Video door phone system

Abstract

To output stable video immediately after beginning of imaging, even if a CMOS imaging element is used for a camera of a front-door slave unit.SOLUTION: A camera 6d of a front-door slave unit 6 includes a CMOS imaging element 2, an ISP 3 for processing an image signal, and an external memory 4 for storing a black level offset value, the ISP 3 includes a black level offset adjustment part 31 for correcting a black level of an image signal outputted by the CMOS imaging element 2, and a register part 34 for presetting the black level offset value to the black level offset adjustment part. The imaging element starts up upon call operation, the black level offset value is loaded to the register part 34 from the external memory 4, the black level offset value of the black level offset adjustment part 31 is uniquely determined, and the ISP3 starts video signal processing of the CMOS imaging element 2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a television intercom system using a CMOS image sensor.

Background Art

[0002] In a solid-state image sensor of an imaging device, an OB (Optical Black) pixel is usually provided to obtain a reference signal of the black level. However, when excessive light such as sunlight is irradiated, the charge generated in the effective pixel region overflows into this OB region, and the OB signal level fluctuates. Since this fluctuation means that the reference of the optical black level fluctuates, a technique for suppressing this has been proposed. For example, in Patent Document 1, an abnormal incidence of excessive light is detected, the video display signal is processed, and an OB pixel for clamping is selected to prevent "black crush". In addition, in Patent Document 2, a fluctuation threshold value of the OB signal is determined, and an unexpected OB signal is suppressed by excluding it.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the case of a television intercom system, when a visitor presses the call button of the outdoor unit, the camera is powered on and an image is displayed on the indoor master unit in the living room. Therefore, when a call is made in a state where excessive light is irradiated, the first displayed image or the recorded image becomes an unstable image with a sense of discomfort. In order to eliminate this, a technique for stabilizing the captured image in a short time is required. However, since the technique of Patent Document 1 calculates the black level to be clamped from the difference from the OB pixel portion, the process takes time. Further, since it is caused by the leakage current to the OB pixel peculiar to the CCD imaging device, it is in a different technical field from the latest CMOS imaging device in which the elements are separated.

[0005] On the other hand, although the technique of Patent Document 2 can shorten the time until convergence, since the clamp level is calculated, the process requires a certain amount of time. Therefore, depending on the subject, an image with a sense of discomfort was displayed immediately after the call. In addition, it became a large-scale system, which was a factor in cost increase.

[0006] Therefore, in view of such problems, an object of the present invention is to provide a television intercom system that can output a stable video immediately after starting imaging even when a CMOS imaging device is used for the camera of the entrance sub-unit.

Means for Solving the Problems

[0007] In order to solve the above problems, the invention of claim 1 is a television intercom system having an entrance sub-unit having a camera for imaging a visitor and a function of calling a resident, and a monitor for displaying the imaging video of the camera and a living room master unit having a function of responding to a call. The camera includes an imaging device having a CMOS imaging device and a video signal processing unit that processes an imaging signal output from the CMOS imaging device. The imaging device has an external memory for storing a black level offset value. The video signal processing unit has a black level offset adjustment unit for correcting the black level of the imaging signal output from the CMOS imaging device, and a register unit for presetting the black level offset value to the black level offset adjustment unit. Furthermore, the CMOS image sensor has a WDR function and outputs imaging signals with different accumulation exposure times. At the same time, the external memory stores a plurality of black level offset values corresponding to the imaging signals with different accumulation exposure times. On the other hand, the register section selects the black level offset value for each imaging region with a different accumulation exposure time and presets it to the black level offset adjustment section. The black level offset adjustment section performs black level correction corresponding to the imaging signals with different accumulation exposure times. The imaging device is activated when the entrance sub-unit is called, the black level offset value is loaded from the external memory to the register unit, the black level offset value of the black level offset adjustment unit is uniquely determined, and the video signal processing unit starts processing the video signal of the CMOS imaging device. According to this configuration, since the black level is set using a preset black level offset value, it is not necessary to calculate the black level to be clamped from the OB signal. Therefore, even if an influence such as excessive light occurs, it is possible to output an easy-to-view image in a short time, and there is no need to provide an OB pixel in the CMOS image sensor. Moreover, even if the imaging device is activated after receiving a call operation, the image displayed on the monitor can be quickly made easy to view, and the problem that it is difficult to identify the visitor displayed due to the influence of excessive light or the like can be solved.

[0008] In addition, Even if the CMOS image sensor outputs imaging signals having a plurality of accumulation exposure times, the black level to be clamped can be selected from an external memory and preset. Therefore, it is possible to satisfactorily display imaging regions having different accumulation exposure times in a short time without calculating from the OB signal. Incidentally, WDR is an abbreviation for Wide Dynamic Range, which is a known technique in which an image sensor outputs imaging signals having different accumulation exposure times, and an image synthesized from them is output.

