JP2009049946A - Image sensing device and door-phone system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image sensing element for suppressing the change of a frame rate and being capable of quickly adjusting a brightness level in the image sensing element adjusting the brightness level through the control of an exposure time in the image sensing element and an amplification factor in a gain amplifier and a door-phone system. <P>SOLUTION: An image sensing device has the image sensing element, the gain amplifier amplifying a video signal and a brightness-level adjusting section adjusting and processing the brightness level adjusting the video signal by controlling the exposure time and the amplification factor of the gain amplifier. The image sensing device contains a first processing for temporarily setting the exposure time and the amplification factor extensively over a plurality of predetermined points, a second processing for detecting the magnitudes of the amplified video signal at every temporarily set point, and a third processing for setting the frame rate on the basis of the result of the detection in a brightness-level adjusting processing. The image sensing device further contains a fourth processing adjusting the exposure time and the amplification factor under the set frame rate in the brightness-level adjusting processing. Such an image sensing device and the door-phone system with the image sensing device are provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an imaging device that captures an image of a subject and generates a video signal, and a door phone system using the imaging device.

  In recent years, with the improvement of security awareness, an imaging device has been adopted as a doorphone slave unit to notify that there are visitors in the room, and the video from the doorphone slave unit is displayed on the doorphone master unit in the room, and the door is opened. A TV door phone that allows you to check who is a visitor before, or even if there is no visitor, you can operate the doorphone slave unit from the indoor doorphone master unit and check for any abnormalities outdoors. The system is spreading.

  Conventionally, the camera of the door phone slave unit and the monitor of the door phone master unit have been displayed in black and white, but recently, products supporting color display are increasing, and the visibility is further improved. In such a TV door phone system, various measures are taken because it is necessary to discriminate visitors and to check for outdoor abnormalities even at night when the outdoors are dark.

  For example, a means for obtaining a sufficient amount of light for an image sensor in a door phone slave unit by incorporating an infrared LED or a white LED in the door phone slave unit and illuminating a visitor or the like with the LED is generally used. However, the method of illuminating the light of the infrared LED to the visitor has the advantage that the visitor is not aware that the light is illuminated, but due to the characteristics of the infrared light, the resulting image is displayed in black and white and the visibility is reduced. There is a problem to do. Also, depending on the color of the subject, it may not be possible to determine with infrared light, and an abnormality may be missed.

  On the other hand, the method of illuminating the light of the white LED to the visitor is unpleasant to the visitor because the image obtained from the door phone slave unit remains in color and the visibility is not lowered, but the visitor is directly illuminated. There is something to think about. In addition, when the outdoor door phone master unit wants to observe the outdoors, the white LED is lit, so that there is also a problem that a person outside the room knows that he is observing the outdoors from the room. In either case of the infrared LED or the white LED, only the vicinity of the door phone slave unit is illuminated, so that even in the imaging range of the door phone slave unit, a dark area that cannot be confirmed is created. There is also a problem.

  There is also a slave unit (imaging device) that can obtain a stable (average brightness level is almost constant) image on the monitor side even if the brightness of the subject fluctuates. In such an imaging apparatus, the luminance level is adjusted by appropriately adjusting the magnitude (amplification factor) of the video signal in accordance with the brightness of the subject. Here, an example of such an imaging apparatus will be described below with reference to FIG.

  The imaging apparatus 100 includes an imaging element 101, a gain amplifier 102, a video signal processing unit 103, a control unit 104, and the like. The image sensor 101 is configured by, for example, a CCD, and an amount of electric charge corresponding to the subject is accumulated for each pixel by being exposed in each frame. This accumulated charge is output to the subsequent stage as a video signal for each frame. Therefore, the magnitude (amplitude) of this video signal represents the luminance of the video.

  The exposure time in each frame can be controlled through an instruction from the control unit 104 with the maximum time determined by the frame rate (number of times the frame is switched per unit time) as an upper limit. Note that the longer the exposure time, the larger the amount of accumulated charge, and the larger the video signal.

  The gain amplifier 102 is provided at the subsequent stage of the image sensor 101 and amplifies the video signal at an amplification factor according to an instruction from the control unit 104. The video signal processing unit 103 performs a predetermined process on the video signal output from the gain amplifier 102 and outputs the processed video signal to a subsequent stage (for example, a master unit in a door phone system). The microcomputer 104 has a calculation control function and controls various processes performed in the imaging apparatus 100.

  With the above configuration, the imaging apparatus 100 can generate and output video data representing a video of a subject for each frame. Further, the exposure time for each frame in the image sensor 101 and the amplification factor in the gain amplifier 102 are adjusted according to the brightness of the subject, and the entire output video or the average luminance within a predetermined range is substantially constant. Adjustment (brightness level adjustment) is made to be.

  More specifically, the brightness level adjustment first sets the exposure time of the image sensor 101 and the gain of the gain amplifier 102 to a certain value (point). At this point, the image pickup device 101 generates a video signal and a gain amplifier 102 amplifies it. Thereafter, the microcomputer 104 calculates a luminance level from the amplified video signal, and determines whether or not the luminance level is within an allowable range set in advance as an appropriate luminance level.

  As a result, if the calculated brightness level exceeds the allowable range, the exposure time in the image sensor 101 is set to be short, or the gain of the gain amplifier 102 is set to be small, and the above determination is executed again. Conversely, if the calculated luminance level is below the allowable range, the exposure time in the image sensor 101 is set to be long or the gain of the gain amplifier 102 is set to be large, and the above determination is executed again. .

  In this way, when a point where the calculated luminance level falls within the allowable range is detected, this point is applied to normal video data generation processing.

  Note that, when the video signal is amplified using the gain amplifier 5, the noise component is also amplified unlike the case where the exposure time in the image sensor 3 is increased. If the gain of the gain amplifier 5 is increased too much, noise increases and the visibility of the image may be reduced.

  Therefore, in the adjustment of the amplification factor of the video signal, the exposure time in the image sensor 3 is controlled first, and only when the amplification factor needs to be further increased, the amplification factor of the gain amplifier is increased. preferable. That is, even if there are a plurality of settings for obtaining the luminance level of the same video signal, the gain of the gain amplifier 5 is as low as possible, and the longer the exposure time in the image sensor 3, the lower the noise and the higher the visibility. Can be obtained.

