CN110537898A

CN110537898A - Manufacturing method of focus-adjustable photoacoustic endoscopic microscope

Info

Publication number: CN110537898A
Application number: CN201910842634.4A
Authority: CN
Inventors: 陈松良; 郭震东; 叶展鸿
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 2019-09-06
Filing date: 2019-09-06
Publication date: 2019-12-06
Anticipated expiration: 2039-09-06
Also published as: CN110537898B

Abstract

The invention discloses a method for manufacturing a focus-adjustable photoacoustic endoscopic microscope, which comprises the steps of manufacturing an endoscope and increasing the depth of field, (i) by adjusting the distance between a single-mode fiber and a lens, the focus position of laser focusing can be changed (namely, the focal length is changed); then, images of different focal planes can be obtained through one-dimensional or two-dimensional scanning; the images are fused, so that the photoacoustic image with the increased depth of field can be equivalently obtained, and the defect of small depth of field is overcome; (ii) the manufacturing method of the focus-adjustable photoacoustic endoscopic microscope provided by the invention has the advantages of small size and high resolution, and overcomes the defects of large size and relatively low resolution.

Description

manufacturing method of focus-adjustable photoacoustic endoscopic microscope

Technical Field

The invention relates to the field of photoacoustic endoscopic microscopes, in particular to a manufacturing method of a photoacoustic endoscopic microscope with an adjustable focus.

Background

Photoacoustic endoscopic imaging is a technical solution based on the use of a miniature imaging head that can be extended into the body to acquire images of internal organs. Photoacoustic endoscopic imaging can be further divided into acoustic resolution photoacoustic endoscopic imaging and optical resolution photoacoustic endoscopic imaging. Acoustic resolution by using focused or unfocused ultrasound transducers, resolution of tens to hundreds of microns can be provided; optical resolution by using a focused laser spot, resolution up to several microns can be achieved. Therefore, optical resolution photoacoustic endoscopic imaging is expected to obtain a clear image of fine tissue, such as capillary vessel imaging, in a endoscopic fashion. However, a characteristic of the focused laser spot is that the smaller the spot size, the smaller the focal depth. That is, the higher the resolution, the smaller the imaging depth of field. From a clinical application perspective, the biological tissue surface of an organ in vivo typically has a variation in elevation. If the imaging depth of field is too small, only a small part of tissues can fall in the depth of field, and a clear image can be obtained; tissues outside the depth of field cannot obtain clear images, and important diagnostic information may be missed.

In recent years, various methods have been proposed to increase the depth of field of optical resolution photoacoustic microscopy and photoacoustic endoscopic imaging. For example, the imaging head is scanned axially (i.e., scanned in the depth direction) using an electronically controlled displacement stage. As another example, an increase in depth of field is achieved by adjusting the focus using an electrically driven adjustable lens. However, the above-mentioned work is mainly used in the optical resolution photoacoustic microscopy imaging system, and the imaging head volume is large, and cannot be used in the endoscopic imaging application. Recently, there have been research groups that have shown a photoacoustic endoscope that can automatically adjust a focus and image a biological tissue having undulations on a surface thereof, thereby obtaining good imaging effects. However, the spatial resolution of this photoacoustic endoscope is only 49 microns, with a small gap compared to the resolution of several microns; in addition, the size of the photoacoustic endoscope is 9 mm, which is large compared to the size of current medical endoscopes, and may not be used for some clinical applications. Another photoacoustic endoscope uses a bessel beam to increase the depth of field and speed the imaging, but still has the problems of too large a size (8 mm) and low resolution (42 μm). Therefore, how to realize a miniaturized, high-resolution, and depth-of-field-increased photoacoustic endoscope is still a challenge, and the design and fabrication thereof are quite worthy of further study.

as can be seen from the above-mentioned studies on the current photoacoustic microscopy imaging technique with increased depth of field, the prior art has the following problems and disadvantages. (i) In the present photoacoustic microscopic imaging system, various techniques for increasing the depth of field of imaging are proposed, but limited by the size of the imaging head, they cannot be directly used for endoscopic imaging. (ii) At present, research groups also show large-depth-of-field photoacoustic endoscopes, but the sizes of devices of the photoacoustic endoscopes are large, so that the convenience of clinical use is limited; and the resolution is relatively low, limiting the image quality.

