JP2008211529A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus for photographing an abnormal state with high image quality and has improved durability. <P>SOLUTION: The imaging device which has a detecting means for detecting a state of a monitoring target, is used in a monitoring system for monitoring the monitoring target and images the monitoring target, wherein the imaging apparatus includes: a means for selecting one of either a normal monitoring mode or an abnormal monitoring mode of a photographing mode on the basis of detection results by the detecting means; and an automatic exposure control means for maintaining a luminance level of an output signal of an imaging device at a constant value. The automatic exposure control means makes different an operation parameter that should be variable with respect to a range with the same brightness of the monitoring target in accordance with the normal monitoring mode or the abnormal monitoring mode. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention generally relates to an imaging apparatus, and more particularly to an imaging apparatus having an automatic exposure control function, and is suitable for, for example, a digital video camera for monitoring.

  In recent years, it has been proposed to use a digital video camera having an automatic exposure (AE) control function as a surveillance camera. In AE control, the brightness of an image can be adjusted to an appropriate value by changing operation parameters such as an electronic shutter speed, an aperture value, and a gain value in accordance with a change in the brightness of the subject.

On the other hand, it is common for surveillance cameras to always shoot without providing time to stop shooting. For this reason, having high durability is desired. In the operating parameters of AE control, unlike the electronic shutter speed and gain value, the diaphragm may cause mechanical problems such as fatigue and wear due to long-time driving. Therefore, Patent Document 1 proposes a control method in which the aperture value is always fixed in order to extend the aperture life.
Japanese Patent Laid-Open No. 08-136968 (page 22, FIG. 11)

  However, fixing the aperture value means that AE control is performed only with the remaining electronic shutter speed and gain value. Here, as the aperture diameter of the stop is smaller, the depth of field can be deepened. Therefore, in order to ensure an appropriate depth of field for the entire monitored area, it is necessary to reduce the aperture diameter of the diaphragm to some extent.

  If the monitoring target is dark, it is necessary to correspond to at least one of the process of slowing down the electronic shutter speed to increase the exposure time and the process of increasing the gain value. However, if the exposure time is longer than one field, the movement of the moving object in the object field becomes awkward, and if the gain value is increased too much, noise in the image becomes conspicuous.

  In the monitoring system, for example, in order to identify an intruder from a photographed image or to determine a situation that causes a fire, it is required to photograph a monitoring target with as high image quality as possible. For this reason, if the control for always fixing the aperture value as in Patent Document 1 is performed, there is a possibility that the image quality in the abnormal state is deteriorated and the request cannot be satisfied.

  The present invention relates to an imaging apparatus that captures an abnormal state with high image quality and has improved durability.

  An imaging apparatus according to an aspect of the present invention is an imaging apparatus that includes a detection unit that detects a state of a monitoring target, is used in a monitoring system that monitors the monitoring target, and images the monitoring target, the detection Based on the detection result by the means, means for selecting and setting the photographing mode from the normal monitoring mode and the abnormality monitoring mode, the aperture value, and the value of the operation parameter including at least one of the shutter speed and the gain value By changing, it has automatic exposure control means for keeping the luminance level of the output signal of the image sensor at a constant value, and the automatic exposure control means is in the normal monitoring mode for the same brightness range of the monitoring target. The operation parameter that is variable according to the abnormality monitoring mode is made different.

  An imaging apparatus control program according to another aspect of the present invention includes a detection unit that detects a state of a monitoring target, is used in a monitoring system that monitors the monitoring target, and images the imaging target. A control program for controlling an apparatus, the step of selecting and setting a photographing mode from a normal monitoring mode and an abnormality monitoring mode based on a detection result by the detection means, an aperture value, and at least a shutter By changing the value of the operation parameter including either the speed or the gain value, the luminance level of the output signal of the image sensor is maintained at a constant value, and the normal monitoring mode is used for the same brightness range of the monitoring target. Or an automatic exposure control step for making the operation parameter variable according to the abnormality monitoring mode. That.

  Further objects and other features of the present invention will become apparent from the preferred embodiments described below with reference to the accompanying drawings.

  ADVANTAGE OF THE INVENTION According to this invention, the imaging device which image | photographed the abnormal condition with high image quality and improved durability can be provided.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a block diagram of a monitoring system 100 according to the first embodiment. The monitoring system 100 includes a camera body 7, a control unit 10, a hard disk drive (HDD: Hard Disc Drive) 12, and a monitor display 13. The monitoring system 100 further includes a smoke sensor 1, an infrared sensor 2, and a microphone 3. The control unit 10 may be integrated with the camera body 7 or may be disposed at a different location as a separate body from the camera body 7.

