Optical system and head-up display system

Abstract

The optical system comprises a display system including a display having first and second display pixels interspersed with each other on the display. The first and second display pixels emit different, overlapping first and second images polarized along a first direction. The display system includes a patterned retarder having a plurality of first and second retarder pixels aligned and positioned in one-to-one correspondence with the first and second display pixels, respectively. The first retarder pixel is configured to receive the first emitted image and transmit the first emitted image as a first output image polarized along the first direction. The second retarder pixel is configured to receive the second emitted image, change the polarization direction, and transmit the second emitted image as a second output image polarized along a second direction. The reflective polarizer is configured to receive the first and second output images and substantially transmit the first output image and substantially reflect the second output image.

Description

[Technical field]

[0001] The present disclosure relates generally to optical systems, and more particularly to optical systems that display virtual first and second output images for viewing by a viewer, and to head-up display systems that include the optical systems. [Background technology]

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

[0003] Some aspects of the present disclosure relate to an optical system including a display system. The display system is configured to output a first output image polarized along a first direction and a second output image polarized along an orthogonal second direction. The display system includes a display having a plurality of first and second display pixels interspersed with each other on the display. The first and second display pixels are configured to emit different respective first and second images polarized along the first direction in superimposed relation. The display system also includes a retarder disposed on the display. The retarder includes a plurality of first and second retarder pixels aligned and registered in one-to-one correspondence with the first and second display pixels, respectively. The first retarder pixel is configured to receive the first outgoing image, not change the polarization direction of the first outgoing image, and transmit the first outgoing image as a first output image polarized along the first direction. The second retarder pixel is configured to receive the second outgoing image, change a polarization direction of the second outgoing image from the first direction to the second direction, and transmit the second outgoing image as a second output image polarized along the second direction. The optical system includes a reflective polarizer configured to receive the first output image and the second output image, substantially transmit the first output image, and substantially reflect the second output image.

[0004] Some other aspects of the present disclosure relate to a head-up display that includes an optical system that displays a first output image and a second output image for viewing by an observer. [Brief description of the drawings]

[0005] Various aspects of the disclosure will now be discussed in more detail with reference to the accompanying drawings. [Figure 1] 1 illustrates a schematic diagram of an optical system according to some embodiments of the present disclosure. [Diagram 2] 1 illustrates a schematic diagram of a retarder pixel and a corresponding display pixel according to some aspects of the present disclosure. [Diagram 3] 1 illustrates a schematic of a reflective polarizer structure according to some aspects of the present disclosure. [Figure 4] 1 illustrates a schematic diagram of a head-up display system including an optical system, according to some embodiments.

[0006] The figures are not necessarily drawn to scale. Like numbers used in the figures refer to like components. However, it will be understood that the use of a number to refer to a component in a particular figure is not intended to limit the component in another figure bearing the same number. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0008] The embodiments of the present disclosure describe systems and methods that use a single imager to create two virtual images in two different image planes, either with the same or orthogonal polarization states. In some aspects, a patterned retarder can be aligned to the image-forming pixels on an LCD imager to generate two interleaved images with orthogonal polarizations. The two interleaved images are then separated into two paths, for example, using a high-contrast reflective polarizer. The polarization of the second path image can be converted to the polarization of the first path image through a quarter-wave layer added to the mirror in the second path.

[0009] Some embodiments will now be described with reference to Figures 1-3. As shown in Figure 1, an optical system (300) includes a display system (200) having a display (100). The display system (200) is configured to output a first output image (50) and a second output image (51). The first output image (50) may be polarized along a first direction (x-axis) and the second output image (51) may be polarized along an orthogonal second direction (y-axis).

