Display device for ambient light detection and method for its operation and manufacture

Abstract

A display device (1) is described, comprising 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 also comprises a filter (70) arranged on or above the sensor (30), the filter (70) being configured to transmit light of a predetermined wavelength range to the sensor (30). Methods for operating and manufacturing such 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. An ambient light sensor (ALS) 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 of the multiple 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 but not display light, i.e., light emitted by the emitters. The sensor can be sensitive to a specific wavelength range in the visible spectrum. The sensor can have a viewing angle. In particular, the viewing angle includes the vertical direction, so that the sensor is an "upward-facing" sensor.The illumination field of the emitters and the field of view of the sensor can overlap at least to some extent. 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 includes a filter. The filter is arranged on or above the sensor. The filter is configured to transmit light of a predetermined wavelength range to the sensor.

[0016] The filter can be called a wavelength filter. The filter is arranged vertically on or above the sensor. If the display device includes more than one sensor, each sensor can be equipped with a corresponding filter. In this case, the filters can be different, so that light of different wavelength ranges is transmitted to the sensor associated with each filter. The filter is designed to filter light, especially ambient light, before it reaches the sensor. This can mean that only a portion of the ambient light, particularly the portion corresponding to the specified wavelength range, reaches the sensor. Light with wavelengths outside the specified wavelength range is prevented from reaching the sensor.

[0017] According to at least one embodiment, a display device comprises a substrate with a main surface. It further comprises 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. It further comprises a sensor in at least one pixel, the sensor being configured to detect light during operation. It further comprises a filter arranged on or above the sensor, the filter being configured to transmit light of a predetermined wavelength range to 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 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 can be used for wavelength-dependent ambient light (ALS) measurement. If multiple pixels encompass a single sensor, the display can be partially or completely equipped with these additional sensors, creating a distributed ambient light sensor. While a localized ambient light sensor will not function if it is obscured, a distributed (delocalized) in-display sensor has redundancies and can therefore function even if the display (e.g., of a smartphone) is partially covered.

[0021] The detection can be synchronized with the pulse width modulation (PWM) of the emitter LEDs to prevent backscattered indicator light from being detected. This allows differentiation between ambient light and indicator light.

[0022] Wavelength-dependent in-display sensors are provided. Possible applications include automatic white balance (AWB) for cameras, AWB for displays, spectral acquisition, and / or ambient light detection (ALS). In particular, it is possible to manage and calibrate the display's color reproduction (automatic white balance) locally and directly.

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

[0024] As a general definition, a micro-LED could be considered any light-emitting diode (LED) – generally not a laser – with a particularly small size. Typically – and this is a very important criterion besides size – a growth substrate is replaced by micro-LEDs, so typical heights of such micro-LEDs are, for example, in the range of 0.5 µm to 10 µm. Fundamentally, 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 often, these micro-LEDs are mounted on wafers with non-destructively removable mounting structures. Currently, micro-LEDs are primarily used in displays. The micro-LEDs form pixels or subpixels and emit light of a defined color.

[0025] 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 applications, particularly smart glasses. Furthermore, other applications are being developed, especially for use in data communication and pixelated lighting. Various notations for micro-LED can be found in the relevant literature, e.g., µLED, µ-LED, uLED, u-LED, or micro-light-emitting diode.

[0026] 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.

[0027] 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.

[0028] According to at least one embodiment, the sensor is designed as a photodiode, wherein the photodiode is embedded in the substrate.

[0029] 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).

[0030] Alternatively, the photodiode is arranged on the main surface of the substrate next to the emitters.

[0031] 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.

[0032] 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.

[0033] 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 to 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 can be used as sensors, reducing the complexity of the manufacturing process. The (micro-)LEDs can be operated 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 driver circuit, supplying voltage to LEDs for photocurrent detection provides a simple and cost-effective solution for implementing detection capabilities in a display device. Using reverse-bias or non-reverse-bias micro-LEDs eliminates the need for additional components beyond the display components.

[0034] According to at least one embodiment, the emitter and the sensor are manufactured using a common manufacturing process.

