Projection lens, optical engine system and photopolymer printer

Abstract

This application provides a projection lens, an optomechanical system, and a photopolymerization printer, relating to the field of 3D printing technology. The projection lens, along its optical axis from the object side to the image side, sequentially includes a first lens with positive optical power, a second lens with negative optical power, a third lens with negative optical power, a fourth lens with positive optical power, a fifth lens with negative optical power, a sixth lens with positive optical power, a seventh lens with positive optical power, an eighth lens with positive optical power, and a ninth lens with positive optical power, wherein the first to ninth lenses are all spherical lenses. The projection lens of this application can still possess low optical distortion and high resolution even when all lenses are spherical lenses. Therefore, this projection lens can achieve good projection quality at a low cost. The optomechanical system of this application includes the aforementioned projection lens. The photopolymerization printer of this application includes the aforementioned optomechanical system.

Description

Technical Field

[0001] This application relates to the field of 3D printing technology, and more specifically, to a projection lens, an optical engine system, and a photopolymerization printer. Background Technology

[0002] The projection lens is a crucial component of the optomechanical system in a UV curing printer, significantly impacting print quality. To ensure optimal projection, aspherical lenses are typically used in projection lenses. However, manufacturing aspherical lenses requires molds, resulting in high costs. Conversely, using only spherical lenses leads to significant optical distortion and poor resolution. Summary of the Invention

[0003] The purpose of this application is to provide a projection lens, an optical engine system, and a light-curing printer that can achieve high projection quality at a lower cost.

[0004] The embodiments of this application can be implemented as follows:

[0005] In a first aspect, this application provides a projection lens, comprising, along its optical axis from the object side to the image side, the following components in sequence:

[0006] A first lens with positive optical power;

[0007] A second lens with negative optical power;

[0008] A third lens with negative optical power;

[0009] A fourth lens with positive optical power;

[0010] A fifth lens with negative optical power;

[0011] A sixth lens with positive optical power;

[0012] A seventh lens with positive optical power;

[0013] An eighth lens with positive optical power;

[0014] A ninth lens with positive optical power;

[0015] Lenses one through nine are all spherical lenses.

[0016] In an optional embodiment, the object-side surface of the first lens is convex, and the image-side surface is concave.

[0017] And / or, the object-side surface of the second lens is convex, and the image-side surface is concave;

[0018] And / or, both the object-side and image-side surfaces of the third lens are concave;

[0019] And / or, both the object-side and image-side surfaces of the fourth lens are convex.

[0020] And / or, both the object-side and image-side surfaces of the fifth lens are concave;

[0021] And / or, the object-side surface of the sixth lens is concave, and the image-side surface is convex;

[0022] And / or, both the object-side and image-side surfaces of the seventh lens are convex.

[0023] And / or, both the object-side and image-side surfaces of the eighth lens are convex.

[0024] And / or, the object-side surface of the ninth lens is convex, and the image-side surface is concave.

[0025] In an optional embodiment, the radius of curvature of the object side of the first lens is 40-50 mm, and the radius of curvature of the image side is 700-800 mm.

[0026] And / or, the radius of curvature of the object side of the second lens is 30-40 mm, and the radius of curvature of the image side is 12-18 mm;

[0027] And / or, the radius of curvature of the object side of the third lens is -30 to -40 mm, and the radius of curvature of the image side is 15 to 20 mm;

[0028] And / or, the radius of curvature of the object side of the fourth lens is 40 to 50 mm, and the radius of curvature of the image side is -35 to -40 mm;

[0029] And / or, the radius of curvature of the object side of the fifth lens is -12 to -18 mm, and the radius of curvature of the image side is 3000 to 5000 mm;

[0030] And / or, the radius of curvature of the object side of the sixth lens is -50 to -70 mm, and the radius of curvature of the image side is -15 to -20 mm;

[0031] And / or, the radius of curvature of the object side of the seventh lens is 80 to 120 mm, and the radius of curvature of the image side is -25 to -30 mm;

[0032] And / or, the radius of curvature of the object side of the eighth lens is 60 to 70 mm, and the radius of curvature of the image side is -100 to -120 mm;

[0033] And / or, the radius of curvature of the object side of the ninth lens is 20-30 mm, and the radius of curvature of the image side is 70-100 mm.