[0010] The display (100) includes a plurality of first display pixels (10) and second display pixels (11) interspersed with one another on the display (100). The first display pixels (10) and second display pixels (11) may be configured to emit different respective first and second images (20) and (21) polarized along a first direction (x-axis). The emitted first and second images (20) and (21) may be superimposed on one another. For example, the optical system (300) superimposes the first image (20) propagating through a first optical path and the second image (21) propagating through a second optical path. The optical path length (L) of the second optical path is 100 nm. B ) is the optical path length of the first optical path (L A ) may be different from the optical path length (L B ) is the optical path length of the first optical path (L A ) may be longer than

[0011] In some embodiments, the display (100) may be, for example, a liquid crystal display (LCD) panel. The LCD panel (100) may be a monochrome type without a color filter, or a color type with RGB pixels. However, the LCD panel (100) according to the present disclosure is not limited to these types. The LCD panel (100) can receive light emitted from a backlight unit (not shown) and generate a first image and a second image. The LCD panel (100) may be a general LCD panel, such as a TTF liquid crystal monitor employing active matrix technology or the like. The LCD panel (100) may include a polarizing filter for absorbing light polarized in one direction and a liquid crystal layer for rotating the polarization direction. In the illustrated embodiment, the first and second image lights carrying the first image (20) and the second image (21) emitted by the first display pixel (10) and the second display pixel (11) of the LCD panel (100) are polarized in the same (first) direction (x-axis).

[0012] In other examples, the display (100) may include an emissive microdisplay, such as an organic light emitting device (OLED) display, and / or a reflective microdisplay, such as a liquid crystal on silicon (LCoS) display or a digital light processing (DLP) device. The display (100) may have any suitable position relative to other optical components. In other embodiments, the display (100) may be a projection display.

[0013] In some embodiments, the display system (200) includes a retarder (30) disposed on the display (100). The retarder (30) includes a retarder pixel. In some embodiments, the retarder pixel includes a plurality of first retarder pixels (40) and second retarder pixels (41). As best shown in FIG. 2, the first retarder pixels (40) are aligned in register with the first display pixels (10), and the second retarder pixels (41) are aligned in one-to-one correspondence with the second display pixels (11). In some aspects, the retarder layer (30) may include a patterned retarder aligned in register with the display pixels on the LCD imager (100). Patterned retarders are described elsewhere in WO 2018 / 151761 (Wheatley et al.) and WO 2019 / 082106 (Etter, Jo A. et al.). A wide variety of patterned polymer retarders can be formed using a combination of coating steps, application of masks and etching steps. The patterned retarder thus formed may be applied onto the surface of the display (100), or may be applied and further formed onto the surface of the display pixels (10, 11).

[0014] In some embodiments, the first retarder pixel (40) may be a zero or full wave retarder and the second retarder pixel (41) may be a half wave retarder. As shown in FIG. 2, the first retarder pixel (40) may be formed to be twice as thick as the second retarder pixel (41). For example, different thicknesses of the retarder pixels may be obtained by forming multiple retarder pixels having a thickness equal to that of the first retarder pixel (40) and then etching some pixels using photolithography or other similar techniques to obtain the thickness of the second retarder pixel (41).

[0015] According to one embodiment, the first retarder pixel (40) is configured to receive the first outgoing image (20) and transmit the first outgoing image (20) as a first output image (50) without changing the polarization direction of the first outgoing image (20). In some aspects, the first outgoing image (20) may be polarized along a first direction (x-axis), and the first output image (50) transmitted by the first retarder pixel (40) may also be polarized along the first direction (x-axis).

[0016] The second retarder pixel (41) is configured to receive the second outgoing image (21) and transmit it by changing the polarization direction of the second outgoing image (21). In some embodiments, the second outgoing image (21) may be polarized along a first direction (x-axis), and the second retarder pixel (41) changes the polarization of the second outgoing image (21) from the first direction (x-axis) to a second direction (y-axis) and transmits the second outgoing image (21) as a second output image (51) polarized along the second direction (y-axis).

[0017] For example, in some embodiments, approximately half of the retarder pixels are configured to transmit a first outgoing image (20) as a first output image (50) polarized along a first direction (x-axis), and approximately half of the retarder pixels are configured to change the polarization and transmit a second outgoing image (21) as a second output image (51) polarized along a second direction (y-axis).

