Patent Publication Number: US-9845546-B2

Title: Sub-surface marking of product housings

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority benefit of U.S. Provisional Application No. 61/252,623, filed Oct. 16, 2009 and entitled “SUB-SURFACE MARKING OF PRODUCT HOUSINGS,” which is hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to marking products and, more particularly, marking outer housing surfaces of electronic devices. 
     Description of the Related Art 
     Consumer products, such as electronic devices, have been marked with different information for many years. For example, it is common for electronic devices to be marked with a serial number, model number, copyright information and the like. Conventionally, such marking is done with an ink printing or stamping process. Although conventional ink printing and stamping is useful for many situations, such techniques can be inadequate in the case of handheld electronic devices. The small form factor of handheld electronic devices, such as mobile phones, portable media players and Personal Digital Assistants (PDAs), requires that the marking be very small. In order for such small marking to be legible, the marking must be accurately and precisely formed. Unfortunately, however, conventional techniques are not able to offer sufficient accuracy and precision. Thus, there is a need for improved techniques to mark products. 
     SUMMARY OF THE INVENTION 
     The invention pertains to techniques or processes for providing markings on products. In one embodiment, the products have housings and the markings are to be provided on sub-surfaces of the housings. For example, a housing for a particular product can include an outer housing surface and the markings can be provided on a sub-surface the outer housing surface yet still be visible from the outside of the housing. Since the markings are beneath the surface of the housing, the markings are durable. The markings provided on products can be textual and/or graphic. The markings can be formed with high resolution. The markings are also able to be dark, even on metal surfaces. 
     In general, the markings (also referred to as annotations or labeling) provided on products according to the invention can be textual and/or graphic. The markings can be used to provide a product (e.g., a product&#39;s housing) with certain information. The marking can, for example, be use to label the product with various information. When a marking includes text, the text can provide information concerning the product (e.g., electronic device). For example, the text can include one or more of: name of product, trademark or copyright information, design location, assembly location, model number, serial number, license number, agency approvals, standards compliance, electronic codes, memory of device, and the like). When a marking includes a graphic, the graphic can pertain to a logo, a certification mark, standards mark or an approval mark that is often associated with the product. The marking can be used for advertisements to be provided on products. The markings can also be used for customization (e.g., user customization) of a housing of a product. 
     The invention can be implemented in numerous ways, including as a method, system, device, or apparatus. Several embodiments of the invention are discussed below. 
     As a method for marking an article, one embodiment can, for example, include at least providing a metal structure for the article, anodizing at least a first surface of the metal structure; and subsequently altering surface characteristics of selective portions of an inner unanodized surface of the metal structure. In one embodiment, the altering of the surface characteristics can be performed by directing a laser output through the anodized first surface of the metal structure towards the inner unanodized surface of the metal structure. 
     As an electronic device housing, one embodiment of the invention can, for example, include at least a housing structure that includes at least an outer portion and an inner portion. The outer portion is anodized and the inner portion is unanodized. In addition, to provide predetermined marking of the electronic device housing, a surface of the inner portion adjacent the outer portion has selectively altered surface regions. 
     As a housing arrangement, one embodiment of the invention can, for example, include a base metal layer, an additional layer, and sub-surface marking indicia. The additional layer has a first bonding surface and a first exterior surface. The first bonding surface is bonded to a first surface of the base metal layer, and the first exterior surface serves as an exterior of the housing arrangement. The sub-surface marking indicia are formed on the first surface of the base metal layer. 
     Other aspects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which: 
         FIG. 1  is a diagram of a marking state machine according to one embodiment of the invention. 
         FIG. 2  is an illustration of a substrate having sub-surface alterations  202  according to one embodiment. 
         FIG. 3  is a flow diagram of a marking process according to one embodiment. 
         FIGS. 4A-4C  are diagrams illustrating marking of a metal structure according to one embodiment. 
         FIG. 5  is a flow diagram of a multi-stage marking process according to another embodiment. 
         FIG. 6  is a flow diagram of a marking process according to one embodiment. 
         FIGS. 7A-7D  are diagrams illustrating marking of a metal structure according to one embodiment. 
         FIG. 8  is a flow diagram of a multi-stage marking process according to another embodiment. 
         FIG. 9  is a flow diagram of a multi-stage marking process according to still another embodiment. 
