Projection lens and 3D printing device

Abstract

The embodiments of the present application provide a projection lens and a 3D printing device. The projection lens includes: a front lens group and a rear lens group arranged in sequence in the direction from the object plane to the image plane, and both lens groups can move along the optical axis according to the projection distance of the projection lens to achieve a fixed focus effect; the optical power of the front lens group is negative, and the front lens group includes: a first lens with positive optical power, a second lens with negative optical power, and a third lens with negative optical power; the optical power of the rear lens group is positive, and the rear lens group includes: a first sub-lens group with negative optical power, an aperture, a second sub-lens group with positive optical power, and a third sub-lens group with positive optical power; the first sub-lens group includes a fourth lens with negative optical power, the second sub-lens group includes a fifth lens and a sixth lens with positive optical power, and the third sub-lens group includes a seventh lens with negative optical power, an eighth lens with positive optical power, a ninth lens with positive optical power, and a tenth lens with positive optical power.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of optical display technology, and more specifically, to a projection lens and a 3D printing device. Background Art

[0002] Currently, there are many types of 3D printers on the market. One type of 3D printer uses UV glue as the printing material. Its working principle is to use the precise irradiation of ultraviolet light to solidify and accumulate the material layer by layer, and finally construct the required three-dimensional shape.

[0003] However, as 3D printing technology expands across various fields, the market is placing increasingly stringent demands on the brightness and resolution of 3D printed products. Against this backdrop, traditional projection lenses used in 3D printing equipment are gradually revealing their limitations, particularly in terms of resolution. They are no longer able to meet the growing demand for high-precision printing, which, to a certain extent, has hindered the further development and promotion of 3D printing technology.

[0004] In view of this, providing a new technical solution to overcome the above technical bottlenecks and improve the resolution of 3D printed products has become a key issue that needs to be urgently addressed in the current industry. Summary of the Invention

[0005] The purpose of this application is to provide a new technology solution for a projection lens with high resolution for 3D printing equipment and a 3D printing equipment.

[0006] In a first aspect, embodiments of the present application provide a projection lens. The projection lens includes a front lens group and a rear lens group arranged sequentially in a direction from an object plane to an image plane, wherein both the front lens group and the rear lens group can be moved along an optical axis according to a projection distance of the projection lens to achieve a fixed focus effect;

[0007] The optical focal length of the front lens group is negative, and the front lens group includes, in the direction from the object plane to the image plane: a first lens with positive optical focal length, a second lens with negative optical focal length, and a third lens with negative optical focal length;

[0008] The optical focal length of the rear lens group is positive, and the rear lens group includes, in the direction from the object plane to the image plane:

[0009] a first sub-lens group with negative optical power, an aperture, a second sub-lens group with positive optical power, and a third sub-lens group with positive optical power;

[0010] The first sub-lens group includes a fourth lens with negative optical power, the second sub-lens group includes a fifth lens and a sixth lens with positive optical power, and the third sub-lens group includes a seventh lens with negative optical power, an eighth lens with positive optical power, a ninth lens with positive optical power, and a tenth lens with positive optical power.

[0011] Optionally, the projection distance D of the projection lens is in the range of: 223mm<D<288mm; and the distance D1 between the surface of the third lens in the front group lens group close to the rear group lens group and the surface of the fourth lens close to the third lens is in the range of: 9.4mm<D1<9.9mm, and the distance D2 between the surface of the tenth lens in the rear group lens group close to the image plane and the surface adjacent to the surface is in the range of: 4.0mm<D2<4.5mm.

[0012] Optionally, when adjusting the projection distance of the projection lens, the front lens group as a whole moves along the optical axis and the rear lens group as a whole moves along the optical axis;

[0013] When the distance D1 between the surface of the third lens element close to the rear lens group and the surface of the fourth lens element close to the third lens element is in the range of 9.4 mm < D1 < 9.9 mm, the movement range of the front lens group is 0.25 mm to 0.35 mm;

[0014] When the distance D2 between the surface of the tenth lens close to the image plane and the surface adjacent to the tenth lens is in the range of 4.0 mm < D2 < 4.5 mm, the movement range of the rear lens group is in the range of 0.25 mm to 0.35 mm.

[0015] Optionally, the ratio range of the effective focal length EFL1 of the front group lens assembly to the effective focal length EFL of the projection lens is: -3.5<EFL1 / EFL<-2.5; and the ratio range of the effective focal length EFL2 of the rear group lens assembly to the effective focal length EFL of the projection lens is: 1.1<EFL2 / EFL<1.4.

[0016] Optionally, the effective focal length range of the front lens group is: -51mm<EFL1<-45mm; the effective focal length range of the rear lens group is: 20mm<EFL2<22mm; the effective focal length range of the projection lens is: 16mm<EFL<18mm.

[0017] Optionally, the first sub-lens group further includes an eleventh lens with negative optical power, and the eleventh lens is arranged relative to the fourth lens and close to the aperture stop;

[0018] The eleventh lens and the fourth lens are both meniscus lenses, and the concave surfaces of the eleventh lens and the fourth lens are arranged opposite to each other.

[0019] Optionally, the refractive index of all lenses in the projection lens does not exceed 1.83, and the Abbe number of all lenses in the projection lens is not less than 31.

[0020] Optionally, the refractive index of the eighth lens, the ninth lens, and the tenth lens is lower than 1.6, and / or the Abbe number of the eighth lens, the ninth lens, and the tenth lens is greater than 60.

