CN103472682B - Based on the method that mask lithography technology and injection mo(u)lding make diffractive micro-optical element - Google Patents

Abstract

A method for manufacturing diffractive micro-optical elements based on mask lithography technology and injection molding, making its manufacture develop towards the direction of miniaturization, mass production, low cost and rapid prototyping. Firstly, use drawing software to make mask pictures of micro-optical elements such as binary gratings and zone plates, and then make photolithographic mask plates on chrome-plated glass plates. Then apply the chromium mask plate to the contact photolithography system, use the photolithography process to make micro-optical element patterns on the metal alloy coated with positive photoresist, and use the electrochemical etching process to etch it, so that The graphics on the chromium mask are transferred to the metal alloy substrate one by one. This kind of metal alloy with graphics can be used as a movable mold core on the injection mold, and the micro-optical components on it can be transferred to the optical surface by the injection mold. on the plastic. The main feature of the method is that it is convenient to replace the mold core, and various diffractive micro-optical elements can be produced by replacing the mold core engraved with different figures.

Description

Method for fabricating diffractive micro-optical elements based on mask lithography and injection molding

technical field

The invention relates to a method for manufacturing diffractive micro-optical elements based on mask photolithography technology and injection molding.

Background technique

In the past, the production of diffractive micro-optical elements mostly adopts traditional photolithography technology. First, a layer of photoresist (photoresist) is coated on a medium such as glass, and the designed micro-optical element pattern is printed by transfer printing. It is copied piece by piece onto the photoresist plate on a dedicated contact exposure lithography machine. Through the traditional photolithography process, micro-optical elements are formed on the photoresist of glass plates or silicon wafers, and then after a piece of micro-magnification detection, qualified devices are selected for ion beam etching. The formed micro-optical elements are not only The area is small, and equipment such as a reactive ion etching machine is also very expensive.

If a micro-optical element with higher diffraction efficiency is required, each piece needs to be overlaid multiple times, and multiple times of ion beam etching must be performed on special equipment such as a reactive ion etching machine, and finally on a glass medium or a silicon wafer. A multi-step micro-optical element is formed. Such a piece-by-piece processing cycle is long and the yield rate is low, which is far from meeting the needs of making micro-optical elements with fine structures.

Contents of the invention

The object of the present invention is to provide a method for manufacturing diffractive micro-optical elements based on mask photolithography technology and injection molding, which has the advantages of convenient operation, high yield and short cycle time.

The present invention is realized in this way, and the realization of the present invention relies on a transmission imaging optical path experimental device made of a diffractive micro-optical element core. The self-designed and manufactured test system includes a purple light source (high-pressure mercury lamp), plug-in mask frame, focusing device, prism beam splitter, CCD camera, 10x precision microscopic objective lens, photoresist plate substrate frame, Z Axis micro-movement stage, X-Y axis precision electronically controlled large-stroke translation stage and microcomputer; the purple light source also includes point fiber optic light source beam expander and collimating mirror, and the plug-in mask frame is located under the purple light source, which is located in the plug-in The middle and one side of the focusing device between the type mask frame and the 10x precision microscopic objective lens are respectively connected to the prism beam splitter and the CCD camera. The rubber plate substrate frame is connected with the Z-axis micro-motion stage and the X-Y axis precision electronically controlled large-stroke translation stage below, and the X-Y-axis precision electronically controlled large-stroke translation stage is connected to a microcomputer. During the operation, the computer software is used to design and generate the micro-optical element pattern on the digital micromirror device (DMD), and then the transmission-type micro-optical element mask is obtained by exposing on the digital lithography machine.

