Exchanging information between time-of-flight distance measuring devices

Abstract

Runtime camera (100), comprising: a lighting unit (110) configured to transmit information to a remote time-of-flight receiver by modulating a light signal (114) to be emitted in accordance with an information-carrying signal (116), wherein the illumination unit (110) is designed to modulate the light signal (114) with a first periodic signal sequence according to a first information symbol of the information-carrying signal (116) and with a second periodic signal sequence according to a second information symbol of the information-carrying signal (116), wherein the first periodic signal sequence and the second periodic signal sequence are phase-shifted by a predetermined value.

Description

TECHNICAL FIELD

[0001] Embodiments generally relate to the field of time-of-flight (ToF) distance measuring devices, such as ToF cameras. BACKGROUND

[0002] This section introduces aspects that may be helpful in facilitating a better understanding of the inventions. Accordingly, the information in this section should be read in this context and should not be understood as a commitment as to what constitutes or does not constitute prior art.

[0003] Time-of-flight (ToF) ranging is one of the most widely used techniques for optical, three-dimensional (3D) measurement. ToF ranging imaging cameras can measure a distance to each pixel within a ToF camera's field of view. This can be achieved by illuminating a scene with modulated light, e.g., infrared light, and measuring a phase shift between an outgoing and an incoming modulated light signal. For each pixel, the corresponding distance can then be calculated from this phase shift. Thus, conventional ToF cameras can use modulated light to illuminate a scene and its reflected version to determine depth information related to one or more objects in the scene.

[0004] DE 10 2013 207 649 A1 describes a time-of-flight camera system that uses at least two different modulation frequencies to improve distance measurement. A distance measurement determines an initial distance-relevant value, while an additional control measurement with lower phase resolution and a different modulation frequency is used for verification. The combination of both measurements enables more precise and robust distance determination, particularly through the detection and correction of potential measurement errors such as overrange or interference.

[0005] DE 20 2007 017 639 U1 describes an optical sensor for detecting objects that transmits status information to an external data receiver via a data light source. The information is converted into a data protocol that can be understood by a multifunctional microcomputer such as a mobile phone. This enables simple and cost-effective readout and configuration of the sensor without the need for special receiving devices.

[0006] EP 2 051 106A1 describes an integrated system for optical communication and laser rangefinding, which serves both data transmission and target identification. The invention combines fast pulsed lasers with retroreflectors to enable bidirectional communication and simultaneous rangefinding. The application is particularly intended for military purposes, such as covert friend-or-foe identification, with security being ensured through encryption, biometric authentication, and self-destruction mechanisms. SUMMARY

[0007] There is a need to provide an improved concept for a runtime camera and system.

[0008] Such a need may be satisfied by the subject matter of any of the claims.

[0009] In the following summary, some simplifications may be made, intended to emphasize and introduce some aspects of the various exemplary embodiments, but such simplifications are not intended to limit the scope of the invention(s). Detailed descriptions of a preferred exemplary embodiment, sufficient to enable those skilled in the art to make and use the inventive concepts, follow in later sections.

[0010] According to a first aspect, embodiments provide a time-of-flight (ToF) camera. The ToF camera comprises an illumination unit configured to transmit information to a remote receiver by modulating a light signal to be emitted according to an information-bearing signal.

[0011] In one or more embodiments, the remote receiver may be a remote ToF receiver, e.g., included in another remote ToF camera. In some embodiments, the illumination unit may also be used to illuminate a scene to be captured by the ToF camera.

[0012] Embodiments further include a corresponding method. The method comprises exchanging information between a ToF camera and a remote ToF receiver by modulating, at the ToF camera, a light signal to be emitted according to an information-bearing signal.

[0013] In some embodiments, the illumination unit is configured to illuminate a scene to be captured by the time-of-flight camera with the light signal.

[0014] Optionally, the illumination unit may be configured to modulate a phase of the light signal according to the information-bearing signal.

[0015] In some embodiments, the information-bearing signal may comprise a non-predetermined baseband signal that conveys useful information to the remote time-of-flight sensor.

[0016] The illumination unit is configured to modulate the light signal with a first periodic signal sequence corresponding to a first information symbol of the information-carrying signal and with a second periodic signal sequence corresponding to a second information symbol of the information-carrying signal. The first periodic signal sequence and the second periodic signal sequence are phase-shifted by a predetermined value.