         FIG. 10A  is a diagrammatic representation of an exemplary housing  1000  on which a mask is to be placed. 
         FIG. 10B  is a diagrammatic representation of the same exemplary housing shown in  FIG. 10A  after a mask has been placed over an exposed stainless steel surface in accordance with one embodiment. 
         FIG. 11  illustrates the product housing having markings according to one exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention pertains to techniques or processes for providing markings on products. In one embodiment, the products have housings and the markings are to be provided on sub-surfaces of the housings. For example, a housing for a particular product can include an outer housing surface and the markings can be provided on a sub-surface the outer housing surface yet still be visible from the outside of the housing. Since the markings are beneath the surface of the housing, the markings are durable. The markings provided on products can be textual and/or graphic. The markings can be formed with high resolution. The markings are also able to be dark, even on metal surfaces. 
     In general, the markings (also referred to as annotations or labeling) provided on products according to the invention can be textual and/or graphic. The markings can be used to provide a product (e.g., a product&#39;s housing) with certain information. The marking can, for example, be use to label the product with various information. When a marking includes text, the text can provide information concerning the product (e.g., electronic device). For example, the text can include one or more of: name of product, trademark or copyright information, design location, assembly location, model number, serial number, license number, agency approvals, standards compliance, electronic codes, memory of device, and the like). When a marking includes a graphic, the graphic can pertain to a logo, a certification mark, standards mark or an approval mark that is often associated with the product. The marking can be used for advertisements to be provided on products. The markings can also be used for customization (e.g., user customization) of a housing of a product. 
     Exemplary embodiments of the invention are discussed below with reference to  FIGS. 1-11 . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes as the invention extends beyond these limited embodiments. 
       FIG. 1  is a diagram of a marking state machine  100  according to one embodiment of the invention. The marking state machine  100  reflects three (3) basic states associated with marking an electronic device. Specifically, the marking can mark a housing of an electronic device, such as a portable electronic device. 
     The marking state machine  100  includes a substrate formation state  102 . At the substrate formation state  102 , a substrate can be obtained or produced. For example, the substrate can represent at least a portion of a housing surface of an electronic device. Next, the marking state machine  100  can transition to a protective surface state  104 . At the protective surface state  104 , a protective surface can be formed or applied to at least one surface of the substrate. The protective surface can be used to protect the surface of the substrate. For example, the protective surface can be a more durable surface than that of the surface. Next, the marking state machine  100  can transition to a sub-surface marking state  106 . At the sub-surface marking state  106 , marking can be produced on a sub-surface of the substrate. In particular, the sub-surface marking can be performed on the substrate below the protective surface. The protective surface is typically substantially translucent to allow the sub-surface marking to be visible through the protective surface. The marking can be provided with high resolution and can be protected. Since the marking is provided on a sub-surface, the marking is not only protected but also has the cosmetic advantage of not being perceptible of tactile detection on the surface. 
       FIG. 2  is an illustration of a substrate  200  having sub-surface alterations  202  according to one embodiment. The sub-surface alterations  202  are provided below an outer surface  204  of the substrate  200 . Given that the outer surface  204  is typically substantially translucent (e.g., clear), the sub-surface alterations  202  are visible by a user through the outer surface  204 . Accordingly, the sub-surface alterations  202  can provide markings on the substrate  200 . Since the markings are provided by the sub-surface alterations  202 , the markings are protected by the outer surface  204 . 
     The substrate  200  can represent at least a portion of a housing of an electronic device. The marking being provided to the substrate can provide text and/or graphics to an outer housing surface of a portable electronic device. The marking techniques are particularly useful for smaller scale portable electronic devices, such as handheld electronic devices. Examples of handheld electronic devices include mobile telephones (e.g., cell phones), Personal Digital Assistants (PDAs), portable media players, remote controllers, pointing devices (e.g., computer mouse), game controllers, etc. 
     The marking is, in one embodiment, particularly well-suited for applying text and/or graphics to a housing of an electronic device. As noted above, the substrate can represent a portion of a housing of an electronic device. Examples of electronic devices, namely, handheld electronic devices, include mobile telephones (e.g., cell phones), Personal Digital Assistants (PDAs), portable media players, remote controllers, pointing devices (e.g., computer mouse), game controllers, etc. 
