JPS61212171A - Exposure control method for plural image pickup devices - Google Patents

Abstract

PURPOSE:To perform the picture processing more accurately in a short time by measuring levels of video signals of the other image pickup devices with the same exposure as the correct exposure of one reference image pickup device and comparing measured results with reference levels set to individual image pickup devices and controlling each image pickup device to its correct exposure to pick up images actually. CONSTITUTION:A center camera 15 is always controlled to the correct exposure independently by its own light reception level control circuit 15E. When the control is started, a camera 11 is controlled to the same exposure as the center camera 15; and at the time indicated by an arrow A when a hot rolling thick steel plate S reaches the high level from a reference value Reb1, the output of a comparator 11C is inverted to the high level, and individual exposure control conditions are satisfied. The hot rolling thick steel plate S is stopped in a prescribed stop position. At this time, an exposure control indicating signal Ti is given to an AND gate 11G simultaneously. Thus, a changeover switch 11S is switched to give an individual camera exposure compensating signal Rsi1 to a motor control circuit 11MC, and the individual exposure control is performed by a light reception level control circuit 11E of the camera 11 itself.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a method for controlling the exposure of each imaging device when combining the fields of view of a plurality of imaging devices, such as television cameras, to obtain one composite field of view. More specifically, for example, when the shape of a hot-rolled thick plate is captured as a composite image by multiple imaging devices and measurements are made based on the video signals, the video signals of each imaging device are By controlling the exposure individually depending on the level, it is possible to prevent backgrounds that are unnecessary for measurement from being clearly imaged, and to capture only the images necessary for measurement. This paper proposes an exposure control method for multiple imaging devices.

[Prior art]

How to join multiple images to get one composite image:
For example, this is a method often used in aerial surveying or remote sensing using artificial satellites.
In such cases, the exposure when each image is captured may be 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. Common.

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; an edge position detection circuit that associates the rising and falling points with the positions of the captured image based on the output signal of the slicer; and an arithmetic device that combines the position information obtained by associating it with the imaging field of view of each two-dimensional imaging device.

[Problem that the invention seeks to solve]

However, the exposure control, specifically the aperture control method, of the 3x3 matrix-arranged television camera used by the inventors in the above-mentioned "plate shape measuring device" is different for each imaging device as described above. Since the conventional method of controlling exposure according to the amount of light received was followed, 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 by software processing when analyzing image signals, and then perform the original analysis processing to determine the thickness during hot rolling. Because the shape of the plate was measured once, data processing took a long time, and the software processing for removing image signals that were not the object of measurement was not necessarily perfect, so there was no risk of incorrect measurements. The reality is that this cannot be said.

[Means for solving problems]

The present invention has been made in view of the above circumstances,
When combining images captured by multiple imaging devices to obtain one composite image, the video signals of each other imaging device are used at the same exposure as the appropriate exposure of the reference imaging device until the imaging is performed. The level is measured, and this result is compared with the standard level set for each imaging device at the time of imaging, and depending on the result, each imaging device is adjusted to its appropriate exposure, or the imaging device that serves as the reference By controlling the exposure to be the same as that of the actual image capture, unnecessary objects other than the object to be imaged are not captured at the time the image capture is performed.
The purpose of this invention is to propose an exposure control method for multiple imaging devices that eliminates the need for software processing to remove unnecessary objects as described above, and thereby allows the original purpose of image processing to be performed more accurately in a shorter time. .

The present invention provides exposure control when an imaging target moving on a predetermined route is stopped at a position on the route and an image is captured in a composite image obtained by combining images respectively captured by a plurality of imaging devices. In the method, the exposure of the reference imaging device is controlled over time so that the level of its video signal matches a predetermined level, and the exposure of each imaging device other than the reference imaging device is controlled depending on the imaging target. Until the image signal stops at the predetermined position, the levels of the video signals are measured at substantially the same exposure as the reference Ni imager;
After the imaging target has stopped at the predetermined position, the measurement results are compared with the reference level set for each imaging device, and the imaging devices whose video signal level is higher (or lower) than the reference level are The imaging device is controlled to match the reference level, and the imaging device whose video signal level is smaller (or larger) than the reference level is controlled to be substantially the same as the imaging device serving as the reference.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on drawings showing embodiments 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 that is applicable to the exposure control method for multiple imaging devices according to the present invention.

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 is equipped with nine television cameras 11 to 19 (see FIG. 2) arranged in a 3×3 matrix as described later, and each camera II to 19 is controlled by the camera control unit 4. In addition, the near-infrared images of the hot-rolled thick steel plate S obtained by each of the cameras 11 to 19 are sent to the camera control unit 4, where they are subjected to preliminary processing such as noise removal and image distortion correction, and then sent to the arithmetic unit 3. is input.

