PATENT DOCUMENT

Publication Number: US-11927988-B2
Application Number: US-202217951393-A
Country: US
Kind Code: B2

Title: Glass cover member for an electronic device enclosure

Abstract:
The disclosure provides members formed from multiple layers as well as enclosures and electronic devices that include the members. The members include glass members formed from multiple layers of glass. In some cases, the members include a protruding feature provided over a camera assembly of the electronic device. The member may define one or more through-holes that extend through the protruding feature. The protruding feature may define a textured region that may be configured to provide a matte or glossy appearance.

Claims:
What is claimed is: 
     
       1. An electronic device comprising:
 an enclosure including a member defining:
 a first portion comprising a first glass layer, the first glass layer defining a base region of an exterior surface of the member; and 
 a second portion comprising a second glass layer bonded to the first glass layer and defining:
 a protruding feature at least partially surrounded by the base region and defined at least in part by the second glass layer; and 
 a hole extending through the first glass layer and the second glass layer; and 
 
 
 a sensor assembly comprising:
 a first portion extending into the hole; and 
 a second portion positioned within the enclosure and below an exterior surface of the protruding feature. 
 
 
     
     
       2. The electronic device of  claim 1 , wherein:
 the second glass layer at least partially defines the exterior surface of the protruding feature; and 
 the second portion of the sensor assembly is positioned adjacent an interior surface of the second portion of the member. 
 
     
     
       3. The electronic device of  claim 2 , wherein:
 the first portion of the sensor assembly comprises an optical module. 
 
     
     
       4. The electronic device of  claim 2 , wherein the sensor assembly includes a biometric sensor. 
     
     
       5. The electronic device of  claim 2 , wherein the sensor assembly includes a health sensor. 
     
     
       6. The electronic device of  claim 1 , wherein the exterior surface of the protruding feature defines a plateau. 
     
     
       7. The electronic device of  claim 1 , wherein:
 the second portion of the member further comprises a third glass layer bonded to the second glass layer; 
 the third glass layer defines the exterior surface of the protruding feature; and 
 the hole is a blind hole. 
 
     
     
       8. An electronic device comprising:
 a display; 
 a sensor assembly; and 
 an enclosure at least partially surrounding the display and the sensor assembly and including a member defining:
 a first portion formed from a first glass layer and having a first thickness; and 
 a second portion formed from the first glass layer and a second glass layer that is bonded to the first glass layer, the second portion having a second thickness greater than the first thickness, and defining:
 a protruding feature; and 
 a hole extending through the protruding feature, at least a portion of the sensor assembly extending into the hole. 
 
 
 
     
     
       9. The electronic device of  claim 8 , wherein an exterior surface of the second portion defines a plateau that is offset with respect to an exterior surface of the first portion. 
     
     
       10. The electronic device of  claim 9 , wherein:
 a bond region joins the first glass layer to the second glass layer; and 
 the bond region is positioned above the exterior surface of the first portion and below the plateau. 
 
     
     
       11. The electronic device of  claim 9 , wherein the first glass layer defines a concave portion of a side surface of the protruding feature. 
     
     
       12. The electronic device of  claim 8 , wherein the first glass layer is fused to the second glass layer. 
     
     
       13. An electronic device comprising:
 an enclosure including a member comprising a first glass layer bonded to a second glass layer, the member defining:
 a first portion formed from the first glass layer and defining a first region of an exterior surface and a first region of an interior surface of the member; and 
 a second portion formed from the first and the second glass layers, having a thickness that is greater than a thickness of the first portion, and defining a through-hole, the second glass layer defining a second region of the exterior surface that is offset with respect to the first region of the exterior surface, and the through-hole extending from a second region of the interior surface to the second region of the exterior surface; and 
 
 a sensor assembly positioned below the second region of the exterior surface and comprising an optical module extending into the through-hole. 
 
     
     
       14. The electronic device of  claim 13 , wherein:
 an end of the optical module is proud of the second region of the exterior surface. 
 
     
     
       15. The electronic device of  claim 13 , wherein the second region of the exterior surface defines an input region for at least one sensor of the sensor assembly. 
     
     
       16. The electronic device of  claim 15 , wherein the second portion of the member defines a button region of the enclosure. 
     
     
       17. The electronic device of  claim 13 , further comprising a display, wherein:
 the member is a first member; and 
 the enclosure further comprises a second member positioned over the display. 
 
     
     
       18. The electronic device of  claim 17 , wherein the second member is formed from a glass ceramic material. 
     
     
       19. The electronic device of  claim 3 , wherein the enclosure further comprises a window provided over the optical module and coupled to the protruding feature. 
     
     
       20. The electronic device of  claim 10 , wherein:
 the sensor assembly comprises an optical module; and 
 the optical module extends past the bond region.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation patent application of U.S. patent application Ser. No. 17/185,723, filed Feb. 25, 2021 and titled “Glass Cover Member for an Electronic Device Enclosure,” which is a nonprovisional application of and claims the benefit of U.S. Provisional Patent Application No. 63/001,294, filed Mar. 28, 2020 and titled “Glass Cover Member for an Electronic Device Enclosure,” the disclosures of which are hereby incorporated herein by reference in their entireties. 
    
    
     FIELD 
     The described embodiments relate generally to a member for an electronic device enclosure. More particularly, the present embodiments relate to a glass cover member formed from two or more layers of glass and defining a protruding feature. 
     BACKGROUND 
     Enclosures for electronic devices traditionally include multiple components. For example, an electronic device may include a housing component and one or more cover members. Enclosure components formed from conventional plastic or metal materials may be shaped and textured using traditional molding and/or machining techniques. However, it may be more difficult to shape or texture enclosure components formed from more brittle materials such as glass. 
     SUMMARY 
     The disclosure provides members for electronic devices which are formed from multiple layers, such as multiple layers of glass. Typically, the member is included in an enclosure for an electronic device. For example, the member may be a glass member included in a cover assembly. Enclosures and electronic devices including the members are also disclosed herein. 
     In some cases, a member defines a feature that protrudes beyond an adjacent region of its exterior surface. As an example, such a protruding feature may be provided over a camera assembly of the electronic device. One or more holes may extend through the protruding feature to facilitate positioning of an optical module such as a camera module. 
     In some examples, a portion of the member including the protruding feature is thicker than a surrounding portion of the member. The thicker portion of a glass member may be formed from a greater number of glass layers than the surrounding portion of the glass member. For example, the thicker portion of the glass member (including the protruding feature) may be formed from two or more glass layers while the surrounding portion may be formed from a single glass layer. The two or more glass layers may be bonded (e.g., fused) together. A composition of each of the glass layers may be substantially the same. The glass member is typically chemically strengthened as described in greater detail below. 
     In some cases, the member retains a layered structure and has a distinct bond region between the layers. For example, a glass member may include a first glass layer extending substantially across the width and the length of the glass member. The glass member may further include a second glass layer having smaller lateral dimensions and at least partially defining the protruding feature. The second glass layer may at least partially define a curved side surface (also referred to as a sidewall) of the protruding feature and the bond region may extend across the protruding feature. In some cases, the protruding feature may comprise a portion of the first glass layer as well as the second glass layer. 
     In some cases, a glass member is formed from two or more glass layers that fuse together so completely that the fusion zone between the glass layers is less distinct. However, one or more artifacts from the fusion process may still be detected upon close examination, as discussed in more detail below. An example of such a glass member may include a first glass component (alternately, a first glass piece or a first glass portion) extending substantially across the width and the length of the glass member and formed from a first glass layer. The glass member may also include a second glass component (alternately, a second glass piece or second glass portion) at least partially defining the protruding feature and formed from a second glass layer. The protruding feature may also comprise some of the first glass component in addition to the second glass component. 
     In some examples, the protruding feature may define a first textured region and the adjacent portion of the member may define a second textured region. In some cases, the first textured region may have different properties than the second textured region. For example, the first textured region may have a different gloss than the second textured region. The gloss may be measured for light incident at a particular angle (e.g., 60 degrees) with respect to the surface normal and the value of the gloss may be specified in terms of gloss units as described in greater detail with respect to  FIG.  10   . 
     The disclosure provides an electronic device comprising a display and an enclosure including a front cover assembly including a front member positioned over the display and a rear cover assembly including a rear member. The rear member defines a feature that protrudes with respect to a base region of an exterior surface of the rear member. The rear member comprises a first glass component defining the base region of the exterior surface and a second glass component bonded to the first glass component and at least partially defining the feature. The electronic device further comprises a camera assembly coupled to an interior surface of the rear cover assembly, the camera assembly comprising a camera module positioned at least partially within a hole extending through the first glass component and the second glass component. 
     The disclosure also provides an electronic device comprising an enclosure including a housing member defining a side surface of the electronic device and a rear cover assembly coupled to the housing member and including a rear member. The rear member comprises a first glass component defining a base region of an exterior surface of the rear member and a first portion of a hole extending through the rear member. The rear member further comprises a second glass component bonded to the first glass component and defining a second portion of the hole extending through the rear member and a top surface of a protruding feature extending from the base region of the exterior surface, the top surface defining an opening of the hole. The electronic device further comprises a camera assembly coupled to the rear cover assembly and comprising a camera module positioned in the first and the second portions of the hole. 
     The disclosure further provides an electronic device comprising an enclosure and a sensor assembly. The enclosure comprises a rear glass member comprising a first glass piece and a second glass piece. The first glass piece defines a base region of an exterior surface of the rear glass member and a first portion of a protruding feature, the first portion extending from the base region. The second glass piece is fused to the first glass piece and defines a second portion of the protruding feature, the second portion defining a plateau region of the protruding feature. The sensor assembly is coupled to an interior surface of the rear glass member and comprises a sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like elements. 
         FIG.  1 A  shows a front view of an example electronic device including a member formed from multiple layers. 
         FIG.  1 B  shows a rear view of the electronic device of  FIG.  1 A . 
         FIG.  2    shows a partial cross-section view of an electronic device including an example rear cover assembly and a camera assembly. 
         FIG.  3    shows a partial cross-section view of an electronic device including an additional example rear cover assembly and a camera assembly. 
         FIG.  4    shows a partial cross-section view of an electronic device including a further example rear cover assembly and a camera assembly. 
         FIG.  5    shows a partial cross-section view of an electronic device including a rear cover assembly and a sensor assembly. 
         FIG.  6    shows a partial cross-section view of an example member. 
         FIG.  7    shows a partial cross-section view of another example of a member. 
         FIG.  8    shows a partial cross-section view of an additional example of a member. 
         FIG.  9    shows a partial cross-section view of a further example of a member. 
         FIG.  10    shows a detail view of a textured region of a member. 
         FIG.  11    shows a flow chart of an example process for forming a glass member. 
         FIGS.  12 A,  12 B, and  12 C  schematically show cross-section views of stages of an example process for forming a member. 
         FIGS.  13 A,  13 B, and  13 C  schematically show cross-section views of stages of an additional example process for forming a member. 
         FIGS.  14 A,  14 B, and  14 C  schematically show cross-section views of stages of another example process for forming a member. 
         FIGS.  15 A,  15 B, and  15 C  schematically show cross-section views of stages of a further example process for forming a member. 
         FIGS.  16 A and  16 B  schematically show a top view of stages in a fusion operation in a process for forming a member. 
         FIG.  17    schematically shows a cross-section view of a member after chemical strengthening. 
         FIG.  18    shows a block diagram of a sample electronic device that can incorporate a member. 
     
    
    
