Standard wedge-shaped profile of glass laminate for ghost reduction

Abstract

The head-up display includes a windshield (10) having a standard wedge profile, an embedded reflective polarizer (20) for p-polarized light, and a display (40). The reflective polarizer is disposed between and spaced apart from the outermost opposite-facing first and second major glass surfaces (11, 12) of the windshield. The head-up display creates a virtual image for viewing by the eyes of an occupant. The image emitted by the display may include first image light rays emanating from a predetermined area of ​​the display and incident on the outermost first major glass surface of the windshield at an angle of incidence greater than about 60 degrees, wherein at least 90% of the incident first emitted image light rays are polarized in the plane of incidence of the first emitted image light rays. The head-up display includes a windshield (10) having a standard wedge profile, an embedded reflective polarizer (20) for p-polarized light, and a display (40). The reflective polarizer is disposed between and spaced apart from the outermost, opposite-facing first and second major glass surfaces (11, 12) of the windshield. The head-up display creates a virtual image for viewing by the eyes of an occupant. The image emitted by the display may include first image light rays emanating from a predetermined area of ​​the display and incident on the outermost, first major glass surface of the windshield at an angle of incidence greater than about 60 degrees, wherein at least 90% of the incident first emitted image light rays are polarized in the plane of incidence of the first emitted image light rays.

Description

Summary of the Invention

[0001] In some aspects herein, a head-up display for viewing by the eyes of a vehicle occupant is provided, including a windshield and a display. In some embodiments, the windshield includes a reflective polarizer disposed between first and second oppositely-facing outermost major glass surfaces of the windshield and spaced apart from the first and second oppositely-facing outermost major glass surfaces, wherein the reflective polarizer reflects at least 15% of incident light having a first polarization state and transmits at least 60% of incident light having an orthogonal second polarization state for substantially normally incident light and for at least a first wavelength within the visible wavelength range spanning from about 420 nm to about 680 nm. In some embodiments, the display includes an active display area having a maximum lateral dimension D configured to emit an image. The head-up display forms a virtual image of the emitted image for viewing by the eyes of the occupant. In some embodiments, the distance between the virtual image and the eyes of the occupant may be at least 2 meters. In some embodiments, the active display area has a display center and a predetermined area that includes the display center, the predetermined area having a maximum lateral dimension d, and a ratio d / D that is less than or equal to about 0.25. In some embodiments, the windshield can be configured to receive an image emitted by the active display area and reflect at least a portion of the received image toward the eyes of an occupant. For at least one first location within the predetermined area of ​​the active display area, the emitted image can include first emitted image light rays that emanate from the first location and are incident on a first outermost major glass surface of the windshield at an angle of incidence greater than about 60 degrees, and at least 90% of the incident first emitted image light rays are polarized in the plane of incidence of the first emitted image light rays.

[0002] In some aspects of the present disclosure, a vehicle windshield is provided, the windshield being disposed between a first glass segment and a second glass segment and including a reflective polarizer bonded to the first glass segment and the second glass segment. In some embodiments, the first glass segment and the second glass segment have respective average thicknesses t1 and t2, where t2 is equal to or greater than t1. In some embodiments, the first glass segment and the second glass segment each include opposing inner and outer glass interfaces, and the inner interfaces of the first and second glass segments face the reflective polarizer. In some embodiments, the outer glass interfaces of the first and second glass segments face away from the reflective polarizer and may form respective angles θ1 and θ2 with the reflective polarizer, where at least one of θ1 and θ2 has a value of about 0.0010 to about 0.0060 degrees.

[0003] In some aspects of the present disclosure, a head-up display is provided that forms a virtual image for viewing by the eyes of a vehicle occupant, including a glass windshield and a display. In some embodiments, the glass windshield includes oppositely facing outermost first and second glass interfaces and a reflective polarizer embedded within the glass windshield and spaced apart from the outermost first and second glass interfaces. For substantially normally incident light and for at least a first wavelength within the visible wavelength range spanning from about 420 nm to about 680 nm, the reflective polarizer reflects at least 15% of incident light having a first polarization state and transmits at least 60% of incident light having an orthogonal second polarization state. In some embodiments, the display may be positioned closer to the first glass interface and farther from the second glass interface and may include an active display area configured to emit an image. In some embodiments, at least first and second emitted image light rays, angularly spaced by a first angle and emitted from the same location within the active display area within the same emission surface, may be incident on the windshield at an angle of incidence greater than about 60 degrees within the same incident surface coincident with the emission surface and may be reflected by the windshield as at least respective first and second reflected image light rays angularly spaced by a second angle, the first and second reflected image light rays being incident on the eyes of an occupant, the second angle being at least 20% less than the first angle.

[0004] In some aspects of the present disclosure, an optical laminate for use in a vehicle windshield is provided, comprising a reflective polarizer disposed between a first polymer film and a second polymer film. In some embodiments, each of the first polymer film and the second polymer film may comprise a first major surface facing the reflective polarizer and bonded to the reflective polarizer, and an opposite second major surface facing away from the reflective polarizer, wherein the second major surfaces of the first polymer film and the second polymer film form angles ω1 and ω2, respectively, with the reflective polarizer, and at least one of ω1 and ω2 has a value of about 0.0010 to about 0.0060 degrees.

