Display device, method for operating a display device and method for manufacturing a display device

Abstract

A display device (1) comprises a substrate (10) with a main surface (12) and a plurality of emitters (20) arranged in pixels (2) on the main surface (12) of the substrate (10), each emitter (20) comprising a light-emitting diode (LED) configured to emit light during operation. It further comprises a sensor (30) in at least one pixel (2), the sensor (30) being configured to detect light during operation. It further comprises at least one evaluation circuit (40) configured to evaluate the proximity of an object (100) above the display device (1) based on the light detected by the sensor (30). A method for operating a display device (1) and a method for manufacturing a display device (1) are also described. The emitters and sensors can be configured as micro-LEDs.

Description

[0001] A display device, a method for operating a display device, and a method for manufacturing a display device are specified.

[0002] Displays, especially micro-LED displays, have many metal layers to fan out the driver signal to the emitters. They are therefore not very transparent, so behind-display sensor technologies cannot be used as they are with OLED displays, for example. A proximity sensor can be located outside the display, for example, at a notch.

[0003] At least one function of certain embodiments is to provide in-display sensors.

[0004] This problem is solved by the subject matter and the methods according to the independent claims. Advantageous embodiments and further developments of the subject matter and the methods are characterized in the dependent claims and are also disclosed by the following description and the drawings.

[0005] According to at least one embodiment, a display device is specified.

[0006] The display device includes a display. For example, the display device is a touchscreen, a smartwatch, a smartphone, a tablet, a dashboard, or an automotive instrument panel, or is integrated into one of these.

[0007] According to at least one embodiment, the display device comprises a substrate with a main surface.

[0008] The substrate can also be referred to as a support or backplane. For example, the substrate is designed as a silicon backplane or a flex plane. The substrate can be, for example, a film or comprise one. Thus, the substrate can be rigid or flexible. The substrate has a principal plane of extension. Here and in the following, lateral directions refer to directions parallel to the principal plane of extension. The vertical direction refers to a direction perpendicular to the principal plane of extension. The main surface of the substrate is parallel to the principal plane of extension.

[0009] According to at least one embodiment, the display device comprises a plurality of emitters arranged in pixels on the main surface of the substrate.

[0010] This can mean that the emitters are arranged in groups. The pixels can form rectangular or square areas on the main surface of the substrate, with these areas being adjacent to one another. The pixels form the display of the display device. Each pixel can include one or more emitters. Furthermore, each pixel can include wiring to electrically connect the emitters. The pixels and / or the emitters within the pixels can be operated individually or in groups. The fact that the emitters are arranged on the main surface of the substrate can mean that they are attached to the main surface. This can mean that they are not integrated or embedded in the substrate. For example, they are attached to the substrate by means of a transfer process, in particular a mass transfer process, whereby a plurality of emitters are attached to the substrate simultaneously.

[0011] According to at least one embodiment, each emitter comprises a light-emitting diode, LED, which is configured to emit light during operation.

[0012] Here and in the following, "light" can refer to electromagnetic radiation in general. Each emitter, for example, is configured to emit electromagnetic radiation in a principal emission direction during intended operation. The principal emission direction is preferably perpendicular to the main surface of the substrate. In particular, each emitter is configured to emit electromagnetic radiation with a principal wavelength in the spectral range visible to the human eye, i.e., between 380 nm and 750 nm. Different emitters can emit light in different wavelength ranges. Each pixel can comprise one or more emitters, i.e., one or more LEDs. Each pixel can comprise at least three LEDs (e.g., red, green, blue) to cover the visible wavelength range.Each pixel can also include more than three LEDs to provide a certain degree of redundancy and / or additional functionality.

[0013] According to at least one embodiment, the display device comprises a sensor in at least one pixel, wherein the sensor is configured to detect light during operation.

[0014] In other words, the display device includes at least one sensor. In other words, at least one pixel of the plurality of pixels in the display device includes a sensor. This can mean that the pixel includes only the sensor, or the sensor in addition to one or more emitters. In particular, the pixel includes the sensor and at least three emitters to cover the visible wavelength range. That the sensor is configured to detect light during operation can mean that the sensor is configured to detect ambient light and / or display light, for example, after reflection from an object. Display light refers to light emitted by the emitters of the display device. The sensor may be sensitive to a specific wavelength range in the visible spectrum. The sensor may have a viewing angle.In particular, the viewing angle includes the vertical direction, making the sensor an "upward-facing" sensor. The illumination field of the emitters and the field of view of the sensor can at least overlap. The display device can include more than one sensor, distributed across individual pixels of the display device. It is also possible for more than one sensor to be located within a single pixel. With two or more sensors in the display device, the sensors can be sensitive to light in different wavelength ranges.

[0015] According to at least one embodiment, the display device comprises at least one evaluation circuit. The evaluation circuit is configured to assess the proximity of an object above the display device based on the light detected by the sensor.

[0016] For example, the evaluation circuitry is integrated into the substrate. However, it is also possible for the evaluation circuitry to be located on the main surface of the substrate next to the pixels or within the pixels themselves. The evaluation circuitry can also be located on the opposite back side of the substrate and electrically connected to the pixels via through-substrate vias (TSVs). Furthermore, the evaluation circuitry can be located in or on another substrate. The presence of an object above the display device can mean that the object is positioned vertically above the display, particularly in the direction in which light is emitted by the emitters and in which the at least one sensor is facing. Thus, the ambient light to be detected by the sensor can be obscured by the object. Additionally, display light, i.e., light emitted by the emitters, can be reflected by the object.By evaluating the shaded ambient light and / or the reflected light, the proximity of an object above the display can be determined. The evaluation circuit is electrically connected to the sensor or sensors to evaluate the light intensity detected by the sensor(s). Additionally, the evaluation circuit can include circuits for driving and supplying voltage to the emitters. Thus, the evaluation circuit can include driver circuits for the emitters and be electrically connected to at least some of the emitters in the pixels. The display device can include more than one evaluation circuit. For example, each evaluation circuit is assigned to a group of pixels, e.g., a group of 16 x 16 pixels. The respective evaluation circuit can drive the emitters and evaluate signals from sensors in the specified group of pixels.

