JP2002335492A - Recording device for crime prevention system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording device for crime prevention system that can save a recording capacity of a recording medium without deteriorating the reliability of the crime prevention system. SOLUTION: An ordinary state of a photographing object is stored as a reference image (S102). A photographed image and the reference image are compared by corresponding pixels (S108). When by the result of comparison processing it is confirmed that there is a change in the photographed image, a compression rate in the image compression processing is relatively set lower (S112), when it is confirmed that there is no change in the photographed image, the compression ratio in the image compression processing is set relatively higher (S114), and the photographed image is compressed at a set compression rate and the compressed image is recorded on a recording medium (S116).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a security system to be installed in a bank, a late-night store, and the like, and more particularly, to a recording device for images captured by a security camera.

[0002]

2. Description of the Related Art Conventionally, security cameras have been installed in late-night stores and banks such as convenience stores for security reasons, and the inside of the store is constantly photographed. By operating the camera, an effect of preventing crime such as robbery can be obtained, and the recorded image may be used as evidence for identifying a criminal who caused the crime. In such a security system, the crime is unpredictable, so the security camera must always be operated, and images taken by the security camera are sampled and recorded at a predetermined cycle, and the Saved for a period. Therefore, in the security system, a recording medium having an enormous recording capacity for image recording is required.

[0003]

However, despite the necessity of an enormous recording capacity, the recorded images are reproduced and used only when an abnormal situation such as a crime occurs. Therefore, in order to save the recording capacity, it is conceivable to compress and record the image. When compressing and recording an image, the compression ratio is inversely proportional to the recording capacity. Therefore, it is desirable to compress the image at the highest possible compression ratio from the viewpoint of saving the recording capacity. On the other hand, since the accuracy of the reproduced image is reduced in proportion to the compression ratio, if the compression ratio is too high, the deterioration of the image becomes remarkable. Therefore, when a high-precision image is required, for example, when a person is specified in a criminal investigation or the like, a recorded image subjected to image compression at a high compression ratio becomes unreliable. I will.

As described above, even when a captured image is recorded by compressing the image, the image compression must be performed at a low compression ratio from the viewpoint of reliability as a security system, and the recording capacity is reduced. There was a problem that it was difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide an economical and highly reliable recording device for a security system.

[0006]

An image recording apparatus of a security system according to the present invention is a security system that operates a video camera constantly and records the occurrence of an abnormal situation. A reference image recording unit that records a digital image based on the reference image as a reference image, and compares a captured image, which is a digital image based on an image captured by a camera after capturing the reference image, with the corresponding reference image for each corresponding pixel. Detecting means for detecting a change in the shooting target of the video camera based on the captured image, a shot image recording means for compressing and recording the shot image, and a shot image in the shot image recording means when a change in the shooting target is detected by the detecting means Of the photographed image in the photographed image recording means when the change of the photographing target is not detected by the detecting means. Characterized in that it comprises a compression rate setting means for setting low.

Optionally, the detecting means detects a change in the object to be photographed for each frame, and the compression rate setting means sets a compression rate for each frame. Alternatively, the detecting means may be 1
The reference image and the captured image for a frame are divided into a plurality of regions, and a change in a photographing target is detected for each region, and the compression ratio setting means sets a compression ratio for each of the plurality of regions.

Optionally, the detecting means changes the object to be photographed when the ratio of the total number of pixels of the photographed image having luminance or color information different from that of the pixels of the reference image to the total number of pixels to be compared exceeds a predetermined value. Judge that it has occurred.

Optionally, the detecting means determines that a change has occurred in the object to be photographed when the ratio of pixels having different luminance or color information in the photographed image in succession exceeds a predetermined value. .

Optionally, the detecting means extracts a contour shape of a continuous area occupied by pixels having luminance or color information different from the pixels of the reference image in the photographed image, and the contour shape has a predetermined pattern shape. When they substantially match, it is determined that a change has occurred in the imaging target.

Optionally, the photographed image in the photographed image recording means when the change of the photographed object is detected by the detecting means may be uncompressed.

