Simultaneous data transmission and depth image recording using a time-of-flight camera

Abstract

The present disclosure relates to a technology for simultaneous data transmission and depth image recording using a time-of-flight camera, for example, for simultaneous time-of-flight (ToF) measurement and information signal transmission. An information signal is superimposed on a series of light pulses by emitting the series of light pulses in groups of N fixed-spaced pulses and selectively changing the time interval between successive groups of pulses, so that changes in the time intervals produced between successive groups of emitted pulses indicate the value of the information signal. Pixels configured to demodulate received light using a pulse reference signal derived from a modulated signal are controlled to generate pixel signal values, each of which indicates the time of flight from a ToF measuring device to an object and back. The control includes changing the time interval between successive groups of reference signal pulses in the same manner as changing the time interval between emitted pulses, so that the superposition of the information signal has no effect on the ToF measurement.

Description

Technical Field

[0001] The present disclosure relates generally to time-of-flight (ToF) measurements, and more particularly to techniques for superimposing data on emitted light for ToF measurements. Background Art

[0002] In optical sensing applications, depth measurement (i.e., measurement of the distance to various features of one or more objects with respect to an image sensor) can be performed as so-called time-of-flight (ToF) measurements, which are distance measurements determined using the speed of light and an image / pixel sensor. The distance to the object of interest is typically calculated per pixel, and once calculated, the distance can be used for depth detection, gesture identification, object detection, etc. The per-pixel distances are combined to create an output (such as a depth map providing a three-dimensional image). Instead of or in addition to a depth map, other types of outputs (such as point clouds, intensity images, etc.) can be generated. ToF measurement technology is increasingly found in portable electronic devices (such as cellular phones and "smart" devices).

[0003] Many conventional TOF measurement methods require multiple consecutive exposures (also called copies). Each exposure requires light generated by an amplitude-modulated light source, which uses a modulation signal relative to a reference signal applied to a pixel at a corresponding phase, and the pixel demodulates the light reflected from one or more objects of interest, and the phase is different for different exposures. For example, one method requires four separate exposures with phases of the modulation signal at 0°, 90°, 180°, and 270° relative to the reference signal. The measurement information from the four exposures is collected and compared to determine the depth map. For high-precision measurements with an extended clear range, more exposures (e.g., up to nine separate raw measurements) can be performed. This conventional method, as well as several variants and supporting hardware, are described in detail in U.S. patent application No. 16 / 176,817 (titled "Image Sensor with Interleaved Hold for Single-Readout Depth Measurement") filed on October 31, 2018 for the purpose of providing background for the present invention, the entire contents of which are incorporated herein by reference. Summary of the Invention

[0004] This article describes a technology for simultaneously performing time-of-flight (ToF) measurement and data transmission. According to some embodiments described below, data is superimposed on a series of light pulses formed by amplitude-modulated light of a modulated signal having a frequency f by emitting a series of light pulses in N groups of fixed-interval pulses and selectively changing the time interval between successive groups of pulses, whereby the change in the time interval generated between successive groups of transmitted pulses indicates the data value being transmitted. Pixels configured to demodulate received light using a pulse reference signal derived from the modulated signal are controlled to generate pixel signal values, each pixel signal value indicating the time of flight from the ToF measurement device to the object and back. The control includes changing the time interval between successive groups of reference signal pulses in the same manner as the time interval between the transmitted pulses is changed, so that the superposition of data has no effect on the ToF measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 is a diagram illustrating a time-of-flight measurement system according to some embodiments described herein.

[0006] Figure 2 An exemplary photonic mixing device (PMD) is shown.

[0007] Figure 3 Schematic diagram showing the principle of phase measurement according to the time-of-flight (TOF) technique.

[0008] Figure 4A and Figure 4B The principle of combined ToF measurement and data transmission according to some embodiments is shown.

[0009] Figure 5 is a flow chart illustrating a method for measuring pulsed communication data via ToF according to some embodiments.

