Polarization-optimized head-up display

Abstract

An optical system comprising: a display including an active display area having a maximum lateral dimension D and configured to emit an image for viewing by an eye of a viewer, the active display area including a center of the display and a predetermined area including the center of the display, the predetermined area having a maximum lateral dimension d such that d / D ≤ 0.25; a windshield of a vehicle; and an optical film configured to receive an image emitted by the active display area and reflect or transmit at least a portion of the received image toward the windshield, the windshield being configured to receive an image reflected or transmitted by the optical film and reflect at least a portion of the received image toward the eye such that for at least one first position within the predetermined area of ​​the active display area, the emitted image includes a first emitted image cone emitted from the first position, the first emitted image cone including a first emitted central image ray emitted from the first position, wherein the optical film is oriented such that the first emitted central image ray is polarized substantially within an incident plane when incident on the windshield.

Description

Summary of the invention

[0001] In some aspects of the present specification, an optical system is provided, the optical system including a display having an active display area, the active display area having a maximum lateral dimension D and being configured to emit an image for viewing by an eye of a viewer, the active display area including a center of the display and a predetermined area including the center of the display, the predetermined area having a maximum lateral dimension d, such that d / D≤0.25; a windshield of a vehicle; and an optical film, the optical film being configured to receive an image emitted by the active display area and to reflect or transmit at least a portion of the received image toward the windshield, the windshield being configured to receive an image reflected or transmitted by the optical film and to reflect at least a portion of the received image toward the eye, such that for at least one first position within the predetermined area of ​​the active display area, the emitted image includes a first emitted image cone emitted from the first position, the first emitted image cone including a first emitted central image ray emitted from the first position, wherein the optical film is oriented so that the first emitted central image ray is polarized substantially within an incident plane when incident on the windshield. BRIEF DESCRIPTION OF THE DRAWINGS

[0002] Figure 1 is a top schematic diagram of a head-up display as seen in the prior art;

[0003] Figure 2A is a cross-sectional view of a polarization-optimized head-up display system according to an embodiment of the present specification;

[0004] Figure 2B is a front view of a display system and an optical film according to an embodiment of the present specification;

[0005] Figure 2C illustrates various types of polarization associated with an absorbing polarizer according to embodiments of the present specification;

[0006] Figure 2D is a side view of an absorbing polarizer according to an embodiment of the present specification;

[0007] Figure 3 is a cross-sectional view of a reflective polarizer according to an embodiment of the present specification;

[0008] Figure 4 is a cross-sectional view of a polarization-optimized head-up display system according to an alternative embodiment of the present specification;

[0009] Figure 5 is a cross-sectional view of a polarization-optimized heads-up display system according to another alternative embodiment of the present specification; and

[0010] Fig. 6A and Figure 6B is a graph illustrating the impact of a polarization optimized heads-up display according to an embodiment of the present description. DETAILED DESCRIPTION

[0011] In the following description, reference is made to the accompanying drawings, which form a part of the present invention and in which various embodiments are shown by way of example. The drawings are not necessarily drawn to scale. It should be understood that other embodiments may be conceived and carried out without departing from the scope or essence of the present description. Therefore, the following specific embodiments should not be considered to have a limiting meaning.