  For these reasons, usually, when the calculated luminance level is higher than the allowable range, the gain of the gain amplifier 102 is first lowered to approach the target value. However, if the luminance signal level is still higher than the allowable range, the exposure time in the image sensor 101 is shortened to approach the target value.

  On the other hand, when the luminance level is lower than the allowable range, the exposure time of the image sensor 101 is first lengthened to approach the target value. However, if the luminance level is still lower than the allowable range, control is performed to increase the gain of the gain amplifier 102. This is because, as described above, it is more likely that an image with less noise can be obtained if the gain of the gain amplifier 102 is kept small.

  Here, since the maximum value of the exposure time in the image sensor 101 depends on the frame rate, for example, in order to extend the exposure time beyond the time of one frame, it is necessary to lower the frame rate. For example, in the device described in Patent Document 1, the amount of light input to the solid-state image sensor is increased by reducing the frame rate of the solid-state image sensor from that during normal operation and taking the exposure time longer than the maximum time during normal operation. Is used. In such a case, for example, in the case of a solid-state imaging device using a global shutter that normally operates at 30 frames / second, the maximum exposure time is about 33 milliseconds, but is reduced to 15 frames / second at low illumination. The maximum exposure time is extended to about 66 milliseconds, and the amount of light obtained is doubled.

  However, it is preferable to reduce the frame rate to the minimum necessary since the number of frames per unit time of the video displayed on the monitor is reduced accordingly. In particular, when capturing a subject with rapid movement, attention must be paid because blurring may become noticeable.

  Further, Patent Document 2 proposes a method that can output AE (automatic exposure), AF (autofocus), and AWB (auto white balance) control when the frame rate is low, with a smooth moving image without a sense of incongruity. ing. In this case, for example, what is normally controlled once in 3 frames can be smoothly changed by 1/3 of the control amount for each frame at a low frame rate, and a moving image without a sense of incongruity can be obtained.

JP 2006-50350 A Japanese Patent Laid-Open No. 11-113008

  However, according to the method described above, since the frame rate becomes low at low illuminance such as at night, it takes time to control the brightness level, so that the user waits until the optimal image is obtained with the doorphone master unit. There's a problem. For example, when the frame rate changes from 30 frames / second to 1 frame / second, if the frame rate changes one frame at a time, it takes about 3 seconds.

  Also, when the exposure time and gain amplifier are automatically controlled when the frame rate reaches 1 frame / second, it takes 1 second for each frame even if frame control is performed. It may be considered that it takes at least 3 seconds, and in some cases, 10 seconds or more until an optimal video is displayed.

  As described above, in the brightness level adjustment process, repeating the process of adjusting the exposure time and gain amplifier when the frame rate is lowered may hinder the speed of the brightness level adjustment process. Therefore, in view of the above-described problems, the present invention adjusts the luminance level through adjustment of the exposure time in the image sensor and the gain in the gain amplifier, and the luminance level can be adjusted quickly by suppressing the change in the frame rate. An object of the present invention is to provide an imaging device and a door phone system that can be used.

  In order to achieve the above object, an imaging apparatus according to the present invention stores an electric charge corresponding to an exposure time for each frame, generates an image signal of a subject based on the electric charge, and amplifies the video signal. A gain amplifier to be output, and a process for adjusting the luminance level related to the video signal to be close to a predetermined target value by adjusting the exposure time and the amplification factor in the gain amplifier (referred to as “brightness level adjustment process”). A brightness level adjustment unit that performs the first step of temporarily setting the exposure time and the amplification factor over a plurality of predetermined points; and the point at which the temporary setting is performed A second process for detecting the magnitude of the amplified video signal, a third process for setting a frame rate based on the detection result, and the set frame rate. Under rate, the luminance level of the video signal is a so as to approach a predetermined target value, a configuration and a fourth process of adjusting the gain and the exposure time (first configuration).

  According to this configuration, the frame rate is set by performing the first process to the third process, and then the exposure time and the gain in the gain amplifier are adjusted under the set frame rate. It has become. Therefore, in the brightness level adjustment process, if the frame rate is lowered, it is possible to avoid repeating the process of adjusting the exposure time and gain amplifier, and the brightness level adjustment process can be speeded up. .

  In the first configuration, the detection result may be a configuration (second configuration) that is also used for adjusting the exposure time and the amplification factor in the fourth processing. According to this configuration, the results of the first process and the second process can be used also for the fourth process, so that it is possible to further improve the speed of the brightness level adjustment process.

  An image pickup apparatus according to the present invention stores an electric charge corresponding to an exposure time for each frame, generates an image signal of a subject based on the electric charge, a gain amplifier that amplifies and outputs the video signal, Brightness level adjustment for adjusting the brightness level of the video signal so as to approach a predetermined target value by adjusting the exposure time and the gain in the gain amplifier (referred to as “brightness level adjustment processing”) And a frame rate setting unit that performs a process for setting a frame rate in the luminance level adjustment process (referred to as “frame rate setting process”), the frame rate setting process including the exposure time and the amplification factor First processing for temporarily setting a plurality of predetermined points, and the amplified video signal for each of the temporarily set points. A second process of detecting the size, based on the detection result and a third process of setting the frame rate, the structure is a process comprising (a third configuration).

  According to this configuration, since the frame rate set by the frame rate setting unit is adopted in the luminance level adjustment processing, avoiding repeated processing such as adjusting the exposure time and gain amplifier when the frame rate is lowered. Thus, it is possible to speed up the brightness level adjustment process. The frame rate setting process can be executed independently of the brightness level adjustment process.

  Further, in any one of the first to third configurations, there is provided time measuring means for measuring time, and when the arrival of a predetermined time is detected through the time measuring means, the brightness level adjusting process or the frame rate is detected. It is good also as a structure (4th structure) by which a setting process is performed. According to this configuration, the brightness level adjustment process can be performed according to the time, so that the convenience of the apparatus can be improved.

  An image pickup apparatus according to the present invention stores an electric charge corresponding to an exposure time for each frame, generates an image signal of a subject based on the electric charge, a gain amplifier that amplifies and outputs the video signal, A brightness level adjustment unit that performs a process of adjusting a brightness level related to the video signal by adjusting the exposure time and an amplification factor in the gain amplifier (referred to as “brightness level adjustment process”); The level adjustment process includes a fifth process for temporarily setting the exposure time and the amplification factor to any one of a plurality of predetermined points, and the amplified video signal for the temporarily set points. A sixth process for detecting the size and determining whether or not the detection result is within a predetermined allowable range; and changing the contents of the temporary setting until the detection result is within the allowable range. A seventh process for repeating the fifth process and the sixth process, and an eighth process for setting the frame rate based on the contents of the temporary setting when the detection result falls within the allowable range; (9th process for adjusting the exposure time and the amplification factor so that the luminance level related to the video signal approaches a predetermined target value under the set frame rate) 5).