       FIG. 3  is a flow diagram of a marking process  300  according to one embodiment. The marking process  300  can be performed on an electronic device that is to be marked. The marking process  300  is, for example, suitable for applying text or graphics to a housing (e.g., an outer housing surface) of an electronic device. The marking can be provided such that it is visible to users of the electronic device. However, the marking can be placed in various different positions, surfaces or structures of the electronic device. 
     The marking process  300  can provide  302  a metal structure for an article to be marked. The metal structure can pertain to a metal housing for an electronic device, such as a portable electronic device, to be marked. The metal structure can be formed of one metal layer. The metal structure can also be formed of multiple layers of different materials, where at least one of the multiple layers is a metal layer. The metal layer can, for example, be or include aluminum, titanium, niobium or tantalum. 
     After the metal structure has been provided  302 , a surface of the metal structure can be anodized  304 . Typically, the surface of the metal structure to be anodized  304  is an outer or exposed metal surface of the metal structure. The outer or exposed surface typically represents an exterior surface of the metal housing for the electronic device. Thereafter, surface characteristics of selected portions of an inner unanodized surface of the metal structure can be altered  306 . The inner unanodized surface can be part of the metal layer that was anodized, or part of another layer that was not anodized. The surface characteristics can be altered  306  using a laser, such as an infrared wavelength laser (e.g., picosecond pulsewidth infrared laser). For example, one specific suitable laser is a six (6) Watt infrared wavelength picosecond pulsewidth laser at 1000 KHz with a scan speed of 50 mm/sec. Following the block  306 , the marking process  300  can end. 
       FIGS. 4A-4C  are diagrams illustrating marking of a metal structure according to one embodiment.  FIG. 4A  illustrates a base metal structure  400 . As an example, the base metal structure  400  can be formed of aluminum, titanium, niobium or tantalum.  FIG. 4B  illustrates the base metal structure  400  after an upper surface has been anodized to form an anodized surface  402 . The thickness of the anodized surface  402  can, for example, be about 5-20 microns. After the anodized surface  402  has been formed on the base metal structure  400 ,  FIG. 4C  illustrates altered surfaces  404  being selectively formed on an inner unanodized surface  406 . The altered structures  404  are formed by optical energy  408  produced by a laser  410  (e.g., infrared wavelength laser). The altered surfaces  404  combine to provide marking of the metal structure. For example, the altered surfaces  404  appear to be black and thus when selectively formed can provide marking. The resulting marking is visible through the anodized surface  402  which can be substantially translucent. If the anodized surface  402  is primarily clear, the resulting marking can be appear as black. The marking can also be provided in gray scale. If the anodized surface is dyed or colored, the markings may appear in different colors. 
       FIG. 5  is a flow diagram of a multi-stage marking process according to another embodiment. As shown in  FIG. 5 , a substrate  500  can be provided to an anodizing process that causes an anodized surface  504  to be formed on at least one surface of the substrate  500 . The substrate  500  includes an exposed surface  502 . The anodizing provided by the anodizing process serves to anodize the exposed surface  502 . Once anodized, the exposed surface  502  is an anodized exposed surface  502 ′. After the substrate  500  has been anodized by the anodizing process, the anodized substrate  500 ′ can be provided to a marking process. The marking process operates to produce altered surfaces  506  to the anodized substrate  500 ′ below the anodized exposed surface  502 ′. The altered surfaces  506  provide the marking to the anodized substrate  500 ′. By controlling size, placement and/or darkness of the altered surfaces  506 , the marking can be selectively provided to the anodized substrate  500 ′. 
       FIG. 6  is a flow diagram of a marking process  600  according to one embodiment. The marking process  600  can, for example, be performed by a marking system that serves to mark an electronic product. The marking process  600  can be performed on an electronic device that is to be marked. The marking process  600  is, for example, suitable for applying text or graphics to a housing (e.g., an outer housing surface) of the electronic device. The marking can be provided such that it is visible to a user of the electronic device. The marking can be placed in various different positions, surfaces or structures of the electronic device. 
