KR20100125675A - Method for controlling monitoring camera, and monitoring camera adopting the same - Google Patents

Abstract

PURPOSE: A method for controlling a monitoring camera and a monitoring camera applying the same are provided to have subject distance per location of a focus lens by focusing result. CONSTITUTION: An optical system including a lens unit and a filter unit optically processes the light from a subject. The lens unit of the optical system includes a zoom lens and a focus lens. A photoelector transform unit(OEC) of a CCD(Charge Coupled Device) or CMOS(Complementary Metal-Oxide-Semiconductor) transforms the light form the optical system into an electrical analogy signal. An infrared ray generation unit(113) including a plurality of infrared diamonds radiates infrared ray in night time action mode. A video-signal generates unit transforms a digital image data from a digital signal processor into a video signal(SVID) which is an analog image signal.

Description

Method for controlling monitoring camera, and monitoring camera adopting the same}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a surveillance camera and a surveillance camera employing the same, and more particularly, to a surveillance camera control method for emitting infrared rays in a night operation mode and a surveillance camera employing the same.

Basically, the surveillance camera is preferably hidden from the surveillance object. Therefore, it is not preferable to emit visible light for illumination in the night operation mode.

To this end, in the night operation mode, the infrared light emitted by the photoelectric conversion unit of a charge coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS) is not visible to a person.

In the surveillance camera as described above, when a large amount of infrared rays is emitted, a normal image can be obtained from a distant subject, but there is a problem in that an image that is difficult to recognize due to saturation of luminance of a subject image at a short distance is saturated.

On the contrary, when the amount of infrared radiation is relatively small, a normal image can be obtained from a subject at a short distance, but there is a problem that a dark and difficult to recognize image is obtained from a remote object.

SUMMARY OF THE INVENTION An object of the present invention is to provide a control method of a surveillance camera capable of increasing image reproducibility regardless of a subject distance, and a surveillance camera employing the same.

The method of the present invention is a control method of a surveillance camera that emits infrared rays in a night mode of operation, comprising steps (a) to (c).

In step (a), focusing is performed according to the input image to adjust the position of the focus lens. In step (b), the object distance corresponding to the position of the focus lens is obtained. In the step (c), the amount of infrared light emitted is changed according to the object distance.

The surveillance camera of the present invention includes a focus lens, an infrared ray generator, and a main controller, and emits infrared rays in a night operation mode. Here, the control method used in the main control unit includes steps (a) to (c).

In step (a), focusing is performed according to the input image to adjust the position of the focus lens. In step (b), the object distance corresponding to the position of the focus lens is obtained. In the step (c), the infrared ray generating unit is controlled according to the subject distance, so that the amount of infrared rays emitted is changed.

According to the control method of the surveillance camera of the present invention and the surveillance camera employing the same, the subject distance is obtained for each position of the focus lens based on the focusing result. In addition, the amount of infrared rays emitted is changed in accordance with the object distance. Accordingly, the following effects can be obtained.

First, when the subject is near from the surveillance camera, the luminance of the subject image does not saturate as the emission amount of infrared rays is reduced.

Second, when the subject is far from the surveillance camera, bright and clear images are obtained from the subject as the amount of infrared rays is increased.

In conclusion, according to the method for controlling the surveillance camera of the present invention and the surveillance camera employing the surveillance camera, the reproducibility of the image may be increased regardless of the object distance.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 shows a surveillance system to which surveillance cameras 1a, 1b and 1c are applied according to an embodiment of the present invention.

Referring to FIG. 1, the surveillance cameras 1a, 1b, 1c communicate with a digital video recorder DVR 2 as a recording device via a communication channel D _COM , via a video signal channel S _VID . The live-view video signal is transmitted to the digital video recorder 2.

Here, in the night operation mode, an infrared ray is emitted that a photoelectric conversion unit of a Charge Coupled Device (CCD) or a Complementary Metal-Oxide-Semiconductor (CMOS) can accommodate, although it is unrecognizable to a person.

FIG. 2 shows the internal configuration of any surveillance camera 1a or 1b or 1c of FIG. 1. FIG. 3 shows an incident side structure of the surveillance camera of FIG. 2.

