Integrated 3D printing method based on digital holographic projection

Abstract

The present invention discloses an integrated 3D printing method based on digital holographic projection, which belongs to the fields of optical holography, digital holographic imaging and additive manufacturing technology. The method of the present invention first obtains a digital hologram containing complete three-dimensional information of the target object, then outputs it completely on a spatial light modulator, and at the same time superimposes the digital hologram with a Fresnel lens phase or a blazed grating phase; uses a real image projection device to form a real image projection of the target object, uses a first baffle to block the zero-order light spot generated by the holographic recording principle, and uses a second baffle to block and eliminate the zero-order bright spot reflected by the spatial light modulator itself and then converged by the magnifying lens; then uses a transparent container with a light filtering and anti-reflection effect to hold liquid photosensitive resin; finally, places the container holding the liquid photosensitive resin in the three-dimensional real image projection area of ​​the object, completely wraps the projection, and waits for the completion of the light curing reaction to obtain a 3D printed product.

Description

Technical Field

[0001] The present invention belongs to the technical fields of optical holography, digital holographic imaging and additive manufacturing, and specifically relates to an integrated 3D printing method based on digital holographic projection. Background Art

[0002] Additive Manufacturing (AM) is an industrial manufacturing technology also known as 3D printing. Unlike traditional manufacturing methods, AM creates three-dimensional objects by stacking materials, rather than removing material from raw materials through cutting or subtracting to obtain the desired shape. The application of AM technology significantly reduces the production cycle and cost of customized manufacturing, and also significantly reduces the cost of mold opening and testing for large-scale manufacturing. It also fundamentally ensures the replacement and restoration of obsolete components in specialized fields such as aerospace and medical implants.

[0003] Existing Technology: "The History of 3D Printing: From the 1980s to Today" recounts the rapid development of 3D printing since its concept was first proposed by Hideo Kodama in the 1980s. In 1986, Charles Hull invented the world's first 3D printing technology: SLA (Stereolithography), which uses light (usually ultraviolet light) to solidify liquid photosensitive resin materials to create objects. This technology uses a laser beam to scan the model's slice pattern, solidifying the photosensitive resin layer by layer. This ushered in the era of rapid prototyping (RP) through layer-by-layer additive manufacturing, significantly reducing mold material costs compared to traditional mold-making methods such as cutting and milling. Subsequently, two other 3D printing technologies, SLS (Selective Laser Sintering), which uses a laser to melt special powdered resin materials to create objects layer by layer, and FDM (Fused Deposition Modeling), which extrudes molten material to create objects layer by layer, were invented by Carl Deckard and Scott Crump, respectively. These three technologies each have their own advantages in meeting different rapid modeling needs, and are also the main additive manufacturing technologies used in the market.

[0004] The existing technology "Based on visible light of the mask projection stereolithography" discloses a surface projection SLA light curing method, which further improves the SLA printing efficiency based on the traditional point-by-point printing method. At the same time, compared with the other two traditional methods, it has obvious advantages in precision, accuracy, and printing quality. However, in terms of printing efficiency, since the light curing process requires waiting for the material to be fully stable, the printing speed still faces challenges.

[0005] Digital holography (DH) technology is an extension of traditional optical holography in the computer field. It is based on the digital calculation of optical holography. By deducing the principles of traditional optical holographic recording, it uses computers to calculate the holographic image of a virtual scene, and finally adapts it to a suitable display device to restore the holographic image to a three-dimensional real image of the object, showing three-dimensional information of the object far beyond traditional two-dimensional imaging technology.

[0006] Chinese patent application number 202210019377.6, titled "A Photocuring 3D Printing Device and Process Method," discloses an integrated printing method for digital holographic 3D projection. While theoretically improving 3D printing efficiency compared to traditional SLA point-by-point and surface-by-surface printing methods, it fails to address the following two technical issues in practical implementation scenarios:

[0007] (1) When traditional optical holography and digital holography based on its principles generate holographic images that restore the original image of an object, a zero-order DC component will exist at the center of the image, which has a great impact on the quality of the restored image.

[0008] Researchers have made a lot of attempts to deal with the zero-order light spot caused by traditional holographic algorithms. The early response method was to set a baffle near the light spot formed by the zero-order component to directly filter out this interference physically, but doing so would cause a portion of the image light to be lost. In 1979, Professor Ting-Chung Poon proposed the optical scanning holography (OSH) technology in Optical Letters. The principle is to use the interference of the reference light frequency shift and the object light of the original frequency to filter and eliminate the zero-order DC component. Since the technology was proposed, it has been applied to many fields such as fluorescence imaging, remote sensing technology, and image encryption due to its advantages such as high resolution and non-contact. However, since this technology needs to perform discrete calculations for each pixel for the generation and restoration of holograms at the same depth, the operating efficiency is relatively low.

