FIELD

The present invention relates to an apparatus and a method for coating surfaces of optical elements.

BACKGROUND

Optical elements (e.g. lenses) are often required to be coated, for example, Anti-Reflection coating, Reflective coating, Band-Pass coating, Hard-coating etc. to enhance performance or to attain certain functions. Some of these optical elements have complex geometry and have multi-faceted surfaces to be coated. Selective coating is conducted on the required surfaces to be coated usually using masking jigs. The use of such masking jigs enable coating of each surface, one at a time, and in a sequential manner. Each surface to be coated has to be subject to the required masking by the masking jigs to cover any surface that is not to be coated, and to expose the surface to be coated. The coating process for several surfaces requires the optical element to be transferred from one masking jig to another. This process is inefficient, and has low yield and high manufacturing cost.

SUMMARY

According to an example of the present disclosure, there are provided an apparatus and a method for coating surfaces of optical elements, as claimed in the independent claims. Some optional features are defined in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the present disclosure will be better understood and readily apparent to one skilled in the art from the following written description, by way of example only and in conjunction with the drawings, in which:

Fig. 1 shows an optical element with 3 surfaces S1 to S3, wherein each surface is to be subject to coating with one or more layers of material.

Fig. 2 shows a cross-sectional side view of an apparatus according to an example of the present disclosure for holding the optical element of Fig. 1 in position for multi-surface coating.

Fig. 3 shows top perspective views of the apparatus of Fig. 2 and a plurality of the apparatus for holding a plurality of optical elements.

Fig. 4 (Prior Art) shows how the surfaces of the optical element of Fig. 1 may be coated in a conventional coating process.

Fig. 5 (Prior Art) shows more details on how the surfaces of the optical element of Fig. 1 may be coated in a conventional coating process.

Fig. 6 (Prior Art) shows examples of conventional masking jigs used for exposing only one surface of each optical element placed in the jigs for surface coating.

Fig. 7 illustrates how a plurality of apparatuses according to examples of the present disclosure is used during surface coating of a plurality of optical elements.

Fig. 8 shows examples of top and bottom sections of an apparatus similar to the apparatus of Fig. 2 that are configured to be assembled to form the apparatus of Fig. 2. Fig. 9 is a bottom perspective view of the apparatus of Fig. 8 after assembly of the top and bottom sections.

Fig. 10 is a top perspective view of the apparatus of Fig. 8 after assembly of the top and bottom sections.

Fig. 11 is a top perspective view of the apparatus of Fig. 8, illustrating in greater detail the top section of the apparatus.

Fig. 12 is a side perspective view of the apparatus of Fig. 8, illustrating side portions of the apparatus.

Fig. 13 shows a plurality of optical elements, wherein some of them are already placed in a bottom portion of a holder of the apparatus of Fig. 8 and one of them is about to be placed in such bottom portion of the holder.

Fig. 14 illustrates a method of producing optical elements with coatings coated by a method according to an example of the present disclosure.

Fig. 15 illustrates installations in a coating chamber in a machine for coating multiple surfaces of optical elements placed in a plurality of the apparatuses in Fig. 7.

Fig. 16 is a photograph showing how the machine of Fig. 15 may look like and when it is being operated on.

Fig. 17 is a photograph showing conventional masking jigs and the apparatus of Fig. 8.

Fig. 18 (Prior Art) is a photograph showing a close up view of conventional masking jigs.

Fig. 19 is a photograph showing an injection moulded optical element of Fig. 1.

Fig. 20 is a photograph showing the optical element of Fig. 19 joint to a sprue.

These figures are not drawn or adjusted to scale and are intended merely for illustrative purposes.

DETAILED DESCRIPTION

An example of the present disclosure relates to an apparatus and a method for selective coating on multi-faceted surfaces of a plurality of optical elements. The apparatus and method can be applied for masking each multi-faceted optical element and subject an unmasked and exposed surface or surfaces of the multi-faceted optical element to selective (optical) coating requirements. Each optical element can be a lens for light manipulation. The optical elements may each be made of transparent material such as glass, plastic and the like. In the case of plastic, the optical elements made be made via injection moulding.

The apparatus and method are particularly useful when the optical elements are very small and difficult to handle. Examples of the coating to be performed include Anti-Reflection coating, Reflective coating, Band-Pass coating, Hard-coating etc. There will be present one or more layers of material corresponding to each type of coating. The coating of the one or more layers of material on the surfaces of the optical elements may be conducted in a physical vapour deposit (PVD) chamber and PVD can be involved.

