JP2016091346A - License plate reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a processing load necessary for reading.SOLUTION: An installation body is erected in the upper space of a running traffic lane so as to traverse the running traffic lane on which a vehicle carrying a license plate travels. Line sensor imaging means having a line sensor in which imaging devices are arranged in a line is installed such that the arrangement direction of the imaging devices traverses the running traffic lane and the vehicle traveling along the running traffic lane can be imaged from obliquely upward of the vehicle. A license plate is read on the basis of the image of the license plate included in a two-dimensional image generated from time series line sensor images imaged by the line sensor imaging means.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a license plate reading device that reads a license plate of a running vehicle.

Conventionally, as a license plate reading device that reads a license plate of a running vehicle, an imaging camera having a high-resolution image sensor is arranged corresponding to each traveling lane, and among images captured by each imaging camera, Processes multiple frame images showing the license plate, reads each imaged camera, references the reading results of the multiple cameras, complements the character string, and improves the accuracy of license plate reading (For example, refer to Patent Document 1).
In addition, as a conventional license plate reader, there is an area sensor that can be imaged across multiple lanes in the width direction, for simultaneous monitoring of multiple lanes and for vehicles that run across lanes in the imaging area In some cases, an image is captured (see Patent Document 2).
Furthermore, as a camera used for a license plate reading device, there is a camera that captures a specific lane by combining a camera with a relatively wide angle and a low resolution with a PTZ camera capable of adjusting an imaging direction and zoom with a small angle of view ( (See Patent Document 3).

JP 2009-169827 A JP 2014-191763 A JP 2013-182550 A

However, in Patent Document 1, a large number of frame images showing a license plate are identified from all the frame images captured by each imaging camera, and the number of frame images thus identified is processed to obtain a license plate. In this case, there is a possibility that the processing load required for the reading becomes very large.
In addition, in Patent Document 2, high-resolution imaging is indispensable for simultaneous monitoring of multiple lanes using an area sensor and imaging corresponding to a vehicle traveling across lanes. In the case of an area sensor, since the sensitivity decreases as the resolution increases, there is a problem in that satisfactory image accuracy cannot be obtained and feasibility is poor.
Furthermore, in Patent Document 3, the imageable area is limited to only a specific lane and is limited in the width direction. For example, it is difficult to image a vehicle traveling across lanes with the camera. there were.

  The present invention has been made paying attention to such problems, and can reduce the processing load required for reading, and can simultaneously capture a wide imaging target such as a vehicle traveling in a plurality of lanes with high resolution. An object of the present invention is to provide a license plate reader capable of imaging and processing with high sensitivity.

In order to solve the above-mentioned problem, a license plate reading device according to claim 1 of the present invention provides:
A construction body constructed in a space above the traveling lane so as to cross the traveling lane in which the vehicle on which the license plate is mounted travels;
The image sensor has a line sensor arranged in a line, the array direction of the image sensor is a direction crossing the travel lane, and the vehicle traveling in the travel lane can be imaged from an obliquely upper side of the vehicle A line sensor imaging means installed on the installation body so that
Time-series two-dimensional image generation means for generating a two-dimensional image from a time-series line sensor image imaged by the line sensor imaging means;
Reading means for reading the license plate based on the image of the license plate included in the two-dimensional image generated by the time-series two-dimensional image generating means;
It is characterized by having.
According to this feature, compared to the case where a large number of frame images are processed using an imaging camera having a conventional image sensor, the line sensor imaging unit is used to generate the time-series line sensor image. Since the license plate can be read by sequentially processing only the time-series two-dimensional image, the processing load in the reading process can be greatly reduced, and the use of a line sensor, for example, 8192 pixels or 16384 pixels. High-resolution sensors such as multiple lanes can be obtained, and a suitable sensor can be selected according to a wide imaging target such as multiple lanes, and a high-sensitivity and high-speed scan rate can be easily realized compared to area sensors. It is possible to image an object moving at high speed with high resolution.

