JPH0622217A - X-ray television camera device - Google Patents

Abstract

PURPOSE:To pick up an image of an object by taking precedence of the S/N or the resolution over the other in the X-ray television camera device. CONSTITUTION:A gain setting section 10 setting two gains or over with respect to the scanning mode is provided to a video amplifier circuit 7 amplifying a video signal from a television camera 6 and an iris drive control section 11 to adjust a variable optical iris 5 in interlocking with the gain setting is provided to make the signal level sent to a picture processing section 8 at the output of the television camera 6 nearly constant. Thus, the image pickup is implemented by taking the precedence of the S/N or the resolution over the other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging system for taking an image of a diagnostic region of a subject using X-rays in, for example, a medical digital radiography apparatus (hereinafter abbreviated as "DR apparatus"). The present invention relates to an X-ray television camera device, and more particularly to an X-ray television camera device capable of giving priority to S / N ratio or resolution according to an object to be imaged.

[0002]

2. Description of the Related Art In a conventional X-ray television camera device of this type, as shown in FIG. 2, an X-ray image emitted from an X-ray tube device 1 and transmitted through a subject 2 is made incident and converted into a visible optical image. An image intensifier (hereinafter abbreviated as “II”) 3, a lens system 4 that receives and forms a visible optical image from the II 3, and a lens 4 provided near the lens system 4 to adjust the amount of transmitted light. Movable optical diaphragm 5 and the lens system 4
And a television camera 6 for converting a visible optical image guided by the movable optical diaphragm 5 into an electric signal, and a video amplifier circuit 7 for amplifying a video signal from the television camera 6. Although not shown in FIG. 2, the television camera 6 has an image pickup tube provided therein with, for example, a blocking photoconductive film. Reference numeral 8 indicates an image processing unit for inputting the video signal output from the video amplification circuit 7 and performing image processing, and reference numeral 9 indicates an automatic control for controlling the amount of X-ray emission from the X-ray tube device 1. The exposure control part is shown.

Such an X-ray television camera device is used in the medical field, which has relied on conventional X-ray films,
Convenience such as development and the like, and the convenience of being able to obtain an image immediately have been noticed and applied. The television camera 6 used for this is required to have a high resolution and a high S / N ratio. In this case, the S / N ratio of the television camera 6 can be improved by increasing its signal current. Therefore, in the DR device, the condition is set to increase the signal current as much as possible before use. For example, in a television camera 6 having an image pickup tube provided with a blocking photoconductive film, as shown in FIG.
Since the signal current is saturated at 0 lux), set the maximum illuminance of the input (for example, 100 lux) so that the signal current is as close as possible to the saturation point (for example, 4000 nA) within the range that does not exceed the saturation point. I was adjusting the input conditions. The input illuminance to the TV camera 6 is X
The adjustment is made by controlling the X-ray condition for the ray tube device 1 and the open / closed state of the movable optical diaphragm 5, and the signal current of the television camera 6 corresponding to the above input illuminance is
The gain of the video amplification circuit 7 for the television camera 6 is determined so as to correspond to the full-scale magnitude of the signal input to the image processing unit 8 shown in FIG.

[0004]

However, in such a conventional X-ray television camera apparatus, the television camera 6 is used.
There was only one condition setting that was set so as to optimize the S / N ratio. This was based on the recognition that the resolution hardly deteriorates even if the S / N ratio of the television camera 6 is increased (that is, the signal current is increased). However, it has recently been found that an increase in the signal current of the television camera 6 leads to deterioration in resolution. An example of the measurement result is shown in FIGS. 4 and 5.
FIG. 4 shows the case of the 1000-line scanning mode, and FIG. 5 shows the case of the 2000-line scanning mode. In any scanning mode, the amplitude modulation degree decreases as the signal current increases, which indicates that the resolution deteriorates.
That is, it is found that the resolution of the television camera 6 depends on the signal current, and the dependency is more remarkable in the 2000-line scanning mode than in the 1000-line scanning mode, as is clear from FIGS. 4 and 5. is there.

FIG. 6 shows the signal current dependency of the S / N ratio and the resolution, including the S / N ratio curve of the television camera 6. This figure is standardized by the data of signal current 100nA, but the plot points with triangle marks are
The figure shows the case of 1000-line scanning mode, where the circled plot points are 20.
00 shows the case of the main scanning mode. As is clear from this figure, as the signal current increases, the S / N ratio increases in proportion, but the resolution gradually deteriorates. That is, it can be said that the S / N ratio and the resolution have a trade-off relationship with each other. For this reason, it has been impossible to shoot with priority given to the resolution according to the shooting target with a single condition setting that uniquely sets the optimum S / N ratio as in the conventional case. Therefore, although a better resolution can be obtained depending on the shooting target, an image with an insufficient resolution may be obtained.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an X-ray television camera apparatus which can cope with such problems and give priority to S / N ratio or resolution depending on the object to be imaged. To do.