[0021] Optionally, the Abbe number of the fifth lens is greater than 65.

[0022] Optionally, curvatures of two adjacent surfaces of the seventh lens and the eighth lens are different.

[0023] In a second aspect, embodiments of the present application further provide a 3D printing device, wherein the 3D printing device includes the projection lens as described in the first aspect.

[0024] One of the technical effects of this application is:

[0025] The embodiment of the present application provides a projection lens. The projection lens includes a front lens group and a rear lens group, which are used in combination. By moving the front lens group and the rear lens group, the projection lens can ensure the imaging quality under different projection distances and ensure the quality of 3D printing. By reasonably allocating the optical power of the front lens group and the optical power of the rear lens group, the distortion and field curvature are corrected. The projection lens of this structure uses a small number of lenses, has a simple structure, and has a high resolving power. It can have a high resolution. At a resolution of 93lp / mm, the MTF is not less than 70%; and the lens distortion is small, the absolute value of the distortion is less than 0.2%, and the image plane is telecentric (Telecentric CRA angle <1°), which ensures uniform illumination of the image plane, achieves imaging quality far beyond what can be achieved with existing technologies, and improves the quality of 3D printing.

[0026] Other features and advantages of the present specification will become apparent from the following detailed description of exemplary embodiments of the present specification with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the specification and, together with the description, serve to explain the principles of the specification.

[0028] Figure 1 Shown is a structural diagram of an embodiment of a projection lens provided in an embodiment of the present application.

[0029] Figure 2 Shown Figure 1 MTF diagram of the projection lens at a projection distance of 287.1mm.

[0030] Figure 3 Shown Figure 1 Field curvature distortion diagram of the medium projection lens at a projection distance of 287.1mm.

[0031] Figure 4 Shown Figure 1 MTF diagram of the projection lens at a projection distance of 224.47mm.

[0032] Figure 5 Shown Figure 1 Field curvature distortion diagram of the medium projection lens with a projection distance of 224.47mm.

[0033] Figure 6 Shown is a structural diagram of another embodiment of the projection lens provided in an embodiment of the present application.

[0034] Figure 7 Shown Figure 6 MTF diagram of the projection lens at a projection distance of 287.1mm.

[0035] Figure 8 Shown Figure 6 Field curvature distortion diagram of the medium projection lens at a projection distance of 287.1mm.

[0036] Figure 9 Shown Figure 6 MTF diagram of the projection lens at a projection distance of 224.47mm.

[0037] Figure 10 Shown Figure 6 Field curvature distortion diagram of the medium projection lens with a projection distance of 224.47mm.

[0038] Description of reference numerals:

[0039] 100, projection lens; 200, front lens group; 300, rear lens group; 301, first sub-lens group; 302, second sub-lens group; 303, third sub-lens group;

[0040] 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Fifth lens; 6. Sixth lens; 7. Seventh lens; 8. Eighth lens; 9. Ninth lens; 10. Tenth lens; 11. Eleventh lens;

[0041] 21. Equivalent galvanometer; 22. Equivalent prism; 23. Image source; 24. Aperture. DETAILED DESCRIPTION

[0042] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application.

[0043] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present disclosure, its application, or uses.

[0044] Techniques and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the techniques and equipment should be considered part of the specification.

[0045] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0046] It should be noted that like reference numerals and letters refer to like items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0047] An embodiment of the present application provides a projection lens 100. This projection lens 100 is used in 3D printing equipment. When used in 3D printing equipment, the projection lens 100 can be paired with a DMD chip, achieving high resolution and high-quality imaging. Furthermore, the projection lens 100 can also be used in other types of equipment requiring projection.

[0048] Reference Figure 1 and Figure 6 The projection lens 100 includes: a front lens group 200 and a rear lens group 300 arranged in sequence in the direction from the object plane to the image plane. The front lens group 200 and the rear lens group 300 can both move along the optical axis according to the projection distance of the projection lens to achieve a fixed focus effect.

[0049] The front lens group 200 has a negative optical power. The front lens group 200 includes, in the direction from the object plane to the image plane: a first lens 1 with a positive optical power, a second lens 2 with a negative optical power, and a third lens 3 with a negative optical power.

[0050] The optical focal length of the rear lens group 300 is positive. The rear lens group 300 includes, in the direction from the object plane to the image plane: a first sub-lens group 301 with negative optical focal length, an aperture 24, a second sub-lens group 302 with positive optical focal length, and a third sub-lens group 303 with positive optical focal length.

[0051] The first sub-lens group 301 includes a fourth lens 4 with negative optical power, the second sub-lens group 302 includes a fifth lens 5 and a sixth lens 6 with positive optical power, and the third sub-lens group 303 includes a seventh lens 7 with negative optical power, an eighth lens 8 with positive optical power, a ninth lens 9 with positive optical power, and a tenth lens 10 with positive optical power, wherein the curvatures of two adjacent surfaces of the seventh lens 7 and the eighth lens 8 are different.

[0052] In the embodiments of the present application, projection lens 100 is primarily used in 3D printing equipment. The image plane is the end that receives light, and the object plane is the end where the object is located. Light is irradiated by the DMD chip for processing before being imaged by projection lens 100. The image is then projected onto a resin layer, which is then cured using a light source to ultimately form a 3D object. As will be appreciated, projection lens 100 also includes a lens barrel, which secures and protects the various lenses, forming a stable lens structure.

