Imaging system with electric current-controlled illumination

Abstract

When the image sensor does not provide a direct signal indicating exposure time, this solution provides precise control of the illumination source within the imaging system. [Solution] The imaging system comprises an image sensor configured to capture images of a scene at a periodic frequency, an illumination source for illuminating the scene, and a measurement and control circuit. The measurement and control circuit continuously measures a current to and from the image sensor, continuously detects periodically repeating high and low levels of the measured current, and controls the illumination source to repeatedly switch between an on state and an off state at an illumination frequency equal to the switching frequency of the periodically repeating high and low levels of the detected measured current, so that the illumination source is on during exposure of the image sensor.

Description

Technical Field

[0001] The present disclosure relates to an imaging system with current-controlled illumination, and in particular is designed to optimize power consumption by synchronizing the exposure time of an image sensor with the illumination. The present disclosure further relates to a method of controlling an illumination source, such as an infrared light-emitting diode (LED), to illuminate a scene during the exposure time of an image sensor, even in a system where the image sensor lacks a dedicated exposure signal output.

Background Art

[0002] In modern network camera systems, infrared (IR) illumination plays an important role in capturing clear images under low-light conditions. Typically, these systems rely on IR light-emitting diodes (LEDs) to illuminate the scene, ensuring that the image sensor can capture detailed images even in the dark. With current technology, IR LEDs are often continuously powered, regardless of whether the image sensor is actively capturing an image. This approach ensures that sufficient illumination is available when needed, but leads to significant power consumption.

[0003] A common practice to reduce power consumption is to synchronize IR illumination with the exposure time of the image sensor. In systems where the image sensor provides a dedicated output signal indicating the exposure time, this synchronization can be effectively implemented. However, not all image sensors have such an output signal, which makes it difficult to control the IR illumination.

[0004] Existing solutions have two drawbacks. First, in systems lacking an exposure signal from the image sensor, there is no simple way to accurately match the IR illumination with the sensor's exposure time. As a result, it leads to continuous or overly long periods of operation of the IR LED, resulting in increased power consumption and reduced operating efficiency. Second, even in systems where some form of synchronization is possible, relying on external signals or complex configurations can complicate the design and increase costs.

[0005] Therefore, an object of this disclosure is to provide a solution that enables precise control of IR illumination in a network camera system, particularly when the image sensor does not provide a direct signal indicating exposure time. The objective of this solution is to optimize power consumption by ensuring that the IR LEDs are active when needed, and thus improve the energy efficiency of the camera system without requiring further signals from the sensor. [Overview of the project]

[0006] This disclosure relates to an imaging system comprising an image sensor configured to capture images of a scene at a periodic frequency, an illumination source for illuminating the scene, and a measurement and control circuit. The measurement and control circuit is configured to continuously measure a current to and from the image sensor, continuously detect periodically repeating high and low levels of the measured current, and control the illumination source to repeatedly switch between an on state and an off state at an illumination frequency equal to the switching frequency of the periodically repeating high and low levels of the detected measured current, so that the illumination source is on during exposure of the image sensor.

[0007] This system enables precise synchronization of the image sensor's exposure time with the illumination source, thereby optimizing energy consumption within the network camera system. By monitoring the current flowing to and from the image sensor, the system can detect current patterns correlated with the sensor's exposure time. This allows the illumination source to be active only when the image sensor is actively capturing images, reducing unnecessary power consumption. This is particularly beneficial in systems where the image sensor does not provide a direct signal indicating its exposure time, because the invention uses detected current fluctuations to infer the appropriate timing for illumination.

[0008] The inventors noticed a correlation between the periodically repeating high-level and low-level switching frequency of the current and the exposure frequency, and that this correlation could be used to control the illumination source. This made it possible to control the illumination source using an illumination frequency equal to the detected periodically repeating high-level and low-level switching frequency, without requiring a direct signal from the image sensor indicating when the image sensor is actively exposing, but instead. The inventors observed that the image sensor consumes a changing amount of current during its operating cycle, with distinct peaks and troughs corresponding to different phases of sensor operation. Specifically, there is a noticeable increase in current consumption during the exposure phase when the sensor is capturing image data. This higher level is followed by a decrease during idle or non-exposure times. These repeating high and low current levels repeat at frequencies that match the periodic exposure frequency of the image sensor. This correlation between current consumption and exposure frequency allows the system to indirectly determine the exposure time of the sensor by continuously monitoring the sensor's current. This implementation is particularly advantageous in systems where the image sensor and control circuit are located in separate units, or in systems where access to the external exposure signal is limited or not feasible.

