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EP-4416549-B1 - CURVED SEE-THROUGH LIGHTGUIDE WITH INTERMEDIATE FOCUS

EP4416549B1EP 4416549 B1EP4416549 B1EP 4416549B1EP-4416549-B1

Inventors

  • GLIK, Eliezer
  • CAKMAKCI, OZAN

Dates

Publication Date
20260506
Application Date
20221011

Claims (14)

  1. A head-mounted display (100), comprising: a microdisplay (422) configured to emit light (434) representative of an image; and an incoupler (424) including an optics relay (430) configured to receive the light (434) representative of the image and provide the light (434) to a curved lightguide (420) such that an intermediate image (432) based on the image is formed in the curved lightguide (420), wherein the curved lightguide (420) is configured to output light based on the intermediate image (432), an optical output system (426) configured to receive the light based on the intermediate image (432) and direct the light to an eye (440) of a user as output light (438), wherein the incoupler (424) comprises freeform grating structures, and wherein the freeform grating structures of the incoupler (424) are configured to apply a pre-distortion to light forming the intermediate image (432), wherein a distortion of the output light (438) applied by, for example, surfaces of the optical output system (426), outside light, or both, cancels out at least a portion of the pre-distortion.
  2. The head-mounted display (100) of claim 1, wherein the optical output system (426) is configured to direct the light based on the intermediate image (432) towards a lens of an optical combiner.
  3. The head-mounted display (100) of claim 2, wherein the optical output system (426) comprises a retroreflector configured to receive the light based on the intermediate image (432) and reflect the light based on the intermediate image (432) back toward a portion of the curved lightguide (420), the portion of the curved lightguide (420) being configured to reflect the light to the eye (440) of the user.
  4. The head-mounted display (100) of claim 2, wherein the optical output system (426) comprises a wedge-shaped outcoupler.
  5. The head-mounted display (100) of claim 4, wherein the wedge-shaped outcoupler includes a reflective optical coating disposed on a surface of the wedge-shaped outcoupler.
  6. The head-mounted display (100) of claim 2, wherein the optical output system (426) comprises a partial mirror outcoupler configured to reflect the light based on the intermediate image (432) towards the lens of the optical combiner.
  7. The head-mounted display (100) of claim 2, wherein the optics relay (430) is configured to magnify the image by a predetermined power to form the intermediate image (432).
  8. The head-mounted display (100) of any of claims 1 to 7, wherein the curved lightguide (420) includes one or more freeform surfaces.
  9. The head-mounted display (100) of any of claims 1 to 8, further comprising an F stop configured to filter at least a portion of the light representative of an image.
  10. The head-mounted display (100) of claim 9, wherein the intermediate image (432) is based on the filtered at least a portion of the light representative of the image.
  11. The head-mounted display (100) of any of claims 1 to 10, wherein the lightguide (420) comprises a first non-planar major surface and a second non-planar major surface configured to reflect light received from the incoupler (424) and provide the light to the optical output system (426).
  12. A method, comprising: emitting, by a microdisplay (422), light representative of an image; receiving, at an incoupler (424) including an optics relay (430), the light representative of the image; and providing, by the optics relay (430), the light to a curved lightguide (420) such that an intermediate image (432) based on the image is formed in the curved lightguide (420), receiving, by an optical output system (426), the light based on the intermediate image (432) and directing the light to an eye (440) of a user as output light, whereir the incoupler (424) comprises freeform grating structures; and applying a pre-distortion to light forming the intermediate image (432) by the freeform grating structures of the incoupler (424) so that a distortion of the output light applied by, for example, surfaces of the optical output system (426), outside light, or both, cancels out at least a portion of the pre-distortion.
  13. The method of claim 12, wherein the optical output system (426) is configured to reflect the light based on the intermediate image (432) towards a lens of an optical combiner.
  14. The method of claim 13, wherein the optical output system (426) comprises a retroreflector configured to receive the light based on the intermediate image (432) and reflect the light based on the intermediate image (432) back towards a portion of the curved lightguide (420), the portion of the curved lightguide (420) being configured to reflect the light to the eye (440) of the user.