[0053] The projection lens 100 is composed of a front lens group 200 and a rear lens group 300, both of which are capable of movement along the optical axis. However, the movement of the front lens group 200 and the rear lens group 300 along the optical axis does not necessarily qualify the projection lens as a zoom lens. A zoom lens is one that uses the movement of the lens groups to increase or decrease the size of the projected image at a given projection distance.

[0054] In this embodiment, the movement of the front lens group 200 and the rear lens group 300 along the optical axis achieves a fixed focus effect. Specifically, at the same projection distance, the projection lens has only one focus position, which means that the size of the image projected by the projection lens cannot be adjusted at that projection distance.

[0055] Specifically, both the front lens group 200 and the rear lens group 300 can be moved along the optical axis according to the projection distance of the projection lens to achieve focus at a specific position, where the focus position is related to the projection distance. Since both the front lens group 200 and the rear lens group 300 can be moved along the optical axis according to the projection distance of the projection lens to achieve focus, the projection lens of this embodiment can adapt to projection requirements at different projection distances.

[0056] When the projection distance changes, the front lens group 200 and the rear lens group 300 will move accordingly along the optical axis to enable the projection lens to project a clear image at the new distance. Through this movement and adjustment, the lens can refocus to achieve a fixed focus effect and ensure image clarity.

[0057] The projection lens provided in this application can adapt to different projection distances and image size requirements. For example, when the projection distance is short, the lens assembly may need to be moved to a certain position to obtain a clear image. When the projection distance becomes longer or the image size needs to be adjusted, the lens assembly is moved again to an appropriate position, thereby meeting the requirements of various projection scenarios.

[0058] Front lens group 200 is located close to the object plane and has negative optical power. It comprises a first lens 1, a second lens 2, and a third lens 3. The positive optical power of first lens 1 converges light. Second lens 2 diverges light, reducing aberrations. Third lens 3 further diverges light, optimizing the light propagation path. By properly distributing the optical power of second and third lenses 2 and 3, the reduction in image plane illumination caused by excessive light divergence can be avoided.

[0059] In a specific embodiment, referring to Figure 1 and Figure 6 The first lens 1, the second lens 2, and the third lens 3 are all meniscus lenses. A meniscus lens specifically refers to a structure with a convex surface on one side and a concave surface on the other side. The focal length of a meniscus lens can be positive or negative. In the front lens group 200, the first lens 1 is a positive meniscus lens, and the second lens 2 and the third lens 3 are negative meniscus lenses.

[0060] In the front lens group 200, a combination of positive and negative lenses is used. When the front lens group 200, which includes both positive and negative lenses, is used in conjunction with the rear lens group 300, the projection lens 100 can achieve high-resolution, high-quality imaging and adapt to varying projection distances and image sizes. For example, by moving at least one of the lens groups in the front lens group 200 and the rear lens group 300 along the optical axis, the focal length of the projection lens 100 can be adjusted, ensuring that the projected image remains clear at varying projection distances. For example, in 3D printing, when the distance between the printing platform and the lens changes, focusing can be used to maintain the sharpness of the projected image. Furthermore, the aberration correction capabilities of the meniscus lens combination (such as spherical aberration and field curvature) remain stable during focusing, preventing image quality degradation caused by focusing adjustments.

[0061] Preferably, the front lens group 200 and the rear lens group 300 are coordinated to move and adjust according to the actual projection distance of the projection lens 100. By cooperating with each other, the two can effectively ensure that the projected image always remains clear under different projection distance conditions, thereby meeting diverse projection needs.

[0062] Reference Figure 1 and Figure 6 The rear lens group 300 includes a first sub-lens group 301, an aperture 24, a second sub-lens group 302 and a third sub-lens group 303.

[0063] The optical power of the first sub-lens group 301 is negative. Figure 1 , the first sub-lens group 301 includes a fourth lens 4 with negative optical power. Figure 6 The first sub-lens group 301 includes a fourth lens 4 with negative optical power and an eleventh lens 11 with negative optical power.

[0064] For example, referring to Figure 1, the fourth lens 4 is a meniscus lens, specifically a negative meniscus lens. Figure 6 , the fourth lens 4 and the eleventh lens 11 are both negative meniscus lenses.

[0065] The optical power of the second sub-lens group 302 is positive. Figure 1 and Figure 6 The second sub-lens group 302 includes a fifth lens 5 and a sixth lens 6 with positive optical power.

[0066] For example, referring to Figure 1 The fifth lens 5 is a plano-convex lens, the sixth lens 6 is a meniscus lens, and the convex surfaces of the two lenses are arranged adjacent to each other.

[0067] For example, referring to Figure 6 , the fifth lens 5 is a meniscus lens, and the sixth lens 6 is a biconvex lens.

[0068] The optical power of the third sub-lens group 303 is positive. Figure 1 and Figure 6 The third sub-lens group 303 includes a seventh lens 7 with negative optical power, an eighth lens 8 with positive optical power, a ninth lens 9 and a tenth lens 10.

[0069] For example, referring to Figure 1 , the seventh lens 7 is a biconcave lens, the eighth lens 8 is a meniscus lens, the ninth lens 9 and the tenth lens are both biconvex lenses. Figure 6 , the seventh lens 7 is a biconcave lens, the eighth lens 8 is a meniscus lens, the tenth lens 10 is a plano-convex lens, and the ninth lens 9 is a biconvex lens.

[0070] In rear lens group 300, first sub-lens group 301 has a negative optical power, which can expand the incident light beam and reduce aberrations (such as spherical aberration and coma). For example, a negative meniscus lens can be used in first sub-lens group 301 to balance aberrations in conjunction with the rear positive lens group.

