Description

Title of Invention: DOME CAMERA

Technical Field [0001]

The present invention relates to a dome camera including a dome cover for covering a camera lens.

Background Art [0002]

A dome camera is used as a surveillance camera or the like. In such a surveillance camera, a camera lens is covered by a dome cover, and the camera lens is protected by the dome cover. Also, a general surveillance camera includes a pan tilt function (a function of rotating a camera lens in a pan direction and a tilt direction) and a zoom function.

[0003]

A conventional dome camera includes a hemispherical dome cover, and the center of rotation of a camera lens is arranged to be on the optical axis and to coincide with the center of the dome cover. It is known that a good image is obtained according to this arrangement.

[0004]

However, according to the arrangement of the camera lens as described above, when capturing an image in a direction at a large tilt angle (a direction near the horizontal direction), vignetting occurs, and a good image is not obtained. Accordingly, a technique of offsetting the camera lens from the center of the dome cover in a zenith direction is conventionally proposed (for example, see Patent Literatures 1 and 2).

[0005]

By offsetting the camera lens in the zenith direction of the dome cover, capturing of an image in a direction at a large tilt angle (a direction near the horizontal direction) is enabled without the vignetting occurring.

[0006]

However, with a conventional dome camera, since the camera lens is offset from the center of the dome cover, aberration due to a lens effect of the dome cover occurs, and the image quality is deteriorated due to this aberration. That is, in the case of capturing an image in a direction at a large tilt angle (a- direction near the horizontal direction), securing of a wide field of view and reduction in the image quality deterioration are in the relationship of tradeoff, and it is extremely difficult to achieve both of the two.
Citation List Patent Literature

[0007]

Patent Literature 1: Japanese Patent Application Laid-Open No. 2005-300659

Patent Literature 2: Japanese Patent Application Laid-Open No. 2005-221637
Summary of Invention Technical Problem

[0008]

The present invention is made in view of the background described above. The object of the present invention is to provide a dome camera capable of achieving both securing of a wide field of view and reduction in the image quality deterioration in a case of capturing an image in a direction at a large tilt angle (a direction near the horizontal direction).
Solution to Problem

[0009]

One mode of the present invention is a dome camera, and this dome camera includes a camera lens capable of rotating in a tilt direction, a dome cover for covering the camera lens, and filter insertion means for inserting a polarizing filter or a partially darkening filter on an optical axis of the camera lens as a tilt angle of the camera lens whose tilt rotation axis is positioned more in a zenith direction than a center position of the dome cover becomes larger than a predetermined threshold angle.

[0010]

As will be described below, the present invention includes other modes. Thus, the disclosure of the invention intends to provide some modes of the present invention, and does not intend to limit the scope of the invention described and claimed herein.

Brief Description of Drawings

[0011]

[Figure 1] Figure 1 is an explanatory diagram of a dome camera according to a first embodiment (tilt angle: large) .

[Figure 2] Figure 2 is an explanatory diagram of the dome camera according to the first embodiment (tilt angle: small).

[Figure 3] Figure 3 is a perspective view of a lens unit according to the first embodiment (polarizing filter: inserted position).

[Figure 4] Figure 4.is a perspective view of the lens unit according to the first embodiment (polarizing filter: retracted position).

[Figure 5] Figure 5 is a perspective view of a lens unit according to a modified example of the first embodiment (darkening filter: inserted position).

[Figure 6] Figure 6 is a diagram of relationships of a tilt angle to the amount of offset and insertion/non-insertion of a filter according to the first embodiment.

[Figure 7] Figure 7 is a diagram of a relationship between a zoom factor and insertion/non-insertion of a filter according to the first embodiment.

[Figure 8] Figure 8 is a diagram of a relationship between a zoom factor and insertion/non-insertion of a filter according to a modified example of the first embodiment.

[Figure 9] Figure 9 is an explanatory diagram of a filter insertion area according to the first embodiment.

[Figure 10] Figure 10 is a perspective view of a camera unit according to a second embodiment.

[Figure 11] Figure 11 is a front view of the camera unit according to the second embodiment (polarizing filter inserted position).

[Figure 12] Figure 12 is a front view of the camera unit according to the second embodiment (infrared cut filter inserted position).

[Figure 13] Figure 13 is a front view of the camera unit according to the second embodiment (optical glass inserted position).

[Figure 14] Figure 14 is a perspective view of a filter switching mechanism according to a modified example of the second embodiment.

[Figure 15] Figure 15 is a perspective view of the filter switching mechanism according to the modified example of the second embodiment (at a time of polarizing filter insertion).

Description of Embodiments [0012]

A detailed description of the present invention is given below. However, the detailed description and the appended drawings are not to limit the invention.

[0013]

A dome camera of the present invention is configured to include a camera lens capable of rotating in a tilt direction, a dome cover for covering the camera lens, and filter insertion means for inserting a polarizing filter or a partially darkening filter on an optical axis of the camera lens as a tilt angle of the camera lens whose tilt rotation axis is positioned more in a zenith direction than a center position of the dome cover becomes larger than a predetermined threshold angle.