[0018] In some embodiments, the optical system (300) includes a reflective polarizer (60). The pixelated output from the display system (200) with orthogonal polarization states is directed to the reflective polarizer (60). Reflective polarizers generally include a material that transmits light of a first polarization and reflects light of a second, different polarization. Examples of reflective polarizers include, but are not limited to, diffusely reflective polarizers, multilayer reflective polarizers, and cholesteric reflective polarizers. The reflective polarizer (60) may be a broadband reflective polarizer or a notch reflective polarizer. In other examples, the reflective polarizer (60) may be one or more of an absorbing linear polarizer, a multilayer polymeric reflective polarizer, or a stack of reflective polarizers, which substantially transmits light with a first polarization state and substantially reflects light with an orthogonal second polarization state. A substantially uniaxially oriented reflective polarizer is available from 3M Company under the tradename Advanced Polarizing Film 5 or APF. Other types of multilayer optical film reflective polarizers (e.g., Dual Brightness Enhancement Film or DBEF, available from 3M Company) may also be used. Other types of reflective polarizers (e.g., wire grid polarizers) may also be used.

[0019] According to certain embodiments, the reflective polarizer (60) may include a plurality of alternating first polymer layers (61) and second polymer layers (62), as shown in Figure 3. The number of the plurality of polymer layers may be at least 50, at least 100, at least 150, or at least 200 in total. Each of the first polymer layers (61) and second polymer layers (62) may have an average thickness of less than about 500 nm, less than about 450 nm, or less than about 400 nm. In some cases, the first polymer layers and second polymer layers may be stacked with alternating isotropic and anisotropic layers. Reflective films (e.g., reflective polarizers) comprising multiple polymer layers are described, for example, in U.S. Patent Nos. 5,882,774 (Jonza et al.), 6,179,948 (Merrill et al.), and 6,783,349 (Neavin et al.), each of which is incorporated herein by reference to the extent not inconsistent therewith. In some embodiments, the polymer layer comprises one or more of polycarbonate, polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), glycol-modified polyethylene terephthalate (PETG), polyethylene naphthalate (PEN), and PEN / PET copolymers.

[0020] In some embodiments, the reflective polarizer (60) may include skin layers (63, 64) disposed on the opposing top and bottom surfaces of a plurality of alternating first and second polymer layers (61, 62). The skin layers (63, 64) may have a thickness greater than about 1 micrometer. In some cases, the thickness of the core polymer layer may be about 10 to 300 micrometers, and the thickness of the skin layers may be, but is not limited to, 50 to 200 micrometers. The skin layers and the core polymer layer may be bonded together using an adhesive. The skin layers (63, 64) may be made of, for example, polycarbonate or polycarbonate alloy, polyethylene terephthalate (PET), polystyrene (PS), or a combination thereof.

[0021] In some embodiments, the output of one set of retarder pixels may be transmitted from the reflective polarizer (60), while the output of the other set of retarder pixels may be reflected from the reflective polarizer (60). For example, as seen in FIG. 1, the reflective polarizer (60) may be configured to receive the first output image (50) and the second output image (51) transmitted by the respective first retarder pixel (40) and second retarder pixel (41), and to substantially transmit the first output image (50) and substantially reflect the second output image (51). In the illustrated embodiment, the reflective polarizer (60) transmits the first output image (50) along a third direction (z-axis) orthogonal to the first direction (x-axis) and the second direction (y-axis), and reflects the second output image (51) along the first direction (x-axis).

[0022] In some aspects, the reflective polarizer (60) can be said to substantially transmit the first output image (50) polarized along the first direction (x-axis) if at least 60% of the first output image (50) is transmitted from the reflective polarizer (60). In some aspects, at least 70%, at least 80%, or at least 90% of the first output image (50) can be transmitted from the polarizer (60). The reflective polarizer (60) can be said to substantially reflect the second output image (51) having a second orthogonal polarization state (y-axis) if at least 60% of the second output image (51) is reflected from the reflective polarizer (60). In some embodiments, at least 70%, at least 80%, or at least 90% of the second output image (51) having an orthogonal polarization state is reflected from the polarizer (60).