The invention includes the following steps: (1) Manufacturing the metal alloy mold core of the micro-optical element: firstly, using the above-mentioned transmission-type imaging optical path experimental device, a photolithography mask plate of the optical element is produced on a chrome film glass glue plate. Use graphic editing design software to design the micro-optical element mask on a microcomputer, and first obtain a micro-optical element mask on a digital lithography machine (the original version can be designed with a 10-fold magnification of the finished micro-optical element). The beam emitted by the purple light source (high-pressure mercury lamp) is expanded and collimated by the fiber point light source, and then directly irradiated on the plug-in mask (original version), and the beam transmitted by the prism beam splitter is then condensed by 10 times The objective lens projects the pattern on the mask (original plate) onto the metal alloy substrate coated with photoresist, and makes the image on the photoresist plate the clearest (10:1 reduced image) through the focusing device. The transmitted light beam is required to be coaxial with the microscopic objective lens and the photoresist plate. Due to the function of the prism beam splitter, the clarity of the imaging can be monitored on the CCD camera during focusing. The X-Y axis precision electronically controlled large-stroke translation stage and the Z-axis micro-motion stage can accurately project the 10-fold reduced graphics onto the photoresist plate;

Diffractive micro-optical elements are produced on metal alloys by photolithography technology. The design and manufacture of mold cores are obtained by transferring the patterns of micro-optical elements to metal alloy substrates by means of electrochemical etching. This movable injection mold The core can be used as a movable embedded core on the injection mold core;

Requirements for embedded mold cores: the first is the manufacturing process and method of the mold core; the second is that the embedded mold core is easy to replace, and the same injection mold can be used to replace the mold cores with different design patterns to produce various patterns. A corresponding pattern of diffractive micro-optical elements.

(2) Injection molding production of diffractive micro-optical elements: metal alloy substrate grinding and polishing—→substrate pretreatment (cleaning)—→photoresist leveling—→pre-baking—→exposure—→post-baking—→development— →hardening film—→electrochemical etching of metal substrate—→glue removal—→metal alloy mold core—→injection mold assembly—→injection molding machine injection—→injection finished product (micro-optical elements remain on the optical plastic);

The design and manufacture of injection molds are the key technology for the replication by injection molding. The design and fabrication of injection molds requires that the existing replication technology can reproduce with high fidelity, and can make the diffraction efficiency and uniformity of the surface micro-optical elements close to the value of the original microstructure;

Injection mold is the main tool for duplication molding of diffractive micro-optical elements, and generally speaking, these injection molding replicas are usually produced in batches, so it is required that plastic injection molds should have high efficiency, high quality and less or no processing after molding. Due to the characteristics of reprocessing (mold repairing), the core material is high-temperature nickel-based metal alloy;

The design and manufacture of the precision injection mold is one of the most critical parts of the present invention, because the quality of the mold is directly related to the quality of the finished components. The design of the precision injection mold used in this test is mainly divided into three parts: the design of the runner, the design of the cavity, and the design of the cavity for placing the embedded master core. The design of the runner and the core cavity is designed and arranged according to the requirements of the cavity. The runner is the gate channel for the molten optical plastic to enter each cavity in the multi-cavity smoothly from the main channel; the cavity part mainly constitutes the overall external shape of the diffractive micro-optical element product; the mold core of the cavity part is also It is the master nickel-based metal alloy substrate, on which there are diffractive micro-optical element patterns formed after exposure and electrochemical etching, which mainly constitute the detailed shape of the micro-optical element product. Since the finished product of the diffractive micro-optical element has high requirements on the integrity, the ejector bar of the optical plastic product was not set in the injection mold design of this experiment, but the side wall of the mold core cavity was designed as a slope with a certain taper. That is, when the mold is opened, the injection molded workpiece is directly pulled out through the pull rod, so that the finished micro-optical element can be demolded by itself.

The present invention utilizes the photolithography process to first obtain the micro-optical element mold core of hard metal alloy material, just like a miniature steel seal stamp, embeds in the mold core of the specially designed injection mold, utilizes the PMMA of optical grade, CR-39, Transparent optical materials such as PC or PS can be rapidly molded on existing precision injection molding machines.