[0012] In modern head-up display (HUD) systems, a display such as, for example, a liquid crystal display (LCD) projects an image onto the windshield of a vehicle, where the image can be viewed by the operator or occupants of the vehicle. A common problem in HUD systems is the problem of "ghosting," when the projected image reflects off both the front glass-air interface (the inside surface of the windshield) and the rear glass-air interface (the outside surface of the windshield), then the two reflected images "bounce" to the viewer at different angles of incidence, thereby forming a primary image and an apparent second or "ghost" image that is offset from the primary image, which may reduce the legibility of the displayed information. A common approach to addressing this ghosting problem is for windshield manufacturers to form a wedge shape between the outer and inner surfaces of the windshield. That is, the outer glass-air interface is placed at a slightly different angle than the inner glass-air interface, with the intent to align the two reflected images into a single image, at least for an ideal viewing angle (e.g., that of a driver of average height). Another solution to the ghosting problem is to embed a weakly reflective polarizer between the two pieces of glass (i.e., sandwiched between the inner and outer sheets of glass) instead of forming a wedge shape in the windshield so that linearly polarized light reflects off the reflective polarizer. One such example of a reflective polarizer is the 3M TM Windshield composite film (3M TN Windshield Combiner Film, 3M TMWCF). When a reflective polarizer is used, image rays from the display (e.g., image rays with a P polarization state or P-polarized image rays) are linearly polarized and directed toward the windshield at a Brewster angle or an angle 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, impinges on the reflective polarizer, and at least a portion of the P-polarized light is reflected back toward the viewer as a single image (i.e., the only reflection of the image comes from the reflective polarizer, not the inner or outer glass-air interface). For incident angles close to the Brewster angle, this approach is very suitable for strongly reducing ghost images from the front glass-air interface and the rear glass-air interface. However, as the HUD image becomes wider, and when the image is displayed at a horizontal skew angle relative to the observer (e.g., due to the inherent curve of the windshield, or the angle from the driver to the image), the P-polarized image rays as defined based on the axial incident ray are converted into a mixture of P-polarized light and S-polarized light, resulting in higher ghost image reflections.

[0013] According to some aspects of the present specification, an optical system is described that is based on optimizing output polarization according to windshield tilt and skew angles. In some embodiments, the optimization can be performed in the display itself. In some embodiments, the optimization can be performed at any appropriate point in the light path from the display to the windshield. For example, the optimization can occur by controlling the orientation of an optical film (such as a reflective polarizer) in the light path or the orientation of an optical reflector (e.g., a mirror for bending the light path), the orientation of a beam splitter in the light path, or the orientation of a delay layer (e.g., a quarter wave plate or a half wave plate) in the light path. These examples are not intended to be limiting.

[0014] In some embodiments, an optical system (e.g., a head-up display or HUD) includes a display, a windshield of a vehicle, and an optical film configured to receive an image emitted by the display and reflect or transmit at least a portion of the received image toward the windshield. In some embodiments, the display may be a liquid crystal display (LED), an organic light emitting display (OLED), a digital light processing (DLP) display, or any other appropriate picture generation unit (PGU). In some embodiments, the display may have an active display area having a maximum lateral dimension (i.e., the diagonal of the active display area) D, and may be configured to emit an image for viewing by the eyes of a viewer such as the eyes of an operator of a vehicle. In some embodiments, the active display area may include a display center (i.e., the physical center of the display in both horizontal and vertical dimensions) and a predetermined area surrounding and including the center of the display (i.e., the predetermined area is a subset or portion of the overall active display area). In some embodiments, the predetermined area may have a maximum lateral dimension d, such that the ratio d / D is less than or equal to about 0.25 (i.e., the predetermined area may be about one-quarter of the overall active display area). In some embodiments, the ratio d / D can be less than or equal to about 0.2, about 0.15, or about 0.1.

[0015] In some embodiments, the optical system can be centered on an optical axis that can extend from a center point of the display to the windshield and into the viewer's eyes. In some embodiments, the optical axis can be defined by the first emitted central image ray.

[0016] In some embodiments, the windshield can be a glass windshield. In some embodiments, the windshield can be curved in the horizontal direction, the vertical direction, or both. In some embodiments, the windshield can be at an angle of inclination (i.e., angled toward the operator from the vertical direction). In some embodiments, the windshield can include a first interface (e.g., an interior glass / air interface) having a corresponding Brewster angle, such that the first emitted central image ray is incident on the first interface of the windshield at the Brewster angle.

