JP5429988B2 - Vehicle monitoring system - Google Patents

Description

  The present invention relates to a vehicle monitoring system that images a license plate of a vehicle traveling on a road or the like with a monitoring camera.

2. Description of the Related Art A vehicle monitoring system is known in which a license plate of a vehicle is imaged with a monitoring camera on the road or the like. Conventionally, as such a vehicle monitoring system, when a vehicle detection sensor detects a vehicle, the vehicle is imaged by a camera, a brightness value of a license plate is calculated, and an aperture value of the camera is adjusted based on the brightness value. There has been proposed an automatic license plate recognition method and apparatus for imaging again, so that different types of license plates can be clearly imaged with one camera (see, for example, Patent Document 1). In addition, a vehicle number recognition device is disclosed in which a lighting device that is normally off is turned on only when the pyroelectric sensor detects the vehicle at a distance from the field of view of the camera, and consumes less power and has a longer life. (For example, refer to Patent Document 2).
In addition, when a license plate of a vehicle passing through a predetermined outdoor location is imaged with a camera, and an image signal obtained from the camera is processed to read a vehicle number, γ when obtaining an image signal between daytime and nighttime It has been proposed to correct the image in advance on the computer side (see Patent Document 3).

  Since the vehicle monitoring system having such a vehicle monitoring camera is used day and night, the subject (vehicle) is an infrared projector using a light emitting diode (hereinafter abbreviated as “LED”) that emits infrared light at night. ). In an infrared projector having an LED attached to a housing, it is important that the license plate can be clearly imaged. However, the license plate includes a mixture of a self-emission type license plate and a non-emission type license plate. For this reason, if the output of the infrared projector is set so as to emit light with the optimum light emission intensity for imaging one license plate, the other license plate may not be clearly imaged.

  For example, many license plates used in Japan are non-emission type license plates, so if you set the light emission intensity to be optimal for imaging non-emission type license plates, the brightness will be higher when imaging self-emission type license plates. It becomes high and halation occurs in the image. On the other hand, if the light emission intensity is set to be optimal for imaging the self-luminous license plate, the amount of light applied to the non-light-emitting license plate is insufficient, and a clear image cannot be obtained.

Japanese Patent Laid-Open No. 08-287390 Japanese Patent Laid-Open No. 10-261190 JP 2002-300437 A

  The present invention has been made in view of the above circumstances, and determines the type of the license plate based on the luminance value of the license plate of the vehicle measured by the luminance sensor, with the optimum emission intensity for imaging of the determined license plate. An object of the present invention is to provide a vehicle monitoring system that can control the output of an infrared projector to clearly image all license plates.

The present invention is a vehicle monitoring system including a vehicle monitoring camera that images a vehicle and an infrared projector that illuminates the vehicle, a laser sensor that detects the passage of the vehicle traveling on a road surface, and the vehicle A brightness sensor that measures the brightness value of the license plate, and a control unit that controls the light emission intensity of the infrared projector, wherein the vehicle monitoring camera opens the shutter, images the license plate, closes the shutter, and the control When the luminance value of the license plate measured by the luminance sensor is lower than a predetermined threshold, the unit emits light from the infrared projector with a first light emission intensity that is a relatively high light emission intensity, When the brightness value of the license plate measured by the brightness sensor is higher than a predetermined threshold value, the first emission intensity is increased. Light is emitted from the infrared projectors in a more relatively low second emission intensity, the brightness sensor measures the luminance value of the number plate of the vehicle after closing and the shutter before opening the shutter, the shutter If the brightness value measured before opening is the same as the brightness value measured after opening the shutter, the next time the vehicle passes, the brightness value measured before opening the shutter and the shutter are When the brightness value measured after opening is different, the vehicle monitoring camera opens the shutter again and images the license plate .

  With this configuration, the infrared projector always emits light with the optimum intensity for imaging with respect to different types of license plates, and it is possible to clearly capture images of any type of license plates.

  In the vehicle monitoring system according to the present invention, the threshold value can discriminate between a luminance value of a self-luminous license plate measured by the luminance sensor and a luminance value of a non-luminous license plate. Including.

  With this configuration, the license plate brightness can be determined by comparing the brightness value of the license plate measured by the brightness sensor with a threshold value, and the infrared projector emits light with the optimum intensity for imaging the determined license plate. Thus, all the license plates can be imaged clearly.

  Furthermore, the present invention provides the vehicle monitoring system, wherein the infrared projector is provided in a rectangular box-shaped housing having an opening on one vertical surface, and in the vicinity of the opening of the housing, and includes a plurality of infrared LEDs. And a planar light emitter composed of an LED substrate arranged in a plane.

  With this configuration, the planar light emitter can be configured in a compact manner, and the vehicle can be imaged by the surveillance camera regardless of day and night and without being noticed by the driver.

  According to the present invention, the type of the license plate is determined based on the luminance value of the vehicle license plate measured by the luminance sensor, and the output of the infrared projector is controlled with the optimum light emission intensity for imaging the determined type of license plate. Therefore, it is possible to provide a vehicle monitoring system that can clearly image all types of license plates.

