CN116093714A - Photoacoustic signal generation 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

Photoacoustic signal generation device and method

Technical Field

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

Background

When a short pulse laser is irradiated into tissue, the tissue thermally expands due to absorption of laser energy, producing an ultrasonic signal, a phenomenon known as the photoacoustic effect. The photoacoustic imaging technology combines the advantages of high contrast of pure optical imaging and high penetration depth of pure ultrasonic imaging, and has no damage, no ionization effect and the like. Photoacoustic imaging is mainly divided into two major categories, namely photoacoustic tomography (PACT) and photoacoustic microscopy (PAM), and the two imaging modes have different requirements on imaging depth and spatial resolution, so that when different imaging applications are carried out, the component parameters of the photoacoustic imaging system need to be adjusted and selected.

The pulse width is limited by the difficulty in tuning the pulse width of one laser in the existing laser technology, meanwhile, PACT requires pulse energy to reach a larger imaging depth in mJ level, but pulse repetition frequency is limited by large energy, only in Hz level can be reached, imaging speed is severely limited, PAM generally requires energy in nJ-uJ level, and therefore the pulse laser with high repetition frequency (in MHz level can be reached) can be fully utilized, higher imaging speed is achieved, pulse energy and repetition frequency are difficult to be compatible, and development of photoacoustic imaging is limited.

In the prior art, a plurality of lasers with different parameters are required to be purchased to meet the requirements of photoacoustic researches on different materials or different application fields, a nanosecond laser is generally used as a light source for generating photoacoustic signals in the photoacoustic imaging field, and the generation mode of nanosecond pulses limits the repetition frequency of the pulses, so that the improvement of parameters such as the signal-to-noise ratio and the imaging speed of the photoacoustic signals is limited, and the development of the photoacoustic imaging field is further limited to a certain extent. Therefore, a laser with a relatively high pulse repetition rate, a relatively high pulse width, a relatively high energy and a relatively high repetition rate is needed to meet the above requirements, so as to realize a pulse output with a arbitrarily adjustable pulse width, a arbitrarily adjustable repetition rate and a arbitrarily adjustable energy, and improve the flexibility of a light source and the photo-acoustic imaging performance.

Disclosure of Invention

The embodiment of the invention provides a photoacoustic signal generating device and a photoacoustic signal generating method, wherein laser is utilized to obtain a laser pulse cluster with any time domain width through an active optical fiber loop, and the time domain width, energy, repetition frequency, shape and intra-cluster pulse interval of the laser pulse cluster are all adjustable, so that the flexibility of a light source is greatly improved, and the problem that the repetition frequency of a nanosecond laser is difficult to lift is solved.

According to an aspect of the present invention, there is provided a photoacoustic signal generating apparatus, including a light source module and a photoacoustic signal detecting module, the light source module is configured to output a pulse cluster including a plurality of ultrashort pulses, a time domain width, energy, a repetition frequency, an intra-cluster pulse interval, and an intra-cluster pulse number of the pulse cluster are all adjustable, the pulse cluster is incident on an object to be measured to excite a photoacoustic signal, and the photoacoustic signal detecting module is configured to detect the photoacoustic signal;

the light source module comprises a seed source, an active optical fiber ring and a first modulator, wherein the active optical fiber ring comprises a coupler, a circulator, an active optical fiber, a chirped fiber Bragg grating, a pumping source, a second modulator and a delayer, the coupler comprises a first input end, a second input end, a first output end and a 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 into an optical fiber ring, the second end of the circulator is connected with the first end of the active optical fiber, 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 configured to emit a seed pulse, the seed pulse being incident into the active fiber ring;

when the seed pulse is transmitted in the active optical fiber loop, the second modulator modulates the circulation times of the pulse to adjust the quantity of the pulse in the cluster, the delay device modulates the circulation time of the pulse to adjust the interval of the pulse in the cluster, the chirped fiber Bragg grating provides negative dispersion to compensate the pulse broadening of the seed pulse in the active optical fiber loop, and the pump source and the active optical fiber provide gain to adjust energy;

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

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

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

Optionally, the light source module further comprises a pulse compressor, and an input end of the pulse compressor is connected with an output end of the amplifier.