[0035] This can mean that at least some of the 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 the 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.

[0036] According to at least one embodiment, the display device comprises a plurality of sensors configured to detect light during operation, wherein the sensors are distributed across the display in respective pixels of the display device and wherein each sensor is provided with a respective filter configured to transmit light of a predetermined wavelength range to the sensor.

[0037] 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. Accordingly, all features disclosed for the filter are also disclosed for the respective filter assigned to each of the 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 sensors can be identical or different. That the sensors are different can mean that their sensitivities for certain wavelengths differ from one another. However, at least some of the sensors can have the same or similar sensitivities for certain wavelength ranges.Furthermore, the filters assigned to each sensor can be the same or different. This means that the filters transmit light in the same or different wavelength ranges. Specifically, at least some of the filters are identical. The multiple sensors arranged in individual pixels form a distributed spectral sensor, which offers more redundancy than a local sensor (e.g., in a notch of the display or a dedicated area behind the display). It is also less susceptible to interference, such as from hair, fingers, dirt, or dust obstructing the sensor. Integrating the spectral sensor into the display eliminates the need for notches without requiring the sensor to be located behind the display, as is the case with behind-OLED sensors.Since the sensors are distributed across the display, the distributed spectral sensor has a 2D spatial resolution.

[0038] According to at least one embodiment, different spectral channels are formed by the plurality of sensors and filters, with each spectral channel being sensitive to a respective wavelength range.

[0039] Thus, the display device comprises a plurality of spectral channels. A specific spectral channel is formed by sensor-filter pairs configured to detect light within a particular wavelength range. Combinations of different sensors and filters result in a plurality of distinct spectral channels and therefore a distributed spectral sensor for the display device.

[0040] According to at least one embodiment, at least one spectral channel with a density is placed above the display that differs from the density of at least one other spectral channel.

[0041] The individual channels can be arranged at different densities to match or balance the overall spectral sensitivity of the channels. For example, to compensate for a first channel with lower capture efficiency than a second channel, more sensor-filter pairs forming the first channel can be placed in the display than sensor-filter pairs forming the second channel. In other words, the difference in EQE across the various color channels can be balanced by placing more sensors of lower-sensitivity channels and fewer of high-sensitivity channels.

[0042] Additionally or alternatively, sensors of at least one spectral channel are driven with a gain rate that differs from the gain rate of sensors of at least one other spectral channel. The channels, and in particular the respective sensors, can be driven with different gain rates to adjust or compensate for the overall spectral sensitivity of the channels.

[0043] According to at least one embodiment, pixels of a first group comprise a respective sensor designed as a blue or green micro-LED and configured to be supplied with voltage for the purpose of detecting a photocurrent.

[0044] According to at least one embodiment, pixels of a second group comprise a respective sensor designed as a red micro-LED and configured to be supplied with voltage for the purpose of detecting a photocurrent.

[0045] It is also possible for pixels to include both blue / green and red micro-LEDs used as sensors. In other words, the display device includes red, blue, and / or green micro-LEDs used as sensors. Blue, green, and red micro-LEDs refer to micro-LEDs that emit light in the blue, green, and red wavelength ranges, respectively, when forward-biased. The external quantum efficiency (EQE) of red, green, and blue light-emitting micro-LEDs in reverse bias or without voltage has been found to reach values ​​above 20%, depending on the wavelength being detected. Blue and green micro-LEDs cover a wavelength range of approximately 350 nm to 500 nm, while red micro-LEDs cover a wavelength range of approximately 450 nm to 650 nm. Thus, the display device can use both red and blue / green micro-LEDs as sensors to cover the entire visible spectrum.

[0046] According to at least one embodiment, the filter is designed as an interference filter or as a color filter.

[0047] This also applies to the majority of filters associated with most sensors. Interference filters comprise several layers of materials with different refractive indices and thicknesses. The selection of these materials allows specific wavelengths of light to be transmitted or blocked through the interference of light waves. For example, an interference filter might include a stack of dielectric and / or metallic layers. In the case of a color filter, the filter might include, for example, glass, plastic, or resin to selectively transmit certain wavelengths of light and block others.