A license plate reader according to claim 2 of the present invention is the license plate reader according to claim 1,
An illumination unit that illuminates the imaging region of the line sensor imaging unit in a strip shape is provided.
According to this feature, since the illumination range is narrow, the license plate can be satisfactorily read without dazzling the driver, and the power consumption required for illumination can be suppressed.

The license plate reader according to claim 3 of the present invention is the license plate reader according to claim 2,
The image sensor is an infrared image sensor,
The illumination means illuminates the band-shaped imaging region with infrared rays that can be imaged by the infrared imaging element.
According to this feature, since the infrared light that cannot be visually recognized by the driver is used, the license plate can be read well without further dazzling the driver.

The license plate reader according to claim 4 of the present invention is the license plate reader according to any one of claims 1 to 3,
Vehicle color specifying means for specifying the color of a vehicle traveling in the travel lane,
The vehicle color data of the vehicle specified by the vehicle color specifying means is stored in association with the read data by the reading means.
According to this feature, the color of the read license plate vehicle can also be understood.

The license plate reader according to claim 5 of the present invention is the license plate reader according to claim 4,
The image sensor is a monochrome image sensor,
The vehicle color specifying means includes color image imaging means arranged in parallel with the line sensor imaging means on the installation body so as to be able to take an image of the traveling lane, and based on a color image taken by the color image imaging means. It is characterized by specifying the color of the vehicle.
According to this feature, since the image sensor of the line sensor can be monochrome, the color of the vehicle can be specified while increasing the resolution of the line sensor.

The license plate reader according to claim 6 of the present invention is the license plate reader according to any one of claims 1 to 5,
Only one line sensor imaging means is provided for a plurality of traveling lanes.
According to this feature, the installation cost of the license plate reader can be reduced, and the license plate can be satisfactorily read without increasing the processing load even when the vehicle moves in the lane.

It is a perspective view which shows the structural example of the license plate reader in an Example. It is a block diagram which shows the structural example of the license plate reader in an Example. It is a flowchart which shows an example of the processing content of the image processing performed in the image processing apparatus of a license plate reader. It is explanatory drawing which shows the processing condition of the two-dimensional image imaged with the license plate reader.

  An embodiment for implementing a license plate reading apparatus according to the present invention will be described below based on an example.

  A license plate reading apparatus according to an embodiment will be described with reference to FIGS.

  As shown in FIG. 1, the license plate reading apparatus of the present embodiment includes an infrared line sensor in which infrared imaging elements are arranged in a line, and an infrared optical mechanism for performing imaging by the infrared line sensor. The infrared line sensor camera 10 and an area sensor that is used for specifying the color of a vehicle passing therethrough and in which two-dimensional imaging elements for visible light are arranged in a two-dimensional plane are used for imaging by the area sensor. An area sensor camera 20 having an optical mechanism for the above, a line illuminating device 12 for irradiating near-infrared rays for illuminating the bright line-like imaging region of the infrared line sensor camera 10 in a strip shape, and so as to cross the traveling lane of the vehicle An infrared line sensor camera 10, an area sensor camera 20, and a line illumination device 12 are installed in the space above the travel lane. A bridging member 5 installed is, these infrared line sensor camera 10, the main unit 1 the area sensor camera 20 and the line illumination device 12 is connected, is mainly composed.

  The erection body 5 used in the present embodiment is a steel structure, and has two struts erected on the side of the passage, and a bridge pier spanned between the two struts. The infrared line sensor camera 10, the area sensor camera 20, and the line illumination device 12 are suspended from the pier at approximately the center position of the pier body, that is, above the center lane of the three lanes. Thus, the vehicle passing through the traveling lane is installed at a height position of about 5 meters from the road surface so as to capture an image from a predetermined angle obliquely upward. In addition, as described above, the erection body of the present invention is not necessarily limited to the one composed of the two support columns erected on both sides of the traveling lane and the piers spanned between the support columns, For example, it may be composed of one strut body that is erected only on one side of the passage and a pier body that is horizontally supported from the strut body and is constructed above the traveling lane.

