Pixel unit, image sensor, and method for operating a pixel unit

Abstract

A pixel unit (10) comprises a plurality of pixels (11), each pixel (11) comprising a photodiode (12), a readout circuit (13), the readout circuit comprising a first readout component (14) and a second readout component (15), wherein a first group of pixels (11) is configured to detect electromagnetic radiation in a first wavelength range, and a second group of pixels (11) is configured to detect electromagnetic radiation in a second wavelength range, the first readout component (14) is connected to the first group of pixels (11), and the second readout component (15) is connected to the second group of pixels (11), the first wavelength range being different from the second wavelength range, and the second readout component (15) comprising a plurality of storage capacitors (16), wherein each pixel (11) of the second group of pixels (11) is assigned to at least one of the storage capacitors (16), or the second readout component (15) comprises a memory element (17). In addition, a method for operating the pixel unit (10) is provided.

Description

[0001] The present invention relates to a pixel unit, an image sensor and a method for operating a pixel unit.

[0002] Image sensors can be operated in rolling shutter mode or global shutter mode. In rolling shutter mode, the pixels of the pixel matrix are illuminated by a light source. During illumination, the pixels are sequentially exposed and read out row by row, so that the readout process occurs in a repetitive, rolling manner. This means that the pixel matrix is illuminated during the entire readout process. Rolling shutter mode allows for high resolution of the image sensor.

[0003] In global shutter mode, all pixels of the pixel matrix are exposed during the same time. Therefore, a significantly shorter illumination time is required compared to rolling shutter mode. However, the readout circuitry for global shutter mode consumes more space in the image sensor than that for rolling shutter mode. Furthermore, the resolution of an image sensor operating in global shutter mode is lower than that of an image sensor operating in rolling shutter mode.

[0004] One object is to provide a pixel unit with improved accuracy. Another object is to provide an image sensor that can operate efficiently and with improved accuracy. Another object is to provide a method for operating a pixel unit with improved accuracy.

[0005] These objects are achieved by the subject-matter of the independent claims. Further developments and embodiments are described in the dependent claims.

[0006] According to at least one embodiment of the pixel unit, the pixel unit includes a plurality of pixels, each pixel including a photodiode. The pixels can be arranged in a two-dimensional array or a pixel matrix. Each of the photodiodes is configured to convert electromagnetic radiation into an electrical signal. The pixels can be arranged adjacent to each other in a lateral direction, wherein the lateral direction is parallel to the main extension plane of the pixel unit. The pixel unit includes, for example, at least one million pixels.

[0007] The pixel unit also includes a readout circuit, the readout circuit including a first readout component and a second readout component. The readout circuit can be configured to read out the electrical signal provided by the photodiode. The readout circuit can include an output at which the electrical signal of the photodiode can be provided. The readout circuit can also be configured to operate the pixel. The first readout component and the second readout component can be configured to operate independently of each other.

[0008] The first set of pixels is configured to detect electromagnetic radiation in a first wavelength range. The first set of pixels can include a plurality of pixels. For example, the first set of pixels includes at least 1 million pixels. The first wavelength range can include a plurality of wavelengths.

[0009] The second set of pixels is configured to detect electromagnetic radiation in a second wavelength range. The second set of pixels can include a plurality of pixels. For example, the second set of pixels includes at least 1 million pixels. The second wavelength range can include a plurality of wavelengths.

[0010] The first readout component is connected to the first group of pixels. This can mean that each pixel of the first group of pixels is connected to the first readout component. The first readout component is electrically connected to the first group of pixels. The first readout component can be configured to read out the electrical signal provided by the photodiode of the first group of pixels.

[0011] The second readout component is connected to the second group of pixels. This can mean that each pixel of the second group of pixels is connected to the second readout component. The second readout component is electrically connected to the second group of pixels. The second readout component can be configured to read out the electrical signal provided by the photodiode of the second group of pixels.

[0012] The first wavelength range is different from the second wavelength range. This can mean that the first wavelength range includes a wavelength range that is different from the wavelengths included in the second wavelength range.

[0013] The second readout unit comprises a plurality of storage capacitors, wherein each pixel of the second group of pixels is assigned to at least one of the storage capacitors, or the second readout unit comprises a memory element. It is also possible that the second readout unit comprises a plurality of storage capacitors, wherein each pixel of the second group of pixels is respectively assigned to at least one of the storage capacitors, or the second readout unit comprises a memory element. This means that the second readout circuit comprises a plurality of storage capacitors, or comprises a memory element. Each of the pixels of the second group of pixels can be respectively assigned to exactly one of the storage capacitors. This means that each of the storage capacitors is only connected to one of the pixels of the second group of pixels. It is also possible that each pixel of the second group of pixels is respectively assigned to two storage capacitors. Alternatively, at least two of the pixels of the second group of pixels can be assigned to the same storage capacitor. The memory element is, for example, a static random access memory or a dynamic random access memory.

