WO2021258290A1

WO2021258290A1 - Sensing device and electronic device comprising the sensing device

Info

Publication number: WO2021258290A1
Application number: PCT/CN2020/097737
Authority: WO
Inventors: Kenichi Takatori
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2020-06-23
Filing date: 2020-06-23
Publication date: 2021-12-30
Also published as: CN115769201A

Abstract

The present invention relates to a sensing device comprising a light emitter having a first surface and a second surface opposite to the first surface, the light emitter comprising a plurality of light emitting elements configured to emit light toward the first surface; and a light detector opposed to the second surface of the light emitter, the light detector comprising a plurality of light detecting elements configured to convert light to an electric signal, wherein the light emitter has a mask configured to absorb or reflect light such that intensity of light entering the first surface is modulated by the mask before the light impinges on the light detecting elements.

Description

SENSING DEVICE AND ELECTRONIC DEVICE COMPRISING THE SENSING DEVICE

FIELD OF THE INVENTION

The present invention relates to a sensing device and an electronic device comprising the sensing device.

BACKGROUND OF THE INVENTION

Recently, personal identification using fingerprints has been employed in mobile communication devices such as smartphones. A fingerprint sensor for reading a fingerprint has been conventionally installed outside a screen for displaying information. However, since larger screens, more compact devices, and more sophisticated designs are required, display devices integrating a fingerprint sensor in a screen have been proposed. Furthermore, display devices integrating a camera have been proposed for mobile communication devices employing face identification in order to realize larger screens, more compact devices, and more sophisticated designs. Such a display device generally includes a display for displaying an image and a light detector superimposed on the display for reading an image.

Such a conventional display device incorporating a light detector comprises: a display comprising light emitting elements (pixels) for emitting light; a cover for protecting the display and allowing light emitted from the display toward the outside of the display device to transmit therethrough; and a light detector superposed under the display, arranged opposite to the cover relative to the display, and comprising light detecting elements for detecting light. The display emits light for displaying an image. When detecting a fingerprint, light emitted from the display is reflected by an object (for example, a fingertip of a user) , transmits through the display, and reaches the light detecting elements. Since the display device can obtain a reflection pattern of the object, i.e. a surface shape of the object (for example, a fingerprint) from signals of light which has reached the light detecting elements, an image sensor display integrating an image sensor therein can be realized.

For such a sensing device, it is important to identify which part of the object reflected the light which has impinged on the light detecting element. If the reflection position is not appropriately specified, the accuracy of detecting the surface shape of the object may not achieve a required level. In particular, optical crosstalk caused by light reflected from different positions of the object entering the same light detecting element should be reduced or prevented.

With respect to such a problem of optical crosstalk, a configuration of an image sensor display with a microlens arranged on a surface of a light detecting element to allow only light reflected by an object in a specific direction to project on the light detecting element has been proposed. However, such a lens has problems of degrading an image quality and a view angle of the light detector, increasing a thickness of the sensing device due to its complicated structure, and increasing its cost.

On the other hand, a lensless camera using a coded mask plate instead of a microlens has also been proposed. For example, Japanese Patent Application Publication No. 2018-098758 discloses an image capturing device without a focus lens comprising an image sensor and a coded mask plate having a particular pattern, which is referred to as Fresnel Zone Plate, over the image sensor. However, such a mask plate also increases a thickness of the sensing device. Furthermore, if a mask plate is inserted between the light emitter and the light detector of the image sensor display, it is also necessary to provide an optical collimator between the light emitter and the mask in order to cut off scattered light. Such an optical collimator also increases a thickness of the sensing device, and decreases intensity of light which impinges on the light detector and incident angles to the light detector.

Therefore, there is a need for a sensing device having no additional optics or only minimal optics and a method of operation thereof.

SUMMARY OF THE INVENTION

The present invention provides a sensing device having no additional optics or only minimal optics to increase intensity and incident angles of light to the light detector while reducing or preventing optical crosstalk, and provides an electronic device comprising the sensing device.

One aspect of the present invention is a sensing device comprising:

a light emitter having a first surface and a second surface opposite to the first surface, the light emitter comprising a plurality of light emitting elements configured to emit light toward the first surface; and

a light detector opposed to the second surface of the light emitter, the light detector comprising a plurality of light detecting elements configured to convert light to an electric signal,

wherein the light emitter has a mask configured to absorb or reflect light such that intensity of light entering the first surface is modulated by the mask before the light impinges on the light detecting elements.

In the above aspect of the sensing device, the light emitter may comprise a transparent layer configured to allow light to pass therethrough; and the transparent layer may have a non-transparent portion made of a material which absorbs or reflect light, and the non-transparent portion may serve as the mask.

In the above aspect of the sensing device, the light emitter may comprise a non-transparent layer configured to absorb or reflect light; and the non-transparent layer may have a transparent portion made of a material which allows light to pass therethrough and a non-transparent portion made of a material which absorbs or reflects light, and the non-transparent portion may serve as the mask.