As described above, according to the present invention, since a captured image is image-compressed and recorded on a recording medium in accordance with a change in a photographing target, recording on the recording medium can be performed without lowering the reliability of the security system. Saves space.

According to the configuration in which the reference image and the photographed image are divided into a plurality of block regions and the occurrence of a change in the photographing target is determined for each block region, the recording capacity of the recording medium can be more effectively saved. .

In the detection means, if the ratio of the total number of pixels of the photographed image having luminance or color information different from that of the pixels of the reference image is used as a criterion for judging whether or not the photographing object has changed, simple control The saving of recording capacity can be achieved.

In the detection means, if the ratio of pixels occupied by pixels having luminance or color information different from the pixels of the reference image continuously in the captured image is used as a criterion for determining whether or not the object to be captured has changed, It is possible to eliminate a change in the imaging target due to factors other than the above. Therefore, the recording capacity of the recording medium can be saved more effectively.

In the detecting means, the contour of a continuous region occupied by pixels having different luminance or color information from the pixels of the reference image in the photographed image is matched with a predetermined pattern shape, thereby causing a change in the photographed object. According to the configuration for determining whether or not the photographing target is changed, it is possible to more accurately specify the cause of the change in the imaging target. Therefore, the reliability of the recording device of the security system is further improved.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a recording device of a security system to which the first embodiment according to the present invention is applied. The video camera 10 is a security camera installed in an ATM corner of a bank, near a cash register in a convenience store, or the like. Analog image information for one frame captured by the video camera 10 is stored in an A / D
The data is sent to an (analog / digital) converter 21 and converted into digital image information for one frame. The digital image information for one frame is subjected to predetermined image processing in an image signal generation circuit 23 under the control of the system controller 22, and an image signal for one frame is generated.

The system controller 22 controls the recording device 2
0 is a microcomputer, for example, a central processing unit (CPU), a program for executing various routines, a read-only memory (ROM) for storing constants and the like, and a write for temporarily storing data and the like. / Readable memory (RAM).

The image signal for one frame generated by the image signal generation circuit 23 is supplied to a first memory (RAM) 24.
Is stored temporarily. Registration mode setting switch 25
Is a switch for setting a registration mode for registering the image information stored in the RAM 24 as a reference image.
The reference image is a photographed image of a photographing target in a normal state before an abnormal situation occurs, and is an image serving as a reference for a comparison process described later. When the reference image registration mode is set by operating the registration mode setting switch 25, the image information for one frame stored in the RAM 24 is stored in the second memory (EE).
(PROM) 26 as a reference image.

If the reference image registration mode is not set, the image information for one frame stored in the RAM 24 is input to the compression processing circuit 27. Compression processing circuit 27
Then, image information for one frame is compressed. The image compression processing in the compression processing circuit 27 is executed in one of the high compression mode and the low compression mode based on a command from the system controller 22. The high compression mode is a mode for compressing an image obtained by shooting a shooting target in a normal state, and performs image compression at a relatively high compression rate. The low compression mode is a mode for compressing an image obtained by capturing an image of a subject in a changed state, and performs image compression at a relatively low compression rate.
The compressed image information is recorded on a recording medium 29 such as a magnetic tape, magnetic disk, or optical disk via a recording medium control circuit 28.

If one frame of image information is processed by the image compression circuit 27 in the high compression mode, the image quality of the reproduced image is degraded, but the recording capacity of the recording medium 29 can be saved. Further, according to the low compression mode, the image quality of the reproduced image becomes highly accurate, and a highly reliable image can be obtained in the above-described search and the like.

The manual switch 30 forcibly sets the image compression processing mode in the compression processing circuit 27 to a low compression mode,
Alternatively, it is a switch for setting to the non-compression mode. Further, an external device (not shown) such as an emergency bell is connected to the recording device 20, and an external signal SI from the external device is output.
When G is input to the system controller 22, the processing mode of image compression in the compression processing circuit 27 is forcibly set to the low compression mode or the non-compression mode as in the case of operating the manual switch 30.