     The use of cross-hatching or shading in the accompanying figures is generally provided to clarify the boundaries between adjacent elements and also to facilitate legibility of the figures. Accordingly, neither the presence nor the absence of cross-hatching or shading conveys or indicates any preference or requirement for particular materials, material properties, element proportions, element dimensions, commonalities of similarly illustrated elements, or any other characteristic, attribute, or property for any element illustrated in the accompanying figures. 
     Additionally, it should be understood that the proportions and dimensions (either relative or absolute) of the various features and elements (and collections and groupings thereof) and the boundaries, separations, and positional relationships presented therebetween, are provided in the accompanying figures merely to facilitate an understanding of the various embodiments described herein and, accordingly, may not necessarily be presented or illustrated to scale, and are not intended to indicate any preference or requirement for an illustrated embodiment to the exclusion of embodiments described with reference thereto. 
     DETAILED DESCRIPTION 
     Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. It should be understood that the following descriptions are not intended to limit the embodiments to one preferred implementation. To the contrary, the described embodiments are intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the disclosure and as defined by the appended claims. 
     The following disclosure relates to members for electronic devices. In some cases, the member defines a protruding feature that is offset with respect to an adjacent portion of the member. As an example, the member may be part of a rear cover assembly and the protruding feature may be provided over a camera assembly and/or a sensor assembly. One or more openings may be provided in the protruding feature to facilitate positioning of an optical module such as a camera module in the opening(s). In some cases, the member is a glass member. In additional cases, the member includes a glass layer bonded to another layer such as a ceramic or glass ceramic layer. 
     In some cases, a portion of the member that includes the protruding feature is thicker than an adjacent portion of the member. As described herein, a thicker portion of a member may be produced by joining multiple sheets or layers together. Forming the thicker portion of a glass member by layering multiple pieces of glass, rather than by using a single piece of glass, can reduce the amount of machining needed to produce the desired shape and/or surface texture of the protruding feature. 
     In some examples, the thicker portion of the glass member is formed from two or more glass layers that are bonded (e.g., by fusion) together. As described herein, the process of fusion bonding the glass layers can produce a glass member that is resistant to damage due to impact and/or bending of the glass member in use. In addition, the glass members described herein can have a strength sufficient to withstand the machining operations used to produce the desired shape of the glass member. 
     In some cases, the glass member may comprise a layer structure and distinct bond region(s) joining the glass layers. For example, the thicker portion of the glass member (including the protruding feature) may comprise two or more glass layers while the surrounding portion may comprise a single glass layer. A first glass layer may extend substantially across the length and width of the glass member and define the surrounding portion. A second glass layer having smaller lateral dimensions may at least partially define the protruding feature. The two or more glass layers may be fused together or otherwise coupled to produce a strong bond between the glass layers. 
     In additional cases, the glass member is formed from two or more glass layers that fuse together so completely that a distinct fusion zone may be difficult to detect upon visual inspection (but may be detectable in other ways). For example, the glass member may include a first glass component (alternately, first glass portion) extending substantially across the glass member and formed from a first glass layer. The glass member may also include a second glass component (alternately, second glass portion) at least partially defining the protruding feature and formed from a second glass layer. The second glass component partially overlies the first glass component, which typically has larger lateral dimensions. In some examples, the protruding feature is defined by the first glass component in addition to the second glass component, as described herein with respect to  FIGS.  7  to  9   . As discussed in more detail below, one or more fusion artifacts may be detected even when a distinct fusion zone or planar boundary between the first and the second glass components may not be visually apparent. 
     In some cases, a composition of each of the glass layers may be substantially the same. Including glass layers with similar compositions in the glass member can enhance fusion between adjacent glass layers. The glass member may be chemically strengthened to enhance its resistance to impact and/or bending. When the glass member is chemically strengthened, zones of the glass layers that have not been ion-exchanged may have substantially the same composition, as discussed in more detail with respect to  FIG.  17   . 
     A member as described herein may have one or more textured regions configured to provide certain properties while minimizing other properties that are less desirable. For example, a textured region may be configured to have roughness parameters that provide particular levels of optical properties such as gloss and/or transmissive haze, while avoiding an overly rough or sharp “feel.” The texture may provide a balance of functionality. For example, increasing the value of a roughness parameter to reduce the gloss or increase the haziness of the surface may, in some cases, provide an overly rough “feel” and/or undesirably reduce the cleanability of the surface. In some cases, different regions of the member may have different textures in order to provide different properties to the different regions. 
     For example, the protruding feature may define a textured region and another portion of the member may define another textured region having different properties than that of the protruding feature. In some cases, a top surface of the protruding feature may have a texture which is different from a texture of the rest of the exterior surface (e.g., the remainder of the exterior surface of the member). The properties of a textured region of a member typically influence the properties of a corresponding region of a cover assembly including the member. For example, a low gloss region of the member can produce a corresponding low gloss region of the cover assembly. The description of texture parameters and properties provided with respect to  FIG.  10    is generally applicable herein and, for brevity, is not repeated here. 
     These and other embodiments are discussed below with reference to  FIGS.  1 A to  18   . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes only and should not be construed as limiting. 
       FIG.  1 A  shows a front view of an example electronic device  100  including a member as described herein. The electronic device  100  may be a mobile telephone (also referred to as a mobile phone). In additional embodiments, the electronic device  100  may be a notebook computing device (e.g., a notebook or laptop), a tablet computing device (e.g., a tablet), a portable media player, a wearable device (e.g., a watch), or another type of portable electronic device. The electronic device  100  may also be a desktop computer system, computer component, input device, appliance, or virtually any other type of electronic product or device component. 
     As shown in  FIG.  1 A , the electronic device  100  has an enclosure  110  including a cover assembly  122 . The cover assembly  122  may at least partially define a front surface  102  of the electronic device  100 . In this example the cover assembly  122  defines a substantial entirety of a front surface of the electronic device  100 . The cover assembly  122  is positioned over the display  144  and may define a transparent portion positioned over the display  144 . The enclosure  110  may at least partially surround the display  144 . It should be understood that use of the terms “front” or “rear” to describe an orientation of an electronic device in the drawings does not imply that the electronic device must be operated in a specific orientation. 
     As shown in  FIG.  1 A , the enclosure  110  further includes a housing member  112  (which may also be referred to simply as a housing or a housing component). The cover assembly  122  may be coupled to the housing member  112 . For example, the cover assembly  122  may be coupled to the housing member  112  with an adhesive, a fastener, an engagement feature, or a combination thereof. 
     The housing member  112  may at least partially define a side surface  106  of the electronic device  100  and may include one or more metal members (e.g., one or more metal segments) or one or more glass members. In this example, the housing member  112  defines all four sides or a continuous side surface of the electronic device  100 . As shown in  FIG.  1 A , the housing member  112  is formed from a series of metal segments ( 114 ,  116 ) that are separated by polymer or dielectric segments  115  that provide electrical isolation between adjacent metal segments. For example, a polymer segment  115  may be provided between a pair of adjacent metal segments. One or more of the metal segments ( 114 ,  116 ) may be coupled to internal circuitry of the electronic device  100  and may function as an antenna for sending and receiving wireless communication. 
     The housing member  112  may define one or more openings or ports. As shown in  FIG.  1 A , the metal segment  116  of the housing member  112  defines an opening  117 . The opening  117  may allow (audio) input or output from a device component such as a microphone or speaker or may contain an electrical port or connection. 
     A cover assembly such as the cover assembly  122  typically includes a cover member  132 , also referred to herein simply as a member. As shown in  FIG.  1 A , the cover assembly  122  is a front cover assembly and the member  132  is a front member. In some cases, a cover assembly may be formed from multiple layers. For example, a front cover assembly may include one or more glass layers, glass ceramic layers, polymer layers, and/or various coatings and layers. As an example, a cover assembly may include one or more glass layers defining a (cover) member and one or more coatings on the exterior surface and/or interior surface of the member. In some cases, the member  132  may be a glass member. In additional cases, the member  132  may be a composite member formed by bonding a glass layer to a layer of a glass ceramic material or a layer of a ceramic material, such as sapphire. In some cases, the glass ceramic material or ceramic material may be transparent to visible light, infrared radiation, ultraviolet radiation, or combinations thereof. 
     Typical cover assemblies herein are thin, and typically include a cover member that is less than 5 mm in thickness, and more typically less than 3 mm in thickness. In some aspects, a member of a cover assembly, such as the members  132  and  134 , can have a thickness from about 0.1 mm to 2 mm, from about 0.3 mm to 3 mm, from 0.5 mm to 2.5 mm, from 0.5 mm to 2 mm, or from 0.2 mm to 1 mm. In some cases, a member and a cover assembly including the member may have a non-uniform thickness, such as described in further detail below with respect to the member  134  and the rear cover assembly  124 . A member such as the members  132  and  134  may extend laterally across the cover assembly, such as substantially across the width and the length of the cover assembly. 
     Although the cover assembly  122  is shown in  FIG.  1 A  as being substantially planar, the principles described herein also relate to cover assemblies and members thereof that define a protruding feature (such as shown in  FIGS.  1 B,  2 - 9 ,  12 C,  13 C,  14 C,  15 C, and  17   ), a recessed feature, and/or one or more curved surfaces. In embodiments, a member of a cover assembly may be three-dimensional or define a contoured profile. For example, the member may define a peripheral portion that is not coplanar with respect to a central portion. The peripheral portion may, for example, define a side wall of a device housing or enclosure, while the central portion defines a front surface (which may define a transparent window that overlies a display). In addition, a cover assembly such as the cover assembly  122  may define a hole, such as the hole  153 , to allow (audio) input or output from a device component such as a microphone or speaker. 
       FIG.  1 B  shows a rear view of the electronic device  100 . As shown in  FIG.  1 B , the enclosure  110  includes a cover assembly  124 , which defines a rear surface  104  of the electronic device. In the example of  FIG.  1 B , the cover assembly  124  defines a substantial entirety of the rear surface of the electronic device. In some cases, the electronic device  100  includes a camera assembly and/or a sensor assembly coupled to an interior surface of the cover assembly  124  (as shown in  FIGS.  2  to  5   ). 
     The cover assembly  124  includes a cover member  134  also referred to herein simply as a member. As shown in  FIG.  1 B , the cover assembly  124  is a rear cover assembly and the member  134  is a rear member. In some cases, the member  134  is a glass member. As described in greater detail below, in some cases at least a portion of a glass member is formed from two or more glass layers that are bonded (e.g., fusion bonded) together. The cover assembly  124  may further include a smudge-resistant coating, a cosmetic coating, or a combination thereof. 
     As shown in  FIG.  1 B , the cover assembly  124  defines a feature  126  that protrudes or is offset with respect to a portion  129  of the cover assembly  124 . The feature  126  may also be referred to herein as a protruding feature. The portion  129  may also be referred to herein as a base portion and may define a base region of the exterior surface of the cover assembly  124 . The portion  129  may be adjacent to the protruding feature and may at least partially surround the protruding feature. 
     As shown in  FIG.  1 B , an exterior surface of the protruding feature  126  defines a raised region  127 . The raised region  127  may define a top or outermost surface of the protruding feature  126 . In the example of  FIG.  1 B , the raised region  127  generally defines a plateau and the exterior surface of the protruding feature  126  further defines a side region  128  (also referred to herein as a side surface). The side region  128  extends between the raised region  127  and the exterior surface of the base portion  129 . In the example of  FIG.  1 B , the protruding feature  126  further defines a set of openings  167  in the raised region  127 . An opening  167  may correspond to the entrance to (or exit from) a hole (also referred to herein as a through-hole) that extends through the cover assembly from the raised region  127  to an interior surface of the cover assembly. The description of through-holes provided with respect to  FIGS.  2  to  4    is generally applicable herein and, for brevity, is not repeated here. 
     The combined thickness of a portion of the cover assembly  124  including the protruding feature  126  may be greater than that of the portion  129  and may be at least 10%, 25%, or 50% and up to about 250% thicker than the thickness of the portion  129 . In some cases, the thickness of the thicker portion of the cover assembly (including the protruding feature) is greater than about 1 mm and less than or equal to about 2 mm or about 2.5 mm. The thickness of the base portion  129  may be greater than about 0.3 mm and less than about 0.75 mm or greater than about 0.5 mm and less than about 1 mm. The amount of protrusion or offset between the raised region  127  and an exterior surface of the portion  129  may be from about 0.5 mm to about 1.5 mm or from about 0.75 mm to about 2 mm. The size of the protruding feature  126  may depend at least in part on the size of a camera assembly or other device component underlying the protruding feature. In some embodiments, a lateral dimension (e.g., a width) of the protruding feature may be from about 5 mm to about 30 mm, from about 10 mm to about 20 mm, or from about 15 mm to 30 mm. 
     The shape of the member  134  may generally correspond to the shape of the cover assembly  124 . Typically, the member  134  also includes a feature that protrudes with respect to a base region of the exterior surface of the member as shown in more detail in the cross-section views of  FIGS.  2  to  9    (e.g., the protruding feature  636  of  FIG.  6   ). A portion of a member including the protruding feature may be thicker than an adjacent portion of the member. In some cases, the thicker portion of a glass member is formed from a greater number of glass layers than the surrounding portion of the glass member, as described in further detail with respect to at least  FIGS.  6  to  9  and  11  through  15 C . The description provided with respect to  FIGS.  6  to  9  and  11  through  15 C  is generally applicable herein and, for brevity, is not repeated here. The member  134  may extend across a substantial entirety of the rear of the electronic device  100 . More generally, a member having a protruding feature may extend across a front, a rear, and/or a side surface of the electronic device and in some cases may extend over less than an entirety of one or more of these surfaces. 
     The protruding feature  126  may define a textured region  156  of the electronic device  100 . The textured region  156  may have a texture configured to provide a desired appearance to an exterior surface of the electronic device  100 . In addition, the texture of the textured region  156  may be configured to provide a particular “feel” to the electronic device, configured to be amenable to cleaning, or both. In some cases, the textured region  156  may extend over both the raised region  127  and the side region  128 . In other cases, the textured region  156  may extend over a raised region  127  but may not substantially extend over the side region  128 . 
     In some cases, the textured region  156  has at least one roughness parameter greater than that of a polished surface, such as a conventionally polished surface. For example, the textured region  156  may have a texture that produces a matte appearance (e.g., a semi-gloss or a low gloss appearance). In addition, the textured region  156  may have a texture that produces an at least partially translucent or hazy appearance. In other cases, the textured region  156  has at least one roughness parameter similar to that of a polished surface. The description of textures provided with respect to  FIG.  10    is generally applicable herein and, for brevity, is not repeated here. 
     The texture of the textured region  156  may be similar to or different from that of another portion of the cover assembly. For example, the base portion  129  may define a textured region  159  and the texture of the textured region  156  may be different from a texture of the textured region  159 . In addition, when the textured region  156  does not extend over the side region  128 , a texture of the side region  128  may be similar to the texture of the textured region  159 . 
     In some cases, the textured region  156  has at least one roughness parameter greater than that of a polished surface, such as a conventionally polished surface, and the textured region  159  has a texture similar to that of a polished surface. In such cases, the textured region  156  may have a lower gloss than the textured region  159 . In other cases, the textured region  156  has a roughness parameter similar to that of a polished surface and the textured region  159  has a texture greater than that of a polished surface. Methods for forming textures on the member  134  of the cover assembly  124  are discussed with respect to  FIG.  11    and those details are generally applicable herein. 
     The electronic device  100  may include a camera assembly. The camera assembly may include one or more optical modules. The example of  FIG.  1 B  shows three optical modules  177 , but more generally the camera assembly may define any number of optical modules  177 , such as one, two, three, four, or five optical modules. Each of the optical modules  177  may be substantially flush with, proud of (alternately, protrudes), or recessed with respect to the textured region  156 . In some cases, the camera assembly may be part of a sensor array. 
     The optical modules  177  may include, but are not limited to, a camera module, an illumination module, a sensor, and combinations thereof. In some cases, the optical modules  177  include multiple camera modules. When the optical modules include multiple camera modules, each of the camera modules may have a different field of view or other optical property. In some cases, a camera module includes an optical sensing array and/or an optical component such as a lens, filter, or window. In additional cases, a camera module includes an optical sensing array, an optical component, and a camera module housing surrounding the optical sensing array and the optical components. The camera module may also include a focusing assembly. For example, a focusing assembly may include an actuator for moving a lens of the camera module. In some cases, the optical sensing array may be a complementary metal-oxide semiconductor (CMOS) array or the like. In some cases, a sensor may include a depth measuring sensor (e.g., a time of flight sensor), an ambient light sensor, an infrared sensor, an ultraviolet light sensor, a health monitoring sensor, a biometric sensor (e.g., a fingerprint sensor), or the like. 
     An optical module  177  may be positioned at least partially within an opening  167  in the textured region  156 , as shown in  FIG.  1 B . The optical module  177  may also be positioned at least partially within a through-hole in the cover assembly  124  (as shown in the partial cross-section views of  FIGS.  2  to  4   ). The camera assembly may be coupled to an interior surface of the cover assembly as shown in  FIGS.  2  to  4   . 
     In additional cases, a protruding feature  126  of the electronic device  100  can accommodate one or more sensor components in addition to or as an alternate to the optical modules of the camera assembly. For example, the electronic device may include an electronic device component such as a microphone or another type of sensor. These one or more sensor components may be part of a sensor assembly. The sensor assembly may in turn be part of a sensor array. 
