JPH0528323B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method of controlling the exposure of each imaging device when combining the fields of view of a plurality of imaging devices, such as a television camera, to obtain one composite field of view, and more specifically, For example, when the shape of a hot-rolled thick plate is captured as a composite image by multiple imaging devices and measured based on the video signal, the exposure is adjusted according to the level of the video signal of each imaging device. Exposure control method for multiple imaging devices to capture only images necessary for measurement without clearly capturing backgrounds that are not necessary for measurement by controlling the images individually. This is what we propose. [Prior Art] A method of joining multiple images to obtain one composite image is a method often used, for example, in hollow surveying or remote sensing using artificial satellites. The exposure when an image is captured is generally configured such that the amount of light received by the imaging device at the time the image is captured is always constant depending on the characteristics of the imaging device. Therefore, in such a composite image, differences in image density, differences in tone, etc. are often clearly visible at the joints. By the way, the inventors of the present application have proposed a "plate shape measuring device" (Japanese Patent Application No. 147248/1982) that uses a composite image obtained by a plurality of imaging devices as described above. Specifically, nine television cameras arranged in a 3 x 3 matrix take self-luminous near-infrared images of a hot-rolled thick plate and create one composite image. The image processing is performed to detect the position of each edge of the plank, which ultimately measures the shape of the plank (planar shape, more specifically external dimensions and linearity). A plurality of two-dimensional imaging devices arranged to image a portion of each plate, image signals obtained by the imaging devices, and a signal obtained by changing the level of the image signal and delaying the image. a slicer that creates a signal indicating the rising and falling points of a signal, and the rising edge and the rising edge based on the output signal of the slicer
The present invention is characterized by comprising an edge position detection circuit that associates a falling point with a position of a captured image, and an arithmetic unit that associates and synthesizes the position information obtained by the edge position detection circuit with the imaging field of view of each two-dimensional imaging device. shall be. [Problems to be Solved by the Invention] However, the inventors of the present application do not know how to control the exposure of a television camera arranged in a 3x3 matrix, specifically, the aperture control method, which was used in the above-mentioned "plate shape measuring device". Since this method follows the conventional general method of controlling exposure according to the amount of light received by each image pickup device individually as described above, the following problems existed. Exposure control, ie, aperture control, for each of the nine television cameras is to appropriately open and close the aperture so that the peak level of the imaged video signal is constant. Therefore, when capturing a near-infrared image of a hot-rolled thick plate on a relatively low-temperature background, the hot-rolled thick plate has a high video signal level (usually expressed as white in television images). ), so the aperture of the television camera is narrowed down so that the image of the plate being hot-rolled is within its field of view, and conversely, the aperture of the television camera is that the image of the plate being hot-rolled is not within its field of view. is close to full throttle. In a TV camera where the aperture is close to fully open, rolling line components such as rollers and side guides reflect near-infrared rays from the thick plate being hot-rolled, and the image is captured as a near-infrared image. Therefore, when such image signals are analyzed, the image of the roller or side guide may be mistakenly recognized as the image of the thick plate being hot rolled, which is the actual object of measurement, resulting in erroneous measurements. become. Therefore, in order to avoid the above-mentioned erroneous measurements, it is necessary to remove images that are not the actual measurement target through software processing when analyzing the image signal, and then perform the original analysis processing to determine whether the image signal is being measured during hot rolling. Because we were measuring the shape of a thick plate, it took a long time to process the data, and the software processing to remove image signals that were not part of the measurement target was not always perfect.