Disclosure of Invention

The present invention is directed to a method for manufacturing a photoacoustic endoscope with an adjustable focus, which solves the above problems.

the technical problem solved by the invention can be realized by adopting the following technical scheme:

A manufacturing method of a focus-adjustable photoacoustic endoscopic microscope comprises the steps of manufacturing an endoscope and increasing the depth of field, wherein the manufacturing of the endoscope comprises the following steps:

(1) Fixing the single-mode optical fiber in the first plastic tube;

(2) Firstly, inserting the first plastic pipe into a second plastic pipe with a side window; then, fixing the outer part of the first plastic pipe and a first glass pipe with a semicircular opening together by ultraviolet glue at the side window of the second plastic pipe; then, a second glass tube is sleeved in the single-mode optical fiber and fixed together with the single-mode optical fiber; the single-mode optical fiber, the first plastic pipe, the first glass pipe with the semicircular opening and the second glass pipe are fixed together to form a sub-component A;

(3) Firstly, sleeving a first steel pipe into a second glass pipe, and fixing the first steel pipe and the second glass pipe with a side window; then, fixing a lens on the first steel pipe; a second plastic tube with a side window, a first steel tube and a lens are fixed together to form a sub-component B; in the imaging process, a transmission device is connected with the first glass tube with the semicircular opening to drive the sub-component A, and the sub-component B is kept still, so that the purpose of adjusting the distance between the optical fiber and the lens is achieved, and the focus can be adjusted;

(4) firstly, sleeving a second steel pipe with a hollow window with a 45-degree inclined plane at one end into the first steel pipe and fixing the second steel pipe together; then, fixing the gold-plated PET film on the inclined plane hollow window; the gold-plated PET film is used for 90-degree reflection of laser and transmission of ultrasonic signals; finally, fixing a miniature piezoelectric ultrasonic detector on the outer side of the second steel pipe so that the miniature piezoelectric ultrasonic detector can receive ultrasonic signals passing through the hollow window;

The increase of the depth of field comprises the following steps:

(1) adjusting the distance d between the single-mode fiber and the lens, including da and db; obtaining corresponding focal length f, including fa and fb, which are the distance from the lens to the gold-plated film and the distance from the gold-plated film to the focal point respectively;

(2) performing one-dimensional or two-dimensional scanning by using an endoscope to obtain an image of an f1 focal plane and an image of an f2 focal plane;

(3) Gradually adjusting the focus to obtain images of more focal planes;

(4) And image fusion: selecting only data in the inherent focal depth range of an image of a certain focal plane; and stacking and combining the data of different focal planes along the depth direction to obtain three-dimensional data with large depth of field.

further, the second plastic pipe comprises a section of closed pipe and a section of opening 270-degree side window, and the position of the side window of the second plastic pipe is the part for connecting the section of closed pipe.

further, the wavelength of the single-mode optical fiber is 400-680 nanometers.

compared with the prior art, the invention has the following beneficial effects:

The invention provides a new method for manufacturing a focus-adjustable photoacoustic endoscopic microscope, which comprises the following steps: (i) by adjusting the distance between the single-mode fiber and the lens, the focal position of the laser focus can be changed (i.e. the focal length is changed). Images of different focal planes can then be obtained by one-dimensional or two-dimensional scanning. And the images are fused, so that the photoacoustic image with the increased depth of field can be equivalently obtained, and the defect of small depth of field is overcome. (ii) The manufacturing method of the focus-adjustable photoacoustic endoscopic microscope provided by the invention has the advantages of small size and high resolution, and overcomes the defects of large size and relatively low resolution. Technically, the problems of resolution, depth of field, endoscope size and the like are considered at the same time, and the endoscope is optimally designed. In particular, the following advantages are provided: (i) high resolution, (ii) large depth of field, (iii) small size.

The advantages of the invention include: (1) high resolution and increased depth of field: the resolution is 3-5 microns, and the single red blood cell can be analyzed; the depth of field can reach more than 3 mm, and the method can be used for solving the problem that the tissue image in the defocusing area is blurred due to irregular fluctuation of the surface of the biological tissue in the clinical endoscopic application. (2) The endoscope has small size: because the used components are small in size, including a lens, a miniature piezoelectric ultrasonic probe and the like, and related components for focus adjustment are also optimally designed, the diameter of the endoscope is only 2.8 mm, and the endoscope is more convenient to apply in medical endoscopy. (3) It is worth mentioning that the function of adjustable focus is realized by the optical mechanical design, so that the electromagnetic interference problem is avoided, and the endoscope is more suitable for clinical and living body endoscopic imaging applications.

