JP4333462B2 - Moving object detection device - Google Patents

Description

  The present invention relates to a moving object detection apparatus that picks up an image at a predetermined cycle, extracts a difference between the plurality of images from the plurality of picked-up images at every predetermined difference cycle, and detects a moving object.

  2. Description of the Related Art Conventionally, there is a technique that detects an object moving by taking an image around a vehicle at a predetermined cycle using a camera, extracting a difference between a plurality of taken images (see, for example, Patent Document 1).

  As a method for extracting a difference between a plurality of images captured using such a camera, an inter-frame difference method and a background difference method can be cited.

  The inter-frame difference method extracts a difference between a plurality of images at a predetermined difference period for a plurality of images captured using a camera. As shown in FIGS. 5A and 5B, when there is a difference between the image before movement and the image after movement, only the moved object is extracted and the difference is extracted as shown in the difference image of FIG. Appears as In the example shown in FIGS. 5A to 5C, the moved object A appears in the difference image, and the non-moving object B does not appear in the difference image. In this way, only the moved object A is extracted.

  In the background difference method, a background image captured in advance is recorded, and a difference between the background image and an image captured by the camera is extracted. As shown in FIGS. 6A and 6B, when there is a difference between the background image and the image after entering the object, as shown in the difference image in FIG. appear. In the example shown in FIGS. 6A to 6C, the object C that has entered appears in the difference image, and the object D included in the background image does not appear in the difference image. Only the moving object C is extracted.

Since these methods can detect objects that move with relatively high accuracy with simple processing, for example, an anti-theft device that detects an intruder into a vehicle and generates a notification or alarm to the user or around the vehicle The image is displayed on a display, and is used in a visual assistance system that detects a pedestrian, bicycle, or the like in the vicinity of the vehicle and notifies the driver.
JP 2003-44996 A

  The above-mentioned visual assistance system prevents, for example, accidents involving right and left turns by detecting bicycles or motorcycles in the vicinity of the vehicle and warning the driver when the vehicle is parked waiting for a signal to turn right or left. It becomes possible to do.

  However, in such a case, if the blinker of the vehicle blinks when the vehicle turns right or left, the luminance of the portion imaged by the camera may change due to the blinking of the blinker. In this way, if the brightness of the part imaged by the camera changes, in the system that detects objects using the inter-frame difference method or the background difference method, there is no moving object, but there is an object that moves. The problem of misunderstanding is caused.

  FIG. 7 is a diagram showing a blinker signal for blinking the blinker at a predetermined cycle and a luminance characteristic of the blinker blinking at a predetermined cycle according to the input of the blinker signal. The blinker blinks once or twice per second by law. In addition, since an incandescent light bulb is used in many of the winkers, it has a characteristic that it slowly becomes brighter with respect to the rise of the winker signal and becomes darker with respect to the fall of the winker signal.

  In addition, the luminance around the winker, such as the vehicle body and the road surface around the vehicle, also changes in the same cycle due to the change in the luminance of the winker.

  Then, as shown in FIG. 8 (a), when the brightness of the part imaged by the camera changes due to the change in the brightness of the blinker, the moving object is moved even if the object does not move, as shown in FIG. 8 (b). I misunderstand that there is.

  As a result, there is a problem that bicycles and the like in the vicinity of the vehicle cannot be detected correctly due to the blinking of the blinker even though there are many accidents involving turning right and left.

  The present invention has been made in view of the above problem, and an object of the present invention is to detect a moving object without being affected by a change in luminance even when the luminance of a portion to be imaged changes periodically.

In order to achieve the above object, according to the first aspect of the present invention, images are taken at a plurality of timings, and a difference between a plurality of images is extracted and moved from a plurality of taken images every predetermined difference period. A moving object detection device for detecting an object to be captured, which captures an image at a predetermined cycle and outputs a plurality of captured images, and a cycle for acquiring a luminance change cycle of a portion captured by the imaging unit The acquisition unit and the image captured by the imaging unit are divided into a plurality of areas, and the luminance change period of the portion captured by the imaging unit acquired by the period acquisition unit and the imaging unit capture an image for each divided region. And a matching means for matching the difference period.

