Optical system for HUD system

Abstract

The optical system includes a display including an active display area configured to emit an image. The active display area includes a predetermined area including a display center. The vehicle's windshield includes an embedded reflective polarizer. The reflective polarizer reflects approximately 20% to approximately 40% of incident light polarized along a first direction and transmits at least 60% of incident light polarized along a second direction. The reflective polarizer receives the image emitted by the active display area and reflects a portion toward the eye. For at least one first location within the predetermined area, the emitted image includes an image cone having an emanating central image ray emanating from the first location. The emanating central image ray is polarized along a third direction when incident on the windshield in a plane of incidence. The first and third directions are substantially parallel to the plane of incidence.

Description

[Technical Field]

[0001] The present disclosure relates generally to optical systems, and more particularly to optical systems for head-up display systems. [Background technology]

[0002] Electronic displays are provided in many applications to render digital information to an observer. A heads-up display (HUD) allows an observer to observe not only the information but also the view through the HUD due to the HUD's transparent nature. Thus, the observer can observe the displayed information without losing the ability to observe the real world through the HUD. While HUD systems have been developed specifically for use in high-speed vehicles such as aircraft, they are now increasingly being considered as a feature of other vehicles, including automobiles. On a smaller scale, HUD systems are used as goggle lenses or helmet visors, or in various other virtual reality (VR) applications. HUDs can be implemented on various surfaces and windows, such as the vehicle's windshield. Therefore, vehicle operation information, such as the vehicle's speed and / or navigation direction, can be appropriately displayed to the vehicle occupant, for example, on the windshield. Summary of the Invention

[0003] Some aspects of the present disclosure relate to optical systems that include a display (10) having an active display area. large size The active display area includes a display center and a predetermined area that includes the display center. The predetermined area includes a maximum large sizeThe optical system further includes a vehicle windshield having a reflective polarizer embedded therein. For substantially normally incident light and for at least one wavelength between about 420 nm and about 670 nm, the reflective polarizer reflects between about 20% and about 40% of incident light polarized along a first direction and transmits at least 60% of incident light polarized along an orthogonal second direction. The reflective polarizer is configured to receive an image emitted by the active display area and reflect a portion of the received image toward the eye. For at least one first location within a predetermined region of the active display area, the emitted image includes a first emitted image cone emitted from the first location. The first emitted image cone includes a first emitted central image ray emitted from the first location. The first emitted central image ray is substantially polarized along a third direction when incident on the windshield in the plane of incidence. The first and third directions are substantially parallel to the plane of incidence.

[0004] Some other aspects of the present disclosure relate to an optical system including a display having an active display area. The active display area is configured to emit an image for viewing by an eye of an observer. The optical system further includes a vehicle windshield having a reflective polarizer embedded therein. For substantially normally incident light and for at least one wavelength between about 420 nm and about 670 nm, the reflective polarizer reflects between about 20% and about 40% of the incident light polarized along a first direction and transmits at least 60% of the incident light polarized along an orthogonal second direction. The reflective polarizer is configured to receive the image emitted by the active display area and reflect a portion of the received image toward the eye. The eye is configured to view a virtual image of the reflected image. The virtual image is then large size The predetermined virtual image area includes a modulus D', a virtual image center, and a predetermined virtual image area including the virtual image center. large sizeThe optical system has a modulus d', where d' / D'≦0.25. For at least one first location within a given virtual image area, the first location has a corresponding second location within the active display area. Image light emitted by the active display area from the second location is substantially polarized along a third direction when incident on the windshield in the plane of incidence. The first and third directions are substantially parallel to the plane of incidence. [Brief explanation of the drawings]

[0005] Various aspects of the present disclosure will be discussed in more detail with reference to the accompanying drawings. [Figure 1] 1 shows a vehicle having a windshield onto which an image is projected by a head-up display (HUD) system. [Figure 2] 1 illustrates a schematic diagram of an optical system according to some embodiments of the present disclosure. [Figure 3] 1A and 1B illustrate schematic diagrams of active display areas of a display of an optical system according to some embodiments. [Figure 4] 1A-1C are schematic illustrations of virtual images of an image reflected by a windshield having a reflective polarizer, according to some embodiments. [Figure 5] 1A and 1B illustrate schematic diagrams of reflective polarizer structures according to some aspects of the present disclosure. [Figure 6] 1 illustrates a schematic diagram of an optical system according to some aspects of the present disclosure. [Figure 7] 10A-B schematically illustrate the relative orientation of the optical axis of a windshield having a reflective polarizer and the plane of incidence of light rays projected toward an observer, according to some aspects of the present disclosure.