In the above aspect of the sensing device, the light emitter may comprise a substrate layer, a light emitting element control layer having a plurality of light emitting element control circuits configured to control the plurality of light emitting elements, a light emitting element layer including the plurality of light emitting elements, and a cover layer covering the light emitting element layer; and the mask may be formed in at least one of the substrate layer, the light emitting element control layer, the light emitting element layer, and the cover layer.

In the above aspect of the sensing device, the light emitter may comprise a light emitting element control layer having a plurality of light emitting element control circuits configured to control the plurality of light emitting elements; the light emitting element control layer may have circuit arrangement including the light emitting element control circuits and wirings; and at least a portion of the mask may be formed by the circuit arrangement of the light emitting element control layer.

In the above aspect of the sensing device, the light emitter may comprise a light shielding layer between the light emitting elements and the second surface, the light shielding layer having a non-transparent layer configured to absorb or reflect light and a transparent portion configured to allow light to pass therethrough; and the non-transparent portion of the light shielding layer may serve as the mask.

In the above aspect of the sensing device, the light emitter may comprise a touch sensor layer between the light emitting elements and the first surface; and the mask may be formed in the touch sensor layer.

In the above aspect of the sensing device, the mask may have a random pattern or a regular pattern.

In the above aspect of the sensing device, the mask may have a pattern composed of a plurality of concentric circles.

In the above aspect of the sensing device, the mask may have a pattern made of combination of square sub patterns composed of parallel lines.

In the above aspect of the sensing device, each of the light emitting elements may have an aperture configured to allow light to pass therethrough; and one or more apertures may be partially covered by the mask.

The above aspect of the sensing device may further comprise an image processor configured to process image data obtained from the electric signal output by the light detecting elements to reproduce an image.

In the above aspect of the sensing device, the light emitting elements may be organic light emitting diodes.

Another aspect of the present invention is an electronic device comprising the above sensing device.

The embodiments of the present invention provide a sensing device having no additional optics or only minimal optics to increase intensity and incident angles of light to the light detector while reducing or preventing optical crosstalk, and provides an electronic device comprising the sensing device.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood from the following detailed description of non-limiting embodiments thereof, and from examining the accompanying drawings, in which:

Figure 1 shows an exploded perspective view of the sensing device according to the first embodiment of the present invention;

Figure 2 shows a further exploded perspective view of the sensing device according to the first embodiment of the present invention;

Figure 3 shows a cross sectional view of the sensing device according to the first embodiment of the present invention;

Figure 4 shows an enlarged view of the portion surrounded by the dashed-dotted line in Figure 3;

Figure 5 shows examples of patterns for the mask of the sensing device according to the first embodiment of the present invention;

Figures 6 (A) to (F) show cross sectional views of modifications of the sensing device according to the first embodiment of the present invention;

Figures 7 (A) and (B) show a schematic view of the operation of the sensing device according to the first embodiment of the present invention;

Figure 8 shows a schematic view of an electronic device comprising the sensing device according to the first embodiment of the present invention;

Figure 9 shows a cross sectional view of the sensing device according to the second embodiment of the present invention;

Figure 10 shows a cross sectional view of the sensing device according to the third embodiment of the present invention;

Figure 11 shows a plane view of the sensing device according to the third embodiment of the present invention; and

Figure 12 shows a cross sectional view of the sensing device according to the fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Definitions

Herein, “formed in X” means being formed inside X or being formed on one or both surfaces of X.

Herein, the terms “transparent” and “allow light to pass” means that transmittance is more than 70%for at least one wavelength within 380 nm to 1,200 nm (visible and near-infrared region) . The terms “non-transparent” and “absorb or reflect light” means that transmittance is less than 30%for at least one wavelength within 380 nm to 1,200 nm due to absorbance and/or reflectance.

First Embodiment

[Constitution of the sensing device]

Figure 1 shows an exploded perspective view of the sensing device 1 according to the first embodiment of the present invention. The orthogonal coordinate axes x, y, and z are set such that a light exit/entrance surface of the sensing device 1 extends substantially parallel to the x-y plane and the component layers of the sensing device 1 are stacked in the z direction. More specifically, the +z direction is defined as the direction in which an emitted light 16 exits the sensing device 1 in Figure 1, and the -z direction is defined as the direction in which a reflected light 17 enters the sensing device 1 in Figure 1. The terms “above” and “under” are used herein to represent the positional relationship in the +z direction: “A above B” means that the z coordinate of A is greater than that of B, and “Aunder B” means that the z coordinate of A is less than that of B. The terms “upper” and “lower” are used with respect to the +z direction as well.

The sensing device 1 includes a light emitter 10, a light detector 12, and an image processor 14.

