Method and device for characterizing a time-of-flight sensor and / or a cover covering it

Abstract

Embodiments of the present disclosure relate to a method and apparatus for characterizing a time-of-flight sensor and / or a cover covering the same. A method (100) for characterizing a time-of-flight sensor and / or a cover covering the time-of-flight sensor is provided. The method comprises performing at least one coded modulation measurement with the time-of-flight sensor to obtain measurement data about light reflected from the cover back to the time-of-flight sensor. A measurement range of the time-of-flight sensor is configured to terminate behind the cover at once for the at least one coded modulation measurement. Furthermore, the method comprises determining feature data based on the measurement data, wherein the feature data is indicative of a quantity related to the time-of-flight sensor and / or the cover.

Description

Technical Field

[0001] This disclosure relates to time-of-flight (ToF) sensing. Specifically, examples relate to a method and apparatus for characterizing a ToF sensor and / or characterizing a cover over a ToF sensor. Background Technology

[0002] ToF modules are typically covered by a cover glass to protect them from environmental influences. However, the cover glass can affect measurements of the ToF module. Additionally, various other characteristics, such as temperature, can alter the measurements taken from the ToF module.

[0003] Therefore, it may be necessary to characterize the ToF sensor and / or the cover that covers the ToF sensor. Summary of the Invention

[0004] This requirement can be met by the subject matter of the appended claims.

[0005] One example relates to a method for characterizing a Time-of-Flight (ToF) sensor and / or a cover covering the ToF sensor. The method includes: performing at least one coded modulation measurement with the ToF sensor to obtain measurement data regarding light reflected back from the cover to the ToF sensor. The measurement range of the ToF sensor is configured to terminate immediately after the cover is applied for at least one coded modulation measurement. Additionally, the method includes: determining characteristic data based on the measurement data. This characteristic data indicates quantities associated with the ToF sensor and / or the cover.

[0006] Another example relates to an apparatus for characterizing a ToF sensor and / or a cover covering the ToF sensor. The apparatus includes: a ToF sensor configured to perform at least one coded modulation measurement to obtain measurement data about light reflected back to the ToF sensor from the cover. The measurement range of the ToF sensor is configured to terminate immediately after the cover for at least one coded modulation measurement. The apparatus also includes: processing circuitry configured to determine characteristic data based on the measurement data. The characteristic data indicates a quantity associated with the ToF sensor and / or the cover. Attached Figure Description

[0007] The following will describe some examples of apparatus and / or methods by way of example only and with reference to the accompanying drawings, wherein

[0008] Figure 1 The flowchart illustrates an example of a method for characterizing a ToF sensor and / or characterizing a cover over a ToF sensor;

[0009] Figure 2 An exemplary arrangement of the ToF sensor and the cover is illustrated; and

[0010] Figure 3An example of a device for characterizing a ToF sensor and / or characterizing a cover that covers a ToF sensor is illustrated. Detailed Implementation

[0011] The various examples will now be described more fully with reference to the accompanying drawings, which illustrate some of the examples. In the drawings, the thickness of lines, layers, and / or regions may be exaggerated for clarity.

[0012] Therefore, while other examples can be various modifications and alternatives, some specific examples are shown in the figures and will be described in detail thereafter. However, this detailed description does not limit the other examples to the specific forms described. Further examples may cover all modifications, equivalents, and alternative examples falling within the scope of this disclosure. Throughout the description of the figures, identical or similar numbers refer to identical or similar elements that, when compared with each other, can be implemented identically or in modified forms while providing identical or similar functionality.

[0013] It is important to understand that when a component is referred to as being "connected" or "coupled" to another component, these components can be directly connected or coupled, or connected or coupled via one or more intermediate components. If "or" is used to combine two components A and B, it should be understood, unless otherwise explicitly or implicitly defined, to disclose all possible combinations: only A, only B, and A and B. Alternative wording for the same combination is "at least one of A and B" or "A and / or B." With the necessary modifications, this also applies to combinations of more than two components.

