WO2015113408A1 - 光固化型3d打印设备及其图像曝光系统 - Google Patents

光固化型3d打印设备及其图像曝光系统 Download PDF

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Publication number
WO2015113408A1
WO2015113408A1 PCT/CN2014/088725 CN2014088725W WO2015113408A1 WO 2015113408 A1 WO2015113408 A1 WO 2015113408A1 CN 2014088725 W CN2014088725 W CN 2014088725W WO 2015113408 A1 WO2015113408 A1 WO 2015113408A1
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Prior art keywords
micro
light
micromirror
spot
exposure system
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PCT/CN2014/088725
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English (en)
French (fr)
Inventor
侯锋
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上海普利生机电科技有限公司
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Priority to EP14880796.9A priority Critical patent/EP3101477B1/en
Priority to US15/115,076 priority patent/US10156793B2/en
Publication of WO2015113408A1 publication Critical patent/WO2015113408A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/10—Processes of additive manufacturing
    • B29C64/106—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material
    • B29C64/124—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material using layers of liquid which are selectively solidified
    • B29C64/129—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material using layers of liquid which are selectively solidified characterised by the energy source therefor, e.g. by global irradiation combined with a mask
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/20—Apparatus for additive manufacturing; Details thereof or accessories therefor
    • B29C64/264—Arrangements for irradiation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y30/00—Apparatus for additive manufacturing; Details thereof or accessories therefor
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/0037—Production of three-dimensional images
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/20—Exposure; Apparatus therefor
    • G03F7/2002—Exposure; Apparatus therefor with visible light or UV light, through an original having an opaque pattern on a transparent support, e.g. film printing, projection printing; by reflection of visible or UV light from an original such as a printed image
    • G03F7/201—Exposure; Apparatus therefor with visible light or UV light, through an original having an opaque pattern on a transparent support, e.g. film printing, projection printing; by reflection of visible or UV light from an original such as a printed image characterised by an oblique exposure; characterised by the use of plural sources; characterised by the rotation of the optical device; characterised by a relative movement of the optical device, the light source, the sensitive system or the mask
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/70058—Mask illumination systems
    • G03F7/702—Reflective illumination, i.e. reflective optical elements other than folding mirrors, e.g. extreme ultraviolet [EUV] illumination systems
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/70416—2.5D lithography

Definitions

  • the present invention relates to a photocurable 3D printing device, and more particularly to an image exposure system for a photocurable 3D printing device.
  • 3D printing technology is based on computer three-dimensional design model. Through software layered discrete and numerical control molding system, laser beam, hot melt nozzle, etc. are used to layer metal powder, ceramic powder, plastic, cell tissue and other special materials layer by layer. Bonding, and finally superimposed to create a physical product. Different from the traditional manufacturing industry, the raw materials are shaped and cut by the machining methods such as mold and milling to make the finished product different. 3D printing transforms the 3D solid into several 2D planes, which are processed by material processing and layer by layer. Reduced manufacturing complexity. This digital manufacturing model does not require complicated processes, does not require a large machine tool, does not require a lot of manpower, and can directly generate any shape parts from computer graphics data, so that manufacturing can be extended to a wider production crowd.
  • the photocuring method is based on the principle that the photosensitive resin is cured by ultraviolet light, and the material is cumulatively formed, and has the characteristics of high molding precision, good surface smoothness, and high material utilization rate.
  • Fig. 1 shows the basic structure of a photocurable 3D printing apparatus.
  • This 3D printing apparatus 100 includes a material tank 110 for accommodating photosensitive resin, an image exposure system 120 for curing the photosensitive resin, and a lifting table 130 for joining molded workpieces.
  • the image exposure system 120 is positioned above the material tank 110 and can illuminate the beam image to cure a layer of photosensitive resin on the level of the material tank 110.
  • the image exposure system 120 illuminates the image of the light beam to cause a layer of the photosensitive resin to be cured, the surface of the cured photosensitive resin which is driven by the lifting table 130 is slightly lowered, and the photosensitive resin is evenly spread on the top surface of the solidified workpiece by the squeegee 131. Wait for the next shot. In this cycle, a three-dimensional workpiece that is incrementally formed by layer will be obtained.
  • the image exposure system 120 typically uses a laser forming technique or a Digital Light Procession (DLP) projection technique.
  • DLP Digital Light Procession
  • Laser forming technology uses a laser scanning device for point-by-point scanning. But due to the speciality of photosensitive resin Sex, laser power can not be too large, otherwise it will damage the resin. Therefore, the laser moving speed is limited to several meters to ten meters/second, resulting in a molding speed that is too slow.
  • DLP projection imaging technology is implemented using a Digital Micromirror Device (DMD) to control the reflection of light.
  • the digital micromirror component can be viewed as a mirror. This mirror is made up of hundreds of thousands or even millions of micromirrors. Each micromirror represents a pixel, and the image is composed of these pixels. Each micromirror can be independently controlled to determine whether to reflect light to the projection lens. Eventually, the entire mirror reflects the desired beam image.
  • DMD applications have many advantages in 3D printing. For example, it can process ultraviolet light below 400 nm without fear of damage, but its limited resolution limits its development. For example, the highest resolution commonly used in current DMD is 1920 ⁇ 1080. However, this resolution can only produce objects with an area of 192 ⁇ 108 mm in 3D printing with a common accuracy of 0.1 mm, which significantly limits its application.
  • the technical problem to be solved by the present invention is to provide a photocurable 3D printing apparatus and an image exposure system therefor.
  • an image exposure system for a 3D printing device comprising: a spatial light modulator having a plurality of micromirrors, each micromirror corresponding to a pixel for being used according to a control signal Adjusting a direction of reflection of the light irradiated thereon, the reflection direction including a first direction and a second direction, wherein each of the micromirrors is a concave mirror, and the light irradiated thereon is concentrated to a size smaller than a pixel corresponding to the micromirror a micro-spot of size; a light source that generates a light beam that illuminates the spatial light modulator; and a projection lens that is aligned with the first direction of the spatial light modulator to cause the light source to be projected through the micro-spot array formed by each micro-mirror a surface of the photosensitive material; a micro-displacement driving mechanism connected to the spatial light modulator, capable of driving the spatial light
  • the images formed by the micro-spot arrays of the respective exposures on the surface of the photosensitive material do not substantially overlap each other.
  • the image formed by each of the exposed micro-spot arrays is covered with the photosensitive material Material surface.