[0005] In some aspects herein, a windshield is provided for use in a heads-up display (HUD) of a vehicle. When the windshield is assembled to the vehicle, the HUD is configured to form a virtual image of an image emitted by a display of the HUD for viewing by the eyes of an occupant of the vehicle, the distance between the virtual image and the eyes of the occupant being between about 2 meters and about 16 meters, and for each image ray emitted from a central region of the display and incident on the windshield at an angle of incidence between about 64 degrees and about 70 degrees, the emitted image ray is reflected by outermost first and second surfaces of the windshield as respective first and second reflected image ray, the first and second reflected image ray propagating toward the occupant's eyes, forming an angle between the first and second reflected image ray, the angle between the first and second surfaces being selected such that the angle between the first and second reflected image ray is less than about 0.04 degrees. [Brief explanation of the drawings]

[0006] [Figure 1A] FIG. 1 is a cutaway side view of a head-up display according to an embodiment of the present disclosure. [Figure 1B] 10A-10C are diagrams of various windshield profile shapes according to an embodiment of the present disclosure. [Figure 1C] 10A-10C are diagrams of various windshield profile shapes according to an embodiment of the present disclosure. [Figure 2] 1 is a front view of a display for a head-up display according to an embodiment of the present disclosure. [Figure 3] 10 illustrates in detail the interaction of the windshield with image rays in a head-up display, according to one embodiment herein. [Figure 4] FIG. 1 is a cutaway side view of an optical stack for a head-up display according to an embodiment herein. [Figure 5] FIG. 1 illustrates a cutaway side view of a windshield for a head-up display according to an embodiment herein. DETAILED DESCRIPTION OF THE INVENTION

[0007] In the following description, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration various embodiments. The drawings are not necessarily to scale. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the specification. Accordingly, the following detailed description is not to be taken in a limiting sense.

[0008] A common problem in vehicle head-up display (HUD) systems is the appearance of ghost images created by reflections from both the inside and outside surfaces of the vehicle's windshield. That is, current HUD systems rely on the reflectivity of the windshield's glass-to-air interface to project a virtual image that is viewable at some perceived distance in front of the observer's (e.g., the driver's) eyes. Unfortunately, a windshield has two glass-to-air interfaces: one on the inside of the windshield (i.e., facing the driver) and one on the outside of the windshield. Because the two outside surfaces (i.e., the surface facing the inside of the vehicle and the surface facing the outside of the vehicle) are spaced apart by some distance (i.e., the thickness of the windshield), the reflected image rays from the inside glass-to-air interface and the outside glass-to-air interface do not align, creating ghost images that reduce the clarity and perceived brightness of the intended virtual image.

[0009] One way to reduce the ghosting problem is through angle compensation, which is achieved by creating a wedge-shaped thickness profile for the windshield, which reflects the forward and rearward images and significantly reduces the angular displacement between them. However, this angle compensation approach requires a unique, customized thickness profile for each windshield design and / or orientation, depending on the windshield's rake and skew angles. In addition, each unique thickness profile is designed to provide near-perfect angle compensation for a limited range of viewing positions. That is, a thickness profile that works well for a tall driver may not work well for a smaller driver (i.e., whose eyes are positioned lower due to the driver's shorter height) who has a different viewing angle.

[0010] A second method for reducing ghosting is to embed a weakly reflective polarizer between two pieces of glass (i.e., sandwiched between the inner and outer glass layers of a windshield) and reflect linearly polarized light onto the reflective polarizer. One such example of a reflective polarizer is the 3M™ Windshield Combiner Film (3M™ WCF) manufactured by 3M Corporation. When a reflective polarizer is used, image light from the display is linearly polarized (e.g., in a P polarization state, or P-polarized image light) and directed toward the windshield at an angle close to or very close to the Brewster angle. The Brewster angle is the angle of incidence at which P-polarized light passes through the inner glass-air interface without reflection and strikes the reflective polarizer, and at least a portion (e.g., 30%) of the P-polarized light is reflected toward the viewer as a single image (i.e., the image is reflected only by the reflective polarizer and not by the inner or outer glass-air interfaces). Because reflective polarizers are only weak P-polarized reflectors, they enable the use of HUDs that output P-polarized light that only weakly reflects at the glass-air interface for windshield angles of incidence close to the Brewster angle. If the ghost image brightness is sufficiently low, even angular displacement from the main image does not reduce the readability of the HUD image. However, the range of incidence angles where ghost brightness reduction is sufficient to maintain HUD image readability is limited. If the HUD field of view is large and / or the windshield rake angle is not optimal, incidence angles far from the Brewster angle may produce P-polarized reflections from the glass-air interface that are bright enough to reduce image readability. Adding an anti-reflective coating to one or both windshield glass surfaces can reduce ghost brightness, but this is expensive and reduces the durability of the windshield surface.

[0011] According to some aspects of the present specification, methods and systems are provided for generating a single standard (i.e., non-customized) windshield wedge profile that can be combined with a weakly reflective polarizer to provide an improved virtual image (e.g., reduced ghosting) over a larger range of viewing angles and can be used with windshields of various rake and skew angles.

[0012] According to some aspects of the present disclosure, a head-up display for viewing by an occupant of a vehicle includes a windshield including a reflective polarizer and a display. For purposes of this disclosure, the term "passenger" shall be used to refer to any occupant of the vehicle, including, but not limited to, the operator or driver of the vehicle. In some embodiments, the reflective polarizer may be disposed between and spaced apart from the outermost, opposite-facing first and second major glass surfaces of the windshield (i.e., "sandwiched" between the inner and outer glass layers of the windshield). In some embodiments, the reflective polarizer may be embedded within the windshield. For substantially normally incident light, and for at least a first wavelength in the visible wavelength range spanning from about 420 nm to about 680 nm, the reflective polarizer may reflect at least 15% of incident light having a first polarization state (e.g., linear P-polarized light, or P-polarized light) and transmit at least 60% of incident light having an orthogonal second polarization state (e.g., linear S-polarized light, or S-polarized light). The use of P-polarized and S-polarized polarization types is used as one possible example and is not intended to be limiting in any way. In alternative embodiments, other polarization states may be used.

