Columnar lens of naked eye stereoscopic display device for reducing moire fringes

Abstract

The invention relates to a lens arrangement comprising a profile surface extending in an x-direction and a y-direction; and has a z-direction profile perpendicular to the profile surface. The profile surface defines an array of elongate lens elements having lens surfaces that intersect one another along an intersection line. At least one intersection line in the lens arrangement is a curved intersection line including one or more curved segments curved in the x-direction and / or the z-direction. A lenticular lens having such a curved line is capable of reducing moire fringes when placed on an array of display pixel elements in a naked eye stereoscopic display device. Therefore, the invention also relates to a naked eye stereoscopic display device which comprises the lens device and an array of display pixel elements.

Description

Technical Field

[0001] The present invention relates to a lens device, a method for preparing such a lens device, a lens assembly comprising such a lens device, a naked-eye stereoscopic display device comprising such a lens device or such a lens assembly, and a method for reducing moire fringes in a naked-eye stereoscopic display device. Background Art

[0002] Auto-stereoscopic displays play an increasingly important role in virtual reality and augmented reality applications. One of the most prominent features of auto-stereoscopic displays is that they allow viewers to perceive the depth of the displayed image (stereoscopic vision) without wearing glasses or other special eyewear. In addition, this principle works even if the viewer moves relative to the auto-stereoscopic display.

[0003] The key to this technology lies in a screen composed of lenticular lenses, or parallax barriers, placed in front of an array of pixels. This enables the pixel output (i.e., light) to be directed in a specific spatial direction, allowing selective illumination of one eye in a pair of eyes. By precisely controlling the pixels, the screen can simultaneously direct a left-eye image to the viewer's left eye, and a right-eye image to the viewer's right eye. The resulting stereoscopic image can provide the viewer with a perception of depth, with elements of the image appearing either in front of the display or further away ("behind the display").

[0004] However, many conventional naked-eye stereoscopic displays suffer from the problem of moiré fringes. Both lenticular lenses and parallax barriers are regular structures consisting of semi-cylindrical microlenses (lenticular lenses) or elongated slits, which are arranged parallel to each other. The superposition of such a regular structure and the (equally regular) pixel array may cause the viewer to perceive moiré fringes, which are generally disturbing to the viewer. Moiré fringes not only destroy the displayed image, but also make the screen itself visible, for example, reflections can also produce similar effects. This destroys the illusion of a "free-floating" three-dimensional image in the environment in front of and behind the screen.

[0005] To date, much effort has been made to reduce or even completely eliminate moiré in such displays. For example, the pixels that contribute most to the moiré can be identified and their pixel output modified in a specific way. However, this can have undesirable side effects such as reduced resolution and / or reduced display brightness. This also requires valuable processor capacity. Other solutions involve the combined application of specific pixel shapes and pixel arrangements with specific lens tilt angles. However, this limits the design opportunities for naked-eye stereoscopic display devices and makes the manufacturing process more demanding, as even tilt deviations as small as a fraction of a degree can cause moiré. Summary of the invention

[0006] Therefore, it is an object of the present invention to find a solution to the occurrence of moiré patterns without causing one or more of the above mentioned side effects. Another object of the present invention is to provide a solution that is simpler than the solutions known in the art. More generally, it is an object of the present invention to improve the viewing experience of viewers of naked eye stereoscopic displays.

[0007] It has now been found that one or more of these objects can be achieved by making specific modifications to the lenticular lenses of a naked-eye stereoscopic display.

[0008] The invention therefore relates to a lens arrangement (1) having a profiled surface (2), said profiled surface (2):

[0009] - extends in the x-direction and in the y-direction perpendicular to the x-direction; and

[0010] - has a profile in the z direction perpendicular to the profile surface (2),

[0011] The profiled surface (2) defines an array of elongated lens elements (3) which:

[0012] - has a lens length in the y direction;

[0013] - are arranged in parallel with each other; and

[0014] - having lens surfaces intersecting each other along an intersection line (4);

[0015] At least one of the intersection lines (4) is a curved intersection line.

