High-efficiency high-definition distortionless objective lens system for 3D printing

Abstract

The embodiment of the utility model discloses a high-efficiency high-definition distortionless objective lens system for 3D printing. The high-efficiency high-definition distortionless objective lens system comprises a first group lens with positive focal power, a diaphragm, a second group lens with a positive light angle and an imaging surface which are coaxially arranged, the diaphragm is positioned between the first group lens and the second group lens; the first group lens comprises a first lens with negative focal power, a second lens with negative focal power and a third lens with positive focal power which are coaxially arranged in sequence; and the second group lens comprises a fourth lens with negative focal power, a fifth lens with negative focal power and a sixth lens with positive focal power which are coaxially arranged in sequence. By implementing the system provided by the embodiment of the utility model, image quality can be optimized, distortion can be reduced, relative illumination can be improved, and short-distance projection can be realized.

Description

Technical Field

[0001] The utility model relates to the technical field of 3D printing, and in particular to a high-efficiency, high-definition, distortion-free objective lens system for 3D printing. Background Art

[0002] As a rapid prototyping technology, 3D printing technology meets people's needs for efficient, fine, personalized and customized products with its special production method. Today, it is no longer limited to the fields of industrial design or mechanical manufacturing, but is widely used in many fields such as jewelry, food, construction, medical care, education, automobiles, aerospace, etc. Among them, photocuring 3D printing technology uses the activation energy of ultraviolet light to cure unsaturated polyester resin, which is a common molding method. The photocuring molding method uses liquid resin to project the pattern onto the resin plane through a printer. The resin absorbs the light intensity and solidifies. In this way, the structure of the object is constructed layer by layer, that is, first print a layer, correct the shape, then pour in the resin, and repeat the previous steps.

[0003] However, the current 3D printing technology still has some shortcomings. Most light-curing 3D printing lenses have pixel texture on the surface of the printed model, which is not smooth enough; the local exposure distribution of the model is uneven, and the thickness varies, which is particularly obvious when printing very fine parts; the light source undergoes trapezoidal deformation, resulting in data deviation; the physical deviation caused by the refraction of the lens causes barrel distortion or pincushion distortion in a single layer.

[0004] Therefore, it is necessary to design a new system to optimize image quality, reduce distortion, improve relative illumination, and achieve short-distance projection. Utility Model Content

[0005] The technical problem to be solved by the utility model is to provide a high-efficiency, high-definition, distortion-free objective lens system for 3D printing.

[0006] In order to solve the above technical problems, the purpose of the utility model is achieved through the following technical solutions: to provide a high-efficiency, high-definition, distortion-free objective lens system for 3D printing, comprising: a first group of lenses with positive focal power, an aperture, a second group of lenses with positive optical angles, an optical component and an imaging surface, which are coaxially arranged; the aperture is located between the first group of lenses and the second group of lenses;

[0007] The first group of lenses includes a first lens with negative optical power, a second lens with negative optical power, and a third lens with positive optical power, which are coaxially arranged in sequence; the second group of lenses includes a fourth lens with negative optical power, a fifth lens with negative optical power, and a sixth lens with positive optical power, which are coaxially arranged in sequence.

[0008] A further technical solution is that the first lens, the second lens, the third lens and the sixth lens are glass lenses respectively.

[0009] A further technical solution is as follows: the fourth lens and the fifth lens are respectively glass spherical double-cemented lenses.

[0010] A further technical solution is: the ratio of the focal length of the first group of lenses to the focal length of the objective lens system is 6.68.

[0011] A further technical solution is: the ratio of the focal length of the first lens to the focal length of the first group of lenses is -0.59.

[0012] A further technical solution is: the ratio of the focal length of the second lens to the focal length of the first group of lenses is -0.46.

[0013] A further technical solution is: the ratio of the focal length of the third lens to the focal length of the first group of lenses is 0.45.

[0014] A further technical solution is: the ratio of the focal length of the second lens group to the focal length of the objective lens system is 2.07.

