JP2002238029A - Image storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image storage device, having a storage element that has a long image storage period per unit storage capacity. SOLUTION: A compressed image storage section 57 stores a coded signal Hk obtained by compressing a picked-up image, and a circuitry from a decoding section 33 to a digital/analog conversion section 11 expands the coded signal Hk reproduced from the compressed image storage section 57. The compressed image storage section 57 is provided with the storage element, that can store the coded signals Hk for a prescribed period and stores the coded signals Hk for a prescribed period from the present back to the past. Since the compressed image storage section 57 of the image storage device 181 stores the coded signals Hk, that are compressed and have less information quantity, the capacity of the storage element provided to the compressed image storage section 57 to store images worth a prescribed period can be saved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image storage device suitable for coupling to a monitoring device for detecting the occurrence of an abnormality based on an image picked up by a television camera.

[0002]

2. Description of the Related Art A monitoring device that automatically detects and reports occurrence of an abnormality by analyzing an image while constantly monitoring an image picked up by a television camera has been used. A monitoring system having a form in which a plurality of monitoring units usually provided for each television camera and a control unit for centrally controlling the monitoring units are connected by a communication line is one type of this monitoring device.

Also, an image storage device that stores image signals sequentially and stores the image signals for a certain period of time in the past can also be used for monitoring an abnormality by reproducing an image when an abnormality has occurred. The use of abnormality monitoring in the field is increasing.

[0004]

However, the conventional monitoring apparatus merely processes the image signal transmitted from the television camera as it is or simply digitizes it. For this reason, there has been a problem that the abnormality detection unit that determines whether an abnormality has occurred reacts unnecessarily and sensitively. In addition, since this abnormality detection unit requires a complicated operation, there is a problem that the circuit scale becomes large. Above all, the monitoring system has a problem that a communication line connecting the monitoring unit and the control unit requires a high information transmission capacity.

Further, the image storage device has good operability,
For reasons such as durability, it is suitable to use a semiconductor storage element such as a RAM as a storage medium for storing an image. However, in a conventional image storage device, an image signal transmitted from a television camera or the like is simply digitized. Since the image was only stored, the image storage period was short and limited. Alternatively, a storage element having a large storage capacity is required to store images for a predetermined period.

An object of the present invention is to provide an image storage device having a long image storage period per storage capacity of a storage element.

[0007]

According to a first aspect of the present invention, there is provided an image storage device for sequentially storing image signals and storing the image signals for a certain period of time in the past by compressing the image signals. An image compression means for obtaining a compressed image signal, and a compressed image accumulating means for sequentially storing the compressed image signal to accumulate the compressed image signal for a certain period of time in the past.

The apparatus according to a second aspect of the present invention is the image storage apparatus according to the first aspect, further comprising an image decompression means for obtaining a reconstructed image signal by decompressing the compressed image signal stored by the compressed image storage means. It is characterized by having.

A third aspect of the present invention is the image storage device according to the second aspect of the present invention, wherein the compressed image storage means is configured to start or end at a point in time when the control signal is input in response to the control signal. And outputting the stored compressed image signal for a predetermined period including the current time.

The device according to a fourth aspect of the present invention is the image storage device according to the third aspect of the present invention, further comprising abnormality detecting means for detecting occurrence of an abnormality based on an image picked up by a television camera. Is characterized in that a signal of the captured image is input as the image signal, and the abnormality detection unit inputs the control signal to the compressed image storage unit when the occurrence of the abnormality is detected.

According to a fifth aspect of the present invention, in the image storage device of the fourth aspect, the abnormality detecting means detects a change in a signal amount of the compressed image signal per fixed screen; Abnormality determining means for determining that there is an abnormality when a change in the signal amount detected by the signal amount change detecting means is equal to or more than a predetermined amount.

A sixth aspect of the present invention is the image storage device according to the fifth aspect, wherein the image compression means irreversibly compresses the image signal to obtain an irreversible compressed image as the compressed image. A lossless compression unit is provided, and the abnormality detection unit detects the occurrence of the abnormality by analyzing the reconstructed image.

A device according to a seventh aspect of the present invention is the image storage device according to the second aspect, wherein the image compressing means and the image decompressing means are connected via a communication line.

An apparatus according to an eighth aspect of the present invention is the image storage apparatus according to the first aspect, wherein the compressed image storage means starts or ends at a point in time when the first control signal is input in response to the first control signal. The compressed image signal for a fixed period or a fixed period including the time point is fixedly held, and the held compressed image signal is output in response to a second control signal.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <1. First Reference Technology> FIG. 1 is a block diagram showing the overall configuration of an apparatus according to this reference technology.
This device 100, which is an example of a monitoring device, obtains a low-quality image by performing a compression operation on a high-quality image obtained by imaging with a television camera, and analyzes the obtained low-quality image. Automatically detects the occurrence of abnormality. To compress an image, for example, JPEG (Joint Photogra
An image compression technology based on the “JPEG algorithm” proposed by the Phic Expert Group) is used.

Although the JPEG algorithm was originally proposed with the aim of standardizing the color still image coding system, the so-called "intra-frame coding" technology is also used for dynamic images constantly transmitted by television cameras. Can be used as one. Intra-frame encoding is a technique for compressing a dynamic image using only a dynamic image for one screen, that is, a correlation within one frame, without considering a correlation between different frames.

Detecting the correlation between frames, in particular, detecting the motion of an image requires costly processing.
Apparatus for performing image compression becomes expensive. This device 10
0 uses the “intra-frame coding” technique,
There is an advantage that the device is simple and inexpensive. Also,
Since there is no need to provide a special semiconductor memory device for decoding a signal encoded using the correlation between frames, the device can be simplified and reduced in cost in this respect as well.

<1-1. Image Compression and Image Decompression> As shown in FIG. 1, an analog / digital converter (A / D converter) 1 provided in the apparatus 100 includes an NTSC transmitted from an external television camera. The signal is always input. The NTSC signal is a color image signal based on the NTSC system, which is a standard system for transmitting a color television signal, and has three components of a luminance signal and two types of color difference signals. The A / D conversion unit 1 converts an analog NTSC signal into a digital signal.

The digitized NTSC signal is sent to the color space converter 2. The color space conversion unit 2 converts the input digital NTSC signal into, for example, a color signal Pm (m = m = m) representing the density of each component of the RGB color system for each pixel.
0, 1,...). One color signal Pm is composed of, for example, 8 bits so that the density of one color of one pixel is represented by, for example, 256 gradations. The pixel is a minimum unit constituting a screen, and is arranged in a matrix along two scanning directions orthogonal to each other on the screen, for example. The color space conversion unit 2 executes conversion while referring to a conversion table 3 in which conversion coefficients and the like are stored in a storage medium such as a ROM.

The color signals Pm are sequentially transmitted to the frequency space conversion unit 4. The frequency space conversion unit 4 performs a predetermined mathematical process to obtain a color signal Pm
Is a frequency conversion coefficient Sij which is a component in the frequency space.
(I, j = 0, 1,...). In the example in which the JPEG algorithm is used, the frequency space conversion unit 4 first converts a row of the input color signals Pm (m = 0, 1,...) Into two orthogonal scanning directions on the screen. × 8
(= 64) Pixels are divided into blocks each of which is arranged in a matrix. Then, 64 color signals Pxy (x, y = 0 to 7) expressing the color density of the pixels in each block
Each time a two-dimensional discrete cosine transform is performed, and as a result, 64
Discrete cosine transform coefficients (DCT coefficients) Suv (u,
v = 0 to 7) are output.

The frequency conversion coefficients Sij (i, j = 0, 1,
..) Are sequentially transmitted to the quantization unit 5. The quantization unit 5 performs quantization on the frequency transform coefficient. That is, the position of each frequency conversion coefficient Sij is designated (i,
For each j) (in other words, for each spatial frequency), quantization is generally performed with a different step width (step size). The quantization unit 5 performs quantization with reference to a quantization table 6 in which a storage medium such as a ROM stores a step width and the like for each spatial frequency. The quantization coefficient Rij (i, j = 0, 1,...) Obtained in this way is output from the quantization unit 5.

In an example in which the JPEG algorithm is used, 64 DCT coefficients Suv (u, v = 0 to 7) define a step width for each coefficient position (u, v).
The number of coefficients Quv (u, v = 0 to 7) are prepared in the quantization table 6. Then, the quantization unit 5 executes division by dividing the DCT coefficient Suv by the coefficient Quv, and converts the quotient to an integer, thereby obtaining the quantization coefficient Ruv (u,
v = 0 to 7) are obtained.

