JP6385123B2 - Surveillance camera and cover used therefor - Google Patents

Description

The present invention, Ru der relates surveillance camera and a cover used for this.

  In recent years, with the rapid expansion of the surveillance market, the demand for surveillance cameras has increased. Surveillance cameras are required to be able to respond widely to changes in the imaging environment because they are installed regardless of indoors or outdoors, and need to be operated constantly regardless of day or night.

  In addition, as a surveillance camera set on the ceiling or wall of a facility, a dome-shaped cover (dome cover) is provided as an imaging device cover that covers an imaging main body (camera main body) including an imaging optical system and an imaging element. An imaging device is known. This is for the purpose of surveillance capable of switching the shooting range in the pan direction and the tilt direction while protecting the camera from attacks by intruders and damage from wind and rain.

  In general, the dome cover is formed with a thickness of about several millimeters by a plastic material such as polymethyl methacrylate (PMMA) or polycarbonate (PC). Depending on the application and purpose, there are specifications with different transmittances such as a transparent type and a smoke color type.

  The dome cover called the clear type has the same condition as the shooting environment of only the camera body without the dome cover, with the role of protecting the camera body, without impairing the transmittance and surface accuracy as much as possible. It is demanded. On the other hand, in the smoke type, the transmittance of the dome cover is lowered in order not to notice the monitoring and the direction of the camera. As described above, the clear dome or the smoke dome is selected according to the purpose of use.

  By the way, since monitoring is performed day and night, once the dome cover is installed together with the monitoring camera, the smoke state and the clear state cannot be changed according to the monitoring state. For example, if a smoke dome is installed, it is difficult for shooting to occur in a situation where a sufficient amount of light can be secured such as during the daytime, but the amount of light is insufficient in a smoked state at night. Therefore, the dome cover is required to be able to switch between the clear state and the smoked state without having to replace the dome cover.

  Therefore, in order to change the transmittance of the dome cover in a single dome, the dome cover is divided into a plurality of regions having different transmittances (the dome thicknesses are different), and the dome cover is rotated to receive light from the camera body. There is known an imaging apparatus that adjusts (Patent Document 1).

  Some surveillance cameras have an IRC (infrared cut) filter switching mechanism to cope with day and night surveillance (Patent Document 2). This is because during daytime when it is easy to secure the amount of light, the IRC filter is inserted into the optical path as a day mode to perform color photography. It is used for shooting.

  In the day mode, it is possible to obtain a color image with no sense of incongruity to the human appearance without allowing infrared light to reach an image sensor having sensitivity in the infrared region in consideration of color balance. In the night mode, it is possible to monitor a monochrome image in which the wavelength of the near-infrared region is taken into the imaging element and the light quantity is secured.

  In addition, in surveillance cameras and video camera lenses, a combination of a plurality of diaphragm blades forming an aperture opening and a ND (Neutral density) filter switching mechanism is generally used as a means for adjusting exposure. (Patent Document 3). This is because, when imaging a high-luminance subject, if the aperture diameter is reduced to reduce the amount of light (small aperture state), the resolution deteriorates due to the effect of diffraction, but the aperture diameter is maintained and inserted into the optical path. The amount of light is reduced by the ND filter.

JP 2010-177869 A JP 11-239356 A JP 2009-186673 A

  However, in Patent Document 1, molding is difficult because the thickness of the dome cover is not constant, and a moving mechanism is also required to follow the dome cover itself when changing the monitoring direction by pan / tilt adjustment of the imaging device. There is a problem. Similar to the moving mechanism of Patent Document 1, when the filter switching mechanisms of Patent Documents 2 and 3 are provided, there are problems in miniaturization and durability of the mechanism. In Patent Document 3, there is a problem that a ghost caused by reflection on the ND surface or an image (optical performance) caused by ND surface accuracy is easily deteriorated.

An object of the present invention is to use a surveillance camera that can take an image without using a mechanical movable part except for a mechanical movable part for the pan direction and the tilt direction in response to a change in an imaging environment or imaging conditions. To provide a cover.

