CN116093714A - A photoacoustic signal generating device and method - Google Patents

Abstract

The embodiment of the invention discloses a photoacoustic signal generating device and a photoacoustic signal generating method, wherein the device comprises a light source module and a photoacoustic signal detecting module, the light source module is used for outputting pulse clusters comprising a plurality of ultrashort pulses, the time domain width, the energy, the repetition frequency, the pulse interval in the clusters and the pulse quantity in the clusters of the pulse clusters are all adjustable, the pulse clusters are incident to an object to be detected to excite a photoacoustic signal, the photoacoustic signal detecting module is used for detecting the photoacoustic signal, the laser pulse clusters with any time domain width are obtained through an active optical fiber loop, and the time domain width, the energy, the repetition frequency, the shape and the pulse interval in the clusters of the laser pulse clusters are all adjustable, so that the flexibility of the light source is greatly improved, and the problem that the repetition frequency of nanosecond laser is difficult to lift is solved.

Description

A photoacoustic signal generating device and method

technical field

The invention relates to the field of laser technology, in particular to a photoacoustic signal generating device and method.

Background technique

When a short-pulse laser is irradiated into a tissue, the tissue thermally expands due to the absorption of laser energy, and an ultrasonic signal is generated. This phenomenon is called the photoacoustic effect. Photoacoustic imaging technology combines the high contrast of pure optical imaging with the high penetration depth of pure ultrasound imaging, and has the advantages of no damage and no ionization effect. Photoacoustic imaging is mainly divided into two categories: photoacoustic tomography (PACT) and photoacoustic microscopy (PAM). These two types of imaging methods have different requirements for imaging depth and spatial resolution, which requires different imaging In application, it is necessary to adjust and select the component parameters of the photoacoustic imaging system.

In the current laser technology, the pulse width is limited by the difficulty of tuning the pulse width of a laser. At the same time, PACT requires the pulse energy to be on the order of mJ to achieve a large imaging depth, but the pulse repetition frequency is restricted by large energy and can only reach Hz level, which seriously limits the imaging speed, and PAM generally requires energy in the nJ-uJ level, which can make full use of pulsed lasers with high repetition rate (up to MHz level) to achieve higher imaging speed, pulse energy It is difficult to balance with the repetition rate, which limits the development of photoacoustic imaging.

In the prior art, it is necessary to purchase multiple lasers with different parameters to meet the demand for photoacoustic research on different materials or different application fields, which consumes a lot. In the field of photoacoustic imaging, nanosecond lasers are generally used as light sources for generating photoacoustic signals. The generation method of nanosecond pulses limits the pulse repetition frequency, thereby limiting the improvement of photoacoustic signal signal-to-noise ratio, imaging speed and other parameters, which in turn limits the development of photoacoustic imaging to a certain extent. Therefore, there is an urgent need for a laser with a high pulse repetition frequency, adjustable pulse width, energy, and repetition frequency to meet the above requirements, so as to achieve arbitrarily adjustable pulse output with pulse width, repetition frequency, and energy, and improve the flexibility of the light source. and photoacoustic imaging performance.

Contents of the invention

The embodiment of the present invention provides a photoacoustic signal generating device and method. The device uses a laser to obtain a laser pulse cluster with an arbitrary time domain width through an active optical fiber loop. The laser pulse cluster time domain width, energy, repetition frequency, The shape and the pulse interval in the cluster can be adjusted, which greatly increases the flexibility of the light source and solves the problem that the repetition rate of nanosecond lasers is difficult to increase.

According to one aspect of the present invention, a photoacoustic signal generating device is provided, including a light source module and a photoacoustic signal detection module. The repetition frequency, the pulse interval in the cluster and the number of pulses in the cluster can be adjusted. The pulse cluster is incident on the object to be measured to excite the photoacoustic signal, and the photoacoustic signal detection module is used to detect the photoacoustic signal;

Wherein, the light source module includes a seed source, an active fiber ring and a first modulator, and the active fiber ring includes a coupler, a circulator, an active fiber, a chirped fiber Bragg grating, a pump source, a second modulator and a delayer , the coupler includes a first input terminal, a second input terminal, a first output terminal and a second output terminal, the first input terminal is connected to the output terminal of the seed source, and the first output terminal is connected to the input terminal of the first modulator, The second output end, the first end of the circulator, the third end of the circulator, the second modulator, the delayer and the second input end are connected to form an optical fiber ring, and the second end of the circulator is connected to the first end of the active optical fiber connected, the second end of the active optical fiber is connected with the first end of the chirped fiber Bragg grating, and the second end of the chirped fiber Bragg grating is connected with the output end of the pumping source.

