Patent Publication Number: US-2020278541-A1

Title: Aspheric mirror for head-up display system and methods for forming the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Ser. No. 62/589,172 filed on Nov. 21, 2017, the content of which is relied upon and incorporated herein by reference in its entirety. 
    
    
     BACKGROUND ART 
     Head-Up Display or Heads-Up Display (HUD) systems project visual information onto a transparent surface so that users can see the information without diverting their gaze away from their primary view. HUD systems typically use a mirror to reflect and project an image onto the transparent surface. One application for HUD systems is in transportation, such as automobiles, aircraft, marine craft, and other vehicles. For example, HUD systems can be deployed in vehicles so that an operator or driver of the vehicle can see information relevant to the operation of the vehicle while maintaining a forward gaze and without having to look down or away towards a display screen. Thus, HUD systems are believed to improve safety by minimizing the need for a vehicle operator to look away from a safe operating viewpoint. 
     However, HUD systems have often suffered from poor optical quality in the projected image, which may result in an undesirable aesthetic quality to the projected image. Poor optical quality may even decrease the safety of HUD systems, because blurry or unclear projected images can make it more difficult for users to read or understand the projected information, resulting in increased user processing time of the information, delayed user reaction time based on the information, and increased user distraction. Reduced optical quality can result from the mirror used in the HUD system. 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     Thus, there remains a need for HUD systems, and particularly improved mirrors for HUD systems, that have improved optical quality. 
     Solution to Problem 
     In some embodiments of the present disclosure, a glass-based preform for a mirror of a heads-up display (HUD) system is provided. The glass-based preform comprises a glass-based substrate having a first major surface, a second major surface opposite to the first major surface, and a minor surface connecting the first and second major surfaces. In addition, the preform includes a first chamfer at an edge of the first major surface, the first chamfer having a first end at an intersection of the first chamfer and the first major surface and having a second end at an intersection of the first chamfer and the minor surface, and can also include a second chamfer at an edge of the second major surface, the second chamfer having a first end at an intersection of the second chamfer and the second major surface and having a second end at an intersection of the second chamfer and the minor surface. The first chamfer has a different size or shape from the second chamfer. 
     In additional embodiments, a mirror for a HUD system is provided, comprising the glass-based preform with a glass-based substrate having a first major surface, a second major surface opposite to the first major surface, and a minor surface connecting the first and second major surfaces. In addition, the preform includes a first chamfer at an edge of the first major surface, the first chamfer having a first end at an intersection of the first chamfer and the first major surface and having a second end at an intersection of the first chamfer and the minor surface, and can also include a second chamfer at an edge of the second major surface, the second chamfer having a first end at an intersection of the second chamfer and the second major surface and having a second end at an intersection of the second chamfer and the minor surface. The first chamfer has a different size or shape from the second chamfer. The mirror further comprises a reflective layer on the first major surface of the glass-based preform. The glass-based substrate has a first radius of curvature such that the first major surface has a concave shape and the second major surface has a convex shape, the first radius of curvature being measured with respect to a first axis of curvature. The glass-based substrate can have a second radius of curvature measured with respect to a second axis of curvature different from the first axis of curvature, where the first axis of curvature is perpendicular to the second axis of curvature. In some embodiments, the first major surface has an aspheric shape. 
     In further embodiments, a method of forming a three-dimensional mirror is provided, the method comprising providing a glass-based mirror preform including a first major surface having an edge with a first chamfer, a second major surface opposite to the first major surface and having an edge with a second chamfer, and a minor surface connecting the first and second major surfaces, the second chamfer having a different size or shape than the first chamfer. The method also includes disposing the glass-based preform on a molding apparatus having a curved support surface with the second major surface facing the curved support surface, and conforming the glass-based preform to the curved support surface to form a curved mirror substrate having a first radius of curvature. 
     In another embodiment, a heads-up display (HUD) projection system is provided. The HUD system comprises a display unit configured to display an image to be viewed by a user of a HUD system; and a mirror configured to reflect the image to a viewing area viewable by the user. The mirror comprises a glass-based substrate having a first major surface that is reflective, a second major surface opposite to the first major surface, and a minor surface connecting the first and second major surfaces, a first chamfer at an edge of the first major surface, the first chamfer having a first end at an intersection of the first chamfer and the first major surface and having a second end at an intersection of the first chamfer and the minor surface, and a second chamfer at an edge of the second major surface, the second chamfer having a first end at an intersection of the second chamfer and the second major surface and having a second end at an intersection of the second chamfer and the minor surface. The first chamfer has a different size or shape from the second chamfer. 
     In another embodiment, a method of forming a three-dimensional mirror is provided. The method includes providing a glass-based mirror preform having a first major surface, a second major surface opposite to the first major surface, and a minor surface connecting the first and second major surfaces, the glass preform having a flat shape; forming a first chamfer at an edge of the first major surface; forming a second chamfer at an edge of the second major surface, the second chamfer having a different size or shape from the first chamfer; disposing the glass-based preform on a molding apparatus having a curved support surface with the second major surface facing the curved support surface; and conforming the glass-based preform to the curved support surface to form a curved mirror substrate having a first radius of curvature. The conforming of the glass-based preform to the curved support surface is performed at a temperature that is less than a glass transition temperature of the glass-based preform, and a temperature of the glass-based substrate may not be raised above the glass transition temperature of the glass-based substrate during or after the conforming. 
     In another embodiment, a heads-up display (HUD) system is provided, comprising a projection surface for viewing a projected image by a user of the HUD system; a display unit configured to produce an image to be viewed by the user on the projection surface; and a mirror configured to reflect the image to the projection surface to form the projected image. The mirror includes a glass-based substrate having a first major surface that is reflective, a second major surface opposite to the first major surface, and a minor surface connecting the first and second major surfaces; a first chamfer at an edge of the first major surface, the first chamfer; and a second chamfer at an edge of the second major surface, wherein the first chamfer has a different size or shape from the second chamfer. 
     In another embodiment, a heads-up display (HUD) projection system is provided, comprising a display unit configured to display an image to be viewed by a user of a HUD system; and a mirror configured to reflect the image to a viewing area viewable by the user. The mirror includes a glass-based substrate having a first major surface that is reflective, a second major surface opposite to the first major surface, and a minor surface connecting the first and second major surfaces, and a chamfer at an edge of the first major surface, the chamfer having a first length. 
     Additional features and advantages of the claimed subject matter will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the claimed subject matter as described herein, including the detailed description which follows, the claims, as well as the appended drawings. 
     It is to be understood that both the foregoing general description and the following detailed description present embodiments of the present disclosure, and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments and together with the description serve to explain the principles and operations of the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       For the purposes of illustration, there are forms shown in the drawings that are presently preferred, it being understood, however, that the embodiments disclosed and discussed herein are not limited to the precise arrangements and instrumentalities shown. 
         FIG. 1  is an illustration of HUD system in a vehicle according to some embodiments of the present disclosure. 
         FIG. 2  is a pictorial depiction of an automobile driver&#39;s viewpoint when using the HUD system of  FIG. 1 , according to some embodiments. 
         FIG. 3  is a photographic of an example of a combiner used in HUD systems according to some embodiments of the present disclosure. 
         FIG. 4  is a pictorial depiction of an automobile driver&#39;s viewpoint when using a HUD system with a combiner similar to the one shown in  FIG. 3 , according to some embodiments. 
         FIG. 5  is a photograph of three example mirrors for HUD systems according to some embodiments. 
         FIG. 6  is an illustration of an aspheric mirror for a HUD system according to some embodiments. 
         FIGS. 7A and 7B  are schematic representations of a symmetrical edge of a 2D-preform substrate and a 3D-formed substrate, respectively, for a HUD system. 
         FIGS. 8A and 8B  are schematic representations of an asymmetrical edge of a 2D-preform substrate and a 3D-formed substrate, respectively, for a HUD system according to some embodiments of the present disclosure. 
         FIG. 9  is a schematic of an asymmetrical edge of a 3D-formed substrate for a HUD system according to some embodiments. 
         FIG. 10  is a pictorial depiction of a vacuum-based forming surface according to some embodiments of the present disclosure. 
         FIGS. 11A and 11B  are cross-section views of an edge of a substrate on the vacuum-based forming surface of  FIG. 10 . 
         FIG. 12  shows a photographic comparison of the optical quality of a typical mirror substrate for a HUD system to a mirror substrate according to some embodiments of the present disclosure. 
         FIG. 13  shows steps in a method of forming a mirror or mirror substrate according to some embodiments of the present disclosure. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     In the following description, like reference characters designate like or corresponding parts throughout the several views shown in the figures. It is also understood that, unless otherwise specified, terms such as “top,” “bottom,” “outward,” “inward,” and the like are words of convenience and are not to be construed as limiting terms. In addition, whenever a group is described as comprising at least one of a group of elements and combinations thereof, it is understood that the group may comprise, consist essentially of, or consist of any number of those elements recited, either individually or in combination with each other. 
     Similarly, whenever a group is described as consisting of at least one of a group of elements or combinations thereof, it is understood that the group may consist of any number of those elements recited, either individually or in combination with each other. Unless otherwise specified, a range of values, when recited, includes both the upper and lower limits of the range. As used herein, the indefinite articles “a,” and “an,” and the corresponding definite article “the” mean “at least one” or “one or more,” unless otherwise specified. 
     The following description of the present disclosure is provided as an enabling teaching thereof and its best, currently-known embodiment. Those skilled in the art will recognize that many changes can be made to the embodiment described herein while still obtaining the beneficial results of the present disclosure. It will also be apparent that some of the desired benefits of the present disclosure can be obtained by selecting some of the features of the present disclosure without utilizing other features. Accordingly, those who work in the art will recognize that many modifications and adaptations of the present disclosure are possible and may even be desirable in certain circumstances and are part of the present disclosure. Thus, the following description is provided as illustrative of the principles of the present disclosure and not in limitation thereof. 
     Those skilled in the art will appreciate that many modifications to the exemplary embodiments described herein are possible without departing from the spirit and scope of the present disclosure. Thus, the description is not intended and should not be construed to be limited to the examples given but should be granted the full breadth of protection afforded by the appended claims and equivalents thereto. In addition, it is possible to use some of the features of the present disclosure without the corresponding use of other features. Accordingly, the following description of exemplary or illustrative embodiments is provided for the purpose of illustrating the principles of the present disclosure and not in limitation thereof and may include modification thereto and permutations thereof. 
     HUD systems can be used to provide a wide variety of types of information for improved safety and convenience of users. In transportation, for example, information relevant to vehicle operation, such as vehicle gauges or navigation, can be projected to an area in front of a driver. This can include real-time information on vehicle speed, fuel level, climate control settings, entertainment settings, turn-by-turn navigation indicators, estimated time of arrival, and alerts related to speed, traffic, or dangerous conditions. Information can be presented as text, symbols, pictures, videos, animation, and one or more colors. These are examples only, and embodiments of this disclosure are not intended to be limited to these examples. 
     In some embodiments of the present disclosure, a HUD system can include an image generating device and one or more optical components for directing or projecting an image from the image generating device to an area that is easily visible to a user. The image generating device can include a cathode ray tube (CRT) display, a light-emitting diode (LED) display, a liquid crystal display (LCD) assembly, laser projection system, or other type of display known by those of ordinary skill in the art. The HUD system may also include a computer or processor for generating the images produced by these displays. The optical components may include some combination of lenses, beam splitters, mirrors, and combiner, for example. The combination of components of a HUD system can be configured to produce collimated light. 
     The collimated light is projected onto a combiner that is in a field of view of a user so that the user can see the projected image and the normal field of view simultaneously. For example, in vehicular applications, the combiner can be a windshield. Alternatively, the combiner can be a separate component that is built into the vehicle, or a portable component that can be mounted in the vehicle in a location where a driver or passenger can see the projected image on a transparent surface of the combiner. The mirror can include a reflective coating on a curved substrate. The curved substrate may be spherical, aspherical, a Fresnel shape, and/or diffractive. In one preferred embodiment, the mirror has a reflective surface or coating on a concave, aspherical surface. 
       FIG. 1  shows an example of a HUD system  100  according to some embodiments of the present disclosure. The HUD system  100  is shown in an automobile, but embodiments can be used in various vehicles or non-vehicular applications. A driver D is shown with hands the steering wheel W of the vehicle V. The HUD system  100  is incorporated into the dash  110  of the vehicle V, and includes a programmable graphical unit (PGU)  102  connected to an image source  103  configured to produce an image based on a signal from the PGU  102 . That image is reflected by a flat mirror  104  towards a curved mirror  106 . From the curved mirror  106 , the image is projected toward the windshield  108  and onto a projection area  112  of the windshield  108 . The HUD system  100  can be configured so that the projection area  112  is within the normal line of sight of the driver D while driving the vehicle V. For example, the projection area  112  can be positioned so that the projected image is overlaid on the road as seen from the driver&#39;s perspective. An example of this scenario is shown in the illustration of  FIG. 2 . 
     While the projection area  112  is located on the windshield  108  in  FIGS. 1 and 2 ,  FIGS. 3 and 4  show an alternative embodiment in which a combiner  208  is used for the location of the projection area  212 . The combiner  208  can be built into the dash  210  of a vehicle or can be a portable or separable component that is positioned on top of the dash  210 . 