The image quality can be adjusted by changing the value of the coefficient Quv. When the coefficient Quv is set to a small value, the value of the quantization coefficient Ruv increases, and a high-quality image that is the same as or close to the original image can be obtained. Conversely, if the coefficient Quv is set to a large value, the value of the quantization coefficient Ruv decreases, so that the amount of information decreases, but the image quality deteriorates. As described above, the coefficient Q prepared in the quantization table 6
By changing the value of uv, the image quality and the amount of information can be freely controlled.

The quantization coefficient Rij is sent to the inverse quantization unit 7. The inverse quantization unit 7 performs an operation opposite to that of the quantization unit 5. For this purpose, the quantization table 6 referred to by the quantization unit 5 is commonly referred to in the inverse quantization unit 7. The frequency transform coefficient S′ij obtained by reconstructing by the inverse quantization unit 7 is no longer necessarily the same as the original frequency transform coefficient Sij, and the image quality deteriorated by the quantization unit 5 is not restored.

The frequency transform coefficient S'ij is input to a frequency space inverse transform unit 8 that performs an operation reverse to that of the frequency space transform unit 4, and as a result, a color signal P'm is output. The color signal P′m is further input to a color space inverse conversion unit 9 that performs an operation opposite to the color space conversion unit 2, and as a result, a digital NTSC signal is reconstructed. The color space inverse conversion unit 9 performs conversion while referring to a conversion table 10 in which conversion coefficients and the like are stored in a storage medium such as a ROM.

The digital NTSC signal (reconstructed image signal) output from the color space inverse converter 9 is converted into an analog signal through a digital / analog converter (D / A converter) 11, and is converted to an external image receiving device such as a CRT. Sent to Since this NTSC signal has passed through the quantization unit 5, A
It is not always the same as the original NTSC signal input to the / D conversion unit 1. When the image quality is degraded by the quantization unit 5, the degraded image is not restored, and the degraded low-quality image is drawn on the image receiving device. As described above, the image compression performed in the process from the color space conversion unit 2 to the quantization unit 5 and the subsequent inverse quantization unit 7 to the color space inverse conversion unit 9
The image decompression performed in the process leading to is irreversible.

<1-2. Abnormality Detection and Image Quality Control> The digital NTSC signal output from the color space inverse converter 9 is a D / A
At the same time as being input to the converter 11, it is also input to the motion detector 12 and the feature point extractor 13. The motion detection unit 12 performs arithmetic processing on the input NTSC signal,
This is a device for detecting a moving object, that is, a moving part in an image represented by the NTSC signal. The motion detection unit 12 detects a moving object by comparing images between different frames, for example. Feature point extraction unit 1
No. 3 detects a portion satisfying a feature point specified in advance in the image. For example, detection of the edge of the object is performed.

The detection results obtained by the motion detector 12 and the feature point extractor 13 are input to the abnormality determiner 14. The abnormality determination unit 14 determines whether a predetermined condition corresponding to the occurrence of abnormality is satisfied based on the moving object detected by the motion detection unit 12 and the feature points detected by the feature point extraction unit 13. . If the condition is satisfied, an alarm signal for notifying the occurrence of an abnormality is sent to the outside, and a control signal for instructing the image quality control unit 15 to change the image quality is sent.

The image quality control unit 15 is based on the control signal from the abnormality determination unit 14, and the contents of the conversion table 3 referred to by the color space conversion unit 2, and the quantization referred to by the quantization unit 5 and the inverse quantization unit 7. The contents of the table 6 and the contents of the conversion table 10 cited by the color space inverse conversion unit 9 are changed. The conversion table 3, the quantization table 6, and the conversion table 10 store a plurality of types of contents in advance, and the image quality control unit 15 instructs the color space conversion unit 2 or the like to select one of them. . Alternatively, each table uses, for example, a RAM as a storage medium, and the content stored in each table is always one, and the content is stored in the image quality control unit 15.
May be configured to be rewritten.

As described above, the image quality of the image (reconstructed image) output by the color space inverse conversion unit 9 is changed by changing the contents of the tables referred to.

The image quality control unit 15 controls so that a low-quality image with a high compression ratio suitable for abnormality determination is obtained during a period until the abnormality determination unit 14 detects the occurrence of an abnormality, that is, a normal period. During the abnormal period after the detection of, is controlled so that a high-quality image with a low compression ratio suitable for visual monitoring is obtained.

For example, in the normal period, only the low spatial frequency component, that is, the low frequency component, of the frequency conversion coefficient Sij obtained by the conversion by the frequency space converting unit 4 selectively appears strongly, and the high frequency component disappears. Or, control is performed so as to take out the retreated image. A so-called mosaic image is one example. By doing so, it is possible to prevent an excessive reaction in the abnormality detection and to detect
2. The calculations in the feature point extraction unit 13 and the abnormality determination unit 14 are simplified. That is, it is possible to simplify the configuration of these device parts.

On the other hand, during the abnormal period after the abnormality is detected, a high-quality image can be obtained, so that the observer can visually monitor the image displayed on the image receiving device. In addition, by starting the recording of a high-quality image on an external VTR (image recording apparatus) by using the alarm signal as a trigger, it becomes possible for the observer to perform visual verification later.

The image quality controller 15 receives an external control signal from the outside together with the control signal from the abnormality determiner 14. An external control signal (first external control signal) for instructing reset (cancel) by the operation of the observer is transmitted to the image quality control unit 15.
, The operation is returned from the operation in the abnormal period to the operation in the normal period. That is, the contents of each of the tables referred to are changed again so that a low-quality image with a high compression ratio suitable for abnormality determination is obtained.

Further, by appropriately inputting an external control signal (second external control signal) by an operation of a supervisor or the like,
It is also possible to select and output a desired image quality irrespective of the determination by the abnormality determination unit 14.

In the above description, the image quality control unit 15
Changed the contents quoted for any of the conversion table 3, the quantization table 6, and the conversion table 10 corresponding to the two operation periods.
The contents of the quantization table 6 may be changed. Also in this case, a low-quality reconstructed image and a high-quality reconstructed image can be selectively obtained. However, by changing the conversion tables 3 and 10 in addition to the quantization table 6, it is possible to obtain an image most suitable for both abnormality determination and visual monitoring.

FIG. 2 is an explanatory diagram showing the time course of image information obtained by the color space inverse converter 9 and subjected to analysis for abnormality detection in comparison with the conventional apparatus. In FIG.
A rectangular frame schematically shows one frame of image information. Then, the thickness of each image information in the time direction represents a transmission period of each image information.

As shown in FIG. 2, the conventional apparatus always obtains high-quality image information HP having a large amount of information.
In the device 100, low-quality image information LP that has a small amount of information in a normal period, is easy to calculate, and is suitable for abnormality detection is obtained. When an abnormality occurs, the image quality is changed in response to a control signal from the abnormality determination unit 14 requesting a change in the image quality. As a result, during the abnormal period, high-quality image information HP suitable for visual monitoring continues. can get. The operation returns to the normal period in which the low-quality image information LP is obtained by the external signal instructing the reset.

<1-3. Operation Flow> FIG. 3 is a flowchart showing the operation flow of the apparatus 100. As shown in FIG. 3, when the operation of the apparatus 100 is started, first, in step S1, the captured image obtained by capturing the image with the television camera is compressed. This step is executed by the color space conversion unit 2 to the quantization unit 5. Next, in step S2, a reconstructed image is obtained by expanding the compressed image. This step is executed by the inverse quantization unit 7 to the inverse color space conversion unit 9.

Next, the process proceeds to step S3, where the motion detection unit 12 and the feature point extraction unit 13 perform motion detection and feature point extraction on the reconstructed image. Next,
In step S4, abnormality determination is performed by the abnormality determination unit 14. In a period during which the determination result of no abnormality is obtained in step S4, that is, in a normal period, step S1
To Step S4 are repeatedly executed. During this period, compression and decompression are performed at a high compression ratio so that a low-quality reconstructed image suitable for abnormality determination is obtained.

In step S4, if a determination result indicating that there is an abnormality is obtained, the process proceeds to step S5, where an alarm signal is sent out by the abnormality determination unit 14. Subsequently, steps S6 to S8 are performed by the image quality control unit 15. That is, the contents of each of the tables referred to are changed so that a high-quality image suitable for visual monitoring is obtained.

Then, in step S9, the compression of the image by the quantization unit 5 from the color space conversion unit 2 is executed. Next, in step S9, the image is expanded by the inverse quantization unit 7 and the inverse color space conversion unit 9. Next. In step S11, the image quality control unit 15 determines whether the abnormality has been eliminated. This determination is made, for example, by determining whether or not an external control signal for instructing reset (cancel) has been input by an operation of a supervisor.

In step S11, during the period during which it is not determined that the abnormality has been resolved, that is, during the abnormal period, the steps S9 to S11 are repeatedly executed. During this period, compression and decompression are performed at a low compression ratio so that a high-quality reconstructed image suitable for visual monitoring is obtained.