[0016] The lens device (1) may be a cylindrical lens or a mold for preparing a cylindrical lens.

[0017] The present invention also relates to a naked-eye stereoscopic display device, which comprises an array (9) of display pixel elements as described above and a cylindrical lens.

[0018] The invention also relates to a method for manufacturing a lens arrangement having a profiled surface defining an array of elongated lens elements, the method comprising:

[0019] - Providing a sheet having an engravable surface, the sheet:

[0020] extends in an x-direction and in a y-direction perpendicular to the x-direction; and

[0021] having a z-direction perpendicular to said engravable surface;

[0022] - providing an apparatus comprising a chisel, the shape of which corresponds in negative relief to the cross-sectional shape of an elongated lens element in a lens arrangement manufactured by the method;

[0023] - subsequently engraving a plurality of parallel elongated lens elements in the sheet using a chisel by moving the chisel in the y-direction of the sheet to form a profiled surface, wherein the lens elements formed in the sheet intersect each other at intersection lines;

[0024] During the movement of the chisel in the z direction, the chisel is moved in the x direction and / or the z direction, thereby forming a curved intersection line.

[0025] The present invention also relates to a method for manufacturing a naked-eye stereoscopic display device, which comprises using a cylindrical lens as described above, or using a lens assembly comprising an array of display pixel elements as described above and a cylindrical lens.

[0026] The present invention also relates to a method for reducing moire fringes in a naked-eye stereoscopic display device, which comprises using a cylindrical lens as described above, in particular by aligning an array of display pixel elements with the cylindrical lens as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A first lens arrangement according to the invention is schematically shown.

[0028] Figure 2 A second lens arrangement according to the invention is schematically shown.

[0029] Figure 3 A third lens arrangement according to the invention is schematically shown.

[0030] Figure 4 A fourth lens arrangement according to the invention is schematically shown.

[0031] Figure 5 A fifth lens arrangement according to the invention is schematically shown.

[0032] Figure 6 A sixth lens arrangement according to the invention is schematically shown.

[0033] Figure 7 A seventh lens arrangement according to the invention is schematically shown.

[0034] Figure 8 A lens assembly according to the invention is schematically shown. DETAILED DESCRIPTION

[0035] The drawings do not limit the invention to the specific embodiments disclosed therein and described in this specification. The elements in the drawings are shown for simplicity and clarity and are not necessarily drawn to scale, with emphasis placed on clearly illustrating the principles of the invention. For example, the size of the lens elements and the degree of curvature of the intersection lines between them cannot be inferred from the drawings. The shapes and configurations of the pixel elements shown in the drawings are not intended to reflect actual conditions. Furthermore, their sizes relative to the size of the lens elements cannot be inferred from the drawings.

[0036] Furthermore, the terms "first", "second", and the like in the description and the claims, if any, are generally used to distinguish between similar elements or items and not necessarily to describe a sequential or chronological order.

[0037] In the context of the present invention, the term "viewer" refers to a person who is able to consume (especially watch) the content presented by the autostereoscopic display device. Throughout the text, references to the viewer will use masculine terms such as "he", "him" or "his". This is only for the purpose of clarity and brevity, and it should be understood that feminine terms such as "she" and "her" are equally applicable.

[0038] In the context of the present invention, the term "moire" refers to a pattern perceived by a viewer (a "moire pattern") that appears due to the superposition of two real patterns that are slightly misaligned, slightly rotated, and / or have slightly different pitches. In addition, moire may also appear when the pitch of one pattern is almost (but not exactly) an integer multiple (2, 3, 4, etc.) of the pitch of the other pattern. In the present invention, the moire that is reduced or overcome generally involves the superposition of the pattern of the pixel array and the pattern of the lens array.

