Pixel structure for optical distance measurement on an object and distance detection system with such a pixel structure
Patent Information
- Application Number
- DE102014215972
- Authority / Receiving Office
- DE · DE
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2014-08-12
- Publication Date
- 2025-11-06
- Estimated Expiration
- 2034-08-12
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
[0001] The present invention relates to a pixel structure for optical distance measurement of an object and to a distance detection system comprising such a pixel structure. The invention further relates to a pixel architecture for implementing distance-measuring image sensors and control methods.
[0002] Non-contact, distance-measuring sensors based on electromagnetic waves as sensing elements are considered a core technology that enables applications in areas such as consumer electronics, automotive, industrial applications, and security and surveillance. For real-time applications, it is desirable to use scannerless, pulse-time-of-flight-based methods. Furthermore, these applications typically require high immunity to external influences, such as parasitic ambient light, and should enable accurate measurements even with large dynamic variations (caused by potentially different surface properties, distance differences, and background light variations). Sensors that operate correctly under such parameters enable applications such as...Inspection and positioning systems, imaging systems in the automotive sector (e.g., passenger monitoring, airbag control systems, general safety systems, lane detection, early accident detection, pedestrian monitoring, parking assistance, input instruments for electronics), in industrial image sensor technology (e.g., in robotics, specifically autonomous service robots, route planning, object identification or driverless vehicles, in safety systems for machines and objects or in object measurement and conveyor belt systems), in security and surveillance (e.g., monitoring of hazardous areas, people monitoring and counting or intelligent traffic control), and in consumer applications (e.g., video games and entertainment, autonomous robotics or gesture recognition for handhelds, laptops, etc.). State of the art
[0003] For the applications mentioned, it is necessary to implement methods that are robust against background influences. In principle, active methods are typically used for this purpose, in which the measuring system emits electromagnetic waves, enabling measurements even in the dark. The dynamic range from which a scene is formed thus consists of the surface properties of the scene (reflectances), any tolerable background radiation, and the actual distance information. In principle, interferometry, triangulation, and pulse transit-time measurement are conceivable for implementing such systems. However, the first two methods require a certain amount of mechanical effort, making them impractical for cost reasons. Furthermore, for example...Stereoscopy, a commonly used technique classified as triangulation, is known to be susceptible to imaging errors and requires immense computational resources, which impairs real-time capability. Therefore, time-of-flight (ToF) systems are core technologies for the applications listed above.
[0004] Time-of-flight methods can, in principle, be implemented via direct transit-time measurement (stopwatch approach) or via indirect modulation techniques. The direct approach is potentially extremely susceptible to background noise, as the stopwatch can be triggered by parasitically scattered background light or thermally generated electron-hole pairs. With indirect methods, a fundamental distinction must be made between continuous and pulsed modulation of electromagnetic waves. Distance information can, in principle, be obtained via homodyne and heterodyne demodulation, cross-correlation, or dedicated short-time integration / sampling methods. However, continuous modulation also necessitates the continuous absorption of ambient light, which can both saturate the sensor and impair repeatability.To reduce this effect, the active irradiance would have to be increased relative to the background light, which is limited by eye safety requirements and the power budget of the active light source. Furthermore, continuous modulation leads to an ambiguous interpretation of distance depending on the modulation's periodicity. A modulation frequency of 20 MHz, for example, would provide unambiguous distance information up to 7.5 m. Objects farther from the sensor would be interpreted as being closer due to the periodicity.
[0005] Common methods for background light suppression in indirect propagation delay or phase measurement derive directly from demodulation principles. In the simple mixing method (homodyne / heterodyne), the downmixed modulation signal results in a DC (homodyne) or low-frequency signal (heterodyne) containing the phase / distance information. Ambient light that does not correspond to the modulation frequency generates modulation products during downmixing, which can be filtered. However, this requires complex circuitry, which introduces new sources of inaccuracy. Integrating methods, in principle, allow for improved accuracy because the signal can be amplified over a corresponding integration time. Cross-correlation receivers, for example, are based on this principle, suppressing background influences with increasing integration time if these are uncorrelated with respect to the signal.
[0006] A widely used method for distance measurement based on continuous modulation is the sampling method, in which a sine function is sampled four times at 90° phase differences using short-time integrators. These short-time integrators can be implemented with low noise in the charge domain. Ideally, the distance information can then be calculated using a function that takes a rational function as the argument of a trigonometric function. Both the numerator and denominator of this function contain only subtractions of the correspondingly phase-shifted, stored signals, thus eliminating the ambient light component, which is equally (deterministically) associated with all signals—provided the variation in ambient light does not violate the Nyquist-Shannon theorem. However, a detector can quickly reach saturation due to the continuous modulation and the resulting amount of ambient light picked up.However, even if saturation is not reached, the correspondingly long exposure to ambient light results in increased non-deterministic inaccuracy. As an alternative to sinusoidal modulation and corresponding sampling with short-time integrators, modulation methods based on rectangular modulation are also common, which can also be demodulated with short-time integrators. A disadvantage here, as with sinusoidal modulation, is the potentially large amount of accumulated background light.
[0007] A dedicated method that circumvents this problem is the pulse-modulated indirect time-of-flight (PM-ToF) method. In this measurement technique, the signal energy of the active irradiance is concentrated in a short time interval, thus inherently improving the signal-to-ambient light ratio. This is advantageous because eye safety regulations permit higher irradiance levels for short intervals. Typically, multiple accumulations are also performed in this method to improve repeatability. If it is permissible to increase the signal intensity more by using a lower repetition rate than the resulting reduction in integration time due to the lower repetition rate, a higher ratio of signal-related stored charges to ambient light-related stored charges results, and repeatability can be improved; the sensor saturates less quickly due to ambient light.Furthermore, this method has the advantage of increasing the unambiguous measurement range due to the reduced repetition rate. With a duty cycle of, for example, 1 / 1000 and a pulse width of 30 ns, distances up to 4.5 m can be interpreted unambiguously. Objects located between 4.5 m and 4.5 km would not result in a signal. Objects between, for example, 4500 m and 4504.5 m would theoretically fall back within the integration range. However, this is generally negligible in practical implementations because the spherical spread of the active illumination and the diffuse reflection of the scene result in a negligible signal strength for such distant objects.
[0008] A readily available demodulation method for pulse-modulated, indirect pulse transit-time measurement is multiple short-time integration (MST). Originally, this method employed two MSTs, requiring the elimination of ambient light by capturing a second frame without active illumination. Some methods utilize at least three MSTs, allowing the determination of the three unknowns—reflectance, background light, and distance—and enabling background light to be captured at the repetition rate of the active illumination. This, in principle, allows for significantly higher aliasing frequencies with respect to tolerable ambient light.Such a structure is based on the connection of a photoactive region, which is linked via at least four control electrodes to at least three storage regions and one discharge region, resulting in at least three short-term integrators and enabling the discharge of charge carriers generated by ambient light that occur outside the short-term integration windows. Possible implementations can be based on "photogate structures" or modified "pinned photodiodes".
[0009] Since high temporal resolutions are required for pulse transit-time measurements, implementations based on, for example, the lateral drift field detector are generally more suitable than "photogate structures". A possible implementation of a pixel architecture using the lateral drift field detector is described in Fig. 11a and Fig. Figure 11b shows the corresponding timing diagram. Fig. 12 shown.
[0010] According to Fig. 12. At least two short-time integrators (TX1 / TX2) of different lengths and / or time offsets are synchronized with the emission of a modulated electromagnetic wave. A first part of the reflected electromagnetic wave packet is accumulated – in this example – in the first short-time integration window (TX1) and a second part in a second short-time integration window (TX2).
[0011] A third short-time integrator (TX3) is used as a background light reference, ideally triggered outside the time range in which the reflected "light pulse" is expected. Distance, reflectance, and background light can thus be determined from the three independent signals stored in the three corresponding memory nodes.
[0012] As it is in Fig. As shown in Figure 11a, the three short-term integrators TX1-TX3 are implemented by transfer gates that connect a photoactive region with the associated storage nodes FD1-FD3. To prevent parasitically generated charge carriers from crosstalking into the storage nodes outside the short-term integration windows TX1-TX3, the photoactive region is connected to a discharge region DD via another transfer gate (TX4). This discharge region is permanently at a reference potential, allowing charge carriers to be discharged in a controlled manner.
[0013] As in Fig. As shown in Figure 11b, the photodetector is designed such that an n-shaped well is formed in the photoactive region. This well is separated from defects, such as those that can be dominant on a Si-SiO2 layer (gate oxide), by a p+ layer, resulting in a low dark current. The n-shaped well also exhibits a dopant concentration gradient, which generates an intrinsic drift field, causing photogenerated charge carriers to be propagated instantaneously towards the storage nodes.
[0014] In the area below the so-called Collection Gate (CX), which forms the connection between the photoactive area and the transfer gates / storage nodes, a preferred direction is permanently defined by connecting to the corresponding control electrodes TX1-TX4. This is achieved by always connecting three of the control electrodes to a low potential, thus creating potential barriers, while the remaining electrode is connected to a higher potential, thereby reducing any potential barrier and establishing a preferred direction.
[0015] Accordingly Fig. 12. In this application, these preferred directions are varied in such a way that pulse transit time measurement becomes possible. The CX is, in principle, optional – the transfer gates could also be directly connected to a photoactive region. However, such a gate allows the surface potential to be varied by connecting it to a variable reference potential, so that this degree of freedom can contribute to enabling a monotonically increasing potential profile from the photoactive region towards the storage node selected by connecting a transfer gate.
[0016] When implementing high-speed detectors for the pulse-modulated, indirect time-of-flight measurement method described above, it becomes apparent that a speed advantage, e.g., achieved by varying the dopant concentration in the photoactive region, would be reduced by attaching multiple electrodes to connect several short-time integrators to a single photoactive region. This is because the technology necessitates a large "Collection Gate" (CX), under which the potential may be somewhat flat in practice, and a corresponding reduction in charge carrier transfer speed through dedicated design of the photoactive region would be achieved.Furthermore, the desire to include multiple storage nodes and associated control electrodes to implement the function of different short-term integrators, and any drainage areas and associated electrodes to implement the removal of extraneous light-related, generated charge carriers, results in an unavoidable asymmetry (see . Fig. 11a). This is characterized by the fact that charge carriers may have to travel different paths to reach different storage nodes, resulting in different time resolutions.
[0017] Furthermore, different orientations and proximitys of the storage nodes result in a mismatch in storage node capacity, leading to varying sensitivities in the conversion of photogenerated charge carriers into electrical signals such as voltage. This can be problematic because, apart from a gain mismatch, which could be easily corrected with flat-field correction, it results in different saturation levels and varying effects of nondeterministic disturbances (reset noise, circuit noise). Moreover, the presence of multiple diffusion regions with different potentials—which inevitably arise during a measurement—can lead to a potentially detrimental potential distribution and the parasitic definition of preferred directions.
[0018] For example, charge carriers generated deep below the detector's space charge region, and thus outside the control region, can diffuse into areas where a preferred direction is defined again—not by the control electrodes or the gradient in the photoactive region, but by, for example, a potential maximum at the draining diffusions. In the worst case, such a mismatch could be so pronounced that one of the short-term integrators would operate significantly differently from the others, making it impossible to achieve simultaneous background light subtraction with the laser pulse acquisition. In this case, two consecutive frames (one with active illumination and one without) would have to be subtracted to achieve background light subtraction, which, however, results in significantly reduced aliasing frequencies with respect to the tolerable background light.
[0019] US 2010 / 0303299A1 discloses a depth sensor comprising a light source, a detector, and a signal processor. The light source transmits a source signal to the target according to a transmit control signal with reference times.
[0020] US 2008 / 0157012 A1 discloses an image data generation device comprising a photoelectric sensor with an arrangement of pixel generation units, each of which includes a photoelectric conversion element and a floating diffusion.
[0021] US 2011 / 0085043A1 discloses an image acquisition device comprising an infrared blocking filter, an image acquisition device with a plurality of pixels for capturing light transmitted through the infrared blocking filter, and four optical filters arranged on a light-capturing surface of the image acquisition device.
[0022] US 2004 / 0021057A1 relates to a distance measuring device and a photosensor circuit. By pulsing a light source, an object is illuminated, and the phase difference between the light reflected by the object and the original phase of the light source is measured to determine the distance to the object.
[0023] US 2009 / 0114802A1 relates to a method and apparatus for image generation. The image generation method emits light of a predetermined wavelength onto a target object at a predetermined interval.
[0024] US 2011 / 0129123A1 refers to an image sensor comprising a clock signal generator configured to generate and output at least a first and second clock signal, a plurality of pixels configured to generate associated distance signals based on corresponding clock signals from the at least first and second clock signals, and light reflected from an object.
[0025] DE 10 2008 018 718 A1 relates to an optical distance meter with a pulsed radiation source, which is designed to emit a radiation pulse with a pulse duration tp that is shorter than the radiation pulse period during a temporally continuous radiation pulse period and not to emit a radiation pulse during a temporally continuous dark period.
[0026] DE 10 2009 037 596 A1 refers to a concept for optical distance measurement, in which a radiation pulse is emitted in the direction of a measurement object.
