An acoustic holography generation method for ultralong high-resolution acoustic beam focusing

Abstract

The application discloses a kind of for super-long high-resolution acoustic beam focusing acoustic hologram generation method, comprising: the source plane phase of the M target surfaces of the M focal points of the jth iteration is determined when the jth iteration;M focal points of the jth iteration are numbered, and acoustic holographic lens is generated based on numbering, and the mask plate of target surface is generated according to acoustic holographic lens;The jth coefficient is generated, and the jth global sound source phase is generated according to the jth coefficient, mask plate and source plane phase;Whether the jth global sound source phase and the amplitude of target surface satisfy the condition based on the degree of approach of the jth M focal points of sound pressure amplitude;If yes, acoustic hologram is generated according to the jth global sound source phase;Otherwise, the spacing of the M focal points of the jth iteration is adjusted, the M focal points of the jth optimization are obtained and the j+1th iteration is carried out until acoustic hologram is generated.The application can form super-long distance ultrasonic focusing under the premise of ensuring the diameter of small acoustic beam.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of acoustics, and particularly relates to a method for generating acoustic holography for focusing of an ultralong high-resolution acoustic beam. BACKGROUND

[0002] In the prior art, ultrasonic waves are widely used in medical imaging and treatment, and an ultralong ultrasonic beam is beneficial to increasing the depth of field of ultrasonic imaging and applied to special photoacoustic imaging, but the focusing length of an ultrasonic transducer is limited by the diffraction limit of the acoustic beam, and a traditional acoustic lens cannot usually realize ultralong focal length and high-resolution imaging.

[0003] Therefore, a new method is needed to break through this limitation and realize great elongation of the acoustic beam length while ensuring a small acoustic beam diameter to meet higher medical and industrial application requirements. SUMMARY

[0004] In order to solve the above problems existing in the prior art, the application provides a method for generating acoustic holography for focusing of an ultralong high-resolution acoustic beam.

[0005] The technical problem to be solved by the application is solved by the following technical scheme:

[0006] The application provides a method for generating acoustic holography for focusing of an ultralong high-resolution acoustic beam, comprising:

[0007] In the jth iteration, the source plane phase of the M target surfaces corresponding to the M focal points in the jth iteration is determined to obtain the M source plane phases in the jth iteration; each target surface is perpendicular to the propagation direction of the ultrasonic waves emitted by the transducer, and each target surface has a focal point; j is an integer greater than or equal to 1; the M focal points in the jth iteration are the M focal points optimized in the j-1th iteration; when j is 1, the M focal points in the jth iteration are M focal points uniformly distributed in a preset distance along the propagation direction of the ultrasonic waves; M is a positive integer;

[0008] The M focal points in the jth iteration are numbered, an acoustic holography lens with a size of n*n is generated based on the numbering, and M mask plates corresponding to the M target surfaces are generated according to the acoustic holography lens; n is a preset integer;

[0009] The coefficients in the jth iteration are generated based on the coefficients in the j-1th iteration, when the coefficients in the jth iteration are less than or equal to a preset upper limit value, the global acoustic source phase in the jth iteration is generated according to the coefficients in the jth iteration, the M mask plates and the M source plane phases in the jth iteration; when j is 1, the coefficients in the j-1th iteration are a preset initial value;

[0010] determine whether the approaching degree of the sound pressure amplitude of the M focus points of the jth time meets a condition based on the jth global sound source phase and the measured amplitude of the M target surfaces; if yes, generate an acoustic hologram according to the jth global sound source phase; otherwise, adjust the interval between adjacent focus points of the M focus points of the jth time in the propagation direction of the ultrasonic wave to obtain the M focus points after optimization of the jth time, and perform the j+1th iteration according to the M focus points after optimization of the jth time until the acoustic hologram is generated.

[0011] In some embodiments, the method further comprises:

[0012] When the coefficient of the jth time is greater than the preset upper limit value, select the sound pressure amplitude of the M focus points with the minimum approaching degree from the sound pressure amplitude of the M focus points of the 1st time to the sound pressure amplitude of the M focus points of the j-1th time; wherein the sound pressure amplitude of the M focus points with the minimum approaching degree is the sound pressure amplitude of the M focus points of the xth time; x is an integer greater than or equal to 1 and less than or equal to j-1;

[0013] Generate an acoustic hologram according to the xth global sound source phase.