[0017] In some embodiments, the illumination unit may be configured to modulate the light signal according to a non-coherent modulation scheme.

[0018] In some embodiments, the illumination unit may be configured to modulate the light signal according to a differential modulation scheme.

[0019] In one embodiment, the illumination unit is configured to modulate the light signal according to a phase difference modulation scheme (DPSK modulation scheme; DPSK = Differential Phase Shift Keying).

[0020] In some embodiments, the information-carrying signal includes a predefined synchronization signal to enable the remote time-of-flight sensor to synchronize with a phase of the emitted light signal.

[0021] In one or more embodiments, the illumination unit may be configured to wirelessly emit the light signal to the remote time-of-flight receiver.

[0022] In one embodiment, the light signal is an infrared light signal.

[0023] Optionally, the time-of-flight camera may further comprise a detector configured to detect a further information-bearing signal contained in a light signal emitted from a remote time-of-flight camera.

[0024] In some embodiments, the detector may be configured to also include at least a portion of a scene to be captured by the time-of-flight camera.

[0025] In one or more embodiments, the detector may be configured to detect the further information-bearing signal based on a non-coherent detection scheme.

[0026] In some embodiments, the detector may include at least one photonic mixing device (PMD) pixel to receive the modulated light signal.

[0027] In one embodiment, the PMD pixel may be coupled to a reference signal unit to downconvert the received modulated light signal to a baseband range using a reference signal.

[0028] In some embodiments, the reference signal unit may be configured to adjust a phase of the reference signal based on a predefined synchronization signal included in the further information-carrying signal.

[0029] According to a further aspect, embodiments provide a ToF receiver with at least one PMD pixel, comprising a ToF sensor configured to detect an information-carrying signal contained in a light signal phase-modulated according to the information-carrying signal, which is emitted from a remote light source. The PMD pixel is coupled to a reference signal unit for downconverting the received, phase-modulated light signal to the baseband range using a reference signal.

[0030] In one or more embodiments, the ToF receiver may be included in a ToF camera. In some embodiments, the ToF sensor may be a ToF pixel, e.g., a pixel of a photonic mixing device (PMD). In some embodiments, the remote light source may be included in an illumination unit of a remote ToF camera.

[0031] Embodiments further include a corresponding method. The method comprises, at a ToF receiver with at least one PMD pixel, detecting an information-carrying signal contained in a light signal phase-modulated according to the information-carrying signal, which is emitted from a remote light source. The received, phase-modulated light signal is downconverted to the baseband range using a reference signal. For this purpose, the PMD pixel is coupled to a reference signal unit. One or more conventional ToF pixels can be used for this purpose.

[0032] Embodiments also include a system comprising a first and a second ToF camera. The first ToF camera includes an illumination unit configured to transmit information to a second ToF camera by modulating a phase of a light signal to be emitted according to an information-carrying signal. The second ToF camera includes a ToF sensor having at least one PMD pixel configured to detect the information-carrying signal contained in the emitted light signal of the first ToF camera, which is phase-modulated according to the information-carrying signal. The PMD pixel is coupled to a reference signal unit for downconverting the received, phase-modulated light signal to the baseband range using a reference signal. This may enable a plurality of ToF cameras to communicate with each other.

[0033] Embodiments further include a method for exchanging information between a first and a second ToF camera. The method includes modulating a phase of a light signal to be emitted from the first ToF camera according to an information-carrying signal, and detecting, with the second ToF camera having at least one PMD pixel, the information-carrying signal contained in the emitted light signal of the first ToF camera, which is phase-modulated according to the information-carrying signal. The received, phase-modulated light signal is downconverted to the baseband range using a reference signal. For this purpose, the PMD pixel is coupled to a reference signal unit.

[0034] Some embodiments comprise digital circuitry installed within a ToF camera for executing the corresponding method. Such digital control circuitry, e.g., a digital signal processor (DSP), a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), or a general-purpose processor, must be programmed accordingly. Thus, yet further embodiments provide a computer program with program code for executing embodiments of one of the above-mentioned methods or at least one or more steps thereof, when the computer program is executed on a computer on a programmable hardware device.

