Determining the tilt and pitch of a autostereoscopic display

Abstract

Generating and displaying a test pattern on an autostereoscopic display, capturing one or more images of the displayed test pattern, determining a first phase at a first position within the image, determining a second phase at a second position within the image, and determining an inclination of an optical element based on a difference between the first phase and the second phase, a system and method are provided for determining the inclination and optionally the pitch distance of an autostereoscopic display. Advantageously, the first position and the second position are offset from each other horizontally and vertically according to an assumed value of the inclination. This enables an inclination measurement that is less affected by errors in the assumed pitch distance. In particular, the inclination can be determined first, substantially independently of the pitch distance, and then the pitch distance can be determined based on the determined inclination. Thereby, the inclination and optionally the pitch distance can be determined more accurately and / or more quickly.

Description

Technical Field

[0001] The present invention relates to a system and method for determining the tilt and optionally the pitch distance of an autostereoscopic display. The present invention further relates to a computer-readable medium including instructions configured to cause a processor system to implement the method.

Background Art

[0002] An increasing number of display devices, such as televisions, tablets, and smartphones, are equipped with 3D displays to provide users with a sense of depth when viewing content on such devices. Autostereoscopic displays provide a sense of depth and three-dimensionality without the viewer having to wear polarized glasses, color filter-based glasses, or shutter-based glasses. For that purpose, an autostereoscopic display includes optical components, such as an array of optical elements, that enable the display to emit a viewing cone from each given point on the 3D display, the viewing cone including at least a left view and a right view of the scene. This enables the viewer to see different images with each eye when properly positioned.

[0003] An "automultiscopic" display, a particular type of autostereoscopic display sometimes specifically referred to as such, provides a viewer with a series of views of a scene represented by 3D image data, usually within what is commonly referred to as a viewing cone. This allows the viewer to assume multiple positions within the viewing cone, for example, to experience motion parallax while maintaining a three-dimensional perception of the scene. Some displays are capable of emitting such a series of views within each of a series of repeated viewing cones.

[0004] U.S. Patent No. 6,064,424 describes an example of an autostereoscopic display having an array of parallel lenticular elements superimposed on a display, where the lenticular elements are inclined with respect to the display pixel columns. Due to this inclination, it is said that the reduction in the experienced display resolution is distributed over both the horizontal and vertical resolutions.

[0005] To display content on an autostereoscopic display having an array of optical elements, an output image can be generated based on 3D image data by the autostereoscopic display or a device connected thereto. This can involve a step of "interleaving", "weaving", or "interdigitization" in which, for each display element of the display, it is determined which image data from which view is to be displayed by each display element. Such interleaving typically takes into account the type and configuration of the array of optical elements within the display, which may include the inclination of the optical elements with respect to the display panel and the pitch distance between the optical elements. The inclination can be expressed as, or in relation to, the angle of the major longitudinal axis of the optical element with respect to the column direction of the array of display elements, although it may also be expressed in a different way in relation to, for example, the row direction of the array of display elements.

[0006] Although an autostereoscopic display may be designed to have a specific inclination and pitch distance, manufacturing tolerances can cause the actual inclination and / or pitch distance values to deviate from those nominal values selected during the design phase. Therefore, it is desirable to be able to measure the inclination and pitch distance of the autostereoscopic display so that interleaving can be adapted to the actual values of the inclination and pitch distance.

[0007] https: / / arxiv.org / abs / 1606.07166The paper "3D Display Calibration by Visual Pattern Analysis" by Hwang et al., which is available, describes a display calibration method. In this method, a pattern image is displayed on a panel, and a camera takes two pictures of the pattern at different positions. Then, based on a quantitative model, display parameters including pitch and tilt angle are determined from the patterns observed in the captured images.

[0008] Unfortunately, the measurement accuracy obtained by Hwang et al. is insufficient for high-resolution autostereoscopic displays, at least for tilt.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Non-Patent Documents

[0010]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0011] The object of the present disclosure is to enable the measurement of at least the inclination and optionally the pitch distance of an autostereoscopic display in a more accurate manner.

Means for Solving the Problems

[0012] The following aspects of the present invention relate to an autostereoscopic display, the autostereoscopic display comprising: - a display panel comprising an array of display elements; and - an array of elongated optical elements for redirecting the light emitted by the display elements in mutually different directions, the optical elements being arranged in parallel with each other at a pitch distance and their major longitudinal axes being oriented in an inclined state with respect to the array of display elements. and.

[0013] According to a first aspect of the present invention, a method for determining the inclination of an autostereoscopic display is provided. The method comprises: - assigning a phase to each display element based on an estimated value of the pitch distance and an estimated value of the inclination, the phase indicating the direction in which the light emitted by each display element is redirected; - generating display data including uniquely identifiable image content for each phase of the set of assigned phases based on the assigned phases; - outputting the display data to the autostereoscopic display for display; - capturing one or more images of the display panel when the display data is displayed by the autostereoscopic display; - determining the inclination by analyzing the one or more captured images; and the analysis of the one or more captured images comprises: - determining a first phase based on the uniquely identifiable image content indicated at a first position on the display panel at the first position; - At a second position on the display panel, determining a second phase based on uniquely identifiable image content indicated at the second position, wherein the first position and the second position are offset from each other horizontally and vertically according to an estimated value of the tilt; - determining the tilt of the optical element based on the difference between the first phase and the second phase; and including.

