Ultrasonic array element multiplexing device and method suitable for photoacoustic imaging system

Abstract

The invention discloses an ultrasonic array element multiplexing device and method suitable for a photoacoustic imaging system. The device comprises an ultrasonic transducer array, an off-axis eccentric wheel and a driving motor. The driving motor is connected to a bearing of the off-axis eccentric wheel, and drives the off-axis eccentric wheel to rotate through the bearing. The off-axis eccentric wheel is connected to the ultrasonic transducer array through a pivot, and the continuous rotational motion of the driving motor is converted into a reciprocating rotational motion of the ultrasonic transducer array through the oscillation of the off-axis eccentric wheel. The ultrasonic transducer array rotates at an equal angle at the same time interval defined by the repetition rate of laser pulses, and the built-in object to be measured receives m laser pulses in a single reciprocating rotational motion cycle of the ultrasonic transducer array, so as to realize n-fold multiplexing of the array elements of the ultrasonic transducer array. When n=2, m=2; when n>2, m=2n. The invention effectively improves the resolution and clarity of photoacoustic imaging without increasing the number of array elements and the volume of the ultrasonic array.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoacoustic imaging, and more specifically, relates to an ultrasonic array element multiplexing device and method suitable for a photoacoustic imaging system. Background Art

[0002] Photoacoustic imaging is an imaging method based on the photoacoustic effect. Generally speaking, in photoacoustic imaging, a pulsed laser is used to irradiate the imaging site. A portion of the absorbed light energy will be converted into heat energy, causing the nearby tissue to undergo thermoelastic expansion, thereby forming a broadband (megahertz level) ultrasonic emission. This ultrasonic wave can be detected by an ultrasonic transducer, which is the main detector used in general ultrasound angiography.

[0003] To obtain clear photoacoustic images in a relatively large area, the number of array elements in the ultrasonic transducer must be high enough. Ideally, the array element spacing of the ultrasonic transducer array should be half the length of the ultrasonic wave. For example, for a 3MHz device with a sound speed of 1500m / s, adjacent ultrasonic array elements need to be spaced 0.5mm apart. If the circumference of the ultrasonic transducer array is 660mm, a total of 1320 ultrasonic array elements are required. For imaging systems with higher resolution requirements, shorter wavelength ultrasonic waves should be selected, so more array elements will be required. The increase in the number of ultrasonic array elements will greatly increase the difficulty and cost of making ultrasonic transducer arrays. Summary of the invention

[0004] In view of at least one defect or improvement need of the prior art, the present invention provides an ultrasound array element multiplexing device and method suitable for a photoacoustic imaging system, which aims to solve the problem that high imaging resolution requires more array elements and a larger ultrasound array volume.

[0005] To achieve the above object, according to one aspect of the present invention, there is provided an ultrasonic array element multiplexing device suitable for a photoacoustic imaging system, comprising an ultrasonic transducer array, an off-axis eccentric wheel and a drive motor;

[0006] The driving motor is connected to the bearing of the off-axis eccentric wheel, and the off-axis eccentric wheel is driven to rotate through the bearing; the off-axis eccentric wheel is connected to the ultrasonic transducer array through a pivot, and the continuous rotation motion of the driving motor is converted into the reciprocating rotation motion of the ultrasonic transducer array through the oscillation of the off-axis eccentric wheel;

[0007] The ultrasonic transducer array rotates at equal angles at the same time interval defined by the repetition rate of the laser pulses, and the built-in object to be tested receives m laser pulses in a single reciprocating rotation cycle of the ultrasonic transducer array, thereby realizing n-fold multiplexing of the array elements of the ultrasonic transducer array; wherein, when n=2, m=2; and when n>2, m=2n.

[0008] Preferably, in the above-mentioned ultrasonic array element multiplexing device, when n=2 or 3, the driving motor rotates at a constant speed to drive the ultrasonic transducer array to perform reciprocating rotational motion.

[0009] Preferably, in the ultrasonic array element multiplexing device, when n=4 or 5, the drive motor rotates at a constant acceleration in each quarter rotation period to drive the ultrasonic transducer array to perform reciprocating rotation. In a single rotation period of the drive motor, the first quarter period has the same speed and acceleration value as the third quarter period, the second quarter period has the same speed and acceleration value as the fourth quarter period, and the acceleration value of the second quarter period is the opposite of the acceleration value corresponding to the first quarter period.

