JP4730588B2 - Vehicle perimeter monitoring system - Google Patents

Description

  The present invention relates to a vehicle periphery monitoring system that provides an occupant with information on obstacles existing around a vehicle.

  As such a vehicle periphery monitoring system, Patent Document 1 shown below describes an invention of a periphery monitoring device that monitors an environment around a moving body such as a vehicle and displays an image of a field of view at a desired position. . In this document, as an example, a device that monitors the periphery of a vehicle and appropriately displays an object or the like that becomes an obstacle during parking is shown. According to this example, the rear of the vehicle has a camera that captures the rear, and the CPU calculates graphic calculation and parking guidance based on the acquired image, vehicle running speed, steering state, turning state, etc. Processing is done. These calculation results are displayed on a monitor in the vehicle.

JP 2005-20558 (paragraphs 20-29, FIG. 5)

  Here, if the surroundings are bright, such as in the daytime, a good image can be acquired by the camera at the rear of the vehicle. The acquired image is subjected to various image processing. As an example, there are contour enhancement and edge detection for clarifying the boundary between an obstacle such as a vehicle parked around the vehicle and the road surface. In a situation where the surroundings are bright, such as during the daytime, the acquired image has sufficient contrast, so that contour enhancement, edge detection, and the like can be performed well.

  On the other hand, in a dark environment such as at night, it is difficult for the acquired image to have sufficient contrast due to insufficient sensitivity of the camera. For this reason, for example, a lighting device such as a tail lamp or a reverse lamp is turned on to brighten a shooting range so that an acquired image has sufficient contrast. However, when the target vehicle has a dark color such as black or dark blue, the contrast between the shadow of the vehicle by the lighting device and the vehicle may become weak. When the lighting device is turned on in this way, the surroundings are naturally darker than in the daytime, so the contrast of the captured image is weaker than in the daytime. For this reason, the contrast of the boundary between the dark-colored vehicle and its shadow is further weakened, which hinders accurate contour enhancement and edge extraction.

  The present invention has been made in view of such a problem, and is not affected by the shadow of an obstacle caused by lighting a lighting device of a vehicle even in a dark environment such as at night, and the contour of the obstacle. An object of the present invention is to provide a vehicle periphery monitoring system that makes it possible to extract the vehicle.

The characteristic configuration of the vehicle periphery monitoring system for providing information on obstacles existing on the front side or the rear side of the vehicle according to the present invention for achieving the above object to the occupant by the notification device,
An imaging device that captures a scene on the front side or the rear side of the vehicle, an image processing unit that performs image processing on an image captured by the imaging device, and the obstacle based on an image processing result of the image processing unit A control unit for detecting, and a predetermined pattern having a pattern for extracting an outline of the obstacle in a situation where the periphery is darker than in the daytime and provided at predetermined intervals on the left and right in the vehicle width direction of the photographing device And an illumination device that irradiates illumination light in the left-right direction opposite to the vehicle width direction with the imaging device interposed therebetween .

  Reflected light from an obstacle that has been irradiated with illumination light having a predetermined pattern is incident on the imaging device, and a pattern image corresponding to the predetermined pattern is reproduced in the captured image. On the other hand, the reflected light of a predetermined pattern reflected from the ground (road surface) and the wall surface present at a position different from the obstacle in the three-dimensional space forms a pattern image different from the pattern image corresponding to the reflection by the obstacle. Or since it is far away from an obstacle, attenuation of both illumination light and reflected light is large, and pattern images cannot be formed. Accordingly, the pattern image reproduced on the photographed image is discontinuous at the boundary between the obstacle that appears to be present on the same plane as viewed from the photographing device and the background (ground or wall surface). . In a normal captured image, the boundary between the obstacle and the shadow of the obstacle may be unclear as described above. However, according to this feature configuration, the boundary can be clearly recognized by the discontinuity of the pattern image generated at the boundary between the obstacle and the shadow of the obstacle as described above. As a result, even when the surroundings are darker than in the daytime, the contour of the obstacle can be extracted without being affected by the shadow of the obstacle, and the information on the obstacle can be extracted through a notification device such as a monitor device in the passenger compartment. Can be provided.

