JP2005311798A - Imaging device and imaging method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To photograph image of a photographic target, from a traveling vehicle, using an appropriate exposure time. <P>SOLUTION: First and second image inputting means (5 and 7) are arranged at the front side and rear side of a vehicle traveling direction, respectively, and first, a first image input device (5) photographs the photographing target (9). The brightness of the image, photographed by the first image input device (5), is calculated, and an optimum exposure time of the second input device (7) is set at a photographing position of the first image input device (5) on the basis of the brightness. The exposure time of the second image input device (7) is set to the calculated optimum exposure time at a timing when the second image input device (7) reaches the photographing position of the first image input device (5). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus that captures an object to be photographed from a traveling vehicle, and more particularly to an imaging apparatus and an imaging method that are suitable for use when capturing an image of a structure around a track in a new traffic system or the like.

In an image input device such as a television camera using a solid-state image sensor, exposure control is executed in order to cope with a change in illuminance of a subject. That is, for example, a liquid crystal filter is disposed on the light incident surface side of the solid-state image sensor, and the light transmittance of the liquid crystal filter is changed according to the video output level of the solid-state image sensor. When the light transmittance of the liquid crystal filter increases beyond the variable range, the charge accumulation time of the solid-state imaging device is shortened (see, for example, Patent Document 1).
Actual Kaihei 1-159470

  However, since the above prior art is exposure control based on feedback control, when the image input means is disposed in a traveling vehicle, an appropriate exposure according to a change in illuminance of the subject is caused due to a delay in exposure control. It has a problem that it cannot be realized.

  In view of such a situation, an object of the present invention is to set an appropriate exposure time corresponding to the brightness of a shooting target, and to appropriately capture an image of the shooting target from a traveling vehicle, and It is to provide an imaging method.

  The imaging apparatus according to the present invention includes first and second image inputs arranged on the front side and the rear side in the running direction of the vehicle, respectively, in order to take an image of a shooting target from the running vehicle with an appropriate exposure time. Means, brightness detection means for detecting the brightness of the image to be photographed by the first image input device, and a second image at the photographing position of the image based on the brightness of the image. Optimal exposure time setting means for setting an optimal exposure time of the input device, and the optimal exposure time at the timing when the second image input device reaches the photographing position of the first image input device. Exposure time instructing means for instructing as an exposure time for the input device.

  In the case where the subject to be photographed is a welded portion of a reaction plate for a linear motor that is intermittently present in the traveling direction of the vehicle, illumination means for illuminating the welded portion so that the brightness of the welded portion is brighter than the surrounding brightness. The brightness detection means is further provided, wherein the brightness detection means detects a range of the welded portion based on the brightness of the welded portion photographed by the first image input device and the surrounding image. And calculating means for calculating the brightness of the range of the welded portion as the brightness of the photographing object.

ここで、ｘは前記溶接部範囲における画素の横方向の位置、ｙは該溶接部範囲における画素の縦方向の位置、Ｉ（ｘ、ｙ）は位置（ｘ、ｙ）の画素の輝度値、Ｂは溶接部範囲、Ｎは溶接部範囲に含まれる画素の数である。 The brightness of the range of the weld can be calculated according to the following formula.

Where x is the horizontal position of the pixel in the weld zone, y is the vertical position of the pixel in the weld zone, I (x, y) is the luminance value of the pixel at position (x, y), B is the weld zone and N is the number of pixels included in the weld zone.

  In the imaging method according to the present invention, first and second image input means are arranged on the front side and the rear side in the running direction of the vehicle, respectively, in order to take an image of the shooting target from the running vehicle with an appropriate exposure time. Based on the brightness of the image, the step of photographing the photographing object by the first image input device, the step of calculating the brightness of the image photographed by the first image input device, And setting the optimum exposure time of the second image input device at the photographing position, and at a timing when the second image input device reaches the photographing position of the first image input device. Setting the exposure time of the image input device to the optimum exposure time.

  In the case where the object to be photographed is a welded portion of a reaction plate for a linear motor that is intermittently present in the traveling direction of the vehicle, the step of illuminating the welded portion so that the brightness of the welded portion is brighter than the surrounding brightness. The step of adding and calculating the brightness of the image includes detecting the range of the weld based on the brightness of the image of the weld and its surroundings photographed by the first image input device; Calculating the brightness of the range of the weld as the brightness of the object to be photographed. In this case, the brightness of the range of the welded portion can be calculated according to the above formula.