FIG. 2 is a flowchart showing a procedure of image recording according to the first embodiment. Step S10
At 0, it is checked whether the reference image registration mode is set. When the registration mode setting switch 25 is operated and it is confirmed that the reference image registration mode is set, the process proceeds to step S102, where the image information for one frame stored in the RAM 24 is read out, and the EEPRO
It is stored in M26 as a reference image. On the other hand, step S
If it is determined in step 100 that the reference image registration mode is not set, the process proceeds to step S104. Step S10
4, the image information for one frame stored in the RAM 24 is read out, and the RAM information in the system controller 22 is read out.
It is taken in.

Next, in step S106, it is confirmed whether the manual switch 30 has been operated or an external signal SIG has been input from the above-mentioned external device. If neither the operation of the manual switch 30 nor the input of the external signal SIG has occurred, the process proceeds to step S108, and the comparison processing routine is executed.

FIG. 3 is a flowchart showing the processing procedure of the comparison processing routine executed in step S108.
In step S200, the image change flag F_CH is set to “0”.
Is set and initialized. Image change flag F_CH
Is a flag for indicating that a change has occurred in the captured image captured in the RAM in the system controller 22 with respect to the reference image stored in the EEPROM 26.

Next, in step S202, the EEPRO
Reference image in M26 and RA of system controller 22
The captured image in M is read, and a difference in luminance value is calculated for each corresponding pixel. In step S204, a binarization process of the difference between the luminance values is performed. That is, the difference between the luminance values of the pixels is compared with a predetermined threshold value, and “0” (white) if the difference is equal to or smaller than the threshold, and “1” if the difference exceeds the threshold.
(Black) is set as difference data for each pixel of the captured image read from the RAM of the system controller 22.

In step S206, the number of pixels whose difference data is black is counted and set to a variable NB.
Next, in step S208, the value of the variable NB is compared with the threshold value S1. If the value of the variable NB is larger than the threshold value S1, it is determined that a change has occurred in the captured image with respect to the reference image, the process proceeds to step S210, and the image change flag F_
“1” is set in CH. On the other hand, if the value of the variable NB is equal to or smaller than the threshold value S1, it is determined that no change has occurred in the captured image, the process of step S210 is not performed, and the image change flag F_CH is set in the initialization process of step S200. The initial value “0” is not changed.

Thus, the comparison processing routine ends. When the comparison processing routine ends, the value of the image change flag F_CH is checked in step S110 in FIG.
It is checked whether or not the captured image stored in the RAM in the system controller 22 has changed with respect to the reference image stored in the EEPROM 26. When it is confirmed that “1” is set in the image change flag F_CH and the captured image is changed, the process proceeds to step S112. Step S1
In 12, the processing mode of the compression processing circuit 27 is set to the low compression mode. On the other hand, in step S110, “0” is set in the image change flag F_CH, and the EEP
System controller 2 for the reference image in ROM
When it is confirmed that the photographed image in the RAM in 2 has not changed, the process proceeds to step S114. In step S114, the processing mode of the compression processing circuit 27 is set to the high compression mode.

When the image compression processing mode is set in step S112 or S114, the flow advances to step S116. In step S116, based on the processing mode set in step S112 or S114, the compression processing of the captured image taken into the RAM in the system controller 22 is executed by the compression processing circuit 27, and is recorded on the recording medium 29.

If it is confirmed in step S106 that either the operation of the manual switch 30 or the input of the external signal SIG has occurred, the processing in steps S108 and S110 is not executed, and step S112 is executed. . The case where the user operates the manual switch 30 or the case where there is an input of the external signal SIG in conjunction with the operation of the emergency bell means a case where an emergency such as a burglary has occurred.
In such a case, the captured image to be recorded is likely to be used as evidence in a subsequent search, so the image compression processing mode is forcibly set to the low compression mode so that the reproduced image has high accuracy. Is done.

