Optical System

Abstract

An optical system (200) that allows an observer (10) to simultaneously view an image produced by an electronic display (20) and a real-world object (30b) includes a reflective polarizer (41) as an image combiner for a head-mounted display, and an absorbing polarizer (42) deployed within the same combiner to reduce glare by minimizing ambient reflections from the reflective polarizer. To prevent the absorbing polarizer (42) from blocking a linearly polarized source from transmitting through the combiner, a weakly absorbing polarizer is provided that allows transmission of the polarized source while still minimizing glare.

Description

[Technical field]

[0001] The present disclosure relates generally to optical systems and see-through optical systems for displaying images. [Background technology]

[0002] An optical system may be included in a head-mounted display (HMD) to provide an image to a viewer, and may include a display panel and various optical components between the display panel and the viewer's eyes. Summary of the Invention

[0003] Various aspects and embodiments described herein relate to optical systems having folded optical paths.

[0004] Some aspects of the present disclosure relate to an optical system for displaying a first image and a second image to an observer. The optical system includes a first display and a second display that are different, and an optical stack. The optical stack is configured to receive a first light beam from the first display and reflect the received first light beam for viewing by the observer. The optical stack is further configured to receive a second light beam from the second display, different from the first light beam, and transmit the received second light beam for viewing by the observer. The optical stack includes a reflective polarizer facing the first display, and an absorbing polarizer disposed on the reflective polarizer and facing the second display. Each of the reflective polarizer and the absorbing polarizer includes orthogonal pass and block axes. For substantially normally incident light having a wavelength in the range of about 400 nm to about 700 nm, the reflective polarizer reflects at least 70% of the incident light polarized along the block axis of the reflective polarizer and transmits at least 70% of the incident light polarized along the pass axis of the reflective polarizer. The absorbing polarizer absorbs at least 50% and up to 85% of the incident light polarized along the block axis of the absorbing polarizer and transmits at least 70% of the incident light polarized along the pass axis of the absorbing polarizer. The block axis of the reflective polarizer and the block axis of the absorbing polarizer form an angle of about 5 degrees to about 40 degrees with respect to each other.

[0005] Some other aspects of the present disclosure relate to a see-through optical system for displaying a virtual image to an observer. The system includes a first display configured to emit a first image having a first polarization state and an optical stack curved along two mutually orthogonal directions. The optical stack is configured to receive the emitted first image and reflect the received first image for viewing by the observer. The observer can view a magnified virtual image of the first image and receive and view a polarized real-world object in the real-world scene through the optical stack. For light having at least one wavelength within a predetermined wavelength range and propagating along a substantially normal incidence direction, the optical stack reflects at least 70% of the incident light polarized along a first polarization state and absorbs at least 50% and up to 85% of the incident light having an orthogonal second polarization state. When the optical stack is continuously rotated at least 180 degrees about the light entering the optical stack from the polarized real-world object, the polarized real-world object remains observable by the observer.

[0006] These and other aspects of the present application will become apparent from the following Detailed Description of the Invention. However, the above Summary should not be construed in any manner as a limitation on the claimed subject matter, which is defined solely by the appended claims. [Brief description of the drawings]

[0007] Various aspects of the disclosure will now be discussed in more detail with reference to the accompanying drawings. [Figure 1] FIG. 1 is a schematic diagram of an optical system according to certain aspects of the present disclosure. [Diagram 2] FIG. 2 is a schematic diagram of the angular direction of light passing through various axes of a reflective polarizer and an absorbing polarizer according to certain embodiments. [Diagram 3] 1 is a graph showing transmission in an optical system having a reflective polarizer. [Figure 4] 1 is a graph showing transmission in an optical system having an absorbing polarizer. [Diagram 5] 1 is a graph showing transmission in an optical system having a combination of a reflective polarizer and an absorptive polarizer.

[0008] 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

[0009] The optical systems herein may be used in head-mounted displays to provide a wide field of view in a thin, compact system. In some embodiments, the optical system may include one or more optical lenses and reflective and absorbing polarizers, each of which may be disposed on or within the one or more lenses to provide a folded optical path between an image source and a viewer.