Drawings

fig. 1 is a manufacturing step diagram of the photoacoustic endoscopic microscope with adjustable focus according to the present invention.

fig. 2 is a schematic view of the steps for implementing the depth of field increase of the photoacoustic endoscopic microscope with adjustable focus.

Fig. 3 shows the lateral resolution and depth of field obtained by simulation and experiment.

fig. 4 is a photoacoustic image of a leaf phantom obtained using the photoacoustic endoscopic microscope.

fig. 5 is a photoacoustic image of a hair line of a human body obtained by using the photoacoustic endoscopic microscope.

fig. 6 is a schematic view of an imaging system of the photoacoustic endoscopic microscope with an adjustable focus.

Fig. 7 is a photoacoustic image of a mouse pupil blood vessel obtained using the photoacoustic endoscopic microscope.

Fig. 8 is a photoacoustic image of a blood vessel of an ear of a mouse obtained using the photoacoustic endoscopic microscope.

Fig. 9 is a photoacoustic image of zebra fish pigment obtained using the photoacoustic endoscopic microscope.

Detailed Description

In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further described with the specific embodiments.

Referring to fig. 1 to 9, the method for manufacturing a focus-adjustable photoacoustic endoscopic microscope according to the present invention includes manufacturing an endoscope and increasing a depth of field, wherein the manufacturing of the endoscope includes the following steps:

(1) As shown in fig. 1 (i), a single mode optical fiber 1 is fixed in a first plastic tube 2;

(2) as shown in fig. 1 (ii), the first plastic tube 2 is first inserted into a second plastic tube 3 with a side window. The second plastic tube comprises a two-section closed tube and a side window with an opening of about 270 degrees, and the side window of the second plastic tube is positioned as a part for connecting the two-section closed tube. Then, fixing the outer part of the first plastic pipe 2 and a first glass pipe 4 with a semicircular opening together at the side window of the second plastic pipe 3 by ultraviolet glue; then, a second glass tube 5 is fitted into the single-mode optical fiber 1 and fixed thereto. That is, the single-mode optical fiber 1, the first plastic tube 2, the first glass tube 4 and the second glass tube 5, which are semicircular-open, are fixed together as a sub-component a (also referred to as a linear displacement unit);

(3) as shown in (iii) of fig. 1, a first steel tube 6 is sleeved into a second glass tube 5 and fixed with a second plastic tube 3 with a side window; then, a lens 7 is fixed on the first steel pipe 6; a second plastic tube 3 with a side window, a first steel tube 6, and a lens 7 are fixed together to form a sub-component B (also called a stationary unit); in the imaging process, a transmission device (namely a one-dimensional displacement table, not shown in the figure) is connected with the first glass tube 4 with the semicircular opening to drive the sub-component A, and the sub-component B is kept still, so that the purpose of adjusting the distance between the optical fiber and the lens is achieved, and the focus can be adjusted;

(4) As shown in (iv) of fig. 1, firstly, sleeving a second steel pipe 8 with a 45-degree inclined hollow window at one end into a first steel pipe 6 and fixing the two steel pipes together; then, fixing the gold-plated PET film 9 on the inclined hollow window; the gold-plated PET film 9 is used for 90 ° reflection of laser light and transmission of ultrasonic signals; finally, a micro piezoelectric ultrasonic detector 10 is fixed on the outer side of the second steel pipe 8 (the electric wire part is tightly attached to the outer side of the steel pipe 8, and the micro piezoelectric ultrasonic detector 10 is placed at the projection position from the central point to the bottom of the hollow window), so that the micro piezoelectric ultrasonic detector can receive the ultrasonic signal passing through the hollow window.

The increase of the depth of field comprises the following steps:

(1) Adjusting the distance d between the single-mode fiber and the lens, such as da and db in fig. 2(a) and 2 (b); obtaining corresponding focal lengths f, as fa and fb in fig. 2(a) and 2(b), fa and fb being the distance from the lens to the gold-plated film plus the distance from the gold-plated film to the focal point, respectively;

(2) And performing one-dimensional or two-dimensional scanning by using the endoscope to obtain an image of a certain focal plane. As in fig. 2(a), it is expected that an image of the f1 focal plane is obtained; whereas in fig. 2(b), it is expected that an image of the f2 focal plane is obtained;

(3) in addition to f1 and f2 shown in fig. 2, the focus is adjusted step by step, and more images of the focal planes (f3, f4, f5 …) can be obtained. The step size parameter of the focal length adjustment may be determined by the inherent depth of field of the focused beam.