To achieve the above object, the monitoring camera according to the present invention includes an imaging unit having an imaging optical system, a mechanical movable portion which can change the orientation of the imaging unit, and a cover for housing the image pickup unit, the a surveillance camera having the imaging unit is capable of changing the direction inside of the cover, at least a portion of said cover is variable transmittance elements for controlling the amount of light passing through the imaging optical system The amount of light transmitted through the imaging optical system is controlled by changing the voltage applied to the transmittance variable element.

The cover according to the present invention is a cover that houses an imaging unit including an imaging optical system and a surveillance camera having a mechanical movable unit that can change the orientation of the imaging optical system , and is at least one of the covers. The unit is configured using a variable transmittance element for controlling the amount of light transmitted through the imaging optical system, and the amount of light transmitted through the imaging optical system changes a voltage applied to the transmittance variable element. It is controlled by.

According to the present invention, it is possible to take an image without passing through the mechanical movable part except for the mechanical movable part for the pan direction and the tilt direction in response to a change in the imaging environment or imaging conditions .

It is a perspective view of an imaging device which has a dome cover concerning an embodiment of the present invention. It is sectional drawing of the imaging device which concerns on 1st Embodiment. It is explanatory drawing of the zoom lens as an imaging optical system. It is a spectral characteristic figure of the dome cover concerning a 1st embodiment. 3 is a flowchart of the imaging apparatus according to the first embodiment. It is sectional drawing of the imaging device which concerns on 2nd Embodiment. It is a spectral characteristic figure of the dome cover concerning a 2nd embodiment. It is a flowchart of the imaging device which concerns on 2nd Embodiment. It is explanatory drawing of the prior art for demonstrating 3rd Embodiment. It is sectional drawing of the imaging device which concerns on 3rd Embodiment. 10 is a flowchart of an imaging apparatus according to a third embodiment.

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

<< First Embodiment >>
( Surveillance camera )
1 to 3, a dome type camera as a surveillance camera (hereinafter referred to as an imaging device) according to the present embodiment is an imaging main body unit including imaging optical systems 34 and 35 including an optical axis 26 and an imaging element 28. Camera body 14 and a dome cover 15 covering the camera body 14. In the imaging apparatus, the casing 11 is held on a ceiling, a wall, or the like, and can be rotated around a fulcrum 25 in at least one of the pan direction 12 and the tilt direction 13.

The imaging optical system in the camera body 14 is a lens optical system (zoom lens) having a zoom function for moving a plurality of lens groups (image plane correction group 34, zooming group 35), and each lens in FIG. The arrows indicate the movement locus for zooming and image plane correction. In FIG. 3, reference numeral 32 denotes a stop ( aperture stop ), and 36 denotes a face plate portion corresponding to an IRC filter (described later) or LPF (low pass filter).

(Dome cover)
The dome cover 15 in the present embodiment has a transmittance control element such as an electrochromic element (EC element) as a physical property element (transmittance variable element) that reversibly controls the light transmission amount by changing an applied voltage. Provide for all or part of the cover area. That is, in the present embodiment, the dome cover region of the dome cover 15 is entirely formed of an EC element as a transmittance variable element, or part of the dome cover region of the dome cover formed of a plastic material (resin material) or the like. An EC element is incorporated.

  When the EC element is incorporated in a part of the dome cover region, it is preferable to use a region corresponding to the optical path of the imaging optical system (a region where the optical axis 26 of the imaging optical system faces).

  An EC element is a physical element in which a transparent electrode, an EC material, an electrolyte, and the like are laminated on a glass substrate, and ions moved from the electrolyte by an applied voltage between the transparent electrodes and the EC material react electrochemically and color. . In this way, the EC element can change its transmission wavelength band and transmittance by a chemical reaction by electricity, and is discolored by applying a voltage, and the transmittance at the time of decoloring compared with a liquid crystal element or the like. It has high characteristics, is hardly affected by polarized light, and has memory characteristics. And according to the variation | change_quantity of an applied voltage, the light transmittance can be changed in steps or continuously.