Optionally, the delay comprises a first collimator and a second collimator, the distance between the first collimator and the second collimator being adjustable to adjust the transit time of the pulse within the active fiber loop.

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

Optionally, 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.

Optionally, the photoacoustic signal detecting module further includes:

the displacement platform is used for bearing an object to be measured;

the light beam adjusting unit comprises at least one reflecting mirror and at least one converging lens, the reflecting mirror is used for changing the transmission direction of the pulse cluster, and the converging lens is used for converging the pulse cluster to an object to be measured.

According to another aspect of the present invention, there is provided a photoacoustic signal generating method, suitable for use in any one of the photoacoustic signal generating apparatuses described above, comprising:

the seed source outputs a seed pulse;

the seed pulse is transmitted through an active optical fiber ring to form a plurality of pulse clusters, and the pulse clusters are modulated into pulse clusters with preset time domain width, preset energy, preset repetition frequency, pulse intervals in the clusters and pulse quantity in the clusters through a first modulator;

the pulse cluster is incident to an object to be detected, and a photoacoustic signal is excited;

the photoacoustic signal detection module is used for detecting a photoacoustic signal.

The embodiment of the invention provides a photoacoustic signal generating device, which comprises a light source module and a photoacoustic signal detecting module, wherein the light source module is used for outputting a pulse cluster comprising a plurality of ultrashort pulses, the time domain width, energy, repetition frequency, intra-cluster pulse interval and intra-cluster pulse quantity of the pulse cluster are all adjustable, the pulse cluster is incident to an object to be detected to excite a photoacoustic signal, and the photoacoustic signal detecting module is used for detecting the photoacoustic signal; the light source module comprises a seed source, an active optical fiber ring and a first modulator, wherein the active optical fiber ring comprises a coupler, a circulator, an active optical fiber, a chirped fiber Bragg grating, a pumping source, a second modulator and a delayer, the coupler comprises a first input end, a second input end, a first output end and a 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 into an optical fiber ring, the second end of the circulator is connected with the first end of the active optical fiber, 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. The laser pulse cluster with arbitrary time domain width is obtained through the active optical fiber loop by utilizing laser, the time domain width, the energy, the repetition frequency, the shape and the pulse interval in the cluster of the laser pulse cluster are all adjustable, so that the flexibility of the light source is greatly improved, and the problem that the repetition frequency of the nanosecond laser is difficult to lift is solved.

It should be understood that the description in this section is not intended to identify key or critical features of the embodiments of the invention or to delineate the scope of the invention. Other features of the present invention will become apparent from the description that follows.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic structural diagram of a photoacoustic signal generating apparatus according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of another photoacoustic signal generating apparatus according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of another photoacoustic signal generating apparatus according to an embodiment of the present invention;

fig. 4 is a schematic structural diagram of a photoacoustic signal generating apparatus according to an embodiment of the present invention;

fig. 5 is a schematic structural diagram of a photoacoustic signal generating apparatus according to an embodiment of the present invention;

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

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

Detailed Description

In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.

It should be noted that the terms "first," "second," and the like in the description and the claims of the present invention and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the invention described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed or inherent to such process, method, article, or apparatus.

Fig. 1 is a schematic structural diagram of a photoacoustic signal generating apparatus according to an embodiment of the present invention, as shown in fig. 1, the photoacoustic signal generating apparatus specifically includes: the photoacoustic detection device comprises a light source module 10 and a photoacoustic signal detection module 20, wherein the light source module 10 is used for outputting a pulse cluster comprising a plurality of ultra-short pulses, the time domain width, the energy, the repetition frequency, the intra-cluster pulse interval and the intra-cluster pulse number of the pulse cluster are all adjustable, the pulse cluster is incident to an object to be detected (not shown in fig. 1) to excite a photoacoustic signal, and the photoacoustic signal detection module 20 is used for detecting the photoacoustic signal;

the light source module 10 includes a seed source 11, an active optical fiber ring 12 and a first modulator 13, 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, a second modulator 127 and a retarder 126, the coupler 121 includes a first input end, a second input end, a first output end and a second output end, the first input end is connected with the output end of the seed source 11, the first output end is connected with the input end of the first modulator 13, the second output end, a first end a of the circulator 122, a third end c of the circulator 122, the second modulator 127, the retarder 126 and the second input end are connected into an optical fiber ring, a 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 second end 124 of the chirped fiber bragg grating is connected with the output end of the pump source 125. The seed source 11 outputs ultrashort pulses having a temporal width on the order of picoseconds or femtoseconds.

