Proximity object detection for monitoring a video camera

Abstract

A proximity object detection method for a surveillance camera is provided. A method, apparatus, and computer program product for determining the presence of an object near the lens (301) of a camera located in a monitored scene are also provided. A first infrared illumination source (302) arranged to illuminate the scene from a first angle is activated. A first image (304) is acquired by an image capture device (300). The first infrared illumination source (302) is deactivated, and a second infrared illumination source (306) arranged to illuminate the scene from a second angle is activated. A second image (308) is acquired by the image capture device (300). The intensity information of the first image (304) and the second image (308) is compared to determine the presence of an object near the lens (301).

Description

Technical Field

[0001] This invention relates to cameras, and more particularly to detecting objects located near the lens of a camera. Background Technology

[0002] Camera health monitoring is becoming increasingly popular, especially in large surveillance systems that may contain hundreds or thousands of cameras, where manually monitoring the status of each camera is practically impractical. A common problem with surveillance cameras, whether indoors or outdoors, is that spiders and insects are attracted to the infrared light often built into the cameras.

[0003] Insects (e.g., butterflies, moths, etc.) and spiders can sit on the lens itself or be located near the lens, thus obstructing the camera's field of view and making the camera less useful for detecting events occurring in the scene being monitored by the camera. It can also trigger false alarms when an insect or spider moves within the lens or field of view, as camera analysis software may interpret its movement as movement within the scene rather than movement near or on the lens itself.

[0004] Furthermore, spiders (and some insects in particular) may leave "belongings" in front of the lens. An example of such objects is a spider web. When smaller insects and spiders are attracted to the infrared light from the camera, they tend to leave their belongings in front of the lens. When an object (such as a spider web) is illuminated by the camera's light, especially if the object contains water droplets, a significant portion of the light is reflected back to the camera's sensor, rendering the camera more or less unusable for surveillance purposes until the object is removed. There is also the possibility that the camera could be tampered with for unauthorized purposes, for example, by placing an object near the lens to blur it.

[0005] For at least these reasons, there is a desire for a method that automatically detects objects approaching the lens, so as to avoid false alarms and / or obtain instructions that require certain actions to be taken on the camera (e.g., removing obstacles). Summary of the Invention

[0006] According to a first aspect, the present invention relates to a method for determining the presence of an object near a lens in a computer system, wherein an image capturing device monitors a scene through a lens. The method includes:

[0007] • Activate the first infrared illumination source positioned to illuminate the scene from a first angle;

[0008] • Acquire the first image using an image capture device;

[0009] • Deactivate the first infrared illumination source and activate the second infrared illumination source, which is positioned to illuminate the scene from a second angle;

[0010] • Acquire a second image using an image capture device; and

[0011] • Compare the intensity information of the first and second images to determine the presence of objects near the lens.

[0012] This provides an improved method for detecting objects near the lens, and typically requires no modification to the camera's hardware setup, as traditional cameras often have illuminators that can be controlled to illuminate the scene from different angles. Because the presence of objects near the lens can be automatically determined, the number of false alarms can be reduced, and appropriate alerts can be generated when attention to any events related to the camera is needed. It also reduces the need for manual intervention and monitoring of individual camera feeds, and thus can also help save on the cost of maintaining the camera system.

[0013] According to one embodiment, a first infrared illumination source and a second infrared illumination source are arranged to illuminate the object with substantially equal intensity and wavelength. Equal intensity and wavelength create conditions as similar as possible for illumination from both sides and eliminate any differences that might occur between illuminated objects with different reflectivity to different wavelengths. This also facilitates image comparison and makes it easier and clearer to identify differences arising purely from illumination from two different angles.

[0014] According to one embodiment, the first infrared illumination source and the second infrared illumination source each include one or more infrared light-emitting diodes (LEDs). LEDs are standard components in most cameras, requiring no major modifications to the camera hardware by using existing parts. The number of LEDs in each illumination source may also vary. In some cases, a single LED in each light source may be sufficient, while in others, multiple LEDs may be required per illumination source.