[0010] Figure 6 is a block diagram illustrating components of an exemplary ToF measurement device in accordance with some embodiments. DETAILED DESCRIPTION

[0011] As described above, time-of-flight (ToF) measurement devices emit modulated light that is used to measure the distance to nearby objects and scenes. Modulated light can also be used for communication purposes. Combining optical communication with ToF depth sensing can provide any of the many benefits for communication (such as location-aware communication), for example: where communication is combined with positioning, and / or for short-range secure communication that is resistant to relay attacks. Location-aware optical communication between portable devices can benefit from ToF depth sensing, where the depth information indicates the distance to the communication partner, while the position of the partner device in the image indicates the direction.

[0012] However, transmitting data optically requires energy, which may be limited on some devices. In addition, the amount and intensity of light emitted to transmit data may be subject to strict regulatory constraints (e.g., for eye safety reasons). Therefore, reducing the amount of light energy required to perform the required communication and depth sensing functions can be very important.

[0013] This article describes a technique for combining depth sensing and data transmission. This means that data is transmitted to other devices on the same modulated light as the light used for ToF measurements. In other words, data can be superimposed on the modulated light used for ToF measurements (e.g., for depth imaging).

[0014] The present invention will now be described with reference to the accompanying drawings, in which like reference numerals are used to refer to similar elements throughout, and in which the structures and devices shown are not necessarily drawn to scale. In this disclosure, the terms "image" and "image sensor" are not limited to images or sensors involving visible light, but encompass the use of visible light and other electromagnetic radiation. Therefore, the term "light" as used herein is broad and refers to visible light as well as infrared and ultraviolet radiation.

[0015] Figure 1 The basic principle of the well-known continuous wave (CW) time-of-flight (TOF) measurement is shown. A light source 110 (such as a light emitting diode (LED) or a vertical cavity surface emitting laser (VCSEL)) is modulated with an electrical signal (e.g., a 300 MHz RF sinusoidal signal) so that the light source 110 emits an amplitude-modulated optical signal toward a target scene 120. Traveling at the speed of light c, the light signal reflects from one or more objects in the scene 120 and returns to the pixel array 135 in the TOF sensor 130, where the time of flight to the target scene 120 and back imposes a phase shift on the light signal received at the pixel array 135 relative to the originally emitted light signal.

[0016] The modulation signal 137 used to modulate the emitted light or a phase-shifted version thereof is also provided to the pixels in the pixel array 135 as a reference signal to correlate with the modulation signal superimposed on the reflected optical signal (in fact, the reflected optical signal is demodulated by each pixel in the pixel array 135).

[0017] While the structure and design of light-sensing pixels can vary, each pixel in pixel array 135 can, in some examples, be a photonic mixing device or PMD. Figure 2The basic structure of an exemplary PMD is shown, comprising readout diodes A and B and modulation gates A and B. When the photogates / diodes receive incident light, a reference signal is applied differentially to modulation gates A and B, creating a gradient in potential across the p-substrate. A differential sensor signal is generated across readout diodes A and B. The sensor signal from the pixel can be integrated over time to determine phase measurement information.

[0018] The difference between the voltages at the Read-A and Read-B nodes of the PMD corresponds to the correlation between the modulated optical signal detected by the photodiode structure in the illustrated device and a reference signal applied between the Mod-A and Mod-B nodes of the device. Thus, as discussed in further detail below, the PMD (and other photosensitive pixel structures) demodulates the modulated optical signal reflected from the target scene 120, producing a pixel signal value (in this case, the difference between the voltages at Read-A and Read-B) that is indicative of the distance traveled by the reflected optical signal.

[0019] While the modulating signal can take various forms, the principles behind this correlation / demodulation are easiest to see when a sinusoidal signal is used as the modulating signal. If the modulating signal g(t) and the received signal s(t) have a modulation amplitude "a" and a phase shift as given by

[0020] m(t) = cos(ωt), and

[0021]

[0022] Then the correlation between the received signal and the reference signal is given by:

[0023]

[0024] This is the phase difference between the two signals It will be appreciated that for periodic modulated signals, the correlation may be performed for an extended period of time (eg, several periods of the modulated signal) to improve the signal-to-noise ratio of the resulting measurement.