     Embodiments of this disclosure are not limited to one or more particular arrangements of the optical components of a HUD system, as persons of ordinary skill in the art will understand the basic arrangement of components in a HUD system. The present disclosure is directed primarily to the curved mirrors used in HUD systems.  FIG. 5  shows examples of curved mirrors  301 ,  302 , and  303  used in HUD systems. The mirrors in HUD system generally have an aspheric reflective surface, which can be a reflective coating formed on an aspheric surface of a mirror substrate. An aspheric or aspherically shaped surface has multiple radii of curvature. In particular, in the case of a four-sided mirror as shown in  FIG. 5 , for example, an aspheric surface has a different radius of curvature along each of the four edges. Thus, as shown in  FIG. 6 , a mirror  400  has a reflective surface  408  that is aspherically shaped with a radius of curvature R 1  along a first edge, a radius of curvature R 2  along a second edge, a radius of curvature R 3  along a third edge, and a radius of curvature R 4  along a fourth edge. Because the surface  408  is aspherically shaped, R 1 ≠R 2 ≠R 3 ≠R 4 .  FIG. 6  also shows how different points on the curved surface  408  have been displaced by varying amounts a-e with respect to a two-dimensional plane connecting the four corners of the mirror  400 . In some embodiments, a≠b≠c≠d. 
     However, the authors of the present disclosure realized that improvements were needed in the design of and the methods of forming the curved mirrors used in HUD systems. For example, to prevent degradation of image quality as the image is reflected by the curved mirror, the mirror should have a high level of shape accuracy and surface roughness. For example, a shape precision of less than 50 μm and a surface roughness (Ra) of less than 3 nm is desirable. A particular type of optical distortion that occurs in mirrors for HUD systems is referred to as edge distortion, which is optical distortion of light reflected at or near the edge of the mirror. In existing HUD systems, optically impactful imperfections may be introduced into the mirror during manufacturing or shaping of the mirror. The most common methods for forming 3D-shaped mirrors or mirror substrates can be divided into two categories: pressing methods and vacuum-forming methods. Both pressing and vacuum-forming methods, however, can have disadvantages. 
     In a pressing method, upper and lower molds are used to press the substrate, such as a glass substrate, by physical force. For example, the upper mold may be pressed into a lower mold with a 2D glass preform disposed between the two molds, and the glass preform is formed according to the shape of a surface on one or both of the molds. As a result, mold imprints may be left on both the concave and convex surfaces of the formed glass substrate, which then requires polishing. In addition, due to deviations in the contours of the upper and lower molds, it can be difficult to precisely match the contours of the upper and lower molds, and thus difficult to achieve a precise shape for the formed glass substrate. For example, the specification for aspheric mirror contours can be less than ±25 μm, while the mold contour deviation after machining is normally 30-50 μm. 
     In a vacuum forming method, a single mold (e.g., lower mold) can be used, where vacuum holes are formed in the surface of the mold. A flat (2D) glass sheet is disposed on the surface of the mold and vacuum pressure is supplied via the vacuum holes to conform the glass to the curved (3D) surface of the mold. However, it is difficult to avoid the formation of vacuum hole marks on the surface of the formed glass substrate. These vacuum hole marks or manufacturing artifacts can impair the optical performance of the substrate or the finished mirror. In addition, typical vacuum forming methods can require higher forming temperatures compared to pressing methods. Higher forming temperatures can affect surface quality and form defects such as dimples, pits, and imprints. Vacuum forming can be performed on a mirror preform, which is a substrate that is pre-cut to the desired size before forming into a 3D shape with vacuum forming, or on an oversized sheet of glass, which is cut to the desired size after forming into a 3D shape with vacuum forming. Both preform-based and oversized-glass-based vacuum forming have certain advantages and disadvantages. 
     Oversized-glass-based forming, for example, has advantages of achieving good edge quality due to edge cutting, and good surface roughness due to lower forming temperatures. However, oversized-glass-based forming requires the added steps of cutting the glass after forming; has low glass utilization due to trim glass or waste glass after forming; requires edge polishing and/or chamfering after cutting; and requires larger equipment even though the eventual finished product may be the same size as that formed in preform-based forming. 
     On the other hand, in preform-based vacuum forming, there is no need to cut the mirror substrate after vacuum forming, which reduces the production of waste or cullet glass. In addition, preform-based forming can be a more simple process and more cost effective. However, in a preform-based vacuum forming method, it is difficult or impossible to apply a relatively uniform vacuum pressure over the entire surface of the glass sheet due to vacuum leaks at one or more edges of the glass preform, due at least in part to vacuum leakage between the preform and the mold. For example, if the formed glass is to have a single radius of curvature, the short-side edge of the preform may maintain contact with the mold surface until forming is complete, but the vacuum will leak along the long-side edge of the preform. In the case of more complex curvature or an aspheric mold surface (and aspheric formed substrate), only discrete points of the glass sheet, such as the four corners, may contact the mold surface throughout forming, which results in vacuum leakage along all edges of the glass substrate. Also, for forming an aspheric mirror, it is possible for the corner of the mirror or mirror substrate to chip or break, which occurs when only the corners of the mirror substrate are in contact with the mold and an external force (e.g., vacuum pressure, mold pressing force) is applied, thus concentrating pressure at the four corners of the substrate. As such, higher forming temperature (and lower viscosity of the substrate) is used to conform the glass onto the mold surface more completely, and to reduce the stress near the corners to reduce chipping. However, as discussed above, higher temperatures cause surface degradation of the glass substrate and decreased optical performance. Even with higher temperatures, edge distortion of the mirror occurs. 
     Investigators behind the present disclosure have discovered techniques to improve the mirrors formed using vacuum-based forming methods. In some preferred embodiments, these techniques may be particularly well-suited for the preform-based forming methods. However, some embodiments are not limited to mirrors made using the preform-based forming methods, nor even to vacuum-based methods, generally. One problem addressed by the embodiments of the present disclosure is that of edge distortion. As mentioned above, when using vacuum forming methods, it can be difficult to achieve a uniform vacuum and uniform conformation of the mirror substrate to the mold. It can be particularly difficult to conform the mirror substrate to the desired shape at or near the edges of the substrate, which causes edge distortion and degrades the quality of the image reflected by the mirror near the edge. Therefore, embodiments of the present disclosure provide mirrors and/or mirror substrates with improved optical performance at the edge, and methods of forming the same. 
     As shown in  FIGS. 7A and 7B , a conventional mirror for a HUD system has a symmetrical, chamfered edge. In particular,  FIG. 7A  shows a 2D preform  500  having a first major surface  502  that is the mirror-side of the preform, a second major surface  504  opposite the first major surface  502 , and a minor surface  503  between the first and second major surfaces  502  and  504 . The edges of the first and second major surfaces  502  and  504  have a first chamfer  506  and a second chamfer  508 , respectively, which are symmetrical. That is, the first chamfer  506  at the edge of the first major surface  502  and the second chamfer  508  at the edge of the second major surface  504  have the same size and/or shape, resulting in a symmetric profile when viewed in cross-section, as shown in  FIG. 7A .  FIG. 7B  shows the resulting three-dimensional (3D) or curved mirror substrate  500 ′ after forming the 2D preform  500  of  FIG. 7A . 
     The geometry of the first and second chamfers  506  and  508  can be described by the x- and y-components of the chamfered surface. As used herein, the x-component refers to a distance measured in a direction parallel to the first or second major surface of a two-dimensional preform. The y-component refers to a distance measured in a direction perpendicular to the first or second major surface of the two-dimensional preform, or parallel to the minor surface of the two-dimensional preform. In  FIGS. 7A and 7B , the first chamfer  506  has an x-component x 1  and a y-component y 1 , while the second chamfer  508  has an x-component x 2  and a y-component y 2 . The dimensions of x 1 , y 1 , x 2 , and y 2  can range from about 0.2 to about 0.3 mm, for example, where x 1  is the same as x 2  and y 1  is the same as y 2 . Thus, this conventional form of chamfering can be considered symmetrical chamfering. 
     However, investigators of the present disclosure found that asymmetrical chamfering of a mirror or mirror preform can reduce edge distortion. In some preferred embodiments, the asymmetrical chamfering takes the form of a larger chamfer on the mirror-side of the mirror or mirror substrate. A “larger” chamfer is a chamfer that has a larger x-component. For example,  FIGS. 8A and 8B  show a 2D preform  600  and a 3D or curved mirror substrate  600 ′ with asymmetrical chamfers. In particular,  FIG. 8A  shows a 2D preform  600  having a first major surface  602  that is a mirror-side of the substrate, a second major surface  604  opposite the first major surface  602 , and a minor surface  603  between the first and second major surfaces. The edges of the first and second major surfaces  602  and  604  have a first chamfer  606  and a second chamfer  608 , respectively, which are asymmetrical. That is, the first chamfer  606  at the edge of the first major surface  602  and the second chamfer  608  at the edge of the second major surface  604  have different sizes and/or shapes, resulting in an asymmetric profile when viewed in cross-section, as shown in  FIG. 8A . Due to the chamfers, the minor surface  603  has a decreased thickness t 2 , which is less than a thickness t 3  between the first and second major surfaces  602  and  604  in an un-chamfered section of the substrate  600 . In some preferred embodiments, the thickness t 3  can be about 1.0 mm to about 3.0 mm; about 2.0 mm; less than about 1.0 mm; or about 0.3 mm to about 1.0 mm.  FIG. 8B  shows the resulting 3D or curved mirror substrate  600 ′ after forming the 2D preform  600  of  FIG. 8A . 
     Similar to  FIGS. 7A and 7B , the geometry of the first and second chamfers  606  and  608  can be described by the x- and y-components of the chamfered surface. In  FIGS. 8A and 8B , the first chamfer  606  has an x-component x 1 ′ and a y-component y 1 ′, while the second chamfer  608  has an x-component x 2 ′ and a y-component y 2 ′. However, x 1 ′ and x 2 ′ are not equal, resulting in the asymmetric profile. In particular, the x-component of the mirror-side, x 1 ′, is larger than the x-component on the back or non-mirror side, x 2 ′. In some embodiments, the dimensions of x 1 ′ can be, for example, about 0.5 to about 3.0 mm. If x 1 ′ is too large (e.g., in some embodiments, over 3.0 mm), then the effective area of the mirror can become too small, which is not preferable. The dimensions of y 1 ′, x 2 ′, and y 2 ′ can be, for example, about 0.2 to about 0.3 mm. If the second chamfer  608  on the side of the second major surface  604  is too large (e.g., larger than about 0.2 mm to about 0.3 mm, in some embodiments), the formability is deteriorated and the corner accuracy decreases. However, embodiments are not limited to these dimensions. Thus, this approach results in an asymmetrical profile at the edge of the mirror or mirror substrate. 
     While chamfers can be measured using the length of the chamfer, or the x- and y-components of the chamfer as discussed above, chamfer geometry can also be described with reference to an angle of inclination of the chamfer surface relative to a surface of the substrate. For example, in  FIGS. 8A and 8B , the first chamfer  606  includes an inclined surface with a first end intersecting the first major surface  602  and a second end intersecting the minor surface  603 . The inclined surface is at an angle with respect to the first major surface  602 . Similarly, the second chamfer  608  includes an inclined surface that is at an angle with respect to the second major surface  604 . In some embodiments, the angles of the chamfers can be, for example, about 5 degrees to about 45 degrees. In some embodiments, the angle of the first chamfer  606  can be, for example, about 3 degrees to about 31 degrees; the angle of the second chamfer  608  can be about 33 degrees to about 57 degrees. 
     The asymmetric chamfering of the substrate edge results in improved formability and alleviates the visibility of distorted images reflected by the edge of the mirror. In the case of edge distortion, the angle of reflection of the display image changes due to the inclination of the chamfered surface, which can prevent the distorted image from being seen by the user. This can result in a projected image with no perceived edge distortion. Edge formability is thought to be improved by thinning of the edge area due to the large chamfer, which makes the edge area more formable. For example, when using identical vacuum pressure, the edge contour deviation relative to the computer-aided design (CAD) model decreases and the contour accuracy increases for an asymmetric edge as compared to a non-asymmetric edge. This improvement in contour accuracy reduces image distortion. In addition, the asymmetric chamfering can help prevent unwanted or dangerous light from entering the glass edge and being directed toward the eyes of a user of the HUD system. Such unwanted light may include sunlight, for example, which can distract drivers or interfere with their vision. 
     While the embodiments in  FIGS. 8A and 8B  show both first and second chamfers  606  and  608 , some embodiments of the present disclosure can include a chamfer only on the reflective side of the mirror substrate (i.e., the first chamfer  606 ). Thus, it is possible to achieve the advantages discussed herein of asymmetrical chamfering without having the second chamfer  608 , or without a particular design or geometry for the second chamfer. However, it may still be beneficial to have a second chamfer  608  on the back side of the substrate to remove a sharp edge from the edge, and to improve edge formability. 
       FIG. 9  shows an example of how the above-described improved edge performance is achieved by the asymmetric chamfer. In particular,  FIG. 9  shows a cross-section view of an edge area a 3D formed mirror  650  with a first major surface  652  that is reflective and concave. The mirror  650  also has a second major surface  654  opposite the first major surface  652 , and a minor surface  653  between the first and second major surfaces  652  and  654 . The edge of the mirror  650  has an asymmetric chamfer with a larger chamfer surface  656  on the side of the first major surface  652 , and a smaller chamfer surface  658  on the rear side. Incident light L is that is incident on the effective area of the mirror  650  is reflected as L rs  toward the user so that the reflected light is visible to the user. However, incident light L ie  that is incident on the chamfer surface  656  is reflected as L re  in a direction that makes it not visible to the user of the HUD system. 
     As discussed above, embodiments of this disclosure include forming a curved or 3D mirror substrate using vacuum forming methods. In one aspect, the vacuum forming method uses a mold  700 , as shown in  FIG. 10 . Mold  700  has a forming surface  702  that is shaped to a desired shape of the 3D mirror or mirror substrate. The mold  700  can optionally include a housing  706  surrounding the perimeter of the forming surface  702  and defining a space in which the mirror preform is placed for forming. To conform the mirror substrate (not shown) to the forming surface  702 , vacuum pressure is supplied through one or more vacuum holes. However, as discussed above, vacuum holes can leave manufacturing artifacts in the form of imperfections where the substrate contracted the vacuum holes. Thus, mold  700  does not include vacuum holes in an area that will contact the effective area of the mirror substrate. Instead, the mold  700  has a ditch-type vacuum hole  704  at a periphery of the forming surface  702 . The ditch-type vacuum hole  704  is positioned to be underneath the larger chamfer of the reflective-surface-side of the mirror when the mirror preform is placed on the mold  700 . In addition, the ditch-type vacuum hole  704  is positioned to remain underneath the larger chamfer of the reflective-surface-side of the mirror when the mirror preform during forming of the 3D mirror substrate on the mold  700 . Due to the position of the ditch-type vacuum hole  704  relative to the larger chamfer, any imperfection or artifact resulting from the ditch-type vacuum hole  704  will not be apparent to a user of a HUD system because the imperfection will not be located in the effective area of the mirror. As used herein, the effective area is a portion of the mirror or mirror substrate that will reflect the image to be projected and viewed by the user, and is located within the chamfered edge area of the mirror or mirror substrate. 