[0010] Preferably, in the above-mentioned ultrasonic array element multiplexing device, when n>5, the driving motor rotates with a varying acceleration in each quarter cycle of rotation to drive the ultrasonic transducer array to perform reciprocating rotational motion; wherein, in a single rotation cycle of the driving motor, the first quarter cycle and the third quarter cycle have the same speed and acceleration value, the second quarter cycle and the fourth quarter cycle have the same speed and acceleration value, and the acceleration value of the second quarter cycle is the opposite of the acceleration value corresponding to the first quarter cycle.

[0011] Preferably, in the ultrasonic array element multiplexing device, the pivot adopts a frame spring.

[0012] Preferably, the ultrasonic array element multiplexing device further comprises a support bearing, the ultrasonic transducer array is mounted on the support bearing, and the support bearing is used to support the axial rotational movement of the ultrasonic transducer array.

[0013] Preferably, in the ultrasonic array element multiplexing device, the driving motor is a stepping motor or a servo motor.

[0014] According to another aspect of the present invention, there is also provided an ultrasound array element multiplexing method applicable to a photoacoustic imaging system, comprising:

[0015] Driving the ultrasonic transducer array to perform reciprocating rotational motion, wherein the ultrasonic transducer array rotates at equal angles at the same time interval defined by the repetition rate of the laser pulses;

[0016] In a single reciprocating rotation motion cycle of the ultrasonic transducer array, m laser pulses are applied to the object to be measured built into the ultrasonic transducer array to achieve n-fold multiplexing of the array elements of the ultrasonic transducer array; wherein, when n=2, m=2; when n>2, m=2n.

[0017] The ultrasonic transducer array receives the ultrasonic waves generated by the object to be tested under the action of the laser pulse and forms a photoacoustic image.

[0018] Preferably, in the above-mentioned ultrasonic array element multiplexing method, when n=2 or 3, the driving motor rotates at a constant speed to drive the ultrasonic transducer array to perform reciprocating rotational motion;

[0019] When n=4 or 5, the driving motor rotates at a constant acceleration in each quarter cycle of rotation to drive the ultrasonic transducer array to perform reciprocating rotational motion;

[0020] When n>5, the driving motor rotates at a varying acceleration in each quarter cycle of rotation to drive the ultrasonic transducer array to perform reciprocating rotational motion;

[0021] In a single rotation cycle of the drive motor, the first quarter cycle and the third quarter cycle have the same acceleration, and the accelerations of the second quarter cycle and the fourth quarter cycle are the opposite of the acceleration corresponding to the first quarter cycle.

[0022] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0023] The present invention provides an ultrasonic array element multiplexing device and method suitable for a photoacoustic imaging system. A driving motor drives an ultrasonic transducer array to rotate via an off-axis eccentric wheel, and the continuous rotational motion of the driving motor is converted into a reciprocating rotational motion of the ultrasonic transducer array via the oscillation of the off-axis eccentric wheel. In a single reciprocating rotational motion cycle of the ultrasonic transducer array, multiple laser pulses are applied to an object to be measured inside the ultrasonic transducer array, and the ultrasonic transducer array rotates at equal angles at the same time interval defined by the repetition rate of the laser pulses, thereby realizing multiple multiplexing of array elements of the ultrasonic transducer array, and effectively improving the resolution and clarity of photoacoustic imaging without increasing the number of array elements and the volume of the ultrasonic array. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic diagram of the composition structure of an ultrasonic array element multiplexing device provided in an embodiment of the present invention;

[0025] Figure 2 is a schematic diagram of the rotation position of the ultrasonic transducer array provided by an embodiment of the present invention;

[0026] Figure 3 is a schematic diagram of the stretching distance of the ultrasonic transducer array provided by an embodiment of the present invention and its distribution mapped on a sine function image;

[0027] In all the drawings, the same reference numerals represent the same technical features, specifically: 1 - ultrasonic transducer array; 2 - support bearing; 3 - pivot; 4 - motor rotation center; 5 - off-axis eccentric wheel; 6 - eccentric wheel bracket; 7 - bearing. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0029] Figure 1 is a schematic diagram of the composition structure of the ultrasonic array element multiplexing device suitable for the photoacoustic imaging system provided in this embodiment, see Figure 1 , the ultrasonic array element multiplexing device comprises an ultrasonic transducer array 1, an off-axis eccentric wheel 5 and a driving motor (not shown in the figure);