The light emitter 10 has a plurality of light emitting elements 30. The light emitting elements 30 are spaced from each other and arranged in a matrix in an x-y plane view. The light emitting elements 30 are configured to emit light 16 to the outside of the sensing device 1. Each of the light emitting elements 30 has an aperture A through which light 17 can pass from the upper side to the lower side in Figure 1. The aperture A may be a physical hole through one or more layers, or may not be a physical hole but be a transparent portion configured to allow light to pass therethrough. Herein, both are referred to as “aperture” .

The light detector 12 has a plurality of light detecting elements 50. The light detecting elements 50 are arranged in a matrix correspondingly to the light emitting elements 30 in an x-y plane view. In other words, each of the light detecting elements 50 of the light detector 12 is positioned under the corresponding light detecting element 30 of the light emitter 10. The light detecting elements 50 are configured to detect light 17 which has been emitted from the light emitting elements 30 and reflected by an outside object 18, and to convert light to an electric signal.

Figure 2 shows a further exploded perspective view of the sensing device 1 according to the first embodiment. The light emitter 10 includes a first transparent layer T1, a non-transparent layer NT, and a second transparent layer T2 in this order in the -z direction.

The first transparent layer T1 allows the reflected light 17 to pass therethrough. The first transparent layer T1 includes a cover layer 20, a transparent layer 32, and a light emitting layer 34. The details of each layer will be described below.

The non-transparent layer NT has the aperture A which allows the reflected light 17 to pass therethrough. The non-transparent layer NT prevents the light 17 from passing therethrough except for the light passing through the aperture A. The non-transparent layer NT includes a reflecting electrode layer 36, a light emitting element control layer 24, and a light shielding layer 26. The details of each layer will be described below.

The second transparent layer T2 has a mask M configured to prevent the light 17 from passing therethrough. In other words, the mask M absorbs or reflects the light 17. The second transparent layer T2 allows the light 17 to pass therethrough except for the positions where the mask M is formed. The mask M has a random pattern or a regular pattern (herein a mask with a random or regular pattern is also referred to as “coded mask” ) . The second transparent layer T2 includes a first substrate layer 28. The detail of the first substrate layer 28 will be described below.

From the above definition, the transmittances of the first transparent layer T1 and the second transparent layer T2 are more than 70%for at least one wavelength within 380 nm to 1,200 nm whereas the transmittance of the non-transparent layer NT except for the aperture A is less than 30%for at least one wavelength within 380 nm to 1,200 nm.

The light 17, which has been emitted from the light emitter 10 and then reflected by the object 18, passes through the first transparent layer T1, the aperture A of the non-transparent layer NT, and the second transparent layer T2 having the mask M, and then reaches the light detecting elements 50 of the light detector 12. The intensity of the reflected light 17 which is detected by the light detecting elements 50 has been modulated by the coded mask M. The light detector 12 outputs image data from detection results of the intensity-modulated light 17. The image processor 14 processes the image data from the light detector 12 to reproduce an original image of the object 18 using a computer algorithm.

Figure 3 shows a cross sectional view of the sensing device 1 according to the first embodiment and Figure 4 shows an enlarged view of the portion surrounded by the dashed-dotted line in Figure 3. The sensing device 1 includes the light emitter 10 and the light detector 12 which are coupled to each other by an interface 11.

The light emitter 10 has a first surface 10a, which the emitted light 16 exits and the reflected light 17 enters, and a second surface 10b opposite to the first surface 10a. The light emitter 10 includes the cover layer 20, the light emitting element layer 22, the light emitting element control layer 24, the light shielding layer 26, and the first substrate layer 28 in this order in the -z direction from the first surface 10a to the second surface 10b.

The cover layer 20 covers the light emitting elements 30 and is configured to protect the components of the sensing device 1. The cover layer 20 is transparent to allow light from the light emitting elements 30 to exit the sensing device 1 and allow light from the outside, e.g. light reflected by the object 18, to enter the sensing device 1. In this embodiment, the upper surface 20a of the cover layer 20 is the first surface 10a of the light emitter 10.

The light emitting element layer 22 is under the cover layer 20. The light emitting element layer 22 includes a plurality of light emitting elements 30. In this embodiment, the light emitting elements 30 are organic light emitting diodes (OLEDs) . Any known OLEDs are available for the light emitting elements 30. Alternatively, the light emitting elements 30 may be inorganic light emitting diodes. The light emitting elements 30 may also be micro LEDs. Further alternatively, a known constitution of a liquid crystal display is also available as the light emitter 10.

Each of the light emitting elements 30 includes a transparent electrode layer 32, a light emitting layer 34, and a reflecting electrode layer 36 in this order in the -z direction. The transparent electrode layer 32 serves as an anode of an OLED. For example, the transparent electrode layer 32 may be made of a transparent conductive material such as indium tin oxide (ITO) . The reflecting electrode layer 36 serves as a cathode of an OLED and is configured to reflect light. For example, the reflecting electrode layer 36 may be made of a light reflecting conductive material such as aluminum. The light emitting layer 34 is between the transparent electrode layer 32 and the reflecting electrode layer 36 and has a known layer structure in an OLED, e.g. including a hole injection layer, a hole transport layer, an emissive layer, an electron transport layer, and an electron injection layer.