In step S11, if a result of the determination that the abnormality has been eliminated is obtained, the process proceeds to step S12, and the abnormality determination unit 14 stops sending the alarm signal. Subsequently, steps S13 to S15 are executed by the image quality control unit 15. That is, the contents of each of the tables referred to are changed so that a low-quality reconstructed image suitable for abnormality detection is obtained. Then, the process returns to step S1.

<2. Second Reference Technology> FIG. 4 is a block diagram showing an overall configuration of an apparatus according to a second reference technology. The monitoring device 110 is an example of a monitoring system. Apparatus 1
In 10, a monitoring unit 200, which is a device part for performing a compression operation on an image obtained by imaging with a television camera, and a control for automatically detecting the occurrence of an abnormality by decompressing and analyzing the compressed image The unit 300 is separated and connected by a communication line 250. Communication line 25
0 may be either wired or wireless. In the case of wireless, the communication line 250 is the same as the natural space itself, and is not an artificially prepared facility.

In this apparatus 110, for example, an image compression technique based on the JPEG algorithm can be used to compress the image. In the following drawings, the same parts as those of the apparatus 100 of FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

<2-1. Surveillance Unit 200> As shown in FIG. 4, an analog / digital converter (A / D converter) 1 provided in the surveillance unit 200 has an analog format transmitted from an external television camera. Is always input. The NTSC signal is digitized by the A / D converter 1 and then compressed from the color space converter 2 through the quantizer 5 to obtain a quantized coefficient Rij.

The quantization coefficient Rij obtained by the quantization unit 5
Is input to the encoding unit 21 provided in the next stage. The encoding unit 21 first performs a so-called series conversion in which the quantization coefficients Rij are rearranged according to a certain rule. The rearrangement rules employed in this conversion are set so that the amount of compression is maximized when encoding for compressing the information amount is performed subsequently without changing the image quality. In the example using the JPEG algorithm, so-called zigzag conversion is performed for each quantization coefficient Ruv (u, v = 0 to 7) for one block. That is, the quantization coefficient Ruv (u, v =
The quantization coefficients Ruv (u, v = 0 to 7) are rearranged from the order along the rows and columns of the matrix of 8 × 8 in which 0 to 7) are arranged to the so-called zigzag order. .

Subsequently, the encoding unit 21 calculates the quantized coefficients Rn (n = 0, 1,...) Obtained by the rearrangement.
Encoding corresponding to so-called entropy compression is performed. The encoding unit 21 performs encoding with reference to a code generation table 22 in which codes and the like are stored in a storage medium such as a ROM. Code sequence Hk obtained by encoding
(K = 0, 1,...) Realizes further compression of the information amount without deteriorating the image quality of the image supplied by the quantization coefficient Rij input to the encoding unit 21. That is, the encoding unit 21 reversibly realizes further image compression by performing the encoding.

In the example using the JPEG algorithm,
Quantization coefficient Rn for one block (n = 0, 1,...)
Each time, coding based on the Huffman coding method is performed. Then, in the code generation table 22, information for executing Huffman coding corresponding to a so-called Huffman code table is prepared in advance.

The coded signal Hk having a small amount of information transmitted from the coding unit 21 is, for example, one frame worth of the communication line 250.
Are temporarily stored in the code buffer 23 in order to adjust the timing of sending them together. The code buffer 23 is composed of, for example, a RAM. Then, the data is sequentially read by the communication control unit 24 at an appropriate time, and is sequentially transmitted to the communication line 250. The communication control unit 24 is an input / output interface for the communication line 250,
In response to a control signal transmitted from 0, it has a function of adjusting the timing of transmitting the encoded signal Hk.

The communication control unit 24 also has a function of controlling the operation of the image quality control unit 25 based on a control signal sent from the control unit 300. The image quality control unit 25 changes the contents of the cited conversion table 3, quantization table 6, and code generation table 22 in response to a control signal from the communication control unit 24.

<2-2. Control Unit 300> Next, in the control unit 300, the encoded signal Hk transmitted by the monitoring unit 200 is input from the communication line 250 to the communication control unit 31. The communication control unit 31 is an input / output interface with respect to the communication line 250, and has a function of appropriately taking in the encoded signal Hk transmitted from one or more monitoring units 200. Further, the communication control unit 31 also plays a role of transmitting a control signal to the communication control unit 24 of the monitoring unit 200.

The coded signal Hk taken in is temporarily stored in the code buffer 32 to adjust the timing. Then, the encoded signal Hk is transmitted from the code buffer 32 to the decoding unit 33 as appropriate. The decoding unit 33 reconstructs the quantization coefficient Rij from the coded signal Hk by performing an operation reverse to that of the coding unit 21. Since the encoding by the encoding unit 21 and the decoding by the decoding unit 33 are reversible operations, the decoding unit 33 reproduces the same signal as the quantization coefficient Rij input to the encoding unit 21. You. In the decoding unit 33, the encoding unit 21
Are referred to the same code generation table 22 as the one referred to.

The reconstructed quantized coefficient Rij passes through the inverse quantization unit 7 and the inverse color space conversion unit 9 to be further expanded and reproduced as a digital NTSC signal.
The reproduced NTSC signal (reconstructed image signal) is converted into an analog signal through a digital / analog converter (D / A converter) 11 and transmitted to an external image receiving device such as a CRT. Since the NTSC signal has passed through the quantization unit 5 of the monitoring unit 200, it is not always the same as the original NTSC signal input from the television camera to the A / D conversion unit 1. When the image quality is degraded by the quantization unit 5, the degraded image is not restored, and the degraded low-quality image is drawn on the image receiving device.

<2-3. Abnormality Detection and Image Quality Control> The digital NTSC signal output from the color space inverse converter 9 is
/ A conversion unit 11 and the motion detection unit 12
Is also input to the feature point extraction unit 13. The motion detection unit 12 and the feature point extraction unit 13 detect a moving object and a feature point, respectively.
It is sent to the abnormality determination unit 14. In the abnormality determination unit 14,
Based on these results, it is determined whether a predetermined condition corresponding to the occurrence of an abnormality is satisfied. When the condition is satisfied, an alarm signal for notifying the occurrence of an abnormality is sent to the outside, and a control signal for instructing the image quality control unit 35 to change the image quality is sent.

The image quality control unit 35 changes the contents of the conversion table 10, the quantization table 6, and the code generation table 22 referred to in the control unit 300 based on the control signal from the abnormality determination unit 14, and at the same time, Monitoring unit 2 through communication control unit 31 and communication line 250
A control signal is sent to 00. In the monitoring unit 200, the control signal is received by the communication control unit 24 and sent to the image quality control unit 25. The image quality control unit 25
Based on this control signal, the conversion table 3, the quantization table 6, and the
The contents of the code generation table 22 are changed.

As described above, both the monitoring unit 200 and the control unit 300 change the contents of the tables referred to, thereby changing the image quality of the image reproduced by the control unit 300.

The image quality control units 25 and 35 are
During the normal period until the occurrence of an abnormality is detected, control is performed so that a low-quality image with a high compression ratio suitable for abnormality determination is obtained. Control is performed to obtain an image of high quality. By doing so, similarly to the device of the first reference technology, it is possible to prevent an excessive reaction in the abnormality detection, and to simplify the calculations in the motion detector 12, the feature point extractor 13, and the abnormality determiner 14. Is done. That is, it is possible to simplify the configuration of these device parts. On the other hand, during the abnormal period, a high-quality image is obtained, so that visual monitoring becomes possible.

The image quality controller 35 receives an external control signal from the outside together with the control signal from the abnormality determiner 14. By inputting an external control signal (first external control signal) for instructing a reset to the image quality control unit 15, the operation from the abnormal period to the operation in the normal period is performed. Further, by appropriately inputting an external control signal (second external control signal), a desired image quality can be selected and output irrespective of the determination by the abnormality determination unit 14.

As described above, the monitoring system 110 separates the device portion for compressing the image and the device portion for expanding and reproducing the image in the monitoring device 100 of the first reference technology, and connects them to each other by the communication line. It has a form.
For this reason, it is possible to install those device parts far apart from each other.

The most desirable mode of use is a mode in which the control unit 300 is installed at a place where the observer performs monitoring and operation, and the monitoring unit 200 is installed adjacent to the television camera at a place to be monitored. . Since a compressed signal with a small amount of information is transmitted to the communication line 250 connecting the monitoring unit 200 and the control unit 300, a long distance connecting the place to be monitored and the place to be operated is connected. As the communication line 250, a simple communication line with a low information transmission capacity can be used.