  If the angle at which the vehicle passing through the traveling lane is imaged is large, even if the license plate is imaged, the width in the time-series direction of the time-series two-dimensional image becomes very small, and the number of the plate, etc. As will be described later, the accuracy of recognition is reduced even when image correction is performed. On the other hand, if the imaging angle is small, the distance between the infrared line sensor camera 10 and the vehicle to be imaged is small. Increases the possibility that the license plate cannot be imaged due to the influence of vibration and the shadow of the vehicle ahead, and therefore it is preferable to set the angle in the range of 30 to 45 degrees.

  As shown in FIG. 1, the area sensor camera 20 only needs to be installed so that the imaging position (angle of view) substantially matches the imaging position of the infrared line sensor camera 10. It is only necessary that the vehicle corresponding to the made license plate can be identified from the horizontal position of the image by the infrared line sensor camera 10 and at the time of imaging.

  In this embodiment, the line sensor camera 10 and the area sensor camera 20 have a built-in anti-shake mechanism (not shown) for preventing a shake caused by vibration accompanying the passage of the vehicle. In addition to these anti-blur mechanisms, although not shown in the figure, the strut body prevents vibration from a vehicle passing through the road from being transmitted to the strut body, and vibration is further propagated from the strut body to the pier body. An anti-vibration part is provided to prevent the body from shaking, and the vibration caused by the passing vehicle propagates to the pier body, causing the pier body to sway, making it impossible to capture good images. Although it is possible to prevent the reading accuracy from being deteriorated, the present invention is not limited to this. For example, an anti-shake mechanism built in the line sensor camera 10 or the area sensor camera 20 is used. In the case where only sufficient vibration countermeasures can be taken, it is not necessary to provide a vibration isolating portion on these erected bodies 5.

  The infrared line sensor camera 10 includes an infrared line sensor (monochrome) capable of capturing a one-dimensional linear image, an infrared optical mechanism such as an infrared lens for enabling imaging by the infrared line sensor (monochrome), A known anti-shake mechanism for preventing shake due to vibration is provided.

  As these infrared line sensors (monochrome), known infrared line sensors can be used.

  Since these infrared line sensors can form signal lines on both sides of the image sensor, a high-definition and high-sensitivity sensor can be obtained at a lower cost than an area sensor. Since the number of elements of these infrared line sensors is the resolution of the obtained time-series two-dimensional image, it is sufficient to use one according to the number of lanes on the road where the infrared line sensor camera 10 is installed.

  For example, by using a commercially available infrared line sensor with a resolution of 8192 pixels, even if three-lane simultaneous monitoring of a driving lane of 3.6 meters is performed as in this embodiment, it is 1.3 to 1.5. A horizontal resolution of about millimeter / pixel can be realized. This corresponds to a resolution of 220 to 250 pixels with respect to the lateral size of one license plate, which is sufficient for reading by image processing (vehicle number recognition).

  In other words, the number of pixels of the infrared line sensor to be used is the number of pixels required for reading (vehicle number recognition) by image processing with respect to the lateral size of one license plate when the total width of the lane to be imaged is imaged. A number (for example, 200 pixels) may be assigned.

  On the other hand, the resolution of the area sensor camera 20 may be any resolution as long as the color of the vehicle can be specified. Therefore, the resolution of the area sensor camera 20 may be lower than that of the infrared line sensor camera 10, but to specify the color of the vehicle. It is necessary to use a visible light image sensor. However, when a visible light imaging device is used and a visible light illumination device is used for imaging, the vehicle is irradiated with visible light from an obliquely upper front of the vehicle, which dazzles the driver. Therefore, it is preferable to use a high-sensitivity imaging camera using a high-sensitivity imaging element so that imaging can be performed without using a visible light illumination device. In addition, as a high sensitivity imaging camera, the commercially available high sensitivity imaging camera can be utilized suitably.

  As described above, in this embodiment, the camera for color plate reading (vehicle number recognition) and the camera for specifying the color of the vehicle are separate cameras, so that the color of the vehicle can be specified. The camera to be used can be a highly sensitive visible light camera, and as a result, the color of the vehicle can be specified without irradiating the vehicle with visible light.

