Light source monitoring

Abstract

To monitor operation of an illumination module to ensure that safety guidelines and / or requirements are satisfied.SOLUTION: A system such as an imaging system may include an illumination module. The illumination module may include a light source monitoring system. The light source monitoring system may sample a light source signal and aggregate the samples into data chunks. The light source monitoring system may selectively aggregate the data chunks to form groups of a monitoring time window. The light source monitoring system may detect a fault based on a value characterizing light source performance during the monitoring time window.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates generally to light source monitoring, and more particularly to light source monitoring in imaging systems. [Background technology]

[0002] As an example, a time-of-flight (TOF) sensor for an imaging system may include an illumination module and a sensor module. The illumination module may include one or more light sources that emit light to illuminate an image scene. The emitted light may reflect off one or more objects and be received by pixels in the sensor module to generate corresponding electrical charges. The sensor module may perform time-of-flight sensing calculations based on the generated electrical charges to determine depth and other scene information.

[0003] It may be desirable to monitor the operation of a lighting module to ensure that safety guidelines and / or requirements are met. [Brief explanation of the drawings]

[0004] [Figure 1] FIG. 1 is a diagram of an exemplary system having a lighting module, according to some embodiments. [Figure 2] FIG. 1 illustrates an exemplary lighting module and sensor module, according to some embodiments. [Figure 3] FIG. 1 illustrates an exemplary lighting module with a light source monitoring system, according to some embodiments. [Figure 4] 1 is a diagram of an exemplary light source monitoring system, according to some embodiments. [Figure 5] 1 is a diagram of an exemplary sampling and monitoring of a light source signal based on grouping of data chunks, according to some embodiments. [Figure 6] FIG. 2 is a diagram of an exemplary circuit for implementing a light source monitoring system, according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0005] An electronic system may include an illumination module having one or more light sources that provide illumination, such as infrared light illumination, visible light illumination, and / or light illumination at other wavelengths. The illumination module may pose a risk if it operates improperly due to, for example, one or more system faults. Therefore, it may be desirable to monitor the operation of the illumination module. In some examples, the light sources may operate at high frequencies using control signals at one or more frequencies between 30 MHz and 200 MHz and may operate in different modes, making sampling and monitoring the light source signals even more challenging given the large number of samples required and the various desired sampling time windows associated with the different operating modes.

[0006] To monitor the operation of the lighting module and the light sources therein, the lighting module may include a light source monitoring system. The light source monitoring system may sample the state of the light source signal over time. The light source monitoring system may aggregate sampled data into data values (sometimes referred to herein as data chunk values), each associated with a data chunk, and may further aggregate multiple data chunk values into data values (sometimes referred to herein as data group values), each associated with a group or grouping of data chunks. Specifically, the monitoring system may selectively generate data chunk values, each sized to average a desired number of samples and / or samples of a desired period, and may selectively generate data group values to sum a desired number of suitably sized data chunk values to form a desired monitoring time window for a given monitor. The monitoring time window may be a moving time window characterized by a moving sum as the data group values being monitored. Multiple such monitors may be provided to analyze light source performance in parallel over various monitoring time windows.

[0007] By monitoring sample data with different groupings of selected data chunks associated with different monitoring windows, the light source monitoring system can provide flexible and / or simultaneous monitoring for a variety of different operating modes. The use of different data chunks and different groupings of data can help reduce the number of samples processed by the light source monitoring system and can be particularly useful in real-time monitoring of high frequency operation, which is typically characterized by the processing of a relatively large number of data points over a short period of time.

[0008] Configurations in which the illumination module forms part of an imaging system, such as a time-of-flight (TOF) imaging system, may be described herein as examples. In some exemplary configurations, the imaging system may be part of an automotive system or vehicle, a digital camera, a computer, a mobile phone, or another type of electronic system. The illumination module in the imaging system may illuminate the surrounding environment, thereby assisting in collecting light to capture one or more image frames containing information about the surrounding environment. The imaging system may have a sensor circuit including an array of one or more image sensor pixels, which may also be referred to herein as sensor pixels or pixels. Active pixels in the array may include a photosensitive element, such as a photodiode, that converts incident light into an electric charge. The array may have any number of pixels (e.g., hundreds or thousands or more). The sensor circuit may include control circuitry, such as circuitry for controlling the pixels, and readout circuitry for reading out image signals corresponding to the electric charges generated by the photosensitive elements. If desired, the illumination module with a light source monitoring system may form part of other systems, such as non-imaging systems.

[0009] FIG. 1 is a diagram of an exemplary system having an illumination module, such as an imaging system 10 that captures images using sensor circuitry. The imaging system 10 of FIG. 1 may be a stand-alone camera, a mobile phone, a tablet computer, a webcam, a video camera, a video surveillance system, an automotive imaging system, a video game system with imaging capabilities, an augmented reality and / or virtual reality system, an unmanned aerial system (e.g., a drone), an industrial system, or any other desired imaging system or device that captures image data. A camera module 12 (sometimes referred to as an imaging module) can be used to convert incident light into digital image data. The camera module 12 can include one or more corresponding sensor modules 16 (sometimes referred to as image sensor modules or image sensors). During an image capture operation, light from a scene can be focused onto the sensor module 16 by one or more corresponding lenses. The sensor module 16 can include, by way of example, circuitry for generating analog pixel image signals and circuitry for converting the analog pixel image signals into corresponding digital image data. The digital image data can be provided to storage and processing circuitry 18.