[0017] According to at least one embodiment, a display device comprises a substrate with a main surface and a plurality of emitters arranged in pixels on the main surface of the substrate, each emitter comprising a light-emitting diode (LED) configured to emit light during operation. The display device further comprises a sensor in at least one pixel, the sensor being configured to detect light during operation. The display device further comprises at least one evaluation circuit configured to assess the proximity of an object above the display device based on the light detected by the sensor.

[0018] The display device described here is based, among other things, on the following considerations.

[0019] Displays, especially micro-LED displays, have many metal layers to fan out the driver signal to the emitters. They are therefore not very transparent, and behind-display sensor technologies cannot be used as they are with OLED displays, for example. It is therefore advantageous to use an in-display sensor technology, where the sensor is embedded and integrated into the display in such a way that no display notch is required. In other words, by integrating the proximity sensor into the display, all notches are eliminated without the need for behind-display sensors.

[0020] The sensor can be embedded in the display. It detects objects near the display by sensing backscattered display light and / or ambient light. If multiple pixels comprise a single sensor, the display can be partially or completely equipped with these additional sensors.

[0021] The detection can be synchronized with the pulse-width modulation (PWM) of the LEDs, allowing differentiation between backscattered indicator light and ambient light. The difference signal between the two detection channels provides the contours of the objects.

[0022] This enables in-display depth and / or proximity sensing. Potential applications for in-display depth and / or proximity sensing include smart surfaces, hover detection, predictive touch detection, and distance measurement.

[0023] According to at least one embodiment, each emitter is formed by a micro-LED.

[0024] Broadly speaking, a micro-LED could be any light-emitting diode (LED) – generally not a laser – with a particularly small size. Typically – and this is a very important criterion besides size – micro-LEDs are built up using a substrate, so typical heights of such micro-LEDs range from 0.5 µm to 10 µm. A micro-LED does not necessarily have to have a rectangular emission surface. For example, an LED could have an emission surface where, when viewed from above, each lateral dimension of the emission surface is less than or equal to 100 µm or less than or equal to 70 µm. For rectangular micro-LEDs, for instance, an edge length – particularly when viewed from above – of less than or equal to 70 µm or less than or equal to 50 µm is often cited as a criterion.Most micro-LEDs are mounted on wafers with non-destructively removable mounting structures. Currently, micro-LEDs are primarily used in displays. They form pixels or subpixels and emit light of a defined color. Due to their small pixel size and high density with close spacing, micro-LEDs are suitable for applications such as small monolithic displays for AR (Augmented Reality) applications, particularly smart glasses. Further applications are also being developed, especially for data communication and pixelated lighting. Various notations for micro-LED can be found in the relevant literature, such as µLED, µ-LED, uLED, u-LED, or micro-light-emitting diode.

[0025] According to at least one embodiment, the pixels are designed as RGB pixels in which a first emitter configured to emit red light, a second emitter configured to emit green light, and a third emitter configured to emit blue light are arranged.

[0026] In particular, each emitter is designed to emit radiation of a different principal wavelength. A principal wavelength is defined as a wavelength in an emission spectrum at which the intensity reaches a global maximum. For example, a first emitter is designed to emit red radiation during operation, a second emitter to emit green radiation during operation, and a third emitter to emit blue radiation during operation. Such an arrangement of red, green, and blue (RGB arrangement) is particularly suitable for a pixel in a display device. Red light, for example, can refer to light in a wavelength range of 640 nm to 780 nm. Green light, for example, can refer to light in a wavelength range of 490 nm to 570 nm.Blue light can refer to light in a wavelength range of 430 nm to 490 nm. Thus, the entire visible spectrum is covered by additive color mixing of the three components red, green, and blue. As mentioned above, the emitters can be formed by individual LEDs, particularly micro-LEDs. Depending on the light color, the LEDs can comprise different semiconductor materials, such as gallium arsenide (GaAs), gallium arsenide phosphide (GaAsP), gallium phosphide (GaP), aluminum indium gallium phosphide (AlInGaP), indium gallium nitrogen (InGaN), and / or gallium nitride (GaN). In one possible embodiment, each pixel is configured as an RGB pixel, comprising a red light emitter, a green light emitter, and a blue light emitter. The pixel can also include more than one emitter for each color, for example, to provide a degree of redundancy.

[0027] According to at least one embodiment, the sensor is designed as a photodiode, wherein the photodiode is embedded in the substrate.

[0028] This can mean that the photodiode (PD) is integrated into and / or formed within the substrate. Thus, the photodiode is an embedded photodiode. Specifically, if the substrate comprises silicon, the photodiode can be a silicon photodiode, but other materials are also possible. For efficiency reasons, the silicon photodiode can be larger and thicker than the emitters in later directions. Silicon photodiodes are suitable for detecting visible light. The substrate on which the emitters are arranged thus has additional sensor functions. The emitters can be located on areas of the substrate outside the photodiode(s).

[0029] Alternatively, the photodiode is arranged on the main surface of the substrate next to the emitters.

[0030] Such a photodiode can form a separate detector chip. In particular, the photodiode can be a micro-PD. This can mean that the photodiode is similar in size to each of the emitters, especially if these are designed as micro-LEDs. It is also possible that the photodiode is larger for efficiency reasons. If the photodiode is mounted on the substrate, its thickness can preferably be similar to or equal to the thickness of the emitters. Mounting the photodiode on the substrate can mean that it is attached to the substrate, for example, by a (mass) transfer process. Mounting the photodiode next to the emitters can mean that the photodiode and the emitters are arranged in a common pixel.

[0031] According to at least one embodiment, the sensor is designed as an LED, in particular as a micro-LED, which is arranged on the main surface of the substrate next to the emitters and is configured to be supplied with voltage for the detection of a photocurrent.