Fig. 1 shows a perspective view of an optical element 100 with 3 surfaces S1 to S3, wherein each surface is to be subject to coating with one or more layers of material with the help of the aforementioned apparatus and the method. The optical element 100 is generally in a shape of a cube (or in other examples, a right rectangular prism) with a planar cut at a bottom rear portion to provide a flat surface S3. S3 is at an angle relative to vertically disposed surfaces of the optical element 100, such as a front facing surface 104. S3 is also at an angle relative to horizontally disposed surfaces of the optical element 100, such as a top facing surface 102. S1 and S2 are hemispherical surfaces. S1 is disposed on the top facing surface 102 and S2 is disposed on the front facing surface 104. The top facing surface 102 and the front facing surface 104 are orthogonal to each other. The optical element 100 of Fig. 1 is just one example of an optical element that may be worked on by the aforementioned apparatus. There can be other types of optical elements with other shapes. The aforementioned apparatus is constructed accordingly to suit the shape of the optical element. In the example as follow, the apparatus described is constructed to suit the shape of the optical element 100.

Fig. 19 is a photograph showing a close up view of how an example of an injection moulded optical element of Fig. 1 featuring the S3 surface looks like in reality.

® Fig. 20 is a photograph showing a close up view of how the optical element of Fig. 1 looks like when it is still joint to a sprue after injection moulding. In this case, the sprue refers to pieces of plastic, which has solidified to join a number of small moulded plastic items. Fig. 2 shows a cross-sectional side view of an example of an apparatus 200 of the aforementioned apparatus for holding the optical element 100 of Fig. 1 in position for multisurface coating. In the present example, the apparatus 200 comprises a top masking jig 214 and a bottom masking jig 216. The apparatus 200 is formed by assembling the top masking jig 214 to the bottom masking jig 216. The apparatus 200 provides a holder for holding the optical element 100. In particular, after assembly of the two jigs 214 and 216, the apparatus 200 has a holding space 212 at its centre for holding the optical element 100. The optical element 100 can be placed in the bottom masking jig 216 first, followed by covering the top masking jig 214 over the bottom masking jig 216 to hold the optical element 100 within the space 212. The space 212 is formed in a shape for holding the optical element 100 firmly to prevent the optical element 100 from moving during surface coating process. A horizontal line A-A cuts across the apparatus 200 in Fig. 2. The line A-A is a dividing line for the top masking jig 214 and the bottom masking jig 216 and indicates where the top masking jig 214 is to be assembled to the bottom masking jig 216. When assembled, the apparatus 200 comprises a plurality of openings, in particular, an opening 202 for the S1 surface of the optical element 100, an opening 206 for the S2 surface of the optical element 100, and an opening for the S3 surface of the optical element 100. There are present a plurality of walls 220, 222 and 224, that are spaced apart and shaped to isolate and expose each surface of the optical element 100 to be subject to coating with a layer of material. These plurality of walls 220, 222 and 224 provide the required masking effect to isolate and expose the surfaces S1 to S3 to be coated.

The example of Fig. 2 only shows two sections that can be assembled to form the apparatus 200, wherein these two sections are the top masking jig 214 and the bottom masking jig 216 respectively. However, in another example, there can be more than two of such sections that can be assembled to form the apparatus 200. Furthermore, these sections may be configured to enable them to attach, join, adhere, or clip-on to one another to provide secure assembly of the apparatus 200. These sections should be held against one another firmly during surface coating. In one example, pressure may also be applied on the sections to hold them together during surface coating.

In another example, the apparatus may be a single piece of article and is not divided into sections. In this case, one of the plurality of openings of the apparatus may be configured to load an optical element into the holder of the apparatus. The optical element may be secured in the holder by applying pressure on the optical element through one of the openings of the apparatus against the walls of the apparatus. The apparatus may also be configured to have a cover to close the opening for loading the optical element.

Fig. 3 shows a cross-sectional cutaway top perspective view 3A of the apparatus 200 of Fig. 2 and a top perspective view 3B of a plurality of the apparatus 200 for holding a plurality of optical elements. The perspective view 3A shows that the apparatus 200 is configured for holding more than one of the optical element 100 of Fig. 1. The apparatus 200 comprises a plurality of holders such as 300a and 300b, wherein each holder (e.g. 300a or 300b) holds one of the plurality of the optical element 100. The perspective view 3A of the apparatus 200 shows a plurality of openings such as the openings 202, 206 and 204 for S1 , S2 and S3 surfaces of the optical element 100 respectively, shows the optical element 100 being held in the holder 300a, and shows a plurality of walls such as 220, 222 and 224. The plurality of walls such as 220, 222 and 224 are for isolating and exposing each surface of the optical element 100 to be coated. These plurality of walls are arranged to form recesses such as 302, 304, 306, and 308, wherein each recess has a depth to ensure each surface of the optical element 100 to be coated is sufficiently isolated (i.e. masked from other surfaces) and exposed for surface coating to be performed. In the present example, each recess has a shape of an inverted truncated pyramid with a centre exposing a surface of the optical element 100 to be coated. The recesses for exposing the S1 and S2 surfaces of the optical element 100 have about the same dimensions as the area to be exposed for coating are about the same size. The recess in the apparatus 200 for exposing the S3 surface of the optical element 100 has wider dimensions compared to the recess for exposing the S1 and S2 surfaces because S3 has larger dimensions compared to the surfaces of S1 and S2 to be coated.

