Dual-sided light redirecting film

Abstract

An optical system includes a display and a light redirecting film having a first side with first redirecting microstructures, an opposing second side with second redirecting microstructures, and an internal angle-limiting optical component disposed between the first side and the second side. The light redirecting film is disposed between the display and a viewer. Each redirecting microstructure of the first redirecting microstructures has a first light-transmitting facet disposed at a first angle, each redirecting microstructure of the second redirecting microstructures has a first light-transmitting facet disposed at a second angle. When light rays from the display pass first through the second side of the film and are transmitted through the internal angle-limiting optical component and exit the first side of the film, a direction of the light rays entering the second side of the light redirecting film is preserved when the light rays are transmitted for viewing by the viewer.

Description

PA101644W002DUAL-SIDED LIGHT REDIRECTING FILMSummary

[0001] In some aspects of the present description, an optical system is provided, the optical system including a display configured to emit an image for viewing by a viewer and including a first display surface, and a light redirecting film including a first side with a first plurality of redirecting microstructures, an opposing second side with a second plurality of redirecting microstructures, and an internal angle-limiting optical component disposed between the first side and the second side. The light redirecting film is disposed between the first display surface and the viewer, wherein each redirecting microstructure of the first plurality of redirecting microstructures has a first light-transmitting facet disposed at a first angle, and each redirecting microstructure of the second plurality of redirecting microstructures has a corresponding first light-transmitting facet disposed at a second angle. When light rays are emitted by the first display surface and pass first through the second side of the light redirecting film and are transmitted through the internal anglelimiting optical component and exit the first side of the light redirecting film, a direction of the light rays entering the second side of the light redirecting film is substantially preserved when the light rays are transmitted by the first side of the light redirecting film for viewing by the viewer.

[0002] In some aspects of the present description, a light redirecting film is provided, the light redirecting film including a first side with a first plurality of redirecting microstructures, an opposing second side with a second plurality of redirecting microstructures, and an internal anglelimiting optical component disposed between the first side and the second side. Each redirecting microstructure of the first plurality of redirecting microstructures has a first light-transmitting facet disposed at a first angle, and each redirecting microstructure of the second plurality of redirecting microstructures has a corresponding first light-transmitting facet disposed at a second angle. The first angle and the second angle are substantially the same angle. When light rays enter the second side of the light redirecting film and are transmitted through the internal angle-limiting optical component and exit the first side of the light redirecting film, a direction of the light rays entering the second side of the light redirecting film is substantially preserved when the light rays are transmitted by the first side of the light redirecting film for viewing by the viewer.

[0003] In some aspects of the present description, an optical system is provided, the optical system including a display configured to emit an image for viewing by a viewer and including a first display surface, and a light redirecting film comprising a first side with a first plurality of redirecting microstructures and an opposing second side, and an internal angle- limiting optical component disposed between the first side and the second side. The light redirecting film isdisposed between the first display surface and the viewer. Each redirecting microstructure of the first plurality of redirecting micro structures has a first light-transmitting facet disposed at a first angle and a second facet comprising a light-absorbing cover layer, the first light-transmitting facet and the second facet meeting at a peak in the redirecting microstructure. When light rays are emitted by the first display surface and pass first through the second side of the light redirecting film and are transmitted through the internal angle- limiting optical component and exit the first side of the light redirecting film, a direction of the light rays entering the second side of the light redirecting film is modified when the light rays are transmitted by the first side of the light redirecting film for viewing by the viewer.Brief Description of the Drawings

[0004] FIGS. 1 A and IB provide details on a light redirecting film, in accordance with an embodiment of the present description;

[0005] FIG. 2A shows a typical display system in the prior art, and FIG. 2B shows a display system using a light redirecting film, in accordance with an embodiment of the present description;

[0006] FIG. 3 A illustrates angles of light redirecting microstructures and optical paths for a light redirecting film, and FIG. 3B shows an embodiment of a display with light redirecting microstructures, in accordance with an embodiment of the present description;

[0007] FIGS. 4 A and 4B provide details on light redirecting systems which do not include a light absorbing cover layer on facets of the redirecting microstructures, in accordance with an embodiment of the present description;

[0008] FIG. 5 shows an embodiment of a display system featuring a display with light redirecting structures on opposing sides of the display, in accordance with an embodiment of the present description; and

[0009] FIGS. 6A and 6B illustrate display systems with light redirecting structures on only one side, in accordance with embodiments of the present description.Detailed Description

[0010] In the following description, reference is made to the accompanying drawings that form a part hereof and in which various embodiments are shown by way of illustration. The drawings are not necessarily to scale. It is to be understood that other embodiments arecontemplated and may be made without departing from the scope or spirit of the present description. The following detailed description, therefore, is not to be taken in a limiting sense.

[0011] Head-Up Displays (HUDs) have become increasingly prevalent in automotive and other display applications due to their ability to project critical information directly into the viewer's line of sight, thereby enhancing safety and user experience. Traditional HUD systems typically employ a Picture Generation Unit (PGU, e.g., a display) that projects an image onto a transparent combiner, such as the windshield or a dedicated screen. This image is then reflected into the viewer's eyes, creating a virtual image that appears to float in front of the vehicle.

[0012] In recent years, waveguide-based HUD systems have gained attention for their potential to offer compact designs and advanced functionalities, such as long virtual image distances and three-dimensional image formation. These systems use a flat slab of glass or plastic, known as a waveguide, to guide image light from a projector to the windshield, where it is reflected toward the viewer. The waveguide HUD systems are particularly attractive to Original Equipment Manufacturers (OEMs) due to their promise of combining small package size with high-performance imaging capabilities.

