Abstract: An electronic device may include a display system with a pixel array and a catadioptric lens. The display system may include a linear polarizer through which image light from the pixel array passes and a first quarter wave plate through which the light passes after passing through the polarizer. The lens may include a partial mirror, a second quarter wave plate, and a reflective polarizer. A third quarter wave plate may be formed between the linear polarizer and the pixel array to mitigate ghost images. Control circuitry may predict potential ghost images based on the geometry of the lens and data from an image frame. Tone mapping circuitry may adjust contrast of the image frame within a region overlapping the predicted ghost image. The control circuitry may adjust luminance of the image frame outside of the region overlapping the predicted ghost image.

Abstract: A head-mounted device may have catadioptric lenses that each include a partial mirror, a quarter wave plate, and a polarizer. An optical system in the head-mounted device may have an infrared light-emitting device and an infrared light-sensing device. The optical system may illuminate a user's eyes in eye boxes and may gather measurements from the illuminated eye boxes for eye tracking and other functions. The optical system may operate through the catadioptric lenses. To enhance optical system performance, the polarizers may be wire grid polarizers that are formed from conductive lines that exhibit enhanced infrared transmission and/or the quarter wave plates may be formed from cholesteric liquid crystal layers that serve as quarter wave plates at visible wavelengths and that do not serve as quarter wave plates at infrared wavelengths.

Abstract: A head-mounted device may have optical modules that present images to a user's left and right eyes. Each optical module may have a lens support structure that supports a display and a fixed lens. Vision correction lenses may be removably coupled to the fixed lenses to help customize the head-mounted device to the vision of a particular user. A user may view images on the displays through the removable and fixed lenses from eye boxes. The optical modules may include infrared light sources that supply infrared light to the eye boxes and infrared light sensors such as infrared cameras for gaze tracking and authentication. The lenses may have optical surfaces covered with coating that enhance optical performance and may have edge surfaces that are provided with structures to help reduce stray light reflections. The lenses may be configured to pass visible and infrared light.

Abstract: A head-mounted device may have catadioptric lenses that each include a partial mirror, a quarter wave plate, and a polarizer. An optical system in the head-mounted device may have an infrared light-emitting device and an infrared light-sensing device. The optical system may illuminate a user's eyes in eye boxes and may gather measurements from the illuminated eye boxes for eye tracking and other functions. The optical system may operate through the catadioptric lenses. To enhance optical system performance, the polarizers may be wire grid polarizers that are formed from conductive lines that exhibit enhanced infrared transmission and/or the quarter wave plates may be formed from cholesteric liquid crystal layers that serve as quarter wave plates at visible wavelengths and that do not serve as quarter wave plates at infrared wavelengths.

Abstract: A head-mounted display may include a display system and an optical system that are supported by a housing. The optical system may be a catadioptric optical system having one or more lens elements. In one example, the optical system includes a single lens element and a retarder that is coated on a curved surface of the lens element. The retarder may be coated on an aspheric concave surface of the lens element. In another example the retarder may be coated on an aspheric convex surface of the lens element. One or more components of the optical system may be formed using a direct printing technique. This may allow for one or more adhesive layers and one or more hard coatings to be omitted from the optical system. A lens element may be directly printed on the display system to improve alignment between the optical system and the display system.

Abstract: An electronic device may have a support structure that supports a display and lenses. Each lens may be a reflective lens such as a catadioptric lens that receives polarized image light from the display and provides a corresponding image to an eye box. The display may be an emissive display with pixels that include light-emitting diodes. The light-emitting diodes may be overlapped by a light recycling layer such as a reflective polarizer or cholesteric liquid crystal layer. The light recycling layer recycles emitted light to enhance display efficiency.

Abstract: A head-mounted display may include a display system and an optical system that are supported by a housing. The optical system may be a catadioptric optical system having one or more lens elements. In one example, the optical system includes a single lens element and a retarder that is coated on a curved surface of the lens element. The retarder may be coated on an aspheric concave surface of the lens element. In another example the retarder may be coated on an aspheric convex surface of the lens element. One or more components of the optical system may be formed using a direct printing technique. This may allow for one or more adhesive layers and one or more hard coatings to be omitted from the optical system. A lens element may be directly printed on the display system to improve alignment between the optical system and the display system.

Abstract: Display structures and methods of manufacture of display structure including a display panel with a curved three-dimensional film contour are described. In an embodiment, a display panel includes display area with a main body area and a plurality of petals extending from the main body area. The petals are folded into a curved three-dimensional (3D) film contour, and are separated by corresponding trenches between petals. The trenches may be filled with various seam hiding materials to visually obscure the trenches.

Abstract: A head-mounted display may include a display system and an optical system that are supported by a housing. The optical system may be a catadioptric optical system having one or more lens elements. In one example, the optical system includes a single lens element and a retarder that is coated on a curved surface of the lens element. The retarder may be coated on an aspheric concave surface of the lens element. In another example the retarder may be coated on an aspheric convex surface of the lens element. One or more components of the optical system may be formed using a direct printing technique. This may allow for one or more adhesive layers and one or more hard coatings to be omitted from the optical system. A lens element may be directly printed on the display system to improve alignment between the optical system and the display system.