The pulse laser is transmitted in the optical fiber with energy loss, the pump source 125 can transmit the pump light and absorb the pump light by the active optical fiber 123 and amplify the pulse laser, and meanwhile, the dispersion of the chirped fiber bragg grating 124 is opposite to that of the active optical fiber 123, so as to compensate the difference of spectrum phases, thereby obtaining ultra-short pulses with the same duration, and the combined setting of the pump source 125 and the active optical fiber 123 can obtain the pulse cluster envelope of preset energy by actively adjusting the gain or loss of the optical fiber loop. The second modulator 127 is used to control the number of pulses contained in the pulse train, and when the number of pulses reaches a desired number, the second modulator 127 turns off and interrupts the laser pulse cycle within the active fiber loop, thereby forming the pulse train.

It should be noted that the second modulator 127 and the retarder 126 are connected in the active optical fiber loop 12, and the positions and the connection sequence of the second modulator 127 and the retarder 126 in the loop are not limited in this embodiment, and the positions and the sequence of the second modulator 127 and the retarder 126 shown in fig. 1 are only referred to, and are not limiting in the embodiment of the present invention.

It will be appreciated that the pulse output by the seed source 11 is input from the first input end of the coupler 121, the same pulse (for example, the splitting ratio may be 50:50) may be output from the first output end and the second output end of the coupler 121, and enter the first modulator 13 through the first output end and enter the circulator 122 (the first end, i.e. the a end, of the circulator) through the second output end, the pump source 125, the chirped fiber bragg grating 124 and the active fiber 123 are sequentially connected, and enter the second end, i.e. the b end, of the circulator 122, to act as gain or loss for the pulse laser in the fiber loop, and then enter the coupler 121 through the third end, i.e. the c end, of the circulator 122, through the second input end after passing through the second modulator 127 and the delay 126, when the pulse reaches the required number in the second modulator 127, the second modulator 127 closes and interrupts the laser pulse circulation in the active optical fiber loop to form a pulse cluster, the delayer 126 can adjust the time interval of two adjacent pulses in the pulse cluster envelope by adjusting the single circulation time of the pulses in the active optical fiber loop 12 so as to change the time domain width and energy of the pulse cluster envelope, the two pulses enter the first modulator 13 from the first output end of the coupler 121, the second output end of the coupler 121 enters the circulator 122 and repeats the above process, the modulated pulse cluster envelope output by the first output end of the coupler 121 picks up a pulse sequence by the first modulator 13, synthesizes ultrashort pulse clusters with any time width and any repetition frequency, and transmits the ultrashort pulse clusters to the detection module 20 to detect an object to be detected to generate corresponding photoacoustic signals.

Illustratively, a seed pulse sequence with a certain repetition frequency is emitted from the seed source 11, the seed pulse sequence is input to the coupler 121, the same single seed pulse is output from the first output end and the second output end of the coupler 121, after the single seed pulse output from the second output end is transmitted in the active optical fiber ring 12, the time for reaching the second input end of the coupler 121 is later than the second pulse emitted from the seed source 11, the two pulses form a pulse cluster with two pulses, after the two pulses are transmitted through the active optical fiber ring 12 again, the time for reaching the coupler 121 is later than the third pulse emitted from the seed source 11, a pulse cluster with three pulses is formed, and the above process is repeated, so that a pulse cluster with multiple pulses can be obtained. The second modulator 127 may control the number of pulses in the pulse cluster, the delay 126 may control the time interval between two pulses in the pulse cluster, the first modulator 13 may select a desired pulse cluster, and the active fiber 123 may control the gain, so as to achieve that the pulse cluster time domain width, energy, repetition frequency, shape and intra-cluster pulse interval are all adjustable. It will be appreciated that if the second modulator 127 controls the pulse train to include n ultrashort pulses, then the active fiber loop 12 outputs n pulse trains including one pulse, two pulses … …, and n pulses, and then the first modulator 13 filters out the first n-1 pulse trains, passing through the pulse trains including n pulses.