[0014] In some embodiments, the numbering of the M focus points of the jth time, the generation of the acoustic holographic lens with a size of n*n based on the numbering, and the generation of the M mask plates corresponding to the M target surfaces based on the acoustic holographic lens comprise:

[0015] Number the M focus points of the jth time, and generate n*n first matrices according to the numbering; the elements in each first matrix are the numbers of the M focus points of the jth time;

[0016] Combine the n*n first matrices to obtain a second matrix with n*n*M elements; the second matrix is the acoustic holographic lens;

[0017] For the ith target surface, set the elements in the second matrix with the number of the ith target surface to 1 and the remaining elements to 0 to obtain the mask plate of the ith target surface; i is an integer and the value of i is 1 to M.

[0018] In some embodiments, the generation of the coefficient of the jth time based on the coefficient of the j-1th time, when the coefficient of the jth time is less than or equal to the preset upper limit value, the generation of the jth global sound source phase based on the coefficient of the jth time, the M mask plates and the M source plane phase of the jth time, comprise:

[0019] Increase the coefficient of the j-1th time by a preset increment to obtain the coefficient of the jth time;

[0020] When the coefficient of the j-th iteration is less than or equal to the preset upper limit value, the phase adjuster of the i-th target surface is generated according to the coefficient of the j-th iteration and the preset focusing index corresponding to the i-th target surface; i is an integer, and the value of i ranges from 1 to M;

[0021] Based on the j-th phase adjuster of the i-th target surface, the j-th source plane phase of the i-th target surface, and the mask of the i-th target surface, generate the updated source plane phase of the i-th target surface;

[0022] The updated source plane phases of the M target surfaces are summed to obtain the j-th global sound source phase.

[0023] In some embodiments, the expression for the updated source plane phase of the i-th target surface is as follows:

[0024] P′(x,y,f i )=[P(x,y,f i )-Pa i ]×L i (x,y);

[0025] Where P′(x,y,f) i f represents the updated source plane phase of the i-th target surface. i Let P(x,y,f) represent the i-th focal point of the j-th ultrasound, which is located on the i-th target surface. Let x and y represent the coordinates of the i-th focal point of the j-th ultrasound on the i-th target surface. The i-th target surface is perpendicular to the direction of ultrasound propagation. i Pa represents the j-th source plane phase of the i-th target surface. i L represents the phase adjuster of the i-th target surface at the j-th time. i (x,y) represents the mask template of the i-th target surface.

[0026] In some embodiments, determining whether the degree of convergence of the sound pressure amplitudes of the M focal points in the j-th iteration satisfies a condition based on the global sound source phase and the amplitudes of the M target surfaces measured in the j-th iteration includes:

[0027] Based on the global sound source phase of the j-th time and the amplitude of the M target surfaces measured, determine the M sound pressure amplitudes corresponding to the M focal points of the j-th time.

[0028] The ratio of the sound pressure amplitude at the i-th focal point in the j-th iteration to the average of the M sound pressure amplitudes is obtained; i is an integer and i ranges from 1 to M.

[0029] determining whether the absolute value of the difference between the ratio of each of the M focal points in the jth time and 1 is less than or equal to a preset threshold value; if yes, it is represented that the degree of approximation of the sound pressure amplitude of the M focal points in the jth time meets the condition; if the absolute value of the difference between the ratio of at least one of the M focal points in the jth time and 1 is greater than the preset threshold value, it is represented that the degree of approximation of the sound pressure amplitude of the M focal points in the jth time does not meet the condition.

[0030] In some embodiments, the adjusting the interval between adjacent focal points in the M focal points in the jth time in the propagation direction of the ultrasonic wave to obtain the M focal points after the jth optimization comprises:

[0031] determining a new coordinate value of the ith focal point in the jth time in the propagation direction of the ultrasonic wave according to the ratio of the ith focal point in the jth time, the interval between the ith focal point in the jth time and the (i-1)th focal point in the jth time in the propagation direction of the ultrasonic wave, and the coordinate value of the (i-1)th focal point in the jth time in the propagation direction of the ultrasonic wave, to adjust the interval between the ith focal point in the jth time and the (i-1)th focal point in the jth time in the propagation direction of the ultrasonic wave;

[0032] taking the M focal points in the jth time whose interval between adjacent two focal points in the propagation direction of the ultrasonic wave is adjusted as the M focal points after the jth optimization; i is an integer and i is 1 to M.