[0034] In an optional embodiment, the thickness of the first lens is 5 to 7 mm;

[0035] And / or, the thickness of the second lens is 3.5–5 mm;

[0036] And / or, the thickness of the third lens is 1.2–1.8 mm;

[0037] And / or, the thickness of the fourth lens is 5–7 mm;

[0038] And / or, the thickness of the fifth lens is 1.2–1.8 mm;

[0039] And / or, the thickness of the sixth lens is 4–6 mm;

[0040] And / or, the thickness of the seventh lens is 4–6 mm;

[0041] And / or, the thickness of the eighth lens is 4–6 mm;

[0042] And / or, the thickness of the ninth lens is 4 to 6 mm.

[0043] In an optional implementation, the focal length f of the projection lens satisfies: 8mm ≤ f ≤ 30mm.

[0044] In an optional implementation, the focal length f1 of the first lens and the focal length f of the projection lens satisfy: 1≤f1 / f≤8;

[0045] And / or, the focal length f2 of the second lens and the focal length f of the projection lens satisfy: -7≤f2 / f≤-0.5;

[0046] And / or, the focal length f3 of the third lens and the focal length f of the projection lens satisfy: -7≤f3 / f≤-0.5;

[0047] And / or, the focal length f4 of the fourth lens and the focal length f of the projection lens satisfy: 0.5≤f4 / f≤7;

[0048] And / or, the focal length f5 of the fifth lens and the focal length f of the projection lens satisfy: -8≤f5 / f≤-0.5;

[0049] And / or, the focal length f6 of the sixth lens and the focal length f of the projection lens satisfy: 0.5≤f6 / f≤9;

[0050] And / or, the focal length f7 of the seventh lens and the focal length f of the projection lens satisfy: 0.5≤f7 / f≤6;

[0051] And / or, the focal length f8 of the eighth lens and the focal length f of the projection lens satisfy: 1≤f8 / f≤7;

[0052] And / or, the focal length f9 of the ninth lens and the focal length f of the projection lens satisfy: 1≤f9 / f≤7.

[0053] In an optional implementation, the aperture value F of the projection lens satisfies: 1.4 ≤ F ≤ 16.

[0054] In an optional implementation, the first to ninth lenses are all glass lenses.

[0055] In an optional embodiment, the projection lens further includes an aperture stop disposed between the fourth lens and the fifth lens.

[0056] In an optional embodiment, the projection lens further includes a light valve disposed on the image side of the ninth lens.

[0057] In an optional implementation, the projection lens further includes a prism disposed between the light valve and the ninth lens.

[0058] Secondly, this application provides an optical engine system including a projection lens according to any of the foregoing embodiments.

[0059] Thirdly, this application provides a photocurable printer, including the optomechanical system provided in the second aspect above.

[0060] The beneficial effects of the embodiments of this application include:

[0061] The projection lens provided in this application comprises, along its optical axis from the object side to the image side, a first lens with positive optical power, a second lens with negative optical power, a third lens with negative optical power, a fourth lens with positive optical power, a fifth lens with negative optical power, a sixth lens with positive optical power, a seventh lens with positive optical power, an eighth lens with positive optical power, and a ninth lens with positive optical power, wherein the first to ninth lenses are all spherical lenses. The projection lens of this application employs nine lenses, and by rationally setting the positive and negative relationships and arrangement of the optical powers of each lens, it achieves low optical distortion and high resolution even though all lenses are spherical. Therefore, this projection lens can achieve good projection quality at a low cost.

[0062] The optomechanical system provided in this application includes the aforementioned projection lens, and the optical curing printer provided in this application includes the aforementioned optomechanical system, thus also having the characteristics of lower cost and better print quality. Attached Figure Description

[0063] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0064] Figure 1 This is a schematic diagram of a projection lens in one embodiment of this application;

[0065] Figure 2 Table 1 shows the optical distortion diagram of the projection lens in the embodiment;

[0066] Figure 3 Table 1 shows the MTF curves of the projection lenses in the embodiments.