The reality is that there is no possibility of erroneous measurements. [Means for Solving the Problems] The present invention has been made in view of the above-mentioned circumstances, and is aimed at obtaining a single composite image by combining images taken by a plurality of imaging devices. The level of the video signal of each other imaging device is measured at the same exposure as the proper exposure of the reference imaging device, and this result is used as the standard level set for each imaging device at the time of imaging. By comparing the results and controlling each imaging device to its own appropriate exposure, or to the same exposure as the standard imaging device, and performing actual imaging, it is possible to detect objects other than the imaging target at the time of imaging. By preventing unnecessary objects from being imaged, software processing to remove unnecessary objects as mentioned above is not required, and as a result, the original purpose of image processing can be performed more accurately in a shorter time. The purpose is to propose an exposure control method for equipment. The present invention provides exposure when an imaging target moving on a predetermined route is stopped at a predetermined position on the route and imaged by a plurality of imaging devices provided to combine images captured by each of the imaging devices. In the control method, the exposure of the reference imaging device in which the imaging object stopped at the predetermined position occupies the entire imaging field of view is as follows:
The level of the video signal is controlled over time to match a predetermined level, and the exposure of each imaging device other than the reference imaging device is controlled at the level of the video signal until the imaging target stops at the predetermined position. is measured at substantially the same exposure as that of the reference imaging device, and the measurement result is compared with a reference level set for each imaging device after the imaging target has stopped at the predetermined position, and the image is Imaging devices whose signal level is higher (or lower) than the reference level are controlled to match the respective reference levels, and imaging devices whose video signal level is lower (or higher) than the reference level are controlled to match the reference level. It is characterized in that it is controlled substantially the same as. [Example] Hereinafter, the present invention will be described in detail based on drawings showing examples thereof. Note that since a television camera is used as the imaging device in this embodiment, the exposure is performed only by controlling the opening of the aperture. FIG. 1 is a schematic diagram showing the general configuration of a plate shape measuring device to which the exposure control method for multiple imaging devices according to the present invention is applied. A reversible rolling mill M is installed in a rolling line in which a large number of rollers R, R, . . . are arranged side by side. This reversible rolling mill M rolls a hot-rolled thick steel plate S that is moved on rollers R, R, . . . in both directions indicated by the white arrows. A camera house 1 is provided above one side of the reversible rolling mill M. The camera house 1 has nine television cameras 11 arranged in a 3x3 matrix as described later.
- 19 (see Fig. 2), each camera 11 - 19 is controlled by the camera control section 4, and the near-infrared image of the hot rolled thick steel plate S taken by each camera 11 - 19 is controlled by the camera control unit 4. After being sent to the unit 4 and subjected to preliminary processing such as noise removal and image distortion correction, it is input to the arithmetic unit 3. The computing device 3 analyzes the image signals of each of the nine cameras 11 to 19, detects the edge position of the hot rolled thick steel plate S within the field of view of each camera 11 to 19, and synthesizes the results to determine the hot rolled thickness. The entire shape of the steel plate S is measured. In this way, the shape of the hot-rolled thick steel plate S is measured, and its characteristic elements are provided to the control device 2. The control device 2 is the calculation device 3
Based on the characteristic elements of the shape of the hot-rolled thick steel plate S given by, the reversible rolling mill M, the driving devices (not shown) of the rollers R, R, etc. are controlled via the rolling mill control device 5, Thereby, the hot-rolled thick steel plate S is rolled into a specified shape. Figure 2 shows each camera 11 to 1 in camera house 1.
9 is a schematic diagram showing the relative position of the imaging field of view 111 to 119 and the hot-rolled thick steel plate S to be imaged. In the camera house 1, nine cameras 11 to 19 are arranged in a 3×3 matrix as shown in FIG. The cameras 11 to 14 and 16 to 19 other than the camera 15 located at the center are centrally located vertically above the field of view 115 of the central camera 15. The camera 15 is located at the center and enables imaging of the tilted field of view.
The fields of view 111 to 1 are arranged around the field of view 115 of
14, 116 to 119 are set. As a result, nine cameras 11 to 19 are installed in a relatively small area compared to the size of the hot rolled thick steel plate S to be measured.
