Optical system and heads up display

Abstract

An optical system includes a display panel, a first mirror, and a second mirror. For a substantially collimated incident light and a visible wavelength range extending from 420 nm to 680 nm, for a first incident angle of less than 10 degrees, the first mirror has an average optical transmittance of greater than 65% for a first polarization state, an average optical reflectance of greater than 80% for an orthogonal second polarization state, and an average optical transmittance of less than 0.1% for the second polarization state, and the second mirror has an average optical reflectance of at least 30% for at least one of the first and second polarization states. For the second polarization state, the average optical transmittance of the first mirror decreases when the incident angle increases from the first incident angle to a second incident angle greater than 20 degrees.

Description

PA102836W002OPTICAL SYSTEM AND HEADS UP DISPLAYTechnical Field

[0001] The present disclosure relates to an optical system, and a heads up display for use in a vehicle.Background

[0002] Display systems, for example, display systems which are used outdoors, may be exposed to temperatures which may damage one or more components of the display systems and / or negatively impact a performance of the display systems. Another example of such display systems is a heads up display system, which is widely used inside vehicles for displaying information for its occupants.

[0003] Therefore, improved solutions may be desired for managing temperatures of such display systems to protect them from damage.Summary

[0004] In a first aspect, the present disclosure provides an optical system. The optical system includes a display panel configured to emit an image light. The optical system further includes a first mirror configured to receive the emitted image light at a first oblique incident angle and reflect the received emitted image light as a first reflected image light. The optical system further includes a second mirror configured to receive the first reflected image light at a second oblique incident angle and reflect the first reflected image light as a second reflected image light for viewing by a viewer. For a substantially collimated incident light and a visible wavelength range extending from about 420 nanometers (nm) to about 680 nm, for a first incident angle of less than about 10 degrees, the first mirror has an average optical transmittance of greater than about 65% for a first polarization state, an average optical reflectance of greater than about 80% for an orthogonal second polarization state, and an average optical transmittance of less than about 0.1% for the second polarization state, and the second mirror has an average optical reflectance of at least 30% for at least one of the first and second polarization states. For the second polarization state, the average optical transmittance of the first mirror decreases when the incident angle increases from the first incident angle to a second incident angle of greater than about 20 degrees.

[0005] In a second aspect, the present disclosure provides a heads-up display (HUD) for use in a vehicle. The HUD includes a display panel configured to emit a polarized image light. The HUD further includes a reflective polarizer and a second mirror, such that the emitted polarized image light propagates toward an occupant of the vehicle after being reflected first by the reflective polarizer and then by the second mirror. For a substantially collimated incident light, and for each of a blue wavelength range extending from about 420 nm to about 470 nm, a green wavelength range extending from about 500 nm to about 560 nm, and a red wavelength range extending from about 630 nm toabout 680 nm, for a first incident angle of less than about 10 degrees, the first mirror has an average optical transmittance of greater than about 65% for a first polarization state, an average optical reflectance of greater than about 80% for an orthogonal second polarization state, and an average optical transmittance of less than about 0.1% for the second polarization state, and the second mirror has an average optical reflectance of at least 30% for at least one of the first and second polarization states. For the second polarization state and the first incident angle, a plot of an optical transmittance of the reflective polarizer as a function of wavelength includes a band edge along which the optical transmittance increases by at least 40% when the wavelength increases by less than about 100 nm. A mid-point of the band edge is at a mid-point wavelength of less than about 830 nm. A best linear fit to the band edge has a positive slope that increases when the incident angle increases from the first incident angle to a second incident angle of greater than about 20 degrees.

[0006] In a third aspect, the present disclosure provides an optical system. The optical system includes a display panel configured to emit an image light. The optical system further includes an illumination source including a plurality of light sources for providing illumination to the display panel. The optical system further includes a reflective polarizer disposed between the illumination source and the display panel. For a substantially collimated substantially normally incident light and a visible wavelength range extending from about 420 nm to about 680 nm, for a first incident angle of less than about 10 degrees, the reflective polarizer has an average optical transmittance of greater than about 65% for a first polarization state, an average optical reflectance of greater than about 80% for an orthogonal second polarization state, and an average optical transmittance of less than about 0.1% for the second polarization state. For the second polarization state, the average optical transmittance of the reflective polarizer decreases when the incident angle increases from the first incident angle to a second incident angle of greater than about 20 degrees.

[0007] The details of one or more examples of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims.Brief Description of the Drawings

[0008] Exemplary embodiments disclosed herein may be more completely understood in consideration of the following detailed description in connection with the following figures. 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 given figure is not intended to limit the component in another figure labeled with the same number.

[0009] FIG. 1 shows a schematic view of an optical system, according to an embodiment of the present disclosure;

[0010] FIG. 2 shows a schematic view of a display panel, according to an embodiment of the present disclosure;

[0011] FIG. 3 shows a schematic view of curved first and second mirrors, according to an embodiment of the present disclosure;

[0012] FIG. 4 shows a schematic view of a vehicle, according to an embodiment of the present disclosure;

[0013] FIG. 5 A shows a schematic sectional view of a first mirror, a second mirror, and a third mirror, according to another embodiment of the present disclosure;

[0014] FIG. 5B shows a detailed schematic sectional view of the first mirror and the second mirror, according to an embodiment of the present disclosure;

[0015] FIG. 6 shows a graph depicting an optical transmission versus wavelength of the first mirror, for a substantially collimated incident light incident at a first incident angle, and for a first polarization state, according to an embodiment of the present disclosure;

[0016] FIG. 7 A shows a graph depicting an optical transmission versus wavelength of the first mirror, for the substantially collimated incident light incident at the first incident angle, and for a second polarization state, according to an embodiment of the present disclosure;

[0017] FIG. 7B shows a magnified graph depicting the optical transmission versus wavelength of the first mirror, for the substantially collimated incident light incident at the first incident angle, and for the second polarization state, according to an embodiment of the present disclosure;

[0018] FIG. 8A shows a graph depicting an optical transmission versus wavelength of the first mirror, for the substantially collimated incident lights incident at respective first and second incident angles, and for the second polarization state, according to an embodiment of the present disclosure;

[0019] FIG. 8B shows a magnified graph depicting the optical transmission versus wavelength of the first mirror, for the substantially collimated incident lights incident at the respective first and second incident angles, and for the second polarization state, according to an embodiment of the present disclosure;

[0020] FIG. 9 shows a graph depicting best linear fits to continuous portions of band edges of respective plots of average optical transmittances, for the respective first and second incident angles, according to an embodiment of the present disclosure.