[0067] Figure 4 This is a schematic diagram of an optomechanical system in one embodiment of this application.

[0068] Icons: 10-Optical system; 11-Projection device; 010-Projection lens; 020-Irradiation assembly; 030-Target imaging surface; 110-First lens; 120-Second lens; 130-Third lens; 140-Fourth lens; 150-Fifth lens; 160-Sixth lens; 170-Seventh lens; 180-Eighth lens; 190-Ninth lens; 200-Aperture stop; 300-Prism; 400-Light valve; 410-Light valve protective glass. Detailed Implementation

[0069] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0070] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0071] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0072] In the description of this application, it should be noted that if terms such as "upper," "lower," "inner," or "outer" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0073] Furthermore, the terms "first," "second," ... "ninth," etc., are used only for distinguishing descriptions and should not be interpreted as indicating or implying relative importance.

[0074] It should be noted that, where there is no conflict, the features in the embodiments of this application can be combined with each other.

[0075] Projection lenses are used in many devices, such as projectors, scanners, and UV printers. The structure of the projection lens has a significant impact on the quality of the projected image. Taking the projection lens in a UV printer as an example, the light emitted by the illumination device passes through the projection lens to form a proper light path, creating an image at the ink tray. The printing material in the tray then solidifies due to the light. Therefore, image quality directly affects printing accuracy, and consequently, the quality of the 3D printed product. Existing projection lenses typically use a large number of lenses, such as ten or more, resulting in a larger device size. Furthermore, to ensure image quality, aspherical lenses are usually used. However, aspherical lenses require molds in the early stages, leading to high investment costs. Moreover, due to the processing characteristics of aspherical lenses, production capacity is limited.

[0076] To overcome the shortcomings of the prior art, embodiments of this application provide a projection lens that has lower cost and higher image quality. Furthermore, embodiments of this application also provide an optomechanical system and a photopolymerization printer, which include the aforementioned projection lens.

[0077] Figure 1 This is a schematic diagram of a projection lens 010 in one embodiment of this application. Please refer to... Figure 1 The lens assembly provided in this embodiment extends along its optical axis (i.e., the dashed line L in the figure) from the object side ( Figure 1 (middle is left) to image side ( Figure 1 The image (right side in the middle) sequentially includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, a seventh lens 170, an eighth lens 180, and a ninth lens 190. The first lens 110 has positive optical power, the second lens 120 has negative optical power, the third lens 130 has negative optical power, the fourth lens 140 has positive optical power, the fifth lens 150 has negative optical power, the sixth lens 160 has positive optical power, the seventh lens 170 has positive optical power, the eighth lens 180 has positive optical power, and the ninth lens 190 has positive optical power. When a lens has positive optical power, it has a converging effect on the light beam; when a lens has negative optical power, it has a diverging effect on the light beam.

[0078] In the embodiments of this application, the first lens 110 to the ninth lens 190 are all spherical lenses, that is, the first lens 110, the second lens 120, the third lens 130, the fourth lens 140, the fifth lens 150, the sixth lens 160, the seventh lens 170, the eighth lens 180 and the ninth lens 190 are all spherical lenses.

[0079] The projection lens 010 provided in this embodiment of the application, through the reasonable setting of the positive and negative relationships of the optical power of each lens and their arrangement order, can ensure a good imaging effect while using a small number of lenses, which is beneficial to the miniaturization of the device. Furthermore, all lenses are spherical lenses, which can significantly reduce manufacturing costs.

