EP4111499A1

EP4111499A1 - Multiple resolution display screen and method for producing same

Info

Publication number: EP4111499A1
Application number: EP21706962.4A
Authority: EP
Inventors: Olivier JEANNIN; Ivan-Christophe Robin
Original assignee: Aledia
Current assignee: Aledia
Priority date: 2020-02-26
Filing date: 2021-02-25
Publication date: 2023-01-04
Also published as: US20230097333A1; FR3107611B1; FR3107611A1; WO2021170708A1

Abstract

The invention relates to a display screen (10) intended to display a multiple resolution image and comprising a plurality of pixels (110, 120) distributed on a support (100), the screen (10) being characterised in that it comprises a first zone (11) of a surface (101) of the support (100) having a first density of pixels (110) allowing a first portion of the image to be displayed with a first resolution, and a second zone (12) of the surface (101) of the support (100) having a second density of pixels (120) strictly greater than the first density, allowing a second portion of the image to be displayed with a second resolution. The invention also relates to a display system comprising such a screen and a method for manufacturing this screen.

Description

Multiple resolution display screen and production method TECHNICAL FIELD

The invention relates to the field of display screens. It finds a particularly advantageous application in the field of virtual reality or augmented reality helmets. The invention can also be applied to virtual reality rooms. STATE OF THE ART

Resolution, expressed in pixel density, is a primary characteristic of display screens. It must be high enough so that the human eye is not able to perceive a pixelation phenomenon, under normal conditions of use of the screen. The resolving power of the eye is approximately one minute of arc, which corresponds to an angle α of the order of 0.017 °, as illustrated in figure 1. This resolving power is limited by the density of cones at the most sensitive part of the retina, the fovea. For an observer, the objects contained in the angular sector of angle a of FIG. 1 are not seen in a distinct manner. They are not resolved by the eye of the beholder. The angle a therefore corresponds to the limit of resolution of the eye.

A simple trigonometric relation makes it possible to determine what separation distance h between two objects is necessary for a human eye located at an observation distance d to perceive them distinctly.

Thus, in FIG. 1, two pixels a, b of the screen 1 separated by the distance h can be distinguished by the human eye located at the distance d from the screen 1, if h ³ 2d. tan |. On the contrary, if h <2d. the human eye will not see the two pixels a, b distinctly.

To avoid the phenomenon of pixelation, the separation distance h between two adjacent pixels must therefore be less than the distance 2d. "3. 10 ^_4 d.

This separation distance h between two adjacent pixels determines the screen resolution. This is generally expressed in pixels per inch or ppi (pixels per inch according to English terminology).

It appears that the screen resolution should be higher the closer the viewer is to the screen. Three screen resolution estimates are presented below, for three viewing distances corresponding to so-called distant, intermediate, and near viewing conditions. In conditions of distant observation, for d "3 meters for example, a screen resolution of 25 ppi is sufficient to avoid the phenomenon of pixelation. This corresponds to a separation distance between pixels of the order of 1 mm. Such a screen resolution is easily and inexpensively achievable. Such a screen is suitable, for example, for television and digital billboard applications.

In intermediate observation conditions, for d "40 centimeters for example, a resolution of 210 ppi becomes necessary to avoid the phenomenon of pixelation. The distance separating two pixels is here of the order of 120 pm. Such a screen resolution is achievable at a cost compatible with the manufacture of consumer applications, for example by using pixel control circuits based on TFT thin film transistor technologies (Thin Film Transistors according to the English terminology). Saxon). The applications targeted here by these display screens are, for example, computers and telephones.

In close observation conditions, for d "4 centimeters for example, a resolution greater than or equal to 2000 ppi becomes necessary to avoid the phenomenon. pixelation. The distance separating two pixels is here of the order of 12 μm. Such a screen resolution becomes difficult to achieve using TFT-based technologies. Such a screen resolution is achievable by using, for example, pixel driver circuits based on CMOS transistor technologies. However, the manufacturing cost is too high to target consumer applications, such as virtual reality or augmented reality headsets.

Another problem associated with these screens displaying a resolution greater than or equal to 2000 ppi relates to the quantity of digital data to be transmitted for display. Typically, for a virtual reality headset with two screens - for each user's eye, each screen has a characteristic dimension, for example a diagonal, of the order of 2 to 3 inches. The user thus benefits from a large field of vision, with an aperture of the order of 100 ° to 120 °. This improves the user's immersion in the virtual reality projected from the screens of the headset. Such a screen size associated with such a resolution involves a large amount of pixels, typically greater than 12 megapixels (MPix).

For a virtual reality headset, the number of images per second fps (frames per second according to the English terminology) must be high, for example 120 fps, to improve the fluidity and the feeling of comfort perceived by the user. For conventional coding in 10 bits per sub-pixel and 3 sub-pixels per pixel

(typically a red subpixel, a green and a blue), the quantity of data to be transmitted per second to such a screen is very large, typically greater than 40 Gbits / s.

Such a digital data rate requires significant resources, incompatible with general public use. In addition, the data transmission capabilities of the optic nerve are limited so that not all data displayed by such a screen is processed by the human eye.

In practice, the retina of the human eye is made up of different retinal areas, as shown in Figure 2. Only the most sensitive area of the retina, fovea 1, has the eye's maximum resolving power. human. The resolving power of fovea 1 can be 10 times greater than that of surrounding areas 2, 3 of retina 4.

The fovea 1 has an area of about 0.5 mm in diameter and a field of view of about 1.5 °, while the retina 4 itself has a total area of about 5.5 mm in diameter at the back of the eye, and a field of view of approximately 100 °. A known solution for limiting the quantity of data to be transmitted therefore consists in projecting an image with multiple resolution on the retina as a function of the different retinal areas. The fovea will thus see an image part at high resolution (> 2000 ppi), while the surrounding retinal areas will see complementary image parts at lower resolution.

