FR3139236A1 - Imaging device - Google Patents

Abstract

Imaging device The present description concerns an imaging device comprising a display screen (1, 2), an image sensor (5) in organic technology under the display screen, and a semi-opaque level, filtering the radiation visible, between respective active layers of the screen and the sensor. Figure for abstract: Fig. 8

Description

Imaging device

This description generally concerns imaging systems and, more particularly, devices combining a display function via a display screen and an acquisition function via an image sensor.

Many mixed systems or devices are known, having functions of display or projection of images and acquisition or detection of images.

Among these systems, imagers or image sensors have already been proposed comprising photodetectors based on organic active layers associated with display devices.

There is a need to improve imaging systems combining display screen and photodetector matrix.

One embodiment overcomes all or part of the drawbacks of known systems.

One embodiment provides an imaging device comprising:
- a display screen;
- an organic technology image sensor under the display screen; And
- a semi-opaque level, filtering visible radiation, between respective active layers of the screen and the sensor.

According to one embodiment, the semi-opaque level is located between the screen and the sensor.

According to one embodiment, the semi-opaque level is integrated into the display screen.

According to one embodiment, the semi-opaque level is integrated into the sensor.

According to one embodiment, said semi-opaque level includes an angular filter.

According to one embodiment, the display device further comprises a light source emitting at least in the near infrared.

According to one embodiment, said source is on one of the lateral sides of the device, emits parallel to a plane in which the device fits, and is associated with a textured waveguide.

According to one embodiment, the light source and the textured waveguide are under the image sensor.

According to one embodiment, the device comprises in order:
- an image sensor consisting of a substrate surmounted by photodetectors made of organic semiconductor materials;
- an angular filter;
- an emissive layer made of organic emissive diodes;
- a covering layer.

According to one embodiment, the device further comprises a semi-opaque layer on or under, and in contact with the angular filter.

According to one embodiment, the device further comprises, between the angular filter and the organic emissive layer, a textured waveguide and a semi-opaque layer.

According to one embodiment, the semi-opaque level filters visible radiation by more than 99.5% and allows at least 1% of near-infrared radiation to pass.

These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments given on a non-limiting basis in relation to the attached figures, among which:

there is a very schematic sectional view of layers or levels constituting a display device;

there is a very schematic sectional view more detailed than that of the ;

there is a very schematic and simplified sectional view of one embodiment of an imaging device;

there is a very schematic sectional view of an embodiment of the device of the ;

there is a very schematic sectional view of another embodiment of the device of the ;

there is a very schematic sectional view of another embodiment of the device of the ;

there is a very schematic sectional view of another embodiment of the device of the ;

there is a very schematic sectional view of another embodiment of the device of the ;

there is a very schematic sectional view of another embodiment of the device of the ; And

there is a very schematic sectional view of another embodiment of the device of the .

The same elements have been designated by the same references in the different figures. In particular, the structural and/or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

For the sake of clarity, only the steps and elements useful for understanding the embodiments described have been represented and are detailed. In particular, the control and reading or interpretation electronics of the device described have not been detailed, the embodiments described being compatible with the usual electronic control and reading circuits.

Unless otherwise specified, when we refer to two elements connected to each other, this means directly connected without intermediate elements, and when we refer to two elements connected (in English "coupled") to each other, this means that these two elements can be connected or be linked via one or more other elements.

In the following description, when referring to absolute position qualifiers, such as "front", "back", "up", "down", "left", "right", etc., or relative, such as the terms "above", "below", "superior", "lower", etc., or to qualifiers of orientation, such as the terms "horizontal", "vertical", etc., it is referred to unless otherwise specified, to the orientation of the figures or to a system in a normal position of use.

Unless otherwise specified, the expressions "approximately", "approximately", "substantially", and "of the order of" mean to the nearest 10% or 10 degrees, preferably to the nearest 5% or 5 degrees.

