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KR-20260064511-A - Image-capturing system with current-controlled illumination

KR20260064511AKR 20260064511 AKR20260064511 AKR 20260064511AKR-20260064511-A

Abstract

The present disclosure relates to an image capturing system (100) comprising: an image sensor (101) configured to capture an image of a scene at a periodic rate; a light source (102) for illuminating the scene; and a measurement and control circuit (108) configured to continuously measure a current (200) from/to the image sensor (101), configured to continuously detect a periodically alternating high level (202) and a low level (203) of the measured current (200), and configured to control the light source (102) so that the light source (102) operates alternately between an ON state and an OFF state at a light frequency equal to the switching frequency of the detected periodically alternating high level (202) and low level (203) of the measured current (200), thereby keeping the light source (102) in an ON state during the exposure of the image sensor (101). The disclosure also relates to a method (300) for controlling a light source for illuminating a scene during the exposure of the image sensor. The present disclosure relates to a method for controlling a light source for illuminating a scene during the exposure of the image sensor.

Inventors

  • 마커스 그라웨

Assignees

  • 엑시스 에이비

Dates

Publication Date
20260507
Application Date
20250917
Priority Date
20241030

Claims (15)

  1. As an image capturing system (100), An image sensor (101) configured to capture images of a scene at a periodic rate; A light source (102) for illuminating the above scene; and It includes a measurement and control circuit (108), and The above measurement and control circuit (108) is, Continuously measuring the current (200) from/to the image sensor (101); Continuously detecting periodically alternating high and low levels (202; 203) of the measured current (200); and An image capturing system (100) that controls the light source (102) to alternate between an on state and an off state at a light frequency equal to the detected switching frequency of the periodically alternating high level and low level (202; 203) of the measured current (200), so that the light source (102) becomes on during exposure of the image sensor (101).
  2. In paragraph 1, An image capturing system (100) in which at least one of the image sensor (101) and the measurement and control circuit (108) is disposed on different units (106; 110), such as when disposed on different printed circuit boards.
  3. In paragraph 1, An image capturing system (100) in which the image sensor (101) and the light source (102) are placed in different units (106; 107).
  4. In paragraph 1, The above measurement and control circuit (108) is configured to generate an enable signal (204a; 204b) for controlling whether the light source (102) illuminates the scene or not, in an image capturing system (100).
  5. In paragraph 1, The above 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 (204a; 204b) for controlling the light source (102) to illuminate or not illuminate the scene, in an image capturing system (100).
  6. In paragraph 1, An image capturing system (100), wherein the high level (202) is a current level higher than a predefined current threshold (201), and the low level (203) is a current level lower than the predefined current threshold (201).
  7. In paragraph 1, The image sensor (101) is configured to capture images of a scene at a rate of at least 10 frames per second, preferably at least 30 frames per second, which corresponds to an illumination frequency of at least 10 Hz, in an image capturing system (100).
  8. In paragraph 1, The image capturing system (100) has a measured current (200) having distinct high current levels and low current levels (202; 203) corresponding to the active and inactive states of the image sensor.
  9. In paragraph 8, The above measurement and control circuit (108) is configured to determine whether the image sensor is active or inactive by comparing the measured current (200) with a predefined threshold value (201), in an image capturing system (100).
  10. In paragraph 1, The above measurement and control circuit (108) is configured to determine the time period during which the image sensor (101) performs exposure based on the detected level or change of the measured current (202), in an image capturing system (100).
  11. In Paragraph 10, The above measurement and control circuit (108) is configured to convert a change in the measured current (202) into a time period during which the image sensor (101) performs an exposure, according to a predetermined relationship and/or function, in an image capturing system (100).
  12. In Paragraph 10, The above measurement and control circuit (108) is configured to determine the time period during which the image sensor (101) performs exposure using a model of the image sensor (101), in an image capturing system (100).
  13. In paragraph 1, The above measurement and control circuit (108) is configured to control the light source (102) to alternate between an on state and an off state with a predetermined time offset for a distinct change in the measured current (200), in an image capturing system (100).
  14. In paragraph 1, The above lighting source is an infrared lighting source, such as an infrared light-emitting diode, image capturing system (100).
  15. A method (300) for controlling a light source for illuminating a scene during the exposure of an image sensor, wherein the method comprises: Step (301) of configuring an image sensor to capture images of a scene at a periodic rate; Step (302) of continuously measuring the current from/to the image sensor; Step (303) of continuously detecting periodically alternating high and low levels of the measured current; and A method comprising the step (304) of controlling the light source to alternate between an on state and an off state at a light frequency equal to the detected switching frequency of the periodically alternating high and low levels of the measured current so that the light source becomes on during the exposure of the image sensor.