[0080] Furthermore, in this embodiment, the object-side surface of the first lens 110 is convex, and the image-side surface is concave; the object-side surface of the second lens 120 is convex, and the image-side surface is concave; both the object-side and image-side surfaces of the third lens 130 are concave; both the object-side and image-side surfaces of the fourth lens 140 are convex; both the object-side and image-side surfaces of the fifth lens 150 are concave; the object-side surface of the sixth lens 160 is concave, and the image-side surface is convex; both the object-side and image-side surfaces of the seventh lens 170 are convex; both the object-side and image-side surfaces of the eighth lens 180 are convex; and the object-side surface of the ninth lens 190 is convex, and the image-side surface is concave. It should be understood that the object-side surface of a lens is the side facing the object, i.e., the left side in the figure; and the image-side surface of a lens is the side facing the image, i.e., the right side in the figure. In other optional embodiments, the shapes of the first lens 110 to the ninth lens 190 may partially adopt the above-described shapes, or may be completely different from the above-described shapes, but the positive and negative relationship of the optical power of each lens should remain unchanged.

[0081] Furthermore, the object-side radius of curvature of the first lens 110 is 40–50 mm, and the image-side radius of curvature is 700–800 mm; the object-side radius of curvature of the second lens 120 is 30–40 mm, and the image-side radius of curvature is 12–18 mm; the object-side radius of curvature of the third lens 130 is -30 to -40 mm, and the image-side radius of curvature is 15–20 mm; the object-side radius of curvature of the fourth lens 140 is 40–50 mm, and the image-side radius of curvature is -35 to -40 mm; and the object-side radius of curvature of the fifth lens 150 is -12 to -18 mm. The curvature radius of the image side of the sixth lens 160 is 3000–5000 mm; the curvature radius of the object side of the seventh lens 170 is -50–70 mm, and the curvature radius of the image side is -15–20 mm; the curvature radius of the object side of the seventh lens 170 is 80–120 mm, and the curvature radius of the image side is -25–30 mm; the curvature radius of the object side of the eighth lens 180 is 60–70 mm, and the curvature radius of the image side is -100–120 mm; the curvature radius of the object side of the ninth lens 190 is 20–30 mm, and the curvature radius of the image side is 70–100 mm. In the above embodiments, a positive curvature radius indicates that the surface arches towards the object side (left), and a negative curvature radius indicates that the surface arches towards the image side (right). In other words, when the radius of curvature of the object's side is positive, it is a convex surface, and when the radius of curvature is negative, it is a concave surface; when the radius of curvature of the image's side is positive, it is a concave surface, and when the radius of curvature is negative, it is a convex surface.

[0082] Furthermore, the thickness of the first lens 110 is 5–7 mm; the thickness of the second lens 120 is 3.5–5 mm; the thickness of the third lens 130 is 1.2–1.8 mm; the thickness of the fourth lens 140 is 5–7 mm; the thickness of the fifth lens 150 is 1.2–1.8 mm; the thickness of the sixth lens 160 is 4–6 mm; the thickness of the seventh lens 170 is 4–6 mm; the thickness of the eighth lens 180 is 4–6 mm; and the thickness of the ninth lens 190 is 4–6 mm. It should be noted that the thicknesses of each lens defined above refer to the thickness at the position where the optical axis passes through (i.e., the center position). In other optional embodiments, the thickness of each lens may be partially selected from the above-described thickness limitations, or each lens may adopt entirely other thickness values.

[0083] Furthermore, the focal length f of the projection lens 010 satisfies: 8mm ≤ f ≤ 30mm. This focal length f is the combined focal length of the nine lenses from the first lens 110 to the ninth lens 190.

[0084] In this embodiment, the relationship between the focal length of each lens and the focal length f of the projection lens 010 is as follows:

[0085] The focal length f1 of the first lens 110 and the focal length f of the projection lens 010 satisfy: 1≤f1 / f≤8;

[0086] The focal length f2 of the second lens 120 and the focal length f of the projection lens 010 satisfy: -7≤f2 / f≤-0.5;

[0087] The focal length f3 of the third lens 130 and the focal length f of the projection lens 010 satisfy: -7≤f3 / f≤-0.5;

[0088] The focal length f4 of the fourth lens 140 and the focal length f of the projection lens 010 satisfy: 0.5≤f4 / f≤7;

[0089] The focal length f5 of the fifth lens 150 and the focal length f of the projection lens 010 satisfy: -8≤f5 / f≤-0.5;

[0090] The focal length f6 of the sixth lens 160 and the focal length f of the projection lens 010 satisfy: 0.5≤f6 / f≤9;

[0091] The focal length f7 of the seventh lens 170 and the focal length f of the projection lens 010 satisfy: 0.5≤f7 / f≤6;

[0092] The focal length f8 of the eighth lens 180 and the focal length f of the projection lens 010 satisfy: 1≤f8 / f≤7;

[0093] The focal length f9 of the ninth lens 190 and the focal length f of the projection lens 010 satisfy: 1≤f9 / f≤7.