The reflecting electrode layer 36 has a first aperture A1 configured to allow light to pass therethrough. In this embodiment, the first aperture A1 is a hole physically formed through the reflecting electrode layer 36. However, the first aperture A1 may not be a physical hole, but be a portion of the reflecting electrode layer 36 which is made of a transparent material different from the surrounding reflecting material.

The light emitting element control layer 24 is under the light emitting element layer 22. The light emitting element control layer 24 has a plurality of light emitting element control circuits 38. Each of the light emitting element control circuits 38 is connected to each of the light emitting elements 30 via a via hole (not shown) . The light emitting element control layer 24 includes thin film transistors (TFTs) and wirings complexly arranged thereon which prevent light from passing through the light emitting element control layer 24. However, the light emitting element control layer 24 has a second aperture A2 configured to allow light to pass therethrough. The second aperture A2 is provided under the first aperture A1 of the reflecting electrode layer 36, i.e. at the same position as the first aperture A1 in an x-y plane view. The diameter of the aperture A2 may or may not be the same as that of the aperture A1. In this embodiment, the second aperture A2 is a physical hole through the light emitting element control layer 24. However, instead of providing a physical hole, the second aperture A2 may be embodied by arranging the TFTs and wirings on the light emitting element control layer 24 so as not to cover the position in which the second aperture A2 should be formed.

The light shielding layer 26 is under the light emitting element control layer 24. The light shielding layer 26 is made of a material which absorbs or reflects light and configured to prevent light from passing therethrough toward the second surface 10b of the light emitter 10. The light shielding layer 26 has a third aperture A3 configured to allow light to pass therethrough. The third aperture A3 is provided under the first and second apertures A1, A2, i.e. at the same position as the first and second apertures A1, A2 in an x-y plane view. The diameter of the aperture A3 may or may not be the same as that of the apertures A1, A2. The first, second, and third apertures A1, A2, A3 form together the aperture A of the non-transparent layer NT of the light emitter 10 as a whole. It should be noted that the light shielding layer 26 may be omitted.

The first substrate layer 28 is under the light shielding layer 26. The first substrate layer 28 is made of a transparent material and serves as a base for the light emitter 10. The first substrate layer 28 has a mask M configured to absorb or reflect light. In this embodiment, the mask M is formed on a lower surface 28b of the first substrate layer 28, i.e. the second surface 10b of the light emitter 10, as shown in Figures 3 and 4. However, the mask M may be formed on an upper surface 28a of the first substrate layer 28, formed inside the first substrate layer 28, or formed through the entire thickness of the first substrate layer 28. The mask M is formed to partially overlap with the aperture A of at least one light emitting element 30 in an x-y plane view.

An interface 11 is between the light emitter 10 and the light detector 12 and couples them to each other. The interface 11 can be made of a transparent material. For example, the interface 11 is an adhesive layer made of transparent adhesive to couple the second surface 10b of the light emitter 10 to the upper surface 12a of the light detector 12. The adhesive may be applied over the entire second surface 10b of the light emitter 10 and the entire upper surface 12a of the light detector 12 (see Figure 3) , or applied only on the peripheries of the second surface 10b of the light emitter 10 and the upper surface 12a of the light detector 12 such that there is space defined by the second surface 10b of the light emitter 10, the upper surface 12a of the light detector 12, and the surrounding peripheral adhesive. In this case, the interface 11 is made of an inner empty space and a outer transparent material surrounding the inner empty space.

The light detector 12 includes a light detecting element layer 40, a light detecting element control layer 42, and a second substrate layer 44 in this order in the -z direction.

The light detecting element layer 40 has a plurality of light detecting elements 50. Each of the light detecting elements 50 is positioned under each of the light emitting element 30. Each of the light detecting elements 50 is arranged to detect light passing through the aperture A of the light emitting element 30 above the light detecting element 50. Thus, each of the light detecting elements 50 at least partially overlaps with each of the apertures A in an x-y plane view.

The light detecting element control layer 42 is under the light detecting element layer 40. The light detecting element control layer 42 has a plurality of light detecting element control circuits 52. Each of the light detecting element control circuits 52 is connected to each of the light detecting elements 50 via a via hole (not shown) . The light detecting element control circuits 52 are configured to process electric signals transmitted by the light detecting elements 50 in response to light. The light detecting element control circuits 52 may be connected to the image processor 14. The image processor 14 processes image data obtained from the electric signals output by the light detecting elements 50 to reproduce an original image of the object 18.

The second substrate layer 44 is under the light detecting element control layer 42. The second substrate layer 44 is made of any substrate material and serves as a base for the light detector 12.

Other layers may be interposed between the above layers. The above layers may be also arranged in a different order.

