JP2008158659A - Vehicle imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle imaging apparatus recognizing a license plate with high image quality and imaging a driver in a simple structure. <P>SOLUTION: The vehicle imaging apparatus comprises a camera part having a vertically long field covering from a license plate to the driver's seat of a large-sized vehicle. The camera part is about 140 cm high. The vehicle imaging apparatus further comprises an upper lighting part disposed above the camera part to light the driver's seat of a large-sized vehicle, and a lower lighting part disposed under the camera part to illuminate the driver's seat and license plate of a standard-sized vehicle. The lighting parts use LEDs having a center wavelength of 780 nm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a vehicle photographing apparatus that is installed on a roadside and photographs a vehicle.

  In order to identify information on vehicles that have passed at highway toll booths or the like, a device that takes a license plate and reads the information on the license plate by image recognition processing is used.

  Patent Document 1 describes a technique related to recognition of a light type license plate.

In Patent Document 2, as a technique related to smear processing of an electronic imaging device, a solid-state imaging device of the electronic imaging device is arranged vertically, and a railway monitoring stereo camera that shifts the smear generation direction of the fixed imaging device and the vertical direction of the imaging target is disclosed. Is described.
JP-A-11-339176 JP 2005-64612 A

  There is a need for a technology that can recognize license plates more accurately. Further, in order to identify the vehicle, an image obtained by photographing the driver of the vehicle is required. There is a need for a simple device that meets these requirements.

  An object of the present invention is to provide a vehicle photographing apparatus that enables recognition of a high-quality license plate and photographing of a driver with a simple configuration.

  In the following, means for solving the problem will be described using the numbers used in [Best Mode for Carrying Out the Invention] in parentheses. These numbers are added to clarify the correspondence between the description of [Claims] and [Best Mode for Carrying Out the Invention]. However, these numbers should not be used to interpret the technical scope of the invention described in [Claims].

  A vehicle photographing device (10) according to the present invention includes a camera unit (20) having a vertically long field of view covering from a license plate to a driver seat of a large vehicle. The height of the camera unit (20) is about 140 cm. The vehicle photographing device (10) is further installed above the camera unit (20), and is installed below the upper illumination unit (22) for illuminating the driver's seat of a large vehicle and the camera unit (20). And a lower illumination part (24) for illuminating the license plate. Those illumination units illuminate with an LED having a central wavelength of 780 nm.

  More specifically, the vehicle photographing device (10) according to the present invention is a vehicle on a road via a casing (18) installed on the road side of the road (2) and a lens installed on the casing (18). The camera unit (20) that performs the shooting of (4), the upper illumination unit (22) that is installed above the lens of the housing (18) and illuminates the upper illumination range (L7, L8), and the housing (18) ) And a lower illumination unit (24) that illuminates the lower illumination range (L1 to L6).

  In the vehicle photographing device (10) according to the present invention, when the housing (18) is installed on the ground, the vertical distance between the lens and the road surface of the road (2) is 130 cm or more and 150 cm or less.

  In the vehicle photographing device (10) according to the present invention, the upper illumination range (L7, L8) is directed toward the face of the driver of the large vehicle.

  In the vehicle photographing device (10) according to the present invention, the lower illumination unit (24) is inclined with respect to the first substrate, the first light emitting diode unit (26) installed on the first substrate, and the first substrate. A second substrate, and a second light emitting diode portion (30) set on the second substrate and set at a position where the illumination range is lower than that of the first light emitting diode portion.

  In the vehicle photographing device (10) according to the present invention, the range (L5, L6) illuminated by the first light emitting diode part (26) is narrower than the range (L1, L2) illuminated by the second light emitting diode part (30).

  In the vehicle photographing device (10) according to the present invention, the range (L5, L6) illuminated by the first light emitting diode unit is directed toward the face of the driver of the vehicle to be photographed, and the range illuminated by the second light emitting diode unit. (L1, L2) is directed in the direction of the license plate of the vehicle being photographed.

  In the vehicle photographing device (10) according to the present invention, the second light emitting diode unit (30) includes a plurality of light emitting diodes whose optical axes are not parallel to each other.