  The line illumination device 12 is capable of emitting near infrared light that can be imaged by the infrared line sensor camera 10 in a band shape. Specifically, an infrared LED serving as a light emitting light source is arranged in a line, and a cylindrical lens that converts near-infrared light emitted from the infrared LED into a strip-shaped light beam is provided.

  In the present embodiment, the line illumination device 12 is illustrated as having a single-row infrared LED and a cylindrical lens, but the present invention is not limited to this, and the infrared line sensor camera 10 is Needless to say, any device capable of emitting near-infrared light that can be imaged can be used as an illumination device. However, by using the line illumination device 12 as the illumination device as in this embodiment, a useless area is not illuminated, so that the power consumption of the device can be suppressed.

  The width of the band-shaped irradiation range irradiated by these line illumination devices 12 may be one pixel width of the imaging range as long as the imaging range of the infrared line sensor camera 10 can be illuminated. Since alignment with the infrared line sensor camera 10 becomes very difficult, there is a possibility that the illumination area of the line illumination device 12 may be moved away from the imaging position of the infrared line sensor camera 10 due to vibration or the like. It is preferable to have a certain width, but conversely, if the width of the illumination region is wide, it is necessary to increase the amount of light emitted from the infrared LED, and the power consumption of the infrared LED increases. What is necessary is just to make it the minimum width, for example, about 5-10 cm.

  In the present embodiment, the irradiation of the line illumination device 12 is continuous irradiation. However, the present invention is not limited to this, and the infrared line sensor camera 10 is intended to reduce power consumption associated with irradiation. The infrared LED may be caused to emit light only at the timing when the image is scanned.

  Next, the main device 1 will be described with reference to FIG. As shown in FIG. 2, the infrared line sensor camera 10, the area sensor camera 20, and the line illumination device 12 are connected to the main body device 1.

  The main body apparatus 1 includes a control computer 50 that controls the operation of the entire reading apparatus, and an image processing apparatus 25 that includes a device such as a DSP for performing image processing. The infrared line sensor camera 10 and the area sensor camera 20 are connected, and image data captured by the infrared line sensor camera 10 and the area sensor camera 20 are input to the image processing device 25.

  In addition, an image processing memory 26 is connected to the image processing device 25, and an image or the like can be stored in the image processing memory 26 for the image processing device 25 to perform image processing.

  The image processing device 25 includes a two-dimensional image generation process for generating a time-series two-dimensional image by stacking images from the connected infrared line sensor camera 10 in a predetermined storage area of the image processing memory 26 in a time-series manner. The license plate and the color of the vehicle are specified based on the time series two-dimensional image generated by the unit, the two-dimensional image generation processing unit, and the visible light image captured by the area sensor camera 20. An image recognition processing unit that performs image recognition processing (see FIG. 3) is provided.

  The two-dimensional image generation processing unit acquires line sensor images from the infrared line sensor camera 10 at a preset scan rate in consideration of the speed of the passing vehicle, and sequentially stacks the acquired line sensor images. This is a functional unit that generates a series two-dimensional image and stores it in the image processing memory 26.

  Therefore, the resolution in the time-series direction of the time-series two-dimensional image generated by the two-dimensional image generation processing unit depends on the scan rate. If the speed of the passing vehicle increases, the license plate is reflected. Although the number of line sensor images will decrease, the speed of vehicles passing on ordinary roads is 50-100 km / h, even if the vehicles pass at 100 km / h, at a scan rate of about 20 kHz. By acquiring the line sensor image, the resolution in the time series direction of the time series two-dimensional image can be secured at 200 pixels or more, and generally, the scan rate of the line sensor image is about several hundreds KHz, so it passes. It is only necessary to set a scan rate that can ensure a resolution of 200 pixels or higher that allows image recognition processing even at the maximum speed of the vehicle. .

  Although not implemented in this embodiment, these scan rates may be changed according to the speed of the vehicle. For example, if the road is congested and the vehicle speed is low, the scan rate is reduced. If the vehicle speed is equal to or higher than a certain speed (for example, 40 km / h), a preset scan rate is set. Alternatively, when the speed of the vehicle exceeds the upper limit speed (for example, 100 Km / h), scanning may be temporarily performed at a scan rate faster than a preset scan rate.