[0071] exist Figure 6 In the CMOS image sensor, the double negative meniscus lens combination can further enhance the divergence capability while simultaneously dispersing the aberration correction pressure through curvature optimization.

[0072] In the second sub-lens group 302 of the rear lens group 300, the optical power of the second sub-lens group 302 is positive, and the positive optical power of the second sub-lens group 302 converges light. The positive optical power combination of the fifth lens 5 and the sixth lens 6 can correct spherical aberration, coma and astigmatism.

[0073] In the third lens sub-group 303 of the rear lens group 300, the optical power of the third lens sub-group 303 is positive. From the object plane to the image plane, the optical power of the lenses is negative, positive, positive, and positive. The negative power lens (the seventh lens element 7) is used to diverge light. The eighth lens element 8 is used to converge light. The ninth lens element 9 further converges light. The tenth lens element 10 fine-tunes the focus of the light. The third lens sub-group 303 works in conjunction with the other lens groups to minimize spherical aberration, coma, astigmatism, and field curvature, achieving high-resolution imaging for the projection lens 100.

[0074] In the rear lens group 300 , the aperture 24 is located behind the first sub-lens group 301 , which can balance the aberration correction pressure of the front lens group and the rear lens group, thereby improving the overall imaging quality.

[0075] In the embodiment of the present application, the front lens group 200 and the rear lens group 300 are used in combination. By moving the front lens group 200 and the rear lens group 300, the projection lens 100 can ensure image quality and 3D printing quality under different projection distances. By reasonably allocating the optical power of the front lens group 200 and the rear lens group 300, the front lens group 200 corrects spherical aberration through a combination of positive, negative, and negative optical power lenses to reduce the focus difference between the center and edge light. The rear lens group 300 further corrects spherical aberration through three-letter lens groups to ensure uniform focus on the image plane and improve image quality. The front lens group 200 and the rear lens group 300 reasonably allocate optical power to correct distortion and field curvature. The projection lens 100 of this structure uses a small number of lenses, has a simple structure, and has high resolving power, which can achieve high resolution. At a resolution of 93lp / mm, the MTF is not less than 70%. In addition, the lens distortion is small, with the absolute value of the distortion less than 0.2%. The image plane is telecentric (Telecentric CRA angle <1°), ensuring uniform illumination on the image plane, achieving imaging quality far exceeding that achieved by existing technologies, and improving the quality of 3D printing.

[0076] In an optional embodiment of the present application, in the rear lens group 300, the curvatures of the adjacent surfaces of the negative-power seventh lens element 7 and the positive-power eighth lens element 8 are different. This means that the seventh and eighth lenses 7 and 8 are non-cemented lenses, meaning there is no optical glue between them. This improves the structural stability of the projection lens 100 during use. Cemented lenses can yellow and crack under UV light, affecting image quality. The non-cemented design of the seventh and eighth lenses 7 and 8, secured by independent lens mounts, prevents damage from UV wavelengths.

[0077] In the embodiment of the present application, the projection distance D of the projection lens 100 is in the range of 223 mm < D < 288 mm; and the distance D1 between the surface of the third lens 3 close to the rear lens group 300 and the surface of the fourth lens 4 close to the third lens 3 is in the range of 9.4 mm < D1 < 9.9 mm. The distance D2 between the surface of the tenth lens 10 in the rear lens group 300 close to the image plane and the surface adjacent to the surface is in the range of 4.0 mm < D2 < 4.5 mm.

[0078] It should be noted that, when the projection distance D of the projection lens 100 is determined, the above-mentioned parameters D1 and D2 are unique, that is, they only correspond to a set of determined values.

[0079] In this embodiment, this projection distance range is suitable for desktop or small to medium-sized industrial 3D printing equipment, enabling high-precision printing in limited spaces. For example, in a desktop 3D printer, a minimum projection distance of 223mm can accommodate compact device structures, while a maximum projection distance of 285mm can meet the needs of larger-format printing. For example, the projection distance D of the projection lens 100 can be 224mm, 224.47mm, 225mm, 230mm, 240mm, 250mm, 260mm, 270mm, 280mm, or 287.1mm.

[0080] In this embodiment, the relative positions of the lenses in the optical path are changed by moving the front lens group 200 and / or the rear lens group 300 in the lens system to compensate for image blur caused by changes in projection distance or aberrations. For example, when the projection distance changes, the values ​​of parameters D1 and D2 are readjusted to adapt to the new projection distance.

[0081] The distance D1 between the surface of the third lens element 3 closest to the rear lens group 300 and the surface of the fourth lens element 4 closest to the third lens element 3 is 9.4mm < D1 < 9.9mm. This distance range optimizes the light propagation path and reduces spherical aberration, coma, and astigmatism by controlling the air gap between the front lens group 200 (negative power) and the rear lens group 300 (positive power). For example, D1 can be 9.8mm, 9.81mm, 9.7mm, 9.75mm, 9.6mm, or 9.5mm.

[0082] The distance D2 between the surface of the tenth lens 10 near the image plane and the surface adjacent to it is: 4.0mm < D2 < 4.5mm. For example, the distance D2 between the surface of the tenth lens 10 near the image plane and the surface of the equivalent galvanometer 21 is: 4.0mm < D2 < 4.5mm. The range of D2 directly affects the image plane position and depth of focus (DOF), ensuring that materials of different layer thicknesses can be clearly imaged during the 3D printing process, improving resolution and enhancing printing quality. For example, the D2 distance can be: 4.1mm, 4.12mm, 4.16mm, 4.2mm, 4.3mm, 4.4mm, 4.41mm, 4.44mm.