  According to this configuration, the frame rate is set, and then the exposure time and the gain in the gain amplifier are adjusted under the set frame rate. Therefore, in the brightness level adjustment process, if the frame rate is lowered, it is possible to avoid repeating the process of adjusting the exposure time and gain amplifier, and the brightness level adjustment process can be speeded up. .

  Furthermore, since it is not necessary to execute the fifth process and the sixth process after the detection result falls within the allowable range, the speed of the process can be further improved.

  Further, in the fifth configuration, a storage means for storing the temporary setting contents when the detection result falls within the allowable range in the luminance level adjustment processing is provided, and the fifth processing in the next luminance level adjustment processing is performed. As the contents of the temporary setting, what is stored in the storage means may be applied first (sixth structure).

  According to this configuration, when the brightness of the subject in the previous brightness level adjustment process does not change significantly from this time, the possibility that the detection result falls within the allowable range at an early stage increases. Therefore, it is possible to speed up the brightness level adjustment process.

The image pickup apparatus according to the present invention stores an electric charge corresponding to an exposure time for each frame, generates an image signal of a subject based on the electric charge, and adjusts at least the exposure time, whereby the video signal A luminance level adjustment unit that performs a process for adjusting the luminance level related to the predetermined target value (referred to as “brightness level adjustment process”) and a plurality of types of frame rates applied to the luminance level adjustment process ( A frame rate setting unit that performs processing (referred to as “frame rate setting processing”) set to any of F1, F2,... A ninth process for adjusting the video signal to the highest luminance level that can be realized when the frame rate is Fx (1 ≦ x ≦ n, initially x = 1), Until the luminance level of the performed video signals integer is the above target value, while increasing the x one by one, and the tenth process of repeating the ninth process,
A configuration (seventh configuration) is included that includes an eleventh process for setting the Fx when the luminance level is equal to or higher than the target value as a frame rate applied to the luminance level adjustment processing.

  According to this configuration, the frame rate is set, and the exposure time and the gain in the gain amplifier are adjusted under the set frame rate. Therefore, in the brightness level adjustment process, if the frame rate is lowered, it is possible to avoid repeating the process of adjusting the exposure time and gain amplifier, and the brightness level adjustment process can be speeded up. .

  In addition, the frame rate applied to the brightness level adjustment process can be set as large as possible while allowing the brightness level of the video signal to be adjusted appropriately.

  In addition, if the door phone system has a configuration (eighth configuration) including the imaging device according to any one of the first to seventh configurations, it is possible to realize a door phone system that can enjoy the advantages of the above configuration. is there.

  In the eighth configuration, a slave unit including the imaging device, and a master unit that starts video display based on a video signal transmitted from the imaging device when an instruction to start imaging is given by the user, The luminance level adjustment process may be configured to be executed prior to the start of the video display when the imaging start instruction is given (a ninth configuration).

  One of the slave units including the imaging device according to the fifth or sixth configuration and a master unit including a video display device that displays a video based on a video signal transmitted from the imaging device. The video based on the video signal generated by any of the fifth to eighth processes may have a configuration (tenth configuration) provided with a display preventing means for preventing the video from being displayed.

  More specifically, as the tenth configuration, the display preventing unit prevents the video signal generated by any of the fifth to eighth processes from being transmitted from the slave unit to the master unit. A configuration (an eleventh configuration) may be employed in which video based on the video signal is not displayed.

  According to this configuration, it is possible to avoid discomfort to the user by displaying a video signal that is not intended for display.

  As described above, according to the imaging apparatus and the door phone system of the present invention, the frame rate is set, and then the exposure time and the gain in the gain amplifier are adjusted under the set frame rate. ing. Therefore, in the brightness level adjustment process, if the frame rate is lowered, it is possible to avoid repeating the process of adjusting the exposure time and gain amplifier, and the brightness level adjustment process can be speeded up. .

  The embodiment of the present invention is composed of one slave unit with a camera (hereinafter simply referred to as “slave unit”), one master unit with a display function (hereinafter simply referred to as “master unit”), and the like. As an example, a TV door phone system (hereinafter simply referred to as a “door phone system”) that can adjust the brightness level in a short time while changing the frame rate of the solid-state imaging device to improve night vision performance. explain. FIG. 1 shows a configuration diagram of the door phone system according to the present embodiment. As shown in the figure, the door phone system is configured such that the slave unit 1 and the master unit 2 are connected by a signal line 16 serving as a signal transmission path between them.

  First, the slave unit will be described. The handset 1 is generally assumed to be installed outdoors. When a visitor presses an operation switch, the handset 1 is notified to a user in the room and the video and audio of the visitor are transmitted. It has a function of transmitting to the parent device 2 installed indoors and playing back sound from the parent device 2. As shown in FIG. 1, the slave unit 1 includes an image sensor 3, a TG 4, a gain amplifier 5, an A / D conversion circuit 6, a video signal processing circuit 7, a frame control circuit 8, a frame memory 9, a video encoder 10, and a multiplexing unit. A separation circuit 11, a sound control circuit 12, a speaker / microphone 13, an operation switch 14, and a slave device control microcomputer 15 are provided.

  The image sensor 3 captures a subject such as a visitor or an outdoor landscape, and transmits the information as a video signal to a subsequent circuit. More specifically, it is composed of, for example, a CCD or the like. Each pixel is exposed for each frame, and charges corresponding to the subject are stored and output as a video signal to the subsequent stage. Therefore, even if the subject has the same brightness, the video signal becomes larger (the luminance level is higher) when the exposure time is longer.

  The TG [Timing Generator] 4 generates signals related to various timings necessary for driving the image sensor 3 and outputs the signals to the image sensor 3.

  The gain amplifier 5 plays a role of amplifying the video signal transmitted from the image sensor 3 at an arbitrary magnification.

  The A / D conversion circuit 6 converts the video signal amplified by the gain amplifier 5 into a digital signal.