  The camera body 7 is a digital video camera that can capture moving images and still images. The camera body 7 is mounted on the electric camera platform 6 and changes the imaging range in the up and down (hereinafter referred to as “tilt”) and left and right (hereinafter referred to as “pan”) directions via the control unit 10. Can do. Further, as will be described later, the camera body 7 includes a vibration detection circuit that detects that the camera body 7 is vibrating and a moving body detection circuit that detects the presence of a moving body in the object scene. . These circuits may be separate from the camera body 7.

  The imaging signal 8 acquired by the camera body 7 is output to the control unit 10 and distributed to the HDD recording device 12 and the monitor display 13. The camera body 7 transmits a mode identification signal 11 to the HDD recording device 12. The mode identification signal 11 is a signal that becomes active only in the abnormality monitoring mode.

  The HDD recording device 12 records an image generated from the received imaging signal 8 via the control unit 10. The monitor display 13 displays an image generated from the imaging signal 8 so that a monitor (user) can visually recognize the image. FIG. 2 is a schematic block diagram showing an example of the configuration of the HDD recording device 12. The HDD recording device 12 includes an encoder 1503 and a recording unit 1515 as shown in FIG.

  In this embodiment, the encoder 1503 compresses the imaging signal 8 by a compression method generally called MPEG (Moving Picture Experts Group). As such a compression method, MPEG1, MPEG2 and MPEG4 having different compression performances can be applied. The encoder 1503 includes a motion compensation inter-frame prediction unit 1504 and a discrete cosine transform unit (DCT: Discrete Cosine Transform) 1505. The encoder 1503 further includes a quantization unit 1506 and a variable length coding unit (VLC: Variable Length Coding) 1507.

  The motion-compensated inter-frame prediction unit 1504 compresses the image pickup signal 8 by repeatedly using the same data in an area where there is little movement or change in the object scene, or by thinning out an image in an image with a lot of movement or change. The DCT 1505 converts the amplitude signal output from the motion compensation inter-frame prediction unit 1504 into a frequency signal. The quantization unit 1506 compresses the signal by performing processing such as omitting inconspicuous and detailed signals on the output signal of the DCT 1505 for each frequency band. The VLC 1507 reduces the redundancy of the output signal of the quantization unit 1506 as digital data. For example, in the case of a signal containing many consecutive 0s, the signal is compressed by replacing it with some other numerical code.

  The recording unit 1515 receives an output signal of the VLC 1507, that is, a signal obtained by compressing and reducing the imaging signal 8. The recording unit 1515 includes a signal processing unit 1510 and a magnetic recording unit 1512. The signal processing unit 1510 converts the signals output from the VLC 1507 into a file that generates image data. The magnetic recording unit 1512 records and stores image data on the magnetic disk 1514 whose rotation is controlled by the rotation control unit 1513 using a magnetic head. Note that the input signal amount per unit time to the recording unit 1515 is called “recording rate”, and the smaller the recording rate, the longer the recording is performed when the magnetic disk 1514 having the same specification is used. Can do. However, the image quality of the recorded image deteriorates as the recording rate decreases. Of course, the recording method is not limited to the one using magnetism, and an optical recording method may be used.

  In this embodiment, the quantization unit 1506 of the encoder 1503 compresses the information amount of the signal by reducing it for each frequency band. The degree of compression of this signal is changed to the mode identification signal 11 from the camera body 7. Change accordingly. Specifically, when the camera body 7 determines that some abnormality has occurred in the field to be photographed, the recording rate is increased to record with fine image quality, and when it is determined that no abnormality has occurred, the recording rate Is reduced to reduce the recording capacity of image data.

  Returning to FIG. 1, the control unit 10 transmits control and time information 9 to the camera body 7, and the camera body 7 always acquires an accurate time at the time of shooting based on this time information. Scene A 101, scene B 102, scene C 103,..., Scene N 104 are imaging ranges including the monitoring target of the camera body 7. FIG. 3 shows an example of the imaging range and the imaging method. In the figure, the vertical axis represents the imaging range, and the horizontal axis represents the imaging method. The shooting method includes zoom magnification, operation by the electric camera platform 6 and imaging time in each scene, and these are set by the control unit 10. The operation of the electric camera platform 6 includes coordinates in the pan direction and the tilt direction. For example, in the scene A101, imaging is performed for one minute with double zooming in the left 30 ° pan direction and the upper 20 ° tilt direction.

  The camera body 7 sequentially moves the imaging range to the position of each designated scene via the electric pan head 6 and performs imaging. When imaging of the scene N104 is completed, the process returns to the scene A101 again to continue imaging. Such an operation is repeated infinitely. Note that the number of camera bodies 7 may be increased. For example, a configuration in which a plurality of camera bodies are prepared and one camera body 7 is in charge of one scene is also conceivable.