Optionally, the seed source is used to emit seed pulses, and the seed pulses are incident into the active optical fiber ring;

When the seed pulse is transmitted in the active fiber ring, the second modulator modulates the cycle number of the pulse to adjust the number of pulses in the cluster, the delayer modulates the cycle time of the pulse to adjust the pulse interval in the cluster, and the chirped fiber Bragg grating provides negative dispersion to Compensate the pulse broadening of the seed pulse in the active fiber ring, the pump source and the active fiber provide gain to adjust the energy;

The first modulator and the second modulator modulate the time domain width and repetition frequency.

Optionally, the second output end of the coupler is connected to the first end of the circulator, the third end of the circulator is connected to the input end of the second modulator, and the output end of the second modulator is connected to the first end of the delayer connected, and the second end of the delayer is connected to the second input end.

Optionally, the light source module further includes an amplifier, and an input end of the amplifier is connected to an output end of the first modulator.

Optionally, the light source module further includes a pulse compressor, and the input end of the pulse compressor is connected to the output end of the amplifier.

Optionally, the delayer includes a first collimator and a second collimator, and the distance between the first collimator and the second collimator is adjustable, so as to adjust the transmission time of the pulse in the active optical fiber ring.

Optionally, the optical fiber used in the active optical fiber ring is a polarization maintaining optical fiber.

Optionally, the first modulator includes an acousto-optic modulator or an electro-optic modulator, and the second modulator includes an acousto-optic modulator or an electro-optic modulator.

Optionally, the photoacoustic signal detection module also includes:

Displacement platform, the displacement platform is used to carry the object to be measured;

The beam adjusting unit includes at least one reflector and at least one converging lens, the reflector is used to change the transmission direction of the pulse cluster, and the converging lens is used to converge the pulse cluster to the object to be measured.

According to another aspect of the present invention, a method for generating a photoacoustic signal is provided, which is suitable for any of the above photoacoustic signal generating devices. The method for generating a photoacoustic signal includes:

The seed source outputs the seed pulse;

The seed pulses are transmitted through the active optical fiber ring to form multiple pulse clusters, which are modulated by the first modulator into pulse clusters with preset time domain width, preset energy, preset repetition frequency, pulse interval within the cluster and the number of pulses within the cluster;

The pulse cluster is incident on the object to be measured to excite the photoacoustic signal;

The photoacoustic signal detection module is used for detecting photoacoustic signals.

A photoacoustic signal generating device provided by an embodiment of the present invention includes a light source module and a photoacoustic signal detection module. The light source module is used to output a pulse cluster including a plurality of ultrashort pulses. The time domain width, energy, repetition frequency, and The pulse interval and the number of pulses in the cluster can be adjusted. The pulse cluster is incident on the object to excite the photoacoustic signal, and the photoacoustic signal detection module is used to detect the photoacoustic signal. and the first modulator, the active fiber ring includes a coupler, a circulator, an active fiber, a chirped fiber Bragg grating, a pump source, a second modulator and a delayer, and the coupler includes a first input port, a second input end, the first output end and the second output end, the first input end is connected with the output end of the seed source, the first output end is connected with the input end of the first modulator, the second output end, the first end of the circulator, The third end of the circulator, the second modulator, the delayer and the second input end are connected to form an optical fiber ring, the second end of the circulator is connected to the first end of the active optical fiber, and the second end of the active optical fiber is connected to the chirped The first end of the fiber Bragg grating is connected, and the second end of the chirped fiber Bragg grating is connected with the output end of the pumping source. The laser pulse cluster with arbitrary time-domain width is obtained by using the laser through the active fiber loop. The time-domain width, energy, repetition frequency, shape and pulse interval of the laser pulse cluster can be adjusted, which greatly increases the flexibility of the light source. , which solves the problem that the repetition rate of nanosecond lasers is difficult to increase.

It should be understood that the content described in this section is not intended to identify key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will be easily understood from the following description.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained based on these drawings without creative effort.

FIG. 1 is a schematic structural diagram of a photoacoustic signal generating device provided by an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of another photoacoustic signal generating device provided by an embodiment of the present invention;

Fig. 3 is a schematic structural diagram of another photoacoustic signal generating device provided by an embodiment of the present invention;

Fig. 4 is a schematic structural diagram of another photoacoustic signal generating device provided by an embodiment of the present invention;

5 is a schematic structural diagram of another photoacoustic signal generating device provided by an embodiment of the present invention;

Fig. 6 is a schematic diagram of a method for generating a photoacoustic signal according to an embodiment of the present invention.

Among them, 10-light source module, 20-photoacoustic signal detection module, 11-seed source, 12-active optical fiber ring, 13-first modulator, 14-amplifier, 15-pulse compressor, 121-coupler, 122 -circulator, 123-active fiber, 124-chirped fiber Bragg grating, 125-pump source, 126-delay, 127-second modulator, 1261-first collimator, 1262-second collimator device, 21-displacement platform, 22-beam adjustment unit, 221-mirror and 222-converging lens.