[0015] A further technical solution is as follows: the ratio of the focal length fG4 of the fourth lens to the focal length of the second lens group is -1.11;

[0016] The ratio of the focal length fG5 of the fifth lens to the focal length of the second lens group is 1.24;

[0017] The ratio of the focal length fG6 of the sixth lens to the focal length of the second lens group is 1.11.

[0018] A further technical solution is: the gap between the third lens and the STO ranges from 10 mm to 15 mm.

[0019] Compared with the prior art, the utility model has the following beneficial effects: the utility model optimizes image quality, reduces distortion, improves relative illumination, and realizes short-distance projection by setting a first group lens with positive focal power, an aperture, a second group lens with positive light angle, an optical component, and an imaging surface, and performing special settings on the lenses of the first group lens and the second group lens, such as sequence and focal power.

[0020] The utility model is further described below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 A schematic structural diagram of a high-efficiency, high-definition, distortion-free objective lens system for 3D printing provided by an embodiment of the utility model;

[0023] Figure 2 The spatial frequency MTF diagram provided by the embodiment of the utility model;

[0024] Figure 3 A dot matrix diagram provided for an embodiment of the utility model;

[0025] Figure 4 Field curvature distortion provided by the embodiment of the utility model Figure 1

[0026] Figure 5 Field curvature distortion provided by the embodiment of the utility model Figure 2 ;

[0027] Figure 6 A relative illumination diagram of a lens provided in an embodiment of the utility model;

[0028] Description of the symbols in the figure:

[0029] 1. First group of lenses; 2. Aperture; 3. Second group of lenses; 4. Galvanometer; 5. Beam splitter; 6. DMD protection glass; 7. Image plane; G1. First lens; G2. Second lens; G3. Third lens; G4. Fourth lens; G5. Fifth lens; G6. Sixth lens. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0031] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0032] It should also be understood that the terms used in this utility model specification are only for the purpose of describing specific embodiments and are not intended to limit the utility model. As used in this utility model specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0033] It should be further understood that the term “and / or” used in the present specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0034] See also Figure 1 , Figure 1 A schematic diagram of the structure of a high-efficiency, high-definition, distortion-free objective lens system for 3D printing provided by the embodiment of the utility model; the system can be used in the process of 3D printing, and the system is based on a 3D printing optical engine system of an image source such as DLP technology or LED. DLP (Digital Lighting Processor) technology is a spatial light modulation technology based on a DMD (Digital Mirror Device) chip, which has the advantages of fast response, high efficiency and high reliability. It can not only be used in the field of projection display, but also has a wider application in industry; the DMD chip is composed of a series of micron-level reflector arrays, and the switching speed of each pixel micro-reflector reaches 32kHz. It has a wide spectral range, not only suitable for the visible spectrum range, but also can support ultraviolet UV to near-infrared NIR bands; the system of this embodiment is applied to a large aperture and high-brightness lens for photocuring 3D printing, and the lens can be matched with an LED light source of 0.3inc or less or a DMD chip. The lens has a series of advantages such as no distortion, high brightness, short working distance, extremely high imaging quality, and a small number of lenses.

[0035] See also Figure 1 The high-efficiency, high-definition, distortion-free objective lens system for 3D printing comprises: a first lens group 1 with positive focal power, an aperture 2, a second lens group 3 with positive optical angle, an optical component and an imaging surface 7, which are coaxially arranged; the aperture 2 is located between the first lens group 1 and the second lens group 3;

[0036] The first lens group 1 includes a first lens G1 with negative optical power, a second lens G2 with negative optical power, and a third lens G3 with positive optical power, which are coaxially arranged in sequence; the second lens group 3 includes a fourth lens G4 with negative optical power, a fifth lens G5 with negative optical power, and a sixth lens G6 with positive optical power, which are coaxially arranged in sequence.

[0037] In addition, the optical component includes a galvanometer mirror 4 , a beam splitter prism 5 , and a DMD protection glass 6 which are coaxially arranged in sequence.

[0038] The imaging plane 7 mentioned above includes but is not limited to the DMD imaging plane 7 .