2 and 3, the surveillance camera in the surveillance system according to the present invention is an optical system (OPS), photoelectric conversion unit (OEC), CDS-ADC (Correlation Double Sampler and Analog-to-Digital Converter, 101), timing A circuit 102, a digital signal processor (DSP) as a controller, a video-signal generator 108, an infrared generator 113, an aperture motor M _A , a zoom motor M _Z , Focus motor M _F , filter motor M _D , driver 110, and micro-controller 112.

The optical system OPS including the lens unit 301 and the filter unit 302 optically processes light from a subject.

The lens unit 301 of the optical system OPS includes a zoom lens ZL and a focus lens FL. In the filter unit 302 of the optical system OPS, an optical low pass filter (OLPF) used in the night mode of operation removes optical noise of high frequency content. Infra-Red cut filter (IRF) used in daytime operation mode cuts off the infrared component of incident light.

A photoelectric conversion unit (OEC) of a charge coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS) converts light from an optical system (OPS) into an electrical analog signal. Here, the digital signal processor 107 as the main controller controls the timing circuit 102 to control the operations of the photoelectric conversion unit OEC and the Correlation Double Sampler and Analog-to-Digital Converter 101. .

The CDS-ADC 101 processes the analog video signal from the photoelectric converter (OEC), removes the high frequency noise, adjusts the amplitude, and converts the digital video data. This digital image data is input to the digital signal processor 107.

The digital signal processor 107 performing overall control processes the digital signal from the CDS-ADC element 101 to generate digital image data classified into luminance and chroma signals.

The infrared ray generator 113 including a plurality of infrared diodes emits infrared rays as infrared rays in the night operation mode.

The video-signal generator 108 converts digital image data from the digital signal processor 107 into a video signal S _VID which is an analog image signal.

The digital signal processor 107 communicates with the digital video recorder (DVR, 2 of FIG. 1) as a recording device via the micro-controller 112 as a communication interface and the communication channel (D _{COM of} FIG. 1), and the video signal channel. The video signal from the video-signal generator 108 is transmitted to the digital video recorder 2 via S _VID .

The digital signal processor 107 controls the driving unit 110 to drive the aperture motor M _A , the zoom motor M _Z , the focus motor M _F , and the filter motor M _D. The aperture motor M _A drives the aperture (not shown), the zoom motor M _Z drives the zoom lens ZL, and the focus motor M _F drives the focus lens FL. The filter motor M _D drives the optical low pass filter OLPF and the infrared cut filter IRF in the filter unit 302.

FIG. 4 is a graph for explaining a basic principle of focusing performed by the digital signal processor 107 which is a main controller of the surveillance camera of FIG. 2. In FIG. 4, reference numeral DS indicates the number of drive steps as the position of the focus lens (FL in FIG. 3). Reference numeral FV denotes a focus value in which difference values between adjacent pixel data are summed and thus called frame contrast between adjacent pixel data. Reference numeral DS _I indicates the drive step number of the focus lens FL at the set upper limit position. Reference numeral DS _FOC denotes the number of driving steps of the focus lens FL at the position of the maximum focus value FV _MAX of the setting movement area DS _I to DS _S , and DS _S denotes the focus lens ( The number of drive steps of FL) is indicated, respectively.

2 to 4, the digital signal processor 107 as the main control unit obtains the focus value FV, which is the frame contrast at each of the positions of the focus lens FL, while moving the focus lens FL to obtain the maximum focus value. Find the position of (FV _MAX ) (DS _FOC ).

That is, the difference values between adjacent pixel data are summed for each position of the focus lens FL, and the focus lens FL is moved to the position DS _FOC where the sum result value FV is greatest.

5 is a flow diagram of the basic algorithm performed by the digital signal processor 107 of FIG. 2 to 5, the basic algorithm of FIG. 2 will be described.

When the average luminance of the input image is larger than the reference luminance (step S51), the digital signal processor 107 causes the optical low pass filter OLPF to be out of the incident region, and the infrared cut filter IRF is positioned in the incident region. (Step S52). Of course, the driving unit 110 drives the filter motor M _D in accordance with the control signal from the digital signal processor 107. Next, the digital signal processor 107 performs the weekly operation mode (step S53).

