JP6195494B2 - Wireless communication system - Google Patents

Description

  The present invention relates to a wireless communication system including a wireless transmitter and a wireless controller capable of wireless communication with each other.

  Conventionally, a security system that detects an abnormality such as an intrusion abnormality or a fire abnormality that occurs in a monitoring area such as a house has been widely used. Such a security system includes a sensor and a camera arranged in a monitoring area and a security controller as a central controller, and communication between them is performed by wireless communication in consideration of workability and aesthetics. May be used. When transmitting a camera image or the like in such a security system, the transmission bandwidth between the transmitter and the receiver becomes narrow due to the influence of radio waves in the monitoring area, and the display image on the reception side security controller may be lost.

  To deal with such a problem, Patent Document 1 includes a transmission device that transmits a video signal and a reception device that receives the video signal and displays an image, and the reception device transmits a reception transmission rate that represents the reception state of the video signal. A transmission / reception system is disclosed in which the transmission means controls the transmission transmission rate of the video signal and the video resolution based on the reception transmission rate.

  Patent Document 2 includes an image transmission device that wirelessly transmits image data and an image reception device that receives image data wirelessly transmitted from the image transmission device. The image reception device transmits error information of a received signal to the image transmission device. An image transmission system is disclosed in which the image transmission apparatus sets the image size or frame rate of image data to be transmitted to the image reception apparatus based on the received error information.

  Patent Document 3 includes an image transmission device and an image reception device, and the image transmission device determines the state of the communication channel based on information on the busy state of the communication channel used for wireless communication. An image communication system is disclosed in which notification information for notifying a change in communication channel is transmitted by wireless communication according to the result of the communication, and the image receiving apparatus changes a communication channel to be used for wireless communication when the notification information is received. ing.

JP 2005-191933 A JP 2004-064300 A JP 2011-091608 A

  In wireless communication systems such as Patent Documents 1 to 3, for example, the image quality of a wirelessly transmitted image or a communication channel is dynamically controlled according to the wireless transmission environment, thereby eliminating a display image defect in a receiving-side device. Image transmission can be performed so as to prevent as much as possible. However, for example, when a wireless LAN is used as the wireless communication means, when the wireless communication system attempts to change the communication channel, a blank time during which communication cannot be performed for a certain period of time occurs due to restart of the access point. Also, depending on the frequency band used, the wireless communication system detects the presence or absence of interference with weather radar or the like by the DFS (Dynamic Frequency Selection) function when the communication channel is changed, so that a blank time that cannot be communicated for about one minute occurs. . In a wireless communication system such as a security system, if such a blank time occurs frequently, the image cannot be confirmed when monitoring the image, and the usability for the user is significantly reduced.

  Therefore, an object of the present invention is to provide a wireless communication system that suppresses the occurrence of a blank time during which wireless communication cannot be performed while preventing loss of a display image in a wireless controller that receives image data from a wireless transmitter as much as possible.

  As one aspect of the present invention, a wireless communication system including a wireless transmitter and a wireless controller capable of wireless communication with each other is provided. In this wireless communication system, the wireless transmitter has an image acquisition unit that acquires image data, an image quality adjustment unit that adjusts the image quality of the image data according to an image quality adjustment instruction from the wireless controller, and an image quality adjustment unit that adjusts the image quality. A wireless communication processing unit that transmits the adjusted image data to the wireless controller, and the wireless controller uses a comparison result between the data amount of the image data received from the wireless transmitter within the first time and the image quality adjustment threshold value. A communication channel between the wireless transmitter and the wireless controller based on the quality of the signal received within a second time longer than the first time, and an image quality adjustment determination unit that outputs a corresponding image quality adjustment instruction to the wireless transmitter A channel change determination unit that determines whether to change the channel and a channel change processing unit that changes the communication channel according to the determination result of the channel change determination unit. To.

  Moreover, as another aspect of the present invention, a wireless communication system including a wireless transmitter and a wireless controller capable of wireless communication with each other is provided. In this wireless communication system, a wireless transmitter transmits an image acquisition unit that acquires image data, an image quality adjustment unit that adjusts the image quality of the image data, and image data whose image quality is adjusted by the image quality adjustment unit to the wireless controller. A wireless communication processing unit, and an image quality adjustment determination unit that outputs to the image quality adjustment unit an image quality adjustment instruction according to a comparison result between the amount of image data transmitted to the wireless controller and the image quality adjustment threshold within a first time period, And the radio controller determines whether to change the communication channel between the radio transmitter and the radio controller based on the quality of the signal received within a second time longer than the first time. It comprises a determination unit and a channel change processing unit that changes the communication channel according to the determination result of the channel change determination unit.

  The image quality adjustment determination unit uses at least the first image quality adjustment threshold and the second image quality adjustment threshold smaller than the first image quality adjustment threshold as the image quality adjustment threshold, and data of image data within the first time period. It is preferable to output an image quality adjustment instruction for improving the image quality if the amount is equal to or greater than the first image quality adjustment threshold, and to output an image quality adjustment instruction for decreasing the image quality if the amount of data is equal to or less than the second image quality adjustment threshold.

  The channel change determination unit determines that the communication channel change is in a standby state if the data amount of image data received from the wireless transmitter within the second time is equal to or less than a channel change threshold for determining the channel change. When the number of times determined to be a state exceeds a predetermined number, it is preferable to determine to change the communication channel.

  The channel change threshold is preferably a threshold corresponding to the number of image frames smaller than the image quality adjustment threshold.