[0014]

According to this configuration, when the tilt angle of the camera lens becomes large, a polarizing filter or a partially darkening filter (a darkening filter by which incident light is partially blocked) is inserted on the optical axis of the camera lens. With the polarizing filter or the partially darkening filter, the image quality may be prevented from deteriorating due to offsetting of the camera lens. Accordingly, securing of a wide field of view and reduction in the image quality deterioration may both be achieved in the case of capturing an image in a direction at a large tilt angle
(a direction near the horizontal direction).

[0015]

Also, according to the dome camera of the present invention, the partially darkening filter may include a blocking area that blocks half of a field of view of the camera lens, and the blocking area may be set across half a range on an opposite side of the zenith direction of the dome cover.

[0016]

According to this configuration, in the case of capturing an image in a direction at a large tilt angle (a direction near the horizontal direction), light is blocked by the blocking area of the partially darkening filter on half the range on the opposite side of the zenith direction of the dome cover. The range where light is blocked is assumed to correspond to a part where the molding precision of the dome cover is not very high and which causes deterioration of the image quality. By blocking light at this part, deterioration of the image quality can be suppressed.

[0017]

Also, according to the dome camera of the present invention, the camera lens may include a zoom function, and when a zoom factor of the camera lens is within a range of factors on a TELE-end side greater than a predetermined threshold factor, the filter insertion means may insert the polarizing filter or the partially darkening filter on the optical axis of the camera lens.

[0018]

According to this configuration, when the zoom factor of the camera lens is set on the TELE-end side, the polarizing filter or the partially darkening filter is inserted on the optical axis of the camera lens, and the image quality may be prevented, by the polarizing filter or the partially darkening filter, from deteriorating due to the offset of the camera lens. Additionally, when the zoom factor of the camera lens is set on a WIDE-end side, the image quality is not so deteriorated, and in this case, the polarizing filter or the partially darkening filter does not have to be inserted regardless of the tilt angle of the camera lens.

[0019]

Furthermore, according to the dome camera of the present invention, the polarizing filter or the partially darkening filter may be inserted in front of the camera lens.

[0020]
According to this configuration, the polarizing filter or the partially darkening filter is inserted in front of the camera lens, and light before entering the camera lens is polarized by the polarizing lens or is partially blocked by the partially darkening filter. That is, light which has been polarized by the polarizing lens or light which has been partially blocked by the partially darkening filter enters the camera lens. Deterioration of the image quality due to the offset of the camera lens may thereby be suppressed.

[0021]

Moreover, according to the dome camera of the present invention, the polarizing filter may be inserted in front of an image sensor using switching means for an infrared cut filter and an optical glass.

[0022]

According to this configuration, the polarizing filter may be inserted using the switching means for an infrared cut filter and an optical glass. By using a mechanism already provided (the switching mechanism for an infrared cut filter and an optical glass) , the number of parts may be reduced compared to a case of separately providing a dedicated mechanism, and the manufacturing cost may be reduced and miniaturization is enabled.

[0023]
According to the present invention, in the case of capturing an image in a direction at a large tilt angle (a direction near the horizontal direction), both securing of a wide field of view and reduction in the image quality deterioration may be achieved.

[0024]

Hereinafter, the dome camera of an embodiment of the present invention will be described with reference to the drawings. In the present embodiment, a case of a dome camera which is used as a surveillance camera or the like is illustrated.

0025]

(First Embodiment)

A configuration of a dome camera of a first embodiment of the present invention will be described with reference to the drawings. Figures 1 and 2 are explanatory diagrams of the dome camera of the present embodiment. Figures 3 and 4 are perspective views of a lens unit of the dome camera of the present embodiment.

[0026]

As shown in Figures 1 and 2, a dome camera 1 includes a base 2 to be attached to a ceiling, a wall or the like, and a dome cover 3 to be attached to the base 2. A lens unit 5 including a camera lens 4 is provided inside the dome cover 3. The lens unit 5 is accommodated inside a housing configured from the base 2 and the dome cover 3, and the camera lens 4 is covered by the dome cover 3. This camera lens 4 includes a zoom function.

[0027]
A pan motor and a tilt motor are provided to the dome camera 1, and the lens unit 5 (the camera lens 4) is capable of rotating in a pan direction and a tilt direction by the driving forces of the pan motor and the tilt motor. The operation of these motors (the pan motor, the tilt motor) is controlled by a control unit such as a microcomputer.

[0028]

As shown in Figures 3 and 4, a polarizing filter 6 is provided to the lens unit 5. The polarizing direction of the polarizing filter 6 is a vertical direction (a height direction) or a horizontal direction (a lateral direction). A support member 8 having an arc-shaped guide portion 7 extends from an upper portion of the polarizing filter 6. Two guide pins 9 are provided in a protruding manner on each of the left and right sides of the arc-shaped guide portion 7. A left and right pair of guide plates 10 is provided at an upper portion of the lens unit 5. The guide portion 7 of the support member 8 is sandwiched by the left and right pair of guide plates 10, and the guide pins 9 are inserted, in a slidable manner, in an arc-shaped slot 11 provided to the guide plates 10.