[0015] According to one embodiment, the method further includes: deactivating a second infrared illumination source and activating a third infrared illumination source arranged to illuminate the scene from a third angle; acquiring a third image; and comparing the intensity information of the first, second, and third images to determine the presence of an object near the lens. The ability to use more than two infrared illumination sources allows for better determination of object presence, both because more images can be acquired and because it allows for pairwise comparisons between the three images. This results in greater certainty when determining the presence of objects near the lens.

[0016] According to one embodiment, the method further includes: activating and deactivating a third infrared illumination source together with activating and deactivating a first infrared illumination source; and activating and deactivating a fourth infrared illumination source together with activating and deactivating a second infrared illumination source, wherein the first and third infrared illumination sources are arranged substantially orthogonal to the second and fourth infrared illumination sources. Using two sets of illumination sources arranged substantially orthogonally to each other not only provides good illumination but also enhances any intensity differences that may occur due to the object being near the lens, thereby improving the accuracy of detecting such objects.

[0017] According to one embodiment, comparing intensity information includes: compensating for the overall intensity difference between a first image and a second image; determining whether any local intensity difference exists; and, in response to a definitive determination of the existence of a local intensity difference, providing an indication of the presence of an object near the lens. Intensity comparison is computationally low-cost, and by first compensating for the overall intensity difference, any local intensity difference will be more clearly displayed in the image comparison, thereby allowing for easy determination of the presence of an object near the lens.

[0018] According to one embodiment, the method further includes: comparing a local intensity difference pattern with a reference intensity difference pattern; and providing an indication of the presence of an object near the lens when a match exists between the local intensity difference pattern and the reference intensity difference pattern. Having different reference intensity patterns not only allows for the detection of objects near the lens but also, at least to some extent, the identification of what the object might be. For example, a butterfly may provide a different intensity pattern than a spider web or a person tampering with the camera, and may require a different type of action. Therefore, different types of alerts can be generated based on what the most likely object is.

[0019] According to one embodiment, the method may further include using a neural network to evaluate local intensity differences and determine the presence or absence of objects located near the lens. Similar to the above, the neural network can be taught to automatically identify specific objects based on intensity distributions.

[0020] According to one embodiment, the method may include sending a notification to a camera operator in response to determining the presence of an object near the lens. As described above, the notification can be automatically generated based on the detection result. Various types of notifications may also exist, or different types of personnel may be notified depending on what the object might be. For example, addressing camera tampering may be more urgent than detecting a spider web.

[0021] According to one embodiment, the object can be a spider, an insect, an item made of a spider, or an item made of an insect. These are some examples of various insects and "items" that are common causes of problems in environments where surveillance cameras are installed.

[0022] According to one embodiment, acquiring a first image and a second image via an image capture device includes: acquiring several short-exposure images and combining the short-exposure images into a first image and a second image, respectively. This is useful when the scene being monitored by the camera involves a great deal of movement, such as when the camera is looking at a wave-like surface of water, or when the branches and leaves of a tree in the background are moving in the wind. By adding or averaging several short-exposure images of this type, such movement can be eliminated, and more accurate identification of objects approaching the lens can be obtained.

[0023] According to one embodiment, acquiring an initial image and acquiring a final image via an image capture device includes: acquiring several short-exposure images and combining the short-exposure images into an initial image and a final image, respectively. For both the initial and final images, advantages similar to those described in the preceding paragraphs can be obtained.

[0024] According to a second aspect, the present invention relates to a system for determining the presence of an object located near a lens, wherein an image capture device monitors a scene through the lens. A memory contains instructions that, when executed by a processor, cause the processor to perform a method comprising:

[0025] • Activate the first infrared illumination source positioned to illuminate the scene from a first angle;

[0026] • Acquire the first image using an image capture device;

[0027] • Deactivate the first infrared illumination source and activate the second infrared illumination source, which is positioned to illuminate the scene from a second angle;

[0028] • Acquire a second image using an image capture device; and

[0029] • Compare the intensity information of the first and second images to determine the presence of objects near the lens.

[0030] The advantages of this system correspond to the advantages of this method, and can be similarly varied.