[0013] In some embodiments, the display may be a liquid crystal display (LCD), an organic light-emitting display (OLED), a digital light processing (DLP) display, or any other suitable image generating unit. In some embodiments, the display may include an active display area having a maximum horizontal dimension D (e.g., the diagonal of a rectangular display) configured to emit an image. The head-up display may create a virtual image of the emitted image for viewing by the eyes of the vehicle occupant (e.g., the image is projected onto the surface of the windshield, and the image (virtual image) is perceived as floating in some space beyond the windshield). In some embodiments, the spacing between the virtual image and the eyes of the vehicle occupant (i.e., the perceived distance between the viewer's eyes and the virtual image) may be at least about 2 meters. In some embodiments, the active display area has a display center and a predetermined area (e.g., a subarea of ​​the active display area) that includes the display center. In some embodiments, the predetermined area may have a maximum horizontal dimension d, and the ratio d / D is less than or equal to about 0.25. In other words, the predetermined area is an area that is smaller than the entire active display area and is located near and includes the center of the active display area.

[0014] In some embodiments, the windshield can be configured to receive an image emitted by the active display area and reflect at least a portion of the received image toward the eyes of an occupant. For at least one first location within a predetermined region of the active display area, the emitted image can include first emitted image light rays that emanate from the first location and impinge on a first outermost major glass surface (i.e., the interior, occupant-facing surface) of the windshield at an angle of incidence greater than about 60 degrees (e.g., in a range of about 64 degrees to about 70 degrees), wherein at least 90% of the incident first emitted image light rays are polarized in the plane of incidence of the first emitted image light rays.

[0015] In some embodiments, at least one of the first and second opposing outermost major glass surfaces of the windshield may form a wedge angle with the reflective polarizer of about 0.0010 degrees to about 0.0060 degrees. In some embodiments, the wedge angle may be such that the entire windshield laminate is thickest near the top edge and thinner near the bottom edge.

[0016] According to some aspects of the present disclosure, a vehicle windshield is disposed between a first (inner) glass segment and a second (outer) glass segment, and includes a reflective polarizer bonded to the first (inner) glass segment and the second (outer) glass segment. In some embodiments, the first glass segment and the second glass segment have respective average thicknesses t1 and t2, where t2 is equal to or greater than t1. In some embodiments, the first glass segment and the second glass segment each include opposing inner and outer glass interfaces, and the inner interfaces of the first glass segment and the second glass segment (e.g., interfaces between each glass segment and another, different material) face the reflective polarizer. In some embodiments, the outer glass interfaces of the first glass segment and the second glass segment face away from the reflective polarizer and may form respective angles θ1 and θ2 with the reflective polarizer, where at least one of θ1 and θ2 has a value of about 0.0010 to about 0.0060 degrees. In other words, the outer glass interface may be angled relative to the embedded reflective polarizer to create a slightly wedge-shaped cross-sectional profile of the windshield laminate.

[0017] According to some aspects of the present disclosure, a head-up display that forms a virtual image for viewing by the eyes of a vehicle occupant includes a glass windshield and a display. In some embodiments, the glass windshield includes oppositely facing outermost first and second glass interfaces (i.e., interfaces between the windshield and another dissimilar material, such as air), and a reflective polarizer embedded within the glass windshield and spaced apart from the outermost first and second glass interfaces. For substantially normally incident light and for at least a first wavelength within the visible wavelength range spanning from about 420 nm to about 680 nm, the reflective polarizer reflects at least 15% of incident light having a first polarization state (e.g., P-polarized light) and transmits at least 60% of incident light having an orthogonal second polarization state (e.g., S-polarized light). In some embodiments, the display may be positioned closer to the first glass interface and farther from the second glass interface (i.e., disposed within the vehicle closer to the inner surface of the windshield) and may include an active display area configured to emit an image. In some embodiments, at least first and second emitted image light rays, angularly spaced by a first angle and emitted from the same location within the active display area within the same emission plane, may be incident on the windshield at an angle of incidence greater than about 60 degrees within the same incident plane coincident with the emission plane and reflected by the windshield as at least respective first and second reflected image light rays angularly spaced by a second angle, the first and second reflected image light rays incident on the eyes of an occupant, the second angle being at least 20% less than the first angle. Stated another way, in some embodiments, the windshield may be configured such that the angle between the first reflected image ray and the second reflected image ray (as seen by the occupant's eye) (i.e., the second angle) is smaller than the angle between the first emitted image ray and the second emitted image ray (i.e., the first angle). In some embodiments, the second angle may be such that the first reflected image ray and the second reflected image ray are substantially coincident.

[0018] In some embodiments, at least a third emitted image ray may be angularly spaced from the first and second emitted image ray by a third and fourth angle, respectively, and emitted from the same location within the active display area within the emission plane. The third emitted image ray is incident on the windshield at an angle of incidence greater than about 60 degrees within an incidence plane consistent with the emission plane, and is reflected by the windshield as a third reflected image ray angularly spaced from the first and second reflected image ray by a first and sixth angle, respectively, the third reflected image ray being incident on an eye of an occupant, the fifth and sixth angles being at least 20% smaller than the respected third and fourth angles. In other words, in some embodiments, the windshield may be configured such that the angles between the first, second, and third reflected image rays (as seen by the eyes of the occupant) are less than the angles between the first, second, and third emitted image rays, respectively. In some embodiments, the fifth and sixth angles may be such that the first, second, and third reflected image rays are substantially coincident.

[0019] According to some aspects of the present disclosure, an optical stack for use in a vehicle windshield includes a reflective polarizer disposed between a first polymer film and a second polymer film. In some embodiments, each of the first and second polymer films may include a first major surface facing the reflective polarizer and bonded to it, and an opposite second major surface facing away from the reflective polarizer, where the second major surfaces of the first and second polymer films form respective angles ω1 and ω2 with the reflective polarizer, with at least one of ω1 and ω2 having a value of about 0.0010 to about 0.0060 degrees. In other words, each of the second major surfaces (opposite the reflective polarizer) of the first and second polymer films may be angled relative to the reflective polarizer such that the optical stack has a wedge-shaped cross-sectional profile. In some embodiments, at least one of the first and second polymer films may comprise polyvinyl butyral (PVB). In some embodiments, angles ω1 and ω2 may be substantially the same. In some embodiments, angles ω1 and ω2 may be different. In some embodiments, the first polymer film and the second polymer film may have different average thicknesses.