[0013] Despite the advancements in HUD technology, several significant challenges remain unaddressed. One of the primary issues with waveguide HUD systems is the reflection of sunlight off the flat waveguide surface, which can cause glare and impair the viewer's ability to see the projected image clearly. This problem is exacerbated by the need to maintain a small package size, as lowering the waveguide into the dashboard to avoid direct sunlight reflection requires additional dashboard volume, thereby negating one of the key benefits of waveguide HUD systems.

[0014] In standard HUD systems, the PGU often uses an LCD imager that is tilted relative to the projected beam direction to avoid retroreflected sunlight and to aid in producing the desired virtual image orientation. However, LCDs are known to exhibit decreased contrast at viewing angles away from the axial direction. This contrast degradation can be particularly noticeable along certain ray orientations, depending on the LCD technology used, such as In-Plane Switching (IPS) displays. This results in a less clear and less vibrant image, which can detract from the overall effectiveness of the HUD.

[0015] Given these deficiencies, there is a clear need for innovative solutions that can address the issues of sunlight glare in waveguide HUD systems and contrast degradation in tilted LCD imagers. Such solutions should ideally maintain the compact form factor of waveguide HUDs while enhancing image clarity and contrast. The development of advanced optical films and structures that can mitigate these problems without compromising on the design and functionality of HUD systems is essential for the continued advancement and adoption of this technology in automotive and other display applications.

[0016] The present description relates to an optical system designed to enhance the performance of display technologies, particularly in applications such as automotive Head-Up Displays (HUDs). The system includes a display configured to emit an image and a light redirecting film that optimizes the directionality and quality of the emitted light. This detailed description outlines the components and functionality of the optical system, emphasizing the use of dual-sided redirecting microstructures and an internal angle-limiting optical component.

[0017] The display is configured to emit an image for viewing by a viewer. It includes a first display surface from which light rays are emitted. This display can be any suitable type, such as an LCD, OLED, or other emissive or transmissive display technologies. The light redirecting film is a critical component of the optical system, positioned between the first display surface and the viewer. This film has a first side with a first plurality of redirecting microstructures and an opposing second side with a second plurality of redirecting microstructures, separated by an internal angle-limiting optical component. Each microstructure on the first side has a lighttransmitting facet disposed at a first angle, while each microstructure on the second side has a corresponding facet disposed at a second angle. This configuration ensures that light rays emitted from the first display surface, passing through the second side, the internal component, and exiting the first side, maintain their direction, thereby preserving the image's integrity for the viewer.

[0018] Light rays emitted by the first display surface first encounter the second side of the light redirecting film. The second plurality of redirecting microstructures, with their first lighttransmitting facets disposed at a second angle, initially interact with these light rays. The light rays then pass through the internal angle-limiting optical component, which may include elements such as louver films or liquid crystal display panels, designed to limit the angle of light transmission. Upon exiting the internal component, the light rays encounter the first side of the light redirecting film. The first plurality of redirecting microstructures, with their first light-transmitting facets disposed at a first angle, further manage the direction of the light rays. This dual-sided interaction ensures that, at least in some embodiments, the direction of the light rays is substantially preserved, providing a clear and undistorted image to the viewer.

[0019] The internal angle-limiting optical component of the light redirecting film plays a crucial role in the system. In some embodiments, it may be a louver film, which comprises a plurality of louvers oriented to allow the transmission of light rays substantially parallel to the louvers while preventing external light from reaching the first display surface. Each redirecting microstructure on the first and second sides of the film may include additional facets, such as second facets disposed at angles orthogonal to the film's surface or covered with light-absorbing layers. These design features help to further control light direction and minimize issues such as ghosting or stray light.

[0020] According to some aspects of the present description, an optical system includes a display configured to emit an image for viewing by a viewer and including a first display surface, and a light redirecting film comprising a first side with a first plurality of redirecting microstructures, an opposing second side with a second plurality of redirecting microstructures, and an internal angle-limiting optical component disposed between the first side and the second side.

[0021] In some embodiments, the light redirecting film may be disposed between the first display surface and the viewer, and each redirecting microstructure of the first plurality of redirecting microstructures has a first light-transmitting facet disposed at a first angle, and each redirecting microstructure of the second plurality of redirecting microstructures has a corresponding first light-transmitting facet disposed at a second angle. In some embodiments, the first angle and the second angle may be substantially the same relative to a same surface of the light redirecting film. In other embodiments, the first angle and second angle may be different.

[0022] In some embodiments, when light rays (e.g., image rays) are emitted by the first display surface and pass first through the second side of the light redirecting film (being redirected by refraction passing through the first facet of the redirecting microstructures of the second side to a direction different than the input direction), and are transmitted through the internal anglelimiting optical component (as the light rays are within the range of angles which are allowed to be transmitted by the internal angle-limiting optical component), and exit the first side of the light redirecting film (and are again redirected into a new output direction by the first facets of the redirecting microstructures of the first side to an output direction), a direction of the light rays entering the second side of the light redirecting film (the input direction) is substantially preserved when the light rays are transmitted by the first side of the light redirecting film (at the output direction) for viewing by the viewer.

