JP2005055318A - Road surface photographing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of photographing a long road surface in a fixed photographing condition. <P>SOLUTION: This road surface photographing device 10 is equipped with a vehicle 20 running on the road, an in-vehicle light group 36 for illuminating the road surface 28, and an in-vehicle camera 22 for photographing the road surface 28 illuminated by the light group 36. In the road surface photographing device 10, the road surface 28 is illuminated by the light group 36, and the road surface 28 illuminated by the light group 36 is photographed by a camera 22. Hereby, the long road surface 28 can be photographed continuously in the fixed photographing condition in the nighttime when nothing throws a shadow by the sun does not fall. A clear road surface image wherein nothing throws a shadow can be acquired by photographing continuously in the fixed photographing condition. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a road surface photographing apparatus.

The road surface is thin and long, making it difficult to shoot. If you take a picture from a high position using an airplane, you can take a picture of a long road at once, but you cannot take pictures with pixels that are fine enough to investigate the condition of the road (such as cracks or peeling). . In addition, the road surface immediately below the vehicle traveling on the road cannot be photographed.
Therefore, the present applicant has developed a technique for photographing a road surface while traveling with a road surface photographing camera mounted thereon. This technique is disclosed in Patent Document 1. In this technique, a line camera is used. The line camera captures a linear region that extends for one lane in the vehicle width direction and extends a predetermined distance (for example, 1 mm) in the vehicle traveling direction. Every time the vehicle travels a predetermined distance (for example, 1 mm), by repeating the imaging of the linear region, a thin and long road surface can be imaged with fine pixels.
When a linear region with a width of about 1 mm is photographed from a vehicle that cannot avoid vertical vibration by traveling on the road, a linear region far in the traveling direction is photographed first due to the longitudinal vibration of the vehicle, Since it is inevitable that a linear area close to the vehicle will be captured later, it is expected that the road surface image will not be reproduced even if the captured pixels are continued in the order in which they were captured. Actually, the shooting order of the linear area and the order along the traveling direction of the linear area do not reverse, and the road surface image can be reproduced by continuing the pixels shot in the shooting order. confirmed. When this road surface photographing technique is used, it is possible to photograph a thin and long road surface with a resolution that can check the state of the road surface (for example, the presence or absence of cracks and peeling).

JP 2002-54911 A

However, the road surface imaging technique described in Japanese Patent Application Laid-Open No. 2002-54911 still has room for improvement. A shadow of a road installation (for example, a signal or a traffic sign) is projected on the road surface. In addition, the shooting range of the in-vehicle line camera becomes a shadow of the shooting vehicle itself or a shadow of another vehicle. From the photographing result, it is not clear whether the image is dark because the shadow is photographed or whether the image is dark because the surface of the road having low reflectivity is photographed, and a road surface image photographed under a certain condition cannot be obtained.
The present invention has been made to solve the above-described problems, and provides a technique capable of photographing a long road surface under a certain photographing condition.

The road surface photographing device of the present invention includes a vehicle traveling on a road, a vehicle-mounted light group that illuminates the road surface, and a vehicle-mounted camera that captures a road surface illuminated by the light group.
The road surface photographing device illuminates the road surface with the light group, and photographs the road surface illuminated with the light group with a camera. For this reason, it is possible to continue photographing a long road surface under certain photographing conditions at night when the shadow of the sun is not reflected. It is possible to obtain a clear road surface image that is continuously photographed under a certain photographing condition and no shadow is reflected.

In the above road surface photographing device, it is preferable to have at least two lights whose optical axes are directed in different directions.
When the extending direction of the crack on the road surface coincides with the direction of the optical axis of the light, the most part in the crack is illuminated by the light. For this reason, the difference in brightness between the crack and its surroundings is reduced, and the crack cannot be clearly photographed. If at least two lights with different optical axes are used, even if the optical axis of one light coincides with the direction in which the crack extends, the light with a different optical axis direction causes a shadow in the crack. . For this reason, it is possible to photograph the crack clearly.

In the above road surface photographing device, it is preferable that the in-vehicle camera is disposed near the vehicle center in the vehicle width direction, and the light group illuminates the road surface on the vehicle side side more brightly than the road surface near the vehicle center in the vehicle width direction.
When the camera is disposed near the center of the vehicle in the vehicle width direction, the road surface on the side of the vehicle is separated from the camera, and the road surface near the center of the vehicle is photographed in a positional relationship close to the camera. The image captured by the camera becomes darker as the distance between the road surface and the camera increases. When the light group illuminates the road surface on the vehicle side brighter than the road surface on the vehicle center side in the vehicle width direction, it is possible to prevent the road surface on the vehicle side side from being photographed darker than the road surface on the vehicle center side.

