# US 2016/0243649 A1 · Optical system for 3d printing and control method thereof

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- Number: US 2016/0243649 A1
- Document ID: US20160243649A1
- Status: Published application
- Kind: A1
- Application number: 14/762,333
- Filed: 2014-07-17
- Published: 2016-08-25
- Earliest claimed: 2014-07-10
- Assignees: Guangzhou Institute of Advanced Technology, Chinise Academy of Sciences
- Applicants: Guangzhou Institute of Advanced Technology, Chinise Academy of Sciences
- Inventors: Zhu ZHENG; Olaf EICHSTAEDT; Yunpeng REN; Ruxu DU
- Web page: https://patentgrep.com/patent/US20160243649A1

## CPC

- B29C 64/153: using layers of powder being selectively joined, e.g. by selective laser sintering or melting
- B22F 10/28: Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
- B22F 10/80: Data acquisition or data processing
- B22F 12/44: characterised by the configuration of the radiation means
- B23K 26/0648: {comprising lenses}
- B23K 26/067: Dividing the beam into multiple beams, e.g. multi-focusing
- B23K 26/342: Build-up welding
- B29C 64/393: for controlling or regulating additive manufacturing processes
- B29C 67/00: Shaping techniques not covered by groups B29C39/00 - B29C65/00, B29C70/00 or B29C73/00
- B33Y 30/00: Apparatus for additive manufacturing; Details thereof or accessories therefor
- B29K 2105/251: {Particles, powder or granules (expandable particles B29K2105/046)}
- B33Y 10/00: Processes of additive manufacturing
- B33Y 50/02: for controlling or regulating additive manufacturing processes
- Y02P 10/25: Process efficiency
- 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 (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00)
- B22F: WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER (making alloys by powder metallurgy C22C); APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B33Y: 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
- B29K: INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR {MOULDS, } REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

The present invention discloses an optical system for 3D printing and a control method thereof. The system comprises a laser device, a beam expanding system, a beam splitter, a spatial light modulator and a focusing system. The spatial light modulator is connected with a computer and configured to generate a modulation pattern after receiving the target modulation pattern generated by the computer. A light beam emitted by the laser device is expanded into a parallel light beam by the beam expanding system and then irradiates on the beam splitter. A part of the expanded light beam reaches the spatial light modulator for modulation after passing through the beam splitter, then the modulated light beam is reflected to the beam splitter, and a part of the modulated light beam is focused by the focusing system and then irradiates on a target plane for 3D printing.

## Claims

### Claim 1

An optical system for 3D printing, comprising a laser device (1), a beam expanding system (2), a beam splitter (3), a spatial light modulator (4) and a focusing system (5), characterized in that the spatial light modulator (4) is connected with a computer for generating a target modulation pattern and configured to generate a modulation pattern after receiving the target modulation pattern generated by the computer; a light beam emitted by the laser device (1) is expanded into a parallel light beam having a large diameter by the beam expanding system (2) and then irradiates on the beam splitter (3); a part of the expanded light beam reaches the spatial light modulator (4) for modulation after passing through the beam splitter (3), then the modulated light beam is reflected to the beam splitter (3), and a part of the modulated light beam is focused by the focusing system (5) and then irradiates on a target plane (6) for 3D printing.

### Claim 2 (depends on 1)

The optical system for 3D printing according to claim 1, characterized in that the beam expanding system (2) comprises a negative lens (21) and a positive lens (22), the axis of the negative lens (21) and the axis of the positive lens (22) being on a same line, the light beam emitted by the laser device (1) being expanded into a parallel light beam having a large diameter successively by the negative lens (21) and the positive lens (22).

### Claim 3 (depends on 1)

The optical system for 3D printing according to claim 1, characterized in that the spatial light modulator (4) is a reflector type digital micromirror device, and the focusing system is a cylindrical lens.

### Claim 4 (depends on 1)

The optical system for 3D printing according to claim 1, characterized in that the spatial light modulator (4) is a phase type liquid crystal spatial light modulator, and the focusing system is a positive lens.