Even with this configuration, a sufficient viewing area is ensured. Then, the hot rolled thick steel plate S is attached to each camera 11 to
Composite visual field 110 from visual fields 111 to 119 of 19
, i.e., the field of view 11 of the central camera 15
The cameras 11 to 19 take an image of the hot rolled thick steel plate S and measure the shape thereof based on the images taken by the cameras 11 to 19 in a state where the hot rolled thick steel plate S is located so that the entire area of the hot rolled thick steel plate S is occupied by the hot rolled thick steel plate S. Note that the composite field of view 110 is set so that the edges of the composite field of view 110 of each of the cameras 11 to 19 and the edge of the hot-rolled thick steel plate S are not parallel but intersect with each other at a slight angle. This is the direction of the scanning line of each camera 11 to 19 and the hot rolled thick steel plate S.
This is because if the direction of the edge matches the direction of the edge, accurate detection becomes somewhat difficult. FIG. 3 is a schematic diagram showing the configuration of the aperture control mechanism of each camera 11-19. In the figure a, the central camera 15 is shown, and in the same figure b, the other cameras 11 to 14, 16 to
19 aperture control mechanisms are shown. Central camera 15 connects other cameras 11 to 14, 16
This is a camera that serves as a reference for the aperture control of cameras 15 to 19, and is configured to perform optimal aperture control based on the characteristics of the image sensor of the camera 15. That is, the video signal captured by the camera 15 is once given to the peak hold circuit 15P, and its peak level is given as the level _IL5 of the video signal of the camera 15 to the light reception level control circuit 15E. The light reception level control circuit 15E is given a target level Rea ₅ of the video signal of the camera 15.
The level IL ₅ of the video signal is subtracted from this target level Rea ₅ , and the result is multiplied by a gain K to create a central camera exposure correction signal Rsm. The central camera exposure correction signal Rsm is then applied to a motor control circuit 15MC, converted into a drive signal DS to be applied to the motor 15M for controlling opening and closing of the aperture of the lens system 15l, and applied to the motor 15M. As a result, the exposure of the camera 15 is such that the peak level of the video signal is always at the target level Rea ₅
is controlled in the direction that matches. The central camera exposure correction signal Rsm for controlling the aperture opening/closing of the camera 15 is also given to the received light level control circuits 11E to 14E and 16E to 19E of the other cameras 11 to 14 and 16 to 19 at the same time. FIG. 3b shows cameras 11 to 11 other than the central camera 15.
Although aperture control mechanisms 14, 16 to 19 are shown, basically the aperture control mechanisms of each camera 11 and the like are individually performed in the same manner as the central camera 15 described above.
The video signal of the camera 11 (or 12-14, 16-19) is temporarily transferred to the peak hold circuit 11P (or 1
2P to 14P, 16P to 19P), and the peak level is given to the camera 11 (or 12 to 14,
16 to 19) video signal level IL ₁ (or IL ₂ to
IL ₄ , IL ₆ to _{IL 9} ) as the light receiving level control circuit 11
E (or 12E-14E, 16E-19E). Light reception level control circuit 15E (or 12
E~14E, 16E~19E), camera 15
(or 12 to 14, 16 to 19) the target level of the video signal Rea ₁ (or Rea ₂ to _{Rea 4} ,
Rea ₆ to Rea ₉ ) is given, and from this target level Rea ₅ (or Rea ₂ to Rea ₄ , Rea ₆ to Rea ₉ ), the video signal level IL ₁ (or IL ₂ to _{IL 4} , IL ₆ to ₉ ) is subtracted, and this result is multiplied by the gain K to obtain the individual camera exposure compensation signal Rsi ₁ (or Rsi ₂ ~ Rsi ₄ , Rsi ₆
~Rsi ₉ ) is created. This individual camera exposure compensation signal Rsi ₁ (or Rsi ₂ ~ Rsi ₄ , Rsi ₆ ~ Rsi ₉ ) is transmitted through the changeover switch 11S (or 12S ~ 14S, 16S ~
19S). In addition,
Changeover switch 11S (or 12S to 14S, 1
The center camera exposure correction signal Rsm output from the received light level control circuit 15E of the center camera 15 described above is applied to the other terminals of the center camera 15 (6S to 19S). On the other hand, the peak hold circuit 11P (or 12P
The level IL ₁ (or IL ₂ - IL ₄ , IL ₆ - IL ₉ ) of the video signal of the camera 11 (or 12 - 14, 16 - 19) which is the output of the comparator 11C (or 12C~14C, 16C~19C)
It is also applied to the - (minus) input terminal of the .