       FIGS. 11A and 11B  show details view of forming surface  802  near the edge of a mirror preform  800 . The resulting formed mirror substrate  800 ′ is also shown in  FIGS. 11A and 11B . The preform  800  is placed on the forming surface  802  such that the first major surface  801  (reflective-side of mirror) faces up and away from the forming surface  802 , and the second major surface  804  faces the forming surface  802 . Thus, with the first major surface  801  facing up, the larger chamfer  810  will also face up and away from the forming surface  802 . After forming, the second major surface  804  conforms to the forming surface  802 . When the preform  800  is placed in the mold, there is a gap d 1  between the minor surface  803  of the preform  800  and the vertical wall  807  of the housing  806  of the mold. The gap d 1  is sufficiently large enough to allow for easy placement and removal of the mirror substrate before and after forming. Alternatively, the gap d 1  may be non-existent prior to forming. After forming, the minor surface  803  will move to a distance of d 2  from the vertical wall  807  due to the curvature of the formed mirror substrate  800 ′, wherein d 2  is larger than d 1 . The mold is designed such that d 3  will be smaller than a distance from the vertical wall  807  to the ditch-type vacuum hole  808 . In other words, even after forming is completed, the ditch-type vacuum hole  808  will remain covered by the formed mirror substrate  800 ′ so that suction is not lost and the mirror substrate remains in conformity with the forming surface  802 . Thus, after forming, there is a non-zero distance d 3  between the opening of the ditch-type vacuum hole  808  in the forming surface  802  and the minor surface  803 ′ of the curved mirror substrate  800 ′. The distance d 3  is smaller than a length l 1  of the first chamfer  810 , where l 1  is defined as a straight-light distance from the minor surface  803 ′ of the formed mirror substrate  800 ′ to the intersection of the chamfer with the first major surface  801 ′. In some embodiments, l 1  can be about 1.0 to about 3.0 mm, whereas d 3  can be about 0.5 mm to about 3.0 mm. Because d 3  is smaller than 1 1 , any ditch-line artifact remaining in the mirror substrate from the ditch-type vacuum hole will be covered by the chamfer on the reflective-surface-side of the formed mirror, so that the defect is not visible to a user. 
       FIG. 12  shows a comparison between a 3D mirror substrate  900  using normal chamfering (left) and a 3D mirror substrate  910  using asymmetric chamfering (right). The asymmetric chamfering example shows superior optical performance at the edge  912 , without the distortion shown at the edge  902  of the normal chamfering example. 
       FIG. 13  shows a method of forming a mirror or mirror substrate, according to one or more embodiments of this disclosure. The method includes a step S 1  of creating a preform mirror substrate by cutting a sheet of glass to the desired preform shape. After cutting, a washing step S 2  may be performed to clean the preform, followed by a step S 3  of vacuum forming the preform into a 3D formed substrate. Lastly, one or more post-processing steps S 4  can be performed, including edge or surface finishing or coating, or mounting the curved mirror in some part of the HUD system. 
     The reflective surface can be formed via sputtering, evaporation (e.g., CVD, PVD), plating, or other methods of coating or supplying a reflective surface known to those of ordinary skill in the art. The reflective surface can include one or more metallic/ceramic oxides, metallic/ceramic alloys, for example. The reflective surface is formed on the 3D formed substrate after forming the substrate to a curved or aspheric shape. However, embodiments are not limited to this order, and it is contemplated that a 3D mirror can be formed from a 2D preform having a reflective surface. 
     In some embodiments, a glass-based preform for a mirror of a heads-up display (HUD) system is provided. The glass-based preform comprises a glass-based substrate having a first major surface, a second major surface opposite to the first major surface, and a minor surface connecting the first and second major surfaces. In addition, the preform includes a first chamfer at an edge of the first major surface, the first chamfer having a first end at an intersection of the first chamfer and the first major surface and having a second end at an intersection of the first chamfer and the minor surface, and can also include a second chamfer at an edge of the second major surface, the second chamfer having a first end at an intersection of the second chamfer and the second major surface and having a second end at an intersection of the second chamfer and the minor surface. The first chamfer has a different size or shape from the second chamfer. 
     In one aspect, first chamfer has a first length, the second chamfer has a second length, and the first length is different than the second length. The first length can be greater than the second length. The first length is measured in a direction that is in-plane with the first major surface at the intersection with the first chamfer and is measured from the first end of the first chamfer to a plane that is co-planar with the minor surface at the second end of the first chamfer. Similarly, the second length is measured in a direction that is in-plane with the second major surface and is measured from the first end of the second chamfer to a plane that is co-planar with the minor surface at the second end of the second chamfer. In some embodiments, the first length is at least about 1.0 mm; is from about 1.0 mm to about 3.0 mm; or is about 2.0 mm. 
     The first chamfer can include a first inclined surface at a first angle measured with respect to the first surface, wherein the first inclined surface intersects the first major surface at a first distance of about 0.5 mm to about 3 mm from a minor plane co-planar with the minor surface at the second end of the first chamfer, and intersects the minor surface at a second distance of about 0.2 mm to about 0.3 mm from a first major plane co-planar with the first major surface at the first end of the first chamfer. The second chamfer can include a second inclined surface at a second angle measured with respect to the second surface, wherein the second inclined surface intersects the second major surface at a first distance of about 0.2 mm to about 0.3 mm from a minor plane co-planar with the minor surface at the second end of the second chamfer, and intersects the minor surface at a second distance of about 0.2 mm to about 0.3 mm from a second major plane co-planar with the second major surface at the first end of the first chamfer. The first angle can be about 3 degrees to about 31 degrees, and the second angle can be about 33 degrees to about 57 degrees. In some embodiments, he first angle is from about 5 degrees to about 45 degrees, and the second angle is from about 5 degrees to about 45 degrees. 
     In another aspect of some embodiments, the first chamfer comprises a first inclined surface at a first angle measured with respect to the first surface, and the second chamfer comprises a second inclined surface at a second angle measured with respect to the second surface, and the first angle is different than the second angle. The first angle is smaller than the second angle. The first inclined surface extends from the first edge to the second edge of the first chamfer, and the second inclined surface extends from the first edge to the second edge of the second chamfer. 
     In aspects of some embodiments, at least a portion of the first major surface is reflective. The portion of the first major surface that is reflective can have a reflective coating on the glass-based substrate, and the reflective coating can include a metal, a metal oxide, a ceramic oxide, or a metal-ceramic alloy. In some aspects, the reflective coating comprises aluminum or silver. 
     A length of the first inclined surface as measured in a direction parallel to the first major surface can be about 0.5 mm to 3 mm, and a length of the first inclined surface as measured in a direction parallel to the minor surface can be about 0.2 mm to 0.3 mm. A length of the second inclined surface as measured in a direction parallel to the second major surface can be about 0.2 mm to 0.3 mm, and a length of the second inclined surface as measured in a direction parallel to the minor surface can be about 0.2 mm to 0.3 mm. As an aspect of some embodiments, the glass-based substrate has a thickness that is less than or equal to 3.0 mm; from about 0.5 mm to about 3.0 mm; from about 0.5 mm to about 1.0 mm; or from about 1.0 mm to about 3.0 mm. 
     In another embodiment, a mirror for a HUD system is provided, comprising the glass-based preform of any one of the above embodiments. The mirror further comprises a reflective layer on the first major surface of the glass-based preform. The glass-based substrate has a first radius of curvature such that the first major surface has a concave shape and the second major surface has a convex shape, the first radius of curvature being measured with respect to a first axis of curvature. The glass-based substrate can have a second radius of curvature measured with respect to a second axis of curvature different from the first axis of curvature, where the first axis of curvature is perpendicular to the second axis of curvature. In some embodiments, the first major surface has an aspheric shape. 
     In another embodiment, a method of forming a three-dimensional mirror is provided, the method comprising providing a glass-based mirror preform including a first major surface having an edge with a first chamfer, a second major surface opposite to the first major surface and having an edge with a second chamfer, and a minor surface connecting the first and second major surfaces, the second chamfer having a different size or shape than the first chamfer. The method also includes disposing the glass-based preform on a molding apparatus having a curved support surface with the second major surface facing the curved support surface, and conforming the glass-based preform to the curved support surface to form a curved mirror substrate having a first radius of curvature. 
     In aspects of some of the embodiments, the conforming of the glass-based preform to the curved support surface is performed at a temperature that is less than a glass transition temperature of the glass-based preform. A temperature of the glass-based substrate may not be raised above the glass transition temperature of the glass-based substrate during or after the conforming. 
     In additional aspects of some of the embodiments, the curved support surface has a concave shape, and the concave shape can be an aspheric shape. The curved support surface can also comprise a vacuum chuck with at least one opening in the curved support surface. The method can further include supplying a vacuum to the at least one opening to conform the curved glass blank to the curved support surface. The at least one opening can be a ditch-type vacuum hole. 
     The first chamfer is formed in the first major surface such that the first chamfer begins in the first major surface at a first distance from the minor surface, wherein, when the glass-based preform is disposed on the curved support surface, the at least one opening is a second distance from the minor surface, and wherein the first distance is greater than or equal to the second distance. The molding apparatus can include a raised perimeter surface or wall adjacent the curved support surface and defining a space on the curved support surface in which the glass-based preform is to be disposed. The first chamfer is formed in the first major surface such the first chamfer begins in the first major surface at a first distance from the minor surface, wherein the at least one opening is a second distance from the raised perimeter surface or wall, and the first distance is greater than or equal to the second distance; or the first distance is greater than the second distance. 
     The method can further include forming a reflective layer on the first major surface. The reflective layer can be formed by sputtering, plating, or vapor deposition of a material of the reflective layer onto the first major surface. The reflective layer comprises a metal, a metal oxide, a ceramic oxide, or a metal-ceramic alloy; and can include aluminum or silver. The reflective layer is formed on the first major surface after forming the curved mirror substrate to form an aspheric mirror. 
     As an aspect of some embodiments, the first chamfer comprises a first inclined surface at a first angle measured with respect to the first surface, the first inclined surface having a first length, wherein the second chamfer comprises a second inclined surface at a second angle measured with respect to the second surface, the second inclined surface having a second length, and wherein the first length is different than the second length, or can be greater than the second length. The first length is measured in a direction that is in-plane with the first major surface and is measured from an intersection of the first inclined surface and the first major surface to a plane that is co-planar with the minor surface, and the second length is measured in a direction that is in-plane with the second major surface and is measured from an intersection of the second inclined surface and the second major surface to a plane that is co-planar with the minor surface. The first length can be at least about 1.0 mm; from about 1.0 mm to about 3.0 mm; or about 2.0 mm. The first inclined surface intersects the first major surface at about 0.5 mm to about 3 mm from a first plane co-planar with the minor surface, and intersects the minor surface at about 0.2 mm to about 0.3 mm from a second plane co-planar with the first major surface. The second inclined surface intersects the second major surface at about 0.2 mm to about 0.3 mm from a plane co-planar with the minor surface, and intersects the minor surface at about 0.2 mm to about 0.3 mm from a plane co-planar with the second major surface. 
     In another aspect of some of the embodiments of the method, the first chamfer defines a first inclined surface at a first angle measured with respect to the first surface, and the second chamfer defines a second inclined surface at a second angle measured with respect to the second surface, and the first angle is different than the second angle. The first angle can be smaller than the second angle. 
     In an additional embodiment, a heads-up display (HUD) projection system is provided. The HUD system comprises a display unit configured to display an image to be viewed by a user of a HUD system; and a mirror configured to reflect the image to a viewing area viewable by the user. The mirror comprises a glass-based substrate having a first major surface that is reflective, a second major surface opposite to the first major surface, and a minor surface connecting the first and second major surfaces, a first chamfer at an edge of the first major surface, the first chamfer having a first end at an intersection of the first chamfer and the first major surface and having a second end at an intersection of the first chamfer and the minor surface, and a second chamfer at an edge of the second major surface, the second chamfer having a first end at an intersection of the second chamfer and the second major surface and having a second end at an intersection of the second chamfer and the minor surface. The first chamfer has a different size or shape from the second chamfer. 
     The first chamfer has a first length, the second chamfer has a second length, and the first length is different than the second length, and the first length is greater than the second length. The first length is measured in a direction that is in-plane with the first major surface at the intersection with the first chamfer and is measured from the first end of the first chamfer to a plane that is co-planar with the minor surface at the second end of the first chamfer, and the second length is measured in a direction that is in-plane with the second major surface and is measured from the first end of the second chamfer to a plane that is co-planar with the minor surface at the second end of the second chamfer. The first length can be at least about 1.0 mm; from about 1.0 mm to about 3.0 mm; or about 2.0 mm. 
     The first chamfer can include a first inclined surface at a first angle measured with respect to the first surface, wherein the first inclined surface intersects the first major surface at a first distance of about 0.5 mm to about 3 mm from a minor plane co-planar with the minor surface at the second end of the first chamfer, and intersects the minor surface at a second distance of about 0.2 mm to about 0.3 mm from a first major plane co-planar with the first major surface at the first end of the first chamfer. The second chamfer can include a second inclined surface at a second angle measured with respect to the second surface, wherein the second inclined surface intersects the second major surface at a first distance of about 0.2 mm to about 0.3 mm from a minor plane co-planar with the minor surface at the second end of the second chamfer, and intersects the minor surface at a second distance of about 0.2 mm to about 0.3 mm from a second major plane co-planar with the second major surface at the first end of the first chamfer. The first angle is about 3 degrees to about 31 degrees, and the second angle is about 33 degrees to about 57 degrees. In some embodiments, the first angle is from about 5 degrees to about 45 degrees, and the second angle is from about 5 degrees to about 45 degrees. 
     In additional aspects of the some embodiments, the first chamfer comprises a first inclined surface at a first angle measured with respect to the first surface, and the second chamfer comprises a second inclined surface at a second angle measured with respect to the second surface, and the first angle is different than the second angle. The first angle is smaller than the second angle. The first inclined surface extends from the first edge to the second edge of the first chamfer, and the second inclined surface extends from the first edge to the second edge of the second chamfer. 
     As aspects of some embodiments, the first major surface has a first radius of curvature such that the first major surface has a concave shape and the second major surface has a convex shape, the first radius of curvature being measured relative to a first axis of curvature. The mirror has a second radius of curvature that is measured relative to a second axis of curvature different from the first axis of curvature, where the first axis of curvature can be perpendicular to the second axis of curvature. The first major surface can have an aspheric shape. The first major surface that is reflective can include a reflective coating on the glass-based substrate, and the reflective coating can comprise a metal, a metal oxide, a ceramic oxide, or a metal-ceramic alloy, and may include aluminum or silver. 