  The video signal processing circuit 7 performs various processes for improving the visibility in the video for the video signal converted into a digital signal by the A / D conversion circuit 6.

  The frame control circuit 8 is provided in the subsequent stage of the video signal processing circuit 7 and plays a role of sending a video signal having a constant frame rate to the subsequent video encoder 10 even when the frame rate becomes low.

  The frame memory 9 functions as a memory used by the frame control circuit 8 to send a video signal having a constant frame rate to the subsequent video encoder.

  The video encoder 10 converts the digital video signal output from the frame control circuit 8 into an analog video signal.

  The demultiplexing / demultiplexing circuit 11 multiplexes the analog video signal transmitted from the video encoder 10, the audio signal transmitted from the microphone of the slave unit 1, and the operation signal transmitted from the operation switch 14 to multiplex the master unit 2. It has a function to transmit to the side. It also has a function of separating power and audio signals transmitted from the master unit 2 side for operating the slave unit 1.

  The voice control circuit 12 has a function of amplifying the voice signal transmitted from the master unit 2 and separated by the demultiplexing / demultiplexing circuit 11 and sending the amplified signal to the speaker. Also, it has a function of sending an audio signal input from the microphone of the handset 1 to the multiplexing / demultiplexing circuit 11.

  The speaker / microphone 13 has a function of reproducing the voice signal sent from the voice control circuit 12 or converting the voice of the visitor into an electric signal and sending it to the voice control circuit 12.

  It is assumed that the operation switch 14 is mainly operated by a visitor. When this operation is performed, the slave unit control microcomputer 15 notifies the master unit 2 installed in the room that there was a visitor.

  The slave control microcomputer 15 controls the TG 4, the gain amplifier 5, the video signal processing circuit 7, the frame control circuit 8, the video encoder 10, and the like using various setting values recorded in advance, and the video of the subject. Is controlled so as to be in an optimum state, and other control of the slave unit 1 in general is performed. In addition, the subunit | mobile_unit control microcomputer 15 has also recorded beforehand the various table values used for exposure control of the image pick-up element 3. FIG.

  Next, the master unit 2 will be described. The base unit 2 is generally assumed to be installed indoors. When there is a visitor, the base unit 2 displays an image transmitted from the slave unit 1 or makes a call with the visitor via the slave unit 1. It has a function to do. The master unit 2 includes a demultiplexing / separating circuit 17, an audio control circuit 18, a speaker / microphone 19, a video decoder 20, an LCD controller 21, an LCD panel 22, an operation switch 23, a master control microcomputer 24, and the like. .

  The demultiplexing / demultiplexing circuit 17 receives and demultiplexes the multiplexed video signal, audio signal, and operation signal from the operation switch 14 transmitted from the slave unit 1, and the audio control circuit 18, video decoder of the main unit 2. A function of transmitting to the slave unit 1 by multiplexing the audio signal input from the microphone of the master unit 2 and the power for operating the slave unit 1 to the circuit 20 and the master unit control microcomputer 24 ing.

  The audio control circuit 18 amplifies the audio signal sent from the demultiplexing / demultiplexing circuit 17 and sends it to the speaker of the parent device 2 or the audio signal input from the microphone of the parent device 2 to the demultiplexing / separating circuit 17. It has a function to send.

  The speaker / microphone 19 reproduces the audio signal sent from the audio control circuit 18 or converts the user's voice into an electric signal and sends it to the audio control circuit 18.

  The video decoder 20 converts the analog video signal transmitted from the slave unit 1 separated by the multiplexing / separating circuit 17 into a digital video signal.

  An LCD [Liquid Crystal Display] controller 21 converts a digital video signal input from the video decoder 20 into a signal format that can be displayed on the LCD panel 22, and creates a timing signal necessary for operating the LCD panel 22. Or do.

  The LCD panel 22 displays an image captured by the slave unit 1 based on the control of the LCD controller 21.

  As the operation switch 23, for example, a button switch or a remote controller is employed, and it is assumed that the operation switch 23 is mainly operated by a user. Thereby, it is possible to cause the base unit 2 to perform processing reflecting the user's intention.

  The base unit control microcomputer 24 generally controls each process performed in the base unit 2 such as control of the LCD controller 21, the video decoder 20, and the demultiplexing / separating circuit 17.

  Next, the operation content of the door phone system according to the present embodiment will be described.

  During normal standby (when there are no visitors), the slave unit 1 and the master unit 2 are in a so-called standby mode. At this time, the master unit 2 supplies the slave unit 1 with a minimum amount of power that allows the slave unit 1 to operate in the standby mode.

  When there is a visitor and the visitor operates the operation switch 14 of the slave unit 1, the slave unit control microcomputer 15 returns from the standby mode, and the operation switch 14 is switched via the demultiplexing circuit 11 and the signal line 16. An operation signal is transmitted to the main unit 2. The transmitted operation signal is separated by the demultiplexing / separating circuit 17 of the parent device 2 and sent to the parent device control microcomputer 24.

  As a result, the base unit control microcomputer 24, which has recognized that there was a visitor, increases the amount of power supplied to the slave unit 1 from the demultiplexing / separating circuit 17 to such an extent that it can be imaged, and calls through the speaker / microphone 19. Make a sound and tell the users in the room that there was a visitor. And in the subunit | mobile_unit 1 which received electric power sufficient to image, the subunit | mobile_unit control microcomputer 15 drives the image pick-up element 3 by controlling TG4, and images the visitor who is a to-be-photographed object.

  Information on the subject imaged by the imaging device 3 is converted into a video signal, and then input to the gain amplifier 5, where the video signal is amplified according to the brightness of the subject. The video signal amplified by the gain amplifier 5 is sent to the A / D conversion circuit 6 and converted into a digital video signal. The digital video signal converted by the A / D conversion circuit 6 is input to the video signal processing circuit 7.

  The video signal processing circuit 7 performs various automatic operations such as automatic white balance control, automatic black level control, and automatic exposure control together with the slave unit control microcomputer 15 in addition to processing such as gamma correction and edge correction in order to improve the visibility of the video. Take control. The video signal whose visibility is enhanced by the video signal processing circuit 7 is input to the frame control circuit 7.

  The frame control circuit 7 adjusts the number of frames input from the video signal circuit 7 and the number of frames required by the video encoder 10. For example, in the video encoder 10, when it is necessary to constantly input a video signal having a frame rate of 30 frames / second, when the number of input frames from the video signal processing circuit 7 is only 15 frames / second, the video signal processing circuit 7 The video signal from is temporarily recorded in the frame memory 9.