[0009] In some configurations of imaging systems, different components are placed on separate units, such as separate printed circuit boards. The reasons for this can vary. For example, separate components or subsystems may be purchased and operate as independent systems. The system may also be arranged in this manner for reasons of design flexibility and modularity, signal integrity, or even thermal management. In such systems, adding additional communication channels to synchronize the image sensor and illumination source can add cost and complexity. A system can be obtained in which the illumination is effectively synchronized with the exposure time of the image sensor by continuously measuring the current between the image sensor and the illumination source, and controlling the illumination source to repeatedly switch between on and off states at an illumination frequency equal to the periodically repeating high-level and low-level switching frequency of the detected measured current.

[0010] In all configurations, the current peak is not necessarily equal to the exposure of the image sensor. The current peak may, for example, be related to the image sensor readout. For this reason, the enable signal for controlling the illumination source to illuminate or de-illuminate the scene may be shifted to coincide with the re-exposure of the image sensor, or may include a time offset.

[0011] The disclosed method focuses on controlling an illumination source for illuminating an image sensor during exposure. The method includes configuring the image sensor to capture images at a periodic frequency, continuously measuring a current associated with the sensor, detecting periodic high and low levels of this current, and controlling the illumination source to match the switching frequency of these levels. The method ensures that the illumination is active only during the sensor's exposure time and therefore improves the overall energy efficiency of the system.

[0012] This approach offers significant technical advantages because it does not require additional exposure timing signals or complex synchronization mechanisms between the sensor and the illumination source. The system and method can be implemented with a wide range of image sensors, including those lacking built-in exposure signaling capabilities, thereby providing a flexible and cost-effective solution for various imaging applications. Furthermore, by reducing the operating time of the illumination source only when necessary, the invention also contributes to extending the lifespan of the illumination components. This can be particularly advantageous in systems where maintenance and component replacement are difficult or expensive.

[0013] Those skilled in the art will recognize that the method of controlling an illumination source for illuminating a scene during exposure of an image sensor can be performed using any embodiment of a current imaging system, and vice versa.

[0014] Various embodiments are described herein with reference to the drawings. The drawings are multiple embodiments of the multiple embodiments and are intended to illustrate some of the features of the imaging systems and methods of the present disclosure that control an illumination source for illuminating a scene during exposure of an image sensor, and are not limited to the systems and methods of the present disclosure. [Brief explanation of the drawing]

[0015] [Figure 1] A schematic diagram of one embodiment of the imaging system of this disclosure is shown. [Figure 2] This document shows one embodiment of a measurement and control circuit that measures the current between an image sensor and controls the illumination source. [Figure 3] Two embodiments are shown: the current consumed by the image sensor and the enable signal for controlling the lighting source. [Figure 4] A flowchart of a method according to one embodiment of the method of the present disclosure for controlling an illumination source to illuminate a scene during exposure of an image sensor is shown. [Modes for carrying out the invention]

[0016] This disclosure relates to an imaging system. The imaging system comprises an image sensor configured to capture images of a scene at a periodic frequency, and an illumination source for illuminating the scene. Images captured by the imaging system can form a video sequence.

[0017] The imaging system may use any suitable type of image sensor. Image sensors can be broadly divided into two main types: charge-coupled device (CCD) sensors and complementary metal-oxide-semiconductor (CMOS) sensors. CCD sensors operate by sequentially transferring the charge of each pixel to a readout node, where the signal is amplified and converted into a digital value. CMOS sensors integrate both the pixel array and readout electronics on the same chip, allowing each pixel to be readout independently. Both CCD and CMOS sensors may be used in the imaging systems of this disclosure, depending on the requirements of the application.

[0018] The imaging system further comprises a measurement and control circuit configured to continuously measure a current to and from the image sensor. Preferably, the measurement and control circuit is further configured to continuously detect periodically repeating high and low levels of the measured current. Based on the detected periodically repeating high and low levels of the measured current, the measurement and control circuit may control the illumination source to repeatedly switch between an on state and an off state at an illumination frequency equal to the switching frequency of the periodically repeating high and low levels of the detected measured current. In this way, the illumination source can be controlled to be on during exposure of the image sensor.