It is a figure which shows the structure of the vehicle monitoring system which concerns on embodiment of this invention, (a) is a top view of a vehicle monitoring system, (b) is a side view of this top view The block diagram which shows schematic structure of the vehicle monitoring system which concerns on embodiment of this invention The perspective view which shows the external appearance of the infrared projector which concerns on embodiment of this invention The flowchart for demonstrating the control procedure of the vehicle monitoring system which concerns on embodiment of this invention. Time chart for explaining the operation of the vehicle monitoring system according to the embodiment of the present invention

Hereinafter, a vehicle monitoring system according to an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a vehicle monitoring system according to an embodiment of the present invention. (A) is a plan view of the vehicle monitoring system, and (b) is a side view of the plan view. As shown in the figure, the vehicle monitoring system 10 of the present embodiment is arranged in front of the laser sensor 13 that detects the passage of the vehicle 20 traveling on the road 11 and the traveling direction of the vehicle 20 from the laser sensor 13. It comprises a luminance sensor 14, an infrared projector 15, a vehicle monitoring camera 16, and a control unit 17.

  The laser sensor 13 includes a laser irradiation unit 13a and a laser light receiving unit 13b respectively accommodated in a pair of support columns 12 arranged on both sides crossing the road 11, and the laser L irradiated from the laser irradiation unit 13a. Is received by the laser receiving unit 13b. When the vehicle 20 blocks the laser L emitted from the laser irradiation unit 13a, the laser L cannot be received by the laser light receiving unit 13b, thereby detecting the passage of the vehicle 20.

  The brightness sensor 14, the infrared projector 15, and the vehicle monitoring camera 16 are disposed in front of the laser sensor 13 in the traveling direction of the vehicle 20, and the front side thereof is in the direction of the laser sensor 13, that is, the front surface 21 of the traveling vehicle 20. Is installed toward the license plate 22 of the vehicle 20.

  Thereby, the brightness sensor 14 measures the brightness value of the license plate 22, the infrared projector 15 illuminates the vehicle 20, particularly the vicinity of the license plate 22, and the vehicle monitoring camera 16 is the number illuminated by the infrared projector 15. The plate 22 can be imaged. Moreover, the control part 17 is comprised with the electric circuit containing the microcomputer not shown.

  FIG. 2 is a block diagram showing a schematic configuration of the vehicle monitoring system according to the embodiment of the present invention. As shown in FIG. 2, the vehicle monitoring system 10 of the present embodiment includes a laser sensor 13, a luminance sensor 14, an infrared projector 15, a vehicle monitoring camera 16, a control unit 17, and a power supply unit 18. .

  As shown in FIG. 3, the infrared projector 15 has a configuration in which a planar light emitting body 27 is accommodated in a substantially rectangular box-shaped housing 25 having an opening 26 on one vertical surface. The planar light-emitting body 27 is formed by arranging a large number of infrared LEDs 29 emitting light in a specific wavelength region on the surface of the substrate 28 in, for example, a staggered pattern, and light (infrared rays) emitted from the infrared LEDs 29 is The light is irradiated toward the vicinity of the license plate 22 of the vehicle 20 through the opening 26.

  Next, a control procedure will be described for the vehicle monitoring system 10 according to the embodiment of the present invention configured as described above. FIG. 4 is a flowchart for explaining a control procedure of the vehicle monitoring system according to the embodiment of the present invention.

  When the vehicle 20 passes the laser sensor 13, the vehicle monitoring system 10 detects the passage of the vehicle 20 because the laser L emitted from the laser irradiation unit 13a is blocked by the vehicle 20 and cannot be received by the laser light receiving unit 13b. (Step S101). The luminance sensor 14 measures the luminance value B of the license plate 22 of the vehicle 20 based on the vehicle passing signal from the laser sensor 13 (step S102) and compares it with a preset threshold value S (step S103). .

  If the measured luminance value B of the license plate 22 is lower than the threshold value S (S> B), it is determined in step S104 that the license plate 22 is a non-light emitting license plate, and the shutter of the vehicle monitoring camera 16 is opened. Imaging of the license plate 22 is started (step S105).

  The infrared projector 15 emits infrared light at a first light emission intensity BH that is a relatively high light emission intensity in synchronization with the operation of the shutter of the vehicle monitoring camera 16 (step S106). Then, after closing the shutter of the vehicle monitoring camera 16 (step S107), the luminance sensor 14 again measures the luminance value B1 of the license plate 22 (step S108), and the previously measured luminance value B and the current luminance value B1. To determine whether or not there is a change in luminance value (step S109).

  When there is a change in the brightness value (B1 ≠ B), the process returns to step S105, the shutter is opened and closed, and the first light emission intensity BH, which is a relatively high light emission intensity from the infrared projector 15, is synchronized with this. The license plate 22 is imaged by emitting infrared rays. If there is no change in the brightness value B (B1 = B), the process returns to step S101 and waits for the next vehicle 20 to pass.

