An X-ray imaging apparatus is useful in examining VISCUS of a human body or the interior of an object. X-rays radiated to a human body or an object are detected as an X-ray transmission concentration distribution, i.e., an X-ray image, and this X-ray image is converted into a visible-light image. The visible-light image is further converted into electric image signals, and the X-ray transmission concentration distribution or the X-ray image is displayed on a monitor or the like in real time. Image information is stored in a storage of a computer or the like, for later use.
An X-ray imaging apparatus is provided with: an X-ray generator for generating X-rays; an X-ray image intensifier for intensifying and converting an X-ray image, i.e., the X-rays which are output from the X-ray generator and have passed through an object, into a visible-light image; and a monitor device for displaying an output image which is a visible image obtained by conversion by the X-ray image intensifier. The monitor device can display the output image in real time, since it uses a camera that images the output image of the X-ray image intensifier and outputs electric image signals.
X-rays radiated from the X-ray generator pass through an object and are incident on the X-ray image intensifier in the form of an X-ray image. This X-ray image is first intensified by the X-ray image intensifier and is then converted into a visible-light image. This visible-light image is displayed on the output surface of the X-ray image intensifier as an output image.
The output image on the output surface of the X-ray image intensifier is projected through a lens on the imaging surface of the imaging device of the camera. The image projected on the imaging surface of the imaging device is converted into electric image signals by the imaging device, and is displayed on the monitor device.
In the X-ray imaging apparatus, the imaging device, including the X-ray image intensifier and the camera which are arranged to oppose the X-ray generator, with the object located therebetween, is revolved around the object in an arbitrary direction and moved to an arbitrary position.
In this type of X-ray imaging apparatus, the camera has to be revolved around the object in the opposite direction so that the observer can rotate the image in an arbitrary direction, for the correction of the image direction.
In the above X-ray imaging apparatus, the camera can be revolved, for example, in the following method. A board, on which the camera is mounted along with a circuit for driving the camera and a signal circuit for processing video signals output from the camera, is fixed to a disk-shaped flange. Then, this flange is fixed to a lens support frame secured to the X-ray image intensifier by means of a bearing. In this manner, the camera is allowed to revolve relative to the X-ray image intensifier.
However, this method is disadvantageous in that the signal lines and power supply lines led from the board may be easily twisted when the camera incorporating the imaging device is revolved. In this case, the angle of revolution of the camera must be restricted so as to prevent the signal lines and power supply lines from being twisted. During the observation of the object, therefore, the camera may have to be revolved in the opposite direction so as to move the camera to the intended revolving position, which lengthens the time needed for observation.
FIG. 15 is a schematic illustration showing an example of a presently-available X-ray imaging apparatus capable of rotating an image.
As shown in FIG. 15, the X-ray imaging apparatus 101 comprises: an X-ray image intensifier 111 for intensifying and converting an X-ray image, i.e., X-rays output from the X-ray generator and passing through an object to be imaged, into a visible-light image; and a camera 121, i.e., an imaging device, for imaging the output image produced on the output surface and converting the output image into image signals, thereby enabling a video image to be displayed on a monitor device (not shown).
A support frame 123a is secured on the output side of a housing 115 in which the X-ray image intensifier 111 is arranged.
The camera 121 is made up of: a lens 123 supported by means of the support frame 123a and spaced from the output image 114 of the X-ray image intensifier 111 by a predetermined distance; a CCD imaging device 127 having a disk shape and positioned at the image focus position on a rotatable circuit board 125; a motor 129 for rotating the circuit board 125; and a signal transmission mechanism 131 for transmitting output signals of the imaging device 127, which are sent thereto from the circuit board 125, to an external circuit, and for applying driving power to the imaging device 127. By the circuit board 125, the imaging device 127 is allowed to revolve around the central axis A of a visible-light image transmitted through the lens 123. The circuit board 125 is rotatably held by support frame 125a fixed to the support frame 123a.
The signal transmission mechanism 131 includes: a gear 133 for revolving the imaging device 127 and circuit board 125 in such a manner that the center of the visible-light image output from the lens 123 coincides with the axis of revolution; an electrode drum 137 which is coaxial with the support frame 125a, is supported by a bearing 135 to be rotatable with reference to an auxiliary frame 125b inserted into the support frame 125a, and permits the output signal from the imaging device 127 to be led to an external circuit; and a plurality of brushes 139 which are fixed to the auxiliary frame 125b of the cylindrical support frame 125a and electrically connect ring electrodes 136 of the electrode drum 137 to the signal lines and power supply lines. The electrode drum 137 is coaxial with the center of rotation on which the circuit board 125 and gear 133 are rotated, i.e., with the central axis A of the visible-light image output from the lens 123.