[0009] Claim 2 The invention of 1 in the configuration described in is characterized in that it has a temperature sensor, a plurality of black level offset values associated with different temperatures are stored in an external memory, and the register unit selects the black level offset value to be loaded based on the temperature information obtained from the temperature sensor. According to this configuration, an optimal black level offset value can be used according to the installation environment (imaging temperature, subject illuminance) of the imaging device, and the system is simple and highly versatile.

Effect of the Invention

[0010] According to the present invention, since the black level is set using a preset black level offset value, it is not necessary to calculate the black level to be clamped from the OB signal. Therefore, even if an influence such as excessive light occurs, it is possible to output an easy-to-view video in a short time, and there is no need to provide an OB pixel in the CMOS image sensor. Moreover, even if the imaging device is activated after receiving a call operation, the video displayed on the monitor can be quickly made easy to view, and the problem that the visitor displayed due to the influence of excessive light or the like is difficult to identify can be solved.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments embodying the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an example of an imaging device included in a television intercom system according to the present invention. The imaging device 1 includes a CMOS image sensor 2 which is a solid-state image sensor, an image signal processor (ISP) 3 as a video signal processing unit, and an external memory 4 in which a black level offset value is stored. The CMOS image sensor 2 includes an effective pixel portion 21 in which RGB pixels are arranged in a matrix, and an analog signal amplification portion 22 that amplifies signals. The external memory 4 stores a black level offset value for clamping the black level of the video.

[0013] The ISP3 includes a black level offset adjustment unit 31, a static pixel defect correction unit 32, a white balance gain adjustment unit (WB gain adjustment unit) 33, and a register unit 34 that controls these units. The imaging signal output from the CMOS image sensor 2 is processed in the order of the black level offset adjustment unit 31, the static pixel defect correction unit 32, and the WB gain adjustment unit 33, and is output from the video signal output unit 35.

[0014] The operation of the imaging device 1 configured as described above is as follows. When activated, the CMOS image sensor 2 starts imaging, and at the same time, the register unit 34 loads the black level offset value from the external memory 4 and presets it to the black level offset adjustment unit 31. Note that the black level offset value stored in the external memory 4 is written as an optimized value according to the characteristics of the CMOS image sensor 2 to be used. This black level offset value is set to a value effective for image quality correction particularly during high-temperature operation, and is set for each of RGB.

[0015] The imaging signal output from the CMOS image sensor 2 has its black level corrected (clamped) with the black level offset value downloaded by this black level offset adjustment unit 31. Next, the missing pixel signals are corrected by the static pixel defect correction unit 32, the white balance is adjusted by the WB gain adjustment unit 33, and then it is output from the video signal output unit 35.

[0016] Note that in addition to the first communication IF 34a that communicates with the external memory 4, the register unit 34 has a second communication IF 34b that communicates with the outside. By connecting an external device to this second communication IF 34b, it is possible to change the black level offset value, enabling setting of an optimal black level offset value according to the imaging target, that is, according to the installation environment of the imaging device 1.

[0017] In this way, since the black level is set using the preset black level offset value, it is not necessary to calculate the black level to be clamped from the OB signal. Therefore, even if an influence such as excessive light occurs, the convergence speed of the black reference is fast, and it is possible to output an easy-to-view video in a short time, and there is no need to provide OB pixels in the CMOS image sensor 2. In addition, since it can be configured with a simple circuit, it leads to cost reduction.

[0018] FIG. 2 is a block diagram showing another form of the imaging device 1, and shows a configuration in which the CMOS image sensor 2 has a WDR function of outputting two types of imaging signals with different accumulation exposure times for the bright region and the dark region. The WDR function is a function that allows pixels with a plurality of accumulation exposure times to exist so that blooming does not occur even in a very bright imaging environment and proper exposure is achieved. A plurality of accumulation exposure times are set, and any one of the accumulation exposure times is selected for each pixel according to the brightness, and an imaging signal is generated.

[0019] In FIG. 2, short accumulation exposure is performed in a very bright region, long accumulation exposure is performed in other regions, and a configuration in which two types of imaging signals with different accumulation exposure times are output is shown. Therefore, the external memory 4 stores two types of black level offset values for short accumulation exposure time and long accumulation exposure time, and the ISP 3 includes a WDR region synthesis unit 36 that synthesizes two types of pixels with different accumulation exposure times to generate one image.

[0020] The two types of imaging signals output from the CMOS image sensor 2 are corrected for the black levels of the two types of imaging signals using the two types of black level offset values in the black level offset adjustment unit 31. Next, after being corrected by the static pixel defect correction unit 32, in the WDR region synthesis unit (WDR processing unit) 36, two types of pixels with different accumulation exposure times are synthesized to generate one image. Then, the WB gain is adjusted by the WB gain adjustment unit 33 and output as a video signal.

[0021] In this way, for pixels with different cumulative exposure times, optimal black levels can be set respectively, and video with even better image quality can be output. Here, the CMOS image sensor 2 is configured to output signals with two different cumulative exposure times. However, it may also be configured to output signals with even more, for example, three different cumulative exposure times. In that case, the external memory 4 stores black level offset values corresponding to three different cumulative exposure times.