  According to the present invention, it is possible to set an appropriate exposure time corresponding to the brightness of an object to be imaged and appropriately capture an image of the object to be imaged from a traveling vehicle. Therefore, the present invention is extremely effective as a means for photographing an image of a track peripheral structure such as a new traffic system, for example, a welded portion of a reaction plate for a linear motor or a surface portion of an inner wall of a tunnel.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of an imaging apparatus according to the present invention as viewed from above. As is apparent from this schematic diagram, the imaging apparatus of this embodiment is mounted on a vehicle 3 that travels on a rail 1.

In this imaging apparatus, the image input devices 5 and 7 are disposed on the front side and the rear side in the traveling direction of the vehicle 3 in order to take a picture of the subject 9. As the image input device 5, for example, a CCD camera is used, and as the image input device 7, for example, a CCD camera capable of controlling the exposure time is used.
The brightness calculation device 11 calculates the brightness of an image taken by the image input device 5, and can be constituted by, for example, a personal computer equipped with an image input board.
The vehicle position detection device 13 is provided for detecting the traveling position of the vehicle 3. The vehicle position detection device 13 is composed of, for example, a rotary encoder that operates in accordance with the rotation of a wheel (not shown) of the vehicle 3 and a device that receives information from a ground unit (not shown).
As will be described later, the exposure time control device 15 optimally sets the exposure time of the image input device 7 based on the outputs of the brightness calculation device 11 and the vehicle position detection device 13, and is constituted by a sequencer or the like. Is done.

  The arrangement interval of the image input devices 5 and 7 can be appropriately set in consideration of the traveling speed of the vehicle 3, the frame rate of the image input devices 5 and 7, and the like. For example, when the traveling speed of the vehicle 3 is 10 km / h and the frame rate of the image input devices 7 and 9 is 30 frame / s, the interval between the image input devices 7 and 9 is set to about 40 cm.

  FIG. 2 shows the reaction plate 17 of the linear motor. The reaction plate 17 formed of aluminum or the like is provided between the rails 1 shown in FIG. 1 along the longitudinal direction of the rails 1. As shown in FIG. 3 which is an XX cross-sectional view of FIG. 2, the reaction plate 17 is disposed on a pedestal 19, and welded portions 21 for fixing to the pedestal 19 are provided on both sides thereof in the longitudinal direction. It is formed intermittently along.

When the photographing object 9 shown in FIG. 1 is the welded portion 21 of the reaction plate 17, the image input devices 5 and 7 and the illumination light source 23 are arranged in the posture shown in FIG. In other words, the image input devices 5 and 7 are arranged so that the welded portion 21 enters the field of view from obliquely above, and the illumination light source 23 has its optical axis orthogonal to the upper surface of the reaction plate 17 and the pedestal 19. Placed in.
If the image input device 5 and the illumination light source 23 are arranged as described above, the image input device 5 has an image as shown in FIG. 4, that is, the brightness of the side surface of the reaction plate 17 is remarkably higher than the surrounding area. Take a low image.

Here, a method for detecting the range of the welded portion from the image shown in FIG. 4 will be described.
Based on the mechanical characteristics of the vehicle 3, the optical characteristics of the image input devices 5 and 7, the range R1 where the boundary B1 between the upper surface and the side surface of the reaction plate exists is determined. Therefore, in the range R1, after the luminance is projected in the horizontal direction, the luminance difference is taken in the vertical direction, and the position where the difference becomes maximum is set as the boundary B1. If the thickness of the reaction plate is assumed to be constant, the distance from the boundary B1 to the boundary B2 between the side surface of the reaction plate and the pedestal is constant. Therefore, the position of the boundary B2 is determined based on the position of the boundary B1. .

  Next, the horizontal range RH of the welded portion is determined based on the luminance change in the horizontal direction (the AA direction in FIG. 4) at the upper portion of the boundary B2. As shown in FIG. 5, the luminance in the horizontal direction is small at the side surface portion of the reaction plate 17 and is large at the welded portion 21. Therefore, a luminance threshold value α is determined, and a portion where the luminance is larger than the threshold value α is detected as a horizontal range RH of the welded portion. If the vertical width of the welded portion 21 is regarded as constant, the vertical range RV of the welded portion 21 is determined. The logical product of the range RH and the range RV is set as the range of the welded portion 21.