[0039] Some of the terms introduced hereinafter, such as "lens length", "V-shaped valley", "sharp ridge" and "intersection line", are indicated as extending in the "y-direction". However, it should be understood that in certain embodiments of the invention, these terms also have a component (albeit a very small component) in the x-direction and / or the z-direction, i.e. in embodiments where the curved intersection line comprises one or more curved segments that are curved in the x-direction and / or the z-direction. However, for the sake of clarity, this is not always mentioned. After all, the terms concerned only extend in the y-direction of the lens arrangement of the invention when averaged over the entire lens arrangement.

[0040] The lens arrangement according to the invention is an object comprising a profiled surface, ie a surface having a surface relief or contoured structure.

[0041] In order to clearly describe the present invention, the x-direction, y-direction and z-direction are defined for the lens device according to the present invention. In this article, the y-direction is perpendicular to the x-direction, and the z-direction is perpendicular to the plane defined by the x-direction and the y-direction ((x, y) plane). The surface of the lens device extends in the x-direction and the y-direction, regardless of the surface relief structure extending in the z-direction.

[0042] The profiled surface is shaped as an array of lens elements having an elongated shape (and elongation) in the y-direction, thereby defining a lens length in the y-direction. The lens elements are arranged side by side in the x-direction and extend parallel to each other in the y-direction. When arranged on an array of display pixel elements, such an array of lens elements is a known means for directing the outputs from different pixel elements into mutually different directions so as to enable a stereoscopic image (perceived as a three-dimensional image by the viewer) to be displayed to a viewer.

[0043] In this context, the term "configuration" is used only to describe a specific appearance or shape, not the composition of individual components, since the lens elements are not configured as individual objects. The lens arrangement according to the invention in principle consists of a single component, so that the different lens elements are all part of the same piece of material. Optionally, the cylindrical lenses are provided with a coating and / or a housing. The cylindrical lens elements in the cylindrical lens arrangement of the invention have a convex (round) shape or a concave (hollow) shape, which means that the cylindrical lens arrangement usually comprises only one of these types of cylindrical lens elements.

[0044] A side-by-side configuration is to be understood as a configuration in which adjacent cylindrical lens elements are "in contact" with each other, i.e., in principle, there is no non-cylindrical sandwich surface between two adjacent cylindrical lens elements, such as a flat surface extending along the x-direction and the y-direction (when the lens device is prepared by engraving lens elements on a flat surface of a plate, the flat sandwich surface between two adjacent lens elements will correspond to a surface that has not been engraved).

[0045] The boundary between two adjacent lens elements is represented by an abrupt change in the slope of the profile surface on a cross section defined by the x-direction and the z-direction (i.e., the (x, z) plane). In the case where the lens element has a convex shape, the boundary between the two lens elements can be regarded as a V-shaped valley extending along the y-direction of the profile surface; in the case where the lens element has a concave shape, the boundary between the two lens elements can be regarded as a sharp ridge extending along the y-direction of the profile surface.

[0046] The boundary between two adjacent lens elements is formed by a line that coincides with the lowest point of the V-shaped valley (i.e., the lowest point in the z direction) or with the highest point of the ridge (i.e., the highest point in the z direction). This line is actually the intersection line of the lens surfaces of two adjacent cylindrical lens elements. Therefore, for the purpose of the present invention, this line is represented by the term "intersection line".

[0047] Figure 1 A lens arrangement (1) according to the invention is schematically shown. The lens arrangement comprises a profile surface (2) defining an array of elongated lens elements (3). Each lens element has a lens surface which intersects the lens surface of an adjacent lens element (3) along an intersection line (4). For clarity, Figure 1 It is not shown that one or more intersection lines (4) are curved as required by the present invention. However, the remaining Figure 2-8 The curved intersection line (4) is then clearly shown.

[0048] In addition to the lens length, the lens element also has a lens width. This dimension is defined as the distance between two intersecting lines on either side of the lens element along the y direction, measured in the x-direction. However, this distance is not measured by a line directly connecting the two intersecting lines, but rather by a line projected from the z-direction onto the two intersecting lines. This is to accommodate the deviation that occurs when the line directly connecting the two intersecting lines has a component in the z-direction (as is the case with the cylindrical lens according to the present invention, which will be further explained below).