[0010] A reflective polarizer as an image combiner for a head-mounted display (HMD) with a linearly polarized display provides high display efficiency and effective transmission of the world view. However, about 50% of the ambient light is reflected from the combiner, which creates glare. For example, to a person looking at an HMD user, the ambient light will be reflected from the combiner, which may make it difficult for the user to see through the combiner. To mitigate the glare, an absorbing polarizer can be integrated into the reflective polarizer combiner to form a "dual polarizer combiner." The absorbing polarizer absorbs light of the same polarization state as the light that would be reflected by the reflective polarizer in the combiner, thus mitigating the glare.

[0011] In some cases, the "dual polarizer combiner" may block transmission from polarized light sources, such as active matrix liquid crystal displays, such as TVs, computer monitors, ATMs, kiosks, and the like, as well as segmented liquid crystal displays used in digital calculators, clocks, watches, instrument panels, and the like. Often, these polarized displays have a polarization orientation of 0, 45, or 90 degrees. To alleviate the problem of the "dual polarizer combiner" blocking transmission from polarized light sources, the absorbing polarizer can be rotated to an angle other than one of the three preferred orientations mentioned above. For example, the absorbing polarizer can be rotated to 15 degrees or 35 degrees. In this case, light from polarized light sources having one of the three preferred orientations will be transmitted by the "dual polarizer combiner".

[0012] In some cases where the HMD user rotates his or her head, the image of the polarized source may still be blocked by the dual polarizer combiner when the axis of the absorbing polarizer is aligned with the axis of the polarized source.

[0013] The optical system of the present disclosure includes a reflective polarizer as an image combiner for a head-mounted display. An absorbing polarizer is deployed in the same combiner system to reduce glare by minimizing ambient reflections from the reflective polarizer. To prevent the absorbing polarizer from blocking linearly polarized sources, such as liquid crystal displays, from transmitting through the combiner, a weakly absorbing polarizer is provided that allows transmission of the polarized source while still minimizing glare.

[0014] As shown generally in Figures 1 and 2, an optical system (200) for displaying a first image and a second image to a viewer (10) includes a different first display (20) and a second display (30). In some embodiments, the first display (20) can be an electronic display. In some other embodiments, the second display (30) can be an electronic display (30a), which can emit polarized light. In some aspects, the electronic display (20, 30a) includes one or more of a liquid crystal display (LCD) and an organic light emitting diode (OLED) display. In some embodiments, the electronic display can be substantially flat or planar as shown, curved, or can include multiple flat or planar panels arranged at an obtuse angle relative to one another. The electronic display (30a) can be a billboard, or the like. In some other aspects, the second display (30) is a real-world object (30b) in a real-world scene.

[0015] The optical system (200) includes an optical stack (40). In some embodiments, the optical stack (40) is curved. The optical stack (40) is configured to receive a first light beam (50) from the first display (20) and reflect the received first light beam (50) for viewing by a viewer. The optical stack is further configured to receive a second light beam (60a, 60b) from the second display (30), different from the first light beam (50), and transmit the received second light beam (60a, 60b) for viewing by a viewer.

[0016] In some embodiments, the optical stack includes a reflective polarizer (41) facing the first display (20) and an absorbing polarizer (42) disposed on the reflective polarizer (41) facing the second display (30). The absorbing polarizer may be attached to the reflective polarizer via an adhesive layer (43), such as an optically clear adhesive or the like. The reflective polarizer (41) may be a broadband reflective polarizer or a notch reflective polarizer. In some embodiments, the reflective polarizer (41) may be a high contrast reflective polarizer. In some embodiments, the reflective polarizer (41) may include one or more of a wire grid reflective polarizer and a multilayer polymer reflective polarizer. In other embodiments, the reflective polarizer (41) may be a multilayer optical film polarizer.