  FIG. 4 is a block diagram showing the configuration of the camera body 7. The camera body 7 includes an optical lens 302 including a zoom group lens, a diaphragm 303, and an image sensor 304. The camera body 7 includes a gain controllable amplifier (GCA) 305 and a timing generator (TG) 308. The camera body 7 further includes a signal processing unit 312, a frame memory 313, a vertical vibration sensor 317, a horizontal vibration sensor 318, a vertical vibration detection unit 319, and a horizontal vibration detection unit 320. The camera body 7 further includes a microprocessor 321, an abnormal sound detection unit 323, a moving object detection unit 324, a zoom position sensor 327, a zoom drive unit 328, an aperture drive unit 311, and an aperture value sensor 330. Have. The microprocessor 321 includes a memory such as a RAM and a ROM together with a control unit such as an MPU.

  The light 301 from the subject passes through the optical lens 302 and the diaphragm 303 and forms an image on the light receiving surface of the image sensor 304. The zoom position sensor 327 detects the position of the zoom group lens inside the lens, that is, the focal length of the optical lens 302 and inputs it to the microprocessor 321 as an optical zoom magnification signal.

  The image sensor 304 converts the light 301 received through the optical lens 302 and the diaphragm 303 into an electrical signal and outputs it to the GCA 305. The GCA 305 is an amplifier that can change the amplification factor (gain value), and controls the amplification factor according to the gain control signal transmitted from the microprocessor 321. The output of the GCA 305 is input to the signal processing unit 312 and the microprocessor 321 as an AE output signal.

  The signal processing unit 312 performs various image processing such as gamma correction, white balance, white clip, knee, and the like on the AE output signal to generate and output the imaging signal 8. The imaging signal 8 is also input to the HDD recording device 12 and the monitor display 13 via the control unit 10. The imaging signal 8 is also input to the frame memory 313 and a moving object detection unit 324 that detects the presence or absence of a moving object based on the captured image information.

  With reference to FIG. 5, the operation of the moving object detection unit 324, that is, the detection of a moving object using the frame memory 313 will be described. Here, FIG. 5 is a conceptual diagram for explaining the operation of the moving object detection unit 324.

  The frame memory 313 functions as a one-frame delay element that stores data of one image and outputs the stored data in the next frame.

  As illustrated in FIG. 5, the moving object detection unit 324 divides the image into a finite number of blocks, and obtains a difference signal 504 by performing subtraction processing on the newly obtained image and the image one frame before. Consider a binarized image 505 obtained by binarizing the difference signal 504 for each block. For the stationary subject 506, the binary value of this difference signal is zero. On the other hand, when a moving body 507 such as an intruder is present in at least one of the image of the immediately preceding frame and the image of the next frame, the portion of the moving body 507 is 1. In other words, the moving object 507 can be detected by calculating the logical sum of all the blocks. The interval between frames is 1/30 seconds for a TV signal (NTSC), or 1/60 seconds for a field unit of interlace scanning, but there is no need to be constrained by that for a monitoring imaging apparatus. The frame memory 313 does not need a high-definition image for the purpose of moving object detection, and does not need to capture all pixels. For this reason, the required capacity of the frame memory 313 is small, and the influence on the cost of the entire product is small.

  Returning to FIG. 4, the moving body detection information from the moving body detection unit 324, the smoke detection information from the smoke sensor 1, and the infrared radiation information for detecting intruders and fire from the infrared sensor 2 are input to the microprocessor 321. The The microprocessor 321 includes abnormal sound information from the abnormal sound detection unit 323 using the microphone 3, vertical vibration information from the vertical vibration detection unit 319 using the vertical vibration sensor 317, and horizontal using the horizontal vibration sensor 318. Horizontal vibration information from the vibration detector 320 is also input.

  The microprocessor 321 controls the driving of the zoom position of the optical lens 302 via the zoom drive unit 328 and obtains a zoom magnification signal corresponding to the zoom magnification detected by the zoom position sensor 327. Further, the microprocessor 321 controls the aperture value of the aperture 303 via the aperture driver 311 and obtains a signal corresponding to the aperture value detected by the aperture value sensor 330.

  In addition, the microprocessor 321 stores two types of data, an LUT (lookup table) 601 and an AE reference value 602, in the memory for AE control. As will be described later, the LUT 601 includes abnormality monitoring mode LUT data used when it is estimated that an abnormality has occurred, and normal monitoring mode LUT data used when it is estimated that no abnormality has occurred. It is included. The AE reference value is a target luminance value of the object scene. In the monitoring system 100, AE control is performed so that the luminance value of the AE output signal is equal to the AE reference value.

  Next, the electronic shutter will be described. An electronic shutter control pulse is input from the TG 308 to the image sensor 304. The TG 308 is a circuit that generates various pulses for driving the image sensor 304, and determines the timing based on the electronic shutter control signal transmitted from the microprocessor 321.

  The operation of the electronic shutter will be described below with reference to FIGS. 6 (a) and 6 (b).

  FIG. 6A shows an example of the electronic shutter operation, and the time axis is taken from left to right. The TG 308 generates a charge readout pulse 401 to read out and output the charge generated by exposure on the photodiode of the image sensor 304 in the previous frame period. The previous frame period is a previous field period when an interlace operation is performed as in the NTSC signal.