  The position of the obstacle to be detected is unknown including its presence or absence. However, the installation location of the lighting device and the photographing device that illuminates the obstacle by lighting is known. Therefore, when there is an obstacle, it is possible to know where the shadow by the lighting device is generated depending on the position of the obstacle and whether or not the obstacle is included in the imaging range. Therefore, by projecting illumination light of a predetermined pattern in a predetermined direction including a boundary portion between the shadow (or background) and the obstacle, it is possible to project both the obstacle and the background. If a predetermined pattern of light is projected onto both the obstacle and the background, the imaging apparatus can obtain a reproduction image of the predetermined pattern that becomes discontinuous at the boundary as described above. As a result, it is possible to provide a vehicle periphery monitoring system that can extract the contour of the obstacle without being affected by the shadow of the obstacle even when the periphery is darker than in the daytime.

Since the boundary portion differs depending on the position where the obstacle exists, and the projection is performed on both the obstacle and the background across the boundary, the illumination light of the illumination device projected in a predetermined direction has a certain width. Further, when the obstacle is far from the vehicle, the urgency of extracting the contour is relatively low even if the boundary between the obstacle and the background is not clear. Therefore, a direction that projects a boundary portion assumed when an obstacle exists in the vicinity may be set as a predetermined direction. In this way, the illuminating device can be installed so as to project across the boundary portion between the obstacle and the background whose presence position is unknown including the presence or absence thereof.

The illumination light projected from the illumination device is reflected by an obstacle, and the imaging device captures the reflected light, thereby reproducing a pattern image corresponding to a predetermined pattern. Therefore, it is most preferable to project the pattern light at an angle such that the illumination light of the predetermined pattern is regularly reflected by the obstacle. However, for example, if an obstacle existing on the side of the vehicle is projected at an angle at which the specularly reflected light is incident on the photographing device mounted on the vehicle, a predetermined pattern of light is emitted from the rear of the vehicle. It needs to be projected and is not realistic.

Here, the illumination device is provided at a predetermined interval on the left and right sides in the vehicle width direction of the imaging device, and the obstacle light is irradiated to the obstacle by irradiating the illumination light in the left and right direction across the imaging device. A deeper angle, that is, an angle in a direction close to regular reflection light with respect to the viewing angle from the photographing apparatus to the obstacle can be set.

In the width direction of the vehicle, there are a side that is easily visible to the driver of the vehicle and a side that is not easy to see. Therefore, if there is at least a lighting device that illuminates the side that is not easily viewed by the driver of the vehicle, a certain degree of effect can be obtained as a vehicle periphery monitoring device. However, it is preferable that the illuminating device is provided at predetermined intervals on the left and right sides in the vehicle width direction of the photographing device, so that obstacles in both the width direction of the vehicle can be detected without the influence of shadows. .

If left and right illumination devices are provided, it may be possible to project only the necessary direction when necessary. If the projection is always performed from the illumination device, for example, if the surrounding monitoring in that direction is unnecessary, the projection becomes useless, which is not preferable from the viewpoint of energy saving of the vehicle. Therefore, for example, it is preferable to provide a moving state detection means or the like to detect the traveling direction of the vehicle, and to project the necessary direction only when necessary according to the detection result.

In addition, it is preferable that the photographing device is provided at a central portion in the vehicle width direction.

By providing the imaging device at the center in the vehicle width direction and by providing the left and right irradiation devices so that the distance between the imaging device and the left and right irradiation devices is equal, it is possible to prevent obstacles in both the width direction of the vehicle. It is possible to detect obstacles by irradiating a predetermined pattern of illumination light under the same conditions on the left and right, and capturing images under the same conditions on the left and right.

  Further, it is preferable that the predetermined pattern is any one of a linear slit pattern, a lattice pattern, and a halftone dot pattern.

  When a linear slit pattern is used, a pattern image along the obstacle is reproduced, and a portion where the straight line of the pattern image is interrupted can be recognized as a boundary. Therefore, the boundary between the obstacle and the background can be found preferably. In the case of a lattice pattern, the boundary can be found by linearity in two orthogonal directions. Therefore, the boundary of several directions can be clarified. Alternatively, the boundary can be found by the presence or absence of a grid-like square pattern. When a halftone dot pattern is used, a boundary according to the surface shape of the obstacle can be found depending on whether or not the halftone dot pattern is reproduced.