[0006] The drawings are not necessarily to scale. Like numbers used in the drawings refer to like components. However, it will be understood that the use of a number to refer to a component in a particular drawing is not intended to limit the component in another drawing bearing the same number. 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. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the description. Accordingly, the following detailed description is not to be taken in a limiting sense.

[0008] The term head-up display (HUD) is used herein to refer to such display systems, whether used on the windows or windshields of vehicles such as aircraft, watercraft, or motor vehicles such as automobiles, trucks, and motorcycles, in smaller systems such as goggle lenses or helmet visors, or in a variety of other applications.

[0009] For example, as shown in Figure 1, a HUD system projects an image onto the windshield 40 of a vehicle 110, allowing an observer (e.g., a driver) to observe information in the form of a virtual image. The HUD system may be located behind the steering wheel of the vehicle and generate an image that is projected onto the windshield 40, which then reflects light, for example, toward the driver of the vehicle 110. The HUD system may be configured to display one or more of the following: vehicle operation information, such as vehicle speed; navigation information, such as directions and / or maps; ambient information, such as temperature; communication information, such as radio station or track listings, caller information, and road sign information or road restrictions, such as effective speed limits.

[0010] HUD systems project an image onto a windshield (40) within a range of horizontal skew angles. The projected image is typically reflected on both sides of the windshield. Thus, vehicle occupants observe not only the desired primary virtual image but also a slightly offset secondary image, typically of lower intensity. The latter is commonly referred to as a ghost image. At larger skew angles, the nominally p-polarized HUD output increasingly rotates away from the fast / slow axis of the birefringent windshield combiner film (WCF), causing delays and alterations of the input linearly polarized light in transmission through the WCF and higher rear glass-to-air surface ghost reflections. As HUD systems strive to achieve wider HUD fields of view for AR-HUD applications, horizontal skew angle effects on polarization become increasingly significant. The embodiments described herein address these and other challenges.

[0011] Some embodiments of the present disclosure describe the addition of a bias angle to the WCF orientation in a windshield glass laminate, resulting in minimized retardation effects and rear ghost brightness over a desired range of HUD-WS skew angles. By applying a bias angle to the WCF, the retardation effect on rear ghost reflections can be minimized for skew angles related to the bias angle. Thus, the skew angle region of minimum rear ghost reflection due to S-polarized ghosts can be shifted horizontally by applying a WCF bias angle. This can be particularly important when HUD polarization adjustments are used to ensure that incident light is polarized within its plane of incidence at a given incidence angle and skew angle (or range), because the greater the skew angle of such light rays, the greater the rotation of the plane of incidence from the optical axis of an unbiased WCF.

[0012] An optical system (300) according to some embodiments of the present disclosure is shown in Figure 2. The optical system (300) includes a display (10) having an active display area (11) and a windshield (40) of a vehicle (110) having a reflective polarizer (140) embedded therein. The active display area (11) is configured to emit an image (20) for viewing by an observer's eye (30). The eye is configured to see a virtual image (70) of the reflected image, allowing the observer to observe various types of information, such as speed, fuel level, temperature, warnings, direction, etc., on the windshield.

[0013] The display 10 may be a conventional system that projects a visible light beam or image and may include a liquid crystal display (LCD) or an organic light emitting display (OLED). Displays may also include known elements such as electroluminescent panels, incandescent or phosphorescent light sources, CRTs, LEDs, and lenses, collimators, reflectors, and / or polarizers. The emitted light may be substantially monochromatic, polychromatic, narrowband, or broadband, but preferably overlaps at least a portion of the (visible) spectrum from approximately 400 to 700 nm. Light emitted by the active display area 11 of the display 10 toward the windshield 40 is substantially linearly polarized. The display 11 may be understood to emit light over a finite angular cone; however, for ease of explanation, only one light ray 24, hereafter referred to as the first emitted central image ray, is shown. Additionally, the display (11) may also include mechanisms such as tilting mirrors or displacement means for changing the angle and / or position of the emitted light to accommodate viewers at different positions or heights. In some embodiments, the display (11) may be a projection system.