[0048] According to at least one embodiment, the filter is arranged on the sensor.

[0049] This can mean that the filter is applied directly to the sensor, so that it is in physical contact with a sensitive surface of the sensor. This configuration advantageously allows for proper filter function without lateral leakage.

[0050] According to at least one embodiment, the display device further comprises a transparent cover that covers the pixels.

[0051] 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.

[0052] According to at least one embodiment, the filter is arranged on the cover.

[0053] This can mean that the filter is attached to, mounted on, or structured within the cover. The filter can be located on the side of the cover facing the sensor or on the side facing away from the sensor. It is also possible for the filter to be integrally formed with the cover. This allows the filter(s) to be aligned with the respective sensor on or within the substrate. The sensor does not require further processing, such as the application and structuring of filter layers. By placing the filter on the cover, no filter structuring is required on the display components themselves.

[0054] According to at least one embodiment, the display device also includes a control circuit.

[0055] For example, the control circuitry is integrated into the substrate. However, it is also possible for the control circuitry to be located on the main surface of the substrate, adjacent to the pixels, or within the pixels themselves. The control circuitry can also be located on the opposite back surface of the substrate and electrically connected to the pixels via through-substrate vias (TSVs). Furthermore, the control circuitry can be located in or on another substrate. The control circuitry can include circuitry for driving the emitters and supplying them with voltage. Thus, the control circuitry can include emitter drive circuitry and be electrically connected to at least some of the emitters within the pixels. The display device can include more than one control circuitry. For example, each control circuitry is associated with a group of pixels, such as a group of 16 x 16 pixels.The respective control circuit can control the emitters and evaluate signals from sensors in the aforementioned group of pixels.

[0056] In one embodiment, the control circuit is configured to evaluate ambient light around the display based on the light detected by one or more sensors. In particular, the color composition of the ambient light can be analyzed.

[0057] Additionally or alternatively, the control circuit is configured to evaluate flicker noise based on the light detected by one or more sensors. Therefore, the display's refresh rate can be adjusted based on a detected flicker frequency.

[0058] Additionally or alternatively, the control circuit is configured to evaluate the color of objects near the display based on the light detected by one or more sensors. For example, light from nearby objects is scattered and strikes the sensor(s).

[0059] Additionally or alternatively, the control circuit is configured to adjust the white balance of the display based on the light detected by one or more sensors. White balance ensures that the display colors appear natural under varying lighting conditions. It corrects the color temperature of the light to ensure that white is perceived as a neutral hue. The control circuit can be configured to analyze the detected ambient light to determine the prevailing color temperature. Based on the detected color temperature, the control circuit can then adjust the emitter's color channels (e.g., red, green, blue).

[0060] Additionally or alternatively, the control circuitry is configured to adjust the display's color calibration based on the light detected by one or more sensors. Color calibration refers to the process of adjusting and aligning the colors produced by the display to ensure accurate and consistent color reproduction. This can be important because displays can vary in color accuracy due to manufacturing differences, aging, or other factors.

[0061] Additionally or alternatively, the control circuit is configured to dynamically adjust the color and brightness of the light emitted by the display based on the light detected by one or more sensors. This can specifically mean that a feedback loop is activated in which the display light is continuously adjusted based on the detected ambient light and feedback from the system itself. In this way, the display device can regulate itself and maintain a desired state or performance.

[0062] 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.

[0063] 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 principal surface of a substrate, a sensor in at least one pixel and a filter on or above the sensor.

[0064] According to at least one embodiment, the method comprises emitting light through the emitters, each emitter comprising a light-emitting diode (LED). In particular, light is emitted from the emitters in a principal direction perpendicular to the main surface of the substrate. Each emitter / LED has an illumination field.

[0065] According to at least one embodiment, the method comprises filtering ambient light through the filter and transmitting light of a predetermined wavelength range to the sensor. In particular, the filter can be configured as a wavelength filter. Ambient light refers to light that is not emitted by the emitters but originates from other light sources outside the display device. Ambient light can include light in a plurality of wavelength ranges. The filter can filter the ambient light such that only a portion of the original wavelength spectrum is transmitted to the sensor.

