Hybrid image data correction system and correction method

Abstract

The application belongs to the technical field of calculation, and is a kind of mixed image data correction system and correction method, comprising: before starting work, the first industrial robot travels according to the preset path, continuously shoots the image of the road surface below in the process of traveling, and obtains the position information of the mark area and the illumination intensity in each image, and generates the standard image information corresponding to the preset path;The first industrial robot sends the standard image information to the host computer to synchronize all industrial robots through the host computer;After starting work, the industrial robot travels according to the preset path, continuously shoots the image of the road surface below in the process of traveling, and obtains the position information of the mark area and the illumination intensity in each image, compares the position information and the illumination intensity with the corresponding standard image information to judge whether the travel is deviated and whether the ambient illumination intensity is changed, thereby reducing the computing power required when the industrial robot judges and compares, and reducing the comparison time.

Description

Technical Field

[0001] This invention belongs to the field of computing technology, specifically relating to general image data processing, and more particularly to a hybrid image data correction system and correction method. Background Technology

[0002] Industrial robots are used in large warehouses to handle goods, and many robots work simultaneously. When they meet, they need to stop and avoid each other, resulting in frequent start-stop operations. This can easily lead to deviations and prevent them from accurately following the preset path. The industrial processors used in these robots to ensure stable operation have low computing power. Furthermore, these robots use pure vision technology to reduce the mutual interference between sensors. However, visual recognition robots with fixed paths need to acquire relevant parameters for calibration during operation. Acquiring these calibration parameters consumes a lot of computing power and processing time, making it difficult to quickly and promptly calibrate the errors caused by repeated start-stop operations.

[0003] Therefore, due to the large amount of computing power and processing time required for the calibration process, which leads to the slow response and slow speed of industrial robots during movement, it is necessary to design a hybrid image data correction system and correction method.

[0004] It should be noted that the information disclosed in this background section is only for understanding the background technology of this application concept, and therefore, the above description is not considered to constitute prior art information. Summary of the Invention

[0005] This disclosure provides at least one hybrid image data correction system and correction method.

[0006] In a first aspect, embodiments of this disclosure provide a hybrid image data correction system, comprising: The host computer and several industrial robots; The industrial robot communicates wirelessly with the host computer. Before starting work, the first industrial robot travels along a preset path and continuously takes images of the road surface below during the journey. It also obtains the location information of the marked areas and the light intensity in each image to generate standard image information corresponding to the preset path. The first industrial robot sends standard image information to the host computer, which then synchronizes it to all industrial robots. After starting work, the industrial robot travels according to a preset path, continuously taking images of the road surface below during the journey, and obtaining the position information and light intensity of the marked areas in each image. The position information and light intensity are compared with the corresponding standard image information to determine whether the journey has deviated and whether the ambient light intensity has changed.

[0007] In one alternative implementation, a camera is provided on the bottom of the industrial robot near the head, and the camera has a fixed focal length and cannot autofocus. The camera is electrically connected to the control module in the industrial robot; The head of the industrial robot is equipped with a light shield, which extends downwards and protrudes from the bottom surface of the industrial robot. The light-transmitting plate has light-transmitting holes; The control module is configured to control the camera to capture images of the ground beneath the industrial robot; As the industrial robot moves, ambient light passes through the light-transmitting hole and forms a strip-shaped area within the camera's field of view.

[0008] In one optional implementation, before starting work, during the first industrial robot's journey along a preset path, the corresponding control module is configured to control the camera to expose the strip area with a preset aperture range and continuously capture images of the ground below, obtain the position of the strip area in each image, reduce the preset aperture range to slightly larger than the strip area, and fully cover the strip area. At this time, the aperture range is recorded as the aperture mark range, and the part within the strip area of ​​the image is processed to obtain grayscale values. The preset aperture range is much larger than the range of the strip area.