[0009] (2) Due to the design and manufacturing process of the spatial light modulator, the filling gaps between the micro-units used for phase modulation will cause the outgoing image light after the incident light is modulated to form an uneliminable zero-order bright spot at the center of the imaging area due to the focusing of the imaging lens.

[0010] However, the existing technology's implementation idea of ​​simultaneous direct projection from three orthogonal directions, X, Y, and Z, will result in the intersection and combined effect of two zero-order bright spots in the three directions, which will seriously reduce the imaging quality of the effective image light in the printing area, making it impossible to achieve the effect described in the theory normally. How to reduce or eliminate the influence of the above two zero-order bright spots has become an urgent problem waiting to be solved. Summary of the Invention

[0011] The purpose of the present invention is to overcome the above-mentioned defects of the prior art and provide an integrated 3D printing method based on digital holographic projection.

[0012] The technical problem proposed by the present invention is solved as follows:

[0013] An integrated 3D printing method based on digital holographic projection comprises the following steps:

[0014] Step 1. Using optical off-axis holographic recording or digital modeling, the target object is viewed downward from a number of directions spaced evenly apart on the same horizontal plane, centered on the target object. A digital hologram containing complete three-dimensional information about the target object is obtained at the set off-axis angles.

[0015] Step 2. For each digital hologram acquired in each direction, a corresponding real image projection device is provided; each set of real image projection devices is located on the same horizontal plane, and the angle between two adjacent sets of real image projection devices is the same as in Step 1; each set of real image projection devices is centered on the 3D printing position and looks down at the 3D printing position;

[0016] The real image projection device includes a laser source, a 4-f system, a polarizer, a spatial light modulator, an analyzer, a magnifying lens and a filter, wherein a first baffle is provided at the center of the filter;

[0017] The size of the digital hologram of the target object in each direction is adjusted by a computer so that the digital hologram in each direction is fully output on the spatial light modulator in the corresponding direction. At the same time, the digital hologram is superimposed with the phase of the Fresnel lens or the phase of the blazed grating.

[0018] Step 3. In each group of real image projection devices, a laser is emitted. After the laser is expanded by a 4-f system, it passes through a polarizer to improve the polarization purity of the laser after emission, and then is obliquely incident on a spatial light modulator at an angle θ. The spatial light modulator modulates and reflects the light from the angle θ to generate a holographic zero-order light spot and a restored image light. The angle between the holographic zero-order light spot and the restored image light is θ. Before the holographic zero-order bright spot enters the 3D printing position, it is blocked and eliminated by a first baffle. The restored image light reflected after modulation further passes through the analyzer, the magnifying lens, and the filter and is output at the 3D printing position. The restored image light modulated by the spatial light modulator also generates a zero-order light spot after being magnified by the magnifying lens. The second baffle in the filter is used to filter out the zero-order light spot formed by the restored image light passing through the magnifying lens, thereby forming a real image projection of the target object in the corresponding direction. The real image projections of the target object in each direction formed by all real image projection devices are superimposed on each other at the 3D printing position, thereby outputting a clear and complete real image projection of the target object.

[0019] Step 4. Build a container using a material that is transparent to light of a set wavelength and suppresses light of other wavelengths. Fill the container with a photosensitive resin liquid that is sensitive to light of the corresponding set wavelength. When irradiated with light of the corresponding set wavelength, the photosensitive resin liquid undergoes a phase change and solidifies.

[0020] Step 5. Place the container prepared in step 4 at the 3D printing position so that the container completely wraps the real image projection of the object; through the photocuring reaction of the photosensitive resin liquid, the photosensitive resin liquid in the area where the real image projection of the target object is located will gradually condense and solidify to form an integrated 3D printed model.

[0021] Furthermore, in step 1, the process of obtaining a digital hologram by optical off-axis holographic recording is as follows:

[0022] The laser emits laser light, which is divided into two beams by the first beam splitter; one beam of laser light is reflected by the first plane mirror and then passes through the object and the first convex lens to form object light; the other beam of laser light is reflected by the second plane mirror and transmitted by the second convex lens in sequence, and interferes with the object light at a set off-axis angle θ, and simultaneously converges on the photodetector; the photodetector collects photoelectric information as an output signal and inputs it into the computer, which then demodulates the output signal of the photodetector to obtain a digital hologram of the target object.

