apparatus 1C according to the present embodiment includes a detection unit 20C and a first reference signal generation unit 40C instead of the detection unit 20B and the reference sound wave generation unit 40 included in the observation apparatus 1B according to the third embodiment. The detection unit 20 _< / b _> C includes a summer 23 for calculating the sum of input signals between the transducer dn and the square detector 21. The configuration other than the detection unit 20C and the first reference signal generation unit 40C is the same as that of the observation device 1B of the third embodiment.

The first reference signal generator 40C includes a frequency shifter 41, but differs from the reference sound wave generator 40 of the third embodiment in that the transducer 42 is not included. The first reference signal generator 40C receives the sine wave output from the signal generator SG as a signal r (t), and modulates the input signal with the frequency shifter 41 to generate a first reference signal. Frequency shifter 41 shifts the sine wave of the frequency omega ₀ to frequency ω _{0 +} Ω. A first reference signal r ′ (t) having a frequency ω ₀ + Ω is generated as a second wave and output to the detection unit 20C.

The diffracted sound wave generated from the object in the diffracted sound wave generator 10 is output to the detector 20C as the first wave. On the other hand, the first reference signal r ′ (t) is output to the adder 23 of the detection unit 20C as the second wave. The adder 23 adds the first wave and the second wave for each time, and outputs the result to the square detector 21 for each time. In other words, adder 23, in the third embodiment has the same operation and the first wave and the second wave in the microphone d _n is multiplexed. In the detection unit 20C, the processing after the square detector 21 arranged in the subsequent stage of the adder 23 is the same as that in the third embodiment. In this manner, the detection unit 20C causes heterodyne interference between the sum of the outputs of the microphones in the second direction and the first reference signal r ′ (t).

  The adder 23, the square detector 21 and the low-pass filter 22 are collectively referred to as a heterodyne detector 24. The heterodyne detector 24 may include a multiplier 21A and a low-pass filter 22 as shown in FIG. In the case of this configuration, the first wave and the second wave r ′ (t) are input to the multiplier 21A. In the multiplier, the sum frequency and the difference frequency of the first and second waves shown in the equation (17) appear. That is, the multiplier 21 </ b> A plays a role equivalent to a combination of the adder 23 and the square detector 21. As a result, the heterodyne detector 24 (FIG. 11) including the multiplier 21A and the low-pass filter 22 is different from the heterodyne detector 24 (FIG. 10) including the adder 23, the square detector 21 and the low-pass filter 22. , Output the same signal.

In the present embodiment, the transducer d _n of the detection unit 20C, were the same as in the first embodiment. That is, the detection unit 20C has been described as a transducer d _n extending in a plurality of Y-direction. However, the detection unit 20C is not limited to such a configuration. For example, the transducer d _n of the detection unit 20C, a second embodiment M microphones described in d _n ^(m) is formed side by side in the Y-direction (second direction), it is arranged towards the Y direction M microphones d _n ^(m) may be one which is not electrically connected on the output side. In this case, the calculation unit 30C needs to include each output summer 35 that obtains the sum of 1 to M, like the calculation unit 30A (FIGS. 4 to 8) described in the second embodiment.

(Fifth embodiment)
In the third and fourth embodiments, the reference sound wave generator 40 and the reference signal generator 40C generate and output the reference sound wave and the reference signal, respectively, using the sine wave generated by the signal generator SG as the reference signal source. It was. The observation apparatus 1D of the fifth embodiment is different from the third and fourth embodiments in that a diffracted sound wave is used as a signal generation source of a reference signal. The other points are the same as in the third and fourth embodiments.

  If a diffracted sound wave generated from the object 2 is observed at a position sufficiently distant from the object 2 so as to be regarded as an infinite distance or an infinite distance, a Francophor diffraction image of the object 2 is obtained. The wave at the center of the image in the Franforfer diffraction image is called a zeroth-order diffracted sound wave. A wave that is not affected by scattering or a wave that is less affected by scattering appears at the center of the Franforfer diffraction image. Therefore, the 0th-order diffracted sound wave and the diffracted sound wave regarded as the 0th-order diffracted sound wave are waves that are not affected by scattering by the object 2 or waves that are less affected by scattering. Such a wave that is not affected by the scattering by the object 2 or a wave that is less influenced by the scattering is referred to as a substantially zeroth-order diffracted sound wave.