One solution is to degrade the image resolution of a high-definition screen out of the fovea's field of view, via an eye movement tracking system. This reduces the amount of data displayed. However, the manufacture of such a high-resolution screen remains expensive and complex. In addition, the user's field of view is reduced when looking at the edge of the screen.

Document US 2018/284451 A1 discloses, for example, a degraded display at the periphery of the image, so as to reduce the resolution around the foveal zone. This image processing is done a posteriori, for example in software. However, the amount of data remains unchanged. Additional processing is applied to the display, which requires an additional layer of hardware or software.

Another solution disclosed by document EP3330772 A1 consists in forming for each eye of the user a composite image from a contextual image and a high-resolution thumbnail superimposed on the contextual image. The pop-up image is projected by a low-resolution first source screen and the thumbnail is projected by a second high-resolution source screen.

The high-resolution screen here is reduced in size. This solution is nevertheless complex. It indeed requires great precision in the superposition of the projected images. Its cost also remains high. It requires several source screens from which the composite image is formed. The user's field of view is further reduced when looking at the edge of the pop-up image.

Document US 2017/236466 A1 discloses a solution for reducing the amount of data of the image formed on the display screen. According to this solution, a single piece of data is assigned to a group of several pixels of a low-resolution area displayed on the screen. This solution requires an additional hardware layer, typically a dedicated controller, to perform this logical processing of the data assigned to the pixels.

The present invention aims to at least partially overcome some of the drawbacks mentioned above. In particular, an object of the present invention is to provide a display screen with multiple resolution limiting the complexity and / or the cost of manufacture.

Another object of the present invention is to provide a method of manufacturing such a display screen. Another object of the present invention is to provide a display system making it possible to improve the observer's field of view.

The other objects, features and advantages of the present invention will become apparent on examination of the following description and the accompanying drawings. It is understood that other advantages can be incorporated. ABSTRACT

To achieve the objectives mentioned above, the present invention provides according to a first aspect a display screen intended to display an image of multiple resolution and comprising a plurality of pixels distributed on a support.

Advantageously, the screen comprises a first zone of one face of the support having a first density of pixels making it possible to display a first part of the image with a first resolution, and a second zone of the face of the support having a second density. of pixels strictly greater than said first density, making it possible to display a second part of the image with a second resolution. Thus, this screen makes it possible to display an image comprising at least a first image portion exhibiting the first so-called "low" resolution and at least a second image portion exhibiting the second so-called "high" resolution. Advantageously, the pixel density necessary to form the high resolution image portion is found on the second area only. The total pixel density of the screen is thus reduced compared to that of a known high definition screen. The solution proposed by the present invention brings together on one and the same screen at least two display zones of different resolutions, unlike the solution disclosed by document EP3330772 A1 using two source screens cooperating to display a composite image by superimposing the images. sources. The complexity and cost of such a screen are therefore reduced compared to existing solutions.

The solution adopted in the context of the present invention is based on a material construction of differentiated pixel areas within the same screen. Thus, the screen natively comprises pixels distributed according to different densities. Unlike the solutions of the prior art, this differentiation between the first and second pixel densities is not obtained by a posteriori processing making it possible to locally and artificially reduce the pixel density of a screen comprising a homogeneous pixel density. Thus, groupings of pixel data as disclosed in document US 2017/236466 A1, or software or optical processing making it possible to deform the displayed image with low-resolution areas and high-resolution areas as disclosed in document US 2018/284451 A1, are based on totally different principles and contrary to that of the present invention. This screen can advantageously be implemented in a virtual reality headset with an eye movement tracking system, so that the fovea perceives the high-resolution image part, and the less areas. sensitive retina perceive the surrounding image portion at low resolution.

This screen can also be implemented in a virtual reality room. Such a room is configured so as to allow a direct view without glasses of the image displayed by the screen (s). An eye movement tracking system, suitable for such a virtual reality room environment, can also be used in cooperation with the screen (s) according to the first aspect of the invention.

The sizes and / or the resolutions of the first and second areas of the screen are preferably suited to the intended application. For example, in the context of an application of such a screen to a virtual reality headset, the total surface area of the screen may be less than 25 cm ² . The second zone may in this case have an area less than or equal to 1 mm ² and a resolution greater than 2000 ppi. In the context of an application of such a screen to a virtual reality room, the total surface area of the screen may be greater than 1500 cm ² . The second zone may in this case have an area of a few cm ² to a few tens of cm ² and a resolution greater than 250 ppi.

The invention provides according to a second aspect a display system comprising a display screen according to the first aspect, a projection optical system configured to project the image displayed by the screen to an eye of an observer, and a system for tracking the movements of the observer's eye configured to control the projection of the image to said movements, so as to project the second part of the image displayed by the second zone onto the fovea of the eye of the observer observer.

This display system advantageously makes it possible to project an image of multiple resolution in which the high resolution and low resolution parts are fixed relatively to each other. This display system can advantageously be implemented in a virtual reality headset.

In existing solutions, the high-resolution part of the image moves relatively to the fixed contextual low-resolution part. In an extreme angular observation position, at the limit of movement of the observer's eyes, the high-resolution part is then at the edge of the low-resolution part. Although the fovea still perceives the high-resolution image portion, part of the retina no longer perceives the surrounding contextual image. The observer's field of view is therefore reduced when he looks at these extreme angular positions, at the limit of movement of the eyes.

On the contrary, according to the invention, the projection of the whole image moves, so that the observer always perceives, in the same proportions, the same low-resolution and high-resolution parts of the multiple-resolution image, whatever or the angular position of the eyes. The fovea and the retina always perceive the same image size. This is to avoid truncating the viewer's field of view. For virtual or augmented reality applications, this improves the viewer's immersion.