Unless otherwise specified, the expressions "all elements", "all elements", "each element", mean between 95% and 100% of the elements. In the remainder of the description, unless otherwise specified, a layer or film is said to be opaque to radiation when the transmittance of the radiation through the layer or film is less than 10%. In the remainder of the description, unless otherwise specified, a layer or film is said to be transparent to radiation when the transmittance of the radiation through the layer or film is greater than 10%, preferably greater than 50%. According to one embodiment and unless otherwise specified, for the same optical system, all the elements of the optical system which are opaque to radiation have a transmittance which is less than half, preferably less than a fifth, more preferably less than a tenth, of the lowest transmittance of the elements of the optical system transparent to said radiation. In the remainder of the description, “useful radiation” refers to the electromagnetic radiation passing through the optical system in operation. In the remainder of the description, an optical element formed on one face of a support whose maximum dimension, measured parallel to said face, is greater than 1 μm and less than 1 mm, is called "micrometric-sized optical element".

Embodiments of optical systems will now be described for optical systems comprising a matrix of micrometric-sized optical elements in the case where each micrometric-sized optical element corresponds to a micrometric-sized lens, or microlens, composed of two diopters. . However, it is clear that these embodiments can also be implemented with other types of micrometric-sized optical elements, each micrometric-sized optical element being able to correspond, for example, to a micrometric-sized Fresnel lens, to a micrometer-sized gradient index lens or to a micrometer-sized diffraction grating.

In the remainder of the description, visible light is electromagnetic radiation whose wavelength is between 400 nm and 700 nm, and, in this range, green light is electromagnetic radiation whose wavelength is between 400 nm. nm and 600 nm, more preferably between 470 nm and 600 nm. Infrared radiation is electromagnetic radiation whose wavelength is between 700 nm and 1 mm. In infrared radiation, we distinguish in particular near-infrared radiation whose wavelength is between 700 nm and 1.7 μm, more preferably between 850 nm and 940 nm.

Among the display devices, some are equipped with polarizers in order to avoid reflections likely to occur on lower layers of the device integrating the screen and which disrupt visual comfort (human perception in the visible).

Other display devices are equipped, in place of these polarizers, with opaque layers (with a transparency of less than 0.5% in the visible), added to the optical components to mask the reflections of the radiation, coming from the exterior or emitted by the emissive layer of the display device, which may occur on the lower layers.

There is a very schematic sectional view of layers or levels constituting a display device.

In a simplified manner, a display screen without polarizer, as illustrated in and of the type to which the embodiments described apply, successively comprises a layer or coverage level 1 (Cover layer), an emissive layer or emissive level 2 (Emitting layer) and an opaque layer or level 3 (Opaque layer). Although we refer to a “layer”, the corresponding level can in practice consist of several stacked layers.

There is a very schematic sectional view more detailed than that of the .

The transparent covering layer or level 1 is for example made of glass and/or based on plastic film and has a thickness of a few tens to a few hundred microns, for example of the order of 300 µm. In the example of the , layer 1 successively comprises, from the upper face, a protective film 12 (Protective film) with hard coating (“protective film with Hard Coating or HC”) having a thickness of around 90 µm, a plastic film 14 ( Plastic film or “Plastic film”) and an ultra-thin glass 16 (Ultrathin glass or “Ultra thin glass”), the layers 14 and 16 having for example a cumulative thickness of the order of 230 µm.

Emissive layer 2 (OLED screen or “OLED display”) is an OLED display screen based on organic emissive diodes, formed on a rigid (for example glass) or flexible (for example polyamide - PI) substrate. Layer 2 includes color filters and a black matrix in such a way that the transparency in the visible is reduced (the transparency in the visible is for example less than 0.5%) as well as in the near infrared (the transparency in the near infrared is for example less than 3%). The thickness of the OLED 2 screen is for example a few hundred microns, for example between approximately 100 and approximately 250 µm, for example of the order of 250 µm.

The opaque layer or level 3 is made up of one or more opaque layers in the visible and near infrared (the transparency in the visible and near infrared is for example less than 0.5%) whose thickness is a few dozen at a few hundred microns, for example of the order of 300 µm. In the example of the , layer 3 comprises a black layer 32 (Black layer) on a rigid black layer (Rigid black layer).