[Mask]

The mask M will be described in detail. In this embodiment, the mask M is formed on the second surface 10b of the light emitter 10, i.e. the lower surface 28b of the first substrate layer 28. The mask M is provided to block at least a portion of light passing through the aperture A of the light emitter 10. Any light reflecting material or light absorbing material known by a person skilled in the art can be employed as a material of the mask M. For example, a masking material which absorbs light, such as carbon back or a non-conductive black pigment, or a masking material which reflects light, such as conductive metal or alloy, known by a person skilled in the art, can be employed as the material of the mask M. The mask M can be formed by any method such as depositing or printing a mask material on the surface of the first substrate layer 28. The mask M is arranged to cover a portion of the light detecting elements 50 and is configured to block light 17-3 from a particular direction and allow light 17-1, 17-2 from other directions to pass toward the light detecting element 30 as shown in Figure 4.

Since the light from the outside is partially blocked (absorbed or reflected) , scattered, and/or diffracted by the mask M, a modulated intensity of the light is detected by the light detecting elements 50 and a modulated image is obtained. The modulated image is processed by the image processor 14 to reproduce the original image, e.g. of the object 18 which has reflected the light.

[Pattern of the mask]

Figure 5 shows examples of patterns for the mask M of the sensing device 1 according to the first embodiment in an x-y plane view.

The mask M can be formed in any patterns. For example, the mask M may be in a random pattern as shown in Figure 5 (A) . Such a random pattern may be generated by computer simulation for better image reproducibility, e.g. in consideration of the arrangement of the components of the sensing device 1 such as the layers or the apertures A, the refractive indices of the layers of the sensing device 1, etc. However, the mask M may also be in a regular pattern. For example, the mask M may be in a pattern composed of a plurality of concentric circles as shown in Figure 5 (B) or in a pattern of combination of square sub patterns as shown in Figure 5 (C) . In Figure 5 (C) , each square sub pattern has parallel straight lines spaced from each other at constant interval, and the direction of the lines in each sub pattern is generally perpendicular to the direction from the center of the entire pattern to the center of the sub pattern. The farther a sub pattern is from the center of the entire pattern, the smaller the interval of the lines is.

A plate having a pattern of concentric circles in which an interval between adjacent concentric circles is in inverse proportion to the radius of the circle as shown in Figure 5 (B) is referred to as a “Fresnel Zone Plate (FZP) ” . When a FZP pattern is used for the mask pattern, a Moire fringe image is generated by the FZP pattern, which makes Fourier transform calculation easier and thus reduces calculation cost for reproducing an original image. In addition, the pattern shown in Figure 5 (C) can also generate a Moire fringe image and thus reduce calculation cost. Furthermore, the square pattern in Figure 5 (C) is suitable for an electronic device having a square display. It should be noted that any of the above patterns may also be applied to a sensing device having a stretchable screen, which requires more careful image processing.

[Position of the mask]

In this embodiment, the mask M is formed on the second surface 10b of the light emitter 10 (see Figures 3 and 4) . However, the mask M may be formed in any layer (s) as long as at least a portion of the mask M overlaps with a portion of the aperture A in an x-y plane view. For example, the mask M may be formed in the cover layer 20, the transparent electrode layer 32, or the light emitting layer 34. By way of example, Figures 6 (A) to (C) show cross sectional views of modifications of the sensing device 1. Figure 6 (A) shows that the mask M is formed on the outer surface of the cover layer 20, i.e. on the first surface 10a of the light emitter 10. Figure 6 (B) shows that the mask M is formed in the transparent electrode layer 32. Figure 6 (C) shows that the mask M is formed in the light emitting layer 34. When the mask M is formed on the outermost layer of the sensing device 1 as shown in Figure 6 (A) , since the mask M can be fabricated in the last step of the fabrication of the sensing device 1, the step of fabricating the mask M can be easily added to a conventional fabrication process.

Alternatively, the mask M may be provided by forming a transparent portion in the non-transparent layer such as the reflecting electrode layer 36, the light emitting element control layer 24, or the light shielding layer 26. In this case, since these layers originally absorb or reflect light, a portion thereof in which the above transparent portion is not formed serves as the mask M. For example, when the light emitting element control layer 24 is also used as the mask M, a circuit arrangement is determined such that the light blocking TFTs or wirings serve as the mask M as a whole. By way of example, Figures 6 (D) to (F) show cross sectional views of modifications of the sensing device 1. Figure 6 (D) shows that the reflecting electrode layer 36 serves as the mask M. Figure 6 (E) shows that the light emitting element control layer 24 serves as the mask M. Figure 6 (F) shows that the light shielding layer 26 serves as the mask M.

It should be noted that Figures 3 and 4 show only one light emitting element 30, only one light detecting element 4, and only one mask M for the sake of simplicity. In addition, the mask M may also be formed in one or more of the above layers.

[Distance between the mask and the light detecting elements]

It is preferable that the distance between the mask M and the light detecting elements 50 is 0.01%to 0.1%of the distance between the object 18 to be detected and the mask M. For example, when the distance between the object 18 and the mask M is expected to be 30 cm, the distance between the mask M and the light detecting elements 50 is preferably 30 μm to 300 μm. If the mask M is provided on the second surface 10b of the light emitter 10, the thickness of the interface 11 is preferably 30 μm to 300 μm.