[0020] In some embodiments, the optical laminate may be disposed between a first glass segment and a second glass segment (i.e., glass layers) and bonded to the first glass segment and the second glass segment, with the second major surfaces of the first polymer film and the second polymer film facing and bonded to the respective first glass statement and the second glass statement. In some embodiments, the first glass segment and the second glass segment may have a substantially flat rectangular cross-sectional profile (i.e., little or no wedge shape). In some embodiments, at least one of the first glass segment and the second glass segment may have a wedge-shaped cross-sectional profile. In some embodiments, the first glass segment and the second glass segment may have substantially the same average thickness. In some embodiments, the first glass segment and the second glass segment may have different average thicknesses. In some embodiments, the spacing between the second major surface of the first polymer film and the second major surface of the second polymer film at the bottom of the windshield can be smaller than the spacing between the second major surface of the first polymer film and the second major surface of the second polymer film at the top of the windshield. In other words, the polymer films and / or reflective polarizers can be configured such that the windshield has a substantially wedge-shaped profile, with the top of the optical stack being thicker than the bottom.

[0021] According to some aspects of the present disclosure, a windshield for use in a vehicle head-up display (HUD) is mounted on a vehicle, the HUD configured to generate a virtual image of an image emitted by a display of the HUD for viewing by the eyes of an occupant of the vehicle. In some embodiments, there may be a distance between the virtual image and the eyes of the occupant of the vehicle of at least 2 meters to about 16 meters. For each image ray emanating from a central region of the display and incident on the windshield at an angle of incidence between about 64 degrees and about 70 degrees, the emitted image ray is reflected by a first surface and a second surface that are outermost on the windshield as a respective first reflected image ray and a respective second reflected image ray, the first reflected image ray and the second reflected image ray propagating toward the eyes of the occupant, forming an angle between the first reflected image ray and the second reflected image ray, the angle between the first surface and the second surface being selected (designed) such that for any ray of light that forms a virtual image at a distance of about 2 to 16 meters, the angle between the first reflected image ray and the second reflected image ray is less than about 0.04 degrees.

[0022] In some embodiments, the windshield may have an average thickness of less than about 10 mm, less than about 8 mm, less than about 6 mm, or less than about 5 mm. In some embodiments, the angle between the first and second outermost surfaces of the windshield is about 0.004 to 0.01 degrees. In some embodiments, the distance between the virtual image and the occupant's eyes may be about 2 meters to about 4 meters, and the angle between the first and second outermost surfaces of the windshield may be about 0.01 degrees.

[0023] 1A is a cutaway side view of a head-up display in accordance with the present disclosure. The head-up display (HUD) 300 includes a display 40 and a windshield 10. The display 40 is configured to emit an image (emitted image 50), at least a portion of which may be reflected from the windshield 10 to the eyes of a vehicle occupant 310 (e.g., a driver) as a reflected image 52. The vehicle occupant 310 may then perceive the reflected image 52 as a virtual image 51 that is perceived by the vehicle occupant 310 to be at some separation distance S from the vehicle occupant 310 (e.g., perceived as being superimposed on the road or terrain visible to the vehicle occupant 310 through the windshield 10).

[0024] In some embodiments, windshield 10 may include a reflective polarizer 20 disposed between and spaced apart from an opposite-facing first outermost major glass surface 11 (e.g., an interior windshield surface facing the driver) and a second outermost major glass surface 12 (e.g., an exterior windshield surface facing away from the driver). In some embodiments, first outermost major glass surface 11 may be the exterior glass interface of a first glass segment 13, and second outermost major glass surface 12 may be the exterior glass interface of a second glass segment. Additionally, first glass segment 13 may have a first innermost glass surface 13a, and second glass segment 14 may have a second innermost glass surface 14a, and reflective polarizer 20 may be disposed between first glass segment 13 and second glass segment 14 and bonded to first glass segment 13 at first innermost glass surface 13a and bonded to second glass segment 14 at second innermost glass surface 14a. In some embodiments, first glass segment 13 may have an average thickness t1, and second glass segment 14 may have an average thickness t2, where t2 is greater than or equal to t1.

[0025] In some embodiments, the first outermost major glass surface 11 of the first glass segment 13 may be at an angle θ1 relative to the surface of the reflective polarizer 20 (i.e., with the first innermost glass surface 13a). In some embodiments, the second outermost major glass surface 12 may be at an angle θ2 relative to the surface of the reflective polarizer 20 (i.e., with the second innermost glass surface 14a). In some embodiments, at least one of θ1 and θ2 may have a value of about 0.0010 to about 0.0060 degrees. In some embodiments, θ1 and θ2 may be the same angle. In some embodiments, θ1 and θ2 may be different angles. The angles θ1 and θ2 may be selected so that the windshield 10 has an overall wedge angle θw, which may reduce the angular displacement between the image light rays from the reflected primary image and the image light rays from the reflected ghost image. In some embodiments, reducing the angular displacement between the main image rays and the ghost image rays, combined with the reflective polarizer 20, may enable the use of a single (i.e., non-customized) windshield wedge configuration across a variety of windshield and vehicle geometries. Stated another way, combining the benefits of a wedge-shaped window profile with a reflective polarizer may reduce image ghosting for at least a portion of different operating scenarios (i.e., scenarios defined by viewing angle, occupant height and position, windshield distance, virtual image distance, etc.) without requiring a new windshield wedge configuration for each different operating scenario.

[0026] In some embodiments, first glass segment 13 has a single-layer structure, where the wedge-shaped profile (i.e., angle θ1) is created by the shape of the glass itself (i.e., one glass layer is thicker near the edge than the other). In some embodiments, it may be advantageous for first glass segment 13 to have a multi-layer structure, where the wedge shape is formed by an inner layer 13p disposed adjacent to and bonded to an outer, substantially flat glass layer 13g. Similarly, in some embodiments, second glass segment 14 may have a multi-layer structure, where the wedge shape is formed by inner layer 14p and outer, substantially flat glass layer 14g.