[0049] Figure 7 The definition of the lens width (7) is shown in the figure showing a cross-sectional view of the lens device (1) of the present invention in the (x, z) plane. On either side of the lens element (3), there are valleys (5) defining an intersection line (therefore not shown) perpendicular to the plane of the drawing. The valleys (5) on either side of the lens element (3) have different positions in the z direction, the difference being represented by the two horizontal dashed lines (6). The distance between the two valleys projected in the z direction forms the lens width (7).

[0050] Furthermore, the text may mention that elongated objects that are not completely straight are arranged parallel to each other. The term "parallel" means that the objects are arranged side by side with their longest dimensions facing each other. In this way, their arrangement is considered to be parallel.

[0051] The lens elements in the prior art lens arrangements are all straight and have the same shape. However, this is not the case in the lens arrangements of the present invention, where the lens elements are curved in the x-direction and / or the z-direction. A certain curvature may apply to all lens elements (so they are still the same); or different lens elements may have different curvatures (so not all lens elements are the same).

[0052] When the lens element is curved, one or both of the two intersection lines on either side of the lens element have a curvature. Thus, the invention is characterized in that the cylindrical lens comprises at least one intersection line which is a curved intersection line. The curvature may be in the x-direction and / or the z-direction.

[0053] A curved intersection line is a line that has at least one curved section. The term "curved" means that the line is not straight, but rather curved. This curvature is usually a smooth change in the direction of the line. But it can also be an abrupt change, such as a corner or a zigzag.

[0054] The curved intersection line can be curved along its entire length or along a portion of its entire length. In the latter case, the intersection line, for example, includes one or more curved segments and one or more straight segments.

[0055] In the context of the present invention, a segment of an intersection line may include a specific portion of the intersection line or the entire intersection line. In addition, a curved segment of an intersection line may be any segment that does not contain a straight portion. A curved segment may be adjacent to other curved segments without having a straight segment between the curved segments.

[0056] Typically, a curved intersection line is a line that includes one or more curved segments. For example, one or more curved segments are curved in the x-direction, one or more curved segments are curved in the z-direction, or one or more curved segments are curved in both the x-direction and the z-direction. It is also possible to have segments with different curvatures in a single lens element, such as at least one segment curved in the x-direction and at least one segment curved in the z-direction.

[0057] Figure 2 and Figure 3 are perspective views of first and second lens arrangements (1) according to the invention. They show two adjacent lens elements (3) sharing a common intersection line (4). Figure 2 In , the intersection line (4) has curvature only in the x-direction. Figure 3 In , the intersection line (4) has curvature only in the z direction.

[0058] Figures 4 to 6 are schematic top views of three different embodiments according to the present invention. They show lens elements (3) and curved intersection lines (4), wherein the curved intersection lines (4) are curved along the x-direction. In these figures, the different shapes and relative arrangements of the intersection lines (4) are emphasized.

[0059] exist Figure 4 In the embodiment of the present invention, the curved intersection lines (4) differ in that they have different curvatures. The displacement of the lens elements (3) in the middle part of the lens arrangement (1) in the x-direction is greater than that of the lens elements (3) above and below. The displacement of the lens elements (3) in the middle part (having the largest displacement) exceeds several times the maximum lens width.

[0060] exist Figure 5 In the embodiment, the curved intersection lines (4) all have the same curvature but different "phases", so that the lens width of the lens element (3) varies along the y direction.

[0061] exist Figure 6 In the embodiment of the present invention, the curved intersection lines (4) are all identical and have the same "phase", so that the lens element (3) has a constant lens width along the y direction.

[0062] For purposes of the present invention, the extent of the curvature of the intersection line in the x-direction is described by the variation of the intersection line in the x-direction, which variation is the range of distances over which the intersection line has curvature in the x-direction. These variations are defined by relating them to the average lens width. To do this, the average lens width is multiplied by a factor within a specific range. In the lens arrangement of the present invention, the curved intersection line can exhibit a variation in the x-direction of up to 1.0 times the average lens width, where the average lens width is defined as the length of the array in the x-direction divided by the number of lens elements present in the x-direction.