First, use AUTOCAD or L-EDIT and other drawing software to design the mask pictures of some basic diffractive optical elements, such as binary grating, Dammaann grating, Ronchi grating, Fresnel zone plate, etc. It is introduced into a computer and exposed on a chrome-coated glass glue plate by a digital lithography machine to produce a photolithography mask. Then apply the chrome mask to the self-designed and manufactured projection transmission lithography system, use photolithography technology to fabricate an array of diffractive micro-optical elements on a hard metal alloy substrate coated with positive photoresist, and then use electrochemical The etching process etches the metal alloy substrate, so that the patterns on the mask plate are transferred to the metal alloy substrate one by one, and the patterned metal alloy substrate can be used as a movable mold core on the injection mold.

The design and manufacture of injection molds are the key technology for the replication by injection molding. Use AUTOCAD and other drawing software to design array diagrams and mold drawings for making diffractive micro-optical elements, process and manufacture corresponding injection molds, and transfer the arrays of diffractive optical elements on metal alloy substrates to optical plastics using injection molds. The injection mold designed by this invention is different from ordinary fixed injection molds. Its main feature is that it is quite convenient to replace the mold core. Under the condition that the external dimensions of the mold and mold core remain unchanged, the same set of mold and mold core can be used and replaced. The mold cores engraved with different micro-optical element patterns can produce diffractive micro-optic elements with various design patterns, and at least eight different micro-optical element mold cores can be assembled on one mold core.

The technical effects of the present invention are: the present invention not only realizes the mass production of micro-optical elements, but also greatly shortens the production cycle, facilitates the replacement of mold cores, and has low single-piece cost and high yield in mass production. It also has the advantage of being convenient to replace the mold core, and various diffractive micro-optical elements can be produced by replacing the mold core engraved with different patterns.

Description of drawings

Fig. 1 Schematic diagram of the structure of the transmission imaging optical path experimental device.

Fig. 2 Process block diagram of the manufacturing method of the metal alloy substrate (mold core).

Fig. 3 is a schematic diagram of the production process of the miniature projection exposure mold core.

Fig. 4 Microscopic enlarged view of the surface of the diffractive micro-optical element after electrochemical etching.

Figure 5. Metal alloy mold core diagram after etching of diffractive micro-optical elements.

Figure 6 is a sectional view of the overall assembly of the mold.

Fig. 7 Schematic diagram of the layout of the mold core and runners of the micro-optical element.

Figure 8 Diffraction patterns of micro-optical elements when He-Ne laser (633nm) is normal incident.

In the figure, 1. Purple light source 2. Plug-in mask frame 3. Prism beam splitter 4. Focusing device 5. CCD camera 6. 10x precision microscopic objective lens 7. Photoresist plate substrate holder 8. Z Axis micro-motion stage 9, X-Y axis precision electronically controlled large-stroke translation stage 10, microcomputer.

detailed description

The present invention will be described in further detail below in conjunction with the embodiments and with reference to the accompanying drawings.

Example 1, Fabrication of a core for a diffractive micro-optical element Transmissive optical path experimental device

The present invention uses L-EDIT, AUTOCAD and other image editing and design software to set the resolution of the graphics to be consistent with the minimum resolution of the digital micromirror device (DMD) or to have an integer relationship. Templates (aka masters). As shown in Figure 1, the beam emitted by the purple light source 1 (high-pressure mercury lamp) is expanded and collimated by the fiber point light source, and then directly irradiates the plug-in mask 2 (master plate), and is transmitted through the prism beam splitter 3 The output beam is projected on the metal alloy substrate coated with photoresist through the 10 times reduction objective lens 6, and the image on the photoresist plate 7 in the substrate holder is the most imaged by the focusing device 4. Clear (10:1 scaled down image). Due to the effect of the prism beam splitter 3, the clarity of focusing can be monitored on the CCD camera 5. The X-Y axis precision electronically controlled large-stroke translation stage 9 and the Z-axis micro-motion stage 8 can accurately project the 10-fold reduced pattern onto the metal alloy substrate of the photoresist plate.