  According to the wireless communication system of the present invention, it is possible to suppress the occurrence of blank time during which wireless communication cannot be performed while preventing loss of a display image in a wireless controller that receives an image from a wireless transmitter as much as possible.

It is a schematic block diagram of a security system. It is a schematic block diagram of an image display apparatus. It is a functional block diagram of the control part of an image display apparatus. It is a schematic block diagram of a camera unit. It is the flowchart which showed the operation example of the image reception process. 6 is a flowchart illustrating an operation example of image quality adjustment processing. It is the flowchart which showed the operation example of the communication quality determination process.

  Hereinafter, embodiments of a wireless communication system according to the present invention will be described with reference to the drawings.

  For example, in a wireless communication system such as a security system, when the image quality and communication channel of a wirelessly transmitted image are dynamically controlled in accordance with the wireless transmission environment, the user who refers to the image on the receiving side is asked how to use it. It is preferable to consider whether or not. For example, when monitoring images with a security system used in a house, etc., it is installed outside the house in the monitoring area, unlike a security system in which a supervisor monitors the monitoring image in a security room or monitoring center. When the situation around the selected camera is anxious, the user mainly checks the image from the camera for a very short time. Therefore, in a security system used in a house or the like, there is a tendency that it is preferable to immediately transmit even a slightly lower image quality than to transmit a high-definition image over time. For this reason, in a wireless communication system such as a security system, if the process of changing the communication channel according to the wireless transmission environment is frequently performed, a blank time during which wireless communication cannot be performed frequently occurs, and the usability of the user is significantly reduced. It will be.

  Therefore, the wireless communication system of the present embodiment adjusts the image quality of the image data in accordance with the transmission amount from the wireless transmitter to the wireless controller within the first time, and within a second time longer than the first time. The communication channel is changed according to the quality of the signal received by the wireless controller. That is, in the wireless communication system, the monitoring time of the wireless transmission environment when determining the change of the communication channel is set longer than the monitoring time of the wireless transmission environment when determining the adjustment of image quality. As a result, in the wireless communication system, even when the communication efficiency between the wireless transmitter and the wireless controller is reduced, the image quality adjustment is performed with priority and the wireless communication is performed without changing the communication channel as much as possible. To continue.

  FIG. 1 is a schematic configuration diagram of a security system 1. The security system 1 is installed in a house or the like serving as a monitoring area 2 and monitors whether there is an abnormality in the monitoring area 2. The security system 1 includes an image display device 10 and a plurality of camera units 20. The security system 1 is an example of a wireless communication system, and the image display device 10 and the plurality of camera units 20 can wirelessly communicate with each other via a wireless network such as a wireless LAN. Below, although the case where the monitoring area 2 by the security system 1 is a house is explained as an example, the monitoring area 2 may be a place other than a house such as a store or a business office.

  The image display device 10 is an example of a wireless controller, and is installed on a wall surface in a house. The image display device 10 receives image data from the camera unit 20 and displays it. The image display device 10 is connected to a center device 41 in the monitoring center 40 via a communication network 50 such as the Internet. The image display device 10 is, for example, a security device that transmits an abnormality signal to a remote center device 41 when it receives a detection signal indicating that an abnormality such as an intruder has been detected from a security sensor (not shown) installed in the monitoring area 2. is there. Alternatively, the image display device 10 may be an interphone or an image monitoring monitor.

  The camera unit 20 is an example of a wireless transmitter, and is installed at various locations such as the outer periphery of a house that is the monitoring area 2. The camera unit 20 transmits the captured image data to the image display device 10.

  The monitoring center 40 is a facility provided with a center device 41 operated by a security company or the like, and a controller constantly monitors the monitoring area 2. The center device 41 is composed of one or a plurality of computers. In the monitoring center 40, based on the abnormality signal received by the center device 41 from the image display device 10, information on the monitoring area 2 to be dealt with is displayed on the display unit 42, and confirmation processing for the user or security for the monitoring area 2 is performed. Necessary measures are taken, such as instructions for coping with staff.

  FIG. 2 is a schematic configuration diagram of the image display device 10. The image display device 10 includes a wireless communication unit 11, a center communication unit 12, a display unit 13, an operation unit 14, a storage unit 15, and a control unit 16.

  The wireless communication unit 11 is configured as a so-called wireless LAN access point that complies with, for example, any of the IEEE 802.11 standards. The wireless communication unit 11 performs wireless communication with the camera unit 20 in accordance with any of the IEEE 802.11 standards.

  The center communication unit 12 is connected to the communication line network 50 and makes an emergency call to the center device 41 via the communication line network 50. Identification information set in advance in the image display device 10 is added to the communication with the center device 41 by the center communication unit 12.

  The display unit 13 is a display device configured with a liquid crystal display. The display unit 13 is configured by, for example, a liquid crystal touch panel display integrated with the operation unit 14. The display unit 13 displays image data received from the camera unit 20, an operation setting screen, and the like.

  The operation unit 14 is configured by, for example, a liquid crystal touch panel display integrated with the display unit 13, and has various input icons displayed as operation symbols on the liquid crystal touch panel display. The operation unit 14 is operated by a user when selecting a camera unit 20 to be checked for an image or operating an emergency call. When an icon is selected by the user, the operation unit 14 inputs a corresponding signal to the control unit 16.

  For example, when a user selects a specific camera unit 20 by operating the operation unit 14, image data is acquired from the camera unit 20 via the wireless communication unit 11, and the current captured image is displayed on the liquid crystal touch panel display. Is displayed. The operation unit 14 has a recording / stop icon, and when the user operates this while the image data is displayed, the displayed image data is recorded or stopped. In addition, the operation unit 14 has an emergency notification icon, and when the user operates this, an emergency notification is sent to the center device 41.