[0017] The reflective polarizer (41) has orthogonal pass and block axes (A1 and B1). The absorbing polarizer (42) has orthogonal pass and block axes (A2 and B2). In some embodiments, for substantially normally incident light having a wavelength in the range of about 400 nm to about 700 nm, the reflective polarizer (41) reflects at least 70% of the incident light polarized along the block axis (B1) of the reflective polarizer (41) and transmits at least 70% of the incident light polarized along the pass axis (A1) of the reflective polarizer (41). The absorbing polarizer (42) absorbs at least 50% and up to 85% of the incident light polarized along the block axis (B2) of the absorbing polarizer (42) and transmits at least 70% of the incident light polarized along the pass axis (A2) of the absorbing polarizer (42). In some embodiments, the absorbing polarizer absorbs at least 60% and up to 85% of the incident light polarized along the block axis (B2) of the absorbing polarizer. In some other embodiments, the absorbing polarizer absorbs at least 60% and up to 80% of the incident light polarized along the block axis (B2) of the absorbing polarizer. In some other embodiments, the absorbing polarizer absorbs at least 70% and up to 85% of the incident light polarized along the block axis (B2) of the absorbing polarizer. In some other embodiments, the absorbing polarizer absorbs at least 70% and up to 80% of the incident light polarized along the block axis (B2) of the absorbing polarizer.

[0018] For example, as graphically represented in FIG. 3, for substantially normally incident light having a wavelength in the range of about 400 nm to about 700 nm, the transmission in an optical system having a multilayer optical film, such as a high contrast two-packet reflective polarizer, is about 85% to 90% in the pass axis, with little or no transmission in the block axis.

[0019] In another example, as graphically represented in FIG. 4, for substantially normally incident light having a wavelength in the range of about 400 nm to about 700 nm, the transmittance in an optical system having a weakly absorbing polarizer is about 75% to about 85% in the pass axis and about 10% to 35% in the block axis.

[0020] In some aspects, the block axis (B1) of the reflective polarizer (41) and the block axis (B2) of the absorbing polarizer (42) form an angle (bias) (θ) with respect to each other. The angle (θ) can be from about 5 degrees to about 40 degrees. In some embodiments, the angle (θ) between the block axis (B1) of the reflective polarizer (41) and the block axis (B2) of the absorbing polarizer (42) can be from about 10 degrees to about 30 degrees, or from 15 degrees to 25 degrees.

[0021] For example, Figure 5 shows the transmission in an optical system having a combination of a reflective polarizer and a weakly absorbing polarizer, where the angle (θ) between the block axis (B1) of the reflective polarizer and the block axis (B2) of the absorbing polarizer is about 22.5 degrees. For substantially normally incident light having a wavelength in the range of about 400 nm to about 700 nm, the absorbing polarizer transmits about 5% of the incident light polarized along the block axis of the absorbing polarizer. Such transmission in the block axis may be sufficient to allow a viewer to see, for example, a second display (30a) that emits polarized light.

[0022] Another embodiment of the present disclosure relates to a see-through optical system (200) for displaying a virtual image (21) to an observer (10). The system includes a first display (20) configured to emit a first image (50) having a first polarization state (x) and an optical stack (40) curved along two mutually orthogonal directions (x, y). An eyepiece of the observer (10) together with the optical stack (40) forms a magnified virtual image (21) of the image (50) emitted by the first display (20).

[0023] The optical stack (40) is configured to receive the emitted first image (50) and reflect the received first image (50) for viewing by the observer (10). The observer can view a magnified virtual image (21) of the first image (20) and receive and view polarized real-world objects (30a) in the real-world scene through the optical stack (40). In some embodiments, for light (70) having at least one wavelength within a predetermined wavelength range and propagating along a substantially normal incidence direction (71), the optical stack (40) reflects at least 70% of the incident light polarized along a first polarization state and absorbs at least 50% and up to 85% of the incident light having an orthogonal second polarization state (y). As the optical stack (40) is continuously rotated at least 180 degrees about the light (60a) entering the optical stack (40) from the polarized real-world object (30a), the polarized real-world object (30a) remains observable by the observer.