[0021] FIG. 10 shows a schematic view of an optical system, according to another embodiment of the present disclosure;

[0022] FIG. 11A shows a graph depicting maximum display temperature versus time for the first mirror and a comparative film, according to an embodiment of the present disclosure; and

[0023] FIG. 11B shows a magnified graph depicting maximum display temperature versus time for the first mirror and the comparative film, according to an embodiment of the present disclosure.Detailed Description

[0024] In the following description, reference is made to the accompanying figures that form a part thereof and in which various embodiments are shown by way of illustration. It is to beunderstood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense.

[0025] In the following disclosure, the following definitions are adopted.

[0026] As used herein, all numbers should be considered modified by the term “about”. As used herein, “a,” “an,” “the,” “at least one,” and “one or more” are used interchangeably.

[0027] As used herein as a modifier to a property or attribute, the term “generally”, unless otherwise specifically defined, means that the property or attribute would be readily recognizable by a person of ordinary skill but without requiring absolute precision or a perfect match (e.g., within + / - 20 % for quantifiable properties).

[0028] The term “substantially”, unless otherwise specifically defined, means to a high degree of approximation (e.g., within + / - 10% for quantifiable properties) but again without requiring absolute precision or a perfect match.

[0029] The term “about”, unless otherwise specifically defined, means to a high degree of approximation (e.g., within + / - 5% for quantifiable properties) but again without requiring absolute precision or a perfect match.

[0030] As used herein, the terms “first” and “second” are used as identifiers. Therefore, such terms should not be construed as limiting of this disclosure. The terms “first” and “second” when used in conjunction with a feature or an element can be interchanged throughout the embodiments of this disclosure.

[0031] As used herein, “at least one of A and B” should be understood to mean “only A, only B, or both A and B”.

[0032] Display systems, for example, display systems which are used outdoors, may be exposed to temperatures which may damage one or more components of the display systems and / or negatively impact a performance of the display systems. Another example of such display systems is a heads up display system, which is widely used inside vehicles for displaying information for its occupants.

[0033] Therefore, improved solutions may be desired for managing temperatures of such display systems to protect them from damage.

[0034] The present disclosure relates to an optical system. The optical system includes a display panel configured to emit an image light. The optical system further includes a first mirror configured to receive the emitted image light at a first oblique incident angle and reflect the received emitted image light as a first reflected image light. The optical system further includes a second mirror configured to receive the first reflected image light at a second oblique incident angle and reflect the first reflected image light as a second reflected image light for viewing by a viewer. For a substantially collimated incident light and a visible wavelength range extending from about 420 nanometers (nm) to about 680 nm, for a first incident angle of less than about 10 degrees, the first mirror has an average optical transmittance of greater than about 65% for a first polarization state, anaverage optical reflectance of greater than about 80% for an orthogonal second polarization state, and an average optical transmittance of less than about 0.1% for the second polarization state, and the second mirror has an average optical reflectance of at least 30% for at least one of the first and second polarization states. For the substantially collimated incident light and the visible wavelength range: for the second polarization state, the average optical transmittance of the first mirror decreases when the incident angle increases from the first incident angle to a second incident angle of greater than about 20 degrees.

[0035] The first mirror of the optical system may therefore substantially block the substantially collimated incident light for the first incident angle, and for the second polarization state. Moreover, since for the second polarization state, the average optical transmittance of the first mirror decreases when the incident angle increases from the first incident angle to the second incident angle, the first mirror may further block the substantially collimated incident light having the second polarization state and incident at greater oblique angles (i.e., greater than about 20 degrees). Therefore, the optical system of the present disclosure including the first mirror may protect one or more components of the optical system (e.g., the display panel) from an external light from an external light source external to the optical system.

[0036] Referring now to figures, FIG. 1 shows a schematic view of an optical system 300, according to an embodiment of the present disclosure.

[0037] The optical system 300 includes a display panel 10 configured to emit an image light 11. In some embodiments, the display panel 10 includes an organic light emitting diode (OLED) display panel. In some embodiments, the display panel 10 includes a liquid crystal display (LCD) panel.

[0038] In some embodiments, the optical system 300 may be a heads up display (HUD) and may be interchangeably referred to as “the HUD 300” herein. In some embodiments, the HUD 300 includes the display panel 10. In some embodiments, the emitted image light 11 may polarized and may be interchangeably referred to as “the polarized image light 11” herein. In such cases, the display panel 10 is configured to emit the polarized image light 11.

[0039] The optical system 300 further includes a first mirror 20 configured to receive the emitted image light 11 at a first oblique incident angle al and reflect the received emitted image light 11 as a first reflected image light 12.

[0040] The optical system 300 further includes a second mirror 30 configured to receive the first reflected image light 12 at a second oblique incident angle a2 and reflect the first reflected image light 12 as a second reflected image light 13 for viewing by a viewer 40.

[0041] In some embodiments, each of the first and second oblique incident angles al, a2 is in a range from about 30 degrees to about 60 degrees.

[0042] In some embodiments, each of the first and second oblique incident angles al, a2 is in a range from about 35 degrees to about 55 degrees, or about 40 degrees to about 50 degrees. In some embodiments, each of the first and second oblique incident angles al, a2 is about 45 degrees.