[0025] The phase difference between the transmitted optical signal and the received reflection of that signal (which is proportional to the distance traveled by the optical signal) can be extracted using the N-phase shift technique. This requires sampling the correlation function at N different points (e.g., by performing the correlation using N different phase shifts of the reference signal relative to the modulated signal g(t)). At least two measurements are required to calculate this phase shift and thus determine the distance traveled. This is typically done using four different phase shifts at 0, 90, 180, and 270 degrees, as this allows for simple cancellation of systematic offsets in the correlation results. See Figure 3 , which shows how the correlations A0 and A1 at 0 and 90 degrees, respectively, correspond to a first phase vector having an "ideal" component corresponding to the actual difference traveled by the optical signal and a systematic component reflecting systematic errors in the measurement and readout. Similarly, the correlations A2 and A3 at 180 and 270 degrees, respectively, correspond to a second phase vector pointing in the opposite direction, having exactly opposite "ideal" components and identical systematic components. In the figure, the ideal component is represented by the vector from the origin to the circle, while the systematic error component is represented by the smaller vector. The actual phase It can be calculated as follows:

[0026]

[0027] In this phase, the distance or "depth" to the target scene 120 can be calculated as follows:

[0028]

[0029] where f mod is the frequency of the modulating signal. It will be appreciated that due to "phase wrapping," this distance calculation has ambiguous results, as it is impossible to determine from a single distance calculation whether the distance traveled is less than a single wavelength or multiple wavelengths of the modulating waveform. Various techniques for resolving this ambiguity are well known, such as incorporating amplitude information obtained from the reflected optical signal and / or repeating measurements using different modulation frequencies, but a detailed discussion of these techniques is not necessary for a full understanding of the techniques of the present disclosure and is therefore beyond the scope of this disclosure.

[0030] Figure 4A and Figure 4B The basic principles of an example technique for superimposing data transmission on modulated light for ToF measurement are shown. Figure 4A The relationship between the emitted illumination signal and the reference signal applied to the demodulation pixel for a conventional continuous wave ToF measurement using rectangular pulses for intensity modulation of the emitted light is shown. As can be seen in the figure, a given exposure may involve the transmission of a series of fixed-spaced pulses (e.g., Figure 4A For an exposure where the phase difference between the illumination signal and the reference signal is zero, as shown in the figure, the reference signal applied to the pixel can be effectively the same as the amplitude modulation applied to the emitted light. Figure 4AIn ToF measurement, this is seen as a "pixel reference signal" that consists of a series of regularly spaced pulses aligned with the illumination signal. The exposure can have a duration of one or more milliseconds (e.g., with a reference frequency of 100 MHz), which means that the exposure can include hundreds of pulses. The ToF measurement device correlates the light pulses reflected from the object with the reference signal, integrating the correlation over these pulses to produce a phase measurement that is proportional to the distance to the object or scene of interest. As shown in Figure 4A As shown in , it will be appreciated that when the pulses are rectangular, the measurement is effectively a measure of the alignment between the received light pulse and the reference signal, which manifests itself as increasing misalignment between the received light pulse and the reference pulse as the distance to the illuminated object increases (within the ambiguity distance).

[0031] As mentioned above, a given exposure may consist of a series of dozens or hundreds of regularly spaced pulses. Figure 4A Only a small portion of these pulses is shown. Data can be superimposed on the emitted light by grouping the pulses into groups of N pulses, where each group of pulses is transmitted with a fixed interval between the N pulses. In other words, the time interval between pulses within a given group is constant. However, as the degree of information being transmitted varies, the interval between successive groups (i.e., the time interval) can be varied. An example of this variation is shown in FIG. Figure 4B , which shows an example where N=2 (ie, there are two pulses per group in the illumination signal). As shown, the time interval between pulses within a given group is constant across all groups and is equal to t p However, the time interval between consecutive groups can be changed from this "normal" time interval t p changes, and uses the changes to transmit information. Figure 4A In the example shown in FIG, the second set of pulses is delayed by an additional time relative to the first set of pulses. The third set of pulses is delayed by different additional times relative to the second set of pulses

[0032] These different time delays can transmit data values ​​to a remote receiver that can detect these delays (e.g., The delay indication value is "0", and The delays indicated by the grouping are "1". Note that this is just one exemplary embodiment (some embodiments may utilize additional delays to provide a more complex modulation alphabet, e.g., such that each delay carries more than one bit value). For example, if four different delays are used between groups, each delay may indicate one of four possible combinations of two bits. More complex modulation alphabets are possible.