The substantially zero order diffraction waves, when the unit vectors s and the object 2 velocity vector V of the scattering direction is substantially perpendicular, with scattering unit vector s as a Doppler shift frequency omega _d is substantially 0 as shown in (3) It is a diffracted sound wave. Second wave described in the third and fourth embodiments are the waves that are not irradiated to the object 2, it can be said that the Doppler shift frequency omega _d is a wave of 0. Therefore, the substantially 0th-order diffracted sound wave can be used as the second wave that is a reference wave.

FIG. 12 shows a configuration of an observation apparatus 1D according to the fifth embodiment. In the observation apparatus 1 </ b> D, a microphone _dr is provided between the diffracted sound wave generation unit 10 and the detection unit 20. In the fourth embodiment, while the reference wave generator 40C is inputting a signal from the signal generator SG, in the present embodiment, the second reference signal generating unit 40D inputs a signal from the microphone d _r This is different from the fourth embodiment. Other points are the same as in the fourth embodiment.

  That is, the second reference signal generation unit 40D receives a sound wave that appears at the center of the Franforfer diffraction image of the object 2, converts the input sound wave into an electrical signal, and then modulates the frequency shifter 41 with the signal. A second reference signal is generated. Then, the detection unit 20 causes heterodyne interference between the sum of the microphone outputs in the second direction and the second reference signal. This will be specifically described below.

The microphone _dr is disposed on a surface sufficiently away from the object 2. The microphone _dr receives the diffracted sound wave output from the diffracted sound wave generator 10 and outputs an output signal r (t) converted into an electric signal. Microphone d _r is a position which can be regarded as furan Forfar diffraction image or furan Forfar diffraction image plane by waves of the object 2, since it is located at the center of the image, waves microphone d _r is detected is substantially It can be regarded as a 0th-order diffracted sound wave. Accordingly, the waveform output microphone d _r is r (t) is available as a second wave. Microphone _{d r} outputs the output signal r (t) to a second reference signal generating unit 40D. Second reference signal generating unit 40D is a sine wave of a frequency .omega. ₀ after having allowed to transition to the frequency omega _{0 +} Omega by frequency shifter 41, the second reference signal r having the frequency ω _{0 +} Ω '(t) of the It outputs to the detection part 20 as 2 waves. Since the process after the detection part 20 is the same as 4th Embodiment, description is abbreviate | omitted.

As described above, in this embodiment, it converts the diffracted waves received by the microphone d _r into electrical signals, and outputs a second wave to the detector 20. Here, in terms of a sine wave of a frequency .omega. ₀ was the transition to the frequency omega _{0 +} Omega by frequency shifter diffraction waves received by the microphone d _r (second reference wave generating unit), sound waves by the microphone (second reference converted into sound waves) may output the second wave of the transducer d _n of the detection unit 20 as sound waves. In this case, as in the third embodiment, since the first wave and the second wave is input to the detection unit 20, signal superposition of these waves is output from the transducer d _n of the detection unit 20 Is done. In this case, the processing after the detection unit 20 is the same as that in the third embodiment, and thus description thereof is omitted.

  As described above, in the observation apparatus 1D according to the present embodiment, the reference signal source is not obtained from the signal generator SG in the heterodyne measurement, but the substantially 0th order diffraction that is not subjected to Doppler frequency shift among the diffracted sound waves from the object. Sound waves are used as the signal r (t). As described above, by using the approximately zeroth-order diffracted sound wave as the reference wave, heterodyne measurement can be performed as in the third and fourth embodiments.

(Sixth embodiment)
In the above, the detection unit 20, a configuration has been described with a two-dimensional microphone d _n which are arranged in parallel in the X direction and the Y-direction ^(m). Moreover, the transducer which converts a sound wave into an electric signal was described by the general name called a microphone. In the observation apparatus of the present embodiment has a configuration microphone d _n of ^(m) are different. First, the principle of a microphone that converts sound waves into electrical signals will be described.