[0023] Furthermore, when obtaining a digital hologram through digital modeling calculation, the target object is discretized into multiple layers of slices with equal spacing along the axial direction, and a digital hologram is calculated for each layer of slices and superimposed to obtain a digital hologram with complete three-dimensional information of the object;

[0024] For an object divided into M layers along the z-axis, the digital hologram recorded from the object light source is expressed as:

[0025]

[0026] Among them, g(x s ,y s ) represents the hologram of the target object, 1≤m≤M, x s and y s Represent the horizontal and vertical coordinates of the target object hologram, z m Indicates the depth of the target object’s mth slice; O(x m ,y m ;z m ) represents the same depth z m A collection of all light points below;

[0027] For O(x m ,y m ;z m ) in the image, let it be a point light source δ(x-x0, y-y0) at depth z m The point spread function h(x, y, z m ) to the impulse response of the point light source δ(x-x0, y-y0) is:

[0028]

[0029] Where x and y represent the horizontal and vertical coordinates of the airspace, respectively; x0 and y0 represent the horizontal and vertical coordinates of the point light source, respectively; δ represents the impact function; j is the symbol of the imaginary part; k0 is the wave number, k0 = 2π / λ, λ is the laser wavelength, and * represents the convolution operation.

[0030] Furthermore, in step 4, the wavelength is set to 200-800nm, and the material used to build the container is transparent to light in the 200-800nm ​​band and can filter out light in other wavelength bands; the material used for the photosensitive resin liquid is any one of the free radical photocuring, cationic photocuring, free radical-cationic mixed photocuring and mercapto-ene photopolymerization systems that meets the set wavelength band, is sensitive to light in the 200-800m band, and will cause a polymerization reaction when exposed to light, thereby completing curing.

[0031] Furthermore, a supporting platform is provided at the bottom area of ​​the real image projection of the target object to prevent the formed part from moving in the photosensitive resin container due to gravity during the printing process, which may cause the failure of the entire printing process.

[0032] The beneficial effects of the present invention are:

[0033] In actual implementation of the theoretical principle of integrated 3D printing based on digital holographic projection, the method described in the present invention considers and applies innovative technical means to eliminate the impact of zero-order DC light spots on printed image quality caused by holographic image generation and insufficient fill factor of the spatial light modulator. A first baffle is used to block the zero-order light spots generated by the holographic recording principle, and a second baffle is used to block and eliminate the zero-order bright spots reflected by the spatial light modulator itself and concentrated by the magnifying lens.

[0034] The method of the present invention uses a method based on digital holographic projection to achieve integrated 3D printing of objects. It uses a digital hologram restoration method to obtain the three-dimensional information of the object contained in the digital hologram and restore it to the object's 3D projection. Unlike the stacked additive manufacturing method of the prior art, the method of the present invention improves printing efficiency and the longitudinal strength of the printed product while performing a single molding process.

[0035] The method of the present invention adopts the SLA photosensitive resin printing method based on the properties of digital holographic restoration, which is significantly superior to other currently widely used additive manufacturing methods in terms of printing efficiency and simplified printing equipment structure.

[0036] The method of the present invention has the characteristics of not requiring a mechanical structure and being an integrated single-shot molding. The basic example structure is not only simple to implement and easy to operate, but also highly practical and suitable for popularization and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the system structure of the method of the present invention;

[0038] Figure 2 Schematic diagram of the structure of the optical off-axis holographic recording system in the method of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0040] This embodiment provides an integrated 3D printing method based on digital holographic projection, such as Figure 1 As shown, the following steps are included:

[0041] Step 1. Through optical off-axis holographic recording or digital modeling calculation, the target object is viewed from several directions at evenly spaced angles on the same horizontal plane, with the target object as the center. A digital hologram containing the target object's complete three-dimensional information is obtained in each direction at the set off-axis angles.

[0042] In this embodiment, the target object is viewed downward from three angles spaced 120 degrees apart on the same horizontal plane to obtain digital holograms of the target object at the three angles, including the three-dimensional spatial information of the target object at the three angles.