[0007]

In order to achieve the above object, an X-ray television camera device according to the present invention is adapted to form an X-ray image emitted from an X-ray tube device and transmitted through a subject into a visible optical image. An image intensifier for conversion, a lens system for making a visible optical image from the image intensifier incident and form an image, a movable optical diaphragm provided near the lens system for adjusting the amount of transmitted light, and the lens system. And an X-ray television camera device comprising a television camera for converting a visible optical image guided by a movable optical diaphragm into an electric signal, and an image amplification circuit for amplifying a video signal from the television camera. The circuit is provided with means for setting two or more gains for one scanning mode, and drive control means for adjusting the movable optical diaphragm in conjunction with these gain settings. Provided, in which as the signal level to be sent to the image processing unit on the output side of the television camera substantially constant.

[0008]

In the X-ray television camera device thus constructed, the gain setting means provided in the image amplification circuit sets two or more gains for one scanning mode and the movable optical diaphragm is provided. The drive control means operates so as to adjust the aperture amount in conjunction with the above gain setting. As a result, the signal level sent to the image processing unit on the output side of the television camera can be made substantially constant, and the S / N ratio or the resolution can be prioritized for shooting depending on the shooting target.

[0009]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of an X-ray television camera device according to the present invention. This X-ray television camera device serves as an imaging system for taking an image of a diagnostic region of a subject using X-rays in, for example, a medical DR device. As shown in the figure, II3 and lens system 4 are used. A movable optical diaphragm 5, a television camera 6, and an image amplification circuit 7, and further includes a gain setting unit 10 and a diaphragm drive control unit 1.
1 and.

The above II3 is for converting an X-ray image emitted from the X-ray tube device 1 shown in FIG. 2 and transmitted through the subject 2 into a visible optical image. For example, the X-ray image is incident from the input surface. Then, the X-ray fluorescence intensifier tube is used for converting into an electronic image and then converting into a fluorescent image on the output surface for output. The lens system 4 is II3 above.
A visible optical image emitted from the output surface is incident to be imaged on a television camera 6 described later, and for example, a plurality of lenses are combined in a tandem manner on the same optical axis. The movable optical diaphragm 5 adjusts the amount of light transmitted from the lens system 4 to the television camera 6, is provided near the lens system 4 on the optical axis of the lens system 4, and drives a motor or the like. It can be opened and closed by the source 12.

The television camera 6 receives a visible optical image guided by the lens system 4 and the movable optical diaphragm 5 and converts the visible optical image into an electric signal. And an image pickup tube provided with. And
The video amplifier circuit 7 inputs and amplifies the video signal output from the television camera 6. The output signal from the video amplifier circuit 7 is input to the subsequent image processing unit 8 and A / D converted in the image processing unit 8 to perform various image processing such as logarithmic conversion and image density conversion. It is supposed to be done.

Here, in the present invention, the video amplifier circuit 7 is provided with a gain setting section 10 and the movable optical diaphragm 5 is provided with a diaphragm drive control section 11. The gain setting unit 10 serves as means for setting two or more gains for one scanning mode of the video amplifier circuit 7, and a resistor R _{1 having} a predetermined value for the video amplifier circuit 7 is provided. R ₂ is provided in parallel, and switches S ₁ and S ₂ for connecting or disconnecting these resistors R ₁ and R ₂ to the circuit are provided. And one switch S
Only _one set to a value that is a gain of the video amplifier circuit 7 by connecting a resistor R ₁ as an on, a video amplifier circuit 7 by connecting a resistor R ₂ only other switch S ₂ as on The gain of is set to another value.

Further, the diaphragm drive control section 11 controls the gain
The movable optical diaphragm 5 is linked with the gain setting by the setting unit 10.
The above-mentioned movable optical diaphragm
Resistor for controlling the voltage supplied to the drive source 12
Bowl R₃And the resistor R₃Provided in
For example, two taps T₁, T₂To the power source E or
Switch S to disconnect₃, S_FourIs provided. That
One switch S ₃Only the first tap as on
T₁Driving a certain voltage from the power supply E by connecting
Power source 12 and the other switch S_FourTurn on only
Second tap T₂Power source E to other by connecting
The voltage of the value is supplied to the drive source 12.

At this time, the mode setting unit 13 switches the gain setting in the gain setting unit 10. The mode setting device 13 switches between the 1000-line scanning mode and the 2000-scanning mode, and switches between cases where the object to be photographed is thick or thin.
The aperture drive control unit 11 is switched at the same time when 0 is switched. For example, when one of the switches S ₁ of the gain setting section 10 is turned on by operating the mode setter 13 to set a certain gain value, one switch S ₃ of the diaphragm drive control section 11 is turned on in conjunction with this. The movable optical diaphragm 5 is adjusted to a certain diaphragm amount via the drive source 12. As a result, the signal level of the video signal sent from the video amplifier circuit 7 to the image processing unit 8 becomes substantially constant.