  • the size of the micro-spot is less than, equal to, or slightly larger than half the pixel size corresponding to the micromirror.
  • each micromirror is f
  • the pixel size corresponding to the micromirror is p
  • the half angle of the light beam incident on each micromirror is ⁇
  • the image height of the microscopic spot is a.
  • the maximum half angle of the outgoing light is W, which satisfies:
  • each of the exposed micro-spot arrays contains different image information.
  • the ratio of the size of the micro-spot to the pixel size of the micro-mirror is about 1:2, 1:3 or 1:4.
  • the number of exposures of the light source is 4, 9 or 16 times.
  • the spatial light modulator is a digital micromirror element.
  • the micro-displacement driving mechanism is a piezoelectric ceramic.
  • the invention also provides an image exposure system for a 3D printing device, comprising: a spatial light modulator having a plurality of micromirrors, each micromirror corresponding to a pixel for controlling the reflection direction of the light irradiated thereon according to the control signal
  • the reflection direction includes a first direction and a second direction, wherein each of the micromirrors is a concave mirror to converge the light irradiated thereon into a microscopic spot having a size smaller than a pixel size corresponding to the micromirror; the light source will be generated a light beam illuminating the light on the spatial light modulator; a projection lens aligned with the first direction of the spatial light modulator to cause the light source to be projected onto the surface of the photosensitive material through an array of micro-spots formed by the respective micromirrors; a lens disposed between the spatial light modulator and the surface of the photosensitive material, the deflecting lens being deflectable about at least one axis of rotation
  • the present invention also proposes a photocurable 3D printing apparatus comprising the image exposure system as described above.
  • the present invention adopts the above technical solution to make the photosensitive material be combined with the micro-mirror of the digital micro-mirror element by combining the micro-mirror of the digital micro-mirror element with the concave mirror as compared with the prior art.
  • the surface of the material fills the exposure spot, and then different imaging information is used for each exposure, which can double the resolution of the imaging, thereby improving the printing accuracy.
  • Fig. 1 shows the basic structure of a photocurable 3D printing apparatus.
  • FIG. 2 shows an image exposure system of a 3D printing apparatus according to an embodiment of the present invention.
  • 3A-3C are block diagrams showing the digital micromirror elements of the image exposure system of Fig. 2.
  • Figure 4 illustrates the operation of a digital micromirror component of an image exposure system.
  • Figure 5 shows an image of a direct projection of a DMD element.
  • Figure 6 is a view showing a concentrated optical path of a single micromirror of the digital micromirror device shown in Figure 3 at a deflection angle of 0°.
  • Figure 7 is a view showing a concentrated optical path of a single micromirror of the digital micromirror device shown in Figure 3 at a +12° deflection angle.
  • Figure 8 is a view showing a concentrated optical path of a single micromirror of the digital micromirror device shown in Figure 3 at a deflection angle of -12°.
  • Figure 9 is a view showing an image formed on the surface of a photosensitive material by one exposure of the image exposure system of the embodiment of the present invention.
  • Figure 10 is a view showing an image formed on the surface of a photosensitive material by the exposure of the image exposure system of the embodiment of the present invention.
  • Figure 11 is a diagram showing the image extraction of the image exposure system of the embodiment of the present invention.
  • Fig. 12 shows an image exposure system of a 3D printing apparatus of another embodiment of the present invention.
  • Figure 13 is a schematic illustration of the optical path of the deflecting lens of the image exposure system of Figure 12, undeflected.
  • Fig. 14 is a view showing the optical path of the deflecting lens of the image exposure system shown in Fig. 12 deflected.
  • Embodiments of the present invention describe a 3D printing device and its image exposure system that uses digital micromirror elements as an area array image source.
  • the image exposure system 200 of the present embodiment includes a light source 201, a band pass color filter 202, an integrator rod 203, a relay optical element 204, a mirror 205, a digital micromirror element 206, and a TIR (Total Internal Reflection) prism. 207. Projection lens 208 and controller (not shown). For the sake of brevity, devices not related to the present invention are not shown.
  • Light source 201 is used to generate a beam of light that needs to be illuminated onto digital micromirror element 206.
  • the wavelength of the light emitted by the source 201 is a function of the photosensitive material that is cured.
  • the light beam may be violet to ultraviolet light having a wavelength below 430 nm, such as 360-405 nm.
  • a plurality of optical devices are disposed between the light source 201 and the digital micromirror element 206.
  • the light emitted by the UHP bulb is concentrated into a light spot through the reflective bowl. This spot passes through the band pass filter 202 to filter out the light that is not required to cure the photosensitive material, and then homogenizes the beam through the integrator rod 203, and is then irradiated to the TIR prism 207 by the mirror 205 and the lens group (if necessary).
  • the TIR prism 207 reflects the light onto the digital micromirror element 206.
  • the light is reflected by the digital micromirror element 206 and then irradiated onto the surface of the photosensitive material via the TIR prism 207 and the projection lens 208.
  • Digital micromirror element 206 is used as a spatial light modulator in the present invention.
  • 3A is a structural view showing a digital micromirror device of the image exposure system shown in FIG. 2
  • FIG. 3B is a view showing a single pixel structure of FIG. 3A
  • FIG. 3C is a side view of FIG. 3B.
  • the digital micromirror device can be simply described as a semiconductor optical switch in which tens to millions of pixels are concentrated on a CMOS silicon substrate.
  • One pixel 310 includes a micro mirror 311, each of which has a size of, for example, ten micrometers.
  • the micromirror 311 is mounted on and held by a support post 312 which projects downwardly from the center of the micromirror and reaches the center of the yoke 313 along its torsion axis.
  • the center of mass of the micromirror 311 is balanced on the yoke 313.
  • the yoke 313 is axially supported by a pair of twist hinges 314 along its central axis.
  • the other end of the twist hinge 314 extends to and is mounted to a support stud 315 which is at the top of the corresponding support post 316. form.
  • a pair of raised micromirror address electrodes 317 and 318 are supported by corresponding addressing support posts 319 and 320.
  • the rotation of the micromirrors of the digital micromirror element is controlled by a digital drive signal from the SRAM.
  • the SRAM When a digital signal is written to the SRAM, the SRAM outputs an address voltage to the digital micromirror element. Addressing voltage applied to One of the two address pads 322 and 323 is coupled to one of the respective raised micromirror address electrodes 317 and 318 via associated electrode support posts 319 and 320.