[0032] The fact that the sensor is implemented as a (micro)LED can mean that the sensor and the emitter have the same or a similar structure. In particular, the sensor and emitter may be formed by a common stack of semiconductor layers. Designed as an LED, the sensor can emit light when it is supplied with a voltage, especially when the sensor is forward-biased. However, when the sensor is not energized or is reverse-biased, it is configured to detect a photocurrent depending on the light incident on the sensor. The external quantum efficiency (EQE) of red, green, and blue light-emitting micro-LEDs has been found to reach values ​​above 20% in reverse bias or without voltage, depending on the wavelength to be detected.The red, green / blue light-emitting micro-LEDs used in combination as sensors cover the entire visible spectrum. In other words, the EQE curves of the blue or green and the red micro-LEDs match and cover the visible wavelength range. This allows additional red or blue / green micro-LEDs to be placed in some or all pixels for detection. As mentioned above, the pixels can already include additional (micro-)LEDs for redundancy. These additional emitters could be used as sensors, thus reducing the complexity of the manufacturing process. The (micro-)LEDs can be powered and energized depending on whether they are used as emitters or as sensors. Dynamic use as both emitters and sensors is also possible. This means that an emitter can be used as a sensor by dynamically changing its electrical voltage, for example.By integrating a multiplexer into the drive circuit. Supplying LEDs with voltage to detect a photocurrent represents a simple and cost-effective solution for providing detection functions to a display device.

[0033] According to at least one embodiment, the emitter and the sensor are manufactured using a common manufacturing process.

[0034] This can mean that at least some process steps for manufacturing the emitters can also be used for manufacturing the sensor. This is especially true if both the emitters and the sensor are designed as (micro)LEDs. Thus, the emitters and the sensor can be manufactured on a common substrate and simultaneously transferred to the substrate of the display device. This simplifies the manufacturing of the display device and reduces costs. It is also possible to transfer all display LEDs with double the density for redundancy, avoiding the need to repair defective LEDs. LEDs that are not used for light emission but are still functional can be used for sensing. This would mean that the sensor has less than 100% coverage but could still offer satisfactory functionality.

[0035] According to at least one embodiment, the display device comprises a plurality of sensors configured to detect light during operation, the sensors being distributed across the display in respective pixels of the display device.

[0036] All features disclosed for the sensor are also disclosed for the plurality of sensors. The sensor mentioned above can be one of the plurality of sensors. In one possible embodiment, each pixel includes at least one sensor. However, it is also possible that only a subset of pixels includes at least one sensor. For example, every second or every third pixel includes a sensor. Preferably, the sensors are evenly distributed. The plurality of sensors arranged in respective pixels form a distributed proximity sensor, which has more redundancy than a local sensor (e.g., at a notch of the display or a special area behind the display). It is also less sensitive to interference, such as hair, dirt, or dust obscuring the sensor.By integrating the proximity sensor into the display, all notches are eliminated without the need for the sensor to be located behind the display, as is the case with behind-OLED sensors. Because the sensors are distributed across the display, the distributed proximity sensor has a 2D spatial resolution.

[0037] According to at least one embodiment, the viewing angle of at least one sensor differs from the viewing angle of at least one other sensor within the display device.

[0038] This can mean that the fields of view of the individual sensors may differ. However, the fields of view can overlap. For example, some sensors are configured to detect light from a first direction, while others are configured to detect light from a second direction, with the first and second directions being different. The first and second directions may, however, share a common directional component. Different viewing angles may be implemented to provide additional spatial information.

[0039] According to at least one embodiment, the display device further comprises an aperture and / or a light barrier and / or a microlens, which are assigned to a respective sensor, wherein the aperture, the light barrier and the microlens are configured to define the viewing angle of the respective sensor.

[0040] Multiple light barriers, apertures, and / or microlenses can be incorporated. Each aperture, light barrier, or microlens can be assigned to a specific sensor or set of multiple sensors. For example, the aperture and / or light barrier may comprise an opaque material such as a metal layer or an opaque plastic. The aperture and / or light barrier can prevent light from reaching the sensor from an unwanted direction. For example, the aperture may be positioned vertically above the sensor, allowing only light from a vertical direction to reach the sensor. The light barrier may be positioned offset above the sensor or on a lateral side of the sensor, blocking light coming from that side. The microlens may be positioned centrally above the sensor or offset laterally. This allows light from different directions to be focused onto the sensor surface.The microlens can be part of a microlens array. For example, the microlens array is formed by wafer-level optics (WLO). Using the aperture, light barrier, and microlens, the sensors can have different viewing angles. These different viewing angles can be implemented to capture additional spatial information. Shielding elements such as apertures and light barriers enable 2D spatial resolution of the sensor. Furthermore, with micro-optical elements like microlenses, it is possible to resolve depth information. With such a 3D in-display full-area proximity sensor, hover detection is also possible, enabling predictive touch. Predictive touch means detecting a nearby object before actual contact, which is a beneficial feature for touch surfaces.

[0041] According to at least one embodiment, the display device further comprises a transparent cover that covers the pixels.

[0042] The cover is transparent to visible light. For example, the cover may be made of glass or a transparent plastic material. The cover can be positioned directly over the emitters and the sensor(s). Alternatively, the cover may be positioned at a distance from the emitters and the sensor(s). The cover protects the emitter and the sensor(s). Furthermore, the cover may offer additional functionality, such as a touchscreen.

[0043] According to at least one embodiment, the light barrier and / or the aperture and / or the microlens are structured on the cover.

[0044] This can mean that the light barrier and / or the aperture and / or the microlens are attached to or mounted on the cover. It is also possible that these components are integrally formed with the cover. In particular, the microlenses can be monolithically integrated into the cover. This makes it possible to align the light barrier and / or the aperture and / or the microlens with the respective sensor on or in the substrate.

[0045] According to at least one embodiment, the light barrier is designed as a wall that is attached to the substrate next to the respective sensor.

[0046] As mentioned above, the light barrier can be positioned on a lateral side of the sensor, blocking light coming from that side. The barrier can be attached to the substrate or be integral to it. Attaching the barrier to the substrate facilitates alignment with the sensor.

[0047] According to at least one embodiment, the evaluation circuit is configured to generate a first detection signal using the ambient light detected by the sensor, which is shaded by the object.

[0048] Alternatively or additionally, the evaluation circuit is set up to generate a second detection signal using the light detected by the sensor, which is emitted by the emitter and reflected by the object.

[0049] The first and second detection signals can be signals corresponding to the intensity of the detected light. As mentioned above, the sensor can be configured to detect ambient light. When an object appears or moves above the display, the ambient light is shaded by the object, reducing the light intensity. In this way, a shadow image can be generated. Furthermore, the sensor can be configured to detect light emitted by the emitters and reflected by an object above the display. The closer an object is, the higher the intensity of the backscattered display light. Thus, an image of the backscattered display light can be generated. The evaluation circuit uses the readings from one or more sensors to determine that an object is above the display.By analyzing changes in the size and shape of the generated images, as well as the intensity of the captured light, the distance of the object to the display can also be determined. Furthermore, it is possible to detect movement of the object, such as a user's finger. Thus, the first and second detection signals can be used to recognize proximity, depth, and gestures.