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 unit W2 performs reversible rolling 11131 via the rolling mill control device 5 based on the characteristic elements of the shape of the hot rolled thick steel sheet S given from the calculation device 3.
It controls the driving devices (not shown) of rollers R, R, etc., and thereby rolls and forms the hot rolled thick steel plate S into a designated shape.

FIG. 2 is a schematic diagram showing the arrangement of the cameras 11 to 19 in the camera house I, their imaging fields of view 111 to 119, and the relative position of the hot rolled thick steel plate S to be imaged.

The camera house 1 has nine cameras 11 as shown in Figure 2.
~19 are arranged in a 3x3 matrix,
These cameras 11 to 19 have respective fields of view 111 to 1
Rather than being arranged vertically above the center of the central camera 15, they are arranged centrally at a position centered vertically above the field of view 115 of the central camera 15, and each camera 11 other than the camera 15 located at the center ~14.16~19 respectively enable imaging of the tilted field of view, and the respective fields of view 111~114.116 are placed around the field of view 115 of the central camera 15.
~119 is set. As a result, compared to the size of the hot-rolled thick steel plate S that is the object of measurement, the
Even in a configuration in which cameras 11 to 19 are arranged, a sufficient viewing area is ensured.

Then, the hot-rolled thick steel plate S is located approximately in the center of the composite field of view 110 formed by the fields of view 111-119 of each camera 11-19,
That is, the cameras 11 to 19 are positioned so that the entire field of view 115 of the central camera 15 is occupied by the hot rolled thick steel sheet S, and the shape measurement is performed based on the imaging of the hot rolled thick steel sheet Fis. be exposed.

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 steel plate S are not parallel but intersect at a slight angle. This is because if the direction of the scanning line of each of the cameras 11 to 19 matches the direction of the edge of the hot-rolled thick steel plate S, 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 same figure (al shows the aperture control mechanism of the central camera 15, and fbl shows the aperture control mechanism of the other cameras 11 to 14 and 16 to 19.

The central camera 15 is a camera that serves as a reference for the aperture control of the other cameras II to 14, 16 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,
The peak level is the level IL of the video signal of the camera 15.
, are applied to the light reception level control circuit 15E. The light reception level control circuit 15H is given a target level Rea5 of the video signal of the camera 15, and the level rL5 of the video signal is subtracted from this target level Rea5, and this result is multiplied by the gain K and the central camera An exposure compensation signal Rsm is created. The central camera exposure correction signal R3l11 is then given to the motor control circuit 15Mc, which controls the motor 1 for controlling opening and closing of the aperture of the lens system 15J.
It is converted into a drive signal DS to be applied to the motor 15M, and is applied to the motor 15M. As a result, the exposure of the camera 15 is
The peak level of the video signal is always the target level Rea5
is controlled in the direction that matches.

The central camera exposure correction signal Rsn+ for controlling the opening/closing of the aperture of this camera 15 is simultaneously applied to the other cameras 11 to 15.
14.16-19 light reception level control circuits LIE-14E
.

Also given in 16E-19E.

Part 3) shows an aperture control mechanism for cameras 11 to 14 and 16 to 19 other than the central camera 15, but basically the aperture control mechanism for each camera 11, etc. Control takes place. Camera 11 (or 12-14
．． 16 to 19) are once sent to the peak hold circuit 1.
1P (or 12P~1,1)', 16P~19P), and its peak level is given to camera 11 (or 12~1,1)', 16P~19P).
14.Rehe 7LzlL1 of the video signal of 16-19)
(or rL2~rt, 4゜■L6~IL9) as the light receiving level control circuit LIE (or 12E~14H, 161E
~19E). Light reception level control circuit 15E (
or 12E to 14E, 16E to 19E), the target level Read (or Rea2 to Rea4.
Rea6 to Rea9) are given, and this target level Rea5 (or Rea2 to Rea4, Rea6
~Reag) to the video signal level I1. ．． (or ■
L2~'L411L6~9) is subtracted, and this result is multiplied by gain K to produce an individual camera exposure compensation signal R51l.
(or R512 to R514°R516 to R519) are created. This individual camera exposure correction signal R51l (or R512 to R514, R516 to Rsig) is applied to the changeover switch 11S (or 12S to 14S).

16S to 19S). In addition, the changeover switch 11S (or 12s to 14S, 16
The other terminal of the terminals (S to 19S) is connected to the central camera 1 described above.
A center camera exposure correction signal Rsm'' output from the light reception level control circuit 15E of No. 5 is given.