When the average luminance of the input image is not greater than the reference luminance (step S51), the digital signal processor 107 causes the infrared cut-off filter (IRF) to deviate from the incident region, and the optical low pass filter (OLPF) to the incident region. Control to position (step S54). Of course, the driving unit 110 drives the filter motor M _D in accordance with the control signal from the digital signal processor 107. Next, the digital signal processor 107 performs a night mode of operation (step S55). This night operation mode will be described in detail with reference to FIGS. 6 to 14.

All of the above steps S51 to S55 are repeatedly performed until the end signal is generated (step S56).

6 illustrates a first example of the infrared ray generator 113 of FIG. 2.

2 and 6, the infrared ray generator 113 includes the first infrared diode groups D1 to D16, the first switch SW1, the second infrared diode groups D17 to D32, and the second switch SW2. ).

The digital signal processor 107 selectively turns on each of the first infrared diode groups D1 to D16 and the second infrared diode groups D17 to D32 according to the object distance. Related contents are described with reference to FIG. 7.

FIG. 7 is a flowchart of the night operation mode S55 of FIG. 5 performed by the digital signal processor 107 of FIG. 2 when the infrared ray generator 113 of FIG. 6 is used.

6 and 7, the night operation mode S55 of FIG. 7 will be described.

First, the digital signal processor 107 of FIG. 2 performs focusing according to the input image to adjust the position (DS of FIG. 4) of the focus lens (FL of FIG. 3) (step S701). This is as described in detail with reference to FIG. 4.

Next, the digital signal processor 107 reads the object distance corresponding to the position of the focus lens FL (DS _{FOC in} FIG. 4) from a look-up table (step S702). Here, it is well known that the subject distance can be obtained according to the position DS _FOC of the focus lens FL.

Next, the digital signal processor 107 determines whether or not the read object distance is within the near range (step S703).

When the subject distance is in the near range, the digital signal processor 107 turns on any one of the first infrared diode group D1 to D16 and the second infrared diode group D17 to D32 in the infrared ray generator 113. (On) (step S704).

For example, the digital signal processor 107 turns the first switch SW1 on in response to the first switching control signal S _G1 and the second switch in response to the second switching control signal S _G2 . Turn off (SW2). Accordingly, the first infrared diode groups D1 to D16 are turned on, and the second infrared diode groups D17 to D32 are turned off.

If the object distance does not belong to the near range, the digital signal processor 107 turns on both the first infrared diode groups D1 to D16 and the second infrared diode groups D17 to D32 in the infrared ray generator 113. (Step S705).

For example, the digital signal processor 107 turns the first switch SW1 on in response to the first switching control signal S _G1 and the second switch in response to the second switching control signal S _G2 . Turn on (SW2). Accordingly, the first infrared diode groups D1 to D16 are turned on, and the second infrared diode groups D17 to D32 are turned on.

Meanwhile, steps S706 and S707 may be added in case the accuracy of the focusing operation (step S701) is lowered.

The digital signal processor 107 determines whether the average brightness of the input video is higher than the upper limit brightness (step S706). If the average brightness of the input image is higher than the upper limit brightness, the digital signal processor 107 controls the driver 110 to reduce the exposure amount by a set amount (step S707).

All the above steps are repeatedly performed until the end signal is generated (step S708).

8 illustrates a second example of the infrared ray generator 113 of FIG. 2.

2 and 8, the infrared ray generating unit 113 includes the first infrared diode groups D1 to D11, the first switch SW1, the second infrared diode group D12 to D22, and the second switch SW2. , The third infrared diode group D23 to D33, and the third switch SW3.

The digital signal processor 107 selectively turns on each of the first infrared diode groups D1 to D11, the second infrared diode groups D12 to D22, and the third infrared diode groups D23 to D33 according to the object distance. On). Related contents are described with reference to FIG. 9.

FIG. 9 is a flowchart of the night operation mode S55 of FIG. 5 performed by the digital signal processor 107 of FIG. 2 when the infrared ray generator 113 of FIG. 8 is used.

8 and 9, the night operation mode S55 of FIG. 9 will be described.

First, the digital signal processor 107 of FIG. 2 performs focusing according to the input image to adjust the position (DS of FIG. 4) of the focus lens (FL of FIG. 3) (step S901). This is as described in detail with reference to FIG. 4.

Next, the digital signal processor 107 reads the object distance corresponding to the position of the focus lens FL (DS _{FOC in} FIG. 4) from a look-up table (step S902). As described above, it is well known that the subject distance can be obtained according to the position DS _FOC of the focus lens FL.