[0027] The object of the present invention is to create a pixel structure and a distance detection system that enables accurate and / or fast distance detection.
[0028] This problem is solved by the subject matter of the independent patent claims.
[0029] A key concept of the present invention is the recognition that deviations (mismatches) regarding charge carrier transport within a pixel can be reduced by the pixel comprising subpixels, each subpixel having a photoactive area and at least one evaluation capacity configured to receive charge carriers generated in the photoactive area. Deviations from an ideal state can occur (within manufacturing tolerances) essentially the same for each subpixel and each evaluation capacity, thus reducing deviations in the transfer properties between charge carriers transported into the evaluation capacities and enabling precise detection. Furthermore, systematic measurement errors, which, for example,aliasing (folding or interference) caused at least partially by extraneous light can be reduced within a single acquisition cycle, thus eliminating the need for a further (correction) frame and saving time, allowing for rapid distance measurement.
[0030] According to one embodiment, a pixel structure for optical distance measurement of an object comprises at least one pixel, which includes a first subpixel, a second subpixel, and a third subpixel. The first subpixel comprises a first photoactive area, a first storage node, and a first evaluation gate. The first evaluation gate is located adjacent to the first evaluation capacity and the first photoactive area of the first subpixel and is configured to control the transport of charge carriers generated in the first photoactive area from the first photoactive area to the first evaluation capacity. The second subpixel comprises a second photoactive area, a second storage node, and a second evaluation gate, the second evaluation gate being located adjacent to the second evaluation capacity and the second photoactive area of the second subpixel.The second evaluation gate is configured to control the transport of charge carriers generated in the second photoactive area from the second photoactive area to the second evaluation capacity. The third subpixel comprises a third photoactive area, a third storage node, and a third evaluation gate. The third evaluation gate is adjacent to the third evaluation capacity and the third photoactive area of the third subpixel and is configured to control the transport of charge carriers generated in the third photoactive area from the third photoactive area to the third evaluation capacity.
[0031] An advantage of this embodiment is that the three subpixels can be structured similarly or identically, so that the transport of the charge carriers can take place under the same conditions and with the same deviations for the subpixels, and the deviation between the subpixels is small.
[0032] According to a further embodiment, a pixel structure for optical distance measurement of an object comprises at least one pixel, which includes a first subpixel and a second subpixel. The first subpixel comprises a first photoactive area, a first storage node, a second storage node, and a first and second evaluation gate. The first evaluation gate is adjacent to the first storage node and the first photoactive area of the first subpixel. The second evaluation gate is adjacent to the second storage node and the first photoactive area of the first subpixel. The first and second evaluation gates are each configured to control the transport of charge carriers generated in the first photoactive area from the first photoactive area to their respective adjacent storage nodes. The second subpixel comprises a third storage node and a third evaluation gate.The third evaluation gate is formed and configured adjacent to the third storage node and the second photoactive area of the second subpixel to control the transport of charge carriers generated in the second photoactive area from the second photoactive area to the storage node.
[0033] An advantage of this embodiment is that, based on charge carriers transported to two of the three storage nodes, distance and / or reflectance information regarding the object can be provided, and that, based on charge carriers transported to the remaining storage node, error correction can be performed with respect to background light or background radiation, which also generates charge carriers in the photoactive areas based on radiation from the object region. Alternatively, the functionalities, i.e., the respective information, of the charge carriers generated in the respective photoactive areas can also be evaluated in a reversed manner.
[0034] An advantage of both previously described embodiments is that, with an arrangement of only two subpixels, the surface area required can be small. The pixel structures of the preceding embodiments can be arranged two-dimensionally for area-based distance measurement, but also in a line form (line sensor, 1-dimensional) or in a point form (point sensor).
[0035] According to an advantageous embodiment of the previously described model, the second subpixel further comprises a fourth storage node and a fourth evaluation gate, wherein the fourth evaluation gate is located adjacent to the fourth storage node and the second photoactive area of the second subpixel. The fourth evaluation gate is configured to control the transport of charge carriers generated in the second photoactive area from the second photoactive area to the fourth storage node.
[0036] According to another embodiment, subpixels of a pixel are congruent.
[0037] An advantage of this embodiment is that, in the case of congruent, i.e. identical geometries, such as those of main page surfaces, geometric deviations that, for example, influence a charge carrier transport speed from photoactive areas to storage nodes, are further reduced between subpixels.
[0038] According to another embodiment, a pixel structure comprises a plurality of pixels arranged two-dimensionally offset from one another.
[0039] An advantage of this embodiment is that the object area can be detected with respect to several object sub-areas, for example one object sub-area per pixel.
[0040] According to another embodiment, a first color filter with a first transmission wavelength range (e.g., a red range) is arranged with respect to a first pixel, and a second color filter with a second transmission wavelength range (e.g., a blue range) is arranged with respect to a second pixel.
[0041] An advantage of this embodiment is that, in addition to determining distance, reflectance, and / or background light information, a color image for each pixel can be acquired, allowing the derivation of color images with depth information (RGBZ images). Furthermore, in addition to the arranged color filters, additional color information can be derived based on a combination (e.g., a difference calculation) of color information obtained from the color filters.
[0042] According to a further embodiment, a device comprises a pixel structure and a control circuit for controlling the pixel structure. The control circuit is configured to cyclically control the first evaluation gate during a first control interval synchronized with a radiation pulse from a radiation source, so that first charge carriers generated during the first control interval can be transported from the respective photoactive area to the first storage node. The control circuit is further configured to cyclically control the second evaluation gate during a second control interval synchronized with the radiation pulse of the radiation source and time-shifted with respect to the first control interval, so that second charge carriers generated during the second control interval can be transported from the respective photoactive area to the second storage node.The control circuit is further configured to cyclically control the third evaluation gate during the third control interval, which is time-shifted relative to the first and second control intervals, so that third charge carriers generated during the third control interval can be transported from a respective photoactive area to the third storage node. The third storage node can be located at the first subpixel, as described above, if the pixel comprises at least two subpixels, or at the third subpixel if the subpixel comprises at least three subpixels. The control intervals can be completely (non-overlapping) or partially (partially overlapping) time-shifted.
[0043] An advantage of this embodiment is that, based on an evaluation of charge carriers generated in the photoactive areas during the three control intervals, information regarding distance, reflectance and background light can be obtained.
[0044] According to a further embodiment, the control circuit is configured to cyclically and continuously activate a first discharge gate, located adjacent to the respective photoactive area from which the first charge carriers are transported to the first storage node, during a period outside the first control interval, in order to connect the respective photoactive area to a respective reference potential terminal. The control circuit is further configured to cyclically and continuously activate a second discharge gate, located adjacent to the respective photoactive area from which the second charge carriers are transported to the second storage node, during a period outside the second control interval, in order to connect the respective photoactive area to a respective reference potential terminal.The control circuit is further designed to cyclically control a third discharge gate, which is located adjacent to the respective photoactive area from which the third charge carriers are transported to the third storage node, continuously during a time outside the third control interval in order to connect the respective photoactive area with the respective reference potential connection.
[0045] An advantage of this embodiment is that an (electrical) connection between the photoactive area and a reference potential terminal allows charge carriers generated in the photoactive areas between the activation intervals (i.e., outside of the respective activation interval) to be discharged to the respective reference potential terminal. This ensures that only the charge carriers generated during an activation interval are transported to the respective storage node. Based on the quantity of charge carriers generated in the first, second, and / or third activation interval in the respective photoactive area, distance information about the object can be obtained or determined.
[0046] According to a further embodiment, a distance sensing system comprises a pixel structure and a radiation source configured to emit a radiation pulse. The photoactive areas of the subpixels are configured to generate charge carriers based on the radiation pulse reflected by an object. A control circuit of the distance sensing system is configured to provide distance information regarding the object and the pixel structure based on a distance to the radiation source.
[0047] An advantage of this embodiment is that synchronization of the radiation source with respect to the control of the photoactive areas or the evaluation and / or discharge gates is simplified compared to an implementation in which the radiation source is part of another device, if the radiation source, the pixel structure and the control circuit are part of a common system.
[0048] According to another embodiment, the radiation source of a distance detection system is designed to emit the radiation pulse with a low duty cycle of less than or equal to 0.5, i.e., 50%.
[0049] An advantage of this embodiment is that, based on a low duty cycle, the signal energy of the radiation pulse can be focused in a short time interval, so that, in accordance with eye safety regulations, a higher irradiance and thus a large difference between signal energy and background light energy can be achieved while complying with regulations.
[0050] Further advantageous embodiments are the subject of the dependent patent claims.
[0051] Preferred embodiments of the present invention are explained below with reference to the accompanying drawings. These show: Fig. 1 a schematic block diagram of a pixel structure for optical distance measurement on an object, in which a pixel has three subpixels according to an embodiment; Fig. 2 a schematic block diagram of a pixel structure for distance measurement on the object, in which a pixel has two subpixels according to an embodiment; Fig. 3 a schematic block diagram of a pixel structure in which the pixel has three subpixels that have the same function and the same elements according to an embodiment; Fig. 4 a schematic block diagram of a pixel structure with one pixel, which has the three subpixels with a modified arrangement according to an embodiment; Fig. 5 a schematic top view of a pixel structure having a plurality of pixels arranged two-dimensionally offset from each other according to an embodiment; Fig. 6 a schematic block diagram of a device comprising a pixel structure and a control circuit connected to the pixel structure, according to an exemplary embodiment; Fig. 7a a schematic flowchart of a method for determining distance information, reflectance information and background light information according to an exemplary embodiment; Fig. 7b-e show in relation to Fig. 7a Alternative timings for controlling the discharge gates TX1 and TX2 with respect to the light pulse with duration T p , over a time axis t according to exemplary embodiments; Fig. 8a A schematic block diagram of an exemplary arrangement of the storage nodes within the subpixels as it is used for the Fig. 1 is described with reference to the procedure as it is regarding Fig. 7a is described according to an exemplary embodiment; Fig. 8b an arrangement of the subpixels as shown in Fig. 2 is described, with reference to the procedure as it is regarding Fig. 7a is described according to an exemplary embodiment; Fig. 8c an alternative arrangement of the pixel structure from Fig. 8b according to an exemplary embodiment; Fig. 9 a schematic block diagram of a distance detection system that has the pixel structure according to Fig. 1, comprising the control circuit and the radiation source according to an exemplary embodiment; Fig. 10 an exemplary comparison of transmission and blocking ranges of color filters; Fig. 11a a schematic top view of a pixel structure according to the state of the art; Fig. 11b a schematic cross-sectional view of the pixel structure from Fig. 11a; and Fig. 12 a schematic timing of a procedure for evaluating the pixel structure from Fig. 11 according to the state of the art.
[0052] The following refers to the arrangement of transfer gates at photoactive areas where charge carriers are generated based on electromagnetic radiation. These charge carriers are transported via the transfer gates to storage nodes and, if necessary, to discharge areas. Elements referred to below as evaluation gates are transfer gates designed to control the transport of charge carriers to a specific evaluation capacity. Elements referred to below as discharge gates are transfer gates designed to control the transport of charge carriers to a specific discharge area. Discharge gates and evaluation gates can be identical in design; the different terminology serves only to distinguish them from one another.
[0053] Before exemplary embodiments of the present invention are explained in detail below with reference to the drawings, it should be noted that identical, functionally equivalent or equivalent elements, objects and / or structures in the different figures are provided with the same reference numerals, so that the description of these elements shown in different exemplary embodiments is interchangeable or can be applied to one another.
[0054] Fig. Figure 1 shows a schematic block diagram of a pixel structure 10 for optical distance measurement of an object 12. The pixel structure 10 comprises a pixel 14, which includes a first subpixel 16a, a second subpixel 16b, and a third subpixel 16c. The first subpixel 16a includes a photoactive area 18a configured to generate charge carriers based on electromagnetic radiation 22r received by the photoactive area 18a. The first subpixel 16a further includes an evaluation gate 24a and a storage node 26a located at the evaluation gate 24a. The evaluation gate 24a is designed to transport the charge carriers generated in the photoactive area 18a in an active state from the photoactive area 18a to the storage node 26a, or to control a transport of charge carriers from the photoactive area to the storage node 26a.The electromagnetic radiation 22r can be generated based on a radiation pulse emitted in the direction of the object 12, whereby the radiation pulse can have a time-varying intensity (e.g. on / off), so that the electromagnetic radiation 22r can also have a time-varying intensity and is only received by the pixel structure 10 at certain times.
[0055] The photoactive region 18a can, for example, be a silicon semiconductor material with a crystalline structure. Electromagnetic radiation 22r emanating from the object 12, for example, emitted or reflected, can contain photons that enter the pixel structure 10 and strike the photoactive region 18a. The photons of the electromagnetic radiation 22r can generate electron-hole pairs in the crystalline structure of the silicon semiconductor material. As a result of the irradiation by the electromagnetic radiation 22r, charge carriers can thus accumulate in the photoactive region 18a, i.e., be generated there.