[0009] In one optional implementation, the standard image information includes the position of the bar region corresponding to each image, the gray value of the bar region, and the aperture mark range.

[0010] In one optional implementation, after the industrial robot starts working, as it travels along a preset path, the corresponding control module is configured to control the camera to continuously capture images of the ground below. The aperture range of each image is the range marked by the corresponding aperture. The position of the bar area and the gray value of the bar area are obtained in each image to determine whether the travel is deviated and whether the ambient light intensity has changed.

[0011] In one optional implementation, if the position of the bar region in the current image does not coincide with the position of the bar region in the corresponding standard image information, it is determined that the current industrial robot's travel path has deviated. If the grayscale value of the bar region in the current image is different from the grayscale value of the bar region in the corresponding standard image information, then the change in ambient light intensity is determined.

[0012] In one alternative implementation, after the industrial robot starts working, if there are blurry areas in the acquired image while it is traveling along a preset path, it is determined that there are obstacles in the preset path.

[0013] In one alternative implementation, before starting work, the first industrial robot travels along a preset path and records the standard travel time. After starting work, the industrial robot travels according to the preset path and records the actual travel time. If the actual travel time is different from the standard travel time, the control module in the currently traveling industrial robot judges that there is a deviation in the travel path.

[0014] In one optional implementation, before starting work, the first industrial robot travels according to a preset path. If the proportion of images containing complete strip regions in the acquired images is less than a preset percentage, the control module in the first industrial robot determines that the position of the light-transmitting hole does not meet the requirements. After adjusting the position of the light-transmitting hole, the first industrial robot travels according to the preset path again until the proportion of images containing complete strip regions in the acquired images is greater than or equal to the preset percentage. At this time, it is determined that the position of the light-transmitting hole meets the requirements. The position information of the marked areas and the light intensity in each image acquired during the last travel are used as the standard image information corresponding to the preset path.

[0015] Secondly, embodiments of this disclosure also provide a correction method using the above-described hybrid image data correction system, comprising: Before starting work, the first industrial robot travels along a preset path and continuously takes images of the road surface below during the journey. It also obtains the location information of the marked areas and the light intensity in each image to generate standard image information corresponding to the preset path. After starting work, the industrial robot travels according to a preset path, continuously taking images of the road surface below during the journey, and obtaining the position information and light intensity of the marked areas in each image. The position information and light intensity are compared with the corresponding standard image information to determine whether the journey has deviated and whether the ambient light intensity has changed.

[0016] The beneficial effects of this invention are as follows: This hybrid image data correction system includes a host computer and several industrial robots; the industrial robots communicate wirelessly with the host computer; before starting work, the first industrial robot travels according to a preset path and continuously captures images of the road surface below during its travel, acquiring the position information and light intensity of marked areas in each image, and generating standard image information corresponding to the preset path; the first industrial robot sends the standard image information to the host computer, which then synchronizes it to all industrial robots; after starting work, the industrial robots travel according to the preset path, continuously capturing images of the road surface below during their travel, acquiring the position information and light intensity of marked areas in each image, and comparing the position information and light intensity with the corresponding standard image information to determine whether the travel has deviated and whether the ambient light intensity has changed, thereby reducing the computing power required for industrial robots to make judgments and comparisons, and reducing the comparison time.

[0017] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained through the structures particularly pointed out in the description and the drawings.

[0018] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 A schematic block diagram of a hybrid image data correction system provided in this disclosure embodiment; Figure 2 This is a schematic diagram of the structure of an industrial robot provided in an embodiment of the present disclosure; Figure 3 This is a schematic diagram of aperture variation provided in an embodiment of the present disclosure.

