The present disclosure generally relates to display panels, and specifically to calibrating brightness and colors in such display panels using detector array measurement.
An electronic display panel includes pixels that display a portion of an image by emitting one or more wavelengths of light from various sub-pixels. When input indicating the same brightness across all pixels is received, the electronic display panel should display the same luminance across its entire surface. However, various variances during the manufacturing process cause non-uniformities in luminance of pixels and sub-pixels. For example, variations in flatness of a carrier substrate, variations in a lithography light source, temperature variations across the substrate, or mask defects may result in the electronic display panel having transistors with non-uniform emission characteristics.
As a result, different sub-pixels driven with the same voltage and current will emit different intensities of light (also referred to as brightness). In another example, “Mura” artifact or other permanent artifact causes static or time-dependent non-uniformity distortion in the electronic display panel, due to undesirable electrical variations (e.g., differential bias voltage or voltage perturbation). Variations that are a function of position on the electronic display panel cause different display regions of the electronic display panel to have different luminance. If these errors systematically affect sub-pixels of one color more than sub-pixels of another color, then the electronic display panel has non-uniform color balance as well.
These spatial non-uniformities of brightness and colors decrease image quality and limit applications of the electronic display panels. For example, virtual reality (VR) systems typically include an electronic display panel that presents virtual reality images. These spatial non-uniformities degrade user experience and immersion in a VR environment.
A system calibrates luminance parameters of an electronic display panel using detector array measurements. The system may calibrate luminance parameters of the electronic display panel by causing a relative translational movement in a length direction or a width direction of the electronic display panel in a rolling manner.
In some embodiments, the system includes a luminance detection device, an actuator and a computing device. The luminance detection device may include a plurality of detectors arranged along a width or length of the electronic display panel to simultaneously measure luminance parameters of at least one row or column of areas in the electronic display panel. Each of the plurality of detectors covers an area in the at least one row or column of the electronic display panel. The actuator causes a relative translational movement in a length direction or a width direction of the electronic display panel. The computing device is coupled to the luminance detection device to receive the measured luminance parameters, and the computing device generates calibration data for adjusting brightness of areas of the electronic display panel by processing the measured luminance parameters.
The figures depict embodiments of the present disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles, or benefits touted, of the disclosure described herein.
The figures use like reference numerals to identify like elements. A letter after a reference numeral, such as “120A,” indicates that the text refers specifically to the element having that particular reference numeral. A reference numeral in the text without a following letter, such as “120,” refers to any or all of the elements in the figures bearing that reference numeral (e.g. “actuator 120” in the text refers to reference numerals “actuator 120A” and/or “actuator 120B in the figures).
The actuator 120 is an apparatus that causes a relative translational movement in a length direction or a width direction of the electronic display panel 110. The actuator 120 may be an electromechanical actuator (e.g., an electrostatic actuator and an electromagnetic actuator). The relative translational movement is in a direction that is orthogonal to a direction in which the luminance detection device 130 extends.
In the embodiment of
The luminance detection device 130 measures luminance parameters of at least one row or column of areas in the electronic display panel 110. Examples of an area may include a pixel, a sub-pixel, a group of sub-pixels, or a group of pixels. The luminance parameters describe parameters associated with an area of the electronic display panel 110. Examples of the luminance parameters associated with the area may include a brightness level, a color value, or both. The brightness level of an area represents an overall light intensity of the area. The color value of an area is represented by a combination of brightness levels of sub-pixels of the area. In some embodiments, the luminance detection device 130 measures luminance parameters of one row or column of areas in the electronic display panel 110, as described below with respect to
In some embodiments, the luminance detection device 130 includes a plurality of band-pass filters (not shown) between the electronic display panel 110 and sensors of the luminance detection device 130. Each band-pass filter passes light within a predetermined range of wavelengths (e.g., red light, green light or blue light). The luminance detection device 130 includes a sensor (not shown) for receiving light emitted from the electronic display panel 110. For example, a sensor of the photo-detector is a sensing component that light is incident on.
The computing device 140 controls the actuator 120, and the luminance detection device 130 for calibrating the electronic display panel 110. Additionally and/or alternatively, the computing device 140 controls the electronic display panel 110. For example, the computing device 140 generates commands to instruct the actuator 120 to cause a relative translational movement in a length direction or a width direction of the electronic display panel 110. The computing device 140 generates commands to instruct the luminance detection device 130 to simultaneously measure luminance parameters of at least one row or column of areas in the electronic display panel 110.