The invention also provides, according to a third aspect, a method of manufacturing a display screen intended to display an image of multiple resolution and comprising a first zone having a first density of pixels making it possible to display a first part of the image. with a first resolution, and a second area having a second pixel density strictly greater than said first density, making it possible to display a second part of the image with a second resolution. This method comprises in particular the following steps: - Providing a support capable of receiving a plurality of pixels,

Provide at least one donor substrate comprising pixels at a base density between the first pixel density and the second pixel density,

Carry out with a first buffer a first transfer onto the support, for example by mass transfer technology, of a first set of pixels having the first density from the at least one donor substrate, so as to form the pixels of the first zone,

Carry out with a second pad of dimensions smaller than those of the first pad at least one second transfer onto the support, for example by mass transfer technology, of at least a second set of pixels from the at least one donor substrate, so as to form the pixels of the second area of the screen having the second pixel density.

This process makes it possible to form on the same support two zones having different densities of pixels. The first buffer is configured to form at least the pixels of the first zone, by transferring pixels from the donor substrate. According to one possibility, this first transfer also makes it possible to transfer pixels intended to form part of the second zone. The first transfer of pixels is thus optimized.

The second transfer of pixels is intended to form the pixels of the second zone. It can be performed on a portion of the medium devoid of pixels, via a second buffer configured to transfer a set of pixels directly exhibiting the second pixel density. Alternatively, it can be carried out on a part of the support already comprising pixels transferred during the first transfer, via a second buffer configured to transfer a set of pixels having a complementary pixel density. The pixels of this set of pixels are therefore transferred between the pixels already present, so as to increase the pixel density to reach the second pixel density and thus form the second area of the screen. This second transfer can be repeated several times until the second pixel density is reached. The second buffer may be configured to transfer one or more sets of pixels having the first pixel density. It can be structurally identical to the first buffer, with a transfer zone of reduced dimensions compared to that of the first buffer. Such a process comprising at least two successive transfers from at least one donor substrate makes it possible to manufacture a multiple-resolution screen while limiting the number of steps and the complexity of the process. The mass transfer technology also makes it possible to reduce the production costs of such a screen.

BRIEF DESCRIPTION OF THE FIGURES

The aims, objects, as well as the characteristics and advantages of the invention will become more apparent from the detailed description of embodiments of the latter which are illustrated by the following accompanying drawings in which:

Figure 1 illustrates schematically the resolving power of the human eye.

Figure 2 schematically illustrates different areas of the retina of the human eye.

FIG. 3A schematically illustrates a distribution of the pixels of a display screen according to an embodiment of the present invention. FIG. 3B schematically illustrates a distribution of the pixels of a display screen according to another embodiment of the present invention.

Figure 4A schematically illustrates in section the pixels of a display screen according to one embodiment of the present invention. Figure 4B schematically illustrates in section the pixels of a display screen according to another embodiment of the present invention.

Figure 5 schematically illustrates a display system according to one embodiment of the present invention.

Figures 6A and 6B schematically illustrate a display system according to another embodiment of the present invention.

The drawings are given by way of example and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate understanding of the invention and are not necessarily on the scale of practical applications. In particular, the dimensions of the pixels and of the various parts of the screen and of the display system are not representative of reality. The path of light rays through the display system is also not necessarily representative of reality.

DETAILED DESCRIPTION

Before starting a detailed review of embodiments of the invention, it is recalled that the invention according to its first aspect includes in particular the optional characteristics below which can be used in combination or alternatively.

According to one example, the second pixel density is at least five times, preferably ten times greater than the first pixel density. According to one example, the first pixel density is between 200 pixels per inch (ppi according to English terminology) and 3000 ppi. This dimensioning is particularly suitable for small screens that can be integrated into virtual reality headsets. According to another example, the first pixel density is between 50 ppi and 250 ppi. This dimensioning is particularly suitable for large screens that can be integrated into virtual reality rooms.

According to one example, the second pixel density is between 3000 ppi and 15000 ppi. This dimensioning is particularly suitable for small screens that can be integrated into virtual reality headsets. According to another example, the second pixel density is between 250 ppi and 2000 ppi. This dimensioning is particularly suitable for large screens that can be integrated into virtual reality rooms. According to one example, the second zone has an area less than 4 mm ² , preferably less than or equal to 1 mm ² . This dimensioning is particularly suitable for small screens that can be integrated into virtual reality headsets. According to another example, the second zone has a lower surface area of 100 mm ² , preferably less than or equal to 10 mm ² . This dimensioning is particularly suitable for large screens that can be integrated into virtual reality rooms. This makes it possible to reduce the costs of the screen and to limit the total quantity of digital data to be transmitted for the display, without degrading the perception by the fovea of the high-resolution image part. According to one example, the second zone is surrounded by the first zone.

According to one example, the second zone is located at the center of the first zone.

According to one example, at least the pixels of the second zone are smart pixels each comprising dedicated control electronics, said smart pixels each having a width less than or equal to 50 μm, preferably less than or equal to 25 μm. The control electronics of such a smart pixel are typically integrated directly under the LEDs or pLEDs forming the subpixels of this smart pixel. The second area is preferably only made from such smart pixels. In this case, the second zone does not use control electronics based on TFT-type technologies. This allows the second pixel density to be increased to achieve high resolutions, typically greater than 2000 ppi.

According to one example, the display screen comprises at least one other area at least partially separating the first and second areas, said at least one other area having a pixel density between the first pixel density and the second pixel density. , said at least one other zone making it possible to display at least one other part of the image with at least one other intermediate resolution comprised between the first and second resolutions. This makes it possible to generate a gradual transition between the first and second zones. This optionally makes it possible to follow the sensitivity profile of the retina presented in FIG. 2. According to one example, the first and second pixel densities and the pixel density of the at least one other zone are chosen so as to display an image. multiple resolution having a variation in resolution between the first and second parts of the image and the at least one other part of the image, which is similar to a sensitivity profile of a retina of a human eye. This improves the user's perception. According to one example, the first and second pixel densities and the pixel density of the at least one other area are chosen so as to display a multi-resolution image having a linear variation in resolution between the first and second parts of the image. image and at least one other part of the image. This simplifies the design of the display screen.