[0043] Optical holography based on off-axis reference light places the reference light at a different axial position than the object light, thereby offsetting the light spot generated by the zero-order component to minimize its impact on the image quality. Because off-axis holography is based on the principles of traditional on-axis optical holography, it can perform a comprehensive calculation of the light field distribution. This results in higher hologram calculation and restoration efficiency than OSH technology, and the object image is less affected by the zero-order component.

[0044] The digital hologram of the target object is obtained by optical off-axis holography. The off-axis reference light interferes with the object light of the object to be recorded, and the digital hologram corresponding to the object is obtained by recording and demodulating with the photoelectric sensor. The process of obtaining the digital hologram by optical off-axis holographic recording is realized by the holographic recording system. Its structural flow diagram is shown in the figure. Figure 2 As shown, the laser emits laser light, which is split into two beams by the first beam splitter BS1. One beam is reflected by the first plane mirror M1, passes through the object and the first convex lens L1, and forms the object beam. The other beam is reflected by the second plane mirror M2 and transmitted through the second convex lens L2. It interferes with the object beam at a set off-axis angle θ and converges onto the photodetector PD. The photodetector collects photoelectric information as an output signal and inputs it into the computer PC. The output signal of the photodetector is then demodulated to obtain a digital hologram of the target object. In this embodiment, the laser emits laser light with a wavelength of 632nm.

[0045] The digital hologram is obtained by digital modeling and calculation. The process of simulating optical off-axis holography is as follows:

[0046] The target object is discretized into multiple layers with equal spacing along the axial direction, and a digital hologram is calculated for each layer and superimposed to obtain a digital hologram with complete three-dimensional information of the object.

[0047] The impulse response of the point spread function h(x, y, z0) to the point light source δ(x-x0, y-y0) at depth z0 is:

[0048]

[0049] Where x and y represent the horizontal and vertical coordinates of the airspace, respectively; x0 and y0 represent the horizontal and vertical coordinates of the point light source, respectively; δ represents the impact function; j is the symbol of the imaginary part; k0 is the wave number or propagation constant; k0 = 2π / λ, λ is the laser wavelength, and * represents the convolution operation.

[0050] The holographic light intensity distribution g(x, y) of the off-axis digital holographic system at the same depth z0 can be expressed as:

[0051]

[0052] Where a is the amplitude of the reference light, and z0 represents the distance from the target object layer to the light intensity recording device.

[0053] The holographic light intensity distribution expression of the off-axis digital holographic system can be decomposed into:

[0054]

[0055] in, The three separated terms are then convolved with the conjugate phase of the point spread function (implemented by the magnifying lens in the real image projection device) to achieve Fourier transform results, which respectively represent the zero-order DC of off-axis holographic restoration, the holographic real image at the restoration position, and the holographic virtual image in the opposite direction of the restoration position.

[0056] For an object divided into M layers, the hologram recorded from the object light source is expressed as:

[0057]

[0058] Among them, g(x s ,y s ) represents the hologram of the object, x s and y s They represent the horizontal and vertical coordinates of the object hologram respectively. For a discrete slice object, it is assumed that it is divided into M layers along the z axis. m Indicates the depth of the target object’s mth slice; O(x m ,y m ;z m ) represents the collection of all object light points at the same depth.

[0059] Step 2. For each digital hologram acquired in each direction, a corresponding real image projection device is provided; each set of real image projection devices is located on the same horizontal plane, and the angle between two adjacent sets of real image projection devices is the same as in Step 1; each set of real image projection devices is centered on the 3D printing position and looks down at the 3D printing position;

[0060] The real image projection device includes a laser source, a 4-f system, a polarizing film 1, a spatial light modulator SLM, a polarizing film 2, a magnifying lens and a filtering film;

[0061] The size of the digital hologram of the target object in each direction is adjusted by a computer, so that the digital hologram in each direction is fully output on the spatial light modulator in the corresponding direction. At the same time, the digital hologram is superimposed with the phase of the Fresnel lens or the blazed grating to separate the zero-order light spot generated by the spatial light modulator itself and the restored image light.