[0050] According to at least one embodiment, the evaluation circuit is configured to calculate a difference signal from the first detection signal and the second detection signal.

[0051] A difference signal between the shadow image from the ambient light and the backscattered indicator light results in a high contrast of the object edges (differential lock-in detection). For example, the indicator light backscattered by a fingertip and the ambient light shadowed by the fingertip are used for finger tracking detection.

[0052] This enables hover detection. Hover detection means detecting an object at a distance of 1 to approximately 20 mm from the display (without touching the display). Tracking hover movements can be used for "mouseover" effects and other display user interactions where aiming without action is essential (anticipatory touch). Prior art hover detection is possible with a stylus connected to the display via electrical feedback. The present disclosure enables hover detection of one or more fingertips, as the display device allows high-resolution 3D near-field scanning to track the finger on the display. To detect the object's distance from the display, the sensors can be equipped with micro-optics (as mentioned above) to obtain left- and right-facing images and calculate the distance from the image displacement.Relative distance changes during continuous tracking can also be derived from changes in shape size and intensity in the backscattered indicator light.

[0053] Furthermore, a method for operating a display device is specified. The operating method can preferably be carried out using the display device described above. This means that all features disclosed for the display device are also disclosed for the method of operating the display device, and vice versa.

[0054] According to at least one embodiment, the method for operating the display device is carried out with a display device comprising a plurality of emitters arranged in pixels on a main surface of a substrate, a sensor in at least one pixel and at least one evaluation circuit.

[0055] According to at least one embodiment, the method comprises emitting light by the emitters, each emitter comprising a light-emitting diode (LED). In particular, light is emitted by the emitters in a principal direction perpendicular to the main surface of the substrate. Each emitter / LED has an illumination field.

[0056] According to at least one embodiment, the method comprises the detection of light by the sensor. The detected light can be ambient light and / or light emitted by the emitters that is reflected by an object above the display device. Preferably, the emitters and the sensor are arranged such that the display light does not reach the sensor directly, but only via reflection from an object. For example, light barriers are arranged between the emitters and the sensor and / or the sensor is located outside the illumination field of the emitters.

[0057] According to at least one embodiment, the method comprises evaluating the proximity of an object above the display device using the evaluation circuitry based on the detected light. The proximity of the object can be determined by the ambient light detected by the sensor, which is shaded by the object. It is also possible for the proximity of the object to be determined by backscattered display light, i.e., light emitted by the emitters and reflected by the object.

[0058] According to at least one embodiment, the method for operating a display device, wherein the display device comprises a plurality of emitters arranged in pixels on a main surface of a substrate, a sensor in at least one pixel, and at least one evaluation circuit, comprises the emission of light by the emitters, each emitter comprising a light-emitting diode (LED). It further comprises the detection of light by the sensor. It further comprises the evaluation circuit assessing the proximity of an object above the display device based on the detected light.

[0059] This enables in-display proximity detection. The sensor is embedded in the display. It detects objects near the display by sensing backscattered display light and / or ambient light. This allows for in-display depth and / or proximity sensing. If multiple pixels encompass a single sensor, the display can be partially or fully equipped with these additional sensors, providing a specific spatial resolution. Potential applications for in-display depth and / or proximity detection include smart surfaces, fingerprint recognition, hover detection, and distance measurement.

[0060] According to at least one embodiment, the method further comprises adjusting the brightness of the emitted light by pulse width modulation.

[0061] Pulse-width modulation (PWM) for LEDs is a technique used to control the brightness of an LED by varying the duration of a pulsed electrical signal. With PWM, the LED is rapidly switched on and off at a fixed frequency, and the average light intensity perceived by the human eye depends on the ratio of the time the LED is on (on state) to the time it is off (off state) during each cycle. PWM is an efficient and effective method for controlling LED brightness without altering the LED's forward current.

[0062] According to at least one embodiment, light detection includes detecting ambient light when the emitters are in a switched-off state during pulse width modulation, and / or detecting reflected light when the emitters are in a switched-on state during pulse width modulation.

[0063] This allows the detection to be synchronized with the pulse-width modulation of the LEDs, enabling differentiation between backscattered indicator light and ambient light. Furthermore, the differential signal from both detection channels provides contours of the objects.

[0064] According to at least one embodiment, light detection is performed continuously during pulse width modulation, and the detected light is evaluated by filtering a detection signal in the frequency domain.

[0065] This can mean that both the indicator light and ambient light are detected throughout the entire PWM cycle, i.e., during the on and off states of the LEDs. Thus, the detection signal contains information about the ambient light and the backscattered indicator light. By knowing the PWM frequency of the PWM post-processing, it is possible to distinguish between the two channels.

[0066] According to at least one embodiment, the method further comprises evaluating a distance between the object and the display device, wherein the distance is determined by evaluating an intensity of the reflected light and / or by evaluating an image displacement detected by at least two groups of sensors with different viewing angles, and / or by evaluating a change in the shape size of an image detected by a plurality of sensors.

[0067] The object's distance can be measured from the main surface of the substrate, the emitting surfaces of the emitters, the sensor's detection surface, or the display cover. The object's distance from the display can be determined by evaluating the intensity of reflected light. The closer the object is to the display, the higher the intensity of the backscattered display light. In particular, relative distance changes during continuous tracking can be derived from changes in the intensity of the backscattered display light. Additionally or alternatively, the object's distance from the display can be determined by evaluating the image shift detected by at least two sets of sensors with different viewing angles. As mentioned above, the viewing angle of the sensors can be modified by apertures, light barriers, and / or microlenses.For example, left- and right-facing sensors can be implemented. Right- and left-facing pixels can be evenly distributed across the entire display, resulting in a left- and right-facing image sensor. These left- and right-facing image sensors see shifted shadow images of nearby objects (ambient light being shaded by the object). The shift of the images depends on the object's distance. By analyzing the two images, distance information can be extracted. This method is perhaps similar to phase-detection autofocus in cameras. Additionally or alternatively, relative distance changes in continuous tracking can also be derived from changes in the shape size of an image captured by multiple sensors.

