Magic Leap Patent | Virtual/augmented reality system having dynamic region resolution

Patent: Virtual/augmented reality system having dynamic region resolution

Publication Number: 10176639

Publication Date: 2019-01-08

Applicants: Magic Leap

Abstract

A virtual image generation system and method is provided. A plurality of synthetic image frames of the three-dimensional scene are rendered, and sequentially displayed to an end user. Each of the displayed image frames has a non-uniform resolution distribution.

Background

Modern computing and display technologies have facilitated the development of systems for so-called “virtual reality” or “augmented reality” experiences, wherein digitally reproduced images or portions thereof are presented to a user in a manner where they seem to be, or may be perceived as, real. A virtual reality (VR) scenario typically involves presentation of digital or virtual image information without transparency to other actual real-world visual input, whereas an augmented reality (AR) scenario typically involves presentation of digital or virtual image information as an augmentation to visualization of the actual world around the end user.

For example, referring to FIG. 1, an augmented reality scene 4 is depicted wherein a user of an AR technology sees a real-world park-like setting 6 featuring people, trees, buildings in the background, and a concrete platform 8. In addition to these items, the end user of the AR technology also perceives that he “sees” a robot statue 10 standing upon the real-world platform 8, and a cartoon-like avatar character 12 flying by which seems to be a personification of a bumble bee, even though these elements 10, 12 do not exist in the real world. As it turns out, the human visual perception system is very complex, and producing a VR or AR technology that facilitates a comfortable, natural-feeling, rich presentation of virtual image elements amongst other virtual or real-world imagery elements is challenging.

VR and AR systems typically employ head-worn displays (or helmet-mounted displays, or smart glasses) that are at least loosely coupled to a user’s head, and thus move when the end user’s head moves. If the end user’s head motions are detected by the display system, the data being displayed can be updated to take the change in head pose (i.e., the orientation and/or location of user’s head) into account.

As an example, if a user wearing a head-worn display views a virtual representation of a three-dimensional (3D) object on the display and walks around the area where the 3D object appears, that 3D object can be re-rendered for each viewpoint, giving the end user the perception that he or she is walking around an object that occupies real space. If the head-worn display is used to present multiple objects within a virtual space (for instance, a rich virtual world), measurements of head pose can be used to re-render the scene to match the end user’s dynamically changing head location and orientation and provide an increased sense of immersion in the virtual space.

Head-worn displays that enable AR (i.e., the concurrent viewing of real and virtual elements) can have several different types of configurations. In one such configuration, often referred to as a “video see-through” display, a camera captures elements of a real scene, a computing system superimposes virtual elements onto the captured real scene, and a non-transparent display presents the composite image to the eyes. Another configuration is often referred to as an “optical see-through” display, in which the end user can see through transparent (or semi-transparent) elements in the display system to view directly the light from real objects in the environment. The transparent element, often referred to as a “combiner,” superimposes light from the display over the end user’s view of the real world.

VR and AR systems typically employ a display system having a projection subsystem and a display surface positioned in front of the end user’s field of view and on which the projection subsystem sequentially projects image frames. In true three-dimensional systems, the depth of the display surface can be controlled at frame rates or sub-frame rates. The projection subsystem may include one or more optical fibers into which light from one or more light sources emit light of different colors in defined patterns, and a scanning device that scans the optical fiber(s) in a predetermined pattern to create the image frames that sequentially displayed to the end user.

Because a VR or AR system interfaces closely with the human visual system, the resolution of each image frame need only match the resolution of the human eye to provide the correct visual stimulus. To this end, the resolution of the each image frame is typically set to the maximum resolution of the human eye. However, because the scanning frequency of any particular system is a function of the image frame resolution due to both software and hardware limitations (i.e., the frequency at the respective image frames are graphically rendered (software) and actually presented to the end user via the scanner (hardware)), attempting to match the image frame resolution to the maximum resolution of the human eye adds constraints to the AR and VR system that may either result in scanning frequencies that may not optimize the viewing experience of the end user and/or require prohibitively more expensive componentry of the AR or VR system necessary to implement the increased processing and scanning speed required to generate and present the higher resolution image frames.

There, thus, is a need to reduce the overall resolution and/or hardware/software processing cost of an image frame generated and present to an end user in a virtual reality or augmented reality environment.

Summary

Embodiments of the present invention are directed to devices, systems and methods for facilitating virtual reality and/or augmented reality interaction for one or more users.

In accordance with one aspect of the present inventions, a method of operating a virtual image generation system is provided. The method comprises rendering a plurality of synthetic image frames of a three-dimensional scene, and sequentially displaying the plurality of image frames to the end user

Significantly, each of the displayed image frames has a non-uniform resolution distribution. In one method, each of the image frames is rendered with the non-uniform resolution distribution. In another method, each of the displayed image frames is rendered with a uniform resolution distribution, in which case, displaying the respective image frame comprises incorporating the non-uniform resolution distribution into the already rendered image frame. The resolution distribution of each of the displayed image frames may have a slope that matches or is even greater than the slope of an acuity distribution of an eye of the end user. The respective image frame may be displayed by scanning the image frame, e.g., in a spiral pattern, such that the non-uniform resolution distribution radially varies, or in a raster pattern, such that the non-uniform resolution distribution varies rectilinearly.