     The marking process  600  can obtain  602  a substrate for a housing arrangement. Here, it is assumed that the electronic product to be marked includes a housing and that such housing is to be marked. After the substrate for the housing arrangement has been obtained  602 , a laminate material can be adhered  604  to a surface of the substrate. In this embodiment, the laminate material is adhered  604  to the surface of the substrate to provide strength, cosmetic appeal, etc. For example, if the substrate is a metal, such as stainless steel, then the laminate layer can pertain to aluminum) or other material capable of being anodized). 
     Next, portions of the substrate can be masked  606 . Here, since the substrate is going to undergo an anodization process, those portions of the substrate that are not to be anodized can be masked  606 . Masking prevents an anodization to certain surfaces of the substrate or the laminate material adhered to the substrate. After portions of the substrate or laminate material are masked, the laminate material (that is not been masked off) can be anodized  608 . Following the anodization, the mask can be removed  610 . 
     Thereafter, laser output from a laser can be directed  612  to selected portions of the substrate beneath the anodized laminate material, thereby marking of the substrate. Consequently, the marking is provided by the altered regions that are below the surface. These altered regions can be induced by the laser output on the surface of the substrate below the laminate material. Following the block  612 , the marking process  600  can end since the laser serves to produce altered regions below the outer surface of the laminate material. 
       FIGS. 7A-7D  are diagrams illustrating marking of a metal structure according to one embodiment.  FIG. 7A  illustrates a base metal layer  700 . The base metal layer  700  can be a metal, such as stainless steel.  FIG. 7B  illustrates the base metal layer  700  after an outer metal layer  702  is provided on the base metal layer  700 . The outer metal layer  702  can be a metal, such as aluminum, titanium, niobium or tantalum.  FIG. 7C  illustrates the metal structure  700  after the outer metal layer  702  has been anodized to form an anodized layer  704 . After the anodized layer  704  has been formed, the outer metal layer  702  includes an outer portion representing the anodized layer  704  and an inner portion representing the unanodized portion of the outer metal layer  702 .  FIG. 7C  also illustrated a representative boundary  706  between the outer portion and the inner portion of the anodized layer  704 . Next,  FIG. 7D  illustrates altered surfaces  708  being selectively formed at the representative boundary  706 . For example, the altered surfaces  708  can be formed on the unanodized portion of the outer metal layer  702 . The altered structures  704  combine to provide marking of the metal structure. For example, the altered surfaces  708  appear to be black and thus when selectively formed can provide marking. The resulting marking is visible through the anodized surface  702  which can be substantially translucent. If the anodized surface  702  is primarily clear, the resulting marking can be appear as black. The marking can also be provided in gray scale. If the anodized surface is dyed or colored, the markings may appear in different colors. 
       FIG. 8  is a flow diagram of a multi-stage marking process  800  according to another embodiment. The marking process  800  can begin with a substrate  802  representing at least a portion of an article to be marked. As shown in  FIG. 8 , a substrate  802  can have a layer of material  804  adhered thereto. The layer of material  804  can generally formed from anodizable metals, i.e., metals which may be anodized. In one embodiment, the layer of material  804  can be aluminum, titanium, niobium or tantalum. The substrate  802  can be generally formed from non-anodizable metals, such as stainless steel. 
     The substrate  802  with the layer of material  804  can be provided to a masking process. At the masking process, portions of the substrate  802  can be “masked off” with mask material  806  that blocks anodization. The masking process generally does not mask off regions of the layer of material  804  but in some circumstances it may be desirable to do so. 
     After the masking has been completed at the masking process, the substrate  802  having the layer of material  804  and the mask  806  can be provided to an anodizing process. The anodizing process causes at least a portion of the layer of material  804  to be anodized. An anodized layer of material  804 ′ is formed by the anodizing process. The anodized layer of material  804 ′ is typically only anodized part way into the layer of material  804 . A boundary  808  is established in the layer of material  804  between the anodized portion and the unanodized portion. The mask material  806  prevents anodization or damage to the substrate  802  during anodization. 
     Following anodization at the anodizing process, the substrate  802 , the anodized layer of material  804 ′ and the mask material  806  are provided to a de-masking process. At the de-masking process, the mask material  806  that was previously applied can now be removed since the anodization has been completed. Hence, following de-masking, the substrate  802  and the anodized layer of material  804 ′ remain. 