  The storage unit 15 is configured by a ROM, RAM, or HDD, stores identification information for identifying itself, various programs, and the like, and further stores various information for operating the image display device 10. For example, the storage unit 15 is configured to communicate image data that has been instructed to be recorded from the operation unit 14, preset setting information such as the network name (ESSID) and authentication information of the wireless communication unit 11, and communication by the wireless communication unit 11. The communication information to be used is stored.

  The communication information includes, for example, an image parameter history in which image parameters at the time of previous communication for each camera unit 20 are associated with time information indicating communication time, and a communication channel of a wireless LAN that can be used by the security system 1 ( Information such as a channel table in which a radio frequency band) is recorded. The image parameter is, for example, setting information such as a definition (image size and compression rate) that is a spatial image quality adjustment, and a frame rate (an imaging interval by the camera unit 20) that is a temporal image quality adjustment. For example, the definition and the frame rate are each set to any value determined discretely within the range of values that can be used in the security system 1. In the present embodiment, the definition and the frame rate are collectively referred to as “image quality”.

  The control unit 16 includes a microcomputer including a CPU, a ROM, a RAM, and the like and peripheral circuits thereof, and controls each unit described above.

  FIG. 3 is a functional block diagram of the control unit 16 of the image display apparatus 10. The control unit 16 includes an image reception processing unit 161, a reception monitoring unit 162, an image quality adjustment determination unit 163, and a channel change determination as functional modules realized by the microcomputer and the computer program executed on the microcomputer. Unit 164 and a channel change processing unit 165.

  When the camera unit 20 is designated by the operation unit 14, the image reception processing unit 161 transmits an image request signal to the camera unit 20 and starts an image reception process with the camera unit 20. At this time, the image reception processing unit 161 refers to the image parameter history stored in the storage unit 15 and the image quality of the camera unit 20 is the lowest among the image parameters used in the last image reception processing, for example. Extract image parameters. Then, the image reception processing unit 161 transmits an image quality adjustment instruction for instructing the target camera unit 20 to use the image parameter to the camera unit 20. Further, when the operation unit 14 instructs the end of the image reception process, the image reception processing unit 161 transmits an image stop signal to the camera unit 20 that is transmitting the image, and the image reception process with the camera unit 20 is performed. Exit.

  The reception monitoring unit 162 counts the data amount of the image data received from the camera unit 20 during the execution of the image reception process. The reception monitoring unit 162 causes the image display device 10 to appropriately receive image data by causing the image quality adjustment determination unit 163 and the channel change determination unit 164 to perform image quality adjustment processing and communication quality determination processing, which will be described later, respectively. Monitor whether or not.

  The reception monitoring unit 162 counts elapsed time using a timer (not shown), and for example, an image frame to be received by the image display apparatus 10 within a unit time T1 (for example, 5 seconds) from the frame rate of the currently designated image data. The ratio of the number of image frames actually received within the unit time T1 to the number (that is, frame rate × T1) is obtained. This ratio is hereinafter referred to as “frame reception rate”. Then, the reception monitoring unit 162 outputs the frame reception rate to the image quality adjustment determination unit 163 every unit time T1, and causes the image quality adjustment determination unit 163 to execute image quality adjustment processing for changing the image parameter of the camera unit 20. . As described above, the reception monitoring unit 162 causes the image quality adjustment determination unit 163 to change the image parameter according to the relative degree in which the image data can be received within the unit time T1.

  The reception monitoring unit 162 counts the number of image frames actually received from the camera unit 20 within a unit time T2 (for example, 15 seconds). The unit time T2 is set to a time longer than the unit time T1 for the image quality adjustment process. Then, the reception monitoring unit 162 outputs the number of image frames for each unit time T2 to the channel change determination unit 164, and causes the channel change determination unit 164 to execute communication quality determination processing. As described above, the reception monitoring unit 162 causes the channel change determination unit 164 to determine whether or not the channel change is necessary according to the amount of image data actually received within the unit time T2.

  The reception monitoring unit 162 is actually received within the unit time T1 with respect to the total data amount (that is, bit rate × T1) that the image display apparatus 10 should receive within the unit time T1 from the bit rate of the wireless communication. The ratio of the amount of image data may be obtained, and this ratio may be output to the image quality adjustment determination unit 163 instead of the frame reception rate. Further, the reception monitoring unit 162 may output the value of the amount of image data (number of bytes) actually received from the camera unit 20 within the unit time T2 to the channel change determination unit 164.

  The image quality adjustment determination unit 163 executes image quality adjustment processing every unit time T1 (for example, 5 seconds). The unit time T1 is an example of a first time. In the image quality adjustment process, the image quality adjustment determination unit 163 outputs to the camera unit 20 an image quality adjustment instruction according to the comparison result between the data amount of the image data received from the camera unit 20 and the image quality adjustment threshold within the unit time T1. To do. For this purpose, the image quality adjustment determination unit 163 first receives the frame reception rate acquired from the reception monitoring unit 162 (that is, the image actually received for the number of image frames that the image display device 10 should receive within the unit time T1). The ratio of the number of frames) is compared with an image quality adjustment threshold value to determine whether image quality adjustment is necessary.

