Off-axis tiled projection objective system for 3D printing

Abstract

The application provides an off-axis splicing projection objective lens system for 3D printing, which comprises, along an optical axis, an image generator set, a protective glass, a light splitting device, an off-axis lens set and a common lens set in sequence from an object plane to an imaging plane. The off-axis splicing projection objective lens system for 3D printing provided by the application adopts two small-size image generators, and the optical system is modularized, and only the off-axis lens set can be vertically adjusted, so that the overlap of two projection frames and the size of the overlap range are realized. Except for the off-axis lens set, the same optical system is shared, and the cost, volume, image quality and resolution are reasonably balanced, and the system has a series of advantages such as high integration, small volume, easy manufacturing, reasonable tolerance, low cost and high imaging quality, and has high practical application value.

Description

Technical Field

[0001] This invention relates to the field of optical lens technology, and in particular to an off-axis splicing projection lens system for 3D printing. Background Technology

[0002] 3D printing technology, as a rapid prototyping technology, fulfills people's pursuit of efficient, precise, personalized, and customized products through its unique manufacturing methods. To date, this technology has expanded beyond simply providing models and prototypes for industrial design or mechanical manufacturing. Its applications span jewelry, food, industrial design, architecture, engineering, automotive, aerospace, medical industry, education, geographic information systems, civil engineering, and the military. The principle of photopolymer 3D printing technology is that the activation energy generated by ultraviolet light, the highest energy in the spectrum, breaks the C-C bonds in unsaturated polyester resin, generating free radicals that thus cure the resin.

[0003] Currently, with the improvement of the mechanical stability, processing accuracy, and surface roughness of 3D printed parts, there is a growing pursuit of larger printing formats. Larger formats can print larger parts or print multiple parts simultaneously, thereby improving printing efficiency.

[0004] Current 3D printing systems can only increase the image size by increasing the image generator size or arranging multiple optical engines. Larger image generators have lower yield rates and stability; arranging multiple optical engines increases the size of the 3D printer and makes adjusting their positions difficult. Both solutions significantly increase hardware costs. Therefore, designing an off-axis splicing projection lens system for 3D printing is essential. Summary of the Invention

[0005] The purpose of this invention is to provide an off-axis splicing projection lens system for 3D printing. It employs two small-sized image generators and a modular optical system design. Only the off-axis lens group can be finely adjusted in the vertical direction, thereby achieving the overlap of the two projection images and the size of the overlap range. Except for the off-axis lens group, all other components share the same optical system. It reasonably balances cost, size, image quality, and resolution, and has a series of advantages such as high integration, small size, ease of manufacturing, reasonable tolerance, low cost, and high imaging quality. It has high practical application value.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] An off-axis splicing projection lens system for 3D printing, comprising, in sequence along the optical axis from the object plane to the imaging plane: an image generator group, a protective glass, a beam splitter, an off-axis lens group, and a common lens group;

[0008] The image generator group includes a first image generator and a second image generator, wherein the second image generator is disposed on the upper side of the first image generator;

[0009] The off-axis lens group includes a first off-axis lens group and a second off-axis lens group. The first off-axis lens group and the second off-axis lens group are respectively set for the first image generator and the second image generator. The first off-axis lens group and the second off-axis lens group each include a first lens GM1 and a second lens G2.

[0010] The shared lens group includes the third lens GM3, the fourth lens G4, the fifth lens G5, the sixth lens G6, the seventh lens G7, the eighth lens G8, the ninth lens G9, the tenth lens G10, the eleventh lens GM11, the twelfth lens G12, and the thirteenth lens G13.

[0011] Optionally, the first lens GM1, the second lens G2, the third lens GM3, the fourth lens G4, the fifth lens G5, the sixth lens G6, the seventh lens G7, the eighth lens G8, the ninth lens G9, the tenth lens G10, the eleventh lens GM11, the twelfth lens G12, the thirteenth lens G13, the beam splitter, and the protective glass are all made of glass.

[0012] The first lens GM1, the third lens GM3 and the eleventh lens GM11 are all aspherical lenses, and the object side surface of the seventh lens G7 is provided with an aperture stop.

[0013] Optionally, the ratio of the length L of the first lens GM1 to the thirteenth lens G13 to the length BFL of the first lens GM1 from the object side surface to the imaging surface is 8 < |L / BFL| < 10.

[0014] Optionally, the focal length f of the shared lens group and the focal length f of the off-axis lens group are... GM1G2 The ratio is 1 < |f / f GM1G2 |<2.

[0015] Optionally, the ratio of the focal length f6 of the sixth lens G6 to the focal length f7 of the seventh lens G7 is 5 < |f6 / f7| < 6.