It is possible to determine which component of the sensing device 1 is suitable for the mask M based on an expected distance between an object to be detected and the mask M. For example, when a distance between an object and the mask M is expected to be relatively large, it is preferable to provide the mask M on the first surface 10a of the light emitter 10 farthest from the light detecting elements 50 as shown in Figure 6 (A) . On the other hand, when a distance between an object and the mask M is expected to be relatively small, it is preferable to provide the mask M on the second surface 10b of the light emitter 10 closest to the light detecting elements 50 as shown in Figure 3.

[Operation of the sensing device]

Figure 7 shows a schematic view of the operation of the sensing device 1 according to the first embodiment. Since the sensing devices 1 shown in Figures 6 (A) to (F) are merely different from the sensing device 1 in Figure 3 in terms of the location of the mask M, the sensing devices 1 shown in Figures 6 (A) to (F) can employ the same operation method.

Figures 7 (A) and (B) schematically show the arrays of the light emitting elements 30, the masks M, and the light detecting elements 50, and the object 18 to be detected in front of the sensing device 1. All the light emitting elements 30 may emit light while only a part of the light emitting elements 30 may emit light, e.g. in a predetermined pattern. For the sake of simplicity, Figure 7 (A) depicts only light emitted from the light emitting element 30-1 and Figure 7 (B) depicts only the reflected light thereof.

Figure 7 (A) shows that the light emitted from the light emitting element 30-1 irradiates the object 18 to be detected. The object 18 is, for example, a surface of a finger of a user. Figure 7 (B) shows that the light 17-1 reflected in a particular direction among the light reflected from the object 18 passes through the aperture A and impinges on the light detecting element 50 without being blocked by the mask M or other components. On the other hand, the light 17-2, 17-3 reflected in other directions is blocked by the mask M and therefore does not reach the light detecting element 50. Moreover, from the viewpoint of the light detecting elements 50, the light detecting element 50-1 detects only the light 17-4 reflected from a particular location (s) on the object 18 and cannot detect the light 17-2, 17-5 reflected from other locations on the object 18. Since only the light 17-4 reflected from the object 18 in a particular direction impinges on the light detecting element 50-1, optical crosstalk caused by light 17-2, 17-4 reflected from other locations on the object 18 in other directions can be reduced or prevented. Accordingly, the light detecting elements 50 can detect reflection from a particular location (s) on the object 18. By integrating and processing this information over the light detecting element layer 20, the reflection pattern of the surface of the object 18, i.e. the surface shape of the object 18 can be accurately detected.

In this way, the coded mask M incorporated into the light emitter 10 modulates (i.e. encodes) the original image of the object 18 and the modulated image is detected by the light detecting elements 50. The modulated image can be mathematically processed (i.e. decoded) to reproduce the original image of the object 18 based on precise information of the structure of the coded mask M as well as the apertures A.

As the mask M is incorporated into the light emitter 10, in particular into one or more essential components of the light emitter 10, a separate mask plate is not required. Moreover, an optical collimator between the light emitter 10 and the mask M is not required. Therefore, the entire thickness of the sensing device 1 and the manufacturing cost thereof can be reduced. Since there is no loss in light intensity by passing an optical collimator, it is also possible to detect light having smaller intensity than a system with an optical collimator. Moreover, due to absence of an optical collimator, it is also possible to achieve a wider field of view of the light detecting elements 50 than a system with an optical collimator. In other words, incident angles of light to the light detector can be increased.

Furthermore, according to the above method of operation, mapping of a depth direction (herein the z direction) of the object 18 becomes easier since a very clear image can be easily reconstructed. If light emitted from a particular light emitting element 30 is reflected on a portion of the surface of the object 18 which is close to the sensing device 1, the reflected light impinges on a light detecting element 50 which is close to the light emitting element 30. On the other hand, if light emitted from the same light emitting element 30 is reflected on a portion of the surface of the object 18 which is far from the sensing device 1, the reflected light may impinge on a light detecting element 50 which is far from the light emitting element 30. Therefore, by identifying the position of the light detecting element 50 on which light impinges when a particular light emitting element 30 emits light, a two-dimensional mapping of the depth direction of the surface shape of the object 18 can be realized without a long computation time and large computational power, which were previously required. This is advantageous, in particular in the field of face recognition in which a depth direction detection is important.

The respective light emitting elements 30 are configured to emit light having different wavelengths. For example, the light emitting element layer 22 can have a first light emitting element 30-1 configured to emit red light, a second light emitting element 30-2 configured to emit green light, and a third light emitting element 30-3 configured to emit blue light. In this case, a difference in reflectance of the object 18 for each wavelength may be detected, and a composition of the object 18 may be detected by comparing the detection result with reference data. For example, when reflectance of a human skin for each wavelength is stored as a reference data, the sensing device 1 may determine whether the object 18 is a finger of a user or, for example, a mold of a fingerprint copied on a resin by measuring the reflectance of the object 18 for each wavelength, and provide more secure fingerprint identification. Combination and number of colors to be used may be appropriately changed in response to types of an object to be detected or applications.

