Swept laser and optical coherence tomography system

Abstract

The embodiment of the present application provides a frequency sweeping laser and an optical coherence tomography system, wherein the frequency sweeping laser comprises: a beam generating assembly for emitting a first beam; an acousto-optic deflector, wherein the first beam is diffracted in the acousto-optic deflector to obtain a first diffracted light; a first reflecting assembly, comprising a first reflecting surface and a second reflecting surface symmetrically arranged, wherein the first reflecting surface and the second reflecting surface reflect the first diffracted light back to the second surface; the second surface receives the first diffracted light incident in a second incident direction, wherein the second incident direction is opposite to the first incident direction, the first diffracted light is diffracted in the acousto-optic deflector to obtain a second diffracted light of the first diffracted light, and the second diffracted light is emitted from the first surface in a second exit direction; a wavelength selective reflecting element, wherein the second diffracted light is received and reflected back to the beam generating assembly. The embodiment of the present application can increase the scanning range of the laser output by the frequency sweeping laser.

Description

Technical Field

[0001] The present application belongs to the field of laser technology, and in particular relates to a frequency-sweeping laser and an optical coherence tomography system. Background Art

[0002] Optical Coherence Tomography (OCT) is a new type of non-destructive optical imaging technology. It uses the basic principle of weak coherent light interferometer. For example, it can detect the back reflection or scattering signal of the incident weak coherent light at different depths of the sample to be tested. By analyzing the interference signal, the depth information of the sample to be tested is extracted, and a two-dimensional tomographic image or three-dimensional image information of the sample to be tested is given. The advantages of OCT mainly include high resolution, high speed, high sensitivity, in vivo, non-invasive, and independent lateral and longitudinal resolutions. Because the axial resolution of OCT can reach the micron level and is easy to miniaturize, its application research in skin, cardiovascular disease, gastrointestinal disease, early diagnosis of cancer, etc. is becoming more and more extensive.

[0003] Generally speaking, the OCT process is as follows: first, the wavelength is scanned quickly by a swept laser, and then the intensity of the interference signal of the wavelength is detected with a point detector to obtain an interference spectrum; finally, the interference spectrum is Fourier transformed to obtain the microscopic structure information of the object, that is, to obtain a tomographic image of the sample to be tested.

[0004] However, the inventors of the present application have discovered that the scanning range or scanning depth of the laser output by the current frequency-sweeping laser is relatively small, so that the tomographic image of the sample to be tested obtained contains only less information, which is not conducive to the research and observation of the sample to be tested. Summary of the invention

[0005] The embodiments of the present application provide a frequency-sweeping laser and an optical coherence tomography system, which can increase the scanning range of the laser output by the frequency-sweeping laser, so that the acquired tomographic image of the sample to be tested can contain more information.

[0006] In a first aspect, an embodiment of the present application provides a frequency sweeping laser, which includes: a beam generating component for emitting a first beam; an acousto-optic deflector located on a propagation path of the first beam, the acousto-optic deflector including a first surface and a second surface that are arranged opposite to each other, the first surface receiving the first beam incident in a first incident direction, the first beam diffracting in the acousto-optic deflector to obtain a first diffracted light of the first beam, the first diffracted light emitting from the second surface in a first exit direction; a first reflecting component located on a propagation path of the first diffracted light, the first reflecting component including a first reflecting surface and a second reflecting surface that are symmetrically arranged, the first reflecting surface receiving the first diffracted light and reflecting the first diffracted light to the second A reflecting surface, and a second reflecting surface reflects the first diffracted light back to the second surface; the second surface receives the first diffracted light incident in a second incident direction, the second incident direction is opposite to the first incident direction, the first diffracted light is diffracted in the acousto-optic deflector to obtain a second diffracted light of the first diffracted light, the second diffracted light is emitted from the first surface in a second emitting direction, the second emitting direction is opposite to the first emitting direction; a wavelength selective reflecting element is located on the propagation path of the second diffracted light, is used to receive the second diffracted light, and reflect the second diffracted light back to the first surface, the second diffracted light then passes through the acousto-optic deflector, the second reflecting surface, the first reflecting surface and the acousto-optic deflector in sequence and returns to the light beam generating component.

[0007] In a second aspect, an embodiment of the present application provides an optical coherence tomography system, and the optical coherence tomography system includes a swept frequency laser as provided in the first aspect.