Detailed ways

In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only It is an embodiment of a part of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

It should be noted that the terms "first" and "second" in the description and claims of the present invention and the above drawings are used to distinguish similar objects, but not necessarily used to describe a specific sequence or sequence. It is to be understood that the data so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein can be practiced in sequences other than those illustrated or described herein. Furthermore, the terms "comprising" and "having", as well as any variations thereof, are intended to cover a non-exclusive inclusion, for example, a process, method, system, product or apparatus comprising a sequence of steps or elements is not necessarily limited to the expressly listed instead, may include other steps or elements not explicitly listed or inherent to the process, method, product or apparatus.

FIG. 1 is a schematic structural diagram of a photoacoustic signal generating device provided by an embodiment of the present invention. As shown in FIG. 1 , the photoacoustic signal generating device specifically includes: a light source module 10 and a photoacoustic signal detection module 20. Output a pulse cluster including multiple ultrashort pulses. The time domain width, energy, repetition frequency, pulse interval and pulse number of the pulse cluster can be adjusted. The pulse cluster is incident on the object to be measured (not shown in Figure 1) To excite the photoacoustic signal, the photoacoustic signal detection module 20 is used to detect the photoacoustic signal;

Wherein, the light source module 10 includes a seed source 11, an active optical fiber ring 12 and a first modulator 13, and the active optical fiber ring 12 includes a coupler 121, a circulator 122, an active optical fiber 123, a chirped fiber Bragg grating 124, a pump Source 125, second modulator 127 and delayer 126, coupler 121 includes first input end, second input end, first output end and second output end, first input end is connected with the output end of seed source 11, The first output terminal is connected to the input terminal of the first modulator 13, the second output terminal, the first terminal a of the circulator 122, the third terminal c of the circulator 122, the second modulator 127, the delayer 126 and the second The input end is connected into an optical fiber ring, the second end b of the circulator 122 is connected with the first end of the active optical fiber 123, the second end of the active optical fiber 123 is connected with the first end of the chirped fiber Bragg grating 124, and the chirped optical fiber The second end 124 of the Bragg grating is connected to the output end of the pumping source 125 . The seed source 11 outputs ultrashort pulses, and the time domain width of the ultrashort pulses is on the order of picoseconds or femtoseconds.

Among them, there is energy loss in the transmission of the pulsed laser in the optical fiber, the pumping light can be delivered by the pump source 125 and absorbed by the active optical fiber 123 to amplify the pulsed laser, while the dispersion of the chirped fiber Bragg grating 124 and the dispersion of the active optical fiber 123 On the contrary, for compensating the difference in spectral phase to obtain ultrashort pulses with the same duration, the combined setting of the pump source 125 and the active fiber 123 can obtain the preset energy by actively adjusting the gain or loss of the fiber loop Pulse cluster envelope. The second modulator 127 is used to control the number of pulses contained in the pulse cluster. When the pulse reaches the required number, the second modulator 127 is turned off and interrupts the laser pulse cycle in the active fiber loop, thereby forming a pulse cluster.

It is worth noting that the second modulator 127 and the delayer 126 are connected in the active optical fiber ring 12. In this embodiment, the position and connection sequence of the second modulator 127 and the delayer 126 in the ring are not limited. The positions and order of the second modulator 127 and the delayer 126 shown in FIG. 1 are for reference only, and are not intended to limit the embodiment of the present invention.

It can be understood that the pulse output by the seed source 11 is input by the first input terminal of the coupler 121, and the same pulse can be output by the first output terminal and the second output terminal of the coupler 121 (for example, the splitting ratio can be 50:50) , respectively enter the first modulator 13 through the first output end, enter the circulator 122 (the first end of the circulator, that is, end a) through the second output end, the pump source 125, the chirped fiber Bragg grating 124 and the active The optical fiber 123 is connected sequentially and connected to the second end of the circulator 122, i.e. the b end, which plays a role in gain or loss for the pulsed laser in the fiber loop, and then the third end of the circulator 122, i.e. the c end, After passing through the second modulator 127 and the delayer 126, enter the coupler 121 through the second input port, and when the pulse reaches the required number in the second modulator 127, the second modulator 127 closes and interrupts the active optical fiber loop The laser pulse cycles to form a pulse cluster, and the delayer 126 can adjust the time interval between two adjacent pulses in the pulse cluster envelope by adjusting the single cycle time of the pulse in the active optical fiber ring 12, so as to change the pulse cluster envelope The time-domain width and energy of the network, then respectively enter the first modulator 13 from the first output end of the coupler 121, enter the circulator 122 from the second output end of the coupler 121 and repeat the above-mentioned process, the first output end of the coupler 121 The modulated pulse cluster envelope output by the output terminal is picked up by the first modulator 13, synthesizes an ultrashort pulse cluster with any time width and any repetition frequency, and transmits it to the photoacoustic detection module 20 to detect the object to be tested to generate a corresponding photoacoustic signal.