The embodiment of the invention provides a photoacoustic signal generating device, which comprises a light source module and a photoacoustic signal detecting module, wherein the light source module is used for outputting a pulse cluster comprising a plurality of pulses, the time domain width, the energy, the repetition frequency, the pulse interval in the cluster and the pulse quantity in the cluster of the pulse cluster are all adjustable, the pulse cluster is incident to an object to be detected to excite a photoacoustic signal, and the photoacoustic signal detecting module is used for detecting the photoacoustic signal; the light source module comprises a seed source, an active optical fiber ring and a first modulator, wherein the active optical fiber ring comprises a coupler, a circulator, an active optical fiber, a chirped fiber Bragg grating, a pumping source, a second modulator and a delayer, the coupler comprises a first input end, a second input end, a first output end and a 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 into an optical fiber ring, the second end of the circulator is connected with the first end of the active optical fiber, 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. The laser pulse cluster with any time domain width is obtained through the active optical fiber loop by utilizing laser, the time domain width, the energy, the repetition frequency, the shape and the pulse interval in the cluster of the laser pulse cluster are all adjustable, so that the flexibility of the light source is greatly improved, and the problem that the repetition frequency of the laser is difficult to lift is solved.

In the above process, the pulse laser enters the coupler to the pulse cluster coupled out of the plurality of pulses, and the time domain width, the energy, the repetition frequency, the pulse interval in the cluster and the number of pulses in the cluster of the pulse cluster are adjusted, and with continued reference to fig. 1, the following is specifically described:

optionally, the seed source 11 is configured to emit a seed pulse, and the seed pulse is incident into the active optical fiber ring 12;

while the seed pulses are transmitted within the active fiber ring 12, the second modulator 127 modulates the number of cycles of the pulses to adjust the number of pulses within the cluster, the delay 126 modulates the cycle time of the pulses to adjust the inter-cluster pulse spacing, the chirped fiber bragg grating 124 provides negative dispersion to compensate for the pulse broadening of the seed pulses within the active fiber ring 12, and the pump source 125 and the active fiber 123 provide gain to adjust the energy;

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

Wherein, during the pulse laser enters the coupler 121 to couple out the pulse clusters of a plurality of pulses, energy loss exists in the transmission process of the laser in the active optical fiber ring 12, and the pump source 125 and the active optical fiber 123 can provide gain for the laser transmitted in the active optical fiber 123 to adjust energy;

the second modulator 127 accumulates the pulses and counts the number, and when the pulses reach the required number, the second modulator closes and interrupts the laser pulse circulation in the active fiber loop to form pulse clusters, and the second modulator 127 modulates the circulation times of the pulses to adjust the pulse number in the clusters, if the required number of pulses is larger, the pulse circulation times can be increased, if the required number of pulses is smaller, the pulse circulation times can be reduced, and the specific circulation times are not limited.

The delay 126 may adjust the time interval between two adjacent pulses in the pulse cluster envelope by adjusting the single cycle time of the pulses within the active fiber loop 12 to vary the time domain width of the pulse cluster envelope.

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

Illustratively, the seed source emits pulses of the order of fs of the seed, and the pulse interval of the order of sub-ps-ns can be modulated by increasing the cycle time of the pulses through a delay device; the seed source emits the pulse with the seed pulse energy of pJ level, and the pulse cluster with the pulse energy of nJ-mJ level can be output through the gain of the pump source and the active optical fiber; the repetition frequency of the modulation of the pulse train by the first modulator 13 may be 10Hz-MHz.

According to the photoacoustic signal generating device provided by the embodiment of the invention, the circulation times of pulses can be modulated by the second modulator to adjust the pulse quantity in the cluster, the delayer adjusts the single circulation time of seed pulses in the active optical fiber ring to change the pulse interval in the cluster, the chirped fiber Bragg grating compensates dispersion, the pump source and the active optical fiber provide gain to adjust energy, the first modulator and the second modulator modulate the time domain width and the repetition frequency, pulse clusters with any time width and any repetition frequency are output for the photoacoustic detection module to detect an object to be detected to generate corresponding photoacoustic signals, the time domain width, the energy, the repetition frequency, the shape and the pulse interval in the cluster of the output laser pulse clusters are all adjustable, so that the flexibility of a light source is greatly improved, and the problem that the repetition frequency of a laser is difficult to lift is solved.