  There are methods for converting a change in sound pressure into an electric signal based on various principles. For example, as a microphone, an electrostatic microphone, an electrodynamic microphone, an optical microphone, and the like are known. The principle of the electrostatic microphone will be described with reference to FIG. An electrostatic microphone M1 shown in FIG. 13 includes a diaphragm 51, a fixed plate 52, and a voltmeter 53. The diaphragm 51 and the fixed plate 52 are arranged in parallel with a predetermined distance d, and constitute a capacitor. The electric charge is stored in advance between the diaphragm 51 and the fixed plate 52 (fixed electrode) constituting the capacitor, and the distance between the diaphragm 51 and the fixed plate 52 changes when the sound pressure strikes the diaphragm 51. As a result, a change in voltage value detected by the voltmeter 53 is obtained as a change in sound pressure by changing the capacitance of the capacitor.

  Next, the principle of the electrodynamic microphone will be described with reference to FIG. The electrodynamic microphone M2 shown in FIG. 14 includes a permanent magnet rod 61, a coil 62, and a diaphragm 63. The electrodynamic microphone M <b> 2 is configured by winding a coil 62 around a fixed permanent magnet rod 61. Here, the permanent magnet rod 61 corresponds to a fixed plate referred to as the electrostatic microphone M1, and the coil 62 corresponds to a diaphragm referred to as the electrostatic microphone M1. When the sound wave is input, the coil and the vibration plate 63 are connected, so the vibration of the vibration plate 63 causes the coil 62 to vibrate left and right. As a result, electromagnetic induction occurs, and a voltage change between the coils is output, which is obtained as a sound pressure change.

  Next, the principle of the optical microphone will be described with reference to FIGS. The optical microphone measures minute fluctuations in the gap d between the diaphragm and the fixed plate caused by sound pressure by optical interference measurement.

  The structure of the optical microphone will be described below in comparison with the electrostatic microphone. FIG. 15 is an example of the configuration of an optical microphone. The optical microphone M3 shown in FIG. 15 includes a mirror 71, a half mirror 72, a laser light source 74, a beam splitter 75, and a photodiode (photocell) 76. In the optical microphone M3, the mirror 71 corresponds to a diaphragm, and the half mirror 72 corresponds to a fixed plate. In the optical microphone M <b> 3, a laser beam is output from the laser light source 74, and this laser beam is incident on the mirror 71 and the half mirror 72 via the beam splitter 75. Part of the incident light is transmitted by the half mirror 72 and reaches the mirror 71. The remaining part is reflected by the half mirror 72 and reaches the beam splitter 75. The light that reaches the mirror 71 is reflected and reaches the beam splitter 75. A part of the light reaching the beam splitter 75 reaches the photodiode 76, and the light intensity is converted into an electric signal. At this time, the sound wave hits the mirror, and the position of the mirror 71 changes, whereby the gap d between the mirror 71 and the half mirror 72 changes. The gap d and the electrical signal I output from the photodiode 76 have a predetermined relationship in the amount of change. Therefore, the sound pressure of the incident sound wave can be measured by the optical microphone M3.

FIG. 16 is another example of the configuration of the optical microphone. The optical microphone M4 shown in FIG. 16 has a structure in which the half mirror 72 that is a fixed plate in the optical microphone M3 is disposed by folding back 90 degrees, and the half mirror 72 is replaced with a mirror 72A. In the optical microphone M4, the mirror 71 corresponds to a diaphragm and the mirror 72A corresponds to a fixed plate. In the optical microphone M4, a laser beam is output from the laser light source 74, and this laser beam enters the mirror 71 and the mirror 72A via the beam splitter 75. The light reflected from the mirrors 71 and 72A reaches the beam splitter 75 again. Some of these lights reach the photodiode 76, and the light intensity is converted into electrical signals. In this case, by displacing the optical axis direction by the sound pressure position of the mirror 71 which corresponds to the vibration plate, the difference between the distance l ₂ between the distance l ₁ and the mirror 72A and a beam splitter mirror 71 and the beam splitter 75 d = | l ₁ −l ₂ | changes. There is a predetermined relationship between the difference d and the electrical signal I output from the photodiode 76. Therefore, the sound pressure of the incident sound wave can be measured by the optical microphone M4.