[0019] Figure 1 shows a schematic diagram of one embodiment of the imaging system 100 of the present disclosure. In this embodiment, there are three separate units 106, 107, and 110, which are typically printed circuit boards for an image sensor 101, an illumination source 102, and a measurement and control circuit 108, respectively. The measurement and control circuit 108 comprises a measurement circuit 104, such as at least one shunt resistor for measuring current, and a control circuit 105, such as a comparator for generating an enable signal to control the illumination source to illuminate or de-illuminate the scene.

[0020] Figure 2 shows one embodiment of a measurement and control circuit 108 that measures current to and from an image sensor 101 and controls the illumination source. As can be seen in the figure, there is a current to the image sensor 101. The voltage across the current sensing resistor is measured by a measurement circuit 104 implemented as a current sensing amplifier. Those skilled in the art will understand that measuring current can be done indirectly by measuring voltage. The term “measuring current” should be interpreted broadly to cover any measurement that directly or indirectly measures current. The measured current is then amplified using amplifier 109. The amplified signal can then be used to generate an enable signal to control the illumination source to illuminate or de-illuminate the scene. This can be done, for example, by a comparator circuit 105 implemented as a Schmitt trigger.

[0021] Image sensors and measurement and control circuits may be located on different units, such as different printed circuit boards (PCBs). This configuration arises, for example, when system components, including the image sensor and control circuit, are sourced as separate pre-assembly modules. Such systems often integrate independently designed and manufactured components, which may result in limited access to certain internal signals, such as explicit on / off or exposure signals from the image sensor.

[0022] When the image sensor and control circuit are located on separate PCBs, the control system does not have direct access to the exposure signal, which typically indicates when the sensor is exposed. In systems designed to integrate the sensor and control circuit, this signal is often readily available and used to synchronize the illumination source with the sensor's activity. However, in modular systems where components are located on different units, this signal may not be available or accessible, because the multiple components have independent properties, making direct synchronization between the illumination source and the image sensor more difficult.

[0023] As a result, in such a plurality of configurations, it may be possible to measure the current flowing between the image sensor in order to infer its operating state. By monitoring the current, the system can detect patterns or variations correlated with the exposure time of the sensor even without a direct exposure signal. This approach enables indirect synchronization of the illumination source with the activity of the sensor, ensuring that the illumination is activated only when the sensor is capturing an image, despite the separation of components on different units or PCBs.

[0024] In terms of implementation, the connection between the image sensor and the measurement and control circuit can be established via a cable or a connector. This connection can be designed to accommodate high-speed data transmission and accurate synchronization between the image sensor and the measurement and control circuit.

[0025] Similarly, the image sensor and the illumination source can be arranged in different units, such as separate printed circuit boards (PCBs) or modules. This setup can occur when system components, including the image sensor and the illumination source, are purchased or assembled as independent units rather than as an integrated system. In such cases, the illumination source is not directly coupled to the control circuit of the image sensor, and it is difficult to obtain a direct signal from the image sensor to control the illumination.

[0026] In one embodiment, the measurement and control circuit is configured to generate an enable signal for controlling the illumination source to repeatedly switch between an on state and an off state. The enable signal is an electrical signal that determines whether the illumination source is powered on or powered off based on the current measured from the image sensor. This setup enables the illumination source to be switched on only when the image sensor is actively capturing an image. As a result, the power consumption can be significantly reduced compared to the case of continuously operating the illumination source. The enable signal can be designed as a digital pulse or a binary signal depending on the type of the illumination source and the requirements of the system.

[0027] Figure 3 shows two embodiments of the current 200 consumed by the image sensor and enable signals (204a, 204b) for controlling the illumination source. The current has periodically repeating high levels 202 and low levels 203. The high level 202 may be defined as a current level higher than a predetermined current threshold 201, and the low level 203 may be defined as a current level lower than the predetermined current threshold 201. The measurement and control circuit may be configured to compare the measured current with a predetermined threshold to determine whether the image sensor is active or inactive. Based on this, the measurement and control circuit may then generate enable signals (204a, 204b) for controlling the illumination source to illuminate or de-illuminate the scene. These enable signals can be generated in various ways. In Figure 3, there are two embodiments of the enable signals (204a, 204b). The enable signal 204a lags slightly behind the high level 202 of the current 200. The enable signal 204b is slightly wider than the high level 202 of the current 200. In both embodiments, the current 200 (with periodically repeating high levels 202 and low levels 203) and the enable signals (204a and 204b, respectively) have the same frequency. Thus, this embodiment can be adapted according to known or assumed timing relationships between current consumption and exposure of the image sensor.