[0056] The evaluation gate 24a can, for example, be configured as a transfer gate. The evaluation gate can be controlled between at least two states, e.g., via a field effect. During activation (switch-on), or at the point in time when a "conductive channel" is realized by inversion of the semiconductor, the conductive channel can be configured such that a rising potential profile is created. This causes charge carriers from the photoactive region 18a to be propagated to an electrode of this transfer gate that faces away from the photoactive region 18a, and only there do they cause a potential discharge. This allows for a depletion of the photoactive region 18a towards the storage node. Alternatively or additionally, the transport of the charge carriers can be controlled, e.g., based on a potential profile generated by the evaluation gate 26a. This potential profile allows for a redirection of the charge carrier flow direction.In simplified terms, evaluation gate 24a can be a switch element that has an open, possibly non-conductive or partially conductive state and a closed, conductive state. The closed state can also be referred to as the active state. Alternatively, evaluation gate 24a can be an element with a switching function that controls the direction of load transport in a time-variant manner. For example, load carriers can be transported to a discharge area when the evaluation gate is not activated (or activated), and load carriers can be transported to a storage node when the evaluation gate is activated (or not activated). The transition between the activated and unactivated states can be discrete or continuous. The transport can occur through and / or laterally and / or vertically past the evaluation gate, so that, for example,A so-called draining-only structure is implemented. Transport can therefore be based on modifying, removing, or creating a potential barrier between the photoactive area and the storage node or other elements, such as a drainage area.
[0057] The storage node 26a can be implemented as a floating-diffusion region, a capacitor, or another capacitive element, for example, through capacitive coupling and / or by interconnection with metal-insulator-metal (MIM), metal-oxide-semiconductor (MOS), metal-metal capacitors, or the like. The storage node 26a enables the storage of photogenerated charge and its conversion into an electrical voltage. In a floating-diffusion region, this conversion can be achieved, for example, by degenerating the semiconductor, allowing the floating diffusion to be fed to a readout circuit via a Schottky contact. An intrinsic depletion layer and the diffusion capacitance of the floating diffusion form part of the effective evaluation capacitance, which can also be referred to as the sense node capacitance.
[0058] The storage node 26a is designed to receive and store charge carriers generated over a period of time in the photoactive region 18a. Charge carriers in the photoactive region 18a can lead to a variation in the potential profile between the photoactive region 18a and the storage node 26a and / or to the formation of an electromagnetic field between these elements, so that when the evaluation gate 24a is in the active state, the charge carriers are transported wholly or partially from the photoactive region 18a to the storage node 26a. In other words, in charge-transfer-based detectors (such as pinned photodiodes, lateral drift field detectors, photogate structures, etc.), the potential profile can be designed by appropriately designing the detectors so that the potential maximum lies in the storage node even without a (control) signal. This enables a rising potential profile, or...An electric field can be generated even without varying the potential through the generation of charge carriers. The various charge-based detector types share this characteristic (with suitable design) but differ in the achievable parameters, such as sensitivity, charge transfer rate, noise, or the amount of charge that can be handled. The storage node 26a, in conjunction with the photoactive area 18a and the evaluation gate 24a, can thus form a short-term integrator. The storage node 26a can be referred to as the evaluation capacity.
[0059] The second subpixel 16b has the same structure as the first subpixel 16a. The second subpixel 16b includes a photoactive area 18b, which has the same function as the photoactive area 18a. The subpixel 16b also includes an evaluation gate 24b, which is located adjacent to the photoactive area 18b and has the same function as the evaluation gate 24a. The subpixel 16b also includes a storage node 26b, which is located adjacent to the evaluation gate 24b and has the same function as the storage node 26a.
[0060] The third subpixel comprises a photoactive area 18c, which has the same function as photoactive areas 18a and 18b. Subpixel 16c also includes an evaluation gate 24c, which is located adjacent to photoactive area 18c and has the same function as evaluation gates 24a and 24b. Subpixel 16c also includes a storage node 26c, which is located adjacent to evaluation gate 24c and has the same function as storage nodes 26a and 26b.
[0061] This means that subpixels 16a, 16b, and 16c are functionally identical. The photoactive regions 18a, 18b, and / or 18c could, for example, be photosensitive areas of pinned photodiodes, photogate structures, lateral third-field detectors, or the like.
[0062] Based on charge carriers generated in the photoactive areas 18a, 18b, and 18c, or based on charge carriers transported to the storage nodes 26a, 26b, and 26c, a distance 28 between the object 12 and the pixel structure 10 can be determined. This can be achieved, for example, by detecting and / or evaluating the time-of-flight difference between the emission of electromagnetic radiation towards the object 12 and the arrival of the (reflected) electromagnetic radiation 22r. A source of the electromagnetic radiation can be located adjacent to the pixel field, i.e., the pixel structure 10, or at another location with a known distance and orientation angle relative to the emission direction of the pixel structure 10, so that, based on a distance / time calculation (stopwatch function), the time of flight of the electromagnetic radiation from the radiation source to the pixel structure 10 can be converted into a path length.
[0063] The subpixels 16a, 16b, and / or 16c can be addressed simultaneously, with a time delay, and / or with a time overlap. This means that charge carriers from the photoactive area 18a can be transported to the storage node 26a in a first time interval, charge carriers from the photoactive area 18b can be transported to the storage node 26b in a second time interval, and / or charge carriers from the photoactive area 18c can be transported to the storage node 26c in a third time interval. Two of the time intervals can be arranged consecutively. This allows the two time intervals to be arranged so that, for example, if the electromagnetic radiation is emitted in a pulsed manner (e.g., on / off), the entire reflected pulse of the reflected electromagnetic radiation 22r can each be partially captured.The entirety of the reflected pulse 22r can, for example, generate a first charge quantity in the photoactive region 18a and a second charge quantity in the photoactive region 18b. A ratio of the two charge carrier quantities in the photoactive regions 18a and 18b, or in the storage nodes 26a and 26b, can be converted into distance information regarding the distance 28. Alternatively, the electromagnetic radiation can also be emitted continuously with a constant or variable intensity, for example from a radiation source. Alternatively, the first charge quantity can also be generated in the photoactive region 18b or 18c. The second charge quantity, or quantity of charge carriers, can alternatively also be generated in the photoactive region 18a or 18c.
[0064] If, for example, the energy of the emitted electromagnetic radiation reflected by object 12 is known, reflectance information (i.e., a measure of the reflected electromagnetic radiation 22r) can be determined by the ratio of the charge carriers generated in the photoactive areas 18a and 18b and / or transported to the storage nodes 26a and 26b on the one hand, and the energy of the emitted electromagnetic radiation on the other. If no (to be considered) background light is present, or its effects are negligible, the distance and reflectance information can also be obtained without additional knowledge of the energy. In this case, two unknowns (distance and reflectance) and two independent signals from the storage nodes 26a and 26b can be obtained. A corresponding system of equations would thus be uniquely determined.
[0065] The subpixels 16a, 16b, and / or 16c, projected onto a surface, can be arranged in a planar arrangement, meaning that the subpixels 16a, 16b, and / or 16c are spaced apart from each other in at least one spatial direction. The distance information regarding object 12 and pixel 14 can thus be obtained based on three spatially spaced photoactive areas 18a, 18b, and / or 18c, or based on the storage nodes 26a, 26b, and / or 26c. The distance information can therefore describe the distance 28 with respect to an area of the photoactive areas 18a, 18b, and / or 18c and an intervening area. The intervening area can, for example, be an area spanned by the subpixels 16a, 16b, and / or 16c. The distance 28 can refer to a reference point of the intervening area. The reference point can be an edge point.Alternatively, the reference point can be a geometric center point of the intervening area.
[0066] Pixel 14 can also be referred to as a superpixel or macropixel, comprising subpixels 16a, 16b, and / or 16c. Distance information, such as the distance 28 between object 12 and pixel 14, can be obtained with respect to these three subpixels 16a, 16b, and 16c, so that the distance 28 with respect to the pixel can be referenced to a reference point, such as a geometric midpoint between subpixels 16a, 16b, and / or 16c. Pixel 14 can comprise exactly three subpixels, 16a, 16b, and 16c. Alternatively, pixel 14 can also comprise additional subpixels.
[0067] In other words, the evaluation gate can control charge transport by shaping a potential profile so that charge carriers are preferentially propagated to, for example, the storage nodes. This can be prevented by the control gate overriding this preference by making the potential profile steeper towards another element, such as a discharge node.
[0068] Fig. Figure 2 shows a schematic block diagram of a pixel structure 20 for distance measurement of the object 12. The pixel structure 20 comprises a pixel 14', which includes a first subpixel 16'a and a second subpixel 16b. The first subpixel 16'a comprises the photoactive area 18a, on which the evaluation gate 24a and the evaluation gate 24b are located. The storage node 26a is located at the evaluation gate 24a. The storage node 26b is located at the evaluation gate 24b. The subpixel 16'a differs from the subpixel 16a in that two evaluation gates 24a and 24b are located at the photoactive area 18a. The two evaluation gates 24a and 24b can be controlled with a time offset from each other and / or with a time overlap, so that charge carriers generated in the photoactive area 18a can be transported to the respective storage nodes 26a and 26b during the active states of the evaluation gates 24a and 24b.
[0069] This allows only one photoactive area 18a to be arranged for the detection of charge carrier quantities at two control intervals. This enables a space-efficient implementation, as the installation space can be reduced compared to the pixel structure 10.
[0070] The subpixel 16b comprises the photoactive area 18b, the evaluation gate 24c, and the storage node 26c. Information based on the evaluation of charge carriers transported to storage nodes 26a, 26b, or 26c can be used to correct the background light information. Each piece of information from the three short-term integrators (shutters) is a function of several variables, including distance, reflectance, and background light. Switching a shutter to capture only ambient light depends on both the object's reflectance and the background light.
[0071] Charge carriers detected by the other two shutters, based on a light pulse emitted towards the object and causing electromagnetic radiation 22r, are each dependent on reflectance, distance, and background light. A combination of the three independent signals (information without electromagnetic radiation 22r and information with electromagnetic radiation 22r) allows conclusions to be drawn about the three unknowns.
[0072] The evaluation gates 24a and 24b can be arranged symmetrically on the photoactive region 18a. The symmetry can, for example, refer to an axis of symmetry 27 of the photoactive region 18a, with respect to which the photoactive region 18a is arranged in a mirror-symmetric manner. Alternatively, the evaluation gates 24a and 24b can also be arranged in a point-symmetric or rotation-symmetric manner on or around the photoactive region 18a. The symmetry enables the charge carriers generated in the photoactive region 18a to be transported to the storage nodes 26a and 26b to the same extent and / or at the same speed, so that, for example, two equally long and temporally offset activation intervals of the evaluation gates 24a and 24b, with a constant intensity of the electromagnetic radiation 22r, result in approximately equal quantities of charge carriers being transported to the storage nodes 26a and 26b.This leads to a high degree of comparability of the measurements.
[0073] For example, if the charge carriers transported to storage nodes 26a and 26b are used to determine the distance and reflectance information regarding object 12, a background light correction can be performed based on the charge carriers transported to storage node 26c. This allows for a more compact design compared to pixel structure 10. Furthermore, the photoactive area 18a can be made larger compared to pixel structure 10 while maintaining the more compact design, thus generating a higher quantity of charge carriers, which can lead to a higher signal strength and consequently reduced noise effects and higher measurement precision.
[0074] Alternatively, if, for example, the distance and reflectance information is determined based on charge carriers generated in the photoactive areas 18a and 18b, the respective storage node 26a or 26b for obtaining the charge carriers for determining the background light correction can be arranged in the subpixel 16'a to save space when the storage node 26b or 26a is evaluated to determine the distance and reflectance information.
[0075] Optionally, subpixel 16b includes an additional evaluation gate 24d, to which an optional storage node 26d is attached. This allows subpixel 16a and the optionally extended subpixel 16b to be executed congruently, resulting in high comparability of the measurements. For example, one of the two drive intervals, in which charge carriers are delivered to storage nodes and used to determine distance and reflectance information, can be obtained in two subpixels 16'a and 16b. Based on charge carriers transported to the other storage node, a correction regarding the background light information for each subpixel can be obtained, thus increasing the accuracy of the determined information.If the distance and reflectance information is determined based on the charge carriers generated in the photoactive regions 18a and 18b, a high degree of homogeneity of the determined information can be obtained with respect to an area assigned to pixel 14'. The area assigned to pixel 14' could, for example, be a sub-area of the object detected by the pixel or the image area of the pixel.
[0076] Pixel 14' can comprise exactly two subpixels, 16'a and 16'b. Alternatively, it can also contain other subpixels, such as subpixel 16'c.
[0077] The embodiments described below relate to pixel structures that have at least one pixel with three subpixels. The functionality described for these embodiments can alternatively also be obtained if a pixel is implemented according to the embodiments of pixel structure 20, i.e., the explanations listed below are also to be understood as advantageous further developments of pixel structure 20.