  FIG. 17 is another example of the configuration of the optical microphone. The optical microphone M5 shown in FIG. 17 has a different mirror reflectivity compared to the optical microphone M3. In the optical microphone M3, the reflectance of the half mirror 72 is about 50%, while the mirror 71 and the mirror 72B of the optical microphone M5 both have a reflectance of 95% or more. Here, it is known that the transmission intensity is maximized when there is a relationship of equation (19) between the gap d between the mirror 71 and the mirror 72B and the wavelength. In the formula (19), m is an arbitrary integer, and λ is a wavelength. An optical element composed of the mirror 71 and the mirror 72B is known as a Fabry-Perot interferometer.

  In the optical microphone M5, the reflected light becomes strong under conditions other than those described above. When such an interferometer is used, the reflected light intensity changes due to the gap d between the mirror 71 and the mirror 72B being displaced by the displacement of the mirror 71 in the optical axis direction due to the sound pressure. The intensity change is captured by the photodiode 76 and converted into an electric signal. That is, there is a predetermined relationship between the gap d and the electrical signal I output from the photodiode 76. Therefore, the sound pressure of the incident sound wave can be measured by the optical microphone M5.

  In order to form the above-described three types of optical microphones as a basic pixel in a two-dimensional array, a diaphragm, a fixed plate, a beam splitter, a laser light source, and a photodiode may be simply arranged in parallel to form a two-dimensional array. On the other hand, as shown in FIG. 18, only one diaphragm 71, fixed plate 72, laser light source 74, and beam splitter 75 may be arranged, and only the photodiodes 76 may be arranged in a two-dimensional array. With the configuration shown in FIG. 18, efficient two-dimensional pixelization can be achieved.

  In such a configuration, the size of the diaphragm 71 and the fixed plate 72 is, for example, 10 × 10 mm square. The cross-sectional size of the laser beam output from the laser light source 74 may be a size that covers the entire diaphragm 71 and fixed plate 72. The beam splitter 75 may be of a size that can split the size of the laser beam into two. The lens 81 and the lens 82 form a 4f optical system and forms an image on the light receiving surface of the photodiode 76 in which the reflected light from the diaphragm 71 is two-dimensionally arrayed. In the 4f optical system, the rear focal plane of the lens 81 and the front focal plane of the lens 82 coincide, the front focal plane of the lens 81 coincides with the plane of the diaphragm 71, and the rear focal plane of the lens 82 is 2. This means a configuration that matches the light receiving surface of the two-dimensional photodiode 76. The optical microphone M6 shown in FIG. 18 shows a state in which a plurality of photodiodes 76 existing in the YZ plane are arranged. Actually, these photodiodes 76 are also arranged in the X-axis direction. The optical microphone M6 outputs data representing the sum in the Y direction of the plurality of photodiodes 76 at each time.

As described above, in the present embodiment, only one diaphragm 71, fixed plate 72, laser light source 74, and beam splitter 75 are arranged, and only the photodiodes 76 are arranged in a two-dimensional array, and a plurality of photodiodes 76 are arranged. A microphone that outputs data representing the sum in the Y direction at each time has been described. That is, the microphone according to the present embodiment includes a vibration plate 71 that vibrates by an input sound wave, a fixed plate 72 that is arranged with a predetermined distance from the vibration plate, a laser light source 74, a beam splitter 75, a light And a photodiode 76 for converting the intensity into an electric signal. The photodiode 76 is arranged in parallel in the first direction and the second direction, and data representing the sum in the second direction is obtained for each position in the first direction. Output at time. The detection unit 20 according to the first to fifth embodiments have been provided with a two-dimensional microphone d _n which are arranged in parallel in the X direction and the Y-direction ^(m), such a plurality of microphones d _n ^(m) Instead, the microphone described in the present embodiment may be applied to the detection unit 20 of the first to fifth embodiments. In the case of the optical microphones M1 to M6, the detection sensitivity may be improved by optical heterodyne interferometry.