  On the other hand, if the measured brightness value B of the license plate 22 is higher than the threshold value S (S <B) in step S103, it is determined in step S204 that the license plate 22 is a self-luminous license plate, and vehicle monitoring is performed. The shutter of the camera 16 is opened and imaging of the license plate 22 is started (step S205).

  The infrared projector 15 emits infrared light with the second light emission intensity BL, which is a relatively low light emission intensity, in synchronization with the operation of the shutter of the vehicle monitoring camera 16 (step S206). Then, after closing the shutter of the vehicle monitoring camera 16 (step S207), the luminance sensor 14 again measures the luminance value B1 of the license plate 22 (step S208), and the previously measured luminance value B and the current luminance value B1. To determine whether or not there is a change in luminance value (step S209).

  When there is a change in the brightness value (B1 ≠ B), the process returns to step S205 to open and close the shutter, and in synchronization with this, the second light emission intensity BL that is a relatively low light emission intensity from the infrared projector 15 is used. The license plate 22 is imaged by emitting infrared rays. If there is no change in the brightness value B (B1 = B), the process returns to step S101 and waits for the next vehicle 20 to pass.

  By controlling in such a procedure, the vehicle monitoring system 10 operates as shown in FIG. FIG. 5 is a time chart for explaining the operation of the vehicle monitoring system according to the embodiment of the present invention.

  When the vehicle 20 passes through the laser sensor 13, as shown in FIG. 5A, a passing signal P of the vehicle 20 is output, and as a result, as shown in FIG. 5B (left half), the luminance sensor 14 is output. Measures the luminance value B of the license plate 22. As shown in FIGS. 5C and 5D, when the luminance value B is lower than the threshold value S (S> B), the infrared projector 15 determines that the light emitting license plate 22 is used, and the infrared projector 15 has a relatively high emission intensity. The license plate 22 is brightly illuminated by emitting infrared rays with the first emission intensity BH, and the shutter of the vehicle monitoring camera 16 is opened and closed to image the license plate 22. The number plate 22 is imaged a plurality of times each time the luminance value B changes.

  On the other hand, as shown in FIG. 5B (right half), when the luminance value B is higher than the threshold value S (S <B), it is determined that the light-emitting license plate 22 is used, and FIGS. ), The infrared projector 15 emits infrared rays with a second emission intensity BL, which is a relatively low emission intensity, illuminates the license plate 22, and opens and closes the shutter of the vehicle monitoring camera 16 to open the license plate. 22 is imaged. The number plate 22 is imaged a plurality of times each time the luminance value B changes.

  As described above, according to the vehicle monitoring system according to the embodiment of the present invention, the type of the license plate is determined based on the brightness value of the license plate, and the infrared projector emits light with the optimal light emission intensity for imaging. Regardless of the type of license plate, it is always possible to capture a clear image.

  In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably.

10 Vehicle monitoring system 11 Road (road surface)
DESCRIPTION OF SYMBOLS 13 Laser sensor 14 Luminance sensor 15 Infrared projector 16 Vehicle monitoring camera 17 Control part 20 Vehicle 22 Number plate 25 Case 26 Opening part 27 Planar light-emitting body 28 LED board 29 Infrared LED
B Luminance value BH First emission intensity BL Second emission intensity S Threshold

Claims (3)

A vehicle monitoring system comprising a vehicle monitoring camera that images a vehicle and an infrared projector that illuminates the vehicle,
A laser sensor for detecting the passage of the vehicle traveling on the road surface;
A brightness sensor for measuring the brightness value of the license plate of the vehicle;
A control unit for controlling the light emission intensity of the infrared projector,
The vehicle monitoring camera opens a shutter, images a license plate and closes the shutter,
The controller is
When the brightness value of the license plate measured by the brightness sensor is lower than a predetermined threshold, the infrared projector emits light with a first light emission intensity that is a relatively high light emission intensity,
When the brightness value of the license plate measured by the brightness sensor is higher than a predetermined threshold, the infrared projector emits light with a second light emission intensity relatively lower than the first light emission intensity ,
The brightness sensor measures the brightness value of the license plate of the vehicle before opening the shutter and after closing the shutter,
If the brightness value measured before opening the shutter and the brightness value measured after opening the shutter are the same, wait for the next vehicle to pass,
When the brightness value measured before opening the shutter is different from the brightness value measured after opening the shutter, the vehicle monitoring camera opens the shutter again and images the license plate. . The vehicle monitoring system according to claim 1,
The vehicle monitoring system, wherein the threshold value can distinguish between a luminance value of a self-luminous license plate measured by the luminance sensor and a luminance value of a non-luminous license plate. The vehicle monitoring system according to claim 1,
The infrared projector is
A rectangular box-shaped housing having an opening on one vertical surface;
A planar light-emitting body that is provided in the vicinity of the opening of the housing and is constituted by an LED substrate in which a plurality of infrared LEDs are arranged in a plane;
A vehicle monitoring system comprising:

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