[0023] In some embodiments, the optical system (300) may include a mirror (70) configured to receive and reflect the second output image (51) having a polarization in an orthogonal second direction (y-axis) and reflected by the reflective polarizer (60). In some aspects, the second retarder (80) is disposed between the reflective polarizer (60) and the mirror (70). In some embodiments, the second retarder (80) may be a quarter-wave retarder. In the illustrated embodiment, light carrying the second output image (51) having a polarization in the second direction (y-axis) passes through the quarter-wave retarder (80) and a substantial portion of the light is reflected by the mirror (70). For example, the mirror may be a highly reflective mirror having a reflectivity of more than 99.5%. The light reflected by the mirror (70) passes through the quarter-wave retarder (80), which converts the light polarized in the second direction (y-axis) to light polarized in the first direction (x-axis). This double pass of light carrying the second output image (51) through the quarter wave retarder (80) transforms the polarization state of the second output image (51) to have the same polarization state as the first output image (50).

[0024] In a particular embodiment, the second retarder (80) may be a film laminated on the reflective polarizer (60) or a coating applied to the reflective polarizer (60). For example, the second retarder layer (80) may be an oriented polymer film laminated on the reflective polarizer (60) or a liquid crystal polymer coating on the reflective polarizer (60). Suitable coatings for forming a quarter-wave retarder include, but are not limited to, linear photopolymerizable polymer (LPP) materials and liquid crystal polymer (LCP) materials as described elsewhere.

[0025] Here, L A is the optical path length of the first optical path for generating image A, L B is the optical path length of the second optical path for generating image B, f is the focal length of the mirror (70), L A <L B <f implies that both image A and image B generated by the optical system (300) are virtual images, and image B has a longer virtual image distance (VID). The different distances of the optical paths L A and the optical path L B from the mirror focal length generate a near-field virtual image and a far-field virtual image, respectively.

[0026] Referring to FIG. 4, a head-up display (HUD) system (400) includes an optical system (300). The optical system (300) has been previously described with reference to FIGS. 1-3. The HUD system (400) displays a virtual image generated by the first output image (50) and the second output image (51) for viewing by an observer (90). The HUD system (400) may be a HUD in a vehicle, and the observer (90) may be an occupant of the vehicle. In some embodiments, the HUD in a vehicle (400) may include a windshield (110) of the vehicle. An output image including both a near-field image and a far-field image from the optical system (300) may be displayed on the windshield (110) for viewing by the observer (90). The HUD (400) may be configured to display one or more of vehicle operation information, such as vehicle speed, navigation information, such as directions and / or maps, surrounding information, such as temperature, communication information, such as radio station or track listings, caller information, and restrictions, such as road sign information or effective speed limits.