Embodiment 2, the technological process of making the metal alloy mold core of the diffractive micro-optical element

Grinding and polishing of metal alloy substrates—→substrate pretreatment (cleaning)—→photoresist leveling—→pre-baking—→exposure—→post-baking—→development—→hard film—→electrochemical etching of metal substrates Corrosion—→removing glue—→metal alloy mold core—→injection mold assembly—→injection molding machine injection—→injection finished product (micro-optical components remain on the optical plastic);

1. Grinding and polishing of the metal alloy substrate: the nickel-based metal alloy is wire-cut into the required disc shape, and the thickness of the substrate is about 3-5mm. To make it into an injection mold core that can be used many times, its surface must be polished Grinding into a mirror surface can produce high-quality finished products;

Coarse grinding can be done with metallographic sandpaper, and fine grinding can be done using the existing equipment—optical fiber grinder. The optical fiber polishing machine has a very flat solid chassis, and the grinding sheet matching the size of the chassis is flatly pasted on the chassis, and the nickel-based metal alloy substrate is fixed on the jig with an adhesive, and the jig is pressed against the grinding by the pressure rod. On-chip, pressure is applied to the back of the metal sheet through a clamp, which can compensate for the pressure difference between the center and the edge. There is a weight on the pressure rod to adjust the downward force of the clamp on the metal sheet. Start the grinder, set the grinding rate, and the chassis starts to rotate at a constant speed. It should be noted that the chassis must be hard and flat, so that the metal sheet can be polished evenly, so that the surface of the metal sheet is flat and meets the requirements of the mirror surface;

During the whole grinding process, a small amount of water needs to be continuously added to the grinding sheet, and it usually takes 20 minutes to change the grinding sheet. The replacement sequence of the grinding sheet is generally from coarse to fine. The grinding sheets used in the test are 15μm, 6μm, 3μm, 1.5 μm. The surface of the metal substrate after grinding contains residual metal powder and some other stains, which need to be processed before the photoresist can be spin-coated;

2. Pretreatment of the substrate: First, put the metal alloy substrate in a NAOH solution with a concentration of more than 5% to clean it, rinse it with clean water, then put the metal substrate in an ultrasonic cleaning machine for cleaning for a few minutes, and then use it Rinse with ionized water or distilled water until the water film on the surface of the metal substrate is complete;

The cleaned metal substrate should be dried immediately, and the moisture on the surface of the metal substrate should be dried with filtered compressed air to prevent water stains on the surface. Then put the metal substrate into an oven at about 100°C and heat it for 2 minutes to keep the surface of the metal substrate dry before coating the photoresist to enhance the adhesion;

3. Coating: When rotating the glue, place the metal substrate on the vacuum adsorption tray of the glue homogenizer, first set the low speed rotation for 10 seconds, let the photoresist spread after dispensing, and then set the high speed rotation for 15~ 20 seconds, so that the photoresist evenly adheres to the surface of the metal substrate. The thickness of the photoresist on the surface of the metal substrate is mainly determined by the viscosity of the photoresist and the rotation speed when applying the glue: in the case of 3500-4500 rpm of the homogenizer, the thickness of the photoresist is about 1 micron ;

4. Pre-baking: Put the glue-coated metal substrate photoresist plate into the oven, adjust the oven temperature to 110°C, and bake for 5 minutes. To fully dry the photoresist film to increase the adhesion of the photoresist to improve the corrosion resistance of the glue;

5. Exposure: including alignment and exposure. Alignment is to make the micro-optical element pattern on the reticle and the metal substrate that has been glued are in focus after miniaturization. The experiment used a high-pressure mercury lamp ultraviolet light source. For the transmission optical path of micro-optical components, put the glued metal substrate on the stage, and then put the micro-optical component graphics master made by digital lithography machine on the plug-in mask holder, Use the focusing device to make the graphic image on the photoresist plate the clearest (10:1 reduced image). Expose according to the time determined by the experiment (generally 10-20 seconds);