[0033] In some embodiments, the expression of the new coordinate value of the ith focal point in the jth time in the propagation direction of the ultrasonic wave is as follows:

[0034] l(j,i)=[l(j-1,i)-l(j-1,i-1)]×R(j,i)+l(j,i-1);

[0035] Wherein, l(j,i) represents the new coordinate value of the ith focal point in the jth time in the propagation direction of the ultrasonic wave, l(j-1,i) represents the coordinate value of the ith focal point in the jth time in the propagation direction of the ultrasonic wave, l(j-1,i-1) represents the coordinate value of the (i-1)th focal point in the jth time in the propagation direction of the ultrasonic wave, R(j,i) represents the ratio of the ith focal point in the jth time, and l(j,i-1) represents the new coordinate value of the (i-1)th focal point in the jth time in the propagation direction of the ultrasonic wave.

[0036] In some embodiments, the generating an acoustic hologram according to the jth global sound source phase comprises:

[0037] converting the jth global sound source phase into the thickness of the acoustic hologram to obtain the acoustic hologram.

[0038] In some embodiments, the preset integer n is the ratio of the size of the transducer to the resolution of the acoustic hologram to be generated.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] This invention combines acoustic holography algorithms with spatial phase multiplexing, enabling a single acoustic holographic lens to focus the sound field at different depths in space. By using focal position iteration and phase adjustment to adjust the uniformity and diameter of the focused sound beam, it achieves the technical effect of forming ultra-long-distance ultrasonic focusing in space while ensuring a small sound beam diameter. It can be used in fields such as medical ultrasound imaging, industrial non-destructive testing, photoacoustic imaging, and non-contact particle capture.

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0042] Figure 1 This is a schematic flowchart of an acoustic holography generation method for ultra-long, high-resolution acoustic beam focusing provided by an embodiment of the present invention;

[0043] Figure 2 This is an acoustic holographic thickness map generated in a body of water, provided in an embodiment of the present invention;

[0044] Figure 3 The generation method provided by the embodiments of the present invention Figure 2 A scene diagram of the acoustic holographic thickness map shown;

[0045] Figure 4 This is the spatial sound field measured using a hydrophone, as provided in the embodiments of the present invention;

[0046] Figure 5 This is provided by the embodiments of the present invention. Figure 2 The lateral amplitude of the acoustic holographic thickness map shown is when the acoustic beam diameter is at its maximum.

[0047] Figure 6 This is provided by the embodiments of the present invention. Figure 2 The acoustic holographic thickness map shown represents the acoustic beam amplitude along the axial direction of the ultrasonic transducer. Detailed Implementation

[0048] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0049] Figure 1 This is a flowchart illustrating a method for generating acoustic holograms using ultra-long, high-resolution acoustic beam focusing, as provided in an embodiment of the present invention. Figure 1 As shown, the method includes:

[0050] S101, determining a source plane phase of each target surface corresponding to each focus point in the jth iteration, to obtain M source plane phases in the jth iteration; each target surface is perpendicular to the propagation direction of the ultrasonic wave emitted by the transducer, and each target surface has one focus point; j is an integer greater than or equal to 1; the M focus points in the jth iteration are the M focus points after the j-1th optimization; when j is 1, the M focus points in the jth iteration are M focus points uniformly distributed in a preset distance along the propagation direction of the ultrasonic wave; M is a positive integer.

[0051] Here, the model and size of the transducer, the diameter of the focus point, the size of M, and the preset distance can be set according to actual needs, and the present application does not limit them. For example, the size of the transducer can be 25mm, the ultrasonic center frequency can be 4MHz, the diameter of each focus point can be 0.2mm, the preset distance can be 17-37mm, and M can be 100.

[0052] Here, the iterative angular spectrum algorithm (also known as angular spectrum iterative algorithm) can be used to determine the source plane phase of each target surface corresponding to each focus point in the jth iteration.