[0014] According to a further aspect of the present invention, a non-transitory computer-readable medium is provided, the medium including data representing instructions configured to cause a processor system to perform the method.

[0015] According to a further aspect of the present invention, a system for determining the tilt of an autostereoscopic display is provided. The system includes: - a display output interface to the autostereoscopic display; - a camera interface to a camera arranged to capture an image of the display panel of the autostereoscopic display; - a processing subsystem; and the processing subsystem includes: - Assigning a phase to each display element based on an estimated pitch distance and an estimated tilt, wherein the phase indicates the direction in which light emitted by each display element is redirected; - Generating display data including uniquely identifiable image content for each phase of the assigned set of phases based on the assigned phases; - Outputting the display data to the autostereoscopic display for display via the display output interface; - Capturing one or more images of the display panel when the display data is being displayed by the autostereoscopic display via the camera interface; - Determining the tilt by analyzing the one or more captured images. configured to perform, the analysis of one or more captured images is: - at a first position on the display panel, determining a first phase based on uniquely identifiable image content indicated at the first position; - at a second position on the display panel, determining a second phase based on uniquely identifiable image content indicated at the second position, wherein the first position and the second position are offset from each other horizontally and vertically according to an estimated value of the tilt; - determining the tilt of the optical element based on the difference between the first phase and the second phase and includes.

[0016] The above measurements involve characterizing an autostereoscopic display comprising a display panel such as an LCD panel, an OLED panel, or a microLED panel. An array of elongated optical elements can be stacked on top of the display panel, i.e., covering the light-emitting side of the display panel, to redirect light emitted in mutually different directions by the display elements of the display panel. The optical elements can be arranged in parallel with each other at a pitch distance, and their major longitudinal axes can be oriented in a tilted state with respect to the array of display elements. An autostereoscopic display of the type described in this paragraph is known per se. For example, U.S. Patent No. 6,064,424 describes an example of such a display.

[0017] It may be desirable to determine the tilt and optionally the pitch distance of such an autostereoscopic display. The above measurements can be used to determine the actual values of the tilt and optionally the pitch distance in a more accurate manner using initial estimated values of the tilt and pitch distance. The initial estimated values can be, for example, nominal values of the tilt and pitch distance as obtained from manufacturing specifications. Since the actual values of the tilt and pitch distance may deviate from the initial estimated values, a test pattern is generated and shown on the display. The test pattern includes uniquely identifiable image content for at least some of the phases based on which the display can be addressed. To generate the test pattern, the estimated values of the tilt and pitch distance can be used to determine which display element corresponds to which phase in order to assign each uniquely identifiable image content to each display element. Then, at at least two locations (i.e., positions) on the screen, the phase can be measured by capturing one or more images on the light-emitting side of the display and analyzing the captured images to identify the uniquely identifiable image content at both locations. As is known per se, the difference in phase at two locations can indicate the difference between the actual values of the tilt and pitch distance and the estimated values of the tilt and pitch distance. Conventionally, for example, the estimated values of the tilt and pitch distance may be corrected based on the said difference by an iterative process that can converge to an approximation of their actual values from the initial estimated values of the tilt and pitch distance.

[0018] Unfortunately, the phase difference observed at two locations on the screen can be due to a tilt mismatch, i.e., due to a mismatch between the estimated and actual values of the tilt, but can also be due to a pitch distance mismatch, or both mismatches. As a result, it may not immediately be clear whether the estimated value of the tilt should be corrected, or the estimated value of the pitch distance should be corrected, or both. This can result in the determined tilt and pitch distance being lower than the desired accuracy, or, when determined iteratively, the determination taking a long time (being slower) to converge.

[0019] The above measurement involves measuring the phase at two or more different locations on the screen, and these locations can be offset horizontally and vertically relative to each other according to the estimated value of the tilt. As a result, the locations where the phase is measured are on a line tilted according to the estimated value of the tilt. The horizontal and vertical offsets of the locations can exactly match the estimated value of the tilt, but they may also approximately match, for example, within a certain range. Also, the phase difference measured at two or more different locations on the screen can be used to correct the estimated value of the tilt instead of simultaneously correcting the estimated values of the tilt and the pitch distance. This makes it possible to decouple the tilt measurement from the pitch measurement at least to some extent. In particular, the tilt can be first determined with little relation to the pitch distance, and then the pitch distance can be determined based on the determined tilt. In this way, the tilt and optionally the pitch distance can be determined more accurately and, if determined iteratively, (more) quickly.

[0020] An exemplary experiment shows that the accuracy is improved by one order of magnitude compared to the method of "3D Display Calibration by Visual Pattern Analysis" by Hwang et al. This reveals that the claimed system and method are particularly suitable for high-resolution displays such as 4K and 8K displays and higher.

[0021] Optionally, the first phase and the second phase are each determined based on uniquely identifiable image content within each measurement area at each respective position on the display panel. Instead of determining the phase only at the selected locations on the screen, the phase can be determined within a measurement area that can be defined around the selected locations, for example, based on the average selection or majority vote of uniquely identifiable image content within each measurement area. In this way, the phase can be determined with higher accuracy than when the phase measurement is based on only a single location.

