An objective lens system for 3D printing

Abstract

The present invention provides an objective lens system for 3D printing, comprising: a printing surface, a first lens group, a diaphragm, a second lens group, a galvanometer scanner, a beam splitter, a protective glass, and an image source arranged in sequence; the first lens group is used to adjust the size of the projection field of view and balance the field curvature of the system, the second lens group is used to balance the aberrations and chromatic aberrations of the system, the diaphragm is used to control the light incident amount of the light emitted by the image source; the beam splitter is used to split the light beam of the light emitted by the image source, the image source is used to emit light, the protective glass is used to protect the image source, and the galvanometer scanner is used to improve the resolution of the objective lens system; the present invention solves the problem in the prior art that the consistency of the frame size refracted by the DLP printing system cannot ensure the consistency of the printing accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of light projection, and particularly to an objective lens system for 3D printing. Background Art

[0002] Currently, there are still many deficiencies in 3D printing. For example, the mechanical properties of the printed parts are unstable, there are deficiencies in processing accuracy and surface roughness, etc., and the distortion of the system does not meet the requirements in some special printing scenarios. For this reason, with the development of material technology and hardware equipment technology, the desire to apply this technology to the manufacturing of terminal parts is becoming more and more urgent, so higher technical requirements are put forward for 3D printing equipment.

[0003] Most existing DLP printing systems are generally image-space telecentric systems. The size of the projected picture generally changes with the working distance, and the consistency of the projected picture size cannot be ensured, resulting in different projected pixel sizes, thus affecting the consistency of printing accuracy. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide an objective lens system for 3D printing, which solves the problem that the consistency of the refracted picture size in the existing DLP printing system cannot be ensured and affects the consistency of printing accuracy.

[0005] To achieve the above purpose, the present invention provides the following solution:

[0006] An objective lens system for 3D printing, comprising:

[0007] A printing surface, a first lens group, a diaphragm, a second lens group, a galvanometer, a beam splitter, a protective glass, and an image source arranged in sequence;

[0008] The first lens group is used to regulate the size of the projection field angle and balance the system field curvature, the second lens group is used to balance the system aberration and chromatic aberration, the diaphragm is used to control the light input amount of the light emitted by the image source; the beam splitter is used to split the light beam emitted by the image source, the image source is used to emit light, the protective glass is used to protect the image source, and the galvanometer is used to improve the resolution of the objective lens system;

[0009] The first lens group includes:

[0010] A first lens, a second lens, and a third lens arranged in sequence, wherein both the first lens and the third lens are lenses with positive optical power, and the second lens is a lens with negative optical power;

[0011] The second lens group includes:

[0012] The fourth lens, the fifth lens, and the sixth lens are arranged in sequence, where the fourth lens and the fifth lens are cemented lenses, the fourth lens is a lens with negative optical power, and the fifth lens and the sixth lens are both lenses with positive optical power.

[0013] Preferably, the first lens to the seventh lens are all spherical lenses.

[0014] Preferably, the ratio of the focal length of the first lens to the focal length of the first lens group is 1.265, the ratio of the focal length of the second lens to the focal length of the first lens group is -0.971, and the ratio of the focal length of the third lens to the focal length of the first lens group is 0.244.

[0015] Preferably, the ratio of the focal length of the fourth lens to the focal length of the second lens group is -0.174, the ratio of the fifth lens to the focal length of the second lens group is 0.320, and the ratio of the focal length of the sixth lens to the focal length of the second lens group is 1.292.

[0016] Preferably, the full-field MTF of the objective lens system is greater than 0.58.

[0017] Preferably, the full-field RMS of the objective lens system is less than 3.8um.

[0018] Preferably, the system distortion of the objective lens system is less than 0.009%, and the TV distortion amount of the objective lens system is less than 0.007%.

[0019] Preferably, the field angles of the objective lens system are all within 1 degree.

[0020] Preferably, the lens of the objective lens system is a 0.3-inch DMD chip.

