JP2004343614A - Filter switching mechanism for video camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filter switching mechanism for a video camera capable of imaging a color video image by placing an infrared ray cut filter coaxially with an imaging direction in the case of ordinary illuminance and imaging a black/white video image by removing the infrared ray cut filter from on the optical path at low illuminance. <P>SOLUTION: The filter switching mechanism is characterized in that the mechanism is provided with a spatial filter 19 or the infrared ray cut filter 20 supported by a filter holder 18 coaxially depositable in an imaging direction, a first yoke 21 located at an outer circumference of the turning filter switching mechanism, a coil 24 is wound and fixed orthogonally to the first yoke 21, a power supply 24 supplies a drive current to the coil 24, an end of a second yoke 23 provided in parallel with the first yoke 24 is connected to the first yoke 24, and a magnet 22 is provided onto the second yoke 23 in opposition to the first yoke 24. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
According to the present invention, the sensitivity is increased by arranging an infrared cut filter on the optical path at normal illuminance and capturing an image in a color image, and removing the infrared cut filter from the optical path and capturing an image in black and white image at a low illuminance. And a filter switching mechanism of the video camera.
[0002]
[Prior art]
In a conventional video camera, an infrared cut filter and a low-pass filter are arranged on the optical path of the camera, that is, coaxially with the imaging direction of the imaging device. By arranging the infrared cut filter on the optical path, it is possible to cut the light in the infrared region that cannot be seen by human eyes, and to maintain the balance of the color image. Further, by arranging the low-pass filter on the optical path, it is possible to prevent the occurrence of moire in an image.
[0003]
[Patent Document 1]
JP-A-11-72689 (FIG. 1)
[0004]
[Problems to be solved by the invention]
In a conventional video camera, an infrared cut filter is always arranged coaxially with an imaging direction on the assumption that an image is captured in a color image. However, in the case of low illuminance, it is desirable to capture an image in black and white video using light of infrared wavelengths effectively. That is, in the configuration of the related art, there is a problem that the infrared cut filter cannot be inserted / removed with the switching of the image type.
[0005]
The present invention has been made to solve the above-described problems, and provides a filter switching mechanism that removes an infrared cut filter from the optical path, so that the infrared cut filter is coaxial with the imaging direction at normal illuminance. It is an object of the present invention to obtain a filter switching mechanism of a video camera which can be arranged and picked up with a color image, removes an infrared cut filter from an optical path at low illuminance, and picks up a black and white image.
[0006]
[Means for Solving the Problems]
A filter switching mechanism for a video camera according to the present invention includes a rotating shaft provided in parallel with the imaging direction of the video camera, a rotating unit rotating about the rotating shaft, and a filter held by the rotating unit coaxial with the imaging direction. A first yoke provided on the outer periphery of the rotating portion, a coil portion wound and fixed orthogonal to the first yoke portion, and a drive current supplied to the coil portion. A power supply section, a second yoke section provided in parallel with the first yoke section and having an end connected to the first yoke section, and a magnet provided on the second yoke section to face the first yoke section. And a stop unit for abutting the rotation of the rotating unit to arrange the filter coaxially with the imaging direction.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
First Embodiment of the Invention
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an external view of a video camera having a filter switching mechanism according to Embodiment 1 of the present invention. FIG. 2 is an exploded perspective view of the video camera shown in FIG. The camera 1 includes a main body 2, a camera head mounting plate 3, an imaging unit 4, a front chassis 5, a flange back adjustment screw 6, a spring 7, an E-ring 8, a lens 9, and a lens cover 10.
[0008]
FIG. 3 is an exploded perspective view of the imaging unit 4 shown in FIG. The imaging unit 4 includes an imaging element substrate 11, an imaging element 12, a low-pass filter 13, an imaging element substrate mounting screw 14, a filter switching unit 15, a cover 16, and a cover mounting screw 17. The low-pass filter 13 is attached to the image sensor 12 by bonding.
[0009]
The filter switching unit 15 further includes a filter holder 18, a spatial filter 19, an infrared cut filter 20, a first yoke 21, a magnet 22, a second yoke 23, a coil 24, a coil holder 25, a coil substrate 26, and a coil connected to a power supply. It is composed of a power cable 27. The spatial filter 19 and the infrared cut filter 20 are fixed to the filter holder 18 and the coil 24 is fixed to the coil holder 25, respectively. The lead wire of the coil 24 is electrically connected to a coil power cable 27 via a coil board 26, and the coil 24 is supplied with power through the coil power cable 27.