[0063] The variation in the x direction may also be greater than 1.0 times the average lens width, for example, up to 2.0, 5.0, or 10 times the average lens width (see Figure 4 ). Such a large change requires that adjacent intersection lines also undergo a similar change in the x-direction. Otherwise, the lens elements either become too small or too far apart to define the intersection lines. This is explained in the following paragraphs.

[0064] Typically, the intersection lines are allowed to vary in the x-direction only if the spacing of the two intersection lines on either side of the lens element does not decrease too much, because too small a spacing would make the lens element too narrow, resulting in a lens element with a field of view that is too small to provide a good viewing experience. Therefore, 0.60 times the average lens width is usually used as the minimum spacing. There is also an upper limit on the spacing of the two intersection lines, because it cannot exceed the span that can be achieved in the x-direction for a lens element of a given shape. 1.40 times the average lens width is usually used as the maximum.

[0065] Therefore, in a lens arrangement according to the present invention, two adjacent intersection lines are typically separated by a varying distance ranging from 0.60 to 1.40 times the average lens width measured along the x-direction, where the average lens width is defined as the length of the array in the x-direction divided by the number of lens elements present in the x-direction.

[0066] The varying distance between the two intersection lines can also vary within the following ranges: 0.65 to 1.35 times, 0.70 to 1.30 times, 0.75 to 1.25 times, 0.80 to 1.20 times, 0.85 to 1.15 times, 0.90 to 1.10 times, 0.93 to 1.07 times, or 0.95 to 1.05 times the average lens width.

[0067] For purposes of the present invention, the extent of the curvature of the intersection line in the z direction is described by the variation of the intersection line in the z direction, which variation is the range of distances in the z direction over which the intersection line bends. These values ​​are also defined by relating them to an average lens width. To do this, the average lens width is multiplied by a factor within a specified range. In the lens arrangement of the present invention, the curved intersection line can exhibit a variation in the z direction of up to 1.0 times the average lens width, where the average lens width is defined as the length of the array in the x direction divided by the number of lens elements present in the x direction.

[0068] The change in the z direction can also be greater than 1.0 times the average lens width, and the change can be, for example, up to 2.0 times, 3.0 times, or 5 times the average lens width. Such large changes require that adjacent intersection lines experience similar changes in the z direction. Otherwise, it may result in one lens element being too tall relative to another adjacent lens element.

[0069] Some or all of the curved intersection lines may also have substantially the same shape. When two such intersection lines are located on either side of a lens element, the lens element may have a constant lens width (see, e.g. Figure 6 ).

[0070] Thus, in the lens arrangement of the invention, there may be at least one lens element whose lens width is substantially constant over its lens length. However, the number of such lens elements is usually greater. The number of lens elements is preferably defined as a percentage of the total number of lens elements that are part of the lens arrangement of the invention. For example, the percentage of such lens elements is at least 10%, at least 25%, at least 50%, at least 75%, at least 90% or at least 95%.

[0071] Typically, in a lens arrangement according to the invention, at least 50% of the intersection lines are curved intersection lines. This percentage may also be at least 10%, at least 20%, at least 30%, at least 40%, at least 60%, at least 70%, at least 80%, at least 90% or at least 95%. It is also possible that all intersection lines are curved intersection lines.

[0072] In the lens device according to the present invention, a plurality of (x, z) planes perpendicular to the lens length of the lens element can be defined. The aspect ratio x:z of the cross-sectional shape of the lens element in each (x, z) plane can be in the range of 6:1 to 3:1, in particular in the range of 5:1 to 4:1.

[0073] The lens elements in prior art cylindrical lenses have focal lengths that enable them to focus light along a focal line parallel to the length of the lens (ie, the y-direction). Such a focal line is the collection of focal points that together form the focal line.