  The image quality adjustment determination unit 163 uses, for example, an upper adjustment threshold, a lower adjustment threshold, and a minimum threshold described below as the image quality adjustment threshold. The upper adjustment threshold is a threshold for the frame reception rate for determining whether or not to output an image quality adjustment instruction for improving the image quality. The upper adjustment threshold is an example of a first image quality adjustment threshold, and is set to a high value such as 0.9 corresponding to a state in which the image display apparatus 10 can receive most of the image data transmitted from the camera unit 20. Is set. The lower adjustment threshold is an example of a second image quality adjustment threshold, and is a threshold for a frame reception rate for determining whether or not to output an image quality adjustment instruction for reducing the image quality. The lower adjustment threshold value is smaller than the upper adjustment threshold value, and is set to a value such as 0.5 corresponding to a state where the transmitted image data is not received much. The minimum threshold is a threshold for the frame reception rate for determining whether or not to output an image quality adjustment instruction for reducing the image quality to the lowest value that can be set. The minimum threshold value is set to a value such as 0.25 corresponding to the fact that the transmitted image data is hardly received, being smaller than the lower adjustment threshold value.

  For example, the image quality adjustment determination unit 163 determines that the adjustment for improving the image quality is performed when the frame reception rate is equal to or higher than the upper adjustment threshold (for example, 0.9 or higher). At this time, the image quality adjustment determination unit 163 determines the one set by one step higher the definition or frame rate currently set as a new image parameter.

  The image quality adjustment determination unit 163 determines a new image parameter for improving the image quality, for example, by the following procedure. First, if the frame rate is not the maximum within the settable range, the definition is not changed and the frame rate is increased by one step. If the frame rate is maximum but the definition is not the maximum within a settable range, the frame rate is not changed and the definition is increased by one step. If both the frame rate and the definition are maximal, the image quality cannot be increased any further, so neither the frame rate nor the definition is changed. In the above procedure, the frame rate is preferentially increased over the definition, but conversely, the definition may be preferentially increased over the frame rate.

  In addition, the image quality adjustment determination unit 163 determines that the adjustment for reducing the image quality is performed when the frame reception rate is greater than the minimum threshold and less than or equal to the lower adjustment threshold (for example, greater than 0.25 and 0.5 or less). . At this time, the image quality adjustment determination unit 163 determines, as a new image parameter, a value obtained by lowering the currently set definition or frame rate by one step.

  The image quality adjustment determination unit 163 determines a new image parameter for reducing the image quality, for example, in the following procedure. First, if the definition is not the minimum within the settable range, the frame rate is not changed and the definition is lowered by one step. If the definition is the minimum but the frame rate is not the minimum within the settable range, the definition is not changed and the frame rate is lowered by one step. If both the frame rate and the definition are minimal, the image quality cannot be lowered any further, so neither the frame rate nor the definition is changed. In the above procedure, the definition is preferentially made smaller than the frame rate, but conversely, the frame rate may be made preferentially smaller than the definition.

  Also, the image quality adjustment determination unit 163 determines that adjustment is performed to reduce the image quality to the lowest value that can be set if the frame reception rate is equal to or lower than the minimum threshold (for example, 0.25 or lower). At this time, the image quality adjustment determination unit 163 determines the lowest definition and frame rate within the settable range as new image parameters.

  Then, the image quality adjustment determination unit 163 transmits an image quality adjustment instruction for instructing the camera unit 20 to use a new image parameter to the camera unit 20, and the new image parameter is stored in the image parameter history of the storage unit 15. To remember.

  On the other hand, if the frame reception rate is greater than the lower adjustment threshold and less than the upper adjustment threshold (for example, greater than 0.5 and less than 0.9), the image quality adjustment determination unit 163 determines that the image quality is not adjusted and remains as it is. The image quality adjustment process ends.

  The channel change determination unit 164 performs a communication quality determination process every unit time T2 (for example, 15 seconds). The unit time T2 is an example of a second time longer than the first time. In the communication quality determination processing, the channel change determination unit 164 communicates between the camera unit 20 and the image display device 10 based on the quality of the signal received by the image display device 10 within the unit time T2 longer than the unit time T1. It is determined whether or not to change. For example, the channel change determination unit 164 determines whether or not to change the communication channel based on the comparison result between the data amount of the image data received from the camera unit 20 and the channel change threshold within the unit time T2. For this purpose, the channel change determination unit 164 first compares the number of image frames within the unit time T2 acquired from the reception monitoring unit 162 with a channel change threshold value, and determines whether or not a communication channel change is necessary.

  The channel change threshold is a threshold for the number of image frames for the channel change determination unit 164 to determine whether or not the image display apparatus 10 is in a state equal to the state in which no image data can be received. Is done. The channel change threshold is a threshold corresponding to the number of image frames that is smaller than the lowest minimum threshold among the above three image quality adjustment thresholds.

  For example, if the number of image frames received within the unit time T2 is equal to or less than the channel change threshold (for example, 0), the channel change determination unit 164 determines that the communication channel change is in a preliminary state. Even if the image display device 10 is not able to receive any image data, the channel change determination unit 164 does not immediately determine that the communication channel is changed, but temporarily determines that the state is a preliminary state for changing the communication channel. To do. Then, the channel change determination unit 164 determines when the number of times of determination with the standby state exceeds a predetermined number of times (that is, when the state in which image data cannot be received over the long term has not improved). It is determined for the first time that the communication channel is changed.

  If the number of image frames received within the unit time T2 is less than or equal to the channel change threshold, the channel change determination unit 164 displays, for example, “Connecting” on the display unit 13 and the frame reception rate from the camera unit 20. Informs the user of the current transmission situation where the At this time, if the current image parameter does not have the lowest image quality, the channel change determination unit 164 transmits an image quality adjustment instruction for reducing the image quality to the lowest image quality to the camera unit 20 and stores the image parameter with the lowest image quality in the storage unit 15. Store in the image parameter history. Further, the channel change determination unit 164 counts the number of times that the standby state is determined in total after the currently executing image reception process is started. Alternatively, the channel change determination unit 164 may count the number of times that the security system 1 has been determined to be in the preliminary state after the security system 1 is activated.