In the above road surface photographing device, the in-vehicle light group illuminates a range that is long in the vehicle width direction and short in the vehicle traveling direction, and the in-vehicle camera is a line camera that shoots along the line extending in the vehicle width direction within the illumination range. Is preferred.
According to the above combination, the light group may locally illuminate a short range in the vehicle traveling direction. It is possible to illuminate at high illuminance with a low number of lights and low power consumption. The longer the illumination time with a line camera, the shorter the illumination time. Since shooting is performed with strong local illumination, shooting can be performed while the vehicle is traveling at high speed.

  By using the above road surface photographing device, a road surface image obtained by photographing a road surface having a width of 3.25 m or more and a length of 100 m or more with pixels of 1 mm × 1 mm or less. A road surface image that is not reflected can be taken. This road surface image has been unable to be obtained by conventional techniques and is extremely effective.

The main features of the embodiments described later will be described.
(1) The road surface photographing device includes a measurement vehicle, an illumination unit, a photographing unit, and the like. The illumination part is attached to the front part of the measurement vehicle (microbus). Fourteen lights are provided in the illumination unit. The light illuminates the road surface in front of the road surface photographing device. The optical axis of the light is in a different direction.
(2) The photographing unit has a boom and a line camera. The boom is mounted on the roof of the measuring vehicle. The front end of the boom overhangs in front of the illumination unit. The line camera is attached to the front end of the boom and photographs the road surface from above.
(3) The road surface photographing device travels while illuminating the road surface with lights at night, and continuously captures the illuminated road surface with a line camera.

A road surface photographing apparatus 10 according to an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the road surface photographing device 10 includes a measurement wheel 20, a photographing unit 12, a rotary encoder 18, a control device 16, a storage device 15, and an illumination unit 14.
As shown in FIG. 2, the photographing unit 12 is fixed to a roof carrier 26 attached on the roof 20 a of the measuring wheel 20, and includes a boom 24 and a line camera 22. The tip of the boom 24 is overhanging forward of the front end of the illumination unit 14. The line camera 22 is attached to the lower part of the tip of the boom 24 and photographs the road surface 28 from directly above along the direction perpendicular to the traveling direction of the measuring vehicle 20 (the width direction of the road surface 28). The line camera 22 captures an image input through the lens with an image sensor such as a CMOS or CCD. The line camera 22 has 4096 image sensors, and each image sensor images “1 mm × 1 mm”, so that the image can be taken over a length of 4096 mm at a time. 4096mm is slightly larger than the width of one lane.

As shown in FIG. 1, the rotary encoder 18, the control device 16, and the storage device 15 are attached to the measurement wheel 20. The measuring wheel 20 is a microbus modified for measurement. The rotary encoder 18 is in contact with the road surface 28, and includes a rotation unit 18a that rotates as the road surface photographing apparatus 10 travels, and a rotation detection unit (not shown) that detects the rotation of the rotation unit 18a. The rotary encoder 18 outputs a pulse every time the road surface photographing device 10 travels 1 mm.
The storage device 15 stores the input data in a distributed manner on a plurality of hard disks.
A line camera 22, a rotary encoder 18, and a storage device 15 are connected to the control device 16. The control device 16 is a computer including a CPU, a ROM, a RAM, and the like. The control device 16 executes a control program stored in the ROM using the pulse signal input from the rotary encoder 18, and sends a control signal (exposure start signal) for each designated number of pulses to the line camera 22. Is output to the line camera 22 every time the road surface photographing device 10 travels 1 mm. Accordingly, the road surface 28 is continuously photographed by the line camera 22. Further, the control device 16 grasps the travel distance of the road surface photographing device 10 after starting photographing of the road surface 28 based on the pulse signal input from the rotary encoder 18. Then, the control device 16 associates each photographed image data with the travel distance of the road surface photographing device 10 after starting the photographing of the road surface, and causes the storage device 15 to store them.
When the road surface photographing device 10 travels, it is unavoidable that the road surface photographing device 10 itself sways due to road surface unevenness. When the road surface photographing device 10 is pitched (pitched), the optical axis of the line camera 22 is repeatedly directed forward or backward along the traveling direction. For this reason, it has been considered that a clear road surface image cannot be captured with the configuration of the road surface photographing device 10. The inventor challenged the technical common sense and actually photographed the road surface 28 with the road surface photographing device 10, and was able to photograph a clear road surface image. The clear road surface image can be captured in this way because the pitching period associated with the traveling of the road surface image capturing device 10 is not so fast, and its influence can be substantially ignored.