  In the vehicle photographing apparatus (10) according to the present invention, both the first light emitting diode part (26) and the second light emitting diode part (30) illuminate with light emitting diodes having a wavelength center value of 770 nm or more and 790 nm or less.

  In the vehicle photographing device (10) according to the present invention, the camera unit (20) includes a CCD image sensor (55) for transferring the charge generated by the light receiving element (56) to the horizontal transfer CCD (60) by the vertical transfer CCD (58). The horizontal transfer CCD (60) is installed in a direction to transfer charges parallel to the vertical direction of the visual field and closer to the road (2) of the visual field.

  In the vehicle photographing device (10) according to the present invention, the field of view is a rectangle that is long in the vertical direction.

  In the vehicle photographing apparatus (10) according to the present invention, the camera unit (20) is provided by a light receiving element arranged on a plane perpendicular to the optical axis set to face downward from the horizontal toward the subject. Take a picture.

  ADVANTAGE OF THE INVENTION According to this invention, the vehicle imaging device which enables recognition of a high quality license plate and a driver | operator's imaging | photography with a simple structure is provided.

  The best mode for carrying out the vehicle photographing apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 shows a toll gate where a vehicle photographing apparatus is installed. The toll gate lane 2 includes a vehicle detection unit 6 that detects a vehicle 4 entering from the entrance side, an antenna 8 that performs wireless communication with an onboard device mounted on the vehicle 4, and a vehicle detection unit 6 that is installed on a roadside island. The vehicle photographing device 10 for photographing the front of the vehicle detected in step 3 from the downstream side of the vehicle, the booth 12 on which the staff on the business operator side managing the toll booth waits, and permission or stop is given to the exit of the vehicle from the toll gate A start controller 14 to be applied and a monitoring camera 16 for monitoring the state of the traveling lane 2 are installed. The distance in the extension direction of the traveling lane 2 between the vehicle detection unit 6 and the vehicle photographing device 10 is about 4 m to 4.5 m.

  FIG. 2 shows the appearance of the vehicle photographing device 10. The vehicle photographing device 10 includes a leg portion 17 that is installed on an island on the road side of the traveling lane 2 and a casing 18 that is installed on the leg portion 17. A camera unit 20, an upper illumination unit 22, and a lower illumination unit 24 are installed in the housing 18. The upper illumination unit 22 is for illuminating the vicinity of the driver's seat of a large vehicle, and is installed on the upper side of the camera unit 20. The lower illumination unit 24 is for illuminating the vicinity of the driver's seat and the license plate of a normal vehicle, and is installed below the camera unit 20.

  If the illumination is concentrated on the upper side of the camera unit 20, the illumination efficiency in the vicinity of the license plate is not preferable. Furthermore, since the height of the device is high, the prospect of the toll booth is hindered, and the center of gravity is high, so that the vibration of the device increases, which is not preferable. As in the present embodiment, the illumination for illuminating the vicinity of the large vehicle driver is divided into two parts on the upper side of the camera unit 20 and the other side on the lower side of the camera unit 20, thereby reducing the apparatus height and improving the efficiency. Good lighting can be realized.

  The camera unit 20 includes a lens that opens on the front side of the housing 18 in order to photograph the front side of the vehicle on the entrance side of the toll gate, that is, on the upstream side of the travel lane 2. The height of the optical axis in this lens is set to 1.3 m or more and 1.5 m or less, preferably about 1.4 m, based on the height of the road surface of the traveling lane 2.

  If the position of the photographing lens of the camera unit 20 is too low, the driver's face may be hidden by the console when photographing a large vehicle with a high driver's seat. If the position of the taking lens is too high, the driver's face may be hidden by the rearview mirror when shooting a normal car. In order to clearly photograph the driver's seat in both ordinary and large vehicles, it is desirable that the height of the optical axis in the lens be set in the above range.

  The vertical field of view of the camera unit 20 is 2.8 m. When the camera position is half (1.4 m) or more of the vertical field of view, the optical axis of the camera is set to face below the horizontal toward the subject, and the influence of direct sunlight can be reduced. .

  The upper illumination unit 22 includes a right LED panel and a left LED panel. The lower illumination unit 24 includes an upper first illumination unit 26, an intermediate second illumination unit 28, and a lower third illumination unit 30. Each of the first illumination unit 26, the second illumination unit 28, and the third illumination unit 30 includes a right LED panel and a left LED panel.

