TW201314267A - Autostereoscopic display device - Google Patents

Abstract

An autostereoscopic display device uses a display arrangement such as an emissive display arrangement or a reflective display arrangement and an autostereoscopic lens arrangement. A light controlling layer is provided between the display arrangement and the lens arrangement, with a refractive index lower than the surrounding materials. This reduces waveguiding in the lens arrangement by increasing the total internal reflection for shallow angles (near the plane of the display) before the light enters the lens arrangement.

Description

Autostereoscopic display device

The present invention relates to an autostereoscopic display device comprising a display panel having one display pixel array for producing a display and an imaging configuration for directing different views to one of different spatial locations.

A first example of an imaging configuration for one of such types of displays is, for example, one of the slits that are sized and positioned relative to the underlying pixels of the display. In a pair of video designs, the viewer can perceive a 3D image with the condition that his/her head is in a fixed position. The barrier is positioned in front of the display panel and is designed to direct light from odd pixel rows and even pixel rows to the left and right eyes of the viewer, respectively.

One disadvantage of this type of dual view display design is that the viewer must be in a fixed position and can only move about 3 cm to the left or right. In a more preferred embodiment, there are no two sub-pixel rows below each slit, but there are several sub-pixel rows. In this way, the viewer is allowed to move left and right and always perceive a stereoscopic image in his/her eyes.

This barrier configuration is easy to produce but not optically efficient. Therefore, a preferred alternative uses a lens configuration as the imaging configuration. For example, an array of elongated convex mirror elements extending parallel to one another and overlying the pixel array can be provided and viewed through the convex mirror elements.

The convex mirror-like elements are provided as a thin layer of elements, each of which is an elongated semi-circular convex mirror-like element. The convex mirror-like elements extend along a row direction of the display panel, wherein each convex mirror element is covered with a respective group Two or more adjacent display pixel rows.

In a configuration in which, for example, each microlens is associated with two rows of display pixels, the display pixels in each row provide a vertical segment of a respective two-dimensional sub-image. The convex thin layer directs the two segments and corresponding segments from the display pixel rows associated with the other microlenses to the left and right eyes of the user positioned in front of the thin layer to enable the use A single stereo image was observed. The thin layer of convex mirror elements thus provides a light output guiding function.

In other configurations, each microlens is associated with a group of four or more adjacent display pixels in a column direction. The corresponding display pixel rows in each group are suitably configured to provide a vertical segment from one of the respective two-dimensional sub-images. As a user's head moves from left to right, a series of continuous, different, stereoscopic views are perceived to form, for example, a look around.

Autostereoscopic displays are known to use liquid displays to produce images.

There is increasing interest in the use of emissive displays such as electroluminescent displays, such as organic light emitting diode (OLED) displays, because such displays do not require a polarizer and potentially should be capable of providing and using one The enhanced efficiency of LCD panels that are continuously illuminated is due to the fact that the pixels are turned off when not being used to display an image.

There is also growing interest in the use of reflective displays such as electrophoretic displays and electrowetting displays.

The present invention is based on the use of a system of emission or reflection display configurations within an autostereoscopic display system.

An emissive display such as an OLED display and a counter such as an electrophoretic display The obvious difference between a radiation display and an LCD display is how to emit light from a pixel. OLED pixels are emitters that emit light over a wide range of directions, and electrophoretic pixels are reflectors that reflect light over a wide range of directions. In accordance with the present invention, such emitters and reflectors are also referred to as diffuse emitters and diffuse reflectors, respectively. For a conventional (2D) display, an OLED display has a distinct advantage over an LCD display that requires a backlight and emits light with only a narrow beam without special measures. However, diffuse emission of OLED materials also poses a challenge because a large amount of light is recirculated inside the organic layer without being emitted, resulting in an inefficiency. For improvement, various solutions have been sought to improve the external coupling of light emitted from the OLED.

However, this improvement in 2D displays is actually a problem with 3D autostereoscopic OLED displays. The solution for increasing the light output cannot be used in autostereoscopic mirror-like displays because light intended to be emitted from a convex mirror lens can be reflected in the glass to an adjacent lens. This reduces contrast and increases crosstalk.

Reflective displays such as electrophoretic displays and electrowetting displays can result in disadvantages similar to those described above for emissive displays in the form of OLED displays.