[0022] Optionally, the first position and the second position are respectively arranged vertically at the upper half and the lower half of the display panel, preferably at the upper one-third and the lower one-third of the display panel, more preferably at the upper one-fourth and the lower one-fourth of the display panel. Since the phase error caused by the error of the estimated value of the inclination and the pitch distance accumulates horizontally from the first column to the last column of the display panel, for example, and accumulates vertically from the first row to the last row of the display panel, for example, a larger error can be predicted when the locations where the phase is measured are vertically separated. By appropriately separating the locations, the sensitivity to the error is increased, thereby potentially improving the accuracy of the determined inclination.

[0023] Optionally, the first position and the second position are respectively arranged horizontally at the left half and the right half of the display panel, preferably at the left one-third and the right one-third of the display panel, more preferably at the left one-fourth and the right one-fourth of the display panel. The positions described in the preceding paragraph are well-suited for inclinations from vertical to 45 degrees or up to the diagonal of the display, but these positions may not be very suitable for inclinations beyond that and up to horizontal. For such inclinations, different positions along the horizontal axis, such as the above-described positions on the left and right sides of the display panel, may be preferred.

[0024] Optionally, the inclination is: - When the difference between the first phase and the second phase exceeds a threshold value: Adjusting the estimated value of the inclination based on the difference, Relocating the first position and / or the second position to adjust the offset for the adjusted estimated value of the inclination, And redetermining the first phase and / or the second phase at the relocated first position and / or the second position, - When the difference between the first phase and the second phase is below the threshold value, outputting the estimated value of the inclination as the determined inclination, And is determined iteratively.

[0025] Optionally, the method includes determining one or more intermediate phases based on uniquely identifiable image content indicated at one or more intermediate positions between a first position and a second position, and the processing subsystem is further configured to do so, and the difference is a measurement applied to the first phase, the second phase, and the one or more intermediate phases. Measuring the phase at three or more locations on the screen, for example, may further improve the accuracy when determining the tilt. The above relates to the following: In the case of an autostereoscopic display having a repeated viewing cone, the observation that the difference between the first phase and the second phase is zero does not guarantee that the estimated tilt is the same as the actual tilt because the phase can only be measured with the pitch distance as the law. Usually, when measuring the horizontal phase difference, for example, it may be assumed that the phase difference is less than one pitch distance due to manufacturing requirements (e.g., the accuracy required for adhesion). However, when the phase difference is determined between locations that are vertically offset, the phase difference may exceed the value represented by one pitch distance. In such a situation, it may be advantageous to measure the phase at an intermediate location along the line from the first location to the second location. Specifically, if the estimated tilt matches the actual tilt, the same phase should be observed at all three locations. Therefore, if the phases at all three locations do not match, it may indicate that there is an error in the tilt estimation. Furthermore, by selecting the third location asymmetrically between the first and second locations, i.e., not directly in the middle of both locations, when the actual phase difference is a multiple of twice the pitch distance, it may be possible to avoid the difference being detected as zero. Preferably, the third location is located at a fraction n / d of the distance between both locations, where d is large even when all common factors in n and d are removed. Optionally, four or more locations may be used to further improve the accuracy of determining the value of the tilt.

[0026] Optionally, the method includes determining a pitch distance based on the determined slope, and the processing subsystem is further configured to determine a pitch distance based on the determined slope. Once the slope is determined, the determined slope can be used to determine the pitch distance in a known manner. That is, when generating a test pattern for determining the pitch difference, the determined slope may be used in the phase calculation. By doing so, the observed phase difference may mainly be due to the difference between the estimated value and the actual value of the pitch distance, and not due to or to a lesser extent due to the difference between the estimated value and the actual value of the slope. This may enable the pitch distance to be determined more accurately, and if determined iteratively, it may be possible to determine it more quickly.

[0027] Optionally, determining the pitch distance comprises: - Reassigning a phase to each display element based on an estimated value of the pitch distance and the determined slope, - Generating further display data including uniquely identifiable image content for each phase of the set of reassigned phases based on the reassigned phases, - Outputting the further display data to an autostereoscopic display for display, - When the display data is displayed by the autostereoscopic display, capturing one or more further images of the display panel, - Determining the pitch distance of the optical element by analyzing the one or more further captured images and the analysis of the one or more further captured images comprises: Determining a first further phase at a first further position on the display panel based on the uniquely identifiable image content shown at the first further position, Determining a second further phase at a second further position on the display panel based on the uniquely identifiable image content shown at the second further position, wherein the second further position is offset from the first further position Determining the pitch distance of an optical element based on the difference between a first additional phase and a second additional phase comprises.

[0028] Optionally, the offset between the first additional phase and the second additional phase is different in the horizontal direction from the tilt.

[0029] Optionally, the uniquely identifiable image content includes a different grayscale and / or a different color for each phase of the assigned set of phases.

[0030] Optionally, the method includes obtaining an estimated value of the tilt and / or an estimated value of the pitch distance from target specifications used for the manufacture of an autostereoscopic display, and the processing subsystem is further configured to do so.