[0021] In the picture: 1. Industrial robot, 2. Camera, 3. Light shield, 4. Light-transmitting hole, 5. Preset aperture range, 6. Strip area, 7. Aperture marking range. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] As used herein, the phrases “in one embodiment,” “according to one embodiment,” “in some embodiments,” etc., generally refer to the fact that a particular feature, structure, or characteristic following the phrase can be included in at least one embodiment of this disclosure. Therefore, a particular feature, structure, or characteristic can be included in more than one embodiment of this disclosure, such that these phrases do not necessarily refer to the same embodiment. As used herein, the terms “example,” “exemplary,” etc., are used to “serve as an example, instance, or illustration.” Any implementation, aspect, or design described herein as “example” or “exemplary” is not necessarily to be construed as preferred or superior to other implementations, aspects, or designs. Rather, the use of the terms “example,” “exemplary,” etc., is intended to present concepts in a specific manner.

[0024] Industrial robots employ pure vision technology during movement to reduce the mutual interference between sensors. Industrial robots with fixed-path vision recognition need to acquire relevant parameters for calibration during operation, and the process of acquiring calibration parameters consumes a lot of computing power and processing time.

[0025] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0026] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0027] like Figure 1As shown, at least one disclosed embodiment provides a hybrid image data correction system, including: a host computer and several industrial robots 1; the industrial robots 1 communicate wirelessly with the host computer; before starting work, the first industrial robot 1 travels according to a preset path and continuously captures images of the road surface below during travel, and obtains the position information and light intensity of the marked areas in each image, generating standard image information corresponding to the preset path; the first industrial robot 1 sends the standard image information to the host computer to synchronize it to all industrial robots 1; after starting work, the industrial robots 1 travel according to the preset path and continuously capture images of the road surface below during travel, and obtain the position information and light intensity of the marked areas in each image, comparing the position information and light intensity with the corresponding standard image information to determine whether the travel is deviated and whether the ambient light intensity has changed, thereby reducing the computing power required for the industrial robot 1 to make judgments and comparisons, and reducing the comparison time.

[0028] In this embodiment, multiple industrial robots 1 can travel along the same preset path.

[0029] In this embodiment, before starting work, the first industrial robot 1 completes the calibration work by traveling along a preset path and obtains standard image information, so that each industrial robot 1 can judge whether the travel is deviated and whether the ambient light intensity changes during the travel along the preset path after starting work.

[0030] In this embodiment, the industrial robot 1 and the host computer can transmit data wirelessly.

[0031] like Figure 2 As shown, in one optional embodiment, a camera 2 is provided at the bottom of the industrial robot 1 near its head. The camera 2 has a fixed focal length and cannot autofocus. The camera 2 is electrically connected to the control module in the industrial robot 1. A light shield 3 is provided at the head of the industrial robot 1, and the light shield 3 extends downward beyond the bottom surface of the industrial robot 1. A light-transmitting hole 4 is provided on the light shield 3. The control module is configured to control the camera 2 to capture images of the ground below the industrial robot 1. During the movement of the industrial robot 1, ambient light passes through the light-transmitting hole 4 and forms a strip-shaped area 6 in the area captured by the camera 2.

[0032] In this embodiment, the control module of the industrial robot 1 only needs to perform grayscale processing on the image portion within the strip region 6 to determine changes in light intensity, and compare the position of the strip region 6 in the current image with the position of the strip region 6 in the corresponding standard image information to determine whether the driving path of the industrial robot 1 is abnormal. This reduces the computing power required in the processing and comparison process and speeds up the processing and comparison time.

[0033] In this embodiment, continuously taking pictures of the road surface below during driving can be done by taking one picture at preset time intervals, or by setting several markers in the preset path and taking pictures when the vehicle reaches a marker, etc.

[0034] In this embodiment, since the focal length of camera 2 is fixed and it cannot autofocus, after capturing an image, it is only necessary to determine whether the relative position between camera 2 and the ground has changed based on whether the image is clear. Under normal circumstances, the image is clear. However, if the industrial robot 1 encounters obstacles such as being raised or its tires are worn, the relative position between camera 2 and the ground changes, resulting in an unclear image. Therefore, when the image is unclear, the control module can directly determine that the industrial robot 1 has encountered obstacles such as being raised or its tires are worn. At this time, the control module can send an alarm signal to the host computer to indicate that there is an obstacle on the preset path or that the industrial robot 1 has abnormalities such as tire wear and needs to be repaired.