[0066] According to at least one embodiment, the method further comprises the sensor detecting the light transmitted through the filter. Thus, the detected light can be filtered ambient light. Preferably, the emitters and the sensor are arranged such that the indicator light, i.e., the light emitted by the emitters, is not detected by the sensor. 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, and / or the sensor is deactivated when the emitters are switched on.

[0067] 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 a filter arranged on or above the sensor, comprises the emission of light by the emitters, each emitter comprising a light-emitting diode (LED). It further comprises filtering ambient light through the filter and transmitting light of a predetermined wavelength range to the sensor. It further comprises the detection of the light transmitted through the filter by the sensor.

[0068] This enables in-display sensing, particularly spectral sensing. The sensor can be embedded in the display. The sensor can be used for wavelength-dependent ambient light measurement (ALS). If multiple pixels encompass a single sensor, the display can be partially or completely equipped with these additional sensors, thus creating a distributed ambient light sensor. Potential applications include automatic white balance (AWB) for cameras, AWB for displays, spectral measurement, and / or ambient light measurement (ALS). In particular, it allows for local and direct management and calibration of the display colors (automatic white balance).

[0069] According to at least one embodiment, the method further includes adjusting the brightness of the emitted light by pulse width modulation.

[0070] 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 changing the LED's forward current.

[0071] According to at least one embodiment, the light measurement is performed when the emitters are in the switched-off state during pulse width modulation.

[0072] This allows the detection to be synchronized with the pulse-width modulation of the LEDs. This prevents the light emitted by the LEDs from being detected by the sensor. This enables the differentiation between ambient light and display light. For ambient light detection, flicker detection, white balance, etc., the ambient light can be measured and disruptive overlaps with the display light avoided.

[0073] According to at least one embodiment, the light detection is carried out continuously during the pulse width modulation and the detected light is evaluated by filtering a detection signal in the frequency domain.

[0074] This can mean that the light is detected throughout the entire PWM cycle, i.e., during the on and off states of the LEDs. Therefore, the detection signal contains information about the ambient light and the (backscattered) display light. Knowing the PWM frequency allows for post-processing to filter out the display light channel from the detection signal and obtain only the ambient light channel.

[0075] According to at least one embodiment, the method further comprises, based on the detected light, evaluating the ambient light around the display. Additionally or alternatively, the method further comprises, based on the detected light, evaluating flicker noise. Additionally or alternatively, the method further comprises, based on the detected light, evaluating the color of objects near the display. Additionally or alternatively, the method further comprises, based on the detected light, adjusting the white balance of the display. Additionally or alternatively, the method further comprises, based on the detected light, adjusting the color calibration of the display. Additionally or alternatively, the method further comprises, based on the detected light, dynamically adjusting the color and brightness of the emitted display light.

[0076] Furthermore, a method for manufacturing a display device is provided. All features disclosed for the display device are also disclosed for the method for manufacturing the display device, and vice versa.

[0077] 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. The substrate may include, for example, silicon or a film.

[0078] 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.

[0079] 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.

[0080] 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 manufactured and simultaneously transferred to the substrate using a single fabrication process. The sensor and emitters can differ only in how they are supplied with voltage. For example, the sensor could be a (micro)LED with or without a reverse voltage.

[0081] The method for manufacturing the display device further comprises forming a filter on or above the sensor, wherein the filter is configured to transmit light of a predetermined wavelength range to the sensor. The filter can be formed by applying one or more filter layers to the sensor or to a transparent cover that covers the emitter and the sensor. The filter can, for example, be designed as a multilayer interference filter or as a color filter. The filter can be referred to as a wavelength filter.

[0082] Advantageously, a display device with in-display spectral sensing can be manufactured. With more than one sensor, a distributed ambient light sensor (ALS) is formed, which offers multiple redundancies compared to a single ALS in a display notch. It also functions even if the sensor is partially obscured. Furthermore, an in-display sensor can manage and calibrate the display's color reproduction (automatic white balance) locally and directly. If (micro)LEDs are used as sensors, manufacturing can be simplified, as both the emitters and the sensor have the same structure and can be produced using a common manufacturing process.