Exemplarily, the seed pulse sequence of a certain repetition frequency is emitted by the seed source 11, and the input coupler 121 outputs the same single seed pulse from the first output terminal and the second output terminal of the coupler 121, and the output from the second output terminal After the single seed pulse is transmitted in the active optical fiber ring 12, the time to reach the second input end of the coupler 121 is slightly later than the second pulse emitted by the seed source 11. These two pulses form a pulse cluster with two pulses, and the two pulses form a pulse cluster with two pulses. After the pulse is transmitted through the active optical fiber ring 12, the time to reach the coupler 121 is slightly later than the third pulse emitted by the seed source 11, then a pulse cluster with three pulses is formed, and the above process can be repeated to obtain multiple pulses. pulse cluster. The second modulator 127 can control the pulse quantity in the pulse cluster, and the time delay device 126 can control the time interval between two pulses in the pulse cluster, and the first modulator 13 can select the required pulse cluster, and the active optical fiber 123 can Control the gain to realize the adjustment of pulse cluster time domain width, energy, repetition frequency, shape and pulse interval within the cluster. It can be understood that if the second modulator 127 controls the pulse cluster to include n ultrashort pulses, the active optical fiber ring 12 outputs n kinds of pulse clusters including one pulse, two pulses... and n pulses, and then the first A modulator 13 filters out the first n-1 bursts, passing bursts comprising n pulses.

A photoacoustic signal generation device provided by an embodiment of the present invention includes a light source module and a photoacoustic signal detection module. The pulse interval and the number of pulses in the cluster can be adjusted. The pulse cluster is incident on the object to excite the photoacoustic signal, and the photoacoustic signal detection module is used to detect the photoacoustic signal. A modulator, the active fiber ring includes a coupler, a circulator, an active fiber, a chirped fiber Bragg grating, a pump source, a second modulator and a delayer, and the coupler includes a first input end, a second input end, The first output end and the second output end, the first input end is connected with the output end of the seed source, the first output end is connected with the input end of the first modulator, the second output end, the first end of the circulator, the circulator The third end of the circulator, the second modulator, the delayer and the second input end are connected to form a fiber ring, the second end of the circulator is connected to the first end of the active fiber, the second end of the active fiber is connected to the chirped fiber Bragg The first end of the grating is connected, and the second end of the chirped fiber Bragg grating is connected with the output end of the pumping source. The laser pulse cluster with arbitrary time-domain width is obtained by using the laser through the active fiber loop. The time-domain width, energy, repetition frequency, shape and pulse interval of the laser pulse cluster can be adjusted, which greatly increases the flexibility of the light source. , and at the same time solve the problem that the repetition rate of the laser is difficult to increase.

In the above process, the pulsed laser enters the coupler to couple out the pulse cluster of multiple pulses, and adjusts the time domain width, energy, repetition frequency, pulse interval in the cluster and the number of pulses in the cluster. Continue to refer to Figure 1. details as follows:

Optionally, the seed source 11 is used to emit seed pulses, and the seed pulses are incident into the active optical fiber ring 12;

When the seed pulse is transmitted in the active fiber ring 12, the second modulator 127 modulates the number of cycles of the pulse to adjust the number of pulses in the cluster, the delayer 126 modulates the cycle time of the pulse to adjust the pulse interval in the cluster, and the chirped fiber Bragg grating 124 Negative dispersion is provided to compensate the pulse broadening of the seed pulse in the active fiber ring 12, and the pump source 125 and the active fiber 123 provide gain to adjust energy;

The first modulator 13 and the second modulator 127 modulate the time domain width and repetition frequency.

Wherein, during the pulse cluster process from the pulse laser entering the coupler 121 to coupling out multiple pulses, there is energy loss in the transmission process of the laser in the active fiber ring 12, which can be pumped by the pump source 125 and the active fiber 123 to the active fiber Laser beams transmitted within 123 provide gain to regulate energy;

The second modulator 127 accumulates pulses and counts the number. When the pulse reaches the required number, the second modulator is turned off and interrupts the laser pulse cycle in the active fiber loop to form a pulse cluster. The second modulator 127 modulates the cycle of pulses The number of pulses in the cluster can be adjusted by adjusting the number of pulses. If the number of pulses required is large, the number of pulse cycles can be increased. If the number of pulses required is small, the number of pulse cycles can be reduced. The specific number of cycles is not limited.

The delayer 126 can adjust the time interval between two adjacent pulses in the pulse cluster envelope by adjusting the single cycle time of the pulse in the active optical fiber ring 12, so as to change the time domain width of the pulse cluster envelope.

The first modulator 13 can set the modulation frequency of the pulse cluster by picking up the coupled out pulse cluster.