[0035] In this embodiment, the working environment of the industrial robot 1 can be an indoor space such as a factory, where the lighting is stable. Therefore, through a single calibration, the comparison standard of each industrial robot 1 can be fixed for subsequent work, that is, the standard image information is fixed.

[0036] like Figure 3 As shown, in one optional implementation, before starting work, during the process of the first industrial robot 1 traveling according to a preset path, the corresponding control module is configured to control the camera 2 to expose the strip area 6 with a preset aperture range 5 and continuously capture images of the ground below, obtain the position of the strip area 6 in each image, reduce the preset aperture range 5 to be slightly larger than the strip area 6, and fully cover the strip area 6. At this time, the aperture range is recorded as the aperture mark range 7, and the part within the strip area 6 of the image is processed into grayscale to obtain grayscale values; the preset aperture range 5 is much larger than the range of the strip area 6.

[0037] In this embodiment, the image is exposed using an aperture to more accurately obtain the grayscale value of the corresponding bar region 6 in the image.

[0038] In this embodiment, during the calibration process, the first industrial robot 1 first uses a larger preset aperture range 5 when taking pictures. Then, after acquiring the image, it reduces the corresponding aperture range according to the position of each strip area 6. In subsequent work, when taking pictures, the industrial robot 1 only needs to adjust the aperture to the aperture mark range 7. The aperture range is reduced, which further reduces the computing power and time required for image processing and improves the reaction speed of the industrial robot 1.

[0039] In one optional implementation, the standard image information includes the position of the bar region 6 corresponding to each image, the gray value of the bar region 6, and the aperture mark range 7.

[0040] In one optional implementation, after the industrial robot 1 starts working, during the process of traveling according to the preset path, the corresponding control module is configured to control the camera 2 to continuously capture images of the ground below. The aperture range of each image is the corresponding aperture mark range 7. The position of the bar region 6 and the gray value of the bar region 6 of each image are obtained to determine whether the travel is deviated and whether the ambient light intensity has changed.

[0041] In one optional implementation, if the position of the bar region 6 in the current image does not coincide with the position of the bar region 6 in the corresponding standard image information, it is determined that the current driving path of the industrial robot 1 has deviated; if the gray value of the bar region 6 in the current image is different from the gray value of the bar region 6 in the corresponding standard image information, it is determined that the ambient light intensity has changed.

[0042] In this embodiment, when there is no problem with the driving path, the position of the bar region 6 in the image currently captured by the industrial robot 1 should be the same as the position of the bar region 6 in the corresponding standard image information. Therefore, if there is a deviation between the two, it is determined that there is a problem with the driving path. At this time, an alarm message is sent to the host computer, and the staff can go to the scene to determine the specific reason for the problem with the driving path.

[0043] In one alternative implementation, after starting work, if the acquired image contains blurry areas while the industrial robot 1 is traveling along a preset path, it is determined that there are obstacles in the preset path.

[0044] In one optional implementation, before starting work, the first industrial robot 1 travels along a preset path and records the standard travel time; after starting work, the industrial robot 1 travels along the preset path and records the actual travel time. If the actual travel time is different from the standard travel time, the control module in the currently traveling industrial robot 1 determines that there is a deviation in the travel path.

[0045] In this embodiment, if the time taken to complete the preset path during operation is different from the time taken during calibration, it can also indicate that there is an abnormality in the path of the industrial robot 1, and an alarm needs to be triggered for judgment and handling.