Also, the imaging apparatus has a sensitivity in the near-infrared light, the lighting device is suitable to include near-infrared light in a part or all of the light irradiation.

If invisible near-infrared light is used as illumination light, this boundary is suitably used not only when it is desired to suppress the influence of shadows, but also when the boundary between the obstacle and the background is unclear due to insufficient ambient illuminance. Can be found. Further, since the obstacle is not irradiated with the predetermined pattern of visible illumination light, it is possible to monitor the surroundings without making a third party feel uncomfortable.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an example of mounting a vehicle periphery monitoring system according to the present invention on a vehicle. FIG. 2 is a schematic block diagram of the vehicle periphery monitoring system according to the present invention. A vehicle 1 shown in FIG. 1 is a moving body on which a vehicle periphery monitoring system according to the present invention is mounted. The vehicle 1 is provided with a camera 3 that captures a scene behind the vehicle 1 as a photographing device. The imaging device may be provided on the front side of the vehicle 1 or may be provided on both the front side and the rear side, but in this example, a case where it is provided on the rear side will be described. The vehicle 1 also includes an additional lighting device 4 other than a lighting device such as a vehicle width lamp, which will be described later.

An image taken by the camera 3 is a surrounding monitoring ECU (Electronic Control Unit) 5.
The image processing unit performs image processing such as edge extraction and contour enhancement. The result of this image processing is provided to the occupant via the monitor 6a and the speaker 6b as a notification device. The periphery monitoring ECU 5 includes a display control unit and a control unit in addition to the image processing unit. The display control unit controls display on the monitor 6a. An image captured by the camera 3 is displayed, the image processing result or the determination result determined by the control unit based on the image processing result is superimposed as a superimpose on this image, or a guideline is superimposed. The determination result of the control unit is also transmitted to other ECUs of the vehicle 1. For example, if information indicating that the vehicle is too close to the obstacle is transmitted to the brake control ECU 8, the brake control ECU 8 operates the brake device to stop the vehicle 1.

  In addition, not only the image image | photographed with the camera 3 but the information from various movement state detection means 7 is considered in these determinations. For example, the steering angle sensor 7a for detecting the operation of the steering 9a, the wheel speed sensor 7b for detecting the rotation of the wheel, the shift lever switch 7c for detecting the shift position of the shift lever 9c, and the like correspond to the moving state detecting means. . Based on the information from these moving state detection means 7, the periphery monitoring ECU 5 calculates the traveling direction, traveling speed, predicted course, and the like of the vehicle 1.

  FIG. 3 is an explanatory diagram showing the initial movement when the vehicle 1 parks in parallel behind the parked vehicle 2 as an obstacle. The vehicle 1 proceeds to the rear of the parked vehicle 2 along a route as indicated by an arrow in FIG. At this time, the camera 3 of the vehicle 1 shoots a scene in the shooting range V.

  FIG. 4 is an explanatory diagram illustrating an example in which the shadow S of the parked vehicle 2 is generated in the shooting range V of the camera 3. In FIG. 4, for ease of explanation, the vehicle 1 and the parked vehicle 2 are in a substantially parallel state. In FIG. 4, an imaging range V formed between the right visual field limit VR and the left visual field limit VL indicates the viewing angle of the camera 3 mounted on the vehicle 1. When the illuminance around the vehicle 1 is not sufficient, such as at night, the illuminance is increased by illuminating the range of the viewing angle with the illumination means. Between the solid line LR and the solid line LL, the range which the lamp light reaches when at least one of the lighting devices mounted on the vehicle 1, for example, a tail lamp, a stop lamp, etc. is turned on is shown.

  A lamp light boundary line LS indicated by a dotted arrow is a line connecting the corner portion C which is the outermost contour of the parked vehicle 2 and the lighting device to be lit. Within the photographing range V, the light from the lighting device is blocked and a shadow S appears at a portion located outside the lighting light boundary line LS in the vehicle width direction of the vehicle 1. A viewing angle VS (indicated by a solid line arrow) when the corner portion C of the parked vehicle 2 is viewed from the camera 3 is directed toward the outside of the vehicle 1 with respect to the lighting light boundary line LS, as shown in FIG. Therefore, the viewing angle VS also captures the shadow S of the parked vehicle 2 caused by the lighting device that lights up beyond the corner portion C of the parked vehicle 2. And as shown in FIG. 5, the shadow S of the parked vehicle 2 appears in the background part which is the normal road surface and wall surface on a picked-up image. When the vehicle body color of the parked vehicle 2 is a dark color such as black or dark blue, the contrast between the parked vehicle 2 and the shadow S is low. As a result, it becomes difficult to determine the boundary portion of the parked vehicle 2 in the image processing by the periphery monitoring ECU 5. That is, when the vehicle 1 moves as shown in FIG. 3, it becomes difficult to detect the corner portion C that is closest to the vehicle 1 with high accuracy.