[0014] Each of the storage capacitors can be formed by a sample-and-hold stage. This means that each storage capacitor can be connected to a switch. Each sample-and-hold stage can be configured to receive one or more electrical signals from the photodiodes of the second group of pixels and to store the corresponding electrical charge on the storage capacitor for a predetermined time interval. In this way, the analog signals detected by the photodiodes of the second group of pixels are converted into digital signals. The storage capacitors can be configured to receive electrical signals from the photodiodes sequentially or in groups. This means that the electrical signals of the photodiodes of the second group of pixels are transmitted sequentially to the corresponding storage capacitors, for example during illumination with a light source. It is also feasible that the storage capacitors are configured to receive electrical signals from the photodiode groups simultaneously. The photodiode groups are, for example, arranged in a row of pixels. Each row of photodiodes can form a separate photodiode group.

[0015] The storage capacitors are further configured to be read out one after another or sequentially by the second readout component. The storage capacitors are configured to be read out after the photodiodes are exposed to the light source. For example, the load stored on the storage capacitors can be transferred to the column bus of the second readout component. In this way, the storage capacitors are read out. Reading the information stored on the storage capacitors means transferring the electrical load stored on the storage capacitors to another unit of the second readout component, for example to the column bus. The loads stored on the storage capacitors are not transferred to another unit of the second readout component at the same time, but sequentially. In this way, the electrical signals obtained by each photodiode of the second group of pixels are read out separately from each other. This way of reading out the information of the storage capacitors allows for a high resolution of the pixel unit or an image sensor comprising a pixel unit.

[0016] The storage capacitors can be connected in parallel with each other. A switch can be provided between two adjacent storage capacitors.

[0017] If the second readout component comprises a memory element, each of the photodiodes of the second group of pixels is connected to the memory element. Each of the photodiodes of the second group of pixels can be connected to the memory element via an analog-to-digital converter. This means that the electrical signals provided by the photodiodes are converted into digital signals before they are transmitted to the memory element. The memory element can be configured to receive the electrical signals provided by the photodiodes of the second group of pixels sequentially or in groups. This means that the electrical signals of the photodiodes are transmitted to the memory element sequentially. The electrical signals of the photodiodes can be transmitted to the memory element during illumination with the light source. It is also feasible that the electrical signals from the photodiode groups are transmitted to the memory element simultaneously. The photodiode groups are, for example, arranged in a row of pixels. Each row of photodiodes can form a separate photodiode group.

[0018] The memory element is configured to be read out sequentially. This means that the electrical signals provided by the photodiodes of the second group of pixels are stored in the memory element. The stored information about the electrical signals of the photodiodes is read out sequentially. This means that the electrical signals provided by the photodiodes of the second group of pixels are read out from the memory element one after another. In this case, readout means that the electrical signals are further transmitted from the memory element. The electrical signals provided by the photodiodes of the second group of pixels are read out from the memory element after the photodiodes are exposed to the light source. Reading out information from the memory element can include transmitting the electrical signals received by the photodiodes of the second group of pixels to another unit of the second readout component, such as a column bus. In this way, the electrical signals obtained by each photodiode of the second group of pixels are read out separately from each other. This way of reading out information from the memory element allows for a high resolution of the pixel unit or an image sensor comprising a pixel unit.

[0019] The two alternatives provided for the arrangement of the second readout component differ in the storage of the electrical signals provided by the photodiodes of the second group of pixels. According to a first alternative, the electrical signals of the photodiodes of the second group of pixels are stored in a storage capacitor. According to a second alternative, the electrical signals of the photodiodes of the second group of pixels are stored in a memory element. For both alternatives, the electrical signals are obtained by the photodiodes of the second group of pixels and the stored information is read out sequentially, rather than simultaneously. Compared to the sequential transmission of the stored information, the transmission of the electrical signals from the photodiodes to the second readout component is significantly faster because the electrical signals are temporarily stored by the storage capacitor or memory element. The further transmission of the electrical signals from the storage capacitor or memory element can occur during or after illumination. As a result, the illumination time can be kept short. Despite the rapid transmission of the electrical signals to the second readout component during illumination, high resolution can still be achieved due to the sequential transmission of the stored information from the second readout component.

[0020] For the pixel unit described in this article, two different ways of reading out the electrical signals from the photodiodes can be combined. The photodiodes of the first group of pixels can be read out independently of the photodiodes of the second group of pixels. The first group of pixels and the second group of pixels are configured to detect electromagnetic radiation in different wavelength ranges. The pixel unit described in this article allows different detection methods for these different wavelength ranges. For example, different safety precautions must be taken into account for detecting visible light and infrared light. If the pixel unit is composed of an electronic device operated by a user, the exposure to infrared radiation should be kept short enough to avoid damaging the user's eyes. Moreover, the intensity of the electromagnetic radiation should not be too high. In order to reduce the power consumption of the light source, short illumination times are also desired.