(4) And image fusion: selecting only data in the inherent focal depth range of an image of a certain focal plane; by stacking and combining the data of different focal planes in the depth direction, three-dimensional data with large depth of field can be obtained. That is, the above method can equivalently increase the depth of field.

In order to solve the defects of the existing 'high-resolution (several microns) photoacoustic endoscope' and 'focus-adjustable photoacoustic endoscope' (the defect of the former is that the depth of field is small, and the defect of the latter is that the size is large and the resolution is relatively low), the invention adopts the following technical means: (i) in terms of increasing the depth of field, we use a focus-adjustable design. Compared with the current high-resolution (several microns) photoacoustic endoscope, the special design capable of adjusting the distance between the single-mode fiber and the lens is adopted, the effect of adjusting the focal length is further achieved, and then the depth of field is equivalently increased by fusing images of different focal planes. (ii) In increasing resolution and reducing endoscope size, many miniature components and designs are used. Compared with the current focus-adjustable photoacoustic endoscope, the lens used by the endoscope is only 2 millimeters, and the lens can realize high resolution of several micrometers; in addition, related parts for realizing focus adjustment are optimally designed, and the size of the endoscope is reduced as much as possible.

the main idea of the method is as follows: (i) the invention proposes to use a 2mm lens and introduce a design with adjustable focal length; the lens can obtain high resolution of 3-5 microns and keep a certain working distance (or focal length); compared with the use of a double-gradient-index lens, the manufacturing is easier; the innovative design with adjustable focal length can increase the depth of field, so that the high resolution and the large depth of field can be obtained simultaneously. (ii) The present invention uses a 2mm lens, which in addition to the above mentioned ability to achieve high resolution of a few microns, enables a significant reduction in endoscope size.

In fig. 2, (a) is adjusted to the focal length fa, and (b) is adjusted to the focal length fb.

In fig. 4 (a), a photograph of a leaf phantom is shown, and a dotted line region is a region where photoacoustic imaging is performed. (b) And fusing the photoacoustic images after 8 different focal planes. (c) Depth-coded photoacoustic images. Fig. b and c share the same scale.

The region surrounded by concentric circles with a broken line in fig. 5 represents an imaging region. Regions I, II, and III represent the imaging areas of the representative inner, middle, and outer layers, respectively. All figures share the same scale.

In fig. 7 (a-c) photoacoustic images at different focal planes, where the focal plane of diagram (a) falls near the dashed area a, so a sharper image can be obtained for this area; the focal plane of plot (B) then falls near dashed region B, so a sharper image can be obtained for this region; the focal plane of the plot (C) then falls near the dashed region C, so a sharper image can be obtained for this region. (d) And after the photoacoustic images of different focal planes are fused, most areas show clear images. (e) And displaying the photoacoustic image in three dimensions. (f) Depth-coded photoacoustic images. Figures a-d and f share the same scale.

In fig. 8 (a-c) photoacoustic images at different focal planes, where the focal plane of graph (a) falls near the dashed area (i), so a sharper image can be obtained for this area; the focal plane of plot (b) then falls near dashed region (ii), so a sharper image can be obtained for this region; the focal plane of plot (c) then falls near dashed region (iii), so a sharper image can be obtained for this region. (d) And after the photoacoustic images of different focal planes are fused, most areas show clear images. (e) Depth-coded photoacoustic images. All figures share the same scale.

FIG. 9 is a diagram of the photoacoustic images of (a-c) different focal planes, where the focal plane of diagram (a) falls near the dashed area (i), and thus a sharper image can be obtained for that area; the focal plane of plot (b) then falls near dashed region (ii), so a sharper image can be obtained for this region; the focal plane of plot (c) then falls near dashed region (iii), so a sharper image can be obtained for this region. (d) And after the photoacoustic images of different focal planes are fused, most areas show clear images. (e) Depth-coded photoacoustic images. All figures share the same scale.