(Seventh embodiment)
In the first to sixth embodiments, the case where the detection surface of the detection unit is arranged on the Fresnel diffraction image surface of the object 2 has been described. In the present embodiment, a computing unit configuration in which the detection surface of the detection unit is arranged on a surface different from the Fresnel diffraction image surface of the object 2, and the detection surface of the detection unit is a Fresnel diffraction image of the object 2. A description will be given in comparison with the computing unit 30 of the first embodiment arranged on the surface. In addition, by using a reflection lens (mirror lens) using a reflection plate that reflects sound waves, an image of the object 2 formed on the detection surface of the detection unit is converted into a Fresnel diffraction image, a Francophor diffraction image, and an object image. Can be converted to each other.

  When the detection surface of the detection unit is disposed on a surface different from the Fresnel diffraction image surface of the object 2, the configuration of the computing unit is different from that of the first to sixth embodiments. FIG. 19 shows a computing unit configuration in the case where the detection surface of the detection unit is arranged on the Franforfer diffraction image surface of the object 2. In the arithmetic unit 30F in this case, as shown in FIG. 19, the third Fourier transform unit 33 is configured by only the first fourth Fourier transform unit 33A as compared with the arithmetic unit 30 in the first embodiment. In other respects, other configurations are the same. The first fourth Fourier transform unit 33A performs a Fourier transform on the variable x (Fourier transform on the variable x in the above equation (11)).

  FIG. 20 shows a computing unit configuration in the case where the detection surface of the detection unit is arranged on the imaging surface of the object 2. In the arithmetic unit 30G in this case, as shown in FIG. 20, the third Fourier transform unit 33 includes a first fourth Fourier transform unit 33A, a secondary phase division unit 36, and a second fourth Fourier transform unit 33B. It has. That is, the configuration of the calculator 30G is the same as that of the calculator 30 in the first embodiment. The first fourth Fourier transform unit 33A and the second fourth Fourier transform unit 33B perform Fourier transform related to the variable x (Fourier transform related to the variable x in equation (11) above) or inverse Fourier transform related to the variable x. The secondary phase division unit 36 divides the data output from the first fourth Fourier transform unit 33A by the secondary phase H (x) as shown in the equation (10).

  Focusing on the Fourier transform unit, in both of the arithmetic units 30F and 30G, a first Fourier transform unit 31 that performs a one-dimensional Fourier transform on a time variable, a second Fourier transform unit 32 that performs a one-dimensional Fourier transform on a frequency, And a third Fourier transform unit 33 that performs a one-dimensional Fourier transform in the first direction. Note that the positions of the second Fourier transform unit 32 and the third Fourier transform unit 33 may be interchanged. When the object 2 is arranged on a surface different from the Fresnel diffraction image surface, the arithmetic unit configuration of the present embodiment can be applied to the second to sixth embodiments. For example, when the detection surface of the detection unit is arranged on the Franforfer diffraction image surface of the target object 2, instead of the third Fourier transform unit 33 (FIGS. 4 to 8) of the calculation unit 30A of the second embodiment. The third Fourier transform unit 33 (FIG. 19) of the calculation unit 30F of the present embodiment may be used. Similarly, when the detection surface of the detection unit is disposed on the imaging plane of the target object 2, this is replaced with the third Fourier transform unit 33 (FIGS. 4 to 8) of the calculation unit 30 </ b> A of the second embodiment. It is good also as using the 3rd Fourier-transform part 33 (FIG. 20) of the calculating part 30G of embodiment.