[0030] The driving motor is connected to the bearing 7 of the off-axis eccentric wheel 5, and the off-axis eccentric wheel 5 is driven to rotate through the bearing 7; the off-axis eccentric wheel 5 is connected to the ultrasonic transducer array 1 through the pivot 3, and the continuous rotation motion of the driving motor is converted into the reciprocating rotation motion of the ultrasonic transducer array 1 through the oscillation of the off-axis eccentric wheel 5;

[0031] Please continue reading Figure 1 In actual application, the ultrasonic transducer array 1 is generally mounted on a support bearing 2, and the ultrasonic transducer array 1 realizes axial rotational motion under the support of the support bearing 2. The support bearing 2 can be a ball bearing or a roller bearing, a bearing that can rotate a full circle or a bearing that can reciprocate at an angle, and this embodiment does not impose any specific restrictions. The rotational swinging motion of the ultrasonic transducer array 1 is generated by the rotational motion of the off-axis eccentric wheel 5 connected thereto. The off-axis eccentric wheel 5 is mounted on an eccentric wheel bracket 6 and is directly or indirectly connected to the ultrasonic transducer array 1 through a pivot 3. In a specific example, the pivot 3 is a rectangular frame made of a reinforced frame spring. The off-axis eccentric wheel 5 can be driven by a stepper motor or a servo motor. Through the above structure, the continuous rotational motion of the drive motor can be converted into the back-and-forth swinging motion of the ultrasonic transducer array 1 through the oscillation of the off-axis eccentric wheel 5.

[0032] The driving motor drives the off-axis eccentric wheel 5 to rotate once, and the axis of the off-axis eccentric wheel 5 ( Figure 1The motor rotation center 4 in the ultrasonic transducer array 1 successively approaches and moves away from the ultrasonic transducer array 1, so that the ultrasonic transducer array 1 completes a reciprocating rotation motion. In a single reciprocating rotation motion cycle of the ultrasonic transducer array 1, m laser pulses are applied to the object to be measured inside the ultrasonic transducer array 1 through the laser generator, and the ultrasonic transducer array 1 rotates at an equal angle at the same time interval defined by the repetition rate of the laser pulse (i.e., the emission time interval between two laser pulses), thereby realizing n-fold multiplexing of the array elements of the ultrasonic transducer array 1; wherein, when n=2, m=2; and when n>2, m=2n.

[0033] Figure 2 is a schematic diagram of the rotation process of the ultrasonic transducer array provided in this embodiment. Figure 2 In FIG. 1 , FIG. (a) shows an ultrasonic transducer array in a stationary state, wherein the ultrasonic transducer array includes a plurality of array elements arranged at equal intervals, and the ultrasonic transducer array is controlled to rotate to a position where the array element interval is divided into two equal parts, such as Figure 2 As shown in (b), n=2, which is recorded as a 2-degree rotation; a laser pulse is applied to the ultrasonic transducer array before and after the 2-degree rotation, respectively, to achieve double multiplexing of the array elements of the ultrasonic transducer array without increasing the number of array elements; Figure 2 (c) The ultrasonic transducer array is controlled to rotate 3 degrees, n=3, and a laser pulse is applied to the ultrasonic transducer array before and after the 3-degree rotation. Without increasing the number of array elements, 3 times multiplexing of the array elements of the ultrasonic transducer array can be achieved.

[0034] The present invention adopts a method of rotating the ultrasonic transducer array to multiple graduation positions within the array element spacing, so that the array elements of the ultrasonic transducer array are reused without increasing the ultrasonic array element entities, thereby achieving the effect of multiplying the number of ultrasonic array elements by n times.

[0035] In practical applications, the rotational motion of the ultrasonic transducer array should meet the following conditions:

[0036] 1. Accurate location;

[0037] 2. The ultrasound transducer array must rotate at equal angles at the same time interval defined by the laser pulse repetition rate.

[0038] 3. Due to the limitation of the length of the cable connecting the ultrasonic transducer array, the rotation angle cannot be too high.

[0039] 4. Due to the high inertia of the system, it is necessary to keep the drive motor rotating in one direction and keep the acceleration as minimum as possible.

[0040] The rotation angle α of the ultrasonic transducer array is proportional to the sine value of the rotation angle θ of the drive motor, that is, α=k·sinθ. For a fixed system, k is a constant and does not change in the following division discussion.