[0083] In this embodiment, by moving the front lens group 200 and / or the rear lens group 300 within the lens, the lens group spacing and position are optimized, aberrations are compensated, and the depth of focus (the depth of focus refers to the range within which the image plane can move along the optical axis while still maintaining a clear image) is extended, ensuring a clear image at a fixed projection distance. In 3D printing, the projection distance must be adjusted based on the format or process requirements, and then the image quality is optimized through focusing. These two factors work together to ensure print quality.

[0084] In the embodiment of the present application, the throw ratio of projection lens 100 is 1.3-1.6. The throw ratio refers to the ratio of projection distance to image width. Because the throw ratio affects image quality and cost, in this embodiment, the throw ratio of projection lens 100 is set to be greater than 1.3 and less than 1.6. Exemplary throw ratios of projection lens 100 are 1.4, 1.5, 1.6, 1.495, and so on. This allows for achieving higher brightness and clearer images while meeting the aforementioned projection distance, thereby improving print quality.

[0085] In a further embodiment of the present application, when adjusting the projection distance of the projection lens, the front lens group 200 moves along the optical axis as a whole and the rear lens group 300 moves along the optical axis as a whole;

[0086] When the distance D1 between the surface of the third lens 3 close to the rear lens group 300 and the surface of the fourth lens 4 close to the third lens 3 is in the range of 9.4 mm < D1 < 9.9 mm, the movement range of the front lens group 200 is in the range of 0.25 mm to 0.35 mm.

[0087] When the distance D2 between the surface of the tenth lens 10 close to the image plane and the surface adjacent to the tenth lens 10 is in the range of 4.0 mm < D2 < 4.5 mm, the movement range of the rear lens group 300 is in the range of 0.25 mm to 0.35 mm.

[0088] In this embodiment, when the projection distance of the projection lens needs to be adjusted, the front lens group 200 and the rear lens group 300 will move as a whole along the optical axis. This design allows the projection lens to adapt to different projection distances, thereby projecting clear images at the new distance and meeting diverse projection needs.

[0089] In this embodiment, when D1 meets the aforementioned range, the front lens group 200 moves within a relatively precise interval to ensure that the projection lens can function properly and achieve good imaging results when adjusting the projection distance. When D2 meets the aforementioned requirements, the movement of the rear lens group 300 can coordinate with the movement of the front lens group 200 to achieve clear imaging at different projection distances.

[0090] For example, when the D1 range is 9.4 mm < D1 < 9.9 mm, the movement range of the front lens group 200 can be 0.28 mm, 3 mm, etc.; when the D2 range is 4.0 mm < D2 < 4.5 mm, the movement range of the rear lens group 300 can be 0.28 mm, 0.3 mm, etc.

[0091] In the embodiment of the present application, the ratio of the effective focal length EFL1 of the front lens group 200 to the effective focal length EFL of the projection lens 100 is in the range of: -3.5<EFL1 / EFL<-2.5; and the ratio of the effective focal length EFL2 of the rear lens group 300 to the effective focal length EFL of the projection lens 100 is in the range of: 1.1<EFL2 / EFL<1.4.

[0092] In this embodiment, the front lens group 200 (with a negative EFL1 value) acts as a diverging lens group, diverging the incident light and expanding the beam aperture, providing greater scope for aberration correction in the rear lens group 300. This ratio ensures that the divergence of the front lens group 200 matches the convergence of the rear lens group 300, keeping overall system aberrations (such as field curvature and distortion) within a reasonable range.

[0093] Rear lens group 300 (with a positive EFL2 value) acts as a converging lens group, responsible for converging diverging light onto the image plane to form a sharp image. This ratio range optimizes rear lens group 300's aberration correction capabilities, reducing high-order aberrations such as chromatic aberration and astigmatism.

[0094] In the embodiment of the present application, the ratio of the effective focal length EFL1 of the front lens group 200 to the effective focal length EFL of the projection lens 100 is in the range of: -3.5<EFL1 / EFL<-2.5. Exemplarily, the ratio EFL1 / EFL can be: -3.4, -3.3, -3.2, -3.1, -3.0, -2.9, -2.8, -2.7, -2.6.

[0095] The ratio of the effective focal length EFL2 of the rear lens group 300 to the effective focal length EFL of the projection lens 100 is in the range of 1.1<EFL2 / EFL<1.4. For example, the ratio EFL2 / EFL may be 1.2, 1.25, 1.3, or 1.35.

[0096] In the embodiment of the present application, the effective focal length range of the front lens group 200 is: -51mm<EFL1<-45mm; the effective focal length range of the rear lens group 300 is: 20mm<EFL2<22mm; and the effective focal length range of the projection lens 100 is: 16mm<EFL<18mm.

[0097] In the embodiments of this application, the effective focal length range of the front lens group 200, rear lens group 300, and projection lens 100 is limited. The negative focal power of the front lens group 200 and the positive focal power of the rear lens group 300 work together to correct aberrations and ensure clear imaging. This focal length range optimizes spot size and energy density uniformity, improving printing accuracy. Furthermore, this rational focal length range design reduces lens size, improving image quality and resolution while also reducing the lateral size of the projection lens 100.