[0017] In some embodiments, the optical film may be configured to receive an image emitted by the active display area and reflect or transmit at least a portion of the received image toward the windshield. In some embodiments, the windshield may be configured to receive an image reflected or transmitted by the optical film and reflect at least a portion of the received image toward the eye. For at least one first position within a predetermined area of ​​the active display area, the emitted image may include a first emitted image cone emitted from the first position. In some embodiments, the first emitted image cone may include a first emitted central image ray emitted from the first position. In some embodiments, the optical film may be oriented so that the first emitted central image ray is substantially polarized within the incident plane when incident on the windshield. In other words, the orientation of the optical film may be adjusted (e.g., rotated) so that at least the central image ray is "adjusted" to have a polarization within the incident plane when the image ray is projected on the windshield. In some embodiments, the optical film may be oriented so that at least about 90% or at least about 95% of the polarization of the first emitted central image ray is within the incident plane when the first emitted central image ray is incident on the optical film.

[0018] In some embodiments, the optical film can be a reflective polarizer. In some embodiments, for substantially vertical incident light and for at least one visible light wavelength within a visible light wavelength range extending from about 420 nm to about 670 nm, the reflective polarizer reflects between about 20% and about 40% 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., light having a linear S polarization type or S-polarized light). In some embodiments, the reflective polarizer can be a multilayer optical film comprising a plurality of layers having a total of greater than about 30, or a total of greater than about 50, or a total of greater than about 100. In some embodiments, the plurality of layers of the reflective polarizer comprises a plurality of alternating first and second layers. In some embodiments, each of the first and second layers may have an average thickness of less than about 500 nm. In some embodiments, the difference between the refractive index of the first and second layers along the first polarization state may be greater than about 0.05. In some embodiments, for substantially normally incident light and for at least one infrared wavelength in a wavelength range extending from about 700 nm to about 1500 nm, the reflective polarizer can reflect at least 40% of the incident light in at least one of the first polarization state and the second polarization state. In other words, in some embodiments, the reflective polarizer can be used to reflect heat from sunlight to prevent heat from entering the HUD system.

[0019] In some embodiments, the optical film can be an absorbing polarizer. In some embodiments, for substantially normal incident light, the absorbing polarizer can transmit at least 60% of the incident light polarized in a first direction and absorb at least 60% of the incident light polarized in an orthogonal second direction, wherein the first emitted central image ray is polarized in a third direction when incident on the absorbing polarizer, and the first direction and the third direction form an oblique angle greater than about 5 degrees.

[0020] In some embodiments, the optical film can be an optical reflector (e.g., an optical mirror). In some embodiments, the optical reflector 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 windshield. In some embodiments, the windshield can be configured to receive an image reflected by the optical reflector and reflect at least a portion of the received image toward the eyes of a viewer. In some embodiments, the optical reflector can be oriented so that the first emitted central image ray is substantially polarized in the incident plane when incident on the windshield. In some embodiments, for substantially vertically incident light and for at least one visible light wavelength within the visible light wavelength range extending from about 420 nm to about 670 nm, the optical reflector can reflect at least 60% of the incident light polarized in each of the mutually orthogonal first and second directions (e.g., linear P-polarized light and linear S-polarized light). In some embodiments, the optical reflector transmits at least 40% of incident light polarized in at least one of a mutually orthogonal first direction and a second direction for substantially normally incident light and for at least one infrared wavelength within a wavelength range extending from about 700 nm to about 1500 nm. In some embodiments, the optical reflector can be a multilayer optical film comprising a plurality of alternating first and second layers, each of the first and second layers having an average thickness of less than about 500 nm.

[0021] In some embodiments, the optical system may further include a delay layer (e.g., a quarter wave plate or a half wave plate) disposed between the optical film and the windshield. In some embodiments, the optical film may be an optical reflector configured to receive an image emitted by the active display area and reflect at least a portion of the received image toward the windshield. In some embodiments, the windshield may be configured to receive an image reflected by the optical reflector after the reflected image passes through the delay layer, and reflect at least a portion of the received image toward the eye. In some embodiments, the delay layer is oriented so that the first emitted central image ray is substantially polarized in the incident plane when incident on the windshield.