[0023] In some embodiments, the internal angle-limiting optical component may include a louver film. In some embodiments, the louver film may include a plurality of louvers oriented to allow the transmission of light rays substantially parallel to the louvers and to prevent the transmission of an external light (e.g., sunlight incident on the light redirecting film) from reaching the first display surface. In some embodiments, the louvers may be light absorbing such that the external light is substantially absorbed by the louvers. In some embodiments, the external light may also be reflected by the first facets of the first plurality of redirecting microstructures at an angle which will not reach the viewer, before it enters the light-redirecting film (i.e., the first angle of the first facets may be configured such that external light is substantially reflected back toward the source and away from an optical path leading to the viewer).

[0024] In some embodiments, each redirecting microstructure of at least one of the first plurality of redirecting microstructures and the second plurality of redirecting microstructures may include a second facet disposed at an angle that is substantially orthogonal to the first side of the light redirecting film. In some such embodiments, the first facet and second facet may meet at a peak, creating a redirecting microstructure with a substantially wedge-shaped or triangular-shaped profile. In some embodiments, embodiments, the redirecting microstructures of at least one of the first plurality of redirecting micro structures and the second plurality of redirecting microstructures may be linear structures which extend across a width (e.g., a y-direction) of the light -redirecting film and are arranged along an orthogonal length (e.g., an x-direction) of the light redirecting film.

[0025] In some embodiments, each redirecting microstructure of at least one of the first plurality of redirecting microstructures and the second plurality of redirecting microstructures may include a second facet, and the second facet may have a light-absorbing cover layer (e.g., a louver or layer which substantially absorbs incident light).

[0026] In some embodiments, the light-absorbing cover layer may be substantially conformally coated on, and cover at least 70%, or at least 75%, or at least 80%, or at least 85% or at least 90%, or at least 95% of the second facets. In some embodiments, the cover layer may have an average thickness of greater than about 0.05, or greater than about 0.1, or greater than about 0.15, or greater than about 0.2, or greater than about 0.25, or greater than about 0.3, or greater than about 0.35, or greater than about 0.4, or greater than about 0.45, or greater than about 0.5, or greater than about 0.55, or greater than about 0.6, or greater than about 0.65, or greater than about 0.7, or greater than about 0.75, or greater than about 1.0, or greater than about 1.25, or greater than about 1.5, or greater than about 2, or greater than about 2.5, or greater than about 3 microns.

[0027] In some embodiments, the light-absorbing cover layer may be deposited by layer-by- layer (LbL) deposition, sometimes referred to as LbL coating, LbL assembly, or LbL selfassembly. This coating method is based upon sequential, self-limiting adsorption of materials with complementary groups, and thus can provide substantially conformal coatings on structured surfaces. The complementary functional groups are most commonly positively-charged (e.g., amines) and negatively-charged (e.g., carboxylic acids, sulfonic acids, phosphonic acids) groups. Typical materials include polyelectrolyte polymers and / or nanoparticles such as surface-modified pigments (e.g., carbon black) or metal oxides. More details on LbL coating of a microstructured surface followed by selective removal of that coating via reactive ion etching (RIE) are provided in WO2019118685 (Schmidt et al.), incorporated herein by reference.

[0028] In some such embodiments, the light absorbing cover layer may include a plurality of light absorbing particles. In some such embodiments, the light absorbing particles may include one or more of a dye, a pigment, a polyelectrolyte, and a carbon black. In some such embodiments, thelight absorbing cover layer may have an optical density of greater than about 0.1, or greater than about 0.2, or greater than about 0.4, or greater than about 0.6, or greater than about 0.8, or greater than about 1, or greater than about 1.1, or greater than about 1.2, or greater than about 1.3, or greater than about 1.5, or greater than about 2, or greater than about 2.5, or greater than about 3, or greater than about 3.5, or greater than about 4, or greater than about 4.5, or greater than about 5, or greater than about 5.5, or greater than about 6.

[0029] In other embodiments, the internal angle-limiting optical component may be replaced by a liquid crystal display panel, wherein a first, input direction of the light rays entering the second side of the light redirecting film is altered to a second, transmitting direction by the second plurality of light redirecting microstructures such that the light rays pass through the liquid crystal display panel at angles substantially orthogonal to an input surface of the liquid crystal display panel. In some embodiments, the second, transmitting direction of the light rays exiting the first side of the light redirecting film may be altered by the first plurality of light redirecting microstructures to a third direction which substantially matches the first direction.

[0030] It should be noted, the internal angle-limiting optical component of the light redirecting film is not meant to be limited to a louver film but may be any type of layer or component which limits the transmission of light in a manner similar to a louver film or a display panel. That is, the internal angle-limiting optical component may be any component which allows for the transmission of light rays along an intended optical path between the second side and first side of the light-redirecting film, while preventing the transmission of unwanted, external light (e.g., sunlight) incident at angles which are beyond the acceptable range of angles allowed by the internal angle-limiting optical component.

[0031] According to some aspects of the present description, a light redirecting film includes a first side with a first plurality of redirecting microstructures, an opposing second side with a second plurality of redirecting microstructures, and an internal angle- limiting optical component disposed between the first side and the second side. In some embodiments, each redirecting microstructure of the first plurality of redirecting microstructures may have a first lighttransmitting facet disposed at a first angle, and each redirecting microstructure of the second plurality of redirecting microstructures may have a corresponding first light-transmitting facet disposed at a second angle. In some embodiments, the first angle and the second angle may be substantially the same. In other embodiments, the first angle and the second angle may be different, and may be configured to as required depending on the angles of light transmission required by the optical system in which the light redirecting film is used.