[0039] In this embodiment, the aperture 2 is used to control the amount of light emitted by the light source lens group, the light source lens group is used to emit light and collimate the emitted light, the first lens group G1 is used to adjust the projection field angle and balance the system field curvature, and the second lens group G2 is used to balance the system aberration and chromatic aberration.

[0040] Specifically, after the light emitted by the light source is controlled by the aperture 2, the light is adjusted and corrected through the combination of the first group lens 1 and the second group lens 3 to obtain the desired imaging effect; after the light is distributed by the galvanometer 4 and the beam splitter prism 5, it is processed by the DMD component and projected onto the imaging surface 7 through the optical system to form the desired image; the entire system achieves collimation, focusing and correction of the light by adjusting the position and properties of different lenses and distributing them through the galvanometer 4 and the beam splitter prism 5, thereby obtaining a high-efficiency, high-definition and distortion-free imaging effect.

[0041] Specifically, the light source emits light, and the aperture 2 is located between the light source and the objective lens, which is used to control the amount of light entering and ensure the clarity and contrast of the image. The first group of lenses 1 is composed of three lenses, which are lenses with negative optical power, negative optical power and positive optical power, respectively; the function of this group of lenses is to adjust the size of the projection field angle and balance the field curvature of the system. The lens with negative optical power can expand the field angle, while the lens with positive optical power is used to balance the field curvature of the system. The second group of lenses 3 is also composed of three lenses, which are lenses with negative optical power, negative optical power and positive optical power, respectively; the function of this group of lenses is to balance the aberration and chromatic aberration of the system, the lens with negative optical power can correct the aberration of the system, and the lens with positive optical power is used to correct chromatic aberration. The optical components include a galvanometer 4, a beam splitter prism 5 and a DMD protective glass 6; the galvanometer 4 is used to adjust the direction of the light path so that the light is accurately projected onto the DMD (digital micromirror assembly); the beam splitter prism 5 is used to split the light into two paths, usually one for imaging and the other for auxiliary functions; the DMD protective glass 6 is used to protect the DMD assembly. The imaging surface 7 refers to the DMD image surface 7, and the DMD is a digital micromirror assembly, which is used to adjust the light and project the image to a specified position.

[0042] The design of the above system takes into account the balance of optical performance to achieve high-quality imaging, and is particularly suitable for applications that require high-precision imaging, such as 3D printing. Comprehensive consideration and balance of actual application scenarios, manufacturing, cost, distortion, image quality, projection brightness, etc., has a series of advantages such as high imaging quality, a small number of lenses, and low distortion. What is particularly special is that the objective lens system of the present invention has excellent image quality, minimal distortion, full field MTF greater than 0.8, optical distortion less than 0.02%, reduced pixel texture, and eliminated distortion.

[0043] In one embodiment, the first lens G1 , the second lens G2 , the third lens G3 and the sixth lens G6 are glass lenses respectively.

[0044] In one embodiment, the fourth lens G4 and the fifth lens G5 are both glass spherical double-cemented lenses.

[0045] Glass lenses and glass spherical double-cemented lenses have good optical properties, such as high transmittance, low scattering rate and good optical diffraction resistance, which help to maintain imaging clarity and contrast; glass materials have good stability and durability, and can maintain the shape and performance of the lens stable under different environmental conditions, which is conducive to the long-term stable operation of the system; the processing technology of glass materials is relatively mature, and can achieve precise shape and surface quality, which is conducive to the manufacture of high-quality lens components; glass materials have different refractive indices, and the optical properties of the lens can be adjusted by selecting different types of glass materials to meet specific imaging needs; glass materials may be more cost-effective than other materials (such as plastics), but in some cases, their superior optical properties and stability can reduce the maintenance cost and performance loss of the system.

[0046] In one embodiment, the ratio of the focal length of the first lens group 1 to the focal length of the objective lens system is 6.68.

[0047] In one embodiment, the ratio of the focal length of the first lens G1 to the focal length of the first lens group 1 is -0.59.