Further, the computing device 140 receives the measured luminance parameters from the luminance detection device 130 and generates calibration data for adjusting brightness of areas of the electronic display panel 110 by processing the received measured luminance parameters. In some embodiments, a calibration process involves providing known (e.g., predetermined) and uniform input to the electronic display panel 110. A uniform input may be, e.g., instructions for the electronic display panel 110 to emit a white image with equal brightness levels for each individual pixel. The predetermined input includes predetermined luminance parameters, e.g., brightness level and color value for each individual sub-pixel in a pixel, brightness level and color value for each individual pixel, or some combination thereof. The computing device 140 determines calibration data based on differences between the measured luminance parameters of areas and corresponding predetermined luminance parameters.
The calibration data describes data associated with one or more adjustments (e.g., brightness adjustment, color adjustment, or both) of luminance parameters of the areas. An adjustment adjusts a luminance parameter of one or more areas such that the corresponding luminance parameter of the one or more areas is within a range of luminance parameters (e.g., a range of brightness levels, or a range of color values, or both). The determined calibration data may include a correction voltage for adjusting a change in a drive voltage of the TFT. In some embodiments, the computing device 140 calibrates the electronic display panel 110 based on luminance parameters measured by the luminance detection device 130 at a sub-pixel level. For example, the computing device 140 generates commands to instruct the electronic display panel 110 to display sub-pixels with the same color (e.g., red sub-pixels, green sub-pixels, or blue sub-pixels). After obtaining the calibration data, the computing device 140 updates the electronic display panel 110 with the determined calibration data so that the calibration data can be applied during the normal use of the electronic display panel 110.
As shown in
The input interface 142 may be any user input device including a touch-screen, a pointing device and a keyboard. In some embodiments, the computing device 140 may be configured to receive input (e.g., commands) from the input interface 142 from a user.
The memory 144 stores information instructions for operating the actuator 120A and the luminance detection device 130.
The processor 146 controls the actuator 120 and the luminance detection device 130. For example, as shown in
In some embodiments, the processor 146 controls operation of the actuator 120. For example, as shown in
The output interface 150 is a component for providing the result of computation in various forms (e.g., text, image, or audio signals). For example, the output interface 150 may be a display that depicts the calibration data. The network interface 148 enables the computing device 140 to communicate with the electronic display panel 110, the actuator 120A, the luminance detection device 130, an external source (not shown in
During the calibration operation, the actuator 120A is operated by the processor 146 to move the electronic display panel 110 to an initial position. Then the luminance detection device 130 is operated to measure luminance parameters of at least one row or column of the electronic display panel 110. The actuator 120A is then operated by the processor 146 to move the luminance detection device 130 to a second position. If the luminance detection device 130 measures first three rows (e.g., the first, the second and the third row) at the initial position, the second position of the luminance detector 130 will be set to detect the next three rows. Then the luminance detection device 130 measures luminance parameters at the second position. The moving and measuring processes are repeated until the luminance detection device 130 measures all the rows or columns of the electronic display panel 110.
The calibration data may be determined based on differences between the measured luminance parameters of each of the areas and corresponding predetermined luminance parameters. For example, the processor 146 retrieves predetermined luminance parameters and measured luminance parameters of each of the areas stored in the memory 144, compares the measured luminance parameters of each of the areas with corresponding predetermined luminance parameters, calculates differences between the measured luminance parameters of each the areas and corresponding predetermined luminance parameters and then determines the calibration data based on the calculated differences. For example, for each of the areas, the processor 146 determines a correction drive voltage of the TFT that drives a corresponding area to reduce the difference within an acceptable range.
The calibration data may be in the form of a calibration LUT based on determined calibration data for the areas in the electronic display panel 110. The created calibration LUT includes measured luminance parameters of an individual area, predetermined luminance parameters of corresponding areas, and correction factors associated with the luminance parameters of corresponding areas. The created calibration LUT may be stored in the electronic display panel 110.
The processor 146 generates commands to instruct the actuator 120B to make translational movement of the luminance detection device 130 in a rolling manner such that no two areas in one row or column are below each of the plurality of detectors in the luminance detection device 130, over the same time period, as described above with reference to
Examples of Display Panel Calibration using Detector Array Measurement
The luminance detection device 130 may include a plurality of detectors arranged along a width or length of an electronic display panel 110. Examples of the luminance detection device 130 may include one-dimensional detector array, or multiple one-dimensional detector arrays. Each of the plurality of detectors covers an area in the at least one row or column of the electronic display panel 110. In some embodiments, each of the plurality of detectors is a photo-detector. The photo-detector detects light from an area in the electronic display panel 110, and converts light received from the area into voltage or current. Examples of the photo-detector may include a photodiode, a photomultiplier tube (PMT), or a solid state detector. The photo-detector can be coupled with an analog-to-digital converter (ADC) (not shown) to convert voltage analog signals or current analog signals into digital signals for further processing.