[0083] According to at least one embodiment, the method further comprises forming recesses on the main surface of the substrate, wherein a respective emitter or sensor is placed in each recess.

[0084] In the case of a silicon or glass substrate, the formation of recesses can involve an etching process. Alternatively, recesses can also be formed, for example, by a forming process or thermocompression. The emitters and / or the sensor can be inserted into the recesses using a pick-and-place method or, preferably, a mass transfer method, e.g., using an elastomeric stamp. When the emitters and the sensor are arranged in recesses of the substrate, a planarized substrate surface can be provided.

[0085] 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 1 to 3 show display devices according to embodiments of the present invention. Fig. Figure 4 shows the external quantum efficiency of micro-LEDs when they are supplied with voltage to detect a photocurrent. Fig. Figures 5 to 7 show display devices according to other embodiments of the present invention. Fig. Figure 8 shows the transmission properties of different filters. Fig. Figure 9 shows the transmission properties of Fig. 8, folded with the external quantum efficiencies according to Fig. 4. Fig. Figure 10 shows a display device according to a further embodiment of the present invention. Fig. Figure 11 shows a method for operating a display device according to one embodiment. Fig. Figure 12 shows a method for manufacturing a display device according to one embodiment.

[0086] Fig. Figure 1 shows a cross-sectional view of a display device 1 according to one embodiment. The display device 1 comprises a substrate 10 with a main surface 12. 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. Furthermore, a sensor 30 is integrated into at least one of the pixels 2, the sensor 30 being configured to detect light during operation. Fig. 1 a cross-section of only one pixel 2. The display device further comprises a filter 70 which is arranged on or above the sensor 30, wherein the filter 70 is configured to transmit light of a predetermined wavelength range to the sensor 30.

[0087] For example, each emitter 20 is formed by a micro-LED. Furthermore, the sensor 30 can be configured as a photodiode, with the photodiode arranged on the main surface 12 of the substrate 10 adjacent to the emitters 20. Alternatively, the sensor 30 is configured as an LED, in particular a micro-LED, arranged on the main surface 12 of the substrate 10 adjacent to the emitters 20 and configured to be supplied with voltage to detect a photocurrent. However, if the sensor 30 is configured as a photodiode, it is also possible for the photodiode to be embedded in the substrate 10 (not shown). Furthermore, the filter 70 can be configured as an interference filter or as a color filter.

[0088] In the embodiment of Fig. The display device 1 further comprises a transparent cover 60. The cover 60 is arranged vertically above the main surface 12 of the substrate 10, so that the emitter 20 and the sensor 30 are covered. The filter 70 is arranged on the cover 60. As shown in Fig. As shown in Figure 1, the filter can be arranged on a side of the cover 60 facing the sensor 30.

[0089] In Fig. Figure 2 shows another embodiment of the display device 1. The embodiment of Fig. 2 differs from the embodiment of Fig. 1 by placing the filter directly on the sensor 30.

[0090] The Fig. 3a and Fig. Figure 3b shows different embodiments of a respective pixel 2 within the display device 1 in a top view. According to the Fig. 3a and Fig. In 3b, 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. 3a and Fig. 3b each has a sensor 30 arranged along the diagonal of the emitters 20. The sensor 30-1 of pixel 2 according to Fig. 3a can be formed by an LED, in particular a micro-LED, which can emit blue or green light in forward-biased mode. However, the LED is configured to be energized for the detection of a photocurrent. That is, the LED is configured to operate in reverse bias or without voltage. It has been found that blue or green micro-LEDs in reverse bias 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. 3b is formed by an LED, in particular a micro-LED, which can emit red light in forward-biased mode. However, the LED is configured to be energized for photocurrent detection. That is, the LED is configured to operate in reverse bias or without voltage. It has been found that red micro-LEDs 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, by using reverse-biased or without-voltage (micro-)LEDs for red and blue / green light, the visible wavelength range is covered.