[0008] The inventor of the present application has found that a Doppler frequency shift occurs when the light beam passes through the acousto-optic deflector, and the superposition of the Doppler frequency shift will cause the scanning range of the laser output by the frequency sweeping laser to become smaller. In view of this, the embodiment of the present application provides a frequency sweeping laser and an optical coherence tomography system, by setting a symmetrical first reflection surface and a second reflection surface, after the first light beam passes through the acousto-optic deflector to diffract and obtain the first diffracted light, the first diffracted light is reflected back to the acousto-optic deflector through the first reflection surface and the second reflection surface, and the direction in which the first diffracted light enters the acousto-optic deflector is opposite to the direction in which the first light beam enters the acousto-optic deflector. In this way, the Doppler frequency shift that occurs when the first diffracted light enters the acousto-optic deflector is opposite to the frequency shift direction of the Doppler frequency shift that occurs when the first light beam enters the acousto-optic deflector, and the Doppler frequency shifts generated by the two can be offset, thereby weakening or even eliminating the Doppler frequency shift of the first light beam in the acousto-optic deflector, thereby increasing the scanning range of the laser output by the frequency sweeping laser, so that the tomographic image of the sample to be tested obtained can contain more information.

[0009] In addition, since the light enters the acousto-optic deflector twice from the incident acousto-optic deflector to the light incident wavelength selective reflection element, that is, two diffraction deflections occur, the deflection angle of the light actually changes from θ to 2θ. In this way, the angle range at which the light can be incident on the wavelength selective reflection element is increased to twice the original, so the wavelength range of the diffracted light of the preset wavelength returned by the wavelength selective reflection element can become wider, thereby further increasing the scanning range of the laser output by the swept laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solution of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0011] Figure 1 A schematic diagram for generating Doppler frequency shift;

[0012] Figure 2 A schematic diagram of the structure of a frequency-sweeping laser provided in an embodiment of the present application;

[0013] Figure 3 A schematic diagram of a partial structure of a frequency sweeping laser provided in an embodiment of the present application;

[0014] Figure 4 A schematic diagram of the structure of a corner reflector in a frequency-sweeping laser provided in an embodiment of the present application;

[0015] Figure 5 Schematic diagram of the propagation path of level 0 light;

[0016] Figure 6 Another structural schematic diagram of a frequency sweeping laser provided in an embodiment of the present application;

[0017] Figure 7 A schematic diagram of another structure of a frequency-sweeping laser provided in an embodiment of the present application;

[0018] Figure 8 A schematic diagram of another structure of a frequency-sweeping laser provided in an embodiment of the present application;

[0019] Fig. 9 A schematic diagram of another structure of a frequency sweeping laser provided in an embodiment of the present application. DETAILED DESCRIPTION

[0020] The features and exemplary embodiments of various aspects of the present application will be described in detail below. In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, rather than to limit the present application. For those skilled in the art, the present application can be implemented without the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present application by illustrating the examples of the present application.

[0021] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "include..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0022] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0023] Before describing the technical solutions provided by the embodiments of the present application, in order to facilitate the understanding of the embodiments of the present application, the present application first specifically describes the problems existing in the prior art:

[0024] As mentioned above, the OCT process is as follows: first, the wavelength is scanned quickly by a frequency-sweeping laser, and then the intensity of the interference signal of the wavelength is detected with a point detector to obtain an interference spectrum; finally, the interference spectrum is Fourier transformed to obtain the microscopic structure information of the object, that is, to obtain a tomographic image of the sample to be tested.

[0025] However, the inventors of the present application have found that the scanning range or scanning depth of the laser output by the current frequency sweeping laser is relatively small, which results in the obtained tomographic image of the sample to be tested only containing less information on the depth level, which is not conducive to the study and observation of the sample to be tested. Taking the sample to be tested as an eye as an example, assuming that the distance between the lens and the optic nerve head in the eye is 10 mm, and the scanning depth of the laser output by the current frequency sweeping laser is only 4 mm, then only one of the lens and the optic nerve head can be presented on the obtained tomographic image, and the lens and the optic nerve head cannot be presented on one tomographic image at the same time, which is not conducive to the study and observation of the eye as a whole.

[0026] In order to solve the technical problem that the scanning range of the laser output by the frequency-sweeping laser is small, the inventor of the present application first studied and analyzed the root cause of the above technical problem. The specific research and analysis process is as follows:

[0027] The inventor of this application discovered that Figure 1 As shown, each time the incident light beam 101 passes through the acousto-optic deflector 102, a Doppler frequency shift occurs. The so-called Doppler frequency shift can be understood as the frequency of the ultrasonic signal 103 transmitted in the acousto-optic deflector 102 being superimposed on the frequency of the incident light beam 101, causing the frequency of the incident light beam 101 to change (increase or decrease). Figure 1 The Y1' direction in the figure) and the propagation direction of the ultrasonic signal (such as Figure 1 When the propagation direction of the incident light beam 101 (e.g., Figure 1 When the Y2' direction in the image is opposite to the propagation direction of the ultrasonic signal, the frequency of the incident light beam 101 decreases. Due to the existence of Doppler frequency shift, the line width of the laser output by the frequency sweeping laser becomes wider, the coherence length of the laser becomes shorter, and the scanning range of the laser output by the frequency sweeping laser becomes smaller.