[0041] Figure 3 is a schematic diagram of the stretching distance of the ultrasonic transducer array provided in this embodiment and its distribution mapped on the sine function image, see Figure 3 The upper part of the figure represents the stretching distance corresponding to the reciprocating rotation process of the ultrasonic transducer array, the black dots in the figure represent the emission time of the laser pulse, and the lower part represents the distribution of the laser pulse on the sinusoidal function image corresponding to the reciprocating rotation process.

[0042] This embodiment specifies that the eccentricity of the axis position perpendicular to the circumference of the ultrasonic transducer array is 0. When the rotation index n is 2 or 3, the driving motor rotates at a constant speed to meet the condition that the rotation angle of the ultrasonic transducer array is also kept constant within a constant time interval.

[0043] See also Figure 3 For 2 divisions, the driving motor rotates one circle for every two laser pulses, and the laser pulse is applied when the off-axis eccentric wheel rotates to two extreme eccentric positions (toward the ultrasonic transducer array and away from the ultrasonic transducer array). The rotation angles corresponding to the emission moments of the laser pulses are: θ = π / 2 and θ = 3π / 2.

[0044] For the case of 3 divisions, the driving motor rotates one circle for every six laser pulses, and the rotation angles corresponding to the laser pulse emission are: θ=0, θ=π / 3, θ=2π / 3, θ=π, θ=4π / 3 and θ=5π / 3.

[0045] For higher rotation indexing numbers n, the drive motor with uniform motion cannot meet the conditions, so the speed of the drive motor must change during the rotation process. For 4 and 5 indexings, a constant acceleration can be applied to the drive motor so that the drive motor rotates at a constant acceleration in each quarter cycle of rotation to drive the ultrasonic transducer array to perform reciprocating rotational motion, which will minimize the load on the drive motor. In a single rotation cycle of the drive motor, the first quarter cycle has the same speed and acceleration values ​​as the third quarter cycle, the second quarter cycle has the same speed and acceleration values ​​as the fourth quarter cycle, and the acceleration value of the second quarter cycle is the opposite of the acceleration value corresponding to the first quarter cycle.

[0046] Please continue reading Figure 3 , when the rotation index n = 4, the constant acceleration of the drive motor is calculated as follows:

[0047] In the first quarter cycle of the driving motor rotation, if θ1 = 0 (no laser pulse), the ultrasonic transducer array needs two rotation positions with the same interval, which are denoted as θ2 and θ3;

[0048] The rotation angle of the drive motor is converted into the rotation angle of the ultrasonic transducer array, and the following formula is obtained:

[0049]

[0050] Each rotational position of the ultrasonic transducer array corresponds to the moment:

[0051]

[0052] The time interval between two adjacent laser pulses is T = Δt / 2, T is a known number, so Δt can be calculated;

[0053] The acceleration a1 and velocity v1 of the first quarter cycle are defined by conditions (19) and (20) close to θ = π / 2:

[0054]

[0055] 3sinθ2=sinθ3 (20)

[0056] By solving equations (19) and (20) together, we can obtain θ2, θ3, v1, and a1. That is, in the first quarter cycle of the drive motor, its acceleration is a1. In the third quarter cycle of the drive motor, its acceleration is the same as the first quarter cycle, which is a constant value a1. In the second and fourth quarter cycles of the drive motor, its acceleration is a constant value -a1.

[0057] When the rotation index n = 5, the acceleration of the drive motor is calculated as follows:

[0058] In the first quarter cycle of the driving motor rotation, if θ1 = 0 (with laser pulse), the ultrasonic transducer array needs two rotation positions with the same interval, which are denoted as θ2 and θ3;

[0059] The rotation angle of the drive motor is converted into the rotation angle of the ultrasonic transducer array, and the following formula is obtained:

[0060]

[0061] Where k is a constant;

[0062] Each of the rotation positions corresponds to the moment:

[0063]

[0064] Total time for one rotation cycle:

[0065] The time interval between two adjacent laser pulses is T = 2Δt / 5, T is a known number, so Δt can be calculated;

[0066] The acceleration a1 and velocity v1 of the first quarter period are defined by conditions (23) and (24) close to θ = π / 2:

[0067]

[0068] 2sinθ2=sinθ3 (24)

[0069] By solving equations (23) and (24) together, we can obtain θ2, θ3, v1, and a1. In the first and third quarter cycles of the drive motor's rotation, its acceleration is a1. In the second and fourth quarter cycles of the drive motor's rotation, its acceleration is -a1.