[0098] In this embodiment, the effective focal length range of the front lens group 200 is: -51mm<EFL1<-45mm. Exemplarily, the effective focal length range of the front lens group 200 is -50mm, -50.735mm, -49mm, -48mm, -47mm, -46mm, and -48.862mm.

[0099] The effective focal length range of the rear lens group 300 is: 20 mm < EFL2 < 22 mm. For example, the effective focal length range of the rear lens group 300 is: 20.5 mm, 21 mm, 21.5 mm, 21.679 mm, and 21.881 mm.

[0100] The effective focal length range of the projection lens 100 is: 16 mm < EFL < 18 mm. For example, the effective focal length range of the projection lens 100 is: 16.5 mm, 17 mm, 17.195 mm, 17.216 mm, and 17.5 mm.

[0101] Reference Figure 1 The projection lens 100 includes 10 lenses. The effective focal length of the front lens group 200 is -45.862mm, the effective focal length of the rear lens group 300 is 21.679mm, and the EFL of the projection lens 100 is 17.216mm. While the position of the front lens group 200 changes with the projection distance, the effective focal length of the projection lens 100 and the effective focal length of the front lens group 200 do not change.

[0102] Or refer to Figure 6 The projection lens 100 includes 11 lenses. The effective focal length of the front lens group 200 is -50.735mm, the effective focal length of the rear lens group 300 is 21.881mm, and the EFL of the projection lens 100 is 17.195mm. While the position of the rear lens group 300 changes with the projection distance, the effective focal length of the projection lens 100 and the effective focal length of the rear lens group 300 do not change.

[0103] In the examples of this application, refer to Figure 6 The first sub-lens group further includes an eleventh lens 11 with negative optical power, and the eleventh lens 11 is arranged relative to the fourth lens 4 and close to the aperture 24;

[0104] The eleventh lens 11 and the fourth lens 4 are both meniscus lenses, and the concave surfaces of the eleventh lens 11 and the fourth lens 4 are arranged opposite to each other.

[0105] In this embodiment, both the eleventh lens element 11 and the fourth lens element 4 are negative-power meniscus lenses, with the eleventh lens element 11 positioned closer to the aperture 24. This design primarily serves to diverge light, expand the beam aperture, and provide greater scope for aberration correction in subsequent lens groups. Furthermore, the proximity of the eleventh lens element 11 to the aperture 24 optimizes aperture 24 aberrations (such as coma), improving overall system image quality.

[0106] In the embodiment of the present application, the refractive index of all lenses in the projection lens 100 does not exceed 1.83, and the Abbe number of all lenses in the projection lens 100 is not less than 31.

[0107] In this embodiment, the optical performance parameters of projection lens 100 are strictly limited. Specifically, the refractive index of all lenses in projection lens 100 is controlled to be within a range of no more than 1.83, and the Abbe number of all lenses is no less than 31. In the application scenario set by this embodiment, if lenses made of materials with high refractive index and low Abbe number are exposed to UV light, their ability to penetrate light is extremely weak, resulting in a significant decrease in the brightness of the projected image, and thus failing to meet the performance requirements for normal use of the projection lens.

[0108] In the embodiment of the present application, the refractive indexes of the eighth lens 8 , the ninth lens 9 , and the tenth lens 10 are all lower than 1.6, and / or the Abbe numbers of the eighth lens 8 , the ninth lens 9 , and the tenth lens 10 are all greater than 60.

[0109] In this embodiment, in the projection lens 100, the optical power of the eighth lens 8, the ninth lens 9, and the tenth lens 10 of the third sub-lens group in the rear lens group 300 are all positive, and the refractive index of these three lenses is lower than 1.6 and the Abbe number is greater than 60.

[0110] In this embodiment, three positive-power lenses work together with other lenses in projection lens 100 to correct for spherical aberration, coma, chromatic aberration, field curvature, and distortion, achieving high-resolution imaging. Furthermore, low-refractive-index, high-Abbe-number materials reduce costs, improve processing yields, and are suitable for large-scale production. The centralized optical power design of the three positive-power lenses shortens the lens length, making them suitable for compact 3D printing equipment.

[0111] In the embodiment of the present application, the Abbe number of the fifth lens 5 is greater than 65.

[0112] In this embodiment, the Vd of the first lens behind the aperture 24 (close to the image plane) is greater than 65, that is, the Vd of the lens closest to the aperture 24 in the second sub-lens group is greater than 65.

[0113] In this embodiment, the first lens after the aperture 24 is located at a key position in the optical path, and its dispersion characteristics directly affect the chromatic aberration of the projection lens 100. A high Abbe number lens can reduce the difference in refraction angles of light of different wavelengths, thereby reducing chromatic aberration.

[0114] In addition, high Abbe number materials generally have a lower refractive index, which can reduce spherical aberration and coma. Furthermore, by optimizing the lens shape (such as a meniscus), field curvature and distortion can be further corrected.

[0115] In the embodiment of the present application, the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, the eighth lens 8, the ninth lens 9, and the tenth lens 10 are all glass lenses; or the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the eleventh lens 11, the fifth lens 5, the sixth lens 6, the seventh lens 7, the eighth lens 8, the ninth lens 9, and the tenth lens 10 are all glass lenses.

[0116] In this embodiment, the lens in the projection lens 100 is made of all-glass material, which can still maintain high transmittance in the 365 nm-405 nm band. Specifically, the transmittance at a wavelength of 385 nm is greater than 80% (Transmittance>80% @385nm), which effectively ensures the light transmission efficiency and provides a basis for high-brightness printing.