[0027] In some embodiments, the inner layers 13p and 14p may be polymer films. In some embodiments, the inner layers 13p and 14p may comprise polyvinyl butyral (PVB), polyurethane, polyolefin, acrylate, or any other suitable material. For example, in some embodiments, polyvinyl butyral (PVB) may be used in the manufacture of safety glass for the automotive industry, such as in windshields. In some embodiments, two glass sheets (e.g., layers 13g and 14g) may be combined with PVB interlayers (e.g., layers 13p and 14p), each having a given thickness, composition, and properties. In some embodiments, a reflective polarizer 20 may be included in the layers, as described elsewhere herein. This laminated combination may be subjected to an autoclave cycle consisting of elevated temperatures and pressures (e.g., at 20 to 140°C, in the range of 18 to 10 atmospheres, for a duration of 30 minutes to 2 hours or more). In some embodiments, the PVB film may be constructed in a wedge shape within a windshield (e.g., for head-up display applications, as described herein). Wedge-type PVB may be manufactured by a process of melt extrusion with a plasticizer using a die with an appropriate wedge profile to create the appropriate wedge dimensions in the final product. This process is merely an exemplary process and is not intended to be limiting in any way. Any suitable method of creating a wedge profile in the windshield can be used, including the use of a wedge-shaped inner layer (e.g., PVB), a wedge-shaped reflective polarizer, one or more wedge-shaped glass segments, or a combination thereof.

[0028] In some embodiments, the wedge angle θ between the first outermost major glass surface 11 and the second outermost major glass surface 12 can vary depending on the location of incidence of the incoming image light (i.e., one or both of the outermost major glass surfaces 11 and 12 can be curved). FIGS. 1B and 1C show alternative windshield embodiments in which the wedge angle varies based on the location of incidence. In FIG. 1B, the second outermost major glass surface 12 is curved, and the wedge angle θ at location 15a can be different from the wedge angle θ at location 15b. In other embodiments, the first outermost major glass surface 11 can alternatively or additionally be curved. In the embodiment of FIG. 1C, the second outermost major glass surface 12 is curved, and the first outermost major glass surface 11 is substantially straight (i.e., flat). Other relationships between the outermost major glass surfaces 11 and 12 (ie, other wedge-shaped profiles) may be within the scope of this disclosure.

[0029] In some embodiments, reflective polarizer 20 may reflect at least 15%, at least 20%, or at least 30% of incident light having a first polarization (e.g., P-polarized type light or P-polarized light) for substantially normally incident light and for at least one wavelength in the visible wavelength range spanning from about 420 nm to about 680 nm, and may transmit (i.e., allow to pass) at least 60%, at least 70%, or at least 80% of incident light having a second polarization (e.g., S-polarized type light or S-polarized light). In other words, in some embodiments, reflective polarizer 20 may be a weak reflector with respect to light of the first polarization state.

[0030] 1A and 2, in some embodiments, the display 40 may include an active display area 41 configured to emit an emitted image 50. In some embodiments, the emitted image 50 may include a first emitted image ray 53, a second emitted image ray 55, and a third emitted image ray 56 that are emitted from substantially the same location 44 and in the same emission plane (e.g., the x-z plane shown in FIG. 1A). In some embodiments, the first emitted image ray 53 may be emitted at an angle α1 relative to the second emitted image ray 55. The first emitted image ray 53 and the second emitted image ray 55 may be incident on the windshield 10 at respective incident angles β1 and β2 in the same incidence plane (e.g., the x-z plane in FIG. 1A). In some embodiments, β1 and β2 may be greater than about 60 degrees. The first emitted image light ray 53 may be reflected by the windshield 10 as a first reflected image light ray 53a, and the second emitted image light ray 55 may be reflected by the windshield 10 as a second reflected image light ray 55a. In some embodiments, the first reflected image light ray 53a and the second reflected image light ray 56a may be angularly spaced apart by a second angle α2, which is less than the first angle α1 (e.g., about 25%, about 20%, or about 15% less). Stated differently, the angles θ1 and θ2 may be selected such that the angle between the reflected image light rays 53a and 55a is reduced relative to the angle between the emitted image light rays 53 and 55a. In some embodiments, the first reflected image light ray 53a and the second reflected image light ray 55a may be coincident.

[0031] Similar to the discussion above, the third emitted image ray 56 may be angularly spaced a third angle α3 from the first emitted image ray 53 and a fourth angle α4 from the second emitted image ray 55. The third emitted image ray 56 may be incident on the windshield 10 in the incident plane (xz plane) at an incident angle β3, where β3 is greater than about 60 degrees. In some embodiments, the third emitted image ray 56 may be reflected from the windshield 10 as a third reflected image ray 55a, with the first reflected image ray 53a angularly spaced a fifth angle α5 from the third reflected image ray 56a and the second reflected image ray 55a angularly spaced a sixth angle α6 from the third reflected image ray 56a, the fifth angle α5 and the sixth angle α6 being less than the respective third angle α3 and fourth angle α4. In some embodiments, the first reflected image ray 53a, the second reflected image ray 55a, and the third reflected image ray 56a may be coincident.

[0032] It should be noted that each of the first emitted image ray 53, the second emitted image ray 55, and the third emitted image ray 56 may be reflected from a different surface of the windshield 10. For example, as shown in FIG. 1A , the first emitted image ray 53 is reflected from the reflective polarizer 20, the second emitted image ray 55 is reflected from the first outermost major glass surface 11 of the first glass segment 13, and the third emitted image ray 56 is reflected from the inside of the second outermost major glass surface 12 of the second glass segment 14.

[0033] FIG. 2 provides a front view of display 40 (looking at active display area 41) for head-up display 300 of FIG. 1A and can be considered simultaneously with FIG. 1A for the following discussion. Display 40 has active display area 41 configured to emit image 50 (e.g., an image defining information for display to an occupant on a HUD). Active display area 41 has a maximum horizontal dimension D and defines a predetermined central region 43 that includes display center 42 and first location 44 (i.e., the emission location of first emitted image ray 53, second emitted image ray 55, and third emitted image 56 per the discussion of FIG. 1A). Predetermined central region 43 has a maximum horizontal dimension d, with the ratio d / D being less than or equal to about 0.25.