[0043] In some embodiments, the optical system 300 includes a third mirror 60 configured to receive the second reflected image light 13 at a third oblique incident angle a3 and reflect the second reflected image light 13 as a third reflected image light 14 for viewing by the viewer 40.

[0044] In some embodiments, the optical system 300 is configured to display a virtual image 15 of an image 16 formed and emitted by the display panel 10 to the viewer 40.

[0045] In the illustrated embodiment of FIG. 1, the optical system 300 includes an optical detector 80. The optical detector 80 may be disposed on a same side of the first mirror 20 as of the viewer 40, i.e., a side opposite to the second mirror 30.

[0046] FIG. 2 shows a schematic view of the display panel 10, according to an embodiment of the present disclosure.

[0047] In some embodiments, the display panel 10 includes a plurality of blue, green, and red pixels 10b, 10g, lOr configured to emit the image light 11 shown in FIG. 1. In some embodiments, the plurality of blue, green, and red pixels 10b, 10g, lOr is configured to emit a blue light, a green light, a red light, respectively.

[0048] In some embodiments, the blue light has at least one blue wavelength in a blue wavelength range extending from about 420 nanometers (nm) to about 470 nm. In some embodiments, the green light has at least one green wavelength in a green wavelength range extending from about 500 nm to about 560 nm. In some embodiments, the red light has at least one red wavelength in a red wavelength range extending from about 630 nm to about 680 nm.

[0049] FIG. 3 shows a schematic view of curved first and second mirrors 20’, 30’, according to an embodiment of the present disclosure.

[0050] In some embodiments, at least one of the first and second mirrors 20, 30 is curved. Specifically, in some embodiments, the first mirror 20 may be the curved first mirror 20’ and the second mirror 30 may be the curved second mirror 30’ . In some embodiments, each of the first and second mirrors 20, 30 is curved, i.e., the curved first and second mirrors 20’, 30’ .

[0051] FIG. 4 shows a schematic view of a vehicle 315, according to an embodiment of the present disclosure.

[0052] Referring to FIGS. 1 and 4, in some embodiments, the viewer 40 is a passenger 305 of the vehicle 315. In some embodiments, the viewer 40 is a driver 310 of the vehicle 315. In some embodiments, one or more of “the passenger 305” and / or as “the driver 310” may be interchangeably referred to as “the occupant 305, 310” herein. In some embodiments, the viewer 40 is the occupant 305, 310 of the vehicle 315.

[0053] In some embodiments, the second mirror 30 is included by a windshield 320 of the vehicle 315. In some embodiments, the third mirror 60 is included by the windshield 320 of the vehicle 315.

[0054] In some embodiments, “the first mirror 20” may be a reflective polarizer and may be interchangeably referred to as “the reflective polarizer 20” herein.

[0055] The HUD 300 is configured to be used in the vehicle 315. The HUD 300 includes the reflective polarizer 20 and the second mirror 30 such that the emitted polarized image light 11 propagates toward the occupant 305, 310 of the vehicle 315 after being reflected first by the reflective polarizer 20 and then by the second mirror 30.

[0056] Specifically, the emitted polarized image light 11 propagates as the third reflected image light 14 toward the occupant 305, 310 of the vehicle 315 after being reflected first as the first reflected image light 12 by the reflective polarizer 20 and then by the second mirror 30 as the second reflected image light 13.

[0057] FIG. 5 A shows a schematic sectional view of the first mirror 20, the second mirror 30, and the third mirror 60, according to another embodiment of the present disclosure.

[0058] A coordinate system including mutually perpendicular X, Y, and Z-axes is also illustrated in FIG. 5A. The X and Y-axes are in-plane axes of the first mirror 20, the second mirror 30, and the third mirror 60, while the Z-axis is a transverse axis disposed along a thickness of the first mirror 20, the second mirror 30, and the third mirror 60. In other words, the X and Y-axes are along a plane of the first mirror 20, the second mirror 30, and the third mirror 60 defining a X-Y plane, and the Z-axis is perpendicular to the X-Y plane of the first mirror 20, the second mirror 30, and the third mirror 60.

[0059] FIG. 5 A further shows substantially collimated incident lights 41, 42 incident on the first mirror 20, the second mirror 30, and the third mirror 60.

[0060] The substantially collimated incident light 41 is incident at a first incident angle bl. The first incident angle bl is less than about 10 degrees.

[0061] In some embodiments, the first incident angle bl is less than about 8 degrees, less than about 6 degrees, less than about 4 degrees, less than about 2 degrees, or less than about 1 degree. In some embodiments, the first incident angle bl is about 0 degree.

[0062] The substantially collimated incident light 42 is incident at a second incident angle b2. The second incident angle b2 is greater than about 20 degrees.

[0063] In some embodiments, the second incident angle b2 is greater than about 25 degrees, greater than about 30 degrees, greater than about 35 degrees, greater than about 40 degrees, greater than about 45 degrees, greater than about 50 degrees, greater than about 55 degrees, or greater than about 60 degrees. In some embodiments, the second incident angle b2 is about 30 degrees.

[0064] FIG. 5B shows a detailed schematic sectional view of the first mirror 20 and the second mirror 30, according to an embodiment of the present disclosure.

[0065] In some embodiments, at least one of the first and second mirror 20, 30 includes a plurality of alternating first and second polymeric layers 21, 22 numbering at least 10 in total.

[0066] In some embodiments, at least one of the first and second mirror 20, 30 includes the plurality of alternating first and second polymeric layers 21, 22 numbering at least 20, at least 50, at least 100, at least 150, at least 200, at least 250, at least 300, at least 350, or at least 400 in total.

[0067] In some embodiments, each of the first and second polymeric layers 21, 22 has an average thickness t of less than about 500 nm. The term “average thickness f ’, as used herein, refers to an average of thicknesses measured at multiple points across a plane (i.e., the X-Y plane) of each of the first and second polymeric layers 21, 22.

