Facebook Patent | Hybrid fresnel lens with reduced artifacts

Patent: Hybrid fresnel lens with reduced artifacts

Publication Number: 10133076

Publication Date: 2018-11-20

Applicants: Facebook Technologies, LLC

Abstract

A lens defined by a first lens surface and a second lens surface opposite to the first lens surface is disclosed. A first portion of the first lens surface is defined by a smooth surface profile function, and a second portion of the first lens surface is defined by a Fresnel surface profile function. The second portion of the first lens surface is around the first portion of the first lens surface. Also disclosed is a display device that includes the lens and an array of light emitting devices coupled with the lens for outputting light through the lens.

BACKGROUND 

Head-mounted display devices (also called herein head-mounted displays) are gaining popularity as means for providing visual information to user. However, the size and weight of conventional head-mounted displays have limited applications of head-mounted displays.

SUMMARY 

Accordingly, there is a need for head-mounted displays that are compact and light, thereby enhancing the user’s virtual-reality and/or augmented reality experience.

Fresnel lenses provide apertures and focal lengths comparable to conventional lenses. Because Fresnel lenses are typically thinner and lighter than conventional lenses of similar performance features (e.g., aperture and/or focal length), replacing conventional lenses in head-mounted displays with Fresnel lenses can reduce the size and weight of the head-mounted displays. However, Fresnel lenses suffer from diffractions associated with Fresnel structures, and thus, their use in imaging applications is limited.

Thus, there is a need for lenses that are compact and light while maintaining the quality of projected images.

The above deficiencies and other problems associated with conventional lenses are reduced or eliminated by the disclosed lens. In some embodiments, the lens is included in a display device. In some embodiments, the device is a head-mounted display device. In some embodiments, the device is portable.

In accordance with some embodiments, a lens is defined by a first lens surface and a second lens surface opposite to the first lens surface. A first portion of the first lens surface is defined by a smooth surface profile function, and a second portion of the first lens surface is defined by a Fresnel surface profile function. The second portion of the first lens surface is around the first portion of the first lens surface.

In accordance with some embodiments, a display device includes a lens described herein and an array of light emitting devices coupled with the lens for outputting light through the lens.

Thus, the disclosed embodiments provide compact and light weight display devices with increased efficiency, effectiveness, and user satisfaction with such devices.

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