[0014] The terminology used in this document to describe specific examples is not intended to limit other examples. Whenever the use of singular forms such as “a,” “an,” and “the” and the use of only a single element is neither explicitly nor implicitly defined as mandatory, other examples may also use multiple elements to implement the same functionality. Similarly, when functionality is subsequently described as being implemented using multiple elements, other examples may implement the same functionality by using a single element or a processing entity. It should also be understood that when the terms “comprises,” “comprising,” “includes,” and / or “including” are used, they specify the presence of the stated feature, integer, step, operation, process, action, element, and / or component, but do not preclude the presence or addition of one or more other features, integers, steps, operations, processes, actions, elements, components, and / or any grouping thereof.

[0015] Unless otherwise defined, all terms (including technical and scientific terms) are used herein with the common meaning in the field to which their examples belong.

[0016] Figure 1 A flowchart illustrating an example of a method 100 for characterizing a ToF sensor and / or a cover over which the ToF sensor is located is shown below. Further reference will follow. Figure 2 To describe method 100, this Figure 2 An exemplary arrangement of a ToF sensor 210 and a cover 220 covering the ToF sensor 210 is illustrated.

[0017] Method 100 includes performing at least one coded modulation (CM) measurement using the ToF sensor 210 to obtain measurement data of light reflected back to the ToF sensor 210 from the cover 220. Generally, any number of CM measurements can be performed. For example, exactly one (i.e., a single) CM measurement can be performed to obtain measurement data. In other examples, at least two, three, four, or more CM measurements can be performed to obtain measurement data. In other words, the measurement of the cover 220 comprises one or more frames.

[0018] As from Figure 2 As can be seen, in each CM measurement, light 201 is emitted by the illumination element 211 of the ToF sensor 210. The illumination element 211 generates light 201 based on an illumination signal, which exhibits a series of alternating high and low pulses with varying durations (lengths). Therefore, light 201 is a series of light pulses with varying pulse lengths and varying pulse intervals. For example, the illumination element 211 may include one or more light-emitting diodes (LEDs) or one or more laser diodes (e.g., one or more vertical cavity surface-emitting lasers (VCSELs)) that are excited based on the illumination signal.

[0019] Light 201 is reflected from cover 220 back to ToF sensor 210. Specifically, light 201 is reflected (at least partially) from cover 220 to light-catching element 212 of ToF sensor 210. Light 201 may be reflected on the surface of cover 220 and / or inside cover 220. The reflected light is... Figure 2Reference numeral 202 is used in the accompanying drawings. The reflected light 202 reaches the ToF sensor 210 but does not leave the module. The light-catching element 212 measures the reflected light 202. The light-catching element 212 may include various components, such as, for example, optical components (e.g., one or more lenses) and electronic circuitry. For example, the electronic circuitry may include an image sensor and driver electronics for the image sensor, which includes multiple photosensitive elements or pixels (e.g., each image sensor includes a photon mixer device (PMD)). All or only selected photosensitive elements / pixels of the multiple photosensitive elements / pixels may be used to measure the reflected light 202. A reference signal is used to drive the electronic circuitry (e.g., photosensitive elements or pixels) of the light-catching element 212 to measure the reflected light 202. Similar to what has been described above for the illumination signal used to drive the illumination element 211, the reference signal exhibits a series of alternating high and low pulses with varying durations (lengths). Note that the illumination signal used for CM measurement and the reference signal may be the same, time-shifted (phase-shifted) relative to each other, and / or different from each other. In addition, if more than one CM measurement is performed, different lighting signals and / or reference signals can be used for individual CM measurements.

[0020] Typically, the illumination element 211 and the light-catching element 212 are arranged (at least partially) in a common cavity covered by a cover 220 to protect the ToF sensor 210 from dust, moisture, dirt, etc. The cover 220 can be made of, for example, glass, plastic, or any other suitable material. For example, the cover 220 can be a glass cover for a mobile phone or automotive ToF system. In some examples, the cover 220 can be a display (such as an OLED (organic light-emitting diode) display or a micro-LED display) or part thereof. It should be noted that the cover 220 can be any element capable of protecting the ToF sensor 210 from the surrounding environment and being at least partially transparent to the modulated light 201 emitted by the illumination element 211.