The operation of the first embodiment will be described with reference to FIG. FIG. 4A shows a reference image stored in the EEPROM 26. For this reference image, R
If the captured image stored in the AM 24 has not changed, it is compressed in the high compression mode and recorded on the recording medium 29. Therefore, although the image quality of the reproduced image is deteriorated as shown in FIG. 4B, the reliability of the security system does not decrease because the photographing target is in the same state as normal. On the other hand, since the image is compressed at a relatively high compression rate and recorded on the recording medium 29, the recording capacity of the recording medium 29 is saved.

The RA of the reference image shown in FIG.
When a change occurs in the captured image stored in M24, the captured image is compressed in the low compression mode and recorded on the recording medium 29.
A high-quality image as shown in FIG. 4C is reproduced. Therefore, it is easy to identify a portion where a change has occurred in the captured image (the person in FIG. 4C), and the reliability as a security system is high.

FIG. 5 is a flowchart showing a modified example of the comparison processing routine executed in step S108 of FIG. The processing from steps S300 to S304 is the same as the processing from steps S200 to S204 in the routine of FIG. That is, “0” is set in the image change flag F_CH.
Is set (S300), and the system controller 22
The captured image read from the RAM of the EEPROM 26
Is compared with the reference image read from each pixel, and difference data of the luminance value is calculated (S302), and the difference data is binarized (S304).

Next, in step S306, the number of pixels constituting a continuously black region is counted, and a variable NN
B1 to NNBn are set. Variables NNB1 to NNB
The total number of n is variable according to the number of regions that are determined to be continuously black in the captured image as a result of the processing in step S304. In step S308, the variable NN
The maximum value among the values of B1 to NNBn is compared with the threshold value S2. For example, when a security system is installed in an ATM corner of a bank and a situation in which a user left an object left behind by the ATM corner is photographed, the photographed image changes with respect to the reference image. Is determined. However, in the security system introduced in the ATM corner, it is the person who must be specified by comparison with the reference image, and among the factors that cause a change in the reference image, the ratio occupied in the image is the largest. Is a person. Therefore, the variables NNB1 to NNB are compared with the threshold value S2 in step S308.
This is the maximum value among the values of n.

In steps S308, the variables NNB1 to NNB
It is confirmed that the maximum value of n is larger than the threshold value S2,
If it is determined that the cause of the change in the captured image is a person, the process proceeds to step S310. In step S310,
“1” is set to the image change flag F_CH. On the other hand, when it is confirmed in step S308 that the maximum value of the variables NNB1 to NNBn is equal to or smaller than the threshold value S2, it is determined that even if a change occurs in the captured image with respect to the reference image, it is caused by a factor other than a person. It is determined, and the process of step S310 is not performed.

As described above, in this modification, the presence or absence of a change in the captured image is determined based on the number of pixels that are continuously black, that is, the size of the area that has changed with respect to the reference image. Therefore, even if something other than a person is photographed, image compression is not performed in the low compression mode,
The recording capacity of the recording medium 29 is further reduced.

FIG. 6 is a flowchart showing another modified example of the comparison processing routine executed in step S108 of FIG. The processing from steps S400 to S404 is the same as the processing from steps S200 to S204 in the routine of FIG. That is, “0” is set to the image change flag F_CH (S400), and the captured image read from the RAM of the system controller 22 is stored in the EEPROM.
The reference image read from M26 is compared with each pixel, and difference data of luminance values is calculated (S402), and the difference data is binarized (S404).

In step S406, based on the result of the binarization process in step S404, the contour of the area of the pixel that is continuously black is detected. Next, step S408
Then, a process of cutting out the area within the contour as a single pattern shape (hereinafter, “filled shape”) is executed. In step S410, the filled shape is compared with a plurality of predetermined patterns. When there are a plurality of pixel regions that are continuously black, the processes of steps S406 to S410 are performed for all the regions.

In step S412, it is checked whether there is a predetermined pattern that matches the fill shape. If there is a predetermined pattern that matches the fill shape, the process proceeds to step S414. In step S414, "1" is set to the image change flag F_CH, and this routine ends. On the other hand, in step S412, when it is confirmed that the fill shape does not match any of the predetermined patterns (when there are a plurality of fill shapes, it is confirmed that there is no predetermined pattern shape that matches with any of the fill shapes). ), The process of step S414 is not performed, and the present routine ends.