  In this way, in the present embodiment, the whole or part of the dome cover region (corresponding to the EC element) can be switched to the clear state or the smoke state via the voltage control unit 21 (FIG. 2) as the control means. It has become. Examples of such EC element materials (EC materials) include tungsten oxide, iridium oxide, viologen derivatives, viologen polymers, metal phthalocyanines, and polythiophenes.

(Permeability characteristics of dome cover)
FIG. 4 shows the transmittance characteristics of the dome cover in this embodiment. In FIG. 4, the spectral characteristic (A) represents an example of a transmittance characteristic called a normal clear dome (clear state). When the smoke state is desired, the transmittance of the EC element is changed as shown in FIGS.

  For example, in a daytime or a bright room where there is a sufficient amount of light, the camera is kept in a smoked state so as not to be aware of the surveillance camera (FIG. 4B or 4C), and at night or when the room is turned off. Then, the transmittance is controlled to make it clear (FIG. 4A). In other words, in the present embodiment, repetitive control is performed so that these states are reversibly changed (transmittance change) in accordance with the amount of light around the imaging apparatus.

  With respect to such light amount control (transmission change), the present embodiment is characterized in that the following conditional expression is satisfied.

1.4 <Tλmax / Tλmin (1)
Tλmax: Maximum transmittance controllable by an EC element at a wavelength λ [nm] (400 <λ <700)
Tλmin: minimum transmittance that can be controlled by the EC element at wavelength λ [nm] (400 <λ <700)
This is a condition for providing an effect of 0.5 steps or more as a diaphragm effect by a change in transmittance. If the lower limit of conditional expression (1) is exceeded, the difference in transmittance due to switching between the clear state and the smoked state is reduced, and the effect of the smoked state for hiding the presence of the camera as the imaging device in the dome cover is reduced. It is not preferable.

  In order to prevent the camera inside the dome cover from being recognized as a smoke state, the following conditional expression range is more preferable.

1.6 <Tλmax / Tλmin (1a)
In addition, when the transmittance of the dome cover in the smoked state is T_dome (%), it is preferable that the following condition is satisfied.

T_dome <55 (A)
(Transmittance control flow)
The flow of transmittance control in the camera body is performed as shown in FIG. In the present embodiment, by providing a luminance measuring unit 22 (FIG. 2) that measures the luminance of the outside world (outside of the imaging device, surrounding environment of the imaging device ), a signal is sent to the voltage control unit 21 according to the brightness of the monitoring area. The transmission control amount is set in advance according to the transmitted information. That is, when it is determined that the external environment (outside of the imaging apparatus) is bright and a smoked state is necessary based on the luminance information, the smoked state where the spectral characteristics (B) and (C) are obtained is maintained. On the other hand, when it is determined that the outside world is dark and a clear state is necessary, transmittance control is performed so that the spectral characteristic (A) is obtained.

  According to the present embodiment as described above, it is possible to switch between the characteristics of the clear dome (clear state) and the smoke dome (smoked state) in a single dome. Thereby, the selection and exchange work of the conventional clear dome and smoke dome which are separately prepared can be made unnecessary.

<< Second Embodiment >>
The present embodiment shown in FIG. 6 does not have a mechanism that allows the dome cover to have an infrared cut filter (IRC filter) function for suppressing the near-infrared transmittance, and allows the IRC filter to be taken in and out of the conventional optical path ( The IRC filter is not provided in the optical path).

  That is, conventionally, the IRC filter is inserted into the optical path during daytime color photography (day mode), and the IRC filter is retracted from the optical path (night mode) in an environment where the amount of light is insufficient, such as at night. Turn the dome cover on and off electrically.

Specifically, in this embodiment, the imaging mode (day mode) in which the transmittance of the EC element is changed according to the amount of light outside the imaging apparatus as an imaging environment to change to the smoke state, and the transmittance control of the EC element is not performed. An imaging mode (night mode) that transmits light in the near infrared region is selectively executed. That is, in the day mode, the infrared component of the imaging light reaching the imaging device is reduced, and in the night mode, the infrared component of the imaging light reaching the imaging device is not reduced.