[0033] More generally, at least three basic ways of transmitting data via these time delays are possible, which generally correspond to on-off keying, pulse position modulation, and phase shift keying. Depending on the on-off keying method, a "1" or a "0" is transmitted with or without an additional delay between adjacent groups of pulses. In pulse position modulation, the information is carried by the specific length of the delay between adjacent groups of pulses, which can be very long relative to the spacing between the pulses within each group (the information can represent an analog quantity or one of a predetermined number of quantization levels). With phase shift keying (i.e., in Figure 4B In the method shown in , the variability in delay is the fraction of the interval from pulse to pulse within a given group, so that the phase of one group of pulses carries information relative to the previous group. In general, this can be a representation of an analog quantity, or one of a predetermined number of quantization levels. As described below, the phase shift keying method allows the use of a ToF sensor (e.g., with PMD pixels) in a receiving device to directly demodulate the information.

[0034] Importantly, when transmitting data while performing ToF measurements, the reference signal of the transmitting device (which is applied to pixels that demodulate light signals reflected from one or more objects of interest) is adjusted in a manner that directly corresponds to the timing adjustments of the transmitted light pulses. Thus, each time the delay between two consecutive groups of N pulses in the transmitted light pulse train is adjusted to convey a data value, the reference signal is adjusted exactly the same way. This is achieved in Figure 4B As a result, because the phase / timing relationship between each received pulse reflected from the object of interest and its corresponding reference pulse remains unchanged, these adjustments to the spacing between groups of transmitted light pulses are invisible to (i.e., have no effect on) the correlation processing performed by the pixels performing the ToF measurement.

[0035] However, a separate receiving device can be configured to detect the delay variation between successive groups of N pulses and, therefore, the data carried by the transmitted optical pulse train. It should be noted that this can be accomplished using one or more PMDs and a receive reference signal that is synchronized with the basic modulation signal used by the transmitting device. For example, a clock in the receiving device can first be synchronized with a sequence of fixed-interval pulses received from the transmitting device and used to generate a corresponding periodic receive reference signal and t p The timing of each set of N pulses received from the transmitting device is then compared to this received reference signal using one or more PMDs. This is effectively a phase measurement, similar to that conventionally performed in a ToF sensor, but with a correlation length that only extends to N pulses, resulting in one phase measurement for each set of N pulses. Figure 4BIf the transmitted pulses are done as shown in , the first set of N pulses will produce a phase measurement of 0 degrees because the first set of N pulses will be synchronized with the regular pulse sequence from the transmitting device and aligned with the received reference signal generated in the receiving device. However, the second set of N pulses will result in a measurement of 180 degrees because these pulses will be offset from the received reference signal by half the pulse width t p For example, a difference of 180 degrees from the previous group can be interpreted as "0" or some other data value. Similarly, the third group of N pulses will result in a measurement of 90 degrees because these pulses will be offset from the reference signal used by the receiving device by one-quarter of the pulse width t p ; The difference between this measurement and the previous measurement (270 degrees) can be interpreted as a second data value (e.g., "1").

[0036] As in Figure 4A and Figure 4B As seen in the example shown in FIG, after each set of N pulses is transmitted, in addition to the phase delay or In addition, there is t p This delay allows the emitted pulse to travel from the illuminated object back to the sensor. For example, for short-range ToF, using only four-phase measurements, t p It can simply be T / 2, where T is the period of the modulated signal. However, for long-range ToF, for example, where eight phase measurements are used, t p Can be extended to cover the maximum travel time (time of flight) of light from the camera to the scene and back.