[0094] In alternative embodiments, only a portion of the focal length relationships of the lenses described above may be used.

[0095] Optionally, the aperture value F of the projection lens 010 satisfies: 1.4≤F≤16; in a specific embodiment, the aperture value F of the projection lens 010 is 2, and a larger aperture value can ensure sufficient light transmission.

[0096] In this embodiment, the first lens 110 to the ninth lens 190 are all glass lenses. Glass lenses are low in cost and have better resistance to UV light, making them more suitable for use in UV curing printers and ensuring lens lifespan (while plastic lenses are prone to yellowing or burning). In other optional embodiments, especially in applications with low light intensity, the first lens 110 to the ninth lens 190 may be made of plastic, or a combination of plastic and glass.

[0097] Furthermore, the projection lens 010 also includes an aperture stop 200, which is positioned between the fourth lens 140 and the fifth lens 150. The aperture stop 200 can limit the position of the beam edge, thereby limiting the field of view.

[0098] In this embodiment, the projection lens 010 also includes a light valve 400, which is disposed on the image side of the ninth lens 190. The light valve 400 is a device with light modulation function, which can control the deflection of light. Typically, a light source is disposed on the side of the light valve 400 away from the ninth lens 190. The light valve 400 determines whether light can enter the projection lens 010, so that the light entering the lens corresponds to the final image. The type of light valve 400 can be a digital micromirror device (DMD) light valve 400, a liquid crystal (LCD) light valve 400, or a liquid crystal on silicon (LCOS) light valve 400, etc. In this embodiment, the diagonal length of the display area of ​​the light valve 400 is 0.2″ to 1″.

[0099] In this embodiment, the projection lens 010 also includes a light valve protective glass 410, which is disposed between the light valve 400 and the ninth lens 190 to protect the light valve 400.

[0100] In this embodiment, the projection lens 010 further includes a prism 300, which is disposed between the light valve 400 and the ninth lens 190. The prism 300 in this embodiment can be a TIR prism or an RTIR prism, and its design is equivalent to a flat glass plate.

[0101] Based on the reversibility of light, in other embodiments, the light valve 400 and the prism 300 may also be disposed on the object side of the first lens 110, with the prism 300 disposed between the light valve 400 and the first lens 110.

[0102] Optionally, the projection lens 010 provided in this embodiment matches light waves of 350nm to 500nm, which can be a single waveband or a waveband of a certain width within this range. The clear projection surface range is from 0.1m to infinity.

[0103] In one specific embodiment of this application, the parameters of the projection lens 010 are shown in Table 1.

[0104] Table 1:

[0105]

[0106]

[0107] In Table 1, the thickness of the object surface represents the distance (air thickness) between the object surface and the object-side surface of the first lens 110. Each lens, prism 300, and light valve protective glass 410 has two thickness values: the first (upper) thickness is its own thickness, and the second (lower) thickness is the distance (air thickness) between that component and the next component. The thickness value of the aperture 200 refers to the distance from the aperture 200 to the object-side surface of the fifth lens 150.

[0108] When the projection lens 010 is used in a photopolymer printer, the light-emitting surface of the light source in the optical engine system can be set at the image plane position, while the material tray is located at the object plane position, so that the projected image can be projected onto the printing material at the bottom of the material tray, allowing it to solidify and form according to the projected image.