  In addition, when the detection surface of the detection unit is disposed on the imaging surface of the object 2, the secondary phase H (x) in Equation (11) can be regarded as substantially 1. In addition, since the first fourth Fourier transform unit 33A and the second fourth Fourier transform unit 33B perform computations that cancel each other, the computation is substantially performed by the third Fourier transform unit 33 of the computation unit 30G. It will not be. However, since the detection surface of the detection unit is arranged on the imaging plane of the target object 2, the image obtained by the detection unit is spatially subjected to a one-dimensional Fourier transform in the first direction. . If it sees as the whole observation apparatus, it can be said that the one-dimensional Fourier transformation regarding the 1st direction is performed.

  With such a configuration, even in the observation apparatus of the present embodiment, an image of the moving object 2 can be obtained with high sensitivity even when a detection unit with a low signal acquisition rate is used. Moreover, in the observation apparatus of this embodiment, even if the output sides of M microphones arranged in parallel in the Y direction are electrically connected, signals detected by the individual microphones can be separated. As a result, a two-dimensional diffraction image can be obtained without scanning the irradiated sound wave. For example, an image of the moving object 2 can be obtained at a speed M times faster than a two-dimensional detector having M pixels in the Y direction and N pixels in the X direction. Furthermore, even when the detection surface of the detection unit is arranged on a surface different from the Fresnel diffraction image surface of the object 2, an image of the object 2 can be appropriately obtained.

(Modification)
In the observation apparatuses of the first to seventh embodiments described above, the embodiments in which the detection surface of the detection unit is arranged on the same kind of diffraction image plane in the first direction and the second direction have been described. However, on the detection surface of the detection unit, different types of diffractive image surfaces are formed in the first direction and the second direction by a reflection lens (mirror lens) using a reflection plate having different actions in the first direction and the second direction. It may be arranged on the formed surface. In this case, in the observation apparatus, an arithmetic unit corresponding to the diffraction image plane formed in the first direction is used.

  For example, the detection surface of the detection unit is a surface on which the Fresnel diffraction image of the object 2 is formed in the first direction, and is disposed on the surface on which the Franforfer diffraction image of the object is formed in the second direction. In this case, an image of the target portion 2 can be obtained by using the computing unit 30 of the first embodiment. In addition, the detection surface of the detection unit is disposed on the surface on which the franphofer diffraction image of the object 2 is formed in the first direction and on which the Fresnel diffraction image of the object is formed in the second direction. In this case, an image of the target portion 2 can be obtained by using the computing unit 30F of the seventh embodiment. Therefore, different types of diffraction image planes are formed in the first direction and the second direction by the reflection lens (mirror lens) using the reflection plate having a detection surface of the detection unit that has different actions in the first direction and the second direction. Even if it is a case where it arrange | positions on the surface by which it was carried out, the image of the object part 2 can be obtained with the calculating parts 30, 30F, and 30G demonstrated above.

  In the observation devices of the first to seventh embodiments described above, when the speed of the object 2 changes, frequency modulation occurs in the Doppler signal, and the finally obtained image of the object 2 expands and contracts in the flow direction. In order to correct such expansion and contraction, the observation apparatus of the present embodiment may further include a speed detection unit that detects the moving speed of the object 2. The calculation unit may perform correction related to the speed change of the target object 2 in the time direction one-dimensional Fourier transform or two-dimensional Fourier transform based on the speed of the target object 2 detected by the speed detection unit. good. Or based on the speed of the target object 2 detected by the speed detector, the photographing timing of the detector may be set.

  This speed detector may be any one, but the object 2 can also be detected by detecting the frequency of the signal at the diffracted sound wave arrival position on the detection surface using the relationship between the moving speed and the Doppler shift amount. Can be obtained. In this case, for example, the speed detection unit may be independently provided with a microphone for obtaining the moving speed of the object 2 on a part of the detection surface of the detection unit.

  In the above description, the case where the object 2 moves in one direction on the ξη plane has been described. The present invention is also applicable when the object 2 reciprocates in the ζ direction perpendicular to the ξη plane. In this case, since a Doppler shift occurs in the radial direction on the detection surface, a detector having a pixel structure in the circumferential direction and each pixel extending radially is used.