[0037] It should be understood that the phase delay The introduction of α extends the exposure time. If the data is only superimposed on a relatively small portion of the transmitted pulse, this effect can be very small. Furthermore, it should be understood that although the overall exposure time is extended, the transmitted energy remains unchanged because the delay between the transmitted pulses is extended.

[0038] In a straightforward approach, the receiving device aligns with a train of pulses spaced at fixed intervals so that it can detect the phase value conveyed by each set of pulses. In a different approach, each phase value is conveyed using two sets of pulses, with the second set shifted by a known phase (such as 90 degrees) relative to the first. In this manner, the demodulation device obtains two samples of each transmitted symbol (one sample for each of the two sets). In this manner, a phase value indicating the delay between one set of pulses and the previous set of pulses can be calculated directly from the two samples.

[0039] In some embodiments, as indicated above, the clock at the receiving device can be synchronized with the corresponding clock at the transmitting device so that a receive reference signal can be generated. Before superimposing the data on the subsequent pulses, by causing the transmitting device to emit a series of pulses without superimposed modulation, the generation of a receive reference signal can be facilitated so that the receiving device can detect the timing of the unmodulated pulse sequence and generate a receive reference signal for detecting the data subsequently transmitted. An example technique for synchronizing a receiving ToF measurement device to an externally generated optical signal is described in U.S. Patent Application Publication No. US2018 / 0259628A1, the entire contents of which are incorporated herein by reference. However, it should be understood that other techniques for synchronizing the transmitting device and generating a reference for detecting transmitted data can be used. It should also be understood that although, as described above, the receiving device can use a PMD or other pixel sensor to detect the transmitted data, the receiving device can alternatively use any of a variety of photodetector devices to implement detection of data from the received optical signal. Therefore, while the techniques described herein can be used to transmit from one ToF measurement device to another ToF measurement device, with each ToF measurement device using its own corresponding ToF sensor to implement its own corresponding transmit and receive functions, the techniques described herein can also be used to transmit from a ToF measurement to another device that only includes an optical receiver.

[0040] In view of the above technology, it should be understood that Figure 5 is a process flow diagram illustrating an example method for communicating an information signal (which may be an analog or digital signal) via a ToF measurement pulse in a ToF measurement device. As shown at block 510, the method includes the step of transmitting a series of light pulses formed by amplitude-modulated light using a modulation signal, wherein transmitting the series of light pulses includes superimposing the information signal on the series of light pulses by transmitting a series of N light pulses, wherein each group of N pulses is transmitted at a fixed interval, and selectively varying the time interval between successive groups of transmit pulses in response to the information signal, such that the varying time interval between successive groups of transmit pulses indicates the value of the information signal. In some embodiments, the frequency f of the modulation signal can be selected to provide a desired unambiguous measurement range. For example, in some embodiments, f can be approximately 100 MHz to provide an unambiguous measurement range of approximately 1.5 meters. In some embodiments, N can be a relatively small number (such as 2-10), while in other embodiments, N can be a larger number (e.g., 10-100) to provide a greater signal-to-noise ratio in the receiving device.

[0041] As shown at block 520, the method further includes the step of controlling one or more pixels configured to demodulate the received light using a pulse reference signal derived from the modulation signal to generate corresponding pixel signal values, each of the one or more pixel signal values ​​indicating the time of flight from the ToF measurement device to the object and back to the ToF measurement device. The control includes varying the time interval between successive groups of reference signal pulses in a manner corresponding to the variation in the time interval between successive groups of transmitted pulses; as described above, this effectively renders the ToF sensor in the transmitting device invisible to the varying time interval between the groups of transmitted light pulses. It should be understood that the control step shown in block 520 is performed substantially simultaneously with the step of transmitting the series of light pulses shown in block 510.