     A variety of sensors may be positioned within and/or adjacent to a protruding feature. For example, a health monitoring sensor may be positioned at least partially within or adjacent to a protruding feature of a wearable device, such as a watch. As another example, a protruding feature may define a key region, a button region, or a trackpad region of a laptop or a phone. A biometric sensor, a touch sensor, a proximity sensor, or the like may be positioned within or adjacent to the protruding feature. The description of sensors provided with respect to  FIG.  18    is generally applicable herein and, for brevity, is not repeated here. In some cases, the protruding feature includes an opening, such as opening  169  of  FIG.  1 B , and the additional electronic device component is positioned within or below the opening. In additional cases, a sensor assembly may be positioned adjacent to a protruding feature as shown in  FIG.  5   . 
     The electronic device  100  may also include components in addition to a display and a camera assembly. These additional components may comprise one or more of a processing unit, control circuitry, memory, an input/output device, a power source (e.g., battery), a charging assembly (e.g., a wireless charging assembly), a network communication interface, an accessory, and a sensor. Components of a sample electronic device are discussed in more detail below with respect to  FIG.  18    and the description provided with respect to  FIG.  18    is generally applicable herein. 
       FIG.  2    shows a partial cross-section view of an electronic device  200  including an example rear cover assembly and a camera assembly. The electronic device  200  may be similar to the electronic device  100  of  FIGS.  1 A and  1 B  and the cross-section may be taken along A-A. The electronic device  200  includes a cover assembly  222  at the front and a cover assembly  224  at the rear of the electronic device  200 . Each of the cover assembly  222  and the cover assembly  224  is coupled to a housing member  214 , such as with an adhesive, a fastener, or a combination thereof. The housing member  214  may be similar to the housing member  112  and/or the segments  114  and  116  of the housing member  112  of  FIG.  1 A . The housing member  214  at least partially defines an interior cavity  205  of the electronic device  200 . 
     The cover assembly  222  includes a member  232  and the cover assembly  224  includes a member  234 . The member  234  may be a glass member and in some cases the member  232  may also be a glass member. The cover assembly  224  defines a feature  226  that protrudes with respect to a portion  229  of the cover assembly  224 . A feature which protrudes with respect to another portion of the cover assembly, such as the feature  226 , may also be referred to generally herein as a protruding feature. Typically, at least part of the portion  229  is substantially adjacent the protruding feature  226 . The portion  229  may also be referred to herein as a base portion  229 . As shown in  FIG.  2   , a portion of the cover assembly  224  including the protruding feature  226  and an underlying portion of the cover assembly is thicker than the portion  229 . The protruding feature  226  and the underlying portion collectively may be referred to as a thicker portion of the cover assembly  224 . 
     The member  234  may also include a protruding feature as shown in more detail in the cross-section views of  FIGS.  6  to  9 ,  12 C,  13 C,  14 C, and  15 C  (e.g., the protruding feature  636  of  FIG.  6   ). Similarly to the cover assembly  224 , the protruding feature of the member  234  may be part of a thicker portion of the member as compared to an adjacent portion of the member  234 . In some cases, the thicker portion of a glass member is formed from a greater number of glass layers than the adjacent portion of the glass member, as described in further detail with respect to  FIGS.  6  to  9  and  11  to  15 C . In some cases, the member  234  is a glass member and includes a first glass component  299  (e.g., formed from a first glass layer), a second glass component  296  (e.g., formed from a second glass layer), and a boundary region  295  between the first and second glass components. The second glass component  296  has a smaller lateral dimension (e.g., a width) than the first glass component  299  and thus only partially overlies the first glass component. The position of the boundary region shown in  FIG.  2    is not intended to be limiting and additional examples are shown in  FIGS.  6  to  9 ,  12 C,  13 C,  14 C, and  15 C . In some cases, the boundary region  295  may be distinct and readily detected upon visual inspection, while in other cases the boundary region may be detectable in other ways, as described in more detail with respect to at least  FIGS.  6  and  11   .  FIGS.  6  to  9 ,  12 C,  13 C,  14 C, and  15 C  also illustrate the portion of the member underlying the protruding feature. The underlying portion of the cover assembly includes this underlying portion of the member as well as any coatings along the interior surface of the member. The description provided with respect to  FIGS.  6  to  9  and  11  to  15 C  is generally applicable herein and, for brevity, is not repeated here. 
     As shown in  FIG.  2   , the cover assembly  224  further defines an exterior surface  244 . A region  247  of the exterior surface  244  is defined by the protruding feature  226  and a region  249  of the exterior surface  244  is defined by the portion  229 . The region  247  of the exterior surface protrudes or is raised with respect to the region  249  and may therefore be referred to as a raised region, an offset region, an outer region, or simply as a top surface of the protruding feature  226 . As an example, the raised region  247  of the exterior surface may define a plateau. The region  249  of the exterior surface may be referred to herein as a base region of the exterior surface. A region  248  of the exterior surface  244  may extend between the region  247  and the region  249  of the exterior surface and may define a side surface of the protruding feature  226 . As schematically shown in  FIG.  2   , the region  247  may include a textured region. In the example of  FIG.  2   , the region  247  has a rougher texture than the regions  248  and  249 . The example of  FIG.  2    is not limiting and in some cases the region  247  may have a smoother texture than the regions  248  and  249 . More generally, the region  247  may have a texture similar to or different from that of another region of the exterior surface as previously described with respect to  FIG.  1 B . The description with respect to  FIG.  1 B  is generally applicable herein and, for brevity, is not repeated here. 
     The electronic device  200  further includes a display  274  and a touch sensor  272  provided below the front cover assembly  222 . The display  274  and the touch sensor  272  may be coupled to the front cover assembly  222 . The display  274  may be a liquid-crystal display (LCD), a light-emitting diode (LED) display, an LED-backlit LCD display, an organic light-emitting diode (OLED) display, an active layer organic light-emitting diode (AMOLED) display, and the like. The touch sensor  272  may be configured to detect or measure a location of a touch along the exterior surface of the front cover assembly  222 . 
     The electronic device  200  further includes a camera assembly  275 . The partial cross-section view of  FIG.  2    shows two optical modules ( 277 ,  278 ) of the camera assembly  275 . As shown in  FIG.  2   , the camera assembly  275  is coupled to the cosmetic coating  260 . In examples where the cosmetic coating does not extend under the protruding feature, the camera assembly  275  may be coupled more directly to the interior surface of the member  234 . In some cases, the camera assembly  275  may be coupled to the interior surface  242  of the cover assembly  224  with an adhesive bond, as may be provided by an adhesive layer. As an additional example, the camera assembly  275  may be coupled to the interior surface of the cover assembly  224  with a fastener or other form of mechanical attachment. 
     The camera assembly  275  further includes a support structure  276  that is coupled to an interior surface  242  of the cover assembly  224 . The support structure  276  may be configured to hold various elements of the camera assembly  275  in place. For example, each of the optical modules  277  and  278  and a circuit assembly  279  may be mounted to the support structure  276 . In some cases, the support structure  276  may include a plate, a bracket, or a combination thereof. The shape of the support structure  276  is not limited to the example of  FIG.  2   . While the support structure  276  is shown as a flat element, in other examples a support structure may be machined, cast, or molded to have a non-planar profile that is configured to receive elements of the camera assembly. The circuit assembly  279  may include a printed circuit board (PCB). 
     The support structure  276  and the coupling between the camera assembly  275  and the interior surface of the cover assembly  224  may be configured to limit bending of the member  234  in the vicinity of the protruding portion  226 . For example, the support structure  276  may be configured to limit bending that would tend to increase outwards curvature of the region  247  of the protruding portion  226  (and increase its convexity). Limiting bending of the protruding region can limit bending-induced tensile stress along the textured region  256 . Further, the coupling between the camera assembly  275  and the interior surface  242  of the cover assembly  224  may be sufficiently rigid so that the position of a neutral axis of the combination of the cover assembly  224  and the camera assembly  275  is shifted as compared to the corresponding neutral axis of the cover assembly  224  alone. For example, the neutral axis of the combination of the cover assembly  224  and the camera assembly  275  may be shifted inward, away from the exterior surface  244 , as compared to the corresponding neutral axis of the cover assembly  224  alone. In some cases, the shifting of the neutral axis may be most pronounced in the protruding feature  226  of the cover assembly  224 . 
     As previously described with respect to  FIG.  1 B , the cover assembly  224  may define holes  237  and  238  extending through the protruding portion  226 . Holes  237  and  238  may also be referred to herein as through-holes. As shown in  FIG.  2   , the member  234  also at least partially defines the holes  237  and  238 . The cover assembly  224  further defines openings  267  and  268  to the holes  237  and  238 . The openings  267  and  268  are located in the region  247 , which may be a textured region. 
     The first optical module  277  and the second optical module  278  are respectively aligned with the through-holes  237  and  238 . As shown in  FIG.  2   , the first optical module  277  extends substantially through the first through-hole  237  and the second optical module  278  extends substantially through the second through-hole  238 . In the example of  FIG.  2   , an end of each of the optical modules  277  and  278  extends beyond (protrudes beyond) the opening ( 267  or  268 ) in the surface region  247 . In additional examples, an end of an optical module may be flush with an opening in a surface region of the protruding feature or recessed with respect to this surface region, as shown in  FIGS.  3  and  4   . In some cases, an electronic device may include at least one optical module that is flush with or extends beyond an opening in the surface region  247  and another optical module that is recessed with respect to the surface region  247 . 
     As previously described with respect to  FIG.  1 B , an optical module may comprise a camera module, an illumination module, an optical sensor, or the like. Typically, the camera assembly  275  includes at least one camera module and may include two, three, four or five camera modules. The camera module is electrically connected to the circuit assembly  279 . As shown in  FIG.  2   , separate windows  287  and  288  are provided over the through-holes  237  and  238  and retaining component  286  holds the windows  287  and  288  in place. For example, the retaining component  286  may be a ring, such as a metal ring, which surrounds the end of the optical module. Alternately, an optical module may include a window as part of its optical components, with the window being positioned within its housing. The windows may protect underlying components (e.g., cameras, lenses, other sensors), and may define part of the exterior surface of the cover assembly. 
     The cover assembly  224  further includes a cosmetic or decorative coating  260  disposed along an interior surface  233  of the member  234 . In some cases, the cosmetic coating  260  may define an interior surface  242  of the cover assembly. When the cover assembly and member over the cosmetic coating are textured, the appearance of the electronic device may be due to the combined effect of the textured region and the cosmetic coating. As shown in  FIG.  2   , the cosmetic coating  260  is positioned underneath the portion  229  of the cover assembly  224  and in some cases may provide the portion  229  with a desired color. In additional cases, the cosmetic coating  260  may function as a masking layer. In the example of  FIG.  2   , the cosmetic coating  260  extends under the protruding feature  226  and the protruding feature  226  may have a color similar to the portion  229 . In other cases, the cosmetic coating may not extend under the protruding feature  226  and the protruding feature  226  may appear to have a color different from the portion  229  or may appear substantially colorless. For example, the absolute value of each of a* and b* may be less than 5, less than 3, or less than or equal to 2 and the value of L* may be greater than 90, greater than 95, or greater than 98 when the protruding feature appears substantially colorless. 
     In some cases, the cosmetic coating  260  comprises a polymer. The cosmetic coating  260  may comprise at least 40%, 50%, 60%, or 70% of the polymer and may therefore be referred to as a polymer-based coating or a polymeric coating. When the cosmetic coating  260  further comprises a colorant, the polymer may act as a binder for the colorant. The colorant (e.g., a pigment) may be substantially dispersed in a matrix of the polymer. As examples, the polymer may be polyester-based, epoxy-based, urethane-based, or based on another suitable type of polymer or copolymer. The cosmetic coating  260  may further comprise optional additives such as one or more extenders, diluents, polymerization initiators, and/or stabilizers. In some embodiments, the polymer has a cross-linked structure. 
     In some cases, the cosmetic coating may include a color layer (e.g., an ink, dye, paint, etc.) and/or a metal layer. As previously described, the cosmetic coating  260  may include at least one color layer. The color layer may comprise a polymer and a colorant dispersed in the polymer and may be transparent, translucent, or opaque. More generally, any pigment, paint, ink, dye, sheet, film, or other layer may be used as the cosmetic coating  260  or a portion thereof. In some embodiments, the cosmetic coating  260  is a multilayer coating that includes a first color layer and a second color layer. Each of the color layers may be transparent, translucent, or opaque. Each of the color layers may include the same colorant or different color layers may include different colorants. The thickness of each of the color layers in the cosmetic coating  260  may be from about 2 microns to about 10 microns. 
     The color layer(s) and the cosmetic coating  260  may have a chromatic color or an achromatic color. The color of the cosmetic coating  260  may be characterized using a color model. For example, in the hue-saturation-value (HSV) color model, the hue relates to the wavelength(s) of visible light observed when the color feature is viewed (e.g., blue or magenta) and the value relates to the lightness or darkness of a color. The saturation relates to the perceived colorfulness as judged in proportion to its brightness. As another example, coordinates in CIEL*a*b* (CIELAB) color space may be used to characterize the color, wherein L* represents brightness, a* the position between red/magenta and green, and b* the position between yellow and blue. 
     In some cases, the cosmetic coating  260  may include multiple layers. As examples, the cosmetic coating  260  may include one or more color layers, a metal layer, an optically clear layer, an optically dense layer, and combinations thereof. In additional cases, the cosmetic coating need not include a color layer, but may include one or more of an optically dense layer and a metal layer. 
     For example, the cosmetic coating  260  may include an optically dense layer. The optically dense layer may substantially reduce or prevent transmission of visible light, thereby “blocking” the view through the cover assembly  224  of components positioned behind the optically dense layer. In addition, the optical properties of the optically dense layer may be configured to adjust the lightness and/or the chroma of the cosmetic coating  260 . 
     For example, the optical density of the optically dense layer may be described by OD=log 10  (initial intensity/transmitted intensity) and may be greater than or equal to 1, greater than or equal to 2, or greater than or equal to 3. Generally, the optically dense layer comprises a polymer. The optically dense layer may further comprise one or more pigments, dyes, or a combination thereof. As an example, the optically dense layer has a substantially wavelength independent (neutral) reflectance and/or absorption spectrum over the visible range. In addition, the optically dense layer may have an achromatic characteristic color. The thickness of the optically dense layer may be from about 2 microns to about 10 microns. 
     In further embodiments, the cosmetic coating  260  may comprise a metal layer in addition to one or more color layers. Such a metal layer may give a metallic effect to the cosmetic coating as seen through the cover assembly  224 . When used to form a metallic marking, the metal layer may be a partial layer (e.g., having a smaller lateral dimension than a color layer). For example, the metal of the layer may be selected from aluminum, copper, nickel, silver, gold, platinum, and alloys thereof. In some cases, the metal layer may be configured to at least partially transmit visible light. For example, the metal layer may have a thickness greater than about 0.5 nm and less than 10 nm, less than 5 nm, less than 3 nm, less than 2 nm, or less than 1 nm. Thicker metal layers may be used for forming an indicium or another marking under the member. The marking may be in the form of an image, a pattern, text, a glyph, a symbol, indicia, a geometric shape, or a combination thereof. 
     The metal layer may be disposed along an interior surface of the member  234 . In some cases, the metal layer may be used in combination with an optically clear layer. The optically clear layer may have one or more mechanical properties (e.g., modulus, hardness and/or toughness) that limit or prevent propagation of cracks from the metal layer into the member  234 . The optically clear layer may be a polymeric layer and may have a thickness from about 1 micron to about 5 microns. The optically clear layer may be disposed along the interior surface  233  of the member  234 , the metal layer may be positioned between the optically clear layer and the optically dense layer, a first color layer may be positioned between the metal layer and the optically dense layer, and a second color layer may be positioned between the first color layer and the optically dense layer. 
     In addition, the cosmetic coating may comprise additional polymeric layers behind and disposed along the optically dense layer. If components of the electronic device are glued to the cosmetic coating, these additional layers may include a protective layer that protects the color layers of the multilayer coating from damage due to the glue. The additional layers may further include a layer inward of the protective layer that facilitates adhesion of the cosmetic coating to the glue. 
       FIG.  3    shows a partial cross-section view of an electronic device  300  including an additional example rear cover assembly and a camera assembly. The electronic device  300  may be similar to the electronic device  100  of  FIGS.  1 A and  1 B  and the cross-section may be taken along A-A. The electronic device  300  includes a cover assembly  322  at the front and a cover assembly  324  at the rear of the electronic device  300 . Each of the cover assembly  322  and the cover assembly  324  is coupled to a housing member  314 , such as with an adhesive, a fastener, or a combination thereof. The housing member  314  may be similar to the housing member  112  and/or the segments  114  and  116  of the housing member  112  of  FIG.  1 A . The housing member  314  at least partially defines an interior cavity  305  of the electronic device  300 . 
     The cover assembly  322  includes a member  332  and the cover assembly  324  includes a member  334 . The member  334  may be a glass member and in some cases the member  332  may also be a glass member. The cover assembly  324  defines a protruding feature  326  that protrudes with respect to a base portion  329 . Typically, the member  334  also includes a protruding feature as shown in more detail in the cross-section views of  FIGS.  6  to  9 ,  12 C,  13 C,  14 C, and  15 C  (e.g., the protruding feature  636  of  FIG.  6   ). As previously described with respect to the cover assembly  224 , the protruding feature of the member  334  may be part of a thicker portion of the member as compared to an adjacent portion of the member. In some cases, the member  334  is a glass member and the thicker portion of the member  334  is formed from a greater number of glass layers than the adjacent portion of the member, as described in further detail with respect to at least  FIGS.  6  to  9  and  11  to  15 C . The member  334  may be a glass member comprising a first glass component and a second glass component or may be a composite member as described with respect to  FIGS.  1 B,  2 ,  6  to  9 , and  11    and that description is not repeated here. 
     In a similar fashion as described for  FIG.  2   , the cover assembly  324  defines an exterior surface  344 . A region  347  of the exterior surface  344  is defined by the protruding feature  326  and a region  349  of the exterior surface  344  is defined by the base portion  329 . As shown in  FIG.  3   , a region  348  of the exterior surface  344  extends between the region  347  and the region  349  and may define a side surface of the protruding feature  326 . The cover assembly  324  may define holes  337  and  338  extending through the protruding feature  326  and defining openings  367  and  368  at an external surface of the protruding feature  326 . 
     In a similar fashion as previously described with respect to  FIGS.  1 B and  2   , the different regions of the exterior surface  344  may have similar textures to each other or may have different textures from each other. In the example of  FIG.  3   , the regions  349  and  348  have a smoother texture than the region  347 . In additional embodiments, the regions  349  and  348  have a rougher texture than the region  347  or the region  348  may have a texture similar to that of the region  349  and/or the region  347 . Further, the discussion of surface textures provided with respect to  FIGS.  1 B and  2    is applicable herein but, for brevity, is not repeated here. 