  • a bias voltage is applied to the bias/reset bus 321 and applied to the yoke 313 via the support post 316, the support stud 315 and the twist hinge 314, and to the micromirror 301 via the support 312.
  • an address voltage is generated on the corresponding corresponding address electrode 322 or 323, and electrostatic attraction is generated at two places, as shown at 30 and 32, or 34 and 36.
  • an address voltage is applied to one of the two address electrodes 317 and 318 to determine which of the micro mirror 301 and the yoke 313 is applied once the voltage is applied to the bias bus 321 and the yoke 313 and the micro mirror 301. The direction is rotated.
  • Figure 4 illustrates the operation of a digital micromirror component of an image exposure system.
  • the working principle of the digital micromirror device is to reflect the required light to the projection lens by means of each micromirror, and to absorb the unwanted light through the light absorber to realize the projection of the image, and the illumination direction is by electrostatic action. By controlling the angle of the micromirror.
  • Each of the micromirrors on the digital micromirror element is electrostatically tilted to an on or off state by addressing the memory cells under each micromirror with a binary planar signal.
  • the technique of determining in which direction each micromirror is tilted is called pulse width modulation (PWM).
  • PWM pulse width modulation
  • the micromirror can be switched more than 1000 times in one second.
  • the light from the projection lamp passes through the collecting lens and the color filter, and then is irradiated onto the micromirror.
  • the direction in which the digital micromirror element is aligned with the projection lens 208 is taken as the 0° position.
  • the incident light is directly incident on the digital micromirror element at 24°.
  • the incident light When a certain micromirror of the digital micromirror device is at an "on" position, that is, +12°, the incident light is reflected by it, enters the projection lens 208 disposed at the 0° position, and forms a projected image on the surface of the photosensitive material; When the lens is at the "off" position, i.e., -12, the incident light is reflected therethrough into the light absorber 210 disposed at the 48° position without illuminating the surface of the photosensitive material.
  • the micromirror has a "flat" position at which the incident light is reflected by it and exits at an angle of 24°.
  • each of the micromirrors of the digital micromirror element is designed as a concave mirror, with the following rigorously designed illumination system, the light illuminating thereon can be concentrated to a size smaller than the size of the micromirror The micro spot.
  • Figure 6 is a view showing a concentrated optical path of a single micromirror of the digital micromirror device shown in Figure 3.
  • Figure 7 is a view showing a concentrated optical path of a single micromirror of the digital micromirror device shown in Figure 3 at a +12° deflection angle. Referring to Figures 6 and 7, a parallel beam having an angle is incident on a micromirror 501 having concave mirror characteristics.
  • the focal length f of the concave micromirror 501 is 60 ⁇ m
  • the pixel size p corresponding to the micromirror is 14 ⁇ m
  • the half angle ⁇ of the light beam is 3.5°
  • the image height a of the microscopic spot reflected by the micromirror is:
  • an image having a size of 7.3 ⁇ m appears in front of the micromirror, and its size is about 1/2 of the pixel size.
  • the aperture value Fno is calculated as follows:
  • the incident light of 24° is reflected by the micromirror deflected by +12° into the emitted light of 0°, and the light enters the projection lens at 0°, and the lens can pass all the light by using only 2.8 aperture value.
  • the focal plane of the lens is no longer located on the micromirror of the digital micromirror element, but on the array of micro-spots in front of the digital micro-mirror element, so that an array of micro-spots much smaller than the original micro-mirror area is projected onto the photosensitive On the surface of the material, the surface of the photosensitive material is finally imaged to form an exposure spot.
  • Another advantage of convergence is that after the convergence, although the area of the micro-spot is reduced, the brightness of the micro-spot is increased in the same proportion, so that when the micro-spot is finally imaged on the surface of the photosensitive material, the curing area is reduced, and the curing time is shortened in the same proportion. After the secondary exposure, the micro-spot will fill the entire resin surface. At this time, the total exposure time and direct exposure required for curing are substantially unchanged while improving the projection resolution.
  • Figure 8 is a view showing a concentrated optical path of a single micromirror of the digital micromirror device shown in Figure 3 at a deflection angle of -12°. It can be seen that the light at this time is deflected to 48° and is absorbed by the light absorber 210 at this position. At this time, the beam angle is limited to 48° ⁇ 10.065°, that is, the minimum beam angle is 48-10.065° ⁇ 38°, which is much larger than the acceptable ⁇ 10.065° of the projection lens, and does not enter the optical path.
  • the spot size will be slightly larger than the actual calculation, and the shape of the spot may also become circular, which requires adjustment of the aforementioned parameters in actual experiments. Determine the final data.
  • Figure 9 is a view showing the image exposure system of the embodiment of the present invention formed by one exposure on the surface of the photosensitive material. Image.
  • the resulting image will occupy almost the entire projected area (see Figure 5). Comparing Fig. 5 with Fig. 9, it can be seen that after the convergence of the micromirrors which are concave mirrors, the size of the microspots in the image is reduced.
  • the size of the imaging spot can be controlled by precisely designing the shape of the illumination system and the concave mirror. For example, the ratio of the imaging spot size to the pixel size (the size of the micromirror) can be made 1:2, that is, the ratio of the areas is 1:4.
  • the ratio of imaging spot size to pixel size can be approximately 1:3 or 1:4.
  • the reason for taking an integer multiple here is to insert a new micro-spot in the blank portion of each micro-spot in consideration of the subsequent micro-displacement.
  • a blank is left between the spots. To this end, these blanks are filled by multiple exposures so that the spot fills the entire surface of the photosensitive material.
  • the digital micromirror device 206 is coupled to a micro-displacement drive mechanism 209.
  • the micro-displacement drive mechanism 209 is capable of driving the digital micro-mirror element 206 to move in the x-direction and the y-direction to fine tune the position at which the micro-spot array is projected onto the surface of the photosensitive material.
  • the x and y directions are in the same plane, and this plane is perpendicular to the optical axis z of the image exposure system.
  • the micro-spot array of the digital micro-mirror element 206 is imaged at a first position on the surface of the photosensitive material; when the micro-displacement drive mechanism 209 drives the digital micro-mirror element 206 in one direction ( In the x or y direction) micro-displacement, the entire micro-spot array of the digital micro-mirror element 206 will be imaged with a slight displacement of the digital micro-mirror element 206 to a position other than the first position of the surface of the photosensitive material.
  • FIG. 10 is a view showing an image formed on the surface of a photosensitive material by the exposure of the image exposure system of the embodiment of the present invention. Referring to FIG.