  On the other hand, the video signal output to the video encoder 10 is asynchronous with the video signal input from the video signal processing circuit 7, and always reads out a video signal having a frame rate of 30 frames / second from the frame memory 9 and sends it to the video encoder 10. Is output. In such a configuration, depending on the number of frames of the video signal input from the video signal processing circuit 7, the video signal output to the video encoder 10 may have a plurality of frames of the same video signal. Even if the number of imaging frames from 3 changes, it is possible to output a video signal having a prescribed number of frames to the video encoder 10 at all times.

  The video signal input to the video encoder 10 is converted into an analog video signal and input to the demultiplexing / demultiplexing circuit 11. The voice signal of the visitor input from the microphone / speaker 13 of the slave unit 1 is input to the demultiplexing / demultiplexing circuit 11 via the voice control circuit 12. The video signal and the audio signal input to the demultiplexing / demultiplexing circuit 11 are multiplexed and transmitted to the parent device 2 through the signal line 16.

  The multiplexed signal is separated into a video signal and an audio signal by the multiplexing / separating circuit 17 of the base unit 2. The video signal is input to the video decoder 20 and converted into a digital video signal, while the audio signal is input to the audio control circuit 18.

  The digital video signal converted by the video decoder 20 is input to the LCD controller 21 and converted into a signal format that can be displayed on the LCD panel 22. The converted signal is input to the LCD panel 22, and an image captured on the handset 1 side is displayed on the LCD panel 22. The audio signal input to the audio control circuit 18 is amplified and then input to the speaker / microphone 19 to be reproduced as audio.

  The user's voice is converted into a voice signal by the speaker / microphone 19 on the base unit 2 side, and is input to the multiplexing / demultiplexing circuit 17 via the voice control circuit 18 and multiplexed. The multiplexed signal is transmitted to the slave unit 1 through the signal line 16. Then, it is separated by the multiplexing / demultiplexing circuit 11 of the handset 1 and inputted to the voice control circuit 12. The sound signal input to the sound control circuit 12 is amplified and then input to the speaker / microphone 13 to reproduce the sound of the user in the room. By repeating the above operations, the indoor user can make a call while confirming the video of the outdoor visitor.

  By the way, in the subunit | mobile_unit 1, even if a to-be-photographed object is too bright or too dark, the brightness | luminance level adjustment process is made so that the image | video of an appropriate luminance level may be displayed on the LCD panel 22 by the side of the main | base station 2. It has become. This brightness level adjustment processing is realized through adjustment of the exposure time in the image sensor 3 and the gain in the gain amplifier 5. In order to extend the upper limit of the exposure time, the frame rate can be adjusted as appropriate.

  Hereinafter, the content of the brightness level adjustment process in the door phone system according to the present embodiment will be described in more detail.

  First, in the door phone system, assuming that the normal frame rate is f, the door phone system is variable in four stages of f, f / 2, f / 3, and f / 4. The smaller the frame rate, the longer the exposure time in each frame can be set. The maximum value (AGCMAX) of the gain obtained by the gain amplifier 5 is twice the gain (SHTMMAX_F1) obtained by controlling the exposure time at the frame rate f.

  However, the maximum amplification factor in the control of the gain amplifier 5 when the frame rates are f, f / 2, and f / 3 is 1/2 of AGCMAX. This is because if the gain by the gain amplifier 5 is further increased, the influence of noise may become a problem. However, when the frame rate is f / 4, the maximum gain on control of the gain amplifier 5 is also AGCMAX. In this case, it is not possible to extend the exposure time by further reducing the frame rate, and as a result, priority can be given to the amplification factor even if there is some influence of noise.

  In the brightness level adjustment processing in the door phone system according to the present embodiment, when the frame rate is f, which is the maximum setting of the system, the gain due to the exposure time of the image sensor 3 with respect to the subject illuminance and the gain change due to the gain amplifier 5 The situation is shown on the left side of FIG. Here, the solid line indicates amplification by the image sensor 3 (exposure time), and the broken line indicates amplification by the gain amplifier 5. Further, a change state of the combined amplification factor obtained by combining these amplification factors is indicated by a solid line on the right side of FIG. Each figure is in dB notation (logarithmic graph notation), and the dotted line shows a case where amplification by the gain amplifier 5 is possible up to AGCMAX for reference.

  Here, “SHTMAX_F1” is the maximum gain obtained by controlling the exposure time of the image sensor 3 when the frame rate is f, and “AGCMAX” is the maximum gain obtained by the gain amplifier 5. Note that enlarging the video signal by extending the exposure time can be considered in the same way as amplifying the video signal obtained by the exposure time before extending, so it is included in the “amplification” here. To do.

  “ILM1_F1” is a lower limit value of illuminance at which the luminance level can be appropriately adjusted by controlling the exposure time of the image sensor 3, and is an upper limit value of illuminance at which amplification by the gain amplifier 5 is started. “ILM2_F1” is a lower limit value of illuminance in which the luminance level can be appropriately adjusted by controlling the gain of the gain amplifier 5 when the maximum control range of the gain of the gain amplifier 5 is set to 1/2 of AGCMAX. . “ILM3_F1” is a lower limit value of illuminance in which the luminance level can be appropriately adjusted by controlling the gain of the gain amplifier when the gain of the gain amplifier 5 is AGCMAX.

  When the subject illuminance is between ∞ and ILM1_F1, the luminance signal level is adjusted by controlling the exposure time of the image sensor 3, and when the subject illuminance is between ILM1_F1 and ILM2_F1, the gain of the gain amplifier 5 is adjusted to adjust the luminance level. Make adjustments.

  Since the control based on the exposure time of the image sensor 3 and the control of the gain of the gain amplifier 5 operate in conjunction with each other, the maximum value of the gain that can be added as a system at the frame rate f is the exposure time of the image sensor 3. The gain is obtained by adding 1/2 of AGCMAX by the control of SHTMAX_F1 by the control and the gain control of the gain amplifier 5 (hereinafter referred to as “M1” as appropriate), and the luminance level of the subject is appropriately set between ∞ and ILM2_F1. It is possible to adjust. Note that when the illuminance of the subject is lower than ILM2_F1, a higher amplification factor cannot be applied at the frame rate f, and the luminance level cannot be adjusted appropriately.