[0035] Embodiments may combine 3D image generation and data exchange on 3D ToF cameras. SHORT DESCRIPTION OF THE CHARACTERS

[0036] Some embodiments of devices and / or methods are described below solely by way of example and with reference to the accompanying figures, in which: Fig. 1 shows a ToF camera according to an embodiment; Fig. 2 shows a system of multiple ToF cameras according to an embodiment; Fig. 3 shows an example of an information-carrying signal; and Fig. 4a,b show exemplary implementations of a detection circuit arrangement for an information-bearing signal. DETAILED DESCRIPTION

[0037] Various examples will now be described in more detail with reference to the accompanying drawings, which illustrate some examples. In the figures, the thickness of lines, layers, and / or regions may be exaggerated for clarity.

[0038] Accordingly, while various modifications and alternative forms of further examples are possible, the illustrative examples in the figures are described in detail herein. It should be understood, however, that the examples are not intended to limit the examples to the particular forms disclosed; rather, the examples are intended to cover all modifications, equivalents, and alternatives within the scope of the disclosure. Throughout the description of the figures, like numerals refer to like or similar elements.

[0039] It is understood that when an element is described as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or intervening elements may be present. Conversely, when an element is described as being "directly connected" or "coupled" to another element, no intervening elements are present. Other words used to describe the relationship between elements should be interpreted similarly (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.).

[0040] The terminology used herein is for the purpose of describing illustrative examples only and is not intended to be limiting of further examples. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise. It is further understood that the terms "comprises," "comprising," "having," and / or "comprising," as used herein, indicate the presence of specified features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0041] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which examples belong. Furthermore, it is understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an idealized or overly formal sense unless expressly defined as such.

[0042] Fig. 1 illustrates a schematic block diagram of a time-of-flight (ToF) camera 100 according to one embodiment.

[0043] The ToF camera 100 may be an example of a distance-measuring imaging device that resolves a distance based on the known speed of light and by measuring the time of flight of a light signal between the camera 100 and an object for each point in the camera's field of view. The ToF camera 100 may be a standalone ToF camera or may be incorporated into another device, such as a smartphone, a tablet PC, a laptop PC, or the like. According to embodiments, the ToF camera 100 may communicate simultaneously with other ToF devices.

[0044] The ToF camera 100 has an illumination unit 110 comprising a light emitter 112, an optics assembly 120, an image sensor 130, a driver circuit 140, and a processor unit 150. According to embodiments, the illumination unit 110, or more precisely its light emitter 112, is configured to exchange / communicate information with a remote receiver (not shown) by modulating light or a light signal 114 to be emitted according to an information-bearing signal 116.

[0045] As a result, at least a portion of the information-bearing signal 116 may not be predetermined, ie, may not be known in advance, and may depend on actual information to be transmitted from the camera 110 to the remote or long-distance receiver. The information-bearing signal 116 may therefore carry useful information to be transmitted from the ToF camera 100 to the remote receiver, which may be a remote ToF ranging device or receiver, such as another ToF camera in some embodiments. However, ToF receivers are also possible in other devices, such as smartphones, tablet PCs, laptop PCs, or the like.

[0046] In some embodiments, the information-bearing signal may comprise one or more non-predetermined digital baseband signals for conveying useful information to the remote receiver. For example, the information-bearing signal 116 may comprise information about an image captured by the camera 100 and / or 3D information thereof. For another example, the information-bearing signal 116 may comprise information about the camera 100, such as configuration information of the camera. Thus, the configuration information may include predefined and camera-specific modulation sequences for modulating the emitted light 114. By communicating the camera-specific modulation sequence to other ToF cameras, the latter may select other orthogonal modulation sequences to reduce mutual interference between the multiple 3D cameras in proximity to each other.

[0047] In some embodiments, a modulator 118 of the illumination unit 110 can be configured to modulate a phase of the light signal according to the information-bearing signal 116. The modulator 118 can thus be configured to perform a phase modulation of the light signal 114. Alternatively or additionally, the amplitude of the light signal 114 can also be modulated based on the information-bearing signal 116.

[0048] In some embodiments, the modulator 118 may be configured to modulate the light 114 according to a non-coherent modulation scheme. In this way, the transmitting ToF camera 110 and the remote receiver do not need to be phase-locked to detect the information-bearing signal, which may lead to less complex implementations. For example, the light signal 114 may be modulated according to a differential modulation scheme, such as differential phase shift keying (DPSK). Here, data from the information-bearing signal may be used to change, rather than adjust, the phase of the light 114 to be emitted.