ここで、ｘは画素の横方向の位置、ｙは画素の縦方向の位置、Ｉ（ｘ、ｙ）は位置（ｘ、ｙ）の画素の輝度値、Ｂは溶接部範囲、Ｎは溶接部範囲に含まれる画素の数である。 Hereinafter, the operation of the imaging apparatus according to the present invention will be described. FIG. 6A shows a state in which the image input device 5 is located at the position P. At this time, the image obtained by the image input device 5 has a configuration in which pixels having a certain luminance within a range of 0 to 255 are arranged vertically and horizontally as shown in FIG. 9, for example.
The brightness calculation device 11 (see FIG. 1) detects the range 21 ′ of the welded portion in the image of FIG. 9 by the above method, and calculates the brightness of the range 21 ′. The brightness i of this weld zone range is calculated based on the following equation.

Here, x is the horizontal position of the pixel, y is the vertical position of the pixel, I (x, y) is the luminance value of the pixel at the position (x, y), B is the weld zone, and N is the weld zone. The number of pixels included in the range.

  The exposure time control device 15 determines the image at the position P based on the brightness of the weld zone 21 ′ calculated by the brightness calculation device 11 and the position of the vehicle 3 detected by the vehicle position detection device 13. The optimum exposure time of the input device 7 is set and held. Further, the exposure time control device 15 constantly monitors the vehicle position information sent from the vehicle position detection device 13, and when the position of the vehicle 3 changes until the image input device 7 reaches the position immediately before the position P. The image input device 7 is instructed about the held exposure time, that is, the optimum exposure time of the image input device 7 at the position P.

FIG. 7 shows a specific example of the configuration of the exposure time control device 15. In the figure, the brightness-exposure time conversion unit 151 is based on the information indicating the brightness of the welded part range 21 ′ sent from the brightness calculation device 11, and the brightness of the welded part range 21 ′. Is converted into the optimum exposure time of the image input device 7.
The above-described conversion process in the brightness-exposure time conversion unit 151 corresponds to a short exposure time when the brightness of the conversion table as shown in FIG. It is executed using a conversion table that corresponds to a long exposure time when it is small. The relationship shown in FIG. 10 can be obtained in advance by experiment or simulation.

  The position conversion unit 152 converts vehicle position information sent from the vehicle position detection device 13 into position information of the image input device 5. In the conversion by the position conversion unit 152, the time required for photographing by the image input device 5 and the time required for the brightness calculation device 11 to calculate the brightness are considered. The position conversion unit 153 converts the vehicle position information into position information of the image input device 7. The position information output from the position conversion units 152 and 153 is given to the exposure time transmission unit 154.

  In the exposure time control unit 15 configured as described above, when information indicating the brightness of the welded part range 21 ′ is sent, the optimum exposure time which is the output of the brightness-exposure time conversion unit and the conversion are converted. The position of the image input device 5 that is the output of the unit 152 is written in the position-exposure time correspondence table 155. Then, at the timing when the position of the image input device 7, which is the output of the conversion unit 153, approaches any position on the position-exposure time correspondence table 155, the exposure time corresponding to that position is the position-exposure time correspondence table 15. Is read from. The exposure time information read from the table 15 is instructed to the image input device 7 as exposure time information for the image input device 7, whereby the exposure time of the image input device 7 is indicated in the reaction plate 17. The exposure time is controlled to be optimal for photographing the welded portion 21.

  As described above, according to the imaging apparatus according to the present embodiment, the brightness of the welded portion 21 that is a subject to be photographed is calculated based on the image output of the preceding image input apparatus 5, and the optimum exposure for this brightness is calculated. Since the time is set in the subsequent image input device 7, an image of the welded portion 21 can be taken with an appropriate exposure time in the traveling vehicle.

  Although the said embodiment is applied to imaging | photography of the welding part 21 of the reaction plate 17, this invention is applicable also to imaging | photography of other imaging | photography objects, for example, the inner surface of a tunnel. In this case, the brightness of the image photographed by the image input device 5 can be obtained, for example, by taking the average of the luminance values of the pixels constituting the image.

Here, as shown in FIG. 8, the exposure control in the case where the light reflection inhibition portion 9a due to rust, dirt, etc. is present in the photographing object 9 will be considered.
In order to appropriately capture an image of the light reflection inhibition unit 9, as shown by a dotted line in FIG. 8A, the exposure time at the time of imaging of the light reflection inhibition unit 9 is the exposure time when imaging other parts. Need to be longer. When the exposure control is not performed, as shown by a solid line in FIG. 8A, the exposure time suitable for photographing the other part is fixedly set. I can't get an image.