[0070] For higher division numbers, the acceleration of the drive motor in each quarter cycle of rotation must also change. When the rotation division n>5, the drive motor rotates with a changing acceleration in each quarter cycle of rotation to drive the ultrasonic transducer array to perform reciprocating rotation; in a single rotation cycle of the drive motor, the first quarter cycle has the same speed and acceleration value as the third quarter cycle, the second quarter cycle has the same speed and acceleration value as the fourth quarter cycle, and the acceleration value of the second quarter cycle is the opposite of the acceleration value corresponding to the first quarter cycle.

[0071] Please continue reading Figure 3 , the following discusses the case where n is an even number and an odd number respectively:

[0072] When n is an even number, in the first quarter cycle of the driving motor rotation, that is, the part where θ goes from 0 to π / 2, if θ1=0, the ultrasonic transducer array needs n / 2 rotation positions (angles) with the same interval, which are recorded as θ t , where t∈(2,…,n / 2+1), the time interval between adjacent rotation positions is equal, which is 2Δt / n. In order to maintain symmetry, the time interval between θ1=0 and θ2 should be equal to Δt / n. Similarly, symmetrically, θ n / 2+1 and θ n / 2+2 =π / 2 should also be equal to Δt / n.

[0073] The rotation angle of the drive motor is converted into the rotation angle of the ultrasonic transducer array, and the following formula is obtained:

[0074]

[0075] The moment corresponding to each rotation position:

[0076]

[0077] The time interval between two adjacent laser pulses is T = 2Δt / n;

[0078] The interval [θ i ,θ i+1 The acceleration a in i and speed v i Defined by conditions (27) and (28) close to θ = π / 2:

[0079]

[0080]

[0081] Solving equations (27) and (28) together, we obtain

[0082] Other θ i According to equation (25), the acceleration and velocity in other intervals can be obtained by recursively extrapolating to i=1, that is:

[0083]

[0084] until

[0085]

[0086] At this point, the speed and acceleration values ​​between two adjacent rotation positions in the first quarter cycle of the rotation of the drive motor can be respectively calculated.

[0087] When n is an odd number, in the first quarter cycle of the driving motor rotation, if θ1=0, the ultrasonic transducer array still needs (n-1) / 2 rotation positions with the same interval, denoted by θ t , where t∈(2,…,(n+1) / 2);

[0088] The rotation angle of the drive motor is converted into the rotation angle of the ultrasonic transducer array, and the following formula is obtained:

[0089]

[0090] The time corresponding to each rotation position:

[0091]

[0092] The interval [θ i ,θ i+1 The acceleration a in i and speed v iDefined by conditions (33) and (34) close to θ = π / 2:

[0093]

[0094]

[0095] Solving equations (33) and (34) together, we obtain

[0096] Other θ i According to equation (31), the acceleration and velocity in other intervals can be obtained by recursively extrapolating to i=1, that is:

[0097]

[0098]

[0099] At this point, the speed and acceleration values ​​between two adjacent rotation positions in the first quarter cycle of the rotation of the drive motor can be respectively calculated.

[0100] Since the time interval T of the laser pulses is known, Δt can be determined, and then the absolute values ​​of the speed and acceleration of the drive motor can be calculated according to the above equations.

[0101] When a servo motor is selected as the driving motor, the original position of the servo motor is defined as θ=0, and the position curve of the servo motor is calculated by the rotation angle θ(t) of the motor defined by the speed and acceleration function calculated by the above formula.

[0102] When a stepper motor is selected as the driving motor, the stepper motor can provide step pulses according to the inverse function of the rotation angle θ(t), that is, t(θ).