[0021] According to the specific embodiments provided by the present invention, the following technical effects of the present invention are disclosed:

[0022] The present invention provides an objective lens system for 3D printing. The chief ray of the lens of the objective lens system of the present invention and the object-side chief ray are both parallel to the optical axis. As the working distance changes, the size of the projected picture is fixed, improving the imaging quality of the projection lens of the objective lens system and reducing the cost of the lens. Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0024] Figure 1 Structural diagram of an objective lens system for 3D printing provided by an embodiment of the present invention;

[0025] Figure 2 Spatial frequency MTF diagram provided by an embodiment of the present invention;

[0026] Figure 3 Field curvature evaluation diagram provided by an embodiment of the present invention;

[0027] Figure 4 Distortion evaluation diagram provided by an embodiment of the present invention;

[0028] Figure 5 Relative illumination diagram provided by an embodiment of the present invention;

[0029] Figure 6 Chief ray angle diagram provided by an embodiment of the present invention.

[0030] Explanation of reference numerals:

[0031] 1 - Printing surface, 2 - First lens group, 3 - Diaphragm, 4 - Second lens group, 5 - Galvanometer scanner, 6 - Beam splitter device, 7 - Protective glass, 8 - Image source, G1 - First lens, G2 - Second lens, G3 - Third lens, G4 - Fourth lens, G5 - Fifth lens, G6 - Sixth lens. Detailed implementation manners

[0032] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0033] The object of the present invention is to provide an objective lens system for 3D printing, which solves the problem in the prior art that in an AR - HUD, due to the diffusion film not being able to completely randomize the light, bright spots of the lens exit pupil can be seen when looking at the lens through the diffusion film, resulting in low imaging quality.

[0034] To make the above - mentioned objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0035] As Figure 1 shown, the present invention provides an objective lens system for 3D printing, including:

[0036] The printing surface 1, the first lens group 2, the diaphragm 3, the second lens group 4, the galvanometer scanner 5, the beam splitter device 6, the protective glass 7, and the image source 8 arranged in sequence;

[0037] The first lens group 2 is used to adjust the size of the projection field of view and balance the system field curvature. The second lens group 4 is used to balance the system aberrations and chromatic aberrations. The aperture stop 3 is used to control the amount of light entering from the light source 8. The beam splitter 6 is used to split the light beam emitted by the light source 8. The light source 8 is used to emit light. The protective glass 7 is used to protect the light source 8. The galvanometer 5 is used to improve the resolution of the objective lens system.

[0038] The first lens group 2 includes:

[0039] The first lens G1, the second lens G2, and the third lens G3 arranged in sequence, where both the first lens G1 and the third lens G3 are positive focal length lenses, and the second lens G2 is a negative focal length lens.

[0040] The second lens group 4 includes:

[0041] The fourth lens G4, the fifth lens G5, and the sixth lens G6 arranged in sequence, where the fourth lens G4 and the fifth lens G5 are cemented lenses, the fourth lens G4 is a negative focal length lens, and both the fifth lens G5 and the sixth lens G6 are positive focal length lenses.

[0042] Furthermore, the first lens G1 to the seventh lens are all spherical lenses.

[0043] Specifically, the ratio of the focal length of the first lens G1 to the focal length of the first lens group 2 is 1.265. The ratio of the focal length of the second lens G2 to the focal length of the first lens group 2 is -0.971. The ratio of the focal length of the third lens G3 to the focal length of the first lens group 2 is 0.244.

[0044] Specifically, the ratio of the focal length of the fourth lens G4 to the focal length of the second lens group 4 is -0.174. The ratio of the fifth lens G5 to the focal length of the second lens group 4 is 0.320. The ratio of the focal length of the sixth lens G6 to the focal length of the second lens group 4 is 1.292.

[0045] Specifically, Table 1 is the specific parameter table of the objective lens system, as shown in Table 1 below:

[0046] Table 1 Specific Parameter Table of the Objective Lens System

[0047]

[0048]

[0049] Furthermore, the full-field MTF of the objective lens system is greater than 0.58.