[0048] In one embodiment, the ratio of the focal length of the second lens G2 to the focal length of the first lens group 1 is -0.46.

[0049] In one embodiment, the ratio of the focal length of the third lens G3 to the focal length of the first lens group 1 is 0.45.

[0050] In one embodiment, the ratio of the focal length of the second lens group 3 to the focal length of the objective lens system is 2.07.

[0051] In one embodiment, the ratio of the focal length fG4 of the fourth lens G4 to the focal length of the second lens group 3 is -1.11;

[0052] The ratio of the focal length fG5 of the fifth lens G5 to the focal length of the second lens group 3 is 1.24;

[0053] The ratio of the focal length fG6 of the sixth lens G6 to the focal length of the second lens group 3 is 1.11.

[0054] In one embodiment, the gap between the third lens G3 and STO is in a range of 10 mm to 15 mm.

[0055] In one embodiment, the gap between the STO and the fourth lens G4 ranges from 8 mm to 12 mm.

[0056] Achieve a specific focal length ratio to achieve the desired imaging characteristics or optical functions. By adjusting the focal length ratio of different lenses and the gap between lenses, the optical performance of the system, such as focusing ability, zoom range, distortion correction, etc., can be controlled.

[0057] In this embodiment, the fourth lens G4 and the fifth lens G5 are cemented lenses. A double cemented lens is placed behind the STO aperture 2, and its low refractive index and high refractive index material combination effectively reduces the secondary spectrum of the system; G4 is a low refractive index material (1.55<n4<1.65), and the fifth lens G5 is a high refractive index material (1.7<n5<1.8), where nd is the refractive index of the dth lens, and d is a positive integer greater than 0.

[0058] The objective lens system ensures that the incident angle of the principal ray in each field of view is completely matched with the light cone angle and angular vector of the image source while correcting the aberration, thereby improving the image quality and efficiency of the entire imaging system. The CRA range is within ±0.5°. CRA refers to the angle between the principal ray and the image plane 7. Specifically, the parameters of the objective lens system are shown in Table 1.

[0059] Table 1. Specific parameters of objective lens system

[0060]

[0061]

[0062] The projection lens is obtained based on the specific parameters of each lens mentioned above; in addition, the spatial frequency MTF diagram of the entire system is as follows Figure 2As shown, the MTF (Modulation Transfer Function) index is the most accurate and scientific evaluation standard for lenses at present. The ordinate is contrast, and the closer it is to 1, the better the lens imaging. The abscissa represents resolution, in units of line pairs per millimeter. The image source pixel size used in this embodiment is 27.5um, and the corresponding design resolution is 18 line pairs per millimeter. Projection lenses generally require that the MTF value of each field of view is at least 0.3 in the design, and the MTF values ​​of each field of view in the embodiment of the present application are all above 0.8.

[0063] Also, see Figure 3 After passing through the optical system, many light rays emitted from one point no longer converge at the same point due to aberration, but form a diffuse pattern scattered in a certain range. The smaller the spot radius of each field of view, the better the imaging quality it represents. Generally, the full field of view RMS is less than the pixel size (27.5um), which is an excellent level. The full field of view RMS of this embodiment is less than 2um, which is an excellent level.

[0064] See also Figure 4 and Figure 5 , the ordinate in the figure represents the field of view angle of the lens. The abscissa of the field curvature graph represents the magnitude of the field curvature value, and the abscissa of the distortion graph represents the amount of distortion. Distortion is a very important indicator of a projection lens; the system distortion of this embodiment is within 0.02%, and the system distortion is excellent.

[0065] See also Figure 6 , the system edge illumination of this embodiment reaches 95.4%, so that the uniformity of the projection effect of the system imaging surface 7 will be very good. Relative illumination refers to the ratio of the illumination of different coordinate points on the image plane to the illumination of the center point. The ordinate represents the normalized illumination value, and the abscissa represents the field of view angle of the lens. Under the same conditions, the smooth transition of the relative illumination curve of each field of view represents uniform illumination within the projection frame, and the closer the relative illumination value of each field of view is to 1, the higher the final projection brightness.