According to this modification, even if there is a continuous black pixel area in the photographed image, it is not determined that the photographed image has changed unless its shape matches the predetermined pattern. . In other words, the cause of the change in the captured image is determined more accurately. Therefore, if the present invention is applied to, for example, a security system introduced at an ATM corner as described above, it becomes possible to compress and record an image in the low compression mode only when a person is being photographed, and to more effectively use a recording medium. Recording capacity is saved.

FIGS. 7 and 8 are flowcharts showing a procedure of image recording performed in a recording device of a security system to which the second embodiment according to the present invention is applied. FIG.
Steps S500 to S504 of FIG.
The same processing as in steps S00 to S104 is performed. That is, if the registration mode setting switch 25 is operated and the reference image registration mode is set (YE in S500).
S), the reference image is stored in the EEPROM 26 (S502). If the registration mode setting switch 25 has not been operated and the reference image registration mode has not been set (NO in step S500), one frame of image information stored in the RAM 24 is read out, and the system controller 22 (S50)
4).

In step S506, step S1 in FIG.
As in step 06, it is confirmed whether the manual switch 30 has been operated or whether an external signal SIG has been input from the above-described external device.
If none of the inputs has occurred, step S50
Proceed to 8. In step S508, the reference image and the captured image are each divided into a plurality of block regions of M columns × N rows. In the second embodiment, the reference image and the captured image are divided into a total of 16 block areas (A1 to A16) of 4 columns × 4 rows as shown in FIG.

Next, the process proceeds to step S510 in FIG. In step S510, "1" is set to a variable v for specifying a column of a block area, and in step S512, "1" is set for a variable u for specifying a row of a block area, and each is initialized. . Next, step S514
Then, the data of the pixels constituting the area corresponding to the block area An (v, u) is read for each of the reference image and the captured image, and the comparison processing routine is executed in step S516.

The processing procedure of the comparison processing routine executed in step S516 is the same as the processing procedure of the flowchart shown in FIG. In the calculation processing of the difference data for each pixel in step S202, the area corresponding to the block area An (v, n) of the reference image in the EEPROM 26 and the block area An (v) of the captured image in the RAM of the system controller 22 are used. , N), the difference between the luminance values of the pixels in the region corresponding to (n) is calculated.

When the comparison processing routine ends, the process returns to step S516 in FIG. 8, and then proceeds to step S518.
Proceed to. In step S518, the image change flag F_C
The value of H is checked. The image change flag F_CH is set to “1”, and the area corresponding to the block area An (v, n) of the reference image in the EEPROM 26 is compared with the block area An ( If it is confirmed that a change has occurred in the area corresponding to (v, n), the process proceeds to step S520. In step S520, the processing mode of the image compression of the captured image performed by the compression processing circuit 27 is set to the low compression mode. On the other hand, in step S518, the EEP
Block area An (v, n) of the reference image in ROM 26
When it is confirmed that the area corresponding to the block area An (v, n) of the captured image in the RAM of the system controller 22 has not changed with respect to the area corresponding to
Proceed to step S522. In step S522, the above-described processing mode is set to the high compression mode.

When the image compression processing mode is set in step S520 or S522, the flow advances to step S524 to execute a compression process for a region corresponding to the block region An (v, n) of the captured image.

Next, in step S526, it is checked whether the value of the variable u is equal to "4" (the maximum value of the row number of the divided area, see FIG. 9). If the value of the variable u is not equal to “4”, the process proceeds to step S528, and after the value of the variable u is incremented by “1”, the process returns to step S514, and the subsequent processing is executed. If it is confirmed in step S526 that the value of the variable u is equal to "4", the process proceeds to step S530. In step S530, it is checked whether the value of the variable v is equal to "4" (the maximum value of the column number of the divided area, see FIG. 9). When the value of the variable v is not equal to “4”, the process proceeds to step S532, and after the value of the variable v is incremented by “1”, the process returns to step S512, and the subsequent processing is executed. That is, the processes from steps S514 to S524 are repeatedly executed so as to be performed on all the regions corresponding to the block regions A1 to A16.