[0010] The storage and processing circuitry 18 may include one or more integrated circuits, such as digital signal processing circuitry, image processing circuitry, microprocessors, storage devices such as random access memory and non-volatile memory, and / or other types of processing and / or memory circuitry. The storage and processing circuitry 18 may be implemented using components separate from and / or components forming part of the camera module 12. If the storage and processing circuitry 18 is implemented on an integrated circuit different from the integrated circuit implementing the camera module 12, the integrated circuit having the circuitry 18 may be vertically stacked on or co-packaged with the integrated circuit of the camera module 12. Image data captured by the camera module 12 may be processed and stored using the processing circuitry 18. By way of example, the captured image data may be processed using an image processing engine on the processing circuitry 18, using a digital signal processing engine on the processing circuitry 18, using an imaging mode selection engine on the processing circuitry 18, and / or using other portions of the processing circuitry 18. The processed image data may be provided to equipment external to camera module 12 and / or imaging system 10, such as a computer, an external display, and / or other device, as needed, using wired and / or wireless communication paths coupled to processing circuitry 18.

[0011] Illustratively, in some configurations described herein, camera module 12 may implement a time-of-flight (TOF) sensor or camera. In these configurations, camera module 12 may include illumination module 14 configured to emit light to illuminate the image scene, or more specifically, one or more objects within the image scene. Sensor module 16 may be configured to collect reflected versions of the emitted light and generate TOF information of the image scene, such as depth or distance information for one or more of the objects, a depth or distance map of the image scene, visible and / or infrared images of the image scene, and / or other TOF information.

[0012] FIG. 2 is a diagram of an exemplary illumination module and sensor module, such as the illumination module and sensor module in the imaging module 12 of FIG. 1. As shown in FIG. 2, the illumination module 14 may emit light, and the sensor module 16 may receive corresponding reflected light after the emitted light reflects off one or more objects 20, or generally off an image scene including the objects 20. The illumination module 14 may include one or more light sources, which may also be referred to herein as light emitters or lighting devices. In the example of FIG. 2, the light sources emit light 22 that reaches the one or more objects 20 and reflects off the one or more objects 20 as reflected light 24. The objects 20 may include any suitable objects (inanimate or animate) at different depths within the scene.

[0013] The reflected light 24 may be received at the sensor module 16, or more specifically, at one or more photosensitive elements within the active image pixels of the sensor module 16. The driver circuitry and / or control circuitry may control the pixels of the sensor module 16 to generate one or more image frames based on the reflected light 24 by providing control signals to transistors or other operating elements within the pixels. Specifically, based on the control signals received from the driver circuitry and / or control circuitry, the pixels may generate different charge portions in response to the reflected light 24 during an integration or exposure period, perform a readout operation on the generated charge portions during a readout period, and / or perform other suitable operations during other periods.

[0014] As an example, in some exemplary configurations described herein, the sensor module 16 may include a pixel array including sensor pixels arranged in rows and columns. Pixel control circuits may be coupled to lines (e.g., rows) of pixels in the array, and pixel readout circuits may be coupled to lines (e.g., columns) of pixels in the array. The pixel control circuits may receive row and / or column addresses from the timing control circuitry and provide corresponding row and / or column control signals, such as reset, anti-blooming or global shutter, pixel selection, modulation, storage, charge transfer, readout, and sample and hold control signals, to the pixels via row and / or column control paths. One or more column and / or column readout paths may be coupled to each line of pixels in the array. These readout paths may be used to read out image signals from the pixels and to provide bias signals (e.g., bias currents or bias voltages) to the pixels. The pixel readout circuitry can receive image signals, such as analog pixel values, generated by the pixels and can include memory circuits for storing calibration signals (e.g., reset level signals, reference level signals) and / or image signals (e.g., image level signals) read out from the array, amplification or multiplication circuits, analog to digital conversion (ADC) circuits, biasing circuits, latch circuits for selectively enabling or disabling different portions of the readout circuitry, or other circuits coupled to and / or for reading out image signals from one or more pixels in the array. The readout circuitry can provide the resulting digital pixel data to control and processing circuitry 18 (FIG. 1) for further processing, such as digital signal processing.

[0015] Optionally, the pixel array may also be provided with a filter array having multiple color and / or infrared filter elements (each overlapping one or more pixels), thereby allowing a single image sensor to sample light of different colors or wavelength sets. Generally, filter elements of any desired color and / or wavelength and in any desired pattern may be formed over any desired number of image pixels. In a time-of-flight sensing implementation using the illumination module 14 of FIGS. 1 and 2, the pixel array may include a corresponding filter array that passes light having the color and / or frequency emitted from the illumination module 14.

[0016] Imaging module 12 of Figure 1 may be configured to perform indirect TOF measurements based on a phase difference between a modulated light signal, such as modulated light 22 emitted by illumination module 14 of Figure 2, and a reflected modulated light signal, such as light 24 from an image scene, received by sensor module 16 of Figure 2. In these indirect TOF configurations, sensor module 16 may include an array of active pixels, each active pixel configured to modulate (demodulate) a received light signal based on a modulation control signal having a modulation frequency received at a corresponding pixel transistor to separate charge generated by the photosensitive element into corresponding charge portions that can be used to generate TOF information.

[0017] 1 may be configured to perform direct TOF measurements in a pulsed mode. In a direct TOF configuration, the sensor module 16 may directly measure the time difference between when a pulse of emitted light 22 is transmitted and when a corresponding reflected version of the pulse (e.g., a pulse of reflected light 24) is received and detected by an array of active pixels within the sensor module 16 to generate TOF information.

[0018] The TOF sensors described in connection with Figures 1 and 2 are merely exemplary. Illumination module 14 and sensor module 16 may each include other suitable circuitry, such as power management and supply circuitry, processing circuitry, control circuitry, readout circuitry, timing circuitry, and / or clock generation circuitry. Although illumination module 14 and sensor module 16 are shown as separate modules in Figures 1 and 2, this is merely exemplary. If desired, illumination module 14 and sensor module 16 may be coupled to or include shared circuitry within the camera module system, such as shared power management and / or supply circuitry, shared modulation / demodulation circuitry, shared clock generation circuitry, shared timing controller, shared signal generation circuitry, shared control circuitry, and / or shared storage circuitry.