[0031] According to a fourth aspect, the present invention relates to a computer program for determining the presence of an object located near a lens, wherein an image capturing device monitors a scene through a lens. The computer program includes instructions corresponding to the following steps:

[0032] • Activate the first infrared illumination source positioned to illuminate the scene from a first angle;

[0033] • Acquire the first image using an image capture device;

[0034] • Deactivate the first infrared illumination source and activate the second infrared illumination source, which is positioned to illuminate the scene from a second angle;

[0035] • Acquire a second image using an image capture device; and

[0036] • Compare the intensity information of the first and second images to determine the presence of objects near the lens.

[0037] The computer program includes advantages corresponding to this method and can be similarly varied.

[0038] Details of one or more embodiments of the invention are set forth in the accompanying drawings and the following description. Other features and advantages of the invention will become apparent from the specification, drawings, and claims. Attached Figure Description

[0039] Figure 1 This is a flowchart illustrating a method 100 for determining whether an object is present near a lens according to one embodiment.

[0040] Figure 2 This is a flowchart illustrating a method 200 for determining whether an object is present near a lens according to one embodiment.

[0041] Figure 3 This is a schematic diagram illustrating a camera 300 with a separate IR illumination source according to one embodiment, an image captured by the camera, and an image analysis component.

[0042] In the various figures, the same reference numerals indicate the same elements. Detailed Implementation

[0043] As described above, one object of various embodiments of the present invention is to automatically detect objects approaching the lens, thereby avoiding false alarms and / or obtaining indications that certain actions need to be taken on the camera (e.g., removing obstacles). The invention stems from the general principle that objects approaching a camera lens appear different when illuminated from different angles (i.e., they have different intensities in the image). Therefore, when two images are recorded by the camera and captured from different angles using IR illumination, objects in the images will appear different (i.e., they have different intensities in the acquired images). Thus, by comparing the acquired images, and particularly by looking for local intensity differences between the acquired images, the presence of an object near the lens can be inferred. What is considered "approaching" can vary depending on the specific circumstances, but as a general guideline, "approaching" the camera herein refers to an object located within approximately 0.5 meters of the camera and preferably within 0.2 meters of the camera lens. In response to the detection of an object, an appropriate alarm can be generated to address the problem. Various embodiments will now be described in further detail by way of example and with reference to the accompanying drawings.

[0044] Figure 1 This is a flowchart illustrating a method 100 for determining the presence of an object near a lens according to one embodiment. The method 100 can be executed automatically at various intervals as needed to effectively detect objects located near the lens. (As in...) Figure 1 As can be seen, method 100 begins by activating the first infrared illumination source (step 102). This is in Figure 3 The schematic map shows that Figure 3 A surveillance camera 300 with an activated first infrared illumination source 302 is schematically shown. Typically, infrared illumination sources comprise several IR LEDs, which is standard practice in most cameras used for surveillance. However, IR LEDs are not the only type of illuminator that can be used in conjunction with this invention; other types of illuminators, such as laser diodes, can also be used.

[0045] Next, capture the first image (step 104). Figure 3 In this context, the image is schematically shown as image #1, 304. Images are typically captured using the same type of image capture method as that used by camera 300 during normal operation, for example, using a CMOS sensor combined with rolling shutter technology.

[0046] When the first image has been captured, the first infrared illumination source 302 is turned off, and the second infrared illumination source 306 is turned on (step 106). Typically, the first infrared illumination source 302 and the second infrared illumination source 306 are located on opposite sides of the lens 301 to illuminate the object at two opposite angles (e.g., top and bottom, or left and right, etc.). However, it should be noted that this is not mandatory, and a small angular distance may exist between the first infrared illumination source 302 and the second infrared illumination source 306. One or more IR LEDs may also be part of the first group 302 and the second group 306. Furthermore, it should be noted that although the first infrared illumination source 302 and the second infrared illumination source 306 are located on opposite sides of the lens 301, they can illuminate the object at two opposite angles (e.g., top and bottom, or left and right, etc.). Figure 3 These are shown as being integrated into camera 300, but they can also be separate units placed outside camera 300 itself (e.g., on either side). With the second infrared illumination source turned on, the second image 308 is acquired in the same manner as acquiring the first image 304 (step 108).