  In this example, the accumulated charge reset pulse 402 having a function of clearing the remaining charge accumulated after reading and starting the accumulation of charges in the next field is output immediately after the charge reading pulse 401. Then, when a predetermined time elapses after the reset pulse 402 is output, the accumulated charge is read out by the charge readout pulse 401 as in the previous field, and is output as an imaging signal. The time from the output of the reset pulse 402 to the output of the charge readout pulse 401 is the charge accumulation time 403. If the output timings of the charge readout pulse 401 and the accumulated charge reset pulse 402 are repeated every one vertical blanking interval (1V) with this interval maintained, the charge accumulation time 403 becomes substantially equal to one frame or one field. That is, in the case of one field of the NTSC signal, the charge accumulation time 403 is about 1/60 second.

  FIG. 6B shows an example of the operation of the electronic shutter when the shutter is at a higher speed than in FIG. 6A, and the time axis is taken from left to right. The charge accumulation time 403 is made shorter than that shown in FIG. 6A by outputting the accumulated charge reset pulse 402 after a time has elapsed after the first charge readout pulse 401. That is, in the electronic shutter operation of this embodiment, the control of the electronic shutter speed, that is, the control of the charge accumulation time is performed by controlling the output timing of the reset pulse 402 for determining the charge accumulation time 403. If it is set to 1/500 seconds, the output timing of the reset pulse 402 may be set so that the charge accumulation time 403 becomes 1/500 seconds.

  Thus, by controlling the output timing of the pulses generated by the TG 308 and input to the image sensor 304, the exposure time of the image sensor 304 can be controlled separately from the mechanical aperture 303. .

  Details of the program AE control of the camera body 7 will be described below. Program AE control refers to exposure control in which operation parameters are programmed in advance in association with the brightness (luminance) of the object scene. There are three operation parameters in the AE control of the present embodiment: an aperture value, an electronic shutter speed, and a gain value (amplification factor). The exposure amount determined by the combination of the aperture value, the electronic shutter speed, and the gain value is hereinafter referred to as an exposure control amount. The LUT 601 stored in the microprocessor 321 is a table that describes how the operation parameters are changed correspondingly according to the brightness of the subject. The LUT data in the abnormality monitoring mode and the LUT data in the normal monitoring mode included in the LUT 601 have different combinations of values taken by the operating parameters of the aperture value, the electronic shutter speed, and the gain value even with the same exposure control amount. Exists.

  The microprocessor 321 reads the LUT 601 and the AE reference value 602, and performs feedback control by changing operation parameters so that the luminance level of the AE output signal becomes equal to the AE reference value 602. It is assumed that there are no variable elements in the signal processing unit 312 of this embodiment. Further, the signal to be compared with the AE reference value 602 is not limited to the AE output signal, but may be a signal generated based on the output of the image sensor 304, and may be the image signal 8.

  FIG. 7 is a flowchart of the AE control operation of the microprocessor 321. First, the microprocessor 321 performs power-on and initialization (step S701), and reads the AE reference value 602 (step S702). Next, the microprocessor 321 reads the LUT data in the normal monitoring mode and the abnormality monitoring mode of the LUT 601 (step S703). When the process of this step is executed for the first time after the power is turned on, the LUT data in the normal monitoring mode is selected and set as an initial value. Next, the microprocessor 321 reads the AE output signal output from the GCA 305 (step S704). The luminance value obtained from the AE output signal is compared with the AE reference value 602, and servo control by software is performed. First, an aperture value signal obtained by the aperture value sensor 330 is read (step S705). Then, a gain control signal that is a signal for controlling the GCA 305 is read (step S706). Further, an electronic shutter control signal, which is a signal for controlling the electronic shutter speed, is read (step S707). When the AE output signal obtained from the GCA 305 is appropriate, that is, when the luminance value of the object scene obtained from the AE output signal is equal to the AE reference value 602 or the difference is small, the operation parameter is set as an appropriate value. It waits while maintaining (step S710). Then, the AE output signal obtained from the GCA 305 is read again (step S704). The standby in step S710 is a process of adjusting time in order to change the change of the imaging signal 8 in units of one frame or one field. On the contrary, when the AE output signal obtained from the GCA 305 is not appropriate, that is, when the luminance value of the object scene obtained from the AE output signal is away from the AE reference value 602, a control subroutine for changing the operation parameter ( Control goes to step S709). In this control subroutine, one of the operation parameters is selected according to the current exposure control value, and the selected operation parameter is changed by one step. Then, after waiting for a predetermined time (step S710), the process returns to step S704 for reading the AE output signal output from the GCA 305 in the same manner, and this process is repeated. Here, the change of the operation parameter is limited to one step. If the luminance level of the AE output signal is suddenly changed, the image generated from the imaging signal 8 becomes unsightly with a large luminance change. It is because it ends up.