[0019] In some example configurations, the illumination module may be separate from the sensor module, may be external to the imaging module, and / or may be within another (non-imaging) system.

[0020] It may be desirable to provide monitoring of a lighting module regardless of the type of system or module in which the lighting module is installed and / or the type of system or module in which the lighting module operates. This may help to ensure that different types of faults in the lighting module can be quickly and efficiently identified and / or that desired fault mitigation techniques can be implemented to reduce the harm that they may cause to the surrounding environment.

[0021] Figure 3 shows an exemplary lighting module including a monitoring system. In the example of Figure 3, a lighting module, such as lighting module 14 of Figures 1 and 2, may include one or more light sources 30, a modulation driver 32 (sometimes referred to herein as a driver circuit or a light source driver circuit), a clock generation circuit 34, and a light source monitoring system 36.

[0022] Light source 30 may include one or more lasers or laser diodes, one or more light emitting diodes (LEDs), and / or one or more other suitable types of light source or illumination source. Light source 30 may emit light of any suitable wavelength, such as visible light, infrared light, and / or other wavelengths of light.

[0023] The light sources 30 may be controlled and driven by a corresponding driver circuit, such as driver circuit 32, coupled to each of the light sources 30. The driver circuit 32 may provide a drive signal (sometimes referred to as a control signal) having any suitable characteristics, such as a suitable waveform, a suitable peak amplitude or power, a suitable periodicity or frequency, and / or other characteristics, to each light source 30 to emit light 22 having the corresponding desired characteristics. By way of example, in some configurations described herein, the driver circuit 32 may provide a drive signal having a high or low state in each phase of a clock signal having one or more frequencies between 30 MHz and 200 MHz. The drive signal may cause the light source 30 to generate modulated light 22 having optical pulses based on the high and low states of the drive signal.

[0024] By way of example, the drive signal may be in a high state for two consecutive periods (clock phases) of the clock signal during which the light source 30 is active and emits light 22, a low state for two subsequent periods (clock phases) of the clock signal during which the light source 30 is inactive and does not emit light 22, and / or a high state and then a low state for two subsequent periods (clock phases) of the clock signal during which the light source 30 is active for a first clock phase and then inactive for a second clock phase. This sequence of high and low states of the drive signal is merely exemplary.

[0025] The driver circuit 32 may be coupled to a clock generation circuit 34. The clock generation circuit 34 may include a phase locked loop (PLL) that provides a clock signal to the driver circuit 32. The driver circuit 32 may provide a corresponding drive signal to the light source 30 based on the clock signal.

[0026] To provide a (laser) light safety system, the lighting module 14 may include a light source monitoring system 36. To reduce the number of components required to monitor the operation of the lighting module 14 and / or to reduce disruption to existing lighting module architecture, the light source monitoring system 36 may be coupled to the driver circuit 32 and / or the light source 30 such that the monitoring system 36 receives drive signals provided to the light source 30 from the driver circuit 32. As an example, the monitoring system 36 may be electrically connected to drive contact pads on the driver circuit 32 and / or the light source 30 that carry the drive signals. Specifically, the monitoring system 36 may sample the drive signals over time to generate sample data for monitoring.

[0027] If desired, instead of or in addition to sampling the drive signal, the monitoring system 36 may sample other signals transmitted within, received by, and / or output by the lighting module 14. In one exemplary configuration, instead of or in addition to sampling the drive signal, the monitoring system 36 may include one or more photodetectors that sample optical signals (e.g., light 22) to generate sample data for monitoring. Generally, any desired electrical and / or optical light source signals of the light source may be sampled for monitoring.

[0028] By way of example, in some exemplary configurations described herein, the sampled electrical and / or optical light source signals may be modulated at high frequencies. Thus, a large number of samples may be generated over time. Additionally, in some applications, such as TOF detection, the illumination module 14 may operate (e.g., in conjunction with the sensor module 16) with different operational modules corresponding to different imaging modes. By way of example, the illumination module 14 may emit light for different image exposure periods, different image frame depths, and / or other operational modes. The light emission may be monitored for each of these different operational modes, generally over various time intervals or monitoring time windows, to adequately characterize the performance of the illumination module, to determine whether operation in any of these modes exceeds light emission limits, and / or to determine whether different system faults have occurred. Effectively monitoring the performance of the illumination module, especially in these high-frequency multi-mode configurations and in real time, may be challenging. Collective data processing may be advantageous.

[0029]

[0023] Figure 4 illustrates an exemplary light source monitoring system, such as monitoring system 36 of Figure 3, configured to monitor a light source signal based on data chunks and data groups. As shown in Figure 4, light source monitoring system 36 may include a data chunking circuit 40, a data chunk grouping circuit 42, and a fault (or failure) detection circuit 44.

[0030] Specifically, the data chunking circuit 40 can aggregate, organize, or otherwise process data samples obtained from the observed drive signal (or light signal) into data chunks of different sizes to generate corresponding data chunk values. Illustratively, in some configurations described herein, the sample numbers are represented by a bit stream of binary 0s and 1s, with each value of 0 or 1 being a sample. A value of 0 can indicate a time (period) during which the light source is inactive (not producing light), and a value of 1 can indicate a time (period) during which the light source is active (producing light). Each value in the bit stream can correspond to or indicate a state of the drive signal or light signal at a corresponding clock phase of a clock signal used to generate the drive signal provided to the light source 30. For example, a high state of the signal can indicate that the light source is active, and a low state of the signal can indicate that the light source is inactive. If corresponding to a drive signal, the value of the bit stream can be detected by a digital counter in the system 36 coupled to the signal path carrying the drive signal. If corresponding to an optical signal, the value of the bit stream may correspond to the detected on-off state of the light emitted by light source 30 and may be detected by a photodetector within system 36 .