[0109] Figure 2 Table 1 shows the optical distortion diagram of the projection lens 010 in the embodiment. Figure 3 Table 1 shows the MTF diagram of the projection lens 010 in the embodiment. From... Figure 2 and Figure 3 As can be seen, the projection lens 010 provided in this embodiment has small distortion, and at a cutoff frequency of 93 lp / mm, the lens's MTF design value is >0.7 (in the prior art, a value >0.4 is generally considered acceptable), resulting in stronger resolution and sharper projected text and images.

[0110] The optical engine system provided in this embodiment includes the projection lens 010 provided in the above embodiment. Figure 4 This is a schematic diagram of an optomechanical system 10 in one embodiment of this application. Figure 1As shown, the optomechanical system 10 includes two projection devices 11, each including a projection lens 010 and an irradiation component 020 as provided in the aforementioned embodiments. The irradiation component 020 is used to form a light beam passing through the projection lens 010 to form a projected image on the target imaging surface 030. The optomechanical system 10 of this application includes two projection devices 11, each capable of forming a projected image on the same target imaging surface 030. In optional other embodiments, the optomechanical system 10 may include only one projection device 11, or include more projection devices 11. With two or more projection devices 11, two or more projected images can be formed on the target imaging surface 030, and these projected images can be stitched together or overlapped. When this optomechanical system 10 is applied to a photopolymer printer, the overlap of the two or more projected images can accelerate the curing speed of the photopolymer material, i.e., increase the printing speed. This method of increasing printing speed places lower demands on the power of individual irradiation components 020 and the performance of individual light valves 400, thus improving their lifespan and reducing heat dissipation requirements. Furthermore, increasing the number of projection devices 11 to increase total optical power reduces the performance requirements of individual irradiation components 020, resulting in a higher upper limit for total optical power and making it easier to increase printing speed. Additionally, by stitching together the projected images, it can be used to print larger devices. Moreover, by integrating multiple projection devices 11 into a single device, the optomechanical system 10 improves accuracy and consistency, simplifies assembly processes, and consequently enhances printing speed and scalability.

[0111] The photopolymer printer (not shown in the figure) provided in this application embodiment includes the optomechanical system 10 provided in the foregoing embodiment. It should be understood that the photopolymer printer also includes other related components for realizing 3D printing, such as a forming platform, a material tray, etc. The arrangement and working principle of the related components can be referred to the prior art, and will not be described in detail here.

[0112] In summary, the projection lens 010 provided in this application comprises, along its optical axis from the object side to the image side, a first lens 110 with positive optical power, a second lens 120 with negative optical power, a third lens 130 with negative optical power, a fourth lens 140 with positive optical power, a fifth lens 150 with negative optical power, a sixth lens 160 with positive optical power, a seventh lens 170 with positive optical power, an eighth lens 180 with positive optical power, and a ninth lens 190 with positive optical power. All of these lenses, from the first lens 110 to the ninth lens 190, are spherical lenses. The projection lens 010 of this application employs nine lenses. By rationally setting the positive and negative relationships and arrangement of the optical powers of each lens, it achieves low optical distortion and high resolution even when all lenses are spherical. Therefore, this projection lens 010 can achieve good projection quality at a low cost.

[0113] The optomechanical system 10 provided in this application includes the projection lens 010 described above, and the optical curing printer provided in this application includes the optomechanical system 10 described above. Therefore, it also has the characteristics of lower cost and better printing quality.

[0114] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A projection lens, characterized in that, Along its optical axis from the object side to the image side, it includes, in sequence: A first lens with positive optical power; A second lens with negative optical power; A third lens with negative optical power; A fourth lens with positive optical power; A fifth lens with negative optical power; A sixth lens with positive optical power; A seventh lens with positive optical power; An eighth lens with positive optical power; A ninth lens with positive optical power; The first lens through the ninth lens are all spherical lenses; The projection lens has a total of nine lenses; The object-side surface of the first lens is convex, and the image-side surface is concave. The object-side surface of the second lens is convex, and the image-side surface is concave. Both the object-side and image-side surfaces of the third lens are concave. Both the object-side and image-side surfaces of the fourth lens are convex. Both the object-side and image-side surfaces of the fifth lens are concave. The object-side surface of the sixth lens is concave, and the image-side surface is convex. Both the object-side and image-side surfaces of the seventh lens are convex. Both the object-side and image-side surfaces of the eighth lens are convex. The object-side surface of the ninth lens is convex, and the image-side surface is concave. The focal length f of the projection lens satisfies: 8mm≤f≤30mm.