[0031] Optionally, the array of elongated optical elements is a lenticular lens sheet.

[0032] It is to be understood by those skilled in the art that two or more of the above-described embodiments, implementations, and / or optional forms of the present disclosure may be combined in any useful way.

[0033] Any modifications and variations of any system, any computer-implemented method, or any computer-readable medium, which correspond to the described modifications and variations of the other forms of the above entities, can be implemented by those skilled in the art based on this description.

[0034] These and other aspects of the present disclosure will become apparent from and be elucidated further with reference to the embodiments described by use of examples in the following description and with reference to the accompanying drawings.

Brief Description of the Drawings

[0035]

Figure 1

Figure 2

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DETAILED DESCRIPTION OF THE INVENTION

[0036] Note that the figures are purely illustrative and not drawn to scale. In the figures, elements corresponding to elements already described may have the same reference numerals.

[0037] FIG. 1 shows a 3D display 140 in the form of an autostereoscopic 3D display, which is configured to enable stereoscopic viewing of the content displayed thereon without the user having to wear glasses. To enable stereoscopic viewing, the 3D display 140 typically includes a display panel 150 comprising an array of light-emitting or light-modulating elements. Such types of elements may also be referred to elsewhere as "display elements". The 3D display 140 is further shown to include an array of optical elements 160 for redirecting the light generated by the display panel 150 in different directions. Although not explicitly shown in FIG. 1, the array of optical elements 160 may comprise or consist of an array of elongated optical elements such as lenticular elements. The display panel 150 may be appropriately arranged such that a series of views 0-5 are emitted from the 3D display 140 in the form of a viewing cone 11 and may cooperate with the array of optical elements 160, and this viewing cone is repeated and a series of viewing cones 20 are emitted. In this regard, for purposes of illustration, it should be noted that FIG. 1 shows that a series of views includes six views 0-5 and that the 3D display 140 emits views 0-5 within viewing cone 11 and within two adjacent viewing cones 10, 12. However, it should be understood that a series of views may consist of any number of views, such as 2, 5, 10, 20, 30, etc., and that the repetition of the viewing cones may continue beyond the adjacent viewing cones 10, 12.

[0038] A series of views 0-5 may represent a series of images. Thus, when a viewer looks at one of the series of views 0-5, the viewer may perceive each one of the series of images. The series of images, in terms of the content of the images, may correspond to a camera positioned in front of a scene and moving from left to right in front of and relative to said scene. As such, a viewer positioned at a viewing position 30 within viewing cone 11 may perceive two different views 2, 3, thereby enabling stereoscopic viewing of the above scene. It should be noted that a series of views may include partial views or may be entirely composed of partial views.

[0039] Note that the 3D display of the above configuration and the method of processing a series of images to be displayed as a series of views are known per se. For example, U.S. Patent No. 6,064,424 discloses an autostereoscopic display device having lenticular elements and discusses the relationship between the display elements and the lenticular elements. U.S. Patent No. 6,064,424 also discloses that the lenticular elements can be arranged in parallel with each other at a pitch distance p, and their major longitudinal axes can be oriented at an inclination angle s with respect to the array of display elements. The pitch distance (also simply referred to as "pitch" in other places) and the inclination angle (also simply referred to as "tilt" in other places) represent parameters characterizing the optical design of the 3D display 140. The tilt can be defined in various ways, for example, with respect to the column direction of the array of display elements or with respect to the row direction of the array of display elements.

[0040] FIG. 2 shows a cross-section of an array 160 of optical elements. In this example, the array 160 of optical elements is composed of a lenticular sheet having a substrate 162 with a contour surface defining an array of lenticular elements. Each lenticular element 164 may be an elongated cylindrical lens element, and the array of optical elements is a one-dimensional array formed by lenticular elements arranged in parallel. FIG. 2 shows a cross-section of the array 160 that is parallel to the rows of the pixel grid of the display panel. Note that such an array 160 of optical elements is known per se. Further note that the array 160 of optical elements can take any other suitable form, such as a plurality of multi-faceted lens elements, a two-dimensional array, etc. FIG. 2 further illustrates the pitch distance using the symbol "w". The pitch distance is often represented by the number of pixels or sub-pixels. The value of the pitch distance can be selected based on the dimensions of the underlying pixels for a particular nominal viewing distance.

[0041] Figure 3 shows an array of optical elements that are tilted by an angle θ° with respect to the display panel. The tilt angle can be defined in degrees, but furthermore, it can be defined in radians or in any other quantity, and it should be noted, for example, that it can be related to the number of horizontal and vertical display elements that the optical element crosses, and the relationship with the tilt angle expressed in radians can be defined as an arctangent. In general, the tilt can be related to the angle at which the optical element is placed with respect to the pixel grid. By using the pitch and tilt in combination, it is possible to determine, for each sub-pixel, its phase with respect to the lens, i.e., through which part of the lens the underlying pixel grid is observed by the viewer. As illustrated in Figure 2, under the understanding that the exact phase further depends on the viewing distance, the lateral position, and the distance between the array of optical elements and the underlying sub-pixels, for example, assuming that the entire left side of the lens has a value of 0.0, the center of the lens has a value of 0.5, and the entire right side of the lens has a value of 1.0, the phase can be defined, for example, as representing the horizontal position of each display element with respect to the optical element that redirects the light emitted by each display element.