[0049] It should be noted that other embodiments may also utilize coherent transmission or modulation schemes, such as phase shift keying (PSK) or quadrature amplitude modulation (QAN). In such cases, the information-bearing signal 116 may be supplemented with a predefined synchronization or training signal to enable the remote receiver to estimate and synchronize with the phase of the emitted, modulated light signal. Coherent transmission / reception schemes may allow the detection of both an unknown transmitted information-bearing signal 116 and a distance between a transmitting device and a remote receiving device.

[0050] In addition to exchanging information, the illumination unit 110 can also be configured to illuminate a scene to be captured by the time-of-flight camera 100. Thus, the light emitter 112 can be configured to wirelessly, i.e., without cables or fibers, emit the light 114 toward the scene and / or the remote receiver, which should be in the field of view of the illumination unit 110 in order to be able to receive the modulated light 114. Since the light 114 can be modulated at speeds of several to hundreds of megahertz, light-emitting diodes (LEDs) or laser diodes, for example, can form the light emitter 112. The illumination unit 110 can use infrared light to make the illumination unobtrusive. Thus, the light signal 114 may be an infrared light signal covering wavelengths from 340 THz down to 300 GHz, which corresponds to wavelengths from 700 nm to 1 mm.

[0051] The optics assembly 120 may include one or more lenses 122 to capture reflected light and image the captured scene / environment onto the image sensor 130. The optics assembly 120 may further include one or more optical bandpass filters to pass light of the same wavelength as the light emitted from the illumination unit 110. Optical bandpass filters can help suppress unwanted background light.

[0052] The image sensor 130 can have one or more depth-sensitive pixels 132 to capture at least part of a scene in the half-space in front of the time-of-flight camera 100. The depth-sensitive pixels can be configured to measure the time it takes for the light 114 to travel from the illumination unit 110, i.e., from the camera 100, to an illuminated object and back. Thus, the depth-sensitive pixels 132 of the image sensor 130 can each be considered ToF sensors, and the image sensor 130 can be considered a ToF receiver. Other ToF receivers that are not embedded in a ToF camera are also conceivable. Examples of ToF sensors include PMD pixels (PMD = Photonic Mixing Device) to receive the modulated light signal.As one of ordinary skill in the art will appreciate upon review of the present disclosure, a PMD pixel is a surface-channel semiconductor device capable of simultaneously performing a mixing and charge integration process in its photosensitive region. A PMD pixel can be fabricated using conventional complementary metal oxide semiconductor (CMOS) techniques.

[0053] In some embodiments, one or more ToF pixels / detectors 132 of the image sensor 130 may alternatively or additionally be configured to detect an information-bearing signal contained in a light signal emitted from a remote ToF camera (not shown) and captured by the ToF camera 100. Depending on the underlying modulation scheme, the information-bearing signal may be detected based on coherent or non-coherent detection schemes. While phase synchronization between the emitted / transmitted light signal and the received light signal is required for coherent detection schemes, phase synchronization is not necessary for non-coherent detection schemes, such as DPSK.

[0054] Both the illumination unit 110 and the image sensor 130 of the ToF camera 100 can be controlled by high-speed signals supplied by the driver circuitry 140. Such signals can be very precise to achieve high resolution. For example, if the signals between the illumination unit 110 and the sensor 130 are shifted by only 10 picoseconds, the detected distance can change by 1.5 mm. The distance and / or the estimated value of the received, information-bearing signal can be determined, for example, using the processor unit 150.

[0055] Referring now to Fig. Figure 2 schematically illustrates a communication system 200 comprising a plurality of ToF cameras 100-1, 100-2, 100-3. According to embodiments, the plurality of ToF cameras 100-1, 100-2, 100-3 can exchange information with each other.

[0056] As explained above, a first ToF camera 100-1 comprises an illumination unit 110-1 configured to exchange information with or send information to a second ToF camera 100-2 or 100-3 by modulating a light signal to be emitted according to an information-bearing signal. The second ToF camera 100-2 or 100-3 comprises one or more ToF sensors configured to detect the information-bearing signal contained in the emitted light signal of the first ToF camera 100-1. Those skilled in the art will recognize that communication between the ToF cameras 100-1, 100-2, and 100-3 may each be bidirectional. Thus, each of the ToF cameras 100-1, 100-2, 100-3 may include both an optical transmitter and an optical receiver circuitry, as explained above.It is noted that other ToF devices, which do not necessarily have to be ToF cameras, may also be part of the communication system 200.