2. The projection lens according to claim 1, characterized in that, The object-side radius of curvature of the first lens is 40~50mm, and the image-side radius of curvature is 700~800mm; And / or, the radius of curvature of the object side of the second lens is 30~40mm, and the radius of curvature of the image side is 12~18mm; And / or, the radius of curvature of the object side of the third lens is -30 to -40 mm, and the radius of curvature of the image side is 15 to 20 mm; And / or, the radius of curvature of the object side of the fourth lens is 40~50mm, and the radius of curvature of the image side is -35~-40mm; And / or, the radius of curvature of the object side of the fifth lens is -12 to -18 mm, and the radius of curvature of the image side is 3000 to 5000 mm; And / or, the radius of curvature of the object side of the sixth lens is -50 to -70 mm, and the radius of curvature of the image side is -15 to -20 mm; And / or, the radius of curvature of the object side of the seventh lens is 80~120mm, and the radius of curvature of the image side is -25~-30mm; And / or, the radius of curvature of the object side of the eighth lens is 60~70mm, and the radius of curvature of the image side is -100~-120mm; And / or, the radius of curvature of the object side of the ninth lens is 20~30mm, and the radius of curvature of the image side is 70~100mm.

3. The projection lens according to claim 1, characterized in that, The thickness of the first lens is 5~7mm; And / or, the thickness of the second lens is 3.5~5mm; And / or, the thickness of the third lens is 1.2~1.8mm; And / or, the thickness of the fourth lens is 5~7mm; And / or, the thickness of the fifth lens is 1.2~1.8mm; And / or, the thickness of the sixth lens is 4~6mm; And / or, the thickness of the seventh lens is 4~6mm; And / or, the thickness of the eighth lens is 4~6mm; And / or, the thickness of the ninth lens is 4~6mm.

4. The projection lens according to claim 1, characterized in that, The focal length f1 of the first lens and the focal length f of the projection lens satisfy: 1≤f1 / f≤8; And / or, the focal length f2 of the second lens and the focal length f of the projection lens satisfy: -7≤f2 / f≤-0.5; And / or, the focal length f3 of the third lens and the focal length f of the projection lens satisfy: -7≤f3 / f≤-0.5; And / or, the focal length f4 of the fourth lens and the focal length f of the projection lens satisfy: 0.5≤f4 / f≤7; And / or, the focal length f5 of the fifth lens and the focal length f of the projection lens satisfy: -8≤f5 / f≤-0.5; And / or, the focal length f6 of the sixth lens and the focal length f of the projection lens satisfy: 0.5≤f6 / f≤9; And / or, the focal length f7 of the seventh lens and the focal length f of the projection lens satisfy: 0.5≤f7 / f≤6; And / or, the focal length f8 of the eighth lens and the focal length f of the projection lens satisfy: 1≤f8 / f≤7; And / or, the focal length f9 of the ninth lens and the focal length f of the projection lens satisfy: 1≤f9 / f≤7.

5. The projection lens according to any one of claims 1-4, characterized in that, The aperture value F of the projection lens satisfies: 1.4≤F≤16.

6. The projection lens according to any one of claims 1-4, characterized in that, All of the first to the ninth lenses are glass lenses.

7. The projection lens according to any one of claims 1-4, characterized in that, The projection lens also includes an aperture stop, which is disposed between the fourth lens and the fifth lens.

8. The projection lens according to any one of claims 1-4, characterized in that, The projection lens also includes a light valve, which is disposed on the image side of the ninth lens.

9. The projection lens according to claim 8, characterized in that, The projection lens also includes a prism, which is disposed between the light valve and the ninth lens.

10. An optomechanical system, characterized in that, The projection lens includes any one of claims 1-9.

11. A photopolymer printer, characterized in that, Includes the optomechanical system as described in claim 10.

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