[0068] Furthermore, a method for manufacturing a display device is specified. All features disclosed for the display device are also disclosed for the method for manufacturing the display device, and vice versa.

[0069] The method for manufacturing the display device includes providing a substrate. The substrate is, for example, a backplane or a flex-plane, or is formed from one.

[0070] The method for manufacturing the display device further comprises depositing a plurality of emitters onto a major surface of the substrate, wherein the emitters are arranged in pixels and each emitter comprises a light-emitting diode, LED, configured to emit light during operation. In particular, the emitters are formed by micro-LEDs, and the depositing of the emitters onto the substrate comprises a mass transfer of the emitters from a support substrate to the substrate of the display device. For example, an elastomeric stamp is used for the mass transfer.

[0071] The method for manufacturing the display device further comprises forming a sensor in at least one pixel, wherein the sensor is configured to detect light during operation.

[0072] Forming the sensor can involve embedding a photodiode in the substrate. This might mean, for example, that the substrate is a semiconductor substrate and the photodiode is formed within the substrate through a semiconductor fabrication process, such as a CMOS process. Thus, the photodiode is integrated into the substrate. Alternatively, forming the sensor can involve attaching a photodiode to the main surface of the substrate alongside the emitters. This might mean that the photodiode forms a single detector chip that is transferred to and attached to the substrate. For example, the photodiode could be a micro-photodiode and would be transferred to the substrate in a similar manner to the emitters, particularly by means of a further mass transfer.As another alternative, the sensor design can involve attaching an LED to the main surface of the substrate next to the emitters and supplying this LED with voltage to detect a photocurrent. This "sensor LED" can have a similar or identical structure to the "emitter LEDs." Thus, the sensor and emitters can be formed through a single fabrication process and simultaneously transferred to the substrate. The sensor and emitters can differ only in how they are supplied with voltage. For example, the sensor could be a (micro)LED operated in reverse bias or not supplied with any voltage at all.

[0073] The method for manufacturing the display device further comprises providing at least one evaluation circuit configured to assess the proximity of an object above the display device based on the light detected by the sensor. The evaluation circuit can be integrated into the substrate. It can be an integrated circuit (IC) and provide additional functions. Alternatively, the evaluation circuit can be attached to the substrate. In this case, the evaluation circuit can be implemented as a micro-IC, i.e., an integrated circuit that can be detached and transferred as a silicon wafer with a high density of integrated circuits. The evaluation circuit can also be attached to a separate substrate and connected to the pixels via electrical connections, such as a flexible connection.

[0074] The following description of the figures can further illustrate and explain aspects of the display device, the operating procedure, and the manufacturing process. Components and parts of the display device that are functionally identical or have the same effect are designated with the same reference numerals. Identical or substantially identical components and parts may only be described with reference to the figures in which they first appear. Their description is not necessarily repeated in subsequent figures. Fig. Figures 1a to 1c show different examples of the integration of sensors into a display device. Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8 to Fig. Figure 9 shows display devices according to embodiments of the present invention. Fig. 10, Fig. 11, Fig. 12, Fig. 13 to Fig. Figure 14 shows methods for operating a display device according to embodiments of the present invention. Fig. Figure 15 shows the external quantum efficiency of micro-LEDs when they are supplied with voltage to detect a photocurrent.

[0075] In the Fig. Figures 1a to 1c show different examples of the integration of sensors 30 into a display device 1. The sensor 30 can be a proximity sensor or the like. Fig. Figure 1a shows a display device 1 in a top view. The display device 1 comprises a display area. A sensor 30 is located outside the display area at a notch of the display. The disadvantages of such a display device 1 are that the display area is reduced in size and that the sensor 30 is not a distributed sensor 30, but a single sensor which is susceptible to interference. For example, the sensor 30 could be obscured by hair, dust, or other dirt.

[0076] Fig. Figure 1b shows another example of a display device 1 with a sensor 30. In this example, the sensor 30 is located behind the display area, which is possible if the display device 1 is or includes a transparent display such as an OLED display. However, even in this case, the sensor 30 is limited to a relatively small sensor area behind the display.

[0077] Fig. Figure 1c shows an embodiment of the present invention. The display device 1 comprises a substrate 10 with a main surface 12 (shown in the figures). Fig. 5a and Fig. 5b). A plurality of emitters 20 are arranged in pixels 2 on the main surface 12 of the substrate 10, each emitter 20 comprising a light-emitting diode, LED, configured to emit light during operation (see following figures). Furthermore, a sensor 30 is integrated into at least one of the pixels 2, the sensor 30 being configured to detect light during operation (see following figures). The display device further comprises at least one evaluation circuit 40 (shown in the Fig. 5a and Fig. 5b), wherein the evaluation circuit is set up to determine the proximity of an object 100 based on the light detected by sensor 30 (see e.g. Fig. 12 and Fig. 13) to be evaluated via the display device 1.

[0078] For example, each pixel 2, or at least a subset of the majority of pixels 2, comprises a respective sensor 30. Thus, the sensor area can be large, forming a distributed proximity sensor 30. A distributed proximity sensor has more redundancy than a local sensor and is less susceptible to interference. By integrating the proximity sensor 30 into the display, all notches are removed from the display without requiring the sensor to be positioned behind the display, as is the case, for example, with behind-OLED sensors. The display does not need to be transparent.