[0022] Turning now to the accompanying drawings, Figure 1 is a top schematic diagram of a head-up display as seen in the prior art. Figure 1As shown, a typical head-up display 200 projects an image onto a windshield 40 where it is seen by a viewer 30 as a reflected image 22. Most windshields available today are sometimes oriented horizontally (e.g., Figure 1 The curved surface is curved in both the vertical direction (i.e., from top to bottom, as viewed by the viewer 30) and in the vertical direction (i.e., from top to bottom). Figure 1 As shown, the image projected by the HUD 200 onto the windshield 40 is projected onto the windshield at a horizontal offset angle of about 10 degrees, which is not uncommon for modern cars and may even be greater than 10 degrees. It is also important to note that the position of the HUD 200 may vary depending on the type of vehicle, and the position of the HUD 200 may be set at a position greater than Figure 1 The points shown are at points further away from viewer 30 (thus imparting a greater skew angle to reflected image 22). When an image is projected as primarily P-polarized light relative to the axial plane of incidence (that is, relative to the optical axis), the light is converted to a mixture of P-polarized light and S-polarized light due to projection onto a surface having a significant horizontal skew angle. This increased S-polarized component can result in an increase in ghosting seen by viewer 30.

[0023] Figure 2A is a cross-sectional view of a polarization-optimized head-up display system according to the present specification. In some embodiments, a polarization-optimized head-up display (HUD) 300 includes a display 10, such as an LED, OLED, or other PGU. The display 10 is configured to emit an image 20 along an optical axis 60 so that the image will be projected onto a windshield 40 having a first interface 44 (e.g., an interface between air and glass on the inside of the windshield 40). The emitted image 20 includes an emission light cone 23 that is emitted from a first position 14 on the display and includes an emission central image ray 24. In some embodiments, the emitted image 20 passes through an optical film 50, wherein at least a portion 21 of the image is transmitted through the optical film to be projected onto the windshield 40. Then, at least a portion 21 of the image is reflected off the windshield as a reflected image 22, which travels to the eye of a viewer 30. In some embodiments, the central image ray 24 may coincide with the optical axis 60.

[0024] In some embodiments, the windshield 40 may include an inner reflective polarizer layer 140 (e.g., a polymer film reflective polarizer sandwiched between an inner glass layer and an outer glass layer). In some embodiments, the inner reflective polarizer layer can be a weakly reflective polarizer that reflects between 20% and 40% of incident light having a first polarization state and transmits at least 60% of incident light having an orthogonal second polarization state. The reflective polarizer 140 is referred to elsewhere herein. Figure 3 This is discussed in more detail in the discussion of .

[0025] Figure 2B is a front view of the display 10 and optical film 50, which shows additional details. It is best to examine the display 10 and optical film 50 in a front-to-back manner. Figure 2A and Figure 2B for the following discussion. A predetermined region 13 of the active display area 11 of the display 10 includes a display center 12 (the physical center of the display in both horizontal and vertical dimensions) and a first location 14 of an emitted light cone 23. In some embodiments, the first location 14 and the display center 12 can be co-located (i.e., can be the same point). The emitted light cone 23 includes at least a first emitted central image ray 24 that is emitted by the display 10, travels through the optical film 50, reflects from the windshield 40, and continues to the eye of the viewer 30. In some embodiments, the first emitted central image ray 24 can coincide with the optical axis 60, or can be substantially parallel to the optical axis 60. Go to Figure 2B , the predetermined area 13 may have a maximum lateral dimension d, and the active display area 11 may have a maximum lateral dimension D, such that the ratio of d / D is less than or equal to about 0.25, or about 0.2, or about 1.5, or about 1.0. In other words, the predetermined area 13 represents the central portion of the active display area 11.

[0026] In some embodiments, the optical film 50 can be oriented (e.g., rotated) such that the first emitted central image ray 24 will be substantially polarized within the plane of incidence when incident on the windshield 40. In other words, the optical film 50 can be rotated or otherwise oriented from a "conventional" orientation such that the polarization of the first emitted central image ray 24 will be substantially polarized at the point of incidence on the windshield 40, which, as previously discussed, can be at a large skew angle on the curved windshield 40 relative to the viewer 30. In this way, the system can compensate for any ghosting seen by the viewer 30 due to the skew angle of the windshield.