[0078] Fig. Figure 3 shows a schematic block diagram of a pixel structure 30, which comprises a pixel 32 with three subpixels 16a, 16b, and 16c that have the same function and identical elements. In this context, identical elements mean that each element has the same or comparable function. With regard to the evaluation gate 24a (TX1) of subpixel 16a, the evaluation gate 24b (TX2) of subpixel 16c, and the evaluation gate 24c (TX3) of subpixel 16c, this means, for example, that the evaluation gates 24a-c can each be implemented as transfer gates. The transfer gates may have different structures or types but exhibit the same or similar behavior with respect to their switching function. Alternatively, the respective elements can also be identical.
[0079] Each subpixel 16a-c has a photoactive area (photoactive area 18a, 18b, or 18c). Subpixels 16a-c also have storage nodes 26a (FD1), 26b (FD2), or 26c (FD3).
[0080] Adjacent to the photoactive areas 16a-c is an optional collection gate (CX) CX1, CX2, or CX3, through which the charge carriers generated in the photoactive areas 18a-c can be transported away. The respective evaluation gate 24a-c is located at the respective collection gate CX1-3 of the respective subpixel 16a-c. A discharge gate TX4 is located at the collection gate CX1. The discharge gate TX4, like the evaluation gates 24a-c, is a switching element or a transfer gate. The discharge gate TX4 can be controlled such that the charge carriers from the photoactive area 18a are transported to a discharge area DD1, which is located at the discharge gate TX4. A potential U is applied to the collection gates CX1-3. CGThe optional collection gates (CX1-3) can be configured to control the collection gates. An arrangement of these gates allows for the use of one degree of freedom to influence the surface potential in a specific region of the respective photoactive area 18a-c, thereby achieving a desired potential profile. The collection gate (CX1-3) can be controlled by setting it to a suitable analog value, thus eliminating the need for a (potentially binary) change in a switching state. In principle, the transfer gates (TX1-6) can also be directly connected to the respective photoactive area 18a-c.
[0081] In particular, the evaluation gate TX1 and the discharge gate TX4 can be controlled at different and / or overlapping times and / or time intervals, so that, for example, the evaluation gate TX1 or the discharge gate TX4 is closed, i.e., conductive, and the charge carriers from the photoactive area 18a are transported to the storage node 26a or to the discharge area DD1.
[0082] Based on the functionally identical structure of subpixels 16a, 16b, and 16c, the second subpixel, 16b, adjacent to the photoactive area 16b, has a collection gate CX2 and a discharge gate TX5 with a discharge area DD2 located thereon. The third subpixel, 16c, adjacent to the photoactive area 18c, has a collection gate CX3 and a discharge gate TX6 with a discharge area DD3 located thereon.
[0083] Subpixels 16a, 16b, and 16c form pixel 32. A first reference potential vddpix1 can be applied to the first discharge area DD1, meaning that, if the discharge gate TX4 is conducting, the charge carriers from the photoactive area 18a can be at least partially discharged from the photoactive area 18a via discharge area DD1. The second discharge area DD2 can be connected to a second reference potential vddpix2, so that, if the discharge gate TX5 is conducting, the charge carriers generated in the photoactive area 18b can be at least partially discharged via discharge area DD2. A third reference potential vddpix3 can be applied to the third removal region DD3, so that charge carriers generated in the photoactive region 18c can be removed at least partially via the removal region DD3 if the removal region TX6 is conductive.
[0084] The three reference potentials vddpix1, vddpix2, and vddpix3 can have different potentials, for example, more than 1 V, more than 3 V, or more than 5 V. Different electrical voltages (potentials) can allow for adjustment of the charge carrier outflow rate. Alternatively, the reference potentials vddpix1, vddpix2, and / or vddpix3 can have the same potential value and be connected together, forming a common reference potential vddpix. This common reference potential vddpix allows for a uniform outflow rate of charge carriers to the discharge regions DD1, DD2, and / or DD3.
[0085] The discharge gates TX4, TX5, and TX6 can be controlled to discharge charge carriers generated in photoactive regions 18a-c. During a measurement interval, the discharge gates TX4, TX5, and TX6 can be in a non-conducting state, while the evaluation gates TX1, TX2, and TX3 can be in a conducting state. This can be achieved by controlling the respective gates TX1-6. At the end of each measurement interval, the evaluation gate TX1 can be switched to a non-conducting state and the discharge gate TX4 to a conducting state, so that, to a first approximation, only those charge carriers generated in photoactive region 18a during the measurement interval are transported to the storage node FD1.
[0086] The evaluation gate TX1 can be controlled, for example, by applying an electrical signal (potential) U. TX1This occurs at the evaluation gate TX1. For example, a high potential of voltage U can be applied. TX1 The conducting state and the application of a low potential can cause a different, for example, non-conducting state. Alternatively, the states (conducting / non-conducting) can also be mutually reversed with respect to the applied potentials (high / low). The evaluation gate TX2 can also be controlled in this way using a signal U. TX2 and control of the evaluation gate TX3 by means of a signal U TX3 This can be done. The discharge gates TX4-6 can be controlled by means of signals U. TX4 -U TX6 take place.
[0087] The storage node FD1 can be connected to a reset potential FD1 via a reset transistor M1-1. The reset transistor is, for example, an NMOS transistor (NMOS: n-type metal oxide semiconductor). One terminal of the storage node FD1 is connected to a source terminal of the reset transistor M1-1. The reset potential FD1 can be applied to a gate terminal of the reset transistor M1-1. A reference potential vddpix4, for example, can be applied to a drain terminal of the reset transistor M1-1. A bulk terminal of the reset transistor M1-1 can be connected to a local or global reference potential, such as ground, i.e., a voltage potential of 0 V.This means that when the reset potential VD1 is applied to the gate terminal of the reset transistor M1-1, charge carriers can flow out of an evaluation area of the memory node FD1, and the memory node FD1 is cleared, i.e., reset. Clearing or resetting allows a new charge to be stored in a future measurement cycle. Alternatively, the reset transistor M1-1 can also be implemented as a different switching element, for example, as a suitably modified PMOS transistor (PMOS: p-type metal oxide semiconductor).
[0088] Resetting the storage node FD1 allows for the removal of ambient light-induced charge carriers, thus reducing ambient light-induced errors in the measurement signal. This can reduce or prevent saturation of the photoactive region due to ambient light, further increasing measurement accuracy.
[0089] Similarly, an evaluation area of the memory node FD2 of the second subpixel 16b can be connected to a reset potential FD2 via a reset transistor M1-2. A reference potential vddpix5 can be applied to the reset transistor M1-2.
[0090] Similarly, the third subpixel 16c has a reset transistor M1-3 with a gate terminal to which a third reset potential FD3 can be applied. A drain terminal of the reset transistor M1-3 can be connected to a reference potential vddpix 6. The reference potentials vddpix4, vddpix5, and vddpix6 can be interconnected and have the same value, i.e., the same potential. Furthermore, the reference potentials vddpix1, vddpix2, vddpix3, vddpix4, vddpix5, and / or vddpix6 can be interconnected to form the reference potential vddpix. This means that between an evaluation area of a storage node FD1-3 and a reference potential vddpix4-6, switches M1-1, M1-2 or M1-3, which can be controlled via reset potentials Reset FD1 - Reset FD3, are connected, enabling a reset of the respective storage node FD1-3.
[0091] A gate terminal of an amplifier transistor M2-1 is connected between the memory node FD1 and the reset transistor M1-1 of the first subpixel 16a. A drain terminal of the amplifier transistor M2-1 is connected to a supply potential vdda-HV. A bulk terminal of the amplifier transistor M2-1 is connected to the reference potential (ground). A source terminal of the amplifier transistor M2-1 is connected to a drain terminal of a selector switch M3-1, which is a MOS transistor. A gate terminal of the selector switch M3-1 is connected to a row select potential. A test potential (measurement voltage U) is connected to a source terminal of the selector switch M3-1. out1 ) available for retrieval.
[0092] This means that the amplifier transistor M2-1 is designed to amplify the charge carriers, a current generated by the charge carriers, or the charge carriers themselves (current or charge carrier amplification) and to apply a signal amplitude to an electrical potential. Applying the selection potential (row selection) to the drain terminal of the selection switch M3-1 allows the amplified potential (signal) U to be tapped. out1The described configuration can also be referred to as a common drain configuration (or source follower circuit) and can exhibit a voltage gain of less than 1. A current or charge gain factor can be greater than 1. The input current, for example, is purely parasitic and can range in magnitude from fA to pA. A signal output current can be relatively large, on the order of nA to µA. This allows a column capacitance large relative to the evaluation capacitance (or floating capacitance) to be recharged, thus generating large voltages based on relatively small charges. Controlling the pixel structure 30 can include regulating the resulting current to a constant value, thereby linearizing the voltage transfer characteristic, which can exhibit a gain of less than 1.
[0093] The operation of the first subpixel 16a can comprise two or more time intervals that repeat cyclically. In a first time interval, charge carriers can be discharged from the memory node FD1 by controlling the reset transistor M1-1. In a second time interval, if, for example, the reset transistor M1-1 is not conducting, the potential or signal U out1 If storage nodes are not reset or only partially reset between cycles, charge carriers stored in previous cycles can be retained. This allows for an averaging of charge carriers over two or more cycles, which can lead to a reduction in measurement noise. Alternatively, an evaluation and reset can take place in each cycle.
[0094] Similarly, subpixels 16b and 16c each have an amplifier transistor M2-2 and M2-3, respectively, and a selection transistor M3-2 and M3-3, respectively. With respect to the second subpixel 16b, the signal (measured voltage) U out2 and with respect to the third subpixel, the signal (measured voltage) U out3 tappable. The signals or measuring voltages U out1 , U out2 and / or U out3 Each can correspond to the potential provided by the amplifier transistors M2-1, M2-2 and / or M2-3.
[0095] As an alternative to the amplifier transistors M2-1, M2-2, and M2-3, a different amplifier circuit, such as a differential amplifier or operational amplifier, can also be used. The illustrated circuit of the reset transistors M1-1, M1-2, and M1-3, the amplifier transistors M2-1, M2-2, and M2-3, and the selection transistors M3-1, M3-2, and M3-3 is merely an example. Alternatively, a different circuit can be used that allows for the resetting and / or evaluation of generated charge carriers.
[0096] Although the transistors and gates are described as MOS-based transistors with source, drain, and gate terminals, insulated gate bipolar transistors (IGBTs) can alternatively be used, which have a complementary gate, collector, and emitter terminal. Alternatively or additionally, bipolar transistors and / or junction field-effect transistors (JFETs) can also be used.
[0097] Although the pixel structure 30 has been described in such a way that the optional collection gates (CX1-3) are arranged, the pixel structure 30 can also be implemented wholly or partially without them.
[0098] An advantage of such an arrangement is that a detected object or a region of the detected object can be independently detected by three subpixels 16a, 16b, and 16c, and the detected charge carriers can be evaluated independently. Due to the identical structure of subpixels 16a, 16b, and 16c, deviations from symmetry with respect to pixel 32 or each subpixel 16a-c can be reduced or minimized, so that deviations between measurement results of individual subpixels 16a, 16b, and 16c are also reduced or minimized, thus increasing measurement accuracy.
[0099] In other words, a pixel architecture of pixel structure 30, in combination with a suitable method, enables the operation of this pixel architecture, which in this combination avoids the previously mentioned disadvantages of the prior art and allows for precise and / or rapid evaluation of the distance information. In return, photoactive area or a fill factor (i.e., the proportion of active area per total area) can be sacrificed, for example, by arranging three photoactive areas 16a-c instead of one. Any potential signal loss can be compensated for by efficient charge carrier transfer.
[0100] The disadvantages described above result, at least in part, from the desire to bind the photoactive area of a pixel to multiple short-time integrators and any necessary discharge elements. These disadvantages can be reduced or eliminated if this need is removed and subpixels are implemented to perform the corresponding intake of background light and laser. Each of the subpixels could implement a reduced number of short-time integrators and discharge elements. Fig. Figure 3 illustrates an example of a subdivision into three subpixels 16a-c. In each of the subpixels 16a-c, at least one separate photoactive area 18a-c is connected to at least one storage node FD1-3 and at least one discharge area DD1-3. This enables the realization of instantaneous (i.e., immediate) acceleration of the charge carriers towards the storage nodes FD1-3 by incorporating a drift field. The geometry of the collection node CX can be significantly reduced compared to the prior art, potentially resulting in a significantly reduced charge carrier transfer time. Furthermore, the division into, for example, three subpixels allows for a considerably improved symmetry of each storage node FD1-3 with respect to the respective photoactive area 18a-c, which can simplify the alignment of a pixel to a model and / or be beneficial for all subpixels / shutters / short-term integrators, i.e.,for any part of the pixel structure, the same performance is enabled or guaranteed, so that the backlight subtraction can be realized simultaneously with the signal acquisition, resulting in an aliasing frequency with respect to the tolerable backlight of . f tolerable ambient light = fRepetition−active−lighting module2 (i.e., the repetition frequency of the active module (pixel) divided by 2). Typically, this is several kHz, for example, more than 2 kHz, more than 5 kHz, or more than 10 kHz.