[0079] The Fig. 2a and Fig. Figure 2b shows different embodiments of a respective pixel 2 within the display device 1. According to the Fig. 2a and Fig. In 2b, pixel 2 is configured as an RGB pixel 2, in which a first emitter 20-1, configured to emit red light, a second emitter 20-2, configured to emit green light, and a third emitter 30-3, configured to emit blue light, are arranged. The emitters 20 are configured as LEDs, specifically micro-LEDs. The emitters 20 are arranged along a diagonal of pixel 2. However, other arrangements are also possible. Furthermore, pixel 2 comprises Fig. 2a and Fig. 2b each has a sensor 30 arranged along the diagonal of the emitters 20. The sensor 30-1 of pixel 2 according to Fig. 2a is formed by an LED, in particular a micro-LED, which, when operated in the forward direction, can emit blue or green light. However, this LED is configured to be energized for the detection of a photocurrent. That is, this LED is configured to be operated in the reverse direction or without voltage. It has been found that blue or green micro-LEDs operated in the reverse direction can generate a photocurrent with an external quantum efficiency of about 20% or more in a wavelength range between 350 nm and 500 nm. The sensor 30-2 of pixel 2 according to Fig. 2b is formed by an LED, in particular a micro-LED, which, when operated in the forward direction, can emit red light. However, the LED is configured to be energized to detect a photocurrent. That is, the LED is configured to be operated in reverse bias or without voltage. It has been found that red micro-LEDs operated in reverse bias can generate a photocurrent with an external quantum efficiency of about 20% or more in a wavelength range between 500 nm and 650 nm. Thus, the visible wavelength range is covered for red and blue / green light by (micro-)LEDs operated in reverse bias or without voltage.The display device 1 can comprise different subgroups of pixels 2, wherein pixels 2 of a first subgroup include a blue / green LED used as a sensor 30, and pixels 2 of a second subgroup include a red LED used as a sensor 30. It is also possible for blue / green LEDs and red LEDs used as sensors 30 to be configured in the same pixel 2. Since both the emitters 20 and the sensors 30 are implemented as (micro)LEDs, they can be manufactured using a common fabrication process.

[0080] Fig. Figure 3 shows another embodiment of pixels 2 in a display device 1. As in the embodiment of Fig. 2a and Fig. 2b, the pixels 2 are configured as RGB pixels 2. The pixels 2 are arranged side by side. The embodiment according to Fig. 3 differs from the embodiments according to the Fig. 2a and Fig. 2b by the fact that the sensor 30 is configured as a photodiode, in particular as a micro-photodiode. The sensors 30 can be discrete micro-photodiodes, which, similar to the emitters 20, are fabricated for mass transfer onto a display backplane or flex-plane. This means that the sensors are arranged on a main surface of a substrate 1, on which the emitters 20 are also arranged.

[0081] Fig. Figure 4 shows an embodiment of pixels 2 in a display device 1 similar to that shown in Fig. 3. Here, the sensor 30 is designed as a photodiode embedded in the substrate 10, on which the emitters 20 are arranged. With silicon backplanes as the substrate, the sensors can be embedded directly in the backplane, including the readout IC. The micro-photodiodes can be silicon-based, but other materials are also possible. The size of the photodiode sensors 30 can be similar to the size of the emitters 20, as shown in the Fig. 3 and Fig. 4 shown.

[0082] In the Fig. 5a and Fig. Figure 5b shows further embodiments of the display device 1. The display device 1 comprises the substrate 10. The emitters 20 and the sensor 30 are arranged on the main surface 12 of the substrate 10. For example, the Fig. 5a and Fig. 5b respective cross-sections of a pixel 2, such as pixel 2 from Fig. 2. In the display devices 1 of the Fig. 5a and Fig. In 5b, the evaluation circuit 40 is integrated into the substrate 10. However, it is also possible that the evaluation circuit 40 is arranged in or on a separate carrier that is electrically connected to the pixels 2 of the display device 1. The display device 1 of the Fig. 5a and Fig. 5b further comprises a transparent cover 60. The cover is arranged vertically over the main surface 12 of the substrate 10, so that the emitter 20 and the sensor 30 are covered. Fig. Figure 5a shows a light barrier 52 on a left lateral side of the sensor 30, while Fig. 5b shows a corresponding light barrier 52 on a right lateral side of the sensor 30. The light barrier 52 is configured to define a viewing angle of the respective sensor 30. Thus, the light barrier 52 defines in Fig. 5a a right-facing viewing angle R of the sensor 30, while the light barrier 52 in Fig. 5b defines a left-facing viewing angle L of the sensor 30. The light barriers 52 are designed as opaque walls that are attached to the substrate 10 next to the respective sensor 30. They can also be attached to the cover 60. The display device 1 can comprise different groups of pixels 2, wherein pixel 2 of a first group comprises a sensor 30 with a right-facing viewing angle R and pixel 2 of a second group comprises a sensor 30 with a left-facing viewing angle L. It is also possible for sensors with left- and right-facing viewing angles L, R to be arranged in a common pixel 2. Thus, the viewing angle of at least one sensor 30 differs from the viewing angle of at least another sensor 30 within the display device 1.In this context, the terms "right" and "left" are to be understood only as directional indications in a specific orientation of the display device 1. The directions can be reversed or changed to "up" and "down" if the display device 1 is rotated.

[0083] Fig. Figure 6 shows a display device 1, which is located in Fig. The diagram shown is similar to the one in Figure 5. Substrate 10 and evaluation circuit 40 have been omitted for clarity. Fig. In Figure 6, the light barrier 52 is designed as an opaque layer structured on the cover 60 on a side of the cover 60 facing the sensor 30. The light barrier 52 covers part of the sensor 30. As in the example of Fig. As shown in Figure 6, the light barrier 52 can cover a right sensor area of ​​the sensor 30, thus defining a left-facing viewing angle L. Similarly, a right-facing viewing angle R can be defined by covering a left sensor area.

[0084] Fig. Figure 7 shows a similar display device 1 as Fig. 6. Here, the light barrier forms an aperture 50, which is structured on the cover 60. The aperture 50 blocks light coming from lateral directions, thus defining a forward-facing viewing angle C of the sensor 30. Therefore, with blocking structures such as light barriers 52 and apertures 50, the sensitivity of the sensors 30 can be directed in specific directions to enable spatial tracking of nearby objects 100.

[0085] In the examples of Fig. In Figures 8a to 8c, different viewing angles L, R, C of the sensors 30 are defined by means of microlenses 54 located on or integrated into the cover 60. That is, each sensor 30 is assigned a microlens 54, with the microlens 54 being aligned laterally with the sensor 30. The microlens 54 can be positioned centrally above the sensor 30 to define a forward-facing viewing angle C (see Figure 8a to 8c). Fig. 8a). The microlens 54 can also be positioned offset above the sensor 30 to define a left or right viewing angle L, R ( Fig. 8b and Fig. 8c). Microlenses 54 in the cover 60 can be configured as wafer-level optics.