[0034] Figure 3 provides additional details regarding the interaction of image rays with the windshield 10 of Figure 1A. In some embodiments, first emitted image rays 53 (for example) are incident on the first outermost major glass surface 11 of the windshield 10 at an incident angle β1, where β1 is greater than about 60 degrees. In some embodiments, at least 90%, or at least 95%, of the first emitted image rays 53 are polarized in the plane of incidence P1 of the first emitted image rays 53 (shown in Figure 3 as ray portion 54). Stated another way, the first emitted image rays 53 are substantially polarized in the plane of incidence P1.

[0035] In some embodiments, the wedge angle required for a windshield herein may be created using an optical stack embedded within a laminated windshield, with one or more layers of the optical stack angled to create the required wedge angle. Figures 4 and 5 provide cutaway side views of one embodiment of an optical stack for a head-up display (e.g., for use in a laminated windshield) according to the present disclosure. For the following discussion, Figures 4 and 5 can be considered simultaneously. Figure 4 illustrates an optical stack 60 that may be used in a windshield 70 (Figure 5) in some embodiments. In some embodiments, the optical stack 60 includes a reflective polarizer 20 disposed between a first polymer film 80 and a second polymer film 90. The polymer film 80 includes a first major surface 81 (facing and bonded to the reflective polarizer 20) and an opposing second major surface 82 facing away from the reflective polarizer 20. The polymer film 90 includes a first major surface 91 (facing and bonded to the reflective polarizer 20) and an opposite second major surface 92 facing away from the reflective polarizer 20. In some embodiments, the second major surface 82 of the polymer film 80 forms an angle ω2 with the reflective polarizer 20, and the second major surface 92 of the polymer film 90 forms an angle ω1 with the reflective polarizer 20, with at least one of ω1 and ω2 having a value of about 0.0010 to about 0.0060 degrees. In some embodiments, ω1 and ω2 may have different values. In some embodiments, ω1 and ω2 may have substantially the same value. One example of a material used for the first polymer film 80 and the second polymer film 90 is polyvinyl butyral (PVB), although any suitable polymer material may be used. In some embodiments, the first polymer film 80 and the second polymer film 90 may each have a different average thickness. In some embodiments, each of the first polymer film 80 and the second polymer film 90 may have substantially the same average thickness.

[0036] 5, optical stack 60 (detailed in FIG. 4) may be disposed between first glass segment 100 and second glass segment 110 and bonded to first glass segment 100 and second glass segment 110. That is, first major surface 81 of polymer film 80 may be bonded to first glass segment 100, and first major surface 91 of polymer film 90 may be bonded to second glass segment 110. In some embodiments, one or both of first glass segment 100 and second glass segment 110 may be wedge-shaped. In some embodiments, one or both of first glass segment 100 and second glass segment 110 may be substantially flat, and the wedge angle θ required for windshield 70 may be 0.05. w is provided primarily by angles ω1 and ω2 of first polymer film 80 and second polymer film 90, respectively. In some embodiments, spacing S1 between second major surface 82 of polymer film 80 and second major surface 92 of polymer film 90 may be smaller at one edge (e.g., bottom edge) of windshield 70 than at the opposite edge (e.g., opposite top edge).

[0037] Terms such as "about" will be understood by those of ordinary skill in the art in the context in which they are used and described herein. Where the use of "about" as applied to quantities expressing feature sizes, amounts, and physical characteristics is not clear to those of ordinary skill in the art in the context in which it is used and described herein, "about" will be understood to mean within 10 percent of a particular value. A quantity given as about a particular value may be exactly that particular value. For example, where it is not clear to those of ordinary skill in the art in the context in which it is used and described herein, an amount having a value of about 1 means that the amount has a value between 0.9 and 1.1, and may be 1.

[0038] Terms such as "substantially" will be understood by those skilled in the art in the context in which they are used and described herein. If the use of "substantially equal" is not clear to those skilled in the art in the context in which it is used and described in the present invention, "substantially equal" means approximately equal, where "about" is as described above. If the use of "substantially parallel" is not clear to those skilled in the art in the context in which it is used and described herein, "substantially parallel" means within 30 degrees of parallel. Directions or surfaces described as substantially parallel to each other may, in some embodiments, be within 20 degrees or within 10 degrees of parallel, or may be parallel or nominally parallel. If the use of "substantially aligned" is not clear to those skilled in the art in the context in which it is used and described in the present invention, "substantially aligned" means aligned within 20% of the width of the objects being aligned. Objects described as being substantially aligned may, in some embodiments, be aligned within 10% or within 5% of the width of the objects being aligned.

[0039] All of the above-referenced references, patents, or patent applications are hereby incorporated by reference in their entirety. In the event of any inconsistency or contradiction between the portions of the incorporated references and this application, the information in the foregoing description shall prevail.