According to one example, the display screen has, in a main extension plane, a characteristic dimension, for example a diagonal, between 2 inches and 10 inches. This dimensioning is particularly suitable for small screens that can be integrated into virtual reality headsets. According to another example, the display screen has, in a main extension plane, a characteristic dimension, for example a diagonal, between 20 inches and 70 inches. This dimensioning is particularly suitable for large screens that can be integrated into virtual reality rooms.

The invention according to its second aspect comprises in particular the optional characteristics below which can be used in combination or alternatively:

According to one example, the display system further comprises a body, and the system for tracking the movements of the observer's eye is configured to modify the positions of the screen and / or the projection optical system relative to the image. body.

According to one example, the projection optical system comprises a curved mirror facing the screen configured to reflect the image displayed by the screen, and a focusing lens facing the observer configured to focus on the retina of the screen. 'eye said reflected image.

According to one example, the screen is fixed relative to the body and the projection optical system is at least partly mobile relative to the body, the position of the projection optical system being modified by a displacement of the focusing lens and / or of the mirror. curved relative to the body of the display system.

According to one example, the projection optical system comprises a lens system facing the screen configured to transmit the image displayed by the screen, and a curved mirror facing the observer configured to reflect said transmitted image in the direction of eye of the beholder.

According to one example, the projection optical system is fixed relative to the body and the screen is at least partly mobile relative to the body, the position of the screen being modified by a displacement of the screen in a main extension plane. of the screen, relative to the body of the display system. According to one example, the projection optical system is configured to project the image displayed by the screen with a magnification greater than or equal to 1.

The invention according to its second aspect comprises in particular the optional characteristics below which can be used in combination or alternatively: According to one example, the at least one donor substrate comprises a first donor substrate comprising pixels having the first pixel density and a second donor substrate comprising pixels having the second pixel density.

According to one example, the first transfer is performed from the first donor substrate and at least a second transfer is performed once from the second donor substrate.

According to one example, the at least one donor substrate is a single donor substrate comprising pixels having only the first pixel density.

According to one example, the first transfer is configured to form the pixels of the first zone and part of the pixels of the second zone, and the second transfer is repeated several times to complete the pixels of the second zone, so as to reach the second pixel density in the second area.

According to one example, the pixels are intelligent pixels each comprising dedicated control electronics, said intelligent pixels each having a width less than or equal to 50 μm, preferably less than or equal to 25 μm.

Unless there is any incompatibility, it is understood that the various aspects of the invention, the display screen, the display system and the manufacturing process, may include, mutatis mutandis, all or part of the characteristics set out above.

The invention can therefore also be implemented in the context of virtual reality or augmented reality devices.

In the present invention, the display screen is one and the same continuous screen comprising at least two different pixel densities on one and the same continuous face configured to display at a given time a single and same image of multiple resolution. By multiple resolution image is meant an image simultaneously presenting at least a first image part according to a first resolution and at least a second image part according to a second resolution different from the first resolution.

A pixel of an image corresponds to the unitary element of the image displayed by a display screen. For the formation of a color image, each color pixel generally comprises at least three components of emission and / or conversion of a luminous flux, also called sub-pixels.

In the following, these subpixels each emit a light flux substantially in one color (for example, red, green and blue). The color of a pixel perceived by an observer comes from the superposition of the different luminous fluxes emitted by the sub-pixels.

A pixel, although it can consist of several subpixels, forms a well-defined entity. The solution adopted in the context of the present invention provides for two different densities of this same entity. It is understood that the density of pixels cannot be compared or equated with the density of sub-pixels. A person skilled in the art knows perfectly well how to distinguish a density of pixels, for example expressed in ppi, from a density of sub-pixels or of elements composing said pixels.

Typically, an LED or pLED emits the luminous flux associated with a sub-pixel. In the present application, by LED size is meant its main extension dimension in the plane of the support. The size of a sub-pixel is therefore directly correlated with the size of LEDs.

In the present patent application, the terms “light-emitting diode”, “LED” or simply “diode” are used synonymously. An "LED" can also be understood as a "micro-LED".

Pixel density is an area density expressed in ppi (pixels per inch), according to the most common notation and unless otherwise specified. In the present patent application, the terms “concentration” and “density” are synonymous.

The term “matrix” is understood to mean a table in the form of rows and columns. For example, a matrix may include a plurality of rows and a plurality of columns, or a single row and a plurality of columns, or a plurality of rows and a single column.

Unless explicitly stated, it is specified that, in the context of the present invention, the relative arrangement of an element interposed between two other elements does not necessarily mean that the elements are directly in contact with each other.

The manufacturing steps of the different elements are understood in a broad sense: they can be carried out in several sub-steps which are not necessarily strictly successive.

The terms “substantially”, “approximately”, “of the order of” “similar” mean, when they relate to a value, “within 10%” of this value or, when they relate to an angular orientation, “within 10 °” of this orientation. Thus, a direction substantially normal to a plane means a direction having an angle of 90 ± 10 ° with respect to the plane.

Construction analysis or reverse engineering methods can be used to determine whether a screen includes the characteristics described in this application. These techniques make it possible in particular to determine whether the display screen comprises an area with a high density of pixels, as described in the present invention. An analysis of the distribution of the pixels on the screen support can be carried out, for example, from optical microscopy measurements on the deconstructed screen. These techniques also make it possible to determine what type of control electronics are associated with the pixels, in particular if the control electronics are based on transistors integrated directly under the LEDs / pLEDs forming the subpixels of an intelligent pixel.