     After the substrate  802  has been masked by the masking process, anodized by the anodizing process and de-masked by the de-masking process, the anodized substrate  802  with the anodized layer of material  804 ′ can be provided to a marking process. At the marking process, the anodized layer of material  804 ′ can be further processed to produce altered surfaces  810  at the boundary  808  in the anodized layer of material  804 ′. The altered surfaces  810  are thus below the surface of the anodized layer of material  804 ′. That is, in one embodiment, the altered surfaces  810  are induced into the unanodized portion of the layer of material  804 ′ (i.e., portion below the boundary  808 ) as shown in  FIG. 8 . The altered surfaces  810  provide the marking to the layer of material  804 . By controlling size, placement and/or darkness of the altered surfaces  810 , the marking can be selectively provided to the article utilizing the substrate  802  and the anodized layer of material  804 ′. However, in an alternative embodiment, the altered surfaces  810  can be additionally or alternatively formed on the surface of the substrate  802  below the layer of material  804 ′. 
     The strength associated with stainless steel is generally desirable in the formation of housing walls for portable electronic devices including, but not limited to including, mobile phones (e.g., cell phones), portable digital assistants and digital media players. The stiffness associated with stainless steel is also desirable. However, the cosmetic properties of stainless steel are often lacking. To provide a cosmetic surface for a housing that effectively derives its strength from a stainless steel layer, an anodizable material may be clad to at least one surface of the stainless steel layer and then anodized. In one embodiment, a housing may include a stainless steel core that is substantially sandwiched between two layers of anodized material, e.g., anodized aluminum, which have a relatively high bond strength. The layers of anodized material effectively form cosmetic surfaces for the housing, while the stainless steel core provides structural strength, as well as stiffness, for the housing. 
       FIG. 9  is a flow diagram of a multi-stage marking process  900  according to still another embodiment. The marking process  900  can begin with a substrate  902  representing at least a portion of an article to be marked. In this embodiment, the substrate  902  is a layer of stainless steel. The substrate  902  can be can be provided to a laminating process. At the laminating process, the substrate  902  can have a layer of material  904  adhered thereto. The layer of material  904  can generally formed from anodizable metals, i.e., metals which may be anodized. In one embodiment, the layer of material  904  can be aluminum, titanium, niobium or tantalum. The layer of material  904  can be adhered to the substrate  904  by directly bonding the layer of material  904  to the substrate  902 . For example, a cladding process can be used to bond the layer of material  904  to the substrate. As will be understood by those skilled in the art, a cladding is the bonding of metals substantially without an intermediate bonding agent and substantially without remelting the metals. Cladding may take a variety of different forms including, but not limited to including, standard cladding in which layer of material  904  and substrate  902  are pressed together with roller under high pressure, or fine cladding in which layer of material  904  and substrate  902  are placed in a vacuum and rolled together after a chemical process is performed. 
     Following the laminating process, the substrate  902  with the layer of material  904  can be provided to a masking process. At the masking process, portions of the substrate  902  can be “masked off” with mask material  906  that blocks anodization. The masking process generally does not mask off regions of the layer of material  904  but in some circumstances it may be desirable to do so. 
     After the masking has been completed at the masking process, the substrate  902  having the layer of material  904  and the mask  906  can be provided to an anodizing process. The anodizing process causes at least a portion of the layer of material  904  to be anodized. An anodized layer of material  904 ′ is formed by the anodizing process. The anodized layer of material  904 ′ may be anodized fully or part way into the layer of material  904 . The mask material  906  prevents anodization or damage to the substrate  802  during anodization. 
     Following anodization at the anodizing process, the substrate  902 , the anodized layer of material  904 ′ and the mask material  906  are provided to a de-masking process. At the de-masking process, the mask material  806  that was previously applied can now be removed since the anodization has been completed. Hence, following de-masking, the substrate  902  and the anodized layer of material  904 ′ remain. 
     After the substrate  902  has been masked by the masking process, anodized by the anodizing process and de-masked by the de-masking process, the anodized substrate  902  with the anodized layer of material  904 ′ can be provided to a marking process. At the marking process, the anodized layer of material  904 ′ can be further processed to produce altered surfaces  910  on the surface of the substrate  902  below the anodized layer of material  904 ′. The altered surfaces  910  are thus below the surface of the anodized layer of material  904 ′. That is, in one embodiment, the altered surfaces  910  are induced into the surface of the substrate  902  beneath at least the anodized portion of the layer of material  904 ′. The altered surfaces  910  provide the marking to the substrate  902 . By controlling size, placement and/or darkness of the altered surfaces  910 , the marking can be selectively provided to the article that uses the substrate  902 . 
