CN112269241A

CN112269241A - Projection lens suitable for DLP photocuring 3D printing

Info

Publication number: CN112269241A
Application number: CN202011317285.3A
Authority: CN
Inventors: 何磊
Original assignee: Sichuan Changhong Electric Co Ltd
Current assignee: Sichuan Changhong Electric Co Ltd
Priority date: 2020-11-20
Filing date: 2020-11-20
Publication date: 2021-01-26

Abstract

The invention discloses a projection lens suitable for DLP photocuring 3D printing, which comprises a first group lens with a positive focal length, a diaphragm, a second group lens with a positive focal length, a galvanometer, a prism, a DMD window and an imaging surface which are sequentially arranged along an optical axis. The lens has the characteristics of good illumination uniformity, high imaging resolution and ultralow distortion, and the contrast full-field of view is higher than 0.99.

Description

Projection lens suitable for DLP photocuring 3D printing

Technical Field

The invention relates to the technical field of lenses, in particular to a projection lens suitable for DLP photocuring 3D printing.

Background

DLP is an abbreviation for "Digital Light processing", i.e. Digital Light processing. That is, the image signal is digitally processed and then light projected, which is a technology for displaying visual digital information based on the digital micromirror device, DMD, developed by texas instruments, usa.

Photocuring (SLA) is a multi-vision 3D printing process that is more similar to traditional printing. Just as toner accumulates on paper, 3D printers can accumulate layers of data in a series of 2D cross sections, so that the layers are stacked one on top of the other to create a 3D object. In the case of the SLA technique, the material is a resin that is curable with an Ultraviolet (UV) light source. When the resin is cured, its monomers can crosslink to create a polymer chain-a solid material can occur.

When SLA technology is combined with DLP technology, the DMD will be illuminated by a UV light source. The pixels of the DMD are then isolated and the picture is projected onto the resin layer, then a series of sections occurs, which can make up the 3D object. The choice of DLP technology can provide advantages such as optical skill to image individual pixels from the DMD rather than having the light source directly on the resin, which can optimize resolution and feature size.

Disclosure of Invention

The invention aims to provide a projection lens suitable for DLP photocuring 3D printing, and the photocuring 3D printing utilizing the DLP technology has the following advantages: the printing precision is high, and the surface of an object is smooth; the printing speed is high.

The invention realizes the purpose through the following technical scheme:

the utility model provides a projection lens suitable for DLP photocuring 3D prints, includes the first group lens that have positive focal length, diaphragm, the second group lens that have positive focal length, galvanometer, prism, DMD window and the image plane of arranging in proper order along the optical axis.

Preferably, the first group of lenses includes first to fifth lenses; the second group of lenses includes sixth to ninth lenses.

Preferably, the first lens and the eighth lens are glass aspheric lenses, and the other lenses are glass spherical lenses; the fourth lens and the fifth lens are cemented lenses.

Preferably, the first lens, the second lens and the sixth lens have negative focal power, and the third lens, the cemented lens (fourth and fifth lenses), the seventh lens, the eighth lens and the ninth lens have positive focal power.

Preferably, the expression of the aspherical lens surface type is:

wherein Z represents the distance in the optical axis direction of a point on the aspherical surface from the vertex of the aspherical surface, and ρ represents notDistance from a point on the sphere to the optical axis, c represents the center curvature of the aspheric surface, k represents the conic power, A_nRepresenting the aspheric higher order degree.

Preferably, the stop is disposed between the cemented lens and the sixth lens.

Preferably, all the lenses are glass materials, and the optical constants of the glass materials satisfy the following conditional expressions: 1.48 < N_d＜1.9，20＜V_d< 85, wherein N_d、V_dRespectively, the refractive index and abbe number of the optical material used for d light.

The invention has the beneficial effects that:

the projection lens suitable for DLP photocuring 3D printing has the characteristics of good illumination uniformity, high imaging resolution and ultralow distortion, the contrast full-field of view is higher than 0.99, and the lens is made of glass materials and has good transmittance on a 405nm wave band.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the embodiments or the drawings needed to be practical in the prior art description, and obviously, the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 is an optical structural diagram of a lens barrel according to the present application.

Fig. 2 is a graph of MTF of each field of view of the lens of the present application.

Fig. 3 is a dot-sequence diagram of the lens of the present application.

Fig. 4 is a field curvature distortion diagram of the lens of the present application.

Fig. 5 is a relative illuminance diagram of the lens of the present application.

Fig. 6 is a vertical axis chromatic aberration diagram of the lens of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without any inventive step, are within the scope of the present invention.