[0028] In view of the above research findings of the inventors, the embodiments of the present application provide a frequency-sweeping laser and an optical coherence tomography system, which can solve the technical problem in the related art that the scanning range of the laser output by the frequency-sweeping laser is small.

[0029] The technical concept of the embodiment of the present application is that a symmetrical first reflection surface and a second reflection surface are set in the frequency sweeping laser, and after the first light beam is diffracted by the acousto-optic deflector to obtain the first diffracted light, the first diffracted light is reflected back to the acousto-optic deflector through the first reflection surface and the second reflection surface, and the direction in which the first diffracted light enters the acousto-optic deflector is opposite to the direction in which the first light beam enters the acousto-optic deflector. In this way, the Doppler frequency shift that occurs when the first diffracted light enters the acousto-optic deflector is opposite to the frequency shift direction of the Doppler frequency shift that occurs when the first light beam enters the acousto-optic deflector, and the Doppler frequency shifts generated by the two can be offset, thereby weakening or even eliminating the Doppler frequency shift of the first light beam in the acousto-optic deflector, thereby increasing the scanning range of the laser output by the frequency sweeping laser, so that the tomographic image of the sample to be tested obtained can contain more information.

[0030] The following first introduces the swept frequency laser provided in the embodiment of the present application.

[0031] like Figure 2 As shown, the swept frequency laser 20 provided in the embodiment of the present application includes a beam generating component 201, an acousto-optic deflector 202, a first reflection component 203 and a wavelength selective reflection element 204. Exemplarily, the beam generating component 201 may be a component including a laser gain medium and a pump source, for example, the beam generating component 201 may include a laser gain chip, which is not limited in the embodiment of the present application. The beam generating component 201 is used to emit a beam. For the sake of distinction and description, the beam emitted by the beam generating component 201 is referred to as the first beam s.

[0032] The acousto-optic deflector 202 is located on the propagation path L1 of the first light beam s. The acousto-optic deflector 202 includes a first surface 202a and a second surface 202b that are arranged opposite to each other. The first surface 202a receives a light beam s incident in a first direction (eg, Figure 2 The first light beam s is incident on the acousto-optic deflector 202 in the Y1 direction, and the first light beam s is diffracted in the acousto-optic deflector 202 to obtain a first diffracted light s1 of the first light beam s. The first diffracted light s1 is emitted from the second surface 202b in a first exit direction (such as Figure 2 The optical fiber is emitted in the Y2 direction).

[0033] The first reflective component 203 is located on the propagation path L2 of the first diffracted light s1. The first reflective component 203 includes a first reflective surface 203a and a second reflective surface 203b symmetrically arranged. The first reflective surface 203a receives the first diffracted light s1 and reflects the first diffracted light s1 to the second reflective surface 203b. The second reflective surface 203b reflects the first diffracted light s1 back to the second surface 202b of the AOD 202.

[0034] The second surface 202b of the AOD 202 receives the light incident from a second incident direction (eg Figure 2The first diffracted light s1 is incident in the Y3 direction of the AOD 202. It is worth noting that the second incident direction is opposite to the first incident direction. The first diffracted light s1 is diffracted in the AOD 202 to obtain the second diffracted light s2 of the first diffracted light s1. The second diffracted light s2 is emitted from the first surface 202a of the AOD 202 in the second exit direction (as Figure 2 It is worth noting that the second emission direction is opposite to the first emission direction.

[0035] The wavelength selective reflection element 204 is located on the propagation path L3 of the second diffracted light s2, and is used to receive the second diffracted light s2 and reflect the second diffracted light s2 back to the first surface 202a of the acousto-optic deflector 202, and the second diffracted light s2 then passes through the acousto-optic deflector 202, the second reflection surface 203b, the first reflection surface 203a and the acousto-optic deflector 202 in sequence and returns to the light beam generating component 201.