Then, the comparator 11C (or 12C to 14C, 1
6C to 19C) is the reference value Reb ₁ (or
Rea ₂ ~ Rea ₄ , Rea ₆ ~ _{Rea 9} ) are given,
−Level IL ₁ of the video signal input to the input terminal
(or IL ₂ ~ _{IL 4} , IL ₆ ~ ₉ ) is the reference value Reb ₁ (or Rea ₂ ~ Rea ₄ , Rea ₆ ~
When the level becomes higher than Rea ₉ ), a high level signal is output from the output terminal and applied to one input terminal of the AND gate 11G (or 12G to 14G, 16G to 19G). AND gate 11G (or 12G to 14G, 16
G to 19G) is connected to the other input terminal of the camera 11.
(or 12 to 14, 16 to 19) are given an exposure control instruction signal Ti from the camera control section 4 which instructs the timing at which exposure control should be performed individually by its high level output. Therefore, this exposure control instruction signal Ti and the comparator 11C (or 12C to 14
C, 16C to 19C) are both at high level, AND gate 11G (or 12
G to 14G, 16G to 19G) send high level signals to the light receiving level control circuit 11E (or 12E to 1
4E, 16E to 19E) changeover switch 11S
(or 12S to 14S, 16S to 19S),
Changeover switch 11S (or 12S to 14S, 1
6S to 19S) from the normal connection state to the other terminal to which the central camera exposure compensation signal Rsm is applied, to the individual camera exposure compensation signal Rsi ₁ (or Rsi ₂ to Rsi ₄ , Rsi ₆ to Rsi ₉ ) Switch the connection to one terminal where . Changeover switch 11S (or 12S~14S,
When 16S to 19S) are in the normal connection state, the central camera exposure compensation signal Rsm is normally given to the common terminal, or the individual camera is given to the common terminal when the connection state is switched due to the establishment of the individual exposure control condition. Exposure compensation signal Rsi ₁ (or Rsi ₂ ~
Rsi ₄ , Rsi ₆ to Rsi ₉ ) are given to the motor control circuit 11MC (or 12MC to 14MC, 16MC to 19MC), and the lens system 15l (or 12l to 14l,
16l to 19l) is converted into a drive signal DS for controlling the opening and closing of the aperture, and the motor 15M (or 12M
~14M, 16M~19M). The individual camera exposure control instruction signal Ti indicates that the hot rolled thick steel plate S has a composite field of view 1 from each camera 11 to 19.
10, and is held from the time when the measurement start signal is output from the control device 2 until the measurement is completed. Therefore, each of the cameras 11 to 11 other than the central camera 15
14, 16 to 19, the central camera exposure correction signal Rsm output from the light reception level control circuit 15E of the central camera 15 controls each motor until the hot rolled thick steel plate S stops at a predetermined position within the composite field of view 110. Circuit 11MC~14MC, 16MC~
19MC, the same exposure control as that of the central camera 15 is performed. Then, the hot rolled thick steel plate S stops at a predetermined position and the exposure control instruction signal Ti
At the time when each video signal IL ₁ ~
IL ₄ , IL ₆ to _{IL 9} are the respective reference values Reb ₁ to Rea ₄ ,
When the level is higher than Rea ₆ to _{Rea 9} , the changeover switches 11S to 14S and 16S to 19S are switched and the respective motor control circuits 11MC
Individual camera exposure correction signals Rsi ₁ to Rsi ₄ , Rsi ₆ to Rsi ₉ are applied to 14 MC and 16 MC to 19 MC, respectively, and individual exposure control is performed by each of the cameras 11 to 14 and 16 to 19, respectively. The method of the present invention is carried out using nine television cameras installed in the plate shape measuring device for hot-rolled thick steel plate S configured as described above. Explain. In addition, in the left half of FIG. 4, each camera 11 to 1 other than the central camera 15, which serves as a reference for exposure control, is
4, 16 to 19, the exposure control of the camera 11 is shown as an example in the case where the hot rolled thick steel plate S enters from the left side of the field of view 111. Also,
The exposure of the central camera 15 is always adjusted appropriately by its own light receiving level control circuit 15E, and when the image is actually taken, the hot rolled thick steel plate S covers all or most of the field of view 115. Therefore, the aperture is controlled to be quite narrow. At the beginning of the control, the exposure control of the camera 11 is controlled in the same way as the exposure control of the central camera 15.