[0022] FIG. 3 is a block diagram showing still another form of the imaging device 1. It is significantly different from the form of FIG. 1 in that it includes a temperature sensor 5. The temperature sensor 5 is arranged to measure the external temperature at which the CMOS image sensor 2 performs imaging, and the measured temperature information is transmitted to the register unit 34. Also, the external memory 4 stores a plurality of black level offset values associated with specific different temperatures. The temperature sensor 5 is connected to the second communication IF 34b of the register unit 34. The register unit 34 obtains temperature information from the temperature sensor 5, loads the black level offset value associated with the temperature corresponding to the obtained temperature from the external memory 4, and presets it to the black level offset adjustment unit 31. As a result, according to the installation environment (imaging temperature, subject illuminance) of the imaging device 1, the black level can be set using an optimal black level offset value, improving versatility.

[0023] FIG. 4 is an explanatory diagram of a video door phone system 10 including a door sub-unit 6 installed at the entrance and a living room master unit 7 installed in the living room, for a visitor to call a resident. The door sub-unit 6 is provided with a call button 6a for calling a resident, a microphone 6b and a speaker 6c for communication, and a camera 6d for imaging a visitor. The imaging device 1 is incorporated in the camera 6d. Also, the living room master unit 7 is provided with a call button 7a for responding to a call, a microphone 7b and a speaker 7c for communication, and a monitor 7d for displaying the imaging video of the camera 6d. The door sub-unit 6 and the living room master unit 7 are connected by a transmission line L.

[0024] When the call button 6a of the entrance unit 6 is pressed to receive a call operation, a call signal is transmitted to the in-room master unit 7, and at the same time, the camera 6d is activated and the captured image is transmitted to the in-room master unit 7. That is, the internal imaging device 1 is activated and starts transmitting an imaging signal. At this time, since the black level is adjusted and output with a preset black level offset value, an image that can be easily confirmed in a short time is displayed on the monitor 7d of the in-room master unit 7.

[0025] Then, the in-room master unit 7 that has received the call signal emits a call sound, and the captured image of the camera 6d is displayed on the monitor 7d. When the call button 7a is pressed after receiving the call, a communication path is formed with the entrance unit 6, and the responding resident can communicate while confirming the visitor on the monitor 7d.

[0026] In this way, even if the camera 6d is activated after receiving the call operation, that is, even if the internal imaging device 1 is activated, it does not require time to calculate the offset value of the black level thereafter, so the image displayed on the monitor 7d can be quickly made easy to view. Therefore, it is possible to solve the problem that it is difficult to identify the visitor displayed on the monitor 7d due to the influence of excessive light or the like.

[0027] Although the video door phone system 10 that starts imaging by operating the call button 6a has been described, the imaging device 1 of the present invention can also be applied to other systems. For example, it is also suitable for a surveillance camera equipped with a human sensor that senses the approach of a person and starts imaging.

Explanation of reference numerals

[0028] 1 ··· Imaging device, 2 ··· CMOS image sensor, 3 ··· ISP (video signal processing unit), 4 ··· External memory, 5 ··· Temperature sensor, 31 ··· Black level offset adjustment unit, 34 ··· Register unit, 36 ··· WDR region synthesis unit (WDR processing unit), 6 ··· Entrance unit, 6d ··· Camera, 7 ··· In-room master unit, 10 ··· Video door phone system.

Claims

1. A video door phone system having a door sub-unit equipped with a camera for imaging visitors and a function for calling residents, and a living room main unit equipped with a monitor for displaying the imaging video of the camera and a function for responding to calls, wherein the camera comprises an imaging device having a CMOS image sensor and a video signal processing unit for processing an imaging signal output from the CMOS image sensor, wherein the imaging device has an external memory for storing a black level offset value, while the video signal processing unit has a black level offset adjustment unit for correcting the black level of the imaging signal output from the CMOS image sensor, and a register unit for presetting the black level offset value to the black level offset adjustment unit, furthermore, the CMOS image sensor has a WDR function and outputs imaging signals with different accumulation exposure times, and the external memory stores a plurality of black level offset values corresponding to the imaging signals with different accumulation exposure times, while the register unit selects a black level offset value for each imaging region with different accumulation exposure times and presets it to the black level offset adjustment unit, and the black level offset adjustment unit performs black level correction corresponding to imaging signals with different accumulation exposure times, wherein the imaging device is activated when the door sub-unit is called, the black level offset value is loaded from the external memory to the register unit, the black level offset value of the black level offset adjustment unit is uniquely determined, and the video signal processing unit starts processing the video signal of the CMOS image sensor. A video door phone system characterized by the above.

2. having a temperature sensor, and a plurality of black level offset values associated with different temperatures are stored in the external memory, wherein the register unit selects the black level offset value to be loaded based on the temperature information obtained from the temperature sensor. The video door phone system according to Claim 1, characterized by the above.

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