[0036] Specifically, the extension direction of the wavelength selective reflection element 204 (eg Figure 2 Y5 direction shown) and the first direction (as shown Figure 2 The angle between the wavelength selective reflection element 204 and the first direction (in the Y direction shown in FIG. 1 ) is greater than 0 degrees. In this way, since the wavelength selective reflection element 204 is inclined, that is, there is a certain angle with the first direction, the second diffracted light s2 will be reflected back to the light beam generating component 201 by the wavelength selective reflection element 204 in a littrow mode. That is, the wavelength selective reflection element 204 can receive the second diffracted light s2 and reflect the second diffracted light s2 back to the first surface 202a of the acousto-optic deflector 202 along the propagation path L3 when the second diffracted light s2 enters the wavelength selective reflection element 204. Then, the second diffracted light s2 passes through the acousto-optic deflector 202, the second reflection surface 203b, the first reflection surface 203a and the acousto-optic deflector 202 in sequence and returns to the light beam generating component 201, so as to select the second diffracted light s2 of the preset wavelength from the first light beam s.

[0037] Exemplarily, the wavelength selective reflection element 204 may be a reflection mirror with a step-shaped structure or a sloped structure on the reflection surface, and the step-shaped structure or the sloped structure may be used to reflect the second diffracted light s2. In some specific examples, the wavelength selective reflection element 204 may include a grating.

[0038] In the embodiment of the present application, a symmetrical first reflection surface 203a and a second reflection surface 203b are set in the frequency sweeping laser 20. After the first light beam s is diffracted by the acousto-optic deflector 202 to obtain the first diffracted light s1, the first diffracted light s1 is reflected back to the acousto-optic deflector 202 by the first reflection surface 203a and the second reflection surface 203b, and the direction in which the first diffracted light s1 enters the acousto-optic deflector 202 is opposite to the direction in which the first light beam s enters the acousto-optic deflector 202. In this way, the Doppler frequency shift generated when the first diffracted light s1 enters the acousto-optic deflector 202 is opposite to the frequency shift direction of the Doppler frequency shift generated when the first light beam s enters the acousto-optic deflector 202, and the Doppler frequency shifts generated by the two can be offset, thereby weakening or even eliminating the Doppler frequency shift of the first light beam s in the acousto-optic deflector 202, thereby increasing the scanning range of the laser output by the frequency sweeping laser, so that the acquired tomographic image of the sample to be tested can contain more information.

[0039] In addition, since the light enters the acousto-optic deflector 202 twice from the incident acousto-optic deflector 202 to the light incident wavelength selective reflection element 204, that is, two diffraction deflections occur, the deflection angle of the light actually changes from θ to 2θ. In this way, the angle range at which the light can be incident on the wavelength selective reflection element 204 is increased to twice the original, so the wavelength range of the diffracted light of the preset wavelength returned by the wavelength selective reflection element 204 can become wider, thereby further increasing the scanning range of the laser output by the swept laser.

[0040] For ease of understanding, the implementation principle of canceling Doppler frequency shift is described in detail below with reference to some specific examples.

[0041] like Figure 3 As shown, according to some embodiments of the present application, the acousto-optic deflector 202 may optionally include an ultrasonic generating element 2021 and a crystal 2022, wherein the ultrasonic generating element 2021 and the crystal 2022 are arranged along a first direction (eg Figure 3 The ultrasonic generating element 2021 is used to generate and transmit an ultrasonic signal B to the crystal 2022. The propagation direction of the ultrasonic signal B can be parallel to the first direction. Driven by the ultrasonic signal, the medium in the crystal undergoes an acousto-optic effect to form a grating G. The grating G is arranged along the second direction (such as Figure 3 The second direction extends in the X direction in the image, and the grating G can be used to diffract the light beam passing through the grating G, such as diffracting the first light beam s passing through the grating G, and can also diffract the first diffracted light s1 passing through the grating G. The second direction intersects the first direction, for example, the second direction can be perpendicular to the first direction.

[0042] It is worth noting that the first light beam s is incident on the first incident direction of the acousto-optic deflector 202 (eg Figure 3The angle ω1 between the Y1 direction in the image and the propagation direction of the ultrasonic signal B is less than 90 degrees. The first diffracted light s1 is incident on the second incident direction of the acoustic-optic deflector 202 (such as Figure 3 The angle ω2 between the first light beam s and the ultrasonic signal propagation direction (Y3 direction in the figure) is greater than 90 degrees. That is, the first light beam s and the ultrasonic signal B are in the "same direction" within a certain distance, the first light beam s undergoes a Doppler frequency shift (the first Doppler frequency shift), and the frequency of the first light beam s increases, such as the frequency increases by Δf. The first diffracted light s1 and the ultrasonic signal B are in the "opposite direction" within a certain distance, the first diffracted light s1 undergoes a Doppler frequency shift (the second Doppler frequency shift), and the frequency of the first diffracted light s1 decreases, such as the frequency decreases by Δf, thereby offsetting the frequency Δf increased during the first Doppler frequency shift.