     In some embodiments, the display unit comprises an LCD, LED, OLED, or μLED display panel, or includes a projector. The HUD system can further include a projection surface configured to display a projected image to a user of the HUD system, wherein the mirror is configured to reflect the image produced by the display unit to form the projected image on the projection surface. The projection surface has a curvature corresponding to a curvature of the mirror, and the curvature of the projection surface is substantially the same as the curvature of the mirror. The projection surface can be a windshield or a combiner. Also, the projection surface can have an aspheric shape. 
     The glass-based substrate has a thickness that is less than or equal to 3.0 mm; from about 0.5 mm to about 3.0 mm; from about 0.5 mm to about 1.0 mm; or from about 1.0 mm to about 3.0 mm. 
     In aspects of some embodiments of the HUD projection system, the second major surface comprises one or more manufacturing artifacts, wherein the manufacturing artifacts are confined to a perimeter region of the second major surface, the perimeter region extending from the edge of the second major surface to a distance that is less than the first length. The manufacturing artifacts can be vacuum suction artifacts from a process of bending the mirror. 
     In some additional embodiments, a method of forming a three-dimensional mirror is provided. The method includes providing a glass-based mirror preform having a first major surface, a second major surface opposite to the first major surface, and a minor surface connecting the first and second major surfaces, the glass preform having a flat shape; forming a first chamfer at an edge of the first major surface; forming a second chamfer at an edge of the second major surface, the second chamfer having a different size or shape from the first chamfer; disposing the glass-based preform on a molding apparatus having a curved support surface with the second major surface facing the curved support surface; and conforming the glass-based preform to the curved support surface to form a curved mirror substrate having a first radius of curvature. The conforming of the glass-based preform to the curved support surface is performed at a temperature that is less than a glass transition temperature of the glass-based preform, and a temperature of the glass-based substrate may not be raised above the glass transition temperature of the glass-based substrate during or after the conforming. 
     As aspects of some embodiments, the curved support surface has a concave shape, and the concave shape can be an aspheric shape. The curved support surface can include a vacuum chuck with at least one opening in the curved support surface, and the method may further include supplying a vacuum to the at least one opening to conform the curved glass blank to the curved support surface. The at least one opening is a ditch-type vacuum hole. The first chamfer is formed in the first major surface such that the first chamfer begins at a first distance from the minor surface. When the glass-based preform is disposed on the curved support surface, the at least one opening is a second distance from the minor surface, wherein the first distance is greater than or equal to the second distance. In aspects of some embodiments, the molding apparatus comprises a raised perimeter surface or wall adjacent the curved support surface and defining a space on the curved support surface in which the glass-based preform is to be disposed. The first chamfer is formed in the first major surface such the first chamfer begins at a first distance from the minor surface, the at least one opening is a second distance from the raised perimeter surface or wall, and the first distance is greater than or equal to the second distance, or the first distance is greater than the second distance. 
     The method can further include forming a reflective layer on the first major surface. The reflective layer is formed by sputtering, plating, or vapor deposition of a material of the reflective layer onto the first major surface, and the reflective layer comprises a metal, a metal oxide, a ceramic oxide, or a metal-ceramic alloy, and can include aluminum or silver. The reflective layer is formed on the first major surface after forming the curved mirror substrate to form an aspheric mirror. 
     As aspects of some embodiments, the first chamfer comprises a first inclined surface at a first angle measured with respect to the first surface, the first inclined surface having a first length, the second chamfer comprises a second inclined surface at a second angle measured with respect to the second surface, where the second inclined surface having a second length, and the first length is different than the second length, or the first length is greater than the second length. The first length is measured in a direction that is in-plane with the first major surface and is measured from an intersection of the first inclined surface and the first major surface to a plane that is co-planar with the minor surface, and the second length is measured in a direction that is in-plane with the second major surface and is measured from an intersection of the second inclined surface and the second major surface to a plane that is co-planar with the minor surface. The first length can be at least about 1.0 mm; from about 1.0 mm to about 3.0 mm; or about 2.0 mm. The first inclined surface intersects the first major surface at about 0.5 mm to about 3 mm from a first plane co-planar with the minor surface, and intersects the minor surface at about 0.2 mm to about 0.3 mm from a second plane co-planar with the first major surface. The second inclined surface intersects the second major surface at about 0.2 mm to about 0.3 mm from a plane co-planar with the minor surface, and intersects the minor surface at about 0.2 mm to about 0.3 mm from a plane co-planar with the second major surface. The first angle is smaller than the second angle. 
     In another embodiment, a heads-up display (HUD) system is provided, comprising a projection surface for viewing a projected image by a user of the HUD system; a display unit configured to produce an image to be viewed by the user on the projection surface; and a mirror configured to reflect the image to the projection surface to form the projected image. The mirror includes a glass-based substrate having a first major surface that is reflective, a second major surface opposite to the first major surface, and a minor surface connecting the first and second major surfaces; a first chamfer at an edge of the first major surface, the first chamfer; and a second chamfer at an edge of the second major surface, wherein the first chamfer has a different size or shape from the second chamfer. The first chamfer has a first end at an intersection of the first chamfer and the first major surface and has a second end at an intersection of the first chamfer and the minor surface, and the second chamfer has a first end at an intersection of the second chamfer and the second major surface and has a second end at an intersection of the second chamfer and the minor surface. The first chamfer has a first length, the second chamfer has a second length, and the first length is different than the second length, or the first length is greater than the second length. 
     As an aspect of some embodiments, the first chamfer has a first length, the second chamfer has a second length, and the first length is different than the second length, where the first length is measured in a direction that is in-plane with the first major surface at the intersection with the first chamfer and is measured from the first end of the first chamfer to a plane that is co-planar with the minor surface at the second end of the first chamfer, and the second length is measured in a direction that is in-plane with the second major surface and is measured from the first end of the second chamfer to a plane that is co-planar with the minor surface at the second end of the second chamfer. The first length is at least about 1.0 mm; is from about 1.0 mm to about 3.0 mm; or is about 2.0 mm. 
     As another aspect of some embodiments, the first chamfer comprises a first inclined surface at a first angle measured with respect to the first surface, wherein the first inclined surface intersects the first major surface at a first distance of about 0.5 mm to about 3 mm from a minor plane co-planar with the minor surface at the second end of the first chamfer, and intersects the minor surface at a second distance of about 0.2 mm to about 0.3 mm from a first major plane co-planar with the first major surface at the first end of the first chamfer. The second chamfer comprises a second inclined surface at a second angle measured with respect to the second surface, wherein the second inclined surface intersects the second major surface at a first distance of about 0.2 mm to about 0.3 mm from a minor plane co-planar with the minor surface at the second end of the second chamfer, and intersects the minor surface at a second distance of about 0.2 mm to about 0.3 mm from a second major plane co-planar with the second major surface at the first end of the first chamfer. The first angle is about 3 degrees to about 31 degrees, and the second angle is about 33 degrees to about 57 degrees; or the first angle is from about 5 degrees to about 45 degrees, and the second angle is from about 5 degrees to about 45 degrees. The first angle can be different than the second angle, and the first angle can be smaller than the second angle. A length of the first inclined surface as measured in a direction parallel to the first major surface is about 0.5 mm to 3 mm, and a length of the first inclined surface as measured in a direction parallel to the minor surface is about 0.2 mm to 0.3 mm. A length of the second inclined surface as measured in a direction parallel to the second major surface is about 0.2 mm to 0.3 mm, and a length of the second inclined surface as measured in a direction parallel to the minor surface is about 0.2 mm to 0.3 mm. 
     In some aspects of the embodiments, the first major surface has a first radius of curvature such that the first major surface has a concave shape and the second major surface has a convex shape, the first radius of curvature being measured relative to a first axis of curvature. The first major surface can also have a second radius of curvature that is measured relative to a second axis of curvature that is different from the first axis of curvature. The first axis of curvature is perpendicular to the second axis of curvature. The first major surface can have an aspheric shape, and the aspheric shape corresponds to a shape of the projection surface. The first major surface that is reflective comprises a reflective coating on the glass-based substrate. The reflective coating comprises a metal, a metal oxide, a ceramic oxide, or a metal-ceramic alloy, and the metal can be aluminum or silver. 
     In aspects of embodiments of the HUD system, the display unit comprises an LCD, LED, OLED, or μLED display panel, and can include a projector. 
     The glass-based substrate has a thickness that is less than or equal to 3.0 mm; from about 0.5 mm to about 3.0 mm; from about 0.5 mm to about 1.0 mm; from about 1.0 mm to about 3.0 mm; or about 2.0 mm. 
     As an aspect of some embodiments, the chamfering of the first major surface is configured to reduce edge distortion of the projected image. The chamfering of the first major surface can be configured to reduce an amount of unwanted light reflected toward the user. The projection surface can be a windshield of a vehicle, or a combiner configured to be mounted in a vehicle interior. 
     In some other embodiments, a heads-up display (HUD) projection system is provided, comprising a display unit configured to display an image to be viewed by a user of a HUD system; and a mirror configured to reflect the image to a viewing area viewable by the user. The mirror includes a glass-based substrate having a first major surface that is reflective, a second major surface opposite to the first major surface, and a minor surface connecting the first and second major surfaces, and a chamfer at an edge of the first major surface, the chamfer having a first length. 
     As aspects of some embodiments, the first length is measured in a direction that is in-plane with the first major surface and is measured from an intersection of the first inclined surface and the first major surface to a plane that is co-planar with the minor surface, and the first length is at least about 1.0 mm; is from about 1.0 mm to about 3.0 mm; or is about 2.0 mm. The chamfer intersects the first major surface at about 0.5 mm to about 3 mm from a first plane co-planar with the minor surface, and intersects the minor surface at about 0.2 mm to about 0.3 mm from a second plane co-planar with the first major surface. 
     The mirror has a first radius of curvature such that the first major surface has a concave shape and the second major surface has a convex shape, the first radius of curvature being relative to a first axis of curvature. The mirror can also have a second radius of curvature that is relative to a second axis of curvature different from the first axis of curvature, where the first axis of curvature is perpendicular to the second axis of curvature. In some preferred embodiments, the first major surface has an aspheric shape. 
     The first major surface that is reflective comprises a reflective coating on the glass-based substrate, where the reflective coating comprises a metal, a metal oxide, a ceramic oxide, or a metal-ceramic alloy, and can include aluminum or silver. The display unit can include an LCD, LED, OLED, or μLED display panel, and/or a projector. The HUD system can further include a projection surface for viewing a projected image by a user of the HUD system, where the display unit configured to produce an image, and the mirror is configured to reflect the image to form the projected image on the projection surface. The projection surface has a shape that is substantially the same as a shape of the mirror, where the projection surface is a windshield or a combiner, and the projection surface can have an aspheric shape. 
     In some embodiments, the second major surface comprises one or more manufacturing artifacts, and the manufacturing artifacts are confined to a perimeter region of the second major surface at a distance from the edge of the second major surface that is less than the first length. The manufacturing artifacts are vacuum suction artifacts from a process of bending the mirror. 
     The glass-based substrate has a thickness that is less than or equal to 3.0 mm; from about 0.5 mm to about 3.0 mm; from about 0.5 mm to about 1.0 mm; from about 1.0 mm to about 3.0 mm; or about 2.0 mm. 
     Suitable glass substrates for mirrors in HUD systems can be non-strengthened glass sheets or can also be strengthened glass sheets. The glass sheets (whether strengthened or non-strengthened) may include soda-lime glass, aluminosilicate, boroaluminosilicate or alkali aluminosilicate glass. Optionally, the glass sheets may be thermally strengthened. 
     Suitable glass substrates may be chemically strengthened by an ion exchange process. In this process, typically by immersion of the glass sheet into a molten salt bath for a predetermined period of time, ions at or near the surface of the glass sheet are exchanged for larger metal ions from the salt bath. In one embodiment, the temperature of the molten salt bath is about 430° C. and the predetermined time period is about eight hours. The incorporation of the larger ions into the glass strengthens the sheet by creating a compressive stress in a near surface region. A corresponding tensile stress is induced within a central region of the glass to balance the compressive stress. 
     Exemplary ion-exchangeable glasses that are suitable for forming glass substrates are soda lime glasses, alkali aluminosilicate glasses or alkali aluminoborosilicate glasses, though other glass compositions are contemplated. As used herein, “ion exchangeable” means that a glass is capable of exchanging cations located at or near the surface of the glass with cations of the same valence that are either larger or smaller in size. One exemplary glass composition comprises SiO 2 , B 2 O 3  and Na 2 O, where (SiO 2 +B 2 O 3 )≥66 mol. %, and Na 2 O≥9 mol. %. In an embodiment, the glass sheets include at least 6 wt. % aluminum oxide. In a further embodiment, a glass sheet includes one or more alkaline earth oxides, such that a content of alkaline earth oxides is at least 5 wt. %. Suitable glass compositions, in some embodiments, further comprise at least one of K 2 O, MgO, and CaO. In a particular embodiment, the glass can comprise 61-75 mol. % SiO 2 ; 7-15 mol. % Al 2 O 3 ; 0-12 mol. % B 2 O 3 ; 9-21 mol. % Na 2 O; 0-4 mol. % K 2 O; 0-7 mol. % MgO; and 0-3 mol. % CaO. 
     A further exemplary glass composition suitable for forming glass substrates comprises: 60-70 mol. % SiO 2 ; 6-14 mol. % Al 2 O 3 ; 0-15 mol. % B 2 O 3 ; 0-15 mol. % Li 2 O; 0-20 mol. % Na 2 O; 0-10 mol. % K 2 O; 0-8 mol. % MgO; 0-10 mol. % CaO; 0-5 mol. % ZrO 2 ; 0-1 mol. % SnO 2 ; 0-1 mol. % CeO 2 ; less than 50 ppm As 2 O 3 ; and less than 50 ppm Sb 2 O 3 ; where 12 mol. %≤(Li 2 O+Na 2 O+K 2 O)≤20 mol. % and 0 mol. %≤(MgO+CaO)≤10 mol. %. 
     A still further exemplary glass composition comprises: 63.5-66.5 mol. % SiO 2 ; 8-12 mol. % Al 2 O 3 ; 0-3 mol. % B 2 O 3 ; 0-5 mol. % Li 2 O; 8-18 mol. % Na 2 O; 0-5 mol. % K 2 O; 1-7 mol. % MgO; 0-2.5 mol. % CaO; 0-3 mol. % ZrO 2 ; 0.05-0.25 mol. % SnO 2 ; 0.05-0.5 mol. % CeO 2 ; less than 50 ppm As 2 O 3 ; and less than 50 ppm Sb 2 O 3 ; where 14 mol. %≤(Li 2 O+Na 2 O+K 2 O)≤18 mol. % and 2 mol. %≤(MgO+CaO)≤7 mol. %. 
     In a particular embodiment, an alkali aluminosilicate glass comprises alumina, at least one alkali metal and, in some embodiments, greater than 50 mol. % SiO 2 , in other embodiments at least 58 mol. % SiO 2 , and in still other embodiments at least 60 mol. % SiO 2 , wherein the ratio 
     