  Similarly to FIG. 2, FIG. 3 shows changes in the amplification factor by the exposure time of the image sensor 3 with respect to the subject illuminance, the amplification factor by the gain amplifier 5, and the composite amplification factor when the frame rate is f / 2. FIG. 4 shows the case where the rate is f / 3, and FIG. 5 shows the case where the frame rate is f / 4. Further, FIG. 6 shows a change state of the combined amplification factor when the frame rate is f and when it is f / 4.

  As described above, when the frame rate is f / 2, it is possible to adjust the luminance level by changing the combined amplification factor with SHTMAX_F2 + AGCMAX / 2 (= M2) as the upper limit between the subject illuminance between ∞ and ILM2_F2. . Similarly, when the frame rate is f / 3, it is possible to adjust the luminance level by changing the combined amplification factor with SHTMAX_F3 + AGCMAX / 2 (= M3) as the upper limit when the subject illuminance is between ∞ and ILM2_F3. Similarly, when the frame rate is f / 4, it is possible to adjust the luminance level by changing the combined amplification factor with SHTMAX_F4 + AGCMAX as the upper limit when the subject illuminance is between ∞ and ILM3_F4.

  As shown in each figure, by lowering the frame rate, the AGCMAX that is the maximum value of the gain of the gain amplifier 5 does not change, but the SHTMAX value that is the gain obtained by controlling the exposure time of the image sensor 3 increases. . Specifically, as can be seen in FIG. 6, when the frame rate is f / 4, the SHTMAX value is almost four times that of the case where the frame rate is f, and the adjustment range of the composite amplification factor is greatly expanded. ing. Accordingly, the illuminance range in which an appropriate luminance level can be adjusted is extended from ∞ to ILM2_F1 to ∞ to ILM3_F4. Therefore, it is possible to obtain an image with an appropriate luminance level even when the subject has lower illuminance.

  However, as described above, reducing the frame rate reduces the number of frames per unit time. Therefore, in order to maintain the smoothness of the moving image, it is desirable to reduce the frame rate to the minimum necessary. Under such circumstances, the general luminance level adjustment processing is generally executed generally along the flow shown below.

  First, after setting the frame rate to f, which is the maximum value, the exposure time of the image sensor is set so that the luminance level of the video signal approaches a predetermined target value (for example, an allowable error range centered on the target value). Control to fit within. However, if an appropriate luminance level of the video signal cannot be obtained only by controlling the exposure time, the gain of the gain amplifier is also controlled.

  In these controls, the processing is completed when an appropriate luminance level of the video signal is obtained, but when the appropriate luminance level of the video signal is not yet obtained because the subject is too dark, the frame rate is set to f. To f / 2 (that is, the exposure time adjustable range is widened), and the exposure time of the image sensor and the gain of the gain amplifier are controlled again to obtain an appropriate luminance level of the video signal. Try to control as you can.

  If an appropriate luminance level of the video signal cannot be obtained even with this control, the exposure time of the image sensor and the gain amplifier gain are controlled while further changing the frame rate in order of f / 3 and f / 4. Attempt to obtain an appropriate video signal level.

  However, in such a flow process (automatic exposure process), when an extremely low illuminance object is imaged, the process of adjusting the exposure time and gain amplifier is repeated if the frame rate is lowered. It takes time to obtain the optimal video brightness level. In particular, a system using an extremely low frame rate is a serious problem because it takes a long time to obtain an image of one frame.

  Therefore, in the brightness level adjustment process in the door phone system of the present embodiment, the frame rate is determined in advance prior to the automatic exposure process. More specifically, it is executed along the flow shown in the flowchart of FIG.

  When the timing at which the brightness level adjustment processing is to be executed has arrived, first, the frame rate of the image sensor 3, the exposure time, and the gain of the gain amplifier 5 in the slave unit 1 are measured at a measurement point (measurement condition) 1 shown in FIG. Temporarily set. Then, in this temporarily set state, the luminance level of the video signal (the one generated by the image pickup device 3 on a trial basis) is measured (step S11).

  Note that the amplification factor of the video signal at the measurement point 1 shown in FIG. 8 is the upper limit (M1) of the amplification factor that can be adjusted by the exposure time and the amplification factor of the gain amplifier when the frame rate is f as shown in FIG. It is almost equivalent. Therefore, if the luminance level measured at the measurement point 1 is equal to or higher than the target value, the luminance level is brought close to the target value by adjusting the exposure time and the gain of the gain amplifier 5 while keeping the frame rate at f. Is possible. Similarly, the amplification factor of the video signal at the measurement point 2 is almost equal to the upper limit (M2) of the amplification factor that can be adjusted by the exposure time and the amplification factor of the gain amplifier when the frame rate is f / 2. The amplification factor of the video signal at the measurement point 3 is substantially equal to the upper limit (M3) of the amplification factor that can be adjusted by the exposure time and the amplification factor of the gain amplifier when the frame rate is f / 3.

  As a result of the measurement in step S11, if the measured luminance level is equal to or higher than a predetermined target value (within a predetermined allowable range) (Y in step S12), the luminance level can be appropriately adjusted even if the frame rate remains f. It is expected. Therefore, the frame rate is set to f (step S13).

  However, if the measured luminance level is lower than the predetermined target value (N in step S12), the exposure time sufficient to appropriately adjust the luminance level cannot be secured if the frame rate remains f, and the frame Expected to lower the rate. Therefore, next, the content of the temporary setting is changed to the measurement point 2 and the luminance level of the video signal is measured again (step S14).

  As a result, if the measured luminance level is equal to or greater than a predetermined target value (within a predetermined allowable range) (Y in step S15), the luminance level can be appropriately adjusted by setting the frame rate to f / 2. Expected. Therefore, the frame rate is set to f / 2 (step S16).

  However, if the measured luminance level is lower than the predetermined target value (N in step S15), even if the frame rate is set to f / 2, it is not possible to secure an exposure time that can appropriately adjust the luminance level. It is expected that the frame rate will need to be further reduced. Therefore, next, the content of the temporary setting is changed to the measurement point 3, and the luminance level of the video signal is measured again (step S17).

  As a result, if the measured luminance level is equal to or greater than a predetermined target value (within a predetermined allowable range) (Y in step S18), the luminance level can be adjusted appropriately by setting the frame rate to f / 3. Expected. Therefore, the frame rate is set to f / 3 (step S19).