  The line lighting device 12 is connected to the control computer 50, and lighting control of the line lighting device 12 and monitoring of the lighting state are performed in the control computer 50.

  The control computer 50 of the present embodiment is also connected to a display device 30 for displaying and outputting recognition result data and a storage device 40 for storing recognition result data.

  The display device 30 is not an essential device. Instead of the display device 30, a communication device for transmitting recognition result data stored in the storage device 40 to the outside, or an external device that can be attached to and detached from the main body device 1. An interface for connecting a storage device may be provided.

  The control computer 50 of this embodiment is provided with a ROM (not shown) that is a nonvolatile memory in which a control program and the like are stored, and a real-time clock (RTC) that can output date and time information. .

  Here, the recognition result data of this embodiment stored in the storage device 40 will be described. As shown in FIG. 2, the recognition result data of this embodiment passes through the vehicle and the license plate is read. Corresponding to the date and time (almost the same as the passage time of the vehicle), the license plate recognition result (read result), the file name of the line sensor image of the license plate to be recognized, the specified vehicle color, the vehicle color The file name of the image of the area sensor used for identification is stored, and the license plate and color of the vehicle that has passed and the date and time of passage can be identified.

  It should be noted that the form of the recognition result data in the present embodiment is an example, and needless to say, the recognition result data may be in a form different from that in the present embodiment.

  FIG. 3 is a flowchart showing an example of image recognition processing executed by the image recognition processing unit of the present embodiment. In the image recognition processing, first, it is determined whether or not it is the execution timing of image recognition (step S1). That is, in this embodiment, since an infrared line sensor is used, it is impossible to perform image recognition using only one line sensor image captured by the infrared line sensor. Image recognition is performed at the timing when a time-series two-dimensional image is accumulated by a line sensor image of about 200 pixels, which is the number of pixels required for the image (for example, every 20 milliseconds when 200 pixels are accumulated in the case of 20 KHz) To do.

  When it is the execution timing of the image recognition (step S1; Yes), the newly accumulated 200 pixels of the time-series two-dimensional image stored in the image processing memory 26 and the immediately preceding one are accumulated. A region corresponding to a total of 300 pixels corresponding to 100 pixels is specified and extracted as a processing target region (step S2).

  In this way, in this embodiment, as the processing target area, the newly accumulated 200 pixels and the area of 300 pixels in total, which is 100 pixels accumulated immediately before, are specified and extracted. As shown in FIG. 4, the processing target area moves half by half and is used for processing. For example, as shown in the end position of the area n + 2, the entire license plate is still imaged at the timing of image recognition. If not, that is, even if the license plate is passing the imaging area of the infrared line sensor camera 10 at the timing of image recognition, the area n + 3 is specified as the processing area in the next image recognition, Since image recognition is performed with the entire license plate imaged, the accuracy of recognition is reduced even if image recognition is performed intermittently. So that the there is no Rukoto.

  In the present embodiment, an example in which the area to be processed is 300 pixels is illustrated, but the present invention is not limited to this, and the number of pixels in the area to be processed is the interval between image recognitions. It may be determined based on the scan rate or the like.

  Then, it is determined whether or not there is a square area estimated as a license plate to be recognized in the extracted area to be processed. Note that the square region is not limited to one location, and there may be a plurality of locations.

  If there is no region to be recognized (step S3; No), the process returns to step S1, while if there is a region to be recognized, the target region is used to increase the recognition accuracy in the region to be recognized. Image correction processing is performed (step S4). In the present embodiment, as described above, since three lanes are imaged by one infrared line sensor camera 10, as shown in FIG. 4, the shape of the license plate image of the vehicle passing through the center lane and the right lane Since the shape of the license plate image of the vehicle passing through and the shape of the license plate image of the vehicle passing through the left lane are different, the shape of the license plate image is corrected to a front view image suitable for image recognition.