  • the projected image A is formed;
  • the micro-displacement driving mechanism 209 is moved by a distance of 1/2 pixel in the x direction, the micro-spot array is slightly slightly Moving along the horizontal direction in the figure, projecting into the blank between the two columns of micro-spots to form a projected image B;
  • the micro-displacement driving mechanism 209 moves along the y-direction, so that the micro-spot array is slightly along the map.
  • the vertical direction of the movement is shifted by a distance of 1/2 pixel, projected into the space between the two rows of micro-spots to form a projected image C; similarly, the projected image D is formed.
  • the projected image D is already covered with the surface of the photosensitive material.
  • the micro displacement drive mechanism 209 may be a piezoelectric ceramic.
  • the controller of the image exposure system 200 can be used to command the light source 201 to perform multiple exposures while commanding the micro-displacement drive mechanism 209 to perform the movement in both the x and y directions at each exposure.
  • Projection lens 208 is disposed between digital micromirror element 206 and the surface of the photosensitive material of the three dimensional printing device, projecting an array of micro-spots reflected by digital micromirror element 206 onto the surface of the photosensitive material.
  • the positions of the micro-spot arrays of the respective exposures on the surface of the photosensitive material may not substantially overlap each other. This is achieved by controlling the ratio of the pixel size to the size of the spot to be an integer, and the step size of the displacement is just the spot size. This arrangement, which is essentially non-overlapping, avoids a drop in resolution. It can be understood that considering the factors such as the light diffraction effect, a slight overlap helps to compensate for the absence of the non-rectangular edge portion of the micro-spot. Therefore, it is not required that the micro-spots do not overlap at all. In addition, although the superimposition of the micro-spot array is full of the surface of the photosensitive material, it can be understood that not every position in the micro-spot array is a bright spot, but may have a dark spot.
  • each exposed micro-spot array contains different image information.
  • the four micro-light spots D1 in the virtual frame contain different image information. This means that the resolution of the projected pattern is correspondingly four times larger. Therefore, the accuracy of 3D printing is significantly improved.
  • the different image information may be from four different image files that can form a complete image, or four sub-images that are processed after processing one image of the same image file.
  • the shaded pixels indicate that exposure is required, and the unshaded pixels indicate that exposure.
  • the pixel groups ⁇ A1, A3, C1, C3 ⁇ , ⁇ A2, A4, C2, C4 ⁇ , ⁇ B1, B3, D1, D3 ⁇ , and ⁇ B2, B4, D2, can be extracted from the image, respectively.
  • D4 ⁇ is used as 4 sub-images for 4 exposures.
  • the image used by a conventional printing device has a size of at least 4 pixels as shown in FIG. 11 such as ⁇ A1, A2, B1, B2 ⁇ , so the resolution is significantly lower. .
  • the above example is to perform four exposures when the micro-spot size is controlled to be 1/2 of the pixel size. It can be understood that 9 times exposure can be performed when the control micro-spot is 1/3 of the pixel size, 16 exposures can be performed when the control micro-spot is 1/4 of the pixel size, and so on.
  • Fig. 12 shows an image exposure system of a 3D printing apparatus of another embodiment of the present invention.
  • the above-described micro-displacement driving mechanism 209 is replaced with a deflecting lens 211.
  • the deflecting lens 211 can be arranged At any position in the optical path of the digital micromirror element to the photosensitive resin, it is generally disposed at a position close to the projection lens.
  • the deflecting lens 211 is deflectable about at least one axis of rotation to fine tune the position at which the beam is projected onto the surface of the photosensitive material.
  • the aforementioned rotation axis is perpendicular to the optical axis z of the image exposure system.
  • the deflection lens 211 and the digital micromirror element 206 are parallel (and perpendicular to the optical axis z), the light is vertically irradiated on the deflection lens 211 (as shown in FIG. 13). No refraction occurs, the light passes directly through the deflecting lens 211; if the deflecting lens 211 is inclined at an angle around a rotating shaft, light entering the deflecting lens 211 from the air will refract, and the light will refraction when it enters the air from the deflecting lens 211, and the two refractions The angle of refraction is the same, the direction is opposite, and the refracted light will advance in the original direction, but a slight displacement occurs (as shown in Figure 14).
  • this rotation axis may be a rotation axis y located in a plane containing the rotation axis x and perpendicular to the optical axis z, and perpendicular to the rotation axis x.
  • the deflecting lens 211 can be deflected both about the axis of rotation x and about the axis of rotation y.
  • the deflection described above can be combined with multiple exposures to superimpose the beam images of each exposure to fill the surface of the photosensitive material.
  • the light source 201 can be subjected to multiple exposures, and at each exposure, the deflecting lens 211 is commanded to deflect to project the respective exposed beam images to different locations on the surface of the photosensitive material.
  • the controller of the image exposure system 200 can be used to command the light source 201 to perform multiple exposures while simultaneously commanding the deflection lens 211 to perform deflection in both the x and y directions at each exposure.
  • the above embodiment of the present invention can make the surface of the photosensitive material fill the exposure spot by combining the micromirror of the digital micromirror element with a concave mirror, combined with the multiple exposure and the micro-displacement of the digital micromirror element, and then use different imaging for each exposure. Information that increases the resolution of the image and improves the accuracy of the print.