[0086] By means of the aforementioned optical elements 50, 52, 54, the display device 1 can comprise an array of pixels 2, wherein, for example, every second pixel 2 comprises a left-facing sensor 30 and every other pixel 2 comprises a right-facing sensor 30 to form a checkerboard pattern, as in Fig. 9 shown. However, it is also possible that the Pixel 2 will include a forward- or upward-facing sensor 30.

[0087] A display device 1 as shown above can be operated as follows: Light is emitted by the emitters 20. Light is also detected by the sensor 30. The detected light can be ambient light and / or backscattered display light. Furthermore, the proximity of an object 100 above the display device 1 can be evaluated based on the detected light.

[0088] Fig. Figure 10 shows an exemplary operating procedure for evaluating the distance of an object 100, particularly when a plurality of right- and left-facing pixels 2 are evenly distributed across the entire display, resulting in a right- and left-facing image sensor. If an object 100 is located above the display device 1, the ambient light is shaded by the object 100. Thus, the image sensor can generate a shadow image Im. Using the left-facing sensors 30 (left-facing viewing angle), a first instance Im L of the image and by means of the right-facing sensors 30 (right-facing viewing angle) a second instance In R of the image. Between the first instance In L and the second instance R The image has a displacement Δs which depends on the distance of the object 100 to the display device, for example the display cover 60. Fig. Figure 10 shows a situation for three different distances d1 to d3 of an object 100. At a distance d3 (large distance) there is an image shift +Δs between the first instance In L and the second instance R At a distance d2 (medium distance), the image shift vanishes. At a distance d1 (small distance), there is an image shift -Δs between the first instance and the second instance. L and the second instance R By analyzing the two images, distance information can be extracted. Therefore, it is possible to equip the individual sensors 30 with micro-optical elements that divide the majority of sensors 30 into left-facing and right-facing elements. The image shift Δs detected between the right-facing and left-facing images can then be used to determine the distance of the object 100. This method is similar to phase autofocus in cameras.

[0089] The brightness of the light emitted by the emitters 20 can be adjusted by pulse width modulation, PWM, as shown in Fig. Figure 11 shows that the brightness can be adjusted separately for each of the emitters 20, in particular for the red LED 20-1, the green LED 20-2, and the blue LED 20-3. However, the on and off states of the LEDs can be synchronized so that there is a common on phase and a common off phase. In other words, a PWM frequency f can be the same for all emitters 20, as shown in Fig. Figure 11 illustrates this. To detect the indicator light backscattered from a nearby object 100, detection is set to a window TD in the PWM cycle when the indicator is on. To detect ambient light passing around the object 100 near the indicator, detection is set to time frames TA when the indicator is off. The indicator's on states are defined by the pulse-width modulation frequency and the on-time. The presence of a dedicated indicator light detection window TD and a dedicated ambient light detection window TA may refer to a PWM lock-in detection mode of the indicator device 1. Alternatively, light detection is performed continuously during pulse-width modulation, and the detected light is evaluated by filtering a detection signal in the frequency domain. In this way, the detected ambient light and the detected indicator light can be distinguished.

[0090] In the Fig. 12 and Fig. Figure 13 shows the detection of ambient light and the detection of display light. An object 100 is located above the display device 1, of which only the cover 60 is shown. On the left side of Fig. At position 12, the display device 1 is in a mode where ambient light AL is detected, i.e., the display light is switched off. The object 100 casts a shadow on the ambient light 100, so that a shadow image SH is generated by the sensors 30. In other words, the sensors 30 detect a decrease in intensity due to the shadowing of the ambient light AL by the object 100. A first detection signal from the evaluation circuit 40, which uses the sensor data, in turn indicates that the object 100 is near the display device 1. On the right side of Fig. In the 12th stage, the display device 1 is in a mode in which the backscattered display light DL is detected. The closer the object 100 is, the higher the intensity of the backscattered display light DL. A second detection signal from the evaluation circuit 40 again indicates that the object 100 is near the display device 1. The object 100 could, for example, be a user's hand or finger at a distance d from the display device, as shown in Fig. 13 shown.

[0091] The evaluation circuit 40 may calculate a difference signal from the first detection signal and the second detection signal, resulting in a high contrast of the edges of object 100. Such differential lock-in detection is used in Fig. 14 shown. Fig. 14a shows a shadow image SH, which is the fingertip in Fig. 13 can correspond to this. Fig. Figure 14b shows an image of the backscattered indicator light DL that reaches the fingertip in Fig. 13 can correspond to this. Fig. Figure 14c shows a difference image revealing the contours of the fingertip. By capturing the backscattered display light and the shadowed ambient light, it is therefore possible to detect a fingertip located close to (1 mm to 20 mm) the display area. This enables so-called hover detection, which is a contactless finger tracking of one or more fingers.

[0092] In addition to evaluating the distance of object 100 by evaluating the intensity of the detected indicator light reflected by object 100 (as in the Fig. 12 and Fig. 13), or by evaluating an image shift produced by at least two groups of sensors 30 with different viewing angles L, R, C (as in Fig. 10) is recorded, relative distance changes during continuous tracking can also be derived from the evaluation of a change in shape size of the image recorded by a plurality of sensors 30.

[0093] As mentioned above, the at least one sensor (30) can be implemented as an LED, in particular as a micro-LED, which is supplied with voltage to detect a photocurrent. It has been found that the external quantum efficiency, EQE, of red, green, and blue light-emitting micro-LEDs operated in reverse bias or without voltage reaches values ​​above 20%, depending on the wavelength to be detected. This is in Fig.Figure 15 shows the external quantum efficiency of micro-LEDs as a function of wavelength λ. It can be seen that the blue (B) and green (G) micro-LEDs cover a wavelength range of about 350 nm to 500 nm, while red (R) micro-LEDs cover the wavelength range of about 450 nm to 650 nm. Thus, the display device 1 can use both red and blue / green micro-LEDs as sensors 30 to cover the entire visible spectrum. The embodiments of the display device and the methods for operating and manufacturing the display device disclosed herein have been explained to familiarize the reader with new aspects of the idea. Although preferred embodiments have been shown and described, many changes, modifications, equivalents, and substitutions of the disclosed concepts can be made by a person skilled in the art without unnecessarily deviating from the scope of the claims.