By installing a plurality of monitoring units 200 at various locations, it is possible to monitor a plurality of locations intensively at one location using a simple communication line 250 having a small information transmission capacity. For monitoring at a plurality of locations, the monitoring units 200 are deployed at a plurality of locations to be monitored, and the same number of control units 300 are centrally installed at one location.
This can be realized by connecting one to one.

In this apparatus 110, a signal Hk having a higher compression ratio than that of apparatus 100 is transmitted to communication line 250 because encoding is performed. FIG. 5 is an explanatory diagram showing this. That is, in FIG. 5, a rectangular frame schematically shows one frame of signal transmitted to the communication line 250, and the thickness of each signal in the time direction represents each transmission period.

As shown in FIG. 5, the communication line 250
Through the normal period until the control signal HC requesting the high-quality image is transmitted and the abnormal period until the control signal LC requesting the release is transmitted thereafter, the low-quality image information LP shown in FIG. A low-quality coded signal LS and a high-quality coded signal HS having a smaller amount of information than the image information HP are transmitted.

Therefore, if a communication line required by a conventional device for directly transmitting the output of a television camera is used as the communication line 250, as shown in FIG. A large time gap is created. For this reason, a simple communication line 250 having a lower information transmission capacity than the communication line required by the conventional device can be used.

Alternatively, if a communication line required by the conventional device is prepared as the communication line 250, coding from a plurality of monitoring units 200 can be performed using a time gap regardless of a normal period and an abnormal period. The signal Hk is transmitted to the common communication line 2
50 can be transmitted in a time-division manner. As described above, the communication line 250 is connected between the plurality of monitoring units 200.
In other words, in order to multiplex and use the communication line 250, the communication control unit 31 transmits a control signal for distributing the transmission timing to the communication control units 24 of the plurality of monitoring units 200 in a timely manner. Good.

The high-quality coded signal HS has a smaller amount of information than the original signal even if the high-quality coded signal HS has the same image quality as the output image of the television camera by performing a process of coding. In order to further reduce the information amount of the high-quality coded signal HS, even in an abnormal period in which a high-quality image is obtained, the quantizing unit 5 performs processing on a component having a high spatial frequency that is relatively insensitive to the human visual angle. Should perform relatively coarse quantization.
By doing so, without deteriorating the effective image quality,
The amount of information can be further reduced, and the degree of multiplexing of a certain communication line 250 can be further increased, so that the communication line 250 can be shared by more monitoring units 200.

As shown in FIG. 5, the time gap generated between the low-quality coded signals LS in the normal period is longer than the gap between the high-quality coded signals HS in the abnormal period. I have. Utilizing this, for example, a simple communication line 250 having an information transmission capacity capable of transmitting the high-quality coded signal HS transmitted by one monitoring unit 200 is prepared, and a plurality of communication lines 250 are provided only during a normal period. The low-quality coded signal LS from the monitoring unit 200 can be transmitted in a time-division manner.

That is, the communication line 25 is limited only during the normal period.
0 is shared by a plurality of monitoring units 200, and if an abnormality is detected at a location monitored by one monitoring unit 200, only the monitoring unit 200 occupies the communication line 250 during the subsequent abnormal period. It is possible. By doing so, a simple communication line 250 having a low information transmission capacity can be effectively used.

In the above description, the image quality control unit 35
Changed the contents quoted in any of the conversion table 3, the quantization table 6, the code generation table 22, and the conversion table 10 corresponding to the two operation periods. The contents of the quantization table 6 may be changed. Also in this case, a low-quality reconstructed image and a high-quality reconstructed image can be selectively obtained. However, in addition to the quantization table 6, the conversion tables 3, 10
Also, by changing the code generation table 22, it is possible to obtain the most suitable image for both the abnormality determination and the visual monitoring, and it is also possible to obtain the coded signal Hk with the least amount of information.

In the above description, the example in which the image quality control unit 25 operates according to the control signal from the image quality control unit 35 has been described. However, in general, the image quality control unit 25 and the abnormality determination unit 14 are connected in some form, and the image quality control unit 25 responds to the determination result of the abnormality determination unit 14 and determines a predetermined period corresponding to the normal period and the abnormal period. The system may be configured to perform the above operation. Therefore, some device unit including the communication line 250, the communication control unit 31, and the like may be interposed between the image quality control unit 25 and the abnormality determination unit 14 that are coupled to each other.

<2-4. Operation Flow> FIG. 6 is a flowchart showing the operation flow of the monitoring unit 200 in the apparatus 110. When the operation of the device 110 is started, first,
In step S21, an analog NTSC signal is received, and in step S22, the received NTSC signal is received.
The SC signal is converted to a digital format. These steps are executed by the A / D converter 1.

Next, the process proceeds to step S23, where the color space conversion unit 2 performs conversion to a color space, that is, conversion from an NTSC signal to a color signal Pm. Subsequently, the process proceeds to step S24, where the frequency space conversion unit 4 performs conversion into the frequency space, that is, conversion from the color signal Pm into the frequency conversion coefficient Sij. Then, the process proceeds to step S25, where the quantization unit 5 performs quantization, that is, conversion from the frequency conversion coefficient Sij to the quantization coefficient Rij.

Next, in step S26, sequence conversion, that is, rearrangement of the quantization coefficients Rij is performed. Then, proceeding to step S27, the entropy compression, that is, the above-described encoding is performed, and the encoded signal Hk is obtained. These steps are performed by the encoding unit 21. Thereafter, in step S28, the encoded signal Hk
Is transmitted to the communication line 250 in a timely manner. This step is executed by the code buffer 23 and the communication control unit 24.

Thereafter, the flow returns to step S21 to receive a new NTSC signal. Hereinafter, step S2
By repeatedly executing the processes from 1 to S28, the compression operation including the encoding of the constantly input NTSC signal is continuously performed. These steps are performed with reference to three types of tables provided in the monitoring unit 200. By appropriately changing the contents of these tables, compression into images of various image quality is performed.

FIG. 7 is a flowchart showing the operation of the control unit 300. As shown in FIG.
Is started, first, in step S31, a reconstructed image is obtained by performing an image expansion operation including decoding of the encoded signal. This step is executed by the color space inverse conversion unit 9 from the decoding unit 33.

Next, the flow shifts to step S32, where the motion detection section 12 and the feature point extraction section 13 perform motion detection and feature point extraction on the reconstructed image. Next, in step S33, abnormality determination is performed by the abnormality determination unit 14. In the period during which the determination result indicating that there is no abnormality is obtained in step S33, that is, during the normal period, the processes of steps S31 to S33 are repeatedly performed. During this period, the monitoring unit 200 performs compression at a high compression ratio, and the control unit 300 performs expansion corresponding to the low-quality reconstructed image suitable for abnormality determination.

In step S33, if a determination result indicating that there is an abnormality is obtained, the process proceeds to step S34, where an alarm signal is sent out by the abnormality determination unit 14. Subsequently, the image quality control unit 35 performs steps S35 to S3.
Step 7 is executed. That is, the contents of each of the tables referred to are changed so that a high-quality image suitable for the abnormal period is obtained.

Then, in step S38, the image expansion operation including the decoding of the encoded signal is performed by the decoding unit 33 to the inverse color space conversion unit 9. Next. The process proceeds to step S39, and the image quality control unit 35 determines whether the abnormality has been resolved. This determination is made, for example, by determining whether or not an external control signal for instructing reset (cancel) has been input by an operation of a supervisor.

In step S39, during the period in which it is not determined that the abnormality has been resolved, that is, during the abnormal period, steps S38 to S39 are repeatedly executed. During this period, the monitoring unit 200 performs compression at a low compression ratio, and the control unit 300 performs corresponding expansion so that a high-quality reconstructed image suitable for visual monitoring is obtained.

In step S39, if a result of the determination that the abnormality has been resolved is obtained, the process proceeds to step S40, and abnormality determination unit 14 stops sending the alarm signal. Subsequently, steps S41 to S43 are executed by the image quality control unit 35. That is, the contents of each of the tables referred to are changed so that a low-quality reconstructed image suitable for abnormality detection is obtained. Then, the process returns to step S31.

<3. Third Reference Technology> FIG. 8 is a block diagram showing an overall configuration of an apparatus according to a third reference technology. This device 120 is another example of a monitoring system. Also in this device 120, the monitoring unit 40, which is a device portion for performing a compression operation on an image obtained by imaging with a television camera,
0 and a control unit 500 for automatically detecting the occurrence of an abnormality by analyzing the compressed image after decompressing it.
And are separated by a communication line 250.

The device 120 is different from the device 11 of the second reference technology in the configuration of the image quality control unit 41 provided in the monitoring unit 400 and the image quality control unit 42 provided in the control unit 500.
0 is characteristically different, and the other components are the same as the device 110.

