Abstract: This disclosure relates to image capture devices with the ability to perform adaptive white balance correction using a switchable white reference (SWR). In some embodiments, the image capture device utilizes “true white” information to record images that better represent users' perceptions. In other embodiments, the same SWR and camera that dynamically sample ambient lighting conditions are used to determine “true white” in near real-time. In other embodiments, the image capture device comprises a display screen that utilizes the “true white” information in near real-time to dynamically adjust the display. In other embodiments, face detection techniques and/or ambient light sensors may be used to determine which device camera is most closely-aligned with the direction that the user of the device is currently looking in, and using it to capture a “true white” image in the direction that most closely corresponds to the ambient lighting conditions that currently dominate the user's perception.

Abstract: An electronic device may include a display having an array of display pixels and having display control circuitry that controls the operation of the display. The display control circuitry may operate the display in different modes. In a paper mode, display control circuitry may use stored spectral reflectance data to adjust display colors such that the colors appear as they would on a printed sheet of paper. In a low light mode when the ambient light level is below a threshold, the light emitted from the display may be adjusted to mimic the appearance of an incandescent light source. In a bright light mode when the ambient light level exceeds a threshold, the light emitted from the display may be adjusted to maximize readability in bright light. The target white point of the display may be adjusted based on which mode the display is operating in.

Abstract: Systems and methods for reducing or eliminating image artifacts on a dual-layer liquid crystal display (LCD). By way of example, a system includes a first display panel and a second display panel. The system includes a processor coupled to the first display panel and the second display panel, and configured to generate a first image, and to generate a second image to be displayed on the first display panel based on the first image. The processor is configured to interpolate the second image. Interpolating the second image includes adjusting the second image according to a generated objective function bounded by a first constraint. The processor is configured to filter the second image, and to generate a third image to be displayed on the second display panel based on the first image and the second image. The third image is generated to prevent image artifacts on the second display panel.

Abstract: An electronic device may include a display having an array of display pixels and having display control circuitry that controls the operation of the display. The display control circuitry may adaptively adjust the display output based on ambient lighting conditions. For example, in cooler ambient lighting conditions such as those dominated by daylight, the display may display neutral colors using a relatively cool white. When the display is operated in warmer ambient lighting conditions such as those dominated by indoor light sources, the display may display neutral colors using a relatively warm white. Adapting to the ambient lighting conditions may ensure that the user does not perceive color shifts on the display as the user's vision chromatically adapts to different ambient lighting conditions. Adaptively adjusting images in this way can also have beneficial effects on the human circadian rhythm by displaying warmer colors in the evening.

Abstract: An electronic device may include a display having an array of display pixels. The display pixels may include red, green, blue, and white subpixels. Pixel mapping circuitry may convert red-green-blue pixel values in a frame of display data to red-green-blue-white pixel values using a brightness adjustment factor. The brightness adjustment factor may be determined based on ambient lighting conditions. The brightness adjustment factor be determined such that any color distortion resulting from applying the brightness adjustment factor is maintained under a just-noticeable-difference (JND) threshold. White subpixel values may be determined based on the brightness adjustment factor. Pixel rendering circuitry may be used to render red-green-blue-white pixel values onto the physical pixel structure. When a display pixel does not include a subpixel of a particular color, the pixel rendering circuitry may compensate for the missing color using nearby subpixels.

Abstract: An electronic device may include a display having an array of display pixels and having display control circuitry that controls the operation of the display. The display control circuitry may adaptively adjust the spectral characteristics of display light emitted from the display to achieve a desired effect on the human circadian system. For example, the display control circuitry may adjust the spectral characteristics of blue light emitted from the display based on the time of day such that a user's exposure to the display light may result in a circadian response similar to that which would be experienced in natural light. The spectral characteristics of blue light emitted from the display may be adjusted by adjusting the relative maximum power levels provided to blue pixels in the display or by shifting the peak wavelength associated with blue light emitted from the display.

Abstract: A display may have a first stage such as a color liquid crystal display stage and a second stage such as a monochromatic liquid crystal display stage that are coupled in tandem so that light from a backlight passes through both stages. The dynamic range of the display may be enhanced by using the second stage to perform local dimming operations. The pixel pitch of the second stage may be greater than the pixel pitch of the first stage to ease alignment tolerances and reduce image processing complexity. The color stage and monochromatic stages may share a polarizer. A color filter in the color stage may have an array of red, green, and blue elements or an array of white, red, green, and blue elements. The color stage may be a fringe field display and the monochrome stage may be an in-plane switching display or a twisted nematic stage.

Abstract: Systems, methods, and devices for white point calibration using subtractive color measurements are provided. Specifically, a white point of a display may be calibrated using subtractive color measurements rather than merely additive color measurements. In one example, a display having red, green, and blue pixels may measure the responses in a subtractive color space (e.g., CMY) rather than additive color space (e.g., RGB). Measurements of the display response using subtractive color space may involve providing image data to two or more color channels at once. Thus, any crosstalk effect between channels may be accounted for, even though the same crosstalk effect might not be apparent using additive color measurements in which only a single channel color channel were measured.