  Then, the channel change determination unit 164 determines whether or not the number of determinations with respect to the standby state is divisible by a predetermined number of times, that is, whether or not the determination with respect to the standby state has been performed a predetermined number of times. When the channel change determination unit 164 counts the number of times of determination of the spare state since the start of the current image reception process, the predetermined number of times is set to 20, for example. When the channel change determination unit 164 counts the number of times of determination of the standby state after the security system 1 is activated, the predetermined number is set to a larger value, for example, 100 times. Then, when the number of times of determination as the standby state is divisible by a predetermined number, the channel change determination unit 164 determines to change the communication channel. At this time, the channel change determination unit 164 may reset the count of the number of times determined to be the standby state.

  On the other hand, if the number of image frames received within the unit time T2 is larger than the channel change threshold (for example, once or more), the channel change determination unit 164 determines not to change the communication channel, and determines the communication quality as it is. The process ends.

  For example, the channel change determination unit 164 determines whether to change the communication channel based on the SINR (Single to Interference and Noise Ratio) value for the signal received by the image display apparatus 10. May be determined. The SINR is information indicating the degree of influence of interference and noise received by the signal from the camera unit 20 to the image display device 10, and the higher the SINR value, the better the quality of the signal received by the image display device 10. . Therefore, the channel change determination unit 164 calculates the SINR of the received signal every unit time T2 instead of performing the channel change determination based on the number of times determined to be the standby state in the communication quality determination process, and the value May be determined as a preliminary state for changing the communication channel when the value falls below a predetermined threshold.

  When channel change determination unit 164 determines that the communication channel is to be changed, channel change processing unit 165 changes the communication channel according to the determination result. The channel change processing unit 165 performs carrier sense for measuring the received radio wave intensity by scanning each channel (each band of the radio frequency) when the image display device 10 is turned on or at certain time intervals. A communication channel (that is, a low interference level) is stored in the channel table of the storage unit 15. Alternatively, the channel change processing unit 165 may perform carrier sense when the channel change determination unit 164 determines to change the communication channel. The channel change processing unit 165 refers to the channel table in the storage unit 15 and changes the communication channel used by the wireless communication unit 11 to one that can be used other than the currently used communication channel.

  FIG. 4 is a schematic configuration diagram of the camera unit 20. The camera unit 20 includes a setting information storage unit 21, a wireless slave unit communication unit 22, an image acquisition unit 23, an image quality adjustment unit 24, an image storage unit 25, and a control unit 26.

  The setting information storage unit 21 stores a device ID for identifying itself and various programs, and further stores various information for operating the camera unit 20. For example, the setting information storage unit 21 stores in advance a network name (ESSID) and authentication information set by the wireless communication unit 11 of the image display apparatus 10 that is a wireless LAN access point. The setting information storage unit 21 stores image parameters such as a frame rate and a definition included in the image quality adjustment instruction received from the image display device 10.

  The wireless slave unit communication unit 22 is an example of a wireless communication processing unit and has a wireless LAN client function. When activated, the wireless slave unit communication unit 22 scans each band of the radio frequency and searches for the wireless communication unit 11 of the image display device 10 that is a wireless LAN access point. The wireless slave unit communication unit 22 determines a communication channel to be used from a control signal (beacon) output from the wireless communication unit 11 of the image display apparatus 10. Then, the wireless slave unit communication unit 22 connects to the image display device 10 using the network name (ESSID) and authentication information stored in the setting information storage unit 21. When receiving the image request signal from the image display device 10, the wireless slave device communication unit 22 sequentially transmits image data acquired by the image acquisition unit 23 and adjusted in image quality by the image quality adjustment unit 24 to the image display device 10. . Further, when receiving the image stop signal from the image display device 10, the wireless slave unit communication unit 22 ends the transmission of the image data.

  The image acquisition unit 23 acquires image data of the monitoring area 2 on the outer periphery of the house where the camera unit 20 is installed. The image acquisition unit 23 includes an image sensor 231 and an optical system 232.

  The imaging device 231 is a two-dimensional detector configured by a photoelectric converter having sensitivity to near infrared light or visible light, such as a CCD device or a C-MOS device. The image sensor 231 acquires the image signal of the monitoring area 2 at a shooting interval corresponding to the timing signal generated by the control unit 26. The photographing interval is set by the control unit 26 according to the frame rate instructed by the image quality adjustment instruction from the image display device 10.

  The optical system 232 is an imaging optical system such as a lens that forms an image of the monitoring area 2 on the image sensor 231.

  The image quality adjustment unit 24 adjusts the image quality of the image data acquired by the image acquisition unit 23 in accordance with an image quality adjustment instruction from the image display device 10. The image quality adjustment unit 24 includes an A / D converter 241 and an image compression circuit 242.

  The A / D converter 241 performs analog / digital conversion on an analog image signal input from the image sensor 231 at a fixed shooting interval to convert it into a digital image signal (image data).

  The image compression circuit 242 is, for example, H.264 as an image compression encoding method in accordance with the image parameter of definition (image size and compression rate) designated by the image quality adjustment instruction from the image display device 10. The image data input from the A / D converter 241 is compressed in accordance with the H.264 / MPEG-4AVC standard. Therefore, the image compression circuit 242 reduces the image obtained by the image sensor 231 and outputs image data with a smaller number of pixels as the definition set by the image quality adjustment instruction from the image display device 10 is lower. To do.