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

Fig. 2 is a schematic structural diagram of another photoacoustic signal generating apparatus according to an embodiment of the present invention, and referring to fig. 2, an embodiment of the present invention provides a photoacoustic signal generating apparatus specifically including: the optical fiber comprises a light source module 10, a photoacoustic signal detection module 20, a seed source 11, an active optical fiber ring 12, a first modulator 13, an amplifier 14, a coupler 121, a circulator 122, an active optical fiber 123, a chirped fiber bragg grating 124, a pump source 125, a retarder 126 and a 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, the output terminal of the second modulator 127 is connected to the first terminal of the delay 126, and the second terminal of the delay 126 is connected to the second input terminal.

Wherein, the circulator 126 can be an optical fiber circulator; the delay 126 includes, but is not limited to, a single or multiple devices that extend the pulse transmission time, such as a fiber optic delay, or a combination of two collimating lenses, without limitation to the type and model of device.

Optionally, the light source module 110 further comprises an amplifier 14, an input of the amplifier 14 being connected to an output of the first modulator 13.

The amplifier 14 is used for amplifying the pulse cluster with the repetition frequency of the pulse sequence picked up by the first modulator 13, and improving the energy of the pulse cluster. The amplifier 14 includes, but is not limited to, a fiber amplifier, a raman optical amplifier, a semiconductor optical amplifier, and other related types of laser amplifiers, and is not limited in its category and model.

According to the photoacoustic signal generating device provided by the embodiment of the invention, the circulation times of pulses can be modulated by the second modulator to adjust the pulse quantity in the cluster, the circulation time of the pulses can be modulated by the delay device to adjust the pulse interval in the cluster, the chirped fiber Bragg grating compensates dispersion, the pump source and the active fiber provide gain to adjust energy, the first modulator and the second modulator modulate the time domain width and the repetition frequency, pulse clusters with arbitrary time width and arbitrary repetition frequency are output, the energy of the laser pulse clusters output by the laser is further improved through the amplifier, so that a photoacoustic detection module detects an object to be detected to generate a corresponding photoacoustic signal, the energy of the laser pulse clusters output by the laser is improved, and the time domain width, the energy, the repetition frequency, the shape and the pulse interval in the laser pulse clusters are all adjustable, so that the flexibility of a light source is greatly improved.

Further optimizing the photoacoustic signal generating apparatus based on the above embodiment, optionally, the light source module further includes a pulse compressor, and an input end of the pulse compressor is connected to an output end of the amplifier.

Fig. 3 is a schematic structural diagram of another photoacoustic signal generating apparatus according to an embodiment of the present invention, and referring to fig. 3, an embodiment of the present invention provides a photoacoustic signal generating apparatus specifically including: the optical fiber optical device comprises a light source module 10, a photoacoustic signal detection module 20, a seed source 11, an active optical fiber loop 12, a first modulator 13, an amplifier 14, a pulse compressor 15, a coupler 121, a circulator 122, an active optical fiber 123, a chirped fiber bragg grating 124, a pump source 125, a delay 126 and a second modulator 127.

Optionally, the light source module 10 further comprises a pulse compressor 15, an input of the pulse compressor 15 being connected to an output of the amplifier 14.

The pulse compressor 15 is used to compress the pulse train output through the amplifier 14, compensate the broadening generated due to chromatic dispersion during transmission, and shorten the time domain width, and the pulse compressor 15 includes, but is not limited to, related optical devices, such as a volume grating.

According to the photoacoustic signal generating device provided by the embodiment of the invention, the number of pulses in the cluster can be regulated by modulating the circulation times of the pulses through the second modulator, the circulation time of the pulses is modulated by the delayer to regulate the pulse interval in the cluster, the chirped fiber Bragg grating compensates dispersion, the pump source and the active fiber provide gain to regulate energy, the first modulator and the second modulator modulate the time domain width and the repetition frequency, pulse clusters with arbitrary time width and arbitrary repetition frequency are output, the energy of the laser pulse clusters is further improved through the amplifier, the time domain width of the pulse clusters can be further shortened through the pulse compressor, the photoacoustic detection module can detect an object to be detected to generate corresponding photoacoustic signals, and the time domain width, the energy, the repetition frequency, the shape and the pulse interval in the cluster of the output laser pulse clusters are all adjustable, so that the flexibility of the light source is greatly increased.