[0074] When the lens device of the present invention is a cylindrical lens, the above situation is also applicable. In this case, the lens device is made of transparent material, so that it can play the role of a cylindrical lens.

[0075] However, the lens device of the present invention is not necessarily a cylindrical lens. It can also be made of non-transparent materials. In this way, the lens device of the present invention is used, for example, as a lens mold to produce a cylindrical lens, for example, by contacting the molding surface with a (usually liquid) curable resin and then curing the curable resin to produce a solid and transparent lens material to produce a cylindrical lens. Although such lens molds cannot usually be used as lenses (because they are made of non-transparent materials), they still fall within the scope of the present invention because they have the same lens surface as a real cylindrical lens (just a negative surface corresponding to the cylindrical lens). In principle, this lens device of the present invention can be made of any material suitable for use as a mold in a molding process.

[0076] Thus, in an embodiment, the lens device of the present invention is a cylindrical lens, for example a device capable of refracting light as it passes through the lens. In another embodiment, the lens device of the present invention is a mold for making a cylindrical lens.

[0077] Therefore, the lens element of the device of the present invention may not act as a cylindrical lens in some cases, but actually have the same profile as a real cylindrical lens, that is, when the device is made of non-transparent material. In this case, the shape of the lens element can be equivalent to the shape of a real cylindrical lens.

[0078] Therefore, particularly in the case where the lens device of the present invention is made of non-transparent material, the lens elements of such lens device can be considered to have a cross-sectional shape in the (x, z) plane corresponding to the cross-sectional shape of a cylindrical lens having a specific focal length, rather than considering them to be lenses having such a focal length (thus, if the mold is made of lens material, its lens elements will have a specific focal length).

[0079] In a particular embodiment, the lens element can be considered to have a cross-sectional shape in any (x, z) plane that corresponds to the cross-sectional shape of a cylindrical lens with a constant focal length in the (x, z) plane. This means that, in the case where the lens device of the present invention is a cylindrical lens, the focal length of the lens element is constant over the entire length of each lens element (i.e., in the y direction); and, in the case where the lens device of the present invention is a lens mold, the focal length of the lens element of the cylindrical lens prepared from the mold is constant over the entire length of each lens element. It should be understood from this that, in the case where the cylindrical lens is a concave lens, the focus must be identified as a virtual focus. Accordingly, such a cylindrical lens has a constant virtual focus over the entire length of each lens element.

[0080] It should be understood that the shape of the lens elements may only be able to produce an exact focus by approximation, for example because their convex or concave shape is not a perfect parabola. For example, a circular shape may be a good approximation, especially when only relatively small angles of the circle are used. The present invention includes lens arrangements having any such lens elements (e.g., non-parabolic shapes) that can provide useful imaging when applied to a naked-eye stereoscopic display device.

[0081] The invention also relates to a lens assembly (8) comprising an array (9) of display pixel elements as described above and a lens arrangement (1), wherein the lens arrangement (1) is a lenticular lens. The array is typically aligned with the lenticular lens so that the lenticular lens covers at least a portion of the array.

[0082] Figure 8 Such a lens assembly is schematically shown. Due to the curvature of the intersection line, the regular ordering of the lens elements is "broken". Therefore, the display pixel elements cannot find an ordered counterpart in the lens element that may cause the generation of moire fringes. Therefore, the naked eye stereoscopic display device including the lens assembly of the present invention shows less moire fringes than the known naked eye stereoscopic display device.

[0083] The present invention also relates to a naked-eye stereoscopic display device comprising the lens assembly as described above.

[0084] The invention also relates to a naked eye stereoscopic display device comprising an array (9) of display pixel elements as described above and a lens device (1), wherein the lens device (1) is a cylindrical lens. The array is usually aligned with the cylindrical lens so that the cylindrical lens covers at least a part of the array.