[0027] It should be noted that the optical film 50 is Figure 2B 50 is shown as having a rectangular shape that is physically rotated relative to display 10. However, the shape of physical optical film 50 is arbitrary, and what is important is the orientation of the polarization features within optical film 50. Moreover, as will be seen in other embodiments described herein, optimization of the polarization of image ray 24 may be accomplished at other locations along the optical path of image ray 24.

[0028] Figure 2C and Figure 2D The optical film 50 is shown as an embodiment of an absorbing polarizer 70. It is best to examine the Figure 2C and Figure 2DWhen the optical film 50 is an absorbing polarizer 70, for vertically incident light 71 (which may include the central image ray 24), the absorbing polarizer 70 may transmit light along a first direction (polarization direction 72, such as Figure 2C The absorbing polarizer 70 absorbs at least 60% of the incident light 71 polarized in a second direction (polarization direction 73) and absorbs at least 60% of the incident light 71 polarized in an orthogonal second direction (polarization direction 73). In some embodiments, the absorbing polarizer 70 can be oriented so that the light passing through the absorbing polarizer 70 can be polarized in a new third direction 74. In some embodiments, the first direction 72 and the third direction 74 form an oblique angle α greater than about 5 degrees. In other words, and turning Figure 2D , central image ray 24 is incident on absorptive polarizer 70 with polarization direction 72 (shown as 24(p72)), and at least a portion of image ray 24 will emerge from absorptive polarizer 70 with polarization direction 74 (shown as 24(p74)). In other words, the polarization of central image ray 24 is rotated by optical film 50 so that the central image ray is substantially polarized in the plane of incidence on the tilted windshield.

[0029] As about Figure 2A As discussed, windshield 40 may include reflective polarizer 140 embedded in the windshield. Figure 3 1 is a cross-sectional view of one embodiment of such a reflective polarizer 140. In some embodiments, the reflective polarizer 140 can be configured as a multilayer optical film (MOF). In some embodiments, the reflective polarizer 140 includes a plurality of alternating first polymer layers 142 and second polymer layers 143. In some embodiments, the number of alternating first polymer layers 142 and second polymer layers 143 combined can be between 30 and 700. In some embodiments, the first polymer layers 142 and second polymer layers 143 can each have an average thickness of less than about 500 nm.

[0030] In some embodiments, first polymer layer 142 can be substantially isotropic (i.e., exhibiting substantially the same refractive index when measured in different directions). In some embodiments, second polymer layer 143 can be substantially birefringent (i.e., exhibiting two different refractive indices when measured in different orthogonal directions) and have in-plane refractive indices nx and ny along orthogonal directions, wherein the difference between nx and ny is greater than about 0.05, or greater than about 0.03, or greater than about 0.01. In some embodiments, additional layers 141 (e.g., adhesive layers, other substrate layers) can be present on the outer surface of reflective polarizer 140.

[0031] In some embodiments, the reflective polarizer 140 can be relatively weak such that when incident light ray 145 is projected onto the film, and for at least one visible light wavelength within the visible light wavelength range extending from about 420 nm to about 670 nm, the reflective polarizer reflects between about 20% and about 40% of the incident light 145 having a first polarization state (e.g., P-polarized light) and transmits at least 60% of the incident light having an orthogonal second polarization state (e.g., S-polarized light).

[0032] In some embodiments, for substantially normally incident light 145 and for at least one infrared wavelength in the infrared wavelength range extending from about 700 nm to about 1500 nm, the reflective polarizer can reflect at least 40% of the incident light in at least one of the first polarization state and the second polarization state. In some embodiments, this can help reduce the transmission of unwanted heat (into the HUD) generated by sunlight projected on the outer surface of the windshield.