  The IRC filter is sensitive to the near-infrared wavelength of the CMOS or CCD sensor as the image sensor, and the color balance is lost when these light is captured. Therefore, the near-infrared wavelength is cut (adjusted). It is used to improve the color balance. In this embodiment, the wavelength selection function of the EC element constituting the dome cover is used (the dome cover is provided with an IRC filter function), thereby appropriately switching between the day mode and the night mode in a situation where 24-hour monitoring is required. It is configured.

  FIG. 7 shows the spectral characteristics of the EC element of this embodiment (Example 1 and Example 2). This eliminates the conventional IRC filter switching mechanism and enables photographing with good color balance. The material of the EC element (Example 1 and Example 2) can be selected as appropriate.

Here, the present embodiment is characterized in that the following conditional expression is satisfied.
0.6 <T_IRC (600) / T_IRC (550) <0.9 (2-1)
0.2 <T_IRC (650) / T_IRC (550) <0.5 (2-2)
T_IRC (700) / T_IRC (550) <0.15 (2-3)
T_IRC (λ): Spectral transmittance at wavelength λnm This indicates a numerical condition for controlling transmittance according to wavelength in order to achieve good color balance. Exceeding the upper and lower limits of the conditional expression is not preferable because the color balance is lost and faithful color reproduction cannot be performed.

  In conditional expressions (2-1) to (2-3), the region from 550 nm to 700 nm is constrained. However, the dome may be constrained to be adjusted in the UV (short wavelength) region near 400 nm as necessary. It may be given to the cover.

  The flow of transmittance control in the camera body is assumed to be as shown in FIG. That is, when it is determined from the luminance information of the luminance measuring unit 22 that the outside world is dark and it is necessary to set the night mode, the transmittance of the dome cover is not controlled, and light having a wavelength in the near infrared region is transmitted. On the other hand, when it is determined that the day mode is necessary, the transmittance of the dome cover is controlled to cut light having a wavelength in the near infrared region.

  As described above, according to the present embodiment, the IRC filter switching mechanism can be omitted in the imaging apparatus, and the dome cover has a function corresponding to shooting at night or the like while taking color balance into consideration. can do.

<< Third Embodiment >>
In the present embodiment, the dome cover has an ND filter function and does not include a conventional mechanism for inserting and removing the ND filter in the optical path (the ND filter is not provided in the optical path). Conventionally, in order to avoid deterioration of optical performance (resolution) due to the influence of diffraction in a small aperture state in exposure control, an ND filter is used as an optical path while maintaining the aperture (aperture diameter) of the aperture in front of the small aperture state. When the effect of diffraction is not considered, the ND filter is retracted from the optical path).

Such a conventional example is shown in FIG. FIG. 9A shows a diaphragm device composed of two diaphragm blades for light quantity adjustment having a notch, and by controlling the light flux from (a) to (c), the F value (FN _O ) Is enlarged. As shown in (c), the smaller the aperture diameter (small aperture state), the more easily the influence of diffraction.

  FIG. 9B shows a configuration in which an ND filter is attached to the aperture mechanism of FIG. The configuration is such that an ND filter is inserted as FNO is increased (squeezed). When an ND filter is provided in the optical path as in the prior art, the influence of diffraction can be avoided by reducing the amount of light incident on the image pickup device when the ND filter enters the optical path while maintaining the aperture opening. However, in addition to the need for a filter switching mechanism, the optical performance deterioration due to the optical path length difference due to the thickness of the ND filter and the surface accuracy error of the ND filter may be considered.

  On the other hand, in this embodiment, the dome cover has an ND filter function, and the dome cover of the EC element is electrically turned on / off according to the imaging conditions. Specifically, the transmittance control of the EC element is performed when the influence of diffraction in the small aperture state is considered, and the transmittance control of the EC element is not performed when the influence of diffraction is not considered. .