The abnormality determination unit 14 of the control unit 500
When the occurrence of the abnormality is detected, an alarm signal for notifying the occurrence of the abnormality is transmitted to the outside, and a control signal for instructing the image quality control unit 42 to change the image quality is transmitted. Image quality control unit 42
Changes the contents of the conversion table 10, the quantization table 6, and the code generation table 22 referred to in the control unit 500 based on the control signal from the abnormality determination unit 14, and simultaneously changes the contents of the communication control unit 31 and the communication Line 25
A control signal is sent to the monitoring unit 400 through “0”.

In the monitoring unit 400, the control signal is received by the communication control unit 24 and sent to the image quality control unit 41. Based on this control signal, the image quality control unit 41 converts the conversion table 3, the quantization table 6, and the code generation table 2 referred to in the monitoring unit 400.
Change the contents of 2.

FIG. 9 schematically shows the information amount and the transmission timing of the coded signal Hk transmitted from the monitoring unit 400 to the communication line 250 during the normal period until the abnormality determination section 14 detects the occurrence of the abnormality. FIG. In FIG. 9, a rectangular frame schematically shows one frame of signal transmitted to the communication line 250, and the thickness of each signal in the time direction represents each transmission period.

In the normal period, the image quality control units 41 and 42 make it possible to alternately obtain a low-quality image with a high compression rate suitable for abnormality determination and a high-quality image with a low compression rate suitable for visual monitoring. Next, each table is controlled. As a result, FIG.
As shown in (1), after a fixed number of low-quality coded signals LS are transmitted to the communication line 250, another fixed number of high-quality coded signals HS are transmitted. This cycle is then continued iteratively.

As described above, in the device 120, the low-quality image and the high-quality image are alternately obtained in a time-division manner in the normal period, so that both the automatic abnormality determination and the visual monitoring are performed in the normal period. Can be performed simultaneously and in parallel.

During the abnormal period after the abnormality judging unit 14 detects the occurrence of the abnormality, the image quality control units 41 and 42 continuously obtain only high-quality images suitable for visual monitoring, as in the case of the device 110. Control each table as needed. As a result, during the abnormal period, only the high-quality coded signal HS is continuously transmitted to the communication line 250. Unlike a normal period in which high-quality images for visual monitoring are obtained in a form in which frames are thinned out, high-quality images are continuously obtained, so that more precise visual monitoring can be performed.

An external control signal from the outside together with the control signal from the abnormality determining unit 14 is input to the image quality control unit 42. By inputting an external control signal (first external control signal) for instructing reset to the image quality control unit 42, the operation from the abnormal period to the operation in the normal period is performed. Further, by appropriately inputting an external control signal (second external control signal), a desired image quality can be selected and output irrespective of the determination by the abnormality determination unit 14.

Also in this device 120, similarly to device 110, signal Hk whose compression rate has been further increased by encoding is transmitted to communication line 250. Therefore, if a communication line required by the conventional device is prepared as the communication line 250, the communication line 250 is multiplexed regardless of the normal period and the abnormal period, and the communication line 250 is shared by a plurality of monitoring units 400. It is possible to In the case where multiplexing is not performed, the communication line 250 may be a simple communication line having a lower information transmission capacity than a communication line required by a conventional device for directly transmitting the output of a television camera.

<4. Fourth Reference Technology> FIG. 10 is an explanatory diagram showing the configuration of the device of the fourth reference technology and the operation during a normal period. This device 130 is yet another example of a monitoring system. In this apparatus 130 as well, the monitoring unit 600, which is a device part for applying a compression operation to an image obtained by imaging with a television camera, and the occurrence of an abnormality is automatically determined by decompressing and analyzing the compressed image. The control unit 700 for detection is separated and connected by a communication line 250. Further, a plurality of (n in the example of FIG. 10) monitoring units 600 are connected to one control unit 700.

FIG. 11 is a block diagram showing the internal configuration of the apparatus 130. The device 130 is different from the device 1 of the third reference technology in that the monitoring unit 600 includes the memory 45, the configuration of the communication control unit 46, and the configuration of the communication control unit 47 and the image quality control unit 48 included in the control unit 700.
20 is characteristically different, and the other components are the same as the device 120.

The image quality control section 41 of each monitoring unit 600
During the normal period until the abnormality determination unit 14 detects an abnormality, a low-quality image with a high compression rate suitable for abnormality determination and a high-quality image with a low compression rate suitable for visual monitoring are alternately obtained. So that each table in the monitoring unit 600 is controlled. As a result, the communication control unit 46 alternately outputs the low-quality coded signal LS and the high-quality coded signal HS.

FIG. 10 schematically shows this operation. In FIG. 10, a rectangular frame schematically shows one frame of signal output from the communication control unit 46, and the thickness of each signal in the time direction represents each output period. Of the low-quality coded signal LS and the high-quality coded signal HS output by the communication control unit 46, only the low-quality coded signal LS is transmitted to the communication line 250 in the normal period. Moreover, not all of the low-quality coded signals LS are transmitted to the communication line 250, but only one of the n low-quality coded signals LS is transmitted.

That is, one of the n monitoring units 600 is sequentially selected in a certain order, and only the low-quality coded signal LS output by the communication control unit 46 of the selected monitoring unit 600 is transmitted to the communication line 250. Is sent. At the same time, the low-quality coded signal LS and the high-quality coded signal HS
The data is sequentially input to the memory 45. The memory 45 continues to store the low-quality coded signal LS and the high-quality coded signal HS that are not transmitted to the communication line 250 for a certain period of time going back from the present to the past.

To sequentially select one of the n monitoring units 600, the image quality control unit 48 sends a selection signal from the communication control unit 47 to the communication control unit 46 of each monitoring unit 600 via the communication line 250. It is transmitted sequentially in a divided manner.

In the control unit 700, during the normal period, the low-quality coded signal LS is continuously expanded. That is, in the normal period, the image quality control unit 48 controls the control unit 700 so as to obtain a low-quality reconstructed image by expanding the low-quality coded signal LS.
To control each table in.

The communication control unit 47 of the control unit 700
Low quality coded signals LS from n monitoring units 600
Are sequentially received in a time-division manner. For this reason, the control unit 7
At 00, the low-quality coded signals LS from the n monitoring units 600 are similarly sequentially expanded in a time-division manner, and an abnormality is detected based on a reconstructed image obtained by expansion. That is, abnormality detection based on images transmitted from the n monitoring units 600 sequentially proceeds in a time-division manner.
Thus, in the normal period, the n monitoring units 600
Share the communication line 250 and the control unit 700 in a time-sharing manner.

Next, when the abnormality determination unit 14 detects the occurrence of an abnormality, the image quality control unit 48 transmits a predetermined control signal from the communication control unit 47 to the communication control unit 46 of each monitoring unit 600 via the communication line 250. I do. As a result, the monitoring unit 600 that has transmitted the image in which the abnormality has been detected is specified, and the coded signal Hk is transmitted to the communication line 250 only from the specified monitoring unit 600.

The coded signal Hk transmitted at this time is the low-quality coded signal LS and the high-quality coded signal H stored in the memory 45 in the designated monitoring unit 600.
S. That is, the low-quality coded signal LS and the high-quality coded signal HS stored in the memory 45 for a certain period before and after the abnormality is detected are alternately transmitted from the communication control unit 46 to the communication line 250.

When the abnormality judging section 14 detects the occurrence of an abnormality, the image quality control section 48 synchronizes with the timing at which the low-quality coded signal LS and the high-quality coded signal HS are alternately input. Decompression of image quality encoded signal LS and high image quality encoded signal H
Control unit 70 so that the extension of S is performed alternately.
Control each table in 0. As a result, a low-quality reconstructed image and a high-quality reconstructed image are obtained alternately in a time-division manner. Abnormality determination unit 1 based on the low-quality reconstructed image
The abnormality detection by 4 or the like is executed again.

That is, the determination based on the thinned reconstructed image obtained in the normal period is reconfirmed based on the reconstructed image that is not thinned. By doing so, it is possible to suppress the occurrence of a determination error caused by thinning.
In addition, since a high-quality reconstructed image can be obtained together with a low-quality reconstructed image, it is possible to visually confirm occurrence of an abnormality by projecting the image on an external image receiving device.

As a result of the reconfirmation, if it is determined that there is no abnormality, the operation after the abnormality determination unit 14 detects the abnormality, that is, the operation in the reconfirmation period returns to the operation in the normal period. Conversely, when the abnormality is confirmed again, the operation in the reconfirmation period shifts to the operation in the new abnormality period.

That is, when the abnormality determination unit 14 detects the occurrence of the abnormality again, the image quality control unit 48 transmits a predetermined control signal from the communication control unit 47 to the communication control unit 46 of each monitoring unit 600 via the communication line 250. I do. as a result,
The monitoring unit 600 that has transmitted the image in which the abnormality is detected is continuously designated, and the transmission of the encoded signal Hk to the communication line 250 from only the designated monitoring unit 600 is continued.