[0028] The enable signal may be generated based on a predetermined threshold that identifies when the image sensor is in its active exposure phase. The enable signal may be a binary signal or any other suitable signal. The enable signal may also be a more complex signal and / or a pulse-width modulation (PWM) signal, which may allow for finer control of the intensity of the illumination source during sensor exposure. In more advanced systems, the enable signal may also be synchronized with other processes to ensure that the illumination is always optimized for the current imaging conditions.

[0029] In one embodiment of the present disclosure, the imaging system may be configured to work in cooperation with multiple image sensors. The principle of detecting the correlation between current consumption and the exposure frequency of the sensors is also applicable to the multiple-sensor configuration. When multiple image sensors are employed, each sensor may operate with its own exposure cycle and current consumption pattern. In such a case, the system may be modified to synchronize a single shared illumination source across the multiple image sensors or to control separate illumination sources for each individual image sensor. The measurement and control circuits may then measure the current between each image sensor or the total current from all the image sensors. The high and low levels of the measured current may be based on this current. The multiple image sensors may have the same exposure frequency, and the exposure may be optionally shifted relative to one another.

[0030] In one embodiment, the measurement and control circuit includes a measurement circuit, such as at least one shunt resistor, for measuring the current to and from the image sensor. The shunt resistor is a low-resistance component that enables accurate current measurement by generating a voltage drop proportional to the current flowing through the shunt resistor. This voltage drop can then be measured by the control circuit to monitor the current being consumed by the image sensor. Using a shunt resistor provides a simple and reliable method for measuring current without significantly affecting the operation of the image sensor or adding substantial costs to the system.

[0031] A shunt resistor can be placed in series with the power supply to the image sensor to ensure that all current flowing through the sensor is measured. The control circuit may include components such as a comparator and an analog-to-digital converter (ADC) that monitor the voltage drop across the shunt resistor and use this information to detect changes in current. In one embodiment, the system may be designed to continuously monitor the current in real time, allowing for immediate adjustments to the illumination source as the image sensor enters or exits its exposure phase.

[0032] Alternative current measurement methods may also be employed depending on the specific requirements of the system. For example, Hall effect sensors may be used for non-contact current measurement. Non-contact current measurement may be suitable in systems where space is limited or where it is undesirable to introduce additional resistors into the power line.

[0033] In one embodiment, the system is configured such that high current levels are above a predetermined threshold, and low current levels are below this threshold. This threshold-based approach allows the system to reliably distinguish between periods when the image sensor is actively capturing images and periods when the image sensor is idle. The predetermined current threshold can be adjusted based on the characteristics of the image sensor. In some embodiments, the threshold can be adjusted based on environmental factors, such as changes in temperature or supply voltage.

[0034] The threshold can be set at the design stage based on measurements of the image sensor's typical current consumption during the active and idle phases. In one embodiment, the threshold may be set just above the sensor's idle current level to ensure that even a slight increase in current due to sensor startup is detected. Alternatively, the system may be designed to calibrate the threshold during operation, continuously monitoring the current and adjusting the threshold as needed to adapt to changing operating conditions.

[0035] The threshold can also be determined by statistical analysis of current fluctuations over time, which makes it possible to distinguish between random noise and actual changes in current caused by sensor activity.

[0036] As described above, the system of this disclosure continuously detects periodically repeating high and low levels of the measured current consumed by or supplied to the image sensor. These current fluctuations are used to infer the operating state of the image sensor, in particular to identify the period during which the sensor is actively capturing an image. The control circuit uses this information to repeatedly switch the illumination source between an on state and an off state. In this case, the illumination frequency matches the switching frequency of the detected high and low current levels. This ensures that the illumination source conserves power by being synchronized with the activity of the image sensor and becoming active only during the relevant period.

[0037] However, the detected current peaks may not perfectly coincide with the actual exposure time of the image sensor. In some configurations, other processes within the image sensor, such as image readout or data transfer, can also cause current fluctuations unrelated to the exposure state of the image sensor. For example, after the image sensor has captured an image, it may still consume additional current to transfer the image data to a processing unit or memory.