     The electronic device  300  further includes a display  374  and a touch sensor  372  provided below the front cover assembly  322 . The display  374  and the touch sensor  372  may be as previously described for  FIG.  2    and, for brevity, that description is not repeated here. 
     The electronic device  300  further includes a camera assembly  375 . The partial cross-section view of  FIG.  3    shows optical modules  377  and  378  of the camera assembly  375 . The camera assembly  375  further includes a support structure  376  that is coupled to an interior of the cover assembly  324 . As shown in  FIG.  3   , the decorative coating  360  is disposed along an interior surface  333  of the member  334  and extends between the support structure  376  and the member  334 . The support structure  376  may be coupled to the interior surface  342  through the cosmetic coating in a similar manner as previously described for support structure  276 . The support structure  376  may have similar features and functions as support structure  276  and the circuit assembly  379  may have similar features and functions as the circuit assembly  279 . The description provided with respect to support structure  276  is generally applicable herein and, for brevity, is not repeated here. 
     As previously described with respect to  FIG.  2   , the cover assembly  324  may define holes  337  and  338  extending through the protruding portion  326 . The optical module  377  is aligned with the hole  337  and the optical module  378  is aligned with the hole  338 . As shown in  FIG.  3   , the optical module  377  extends substantially through the through-hole  337  and into the opening  367  so that an end of the optical module is flush with the opening and the surface region  347 . In contrast, the optical module  378  extends partially through the through-hole  338  and a window  388  is positioned in the opening  368 . In some cases, a sealing member may seal the opening around an optical module and/or a window to prevent ingress of liquids and/or contaminants. 
     The cover assembly  324  further includes a cosmetic or decorative coating  360  disposed along an interior surface  333  of the member  334 . As shown in  FIG.  3   , the cosmetic coating  360  extends between the support structure  376  and the member  334  and the support structure  376  may be coupled to the interior surface  333  through the cosmetic coating in a similar manner as previously described for support structure  276 . The cosmetic coating  360  may be as previously described for  FIG.  2    and, for brevity, that description is not repeated here. 
       FIG.  4    shows a partial cross-section view of an electronic device  400  including a further example rear cover assembly and a camera assembly. The electronic device  400  may be similar to the electronic device  100  of  FIGS.  1 A and  1 B  and the cross-section may be taken along A-A. The electronic device  400  includes a cover assembly  422  at the front and a cover assembly  424  at the rear of the electronic device  400 . Each of the cover assembly  422  and the cover assembly  424  is coupled to a housing member  414 , such as with an adhesive, a fastener, or a combination thereof. The housing member  414  may be similar to the housing member  112  and/or the segments  114  and  116  of the housing member  112  of  FIG.  1 A . The housing member  414  at least partially defines an interior cavity  405  of the electronic device  400 . 
     The cover assembly  422  includes a member  432  and the cover assembly  424  includes a member  434 . The member  434  may be a glass member and in some cases the member  432  may also be a glass member. The cover assembly  424  defines a protruding feature  426  that protrudes with respect to a base portion  429 . Typically, the member  434  also includes a protruding feature as shown in more detail in the cross-section views of  FIGS.  6  to  9 ,  12 C,  13 C,  14 C, and  15 C  (e.g., the protruding feature  636  of  FIG.  6   ). As previously described with respect to the cover assembly  224 , the protruding feature of the member  434  may be part of a thicker portion of the member as compared to an adjacent portion of the member. 
     In some cases, the member  434  is a glass member and the thicker portion of the glass member is formed from a greater number of glass layers than the adjacent portion of the glass member, as described in further detail with respect to  FIGS.  6  to  9  and  11  to  15 C . The member  434  may comprise a first glass component and a second glass component as described with respect to  FIGS.  1 B,  2  and  6  to  8   , or three glass components as described with respect to  FIG.  9   . In addition, the member  434  may be a composite member and may comprise one or more glass components in combination with one or more glass ceramic or ceramic components, as described with respect to  FIGS.  1 B,  2 ,  6  to  9  and  11   . The description provided with respect to  FIGS.  1 B,  2 ,  6  to  9 , and  11    is generally applicable herein and, for brevity, is not repeated here. 
     The cover assembly  424  may define holes  437  and  438  extending partially through the protruding feature  426 . The holes  437  and  438  do not define openings at the external surface of the protruding feature  426 . Therefore, the surface region  447  of the protruding feature may at least partially define windows ( 467 ,  469 ) for the optical module  477  and  478 . A glass, glass ceramic or ceramic material defining the window  469  may be transparent to visible light, infrared radiation, ultraviolet radiation, or combinations thereof. 
     In a similar fashion as described for  FIG.  2   , the cover assembly  424  defines an exterior surface  444 . A region  447  of the exterior surface  444  is defined by the protruding feature  426  and a region  449  of the exterior surface  444  is defined by the portion  429 . As shown in  FIG.  4   , a region  448  of the exterior surface  444  extends between the region  447  and the region  449  and may define a side surface of the protruding feature  426 . 
     The electronic device  400  further includes a display  474  and a touch sensor  472  provided below the front cover assembly  422 . The display  474  and the touch sensor  472  may be as previously described for  FIG.  2    and, for brevity, that description is not repeated here. 
     The electronic device  400  further includes a camera assembly  475 . The partial cross-section view of  FIG.  4    shows optical modules  477  and  478  of the camera assembly  475 . The camera assembly  475  further includes a support structure  476  that is coupled to an interior of the cover assembly  424 . The support structure  476  may have similar features and functions as support structure  276  and the circuit assembly  479  may have similar features and functions as the circuit assembly  279 . The description provided with respect to the support structure  276  is generally applicable herein and, for brevity, is not repeated here. 
     The optical module  477  is aligned with the hole  437  and the optical module  478  is aligned with the hole  438 . As shown in  FIG.  4   , the optical modules  477  and  478  extend substantially through the holes  437  and  438 . However, since the holes  437  and  438  are blind holes, the optical modules  477  and  478  do not extend to the exterior surface  444  of the cover assembly. 
     The cover assembly  424  further includes a cosmetic or decorative coating  460  disposed along an interior surface  433  of the member  434 . As shown in  FIG.  4   , the cosmetic coating  460  is disposed along an interior surface  433  of the member  434  and extends between the support structure  476  and the member  434 . The support structure  476  may be coupled to the interior surface  442  through the cosmetic coating in a similar manner as previously described for support structure  276 . The cosmetic coating  460  may be as previously described for  FIG.  2    and, for brevity, that description is not repeated here. 
     In a similar fashion as previously described with respect to  FIGS.  1 B and  2   , the different regions of the exterior surface  444  may have similar textures to each other or may have different textures from each other. In the example of  FIG.  4   , the region  447  has a smoother texture than the regions  448  and  449 . Further, the discussion of surface textures provided with respect to  1 B and  2  is applicable herein but, for brevity, is not repeated here. Indeed, any of the texture configurations shown in any of the figures may be used with any of the embodiments described herein. For example, the texture configurations shown in  FIG.  2    or in  FIG.  3    may be implemented in the electronic device  400  (e.g., instead of the texture configuration shown in  FIG.  4   ). 
       FIG.  5    shows a partial cross-section view of an electronic device including a rear cover assembly and a sensor assembly. The rear cover assembly  524  of the electronic device  500  includes a member  534 , which may be a glass member. The cover assembly  524  defines a protruding feature  526  that protrudes with respect to a base portion  529  and defines a raised (or top) surface  527 . Typically, the glass member  534  also includes a protruding feature as shown in more detail in the cross-section views of  FIGS.  6  to  9 ,  12 C,  13 C,  14 C, and  15 C  (e.g., the protruding feature  636  of  FIG.  6   ). The cover assembly  524  further includes a cosmetic or decorative coating  560 , although in other examples a cover assembly need not include a cosmetic or decorative coating. 
     The electronic device  500  also includes a sensor assembly  577 . The sensor assembly  577  includes at least one sensor or sensor module. A variety of sensors may be positioned within and/or adjacent to a protruding feature. For example, a health monitoring sensor may be positioned at least partially within or adjacent to a protruding feature of a wearable device, such as a watch. As another example, a protruding feature may define a key region, a button region, or a trackpad region of a laptop computer, desktop computer, phone, tablet, or any other suitable electronic device. A biometric sensor (e.g., a face or fingerprint recognition sensor or a health monitoring sensor), a touch sensor, a force sensor, a proximity sensor or the like may be positioned within or adjacent to the protruding feature (e.g., within the device and proximate to the protruding feature). In some cases, the sensor assembly may further include other components such as support structure and/or a circuit assembly. In the example of  FIG.  5   , an interior surface of the rear cover assembly  524  is substantially planar adjacent to the sensor assembly. However, this example is not limiting and in additional examples this interior surface may define a recess configured to accommodate at least a portion of the sensor assembly. When the interior surface defines a recess, the thickness of the portion of the member which includes the protruding feature may or may not be thicker than a surrounding portion of the member. 
     The example of  FIG.  5    shows a member  534  which extends across a rear surface of the device  500 , but in additional examples, a member having a protruding feature may extend across a front, a rear, and/or a side surface of the electronic device and in some cases may extend over less than an entirety of one or more of these surfaces. In some cases, the member defining a protruding feature may define a user-facing surface of the electronic device. 
     In some examples, the electronic device  500  may be a wearable electronic device and the protruding feature of the member may define a user-facing surface of the electronic device. The sensor assembly  577  for such an electronic device may include one or more health monitoring sensors such as an electrocardiogram (ecg) sensor, a heart rate sensor, a photoplethysmogram (ppg) sensor, or a pulse oximeter. Further, the sensor assembly may include a sensor to determine whether or not the device is being worn and/or one or more additional sensors (e.g., one or more of the sensors described with respect to  FIG.  18   ). For example, when the wearable electronic device is a watch, the rear cover assembly  524  may define a first portion of the rear surface of the electronic device and may be inset into an opening of a housing structure which defines a second portion of the rear surface of the electronic device. The housing structure may further define a side surface of the electronic device. The watch may further include a front cover assembly which defines a front surface of the electronic device. The front cover assembly may be positioned over a display and a touch sensor. 
       FIG.  6    shows a partial cross-section view of an example member  634  of an electronic device. In some cases, the member (alternately, cover member)  634  is a glass member having two glass components, each formed from a layer of glass. The member  634  is shown in  FIG.  6    with the exterior surface  644  of the member  634  facing upwards. This orientation is rotated with respect to the view of  FIGS.  2  to  5   . The member  634  may be an example of the member  134  of  FIG.  1 B  or any other member or cover member described herein. 
     As shown in  FIG.  6   , the member  634  includes a first component  699  and a second component  696 . A first component, such as the first component  699 , may also be referred to herein as a first portion or as a first constituent. A second component, such as the second component  696 , may also be referred to herein as a second portion or as a second constituent. The first component  699  underlies the second component  696 , and the second component  696  typically has at least one lateral dimension that is smaller than that of the first component  699 . 
     The member  634  may be a glass member, the first component  699  may be a first glass component, and the second component  696  may be a second glass component. In additional cases, the member  634  is a composite member. As one example, the first component  699  is a first glass component and the second component  696  is a glass ceramic or ceramic component (or vice versa). The description of glass ceramic and ceramic components provided with respect to  FIG.  11    is generally applicable herein and, for brevity, is not repeated here. 
     The first component  699  includes or defines the portion  639  of the member  634 , also referred to herein as a base portion  639 . The base portion  639  defines a base region  649  of the exterior surface  644 . The first component  699  also includes the portion  635  underlying the protruding feature  636 . The protruding feature  636  protrudes from or is at least partially offset with respect to the base portion  639 . A protruding feature of a member, such as the protruding feature  636 , may also be referred to generally herein as a feature. 
     The second component  696  of the member may at least partially define the protruding feature  636  of the member  634 . In the example of  FIG.  6   , the second component  696  wholly defines the protruding feature  636 . However, in other examples the second component  696  may partially define the protruding feature, as shown in  FIGS.  7  to  9   . The protruding feature  636  defines a raised region  647  of the exterior surface  644 . The raised region  647  also defines a top surface of the protruding feature in  FIG.  6   . The raised region  647  may define a plateau (a substantially planar surface region). In the example of  FIG.  6   , the raised region  647  of the exterior surface is offset by a distance H 1  from the base region  649  of the exterior surface  644 . The protruding feature  636  also defines a width W 6  and a side region  648  that extends between the raised region  647  and the base region  649  of the exterior surface  644 . 
     The dashed line  695  schematically indicates the boundary region between the first component  699  and the second component  696 . The first component  699  may be bonded to the second component  696  and a boundary region may join the two components. In some cases, the first component  699  may be fused to the second component  696 , such as when the first component  699  is a first glass component and the second component  696  is a second glass component. In such cases, the first component  699  and the second component  696  may be referred to as being fusion bonded. When the first component  699  is fused to the second component  696  the boundary region may also be referred to herein as a fusion zone. In some embodiments, the fusion between the first component  699  and the second component  696  is substantially complete. For example, the boundary or fusion zone between the first component  699  and the second component  696  may include few, if any, voids, and any voids present may be small relative to the thickness of the first and the second components. In other cases, the first component  699  may be bonded to the second component  696  using an intermediate material, such an inorganic or organic material (e.g., an adhesive). The intermediate material may be thin relative to the first and the second components. 
     The first component  699  of the member  636  may be formed from a first layer of glass and the second component  696  of the member may be formed from a second layer of glass. The dashed line  695  may correspond to the boundary between the first layer of glass and the second layer of glass. In some cases, a distinct boundary region may be observed between the first component  699  and the second component  696 . In other cases, a distinct boundary region between the first component  699  and the second component  696  may not be detected by the unaided eye. 
     For example, a distinct fusion zone may not be detected by the unaided eye when the first layer of glass has a composition that is substantially similar to that of the second layer of glass and fusion between the first glass component and the second glass component is substantially complete. In some cases, one or more fusion artifacts may be detected in the fusion zone such as an area of incomplete fusion, a void, a graphite or other impurity particle arising from the thermoforming process, and the like. The size of any fusion artifacts may be sufficiently small that the glass member has the desired strength. For example, a fusion artifact may be less than 50 microns, less than 25 microns, less than 10 microns, or less than 5 microns in size. In some cases, the boundary region and/or a fusion artifact may be observed by sectioning the member  634  and/or using non-destructive techniques. Suitable techniques for observing the boundary region and/or a fusion artifact include, but are not limited to, microscopy, elemental analysis, optical interference detection, ultrasonic detection, and the like. 
     As shown in  FIG.  6   , the member  634  further defines a through-hole, such as the through-hole  662 . The through-hole  662  extends through the protruding feature  636  and the underlying portion  635  of the member  634 . The first component of the member  634  may define a lower or first portion of the through-hole  662  and the second component of the member may define an upper or second portion of the through-hole  662 . 
     The through-hole  662  may allow input to, output from, or placement of a device component such as an optical module as previously described with respect to  FIGS.  1 B and  2  to  4   . The protruding feature  636  may further define an opening  667  to the through-hole, with the opening  667  being located in the raised region  647 . In some cases, the member  634  may define an arrangement, array, or set of through-holes and openings extending through the protruding portion  636 . For example, the member  634  may define any number of through-holes and openings, such as one, two, three, four, or five through-holes and openings. In additional embodiments, the member need not define a through-hole, but may define a window for an underlying optical module as shown in the example of  FIG.  9   . 
     As shown in  FIG.  6   , the raised region  647  of the exterior surface  644  includes a textured region  656 . The textured region  656  may extend across a substantial entirety of the raised region  647  except for the opening(s) such as  667 . For example, the textured region  656  may extend substantially across the plateau defined by the raised region  647 . In some cases, the textured region  656  may be confined to the plateau while in additional cases the textured region  656  may extend across the side region  648  of the exterior surface. If the member  634  is to be uniformly textured, the textured region  656  may extend across the base region  649  as well. 
     In some cases, the base region  649  and the raised region  647  may both define respective textured regions of the exterior surface  644  (also referred to herein as textured surface regions). For example, the raised region  647  may define a first texture and the base region  649  may define a second texture different than the first texture. In some cases, the side region  648  (which may also be referred to as a peripheral region) may define a third texture. As examples, the third texture may be the same as the first texture or the second texture or may be formed by an overlap of the first texture and the second texture. As used herein, a texture may include a relatively smooth texture, such as a texture produced by a polishing process. 
     As schematically illustrated in  FIG.  6   , the texture of the textured region  656  (of the raised region  647 ) may be rougher than the texture of the base region  649 . For example, the textured region  656  may have at least one roughness parameter, such as a root mean square surface height, a root mean square slope, and/or a mean peak curvature, which is greater than that of the base region  649 . In some cases, the base region  649  may not include a textured region or may have a smooth texture that is tactilely and/or visually distinct from that of the textured region  656 . For example, the base region  649  may have a relatively smooth texture resulting from a polishing or a glass forming process, such as a texture corresponding to that of a polished surface. In some cases, the textured region  656  of the raised region  647  may be configured to produce a gloss level that is lower than that of a window or lens of an optical module in the opening  667  (e.g., the window  287  of  FIG.  2   ). The textured region  656  may also be configured to produce a translucent and/or hazy appearance. 
     In other cases, the texture of the textured region  656  may be smoother than the texture of the base region  649 .  FIGS.  4  and  7    show examples of this arrangement. For example, the textured region  656  may have a texture similar to that of a polished surface and the base region  649  may have a rougher texture. 
     In the example of  FIG.  6   , the raised region  647  of the exterior surface is offset by a distance H 1  from the base region  649  of the exterior surface. The thickness T 2  (the distance between the interior surface  642  and the raised region  647 ) is greater than the thickness T 1  (the distance between the interior surface  642  and the base region  649  of the exterior surface). As examples, the ratio T 2 /T 1  may be from about 1.25 to about 3 or from about 1.5 to about 2. In some cases, the protruding feature  636  has a thickness greater than about 1 mm and less than or equal to about 2.5 mm and the base portion  639  has a thickness greater than about 0.5 mm and less than about 1 mm. 