[0101] Since each of the subpixels 16a-c, for example, comprises a separate photoactive area 18a-c, this pixel architecture can exhibit increased symmetry if separate discharge areas (DD1-DD3) are attached to each photoactive area. These discharge areas remove photogenerated charges when the short-term integrators (storage nodes FD1-3) are not selected. An example is shown in Fig. Figure 3 shows a 3-transistor readout circuit. Here, the reset transistors M1-1 to M1-3 define the potential on the memory node before the start of frame acquisition. This can be configured such that during a transfer phase (selection of the corresponding evaluation gate / shutter TX1-3), a monotonically increasing potential profile is realized from the photoactive area 18a-c to the memory node (memory node FD1-3). This potential can then be reduced by storing photogenerated charge carriers, which are primarily introduced into the memory node (memory node FD1-3) during a transfer phase. This allows the in-pixel source follower amplifiers (amplifier transistors) M2-1 to M2-3 to generate an output signal, which is then converted from the data bus to signals U by select transistors M3-1 to M3-3. out1 to U out3can be separated, thus avoiding a short circuit between the outputs of different pixels.
[0102] For this purpose, two or more short-time integrators of different lengths and / or time offsets can be synchronized with the emission of a modulated electromagnetic wave packet, so that at least two independent, time-of-flight-dependent (dependent on the time of flight of the electromagnetic radiation) signals, e.g. U out1 , U out2 and / or U out3 This results in at least one additional short-time integrator, serving as an ambient light reference, enabling a unique mapping of the output signals to the unknowns reflectance, background light, and distance. Dividing the pixel structure into subpixels (e.g., two or three subpixels) can lead to the arrangement of additional discharge areas and, potentially, further electrodes that link photoactive and discharge areas.
[0103] In other words, it shows Fig. 3. A subdivision of the short-term integration function into subpixels to increase the charge carrier transfer rate, symmetry, and tolerable extraneous light aliasing frequency.
[0104] Fig. Figure 4 shows a schematic block diagram of a pixel structure 40 with a pixel 35, which has the three subpixels 16a, 16b and 16c. The subpixels 16a-c differ from the pixel structure 30 as shown in the Fig. As described in Figure 3, the orientation of subpixels 16a-c is altered relative to each other. The second subpixel 16b is rotated relative to the first subpixel 16a by a first angle α1, which, for example, is 90°. The third subpixel 16c is rotated relative to the second subpixel 16b by a second angle α2, which, for example, is also 90°. This means that a principal axis 36a of the first subpixel 16a forms an angle of 90° with a principal axis 36b of the second subpixel 16b. The first subpixel 16a is rotated relative to the third subpixel 16c by a third rotation angle α3, which, for example, is 180°. This means that the principal axis 36b of the second subpixel 16b forms an angle of 90° with a principal axis 36c of the third subpixel 16c.
[0105] Subpixels 16a and 16c have a lateral offset 34°. This means that the angle α3 is only to be understood schematically, since the first principal axis 36a of subpixel 16a and the third principal axis 36c of subpixel 16c do not have a common intersection point and run parallel to each other. The principal axes 36a and 36c are only to be understood schematically and could, for example, represent an axis of symmetry with respect to the photoactive area of the subpixel if the photoactive area is symmetrically structured. Alternatively, the principal axes 36a-c could also describe any other component, an edge, or an orientation thereof.
[0106] Subpixel 16a and subpixel 16c are arranged opposite each other, so that storage nodes FD1 and FD3 and / or drainage areas DD1 and DD3 face each other. This allows for a compact arrangement of the circuitry between subpixels 16a, 16c and / or 16b.
[0107] As indicated by arrows 38a-f, a symmetrical design of the photoactive region 18a-c of a subpixel 16a-c is unnecessary, since the outflow of the generated charge carriers occurs, for example, only in one direction, i.e., towards the storage node FD1, FD2, or FD3, and symmetry for a symmetrical, approximately equally fast outflow of the charge carriers towards a second storage node is not required. This allows for increased degrees of freedom in the design of the photoactive regions. For example, by increasing the extent of one or more photoactive regions 18a-c along a lateral direction 42a, 42b, or 42c, their extent in another direction can be reduced, provided the area of the photoactive regions 18a, 18b, or 18c remains the same.The pixel structure 40 could, for example, exhibit a reduced overall extent parallel to a direction along the width 42b if the widths 42a, 42b, and 42c of the photoactive areas 18a-c are enlarged. The term "width" is used here only as an example and can also describe, for instance, the height, thickness, or length of an extent of the photoactive areas 18a-c.
[0108] Alternatively, the extent of the photoactive areas 18a-c with respect to one, several or all subpixels can be individually or collectively enlarged or reduced.
[0109] The direction towards a viewer of the Fig. The four oriented surfaces of subpixels 16a-c can be understood as the main surface of the subpixels. The main surface of subpixels 16a-c is congruent, for example, with respect to congruent main surface of the photoactive areas 18a-c and a comparable (symmetrical) arrangement of the evaluation gates TX1-3 and / or the storage node FD1-3. Furthermore, the arrangement of the discharge gates TX4-6 and the discharge areas DD1-3 can also be identical, so that the subpixels 16a-c are congruent overall. This allows both the number of charge carriers generated by an impact of electromagnetic radiation and the outflow and / or drift velocities of the charge carriers towards the discharge areas DD1-3 and / or storage node FD1-3 to be comparable between the subpixels 16a-c.
[0110] The pixel structure 40 can alternatively also have only two subpixels, which according to the explanations of the Fig. 2 are formed.
[0111] Alternatively, the subpixels 16a-c can have any other orientation relative to each other. For example, the photoactive areas 18a-c can be arranged facing each other. This allows the photoactive areas 18a-c to be arranged adjacent to each other, so that variation in incident electromagnetic radiation between the photoactive areas 18a-c can be reduced. Alternatively, as is the case, for example, in Fig. As shown in Figure 3, the subpixels 16a-c are arranged in a row structure. This means that the principal axes 36a-c can have any angle to each other and / or be parallel to each other.
[0112] Alternatively or additionally, a different number of subpixels, for example 2, 4, or more, can be arranged at any angle or parallel to each other. For example, the subpixels can be arranged on a circle, a closed or open elliptical, polygonal, or arbitrary curve. Furthermore, the photoactive areas 18a-c and / or the storage nodes FD1-3 can be arranged facing each other. This means that a storage node FD1-3 of one subpixel 16a-c can be oriented towards a photoactive area 18a-c of another subpixel 16a-c.
[0113] The total area of the photoactive regions 18a-c within pixel 40 can be the same as that of a photoactive region in pixel architectures where a pixel has only one photoactive region. Therefore, an arrangement of further subpixels, i.e., a third, fourth, etc., allows for a reduction in the photoactive area of each subpixel 16a-c compared to an arrangement of two subpixels. This means, for example, that a smaller number of charge carriers are generated per subpixel 16a-c when the incident electromagnetic radiation remains constant. A reduced number of charge carriers, in conjunction with a reduced area of the photoactive regions 18a-c, can be transported to the short-term integrators or the storage nodes FD1-3 within a shorter time, leading to faster determination of distance information.Furthermore, a small area of the photoactive regions 18a-c allows for a reduced number of electrodes contacting the photoactive region, i.e. connecting it to an evaluation gate TX1-3, removal gate TX4-6 or collecting node CX1-3.
[0114] In other words, it is conceivable to forgo the symmetry of the subpixels (partial pixels 16a-c) and their clear delineation, and to use this new degree of freedom, for example, for a potentially improved design of the geometry of the photoactive region, i.e., the photoactive area 18a-c. Any potential mismatch, meaning deviations between the discharge velocities of the charge carriers from the photoactive regions, can be reduced or prevented if one or more of the photoactive regions 18a-c are, for example, reduced in area, thus reducing the number of electrodes to be connected per photoactive region. This can lead to the maintenance of a fast charge transfer.
[0115] In other words, for the pixel architecture presented here, in conjunction with the proposed method, it is not necessary to define a preferred direction in the photoactive region. This means that the storage and removal regions do not necessarily have to be placed adjacent to each other. Furthermore, the pixel architecture proposed here imposes no limitations regarding the semiconductor material to be used or the doping type. It should be noted that the subdivision into subpixels can lead to a smaller photoactive region per subpixel, which can result in a lower number of photogenerated charge carriers per time interval. However, these charge carriers can potentially be propagated to the storage nodes with significantly higher time resolution, which is inherently advantageous for the measurement and compensates for the reduction in signal (due to the smaller effective photoactive region area). Fig. Figure 4 shows an alternative implementation concept that can be described as a "merging" of the subpixels at the expense of symmetry. The arrow directions indicate that a wider, but shorter subpixel can be achieved by abandoning the symmetry requirements, which is advantageous with respect to the charge carrier velocities.
[0116] Fig. Figure 5 shows a schematic top view of a pixel structure 50, which has a plurality of pixels 32a-g arranged two-dimensionally offset from one another, i.e., exhibiting a matrix structure. For example, the pixel structure 50 has nine column-shaped sections 44a-i, each comprising six subpixels 16a, 16b, and 16c of a pixel 32ag, respectively.
[0117] A first color filter 46a is arranged with respect to the subpixels of column structure 44a. A second color filter 48a is arranged with respect to the subpixels of column structure 44b, and a third color filter 52a is arranged with respect to the subpixels of column structure 44c. Color filter 46a has a first transmission wavelength range, for example, a red range. The red range can, for example, have a wavelength range of 630 nm to 790 nm. Color filter 48a has a second transmission wavelength range, for example, a green range. The green range can, for example, have a wavelength range of 480 nm to 560 nm. Color filter 52a has a third transmission wavelength range, for example, a blue range. The blue range can, for example, have a wavelength range of 420 nm to 480 nm.This means that the transmission of electromagnetic radiation in a blocking region of the respective color filter 46a, 48a, and 52a to the photoactive regions of subpixels 16a-c of pixels 32a-g, with respect to which the respective color filter 46a, 48a, or 52a is arranged, is reduced or prevented. Thus, charge carriers can be generated in the respective photoactive regions of subpixels 16a-c of pixels 32a-g of a column structure 44a-f, which provide information regarding the color spectrum of the incident electromagnetic radiation.
[0118] In other words, color filters 46a-c, 48a-c and 52a-c are arranged with respect to different subpixels 16a-c of a pixel 32a-g, so that a generation of charge carriers in different subpixels 16a-c of a pixel 32a-g based on different wavelength ranges is possible.
[0119] The color filters 46a, 48a, and 52a can also be transparent to electromagnetic radiation in the infrared range, allowing infrared radiation reflected from an object to pass through the filters. This enables the determination of distance, reflectance, and / or background light information based on the infrared radiation emitted, for example, by a light pulse from a radiation source. Furthermore, a color image of the object can be acquired by filtering individual wavelength ranges using the color filters 46a, 48a, and 52a. The infrared radiation and the color image can be acquired, for example, sequentially or in parallel in subpixels 16a-c and combined to form a color image (e.g., red-green-blue - RGB or cyan-magenta-yellow) with depth information (Z), an RGBZ image.With respect to column structure 44d, a color filter 46b is arranged; with respect to column structure 44e, a color filter 48b; and with respect to column structure 44f, a color filter 52b, which may have the same, overlapping, or different transmission wavelength ranges as color filters 46a, 48a, and 52a, respectively. Furthermore, with respect to column structures 44g-i, color filters 46c, 48c, and 52c are arranged, which may have the same, overlapping, or different transmission wavelength ranges as color filters 46a, 48a, and 52a, respectively.
[0120] In particular, color filters 46b and 46c can have the same transmission wavelength range as color filter 46a, color filters 48b and 48c the same transmission wavelength range as color filter 48a, and color filters 52b and 52c the same transmission wavelength range as color filter 52a. This enables column-wise color scanning of the object or a captured object area.
[0121] A column structure 44a-f can contain any number of identical or differently formed pixels and / or subpixels, that is, a number of pixels greater than or equal to 1 and / or a number of subpixels 16a-c greater than or equal to 2. Alternatively, the multitude of pixels 32a-g can also be arranged in a row structure. Alternatively, the multitude of pixels 32a-g can also be arranged according to another pattern, such as a diamond pattern (diagonal arrangement). Alternatively, the pixels can have a random distribution. Furthermore, the multitude of pixels 32a-g can be arranged in a combination of patterns or arranged in such a way that no pattern can be determined.
[0122] Furthermore, with respect to subpixels 16a-c of one or more pixels 32a-g, only two different color filters may be arranged. Based on an underlying color system, such as additive or subtractive, a remaining third color can be determined by adding or subtracting the two filtered colors.
[0123] Alternatively, a color filter can also be arranged with respect to several or all subpixels of a pixel, so that, for example, one color information is obtained per pixel and a color combination is obtained with respect to several pixels.
[0124] As an alternative to pixels 32a-g, pixel structure 50 can also be formed entirely or partially from pixels 14, 14' and / or pixel 35. Alternatively or additionally, one or more color filters with a different transmission wavelength range and / or a blocking wavelength range can be arranged.
[0125] In other words, a color image (RGB) and a distance image (Z) can be acquired sequentially. Alternatively, subpixels 16a-c or pixels 32a-g can also, at least partially, incorporate another photoactive area, such as a different charge carrier transfer-based photodetector, like a photogate, a pinned photodiode, or a CCD (charged-coupled device). This allows for the parallel acquisition of distance images and color images, so that a combined color-distance image (RGBZ image) can be acquired more quickly.