[0038] To address this potential mismatch, the system may be configured to match an enable signal for controlling the illumination source to a known timing relationship between the actual exposure of the image sensor and the detected current peak. This timing relationship is predetermined based on the known behavior of the image sensor and can be stored in the control circuit. By incorporating this timing adjustment, the system can introduce a slight time offset or delay between the detected current peak and the activation of the illumination source, ensuring that the illumination is precisely aligned with the exposure time, even if the current peak occurs before or after the actual exposure.

[0039] In some embodiments, the system may use a model of the image sensor's current consumption profile. This model takes into account not only the exposure time but also other known timings of operation, such as readout and idle states. This model allows the control circuit to distinguish between current peaks caused by exposure and current peaks caused by other sensor activities. By applying this model when configuring the timing of the enable signal, the system may generate an enable signal for the illumination source that more accurately reflects the sensor's true exposure time.

[0040] The image sensor may be configured to capture images at a frequency of at least 10 frames per second, preferably at least 30 frames per second. This frame rate corresponds to an illumination frequency of at least 10 Hz, ensuring that the illumination source is switched on and off in sync with the exposure time of the image sensor. The ability to operate at higher frame rates is useful for applications requiring real-time video capture. Higher frame rates, such as 60 frames per second or more, may also be supported in some embodiments, depending on the capabilities of the image sensor and the processing power of the system. The image sensor may capture images using either a global shutter or a rolling shutter. A global shutter captures the entire image frame at once. In this method, all pixels on the image sensor are exposed simultaneously, and then the entire frame is read out simultaneously. This means that the entire scene is captured in an instant. A rolling shutter progressively captures the image row by row from top to bottom (or possibly side to side). In this method, each row of pixels on the sensor is exposed at slightly different times, and the sensor reads out the image row by row as the scene is exposed. In the case of a global shutter, the frame rate can be directly converted into exposure frequency. In the case of a rolling shutter, the illumination source is controlled to alternate between on and off states corresponding to the exposure of a full image, i.e., each on state may include several sub-exposures of several rows. With a rolling shutter, there may still be distinct idle periods between each image. Whether a global shutter or a rolling shutter is used, the image sensor can be configured to capture images at appropriate frequencies. In that case, the illumination source can be appropriately controlled to alternate between on and off states.

[0041] The measured current may have distinct high and low current levels that correlate with the active and inactive states of the image sensor. In the context of this disclosure, the active state of an image sensor may refer to the period when the sensor is performing its primary function of capturing or processing images. This typically includes exposure time, during which the sensor's pixels are exposed and image data is stored, as well as other image-related activities such as readout, during which the captured data is transferred from the sensor's pixels to the processing circuitry. During the active state, the image sensor is known to consume a higher current. The inactive state may refer to the period when the image sensor is not actively capturing or processing images. This may be a short idle period between exposures. During this time, the sensor may be in a low-power mode or consuming minimal current, waiting for the next imaging event. The current consumed by the sensor in the inactive state is known to be significantly lower compared to the active state.

[0042] The measurement and control circuit may be configured to compare the measured current with a predetermined threshold to determine whether the image sensor is active or inactive. The predetermined threshold may represent a current level that distinguishes between different operating states of the sensor. A current level above this threshold indicates an active state, and a current level below this threshold indicates an inactive state. The predetermined threshold may be set based on the known behavior of the image sensor, particularly its current consumption during various operating phases, such as exposure, readout, or idle periods. By continuously monitoring current levels and comparing them to this threshold, the system can accurately determine whether the sensor is active or inactive.

[0043] A predetermined threshold can be selected, for example, based on a combination of empirical testing and sensor specifications. In some embodiments, the threshold may be a fixed value based on the typical current consumption during the sensor's active state. In several more advanced embodiments, the threshold may be dynamically adjusted based on operating conditions such as temperature or supply voltage fluctuations. These operating conditions can affect the sensor's current consumption. The control circuit may include an algorithm for automatically adjusting the threshold.

[0044] In one embodiment, the measurement and control circuit is configured to determine the duration for which the image sensor performs exposure based on the detected level or change in the measured current. Thus, “duration” may refer to the duration for which the sensor’s pixels are actively exposed. The system may continuously monitor the power consumed by the sensor and detect an increase in current above a predetermined threshold that marks the start of exposure time. When the current falls below this threshold, exposure time ends. This current-based detection allows the system to determine the exposure time.