[0042] Since the phase of the sub-pixel can determine the direction in which its light is focused by the lens, the image content of the sub-pixel should be selected to match that direction. From the viewer's perspective, the viewer should see a consistent image corresponding to their line-of-sight direction across the entire screen. In other words, image content of the same phase should be observed by the viewer across the entire screen. The phase can be determined based on the pitch and tilt. However, if the values of the pitch or tilt used for rendering deviate from the actual values of the pitch and tilt, image content intended for different phases / directions may appear at different locations on the screen, and the viewer may not be able to visually recognize a consistent image. Therefore, it is desirable that the tilt and optionally the pitch distance of the autostereoscopic display can be characterized in an accurate manner.

[0043] Briefly stated, the following describes a system and method for determining the tilt and optionally the pitch distance of an autostereoscopic display. For that purpose, the system and method generate and display a test pattern on the autostereoscopic display, capture one or more images of the displayed test pattern, determine a first phase at a first position in the one or more captured images, determine a second phase at a second position in the one or more captured images, and determine the tilt of the optical element based on the difference between the first phase and the second phase. Advantageously, the first position and the second position are offset from each other horizontally and vertically corresponding to the assumed tilt value. This makes it possible to make the tilt measurement less susceptible to the influence of errors in the assumed pitch distance. In particular, the tilt can first be determined, generally independently of the pitch distance, and then the pitch distance can be determined based on the determined tilt. Thereby, the tilt and the optional pitch distance can be determined more accurately and / or more quickly in an iterative process.

[0044] FIG. 4 shows a system 200 for determining the tilt of the autostereoscopic display 140. The autostereoscopic display 140 may be of a type as described elsewhere in this specification, for example. The system 200 may include a display output interface 260 to the autostereoscopic display 140 and a camera interface 240 to a camera 250 arranged to capture an image of the display panel of the autostereoscopic display. The system 200 assigns phases to each display element based on an estimated pitch distance and an estimated tilt, generates display data 262 including uniquely identifiable image content for each phase of the set of assigned phases, outputs the display data 262 to the autostereoscopic display 140 for display via the display output interface 260, and captures one or more images 252 of the display panel when the display data is being displayed by the autostereoscopic display via the camera interface 240, and may further include a processing subsystem 220 configured to determine the tilt by analyzing the one or more captured images. The analysis of the one or more captured images includes determining a first phase based on uniquely identifiable image content shown at a first position on the display panel, determining a second phase based on uniquely identifiable image content shown at a second position on the display panel, and determining the tilt of the optical element based on a difference between the first phase and the second phase. In this specification, the first position and the second position may be offset from each other horizontally and vertically according to the estimated tilt, which may be advantageous for reasons as explained with reference to FIGS. 5-6.

[0045] FIG. 5 is useful for exemplifying that the deviation between the nominal value and the actual value of the pitch distance affects the determination of the tilt. As already explained elsewhere, it may be desirable to characterize the tilt of the autostereoscopic display and optionally the pitch distance in an accurate manner. Such characterization can be, for example, by changing the color as described in Jurk, Silvio&Kuhlmey, Mathias&Duckstein, Bernd&de la Barre, Rene, (2016). "Electronical correction of misalignments between optical grid and pixel panel on autostereoscopic displays", or by using image content that is specific to a particular phase and changes over time, which may include rendering image content that appears different for all or at least a subset of the phases. It may also be preferable to be able to locally measure the phase in a plurality of sufficiently separated regions. Then, the phase measurement values within those regions can be compared to determine whether the phase is changing on the screen and, if so, how it is changing, which indicates whether the values of the tilt and pitch distance used to render the image content match the actual optics, i.e., the actual values of the tilt and pitch distance. For example, if the observed phase in a small region on the left side of the screen is the same as the observed phase on the right side of the screen, this may indicate that the estimated value of the pitch distance is correct or at least within a range close to the actual value of the pitch distance.

[0046] To characterize the pitch distance, a horizontal offset between measurement regions may be used because if there is a difference between the actual pitch distance and the initial estimated pitch distance (which can be an assumed pitch distance based on manufacturing or design specifications), the phase will result in a non-constant deviation horizontally from the assumed value, and the phase deviation may vary in space. For example, in an autostereoscopic display designed with a pitch distance of 5 subpixels, unfortunately, if the actual pitch distance deviates by 1% from the designed pitch distance, it becomes approximately 5.01, and after 500 subpixels, the phase may have completed an extra cycle of 5 subpixels and passed through the entire range of the phase. Since this phase deviation can be the same for all lines, a phase deviation pattern occurs horizontally. Similarly, if the deviation is in the tilt rather than the pitch distance, a phase deviation pattern appears, but this time vertically. Therefore, to be able to characterize the deviation in the pitch distance, it is preferable to measure the phase at a horizontally offset location, but to be able to characterize the deviation in the tilt, it is preferable to measure the phase at a vertically offset location.