[0053] S102, numbering the M focus points in the jth iteration, generating an acoustic holographic lens with a size of n*n based on the numbering, and generating M mask plates corresponding to the M target surfaces according to the acoustic holographic lens; n is a preset integer.

[0054] S103, generating the jth coefficient based on the j-1th coefficient, when the jth coefficient is less than or equal to a preset upper limit value, generating the jth global sound source phase according to the jth coefficient, the M mask plates and the M source plane phases in the jth iteration; when j is 1, the j-1th coefficient is a preset initial value.

[0055] S104, determining whether the degree of approximation of the sound pressure amplitude of the M focus points in the jth iteration meets the condition based on the jth global sound source phase and the amplitude of the M target surfaces measured; if yes, S105 is executed, otherwise, S106 is executed.

[0056] S105, generating an acoustic hologram according to the jth global sound source phase.

[0057] S106, adjusting the interval between adjacent focus points in the jth iteration in the propagation direction of the ultrasonic wave to obtain the M focus points after the jth optimization, and performing the j+1th iteration according to the M focus points after the jth optimization until the acoustic hologram is generated.

[0058] In some embodiments, the above method further comprises S107-S108:

[0059] S107, when the coefficient of the jth time is greater than the preset upper limit value, selecting the sound pressure amplitude value of the M focus points with the minimum approaching degree according to the sound pressure amplitude value of the M focus points of the 1st time to the M focus points of the j-1th time; wherein the sound pressure amplitude value of the M focus points with the minimum approaching degree is the sound pressure amplitude value of the M focus points of the xth time; x is an integer greater than or equal to 1 and less than or equal to j-1.

[0060] S108, generating the sound hologram according to the xth global sound source phase.

[0061] In the application, the preset integer n is the ratio of the size of the transducer to the resolution of the sound hologram to be generated. For example, when the size of the transducer is 25mm and the resolution of the sound hologram to be generated is 20μm, n is 125.

[0062] In the application, S102 can be realized by the following steps:

[0063] S1021, numbering the M focus points of the jth time, and generating n*n first matrices according to the numbering; the elements in each first matrix are the numbers of the M focus points of the jth time.

[0064] For example, the M focus points of the jth time can be numbered by integers from 1 to M, so that the number of the 1st focus point is 1, the number of the 2nd focus point is 2, and so on; then, n*n first matrices are randomly generated, and the symbol "*" represents multiplication. Each first matrix has M elements, and the M elements are randomly distributed integer numbers from 1 to M.

[0065] S1022, merging the n*n first matrices to obtain a second matrix with n*n*M elements; the second matrix is a sound holographic lens.

[0066] For example, when n is 125 and M is 100, there are 125*125*100 elements in the second matrix, and the 125*125*100 elements are composed of integer numbers from 1 to M. The occurrence frequency of any integer number from 1 to M in the second matrix is 125*125.

[0067] S1023, for the ith target surface, setting the elements with the number of the ith target surface in the second matrix to 1 and setting the remaining elements to 0 to obtain a mask template of the ith target surface; i is an integer, and the value of i is 1 to M.

[0068] The mask template L of the ith target surface i (x,y) is a two-dimensional matrix, and the value of the element in the matrix is 1 or 0, which is used to identify whether the pixel is allocated to the ith focus f i , that is, is a full 1 matrix.

[0069] The M mask plates corresponding to the M target surfaces can be obtained through step S1023.

[0070] The information can be stored through the spatial phase multiplexing mask method through steps S1021-S1023.

[0071] In the present application, the above S103 can be implemented through the following steps:

[0072] S1031, increase the coefficient of the j-1th time by a preset increment to obtain the coefficient of the jth time.

[0073] Here, the preset increment can be set according to actual needs. The value range of the coefficient can be [0, 2π], that is, the initial preset value of the coefficient is 0 and the preset upper limit value is 2π.

[0074] S1032, when the coefficient of the jth time is less than or equal to the preset upper limit value, generate the jth phase adjuster of the ith target surface according to the coefficient of the jth time and the preset focusing index corresponding to the ith target surface; i is an integer, and the value of i is 1 to M.

[0075] For example, the preset focusing index corresponding to the ith target surface can be i.

