An optical module and a method of connecting the optical module to an optical fibre

Abstract

A laser beam scanner (106a, 106b) for scanning a laser beam (118a, 118b) in at least one dimension, and preferably two dimensions, across a working plane. The laser beam scanner (106a, 106b) comprises a housing (125a, 125b) containing one or more optical components (121a, 121b, 120a, 120b). The housing (125) comprises a light beam input (128) configured to receive a beam delivery optic (132) of an optical fibre (108a, 108b) and a gas channel (135) located such that, when gas is pumped therethrough, a gas flow is generated across a face of the beam delivery optic (132) received in the light beam input (128).

Description

[0001] AN OPTICAL MODULE AND A METHOD OF CONNECTING THE OPTICAL MODULE TO AN OPTICAL FIBRE

[0002] Field of Invention

[0003] This invention concerns an optical module and a method of connecting the optical module to an optical fibre. The invention has particular, but not exclusive, application to a laser beam scanner for scanning a laser beam in at least one dimension, and preferably two dimensions, across a working plane.

[0004] Background

[0005] A fibre-laser typically comprises a delivery optical fibre and a beam delivery optic (BDO) connected to an end of the delivery optical fibre. The beam delivery optic comprises an end-cap (a homogeneous and transparent piece of material), spliced or welded onto the end of the delivery optical fibre. The end cap is used as a way of protecting the tip of the delivery optical fibre against optical damage. Without an end cap, a high-power density would be generated at the air-to-glass interface, which could damage the delivery optical fibre.

[0006] A laser beam scanner typically comprises a laser beam input configured to connect the beam delivery optic to the laser beam scanner such that the laser beam is delivered into a housing of the laser beam scanner. The housing may comprise steering optics, such as a pair of rotatable mirrors, configured to steer the laser beam in two-dimensions across a working plane. The laser beam exits the housing of the laser beam scanner through a window. The connection of the beam delivery optic to the housing is such that, in use, the housing is sealed to dust and the like. An example of such a laser beam scanner is described in W02010 / 026397.

[0007] WO2010 / 026397 discloses that the set-up process of the laser beam scanner is performed in a clean room having a dehumidified dust-free atmosphere such that,when the laser beam scanner is sealed, the atmosphere inside the laser beam scanner is a dehumidified dust-free air atmosphere.

[0008] A problem with current laser beam scanners is that dust can become trapped on and / or in-front of the beam delivery optic during connection of the beam delivery optic to the laser beam scanner. This dust can affect the passage of the laser beam through the laser beam scanner.

[0009] Summary of Invention

[0010] According to a first aspect of the invention there is provided an optical module comprising a housing containing one or more optical components, the housing comprising a light beam input configured to receive a beam delivery optic of an optical fibre and a gas channel located such that, when gas is pumped therethrough, a gas flow is generated across a face of the beam delivery optic received in the light beam input.

[0011] During connection of the beam delivery optic to the optical module gas, such as air, can be pumped through the gas channel to remove any dust that is present. In this way, dust is prevented from being trapped on and / or in-front of the beam delivery optic by the gas flow. The beam delivery optic may comprise an end-cap (e.g. a homogeneous and transparent piece of material), spliced or welded onto the end of the optical fibre.

[0012] The light beam input may comprise a window of material transparent to the light beam. The light beam input may comprise a passageway for the light beam and the window may close the passageway. The gas channel may be configured to generate the gas flow between an external surface of the window and the face of the beam delivery optic. In this way, dust is prevented from being trapped between the beam delivery optic and the window.The gas channel may comprise first and second openings into the passageway. One of the first and second openings may be used to inject gas into the passageway and the other of the first and second openings may be used to remove gas from the passageway. The first and second openings may be located on opposed sides of the passageway. The first and second openings may be located opposite each other, for example diametrically across the passageway. The first and second openings may be arranged to generate a gas knife across a face of the beam delivery optic.

[0013] The passageway may be configured such that the light beam can travel from the beam delivery optic to the at least one optical component in the housing.

[0014] The gas channel may comprise external gas openings in an external face of the housing. At least one of the external gas openings may be connectable to a pressurised gas source or a vacuum source for generating the gas flow in the gas channel.

[0015] The optical module may comprise plugs for plugging the external gas openings.

[0016] In one embodiment, the optical module comprises a laser beam scanner for scanning a laser beam in at least one dimension, and preferably two dimensions, across a working plane. The one or more optical components may comprise a movable mirror for steering the laser beam across the working plane. The one or more optical components may comprise at least two movable mirrors for steering the laser beam across the surface. One of the at least two movable mirrors may be for steering the laser beam across the working plane in a first dimension and the another of the at least two movable mirrors may be for steering the laser beam across the working plane in a second dimension, perpendicular to the first dimension.

[0017] However, it will be understood that the principles may be applied to other optical modules, such as a beam conditioning unit or a detector for receiving light deliveredto the detector by an optical fibre. A beam conditioning unit may control an intensity, shape, and / or spatial quality of the laser beam.