Moreover, the light emitting element layer 22 may have light emitting elements 30 configured to emit infrared light. For example, when the light emitting element control layer 24 or the first substrate layer 28 of the light emitter 10 is made of a material such as polyimide which has a visible light absorption band and transmits infrared light well, it is possible to more efficiently perform light detection by detecting infrared light than detecting visible light. Moreover, the sensing device 1 which can emit and detect infrared light can be applied to a vein authentication system.

Figure 8 shows an electronic device 100 comprising the sensing device 1. The sensing device 1 can be embedded in an electronic device 100 such as a user device, a display device, or a mobile communication device, including a smartphone or a tablet device.

Second Embodiment

A second embodiment of the present invention is different from the first embodiment in that the light emitter 10 of the sensing device 1 includes a touch sensor layer 60. Configurations other than those described below are the same as in the first embodiment.

Figure 9 shows a cross sectional view of the sensing device 1 according to the second embodiment of the present invention.

The light emitter 10 of the sensing device 1 includes a touch sensor layer 60. The touch sensor 60 is configured to detect a touch by a user. A touch sensor constitution having any structure or mechanism can be used as the touch sensor layer 60. For example, the touch sensor layer 60 may be touch-on-encapsulation (TOE) type. A TOE type touch sensor layer includes a transmitter electrode layer and a receiver electrode layer, each layer having an electrode pattern. In the second embodiment, the electrode pattern in the transmitter electrode layer and/or the receiver electrode layer of the touch sensor layer 60 may serve as the mask M. Alternatively, the mask M may be added to the touch sensor layer 60 or other layer (s) , e.g. by deposition or printing.

Third Embodiment

A third embodiment of the present invention is different from the first embodiment in that the apertures A and the light detecting elements 50 have a portion which does not overlap with the light emitting elements 30 in an x-y plane view. Configurations other than those described below are the same as in the first embodiment.

Figure 10 shows a cross sectional view of the sensing device 1 according to the third embodiment of the present invention. Figure 11 shows a plane view of the sensing device 1 according to the third embodiment of the present invention.

As can be seen from Figures 10 and 11, the aperture A is spaced from the light emitting element 30 in an x-y plane view, and the light detecting element 50 is positioned under the aperture A and has a portion which does not overlap with the light emitting element 30 in an x-y plane view. Therefore, the reflecting electrode layer 36 of the light emitting elements 30 has no aperture, and the aperture A is composed of the aperture A2 of the light emitting element control layer 24 and the aperture A3 of the light shielding layer 26. However, it should be noted that since the light emitting element control layer 24 may allow a portion of light to pass therethrough depending on the arrangement of non-transparent elements such as thin film transistors (TFTs) and wirings, the aperture A2 of the light emitting element control layer 24 is not necessarily formed as long as light can at least partially pass through the light emitting element control layer 24 to reach the underlying light detecting elements 50.

It should also be noted that the light detecting element 50 may partially overlap with the light emitting element 30 in an x--y plane view as shown in Figure 11 or may be spaced entirely from the light emitting element 30 in an x-y plane view. In addition, the aperture A may partially overlap with the light emitting element 30 in an x-y plane view. The aperture A at least partially overlaps with the light detecting element 50 in an x-y plane view so as to allow light passing therethrough to reach the underlying light detecting element 50.

The mask M overlaps with a portion of at least one aperture A so as to allow lights 17-1, 17-2 to pass therethrough toward the underlying light detecting element 50 and prevent light 17-3 from passing therethrough. Although the mask M is formed in the first substrate layer 28 in Figure 10, the mask M may be formed in other layer (s) instead of or in addition to the first substrate layer 28.

According to this configuration, it is possible to reduce costs for forming apertures A1 on the reflecting electrode layer 36. Moreover, as it is not necessary to position the apertures A and the light detecting elements 50 under the light emitting elements 30, the degree of freedom in the arrangement of the light emitting element layer 22, the light emitting element control layer 24, and the light detecting element layer 40 is improved.

Fourth Embodiment

A fourth embodiment of the present invention is different from the first embodiment in that there is no aperture in the sensing device 1 and that the light detecting elements 50 have a portion which does not overlap with the light emitting elements 30 in an x-y plane view. Configurations other than those described below are the same as in the first embodiment.

Figure 12 shows a cross sectional view of the sensing device 1 according to the fourth embodiment of the present invention.