In the following, the invention is mainly described through examples relating to an application aimed at virtual reality headsets. It is understood that these examples can be easily adapted for other applications, in particular for an application aimed at virtual reality rooms. Those skilled in the art will thus be able to adapt, mutatis mutandis, the sizing indicated below to the various applications targeted, and in particular to the case of virtual reality rooms. A first embodiment of a display screen according to the invention will now be described with reference to Figure 3A.

The display screen 10 typically comprises a continuous support 100 having a face 101 capable of receiving pixels 110, 120. This face 101 can be flat or curved. It can be opaque, semi-transparent or transparent. It can be rectangular in shape as shown in Figure 3A, or square, or oval or of any shape. The size of this display screen 10, that is to say at least one dimension characteristic of this screen taken in projection in the plane of the sheet, is preferably between 2 inches and 10 inches, and preferably between 2 inches and 5 inches. For certain applications, for example in the field of augmented reality, the size of this display screen 10 may be less than 2 inches, or even 1 inch, or even ½ inch. In the example illustrated in Figure 3A, this characteristic dimension may be the diagonal of screen 10.

The face 101 comprises at least two zones 11, 12 over which the pixels 110, 120 are respectively distributed. The first zone 11 has a first density of pixels 110, for example between 200 ppi and 2000 ppi, and the second zone 12 has a second pixel density 120 different from the first pixel density 110, for example greater than or equal to 2000 ppi. The face 101 is preferably completely covered by these at least two zones 11, 12.

The first zone 11 is intended to display a low resolution contextual image and the second zone 12 is intended to display a high resolution image. The first zone 11 is therefore located around the second zone 12. The first zone 11 surrounds the second zone 12 over the major part of the perimeter of the second zone 12, and preferably over the entire perimeter of the second zone 12.

The first zone 11 preferably extends from a closed contour 121 of the second zone 12 to the edges 102 of the face 101. Its surface preferably covers at least half of the surface of the screen. Its shape preferably matches the shape of the face 101, and the closed contour 121 of the second zone 12.

The pixels 110 of the first zone 11 can be distributed in the form of a first matrix of pixels having a pitch p1 in a first x direction and a pitch p2 in a second y direction. The pitches p1 and p2 can be between 120 μm and 12 μm, so as to obtain a first density of pixels 110 on this first zone 11 between 200 ppi and 2000 ppi. According to one possibility, the pitch p1 is equal to the pitch p2.

The second zone 12 can be substantially square, as illustrated in FIG. 3A, or round or oval or of any shape. It has a closed contour 121 surrounded at least in part by the first zone 11. It is preferably separated from the edges 102 of the face 101, and preferably centered with respect to the face 101, as illustrated in FIG. 3A. . Its surface preferably covers less than half of the surface of the screen. It has, for example, a surface area of less than 4 mm ² , preferably less than or equal to 1 mm ² .

The ratio between the areas of the first and second zones 11, 12 may be greater than 5, and preferably greater than 10.

The pixels 120 of the second zone 12 can be distributed in the form of a second matrix of pixels having a pitch p1 "in the x direction and a pitch p2" in the y direction. The pitches p1 ’and p2’ are preferably less than 12 μm, so as to obtain a second pixel density 120 on this second area 12 greater than 2000 ppi. According to one possibility, the step p1 ’is equal to the step p2’.

Other embodiments of the screen 10 according to the invention can be envisaged. Only the distinct characteristics of the first embodiment are described below, the other characteristics not described being deemed to be identical to those of the first embodiment.

Referring to Figure 3B, a second embodiment of a display screen according to the invention comprises a third area 13 interposed between the first and second areas 11, 12, in the xy plane. This third zone 13 has a third density of pixels 130, for example between 1000 ppi and 2000 ppi. The third pixel density 130 is between the first pixel density 110 and the second pixel density 120.

The third zone 13 is intended to display an image part of intermediate resolution between the low-resolution image part of the first zone 11 and the high-resolution image part of the second zone 12. The third zone 13 is therefore located. around the second zone 12. The first zone 11 is therefore situated around the third zone 13.

The third zone 13 preferably extends from a closed contour 121 of the second zone 12. The first zone 11 preferably extends from a closed contour 131 of the third zone 13.

The first, second and third pixel densities 110, 120, 130 and / or the relative occupancy areas of the first, second and third areas 11, 12, 13 on the face 101 of the screen 10 can be adjusted so as to that the eye does not perceive a halo effect and / or abrupt resolution transition in the displayed image.

For example the first, second and third pixel densities 110, 120, 130 can be chosen so as to reflect the visual acuity profile of the retina, as illustrated in FIG. 2. This makes it possible to improve the perception of the image by the human eye. The relative occupancy surfaces of the first, second and third zones 11, 12, 13 may also reflect the surfaces of the different retinal zones at the back of the eye. The surface of the first zone 11 can be greater than the sum of the surfaces of the second and third zones 12, 13.

According to another example, the first, second and third densities of pixels 110, 120, 130 can be chosen so as to obtain a density profile, along an axis of the xy plane, which is substantially linear. This limits the complexity of the screen.

The pixels 130 of the third zone 13 can be distributed in the form of a third matrix of pixels having a pitch p1 ”according to the first direction x and / a pitch p2” (not illustrated) according to the second direction y. These steps p1 ”and p2” can be between 120 pm and 12 pm, with for example p1 <p1 ”<p1 'and / or p2 <p2” <p2'. These first and second embodiments do not limit the invention. Other areas having other pixel densities may be formed on the screen, for example so as to ensure a gradual transition from the second high resolution area to the first low resolution area. In general, different density profiles and different distribution of the zones can be envisaged, for example so as to obtain a good compromise between the complexity and the cost of manufacturing the screen, and the final perception by the user of the quality. image displayed by this screen.

