JPS6346560B2 - - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a tetrode vacuum tube (hereinafter referred to as a tetrode vacuum tube).
By controlling the X-ray tube voltage using a tetrode tube (referred to as a tetrode tube), it is possible to fully automatically perform cine automatic exposure control by controlling the exposed X-ray dose with fast response speed and low power consumption. X made
This relates to a line control device.

(Prior art) As is well known, when performing X-ray fluoroscopy or X-ray cine imaging of a subject using an X-ray device, the subject's fluoroscopy or X-ray cine photography is moved, and X-ray images are taken from various angles.
Obtaining line images is often performed. In this case, the amount of exposed X-rays is controlled according to the thickness of the subject and the imaging distance, and the output brightness of an X-ray fluorescence intensifier tube (hereinafter referred to as an image intensifier), which is a fluoroscopic display device, is kept at an appropriate level. Automatic control of brightness is required.

Such control operations are generally performed using ABC (Automatic
Brightness Control (automatic brightness adjustment)
Several methods have been put into practical use in the past, and the following four are typical control methods. Namely, (1) A system in which the primary voltage of the high voltage generating transformer is automatically controlled using a slide type autotransformer (single-turn sliding transformer) and a servo motor to control the tube voltage of the X-ray tube.

(2) Automatically control the filament current of the X-ray tube to
A method of controlling the tube current of a wire tube.

(3) A method to control X-ray exposure time.

(4) A method of controlling the X-ray tube voltage by controlling the internal voltage drop of the tetrode tube connected in series with the X-ray tube.

There are four methods.

(Problems to be Solved by the Invention) However, among the above-mentioned methods, methods (1) and (2) both have the drawback of slow response speed.
That is, in method (1) above, there is a problem with the response speed of the servo motor, and in method (2), even if the filament current is changed, the filament temperature does not follow this temperature change, resulting in a time delay. It is.
In addition, in method (3), the exposure time changes for each frame in a series of cine shots, which has the disadvantage of reducing dynamic resolution when imaging fast-moving organs such as cardiovascular organs. be. Furthermore, although the method (4) has sufficient performance in terms of response speed, it has the disadvantage of a narrow control range because the internal voltage drop range of the tetrode tube is narrow (approximately ±10 kVp).

The present invention was made in view of the above circumstances, and
In X-ray tube voltage control when performing ABC,
Auto transformer control is performed at the beginning of radiation exposure, and after a predetermined period of time, the internal voltage drop of the tetrode tube is controlled to control the tube voltage, thereby reducing the narrow control width of the tetrode tube. It is an object of the present invention to provide an X-ray control device that can quickly and automatically adjust brightness over a wide range.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention includes an autotransformer that adjusts the input voltage to a high voltage generator that generates a high voltage to be applied to the X-ray tube. , said X
A tetrode tube connected in series between the ray tube and the output side of the high-pressure generator, and a first grid bias circuit that controls the bias voltage of the first grid to make the tetrode conductive during X-ray irradiation. and a tetrode tube control unit comprising a second grid bias circuit that controls the bias voltage of the second grid to control the internal voltage drop of the tetrode tube, and the brightness of an optically converted image of an X-ray image by the X-ray tube. a comparison circuit that compares the detection signal from this detection circuit with a preset reference signal and outputs a difference signal, and a comparison circuit that compares the output signal from this comparison circuit with a rotation of the anode of the switching means for supplying a control signal to the autotransformer from the start until a predetermined time has elapsed, and supplying it as a control signal to the tetrode tube control unit after the elapse of the predetermined time; The present invention provides an X-ray control device characterized by comprising a time limit means for appropriately setting the predetermined time in order to determine the timing of supplying the output signal of the circuit.