[0043] To completely cancel the Doppler shift, continue to see Figure 3 According to some embodiments of the present application, optionally, the first reflecting surface 203a and the second reflecting surface 203b are symmetrically arranged relative to a preset reference plane J. The reference plane J is perpendicular to any one of the first surface 202a and / or the second surface 202b. Specifically, the projection of any one of the first surface 202a and the second surface 202b on the preset projection plane P is a first line segment l1, and the projection of the reference plane J on the projection plane P is a second line segment l2, and the first line segment l1 is perpendicular to the second line segment l2. Further, the angle between the plane where the first reflecting surface 203a is located and the plane where the second surface 202b is located is a first angle a1, and the angle between the plane where the second reflecting surface is located and the plane where the second surface is located is a second angle a2, and the first angle a1 is equal to the second angle a2.

[0044] In this way, since the first reflecting surface 203a and the second reflecting surface 203b are symmetrically arranged relative to the preset reference plane J, and the first angle a1 is equal to the second angle a2, it can be ensured that the first incident direction of the first light beam s incident on the acousto-optic deflector 202 is parallel and opposite to the second incident direction of the first diffracted light s1 incident on the acousto-optic deflector 202, so that the frequency of the second Doppler frequency shift reduction is equal to the frequency of the first Doppler frequency shift increase, thereby completely offsetting the frequency Δf increased during the first Doppler frequency shift.

[0045] According to some embodiments of the present application, optionally, the first reflective component 203 may include a corner reflector or a prismatic reflector. Figure 4 As shown, taking the corner reflector as an example, the corner reflector 401 may include a base 4011 and a first mirror body 4012 and a second mirror body 4013 disposed on the base 4011, and the first reflecting surface 203a may include a reflecting surface of the first mirror body 4012 (such as Figure 4 The second reflective surface 203b may include a reflective surface of the second mirror body 4013 (such as Figure 4 Similarly, the prism reflector may also include a base and a first mirror body and a second mirror body disposed on the base, the first reflection surface may include the reflection surface of the first mirror body, and the second reflection surface may include the reflection surface of the second mirror body. Different from the corner reflector, the prism reflector may also include a dispersive medium sandwiched between the first mirror body and the second mirror body, while the space between the first mirror body and the second mirror body of the corner reflector is air.

[0046] The inventor of the present application further discovered that Figure 5 As shown in the figure, in addition to the diffracted light, there is also 0th order light in the optical path. The propagation path of 0th order light is as follows: Figure 5 Specifically, the 0th order light of the first light beam s passes through the acousto-optic deflector 202, reaches the second reflection surface 203b directly without diffraction, is then reflected by the second reflection surface 203b to the first reflection surface 203a, passes through the acousto-optic deflector 202 to reach the wavelength selective reflection element 204, and returns to the light beam generating component 201 through the Littrow mode. The existence of the 0th order light will affect the output power and spectral range of the laser output by the swept laser, making the output power of the laser output by the swept laser weaker and the spectral range narrower, so it is necessary to eliminate the 0th order light.

[0047] In order to eliminate the 0th order light in the optical path, such as Figure 6 As shown, according to some embodiments of the present application, optionally, the frequency sweeping laser 20 may further include a 90-degree deflected light rotation element 601 and a first polarizer 602. Exemplarily, the 90-degree deflected light rotation element 601 may include a 90-degree Faraday rotator or a half-wave plate. The 90-degree deflected light rotation element 601 is located on the propagation path L2 of the first diffracted light s1 between the acousto-optic deflector 202 and the first reflective component 203. The 90-degree deflected light rotation element 601 may include a third surface 601a and a fourth surface 601b that are arranged opposite to each other. The third surface 601a receives the first diffracted light s1. After the 90-degree deflected light rotation element 601 converts the horizontal polarized light in the first diffracted light s1 into a vertical polarized light, the first diffracted light s1 is emitted from the fourth surface 601b. The first polarizer 602 is located on the propagation path L2 of the first diffraction light s1 between the fourth surface 601b and the first reflection component 203. The transmission polarization direction of the first polarizer 602 is perpendicular to the direction of the first diffraction light s1 incident on the first polarizer 602, or in other words, the absorption polarization direction of the first polarizer 602 is parallel to the direction of the first diffraction light s1 incident on the first polarizer 602, so as to prevent the passage of horizontally polarized light.

[0048] Since the 0-level light 603 is mainly horizontally polarized light, the first polarizer 602 can block the 0-level light 603 reflected from the first reflection surface 203a, and prevent the 0-level light 603 from returning to the light beam generating component 201. In addition, by adding a 90-degree deflection light rotation element 601, the horizontal polarized light in the first diffracted light s1 can be converted into vertical polarized light, and the reflected second diffracted light s2 can also be converted from vertical polarized light to horizontal polarized light, so that the first diffracted light s1 and the reflected second diffracted light s2 can pass through the first polarizer 602 without obstacles.