[0021] The measurement range of the ToF sensor is configured to terminate immediately (instantly) after the cover for at least one coded modulation measurement according to method 100. Figure 2 This is illustrated exemplarily in the text. Figure 2 The diagram illustrates the measurement range 213 of the ToF sensor 210. This measurement range 213 is the range of distance (depth) from which the ToF sensor 210 can sense the distance from an object to the ToF sensor 210 based on light reflected back from the object. Figure 2In the example, the measurement range 213 begins at a distance d0 from the ToF sensor 210 and ends at a distance d1 from the ToF sensor 210. The distance d1 that limits the measurement range 213 immediately (e.g., instantly) follows the distance d representing the distance from the cover 220 to the ToF sensor 210. c For example, the measurement range 213 of the ToF sensor 210 can terminate less than 50cm, 30cm, 10cm, 5cm, 1cm, or 5mm after the cover 220 (i.e., distance d1 versus distance d). c The difference can be less than, for example, 50cm, 30cm, 10cm, 5cm, 1cm, or 5mm.

[0022] The measurement range of the ToF sensor 210 used for at least one CM measurement can be adjusted by changing the pulse duration (length) of the high and low pulses in the illumination signal and / or reference signal. Additionally, the measurement range of the ToF sensor 210 can be adjusted by changing the time shift (phase shift) between the illumination signal and the reference signal. By modulating the light 201 using CM, the response of the ToF sensor 210 can be limited to a distance similar to the optical path between the ToF sensor 210 and the cover 220. For example, the modulation code based on the illumination signal and reference signal can be selected to have a high slope to mitigate the response of the ToF sensor 210 to reflections from objects behind the cover 220. Therefore, only the light reflected by the cover 220 can be measured.

[0023] The ToF sensor 210 generates and outputs measurement data based on the light arriving at the light-catching element 212. Due to the limitation of the measurement range 213 of the ToF sensor 210, the ToF sensor is (basically) only sensitive to the reflected light 202 arriving at the light-catching element 212 from the cover 220. Therefore, for at least one CM measurement, measurement data is obtained for the light reflected back to the ToF sensor 210 from the cover 220.

[0024] Method 100 additionally includes determining 104 characteristic data based on measurement data of light reflected back from cover 220 to ToF sensor 210. This characteristic data indicates a quantity associated with ToF sensor 210 and / or cover 220.

[0025] Cover 220 is a known object with a known reflectivity at a known fixed distance from ToF sensor 210. Therefore, the optical path of light 201 to cover 220 and back to ToF sensor 210 has a fixed distance. Taking into account the knowledge about cover 220, the reflected light 202 reaching light-trapping element 212 from cover 220 allows for characterization of both ToF sensor 210 and cover 220. Therefore, method 100 can allow for characterization of ToF sensor 210 and sensor 220 by means of characteristic data derived from the measurement of light reflected back to ToF sensor 210 from cover 220.

[0026] Feature data can be of various types and can indicate a variety of quantities related to the ToF sensor and / or cover. Some exemplary types of feature data will be described in detail below. However, it should be noted that this disclosure is not limited to the examples described below.

[0027] According to some examples, the feature data indicates a distance error correction value used to correct the distance value, which is determined based on a depth measurement performed by the ToF sensor 210. ToF sensors (such as ToF sensor 210) typically suffer from distance (depth) measurement errors (offsets) that can depend on various factors, such as temperature or aging. For example, the generation of the illumination signal and the operation of the driving electronics are temperature-dependent. Therefore, temperature can affect the indirect optical path on the cover 220. The distance measurement error needs to be compensated for to obtain a correct distance (depth) measurement result. As described below, the known path distance between the cover 220 and the ToF sensor 210, along with the obtained measurement data, makes it possible to correct this error.

[0028] To obtain the distance error correction value, determining the 104 characteristic data includes: determining the measured distance from the cover 220 to the ToF sensor 210 based on measurement data. In other words, the distance from the cover 220 to the ToF sensor 210 is measured via at least one CM measurement. Additionally, determining the 104 characteristic data includes: determining the distance error correction value based on a comparison between the measured distance from the cover 220 to the ToF sensor 210 and a known distance from the cover 220 to the ToF sensor 210. By comparing the measured distance from the cover 220 to the ToF sensor 210 with the known distance from the cover 220 to the ToF sensor 210, the difference between the measured distance from the cover 220 to the ToF sensor 210 and the actual distance from the cover 220 to the ToF sensor 210 can be determined, and the distance error correction value can be derived from it.