[0033] Figure 4 and Figure 5 A cross-sectional view of an alternative embodiment of a polarization optimized heads-up display system according to the present description is provided. Figure 4 and Figure 5 as well as Figure 2A Many elements in are common. Figure 2A , Figure 4 and Figure 5 Elements in the drawings that share the same numbered reference designators have the same function, and no further description may be provided beyond that presented previously.

[0034] exist Figure 4, the polarization optimized heads-up display system 400 has a "bent" optical path (as defined by the optical axis 60) in which the image 20' is emitted from the active display area 11 of the display 10 and first reflects from the optical reflector 90 (e.g., a mirror, a reflective film, etc.), after which at least a portion of the image 21' is redirected toward the windshield 40. In some embodiments, a retarder layer 100 (e.g., a quarter wave plate or a half wave plate) may be disposed on the optical reflector 90. In some embodiments, one or both of the optical reflector 90 and the retarder layer 100 may be oriented so that the first emitted central image ray 24 is substantially polarized in the plane of incidence when incident on the windshield 40. After the image 21' is reflected from the windshield 40, at least a portion of the image 22' is redirected toward the viewer 30 as a perceived image. In some embodiments, the optical reflector 90 may be substantially flat, curved (e.g., convex or concave to increase power), or free-form. In some embodiments, the optical reflector 90 can be a polarizing reflector capable of polarization rotation without a separate retardation layer 100 (eg, a polarizing reflective multilayer optical film).

[0035] exist Figure 5 , the polarization optimized head-up display system 500 adds an additional bend in the optical path represented by the optical axis 60. The display 10 emits an image 20' from the active display area 11. The image 20' travels toward the optical beam splitter 80. In some embodiments, the optical beam splitter 80 can be a reflective polarizer that substantially reflects incident light of a first polarization state (e.g., linear S-polarized light) and substantially transmits incident light of an orthogonal second polarization state (e.g., linear P-polarized light). In one embodiment, the central image ray 24 can be emitted as light having an S polarization state, reflected by the optical beam splitter 80 to be redirected toward the optical reflector 90. The retarder layer 100 disposed on the optical reflector can then convert the S-polarized light to P-polarized light, which now passes through when at least a portion of the image 21' is redirected back to the optical beam splitter 80. The image 21' is reflected from the windshield 40, where at least a portion of the image 22' is redirected toward the viewer 30. The orientation and rotation angle of beam splitter 80 can be used to set the output polarization seen in the plane of incidence. Figure 4 and Figure 5 In an embodiment, any of the elements including optical beam splitter 80, optical reflector 90 and delay layer 100 may be oriented such that the image (including image rays 24) is substantially polarized at the point of incidence on the tilted windshield 40.

[0036] at last, Fig. 6A and Figure 6B Graphs are provided showing the impact of a polarization optimized heads-up display according to the present description. Fig. 6AProvides the following conditions when no polarization optimization adjustment is performed (i.e., for Figure 2A 10, and a graph showing the percentage of the contrast ratio of a ghost image output by a P-polarized head-up display when the optical film 50 is not rotated relative to the display 10. Fig. 6A The x-axis plots the horizontal deflection angle of the windshield relative to the axial plane (the angle from the axial plane at the image incidence point). The y-axis plots the vertical incidence angle. The dashed rectangular box represents the "eye box" or active viewing area (approximately 5° x 12°) of the displayed image as the operator of the vehicle would see it. Fig. 6A The shaded contours show that the contrast ratio of the ghost image increases significantly toward the right side of the "eye box", being greater than 2 percent and approaching 3 percent.

[0037] Figure 6B The improved performance achieved by the same system when the HUD output polarization is rotated by approximately 5 degrees is shown. Figure 6B Almost the entire "eye box" exhibits less than 1% ghost contrast ratio, greatly reducing the ghost images perceived by the operator.