At the point of arrow a in the time chart of FIG. 4, the hot rolled thick steel plate S to be measured begins to enter the field of view 111 of the camera 11, and the level IL ₁ of the video signal output from the peak hold circuit 11P rises. start. Eventually, the level IL ₁ of the video signal reaches a higher level than the reference value Reb ₁ for performing individual exposure control, in other words, it is recognized that the hot rolled thick steel plate S is being imaged, at the point indicated by arrow A. So, comparator 1
The output of 1C changes to high level and the individual exposure control condition is established. However, the hot rolled thick steel plate S still moves to the point of arrow b and then stops at a predetermined stop position. At this point, a measurement start command is simultaneously output from the control device 2, and an exposure control command signal Ti is applied to the AND gate 11G in the light reception level control circuit 11E.
As a result, the changeover switch 11S is switched from the normal connection state, the individual camera exposure compensation signal Rsi ₁ is given to the motor control circuit 11MC, and the camera 1
Individual exposure control is performed by the light reception level control circuit 11E of the camera 1 itself. By the way, until the camera 11 is switched to individual control, the exposure control of the camera 11 covers the entire field of view even though the hot rolled thick steel plate S occupies only a part of its field of view 111. Since it was controlled in the same manner as the central camera 15, the level IL ₁ of the video signal seems to be insufficient and has not reached the target value Rea ₁ . However, since the exposure control of the camera 11 has been switched to individual control at the point of arrow b, exposure control is performed so that the level IL ₁ of the video signal matches the target value Rea ₁ , and this control is not sufficient. At a stable point, which is indicated by arrow c in FIG. 4, the arithmetic unit 3 starts reading the video signal. By the way, for example, a hot-rolled thick steel plate S enters the synthetic field of view 110 from the camera 16 side (right side in FIG. 1), and the hot-rolled thick steel plate S does not enter the field of view 111 of the camera 11, but only rollers, etc. enter. 4, the exposure control of the camera 11 is the same as that of the central camera 15 until the hot rolled thick steel plate S stops. While the signal Ti is being output, the level IL ₁ of the video signal never becomes higher than the reference value Rea ₁ . Therefore, the exposure control of the camera 11 in this case is the same as that of the central camera 15;
Since the field of view 5 is entirely or mostly occupied by the hot-rolled thick steel plate S, its exposure is narrowed down to a considerable degree, and therefore the camera 11 hardly images the roll or the like. Further, for example, the hot rolled thick steel plate S is connected to the camera 11.
When the object enters the field of view 111 from the left side, passes to the right side, and stops, the level IL ₁ of the video signal becomes as shown by the dotted line in the left half of FIG. 4. In this case, the level IL ₁ of the video signal once becomes higher than the reference value Rea ₁ as the hot rolled thick steel plate S enters the field of view 111. but,
At the point of arrow b when the hot-rolled thick steel plate S stops, in other words, at the time when the exposure control instruction signal Ti is given, the hot-rolled thick steel plate S no longer exists in the field of view 111, so the level of the video signal IL ₁ is the reference value Reb ₁
Since the following is true, the individual exposure control condition does not hold.
The same exposure control as the central camera 15 is performed. Although the camera 11 has been described above as an example, the other cameras 12 to 19 can be controlled in the same manner, that is, either exposure control by individual control or exposure control that is the same as that of the central camera 15 is performed. At the point of arrow e when all of these processes are completed, the hot rolled thick steel plate S starts to be transported to the next process, and the cameras 11 to 19 start moving out of the composite field of view 110. Next, we will discuss the results of the present invention and the conventional general method, that is, when controlling the aperture of each camera individually, and when imaging a hot rolled thick steel plate with all cameras set to the same aperture value as the central camera. This will be explained using Table 1 showing this.