Typically, a display device without polarizer, of the type illustrated in cannot cover an image sensor because the opaque layer 3, useful for avoiding reflections and not disturbing the display, does not allow radiation to pass towards the sensor.

According to the embodiments described, it is planned to modify the structure of the stack of the imaging device in order to allow the association of a display screen without polarizer with an image sensor of particular type.

In the embodiments explained below, the structure of the device is presented in the form of stacks of layers. Note, however, that some of these layers can be engraved locally depending on their function, in particular due to the pixelated nature of the sensor and the display. The stacks described correspond to the useful part of the screen and the sensor and, preferably, to levels which, although locally comprising (per pixel, sub-pixel or group of pixels) patterns, extend over this entire part useful of the device.

Taking the example of the , the embodiments described provide for replacing the opaque layer 3 with a semi-opaque level which will be detailed below and to associate everything with an infrared image sensor in organic technology. A device according to the embodiments described remains devoid of polarizer and is therefore intended for screen applications without polarizer (called “pol-less”).

The embodiments described take advantage of the fact that certain layers of an organic sensor have, independently of their capacity to detect radiation in the visible, an ability to allow sufficient infrared radiation to pass through to excite the organic photodetectors of the sensor. More particularly, the inventors have noted that the detection capacity of organic sensors in the near infrared (more particularly in wavelengths between 840 and 950 nm) is sufficient for a weak radiation passing through a semi-opaque layer ( opaque in the visible but not completely in the infrared) can be used to form an infrared image.

There is a very schematic and simplified sectional view of one embodiment of an imaging device.

According to this embodiment, the opaque layer 3 of a display device of the type illustrated in Figures 1 and 2 is replaced by a semi-opaque level 4 and the assembly is integrated into, or attached to, a device organic image acquisition, or is integrated into, or reported under, a display screen.

In the example of the , the imaging device successively comprises, from a face intended to be observed by a user, a covering layer 1 of the type described above, an OLED screen 2 of the type described above, a semi-opaque level 4 (semi-opaque level or " Semi-opaque level"), an organic sensor 5 (Organic sensor), and a support 6 (Support) of the entire imaging device.

The organic sensor 5 is typically made up of organic semiconductor layers constituting organic photodetectors and a substrate carrying the electronic components (transistor level) for controlling and interpreting the photodetectors.

Preferably, the semi-opaque level 4 is made up of material(s) preserving a transmission of less than 0.5% in the visible while maximizing the transmission in the near infrared.

Preferably, the semi-opaque level 4 consists of a layer or a multilayer having a transparency of less than 0.5% in the visible (opaque in the visible, that is to say filtering at least 99, 5% of visible radiation) and greater than approximately 1% in the near infrared. This level 4 can, alternatively, be integrated into the organic sensor.

The support 6 constitutes the support element of the entire device. Depending on the applications, it may be a plate or localized elements for fixing the imaging device to the system into which it is integrated (for example a mobile phone or a tablet).

In the following figures, for simplicity, support 6 is not shown.

There is a very schematic sectional view of an embodiment of the device of the .

The organic sensor 5 is schematically constituted by a substrate 52 (sensor substrate) on which the organic photodetectors are produced or attached, symbolized in the form of an organic semiconductor layer or level 54 (organic semiconductor or "organic"). semiconductor").

According to this embodiment, the semi-opaque level 4 is made up of an angular filter 42 (Angular filter) which generally equips an organic sensor. Such an angular filter has, as far as the sensor is concerned, the role of avoiding cross-talk phenomena between the pixels of the organic sensor, as well as of improving the sharpness of an image of 'an object placed on the screen. Such a filter is for example made up of pillars or walls laterally separating the pixels from each other, or of a matrix of holes ("pinholes") made in an opaque plate. Preferably, the gap between the walls is then filled with a semi-opaque material. Thus, the angular filter 42 plays both the role of the angular filter of the image and level sensor protecting the display screen from reflection coming from lower levels.