Further, the control signal is transmitted from the communication control unit 46 to the image quality control unit 41. As a result, the image quality control unit 41 changes the contents of the conversion table 3, the quantization table 6, and the code generation table 22 cited in the monitoring unit 600. That is, after receiving the control signal, the image quality control unit 41 controls these tables so that only the high image quality encoded signal HS is continuously output from the encoding unit 21. Further, the communication control unit 46 continuously sends out the high-quality coded signal HS to the communication line 250 without thinning.

At the same time, the image quality controller 48 converts the conversion table 10, the quantization table 6,
And the code generation table 22 as the high-quality coded signal HS
Is controlled so that it can be continuously extended. As a result, in the abnormal period, the monitoring unit 600 in which the abnormality is detected
, High quality images are continuously obtained. For this reason, it becomes possible to continuously visually monitor the monitoring target in which the abnormality is detected.

When the abnormality judging section 14 detects an abnormality, it sends an alarm signal to the outside. When this alarm signal is sent,
It may be at the time of abnormality detection before reconfirmation or after reconfirmation.

As described above, the device 130 of this reference technology is used.
Then, the control unit 700 includes a plurality of monitoring units 600.
In addition to reconstructing the coded signal Hk from the base station in a time-division manner, it also performs abnormality detection at the same time. Therefore, it is possible to connect a plurality of monitoring units 600 to a single control unit 700. Further, since the coded signals Hk from all the monitoring units 600 are transmitted to the communication line 250 in a time-division manner, the communication line 250 may be a simple and inexpensive one having a low transmission capacity.

An external control signal from the outside is input to the image quality control unit 48 together with the control signal from the abnormality determination unit 14. By inputting an external control signal (first external control signal) for instructing reset to the image quality control unit 48, the operation from the abnormal period to the operation in the normal period is performed. In addition, by appropriately inputting an external control signal (second external control signal), it is possible to specify a desired monitoring unit 600 and select a desired image quality irrespective of the determination by the abnormality determination unit 14. is there.

The monitoring unit 600 has a memory 45
However, instead of providing the memory 45, the storage capacity of the code buffer 23 is increased and the code buffer 23
May be stored.

In the above description, the example in which the image quality control unit 41 operates according to the control signal from the image quality control unit 48 has been described. However, in general, the image quality control unit 41 and the abnormality determination unit 14 are connected in some form, and the image quality control unit 41 responds to the determination result of the abnormality determination unit 14 to perform the normal period, the reconfirmation period, and the abnormal period. The system only needs to be configured to perform a predetermined operation corresponding to the period. Therefore, the image quality control unit 41 and the abnormality determination unit 14
Some device unit including the communication line 250, the communication control unit 47, and the like may be interposed therebetween.

The same can be said for the communication control unit 46. Further, the selection signal for selecting one of the n monitoring units 600 may be transmitted by the communication control unit 47 instead of the image quality control unit 48. That is, it is sufficient that the control unit 700 has a device portion that performs a control function for outputting the encoded signal Hk from the n monitoring units 600 in a time-division manner.

<5. Fifth Reference Technology> In the device 130 of the fourth reference technology, based on the determination by the abnormality determination unit 14, the operation automatically changed from the operation in the normal period to the operation in the reconfirmation period and the operation in the abnormal period. Instead, the abnormality determination unit 14
Based on the determination made in step 4, the operation directly shifts from the operation in the normal period to the operation in the abnormal period, the operation is shifted to the operation in the reconfirmation period by the external control signal, and the codes before and after the abnormality detection are stored in the memory 45. The device may be configured such that the coded signal Hk is reconfigured.

Alternatively, the control unit 700 is not provided with the motion detecting section 12, the feature point extracting section 13, and the abnormality determining section 14, and switching to the operation in each of the normal period, the reconfirmation period, and the abnormal period is performed. , The apparatus may be configured to be performed only by the external control signal.

Further, in the fourth reference technology and the system of this reference technology, it is possible to eliminate the operation in the reconfirmation period and to make a transition between the operation in the normal period and the operation in the abnormal period. In this case, during the normal period,
The image quality control unit 41 may control each of the tables 3, 6, and 22 so that only the low image quality encoded signal LS is always obtained.

<6. Sixth Reference Technology> Here, an abnormality detection operation in the devices or systems of the first to fifth reference technologies will be described. FIG. 12 is an example of a high-quality image obtained for a railroad crossing area as a monitoring target. In this monitoring example, when the train is approaching,
Whether an object corresponding to a person or a vehicle is present in the railroad crossing area corresponds to the presence or absence of the abnormality. That is, as illustrated in FIG. 13, if the vehicle is present in the railroad crossing area when the train is approaching, it should be determined that the vehicle is abnormal.

In the conventional monitoring apparatus, a high-quality image illustrated in FIG. 13 is processed, and a noise signal is reduced by flattening an image density frequency (histogram), deleting isolated points, and the like. An object such as a vehicle is confirmed by performing processing and further separating into several regions. In such a process, an accurate shape of the object can be confirmed, but a large amount of processing time is required because the process is required for each pixel. In addition, fine objects unrelated to the determination of abnormality, such as the shape of the groove A of the wheel in FIG.

On the other hand, the image shown in FIG.
FIG. 14 shows an image obtained by reconstructing a compressed image based on the EG algorithm so as to remove all high-frequency components and leave only the lowest frequency component. That is,
The reconstructed image thus obtained is represented by a single representative color for each 8 × 8 block. In FIG. 14, the size of one block is enlarged for convenience.

In the apparatuses or systems according to the first to fifth reference techniques, for example, a low-quality reconstructed image as shown in FIG. Do. By doing so, abnormality detection can be performed quickly with a small amount of calculation. In addition, in the image of FIG. 14, since information unnecessary for abnormality detection is removed, the accuracy of the determination is increased.
Further, as described above, since the compressed image is transmitted to the communication line 250, the traffic of the communication line 250 is greatly reduced.

Further, by adding a noise reduction process such as deleting an isolated point, that is, an isolated block, and then detecting an abnormality, unnecessary information can be further reduced, and the amount of calculation can be further reduced. .

FIG. 15 is a flowchart showing an example of the operation flow in the feature point extraction unit 13. When the process is started, first, in step S51, a reference image (reference image) is compressed and stored. For example, an image when there is no abnormality shown in FIG. 12 is set as a reference image, and this reference image is compressed and reconstructed as shown in FIG. For that purpose, the reconstructed image transmitted from the color space inverse conversion unit 9 when there is no abnormality may be stored.
The feature point extraction unit 13 has a built-in memory, and the compressed reference image is stored in this memory.

Next, in step S52, the reconstructed image transmitted from the color space inverse converter 9 is received. Then, in step S53, one block is replaced with a single representative color. If the reconstructed image transmitted from the color space inverse converter 9 is an image having only the lowest frequency component,
This processing is not particularly necessary. If any high frequency component is included, a single representative color is determined for each block and replaced with this representative color.

Next, in step S54, an isolated point is removed. Subsequently, in step S55, a comparison is made between the image obtained in step S54 and the reference image. That is, a difference value between the two images is calculated for each block. This calculation may be performed, for example, only for an image area necessary for abnormality detection. For example, FIG.
4 may be performed only for the region B and the region C.

Next, in step S56, the difference value is compared with the threshold value for each block. This comparison may be performed, for example, only for the region B and the region C. Then, information below the threshold is deleted. Subsequently, in step S57, it is determined whether there is information other than “0” in both the area B and the area C.

As shown in FIG. 14, when an object that is not in the reference image exists in both the area B and the area C, information that is not “0” exists in both areas.
In this case, the process proceeds to step S58. Conversely, if at least one of the area B and the area C matches the reference image, there is no information other than “0” in the matched area. In this case, the process proceeds to step S59.

In step S58, it is recognized that an object exists in both the area B and the area C. Then, a signal notifying the fact is transmitted to the abnormality determination unit 14. Thereafter, the process returns to step S52.

In the step S59, it is recognized that there is no object in at least one of the area B and the area C. Then, a signal to that effect is transmitted to abnormality determination unit 14. Thereafter, the process returns to step S52.

The abnormality judging section judges the presence or absence of an abnormality based on the signal from the feature point extracting section. In this example, when a signal indicating that “there is an object in both the region B and the region C” is received from the feature point extracting unit 13, it is determined that there is an abnormality, and “at least one of the region B and the region C is included. If a signal indicating that "there is no object" is received, it is determined that there is no abnormality.