Therefore, there is a conflict between the desire to use the emissive display and the reflective display and the desire for low crosstalk in the 3D autostereoscopic display.

According to the present invention, there is provided an autostereoscopic display device comprising: - a display configuration comprising a stack; an autostereoscopic lens arrangement comprising a plurality of transparent displays above the display configuration A mirror in which a plurality of pixels are provided under each lens.

a light control layer interposed between the display configuration and the autostereoscopic lens configuration, wherein the light management layer has a refractive index lower than a material of a layer on each side of the light control layer.

In one embodiment of the invention, the display configuration is an emission display such as an electroluminescent display, for example, an OLED display. In another embodiment of the invention, the display configuration is a reflective display such as an electrophoretic display or an electrowetting display.

The function of the light management layer increases the amount of total internal reflection compared to one of the layers to prevent light at a shallow angle that can affect the waveguide in the lens material from entering the lens material.

When the display configuration has an electroluminescent display configuration of a top emission structure, the layer stack may include a passivation layer, a cathode layer, a light emitting layer, and an anode layer, wherein the passivation layer is adjacent to the light control layer. The light management layer is thus contacted by the lens arrangement on one side and the outermost layer of the layer stack of the electroluminescent display configuration on the other side.

The light management layer preferably has a refractive index less than one of the refractive indices of the material of the lens configuration of at least 0.1 to provide the desired improvement. This refractive index difference can be greater than 0.2 or even greater than 0.3.

For other emission display configurations or reflective display configurations, the light management layer can be stacked on one side by the layer of the display configuration and on the other side by a device substrate.

The light management layer therefore preferably has a refractive index less than one of the refractive indices of the material of the substrate of at least 0.1 to provide the desired improvement. This refractive index difference can be More than 0.2 or even greater than 0.3.

In either case, the light management layer preferably also has a refractive index that is less than at least 0.1 of the outer layer of the display configuration to provide a surface at which total internal reflection occurs. Furthermore, this refractive index difference can be greater than 0.2 or even greater than 0.3.

The lens arrangement preferably comprises glass, although it may instead comprise a transparent polymer or other transparent material. The light management layer can include air and thus provide an array of spacers. The light management layer can instead comprise a solid layer having one of the desired (low) refractive indices so that no spacers are needed.

The autostereoscopic lens configuration may include a plurality of convex mirror lenses extending in a row direction of a pixel or inclined to an acute angle in a row direction of the pixel, wherein each lens covers a plurality of rows of pixels.

If the display configuration is an electroluminescent display configuration, the layer stack of the display preferably includes a cathode layer, a light emitting layer and an anode layer, wherein the cathode layer is adjacent to the light control layer and includes an ITO layer. This defines a top emission display with a transparent top cathode. However, the invention is also applicable to other types of emissive displays and reflective displays.

The present invention also provides a method for displaying a stereoscopic image, the method comprising: - generating a pixelated image using a display configuration comprising a stack; - passing the pixelated image light through a light control layer to an autostereoscopic lens configuration Wherein the light management layer has a refractive index that is lower than a refractive index of a material on an opposite side of the light management layer.

An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which the invention provides an auto-stereoscopic display apparatus using a display configuration and an autostereoscopic lens configuration. A light control layer having a refractive index lower than one of the surrounding material layers is provided between the display configuration and the lens configuration. This reduces the waveguide in the transmissive configuration by increasing the total internal reflection of the shallow angle (near the plane of the display) before the light enters the lens configuration.

In the following, embodiments of the invention will be elucidated in accordance with an electroluminescent display of one of the examples of an emissive display. Those skilled in the art will appreciate that the present invention is applicable not only to auto-stereoscopic display configurations based on convex mirror lenses including any type of emissive display, but also to lenticular shapes including reflective displays of any type. The autostereoscopic display configuration of the lens, as in all such display types the light will be directed (via emission or via reflection) from a pixel to the convex mirror lens over a wide range of directions.

The basic operation of a known 3D autostereoscopic display will first be explained below.

1 is a schematic perspective view of one of the known direct-view autostereoscopic display devices 1 using an LCD panel to produce an image. The known device 1 comprises a liquid crystal display panel 3 which is used as a spatial light modulator to produce a display active matrix type.