[0049] Considering that there is still a small amount of vertically polarized light in the 0-order light, in order to prevent the small amount of vertically polarized light in the 0-order light from returning to the light beam generating component 201, continue to refer to Figure 6 According to some embodiments of the present application, optionally, the swept frequency laser 20 may further include a second polarizer 604, which is located on the propagation path L1 of the first light beam s between the light beam generating component 201 and the acousto-optic deflector 202, and the transmission polarization direction of the second polarizer 604 is parallel to the direction in which the first light beam s is incident on the second polarizer 604, or in other words, the absorption polarization direction of the second polarizer 604 is perpendicular to the direction in which the first light beam s is incident on the second polarizer 604, so as to prevent the passage of vertically polarized light.

[0050] In this way, by adding the second polarizer 604 , the vertically polarized light in the 0th order light 603 from the light beam generating component 201 can be blocked, thereby preventing the vertically polarized light in the 0th order light 603 from entering the optical path and returning to the light beam generating component 201 .

[0051] According to other embodiments of the present application, Figure 6 The embodiment shown is different in that Figure 7 In the illustrated embodiment, the first polarizer 602 can prevent the vertical polarized light from passing through, while the second polarizer 604 is used to prevent the horizontal polarized light from passing through. Specifically, the transmission polarization direction of the first polarizer 602 is parallel to the direction in which the first diffracted light s1 is incident on the first polarizer 602, or in other words, the absorption polarization direction of the first polarizer 602 is perpendicular to the direction in which the first diffracted light s1 is incident on the first polarizer 602, and is used to prevent the vertical polarized light from passing through. The transmission polarization direction of the second polarizer 604 is perpendicular to the direction in which the first light beam s is incident on the second polarizer 604, or in other words, the absorption polarization direction of the second polarizer 604 is parallel to the direction in which the first light beam s is incident on the second polarizer 604, and is used to prevent the horizontal polarized light from passing through.

[0052] In this way, the second polarizer 604 can block the horizontal polarized light in the 0-level light 603 from the light beam generating component 201, and prevent the horizontal polarized light in the 0-level light 603 from entering the optical path and returning to the light beam generating component 201. The first polarizer 602 can block the vertical polarized light in the 0-level light 603 reflected from the first reflecting surface 203a, and prevent the vertical polarized light in the 0-level light 603 from returning to the light beam generating component 201, thereby improving the output power and spectral range of the laser output by the swept laser.

[0053] Correspondingly, by adding a 90-degree deflected light rotation element 601, the vertical polarized light in the first diffracted light s1 can be converted into horizontal polarized light, and the reflected second diffracted light s2 can be converted from horizontal polarized light to vertical polarized light, so that the first diffracted light s1 and the reflected second diffracted light s2 can pass through the first polarizer 602 without obstacles, and the reflected second diffracted light s2 can pass through the second polarizer 604 without obstacles.

[0054] like Figure 8 As shown, according to some embodiments of the present application, optionally, the swept laser 20 may further include a collimating lens 801, and the collimating lens 801 is located on the propagation path L1 of the first light beam s between the light beam generating component 201 and the acousto-optic deflector 202. In some examples, the collimating lens 801 may be specifically located on the propagation path L1 of the first light beam s between the light beam generating component 201 and the second polarizer 604. The collimating lens 801 includes a fifth surface 801a and a sixth surface 801b arranged opposite to each other, and the fifth surface 801a receives the first light beam s. The first light beam s may include a plurality of sub-beams. The plurality of sub-beams in the first light beam s emitted by the light beam generating component 201 are usually scattered in multiple directions. The collimating lens 801 may be used to convert the first light beam s incident on the fifth surface 801a into a first light beam s parallel to the plurality of sub-beams, that is, to convert the scattered light into parallel light. The first light beam s parallel to the plurality of sub-beams is emitted from the sixth surface 801b.

[0055] Thus, by adding the collimating lens 801, the first light beam s emitted by the light beam generating assembly 201 can be converted from scattered light into parallel light, so that more sub-beams are incident on the acousto-optic deflector 202, thereby increasing the output power of the laser.