[0091] This is in Fig. Figure 4 shows the external quantum efficiency of micro-LEDs as a function of wavelength λ. It is evident that the blue (B) and green (G) micro-LEDs cover a wavelength range of approximately 350 nm to 500 nm, while red (R) micro-LEDs cover the wavelength range of approximately 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.

[0092] The display device 1 can comprise different groups of pixels 2, wherein pixels 2 of a first group include a blue / green LED used as a sensor 30, and pixels 2 of a second group 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 can be implemented as (micro)LEDs, they can be manufactured using a common fabrication process.

[0093] For example, each pixel 2, or at least a subset of the plurality of pixels 2, comprises a respective sensor 30. This means that the display device 1 can include a plurality of sensors 30. Each sensor 30 can be equipped with a respective filter 70, which is configured to transmit light of a specified wavelength range to the sensor 30. Thus, the sensor area can be large, forming a distributed spectral sensor 30. A distributed spectral sensor has more redundancy than a local sensor and is less susceptible to interference. By integrating the sensor 30 into the display, all notches are removed from the display without the need to position the sensor behind the display, as is the case, for example, with behind-OLED sensing. The display does not need to be transparent.

[0094] The Fig. Figures 5 to 7 show further embodiments of the display device 1, in which recesses 80 are formed on the main surface 12 of the substrate 10. An emitter 20 or sensor 30 is mounted in each recess 80.

[0095] In Fig. Figure 5 shows that a metal coating 90 can be applied to the side walls and floor of the recess 80 between the substrate 10 and the emitter 20 or sensor 30. The metal coating 90 can serve as the lower electrode for the emitter 20 or sensor 30 and as a reflector. Furthermore, a transparent filler 92 can be arranged on the lateral sides of the emitter 20 / sensor 30 to fill the remaining space of the recess 80. Additionally, a transparent upper electrode 94 is arranged on the main surface 12 of the substrate 10, the transparent filler 92, and the emitter 20 / sensor 30.

[0096] Fig. Figure 6 further shows the transparent cover 60, on which a filter 70 is structured on a side facing the sensor 30. Since there is a gap between the filter 70 and the sensor 30, light leakage from the lateral sides is possible, as indicated by an arrow.

[0097] Light leakage can be prevented if the filter 70 is structured directly on the sensor 30, as shown in Fig. Figure 7 shows that multilayer interference filters 70, metal filters 70, or color filters 70 can be microstructured using standard lithography techniques. The structuring of the filters 70 can be performed, for example, after transferring the sensor to the display plane and after contacting the top surface.

[0098] If the display device 1 comprises a plurality of sensors 30 and filters 70, different spectral channels are formed by the sensor-filter pairs. Each spectral channel is sensitive to a specific wavelength range. The spectral channels are distributed across the entire display, with one or more channels present in each pixel 2.

[0099] The filters 70 can be different, which means they can have different transmission properties. Fig. Figure 8 shows exemplary filter transmission curves for ten different filters F1 to F10 as a function of the wavelength λ. Fig. Figure 9 shows these filter transmission curves, convolved with the spectral quantum efficiency of red and blue micro-LEDs, as in Fig. Figure 4 shows that filters F1 to F3 are placed on blue micro-LEDs operated in reverse bias or without voltage, and filters F4 to F10 are placed on red micro-LEDs operated in reverse bias or without voltage. Fig. Figure 9 shows that the spectral responses to specific wavelength ranges can differ. To tune or balance the overall spectral sensitivity of the spectral channel, the individual channels can be placed at different densities or driven with different gain rates.

[0100] Fig. Figure 10 shows a further embodiment of the display device 1 in a top view. The display device 1 comprises a plurality of pixels 2 that form the display. The plurality of pixels 2 are arranged in an array on the main surface 12 of the substrate 10. The display device 1 further comprises a control circuit 40. Based on the light detected by the one or more sensors 30, the control circuit 40 can be configured to evaluate ambient light around the display and / or flicker noise and / or the color of objects near the display and / or adjust a white balance of the display and / or adjust a color calibration of the display and / or dynamically adjust the color and brightness of the emitted display light. The control circuit 40 is electrically connected to the substrate 10 and the pixels 2 on the substrate 10 via electrical connections 45.The electrical connections 45 can be designed as flexible connections 45. Furthermore, the control circuit 40 and the substrate 10 can be arranged on a common support 15. Alternatively (but not shown), the control circuit can be arranged in or on the substrate 10.