(Function) According to the present invention configured as described above, tube voltage control is performed by the autotransformer until a predetermined time has elapsed from the start of rotation of the anode of the X-ray tube, so to speak, coarse adjustment of the tube voltage is performed. will be carried out. Further, after a predetermined period of time has elapsed, the internal voltage drop of the tetrode tube is controlled, so to speak, the tube voltage is finely adjusted.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of this device, and numeral 1 in the figure is a high voltage generator.
This high voltage generator 1 is comprised of a high voltage generating transformer 2 for boosting a three-phase AC voltage, a high voltage rectifying circuit 3 for rectifying the output of the high voltage generating transformer 2, and tetrode control units 4 and 5, the details of which will be described later. Here, the tetrode control units 4 and 5 have exactly the same configuration, and the tetrode control unit 4 is connected in series to the anode side of the X-ray tube 6, and the tetrode control unit 5 is connected in series to the cathode side of the X-ray tube 6. The tetrode tube is inserted into the tetrode tube so that it has the electrical withstand voltage of each tetrode tube. 7 is a sliding autotransformer whose primary side is connected to a three-phase AC power supply, and the secondary side of this autotransformer 7 is connected via a contact 8 of an electromagnetic switch that closes when "READY" is set on an operation panel (not shown). is connected to the primary side of the high voltage generating transformer 2, and three-phase alternating current that is appropriately adjusted is supplied by this transformer. The sliding autotransformer 7 is provided with a power supply voltage adjustment slider 9 and an output voltage adjustment slider 10, and these sliders 9 and 10 are driven and adjusted by corresponding servo motors 11 and 12, respectively. It is structured as follows. 13 is a servo control circuit for detecting power supply voltage fluctuations and controlling the servo motor 11 for driving and adjusting the power supply voltage adjusting slider 9 of the autotransformer 7 according to the fluctuation; 14 is a differential amplifier to be described later; This is a servo control circuit that controls the servo motor 12 for driving and adjusting the output voltage adjusting slider 10 of the autotransformer 7 according to the sent X-ray tube voltage correction signal, and the circuit controls the X-ray tube voltage. control.

The X-ray tube voltage control system that performs this tube voltage control includes a tube voltage manual setting device 15 using a variable resistor installed on the operation panel and a potentiometer that detects the actual voltage in conjunction with the output voltage adjustment slider 10. Consists of a yometer 16 and a differential amplifier 17,
A difference signal between the tube voltage setting value set by the tube voltage control setting device 15 and the tube voltage corresponding value at the current stage given by the potentiometer 16 is sent to the servo control circuit 12 via the differential amplifier 17 as a correction signal. By applying the voltage, the output voltage of the autotransformer 7 is adjusted so that the set tube voltage is achieved. The relay switching contact 18 provided on the input side of the differential amplifier 17 is switched to the A contact side only when automatic exposure control for cine photography is selected, and is switched to the tube voltage manual setting device 15 side at other times. 1
9 is the object, 20 is the X transmitted through this object 19
An image intensifier 21 captures the X-rays from the ray tube 6, converts the X-ray image into an optical image, and displays it on the output phosphor screen. An optical distributor, 24, which distributes and guides images to the cine camera 22 and television camera 23, respectively, is disposed on the output phosphor screen side of the image intensifier 20, and a prism 2 extracts a portion of the light on the output phosphor screen.
5 is a photomultiplier tube that converts the light extracted by the prism 24 into an electrical signal. The photomultiplier tube 25 and the prism 24 constitute a brightness detection mechanism, and the brightness of the optically converted image of the image intensifier 20 is detected by this brightness detection mechanism. 26 is a DC stabilized power source for supplying power to the photomultiplier tube 25, 27 is an amplifier for amplifying the output signal of the photomultiplier tube 25, and 28 is a waveform shaping device for the output amplified by this amplifier 27. This is a brightness level signal shaping circuit. As the luminance level signal shaping circuit 28, for example, a smoothing circuit, a peak value hold circuit, or the like is normally used. 29 is an appropriate brightness level setter that generates a reference voltage for setting an appropriate brightness level; 30 is a reference value output from the appropriate brightness level setter 29 and an output from the brightness level signal shaping circuit 28; The differential amplifier 31 that outputs the difference signal is a relay switching contact that switches the output of the differential amplifier 30 in two directions and outputs it, and its B contact side is connected to the A contact side of the relay switching contact 18. be. 3
2 is a power synchronization pulse generation circuit that generates a power synchronization pulse, and 33 is this power synchronization pulse generation circuit 32.
a power supply frequency synchronous pulse width modulation circuit, 34, which synchronizes with the pulse output from the circuit and changes the pulse width of the pulse in accordance with the output signal of the differential amplifier 30 sent via the A contact of the relay switching contact 31;
35 is a light emitting element lighting circuit that causes a light emitting element (for example, an LED) 34a to emit light according to a pulse signal output from the modulation circuit 33; Detection diode (solar cell)
It is a light guide that leads to the light receiving element PS by
These 32, 33, 34, 34a, and 35 constitute an internal voltage drop control system of the tetrode tube.