[0029]

Then, when the guide pins 9 slide in the slot 11 of the guide plates 10, the polarizing filter 6 moves in a reciprocating manner between an inserted position (a position of the polarizing filter 6 inserted in front of the camera lens 4, as shown in Figure 3) and a retracted position (a position of the polarizing filter 6 retracted from in front of the camera lens 4, as shown in Figure 4). A motor for a filter is provided to the dome camera 1, and the polarizing filter 6 is enabled to move between the inserted position and the retracted position by the driving force of the motor for a filter. The operation of the motor for a filter is also controlled by a control unit such as a microcomputer.

[0030]

A modified example of the lens unit 5 of the present embodiment is shown in Figure 5. In this modified example, a partially darkening filter 12 is used instead of the polarizing filter 6. The partially darkening filter 12 is a darkening filter that partially blocks incident light. In this case, as shown in Figure 5, the partially darkening filter 12 has a blocking area 13 that blocks half of the field of view of the camera lens 4. This blocking area 13 is set across half the range on the opposite side of the zenith direction of the dome cover 3 (the lower side in Figure 5).

[0031]

Next, an operation of the dome camera 1 of the first embodiment configured in the above manner will be described with reference to the drawings.

[0032]

Figure 6 is a diagram showing, with respect to the dome camera 1 of the present embodiment, a relationship between a tilt angle and the amount of offset and a relationship between the tilt angle and insertion/non-insertion of a filter.

[0033]

Here, the zenith direction of the dome cover 3 serves as the reference for the tilt angle of the camera lens 4. That is, when the camera lens 4 faces the zenith direction of the dome cover 3, the tilt angle is 0 degrees, and when the camera lens 4 faces the horizontal direction, the tilt angle is 90 degrees. Accordingly, the tilt angle becomes smaller as the camera lens 4 is moved toward the zenith direction of the dome cover 3, and the tilt angle becomes larger as the camera lens 4 is moved from the zenith direction toward the horizontal direction.

[0034]
In this case, the amount of offset x is dependent on a tilt angle 9. When the amount of shift between a center P1 of the dome cover 3 and a tilt rotation axis P2 is given as x'0, the amount of offset x is given by the formula below (see Figures 2 and 6).
x = x0 x sinθ

[0035]

Additionally, here, a case is described where the amount of offset x is dependent on the tilt angle 6, as shown in Figure 6, but the scope of the present invention is not limited to such, and the amount of offset may be changed by moving the tilt rotation axis P2 in the zenith direction when the tilt angle becomes greater than 75 degrees, for example.

[0036]

Furthermore, in the present embodiment, when the tilt angle of the camera lens 4 is in a range of 0° to 9s, the polarizing filter 6 is not inserted (the polarizing filter 6 stays at the retracted position). When the tilt angle of the camera lens 4 exceeds 9s, the polarizing filter 6 is inserted (the polarizing filter 6 moves to the inserted position). Here, the tilt angle 9s corresponds to the threshold angle of the present invention. Additionally, the threshold angle 9s may be set to any value according to the use, installation environment of the like of the dome camera.

[0037]

Figure 7 is a diagram showing, with respect to the dome camera 1 of the present embodiment, a relationship between a zoom factor and insertion/non-insertion of a filter. As shown in Figure 7, when the zoom factor is within a range of lx to l0x (a range on a WIDE-end side), the polarizing filter 6 is not inserted (the polarizing filter 6 stays at the retracted position). When the zoom factor enters a range over lOx (a range on a TELE-end side), the polarizing filter 6 is inserted (the polarizing filter 6 is moved to the inserted position). Here, the zoom factor of lOx corresponds to the threshold factor of the present invention.

[0038]

Additionally, the polarizing filter 6 is inserted when the tilt angle is within a large tilt angle range (a range exceeding 75 degrees) and the zoom factor is within the range on the TELE-end side (the range exceeding 10x). That is, even if the tilt angle is within the large tilt angle range (for example, when the tilt angle is 90 degrees), if the zoom factor is within the range on the WIDE-end side, the polarizing filter 6 is not inserted.

[0039]

Figure 8 shows a modified example of control of filter insertion with respect to the zoom factor. As shown in Figure 8, control of filter insertion may be performed with a predetermined hysteresis band. For example, when the zoom factor changes from a small value (a value near the WIDE end) to a large value (a value near the TELE end) , the polarizing filter 6 may be inserted at a first threshold factor z1, and when the zoom factor changes from a large value (a value near the TELE end) to a small value (a value near the TELE end), the polarizing filter 6 may be retracted at a second threshold factor z2 (zl