【table】

〔effect〕

As detailed above, according to the method of the present invention, the imaging results of the imaging target by the plurality of imaging devices can be made almost constant, regardless of the proportion of the visual field of the imaging target whose brightness is considerably different from that of the background. At the same time, it becomes possible to almost erase the background. Therefore, when images captured by these multiple imaging devices are combined and analyzed, there is no need to erase the background through software processing, reducing the time required for data processing. , and its accuracy also improves. In the above embodiment, a case was described in which a bright object on a dark background, such as a self-luminous infrared image of a hot-rolled thick steel plate, was imaged, but in the opposite case,
That is, the present invention is also applicable to the case of a dark object to be imaged on a bright background, and in this case, the comparison result between the level of the video signal of each imaging device and the reference value may be reversed. Moreover, it is of course applicable not only to infrared images but also to ordinary visible light images. Furthermore, in the above embodiment, since a television camera is used as the imaging device, its exposure is controlled only by controlling the aperture opening. However, when a so-called still camera is used as the imaging device, the aperture opening is controlled. Of course, exposure control may be performed based on the correlation between the shutter speed and the shutter speed.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the configuration of a plate shape measuring device for hot-rolled thick steel plates, which is an example of the object of the method of the present invention, and Fig. 2 shows the nine television cameras, their fields of view, and the objects to be imaged. FIG. 3A is a block diagram showing the aperture control mechanism of the central camera serving as a reference; FIG. 3B is a block diagram showing the aperture control mechanism of other cameras; FIG.
The figure is a timing chart of diaphragm control, and FIG. 5 is an explanatory diagram showing the relationship between the viewing position of the central camera and the measuring position of a hot-rolled thick steel plate. 1...Camera house, 11-19...TV camera, 11c-14C, 16C-19C...comparison circuit, 11E-19E...light receiving level control circuit,
11l~19l... Lens system, 111~119...
...TV camera field of view, S...Hot-rolled thick steel plate.

Claims (1)

[Scope of Claims] 1. A plurality of imaging devices provided to combine images taken by each imaging device capture an imaging target moving on a predetermined route by stopping it at a predetermined position on the route. In this exposure control method, the exposure of the reference imaging device in which the imaging object stopped at the predetermined position occupies the entire imaging field of view is controlled over time so that the level of the video signal thereof matches a predetermined level; The exposure of each imaging device other than the reference imaging device is
Until the imaging target stops at the predetermined position, the levels of the video signals are measured at substantially the same exposure as the reference imaging device, and the measurement results are used as the measurement result when the imaging target stops at the predetermined position. After that, the level of the video signal is compared with the reference level set for each imaging device, and the imaging devices whose video signal level is higher than the reference level are controlled to match the respective reference level, and the level of the video signal is set to the reference level. An exposure control method for a plurality of imaging devices, characterized in that imaging devices smaller than the reference imaging device are controlled substantially in the same manner as the reference imaging device. 2. In an exposure control method when an imaging target moving on a predetermined route is stopped at a predetermined position on the route and imaged by a plurality of imaging devices provided to combine images captured by each device. , the exposure of the reference imaging device in which the imaging object stopped at the predetermined position occupies the entire imaging field of view is controlled over time so that the level of the video signal matches a predetermined level; The exposure of each imaging device is
Until the imaging target stops at the predetermined position, the levels of the video signals are measured at substantially the same exposure as the reference imaging device, and the measurement results are used as the measurement result when the imaging target stops at the predetermined position. After that, the level of the video signal is compared with the standard level set for each imaging device, and the imaging devices whose video signal level is lower than the standard level are controlled to match the respective standard level, and the level of the video signal is set to the standard level. 1. An exposure control method for a plurality of imaging devices, characterized in that imaging devices larger than the reference imaging device are controlled in substantially the same manner as the reference imaging device.