Abstract: Compound dichroic polarizers (CDPs) include multiple component dichroic polarizers based on different dichroic dyes and oriented to have different eigenpolarization directions. The component dichroic polarizers can be fixed to each other or to a substrate such as an eyeglass lens. Selection of eigenpolarization orientation and spectrum in a CDP permits color encoding of different SOPs.

Abstract: An electronic device may have a support structure that supports a display and lenses. Each lens may be a reflective lens such as a catadioptric lens that receives polarized image light from the display and provides a corresponding image to an eye box. The display may be an emissive display with pixels that include light-emitting diodes. The light-emitting diodes may be overlapped by a light recycling layer such as a reflective polarizer or cholesteric liquid crystal layer. The light recycling layer recycles emitted light to enhance display efficiency.

Abstract: Exemplary thin-film optical devices have first and second layer groups disposed as a layer stack on a substrate. The first layer group comprises a first PPN layer, a first LCP layer, and a first barrier layer all superposed. The second layer group is superposed relative to the first layer group, and includes a second PPN layer, a second LCP layer, and a second barrier layer all superposed. The first and second layer groups cooperate to polarize multiple wavelengths of an incident light flux in a broadband and/or wide-angle manner Each of the layer groups has an alignment layer, a respective liquid-crystal polymer layer, and a barrier layer.

Abstract: An examination method comprises: generating a received audio signal according to sound generated from rotation of the fan by an audio receiving device; performing Fourier transform on the received audio signal to obtain a reference frequency domain signal; recognizing a plurality of characteristic bands according to the reference frequency domain signal; adjusting the received audio signal according to the characteristic bands respectively to form a plurality of casting audio signals corresponding to frequency components in the characteristic bands respectively; playing the casting signals sequentially by an audio casting device; and recognizing at least one key band among the characteristic bands according to the transmission rate of the hard drive upon playing the casting signals.

Abstract: Exemplary thin-film optical devices have first and second layer groups disposed as a layer stack on a substrate. The first layer group comprises a first PPN layer, a first LCP layer, and a first barrier layer all superposed. The second layer group is superposed relative to the first layer group, and includes a second PPN layer, a second LCP layer, and a second barrier layer all superposed. The first and second layer groups cooperate to polarize multiple wavelengths of an incident light flux in a broadband and/or wide-angle manner Each of the layer groups has an alignment layer, a respective liquid-crystal polymer layer, and a barrier layer.

Abstract: An examination method comprises: generating a received audio signal according to sound generated from rotation of the fan by an audio receiving device; performing Fourier transform on the received audio signal to obtain a reference frequency domain signal; recognizing a plurality of characteristic bands according to the reference frequency domain signal; adjusting the received audio signal according to the characteristic bands respectively to form a plurality of casting audio signals corresponding to frequency components in the characteristic bands respectively; playing the casting signals sequentially by an audio casting device; and recognizing at least one key band among the characteristic bands according to the transmission rate of the hard drive upon playing the casting signals.

Abstract: Exemplary thin-film optical devices have first and second layer groups disposed as a layer stack on a substrate. The first layer group comprises a first PPN layer, a first LCP layer, and a first barrier layer all superposed. The second layer group is superposed relative to the first layer group, and includes a second PPN layer, a second LCP layer, and a second barrier layer all superposed. The first and second layer groups cooperate to polarize multiple wavelengths of an incident light flux in a broadband and/or wide-angle manner. Each of the layer groups has an alignment layer, a respective liquid-crystal polymer layer, and a barrier layer.

Abstract: Compound dichroic polarizers (CDPs) include multiple component dichroic polarizers based on different dichroic dyes and oriented to have different eigenpolarization directions. The component dichroic polarizers can be fixed to each other or to a substrate such as an eyeglass lens. Selection of eigenpolarization orientation and spectrum in a CDP permits color encoding of different SOPs.

Abstract: A linear photopolymerizable polymer (LPP) layer is situated to align liquid crystal molecules in a cholesteric liquid crystal polymer (Ch-LCP) layer situated at or on the LPP layers. The Ch-LCP layer includes a patterned area and an unpatterned area. The patterned area and the un-patterned area have different optical properties. The Ch-LCP layer can be tuned to transmit light of a desired frequency and handedness. Single and multiple-layered LPP/Ch-LCP and/or LPP/LCP structures can be provided as patterned polarizers, patterned retarders and other devices.

Abstract: Exemplary thin-film optical devices have first and second layer groups disposed as a layer stack on a substrate. The first layer group comprises a first PPN layer, a first LCP layer, and a first barrier layer all superposed. The second layer group is superposed relative to the first layer group, and includes a second PPN layer, a second LCP layer, and a second barrier layer all superposed. The first and second layer groups cooperate to polarize multiple wavelengths of an incident light flux in a broadband and/or wide-angle manner. Each of the layer groups has an alignment layer, a respective liquid-crystal polymer layer, and a barrier layer.

Abstract: A linear photopolymerizable polymer (LPP) layer is situated to align liquid crystal molecules in a cholesteric liquid crystal polymer (Ch-LCP) layer situated at or on the LPP layers. The Ch-LCP layer includes a patterned area and an unpatterned area. The patterned area and the un-patterned area have different optical properties. The Ch-LCP layer can be tuned to transmit light of a desired frequency and handedness. Single and multiple-layered LPP/Ch-LCP and/or LPP/LCP structures can be provided as patterned polarizers, patterned retarders and other devices.