Description

Image-capturing system with current-controlled illumination The present disclosure relates to an image capturing system having current-controlled illumination, specifically designed to optimize power consumption by synchronizing the exposure time of an image sensor with the illumination. Additionally, the present disclosure relates to a method for controlling a light source, such as an infrared light-emitting diode (LED), to illuminate a scene during the exposure period of an image sensor, even in a system where the image sensor does not have a dedicated exposure signal output. In modern network camera systems, infrared (IR) illumination plays a key role in capturing clear images under low-light conditions. Typically, these systems use infrared light-emitting diodes (LEDs) to illuminate the scene, enabling the image sensor to capture detailed images even in dark environments. According to conventional technology, IR LEDs are often powered continuously regardless of whether the image sensor is actually capturing an image. While this approach can ensure sufficient illumination when needed, it results in significant power consumption. A common method to reduce power consumption is to synchronize the image sensor's exposure time with the IR illumination. This synchronization can be effectively implemented in systems where the image sensor provides a dedicated output signal indicating the exposure duration. However, since not all image sensors are equipped with such an output signal, there are difficulties in controlling the IR illumination. Solutions based on conventional technology have disadvantages in two aspects. First, in systems where an exposure signal is not provided from an image sensor, there is no direct method to accurately match the timing of the sensor's exposure period with that of the IR illumination. As a result, the IR LED operates continuously or for excessively long periods, leading to increased power consumption and reduced operational efficiency. Second, even in systems capable of a certain form of synchronization, the design becomes complex and costs may increase due to the need for reliance on external signals or complex settings. Accordingly, the object of the present disclosure is to provide a solution that enables precise control of IR illumination in a network camera system even when the image sensor does not provide a signal directly indicating the exposure time. The present solution aims to optimize power consumption and improve the energy efficiency of the camera system by enabling the IR LED to be activated only when necessary without requiring an additional signal from the sensor. Various embodiments are described below with reference to the drawings. The drawings are examples of embodiments and are intended to illustrate some features of an image capturing system and a method for controlling a lighting source to illuminate a scene during the exposure of an image sensor, and are not intended to limit the system and method according to the present disclosure. FIG. 1 illustrates a schematic diagram of one embodiment of an image capturing system according to the present disclosure. FIG. 2 illustrates an example of an implementation of a measurement and control circuit that measures current to or from an image sensor and controls a light source. Figure 3 illustrates an example of current consumed by an image sensor and an example of two enable signals for controlling a light source. FIG. 4 illustrates a flowchart according to one embodiment of the method according to the present disclosure for controlling a lighting source to illuminate a scene during the exposure of an image sensor. The present disclosure relates to an image capturing system. The image capturing system includes an image sensor configured to capture images of a scene at a periodic rate, and a light source for illuminating the scene. Images captured by the image capturing system may form a video sequence. The image capturing system described above may use any suitable type of image sensor. Image sensors can be broadly classified into several types, the most common of which are Charge-Coupled Device (CCD) sensors and Complementary Metal-Oxide-Semiconductor (CMOS) sensors. A CCD sensor operates by sequentially transmitting charges from each pixel to a read node, amplifying the signal, and converting it into a digital value. A CMOS sensor integrates the pixel array and the read electronic circuitry onto the same chip, allowing each pixel to be read independently. Both CCD sensors and CMOS sensors may be used in the image capturing system according to the present disclosure, depending on the application requirements. The image capturing system further includes a measurement and control circuit configured to continuously measure current to or from the image sensor. Preferably, the measurement and control circuit is further configured to continuously detect periodically alternating high and low levels of the measured curre