[0057] Thus, embodiments can support data communication, for example, between different 3D cameras. The cameras can periodically broadcast their own configuration data. Other cameras can receive these parameters and become aware of their environment, e.g., how many other cameras are nearby and / or what configuration they are using. With this information about other users, each camera can adapt / optimize its own configuration, e.g., its modulation frequency and / or sequence, to the environment. Some embodiments can thus dynamically reduce illumination interference between different ToF cameras deployed in proximity to each other.

[0058] Fig. 3 illustrates an example of how an information symbol of an information-carrying signal 116 can modulate a light signal to be emitted.

[0059] Fig. 3 shows, by way of example only for illustrative purposes, a binary symbol alphabet {0; 1}. Those skilled in the art will recognize that M-ary symbol alphabets and higher-order modulation schemes are also covered by embodiments, where M > 2. For the information symbol "0" as well as the information symbol "1," the emitted light signal, which may be near-infrared (NIR) light, may be rectangular in shape, resulting in a first periodic sequence 316-0 and a second periodic sequence 316-1 of light pulses. Thus, the information-bearing signal may comprise a first binary signal sequence 316-0 corresponding to a first information symbol and a different second binary signal sequence 316-1 corresponding to a different second information symbol.A difference between the first sequence 316-0, corresponding to the symbol "0," and the second sequence 316-1, corresponding to the symbol "1," may be a predetermined phase shift of the emitted light sequences, e.g., a phase shift Δφ = 180°. Thus, a phase of the light signal may be modulated according to the information-carrying signal.

[0060] In the exemplary embodiment of Fig. 3, each information symbol {0; 1} comprises several periods of a periodic signal sequence 316-0, 316-1. As explained below, a remote receiver can integrate over these periods to achieve a sufficient signal-to-noise ratio (SNR). Although Fig. 3 illustrates exemplary rectangular signal sequences 316-0, 316-1, the person skilled in the art will recognize that other signal shapes may also apply, e.g. sinusoidal signal shapes.

[0061] At a remote receiving end, e.g., a remote ToF camera, ToF pixels can be designed to detect the phase shift between a received signal and a reference signal, as in Fig. 4a and Fig. 4b. Conventionally, this phase shift depends on the distance to an illuminated target. In the case of data communication, however, the transmitter and receiver may be two different and distributed ToF cameras that may not have the same phase and timing reference (non-coherent detection). In some embodiments, however, the transmitter and receiver may be symbol-synchronized. Such symbol synchronization can be achieved by detecting large phase jumps, for example, or by inserting known training symbols into an information-bearing signal 116.

[0062] Fig. Figure 4a schematically illustrates an exemplary transmit / receive scheme in the form of non-coherent, orthogonal signal generation via differential phase shift keying (DPSK). Here, a demodulator 400-1 can determine changes in the phase of the received signal, rather than the phase (relative to a reference wave) itself. There is no need for the demodulator 400-1 to have a copy of the emitted / transmitted light signal to determine the exact phase of the received signal; it is a non-coherent scheme.

[0063] For example, the optical or light signal 114 for transmitting the information symbol “0” can be encoded without phase shift according to s0(t)={cos(2πft), ⋯0 <t<Tcos(2πft),⋯T<t<2T'

[0064] The optical signal for transmitting the symbol “1” can then be encoded with a phase shift according to s1(t)={cos(2πft),⋯0 <t<Tcos(2πft),⋯T<t<2T'

[0065] Instead of the cosine waveform, any other periodic waveform, such as a rectangular waveform, can be used, as explained previously. The variable f denotes the modulation frequency of the optical signal, and the variable T denotes the symbol duration or integration time of a corresponding receiver. Typically, T can be an integer multiple of 1 / f.