[0047] Continuing to refer to FIG. 5 showing the light-emitting side of the autostereoscopic display 140, two measurement regions 300 and 301 that are vertically offset and cover most of the height of the screen are shown in order to improve accuracy. Each of the diagonal lines 310 and 312 indicates an elongated optical element (e.g., lenticular) that is inclined with respect to the display panel. The left line 310 extends through the middle of the upper measurement region 300, while the right line 312 extends through the middle of the lower measurement region 301. The double arrow indicates the horizontal distance between the elongated optical elements. For reference, it is shown that a dashed line (the "center line") having the same inclination extends through the center of the display panel. For example, if the phases in both measurement regions 300 and 301 are the same, this may suggest that the distance between the elongated optical elements (the width of the double arrow) is an exact multiple of the pitch distance, and this multiple corresponds to the elongated optical elements between the left line 300 and the right line 301. For example, a change in the pitch distance due to the distance between the elongated optical elements continuing around the center line expanding or contracting may cause the phase difference to no longer be an exact multiple of the pitch distance. In such a situation, any differences observed due to the phase difference between the two measurement regions 300 and 301 may be due to a mismatch in the inclination, but may also be due to a mismatch in the pitch distance.

[0048] FIG. 6 shows determining the inclination using a measurement area offset in the horizontal and vertical directions according to the nominal value of the inclination. This figure may be further described below. As will be elucidated elsewhere, it may be advantageous to decouple the measurement of the inclination from the measurement of the pitch distance. Advantageously, such decoupling may be obtained when at least two measurement areas 300, 301 are arranged along the approximate direction of the inclination. This approximate direction may also be referred to elsewhere as an initial estimate value of the inclination and may be obtained, for example, from manufacturing or design specifications. Thus, the measurement areas 300, 301 may be arranged along a line inclined by the value of the initial estimate value of the inclination, as shown by the angle θ° in FIG. 6. By offsetting the measurement areas 300, 301, the phase measurement may be obtained from the same optical element or the same group of optical elements, or may be obtained from substantially the same optical element(s) if the deviation between the initial estimate value of the inclination and the actual value of the inclination is larger. When the measurement areas 300, 301 are arranged along such a line, the deviation of the actually measured value of the pitch distance may not cause a (significant) phase difference between the upper measurement and the lower measurement. Rather, the phase difference measured between the two measurement areas may be due to, or mainly due to, only the deviation from its actually measured value in the inclination. Thus, the inclination measurement may be decoupled from the pitch measurement in that, for example, after the inclination is first determined in the above-described manner, the pitch distance may be determined in a manner in which it is known.

[0049] There are various alternatives for the measurement of inclination as described with reference to FIG. 6. For example, the measurement area can take a shape other than the rectangular shape shown in FIG. 6. In a particular alternative example, the measurement area can be circular, elliptical, etc. Another example is that the size of the measurement area can vary. For example, if the size of the measurement area is such that the phase can be observed at multiple locations within the measurement area, this observed phase can be summarized into one value, for example, by averaging or majority selection. However, this size can also be relatively small such that the phase is observed only at a single measurement location. Yet another example is that three or more measurement areas can be used, and these measurement areas can be located on the inclination lines described above. The relative distance between the measurement areas can be selected asymmetrically and / or non-uniformly. For example, the third measurement area can be located at n / d which is a fraction of the distance between both other measurement areas, where d is large even when all common factors in n and d are removed, and the distance between the measurement areas is large enough to accurately measure different phases at each measurement area. In other examples, four or more measurement areas can be used to further improve the accuracy of determining the value of the inclination.

[0050] Generally, for example, when the difference between the first phase and the second phase exceeds a threshold value, an estimated value of the inclination is adjusted based on the difference, and in order to adjust an offset to the adjusted estimated value of the inclination, the first position and / or the second position is rearranged, and the inclination can be determined iteratively by re-determining the first phase and / or the second phase at the rearranged first position and / or second position. When the difference between the first phase and the second phase is below the threshold value, the estimated value of the inclination can be output as the determined inclination.

[0051] Referring further to the test pattern shown on the autostereoscopic display, it should be noted that the test pattern can take the form of a single image that can include image content that is uniquely distinguishable for each phase of a set of phases assigned to respective positions on the display panel. However, alternatively, the test pattern may be a spatio-temporal or temporal test pattern in which the image content that is uniquely distinguishable for each phase is distributed among different images. In such a temporal (spatio-temporal) test pattern, one image may include a test pattern that is uniquely distinguishable for one phase, while for other phases it may not be uniquely distinguishable, and another image may include a test pattern that is uniquely distinguishable for another phase, where again other phases may not be uniquely distinguishable. For example, the first image may be a white image content at phase zero and include black image content at all other phases, while the second image may be a white image content at phase 1 and include black image content at all other phases, and the third image may be a white image content at phase 2 and include black image content at all other phases, etc. It should also be understood that such temporal (spatio-temporal) test patterns enable, in the systems and methods as described herein, determining which phases are visible from the camera position at respective positions on the display panel.