Further optimizing the photoacoustic signal generating apparatus based on the above embodiment, optionally, the delay may include a first collimator and a second collimator.

Fig. 4 is a schematic structural diagram of still another photoacoustic signal generating apparatus according to an embodiment of the present invention, and referring to fig. 3, an embodiment of the present invention provides a photoacoustic signal generating apparatus specifically including: the optical fiber coupler comprises a light source module 10, a photoacoustic signal detection module 20, a seed source 11, an active optical fiber ring 12, a first modulator 13, an amplifier 14, a pulse compressor 15, a coupler 121, a circulator 122, an active optical fiber 123, a chirped fiber bragg grating 124, a pump source 125, a second modulator 127, a first collimator 1261 and a second collimator 1262.

Optionally, the delay includes a first collimator 1261 and a second collimator 1262, the distance between the first collimator 1261 and the second collimator 1262 being adjustable to adjust the transit time of the pulse within the active fiber loop 12.

Wherein the parameters related to the first collimator and the second collimator are matched, including but not limited to, a fiber collimator, a soller collimator, a general collimator (low energy, medium energy, high energy, low resolution, medium resolution, high resolution), a radiation collimator, etc., and if the transmission time of the pulse in the active fiber loop 12 needs to be prolonged, the distance between the first collimator 1261 and the second collimator 1262 is increased, and if the transmission time of the pulse in the active fiber loop 12 needs to be shortened, the distance between the first collimator 1261 and the second collimator 1262 is reduced, and in particular, the distance length between the first collimator 1261 and the second collimator 1262 is adjusted to be a set value.

According to the photoacoustic signal generating device provided by the embodiment of the invention, the number of pulses in the cluster can be regulated by modulating the circulation times of the pulses through the second modulator, the circulation time of the pulses is modulated by the delayer to regulate the pulse interval in the cluster, the chirped fiber Bragg grating compensates for chromatic dispersion, the pump source and the active fiber provide gain to regulate energy, the first modulator and the second modulator modulate the time domain width and the repetition frequency, pulse clusters with arbitrary time width and arbitrary repetition frequency are output, the energy of the laser pulse clusters is further improved through the amplifier, the time domain width of the pulse clusters can be further shortened through the pulse compressor, the broadening generated due to chromatic dispersion and the like in the compensation transmission process is corrected, so that the photoacoustic detection module detects an object to be detected to generate corresponding photoacoustic signals, and the time domain width, the energy, the repetition frequency, the shape and the pulse interval in the cluster of the output laser pulse clusters are adjustable, so that the flexibility of the light source is greatly increased.

On the basis of the above embodiments, modified embodiments of the above embodiments are proposed, and it is to be noted here that only the differences from the above embodiments are described in the modified embodiments for the sake of brevity of description.

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

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

The related parameters of the devices should be matched with each other, and specific types and models are not limited.

Based on the above embodiment, the photoacoustic signal detection module in the photoacoustic signal generating apparatus is further optimized, and optionally, the photoacoustic signal detection module specifically further includes: the displacement platform and the light beam adjusting unit comprise at least one reflecting mirror and at least one converging lens.

Fig. 5 is a schematic structural diagram of a photoacoustic signal generating apparatus according to an embodiment of the present invention; referring to fig. 3, an embodiment of the present invention provides a photoacoustic signal generating apparatus, which specifically includes: the optical fiber displacement device comprises a light source module 10, a photoacoustic signal detection module 20, a seed source 11, an active optical fiber ring 12, a first modulator 13, an amplifier 14, a pulse compressor 15, a coupler 121, a circulator 122, an active optical fiber 123, a chirped fiber bragg grating 124, a pump source 125, a second modulator 127, a first collimator 1261, a second collimator 1262, a displacement platform 21 and a light beam adjusting unit 22.

Optionally, the photoacoustic signal detecting module 20 further includes:

the displacement platform 21, the displacement platform 21 is used for bearing the object to be measured;

the beam adjusting unit 22 comprises at least one reflecting mirror 221 and at least one converging lens 222, wherein the reflecting mirror 221 is used for changing the transmission direction of the pulse cluster, and the converging lens 222 is used for converging the pulse cluster to an object to be measured.