[0029] Assuming that a distance value is determined based on one or more depth measurements performed by the ToF sensor 210, the ToF sensor 210 is directed to the scene sensed by the ToF sensor 210. Figure 2The method 100, which measures the distance to an object (not shown in the figure), may further include correcting the distance value using a determined distance error correction value. For example, the distance error correction value may be a distance error correction offset added to the distance value or subtracted from the distance value, or it may be a factor multiplied by the distance value. Therefore, distance values ​​suffering from distance measurement errors by the ToF sensor 210 can be corrected to provide error-corrected distance values.

[0030] For example, if the light-capturing element 212 includes a plurality of photosensitive elements or pixels, a corresponding distance error correction value can be determined for each of the plurality of photosensitive elements or pixels, or at least a portion of the photosensitive elements or pixels. In other words, the distance error correction value can be calculated on a pixel-by-pixel basis.

[0031] In other examples, the characteristic data indicates the measured output power of the lighting element 211. The output power of the lighting element 211 may depend on various factors, such as temperature or aging. Assume the reflectivity of the cover 220 is substantially constant. Therefore, the reflected light 202 reaching the light-catching element 212 is proportional to the output power of the lighting element 211. By digitizing the reflected light 202 reaching the light-catching element 212, the current output power of the lighting element 211 can be measured. For example, if the output power of the lighting element 211 drifts due to temperature changes, the drift in output power can be measured and used as an input to the control system (controller) of the lighting element 211 to adjust the emitted optical power. Thus, a constant optical power output of the lighting element 211 can be achieved. For example, a constant optical power output of the lighting element 211 for different temperatures can be achieved. For example, an illumination signal for controlling the lighting element 211 can be generated based on the characteristic data according to method 100. By changing the illumination signal based on the characteristic data, the output power of the lighting element 211 can be controlled. Similarly, duty cycle adaptation, pulse skipping, or exposure time adaptation can be performed based on the feature data to achieve a (substantially) constant average output power of the illumination element 211. For example, a control algorithm for controlling the light emission of the illumination element 211 can receive the feature data as input. Alternatively or additionally, a reference signal for driving the electronic circuitry of the light-catching element 212 can be generated based on the feature data according to method 100. By changing the reference signal based on the feature data, the operation of the light-catching element 212 can be adapted to the measured output power of the illumination element 211.

[0032] When the lighting element 211 includes more than one light source (e.g., LED or VCSEL), method 100 can be applied to each light source separately to measure the output power of the light source of the lighting element 211 separately. Therefore, each light source of the lighting element 211 can be controlled individually based on the corresponding measured output power.

[0033] In some other examples, the characteristic data indicates the condition of the cover. Different conditions of the cover 220 affect its reflectivity and, therefore, may affect (alter) the light emission and / or reception characteristics of the ToF sensor 210. For at least one specific condition of the cover 200, the reflectivity of the cover 220 is known. Therefore, the reflected light 202 can be used to classify the condition of the cover. The condition of the cover 220 may indicate, for example, at least one of the following: the absence of foreign matter on the cover 220; the presence of foreign matter (e.g., dust, droplets) on the cover 220; the presence of dirt on the cover 220; the presence of one or more fingerprints on the cover 220; or the presence of fluid on the cover 220. For example, dirt on the cover 220 may alter its reflectivity, causing the reflected light 202 to exhibit certain characteristics. Therefore, when dirt is present on the cover 220, the measurement data obtained for at least one CM measurement will exhibit certain characteristics. The condition of the cover 220 can be determined by comparing measurement data obtained for at least one CM measurement when dirt is present on the cover 220 with reference data for one or more predefined conditions of the cover 220.

[0034] In some examples, method 100 may also include: outputting feature data to other circuit devices (e.g., application processors).

[0035] Method 100 can be used during the operation of the ToF sensor 210. For example, at least one CM measurement for obtaining measurement data can be performed in the depth measurement sequence for obtaining a depth image. Therefore, the determined feature data can be used during the acquisition of the depth image. For example, if the determined feature data indicates a distance error correction value as described above, the distance error correction value can be used to correct the distance value determined based on the depth measurement sequence during the acquisition of the depth image. Similarly, if the feature data indicates the measured output power of the illumination element 211, the output power of the illumination element 211 during the depth measurement sequence can be controlled based on the measured output power to achieve a (substantially) constant average output power of the illumination element 211 during the depth measurement sequence. At least one CM measurement for obtaining measurement data can be performed at any position in the depth measurement sequence for obtaining a depth image.