[0052] FIG. 7 shows a method 400 for determining the tilt of an autostereoscopic display. The method 400 includes, in the caption "Assign phases to display elements", assigning 410 a phase to each display element based on an estimated pitch distance and an estimated tilt; in the caption "Generate interleaved display data", generating 420 display data including image content uniquely identifiable for each of the assigned phases based on the assigned phases; in the caption "Output the display data to the display", outputting 430 the display data to the autostereoscopic display for display; and in the caption "Capture an image", capturing 440 one or more images of the display panel when the display data is being displayed by the autostereoscopic display. The method 400 may further include, in the caption "Determine the tilt by analyzing the captured image", determining 450 the tilt by analyzing the one or more captured images, and the analysis of the one or more captured images includes, in the caption "Determine a first phase at a first position", determining 452 a first phase at a first position on the display panel based on the image content uniquely identifiable at the first position; in the caption "Determine a second phase at a second position", determining 454 a second phase at a second position on the display panel based on the image content uniquely identifiable at the second position, where the first position and the second position are offset from each other horizontally and vertically according to the estimated tilt, and in the caption "Determine the tilt based on the phase difference", determining 456 the tilt of the optical element based on the difference between the first phase and the second phase. Each step of the method may be performed in any suitable order, e.g., sequentially, simultaneously, or a combination thereof, and may be subject to a particular order required, e.g., by input / output relationships, where applicable.

[0053] In general, each entity described herein can be embodied as or within a device or apparatus. The device or apparatus can comprise one or more (micro)processors that execute appropriate software. The processor of each entity can be embodied by one or more of these (micro)processors. The software that implements the functions of each entity may be downloaded and / or stored in a corresponding memory or memories, e.g., a volatile memory such as RAM or a non-volatile memory such as flash. Alternatively, the processor of each entity can be implemented within the device or apparatus in the form of programmable logic, e.g., as a field programmable gate array (FPGA). Any input and / or output interface can be implemented as the respective interface of the device or apparatus. Each functional unit of each entity can be implemented in the form of a circuit or circuitry. Each entity can also be implemented, for example, distributed across different devices or apparatuses.

[0054] Note that any of the methods described herein, and any of the claims, can be implemented as a computer-executable method, as a computer, as dedicated hardware, or as a combination of both. Instructions for a computer, e.g., executable code, can be stored on a computer-readable medium 500, e.g., in the form of a machine-readable physical mark sequence 510 and / or as a sequence of elements having different electrical, e.g., magnetic, or optical characteristics or values, as shown, for example, in FIG. 8. The executable code can be stored in a transient or non-transient manner. Examples of computer-readable media include memory devices, optical storage devices, integrated circuits, etc. FIG. 8 shows, by way of example, a memory device 500.

[0055] Examples, embodiments, or optional features should not be understood to limit the disclosure claimed in the claims, whether shown as non-limiting or not.

[0056] It should be noted that the above embodiments are illustrative rather than limiting the present disclosure, and those skilled in the art can design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs in parentheses shall not be construed as limiting the claims. The use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those recited within the scope of the claims. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. Expressions such as "at least one of" when associated with a list or group of elements represent a selection of all or any subset of elements from that list or group. For example, the expression "at least one of A, B, and C" should be understood to include only A, only B, only C, both A and B, both A and C, both B and C, or all of A, B, and C. The present disclosure can be implemented using hardware comprising several distinct elements and using a suitably programmed computer. In the claims of a device elucidating several means, some of these means may be embodied by exactly the same device in hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used advantageously.

[0057] The following list of reference numerals is provided to facilitate the interpretation of the drawings and should not be construed as limiting the claims.

Description of the Reference Signs

[0058] View 0 - 5 Viewing cone 10 - 12 Series of viewing cones 20 Stereoscopic position 30 Processor system 120 Interleaved display data 122 140 3D Display 150 Display Panel 160 Array of Optical Elements 162 Substrate 164 Lenticular Element 200 System for Determining the Inclination of an Autostereoscopic Display 220 Processing Subsystem 240 Camera Interface 250 Camera 252 Camera Data 260 Display Output Interface 262 Interleaved Display Data 300, 301 Measurement Windows 310 Inclination Line Passing through the Center of the First Measurement Window 312 Inclination Line Passing through the Center of the Second Measurement Window 314 Middle Line 400 Method for Determining the Inclination of an Autostereoscopic Display 410 Assigning Phases to Display Elements 420 Generating Interleaved Display Data 430 Outputting Display Data to a Display 440 Capturing Images 450 Determining the Inclination by Analyzing the Captured Images 452 Determining the First Phase at the First Position 454 Determining the Second Phase at the Second Position 456 Determining the Inclination Based on the Phase Difference 500 Computer-Readable Medium 510 Non-Temporary Data

Claims

1. A method (400) for determining the tilt of an automated stereoscopic display, Automatic 3D displays, A display panel comprising an array of display elements, An array of elongated optical elements for redirecting light emitted by a display element in mutually different directions, wherein the optical elements are arranged in parallel to each other at a pitch distance, and their main longitudinal axes are oriented in a tilted manner with respect to the array of display elements. Equipped with, The method is Assigning a phase to each display element based on an estimated pitch distance and an estimated tilt (410), wherein the phase indicates the direction in which the light emitted by each display element is redirected, Based on the assigned phases, the system generates display data (420) that includes image content uniquely identifiable for each phase in the set of assigned phases, Outputting display data to an automatic stereoscopic display for display purposes (430), When display data is displayed by an automatic stereoscopic display, capturing one or more images on the display panel (440), The slope is determined by analyzing one or more of the aforementioned capture images (450) The analysis of one or more captured images, including, (452) A first phase is determined at a first position on the display panel based on uniquely identifiable image content shown at the first position, Determining a second phase at a second position on a display panel based on uniquely identifiable image content shown at the second position (454), wherein the first position and the second position are offset horizontally and vertically from each other according to an estimated tilt value, The tilt of the optical element is determined based on the difference between the first phase and the second phase (456) Method (400), including the method (400).