  Hereinafter, the control subroutine for changing the operation parameter in step S709 in FIG. 7 will be described in detail with reference to FIG.

  An exposure control value in the currently set monitoring mode is obtained from the read combination of operation parameters (step S801). When this step is processed for the first time, since the normal monitoring mode is set, the exposure control value in the normal monitoring mode is obtained. Then, based on the comparison result between the current level of the AE output signal and the AE reference value 602, it is determined whether to change the operating parameter for brightening the AE output signal or to change the operating parameter for darkening ( Step S802). Next, in the set monitoring mode, the operation parameter to be actually moved is determined according to the LUT 601 (step S803). When changing the exposure control value to brighten the AE output signal (step S804), one of the control of widening the aperture by one step, slowing the electronic shutter speed by one step, or increasing the gain value by one step. Is performed (step S805). When changing the exposure control value to darken the AE output signal (step S804), one of the control of reducing the aperture by one step, increasing the electronic shutter speed by one step, or decreasing the gain value by one step. Is performed (step S806). Which operation parameter is to be changed is determined by the exposure control value at that time and the data read from the LUT 601 as described above. As described above, the control subroutine controls the operation parameter according to the LUT data in any monitoring mode stored in the LUT 601.

  FIG. 9 is a flowchart in which the microprocessor 321 determines whether an abnormality has occurred and switches between the normal monitoring mode and the abnormality monitoring mode as necessary. This is processed in parallel with the flowchart of the AE control shown in FIG. 7 when the power of the monitoring system 100 is turned on. First, initialization is performed by turning on the power (step S1301). Next, the current time is read from the control and time information 9 (step S1302), and the operation setting time preset in the control unit 10 is read (step S1303). Next, the presence / absence of smoke generation is read from the smoke detection information (step S1304), and the presence / absence of infrared detection is read from the emission infrared information (step S1305). Further, vibration is read from the vertical vibration information and horizontal vibration information (step S1306), the presence / absence of voice detection is read from abnormal sound information (step S1307), and the presence / absence of moving object detection is further read from the moving body detection information (step S1308). Based on the above results, it is determined whether information that can be determined to be abnormal has been detected (step S1309). Specifically, if any factor such as vibration or abnormal noise can be detected from the detection results of steps S1304 to S1308, it is determined that there is an abnormality, and if any factor cannot be detected, an abnormality is detected. Judge that is not. If there is no change in the determination result as to whether or not this is abnormal, the process returns to step 1302. If there is a change in the determination result of the abnormal state, a subroutine (step S1310) for switching between the normal monitoring mode and the abnormal monitoring mode is entered. In this way, if there is no change in the determination result of whether or not there is an abnormality, the monitoring mode set at that time is maintained, and if there is a change in the determination result of whether or not there is an abnormality, the normal monitoring mode is set. Switch the abnormality monitoring mode from one to the other. Here, an upper limit of the duration may be defined only in the abnormality monitoring mode, and when the upper limit time has elapsed after setting in the abnormality monitoring mode, the normal monitoring mode may be forcibly switched.

  FIG. 10 is a diagram for explaining in detail the subroutine for switching the monitoring mode in step S1310. First, of the normal monitoring mode and the abnormality monitoring mode, the operation parameter of the currently set monitoring mode and the exposure control amount at that time are obtained (step S1401). While maintaining the exposure control amount, the currently set LUT data is switched to the LUT data in the other monitoring mode. In order to maintain the obtained exposure control amount, the operation parameter is associated with reference to the LUT data in the other mode (step S1402). Then, the mode identification signal 11 is changed (S step 1403). The mode identification signal 11 is set to 1 in the abnormality monitoring mode and set to 0 in the normal monitoring mode. When the mode identification signal 11 is set to 1, the recording rate is increased to record with fine image quality. When the mode identification signal 11 is set to 0, the recording rate is decreased to reduce the recording capacity of the image data. Then, the control subroutine of FIG. 8 is performed using the monitoring mode LUT data after switching.

  FIGS. 11A and 11B are a table for replacing the LUT data in the normal monitoring mode with a program diagram, and a table for indicating areas for fixing each operation parameter. In both cases, the horizontal axis indicates the field brightness and the exposure control value, and the exposure control value is adapted to the scene (the subject is brighter) with higher brightness toward the left side. Three lines described as the program diagram indicate a gain value 901, an electronic shutter speed 902, and an aperture value 903, respectively. Here, for convenience, exposure control values are classified into three areas, area A, area B, and area C, from the bright area to the dark area of the subject.

  In the brightest area of the subject, that is, area A, AE control with electronic shutter speed 902 with aperture value 903 fixed to a predetermined value near the small aperture end and gain value 901 fixed to the minimum value. I do. If the aperture value is too small, the influence of light diffraction is large, and if the aperture value is too large, the depth of field becomes shallow. Further, increasing the gain value increases noise superimposed on the image data. For this reason, within a range that can be handled by one operation parameter, the brightness of the object scene is adjusted only by the electronic shutter speed 902 while the aperture value and the gain value are fixed.