[0038] Terms such as "about" will be understood by one of ordinary skill in the art in the context of use and description in this specification. If it is not clear to one of ordinary skill in the art in the context of use and description in this specification that "about" should be used to express the amount of feature size, quantity, and physical properties, then "about" will be understood to mean within 10% of the specified value. A quantity given as about a specified value may be exactly the specified value. For example, if it is not clear to one of ordinary skill in the art in the context of use and description in this specification, a quantity having a value of about 1 means that the quantity has a value between 0.9 and 1.1, and the value may be 1.

[0039] One of ordinary skill in the art will understand terms such as "substantially" in the context of use and description in this specification. If the use of "substantially equal" in the context of use and description in this specification is unclear to one of ordinary skill in the art, "substantially equal" will refer to approximately the situation of approximately as described above. If the use of "substantially parallel" in the context of use and description in this specification is unclear to one of ordinary skill in the art, "substantially parallel" will refer to within 30 degrees of parallel. In some embodiments, directions or surfaces described as being substantially parallel to each other may be within 20 degrees or within 10 degrees of parallel, or may be parallel or nominally parallel. If the use of "substantially aligned" in the context of use and description in this specification is unclear to one of ordinary skill in the art, "substantially aligned" will refer to alignment within 20% of the width of the object of alignment. In some embodiments, the objects described as being substantially aligned may be aligned within 10% or within 5% of the width of the object of alignment.

[0040] All references, patents, and patent applications cited above are hereby incorporated by reference in their entirety in a consistent manner. In the event of inconsistencies or conflicts between an incorporated reference portion and the present application, the information in the foregoing description shall prevail.

[0041] Unless otherwise indicated, the description of the elements in the drawings should be understood to apply equally to the corresponding elements in the other drawings. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that the specific embodiments shown and described may be replaced with a variety of alternative and / or equivalent implementations without departing from the scope of the present disclosure. The present application is intended to cover any modification or variation of the specific embodiments discussed herein. Therefore, the present disclosure is intended to be limited only by the claims and their equivalents.

Claims

1. An optical system, comprising: A display comprising an active display area having a maximum lateral dimension D and configured to emit an image for viewing by an eye of a viewer, the active display area comprising a display center and a predetermined area including the display center, the predetermined area comprising a maximum lateral dimension d, d / D≤0.25; The windshield of the vehicle; an optical film configured to receive the image emitted by the active display area and reflect or transmit at least a portion of the received image toward the windshield, the windshield configured to receive the image reflected or transmitted by the optical film and reflect at least a portion of the received image toward the eye, such that for at least one first location within the predetermined area of ​​the active display area, 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, wherein the optical film is oriented such that the first emitted central image ray is polarized substantially within an incident plane when incident on the windshield, and A delay layer, the delay layer is arranged between the optical film and the windshield, wherein the optical film includes an optical reflector, the optical reflector is constructed to receive the image emitted by the active display area and reflect at least a portion of the received image toward the windshield, the windshield is constructed to receive the image reflected by the optical reflector after the reflected image passes through the delay layer and reflect at least a portion of the received image toward the eye, wherein the delay layer is oriented so that the first emitted central image ray is substantially polarized within the incident plane when incident on the windshield.

2. The optical system of claim 1, wherein the windshield comprises a reflective polarizer embedded in the windshield.

3. The optical system of claim 2, wherein for substantially normally incident light and for at least one visible light wavelength within a visible light wavelength range extending from about 420 nm to about 670 nm, the reflective polarizer reflects between about 20% and about 40% of incident light having a first polarization state and transmits at least 60% of incident light having an orthogonal second polarization state.

4. The optical system of claim 3, wherein for the substantially normally incident light and for at least one infrared wavelength within an infrared wavelength range extending from about 700 nm to about 1500 nm, the reflective polarizer reflects at least 40% of the incident light in at least one of the first polarization state and the second polarization state.

5. The optical system of claim 3, wherein the reflective polarizer comprises a plurality of layers totaling greater than about 30 and the plurality of layers comprises a plurality of alternating first and second layers, each of the first and second layers having an average thickness less than about 500 nm, and a difference between a refractive index of the first and second layers along the first polarization state is greater than about 0.05.

Images