The imaging device further comprises one or more light sources 7 (NIR LED) emitting at least, preferably exclusively, near-infrared radiation. This radiation is intended to be emitted towards the outside of the device on the cover layer side 1 so as to be reflected on surfaces close to or distant from the imaging device, these reflections then being captured by the organic sensor 5 after passing through the imaging device. display and the semi-opaque layer.

In the embodiment of the , the light source 7 is located in the upper part of the device, i.e. at a level above the display screen. It is possible, for example, to integrate, into the cover layer 1, a textured waveguide directing, towards the outside of the device, radiation emitted horizontally or laterally by the source 7 from one or more sides of the device.

There is a very schematic sectional view of another embodiment of the device of the .

In relation to the mode of realization of the , the semi-opaque level 4 is here made up of the angular filter 42 and a layer of a semi-opaque material 44 (Semi-opaque layer or “Semi opaque layer”). The use of an additional semi-opaque layer depends on the application and, in particular, on the nature of the angular filter. Likewise, the order of the angular filter 42 and the semi-opaque layer 44 in the stack depends on the application. For example, if the angular filter 42 is, from the point of view of the manufacturing process, integrated into the organic optical sensor 5, it will be preferable for the semi-opaque layer 44 to be between the display screen and the sensor 5.

Examples of light source structures associated with waveguides integrated into a cover layer of an image sensor, which can here be transposed to the cover layer of the display screen, are described in document WO 2018/162842 (B16100). We can draw inspiration from this for the implementation of the embodiments in Figures 4 and 5.

There is a very schematic sectional view of another embodiment of the device of the .

In relation to the mode of realization of the , the near infrared light source 7 is located at the level of the support 6. The latter is, for example, arranged to integrate emitters (in the infrared or near infrared) in the matrix arrangement of the pixels or is textured at the manner of a waveguide to return infrared radiation directed parallel to the plane in which the substrate 52 fits towards the external surface of the device on the display screen side. The substrate 52 is then, for example, transparent or etched.

There is a very schematic sectional view of another embodiment of the device of the .

This embodiment is a mixture of the embodiments of and 6. In other words, in relation to the mode of carrying out the , the light source(s) 7 are at the level of the substrate 52.

There is a very schematic sectional view of another embodiment of the device of the .

According to this embodiment, the light source 7 is placed between the image sensor and the display screen. More precisely, we plan:
under the display screen (under the emissive layer or OLED screen 2), a semi-opaque layer 44;
on the image sensor (on the semiconductor layer of organic materials 54) an angular filter 42; And
between layers 42 and 44, a textured waveguide layer 72 (textured wave guide) illuminated laterally by a light source 7 comprising at least one near-infrared radiation.

An advantage of this embodiment is that it is particularly suitable for superimposing an infrared sensor and a display screen without it being necessary to modify either one. Only the intermediate elements between the two are to be provided if they are not already, for some (for example the angular filter on the sensor side), integrated into the corresponding device.

There is a very schematic sectional view of another embodiment of the device of the .

According to this embodiment, a textured waveguide 72 is provided under the sensor substrate. Such an embodiment is intended for applications in which the substrate 52 of the sensor allows at least near-infrared radiation to pass. Consequently, the radiation intended to be emitted outside from the covering layer 1 can come from the rear of the imaging device. Indeed, as the semi-opaque level (in the example of the , the angular filter 42 of the image sensor) lets near-infrared radiation pass, it is not problematic to provide the light source 7 associated with a textured waveguide under the entire device, in practice, between the substrate 52 (then transparent) of the sensor and the support (6, ) of the device.

there is a very schematic sectional view of another embodiment of the device of the .

This embodiment is a mix between the embodiments of Figures 6 and 9. In other words, compared to the embodiment of the , the semi-opaque level 4 comprises, between the display screen and the image sensor, in order, a layer 42 of semi-opaque material(s) and an angular filter 44.