[0040] Descriptions of elements in a figure should be understood to apply equally to corresponding elements in other figures unless otherwise indicated. While specific embodiments have been illustrated and described herein, those skilled in the art will recognize that the specific embodiments illustrated and described may be replaced by various alternative and / or equivalent embodiments without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Accordingly, the present disclosure is intended to be limited only by the claims and equivalents thereof. In the following, exemplary embodiments are presented. [Item 1] 1. A head-up display for viewing by the eyes of a vehicle occupant, comprising: a windshield comprising a reflective polarizer disposed between and spaced apart from first and second oppositely-facing outermost major glass surfaces of the windshield, the reflective polarizer reflecting at least 15% of the incident light having a first polarization state and transmitting at least 60% of the incident light having an orthogonal second polarization state for substantially normally incident light and for at least a first wavelength within a visible wavelength range spanning from about 420 nm to about 680 nm; a display having a maximum horizontal dimension D and an active display area configured to emit an image, wherein the head-up display forms a virtual image of the emitted image for viewing by the eyes of the occupant, a distance between the virtual image and the eyes of the occupant being at least about 2 meters, the active display area including a display center and a predetermined area including the display center, the predetermined area having a maximum horizontal dimension d, and d / D≦0.25; the windshield is configured to receive the image emitted by the active display area and reflect at least a portion of the received image toward the eye of the occupant, and for at least one first location within the predetermined region of the active display area, the emitted image comprises first emitted image light rays emanating from the first location and incident on the outermost first major glass surface of the windshield at an angle of incidence greater than about 60 degrees, and at least 90% of the incident first emitted image light rays are polarized in a plane of incidence of the first emitted image light rays. Head-up display. [Item 2] Item 1. The head-up display of item 1, wherein the passenger is a driver of the vehicle. [Item 3] Item 1. The head-up display according to item 1, wherein at least one of the first and second main glass surfaces facing oppositely from one another on the outermost side of the windshield forms a wedge angle of approximately 0.0010 to 0.0060 degrees with the reflective polarizer. [Item 4] Item 1. The head-up display of item 1, wherein the reflective polarizer is embedded in the windshield. [Item 5] A vehicle windshield comprising a reflective polarizer disposed between a first glass segment and a second glass segment and bonded to the first glass segment and the second glass segment, the first glass segment and the second glass segment having respective average thicknesses t1 and t2, t2 being equal to or greater than t1, the first glass segment and the second glass segment each having oppositely facing inner and outer glass interface surfaces, the inner interface surfaces of the first glass segment and the second glass segment facing toward the reflective polarizer, and the outer glass interface surfaces of the first glass segment and the second glass segment facing away from the reflective polarizer and forming respective angles θ1 and θ2 with the reflective polarizer, at least one of θ1 and θ2 having a value between about 0.0010 and 0.0060 degrees. Windshield. [Item 6] 1. A head-up display that forms a virtual image for viewing by the eyes of a vehicle occupant, comprising: a glass windshield comprising: first and second oppositely facing outermost glass interfaces; and a reflective polarizer embedded within the glass windshield and spaced apart from the outermost first and second glass interfaces, wherein for substantially normally incident light and for at least a first wavelength within a visible wavelength range spanning from about 420 nm to about 680 nm, the reflective polarizer reflects at least 15% of the incident light having a first polarization state and transmits at least 60% of the incident light having an orthogonal second polarization state; a display positioned closer to the first glass interface and farther from the second glass interface and comprising an active display area configured to emit an image, wherein at least first emitted image light rays and second emitted image light rays, angularly spaced by a first angle and emanating from the same location within the active display area in the same emission plane, are incident on the windshield at an angle of incidence greater than about 60 degrees in the same plane of incidence coincident with the emission plane and are reflected by the windshield as at least respective first reflected image light rays and second reflected image light rays angularly spaced by a second angle, the first reflected image light rays and the second reflected image light rays being incident on the eyes of the occupant, the second angle being at least 20% less than the first angle. Head-up display. [Item 7] 7. The head-up display of claim 6, wherein the first reflected image light beam and the second reflected image light beam are coincident. [Item 8] 7. The head-up display of claim 6, wherein at least a third emitted image ray, angularly spaced from the first emitted image ray and the second emitted image ray by a third angle and a fourth angle, respectively, and emanating from the same location within the active display area within the emission surface, is incident on the windshield in the incidence plane coincident with the emission surface at an angle of incidence greater than approximately 60 degrees and is reflected by the windshield as a third reflected image ray, angularly spaced from the first reflected image ray and the second reflected image ray by a fifth angle and a sixth angle, respectively, wherein the third reflected image ray is incident on the eye of the occupant, and the fifth angle and the sixth angle are at least 20% smaller than the third angle and the fourth angle. [Item 9] 9. The head-up display of item 8, wherein the first reflected image light ray, the second reflected image light ray, and the third reflected image light ray are coincident. [Item 10] 1. An optical stack for use in a vehicle windshield, comprising: a reflective polarizer disposed between a first polymer film and a second polymer film, each of the first polymer film and the second polymer film having a first major surface facing the reflective polarizer and bonded to the reflective polarizer, and an opposite second major surface facing away from the reflective polarizer, the second major surfaces of the first polymer film and the second polymer film forming respective angles ω1 and ω2 with the reflective polarizer, wherein at least one of ω1 and ω2 has a value between about 0.0010 and 0.0060 degrees. [Item 11] Item 11. The optical laminate of item 10, wherein at least one of the first polymer film and the second polymer film comprises polyvinyl butyral. [Item 12] Item 11. The optical laminate according to item 10, wherein ω1 is different from ω2. [Item 13] Item 11. The optical stack of item 10, wherein the first polymer film and the second polymer film have different average thicknesses. [Item 14] A vehicle windshield comprising the optical laminate described in the above item disposed between a first glass segment and a second glass segment and bonded to the first glass segment and the second glass segment, wherein the second main surfaces of the first polymer film and the second polymer film face the first glass segment and the second glass segment, respectively, and are bonded to the first glass segment and the second glass segment. [Item 15] Item 15. The windshield of item 14, wherein at least one of the first glass segment and the second glass segment is not wedge-shaped. [Item 16] Item 15. The windshield of item 14, wherein the windshield is assembled to a vehicle such that the spacing between the second major surface of the first polymer film and the second major surface of the second polymer film is smaller at the bottom of the windshield than at the top of the windshield. [Item 17] 1. A windshield for use in a head-up display (HUD) of a vehicle, wherein when the windshield is assembled to the vehicle, the HUD is configured to generate a virtual image of an image emitted by a display of the HUD for viewing by an eye of an occupant of the vehicle, the distance between the virtual image and the eye of the occupant being between about 2 meters and about 16 meters, and wherein each image ray emanates from a central region of the display and is incident on a first location of the windshield at an angle of incidence between about 64 degrees and about 70 degrees. wherein the emitted image light rays are reflected by first and second outermost surfaces of the windshield as respective first and second reflected image rays, the first and second reflected image rays propagate toward the eyes of the occupant, forming a first angle between the first and second reflected image rays, and a wedge angle between the first and second surfaces at the first position is selected such that the wedge angle is less than approximately 0.04 degrees. [Item 18] Item 18. The windshield of item 17, wherein the wedge angle between the first surface and the second surface varies with the first position. [Item 19] Item 18. The windshield of item 17, wherein the wedge angle between the first surface and the second surface is different for at least two different first positions of the windshield. [Item 20] 18. The windshield of item 17, having an average thickness of less than about 10 mm. [Item 21] Item 18. The windshield of item 17, having an average thickness of less than about 8 mm. [Item 22] 18. The windshield of item 17, having an average thickness of less than about 6 mm. [Item 23] 18. The windshield of item 17, having an average thickness of less than about 5 mm. [Item 24] Item 18. The windshield according to item 17, wherein the wedge angle is about 0.004 to 0.01 degrees. [Item 25] Item 18. The windshield according to item 17, wherein the spacing is about 2 meters to about 4 meters, and the wedge angle is about 0.01 degrees.