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Abstract

一种3D打印设备的图像曝光系统，包括：空间光调制器（206），具有多个微镜（311），用于根据控制信号调节照射到其上的光的反射方向，其中每一微镜（311）为凹面镜，将照射到其上的光会聚成尺寸小于微镜（311）所对应的像素尺寸的微光斑；光源（201），产生一照射到空间光调制器（206）上的光束；投影镜头（208），对准空间光调制器（206）的第一方向，使光源（201）通过各微镜（311）所成的微光斑阵列投射到光敏材料表面；微位移驱动机构，连接空间光调制器（206），能够驱动空间光调制器在相互垂直的第三方向和第四方向移动，以微调微光斑阵列投影到光敏材料表面的位置；以及控制器，命令光源进行多次曝光，在每次曝光时命令微位移驱动机构进行移动，以将各次曝光的微光斑阵列投影到光敏材料表面的不同位置。

Description

光固化型3D打印设备及其图像曝光系统 技术领域
本发明涉及光固化型3D打印设备，尤其是涉及光固化型3D打印设备的图像曝光系统。
背景技术
3D打印技术，是以计算机三维设计模型为蓝本，通过软件分层离散和数控成型系统，利用激光束、热熔喷嘴等方式将金属粉末、陶瓷粉末、塑料、细胞组织等特殊材料进行逐层堆积黏结，最终叠加成型，制造出实体产品。与传统制造业通过模具、车铣等机械加工方式对原材料进行定型、切削以最终生产成品不同，3D打印将三维实体变为若干个二维平面，通过对材料处理并逐层叠加进行生产，大大降低了制造的复杂度。这种数字化制造模式不需要复杂的工艺、不需要庞大的机床、不需要众多的人力，直接从计算机图形数据中便可生成任何形状的零件，使生产制造得以向更广的生产人群范围延伸。
目前3D打印技术的成型方式仍在不断演变，所使用的材料也多种多样。在各种成型方式中，光固化法是较为成熟的方式。光固化法是利用光敏树脂被紫外光照射后发生固化的原理，进行材料累加成型，具有成型精度高、表面光洁度好、材料利用率高等特点。
图1示出光固化型3D打印设备的基本结构。这一3D打印设备100包括用于容纳光敏树脂的物料槽110、用于使光敏树脂固化的图像曝光系统120、以及用于连接成型工件的升降台130。图像曝光系统120位于物料槽110上方，并可照射光束图像使物料槽110液面的一层光敏树脂被固化。每次图像曝光系统120照射光束图像致使一层光敏树脂固化后，升降台130都会带动成型的那层固化的光敏树脂略微下降，并通过刮板131使固化后的工件顶面均匀铺展光敏树脂，等待下一次照射。如此循环，将会得到逐层累加成型的三维工件。
图像曝光系统120通常使用的是激光成型技术或者数字光处理(Digital Light Procession,DLP)投影技术。
激光成型技术是使用激光扫描设备进行逐点扫描。但是由于光敏树脂的特 性，激光功功率不能过大，否则会损伤树脂。因此，激光移动速度被限制在几米到十几米/秒，造成成型速度过慢。
DLP投影成像技术是使用数字微镜元件(Digital Micromirror Device,DMD)控制对光的反射来实现的。数字微镜元件可视为一镜面。这面镜子是由数十万乃至数百万个微镜所组成的。每一个微镜代表一个像素，图像就由这些像素所构成。每一个微镜可独立受控以决定是否反射光线到投影镜头。最终，整面镜子反射出所需的光束图像。DMD应用在3D打印中有很多优点，比如它可以处理400nm以下的紫外光而不用担心受到损害，但是其分辨率有限却制约其发展，比如，目前的DMD常用的最高分辨率为1920×1080。但是，这个分辨率在3D打印中以常用的0.1mm的精度只能产生192×108mm面积的物体，明显限制了其应用。
发明内容
本发明所要解决的技术问题是提供一种光固化型3D打印设备及其图像曝光系统。
本发明为解决上述技术问题而采用的技术方案是提出一种3D打印设备的图像曝光系统，包括：空间光调制器，具有多个微镜，每一微镜对应一像素，用于根据控制信号调节照射到其上的光的反射方向，该反射方向包括第一方向和第二方向，其中每一微镜为凹面镜，将照射到其上的光会聚成尺寸小于该微镜所对应的像素尺寸的微光斑；光源，产生一照射到该空间光调制器上的光束；投影镜头，对准该空间光调制器的该第一方向，使该光源通过各微镜所成的微光斑阵列投射到该光敏材料表面；微位移驱动机构，连接该空间光调制器，能够驱动该空间光调制器在相互垂直的第三方向和第四方向移动，以微调该微光斑阵列投影到该光敏材料表面的位置；以及控制器，命令该光源进行多次曝光，在每次曝光时命令该微位移驱动机构进行移动，以将各次曝光的微光斑阵列投影到该光敏材料表面的不同位置。
在本发明的一实施例中，各次曝光的微光斑阵列在该光敏材料表面所形成的像基本上互不重叠。
在本发明的一实施例中，各次曝光的微光斑阵列所形成的像布满该光敏材 料表面。
在本发明的一实施例中，该微光斑的尺寸小于、等于或略大于该微镜所对应的像素尺寸的一半。
在本发明的一实施例中，假设各微镜的焦距为f，微镜所对应的像素尺寸为p，入射到各微镜的光束的半夹角为β，微光斑的像高为a，出射光最大半角为W，则满足：
tan(β)＝(a/2)/f；
tan(w)＝((a+p)/2)/f；
Fno＝1/(2tan(w))。
在本发明的一实施例中，各次曝光的微光斑阵列包含不同的图像信息。
在本发明的一实施例中，该微光斑的尺寸与该微镜的像素尺寸之比大约为1:2、1:3或1:4。
在本发明的一实施例中，该光源的曝光次数为4、9或16次。
在本发明的一实施例中，该空间光调制器为数字微镜元件。
在本发明的一实施例中，该微位移驱动机构为压电陶瓷。
本发明还提出一种3D打印设备的图像曝光系统，包括：空间光调制器，具有多个微镜，每一微镜对应一像素，用于根据控制信号控制照射到其上的光的反射方向，该反射方向包括第一方向和第二方向，其中每一微镜为凹面镜，以将照射到其上的光会聚成尺寸小于该微镜所对应的像素尺寸的微光斑；光源，将产生一光束照射到该空间光调制器上的光线；投影镜头，对准该空间光调制器的该第一方向，使该光源通过各微镜所成的微光斑阵列投射到该光敏材料表面；偏转镜片，布置在该空间光调制器与该光敏材料表面之间，该偏转镜片能够围绕垂直于该投影镜头的光轴的至少一转轴偏转，以微调该微光斑阵列投影到该光敏材料表面的位置；以及控制器，命令该光源进行多次曝光，在每次曝光时命令该微位移驱动机构进行移动，以将各次曝光的微光斑阵列投影到该光敏材料表面的不同位置。