Next, the digital signal processor 107 determines whether the read object distance belongs to a short range, a medium range, or a far range (step S903).

When the object distance is in the near range, the digital signal processor 107 turns on any one of the first infrared diode groups D1 to D11 to the third infrared diode groups D23 to D33 in the infrared ray generator 113. (On) (step S904).

For example, the digital signal processor 107 turns the first switch SW1 on in response to the first switching control signal S _G1 and the second switch in response to the second switching control signal S _G2 . The switch SW2 is turned off, and the third switch SW3 is turned off by the third switching control signal S _G3 .

Accordingly, the first infrared diode groups D1 to D11 are turned on, the second infrared diode groups D12 to D22 are turned off, and the third infrared diode groups D23 to D33 are turned off. Off).

When the subject distance is in the medium range, the digital signal processor 107 turns on any two groups among the first infrared diode groups D1 to D11 to the third infrared diode groups D23 to D33 in the infrared ray generator 113. (On) (step S905).

For example, the digital signal processor 107 turns the first switch SW1 on in response to the first switching control signal S _G1 and the second switch in response to the second switching control signal S _G2 . The switch SW2 is turned on and the third switch SW3 is turned off by the third switching control signal S _G3 .

Accordingly, the first infrared diode groups D1 to D11 are turned on, the second infrared diode groups D12 to D22 are turned on, and the third infrared diode groups D23 to D33 are turned off. Off).

When the object distance is in the far range, the digital signal processor 107 turns on all of the first infrared diode groups D1 to D11 to the third infrared diode groups D23 to D33 in the infrared ray generator 113. (Step S906).

For example, the digital signal processor 107 turns the first switch SW1 on in response to the first switching control signal S _G1 and the second switch in response to the second switching control signal S _G2 . The switch SW2 is turned on and the third switch SW3 is turned on by the third switching control signal S _G3 .

Accordingly, the first infrared diode groups D1 to D11 are turned on, the second infrared diode groups D12 to D22 are turned on, and the third infrared diode groups D23 to D33 are also turned on. On).

As described above, steps S907 and S908 may be added in case the accuracy of the focusing operation (step S901) is lowered.

The digital signal processor 107 determines whether the average brightness of the input video is higher than the upper limit brightness (step S907). If the average luminance of the input image is higher than the upper limit luminance, the digital signal processor 107 controls the driver 110 to reduce the exposure amount by a set amount (step S908).

All the above steps are repeatedly performed until the end signal is generated (step S909).

FIG. 10 shows a third example of the infrared ray generator 113 of FIG. 2.

2 and 10, the infrared ray generator 113 includes a plurality of infrared diodes D1 to D32 connected in parallel to each other and a switch SW for driving all of them.

The digital signal processor 107 periodically turns on the plurality of infrared diodes D1 to D32, and changes the ratio of the on time for one cycle according to the subject distance or changes the frequency of the subject. Change according to the distance. Related contents are described with reference to FIGS. 11 to 14.

FIG. 11 is a flowchart of an example of the night operation mode S55 of FIG. 5 performed by the digital signal processor 107 of FIG. 2 when the infrared ray generator 113 of FIG. 10 is used.

FIG. 12 illustrates the switching control signal S _A of FIG. 10 that varies according to a range of a subject distance when the night operation mode S55 of FIG. 11 is used. In FIG. 12, reference numeral S _AL denotes a switching control signal S _A when the range of the subject distance is in the far range, and S _AM denotes a switching control signal S _A when the range of the subject distance is in the medium range. , And S _AS each indicate a switching control signal S _A when the range of the object distance is in the near range. In Fig. 12, reference numeral V _H denotes a high level potential, and V _G denotes a ground potential, respectively.

10 to 12, the night operation mode S55 of FIG. 11 will be described.

First, the digital signal processor 107 of FIG. 2 performs focusing according to the input image to adjust the position (DS of FIG. 4) of the focus lens (FL of FIG. 3) (step S1101). This is as described in detail with reference to FIG. 4.

Next, the digital signal processor 107 reads the object distance corresponding to the position of the focus lens FL (DS _{FOC in} FIG. 4) from a look-up table (step S1102).