As shown well in FIG. 2, the illumination unit 14 has a substantially box shape and is attached to the lower part of the front end of the measurement wheel 20. A front window 32 and a side window 33 made of transparent glass are provided on the front surface and both side surfaces of the illumination unit 14. When a light 36 (described later) provided in the illumination unit 14 is turned on at the bottom of the illumination unit 14, light enters the field of view of the driver of the oncoming vehicle or the preceding vehicle from the illumination unit 14. A panel (not shown) for preventing leakage to the lower road surface 28 is attached. A license plate 35 and a traveling light 34 that illuminates the front when traveling at night are attached to the front of the illumination unit 14.
As shown in FIGS. 3 and 4, the illumination unit 14 is provided with 14 lights 36. (In the following, for the sake of convenience of explanation, the lights 36 are denoted by reference numerals L1 to L14. Then, the individual lights 36 are specified using the signs L1 to L14. Identify light 36). The lights 36 of L1 to L12 are mounted inside the illumination unit 14, and when illuminated, the road surface 28 is illuminated through the front window 32 and the side window 33. Lights L13 and L14 are mounted outside the illumination unit 14 and illuminate the road surface 28 when turned on. The light 36 is attached to the illumination unit 14 via a bracket (not shown). The light 36 is a metal halide light.

As shown in FIG. 4, the directions of the optical axes of the lights 36 are different from each other. As shown in FIG. 5, the optical axis of the light 36 viewed from the side is inclined by about 45 degrees with respect to the road surface 28, and the lights 36 of L13 and L14 are inclined. Is inclined about 30 degrees with respect to the road surface 28. The horizontal distance between the lights 36 of L1 to L12 and the point where their optical axes intersect with the road surface 28 is about 80 cm.
The light 36 illuminates the road surface 28 as in the illumination circles H1 to H14 shown in FIG. Illumination circles H1 to H14 indicate portions that are strongly illuminated by the light 36, and the outside of the range is also illuminated by the light 36. The numbers (H1 to H14) given to the illumination circles H1 to H14 correspond to the numbers L1 to L14 of the light 36. For example, the illumination circle H6 is illuminated by the light 36 of L6. Reference numeral 47 indicates a linear region that the line camera 22 captures at a time.

  The road surface photographing device 10 travels while illuminating the road surface 28 with lights 36 at night, and the illuminated road surface 28 is photographed with the line camera 22. The image data photographed by the line camera 22 and stored in the storage device 15 is downloaded to a processing device installed in a road management office or the like, and is further output as a road surface image 40 from the printer. FIG. 6 illustrates a part of the output road surface image 40. In the road surface image 40, a crack 43 in the road surface 28 and a line 42 drawn on both sides of the road surface 28 are photographed. The road surface photographing device 10 of the present embodiment can photograph a road surface image 40 having a width of 3.25 m or more and a length of 100 m or more with 1 mm × 1 mm pixels.

On the road surface 28 in the daytime, a building such as a building by the sun, the road surface photographing device 10 itself, and the shadow of a car traveling in front of the road surface photographing device 10 and right and left are reflected. For this reason, even if the road surface photographing device 10 photographs the road surface 28 in the daytime, a shadow is reflected and a clear road surface image 40 cannot be captured. Since the road illuminance difference between the shadow and the sun is large, both the shadow and the sun cannot be included in the range in which the sensitivity of the line camera 22 is good. In the road surface image 40 picked up by the line camera 22, when the sensitivity is adjusted to the brightness of the shadow, the sunny portion and the white line portion are saturated and white. When the sensitivity is adjusted to the brightness of the sun, the shadow part becomes dark and noise appears.
Of course, no shadows from the sun appear on the road surface 28 at night. Therefore, a clear road surface image 40 can be obtained by photographing the road surface 28 while illuminating with the light 36 at night. There is little traffic at night (especially at midnight). For this reason, it is possible to perform shooting at a slower traveling speed of the road surface photographing device 10. If shooting can be performed with the traveling speed of the road surface photographing device 10 being reduced, the shake of the line camera 22 is reduced, and a clearer road surface image 40 can be photographed. Further, when traveling at night, since the traffic volume is small, the change in the traveling speed of the road surface photographing device 10 can be reduced. If the change in the traveling speed of the road surface photographing device 10 can be reduced, the slip generated between the rotating portion 18a of the rotary encoder 18 and the road surface 28 is reduced. For this reason, imaging accuracy is improved.