Exemplarily, the seed source emits a seed fs level pulse, and the pulse interval can be modulated by increasing the cycle time of the pulse through a delayer; the seed source emits a pulse with a seed pulse energy of the pJ level, through the pump The gain of the pump source and the active optical fiber can output pulse clusters with pulse energy in the order of nJ-mJ; the repetition frequency of the modulated pulse clusters by the first modulator 13 can be 10 Hz-MHz.

In the photoacoustic signal generation device provided by the embodiment of the present invention, the second modulator can modulate the number of pulse cycles to adjust the number of pulses in the cluster, and the delayer adjusts the single cycle time of the seed pulse in the active optical fiber ring to The pulse interval in the cluster is changed, the chirped fiber Bragg grating compensates the dispersion, the pump source and the active fiber provide gain to adjust the energy, the first modulator and the second modulator modulate the time domain width and repetition frequency, and output any time width, any The pulse clusters with repetition frequency are used by the photoacoustic detection module to detect the object to be tested to generate corresponding photoacoustic signals. The time domain width, energy, repetition frequency, shape and pulse interval of the output laser pulse clusters can be adjusted, which greatly increases It not only improves the flexibility of the light source, but also solves the problem that the repetition rate of the laser is difficult to increase.

Based on the above embodiment, the photoacoustic signal generating device is further optimized. Optionally, in the light source module, the third end of the circulator is connected to the input end of the second modulator, and the output end of the second modulator is connected to the first end of the delayer. The second end of the delayer is connected to the second input end; optionally, the light source module includes an amplifier, and the input end of the amplifier is connected to the output end of the first modulator.

Fig. 2 is a schematic structural diagram of another photoacoustic signal generating device provided by an embodiment of the present invention. With reference to Fig. 2, an embodiment of the present invention provides a photoacoustic signal generating device specifically including: a light source module 10, a photoacoustic signal detection module 20. Seed source 11, active optical fiber ring 12, first modulator 13, amplifier 14, coupler 121, circulator 122, active optical fiber 123, chirped fiber Bragg grating 124, pump source 125, delayer 126 and The second modulator 127 .

Optionally, the second output terminal is connected to the first terminal a of the circulator 122, the third terminal c of the circulator 122 is connected to the input terminal of the second modulator 127, and the output terminal of the second modulator 127 is connected to the delayer 126 The first end of the delayer 126 is connected to the second input end of the delayer 126 .

Wherein, the circulator 126 can be a fiber optic circulator; the delayer 126 includes but is not limited to single or multiple devices that can prolong the pulse transmission time, such as an optical fiber delayer, or a combination of two collimating lenses, the category and model of the device No limit.

Optionally, the light source module 110 further includes an amplifier 14 , and an input end of the amplifier 14 is connected to an output end of the first modulator 13 .

Wherein, the amplifier 14 is used to amplify the pulse cluster of the repetition frequency of the pulse sequence picked up by the first modulator 13 to increase its energy. The amplifier 14 includes but is not limited to fiber amplifiers, Raman optical amplifiers, semiconductor optical amplifiers and other related types of laser amplifiers, and the types and models thereof are not limited.

In the photoacoustic signal generation device provided by the embodiment of the present invention, the second modulator can modulate the cycle number of pulses to adjust the number of pulses in the cluster, the delayer can modulate the cycle time of pulses to adjust the pulse interval in the cluster, and the chirped fiber Bragg The grating compensates the dispersion, the pump source and the active optical fiber provide gain to adjust the energy, the first modulator and the second modulator modulate the time domain width and repetition frequency, and output pulse clusters of any time width and repetition frequency, and then through the amplifier, Further increase the energy of the laser pulse cluster output by the laser for the photoacoustic detection module to detect the object to be tested to generate a corresponding photoacoustic signal, increase the energy of the laser pulse cluster output by the laser, the output laser pulse cluster time domain width, energy, The repetition rate, shape, and inter-cluster pulse spacing are all adjustable, which greatly increases the flexibility of the light source.

Based on the above embodiment to further optimize the photoacoustic signal generating device, optionally, the light source module further includes a pulse compressor, and the input end of the pulse compressor is connected to the output end of the amplifier.

FIG. 3 is a schematic structural diagram of another photoacoustic signal generating device provided by an embodiment of the present invention. Referring to FIG. 3 , an embodiment of the present invention provides a photoacoustic signal generating device specifically including: a light source module 10, a photoacoustic signal detection module 20. Seed source 11, active optical fiber ring 12, first modulator 13, amplifier 14, pulse compressor 15, coupler 121, circulator 122, active optical fiber 123, chirped fiber Bragg grating 124, pumping source 125 , delayer 126 and second modulator 127 .

Optionally, the light source module 10 further includes a pulse compressor 15 , the input end of the pulse compressor 15 is connected to the output end of the amplifier 14 .