[0018] According to a second aspect of the invention there is provided a laser processing apparatus comprising an optical module according to the first aspect of the invention and a fibre-laser comprising a delivery fibre and a beam delivery optic, the beam delivery optic received in the light beam input of the optical module.

[0019] The laser processing apparatus may be a powder bed fusion apparatus.

[0020] According to a third aspect of the invention there is provided a method of assembling an optical module according to a first aspect of the invention with a fibre laser comprising a delivery fibre and a beam delivery optic, the method comprises connecting the gas channel to a pressurised gas source or a vacuum source to generate a gas flow in the gas channel and inserting the beam delivery optic into the light beam input during generation of the gas flow.

[0021] The method may further comprise plugging external openings of the gas channel after insertion of the beam delivery optic into the light beam input.

[0022] Description of the Drawings

[0023] Figure 1 is a schematic of a powder bed fusion apparatus comprising an optical module according to an embodiment of the invention;

[0024] Figure 2 is a schematic of steering optics of the optical module illustrated in Figure 1;

[0025] Figure 3 is a sectional view of light beam input of the optical module;

[0026] Figure 4 is a perspective view of the light beam input; andFigure 5 is an enlarged perspective view of the light beam input illustrated in Figures 3 and 4.

[0027] Description of Embodiments

[0028] Referring to Figure 1, a powder bed fusion apparatus according to an embodiment of the invention comprises a build chamber 101 having therein a processing plate 115 defining a build aperture 117, and a build sleeve 116 extending down from the build aperture 117. A build platform 102 is lowerable in the build sleeve 116 such that the build sleeve 116 and the build platform 102 together define a build volume. During a build, the build platform 102 supports a build substrate plate 102a, a powder bed 104 and workpiece (object) 103 as the workpiece is built by selective laser melting or sintering of the powder. The platform 102 is lowered within the build volume under the control of a drive mechanism (not shown) as successive layers of the workpiece / object 103 are formed.

[0029] Layers of powder 104 are formed as the workpiece / object 103 is built by dispensing apparatus (not shown) and a recoater 109. The dispensing apparatus dispenses powder 104 from hopper (not shown) onto the processing plate 115 at a dosing location such that movement of the recoater 109 spreads powder into powder layers of the powder bed 104.

[0030] A plurality of laser beam scanners 106a, 106b are provided for steering a corresponding laser beam 118a, 118b generated by a laser 105a, 105b across selected areas of the powder bed 104 to melt the powder. In this embodiment, the lasers 105a, 105b are fibre lasers that deliver the laser beam to the laser beam scanner 106a, 106b via a delivery optical fibre 108a, 108b and beam deliver optic (BDO) 132a. 132b. Each scanner 106a, 106b directs the laser beam through a window 107 in the build chamber 101.Each laser beam scanner 106a, 106b comprises a housing 125a, 125b containing movable optical components 120’, 120”, in this embodiment rotatable mirrors 120”, 120” (see Figure 2), for steering the corresponding laser beam 118a, 118b across the powder bed 104 and focussing optics 121a for focussing the laser beam 118a, 118b. In Figure 1, the pair of movable optical components 120’, 120” are symbolic represented as features 120a and 120b, respectively, for each laser beam scanner 106a, 106b. The first rotatable mirror 120’ is rotatable about an axis A-A and the second rotatable mirror 120” rotatable about an axis B-B. The first axis A-A is perpendicular to the second axis B-B. Rotation of the first rotatable mirror 120’ moves the laser beam 118 across a surface of the powder bed 104 in a first dimension and rotation of the second rotatable mirror 120” moves the laser beam 118 across a surface of the powder bed 104 in a second-dimension, perpendicular to the first dimension. In Figure 4a, the first dimension in illustrated as the x-direction and the second dimension as the y-direction, but it will be understood that this will be reversed if the scanner 106 is rotated by 90 degrees as may be the case for some of the scanners. Rotation of each mirror 120’, 120” may be driven by a suitable motor, such as a galvanometer 143, 144.

[0031] Referring to Figures 3 to 5, for each scanner 106a, 106b, the laser beam 118a, 118b enters the housing 125 via a light beam input 128 connectable to the BDO 132 and exits the housing 125 via a light beam output 122a, 122b in a mounting face 124a, 124b of the housing 125a, 125b. The light beam output 122a, 122b is a windowed aperture, for example sealed by material transparent to the laser beam 118a, 118b, to protect the optical components from dust and the like. Similarly, the light beam input 128 comprises a laser beam passageway 136 and a window 134 (see Figure 5) of material transparent to the laser beam 118a, 118b that closes the laser beam passageway 136 mid-way along the laser beam passageway 136. In this way the housing 125a, 125b is sealed such that dust and the like cannot enter the housing 125a, 125b and affect the passage of the laser beam 118a, 118b along the optical path defined by the optical components.The light beam input 128 is located in a side of the housing 125 opposite the side comprising the mounting face 124a, 124b. A turning mirror 129a, 129b turns the laser beam 118a, 118b from the light beam input 128 to the movable optical components 120’, 120”.