[0076] For example, the jth phase adjuster of the ith target surface Pa i The expression is: Pa i = PA j × i, wherein PA j represents the coefficient of the jth time.

[0077] S1033, generate the updated source plane phase of the ith target surface according to the jth phase adjuster of the ith target surface, the jth source plane phase of the ith target surface and the mask plate of the ith target surface.

[0078] For example, the expression of the updated source plane phase of the ith target surface is as follows:

[0079] P'(x, y, f i ) = [P(x, y, f i )-Pa i ]×L i (x, y);

[0080] Wherein, P'(x, y, f i ) represents the updated source plane phase of the ith target surface, f irepresents the i-th focus in the j-th time, the i-th focus in the j-th time is located on the i-th target surface, x represents the horizontal coordinate value of the i-th focus in the j-th time on the i-th target surface, y represents the vertical coordinate value of the i-th focus in the j-th time on the i-th target surface, and the i-th target surface is perpendicular to the propagation direction of the ultrasonic wave; P(x, y, f i represents the j-th source plane phase of the i-th target surface, Pa i represents the j-th phase adjuster of the i-th target surface, L i (x, y) represents the mask plate of the i-th target surface.

[0081] M updated source plane phases corresponding to M target surfaces can be obtained through S1033.

[0082] S1034, summing the updated source plane phases of the M target surfaces to obtain the j-th global sound source phase.

[0083] Exemplarily, the expression of the j-th global sound source phase is as follows:

[0084] Here, the diameter of the sound beam can be adjusted through S1031-S1033.

[0085] In the present application, the above S104 can be realized through the following steps:

[0086] S1041, determining M sound pressure amplitudes corresponding to M foci in the j-th time according to the j-th global sound source phase and the amplitudes of the M target surfaces measured.

[0087] Specifically, the j-th global sound source phase can be subjected to ultrasonic propagation inversion with the amplitudes of the i-th target surface measured to obtain the sound pressure amplitude at the i-th focus on the i-th target surface, and in this way, M sound pressure amplitudes corresponding to M foci in the j-th time can be obtained.

[0088] S1042, determining the ratio of the sound pressure amplitude of the i-th focus in the j-th time to the average of the M sound pressure amplitudes to obtain the ratio of the i-th focus in the j-th time.

[0089] Here, the ratio of the i-th focus in the j-th time can be represented as R(j, i).

[0090] S1043, determining whether the absolute value of the difference between the ratio of each focus in the M foci in the j-th time and 1 is less than or equal to a preset threshold value; if yes, it indicates that the approaching degree of the sound pressure amplitude of the M foci in the j-th time satisfies the condition; if the absolute value of the difference between the ratio of at least one focus in the M foci in the j-th time and 1 is greater than the preset threshold value, it indicates that the approaching degree of the sound pressure amplitude of the M foci in the j-th time does not satisfy the condition.

[0091] Here, the preset threshold value can be set according to actual needs, and the application does not limit this.

[0092] In the application, the S105 can be realized by the following steps:

[0093] S1051, convert the jth global sound source phase into the thickness of the acoustic hologram.

[0094] Here, the conversion principle is the existing principle, and the application will not be described here.

[0095] In the application, the "adjusting the interval between adjacent focal points in the propagation direction of the ultrasound wave in the M focal points of the jth time to obtain the M focal points after the jth optimization" in the S106 can be realized by the following steps:

[0096] S1061, according to the ratio of the i-th focal point of the jth time, the interval between the i-th focal point of the jth time and the i-1th focal point of the jth time in the propagation direction of the ultrasound wave, and the coordinate value of the i-1th focal point of the jth time in the propagation direction of the ultrasound wave, determine the new coordinate value of the i-th focal point of the jth time in the propagation direction of the ultrasound wave, to adjust the interval between the i-th focal point of the jth time and the i-1th focal point of the jth time in the propagation direction of the ultrasound wave.