       
         
           
             
               
                 
                   
                     
                       Al 
                       2 
                     
                      
                     
                       O 
                       3 
                     
                   
                   + 
                   
                     
                       B 
                       2 
                     
                      
                     
                       O 
                       3 
                     
                   
                 
                 
                   Σ 
                    
                   
                       
                   
                    
                   modifiers 
                 
               
               &gt; 
               1 
             
             , 
           
         
       
     
     where in the ratio the components are expressed in mol. % and the modifiers are alkali metal oxides. This glass, in particular embodiments, comprises, consists essentially of, or consists of: 58-72 mol. % SiO 2 ; 9-17 mol. % Al 2 O 3 ; 2-12 mol. % B 2 O 3 ; 8-16 mol. % Na 2 O; and 0-4 mol. % K 2 O, wherein the ratio 
     
       
         
           
             
               
                 
                   
                     Al 
                     2 
                   
                    
                   
                     O 
                     3 
                   
                 
                 + 
                 
                   
                     B 
                     2 
                   
                    
                   
                     O 
                     3 
                   
                 
               
               
                 Σ 
                  
                 
                     
                 
                  
                 modifiers 
               
             
             &gt; 
             1. 
           
         
       
     
     In another embodiment, an alkali aluminosilicate glass comprises, consists essentially of, or consists of: 61-75 mol. % SiO 2 ; 7-15 mol. % Al 2 O 3 ; 0-12 mol. % B 2 O 3 ; 9-21 mol. % Na 2 O; 0-4 mol. % K 2 O; 0-7 mol. % MgO; and 0-3 mol. % CaO. 
     In yet another embodiment, an alkali aluminosilicate glass substrate comprises, consists essentially of, or consists of: 60-70 mol. % SiO 2 ; 6-14 mol. % Al 2 O 3 ; 0-15 mol. % B 2 O 3 ; 0-15 mol. % Li 2 O; 0-20 mol. % Na 2 O; 0-10 mol. % K 2 O; 0-8 mol. % MgO; 0-10 mol. % CaO; 0-5 mol. % ZrO 2 ; 0-1 mol. % SnO 2 ; 0-1 mol. % CeO 2 ; less than 50 ppm As 2 O 3 ; and less than 50 ppm Sb 2 O 3 ; wherein 12 mol. %≤Li 2 O+Na 2 O+K 2 O≤20 mol. % and 0 mol. %≤MgO+CaO≤10 mol. %. 
     In still another embodiment, an alkali aluminosilicate glass comprises, consists essentially of, or consists of: 64-68 mol. % SiO 2 ; 12-16 mol. % Na 2 O; 8-12 mol. % Al 2 O 3 ; 0-3 mol. % B 2 O 3 ; 2-5 mol. % K 2 O; 4-6 mol. % MgO; and 0-5 mol. % CaO, wherein: 66 mol. %≤SiO 2 +B 2 O 3 +CaO≤69 mol. %; Na 2 O+K 2 O+B 2 O 3 +MgO+CaO+SrO&gt;10 mol. %; 5 mol. %≤MgO+CaO+SrO≤8 mol. %; (Na 2 O+B 2 O 3 )—Al 2 O 3 ≤2 mol. %; 2 mol. %≤Na 2 O—Al 2 O 3 ≤6 mol. %; and 4 mol. %≤(Na 2 O+K 2 O)—Al 2 O 3 ≤10 mol. %. 
     The chemically-strengthened as well as the non-chemically-strengthened glass, in some embodiments, can be batched with 0-2 mol. % of at least one fining agent selected from a group that includes Na 2 SO 4 , NaCl, NaF, NaBr, K 2 SO 4 , KCl, KF, KBr, and SnO 2 . 
     In one exemplary embodiment, sodium ions in the chemically-strengthened glass can be replaced by potassium ions from the molten bath, though other alkali metal ions having a larger atomic radii, such as rubidium or cesium, can replace smaller alkali metal ions in the glass. According to particular embodiments, smaller alkali metal ions in the glass can be replaced by Ag +  ions. Similarly, other alkali metal salts such as, but not limited to, sulfates, halides, and the like may be used in the ion exchange process. 
     The replacement of smaller ions by larger ions at a temperature below that at which the glass network can relax produces a distribution of ions across the surface of the glass that results in a stress profile. The larger volume of the incoming ion produces a compressive stress (CS) on the surface and tension (central tension, or CT) in the center of the glass. The compressive stress is related to the central tension by the following relationship: 
     
       
         
           
             CS 
             = 
             
               CT 
                
               
                 ( 
                 
                   
                     t 
                     - 
                     
                       2 
                        
                       DOL 
                     
                   
                   DOL 
                 
                 ) 
               
             
           
         
       
