JPS63108884A - Picture monitoring system - Google Patents

Abstract

PURPOSE:To define the change of the on and off of an illumination to be no abnormality and to detect an invader or a fire or the like by extremely shorten ing a stroboscopic light emitting time and measuring a distance according to a time after the light is reflected on a target and until it is returned. CONSTITUTION:A distance picture of a background in which the invader is not present is previously stored in a reference picture memory 27 and when a current picture is compared with a reference picture and there is no abnormal ity such as the invader, the reference picture of the back-ground is updated to the current picture by a reference picture updating circuit 28. When a change object such as an invading object is present, the distance picture is changed and a change picture element having the difference between the current picture and the reference picture larger than a preset value is detected by a change picture element detecting part 29. the change picture element detecting part 29 binarizes the change picture element by a prescribed threshold in a form parameter extracting part 30, a form parameter is extracted from the binarized data to compare with a reference pattern 32 in a check identification part 31. The checked and identified data is decided on an abnormal state or not by a logical decision part 33.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field 1] The present invention relates to an image monitoring system that issues an alarm by detecting a change in a monitoring image.

[Background technology 1] The present inventor has already compared images manually generated from a TV camera,
If the size of the projection obtained by accumulating the values of large change II elements in the X direction and Y direction, respectively, between the current image and the reference side image (previous image) is larger than a certain setting value, the rectangular area is We have proposed a still image transmission method that detects a changed area and transmits the image of the changed area.

Since change detection by projecting the change WZ detects a change in the brightness of the image, changes in illumination or sunlight, shadows, etc. are also detected. Therefore, in this method, in order to detect an intruding object or the like, there is a problem that it is necessary to keep the illumination conditions constant and to set and control the effective time for change detection.

The inventor has also proposed an image monitoring method that detects changes in illuminance and updates the reference image, but in this case it is necessary to clearly distinguish between changes in illuminance and changes due to intruding objects.

On the other hand, the distance a where the value of each pixel is the distance rather than the brightness change
Image-based surveillance methods are being researched.

Typical methods for this include a triangulation method that measures distance by emitting a laser beam and then reflecting it back, and a triangulation method that measures the distance based on the position of the laser beam spot; It measures the time it takes to return. Since in these cases the spot has to be scanned over the NIL object, a scanner is required for this scanning. Some scanners use a mechanical mechanism to rotate a reflecting mirror, but mechanical scanners have problems with accuracy and longevity.

In addition, in the same way as scanning a spot, a slit light (thin linear light) is projected, and while scanning this slit light, the distance is measured by triangulation from the slit image to obtain a three-dimensional distance M1.
Although there is a method of obtaining one image, there is a problem in that it takes a long calculation time to obtain a distance image because calculations are performed sequentially while scanning, similar to slit light.

Note that there is a known example of using distance images to identify objects with fixed shapes such as mechanical parts.

By the way, in the case of image monitoring, since there are various intruding objects and changes, it is considered necessary to perform comparison using characteristics different from those of If machine parts.

Figure 3 shows a known example of optical radar type range 7ing using spot light, quoted from ``Three-dimensional measurement research, recent trends and prospects'' Eizo Information June issue (1986).
In the case of the optical pulse projection type shown in IS3 diagram (a), the laser beam emitted by the pulse laser 1 is scanned against the target 3 by the beam scanner 2, and the reflected beam reflected by the target 3 is divided into 7t) squares. receives the light, discriminates the received light level with a threshold circuit 5, converts the time it takes to reflect and return to the ground using a time-pulse height conversion circuit 6, and averages the average value of the converted signal. The converter 7 performs digital conversion, and the digitally converted data is processed by the combiator 8. In this example, 1c
It is said that the time resolution is high because it travels back and forth over a distance of - in 0.07 ns. Also, PIS3 figure (b
) modulated wave projection phase difference measurement method uses He-Ne laser 9 as A
Modulated to 9MHz with variable WRRS10 controlled by GC,
This modulated light is split by a branch mirror 17, further converted into an electrical signal and sent to the network analyzer 14, and is also projected onto the target 3 by the beam scanner 11, and the reflected beam reflected by the target 3 is further sent to the beam scanner 11.
The received light signal is sent to the network 7 naphizer 14 via the filter 13, where amplitude data and phase difference data are obtained.
This method is said to have a phase difference detection accuracy of 0.1 degrees and a distance detection accuracy of 1c-.

Other methods, such as U.S. Pat. No. 3,727,207, identify an intruding object by detecting that the propagation time for a light beam to reflect from the intruding object and return to the object becomes shorter. However, in this conventional example, the size etc. of the intruding object cannot be identified.