[0032] In some embodiments, when light rays (e.g., image rays from a display) enter the second side of the light redirecting film and are transmitted through the internal angle-limitingoptical component and exit the first side of the light redirecting film, a direction of the light rays entering the second side of the light redirecting film is substantially preserved when the light rays are transmitted by the first side of the light redirecting film for viewing by the viewer. Stated another way, at least in some embodiments, the angle of the light rays entering the light redirecting film via the second side may be substantially the same as the angle of light rays exiting the light redirecting film via the first side, even though the direction of the light rays may be altered first by the second plurality of redirecting microstructures on the second side and again altered by the first plurality of redirecting microstructures on the first side.

[0033] In some embodiments, the internal angle-limiting optical component may limit the transmission of light therethrough to a predetermined angular range relative to a thickness direction (e.g., a z-direction) of the internal angle-limiting optical component. In some embodiments, the angles of light transmitted through the internal angle-limiting optical component may be those angles which are substantially parallel to angle limiting components (e.g., louvers in a louver film) within the internal angle- limiting optical component.

[0034] In some such embodiments, the internal angle-limiting optical component may be a louver film. In some embodiments, the louver film may include a plurality of louvers oriented to allow the transmission of light rays substantially parallel to the louvers and to prevent the transmission of an external light passing into the internal optical component at an angle of incidence greater than about 20 degrees, or about 15 degrees, or about 10 degrees relative to the orientation of the louvers. In some such embodiments, the plurality of louvers may be oriented substantially parallel to a thickness direction (e.g., a z-direction) of the internal angle-limiting optical component. In other embodiments, the plurality of louvers may be oriented at an oblique angle to a thickness direction of the internal angle-limiting optical component (e.g., if the intended optical axis is slanted as it passes through the light-redirecting film).

[0035] In some embodiments, each redirecting microstructure of at least one of the first plurality of redirecting microstructures and the second plurality of redirecting microstructures may include a second facet disposed at an angle that is substantially orthogonal to the first side of the light redirecting film. In some embodiments, the second facet may include a light-absorbing cover layer.

[0036] In some embodiments, the internal optical component may be replaced by a liquid crystal display panel, wherein a first direction of the light rays entering the second side of the light redirecting film is altered to a second direction by the second plurality of light redirecting microstructures such that the light rays pass through the liquid crystal display panel at angles substantially orthogonal to an input surface of the liquid crystal display panel, and the second direction of the light rays exiting the first side of the light redirecting film is altered by the firstplurality of light redirecting microstructures to a third direction which substantially matches the first direction.

[0037] According to some aspects of the present description, a display system may include a liquid crystal display configured to generate an image and a light source configured to emit a substantially collimated light toward the liquid crystal display. In some such embodiments, the liquid crystal display may have a light input side and an opposing light transmitting side, such that collimated light emitted by the light source enters the light input side of the liquid crystal display and exits the light transmitting side of the liquid crystal display. In some embodiments, the light input side of the liquid crystal display may include a first plurality of redirecting microstructures, and the light transmitting side of the liquid crystal display may include a second plurality of redirecting microstructures.

[0038] In some such embodiments, each redirecting microstructure of the first plurality of redirecting microstructures may have a first light-transmitting facet disposed at a first angle, and each redirecting microstructure of the second plurality of redirecting microstructures may have a corresponding first light-transmitting facet disposed at a second angle. In some embodiments, the first angle and the second angle may be substantially identical. In other embodiments, the first angle and the second angle may be different.

[0039] In some embodiments, when the collimated light is emitted by the light source and enters the light input side at an input angle, the collimated light is redirected by the first plurality of redirecting microstructures to a transmission angle substantially matching a light transmission pathway of the liquid crystal display panel. In some embodiments, the collimated light may then be transmitted through the liquid crystal display panel and exit through the light transmitting side. In some such embodiments, the collimated light may be redirected a second time by the second plurality of redirecting microstructures at an output angle which substantially matches the input angle.

[0040] In some embodiments, each redirecting microstructure of at least one of the first plurality of redirecting microstructures and the second plurality of redirecting microstructures may include a second facet disposed at an angle that is substantially orthogonal to the light input side of the liquid crystal display. In some such embodiments, the second facet may include a lightabsorbing cover layer.

[0041] According to some aspects of the present description, a display system may include a liquid crystal display configured to generate an image, and a light source configured to emit a substantially collimated light toward the liquid crystal display. In some embodiments, the liquid crystal display may have a light input side and an opposing light transmitting side, such thatcollimated light emitted by the light source enters the light input side of the liquid crystal display and exits the light transmitting side of the liquid crystal display.

[0042] In some such embodiments, the light transmitting side of the liquid crystal display may have a first plurality of redirecting microstructures, each redirecting microstructure of the first plurality of redirecting microstructures having a first light-transmitting facet disposed at a first angle. In some such embodiments, when the collimated light is emitted by the light source and enters the light input side at an input angle, the collimated light may be transmitted along a light transmission pathway of the liquid crystal display panel. In some embodiments, the collimated light is then transmitted through the liquid crystal display panel and may exit through the light transmitting side. In some embodiments, the collimated light may be redirected by the first plurality of redirecting microstructures at an output angle different from the input angle.

[0043] In some embodiments, each redirecting microstructure of the first plurality of redirecting microstructures may include a second facet disposed at an angle that is substantially orthogonal to the light transmitting side of the liquid crystal display. In some such embodiments, the second facet may include a light absorbing cover layer.