As shown in FIG. 7, when the light having the optical axis 45 illuminates the crack 43, a shadow 46 is generated inside the crack 43. When a shadow 46 (a portion indicated by a thick line) is generated inside the crack 43, the difference in brightness between the crack 43 and the surrounding area becomes large, and the crack 43 can be photographed clearly (clearly).
FIG. 8 schematically shows a state in which the light 36 having a different direction of the optical axis 45 is illuminating the crack 43 in the road surface 28. The crack 43 in FIG. 8 extends in parallel with the traveling direction of the road surface photographing device 10. If the optical axes 45 of all the lights 36 are oriented in only one direction, if the optical axis 45 and the direction in which the crack 43 extends coincide with each other or almost coincide with each other, most of the inside of the crack 43 is illuminated. The For this reason, no shadow is generated inside the crack 43. If there is no shadow inside the crack 43, the crack 43 cannot be photographed clearly. As shown in FIG. 8, when the crack 43 is illuminated by the light 36 having a different optical axis 45 direction, a shadow is always generated in the crack 43 regardless of the direction in which the crack 43 extends. Therefore, the crack 43 can be clearly photographed.
As shown in FIG. 9, the light 36 illuminates the crack 43 so as to look down diagonally forward. For this reason, as shown in FIG. 10, when the crack 43 extends at right angles to the traveling direction of the road surface photographing device 10, the shadow is darker inside the crack 43. Therefore, the crack 43 can be photographed more clearly.

As shown in FIG. 12, the distance between the line camera 22 and the road surface 28 increases as the distance from the line camera 22 in the width direction of the measuring vehicle 20 increases (D1> D2). Further, the image taken by the line camera 22 becomes darker as the distance from the subject to be photographed (road surface 28) increases. For this reason, when the line camera 22 captures the road surface 28 while the brightness of the road surface 28 is constant, in the obtained road image 40, the central portion of the road surface 28 is bright and the side portions of the road surface 28 are dark, which is different from the actual situation. End up. If the light and darkness of the road surface image 40 is different from the actual one, it is difficult to check the state of the road surface 28.
On the other hand, as shown well in FIG. 4, the illumination circles H1 to H12 by the lights 36 of L1 to L12 are distributed almost uniformly. The illumination circle H13 by L13 overlaps with the illumination circles H1 and H3. The illumination circle H14 by L14 overlaps with the illumination circles H10 and H12. Further, since the lights 36 of L13 and L14 are arranged in front of and below the lights 36 of L1 to L12, they are closer to the road surface 28 than the lights 36 of L1 to L12. For this reason, as shown in FIG. 11, the illuminance (brightness) distribution of the road surface 28 along the width direction of the measurement wheel 20 is dark at the center in the width direction of the measurement wheel 20, and then It shows a tendency to become brighter as it moves away from the side.
When the brightness of the road surface 28 is distributed as shown in FIG. 11, the brightness (sensitivity) of the road surface 28 felt as the line camera 22 is the width of the measurement vehicle 20 as shown in FIG. It becomes constant along the direction. Therefore, the contrast of the road surface image 40 photographed by the line camera 22 is prevented from being different from the actual one.
Further, the road surface 28 having a cross-sectional cross section is farther from the line camera 22 on the side than the flat road surface 28. Therefore, when shooting the road surface 28 with a cross-section, the position of the light 36 and the direction of the optical axis are set so that the road surface 28 on the side of the measuring vehicle 20 becomes brighter than when shooting the flat road surface 28. It is preferable to adjust. In this way, it is possible to prevent the light and darkness of the road surface image 40 obtained by photographing the road surface 28 having a cross-section of the cross section from being different from the actual one.