Examples of textured waveguides are described in document WO 2022/112369 (B20175). We can draw inspiration from this for the implementation of embodiments providing textured waveguides to return radiation emitted in a plane parallel to those in which the layers of the device are made.

Examples of angular filters are described in document WO 2022/128873 (B20690). We can take inspiration from this to create the angular filter of the imaging device described by adapting this angular filter so that it filters visible radiation. For example, we could plan to fill the orifices of the angular filter with a semi-opaque material.

The semi-opaque layer 44 can be made from a matrix arrangement respecting the arrangement of the pixels and comprising zones absorbing visible radiation and allowing at least 2% of near-infrared radiation to pass through, or from a uniform layer allowing infrared radiation to pass through. Examples of opaque matrix network structures are described in document EP 3442025 (in particular at its ) and the person skilled in the art will be able to draw inspiration from it for the realization of the embodiments described.

An advantage of the structures described in the present description is that they retain the entire structure of the emissive layer of the OLED screen 2. The display screen can therefore, if necessary, be manufactured separately and then be reported on the underlying stack of the infrared sensor. Preferably, however, the assembly is manufactured by successive deposits with the formation of suitable patterns.

Another advantage of the embodiments described is that it makes it possible to associate an OLED display screen with an infrared image sensor, by associating with one and/or the other a semi-opaque layer filling the role of the anti-reflection layer. The semi-opaque layer, filtering visible radiation, is therefore between respective active layers of the screen and the sensor (integrated into the screen or the sensor or between the two).

In the embodiments where the source 7 of infrared radiation is under the display device, this source preferably does not emit visible radiation in order to avoid an effect similar to the reflections that we wish to avoid. Preferably, whatever the embodiment, the source 7 of infrared radiation is designed to emit only in the infrared, preferably only in the near infrared.

A display device according to the written embodiments may serve as an integrated fingerprint sensor, preferably, under the entire surface of a display screen.

Various embodiments and variants have been described. Those skilled in the art will understand that certain features of these various embodiments and variants could be combined, and other variants will become apparent to those skilled in the art. In particular, the semi-opaque level, provided that it is located between the emissive layer and the organic semiconductor layer of the sensor, can be composed of different layers, or even air gaps, which are usually found on the screen side display or image sensor side.

Finally, the practical implementation of the embodiments and variants described is within the reach of those skilled in the art based on the functional indications given above. In particular, the choice of materials among those indicated is within the reach of those skilled in the art depending on the intended application.

Claims (12)

Imaging device comprising:
a display screen (1, 2);
an image sensor (5) in organic technology under the display screen; And
a semi-opaque level, filtering visible radiation, between respective active layers of the screen and the sensor. Device according to claim 1, in which the semi-opaque level is located between the screen (1, 2) and the sensor (5). Device according to claim 1, in which the semi-opaque level is integrated into the display screen (1, 2). Device according to claim 1, in which the semi-opaque level is integrated into the sensor (1, 2). Device according to any one of claims 1 to 4, wherein said semi-opaque level (4) comprises an angular filter (44). Device according to any one of claims 1 to 4, further comprising a light source (7) emitting at least in the near infrared. Device according to claim 6, in which said source (7) is on one of the lateral sides of the device, emits parallel to a plane in which the device fits, and is associated with a textured waveguide (72). Device according to claim 7, wherein the light source (7) and the textured waveguide (72) are under the image sensor. Device according to any one of claims 1 to 8, comprising in order:
- an image sensor (5) consisting of a substrate (52) surmounted by photodetectors made of organic semiconductor materials (54);
- an angular filter (42);
- an emissive layer (2) made of organic emissive diodes; And
- a covering layer (1). Device according to claim 9, further comprising a semi-opaque layer (44) on or under, and in contact with the angular filter (42). Device according to claims 8 and 10, further comprising, between the angular filter (42) and the organic emissive layer (2), a textured waveguide (72) and a semi-opaque layer (44). Device according to any one of claims 1 to 11, in which the semi-opaque level filters visible radiation by more than 99.5% and allows at least 1% of near-infrared radiation to pass through.