[0068] In some embodiments, each of the first and second polymeric layers 21, 22 has the average thickness t of less than about 450 nm, of less than about 400 nm, of less than about 350 nm, of less than about 300 nm, of less than about 250 nm, or of less than about 200 nm.

[0069] In some embodiments, the at least one of the first and second polymeric layers 21, 22 includes polyethylene naphthalate (PEN).

[0070] In some embodiments, at least one of the first and second polymeric layers 21, 22 includes a co-poly ethylene naphthalate terephthalate copolymer (LmPEN or coPEN). In some embodiments, carboxylate units of the copolymer include about 70 to 95 mole percent naphthalate units and about 5 to 30 mole percent terephthalate units.

[0071] In some embodiments, the carboxylate units of the copolymer include about 80 to 95 mole percent naphthalate units and about 5 to 20 mole percent terephthalate units.

[0072] In either case of PEN, LmPEN, or CoPEN, the first series of layers is substantially birefringent while the second set of layers is substantially non-birefringent, i.e. non-oriented. Additionally, in some cases the non-birefringent layers can be comprised of a blend of copolyester (CoPET) and polycarbonate (PC), i.e. PC:CoPET or non-birefringent coPET. In all cases, it is most preferred for the non-birefrigent material to have a glass transition point (Tg) equal to or greater than 95 °C, and more preferably equal to or greater than 105 °C.

[0073] FIG. 6 shows a graph 600 depicting an optical transmission versus wavelength of the first mirror 20 (shown in FIG. 5A), for the substantially collimated incident light 41 (shown in FIG. 5A), and for a first polarization state, according to an embodiment of the present disclosure.

[0074] The wavelength is expressed in nm in the abscissa. The optical transmission is expressed in percentage (%) in the ordinate.

[0075] The graph 600 includes plots OF Ip, OF2p, OF3p, OF4p, OF5p, OF6p depicting optical transmission versus wavelength for respective samples of optical films OF1, OF2, OF3, OF4, OF5, OF6 of the first mirror 20 or the reflective polarizer 20, for the substantially collimated incident light 41 shown in FIG. 5 A, and for the first polarization state.

[0076] The optical film OF1 includes a first optical film version two and thicker LmPEN outer layer.

[0077] The optical film OF2 includes a second optical film version two and thicker LmPEN outer layer.

[0078] The optical film OF3 includes a first optical film version one and thicker PEN outer layer.

[0079] The optical film OF4 includes a second optical film version one and thicker PEN outer layer.

[0080] The optical film OF5 includes the second optical film version one and thinner PEN outer layer.

[0081] The optical film OF6 includes the first optical film version one and thinner PEN outer layer.

[0082] The first optical film version one includes about 2x325 PEN as the high index layers and a blend of polycarbonate and copolyesters (PC: CoPET) as the index layers. The first optical film version one has a right band edge (RBE) of 860 nm at T10%.

[0083] The first optical film version two includes about 2x325 LmPEN as the high index layers and PQCoPET as the low index layers.

[0084] The second optical film version one includes about 2x325 PEN as the high index layers and PQCoPET as the low index layers. The second optical film version one has a RBE of 750 nm at T10%.

[0085] The second optical film version two includes about 2x325 LmPEN as the high index layers and PQCoPET as the low index layers.

[0086] Table 1 provided below summarizes optical indices of the high index layers PEN and LmPEN and the low index layers PQCoPET.Table 1

[0087] FIG. 7A shows a graph 700 depicting an optical transmission versus wavelength of the first mirror 20 (shown in FIG. 5A), for the substantially collimated incident light 41 (shown in FIG. 5A), and for a second polarization state, according to an embodiment of the present disclosure.

[0088] FIG. 7B shows a magnified graph 710 depicting the optical transmission versus wavelength of the first mirror 20 (shown in FIG. 5 A), for the substantially collimated incident light 41 (shown in FIG. 5A), and for the second polarization state, according to an embodiment of the present disclosure.

[0089] Referring to FIGS. 7A and 7B, the wavelength is expressed in nm in the abscissa. The optical transmission is expressed in percentage (%) in the ordinate.

[0090] The graphs 700, 710 includes plots OFlb, OF2b, OF3b, OF4b, OF5b, OF6b depicting optical transmission versus wavelength for the respective samples of the optical films OF1, OF2, OF3, OF4, OF5, OF6 of the first mirror 20 or the reflective polarizer 20, for the substantially collimated incident light 41, and for the second polarization state.

[0091] Referring to FIGS. 5A, 6, and 7A-7B, for the substantially collimated incident light 41 and a visible wavelength range extending from about 420 nm to about 680 nm, and for the first incident angle bl of less than about 10 degrees, the first mirror 20 has an average optical transmittance of greater than about 65% for the first polarization state, and an average optical reflectance of greater than about 80% for the orthogonal second polarization state.

[0092] In some embodiments, for the substantially collimated incident light 41 and the visible wavelength range, and for the first incident angle bl, the average optical transmittance is greater than about 70%, greater than about 75%, greater than about 80%, or greater than about 85% for the first polarization state.

[0093] In some embodiments, for the substantially collimated incident light 41 and the visible wavelength range, and for the first incident angle bl, the average optical reflectance is greater than about 85%, greater than about 90%, or greater than about 95% for the orthogonal second polarization state.

[0094] In some embodiments, the first polarization state substantially extends along the X-axis and the second polarization state substantially extends along the Y-axis. In some embodiments, the first polarization state may correspond to a p-polarization state, while the second polarization state may correspond to an s-polarization state.

[0095] Further, for the substantially collimated incident light 41, the visible wavelength range, and for the first incident angle bl, the first mirror 20 has an average optical transmittance of less than about 0.1% for the second polarization state.

[0096] In some embodiments, for the substantially collimated incident light 41, the visible wavelength range, and for the first incident angle bl, the first mirror 20 has the average optical transmittance of less than about 0.025%, less than about 0.02%, less than about 0.015%, less than about 0.01%, less than about 0.009%, less than about 0.008%, less than about 0.007%, less than about 0.006%, less than about 0.005%, less than about 0.004%, less than about 0.003%, less than about 0.002%, or less than about 0.001% for the second polarization state.