On the other hand, the peak hold circuit LIP (or 12P to 14P
.

Camera 11 (or 12-16P-19P) output
14°16-19) video signal level IL, (or I
L2~It, 4°IL6~IL9) is - (minus) of comparator 11C (or 12C~14C, 16C~19C)
It is also given to the input terminal. And comparator 11G (
or 12C-14C, 16C to 19C) is the reference value Reb1 (or Rea2 to Rea4 ° Rea6 to Rea
g) is given, and the level IL of the video signal that is input to the - input terminal, (or IL2 to IL4 r I
La~9) is the reference value Reb+ which is input to the ten input terminal
(or Rea2 to Rea4.Rea6 to Rea9), a high level signal is output from the output terminal and the AND gate 11G (or 12G to 14G).

16G to 19G) to one input terminal.

AND game) 11G (or 12G~14G, 16G~
The other input terminal of the camera 11 (or 12
The camera control section 4 provides an exposure control instruction signal Tj that instructs the timing at which the exposure control units 14.16 to 19) should perform individual exposure control by its high-level output. Therefore, this exposure control instruction signal Ti and the comparator 11G (or 1
2C to 14C, 16C to 19C) are both at high level.
G to 14G, 16G to 19G) send high level signals to the light reception level control circuit 11B (or 12E to 14E, 1
61! ~19B) switch 11S (or 125
~143.16S~19S), selector switch 1
1S (or 123 to 145.165 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+ (or R512 to Rst4 + Rst)
6 to R515) is switched to the one terminal provided.

Changeover switch 11S (or 125~148.163~
The central camera exposure correction signal R5tas is normally applied to the common terminal when 19S) is in the normal connection state, or the individual camera exposure correction signal is applied to the common terminal when the connection state is switched due to the establishment of the individual exposure control condition. R
si+ (or R512 to R514, R516wRsi9
) is the motor control circuit llMC (or 12Mc ~ 14M
G.

16MC-19MG), is converted into a drive signal DS for controlling the opening and closing of the aperture of lens system 15J (or 127!~1i, 16A'~19j), and is sent to motor 15M (
or 12M to 14M, 16M to 19M).

The individual camera exposure control instruction signal Ti is a hot-rolled thick steel plate S.
completely stops within the composite field of view 110 of each camera 11 to 19, 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 camera 11 to 14°1 except the central camera 15
6 to 19, until the hot-rolled thick steel plate S stops at a predetermined position within the composite field of view 110, the light reception level control circuit 15F! of the central camera 15! The central camera exposure correction signal Rsta output from each motor control circuit llMC~14
MG, 16MG to 19MG, so the same exposure control as 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 point when the respective video signals l to II, 4
+ IL6 to ILg are the respective reference values Reb1 to R
If the level is higher than ea4 + Rea6~Rea5, changeover switches 115~145.165~1
9S is switched and each motor control circuit 11MG
Individual camera exposure correction signals R511 to R514 and R516 to R519 are given to ~14MC and 16MC to 19MC, 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.The method of the present invention will be explained below according to the time chart shown in FIG. do.

In addition, in the left half of FIG. 4, each of the cameras 11 to 14 and 16 to 19 other than the central camera 15, which is the reference for exposure control, is shown.
- For example, the exposure control of the camera 11 is controlled by the field of view 11.
The case where the hot rolled thick steel plate S enters from the left side of 1 is shown. Further, the exposure of the central camera 15 is always controlled by its own light receiving level control circuit 15[! The aperture is controlled to be considerably narrowed because the hot-rolled thick steel plate S occupies all or most of the field of view 115 at the time when the image is actually taken.

At the beginning of control, exposure control of camera 11 is performed by central camera 1.
The exposure control is performed in the same way as the exposure control shown in FIG. 5, and at the point of arrow a in the time chart of FIG. Level IL of the video signal output from
, begins to rise. Eventually, at the point of arrow A, the level fL1 of the video signal reaches a higher level than the reference value ReJ for performing individual exposure control, in other words, it is recognized that the hot rolled thick steel plate S is being imaged. , the output of the comparator 11G 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 indicated by the arrow mark, 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, changeover switch I
IS is switched from the normal connected state and the motor control circuit l
An individual camera exposure correction signal R51I is given to lMC,
Individual exposure control is performed by the light reception level control circuit 11H of the camera 1 itself.