Among them, the pulse compressor 15 is used to compress the pulse cluster output by the amplifier 14, compensate for the broadening due to dispersion and other reasons in the transmission process, and shorten the time domain width. The pulse compressor 15 includes but is not limited to related optical devices, such as volume gratings.

In the photoacoustic signal generation device provided by the embodiment of the present invention, the second modulator can modulate the cycle number of pulses to adjust the number of pulses in the cluster, the delayer can modulate the cycle time of pulses to adjust the pulse interval in the cluster, and the chirped fiber Bragg The grating compensates the dispersion, the pump source and the active optical fiber provide gain to adjust the energy, the first modulator and the second modulator modulate the time domain width and repetition frequency, and output pulse clusters of any time width and repetition frequency, and then through the amplifier, To further increase the energy of the laser pulse cluster, the pulse compressor can also be used to further shorten the time-domain width of the pulse cluster, so that the photoacoustic detection module can detect the object to be tested to generate a corresponding photoacoustic signal, and the output laser pulse cluster time-domain width , energy, repetition rate, shape and inter-cluster pulse interval are all adjustable, which greatly increases the flexibility of the light source.

Based on the above embodiments to further optimize the photoacoustic signal generating device, optionally, the delayer may include a first collimator and a second collimator.

FIG. 4 is a schematic structural diagram of another photoacoustic signal generating device provided by an embodiment of the present invention. With reference to FIG. 3 , an embodiment of the present invention provides a photoacoustic signal generating device specifically including: a light source module 10, a photoacoustic signal detection module 20. Seed source 11, active optical fiber ring 12, first modulator 13, amplifier 14, pulse compressor 15, coupler 121, circulator 122, active optical fiber 123, chirped fiber Bragg grating 124, pumping source 125 , the second modulator 127 , the first collimator 1261 and the second collimator 1262 .

Optionally, the retarder includes a first collimator 1261 and a second collimator 1262, and the distance between the first collimator 1261 and the second collimator 1262 is adjustable, so as to adjust pulse transmission in the active fiber ring 12 transmission time within.

Wherein, the relevant parameters of the first collimator and the second collimator are matched, including but not limited to fiber collimator, Soller collimator, universal collimator (low energy, medium energy, high energy, low resolution, medium resolution, high resolution) and radiation collimators, etc., if it is necessary to prolong the transmission time of the pulse in the active fiber ring 12, then increase the distance between the first collimator 1261 and the second collimator 1262, if it is necessary to shorten the pulse The transmission time in the active fiber ring 12 then reduces the distance between the first collimator 1261 and the second collimator 1262, and specifically adjusts the distance between the first collimator 1261 and the second collimator 1262 The length is the set value.

In the photoacoustic signal generation device provided by the embodiment of the present invention, the second modulator can modulate the cycle number of pulses to adjust the number of pulses in the cluster, the delayer can modulate the cycle time of pulses to adjust the pulse interval in the cluster, and the chirped fiber Bragg The grating compensates the dispersion, the pump source and the active optical fiber provide gain to adjust the energy, the first modulator and the second modulator modulate the time domain width and repetition frequency, and output pulse clusters of any time width and repetition frequency, and then through the amplifier, To further increase the energy of the laser pulse cluster, the pulse compressor can also be used to further shorten the time-domain width of the pulse cluster, and to correct the broadening caused by dispersion and other reasons during the compensation transmission process, so that the photoacoustic detection module can detect the object to be measured Corresponding photoacoustic signals are generated, and the time-domain width, energy, repetition frequency, shape and pulse interval of the output laser pulse clusters can be adjusted, which greatly increases the flexibility of the light source.

On the basis of the above-mentioned embodiments, modified embodiments of the above-mentioned embodiments are proposed. It should be noted here that, for the sake of brevity, only differences from the above-mentioned embodiments are described in the modified embodiments.

In one embodiment, optionally, the optical fiber used in the active optical fiber ring 12 is a polarization maintaining optical fiber.

In one embodiment, optionally, the first modulator 13 includes an acousto-optic modulator or an electro-optic modulator, and the second modulator 127 includes an acousto-optic modulator or an electro-optic modulator.

The relevant parameters of the above devices should match each other, and there is no limitation on the specific category and model.

Based on the above embodiments, the photoacoustic signal detection module in the photoacoustic signal generating device is further optimized. Optionally, the photoacoustic signal detection module specifically further includes: a displacement platform, and the beam adjustment unit includes at least one mirror and at least one converging lens.

Fig. 5 is a schematic structural diagram of another photoacoustic signal generating device provided by an embodiment of the present invention; referring to Fig. 3 , an embodiment of the present invention provides a photoacoustic signal generating device specifically including: a light source module 10, a photoacoustic signal detection module 20. Seed source 11, active optical fiber ring 12, first modulator 13, amplifier 14, pulse compressor 15, coupler 121, circulator 122, active optical fiber 123, chirped fiber Bragg grating 124, pumping source 125 , the second modulator 127, the first collimator 1261, the second collimator 1262, the displacement platform 21 and the beam adjustment unit 22.