In one method, at least two of the displayed image frames have different non-uniform resolution distribution. In another method, each of the displayed image frames has a plurality of discrete regions (e.g., at least three) having different resolutions. The discrete regions, may be, e.g., annular, rectangular, or sector-shaped. In still another method, the plurality of discrete regions includes a region of highest resolution, in which case, the method may further comprise selecting the region of highest resolution from a field of view template having a plurality of discrete regions, which may overlap each other. In an optional embodiment, the plurality of discrete region may include a region of highest resolution and a region of lower resolution, in which case, the method may further comprise blurring the displayed image frames in the region of lower resolution. The displayed image frames may be blurred, e.g., by dithering scan line in adjacent displayed image frames in the region of lower resolution or by defocusing the displayed image frames in the region of lower resolution.

An optional method comprises estimating a focal point of an eye within a field of view of the end user (e.g., by detecting the focal point of the end user or identifying an object of interest within the field of view of the end user), and generating the non-uniform resolution distribution for each of the displayed image frames based on the estimated focal point. Each of the non-uniform resolution distributions has a region of highest resolution coincident with the estimated focal point. The estimated focal point of the end user may have an error margin to provide a focal range within the field of the view of the end user, in which case, the region of highest resolution may intersect the focal range.

In accordance with a second aspect of the present inventions, a virtual image generation system for use by an end user is provided. The virtual image generation system comprises memory storing a three-dimensional scene, a control subsystem (which may comprise a graphics processor unit (GPU)) configured for rendering a plurality of synthetic image frames of the three-dimensional scene, and a display subsystem configured for sequentially displaying the plurality of image frames to the end user.

In one embodiment, the display subsystem is configured for being positioned in front of the eyes of the end user. In another embodiment, the display subsystem includes a projection subsystem and a partially transparent display surface. The projection subsystem is configured for projecting the image frames onto the partially transparent display surface, and the partially transparent display surface is configured for being positioned in the field of view between the eyes of the end user and an ambient environment. In an optional embodiment, the virtual image generation system further comprises a frame structure configured for being worn by the end user, in which case, the frame structure carries the display subsystem.

Significantly, each of the displayed image frames has a non-uniform resolution distribution. In one embodiment, the control subsystem is configured for rendering each of the image frames with the non-uniform resolution distribution. In another embodiment, the control subsystem is configured for rendering each of the image frames with a uniform resolution distribution, in which case, the display subsystem will be configured for displaying the respective image frame by incorporating the non-uniform resolution distribution into the already rendered image frame. The resolution distribution of each of the displayed image frames may have a slope that matches or is even greater than the slope of an acuity distribution of an eye of the end user. The display subsystem may be configured for displaying the image frames by scanning the image frames. For example, the display subsystem may be configured for scanning each of the image frames in a spiral pattern, in which case, the non-uniform resolution distribution radially varies, or may be configured for scanning the image frames in a raster pattern, in which case, the non-uniform resolution distribution rectilinearly varies.

In one embodiment, at least two of the displayed image frames have different non-uniform resolution distributions. In another embodiment, each of the displayed image frames has a plurality of discrete regions (e.g., at least three) having different resolutions. The shape of the discrete regions may be, e.g., annular, rectangular, or sector-shaped. The plurality of discrete regions may include a region of highest resolution, in which case, the control subsystem may be configured for selecting the region of highest resolution from a field of view template having a plurality of discrete regions, which may overlap with each other. The plurality of discrete region may also include a region of lower resolution, in which case, the control subsystem may be configured for blurring the displayed image frames in the region of lower resolution. For example, if the display subsystem is configured for scanning each of the displayed image frames, the display subsystem may be configured for blurring the displayed image frames by dithering scan lines in adjacent displayed image frames in the region of lower resolution. Or, the display subsystem may be configured for blurring the displayed image frames by defocusing the displayed image frames in the region of lower resolution.

In an optional embodiment, the control subsystem is configured for estimating a focal point of an eye within a field of view of the end user, and generating the non-uniform resolution distribution for each of the displayed image frames based on the estimated focal point. Each of the non-uniform resolution distributions may have a region of highest resolution coincident with the estimated focal point. The estimated focal point of the end user may have an error margin to provide a focal range within the field of the view of the end user, in which case, the region of highest resolution will intersect the focal range. The virtual image generation system may further comprise one or more sensors configured for detecting the focal point of the end user, in which case, the control subsystem may be configured for estimating the focal point from the detected focal point. Or, the control subsystem may be configured for estimating the focal point by identifying an object of interest in the field of view of the end user.

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