[0085] The invention also relates to a method for manufacturing a lens arrangement having a profiled surface defining an array of elongated lens elements, the method comprising:

[0086] - Providing a sheet having an engravable surface, the sheet:

[0087] extending in an x-direction and in a y-direction perpendicular to the x-direction; and

[0088] having a z-direction perpendicular to said engravable surface;

[0089] - providing a device comprising a chisel, the shape of which corresponds on a negative surface to the cross-sectional shape of a lens element in a lens arrangement manufactured by the method;

[0090] - subsequently engraving a plurality of parallel elongated lens elements in the sheet using a chisel by moving the chisel in the y-direction of the sheet to form a profiled surface, wherein the lens elements formed in the sheet intersect each other at intersection lines;

[0091] During the movement of the chisel in the z direction, the chisel is also moved in the x direction and / or the z direction, so that a curved intersection line is formed.

[0092] In this method, a single lens element (or a group of several lens elements, such as 2, 3 or 4) is produced by sequential engraving. In this way, each lens element can be prepared differently from the adjacent lens elements. This can produce any lens arrangement as described above.

[0093] When it is desired that the curved intersection line of the lens arrangement of the present invention include one or more curved segments that are curved only in the z-direction (and not in the x-direction), it is necessary to carve two lens elements that share this intersection line by moving the chisel in exactly the same way, i.e. without any lateral movement in the x-direction and with the same movement in the z-direction (see, for example, Figure 3 ). After all, when two adjacent lens elements are engraved at different depths in the surface, this will produce an intersection line between the two lens elements that exhibits a variation in the x-direction.

[0094] When the curved intersection line of the lens arrangement of the present invention includes one or more curved segments that are curved only in the x-direction (and not in the z-direction), then two lens elements that share such an intersection line are engraved by moving the chisel in exactly the same way for each lens element, i.e., without any movement in the z-direction and without the same lateral movement in the x-direction (see, for example, Figure 2 ). After all, when two adjacent lens elements are engraved with different lateral shifts, this will produce an intersection line between the two lens elements that exhibits a variation in the z-direction.

[0095] The method of the present invention may optionally be followed by a molding step in which the molding surface is contacted with a fluid curing resin, followed by curing the curable resin to produce a cylindrical lens. Alternatively, in the molding step, the molding surface is contacted with a fluid or moldable (e.g., thermoplastic) material at an elevated temperature, followed by cooling the material to produce a cylindrical lens.

[0096] In an embodiment, the method of the present invention is followed by using the manufactured lens device to manufacture a naked-eye stereoscopic display device, wherein the lens device is a cylindrical lens.

[0097] In an embodiment, the method of the present invention is followed by preparing a lens assembly comprising an array of display pixel elements as described above and a lens arrangement, wherein the lens arrangement is a lenticular lens. This typically comprises aligning the array with the lenticular lens such that the lenticular lens covers at least a portion of the array.

[0098] Optionally, the method for preparing a lenticular lens assembly is followed by manufacturing a naked-eye stereoscopic display device by using the prepared lenticular lens assembly.

[0099] The present invention also relates to a method for reducing moire fringes in a naked-eye stereoscopic display device, which comprises using a cylindrical lens as described above. The method particularly comprises aligning the cylindrical lens as described above with an array of display pixel elements.

Claims

1. A lens device (1) having a profiled surface (2), wherein the profiled surface (2): - extends in the x-direction and in the y-direction perpendicular to the x-direction; and - has a profile in the z direction perpendicular to the profile surface (2), The profiled surface (2) defines an array of elongated lens elements (3) which: - has a lens length in the y direction; - are arranged in parallel with each other; and - having lens surfaces intersecting each other along an intersection line (4); At least one of the intersection lines (4) is a curved intersection line.

2. The lens device (1) according to claim 1, wherein the curved intersection line (4) comprises one or more curved segments curved along the x-direction.

3. The lens device (1) according to claim 1 or 2, wherein the curved intersection line (4) comprises one or more curved segments curved in the z-direction.

4. The lens device (1) according to any one of claims 1 to 3, wherein the curved intersection line (4) comprises one or more curved segments curved in the x-direction and in the z-direction.