In the perspective view 3B, there is shown a plurality of the apparatus 200 grouped together in rows and adjacently disposed with respect to one another. Each of the apparatus 200 has an elongate body (e.g. similar to a rod) comprising a plurality of evenly spaced apart and/or adjacently disposed holders such as the holders 300a and 300b in the perspective view 3A. In the present example, the elongate body of the apparatus 200 is shaped as a cuboid. The plurality of holders of the apparatus 200 is formed when the top masking jig 214 and bottom masking jig 216 are combined. When these jigs 214 and 216 are combined, they secure and enclose a plurality of the optical element 100 in a column. The arrangement of the plurality of the apparatus 200 in the view 3B can be used during surface coating process to hold a plurality of the optical element 100 and to have all S1 surfaces of the optical elements 100 face a common coating direction for coating to be applied simultaneously to all the S1 surfaces. It is an advantage compared to conventional methods that, during surface coating, each apparatus 200 can be orientated accordingly to have a target exposed surface face a coating direction for coating to be applied to the target exposed surface.

The line A-A indicating the location of division of the top masking jig 214 and the bottom masking jig 216 is shown in the perspective views 3A and 3B. In the perspective view 3B, a plane B intersecting with line A-A is shown. This plane B is indicative of a slicing plane at which all the top masking jig 214 is divided from the bottom masking jig 216 of each apparatus 200.

Although it is shown in the example of Fig. 3 that the apparatus 200 has a plurality of holders such as 300a and 300b, the apparatus 200 may be configured to have only one holder in another example.

The apparatus 200 may be made of a plastic material or other suitable materials.

With reference to Fig. 4, in a conventional method, the following steps from the manufacture of the optical element 100 of Fig. 1 to the coating of the S1 to S3 surfaces of the optical element 100 may be involved.

Step 1 : The optical element 100 is made. This can be via any volume production process such as injection molding. Step 2: S1 surface of the optical element 100 is coated by masking all other surfaces (including S2 surface of the optical element 100) of the optical element 100 using a first pair of conventional mechanical masking jigs configured to mask all the other surfaces.

Step 3: S2 surface of the optical element 100 is coated by masking all other surfaces (including S1 surface of the optical element 100) of the optical element 100 using a second pair of conventional mechanical masking jigs configured to mask all the other surfaces.

Step 4: S3 surface of the optical element 100 is coated by masking all other surfaces (including S1 and S2 surfaces of the optical element 100) of the optical element 100 using a third pair of conventional mechanical masking jigs configured to mask all the other surfaces.

Fig. 5 helps to elaborate further on the steps 1 to 4 in Fig. 4. In particular, a pair of conventional mechanical masking jigs, comprising of top and bottom masking jigs, M1 , are used for coating a surface of the optical element 100 in a conventional coating process. The pair of top and bottom masking jigs, M1 , can be assembled to each other to form a holder of a plurality of the optical element 100. The bottom masking jig has a plurality of seats 504, wherein each seat is for placing the optical element 100. The top masking jig has a plurality of recesses 502, wherein each recess has an opening to expose only one surface of the optical element 100 when the optical element 100 is placed in each seat in the bottom masking jig and the top masking jig is assembled to the bottom masking jig.

In a masking step 5A at step 2 of Fig. 4, only the S1 surface of the optical element 100 is exposed to a coating material by securing the optical element 100 between the pair of top and bottom masking jigs, M1. The coating of the material on the S1 surface may be conducted in a physical vapour deposit (PVD) chamber of a coating machine, and the coating process is performed via PVD.

In a masking step 5B at step 3 of Fig. 4, the optical element 100 is transferred to another pair of top and bottom masking jigs, M2 (not shown in Fig. 5), which are similar to the pair of top and bottom masking jigs, M1 , for exposing only the S2 surface of the optical element 100 for coating. When the optical element 100 is seated in the bottom masking jig of M2 and is secured by the assembly of the top masking jig of M2 to the bottom masking jig of M2, the S2 surface is coated by exposure to coating material in the PVD chamber.

In a masking step 5C at step 4 of Fig. 4, the optical element 100 is transferred to yet another pair of top and bottom masking jigs, M3 (not shown in Fig. 5), which are similar to the pair of top and bottom masking jigs, M1 , for exposing only the S3 surface of the optical element 100 for coating. Each recess in the top masking jig of M3 for exposing the S3 surface of the optical element 100 has wider dimensions compared to the recess of the top masking jigs of M1 and M2 for exposing S1 and S2 because S3 has larger dimensions compared to the surfaces of S1 and S2 to be coated.

Between the masking steps 5B and 5C, the optical element 100 may have to be rotated as shown by a rotation arrow in Fig. 5 to a different orientation to have the S3 surface coated according to Step 4 of Fig. 4.