[0031] A particular data chunk period may include information from a desired number of samples, such as 1 sample, 2 samples, 3 samples, 4 samples, 8 samples, or any suitable number of data samples. Specifically, data chunking circuitry 40 may generate a data chunk value that is a value indicative of the number of periods during which the light source is active within the data chunk period. In other words, this data chunk value may correspond to the number of samples within the period that have a value of 1.

[0032] The data chunking circuit 40 may also average the number of active periods of the light source over multiple such data chunk periods to generate additional average time chunk values for the additional data chunks. In this manner, these (averaged) time chunk values may include information from a larger number of samples, such as 32 samples (when eight 4-sample values are averaged), 256 samples (when 64 4-sample values are averaged), 2048 samples (when 512 4-sample values are averaged), and / or other suitable numbers of samples.

[0033] The data chunking circuit 40 can generate multiple data chunk values in parallel associated with differently sized data chunks over the same time interval. For example, the data chunking circuit 40 sampling the light source signal can generate 512 10-ns chunks, 64 80-ns chunks, eight 640-ns chunks, and / or one 5120-ns chunk over the same 5,120-ns (nanosecond) time period. For each of the 512 10-ns chunks, the data chunking circuit 40 can generate a first data chunk value indicating the number of active light source periods within the 10-ns time interval. For each of the 64 80-ns chunks, the data chunking circuit 40 can generate a second data chunk value indicating the number of active light source periods within the 80-ns time interval. For each of the eight 640-ns chunks, the data chunking circuit 40 can generate a third data chunk value indicating the number of active light source periods within the 640-ns time interval. For a single 5120 ns sized chunk, the data chunking circuit 40 can generate a fourth data chunk value indicating the number of active light source periods within that 5120 ns time interval. In an exemplary configuration where each 10 ns time interval includes four samples, each 10 ns sized chunk can include four samples of information, each 80 ns sized chunk can include 32 samples of information, each 640 ns sized chunk can include 256 samples of information, and each 5120 ns sized chunk can include 2048 samples of information.

[0034] The sizes and / or durations of the data chunks described above are merely examples, and any suitable size and / or duration of the data chunks may be adjustable based on the implementation of the monitoring system.

[0035] The monitoring system 36 can further aggregate the differently sized data chunk values generated by the data chunking circuitry 40 to generate data group values each associated with a data group or grouping of data chunks. Specifically, the data chunk grouping circuitry 42 in the system 36 can receive each of the data chunk values associated with differently sized data chunks from the data chunking circuitry 40. The data chunk grouping circuitry 42 can use any suitable number of data chunk values associated with data chunks of the same desired size to generate the corresponding data group value. The number and / or size of the data chunks used can be related to and based on the size of the time window being monitored. Multiple such data group values can be constructed using different numbers of data chunks and / or using data chunks of different sizes to provide monitoring at a desired granularity over different monitoring time windows. In other words, the data chunk grouping circuitry 42 can generate group values for multiple monitors in the fault detection circuitry 44.

[0036] In illustrative configurations described herein, a data group value may be the sum of a suitable number of data chunk values and / or any other suitable type of aggregate value containing information about multiple data chunk values. As some examples, data chunk grouping circuit 42 may receive a plurality of chunk values each associated with a 10 ns-sized data chunk and sum up 100 such chunk values to generate a group value for a 1 μs (microsecond) group period, sum up 1000 such chunk values to generate a group value for a 10 μs group period, and / or sum up any suitable number of such chunk values to generate a group value for a corresponding group period of a desired period; data chunk grouping circuit 42 may receive a plurality of chunk values each associated with an 80 ns-sized data chunk and sum up 1000 such chunk values to generate a group value for an 80 μs group period, sum up 4000 such chunk values to generate a group value for a 320 μs group period, and / or sum up any suitable number of such chunk values to generate a group value for a desired period of time. the data chunk grouping circuit 42 may receive a plurality of chunk values each associated with data chunks of 640 ns size and may sum up 1000 such chunk values to generate a group value for a group period of 640 μs, may sum up 4000 such chunk values to generate a group value for a group period of 2560 μs, and / or may sum up any suitable number of such chunk values to generate a group value for a corresponding group period of a desired period; and / or the data chunk grouping circuit 42 may receive a plurality of chunk values each associated with data chunks of 5120 ns size and may sum up 1000 such chunk values to generate a group value for a group period of 5120 μs, and / or may sum up any suitable number of such chunk values to generate a group value for a corresponding group period of a desired period.

[0037] As shown in the above example, the data chunk grouping circuit 42 can generate group values for group periods of various durations, such that different monitors for different monitoring channels in the monitoring system 36, or more specifically, the fault detection circuit 44, can each monitor the performance of the light source over a corresponding group period of duration.

[0038] Specifically, the data chunk grouping circuit 42 may be coupled to a fault detection circuit 44. The fault detection circuit 44 may obtain multiple group values for non-overlapping group periods of the same duration and generate a running sum for a running monitoring period that includes each of the non-overlapping group periods. The fault detection circuit 44 may also obtain a corresponding threshold level for each set of group values. The fault detection circuit 44 may compare the running sum with one or more threshold levels and, based on the comparison, may determine whether a fault has occurred. As an example, if the running sum exceeds one or more threshold levels, the fault detection circuit 44 may output a signal indicating a fault or failure.