Here, for example, the image amplification circuit 7 of the television camera 6 is selected according to the thickness of the object to be photographed of the subject 2 (see FIG. 2).
A case will be described in which the gain is switched to perform shooting. First, when the object to be imaged of the subject 2 is thick, such as the abdomen or chest, it is considered necessary to give priority to a high S / N ratio and a high dynamic range, and the saturation point of the signal current of the TV camera 6 is considered. The gain is set by the gain setting unit 10 so that an image can be taken with a large large signal current. In the case of the 2000-line scanning mode shown in FIG. 5 described above, a low gain is set so that the signal current is, for example, 550 nA.
In this case, the S / N ratio increases, but the resolution deteriorates, as is clear from the curve of the black circle in the graph of FIG. Therefore, the movable optical diaphragm 5 is interlocked by the diaphragm drive control unit 11 so that the video signal input to the image processing unit 8 becomes substantially constant by the amount of increase in the gain of the video amplification circuit 7, and a proper amount is narrowed down. Reduces the amount of light transmitted to the TV camera 6 side. Then, since the optical path diameter (D) in the lens system 4 becomes small, the F number (F / D) becomes large, and the resolution of the lens system 4 is improved.
As a result, the synergistic effect of improving the S / N ratio of the television camera 6 and improving the resolution of the lens system 4 can be obtained.

On the other hand, when the object to be imaged of the subject 2 is thin such as hands and feet, it is considered necessary to prioritize resolution over high dynamic range with a high S / N ratio. The gain setting unit 10 sets the gain 6 so that imaging can be performed with a signal current of, for example, 1/2 to 1/3 of the large signal current 550 nA. In the case of the 2000-line scanning mode shown in FIG. 5 described above, the gain may be set so that the signal current is, for example, 200 nA. In this way, the signal current of the TV camera 6 is changed from 550 nA, for example.
By lowering it to 200 nA, as is apparent from FIG. 5, when focusing on 1600 TV lines, the amplitude modulation degree is improved by about 2.3 times from about 14% to 32%. This improves the resolution.

Incidentally, in FIG. 4 to FIG.
The case of the 00 main scanning mode and the 2000 main scanning mode has been described, but the present invention can be similarly applied to the case of the 500 main scanning mode.

[0018]

Since the present invention is constructed as described above,
The gain setting means provided in the image amplification circuit sets two or more gains for one scanning mode, and the drive control means provided in the movable optical diaphragm interlocks with the above gain setting to set the aperture amount. Can be adjusted. As a result, the signal level sent to the image processing unit on the output side of the television camera is made substantially constant, and S
It is possible to take a picture by giving priority to the / N ratio or the resolution. Therefore, it is possible to obtain an image with a better resolution that should be obtained depending on the shooting target.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an X-ray television camera device according to the present invention,

FIG. 2 is a block diagram showing a conventional X-ray television camera device,

FIG. 3 is a graph showing typical characteristics of input illuminance to the TV camera and signal current,

FIG. 4 is a graph for explaining that an increase in signal current of a TV camera in 1000-scan mode leads to deterioration of resolution.

FIG. 5 is a graph for explaining that an increase in the signal current of the TV camera in the 2000 main scanning mode leads to deterioration of resolution.

FIG. 6 is a graph showing the signal current dependency of the S / N ratio and the resolution of the television camera.

[Explanation of symbols]

1 ... X-ray tube device, 2 ... Subject, 3 ... II, 4 ... Lens system, 5 ... Movable optical diaphragm, 6 ... Television camera,
7 ... Video amplification circuit, 8 ... Image processing unit, 10 ... Gain setting unit, 11 ... Aperture drive control unit, 12 ... Driving source,
13 ... Mode setting device.

Claims (1)

[Claims] 1. An image intensifier for converting an X-ray image radiated from an X-ray tube device and transmitted through a subject into a visible optical image, and a visible optical image from the image intensifier. A lens system for forming an image, a movable optical diaphragm provided near the lens system for adjusting the amount of transmitted light, a television camera for converting a visible optical image guided by the lens system and the movable optical diaphragm into an electric signal, In an X-ray television camera device including a video amplifier circuit for amplifying a video signal from a television camera, the video amplifier circuit is provided with means for setting two or more gains for one scanning mode. , Drive control means for adjusting the movable optical diaphragm in conjunction with these gain settings is provided, and the signal level sent to the image processing unit on the output side of the television camera is made substantially constant. An X-ray television camera device characterized by the above.