[0126] Another advantage of the exemplary in Fig. 1, Fig. 2, Fig. 3 or Fig. The pixel architecture described in section 4, with its 10, 20, 30, or 40 pixels, offers easy applicability for RGBZ imaging. In this architecture, a color filter (RGB) can be applied to each subpixel, which is advantageous because these filters are typically transparent in the infrared range, commonly used for Time-of-Flight (ToF) technology. The coaxial arrangement of the distance and color image acquisition modules and the significantly reduced camera size that would result from combining a color image sensor with a 3D image sensor are also beneficial. With this pixel architecture, the color filters could be applied to the image sensor in strips, representing a cost-effective alternative to the more common Bayer patterns.Furthermore, it may be practical to have a controllable IR bandpass filter, which could be implemented mechanically or electrochemically, to filter out background components during 3D recording, thus reducing or preventing sensor saturation caused by ambient light. Alternatively, a controllable bandpass filter could be positioned relative to one or more pixels of the pixel structure and, for example, be influenced by a control circuit in a time-variant manner with respect to transmission properties such as wavelength passbands and / or transmission coefficients, for instance, to control the passband wavelengths in a time-variant manner. This could be an electronically controllable filter (such as Kerr cells or other filters) that is arranged over a large area relative to the pixel structure, in order to, for example, improve background sensitivity outside the desired time window (t0-t7).
[0127] Alternatively, only two different color filters can be arranged across the multitude of subpixels 16a-c or pixels 32a-g, for example, a red filter and a blue filter. Further color information can be derived by combining the color information obtained using the color filters. For example, in an additive color system, green information can be derived based on the difference between an unfiltered (possibly approximately white) color, i.e., a total information value, and the red or blue information, which offers advantages with regard to color noise. Alternatively or additionally, other color filters, which are at least partially transparent with respect to magenta, cyan, and / or yellow, for example, can be arranged. Furthermore, color information can be derived based on other color systems, such as the subtractive color system.Alternatively or additionally, the filters can be arranged as a combination of fully transparent and partially transparent (color-selective) filters.
[0128] Fig. Figure 6 shows a schematic block diagram of a device 60 comprising a control circuit 54 connected to the pixel 32. The control circuit 54 is configured to receive signals, potentials, and / or currents from the pixel 32 and to control the pixel 32, for example, by the control circuit 54 being configured to output the signals Reset FD1-3, Row Selection, U TX1 - U TX3 and / or U TX4 - U TX6 , as they are in the Fig. 3 are described, to be applied to the device 60. With reference to Fig. 3. The control circuit 54 can be configured to process the signals U out1 , U out2 and / or U out3to be received by pixel 32. The control circuit 54 is configured to determine distance information regarding object 12 based on the quantity of charge carriers generated in the photoactive regions 18a-c. A radiation source 56 can, for example, be configured to emit electromagnetic radiation 22, perhaps in pulse form, such that the electromagnetic radiation 22r is at least partially reflected by object 12 and received by pixel 32.
[0129] To determine the distance information, the control circuit 54 can, for example, be configured to obtain information regarding a position and / or a transmission time and / or interval. Using this information, the distance can be determined, for example, based on transit time calculations (distance = speed x time) and / or trigonometric functions.
[0130] Fig. Figure 7a shows a schematic flow diagram of a procedure 700 for determining the distance information, the reflectance information and background light information, as can be carried out, for example, by the control circuit 54.
[0131] To illustrate the process of a procedure, such as that executable by the control circuit 54, nine graphs 710, 720, 730, 740, 750, 760, 770, 780, and 790 are shown side by side. Graphs 710 to 790 share a common abscissa in the form of a time axis t. Graphs 710 and 720 schematically depict, on their respective ordinates, a normalized energy level E of the electromagnetic radiation emitted by a radiation source (graph 710) or received by the pixel (graph 720). An energy level 58a represents the energy of background light, for example, at the location of the radiation source. An energy level 58b also represents an energy level of the background light, for example, at the location of the pixel structure. The energy levels 58a and 58b can be the same or different.
[0132] Graphs 730 to 790 each have a normalized ordinate V, which is calculated with reference to Fig. 3 the signals that can be applied to the -gates TX1-6 U TX1 to U TX6 or, for graph 790, a combined signal “Reset FDs” (i.e., reset the memory nodes) is shown, which exemplifies a joint control of the signals Reset FD1, Reset FD2 and Reset FD3 in Fig. 3 means. Alternatively, the control of one or more reset signals (Reset FD1 - Reset FD3) can also be done individually.
[0133] In a time interval before time t0, the control circuit 54 is configured to allow charge carriers to flow out of the storage nodes FD1-3 by applying the reset signal FDs. Furthermore, the control circuit 54 is configured to... TX4 , U TX5 and U TX6 to provide so that charge carriers generated in the photoactive areas 18a-c can be transported to the discharge areas DD1-3. In a control interval (t2- The control circuit is configured between two time points t1 and t2 to process the signal U. TX3 to provide and simultaneously the signal U TX6 to deactivate or switch the discharge gate TX6 into a blocking state. This means that charge carriers generated in the photoactive region 18c can be transported to the storage node FD3. The control circuit 54 is designed to operate based on the quantity of charge carriers transported to the storage node FD3 or based on the strength of the signal U. out3 to determine the intensity of the backlight. This means that the control circuit 54 is designed to determine backlight information based on the control interval (t2-t1).
[0134] The control circuit 54 is synchronized in time with the radiation source 56. At time t3, the radiation source 56 is configured to emit electromagnetic radiation 22 in the form of a light pulse with a duration T. p to emit, for example, based on a cyclic clock or based on control by the control circuit 54 or another device. The end of the light pulse is designated at time t5 on the time axis. In other words, the radiation source 56 is designed to emit electromagnetic radiation 22 (possibly in pulses) during a time interval (t5-t3).
[0135] The control circuit 54 is designed to switch the evaluation gate TX1 to a conducting state and the discharge gate TX4 to a non-conducting state during the time interval (t5-t3), so that charge carriers generated in the photoactive area 18a can be transported to the storage node FD1 and the corresponding signal U out1 can be obtained.
[0136] The control circuit 54 is configured to switch the evaluation gate TX2 conducting and the discharge gate TX5 non-conducting during a time interval (t7-t5) that directly follows the time interval (t5-t3), so that charge carriers generated in the photoactive area 18b can be transported to the storage node FD2 and the signal U out2 The electromagnetic radiation 22r, that is, the light pulse, arrives at pixel 32 with a time delay relative to time t3 and is reflected from object 12. The time of flight (ToF) τToF The transit time τ can be described as the time between the emission of the light pulse 22 at the radiation source 56 and the arrival of the reflected light pulse 22 at the pixel 32. The reflected light pulse 22r causes charge carriers to be generated in the photoactive areas 18a and 18b. The transit time τ ToF This causes the reflected light pulse 22r to begin at time t4 (t4 = t3 + τ ToF ) and ending at time t6, when pixel 32 arrives. Time t5 follows time t4, with time t5 preceding time t6 on the time axis. Time t7 follows time t6.
[0137] The time interval (t6-t4) in which the reflected light pulse arrives at pixel 32 partially overlaps with the interval (t5-t3) and partially with the interval (t7-t5). This means that the reflected light pulse 22r can be detected partly by storage node FD1 and partly in storage node FD2 in the form of charge carriers transported there. A hatched area 62a denotes a measure of charge carriers that are generated in the photoactive area 18a and transported to storage node FD1, or a signal strength U. out1 . A hatched area 62b describes a measure of charge carriers that is generated in the photoactive area 18b and transported to the storage node FD3, or an amplitude of the signal U. out2 .
[0138] During the time intervals (t5-t3) and (t7-t5), charge carriers generated based on background radiation in the photoactive regions 18a and 18b can also be transported to the storage nodes FD1 and FD2 and transmit the signals U out1 and U out2 to influence, that is, to distort. This is represented by areas 63a and 63b. This means that the signal accumulated in each case includes background light accumulated over the respective interval. The background light information can relate to the detected object area, such as scattered light that strikes the photoactive areas independently of the radiation source 56. The control device 54 is designed to counteract this distortion based on the signal U. out3 or on the charge carriers that are present during the time interval (t 2- to correct the signal levels transported from t1 to storage node FD3. This can be done, for example, by subtracting the signal levels.
[0139] The control unit 54 can, for example, calculate the sum of the hatched areas 62a and 62b (possibly cleared of backlighting) to determine the total energy of the reflected light pulse. If the control unit 54 is provided with information regarding the energy intensity of the emitted light pulse from the radiation source 56, a measure of the reflectance of the object 12 can be obtained, for example, by subtraction or division. In other words, the sum of the hatched areas 62a and 62b (possibly cleared of backlighting) or the signals U can be used to determine the total energy of the reflected light pulse. out1 and U out2Describe the total energy of the reflected light pulse. A proportion of the total energy of the reflected light pulse relative to the total energy of the emitted light pulse can indicate what proportion of the emitted light pulse is reflected by object 12, thus containing the reflectance information. The control intervals (t2-t1), (t5-t3), and (t7-t5) can cover the same or different time periods.
[0140] The control circuit 54 is designed to process the signals U out1 and U out2 to relate them to each other, for example by calculating a quotient. A quotient of the signals U out1 and U out2A ratio of the shaded areas 62a and 62b (corrected for background radiation / background light or not) can provide information about the proportions of the reflected light pulse received by pixel 32 in the time interval (t5-t3) and in the time interval (t7-t5). Synchronizing the time intervals (t5-t3) and (t7-t5) allows for the determination of the propagation time τ. ToF The runtime τ ToF If the distance between the radiation source 56 and the pixel 32 is known, it can be converted, for example, into a path traveled by the electromagnetic radiation 22.
[0141] If, for example, the radiation source 56 is located adjacent to pixel 32, the distance between a surface of object 12 facing pixel 32 and pixel 32 can be approximated as half the distance traveled by the light pulse.
[0142] Depending on the implemented pixel structure, the allocation of storage nodes 26a-d or FD1-3 can be carried out, for example, according to the explanations for pixel structure 10, pixel structure 20 and / or pixel structure 30.
[0143] The control circuit 54 can be configured to perform the distance determination cyclically. This means that the control circuit can be configured to cyclically, in one cycle, in several cycles, or in each cycle, control the first evaluation gate TX1 during a first control interval (t5-t3) synchronized with a radiation pulse from the radiation source 56, so that the first charge carriers generated during the first control interval (t5-t3) can be transported from the first photoactive area 18a to the first storage node FD1.The control circuit is further configured to control the second evaluation gate TX2 during a second control interval (t7-t5) synchronized with the radiation pulse of the radiation source 56 and lying outside the first control interval (t5-t3), so that second charge carriers generated during the second control interval (t7-t5) can be transported from the second photoactive area 18b to the second storage node FD2. The control circuit is further configured, for example, to control the third evaluation gate TX3 during a third control interval (t7-t5) lying outside the first (t5-t3) and the second control interval (t7-t5). 2- to control t1), so that during the third control interval (t 2- t1) generated charge carriers can be transported from the photoactive area 18c to the third storage node FD3.
[0144] During a time outside the first drive interval (t5-t3), the control circuit 54 is configured to continuously drive the first discharge gate TX4 to connect the first photoactive area 18a to a first reference potential connection vddpix1. During a time outside the second drive interval (t7-t5), the control circuit 54 is configured to drive a second discharge gate TX5 to connect the second photoactive area 18b to a second reference potential connection vddpix2. During a time outside the third drive interval (t 2- t1) the control circuit 54 is designed to control a third discharge gate TX6 to connect the third photoactive area 18c to a third reference potential connection vddpix3.
[0145] The control of the respective discharge gates TX4-6 can occur outside of the other time intervals (t5-t3), (t7-t5) and / or (t 2-t1) wholly or partially, but preferably in a sufficiently large time interval before the first, second and / or third drive interval, so that the respective photoactive area 18a-c is emptied with respect to the generated charge carriers before a measurement interval starts.
[0146] This means that, alternatively, the control of the discharge gates TX4, TX5 and / or TX6 can also be carried out only section by section, i.e. not continuously during a cycle, and can be synchronized, for example, in such a way that a sufficient discharge time of the photoactive areas 18a, 18b and / or 18c is enabled.
[0147] Although the arrangement of the control intervals (t5-t3), (t7-t5), and (t2-t1) has been described as being sequential in time, the control intervals (t5-t3), (t7-t5), and (t2-t1) can also be arranged to overlap completely or partially in time. Acquisition of two independent signals (graphs 730 and 740) or three independent signals (graphs 730, 740, and 750) allows for the determination of distance and reflectance information, and additionally, background light information. Furthermore, the control intervals (t5-t3), (t7-t5), and (t2-t1) can have the same or different lengths.
[0148] Time intervals in which a photoactive area (18a-c) is connected to a reference potential connection (vddpix1-3) via the activation of a respective drain gate (TX4-6) (draining phase) can partially overlap with time intervals in which the respective evaluation gate (TX1-3) is activated (transfer phase). An electrical short circuit between the storage nodes and the reference potentials vddpix1-3 can be prevented by the design of the potential profiles, so that functionality is maintained even if the transfer and draining phases overlap.