Optionally, the photoacoustic signal detection module 20 also includes:

A displacement platform 21, the displacement platform 21 is used to carry the object to be measured;

The beam adjusting unit 22, the beam adjusting unit includes at least one mirror 221 and at least one converging lens 222, the mirror 221 is used to change the transmission direction of the pulse cluster, and the converging lens 222 is used to converge the pulse cluster to the object to be measured.

Among them, the displacement platform 21 can be moved by means of hardware and/or software control, so that the corresponding area of the object to be measured is set for pulse detection to generate a corresponding photoacoustic signal; the mirror 221 includes but is not limited to a plane mirror and other related variable The optical device or combination of the light path; the converging lens 222 includes but not limited to a biconvex lens, a single convex lens and other related focusable optical devices or combinations.

Figure 6 is a schematic diagram of a photoacoustic signal generation method provided by an embodiment of the present invention, which is applicable to the situation of generating a photoacoustic signal, referring to Figure 6 in conjunction with Figure 5, an embodiment of the present invention provides a photoacoustic signal generation method The method is applicable to any one of the above photoacoustic signal generating devices, and the photoacoustic signal generating method includes:

S110, the seed source outputs a seed pulse;

Among them, the seed source can output ultrashort pulses with a repetition rate of tens of megahertz.

S120. The seed pulses are transmitted through the active optical fiber ring to form multiple pulse clusters, which are modulated by the first modulator into pulses with preset time-domain width, preset energy, preset repetition frequency, pulse interval within a cluster, and the number of pulses within a cluster. cluster;

Wherein, the first modulator picks up the pulse sequence, synthesizes a pulse cluster with any time width and any repetition frequency and transmits it to the photoacoustic detection module;

The combined setting of the seed pulse through the pump source and the active fiber can obtain the pulse cluster envelope of any shape by actively adjusting the gain or loss of the fiber loop;

The pulses pass through the second modulator to obtain a pulse cluster envelope with the number of preset pulse sequences;

The pulses pass through a delayer to modulate the cycle time of the pulses to obtain a pulse cluster envelope with a preset inter-cluster pulse spacing.

S130, the pulse cluster is incident on the object to be measured to excite a photoacoustic signal;

S140. The photoacoustic signal detection module is used to detect the photoacoustic signal.

It can be understood that the seed pulse output by the seed source 11 is input by the first input terminal of the coupler 121, and the same pulse can be output by the first output terminal and the second output terminal of the coupler 121 (for example, the splitting ratio can be 50:50 ), enter the first modulator 13 through the first output port respectively, and enter the circulator 122 (the first end of the circulator, that is, the a end) through the second output port, the pump source 125, the chirped fiber Bragg grating 124 and the The source optical fiber 123 is connected in sequence and connected to the second end of the circulator 122, i.e. the b end, which plays a role of gain or loss for the pulsed laser in the fiber loop, and then the third end of the circulator 122, i.e. the c end , enter the coupler 121 through the second input port after passing through the second modulator 127 and the delayer, in the second modulator 127 when the pulse reaches the required number, the second modulator 127 is closed and interrupts the active optical fiber loop The laser pulse cycles to form a pulse cluster, and the delayer 126 can adjust the time interval between two adjacent pulses in the pulse cluster envelope by adjusting the single cycle time of the pulse in the active optical fiber ring 12, so as to change the pulse cluster envelope The time-domain width and energy of the network, then respectively enter the first modulator 13 from the first output end of the coupler 121, enter the circulator 122 from the second output end of the coupler 121 and repeat the above-mentioned process, the first output end of the coupler 121 The modulated pulse cluster envelope output by the output terminal is picked up by the first modulator 13 to synthesize a pulse cluster with any time width and any repetition frequency and transmitted to the photoacoustic detection module 20 to detect the object to be tested to generate corresponding light acoustic signal.

In a photoacoustic signal generation method provided by an embodiment of the present invention, firstly, the seed pulse is output by the seed source; then, the seed pulse is transmitted through an active optical fiber ring to form a plurality of pulse clusters, and is modulated by the first modulator to a preset time Pulse clusters with domain width, preset energy, preset repetition frequency, pulse interval within a cluster, and number of pulses within a cluster, where the second modulator controls the number of pulses in a pulse cluster, and the first modulator picks up the pulse sequence to synthesize an arbitrary time The pulse clusters with width and arbitrary repetition frequency are transmitted to the photoacoustic detection module; specifically include: the combined setting of the seed pulse through the pump source and the active optical fiber can obtain pulse clusters of any shape by actively adjusting the gain or loss of the fiber loop After the envelope, pass through the second modulator to obtain the pulse cluster envelope with the number of preset pulse sequences, and then pass through the delayer to modulate the cycle time of the pulse to obtain the pulse cluster envelope with the pulse interval in the preset cluster; finally, the pulse The cluster is incident on the object to be measured to excite the photoacoustic signal, and the photoacoustic signal detection module is used to detect the photoacoustic signal. Using this method, a laser pulse cluster with arbitrary time-domain width can be obtained through active fiber loop modulation. Flexibility, and solve the problem that the laser repetition rate is difficult to increase.