[0044] In other embodiments, the light input side of the liquid crystal display may include a second plurality of redirecting microstructures, and each redirecting microstructure of the second plurality of redirecting microstructures may have a first light-transmitting facet disposed at a second angle. In some such embodiments, the first angle and the second angle may be substantially the same, and, as a result, the output angle may be substantially the same as the input angle.

[0045] In some such embodiments, each redirecting microstructure of at least one of the first plurality of redirecting microstructures and the second plurality of redirecting microstructures (if present) may include a second facet disposed at an angle that is substantially orthogonal to the first side of the light redirecting film. In some such embodiments, the second facet may include a lightabsorbing cover layer.

[0046] According to some aspects of the present description, an optical system includes a display configured to emit an image for viewing by a viewer and including a first display surface, and a light redirecting film having a first side with a first plurality of redirecting microstructures and an opposing second side, and an internal angle-limiting optical component disposed between the first side and the second side.

[0047] In some embodiments, the light redirecting film may be disposed between the first display surface and the viewer. Each redirecting microstructure of the first plurality of redirecting microstructures has a first light-transmitting facet disposed at a first angle and a second facet including a light-absorbing cover layer (e.g., a layer of particles which substantially absorb lightincident on the particles). In some embodiments, the first light-transmitting facet and the second facet meet at a peak in the redirecting microstructure.

[0048] In some embodiments, when light rays are emitted by the first display surface and pass first through the second side of the light redirecting film and are transmitted through the internal angle- limiting optical component and exit the first side of the light redirecting film, a direction of the light rays entering the second side of the light redirecting film is modified (i.e., redirected by the redirecting microstructures on the first side) when the light rays are transmitted by the first side of the light redirecting film for viewing by the viewer.

[0049] Turning now to the figures, FIGS. 1A and IB provide details on an embodiment of a light redirecting film, according to the present description. FIG. 1 A provides a side, cutaway view of light redirecting film 200. Light redirecting film 200 includes a first side 11 with a first plurality of redirecting microstructures 10, an opposing second side 12 with a second plurality of redirecting microstructures 20. In some embodiments, an internal angle-limiting optical component 30 may be disposed between first side 11 and the second side 12.

[0050] In some embodiments, each redirecting microstructure 10 of the first plurality of redirecting microstructures 10 may have a first light-transmitting facet 13a disposed at a first angle 91 relative to first side 11, and a second facet 14a meeting first light-transmitting facet 13a at a peak 15a. In some embodiments, second facet 14a may be disposed such that it is substantially orthogonal to the first side 11.

[0051] In some embodiments, each redirecting microstructure 20 of the second plurality of redirecting microstructures 20 may have a corresponding first light- transmitting facet 13b disposed at a second angle 92, and a second facet 14b meeting first light-transmitting facet 13b at a peak 15b. In some embodiments, second facet 14b may be disposed such that it is substantially orthogonal to the first side 11 (or second side 12).

[0052] In some embodiments, the second facet 14a / 14b of each redirecting microstructure 10 / 20 of at least one of the first plurality of redirecting microstructures 10 and the second plurality of redirecting microstructures 20 may include a light-absorbing cover layer 22. Stated another way, either each of the redirecting microstructures 10 of the first plurality of redirecting microstructures 10 or each of the redirecting microstructures 20 of the second plurality of redirecting microstructures 20, or both, may include a light-absorbing cover layer 22. In some embodiments, the first angle 91 and the second angle 92 may be substantially the same angle, relative to the angle of the first side 11 or second side 12.

[0053] In some embodiments, the internal angle-limiting optical component 30 may be a louver film. In some such embodiments, the louver film 30 may include a plurality of louvers 35 oriented to allow the transmission of light rays substantially parallel to the louvers 30, and toprevent the transmission of an external light passing into the internal optical component at an angle of incidence greater than about 20 (or about 15, or about 10) degrees relative to the orientation of the louvers 30. In some embodiments, the plurality of louvers 35 may be oriented substantially parallel to a thickness direction (e.g., the z-direction shown in FIG. 1A) of the internal anglelimiting optical component 30. In other embodiments, the plurality of louvers 35 may be oriented at an oblique angle to a thickness direction of the internal angle-limiting optical component 30 (depending on the desired optical path of transmission through the internal angle-limiting component 30).

[0054] It should be noted that light redirecting film 200 may include other layers which are shown in FIG. lAbut not labeled. These layers may include layers such as adhesives (e.g., optically clear adhesives), polymeric substrates, and coatings (e.g., a gloss coating). These additional layers may be used to meet other requirements for the film, such as manufacturing needs, but do not affect the general concepts described herein and are therefore not described in detail.

[0055] FIG. IB shows the light redirecting film 200 in a top-down view, with first side 11 facing out from the page. In some embodiments, the first plurality of redirecting microstructures 10 may extend across a width direction of the first side 11 of light redirecting film 200 (e.g., the y- direction of FIG. IB) and may be arranged along a length direction of light redirecting film 200 (e.g., the x-direction of FIG. 1 A). Although not shown here, the second plurality of redirecting microstructures 20 may be arranged in similar fashion long the length direction (x-direction) on the second side 12 of light redirecting film 200 (e.g., with redirecting microstructures 20 on side 12, not shown, substantially parallel to redirecting microstructure 10 on first side 11. See, for example, the alignment of redirecting microstructure 10 / 20 in FIG. 1A). In some embodiments, lightabsorbing cover layer 22 may extend along the second facet 14a (or second facet 14b of second side 12, not shown) in the y-direction, as shown in FIG. IB, substantially covering (e.g., covering at least 70%of) second facet 14a / 14b.