The displacement platform 21 can move in a hardware and/or software control mode, so that the corresponding area of the object to be detected is set to be detected by the pulse to generate a corresponding photoacoustic signal; mirror 221 includes, but is not limited to, a flat mirror and other related optics or combinations that can change the optical path; the converging lens 222 includes, but is not limited to, a biconvex lens, a single convex lens, and other related focusable optics or combinations.

Fig. 6 is a schematic diagram of a photoacoustic signal generating method according to an embodiment of the present invention, which is applicable to a case of generating a photoacoustic signal, and referring to fig. 6 in conjunction with fig. 5, an embodiment of the present invention provides a photoacoustic signal generating method applicable to any one of the above-mentioned photoacoustic signal generating apparatuses, and the photoacoustic signal generating method includes:

s110, outputting seed pulses by a seed source;

wherein the seed source may output ultrashort pulses at a repetition frequency of tens of megahertz.

S120, seed pulses are transmitted through an active optical fiber ring to form a plurality of pulse clusters, and the pulse clusters are modulated into pulse clusters with preset time domain width, preset energy, preset repetition frequency, intra-cluster pulse intervals and intra-cluster pulse quantity through a first modulator;

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

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

the pulse passes through a second modulator to obtain pulse cluster envelopes of the number of preset pulse sequences;

the pulses pass through a delay to modulate the cycle time of the pulses to obtain a pulse cluster envelope of preset intra-cluster pulse intervals.

S130, the pulse cluster is incident to an object to be detected, and a photoacoustic signal is excited;

and S140, the photoacoustic signal detection module is used for detecting a photoacoustic signal.

It will be appreciated that the seed pulse output by the seed source 11 is input from the first input end of the coupler 121, the same pulse (for example, the splitting ratio may be 50:50) may be output from the first output end and the second output end of the coupler 121, the pulse enters the first modulator 13 through the first output end, the pulse enters the circulator 122 (the first end, i.e., the a end) through the second output end, the pump source 125, the chirped fiber bragg grating 124 and the active optical fiber 123 are sequentially connected, and the pulse laser in the optical fiber loop plays a role of gain or loss, and then enters the coupler 121 from the third end, i.e., the c end, of the circulator 122 through the second input end after passing through the second modulator 127 and the delay, when the pulse reaches the required number, the second modulator 127 is closed and interrupts the laser pulse cycle in the active optical fiber loop, so as to form a pulse cluster, the delay 126 may sequentially connect with the active optical fiber 122 through adjusting the single cycle time of the pulse, thereby adjusting the time of the pulse envelope of the adjacent pulse, and the two pulse envelopes, the pulse clusters are repeatedly coupled from the first end to the second end, the second end of the optical fiber coupler 121 is coupled to the corresponding to the first end, the second end of the coupler 121 is coupled to the corresponding pulse envelope modulator, and the pulse envelope signal is output from the first end of the second end of the coupler 121, and the pulse cluster is coupled to the second end of the corresponding pulse coupler is output, and the pulse signal is output from the first end of the coupler 121, and the pulse coupler is coupled to the pulse coupler is repeatedly coupled to the pulse coupler and the pulse signal to the pulse coupler is output from the pulse coupler 13.

The embodiment of the invention provides a photoacoustic signal generation method, which comprises the steps of firstly, outputting seed pulses by a seed source; then, seed pulses are transmitted through an active optical fiber ring to form a plurality of pulse clusters, the pulse clusters are modulated into pulse clusters with preset time domain width, preset energy, preset repetition frequency, pulse intervals in the clusters and pulse numbers in the clusters through a first modulator, wherein a second modulator controls the pulse numbers in the pulse clusters, the first modulator picks up pulse sequences, synthesizes the pulse clusters with any time width and any repetition frequency, and transmits the pulse clusters to a photoacoustic detection module; the method specifically comprises the following steps: the seed pulse is subjected to combination setting of a pumping source and an active optical fiber, the gain or the loss of an optical fiber loop can be actively regulated to obtain pulse cluster envelopes with any shape, the pulse cluster envelopes with the number of preset pulse sequences are obtained through a second modulator, and then the pulse cluster envelopes with the pulse intervals in the preset cluster are obtained through the circulation time of the pulse modulated through a delay; finally, the pulse cluster is incident to an object to be detected, the photoacoustic signal is excited, and the photoacoustic signal detection module is used for detecting the photoacoustic signal. The method is used for obtaining the laser pulse cluster with any time domain width through active optical fiber loop modulation, the time domain width, energy, repetition frequency, shape and intra-cluster pulse interval of the laser pulse cluster are all adjustable, so that the flexibility of a light source is greatly improved, and the problem that the repetition frequency of a laser is difficult to lift is solved.