     As described above, a substrate to be marked may included areas of exposed stainless steel, or areas in which stainless steel is not substantially covered by a laminant material. Such areas are generally masked prior to an anodizing process to protect the areas of exposed stainless steel from oxidizing or rusting. In one embodiment, an edge of a housing formed from a metal substrate having a laminant material may be masked with a masking material such that substantially only the laminant material, as for example aluminum, is exposed.  FIG. 10A  is a diagrammatic representation of an exemplary housing  1000  on which a mask is to be placed, and  FIG. 10B  is a diagrammatic representation of the same exemplary housing  1000  after a mask  1002  has been placed over an exposed stainless steel surface in accordance with an embodiment. The housing  1000  may be a housing that is to be a part of an overall assembly, as for example a bottom of a cell phone assembly or portable media player. As shown in  FIG. 10B , the mask  1002  is applied to a top edge of the housing  1000 . 
       FIG. 11  illustrates the product housing  1100  having markings  1102  according to one exemplary embodiment. The markings  1102  can be produced on a sub-surface of the product housing  1100  in accordance with any of the embodiment discussed above. In this example, the labeling includes a logo graphic  1104 , serial number  1106 , model number  1108 , and certification/approval marks  1110  and  1112 . 
     The marking processes described herein are, for example, suitable for applying text or graphics to a housing surface (e.g., an outer housing surface) of an electronic device. The marking processes are, in one embodiment, particularly well-suited for applying text and/or graphics to an outer housing surface of a portable electronic device. Examples of portable electronic devices include mobile telephones (e.g., cell phones), Personal Digital Assistants (PDAs), portable media players, remote controllers, pointing devices (e.g., computer mouse), game controllers, etc. The portable electronic device can further be a hand-held electronic device. The term hand-held generally means that the electronic device has a form factor that is small enough to be comfortably held in one hand. A hand-held electronic device may be directed at one-handed operation or two-handed operation. In one-handed operation, a single hand is used to both support the device as well as to perform operations with the user interface during use. In two-handed operation, one hand is used to support the device while the other hand performs operations with a user interface during use or alternatively both hands support the device as well as perform operations during use. In some cases, the hand-held electronic device is sized for placement into a pocket of the user. By being pocket-sized, the user does not have to directly carry the device and therefore the device can be taken almost anywhere the user travels (e.g., the user is not limited by carrying a large, bulky and often heavy device). 
     Additional information on product marking as well as other manufacturing techniques and systems for electronic devices are contained in U.S. Provisional Patent Application No. 61/059,789, filed Jun. 8, 2008, and entitled “Methods and Systems for Manufacturing an Electronic Device,” which is hereby incorporated herein by reference. 
     This application is also references: (i) U.S. Provisional Patent Application No. 61/121,491, filed Dec. 10, 2008, and entitled “Techniques for Marking Product Housings,” which is hereby incorporated herein by reference; (ii) U.S. patent application Ser. No. 12/358,647, filed Jan. 23, 2009, and entitled “Method and Apparatus for Forming a Layered Metal Structure with an Anodized Surface,” which is hereby incorporated herein by reference; and (iii) U.S. patent application Ser. No. 12/475,597, filed May 31, 2009, and entitled “Techniques for Marking Product Housings,” which is hereby incorporated herein by reference. 
     The various aspects, features, embodiments or implementations of the invention described above can be used alone or in various combinations. 
     Different aspects, embodiments or implementations may, but need not, yield one or more of the following advantages. One advantage of the invention is that durable, high precision markings can be provided to product housings. As an example, the markings being provided on a sub-surface of a product housing that not only have high resolution and durability but also provide a smooth and high quality appearance. Another advantage is that the marking techniques are effective for surfaces that are flat or curved. 
     The many features and advantages of the present invention are apparent from the written description. Further, since numerous modifications and changes will readily occur to those skilled in the art, the invention should not be limited to the exact construction and operation as illustrated and described. Hence, all suitable modifications and equivalents may be resorted to as falling within the scope of the invention.