[0021] The pixel unit described in this article also has the advantage that the illumination time for the second group of pixels can be short. The advantage of the short illumination time is that the power consumption of the light source utilized is reduced. Since the information stored on the storage capacitor or in the memory element is read out sequentially, the information obtained by each pixel is transmitted separately. This readout method allows higher resolution and thus improved accuracy of the pixel unit. At the same time, compared with the readout component operating in the global shutter mode, less space is required for the second readout component. Therefore, the arrangement of the pixel unit can be compact. Thus, for the second readout component, the advantages of the global shutter mode and the rolling shutter mode are combined.

[0022] The first readout component can be configured to operate the pixels of the first group of pixels in a rolling shutter mode, or in a global shutter mode. Advantageously, the first readout component can be optimized for the first wavelength range independently of the second readout component.

[0023] According to at least one embodiment of the pixel cell, each of the storage capacitors is connected to an input of an analog-to-digital converter. For example, each storage capacitor group is assigned to an analog-to-digital converter. This means that the second readout component can include a plurality of analog-to-digital converters. Each of the analog-to-digital converters can be connected to a storage capacitor group. The analog-to-digital converters are configured to convert analog electrical signals received at their inputs into digital signals. The analog-to-digital converters can be configured to convert analog electrical signals received from pixels of the second group of pixels after illumination of the pixel cell into digital signals. Compared to analog signals, digital signals can be more easily transmitted and evaluated.

[0024] According to at least one embodiment of the pixel cell, the second readout component includes an analog-to-digital converter, wherein the input of the analog-to-digital converter is configured to be connected to at least one pixel in the second group of pixels, and the output of the analog-to-digital converter is configured to be connected to a memory element. The input of the analog-to-digital converter can be configured to be connected sequentially to different pixels in the second group of pixels. The analog-to-digital converter can be configured to convert analog electrical signals received by pixels in the second group of pixels into digital signals. This means that the electrical signals detected by the pixels in the second group of pixels are converted into digital signals by the analog-to-digital converter. The digital signals are then transmitted to the memory element. The conversion of the electrical signals by the analog-to-digital converter and their transmission to the memory element occur during the illumination period of the pixel cell. This method of transmitting the electrical signals of the pixels in the second group of pixels to the second readout component allows for rapid signal transmission to the memory element. The electrical signals can be transmitted in groups. For example, the electrical signals for each pixel in the second group of pixels are transmitted to the second readout component simultaneously. This means that the pixel cell operates in rolling shutter mode. However, due to the rapid transmission of the electrical signals, the illumination period can be kept short.

[0025] According to at least one embodiment of the pixel unit, the storage capacitors are arranged in groups, wherein each group includes at least two storage capacitors connected to each other. For example, each storage capacitor group includes four storage capacitors. The storage capacitors of a group can be connected to each other in parallel. The load collected or stored by the storage capacitors of a group can be transmitted together. This means that for each group, the load collected by the storage capacitors of the corresponding group can be transmitted together. Moreover, for each group, the load stored on the storage capacitors of the corresponding group can be transmitted simultaneously. By arranging the storage capacitors in groups, the signal-to-noise ratio of the pixel unit can be improved.

[0026] According to at least one embodiment of the pixel unit, the first readout component and / or the second readout component are configured to operate in a rolling shutter mode. In the rolling shutter mode, the photodiode is exposed and the electrical signals obtained by the photodiode are read out sequentially. This means that the first readout component can be configured to sequentially read out the electrical signals obtained by the photodiodes of the first group of pixels. Additionally or alternatively, the second readout component can be configured to sequentially read out the electrical signals obtained by the photodiodes of the second group of pixels. The rolling shutter mode has the advantage of being able to obtain a high resolution of the pixel unit. Therefore, the accuracy of the pixel unit is also improved.

[0027] According to at least one embodiment of the pixel unit, the first group of pixels is configured to detect electromagnetic radiation in the visible light range. This means that the photodiodes of the pixels of the first group of pixels are configured to detect electromagnetic radiation in the visible light range. The visible light range can be 400 nm to 750 nm. Detecting visible light is advantageous for a wide range of applications.

[0028] According to at least one embodiment of the pixel unit, the first group of pixels includes three different types of pixels, wherein each type of pixel is configured to detect electromagnetic radiation in a range different from the range of electromagnetic radiation that the other types of pixels are configured to detect. For example, a first type of pixel of the three types is configured to detect red light in a range of, for example, 550 nm to 750 nm. For example, a second type of pixel of the three types is configured to detect green light in a range of, for example, 470 nm to 550 nm. For example, a third type of pixel of the three types is configured to detect blue light in a range of, for example, 400 nm to 470 nm. In this way, different colors can be detected.