[0066] In one embodiment, the optical distortion of the above-mentioned lens is less than 0.02%; the first lens G1 is made of optical glass with a refractive index of 1.65; the lens adopts a 0.3-inch image source; the lens has a high relative illumination, which is beneficial to improving the uniformity of the optical machine; the lens adopts a lamp source with a wavelength of 405nm as a light source, and the selected lens material has a high transmittance to light with a wavelength of 405nm.

[0067] In addition, the ratio of the combined focal length of the first group lens 1 to the combined optical power of the second group lens 3 is close to 3.2:1; the entire system uses glass lenses, and the thickness of each piece of glass does not exceed 5mm. The overall system length is small and controlled within 84mm;

[0068] In this embodiment, the optical lens satisfies the following conditional formula: 18 < TL / IH < 22; where TL represents the overall optical length of the optical lens, and IH represents the actual semi-image height of the optical lens.

[0069] When the condition 18 < TL / IH < 22 is satisfied, the relationship between the overall length of the lens and the resolution ability can be reasonably balanced. When the value of TL / IH exceeds the upper limit, the overall length of the lens is too large, or in other words, if the overall length is shortened, the image height will be insufficient; when the value of TL / IH exceeds the lower limit, due to the excessive optical power of each lens, it is difficult to correct the lens aberration, and the resolution ability decreases significantly.

[0070] In this embodiment, the optical lens satisfies the following conditional formula: 7.5mm < IH / tanθ < 8.5mm; where IH represents the actual semi-image height of the optical lens, and θ represents the semi-field angle of the optical lens.

[0071] When 7.5mm < IH / tanθ < 8.5mm is satisfied, the distortion of the optical lens can be reasonably limited, and the difficulty of distortion correction can be reduced. When the value of IH / tanθ exceeds the lower limit, the distortion of the lens will increase in the negative direction; when the value of IH / tanθ exceeds the upper limit, the distortion of the lens will increase in the positive direction.

[0072] In this embodiment, the optical lens satisfies the following conditional formula: 1.61 < Nd1 < 1.71; 51 < Vd1 < 56; where Nd1 represents the refractive index of the third lens G3, and Vd1 represents the dispersion coefficient of the first lens G1.

[0073] When 1.61 < Nd1 < 1.71 and 51 < Vd1 < 56 are satisfied, the selection of the glass material of the first lens G1 can be reasonably limited, the aberration of other optical lenses can be balanced, and the beam height can be effectively reduced, which has a great effect on correcting distortion and reducing the aperture of the subsequent lens.

[0074] In this embodiment, the optical lens satisfies the following conditional formula: CRA < 0.5°; where CRA represents the principal ray incident angle of the optical lens on the imaging surface 7.

[0075] When CRA < 0.5° is satisfied, it can well match image sources such as DMD chips or LEDs to achieve a good projection effect.

[0076] In this embodiment, the curvature radii of the first lens G1 and the second lens G2 are matched with positive, negative, negative, and negative, which can effectively control the gentle transition of light, thereby reducing the tolerance sensitivity of these two lenses, and further improving the actual production yield.

[0077] The above-mentioned high-efficiency, high-definition, distortion-free objective lens system for 3D printing has a distortion within 0.02%, which meets the needs of 3D printing equipment; the working distance is 210mm; the relative illumination of the full field of view is higher than 95%, the full field of view MTF is higher than 0.8, and the imaging quality is excellent; the distortion can reach within 0.02%, and the distortion correction is excellent; the lenses are all made of glass material, which can effectively avoid the problem of serious focus deviation caused by the strong energy of the 405nm short-wave light source used in 3D printing and the easy heat absorption of plastic aspheric surfaces; the first lens G1 uses a high-refractive index convex lens, which can effectively reduce the beam height, and has a great effect on correcting distortion and reducing the aperture of subsequent lenses; the spot radius of the spot diagram (<2um) is much smaller than the pixel size (27.5um), which is very suitable for 3D printing, which focuses on spot size and energy concentration. The application advantages are obvious; the selected lens material has a high transmittance of 405nm wavelength light, all exceeding 95% / 10mm, and the entire imaging system absorbs relatively little energy, which can improve the overall brightness, reduce system heat generation, reduce the power and size of heat dissipation devices, and help the stability of 3D printing; the design wavelength is 395nm, 405nm, and 410nm, which includes the wavelength fluctuation of the actual light source, making the lens design more in line with the actual situation; only 6 lenses are used, which effectively reduces the lens cost and assembly difficulty compared to other lens designs with more than ten lenses; large aperture, relative aperture F#1.8, the larger the aperture, the greater the amount of light entering, the higher the corresponding brightness, and the higher the light efficiency; the entire system uses glass spherical lenses, and the thickness of each piece of glass does not exceed 5mm. The overall system length is small and controlled within 84mm.