[0036] In other examples, at least one CM measurement for obtaining measurement data may be performed occasionally, i.e., independently of the depth measurement sequence used to obtain a depth image. For example, at least one CM measurement for obtaining measurement data may be performed if there are no reflective objects in the scene sensed by the ToF sensor 210 that could affect the measurement. Therefore, method 100 may also include: performing one or more depth measurements on the scene using the ToF sensor 210; and determining, based on the one or more depth measurements on the scene (e.g., based on data obtained from the one or more depth measurements), whether any photosensitive element (pixel) in the light-capturing element 212 intended to be used for at least one CM measurement is receiving light reflected back to the ToF sensor 210 from any object in the scene. At least one CM measurement for obtaining measurement data is performed only if no photosensitive element (pixel) intended to be used for at least one CM measurement is receiving light reflected back to the ToF sensor 210 from any object in the scene.

[0037] According to method 100, the feature data may be stored in a (data) memory together with temperature data indicating the temperature at the ToF sensor 210 during at least one CM measurement used to obtain the measurement data. The temperature at the ToF sensor 210 may, for example, indicate the temperature at the illumination element 211, the light-catching element 212, or a sub-element thereof. For example, one or more temperature sensors may be arranged at the ToF sensor 210 to measure the temperature and provide temperature data. The feature data may be stored in the memory together with the temperature data, for example, during operation of the ToF sensor 210 or during factory calibration. The memory may be the memory of the ToF sensor 210 or an external memory accessible to the ToF sensor 210.

[0038] In addition to the feature data, several other feature data points can be stored in memory. Each of these other feature data points is stored together with a corresponding temperature data point indicating the temperature at the ToF sensor 210, the temperature indicated by which the corresponding temperature data point differs from the temperature during at least one CM measurement used to obtain the measurement data. For example, multiple CM measurements can be performed at different temperatures to obtain corresponding feature data points for different temperatures. Therefore, the feature data can be used as calibration data for different temperatures, i.e., temperature-dependent calibration data. To obtain feature data for a target (desired) temperature, method 100 may include: controlling the ToF sensor 210 to heat to the target temperature (e.g., by controlling the ToF sensor 210 to continuously perform ToF measurements until the target temperature is reached) and, once the target temperature has been reached (after reaching the target temperature), performing at least one CM measurement used to obtain the measurement data.

[0039] The stored temperature-related calibration data can be used by the ToF sensor 210 to adjust its operation based on the current temperature (e.g., periodically, repeatedly). For example, method 100 may include measuring the current temperature at the ToF sensor 210 (e.g., using a temperature sensor described above). Additionally, method 100 may include selecting one of the characteristic data and several other characteristic data based on a comparison of the current temperature and the temperature indicated by corresponding temperature information (i.e., several temperature data) stored in memory along with the characteristic data and several other characteristic data. Method 100 may additionally include operating the ToF sensor 210 using the selected characteristic data from the characteristic data and several other characteristic data. For example, if several characterization data indicate corresponding distance error correction values ​​for different temperatures, an appropriate distance error correction value for the current temperature can be selected based on a simple temperature measurement at the ToF sensor 210. Similarly, if several characteristic data points indicate the corresponding measured output power of the lighting element 211 at different temperatures, then appropriate calibration data for controlling the lighting element 211 at the current temperature can be selected based on a simple temperature measurement at the ToF sensor 210. In other words, temperature can be measured only during operation to select the corresponding calibration data for error correction.

[0040] Additionally, the following feature data can be used to update a corresponding feature data stored in memory along with a corresponding temperature data: this feature data is newly determined according to method 100 for the same temperature as indicated by the stored temperature data.

[0041] As described above for various examples, the light reflected by cover 220 can be used for system temperature compensation.

[0042] Still Figure 3 The figure illustrates an example of an apparatus 300 for characterizing a ToF sensor and / or a cover covering the ToF sensor according to the proposed technique. The apparatus 300 includes a ToF sensor 310. The ToF sensor 310 includes an illumination element 311 and a light-catching element 312 for performing ToF measurements according to the technique described above. The illumination element 311 and the light-catching element 312 are arranged in a common cavity 340 covered (at least partially) by a cover 330. Specifically, the ToF sensor 310 is configured to perform at least one CM measurement to obtain measurement data of light reflected back from the cover 330 to the ToF sensor 310. The measurement range of the ToF sensor 310 is configured to terminate immediately after the cover 330 for at least one CM measurement.