[0016] Optionally, the bending direction of the ninth lens G9 is opposite to that of the tenth lens G10, the eleventh lens GM11, the twelfth lens G12, and the thirteenth lens G13, and the focal length f9 of the ninth lens G9 is the same as that of the tenth lens G10, the eleventh lens GM11, the twelfth lens G12, and the thirteenth lens G13. G10G11G12G13 The ratio is 3 < |f9 / f G10G11G12G13 | <4.

[0017] Optionally, the twelfth lens G12 has the opposite optical power to the thirteenth lens G13, and the focal length f of the twelfth lens G12 is... 12 With the focal length f of the thirteenth lens G13 13 The ratio is 1 < |f 12 / f 13 | < 1.2.

[0018] Optionally, the refractive index n4 and Abbe constant v4 of the fourth lens G4 satisfy:

[0019]

[0020] The refractive index n5 and Abbe constant v5 of the fifth lens G5 satisfy:

[0021]

[0022] The fourth lens G4 and the fifth lens G5 form a cemented lens, with the refractive index arranged in descending order and the Abbe constant arranged in descending order.

[0023] According to specific embodiments provided by the present invention, the following technical effects are disclosed: The off-axis splicing projection lens system for 3D printing provided by the present invention comprises, along the optical axis from the object plane to the imaging plane, the following components in sequence: an image generator group, a protective glass, a beam splitter, an off-axis lens group, and a common lens group; the image generator group includes a first image generator and a second image generator, the second image generator being disposed above the first image generator; the off-axis lens group includes a first off-axis lens group and a second off-axis lens group, the first off-axis lens group and the second off-axis lens group being respectively disposed corresponding to the first image generator and the second image generator, and both the first off-axis lens group and the second off-axis lens group include a first lens GM1 and a second lens. G2; The shared lens group includes the third lens GM3, the fourth lens G4, the fifth lens G5, the sixth lens G6, the seventh lens G7, the eighth lens G8, the ninth lens G9, the tenth lens G10, the eleventh lens GM11, the twelfth lens G12, and the thirteenth lens G13; It adopts two small-sized image generators and a modular design of the optical system. Only the off-axis lens group can be finely adjusted in the vertical direction, thereby realizing the overlap of the two projection frames and the size of the overlap range. Except for the off-axis lens group, all share the same optical system, which reasonably balances cost, size, image quality, and resolution. It has a series of advantages such as high integration, small size, easy manufacturing, reasonable tolerance, low cost, and high imaging quality, and has high practical application value. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of an off-axis splicing projection lens system for 3D printing according to an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of the MTF (Mean Transformer Function) of an off-axis splicing projection lens system.

[0027] Figure 3 A schematic diagram of the point array of an off-axis splicing projection lens system;

[0028] Figure 4 This is a schematic diagram of the optical path of an off-axis splicing projection lens system.

[0029] Reference numerals: 1. First off-axis lens group; 2. Second off-axis lens group; 3. Beam splitter; 4. Protective glass; 5. First image generator; 6. Second image generator. Detailed Implementation

[0030] The purpose of this invention is to provide an off-axis splicing projection lens system for 3D printing. It employs two small-sized image generators and a modular optical system design. Only the off-axis lens group can be finely adjusted in the vertical direction, thereby achieving the overlap of the two projection images and the size of the overlap range. Except for the off-axis lens group, all other components share the same optical system. It reasonably balances cost, size, image quality, and resolution, and has a series of advantages such as high integration, small size, ease of manufacturing, reasonable tolerance, low cost, and high imaging quality. It has high practical application value.

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] like Figure 1 As shown, the off-axis splicing projection lens system for 3D printing provided in this embodiment of the invention includes, in sequence along the optical axis from the object surface to the imaging surface: an image generator group, a protective glass 4, a beam splitter 3, an off-axis lens group, and a common lens group;

[0033] The image generator group includes a first image generator 5 and a second image generator 6, with the second image generator 6 disposed above the first image generator 5.

[0034] The off-axis lens group includes a first off-axis lens group 1 and a second off-axis lens group 2. The first off-axis lens group 1 and the second off-axis lens group 2 are respectively set to the first image generator 5 and the second image generator 6. The first off-axis lens group 1 and the second off-axis lens group 2 each include a first lens GM1 and a second lens G2.

[0035] The shared lens group includes the third lens GM3, the fourth lens G4, the fifth lens G5, the sixth lens G6, the seventh lens G7, the eighth lens G8, the ninth lens G9, the tenth lens G10, the eleventh lens GM11, the twelfth lens G12, and the thirteenth lens G13.

[0036] The first lens GM1, the second lens G2, the third lens GM3, the fourth lens G4, the fifth lens G5, the sixth lens G6, the seventh lens G7, the eighth lens G8, the ninth lens G9, the tenth lens G10, the eleventh lens GM11, the twelfth lens G12, the thirteenth lens G13, the beam splitter 3, and the protective glass 4 are all made of glass.