[0056] like Fig. 9As shown, according to some embodiments of the present application, optionally, the beam generating assembly 201 may include a seventh surface 901a and an eighth surface 901b arranged opposite to each other, the seventh surface 901a emits the first beam s, and the eighth surface 901b is provided with an optical fiber output end 901, and the optical fiber output end 901 is used to emit laser light. The swept laser 20 may also include an optical fiber isolator 902 and a laser output port 903, the input end of the optical fiber isolator 902 is electrically connected to the optical fiber output end 901, and the output end of the optical fiber isolator 902 is electrically connected to the laser output port 903, and is used to prevent the laser light from one side of the laser output port 903 from entering the optical fiber output end 901.

[0057] In this way, by adding the optical fiber isolator 902, the laser from the laser output port 903 side can be prevented from entering the optical fiber output end 901, that is, the laser from the laser output port 903 side can be prevented from entering the beam generating component 201 and oscillating, thereby ensuring that the swept frequency laser can output stable laser.

[0058] Continue to see Fig. 9 According to some embodiments of the present application, optionally, the frequency sweeping laser 20 may further include a booster fiber amplifier 904, the input end of the booster fiber amplifier 904 is electrically connected to the output end of the optical fiber isolator 902, and the output end of the booster fiber amplifier 904 is electrically connected to the laser output port 903, for amplifying the power of the laser emitted from the optical fiber output end 901 to the target power.

[0059] In this way, by adding the booster fiber amplifier 904, the power of the laser emitted from the fiber output end 901 can be amplified to the target power to meet the output requirements of different powers.

[0060] Continue to see Fig. 9 According to some embodiments of the present application, optionally, the swept laser 20 may further include at least one of an anti-reflection film 905 and a semi-transparent and semi-reflective film 906. The anti-reflection film 905 may be attached to the seventh surface 901a, and the semi-transparent and semi-reflective film 906 may be attached to the eighth surface 901b.

[0061] Thus, by adding the anti-reflection film 905, the light output rate of the light beam generating component 201 can be increased, and the output power of the laser can be improved. By adding the semi-transparent and semi-reflective film 906, part of the laser can be output through the semi-transparent and semi-reflective film 906, and the other part of the laser can be reflected back to the light beam generating component 201 and multiple light amplification can be achieved through the acousto-optic deflector 202, the first reflection component 203 and the wavelength selective reflection element 204.

[0062] Based on the swept-frequency laser 20 provided in the above embodiment, accordingly, the embodiment of the present application further provides an optical coherence tomography system, and the swept-frequency laser 20 provided in the embodiment of the present application may include the swept-frequency laser 20 provided in the above embodiment.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A frequency-sweeping laser, characterized in that: include: A beam generating assembly, used for emitting a first beam; an acousto-optic deflector, located on a propagation path of the first light beam, the acousto-optic deflector comprising a first surface and a second surface arranged opposite to each other, the first surface receiving the first light beam incident in a first incident direction, the first light beam diffracting in the acousto-optic deflector to obtain a first diffracted light of the first light beam, and the first diffracted light emitting from the second surface in a first emitting direction; a first reflection component, located on a propagation path of the first diffracted light, the first reflection component comprising a first reflection surface and a second reflection surface that are symmetrically arranged, the first reflection surface receiving the first diffracted light and reflecting the first diffracted light to the second reflection surface, and the second reflection surface reflecting the first diffracted light back to the second surface; The second surface receives the first diffracted light incident in a second incident direction, the second incident direction is opposite to the first incident direction, the first diffracted light is diffracted in the acousto-optic deflector to obtain a second diffracted light of the first diffracted light, and the second diffracted light is emitted from the first surface in a second emitting direction, the second emitting direction is opposite to the first emitting direction; A wavelength selective reflecting element is located on the propagation path of the second diffracted light, and is used to receive the second diffracted light and reflect the second diffracted light back to the first surface. The second diffracted light then passes through the acousto-optic deflector, the second reflecting surface, the first reflecting surface and the acousto-optic deflector in sequence and returns to the light beam generating assembly.

2. The swept frequency laser according to claim 1, characterized in that: The acousto-optic deflector comprises an ultrasonic generating element and a crystal, wherein the ultrasonic generating element and the crystal are arranged in sequence along a first direction, the ultrasonic generating element is used to generate and transmit an ultrasonic signal to the crystal, and the propagation direction of the ultrasonic signal is parallel to the first direction; Under the drive of the ultrasonic signal, the medium in the crystal forms a grating, the grating extends along a second direction, the second direction intersects the first direction, and the grating is used to diffract a light beam passing through the grating; The angle between the first incident direction and the propagation direction of the ultrasonic signal is less than 90 degrees, and the angle between the second incident direction and the propagation direction of the ultrasonic signal is greater than 90 degrees.