[0078] The high-efficiency, high-definition, distortion-free objective lens system for 3D printing is configured by providing a first lens group 1 with positive focal length, an aperture 2, a second lens group 3 with positive optical angle, an optical component, and an imaging surface 7, and performing special configurations on the lenses of the first lens group 1 and the second lens group 3, such as sequence and focal length, to optimize image quality, reduce distortion, improve relative illumination, and achieve short-distance projection.

[0079] The above is only a specific implementation of the utility model, but the protection scope of the utility model is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the utility model, and these modifications or replacements should be included in the protection scope of the utility model. Therefore, the protection scope of the utility model should be based on the protection scope of the claims.

Claims

1. A high-efficiency, high-definition, distortion-free objective lens system for 3D printing, characterized in that: include: A first lens group with positive focal power, an aperture, a second lens group with positive optical angle, an optical component and an imaging surface are coaxially arranged; the aperture is located between the first lens group and the second lens group; The first group of lenses includes a first lens with negative optical power, a second lens with negative optical power, and a third lens with positive optical power, which are coaxially arranged in sequence; the second group of lenses includes a fourth lens with negative optical power, a fifth lens with negative optical power, and a sixth lens with positive optical power, which are coaxially arranged in sequence.

2. The high-efficiency, high-definition, distortion-free objective lens system for 3D printing according to claim 1, characterized in that: The first lens, the second lens, the third lens and the sixth lens are glass lenses respectively.

3. The high-efficiency, high-definition, distortion-free objective lens system for 3D printing according to claim 1, characterized in that: The fourth lens and the fifth lens are respectively glass spherical double-cemented lenses.

4. The high-efficiency, high-definition, distortion-free objective lens system for 3D printing according to claim 1, characterized in that: The ratio of the focal length of the first lens group to the focal length of the objective lens system is 6.

68.

5. The high-efficiency, high-definition, distortion-free objective lens system for 3D printing according to claim 1, characterized in that: The ratio of the focal length of the first lens to the focal length of the first lens group is -0.

59.

6. The high-efficiency, high-definition, distortion-free objective lens system for 3D printing according to claim 1, characterized in that: The ratio of the focal length of the second lens to the focal length of the first lens group is -0.

46.

7. The high-efficiency, high-definition, distortion-free objective lens system for 3D printing according to claim 1, characterized in that: The ratio of the focal length of the third lens to the focal length of the first lens group is 0.

45.

8. The high-efficiency, high-definition, distortion-free objective lens system for 3D printing according to claim 1, characterized in that: The ratio of the focal length of the second lens group to the focal length of the objective lens system is 2.

07.

9. The high-efficiency, high-definition, distortion-free objective lens system for 3D printing according to claim 1, characterized in that: The ratio of the focal length fG4 of the fourth lens to the focal length of the second lens group is -1.11; The ratio of the focal length fG5 of the fifth lens to the focal length of the second lens group is 1.24; The ratio of the focal length fG6 of the sixth lens to the focal length of the second lens group is 1.

11.

10. The high-efficiency, high-definition, distortion-free objective lens system for 3D printing according to claim 1, characterized in that: The gap between the third lens and the STO ranges from 10 mm to 15 mm.

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