[0010]
The filter holder 18 is rotatably supported by a filter shaft 15a serving as a rotation shaft, and provided with stoppers 15b and 15c so as to stop at a fixed position. The first yoke 21 passes through the coil 24, and the first yoke 21, the magnet 22, the second yoke 23, and the coil 24 constitute a voice coil motor (hereinafter, referred to as VCM). When a current flows through the coil 24 in this state, the filter holder 18 rotates clockwise or counterclockwise according to the direction of the current, and comes into contact with the stopper 15b or 15c and stops. Even after the filter holder 18 abuts against the stopper 15b or 15c and stops, the current continues to flow through the coil 24, whereby the filter holder 18 is pressed against the stopper 15b or 15c and held at the stop position.
[0011]
FIG. 4 is an explanatory diagram showing the principle of VCM. 24a is a power supply. When a magnetic circuit is configured by the first yoke 21, the magnet 22, and the second yoke 23, a magnetic field is generated in the direction of the arrow in the figure. When a current is applied to the coil 24 in the direction of the arrow, a force is generated in the first yoke 21, the magnet 22, and the second yoke 23 in the direction of the arrow according to Fleming's left-hand rule. When a current flows in the opposite direction, a force is generated in the direction opposite to the arrow. As a result, the filter holder 18 rotates right and left around the filter shaft 15a.
[0012]
FIG. 5 is a block diagram of the filter switching mechanism according to the first embodiment of the present invention. In the figure, 24b is a coil drive circuit, and 30 is a video processing circuit. When light enters the imaging device 12 through the lens 9, the video processing circuit 30 outputs a video signal and notifies the coil drive circuit 24b of brightness information of the video signal. Then, the coil drive circuit 24b determines whether the video signal to be output is a color video or a black-and-white video in accordance with the brightness of the video signal, instructs the video processing circuit 30 with a control signal, and sends the video signal to the coil 24. The direction of the current is determined, and the coil 24 is energized.
[0013]
FIG. 6 is a schematic diagram of an optical system of the camera 1. In the camera 1, the image sensor 12 is arranged coaxially with the lens 9, and the light condensed by the lens 9 is imaged on the image sensor 12. A low-pass filter 13 is arranged on the front surface of the image sensor 12 to prevent moiré from occurring in an image. A filter holder 18 is arranged between the lens 9 and the image sensor 12, and holds the spatial filter 19 and the infrared cut filter 20 in a switchable manner.
[0014]
Next, the operation will be described. The video processing circuit 30 notifies the coil drive circuit 24b of the brightness information of the video signal from the image sensor 12. Then, when the coil drive circuit 24b determines that the illuminance of the video signal is sufficiently high based on the brightness information, it outputs a control signal to the video processing circuit 30 to instruct the video processing circuit 30 to capture a color video. The coil drive circuit 24b supplies a current to the coil 24 in such a direction that the infrared cut filter 20 comes coaxially with the imaging direction of the image sensor 12. Thus, when the camera 1 captures a color image, the infrared cut filter 20 is inserted on the optical path to cut light in the infrared wavelength range that cannot be seen by human eyes, and It is possible to capture a color image while maintaining the color balance.
[0015]
If the coil drive circuit 24b determines that the illuminance of the video signal is low based on the brightness information, it outputs a control signal to the video processing circuit 30 to instruct the video processing circuit 30 to capture a monochrome video. The coil drive circuit 24b allows the coil 24 to supply a current in a direction such that the spatial filter 19 is coaxial with the imaging direction of the image sensor 12. Thus, when the camera 1 captures a monochrome image, the spatial filter 19 is inserted on the optical path. The spatial filter 19 has a function of adjusting the optical distance between the lens 9 and the imaging device 12 by appropriately setting the thickness and the refractive index. By inserting a properly set spatial filter 19 on the optical path, it is possible to keep the focus shift at the time of capturing a monochrome video image to a minimum.
[0016]
At this time, since the infrared cut filter 20 is out of the optical path, the light in the infrared wavelength range is not cut, the light amount to the image sensor 12 increases, and the sensitivity of the camera 1 increases. However, the color balance of the image is lost because of the addition of light in a wavelength range that cannot be seen by the camera, but this is not a problem because the camera 1 outputs a black-and-white image. Thereby, the camera 1 outputs a color image through the infrared cut filter 20 at the time of high illuminance, and outputs a black and white image through the spatial filter 19 at the time of low illuminance.