In addition, as for the triangulation mentioned above, there is
There is No. 89581, and further examples that utilize the parallax between two TV cameras include vtWR No. 119191/1982 and Japanese Patent Laid-Open No. 119192/1982.

[Objective of the Invention 1 The present invention has been made in view of the above-mentioned points, and its purpose is not to treat sudden changes in lighting on/off or sunlight as abnormal changes, but to detect intruders, fires, etc. An object of the present invention is to provide an image monitoring method that can detect false alarms and is free from false alarms.

[Disclosure of the Invention J] The present invention does not rely on Szat, but uses scattered light to project the distance I.
This method obtains a III-level image, so to speak, by making the flashing time of the strobe light extremely short, and measuring the distance by the time it takes for the light to reflect off the target and return.In addition, it focuses the light with a large objective lens, and uses photoelectrons. Since it uses a real image on a sensor array, it is characterized in that it does not require scanning such as spot light or slit light.

The present invention will be explained below with reference to Examples.

FIG. 1 shows the overall configuration of the embodiment, in which a light projector A transmits light from a light emitting element 18 consisting of a laser or an LED to an optical date 1 according to a timing signal from a timing circuit 36.
9 to generate a light pulse of about 1 n5ee. The pulse interval of this optical pulse is set by the optical date 19.The optical pulse that exits the optical date 19 is branched by the optical branching mirror 20 as a start pulse for the time difference measuring section (or phase difference measuring section) 21, and is also diffused. The light is diffused by the lens 22 and becomes scattered light, which illuminates the target 3.

The optical pulse reflected by this target 3 is the objective lens X:
At 23, the image is formed on the photoelectric sensor array 24, and outputted from the photoelectric sensor array 24 as a stop pulse. The time it takes to form a real image on the photoelectric sensor 7 ray 24 varies from sensor cell to sensor cell depending on the distance of the object. The response time of the photoelectric sensor element used in the sensor cell is set to be fast enough to detect a light pulse as a pulse.

Then, the time difference from the start to the stop of the optical pulse for each sensor cell is measured by the time difference measuring section (or phase difference detecting section) 2.
1, it is possible to obtain a distance image of 11 units with a time difference of about 7 n5ee, but in the present invention, the rangefinder 3
The time difference is converted into a distance in a section 25, and the distance image is written into a current image 7-frame memory 26. Here, the width of the optical pulse is set to about 10 psee, which is about 0.07 ns.
A distance accuracy of 1 cm can be achieved with a time difference of ec.

Normally, when distance images are measured by optical wave distance or modulated wave projection phase difference distance measurement, the distance is measured by the phase difference of the modulated wave between the light from the light source and the reflected light, but l! In order to increase the measurement accuracy of the distance, two waves such as tIL 20- and 2000 m are often used, but since the calculation time and circuit are somewhat complicated, this example uses a light pulse that is theoretically simple. A floodlight type is used.

Now, the base S* image memory 27 in FIG. 1 has previously stored a distance image of the background where no intruder is present, and when comparing the current image with the reference image, it was found that there was no usual change in the presence of an intruder, etc. In this case, the reference side update circuit 28 updates the background reference image to the current image. Note that a moving average may be taken as the reference image.

Here, since both the current image and the reference image are distance IaW images, they are not affected by brightness changes like images from a normal TV camera.

Now, when there is a changing object such as an intruding object, the distance 1a II 11 image changes, and the changed pixel detection unit 29 detects changed pixels that are larger than the set value where there is a difference between the current image and the reference image. Since the changed pixels detected in the above are not affected by brightness changes such as illumination, there are fewer false alarms than those detected by normal TV cameras. In order to cut out this changed pixel data, use shape parameter extraction 1!530 to binarize the changed i11 element using a predetermined threshold, and use this binarized data to extract shape parameters such as the area of the connected placement and the circumscribed rectangle. .

This shape parameter is compared and identified by a comparison/identification section 31 with a reference pattern 32 set as a determination reference value. Verification/identification data is further logically judged ff5
33, it is determined whether or not there is an abnormal state.

Since the shapes of intruders and the like change, simple parameters such as area and size can be used as shape parameters, and it is necessary to have a wide range of matching ranges.

Therefore, the logical judgment unit 33 has a knowledge base based on the environmental model judgment condition 34 that an intruder moves and a fire stands still and spreads, and also uses information from external sensors such as other disaster prevention and crime prevention sensors $135. This information is integrated and inferred to determine whether or not there is an abnormal state.

As described above, in this embodiment, a distance image of the target 3 is obtained using a light pulse, and by detecting pixels that change between the reference image consisting of the distance image and the current image, it is possible to determine whether it is in an abnormal state or not. The 1'4 cutoff prevents false alarms from being caused by turning lights on or off or by sudden changes in sunlight (changes in brightness).