[0039] The fault detection circuit 44 may receive group values for different group time periods and may generate a corresponding running sum for each group value for the different group time periods. By way of example, the fault detection circuit 44 may generate a first running sum that sums the group values for 200 1 μs group periods (thereby forming a 200 μs running monitoring time window), a second running sum that sums the group values for 200 10 μs group periods (thereby forming a 2 ms (millisecond) running monitoring time window), a third running sum that sums the group values for 200 80 μs group periods (thereby forming a 16 ms running monitoring time window), a fourth running sum that sums the group values for 200 320 μs group periods (thereby forming a 64 ms running monitoring time window), and a fifth running sum that sums the group values for 200 320 μs group periods (thereby forming a 64 ms running monitoring time window). A fourth moving sum may be obtained by adding the group values for 200 640 μs group periods (thereby forming a moving monitoring time window of 128 ms), a fifth moving sum by adding the group values for 200 2560 μs group periods (thereby forming a moving monitoring time window of 512 ms), a seventh moving sum by adding the group values for 200 5120 μs group periods (thereby forming a moving monitoring time window of 1024 ms), and / or any other suitable moving sum. In this manner, fault detection circuit 44 may include multiple monitors or monitoring channels (e.g., seven in the example above) for monitoring time windows of various durations.

[0040] The number and / or duration of group periods per moving sum as described in the above example are merely exemplary. Any suitable number and / or duration of group periods may be used to generate any suitable number of moving sums for monitoring, as desired. The fault detection circuit 44 may set and / or obtain different threshold levels for comparison with different moving sums, and / or may set and / or obtain the same threshold level for comparison with at least some (e.g., all) of the moving sums.

[0041] Optionally, system 36 may include fault mitigation circuitry coupled to one or more (e.g., all) of the outputs of fault detection circuit 44 and capable of performing one or more mitigation actions in response to a detected fault or failure. By way of example, these mitigation actions may include deactivating one or more faulty light sources, portions of the driver circuitry having a fault, and / or one or more components of lighting module 14, such as the clock generation circuit, adjusting the control signals provided to the light sources, outputting a notification to a user of lighting module 14, and / or other types of mitigation actions. Adjusting the control signals may include reducing the light source output power or otherwise adjusting the operation of the light sources to correct the detected fault or failure.

[0042] 5 is a diagram of an example set of samples in a light source signal, represented as several groups each containing a corresponding number of chunks. In the example of FIG. 5, a signal, such as the signal transmitted from driver circuit 32 to light source 30 in FIG. 3, may include several samples 50 that are acquired and detected by light monitoring system 36.

[0043] The system 36 may acquire samples 50 in data groups 52, each of which further includes several data chunks 54. Specifically, for each data chunk 54, the system 36 may generate a count indicating the number or average number of times a signal is asserted or a light source is active during that chunk. For example, a sampled bit stream may have a value of 1 each time a signal is asserted or a light source is active. The number of times the bit stream has a value of 1 during a chunk may be averaged. For each data group 52, the system 36 may generate a sum that adds up the counts of each of the data chunks 54 included in that data group 52. For each observation or monitoring period, the system 36 may generate an additive sum that adds up the sums for each data group 52 within an observation or monitoring time window. The observation time window may be a moving period of fixed length that is updated and monitored over time, and thus the additive sum may be a moving sum that is also updated over time.

[0044] 5, time period 60 may represent a monitoring time window monitored by system 36. Samples within time period 60 may be represented by data groups 62-1, 62-2, 62-3, ..., 62-N. Each of data groups 62 may include a corresponding set of data chunks 64, each containing information about a non-overlapping subset of samples within time period 60.

[0045] Period 60 may represent a monitoring time window at a particular point in time. In other words, information from groups 62-1 through 62-N may be aggregated (e.g., summed) to generate a value for monitoring. For example, the generated value may be compared to one or more threshold levels that indicate one or more system faults. The time window monitored by system 36 may be a running or moving period that changes over time. Thus, at a later point in time, information from group 62-1 may be removed, information from group 62-(N+1) may be added, and the information from groups 62-2 through 62-N may generate a new value, such as a new sum of moving sums, for monitoring and comparison to one or more threshold levels. In this manner, the operation of the lighting modules may be monitored using a moving time window that generates a moving sum formed from a moving set of groups 52.

[0046] FIG. 5 illustrates an example of an exemplary monitor or monitoring channel within system 36, such as within fault detection circuit 44 of FIG. 4. To provide multiple monitors in detection circuit 44 that monitor performance over multiple observation time windows of varying durations and / or with different granularity, system 36 can organize samples 50 into multiple data chunks of different sizes. The exemplary set of data chunks 54 in FIG. 5 may be of a first size, with each data chunk including four samples. System 36 can further organize the same set of samples 50 into other sets of data chunks of a second size, a third size, a fourth size, and / or any other suitable size. Depending on the granularity and / or size of the monitored time window, system 36 can provide monitors (e.g., within fault detection circuit 44) that each monitor observation time windows having different durations and / or different granularity. Each different observation time window can provide values based on a different number of groups, with each group aggregating chunk values from a different number of data chunks and / or data chunks of different sizes.

[0047] In other words, the duration of the monitoring time window, such as monitoring time window 60, the number of groups 62, the number of data chunks 64, and / or the size (e.g., number of samples) of each of the data chunks and / or each of the data groups may be adjusted for system 36 to provide other monitors in addition to the monitors shown in the example of FIG. 5.

[0048] FIG. 6 is a diagram of an exemplary implementation of a light source monitoring system, such as the light source monitoring system 36 of FIG. 4. As shown in the example of FIG. 6, the data chunking circuit 40 may include one or more counter circuits 70, such as one or more digital counters, an adder circuit 72, a multiplier circuit 74, and multiple averaging circuits 78-1, 78-2, and 78-3. There may be one counter circuit for each light source 30 within the data chunking circuit 40. The counter circuit 70 may detect and count each active state of the light source signal for a corresponding clock phase of the clock signal. The counter circuit 70 may then generate samples indicating the number of active periods of the light source over the clock phase of the clock signal. The counts generated by the counter circuit 70 may be summed by the adder circuit 72 every set number of samples. The set number of samples may be four or any other suitable number. The adder circuit 72 may then generate a count of the number of active periods (e.g., the number of ones in the bitstream) for every set number of periods of the light source signal.