[0056] FIG. 2A shows a typical display system in the prior art. A typical heads-up display (HUD) may include a waveguide 70 (which may include, but not be limited to, a light- transmitting surface of a picture generating unit such as a display) which emits light rays (image rays) 50 toward a surface such as a windshield 80 of a vehicle to be redirected to the eye of a viewer 90 (allowing the viewer 90 to see a virtual image created by image rays 50 projected on windshield 80). However, the angle required for waveguide 70 to properly allow image rays 50 to be reflected toward the eye of the viewer 90 may also allow unwanted external light 60 (e.g., stray sunlight) to be reflected from the surface of waveguide 70 toward the eye of viewer 90, creating unwanted glare and degrading the quality of the virtual image.

[0057] FIG. 2B shows an embodiment of a display system 300 using a light redirecting film according to the present description which addresses the external light issue. A light redirecting film 200 (such as the light redirecting film 200 of FIG. 1 A) is disposed in the optical path of image rays 50 between waveguide 70 and windshield 80. Image rays 50 transmitted by waveguide 70 are first redirected as they pass through redirecting microstructures 20 such that they are substantially parallel to the transmission direction of internal angle-limiting optical component 30. Image rays 50 are thus transmitted through internal angle-limiting optical component 30 and are again redirected by redirecting microstructures 10 to the proper angle for reflecting from windshield 80 to the eye of the viewer 90. Additional details on the redirection of image rays 50 are provided in the discussion of FIG. 3 A elsewhere herein.

[0058] Returning to FIG. 2B, external light 60 passing through windshield 80 is either reflected off of redirecting microstructure 10 (e.g., may be reflected off of the first facet of redirecting microstructures 10, which may be angled to cause external light 60 to be reflected back toward its source or at least away from the optical path to viewer 90. If some of external light 60 manages to pass through redirecting microstructures 10, it may be substantially absorbed by louvers (or other angle-limiting structures) within internal angle-limiting optical component 30. In some embodiments, the louvers may include or be composed of a light-absorbing material, as described elsewhere herein. The light-absorbing cover layer 22 (see, e.g., light- absorbing cover layer 22 on second facets 14a of FIG. 1A) may also substantially absorb external light 60 which is incident upon these surfaces. Each of these described mechanisms may be configured to eliminate or significantly reduced glare and optical effects caused by external light 60, while allowing the transmission of image rays 50 and maintaining or optimizing the quality (e.g., contrast ratio, percent transmission, etc.) of the image rays 50.

[0059] Additional details of the redirecting features of light redirecting film 200 are illustrated in FIG. 3A. Image rays 50 / 50a are emitted by a display or waveguide (such as waveguide 70 of FIG. 2B, not shown here) at an input angle, 9in, and pass through redirecting microstructures 20 on second side 12 of light redirecting film 200. After passing through redirecting microstructures 20, image rays 50 / 50a are redirected to become image rays 50 / 50b transmitting at a new second direction which is substantially parallel to angle-limiting structures (e.g., louvers 35) within the internal angle-limiting optical component 30 (allowing them to be substantially transmitted therethrough). Image rays 50 / 50b then pass through redirecting microstructures 10 on first side 11 of light redirecting film 200, where they are redirected a second time to become image rays 50 / 50c at a new third direction at an output angle, 9out, which is at the proper angle for reflecting from the windshield (or other reflective surface) for viewing by the viewer. In some cases, the angles 9in and 9out are substantially the same angle, such that the direction of travel of image rays 50 / 50a issubstantially the same as the direction of travel of image rays 50 / 50c (i.e., the direction of travel is substantially maintained for image rays 50 before and after passing through light redirecting film 200). It should be noted that, in other embodiments, the angles 9in and Oout may also be different and may be adjusted as needed to meet the transmission and optical path requirements of the optical system. In other, alternate embodiments, the second plurality of redirecting microstructures may be left out of the configuration or may be present but may not have the light-absorbing cover layer on the second facets. These alternate embodiments are discussed in more detail elsewhere herein.

[0060] Also shown in FIG. 3A, external light rays 60 (e.g., sunlight) which encounter the first plurality of redirecting microstructures 10 may be reflected back, or away from the optical path that leads to the eye of the viewer (as also shown in FIG. 2B). In some instances, some portion of the external light 60a may pass through the first plurality of redirecting microstructures 10. In these instances, the transmitted external light 60a may be absorbed by louvers 35 before being passed through to waveguide / display 70.

[0061] FIG. 3B shows an embodiment of a display with light redirecting microstructures, according to the present description. In the embodiment of a light redirecting optical system 200a of FIG. 3B, the internal angle-limiting optical component 30 of the light redirecting film 200 (e.g., that of FIG. 1 A0 is replaced by a liquid crystal display 36. In embodiment 200a, the light redirection is similar to that shown in FIG. 3 A, in that light rays 51 / 5 la from a light source 75 pass through redirecting microstructures 20 on second side 12 of light redirecting optical system 200a, are redirected as light rays 51 / 5 lb through display 36 (in a direction that is substantially orthogonal to display 36, helping to optimize display contrast), pass through display 36 in a direction substantially parallel to the optical transmission axis of display 36, and are then retransmitted in a new output direction as light rays 51 / 51c by redirecting microstructures 10 on first side 11. It should be noted that, as the internal angle-limiting component has been replaced by a display 36, which creates the image to be transmitted for viewing by the viewer, the rays 51 emitted by light source 75 are not yet image rays until they pass through and are selectively transmitted by the individual cells of display 36 (thereby generating the image to be transmitted). The concept of a dual-sided light redirection is preserved in this embodiment, but the location of the picture generating unit (PGU) is internal instead of external. Otherwise, the light-redirecting for the viewer and external light blocking concepts of the embodiment of FIG. 3 A are similar to the embodiment of FIG. 2B.