The display panel 3 has an array of orthogonal display pixels 5 arranged in columns and rows. For the sake of clarity, only a small number of display pixels 5 are shown in the figure. In fact, the display panel 3 may include about one thousand columns and thousands of rows of display pixels 5.

The structure of the liquid crystal display panel 3 commonly used in the autostereoscopic display is completely conventional. In particular, panel 3 includes a pair of spaced apart transparent glass The glass substrate is provided with an aligned twisted nematic liquid crystal or other liquid crystal material. The substrates carry a transparent indium tin oxide (ITO) electrode pattern on their facing surfaces. A polarizing layer is also provided on the outer surface of the substrates.

Each of the display pixels 5 includes opposing electrodes on the substrates with intervening liquid crystal material therebetween. The shape and layout of the display pixels 5 depend on the shape and layout of the electrodes. The display pixels 5 are regularly spaced apart from each other by the gap.

Each display pixel 5 is associated with a switching element such as a thin film transistor (TFT) or a thin film diode (TFD). The display pixels are operative to produce a display by providing addressing signals to the switching elements, and those skilled in the art will be aware of suitable addressing schemes.

The display panel 3 is illuminated by a light source 7, in which case the light source 7 includes a planar backlight extending over the area of the display pixel array. Light from source 7 is directed through display panel 3, with individual display pixels 5 being driven to modulate the light and produce a display.

The display device 1 also includes a convex mirror-like layer 9 disposed above the display side of the display panel 3. The convex mirror-like layer 9 performs a video forming function. The convex mirror-like layer 9 comprises a row of convex mirror-like elements 11 extending parallel to one another, for clarity, one of the convex mirror-like elements is shown only in an exaggerated size.

The convex mirror element 11 is in the form of a convex cylindrical lens in this particular example and serves as a light output directing member to provide different images or images from the display panel 3 to the eyes of a user located in front of the display device 1. .

The device has a controller 13 that controls the backlight and the display panel.

The autostereoscopic display device 1 shown in Fig. 1 is capable of providing several different perspective views in different directions. In particular, each convex mirror element 11 is overlaid Display pixel 5 of a small group in one column. The convex mirror element 11 projects each of the display pixels 5 in a group in a different direction, thereby forming a plurality of different videos. As the user's head moves from left to right, his/her eyes will sequentially receive different ones of the plurality of videos.

In the case of an LCD panel, a light polarizing member must also be used in conjunction with the array described above because the liquid crystal material is birefringent, wherein the light index switching is only applicable to a particular polarized light. The light polarizing member can be provided as part of the display panel or the imaging configuration of the device.

2 shows the principle of operation of one of the convex mirror-like imaging configurations described above and shows a backlight 20, a display device 24 such as an LCD, and a convex mirror array 28. Figure 2 shows how the lenticular configuration 28 directs different pixel outputs to three different spatial locations 22', 22", 22"'. These locations are all in one of the so-called viewing cones in which all of the images are different. The video is repeated in other viewing cones produced by the pixel light transmitted through the adjacent lens. The spatial locations 23', 23", 23"' are in the next viewing cone.

The use of an OLED display eliminates the need for a separate backlight and several polarizers. OLED is expected to become the display technology of the future. However, one of the current problems with OLED displays is the extraction of light from the device. Light extraction from OLEDs can be as low as 20% without any action.

Figure 3 is a schematic illustration of the structure of a single pixel of an OLED display in the form of a reverse emitting structure (i.e., via the substrate).

The display includes a glass substrate 30, a transparent anode 32, a light emitting layer 34, and a mirror cathode 36.

The line represents the path that light can select when it is emitted from one of the points 38 in the organic layer. When light is emitted from a source, it can travel in various directions. When light reaches a transition from one layer to another, the difference between the refractive indices of each of the layers determines whether the light can escape one layer and enter the next layer. The refractive index is dependent on the speed of light in the material and is expressed by Snell's law:

v=speed (m/s)

n = refractive index (no unit)

In the example of FIG. 3, the organic material forming the light-emitting layer 34 has a high refractive index (n = 1.8) and the refractive index of the glass is 1.45.

When the angle of incidence from light having a material having a high refractive index to a material having a material having a low refraction is sufficiently large, light cannot leave the material. When the organic material enters the glass, the angle of incidence is a critical angle and is represented by α = arcsin (n2 / n1). This represents 54 degrees.