[0046] In one optional implementation, before starting work, the first industrial robot 1 travels according to a preset path. If the proportion of images containing complete strip regions 6 in the acquired images is less than a preset percentage, the control module in the first industrial robot 1 determines that the position of the light-transmitting hole 4 does not meet the requirements. After adjusting the position of the light-transmitting hole 4, the first industrial robot 1 travels according to the preset path again until the proportion of images containing complete strip regions 6 in the acquired images is greater than or equal to the preset percentage. At this time, it is determined that the position of the light-transmitting hole 4 meets the requirements. The position information of the marked areas and the light intensity in each image acquired during the last travel are used as the standard image information corresponding to the preset path.

[0047] In this embodiment, during calibration, the position of the light-transmitting hole 4 can be adjusted to include more images with complete strip areas 6, which facilitates comparison and judgment by the industrial robot 1 during subsequent work. The preset percentage can be 80%.

[0048] At least one other disclosed embodiment also provides a correction method using the above-described hybrid image data correction system, comprising: before starting work, a first industrial robot 1 travels according to a preset path and continuously captures images of the road surface below during travel, and obtains the position information and light intensity of the marked areas in each image, generating standard image information corresponding to the preset path; after starting work, the industrial robot 1 travels according to the preset path, continuously captures images of the road surface below during travel, and obtains the position information and light intensity of the marked areas in each image, comparing the position information and light intensity with the corresponding standard image information to determine whether the travel is deviated and whether the ambient light intensity has changed.

[0049] In summary, this hybrid image data correction system includes: a host computer and several industrial robots 1; the industrial robots 1 communicate wirelessly with the host computer; before starting work, the first industrial robot 1 travels according to a preset path and continuously captures images of the road surface below during travel, acquiring the position information and light intensity of marked areas in each image, and generating standard image information corresponding to the preset path; the first industrial robot 1 sends the standard image information to the host computer, which then synchronizes it to all industrial robots 1; after starting work, the industrial robots 1 travel according to the preset path, continuously capturing images of the road surface below during travel, acquiring the position information and light intensity of marked areas in each image, and comparing the position information and light intensity with the corresponding standard image information to determine whether the travel has deviated and whether the ambient light intensity has changed, thereby reducing the computing power required for the industrial robot 1 to make judgments and comparisons, and reducing the comparison time.

[0050] In the description of the embodiments of the present invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances.

[0051] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, terms such as "first," "second," and other numerical terms used herein do not imply order or sequence unless expressly indicated herein. Therefore, without departing from the teachings of the exemplary embodiments, the first element, component, region, layer, or segment discussed above may be referred to as a second element, component, region, layer, or segment.

[0052] Spatially relative terms, such as “inside,” “outside,” “below,” “below,” “down,” “above,” “up,” etc., may be used herein to describe the relationship between one element or feature illustrated in the figures and another element or feature. In addition to the orientations depicted in the figures, spatially relative terms may be intended to cover different orientations of the device in use or operation. For example, if the device in the figure is flipped, an element described as “below” or “below” other elements or features would be oriented as “above” other elements or features. Thus, the example term “below” can cover both above and below orientations. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein are interpreted accordingly.