FIG. 2 shows a specific configuration for obtaining a distance image. Next, the operation up to obtaining a distance image will be explained in detail based on this circuit configuration. First, the light projector A generates a light pulse using a timing pulse from the timing circuit 36. This optical pulse is branched by a branching mirror 20 and enters a diffusing lens converted to amp 2
1c, 7 lips 70 tubes 21 via comparator 21d
e is set, and the counter 211 is started with the output of the 7 lip 70 knob 21e. In other words, the branched optical pulse becomes a start pulse for the time difference measuring section 21. The counter 21f counts up the clock from the clock generator 21g.

On the other hand, 411: The light pulse diffused by the lens 22 is reflected by the target 3, focused by the objective lens 23, and forms a real image on the photoelectric sensor array 24. The electronic shutter 36 is closed at times when it is unnecessary for light to enter the photoelectric sensor 7 ray 24.

The photoelectric sensor 7 ray 24 is provided with a condensing lens 24& for each sensor cell 24m, so that surrounding light is collected at the light receiving portion of each photoelectric sensor cell 24m.

Now, the reflected light pulse reaches the sensor cell 24m and is converted into an electrical signal, passes through the amplifier 37 and the comparator 38, and sets the 7-lip 70 knob 39. The 7-lip 70 knob 39 gives a stop pulse to the counter 21f. Here, 7 lip 70 knob 21e and 7 lip 70 knob 39
Their outputs serve as mutual reset signals. Now, when the counter 21f is given a stop pulse, the counter 21f converts the clock count value to the I! of the distance calculating section 25. JI* exchange circuit 25a
Output to. Distance conversion circuit 25m is count value (time)
Convert to distance. Here, the output of the timing circuit 36 selects the address of the photoelectric sensor array 24 and the address of the current image frame memory 26, so the data selector 2
The sensor cell 24 on the photoelectric sensor array 24 via 5b
Distance data of a specific address of m is written into a selected memory cell of the current image 7-frame memory 26''. The address counter 40 is for setting the address in accordance with the timing signal of the timing circuit 7.

Parallel processing is performed for each sensor cell 24m from each sensor cell 24m to the distance conversion circuit 25a, so both distance Ia images can be obtained for each reflected light pulse, which is a real image for one light pulse. By taking a moving average of the time constant over a plurality of optical pulses, the disturbance can be eliminated by PJI.

Furthermore, if it is possible to lengthen the detection cycle (flI period), the distance calculation for each sensor cell 24a can be parallelized for each line, or a real distance image of the 1 gs sensor cell 24m can be calculated for each optical pulse. You may do so.

Further, in the above embodiment, modulated light may be used instead of using optical pulses, and in this case, the optical date 19 is replaced by a variable Ill.
In this case, a phase difference measuring section is used instead of the time difference measuring section 21.

Effects of the Invention J Since the present invention is configured as described above, it is possible to create a real image ascending distance*W image on the photoelectric sensor array, and therefore there is no need to scan light pulses or modulated light, and [ Through processing, it is possible to create a distance of 111 m quickly, and mechanical troubles during scanning and causes of unstable accuracy are eliminated.
Furthermore, since image monitoring is performed using distance images, there is an effect that false alarms due to changes in brightness of illumination or the like are reduced.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention, FIG. 2 is an overall configuration diagram of essential parts of the same as the above, and FIG. 3 is a configuration diagram of a conventional example. A... Floodlight, 3... Target, 21... Time difference measuring section, 24... Photoelectric sensor array, 24m...
Sensor cell, 25...Distance calculation unit, 26...Current image 7-frame memory.

Claims (2)

[Claims] (1) A photoelectric sensor generates a light pulse consisting of scattered light, and detects the time difference between the light pulse and the light pulse that is reflected by a target, focused by an objective lens, and received as a real image by a two-dimensionally arranged photoelectric sensor array. An image monitoring system characterized in that the distance of a target corresponding to a real image of each sensor cell of an array is calculated, and a distance image is formed in a current image frame memory cell corresponding to each sensor cell. (2) Modulate the light emission of a light emitting element such as a laser or LED with a modulated wave with a long wavelength to generate modulated light consisting of scattered light, and combine the modulated light with a real image reflected by the target and focused by the objective lens. The distance to the target corresponding to the real image of each sensor cell of the photoelectric sensor array is calculated from the phase difference with the received modulated light received by the two-dimensionally arranged photoelectric sensor array, and the current image frame memory cell corresponding to each sensor cell is calculated. An image monitoring method characterized by forming a distance image.