The pixels 110, 120, 130 can be formed by different technologies. They are preferably controlled independently by control electronics. These control electronics are controlled by at least one processor, preferably one and the same processor. Certain elements of the power supply and / or control and / or pilot circuits, such as electrical connection lines, can be common to the pixels 110, 120. With reference to FIG. 4A, the pixels 110, 120 can each be formed from three distinct R, G, B subpixels separated by a subpixel separation distance d ₁₁₀ , d ₁₂₀ .

These R, G, B sub-pixels are typically LEDs or pLEDs emitting respectively at wavelengths comprised in red, green and blue. These pLEDs can each be associated with control electronics based on TFT thin-film transistors (for Thin-Film Transistor). FIG. 4A illustrates such a screen architecture comprising a support 100, for example made of glass, a control layer 200 comprising the control electronics based on TFT, and the pLEDs R, G, B forming the pixels 110, 120 on the upper face 201 of the control layer 200.

The pixels 120 preferably have _{minimum subpixel separation distances d 12} o, typically on the order of one micrometer, so as to achieve a _{minimum pixel size x 120} , typically on the order of 12 µm. Such pixels 120 make it possible to obtain a pixel density of the order of 2000 ppi. The pixels 110 may be identical to pixel 120. Alternatively, as the density of pixels 110 required in the first zone 11 is less than the pixel density required 120 in the second area 12, the pixels 110 may have a size greater than ₁₁₀ x the size x ₁₂₀ of the pixels 120, as illustrated in FIG. 4A. For example, the subpixel separation distances d ₁₁₀ may be of the order of ten micrometers, so as to obtain a pixel size × ₁₁₀ of the order of 60 μm.

Referring to Figure 4B, another technology for manufacturing pixels 110 ", 120" called smart pixels, can be implemented. Document US 2018/0247922 describes such smart pixel technology. In particular, this makes it possible to reduce the manufacturing costs of the screen. It also helps to reduce pixel size and increase pixel density.

According to this technology, smart pixels are manufactured regardless of their final integration into the screen. The control electronics 202 of these intelligent pixels 110 ′, 120 ′ are first manufactured on a first annex substrate, by conventional microelectronic technologies (transistors resulting from a so-called bulk substrate) which are less expensive than TFT technologies. . The R, G, B sub-pixels are also manufactured independently on a second annex substrate. The R, G, B sub-pixels are then associated with the control electronics 202. The intelligent pixels 110 ’, 120’ thus formed are then transferred to the substrate 100, to form the first and second zones 11, 12.

Control electronics 202 based on intelligent pixel bulk transistors 110 ", 120" are significantly less expensive than control electronics based on TFT transistors. Control electronics 202 based on bulk transistors of intelligent pixels 110 ’, 120’ are also less bulky than control electronics based on TFT transistors.

The preliminary and independent formation of the sub-pixels R, G, B from the second annex substrate therefore makes it possible to considerably reduce the sizes of these sub-pixels (case of intelligent pixels), compared with a direct formation of the sub-pixels R , G, B on a control layer 200 as illustrated in FIG. 4A (case of pixels controlled by TFT). The sizes x ' ₁₁₀ , x' ₁₂₀ of the intelligent pixels 110 ', 120' thus formed are therefore considerably reduced (FIG. 4B).

These intelligent pixels 110 ′, 120 ′ each comprising a previously integrated control electronics 202 typically have pixel sizes _x′ -i Ί o, x ′ ₁₂₀ less than or equal to 25 μm, for example of the order of 5.5 μm.

Such intelligent pixels 110 ", 120" make it possible to obtain, after transfer to the substrate 100, a pixel density greater than or equal to 4000 ppi.

Such a screen resolution greater than or equal to 4000 ppi can advantageously be implemented in the second zone 12 configured to display the high-resolution (HR) image part intended to be projected onto the fovea of the eye of the eye. the observer. The cones of the fovea, ie the sensitive cells, can in fact have an elementary angle of view twice as small as that of the other cells of the retina. Consequently, an HR image with a resolution greater than or equal to 4000 ppi projected onto the fovea makes it possible to avoid or limit the phenomenon of pixelation perceived by the observer.

The pixel density depends not only on the size of each of the pixels, but also on the pitch p ^ p ^ and / or p ₂ , p ' ₂ between each of these pixels (FIG. 4B).

The pixel transfer methods advantageously make it possible to adjust the pitch R _ϊ and / or p ₂ , and the pitch p ^ and / or p ' ₂ relating to the first and second zones 11, 12 respectively.

The present invention also relates to a method of manufacturing a display screen as described through the preceding exemplary embodiments. The formation of the first and second areas 11, 12 of the screen is described below.

This method uses in particular at least a first buffer configured to take pixels, preferably intelligent pixels comprising integrated control electronics, formed on a donor substrate. The pixels taken are then transferred to the substrate 100. This substrate 100 can be functionalized and / or transparent and / or flexible in particular. These sampling and transfer steps can be carried out by so-called mass transfer technologies. This helps to reduce costs.

The pixels picked up by the first buffer have a primary density which can be either equal to the pixel density of the donor substrate, or less than the pixel density of the donor substrate. In the latter case, this primary density is fixed by the configuration of the first buffer. The pixels transferred onto the substrate 100 after a first transfer have a density equal to the primary density. The primary density is preferably equal to the first density of pixels of the first zone 11. The first zone 11 is thus formed by a single first transfer. This makes it possible to minimize the number of steps and the duration of the manufacturing process. This also makes it possible to simplify the formation of the first zone 11. Alternatively, if the primary density is lower than the first targeted pixel density, one or more additional transfers can be carried out via the first buffer, so as to increase the pixel density. carried forward until reaching the first pixel density. The pixels transferred at the end of each additional transfer are distributed among the pixels resulting from the previous transfer (s). The first zone 11 can thus be formed in several stages. This makes it possible to use a or donor substrates having a pixel density lower than the first target pixel density.