       FIG.  7    shows a partial cross-section view of another example member  734  of an electronic device. The member (alternately, cover member)  734  may comprise two components  799  and  796 . A boundary region  795  between the two components may be elevated with respect to a base region  749  of the external surface  744  after a shaping operation. In some cases, the member  734  is a glass member comprising two glass components, each formed from a layer of glass. The member  734  is shown in  FIG.  7    with the exterior surface  744  of the member  734  facing upwards. The member  734  may be an example of the member  134  of  FIG.  1 B . The member  734  defines an exterior surface  744 , an interior surface  742 , a protruding feature  736 , and a base portion  739 . The protruding feature defines a width W 7 . 
     As shown in  FIG.  7   , the member  734  includes a first component  799  and a second component  796 . The first component  799  includes the base portion  739 , the portion  735  underlying the protruding feature  736 , and a portion (alternately, part)  737  that defines a lower or first part of the protruding feature  736 . The second component  796  defines an upper or second part of the protruding feature and a raised region  747  of the exterior surface. The region  737  of the first component  799  may define a lower or first part (alternately, portion) of the side surface  748  and the second component  796  may define an upper or second part (alternately, portion) of the side surface  748 . In a similar fashion as described for  FIG.  6   , the raised region  747  may define a plateau and may be offset outwardly from the base region  749  of the exterior surface. 
     In the example of  FIG.  7   , the dashed line  795  schematically indicates the boundary between the first component  799  and the second component  796 . In the example of  FIG.  7    the boundary is offset from the height of the base region  749  of the exterior surface  744  and is offset from the interior surface  742  by a distance H 7  that is greater than the thickness T 3 . In some cases, the first component  799  is fusion bonded to the second component  796 , such as when the first and the second components are glass components. As previously described with respect to  FIG.  6   , fusion between the first component  799  and the second component  796  may be substantially complete or some small regions of incomplete fusion may be present along the boundary. In other examples, the first component  799  may be coupled to the second component  796  using an intermediate material, such an inorganic or organic material (e.g., an adhesive) as previously described with respect to  FIG.  6   . 
     In some cases, the first component  799  may be a first glass component formed from a first layer of glass and the second component  796  may be a second glass component formed from a second layer of glass. The dashed line  795  may correspond to the boundary between the first layer of glass and the second layer of glass. In additional cases, the member  734  is a composite member. As one example, the first component  799  is a first glass component and the second component  796  is a glass ceramic or ceramic component (or vice versa). The description of glass ceramic and ceramic components provided with respect to  FIG.  11    is generally applicable herein and, for brevity, is not repeated here. 
     In some cases, shaping (e.g., machining) of the layers after the first layer is coupled to the second layer causes the boundary between the layers to be offset from the height of the base region  749  of the exterior surface  744  as described in more detail with respect to  FIGS.  11  and  12 A to  12 C . The description provided with respect to  FIGS.  11  and  12 A to  12 C  is generally applicable herein and, for brevity, is not repeated here. In some examples, a distinct boundary region between the first component  799  and the second component  796  may not be readily detected by the unaided eye, while in other examples at least a portion of a boundary region or a fusion artifact may be detected by the unaided eye or using other techniques as previously discussed with respect to  FIG.  6   . The description provided with respect to  FIG.  6    is generally applicable herein and, for brevity, is not repeated here. 
     As shown in  FIG.  7   , the member  734  further defines a through-hole, such as the through-hole  762 . The through-hole  762  extends through the protruding feature  736  and the underlying portion  735  of the member  734 . The first component  799  of the member  734  may define a lower or first portion of the through-hole  762  and the second component  796  of the member may define an upper or second portion of the through-hole  762 . The second component  796  may further define an opening  767  to the through-hole, with the opening  767  being located in the raised region  747 . The arrangement and function of the through-hole may be as previously described with respect to  FIG.  6    and for brevity that description is not repeated here. 
     As shown in  FIG.  7   , a textured region  756  extends across the base region  749  and the side surface  748  of the exterior surface  744 . In the example of  FIG.  7   , the texture of the textured region  756  may be rougher than the texture of the raised region  747 . For example, the raised region  747  may have a polished texture. However, it should be understood that this example is not limiting and the texture of the textured region  756  may be any of the textures described herein, including those described with respect to  FIG.  6   . The thickness T 4  (the distance between the interior surface  742  and the raised region  747 ) is greater than the thickness T 3  (the distance between the interior surface  742  and the base region  749  of the exterior surface). The values and ratios of these thicknesses (T 3  and T 4 ) may be as previously described for the thicknesses T 1  and T 2  of  FIG.  6    and, for brevity, are not repeated here. 
       FIG.  8    shows a partial cross-section view of an additional example of a member  834  of an electronic device. In the example of  FIG.  8   , the member (alternately, cover member)  834  retains a layered structure and a distinct boundary can be detected between the layers. In some cases, the member  834  is formed from two layers of glass and a distinct boundary  895  can be detected between the two glass components formed from the two glass layers. The member  834  is shown in  FIG.  8    with the exterior surface  844  of the member  834  facing upwards. The member  834  may be an example of the member  134  of  FIG.  1 B . The member  834  defines an exterior surface  844 , an interior surface  842 , a protruding feature  836 , and a base portion  839 . The protruding feature defines a width W 8 . 
     The member  834  includes a first component  899  and a second component  896 . In some cases, the first component  899  may be a first glass component formed from a first layer of glass and the second component  896  of the member may be a second glass component formed from a second layer of glass. In additional cases, the member  834  is a composite member. As one example, the first component  899  is a first glass component and the second component  896  is a glass ceramic or ceramic component (or vice versa). The description of glass ceramic and ceramic components provided with respect to  FIG.  11    is generally applicable herein and, for brevity, is not repeated here. 
     The first component  899  includes the base portion  839 , the portion  835  underlying the protruding feature  836 , and a portion (alternately, part)  837  that defines a lower or first part of the protruding feature  836 . The second component  896  defines an upper or second part of the protruding feature  836  and a raised region  847  of the exterior surface. The region  837  of the first component  899  may define a lower or first part of the side surface  848  and the second component  896  may define an upper or second part of the side surface  848 . In a similar fashion as described for  FIG.  6   , the raised region  847  may define a plateau and may be offset outwardly from the base region  849  of the exterior surface. 
     In the example of  FIG.  8    the first component  899  is bonded to the second component  896 . The line  895  schematically indicates the boundary between the first component  899  and the second component  896 . In the example of  FIG.  8   , the boundary indicated by the line  895  is distinct and extends across the protruding feature  836 . In some cases, the line  895  indicates a fusion zone. This boundary is offset from the height of the base region  849  of the exterior surface  844  and is offset from the interior surface  842  by a distance H 8  that is greater than the thickness T 5 . In other examples, the first component  899  may be coupled to the second component  896  using an intermediate material, such an inorganic or organic material (e.g., an adhesive) as previously described with respect to  FIG.  6   . 
     In some cases, the first component  899  of the member  834  may be formed from a first layer of glass and the second component  896  of the member may be formed from a second layer of glass. The solid line  895  may correspond to the boundary region between the first layer of glass and the second layer of glass, which may be detected by the unaided eye across the protruding feature. As previously described with respect to  FIG.  7   , machining of the member  834  after the first layer of glass is coupled to the second layer of glass causes the boundary region between the layers to be offset from the height of the base region  849 . The description provided with respect to  FIGS.  11  and  12 A to  12 C  is generally applicable herein and, for brevity, is not repeated here. 
     As shown in  FIG.  8   , the member  834  further defines a through-hole, such as the through-hole  862 . The through-hole  862  extends through the protruding feature  836  and the underlying portion  835  of the member  834 . The first component  899  of the member  834  may define a lower or first portion of the through-hole  862  and the second component  896  of the member may define an upper or second portion of the through-hole  862 . 
     The through-hole  862  may allow input to, output from, or placement of a device component such as an optical module as previously described with respect to  FIGS.  1 B and  2  to  4   . The protruding feature  836  may further define an opening  867  to the through-hole, with the opening  867  being located in the raised region  847 . The arrangement and function of the through-hole may be as previously described with respect to  FIG.  6    and for brevity that description is not repeated here. 
     As shown in  FIG.  8   , the raised region  847  of the exterior surface  844  includes a textured region  856 . In the example of  FIG.  8   , the texture of the textured region  856  may be rougher than the texture of the base region  849 . However, it should be understood that this example is not limiting and the texture of the textured region  856  may be any of the textures described herein, including those described with respect to  FIG.  6   . In addition, the thickness T 6  (the distance between the interior surface  842  and the raised region  847 ) is greater than the thickness T 5  (the distance between the interior surface  842  and the base region  849  of the exterior surface). The values and ratios of these thicknesses (T 5  and T 6 ) may be as previously described for the thicknesses T 1  and T 2  of  FIG.  6    and, for brevity, are not repeated here. 
       FIG.  9    shows a partial cross-section view of a further example of a member  934  of an electronic device. The member (alternately, cover member)  934  may be formed from three layers (e.g., three layers of glass) in order to provide a “window” over the hole  962 . The member  934  is shown in  FIG.  9    with the exterior surface  944  of the member  934  facing upwards. The member  934  may be an example of the member  134  of  FIG.  1 B . The member  934  defines an exterior surface  944 , an interior surface  942 , a protruding feature  936 , and a base portion  939 . The protruding feature defines a width W 9 . 
     As shown in  FIG.  9   , the member  934  includes a first component  999 , a second component  996 , and a third component  997 . In some cases, the member  934  is a glass member, the first component  999  is a first glass component, the second component  996  is a second glass component, and the third component  997  is a third glass component. In additional cases, the member  934  is a composite member. As one example, the first component  999  is a first glass component, the second component  996  is second glass component, and the third component  997  is a glass ceramic or ceramic component. A glass, glass ceramic or ceramic material defining the third component may be transparent to visible light, infrared radiation, ultraviolet radiation, or combinations thereof. The description of glass ceramic and ceramic components provided with respect to  FIG.  11    is generally applicable herein and, for brevity, is not repeated here. 
     The first component  999  includes the base portion  939 , the portion  935  underlying the protruding feature  936 , and a portion (alternately, part)  937  that defines a lower or first part of the protruding feature  936 . The second component  996  defines an intermediate or second part of the protruding feature. The third component  997  defines an upper or third part of the protruding feature and a raised region  947  of the exterior surface. The portion  937  of the first component  999  may define a lower or first part of the side surface  948 , the second component  996  may define an intermediate or second part of the side surface  948 , and the third component  997  may define an upper or third part of the side surface  948 . In a similar fashion as described for  FIG.  6   , the raised region  947  may define a plateau and may be offset outwardly from the base region  949  of the exterior surface. 
     The dashed lines  995   a  and  995   b  schematically indicate the boundaries between the first component  999 , the second component  996 , and the third component  997 . In the example of  FIG.  9    the boundaries  995   a  and  995   b  are offset from the height of the base region  949  of the exterior surface  944  and are offset from the interior surface  942  by a distances H 9  and H 10 , respectively (each greater than the thickness T 7 ). In some cases, the first component  999  is fusion bonded to the second component  996  and the second component  996  is fusion bonded to the third component  997 , such as when the first, the second, and the third components are glass components. As previously described with respect to  FIG.  6   , fusion between the first component  999  and the second component  996  and between the second component  996  and the third component  997  may be substantially complete or some small regions of incomplete fusion may be present along the boundary. In other examples, the first, the second, and the third components may be coupled using an intermediate material, such an inorganic or organic material (e.g., an adhesive) as previously described with respect to  FIG.  6   . 
     The first component  999  of the member  934  may be formed from a first layer of glass, the second component  996  of the member may be formed from a second layer of glass, and the third component  997  of the member may be formed from a third layer of glass. In some cases, one or more holes are formed in the second layer of glass prior to fusing of the layers of glass in order to facilitate formation of the hole  962 . The dashed lines  995   a  and  995   b  may correspond to the boundary regions between the layers of glass. In some examples a distinct boundary region between the first component  999  and the second component  996  and/or the second component  996  and the third component  997  may not be detected by the unaided eye while in other examples at least a portion of one or more boundary regions or a fusion artifact may be detected by the unaided eye or using other techniques as previously discussed with respect to  FIG.  6   . The description provided with respect to  FIG.  6    is generally applicable herein and, for brevity, is not repeated here. 
     As shown in  FIG.  9   , the member  934  further defines a hole, such as the hole  962 . The hole  962  extends through the second component  996  and the underlying portion  935  of the first component  999  but does not extend through the third component  997 . The hole  962  may also be referred to as a blind hole. The third component  997  therefore can provide a window over the hole  962 . The first component  999  of the member  934  may define a lower or first portion of the hole  962  and the second component  996  of the member may define an upper or second portion of the hole  962 . The hole  962  may allow input to, output from, or placement of a device component such as an optical module as previously described with respect to  FIGS.  1 B and  2  to  4   . The third component  997  of the glass member may function as a window for the optical module. The number of holes may be similar to the number of through-holes previously described with respect to  FIG.  6    and for brevity that description is not repeated here. 
     As shown in  FIG.  9   , the exterior surface  944  includes a textured region  956 . In the example of  FIG.  9   , the texture of the textured region extends across the raised region  947 , the side surface  948 , and the base region. For example, the textured region  956  may have a polished texture. In additional examples, the texture of the textured region  956  may be smoother than the texture of the base region  949  to facilitate its use as a window for an optical component. The thickness T 8  (the distance between the interior surface  942  and the raised region  947 ) is greater than the thickness T 7  (the distance between the interior surface  942  and the base region  949  of the exterior surface). The values and ratios of these thicknesses (T 7  and T 8 ) may be as previously described for the thicknesses T 1  and T 2  of  FIG.  6    and, for brevity, are not repeated here. 
       FIG.  10    shows a detail view of a textured region  1056  of a member  1034 . The textured region  1056  may be an example of the textured region  656  of  FIG.  6    in detail area  1 - 1  or of any other textured region shown herein. In some cases, the textured region  1056  may be defined by a raised region of the exterior surface  1047  of the member  1034 , as previously described with respect to  FIG.  6   . A textured region may also be referred to herein as a textured surface region. 
     The textured region  1056  comprises a plurality of surface features  1080 . The example of the surface features  1080  provided in  FIG.  10    is not limiting and in general the surface features  1080  of a surface region of the member  1034  may define any of a range of shapes or configurations. The surface features  1080  may have a variety of shapes, such as rounded or angular features. As examples, the surface features  1080  may define a circular, oval, polygonal, rectangular, or irregular surface contour. Furthermore, the surface features  1080  may define protrusions, recesses, or a combination thereof and may have any suitable shape and may be pyramidal, conical, cylindrical, arched, have a curved upper surface or a frustum of a shape such as a cone, and so on. 
     As shown in  FIG.  10   , the surface features  1080  may define one or more recesses, such as the surface feature  1084 . A recess may define a minimum point, such as the point  1085 . The surface features  1080  may also define one or more protrusions, such as the surface feature  1086 . A protrusion may define a maximum point, such as the point  1087 . As schematically shown in  FIG.  10   , the surface features  1080  may define a set of minimum points as well as a set of maximum points. The set of maximum points may also be referred to as a set of peaks. The surface features  1080  may define a set of recesses, each recess being positioned between adjacent peaks of the set of peaks. The shapes of the peaks and the valleys are not limited to those schematically shown in  FIG.  10   . For example, at least some of the peaks may have a somewhat larger radius of curvature (and smaller curvature) to provide the desired tactile properties in addition to the desired level of cleanability for the textured surface. 
     In some embodiments, the surface features  1080  define a set of hills and valleys. The hills and valleys may be defined using areal texture analysis techniques as described below. The surface feature  1086  may generally correspond to a hill feature and the surface feature  1084  may generally correspond to a valley feature. In some embodiments, a set of hills and valleys has a substantially uniform spacing between hill features, valley features, or a combination thereof. In additional embodiments, a set of valleys may have a non-uniform or an irregular spacing between hill features and/or valley features. 
     The heights of the surface features  1080  may be measured with respect to a reference surface  1082 . For example, the heights of the hills may be determined from the maximum points (e.g., point  1087 ) and the heights of the valleys may be determined from the minimum points (e.g., point  1085 ). The member  1034  may be an example of the member  134  or any other members described herein. Details of these members are applicable to the member  1034  and, for brevity, will not be repeated here. 
     The surface features  1080  may be configured to provide particular optical properties to one or more surface regions of the member  1034 , as well as to a cover assembly and electronic device including the member  1034 . However, the surface features  1080  defining the texture of the surface region may not be individually visually perceptible. In some cases, the texture of the surface region may cause the member  1034  to appear translucent, rather than transparent. In some cases, the texture may be configured to provide particular levels of such optical properties such as transmissive haze, clarity, gloss, graininess, and combinations thereof. 
     A textured surface region of the member, such as the textured region  1056 , may be configured to provide a specified gloss level to the surface. In some embodiments, the textured region  1056  may have a gloss value of less than about 50 gloss units, less than about 40 gloss units, from 2 gloss units to 20 gloss units, from 2 gloss units to 10 gloss units, from 5 gloss units to 50 gloss units, from 5 gloss units to 20 gloss units, from 10 gloss units to 50 gloss units, from 10 gloss units to 45 gloss units, or from 15 gloss units to 45 gloss units as measured at 60 degrees. The gloss level may be measured in the absence of a cosmetic coating. In additional embodiments the textured region  1056  may have a higher gloss. For example, a textured region  1056  having a relatively high gloss may have a gloss value greater than about 70 gloss units and less than or equal to about 150 gloss units. In some cases, the difference between the gloss of the textured region and another region of the exterior surface may be at least 10% and may be more than 100%. In some cases, the gloss of the textured region may be measured using commercially available equipment and according to ASTM or ISO standard test methods. The angle measurement may refer to the angle between the incident light and the perpendicular to the textured region of the surface. 