  Area B is a subject field whose luminance is darker than the AE reference value 602 even if the electronic shutter speed 902 is the slowest within the allowable range. In the present embodiment, the upper limit of the allowable range of the electronic shutter speed 902 is a value at which the electronic shutter speed is approximately equal to the frame or field frequency of 1/60 seconds, and the dynamic resolution decreases when the electronic shutter speed is further reduced. is there. In area B, the aperture value is fixed to the same value as in area A, the electronic shutter speed 902 is set to the slowest upper limit value, that is, the exposure time is fixed to a value substantially equal to one frame, and the AE based on the gain value 901 is set. Take control. The gain value 901 can generally amplify a signal of about 20 to 30 decibels (10 to 30 times) at maximum. As the gain value 901 is increased, the noise increases proportionally. However, in order to prevent the diaphragm from being worn, the luminance of the object field is adjusted only by the gain value 901 while the aperture value is fixed.

  In the area C, the object scene whose luminance is darker than the AE reference value 602 is targeted even when the electronic shutter speed 902 is set to the upper limit and the gain value 901 is set to the maximum value within the allowable range. The maximum value of the gain value 901 may be experimentally determined in consideration of the amount of noise generated. In area C, since the electronic shutter speed 902 and gain value 901 cannot be used to brighten the AE output signal, the aperture diameter of the remaining aperture value 903, which is the remaining operating parameter, is larger than those in areas A and B. To do.

  As described above, in the normal monitoring mode, the aperture value 903 is changed only in the case of a low-luminance field that cannot be handled only by the electronic shutter speed 902 and the gain value 901. When the brightness of the object scene can be set to an appropriate value using operation parameters other than the aperture value 903, the aperture value 903 is not changed. Therefore, the frequency of driving the diaphragm 303 is reduced, fatigue and wear of the diaphragm 303 can be reduced, and the life of the monitoring system 100 can be extended.

  FIG. 12 is a normal monitoring mode LUT in which operation parameters of the normal monitoring mode are described in the LUT 601. By fixing the aperture value 903 on the aperture side, the depth of field is deepened, and the focusable range is widened. For this reason, the operation of the automatic focus adjustment function for adjusting the focus by moving the lens 302 is also moderated, leading to the extension of the life of the actuator. However, since the aperture value 903 is considered to remain fixed in many cases, the aperture value 903 is set to a slightly opened position (F value = 8) from the state in which the aperture 303 is reduced in consideration of image quality deterioration due to insufficient light quantity. Fixed. The gain value 901 is also fixed to a value (20 dB) that is slightly lower than the upper limit value that can be set in consideration of an increase in noise in the area C.

Thus, the normal monitoring mode is effective not only for the aperture value 903 but also for extending the life of the lens 302 including the actuator. On the other hand, due to insufficient sensitivity due to the fixed aperture value 903, noise increases with an increase in gain value, resulting in a problem that the image quality of the image is deteriorated. However, it is important for the monitoring system 100 to capture high-quality images at the time of abnormality. In other words, if there is no abnormality, priority should be given to durability over high-quality images to avoid incapability of photographing at the time of abnormality. From this point of view, in the present embodiment, the change of the gain value 901 is prioritized over the change of the aperture value 903 in the normal monitoring mode.
FIG. 13A and FIG. 13B are a table for replacing the LUT data in the abnormality monitoring mode with a program diagram, and a table for indicating areas for fixing each operation parameter. In both cases, the horizontal axis represents the field brightness, and the exposure control value adapted to the scene (the subject is brighter) whose brightness is higher toward the left side. Three lines described as the program diagram indicate a gain value 901, an electronic shutter speed 902, and an aperture value 903, respectively. Here, for convenience, exposure control values are classified into three areas, area A, area B, and area C, from the bright area to the dark area of the subject. This program diagram is similar to a standard program diagram of a general video camera different from the surveillance system, and prioritizes image quality over wear of the aperture 303.

  In the area A, in consideration of a decrease in optical resolution due to the light diffraction phenomenon, the aperture value is fixed at a slightly opened position (F value = 16) compared to the state in which the aperture is reduced, and the gain value 901 is fixed at the minimum value. In this state, AE control with electronic shutter speed 902 is performed. Unlike the normal monitoring mode, the aperture value and the range to be fixed on the small aperture side are only area A. Therefore, the aperture value in area A is set one step smaller than the normal monitoring mode.

  Even in the case where the electronic shutter speed 902 is the slowest within the allowable range, the AE control by the aperture value 903 is performed while the gain value 901 is fixed in the area B where the object scene whose brightness is darker than the AE reference value 602 is targeted. I do. In this area B, since the gain value 901 is not increased while being fixed to the minimum value, noise caused by the gain value 901 can be reduced.