     
     where t is the total thickness of the glass sheet and DOL is the depth of exchange, also referred to as depth of layer. 
     According to various embodiments, glass substrates comprising ion-exchanged glass can possess an array of desired properties, including low weight, high impact resistance, and improved sound attenuation. In one embodiment, a chemically-strengthened glass sheet can have a surface compressive stress of at least 300 MPa, e.g., at least 400, 450, 500, 550, 600, 650, 700, 750 or 800 MPa, a depth of layer at least about 20 μm (e.g., at least about 20, 25, 30, 35, 40, 45, or 50 μm) and/or a central tension greater than 40 MPa (e.g., greater than 40, 45, or 50 MPa) but less than 100 MPa (e.g., less than 100, 95, 90, 85, 80, 75, 70, 65, 60, or 55 MPa). 
     Suitable glass substrates may be thermally strengthened by a thermal tempering process or an annealing process. The thickness of the thermally-strengthened glass sheets may be less than about 2 mm or less than about 1 mm. 
     Exemplary glass sheet forming methods include fusion draw and slot draw processes, which are each examples of a down-draw process, as well as float processes. These methods can be used to form both strengthened and non-strengthened glass sheets. The fusion draw process uses a drawing tank that has a channel for accepting molten glass raw material. The channel has weirs that are open at the top along the length of the channel on both sides of the channel. When the channel fills with molten material, the molten glass overflows the weirs. Due to gravity, the molten glass flows down the outside surfaces of the drawing tank. These outside surfaces extend down and inwardly so that they join at an edge below the drawing tank. The two flowing glass surfaces join at this edge to fuse and form a single flowing sheet. The fusion draw method offers the advantage that, because the two glass films flowing over the channel fuse together, neither outside surface of the resulting glass sheet comes in contact with any part of the apparatus. Thus, the surface properties of the fusion drawn glass sheet are not affected by such contact. 
     The slot draw method is distinct from the fusion draw method. Here the molten raw material glass is provided to a drawing tank. The bottom of the drawing tank has an open slot with a nozzle that extends the length of the slot. The molten glass flows through the slot/nozzle and is drawn downward as a continuous sheet and into an annealing region. The slot draw process can provide a thinner sheet than the fusion draw process because only a single sheet is drawn through the slot, rather than two sheets being fused together. 
     Down-draw processes produce glass sheets having a uniform thickness that possess surfaces that are relatively pristine. Because the strength of the glass surface is controlled by the amount and size of surface flaws, a pristine surface that has had minimal contact has a higher initial strength. When this high strength glass is then chemically strengthened, the resultant strength can be higher than that of a surface that has been a lapped and polished. Down-drawn glass may be drawn to a thickness of less than about 2 mm. In addition, down drawn glass has a very flat, smooth surface that can be used in its final application without costly grinding and polishing. 
     In the float glass method, a sheet of glass that may be characterized by smooth surfaces and uniform thickness is made by floating molten glass on a bed of molten metal, typically tin. In an exemplary process, molten glass that is fed onto the surface of the molten tin bed forms a floating ribbon. As the glass ribbon flows along the tin bath, the temperature is gradually decreased until a solid glass sheet can be lifted from the tin onto rollers. Once off the bath, the glass sheet can be cooled further and annealed to reduce internal stress. 
     As discussed in previous paragraphs, an exemplary glass substrate can include a glass sheet of chemically strengthened glass, e.g., Gorilla® Glass. This glass sheet may have been heat treated, ion exchanged and/or annealed. In a laminate structure, the strengthened glass sheet may be an inner layer, and an outer layer may be a non-chemically strengthened glass sheet such as conventional soda lime glass, annealed glass, or the like. The laminate structure can also include a polymeric interlayer intermediate the outer and inner glass layers. The strengthened glass sheet can have a thickness of less than or equal to 1.0 mm and having a residual surface CS level of between about 250 MPa to about 350 MPa with a DOL of greater than 60 microns. In another embodiment the CS level of the strengthened glass sheet is preferably about 300 MPa. Exemplary thicknesses of the glass sheet can range in thicknesses from about 0.3 mm to about 1.5 mm, from 0.5 mm to 1.5 mm to 2.0 mm or more. 
     In a preferred embodiment, the thin chemically strengthened glass sheet may have a surface stress between about 250 MPa and 900 MPa and can range in thickness from about 0.3 mm to about 1.0 mm. In an embodiment where this strengthened glass sheet is included in a laminate structure, the external layer can be annealed (non-chemically strengthened) glass with a thickness from about 1.5 mm to about 3.0 mm or more. Of course, the thicknesses of the outer and inner layers can be different in a respective laminate structure. Another preferred embodiment of an exemplary laminate structure may include an inner layer of 0.7 mm chemically strengthened glass, a poly-vinyl butyral layer of about 0.76 mm in thickness and a 2.1 mm exterior layer of annealed glass. 
     In some embodiments, exemplary glass substrates of embodiments discussed herein can be employed in vehicles (automobile, aircraft, and the like) having a Head-up or Heads-up Display (HUD) system. The clarity of fusion formed according to some embodiments can be superior to glass formed by a float process to thereby provide a better driving experience as well as improve safety since information can be easier to read and less of a distraction. A non-limiting HUD system can include a projector unit, a combiner, and a video generation computer. The projection unit in an exemplary HUD can be, but is not limited to, an optical collimator having a convex lens or concave mirror with a display (e.g., optical waveguide, scanning lasers, LED, CRT, video imagery, or the like) at its focus. The projection unit can be employed to produce a desired image. In some embodiments, the HUD system can also include a combiner or beam splitter to redirect the projected image from the projection unit to vary or alter the field of view and the projected image. Some combiners can include special coatings to reflect monochromatic light projected thereon while allowing other wavelengths of light to pass through. In additional embodiments, the combiner can also be curved to refocus an image from the projection unit. Any exemplary HUD system can also include a processing system to provide an interface between the projection unit and applicable vehicle systems from which data can be received, manipulated, monitored and/or displayed. Some processing systems can also be utilized to generate the imagery and symbology to be displayed by the projection unit. 
     Using such an exemplary HUD system, a display of information (e.g., numbers, images, directions, wording, or otherwise) can be created by projecting an image from the HUD system onto an interior facing surface of a glass-based mirror substrate. The mirror can then redirect the image so that it is in the field of view of a driver. 
     Exemplary glass substrates according to some embodiments can thus provide a thin, pristine surface for the mirror. In some embodiments, fusion drawn Gorilla Glass can be used as the glass substrate. Such glass does not contain any float lines typical of conventional glass manufactured with the float process (e.g., soda lime glass). 
     HUDs according to embodiments of the present disclosure can be employed in automotive vehicles, aircraft, synthetic vision systems, and/or mask displays (e.g., head mounted displays such as goggles, masks, helmets, and the like) utilizing exemplary glass substrates described herein. Such HUD systems can project critical information (speed, fuel, temperature, turn signal, navigation, warning messages, etc.) in front of the driver through the glass laminate structure. 
     According to some embodiments, the HUD systems described herein can use nominal HUD system parameters for radius of curvature, refractive index, and angle of incidence (e.g., radius of curvature R c =8301 mm, distance to source: R i =1000 mm, refractive index n=1.52, and angle of incidence θ=62.08°). 
     Applicants have shown that the glass substrates and laminate structures disclosed herein have excellent durability, impact resistance, toughness, and scratch resistance. As is well known among skilled artisans, the strength and mechanical impact performance of a glass sheet or laminate is limited by defects in the glass, including both surface and internal defects. When a glass sheet or laminate structure is impacted, the impact point is put into compression, while a ring or “hoop” around the impact point, as well as the opposite face of the impacted sheet, are put into tension. Typically, the origin of failure will be at a flaw, usually on the glass surface, at or near the point of highest tension. This may occur on the opposite face, but can occur within the ring. If a flaw in the glass is put into tension during an impact event, the flaw will likely propagate, and the glass will typically break. Thus, a high magnitude and depth of compressive stress (depth of layer) is preferable. 
     Due to strengthening, one or both of the surfaces of the strengthened glass sheets disclosed herein are under compression. The incorporation of a compressive stress in a near surface region of the glass can inhibit crack propagation and failure of the glass sheet. In order for flaws to propagate and failure to occur, the tensile stress from an impact must exceed the surface compressive stress at the tip of the flaw. In embodiments, the high compressive stress and high depth of layer of strengthened glass sheets enable the use of thinner glass than in the case of non-chemically-strengthened glass. 
     Aspect (1) of this disclosure pertains to a glass-based preform for a mirror of a heads-up display (HUD) system, comprising: a glass-based substrate having a first major surface, a second major surface opposite to the first major surface, and a minor surface connecting the first and second major surfaces; a first chamfer at an edge of the first major surface, the first chamfer having a first end at an intersection of the first chamfer and the first major surface and having a second end at an intersection of the first chamfer and the minor surface; and a second chamfer at an edge of the second major surface, the second chamfer having a first end at an intersection of the second chamfer and the second major surface and having a second end at an intersection of the second chamfer and the minor surface, wherein the first chamfer has a different size or shape from the second chamfer. 
     Aspect (2) of this disclosure pertains to the glass-based preform of Aspect (1), wherein the first chamfer has a first length, the second chamfer has a second length, and the first length is different than the second length. 
     Aspect (3) of this disclosure pertains to the glass-based preform of Aspect (2), wherein the first length is greater than the second length. 
     Aspect (4) of this disclosure pertains to the glass-based preform of Aspect (2) or Aspect (3), wherein the first length is measured in a direction that is in-plane with the first major surface at the intersection with the first chamfer and is measured from the first end of the first chamfer to a plane that is co-planar with the minor surface at the second end of the first chamfer, and wherein the second length is measured in a direction that is in-plane with the second major surface and is measured from the first end of the second chamfer to a plane that is co-planar with the minor surface at the second end of the second chamfer. 
     Aspect (5) of this disclosure pertains to the glass-based preform of any one of Aspects (2)-(4), wherein the first length is at least about 1.0 mm. 
     Aspect (6) of this disclosure pertains to the glass-based preform of any one of Aspects (2)-(5), wherein the first length is from about 1.0 mm to about 3.0 mm. 
     Aspect (7) of this disclosure pertains to the glass-based preform of any one of Aspects (1)-(6), wherein the first chamfer comprises a first inclined surface at a first angle measured with respect to the first surface, wherein the first inclined surface intersects the first major surface at a first distance of about 0.5 mm to about 3 mm from a minor plane co-planar with the minor surface at the second end of the first chamfer, and intersects the minor surface at a second distance of about 0.2 mm to about 0.3 mm from a first major plane co-planar with the first major surface at the first end of the first chamfer. 
     Aspect (8) of this disclosure pertains to the glass-based preform of any one of Aspects (1)-(7), wherein the second chamfer comprises a second inclined surface at a second angle measured with respect to the second surface, wherein the second inclined surface intersects the second major surface at a first distance of about 0.2 mm to about 0.3 mm from a minor plane co-planar with the minor surface at the second end of the second chamfer, and intersects the minor surface at a second distance of about 0.2 mm to about 0.3 mm from a second major plane co-planar with the second major surface at the first end of the first chamfer. 
     Aspect (9) of this disclosure pertains to the glass-based preform of Aspect (8), wherein the first angle is about 3 degrees to about 31 degrees, and the second angle is about 33 degrees to about 57 degrees. 
     Aspect (10) of this disclosure pertains to the glass-based preform of Aspect (8), wherein the first angle is from about 5 degrees to about 45 degrees, and the second angle is from about 5 degrees to about 45 degrees. 
     Aspect (11) of this disclosure pertains to the glass-based preform of any one of Aspects (1)-(7), wherein the first chamfer comprises a first inclined surface at a first angle measured with respect to the first surface, and the second chamfer comprises a second inclined surface at a second angle measured with respect to the second surface, and wherein the first angle is different than the second angle. 
     Aspect (12) of this disclosure pertains to the glass-based preform of any one of Aspects (8)-(11), wherein the first angle is smaller than the second angle. 
     Aspect (13) of this disclosure pertains to the glass-based preform of any one of Aspects (7)-(12), wherein the first inclined surface extends from the first edge to the second edge of the first chamfer, and wherein the second inclined surface extends from the first edge to the second edge of the second chamfer. 
     Aspect (14) of this disclosure pertains to the glass-based preform of any one of Aspects (1)-(13), wherein at least a portion of the first major surface is reflective. 
     Aspect (15) of this disclosure pertains to the glass-based preform of Aspect (14), wherein the portion of the first major surface that is reflective comprises a reflective coating on the glass-based substrate. 
     Aspect (16) of this disclosure pertains to the glass-based preform of Aspect (15), wherein the reflective coating comprises a metal, a metal oxide, a ceramic oxide, or a metal-ceramic alloy. 
     Aspect (17) of this disclosure pertains to the glass-based preform of Aspect (15) or Aspect (16), wherein the reflective coating comprises aluminum or silver. 
     Aspect (18) of this disclosure pertains to the glass-based preform of any one of Aspects (1)-(17), wherein a length of the first inclined surface as measured in a direction parallel to the first major surface is about 0.5 mm to 3 mm, and a length of the first inclined surface as measured in a direction parallel to the minor surface is about 0.2 mm to 0.3 mm. 
     Aspect (19) of this disclosure pertains to the glass-based preform of any one of Aspects (1)-(18), wherein a length of the second inclined surface as measured in a direction parallel to the second major surface is about 0.2 mm to 0.3 mm, and a length of the second inclined surface as measured in a direction parallel to the minor surface is about 0.2 mm to 0.3 mm. 
     Aspect (20) of this disclosure pertains to the glass-based preform of any one of Aspects (1)-(19), wherein the glass-based substrate has a thickness that is less than or equal to 3.0 mm. 
     Aspect (21) of this disclosure pertains to the glass-based preform of any one of Aspects (20), wherein the thickness of the glass-based substrate is from about 0.5 mm to about 3.0 mm. 
     Aspect (22) of this disclosure pertains to the glass-based preform of Aspect (21), wherein the thickness of the glass-based substrate is from about 0.5 mm to about 1.0 mm. 
     Aspect (23) of this disclosure pertains to the glass-based preform of Aspect (21), wherein the thickness of the glass-based substrate is from about 1.0 mm to about 3.0 mm. 
     Aspect (24) of this disclosure pertains to the glass-based preform of any one of Aspects (1)-(23), wherein the second major surface comprises one or more manufacturing artifacts, and wherein the manufacturing artifacts are confined to a perimeter region of the second major surface, the perimeter region extending from the edge of the second major surface to a distance that is less than the first length. 
     Aspect (25) of this disclosure pertains to the glass-based preform of Aspect (24), wherein the manufacturing artifacts are vacuum suction artifacts. 
     Aspect (26) of this disclosure pertains to the glass-based preform of Aspect (24) or Aspect (25), wherein the manufacturing artifacts are from a process of bending the mirror. 
     Aspect (27) of this disclosure pertains to a mirror for a heads-up display (HUD) system comprising the glass-based preform of any one of claims  1 - 26 . 
     Aspect (28) of this disclosure pertains to the mirror of Aspect (27), further comprising a reflective layer on the first major surface of the glass-based preform. 
     Aspect (29) of this disclosure pertains to the mirror of Aspect (27) or Aspect (28), wherein the glass-based substrate has a first radius of curvature such that the first major surface has a concave shape and the second major surface has a convex shape, the first radius of curvature being measured with respect to a first axis of curvature. 
     Aspect (30) of this disclosure pertains to the mirror of Aspect (29), wherein the glass-based substrate has a second radius of curvature measured with respect to a second axis of curvature different from the first axis of curvature. 
     Aspect (31) of this disclosure pertains to the mirror of Aspect (30), wherein the first axis of curvature is perpendicular to the second axis of curvature. 
     Aspect (32) of this disclosure pertains to the mirror of any one of Aspects (27)-(31), wherein the first major surface has an aspheric shape. 
     Aspect (33) of this disclosure pertains to a method of forming a three-dimensional mirror, the method comprising: providing a glass-based mirror preform comprising a first major surface having an edge with a first chamfer, a second major surface opposite to the first major surface and having an edge with a second chamfer, and a minor surface connecting the first and second major surfaces, the second chamfer having a different size or shape than the first chamfer; disposing the glass-based preform on a molding apparatus having a curved support surface with the second major surface facing the curved support surface; and conforming the glass-based preform to the curved support surface to form a curved mirror substrate having a first radius of curvature. 