[0049] If desired, the counts generated by summing circuit 72 may be scaled in multiplier circuit 74 by an adjustable scaling factor. By way of example, in some exemplary configurations described herein, the modulation frequency of the light source signal may vary over time, resulting in a varying number of samples over a fixed period. A computation circuit, such as an arithmetic circuit, may be coupled to clock generation circuit 34 of FIG. 3 and may generate the scaling factor based on the frequency of the clock signal generated by clock generation circuit 34. By scaling the number of samples, a count per time interval, rather than a count per sample set, may be generated by multiplier circuit 74.

[0050] The resulting count output from multiplication circuit 74 may be provided along path 76-1 as a count value of a first data chunk or a data chunk of a first size (e.g., a data chunk value of four samples, determined by the number of samples added by addition circuit 72).

[0051] Additionally, the resulting counts output by the multiplication circuit 74 may be communicated over time to a first averaging circuit 78-1. The first averaging circuit 78-1 may average the resulting counts (e.g., eight or another suitable number of counts) output by the multiplication circuit 74 over time. A ceiling function may be applied by a ceiling circuit 80-1 to generate a resulting average count on path 76-2. This average count on path 76-2 may be for a second data chunk or a second-sized data chunk.

[0052] Additionally, the resulting average counts output by averaging circuit 78-1 may be communicated over time to a second averaging circuit 78-2. The second averaging circuit 78-2 may average the resulting average counts (e.g., eight or another suitable number of average counts) output by averaging circuit 78-1 over time. A ceiling function may be applied by ceiling circuit 80-2 to generate another resulting average count on path 76-3. This average count on path 76-3 may be for a third data chunk or a third size data chunk.

[0053] Additionally, the resulting average counts output by averaging circuit 78-2 may be communicated over time to a third averaging circuit 78-3. The third averaging circuit 78-3 may average the resulting average counts (e.g., eight or another suitable number of counts) output by averaging circuit 78-2 over time. A ceiling function may be applied by ceiling circuit 80-3 to generate another resulting average count on path 76-4. This average count on path 76-4 may be for a fourth data chunk or a fourth-sized data chunk.

[0054] In general, any suitable number of averaging circuits 78 and corresponding ceiling circuits 80 may be provided to provide different data chunk values in parallel to the data chunk grouping circuit 42. The averaging circuits 78 may be coupled to the counter 70. Adding circuits 72 and multiplying circuits 74 may be coupled between the averaging circuits 78 and the counter 70, as needed.

[0055] The data chunk grouping circuit 42 may include a multiplexer 82 and a summation circuit 84. A multiplexer, such as multiplexer 82, may have inputs coupled to paths 76-1, 76-2, 76-3, and 76-4. The values communicated on path 76 may represent data chunk values of various sizes, each containing information about a different number of samples. The multiplexer may then select one of the data chunk values on paths 76-1, 76-2, 76-3, and 76-4 to pass to the output of multiplexer 82 based on a control signal received at the multiplexer.

[0056] A summing circuit 84 (sometimes referred to as a group summing circuit) may be coupled to the output of the multiplexer 82. The summing circuit 84 may generate a group value (e.g., a group sum) using a series of data chunk values from one of paths 76-1, 76-2, 76-3, or 76-4 generated over time. As an example, the summing circuit 84 may perform the addition operation described in connection with FIG. 5 when summing or otherwise aggregating the values of data chunks 64-1, 64-2, ..., 64-M to generate the group value for data group 62-3. Because data chunks 64-1, 64-2, ..., 64-M may be the same size, the values of data chunks 64-1, 64-2, ..., 64-M may all be provided on the same path 76 (e.g., path 76-2). In practice, when adding up corresponding data chunk values to generate group values for other data groups 62, such as data groups 62-1, 62-2, 62-N, 62-(N+1), data chunk values from the same path 76 (e.g., path 76-2) may be used, since each group 62 may aggregate data chunk values of the same size.

[0057] Each of these group values, such as the group value of group 62 (FIG. 5), may be generated sequentially based on summing a desired series of data chunk values from the same path 76. As each group value is generated, summing circuit 84 may output the generated value to a memory or data storage circuit coupled to summing circuit 84, such as a first-in-first-out (FIFO) memory circuit 88 in fault detection circuit 44, for storage. Optionally, data chunk grouping circuit 42 may further include a group value shifting circuit 86 coupled between summing circuit 84 and memory circuit 88. Value shifting circuit 86 may adjust the generated group value, or more specifically, trim (e.g., fix or trim a certain number of bits) the redundancy of the group value generated by summing circuit 84 to enable standardized and compact storage in memory circuit 88.

[0058] The fault detection circuit 44 may include a memory circuit 88, a summing circuit 90, and a comparison circuit 92. The memory circuit 88 may be configured to store any suitable number of group values for a number of groups over a monitoring time window. Using FIG. 5 as an example, the memory circuit 88 may store N group values, each corresponding to one of the groups 62-1, 62-2, 62-3, ..., 62-N.

[0059] The summing circuit 90 (sometimes referred to as a moving summing circuit, or generally as a calculation circuit) may be configured to generate a moving sum associated with a moving monitoring time window. Specifically, the summing circuit 90 may obtain a current sum of the N group values for a current monitoring period and provide the current sum to a comparison or comparator circuit 92 within the detection circuit 44. The current sum may be stored in the summing circuit 90. The comparison circuit 92 may compare the current sum to one or more threshold levels. Based on the comparison, the detection circuit 44 may provide an output indicating whether any faults have been detected based on the current sum associated with the current monitoring period.