This principle of multiple transfers from a single donor substrate can be advantageously implemented to form the second zone 12. The first transfer can be used to transfer pixels intended to form part of the second zone. The first transfer of pixels is thus optimized. The second zone 12 is then partly formed at the end of this first postponement.

At least a second transfer of pixels is preferably carried out to complete the formation of the second zone 12. This second transfer can be carried out with the first buffer, by reducing the sampling zone of the first buffer. Alternatively, the second transfer can be performed with a second specific buffer. This second pad may have a sampling surface smaller than that of the first pad. It can also be configured to pick up denser sets of pixels compared to the first buffer. According to one possibility, the first and / or second transfers are made from different donor substrates. These different donor substrates can in particular have different densities of pixels, respectively. The second area 12 can be formed directly in a single step from a donor substrate having the second pixel density. In general, the first and second zones 11, 12 can be formed by combining one or more transfers carried out by one or more buffers from one or more donor substrates. In addition, one or more intermediate areas between the first and second areas 11, 12, having pixel densities between the first and second pixel densities 110, 120, can also be formed according to this method.

The manufacturing steps of the process can therefore be adapted mutatis mutandis to these different possible combinations.

The present invention also relates to a display system comprising a display screen as described through the preceding exemplary embodiments. As illustrated in Figures 5, 6A and 6B, this system typically comprises a body 30, for example in the form of a helmet, in which there is at least one display screen 10, a projection optical system and a movement tracking system. of the observer's eye O.

The projection optical system is configured to project the image displayed by the screen 10 towards the eye O. It can comprise a mirror 41, for example curved, configured. to reflect the image displayed by the screen 10 towards the eye O. It can also include at least one lens 40, 43 configured to optically conjugate the screen 10 and the eye O.

This optical projection system can project the image displayed by the screen 10 with a magnification greater than or equal to 1. The curved mirror 41 makes it possible for example to increase the apparent magnification of the image displayed by the screen 10. L The immersion of the observer in the helmet is thus improved.

The system for tracking the movements of the observer's eye is configured to control the projection of the image displayed by the screen 10 to said movements of the eye O. It is in particular configured to project the image part. HR displayed by the second zone 12 of the screen 10 on the fovea of the eye O of the observer.

This eye tracking system may typically include a camera 50 and a servo system 51, 52. The camera 50 is directed towards the eye and intended to record the movements of the eye O. The servo system is intended to control the movement of the movable elements of the display system, i. e. the screen 10 and / or the mirror 41 and / or the lenses 40, 43 for example, so as to adapt the projection of the image in real time as a function of the angular position of the eye O. The system of servo-control 51, 52 can be of the servomotor type and comprises for example a displacement motor 52 and an electronic control module 51 communicating with the camera 50 and the motor 52. The motor 52 is connected to the movable elements so as to modify their respective positions .

This tracking system can therefore modify the positions of the screen 10 and / or of the projection optical system 40, 41 relative to the body 30, as a function of the positions of the eye O measured by the camera 50. In the example illustrated in FIG. 5, the screen 10 is fixed relative to the body 30 and the projection optical system 40, 41 is at least partly movable relative to the body 30.

In this example, the projection optical system typically comprises a mirror 41 facing the screen 10 and a focusing lens 40 facing the eye O. The mirror 41 is preferably curved and makes it possible to reflect an enlarged image of the screen 10 towards the focusing lens 40. The focusing lens 40 then makes it possible to focus this enlarged image in the eye O of the observer.

The servo system 51, 52 is here configured to move the focusing lens 40 and / or the mirror 41 relative to the body 30 of the display system. the displacement of the mirror 41 can be done by translation along a curved path and / or in a direction normal to the focusing lens 40.

In the example illustrated in Figures 6A, 6B, the screen 10 is at least partly movable relative to the body 30 and the projection optical system 41, 43 is fixed relative to the body 30.

In this example, the projection optical system 43 typically comprises one or more lenses facing the screen 10, an optical guide 44, 45 and a mirror 41 facing the eye O. The projection optical system 43 allows in particular to project the image displayed by the screen 10 along rays parallel to each other (image focused to infinity). These rays then propagate within the optical guide 44, 45 to the mirror 41 located at one terminal end of the optical guide. Optionally, diffractive components can be used to extract the rays at the terminal end of the optical guide. The proximal end of the optical guide can comprise a prism or a filter, for example anti-reflective, through which enter the light rays coming from the projection optical system 43. The rays can then be guided within the optical guide, for example by reflection on the walls of the optical guide. This optical guide may be of the optical fiber type. The mirror 41 is preferably curved and makes it possible to reflect the light rays towards the eye O of the observer.

The servo system (not shown) is here configured to move the screen 10 relative to the body 30 of the display system. For a flat screen 10, this displacement can be done by translation in the plane of the screen 10. For a curved screen 10 (formed for example from a flexible substrate as mentioned above), this displacement can be done. along a curved path. The servo system can also allow a depth adjustment of the screen 10, via a displacement in a direction normal to the screen 10. FIG. 6A shows a first position of the eye O to which corresponds a first position of. screen 10 configured to project the HR image portion at the fovea of eye O. Figure 6B shows a second position of eye O and a corresponding displacement of screen 10 to a second position of so that the HR image part is always projected at the level of the fovea of the O eye.

The invention is not limited to the embodiments described above and extends to all the embodiments covered by the claims.

For example, the display system may include two display screens each for an eye of the observer. This makes it possible in particular to project a stereoscopic image.