[0097] In some embodiments, for the second polarization state, the first incident angle bl, and each of the blue wavelength range, the green wavelength range, and the red wavelength range, the first mirror 20 has an average optical transmittance of less than about 0.1%.

[0098] In some embodiments, for the second polarization state, the first incident angle bl, and each of the blue wavelength range, the green wavelength range, and the red wavelength range, the first mirror 20 has the average optical transmittance of less than about 0.025%, less than about 0.02%, less than about 0.015%, less than about 0.01%, less than about 0.009%, less than about 0.008%, less than about 0.007%, less than about 0.006%, less than about 0.005%, less than about 0.004%, less than about 0.003%, less than about 0.002%, or less than about 0.001%.

[0099] Further, for the substantially collimated incident light 41, the visible wavelength range, and for the first incident angle bl, the second mirror 30 has an average optical reflectance of at least 30% for at least one of the first and second polarization states.

[0100] In some embodiments, for the substantially collimated incident light 41, the visible wavelength range, and for the first incident angle bl, the second mirror 30 has the average optical reflectance of at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, or at least 95% for at least one of the first and second polarization states.

[0101] In some embodiments, for the first incident angle bl, the third mirror 60 has an average optical transmittance of greater than about 65% for the first polarization state, and an average optical reflectance of greater than about 10% for the second polarization state.

[0102] In some embodiments, for the first incident angle bl, the third mirror 60 has the average optical transmittance of greater than about 70%, greater than about 75%, greater than about 80%, or greater than about 85% for the first polarization state, and the average optical reflectance of greater than about 15%, greater than about 20%, greater than about 30%, greater than about 35%, greater than about 40%, greater than about 45%, or greater than about 50% for the second polarization state.

[0103] In some embodiments, for the first incident angle bl and the second polarization state, the third mirror 60 has the average optical reflectance of less than about 95%. In some embodiments, for the first incident angle bl and the second polarization state, the third mirror 60 has the average optical reflectance of less than about 90%, less than about 85%, less than about 80%, less than about 75%, less than about 70%, less than about 65%, or less than about 60%.

[0104] Table 2 provided below summarizes the average optical transmittance of the first mirror 20 (i.e., the optical films OF1-OF6) for the first incident angle bl and the first polarization state, in the visible wavelength range, the blue wavelength range, the green wavelength range, and the red wavelength range.Table 2

[0105] Table 3 provided below summarizes the average optical transmittance of the first mirror 20 (i.e., the optical films OF1-OF6) for the first incident angle bl and the second polarization state, in the visible wavelength range, the blue wavelength range, the green wavelength range, and the red wavelength range.Table 3

[0106] FIG. 8A shows a graph 800 depicting an optical transmission versus wavelength of the first mirror 20 (shown in FIG. 5A), for the substantially collimated incident lights 41, 42 (shown in FIG. 5A), and for the first and second polarization states, according to an embodiment of the present disclosure.

[0107] FIG. 8B shows a magnified graph 810 depicting the optical transmission versus wavelength of the first mirror 20 (shown in FIG. 5A), for the substantially collimated incident lights 41, 42 (shown in FIG. 5 A), and for the second polarization state, according to an embodiment of the present disclosure.

[0108] Referring to FIGS. 8A and 8B, the wavelength is expressed in nm in the abscissa. The optical transmission is expressed in percentage (%) in the ordinate.

[0109] The graph 800 includes the plot OF5p (also shown in FIG. 6) and the plot OF5b (also shown in FIGS. 7A-7B).

[0110] The graph 800 further includes a plot OF5p’ depicting an optical transmission versus wavelength for the sample of the optical film OF5 of the first mirror 20 or the reflective polarizer 20, for the substantially collimated incident light 42 (i.e., incident at the second incident angle b2 shown in FIG. 5A), and for the first polarization state.

[0111] The graph 800 further includes a plot OF5b’ depicting an optical transmission versus wavelength for the sample of the optical film OF5 of the first mirror 20 or the reflective polarizer 20, for the substantially collimated incident light 42, and for the second polarization state.

[0112] The graph 810 includes the plot OF5b and the plot OF5b’ .

[0113] Referring to FIGS. 5A and 8A-8B, in some embodiments, for the second polarization state and the first incident angle bl, the plot OF5b of the optical transmittance of the first mirror 20 as a function of wavelength includes a band edge 51 along which the optical transmittance increases by at least 40% when the wavelength increases by less than about 100 nm.

[0114] For example, in the illustrated embodiment of FIG. 8A, for the second polarization state and the first incident angle bl, the plot OF5b of the optical transmittance of the first mirror 20 as the function of wavelength includes the band edge 51 along which the optical transmittance increases by about 85% in a wavelength range 52 of about 40 nm.

[0115] In some embodiments, for the second polarization state and the first incident angle bl, the plot OF5b of the optical transmittance of the first mirror 20 as the function of wavelength includes theband edge 51 along which the optical transmittance increases by at least 45%, by at least 50%, by at least 55%, by at least 60%, by at least 65%, by at least 70%, by at least 75%, by at least 80%, by at least 85%, or by at least 90% when the wavelength increases by less than about 90 nm, less than about 80 nm, less than about 70 nm, less than about 60 nm, less than about 50 nm, less than about 40 nm, less than about 30 nm, or less than about 20 nm.

[0116] In some embodiments, a mid-point 53 of the band edge 51 is at a mid-point wavelength 54 of less than about 830 nm. In some embodiments, the mid-point 53 of the band edge 51 is at the mid-point wavelength 54 of less than about 820 nm, less than about 810 nm, less than about 800 nm, less than about 790 nm, or less than about 780 nm.