[0014] The active display area (11) of the display may be within the central area of ​​the display (10). The peripheral area surrounding the active display area (11) may form the inactive area of ​​the display, and may form structures such as buttons and speaker ports, as needed. A schematic diagram of the active display area (11) is shown in Figure 3. The active display area (11) is large size The display has a dimension D and includes a display center (12) and a predetermined area (13) including the display center (12). The predetermined area (13) is large size In some embodiments, the maximum value of a given region is large size The maximum value of the active display area large size The dimensional relationship between the diameter and the dimension D may be such that d / D≦0.25. In some embodiments, d / D≦0.20, or d / D≦0.15, or d / D≦0.1.

[0015] A schematic diagram of a virtual image (70) of the reflected image that the eye is configured to see is shown in Figure 4. The virtual image (70) is large size Furthermore, the virtual image (70) includes a virtual image center (12') and a predetermined virtual image area (13') that includes the virtual image center (12'). The predetermined virtual image area (13') is large size In some embodiments, the maximum value of the predetermined virtual image area (13') is large size The modulus d' and the virtual image (70) large size The dimensional relationship between the dimension D' and the thickness D' may be such that d' / D'≦0.25. In some embodiments, d' / D'≦0.20, or d' / D'≦0.15, or d' / D'≦0.1.

[0016] In some embodiments, for at least one first position (14') within the predetermined virtual image area (13'), the first position can have a corresponding second position (14) within the active display area (11). In other embodiments, for each first position (14') within the predetermined virtual image area (13'), the first position has a corresponding second position (14) within the active display area (11). Image light rays (24) emitted by the active display area (11) from the second positions (14) may be substantially polarized along a third direction (15) when incident on the windshield (40) within the plane of incidence (50). In some embodiments, the first direction (x-axis) and the third direction (15) may be substantially parallel to the plane of incidence (50).

[0017] In some embodiments, the reflective polarizer (140) embedded in the windshield (40) can generally comprise a material that transmits light of a first polarization and reflects light of a second, different polarization. Reflective polarizers include, but are not limited to, diffusely reflective polarizers, multilayer reflective polarizers, and cholesteric reflective polarizers. The reflective polarizer (140) can be a broadband reflective polarizer or a notch reflective polarizer. In other examples, the reflective polarizer (140) can be one or more of an absorbing linear polarizer, a multilayer polymeric reflective polarizer, or a laminate of reflective polarizers, which substantially transmits light having a first polarization state (e.g., polarized along a first direction) and substantially reflects light having an orthogonal second polarization state (e.g., polarized along an orthogonal second direction). Substantially uniaxially oriented reflective polarizers are available from 3M Company under the tradenames Advanced Polarizing Film 5 or APF. Other types of multilayer optical film reflective polarizers (e.g., Dual Brightness Enhancement Film or DBEF, available from 3M Company) may also be used. Other types of reflective polarizers (e.g., wire grid polarizers) may also be used.

[0018] According to certain aspects, as best shown in FIG. 5 , the reflective polarizer (140) can include a plurality of layers (141, 142, 143) totaling more than about 30. In some embodiments, the number of layers can total more than 50, or more than 100, or at least 150, or at least 200 polymer layers. The plurality of layers of the reflective polarizer (140) can include a plurality of alternating first layers (142) and second layers (143). Each of the first and second layers can have an average thickness of less than about 500 nm, or less than about 450 nm, or less than about 400 nm. The difference between the refractive index of the first layer (142) and the second layer (143) along the first polarization state or along the first direction can be greater than about 0.05, or greater than about 0.1, or in some cases greater than 0.2.