[0066] Fig. Figure 4a shows a schematic block diagram of a DPSK detector / demodulator 400-1 for an information-bearing signal contained in a received optical or light signal s i (t), where i denotes the transmitted symbol. The example detector 400-1 has a first PMD pixel 402-1 and a second PMD pixel 402-2. Both PMD pixels 402-1, 402-2 are connected to a reference signal source for downconverting (downmixing) the received light signal s i(t) into a lower frequency range, such as the baseband range, using a reference signal r(t) = cos(2πft). The PMD pixel 402-2 uses a -90° phase-shifted version of the reference signal r(t), which in our example is sin(2πft), to downconvert the received light signal s i (t). It should be noted that a phase of the reference signal r(t) and the emitted light signal need not necessarily be aligned for non-coherent detection schemes. However, the reference signal source or unit may be configured to adjust a phase of the reference signal r(t) based on a predefined synchronization or training signal included in the signal s i (t) is included.

[0067] The mixing process at both PMD pixels 402-1, 402-2 can convert baseband signals siI(t) or siQ(t) The baseband signals siI(t) and siQ(t) can be integrated by integrators 404-1, 404-2 for a respective symbol duration T. The integrators 404-1, 404-2 can be included in the PMD pixels 402-1, 402-2, respectively. The outputs of the integrators 404-1, 404-2 can then be converted from analog to digital by analog-to-digital converters (ADCs) 406-1, 406-2, respectively, to yield digital samples x[k] and y[k], where k is the sampling index. Using the digital in-phase (I) samples x[k] and quadrature (Q) samples y[k], known differential digital signal processing 408 can be performed on x[k-1], x[k], y[k-1] to obtain the information symbol estimate for symbol i.

[0068] While the embodiment of Fig. 4a, which generates I and Q components for a received signal, can be particularly advantageous for higher-order modulation schemes, shows Fig. 4b shows a less complex receiver structure 400-2 that uses only one pixel 402 instead of two.

[0069] Fig. Figure 4b shows a schematic block diagram of another implementation of a PSK detector / demodulator 400-2 for an information-bearing signal contained in a received optical or light signal. i (t), where i denotes the transmitted symbol. The example detector 400-2 has only one PMD pixel 402, which is connected to a reference signal source 410 for downconverting (downmixing) the received light signal s i (t) is coupled to a lower frequency range, such as the baseband range, using a plurality of reference signals r n (t, φ n ) with different phases φ nFor example, four reference signals with four phase shifts of φ1 = 0°, φ2 = 90°, φ3 = 180°, and φ4 = 270° can be applied sequentially. During this time, the information symbol should not change. Thus, if the symbol duration is T, the application time of reference signals is r. n (t, φ n ) T / N, where N is the number of different phase shifts (here in this example N = 4). At the output of the pixel 402 there is a sequence of four values ​​A0, A1, A2, A3, which can be stored in the memory 412. These four values ​​can be used to calculate the actual phase of the symbol i, i.e. α[i], via the equation α[i]=arctan(A1−A3A2−A0).

[0070] Those skilled in the art will readily recognize that a ToF camera may also employ more than one ToF sensor 132 to receive an information-bearing signal, resulting in so-called optical SIMO (Single Input Multiple Output) concepts. When a transmitting ToF camera employs more than one light emitter 112, optical MIMO (Multiple Input Multiple Output) transmission scenarios may arise, which may be advantageous for high-speed data communication and / or in constrained environments.

[0071] In summary, embodiments propose the use of ToF pixels, which are traditionally used for distance estimation (3D imaging), i.e., for data reception. Data transmission and / or reception capabilities can be achieved without additional hardware costs. Data transmission can be achieved by properly modulating the emitted light. Embodiments can combine 3D imaging and data transmission on a 3D camera. Data reception and distance estimation can be achieved using standard ToF pixels. Data transmission can be achieved by modulating the emitted infrared light.

[0072] Embodiments can support data communication between different 3D cameras. Thus, each camera can, for example, periodically broadcast its own configuration data. Other cameras can receive these parameters and become aware of the environment (e.g., how many other cameras are nearby? What configuration are they using? etc.). With this information about other users, each camera can adapt / optimize its own configuration (e.g., modulation frequency) to the environment.

[0073] Embodiments may be relevant for applications such as remote configuration, remote control, self-organization of PC / laptop / TV / home stereo, etc.

[0074] Embodiments propose a novel receiver design for optical data transmission with numerous advantages over state-of-the-art solutions. A correlation function can be implemented directly in the optical active region (ToF pixel).