     Aspect (34) of this disclosure pertains to the method of Aspect (33), wherein the conforming of the glass-based preform to the curved support surface is performed at a temperature that is less than a glass transition temperature of the glass-based preform. 
     Aspect (35) of this disclosure pertains to the method of Aspect (33) or Aspect (34), wherein a temperature of the glass-based substrate is not raised above the glass transition temperature of the glass-based substrate during or after the conforming. 
     Aspect (36) of this disclosure pertains to the method of any one of Aspects (33)-(35), wherein the curved support surface has a concave shape. 
     Aspect (37) of this disclosure pertains to the method of Aspect (36), wherein the concave shape is an aspheric shape. 
     Aspect (38) of this disclosure pertains to the method of any one of Aspects (33)-(37), wherein the curved support surface comprises a vacuum chuck with at least one opening in the curved support surface. 
     Aspect (39) of this disclosure pertains to the method of Aspect (38), further comprising supplying a vacuum to the at least one opening to conform the curved glass blank to the curved support surface. 
     Aspect (40) of this disclosure pertains to the method of Aspect (38) or Aspect (39), wherein the at least one opening is a ditch-type vacuum hole. 
     Aspect (41) of this disclosure pertains to the method of any one of Aspects (38)-(40), wherein the first chamfer is formed in the first major surface such that the first chamfer begins in the first major surface at a first distance from the minor surface, wherein, when the glass-based preform is disposed on the curved support surface, the at least one opening is a second distance from the minor surface, and wherein the first distance is greater than or equal to the second distance. 
     Aspect (42) of this disclosure pertains to the method of any one of Aspects (38)-(41), wherein the molding apparatus comprises a raised perimeter surface or wall adjacent the curved support surface and defining a space on the curved support surface in which the glass-based preform is to be disposed. 
     Aspect (43) of this disclosure pertains to the method of Aspect (42), wherein the first chamfer is formed in the first major surface such the first chamfer begins in the first major surface at a first distance from the minor surface, wherein the at least one opening is a second distance from the raised perimeter surface or wall, and wherein the first distance is greater than or equal to the second distance. 
     Aspect (44) of this disclosure pertains to the method of any one of Aspects (41)-(43), wherein the first distance is greater than the second distance. 
     Aspect (45) of this disclosure pertains to the method of any one of Aspects (33)-(44), further comprising forming a reflective layer on the first major surface. 
     Aspect (46) of this disclosure pertains to the method of Aspect (45), wherein the reflective layer is formed by sputtering, plating, or vapor deposition of a material of the reflective layer onto the first major surface. 
     Aspect (47) of this disclosure pertains to the method of Aspect (45) or Aspect (46), wherein the reflective layer comprises a metal, a metal oxide, a ceramic oxide, or a metal-ceramic alloy. 
     Aspect (48) of this disclosure pertains to the method of Aspect (47), wherein the reflective layer comprises aluminum or silver. 
     Aspect (49) of this disclosure pertains to the method of any one of Aspects (45)-(48), wherein the reflective layer is formed on the first major surface after forming the curved mirror substrate to form an aspheric mirror. 
     Aspect (50) of this disclosure pertains to the method of any one of Aspects (33)-(49), wherein the first chamfer comprises a first inclined surface at a first angle measured with respect to the first surface, the first inclined surface having a first length, wherein the second chamfer comprises a second inclined surface at a second angle measured with respect to the second surface, the second inclined surface having a second length, and wherein the first length is different than the second length. 
     Aspect (51) of this disclosure pertains to the method of Aspect (50), wherein the first length is greater than the second length. 
     Aspect (52) of this disclosure pertains to the method of Aspect (50) or Aspect (51), wherein the first length is measured in a direction that is in-plane with the first major surface and is measured from an intersection of the first inclined surface and the first major surface to a plane that is co-planar with the minor surface, and wherein the second length is measured in a direction that is in-plane with the second major surface and is measured from an intersection of the second inclined surface and the second major surface to a plane that is co-planar with the minor surface. 
     Aspect (53) of this disclosure pertains to the method of any one of Aspects (50)-(52), wherein the first length is at least about 1.0 mm. 
     Aspect (54) of this disclosure pertains to the method of Aspect (53), wherein the first length is from about 1.0 mm to about 3.0 mm. 
     Aspect (55) of this disclosure pertains to the method of Aspect (53), wherein the first inclined surface intersects the first major surface at about 0.5 mm to about 3 mm from a first plane co-planar with the minor surface, and intersects the minor surface at about 0.2 mm to about 0.3 mm from a second plane co-planar with the first major surface. 
     Aspect (56) of this disclosure pertains to the method of Aspect (50) or Aspect (55), wherein the second inclined surface intersects the second major surface at about 0.2 mm to about 0.3 mm from a plane co-planar with the minor surface, and intersects the minor surface at about 0.2 mm to about 0.3 mm from a plane co-planar with the second major surface. 
     Aspect (57) of this disclosure pertains to the method of any one of Aspects (33)-(49), wherein the first chamfer defines a first inclined surface at a first angle measured with respect to the first surface, and the second chamfer defines a second inclined surface at a second angle measured with respect to the second surface, and wherein the first angle is different than the second angle. 
     Aspect (58) of this disclosure pertains to the method of Aspect (57), wherein the first angle is smaller than the second angle. 
     Aspect (59) of this disclosure pertains to a heads-up display (HUD) projection system, comprising: a display unit configured to display an image to be viewed by a user of a HUD system; and a mirror configured to reflect the image to a viewing area viewable by the user, the mirror comprising: a glass-based substrate having a first major surface that is reflective, a second major surface opposite to the first major surface, and a minor surface connecting the first and second major surfaces, a first chamfer at an edge of the first major surface, the first chamfer having a first end at an intersection of the first chamfer and the first major surface and having a second end at an intersection of the first chamfer and the minor surface, and a second chamfer at an edge of the second major surface, the second chamfer having a first end at an intersection of the second chamfer and the second major surface and having a second end at an intersection of the second chamfer and the minor surface, wherein the first chamfer has a different size or shape from the second chamfer. 
     Aspect (60) of this disclosure pertains to the HUD projection system of Aspect (59), wherein the first chamfer has a first length, the second chamfer has a second length, and the first length is different than the second length. 
     Aspect (61) of this disclosure pertains to the HUD projection system of Aspect (60), wherein the first length is greater than the second length. 
     Aspect (62) of this disclosure pertains to the HUD projection system of Aspect (60) or Aspect (61), wherein the first length is measured in a direction that is in-plane with the first major surface at the intersection with the first chamfer and is measured from the first end of the first chamfer to a plane that is co-planar with the minor surface at the second end of the first chamfer, and wherein the second length is measured in a direction that is in-plane with the second major surface and is measured from the first end of the second chamfer to a plane that is co-planar with the minor surface at the second end of the second chamfer. 
     Aspect (63) of this disclosure pertains to the HUD projection system of any one of Aspects (60)-(62), wherein the first length is at least about 1.0 mm. 
     Aspect (64) of this disclosure pertains to the HUD projection system of Aspect (63), wherein the first length is from about 1.0 mm to about 3.0 mm. 
     Aspect (65) of this disclosure pertains to the HUD projection system of any one of Aspects (59)-(64), wherein the first chamfer comprises a first inclined surface at a first angle measured with respect to the first surface, wherein the first inclined surface intersects the first major surface at a first distance of about 0.5 mm to about 3 mm from a minor plane co-planar with the minor surface at the second end of the first chamfer, and intersects the minor surface at a second distance of about 0.2 mm to about 0.3 mm from a first major plane co-planar with the first major surface at the first end of the first chamfer. 
     Aspect (66) of this disclosure pertains to the HUD projection system of any one of Aspects (59)-(65), wherein the second chamfer comprises a second inclined surface at a second angle measured with respect to the second surface, wherein the second inclined surface intersects the second major surface at a first distance of about 0.2 mm to about 0.3 mm from a minor plane co-planar with the minor surface at the second end of the second chamfer, and intersects the minor surface at a second distance of about 0.2 mm to about 0.3 mm from a second major plane co-planar with the second major surface at the first end of the first chamfer. 
     Aspect (67) of this disclosure pertains to the HUD projection system of Aspect (66), wherein the first angle is about 3 degrees to about 31 degrees, and the second angle is about 33 degrees to about 57 degrees. 
     Aspect (68) of this disclosure pertains to the HUD projection system of Aspect (66), wherein the first angle is from about 5 degrees to about 45 degrees, and the second angle is from about 5 degrees to about 45 degrees. 
     Aspect (69) of this disclosure pertains to the HUD projection system of any one of Aspects (59)-(64), wherein the first chamfer comprises a first inclined surface at a first angle measured with respect to the first surface, and the second chamfer comprises a second inclined surface at a second angle measured with respect to the second surface, and wherein the first angle is different than the second angle. 
     Aspect (70) of this disclosure pertains to the HUD projection system of Aspect (69), wherein the first angle is smaller than the second angle. 
     Aspect (71) of this disclosure pertains to the HUD projection system of Aspect (69) or Aspect (70), wherein the first inclined surface extends from the first edge to the second edge of the first chamfer, and wherein the second inclined surface extends from the first edge to the second edge of the second chamfer. 
     Aspect (72) of this disclosure pertains to the HUD projection system of any one of Aspects (59)-(71), wherein the first major surface has a first radius of curvature such that the first major surface has a concave shape and the second major surface has a convex shape, the first radius of curvature being measured relative to a first axis of curvature. 
     Aspect (73) of this disclosure pertains to the HUD projection system of Aspect (72), wherein the mirror has a second radius of curvature that is measured relative to a second axis of curvature different from the first axis of curvature. 
     Aspect (74) of this disclosure pertains to the HUD projection system of Aspect (73), wherein the first axis of curvature is perpendicular to the second axis of curvature. 
     Aspect (75) of this disclosure pertains to the HUD projection system of any one of Aspects (59)-(74), wherein the first major surface has an aspheric shape. 
     Aspect (76) of this disclosure pertains to the HUD projection system of any one of Aspects (59)-(75), wherein the first major surface that is reflective comprises a reflective coating on the glass-based substrate. 
     Aspect (77) of this disclosure pertains to the HUD projection system of Aspect (76), wherein the reflective coating comprises a metal, a metal oxide, a ceramic oxide, or a metal-ceramic alloy. 
     Aspect (78) of this disclosure pertains to the HUD projection system of Aspect (76) or Aspect (77), wherein the reflective coating comprises aluminum or silver. 
     Aspect (79) of this disclosure pertains to the HUD projection system of any one of Aspects (59)-(78), wherein the display unit comprises an LCD, LED, OLED, or μLED display panel. 
     Aspect (80) of this disclosure pertains to the HUD projection system of any one of Aspects (59)-(79), wherein the display unit comprises a projector. 
     Aspect (81) of this disclosure pertains to the HUD projection system of any one of Aspects (59)-(80), wherein the glass-based substrate has a thickness that is less than or equal to 3.0 mm. 
     Aspect (82) of this disclosure pertains to the HUD projection system of Aspect (81), wherein the thickness of the glass-based substrate is from about 0.5 mm to about 3.0 mm. 
     Aspect (83) of this disclosure pertains to the HUD projection system of Aspects (82), wherein the thickness of the glass-based substrate is from about 0.5 mm to about 1.0 mm. 
     Aspect (84) of this disclosure pertains to the HUD projection system of Aspect (82), wherein the thickness of the glass-based substrate is from about 1.0 mm to about 3.0 mm. 
     Aspect (85) of this disclosure pertains to the HUD projection system any one of Aspect (58)-(84), further comprising a projection surface configured to display a projected image to a user of the HUD system, wherein the mirror is configured to reflect the image produced by the display unit to form the projected image on the projection surface. 
     Aspect (86) of this disclosure pertains to the HUD projection system of Aspect (85), wherein the projection surface has a curvature corresponding to a curvature of the mirror. 
     Aspect (87) of this disclosure pertains to the HUD projection system of Aspect (86), wherein the curvature of the projection surface is substantially the same as the curvature of the mirror. 
     Aspect (88) of this disclosure pertains to the HUD projection system of Aspect (86) or Aspect (87), wherein the projection surface is a windshield or a combiner. 
     Aspect (89) of this disclosure pertains to the HUD projection system of any one of Aspects (86)-(88), wherein the projection surface has an aspheric shape. 
     Aspect (90) of this disclosure pertains to the HUD projection system of any one of Aspects (59)-(89), wherein the second major surface comprises one or more manufacturing artifacts, and wherein the manufacturing artifacts are confined to a perimeter region of the second major surface, the perimeter region extending from the edge of the second major surface to a distance that is less than the first length. 
     Aspect (91) of this disclosure pertains to the HUD projection system of Aspect (90), wherein the manufacturing artifacts are vacuum suction artifacts. 
     Aspect (92) of this disclosure pertains to the HUD projection system of Aspect (90) or Aspect (91), wherein the manufacturing artifacts are from a process of bending the mirror. 
     Aspect (93) of this disclosure pertains to a method of forming a three-dimensional mirror, the method comprising: providing a glass-based mirror preform having a first major surface, a second major surface opposite to the first major surface, and a minor surface connecting the first and second major surfaces, the glass preform having a flat shape; forming a first chamfer at an edge of the first major surface; forming a second chamfer at an edge of the second major surface, the second chamfer having a different size or shape from the first chamfer; disposing the glass-based preform on a molding apparatus having a curved support surface with the second major surface facing the curved support surface; and conforming the glass-based preform to the curved support surface to form a curved mirror substrate having a first radius of curvature. 
     Aspect (94) of this disclosure pertains to the method of Aspect (93), wherein the conforming of the glass-based preform to the curved support surface is performed at a temperature that is less than a glass transition temperature of the glass-based preform. 
     Aspect (95) of this disclosure pertains to the method of Aspect (93) or Aspect (94), wherein a temperature of the glass-based substrate is not raised above the glass transition temperature of the glass-based substrate during or after the conforming. 
     Aspect (96) of this disclosure pertains to the method of any one of Aspects (93)-(95), wherein the curved support surface has a concave shape. 
     Aspect (97) of this disclosure pertains to the method of Aspect (96), wherein the concave shape is an aspheric shape. 
     Aspect (98) of this disclosure pertains to the method of any one of Aspects (93)-(97), wherein the curved support surface comprises a vacuum chuck with at least one opening in the curved support surface. 
     Aspect (99) of this disclosure pertains to the method of Aspect (98), further comprising supplying a vacuum to the at least one opening to conform the curved glass blank to the curved support surface. 
     Aspect (100) of this disclosure pertains to the method of Aspect (98) or Aspect (99), wherein the at least one opening is a ditch-type vacuum hole. 
     Aspect (101) of this disclosure pertains to the method of any one of Aspects (98)-(100), wherein the first chamfer is formed in the first major surface such that the first chamfer begins at a first distance from the minor surface, wherein, when the glass-based preform is disposed on the curved support surface, the at least one opening is a second distance from the minor surface, and wherein the first distance is greater than or equal to the second distance. 
     Aspect (102) of this disclosure pertains to the method of any one of Aspects (98)-(101), wherein the molding apparatus comprises a raised perimeter surface or wall adjacent the curved support surface and defining a space on the curved support surface in which the glass-based preform is to be disposed. 
     Aspect (103) of this disclosure pertains to the method of Aspect (102), wherein the first chamfer is formed in the first major surface such the first chamfer begins at a first distance from the minor surface, wherein the at least one opening is a second distance from the raised perimeter surface or wall, and wherein the first distance is greater than or equal to the second distance. 
     Aspect (104) of this disclosure pertains to the method of any one of Aspects (101)-(103), wherein the first distance is greater than the second distance. 
     Aspect (105) of this disclosure pertains to the method of any one of Aspects (93)-(104), further comprising forming a reflective layer on the first major surface. 
     Aspect (106) of this disclosure pertains to the method of Aspect (105), wherein the reflective layer is formed by sputtering, plating, or vapor deposition of a material of the reflective layer onto the first major surface. 
     Aspect (107) of this disclosure pertains to the method of Aspect (105) or Aspect (106), wherein the reflective layer comprises a metal, a metal oxide, a ceramic oxide, or a metal-ceramic alloy. 
     Aspect (108) of this disclosure pertains to the method of Aspect (107), wherein the reflective layer comprises aluminum or silver. 