     A textured surface region of the member  1034 , such as the textured region  1056 , may be configured to provide a specified level of transmissive haze to the corresponding portion of the member. In some cases, the transmissive haze of the textured region may be measured using commercially available equipment and according to ASTM or ISO standard test methods. The transmissive haze may relate to the amount of light subject to wide angle scattering (e.g., greater than 2.5 degrees). In some cases, the transmissive haze may be greater than or equal to about 50%, greater than or equal to about 60%, or greater than or equal to about 70%. For example, the transmissive haze may be from about 60% to about 90% or from about 70% to about 80%. As non-limiting examples, the transmissive haze may be measured using a haze-gard i device available from BYK or a GC 5000L variable photometer available from Nippon Denshoku. The transmissive haze scattering may be measured for the cover assembly or member as removed from the electronic device. The transmissive haze of another region of the exterior surface of the member, such as the base region, may be similar to or different from that of textured region  1056 . 
     A textured surface region of the member  1034 , such as the textured region  1056 , may be configured to provide a specified level of clarity to the corresponding portion of the member. The clarity or the transmissive narrow angle scattering of the textured region may be measured using commercially available equipment and according to ASTM or ISO standard test methods. In some cases, the clarity may be less than about 50%, less than about 40%, less than about 30%, less than about 20%, less than about 15%, or less than about 10%. For example, the clarity may be from about 5% to about 30%, from about 5% to about 20%, from about 5% to about 15%, or from about 5% to about 15%. The transmissive narrow angle scattering may be measured using a haze-gard i device available from BYK or a GC 5000L variable photometer available from Nippon Denshoku. A clarity value may be determined from measurements of the intensity in a central region (I central ) and an intensity in a ring around the central region (I ring ). For example, the clarity value may be equal to 100%*(I central −I ring )/(I central +I ring ). The clarity or the transmissive narrow angle scattering may be measured for the cover assembly or member as removed from the electronic device. 
     In some cases, a textured region of the member may be configured to provide a specified level of visual uniformity to the corresponding portion of the member. The level of visual uniformity of another region of the exterior surface of the member, such as the base region, may be similar to or different from that of textured region  1056 . The graininess of a textured region may be measured under diffused illumination using commercially available equipment. The graininess may be measured similarly for a textured region of a cover assembly. In some cases, an image of the textured surface of the member  1034  may be obtained using a digital camera and the lightness of each pixel of the image may be determined, thereby allowing determination of the lightness variation across the textured surface. For example, the BYK-mac device available from BYK may produce a graininess value determined from a histogram of the lightness levels. The graininess of the textured surface may be less than about 1.5 or less than about 1.0. In addition, the graininess may be from about 0.1 to about 1.5, from about 0.1 to about 1.0, from about 0.25 to about 1.5, from about 0.25 to about 1.0, from about 0.5 to about 1.5, or from about 0.5 to about 1.0. These graininess values may be measured prior to application of any cosmetic coating to the member. 
     A textured surface region of the member  1034 , such as the textured region  1056 , may be configured to provide a specified level of cleanability. For example, the texture of the textured region  1056  may be configured so that a root mean square (RMS) height of the features is not overly large. The texture may also be configured so that a size of any recessed surface features is sufficiently large to facilitate cleaning. In addition, the texture may be configured so that the root mean square (RMS) slope and/or the mean peak curvature of the surface features is small enough to provide the desired tactile properties in addition to the desired level of cleanability. 
     Surface texture parameters include areal surface texture parameters such as amplitude parameters, spatial parameters, and hybrid parameters. Surface filtering may be used to exclude surface noise and/or surface waviness before determining the surface texture parameters. In addition, a segmentation technique may be used to determine feature parameters such as the maximum diameter, the minimum diameter, the area, and the perimeter. These parameters may be calculated on the basis of the feature shape as projected onto the reference surface (e.g., a reference plane). Mean values may be determined for a given class of surface features (e.g., hills or valleys). Surface texture parameters and methods for determining these parameters (including filtering and segmentation) are described in more detail in International Organization for Standardization (ISO) standard 25178 (Geometric Product Specifications (GPS)—Surface texture: Areal). 
     These surface texture parameters may be measured using commercially available equipment, including equipment using optical measurement techniques. An example optical measurement technique is interferometry and an example of commercial equipment using this technique is a coherence scanning interferometry profiler (white light), such as a Zygo coherence scanning interferometry optical profiler. Another example optical measurement technique is confocal microscopy and an example of commercial equipment using this technique is a laser scanning confocal microscope, such as a Keyence laser scanning confocal microscope. Images may be tiled to measure a larger area. 
     For example, the surface features  1080  of one or more surface regions of the member  1034  may be characterized, in part, by the heights of the surface features. The height may be measured with respect to a reference surface, such as the arithmetical mean of the surface (schematically shown by line  1082  in  FIG.  10   ). The heights of the surface features  1080  may not be uniform, so that the surface features have a distribution of heights. The magnitude of the heights of the surface features  1080  may fall in the range from zero to about 5 microns, zero to about 2.5 microns, from zero to about 2 microns, from zero to about 1.5 microns, or from zero to about 1 micron. The surface features  1080  may be characterized by the root mean square height Sq or the arithmetic mean height Sa of the surface. The root mean square (RMS) height of the surface features  1080  may be greater than zero and less than about 5 microns, greater than zero and less than about 2.5 microns, greater than zero and less than about 2 microns, greater than zero and less than about 1.5 microns, greater than zero and less than about 1 micron, from about 0.1 microns to about 2.5 microns, from about 0.1 microns to about 2 microns, from about 0.1 microns to about 1.5 microns, from about 0.1 microns to about 1.25 microns, from about 0.1 microns to about 1.0 micron, from about 0.2 microns to about 2.5 microns, from about 0.2 microns to about 2 microns, from about 0.2 microns to about 1.5 microns, from about 0.2 microns to about 1.25 microns, from about 0.2 microns to about 1.0 micron, from about 0.25 microns to about 2.5 microns, from about 0.25 microns to about 2 microns, from about 0.25 microns to about 1.5 microns, from about 0.25 microns to about 1.25 microns, from about 0.25 microns to about 1.0 micron, from about 0.5 microns to about 2.5 microns, from about 0.5 microns to about 2 microns, from about 0.5 microns to about 1.5 microns, from about 0.5 microns to about 1.25 microns, from about 0.5 microns to about 1.0 micron, from about 0.75 microns to about 5 microns, or from about 1 micron to about 5 microns. In some cases, one textured region may be referred to as being rougher than another textured region when it has a greater RMS height. 
     The RMS height of another region of the exterior surface of the member  1034 , such as the base region, may be similar to or different from that of textured region  1056 . For example, the RMS height of the raised region may be greater than that of the base region. For example, the RMS height of the raised region may be at least 10% and less than 150%, at least 10% and less than 100%, or at least 10% and less than 50% greater than that of the base region. In some cases, the RMS height of the base region may be less than 0.5 microns, less than 250 nm, or from 1 nm to about 250 nm. In some cases, the RMS height of the base region may be similar to that of a polished surface, such as from about 1 nm to about 150 nm, from about 1 nm to about 125 nm, from about 1 nm to about 100 nm, from about 1 nm to about 75 nm, from about 1 nm to about 50 nm, from about 1 nm to about 25 nm, or from 1 nm to about 10 nm. 
     In addition, the surface features  1080  of one or more surface regions may be characterized by lateral parameters, such as the distance between peaks. The spacing between peaks may not be uniform, so that there is a distribution of spacings between peaks. The average (mean) distance or spacing between peaks may be referred to as the average pitch or mean pitch. The average pitch may be from about 1 micron to about 20 microns, from about 1 micron to about 15 microns, from about 1 micron to about 10 microns, from about 2.5 microns to about 20 microns, from about 2.5 microns to about 15 microns, from about 2.5 microns to about 10 microns, from about 5 microns to about 40 microns, from about 5 microns to about 20 microns, from about 5 microns to about 15 microns, or from about 5 microns to about 10 microns. 
     In some embodiments, the surface features  1080  of one or more surface regions may be configured so to have a particular ratio of the average height of the peaks to the average spacing of the peaks. For example, the ratio of the RMS height to the mean pitch may be from about 0.01 to about 0.6, from about 0.01 to about 0.3, from about 0.02 to about 0.6, from about 0.02 to about 0.3, from about 0.03 to about 0.6, from about 0.03 to about 0.3, from about 0.04 to about 0.6, or from about 0.04 to about 0.3. 
     The surface features  1080  of one or more surface regions may also be characterized by a lateral size. For example, the surface features  1080  may be characterized by a maximum lateral (or linear) size and a minimum lateral (or linear size). The surface features  1080  may have a maximum lateral size small enough that they are not visually perceptible as individual features. In addition, the lateral size and spacing of the surface features  1080  may be configured so that the member has a sufficiently low level of graininess. 
     The surface features  1080  of one or more surface regions may be characterized by the root mean square slope (Sdq), also referred to as the root mean square gradient. In some embodiments, the root mean square slope may be greater than zero and less than about 1.25, greater than zero and less than about 1, from 0.1 to less than about 1.25, from about 0.1 to less than about 1, from about 0.25 to less than about 1, from about 0.25 to about 0.75, or from about 0.1 to about 0.5. In some cases, the root mean square slope of the raised region is greater than that of the base region. For example, the root mean square slope of the raised region may be at least 10% and less than 60% greater than that of the base region. 
     The surface features  1080  of one or more surface regions may also be characterized by the curvature of the peaks (also referred to as summits), such as by the arithmetic mean summit curvature S sc , also referred to herein as the mean peak curvature. In some embodiments, the arithmetic mean summit curvature is greater than zero and less than about 2.0 microns, greater than zero and less than or equal to about 1.5 microns −1 , from about 0.1 microns −1  to about 2.0 microns −1 , from about 0.1 microns −1  to about 1.5 microns −1 , from about 0.25 microns −1  to about 2.0 microns −1 , from about 0.25 microns −1  to about 1.5 microns −1 , from about 0.5 microns −1  to about 2.0 microns −1 , from about 0.5 microns −1  to about 1.5 microns −1 , from about 0.75 microns −1  to about 2.0 microns −1 , or from about 0.75 microns −1  to about 1.5 microns −1 . In some cases, the mean peak curvature of the raised region is greater than that of the base region. For example, the mean peak curvature of the raised region may be at least 10% and less than 50% greater than that of the base region. 
     The surface features  1080  of one or more surface regions may also be characterized by an autocorrelation length. In some embodiments, the autocorrelation length is from about 1 micron to about 50 microns, from about 2 microns to about 30 microns, or from about 3 microns to about 25 microns. 
       FIG.  11    shows a flow chart of an example process  1100  for forming a glass member from at least two glass layers. Typically, the glass member and each of the glass layers includes a silica-based glass material. The glass material may have a network structure, such as a silicate-based network structure. In some embodiments, the glass material includes an aluminosilicate glass. As used herein, an aluminosilicate glass includes the elements aluminum, silicon, and oxygen, but may further include other elements. Typically, the glass material includes an ion-exchangeable glass material, such as an alkali metal aluminosilicate glass (e.g., a lithium aluminosilicate glass). An ion-exchangeable aluminosilicate glass may include monovalent or divalent ions that compensate for charges due to replacement of silicon ions by aluminum ions. Suitable monovalent ions include, but are not limited to, alkali metal ions such as Li + , Na + , or K + . Suitable divalent ions include alkaline earth ions such as Ca 2+  or Mg 2+ . The description of suitable glass materials provided with respect to  FIG.  11    is generally applicable to the members (cover members) and glass layers described herein. In some cases, each of the glass layers has a substantially similar composition. In additional cases, the glass layers may differ in composition. 
     The glass layers used to form the glass member may be shaped prior to operation  1110  of assembling the glass layers. The glass layers may be shaped to a desired shape and size by machining. In addition, the surfaces of the glass layers may be finished so that adjacent layers can closely contact each other. In some cases, the surfaces of adjacent glass layers are substantially flat and smooth as schematically illustrated in  FIGS.  12 A to  12 C . In other cases, one of the surfaces of the adjacent glass layers is rounded, rather than flat, as schematically illustrated in  FIGS.  14 A and  15 A . In some cases, pilot holes may be formed (e.g., by machining) in one or more of the glass layers, as schematically illustrated in  FIGS.  13 A and  13 B . 
     After the shaping operation, a glass layer forming a first or lower portion of the glass member typically has larger lateral dimensions than the glass layer(s) forming the upper portion(s) of the glass member. In some cases, the thickness of the first glass layer forming the first or lower portion of the glass member is from 0.5 mm to 1.0 mm, or from 0.75 mm to 1.5 mm, and the thickness of the glass layer(s) forming the upper portion(s) of the glass is from 0.75 to 1.5 mm or from 1.0 mm to 2 mm. In some cases, the desired shape of the glass layers includes rounded or chamfered corners. Following the shaping operation, the glass layers may be cleaned, such as by washing. The glass layers may also be etched or plasma treated following the shaping operation. 
     The process  1100  of  FIG.  11    includes an operation  1110  of assembling the glass layers used to form the glass member, thereby forming an assembly of glass layers (also referred to herein as an assembly). In some embodiments, the operation  1110  comprises assembling the first glass layer with the second glass layer to form the assembly of glass layers. In some cases, the layers may be assembled by placing them in contact with one another. In additional cases, the layers may be at least partially bonded during the operation  1110 , such as by laser bonding, optical bonding, or the like. Examples of assemblies of two glass layers are shown in  FIGS.  12 A,  13 A,  14 A, and  15 A . The assembly operation may be performed under clean conditions to limit introduction of foreign matter between the glass layers. 
     As shown in  FIG.  11   , the process  1100  includes an operation  1120  of fusing (also referred to as fusion bonding) the assembly of glass layers to form a fused assembly. Typically, the fusing operation comprises heating the assembly and applying pressure to at least the upper layers of the assembly. The assembly of glass layers may be heated and pressure applied in a thermoforming apparatus, which may also be referred to as a forming tool. In some cases, the assembly is placed on a support surface and a tool-piece such as plunger, piston, or the like contacts the upper layer of the assembly, as schematically illustrated in  FIGS.  12 A and  13 A . For example, the support surface may be substantially flat. 
     The fusing operation may include heating the assembly of glass layers to a temperature between the glass transition temperature and a softening point of each of the glass layers, to a temperature between an annealing point and a softening point of each of the glass layers, or to a temperature between a strain point and a softening point of each of the glass layers. For example, the strain point (viscosity of about 10 14.5  Poise) is the temperature at which internal stress in the glass is relieved in hours. The annealing point (viscosity of about 10 13.2  to 10 13.4  Poise) is the temperature at which internal stress in the glass is relieved in minutes. The dilatometric softening point is defined by a viscosity of about 10 9  to 10 11  Poise while the Littleton softening point is defined by a viscosity of about 10 7.6  Poise; a “softening point” as referred to herein may refer to either of these temperatures. The working point is defined by a viscosity of about 10 4  Poise. The glass transition temperature (viscosity of about 10 12  to 10 13  Poise) is the temperature at which glass transitions from super-cooled liquid to a glassy state. The heating may be performed in several stages. In some cases, the assembly may be heated while the tool-piece rests on the upper layer of the assembly and the assembly as a whole rests on the support surface. 
     The fusing operation may also include applying pressure to at least the upper layers of the assembly. In some cases, the tool-piece contacts the upper layer of the assembly, but not the remainder of the assembly, while pressure is applied to the assembly through the tool-piece. In some cases, the pressure may be greater than that due to the weight of the tool-pieces. In some cases, fusion between the lower layer and the upper layer(s) of the assembly may begin in a central region of the upper layers(s) and then may move outwards towards the sides of the upper layers.  FIGS.  16 A and  16 B  schematically illustrate movement of a fusion front in such a fusion operation.  FIGS.  14 A and  15 A  show examples of layer shapes that may lead to such movement of the fusion front during the fusion operation. 
     The operation of fusing the assembly of glass layers creates an integral fused assembly. The portion of the fused assembly formed from multiple layers of glass typically has a greater thickness than a portion of the fused assembly formed from a single layer of glass. In addition, this thicker portion of the fused assembly protrudes from an adjacent portion of the thinner portion of the fused assembly. The protruding feature of the glass member will be located within this thicker portion, while the base portion will be located within the adjacent thinner portion. Each of the thicker portion and the thinner portion defines an external surface and an internal surface. The operation of fusing the assembly of the glass layers need not achieve complete fusion between the layers. For example, when material is to be removed from the side surfaces of the upper layer(s) of the fused assembly in operation  1130 , some of the material of the upper layer(s) to be removed in operation  1130  need not be completely fused to the lower layer of the fused assembly. 
     In some cases, at least a portion of a boundary region between the glass layers may be detected by the unaided eye or using other techniques after the operation of fusing the glass layers. At least a portion of a boundary region may be detected, for example, as an area of incomplete fusion, as a particle of graphite or another material originating from the thermoforming apparatus, or both. In some cases, the boundary region may be observed by sectioning the glass member and/or using non-destructive techniques. Suitable techniques for observing the boundary region include, but are not limited to, microscopy, elemental analysis, optical interference detection, ultrasonic detection, and the like. As referred to herein, a “glass member,” a “glass layer,” a “glass component,” and/or a “glass piece” may include some relatively small amount of impurities or crystalline material, such as 1% or less, 2% or less, or 5% or less by weight of the member. 
     In other cases, the fusion may be sufficiently complete that a distinct boundary region may not be detected with the unaided eye between the portions of the fused assembly corresponding to the layers of the assembly. For example, a distinct boundary region may not be detected with the unaided eye when the two adjacent layers of glass have a similar composition and fusion between these glass layers is substantially complete. 
     The process  1100  may also include an operation of cooling the fused assembly. The cooling of the fused assembly may be sufficiently gradual that thermally induced residual stresses are minimized. In some cases, the cooling may be performed in several stages. By the way of example, a cooling operation may control the cooling of the fused assembly until the temperature of the fused assembly is less than or equal to the strain point of the glass(es). In some embodiments, a density of the external surface of the thicker portion of the fused assembly is greater than a density of the external surface of the thinner portion of the fused assembly (e.g., adjacent the thicker portion). 