A plurality of line cameras 22 may be arranged along the width direction of the measuring wheel 20. For example, one line camera 22 is arranged at the center position in the width direction of the measuring vehicle 20 to photograph the central portion of the road surface 28, and one line camera 22 is arranged on each side to photograph the shoulder portion of the road surface 28. To do. In this way, if each line camera 22 is configured to photograph a portion of the road surface 28, the actual light and darkness of the road surface 28 can be obtained without changing the illuminance distribution on the road surface 28 along the width direction of the road surface 28. The reproduced road surface image 40 can be taken.
There is no need to

  As already described, the light 36 is a metal halide light. Metal halide lights have high luminous efficiency and high brightness. When a metal halide light is turned on with alternating current power, there is no bias in electrode consumption, so the life is long, and it is widely used for general purposes. On the other hand, in image processing, since a change in brightness is not preferable, a light that is lit with DC power has been used in many cases. In the road surface photographing device 10 of the present embodiment. As shown in FIG. 14, the high-frequency AC power that turns on the light 36 has a rectangular waveform by the inverter. When the AC power waveform is rectangular, the turn-off time of the light 36 when the polarity changes is shortened. Furthermore, since the period of the rectangular waveform is sufficiently shorter than the exposure time of the line camera 22, the amount of light received by the line camera is substantially uniform during all exposure periods. Therefore, the time during which the light 36 is turned off can be substantially ignored, and illumination can be performed by taking advantage of low cost and low power consumption.

  Instead of the line camera 22, an area camera that captures a two-dimensional range can also be used. By directing the area camera substantially directly below, the same effect as that of the line camera 22 can be obtained, but in this case, a plurality of cameras are required to capture a 4 m width. When an area camera is used, an image extending in the width direction of the road surface and the traveling direction of the road surface photographing device 10 can be obtained at one time. However, when photographing directly below, an obstacle such as a vehicle ahead is reflected, or the road surface photographing device. There is a difficulty that 10 itself is reflected. When the optical axis of the area camera is tilted with respect to the vertical direction, the imaging range is expanded, but the accuracy per pixel is not uniform, and the inclination of the road surface 28 is unknown, so a plurality of images are joined in order of the traveling direction. It becomes difficult. For this reason, the imaging by the area camera is generally inferior to that by the line camera 22.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
In addition, the technical elements described in the present specification or drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

1 is a schematic diagram of a road surface photographing apparatus and a measurement vehicle according to an embodiment. 1 is a perspective view of a road surface photographing device and a measurement vehicle according to an embodiment. Explanatory drawing of the light arrangement | positioning which looked at the illumination part which concerns on an Example from the front. Explanatory drawing of the light arrangement | positioning which looked at the illumination part which concerns on an Example from upper direction. Explanatory drawing of the light arrangement | positioning which looked at the illumination part which concerns on an Example from the side. An example of the road surface image which concerns on an Example is shown. Sectional drawing of the crack which entered into the road surface concerning an Example. The schematic diagram of the state which the light is illuminating the crack parallel to a running direction which looked at the illumination part which concerns on an Example from upper direction. The schematic diagram of the state which the light has illuminated the crack which looked at the illumination part and imaging | photography part which concern on an Example from the side. The schematic diagram of the state which the light is illuminating the crack at right angles to a running direction which looked at the illumination part which concerns on an Example from upper direction. The graph which shows the relationship between the measurement vehicle width direction and road surface illumination which concern on an Example. Explanatory drawing of the distance of the line camera which concerns on an Example, and a road surface. The graph which shows the relationship between the measurement vehicle width direction which concerns on an Example, and the illumination intensity as a line camera. The wave form diagram of the alternating current power which lights the light which concerns on an Example.

Explanation of symbols

10: road surface photographing device 12: photographing unit 14: illumination unit 15: storage device 16: control device 18: rotary encoder 20: measuring wheel 20a: roof 22: line camera 24: boom 26: roof carrier 28: road surface 32: front Window 33: Side window 34: Traveling light 35: License plate 36: Light 40: Road surface image 42: Line 43: Crack 45: Optical axis 46: Shadow 47: Linear area

Claims (5)

It is a device that photographs the road surface,
A road surface photographing apparatus comprising: a vehicle traveling on a road; a vehicle-mounted light group that illuminates a road surface; and a vehicle-mounted camera that images a road surface illuminated by the light group.   The road surface photographing device according to claim 1, comprising at least two lights whose optical axes are directed in different directions.   The in-vehicle camera is disposed near the center of the vehicle in the vehicle width direction, and the light group illuminates the road surface on the vehicle side brighter than the road surface near the center of the vehicle in the vehicle width direction. The road surface photographing device described.   The in-vehicle light group illuminates a range that is long in the vehicle width direction and short in the vehicle traveling direction, and the in-vehicle camera is a line camera that captures images along a line extending in the vehicle width direction within the illumination range. 4. The road surface photographing device according to any one of items 1 to 3.   A road surface obtained by photographing a road surface of width 3.25 m or more and length 100 m or more with pixels of 1 mm × 1 mm or less, in which road installations, road vehicles, and shadows thereof are not reflected. image.

Images