[0042] In some embodiments, before the steps shown in blocks 510 and 520, a series of fixed-interval pulses without an information signal superimposed thereon are transmitted to provide a synchronization signal for the receiving device so that the receiving device can adjust the received reference signal for detecting subsequently transmitted data. In some embodiments, the step of transmitting a series of pulses without data superimposed thereon may be repeated from time to time to allow the receiving device to update its synchronization. Figure 5 This is shown at box 505, where this step is shown with a dashed outline to indicate that it need not appear in all embodiments or all instances because, for example, in some embodiments synchronization may be achieved by other means and / or inherited from an earlier transmission.

[0043] In some embodiments, the information signal is an analog signal, and the varying intervals convey the value of the analog information signal. In other embodiments, the information signal is a digital signal, and the intervals between successive sets of transmitted pulses are constrained to a predetermined set (or group) of varying time intervals. For example, the set may include only two varying time intervals, such that a single bit is conveyed with each variation. In other embodiments, the set may include more than two varying intervals, such that each variation conveys more than one bit of information. In some embodiments, the varying time intervals between successive sets of transmitted pulses do not vary from the length of the fixed interval by more than the length of the fixed interval.

[0044] In some embodiments, the time interval between each transmitted set of pulses and the immediately following set of pulses indicates the value of the information signal, which may be an analog value or a digital value. In other embodiments, the pulses are transmitted in pairs of N pulses, where the second set of N pulses in each pair is shifted by a fixed phase (e.g., 90 degrees) relative to the first set of N pulses. As described above, this latter approach allows the phase value to be calculated directly from each pair of N pulses, without regard to the alignment between the received pulses and a reference clock.

[0045] As described above, another ToF measurement device (such as a camera in a handheld phone) can receive the signal and detect the data superimposed on the light pulse. For example, this can be used to detect the presence of other cameras. In some embodiments, each ToF measurement device can use the technology described above to transmit a unique ID. Other ToF measurement devices that receive the signal can detect and identify other cameras. For example, this enables a smartphone equipped with such a ToF measurement device to detect smartphones of other similar devices. This information can be used to determine which devices are used in the same environment, thereby creating a network of deployed devices. The connection between the two ToF cameras on the smartphone can be used to pair the devices (for example, for a universal Bluetooth connection).

[0046] The transmitted signal can also be decoded by electronic circuits using a photodiode as a receiver.

[0047] Figure 6 An example of a ToF measurement device 600 according to several embodiments of the devices and systems of the present disclosure is shown. The ToF measurement device 600 can be used to detect an object (e.g., as shown in target scene 602) and determine the distance to the detected object. The ToF measurement device 600 can be a continuous wave ToF system (such as a ToF system based on a photon modulation device (PMD)). According to the techniques described herein, the ToF measurement device 600 can also be configured to superimpose an information signal on the transmitted light pulse for reception by a remote device.

[0048] The ToF measurement device 600 shown includes a light source 624 configured to amplitude modulate a light beam using a modulation signal and emit the amplitude modulated light toward a scene 602. The amplitude modulation can be based on a reference signal generated by a reference signal generator 608. The reference signal can be, for example, a radio frequency (RF) signal in the MHz range, although other modulation frequencies can be used. The emitted light can include light having a varying wavelength range (such as sunlight and infrared). The emitted light reflects from one or more objects in the scene and returns to the sensor 604.

[0049] The illustrated ToF measurement device 600 further includes a sensor 604 comprising a plurality of pixels configured to generate a corresponding plurality of pixel signal values ​​in response to received light 614, wherein each pixel is configured to obtain its corresponding pixel signal value by demodulating the received light using a reference signal 622. Figure 6 As seen in FIG, received light 602 may be reflected from target scene 602. As described above, while several suitable pixel configurations are possible, one suitable pixel design is the PMD described above.

