Abstract:
One aspect involves: supporting a workpiece with workpiece support structure that includes spaced support parts, a support section supporting the support parts, and a workpiece holding adhesive on each support part, where the adhesives engage respective regions of a surface portion on the workpiece; and supplying a coating material toward a different surface portion of the workpiece. A different aspect involves: supporting a workpiece with workpiece support structure that includes a workpiece support member with a surface portion extending approximately parallel to a direction, and a workpiece support part having two adhesive portions that respectively engage the surface portion on the support member and a surface portion on the workpiece; and supplying a coating material in the direction, toward a different surface portion of the workpiece.

Description:
FIELD OF THE INVENTION 
     This invention relates in general to coating techniques and, more particularly, to techniques for supporting workpieces during a coating process. 
     BACKGROUND 
     When fabricating optical components such as lenses, it is very common to form a coating on an optical surface of the component, where the coating provides desired optical or physical properties. For example, the coating may provide an anti-reflective (AR) characteristic, a filtering characteristic, physical protection for the component, some other characteristic, or a combination of two or more characteristics. These coatings often include multiple layers of different materials that collectively provide the desired characteristic(s). 
     It is often desirable that a coating completely cover an optical surface that is being coated. However, as discussed in more detail later, conventional workpiece support fixtures often support a workpiece in a manner that obstructs at least part of a peripheral portion of the optical surface, and these covered regions do not end up being coated. Consequently, although conventional support fixtures have been generally adequate for their intended purposes, they have not been entirely satisfactory in all respects. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A better understanding of the present invention will be realized from the detailed description that follows, taken in conjunction with the accompanying drawing, in which: 
         FIG. 1  is diagrammatic sectional side view of a conventional coating apparatus, having conventional support fixtures that support conventional workpieces. 
         FIG. 2  is a diagrammatic fragmentary sectional side view of a workpiece and a workpiece support fixture from the apparatus of  FIG. 1 . 
         FIG. 3  is a diagrammatic fragmentary sectional side view similar to  FIG. 2 , but showing a different conventional workpiece supported by the workpiece support fixture. 
         FIG. 4  is a diagrammatic side view, partly in section, showing a workpiece support fixture that embodies aspects of the invention, and that can be used in place of the conventional workpiece support fixture of  FIGS. 1 and 2 , and also showing a workpiece supported in the fixture. 
         FIG. 5  is a diagrammatic fragmentary side view of a portion of the apparatus of  FIG. 4 . 
         FIG. 6  is a diagrammatic fragmentary sectional side view, showing a further embodiment of a workpiece support fixture that embodies aspects of the invention, and that can be used in place of the conventional workpiece support fixture of  FIGS. 1 and 2 , and also showing a workpiece supported in the fixture. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is diagrammatic sectional side view of a conventional coating apparatus  10 . The coating apparatus  10  includes a housing  12  with a chamber  13  therein. During a typical coating operation, a vacuum is maintained in the chamber  13  by a not-illustrated vacuum pump. The housing  12  supports a primary axle  17  for rotation about a primary vertical axis  18 . A support part  19  is supported on the axle  17  within the chamber  13  for rotation with the axle about the axis  18 . In the disclosed embodiment, the support  19  is disk-shaped, but it could alternatively have any other suitable shape. 
     The support part  19  rotatably supports two workpiece support members  21  and  22 . More specifically, two additional vertical axles  23  and  24  are rotatably supported on the support part  19 . These additional axles are spaced circumferentially from each other about the primary axle  17 , and each rotate about a respective additional vertical axis  26  or  27 . The two support members  21  and  22  are each supported on a respective one of the axles  23  and  24  for rotation therewith about the associated axis  26  or  27 . In the disclosed embodiment, the support members  21  and  22  are disk-shaped, but they could each alternatively have any other suitable shape. Although  FIG. 1  shows two workpiece support members  21  and  22 , with respective axles  23  and  24 , it would alternatively be possible to have one or more additional workpiece support members with respective axles, where the axles for all workpiece support members are spaced circumferentially from each other about the primary axle  17 . 