  Each of the eight LED panels included in the upper illuminating unit 22 and the lower illuminating unit 24 has a large number of LEDs (Light Emitting Diodes) installed on the surface facing the front side (upstream direction of the traveling lane 2). Is provided. These eight LED panels can be adjusted in direction independently of each other.

  The vehicle photographing device 10 is installed on an island on the right side or the left side when viewed from the occupant of a vehicle entering from the entrance of the traveling lane 2. FIG. 3 shows a top view when installed on the left island. The vehicle 4 travels from the upstream side of the travel lane 2 (left side as viewed in the figure). It is assumed that the vehicle 4 is a right-hand drive vehicle that is a majority in Japan. The driver's seat 32 is disposed on the right side when viewed from the passenger of the vehicle 4. The vehicle imaging device 10 installed on the island 34L captures a field of view 36L including the front of the vehicle 4 in synchronization with the timing when the vehicle detection unit 6 detects the vehicle, and generates an image 38L.

  The image 38L includes a vehicle image 40L, a driver seat image 44L, and a license plate image 42L corresponding to the vehicle 4, the driver seat 32, and the license plate on the front side of the vehicle. The field of view 36L of the image 38L is vertically long (a rectangle that is long in the vertical direction), and has a field of view that is longer in the vehicle height direction than in the vehicle length direction of the vehicle. Such a vertically long visual field 36L is suitable for photographing both the license plate image 42L and the driver seat image 44L.

  FIG. 4 shows a top view when installed on the right island. The vehicle 4 travels from the upstream side of the travel lane 2. Assume that the vehicle 4 is a right-hand drive vehicle. The vehicle imaging device 10 installed on the island 34R captures the field of view 36R including the front of the vehicle 4 in synchronization with the timing when the vehicle detection unit 6 detects the vehicle, and generates an image 38R.

  The image 38R includes a vehicle image 40R, a driver seat image 44L, and a license plate image 42R corresponding to the vehicle 4, the driver's seat 32, and the license plate on the front side of the vehicle. The arrangement of the front surface of the vehicle 4 in the image 38R is symmetrical to the image 38L in the case of FIG.

  FIG. 5 shows the illumination range of the vehicle photographing apparatus 10 installed on the right island as shown in FIG. Ranges L1 and L2 respectively indicate illumination ranges illuminated by the right LED panel and the left LED panel of the third illumination unit 30 when viewed from the rear side of the vehicle photographing device 10 (downstream side of the traveling lane 2). Ranges L3 and L4 indicate illumination ranges illuminated by the right LED panel and the left LED panel of the second illumination unit 28, respectively. A range L5L6 indicates an illumination range illuminated by the right LED panel and the left LED panel of the first illumination unit 26, respectively. Ranges L7 and L8 indicate illumination ranges illuminated by the right LED panel and the left LED panel of the upper illumination unit 22, respectively.

  The LED panel of the 3rd illumination part 30 is installed so that the range L1, L2 may include the position of the number plate of a vehicle. The LED panel of the second illumination unit 28 is installed such that the ranges L3 and L4 include the height near the face of the driver of the vehicle. The LED panel of the first illumination unit 26 emits spot light for illuminating the vicinity of the driver's face sitting in the driver's seat of the right-hand drive vehicle more brightly. This LED panel illuminates the narrower ranges L5 and L6 more brightly by the LED that collects and irradiates light in a narrower range than the LED panels of the second illumination unit 28 and the third illumination unit 30. The LED panels of the upper illumination unit 22 are installed so that the ranges L7 and L8 include the height in the vicinity of the driver's face of the driver's seat of a large vehicle having a vehicle height higher than that of a normal vehicle.

  Such adjustment of the illumination range is performed by independently adjusting the eight LED panels according to the situation of the toll booth when the vehicle photographing apparatus 10 is installed on the island. As a result, as shown in FIG. 2, the substrates on which the LEDs of the plurality of LED panels are mounted are inclined to each other. By providing a plurality of LED panels that can be adjusted independently in this way, it is easy to realize optimal illumination according to the situation of the toll booth. For example, when the vehicle photographing apparatus 10 is installed on the left island 34L as shown in FIG. 3, the optimum illumination range is greatly different from that in FIG. However, this case can be easily handled by adjusting the angle of the LED panel using the same vehicle photographing apparatus 10.