[0050] The number of pixels, rows, and columns may vary from embodiment to embodiment and may be selected based on factors including desired resolution, intensity, and the like. In one example, these sensor characteristics are selected based on the object to be detected and the expected distance to the object. Thus, for example, the pixel resolution of the pixels in sensor 604 may vary from one embodiment to another. Detection of smaller objects requires higher resolution. For example, finger detection requires a resolution of less than 5 mm per pixel at a distance or range of approximately 0.5 meters. Detection of medium-sized objects, such as hands, requires a resolution of less than 20 mm per pixel at a range of 1.5 meters. Larger objects, such as the human body, require a resolution of less than 60 mm per pixel at approximately 2.5 meters. It should be understood that the above examples are for illustrative purposes only and may vary (including for other objects, resolutions, and distances to be detected). Some suitable resolution examples include VGA - 640x400 pixels, CIF - 352x288 pixels, QQ-VGA - 160x120 pixels, and the like.

[0051] The ToF measurement device 600 also includes a reference signal generator 608. In some embodiments, the reference signal generator 608 can be configured to generate a reference signal 622 having a selectable phase relative to the phase of the signal applied to the light modulation emitted toward the target scene 602, and the reference signal generator 608 can be configured to provide the reference signal 622 to a plurality of pixels in the sensor 604. The image processing system 600 also includes an analog-to-digital converter (ADC) circuit 606, which can include one or more ADCs, operatively coupled to the plurality of pixels in the sensor 604, and providing digital phase or distance measurements to a depth map generator 610. It should be noted that in various embodiments, the depth map generator 610 can be configured to generate a point cloud or other representation or combination of depth data in addition to or in lieu of a depth map.

[0052] For example, the ToF measurement device 600 shown further includes a control circuit device 612, which may include a processor, a controller, and / or other digital logic. In several embodiments, the control circuit device 612 is configured to cause the image processing system 600 to perform the above-mentioned Figure 5A similar method as described herein. Thus, for example, the control circuit device 612 can be configured to control the light source 624 to emit light pulses in groups of N pulses (N pulses in each group of emission pulses are emitted at fixed intervals), and selectively change the time intervals between successive groups of emission pulses in response to the information signal, so that the changing time intervals generated between successive groups of emission pulses indicate the information signal. The control circuit device 612 can also be configured to control one or more pixels in the sensor 604 to demodulate the received light using a pulse reference signal derived from the modulation signal to generate corresponding pixel signal values, wherein each pixel signal value of the one or more pixel signal values ​​indicates the time of flight from the ToF measurement device to an object and back to the ToF measurement device. The control circuit device 612 can also be configured to control the reference signal generator 608 to change the time intervals between successive groups of reference signal pulses in a manner corresponding to the change in the time intervals between successive groups of emission pulses, so that the change in the time intervals between successive groups of emission pulses has no effect on the phase measurement performed using the sensor 604. In various embodiments, the control circuit device 612 can be configured to combine Figure 5 The methods shown are for carrying out any variation of the above techniques.

[0053] In view of the detailed discussion above, it should be understood that the subject matter described herein can be implemented using standard programming and / or engineering techniques to produce software, firmware, hardware, or any combination thereof to control a computer to implement the subject matter of the present disclosure. The term "article of manufacture" as used herein is intended to encompass a computer program accessible from any computer-readable device, carrier, or media. Of course, those skilled in the art will recognize that many modifications may be made to this configuration without departing from the scope or spirit of the claimed subject matter.

[0054] In particular, with respect to the various functions performed by the aforementioned components or structures (assemblies, devices, circuits, systems, etc.), unless otherwise indicated, terms used to describe such components (including references to "devices") are intended to correspond to any component or structure (e.g., functionally equivalent components or structures) that performs the specified function of the component, even if not structurally equivalent to the disclosed structures that perform the functions in the exemplary implementations of the invention shown herein. In addition, although a particular feature of the invention may be disclosed for only one of multiple implementations, that feature may be combined with one or more other features of other implementations as may be desired and advantageous for any given or particular application. In addition, where the terms "comprises," "including," "having," "having," "having," or variations thereof are used in the detailed description and claims, such terms are intended to be inclusive in a manner similar to the term "comprising."