Description

BACKGROUND Wearable electronic eyewear devices include optical systems that magnify a display image and deliver a virtual image into the field of view (FOV) of a user. In some cases, wearable electronic eyewear devices also allow the user to see the outside world through a lens or see-through eyepiece. Some wearable electronic eyewear devices incorporate a near-to-eye optical system to display content to the user. These devices are sometimes referred to as head-mounted displays (HMDs). For example, conventional HMD designs include a microdisplay positioned in a temple or rim region of a head wearable frame like a conventional pair of eyeglasses. The microdisplay generates images, such as computer-generated images (CGI), that are conveyed into the FOV of the user by optical elements such as curved lightguides deployed in the lens (or "optical combiner") of the head wearable display frame. The wearable electronic eyewear device can therefore serve as a hardware platform for implementing augmented reality (AR) or mixed reality (MR). Different modes of augmented reality include optical see-through augmented reality, video see-through augmented reality, or opaque (VR) modes. US 2021/014473 A1 shows a head-mounted display comprising a microdisplay, an incoupler including an optics relay configured to provide light from the microdisplay to a curved lightguide such that an intermediate image is formed in the curved lightguide and an optical output system configured to receive the light based on the intermediate image and direct the light to an eye of a user as output light, wherein the optical output system includes a freeform corrector lens configured to correct distortions introduced by the curved lightguide to the real-world scene. BRIEF DESCRIPTION OF THE DRAWINGS The present disclosure may be better understood, and its numerous features and advantages made apparent to those skilled in the art by referencing the accompanying drawings. The use of the same reference symbols in different drawings indicates similar or identical items. FIGs. 1 and 2 together illustrate a head-mounted display (HMD) employing an optical combiner through which images projected by the HMD are displayed, in accordance with some embodiments.FIG. 3 is a block diagram illustrating an example process for creating an intermediate image in a lightguide, in accordance with some embodiments.FIG. 4 is a diagram illustrating an optics system for forming an intermediate image in a curved lightguide, in accordance with some embodiments.FIG. 5 is a diagram illustrating an optical output system including a partial mirror outcoupler, in accordance with some embodiments.FIG. 6 is a diagram illustrating an optical output system including a retroreflector, in accordance with some embodiments.FIG. 7 is a diagram illustrating an optical output system including a wedge outcoupler, in accordance with some embodiments. SUMMARY OF EMBODIMENTS The present invention relates to a head-mounted display according to independent claim 1 and to a corresponding image displaying method according to independent claim 12. Techniques and systems described herein are directed to forming an intermediate image in a curved lightguide. According to an example embodiment, a head-mounted display can include a microdisplay configured to emit light representative of an image. Additionally, the head-mounted display may include an optics relay configured to receive the light representative of the image and provide the light to a curved lightguide such that an intermediate image based on the image is formed in the curved lightguide. Further, the curved lightguide can be configured to output light based on the intermediate image. The head-mounted display can further include an optical output system configured to receive the light based on the intermediate image and reflect the light based on the intermediate image towards a lens of an optical combiner. The optical output system can include, for example, a retroreflector configured to receive the light based on the intermediate image and reflect the light based on the intermediate image back toward a portion of the curved lightguide. Further, for example, the optical output system can include a wedge-shaped outcoupler. Such a wedge-shaped outcoupler can include a reflective optical coating disposed on a surface of the wedge-shaped outcoupler. Also, for example, the optical output system may include a partial mirror outcoupler configured to reflect the light based on the intermediate image towards the lens of the optical combiner. Additionally, the optics relay can be configured to magnify the image by a predetermined power. The lightguide of the head-mounted display can include one or more freeform surfaces. Further, the head-mounted display can include an F stop configured to filter at least a portion of the light representative of the image. Also, the intermediate image may be based on the filtered at least a portion of the light repre