Claims

1. Display screen (10) intended to display an image of multiple resolution and comprising a plurality of pixels (110, 120) distributed on a support (100), said screen (10) being characterized in that it comprises a first zone (11) of a face (101) of the support (100) having a first density of pixels (110) making it possible to display a first part of the image with a first resolution, and a second zone (12) of the face (101) of the support (100) having a second density of pixels (120) strictly greater than said first density, making it possible to display a second part of the image with a second resolution.

2. Screen (10) according to the preceding claim wherein the second pixel density is at least five times greater, preferably ten times greater than the first pixel density.

3. Screen (10) according to any one of the preceding claims wherein the first pixel density is between 50 pixels per inch (ppi according to English terminology) and 3000 ppi, and the second pixel density is between 250 ppi and 15,000 ppi.

4. Screen (10) according to any one of the preceding claims, in which the second zone (12) has a surface area of less than 4 mm ² , preferably less than or equal to 1 mm ² .

5. Screen (10) according to any one of the preceding claims wherein the second zone (12) is surrounded by the first zone (11).

6. Screen (10) according to any one of the preceding claims wherein the second zone (12) is located at the center of the first zone (11).

7. Screen (10) according to any one of the preceding claims wherein at least the pixels of the second zone are smart pixels (120 ') each comprising dedicated control electronics (202), said smart pixels (120'). each having a width less than or equal to 50 μm, preferably less than or equal to 25 μm.

8. Screen (10) according to any one of the preceding claims comprising at least one other area (13) at least partially separating the first and second areas (11, 12) and having a pixel density (130) between the first. pixel density (110) and the second pixel density (120), said at least one further area (13) for displaying at least one further part of the image with at least one other intermediate resolution between the first and second resolutions.

9. Screen (10) according to the preceding claim wherein the first and second pixel densities (110, 120) and the pixel density (130) of the at least one other area (13) are chosen so as to display a A multi-resolution image exhibiting a linear variation in resolution between the first and second parts of the image and the at least one other part of the image.

10. A screen (10) according to claim 8 wherein the first and second pixel densities (110, 120) and the pixel density (130) of the at least one other area (13) are chosen so as to display a. A multi-resolution image exhibiting a variation in resolution between the first and second part of the image and the at least one other part of the image, which is similar to a sensitivity profile of a retina of a human eye.

11. Screen (10) according to any one of the preceding claims having, in a main extension plane (xy), a characteristic dimension, for example a diagonal, between 2 inches and 10 inches.

12. A display system comprising a display screen according to any one of the preceding claims, a projection optical system (43) configured to project the image displayed by the screen (10) towards an eye (O) d. 'an observer, and a system for tracking the movements of the eye of the observer configured to control the projection of the image to said movements, so as to project the second part of the image displayed by the second zone (12) on the fovea of the observer's eye.

13. A display system according to the preceding claim further comprising a body (30), and wherein the system for tracking the movements of the observer's eye is configured to modify the positions of the screen (10) and / or the optical projection system (43) relative to the body.

14. Display system according to the preceding claim wherein the projection optical system (43) comprises a mirror (41) curved facing the screen (10) configured to reflect the image displayed by the screen, and a focusing lens (40) facing the observer configured to focus on the retina of the eye (O) said reflected image, and in which the screen (10) is fixed relative to the body (30) and the optical system projection (43) is at least partly movable relative to the body (30), the position of the projection optical system (43) being modified by a displacement of the focusing lens and / or of the curved mirror relative to the body (30) display system.

15. The display system of claim 13 wherein the projection optical system (43) comprises a lens system facing the screen (10) configured to transmit the image displayed by the screen (10), and a curved mirror facing the observer configured to reflect said transmitted image towards the eye (O) of the observer, and in which the projection optical system (43) is fixed relative to the body (30) and the the screen (10) is at least partly movable relative to the body (30), the position of the screen (10) being modified by a displacement of the screen (10) in a main extension plane of the screen , relative to the body (30) of the display system.

16. A display system according to any one of claims 12 to 15 wherein the projection optical system (43) is configured to project the image displayed by the screen (10) with a magnification greater than or equal to 1.

17. A method of manufacturing a display screen (10) for displaying an image of multiple resolution and comprising a first area (11) having a first pixel density (110) for displaying a first part of the image. image with a first resolution, and a second area (12) having a second pixel density (120) strictly greater than said first density, making it possible to display a second part of the image with a second resolution, said method comprising the steps following:

- Provide a support (100) capable of receiving a plurality of pixels (110,

120),

- Provide at least one donor substrate comprising pixels according to a base density between the first pixel density and the second pixel density,

- Ffectuer with a first buffer a first transfer on the support (100), for example by mass transfer technology, of a first set of pixels (110) having the first density from the at least one donor substrate, so as to form the pixels of the first zone (11),

- Carry out with a second buffer of dimensions smaller than those of the first buffer at least a second transfer on the support (100), for example by mass transfer technology, of at least a second set of pixels (120) from the at least one donor substrate, so as to form the pixels (120) of the second zone (12) of the screen having the second density of pixels.

18. The method of the preceding claim wherein the at least one donor substrate comprises a first donor substrate comprising pixels (110) having the first pixel density and a second donor substrate comprising pixels (120) having the second pixel density. , and wherein the first transfer is performed from the first donor substrate and the at least one second transfer is performed once from the second donor substrate.

19. The method of claim 17 wherein the at least one donor substrate is a single donor substrate comprising pixels (110) exhibiting only the first pixel density, and wherein the first transfer is configured to form the pixels (110). of the first zone (11) and part of the pixels (120) of the second zone (12), and the second transfer is repeated several times to complete the pixels of the second zone (12), so as to reach the second density number of pixels (120) in the second area (12).

20. A method according to any one of claims 17 to 19 wherein the pixels are smart pixels (110 ', 120') each comprising dedicated control electronics (202), said smart pixels (110 ', 120') having each a width less than or equal to 50 μm, preferably less than or equal to 25 μm.