6. Post-baking: After exposure, it is necessary to bake the exposed metal substrate photoresist plate, that is, post-exposure baking, mainly to reduce the standing wave effect generated during exposure. Due to the high temperature during baking, the photosensitive agent diffuses in the photoresist, so that the boundary between the exposed area and the non-exposed area becomes relatively uniform;

7. Development: Take out the metal substrate after exposure and drying, and develop it under sodium monochromatic light (yellow light). Through development, the exposed part of the positive photoresist absorbs light, the photoresist becomes soluble and is dissolved away, while the unexposed part is left. It is very important to master the development time and temperature in the development process. The developer used in the experiment is a sodium hydroxide solution with a concentration of 3-5‰. The developing temperature is optimally controlled at 21±1°C. The development time is half a minute, and finally fixed with warm water;

8. Hard film: The metal substrate after development must be dried again to strengthen the adhesion between the film and the metal substrate after development, so that the photoresist can play a protective role during etching. The role of generating micro-optics graphics. The choice of the temperature and time of the hardening film is to put the metal substrate in a dryer at 110°C for 2 minutes;

9. Electrochemical etching of the metal substrate: the purpose is to finally transfer the micro-optical element pattern on the photoresist to the metal substrate. Putting the developed and post-baked metal alloy substrate into the prepared electrolyte for etching. Due to the corrosion resistance of the photoresist, the metal surface where the photoresist is attached is protected, and a part of the exposed metal substrate surface will be etched away. The consistent pattern of the micro-optical elements is shown in Figure 3. The formulation and working conditions of the electrochemical etching solution are shown in the table below.

Process recipe serving size Concentrated sulfuric acid (H ₂ SO ₄ ) 900g/L (98% concentration 489.1mL) concentrated phosphoric acid (H ₃ PO ₄ ) 750g/L (98% concentration 441.2mL) Citric acid (C ₆ H ₈ O ₇ ) 60g/L Ammonium citrate (C ₆ H ₅ O ₇ (NH ₄ ) ₃ ) 20g/L Deionized water 50mL Anode current 0.5A Operating Voltage 9V Electrolyte temperature room temperature polishing time 15～40s Anode material Nickel-based metal alloy substrate to be etched cathode material lead plate or stainless steel plate

10. Degumming: After the metal alloy substrate is etched, the surface should be degummed. At room temperature, the etched metal substrate is soaked in a 5% sodium hydroxide solution for 1 to 2 minutes to remove the residual photoresist on the surface of the metal substrate. As shown in Figure 2, it is a schematic diagram of the process flow. Finally, the finished mold core is obtained, and the micro-optical element (concave-convex) pattern is retained on the metal substrate. As shown in Figure 4, binary gratings, Damman gratings, and Longji Diffractive micro-optical elements such as gratings and Fresnel zone plates;

11. The metal alloy mold core has a diameter of 18mm, and its size is compared with that of a dime coin, as shown in Figure 5. The figure lists the physical pictures of several different metal alloy mold cores;

12. Assembling the injection mold, as shown in Figure 6 is the cross-sectional view of the overall assembly of the mold, which can be assembled according to the conventional method. Before installation, 4 kinds (8 pieces) of diffractive micro-optical element nickel-based metal alloy substrates (molds) with graphics will be made. Cores) are embedded in it in turn, and the distribution of the micro-optical element cores is shown in Figure 7;

13. For injection molding by injection molding machine, assemble the injection mold on the precision injection molding machine according to the conventional method, and use optical plastics such as PMMA for blanking;

14. The finished product is injection-molded, and the diffractive micro-optical element is finally retained on the optical plastic; a beam of red helium-neon laser is vertically incident on the finished diffractive micro-optic element. The diffraction pattern of the transmitted light can be obtained, as shown in Figure 8.