If it is confirmed in step S530 that the value of the variable v matches "4" and that the image compression processing in step S524 has been executed in all the areas corresponding to the block areas A1 to A16, the flow advances to step S534. move on. In step S534, the compressed data of all areas corresponding to the block areas A1 to A16 are collectively recorded on the recording medium 29. Thereafter, the process returns to step S500 in FIG.
The following processing is executed.

In step S506 of FIG. 7, whether the manual switch 30 has been operated or the external signal S
When it is confirmed that the IG has been input, step S5
Proceed to 36. In step S536, the processing mode of the image compression is set to the low compression mode. Then, step S
At 538, image compression is performed on the entire captured image, recording processing on the recording medium is performed, and step S538.
Return to 500. When the manual switch 30 is operated,
The case where the external signal SIG is input from the external device is a case where an emergency has occurred, and thus the above-described comparison processing and image compression processing for each block area are not performed, and the entire captured image is low-compression. Mode, the image is compressed
Will be recorded.

As in the first embodiment, the comparison processing routine shown in FIG. 5 or FIG. 6 may be executed in step S516 in FIG. At that time, step S3 in FIG.
It goes without saying that the processing executed in step S402 of FIG. 6 or in step S402 of FIG.

The operation of the second embodiment will now be described with reference to FIGS. In each of FIGS. 10 and 11, a broken line is shown at a position corresponding to the boundary of the block area in order to clearly show the block area shown in FIG.
In addition, in order to avoid complicating the figure, each figure shows a row number and a column number, and the block area is not numbered.
Codes (A1 to A16) shown in FIG. 9 correspond to the respective block areas.

FIG. 10A shows the video camera 10 in a normal state.
Are reference images stored in the EEPROM 26. FIG. 10B shows a state in which a person has entered the shooting area of the video camera 10 and the RAM
After being stored in the image data 24, the captured image is read into the RAM of the system controller 22 in the image compression processing.

In the photographed image of FIG.
When attention is paid to an area where a change occurs with respect to the reference image of (a), an area where a person is captured, that is, A3,
This is an area corresponding to A7, A11 and A15. Therefore, image compression is performed in these areas in the low compression mode, and image compression in the other areas is performed in the high compression mode and recorded on the recording medium 29. As a result, FIG.
The image shown in FIG. 1 (a) is reproduced.

Also, from the state shown in FIG.
When the person moves to the state shown in FIG.
A region where a change has occurred with respect to (a), that is, A6,
Only A10 and A14 are image-compressed in the low compression mode, and the other areas are image-compressed in the high compression mode.
9 recorded. As a result, the image shown in FIG. 11B is reproduced.

As shown in FIGS. 11A and 11B,
Areas unchanged from the reference image of FIG. 10A (A1, A2, A4 to A6, A8 to A8 in FIG. 11A).
A10, A12 to A14, and A16, FIG. 11B
In A1-A5, A7-A9, A11-A13,
A15 and A16) are reproduced with low accuracy, but the area where the person is captured (A3, A3 in FIG. 11A)
A7, A11 and A15, and in FIG.
6, A10, A14) are reproduced with high precision. That is, according to the second embodiment, the identification of the person in the reproduced image is not made difficult, so that the reliability of the security system is not impaired and the recording capacity of the recording medium 29 can be more efficiently saved. Is done.

In the first and second embodiments,
When a change occurs in the captured image, the captured image is image-compressed in the low compression mode and recorded on the recording medium, but is not limited thereto. The compression processing circuit 27 may not perform the substantial image compression processing on the captured image, and may record the image on a recording medium without compression. That is, the processing mode set in step S112 in FIG. 2, step S536 in FIG. 7, and step S520 in FIG. 8 may be set to the non-compression mode in which the compression ratio is zero.