[0045] The measurement and control circuits may be configured to convert the measured change in current into the duration for which the image sensor performs exposure, according to a predetermined relationship and / or function. This approach relies on prior knowledge of the sensor's current consumption profile. In this case, the relationship between the consumed current and the exposure time is established either through empirical testing or sensor specifications. For example, the control circuit may use a simple linear function or a more complex formula that correlates the rise and fall of the current level with the start and end of the exposure phase. This predetermined relationship allows the system to accurately estimate the exposure time without requiring a direct exposure signal.

[0046] Alternatively, the measurement and control circuits may be configured to determine the period during which the image sensor performs exposure using a model of the image sensor. This model can account for various operating factors of the sensor, such as exposure delay, readout time, and current consumption, under various conditions. This model can be pre-calibrated based on a detailed analysis of the sensor's performance, incorporating not only the exposure phase but also other stages such as data readout or power transitions. By using this model, the control circuits can more precisely synchronize the illumination source with the actual exposure time and further compensate for complex sensor behavior beyond simple current fluctuations.

[0047] This disclosure further relates to a method for controlling an illumination source for illuminating a scene during image sensor exposure. Configuring the image sensor to capture images of the scene at a periodic frequency, Continuously measuring the current between the image sensor and the sensor, The measured current is continuously detected as it periodically repeats between high and low levels, This includes controlling the illumination source to repeatedly switch between an on state and an off state at an illumination frequency equal to the periodically repeating high-level and low-level switching frequency of the detected and measured current, so that the illumination source is on during exposure of the image sensor.

[0048] As part of this method, the current between the image sensor and the sensor is continuously measured. This measurement can be performed by various sensing mechanisms, such as shunt resistors, which provide a reliable means of detecting the current consumed by the sensor. Alternatively, other current sensing techniques, such as Hall effect sensors or current transformers, may be employed depending on the specific configuration of the system.

[0049] Once the current is measured, the method further includes continuously detecting periodically repeating high and low levels of the measured current. These high and low current levels indicate the operating state of the image sensor. In this case, the high levels correspond to periods of increased activity, such as the sensor's exposure time, and the low levels correspond to periods when the sensor is idle or performing other non-exposure-related functions. The detection process may include comparing the measured current levels to predetermined thresholds. These thresholds may be set based on a known current consumption profile of the image sensor.

[0050] The method further includes controlling the illumination source to repeatedly switch between an on and off state. In this case, the illumination frequency is equal to the periodically repeating high-level and low-level switching frequency of the detected measured current. This ensures that the illumination source, such as an infrared (IR) LED, is on during exposure of the image sensor, thereby providing sufficient illumination to capture high-quality images in low-light environments. Control of the illumination source can be achieved by generating an enable signal sent to the illumination source based on the detected current level.

[0051] In some embodiments, the timing of the illumination source's on and off states can be adjusted to account for any delay or time offset between the measured current peak and the actual exposure timing of the image sensor. For example, if a known delay exists between the current peak and the start of the exposure time, the enable signal may be configured to shift the activation of the illumination by a predetermined time offset to ensure that the illumination is aligned with the exposure. This timing adjustment can be performed using a variety of techniques, including the use of timers, counters, or delay circuits.

[0052] Figure 4 shows a flowchart of a method (300) according to one embodiment of the method of the present disclosure for controlling an illumination source for illuminating a scene during exposure of an image sensor. The method includes the steps of: configuring the image sensor to capture images of the scene at a periodic frequency (301); continuously measuring a current to and from the image sensor (302); continuously detecting periodically repeating high and low levels of the measured current (303); and controlling the illumination source to repeatedly switch between an on and off state at an illumination frequency equal to the periodically repeating high and low level switching frequency of the detected measured current, so that the illumination source is on during exposure of the image sensor (304).

[0053] In one embodiment of the present disclosure, the measurement and control circuit may include one or more processing units configured to execute instructions stored in memory in order to control a lighting source based on the measured current level.

[0054] As used herein, the term “processing circuit” refers to any electronic circuit or combination of circuits that perform data processing functions. This includes, but is not limited to, microprocessors, microcontrollers, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or any other type of integrated circuit capable of executing instructions or processing data. A processing unit may be responsible for performing control logic, including continuously analyzing measured currents, detecting periodically repeating high and low current levels, and generating enable signals for illumination sources.

[0055] The measurement and control circuits may also include memory components such as random access memory (RAM), read-only memory (ROM), or flash memory.