[0024] In some embodiments, the optical stack (40) of the see-through optical system (200) includes a reflective polarizer (41) facing the first display, and an absorbing polarizer (42) disposed on the reflective polarizer (41) and facing the polarized real-world object (30a). The reflective polarizer (41) and the absorbing polarizer (42) each have orthogonal pass axes (A1, A2) and block axes (B1, B2). The block axis (B1) of the reflective polarizer (41) can be oriented along a first polarization state.

[0025] For substantially normally incident light having a wavelength within a predetermined wavelength range, the reflective polarizer (41) reflects at least 70% of the incident light polarized along the reflective polarizer's block axis (B1) and transmits at least 70% of the incident light polarized along the reflective polarizer's pass axis (A1). The absorbing polarizer (42) absorbs at least 50% and up to 85% of the incident light polarized along the absorbing polarizer's block axis (B2) and transmits at least 70% of the incident light polarized along the absorbing polarizer's pass axis (A2). The block axis (B1) of the reflective polarizer (41) and the block axis (B2) of the absorbing polarizer (42) form an angle (θ) with each other. The angle (θ) can be from about 5 degrees to about 40 degrees. In some embodiments, the angle (θ) between the block axis (B1) of the reflective polarizer (41) and the block axis (B2) of the absorbing polarizer (42) can be from about 10 degrees to about 30 degrees, or from 15 degrees to 25 degrees.

[0026] In some embodiments, the predetermined wavelength range is from about 400 nm to about 700 nm. In some embodiments, the predetermined wavelength range can be a blue wavelength range, a green wavelength range, or a red wavelength range. The at least one wavelength can include at least one blue wavelength, at least one green wavelength, and at least one red wavelength.

[0027] Descriptions of elements in the figures should be understood to apply equally to corresponding elements in other figures unless otherwise indicated. Although specific embodiments have been illustrated and described herein, those skilled in the art will recognize that various alternative and / or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. The present application is intended to cover any adaptations or variations of the specific embodiments described herein. Accordingly, the present disclosure is to be limited only by the claims and their equivalents. The following are exemplary embodiments. [Item 1] 1. An optical system for displaying a first image and a second image to a viewer, comprising: a first display and a second display that are different; An optical laminate, receiving a first beam of light from the first display and reflecting the received first beam of light for viewing by the viewer; configured to receive a second light beam from the second display, different from the first light beam, and transmit the received second light beam for viewing by the viewer, the optical stack comprising: a reflective polarizer facing the first display; an absorbing polarizer disposed on the reflective polarizer and facing the second display; and wherein the reflective polarizer and the absorbing polarizer each have orthogonal pass and block axes, such that for substantially normally incident light having a wavelength in the range of about 400 nm to about 700 nm, the reflective polarizer reflects at least 70% of the incident light polarized along the block axis of the reflective polarizer and transmits at least 70% of the incident light polarized along the pass axis of the reflective polarizer; an optical stack, wherein the absorbing polarizer absorbs at least 50% and at most 85% of the incident light polarized along the block axis of the absorbing polarizer and transmits at least 70% of the incident light polarized along the pass axis of the absorbing polarizer; the block axis of the reflective polarizer and the block axis of the absorbing polarizer form an angle between each other of about 5 degrees to about 40 degrees. [Item 2] 2. The optical system of claim 1, wherein the second display is a real-world object in a real-world scene. [Item 3] Item 2. The optical system of item 1, wherein the reflective polarizer comprises one or more of a wire grid reflective polarizer and a multilayer polymer reflective polarizer. [Item 4] 2. The optical system of claim 1, wherein the angle between the block axis of the reflective polarizer and the block axis of the absorbing polarizer is between about 10 degrees and about 30 degrees. [Item 5] Item 1 , the optical system according to item 1 , wherein the absorbing polarizer transmits approximately 5% of the incident light polarized along the block axis of the absorbing polarizer. [Item 6] 1. A see-through optical system for displaying a virtual image to a viewer, comprising: a first display configured to emit a first image having a first polarization state; an optical stack curved along two mutually orthogonal directions configured to receive the emitted first image and reflect the received first image for viewing by the observer, where the observer views a magnified virtual image of the first image, and where the observer is able to receive and see polarized real-world objects in a real-world scene through the optical stack, whereby for light having at least one wavelength within a predetermined wavelength range and propagating along a substantially normal incidence direction, the optical stack: reflecting at least 70% of the incident light polarized along the first polarization state; an optical stack that absorbs at least 50% and at most 85% of the incident light having an orthogonal second polarization state; A see-through optical system, wherein the polarized real-world object remains observable by the observer when the optical stack is continuously rotated at least 180 degrees about light entering the optical stack from the polarized real-world object. [Item 7] 7. The see-through optical system according to item 6, wherein the predetermined wavelength range is from about 400 nm to about 700 nm. [Item 8] 7. The see-through optical system of item 6, wherein the predetermined wavelength range is a blue wavelength range. [Item 9] 7. The see-through optical system of item 6, wherein the at least one wavelength includes at least one blue wavelength, at least one green wavelength, and at least one red wavelength. [Item 10] Item 7. The see-through optical system according to item 6, wherein the optical laminate comprises: a reflective polarizer facing the first display; an absorbing polarizer disposed on the reflective polarizer and facing the polarized real-world object; The reflective polarizer and the absorbing polarizer each have orthogonal pass and block axes, such that for substantially normally incident light having a wavelength within the predetermined wavelength range: the reflective polarizer reflects at least 70% of the incident light polarized along the block axis of the reflective polarizer and transmits at least 70% of the incident light polarized along the pass axis of the reflective polarizer; the absorbing polarizer absorbs at least 50% and at most 85% of the incident light polarized along the block axis of the absorbing polarizer and transmits at least 70% of the incident light polarized along the pass axis of the absorbing polarizer; the block axis of the reflective polarizer and the block axis of the absorbing polarizer form an angle of about 5 degrees to about 40 degrees with each other; The see-through optical system, wherein the block axis of the reflective polarizer is oriented along the first polarization state.