[0037] The first lens GM1, the third lens GM3 and the eleventh lens GM11 are all aspherical lenses, and the object side surface of the seventh lens G7 is provided with an aperture stop.

[0038] The ratio of the length L of the first lens GM1 to the thirteenth lens G13 to the length BFL of the first lens GM1 from the object side surface to the imaging surface is 8 < |L / BFL| < 10, which realizes the reasonable distribution of the total length of the optical lenses and their air gaps with the back working distance, effectively compressing the total length of the optical system and realizing the miniaturization of the optical system.

[0039] The focal length f of the common lens group and the focal length f of the off-axis lens group GM1G2 The ratio is 1 < |f / f GM1G2 |<2, which enables the off-axis lens group to have a sufficiently strong light collimation and focusing capability that matches the subsequent shared optical system. The off-axis lens group is set to two lenses, which effectively distributes the optical power of the lens and improves the lens's manufacturability.

[0040] The ratio of the focal length f6 of the sixth lens G6 to the focal length f7 of the seventh lens G7 is 5 < |f6 / f7| < 6. Both lenses are meniscus lenses with opposite curvature directions, which cancels out the field curvature generated by each other.

[0041] The bending direction of the ninth lens G9 is opposite to that of the tenth lens G10, the eleventh lens GM11, the twelfth lens G12, and the thirteenth lens G13. The focal length f9 of the ninth lens G9 is the same as that of the tenth lens G10, the eleventh lens GM11, the twelfth lens G12, and the thirteenth lens G13. G10G11G12G13 The ratio is 3 < |f9 / fG10G11G12G13 |<4, the ninth lens, which bends in the opposite direction to the tenth to thirteenth lenses, effectively counteracts the cumulative field curvature of the subsequent lens groups, while also controlling the shape of the subsequent lenses, making the lens shape reasonable and easy to process.

[0042] The twelfth lens G12 has the opposite optical power to the thirteenth lens G13, and the focal length f of the twelfth lens G12 is... 12 The focal length f of the thirteenth lens G13 13 The ratio is 1 < |f 12 / f 13 | < 1.2, the two lenses have opposite optical powers and similar absolute values ​​of focal length, effectively balancing the problem of high system sensitivity caused by the small radius of curvature of short focal length optical system lenses.

[0043] The refractive index n4 and Abbe constant v4 of the fourth lens G4 satisfy:

[0044]

[0045] The refractive index n5 and Abbe constant v5 of the fifth lens G5 satisfy:

[0046]

[0047] The fourth lens G4 and the fifth lens G5 form a cemented lens with refractive indices arranged in descending order and Abbe constants arranged in descending order. This combination of optical properties can effectively reduce the secondary spectrum of the system.

[0048] The off-axis splicing projection lens system is compatible with a maximum image generator size of 0.31 inches. Two image generators with a size no larger than 0.31 inches can achieve a splicing scheme with adjustable overlap range. The first image generator and the first off-axis lens group are placed mirror-symmetrically with the second image generator and the second off-axis lens group along the system's optical axis. The overlap range of the image frame can be adjusted by offsetting the two off-axis lens groups in the vertical direction respectively.

[0049] The parameters of the off-axis splicing projection lens system are shown in Table 1;

[0050] Table 1. Specific parameters of the off-axis splicing projection lens system

[0051]

[0052]

[0053] The coefficients of each order of aspherical lenses GM2 and GM14 are shown in Table 2;

[0054] Table 2. Coefficients of various orders for aspherical lenses GM2 and GM14

[0055]

[0056]

[0057] MTF (Modulation Transfer Function) is currently the most accurate and scientific evaluation standard for lenses. The vertical axis represents contrast ratio; the closer to 1, the better the image quality. The horizontal axis represents resolution, measured in line pairs per millimeter. The projection image used in this embodiment has a pixel size of 125μm, corresponding to a design resolution of 4 line pairs per millimeter. Projection lenses generally require an MTF value of at least 0.3 for each field of view at the design resolution. Figure 2 As shown, the MTF values ​​within the optical zoom focal length of this application embodiment are all above 0.6, exhibiting excellent imaging quality.

[0058] When multiple rays emanating from a single point pass through an optical system, aberrations cause their intersections with the image plane to no longer converge at a single point, forming a diffuse pattern scattered over a certain range, known as a dot plot. Dot plots are one of the most commonly used evaluation methods in modern optical design. In this embodiment, the projection image pixel size is 125μm, and the root mean square radius of the visible field of view is much smaller than 125μm. The dot plot of this embodiment is as follows: Figure 3 As shown.

[0059] The light emitted by the first and second image generators is deflected by the first and second off-axis lens groups, respectively, and then imaged on the receiving surface by a shared lens group. Since the two image generators are the same size, and the two off-axis lens groups are identical and positioned mirror-symmetrically along the system's central optical axis, the images formed by the shared lens system are of the same size but vertically offset, resulting in a partially overlapping image. The overlap amount D is determined by the vertical offset of the off-axis lens groups, as illustrated in the diagram. Figure 4 As shown.