Claims

1. 1. A head-up display for viewing by the eyes of a vehicle occupant, comprising: a windshield comprising a reflective polarizer disposed between first and second oppositely-facing outermost major glass surfaces of the windshield and spaced from the first and second oppositely-facing outermost major glass surfaces, wherein for substantially normally incident light and for at least a first wavelength within a visible wavelength range spanning 420 nm to 680 nm, the reflective polarizer reflects at least 15% of the incident light having a first polarization state and transmits at least 60% of the incident light having an orthogonal second polarization state; a display having a maximum horizontal dimension D and an active display area configured to emit an image, wherein the head-up display forms a virtual image of the emitted image for viewing by the eyes of the occupant, a distance between the virtual image and the eyes of the occupant being at least 2 meters, the active display area including a display center and a predetermined area including the display center, the predetermined area having a maximum horizontal dimension d, and d / D≦0.25; the windshield is configured to receive the image emitted by the active display area and reflect at least a portion of the received image toward the eye of the occupant, and for at least one first location within the predetermined region of the active display area, the emitted image comprises first emitted image light rays that emanate from the first location and are incident on the outermost first major glass surface of the windshield at an angle of incidence greater than 60 degrees, and at least 90% of the incident first emitted image light rays are polarized in a plane of incidence of the first emitted image light rays; at least one of the first and second major glass surfaces facing oppositely from the outermost side of the windshield forms a wedge angle with the reflective polarizer; the first major glass surface is positioned closer to the display than the second major glass surface; Head-up display.

2. The head-up display of claim 1 , wherein the occupant is a driver of the vehicle.

3. 2. The head-up display of claim 1, wherein at least one of the first and second major glass surfaces facing oppositely from one another on the outermost side of the windshield forms a wedge angle with the reflective polarizer of 0.0010 to 0.0060 degrees.

4. The head-up display of claim 1 , wherein the reflective polarizer is embedded within the windshield.

5. 1. A head-up display that forms a virtual image for viewing by the eyes of a vehicle occupant, comprising: a glass windshield comprising: first and second oppositely facing outermost glass interfaces; and a reflective polarizer embedded within the glass windshield and spaced apart from the outermost first and second glass interfaces, wherein for light at substantially normal incidence and for at least a first wavelength within a visible wavelength range spanning 420 nm to 680 nm, the reflective polarizer reflects at least 15% of the incident light having a first polarization state and transmits at least 60% of the incident light having an orthogonal second polarization state; a display positioned closer to the first glass interface and farther from the second glass interface and comprising an active display area configured to emit an image, wherein at least first emitted image light rays and second emitted image light rays, angularly spaced by a first angle and emanating from the same location within the active display area in the same emission plane, are incident on the windshield in the same incidence plane coincident with the emission plane at an angle of incidence greater than 60 degrees and are reflected by the windshield as at least respective first reflected image light rays and second reflected image light rays angularly spaced by a second angle, the first reflected image light rays and the second reflected image light rays being incident on the eyes of the occupant, the second angle being at least 20% less than the first angle. Head-up display.

6. The head-up display of claim 5 , wherein the first reflected image light ray and the second reflected image light ray are coincident.

7. 6. The head-up display of claim 5, wherein at least a third emitted image ray, angularly spaced from the first and second emitted image ray by a third angle and a fourth angle, respectively, and emanating from the same location within the active display area in the emission surface, is incident on the windshield in the incidence plane coincident with the emission surface at an angle of incidence greater than 60 degrees and is reflected by the windshield as a third reflected image ray, angularly spaced from the first and second reflected image ray by a fifth angle and a sixth angle, respectively, the third reflected image ray being incident on the eye of the occupant, the fifth angle and the sixth angle being at least 20% less than the third angle and the fourth angle.

8. The head-up display of claim 7 , wherein the first reflected image light ray, the second reflected image light ray, and the third reflected image light ray are coincident.

9. 1. An optical stack for use in a vehicle windshield, comprising: a reflective polarizer disposed between a first polymer film and a second polymer film, each of the first polymer film and the second polymer film having a first major surface facing the reflective polarizer and bonded to the reflective polarizer, and an opposite second major surface facing away from the reflective polarizer, the second major surfaces of the first polymer film and the second polymer film forming respective angles ω1 and ω2 with the reflective polarizer, wherein at least one of ω1 and ω2 has a value between 0.0010 and 0.0060 degrees.

10. 10. The optical stack of claim 9, wherein at least one of the first polymer film and the second polymer film comprises polyvinyl butyral.

11. The optical laminate according to claim 9, wherein ω1 is different from ω2.

12. 10. The optical stack of claim 9, wherein the first polymer film and the second polymer film have different average thicknesses.

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