After the steps 5A to 5C above, selective coating of the S1 to S3 surfaces of the optical element 100 is completed.

A major difference between the apparatus 200 of Figures 2 and 3 and the conventional masking jigs of Fig. 5 is that the apparatus 200 is a single piece of equipment comprising a plurality of openings for exposing S1 to S3 and the apparatus is orientated accordingly to have the exposed surface face a coating direction for surface coating. In contrast, 3 pairs of conventional masking jigs, each exposing only one of S1 to S3 during coating, have to be used in a conventional surface coating process. Furthermore, there involves a process of transferring each optical element from one pair of conventional masking jigs to another pair of conventional masking jigs. As a result of using the apparatus 200, the yield is greatly improved.

Fig. 6 shows examples of a pair of conventional top and bottom masking jigs 602 and 604 used for exposing only one surface of each optical element 100 of Fig. 1 placed in the jigs 602 and 604 for surface coating. A plurality of recesses 610 for exposing only S1 or S2 of each optical element 100 is present in the top masking jig 602. A plurality of seats 612 configured to accommodate the shape of the bottom portion of the optical element 100 with the S3 surface is present in the bottom masking jig 604. It should be noted that these seats 612 do not have an opening to expose the S3 surface. The top and bottom masking jigs 602 and 604 have clip-on features 606 and 608 to enable the top and bottom masking jigs 602 ant 604 to be clipped on to be assembled to each other. One disadvantage of the pair of conventional top and bottom masking jigs 602 and 604 is that they have to be disassembled and assembled into order to coat S1 and S2 surfaces. They also cannot be used to coat S3 surfaces. Another pair of conventional top and bottom masking jigs has to be provided to coat S3 surfaces.

Fig. 18 is a photograph of a close up view of the pair of conventional top and bottom masking jigs 602 and 604 in Fig. 6 when they are assembled to each other. Fig. 18 shows how they look like in reality.

Fig. 7 illustrates how a plurality of the apparatus 200 of Figures 2 and 3 are used during surface coating of a plurality of the optical element 100 held by each apparatus 200. A top half of Fig. 7 shows a drawing 7A of the plurality of the apparatus 200 grouped together and arranged in a manner that is the same as the plurality of the apparatus 200 in the view 3B of Fig. 3. As mentioned earlier, the arrangement shown in view 3B of Fig. 3 and drawing 7A is meant for simultaneous coating of the exposed S1 surfaces of the plurality of the optical element 100, which are facing a common coating direction. Specifically, in this arrangement, there comprises 6 of the apparatus 200 grouped together and adjacently disposed with respect to each other. Each apparatus 200 comprises 6 holders 702 for holding 6 of the optical element 100 respectively. Each holder 702 has 3 surfaces for exposing the S1 , S2 and S3 surfaces of each optical element 100 respectively. In this arrangement, the coating direction is top down as shown by an arrow in drawing 7A.

A bottom half of Fig. 7 shows a drawing 7B illustrating a method for coating surfaces of a plurality of the optical element 100 of Fig. 1 using the plurality of the apparatus 200. Each apparatus 200 is designed with a rod-like form factor (having a longitudinal profile) and with openings for exposing all surfaces of each optical element 100 held by the apparatus 200 to be coated.

The arrangement shown in the drawing 7A can be a first arrangement to coat all S1 surfaces of all the optical elements 100 held by the plurality of the apparatus 200. PVD can be applied to coat the S1 surfaces. After all the S1 surfaces are coated, each of the apparatus 200 is sequentially rotated by 90 degrees so that the next surface S2 to be coated faces the coating direction indicated by the arrow in drawing 7A. After all the S2 surfaces are coated, each of the apparatus 200 is sequentially rotated by about 135 degrees to face the next S3 surface to be coated in the coating direction indicated by the arrow in drawing 7A. As such, the rotation process of each apparatus 200 in the plurality of grouped apparatuses 200 is repeated until all the target S1 to S3 surfaces are coated.

Specifically, in the present example, during each rotation process, the leftmost first one of the apparatus 200 in drawing 7B is picked up via an action X, and rotated via an action Y by the predetermined angle (e.g. 90 or 135 degrees), followed by the second one of apparatus 200 adjacent to the first one of the apparatus 200, and so on, until the last one of the 6 apparatuses 200 is rotated. After coating of all surfaces of each optical element 100 is completed, each optical element 100 can be removed from the top and bottom masking jigs 214 and 216 of each apparatus 200.

The actions X and Y can be performed manually by a person, or with an orientation device such as pick and place robot arms. The orientation device may also be performed automatically by a pair of clamps or grippers for clamping or gripping sides 706 and 708 of each apparatus 200 that are opposite to each other, and for rotating the apparatus 200 by the predetermined angle (e.g. 90 or 135 degrees) about a longitudinal axis 704 of each apparatus 200. In the present example, the sides 706 and 708 of the each apparatus 200 being clamped or gripped are the sides of the apparatus 200 with the smallest surface area.