### Claim 5 (depends on 1)

A control method of the optical system for 3D printing according to claim 1, comprising:
step 1: after acquiring a planar pattern of each plane of a printing model for 3D printing by a computer, generating a target modulation pattern from the acquired planar pattern and sending the target modulation pattern to the spatial light modulator (4); and
step 2: expanding a light beam emitted by the laser device (1) into a parallel light beam having a large diameter by the beam expanding system (2) and then allowing the light beam to irradiate on the beam splitter (3), allowing a part of the expanded light beam to reach the spatial light modulator (4) for modulation after passing through the beam splitter (3), and allowing a part of the modulated light to be focused by the focusing system (5) and then irradiate on a target plane (6) for 3D printing after the modulated light is reflected to the beam splitter (3).

### Claim 6 (depends on 5)

The control method of an optical system for 3D printing according to claim 5, characterized in that, in step 2, the expanding a light beam emitted by the laser device (1) into a parallel light beam having a large diameter by the beam expanding system (2) specifically is:
expanding the light beam emitted by the laser device (1) into a parallel having a large diameter successively by a negative lens (21) and a positive lens (22).

### Claim 7 (depends on 5)

The control method of an optical system for 3D printing according to claim 5, characterized in that the spatial light modulator (4) is a reflector type digital micromirror device, the focusing system is a cylindrical lens and step 1 specifically is:
after acquiring a planar pattern of each plane of a printing model for 3D printing by a computer, segmenting the acquired planar pattern into a plurality of line segment patterns having a same width, and successively sending the acquired line segment patterns as a target modulation pattern to the reflector type digital micromirror device.

### Claim 8 (depends on 7)

The control method of an optical system for 3D printing according to claim 7, further comprising:
step 3: successively printing, by a 3D printing system, in an order of the successively focused line segment patterns, and moving the 3D printing system or the optical system in a same direction according to the width of the line segment patterns once one line segment pattern is printed.

### Claim 9 (depends on 5)

The control method of an optical system for 3D printing according to claim 5, characterized in that the spatial light modulator (4) is a phase type liquid crystal spatial light modulator, the focusing system is a positive lens, and step 1 specifically is:
after acquiring a planar pattern of each plane of a printing model for 3D printing by a computer, generating a phase-only hologram according to the following steps from the acquired planar pattern and then sending the phase-only hologram as a target modulation pattern to the phase type liquid crystal spatial light modulator;
step 11: forming an incident wave function ƒn(u,v) according to the following formula and on the basis of an initial phase distribution φ0(u,v) of the planar pattern and the amplitude |U(u,v)| of incident light incident on the phase type liquid crystal spatial light modulator:
ƒn(u,v)=|U(u,v)|·eiφ0(u,v);
step 12: performing Fourier transformation to the incident wave function ƒn(u,v):
gn(x,y)=|Gn(x,y)|·eiφn,
where gn(x,y) denotes the Fourier transformation of the incident wave function ƒn(u,v);
step 13: replacing Gn(x,y) with an expectantly modulated amplitude G(x,y) to obtain an intermediate function gn′(x,y):
gn′(x,y)=|G(x,y)|·eiψn;
step 14: performing inverse Fourier transformation to the intermediate function gn′(x,y):
ƒn′(u,v)|Un(u,v)|·eiφn(u,v),
where ƒn′(u,v) denotes the inverse Fourier transformation of the intermediate function gn′(x,y);
step 15: generating an incident wave function ƒn+1(u,v) of the next iteration according to the phase eiφn(u,v) of the inverse Fourier transformation of the intermediate function gn′(x,y) and the amplitude |U(u,v)| of the incident light:
ƒn+1(u,v)=|U(u,v)|·eiφn(u,v); and
step 16: repeating the above steps until a convergence condition is satisfied, and using the inverse Fourier transformation of the intermediate function gn′(x,y) at this moment as a phase-only hologram of the planar pattern.