As shown in fig. 1, the focus-adjustable photoacoustic endoscope in the present embodiment includes a single-mode optical fiber, a 2mm lens, a plastic tube, a glass tube, a steel tube, a gold-plated PET film, and a micro piezoelectric ultrasonic probe. The imaging system is shown in fig. 6, we use 532 nm pulse laser, firstly use the neutral density attenuator 11 to control the laser energy, then adjust the spot shape through the diaphragm 22, and split the beam through the beam splitter 33, part of the laser is received by the light detector (used for triggering signal later), and part of the laser is used for the excitation of the photoacoustic signal. Laser beam expansion is achieved after the laser light used to excite the photoacoustic signal passes through a lens assembly comprising a first lens 44 and a second lens 66 and a pinhole 55. The laser is then coupled into a single mode fiber using a fiber coupler 77. The single mode fiber is controlled by a transmission device for realizing focus adjustment. The water tank is arranged on a three-dimensional displacement object stage, so that the sample can be adjusted more conveniently. The photoacoustic endoscopic microscope can perform plane scanning by using a two-dimensional electric control displacement platform and also can perform rotary scanning by using a rotary motor (not shown in the figure). The signal of the miniature piezoelectric ultrasonic detector is pre-amplified through an amplifier module. Finally, the signals are digitized by an acquisition card and stored by a computer. The present embodiment reduces the outer diameter by using a 2mm lens and a miniature piezoelectric ultrasonic probe; the 2mm lens can realize high resolution and keep a certain working distance; the adjustable focus is realized by changing the distance between the optical fiber and the lens, so that the large depth of field is realized; side-looking imaging is achieved by using gold-plated films (for light reflection and acoustic transmission).

In this embodiment, the lateral resolution of photoacoustic imaging is determined by the focused spot size, the focal length is the distance from the 2mm lens to the focal point (fa or fb in FIG. 2), the working distance is the distance from the outside of the endoscope to the focal point (about f1 or f2 minus the radius of the endoscope in FIG. 2), and the longitudinal resolution is determined by the bandwidth of the miniature piezoelectric ultrasound probe (measured as 45 microns). When the imaging performance is tested, the miniature imaging head can be fixed on the electric control displacement platform, a two-dimensional photoacoustic image can be obtained through one-dimensional scanning, and a three-dimensional photoacoustic image can be obtained through two-dimensional scanning. Then, the images of different focal planes are fused, so that the depth of field can be equivalently increased. Fig. 7 to 9 show that living photoacoustic images of mouse eyes, mouse ears, and zebra fish obtained by two-dimensional (linear) scanning, respectively, show that the photoacoustic endoscopic microscope of the present patent can realize high resolution and large depth-of-field images. When the endoscope is applied, due to the narrow space in the body, the scanning mode cannot be used, but a rotary scanning mode is adopted, and a two-dimensional section photoacoustic image can be obtained; in addition, an endoscope pull-back scanning mode can be matched to realize two-dimensional scanning (namely rotation and pull-up), and a three-dimensional photoacoustic image can be obtained.

In the embodiment, the optical fiber is a single-mode optical fiber with a wavelength of 400-680 nm, and can be applied to photoacoustic functional imaging of blood oxygen saturation. Photoacoustic imaging of blood oxygen saturation typically uses laser wavelengths of 532 nm and 560 nm.

the invention can realize the manufacturing method of the photoacoustic endoscopic microscope with the adjustable focus. The adjustment of the focus is realized by controlling the distance between the single-mode fiber and the lens. By adjusting the focus, images at different focal planes are obtained, and then the images are fused, so that the imaging depth of field can be equivalently increased. It was found experimentally that we can increase the depth of field to > 3 mm and maintain a high resolution of 3-5 microns within this depth of field. In addition, the photoacoustic endoscope has an outer diameter of 2.8 millimeters, facilitating many clinical endoscopic applications. We also used the developed photoacoustic endoscope to image the eyes and ears of mice, and zebrafish in vivo, demonstrating excellent imaging performance of the photoacoustic endoscope. The photoacoustic endoscope provided by the invention can provide high-resolution and high-quality images in a large depth range, and contributes to the clinical application of photoacoustic endoscopic imaging.

with respect to the above-mentioned advantageous effects, theoretical or experimental data are developed below.