本发明还提出一种光固化型3D打印设备，包括如上所述的图像曝光系统。
本发明由于采用以上技术方案，使之与现有技术相比，通过将数字微镜元件的微镜设置为凹面镜，结合多次曝光配合数字微镜元件的微位移可将光敏材 料表面填满曝光光斑，再针对各次曝光使用不同成像信息，可成倍提高成像的分辨率，从而提高打印的精度。
附图说明
为让本发明的上述目的、特征和优点能更明显易懂，以下结合附图对本发明的具体实施方式作详细说明，其中：
图1示出光固化型3D打印设备的基本结构。
图2示出本发明一实施例的3D打印设备的图像曝光系统。
图3A-3C示出图2所示图像曝光系统的数字微镜元件的结构图。
图4示出图像曝光系统的数字微镜元件的工作原理。
图5示出DMD元件直接投影的图像。
图6示出图3所示数字微镜元件的单个微镜在0°偏转角时的会聚光路图。
图7示出图3所示数字微镜元件的单个微镜在+12°偏转角时的会聚光路图。
图8示出图3所示数字微镜元件的单个微镜在-12°偏转角时的会聚光路图。
图9示出本发明实施例的图像曝光系统一次曝光在光敏材料表面上所形成的图像。
图10示出本发明实施例的图像曝光系统4次曝光在光敏材料表面上所形成的图像。
图11示出本发明实施例的图像曝光系统的图像抽取示意图。
图12示出本发明另一实施例的3D打印设备的图像曝光系统。
图13示出图12所示图像曝光系统的偏转镜片未偏转的光路示意图。
图14示出图12所示图像曝光系统的偏转镜片进行了偏转的光路示意图。
具体实施方式
本发明的实施例描述一种3D打印设备及其图像曝光系统，该图像曝光系统使用数字微镜元件作为面阵图像源。
图2示出本发明一实施例的3D打印设备的图像曝光系统。参照图2所示， 本实施例的图像曝光系统200包括光源201、带通滤色片202、积分棒203、中继光学元件204、反射镜205、数字微镜元件206、TIR(Total Internal Reflection,全内反射)棱镜207、投影镜头208以及控制器(图未示出)。为简明起见，不示出与本发明无关的器件。
光源201用来产生需要照射到数字微镜元件206上的光束。光源201所发出的光的波长随固化成型的光敏材料而定。例如，选择UV树脂作为光敏材料时，光束可为紫光至紫外光，其波长在430nm以下，例如360-405nm。
在此实施例中，在光源201和数字微镜元件206之间设置了多个光学器件。如图2所示，在光源201中，UHP灯泡发射出的光线通过反光碗汇聚成一个光点。这一光点通过带通滤色片202滤除固化光敏材料不需要的光线，再通过积分棒203将光束均匀化，再由反射镜205与透镜组(如果需要的话)配合照射到TIR棱镜207上，TIR棱镜207将光线反射到数字微镜元件206上，最后光线经数字微镜元件206反射后，经过TIR棱镜207和投影镜头208照射到光敏材料表面上。
数字微镜元件206在本发明中用作空间光调制器。图3A示出图2所示图像曝光系统的数字微镜元件的结构图，图3B示出图3A的单个像素结构图，图3C示出图3B的侧视图。参考图3A-3C所示，数字微镜元件可被简单描述成为一个半导体光开关，数十到数百万个像素聚集在CMOS硅基片上。一个像素310包括一个微镜311，每一微镜301的尺寸例如为十几微米。为便于调节方向与角度，微镜311由一支撑柱312安装在轭形件313上并被其举起，支撑柱312从微镜中心向下伸出，沿其扭转轴到达轭形件313中心，使微镜311的质量中心在轭形件313上保持平衡。轭形件313由一对扭铰件314沿其中心轴作轴向支撑，扭铰件314另一端伸至一个支撑柱头315并安装在其上，支撑柱头315则是在相应的支撑柱316顶端形成。一对抬起的微镜寻址电极317和318由对应的寻址支撑柱319和320支撑。寻址支撑柱319和320、支撑柱316支撑着寻址电极317和318、扭铰件314，轭形件313离开并处于偏置/复位总线321和一对基板层寻址电极片322和323之上。
数字微镜元件的微镜的转动受控于来自SRAM的数字驱动信号。当数字信号被写入SRAM时，SRAM向数字微镜元件输出寻址电压。寻址电压施加在 两寻址电极片322和323之一，并经相联的电极支撑柱319和320加到相应的举起的微镜寻址电极317和318之一。同时，偏置电压加到偏置/复位总线321上，并经支撑柱316、支撑柱头315和扭铰件314加到轭形件313上，以及经支撑件312加到微镜301上。
通过寻址一个电极317或318，就在举起的对应寻址电极322或323上产生寻址电压，在两处产生静电吸引力，如30和32所示，或34和36所示。有选择地将寻址电压加到两寻址电极317和318之一，可决定一旦电压加到偏置总线321以及轭形件313和微镜301上时微镜301和轭形件313朝哪个方向转动。
图4示出图像曝光系统的数字微镜元件的工作原理。简而言之，数字微镜元件的工作原理就是借助各微镜反射需要的光到投影镜头，同时通过光吸收器吸收不需要的光来实现影像的投影，而其光照方向则是借助静电作用，通过控制微镜的角度来实现的。
通过对每一个微镜下的存储单元以二进制平面信号进行寻址，数字微镜元件上的每个微镜以静电方式倾斜为开或关状态。决定每个微镜倾斜在哪个方向上为多长时间的技术被称为脉冲宽度调制(PWM)。微镜可以在一秒内开关1000多次。控制微镜开和关的状态数目的比例，即可达到控制图像中该点亮度(灰度)的目的。
来自投影灯的光线，通过聚光透镜以及滤色片后，照射到微镜上。如图4所示，以数字微镜元件对准投影镜头208的方向作为0°位置。该入射光线被以24°直接照射在数字微镜元件上。当数字微镜元件的某一微镜在“开”的位置即+12°时，入射光经过其反射，进入设置在0°位置上的投影镜头208，在光敏材料表面上形成一个投影图像；当镜片在“关”的位置即-12°时，入射光经过其反射，进入设置在48°位置上的光吸收器210，而不会照射到光敏材料表面。