  Alternatively, the image compression circuit 242 compresses the image data input from the A / D converter 241 and finally outputs the image data whose image quality is adjusted. The compression rate when the image compression circuit 242 compresses the image data may be set by the control unit 26 according to the definition instructed by the image quality adjustment instruction from the image display device 10. The image compression circuit 242 compresses the image data from the A / D converter 241 at a low compression rate so that the higher the set definition is, the relatively large data amount is.

  Note that the image compression circuit 242 may follow other standards such as the MPEG2 Video standard as an image compression encoding method. Alternatively, the image compression circuit 242 may generate still image data according to the JPEG standard or the like. Further, in the security system 1, a different image compression encoding method may be adopted for each camera unit 20, and a plurality of camera units 20 using different image compression encoding methods may be mixed on the wireless LAN. Alternatively, one camera unit 20 may switch between a plurality of image compression encoding methods.

  The image storage unit 25 is a buffer that holds the image data acquired by the image acquisition unit 23 for a predetermined number of image frames. The image data held in the image storage unit 25 is sequentially deleted when a predetermined buffer period elapses.

  The control unit 26 includes a microcomputer including a CPU, a ROM, a RAM, and the like and peripheral circuits thereof, and controls each unit described above to operate as the camera unit 20.

  The control unit 26 drives the image sensor 231 to acquire the image signal of the monitoring area 2 at the shooting interval corresponding to the frame rate specified by the image quality adjustment instruction from the image display device 10. When the camera unit 20 receives an image quality adjustment instruction for changing the frame rate from the image display device 10, the control unit 26 obtains the camera unit 20 by changing the shooting interval of the image sensor 231 in accordance with the image quality adjustment instruction. The frame rate of the image data to be changed is changed.

  In addition, the control unit 26 may set the image size of the image data output from the image compression circuit 242 according to the definition specified by the image quality adjustment instruction from the image display device 10. In this case, when the camera unit 20 receives an image quality adjustment instruction that changes the definition, the control unit 26 changes the image size set in the image compression circuit 242 in accordance with the image quality adjustment instruction. For example, the control unit 26 may reduce the number of pixels of the image data output from the image compression circuit 242 by a predetermined amount as the definition divided into a plurality of stages decreases by one stage.

  The control unit 26 may set the compression rate of the image data by the image compression circuit 242 according to the definition specified by the image quality adjustment instruction from the image display device 10. In this case, when the camera unit 20 receives an image quality adjustment instruction that changes the definition, the control unit 26 changes the compression rate set in the image compression circuit 242 in accordance with the image quality adjustment instruction. For example, the control unit 26 may decrease the compression rate by the image compression circuit 242 by a predetermined amount as the definition divided into a plurality of steps increases by one step (so that the amount of data after compression increases). ).

  When the image quality adjustment instruction for increasing or decreasing the definition is received, the control unit 26 may change either the image size or the compression rate with priority. For example, the control unit 26 may increase / decrease the image size according to the increase / decrease of the definition while keeping the compression rate constant, or compress the image according to the increase / decrease of the definition while keeping the image size constant. The rate may be increased or decreased. Alternatively, the control unit 26 may increase or decrease both the image size and the compression rate one step at a time according to the level of definition.

  In the above description, the image quality adjustment determination unit 163 determines the new frame rate and definition (image parameter) when the image quality is improved or decreased. However, the control unit 26 determines the new frame rate and definition. You may decide. In this case, when the camera unit 20 receives an image quality adjustment instruction for improving the image quality, the control unit 26 sets the frame rate, for example, until the frame rate reaches a maximum within a settable range while keeping the definition constant. You may enlarge preferentially. On the other hand, when the camera unit 20 receives an image quality adjustment instruction for reducing the image quality, the control unit 26 reduces the definition until, for example, the definition is minimized within a settable range while keeping the frame rate constant. You may make it preferentially small.

  FIG. 5 is a flowchart illustrating an operation example of the image reception process. When the camera unit 20 is designated by the operation unit 14, the image reception processing unit 161 starts the image reception process shown in FIG. 5 with the camera unit 20.

  First, the image reception processing unit 161 refers to the image parameter history stored in the storage unit 15, and the image quality is the lowest among the image parameters used in the last image reception process for the target camera unit 20. Image parameters are extracted (step S1). Then, the image reception processing unit 161 adjusts the image quality for instructing the camera unit 20 to use the image request signal for requesting image data from the target camera unit 20 and the image parameter extracted in step S1. The instruction is transmitted to the target camera unit 20 (step S2). The designated image parameter is stored in the image parameter history of the storage unit 15 together with the current time.

  When the image reception process is started, the reception monitoring unit 162 counts the elapsed time by a timer (not shown), and determines whether or not the image quality adjustment timing has come every unit time T1 (for example, 5 seconds) (step S3). . When the current elapsed time is the image quality adjustment timing (Yes in step S3), the reception monitoring unit 162 causes the image quality adjustment determination unit 163 to execute image quality adjustment processing (step S4).

  When the current elapsed time is not the image quality adjustment timing (No in step S3) or when the image quality adjustment process in step S4 is completed, the reception monitoring unit 162 determines the communication quality determination timing for each unit time T2 (for example, 15 seconds). It is determined whether or not (step S5). When the current elapsed time is the communication quality determination timing (Yes in step S5), the reception monitoring unit 162 causes the channel change determination unit 164 to execute a communication quality determination process (step S6).