[0101] Fig. Figure 11 shows a possible operating method for the display device 1. The method comprises emitting light through the emitters 20, each emitter 20 comprising an LED. In the example shown, the emitters 20 comprise a first emitter 20-1 configured to emit red light, a second emitter 20-2 configured to emit green light, and a third emitter 20-3 configured to emit blue light. The brightness of the emitted light can be adjusted by pulse-width modulation (PWM), as shown in Fig. Figure 11 shows that the brightness can be set separately for each of the emitters 20, specifically 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 ambient light AL using sensor 30, the detection is set to time windows TA during which the display is not switched on. Sensor 30 can be deactivated when the emitters 20 are switched on. The display's switch-on states are defined by the pulse-width modulation frequency and the switch-on duration. A dedicated ambient light detection window TA can refer to a PWM lock-in detection mode of the display device 1. Alternatively, ambient 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 can be distinguished from backscattered display light. Before detection, the ambient light is filtered by filter 70 so that only light of a predefined wavelength range is transmitted to sensor 30.

[0102] In Fig. Figure 12 schematically illustrates the manufacturing process of the display device. The process comprises the following steps, which do not necessarily have to be carried out in this order, but can be carried out in this order.

[0103] In the first step S1, a substrate is provided. The substrate is, for example, designed as a silicon backplane or as a flex plane.

[0104] In an optional second step S2, recesses 80 are formed on a main surface 12 of the substrate 10. For example, the recesses are formed by etching the substrate 10. It is also possible for the recesses to be formed by molds, e.g., embossing dies, thermoforming dies, or injection molding.

[0105] In a third step S3, a plurality of emitters 20 are applied to the 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, configured to emit light during operation. The application of the emitters 20 can involve a transfer process, in particular a mass transfer process, by which a plurality of emitters 20 are applied to the substrate 10 simultaneously. For example, an elastomer stamp is used for the mass transfer.

[0106] In a fourth step S4, a sensor 30 is formed in at least one pixel 2, wherein the sensor 30 is configured to detect light during operation. Forming the sensor 30 can involve embedding a photodiode in the substrate 10, particularly if the substrate 10 is a silicon substrate 10. This can be done using a semiconductor process, e.g., a CMOS process. In this case, forming the sensor 30 can occur before depositing the emitter 20 onto the substrate 10. Forming the sensor 30 can also involve depositing a photodiode on the main surface 12 of the substrate 10 adjacent to the emitters 20. In this case, the photodiode can be formed by a separate detector chip that is transferred to and attached to the substrate 10.The formation of the sensor 30 can also include attaching an LED, in particular a micro-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. The aforementioned detection (micro-)LED can have the same structure as the emitter 20. Thus, it can be formed in the same manufacturing process and transferred to the substrate 10 in the same transfer process as the emitters 20. Supplying the LED with voltage to detect a photocurrent can mean that this detection LED is not supplied with voltage or is reverse-biased.

[0107] In a fifth step S5, a filter 70 is formed on or above the sensor 30, wherein the filter 70 is configured to transmit light of a specified wavelength range to the sensor 30. The formation of the filter 70 can involve applying and structuring one or more filter layers directly onto the sensor 30 or onto a transparent cover 60 that covers the emitter 20 and the sensor 30.

[0108] The embodiments of the display device disclosed herein, as well as the methods for operating and manufacturing the display device, 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.

[0109] 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.

[0110] 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.