[0056] In some embodiments, the measurement and control circuit may include an analog-to-digital converter (ADC) to digitize current measurements from analog sensing components such as shunt resistors or Hall effect sensors. The ADC can convert the measured current into a digital signal. This digital signal is processed by a processing unit to detect high and low current levels.

[0057] The processing circuit may be configured to execute software, firmware, or hardware instructions to perform specific tasks. These tasks may, but are not limited to, include arithmetic operations, logical operations, data manipulation, control functions, communication protocols, and other operations necessary to perform the functions of the present invention.

Claims

1. An imaging system (100), An image sensor (101) configured to capture images of the scene at a periodic frequency, A lighting source (102) for illuminating the aforementioned scene, and The system includes a measuring and control circuit (108), and the measuring and control circuit (108) is: To continuously measure the current (200) between the image sensor (101) and the other party, Continuously detect the periodically repeating high levels (202) and low levels (203) of the measured current (200), and An imaging system (100) is configured to control the illumination source (102) to repeatedly switch between the on and off states at an illumination frequency equal to the periodically repeating switching frequency between high level (202) and low level (203) of the detected measured current (200), such that the illumination source (102) is on during exposure of the image sensor (101).

2. The imaging system (100) according to claim 1, wherein at least the image sensor (101) and the measurement and control circuit (108) are arranged on different units (106, 110) such as different printed circuit boards.

3. The imaging system (100) according to claim 1 or 2, wherein the image sensor (101) and the illumination source (102) are arranged in different units (106, 107).

4. The imaging system (100) according to any one of claims 1 to 3, wherein the measurement and control circuit (108) is configured to generate enable signals (204a, 204b) for controlling the illumination source (102) to illuminate or not illuminate the scene.

5. The imaging system (100) according to any one of claims 1 to 4, wherein the measurement and control circuit (108) comprises a measurement circuit (104), such as at least one shunt resistor for measuring the current, and a control circuit (105), such as a comparator for generating enable signals (204a, 204b) for controlling the illumination source (102) to illuminate or not illuminate the scene.

6. The imaging system (100) according to any one of claims 1 to 5, wherein the high level (202) is a current level higher than a predetermined current threshold (201), and the low level (203) is a current level lower than the predetermined current threshold (201).

7. The imaging system (100) according to any one of claims 1 to 6, wherein the image sensor (101) is configured to capture images of the scene at a frequency of at least 10 image frames per second, preferably at least 30 image frames per second, corresponding to an illumination frequency of at least 10 Hz.

8. The imaging system (100) according to any one of claims 1 to 7, wherein the measured current (200) has distinct high current levels (202) and low current levels (203) that correlate with the active and inactive states of the image sensor.

9. The imaging system (100) according to claim 8, wherein the measurement and control circuit (108) is configured to compare the measured current (200) with a predetermined threshold (201) in order to determine whether the image sensor is in the active state or the inactive state.

10. The imaging system (100) according to any one of claims 1 to 9, wherein the measurement and control circuit (108) is configured to determine the period during which the image sensor (101) performs exposure based on the detected level or change of the measured current (200).

11. The imaging system (100) according to claim 10, wherein the measurement and control circuit (108) is configured to convert the change in the measured current (200) into the period during which the image sensor (101) performs exposure, according to a predetermined relationship and / or function.

12. The imaging system (100) according to claim 10 or 11, wherein the measurement and control circuit (108) is configured to use a model of the image sensor to determine the period during which the image sensor (101) performs exposure.

13. The imaging system (100) according to any one of claims 1 to 12, wherein the measurement and control circuit (108) is configured to control the illumination source (102) to repeatedly alternate between the on state and the off state with a predetermined time offset for a clear change in the measured current (200).

14. The imaging system (100) according to any one of claims 1 to 13, wherein the illumination source is an infrared illumination source such as an infrared illumination light-emitting diode.

15. A method (300) for controlling a light source to illuminate a scene during exposure of an image sensor, The image sensor is configured to capture images of the scene at a periodic frequency (301). Continuously measure the current between the image sensor and the image sensor (302), Continuously detecting the periodically repeating high and low levels of the measured current (303), and A method (300) comprising controlling the illumination source to repeatedly switch between the on state and the off state at an illumination frequency equal to the periodically repeating high-level and low-level switching frequency of the detected measured current, such that the illumination source is on during exposure of the image sensor (304).

Images