Thus, it is apparent that a large amount of light generated in the organic layer never leaves the layer but remains inside the material in which it is reabsorbed and drives another photon to emit or become heat.

The same is true for light that leaves the organic layer and enters the glass substrate. A large amount of light cannot leave the glass at the glass and air interface.

Several solutions have been proposed for ensuring that light emitted from the organic layer is coupled into the glass and used to couple light emitted from the glass into the air.

An overview of various solutions is given in the paper "Light out-coupling strategies in organic light emitting devices" by D.S. Mehta et al. (Proc. of ASID '06, 8-12 Oct, New Delhi).

While OLED devices are typically bottom emitting devices and emit light through the glass substrate, another method implements top emission of the OLED stack such that light is transmitted through a transparent cathode and a thin encapsulant layer is not transmitted through the glass substrate. In general, different methods for increasing light extraction are more (or only) suitable for top-emitting OLED structures or bottom-emitting OLED structures.

The invention is set forth below primarily on the basis of the use of a top emitting OLED display. However, the basic principles behind the present invention are also applicable to a bottom-emitting OLED display, and all embodiments are applicable to a top-emitting OLED structure and a bottom OLED structure.

While known solutions help to improve light extraction efficiency by up to 80% for lighting applications and for 2D displays, they do not provide a better solution for autostereoscopic displays. A problem arises when a lenticular lens is mounted on the OLED display to form an autostereoscopic TV. Even for a top-emitting OLED, light will still be injected into a relatively thick layer of glass, causing the problems highlighted above, and a large amount of light will remain in the waveguide mode in the glass. In general, a convex mirror lens is used to improve light extraction from the glass to the air compared to a bottom emitting OLED, but for a 3D display, this has the side effect of reducing contrast and increasing crosstalk. This is a specific issue for one of the 3D displays. For 2D displays, in many cases, adjacent pixels will display the same color (ie, a white or colored area of a screen, a line of monochrome, etc.) so that if any light escapes from a neighboring pixel, this will only increase The color of expectations. However, in a 3D display, adjacent pixels typically do not have any relationship to each other because adjacent pixels belong to different views and will typically have different color content. So if any light This will seriously affect the quality of the image when it escapes from a neighboring pixel.

In addition, a large amount of light will remain in the waveguide mode in the glass. This part will be reabsorbed.

Figure 4 shows how the light path is affected when a convex mirror lens is applied to a top emission structure. The top emission structure includes a glass substrate 40, a mirrored anode 42, a light emitting layer defining a pixel 44, and a transparent cathode 46. A sealing and passivation layer 48 is interposed between the cathode 46 and the glass mirror array 49.

As illustrated in Figure 4, light is generated in the organic layer and some of the light enters the glass of the convex mirror configuration 49. Some of the light will remain in the waveguide mode by the internal reflection 50 and enter an optical path of a neighboring view (or pixel/subpixel). Here, the light can be reflected back and exited via a lens (as shown for light ray 52) and it can be reabsorbed in the pixel.

If the light does not leave the lens of the adjacent view, it will form a crosstalk.

The present invention provides a solution in which a layer is introduced between the convex mirror lens and an OLED having a low refractive index.

Figure 5 shows an example of the invention in which the layer comprises air. As shown, the air layer 50 is interposed between the top cathode 46 and the convex mirror lens array 49.

Light having a large angle of incidence is reflected back from the air interface into the layer of luminescent material. As a result, less light remains in the waveguide mode inside the glass of the convex mirror-like layer, thus reducing crosstalk between adjacent views.

Layer 50 can be any material having a low refractive index. In this context, a "low" index of refraction is lower than the material of the layer on the opposite side in order to define a critical angle and there is an increased refractive index of total internal reflection.

For example, passivation layer 48 can be a glass or a polycarbonate having a refractive index in the range of 1.3 to 1.6. A lower refractive index of the air of 1.0 means that the critical angle is in the range of 38 to 50 degrees so that all light steeper than the critical angle will be internally reflected at the air interface and thereby prevented from entering the convex mirror. An array of glass.

There will be no internal reflection at the interface between the air layer and the glass of the convex mirror array, due to the presence of an increase in refractive index.

The refractive index of passivation layer 48 can be lower than the refractive index of top layer 46 of the OLED stack.