[0117] In the embodiment of the present application, the projection lens 100 has a large aperture design with an F / # of 2.0. A large aperture can increase the amount of light entering, shortening the exposure time during the 3D printing process, thereby increasing printing speed, while also helping to improve image brightness and contrast.

[0118] Optionally, the projection lens 100 further includes an equivalent galvanometer mirror 21 and an equivalent prism 22, the equivalent prism 22 is disposed between the tenth lens 10 and the image source 23, and the equivalent galvanometer mirror 21 is disposed between the tenth lens 10 and the equivalent prism 22.

[0119] In this embodiment, the equivalent prism 22 is configured to control the image to be emitted in a predetermined shape, thereby obtaining an object of a corresponding shape. The configuration of the equivalent galvanometer 21 can improve the accuracy of the light irradiation position, thereby improving the imaging quality of the projection lens 100.

[0120] In addition, embodiments of the present application further provide a 3D printing device. The 3D printing device includes a projection lens 100 as described above. Since the embodiment of the projection lens 100 of the 3D printing device refers to the projection lens 100 of any of the above embodiments, the effects thereof are not further described here.

[0121] The image source 23 that matches the projection lens 100 is a DMD chip, which can improve the printing quality of 3D printing equipment. The projection lens 100 can achieve a transmittance of 1.3 to 1.6, an aperture value (F / #) of 2.0, and meet low distortion (Optical Distortion <0.2%), high resolution (MTF>70% @ 93lp / mm), and uniform image plane illumination (Telecentric CRA angle <1°). For example, the Telecentric CRA (chief ray angle) refers to the angle between the chief ray originating from each area of ​​the image plane and the optical axis. When the Telecentric CRA is <1°, the system approaches a telecentric optical path, and the chief ray enters the image plane almost parallel to the optical axis.

[0122] Based on the above embodiments, see the attached Figure 1 Table 1 shows the first specific embodiment of this application. Projection lens 100, from the object plane to the image plane, includes: a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, an aperture 24, a fifth lens 5, a sixth lens 6, a seventh lens 7, an eighth lens 8, a ninth lens 9, a tenth lens 10, an equivalent galvanometer 21, an equivalent prism 22, and an image source 23. The effective focal length of the front lens group 200 is -45.862 mm, and the effective focal length of the rear lens group 300 is 21.679 mm. The effective focal length (EFL) of projection lens 100 is 17.216 mm.

[0123] Table 1:

[0124]

[0125] In this embodiment, the lens parameters for different projection distances are shown in Table 2;

[0126] Table 2:

[0127]

[0128] Figure 2 This is a graph of the modulation transfer function (MTF) of the projection lens 100 of this application at a projection distance of 287.1mm. The horizontal line corresponding to 1.0 represents the theoretical curve with no aberrations. The closer to the horizontal line, the better the image quality. As can be seen from the graph, at 93 lp / mm, the MTF exceeds 0.7, indicating excellent resolution and image quality.

[0129] Figure 3 This is the field curvature distortion diagram of the projection lens 100 of this application at a projection distance of 287.1 mm. As can be seen from the diagram, the imaging distortion of the projection lens 100 is less than 0.06%, and the field curvature is less than 0.02 μm. The small field curvature distortion is conducive to high-quality restoration of 3D printing.

[0130] Figure 4 This is a graph showing the modulation transfer function (MTF) of the projection lens 100 of this application at a projection distance of 224.47mm. The horizontal line corresponding to 1.0 represents the theoretically aberration-free curve, and the closer the value is to the line, the better the image quality. As can be seen from the graph, at 93 lp / mm, the MTF exceeds 0.7, indicating excellent resolution and image quality.

[0131] Figure 5 This is the field curvature distortion diagram of the projection lens 100 of this application at a projection distance of 224.47 mm. As can be seen from the diagram, the imaging distortion of the projection lens 100 is less than 0.1%, and the field curvature is less than 12μm. The small field curvature distortion is conducive to high-quality restoration of 3D printing.

[0132] It can be seen that the projection lens 100 of the first embodiment of the present application has high resolution and good imaging quality within the projection distance range.

[0133] Based on the above embodiments, see the attached Figure 6Table 3 shows a second specific embodiment of the present application. Projection lens 100, from the object plane to the image plane, includes: a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, an eleventh lens 11, an aperture 24, a fifth lens 5, a sixth lens 6, a seventh lens 7, an eighth lens 8, a ninth lens 9, a tenth lens 10, an equivalent galvanometer 21, an equivalent prism 22, and an image source 23. The effective focal length of the front lens group 200 is -50.735 mm, the focal length of the rear lens group 300 is 21.881 mm, and the EFL of the projection lens 100 is 17.195 mm.

[0134] Table 3:

[0135]

[0136] In this embodiment, the lens parameters for different projection distances are shown in Table 4;

[0137] Table 4:

[0138]

[0139] Figure 7 This is a graph of the modulation transfer function (MTF) of the projection lens 100 of this application at a projection distance of 287.1mm. The horizontal line corresponding to 1.0 represents the theoretical curve with no aberrations. The closer the distance is to the horizontal line, the better the image quality. As can be seen from the graph, at 93 lp / mm, the MTF exceeds 0.7, indicating excellent resolution and good image quality.

[0140] Figure 8 This is the field curvature distortion diagram of the projection lens 100 of this application at a projection distance of 287.1 mm. As can be seen from the diagram, the imaging distortion of the projection lens 100 is less than 0.06%, and the field curvature is less than 0.03 μm. The small field curvature distortion is conducive to high-quality restoration of 3D printing.