[0027] While specific embodiments have been illustrated and described herein, those skilled in the art will recognize that the specific embodiments illustrated and described may be replaced by various alternative and / or equivalent embodiments without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Accordingly, it is intended that the present disclosure be limited only by the claims and the equivalents thereof. In addition to the respective embodiments, the following aspects are noted. (Appendix 1) 1. A display system configured to output a first output image polarized along a first direction and a second output image polarized along an orthogonal second direction, comprising: a display including a plurality of first and second display pixels interspersed with one another on the display, the first and second display pixels configured to emit superimposed distinct first and second images polarized along the first direction; a retarder disposed on the display and including a plurality of first and second retarder pixels aligned in one-to-one correspondence with the first and second display pixels, respectively, wherein the first retarder pixels are configured to receive the first outgoing image, not change a polarization direction of the first outgoing image, and transmit the first outgoing image as the first output image polarized along the first direction, and the second retarder pixels are configured to receive the second outgoing image, change the polarization direction of the second outgoing image from the first direction to the second direction, and transmit the second outgoing image as the second output image polarized along the second direction; A display system comprising: a reflective polarizer configured to receive the first output image and the second output image, to substantially transmit the first output image, and to substantially reflect the second output image; An optical system comprising: (Appendix 2) 2. The optical system of claim 1, wherein the reflective polarizer transmits at least 80% of the first output image and reflects at least 80% of the second output image. (Appendix 3) 2. The optical system of claim 1, wherein the reflective polarizer transmits the first output image along a third direction perpendicular to the first direction and the second direction, and reflects the second output image along the first direction. (Appendix 4) 2. The optical system of claim 1, wherein the first retarder pixel is a zero or full-wave retarder and the second retarder pixel is a half-wave retarder. (Appendix 5) 2. The optical system of claim 1, wherein the first retarder pixel is twice as thick as the second retarder pixel. (Appendix 6) 2. The optical system of claim 1, further comprising: a mirror configured to receive and reflect the second output image reflected by the reflective polarizer; and a second retarder disposed between the reflective polarizer and the mirror. (Appendix 7) 7. The optical system of claim 6, wherein the second retarder is a quarter wave retarder. (Appendix 8) 2. The optical system of claim 1, wherein the reflective polarizer comprises a plurality of alternating first and second polymer layers, a total of at least 50, each of the first and second polymer layers having an average thickness of less than about 500 nm, and the reflective polarizer further comprises skin layers disposed on opposite upper and lower surfaces of the plurality of alternating first and second polymer layers, the skin layers having a thickness of greater than about 1 micrometer. (Appendix 9) 2. A head-up display comprising the optical system of claim 1, the head-up display displaying the first output image and the second output image for viewing by an observer. (Appendix 10) 10. A head-up display as described in claim 9, wherein the head-up display is a head-up display in a vehicle, the observer is a passenger of the vehicle, and the head-up display includes a windshield of the vehicle.

Claims

1. 1. A display system configured to output a first output image polarized along a first direction and a second output image polarized along an orthogonal second direction, comprising: a display including a plurality of first and second display pixels interspersed with one another on the display, the first and second display pixels configured to emit different respective first and second images polarized along the first direction; a retarder disposed on the display and including a plurality of first and second retarder pixels aligned in one-to-one correspondence with the first and second display pixels, respectively, wherein the first retarder pixels are configured to receive the first image, not change a polarization direction of the first image, and transmit the first image as the first output image polarized along the first direction, and the second retarder pixels are configured to receive the second image, change the polarization direction of the second image from the first direction to the second direction, and transmit the second image as the second output image polarized along the second direction; A display system comprising: a reflective polarizer configured to receive the first output image and the second output image, to substantially transmit the first output image, and to substantially reflect the second output image; Equipped with the reflective polarizer transmits at least 80% of the first output image and reflects at least 80% of the second output image; an optical system, wherein the reflective polarizer transmits the first output image along a third direction orthogonal to the first direction and the second direction, and reflects the second output image along the first direction.

2. A display system configured to output a first output image polarized along a first direction and a second output image polarized along an orthogonal second direction, comprising: a display including a plurality of first and second display pixels interspersed with one another on the display, the first and second display pixels configured to emit different respective first and second images polarized along the first direction; a retarder disposed on the display and including a plurality of first and second retarder pixels aligned in one-to-one correspondence with the first and second display pixels, respectively, wherein the first retarder pixels are configured to receive the first image, not change a polarization direction of the first image, and transmit the first image as the first output image polarized along the first direction, and the second retarder pixels are configured to receive the second image, change the polarization direction of the second image from the first direction to the second direction, and transmit the second image as the second output image polarized along the second direction; A display system comprising: a reflective polarizer configured to receive the first output image and the second output image, to substantially transmit the first output image, and to substantially reflect the second output image; Equipped with a mirror configured to receive and reflect the second output image reflected by the reflective polarizer; and a second retarder disposed between the reflective polarizer and the mirror; The optical system wherein the second retarder is a quarter wave retarder.

3. the first retarder pixel is a zero or full wave retarder and the second retarder pixel is a half wave retarder; 3. The optical system of claim 1, wherein the first retarder pixel is twice as thick as the second retarder pixel.

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