[0053] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A hybrid image data correction system, characterized in that, include: Host computer and several industrial robots (1); The industrial robot (1) communicates wirelessly with the host computer; Before starting work, the first industrial robot (1) travels according to the preset path and continuously takes pictures of the road surface below during the travel, and obtains the position information of the marked area and the light intensity in each picture, and generates standard image information corresponding to the preset path. The first industrial robot (1) sends standard image information to the host computer so that it can be synchronized to all industrial robots (1) through the host computer. After starting work, the industrial robot (1) travels according to the preset path, continuously takes pictures of the road surface below during the travel, and obtains the position information and light intensity of the marked area in each picture. The position information and light intensity are compared with the corresponding standard image information to determine whether the travel is deviated and whether the ambient light intensity has changed. The industrial robot (1) has a camera (2) located at the bottom near the head. The camera (2) has a fixed focal length and cannot autofocus. The camera (2) is electrically connected to the control module in the industrial robot (1); The head of the industrial robot (1) is provided with a light shield (3), which extends downwards from the bottom surface of the industrial robot (1). The light-transmitting plate (3) has a light-transmitting hole (4); The control module is configured to control the camera (2) to capture images of the ground below the industrial robot (1); During the movement of the industrial robot (1), ambient light passes through the light-transmitting hole (4) and forms a strip area (6) in the shooting area of ​​the camera (2). Before starting work, the first industrial robot (1) travels along a preset path. During this process, the corresponding control module is configured to control the camera (2) to expose the strip area (6) with a preset aperture range (5) and continuously capture images of the ground below. The position of the strip area (6) in each image is obtained. The preset aperture range (5) is reduced to be slightly larger than the strip area (6) to fully cover the strip area (6). At this time, the aperture range is recorded as the aperture mark range (7). The part within the strip area (6) of the image is processed to obtain the gray value. The preset aperture range (5) is much larger than the range of the strip area (6).

2. The hybrid image data correction system as described in claim 1, characterized in that, The standard image information includes the position of the bar region (6) corresponding to each image, the gray value of the bar region (6), and the aperture mark range (7).

3. The hybrid image data correction system as described in claim 1, characterized in that, After starting work, the industrial robot (1) travels along a preset path. During this process, the corresponding control module is configured to control the camera (2) to continuously capture images of the ground below. The aperture range of each image is the corresponding aperture mark range (7). The position of the bar area (6) and the gray value of the bar area (6) of each image are obtained to determine whether the travel is deviated and whether the ambient light intensity has changed.

4. The hybrid image data correction system as described in claim 3, characterized in that, If the position of the bar region (6) in the current image does not coincide with the position of the bar region (6) in the corresponding standard image information, it is determined that the current industrial robot (1) has a deviation in its travel path. If the gray value of the bar region (6) in the current image is different from the gray value of the bar region (6) in the corresponding standard image information, then the change in ambient light intensity is determined.

5. The hybrid image data correction system as described in claim 4, characterized in that, After starting work, the industrial robot (1) travels along the preset path. If there are blurry areas in the acquired image, it is determined that there are obstacles in the preset path.

6. The hybrid image data correction system as described in claim 1, characterized in that, Before starting work, the first industrial robot (1) travels according to the preset path and records the standard travel time; After starting work, the industrial robot (1) travels according to the preset path and records the actual travel time. If the actual travel time is different from the standard travel time, the control module in the currently traveling industrial robot (1) judges that there is a deviation in the travel path.

7. The hybrid image data correction system as described in claim 1, characterized in that, Before starting work, the first industrial robot (1) travels according to the preset path. If the number of images containing complete strip regions (6) in the acquired images is less than the preset percentage, the control module in the first industrial robot (1) determines that the position of the light-transmitting hole (4) does not meet the requirements. After adjusting the position of the light-transmitting hole (4), the first industrial robot (1) travels according to the preset path again until the number of images containing complete strip regions (6) in the acquired images is greater than or equal to the preset percentage. At this time, it is determined that the position of the light-transmitting hole (4) meets the requirements. The position information of the marked areas and the light intensity in each image acquired during the last travel are used as the standard image information corresponding to the preset path.

8. A correction method employing the hybrid image data correction system as described in claim 1, characterized in that, include: Before starting work, the first industrial robot (1) travels according to the preset path and continuously takes pictures of the road surface below during the travel, and obtains the position information of the marked area and the light intensity in each picture, and generates standard image information corresponding to the preset path. After starting work, the industrial robot (1) travels according to the preset path, continuously takes pictures of the road surface below during the travel, and obtains the position information and light intensity of the marked area in each picture. The position information and light intensity are compared with the corresponding standard image information to determine whether the travel is deviated and whether the ambient light intensity has changed.

Images