  Specifically, the license plate image of the center lane has a trapezoidal shape as shown in the area n of FIG. 4. Therefore, the trapezoidal shape is corrected to the original rectangular shape of the license plate, and the traveling direction of the vehicle The license plate image of the vehicle passing through the left lane toward the vehicle is a rectangular shape distorted so as to extend toward the left side of the left lane as shown in the area n + 3 in FIG. Since the accompanying distortion is included, the shape of the distorted square is corrected to the original rectangular shape of the license plate. As these corrections, for example, a known affine transformation or the like may be executed.

  In this embodiment, as compared with the case of processing a frame image captured by a conventional area sensor, only one processing target image needs to be processed. Can be greatly reduced, and correction using a more complicated algorithm may be performed as these corrections.

  Then, a vehicle number recognition process is performed on the license plate image corrected in the target area image correction process (in the case of a plurality of license plate images, each license plate image) (step S5).

  In the car number recognition process, specifically, the kanji and hiragana and numbers included in the corrected license plate image are replaced with the kanji and hiragana and numbers used in the license plate stored in the storage device 40 in advance. Reading may be performed by matching and selecting the best match. In addition, as these vehicle number recognition processes, processes, such as well-known character recognition, can also be utilized.

  Then, the process proceeds to step S6, in which the area sensor image frame corresponding to the recognition target area, for example, the frame imaged by the area sensor camera 20 at the closest time and the recognition target area in the image of the frame are displayed. The corresponding position is specified, and the vehicle color corresponding to the specified position is specified by performing binning processing for summing up the colors of adjacent pixels.

  Next, the car number (recognition result) recognized in the car number recognition process, the file name given to the license plate image corrected in the target area image correction process, which is the target of the car number recognition process, and the identification in step S6 The recognition result corresponding to the date and time information obtained from the RTC and the file name given to the image of the area sensor camera 20 of the frame used for specifying the color of the vehicle in step S6 After adding to the data (step S7), the process returns to step S1.

  Of the time-series two-dimensional images of the region specified as the processing target of the image recognition process, an image of 100 pixels that is old in time series is added to the recognition result data in step S6. 26 is erased. However, the erase timing of these processed time-series two-dimensional images may be determined as appropriate from the memory capacity of the image processing memory 26 and the like.

  As described above, according to the license plate reading apparatus of the present embodiment, the license plate can be read using the infrared line sensor camera 10 (line sensor imaging means) including an inexpensive and high-resolution infrared line sensor. Compared with the case where a large number of frame images are processed using an imaging camera having a conventional image sensor, the line sensor imaging means is adopted so that only a time-series two-dimensional image is sequentially obtained. Since the license plate can be read by processing, the processing load in the reading process can be greatly reduced, and it is not necessary to store a large number of these frame images. The storage capacity for storing can also be reduced. In addition, by adopting a line sensor, it is possible to obtain high-resolution sensors such as 8192 pixels and 16384 pixels, and not only a suitable sensor can be selected according to a wide imaging target such as a plurality of lanes, but also compared with an area sensor. Therefore, a high-sensitivity and high-speed scan rate can be easily realized, so that an object moving at high speed can be imaged with high resolution.

  In addition, according to the license plate reading device of the present embodiment, because the line illumination device 12 is used, the illumination range is narrow and infrared light that cannot be visually recognized by the driver is used, so the driver is not dazzled. The license plate can be read well, and the power consumption required for illumination can be suppressed.

  Further, according to the license plate reading device of the present embodiment, since the color of the vehicle is specified by the visible light image captured by the area sensor camera 20, the color of the vehicle of the read license plate can be understood. Since the image sensor of the line sensor can be a monochrome image sensor or infrared image sensor with high resolution, the color of the vehicle can be specified while increasing the resolution of the line sensor.

  In addition, according to the license plate reading device of this embodiment, only one infrared line sensor camera 10 is provided for three lanes that are a plurality of traveling lanes. For example, even when the traveling vehicle is traveling across the lane for moving the lane at the imaging position of the infrared line sensor camera 10, the number is satisfactorily increased without increasing the processing load. The plate can be read.