  Therefore, the vehicle periphery monitoring system according to the present invention prevents the dark shadow S from affecting the captured image so as to weaken the contrast with the parked vehicle 2. That is, the boundary monitoring ECU 5 can sufficiently determine the boundary between the parked vehicle 2 and the background. The vehicle periphery monitoring system according to the present invention includes an illumination device 4 as an additional illumination means separately from the lighting device, and projects at least a viewing angle VS and projects a predetermined pattern of illumination light onto the parked vehicle 2 and the background. ing. Preferably, the projection by the lighting device 4 is performed when the lighting device is in a lighting state. This is because the lighting device is turned off because the surroundings are bright in the daytime or the vehicle 1 is not moved even at night.

FIG. 6 is an explanatory diagram showing an example of the arrangement of the illumination device 4 as the additional illumination means and the camera 3 as the imaging device. FIG. 6A is a configuration example in which the illumination device 4 is provided at a predetermined interval from the camera 3 in the vehicle width direction, and the opposite direction in the width direction of the vehicle 1 is projected across the camera 3. Although details will be described later, with this configuration, the outside of the vehicle 1 is projected more than the viewing angle VS from the camera 3 to the parked vehicle 2. That is, the illumination light of the illumination device 4 reflected by the parked vehicle 2 can be brought closer to the regular reflection light side. Since the amount of reflected light is maximum in the case of regular reflection, a predetermined pattern can be suitably reproduced by the camera 3 in this way.

  FIG. 6B is a configuration example in which the illumination device 4 is provided at substantially the same position as the camera 3 in the vehicle width direction and the same direction as the viewing angle VS of the camera 3 is projected. Although details will be described later, the illumination device 4 can project onto the parked vehicle 2 and the background by projecting a predetermined pattern of illumination light with a certain width in the direction of the viewing angle VS from the camera 3 to the parked vehicle 2. As a result, the boundary between the parked vehicle 2 and the background can be clarified.

  In this example, the illumination device 4 includes a projector 4a and a lens 4b as shown in FIGS. 7 and 8, and projects illumination light having a predetermined pattern. FIG. 8 shows an example of projecting linear slit light. FIG. 9 shows examples of other predetermined patterns. FIG. 9A shows a linear pattern in the horizontal direction. When such a pattern is used, a boundary can be satisfactorily found depending on where the lateral continuity is interrupted. FIG. 9B shows a linear pattern in the vertical direction. When such a pattern is used, the boundary can be found well depending on where the continuity in the vertical direction is interrupted. FIG. 9C shows a lattice pattern. When such a pattern is used, a boundary in both directions can be found by continuity in both the vertical and horizontal directions. Or the boundary according to the surface shape of an obstruction can be found by the presence or absence of a grid-like square pattern. FIG. 9D shows a halftone dot pattern. Also in this case, the boundary according to the surface shape of the obstacle can be found depending on whether or not the halftone dot pattern is reproduced.

  FIG. 10 is a diagram illustrating an example of a captured image that is captured when the illumination device 4 projects the predetermined pattern of FIG. The linear pattern is reproduced only in the portion where the parked vehicle 2 is present. As described above, even when the contrast between the parked vehicle 2 and the background is low, the boundary between the parked vehicle 2 and the background can be specified from the photographed image due to the discontinuity of the linear pattern. it can.

  Moreover, you may comprise so that near infrared light may be included in part or all of the light which the illuminating device 4 projects. In this case, the camera 3 is also sensitive to near infrared light. Near-infrared light is invisible light, so not only when you want to suppress the influence of shadows, but also when the boundary between an obstacle and the background becomes unclear due to insufficient ambient illumination be able to. At this time, since visible light is not projected onto the parked vehicle 2, it is possible to monitor the surroundings without causing a third party to feel uncomfortable.