[0032] The light beam input 128 comprises a connector 133 co-operable with a connector on the BDO 132 to secure the BOD 132 to the housing 125. The laser beam passageway 136 leads from an opening 140 for laser light on an external facing side of window 134 to the inside of the housing 125 on an internally facing side of window 134, allowing a laser beam 118 introduced from the BDO 132 to enter the housing 125.

[0033] A gas channel 135 extends through the housing 125 between a first external opening 137a and a second external opening 137b. The gas channel 135 opens out into the laser beam passageway 136. The gas channel 135 passes over an external face of the window 134, between the window 134 and a face of the BDO 132 when connected to the light beam input 128. The gas channel 135 in this region, as defined by the external surface of the window 134 and the face of the BDO 132 is narrower than other regions 138a, 138b of the gas channel 135 such that a velocity of the gas flow increases in this region to generate a gas knife for removing dust. Plugs or caps 139a, 139b can be inserted into / secured over the external openings 137a, 137b to prevent air and dust from the external environment from entering into the gas channel 135 during use of the laser scanner 106a, 106b.

[0034] During assembly of the BDO 132a, 132a to the laser scanner 106a, 106b, a source of pressurised gas is connected to one of the external openings 137a, 137b to generate a gas flow along the gas channel 135. The gas flow generates the gas knife that removes dust that may have settled on the external surface of the window 134 and the face of the BDO 132a, 132b. The BDO 132a, 132b is connected to the light beam input 128 whilst a gas flow is generated in the gas flow channel such that dust introduced into the location between the BDO 132a, 132b and the window 134 isremoved by the gas flow. After the BDO 123a, 132b has been connected, the external openings 137a, 137b are plugged to prevent dust entering the gas channel during use of the laser scanner 106a, 106b.

[0035] It will be understood that the laser beam scanner described above may be used in laser processing apparatus other than powder bed fusion apparatus, for example laser marking machines. Furthermore, the gas channel for providing gas flow between the face of the beam delivery optic and the window closing the light beam input may be used in optical modules other than laser beam scanners, for example, a beam conditioning unit or a detector for receiving light delivered to the detector by an optical fibre.

Claims

CLAIMS1. A laser beam scanner for scanning a laser beam in at least one dimension, and preferably two dimensions, across a working plane, the laser beam scanner comprising a housing containing one or more optical components, the housing comprising a light beam input configured to receive a beam delivery optic of an optical fibre and a gas channel located such that, when gas is pumped therethrough, a gas flow is generated across a face of the beam delivery optic received in the light beam input.

2. A laser beam scanner according to claim 1, wherein the light beam input comprises a window of material transparent to the light beam.

3. A laser beam scanner according to claim 2, wherein the gas channel is configured to generate the gas flow between an external surface of the window and the face of the beam delivery optic.

4. A laser beam scanner according to claim 2 or claim 3, wherein the light beam input comprises a passageway for the light beam and the window closes the passageway.

5. A laser beam scanner according to claim 4, wherein the gas channel comprises first and second openings into the passageway.

6. A laser beam scanner according to claim 5, wherein the first and second openings are located on opposed sides of the passageway.

7. A laser beam scanner according to any one of the preceding claims, wherein the gas channel comprises external gas openings in an external face of the housing.

8. A laser beam scanner according to claim 7, wherein at least one of the external gas openings is connectable to a pressurised gas source or a vacuum source for generating the gas flow in the gas channel.

9. A laser beam scanner according to claim 7 or claim 8, comprising plugs for plugging the external gas openings.

10. A laser beam scanner according to any one of the preceding claims, wherein the one or more optical components comprise a movable mirror for steering the laser beam across the working plane.

11. A laser beam scanner according to any one of the preceding claims, wherein the one or more optical components comprise at least two movable mirrors for steering the laser beam across the surface.

12. A laser beam scanner according to claim 11, wherein one of the at least two movable mirrors is for steering the laser beam across the working plane in a first dimension and another of the at least two movable mirrors may be for steering the laser beam across the working plane in a second dimension, perpendicular to the first dimension.

13. A laser processing apparatus comprising a laser beam scanner according to any one of claims 1 to 12 and a fibre-laser comprising a delivery fibre and a beam delivery optic, the beam delivery optic received in the light beam input of the optical module.

14. A laser processing apparatus according to claim 13, wherein the laser processing apparatus is a powder bed fusion apparatus.

15. A method of assembling a laser beam scanner according to according to any one of claims 1 to 12 with a fibre laser comprising a delivery fibre and a beam delivery optic, the method comprises connecting the gas channel to a pressurised gas source or a vacuum source to generate a gas flow in the gas channel andinserting the beam delivery optic into the light beam input during generation of the gas flow.

16. A method according to claim 15, comprising plugging external openings of the gas channel after insertion of the beam delivery optic into the light beam input.

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