[0094] It is understood that the disclosure is not limited to the disclosed embodiments and to what has been specifically shown and described above. Rather, features listed in separate dependent claims or in the description may be advantageously combined. Furthermore, the scope of the disclosure includes such variations and modifications as are obvious to a person skilled in the art and fall within the scope of the appended claims.

[0095] The term "comprehensive," as used in the claims or description, does not exclude other elements or steps of a corresponding feature or method. Where the terms "a" or "an" are used in conjunction with features, they do not exclude multiple such features. Furthermore, any reference numerals in the claims should not be interpreted as limiting the scope.

[0096] This patent application claims priority over German patent application 102023125786.2, the disclosure content of which is hereby incorporated by reference. Reference symbol list 1 Display device 2 pixels 10 substrate 12 main area 20 emitters 20-1 first emitter 20-2 second emitter 20-3 third emitter 30 Sensor 30-1 Sensor 30-2 Sensor 40 Evaluation circuit 50 aperture 52 Light barrier 54 microlens 60 Coverage 100 objects AL Ambient light DL indicator light d1-d3 distance L, R, C viewing angle SH silhouette TD indicator light detection window TA ambient light detection window Δs displacement QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 102023125786.2

[0096]

Claims

Display device (1) comprising: - a substrate (10) with a main surface (12), - a plurality of emitters (20) arranged in pixels (2) on the main surface (12) of the substrate (10), each emitter (20) comprising a light-emitting diode, LED, configured to emit light during operation, - a sensor (30) in at least one pixel (2), the sensor (30) being configured to detect light during operation, - at least one evaluation circuit (40) being configured to evaluate the proximity of an object (100) above the display device (1) based on the light detected by the sensor (30) and to determine a distance between the object (100) and the display device (1). Display device (1) according to the preceding claims, wherein each emitter (20) is formed by a micro-LED. Display device (1) according to one of the preceding claims, wherein the pixels (2) are configured as RGB pixels (2) in which a first emitter (20-1) configured to emit red light, a second emitter (20-2) configured to emit green light, and a third emitter (30-3) configured to emit blue light are arranged. Display device (1) according to one of the preceding claims, wherein the sensor (30) is designed as a photodiode, wherein the photodiode is embedded in the substrate (10) or is arranged on the main surface (12) of the substrate (10) next to the emitters (20). Display device (1) according to one of claims 1 to 3, wherein the sensor (30) is designed as an LED, in particular a micro-LED, which is arranged on the main surface (12) of the substrate (10) next to the emitters (20) and is configured to be supplied with voltage for the detection of a photocurrent. Display device (1) according to the preceding claim, wherein the emitter (20) and the sensor (30) are manufactured according to a common manufacturing process. Display device (1) according to one of the preceding claims, comprising a plurality of sensors (30) which are configured to detect light during operation, wherein the sensors (30) are distributed across the display in respective pixels (2) of the display device (1). Display device (1) according to the preceding claim, wherein a viewing angle (L, R, C) of at least one sensor (30) differs from a viewing angle (L, R, C) of at least one other sensor (30) within the display device (1). Display device (1) according to one of the preceding claims, further comprising an aperture (50) and / or a light barrier (52) and / or a microlens (54) which are assigned to a respective sensor (30), wherein the aperture (50), the light barrier (52) and the microlens (54) are configured to define a viewing angle (L, R, C) of the respective sensor (30). Display device (1) according to the preceding claim, further comprising a transparent cover (60) covering the pixels (2), wherein the light barrier (52) and / or the aperture (50) and / or the microlens (54) are structured on the cover (60). Display device (1) according to claim 9, wherein the light barrier (52) is designed as a wall which is attached to the substrate (10) next to the respective sensor (30). Display device (1) according to one of the preceding claims, wherein the evaluation circuit (40) is configured to generate a first detection signal using the ambient light detected by the sensor (30) which is shaded by the object (100), and / or a second detection signal using the light detected by the sensor (30) which is emitted by the emitters (20) and reflected by the object (100). Display device (1) according to the preceding claim, wherein the evaluation circuit (40) is configured to calculate a difference signal from the first detection signal and the second detection signal. Method for operating a display device (1), wherein the display device (1) comprises a plurality of emitters (20) arranged in pixels (2) on a main area (12) of a substrate (10), a sensor (30) in at least one pixel (2), and at least one evaluation circuit (40), the method comprising: - emitting light by the emitters (20), each emitter (20) comprising a light-emitting diode, LED, - detecting light by the sensor (30), - evaluating the proximity of an object (100) above the display device (1) by the evaluation circuit (40) and determining a distance between the object (100) and the display device (1) based on the detected light. Method according to the preceding claim, further comprising adjusting the brightness of the emitted light by pulse width modulation. Method according to the preceding claim, wherein the detection of light comprises: - detection of ambient light when the emitters (20) are in an off state during pulse width modulation, and / or - detection of reflected light when the emitters (20) are in an on state during pulse width modulation. Method according to claim 15, wherein the detection of light during pulse width modulation is carried out continuously and the detected light is evaluated by filtering a detection signal in the frequency domain. A method according to the preceding claim, further comprising evaluating a distance between the object (100) and the display device, wherein the distance is determined by: evaluating an intensity of the detected light reflected by the object (100), and / or: evaluating an image shift detected by at least two groups of sensors (30) with different viewing angles (L, R, C), and / or: evaluating a change in the size of an image of the object (100) detected by a plurality of sensors (30). Method for manufacturing a display device (1), the method comprising: - providing a substrate (10), - attaching a plurality of emitters (20) on a main surface (12) of the substrate (10), wherein the emitters (20) are arranged in pixels (2) and each emitter (20) comprises a light-emitting diode, LED, which is configured to emit light during operation, - forming a sensor (30) in at least one pixel (2), wherein the sensor (30) is configured to detect light during operation, - providing at least one evaluation circuit (40) which is configured to evaluate the proximity of an object (100) above the display device (1) based on the light detected by the sensor (30) and to determine a distance between the object (100) and the display device (1). Method according to the preceding claim, wherein forming the sensor (30) comprises: - embedding a photodiode in the substrate (10) or - attaching a photodiode to the main surface (12) of the substrate (10) next to the emitters (20) or - attaching an LED to the main surface (12) of the substrate (10) next to the emitters (20) and supplying the LED with voltage to detect a photocurrent.

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