     Aspect (109) of this disclosure pertains to the method of any one of Aspects (105)-(108), wherein the reflective layer is formed on the first major surface after forming the curved mirror substrate to form an aspheric mirror. 
     Aspect (110) of this disclosure pertains to the method of any one of Aspects (93)-(109), wherein the first chamfer comprises a first inclined surface at a first angle measured with respect to the first surface, the first inclined surface having a first length, wherein the second chamfer comprises a second inclined surface at a second angle measured with respect to the second surface, the second inclined surface having a second length, and wherein the first length is different than the second length. 
     Aspect (111) of this disclosure pertains to the method of Aspect (110), wherein the first length is greater than the second length. 
     Aspect (112) of this disclosure pertains to the method of Aspect (110) or Aspect (111), wherein the first length is measured in a direction that is in-plane with the first major surface and is measured from an intersection of the first inclined surface and the first major surface to a plane that is co-planar with the minor surface, and wherein the second length is measured in a direction that is in-plane with the second major surface and is measured from an intersection of the second inclined surface and the second major surface to a plane that is co-planar with the minor surface. 
     Aspect (113) of this disclosure pertains to the method of any one of Aspects (110)-(112), wherein the first length is at least about 1.0 mm. 
     Aspect (114) of this disclosure pertains to the method of Aspect (113), wherein the first length is from about 1.0 mm to about 3.0 mm. 
     Aspect (115) of this disclosure pertains to the method of Aspect (110), wherein the first inclined surface intersects the first major surface at about 0.5 mm to about 3 mm from a first plane co-planar with the minor surface, and intersects the minor surface at about 0.2 mm to about 0.3 mm from a second plane co-planar with the first major surface. 
     Aspect (116) of this disclosure pertains to the method of Aspects (110) or (115), wherein the second inclined surface intersects the second major surface at about 0.2 mm to about 0.3 mm from a plane co-planar with the minor surface, and intersects the minor surface at about 0.2 mm to about 0.3 mm from a plane co-planar with the second major surface. 
     Aspect (117) of this disclosure pertains to the method of any one of Aspects (110)-(116), wherein the first angle is smaller than the second angle. 
     Aspect (118) of this disclosure pertains to a heads-up display (HUD) system comprising: a projection surface for viewing a projected image by a user of the HUD system; a display unit configured to produce an image to be viewed by the user on the projection surface; and a mirror configured to reflect the image to the projection surface to form the projected image, the mirror comprising: a glass-based substrate having a first major surface that is reflective, a second major surface opposite to the first major surface, and a minor surface connecting the first and second major surfaces, a first chamfer at an edge of the first major surface, the first chamfer, and a second chamfer at an edge of the second major surface, wherein the first chamfer has a different size or shape from the second chamfer. 
     Aspect (119) of this disclosure pertains to the HUD system of Aspect (118), wherein the first chamfer has a first end at an intersection of the first chamfer and the first major surface and has a second end at an intersection of the first chamfer and the minor surface, and wherein the second chamfer has a first end at an intersection of the second chamfer and the second major surface and has a second end at an intersection of the second chamfer and the minor surface. 
     Aspect (120) of this disclosure pertains to the HUD system of Aspect (118) or Aspect (119), wherein the first chamfer has a first length, the second chamfer has a second length, and the first length is different than the second length. 
     Aspect (121) of this disclosure pertains to the HUD system of Aspect (120), wherein the first length is greater than the second length. 
     Aspect (122) of this disclosure pertains to the HUD system of Aspect (119), wherein the first chamfer has a first length, the second chamfer has a second length, and the first length is different than the second length, wherein the first length is measured in a direction that is in-plane with the first major surface at the intersection with the first chamfer and is measured from the first end of the first chamfer to a plane that is co-planar with the minor surface at the second end of the first chamfer, and wherein the second length is measured in a direction that is in-plane with the second major surface and is measured from the first end of the second chamfer to a plane that is co-planar with the minor surface at the second end of the second chamfer. 
     Aspect (123) of this disclosure pertains to the HUD system of any one of Aspects (120)-(122), wherein the first length is at least about 1.0 mm. 
     Aspect (124) of this disclosure pertains to the HUD system of Aspect (12), wherein the first length is from about 1.0 mm to about 3.0 mm. 
     Aspect (125) of this disclosure pertains to the HUD system of any one of Aspects (118)-(124), wherein the first chamfer comprises a first inclined surface at a first angle measured with respect to the first surface, wherein the first inclined surface intersects the first major surface at a first distance of about 0.5 mm to about 3 mm from a minor plane co-planar with the minor surface at the second end of the first chamfer, and intersects the minor surface at a second distance of about 0.2 mm to about 0.3 mm from a first major plane co-planar with the first major surface at the first end of the first chamfer. 
     Aspect (126) of this disclosure pertains to the HUD system of Aspect (125), wherein the second chamfer comprises a second inclined surface at a second angle measured with respect to the second surface, wherein the second inclined surface intersects the second major surface at a first distance of about 0.2 mm to about 0.3 mm from a minor plane co-planar with the minor surface at the second end of the second chamfer, and intersects the minor surface at a second distance of about 0.2 mm to about 0.3 mm from a second major plane co-planar with the second major surface at the first end of the first chamfer. 
     Aspect (127) of this disclosure pertains to the HUD system of Aspect (126), wherein the first angle is about 3 degrees to about 31 degrees, and the second angle is about 33 degrees to about 57 degrees. 
     Aspect (128) of this disclosure pertains to the HUD system of Aspect (126), wherein the first angle is from about 5 degrees to about 45 degrees, and the second angle is from about 5 degrees to about 45 degrees. 
     Aspect (129) of this disclosure pertains to the HUD system of any one of Aspects (118)-(124), wherein the first chamfer comprises a first inclined surface at a first angle measured with respect to the first surface, and the second chamfer comprises a second inclined surface at a second angle measured with respect to the second surface, and wherein the first angle is different than the second angle. 
     Aspect (130) of this disclosure pertains to the HUD system of Aspect (129), wherein the first angle is smaller than the second angle. 
     Aspect (131) of this disclosure pertains to the HUD system of any one of Aspects (115)-(127), wherein the first major surface has a first radius of curvature such that the first major surface has a concave shape and the second major surface has a convex shape, the first radius of curvature being measured relative to a first axis of curvature. 
     Aspect (132) of this disclosure pertains to the HUD system of Aspect (131), wherein the first major surface has a second radius of curvature that is measured relative to a second axis of curvature that is different from the first axis of curvature. 
     Aspect (133) of this disclosure pertains to the HUD system of Aspect (132), wherein the first axis of curvature is perpendicular to the second axis of curvature. 
     Aspect (134) of this disclosure pertains to the HUD system of any one of Aspects (118)-(133), wherein the first major surface has an aspheric shape. 
     Aspect (135) of this disclosure pertains to the HUD system of Aspect (134), wherein the aspheric shape corresponds to a shape of the projection surface. 
     Aspect (136) of this disclosure pertains to the HUD system of any one of Aspects (118)-(135), wherein the first major surface that is reflective comprises a reflective coating on the glass-based substrate. 
     Aspect (137) of this disclosure pertains to the HUD system of Aspect (136), wherein the reflective coating comprises a metal, a metal oxide, a ceramic oxide, or a metal-ceramic alloy. 
     Aspect (138) of this disclosure pertains to the HUD system of Aspect (137), wherein the metal is aluminum or silver. 
     Aspect (139) of this disclosure pertains to the HUD system of any one of Aspects (118)-(124) and (127)-(138), wherein a length of the first inclined surface as measured in a direction parallel to the first major surface is about 0.5 mm to 3 mm, and a length of the first inclined surface as measured in a direction parallel to the minor surface is about 0.2 mm to 0.3 mm. 
     Aspect (140) of this disclosure pertains to the HUD system of any one of Aspects (118)-(124) and (127)-(139), wherein a length of the second inclined surface as measured in a direction parallel to the second major surface is about 0.2 mm to 0.3 mm, and a length of the second inclined surface as measured in a direction parallel to the minor surface is about 0.2 mm to 0.3 mm. 
     Aspect (141) of this disclosure pertains to the HUD system of any one of Aspects (118)-(140), wherein the display unit comprises an LCD, LED, OLED, or μLED display panel. 
     Aspect (142) of this disclosure pertains to the HUD system of claim any one of Aspects (118)-(141), wherein the display unit is a projector. 
     Aspect (143) of this disclosure pertains to the HUD system of any one of Aspects (118)-(142), wherein the glass-based substrate has a thickness that is less than or equal to 3.0 mm. 
     Aspect (144) of this disclosure pertains to the HUD system of Aspect (143), wherein the thickness of the glass-based substrate is from about 0.5 mm to about 3.0 mm. 
     Aspect (145) of this disclosure pertains to the HUD system of Aspect (144), wherein the thickness of the glass-based substrate is from about 0.5 mm to about 1.0 mm. 
     Aspect (146) of this disclosure pertains to the HUD system of Aspect (144), wherein the thickness of the glass-based substrate is from about 1.0 mm to about 3.0 mm. 
     Aspect (147) of this disclosure pertains to the HUD system of any one of Aspects (118)-(146), wherein the chamfering of the first major surface is configured to reduce edge distortion of the projected image. 
     Aspect (148) of this disclosure pertains to the HUD system of any one of Aspects (118)-(146), wherein the chamfering of the first major surface is configured to reduce an amount of unwanted light reflected toward the user. 
     Aspect (149) of this disclosure pertains to the HUD system of any one of Aspects (118)-(148), wherein the projection surface is a windshield of a vehicle. 
     Aspect (150) of this disclosure pertains to the HUD system of any one of Aspects (118)-(148), wherein the projection surface is a combiner configured to be mounted in a vehicle interior. 
     Aspect (151) of this disclosure pertains to a heads-up display (HUD) projection system, comprising: a display unit configured to display an image to be viewed by a user of a HUD system; and a mirror configured to reflect the image to a viewing area viewable by the user, the mirror comprising: a glass-based substrate having a first major surface that is reflective, a second major surface opposite to the first major surface, and a minor surface connecting the first and second major surfaces, and a chamfer at an edge of the first major surface, the chamfer having a first length. 
     Aspect (152) of this disclosure pertains to the HUD projection system of Aspect (151), wherein the first length is measured in a direction that is in-plane with the first major surface and is measured from an intersection of the first inclined surface and the first major surface to a plane that is co-planar with the minor surface, and wherein the first length is at least about 1.0 mm. 
     Aspect (153) of this disclosure pertains to the HUD projection system of Aspect (151) or Aspect (152), wherein the first length is from about 1.0 mm to about 3.0 mm. 
     Aspect (154) of this disclosure pertains to the HUD projection system of any one of Aspects (151)-(153), wherein the chamfer intersects the first major surface at about 0.5 mm to about 3 mm from a first plane co-planar with the minor surface, and intersects the minor surface at about 0.2 mm to about 0.3 mm from a second plane co-planar with the first major surface. 
     Aspect (155) of this disclosure pertains to the HUD projection system of any one of Aspects (151)-(154), wherein the mirror has a first radius of curvature such that the first major surface has a concave shape and the second major surface has a convex shape, the first radius of curvature being relative to a first axis of curvature. 
     Aspect (156) of this disclosure pertains to the HUD projection system of Aspect (155), wherein the mirror has a second radius of curvature that is relative to a second axis of curvature different from the first axis of curvature. 
     Aspect (157) of this disclosure pertains to the HUD projection system of Aspect (156), wherein the first axis of curvature is perpendicular to the second axis of curvature. 
     Aspect (158) of this disclosure pertains to the HUD projection system of any one of Aspects (151)-(157), wherein the first major surface has an aspheric shape. 
     Aspect (159) of this disclosure pertains to the HUD projection system of any one of Aspects (151)-(158), wherein the first major surface that is reflective comprises a reflective coating on the glass-based substrate. 
     Aspect (160) of this disclosure pertains to the HUD projection system of Aspect (159), wherein the reflective coating comprises a metal, a metal oxide, a ceramic oxide, or a metal-ceramic alloy. 
     Aspect (161) of this disclosure pertains to the HUD projection system of Aspect (159) or Aspect (160), wherein the reflective coating comprises aluminum or silver. 
     Aspect (162) of this disclosure pertains to the HUD projection system of any one of Aspects (151)-(161), wherein the display unit comprises an LCD, LED, OLED, or μLED display panel. 
     Aspect (163) of this disclosure pertains to the HUD projection system of any one of Aspects (151)-(162), wherein the display unit is a projector. 
     Aspect (164) of this disclosure pertains to the HUD projection system of any one of Aspects (151)-(163), wherein the glass-based substrate has a thickness that is less than or equal to 3.0 mm. 
     Aspect (165) of this disclosure pertains to the HUD projection system of Aspect (164), wherein the thickness of the glass-based substrate is from about 0.5 mm to about 3.0 mm. 
     Aspect (166) of this disclosure pertains to the HUD projection system of Aspect (165), wherein the thickness of the glass-based substrate is from about 0.5 mm to about 1.0 mm. 
     Aspect (167) of this disclosure pertains to the HUD projection system of Aspect (165), wherein the thickness of the glass-based substrate is from about 1.0 mm to about 3.0 mm. 
     Aspect (168) of this disclosure pertains to the HUD projection system of any one of Aspects (161)-(167), further comprising a projection surface for viewing a projected image by a user of the HUD system, wherein the display unit configured to produce an image, and the mirror is configured to reflect the image to form the projected image on the projection surface. 
     Aspect (169) of this disclosure pertains to the HUD projection system of Aspect (168), wherein the projection surface has a shape that is substantially the same as a shape of the mirror. 
     Aspect (170) of this disclosure pertains to the HUD projection system of Aspect (168) or Aspect (169), wherein the projection surface is a windshield or a combiner. 
     Aspect (171) of this disclosure pertains to the HUD projection system of any one of Aspects (168)-(170), wherein the projection surface has an aspheric shape. 
     Aspect (172) of this disclosure pertains to the HUD projection system of Aspect (153), wherein the second major surface comprises one or more manufacturing artifacts, and wherein the manufacturing artifacts are confined to a perimeter region of the second major surface at a distance from the edge of the second major surface that is less than the first length. 
     Aspect (173) of this disclosure pertains to the HUD projection system of Aspect (172), wherein the manufacturing artifacts are vacuum suction artifacts from a process of bending the mirror. 
     Aspect (174) of this disclosure pertains to the glass-based preform of any one of Aspects (1)-(26), wherein the glass-based preform comprises strengthened glass. 
     Aspect (175) of this disclosure pertains to the glass-based preform of Aspect (174), wherein the strengthened glass is chemically strengthened. 
     Aspect (176) of this disclosure pertains to the method of any one of Aspects (33)-(58), wherein the glass-based mirror preform comprises strengthened glass. 
     Aspect (177) of this disclosure pertains to the method of Aspect (176), wherein the strengthened glass is chemically strengthened. 
     Aspect (178) of this disclosure pertains to the HUD projection system of any one of Aspects (59)-(92), wherein the glass-based substrate comprises strengthened glass. 
     Aspect (179) of this disclosure pertains to the HUD projection system of Aspect (178), wherein the strengthened glass is chemically strengthened. 
     While this description may include many specifics, these should not be construed as limitations on the scope thereof, but rather as descriptions of features that may be specific to particular embodiments. Certain features that have been heretofore described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and may even be initially claimed as such, one or more features from a claimed combination may in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination. 
     Similarly, while operations are depicted in the drawings or figures in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous 
     Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, examples include from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. 
     It is also noted that recitations herein refer to a component of the present disclosure being “configured” or “adapted to” function in a particular way. In this respect, such a component is “configured” or “adapted to” embody a particular property, or function in a particular manner, where such recitations are structural recitations as opposed to recitations of intended use. More specifically, the references herein to the manner in which a component is “configured” or “adapted to” denotes an existing physical condition of the component and, as such, is to be taken as a definite recitation of the structural characteristics of the component. 
     As shown by the various configurations and embodiments illustrated in the figures, various glass-based structures for head-up displays have been described. 
     While preferred embodiments of the present disclosure have been described, it is to be understood that the embodiments described are illustrative only and that the scope of the invention is to be defined solely by the appended claims when accorded a full range of equivalence, many variations and modifications naturally occurring to those of skill in the art from a perusal hereof.