Next, the digital signal processor 107 determines whether the read object distance belongs to a short range, a medium range, or a far range (step S1103).

When the object distance is in the near range, the digital signal processor 107 periodically turns on all the infrared diodes D1 to D32 in the infrared ray generator 113, but turns it on for one cycle. The ratio of time is 1/3 (step S1104, see S _{AS in} FIG. 12).

When the object distance is in the middle distance range, the digital signal processor 107 periodically turns on all the infrared diodes D1 to D32 in the infrared ray generator 113, but turns it on for one cycle. The ratio of time is made 2/3 (step S1105, see S _AM of FIG. 12).

When the object distance is in the far range, the digital signal processor 107 continues to turn on all the infrared diodes D1 to D32 in the infrared generator 113 during the setting period. (Step S1106, see S _AL of FIG. 12).

As described above, steps S1107 and S1108 may be added in case the accuracy of the focusing operation (step S1101) is lowered.

The digital signal processor 107 determines whether the average brightness of the input video is higher than the upper limit brightness (step S1107). If the average luminance of the input image is higher than the upper limit luminance, the digital signal processor 107 controls the driver 110 to reduce the exposure amount by a set amount (step S1108).

All the above steps are repeatedly performed until the end signal is generated (step S1109).

FIG. 13 is a flowchart of another example of the nighttime operation mode S55 of FIG. 5 performed by the digital signal processor 107 of FIG. 2 when the infrared ray generator 113 of FIG. 10 is used. 14 illustrates the switching control signal S _A of FIG. 10 that varies according to a range of a subject distance when the night operation mode S55 of FIG. 13 is used. In FIG. 14, the same reference numerals as used in FIG. 12 indicate objects of the same function.

10, 13, and 14, the night operation mode S55 of FIG. 13 will be described.

First, the digital signal processor 107 of FIG. 2 performs focusing according to the input image to adjust the position (DS of FIG. 4) of the focus lens (FL of FIG. 3) (step S1301).

Next, the digital signal processor 107 reads the object distance corresponding to the position of the focus lens FL (DS _{FOC in} FIG. 4) from a look-up table (step S1302).

Next, the digital signal processor 107 determines whether the read object distance belongs to a short range, a medium range, or a far range (step S1303).

If the object distance is in the near range, the digital signal processor 107 periodically turns on all the infrared diodes D1 to D32 in the infrared ray generator 113 as the first frequency (step S1304, FIG. See S _{AS in} 14).

When the object distance is in the medium range, the digital signal processor 107 periodically turns on all the infrared diodes D1 to D32 in the infrared ray generator 113 as the second frequency, which is 3/2 times the first frequency. On) (see step S1305, S _{AM in} FIG. 14). That is, the period of the first frequency is 0 to t3, and the period of the second frequency is 0 to t2, which is 2/3 of the frequency.

When the object distance is in the far range, the digital signal processor 107 continues to turn on all the infrared diodes D1 to D32 in the infrared generator 113 during the setting period. (Step S1306, see S _AL of FIG. 14).

As described above, steps S1307 and S1308 may be added in case the accuracy of the focusing operation (step S1101) is lowered.

The digital signal processor 107 determines whether the average brightness of the input video is higher than the upper limit brightness (step S1307). If the average luminance of the input image is higher than the upper limit luminance, the digital signal processor 107 controls the driver 110 to reduce the exposure amount by a set amount (step S1308).

All the above steps are repeatedly performed until the end signal is generated (step S1309).

As described above, according to the method for controlling the surveillance camera and the surveillance camera employing the same, the subject distance is obtained for each position of the focus lens based on the focusing result. In addition, the amount of infrared rays emitted is changed in accordance with the object distance. Accordingly, the following effects can be obtained.

First, when the subject is near from the surveillance camera, the luminance of the subject image does not saturate as the emission amount of infrared rays is reduced.

Second, when the subject is far from the surveillance camera, bright and clear images are obtained from the subject as the amount of infrared rays is increased.

In conclusion, according to the method for controlling the surveillance camera and the surveillance camera employing the same, the reproducibility of the image may be increased regardless of the object distance.

It can be used not only for surveillance cameras but also for all cameras capable of shooting video.

1 is a block diagram illustrating a surveillance system to which surveillance cameras are applied according to an exemplary embodiment.