[0149] The described procedure can be repeated several times to acquire a distance and / or reflectance measurement (frame) in order to increase measurement accuracy. For this purpose, multiple light pulses can be emitted to acquire a frame, and their reflected components can be evaluated.
[0150] The cyclical acquisition of images or frames enables a temporally resolved determination of distance information, which can be combined with motion information. Alternatively, the control circuit 54 can also be configured to perform the distance determination acyclically, stochastically, or deterministically with variable time intervals, or only once.
[0151] In other words, it shows Fig. 7a An exemplary timing diagram of a possible procedure with which the exemplary in Fig. The structure described in section 3 can be operated.
[0152] Alternatively, a pixel structure, as seen in the Fig. 1, Fig. 2 or Fig. As described in section 4, they are operated in this manner.
[0153] As an alternative to a three-subpixel implementation, a solution with two or more subpixels is possible. With two subpixels, backlight subtraction (taking background light information into account) can be achieved via a suitably adapted subpixel structure that provides a short-term integrator for background light capture in at least one subpixel.
[0154] The above descriptions illustrate a possible sequence for acquiring distance-reflectance information. Alternatively, the TX3 signal can also be acquired after TX1 and / or TX2. Charge carriers generated by the light pulse can be removed before the respective measurement interval for TX3. If the three signals TX1-3 are independent of each other, information regarding distance, reflectance, and background light can still be extracted even if the background light information is distorted by charge carriers that were not completely removed beforehand.
[0155] Fig. Figures 7b-e show alternative timings for controlling the discharge gates TX1 and TX2 with respect to the light pulse with duration T. p , over a time axis t.
[0156] Fig. Figure 7b shows an example timing where a drive (Graph 730) of the discharge gate TX1 begins at approximately the same time as the light pulse (Graph 710) and ends after the light pulse. A drive (Graph 740) of the discharge gate TX2 is shorter than a drive duration of the discharge gate TX1 and begins during the light pulse and during the drive of the discharge gate TX1, ending after the light pulse and before the end of the drive of the discharge gate TX1; that is, the drive of the discharge gate TX2 overlaps with the drive of the discharge gate TX1 and the light pulse.
[0157] Fig. Figure 7c shows an example timing where the control of the TX2 exhaust gates is compared to the timing from Fig. 7b begins simultaneously with the light pulse and the activation of the discharge gate TX1 and ends before the light pulse.
[0158] Fig. Figure 7d shows an example timing where the light pulse, the control of the exhaust gate TX1 and the exhaust gate TX2 end approximately simultaneously.
[0159] Fig. Figure 7e shows an example timing where the control of the TX2 exhaust gate is compared to the timing from Fig. 7b is extended and ends after the activation of the discharge gate TX1.
[0160] The duration of the control intervals for the exhaust gates and / or the light pulse can differ from one another and / or have different start or end points. Even if the above descriptions assume an approximately simultaneous start or end to a control event, this simultaneity can be limited by differing signal propagation times from the control device to the respective element, i.e., the radiation source and / or the exhaust gates. Distance information, reflectance information, and / or background light information can be unambiguously determined if unambiguous, i.e., bijective, mappings are provided by the control of the radiation source and / or the exhaust gates. This can be achieved, for example, if the control intervals TX1-3 partially overlap, i.e., are time-shifted and / or have different durations.
[0161] The Fig. 8a, Fig. 8b and Fig. Figures 8c each show a schematic block diagram of an exemplary arrangement of the storage nodes FD1-3 within the subpixels 16a, 16b and, if applicable, 16c, with reference to method 700, wherein the Fig. 8a additionally on Fig. 1 and the Fig. 8b and Fig. 8c additionally on the Fig. 2 refer.
[0162] How it is for the Fig. As described in section 1, the pixel structure has 10 in Fig. 8a three subpixels with one storage node FD1-3 each, each of which is configured to receive charge carriers in one time interval, graphs 730, 740 and 750 respectively.
[0163] The numbers 1, 2 and 3 can be equated, by way of example, with the numbering of the graphs 730 (TX1), 740 (TX2) and 750 (TX3).
[0164] Fig. Figure 8b shows an arrangement of subpixel 16'a and subpixel 16b, where the storage nodes FD1 and FD2 of subpixel 16'a can be used to determine distance and reflectance information (graphs 730 and 740) and background light information (graph 750) can be obtained in subpixel 16b.
[0165] Alternatively, the function of the storage nodes FD1, FD2 and FD3 with respect to graphs 730, 740 and 750 can be arbitrarily swapped.
[0166] Fig. Figure 8c shows an example of an alternative arrangement of the pixel structure 20. Fig. Figure 8b shows subpixel 16'a and a functionally identical subpixel 16'b, meaning that the second subpixel 16'b also has two storage nodes, FD2 and FD3b. Distance and reflectance information can be stored partly in pixel 16'a (for example, graph 730 for FD1) and partly in subpixel 16'b (graph 740 for storage node FD2). Each subpixel 16'a and 16'b has a storage node FD3a and FD3b, respectively, which can be used to determine the background light information (graph 750). The determination of the background light information using storage nodes FD3a and FD3b can be performed simultaneously and / or with a time delay.
[0167] A time delay in which charge carriers are determined for the storage nodes FD3a and FD3b can be used to determine additional information regarding the background light.
[0168] Fig. Figure 9 shows a schematic block diagram of a distance sensing system 90, comprising the pixel structure 10, the control circuit 54 coupled to the pixel structure 10, and the radiation source 56. The control circuit 54 and the radiation source 56 are interconnected, enabling simple synchronization of the control circuit 54 and the radiation source 56. This can be achieved, for example, by a common trigger or a common timer. The radiation source 56 is located adjacent to the pixel structure 10, such that the travel time of the radiation pulse from the radiation source 56 to the object 12 is essentially the same as the travel time of the reflected radiation pulse from the object 12 to the pixel structure 10.
[0169] Alternatively or additionally, another pixel structure 20, 30, 40 and / or 50 can be arranged on or in the distance detection system 90. Alternatively or additionally, the radiation source 56 can also be arranged at a distance from the pixel structure 10.
[0170] The distance detection system 90 can be configured to emit the radiation pulse 22 with a duty cycle of less than or equal to 1%, less than or equal to 0.5%, or less than or equal to 0.1% using the radiation source 56. A set of radiation pulses can have a duty cycle of less than or equal to 50% of a frame detection cycle. A duty cycle of one percent means, for example, that a cycle or interval with a length of, say, 30 µs has a pulse with a width of 30 ns, and another pulse is emitted after 2970 ns. A pulse duration of 30 ns can be derived, for example, from a duty cycle of 1 / 1000, which may be influenced by eye safety criteria, and a detection range of 4.5 m. In other words, the electromagnetic radiation can have 22 radiation pulses with a small duty cycle and therefore pulsed transit times.
[0171] Fig. Figure 10 shows an exemplary comparison of the transmission and blocking ranges of color filters, such as color filters 46a, 48a, and 52a. Filter 46a exhibits a minimum photoresistance and thus a maximum transmission coefficient of approximately 0.85 in a wavelength range of approximately 450 nm. Color filter 48a is designed to filter electromagnetic radiation in the green range and exhibits a minimum photoresistance and thus a maximum transmission coefficient of approximately 0.85 in a wavelength range of approximately 540 nm. Filter 52a is designed to filter electromagnetic radiation in the red range and exhibits a minimum photoresistance and a transmission coefficient greater than 0.95 at wavelengths above 600 nm.
[0172] Fig. Equation 10 further shows that the filter 46a, the filter 48a and the filter 52a exhibit a high transmission coefficient and a low photoresistance in an infrared range with a wavelength greater than 800 nm, meaning that the filters 46a, 48a and 52a are transparent or nearly transparent in the infrared range.
[0173] In other words, it shows Fig. 10 an exemplary comparison of the transmittance characteristics of common color filters, such as those that can be applied cost-effectively to an image sensor.
[0174] Fig. Figure 11a shows a schematic top view of a pixel structure 110 according to the prior art. Three storage nodes FD1, FD2 and FD3 and a removal area DD are arranged on a photoactive area 92. Fig. Figure 11b shows a schematic cross-sectional view of the pixel structure 110.
[0175] In other words, they show Fig. 11a and Fig. 11b a scheme of a ToF pixel based on a lateral drift field photodiode (LDPD) with three short-time integrators and a withdrawal node for eliminating extraneous light outside the short-time integration windows, wherein Fig. 11a offers a top perspective and Fig. 11b shows a cross-section along the transfer direction of the pixel.
[0176] Fig. Figure 12 shows a schematic timing of a procedure for evaluating the pixel structure 110. In other words, it shows Fig. Figure 12 shows an exemplary timing diagram of a state-of-the-art ToF method, which can be iterated multiple times if necessary to improve repeatability. Multiple iterations result in increased measurement time.
[0177] As an alternative to the implementation described here, the photodetector, which enables the proposed pixel architecture, photoactive areas, and associated method, can be implemented using simple pinned photodiodes, photogate structures, or other types of photodiodes where the photoactive area and storage node are separate (such as the lateral drift field detector). The control electrodes (transfer gates) could alternatively be implemented using junction-FET-like (JFET) structures. Furthermore, it is conceivable to partially eliminate electrodes and implement subpixels based on so-called "draining-only" structures. This could potentially lead to a further improvement in charge transfer speed but may result in increased detector design complexity, which is necessary to achieve the required blocking behavior.
[0178] Exemplary implementations enable the acquisition of an RGBZ image without the use of a Bayer pattern and subpixel binning. This avoids the storage nodes having a large sense node capacity due to the pixel structure and binning, which can lead to increased read noise and a mismatched dynamic range. Furthermore, the complexity of designing color filters, as required with a Bayer pattern, can be reduced. Additionally, the acquisition of color and distance information can be achieved using the same subpixels, potentially leading to increased lateral resolution since no additional subpixels are needed to capture color information.
[0179] The above descriptions illustrate implementations in which distance information is obtained based on linearization, i.e., under the assumption that the light pulse has an infinitely steep slope with respect to its intensity variation and the photoactive region has an infinitely high sensitivity, neglecting any delay caused by the photodetector and / or readout electronics. However, a real light pulse and the sensitivity of the photoactive region may exhibit nonlinear slopes with a finite steepness. Such behavior can be approximated using appropriate algorithms to achieve high measurement precision. These algorithms may, for example, include multivariate polynomials and / or coordinate transformations.
[0180] Although some aspects have been described in connection with a device, it is understood that these aspects also constitute a description of the corresponding process, so that a block or component of a device can also be understood as a corresponding process step or as a feature of a process step. Similarly, aspects described in connection with or as a process step also constitute a description of a corresponding block, detail, or feature of a corresponding device.
[0181] In general, embodiments of the present invention can be implemented as a computer program product with program code, wherein the program code is effective in carrying out one of the methods when the computer program product runs on a computer. The program code can, for example, also be stored on a machine-readable medium.
[0182] The embodiments described above merely illustrate the principles of the present invention. It is understood that modifications and variations of the arrangements and details described herein will be obvious to other people skilled in the art. Therefore, it is intended that the invention be limited only by the scope of protection set forth in the following claims and not by the specific details presented herein by way of description and explanation of the embodiments.