  In the above description, the embodiment in which the transmitted wave that diffracts the image of the object in the same direction as the incident wave is acquired by the detection unit has been mainly described. It is clear that it may be acquired with waves. In order to detect the Doppler shift amount with high sensitivity as the light source, the use of laser light having a single frequency can be considered, but the present invention is not limited to this. For example, information on the depth of the phase object can be acquired by using a sound wave including a broadband frequency. In order to measure the Doppler shift of each frequency component, it is conceivable to use a broadband laser beam having a constant phase relationship between the frequency components. As such a light source, for example, a pulse wave can be used.

In the first to seventh embodiments, since the incident wave vector s ₀ is parallel to the Z axis and the inner product with the velocity V is 0, Equation (8) is expressed as ω _d = k · V. However, the incident wave vector s ₀ may not be parallel to the Z axis. In this case, light is input in various incident directions s ₀ , the diffracted sound wave is acquired by the detector, and I (n, ω _d ) for each incident direction s ₀ is obtained by the calculator, and the Fourier diffraction theorem is obtained. The 3D image complex amplitude can also be restored by (Fourier diffraction theorem) or Fourier slice theorem. Control of the angle of incidence of the incident wave s ₀ is by controlling the phase of a plurality of speakers constituting the transducer of the diffraction wave generator, it is possible to change the incident angle of plane waves.

According to the observation device of the above embodiment, an image of the moving object 2 can be obtained with high sensitivity even when a detection unit with a low signal acquisition rate is used. For example, an image of the moving object 2 can be obtained at a speed M times faster than a two-dimensional detector having M pixels in the Y direction and N pixels in the X direction. Even if the output sides of M microphones arranged side by side in the Y direction are electrically connected, the signals detected by the individual microphones can be separated, resulting in a two-dimensional result without scanning the irradiation sound wave. A diffraction image can be obtained.
At this time, since an image corresponding to the modulation frequency is directly obtained, the image can be displayed in real time. Furthermore, if an on-chip arithmetic function camera is used, a reconstructed image of speed can be output directly from the detector.

  According to the observation device of the above embodiment, the number of sensor arrays in the moving direction of the object 2 can be reduced, and the system can be reduced in size and size. Noise superimposition and noise superimposition such as operational amplifiers can be reduced. Therefore, it is possible to perform imaging with high accuracy.

DESCRIPTION OF SYMBOLS 1,1B, 1C, 1D ... Observation apparatus, 10 ... Diffraction sound wave generation part, 12 ... Light source part, 20, 20B, 20C ... Detection part, 21 ... Square detector, 21A ... Multiplier, 22 ... Low pass filter, 23 ... Summation unit, 24 ... heterodyne detector, 30, 30A, 30B, 30C ... arithmetic unit, 31 ... first Fourier transform unit, 32 ... second Fourier transform unit, 33 ... third Fourier transform unit, 33A, 33B ... 4 Fourier transform unit, 34... Specific region cutout unit, 35... Output summing unit, 36... Secondary phase division unit, 40 .. reference sound wave generation unit, 40 C .. first reference signal generation unit, 40 D. Generating part 41 ... Frequency shifter 42 ... Transducer 71 ... Diaphragm 72 ... Fixed plate 74 ... Laser light source 75 ... Beam splitter 76 ... Photo diode 81, 82 ... Lens, M6 ... Optical My , SG ... signal generator.

Claims (13)