[0117] For example, in the illustrated embodiment of FIG. 8 A, the mid-point 53 of the band edge 51 is at the mid-point wavelength 54 of about 773 nm.

[0118] Referring to FIGS. 5A and 8A-8B, for the substantially collimated incident light 42 and the visible wavelength range, for the second polarization state, the average optical transmittance of the first mirror 20 decreases, when the incident angle increases from the first incident angle bl to the second incident angle b2 of greater than about 20 degrees.

[0119] In some embodiments, for the second polarization state, and for each of the blue wavelength range, the green wavelength range, and the red wavelength range, the average optical transmittance of the first mirror 20 decreases when the incident angle increases from the first incident angle bl to the second incident angle b2.

[0120] In some embodiments, for the second polarization state and the second incident angle b2, the plot OF5b’ of the optical transmittance of the first mirror 20 as a function of wavelength includes a band edge 5 lb along which the optical transmittance increases by at least 40% when the wavelength increases by less than about 100 nm.

[0121] For example, in the illustrated embodiment of FIG. 8A, for the second polarization state and the second incident angle b2, the plot OF5b’ of the optical transmittance of the first mirror 20 as the function of wavelength includes the band edge 5 lb along which the optical transmittance increases by about 85% when the wavelength increases by about 40 nm.

[0122] In some embodiments, for the second polarization state and the second incident angle b2, the plot OF5b’of the optical transmittance of the first mirror 20 as the function of wavelength includes the band edge 51b along which the optical transmittance increases by at least 45%, by at least 50%, by at least 55%, by at least 60%, by at least 65%, by at least 70%, by at least 75%, by at least 80%, by at least 85%, or by at least 90% when the wavelength increases by less than about 90 nm, less than about 80 nm, less than about 70 nm, less than about 60 nm, less than about 50 nm, less than about 40 nm, less than about 30 nm, or less than about 20 nm.

[0123] In some embodiments, a mid-point 53b of the band edge 5 lb is at a mid-point wavelength 54a of less than about 830 nm. In some embodiments, the mid-point 53 of the band edge 51 is at the mid-point wavelength 54 of less than about 820 nm, less than about 810 nm, less than about 800 nm,less than about 790 nm, less than about 780 nm, less than about 770 nm, less than about 760 nm, less than about 750 nm, or less than about 740 nm.

[0124] For example, in the illustrated embodiment of FIG. 8 A, the mid-point 53b of the band edge 51 is at the mid-point wavelength 54 of about 738 nm.

[0125] Referring to FIGS. 5A and 8B, in some embodiments, for the visible wavelength range, the second polarization state, and the first incident angle bl, a maximum optical transmittance 55 of the first mirror 20 is less than about 0.15%.

[0126] In some embodiments, for the visible wavelength range, the second polarization state, and the first incident angle bl, the maximum optical transmittance 55 of the first mirror 20 is less than about 0.1%, less than about 0.08%, less than about 0.06%, less than about 0.05%, less than about 0.04%, less than about 0.02%, or less than about 0.01%.

[0127] For example, in the illustrated embodiment of FIG. 8B, for the visible wavelength range, the second polarization state, and the first incident angle bl, the maximum optical transmittance 55 of the first mirror 20 is about 0.018%.

[0128] In some embodiments, for the visible wavelength range, the second polarization state, and the second incident angle b2, a maximum optical transmittance 56 of the first mirror 20 is less than about 0.15%.

[0129] In some embodiments, for the visible wavelength range, the second polarization state, and the second incident angle b2, the maximum optical transmittance 56 of the first mirror 20 is less than about 0.1%, less than about 0.05%, less than about 0.01%, less than about 0.009%, less than about 0.008%, less than about 0.006%, or less than about 0.005%.

[0130] For example, in the illustrated embodiment of FIG. 8B, for the visible wavelength range, the second polarization state, and the second incident angle b2, the maximum optical transmittance 56 of the first mirror 20 is about 0.004%.

[0131] In some embodiments, for the visible wavelength range and the second polarization state, the maximum optical transmittance 55 of the first mirror 20 decreases when the incident angle increases from the first incident angle bl to the second incident angle b2.

[0132] For example, in the illustrated embodiment of FIG. 8B, for the visible wavelength range and the second polarization state, the maximum optical transmittance 55 of the first mirror 20 decreases to the maximum optical transmittance 56 when the incident angle increases from the first incident angle bl to the second incident angle b2.

[0133] Table 4 provided below summarizes the average optical transmittance of the first mirror 20 (i.e., the optical films OF1-OF6) for the second incident angle b2 and the first polarization state, in the visible wavelength range, the blue wavelength range, the green wavelength range, and the red wavelength range.Table 4

[0134] Table 5 provided below summarizes the average optical transmittance of the first mirror 20 (i.e., the optical films OF1-OF6) for the second incident angle b2 and the second polarization state, in the visible wavelength range, the blue wavelength range, the green wavelength range, and the red wavelength range.Table 5

[0135] Table 6 provided below summarizes a difference between the average optical transmittance of the first mirror 20 (i.e., the optical films OF1-OF6) for the first incident angle bl and the average optical transmittance of the first mirror 20 for the second incident angle b2, for the second polarization state, in the visible wavelength range, the blue wavelength range, the green wavelength range, and the red wavelength range.Table 6

[0136] FIG. 9 shows a graph 900 depicting a best linear fit 57a to a continuous portion 57 of the band edge 51 (also shown in FIG. 8A) and a best linear fit 57b to a continuous portion 57c of the band edge 51b (also shown in FIG. 8A), according to an embodiment of the present disclosure.

[0137] In some embodiments, the best linear fit 57a to the continuous portion 57 of the band edge 51 along which the optical transmittance of the first mirror 20 increases by at least 40%, has a positive slope of greater than about 1.5 % / nm.