In this way, the matching unit divides the image captured by the imaging unit into a plurality of regions, and the luminance change cycle of the portion captured by the imaging unit acquired by the cycle acquisition unit and the imaging unit for each divided region. Since the difference period for capturing an image is matched, even if the luminance of the portion to be imaged changes periodically, a moving object can be detected without being affected by the luminance change.

Further, as in the second aspect of the invention, the period acquisition unit includes at least one of an average value, a median value, and a mode value of luminance of some or all pixels of the image captured by the imaging unit. And the luminance change period of the portion imaged by the imaging means can be obtained based on the obtained value .

  A configuration of a moving object detection apparatus according to an embodiment of the present invention is shown in FIG. As shown in the figure, the moving object detection device 1 is attached to a vehicle, picks up an image around the vehicle, outputs a picked up image data, processes the image picked up by the camera 20, and detects a moving object. And a display 30 that displays the processing result of the processing device 10 and an image in accordance with a signal input from the processing device 10.

  The processing device 10 is configured as a normal computer, and includes a CPU 11 that performs various arithmetic processes, a ROM 12 that stores data such as programs, a RAM 13 that temporarily stores data, and an input from the camera 20. An image input unit 14 for outputting image data to the bus, and an interface (I / O in the figure) for inputting / outputting signals to / from external devices such as a winker and a speaker (both not shown) provided in the host vehicle. F)), an image output unit 16 for outputting image data to be displayed on the display 30, and a bus line for connecting these components.

  The interface unit 15 outputs a signal for causing the speaker to generate a buzzer sound and sound. Further, the interface unit 15 receives a winker signal for blinking the winker from a relay provided in a circuit for controlling the winker.

  The CPU 11 reads a program stored in the ROM 12 and writes and reads data to and from the RAM 13 as necessary to perform predetermined arithmetic processing.

  The display 30 has a display screen such as a liquid crystal display, and displays the video on a display surface such as a liquid crystal display in response to an input of a video signal from the image output unit 16.

  The camera 20 is built in the camera built-in door mirror shown in FIG. 2, captures an image (moving image) around the vehicle at a predetermined sampling period, and outputs the captured image as a frame. Note that the sampling frequency (reciprocal of the sampling period) of the camera 20 in this embodiment is 30 frames / second. In addition, the camera 20 may be configured by a plurality of cameras, and may capture a wide-angle range image using a single camera with a built-in prism.

  Further, the vehicle is provided with a plurality of blinkers 40, and when these blinkers 40 blink, the brightness of the peripheral area of the blinkers 40 changes in synchronization with blinking of the blinkers 40 as shown in FIG.

  Further, the object detection area shown in FIG. 2 is an object detectable area of the moving object detection apparatus 1. When the bicycle 50 enters the object detection area, the bicycle 50 is detected as a moving object.

  In the above-described configuration, an image captured at a predetermined sampling period is input from the camera 20 to the processing device 10 and stored in the RAM 13. CPU11 extracts the difference between several images for every predetermined difference period from the several images memorize | stored in RAM13, and performs the difference process which determines whether there exists any difference.

  Next, with reference to FIG. 3, a difference in the difference image due to blinking of the blinker when the blinker blinking period and the difference period are synchronized with each other will be described.

  When the blinker blinking cycle (the blinker signal on / off cycle) and the difference cycle are not synchronized, that is, when the blinker blinking cycle and the difference cycle are not matched, in the difference processing, for example, images of the respective timings of Ta2 and Tb2 The difference will be extracted. In this case, since the luminance between the two images is different due to the blinking of the blinker, as shown in FIG. 3B, even if there is no movement of the object, it appears in the difference image so that there is a moving object.

  On the other hand, when the blinker blinking period and the difference period are synchronized, that is, when the blinker blinking period and the difference period are matched, the blinker signal and the difference period are synchronized. The difference between the images at each timing is extracted. In this case, since the luminance between the two images becomes equal due to the blinking of the blinker, as shown in FIG. 3B, when there is no movement of the object, it does not appear in the difference image.

  Thus, by making the blinker blinking cycle coincide with the difference cycle, it is possible to detect a moving object without being affected by blinking of the blinker.