[0097] Here, the expression of the new coordinate value of the i-th focal point of the jth time in the propagation direction of the ultrasound wave is: l(j,i)=[l(j-1,i)-l(j-1,i-1)]×R(j,i)+l(j,i-1); Wherein, l(j,i) represents the new coordinate value of the i-th focal point of the jth time in the propagation direction of the ultrasound wave, l(j-1,i) represents the coordinate value of the i-th focal point of the jth time in the propagation direction of the ultrasound wave, l(j-1,i-1) represents the coordinate value of the i-1th focal point of the jth time in the propagation direction of the ultrasound wave, R(j,i) represents the ratio of the i-th focal point of the jth time, and l(j,i-1) represents the new coordinate value of the i-1th focal point of the jth time in the propagation direction of the ultrasound wave.

[0098] S1062, the M focal points of the jth time after adjusting the interval between the two adjacent focal points in the propagation direction of the ultrasound wave are taken as the M focal points after the jth optimization; i is an integer and i is 1 to M.

[0099] Here, the adjustment idea of the interval is: if the ratio of the i-th focal point of the jth time is greater than or equal to 1, then linearly increase the interval between the i-th focal point of the jth time and the i-1th focal point of the jth time in the propagation direction of the ultrasound wave; otherwise, linearly decrease the interval between the i-th focal point of the jth time and the i-1th focal point of the jth time in the propagation direction of the ultrasound wave.

[0100] It should be noted that, since the focus is on the target surface, adjusting the interval of the focus in the propagation direction of the ultrasound wave means that a new target surface is generated; thus, when the M focuses after the jth optimization are obtained, it means that the M target surfaces corresponding to the M focuses after the jth optimization are also obtained.

[0101] In the present application, after the M focuses after the jth optimization are obtained, it means that the M focuses after the jth iteration at the j+1th iteration are obtained, and thus the j+1th iteration can be continued using the principles of S101-S105, and the iteration is repeated in this way until the acoustic hologram is generated.

[0102] Here, on the basis of adjusting the acoustic beam diameter through S1031-S1033, the focus position is selected through the focus iteration algorithm through S1034 and S104-S106, and finally the ultralong distance ultrasonic focusing under the premise of ensuring the small acoustic beam diameter can be realized.

[0103] The present application can be applied in the fields of medical ultrasonic imaging, industrial nondestructive testing, photoacoustic imaging, and non-contact particle capture, etc. Figure 2 To generate an acoustic hologram thickness map in a water area; Figure 3 To generate Figure 2 A scene of the acoustic hologram thickness map shown in the figure, which includes an ultrasonic transducer, an acoustic hologram lens, and a water area; Figure 4 To generate Figure 2 The spatial acoustic field measured by a hydrophone when generating the acoustic hologram thickness map shown in the figure; Figure 5 To Figure 2 The transverse amplitude of the acoustic hologram thickness map shown in the figure when the acoustic beam diameter is maximum; Figure 6 To Figure 2 The acoustic beam amplitude in the axial direction of the ultrasonic transducer when generating the acoustic hologram thickness map shown in the figure.

[0104] The present application combines the acoustic hologram algorithm with spatial phase multiplexing, so that a single acoustic hologram lens can realize acoustic field focusing at different depths in space, and the focus position iteration algorithm and phase weighting are used to adjust the uniformity and diameter of the focused acoustic beam, and finally the technical effect of ultralong distance ultrasonic focusing under the premise of ensuring the small acoustic beam diameter in space is realized.

[0105] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" can explicitly or implicitly include one or more features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0106] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and integrate different embodiments or examples described in the specification.

[0107] In the specification, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality. Some measures are described in mutually different embodiments, but this does not mean that these measures cannot be combined to produce good results.

[0108] The above is a further detailed description of the present application in combination with specific preferred embodiments, and the specific implementation of the present application cannot be limited to these descriptions. For those skilled in the art to which the present application belongs, without departing from the concept of the present application, a number of simple deductions or substitutions can be made, which should be regarded as falling within the scope of protection of the present application.