By the way, until it is switched to individual control, camera 11
Although the hot-rolled thick steel plate S occupies only a part of the field of view 111, the exposure control of the central camera 15 is performed in the same manner as the central camera 15 whose entire field of view is occupied by the hot-rolled thick steel plate S. Therefore, the level IL of the video signal seems to be insufficient and has not reached the target value Real. However, since the exposure control of camera 1 has been switched to individual control at the point of arrow mark, exposure control is performed so that the level IL of the video signal matches the target value Real, and this control is sufficiently stable. At the time indicated by arrow C in FIG. 4, reading of the video signal by the arithmetic unit 3 is started.

By the way, for example, the hot rolled thick steel plate S is placed on the camera 16 side (
Enter the synthetic field of view NO.
If the field of view 111 does not include the hot rolled thick steel plate S but only rollers, etc., the exposure control of the camera 11 will stop the hot rolled thick steel plate S, as shown in the right half of FIG. Until this point, the same exposure control as that of the central camera 15 is performed, so the level IL of the video signal changes while the exposure control instruction signal Ti is being output.

There is no case where the level becomes higher than the reference value Rea1.

Therefore, the exposure control of the camera 11 in this case is the same as that of the central camera 15, but the field of view of the central camera 15 is entirely or mostly occupied by the hot rolled thick steel plate S. Therefore, the exposure is limited to a considerable extent, and therefore the camera 11 almost never captures an image of the roll or the like.

Furthermore, for example, the hot rolled thick steel plate S is in the field of view 1 of the camera 11.
11 from the left, passes to the right, and stops, the level of the video signal L1 will be as shown by the dotted line in the left half of FIG.

In this case, the level ■LI of the video signal temporarily changes to the reference value Real as the hot rolled thick steel plate S enters the field of view 111.
It becomes a higher level. However, at the point at which the hot rolled thick steel plate S stops, in other words, the exposure control instruction signal Ti
At the time when is given, the hot-rolled thick steel plate S no longer exists in the field of view 111, so the level IL of the video signal is less than the 11-value ReJ, so the individual exposure control condition is not satisfied. , 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 way, that is, either exposure control is performed by individual control, or exposure control is the same as that of the central camera 15. was carried out,
At the point in time indicated by arrow e when all of these steps have been completed, the transfer of the hot-rolled thick steel plate S to the next process begins, and the cameras 11 to 19 begin to move out of the composite field of view 110.

Next, the present invention and the conventional general method, that is, when each camera individually controls the aperture, and furthermore, when all cameras are set to the same aperture value as the central camera and a hot rolled thick steel plate is imaged, each The results will be explained with reference to Table 1 showing the results.

(Margins below) Table 1 However, A: A camera in which a relatively large part of the field of view is occupied by hot-rolled steel plate S (such as the field of view 118 shown in Figure 2) B: A camera in which a small part of the field of view is occupied by heat Camera occupied by hot-rolled thick steel plate S (field of view 113 etc. shown in Fig. 2) C: Camera in which hot-rolled thick steel plate S does not come into the field of view at all (
(field of view 111 etc. shown in Figure 2) Table 1 shows cases where the hot rolled thick steel plate S occupies the entire field of view 115 of the central camera 15 as shown in Figure 5 (al), and For each case, the aperture value of the central camera and the incident light level of the reflected light from the unwanted object are shown for this aperture value, and for the other cameras, for example, the field of view 114. A indicates a case where the proportion of the hot rolled thick steel plate S in the field of view is relatively large, as in the field of view 113 in FIG. A case where the steel plate S does not exist within the field of view, such as the field of view 111 in FIG. 2, is indicated by C.
For these A, B, and C, the case where the edge position of the steel plate S (which does not exist in case of C) is detected accurately is O
A Δ mark indicates a slightly inaccurate case, and an X mark indicates a case where detection was difficult.

Regarding reflected light from unnecessary objects (rollers, side guides, etc.), mark ○ if it is erased from the image, and mark Δ if it does not affect the analysis (does not require special software processing). X indicates cases where software processing is required to erase images of unnecessary objects during analysis.
Each is indicated by a mark.

In the conventional method of controlling all cameras individually, regardless of the position of the hot-rolled thick steel plate S with respect to the field of view 115 of the central camera 15, the edges of the hot-rolled thick steel plate S themselves are is clearly imaged, and it becomes clear that it does not exist in case C, where the hot-rolled thick steel plate S does not originally exist within the field of view.However, in this state C and the above-mentioned case B, the aperture is wide open. Therefore, unnecessary objects are clearly imaged, which is why they are marked with an X.