     In some cases, a property of the glass varies across the cooled fused assembly. For example, the density of the glass may vary across the cooled fused assembly even though the lower glass layer and the upper glass layer(s) may have substantially the same density prior to the process  1100 . For example, the density of the glass on the raised region (e.g., the plateau region) of the protruding feature may be greater than the density of the glass on the base region of the external surface. 
     As shown in  FIG.  11   , the operation  1100  includes an operation  1130  of shaping and texturing the fused assembly to form the glass member. In some embodiments, the operation of shaping the fused assembly includes at least one step of removing material from the fused assembly. In some cases, the at least one step of removing material from the fused assembly includes at least one mechanical removal step, such as a grinding or polishing step. 
     Typically, material is removed from the external surfaces of both the thicker and the thinner portions of the fused assembly. Material may also be removed from the internal surfaces of the thicker and the thinner portions of the fused assembly. For example, the material removal steps may be used to produce exterior and interior surfaces that are sufficiently level. The amount of material removed from the external surface may be from about 2% to about 30% of the thicker portion and from about 5% to about 40% of the thinner portion. In some cases, the amount of material removed is from about 0.05 mm to about 0.5 mm. This material removal may produce a fusion zone which is elevated with respect to the exterior surface of the base region (e.g., from about 0.05 mm to about 0.5 mm). 
     In some cases, a material removal step may also remove material from the side of the thicker portion of the fused assembly. This material removal step may create the desired side profile of the protruding feature and/or may remove parts of the upper glass layer(s) that have not fused to the lower glass layer as illustrated in  FIGS.  12 A and  12 B . Typically, the fused assembly has a shape corresponding to that of the glass member following these material removal steps. In addition, the operation  1130  may include forming one or more holes and/or enlarging one or more pilot holes in the fused assembly (e.g., by machining). 
     Typically, operation  1130  also includes texturing the fused assembly to produce one or more surface textures (e.g., a polished texture or a rougher texture). Texturing techniques that may be used in the operation  1130  include, but are not limited to, chemical etching, mechanical removal of material such as abrasive treatment, laser ablation, lithography in combination with etching, and combinations thereof. In some cases, a laser ablation technique may involve multiple operations of directing a sequence of laser pulses onto a surface of the fused assembly. In some cases, the member may have multiple textured regions. Each of the various textured regions of the member may have similar textures to each other or may have different textures from each other. Different textures may result from using different process conditions in a single type of texturing process or may result from using different types of texturing processes. In some embodiments, a textured region of the member may have a texture formed by overlap of two different textures. Such a texture may result from using two different texturing processes to create the textured region. 
     The process  1100  also includes an operation  1140  of chemically strengthening the glass member. The operation of chemically strengthening a member may include an ion exchange operation. During the ion exchange operation, ions present in the member can be exchanged for larger ions in an ion-exchanged zone extending from a surface of the member. A compressive stress layer extending from a surface of the member may be formed in the ion-exchanged zone.  FIG.  17    schematically illustrates compressive stress layers formed along various surfaces of a member such as a glass member. In some cases, the operation  1140  includes multiple ion exchange operations. In some embodiments, a compressive stress layer is formed at each of exterior surface and the interior surface of the member. A tensile stress layer may be formed between these compressive stress layers. 
     For example, an ion-exchangeable glass material of the member may include monovalent or divalent ions such as alkali metal ions (e.g., Li + , Na + , or K + ) or alkaline earth ions (e.g., Ca 2+  or Mg 2+ ) that may be exchanged for other alkali metal or alkaline earth ions. If a glass member comprises sodium ions, the sodium ions may be exchanged for potassium ions. Similarly, if the glass member comprises lithium ions, the lithium ions may be exchanged for sodium ions and/or potassium ions. 
     In an example, the chemical strengthening process involves exposing the member to a medium containing the larger ion, such as by immersing the member in a bath containing the larger ion or by spraying or coating the member with a source of the ions. For example, a salt bath comprising one or more ions of interest (e.g., a bath containing potassium ions or a mixture of potassium ions and sodium ions) may be used for ion exchange. Suitable temperatures for ion exchange are above room temperature and are selected depending on process requirements. The ion exchange process may be conducted at a temperature below the strain point of the glass. The member may be cooled following the ion exchange operation. Depending on the factors already discussed above, a compressive stress layer as deep as about 10-250 microns can be formed in a glass member. The surface compressive stress (CS) may be from about 300 MPa to about 1100 MPa. A mask can be used to shield portions of the glass member from ion exchange as desired. Optionally, the member is washed after the ion exchange operation  1140 . 
     When a property of the glass varies across the cooled fused assembly the surface compressive stress and/or the depth of the compressive stress layer may vary across the glass member. For example, a surface compressive stress at the raised region (e.g., the plateau region) of the protruding feature may be greater than a surface compressive stress at the base region of the external surface.  FIG.  17    schematically illustrates differences in the depth of the compressive stress layer along the raised region and the base region of a glass member. As previously discussed, the density of the glass may vary across the cooled fused assembly. 
     Processes for forming members as disclosed herein are not limited to the example of  FIG.  11   . In some cases, a process for forming a composite member may include steps similar to those of process  1100 . For example, a composite member may be formed by bonding a glass layer to a layer of a glass ceramic material. The glass ceramic material may be similar in composition to the glass material of the glass layer. As an additional example, a composite member may be formed by bonding a glass layer to a layer of a ceramic material, such as sapphire (aluminum oxide). The glass ceramic or ceramic material may define the raised or top portion of the protruding feature. In some cases, the glass ceramic or ceramic may be transparent to visible light, infrared radiation, ultraviolet radiation, or combinations thereof. 
       FIGS.  12 A to  12 C  schematically show cross-section views of stages of an example process for forming a member. The member  1234  shown in  FIG.  12 C  may be an example of the member  134  of  FIG.  1 B  or any other member or member described herein. In some cases, the cross-section views perpendicular to the views of  FIGS.  12 A to  12 C  are similar in nature, although the lateral dimensions of the layers and portions may vary. 
       FIG.  12 A  schematically illustrates application of pressure P to an assembly of two layers in order to fuse the layers of the assembly. In the example of  FIG.  12 A , the assembly  1214  includes an upper layer  1276  and a lower layer  1279 . The upper layer  1276  contacts an upper surface  1219  of the lower layer  1279  and the boundary between these layers defines an interface  1215 . As shown in  FIG.  12 A , a side surface  1218  of the upper layer  1276  defines a rounded shape. The example of  FIG.  12 A  is not limiting and the side surface  1218  may define any of a number of shapes, including a substantially planar shape or a substantially planar shape with chamfered or rounded corners. In some cases, the upper layer  1276  and the lower layer  1279  are glass layers. The vertical dashed lines in  FIG.  12 A  schematically indicate a lateral dimension of the upper layer  1276 . 
     A tool-piece  1225  is used to apply pressure to the upper surface  1217  of the upper layer  1276  during the fusing operation. As shown in  FIG.  12 A , the tool-piece may have the form of a plunger with a flat bottom. Typically, the upper layer  1276 , the lower layer  1279 , and the tool-piece  1225  are at an elevated temperature during the thermoforming process. At least a bottom portion of the tool-piece  1225  is typically formed from a material suitable for use at these elevated temperatures. The pressure and the temperature during the fusing operation may be as previously described with respect to operation  1120  of process  1100  and, for brevity, those details are not repeated here. Typically, the layers  1276  and  1279  are supported as the pressure is being applied, such as by a support  1210 . 
       FIG.  12 B  schematically illustrates a fused assembly  1224  formed from two layers. A second component  1286  of the fused assembly  1224  has been formed from the upper layer  1276  and a first component  1289  of the fused assembly has been formed from the lower layer  1279 . The dashed line  1285  divides the first component  1286  from the second component  1289  and may be located at the position of the interface  1215  of  FIG.  12 A . In some cases, each of the upper layer  1276  and the lower layer  1279  are glass layers and each of the first component  1289  and the second component  1286  are glass components. The vertical dashed lines in  FIG.  12 B  schematically indicate a lateral dimension of the second component. 
       FIG.  12 C  schematically illustrates the member  1234  formed by shaping and texturing the fused assembly  1224  of  FIG.  12 B . The member  1234  defines a protruding feature  1236  which in turn defines a raised region  1247  and a side region  1248  of the exterior surface. The member  1234  also defines a base portion  1239  that defines a base region  1249  of the exterior surface  1244 . The raised region  1247  is elevated with respect to a base region  1249  of the exterior surface  1244 . The member  1234  also includes through-holes  1267  and  1268  that extend from the interior surface  1242  to the exterior surface  1244 . The first and second components  1299  and  1296  of the member  1234  are respectively formed from the first and second components  1289  and  1286  of the fused assembly  1224 . The member  1234  may be a glass member and the first and the second components  1299  and  1296  may be glass components. The vertical dashed lines in  FIG.  12 C  schematically indicate a lateral dimension of the protruding feature. 
     Comparison of  FIGS.  12 B and  12 C  shows that material has been removed from the fused assembly  1224  to form the member  1234 , although the amount of material removed is not necessarily shown to scale. For example, material has been removed from an external surface  1229  of the first component  1289  and the external surface  1227  of the second component  1286  of the fused assembly  1224  to produce the external surface  1249  and the external surface  1247  of the member  1234 . 
     In addition, material has been removed from the side surface  1228  of the second component  1286  to form the side surface  1248 . In some cases, the side surface  1228  meets the surface  1229  to define an undercut between the first component  1289  and the second component  1286 . In these cases, sufficient material may be removed from the side surface  1228  that the side surface  1248  defines a smoothly curved profile instead of an undercut. The operation(s) of removing material from the fused assembly  1224  may be any of the material removal steps described with respect to operation  1130  of process  1100  and, for brevity, that description is not repeated here. As shown in  FIG.  12 C , the side surface  1248  defines a smoothly curved profile. For example, the side surface may define a spline between the external surface  1247  and the external surface  1249 . 
     One effect of removing material from the fused assembly  1224  may be that the protruding feature  1236  is at least partly formed from the first component  1299  as well as the second component  1296 . Since the dashed line  1295  that divides the first component  1296  from the second component  1299  is elevated with respect to the exterior surface  1249 , a lower or base part of the protruding feature  1236  is formed from the first component  1299  in  FIG.  12 C . 
     In the example of  FIG.  12 C , the raised region  1247  has a rougher texture than the base region  1249  and the side region  1248 . The example of  FIG.  12 C  is not limiting and in some cases the base region  1249  and the side region  1248  may have a rougher texture than the raised region  1247 . In additional cases, the raised region  1247 , the side region  1248 , and the base region  1249  may all have similar textures. The description of textured regions provided with respect to  FIGS.  6  to  10    is generally applicable here and, for brevity, is not repeated here. 
       FIGS.  13 A to  13 C  schematically show cross-section views of stages of an additional example process for forming a member. In the example of  FIGS.  13 A to  13 C , a layer of the assembly of layers is provided with holes that serve as pilot holes for the through-holes of the member. In some cases, the cross-section views perpendicular to the views of  FIGS.  13 A to  13 C  are similar in nature, although the lateral dimensions of the layers and portions may vary. 
     In the example of  FIG.  13 A , the assembly  1314  includes an upper layer  1376  and a lower layer  1379 . The upper layer  1376  defines a side surface  1318 . The upper layer  1376  includes through-holes  1311  and  1312 . The through-holes  1311  and  1312  can function as pilot holes for the through-holes  1367  and  1368  of the member  1334 . The upper layer  1376  contacts an upper surface  1319  of the lower layer  1379  and the boundary between these layers defines an interface  1315 . The shapes of the upper and lower layers  1376  and  1379  shown in the example of  FIG.  13 A  are not limiting. In additional examples, the lower layer  1379  additionally or alternately includes pilot holes similar to the holes  1311  and  1312 . In some cases, each of the upper layer  1376  and the lower layer  1379  is a glass layer. The vertical dashed lines in  FIG.  13 A  schematically indicate a lateral dimension of the upper layer  1376 . 
     A tool-piece  1325  is used to apply pressure P to the upper surface  1317  of the upper layer  1376  during the fusing operation and a support  1310  may support the assembly  1314  in a similar manner as previously described with respect to  FIG.  12 A . For brevity, that description is not repeated here.  FIG.  13 B  schematically illustrates a fused assembly  1324 . A second component  1386  of the fused assembly  1324  has been formed from the upper layer  1376  and defines an upper surface  1327  and a side surface  1328 . The second component  1386  includes holes  1321  and  1322  that correspond to the holes  1311  and  1312 . A first component  1389  of the fused assembly has been formed from the lower layer  1379  and defines an upper surface  1329 . The dashed line  1385  divides the second component  1386  from the first component  1389  and may be located at the position of the interface  1385  of  FIG.  13 A . When the upper layer  1376  and the lower layer  1379  are glass layers, the first component  1389  and the second component  1386  may be glass components. The vertical dashed lines in  FIG.  13 B  schematically indicate a lateral dimension of the second component. 
       FIG.  13 C  schematically illustrates the member  1334  formed by shaping and texturing the fused assembly  1324  of  FIG.  13 B . The first and the second components  1399  and  1396  of the member  1334  are respectively formed from the first and second components  1389  and  1386  of the fused assembly  1324 . The member  1334  may be a glass member and the first and the second components  1399  and  1396  may be glass components. 
     The member  1334  shown in  FIG.  13 C  may be an example of the member  134  of  FIG.  1 B  or any other member or cover member described herein. The member  1334  defines a protruding feature  1336  that in turn defines a raised region  1347  and a side region  1348  of the exterior surface  1344 . The member  1334  also defines a base portion  1339  that defines a base region  1349  of the exterior surface  1344 . The raised region  1347  is elevated with respect to the base region  1349 . The member  1334  also includes through-holes  1367  and  1368  that extend from the interior surface  1342  to the exterior surface  1344 . The holes  1321  and  1322  provided pilot holes for the through-holes  1367  and  1368 . The vertical dashed lines in  FIG.  13 C  schematically indicate a lateral dimension of the protruding feature. 
     Similarly to the member  1234  of  FIG.  12 C , the protruding feature  1336  is at least partly formed from the first component  1399  as well as the second component  1396  and the dashed line  1395  that divides the first component  1399  from the second component  1396  is elevated with respect to the exterior surface  1349 . In the example of  FIG.  13 C , the raised region  1347  has a smoother texture than the base region  1349  and the side region  1348 . It should be understood that this example is not limiting and the textures of the raised region  1347 , the side region  1348 , and the base region  1347  may be any texture described herein. 
       FIGS.  14 A to  14 C  schematically show cross-section views of stages of an example process for forming a member. In the example of  FIGS.  14 A to  14 C , an upper layer of the assembly of layers defines a localized interface with a lower layer. Fusion can then proceed outward from the localized interface. In some cases, the cross-section views perpendicular to the views of  FIGS.  14 A to  14 C  are similar in nature, although the lateral dimensions of the layers and portions may vary. 
     In the example of  FIG.  14 A , the assembly  1414  includes an upper layer  1476  and a lower layer  1479 . In some cases, the upper layer  1476  is a glass layer and in additional cases each of the upper layer  1476  and the lower layer  1479  is a glass layer. An upper surface  1417  of the upper layer  1476  defines a concave shape while a lower surface  1416  of the upper layer  1476  defines a convex shape. Due to the convex shape of the lower surface  1416 , the interface  1415  between the lower surface  1416  and the upper surface  1419  of the lower layer  1479  is localized. In the example of  FIG.  14 A , the interface  1415  is localized to a central portion of the upper layer  1476 . The shapes of the upper and lower layers  1476  and  1479  shown in the example of  FIG.  14 A  are not limiting. For example, the shape of the side surface  1418  of the upper layer  1476  may be as described with respect to  FIG.  12 A  and, for brevity, that description is not repeated here. 
     During the operation of fusing the assembly  1414 , fusion may start at the interface  1415 . After fusion begins at the interface  1415 , a fusion front can then move outwards towards the side surfaces  1418  of the upper layer.  FIGS.  16 A to  16 B  schematically illustrate such movement of the fusion front. 
       FIG.  14 B  schematically illustrates a fused assembly  1424 . A second component  1486  of the fused assembly  1424  has been formed from the upper layer  1476  and a first component  1489  of the fused assembly has been formed from the lower layer  1479 . For example, the second component  1486  may be a second glass component formed from an upper glass layer and the first component  1489  may be a first glass component formed from a lower glass layer. The dashed line  1485  divides the second component  1486  from the first component  1489  and may be located at the position of the interface  1415  of  FIG.  14 A . The second component  1486  defines an upper surface  1427  and a side surface  1428 . The first component  1489  defines an upper surface  1429 . The vertical dashed lines in  FIG.  14 B  schematically indicate a lateral dimension of the second component. 
       FIG.  14 C  schematically illustrates the member  1434  formed by shaping and texturing the fused assembly  1424  of  FIG.  14 B . The first and second components  1499  and  1496  of the member  1434  are respectively formed from the first and second components  1489  and  1486  of the fused assembly  1424 . When the member  1434  is a glass member, the first and second glass components ( 1499  and  1496 ) of the glass member  1434  are respectively formed from the first and second glass components ( 1489  and  1486 ) of the fused assembly  1424 . 
     The member  1434  shown in  FIG.  14 C  may be an example of the member  134  of  FIG.  1 B  or any other member or cover member described herein. The member  1434  defines a protruding feature  1436  that in turn defines a raised region  1447  and a side region  1448  of the exterior surface. The member  1434  also defines a base portion  1439  that defines a base region  1449  of the exterior surface  1444 . The raised region  1447  is elevated with respect to a base region  1449  of the exterior surface  1444 . The member  1434  also includes through-holes  1467  and  1468  that extend from the interior surface  1442  to the exterior surface  1444 . The vertical dashed lines in  FIG.  14 C  schematically indicate a lateral dimension of the protruding feature. 
     Similarly to the member  1234  of  FIG.  12 C , the protruding feature  1436  is at least partly formed from the first component  1499  as well as the second component  1496  and the dashed line  1495  that divides the first component  1499  from the second component  1496  is elevated with respect to the base region  1449 . In the example of  FIG.  14 C , the side region  1448  is defined by both the first component  1499  and the second component  1496 . The first component  1499  at least partly defines a concave portion of the side region  1448 . 
     In the example of  FIG.  14 C , the raised region  1447  and the side region  1448  have a rougher texture than the base region  1449 . It should be understood that this example is not limiting and the textures of the raised region  1447 , the side region  1448 , and the base region  1447  may be any texture described herein. 
       FIGS.  15 A to  15 C  schematically show cross-section views of stages of a further example process for forming a member. In the example of  FIGS.  15 A to  15 C , an upper layer of the assembly of layers defines a localized interface with a lower layer. Fusion can then proceed outward from the localized interface. In some cases, the cross-section views perpendicular to the views of  FIGS.  15 A to  15 C  are similar in nature, although the lateral dimensions of the layers and portions may vary. 