[0019] In some cases, the first layer (142) and the second layer (143) may be a laminate of alternating isotropic and anisotropic layers. Reflective films (e.g., reflective polarizers) comprising multiple polymer layers are described, for example, in U.S. Patent Nos. 5,882,774 (Jonza et al.), 6,179,948 (Merrill et al.), and 6,783,349 (Neavin et al.), each of which is incorporated herein by reference to the extent not inconsistent herein. In some embodiments, the polymer layer comprises one or more of polycarbonate, polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), glycol-modified polyethylene terephthalate (PETG), polyethylene naphthalate (PEN), and PEN / PET copolymer.

[0020] In some embodiments, the reflective polarizer (140) may include skin layers (141) disposed on the opposite upper and lower surfaces of the plurality of alternating first and second polymer layers (142 and 143). The skin layers (141) may have a thickness greater than about 1 micrometer. In some cases, the total thickness of the plurality of polymer layers (142, 143) may be about 10 to 300 micrometers, and the thickness of the skin layers may be, but is not limited to, 50 to 200 micrometers. The skin layers (141) and the plurality of alternating first and second layers (142 and 143) may be bonded to each other using an adhesive. The skin layers (141) may be made of, for example, polycarbonate or a polycarbonate alloy, polyethylene terephthalate (PET), polystyrene (PS), or a combination thereof.

[0021] In some aspects, for substantially normally incident light (145) and for at least one wavelength between about 420 nm and about 670 nm, a reflective polarizer (140) can be said to substantially reflect incident light (145) if about 20% to 40% of the incident light (145) polarized along a first direction (x-axis) is reflected from the reflective polarizer (140). A reflective polarizer (140) can be said to substantially transmit incident light (145) if at least 60% of the incident light (145) polarized along an orthogonal second direction (y-axis) is transmitted by the reflective polarizer (140). In some embodiments, at least 70%, or at least 80%, or at least 90% of the incident light (145) polarized along the orthogonal second direction (y-axis) can be transmitted by the polarizer (140). In some other embodiments, for substantially normally incident light (145) and for at least one wavelength between about 700 nm and about 1500 nm, the reflective polarizer (140) can reflect at least 40%, or at least 50%, or at least 60-70% of incident light polarized along the first direction (x-axis) or the second direction (y-axis).

[0022] In some embodiments, the reflective polarizer (140) can be configured to receive the image (20) emitted by the active display area (11) and reflect a portion (22) of the received image toward the eye (30). In some aspects, for at least one first location (14) within a predetermined region (13) of the active display area (11), the emitted image includes a first emitted image cone (23) emanating from the first location (14), as best shown in FIG. 6. The at least one first location (14) within the predetermined region (13) of the active display area (11) can be understood to emit light across the first emitted image cone (23), although only one light ray is shown for ease of illustration. In the illustrated embodiment, the first emitted image cone (23) includes a first emitted central image ray (24) emanating from the first location (14). 7, the first emerging central image ray (24) may be substantially polarized along a third direction (15) when it strikes the windshield (40) within a plane of incidence (50). The first direction (x-axis) and the third direction (15) may be substantially parallel to the plane of incidence (50).

[0023] In some embodiments, the third direction (15) can form an angle (α1) with the plane of incidence (50) of less than about 10 degrees, or less than about 5 degrees, as shown in Figure 7. In some other aspects, the first direction (x-axis) can form an angle (α2) with the plane of incidence (50) of less than about 10 degrees, or less than about 5 degrees, or less than about 3 degrees.

[0024] In some embodiments, the first emanating central image ray (24) can be incident on the windshield (40) at an angle of incidence (θ) greater than about 30 degrees, or greater than about 40 degrees, or greater than about 50 degrees.

[0025] In some embodiments, the optical system can be substantially centered on an optical axis (60) that extends from the display center (12) to the eye (30). The optical axis (60) can include a first emanating central image ray (24).

[0026] In some embodiments, the windshield can include glass. In some other embodiments, the windshield can be curved, as shown in the figures. The windshield has a first interface (44) and a corresponding first Brewster angle (θ B In some embodiments, the first emerging central image ray (24) may have a first Brewster angle (θ B ) can be incident on the first boundary surface (44) of the windshield (40).

[0027] HUD image output polarization adjustment, combined with appropriate reflective polarizer lamination angle bias, can significantly and simultaneously reduce the contrast ratio of both front and rear ghosting at skew angles by reducing the S-polarized component of light incident on the reflective surface. For rear ghosting, this typically involves rotating the optic axis to minimize the effect on polarization due to the polarizer retardation.