Claims

1. A method for generating acoustic holograms for ultra-long, high-resolution acoustic beam focusing, characterized in that, include: In the j-th iteration, the source plane phases of the M target surfaces corresponding to the M focal points of the j-th iteration are determined, and the M source plane phases of the j-th iteration are obtained; each target surface is perpendicular to the propagation direction of the ultrasonic wave emitted by the transducer, and each target surface has a focal point; j is an integer greater than or equal to 1; the M focal points of the j-th iteration are the M focal points optimized in the (j-1)-th iteration. When j is 1, the M focal points of the j-th time are M focal points that are uniformly distributed within a preset distance along the propagation direction of the ultrasonic wave; M is a positive integer; The M focal points of the j-th iteration are numbered, and an acoustic holographic lens of size n*n is generated based on the numbering. M mask templates corresponding to the M target surfaces are generated according to the acoustic holographic lens; n is a preset integer. The coefficients of the j-th generation are generated based on the coefficients of the (j-1)th generation. When the coefficients of the j-th generation are less than or equal to a preset upper limit value, the global sound source phase of the j-th generation is generated according to the coefficients of the j-th generation, the M mask templates, and the M source plane phases of the j-th generation. When j is 1, the coefficient of the (j-1)th iteration is a preset initial value; Based on the global sound source phase of the j-th time and the amplitude of the M target surfaces measured, determine whether the degree of convergence of the sound pressure amplitude of the M focal points of the j-th time meets the condition; if so, generate a sound hologram based on the global sound source phase of the j-th time. Otherwise, the spacing between adjacent focal points in the direction of ultrasonic wave propagation is adjusted in the M focal points of the j-th iteration to obtain the M focal points after the j-th optimization. The (j+1)-th iteration is performed based on the M focal points after the j-th optimization until the acoustic hologram is generated.

2. The acoustic holography generation method for ultra-long, high-resolution acoustic beam focusing according to claim 1, characterized in that, The method further includes: When the coefficient of the j-th time is greater than the preset upper limit value, the sound pressure amplitude values ​​of the M focal points with the smallest approximation are selected based on the sound pressure amplitude values ​​of the M focal points from the 1st time to the (j-1)th time; wherein, the sound pressure amplitude values ​​of the M focal points with the smallest approximation are the sound pressure amplitude values ​​of the M focal points of the x-th time; x is an integer greater than or equal to 1 and less than or equal to j-1; A sound hologram is generated based on the x-th global sound source phase.

3. The acoustic holography generation method for ultra-long, high-resolution acoustic beam focusing according to claim 1, characterized in that, The step of numbering the M focal points of the j-th iteration, generating an acoustic holographic lens of size n*n based on the numbering, and generating M mask templates corresponding one-to-one with the M target surfaces according to the acoustic holographic lens includes: The M foci of the j-th iteration are numbered, and n*n first matrices are generated based on the numbering; the elements in each first matrix are the numbers of the M foci of the j-th iteration; The n*n first matrices are merged to obtain a second matrix with n*n*M elements; the second matrix is ​​the acoustic holographic lens. For the i-th target surface, set the element in the second matrix whose value is the number of the i-th target surface to 1, and set the remaining elements to 0 to obtain the mask template of the i-th target surface; i is an integer, and the value of i ranges from 1 to M.

4. The method for generating acoustic holograms for ultra-long, high-resolution acoustic beam focusing according to claim 1, characterized in that, The process of generating the j-th coefficient based on the (j-1)-th coefficient, and generating the j-th global sound source phase based on the j-th coefficient, the M mask templates, and the M source plane phases of the j-th generation when the j-th coefficient is less than or equal to a preset upper limit, includes: The coefficient of the (j-1)th iteration is increased by a preset increment to obtain the coefficient of the j-th iteration; When the coefficient of the j-th iteration is less than or equal to the preset upper limit value, the phase adjuster of the i-th target surface is generated according to the coefficient of the j-th iteration and the preset focusing index corresponding to the i-th target surface; i is an integer, and the value of i ranges from 1 to M; Based on the j-th phase adjuster of the i-th target surface, the j-th source plane phase of the i-th target surface, and the mask of the i-th target surface, generate the updated source plane phase of the i-th target surface; The updated source plane phases of the M target surfaces are summed to obtain the j-th global sound source phase.