  Next, with reference to FIG. 4, the process of CPU11 of the processing apparatus 10 at the time of a vehicle stop is demonstrated. When the power of the moving object detection device 1 is turned on, the CPU 11 periodically performs the process shown in FIG.

  First, it is determined whether or not the winker of the host vehicle is operating (ON). Specifically, whether or not the winker is operating based on whether or not the winker signal that controls blinking of the winker of the host vehicle input via the interface unit 15 is repeatedly turned on and off at a predetermined cycle. Is determined (S100).

  Here, when it is determined that the blinker is operating (determined as YES in S100), the turn-on / off cycle of the blinker signal (blinker blinking cycle) and the difference cycle are matched. In addition, since the blinking period of the blinker is 1 to 2 times per second, the blinking period and the difference period are made to coincide. As a result, the blinker signal and the difference period are synchronized, and the influence of blinking of the blinker can be eliminated (S102).

  Next, difference processing is performed. Specifically, the difference between the plurality of images is extracted from the plurality of images captured by the camera 20 for each difference period, that is, for each turn-on / off period of the blinker signal (S112).

  Next, it is determined whether or not there is a moving object based on whether or not the difference between the plurality of images has been extracted by the difference processing (S114).

  Here, if a moving object is detected, it is determined that there is an obstacle (YES in S114), and an alarm is generated for the driver. Specifically, a signal for generating sound is output to the speaker to generate an alarm from the speaker, and an image signal is output to the display 30 to display the detected object, and this processing is terminated.

  If it is determined in S100 that the blinker is not operating (ON) (NO in S100), the luminance change period of the portion imaged by the camera 20 is measured. Here, for example, a situation is assumed in which the luminance of the portion imaged by the camera 20 changes due to the blinking blinker of the adjacent vehicle. Specifically, with respect to a plurality of images input from the camera 20, an average value of the luminance of all the pixels is obtained for each image, and a luminance change period of a portion captured by the camera 20 is calculated based on the average value. Measure (S104).

  Here, based on whether or not the luminance change period is measured, it is determined whether or not the luminance change has periodicity (S106).

  Here, when the brightness change period is measured, it is determined that the brightness change has periodicity (YES in S106), the measured brightness change period and the difference period are matched (S108), and S112. Proceed to the process.

  In S106, if the luminance change period is not measured, it is determined that the luminance change is not periodic (determined as NO in S106), and the difference period is made to coincide with a predetermined value (S110). Proceed to processing.

  As described above, the moving object detection device 1 includes the camera 20 that captures an image at a predetermined cycle and outputs a plurality of captured images, and the processing device 10 changes the luminance of a portion captured by the camera 20. Therefore, even if the luminance of the portion to be imaged changes periodically, the luminance change period is not affected by the luminance change. , Moving objects can be detected.

  In the above-described embodiment, the imaging unit corresponds to the camera 20, and the period acquisition unit is a process for acquiring the ON / OFF cycle of the winker signal input via the interface unit 15 and the part imaged by the camera 20. The matching means corresponds to S102 and S108 in FIG. 4.

  In addition, this invention is not limited to the said embodiment, Based on the meaning of this invention, it can implement with a various form.

  For example, the CPU in the above embodiment obtains an average value of the luminance of all the pixels of each image for a plurality of images input from the camera in S104 of FIG. 4, and is imaged by the camera based on this average value. Although the example of measuring the luminance change period of the portion has been described, for example, a light receiving sensor may be provided, and the luminance change of the portion imaged by the camera may be detected by the light receiving sensor.

  Further, information that affects the luminance change of the part imaged by the camera, for example, a blinker signal for blinking the blinker of the adjacent vehicle may be acquired by inter-vehicle communication or the like.

  Further, the CPU in the above embodiment obtains an average value of the luminances of all the pixels of each image for a plurality of images input from the camera, and changes in luminance of a portion imaged by the camera based on the average value Although the example of measuring the period of the image is shown, the average value of the luminance of some pixels of each image is obtained, and the luminance change period of the portion imaged by the camera is measured based on the average value. Good.

  Moreover, in the said embodiment, although the case where the brightness | luminance of the part imaged with a camera changes by blinking of the blinker of the own vehicle or an adjacent vehicle was demonstrated to an example, for example, so that the vehicle front may be imaged through a windshield. In the case where a camera is provided in the passenger compartment, it is conceivable that the wiper is imaged by the camera when the wiper is activated. In this case, since it is conceivable that the luminance changes in the portion imaged by the camera due to the operation of the wiper, the CPU only needs to match the difference cycle with the wiper signal for controlling the wiper.