[0028] 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, it is intended that the present disclosure be limited only by the claims and equivalents thereof. In the following, exemplary embodiments are presented. [Item 1] a display having an active display area having a maximum lateral dimension D and configured to emit an image for viewing by an eye of an observer, the active display area comprising a display center and a predetermined area that includes the display center, the predetermined area having a maximum lateral dimension d, where d / D≦0.25; a vehicle windshield having a reflective polarizer embedded therein, wherein for substantially normally incident light and for at least one wavelength between about 420 nm and about 670 nm, the reflective polarizer reflects between about 20% and about 40% of the incident light polarized along a first direction and transmits at least 60% of the incident light polarized along an orthogonal second direction; the reflective polarizer is configured to receive the image emitted by the active display area and reflect a portion of the received image toward the eye; for at least one first location within the predetermined region of the active display area, the emitted image includes a first emitted image cone emitted from the first location, the first emitted image cone includes a first emitted central image ray emitted from the first location, the first emitted central image ray is substantially polarized along a third direction when incident on the windshield in a plane of incidence, the first direction and the third direction being substantially parallel to the plane of incidence; An optical system comprising: [Item 2] Item 1. The optical system of item 1, substantially centered on an optical axis extending from the display center to the eye, the optical axis including the first emerging central image ray. [Item 3] Item 10. The optical system of item 1, wherein the windshield includes a first boundary surface and a corresponding first Brewster angle, and the first emanating central image ray is incident on the first boundary surface of the windshield at the first Brewster angle. [Item 4] Item 1. The optical system of item 1, wherein the third direction forms an angle of less than about 5 degrees with the plane of incidence, and the first direction forms an angle of less than about 5 degrees with the plane of incidence. [Item 5] Item 10. The optical system of item 1, wherein the reflective polarizer comprises a plurality of layers totaling more than about 30, the plurality of layers of the reflective polarizer comprising a plurality of alternating first and second layers, each of the first and second layers having an average thickness less than about 500 nm, a difference between the refractive indices of the first and second layers along the first direction being more than about 0.05, and a number of the plurality of layers of the reflective polarizer totaling more than about 100. [Item 6] Item 10. The optical system of item 1, wherein for the substantially normally incident light and for at least one wavelength between about 700 nm and about 1500 nm, the reflective polarizer reflects at least 40% of the incident light polarized along the first direction or the second direction. [Item 7] Item 14. The optical system of item 1, wherein the first emerging central image ray is incident on the windshield at an angle of incidence greater than about 40 degrees. [Item 8] Item 1. The optical system of item 1, wherein the first emerging central image ray is incident on the windshield at an angle of incidence greater than about 50 degrees. [Item 9] a display having an active display area configured to emit an image for viewing by an observer's eye; 1. A vehicle windshield having a reflective polarizer embedded therein, wherein for substantially normally incident light and for at least one wavelength between about 420 nm and about 670 nm, the reflective polarizer reflects between about 20% and about 40% of the incident light polarized along a first direction and transmits at least 60% of the incident light polarized along an orthogonal second direction, the reflective polarizer being configured to receive the image emitted by the active display area and reflect a portion of the received image toward the eye, the eye being configured to view a virtual image of the reflected image, the virtual image having a maximum lateral dimension of about 100 nm. a windshield having a dimension D', a virtual image center, and a predetermined virtual image area including the virtual image center, the predetermined virtual image area having a maximum lateral dimension d', where d' / D'≦0.25, and for at least one first location within the predetermined virtual image area, the first location has a corresponding second location within the active display area, such that image light emitted by the active display area from the second location is substantially polarized along a third direction when incident on the windshield in a plane of incidence, the first direction and the third direction being substantially parallel to the plane of incidence; An optical system comprising: [Item 10] 10. The optical system of claim 9, wherein for each first position within the predetermined virtual image area, the first position has a corresponding second position within the active display area, and image light rays emitted by the active display area from the second position are substantially polarized along a third direction when incident on the windshield in an incident plane, and the first direction and the third direction are substantially parallel to the incident plane.