[0029] According to at least one embodiment of the pixel unit, the second group of pixels is configured to detect electromagnetic radiation in the infrared range. This means that the photodiodes of the pixels of the second group of pixels are configured to detect electromagnetic radiation in the infrared range. The infrared range can be from 750 nm to several microns. Detecting infrared light is advantageous for a wide range of applications.

[0030] According to at least one embodiment of the pixel unit, the second group of pixels includes at least two different types of pixels, wherein each type of pixel is configured to detect electromagnetic radiation in a range different from the range of electromagnetic radiation that the other types of pixels are configured to detect. The second readout component can include at least two column buses, wherein pixels of a first type are connected to a first of the column buses, and pixels of a second type are connected to a second of the column buses. The column buses of the second readout component can be connected to each other in parallel. In this way, electromagnetic radiation of different wavelengths can be detected.

[0031] According to at least one embodiment of the pixel cell, the readout circuit is arranged on a side of the plurality of pixels facing away from the radiation entry side of the pixel cell. This can mean that the readout circuit is arranged below the plurality of pixels. The readout circuit and the plurality of pixels are stacked on top of each other. Electromagnetic radiation can reach the pixels from the radiation entry side. By arranging the readout circuit and the plurality of pixels above each other, the arrangement of the pixel cell can be designed to be very compact. No space adjacent to the pixels is required for the readout circuit, as it is arranged below the pixels.

[0032] According to at least one embodiment of the pixel unit, the first readout component includes at least two parts that are arranged to be spaced apart from each other. This means that the two parts of the first readout component do not directly contact each other. The two parts of the first readout component can have the same arrangement. The two parts of the first readout component can both be arranged below a plurality of pixels. By utilizing at least two parts of the first readout component, the arrangement of the readout circuit can be compact.

[0033] According to at least one embodiment of the pixel cell, the second readout element is arranged between the two parts of the first readout element in a lateral direction extending parallel to the main extension plane of the pixel cell. The second readout element can be arranged adjacent to the two parts of the first readout element. The two parts of the first readout element and the second readout element can be arranged in a plane extending parallel to the main extension plane of the pixel cell. The second readout element can be arranged in the center of the pixel cell. This arrangement of the two parts of the first readout element and the two parts of the second readout element allows a compact arrangement of the pixel cell.

[0034] In addition, an image sensor is provided. The image sensor includes a plurality of pixel units. The pixel units can be arranged in a two-dimensional array or matrix.

[0035] According to at least one embodiment of the image sensor, the image sensor further includes a light source synchronized with the pixel cells. This may mean that the light source is configured to emit electromagnetic radiation when the pixels are operated and detect electromagnetic radiation. The image sensor may include a control unit configured to simultaneously control the light source and the pixel cells. In this way, the operation of the light source and the pixel cells are synchronized. By synchronizing the operation of the light source with the pixel cells, the illumination duration can be minimized. This reduces the power consumption of the light source.

[0036] In addition, a method for operating a pixel unit is provided. The pixel unit can preferably be used in the method for operating a pixel unit described herein. This means that all features disclosed for the pixel unit and the image sensor are also disclosed for the method for operating the pixel unit, and vice versa.

[0037] According to at least one embodiment of the method for operating a pixel unit, the method includes exposing a plurality of pixels of the pixel unit to electromagnetic radiation, wherein each pixel includes a photodiode, wherein a first group of pixels is configured to detect electromagnetic radiation in a first wavelength range, and wherein a second group of pixels is configured to detect electromagnetic radiation in a second wavelength range. The electromagnetic radiation can be provided by a light source. The light source can be synchronized with the operation of the pixel unit. This means, for example, that the light source is operated and emits electromagnetic radiation only during the time when the photodiode is operating and detecting the electromagnetic radiation.

[0038] The method further includes converting electromagnetic radiation into an electrical signal via a photodiode. During operation, each of the photodiodes converts electromagnetic radiation into an electrical signal. Each of the photodiodes converts electromagnetic radiation emitted by the light source and reaching the corresponding photodiode into an electrical signal.

[0039] The method further comprises transmitting the electrical signals of the pixels of the first group of pixels to a first readout component of a readout circuit of the pixel unit. The electrical signals of the pixels of the first group of pixels can be transmitted to the first readout component simultaneously. It is also feasible that the electrical signals of the pixels of the first group of pixels are transmitted to the first readout component sequentially. This means that the first readout component can operate in a global shutter mode or a rolling shutter mode.