  Further, for example, when a portion imaged by a camera is illuminated by a fluorescent lamp on the road, the blinking cycle of the fluorescent lamp (1/50 Hz or 1/60 Hz which is the cycle of the commercial power supply) is shorter than the sampling cycle of the camera. There is a case. In this case, since the difference period cannot be made shorter than the sampling period, the blinking period of the fluorescent lamp and the sampling period may be synchronized. In this case, for example, a camera that can change the sampling period according to a synchronization signal input from the outside is provided, and the synchronization signal may be synchronized with the period of the commercial power supply. In addition, the luminance change period of the portion imaged by the camera may be matched with the camera sampling period.

  In addition, the luminance of the portion imaged by the camera changes due to various factors such as the influence of blinking of the blinker of the adjacent vehicle in addition to the influence of blinking of the blinker of the own vehicle. In such a case, the image may be divided into a plurality of areas, and a predetermined difference period may be set for each divided area. For example, the image is divided into a plurality of areas, the difference period of the area where the luminance periodically changes due to blinking of the blinker of the own vehicle is matched with the blinking period of the blinker of the own vehicle, and periodically The difference period may be set separately for each area so that the difference period of the region that changes automatically matches the blinking period of the blinker of the adjacent vehicle.

  In the above embodiment, an example in which the inter-frame difference method is applied has been described. However, the present invention can also be applied to the background difference method. For example, when a blinker blinks, if a difference between each image at each timing when the blinker turns off and a background image captured in advance is extracted, a moving object can be detected without being affected by blinking of the blinker.

  In the above embodiment, an example is shown in which an object is detected by a difference between two frames that extracts a difference between two images. For example, an object that moves by a difference between three frames that extracts a difference between three images. May be detected.

  In the above embodiment, an example is obtained in which the average value of the luminance of some or all of the pixels of the captured image is obtained, and the luminance change period of the portion imaged by the imaging unit is obtained based on the average value. As described above, at least one of the average value, median value, mode value, maximum value, etc. of the luminance of some or all pixels of the captured image is obtained, and the luminance change is determined based on the obtained value. You may utilize as a means to acquire a period.

It is a figure which shows the structure of the moving object detection apparatus which concerns on 1st Embodiment of this invention. It is explanatory drawing about the luminance change of the object detection area | region of a moving object detection apparatus, and the peripheral area | region of a winker. It is explanatory drawing about the difference of the difference image by blinking of the blinker in the case where it does not synchronize with the case where it synchronizes with the case where it synchronizes with the blinking period and the difference period of a blinker. It is a flowchart which shows the process of CPU of the processing apparatus at the time of a vehicle stop. It is explanatory drawing about the difference method between frames. It is explanatory drawing about a background difference system. It is a figure which shows the blinker signal and the luminance characteristic of a blinker. It is a figure for demonstrating a subject.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Moving object detection apparatus, 10 ... Processing apparatus, 11 ... CPU, 12 ... ROM, 13 ... RAM, 14 ... Image input part, 15 ... Interface part, 16 ... Image output part, 20 ... Camera, 30 ... Display, 40 ... winker.

Claims (2)

A moving object detection device that detects an object that picks up an image at a plurality of timings, extracts a difference between the plurality of images for each predetermined difference period, and detects a moving object.
Imaging means for capturing an image at the predetermined period and outputting a plurality of captured images;
A period acquisition means for acquiring a period of luminance change of a portion imaged by the imaging means;
The image picked up by the image pickup unit is divided into a plurality of regions, and the luminance change period of the portion imaged by the image pickup unit acquired by the cycle acquisition unit and the difference cycle are matched for each of the divided regions . A moving object detection apparatus comprising: a matching unit;   The period obtaining unit obtains at least one of luminance average value, median value, and mode value of some or all pixels of the image picked up by the image pickup unit, and performs the image pickup based on the obtained value. The moving object detection device according to claim 1, wherein a period of luminance change of a portion imaged by the means is acquired.

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