By designing each holder 702 of the apparatus 200 to have a plurality of openings 710 to expose different surfaces of each optical element 100 for coating, it is possible to coat each of these surfaces sequentially without removing each optical element 100 from the apparatus 200. In this manner, there is a significant reduction of the work required to handle each optical element 100 compared to conventional surface coating processes, which require removal of each optical element from masking jigs and transferring each optical element to different masking jigs to coat different surfaces of the optical element.

Figures 8 to 12 show different views of an example of an apparatus 800 that is similar to the apparatus 200 of Figures 2 and 3.

Specifically, Fig. 8 shows examples of a top section 814 and a bottom section 816 of the apparatus 800 that are configured to be assembled to form the apparatus 800. The apparatus 800 has an elongate body (similar to a rod) comprising a plurality of holders 810 for holding a plurality of optical elements 802 respectively. The top and bottom sections 814 and 816 are correspondingly elongate to provide the elongate body of the apparatus 800 when the top and bottom sections 814 and 816 are assembled. Each optical element of the plurality of optical elements 802 comprises more than one surfaces to be coated. The top section 814 shown in Fig. 8 has a plurality of recesses 820 comprising a plurality of openings 818.

The top and bottom sections 814 and 816 are assembled via connectors 824a and 824b located at opposite ends along a longitudinal axis 822 of the apparatus 800. The opposite ends of the top section 814 have a pair of extensions 804a and 804b respectively forming parts of the connectors 824a and 824b. The opposite ends of the bottom section 816 have a pair of extensions 806a and 806b respectively forming parts of the connectors 824a and 824b. The pair of extensions 806a and 806b comprises apertures 808a and 808b respectively for receiving corresponding protrusions (not shown) disposed on a side of the pair of extensions 804a and 804b. These protrusions are configured to connect to the apertures 808a and 808b respectively so as to assemble the top and bottom sections 814 and 816 together and prevent them from moving relative to each other. It should be appreciated that other forms of assembling the top and bottom sections 814 and 816 may also be possible. The assembly of the top and bottom sections 814 and 816 may be performed by a person manually or via a machine (e.g. a machine having robots configured for the assembly).

Fig. 9 shows the apparatus 800 of Fig. 8 with the top and bottom sections 814 and 816 assembled via the connectors 824a and 824b located at opposite ends 904a and 904b respectively of the apparatus 800. The plurality of optical elements 802 are held securely in the plurality of holders 810 by the top and bottom sections 814 and 816. The elongate body of the apparatus 800 with the longitudinal axis 822 can be seen in Fig. 9. The bottom section 816 shown in Fig. 9 has a plurality of recesses 902 for exposing two surfaces of each of the plurality of optical elements 802.

In one example, the connectors 824a and 824b may have another function, which is to attach to an equipment (or parts of a machine) to enable the apparatus 800 to rotate about the longitudinal axis 822. This can facilitate the performance of the action Y described with reference to Fig. 7.

Fig. 10 is a perspective view of the apparatus 800 of Fig. 8 in assembled form. Fig. 10 shows the plurality of recesses 820 of the top section 814 of the apparatus 800. Each of the plurality of recesses 820 has a plurality of openings 818 for exposing surfaces on a common side of each of the plurality of optical elements 802. Each of the plurality of recesses 820 has substantially truncated cone shape in the present example, and has a depth sufficient to mask the exposed surface from other surfaces of each of the plurality of optical elements 802.

Fig. 11 is a perspective view of the apparatus 800 of Fig. 8 in assembled form. Fig. 11 shows the surfaces 1102 on a common side of each of the plurality of optical element 802 being exposed by the plurality of openings 818 in the plurality of recesses 820 of the top section 814.

Fig. 12 is a side perspective view of the apparatus 800 of Fig. 8 in assembled form. The connector 824b comprising an extension 804b in the top section 814 and the extension 806b in the bottom section 816 is shown in Fig. 12.

Fig. 13 shows an enlarged view of the bottom section 816 of the apparatus 800 of Fig. 8. Three of the plurality of optical elements 802 are shown. In particular one of the optical element 1302 is about to be placed in a bottom portion 810b of one holder of the plurality of holders 810. Another optical element 1304 adjacent to the optical element 1302 is already placed in a respective bottom portion 810b. Similarly, an optical element 1306 adjacent to the optical element 1304 is also placed in a respective bottom portion 810b. A plurality of such bottom portion 810b of the plurality of holders 810 resides in the bottom section 816. Each bottom portion 810b acts like a seat for placing each of the optical elements 1302, 1304 and 1306. Each bottom portion 810b has openings 818 for exposing surfaces of the optical elements 1302, 1304 and 1306.

Fig. 14 illustrates a method of producing optical elements with coatings and provides details on a method for coating multiple surfaces of each of the optical elements (i.e. coating process) according to an example of the present disclosure.