The abnormality determining section 14 further includes the motion detecting section 1
Alternatively, the determination may be made with reference to the signal from the second. For example, whether or not there is a motion in the area C may be added as a condition for determination. When there is no motion in the area C, that is, when the train is stopped, even if an object is confirmed in both the area B and the area C, it is possible to perform a process such as not determining that the object is abnormal.

<7. Seventh Reference Technology> FIG. 16 is a block diagram showing an overall configuration of an apparatus according to a seventh reference technology. This device 140 is yet another example of a monitoring system. Apparatus 1
In 40, the control unit 800 includes a code amount change detection unit 5 instead of the motion detection unit 12 and the feature point extraction unit 13.
1 is characteristically different from the system of the second reference technology, and the configuration and operation of other device parts are the same as those of the second reference technology.
It is the same as the system of the reference technology.

The code amount change detecting section 51 outputs the coded signal Hk
In the normal period in which the low-quality coded signal LS is transmitted, the code amount for one screen, that is, the signal amount of the coded signal Hk for one screen is constantly monitored. Send to The abnormality determination unit 14 compares the amount of change with a predetermined amount that is set in advance, and if the amount of change exceeds the predetermined amount, determines that there is an abnormality, and sends an alarm signal notifying the occurrence of the abnormality to the outside. At the same time, it sends a control signal instructing the image quality control unit 35 to change the image quality. As a result, the operation shifts from the operation in the normal period to the operation in the abnormal period.

As described above, the apparatus 140 detects occurrence of an abnormality by detecting a change in the code amount. When performing fixed point monitoring, unless there is an abnormality, the monitoring unit 200 sends out an encoded signal Hk obtained by compressing a certain image without motion. Therefore, even if the time changes, the amount of the coded signal Hk per screen, that is, the code amount is kept constant. On the other hand, if there is motion in the image, the code amount increases or decreases. Therefore, by detecting a change in the code amount per screen, it is possible to detect the occurrence of an abnormality.

In addition, since the determination is made based on the signal amount of the low-quality coded signal LS corresponding to the low-quality image originally suitable for detecting the abnormality, the abnormality can be determined without waste with a small signal amount. Since the calculation amount of the code amount change detection unit 51 is reduced, the configuration is simplified.

The abnormality determination unit 14 may set the predetermined amount to zero so as to judge that there is a change if the code amount is slightly changed, but set the predetermined amount to a certain value other than zero. You may keep it. In the latter case, the determination can be made more reliable by ignoring such a small change that is not abnormal.

<8. Eighth Reference Technology> FIG. 17 is a block diagram showing an overall configuration of an apparatus according to an eighth reference technology. This device 150 is yet another example of a monitoring system. Apparatus 1
In 50, there is no distinction between the normal period and the abnormal period, the monitoring unit 900 always transmits the coded signal Hk corresponding to the high-quality coded signal HS, and the code amount change detection unit 52 provided in the control unit 950 sets The point that the change in the signal amount for one screen of the image quality coded signal HS is detected is characteristically different from the device 140 of the seventh reference technology. For this reason, the device 15
0, the image quality control units 25 and 35 provided in the device 140
Do not need. Further, the configurations of the conversion tables 3 and 10, the quantization table 6, and the code generation table 22 are also simplified. That is, there is an advantage that the configuration of the device is simple.

In the case of monitoring a fixed point, an abnormality can be detected by monitoring the signal amount of the high-quality coded signal HS as the code amount and catching the change.

<9. Ninth Reference Technology> FIG. 18 is a block diagram showing an overall configuration of an apparatus according to a ninth reference technology. This device 160 is yet another example of a monitoring system. Apparatus 1
The device 140 according to the seventh reference technique is different from the device 140 of the seventh reference technology in that the decoding unit 33 and the inverse quantization unit 7 included in the device 140 are not provided with a device unit for reconstructing an image, and the image quality control units 25 and 35 are not provided. And is characteristically different. Then, the monitoring unit 900 always transmits the coded signal Hk corresponding to the low-quality coded signal LS, and the code amount change detection unit 51 provided in the control unit 960 outputs the signal for one screen of the low-quality coded signal LS. Detect changes in volume.

That is, the apparatus 160 is configured so that visual monitoring is not the purpose and only automatic detection of an abnormality is performed. Therefore, the configuration of the device is significantly simpler than that of the device 140 of the seventh reference technology.

<10. Tenth reference technology> Seventh reference technology
In the ninth reference technology, an example of the monitoring system in which the monitoring unit and the control unit are connected via the communication line 250 has been described. However, the monitoring device may be configured as a monitoring device that does not pass through the communication line 250. The device 170 illustrated in FIG. 19 is obtained by configuring the system 160 of the ninth reference technology as a monitoring device. An apparatus 180 illustrated in FIG. 20 is obtained by configuring the system 140 of the seventh reference technology as a monitoring apparatus.

The image quality control unit 55 controls the conversion tables 3 and 10, the quantization table 6, and the code generation table 22 according to the determination result of the abnormality determination unit 14. The quantization table 6 is shared by the quantization unit 5 and the inverse quantization unit 7, and the code generation table 22 includes the coding unit 21 and the decoding unit 3.
3 and shared. The system according to the eighth reference technology can be similarly configured as a monitoring device.

<11. Eleventh Reference Technology> In monitoring system, code amount change detecting section 51 and abnormality determining section 14
May be provided in the monitoring unit instead of being provided in the control unit. FIG. 21 is a block diagram illustrating an example of such a monitoring system. The system 801 of FIG. 21 includes a code amount change detection unit 51 and an abnormality determination unit 1
4 is characteristically different from the device of the seventh reference technology shown in FIG. 16 in that it is moved from the control unit 141 to the monitoring unit 201.

The result of the judgment by the abnormality judging section 14 is transmitted from the communication control section 24 to the image quality control section 35 through the communication line 250 and the communication control section 31. The image quality control unit 35 and the image quality control unit 25 operate in the same manner as the system 800 of the seventh reference technology according to the determination result from the abnormality determination unit 14.

<12. First Embodiment> FIG. 22 is a block diagram showing the overall configuration of the device of the first embodiment. This device is an example of an image storage device. The image storage device 181 converts the captured image into an A / D converter 1 to a code buffer 2
3, the coded signal Hk obtained by compression is stored in the compressed image storage unit 57, and the coded signal Hk reproduced from the compressed image storage unit 57 is expanded by the decoding unit 33 to the D / A conversion unit 11. Is configured.

The compressed image accumulating section 57 has a storage element capable of storing the coded signal Hk for a certain period, and stores the coded signal Hk sequentially so that the coded signal Hk can be stored from the present time. It accumulates for a certain period going back in the past.
When the external control signal is input, the accumulated coded signal Hk for a certain period after or before the input or for a certain period including the input time is output. The output encoded signal Hk is output to the decoding unit 33
~ Reconfigured by the D / A converter 11.

As described above, in the image storage device 181, since the compressed coded signal Hk having a small amount of information is stored in the compressed image storage unit 57, it is necessary to store the compressed image signal Hk for a predetermined period. The capacity of the storage element included in the image storage unit 57 can be reduced. That is, the size of the image storage device can be reduced. Alternatively, by using a storage element having a predetermined capacity, it is possible to accumulate images for a longer period than before.

The image reconstructed by the decoding unit 33 to the D / A conversion unit 11 can be displayed on an external CRT or the like. Further, by inputting an external control signal at a desired time, images before and after the desired time can be reproduced. Further, by connecting to an external abnormality detection device, the image storage device 181 can be used for monitoring purposes such as reproducing images before and after the occurrence of the abnormality.

Further, the compressed image storage section 57 may be configured to be able to input two types of control signals. That is,
When the first control signal is input, the coded signal Hk for a certain period before and after the first control signal is stored, and then the coded signal Hk is stored.
Is fixedly held, and a new encoded signal Hk is not accumulated. Then, in response to the input of the second control signal, the stored encoded signal Hk is output. By configuring the compressed image accumulating unit 57 in this way, for example, images before and after the occurrence of an abnormality can be held first, and then reproduced at a desired time later to reconfirm the abnormality.

The communication line 250 may be connected between the code buffer 23 and the compressed image storage unit 57, or between the compressed image storage unit 57 and the decoding unit 33. Since the coded signal Hk is transmitted on the communication line 250, a high transmission capacity is not required for the communication line 250.

<13. Second Embodiment> FIG. 23 is a block diagram showing an overall configuration of an apparatus according to a second embodiment. The image storage device 182 includes a code amount change detection unit 51 and an abnormality determination unit 14 that automatically execute abnormality detection based on the encoded signal Hk. Then, the abnormality determination unit 14
Sends a control signal to the compressed image storage unit 57 when it determines that there is an abnormality. The compressed image accumulating unit 57 outputs the accumulated coded signal Hk for a certain period after or before the input of the control signal or for a certain period including the input time.