[0062] Step 3. In each real image projection device, a laser emits laser light. After beam expansion using a 4-f system, the laser beam passes through polarizing film 1 to enhance its polarization purity. The beam then enters the modulation unit of the spatial light modulator (SLM) at an oblique angle θ. The SLM modulates and reflects the light from angle θ, generating a zero-order spot and a restored image beam. The angle between the zero-order spot and the restored image beam is θ. Before the zero-order spot, separated by off-axis holography and reflected from the SLM, enters the 3D printing position, it is blocked by a first blocker. The modulated, reflected restored image beam then passes through analyzer film 2 and a magnifying lens for output. The zero-order spot in the output image beam is caused by insufficient fill factor in the SLM. The structure of the filter film is a transparent glass slide with a small opaque second baffle in the center. The filter is used to block the zero-order light spot caused by the insufficient filling factor of the spatial light modulator. The remaining image light passes through the peripheral transparent area and converges on the 3D printing position to form a real image projection of the target object in the corresponding direction; the real image projections of the target object in each direction formed by all real image projection devices are superimposed on each other at the 3D printing position, thereby outputting a clear and complete real image projection of the target object.

[0063] Step 4. Build a Printing Container using a material that is transmissive to light of a set wavelength and suppresses light of other wavelengths. Fill the Printing Container with a photopolymer liquid that is sensitive to light of the set wavelength. The Printing Container filters out clutter, improving the photopolymer's efficiency in absorbing and utilizing energy from the target object's three-dimensional image. When irradiated with light of the set wavelength, the photopolymer liquid undergoes a phase change and solidifies.

[0064] In this embodiment, the wavelength is set to 200-800nm, and the material used to build the container is transparent to light in the 200-800nm ​​band and can filter out light in other wavelength bands; the material used for the photosensitive resin liquid is any one of the free radical photocuring, cationic photocuring, free radical-cationic mixed photocuring and mercapto-ene photopolymerization systems that meets the set wavelength band, and will cause a polymerization reaction under the irradiation of light in the 200-800nm ​​band to complete the curing.

[0065] Step 5. Place the container prepared in step 4 at the 3D printing position so that the container completely wraps the real image projection of the object; through the photocuring reaction of the photosensitive resin liquid, the photosensitive resin liquid in the area where the real image projection of the target object is located will gradually condense and solidify to form an integrated 3D printed model.

[0066] The process described in step 5, where the photosensitive resin object's 3D real image projection area solidifies into a single model, does not require model layering or platform movement. The printed model is formed in a single, integrated process. A Printing Base can be placed at the bottom of the 3D real image projection to prevent the molded part from moving within the photosensitive resin container due to gravity during printing, potentially causing the entire printing process to fail.

[0067] In summary, the present invention innovatively uses a method based on off-axis digital holographic restoration, spatial light modulator superimposed lens phase and SLA photosensitive resin printing to achieve one-piece 3D printing of objects. Unlike the existing stacked additive manufacturing method, it improves the molding speed and the longitudinal strength of the finished product while performing one-time molding. It is also different from the existing traditional coaxial holographic projection one-piece printing method and can effectively reduce the adverse effects of the zero-order light spot on the printing quality. In terms of printing efficiency and the longitudinal strength of the printed product, it is far superior to other currently widely used layer-by-layer additive manufacturing methods, and in terms of printing quality, it is far superior to other existing coaxial holographic one-piece 3D printing methods. The present invention also has the characteristics of not requiring a mechanical structure and one-piece single molding. It is not only simple to implement and easy to operate, but also has low manufacturing costs and strong practicality. It is suitable for vigorous promotion in this technical field or in technical fields close to this technical field.

[0068] The structures listed above are only basic structures of the present invention as examples and should not be used to limit the scope of protection of the present invention. Any changes or modifications that are made to the main design concept and spirit of the present invention and have no substantive significance, as long as the technical problems they solve are still consistent with the present invention, should be included in the scope of protection of the present invention.