(1) The focus adjustable photoacoustic endoscope is manufactured, and the resolution and the depth of field of the photoacoustic endoscope are measured. According to diffraction limit theory, the lateral resolution can be expressed as:

transverse resolution is 0.51 x lambda/ENA, (formula 1)

wherein lambda is the laser wavelength and ENA is the laser focusing equivalent numerical aperture. The theoretical lateral resolution is the full width at half maximum of the point spread function of the imaging time, ENA is determined by the equation:

ENA is nxd/(2 f), (formula 2)

Where n is the refractive index of the medium, D is the spot size, and f is the focal length. From the above equation, we performed simulations using Zemax software and derived the relevant parameters from the experiments, and the results are shown in fig. 3. d is the distance between the single mode fiber and the lens. First, from the simulation result of Zemax, the variation of the focal length f with d can be obtained (fig. 3 (a)); then, according to equation 2, the variation of the equivalent numerical aperture ENA with d can be calculated (fig. 3 (b)); the variation of the lateral resolution with d can be calculated from equation 1 (FIG. 3 (c)). Fig. 3(d) shows the lateral resolution measured experimentally when d is 5.5 mm. As can be seen from fig. 3, the larger d, the higher the resolution, and the shorter f. That is, the resolution is a trade-off with f. The experiment of FIG. 3 also demonstrates that within a depth of field of > 3 mm (FIG. 3(a)), the resolution can be 3-5 microns (FIG. 3 (c)).

(2) as shown in FIG. 1, the photoacoustic endoscopic microscope component of the present patent comprises a single mode optical fiber, a 2mm lens, a focus adjusting component, a gold-plated PET film, a miniature piezoelectric ultrasonic detector, and the like. By practical assembly we can achieve an endoscope of only 2.8 mm in diameter. This size is useful for many medical endoscopic applications, such as esophageal and gastrointestinal endoscopic imaging.

(3) Next, we used this endoscope for preliminary imaging tests, the sample was a leaf phantom containing ink, the sample was intentionally tilted (the left side is the shallower area and the right side is the deeper area), and the imaging results are shown in FIG. 4. Before the method of focus adjustment and image fusion is used, only a sample on a certain focal plane can be clearly imaged; after using this method, a sharp image can be obtained for most of the area of the sample, as shown in fig. 4(b), due to the equivalent increase in depth of field. Fig. 4(c) is a depth-coded photoacoustic image, where the left side can be seen to be a shallow region and the right side to be a deep region, and the depth of field exceeds 3 mm.

(4) In addition, the endoscope is also used for rotary scanning imaging, and the imaging performance of the endoscope with large depth of field is shown. The sample was human hair and the imaging results are shown in figure 5. When the focal length is short, only the image on the inner side can be seen (as in the graph of fig. 5, f is 3.2mm, the hair in the area I can be seen, but the hair in the areas II and III can not be seen); when the focal length is slightly extended, an image slightly outside can be seen (as in the diagram of fig. 5, f is 4.5mm, the hair of the areas I and II can be seen, but the hair of the area III can not be seen); as the focal length is further extended, the outermost image is visible (as in the 5.7mm f diagram of fig. 5, both the hair strands in regions I, II and III are visible). It should be noted that the graph of fig. 5 with f being 5.7mm can see hair in 3 areas, because the focal length is larger, and therefore the focal depth is also larger, so that the area I still falls within the focal depth. The results of the rotating scanning imaging approach closer to the scanning mode of clinical endoscopic application indicate that the photoacoustic endoscopic microscope developed by us is feasible for clinical endoscopic application.

the foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. A manufacturing method of a focus-adjustable photoacoustic endoscopic microscope is characterized in that: the method comprises the steps of manufacturing an endoscope and increasing the depth of field, wherein the manufacturing of the endoscope comprises the following steps:

(1) fixing the single-mode optical fiber in the first plastic tube;

The increase of the depth of field comprises the following steps:

(3) gradually adjusting the focus to obtain images of more focal planes;

2. The method for manufacturing an adjustable-focus photoacoustic endoscopic microscope according to claim 1, wherein: the second plastic pipe comprises a two-section closed pipe and a section of side window with 270-degree opening, and the position of the side window of the second plastic pipe is the part for connecting the two-section closed pipe.

3. The method for manufacturing an adjustable-focus photoacoustic endoscopic microscope according to claim 1, wherein: the optical wavelength of the single-mode optical fiber is 400-680 nanometers.