Claims

1. 1. An optical system for displaying a first image and a second image to a viewer, comprising: a first display and a second display that are different; An optical laminate, receiving a first beam of light from the first display and reflecting the received first beam of light for viewing by the viewer; configured to receive a second light beam from the second display, the second light beam being different from the first light beam, and to transmit the received second light beam for viewing by the viewer, the optical stack comprising: a reflective polarizer facing the first display; an absorbing polarizer disposed on the reflective polarizer and facing the second display; and wherein the reflective polarizer and the absorbing polarizer each have orthogonal pass and block axes, such that for substantially normally incident light having a wavelength in the range of 400 nm to 700 nm: the reflective polarizer reflects at least 70% of the normally incident light polarized along the block axis of the reflective polarizer and transmits at least 70% of the normally incident light polarized along the pass axis of the reflective polarizer; an optical stack, wherein the absorbing polarizer absorbs at least 50% and at most 85% of the normally incident light polarized along the block axis of the absorbing polarizer and transmits at least 70% of the normally incident light polarized along the pass axis of the absorbing polarizer; The optical system wherein the block axis of the reflective polarizer and the block axis of the absorbing polarizer form an angle with each other of between 5 degrees and 40 degrees.

2. The optical system of claim 1, wherein the second display is a real-world object in a real-world scene.

3. 1. A see-through optical system for displaying a virtual image to a viewer, comprising: a first display configured to emit a first image having a first polarization state; an optical stack curved along two mutually orthogonal directions configured to receive the emitted first image and reflect the received first image for viewing by the observer, where the observer views a magnified virtual image of the first image, and where the observer is able to receive and see polarized real-world objects in a real-world scene through the optical stack, whereby for light having at least one wavelength within a predetermined wavelength range and propagating along a substantially normal incidence direction, the optical stack: reflecting at least 70% of the light polarized along the first polarization state; an optical stack that absorbs at least 50% and at most 85% of the light having an orthogonal second polarization state; A see-through optical system, wherein the polarized real-world object remains observable by the observer when the optical stack is continuously rotated at least 180 degrees about light entering the optical stack from the polarized real-world object.

Images