Claims

1. An integrated 3D printing method based on digital holographic projection, characterized in that: The following steps are involved: Step 1. Using optical off-axis holographic recording or digital modeling, the target object is viewed downward from a number of directions spaced evenly apart on the same horizontal plane, centered on the target object. A digital hologram containing complete three-dimensional information about the target object is obtained in each direction at a predetermined off-axis angle θ. Step 2. For each digital hologram acquired in each direction, a corresponding real image projection device is provided; each set of real image projection devices is located on the same horizontal plane, and the angle between two adjacent sets of real image projection devices is the same as in Step 1; each set of real image projection devices is centered on the 3D printing position and looks down at the 3D printing position; The real image projection device includes a laser source, a 4-f system, a polarizer, a spatial light modulator, an analyzer, a first baffle, a magnifying lens and a filter, wherein a second baffle is provided at the center of the filter; The size of the digital hologram of the target object in each direction is adjusted by a computer so that the digital hologram in each direction is fully output on the spatial light modulator in the corresponding direction. At the same time, the digital hologram is superimposed with the phase of the Fresnel lens or the phase of the blazed grating. Step 3. In each group of real image projection devices, a laser is emitted. After the laser is expanded by a 4-f system, it passes through a polarizer to improve the polarization purity of the laser after emission, and then is obliquely incident on a spatial light modulator at an angle θ. The spatial light modulator modulates and reflects the light from the angle θ to generate a holographic zero-order light spot and a restored image light. The angle between the holographic zero-order light spot and the restored image light is θ. Before the holographic zero-order bright spot enters the 3D printing position, it is blocked and eliminated by a first baffle. The restored image light reflected after modulation further passes through the analyzer, the magnifying lens, and the filter and is output at the 3D printing position. The restored image light modulated by the spatial light modulator also generates a zero-order light spot after being magnified by the magnifying lens. The second baffle in the filter is used to filter out the zero-order light spot formed by the restored image light passing through the magnifying lens, thereby forming a real image projection of the target object in the corresponding direction. The real image projections of the target object in each direction formed by all real image projection devices are superimposed on each other at the 3D printing position, thereby outputting a clear and complete real image projection of the target object. Step 4. Build a container using a material that is transparent to light of a set wavelength and suppresses light of other wavelengths. Fill the container with a photosensitive resin liquid that is sensitive to light of the corresponding set wavelength. When irradiated with light of the corresponding set wavelength, the photosensitive resin liquid undergoes a phase change and solidifies. Step 5. Place the container prepared in step 4 at the 3D printing position so that the container completely wraps the real image projection of the object; through the photocuring reaction of the photosensitive resin liquid, the photosensitive resin liquid in the area where the real image projection of the target object is located will gradually condense and solidify to form an integrated 3D printed model.

2. The integrated 3D printing method based on digital holographic projection according to claim 1, characterized in that: In step 1, the process of obtaining a digital hologram by optical off-axis holographic recording is as follows: The laser emits laser light, which is divided into two beams by the first beam splitter; one beam of laser light is reflected by the first plane mirror and then passes through the object and the first convex lens to form object light; the other beam of laser light is reflected by the second plane mirror and transmitted by the second convex lens in sequence, and interferes with the object light at a set off-axis angle θ, and simultaneously converges on the photodetector; the photodetector collects photoelectric information as an output signal and inputs it into the computer, which then demodulates the output signal of the photodetector to obtain a digital hologram of the target object.

3. The integrated 3D printing method based on digital holographic projection according to claim 1, characterized in that: When obtaining a digital hologram through digital modeling calculation, the target object is discretized into multiple layers of slices with equal spacing along the axial direction. The digital hologram is calculated for each layer of slices and superimposed to obtain a digital hologram with complete three-dimensional information of the object. For an object divided into M layers along the z-axis, the digital hologram recorded from the object light source is expressed as: Among them, g(x s ,y s ) represents the hologram of the target object, 1≤m≤M, x s and y s Represent the horizontal and vertical coordinates of the target object hologram, z m Indicates the depth of the target object’s mth slice; O(x m ,y m ;z m ) represents the same depth z m A collection of all light points below; For O(x m ,y m ;z m ) in the image, let it be a point light source δ(x-x0, y-y0) at depth z m The point spread function h(x, y, z m ) to the impulse response of the point light source δ(x-x0, y-y0) is: Where x and y represent the horizontal and vertical coordinates of the airspace, respectively; k0 and y0 represent the horizontal and vertical coordinates of the point light source, respectively; δ represents the impact function; j is the symbol of the imaginary part, k0 is the wave number, k0 = 2π / λ, λ is the laser wavelength, and * represents the convolution operation.

4. The integrated 3D printing method based on digital holographic projection according to claim 1, characterized in that: In step 4, the wavelength is set to 200-800nm, and the material used to build the container is transparent to light in the 200-800nm ​​band and can filter out light in other wavelength bands; the material used for the photosensitive resin liquid is any one of the free radical photocuring, cationic photocuring, free radical-cationic mixed photocuring and mercapto-ene photopolymerization systems that meets the set wavelength band, is sensitive to light in the 200-800nm ​​band, and will cause a polymerization reaction when exposed to light, completing curing.

5. The integrated 3D printing method based on digital holographic projection according to claim 1, characterized in that: A supporting platform is set at the bottom area of ​​the real image projection of the target object to prevent the formed part from moving in the photosensitive resin container due to gravity during the printing process, which may cause the failure of the entire printing process.

Images