[0047] Finally, image analysis 310 is performed to determine whether an object is present near the lens (step 110). It should be noted that this image analysis 310 is independent of the actual depth of the object itself; it is only related to determining whether an object is present near the lens. This is a significant advantage because depth determination typically requires substantial data processing. The relatively low computational resource requirements of the various embodiments of the invention allow it to be implemented in environments where a large amount of computational resources may not be available (e.g., within the camera itself). Furthermore, the lower computational resource requirements allow for a reduction in the overall power consumption of the camera. This is important not only for reducing heat but also for using LEDs at night, as the camera's power supply is limited by the available power supply according to Ethernet standards.

[0048] In one embodiment, image analysis 310 operates as follows. First, any global intensity difference between the two images is calculated and compensated. Such a global intensity difference may be caused, for example, by exposure differences or IR LED intensity differences. This global intensity difference is the same for all pixels in the image and can be compensated for by adding the global intensity difference to one of the images to eliminate the global intensity difference.

[0049] Next, it is determined whether any local intensity difference pattern exists between the first image 304 and the second image 308. In other words, it is determined whether the intensity of certain areas between the images is greater than that of other areas. If such a local pattern exists, it indicates the presence of an approaching object. In some embodiments, this analysis alone can lead to a definitive determination of an approaching object. In other embodiments, it can serve as an indication that more advanced analysis may be required, for example, where the determined local pattern is compared with a reference intensity difference pattern to identify the type of object. Based on this image analysis, an alarm can be generated for the user of the camera system or some maintenance personnel. Alternatively, the alarm can serve as a trigger for an automated system, such as a wiper, vibration, noise, etc., to remove, for example, spider webs, from areas approaching the lens. Many such variations can be envisioned by those skilled in the art.

[0050] In many cameras, a portion of their housing protrudes a certain distance above and / or to the side of the lens for weather protection (similar to how awnings often protrude above windows on a house). Normally, this protrusion is not visible in the images captured by the lens. However, when a first and a second infrared illumination source are activated, this can sometimes cause light to bounce off the protrusion, creating a weak but consistent intensity difference between the two recorded images when both sources are active. This difference can be addressed by recording two calibration images, each activated in a completely dark room with no objects near the lens, and then storing these calibration images in the camera. When the camera is used later and the first and second images are recorded, each of the two calibration images is subtracted from its respective image before performing the aforementioned image processing. In this way, any intensity difference caused by the camera housing configuration can be accounted for.

[0051] Figure 2 This is a flowchart illustrating a method 200 for determining the presence of an object near a lens, according to different embodiments. Figure 2 In step 201, an initial image is first captured. When the scene is dark (e.g., at night), the initial image is captured with both infrared illumination sources on, and when the scene is bright (e.g., during the day), the initial image is captured with both infrared illumination sources off. Then, with reference to the above... Figure 1 Steps 202-208 are performed in the manner described in steps 102-108. After acquiring the second image in step 208, the final image is acquired in step 209. Similar to the initial image, this final image is also captured with both infrared illumination sources on or off, depending on whether the scene is dark or bright.

[0052] The image analysis in step 210 is similar to that in step 110, but with a significant difference. In addition to the image analysis described in step 110, the initial image captured in step 201 is compared with the final image captured in step 209. If these images, captured with both IR illumination sources on or off, differ from each other, it indicates possible movement in the scene during the capture of the first and second images. That is, any differences detected when comparing the first and second images may not actually be due to an object approaching the lens, but rather due to movement in the scene captured by the camera. Therefore, capturing and comparing the initial and final images on either side of the first and second image capture can serve as a good additional "verification" that the results obtained when comparing the first and second images are indeed valid.

[0053] It should be noted that although the description focuses on two images and two IR illumination sources, the same concept can be extended to any number of images and any number of IR illumination sources. The precise selection of how many images or IR illumination sources to use in a given situation is entirely within the skill of a person skilled in the art.