此外，微镜还有“平”的位置，此时入射光经过其反射，以24°的角度出射。
在本发明的实施例中，数字微镜元件的各个微镜被设计为凹面镜，配合下述经过严格设计的照明系统，可将照射到其上的光会聚成尺寸小于该微镜尺寸 的微光斑。图6示出图3所示数字微镜元件的单个微镜的会聚光路图。图7示出图3所示数字微镜元件的单个微镜在+12°偏转角时的会聚光路图。参考图6和图7所示，具有一定角度的平行光束射入某一具有凹面镜特性的微镜501。假设该凹面的微镜501的焦距f为60μm，微镜所对应的像素尺寸p为14μm，该光束的半夹角β为3.5°，则微镜所反射形成的微光斑的像高a为：
tan(β)＝(a/2)/f；a＝2*f*tanβ＝7.3μm；
即在微镜前出现一个尺寸为7.3μm的像，其尺寸为像素尺寸的约1/2。
设W为出射光最大半角，则有：
tan(w)＝((a+p)/2)/f＝((7.3+14)/2)/60＝0.1775，W＝10.065°；
光圈数值Fno的计算如下：
Fno＝1/(2tan(w))＝2.8。
即光路系统中，24°入射的光线被+12°偏转的微镜反射为0°的出射光，该光线进入位于0°的投影镜头，该镜头只需使用2.8光圈值即可使全部光线通过。同时该镜头的焦平面不再位于数字微镜元件的微镜上，而位于数字微镜元件前面的微光斑阵列上，这样比原来微镜面积小得多的微光斑组成的阵列被投影到光敏材料表面上，最终在光敏材料表面成像，形成曝光光斑。
会聚的另一好处是，经过会聚后，虽然微光斑面积缩小，但微光斑亮度得到同比例提升，这样该微光斑最终成像于光敏材料表面时，固化面积缩小，固化时间同比例缩短，通过多次曝光后，微光斑将填满全部树脂面，这时本发明在提高投影分辨率的同时，固化所需要的总曝光时间和直接曝光基本保持不变。
图8示出图3所示数字微镜元件的单个微镜在-12°偏转角时的会聚光路图。可见，这时的光线被偏转至48°，被位于此位置的光吸收器210吸收。这时光束角被限制在48°±10.065°，即最小光束角在48-10.065°≈38°，远大于投影镜头可以接受的±10.065°，而不会进入光路。
事实上由于聚焦透镜402可能的制造缺陷，特别是光的衍射效应的存在，光斑尺寸会略大于实际计算，而且光斑的形状也可能成为圆形，这需要在实际试验中对前述参数进行调整，以确定最终数据。
图9示出本发明实施例的图像曝光系统一次曝光在光敏材料表面上所形成 的图像。作为比较，如果光线直接通过微镜进行成像，由于微镜间的间隙很小，得到图像会几乎占据全部投影面积(见图5)。比较图5和图9可知，经过呈凹面镜的微镜的会聚后，图像中微光斑的尺寸缩小了。通过精确设计照明系统和凹面镜的形状，可控制成像光斑的大小。举例来说，可使成像光斑尺寸与像素尺寸(微镜的尺寸)之比为1:2，即面积之比为1:4。
此外，可使成像光斑尺寸与像素尺寸之比约为1:3或1:4。这里取整数倍的原因是考虑到后续微位移时，需要在各个微光斑的空白部分插入新的微光斑。
如图9所示，光敏材料表面上一次曝光的图像中，光斑之间留有空白。为此，通过多次曝光来填补这些空白，使光斑布满整个光敏材料表面。
如图2所示，数字微镜元件206连接有微位移驱动机构209。微位移驱动机构209能够驱动数字微镜元件206在x方向和y方向移动，以微调微光斑阵列投影到光敏材料表面的位置。在此，x、y方向在同一平面，且这一平面垂直于图像曝光系统的光轴z。在微位移驱动机构没有驱动数字微镜元件206位移时，数字微镜元件206的微光斑阵列在光敏材料表面的第一位置成像；当微位移驱动机构209驱动数字微镜元件206在一方向(x或y方向)微位移时，数字微镜元件206的整个微光斑阵列将随着数字微镜元件206发生微小的位移，从而在光敏材料表面的第一位置以外的位置成像。
上述的位移可以结合多次曝光，使各次曝光的光斑图像叠加，令光斑布满光敏材料表面。具体地说，可以令光源201进行多次曝光，在每次曝光时，命令数字微镜元件206进行位移以将各次曝光的微光斑阵列投影到该光敏材料表面的不同位置。图10示出本发明实施例的图像曝光系统4次曝光在光敏材料表面上所形成的图像。参照图10所示，在第一次曝光时，形成了投影图像A；在第二次曝光时，由于微位移驱动机构209沿着x方向移动1/2像素大小的距离，使微光斑阵列略微沿图中的水平方向移动，投影到两列微光斑之间的空白中，形成投影图像B；在第三次曝光时，微位移驱动机构209沿着y方向移动，使微光斑阵列略微沿图中的垂直方向移动1/2像素大小的距离，投影到两行微光斑之间的空白中，形成投影图像C；同理，形成投影图像D。投影图像D已布满了光敏材料表面。
微位移驱动机构209可以是压电陶瓷。在实际实施时，可以使用图像曝光系统200的控制器，命令光源201进行多次曝光，同时在每次曝光时命令微位移驱动机构209配合进行x、y两个方向的移动。
投影镜头208布置在数字微镜元件206与三维打印设备的光敏材料表面之间，将数字微镜元件206反射的微光斑阵列投影到光敏材料表面。
需要指出的是，各次曝光的微光斑阵列的叠加虽然布满该光敏材料表面，但是各次曝光的微光斑阵列在光敏材料表面的位置可以基本上互不重叠。这是通过控制像素尺寸与光斑的尺寸之比为整数，且位移的步距刚好为光斑尺寸来实现的。这种基本上互不重叠的设置可以避免分辨率的下降。可以理解，考虑光衍射效应等因素，略微的重叠有助于弥补微光斑非矩形边缘部分的缺失。因此并不要求微光斑之间完全不重叠。此外，微光斑阵列的叠加虽然布满该光敏材料表面，但是可以理解，微光斑阵列中并非每个位置都是亮点，而是可能有暗点。
在本发明的实施例中，各次曝光的微光斑阵列包含不同的图像信息。以图10为例，投影图案D中，虚框内的四个微光斑D1包含互不相同的图像信息。这就意味着，投影图案的分辨率相应变为原来的4倍。因此3D打印的精度得到显著提高。这些不同的图像信息可以是来自可以组成一幅完整图像的4个不同的图像文件，也可以是从同一图像文件的一幅图像经处理后抽取而成的4个子图像。以图11所示实例来说，图像中包含4*4＝16个像素A1-A4,B1-B4,C1-C4,以及D1-D4，有阴影的像素表示需要曝光，无阴影的像素表示无需曝光。在此，可以从图像中分别抽取出像素组{A1,A3,C1,C3}，{A2,A4,C2,C4}，{B1,B3,D1,D3{，以及{B2,B4,D2,D4}，作为4个子图像分别给4次曝光使用。相比之下，传统的打印设备所使用的图像，其每一像素的大小至少为如图11所示的4个像素，如{A1,A2,B1,B2}，因此其分辨率明显更低。