[0040] The method further includes transmitting the electrical signals of the pixels of the second group of pixels to a second readout component of the readout circuit. The electrical signals of the pixels of the second group of pixels are transmitted to the second readout component sequentially. This means that the electrical signals of the pixels of the second group of pixels are transmitted to the second readout component one after another or in groups. The electrical signals of the pixels of the second group of pixels are transmitted to the second readout component during the exposure to the electromagnetic radiation. The transmitted electrical signals are stored in the second readout component.

[0041] The first wavelength range is different from the second wavelength range.

[0042] Transmitting the electrical signals of the pixels of the second group of pixels to the second readout unit includes transmitting the electrical signals of each pixel of the second group of pixels to a corresponding storage capacitor of the second readout unit, or transmitting the electrical signals of each pixel of the second group of pixels to a memory element of the second readout unit. Alternatively, transmitting the electrical signals of the pixels of the second group of pixels to the second readout unit includes transmitting the electrical signals of each pixel of the second group of pixels to at least one corresponding storage capacitor of the second readout unit, or transmitting the electrical signals of each pixel of the second group of pixels to a memory element of the second readout unit.

[0043] If the electrical signals of the pixels of the second group of pixels are transferred to storage capacitors, each pixel is assigned to at least one storage capacitor. This means that the second readout component comprises a plurality of storage capacitors. The electrical signals of the pixels of the second group of pixels can be transferred in groups to the corresponding storage capacitors. This means, for example, that for each row of the pixel cell, the electrical signals of the pixels of this row are transferred simultaneously to the corresponding storage capacitors. The electrical signals of the pixels of different rows are transferred successively. The transfer of the electrical signals of the pixels of the second group of pixels to the storage capacitors occurs during the exposure of the pixel cell to electromagnetic radiation. This means that the pixel cell operates in rolling shutter mode.

[0044] If the electrical signals of the pixels of the second group of pixels are transferred to the memory element, the electrical signals are transferred to the memory element in groups or sequentially. This means, for example, that for each row of the pixel cell, the electrical signals of the pixels in that row are transferred to the memory element simultaneously. The electrical signals of the pixels of different rows are transferred sequentially. The transfer of the electrical signals of the pixels of the second group of pixels to the memory element occurs during the exposure of the pixel cell to electromagnetic radiation. This means that the pixel cell operates in rolling shutter mode.

[0045] According to the method described herein, the first sensing component and the second sensing component can be operated independently of each other. Thus, the first sensing component and the second sensing component can advantageously be optimized for different operations.

[0046] Compared to rolling shutter mode, transmission to the second readout component is possible more quickly because the electrical signal is temporarily stored by the second readout component. After illumination, further transmission of the electrical signal from the second readout component to the output of the pixel cell occurs. Thus, the further readout process occurs after illumination. Therefore, only a short illumination time is required. In addition, due to the sequential transmission of the electrical signal from the second readout component to the output of the pixel cell, high resolution and thus improved accuracy are achieved. Compared to a readout circuit operating in global shutter mode, less space is required for the second readout component.

[0047] According to at least one embodiment of the method, the electrical signals of the pixels of the second group of pixels are transmitted sequentially or in groups to the second readout unit. Since the electrical signals of the pixels are transmitted to a storage capacitor or memory element, the transmission of the electrical signals can be faster than is typically possible for a rolling shutter mode. This allows for a short illumination time and reduces the power consumption of the light source.

[0048] According to at least one embodiment of the method, the first readout component and the second readout component are operated independently of each other. This means that, for example, electrical signals from a photodiode are transmitted to the respective readout components independently of each other. The way in which the first readout component is operated can differ from the way in which the second readout component is operated. Furthermore, the settings of the first readout component differ from the settings of the second readout component. The control unit can be configured to control the first readout component and the second readout component independently of each other. In this way, the pixel unit can be operated more efficiently and with improved accuracy.

[0049] According to at least one embodiment of the method, the electrical signal stored by the storage capacitor is converted into a digital signal by an analog-to-digital converter. The conversion of the electrical signal into a digital signal by the analog-to-digital converter can occur after the pixel unit is illuminated or exposed to electromagnetic radiation. Thus, the conversion of the electrical signal does not extend the illumination period. The second readout component can include multiple analog-to-digital converters, with each storage capacitor group being assigned to one analog-to-digital converter. This readout of the pixels of the second group of pixels allows for a short illumination period.

[0050] According to at least one embodiment of the method, the electrical signal of each pixel of the second group of pixels is converted into a digital signal by an analog-to-digital converter before being transmitted to the memory element. The conversion of the electrical signals of the pixels of the second group of pixels into digital signals and the transmission to the memory element occurs during the illumination or exposure of the pixel unit to electromagnetic radiation. The illumination or exposure can be completed after the electrical signals of the pixels of the second group of pixels are transmitted to the memory element. Therefore, in order to minimize the illumination time, it is required to quickly convert the electrical signals into digital signals.