[0062] FIGS. 4 A and 4B provide details on light redirecting systems which do not include a light absorbing cover layer on facets of the redirecting microstructures. The embodiment of FIG. 4A is similar to the embodiment shown in FIG. 3B, with a display 36 replacing the internal angle-limiting optical component, and without light-absorbing cover layer 22 (see, e.g., light-absorbing cover layer 22 shown in FIG. 3B). In this embodiment of light redirecting system 175, which can still reduce or eliminate unwanted external light (such as sunlight) through reflection from the first light-transmitting facets of redirecting microstructures 10, some light rays 55 from light source 75 may be unintentionally redirected via redirecting microstructures 20 such that they are pass through cells in display 36 for which the light was not intended, creating a ghosting effect on images, such as the checkerboard image illustrated in FIG. 4B. In FIG. 4A, light ray 51 is correctly redirected and passes through display 36 as intended and is transmitted by redirecting microstructures 10 at an angle enabling viewing by the viewer. Light ray 55, however enters through a second facet of a redirecting microstructure 20 and is transmitted at an unintended angle, causing light ray 55 to enter unintended cells of display 36, creating unwanted optical effects. For example, the checkerboard image 150 shown in FIG. 4Amay demonstrate a “ghost” image 152 which can blur or distort the intended displayed image when viewed by the viewer.

[0063] To prevent this ghosting effect, as shown in FIG. 5, light redirecting optical system 200a includes the light- absorbing cover layer 22 on second facets of the redirecting microstructures 20 (and, in some embodiments, also on the second facets of redirecting microstructures 10, as shown in FIG. 5). In this case, light rays 55 from light source 75 are prevented from passing through the second facets of redirecting microstructures 20 by lightabsorbing cover layer 22, and the ghosting issue shown in FIG. 4B is reduced or eliminated entirely.

[0064] Finally, FIGS. 6A and 6B illustrate embodiments of display systems with light redirecting structures on only one side, according to the present description. FIG. 6A shows an embodiment of an optical / display system 305 with a light redirecting film 205 which has redirecting microstructures 10 only on one side of light redirecting film 205 (generally the light transmitting side facing windshield 80). In this embodiment, the direction of image rays 50 emitted by waveguide / display 70 is already configured to pass through the louvers (or other angle-limiting features) of internal angle-limiting optical component 30 (i.e., the image rays 50 are emitted already traveling in a direction substantially parallel to the louvers in optical component 30 and do not need to be redirected on the input side of film 205). The presence of redirecting microstructures 10 on the windshield-facing side of light redirecting film 205 allows for the image rays 50 to be redirected to a new direction corresponding to a proper angle to be reflected from windshield 80 toward the eye of viewer 90, and also to limit or prevent unwanted external light 60 from reaching the waveguide 70.

[0065] FIG. 6B shows a similar one-sided arrangement for a display system 310 with light redirecting optical system 210, which includes display 36 instead of the internal angle-limitingoptical component 30 of the embodiment of FIG. 6A. Similar to the embodiment of FIG. 6A, light rays 51 are emitted by light source 75 in a direction already configured to be transmitted through the display 36 (i.e., selectively transmitted by display 36 to generate an image), and the light / image rays 51 are then redirected to a new second direction upon transmission by light redirecting optical system 210 and the corresponding redirection via redirecting microstructures 10. External light 60 is substantially reduced or eliminated by the combination of the angle of the first facets of redirecting microstructures 10, light-absorbing cover layer 22 on the second facets, and the anglelimiting abilities of the individual cells in display 36.

[0066] It should be noted that variations on the embodiments described or shown in the figures herein are possible and within the scope of the present description. For example, in one alternate embodiment of the light redirecting film 200 (as shown in FIG. 1 A), the light-absorbing cover layer 22 may only be present on either first side 11 of film 200 or second side 12 of film 200, but not on both. That is, the light-absorbing cover layer 22 may not be necessary on both the first plurality of redirecting microstructures 10 and the second plurality of redirecting microstructures 20, depending on the requirements of the optical system. Other alternate embodiments may also be within the scope of the present description.

[0067] Terms such as “about” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “about” as applied to quantities expressing feature sizes, amounts, and physical properties is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “about” will be understood to mean within 10 percent of the specified value. A quantity given as about a specified value can be precisely the specified value. For example, if it is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, a quantity having a value of about 1, means that the quantity has a value between 0.9 and 1.1, and that the value could be 1.

[0068] Terms such as “substantially” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “substantially equal” is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “substantially equal” will mean about equal where about is as described above. If the use of “substantially parallel” is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “substantially parallel” will mean within 30 degrees of parallel. Directions or surfaces described as substantially parallel to one another 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 otherwise clear to one of ordinary skill in the art in the context inwhich it is used and described in the present description, “substantially aligned” will mean aligned to within 20% of a width of the objects being aligned. Objects described as substantially aligned may, in some embodiments, be aligned to within 10% or to within 5% of a width of the objects being aligned.