     In the example of  FIG.  15 A , an assembly  1514  includes an upper layer  1576  and a lower layer  1579 . In some cases, the upper layer  1576  is a glass layer and in additional cases each of the upper layer  1576  and the lower layer  1579  is a glass layer. A lower surface  1516  of the upper layer  1576  defines a convex surface. The upper surface  1517  of the upper layer  1576  may be substantially flat. The upper layer  1576  contacts an upper surface  1519  of the lower layer  1579  and the boundary between these layers defines an interface  1515 . Due to the convex shape of the lower surface  1516 , the interface  1515  is localized. In the example of  FIG.  15 A , the interface  1515  is localized to a central portion of the upper layer  1576 . The shapes of the upper and lower layers  1576  and  1579  shown in the example of  FIG.  15 A  are not limiting. For example, the shape of the side surface  1518  of the upper layer  1576  may be as described with respect to  FIG.  12 A  and, for brevity, that description is not repeated here. 
     During the operation of fusing the assembly  1514 , fusion may start at the interface  1515 . After fusion begins at the interface  1515  a fusion front can then move outwards towards the side surfaces  1518  of the upper layer.  FIGS.  16 A to  16 B  schematically illustrate such movement of the fusion front. 
       FIG.  15 B  schematically illustrates a fused assembly  1524  formed from two layers. A second component  1586  of the fused assembly  1524  has been formed from the upper layer  1576  and a first component  1589  of the fused assembly has been formed from the lower layer  1579 . The second component  1586  may be a second glass component formed from a glass upper layer and a first component  1589  may be a first glass component formed from a glass lower layer. The dashed line  1585  divides the second component  1586  from the first component  1589  and may be located at the position of the interface  1515  of  FIG.  15 A . The second component  1586  defines an upper surface  1527  and a side surface  1528 . The first component  1589  defines an upper surface  1529 . The vertical dashed lines in  FIG.  15 B  schematically indicate a lateral dimension of the second component. 
       FIG.  15 C  schematically illustrates the member  1534  formed by shaping and texturing the fused assembly  1524  of  FIG.  15 B . The first and second components  1599  and  1596  of the glass member  1534  are respectively formed from the first and second components  1589  and  1586  of the fused assembly  1524 . The first and second components  1599  and  1596  may be first and second glass components of the glass member  1534  which are respectively formed from first and second glass components ( 1589  and  1586 ) of the fused assembly  1524 . 
     The member  1534  shown in  FIG.  15 C  may be an example of the member  134  of  FIG.  1 B  or any other member or cover member described herein. The member  1534  defines a protruding feature  1536  that in turn defines a raised region  1547  and a side region  1548  of the exterior surface. The member  1534  also defines a base portion  1539  that defines a base region  1549  of the exterior surface  1544 . The raised region  1547  is elevated with respect to a base region  1549  of the exterior surface  1544 . The member  1534  also includes through-holes  1567  and  1568  that extend from the interior surface  1542  to the exterior surface  1544 . The vertical dashed lines in  FIG.  15 C  schematically indicate a lateral dimension of the protruding feature. 
     Similarly to the member  1234  of  FIG.  12 C , the protruding feature  1536  is at least partly formed from the first component  1599  as well as the second component  1596  and the dashed line  1595  that divides the first component  1599  from the second component  1596  is elevated with respect to the base region  1549 . In addition, the raised region  1547  has a rougher texture than the base region  1549  and the side region  1548  although this example is not limiting and the textures of the raised region  1547 , the side region  1548 , and the base region  1547  may be any texture described herein. 
       FIGS.  16 A and  16 B  schematically illustrate a top view of stages in fusing two layers, with  FIG.  16 B  showing a later stage than  FIG.  16 A . In the example of  FIGS.  16 A and  16 B , fusion begins in a central region of the upper layer and moves outward towards the sides  1628  of the upper layer. In some cases, movement of a fusion front outwards from the center of the upper glass improves fusion between the upper and the lower layers. For example, the size and/or number of voids formed at the interface between the upper and the lower layers may be reduced. The layers shown in  FIGS.  16 A to  16 B  may be as described with respect to  FIG.  11    and, for brevity, that description is not repeated here. In some cases, each of the upper and lower layers are glass layers. 
     As shown in  FIG.  16 A , an upper layer  1676  assembled with a lower layer  1679  has been partially fused to form partially fused assembly  1616 . The upper layer  1676  is bonded to the lower layer  1679  within a fused area  1636  encircled by a dashed line, that schematically illustrates a fusion front  1646 . The fused area  1636  includes a central region of the upper layer  1676 . The arrows schematically illustrate the direction of motion of the fusion front  1646  towards the side  1628  of the upper layer  1676 . For convenience of illustration, the shape of the fusion front  1646  is shown as circular, but this example is not limiting, and the shape of the fusion front need not be circular and may be somewhat irregular. In some cases, the upper layer  1676  may be shaped as described with respect to  FIG.  14 A or  15 A . 
       FIG.  16 B  schematically illustrates a later stage of the fusion operation to bond the upper layer  1676  to the lower layer  1679 . The partially fused assembly  1618  includes fused area  1638  encircled by the dashed line  1648 . The fused area  1638  is greater than the fused area  1636  shown in  FIG.  16 A  and has moved further towards the side  1628  of the upper layer  1676 . The arrows schematically illustrate the direction of motion of the fusion front  1648 . For convenience of illustration, the shape of the fusion front  1648  is shown as circular, but this example is not limiting, and the shape of the fusion front need not be circular and may be somewhat irregular. 
       FIG.  17    schematically shows a cross-section view of a member  1734  after chemical strengthening. The member  1734  may be a glass member. In the example of  FIG.  17   , the chemical strengthening is not uniform over the member  1734 . In particular, the chemical strengthening is different along a raised region  1747  as compared to a base region  1749  of the exterior surface  1744 . 
     In some cases, the member  1734  is formed by fusing two glass layers and the dashed line  1795  schematically illustrates a fusion zone. The member  1734  includes a protruding feature  1736 , a portion  1735  underlying the protruding feature  1736 , and a base portion  1739 . The member also defines a hole  1761  extending through the protruding feature  1736  and the underlying portion  1735 . The member  1734  also includes a textured region  1756  and a side region  1748 . The member  1734  shown in  FIG.  17    may be an example of the member  134  of  FIG.  1 B  or any other member or cover member described herein. 
     In the example of  FIG.  17   , the compressive stress layer  1777  extending from the raised region  1747  differs from the compressive stress layer  1779  extending from the base region  1749  of the exterior surface  1744 . As shown in  FIG.  17   , the depth of the compressive stress layer  1777  is less than the depth of the compressive stress layer  1779 . For example, the difference in the depth may be from 10% to 50% of the depth of the compressive stress layer  1779 . As examples, the depth of the compressive stress layer  1779  may be from 165 microns to 250 microns, from 100 microns to 250 microns, or from 125 microns to 250 microns. Additionally or alternately, a magnitude of the surface compressive stress of the compressive stress layer  1777  may be greater than a magnitude of the surface compressive stress of the compressive stress layer  1779 . For example, the difference in the magnitude of the surface compressive stress may be from 10% to 50% of the magnitude of the surface compressive stress of the compressive stress layer  1779 . Further, a hardness of raised region  1747  may be greater than a hardness of the base region  1749 . The difference in the surface compressive stress and/or depth of these compressive stress layers may be due at least in part to changes in a property of the glass of the protruding feature  1736  during the fusing operation, as previously discussed with respect to FIG.  11 . It should be understood that the compressive stress layers depicted are not necessarily shown to scale. 
     As shown in  FIG.  17   , member  1734  also includes a compressive stress layer  1773  along a region  1743  of the interior surface  1742  defined by the base portion  1739 . The member  1734  also includes a compressive stress layer  1775  along a region  1745  of the interior surface  1742  defined by the portion  1735 . In some cases, the compressive stress layer  1775  may be different than the compressive stress layer  1773 . For example, the compressive stress layer  1775  may have a magnitude of surface compressive stress that is greater than that of the compressive stress layer  1773 . Further the compressive stress layer  1775  may have a depth that is less than that of the compressive stress layer  1773 , so that the compressive stress layer  1775  is shallower than the compressive stress layer  1773 . In some cases, the magnitude and/or the depth of the compressive stress layer  1775  may be similar to that of the compressive stress layer  1777 . 
     The member  1734  also includes a compressive stress layer  1771  extending from a wall surface  1741  defining a through-hole  1761 . A tensile stress layer  1789  is positioned between the compressive stress layers  1779  and  1773 . A tensile stress layer  1787  is positioned between the compressive stress layers  1777  and  1775 . 
     Each of the compressive stress layers  1771 ,  1773 ,  1775 ,  1777 , and  1779  are located in ion-exchanged zones of the member  1734 . The composition of the member in the ion-exchanged zone is modified by the chemical strengthening operation from its composition prior to ion exchange (also referred to as a baseline composition). However, the member  1734  typically includes one or more zones that are substantially free of ion exchange and the composition of the member in these zones may be substantially the same as the composition(s) of the glass layers used to form the fused assembly. As previously discussed, in some cases the glass layers used to form the fused assembly have substantially the same composition. 
     The baseline composition(s) of different portions of the member can thus be compared by comparing the compositions within zones within the different portions that are substantially free of ion-exchange. For example, an ion-exchanged zone extends from the base region  1749  and the compressive stress layer  1779  is located within this ion-exchanged zone. An ion-exchanged zone extends from the region  1743  and the compressive stress layer  1773  is located within this ion-exchanged zone. The composition of a central zone between (also, inward of) these two ion-exchanged zones can therefore establish a baseline composition of the base portion  1739 . Similarly, a baseline composition of the protruding feature  1736  can be established by measuring the composition of a central zone inward of the ion exchanged layers extending from the surfaces  1741 ,  1745 , and  1747 . 
     In some cases, a baseline composition of the protruding feature  1736  can be measured adjacent the fusion zone between a first component and a second component (e.g., first and second glass components) and a baseline composition of the base portion can also be measured adjacent this fusion zone. For example, a composition may be measured 50 microns, 100 microns, 200 microns, 300 microns, or 400 microns away from the fusion zone so long as the composition is not measured within an ion-exchanged zone. When the composition of the glass layers used to form the fused assembly is substantially the same, a baseline composition of the base portion of the member  1734  may be substantially the same as a baseline composition of an upper part of the protruding feature (above the fusion zone  1795 ). For example, a glass member may comprise a first glass component having a first composition adjacent a fusion zone between the first glass component, a second glass component having a second composition adjacent the fusion zone, and the first composition may be substantially equal to the second composition. 
       FIG.  18    shows a block diagram of a sample electronic device that can incorporate a member as described herein, such as a glass cover member. The schematic representation depicted in  FIG.  18    may correspond to components of the devices depicted in  FIGS.  1 A to  17    as described above. However,  FIG.  18    may also more generally represent other types of electronic devices with cover assemblies as described herein. 
     In embodiments, an electronic device  1800  may include sensors  1820  to provide information regarding configuration and/or orientation of the electronic device in order to control the output of the display. For example, a portion of the display  1808  may be turned off, disabled, or put in a low energy state when all or part of the viewable area of the display  1808  is blocked or substantially obscured. As another example, the display  1808  may be adapted to rotate the display of graphical output based on changes in orientation of the device  1800  (e.g., 90 degrees or 180 degrees) in response to the device  1800  being rotated. 
     The electronic device  1800  also includes a processor  1806  operably connected with a computer-readable memory  1802 . The processor  1806  may be operatively connected to the memory  1802  component via an electronic bus or bridge. The processor  1806  may be implemented as one or more computer processors or microcontrollers configured to perform operations in response to computer-readable instructions. The processor  1806  may include a central processing unit (CPU) of the device  1800 . Additionally, and/or alternatively, the processor  1806  may include other electronic circuitry within the device  1800  including application specific integrated chips (ASIC) and other microcontroller devices. The processor  1806  may be configured to perform functionality described in the examples above. 
     The memory  1802  may include a variety of types of non-transitory computer-readable storage media, including, for example, read access memory (RAM), read-only memory (ROM), erasable programmable memory (e.g., EPROM and EEPROM), or flash memory. The memory  1802  is configured to store computer-readable instructions, sensor values, and other persistent software elements. 
     The electronic device  1800  may include control circuitry  1810 . The control circuitry  1810  may be implemented in a single control unit and not necessarily as distinct electrical circuit elements. As used herein, “control unit” will be used synonymously with “control circuitry.” The control circuitry  1810  may receive signals from the processor  1806  or from other elements of the electronic device  1800 . 
     As shown in  FIG.  18   , the electronic device  1800  includes a battery  1814  that is configured to provide electrical power to the components of the electronic device  1800 . The battery  1814  may include one or more power storage cells that are linked together to provide an internal supply of electrical power. The battery  1814  may be operatively coupled to power management circuitry that is configured to provide appropriate voltage and power levels for individual components or groups of components within the electronic device  1800 . The battery  1814 , via power management circuitry, may be configured to receive power from an external source, such as an alternating current power outlet. The battery  1814  may store received power so that the electronic device  1800  may operate without connection to an external power source for an extended period of time, which may range from several hours to several days. 
     In some embodiments, the electronic device  1800  includes one or more input devices  1818 . The input device  1818  is a device that is configured to receive input from a user or the environment. The input device  1818  may include, for example, a push button, a touch-activated button, a capacitive touch sensor, a touch screen (e.g., a touch-sensitive display or a force-sensitive display), a capacitive touch button, a dial, a crown, or the like. In some embodiments, the input device  1818  may provide a dedicated or primary function, including, for example, a power button, volume buttons, home buttons, scroll wheels, and camera buttons. 
     The device  1800  may also include one or more sensors  1820 , such as a force sensor, a capacitive sensor, an accelerometer, a barometer, a gyroscope, a proximity sensor, a light sensor, or the like. The sensors  1820  may be operably coupled to processing circuitry. In some embodiments, the sensors  1820  may detect deformation and/or changes in configuration of the electronic device and be operably coupled to processing circuitry that controls the display based on the sensor signals. In some implementations, output from the sensors  1820  is used to reconfigure the display output to correspond to an orientation or folded/unfolded configuration or state of the device. Example sensors  1820  for this purpose include accelerometers, gyroscopes, magnetometers, and other similar types of position/orientation sensing devices. In addition, the sensors  1820  may include a microphone, an acoustic sensor, a light sensor (including ambient light, infrared (IR) light, ultraviolet (UV) light, optical facial recognition sensor, a depth measuring sensor (e.g., a time of flight sensor), a health monitoring sensor (e.g., an electrocardiogram (ecg) sensor, a heart rate sensor, a photoplethysmogram (ppg) sensor, a pulse oximeter, a biometric sensor (e.g., a fingerprint sensor), or other types of sensing device. 
     In some embodiments, the electronic device  1800  includes one or more output devices  1804  configured to provide output to a user. The output device  1804  may include display  1808  that renders visual information generated by the processor  1806 . The output device  1804  may also include one or more speakers to provide audio output. The output device  1804  may also include one or more haptic devices that are configured to produce a haptic or tactile output along an exterior surface of the device  1800 . 
     The display  1808  may include a liquid-crystal display (LCD), a light-emitting diode (LED) display, an LED-backlit LCD display, an organic light-emitting diode (OLED) display, an active layer organic light-emitting diode (AMOLED) display, an organic electroluminescent (EL) display, an electrophoretic ink display, or the like. If the display  1808  is a liquid-crystal display or an electrophoretic ink display, the display  1808  may also include a backlight component that can be controlled to provide variable levels of display brightness. If the display  1808  is an organic light-emitting diode or an organic electroluminescent-type display, the brightness of the display  1808  may be controlled by modifying the electrical signals that are provided to display elements. In addition, information regarding configuration and/or orientation of the electronic device may be used to control the output of the display as described with respect to input devices  1818 . In some cases, the display is integrated with a touch and/or force sensor in order to detect touches and/or forces applied along an exterior surface of the device  1800 . 
     The electronic device  1800  may also include a communication port  1812  that is configured to transmit and/or receive signals or electrical communication from an external or separate device. The communication port  1812  may be configured to couple to an external device via a cable, adaptor, or other type of electrical connector. In some embodiments, the communication port  1812  may be used to couple the electronic device  1800  to a host computer. 
     The electronic device  1800  may also include at least one accessory  1816 , such as a camera, a flash for the camera, or other such device. The camera may be part of a camera assembly that may be connected to other parts of the electronic device  1800  such as the control circuitry  1810 . 
     As used herein, the terms “about,” “approximately,” “substantially,” “similar,” and the like are used to account for relatively small variations, such as a variation of +/−10%, +/−5%, +/−2%, or +/−1%. In addition, use of the term “about” in reference to the endpoint of a range may signify a variation of +/−10%, +/−5%, +/−2%, or +/−1% of the endpoint value. In addition, disclosure of a range in which at least one endpoint is described as being “about” a specified value includes disclosure of the range in which the endpoint is equal to the specified value. 
     The following discussion applies to the electronic devices described herein to the extent that these devices may be used to obtain personally identifiable information data. It is well understood that the use of personally identifiable information should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining the privacy of users. In particular, personally identifiable information data should be managed and handled so as to minimize risks of unintentional or unauthorized access or use, and the nature of authorized use should be clearly indicated to users. 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.

Metadata:
Filing Date: 20220923
Publication Date: 20240312
Grant Date: 20240312
Priority Date: 20200328
Inventors: POOLE, JOSEPH C
ROGERS, MATTHEW S.
MEMERING, DALE N.
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F1/1656", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/1626", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1686", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K5/0086", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/1656", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/1656", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K5/0217", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K5/0243", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K5/03", "inventive": true, "first": false, "tree": "[]"}, {"code": "C03B23/203", "inventive": true, "first": false, "tree": "[]"}, {"code": "C03C21/002", "inventive": true, "first": false, "tree": "[]"}, {"code": "C03C21/001", "inventive": true, "first": false, "tree": "[]"}, {"code": "C03C21/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1626", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1686", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1626", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1686", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 77809476