  Even in a state where the aperture value 903 is the maximum aperture diameter, AE control is performed using the gain value 901 which is the remaining operation parameter in the area C where the luminance value is darker than the AE reference value 602. Since the increase in the gain value 901 is accompanied by deterioration in image quality due to an increase in noise, control for increasing the gain value 901 is started after the other operating parameters reach the limit values for brightening the luminance signal of the object scene. It is desirable to do.

FIG. 14 is an abnormality monitoring mode LUT in which operation parameters of the abnormality monitoring mode are described in the LUT 601. Here, the areas A, B, and C are controlled by four steps, but smooth and natural control is possible by increasing the number of steps. In this embodiment, only one parameter is variably set in each area, and a configuration in which a plurality of parameters are not set variably is described as an example. However, a configuration in which a plurality of parameters are variable at the same time may be used. . When the normal monitoring mode and the abnormality monitoring mode are compared, if the chance of changing the aperture value 903 is reduced in the normal monitoring mode, the effect of increasing durability can be achieved.
In the monitoring system of this embodiment, as shown in FIG. 3, the imaging range is determined in advance, and the brightness of the object scene can be predicted in advance. Therefore, it is designed so that the expected brightness of the field is within the range of area B throughout the day and night. Therefore, there is a high possibility that AE control is performed using the aperture value 903 when the abnormality monitoring mode is set. Automatic exposure control by changing the aperture value 903 does not cause deterioration of image quality, and there is no demerit that causes unnatural movement of the subject as in the case where the electronic shutter speed 902 is set to high speed or low speed. Obtainable.

  However, if this is also applied to the normal monitoring mode, fatigue or wear accumulates in the diaphragm 303, and durability is reduced. Therefore, in this embodiment, the operation parameters that are variable are made different depending on the normal monitoring mode or the abnormality monitoring mode for the same brightness range to be monitored. Specifically, by adopting a control pattern that uses the aperture value 903 as the main operation parameter only in the abnormality monitoring mode, a configuration is achieved in which the durability of the monitoring system 100 is enhanced and the image quality of the captured image when an abnormality occurs is enhanced. It is doing.

  FIG. 15 is a flowchart of the modification of FIG. Since other configurations are the same as those of the first embodiment, description thereof is omitted. To explain only the parts different from FIG. 9, first, the power is turned on and the internal initialization is performed, and at the same time, the internal counter is reset (step S1601).

  If there is no change in the determination result as to whether there is an abnormality in the branch of step S1309, the process proceeds to step S1602, and it is determined whether the set monitoring mode is the normal monitoring mode. If it is not the normal monitoring mode, the process returns to step S1302, and if it is the normal monitoring mode, the internal counter is incremented by one (step S1603). Next, it is determined whether the value of the internal counter has reached a predetermined constant value (step S1604), and if it is less than the predetermined value, the process returns to step S1302. On the other hand, when the value of the internal counter reaches a constant value, the normal monitoring mode is switched to the abnormality monitoring mode (step S1605), and after driving in the abnormality monitoring mode for a certain time, the normal monitoring mode is restored (step S1606). Then, the internal counter is reset (step S1608), and the process returns to step S1608. By this operation, even if no abnormality is detected for a predetermined period, it is possible to prevent an increase in mechanical friction caused by not moving for a long time by periodically moving the mechanical actuator.

  As mentioned above, although the preferable Example of this invention was described, this invention is not limited to these Examples, A various deformation | transformation and change are possible within the range of the summary. For example, in this embodiment, the microprocessor 321 switches between the normal monitoring mode and the abnormality monitoring mode, but such control may be performed by the control unit 10 or another control device. Such a control device may be installed in a base station away from the monitoring target area where the camera body 7 is arranged. Further, as described above, the area where the aperture value 903 is changed is not limited to the above-described area. As long as the frequency of changing the aperture value 903 in the normal monitoring mode is smaller than that in the abnormality monitoring mode, the area where the aperture value 903 is variable may be distributed in a plurality of areas.

  The object of each embodiment can also be achieved by the following method. That is, a storage medium (or recording medium) in which a program code of software that realizes the functions of the above-described embodiments is recorded is supplied to the system or apparatus. Then, the computer (or CPU or MPU) of the system or apparatus reads and executes the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention. Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also the following cases are included in the present invention. That is, an operating system (OS) running on a computer performs part or all of actual processing based on an instruction of a program code, and the functions of the above-described embodiments are realized by the processing. In other words, when the switching of the monitoring mode and the setting of the operation parameter are controlled by the control device of the base station that is remote from the monitoring target area where the camera body 7 is arranged, it is read and executed by this control device. The program code to be applied also corresponds to the present invention.