  When the current elapsed time is not the communication quality determination timing (No in step S5) or when the communication quality determination process in step S6 is completed, the image reception processing unit 161 instructs the operation unit 14 to end the image reception process. It is determined whether or not it has been done (step S7). When the end of the image receiving process is not instructed (No in step S7), the process returns to step S3. On the other hand, when the end of the image reception process is instructed (Yes in step S7), the image reception processing unit 161 transmits an image stop signal to the camera unit 20 receiving the image (step S8). Thereby, the image reception processing unit 161 ends the image reception process with the camera unit 20. When the image reception process ends, the image reception processing unit 161 stores time information when the image reception process was performed in the image parameter history of the storage unit 15.

  FIG. 6 is a flowchart illustrating an operation example of image quality adjustment processing. If it is determined in step S3 of FIG. 5 that the current elapsed time is the image quality adjustment timing, the image quality adjustment determination unit 163 starts the image quality adjustment process shown in FIG. 6 in step S4 of FIG.

  First, the image quality adjustment determination unit 163 acquires the frame reception rate within the unit time T1 from the reception monitoring unit 162 (step S21). Then, the image quality adjustment determination unit 163 compares the acquired frame reception rate within the unit time T1 with the image quality adjustment threshold (step S22).

  If the frame reception rate acquired in step S21 is equal to or higher than the upper adjustment threshold, the image quality adjustment determination unit 163 determines to perform adjustment for improving the image quality (step S23). At this time, the image quality adjustment determination unit 163 determines the newly set definition or frame rate by one step as a new image parameter (step S24).

  If the frame reception rate acquired in step S21 is greater than the minimum threshold value and less than or equal to the lower adjustment threshold value, the image quality adjustment determination unit 163 determines to perform adjustment for reducing the image quality (step S25). At this time, the image quality adjustment determination unit 163 determines a new image parameter obtained by lowering the currently set definition or frame rate by one step (step S26).

  If the frame reception rate acquired in step S21 is equal to or lower than the minimum threshold value, the image quality adjustment determination unit 163 determines to perform adjustment to reduce the image quality to the lowest value that can be set (step S27). At this time, the image quality adjustment determination unit 163 determines the lowest definition and frame rate within the settable range as new image parameters (step S28).

  Then, the image quality adjustment determination unit 163 transmits an image quality adjustment instruction for instructing the camera unit 20 to use a new image parameter to the camera unit 20 (step S29). At the same time, the image quality adjustment determination unit 163 stores the new image parameter and the current time in the image parameter history of the storage unit 15 (step S30). Thus, the image quality adjustment determination unit 163 ends the image quality adjustment process.

  On the other hand, if the frame reception rate acquired in step S21 is greater than the lower adjustment threshold and less than the upper adjustment threshold, the image quality adjustment determination unit 163 ends the image quality adjustment process as it is without making a determination to adjust the image quality.

  FIG. 7 is a flowchart illustrating an operation example of the communication quality determination process. If it is determined in step S5 of FIG. 5 that the current elapsed time is the communication quality determination timing, in step S6 of FIG. 5, the channel change determination unit 164 starts the communication quality determination process shown in FIG.

  First, the channel change determination unit 164 acquires the number of image frames received within the unit time T2 from the reception monitoring unit 162 (step S41). Then, the channel change determination unit 164 compares the acquired number of image frames within the unit time T2 with a channel change threshold (step S42).

  If the number of image frames within the unit time T2 is equal to or less than the channel change threshold (Yes in step S42), the channel change determination unit 164 displays, for example, “Connecting” on the display unit 13 and the like from the camera unit 20. The user is notified of the current transmission status in which the frame reception rate is decreasing (step S43).

  At this time, the channel change determination unit 164 determines whether or not the current image parameter has the lowest image quality (step S44). If the current image parameter is not the minimum image quality (No in step S44), an image quality adjustment instruction to the minimum image quality is transmitted to the camera unit 20, and the image parameter of the minimum image quality and the current time are stored in the image parameter of the storage unit 15. Store in the history (step S45). On the other hand, if the current image parameter is the lowest image quality (Yes in step S44), the channel change determination unit 164 proceeds to the next step S46 without executing step S45.

  Further, the channel change determination unit 164 determines that the current state is the communication channel change standby state, and increments the count of the number of times that the current image reception process has been determined since the start of the current image reception process by 1 (step S46). Then, the channel change determination unit 164 determines whether or not the number of times of determination with the spare state is divisible by a predetermined number of times, that is, whether or not the number of times of determination with the standby state has been made a predetermined number of times ( Step S47). If the number of times of determination as the spare state is not divisible by a predetermined number of times (No in step S47), the channel change determination unit 164 determines that the communication channel is not changed, and ends the communication quality determination process as it is.

  On the other hand, if the number of times of determination as the standby state is divisible by a predetermined number of times (Yes in step S47), channel change determination unit 164 determines that the communication channel is to be changed, and causes channel change processing unit 165 to change the communication channel. (Step S48). At this time, the channel change determination unit 164 resets the count of the number of determinations with respect to the standby state (step S49), and ends the communication quality determination process.

  If the number of image frames within the unit time T2 acquired in step S41 is larger than the channel change threshold (No in step S42), the channel change determination unit 164 determines that the communication channel is not changed and determines the communication quality as it is. The process ends.