Claims

1. A method for measuring pulsed communication data via ToF in a time-of-flight (ToF) measurement device, the method comprising: Emitting a series of light pulses formed by amplitude modulated light using a modulation signal, wherein emitting the series of light pulses comprises: superimposing an analog information signal on the series of light pulses using pulse position modulation by emitting the series of light pulses in groups of N pulses, the N pulses in each group of emission pulses being emitted at fixed intervals; and selectively varying a time interval between successive groups of emission pulses in response to the analog information signal, such that a resulting variation in the time interval between successive groups of emission pulses indicates a value of the analog information signal; and controlling one or more pixels configured to demodulate received light using a pulsed reference signal derived from the modulation signal to generate corresponding pixel signal values, each of the one or more pixel signal values ​​indicating a time of flight from the ToF measurement device to an object and back to the ToF measurement device, wherein the controlling comprises varying a time interval between successive groups of reference signal pulses in a manner corresponding to the variation in the time interval between the successive groups of transmit pulses.

2. The method of claim 1, wherein prior to said transmitting and said controlling, a series of regularly spaced pulses is transmitted, said series of regularly spaced pulses having no analog information signal superimposed thereon. The method of claim 1 , wherein the analog information signal comprises an identifier for the ToF measurement device.

4. The method of claim 1 , wherein the varying time intervals between the successive sets of transmit pulses do not vary from a length of the fixed interval by more than the length of the fixed interval.

5. The method of claim 1, wherein the time interval between each group of transmit pulses and an immediately subsequent group of transmit pulses indicates a value of the information signal.

6. The method of claim 1 , wherein superimposing the information signal on the series of optical pulses comprises: The series of light pulses are emitted in groups of pairs of N pulses, wherein the second group of N pulses in each pair is shifted by a fixed phase relative to the first group of N pulses. The method of claim 6 , wherein the fixed phase is 90 degrees.

8. A time-of-flight measurement device comprising: a light source configured to emit a series of light pulses formed by amplitude modulating light using a modulation signal; a sensor comprising a plurality of pixels configured to generate a corresponding plurality of pixel signal values ​​in response to received light, wherein each pixel is configured to obtain the corresponding pixel signal value of the pixel by demodulating the received light using a reference signal; a reference signal generator configured to generate the reference signal and provide the reference signal to the plurality of pixels, and A control circuit device is configured to: Controlling the light source to emit the series of light pulses in groups of N pulses, wherein the N pulses in each group of emitted pulses are emitted at fixed intervals; and selectively varying the time intervals between successive groups of transmit pulses using pulse position modulation in response to an analog information signal such that the resulting variation in the time intervals between successive groups of transmit pulses is indicative of a value of the analog information signal; controlling one or more of the pixels to demodulate received light using the reference signal to generate corresponding pixel signal values, each of the one or more pixel signal values ​​indicating a time of flight from a ToF measurement device to an object and back to the ToF measurement device, The reference signal generator is controlled to vary the time intervals between successive groups of reference pulses in a manner corresponding to the variation in the time intervals between the successive groups of transmit pulses.

9. A time-of-flight measurement device according to claim 8, wherein the control circuit is further configured to: before transmitting the pulses in groups of N pulses with varying time intervals between consecutive groups, control the optical emitter to emit a series of fixed-interval pulses without an analog information signal superimposed on the pulses. 10 . The time-of-flight measurement device according to claim 8 , wherein the control circuitry is configured to include an identifier for the time-of-flight measurement device in the analog information signal.

11. A time-of-flight measurement apparatus according to claim 8, wherein the control circuitry is configured to transmit the series of light pulses such that the varying time intervals between successive groups of transmit pulses do not vary from the length of the fixed interval by more than the length of the fixed interval.

12. The time-of-flight measurement device of claim 8, wherein the control circuitry is configured to transmit the series of light pulses such that the time interval between each group of transmit pulses and an immediately subsequent group of transmit pulses indicates a value of the analog information signal.

13. A time-of-flight measurement device according to claim 8, wherein the control circuit device is configured to superimpose the analog information signal on the series of optical pulses by emitting the series of optical pulses in groups of pairs of N pulses, wherein the second group of N pulses in each pair is shifted by a fixed phase relative to the first group of N pulses. The time-of-flight measurement device according to claim 13 , wherein the fixed phase is 90 degrees.

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