Embodiment 3, the injection molding manufacturing method of diffractive micro-optical element

The technique for replicating micro-optical elements containing surface diffractive microstructures is quite critical. It requires existing replication techniques capable of replicating with high fidelity and that can bring the diffraction efficiency and uniformity of surface micro-optical elements close to the values of the original microstructure (binary or multi-stepped structures). Injection mold is the main tool for duplication molding of diffractive micro-optical elements, and generally speaking, these injection molding replicas are usually produced in batches, so it is required that plastic injection molds should have high efficiency, high quality and less or no processing after molding. Due to the characteristics of reprocessing (modification), the core material is high-temperature nickel-based metal alloy.

The design and manufacture of the precision injection mold is one of the most critical parts of the present invention, because the quality of the mold is directly related to the quality of the finished components. As shown in Figure 6, the design of the precision injection mold used in this experiment is mainly divided into three parts: the design of the runner, the design of the cavity, and the design of the cavity for placing the master core mold. The design of the runner and the core cavity is designed and arranged according to the design of the cavity. The runner is the gate channel for the molten optical plastic to enter each cavity in the multi-cavity smoothly from the main channel; the cavity part mainly constitutes the overall external shape of the diffractive micro-optical element product; the mold core of the core mold cavity part also It is the master nickel-based metal alloy substrate, on which there is a diffractive micro-optical element pattern formed after exposure and electrochemical etching, which mainly constitutes the detailed shape of the micro-optical element product.

The layout of the runners is set according to the layout of the cavity, and the two are unified and mutually restricted. Taking the main channel as the center, the layout of the entire runner is 124mm×124mm, the diameter of the cavity is about 18mm, and the thickness is about 3mm. 50mm. There is a cold material hole at the end of the runner to prevent the cold material from entering the cavity. In order to reduce the cost of injection molding, this production adopts the layout of one mold and multiple cavities. There are a total of 8 cavities, which are arranged in a circular shape with the sprue as the center, as shown in Figure 7. Due to the high flatness requirements of diffractive micro-optical elements, each cavity must also be ground and polished to meet the mirror surface requirements. At the same time, in order to ensure uniform heating, a heating wire is also arranged at the bottom of the mold cavity.

The layout of the runners belongs to the balanced distribution, and its characteristics are: the length, cross-sectional size and shape of the runners from the main channel to each cavity are exactly the same, so as to ensure that each cavity can be fed in a balanced manner at the same time, and the injection is completed at the same time. , which not only saves materials, but also is more convenient to manufacture. The diameter of the mold cavity part of the core is 18mm, which is consistent with the diameter of the master nickel-based metal alloy substrate. .

The method of shortening the injection molding time can be to use a larger injection pressure during the injection to shorten the filling time of the optical-grade plastic melt, so when designing the gate, the cross-sectional area of the gate should be small and the runner should be as short as possible, so that It can improve the fluidity of optical plastic melt, so that optical plastics such as PMMA can quickly fill the cavity. Since the finished product of the diffractive micro-optical element has high requirements on integrity, the ejector bar of the finished product was not set in the mold design of this experiment, but the side wall of the cavity was designed as a slope with a certain taper, so that the finished micro-optical element It can be released by itself.

The detection of the finished diffractive micro-optical components mainly includes the detection of the surface topography, surface roughness, number of steps and diffraction efficiency of the component. The surface topography, surface roughness and number of steps of micro-optical components can be mainly observed by micro-profilometer or electron microscope. The most critical index to measure the performance of diffractive micro-optical elements is the size of the diffraction efficiency. A helium-neon laser beam with a wavelength of 633nm is vertically incident on the finished micro-optical element. Since the finished product is an optical plastic with high transparency, the diffraction pattern of the transmitted light can be obtained on the receiving screen, as shown in Figure 8. The optical power meter detects the transmitted light intensity P point by point, and the diffraction efficiency η of the finished micro-optical element copied on the optical plastic can be calculated by using the following formula (where P ₀ is the central maximum light intensity).