A signal generator for generating a signal of a predetermined frequency;
A diffracted sound wave generator that has a light source that generates light by inputting a signal of the predetermined frequency, irradiates the moving object with the light, and generates a diffracted sound wave from the object by a photoacoustic effect When,
The direction on the predetermined plane in which the Doppler shift effect due to the movement of the object is constant in the sound wave that reaches the predetermined plane among the diffracted sound waves generated by the light source by the light source, and the object When the direction perpendicular to the moving direction of the object is the first direction, the direction on the predetermined plane orthogonal to the first direction and the direction parallel to the moving direction of the object is the second direction, The data representing the sum in the second direction of the data that changes with time at a frequency corresponding to the Doppler shift amount of the sound wave that has reached each position on the predetermined plane, and each time for each position in the first direction. A detection unit that outputs to
For data having the position and time in the first direction on the predetermined plane output from the detection unit as variables, a one-dimensional Fourier transform with respect to a time variable, a one-dimensional Fourier transform with respect to a frequency, and a one-dimensional with respect to the first direction An arithmetic unit that performs Fourier transform and obtains data obtained by the one-dimensional Fourier transform as an image of the object;
An observation apparatus comprising: The detection unit has a detection surface on the predetermined plane, and includes a plurality of microphones that receive the sound wave and convert the sound wave into an electric signal on the detection surface,
The observation apparatus according to claim 1, wherein the plurality of microphones are arranged in parallel in the first direction and the second direction, and the microphones in the second direction are electrically connected on the output side thereof. The detection unit has a detection surface on the predetermined plane, and includes a plurality of microphones that receive the sound wave and convert the sound wave into an electric signal on the detection surface,
The plurality of microphones are juxtaposed in the first direction and the second direction;
The observation apparatus according to claim 1, wherein the calculation unit includes output summers that obtain a sum of outputs of the microphones in the second direction. The detection unit has a detection surface on the predetermined plane, and includes a microphone that receives the sound wave on the detection surface and converts the sound wave into an electrical signal;
The microphone has a vibration plate that vibrates by an input sound wave, a fixed plate that is arranged with a predetermined distance from the vibration plate, a laser light source, a beam splitter, and an intensity of light from the laser light source. A photocell for converting into an electrical signal,
The said photocell is arranged in parallel in the said 1st direction and the said 2nd direction, The data showing the sum total about the said 2nd direction are output at each time about each position of the said 1st direction. Observation device. A first reference sound wave generator that inputs a signal of the predetermined frequency from the signal generator and generates a first reference sound wave from the input signal;
The observation apparatus according to claim 2, wherein the detection unit causes heterodyne interference between the diffracted sound wave generated by the object and the first reference sound wave on the detection surface. A first reference signal generator that inputs the signal of the predetermined frequency from the signal generator and generates a first reference signal from the input signal;
The observation device according to claim 2, wherein the detection unit causes heterodyne interference between a sum of outputs of the microphones in the second direction and the first reference signal. Of the diffracted sound waves generated by the object, a sound wave that appears at the center of the Franforfer diffraction image of the object is input, the input sound wave is converted into an electric signal, and then the second reference is made from the electric signal. A second reference signal generator for generating a signal;
The observation device according to any one of claims 2 to 4, wherein the detection unit causes heterodyne interference between a sum of outputs of microphones in a second direction and the second reference signal. Of the diffracted sound waves generated by the object, a sound wave that appears at the center of the Franforfer diffraction image of the object is input, the input sound wave is converted into an electric signal, and then the second reference is made from the electric signal. A second reference sound wave generator for generating sound waves;
The observation device according to claim 2, wherein the detection unit causes heterodyne interference between a diffracted sound wave generated by the object and the second reference sound wave on the detection surface. Among the data obtained by the one-dimensional Fourier transform related to the time variable, the arithmetic unit performs one-dimensional Fourier transform related to the frequency with respect to data in a region including the maximum Doppler shift frequency around the predetermined frequency, and Performing a one-dimensional Fourier transform on the first direction;
The observation apparatus according to any one of claims 1 to 4. Of the data obtained by the one-dimensional Fourier transform relating to the time variable, data of a region including the maximum Doppler shift frequency around the frequency of the signal obtained by modulating the signal of the predetermined frequency with a modulator. A one-dimensional Fourier transform for the frequency and a one-dimensional Fourier transform for the first direction;
The observation apparatus according to any one of claims 5 to 8. A speed detector for detecting the moving speed of the object;
Based on the speed of the object detected by the speed detection unit, the calculation unit performs correction related to the speed change of the object during the Fourier transform.
The observation apparatus according to any one of claims 1 to 10.   The observation apparatus according to claim 1, wherein the diffracted sound wave generator includes a light source that generates broadband light.   The observation apparatus according to claim 1, wherein the diffracted sound wave generator includes a light source that generates a pulse wave as the light.