5. A lens device (1) according to any one of claims 1 to 4, wherein the curved intersection line (4) includes one or more curved segments curved in the x-direction, wherein the variation in the x-direction reaches 1.0 times the average lens width, wherein the average lens width is defined as the length of the array in the x-direction divided by the number of lens elements present in the x-direction.

6. A lens device (1) according to any one of claims 1 to 5, wherein the curved intersection line (4) includes one or more curved segments curved in the z direction, and the variation of the curved segments in the z direction reaches 1.0 times the average lens width, wherein the average lens width is defined as the length of the array in the x direction divided by the number of lens elements present in the x direction.

7. A lens arrangement (1) according to any one of claims 1 to 6, wherein two adjacent intersection lines (4) are separated by a variable distance, the distance being in the range of 0.60 to 1.40 times the average lens width measured along the x-direction, in particular in the range of 0.80 to 1.20 times the average lens width, wherein the average lens width is defined as the length of the array in the x-direction divided by the number of lens elements present in the x-direction.

8. A lens device (1) according to any one of claims 1 to 6, wherein the lens device (1) comprises at least one lens element (3), the lens width of the at least one lens element (3) being substantially constant over its lens length, wherein the lens width is defined as the projected distance in the x-direction between two intersection lines on both sides of the lens element, wherein the projected distance is projected in the z-direction.

9. The lens device (1) according to any one of claims 1 to 8, wherein - defining a plurality of (x, z) planes perpendicular to the lens length of the lens element; and The cross-sectional shape of the lens element in each (x, z) plane has an aspect ratio x:z between 6:1 and 3:1, in particular between 5:1 and 4:

1.

10. The lens device (1) according to any one of claims 1 to 9, wherein - defining a plurality of (x, z) planes perpendicular to the lens length of the lens element; and The cross-sectional shape of the lens element in the (x, z) plane corresponds to the cross-sectional shape of a cylindrical lens with a focal length that is constant along the length of the lens.

11. The lens arrangement (1) according to any one of claims 1 to 10, wherein at least 50%, in particular at least 80%, of the intersection lines (4) are curved intersection lines.

12. The lens arrangement (1) according to any one of claims 1 to 11, wherein the lens arrangement (1) is a cylindrical lens.

13. The lens device (1) according to any one of claims 1 to 11, wherein the lens device (1) is a mold for producing a cylindrical lens.

14. A lens assembly (8) for use in a naked-eye stereoscopic display device, comprising an array (9) of display pixel elements and a lens device (1) according to claim 12.

15. A naked-eye stereoscopic display device, comprising the lens device (1) according to Claim 12, in particular comprising the lens assembly (8) according to Claim 14.

16. A method for manufacturing a lens arrangement having a profiled surface defining an array of elongated lens elements, the method comprising: - Providing a sheet having an engravable surface, the sheet: Extending in the x-direction and in the y-direction perpendicular to the x-direction; and having a z-direction perpendicular to the engravable surface; - providing a device comprising a chisel, the shape of which corresponds in negative profile to the cross-sectional shape of an elongated lens element of the lens arrangement; - subsequently engraving a plurality of parallel elongated lens elements in the sheet using a chisel by moving the chisel in the y-direction of the sheet to form a profiled surface, wherein the lens elements formed in the sheet intersect each other at intersection lines; During the movement of the chisel in the y direction, the chisel is also moved in the x direction and / or the z direction, so that a curved intersection line is formed.

17. The method of claim 16, wherein the method is followed by preparing a lens assembly comprising an array of display pixel elements and a lens arrangement according to claim 12.

18. The method according to claim 16 or 17, wherein the method is followed by manufacturing a naked-eye stereoscopic display device. 19 . A method for manufacturing a naked-eye stereoscopic display device, comprising using the lens device according to claim 12 or the lens assembly according to claim 14 .

20. A method for reducing moire fringes in a naked-eye stereoscopic display device, comprising using a lens arrangement according to claim 12, in particular by aligning an array of display pixel elements with the lens arrangement according to claim 12.

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