  However, if the measured luminance level is lower than the predetermined target value (N in step S18), it is not possible to secure an exposure time enough to adjust the luminance level appropriately even if the frame rate is set to f / 3. It is expected that the frame rate will need to be further reduced. Therefore, the frame rate is set to f / 4, which is the lower limit of the settable frame rate (step S20).

  When the frame rate is set as described above, adjustment of the exposure time and the amplification factor in the gain amplifier 5, that is, the above-described automatic exposure processing is started so that the luminance level is appropriate under the set frame rate. . As described above, in the brightness level adjustment processing in the present embodiment, the frame rate is set appropriately in advance (when the brightness level of the video signal is adjusted to be the highest at the set frame rate, Since it has been confirmed that it is at least the target value), it is not necessary to repeat the process of adjusting the exposure time and gain amplifier when the frame rate is lowered.

  Therefore, the brightness level adjustment process can be performed quickly. As described above, the process (steps S11 to S20) for setting the frame rate prior to the brightness level adjustment process is referred to as “frame rate setting process”. Further, in the frame rate setting process, the appropriateness is determined in order from the measurement point 1, so that the frame rate is not set unnecessarily small.

  In the frame rate setting process described above, the measurement result of the luminance level at each measurement point is used only for determining the frame rate. However, by increasing the number of measurement points, the exposure time in the image sensor 3 and the gain amplifier 5 are increased. It is also possible to predict an appropriate value of the amplification factor at or close to the appropriate value and further reduce the time required for the automatic exposure processing.

  In order to do this, in the frame rate setting process, for example, the luminance level may be measured in order at each measurement point having the contents shown in FIG. Note that the measurement points 4, 6, and 8 in FIG. 10 correspond to the measurement points 1, 2, and 3 in FIG. 8, respectively.

  As a result, if the measured luminance level is equal to or higher than the target value at any of the measurement points 1 to 4, the frame rate is set to f as shown in FIG. If the measured luminance level is equal to or higher than the target value at the measurement point 5 or 6, the frame rate is set to f / 2. If the measured luminance level is equal to or higher than the target value at the measurement point 7 or 8, the frame rate is set to f / 3. If the measured luminance level at the measurement point 8 is below the target value, the frame rate is set to f / 4.

  On the other hand, depending on the measurement point at which the measured luminance level is equal to or higher than the target value, it is predicted that it is appropriate or close to the appropriate value. ) Is determined as shown in FIG. For example, if the luminance level measured at the measurement point 3 is equal to or higher than the target value, the frame rate is set to f, and the appropriate prediction value of the amplification factor by the exposure time is SHTMAX_F1, and the appropriate amplification factor by the gain amplifier The predicted value is determined to be 0. Therefore, in the subsequent automatic exposure process, first, the gain according to the exposure time is set to be SHTMAX_F1, and the gain by the gain amplifier is set to be 0.

  In this way, not only setting the frame rate in advance, but also determining an appropriate predicted value can reduce the processing burden in the subsequent automatic exposure processing, and can speed up the processing. It becomes. Although the number of measurement points is eight here, it is possible to improve the accuracy of the appropriate predicted value by further increasing the number of measurement points.

  Also, when measuring the brightness level at each measurement point in the frame setting process, the result of the previous brightness level adjustment process (which measurement point the brightness level measured at or above the target value) is stored. The stored information can be used to reduce the number of measurements. For example, when the luminance level measured at the measurement point 5 shown in FIG. 10 is equal to or higher than the target value in the previous luminance level adjustment processing, this “measurement point 5” is stored, and this time, the measurement point 5 If the measurement is started from the beginning, there is a high possibility that the number of measurements can be reduced, particularly when the brightness of the subject has not changed significantly from the previous measurement.

  Various patterns can be used as the timing for starting the brightness level adjustment processing (frame setting processing and automatic exposure processing). For example, the child device 1 is activated and immediately before the image captured by the image sensor 3 is transmitted to the display-equipped parent device 2, that is, when the visitor operates the operation switch 14 of the child device 1, or the user of the door phone system However, it is possible to activate the camera-equipped child device 1 by operating the operation switch 23 of the parent device 2 (when the user gives an instruction to start imaging). Further, by using a timer function (time measuring means) in the slave unit control microcomputer 15, the slave unit 1 is activated at regular intervals (for example, every time a predetermined time arrives), and the brightness level adjustment process is started. Good.

  Furthermore, for example, as described above, only the frame setting process may be performed at regular intervals using the timer function (not executed until the automatic exposure process). In this way, when the handset 1 is activated due to an actual visitor or the like, automatic exposure processing is performed at a frame rate determined to be appropriate in advance until an appropriate luminance level is obtained. It is possible to shorten the time. In addition, since only the frame setting process is performed at regular time intervals, the processing burden can be reduced as much as possible.

  Further, it is known that the subject is dark and the exposure time of the image pickup device 3 needs to be increased by reducing the frame rate in the time zone from the evening to the night when the surroundings are dark. Therefore, the appropriate frame rate is determined from the evening to the morning (for example, from 17:00 to 7:00), and the subject brightness is not temporarily measured in other time zones. By setting the rate to f (fastest state), it is necessary to reduce the power consumption by omitting the process of determining an appropriate frame rate during daytime when the subject is bright, while reducing the frame rate because the subject is dark. At night, by determining an appropriate frame rate, it is possible to shorten the time until an appropriate luminance level is obtained.

  Further, in the door phone system in the present embodiment, the video signal is not transmitted to the main unit 2 while the luminance level is measured at each measurement point, and when the automatic exposure control is started. The video signal is transmitted to the main unit 2 for the first time. For this reason, since the base unit 2 does not display video based on video signals generated at each measurement point, it is possible to prevent the user of the door phone system from feeling uncomfortable.

  As mentioned above, although the Example of this invention was described, this invention is not limited to this content, As long as it does not deviate from the main point of this invention, it can be implemented with various modifications.

  The present invention can be used in fields such as door phone systems.