The above embodiments do not limit the scope of the present invention. It will be apparent to those skilled in the art that various modifications, combinations, sub-combinations and alternatives are possible, depending on design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of the present invention.

Claims (10)

1. The photoacoustic signal generating device is characterized by comprising a light source module and a photoacoustic signal detecting module, wherein the light source module is used for outputting a pulse cluster comprising a plurality of ultrashort pulses, the time domain width, the energy, the repetition frequency, the intra-cluster pulse interval and the intra-cluster pulse number of the pulse cluster are all adjustable, the pulse cluster is incident to an object to be detected to excite a photoacoustic signal, and the photoacoustic signal detecting module is used for detecting the photoacoustic signal;

the light source module comprises a seed source, an active optical fiber ring and a first modulator, wherein the active optical fiber ring comprises a coupler, a circulator, an active optical fiber, a chirped fiber Bragg grating, a pump source, a second modulator and a delayer, the coupler comprises a first input end, a second input end, a first output end and a 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 into an optical fiber ring, the second end of the circulator is connected with the first end of the active optical fiber, 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 pump source.

2. The photoacoustic signal generating apparatus of claim 1 wherein the seed source is configured to emit a seed pulse that is incident into the active fiber optic ring;

the second modulator modulates the number of cycles of the pulses to adjust the number of pulses in the cluster, the retarder modulates the cycle time of the pulses to adjust the inter-cluster pulse spacing, the chirped fiber bragg grating provides negative dispersion to compensate for pulse broadening of the seed pulses in the active fiber loop, the pump source and the active fiber provide gain to adjust the energy when the seed pulses are transmitted in the active fiber loop;

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

3. The photoacoustic signal generating apparatus of claim 1 wherein the second output of the coupler is connected to the first end of the circulator, the third end of the circulator is connected to the input of the second modulator, the output of the second modulator is connected to the first end of the delay, and the second end of the delay is connected to the second input.

4. The photoacoustic signal generating apparatus according to claim 1, wherein the light source module further comprises an amplifier, an input terminal of the amplifier being connected to an output terminal of the first modulator.

5. The photoacoustic signal generating apparatus of claim 4 wherein the light source module further comprises a pulse compressor, an input of the pulse compressor being connected to an output of the amplifier.

6. The photoacoustic signal generating apparatus of claim 1 wherein the delay comprises a first collimator and a second collimator, the distance between the first collimator and the second collimator being adjustable to adjust the transit time of the pulse within the active fiber loop.

7. The photoacoustic signal generating apparatus of claim 1 wherein the optical fiber used for the active optical fiber ring is a polarization maintaining optical fiber.

8. The photoacoustic signal generating apparatus 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 apparatus according to claim 1, wherein the photoacoustic signal detecting module further comprises:

the displacement platform is used for bearing the object to be detected;

the light beam adjusting unit comprises at least one reflecting mirror and at least one converging lens, wherein the reflecting mirror is used for changing the transmission direction of the pulse cluster, and the converging lens is used for converging the pulse cluster to the object to be measured.

10. A photoacoustic signal generating method, characterized by being applied to the photoacoustic signal generating apparatus of any one of claims 1 to 9, comprising:

the seed source outputs a seed pulse;

the seed pulse is transmitted through an active optical fiber ring to form a plurality of pulse clusters, and the pulse clusters are modulated into pulse clusters with preset time domain width, preset energy, preset repetition frequency, intra-cluster pulse intervals and intra-cluster pulse quantity through the first modulator;

the pulse cluster is incident to an object to be detected, and a photoacoustic signal is excited;

the photoacoustic signal detection module is used for detecting the photoacoustic signal.

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