[0051] According to at least one embodiment of the method, the storage capacitors are arranged in groups, wherein each group includes at least two storage capacitors and the electrical signals of the storage capacitors of a group are transmitted together. The storage capacitors of each group are interconnected so that the electrical signals stored by the storage capacitors of a group can be transmitted together to the output of the pixel unit. The electrical signals of the storage capacitors of a group can also be transmitted simultaneously. It is also feasible that the electrical signals of the pixels connected to the storage capacitors of a group are transmitted simultaneously to the corresponding storage capacitors. By transmitting the electrical signals of the storage capacitors of a group together, the signal-to-noise ratio of the pixel unit is improved.

[0052] According to at least one embodiment of the method, the electrical signals of at least two pixels of the second group of pixels are simultaneously transmitted to the second readout component, thereby improving the signal-to-noise ratio of the pixel unit.

[0053] The following description of the accompanying drawings further illustrates and explains exemplary embodiments. Functionally identical or having the same effect components are indicated by the same reference numerals. Identical or substantially identical components may be described only with respect to the drawing in which they first appear. Their description is not necessarily repeated in subsequent drawings.

[0054] Figure 1 Shows the principle of global shutter mode operation.

[0055] Figure 2 Illustrate the principle of rolling shutter mode operation.

[0056] Figure 3 The principle of an exemplary embodiment of a method for operating a pixel unit is shown.

[0057] Figure 4A and 4B An exemplary embodiment of a pixel unit is shown.

[0058] Figure 4C Portions of the readout circuitry of an exemplary embodiment of a pixel cell are shown.

[0059] Figure 5A and 5B Another exemplary embodiment of a pixel unit is shown.

[0060] Figure 6 An exemplary embodiment of an image sensor is shown.

[0061] Depend on Figure 1 The principle of global shutter mode operation is shown. Time is plotted on the x-axis. The number of rows in pixel unit 10 is plotted on the y-axis. In global shutter mode, all rows of pixels 11 are exposed simultaneously. This time interval is labeled t1. After illumination with electromagnetic radiation, pixels 11 are read out sequentially. This time interval is labeled t2. This way, illumination time t1 can be kept short.

[0062] Depend on Figure 2 The principle of rolling shutter mode operation is shown. Time is plotted on the x-axis. The number of rows in pixel unit 10 is plotted on the y-axis. In rolling shutter mode, during an illumination period, rows of pixels 11 are successively exposed and read out. The duration of illumination with electromagnetic radiation is designated t1. Compared to global shutter mode, the illumination period is significantly longer. This means that the power consumption of light source 22 is increased.

[0063] exist Figure 3In FIG. 1 , the principle of an exemplary embodiment of a method for operating a pixel unit 10 is shown. Time is plotted on the x-axis. The number of rows in the pixel unit 10 is plotted on the y-axis. Figure 2 For the rolling shutter mode shown in FIG, during illumination with electromagnetic radiation, all rows of pixels 11 are exposed and read out successively. Figure 2 Compared to the rolling shutter mode shown, according to the method for operating the pixel cell 10, the illumination duration t1 is shorter. This is achieved by transferring the electrical signal of the pixel 11 to the storage capacitor 16 or the memory element 17 of the second readout component 15 of the pixel cell 10 during the illumination. The transmission to the storage capacitor 16 or the memory element 17 can be faster than usual for the rolling shutter mode because the electrical signal is temporarily stored by the storage capacitor 16 or the memory element 17. After the illumination, a further transmission of the electrical signal from the storage capacitor 16 or the memory element 17 to, for example, the output 24 of the pixel cell 10 occurs. Thus, a further readout process takes place after the illumination. In this way, a short illumination time is allowed. Thus, the method for operating the pixel cell 10 allows a short illumination duration t1 and a high-resolution readout process.

[0064] exist Figure 4A , a top view of an exemplary embodiment of a pixel unit 10 is shown. The pixel unit 10 includes a plurality of pixels 11, wherein each pixel 11 includes a photodiode 12. The pixels 11 are arranged to Figure 4A The pixels 11 are arranged adjacent to each other in a two-dimensional array (not shown). The pixels 11 are arranged on the radiation entry side 19 of the pixel unit 10. The first group of pixels 11 is arranged to detect electromagnetic radiation in a first wavelength range. The second group of pixels 11 is arranged to detect electromagnetic radiation in a second wavelength range, wherein the first wavelength range is different from the second wavelength range. The first group of pixels 11 is arranged to detect electromagnetic radiation in the visible light range. For this purpose, the first group of pixels 11 includes three different types of pixels 11, wherein each type of pixel 11 is arranged to detect electromagnetic radiation in a range different from the electromagnetic radiation range that the other types of pixels 11 are configured to detect. The second group of pixels 11 is configured to detect electromagnetic radiation in the infrared range.