On the other hand, all cameras are controlled to the same aperture value as the central camera 15, and the entire field of view of the central camera 15 is
, the apertures of all cameras are considerably narrowed down, so there is insufficient light in A and B, that is, the level of the video signal is slightly low, and the edges of the hot-rolled thick steel plate S are slightly unclear. In C, there is no edge of the hot-rolled thick steel plate S, so it is marked with a circle, but since the aperture of each camera is narrowed down to a considerable extent, the light reflected from unnecessary objects is not captured. It is marked with an ○.

All cameras have the same aperture value as the central camera 15,
If only a part of the field of view 115 of the central camera 15 is occupied by hot-rolled thick steel FiS, the aperture of the central camera 15 is opened to some extent, and the apertures of all other cameras are also opened by the same amount as the central camera 15. It's dark.

Therefore, in cases A and B, there is too much light, that is, the level of the video signal becomes too high, making the edge of the hot rolled thick steel plate S unclear, and in case C, the same reason as in other cases C occurs. This will be marked with a circle, but the reflection from an unnecessary object will be imaged very clearly and will be marked with an x.

Now, in the method of the present invention, in case A where the hot rolled thick steel plate S occupies the entire field of view 115 of the central camera 15, the aperture is individually controlled, and in cases B and C, the central camera 15
is controlled to the same aperture value. Therefore, in case A, the aperture value is sufficient for detecting the edges of the hot-rolled thick steel plate S, but the aperture value is such that unnecessary objects are not imaged and is marked with a circle. In addition, in case B, the aperture value is the same as that of the central camera 15, so unnecessary objects are not imaged, and the hot rolled thick steel plate S is taken by the central camera 1.
The image is captured to the same extent as in case 5, and is marked with a circle. Furthermore, in the case of C, since the hot-rolled thick steel plate S does not originally exist, it goes without saying that this is not imaged, but the central camera 15
Since the aperture value is the same as that of , the aperture value is quite narrow, so unnecessary objects are not captured and the image is marked with a circle. As for the reflected light from unnecessary objects, as is clear from the above explanation,
Since it will not be imaged, it will be marked O.

On the other hand, when the hot-rolled thick steel plate S occupies only a part of the field of view 115 of the central camera 15, in A and B, as described above,
In C, the aperture value is controlled to be the same as that of the central camera 15. Therefore, in the case of A and H, it will be marked O as above, and in case C, it will be marked ○ as above, but regarding the reflected light from unnecessary objects, the center camera 15 and the aperture of each camera in case of B and C. Since they are relatively open and have the same value, they are marked with Δ.

From the above, it can be seen that the method of the present invention, when compared to the conventional general method and when all the cameras have the same aperture value as the central camera 15, It is understood that while the inter-rolled thick steel plate S is clearly imaged, unnecessary objects are not imaged at all or are imaged only to the extent that software processing is not required.

〔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. Its accuracy also improves.

In the above embodiment, a case was explained 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. The present invention is applicable, and in this case, the comparison results between the level of the video signal of each imaging device and the reference value may be reversed. Moreover, it goes without saying that it is 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 degree of exposure and the shutter speed.

[Brief Description of the Drawings] 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 subject of implementation of the method of the present invention, and Fig. 2 shows its nine television cameras and their Figure 3 is a plan view showing the positional relationship between the field of view and the hot-rolled thick steel plate that is the object of imaging.
a) is a block diagram showing the aperture control mechanism of the central camera that serves as a reference, A) is a block diagram showing the aperture control mechanism of other cameras, Fig. 4 is a timing chart of aperture control, and Fig. 5
The figure is an explanatory diagram showing the relationship between the field of view position of the central camera and the measurement position of a hot rolled thick steel plate. 1...Camera house 11-19...TV camera 11c-14C, 16C-19C...Comparison circuit 1
1E ~ 19E ... Light reception level control circuit 11J ~
11... Lens system 111-119... Field of view of TV camera S... Hot rolled thick steel plate

Claims (1)

[Claims] 1. A composite image obtained by combining images respectively captured by a plurality of imaging devices is imaged by stopping an imaging target moving on a predetermined route at a position on the route. In this exposure control method, the exposure of the reference imaging device is controlled over time so that the level of its video signal matches a predetermined level, and 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 exposure of the reference imaging device, and the measurement results are used when the imaging target stops at the predetermined position. After the image capture device has stopped, the image capture device is compared with the reference level set for each image capture device, and the image capture devices whose video signal level is higher (or lower) than the reference level are controlled to match the respective reference level, and the image An exposure control method for a plurality of imaging devices, characterized in that an imaging device whose signal level is smaller (or larger) than the reference level is controlled substantially in the same manner as the reference imaging device.