The lower the critical angle, the greater the reduction in light that can be waveguided within the material of the lens. A lower critical angle is obtained by having a larger refractive index difference.

As the electroluminescent display stack is in direct contact with the glass of the convex mirror array (as in a conventional configuration), there is already a boundary at which total internal reflection occurs. In order to increase the angular extent for which internal reflection occurs and thereby reduce the waveguide, the additional material layer should have a refractive index lower than that of the material of the convex mirror array. The additional layer of material also needs to have a refractive index lower than one of the contact layers of the electroluminescent display stack to form a total internal reflection boundary.

Therefore, the additional material has a refractive index lower than a refractive index of the passivation layer (or the cathode without a passivation layer) to form a total internal reflection surface and a refractive index lower than a refractive index of the convex mirror lens. An improvement in the suppression of the waveguide compared to the case without any additional material layer is formed.

If the convex mirror array is a glass, it will typically have a refraction of 1.45. The rate, and the additional material layer should preferably have a refractive index of 1.35 or less.

More generally, the additional layer should have a refractive index lower than the refractive index of the convex mirror material (which may be a polymer rather than glass) of at least 0.1 and lower than the layer of the display panel in contact with the additional material layer ( The refractive index on the opposite side of the additional material layer from the convex mirror array is at least 0.1.

The refractive index may be better than the refractive index of 0.2, 0.3 or more of the layers on the opposite sides of the additional material layer.

The thickness of the additional material layer 50 is not critical, but the thinner the better. A thickness similar to one of the thicknesses of the OLED layers is suitable (hundreds of nanometers), but it may be preferable to increase the thickness beyond the wavelength of the light, for example, to increase to 1 μm to 50 μm. range.

A material having a low refractive index can be inserted during production of the convex thin layer on the OLED display. If the material consists of air, a spacer can be used to maintain a uniform distance between the convex thin layer and the OLED display. These spacers are shown schematically as 52 in FIG. The spacers may be located at each lens boundary as shown or they may be provided less frequently. The spacers may be absorptive and may also extend into the passivation layer 48 to block the optical waveguides within layer 48.

Instead of using air, another material having a low refractive index close to one of the refractive indices of 1.0, such as an aerogel, can be used. More generally, any material having a gradient of SiO2 and TiO2, a nanorod of SiO2, Teflon or the like having at least a lower refractive index than the surrounding layer can be used.

The solution of the present invention is somewhat unreasonable because much effort is often required to ensure a very tight lamination of the convex mirror-like layer to the display. for OLED display, the present invention relates to introducing an air gap or other material spacing that reduces light extraction from the OLED into the convex mirror lens to reduce crosstalk.

The above examples are for a top emission display. The invention can also be applied to a bottom emission display.

Figure 6 shows a bottom emission display. The substrate 40 is interposed between the lens arrangement 49 and the display stack. The display stack includes a transparent anode 42, a luminescent layer 44, and a mirrored cathode 46. In this case, the anode is transparent. A passivation layer 48 is located on top of the stack (relative to substrate 40) above cathode 46. The anode 42 is in direct contact with the additional light management layer 50 shown as a solid in this example.

The anode can be, for example, an ITO having a refractive index of about 1.7.

This additional layer provides the same function of increasing the amount of internal reflection compared to the amount of internal reflection that occurs when the electroluminescent display stack, in particular the anode, is in direct contact with the substrate 40.

Through the study of the schema, the disclosure and the scope of the accompanying patent application, Various variations of the disclosed embodiments can be implemented by those skilled in the art and in the practice of the present invention. In the scope of the patent application, the word "comprising" does not exclude other elements and steps, and the indefinite article "a" or "an" does not exclude the plural. The mere fact that certain measures are recited in the <RTIgt; Any reference signs in the patent application should not be construed as limiting the scope of the invention.