  1, 2, and 6 show the case where two illumination devices 4 are provided, it is not always necessary to provide two when applying the present invention. For example, the lighting device 4 that projects the side that is easily visible from the driver's seat may not be provided, and only the lighting device 4 that projects the side that is difficult to visually recognize from the driver's seat may be provided. However, when a plurality of devices are provided as in the above-described embodiment, there is an advantage that a good surrounding monitoring system can be constructed regardless of the ease of visual recognition from the driver's seat. Moreover, even if there is one illuminating device 4, the projection direction of the illuminating device 4 may be variable, and the single illuminating device 4 may project in a plurality of directions.

Thus, when projecting using only one of the two illumination devices 4 or changing the projection direction of one illumination device 4, the detection result of the moving state detection means 7 is used. Controlled. The moving state detection means 7 includes the steering angle sensor 7a, the wheel speed sensor 7b, and the shift lever switch 7c as described above. For example, the fact that the shift lever switch 7c is detected to be in the back gear is used to determine that the traveling direction is backward. Further, by detecting the direction in which the steering wheel 9a is operated by the steering angle sensor 7a, it is possible to know the traveling direction as to which of the left and right directions is going. In addition, it is possible to know which direction is moving in the left or right direction by detecting the difference in rotation between the left and right wheels by the wheel speed sensor 7b. Furthermore, the traveling speed of the vehicle at this time can also be known.

(Lighting device installation example 1)
Hereinafter, various examples of the installation form of the illumination device 4 will be described. The vehicle 1 will be described using a station wagon type vehicle.
FIG. 11 is a perspective view showing a first installation example of the lighting device 4. FIG. 11 shows an example in which the illumination device 4 is installed at a predetermined interval in the width direction of the camera 3 and the vehicle 1. As shown in the figure, a camera 3 as a photographing device is provided in the center of the vehicle 1 in the width direction, and the lighting device 4 (4L, 4R) is provided in a rear combination lamp unit together with a stop lamp and the like.

(Example 2 of lighting device installation)
FIG. 12 is a perspective view illustrating a second installation example of the lighting device 4. FIG. 12 shows an example in which the illumination device 4 is installed at a predetermined interval in the width direction of the camera 3 and the vehicle 1. As shown in the figure, a camera 3 as a photographing device is provided in the center of the vehicle 1 in the width direction, and the lighting device 4 (4L, 4R) is provided in a rear combination lamp unit together with a vehicle width lamp or the like.

(Lighting device installation example 3)
FIG. 13 is a perspective view illustrating a third installation example of the lighting device 4. FIG. 13 shows an example in which the illumination device 4 is installed at the same position in the width direction of the camera 3 and the vehicle 1. Here, the illumination device 4 may be projected from a single device in a plurality of directions, or may be provided with a plurality of devices in one place. In any case, the illumination device 4 is provided in a garnish which is an exterior part of the vehicle 1 together with the camera 3 as shown in the figure. In the case of this embodiment, the illuminating device 4 may be provided in a license plate lamp which is a lighting device provided in the license plate.

  At this time, the illumination device 4 may be provided in the camera 3. That is, the illumination device 4 and the camera 3 may be integrated. For example, as shown in FIG. 18, a camera unit 3 a as the camera 3 may be provided in the center, and a lighting unit 4 a as the lighting device 4 may be provided on the left and right sides of the camera unit 3 a. As shown in FIG. 19, the camera member 3 </ b> A as the camera 3 and the illumination member 4 </ b> A as the illumination device 4 may be joined to form the camera 3 and the illumination device 4.

(Example 4 of lighting device installation)
FIG. 14 is a perspective view illustrating a fourth installation example of the lighting device 4. FIG. 14 shows an example in which the lighting device 4 is installed at a predetermined interval in the width direction of the camera 3 and the vehicle 1. As shown in the figure, a camera 3 as a photographing device is provided at the center of the vehicle 1 in the width direction, and the illumination devices 4 (4L, 4R) are provided in a bumper that is an exterior part.

(Lighting device installation example 5)
FIG. 15 is a perspective view illustrating a fifth installation example of the lighting device 4. FIG. 15 shows an example in which the illumination device 4 is installed at the same position in the width direction of the camera 3 and the vehicle 1. Here, the illumination device 4 may be projected from a single device in a plurality of directions, or may be provided with a plurality of devices in one place. The illumination device 4 is provided in a bumper which is an exterior part of the vehicle 1 separately from the camera 3 as shown in the figure.