[0138] In some embodiments, the best linear fit 57a has the positive slope of greater than about 1.75 % / nm, greater than about 2 % / nm, greater than about 2.25 % / nm, greater than about 2.5 % / nm, or greater than about 2.75 % / nm. In the illustrated embodiment of FIG. 9, the best linear fit 57a has the positive slope of about 2.9083 % / nm. In some embodiments, the best linear fit 57a has an r-square value R2of 0.9831.

[0139] In an example, the best linear fit 57a is according to Equation 1 provided below: y = 2.9083x - 2192.8 [Equation 1]

[0140] In Equation 1, y denotes the optical transmittance and x denotes the wavelength. In this example, the positive slope = 2.9083 and R2= 0.9831.

[0141] Referring to FIGS. 5A and 9, in some embodiments, the positive slope increases by at least 0.2 % / nm when the incident angle increases from the first incident angle bl to the second incident angle b2.

[0142] In some embodiments, the positive slope increases by at least 0.4 % / nm, by at least 0.6 % / nm, by at least 0.8 % / nm, or by at least 1 % / nm when the incident angle increases from the first incident angle bl to the second incident angle b2.

[0143] In an example, the positive slope of the best linear fit 57a increases to a slope of the best linear fit 57b when the incident angle increases from the first incident angle bl to the second incident angle b2.

[0144] In an example, the best linear fit 57b is according to Equation 2 provided below: y = 3.9978x - 2905.8 [Equation 2]

[0145] In Equation 2, y denotes the optical transmittance and x denotes the wavelength. In this example, the positive slope = 3.9978 and R2= 0.9902.

[0146] Therefore, in the illustrated example of FIG. 9, the positive slope of the best linear fit 57a increases by about 1.0895 % / nm when the incident angle increases from the first incident angle bl to the second incident angle b2.

[0147] FIG. 10 shows a schematic view of an optical system 400, according to another embodiment of the present disclosure.

[0148] The optical system 400 is substantially similar to the optical system 300 of FIG. 1, with like elements designated by like reference characters. However, the optical system 400 has a different configuration.

[0149] The optical system 400 includes an illumination source 1 including a plurality of light sources 2b, 2g, 2r for providing an illumination 3 to the display panel 10.

[0150] Further, the optical system 400 includes a reflective polarizer 70 instead of the reflective polarizer 20 (shown in FIG. 1). The reflective polarizer 70 is substantially similar to the reflective polarizer 20. However, the reflective polarizer 70 is disposed between the illumination source 1 and the display panel 10.

[0151] The reflective polarizer 70 is also shown in FIGS. 5A-5B. As shown in FIG. 5B, in some embodiments, the reflective polarizer 70 includes the plurality of alternating first and second polymeric layers 21, 22.

[0152] In some embodiments, the reflective polarizer 70 is configured to protect the illumination source 1 from an external light 4 from an external light source 5 external to the optical system 400. In some embodiments, the external light 4 includes a spectrum similar to a solar spectrum at least in the visible wavelength range. In some embodiments, the external light source 5 is the sun.

[0153] In some embodiments, the optical system 400 further includes the second mirror 30. In the illustrated embodiment of FIG. 10, the second mirror 30 is configured to receive the emitted image light 11 at a first oblique incident angle cl and reflect the received emitted image light 11 as a first reflected image light 13’ .

[0154] In some embodiments, the optical system 400 further includes the third mirror 60. In the illustrated embodiment of FIG. 10, the third mirror 60 is configured to receive the first reflected image light 13’ at a second oblique incident angle c2 and reflect the first reflected image light 13’ as a second reflected image light 14’ for viewing by the viewer 40.

[0155] FIG. 11A shows a graph 1000 depicting a maximum display temperature versus time for the first mirror 20 (shown in FIG. 5A) and a comparative film, according to an embodiment of the present disclosure.

[0156] FIG. 11B shows a magnified graph 1100 depicting the maximum display temperature versus time for the first mirror 20 and the comparative film, according to an embodiment of the present disclosure.

[0157] Time is expressed in minutes (min) in the abscissa. The maximum display temperature is expressed in Celsius (°C) in the ordinate.

[0158] The graphs 1000, 1100 include curves 1002, 1004. The curve 1002 depicts the maximum display temperature versus time for the comparative film and the curve 1004 depicts the maximum display temperature versus time for the first mirror 20. Specifically, the curve 1004 depicts the maximum display temperature versus time for the sample of the optical film OF5 of the first mirror 20.

[0159] Table 7 provided below summarizes the average optical transmittance of the first mirror 20 (i.e., the optical film OF5) for the first incident angle bl and the second polarization state and theaverage optical transmittance of the comparative film, in the visible wavelength range, the blue wavelength range, the green wavelength range, and the red wavelength range.Table 7

[0160] As is apparent from Table 7, the comparative film has a higher average optical transmission for the substantially collimated incident light 41 incident at the first incident angle bl.

[0161] Table 8 provided below summarizes a difference in the maximum display temperature for the comparative film and the first mirror 20 after 4 minutes.Table 8

[0162] As is apparent from Table 8 and FIGS. 11A-11B, the optical system 300, 400 including the first mirror 20 or the reflective polarizer 20 has a lower maximum display temperature as compared to an optical system (not shown) including the comparative film.

[0163] Referring to FIGS. 1 to 11A-11B, the first mirror 20 of the optical system 300 and the reflective polarizer 70 of the optical system 400 may substantially block the substantially collimated incident light 41 for the first incident angle bl, and for the second polarization state.

[0164] Moreover, since for the second polarization state, the average optical transmittance of the first mirror 20 of the optical system 300 and the reflective polarizer 70 of the optical system 400 decreases when the incident angle increases from the first incident angle bl to the second incident angle b2, the first mirror 20 or the reflective polarizer 70 may further block the substantially collimated incident light 42 having the second polarization state and incident at greater oblique angles (i.e., greater than about 20 degrees).

[0165] Therefore, the optical systems 300, 400 including the first mirror 20 or the reflective polarizer 70 may protect one or more components of the optical system 300, 400 (e.g., the display panel 10 and / or the illumination source 1) from an external light (e.g., the external light 4) from an external light source (e.g., the external light source 5) external to the optical systems 300, 400.