     A drive mechanism  31  such as an electric motor is coupled to the axle  17 , in order to effect rotation of the axle  17  and the support part  19 . A not-illustrated planetary gearing mechanism of a well-known type is provided and, in response to rotation of the support part  19  with respect to the housing  12 , effects rotation of the additional axles  23  and  24  with respect to the support part  19 . Thus, the workpiece support numbers  21  and  22  each undergo planetary movement about the primary axis  18  with respect to the housing  12 . Each of the workpiece support members  21  and  22  has thereon a respective workpiece support fixture  36  or  37 . The workpiece support fixtures  36  and  37  will be described in more detail later. The primary axle  17 , the support part  19 , the additional axles  23  and  24 , the workpiece support members  21  and  22 , and the workpiece support fixtures  36  and  37  collectively serve as a workpiece support mechanism. For simplicity and clarity,  FIG. 1  shows each of the workpiece support members  21  and  22  with just one workpiece support fixture  36  or  37  thereon. However, it would alternatively be possible for each of the workpiece support members  21  and  22  to have a plurality of workpiece support fixtures thereon. 
     Each of the workpiece support fixtures  36  and  37  is configured to removably support a respective workpiece  41  or  42 . The workpieces  41  and  42  each have a surface  43  or  44  on a lower side thereof. The apparatus  10  is used to form respective coatings  51  and  52  on the surfaces  43  and  44  of the workpieces  41  and  42 , in a manner discussed later. In the disclosed embodiment, the workpieces  41  and  42  with the coatings  51  and  52  are each an optical component of a well-known type, such as a lens. Therefore, they are described here only briefly, to the extent necessary to facilitate an understanding of various aspects of the present invention. Further, it should be understood that the coating apparatus  10  is not limited to use for coating optical components, but instead can be used for coating any of a wide variety of other types of workpieces. 
     It would be possible for each of the coatings  51  and  52  to be only a single layer of a single material. But in the disclosed embodiment, the coatings  51  and  52  each happen to include a plurality of different layers, involving the use of one material for some layers, another material for other layers, and so forth. By interleaving different layers of different materials in a known manner, the coatings  51  and  52  can each be given certain desired optical characteristics. For example, the coatings  51  and  52  may each provide an anti-reflective (AR) characteristic that causes little or no reflection of a selected range of wavelengths, such as a range corresponding to visible light. 
     In some cases, the multi-layer coatings  51  and  52  will be configured in a known manner to provide a combination of two or more desired optical characteristics. For example, a given coating might provide an anti-reflection characteristic as to one range of wavelengths, such as visible light, while also filtering out wavelengths in a different range of wavelengths, such as a range associated with laser energy. 
     As another example, if the optical workpiece  41  or  42  happens to be made of a relatively soft material that was selected because it provides certain desirable optical properties, the coating  51  or  52  may be configured to be physically harder than the associated workpiece  41  or  42 , in order to help physically protect the material of the workpiece  41  or  42 . Thus, a given coating  51  or  52  may provide an anti-reflection characteristic, while also being physically harder than the material of the associated workpiece  41  or  42 , in order to help physically protect the workpiece. The discussion here of anti-reflection characteristics, filtering characteristics and hardness characteristics is merely exemplary. The coatings  51  and  52  may each provide some or all of these characteristics, and/or any of a variety of other characteristics, separately or in combination. 
     The coating apparatus  10  includes a source  62  within the housing  12 , in a lower portion of the chamber  13 . The source  62  is spaced downwardly from the support part  19 . The source  62  and the drive mechanism  31  are both controlled by a control unit  64  of a known type. Although  FIG. 1  shows only a single source  62 , it would alternatively be possible to provide two or more sources in the apparatus  10 . In the disclosed embodiment, the source  62  is spaced radially from the primary axis  18 , and is positioned approximately below the path of travel of the workpiece support members  21  and  22 . However, it would alternatively be possible for the source  62  to be positioned at any of a variety of other locations within the housing  12 . 
     The source  62  is a device of a type well known in the art, and is therefore described here only briefly. In the disclosed embodiment, the source  62  is a type of device commonly referred to as an electron beam evaporator. However, the source  62  could alternatively be any other suitable type of device. The source  62  contains two or more different materials that will be used to form respective layers in each of the multi-layer coatings  51  and  52 , and the source can selectively evaporate any of these different materials. At any given point in time, the source  62  will typically be evaporating only one of the multiple materials that it contains. But in some situations, the source may simultaneously evaporate two or more of these different materials. 
     When the source  62  is evaporating a material, a plume of the evaporated material travels upwardly, as indicated diagrammatically by arrows  71 - 74 . The plume  71 - 74  has a dispersion angle  91 . The plume  71 - 74  from the source  62  coats the surfaces  43  and  44  on the workpieces  41  and  42  as the workpieces pass above the source  62 . 