  Note that the function of the image quality adjustment determination unit 163 may be realized by the control unit 26 of the camera unit 20. In this case, instead of the reception monitoring unit 162 obtaining the frame reception rate in the image display apparatus 10 within the unit time T1 and causing the image quality adjustment determination unit 163 to execute the image quality adjustment process, the control unit 26 of the camera unit 20 An image quality adjustment instruction according to the comparison result between the data amount of the image data transmitted to the image display device 10 within the time T1 and the image quality adjustment threshold is output to the image quality adjustment unit 24.

  Therefore, instead of the reception monitoring unit 162 obtaining the frame reception rate in the image display apparatus 10 within the unit time T1, the control unit 26 may, for example, select an image frame to be transmitted by the camera unit 20 within the unit time T1. The ratio of the number of image frames actually delivered to the image display device 10 within the unit time T1 with respect to the number (referred to as “frame transmission rate”) is obtained. Then, instead of the image quality adjustment determination unit 163 executing the image quality adjustment process of FIG. 6 every unit time T1, the control unit 26 performs the image quality adjustment process similar to that of FIG. 6 using the frame transmission rate. As a result, the control unit 26 determines a new image parameter, and outputs an image quality adjustment instruction to the image quality adjustment unit 24 to instruct the image quality adjustment unit 24 to use the image parameter. Then, the image quality adjustment unit 24 adjusts the image quality of the image data acquired by the image acquisition unit 23 in accordance with the image quality adjustment instruction output from the control unit 26.

  When the image quality adjustment process is performed by the camera unit 20, steps S1, S3, and S4 in FIG. 5 are executed as a process of the control unit 26 in the camera unit 20 instead of the image reception process in the image display device 10. However, even when the image quality adjustment process is performed by the camera unit 20, whether or not to change the communication channel is determined on the image display device 10 side. Therefore, the communication quality determination process in FIG. Similarly, it is executed by the channel change determination unit 164.

  As described above, the security system 1 adjusts the image quality of the image data according to the transmission amount from the camera unit 20 to the image display apparatus 10 within the unit time T1, and the image is displayed within the unit time T2 longer than the unit time T1. The communication channel is changed according to the quality of the signal received by the display device 10. In particular, the security system 1 adjusts the image quality until the number of times that the communication channel change is determined to be a preliminary state exceeds a predetermined number even when the image display device 10 has not received any image data. An attempt is made to restore the image data to a state where image data can be received by adjusting the image parameters by processing so that the communication channel is not changed frequently. Thereby, in the security system 1, even if the communication efficiency between the camera unit 20 and the image display device 10 is lowered, wireless communication is not possible while preventing loss of the display image in the image display device 10 as much as possible. Generation of blank time can be suppressed.

DESCRIPTION OF SYMBOLS 1 Security system 10 Image display apparatus 11 Wireless communication part 12 Center communication part 15 Memory | storage part 16 Control part 161 Image reception process part 162 Reception monitoring part 163 Image quality adjustment determination part 164 Channel change determination part 165 Channel change process part 20 Camera unit 23 Image Acquisition unit 24 Image quality adjustment unit

Claims (5)

A wireless communication system including a wireless transmitter and a wireless controller capable of wireless communication with each other,
The wireless transmitter is
An image acquisition unit for acquiring image data;
An image quality adjustment unit that adjusts the image quality of the image data in accordance with an image quality adjustment instruction from the wireless controller;
A wireless communication processing unit for transmitting image data whose image quality has been adjusted by the image quality adjusting unit to the wireless controller;
With
The wireless controller
An image quality adjustment determination unit that outputs to the wireless transmitter an image quality adjustment instruction according to a comparison result between a data amount of image data received from the wireless transmitter within a first time and an image quality adjustment threshold;
A channel change determination unit that determines whether to change a communication channel between the wireless transmitter and the wireless controller based on a quality of a signal received within a second time longer than the first time;
A channel change processing unit that changes the communication channel according to a determination result of the channel change determination unit;
A wireless communication system comprising: A wireless communication system including a wireless transmitter and a wireless controller capable of wireless communication with each other,
The wireless transmitter is
An image acquisition unit for acquiring image data;
An image quality adjustment unit for adjusting the image quality of the image data;
A wireless communication processing unit for transmitting image data whose image quality has been adjusted by the image quality adjusting unit to the wireless controller;
An image quality adjustment determination unit that outputs an image quality adjustment instruction to the image quality adjustment unit according to a comparison result between a data amount of image data transmitted to the wireless controller within a first time and an image quality adjustment threshold;
With
The wireless controller
A channel change determination unit that determines whether to change a communication channel between the wireless transmitter and the wireless controller based on a quality of a signal received within a second time longer than the first time;
A channel change processing unit that changes the communication channel according to a determination result of the channel change determination unit;
A wireless communication system comprising: The image quality adjustment determination unit
As the image quality adjustment threshold, at least a first image quality adjustment threshold and a second image quality adjustment threshold smaller than the first image quality adjustment threshold are used.
If the data amount of the image data within the first time is equal to or greater than the first image quality adjustment threshold, an image quality adjustment instruction for improving the image quality is output, and if the data amount is equal to or less than the second image quality adjustment threshold. The wireless communication system according to claim 1, wherein an image quality adjustment instruction for reducing image quality is output.   The channel change determination unit determines a communication channel change standby state if the amount of image data received from the wireless transmitter within the second time is equal to or less than a channel change threshold for determining a channel change. And the radio | wireless communications system as described in any one of Claims 1-3 which determines with changing a communication channel, if the frequency | count determined with the said preliminary | backup state exceeds the frequency | count determined beforehand.   The wireless communication system according to claim 4, wherein the channel change threshold is a threshold corresponding to the number of image frames smaller than the image quality adjustment threshold.

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