  When the illumination range is illuminated, the license plate and the driver's seat, which are important information for identifying the vehicle, are photographed brighter than other portions. That is, only necessary portions are illuminated and efficient. In particular, it is desirable that the face of the driver's seat is illuminated brighter with spot light, and the license plate is more uniformly illuminated with light that irradiates a wider area than the spot light so that image recognition can be performed satisfactorily.

  The center wavelength of the light emitted from the LED used in the vehicle photographing apparatus 10 is not less than 770 nm and not more than 790 nm, preferably about 780 nm. This wavelength is near the boundary between the red-side end of visible light and the near infrared ray, and the driver's vision is less obscured when the vehicle is illuminated.

  The vehicle 4 may be provided with a light type license plate. The light type license plate emits green light, but a lamp having a second peak wavelength of around 850 nm is used. When the wavelength of the LED is 790 nm or less, it can be clearly photographed without overlapping with the wavelength of the light emitted by the light type license plate. An LED that emits light having a wavelength longer than the second peak wavelength is not desirable because the light emission efficiency is low. Eventually, as described above, it is desirable to use an LED having a center wavelength of 770 nm to 790 nm, particularly about 780 nm.

  Japanese Patent Application Laid-Open No. 2002-133579 discloses a vehicle license plate reading device that captures an image with lighting and non-lighting and recognizes a light-type plate when the lighting is not on. However, the light-type plate of a light vehicle is a bag character in which the outline portion of the character having a line width shines, and it is difficult to perform image recognition processing by imaging according to the method of this document. By illuminating with the LED having the LED wavelength in the present embodiment, the image recognition processing of the bag letter plate can be performed more accurately.

  The illumination light from the LED is not necessarily uniform. In particular, when LEDs with high fabrication accuracy are used, a regular dark and light pattern occurs, such as a relatively dark area between the bright area at the center of the illumination area and the ring-shaped bright area surrounding the center area. There is.

  FIG. 6 is an enlarged view of the substrate of the LED panel having a configuration for more uniformly illuminating. The substrate 46 includes a large number of terminals 48 for mounting LEDs. On the surface of the substrate 46, there is provided a protrusion 50 that swells at a position that interferes with the LED when the LED is attached. The protrusion 50 is formed using a resin, an adhesive, or the like.

  FIG. 7 is a side view of the LED panel. A first LED 52-1 and a second LED 52-2 are depicted. In the case of the normal substrate 46 without the protrusion 50, the optical axis of the LED is perpendicular to the surface of the substrate 46 when the LED is mounted on the terminal 48. However, when the protrusion 50 is provided, the optical axis of the LED mounted on the substrate 46 is inclined with respect to the normal line of the surface of the substrate 46. In addition, the optical axis 54-1 of the first LED 52-1 and the optical axis 54-2 of the second LED 52-2 are inclined with respect to each other. An LED panel on which a large number of LEDs whose optical axes are inclined to each other is mounted, and the light and dark patterns of the individual LEDs are averaged to illuminate the illumination range more uniformly than an LED panel without protrusions 50.

  FIG. 8 is a graph showing the relationship between the illumination range and the brightness of the LED panel configured such that the optical axes of the plurality of LEDs are shifted from each other as shown in FIGS. The horizontal axis shows the angle when viewing the illumination range from the LED. The vertical axis represents the brightness. FIG. 8A shows a case where the optical axis of the LED is perpendicular to the substrate 46. The angles ± 1 ° to ± 6 ° described in FIGS. 8B to 8C indicate the angle formed between the normal line of the substrate 46 and the optical axis of the LED. In the case of FIG. 8A, it can be seen that there is a valley in the vicinity of −4 ° on the horizontal axis, and the illumination is uneven. As the angle between the normal line of the substrate and the optical axis of the LED increases, the valley becomes smaller and the brightness approaches a single mountain shape. However, if the angle becomes too large, the brightness becomes non-uniform again as shown in FIG. Referring to FIG. 8, it is preferable that the LED is installed so that the optical axis of the LED is about ± 2 ° to ± 4 ° with respect to the normal line of the substrate. Such an LED panel is effective when used for the license plate illumination, in which the uniformity of illumination is particularly desired, that is, for the third illumination unit 30.