In Figure 12, no aperture is formed in any layers. As the reflecting electrode layer 36 of the light emitting elements 30 reflects light from the first surface 10a of the light emitter 10, the light detecting elements 50 are offset from the light emitting elements 30 in an x-y plane view. In other words, the light detecting elements 50 have a portion which does not overlap with the light emitting elements 30 in an x-y plane view. Although the light emitting element control layer 24 includes non-transparent elements such as thin film transistors (TFTs) and wirings, light can pass through the light emitting element control layer 24 at an area in which non-transparent elements are not provided. In this embodiment, the light shielding layer 26 serves as the mask M. For example, the light shielding layer 26 has a random pattern or a regular pattern (not shown) composed of non-transparent material. In Figure 12, light 17-1, 17-2 passes through the light emitting element control layer 24 and the light shielding layer 26 (the mask M) whereas light 17-3 is blocked by the mask M in the light shielding layer 26.

In other words, the light emitting element control layer 24 has a first portion which prevents light from passing therethrough and a second portion which allows light to pass therethrough, and the light shielding layer 26 also has a first portion which prevents light from passing therethrough and a second portion which allows light to pass therethrough. The second portion of the light emitting element control layer 24 at least partially overlaps with the second portion of the light shielding layer 26. Light entering the first surface 10a of the light emitter 10 passes through the cover layer 20, the light emitting element layer 22, the second portion of the light emitting element control layer 24, the second portion of the light shielding layer 26, the first substrate layer 28, and the interface 11, and finally reaches the light detecting element 50.

The mask M may be formed in one or more layer (s) other than the light shielding layer 26, and in that case, the light shielding layer 26 may be omitted. It should also be noted that the light detecting elements 50 may be spaced entirely from the light emitting elements 30 in an x-y plane view.

According to this configuration, it is possible to reduce costs for forming apertures A (A1 to A3) on the reflecting electrode layer 36, the light emitting element control layer 24, and the light shielding layer 26. Moreover, as it is not necessary to position the light detecting elements 50 under the light emitting elements 30, the degree of freedom in the arrangement of the light emitting element layer 22 and the light detecting element layer 40 is improved.

Although preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions, and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

A sensing device comprising:

a light emitter having a first surface and a second surface opposite to the first surface, the light emitter comprising a plurality of light emitting elements configured to emit light toward the first surface; and

a light detector opposed to the second surface of the light emitter, the light detector comprising a plurality of light detecting elements configured to convert light to an electric signal,

wherein the light emitter has a mask configured to absorb or reflect light such that intensity of light entering the first surface is modulated by the mask before the light impinges on the light detecting elements.
The sensing device according to claim 1, wherein the light emitter comprises a transparent layer configured to allow light to pass therethrough; and

wherein the transparent layer has a non-transparent portion made of a material which absorbs or reflect light, and the non-transparent portion serves as the mask.
The sensing device according to claim 1, wherein the light emitter comprises a non-transparent layer configured to absorb or reflect light; and

wherein the non-transparent layer has a transparent portion made of a material which allows light to pass therethrough and a non-transparent portion made of a material which absorbs or reflects light, and the non-transparent portion serves as the mask.
The sensing device according to claim 1, wherein the light emitter comprises a substrate layer, a light emitting element control layer having a plurality of light emitting element control circuits configured to control the plurality of light emitting elements, a light emitting element layer including the plurality of light emitting elements, and a cover layer covering the light emitting element layer; and

wherein the mask is formed in at least one of the substrate layer, the light emitting element control layer, the light emitting element layer, and the cover layer.
The sensing device according to claim 1, wherein the light emitter comprises a light emitting element control layer having a plurality of light emitting element control circuits configured to control the plurality of light emitting elements;

wherein the light emitting element control layer has circuit arrangement including the light emitting element control circuits and wirings; and

wherein at least a portion of the mask is formed by the circuit arrangement of the light emitting element control layer.
The sensing device according to claim 1, wherein the light emitter comprises a light shielding layer between the light emitting elements and the second surface, the light shielding layer having a non-transparent layer configured to absorb or reflect light and a transparent portion configured to allow light to pass therethrough; and

wherein the non-transparent portion of the light shielding layer serves as the mask.
The sensing device according to claim 1, wherein the light emitter comprises a touch sensor layer between the light emitting elements and the first surface; and

wherein the mask is formed in the touch sensor layer.
The sensing device according to claim 1, wherein the mask has a random pattern or a regular pattern.
The sensing device according to claim 1, wherein the mask has a pattern composed of a plurality of concentric circles.
The sensing device according to claim 1, wherein the mask has a pattern made of combination of square sub patterns composed of parallel lines.
The sensing device according to claim 1, wherein each of the light emitting elements has an aperture configured to allow light to pass therethrough; and

wherein one or more apertures are partially covered by the mask.
The sensing device according to claim 1, further comprising an image processor configured to process image data obtained from the electric signal output by the light detecting elements to reproduce an image.
The sensing device according to claim 1, wherein the light emitting elements are organic light emitting diodes.
The electronic device comprising display panel and the sensing device according to any one of claims 1 to 13, the display panel and the sensing device are stacked together.