[0103] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An ultrasonic array element multiplexing device suitable for a photoacoustic imaging system, characterized in that: It includes an ultrasonic transducer array, an off-axis eccentric wheel and a driving motor; The driving motor is connected to the bearing of the off-axis eccentric wheel, and the off-axis eccentric wheel is driven to rotate through the bearing; the off-axis eccentric wheel is connected to the ultrasonic transducer array through a pivot, and the continuous rotation motion of the driving motor is converted into the reciprocating rotation motion of the ultrasonic transducer array through the oscillation of the off-axis eccentric wheel; The ultrasonic transducer array rotates at equal angles at the same time interval defined by the repetition rate of the laser pulses, and the object to be tested therein receives m laser pulses in a single reciprocating rotation cycle of the ultrasonic transducer array, thereby realizing n-fold multiplexing of the array elements of the ultrasonic transducer array; when n>2, m=2n; Wherein, when n=4 or 5, the driving motor rotates at a constant acceleration in each quarter cycle of rotation to drive the ultrasonic transducer array to perform reciprocating rotational motion; Wherein, in a single rotation cycle of the drive motor, the first quarter cycle and the third quarter cycle have the same acceleration, and the accelerations of the second quarter cycle and the fourth quarter cycle are the opposite of the acceleration corresponding to the first quarter cycle; When n=4, the constant acceleration of the drive motor is calculated as follows: In the first quarter cycle of the driving motor rotation, if θ1=0, the ultrasonic transducer array needs two rotation positions with the same interval, which are denoted as θ2 and θ3; The rotation angle of the drive motor is converted into the rotation angle of the ultrasonic transducer array, and the following formula is obtained: Where k is a constant; Each of the rotation positions corresponds to the moment: The time interval between two adjacent laser pulses is T = Δt / 2; The acceleration a1 and velocity v1 of the first quarter cycle are defined by conditions (3) and (4) close to θ = π / 2: 3sinθ2=sinθ3 (4) Solve equations (3) and (4) together to obtain θ2, θ3, v1, a1; When n=5, the constant acceleration of the drive motor is calculated as follows: In the first quarter cycle of the driving motor rotation, if θ1=0, the ultrasonic transducer array needs two rotation positions with the same interval, which are denoted as θ2 and θ3; The rotation angle of the drive motor is converted into the rotation angle of the ultrasonic transducer array, and the following formula is obtained: Where k is a constant; Each of the rotation positions corresponds to the moment: Total time for one rotation cycle: The time interval between two adjacent laser pulses is T = 2Δt / 5; The acceleration a1 and velocity v1 of the first quarter period are defined by conditions (7) and (8) close to θ = π / 2: 2sinθ2=sinθ3 (8) Solve equations (7) and (8) together to obtain θ2, θ3, v1, a1; When n>5, the driving motor rotates at a varying acceleration in each quarter cycle of rotation to drive the ultrasonic transducer array to perform reciprocating rotational motion; Wherein, in a single rotation cycle of the drive motor, the first quarter cycle and the third quarter cycle have the same speed and acceleration value, the second quarter cycle and the fourth quarter cycle have the same speed and acceleration value, and the acceleration value of the second quarter cycle is the opposite of the acceleration value corresponding to the first quarter cycle; when n is greater than 5 and n is an even number, the acceleration of the drive motor is calculated as follows: In the first quarter cycle of the driving motor, if θ1=0, the ultrasonic transducer array needs n / 2 rotation positions with the same interval, which are recorded as θ t , where t∈(2,…,n / 2+1); The rotation angle of the drive motor is converted into the rotation angle of the ultrasonic transducer array, and the following formula is obtained: Where k is a constant; Each of the rotation positions corresponds to the moment: Total time for one rotation cycle: The time interval between two adjacent laser pulses is T = 2Δt / n; The interval [θ i ,θ i+1 The acceleration a in i and speed v i Defined by conditions (11) and (12) close to θ = π / 2: Solving equations (11) and (12) together, we obtain Other θ i According to the solution of formula (9), the acceleration and speed of other intervals are obtained by recursion to i=1; when n is greater than 5, when n is an odd number, the acceleration of the drive motor is calculated as follows: In the first quarter cycle of the driving motor, if θ1=0, the ultrasonic transducer array needs (n-1) / 2 rotation positions with the same interval, which are recorded as θ t , where t∈(2,…,(n+1) / 2); The rotation angle of the drive motor is converted into the rotation angle of the ultrasonic transducer array, and the following formula is obtained: The time for each of the rotational positions: The interval [θ i ,θ i+1 The acceleration a in i and speed v i Defined by conditions (15) and (16) close to θ = π / 2: Solving equations (15) and (16) together, we obtain Other θ i According to equation (13), the acceleration and velocity in other intervals are obtained by recursively extrapolating to i=1.