[0043] Additionally, device 300 includes processing circuitry 320. For example, processing circuitry 320 may be a single dedicated processor, a single shared processor, or multiple separate processors (some or all of which may be shared), digital information processor (DSP) hardware, application-specific integrated circuit (ASIC), or field-programmable gate array (FPGA). Processing circuitry 320 may optionally be coupled to, for example, read-only memory (ROM), random access memory (RAM), and / or non-volatile memory for storing software. Processing circuitry 320 is configured to perform processing according to the techniques described above. Specifically, processing circuitry 320 is configured to determine characteristic data based on measurement data. This characteristic data indicates a quantity associated with ToF sensor 310 and / or cover 330.

[0044] Device 300 may also include additional hardware – conventional and / or custom.

[0045] The examples described in this article can be summarized as follows:

[0046] Examples of methods for characterizing a ToF sensor and / or a cover covering the ToF sensor are provided. The method includes: performing at least one coded modulation measurement with the ToF sensor to obtain measurement data about light reflected back to the ToF sensor from the cover. The measurement range of the ToF sensor is configured to terminate immediately after the cover for at least one coded modulation measurement. Additionally, the method includes: determining characteristic data based on the measurement data. This characteristic data indicates quantities related to the ToF sensor and / or the cover.

[0047] According to some examples, the illumination element of the ToF sensor for emitting light and the light-catching element of the ToF sensor for measuring the light reflected from the cover are arranged in a common cavity covered by the cover.

[0048] In some examples, at least two coded modulation measurements are performed to obtain measurement data.

[0049] According to some examples, the feature data indicates a distance error correction value used to correct the distance value, which is determined based on a depth measurement performed by a ToF sensor, and determining the feature data includes: determining the measured distance from the cover to the ToF sensor based on the measurement data; and determining the distance error correction value based on a comparison of the measured distance from the cover to the ToF sensor with a known distance from the cover to the ToF sensor.

[0050] In some examples, the method further includes: using a distance error correction value to correct a distance value indicating the distance from the ToF sensor to an object in the scene sensed by the ToF sensor, wherein the distance value is determined based on a depth measurement performed by the ToF sensor.

[0051] According to some examples, the characteristic data indicates the measured output power of the illumination element of the ToF sensor used to emit light.

[0052] In some examples, the method further includes: generating an illumination signal based on feature data for controlling an illumination element of the ToF sensor; and / or generating a reference signal based on feature data for driving an electronic circuit arrangement of a light-harvesting element of the ToF sensor to measure light reflected from the cover.

[0053] Based on some examples, feature data indicates the condition of the cover.

[0054] In some examples, the condition of the lid indicates at least one of the following: there is no foreign object on the lid; there is a foreign object on the lid; there is dirt on the lid; there are fingerprints on the lid; there is fluid on the lid.

[0055] According to some examples, the method further includes storing the feature data together with temperature data indicating the temperature at a ToF sensor during at least one coded modulation measurement used to obtain the measurement data in a memory.

[0056] In some examples, in addition to the feature data, several other feature data are stored in memory, wherein each of the other feature data is stored together with a corresponding temperature data indicating the temperature at the ToF sensor, the temperature indicated by the corresponding temperature data being different from the temperature during at least one coded modulation measurement used to obtain measurement data, and wherein the method further includes: measuring the current temperature at the ToF sensor; selecting one of the feature data and several other feature data based on a comparison of the current temperature and the temperature indicated by the several temperature data stored in memory together with the feature data and several other feature data; and operating the ToF sensor using the selected feature data from the feature data and several other feature data.

[0057] According to some examples, the ToF sensor includes a light-catching element for measuring light reflected from a cover, and the method further includes: performing one or more depth measurements on a scene using the ToF sensor; determining, based on the one or more depth measurements on the scene, whether any photosensitive element of the light-catching element to be used for at least one coded modulation measurement is receiving light reflected back to the ToF sensor from any object in the scene; and performing at least one CM measurement to obtain measurement data if no photosensitive element to be used for at least one CM measurement is receiving light reflected back to the ToF sensor from any object in the scene.

[0058] In some examples, at least one coded modulation measurement for obtaining measurement data is performed in a depth measurement sequence for obtaining a depth image.