[0111] This patent application claims priority over German patent application 102023125788.9, the disclosure content of which is hereby incorporated by reference. Reference symbol list 1 Display device 2 pixels 10 substrate 12 main area 15 carriers 20 emitters 20-1 first emitter 20-2 second emitter 20-3 third emitter 30 Sensor 30-1 Sensor 30-2 Sensor 40 Control circuit 45 electrical connection 60 Coverage 70 filters 80 recess 90 Metal coating 92 Filler 94 upper electrode AL Ambient light F1-F10 Filter S1-S5 manufacturing steps TA ambient light detection window 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 102023125788.9

[0111]

Claims

[1] 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), wherein the sensor (30) is configured to detect light during operation, - a filter (70) arranged on or above the sensor (30), wherein the filter (70) is configured to transmit light of a specified wavelength range to the sensor (30). [2] Display device (1) according to the preceding claims, wherein each emitter (20) is formed by a micro-LED. [3] 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. [4] 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). [5] 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. [6] Display device (1) according to the preceding claim, wherein the emitter (20) and the sensor (30) are manufactured by a common manufacturing process. [7] 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) and wherein each sensor (30) is provided with a respective filter (70) which is configured to transmit light of a predetermined wavelength range to the sensor (30). [8] Display device (1) according to the preceding claim, wherein different spectral channels are formed by the plurality of sensors (30) and filters (70), each spectral channel being sensitive to a respective wavelength range and - wherein at least one spectral channel is arranged above the display with a density that differs from the density of at least one other spectral channel, and / or - wherein sensors (30) of at least one spectral channel are driven with a gain that differs from a gain of sensors (30) of at least one other spectral channel. [9] Display device (1) according to one of the preceding claims, wherein pixels (2) of a first group comprise a respective sensor (30-1) configured as a blue or green micro-LED and configured to be supplied with voltage for the detection of a photocurrent, and / or wherein pixels (2) of a second group comprise a respective sensor (30-2) configured as a red micro-LED and configured to be supplied with voltage for the detection of a photocurrent. [10] Display device (1) according to one of the preceding claims, wherein the filter (70) is designed as an interference filter or as a color filter. [11] Display device (1) according to one of the preceding claims, wherein the filter (70) is arranged on the sensor (30). [12] Display device (1) according to one of the preceding claims, further comprising a transparent cover (60) covering the pixels (2), wherein the filter (70) is arranged on the cover (60). [13] Display device (1) according to one of the preceding claims, further comprising a control circuit (40) which is configured, based on the light detected by the one or more sensors (30), - To evaluate ambient light around the display and / or - to evaluate spark noise and / or - to evaluate the color of objects near the display and / or - adjust the white balance of the display and / or - to adjust the color calibration of the display and / or - to dynamically adjust the color and brightness of the light emitted by the display. [14] 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 a filter (70) arranged on or above the sensor (30), the method comprising: - Emitting light through the emitters (20), each emitter (20) comprising a light-emitting diode, LED, - Filtering ambient light through the filter (70) and transmitting light of a specified wavelength range to the sensor (30), - Detection of the light transmitted through the filter (70) by the sensor (30). [15] Method according to the preceding claim, further comprising adjusting the brightness of the emitted light by pulse width modulation. [16] Method according to the preceding claim, wherein a light detection - is performed when the emitters (20) are in a switched-off state during pulse width modulation, or - is performed continuously during pulse width modulation and the detected light is evaluated by filtering a detection signal in the frequency domain. [17] A method according to any of the preceding claims, further comprising, based on the detected light: - Evaluating ambient light around the display and / or - Evaluating flicker noise and / or - Evaluating the color of objects near the display and / or - Adjusting the white balance of the display and / or - Adjusting the color calibration of the display and / or - Dynamic adjustment of the color and brightness of the light emitted by the display. [18] Method for manufacturing a display device (1), the method comprising: - Providing a substrate (10), - Attaching a plurality of emitters (20) to a main area (12) of the substrate (10), wherein the emitters (20) are arranged in pixels (2) and each emitter (20) comprises a light-emitting diode, LED, 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, - Forming a filter (70) on or above the sensor (30), wherein the filter (70) is configured to transmit light of a specified wavelength range to the sensor (30). [19] 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 voltage to the LED to detect a photocurrent. [20] Method according to one of claims 18 to 19, further comprising forming recesses (80) on the main surface (12) of the substrate (10), wherein a respective emitter (20) or sensor (30) is placed in each recess (80).

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