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Claims (2)

1. the method making diffractive micro-optical element based on mask lithography technology and injection mo(u)lding, it is characterised in that said method comprising the steps of:

(1) micro optical element metal alloy core rod is made: it is based on transmission-type imaging optical path experimental provision and realizes；

First on chromium film glass offset plate, generate optical element lay photoetching mask plate, utilize graphics edition design software to carry out the design of micro optical element mask on microcomputer, digital photolithography machine first obtains micro optical element mask；10 times that finished product micro optical element figure is body amplifications on mask；The light beam that purple light light source sends is after fiber optic point source expands and collimates, shine directly on instant-plugging mask, through the light beam that prism beam splitter transmits, again through 10 times of final minification object lens by the graphic projection on mask coating photoresist metal alloy substrate on, make figure imaging on photoetching hectograph the most clear by focussing mechanism；And the light beam request transmitted and miniature object lens, photoetching hectograph are coaxial；Due to the effect of prism beam splitter, CCD camera clearly monitors；Figure through 10 times of final minification is accurately projected on photoetching hectograph by the big stroke translation platform of X Y-axis precise electric control and Z axis micropositioner；

Then photoetching technique is utilized to make diffractive micro-optical element on metal alloy, the design and fabrication of core rod is to adopt electrochemical etching method, being transferred to by micro optical element figure and to obtain on metal alloy substrate, this movable injection core is as the embedded core rod of the activity on injection mould die；

(2) injection mo(u)lding of diffractive micro-optical element makes: the electrochemical etching of the pretreatment of metal alloy substrate grinding and polishing → substrate → photoresist spin coating → front baking → exposure → after bake → development → post bake → metal substrate → remove photoresist → metal alloy core rod → injection mold assembling → injection machine injection moulding → injection-molded finished, the core material of wherein said injection mold is high-temperature nickel-based metal alloy, injection mold includes sub-runner, the die cavity of die cavity and the embedded mother matrix core rod of placement, wherein the design of sub-runner and core rod die cavity is all that the requirement according to die cavity designs and arranges；Sub-runner is the gate channel of each die cavity making the optical plastic melted steadily enter from sprue multi-cavity；Cavity portion, the overall exterior shape of main composition diffractive micro-optical element goods；The core rod of core rod cavity portion i.e. mother matrix nickel based metal alloy substrates, have the diffractive micro-optical element figure formed after the technique such as overexposure and electrochemical etching, the detailed shape of main composition micro optical element goods above；Owing to diffractive micro-optical element finished product is significantly high to the requirement of integrity degree, so being not provided with the thick stick that ejects of optical plastic finished product in Injection Mold Design, but core rod cavity lateral is designed as tapered inclined-plane, in order to the demoulding voluntarily of micro optical element finished product.

null2. a kind of method making diffractive micro-optical element based on mask lithography technology and injection mo(u)lding as claimed in claim 1，It is characterized in that the transmission-type imaging optical path experimental provision described in step (1) includes purple light light source、Instant-plugging mask grillage、Focussing mechanism、Prism beam splitter、CCD camera、10 times of miniature object lens of precision、Photoresist sheet substrate frame、Z axis micropositioner、The big stroke translation platform of X Y-axis precise electric control and microcomputer，Wherein purple light light source also includes point source and expands and collimating mirror，The lower section of purple light light source is instant-plugging mask grillage，Centre and the side of the focussing mechanism between instant-plugging mask grillage and 10 times of miniature object lens of precision connect prism beam splitter and CCD camera respectively，The underface of 10 times of miniature object lens of precision is photoresist sheet substrate frame，Photoresist sheet substrate frame connects Z axis micropositioner and the big stroke translation platform of X Y-axis precise electric control of lower section，The big stroke translation platform of X Y-axis precise electric control connects microcomputer.