[0075] Embodiments allow for joint data communication and distance estimation. This can enable distance limiting protocols to prevent wormhole attacks. Distance limiting protocols are cryptographic protocols that allow a verifier V to establish an upper limit on the physical distance to a testing facility P. They are based on timing a delay between sending challenge bits and receiving corresponding response bits. The delay time for responses allows V to calculate an upper limit for the distance, as a round-trip delay time divided by 2x the speed of light. The calculation is based on the fact that electromagnetic waves travel approximately at the speed of light, but cannot travel faster. For example, secure near-field communication (NFC) can be enabled (e.g.Communication is only permitted if the distance is less than 1 cm).

[0076] It is pointed out that the devices described can carry out corresponding processes.

[0077] Examples may further provide a computer program having program code for performing any of the above methods when the computer program is executed on a computer or processor. One skilled in the art would readily recognize that steps of various methods described above may be performed by programmed computers. Herein, some examples are also intended to cover program storage devices, e.g., digital data storage media that are machine- or computer-readable and encode machine-executable or computer-executable programs of instructions, where the instructions perform some or all of the acts of the above-described methods. The non-transitory program storage devices may be, e.g., digital memories, magnetic storage media such as magnetic disks and magnetic tapes, hard disk drives, or optically readable digital data storage media.Also, the examples are intended to cover computers programmed to perform the acts of the methods described above or (field) programmable logic arrays ((F)PLA - (Field) Programmable Logic Arrays) or (field) programmable gate arrays ((F)PGA - (Field) Programmable Gate Arrays) programmed to perform the acts of the methods described above.

[0078] The description and drawings only illustrate the principles of the disclosure. It is therefore to be understood that those skilled in the art can devise various arrangements which, although not expressly described or illustrated herein, embody the principles of the disclosure and are within its spirit and scope. Furthermore, any examples provided herein are generally intended to be for instructional purposes only to assist the reader in understanding the principles of the disclosure and the concepts contributed by the inventor(s) to advance the art, and should be construed as serving without limitation to such specifically recited examples and conditions. Furthermore, all statements herein concerning principles, aspects, and examples of the disclosure, as well as specific examples thereof, are intended to include equivalents thereof.

[0079] Functional blocks referred to as "units for..." (performing a certain function) are to be understood as functional blocks comprising circuits, each configured to perform a certain function. Therefore, a "unit for something" can also be understood as a "unit designed or adapted for something." A unit designed to perform a certain function does not necessarily mean that such a means will perform the function (at a given moment in time).

[0080] Functions of various elements depicted in the figures, including any functional blocks referred to as "means," "means for providing a sensor signal," "means for generating a transmission signal," etc., may be provided through the use of dedicated hardware such as "a signal provider," "a signal processing unit," "a processor," "a controller," etc., as well as hardware capable of executing software in conjunction with associated software. Furthermore, any instance described herein as "means" could be implemented as or correspond to "one or more modules," "one or more devices," "one or more units," etc.When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Furthermore, express use of the term "processor" or "controller" should not be construed as referring exclusively to hardware capable of executing software, and may implicitly include, without limitation, digital signal processor (DSP) hardware, network processor, application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), read-only memory (ROM) for storing software, random access memory (RAM), and non-volatile storage. Other hardware, conventional and / or custom, may also be included.

[0081] Those skilled in the art should understand that all block diagrams herein represent conceptual views of exemplary circuits embodying the principles of the disclosure. Similarly, it should be understood that all flowcharts, state transition diagrams, pseudocode, and the like depict various processes substantially embodied in a computer-readable medium and thus executed by a computer or processor, regardless of whether such a computer or processor is explicitly depicted.

[0082] Furthermore, the following claims are hereby incorporated into the detailed description, where each claim may stand on its own as a separate example. While each claim may stand on its own as a separate example, it should be understood that although a dependent claim may refer to a particular combination with one or more other claims in the claims, other examples may include a combination of the dependent claim with the subject matter of any other dependent or independent claim. These combinations are suggested herein unless it is stated that a particular combination is not intended. Furthermore, features of a claim for any other independent claim are intended to be included, even if that claim is not made directly dependent on the independent claim.

[0083] It should further be noted that methods disclosed in the description or in the claims may be implemented by an apparatus having means for performing each of the respective acts of those methods.

[0084] Furthermore, it should be understood that the disclosure of multiple acts or functions disclosed in the specification or claims should not be construed as being in that particular order. Therefore, the disclosure of multiple acts or functions does not limit them to any particular order unless, for technical reasons, those acts or functions are not interchangeable. Furthermore, in some examples, a single act may include or be divided into multiple subacts. Such subacts may be included and form part of the disclosure of that single act unless expressly excluded.