[0017]
As described above, in the present invention, a filter switching mechanism is provided in which the filter shaft 15a is provided in parallel with the imaging direction of the camera 1 and rotates about the filter shaft 15a. In the filter switching mechanism, the spatial filter 19 or the infrared cut filter 20 held by the filter holder 18 is provided so as to be coaxial with the imaging direction, and the coil 24 is provided on the outer periphery of the filter switching mechanism that rotates the first yoke 21. The power supply 24 supplies a drive current to the coil 24, the end of a second yoke 23 provided in parallel with the first yoke 24 is connected to the first yoke 24, and the magnet is fixed. 22 is provided on the second yoke 23 so as to face the first yoke 24, and the spatial filter 19 or the infrared cut filter 20 is arranged coaxially with the imaging direction by contact with the stopper 15b or the stopper 15c. Is realized with a simple structure.
[0018]
The reason why the VCM is used for the filter switching mechanism according to the present invention will be described. The camera 1 equipped with the present filter switching mechanism is rotated in a pan / tilt direction by a camera turntable (not shown). In addition, the camera 1 may shake up, down, left, and right due to vibration, impact, and the like at the installation location. Therefore, when the moving direction of the filter is the same as the pan / tilt direction or the vibration direction, the rotational moment force of the camera 1 is directly applied to the driving direction of the filter switching mechanism, and in some cases, the filter position is shifted. Also occurs. Therefore, it is desirable that the driving direction of the filter switching mechanism is arranged in the circumferential direction with respect to the optical path of the camera 1. Thereby, regardless of the attitude of the camera 1, no moment is generated in the driving direction of the filter switching mechanism even when acceleration is applied from the outside, so that the filter switching mechanism is less likely to be affected by vibration and impact.
[0019]
Further, if a filter switching mechanism similar to the present invention is to be constituted by a motor having a rotating shaft, it is necessary to dispose the motor and the optical path apart in order to remove the motor body from the optical path of the camera 1. Therefore, the diameter of the filter switching mechanism becomes large, so that the camera 1 body becomes large. Further, in order to reduce the size of the camera 1, a driving mechanism such as a gear for changing the rotation direction of the motor is separately required. Therefore, a VCM that does not require the drive mechanism and can rotate the filter holder 18 around the filter shaft 15a without using a small size is employed as the filter switching mechanism of the present invention.
[0020]
Further, in the filter switching mechanism according to the present invention, since the VCM is used as the drive source, even when the filter holder 18 is in contact with and locked by the stopper 15b or 15c, power consumption increases or vibration occurs. There is an advantage that you do not.
[0021]
Embodiment 2 of the invention
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. FIG. 7 is a schematic diagram of an optical system according to Embodiment 2 of the present invention. In the first embodiment of the invention, one low-pass filter 13 is disposed immediately before the imaging device 12 by bonding. However, the low-pass filters 13 a and 13 b may be integrally superimposed on the infrared cut filter 20 and the spatial filter 19. Good. By doing so, it is possible to easily replace only the image sensor 12.
[0022]
Embodiment 3 of the Invention
Hereinafter, a third embodiment of the present invention will be described with reference to the drawings. FIG. 8 is a schematic diagram of an optical system according to Embodiment 3 of the present invention. When the infrared cut filter 20 is sufficiently thin, the difference in the optical distance between the lens and the imaging device when the infrared cut filter 20 is inserted on the optical path and when it is not inserted can be ignored. In this case, by omitting the spatial filter 19, the filter switching mechanism of the video camera can be realized with a simpler structure.
[0023]
Embodiment 4 of the Invention
Hereinafter, a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 9 is a graph showing the drive current of the coil 24 and the angular velocity of the filter holder 18 used in the first embodiment of the present invention, for example. FIG. 10 is a graph showing the driving current of the coil 24 and the angular velocity of the filter holder 18 used in the fourth embodiment of the present invention. In the first embodiment of the present invention, in order to supply a constant current to the coil 24, the filter holder 18 keeps accelerating until the filter holder 18 contacts one of the stoppers 15b or 15c. There was a drawback that the collision sound was loud. The magnitude of the collision sound is proportional to the angular velocity when the filter holder 18 hits the stopper 15b or 15c.
[0024]
On the other hand, in the present embodiment, for example, a timer (not shown) is provided in the coil drive circuit 24b, and the timer sets the time until the filter folder 18 contacts one of the stoppers 15b and 15c. Then, as shown in FIG. 10, the drive current of the coil 24 until the filter folder 18 comes into contact with either the stopper 15b or 15c is pulsed. Accordingly, the filter holder 18 comes into contact with the stopper 15b or 15c at a substantially constant angular velocity, so that the collision noise can be relatively reduced.