It is a block diagram of the television door phone system which concerns on the Example of this invention. It is a graph which shows the change situation of various amplification factors and synthetic amplification factor in luminance level adjustment processing in case a frame rate is f. It is a graph which shows the change situation of various amplification factors and synthetic amplification factor in luminance level adjustment processing in case a frame rate is f / 2. It is a graph which shows the change condition of various gains and synthetic | combination gain in the luminance level adjustment process in case a frame rate is f / 3. It is a graph which shows the change condition of various gains and synthetic | combination gain in the luminance level adjustment process in case a frame rate is f / 4. It is a graph which shows the change condition of a synthetic | combination amplification factor in the luminance level adjustment process in case a frame rate is f and f / 4. It is a flowchart of the brightness level adjustment process which concerns on the Example of this invention. It is a table | surface which shows the content of the measurement point in a brightness adjustment process. It is explanatory drawing for demonstrating the content of a measurement point. It is a table | surface which shows the content of another measurement point in a brightness | luminance adjustment process. It is a table | surface regarding the measurement result by the measurement point in FIG. It is a block diagram concerning an example of the conventional imaging device.

Explanation of symbols

1 Slave Unit with Camera 2 Master Unit with Display Function 3 Image Sensor 4 TG
DESCRIPTION OF SYMBOLS 5 Gain amplifier 6 A / D conversion circuit 7 Video signal processing circuit 8 Child machine control microcomputer 9 Frame memory 10 Video encoder 11 Demultiplexing circuit 12 Audio control circuit 13 Speaker, microphone 14 Operation switch 15 Child machine control microcomputer 16 Signal line 17 Demultiplexing circuit 18 Audio control circuit 19 Speaker, microphone 20 Video decoder 21 LCD controller 22 LCD panel 23 Operation switch 24 Master control microcomputer

Claims (11)

An image sensor that stores an electric charge according to an exposure time for each frame and generates a video signal of a subject based on the electric charge;
A gain amplifier that amplifies and outputs the video signal;
Brightness level adjustment for adjusting the brightness level of the video signal so as to approach a predetermined target value by adjusting the exposure time and the gain in the gain amplifier (referred to as “brightness level adjustment processing”) And comprising
The brightness level adjustment process includes:
A first process for temporarily setting the exposure time and the amplification factor over a plurality of predetermined points;
A second process for detecting the magnitude of the amplified video signal for each of the temporarily set points;
A third process for setting a frame rate based on the detection result;
A fourth process for adjusting the exposure time and the amplification factor so that the luminance level of the video signal approaches a predetermined target value under the set frame rate;
An imaging apparatus comprising: The result of the detection is
The imaging apparatus according to claim 1, wherein the imaging apparatus is also used for adjusting the exposure time and the amplification factor in the fourth process. An image sensor that stores an electric charge according to an exposure time for each frame and generates a video signal of a subject based on the electric charge;
A gain amplifier that amplifies and outputs the video signal;
Brightness level adjustment for adjusting the brightness level of the video signal so as to approach a predetermined target value by adjusting the exposure time and the gain in the gain amplifier (referred to as “brightness level adjustment processing”) And
A frame rate setting unit that performs a process of setting a frame rate in the brightness level adjustment process (referred to as “frame rate setting process”),
The frame rate setting process
A first process for temporarily setting the exposure time and the amplification factor over a plurality of predetermined points;
A second process for detecting the magnitude of the amplified video signal for each of the temporarily set points;
A third process for setting a frame rate based on the detection result;
An image pickup apparatus characterized in that the process includes: Has a timekeeping means to keep time
The imaging apparatus according to any one of claims 1 to 3, wherein the brightness level adjustment process or the frame rate setting process is executed when arrival of a predetermined time is detected through the time measuring means. . An image sensor that stores an electric charge according to an exposure time for each frame and generates a video signal of a subject based on the electric charge;
A gain amplifier that amplifies and outputs the video signal;
A brightness level adjusting unit that performs a process of adjusting a brightness level related to the video signal (referred to as “brightness level adjustment process”) by adjusting the exposure time and an amplification factor in the gain amplifier;
The brightness level adjustment process includes:
A fifth process of temporarily setting the exposure time and the amplification factor to any one of a plurality of predetermined points;
A sixth process for detecting the magnitude of the amplified video signal for the temporarily set point and determining whether the detection result is within a predetermined allowable range;
A seventh process for repeating the fifth process and the sixth process while changing the contents of the temporary setting until the detection result falls within the allowable range;
An eighth process of setting the frame rate based on the contents of the temporary setting when the detection result falls within the allowable range;
A ninth process for adjusting the exposure time and the amplification factor so that the luminance level of the video signal approaches a predetermined target value under the set frame rate;
An image pickup apparatus characterized in that the process includes: In the brightness level adjustment process, a storage means for storing the contents of the temporary setting when the detection result is within the allowable range,
6. The image pickup apparatus according to claim 5, wherein the temporary setting contents in the fifth process in the next brightness level adjustment process are first applied to those stored in the storage unit. An image sensor that stores an electric charge according to an exposure time for each frame and generates a video signal of a subject based on the electric charge;
A brightness level adjustment unit that performs a process of adjusting the brightness level of the video signal so as to approach a predetermined target value by adjusting at least the exposure time (referred to as “brightness level adjustment process”);
A process for setting the frame rate applied to the brightness level adjustment process to any one of a plurality of types (from the largest to F1, F2,... Fn) (referred to as “frame rate setting process”). A frame rate setting unit for performing
The frame rate setting process
A ninth process for adjusting the video signal to the highest luminance level that can be realized when the frame rate is Fx (1 ≦ x ≦ n, initially x = 1);
A tenth process that repeats the ninth process while increasing the x one by one until the brightness level is equal to or higher than the target value;
An eleventh process for setting the Fx when the luminance level is equal to or higher than the target value as a frame rate applied to the luminance level adjustment process;
An imaging apparatus comprising:   A door phone system comprising the imaging device according to any one of claims 1 to 7. A handset provided with the imaging device;
A master unit that starts video display based on a video signal transmitted from the imaging device when an instruction to start imaging is given by the user;
The brightness level adjustment process includes:
9. The door phone system according to claim 8, wherein the door phone system is executed prior to the start of the video display when an instruction to start the imaging is given. A handset provided with the imaging device according to claim 3 or 7,
A master unit having a video display device for displaying video based on a video signal transmitted from the imaging device,
An intercom system comprising: a display preventing means for preventing video based on a video signal generated by the frame rate setting process from being displayed. The display preventing means includes
The video signal generated by the frame rate setting process is prevented from being transmitted from the slave unit to the master unit, so that a video based on the video signal is not displayed. Door phone system.

Images