FIG. 2 is a block diagram illustrating an internal configuration of any one surveillance camera of FIG. 1.

FIG. 3 is a view illustrating an incident side structure of the surveillance camera of FIG. 2.

FIG. 4 is a graph for explaining a basic principle of focusing performed by a digital signal processor that is a main controller of the surveillance camera of FIG. 2.

5 is a flow diagram of a basic algorithm performed by the digital signal processor of FIG.

6 is a circuit diagram illustrating a first example of the infrared ray generating unit of FIG. 2.

FIG. 7 is a flowchart of the night mode of operation of FIG. 5 performed by the digital signal processor of FIG. 2 when the infrared generator of FIG. 6 is used.

8 is a circuit diagram illustrating a second example of the infrared ray generating unit of FIG. 2.

FIG. 9 is a flowchart of the night mode of operation of FIG. 5 performed by the digital signal processor of FIG. 2 when the infrared generator of FIG. 8 is used.

FIG. 10 is a circuit diagram illustrating a third example of the infrared ray generating unit of FIG. 2.

FIG. 11 is a flowchart of an example of a nighttime operation mode of FIG. 5 performed by the digital signal processor of FIG. 2 when the infrared generator of FIG. 10 is used.

FIG. 12 is a waveform diagram illustrating a switching control signal of FIG. 10 that varies according to a range of a subject distance when the night operation mode of FIG. 11 is used.

FIG. 13 is a flowchart of another example of the nighttime operation mode of FIG. 5 performed by the digital signal processor of FIG. 2 when the infrared generator of FIG. 10 is used.

FIG. 14 is a waveform diagram illustrating the switching control signal of FIG. 10 that varies according to a range of a subject distance when the night operation mode of FIG. 13 is used.

<Description of the symbols for the main parts of the drawings>

1a, 1b, 1c ... surveillance cameras, 2 ... digital video recorder (DVR)

OPS ... optical system, OEC ... photoelectric conversion unit,

101 ... CDS-ADC, 102 ... timing circuit,

107 digital signal processor, 108 video signal generator,

110 drive, 112 microcontroller,

113 ... infrared generator, D1 to D32 ... infrared diodes.

Claims (11)

In the control method of the surveillance camera to emit infrared light in the night operation mode, (a) adjusting the position of the focus lens by focusing according to the input image; (b) obtaining a subject distance corresponding to the position of the focus lens; And (c) controlling a surveillance camera including changing an infrared ray emission amount according to the object distance. The method of claim 1, And controlling the surveillance camera to perform the night operation mode when the average luminance of the input image is not greater than the reference luminance. The method of claim 1, and (d) reducing the exposure amount by a set amount if the average luminance of the input image is higher than the upper limit luminance. The method of claim 1, wherein in step (a), (a1) summing difference values between adjacent pixel data for each position of the focus lens; And (a2) A method for controlling a surveillance camera, comprising moving a focus lens to a position where the summation result in step (a1) is the largest. The method of claim 1, wherein in step (b), And a subject distance corresponding to the position of the focus lens is read from a look-up table. The method of claim 1, wherein in step (c), And a control method of the surveillance camera in which the emission amount of the infrared ray is changed in proportion to the subject distance. A surveillance camera comprising a focus lens, an infrared ray generator, and a main controller, wherein the surveillance camera emits infrared rays in a night operation mode, The control method used in the main control unit, (a) adjusting the position of the focus lens by focusing according to an input image; (b) obtaining a subject distance corresponding to the position of the focus lens; And and (c) controlling the infrared generating unit according to the subject distance to change the emission amount of the infrared ray. The method of claim 7, wherein The infrared generator includes a plurality of infrared diode groups, And each of the plurality of infrared diode groups is selectively turned on according to the subject distance. The method of claim 7, wherein The infrared generating unit includes a plurality of infrared diodes, The plurality of infrared diodes are periodically turned on, the ratio of the on time for one period is changed according to the subject distance. The method of claim 7, wherein The infrared generating unit includes a plurality of infrared diodes, And a plurality of infrared diodes are periodically turned on, the frequency of which changes according to the subject distance. The method of claim 7, wherein Further comprising a stop for adjusting the exposure amount by the control of the main control unit, Surveillance camera when the average brightness of the input image is higher than the upper limit brightness, the exposure decreases by the set amount.

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