[0059] Other examples relate to an apparatus for characterizing a ToF sensor and / or a cover covering the ToF sensor. The apparatus includes: a ToF sensor configured to perform at least one coded modulation measurement to obtain measurement data about light reflected back to the ToF sensor from the cover. The measurement range of the ToF sensor is configured to terminate immediately after the cover for at least one coded modulation measurement. The apparatus also includes: processing circuitry configured to determine characteristic data based on the measurement data. The characteristic data indicates a quantity associated with the ToF sensor and / or the cover.

[0060] According to some examples, the illumination element of the ToF sensor for emitting light and the light-catching element of the ToF sensor for measuring the light reflected from the cover are arranged in a common cavity covered by the cover.

[0061] The examples disclosed herein can provide a ToF reference measurement based on the reflection of the cover (glass).

[0062] With one or more examples described in previous details and Figure 1 The aspects and features mentioned and described may also be combined with one or more other examples to replace the same features in other examples or to additionally introduce features into other examples.

[0063] This specification and accompanying drawings illustrate only the principles of this disclosure. Furthermore, all examples described herein are clearly intended primarily for illustrative purposes to aid the reader in understanding the principles of this disclosure and the concepts contributed by the inventors for further exploration of the field. All statements herein recounting the principles, aspects, and examples of this disclosure, as well as specific examples thereof, are intended to include their equivalents.

[0064] For example, a block diagram can illustrate a high-level circuit diagram implementing the principles of this disclosure. Similarly, flowcharts, operation diagrams, state transition diagrams, pseudocode, etc., can represent various processes, operations, or steps, which can be substantially represented by a computer-readable medium, and thus are performed by a computer or processor, whether or not such a computer or processor is explicitly shown. The methods disclosed in this specification or claims can be implemented by a device having components for each of the corresponding actions of performing these methods.

[0065] It should be understood that the disclosure of multiple actions, processes, operations, steps, or functions in this specification or claims is not to be construed as being in a specific order, unless otherwise expressly or implicitly stated, for example, for technical reasons. Therefore, the disclosure of multiple actions or functions does not limit them to a specific order, unless these actions or functions are not interchangeable for technical reasons. Furthermore, in some examples, a single action, function, process, operation, or step may include or be divided into multiple sub-actions, sub-functions, sub-processes, sub-operations, or sub-steps. Such sub-actions may be included within and part of the disclosure of that single action, unless expressly excluded.

[0066] Furthermore, the following claims are hereby incorporated into the detailed description, wherein each claim may stand alone as an example. While each claim may stand alone as an example, it should be noted that although dependent claims in the claims will refer to a specific combination with one or more other claims, other examples may also include combinations of dependent claims with the subject matter of each of the other dependent claims or independent claims. Such combinations are explicitly presented herein unless it is stated that a particular combination is not intended to be used. Furthermore, even if a claim does not directly depend on an independent claim, it is intended to include features of that claim that relate to any other independent claim.

Claims

1. A method (100) for characterizing a time-of-flight sensor and / or a cover covering the time-of-flight sensor, the method comprising: The time-of-flight sensor is used to perform at least one coded modulation measurement (102) to obtain measurement data about light reflected back from the cover to the time-of-flight sensor, wherein the measurement range of the time-of-flight sensor is configured to terminate immediately after the cover for the at least one coded modulation measurement, wherein the illumination element of the time-of-flight sensor for emitting the light generates the light for the at least one coded modulation measurement based on an illumination signal exhibiting a series of alternating high and low pulses with varying durations, and wherein the electronic circuitry of the light-catching element of the time-of-flight sensor for measuring the light reflected from the cover is driven for the at least one coded modulation measurement based on a reference signal exhibiting a series of alternating high and low pulses with varying durations; Based on the measurement data, characteristic data (104) is determined, wherein the characteristic data indicates a quantity related to the time-of-flight sensor and / or the cover; and For the at least one coded modulation measurement, the pulse durations of the high and low pulses in the illumination signal and the reference signal, as well as the time shift between the illumination signal and the reference signal, are adjusted to mitigate the response of the time-of-flight sensor to reflections from objects behind the cover.

2. The method of claim 1, wherein the lighting element and the light-catching element are arranged in a common cavity covered by the cover.