       FIG. 2  is a diagrammatic fragmentary sectional side view of the workpiece support fixture  36  and the workpiece  41  of  FIG. 1 , where the workpiece is shown without the coating  51 . The workpiece support fixture  36  includes a cylindrical annular sleeve  101 , with an inwardly-projecting annular flange  102  at its lower end. Although the sleeve  101  and flange  102  in the disclosed embodiment are cylindrical, they could alternatively have any other suitable shape, for example in dependence on the shape of the particular workpiece that is to be supported. In  FIG. 2 , the surface  43  on the lower side of the workpiece  41  has a diameter  106 , and the circular opening through the flange  102  has an inner diameter  107 , which is less that the diameter  106 . It is desirable that the apparatus  10  form a coating that covers the entire surface  43 , such that the coating also has a diameter  106 . However, the flange  102  obstructs the peripheral edge of the surface  43 , and prevents it from being coated. Thus, with reference to  FIGS. 1 and 2 , the coating  51  ends up covering only part of the surface  43 , and having a diameter  107 . 
       FIG. 3  is a diagrammatic fragmentary sectional side view similar to  FIG. 2 , but showing a different conventional workpiece  121  that is also an optical lens. The lens  121  has a highly curved convex surface  122  on one side thereof, and a highly curved concave surface  123  on the other side thereof. As a result, the workpiece  121  is relatively thin. The workpiece  121  has an annular, outwardly-facing cylindrical side surface  126  adjacent a peripheral edge of the surface  122 . In addition, the workpiece  121  has an annular, planar edge surface  127  that faces approximately upwardly in  FIG. 3 . 
     As discussed above, the flange  102  on the workpiece support fixture  36  has an inside diameter  107 . The workpiece surface  122  that is to be coated has a diameter  131  that is greater than the diameter  107 . Consequently, when a coating is formed on the surface  122 , the coating has a diameter  107 , and does not cover the peripheral edges of the surface  122 . 
     In the case of the lens or workpiece  121 , there is a further consideration. As noted above, the workpiece  121  is relatively thin. The material of the workpiece  121  may have a coefficient of thermal expansion (CTE) that is different from the CTE of the workpiece support fixture  36 . If the interior of the chamber  13  is heated during a coating operation, the workpiece  121  may expand faster than the fixture  36 , causing compressive forces to be exerted on the workpiece  121  by the fixture  36 , and thereby causing the workpiece  121  to shatter. Similarly, if the interior of the chamber  13  is cooled during a coating operation, and if the fixture  36  contracts more rapidly than the workpiece  121 , the fixture  36  may exert compressive forces on the workpiece  121  that cause it to shatter. 
       FIG. 4  is a diagrammatic side view, partly in section, showing the workpiece  41  and a workpiece support fixture  201 , where the workpiece support fixture  201  embodies aspects of the present invention, and can be used in place of the workpiece support fixture  36  of  FIGS. 1 and 2 . The workpiece support fixture  201  includes several support wires, two of which are visible at  203  and  204  in  FIG. 4 . In the disclosed embodiment, the support wires  203 - 204  are identical, each have a degree of flexibility, and are each made of metal. However, they could alternatively be made of any other suitable material. 
     The support wires are provided at circumferentially spaced locations about the workpiece  41 . Each has a vertical central portion  206  or  207 , and an upper end portion  208  or  209  that is bent to extend horizontally outwardly at a right angle to the associated central portion  206  or  207 . The workpiece support fixture  201  includes a clamping mechanism having two annular clamping elements  211  and  212  that are capable of a small amount of relative vertical movement. The upper end portions  208  and  209  of the wires  203  and  204  are each removably clamped between the clamping elements  211  and  212 . 
     The support wires  203  and  204  each also have a lower end portion  216  or  217  that is bent to extend at approximately a right angle to the associated central portion  206  or  207 , and approximately parallel to an outwardly-facing cylindrical side surface  218  of the workpiece  41 . In this regard,  FIG. 5  is a diagrammatic fragmentary side view of a portion of the apparatus shown in  FIG. 4 , and depicts the lower end portion  217  of the wire  204  and a portion of the side surface  218  on the workpiece  41 . A bead of workpiece adhesive  221  or  222  is provided between the side surface  218  of workpiece  41 , and the lower end portion  216  or  217  of a respective wire  203  or  204 . The workpiece adhesives  221  and  222  are vacuum-compatible, and each bond the workpiece side surface  218  to the lower end portion  216  or  217  of a respective wire  203  or  204 . In the disclosed embodiment, the adhesive used at  221  and  222  is a product that is commercially available under the registered trademark VACSEAL®, for example as catalog part number 05049-AB from Structure Probe, Inc. (SPI® Supplies) of West Chester, Pa. However, it would alternatively be possible to use any other suitable adhesive. 