As shown in
In
In some embodiments, the luminance detection device 130 may include or be combined with an optics block to deliver light from areas of the electronic display panel 110 to the luminance detection device 130. The optics block may include one or more optical elements. Examples of an optical element may include an aperture, a Fresnel lens, a convex lens, a concave lens, a mirror, a beamsplitter, a prism, or an optical filter to collect and deliver light emitted from the electronic display panel 110.
As shown in
As shown in
Alternatively (not shown in
In some embodiments, not all the one-dimensional detector arrays of the luminance detection device 410 are activated by the computing device to measure luminance parameters. For example (not shown in
In some embodiments, the luminance detection device 130 may include a plurality of band-pass filters. Each of the plurality of band-pass filters is integrated with each of the plurality of one-dimensional detector arrays. Different one-dimensional detector arrays may have different band-pass filters with the same or different predetermined range of wavelengths. Alternatively, each of the plurality of band-pass filters is integrated with each of the plurality of detectors. Different detectors may have different band-pass filters with the same or different predetermined ranges of wavelengths.
As shown in
In some embodiments, the plurality of band-pass filters are mounted on a filter wheel. By rotating the filter wheel, one of the plurality of band-pass filters passes light with a predetermined range of wavelengths, and the light is detected by corresponding detectors. In some embodiments, the filter wheel is integrated with one of the plurality of one-dimensional detector arrays.
The filter wheel 640 may include the plurality of band-filters shown in
The system 100 simultaneously measures 710 luminance parameters of at least one row or column of areas in an electronic display panel 110. Examples of an area may include a pixel, a sub-pixel, a group of sub-pixels, or a group of pixels. Examples of the luminance parameters associated with the area may include a brightness level, a color value, or both. In some embodiments, the luminance detection device 130 is a one-dimensional detector array to measure luminance parameters of one row or column of areas in the electronic display panel 110. Examples are described above with respect to
The system 100 causes 720 a relative translational movement in a length direction or a width direction of the electronic display panel 110. The relative translational movement is in a direction that is orthogonal to a direction in which the luminance detection device 130 extends. For example, the system 100 instructs the actuator 120A to make translational movement of the electronic display panel 110 in a length direction or a width direction of the electronic display panel 110. An example is described above with respect to
The system 100 retrieves 730 predetermined luminance parameters of each of the areas. For example, the system 100 retrieves a predetermined brightness level, or a predetermined color value, or both of the area that has been measured by the luminance detection device 130.
The system 100 calculates 740 differences between the measured luminance parameters of each of the areas and corresponding predetermined luminance parameters. In some embodiments, the system 100 may determine a luminance quality to check if differences between calibrated luminance parameters of the areas and corresponding predetermined luminance parameters are within the acceptable ranges.
The system 100 determines 750 the calibration data based in part on the calculated differences for each of the areas. For example, the system 100 determines calibration data to adjust the measured luminance parameters of the area such that the corresponding calibrated luminance parameters of the area are within the acceptable ranges. In another example, if the determined luminance quality indicates that a deviation of the measured luminance parameters of an area relative to corresponding predetermined luminance parameters are less than an associated threshold, the system 100 determines the calibration data based on calculated differences. For example, compared with the predetermined brightness level, the measured brightness level is outside of a range of brightness level. Compared with the predetermined color value, the measured color value is outside of a range of colors values. If the determined luminance quality indicates that a difference between the measured luminance parameters of an area with corresponding predetermined luminance parameters is within an acceptable range, the system 100 determines the calibration data that is the same as original data for driving the area. In such way, the system 100 may determine calibration data for all the pixels. In some embodiments, the system 100 may skip the step for determining the calibration data. In such way, the system 100 determines calibration data for portions of the area included in the electronic display panel.
The system 100 updates 760 the electronic display panel 110 with the determined calibration data. For example, the system 100 generates instructions to instruct the electronic display panel 110 to display the areas based on the calibration data.
The foregoing description of the embodiments has been presented for the purpose of illustration; it is not intended to be exhaustive or to limit the patent rights to the precise forms disclosed. Persons skilled in the relevant art can appreciate that many modifications and variations are possible in light of the above disclosure.
The language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the patent rights be limited not by this detailed description, but rather by any claims that issue on an application based hereon. Accordingly, the disclosure of the embodiments is intended to be illustrative, but not limiting, of the scope of the patent rights.