In the X-ray imaging apparatus 101 shown in FIG. 15, the output signals of the imaging device 127, which are output by way of the circuit board 125, are sent to an external device (not shown) by means of the electrode drum 137 and brushes 139 of the signal transmission mechanism 131.
With this structure, the signal lines and power supply lines attached to the circuit board 125 do not impose any limit on the angle of revolution of the imaging device 127.
In the apparatus shown in FIG. 15, however, the electrode drum 137 is used. Due to the use of this drum, the camera 121 is inevitably long in the direction of the axis around which the camera 121 is revolved.
In addition, the image formed by the camera 121 must be displayed in the center of the display screen without reference to the position of revolution of the camera 121. Since the center of the image which the lens 123 forms based on the output image 114 of the X-ray image intensifier 111 must coincide with the center of the imaging surface of the imaging device 127, the axis of revolution defined by the revolution of the imaging device 127 and the center of the imaging surface of the imaging device 127 must coincide with each other. Further, in order to prevent the resolution from becoming low in the peripheral portions of the image, the plane in which the lens 123 forms an image by the output image 114 must be exactly the same as the imaging surface of the imaging device 127. It is therefore required that the central axis of the lens 123 and the axis defined by the revolution of the imaging device 127 coincide with each other. When the electrode drum 137 is coupled to the bearing 135 and when the bearing 135 is coupled to the auxiliary frame 125b of the support frame 125a, the tilt angle and the eccentricity of each structural member must be within an allowable range. This means that the electrode drum 137 and the support frames 125a and 123a must be fabricated and worked with high precision. This inevitably increases the cost required for manufacturing the structural members and the cost required for assembling them.
Accordingly, an object of the present invention is to provide an X-ray imaging apparatus which enables reduction in both the cost for manufacturing structural members and the cost for assembling them, and which includes a camera that is smaller in size and can be revolved without any restriction even when an object is rotated.
The present invention has been made after due consideration of the problems described above, and is intended to provided an X-ray imaging apparatus comprising: an X-ray image intensifier for converting an X-ray image into a completely-round output visible-light image; an optical lens assembly for focusing the output visible-light image on a predetermined position; a solid-state imaging device arranged at the position where the output visible-light image is focused by the optical lens assembly; a signal processing circuit board for driving the solid-state imaging device and processing output image signals produced therefrom; a support frame, mechanically fixed to the X-ray image intensifier, for mechanically supporting the optical lens assembly, solid-state imaging device and signal processing circuit board; and a revolving mechanism for revolving the solid-state imaging device relative to the X-ray image intensifier such that an optical center axis coincides with the center of revolution of the solid-state imaging device, the signal processing circuit board being arranged such that the optical center axis extends therethrough and the solid-state imaging device being fixed to the signal processing circuit board, the optical lens assembly being coupled to the signal processing circuit board directly or with another member interposed, such that the optical lens assembly and the signal processing circuit board constitute one mechanical body, a rotating motor being fixed to the support frame and rotating the solid-state imaging device, the signal processing circuit board and the optical lens assembly as one body with reference to the support frame, a plurality of slip rings being arranged in the neighborhood of the solid-state imaging device in a concentric manner and being rotatable together with the solid-state imaging device, and electric power and output image signals being supplied to the solid-state imaging device and the signal processing circuit board by way of the slip rings.
In the X-ray imaging apparatus of the present invention, the slip rings may be concentrically fixed to the signal processing circuit board or to a flat plate provided independently of the signal processing circuit board and arranged perpendicular to the optical center axis.
In the X-ray imaging apparatus of the present invention, the optical lens assembly may include an anamorphic lens system incorporating a cylindrical lens, and the solid-state imaging device may have a rectangular image-receiving surface. In this case, the anamorphic lens system forms an elliptical image by enlarging or reducing the output visible-light image of the X-ray image intensifier in one direction, and projects the elliptical image on the rectangular image-receiving surface of the solid-state imaging device such that the longer-axis direction of the elliptical image and that of the image-receiving surface coincide with each other.
In the X-ray imaging apparatus of the present invention, the optical lens assembly may be arranged in the space inside the support frame, and the motor may be arranged in the space surrounding the optical lens assembly.
In the X-ray imaging apparatus of the present invention, the optical lens assembly may include an electrically-driven diaphragm. A signal for driving this diaphragm is supplied by way of the slip rings.
In the X-ray imaging apparatus of the present invention, a cylindrical lens may be used to form an image whose size is reduced in the vertical direction of the solid-state imaging device.