3. The method of claim 1 or claim 2, wherein at least two coded modulation measurements are performed to obtain the measurement data.

4. The method of claim 1, wherein the feature data indicates a distance error correction value for correcting a distance value, the distance value being determined based on a depth measurement performed by the time-of-flight sensor, and wherein determining (104) the feature data comprises: The measured distance from the cover to the time-of-flight sensor is determined based on the measurement data; as well as The distance error correction value is determined by comparing the measured distance from the cover to the time-of-flight sensor with the known distance from the cover to the time-of-flight sensor.

5. The method according to claim 4, further comprising: The distance error correction value is used to correct a distance value indicating the distance from the time-of-flight sensor to an object in the scene sensed by the time-of-flight sensor, wherein the distance value is determined based on a depth measurement performed by the time-of-flight sensor.

6. The method of claim 1, wherein the feature data indicates the measured output power of the lighting element.

7. The method of claim 6, further comprising: Based on the feature data, an illumination signal is generated for controlling the illumination element of the time-of-flight sensor; and / or Based on the characteristic data, a reference signal is generated for the electronic circuitry of the light-catching element of the time-of-flight sensor in order to measure the light reflected from the cover.

8. The method of claim 1, wherein the feature data indicates the condition of the cover.

9. The method of claim 8, wherein the condition of the cover indicates at least one of the following: the cover is free of foreign matter; the cover contains foreign matter; the cover contains dirt; the cover contains fingerprints; or the cover contains fluid.

10. The method according to claim 1, further comprising: The feature data is stored together with temperature data indicating the temperature at the time-of-flight sensor during the at least one coded modulation measurement used to obtain the measurement data in the memory.

11. The method of claim 10, wherein, in addition to the feature data, several other feature data are also stored in the memory, wherein each of the several other feature data is stored together with a corresponding temperature data indicating the temperature at the time-of-flight sensor, the temperature indicated by the corresponding temperature data being different from the temperature during the at least one coded modulation measurement used to obtain the measurement data, and wherein the method further comprises: Measure the current temperature at the time-of-flight sensor; Based on a comparison of the current temperature and the temperature indicated by several temperature data stored in the memory along with the current temperature and other feature data, one of the feature data and several other feature data is selected; and The time-of-flight sensor is operated using the aforementioned feature data and selected feature data from the other few feature data.

12. The method according to claim 1, further comprising: The time-of-flight sensor is used to perform one or more depth measurements on the scene; Based on the one or more depth measurements of the scene, determine whether any photosensitive element of the light-capturing element, to be used for the at least one coded modulation measurement, is receiving light reflected back to the time-of-flight sensor from any object in the scene; as well as If no photosensitive element to be used for the at least one coded modulation measurement is receiving light reflected back to the time-of-flight sensor from any object in the scene, then the at least one coded modulation measurement for obtaining the measurement data is performed.

13. The method of claim 1, wherein the at least one coded modulation measurement for obtaining the measurement data is performed in a depth measurement sequence for obtaining a depth image.

14. An apparatus (300) for characterizing a time-of-flight sensor (310) and / or a cover (330) covering the time-of-flight sensor (310), the apparatus comprising: A time-of-flight sensor (310) is configured to perform at least one coded modulation measurement to obtain measurement data about light reflected back from the cover (330) to the time-of-flight sensor (310), wherein the measurement range of the time-of-flight sensor (310) is configured to terminate immediately after the cover (330) for the at least one coded modulation measurement. as well as Processing circuitry (320) is configured to determine feature data based on the measurement data, wherein the feature data indicates a quantity associated with the time-of-flight sensor (310) and / or the cover (330). The illumination element of the time-of-flight sensor is configured to emit light for the at least one coded modulation measurement based on an illumination signal having a series of alternating high and low pulses of varying duration. The electronic circuitry of the light-trapping element of the time-of-flight sensor is driven for the at least one coded modulation measurement based on a reference signal having a series of alternating high and low pulses of varying durations. For the at least one coded modulation measurement, the pulse durations of the high and low pulses in the illumination signal and the reference signal, as well as the time shift between the illumination signal and the reference signal, are adjusted to mitigate the response of the time-of-flight sensor to reflections from objects behind the cover.

15. The apparatus of claim 14, wherein the illumination element (311) and the light-catching element (312) are arranged in a common cavity (340) covered by the cover (330).

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