Claims

[1] Time-of-flight camera (100), comprising: a lighting unit (110) configured to transmit information to a remote time-of-flight receiver by modulating a light signal (114) to be emitted in accordance with an information-carrying signal (116), wherein the illumination unit (110) is designed to modulate the light signal (114) with a first periodic signal sequence according to a first information symbol of the information-carrying signal (116) and with a second periodic signal sequence according to a second information symbol of the information-carrying signal (116), wherein the first periodic signal sequence and the second periodic signal sequence are phase-shifted by a predetermined value. [2] The time-of-flight camera according to claim 1, wherein the illumination unit (110) is configured to illuminate a scene to be captured by the time-of-flight camera (100) with the light signal (114). [3] The time-of-flight camera according to any one of the preceding claims, wherein the information-bearing signal (116) comprises a non-predetermined baseband signal that carries useful information for the remote time-of-flight sensor. [4] The time-of-flight camera according to one of the preceding claims, wherein the illumination unit (110) is configured to modulate the light signal (114) according to a non-coherent modulation scheme. [5] The time-of-flight camera according to one of the preceding claims, wherein the illumination unit (110) is configured to modulate the light signal (114) according to a differential modulation scheme. [6] The time-of-flight camera according to one of the preceding claims, wherein the illumination unit (110) is configured to modulate the light signal (114) according to a differential phase shift keying (DPSK) modulation scheme. [7] The time-of-flight camera according to any one of the preceding claims, wherein the information-bearing signal (116) comprises a predefined synchronization signal to enable the remote time-of-flight sensor to synchronize with a phase of the emitted light signal (114). [8] The time-of-flight camera according to any one of the preceding claims, wherein the illumination unit (110) is configured to emit the light signal (114) wirelessly to the remote time-of-flight receiver. [9] The time-of-flight camera according to any one of the preceding claims, wherein the light signal (114) is an infrared light signal. [10] The time-of-flight camera according to any one of the preceding claims, further comprising: a detector configured to detect a further information-bearing signal (116) contained in a light signal (114) emitted from a remote time-of-flight camera (100). [11] The time-of-flight camera according to claim 10, wherein the detector is configured to further detect at least a portion of a scene to be detected by the time-of-flight camera (100). [12] The time-of-flight camera according to claim 10 or 11, wherein the detector is configured to detect the further information-bearing signal (116) based on a non-coherent detection scheme. [13] The time-of-flight camera according to any one of claims 10 to 12, wherein the detector comprises at least one PMD (Photonic Mixing Device) pixel to receive the modulated light signal. [14] The time-of-flight camera according to claim 13, wherein the PMD pixel is coupled to a reference signal unit for downconverting the received modulated light signal to the baseband domain using a reference signal. [15] The time-of-flight camera according to claim 14, wherein the reference signal unit is configured to adjust a phase of the reference signal based on a predefined synchronization signal included in the further information-bearing signal. [16] Term receiver, comprising: a time-of-flight sensor having at least one PMD pixel (PMD = Photonic Mixing Device) configured to detect an information-carrying signal (116) contained in a light signal (114) phase-modulated according to the information-carrying signal (116) and emitted from a remote light source, wherein the PMD pixel is coupled to a reference signal unit (410) for downconverting the received phase-modulated light signal to the baseband range using a reference signal. [17] The time-of-flight receiver of claim 16, wherein the time-of-flight receiver is included in a time-of-flight camera (100) and / or wherein the information-bearing signal (116) includes useful information from a remote time-of-flight camera. [18] System comprising: a first time-of-flight camera having an illumination unit (110) configured to transmit information to a second time-of-flight camera by modulating a phase of a light signal (114) to be emitted in accordance with an information-carrying signal (116); and a second time-of-flight camera with a time-of-flight sensor with at least one PMD pixel (PMD = Photonic Mixing Device) which is designed to detect the information-bearing signal (116) contained in the emitted light signal (114) of the first time-of-flight camera which is phase-modulated according to the information-bearing signal (116), wherein the PMD pixel is coupled to a reference signal unit (410) for downconverting the received phase-modulated light signal to the baseband range using a reference signal.

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