[0141] Figure 9 This is a graph of the modulation transfer function (MTF) of the projection lens 100 of this application at a projection distance of 224.47mm. The horizontal line corresponding to 1.0 represents the theoretical curve with no aberrations, and the closer the distance is to the horizontal line, the better the image quality. As can be seen from the graph, at 93 lp / mm, the MTF exceeds 0.7, indicating excellent resolution and good image quality.

[0142] Figure 10This is the field curvature distortion diagram of the projection lens 100 of this application at a projection distance of 224.47 mm. As can be seen from the diagram, the imaging distortion of the projection lens 100 is less than 0.15%, and the field curvature is less than 15μm. The small field curvature distortion is conducive to high-quality restoration of 3D printing.

[0143] It can be seen that the projection lens 100 of the second embodiment of the present application has high resolution and good imaging quality within the projection distance range.

[0144] The above embodiments focus on the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. Considering the simplicity of the text, they will not be repeated here.

[0145] Although some specific embodiments of the present application have been described in detail by way of example, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present application. It should be understood by those skilled in the art that the above examples may be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A projection lens, characterized in that: It comprises a front lens group (200) and a rear lens group (300) arranged in sequence in the direction from the object plane to the image plane, wherein both the front lens group (200) and the rear lens group (300) can be moved along the optical axis according to the projection distance of the projection lens to achieve a fixed focus effect; The optical focal length of the front lens group (200) is negative, and the front lens group (200) comprises, in the direction from the object plane to the image plane: a first lens (1) with positive optical focal length, a second lens (2) with negative optical focal length, and a third lens (3) with negative optical focal length; The optical focal length of the rear lens group (300) is positive, and the rear lens group (300) comprises, in the direction from the object plane to the image plane: A first sub-lens group (301) with negative optical power, a stop (24), a second sub-lens group (302) with positive optical power, and a third sub-lens group (303) with positive optical power; The first sub-lens group (301) includes a fourth lens (4) with negative optical power, the second sub-lens group (302) includes a fifth lens (5) and a sixth lens (6) with positive optical power, and the third sub-lens group (303) includes a seventh lens (7) with negative optical power, an eighth lens (8) with positive optical power, a ninth lens (9) with positive optical power, and a tenth lens (10) with positive optical power.

2. The projection lens according to claim 1, wherein: The projection distance D of the projection lens is in the range of 223 mm < D < 288 mm; and the distance D1 between the surface of the third lens (3) close to the rear lens group (300) and the surface of the fourth lens (4) close to the third lens (3) is in the range of 9.4 mm < D1 < 9.9 mm, and the distance D2 between the surface of the tenth lens (10) in the rear lens group (300) close to the image plane and the surface adjacent to the surface is in the range of 4.0 mm < D2 < 4.5 mm.

3. The projection lens according to claim 2, wherein: When the projection distance of the projection lens is adjusted, the front lens group (200) moves as a whole along the optical axis, and the rear lens group (300) moves as a whole along the optical axis; When the distance D1 between the surface of the third lens (3) close to the rear lens group (300) and the surface of the fourth lens (4) close to the third lens (3) is in the range of 9.4 mm < D1 < 9.9 mm, the movement range of the front lens group (200) is 0.25 mm to 0.35 mm; When the distance D2 between the surface of the tenth lens (10) close to the image plane and the surface adjacent to the surface is in the range of 4.0 mm < D2 < 4.5 mm, the movement range of the rear lens group (300) is in the range of 0.25 mm to 0.35 mm.

4. The projection lens according to claim 1, wherein: The ratio range of the effective focal length EFL1 of the front lens group (200) to the effective focal length EFL of the projection lens is: -3.5<EFL1 / EFL<-2.5; and the ratio range of the effective focal length EFL2 of the rear lens group (300) to the effective focal length EFL of the projection lens is: 1.1<EFL2 / EFL<1.

4.

5. The projection lens according to claim 4, wherein: The effective focal length range of the front lens group (200) is: -51mm<EFL1<-45mm; the effective focal length range of the rear lens group (300) is: 20mm<EFL2<22mm; and the effective focal length range of the projection lens is: 16mm<EFL<18mm.

6. The projection lens according to claim 1, wherein: The first sub-lens group further includes an eleventh lens (11) with negative optical power, and the eleventh lens (11) is arranged relative to the fourth lens (4) and close to the aperture (24); The eleventh lens (11) and the fourth lens (4) are both meniscus lenses, and the concave surfaces of the eleventh lens (11) and the fourth lens (4) are arranged opposite to each other.

7. The projection lens according to any one of claims 1 to 6, wherein: The refractive index of all lenses in the projection lens does not exceed 1.83, and the Abbe number of all lenses in the projection lens is not less than 31.

8. The projection lens according to claim 7, wherein: The refractive indexes of the eighth lens (8), the ninth lens (9) and the tenth lens (10) are all lower than 1.6, and / or the Abbe numbers of the eighth lens (8), the ninth lens (9) and the tenth lens (10) are all greater than 60.

9. The projection lens according to claim 7, wherein: The Abbe number of the fifth lens (5) is greater than 65.

10. The projection lens according to any one of claims 1 to 6, wherein: The curvatures of two adjacent surfaces of the seventh lens (7) and the eighth lens (8) are different.

11. A 3D printing device, characterized in that: The 3D printing device includes the projection lens according to any one of claims 1 to 10.

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