The above specific implementation methods do not constitute a limitation to the protection scope of the present invention. It should be apparent to those skilled in the art that various modifications, combinations, sub-combinations and substitutions may be made depending on design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A photoacoustic signal generating device, characterized in that it comprises a light source module and a photoacoustic signal detection module, the light source module is used to output pulse clusters comprising a plurality of ultrashort pulses, the time domain width and energy of the pulse clusters , repetition frequency, intra-cluster pulse interval and intra-cluster pulse number can be adjusted, the pulse cluster is incident on the object to be measured to excite a photoacoustic signal, and the photoacoustic signal detection module is used to detect the photoacoustic signal; Wherein, the light source module includes a seed source, an active fiber ring and a first modulator, and the active fiber ring includes a coupler, a circulator, an active fiber, a chirped fiber Bragg grating, a pump source, a second modulation and a delayer, the coupler includes a first input terminal, a second input terminal, a first output terminal and a second output terminal, the first input terminal is connected to the output terminal of the seed source, and the first The output end is connected to the input end of the first modulator, the second output end, the first end of the circulator, the third end of the circulator, the second modulator, the delayer and the second input end are connected to form a fiber ring, the second end of the circulator is connected to the first end of the active optical fiber, the second end of the active optical fiber is connected to the chirped fiber Bragg grating The first end is connected, and the second end of the chirped fiber Bragg grating is connected with the output end of the pumping source. 2. The photoacoustic signal generating device according to claim 1, wherein the seed source is used to emit a seed pulse, and the seed pulse is incident into the active optical fiber ring; When the seed pulse is transmitted in the active optical fiber ring, the second modulator modulates the number of cycles of the pulse to adjust the number of pulses in the cluster, and the delayer modulates the cycle time of the pulse to adjust the number of pulses in the cluster. Pulse spacing, the chirped fiber Bragg grating provides negative dispersion to compensate for the pulse broadening of the seed pulse in the active fiber ring, the pump source and the active fiber provide gain to adjust the energy; The first modulator and the second modulator modulate the time domain width and the repetition frequency. 3. The photoacoustic signal generating device according to claim 1, wherein the second output end of the coupler is connected to the first end of the circulator, and the third end of the circulator is connected to the first end of the circulator. The input end of the second modulator is connected, the output end of the second modulator is connected to the first end of the delayer, and the second end of the delayer is connected to the second input end. 4 . The photoacoustic signal generating device according to claim 1 , wherein the light source module further comprises an amplifier, and an input end of the amplifier is connected to an output end of the first modulator. 5 . The photoacoustic signal generating device according to claim 4 , wherein the light source module further comprises a pulse compressor, and an input end of the pulse compressor is connected to an output end of the amplifier. 6. The photoacoustic signal generating device according to claim 1, wherein the delayer comprises a first collimator and a second collimator, and the first collimator and the second collimator The distance between the switches is adjustable to adjust the transmission time of pulses in the active optical fiber ring. 7. The photoacoustic signal generating device according to claim 1, wherein the optical fiber used in the active optical fiber ring is a polarization maintaining optical fiber. 8. The photoacoustic signal generating device according to claim 1, wherein the first modulator comprises an acousto-optic modulator or an electro-optic modulator, and the second modulator comprises an acousto-optic modulator or an electro-optic modulator . 9. The photoacoustic signal generating device according to claim 1, wherein the photoacoustic signal detection module further comprises: a displacement platform, the displacement platform is used to carry the object to be measured; A beam adjustment unit, the beam adjustment unit includes at least one mirror and at least one converging lens, the mirror is used to change the transmission direction of the pulse cluster, and the converging lens is used to converge the pulse cluster to the object to be measured. 10. A photoacoustic signal generation method, characterized in that it is suitable for the photoacoustic signal generation device according to any one of claims 1 to 9, the photoacoustic signal generation method comprising: The seed source outputs the seed pulse; The seed pulses are transmitted through the active optical fiber ring to form a plurality of pulse clusters, which are modulated by the first modulator into preset time-domain width, preset energy, preset repetition frequency, intra-cluster pulse interval and the number of intra-cluster pulses the pulse cluster; The pulse cluster is incident on the object to be measured to excite a photoacoustic signal; The photoacoustic signal detection module is used for detecting the photoacoustic signal.

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