  On the other hand, according to the conventional exposure control described in Patent Document 1 described above, as shown in FIG. 8B, appropriate exposure is performed only on a part of the light reflection inhibition portion 9a due to the delay in exposure control. Since the time is set, it is not possible to properly capture the entire image of the light reflection inhibition unit 9a.

  On the other hand, according to the present invention, as shown by the solid line in FIG. 8A, the exposure time suitable for the light reflection inhibition portion 9a is set during the photographing period of the light reflection inhibition portion 9a. An appropriate image of the light reflection inhibition portion 9a can be obtained.

It is a mimetic diagram of an imaging device concerning the present invention arranged in vehicles which run on a rail. It is a top view which shows the arrangement | positioning form of a reaction plate. It is XX sectional drawing of FIG. FIG. 4 shows a photographed image by an image input device arranged in the form shown in FIG. 3. It is a graph which shows the brightness | luminance change of the image containing a welding part. (A) is a conceptual diagram which shows the state which reached | attained a certain position with the preceding image input device. (B) is a conceptual diagram showing a state in which a subsequent image input apparatus has reached the certain position. It is the block diagram which illustrated the composition of the exposure time control device. (A) is an exposure time setting mode without exposure control, (a) is a conventional exposure time control mode, and (c) is a graph showing an exposure time control mode according to the present invention. It is. It is the schematic diagram which illustrated the pixel arrangement | sequence of the image obtained by an image input device. It is the graph which illustrated the contents of the conversion table used for brightness-exposure time conversion.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Vehicle 5, 7 Image input device 9 Image | photographing object 11 Brightness calculation device 13 Vehicle position detection device 15 Exposure time control device 17 Reaction plate 19 Base 21 Welding part 23 Light source

Claims (6)

An apparatus for photographing an object to be photographed from a running vehicle,
First and second image input means respectively disposed on the front side and the rear side in the running direction of the vehicle;
Brightness detection means for detecting the brightness of the image to be imaged captured by the first image input device;
An optimum exposure time setting means for setting an optimum exposure time of the second image input device at the photographing position of the image based on the brightness of the image;
Exposure time instruction means for instructing the optimum exposure time as an exposure time for the second image input device at a timing when the second image input device reaches the photographing position of the first image input device;
An imaging apparatus comprising: In the case where the object to be imaged is a welded portion of a reaction plate for a linear motor that exists intermittently in the traveling direction of the vehicle,
Illuminating means for illuminating the welded portion so that the brightness of the welded portion is brighter than the surrounding brightness,
The brightness detection means includes
A welded part range detecting means for detecting a range of the welded part based on brightness of the image of the welded part and its surroundings photographed by the first image input device;
Calculating means for calculating the brightness of the range of the welded portion as the brightness of the photographing object;
An image photographing apparatus comprising: The image photographing device according to claim 2, wherein brightness of the range of the welded portion is calculated according to the following formula.

Where x is the horizontal position of the pixel in the weld zone, y is the vertical position of the pixel in the weld zone, I (x, y) is the luminance value of the pixel at position (x, y), B is the weld zone and N is the number of pixels included in the weld zone. A method for photographing an object to be photographed from a running vehicle,
Disposing first and second image input means on the vehicle traveling direction front side and rear side, respectively;
Photographing the photographing object with the first image input device;
Calculating the brightness of an image captured by the first image input device;
Setting an optimal exposure time of the second image input device at the shooting position based on the brightness of the image;
Setting the exposure time of the second image input device to the optimum exposure time at the timing when the second image input device reaches the photographing position of the first image input device;
An imaging method comprising: In the case where the object to be imaged is a welded portion of a reaction plate for a linear motor that exists intermittently in the traveling direction of the vehicle,
A step of illuminating the welded portion so that the brightness of the weld is brighter than the surrounding brightness is further added,
The step of calculating the brightness of the image includes
Detecting a range of the welded portion based on brightness of the image of the welded portion and its surroundings photographed by the first image input device;
Calculating the brightness of the range of the weld as the brightness of the object to be photographed;
The imaging method according to claim 4, further comprising: The imaging method according to claim 5, wherein brightness of the range of the welded portion is calculated according to the following formula.

Where x is the horizontal position of the pixel in the weld zone, y is the vertical position of the pixel in the weld zone, I (x, y) is the luminance value of the pixel at position (x, y), B is the weld zone and N is the number of pixels included in the weld zone.

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