2. The method according to claim 1 (400), wherein the first phase and the second phase are determined, respectively, based on uniquely identifiable image content in each measurement area at each position on the display panel.

3. The method according to claim 2 (400), wherein the first phase and the second phase are determined, in each measurement region, based on average selection or majority selection of uniquely identifiable image content.

4. The first position and the second position are, The upper and lower halves of the display panel, preferably the upper third and lower third of the display panel, more preferably the upper quarter and lower quarter of the display panel, or The method according to any one of claims 1 to 3 (400), wherein the display panel is arranged in the left half and the right half, preferably the left third and the right third of the display panel, and more preferably the left quarter and the right quarter of the display panel, respectively.

5. The slope is, If the difference between the first phase and the second phase exceeds a threshold, Adjusting the estimated slope based on the difference, To adjust the offset to the adjusted estimated value of the slope, the first position and / or the second position are rearranged, By redetermining the first phase and / or the second phase at the relocated first position and / or second position, If the difference between the first phase and the second phase falls below a threshold, the estimated slope is output as the determined slope. The method according to any one of claims 1 to 3, which is determined iteratively (400).

6. The method according to claim 5 (400), further comprising determining one or more intermediate phases at one or more intermediate positions between a first position and a second position, based on uniquely identifiable image content shown at one or more intermediate positions, wherein the difference is a measured difference applied to the first phase, the second phase, and the one or more intermediate phases.

7. The method according to claim 6 (400), wherein one or more intermediate positions are arranged asymmetrically between a first position and a second position.

8. The method according to any one of claims 1 to 3 (400), further comprising determining the pitch distance based on the determined slope.

9. Determining the pitch distance is Based on the estimated pitch distance and determined tilt, the phase is reassigned to each display element. Based on the reassigned phases, generate further display data containing uniquely identifiable image content for each phase in the set of reassigned phases. For display purposes, additional display data is output to the automated stereoscopic display. When display data is shown by an automated stereoscopic display, capturing one or more additional images of the display panel. The pitch distance of the optical element is determined by analyzing one or more of the aforementioned additional capture images. This includes the analysis of one or more additional capture images, Determining a first further phase at a first further position on the display panel, based on uniquely identifiable image content shown at the first further position, Determining a second further phase at a second further position on the display panel based on uniquely identifiable image content shown at the second further position, wherein the second further position is offset from the first further position. The pitch distance of the optical element is determined based on the difference between the first further phase and the second further phase. The method according to claim 8 (400), including the method according to claim 8.

10. The method according to claim 9 (400), wherein the offset between the first further phase and the second further phase differs horizontally from the inclination.

11. The method according to any one of claims 1 to 3 (400), wherein the uniquely identifiable image content includes a different grayscale and / or a different color for each phase in the assigned set of phases.

12. The method according to any one of claims 1 to 3 (400), further comprising obtaining an estimate of the inclination and / or pitch distance from a target specification used for manufacturing an automated stereoscopic display.

13. The method according to any one of claims 1 to 3 (400), wherein the array of elongated optical elements is a lenticular lens sheet.

14. A temporary or non-temporary computer-readable storage medium (500) containing data (510) representing instructions configured to cause a processor system to carry out the method according to any one of claims 1 to 3.

15. A system (200) for determining the tilt of an automated stereoscopic display (140), Automatic 3D displays, A display panel (150) having an array of display elements, An array of elongated optical elements (160) for redirecting light emitted by a display element in mutually different directions, wherein the optical elements are arranged in parallel to each other at a pitch distance, and their main longitudinal axes are oriented in a tilted state relative to the array of display elements. Equipped with, The system A display output interface (260) for an automated stereoscopic display, A camera interface (240) to a camera positioned to capture images of the display panel of an automated stereoscopic display, Processing subsystem (220) and The processing subsystem (220) is equipped with, Based on estimated pitch distance and tilt, a phase is assigned to each display element, where the phase indicates the direction in which the light emitted by each display element is redirected. Based on the assigned phases, display data is generated that includes image content uniquely identifiable for each phase in the set of assigned phases. The system outputs display data (262) to an automatic stereoscopic display for display via a display output interface, When display data is shown by an automatic stereoscopic display via a camera interface, one or more images (252) of the display panel are captured, The slope is determined by analyzing one or more of the aforementioned capture images. It is configured to perform the analysis of one or more captured images, A first phase is determined at a first position (300) on the display panel based on uniquely identifiable image content shown at the first position, A second phase is determined at a second position (301) on the display panel based on uniquely identifiable image content shown at the second position, wherein the first position and the second position are offset horizontally and vertically from each other according to an estimated tilt value. The tilt of the optical element is determined based on the difference between the first phase and the second phase. System (200), including the system.

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