The steps of the method of producing optical elements with coatings commences at a step 1402. In the present example, each the optical elements with coatings being produced is the optical element 100 of Fig. 1 .

In a step 1404, a plurality of the optical element 100 is manufactured via injection moulding.

The plurality of the optical element 100 is de-gated at a step 1406. In the present example, each optical element 100 is de-gated from a sprue to which the optical element 100 is attached to after the injection moulding.

Each optical element 100 is then subject to 100% visual inspection at a step 1408 to check that the produced optical element 100 has no defects. Such visual inspection can be done manually by people or done via a vision system comprising sensors (cameras), processing hardware and software algorithms for image processing. After step 1408, annealing is performed on the plurality of the optical element 100 at a step 1410. Such annealing is a process of heating the plastic optical element, for instance, to half of the melting temperature of the plastic material of the optical element for a moderate period of time before letting the plastic cool back down. When the optical element is reheated in this manner, the material relaxes and moulded stress can be reduced.

After step 1410, the coating process on the target surfaces S1 commences at a step 1412. The coating process involves 4 steps 1 A to 4A as follows.

STEP 1A: In the present example, each optical element 100 is loaded into a plurality of the apparatus 200 of Figures 2 and 3. Each optical element 100 has S1 , S2 and S3 surfaces to be coated. The apparatus 200 can be regarded as a universal masking jig. The optical element 100 may be manually loaded into the apparatus 200 by a person or automated by an equipment or machine that, for instance, has robotic features. The apparatus 200 has an elongate body comprising 6 holders adjacently disposed relative to one another. Each holder has a plurality of openings, wherein more than one of the plurality of openings exposes more than one surfaces of the optical element 100. Each opening exposing a surface is surrounded by walls to mask the exposed surface from other exposed surfaces of the optical element 100. Such masking prevents the coating process of one exposed surface from contaminating another exposed surface that is not yet scheduled for the coating process. The apparatus 200 comprises the top masking jig 214 and the bottom masking jig 216, which have to be assembled to form the apparatus 200 and the holders. At step 1A, each optical element 100 is first placed in a bottom portion (a seat) of each holder of the apparatus 200. The bottom portion is disposed in the bottom masking jig 216 of the apparatus 200. The corresponding top portion of each holder of the apparatus 200 is disposed in the top masking jig 214. After all the bottom portions of the 6 holders are filled up with 6 optical elements respectively, the top portions of each holder in the top masking jig 214 is moved to cover the optical elements, and the top masking jig 214 is connected to the bottom masking jig 216 to secure the optical elements in the holders and between the top and bottom masking jigs 214 and 216.

STEP 2A: A machine for performing the coating process is used. The machine comprises a chamber for coating surfaces of the optical elements via Physical Vapour Deposition. The machine comprises a platform (or plate) for placing a plurality of the apparatus 200, which are loaded with optical elements. The machine also comprises an activating mechanism for activating the coating process in the chamber. The platform is to be placed in the chamber. In the present example, the platform can be referred to as a calotte, and can be segmented into multiple segments. Each segment can be shaped as a sector of a circle. An example of such segment is shown as a segment 1424 in Fig. 14. Each platform may comprise one or more apparatus holders. In the present example, there are 3 aluminium apparatus holders 1420 mounted on the segment 1424. Each of the aluminium holders 1420 may have ribs 1422 for dividing the holders into 3 compartments for holding the plurality of the apparatus 200. At step 2A, each apparatus 200, which is loaded with the optical elements, are placed into the aluminium holders 1420. The plurality of the apparatus 200 are packed as densely as possible in the holders 1420 so as to coat as many optical elements as possible. The placement of the plurality of the apparatus 200 can be performed manually by a person or automated by an equipment or machine that, for instance, has robotic features. In the present example, the plurality of the apparatus 200 containing uncoated optical elements are firstly arranged in a manner similar to the arrangement of the plurality of the apparatus 200 in drawing 7A of Fig. 7. That is, all the S1 surfaces of each optical element 100 is facing a predetermined coating direction so that all the S1 surfaces can be coated simultaneously when surface coating is activated. Once the platform is filled up by the plurality of the apparatus 200 that is packed according to the arrangement to face all S1 surfaces in the predetermined coating direction, the machine is activated to enable the simultaneous coating of all the S1 surfaces. STEP 3A: After all the S1 surfaces are coated, the plurality of apparatus 200 in the coating chamber are moved such that the next surface to be coated faces a predetermined coating direction. The movement of the plurality of apparatus 200 is performed in a similar manner as that describe for drawing 7B. Specifically, in the present example, each individual apparatus 200 is picked up (e.g. via action X in drawing 7B), and rotated or flipped (e.g. via action Y in drawing 7B), so that the next surface, which is all the S2 surfaces of the optical elements, are facing the predetermined coating direction for simultaneous coating. Such movement (picking up) and rotation or flipping may be performed manually by a person or automated by an equipment or machine that, for instance, has robotic features. The plurality of the apparatus 200 may each be placed back in the same location in each aluminium holder 1420 that was placed for S1 surface coating. After the plurality of apparatus 200 are facing all exposed S2 surfaces in the predetermined coating direction, the machine is activated to enable the simultaneous coating of all the S2 surfaces.