(Example of installation of lighting device 6)
FIG. 16 is a perspective view illustrating a sixth installation example of the lighting device 6. FIG. 16 shows an example in which the illumination device 4 is installed at a predetermined interval in the width direction of the camera 3 and the vehicle 1. As shown in the figure, a camera 3 as a photographing device is provided at the center in the width direction of the vehicle 1, and the illumination device 4 (4 </ b> L, 4 </ b> R) is provided in a spoiler that is an exterior part. In the case where the spoiler is provided with a lighting device such as a stop lamp, the lighting device 4 may be installed together with the lighting device.

(Example 7 of lighting device installation)
FIG. 17 is a perspective view showing a fifth installation example of the lighting device 4. FIG. 17 shows an example in which the illumination device 4 is installed at the same position in the width direction of the camera 3 and the vehicle 1. Here, the illumination device 4 may be projected from a single device in a plurality of directions, or may be provided with a plurality of devices in one place. The illumination device 4 is provided in a spoiler which is an exterior part of the vehicle 1 separately from the camera 3 as shown in the figure. Similarly to the above, when the spoiler is provided with a lighting device such as a stop lamp, the lighting device 4 may be installed together with the lighting device.

The perspective view which shows the example of mounting to the vehicle of the vehicle periphery monitoring system which concerns on this invention Schematic block diagram of a vehicle periphery monitoring system according to the present invention Explanatory drawing which shows the initial movement in case the vehicle 1 parks in parallel behind the parked vehicle 2 as an obstacle. Explanatory drawing which shows an example in case the shadow of an obstacle arises in the imaging | photography range of an imaging device The figure which shows the example of the picked-up image image | photographed in FIG. Explanatory drawing which shows an example of arrangement | positioning with an illuminating device and an imaging device. Explanatory drawing which shows an example of the illumination method by an illuminating device Explanatory drawing which shows the example which projects a slit pattern with the illuminating device of FIG. The figure which shows the example of the predetermined pattern projected by the illuminating device The figure which shows the example of the picked-up image by projection of the predetermined pattern of Fig.9 (a) The perspective view which shows the 1st example of installation of an illuminating device. The perspective view which shows the 2nd example of installation of an illuminating device. The perspective view which shows the 3rd example of installation of an illuminating device. The perspective view which shows the 4th example of installation of an illuminating device. The perspective view which shows the 5th example of installation of an illuminating device. The perspective view which shows the 6th example of installation of an illuminating device. The perspective view which shows the 7th example of installation of an illuminating device. The perspective view which shows the example which integrates an imaging device and an illuminating device The perspective view which shows the other example which integrates an imaging device and an illuminating device.

1 vehicle 2 parked vehicle (obstacle)
3 Camera (photographing device)
4 Illumination device 6a Monitor (notification device)
6b Speaker (notification device)
7 Moving state detection means V Shooting range

Claims (4)

In the vehicle periphery monitoring system that provides information on obstacles existing on the front side or rear side of the vehicle to the occupant by the notification device,
A photographing device for photographing a scene on the front side or the rear side of the vehicle;
An image processing unit that performs image processing on an image photographed by the photographing device;
A control unit for detecting the obstacle based on an image processing result of the image processing unit;
Together provided at predetermined intervals in the right and left in the vehicle width direction of the imaging device, the imaging device with illumination light of a predetermined pattern having a pattern for the peripheral to extract the contour of the obstacle in a dark conditions than during daytime A vehicle periphery monitoring system comprising: an illuminating device that irradiates in a direction opposite to the left and right of the vehicle width direction across the vehicle. The vehicle periphery monitoring system according to claim 1, wherein the photographing device is provided at a central portion in the vehicle width direction .   3. The vehicle periphery monitoring system according to claim 1, wherein the predetermined pattern is any one of a linear slit pattern, a lattice pattern, and a halftone dot pattern. The vehicle periphery according to any one of claims 1 to 3, wherein the photographing device has sensitivity to near-infrared light, and the lighting device includes near-infrared light in part or all of the light to be irradiated. Monitoring system.

Images