  The camera unit 20 uses a CCD (Charge Coupled Device) imaging device that is easily available. As a characteristic of the CCD, when intense light is photographed, a light streak called smear may occur. Next, the characteristics will be described.

  FIG. 9 shows the structure of a known CCD. The CCD is arranged in a matrix and receives a light receiving element 56 that generates light by receiving light, a vertical transfer CCD 58 that transfers the charge of the light receiving element 56 in the vertical direction, and a charge transferred by the vertical transfer CCD 58 in the horizontal direction. And a drain portion 62 for discharging unnecessary charges remaining in the vertical transfer CCD 58 at high speed. This CCD generates an image with a horizontally long visual field (that is, the horizontal direction is shorter than the vertical direction). Such CCDs are generally readily available.

  FIG. 10 shows an example of an image taken using the CCD shown in FIG. The vertical direction and the horizontal direction in FIGS. 9 and 10 correspond to each other. When the image 64 includes spotlight 66 with strong light, smear is generated in the vertical direction (charge transfer direction by the vertical transfer CCD) from the position of the spotlight 66. In particular, the smear 68 extending from the position of the spot light 66 toward the opposite side of the horizontal transfer CCD 60 is difficult to erase even by image processing.

  FIG. 11 shows the arrangement direction of the CCD in the camera unit 20 of the vehicle photographing apparatus 10. It is assumed that the vehicle photographing device 10 is installed on the island 34R on the right side of the traveling lane 2. A general CCD in which the field of view is horizontally long and the vertical transfer CCD 58 transfers charges in the vertical direction is rotated 90 degrees and installed in the camera unit 20 to have a vertically long field of view. The rotation direction is a direction close to the traveling lane 2 to be imaged by the horizontal transfer CCD 60.

  FIG. 12 shows an example of an image taken with such a CCD. In the image 64, the vehicle image 40R is shown. When photographing from the right island 34R, spot light 66 reflected by the illumination from the vehicle photographing device 10 is likely to be generated at the left corner of the front end of the vehicle body. With the CCD arrangement as shown in FIG. 11, the smear 68 extending from the spot light 66 extends outward of the vehicle body. For this reason, the smear 68 does not overlap the license plate image 42R or the driver seat image 44R. Therefore, it does not get in the way even if the smear 68 occurs when acquiring information for identifying the vehicle.

  Unlike the case of FIG. 11, when the vehicle imaging device 10 is installed on the left island 34L, the CCD is arranged symmetrically with respect to FIG. That is, as in FIG. 11, the horizontal transfer CCD 60 is arranged so as to be close to the traveling lane 2. In this case, contrary to FIG. 12, spot light is likely to be generated at the right corner toward the front of the vehicle body, and the smear extends toward the right side of the screen, that is, toward the outside of the vehicle body. In this case, the smear does not overlap the license plate or the driver's seat.

FIG. 1 shows the structure of the toll gate. FIG. 2 shows the appearance of the vehicle photographing device. FIG. 3 shows the relationship between the arrangement of the vehicle photographing device and the composition of the photographed image. FIG. 4 shows the relationship between the arrangement of the vehicle photographing device and the composition of the photographed image. FIG. 5 shows the illumination range of the vehicle photographing apparatus. FIG. 6 is an enlarged view of the substrate of the LED panel. FIG. 7 is a side view of the LED panel. FIG. 8 shows the relationship between the illumination range and brightness of the LED panel. FIG. 9 shows the configuration of the CCD. FIG. 10 shows an image taken using a CCD. FIG. 11 shows the arrangement direction of the CCD installed in the vehicle photographing apparatus. FIG. 12 shows the arrangement of smears in an image photographed by the vehicle photographing device.