STEP 4A: The movement and rotation or flipping process performed in step 3A above is repeated to face the next surface to be coated in a predetermined coating direction. Similarly, the movement and rotation or flipping process can be performed manually by a person or automated by an equipment or machine that, for instance, has robotic features. In the present example, the next surfaces to be coated are all the S3 surfaces of the optical elements. After all the S3 surfaces are coated, the plurality of the apparatus 200 containing coated optical elements are removed from the chamber, and the coated optical elements are removed from the plurality of the apparatus 200. Such removal of the plurality of the apparatus 200 and removal of the coated optical elements from each apparatus 200 can be performed manually by a person or automated by an equipment or machine that, for instance, has robotic features. It should be appreciated that the predetermined coating direction for S1 , S2 and S3 surfaces can be the same direction or different direction, depending on the design of the machine.

After the coating step 1412, each coated optical element 100 is subject to 100% visual inspection at a step 1414 to check that the coated optical element 100 has no defects. Such visual inspection can be done manually by people or done via a vision system comprising sensors (cameras), processing hardware and software algorithms for image processing.

A step 1416 commences after the step 1414, in which outgoing quality control (OQC) may be performed and shipment of coated optical elements 1400 to customers takes place. The method producing optical elements with coatings ends at a step 1418.

Fig. 15 illustrates installations in a coating chamber 1500 in the machine described in step 2A of Fig. 14 for coating multiple surfaces of the plurality of the optical element 100 placed in the plurality of the apparatus 200. Each apparatus 200 can be called a universal masking jig (UMJ). The chamber 1500 of the machine is for coating surfaces of the optical elements via Physical Vapour Deposition. The machine comprises a platform, called a calotte 1504 in the example of Fig. 15, for holding the plurality of the apparatus 200, which are loaded with optical elements.

Fig. 15 shows a top view of the calotte 1504 in a drawing 15A. The calotte 1504 is circular in shape and segmented. In the present example, the calotte 1504 is segmented and formed by 4 segments. Each segment is a quadrant of a circle and is detachable from the calotte 1504. The machine may comprise more than one calotte. There are 3 aluminium holders 1420 mounted on a segment 1424 in Fig. 15. This segment 1424 is the same as the one shown in Fig. 14. The plurality of the apparatus 200 are densely packed into each of the aluminium holders 1420 according to an arrangement 1502 with a common exposed surface of the optical elements facing a predetermined coating direction. The plurality of the apparatus 200 packed into each of the aluminium holders 1420 are secured by the aluminium holders 1420. During the coating process, the calotte 1504 rotates about an axis intersecting the origin of the calotte 1504, and perpendicular to the circular plane of the calotte 1504.

Fig. 15 shows a cross-sectional side view of the calotte 1504 in a drawing 15B. When the calotte 1504 rotates during the coating process, coating materials are deposited in a predetermined coating direction on the plurality of the apparatus 200 mounted to the calotte 1504 via an ion cloud.

Fig. 16 is a photograph showing how an example of a machine 1600 described with reference to Fig. 15 looks like when being operated on by an operator 1610. The machine 1600 comprises the coating chamber 1500, which has a door 1604 with a door handle 1606 for closing the chamber 1500 during the coating process. The machine 1600 comprises an activation mechanism 1612 for activating the coating process. The activation mechanism 1612 is a computer in the present example. A display 1602 is connected to the computer to provide a graphical user interface for the operator 1610 to monitor and control the coating process. The machine 1600 has a power switch for turning on or off the coating process and/or switching on or off the machine 1600.

Fig. 17 is a photograph showing an assembled conventional masking jig 1702 comprising the top and bottom masking jigs 602 and 604 of Fig. 6, and two assembled apparatuses 800 of Fig. 8, each comprising the top and bottom sections 814 and 816. It can be seen from Fig. 17 that the length of the assembled conventional masking jig 1702 is about 5cm and the length of each apparatus 800 is about 6.5cm. The length of the apparatus 800 determines the number of optical elements to coat simultaneously.

In summary, in the conventional design of masking jigs for surface coating of an optical element, if there are 3 surfaces of the optical element to be coated, 3 separate masking jigs are required in the surface coating process. The optical element has to be transferred from one jig to another in the process. Excessive handling of the optical element is present and this results in low yield and output, and leads to higher cost. In contrast, for 3 surfaces of an optical element to be coated, only one of the universal masking jig proposed in the examples described in the present disclosure is required in the surface coating process of the optical element for coating all the 3 surfaces. The optical element stays in the jig until all the 3 surfaces are coated. Yield and output is significantly improved, and this can lead to lower cost.