[0069] All references, patents, and patent applications referenced in the foregoing are hereby incorporated herein by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description shall control.

[0070] Descriptions for elements in figures should be understood to apply equally to corresponding elements in other figures, unless indicated otherwise. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and / or equivalent implementations can be substituted for the specific embodiments shown and described 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. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.

Claims

What is claimed:

1. An optical system comprising: a display configured to emit an image for viewing by a viewer and including a first display surface; and a light redirecting film comprising a first side with a first plurality of redirecting microstructures, an opposing second side with a second plurality of redirecting microstructures, and an internal angle-limiting optical component disposed between the first side and the second side; wherein the light redirecting film is disposed between the first display surface and the viewer, wherein each redirecting microstructure of the first plurality of redirecting microstructures has a first light-transmitting facet disposed at a first angle, each redirecting microstructure of the second plurality of redirecting microstructures has a corresponding first light-transmitting facet disposed at a second angle; such that when light rays are emitted by the first display surface and pass first through the second side of the light redirecting film and are transmitted through the internal angle-limiting optical component and exit the first side of the light redirecting film, a direction of the light rays entering the second side of the light redirecting film is substantially preserved when the light rays are transmitted by the first side of the light redirecting film for viewing by the viewer.

2. The optical system of claim 1, wherein the internal angle-limiting optical component comprises a louver film, the louver film comprising a plurality of louvers oriented to allow the transmission of light rays substantially parallel to the louvers and to prevent the transmission of an external light from reaching the first display surface.

3. The optical system of claim 2, wherein each louver of the plurality of louvers comprises a light absorbing material.

4. The optical system of claim 1, wherein each redirecting microstructure of at least one of the first plurality of redirecting microstructures and the second plurality of redirecting microstructures comprises a second facet disposed at an angle that is substantially orthogonal to the first side of the light redirecting film.

5. The optical system of claim 1, wherein each redirecting microstructure of at least one of the first plurality of redirecting microstructures and the second plurality of redirecting microstructures comprises a second facet, the second facet comprising a light-absorbing cover layer.

6. The optical system of claim 1, wherein the first angle and the second angle are substantially the same.

7. A light redirecting film comprising a first side with a first plurality of redirecting microstructures, an opposing second side with a second plurality of redirecting microstructures, and an internal angle-limiting optical component disposed between the first side and the second side; wherein each redirecting microstructure of the first plurality of redirecting microstructures has a first light-transmitting facet disposed at a first angle, each redirecting microstructure of the second plurality of redirecting microstructures has a corresponding first light-transmitting facet disposed at a second angle, wherein the first angle and the second angle are substantially the same; such that when light rays enter the second side of the light redirecting film and are transmitted through the internal angle-limiting optical component and exit the first side of the light redirecting film, a direction of the light rays entering the second side of the light redirecting film is substantially preserved when the light rays are transmitted by the first side of the light redirecting film for viewing by the viewer.

8. The light redirecting film of claim 7, wherein the internal angle-limiting optical component limits the transmission of light therethrough to a predetermined angular range relative to a thickness direction of the internal angle-limiting optical component.

9. The light redirecting film of claim 8, wherein the internal angle-limiting optical component comprises a louver film, the louver film comprising a plurality of louvers oriented to allow the transmission of light rays substantially parallel to the louvers and to prevent the transmission of an external light passing into the internal optical component at an angle of incidence greater than about 20 degrees relative to the orientation of the louvers.

10. The light redirecting film of claim 9, wherein the plurality of louvers are oriented substantially parallel to a thickness direction of the internal angle-limiting optical component.

11. The light redirecting film of claim 9, wherein the plurality of louvers are oriented at an oblique angle to a thickness direction of the internal angle-limiting optical component.

12. The light redirecting film of claim 7, wherein each redirecting microstructure of at least one of the first plurality of redirecting microstructures and the second plurality of redirecting microstructures comprises a second facet disposed at an angle that is substantially orthogonal to the first side of the light redirecting film.

13. The optical system of claim 7, wherein each redirecting microstructure of at least one of the first plurality of redirecting microstructures and the second plurality of redirecting microstructures comprises a second facet, the second facet comprising a light-absorbing cover layer.

14. An optical system comprising: a display configured to emit an image for viewing by a viewer and including a first display surface; and a light redirecting film comprising a first side with a first plurality of redirecting microstructures and an opposing second side, and an internal angle-limiting optical component disposed between the first side and the second side; wherein the light redirecting film is disposed between the first display surface and the viewer, wherein each redirecting microstructure of the first plurality of redirecting microstructures has a first light-transmitting facet disposed at a first angle and a second facet comprising a lightabsorbing cover layer, the first light-transmitting facet and the second facet meeting at a peak in the redirecting microstructure; such that when light rays are emitted by the first display surface and pass first through the second side of the light redirecting film and are transmitted through the internal angle-limiting optical component and exit the first side of the light redirecting film, a direction of the light rays entering the second side of the light redirecting film is modified when the light rays are transmitted by the first side of the light redirecting film for viewing by the viewer.

15. The optical system of claim 14, wherein the internal angle-limiting optical component comprises a louver film, the louver film comprising a plurality of louvers oriented to allow the transmission of light rays substantially parallel to the louvers and to prevent the transmission of an external light from reaching the first display surface.

16. The optical system of claim 15, wherein each louver of the plurality of louvers comprises a light absorbing material.

Images