1‧‧‧Display device/direct view autostereoscopic display device

3‧‧‧Display panel/LCD panel

5‧‧‧ Display pixels

7‧‧‧Light source

9‧‧‧ convex mirror-like thin layer

11‧‧‧ convex mirror elements

13‧‧‧ Controller

20‧‧‧ Backlight

22'‧‧‧ Space location

22"‧‧‧ Space location

22'''‧‧‧ Space Location

23'‧‧‧ Space location

23"‧‧‧ Space location

23'''‧‧‧ Space location

24‧‧‧Display device / column configuration

28‧‧‧ convex mirror array

30‧‧‧ glass substrate

32‧‧‧Transparent anode

34‧‧‧Light emitting layer

36‧‧‧Mirror cathode

38‧‧‧ points

40‧‧‧Glass substrate/device substrate

42‧‧‧Mirror anode/transparent anode/anode layer

44‧‧‧pixel/lighting layer

46‧‧‧Top Cathode/Top Layer/Transparent Cathode/Cathode Layer/Mirror Cathode

48‧‧‧ Passivation layer/sealing and passivation layer

49‧‧‧ convex mirror configuration / autostereo lens configuration

50‧‧‧Internal reflection/air layer/layer/extra material layer/extra light control layer

52‧‧‧Light/spacer

1 is a schematic perspective view of a known autostereoscopic display device; FIG. 2 shows how a convex mirror array provides different views to different spatial positions; FIG. 3 schematically shows a single pixel of an OLED display. Structure, and in the form of a reverse emission structure; Figure 4 shows how the light path is affected when a convex mirror lens is applied to a top emission structure; Figure 5 shows an example of a first pixel structure in accordance with the present invention; 6 shows an example of a second pixel structure in accordance with one aspect of the present invention.

40‧‧‧Glass substrate/device substrate

42‧‧‧Mirror anode/transparent anode/anode layer

44‧‧‧pixel/lighting layer

46‧‧‧Top Cathode/Top Layer/Transparent Cathode/Cathode Layer/Mirror Cathode

48‧‧‧ Passivation layer/sealing and passivation layer

49‧‧‧ convex mirror configuration / autostereo lens configuration

50‧‧‧Internal reflection/air layer/layer/extra material layer/extra light control layer

52‧‧‧Light/spacer

Claims (15)

An autostereoscopic display device comprising: a display configuration comprising a stack; an autostereoscopic lens arrangement (49) comprising a plurality of lenses in the display configuration, wherein a plurality of pixels are provided under each lens; a light control layer (50) interposed between the display configuration and the autostereoscopic lens arrangement (49), wherein the light management layer has the lower layer on each side of the light control layer (50) One of the materials has a refractive index. The device of claim 1, wherein the display configuration is a transmit display configuration. The device of claim 2, wherein the emission display configuration is an electroluminescent display configuration. The device of claim 1, wherein the display configuration is a reflective display configuration. The device of any of claims 1 to 4, wherein the light management layer (50) is contacted by the lens arrangement (49) on one side and by the layer stack of the display configuration on the other side. The device of claim 3, wherein the layer stack comprises a passivation layer (48), a cathode layer (46), a light-emitting layer (44), and an anode layer (42), wherein the passivation layer (48) is adjacent to the light Control layer. The device of any one of claims 1 to 6, wherein the light management layer (50) has a refractive index that is less than a refractive index of the material of the lens configuration (49) of at least 0.1. The device of any one of claims 1 to 6, wherein the light control layer (50) has There is less than one of the refractive indices of the material of the lens configuration that is at least 0.2. The device of claim 1, wherein the light management layer (50) is stacked on one side by the layer of the display configuration and on the other side by a device substrate (40). A device as in any preceding claim, wherein the light management layer (50) has a refractive index that is less than at least 0.1 of an adjacent layer of the display configuration stack. The device of claim 11, wherein the light management layer (50) has a refractive index that is less than at least 0.2 of the adjacent layer of the display configuration stack. A device as claimed in any of the preceding claims, wherein the material of the lens arrangement (49) comprises glass. A device according to any of the preceding claims, wherein the light management layer (50) comprises air, wherein an array of spacers (52) is provided for defining an air gap. A device as claimed in any preceding claim, wherein the autostereoscopic lens arrangement comprises a plurality of convex mirror lenses extending in a row direction of a pixel or inclined at an acute angle to the row direction of the pixel, wherein each lens covers a plurality of rows of pixels. A method for displaying an autostereoscopic image, comprising: generating a pixelated image using a display configuration including a stack, and transmitting the light of the pixelated image to an autostereoscopic lens configuration through a light control layer (50), Wherein the light management layer (50) has a refractive index that is lower than a refractive index of a material on the opposite side of the light control layer.