Examples of the present disclosure may have the following features. The reference numerals of the elements in the Figures resembling the features stated are provided to indicate that they are examples of such features.

An apparatus (e.g. 200 or 800) for coating surfaces of optical elements (e.g. 100, 802, 1302, 1304, or 1306), wherein the apparatus comprises: a body with a holder (e.g. 300a, 300b, 702 or 810) for holding an optical element (e.g. 100, 802, 1302, 1304, or 1306) in position for coating more than one surfaces (e.g. S1 to S3) of the optical element, wherein the holder has a plurality of openings (e.g. 710 or 818), wherein when the optical element is held in position in the holder, the plurality of openings exposes more than one surfaces of the optical element to enable each of the more than one surfaces to be coated with a layer of material.

The body may be elongate and the body has more than one of the holder arranged along the length of the elongate body. The more than one of the holder may be evenly spaced apart along the length of the body.

The body may have more than one sections (e.g. 214 and 216, and 814 and 816) configured to form the holder when the more than one sections are assembled to one another.

The body may have two sections (e.g. 214 and 216, and 814 and 816), one of the two sections comprises a bottom portion (e.g. 810b) of the holder and the optical element is to be placed into the bottom portion of the holder, and the other one of the two sections comprises a top cover of the holder for covering the optical element, wherein the optical element is held within a space (e.g. 212) defined by the bottom portion and the top cover of the holder when the two sections are assembled to form the holder.

The body may be configured to be orientated to direct a surface of the optical element exposed by one of the plurality of openings to face a predetermined direction for coating said exposed surface.

The body may be elongate and comprise connectors (e.g. 824a and 824b) disposed at opposite ends (e.g. 706 and 708, and 904a and 904b) along a longitudinal axis (e.g. 704 or 822) of the body for the sections of the body to connect to one another.

Each of the plurality of openings exposing a surface of the optical element may be surrounded by walls to mask the exposed surface from other exposed surfaces of the optical element.

A machine (e.g. 1600) for coating surfaces of optical elements, wherein the machine comprises: a chamber (e.g. 1500) for coating surfaces of a plurality of optical elements; a platform (e.g. 1504) in the coating chamber configured to have a plurality of the apparatus described above (e.g. 200 or 800) held securely on the platform, wherein the plurality of the apparatus is grouped together to provide a plurality of adjacently disposed holders for holding the plurality of the optical element, and the plurality of the apparatus is arranged on the platform such that a common exposed surface of each of the plurality of the optical element is facing a coating direction for simultaneous coating of the common exposed surface; and an activation mechanism (e.g. 1602) to activate simultaneous coating of the common exposed surface.

The machine may comprise: an orientation device for rotating the bodies of the plurality of the apparatus to direct a surface of each optical element exposed by one of the plurality of openings to face the coating direction for coating said exposed surface.

The platform may comprise a plurality of apparatus holders (e.g. 1420) mounted on the platform for holding the plurality of the apparatus.

A method for coating surfaces of optical elements (e.g. 100, 802, 1302, 1304, or 1306), the method comprising: loading an optical element (e.g. 100, 802, 1302, 1304, or 1306) into a holder (e.g. 300a, 300b, 702 or 810) of a body of an apparatus to be held in position by the holder for coating more than one surfaces (e.g. S1 to S3) of the optical element (e.g. step 1A), wherein the holder has a plurality of openings (e.g. 710 or 818), wherein when the optical element is held in position in the holder, the plurality of openings exposes more than one surfaces of the optical element to enable each of the more than one surfaces to be coated with a layer of material; and coating each of the more than one surfaces of the optical element (e.g. steps 3 A and 4A).

The method may comprise: assembling more than one sections of the body of the apparatus to form the holder.

The method may comprise: orientating the body of the apparatus to direct a surface of the optical element exposed by one of the plurality of openings to face a coating direction for coating said exposed surface (e.g. step 3A or step 4A).

The method may comprise: grouping a plurality of the apparatus to provide a plurality of adjacently disposed holders for holding a plurality of the optical element (e.g. step 2A); and arranging the plurality of apparatus to have a common exposed surface of each of the plurality of the optical element to face the coating direction for simultaneous coating of the common exposed surface of each of the plurality of the optical element (e.g. steps 2A, 3A and 4A).

In the specification and claims, unless the context clearly indicates otherwise, the term “comprising” has the non-exclusive meaning of the word, in the sense of “including at least” rather than the exclusive meaning in the sense of “consisting only of”. The same applies with corresponding grammatical changes to other forms of the word such as “comprise”, “comprises” and so on.

The foregoing written specification is considered to be sufficient to enable one skilled in the art to practice the invention. The present invention is not to be limited.

While the invention has been described in connection with a number of examples and implementations, the invention is not so limited but covers various obvious modifications and equivalent arrangements, which fall within the purview of the appended claims. Although features of the invention are expressed in certain combinations among the claims, it is contemplated that these features can be arranged in any combination and order.