3. The swept frequency laser according to claim 1, characterized in that: The projection of any one of the first surface and the second surface on a preset projection plane is a first line segment, the projection of a preset reference plane on the projection plane is a second line segment, and the first line segment is perpendicular to the second line segment; The first reflecting surface and the second reflecting surface are symmetrically arranged relative to the reference plane, the angle between the plane where the first reflecting surface is located and the plane where the second surface is located is a first angle, the angle between the plane where the second reflecting surface is located and the plane where the second surface is located is a second angle, and the first angle is equal to the second angle.

4. The swept frequency laser according to claim 1, characterized in that: The first reflecting component includes a corner reflector or a prismatic reflector, either of which includes a base and a first mirror body and a second mirror body arranged on the base, the first reflecting surface includes the reflecting surface of the first mirror body, and the second reflecting surface includes the reflecting surface of the second mirror body.

5. The swept frequency laser according to claim 1, characterized in that: The frequency sweeping laser also includes: a 90-degree deflected light rotation element, located on a propagation path of the first diffracted light between the acousto-optic deflector and the first reflective component, the 90-degree deflected light rotation element comprising a third surface and a fourth surface arranged opposite to each other, the third surface receiving the first diffracted light, the 90-degree deflected light rotation element converting horizontally polarized light in the first diffracted light into vertically polarized light, and the first diffracted light then emerges from the fourth surface; A first polarizer is located on a propagation path of the first diffracted light between the fourth surface and the first reflective component, and a transmission polarization direction of the first polarizer is perpendicular to a direction in which the first diffracted light is incident on the first polarizer, so as to prevent horizontally polarized light from passing through.

6. The frequency sweeping laser according to claim 5, characterized in that: The frequency sweeping laser also includes: The second polarizer is located on the propagation path of the first light beam between the light beam generating assembly and the acousto-optic deflector. The transmission polarization direction of the second polarizer is parallel to the direction in which the first light beam is incident on the second polarizer, and is used to prevent the passage of vertically polarized light.

7. The swept frequency laser according to claim 1, characterized in that: The frequency sweeping laser also includes: a 90-degree deflected light rotation element, located on a propagation path of the first diffracted light between the acousto-optic deflector and the first reflective component, the 90-degree deflected light rotation element comprising a third surface and a fourth surface arranged opposite to each other, the third surface receiving the first diffracted light, the 90-degree deflected light rotation element converting vertically polarized light in the first diffracted light into horizontally polarized light, and the first diffracted light then emerges from the fourth surface; A first polarizer is located on a propagation path of the first diffracted light between the fourth surface and the first reflective component, a transmission polarization direction of the first polarizer is parallel to a direction in which the first diffracted light is incident on the first polarizer, and is used to prevent vertically polarized light from passing through; The second polarizer is located on the propagation path of the first light beam between the light beam generating assembly and the acousto-optic deflector. The transmission polarization direction of the second polarizer is perpendicular to the direction in which the first light beam is incident on the second polarizer, and is used to prevent the passage of horizontally polarized light.

8. The frequency sweeping laser according to claim 1, characterized in that: The swept-frequency laser also includes a collimating lens, which is located on the propagation path of the first light beam between the light beam generating assembly and the acousto-optic deflector. The collimating lens includes a fifth surface and a sixth surface that are arranged opposite to each other. The fifth surface receives the first light beam. The first light beam incident on the fifth surface includes a plurality of sub-beams. The collimating lens is used to convert the first light beam incident on the fifth surface into the first light beam in which the plurality of sub-beams are parallel. The first light beam in which the plurality of sub-beams are parallel is emitted from the sixth surface.

9. The frequency sweeping laser according to claim 1, characterized in that: The light beam generating assembly comprises a seventh surface and an eighth surface, the seventh surface and the eighth surface are arranged opposite to each other, the seventh surface emits the first light beam, and the eighth surface is provided with an optical fiber output end, and the optical fiber output end is used to emit laser light; The frequency sweeping laser also includes a fiber isolator and a laser output port, wherein the input end of the fiber isolator is electrically connected to the fiber output end, and the output end of the fiber isolator is electrically connected to the laser output port, for preventing laser light from one side of the laser output port from entering the fiber output end.

10. The swept frequency laser according to claim 1, characterized in that: The light beam generating assembly comprises a seventh surface and an eighth surface, the seventh surface and the eighth surface are arranged opposite to each other, and the seventh surface emits the first light beam; The frequency sweeping laser further includes at least one of an anti-reflection film and a semi-transparent and semi-reflective film, wherein the anti-reflection film is attached to the seventh surface, and the semi-transparent and semi-reflective film is attached to the eighth surface.

11. An optical coherence tomography system, characterized in that: The invention comprises a swept frequency laser as claimed in any one of claims 1 to 10.

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