[0060] For subsequent sums in the running sum set, summing circuit 90 may subtract the oldest group value from the current sum and add the most recent group value (FIG. 5) to the current sum to obtain the subsequent sum. As shown in FIG. 5, the group value of group 62-1 may be subtracted from the illustrated period 60, and the group value of group 62-(N+1) may be added to obtain the subsequent sum for the running period. Summing circuit 90 may obtain the oldest group value from the first entry (deleted first) stored in FIFO memory 88 and may obtain the new group value directly from summing circuit 84 (via shift circuit 85, if necessary). This newly generated subsequent sum is the new current sum and may be compared to one or more threshold levels in comparison circuit 92. This new current sum may then be updated in a similar manner to continue generating the running sum.

[0061] Although one set of grouping and detection components (i.e., multiplexer 82, group summation circuit 84, group value shifting circuit 86, FIFO memory circuit 88, moving summation circuit 90, and threshold comparison circuit 92) is shown in association with chunk grouping circuit 42 and detection circuit 44, this configuration is merely exemplary. As noted above, monitoring system 36 can perform multiple monitoring operations using multiple monitor or monitoring channels in parallel, each for monitoring a different monitoring time window associated with a corresponding moving sum value resulting from group values including a different number of data chunk values. Accordingly, chunk grouping circuit 42 can include one or more additional sets of multiplexer 82, group summation circuit 84, and group value shifting circuit 86, and detection circuit 44 can include one or more additional sets of FIFO memory circuit 88, moving summation circuit 90, and threshold comparison circuit 92 to form these additional monitor or monitoring channels.

[0062] If desired, at least some of these components within circuits 42 and 44 may be shared between components of different monitor channels. By way of example, multiplexer 82 may have a shared output or multiple separate outputs coupled to multiple group summing circuits for different monitor channels, group summing circuit 84 may be used to calculate group values for different monitor channels, group value shift circuit 86 may be shared between group summing circuits for different monitor channels, multiple FIFO memory circuits 88 may be implemented in different portions of a shared memory integrated circuit (e.g., an integrated circuit implementing random access memory), and / or comparison circuit 92 may be shared between different monitor channels.

[0063] 6, an exemplary configuration of data chunking circuit 40 having a counter 70, summing circuit 72, multiplier circuit 74, multiple averaging circuits 78, and multiple ceiling circuits 80 is shown for sampling and chunking samples of a single light source signal. If desired, one or more additional sets of counters 70, summing circuit 72, multiplier circuit 74, averaging circuit 78, and ceiling circuit 80 may be included as part of data chunking circuit 40 for sampling and chunking samples of one or more additional light source signals of a corresponding light source in parallel with the sampling and chunking of samples of the first light source signal. The additional sets of counters 70, summing circuit 72, multiplier circuit 74, averaging circuit 78, and ceiling circuit 80 may in turn comprise corresponding monitoring channels implemented by portions of chunk grouping circuit 42 and detection circuit 44.

[0064] Various embodiments illustrating a light source monitoring system have been described.

[0065] As an example, an imaging system may include a sensor module having an image sensor pixel array, and may include an illumination module having a light source, a driver circuit coupled to the light source, and a light source monitoring system coupled to the light source and configured to receive a light source signal. The light source monitoring system may include a data chunking circuit that generates a plurality of data chunk values based on samples from the light source signal, a grouping circuit that generates a plurality of group values that each aggregate at least some of the plurality of data chunk values, and a fault detection circuit that generates an output signal indicative of a fault based on a monitoring time window characterized by at least some of the plurality of group values.

[0066] As another example, a lighting module may include a light source and a light source monitoring system coupled to the light source and configured to receive a light source signal. The light source monitoring system may include a counter configured to generate samples of the light source signal, a plurality of averaging circuits coupled to the counter, a multiplexer having a plurality of inputs coupled to the plurality of averaging circuits and having an output, a first summing circuit coupled to the output of the multiplexer, a memory circuit coupled to the first summing circuit, a second summing circuit coupled to the memory circuit and the first summing circuit, and a comparison circuit coupled to the second summing circuit.

[0067] As yet another example, a time-of-flight sensor includes a sensor module having an image sensor pixel array, and an illumination module having a light source, a driver circuit coupled to the light source, and a light source monitoring system coupled to the light source and configured to receive a light source signal provided to the light source from the driver circuit. The light source monitoring system may include a first monitor configured to detect one or more faults using the drive signal and a first observation time window having a first duration, and a second monitor configured to detect one or more faults using the drive signal and a second observation time window having a second duration.

[0068] According to one embodiment, an imaging system may include a sensor module having an image sensor pixel array, and may include an illumination module having a light source, a driver circuit coupled to the light source, and a light source monitoring system coupled to the light source and configured to receive a light source signal. The light source monitoring system may include a data chunking circuit that generates a plurality of data chunk values based on samples from the light source signal, a grouping circuit that generates a plurality of group values that each aggregate at least some of the plurality of data chunk values, and a fault detection circuit that generates an output signal indicative of a fault based on a monitoring time window characterized by at least some of the plurality of group values.

[0069] According to another embodiment, multiple data chunk values may each contain information about multiple samples.

[0070] According to another embodiment, the information about the number of samples may include the time the light source signal is asserted.

[0071] According to another embodiment, the plurality of group values may each comprise a sum of the plurality of data chunk values.

[0072] According to another embodiment, the fault detection circuitry may generate a sum of the monitoring time window that sums at least some of the group values.

[0073] According to another embodiment, the fault detection circuitry may perform a comparison of the sum with one or more threshold levels and generate an output signal based on the comparison.