Since the image storage device 182 is provided with the device for performing the abnormality detection as described above, the abnormality detection is automatically performed, and the images before and after the occurrence of the abnormality can be reproduced and reconfirmed. is there. That is, abnormality monitoring can be performed more accurately.

Note that the image storage device 182 is configured to perform abnormality detection by the code amount change detection unit 51 and the abnormality determination unit 14, but the motion detection unit 12 and the feature point extraction unit illustrated in FIG. 13 and the abnormality determination unit 14 may be configured to perform abnormality detection.

Further, as exemplified in FIG. 4, the device may be separated into a monitoring unit and a control unit which are relayed by a communication line 250. At this time, the compressed image storage unit 5
7 may be provided in either the monitoring unit or the control unit. Memory 45 corresponding to compressed image storage unit 57
The monitoring system 130 illustrated in FIG. 11 having an example is an example of the image storage device configured as described above.

<14. Modifications> In the above reference technology, the device portion that performs image compression and image expansion is configured to execute an operation based on the “intra-frame coding” technology. However, the calculation may be performed based on an “inter-frame coding” technique of performing image compression and image expansion in consideration of the correlation between frames.

The apparatus thus configured also includes an abnormality detection unit that detects the occurrence of an abnormality by analyzing a reconstructed image, and an image quality control unit that performs image quality control in combination with the abnormality detection unit. It is possible to obtain reconstructed images having different image qualities between the normal period and the abnormal period. That is, during the normal period, a low-quality reconstructed image with a high compression ratio suitable for abnormality detection is obtained, and after the abnormality is detected, a high-quality reconstructed image with a low compression ratio suitable for visual monitoring is obtained. It is possible to configure the image quality control unit so that

[0157]

According to the first aspect of the present invention, since the image signal is compressed and stored, it is possible to store the image signal for a long period with a small storage capacity.

In the apparatus according to the second aspect of the present invention, since a reconstructed image is obtained from the compressed image by the image expansion means, the stored image can be displayed on an image receiving device such as a CRT.

In the device according to the third aspect of the present invention, the images before and after the control signal is input are output, so that the images before and after the occurrence of the abnormality can be reproduced, for example, for monitoring purposes.

In the apparatus according to the fourth aspect of the present invention, the abnormality detecting means is provided, so that the abnormality is automatically detected. In addition, since the control signal is input when the abnormality detecting unit detects the abnormality, it is possible to reproduce the images before and after the occurrence of the abnormality and to confirm the images again.

In the apparatus according to the fifth aspect of the present invention, when a signal amount per fixed screen, such as one screen, of a compressed image signal obtained by compression changes by a predetermined signal amount or more, the abnormality determining means is used. Is determined to be abnormal. That is, when there is a movement of a predetermined amount or more on the screen, it is determined that there is an abnormality.
For this reason, it is possible to automatically execute fixed point monitoring with a simple configuration.

In the device according to the sixth aspect of the present invention, abnormality detection is performed by irreversibly compressing a captured image and then analyzing a reconstructed image obtained by expanding the image. A reconstructed image obtained by expanding an irreversibly compressed image is a kind of a compressed image having lower image quality than the original captured image. For this reason, unnecessarily sensitive reactions are suppressed, and appropriate abnormality detection is realized.

In the device according to the seventh aspect of the present invention, since the image compression means and the image decompression means are connected to each other by relaying the communication line, they can be remotely located.
In addition, since the compressed image signal is transmitted to the communication line, a high transmission capacity is not required for the communication line.

In the device according to the eighth aspect of the present invention, the images before and after the input of the first control signal are fixedly held, and the held images are output in response to the second control signal. For example, images before and after the occurrence of the abnormality can be reproduced later to reconfirm the abnormality.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an apparatus according to a first reference technology.

FIG. 2 is an explanatory diagram illustrating an operation of the device in FIG. 1;

FIG. 3 is a flowchart showing a flow of an operation of the apparatus of FIG. 1;

FIG. 4 is a block diagram illustrating a configuration of a system according to a second reference technology;

FIG. 5 is an explanatory diagram illustrating an operation of the system in FIG. 4;

FIG. 6 is a flowchart showing a flow of the operation of the monitoring unit of FIG. 4;

FIG. 7 is a flowchart showing an operation flow of the control unit of FIG. 4;

FIG. 8 is a block diagram illustrating a configuration of a system according to a third reference technology.

FIG. 9 is an explanatory diagram illustrating the operation of the system in FIG. 8;

FIG. 10 is an explanatory diagram illustrating an operation of a system according to a fourth reference technology.

FIG. 11 is a block diagram illustrating a configuration of a system according to a fourth reference technology.

FIG. 12 is an explanatory diagram illustrating the operation of the device of the sixth reference technology.

FIG. 13 is an explanatory diagram illustrating the operation of the device of the sixth reference technology.

FIG. 14 is an explanatory diagram for explaining the operation of the device of the sixth reference technology.

FIG. 15 is a flowchart illustrating the operation of the device of the sixth reference technology.

FIG. 16 is a block diagram illustrating a configuration of an apparatus according to a seventh reference technology.

FIG. 17 is a block diagram illustrating a configuration of an apparatus according to an eighth reference technology.

FIG. 18 is a block diagram illustrating a configuration of an apparatus according to a ninth reference technology.

FIG. 19 is a block diagram showing a configuration of a device according to a tenth reference technology.

FIG. 20 is a block diagram showing a configuration of another device according to the tenth reference technology.

FIG. 21 is a block diagram showing a configuration of a system according to the eleventh reference technology.

FIG. 22 is a block diagram illustrating a configuration of a system according to the first embodiment.

FIG. 23 is a block diagram illustrating a configuration of a system according to a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 A / D conversion part (analog-digital conversion means) 2 Color space conversion part 4 Frequency space conversion part (frequency space conversion means) 5 Quantization part (quantization means) 3 Conversion table 6 Quantization table 7 Inverse quantization part (Inverse quantization means) 8 Frequency space inverse transform unit (Frequency space inverse transform means) 9 Color space inverse transform unit 10 Conversion table 11 D / A converter 12 Motion detector (Motion detector) 13 Feature point extractor (Characteristics) Point extraction means) 14 abnormality determination section (abnormality determination section) 15, 55 image quality control section (image quality control section) 21 encoding section (encoding section) 22 code generation table 33 decoding section (decoding section) 25, 35, 41, 42, 48 Image quality control unit 45 Memory (image storage unit) 46 Communication control unit 51, 52 Code amount change detection unit 57 Communication control unit (communication control unit) 100 Monitoring device 110, 12 , 130 monitoring system 200, 400, 600 monitoring unit 300, 500, and 700 control unit 250 communication line.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) FF19 GG02 GG06

Claims (8)

[Claims] 1. An image storage device for sequentially storing image signals to accumulate the image signals for a certain period of time in the past, comprising: an image compression unit that obtains a compressed image signal by compressing the image signal; And a compressed image storage means for storing the compressed image signal for a certain period of time going back in the past by sequentially storing the image signal. 2. The image storage device according to claim 1, further comprising an image expansion unit that obtains a reconstructed image signal by expanding the compressed image signal stored by the compressed image storage unit. Image storage device. 3. The image storage device according to claim 2, wherein the compressed image storage unit determines a point in time when the control signal is input in response to the control signal as a start point or an end point or for the point in time. An image storage device for outputting the compressed image signal stored for a certain period including the compressed image signal. 4. The image storage device according to claim 3, further comprising abnormality detection means for detecting occurrence of an abnormality based on a captured image taken by a television camera, wherein said image compression means includes an image signal. The image storage device according to claim 1, wherein the signal of the captured image is input, and the abnormality detection unit inputs the control signal to the compressed image storage unit when the occurrence of the abnormality is detected. 5. The image storage device according to claim 4, wherein the abnormality detection unit detects a change in a signal amount of the compressed image signal per fixed screen, and the signal amount change detection. An abnormality determining unit that determines that there is an abnormality when a change in the signal amount detected by the unit is equal to or more than a predetermined amount. 6. The image storage device according to claim 5, wherein the image compression unit includes an irreversible compression unit that irreversibly compresses the image signal to obtain an irreversible compressed image as the compressed image. The image storage device, wherein the abnormality detecting means detects the occurrence of the abnormality by analyzing the reconstructed image. 7. The image storage device according to claim 2, wherein the image compression unit and the image expansion unit are connected by relaying a communication line. 8. The image storage device according to claim 1, wherein the compressed image storage unit is provided for a certain period of time starting or ending at a point in time when the first control signal is input in response to the first control signal. Alternatively, the compressed image signal for a certain period including the time point is fixedly held, and the held compressed image signal is output in response to a second control signal.