     With reference to  FIGS. 4 and 5 , it will be noted that the workpiece support fixture  201  cooperates with the side surface  218  of the workpiece  41 , and does not obstruct any portion of the surface  43  that is to be coated. Consequently, the entire surface  43  will be coated by the apparatus  10 . In addition, as mentioned above, the wires  203  and  204  each have a degree of flexibility. Consequently, if the chamber  13  is heated and/or cooled during the coating process, such that the workpiece  41  expands and/or contracts, the wires  203  and  204  will flex slightly to absorb the expansion and/or contraction, without exerting any force on the workpiece that would be sufficient to shatter the workpiece. 
     Although  FIGS. 4 and 5  depict the workpiece support fixture  201  with the workpiece  41  supported therein, the fixture can alternatively support any of a variety of other workpieces, including but not limited to the workpiece  121  shown in  FIG. 3 . For the workpiece  121 , the workpiece adhesives  221  and  222  could adhesively engage either the side surface  126  or the edge surface  127 . 
       FIG. 6  is a diagrammatic fragmentary sectional side view of the workpiece  41 , and a workpiece support fixture  251  that embodies aspects of the invention, and that can be used in place of the fixture  36  of  FIG. 1 . The fixture  251  includes an annular cylindrical support member  256 , with an outside diameter that is approximately equal to the outside diameter of the cylindrical side surface  218  of the workpiece  41 . Alternatively, if the workpiece had a side surface that was not cylindrical, the support member  256  could be configured so that its exterior surface conformed to the shape of the side surface on the workpiece. At its lower end, the support member  256  has a downwardly-facing annular end surface  258 , which is faces and is adjacent a top surface  261  of the workpiece  41 , and which is curved to match the curvature of the workpiece top surface  261 . 
     The workpiece support fixture  251  also includes a piece of flexible, vacuum-compatible tape  271  that extends around both the workpiece  41  and the lower end of the support member  256 , in engagement with each. The tape includes an elongate flexible strip or carrier  273 , with an adhesive layer  274  on the inner side thereof. The lower portion of the adhesive layer  274  engages the side surface  218  on the workpiece  41 , and the upper portion of the adhesive layer engages the lower portion of the outwardly facing side surface on the support member  256 . In the disclosed embodiment, the tape  271  is a product obtained commercially under the trademark KAPTON® from C.S. Hyde Company, Inc. of Lake Villa, Ill. KAPTON® tape is commercially available in a variety of widths and with a variety of different levels of adhesion, and the particular tape selected for use at  271  will depend on factors such as the size and weight of the particular workpiece that is to be supported. Although the disclosed embodiment uses KAPTON® tape, it would alternatively be possible to use any other suitable part. 
     Although  FIG. 6  depicts the workpiece support fixture  251  with the workpiece  41  supported therein, the workpiece support fixture  251  is capable of supporting a wide variety of other types of workpieces, including but not limited to the workpiece shown at  121  in  FIG. 3 . In the case of the workpiece  121 , the lower portion of the adhesive layer  274  on the tape  271  would engage the side surface  126  of the workpiece  121 . 
     It will be noted from  FIG. 6  that, since the tape  271  engages the side surface  218  of the workpiece  41 , the surface  43  that is to be coated remains completely unobstructed. Thus, when the workpiece support fixture  251  is used, the apparatus  10  can form a coating that covers the entire surface  43 , including its peripheral edges. In addition, since the tape  271  is flexible, if the chamber  13  is heated and/or cooled during the coating process, such that the workpiece fixture  251  and/or the workpiece expands and/or contracts, the tape  271  will flex in order to accommodate differences in the rates of expansion and/or contraction of these parts. Consequently, the workpiece support fixture  251  will not exert any forces on the workpiece that would tend to cause the workpiece to shatter. 
     Although a selected embodiment has been illustrated and described in detail, it should be understood that a variety of substitutions and alterations are possible without departing from the spirit and scope of the present invention, as defined by the claims that follow.