[0065] exist Figure 4B In the Figure 4AA view of an exemplary embodiment of a pixel cell 10 is shown, wherein the layers below the plurality of pixels 11 are provided. The pixel cell 10 further comprises a readout circuit 13 comprising a first readout component 14 and a second readout component 15. The first readout component 14 is connected to the first group of pixels 11 and the second readout component 15 is connected to the second group of pixels 11. The first readout component 14 and / or the second readout component 15 are configured to operate in a rolling shutter mode. The second readout component 15 comprises a plurality of storage capacitors 16, wherein each pixel 11 of the second group of pixels 11 is respectively assigned to at least one of the storage capacitors 16. Each of the storage capacitors 16 is connected to an input of an analog-to-digital converter 23.

[0066] The readout circuit 13 is arranged on a side of the plurality of pixels 11 facing away from the radiation entrance side 19 of the pixel unit 10. This means that the readout circuit 13 is arranged below the plurality of pixels 11. Figure 4B , a plane in which the readout circuit 13 is provided is shown.

[0067] The first readout component 14 comprises two portions 20 arranged spaced apart from each other. The second readout component 15 is arranged between the two portions 20 of the first readout component 14 in a lateral direction x extending parallel to the main extension plane of the pixel cell 10.

[0068] Figure 4A and 4B The pixel cell 10 shown operates as follows. The pixels 11 are exposed to electromagnetic radiation which is converted into electrical signals by the photodiode 12. The electrical signals of the pixels 11 of the first group of pixels 11 are transferred to a first readout component 14. The first readout component 14 can be operated in a rolling shutter mode or a global shutter mode. During illumination with electromagnetic radiation, the electrical signals of the pixels 11 of the second group of pixels 11 are transferred to a second readout component 15. Transferring the electrical signals of the pixels 11 of the second group of pixels 11 to the second readout component 15 comprises transferring the electrical signals of each pixel 11 of the second group of pixels 11 to a corresponding storage capacitor 16 of the second readout component 15, or transferring the electrical signals of each pixel 11 of the second group of pixels 11 to a memory element 17 of the second readout component 15. Figure 5A and 5B A second alternative is shown in . The first readout component 14 and the second readout component 15 can operate independently of each other.

[0069] exist Figure 4C In FIG, a portion of the readout section 13 of an exemplary embodiment of the pixel unit 10 is shown. This portion shows a portion of the second readout section 15 of the readout circuit 13. Figure 4C1 shows three of the storage capacitors 16. The storage capacitors 16 are connected in parallel to one another. A switch 18 is provided between each two of the storage capacitors 16. Furthermore, the storage capacitors 16 are connected to the pixel 11 via another switch 18. Furthermore, the storage capacitors 16 are connected to the output 24 of the pixel unit 10 via another switch 18.

[0070] exist Figure 5A , a top view of another exemplary embodiment of the pixel unit 10 is shown. In this top view, Figure 5A The embodiment shown is configured with Figure 4A The settings shown are the same.

[0071] exist Figure 5B In the Figure 5A A view of an exemplary embodiment of a pixel unit 10 is shown, showing a layer disposed below the plurality of pixels 11. Figure 4B The embodiment shown differs in that the second readout unit 15 includes a memory element 17 instead of the storage capacitor 16. The memory element 17 can be a static random access memory. The second readout unit 15 also includes an analog-to-digital converter 23, wherein the input of the analog-to-digital converter 23 is configured to be connected to at least one pixel 11 of the second group of pixels 11, and the output of the analog-to-digital converter 23 is configured to be connected to the memory element 17. In order to transmit the electrical signals of the pixels 11 of the second group of pixels 11 to the memory element 17, each of the electrical signals is converted into a digital signal by the analog-to-digital converter 23 before being transmitted to the memory element 17.

[0072] exist Figure 6 , a top view of an exemplary embodiment of an image sensor 21 is shown. The image sensor 21 includes a plurality of pixel units 10. The pixel units 10 are arranged in a two-dimensional array. The image sensor 21 also includes a light source 22 synchronized with the pixel units 10.