In the first and second embodiments, the change of the photographed image is determined by using the difference of the luminance value for each pixel. However, in the case of a color image, the same processing is performed for each color component, so A highly accurate determination can be made.

The video camera according to the present invention includes not only a camera for shooting a moving image but also a so-called digital still camera for shooting a still image.

[0059]

As described above, according to the present invention, an economical and highly reliable recording device for a security system can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a recording device of a security system to which a first embodiment according to the present invention is applied.

FIG. 2 is a flowchart illustrating a procedure for compressing and recording a captured image according to the first embodiment.

FIG. 3 is a flowchart illustrating a processing procedure of a comparison processing routine between a reference image and a captured image.

FIG. 4 is a diagram showing a reproduced image when a reference image, a captured image having no change with respect to the reference image, and a captured image having a change with respect to the reference image are recorded according to the first embodiment. is there.

FIG. 5 is a flowchart illustrating a processing procedure of a modification of the comparison processing routine.

FIG. 6 is a flowchart showing a processing procedure of another modification of the comparison processing routine.

FIG. 7 is a flowchart illustrating a first half of a processing procedure of compression and recording of a captured image in a recording device of a security system to which a second embodiment according to the present invention is applied;

FIG. 8 is a flowchart illustrating the latter half of the procedure for compressing and recording a captured image in the recording device of the security system to which the second embodiment is applied.

FIG. 9 is a diagram illustrating a block area into which a reference image and a captured image are divided.

FIG. 10 is a diagram illustrating a reference image and a captured image in which a change occurs with respect to the reference image.

FIG. 11 is a diagram illustrating a reproduced image in a case where a captured image having a change with respect to a reference image is recorded according to the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Video camera 20 Recording device 22 System controller 24 1st memory 25 Registration mode setting switch 26 2nd memory 27 Compression processing circuit 29 Recording medium 30 Manual switch

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Claims (7)

[Claims] 1. A security system for constantly operating a video camera and recording the occurrence of an abnormal situation, comprising: a reference image recording means for recording a digital image based on a normal image taken by the video camera as a reference image; A photographed image, which is a digital image based on an image photographed by the camera after photographing the reference image, is compared with the reference image for each corresponding pixel, and a change in a photographing target of the video camera is detected based on the comparison result. A photographing image recording means for compressing and recording the photographed image; and detecting the compression ratio of the photographed image in the photographed image recording means when a change in the photographing target is detected by the detecting means. When the change of the photographing target is not detected by the means, the compression ratio is set lower than the compression ratio of the photographed image in the photographed image recording means Recording apparatus of the security system, characterized in that it comprises a shrinkage rate setting means. 2. The security system according to claim 1, wherein said detecting means detects a change in a photographing target for each frame, and said compression rate setting means sets a compression rate for each frame. Recording device. 3. The detecting means divides the reference image and the photographed image for one frame into a plurality of regions, detects a change in a photographing target for each region, and the compression ratio setting means 2. The recording device for a security system according to claim 1, wherein a compression ratio is set for each area. 4. The method according to claim 1, wherein the detecting unit changes to a photographing object when a ratio of a total number of pixels of the photographed image having luminance or color information different from pixels of the reference image to a total number of pixels to be compared exceeds a predetermined value. 4. The recording device of the security system according to claim 2, wherein it is determined that a security problem has occurred. 5. 5. The detecting means determines that a change has occurred in a photographing target when a ratio of pixels having different luminance or color information from pixels of the reference image in the photographed image continuously exceeds a predetermined value. The recording apparatus for a security system according to claim 2, wherein the recording is performed. 6. The detecting means extracts a contour shape of a continuous area occupied by pixels having luminance or color information different from pixels of the reference image in the photographed image, and the contour shape has a predetermined pattern shape. 4. The recording device of the security system according to claim 2, wherein when substantially coincident with the condition, it is determined that the photographing target has changed. 7. The recording device of the security system according to claim 1, wherein the photographed image in the photographed image recording unit is uncompressed when a change in the photographing target is detected by the detecting unit.