Explanation of symbols

2 ... Run lane 4 ... Vehicle 10 ... Vehicle photographing device 17 ... Leg 18 ... Case 20 ... Camera unit 22 ... Upper illumination unit 24 ... Lower illumination unit 26 ... Lower first illumination unit 28 ... Lower second illumination Part 30 ... Lower third illumination part 32 ... Driver's seat 34L, R ... Island 36L, R ... Field of view 38L, R ... Image 40L, R ... Vehicle image 42L, R ... License plate image 44L, R ... Driver's seat image 46 ... Board 48 ... Terminal 50 ... Projection 52-1 ... First LED
52-2 ... Second LED
54-1, 54-2 ... Optical axis 56 ... Light receiving element 58 ... Vertical transfer CCD
60 ... Horizontal transfer CCD
62 ... Drain 64 ... Image 66 ... Spotlight 68 ... Smear

Claims (16)

A housing installed on the roadside,
A camera unit for photographing the vehicle on the road through a lens installed in the housing;
An upper illumination unit that is installed above the lens of the housing and illuminates the upper illumination range;
A vehicle photographing apparatus comprising: a lower illumination unit that is installed below the lens of the housing and illuminates a lower illumination range. The vehicle photographing device according to claim 1,
When the casing is installed on the ground, a vertical distance between the lens and the road surface of the road is 130 cm or more and 150 cm or less. The vehicle photographing device according to claim 2,
The upper illumination range is directed toward the face of a driver of a large vehicle. The vehicle photographing device according to claim 2 or 3,
The lower illumination unit is
A first substrate;
A first light emitting diode unit installed on the first substrate;
A second substrate inclined with respect to the first substrate;
A second light-emitting diode unit installed on the second substrate and set at a position where the illumination range is lower than that of the first light-emitting diode unit. The vehicle photographing device according to claim 4,
A range in which the first light emitting diode unit illuminates is narrower than a range in which the second light emitting diode unit illuminates. The vehicle photographing device according to claim 4 or 5, wherein
The range illuminated by the first light emitting diode portion is directed toward the face of the driver of the vehicle being photographed, and the range illuminated by the second light emitting diode portion is directed toward the license plate of the vehicle being photographed. Vehicle shooting device. The vehicle photographing device according to any one of claims 4 to 6,
The second light emitting diode unit includes a plurality of light emitting diodes whose optical axes are not parallel to each other. The vehicle photographing device according to any one of claims 4 to 7,
Both the first light emitting diode part and the second light emitting diode part are illuminated by light emitting diodes having a central wavelength value of 770 nm or more and 790 nm or less. The vehicle photographing device according to any one of claims 1 to 8,
The camera unit performs the photographing by a CCD image sensor that transfers a charge generated by a light receiving element to a horizontal transfer CCD by a vertical transfer CCD, and the horizontal transfer CCD is parallel to the vertical direction of the visual field and close to the road of the visual field. Vehicle shooting device installed in the direction of transferring electric charge to. The vehicle photographing device according to claim 9,
The field of view is a rectangle that is long in the vertical direction. The vehicle photographing device according to any one of claims 1 to 8,
The camera unit performs the photographing with a light receiving element arranged on a plane perpendicular to an optical axis set so as to be directed downward from the horizontal toward a subject. A housing installed on the roadside,
A camera unit that opens on the road side and shoots the vehicle through a lens installed in the housing;
A vehicle photographing apparatus comprising: an illumination unit that is installed in the housing and performs illumination with a light emitting diode having a wavelength center value of 770 nm or more and 790 nm or less. The vehicle photographing device according to claim 12,
The camera unit performs the photographing by a CCD image sensor that transfers the charge generated by the light receiving element to the horizontal transfer CCD by the vertical transfer CCD, and the horizontal transfer CCD is parallel to the vertical direction of the visual field and close to the road of the visual field Vehicle shooting device installed in the direction of transferring electric charge to. The vehicle photographing device according to claim 13,
The field of view is a rectangle that is long in the vertical direction. A housing installed on the roadside,
A camera unit that takes an image of the vehicle through a lens that is open on the road side and installed in the housing;
An illumination unit that is installed in the housing and illuminates the vehicle;
The camera unit performs the photographing by a CCD image sensor that transfers the charge generated by the light receiving element to the horizontal transfer CCD by the vertical transfer CCD, and the horizontal transfer CCD is parallel to the vertical direction of the visual field and close to the road of the visual field Vehicle shooting device installed in the direction of transferring electric charge to. The vehicle photographing device according to claim 15, wherein
The field of view is a rectangle that is long in the vertical direction.

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