[0025]
Further, in the filter switching mechanism according to the present invention, since no moment is generated in the driving direction of the filter switching mechanism even when external acceleration is applied as described above, the filter switching mechanism is not easily affected by vibration, impact, and the like. The required driving force is small, and the filter can be held at a predetermined position by continuously energizing the coil 24 with small power consumption. For this reason, in this embodiment, as shown in FIG. 10, the current value after the time set by the timer, that is, the current value after the filter folder 18 abuts on either the stopper 15b or 15c, is used as the filter holder. The value has been lowered to the value required to maintain 18. Thus, the filter holder 18 can be held with a smaller current as compared with the first embodiment, and power can be saved.
[0026]
【The invention's effect】
According to the present invention, a filter switching mechanism for a video camera includes a filter for providing a rotation axis parallel to an imaging direction of the video camera, rotating a rotation unit about the rotation axis, and holding a filter holder unit on the rotation unit. Is provided so as to be coaxial with the imaging direction, a first yoke portion is provided on an outer periphery of the rotating portion, a coil portion is wound and fixed orthogonal to the first yoke portion, and a power supply unit supplies a drive current to the coil unit. And a second yoke portion having an end connected to the first yoke portion and the first yoke portion are provided in parallel with each other, and a magnet portion is provided on the second yoke portion so as to face the first yoke portion. Since the stop unit abuts the rotation of the rotating unit and abuts the filter coaxially with the imaging direction by abutting, the driving direction of the filter switching mechanism is also possible when external vertical and horizontal acceleration is applied regardless of the orientation of the video camera. To mo Cement is not generated, there is an effect capable of providing vibration, less susceptible filter switching mechanism the effect of impact.
[Brief description of the drawings]
FIG. 1 is an external view of a video camera having a filter switching mechanism according to a first embodiment of the present invention.
FIG. 2 is an exploded perspective view of the video camera shown in FIG.
FIG. 3 is an exploded perspective view of the imaging unit 4 shown in FIG.
FIG. 4 is an explanatory diagram showing the principle of VCM.
FIG. 5 is a block diagram of a filter switching mechanism according to the first embodiment of the present invention.
FIG. 6 is a schematic diagram of an optical system of the camera 1.
FIG. 7 is a schematic diagram of an optical system according to a second embodiment of the present invention.
FIG. 8 is a schematic diagram of an optical system according to Embodiment 3 of the present invention.
FIG. 9 is a graph showing a driving current of a coil and an angular velocity of a filter holder used in the first embodiment of the present invention.
FIG. 10 is a graph showing a driving current of a coil 24 and an angular velocity of a filter holder 18 used in Embodiment 4 of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Camera 2 Main body 4 Image sensor unit 9 Lens 12 Image sensor 13 Low-pass filter 15 Filter switching unit 15a Filter shafts 15b, 15c Stopper 18 Filter holder 19 Spatial filter 20 Infrared cut filter 21 First yoke 22 Magnet 23 Second yoke 24 Coil 24a power supply 24b coil drive circuit 27 coil power cable 30 video processing circuit

Claims (6)

A rotation axis provided in parallel with the imaging direction of the video camera,
A rotating unit that rotates about the rotation axis,
A filter holder unit provided so that the filter held by the rotating unit can be arranged coaxially with the imaging direction,
A first yoke portion provided on an outer periphery of the rotating portion;
A coil portion wound and fixed orthogonal to the first yoke portion;
A power supply unit for supplying a drive current to the coil unit;
A second yoke portion provided in parallel with the first yoke portion and having an end connected to the first yoke portion;
A magnet portion provided on the second yoke portion so as to face the first yoke portion;
A filter switching mechanism for a video camera, comprising: a stop for rotating the rotation unit so that the filter is arranged coaxially with an imaging direction by abutting the rotation of the rotation unit. 2. The filter holder according to claim 1, wherein the filter holder holds the infrared cut filter and the spatial filter, and, when the filter holder is stopped at a stop portion by abutment, any one of the filters is arranged coaxially with the imaging direction. The video camera filter switching mechanism. 3. A video camera filter switching mechanism according to claim 2, wherein a low-pass filter is superposed on both the infrared cut filter and the spatial filter. The filter holder holds a thin infrared cut filter that can ignore the distance between the lens of the video camera and the image sensor. 3. The video camera filter switching mechanism according to claim 1, wherein: 5. The video camera according to claim 1, wherein a time until the rotating unit stops at the stop unit is set by a timer, and the driving current during the time is pulsed. Filter switching mechanism. The time until the rotating unit stops at the stop unit is set by a timer, and thereafter, the driving current from the power supply unit is reduced to a predetermined value, and the driving current is reduced to a predetermined value. 3. The filter switching mechanism for a video camera according to item 1.

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