[0054] Furthermore, as mentioned above, instead of capturing a single first image, a single second image, etc., in some implementations, multiple short-exposure images are captured and then combined to form the first image and the second image, respectively. This is advantageous because it allows for taking into account intensity differences caused by movement within the images. For example, a camera may be looking down at the ocean or there may be a tree moving in the wind within the camera's field of view. This setup mitigates the effects of these types of movement, in which several short-exposure images can be captured instead of a single image.

[0055] As those skilled in the art will understand, aspects of the present invention can be implemented as systems, methods, or computer program products. Therefore, aspects of the present invention can take the form of entirely hardware embodiments, entirely software embodiments (including firmware, resident software, microcode, etc.), or embodiments combining software and hardware aspects, which are generally referred to herein as “circuit,” “module,” or “system.” Furthermore, aspects of the present invention can take the form of computer program products contained on one or more computer-readable media having computer-readable program code thereon.

[0056] Any combination of one or more computer-readable media may be used. A computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. A computer-readable storage medium can be, for example, but not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatuses, or devices, or any suitable combination thereof. More specific examples (a non-exhaustive list) of computer-readable storage media will include the following: electrical connections having one or more wires, portable computer floppy disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable optical disc read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof. In the context of this document, a computer-readable storage medium can be any tangible medium that can contain or store programs used by or in connection with an instruction execution system, apparatus, or device.

[0057] A computer-readable signal medium having computer-readable program code contained therein may include, for example, a propagated data signal in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electromagnetic, optical, or any suitable combination thereof. A computer-readable signal medium may be any computer medium that is not a computer-readable storage medium and may transmit, propagate, or transfer a program used by or in connection with an instruction execution system, apparatus, or device.

[0058] The program code contained on a computer-readable medium may be transmitted using any suitable medium, including but not limited to wireless, wired, optical fiber, RF, or any suitable combination thereof. The computer program code for performing the aspects of the invention may be written in any combination of one or more programming languages, including object-oriented programming languages ​​(such as Java, Smalltalk, C++, etc.) and conventional procedural programming languages ​​(such as the "C" programming language or similar programming languages). The program code may be executed entirely on the user's computer, partially on the user's computer as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter case, the remote computer may be connected to the user's computer via any type of network (including a local area network (LAN) or a wide area network (WAN)), or may establish a connection with an external computer (e.g., through the Internet provided by an Internet service provider).

[0059] Aspects of the invention are described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. Each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions / actions specified in the flowchart illustrations and / or one or more block diagrams.

[0060] These computer program instructions may also be stored in a computer-readable medium that can instruct a computer. Other programmable data processing apparatus or other devices operate in a particular manner such that the instructions stored in the computer-readable medium produce an article of art comprising instructions that implement the functions / actions specified in the flowchart and / or one or more block diagrams.

[0061] Computer program instructions may also be loaded onto a computer, other programmable data processing apparatus or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer-implemented process, such that the instructions, which execute on the computer or other programmable apparatus, provide a process for implementing the functions / actions specified in the flowchart and / or one or more block diagrams.

[0062] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of instructions, and the block includes one or more executable instructions for implementing a specified logical function. In some alternative implementations, the functions indicated in the blocks may occur in a non-consecutive order. For example, depending on the functions involved, two consecutively shown blocks may be executed substantially simultaneously, or sometimes they may be executed in reverse order. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented by a special-purpose hardware-based system that performs a specific function or operation or performs a combination of special-purpose hardware and computer instructions.

[0063] Various embodiments of the invention have been described for illustrative purposes, but these descriptions are not intended to be exhaustive or limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. Therefore, many other variations falling within the scope of the claims will be conceived by those skilled in the art.

[0064] The terms used herein are chosen to best explain the principles of the embodiments, the practical application of techniques found in the market, or improvements to the techniques, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for determining the presence of an object located near a lens, wherein, The image capture device monitors a scene through the lens, and the method includes: Activate a first infrared illumination source arranged to illuminate the scene from a first angle; The first image is acquired using the image capture device; The first infrared illumination source is deactivated, and the second infrared illumination source, which is arranged to illuminate the scene from a second angle, is activated; Acquire a second image using the image capture device; and By comparing the intensity information of the first image and the second image, the presence of an object located near the lens can be determined. The comparison intensity information includes: Compensate for the overall intensity difference between the first image and the second image; Determine if any local strength differences exist; and In response to a definitive determination of the existence of a local intensity difference, an indication of the presence of an object located near the lens is provided.