上述的例子是在控制微光斑尺寸为像素尺寸的1/2时，进行4次曝光。可以理解，控制微光斑为像素尺寸的1/3时可以进行9次曝光，控制微光斑为像素尺寸的1/4时可以进行16次曝光，以此类推。
图12示出本发明另一实施例的3D打印设备的图像曝光系统。在本实施例中，用偏转镜片211来代替前述的微位移驱动机构209。偏转镜片211可布置 在数字微镜元件到光敏树脂光路中的任意位置，一般布置在靠近投影镜头的位置。偏转镜片211能够围绕至少一转轴偏转，以微调光束投影到光敏材料表面的位置。前述的转轴均垂直于图像曝光系统的光轴z，在偏转镜片211和数字微镜元件206平行(和光轴z垂直)时，光线垂直照射在偏转镜片211(如图13所示)，这时没有折射现象发生，光线直接经过偏转镜片211；如果偏转镜片211围绕一转轴倾斜一个角度，光线从空气进入偏转镜片211将会产生折射，光线从偏转镜片211进入空气时再次发生折射，两个折射的折射角度相同，方向相反，折射后的光线将按原有方向前进，但是发生微小的位移(如图14所示)。另外，这一转轴可以是位于包含转轴x且垂直于光轴z的平面内，且垂直于转轴x的转轴y。在本发明的实施例中，偏转镜片211可以既能够绕转轴x偏转，也能绕转轴y偏转。
同样地，上述的偏转可以结合多次曝光，使各次曝光的光束图像叠加，令光斑布满光敏材料表面。具体地说，可以令光源201进行多次曝光，在每次曝光时，命令偏转镜片211进行偏转以将各次曝光的光束图像投影到该光敏材料表面的不同位置。
在实际实施时，可以使用图像曝光系统200的控制器，命令光源201进行多次曝光，同时在每次曝光时命令该偏转镜片211配合进行x、y两个方向的偏转。
本发明的上述实施例通过将数字微镜元件的微镜设置为凹面镜，结合多次曝光配合数字微镜元件的微位移可将光敏材料表面填满曝光光斑，再针对各次曝光使用不同成像信息，可提高成像的分辨率，从而提高打印的精度。
虽然本发明已参照当前的具体实施例来描述，但是本技术领域中的普通技术人员应当认识到，以上的实施例仅是用来说明本发明，在没有脱离本发明精神的情况下还可作出各种等效的变化或替换，因此，只要在本发明的实质精神范围内对上述实施例的变化、变型都将落在本申请的权利要求书的范围内。

Claims (12)

  1. 一种3D打印设备的图像曝光系统，包括：
    空间光调制器，具有多个微镜，每一微镜对应一像素，用于根据控制信号调节照射到其上的光的反射方向，该反射方向包括第一方向和第二方向，其中每一微镜为凹面镜，将照射到其上的光会聚成尺寸小于该微镜所对应的像素尺寸的微光斑；
    光源，产生一照射到该空间光调制器上的光束；
    投影镜头，对准该空间光调制器的该第一方向，使该光源通过各微镜所成的微光斑阵列投射到该光敏材料表面；
    微位移驱动机构，连接该空间光调制器，能够驱动该空间光调制器在相互垂直的第三方向和第四方向移动，以微调该微光斑阵列投影到该光敏材料表面的位置；以及
    控制器，命令该光源进行多次曝光，在每次曝光时命令该微位移驱动机构进行移动，以将各次曝光的微光斑阵列投影到该光敏材料表面的不同位置。
  2. 如权利要求1所述的3D打印设备的图像曝光系统，其特征在于，各次曝光的微光斑阵列在该光敏材料表面所形成的像基本上互不重叠。
  3. 如权利要求1所述的3D打印设备的图像曝光系统，其特征在于，各次曝光的微光斑阵列所形成的像布满该光敏材料表面。
  4. 如权利要求1所述的3D打印设备的图像曝光系统，其特征在于，该微光斑的尺寸小于、等于或略大于该微镜所对应的像素尺寸的一半。
  5. 如权利要求1所述的3D打印设备的图像曝光系统，其特征在于，假设各微镜的焦距为f，微镜所对应的像素尺寸为p，入射到各微镜的光束的半夹角为β，微光斑的像高为a，出射光最大半角为W，则满足：
    tan(β)＝(a/2)/f；
    tan(w)＝((a+p)/2)/f；
    Fno＝1/(2tan(w))。
  6. 如权利要求1所述的3D打印设备的图像曝光系统，其特征在于，各次曝光的微光斑阵列包含不同的图像信息。
  7. 如权利要求1所述的3D打印设备的图像曝光系统，其特征在于，该微光斑的尺寸与该微镜的像素尺寸之比大约为1:2、1:3或1:4。
  8. 如权利要求8所述的3D打印设备的图像曝光系统，其特征在于，同时该光源的曝光次数为4、9或16次。
  9. 如权利要求1所述的3D打印设备的图像曝光系统，其特征在于，该空间光调制器为数字微镜元件。
  10. 如权利要求1所述的3D打印设备的图像曝光系统，其特征在于，该微位移驱动机构为压电陶瓷。
  11. 一种3D打印设备的图像曝光系统，包括：
    空间光调制器，具有多个微镜，每一微镜对应一像素，用于根据控制信号控制照射到其上的光的反射方向，该反射方向包括第一方向和第二方向，其中每一微镜为凹面镜，以将照射到其上的光会聚成尺寸小于该微镜所对应的像素尺寸的微光斑；
    光源，将产生一光束照射到该空间光调制器上的光线；
    投影镜头，对准该空间光调制器的该第一方向，使该光源通过各微镜所成的微光斑阵列投射到该光敏材料表面；
    偏转镜片，布置在该空间光调制器与该光敏材料表面之间，该偏转镜片能够围绕垂直于该投影镜头的光轴的至少一转轴偏转，以微调该微光斑阵列投影到该光敏材料表面的位置；以及
    控制器，命令该光源进行多次曝光，在每次曝光时命令该微位移驱动机构进行移动，以将各次曝光的微光斑阵列投影到该光敏材料表面的不同位置。
  12. 一种光固化型3D打印设备，包括如权利要求1-11任一项所述的图像曝光系统。
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