Claims

1. a display having an active display area having a maximum dimension D and configured to emit an image for viewing by an eye of an observer, the active display area comprising a display center and a predetermined area that includes the display center, the predetermined area having a maximum dimension d, where d / D≦0.25; 1. A vehicle windshield comprising a reflective polarizer embedded therein, wherein for normally incident light and for at least one wavelength between 420 nm and 670 nm, the reflective polarizer reflects between 20% and 40% of the incident light polarized along a first direction and transmits at least 60% of the incident light polarized along an orthogonal second direction, the reflective polarizer being configured to receive the image emitted by the active display area and reflect a portion of the received image toward the eye, and wherein the active display area is configured to reflect a portion of the received image toward the eye. a windshield, wherein for at least one first location within the predetermined region of a region, the emitted image includes a first emitted image cone emitted from the first location, the first emitted image cone including a first emitted central image ray emitted from the first location, the first emitted central image ray being polarized along a third direction when incident on the windshield in a plane of incidence, the first direction and the plane of incidence forming an angle of less than 10 degrees, and the third direction and the plane of incidence forming an angle of less than 10 degrees; Equipped with the reflective polarizer is oriented at a bias angle within the windshield to minimize retardation effects and rear ghost brightness over a predetermined range of skew angles; Optical system.

2. The optical system of claim 1 , centered on an optical axis extending from the display center to the eye, the optical axis containing the first emanating central image ray.

3. 2. The optical system of claim 1, wherein the windshield includes a first boundary surface and a corresponding first Brewster angle, and the first emanating central image ray is incident on the first boundary surface of the windshield at the first Brewster angle.

4. The optical system of claim 1 , wherein the third direction forms an angle of less than 5 degrees with the plane of incidence and the first direction forms an angle of less than 5 degrees with the plane of incidence.

5. 2. The optical system of claim 1, wherein the reflective polarizer comprises a plurality of layers totaling more than 100, the plurality of layers of the reflective polarizer including a plurality of alternating first and second layers, each of the first and second layers having an average thickness less than 500 nm, and a difference between the refractive indices of the first and second layers along the first direction being greater than 0.

05.

6. 10. The optical system of claim 1, wherein for the normally incident light and for at least one wavelength between 700 nm and 1500 nm, the reflective polarizer reflects at least 40% of the incident light polarized along the first direction or the second direction.

7. The optical system of claim 1 , wherein the first emanating central image ray is incident on the windshield at an angle of incidence greater than 40 degrees.

8. The optical system of claim 1 , wherein the first emanating central image ray is incident on the windshield at an angle of incidence greater than 50 degrees.

9. a display having an active display area configured to emit an image for viewing by an observer's eye; 1. A vehicle windshield comprising a reflective polarizer embedded therein, wherein for normally incident light and for at least one wavelength between 420 nm and 670 nm, the reflective polarizer reflects between 20% and 40% of the incident light polarized along a first direction and transmits at least 60% of the incident light polarized along an orthogonal second direction; the reflective polarizer is configured to receive the image emitted by the active display area and reflect a portion of the received image toward the eye, the eye being configured to view a virtual image of the reflected image, the virtual image having a maximum dimension D′, a virtual image center, and a front a predetermined virtual image area including the virtual image center, the predetermined virtual image area having a maximum dimension d', where d' / D'≦0.25, and for at least one first location within the predetermined virtual image area, the first location has a corresponding second location within the active display area, such that image light emitted by the active display area from the second location, when incident on the windshield in an incidence plane, is polarized along a third direction, the angle between the first direction and the incidence plane being less than 10 degrees, and the angle between the third direction and the incidence plane being less than 10 degrees; Equipped with the reflective polarizer is oriented at a bias angle within the windshield to minimize retardation effects and rear ghost brightness over a predetermined range of skew angles; Optical system.

10. 10. The optical system of claim 9, wherein for each first location within the predetermined virtual image area, the first location has a corresponding second location within the active display area, and image light emitted by the active display area from the second location is polarized along a third direction when incident on the windshield in an incident plane, the first direction and the incident plane form an angle of less than 10 degrees, and the third direction and the incident plane form an angle of less than 10 degrees.

Images