In any embodiment, as shown in fig. 1, a projection lens suitable for DLP photocuring 3D printing according to the present invention includes a first group lens with a positive focal length, a diaphragm, a second group lens with a positive focal length, a galvanometer, a prism, a DMD window, and an imaging surface, which are sequentially arranged along an optical axis. The first group of lenses comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a fourth lens, wherein the first lens is a glass aspheric lens, the second lens is a glass spherical lens, the third lens is a glass spherical lens, the fourth lens is a glass spherical lens, the fifth lens is a glass spherical lens, and the fourth lens and the fifth lens form a cemented lens; the second group of lenses comprises a sixth glass spherical lens, a seventh spherical glass lens, an eighth glass aspheric lens and a ninth glass spherical lens; the lens uses the lens to be the glass material, can effectively reduce because the plastics lens is heated and the camera lens that leads to runs burnt influence, and this camera lens has the even and high characteristics of imaging quality of illuminance.

The first lens is negative focal power, the second lens is negative focal power, the third lens is positive focal power, the fourth lens and the fifth lens form a cemented lens which is positive focal power, the sixth lens is negative focal power, the seventh lens is positive focal power, the eighth lens is positive focal power, and the ninth lens is positive focal power.

Specific parameters of a lens provided by the present application are shown in table 1:

table 1 specific parameters of the lens of the present application:

wherein the first lens and the eighth lens are aspheric surfaces, and the expression of the aspheric surface type is as follows:

wherein R is the radius of curvature at the vertex of the sphere, K, A_nP is the normalized radial coordinate, an aspheric coefficient.

The first lens and the eighth lens are aspheric lenses, and aspheric coefficients of the aspheric lenses are shown in table 2.

Table 2 aspherical surface coefficients of the aspherical lens of the present application:

this embodiment uses a 0.66 inch DMD chip with a pixel size of 5.4 μ, a corresponding design resolution of 93lp/mm, an effective focal length of 25.15mm, and an F/No. of 2.2.

According to the lens parameters described in table 1, the lens shown in fig. 1 can be obtained. FIG. 2 is an image of MTF variation of a full field with spatial frequency, the closer the MTF is to a diffraction limit, the better the imaging quality is, and the better the imaging quality is when the MTF of each field under the spatial frequency of 93lp/mm is greater than 0.7. FIG. 3 is a dot diagram of each field, and the lens full field RMS is smaller than the pixel size (5.4 μ), so that clear imaging can be realized. FIG. 4 is a distortion diagram of the field curvature of the lens, the left side diagram being an image of the field curvature varying with the field of view, the field curvature being in the range of-0.05 mm to 0.05 mm; the right image is an image with distortion varying with the field of view, and the distortion is controlled within 0.5%. Fig. 5 is an image showing the variation of relative illuminance with the field of view, where the relative illuminance refers to the ratio of the illuminance at one field of view to the central illuminance, and it can be seen that the illuminance is not less than 0.99 at the full field of view. FIG. 6 is a vertical axis chromatic aberration image, the vertical axis chromatic aberration obtained from the image is controlled below 1.7 μ, which is smaller than half pixel size, and the vertical axis chromatic aberration is well controlled.

Compared with the prior art, the method has the following characteristics: the lens is high in resolution and high in imaging quality; the illumination is uniform, and the illumination of the whole field is not less than 0.99; the method has the characteristic of ultralow distortion; the selected glass materials have good transmittance to the wave band of 405 nm.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims. It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition. In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims

1. The utility model provides a projection lens suitable for DLP photocuring 3D prints which characterized in that, includes the first group lens that have positive focal length, diaphragm, the second group lens that have positive focal length, galvanometer, prism, DMD window and the image plane of arranging in proper order along the optical axis.

2. The projection lens suitable for DLP photocuring 3D printing as recited in claim 1, wherein the first group of lenses comprises first to fifth lenses; the second group of lenses includes sixth to ninth lenses.

3. The projection lens suitable for DLP photocuring 3D printing as claimed in claim 2, wherein the first lens and the eighth lens are glass aspheric lenses, and the other lenses are glass spherical lenses; the fourth lens and the fifth lens are cemented lenses; the first lens, the second lens and the sixth lens are negative focal power, and the third lens, the cemented lens, the seventh lens, the eighth lens and the ninth lens are positive focal power.

4. The projection lens suitable for DLP photocuring 3D printing as recited in claim 3, wherein the expression of the aspheric surface type is as follows:

wherein Z represents the distance in the optical axis direction of a point on the aspherical surface from the vertex of the aspherical surface, ρ represents the distance from the point on the aspherical surface to the optical axis, c represents the central curvature of the aspherical surface, k represents the conicity, A_nRepresenting the aspheric higher order degree.

5. The projection lens suitable for DLP photocuring 3D printing as recited in claim 3, wherein the diaphragm is arranged between the cemented lens and the sixth lens.

6. The projection lens suitable for DLP photocuring 3D printing as claimed in claim 1, wherein all the lenses are made of glass materials, and the optical constants of the glass materials satisfy the following conditional expression: 1.48 < N_d＜1.9，20＜V_d< 85, wherein N_d、V_dRespectively, the refractive index and abbe number of the optical material used for d light.

7. The projection lens suitable for DLP photocuring 3D printing as recited in claim 1, wherein the lens adopts a 0.66-inch DMD chip.

8. The projection lens suitable for DLP photocuring 3D printing as recited in claim 1, wherein the lens operating wavelength is 405 nm.