  That is, in FIG. 10 showing the present embodiment, the light amount adjustment is performed by the transmittance control by the dome cover 71 constituted by EC elements and the control of the aperture diameter of the aperture stop 74. The aperture stop diameter is determined by changing the size of the opening 78 by the stop blade 77 as shown in the stop controller 76. For example, up to a range where the diffraction effect of the small aperture does not occur, only the aperture control mechanism 75 controls to reduce the aperture diameter, and when the light amount adjustment (squeezing) is necessary, the aperture control unit 75 does not perform the adjustment. The light amount is adjusted by the dome cover 71.

  FIG. 11 shows a flow of transmittance control in the camera body of the present embodiment. In the present embodiment, when it is determined that the amount of light is insufficient based on the luminance information of the luminance measuring unit 22, the shutter speed setting for proper exposure is performed. When it is determined that the amount of light is sufficient, the aperture diameter is determined, and when it is necessary to reduce the aperture to a level where the influence of diffraction is required, transmittance control is performed. If it is not necessary to reduce the diffraction level to the level at which the influence of diffraction occurs, aperture control using the aperture is performed.

  Here, the light amount adjustment described above is a combination of both the dome cover and the aperture control. However, the light amount may be adjusted (controlled) only by controlling the transmittance of the dome cover. By doing so, the aperture control mechanism in the imaging apparatus can be omitted, which can be advantageous in terms of durability and miniaturization.

  Specific conditions for obtaining more effects regarding the transmittance control in the present embodiment will be described below. In this embodiment, when DNo is the density of the dome cover as the dynamic range of transmittance control, adjustment within the following conditional expression range is possible.

0 <DNo <3.0 (A)
However, the transmittance T when the density is [DN_No] is as follows.

T = 10 ^ (-DNo) ("^" is a power)
This is a condition for adjusting the transmittance from a range of 100% (a state where density control is not performed) to a range of 0.1%. Any transmittance in this range is varied by controlling the EC element of the dome cover.

  Furthermore, when color balance is considered, wavelength dependency is also required. In other words, in the present embodiment, when the transmittance control is performed, the spectral ratio is maintained under a certain condition, and the transmittance is changed so as not to impair the color balance. If this is expressed by a conditional expression, the concentration at the wavelength λ is changed from Dno to Dno ′ (Dno <Dno ′), and the transmittance at the wavelength λ is set to Tλ (Dno) and Tλ (Dno ′), respectively. Make sure that:

0.7 <Xλ / Xλ ′ <1.3 (B)
However, Xλ = Tλ (Dno) / Tλ (Dno ′)
Xλ ′ = Tλ ′ (Dno) / Tλ ′ (Dno ′)
(Λ and λ ′ are arbitrary wavelengths in the range of 400 nm to 700 nm)
As described above, in this embodiment, the dome cover has characteristics equivalent to those of the ND filter, and a configuration in which a small aperture state can be avoided can be obtained, thereby obtaining good optical performance.

(Modification)
As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary. And it is good also as a structure which combined suitably each technical matter (component) demonstrated as different embodiment.

(Modification 1)
In the above-described embodiment, an EC element that reversibly controls the amount of light transmission is shown as a physical element that controls transmittance. However, the present invention is not limited to this, and an element having a function corresponding thereto, for example, An element that irreversibly controls the amount of light transmission may be used.

(Modification 2)
In the embodiment described above, the cover for the imaging device has a dome shape. However, the present invention is not limited thereto, and may be a box shape (a rectangular parallelepiped shape), for example.

(Modification 3)
Further, in the above-described embodiment, as an imaging device in which the camera body is rotated in at least one of the pan direction and the tilt direction, filter switching, etc., except for a mechanical movable unit for the pan direction and the tilt direction. An imaging apparatus capable of imaging without using a mechanical movable part is shown. However, the present invention is not limited to this, and an imaging device that can capture an image without using a mechanical movable part such as filter switching (for example, by increasing the angle of view and panning) is also possible. The imaging device may be fixed without moving in the direction or tilt direction.