[0166] Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as being modified by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in theforegoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein.

[0167] 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

CLAIMS1. An optical system comprising: a display panel configured to emit an image light; a first mirror configured to receive the emitted image light at a first oblique incident angle and reflect the received emitted image light as a first reflected image light; and a second mirror configured to receive the first reflected image light at a second oblique incident angle and reflect the first reflected image light as a second reflected image light for viewing by a viewer, such that for a substantially collimated incident light and a visible wavelength range extending from about 420 nm to about 680 nm: for a first incident angle of less than about 10 degrees, the first mirror has an average optical transmittance of greater than about 65% for a first polarization state, an average optical reflectance of greater than about 80% for an orthogonal second polarization state, and an average optical transmittance of less than about 0.1% for the second polarization state, and the second mirror has an average optical reflectance of at least 30% for at least one of the first and second polarization states; wherein, for the second polarization state, the average optical transmittance of the first mirror decreases when the incident angle increases from the first incident angle to a second incident angle of greater than about 20 degrees.

2. The optical system of claim 1, wherein for the second polarization state, and for each of a blue wavelength range extending from about 420 nm to about 470 nm, a green wavelength range extending from about 500 nm to about 560 nm, and a red wavelength range extending from about 630 nm to about 680 nm, an average optical transmittance of the first mirror decreases when the incident angle increases from the first incident angle to the second incident angle.

3. The optical system of claim 1, wherein for the second polarization state, the first incident angle, and each of a blue wavelength range extending from about 420 nm to about 470 nm, a green wavelength range extending from about 500 nm to about 560 nm, and a red wavelength range extending from about 630 nm to about 680 nm, an average optical transmittance of the first mirror is less than about 0.1%.

4. The optical system of claim 1, wherein for the second polarization state and the first incident angle, a plot of an optical transmittance of the first mirror as a function of wavelength comprises a band edge along which the optical transmittance increases by at least 40% when the wavelength increases by less than about 100 nm, and wherein a mid-point of the band edge is at a mid-point wavelength of less than about 830 nm.

5. The optical system of claim 4, wherein a best linear fit to a continuous portion of the band edge along which the optical transmittance of the first mirror increases by at least 40%, has a positive slope of greater than about 1.5 % / nm.

6. The optical system of claim 5, wherein the positive slope increases by at least 0.2 % / nm when the incident angle increases from the first incident angle to the second incident angle.

7. The optical system of claim 1, wherein for the second polarization state and the second incident angle, a plot of an optical transmittance of the first mirror as a function of wavelength comprises a band edge along which the optical transmittance increases by at least 40% when the wavelength increases by less than about 100, and wherein a mid-point of the band edge is at a mid-point wavelength of less than about 830 nm.

8. The optical system of claim 1, wherein for the visible wavelength range, the second polarization state, and the first incident angle, a maximum optical transmittance of the first mirror is less than about 0.15%.

9. The optical system of claim 1, wherein for the visible wavelength range, the second polarization state, and the second incident angle, a maximum optical transmittance of the first mirror is less than about 0.15%.

10. The optical system of claim 1, wherein for the visible wavelength range and the second polarization state, a maximum optical transmittance of the first mirror decreases when the incident angle increases from the first incident angle to the second incident angle.

11. The optical system of claim 1, wherein the second mirror is comprised by a windshield of a vehicle.

12. A heads up display (HUD) for use in a vehicle, comprising: a display panel configured to emit a polarized image light; and a reflective polarizer and a second mirror, such that the emitted polarized image light propagates toward an occupant of the vehicle after being reflected first by the reflective polarizer and then by the second mirror, wherein for a substantially collimated incident light, and for each of a blue wavelength range extending from about 420 nm to about 470 nm, a green wavelength range extending from about 500 nm to about 560 nm, and a red wavelength range extending from about 630 nm to about 680 nm, for a first incident angle of less than about 10 degrees, the reflective polarizer has an average optical transmittance of greater than about 65% for a first polarization state, an average optical reflectance of greater than about 80% for an orthogonal second polarization state, and an average optical transmittance of less than about 0.1% for the second polarization state, andthe second mirror has an average optical reflectance of at least 30% for at least one of the first and second polarization states; wherein for the second polarization state and the first incident angle, a plot of an optical transmittance of the reflective polarizer as a function of wavelength comprises a band edge along which the optical transmittance increases by at least 40% when the wavelength increases by less than about 100 nm, wherein a mid-point of the band edge is at a mid-point wavelength of less than about 830 nm, and wherein a best linear fit to the band edge has a positive slope that increases when the incident angle increases from the first incident angle to a second incident angle of greater than about 20 degrees.

13. An optical system comprising: a display panel configured to emit an image light; an illumination source comprising a plurality of light sources for providing illumination to the display panel; and a reflective polarizer disposed between the illumination source and the display panel, such that for a substantially collimated substantially normally incident light and a visible wavelength range extending from about 420 nm to about 680 nm: for a first incident angle of less than about 10 degrees, the reflective polarizer has an average optical transmittance of greater than about 65% for a first polarization state, an average optical reflectance of greater than about 80% for an orthogonal second polarization state, and an average optical transmittance of less than about 0.1% for the second polarization state, wherein, for the second polarization state, the average optical transmittance of the reflective polarizer decreases when the incident angle increases from the first incident angle to a second incident angle of greater than about 20 degrees.

14. The optical system of claim 13, wherein reflective polarizer is configured to protect the illumination source from an external light from an external light source external to the optical system.

15. The optical system of claim 13, further comprising: a second mirror configured to receive the emitted image light at a first oblique incident angle and reflect the received emitted image light as a first reflected image light; and a third mirror configured to receive the first reflected image light at a second oblique incident angle and reflect the first reflected image light as a second reflected image light for viewing by a viewer.

Images