[0060] As can be seen from the implementation cases, the lens has a very good MTF (modulation transfer function) at low, medium and high frequencies, which indicates that it has a high resolution effect.

[0061] The off-axis splicing projection lens system is compatible with a maximum image generator size of 0.31 inches. Two image generators with a size no larger than 0.31 inches can achieve a splicing scheme with adjustable overlap range.

[0062] In the implementation method, the optical lens satisfies the following condition:

[0063] CRA < 2°

[0064] In the formula, CRA represents the incident angle of the principal ray on the imaging surface of the optical lens, which can be well matched with the imaging chip to achieve a good projection effect.

[0065] The off-axis splicing projection lens system for 3D printing provided by this invention comprises, along the optical axis from the object plane to the imaging plane, the following components in sequence: an image generator group, a protective glass, a beam splitter, an off-axis lens group, and a common lens group; the image generator group includes a first image generator and a second image generator, with the second image generator disposed above the first image generator; the off-axis lens group includes a first off-axis lens group and a second off-axis lens group, which are respectively disposed corresponding to the first image generator and the second image generator, and each of the first and second off-axis lens groups includes a first lens GM1 and a second lens G2; the common lens group includes a third... Lenses GM3, G4, G5, G6, G7, G8, G9, G10, GM11, G12, and G13 are used. The system employs two small-sized image generators and a modular optical system design. Only the off-axis lens group allows for fine-tuning of its vertical position, thus enabling the overlap of the two projection frames and the size of the overlap range. Except for the off-axis lens group, all components share the same optical system. This design achieves a reasonable balance between cost, size, image quality, and resolution, offering advantages such as high integration, small size, ease of manufacturing, reasonable tolerances, low cost, and high image quality, making it highly valuable for practical applications.

[0066] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. An off-axis splicing projection lens system for 3D printing, characterized in that, Along the optical axis from the object plane to the imaging plane, the components are sequentially: image generator group, protective glass, beam splitter, off-axis lens group, and common lens group; The image generator group includes a first image generator and a second image generator, wherein the second image generator is disposed on the upper side of the first image generator; The off-axis lens group includes a first off-axis lens group and a second off-axis lens group. The first off-axis lens group and the second off-axis lens group are respectively set to correspond to the first image generator and the second image generator. The first off-axis lens group and the second off-axis lens group are each composed of a first lens GM1 and a second lens G2. The shared lens group consists of the third lens GM3, the fourth lens G4, the fifth lens G5, the sixth lens G6, the seventh lens G7, the eighth lens G8, the ninth lens G9, the tenth lens G10, the eleventh lens GM11, the twelfth lens G12, and the thirteenth lens G13. The focal length of the shared lens group focal length of off-axis lens group The ratio is ; The focal length of the sixth lens G6 Focal length of the seventh lens G7 The ratio is .

2. The off-axis splicing projection lens system for 3D printing according to claim 1, characterized in that, The first lens GM1, the second lens G2, the third lens GM3, the fourth lens G4, the fifth lens G5, the sixth lens G6, the seventh lens G7, the eighth lens G8, the ninth lens G9, the tenth lens G10, the eleventh lens GM11, the twelfth lens G12, the thirteenth lens G13, the beam splitter, and the protective glass are all made of glass. The first lens GM1, the third lens GM3 and the eleventh lens GM11 are all aspherical lenses, and the object side surface of the seventh lens G7 is provided with an aperture stop.

3. The off-axis splicing projection lens system for 3D printing according to claim 2, characterized in that, The ratio of the length L of the first lens GM1 to the thirteenth lens G13 to the length BFL of the object-side surface of the first lens GM1 to the imaging plane is: .

4. The off-axis splicing projection lens system for 3D printing according to claim 2, characterized in that, The bending direction of the ninth lens G9 is opposite to that of the tenth lens G10, the eleventh lens G11, the twelfth lens G12, and the thirteenth lens G13. The focal length of the ninth lens G9 is... The focal lengths of the tenth lens G10, the eleventh lens GM11, the twelfth lens G12, and the thirteenth lens G13 The ratio is .

5. The off-axis splicing projection lens system for 3D printing according to claim 2, characterized in that, The twelfth lens G12 has the opposite optical power to the thirteenth lens G13, and the focal length of the twelfth lens G12 is... Focal length of the thirteenth lens G13 The ratio is .

6. The off-axis splicing projection lens system for 3D printing according to claim 2, characterized in that, The refractive index of the fourth lens G4 and Abbe constant satisfy: ； The refractive index of the fifth lens G5 and Abbe constant satisfy: ； The fourth lens G4 and the fifth lens G5 form a cemented lens.

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