(Modification 4)
In the above-described embodiments, the variable focus lens (zoom lens) is shown as the image pickup optical system. However, a fixed focus lens may be used, and the image pickup optical system is not limited to the transmission type optical system but a reflection type optical system. It can also be used.

(Modification 5)
Further, the surface of the dome cover having the above-described transmittance control characteristics (or on the EC element surface) may be coated to improve the transmittance.

(Modification 6)
Further, as a procedure for adjusting the light amount in the third embodiment, a method of alternately using the control of the aperture control unit 75 and the control of the dome cover 71 may be used.

14 .... Camera body, 15 .... Dome cover, 28..Image sensor, 34, 35..Imaging optical system

Claims (14)

An imaging unit comprising an imaging optical system;
A mechanically movable part that enables the orientation of the imaging part to be changed;
A surveillance camera having a cover for accommodating the imaging unit,
The imaging unit can change the direction inside the cover,
At least a part of the cover is configured using a transmittance variable element for controlling the amount of light transmitted through the imaging optical system, and the amount of light transmitted through the imaging optical system is applied to the transmittance variable element. A surveillance camera characterized by being controlled by changing a voltage. The surveillance camera according to claim 1, wherein the variable transmittance element is an electrochromic element. When the maximum transmittance of the electrochromic device with respect to light having a wavelength of 400 nm to 700 nm is Tλmax and the minimum transmittance is Tλmin,
1.4 <Tλmax / Tλmin
The surveillance camera according to claim 2, wherein the following conditional expression is satisfied. The surveillance camera according to claim 1, further comprising an infrared cut filter arranged in an optical path of the imaging optical system. The surveillance camera according to any one of claims 1 to 4, wherein the transmittance variable element has a light transmittance that changes in accordance with a wavelength of light incident on the transmittance variable element. The imaging is executed by an imaging mode in which an infrared component of imaging light transmitted through the imaging optical system is reduced by applying a voltage to the transmittance variable element, and an imaging mode in which the infrared component is not reduced. The surveillance camera according to claim 5. When the spectral transmittance of the transmittance variable element for light with a wavelength of 550 nm is T_IRC (550) and the spectral transmittance of the transmittance variable element for light with a wavelength of 600 nm is T_IRC (600),
0.6 <T_IRC (600) / T_IRC (550) <0.9
The surveillance camera according to claim 5 or 6, wherein the following conditional expression is satisfied. When the spectral transmittance of the transmittance variable element for light with a wavelength of 550 nm is T_IRC (550) and the spectral transmittance of the transmittance variable element for light with a wavelength of 650 nm is T_IRC (650),
0.2 <T_IRC (650) / T_IRC (550) <0.5
The surveillance camera according to claim 5, wherein the following conditional expression is satisfied. When the spectral transmittance of the transmittance variable element for light with a wavelength of 550 nm is T_IRC (550) and the spectral transmittance of the transmittance variable element for light with a wavelength of 700 nm is T_IRC (700),
T_IRC (700) / T_IRC (550) <0.15
The surveillance camera according to claim 5, wherein the following conditional expression is satisfied. The surveillance camera according to claim 1, further comprising an aperture stop disposed in an optical path of the imaging optical system. The monitoring camera according to claim 10, wherein the amount of light transmitted through the imaging optical system is reduced by applying a voltage to the transmittance variable element in a state where the aperture of the aperture stop is set to a predetermined size. Measuring means for measuring the brightness of the surrounding environment of the monitoring camera ;
Control means for controlling the amount of light transmitted through the imaging optical system according to the luminance measured by the measurement means;
The surveillance camera according to claim 1, comprising: The surveillance camera according to claim 1, wherein the cover is a dome cover. A cover that houses an imaging unit including an imaging optical system and a surveillance camera having a mechanical movable unit that can change the orientation of the imaging optical system , at least a part of the cover being transmissive to the imaging optical system The amount of light transmitted through the imaging optical system is controlled by changing a voltage applied to the transmittance variable element. cover.