  Although the embodiments of the present invention have been described with reference to the drawings, the specific configuration is not limited to these embodiments, and modifications and additions within the scope of the present invention are included in the present invention. It is.

  For example, in the above-described embodiment, the image processing device 25 and the control computer 50 are individually illustrated in the main body device 1, but the present invention is not limited to this, and the image processing device 25 The control computer 50 may be integrated.

  Moreover, in the said Example, as shown in FIG. 1, although the number plate reader of this invention was illustrated to the form applied to the road of 3 lanes, this invention is limited to this. Instead, the number of lanes may be one lane, two lanes, or four or more lanes.

  Further, in the above-described embodiment, the form in which the traveling vehicle is imaged from the front side of the vehicle is illustrated, but the present invention is not limited to this, and may be captured from the rear side of the vehicle. In this case, since the up-and-down direction of the license plate is inverted in the time-series two-dimensional image, in addition to the correction of the time-series two-dimensional image described above, image correction that inverts the vertical direction (rotates 180 degrees) is performed. good. In addition, you may make it image from both the front and back of a vehicle.

  Moreover, in the said Example, although the form using an infrared line sensor (monochrome) was illustrated, this invention is not limited to this, The visible light which arranged the highly sensitive color image sensor in 1 row form Using only a visible light line sensor camera equipped with a line sensor, and using a time-series two-dimensional color image generated from the visible light line sensor camera, the license plate is read and the color of the vehicle is specified. good. In this case, since the license plate at the rear of the vehicle is required to be illuminated, the license plate can be read more reliably by setting the imaging direction to the rear.

  Moreover, in the said Example, although the color of the vehicle is specified, this invention is not limited to this, For example, the structure which installs only the infrared line sensor camera 10 and does not install the area sensor camera 20 As such, the color of the vehicle may not be specified.

  Further, although not implemented in the above embodiment, the speed of the traveling vehicle is also identified based on the size of the license plate in the time-series direction in the captured time-series two-dimensional image, and the recognition including the identified speed is performed. The result data may be stored.

DESCRIPTION OF SYMBOLS 1 Main body apparatus 5 Construction body 10 Infrared line sensor camera 12 Line illumination apparatus 20 Area sensor camera 25 Image processing apparatus 26 Memory for image processing 40 Storage apparatus 50 Control computer

Claims (6)

A construction body constructed in a space above the traveling lane so as to cross the traveling lane in which the vehicle on which the license plate is mounted travels;
The image sensor has a line sensor arranged in a line, the array direction of the image sensor is a direction crossing the travel lane, and the vehicle traveling in the travel lane can be imaged from an obliquely upper side of the vehicle A line sensor imaging means installed on the installation body so that
Time-series two-dimensional image generation means for generating a two-dimensional image from a time-series line sensor image imaged by the line sensor imaging means;
Reading means for reading the license plate based on the image of the license plate included in the two-dimensional image generated by the time-series two-dimensional image generating means;
A license plate reading apparatus comprising:   The license plate reading apparatus according to claim 1, further comprising an illumination unit that illuminates an imaging region of the line sensor imaging unit in a strip shape. The image sensor is an infrared image sensor,
The license plate reading apparatus according to claim 2, wherein the illumination unit illuminates the band-shaped imaging region with infrared rays that can be imaged by the infrared imaging element. Vehicle color specifying means for specifying the color of a vehicle traveling in the travel lane,
4. The license plate according to claim 1, further comprising storage means for storing the color data of the vehicle specified by the vehicle color specifying means in association with the read data by the reading means. Reading device. The image sensor is a monochrome image sensor,
The vehicle color specifying means includes color image imaging means arranged in parallel with the line sensor imaging means on the installation body so as to be able to take an image of the traveling lane, and based on a color image taken by the color image imaging means. The license plate reading device according to claim 4, wherein a color of the vehicle is specified.   6. The license plate reading apparatus according to claim 1, wherein only one line sensor imaging unit is provided for a plurality of traveling lanes.

Images