5. The acoustic holography generation method for ultra-long, high-resolution acoustic beam focusing according to claim 4, characterized in that, The expression for the updated source plane phase of the i-th target surface is as follows: P′(x,y,f i )=[P(x,y,f i )-Pa i ]×L i (x,y); Where P′(x,y,f) i f represents the updated source plane phase of the i-th target surface. i Let P(x,y,f) represent the i-th focal point of the j-th ultrasound, which is located on the i-th target surface. Let x represent the lateral coordinate of the i-th focal point of the j-th ultrasound on the i-th target surface, and let y represent the longitudinal coordinate of the i-th focal point of the j-th ultrasound on the i-th target surface. The i-th target surface is perpendicular to the propagation direction of the ultrasound. i Pa represents the j-th source plane phase of the i-th target surface. i L represents the phase adjuster of the i-th target surface at the j-th time. i (x,y) represents the mask template of the i-th target surface.

6. The method for generating acoustic holograms for ultra-long, high-resolution acoustic beam focusing according to claim 1, characterized in that, The determination of whether the convergence of the sound pressure amplitudes of the M focal points in the j-th measurement, based on the phase of the global sound source and the amplitudes of the M target surfaces obtained from the j-th measurement, satisfies the following conditions includes: Based on the global sound source phase of the j-th time and the amplitude of the M target surfaces measured, determine the M sound pressure amplitudes corresponding to the M focal points of the j-th time. The ratio of the sound pressure amplitude at the i-th focal point in the j-th iteration to the average of the M sound pressure amplitudes is obtained; i is an integer and i ranges from 1 to M. Determine whether the absolute value of the difference between the ratio of each of the M focal points in the j-th iteration and 1 is less than or equal to a preset threshold; if so, it indicates that the degree of convergence of the sound pressure amplitude of the M focal points in the j-th iteration meets the condition; if the absolute value of the difference between the ratio of at least one focal point in the j-th iteration and 1 is greater than the preset threshold, it indicates that the degree of convergence of the sound pressure amplitude of the M focal points in the j-th iteration does not meet the condition.

7. The method for generating acoustic holograms for ultra-long, high-resolution acoustic beam focusing according to claim 6, characterized in that, The step of adjusting the spacing between adjacent focal points in the direction of ultrasonic wave propagation among the M focal points of the j-th iteration to obtain the M focal points after the j-th optimization includes: Based on the ratio of the i-th focal point of the j-th iteration, the distance between the i-th focal point of the j-th iteration and the (i-1)-th focal point of the j-th iteration in the direction of ultrasonic wave propagation, and the coordinate value of the (i-1)-th focal point of the j-th iteration in the direction of ultrasonic wave propagation, a new coordinate value of the i-th focal point of the j-th iteration in the direction of ultrasonic wave propagation is determined, so as to adjust the distance between the i-th focal point of the j-th iteration and the (i-1)-th focal point of the j-th iteration in the direction of ultrasonic wave propagation. The M focal points of the j-th iteration, whose spacing between two adjacent focal points in the direction of ultrasonic wave propagation has been adjusted, are taken as the M focal points after the j-th optimization; i is an integer and i ranges from 1 to M.

8. The method for generating acoustic holograms for ultra-long, high-resolution acoustic beam focusing according to claim 7, characterized in that, The expression for the new coordinates of the i-th focus in the direction of ultrasonic wave propagation during the j-th time is as follows: l(j,i)=[l(j-1,i)-l(j-1,i-1)]×R(j,i)+l(j,i-1); Wherein, l(j,i) represents the new coordinate value of the i-th focus in the direction of ultrasonic wave propagation in the j-th iteration, l(j-1,i) represents the coordinate value of the i-th focus in the direction of ultrasonic wave propagation in the j-th iteration, l(j-1,i-1) represents the coordinate value of the (i-1)-th focus in the direction of ultrasonic wave propagation in the j-th iteration, R(j,i) represents the ratio of the i-th focus in the j-th iteration, and l(j,i-1) represents the new coordinate value of the (i-1)-th focus in the direction of ultrasonic wave propagation in the j-th iteration.

9. The method for generating acoustic holograms for ultra-long, high-resolution acoustic beam focusing according to claim 1, characterized in that, The generation of acoustic holography based on the j-th global sound source phase includes: The phase of the j-th global sound source is converted into the thickness of the acoustic hologram to obtain the acoustic hologram.

10. The method for generating acoustic holograms for ultra-long, high-resolution acoustic beam focusing according to claim 1, characterized in that, The preset integer n is the ratio of the transducer size to the resolution of the acoustic hologram to be generated.

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