Abstract: A method is provided for calibrating a display having color channels. Each color channel is capable of adjusting settings for pixel values at gray level entries. The method includes selecting a gray level entry for calibration. The method also includes providing a target white point in chromaticity coordinates (x, y) and a target brightness at the selected gray level entry to the display. The method further includes adjusting the setting for the pixel values for the color channels at the selected gray level entry such that the display achieves the target white point and the target brightness at an adjusted pixel value.

Abstract: This specification describes various embodiments that relate to methods for providing a wideband colorimeter that can include more accurate outputs. In one embodiment, a narrowband instrument, such as a spectrometer or spectrograph, can be used for calibration of a wideband colorimeter, so that more accurate outputs can be provided. In one embodiment, an optical test equipment, which consists of both a wideband colorimeter and a narrowband spectrograph, can be used for providing a more accurately calibrated wideband colorimeter. As an example, a spectra-camera, which is a hybrid system consisting of both a wideband colorimeter and a narrowband spectrograph, can be used for simultaneous testing by both the wideband colorimeter and the narrowband spectrograph. By doing simultaneous testing, accurate calibration of the wideband colorimeter can be achieved.

Abstract: This specification describes various embodiments that relate to methods for providing a wideband colorimeter that can include more accurate outputs. In one embodiment, a narrowband instrument, such as a spectrometer or spectrograph, can be used for calibration of a wideband colorimeter, so that more accurate outputs can be provided. In one embodiment, an optical test equipment, which consists of both a wideband colorimeter and a narrowband spectrograph, can be used for providing a more accurately calibrated wideband colorimeter. As an example, a spectra-camera, which is a hybrid system consisting of both a wideband colorimeter and a narrowband spectrograph, can be used for simultaneous testing by both the wideband colorimeter and the narrowband spectrograph. By doing simultaneous testing, accurate calibration of the wideband colorimeter can be achieved.

Abstract: A calibration system may be provided for calibrating displays in electronic devices during manufacturing. The calibration system may include calibration computing equipment and a test chamber having a light sensor. The calibration computing equipment may be configured to operate the light sensor and the display to gather display intensity performance data for obtaining a display gamma model. The display intensity performance data may be gathered using a range of display control settings that will be used in performing color calibration operations for the display. The calibration computing equipment may be configured to operate the light sensor and the display to gather display color performance data for determining a display white point calibration. Display white point calibration data may be provided to the electronic device and stored in volatile or non-volatile memory in the device or may be permanently stored in circuitry associated with the display.

Abstract: A method is provided for calibrating a display having color channels. Each color channel is capable of adjusting settings for pixel values at gray level entries. The method includes selecting a gray level entry for calibration. The method also includes providing a target white point in chromaticity coordinates (x, y) and a target brightness at the selected gray level entry to the display. The method further includes adjusting the setting for the pixel values for the color channels at the selected gray level entry such that the display achieves the target white point and the target brightness at an adjusted pixel value.

Abstract: This specification describes various embodiments that relate to methods for providing a wideband colorimeter that can include more accurate outputs. In one embodiment, a narrowband instrument, such as a spectrometer or spectrograph, can be used for calibration of a wideband colorimeter, so that more accurate outputs can be provided. In one embodiment, an optical test equipment, which consists of both a wideband colorimeter and a narrowband spectrograph, can be used for providing a more accurately calibrated wideband colorimeter. As an example, a spectra-camera, which is a hybrid system consisting of both a wideband colorimeter and a narrowband spectrograph, can be used for simultaneous testing by both the wideband colorimeter and the narrowband spectrograph. By doing simultaneous testing, accurate calibration of the wideband colorimeter can be achieved.

Abstract: Systems, methods, and devices for white point calibration using subtractive color measurements are provided. Specifically, a white point of a display may be calibrated using subtractive color measurements rather than merely additive color measurements. In one example, a display having red, green, and blue pixels may measure the responses in a subtractive color space (e.g., CMY) rather than additive color space (e.g., RGB). Measurements of the display response using subtractive color space may involve providing image data to two or more color channels at once. Thus, any crosstalk effect between channels may be accounted for, even though the same crosstalk effect might not be apparent using additive color measurements in which only a single channel color channel were measured.

Abstract: A calibration system may be provided for calibrating displays in electronic devices during manufacturing. The calibration system may include calibration computing equipment and a test chamber having a light sensor. The calibration computing equipment may be configured to operate the light sensor and the display to gather display white point information such as the native white point of the display. Temperature data may be gathered from the electronic device during display calibration operations using a thermal sensor. The calibration computing equipment may determine a temperature adaptive target white point based on the gathered temperature data. The calibration computing equipment may be configured to compare the native white point of the display with the temperature adaptive target point. Based on the comparison, the calibration computing equipment may generate corresponding display calibration parameters. The display calibration parameters may be provided to and stored in the electronic device.

Abstract: A calibration system may be provided for calibrating displays in electronic devices during manufacturing. The calibration system may include calibration computing equipment and a test chamber having a light sensor. The calibration computing equipment may be configured to operate the light sensor and the display to gather display intensity performance data for obtaining a display gamma model. The display intensity performance data may be gathered using a range of display control settings that will be used in performing color calibration operations for the display. The calibration computing equipment may be configured to operate the light sensor and the display to gather display color performance data for determining a display white point calibration. Display white point calibration data may be provided to the electronic device and stored in volatile or non-volatile memory in the device or may be permanently stored in circuitry associated with the display.