2. The method according to claim 1, wherein, The first infrared illumination source and the second infrared illumination source are arranged to illuminate the object with equal intensity and wavelength.

3. The method according to claim 1, wherein, Both the first infrared illumination source and the second infrared illumination source include one or more infrared light-emitting diodes.

4. The method according to claim 1, further comprising: The second infrared illumination source is deactivated, and the third infrared illumination source, which is arranged to illuminate the scene from a third angle, is activated; Obtain the third image; as well as The intensity information of the first image, the second image, and the third image is compared to determine the presence of an object located near the lens.

5. The method of claim 1, further comprising: The third infrared illumination source is activated and deactivated together with the first infrared illumination source; as well as The fourth infrared illumination source is activated and deactivated together with the second infrared illumination source. The first infrared illumination source and the third infrared illumination source are arranged orthogonally to the second infrared illumination source and the fourth infrared illumination source.

6. The method of claim 1, further comprising: Compare the local intensity difference pattern with the reference intensity difference pattern; as well as When there is a match between the local intensity difference pattern and the reference intensity difference pattern, it provides an indication of the presence of an object located near the lens.

7. The method of claim 1, further comprising using a neural network to evaluate the local intensity difference and determine the presence or absence of an object located near the lens.

8. The method of claim 1, further comprising: Before capturing the first image, an initial image is captured using both the first infrared illumination source and the second infrared illumination source; After capturing the second image, a final image is captured using both the first infrared illumination source and the second infrared illumination source; The intensity information of the initial image and the final image is compared to determine whether there is movement in the scene; as well as In response to determining that there is no movement in the scene, the determination of the existence of an object located near the camera is verified.

9. The method of claim 1, further comprising: In response to the determination that an object is located near the lens, a notification is sent to the camera operator.

10. The method of claim 1, wherein the object is one or more of a spider, an insect, an article of a spider, and an article of an insect.

11. The method according to claim 1, wherein, Acquiring the first image and the second image through the image capture device includes: acquiring several short-exposure images and combining the short-exposure images into the first image and the second image, respectively.

12. The method according to claim 8, wherein, Both acquiring the initial image and acquiring the final image using the image capture device include: acquiring several short-exposure images and combining the short-exposure images into the initial image and the final image, respectively.

13. A system for determining the presence of an object near a lens, the image capturing device monitoring a scene through the lens, the system comprising: Memory; Image capture device; First infrared illumination source; Second infrared illumination source; as well as processor, The memory contains instructions that, when executed by the processor, cause the processor to perform a method comprising: Activate the first infrared illumination source that is arranged to illuminate the scene from a first angle; The first image is acquired using the image capture device; The first infrared illumination source is deactivated, and the second infrared illumination source, which is arranged to illuminate the scene from a second angle, is activated; Acquire a second image using the image capture device; and By comparing the intensity information of the first image and the second image, the presence of the object located near the lens can be determined. The comparison intensity information includes: Compensate for the overall intensity difference between the first image and the second image; Determine if any local strength differences exist; and In response to a definitive determination of the existence of a local intensity difference, an indication of the presence of an object located near the lens is provided.

14. A non-transitory computer-readable storage medium having program instructions contained therein for determining the presence of an object near a lens, an image capturing device monitoring a scene through the lens, the program instructions being processor-executable to perform a method comprising: Activate a first infrared illumination source arranged to illuminate the scene from a first angle; The first image is acquired using the image capture device; The first infrared illumination source is deactivated, and the second infrared illumination source, which is arranged to illuminate the scene from a second angle, is activated; Obtain the second image; as well as By comparing the intensity information of the first image and the second image, the presence of the object located near the lens can be determined. The comparison intensity information includes: Compensate for the overall intensity difference between the first image and the second image; Determine if any local strength differences exist; and In response to a definitive determination of the existence of a local intensity difference, an indication of the presence of an object located near the lens is provided.

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