Claims
[1] Device (60) comprising: a pixel structure (10; 20; 30; 40; 50) for optical distance measurement on an object (12), comprising the following: at least one pixel (14; 32; 32a-g; 35), comprising a first subpixel (16a), a second subpixel (16b) and a third subpixel (16c) for capturing the object area; wherein the first subpixel (16a) comprises a first photoactive area (18a), a first storage node (26a, FD1) and a first evaluation gate (24a, TX1), wherein the first evaluation gate (24a, TX1) is formed adjacent to the first storage node (26a, FD1) and the first photoactive area (18a) of the first subpixel (16a), and is configured to control the transport of charge carriers generated in the first photoactive area (18a) from the first photoactive area (18a) to the first storage node (26a, FD1); and wherein the second subpixel (16b) comprises a second photoactive area (18b), a second storage node (26b, FD2) and a second evaluation gate (24b, TX2), wherein the second evaluation gate (24b, TX2) is formed adjacent to the second storage node (26b, FD2) and the second photoactive area (18b) of the second subpixel (16b), and is configured to control the transport of charge carriers generated in the second photoactive area (18b) from the second photoactive area (18b) to the second storage node (26b, FD2), wherein the third subpixel (16c) comprises a third photoactive area (18c) and a third storage node (26c, FD3) and a third evaluation gate (24c, TX3), wherein the third evaluation gate (24c, TX3) is formed adjacent to the third storage node (26c, FD3) and the third photoactive area (18c) of the third subpixel (16c), and is configured to control the transport of charge carriers generated in the third photoactive area (18c) from the third photoactive area (18c) to the third storage node (26c, FD3); wherein the device comprises a control circuit (54) for controlling the pixel structure (10; 20; 30; 40; 50), wherein the control circuit (54) is configured to cyclically, to control the first evaluation gate (24a, TX1) during a first control interval (t5-t3) synchronized with a radiation pulse from a radiation source (56), so that first charge carriers generated during the first control interval (t5-t3) can be transported from the respective photoactive area (18a) to the first storage node (26a, FD1), and to control the second evaluation gate (24b, TX2) during a second control interval (t7-t5) synchronized with the radiation pulse (22) of the radiation source (56), so that second charge carriers generated during the second control interval (t7-t5) can be transported from the respective photoactive area (18b) to the second storage node (26b, FD2); and to control the third evaluation gate (24c, TX3) during a third control interval (t2-t1) so that third charge carriers generated during the third control interval (t2-t1) can be transported from a respective photoactive area (18c) to the third storage node (26c, FD3); wherein the control circuit (54) is configured to provide reflectance information and distance information regarding the object (12) in the object area and background light information (63a, 63b) regarding the object area based on a charge of the first charge carriers, the second charge carriers and the third charge carriers. [2] Device according to claim 1, wherein a first main side surface of the first subpixel (16a), a second main side surface of the second subpixel (16b) and a third main side surface of the third subpixel (16c) are congruent. [3] Device (60) comprising: a pixel structure (20) for optical distance measurement on an object (12), comprising the following: at least one pixel (14'), comprising a first subpixel (16'a) and a second subpixel (16b; 16'b) for capturing the object area; wherein the first subpixel (16'a) comprises a first photoactive area (18a), a first storage node (26a, FD1) and a second storage node (26b, FD2), a first (24a, TX1) and a second evaluation gate (24b, TX2), wherein the first evaluation gate (24a, TX1) is formed adjacent to the first storage node (26a, FD1) and the first photoactive area (18a) of the first subpixel (16'a), wherein the second evaluation gate (24b, TX2) is formed adjacent to the second storage node (26b, FD2) and the first photoactive area (18a) of the first subpixel (16'a), wherein the first (24a, TX1) and the second evaluation gate (24b, TX2) are configured to transport data generated in the first photoactive area (18a). to control charge carriers from the first photoactive area (18a) to the respective adjacent storage node (24a-b, TX1-2); wherein the second subpixel (16b; 16'b) comprises a second photoactive area (18b), a third storage node (26c, FD3) and a third evaluation gate (24c, TX3), wherein the third evaluation gate (24c, TX3) is formed adjacent to the third storage node (26c, FD3) and the second photoactive area (18b) of the second subpixel (16b; 16'b), and is configured to control the transport of charge carriers generated in the second photoactive area (18b) from the second photoactive area (18b) to the third storage node (26c, FD3); wherein the device comprises a control circuit (54) for controlling the pixel structure (10; 20; 30; 40; 50), wherein the control circuit (54) is configured to cyclically, to control the first evaluation gate (24a, TX1) during a first control interval (t5-t3) synchronized with a radiation pulse from a radiation source (56), so that first charge carriers generated during the first control interval (t5-t3) can be transported from the respective photoactive area (18a) to the first storage node (26a, FD1), and to control the second evaluation gate (24b, TX2) during a second control interval (t7-t5) synchronized with the radiation pulse (22) of the radiation source (56), so that second charge carriers generated during the second control interval (t7-t5) can be transported from the respective photoactive area (18b) to the second storage node (26b, FD2); and to control the third evaluation gate (24c, TX3) during a third control interval (t2-t1) so that third charge carriers generated during the third control interval (t2-t1) can be transported from a respective photoactive area (18c) to the third storage node (26c, FD3); wherein the control circuit (54) is configured to provide reflectance information and distance information regarding the object (12) in the object area and background light information (63a, 63b) regarding the object area based on a charge of the first charge carriers, the second charge carriers and the third charge carriers. [4] Device according to claim 3, wherein the second subpixel further comprises a fourth storage node (26d) and a fourth evaluation gate (24d), wherein the fourth evaluation gate (24d) is formed adjacent to the fourth storage node (26d) and the second photoactive area (18b) of the second subpixel (16b; 16'b), and is configured to control the transport of charge carriers generated in the second photoactive area (18b) from the second photoactive area (18b) to the fourth storage node (26d). [5] Device according to claim 3 or 4, wherein a first principal side surface of the first subpixel (16a; 16'a) and a second principal side surface of the second subpixel (16b; 16'b) are congruent. [6] Device according to one of the preceding claims, wherein the control circuit is configured to determine the distance information and the reflectance information for a reference point of an area of the first subpixel and the second subpixel. [7] Device according to one of the preceding claims, wherein the control circuit (54) is configured to avoid performing a correction recording of the object area in order to obtain the reflectance information and the distance information. [8] Device according to one of the preceding claims, wherein at least one of the subpixels (16a-c; 16'ab) comprises a collection gate (CX1-3) arranged between the respective photoactive area (18a-c) and the respective evaluation gate (26a-c), and is configured to control the transport of generated charge carriers from the respective photoactive area (18a-c) to the respective evaluation gate (24a-c, TX1-3) through the collection gate (CX1-3). [9] Device according to one of the preceding claims, wherein the pixel structure comprises a plurality of two-dimensionally offset pixels (14; 14'; 32; 32a-g; 35). [10] Device according to one of the preceding claims, in which a first color filter (46ab) with a first transmission wavelength range is arranged with respect to a first subpixel (16a) of a pixel (14; 14'; 32; 32a-g; 35) and a second color filter (48a-b) with a second transmission wavelength range is arranged with respect to a second subpixel (16b) of the pixel (14; 14'; 32; 32a-g; 35). [11] Device according to claim 8, in which a third color filter (52a-b) with a third transmission wavelength range is arranged with respect to a third subpixel (16c) of the pixel (14; 14'; 32; 32a-g; 35). [12] Device according to claim 10 or 11, wherein the pixel structure comprises a plurality of two-dimensionally offset pixels (14; 14'; 32; 32a-g; 35), wherein first color filters (46a-b, 52a-b) are arranged with respect to first subpixels (16a) of the plurality of pixels (14; 14'; 32; 32a-g; 35) and second color filters (48a-b; 52a-b) are arranged with respect to second subpixels (16b) of the plurality of pixels (14; 14'; 32; 32a-g; 35), and the color filters (46a-b, 48a-b, 52a-b) are arranged with respect to the subpixels based on a column-wise arrangement, based on a row-wise arrangement, or based on a Bayer pattern. [13] Device according to one of the preceding claims, wherein each of the subpixels (16a-c; 16'ab) comprises a discharge gate (TX4-6) and a discharge area (DD1-3), wherein the respective discharge gate (TX4-6) is formed adjacent to the respective photoactive area (18a-c) and adjacent to the respective discharge area (DD1-3), and is configured to control the transport of charge carriers generated in the respective photoactive area (18a-c) to the respective discharge area (DD1-3). [14] Device according to claim 13, wherein the respective extraction area (DD1-3) can be connected to a respective reference potential (vddpix, vddpix1-3). [15] Device according to claim 14, wherein the respective reference potentials (vddpix, vddpix1-3) are interconnected to form a potential (vddpix). [16] Device according to one of the preceding claims, wherein the pixel structure further comprises reset transistors (M1-1, M1-2, M1-3) which are connected to the respective memory node (26a-c, FD1-3) and are configured to connect a reference potential (vddpix, vddpix1-3) to the respective memory node (26a-c, FD1-3) when a reset potential (Reset FD1, Reset FD2, Reset FD3) is applied, so that charge carriers stored in the respective memory node are discharged. [17] Device according to one of the preceding claims, wherein the pixel structure further comprises an amplifier circuit (M2-1, M2-2, M2-3) connected to the respective storage node (26a-c, FD1-3), wherein the amplifier circuits (M2-1, M2-2, M2-3) are configured to generate a respective electrical potential based on a quantity of charge carriers stored in the respective storage node (26a-c, FD1-3), wherein the respective electrical potential is configured to provide information regarding the quantity of charge carriers stored in the respective storage node (26a-c, FD1-3). [18] Device according to claim 17, wherein the pixel structure forms an interface between the respective amplifier circuit (M2-1, M2-2, M2-3) and a respective terminal for outputting a respective measuring voltage (U). out1 , U out2 , U out3) has a respective selection switch (M3-1, M3-2, M3-3) connected, wherein the selection switches (M3-1, M3-2, M3-3) are configured to select the respective measuring voltage (U) based on a selection signal (row selection). out1 , U out2 , U out3 ) to be applied to outputs, wherein the respective selection switch (M3-1, M3-2, M3-3) is designed to select the respective measuring voltage (U) out1 , U out2 , U out3 ) based on the respective electrical potential. [19] Device according to one of the preceding claims, wherein the photoactive area of a subpixel is encompassed by a photodetector comprising a pinned photodiode, a photogate structure or a lateral drift field detector. [20] Device according to one of the preceding claims, wherein the control circuit (54) is configured to cyclically, to control a first discharge gate (TX4) that is located adjacent to the respective photoactive area from which the first charge carriers are transported to the first storage node (26a, FD1) in order to connect the respective photoactive area (18a) with a respective reference potential connection (vddpix1, vddpix); to control a second discharge gate (TX5), which is located adjacent to the respective photoactive area from which the second charge carriers are transported to the second storage node (26b, FD2), in order to connect the respective photoactive area (18b) to a respective reference potential connection (vddpix2, vddpix); and to control a third discharge gate (TX6) located adjacent to the respective photoactive area from which the third charge carriers are transported to the third storage node (26c, FD3) in order to connect the respective photoactive area (18c) to a respective reference potential connection (vddpix3, vddpix). [21] Device according to one of the preceding claims, wherein the control circuit (54) is configured to provide distance information (28) or reflectance information regarding the object (12) in the object area based on a set of first and second charge carriers. [22] Device according to one of the preceding claims, wherein the control circuit (54) is configured to synchronize the first control interval (t5-t3) and the second control interval (t7-t5) with respect to the radiation pulse (22) such that the first control interval (t3-t5) and the second control interval (t7-t5) overlap temporally with a time interval (t6-t4) in which a reflected radiation pulse (22r) hits the photoactive areas (18a-c), and wherein the control circuit (54) is configured to determine a reflectance variation of the object (12) reflecting the radiation pulse (22) across the object area from the quantity of the first and second charge carriers under correction (63a-b). [23] Device according to one of claims 1-21, in which a first color filter (46a-b) with a first transmission wavelength range is arranged with respect to a first subpixel (16a) of a pixel (14; 14'; 32; 32a-g; 35) of the pixel structure (10; 20; 30; 40; 50) and a second color filter (48a-b) with a second transmission wavelength range is arranged with respect to a second subpixel (16b) of the pixel (14; 14'; 32; 32a-g; 35) and in which the control device is configured to obtain a first color information based on charge carriers generated in the first subpixel (16a), to obtain a second color information based on charge carriers generated in a second subpixel (16b) and to obtain a third color information based on the first color information and the second color information to obtain colour information regarding the object (12). [24] Device according to claim 23, wherein the control device is configured to obtain the third color information based on a difference between a total information and the first color information and the second color information. [25] Device according to one of claims 1-21, in which a first color filter (46a-b) with a first transmission wavelength range is arranged with respect to a first subpixel (16a) of a pixel (14; 14'; 32; 32a-g; 35) of the pixel structure (10; 20; 30; 40; 50), in which a second color filter (48a-b) with a second transmission wavelength range is arranged with respect to a second subpixel (16b) of the pixel (14; 14'; 32; 32a-g; 35), and in which a third subpixel (16c) of the pixel (14; 14'; 32; 32a-g;35) a third color filter (52a-b) with a third transmission wavelength range is arranged and in which the control device is configured to obtain first color information based on charge carriers generated in the first subpixel (16a), to obtain second color information based on charge carriers generated in a second subpixel (16b), and to obtain third color information relating to the object (12) based on charge carriers generated in the third subpixel. [26] Device according to one of the preceding claims, wherein the control circuit (54) is configured to control a bandpass filter which is arranged with respect to at least one pixel and is configured to influence a transmission property with respect to electromagnetic radiation (22r) through the bandpass filter towards the photoactive area (18c) of a respective subpixel (16a-c; 16'ab) in a time-variant manner. [27] Distance detection system (90) with: a device according to one of the preceding claims; a radiation source (56) configured to emit a radiation pulse (22) in the direction of an object (12); and a control circuit (54) which is coupled to the pixel structure (10; 20; 30; 40; 50) and the radiation source (56) and which is designed to determine distance information regarding the object (12) by means of time-of-flight evaluation. [28] Distance detection system according to claim 27, wherein the control circuit (54) is configured to determine reflectance information regarding the object (12). [29] Distance detection system according to claim 27 or 28, wherein the radiation source (56) is arranged adjacent to the pixel structure (10; 20; 30; 40; 50), such that the transit time of the radiation pulse (22) from the radiation source (56) to the object (12) is substantially the same as the transit time of the reflected radiation pulse (22r) from the object (12) to the pixel structure (10; 20; 30; 40; 50). [30] Distance detection system according to one of claims 27-29, wherein the radiation source (56) is configured to emit the radiation pulse (22) cyclically with a duty cycle of less than or equal to 50%.
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