[0050] Specifically, asFigure 2 As shown in the figure, the MTF (English name: Modulation Transfer Function) index is currently the most accurate and scientific evaluation standard for lenses. The ordinate represents the contrast, and the closer it is to 1, the better the lens imaging. The abscissa represents the resolution, with the unit of line pairs per millimeter. In the embodiment of the present application, the pixel size of the image source 8 is 5.4um, and the corresponding designed resolution is 93 line pairs per millimeter. Generally, the MTF value of each field of view of the projection lens is required to reach above 0.3 in design, while the MTF value of each field of view in the embodiment of the present application is above 0.58.

[0051] Further, the full-field RMS of the objective lens system is less than 3.8um.

[0052] Specifically, the smaller the spot radius of each field of view, the better the imaging quality it represents. Generally, when the full-field RMS is less than the pixel size (5.4um), it belongs to an excellent level. In the embodiment of the present application, the full-field RMS is less than 3.8um, belonging to a very excellent level.

[0053] Further, the system distortion of the objective lens system is less than 0.009%, and the TV distortion amount of the objective lens system is less than 0.007%.

[0054] Specifically, as Figures 3 - 4 shown, the ordinate represents the field angle of the lens. The abscissa of the field curvature diagram represents the magnitude of the field curvature value, and the abscissa of the distortion diagram represents the distortion amount. Distortion is a very important index for projection lenses; the embodiment of the present application applies to a harsh distortion usage scenario. The system distortion in the embodiment of the present application is within 0.009%, and the TV distortion amount is within 0.007%. The system distortion and TV distortion are very excellent.

[0055] As Figure 5 shown, the edge illumination reaches 100%, making the uniformity of the projection effect on the imaging surface of the system very good

[0056] Further, as Figure 6 shown, the field angles of the objective lens system are all within 1 degree. The telecentricity is good, and the system efficiency loss is small.

[0057] Further, the lens of the objective lens system is a 0.3-inch DMD chip.

[0058] Further, the field angle of the lens projected onto the printing surface 1 is within 0.5 degrees.

[0059] Further, the relative illumination of the lens is very high, which is beneficial to improving the uniformity of the optical machine.

[0060] Furthermore, the selected lens material has a high light transmittance for light with wavelengths ranging from 380 nm to 410 nm.

[0061] This embodiment also discloses that the optical lens satisfies the following conditional formula:

[0062] 0.2 < T L / f / IH < 0.3 (1)

[0063] wherein, T L represents the overall optical length of the optical lens, f represents the effective focal length of the optical lens, and IH represents the actual semi-image height of the optical lens.

[0064] When the conditional formula (1) is satisfied, the relationship between the overall length of the lens and the resolution ability can be reasonably balanced. When the value of T L / f / IH exceeds the upper limit, the overall length of the lens is too large (the volume of the imaging system is too large). If the overall length is scaled proportionally or forced to be compressed, the image height will be insufficient; L When the value of T / f / IH is lower than the lower limit, due to the excessive optical power of each lens, it is difficult to correct the lens aberration, and the resolution ability is significantly reduced.

[0065] In an embodiment, the optical lens satisfies the following conditional formula:

[0066] 404 mm < IH / tanθ < 405 mm (2)

[0067] wherein, IH represents the actual semi-image height of the optical lens, and θ represents the semi-field angle of the optical lens.

[0068] When the conditional formula (2) 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. At the same time, the field of view size can be limited, and thus the size of the projection picture can be controlled.

[0069] In an embodiment, the optical lens satisfies the following conditional formula:

[0070] CRA < 1° (3)

[0071] wherein, CRA represents the main ray incident angle of the optical lens on the imaging surface.

[0072] When the conditional formula (3) is satisfied, the DMD chip can be well matched to achieve a good projection effect.

[0073] The beneficial effects of the present invention are as follows:

[0074] The disclosed 3D high-precision printing projection lens of the present invention has small distortion and high power, meeting the requirements of desktop-level high-precision 3D printing equipment.