2. A method for using an ultrasound array element multiplexing device suitable for a photoacoustic imaging system as claimed in claim 1, characterized in that: include: Driving the ultrasonic transducer array to perform reciprocating rotational motion, wherein the ultrasonic transducer array rotates at equal angles at the same time interval defined by the repetition rate of the laser pulses; In a single reciprocating rotational motion cycle of the ultrasonic transducer array, m laser pulses are applied to the object to be tested built into the ultrasonic transducer array to achieve n-fold multiplexing of the array elements of the ultrasonic transducer array; wherein, when n>2, m=2n; wherein, when n=4 or 5, the drive motor rotates at a constant acceleration value in each quarter of the rotational cycle to drive the ultrasonic transducer array to perform reciprocating rotational motion; Wherein, in a single rotation cycle of the drive motor, the first quarter cycle and the third quarter cycle have the same acceleration, and the accelerations of the second quarter cycle and the fourth quarter cycle are the opposite of the acceleration corresponding to the first quarter cycle; When n=4, the constant acceleration of the drive motor is calculated as follows: In the first quarter cycle of the driving motor rotation, if θ1=0, the ultrasonic transducer array needs two rotation positions with the same interval, which are denoted as θ2 and θ3; The rotation angle of the drive motor is converted into the rotation angle of the ultrasonic transducer array, and the following formula is obtained: Where k is a constant; Each of the rotation positions corresponds to the moment: The time interval between two adjacent laser pulses is T = Δt / 2; The acceleration a1 and velocity v1 of the first quarter cycle are defined by conditions (3) and (4) close to θ = π / 2: 3sinθ2=sinθ3 (20) Solve equations (3) and (4) together to obtain θ2, θ3, v1, a1; When n=5, the constant acceleration of the drive motor is calculated as follows: In the first quarter cycle of the driving motor rotation, if θ1=0, the ultrasonic transducer array needs two rotation positions with the same interval, which are denoted as θ2 and θ3; The rotation angle of the drive motor is converted into the rotation angle of the ultrasonic transducer array, and the following formula is obtained: Where k is a constant; Each of the rotation positions corresponds to the moment: Total time for one rotation cycle: The time interval between two adjacent laser pulses is T = 2Δt / 5; The acceleration a1 and velocity v1 of the first quarter period are defined by conditions (7) and (8) close to θ = π / 2: 2sinθ2=sinθ3 (24) Solve equations (7) and (8) together to obtain θ2, θ3, v1, a1; When n>5, the driving motor rotates at a varying acceleration in each quarter cycle of rotation to drive the ultrasonic transducer array to perform reciprocating rotational motion; Wherein, in a single rotation cycle of the drive motor, the first quarter cycle and the third quarter cycle have the same speed and acceleration value, the second quarter cycle and the fourth quarter cycle have the same speed and acceleration value, and the acceleration value of the second quarter cycle is the opposite of the acceleration value corresponding to the first quarter cycle; when n is greater than 5 and n is an even number, the acceleration of the drive motor is calculated as follows: In the first quarter cycle of the driving motor, if θ1=0, the ultrasonic transducer array needs n / 2 rotation positions with the same interval, which are recorded as θ t , where t∈(2,…,n / 2+1); The rotation angle of the drive motor is converted into the rotation angle of the ultrasonic transducer array, and the following formula is obtained: Where k is a constant; Each of the rotation positions corresponds to the moment: Total time for one rotation cycle: The time interval between two adjacent laser pulses is T = 2Δt / n; The interval [θ i ,θ i+1 The acceleration a in i and speed v i Defined by conditions (11) and (12) close to θ = π / 2: Solving equations (11) and (12) together, we obtain Other θ i According to the solution of formula (9), the acceleration and speed of other intervals are obtained by recursion to i=1; when n is greater than 5, when n is an odd number, the acceleration of the drive motor is calculated as follows: In the first quarter cycle of the driving motor, if θ1=0, the ultrasonic transducer array needs (n-1) / 2 rotation positions with the same interval, which are recorded as θ t , where t∈(2,…,(n+1) / 2); The rotation angle of the drive motor is converted into the rotation angle of the ultrasonic transducer array, and the following formula is obtained: The time for each of the rotational positions: The interval [θ i ,θ i+1 The acceleration a in i and speed v i Defined by conditions (15) and (16) close to θ = π / 2: Solving equations (15) and (16) together, we obtain Other θ i According to equation (13), the acceleration and velocity in other intervals are obtained by recursively extrapolating to i=1.

Images