It is a block diagram of the monitoring system by Example 1 of this invention. It is a block diagram of the HDD recording device of the monitoring system shown in FIG. It is a table | surface which shows the imaging range and imaging method shown in FIG. It is a block diagram which shows the structure of the camera main body shown in FIG. It is a conceptual diagram for demonstrating operation | movement of the moving body detection part shown in FIG. It is a figure for demonstrating operation | movement of an electronic shutter speed. 5 is a flowchart of the operation of the microprocessor shown in FIG. It is a flowchart which shows the detail of the control subroutine shown in FIG. 5 is a flowchart in which the microprocessor shown in FIG. 4 switches the photographing mode of the camera body from a normal monitoring mode to an abnormality monitoring mode. 10 is a flowchart showing details of a subroutine for switching the monitoring mode shown in FIG. 9. 6 is a program diagram of operation parameters and a table of control patterns in a normal monitoring mode according to the first embodiment. This is an LUT corresponding to FIGS. 11 (a) and 11 (b). It is the table | surface of the program diagram of the operation parameter in the abnormality monitoring mode of Example 1, and a control pattern. This is an LUT corresponding to FIGS. 13A and 13B. It is a flowchart of the modification of FIG.

Explanation of symbols

1 Smoke sensor (detection means)
2 Infrared sensor (detection means)
3 Microphone (detection means)
7 Camera body (imaging device)
12 HDD recording apparatus 100 Monitoring system 303 Aperture 305 Variable gain amplifier 312 Microprocessor (automatic exposure control means)
317 Vertical vibration sensor (detection means)
318 Horizontal vibration sensor (detection means)
324 Moving object detection unit (detection means)

Claims (9)

An imaging device that has a detecting unit that detects a state of a monitoring target, is used in a monitoring system that monitors the monitoring target, and images the monitoring target,
Based on the detection result by the detection means, a means for selecting and setting the photographing mode between the normal monitoring mode and the abnormality monitoring mode;
Automatic exposure control means for maintaining the brightness level of the output signal of the image sensor at a constant value by changing the aperture value and the value of the operation parameter including at least one of the shutter speed and the gain value;
The imaging apparatus according to claim 1, wherein the automatic exposure control unit varies the operation parameter to be variable for the same brightness range to be monitored according to a normal monitoring mode or an abnormality monitoring mode.   The automatic exposure control means variably sets at least one of a shutter speed and a gain value over the aperture value in the normal monitoring mode for the same brightness range to be monitored, 2. The imaging apparatus according to claim 1, wherein in the abnormality monitoring mode, the aperture value is set to be variable with priority over at least one of the shutter speed and the gain value.   The automatic exposure control means can maintain the luminance level at a constant value by changing at least one of a shutter speed and a gain value in the normal monitoring mode for the same brightness range to be monitored. If possible, the aperture value is fixed, and in the abnormality monitoring mode, the aperture value is set even if the brightness level can be kept constant by changing at least one of the shutter speed and the gain value. The imaging apparatus according to claim 2, wherein the imaging apparatus is variably set.   The automatic exposure control means sets the gain value to be variable over the same brightness range to be monitored in the normal monitoring mode, giving priority to the gain value in the normal monitoring mode, and in the abnormal monitoring mode, the aperture value is set higher than the gain value. 3. The imaging apparatus according to claim 2, wherein the value is set variably with priority.   In the normal monitoring mode, the automatic exposure control unit sets the gain value to be variable by fixing the aperture value in the normal monitoring mode, and fixes the gain value in the abnormality monitoring mode. The imaging apparatus according to claim 2, wherein the aperture value is variably set.   The automatic exposure control means is configured to periodically switch from the normal monitoring mode to the abnormality monitoring mode when the normal monitoring mode is not switched to the abnormality monitoring mode based on the detection result. The imaging apparatus according to claim 1, wherein:   The automatic exposure control means is configured to return to the normal monitoring mode after switching from the normal monitoring mode to the abnormality monitoring mode, based on a detection result by the detecting means, or after a predetermined time. The imaging apparatus according to claim 1, wherein: A recording device that records an image obtained from the output signal of the image sensor with different image quality between the normal monitoring mode and the abnormality monitoring mode;
The image pickup apparatus according to claim 1, wherein the image quality in the abnormality monitoring mode is higher than the image quality in the normal monitoring mode. A control program for detecting a state of a monitoring target, used in a monitoring system for monitoring the monitoring target, and for controlling an imaging device that images the monitoring target;
Based on the detection result by the detecting means, the step of selecting and setting the photographing mode between the normal monitoring mode and the abnormality monitoring mode;
By changing the aperture value and the value of the operation parameter including at least one of the shutter speed and the gain value, the luminance level of the output signal of the image sensor is maintained at a constant value, and the same brightness range of the monitoring target is set. On the other hand, according to the normal monitoring mode or the abnormality monitoring mode, an automatic exposure control step for varying the operation parameter to be variable,
A control program to execute.