[0075] The 3D printing projection lens disclosed by the present invention is compatible with the XPR technology. When using XPR, a 2K resolution can be achieved; when not using XPR, a 720P resolution can be achieved.

[0076] For the 3D printing projection lens disclosed by the present invention, the relative illumination reaches 100%, the full-field MTF is higher than 0.6, and the imaging quality is very excellent; the distortion can reach within 0.0088%, and the TV distortion is within 0.007%.

[0077] For the 3D printing projection lens disclosed by the present invention, all the lenses are made of glass materials, which can effectively avoid the serious problem of focus shift caused by the strong energy of the 405nm short-wave light source used in 3D printing and the easy heat absorption of plastic aspherical surfaces.

[0078] For the 3D printing projection lens disclosed by the present invention, the wavelength range is 380 - 410nm, and it can give consideration to the use of 385nm light source and 405nm light source.

[0079] For the 3D printing projection lens disclosed by the present invention, the spot radius of the point spread function (<3.8um) is much smaller than the pixel size (5.4um), which has obvious advantages for applications such as 3D printing that focus on the spot size and energy concentration.

[0080] For the 3D printing projection lens disclosed by the present invention, the selected lens materials have a high light transmittance for light with a wavelength of 405nm, all exceeding 95% / 10mm. The overall imaging system has relatively little energy absorption, which can improve the overall brightness, reduce the system heat generation, reduce the power and size of the heat dissipation device, and contribute to the stability during 3D printing.

[0081] For the 3D printing projection lens disclosed by the present invention, only 6 spherical lenses are used and no aspherical lenses are used. Compared with the lens designs with more than a dozen lenses, the lens cost and assembly difficulty are greatly reduced.

[0082] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other.

[0083] In this article, specific examples are used to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. An objective lens system for 3D printing, characterized in that, Including: A printing surface, a first lens group, a diaphragm, a second lens group, a galvanometer scanner, a beam splitter, a protective glass, and an image source arranged in sequence; The first lens group is used to regulate the size of the projection field of view and balance the system field curvature. The second lens group is used to balance the system aberration and chromatic aberration. The diaphragm is used to control the light incident amount of the light emitted by the image source. The beam splitter is used to split the light beam emitted by the image source. The image source is used to emit light. The protective glass is used to protect the image source. The galvanometer scanner is used to improve the resolution of the objective lens system; The first lens group includes: A first lens, a second lens, and a third lens arranged in sequence, where the first lens and the third lens are both positive focal length lenses, and the second lens is a negative focal length lens; The second lens group includes: A fourth lens, a fifth lens, and a sixth lens arranged in sequence, where the fourth lens and the fifth lens are cemented lenses, the fourth lens is a negative focal length lens, and the fifth lens and the sixth lens are both positive focal length lenses; The ratio of the focal length of the first lens to the focal length of the first lens group is 1.

265. The ratio of the focal length of the second lens to the focal length of the first lens group is -0.

971. The ratio of the focal length of the third lens to the focal length of the first lens group is 0.244; The ratio of the focal length of the fourth lens to the focal length of the second lens group is -0.

174. The ratio of the fifth lens to the focal length of the second lens group is 0.

320. The ratio of the focal length of the sixth lens to the focal length of the second lens group is 1.

292.

2. The objective lens system for 3D printing according to claim 1, characterized in that, The first lens to the sixth lens are all spherical lenses.

3. The objective lens system for 3D printing according to claim 1, wherein, The full-field MTF of the objective lens system is greater than 0.

58.

4. The objective lens system for 3D printing according to claim 1, characterized in that, The full-field RMS of the objective lens system is less than 3.8um.

5. The objective lens system for 3D printing according to claim 1, characterized in that, The system distortion of the objective lens system is less than 0.009%, and the TV distortion amount of the objective lens system is less than 0.007%.

6. The objective lens system for 3D printing according to claim 1, wherein, The field angles of the objective lens system are all within 1 degree.

7. The objective lens system for 3D printing according to claim 1, characterized in that, The lens of the objective lens system is a 0.3-inch DMD chip.

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