[0074] According to another embodiment, the monitoring time window may be a moving time window that varies over time, and the additive sum may be a moving sum that varies over time.

[0075] According to another embodiment, the fault detection circuit may monitor a monitoring time window for a first monitoring channel of the light source signal and may monitor one or more additional monitoring time windows for one or more additional monitoring channels of the light source signal.

[0076] According to another embodiment, the light source monitoring system may be electrically connected to a path between the light source and the driver circuit that carries the drive signal from the driver circuit to the light source, where the light source signal may be the drive signal.

[0077] According to another embodiment, the light source monitoring system may include a light detector, and the light source signal may be based on light emitted by the light source and detected by the light detector.

[0078] According to another embodiment, a lighting module may include a light source and a light source monitoring system coupled to the light source and configured to receive a light source signal. The light source monitoring system may include a counter configured to generate samples of the light source signal, a plurality of averaging circuits coupled to the counter, a multiplexer having a plurality of inputs coupled to the plurality of averaging circuits and having an output, a first summing circuit coupled to the output of the multiplexer, a memory circuit coupled to the first summing circuit, a second summing circuit coupled to the memory circuit and the first summing circuit, and a comparison circuit coupled to the second summing circuit.

[0079] According to another embodiment, a given averaging circuit of the plurality of averaging circuits may generate a set of average values over time, and the first summing circuit generates a set of group values over time based on the set of average values.

[0080] According to another embodiment, the memory circuit can store a set of group values and the second summation circuit can generate a running sum over time based on the set of group values.

[0081] According to another embodiment, the lighting module may further include a summing circuit and a multiplying circuit, which may be coupled between the counter and the plurality of averaging circuits.

[0082] According to another embodiment, the lighting module may further include a plurality of ceiling circuits that perform a ceiling function on the outputs of the plurality of averaging circuits and that are coupled between the plurality of averaging circuits and the multiplexer.

[0083] According to another embodiment, the lighting module may further include a group value shift circuit that changes the number of bits of the output of the first summing circuit and is coupled between the first summing circuit and the memory circuit.

[0084] According to one embodiment, a time-of-flight sensor may include a sensor module having an image sensor pixel array, and an illumination module having a light source, a driver circuit coupled to the light source, and a light source monitoring system coupled to the light source and configured to receive a light source signal provided to the light source from the driver circuit. The light source monitoring system may include a first monitor configured to detect one or more faults using the drive signal and a first observation time window having a first duration, and a second monitor configured to detect the one or more faults using the drive signal and a second observation time window having a second duration.

[0085] According to another embodiment, the first monitor may generate a first value for the first observation time window based on a first set of average values aggregated from samples of the drive signal, and the second monitor may generate a second value for the second observation time window based on a second set of average values aggregated from samples of the drive signal.

[0086] According to another embodiment, the first set of average values may have average values each including information about a first number of samples, and the second set of average values may have average values each including information about a second number of samples that is greater than the first number of samples.

[0087] According to another embodiment, the second set of mean values may have a greater number of mean values than the first set of mean values.

[0088] The foregoing is merely illustrative of the principles of this invention, and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention. The foregoing embodiments may be implemented individually or in any combination.

Claims

1. 1. An imaging system, comprising: a sensor module having an image sensor pixel array; a lighting module having a light source, a driver circuit coupled to the light source, and a light source monitoring system coupled to the light source and configured to receive a light source signal, the light source monitoring system comprising: a data chunking circuit that generates a plurality of data chunk values based on samples from the light source signal; a grouping circuit for generating a plurality of group values each aggregating at least some of the plurality of data chunk values; a fault detection circuit that generates an output signal indicative of a fault based on a monitoring time window characterized by at least a portion of the plurality of group values.

2. 2. The imaging system of claim 1, wherein the plurality of data chunk values each include information about a plurality of samples, the information about the plurality of samples including a time when the light source signal is asserted, the plurality of group values each include a sum of a plurality of data chunk values, the fault detection circuit generates a sum of the monitoring time window that sums the at least some of the plurality of group values, the fault detection circuit performs a comparison of the sum with one or more threshold levels and generates the output signal based on the comparison, the monitoring time window is a moving time window that varies over time, and the sum is a moving sum that varies over time.

3. The imaging system of claim 1 , wherein the light source monitoring system includes a photodetector, and the light source signal is based on light emitted by the light source and detected by the photodetector.

4. 1. A lighting module, comprising: A light source and a light source monitoring system coupled to the light source and configured to receive a light source signal, the light source monitoring system comprising: a counter configured to generate samples of the light source signal; a plurality of averaging circuits coupled to the counter; a multiplexer having a plurality of inputs coupled to the plurality of averaging circuits and having an output; a first summing circuit coupled to the output of the multiplexer; a memory circuit coupled to the first summing circuit; a second summing circuit coupled to the memory circuit and the first summing circuit; a comparison circuit coupled to the second summing circuit.

5. an adder circuit; a multiplication circuit, the summing circuit and the multiplication circuit being coupled between the counter and the plurality of averaging circuits; a plurality of ceiling circuits that perform a ceiling function on the outputs of the plurality of averaging circuits and are coupled between the plurality of averaging circuits and the multiplexer; 5. The lighting module of claim 4, further comprising: a group value shift circuit that changes a number of bits in an output of the first summing circuit and that is coupled between the first summing circuit and the memory circuit.

6. 1. A time-of-flight sensor, comprising: a sensor module having an image sensor pixel array; a lighting module having a light source, a driver circuit coupled to the light source, and a light source monitoring system coupled to the light source and configured to receive a drive signal provided to the light source from the driver circuit, wherein the light source monitoring system a first monitor configured to detect one or more faults using the drive signal and using a first observation time window having a first duration; a second monitor configured to detect the one or more faults using the drive signal and using a second observation time window having a second duration.

Images