[0073] Reference numerals

[0074] 10 pixel unit

[0075] 11 pixels

[0076] 12 Photodiode

[0077] 13 Readout circuit

[0078] 14 First readout unit

[0079] 15 Second readout unit

[0080] 16 Storage capacitor

[0081] 17 Memory Components

[0082] 18 Switch

[0083] 19 Radiation entry side

[0084] 20 Part of the first reading unit

[0085] 21 Image Sensor

[0086] 22 Light Source

[0087] 23 Analog-to-digital converter

[0088] 24 output

[0089] t1, t2 time intervals

[0090] x horizontal direction

Claims

1. A pixel unit (10), comprising: - a plurality of pixels (11), each pixel (11) comprising a photodiode (12), - a readout circuit (13), said readout circuit comprising a first readout component (14) and a second readout component (15), in - a first group of pixels (11) is configured to detect electromagnetic radiation in a first wavelength range, - a second group of pixels (11) is configured to detect electromagnetic radiation in a second wavelength range, - the first readout component (14) is connected to the first group of pixels (11), - the second readout means (15) is connected to the second group of pixels (11), - the first wavelength range is different from the second wavelength range, - the pixel unit is configured to transmit the electrical signals of the pixels (11) of the second group of pixels (11) to the second readout component (15) during the irradiation with electromagnetic radiation, and - the second readout means (15) comprises a plurality of storage capacitors (16), wherein each pixel (11) of the second group of pixels (11) is assigned to at least one of the storage capacitors (16), or - the second readout means (15) comprises a memory element (17), - the storage capacitor (16) is configured to store the electrical signal of the photodiode (12) of the second group of pixels (11), or the memory element (17) is configured to store the electrical signal of the photodiode (12) of the second group of pixels (11), - the storage capacitor (16) or the memory element (17) is configured to be read out sequentially after exposure to electromagnetic radiation.

2. The pixel unit (10) according to claim 1, wherein Each of the storage capacitors (16) is connected to an input of an analog-to-digital converter (23).

3. The pixel unit (10) according to claim 1, wherein The second readout component (15) includes an analog-to-digital converter (23), wherein an input of the analog-to-digital converter (23) is configured to be connected to at least one pixel of the second group of pixels (11), and an output of the analog-to-digital converter (23) is configured to be connected to the memory element (17).

4. The pixel unit (10) according to claim 1, wherein The first readout component (14) and / or the second readout component (15) are configured to operate in a rolling shutter mode.

5. The pixel unit (10) according to claim 1, wherein The first set of pixels (11) is configured to detect electromagnetic radiation in the visible range.

6. The pixel unit (10) according to claim 1, wherein The second set of pixels (11) is configured to detect electromagnetic radiation in the infrared range.

7. The pixel unit (10) according to claim 1, wherein The readout circuit (13) is arranged on a side of the plurality of pixels (11) facing away from a radiation entrance side (19) of the pixel unit (10).

8. The pixel unit (10) according to claim 1, wherein The readout circuit (13) and the plurality of pixels (11) are stacked on each other.

9. The pixel unit (10) according to claim 1, wherein The first readout member (14) comprises at least two parts (20) arranged to be spaced apart from each other.

10. The pixel unit (10) according to claim 9, wherein: The second readout component (15) is arranged between the two parts (20) of the first readout component (14) in a transverse direction (x) extending parallel to a main extension plane of the pixel unit (10).

11. An image sensor (21), comprising a plurality of pixel units (10) according to claim 1, and a light source (22) synchronized with the pixel units (10).

12. A method for operating a pixel unit (10), the method comprising the following steps: - exposing a plurality of pixels (11) of the pixel unit (10) to electromagnetic radiation, wherein: Each pixel (11) comprises a photodiode (12), wherein a first group of pixels (11) are configured to detect electromagnetic radiation in a first wavelength range, and wherein a second group of pixels (11) are configured to detect electromagnetic radiation in a second wavelength range, - converting electromagnetic radiation into an electrical signal by means of said photodiode (12), - transmitting the electrical signals of the pixels (11) of the first group of pixels (11) to a first readout component (14) of a readout circuit (13) of the pixel unit (10), - during the irradiation with electromagnetic radiation, transmitting the electrical signals of the pixels (11) of the second group of pixels (11) to a second readout component (15) of the readout circuit (13), wherein - the first wavelength range is different from the second wavelength range, and - transmitting the electrical signals of the pixels (11) of the second group of pixels (11) to the second readout means (15) comprising - transferring the electrical signal of each pixel (11) of the second group of pixels (11) to a corresponding storage capacitor (16) of the second readout means (15), - alternatively, transmitting the electrical signal of each pixel (11) of the second group of pixels (11) to a memory element (17) of the second readout means (15), - the electrical signals of the photodiodes (12) of the second group of pixels (11) are stored in the storage capacitor (16), or the electrical signals of the photodiodes (12) of the second group of pixels (11) are stored in a memory element (17), - The stored information is read out sequentially after exposure to electromagnetic radiation.

13. The method according to claim 12, wherein: The electrical signals of the pixels (11) of the second group of pixels (11) are transmitted to the second readout unit (15) in sequence or in groups.

14. The method according to claim 12, wherein: The first readout component (14) and the second readout component (15) operate independently of each other.

15. The method according to claim 12, wherein: The electrical signal stored by the storage capacitor (16) is converted into a digital signal by an analog-to-digital converter (23).

16. The method according to claim 12, wherein: The electrical signal of each pixel (11) of the second group of pixels (11) is converted into a digital signal by an analog-to-digital converter (23) before being transmitted to the memory element (17).

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