36 is an X-ray exposure timer that is triggered by the shutter synchronization signal of the cine camera 22 or an output signal of a gate circuit to be described later, and outputs a signal for a preset time to operate the tetrode control units 4 and 5; 38 is a trigger pulse generation circuit that generates a trigger pulse for performing test X-ray exposure; 38 is a test X-ray exposure time control circuit that generates a control signal for performing test X-ray exposure; 39;
is a gate circuit that is gate-controlled by this control signal and supplies a trigger pulse generated by the trigger pulse generation circuit 37 to the X-ray exposure timer 36. The test X-ray exposure time control circuit 38 is composed of, for example, a one-shot multivibrator circuit, and is triggered by a setup (steady rotation) signal from an X-ray tube rotor node drive circuit (not shown).

On the other hand, the tetrode control units 4 and 5 are constructed as shown in FIG. 2, and as mentioned above, since these units 4 and 5 are constructed in the same way, the same parts are given the same reference numerals. Explain details.

The output signal of the timer 36 is introduced into the input terminals A and B, and is appropriately adjusted by the high voltage transformer 117. In order to improve responsiveness to the X-ray exposure signal from the timer 36, it is appropriate to use a transformer made of a ferrite core as the high voltage transformer 117. The secondary voltage of the high-voltage transformer 117 is rectified by two full-wave rectifier circuits 118a and 118b, each of which has a resistor of 1.
19a, 119b, capacitors 120a, 120
The current is applied as a base current to the bases of switching transistors 121a and 121b via a smoothing circuit made up of transistors 121a and 121b. These 118, 119, 1
The circuit composed of transistors 121a and 121 is constructed by providing two circuits a and b in parallel with each other to provide a withstand voltage.
121b part only 121a emitter
It is connected to the collector of b. Also, input terminal C,
A constant voltage, for example, AC 100 V, is always applied to D, and this voltage is supplied to the primary winding of the transformer 123 via the high voltage transformer 122. The secondary winding of this transformer 123 has two first grid bias supply windings 124a, 124b, a filament voltage supply winding 125 and a second grid bias supply winding 126,
The secondary voltage generated at
to the first grid of the tetrode tube. Note that the positive side of the smoothing circuit is also connected to the collector of the transistor 121, and also serves as the power supply voltage of this transistor 121.

That is, the transistor 121 is connected between the cathode of the tetrode tube and the first grid, and is normally in an off state. When the X-ray exposure signal from the timer circuit 9 is applied to the input terminals A and B, the transistor 121 is turned on, and the tetrode tube is also turned on to short-circuit between the cathode of the tetrode tube and the first grid.

Further, the winding 125 is directly connected to the tetrode tube 4.
It is connected to the cathodes of a and 5a, and serves as a power source for heating the filament.

Further, the voltage generated in the winding 126 is rectified by a full-wave rectifier circuit 127a, and is connected to a smoothing circuit composed of a resistor 132 and a capacitor 133 through a transistor 131 inserted in series, and the first of the tetrode tubes 4a and 5a. Connected to 2 grids. Further, the above-mentioned light receiving element PS is connected to the base of the transistor 131 and receives the optical signal from the light guide 35.
The transistor 131 operates according to a signal from the .

Next, the operation of this apparatus having the above configuration will be explained. When a desired tube voltage is set by the tube voltage control setter 15, this set value is given to the servo motor 12 via the differential amplifier 17, and the autotransformer 7
The output side of is set to this set value. When power is supplied to the high voltage generator 1 via the contact 8 from the autotransformer 7 to which a three-phase AC power supply is applied, the high voltage in the high voltage generator 1 is set to this setting value. A high voltage corresponding to the primary applied voltage is output from the secondary side of the transformer 2. After this high voltage output is rectified by the high voltage rectifier circuit 3,
Tetrode tube 4 of tetrode control unit 4, 5
a, 5a.

On the other hand, the tetrode control units 4 and 5 have a configuration as shown in FIG.
When turned on, the first grids of the tetrode tubes 4a and 5a are set to cathode potential to turn them on, and the transistor 121 is turned on by a signal from the X-ray exposure timer 36. Therefore, for example, the trigger pulse generation circuit 37 and the test X-ray exposure time control circuit 38 are operated, and a signal is given to the X-ray exposure timer 36 via the gate circuit 39. Then, the X-ray exposure timer 36 operates and outputs a signal for a preset time to apply it to the base of the transistor 121. As a result, this transistor 121 is turned on while the signal is being input, and the tetrode tube 4 is turned on.
The first grid potential of a and 5a is set to the cathode potential. Therefore, since the tetrode tubes 4a and 5a are turned on, the high-pressure rectified output of the high-pressure rectifier circuit 3 is applied to the X-ray tube 6 via the tetrode tubes 4a and 5a, and the X-ray tube 6 emits X-rays. do.

The exposed X-rays pass through the subject 19 and enter the input surface of the image intensifier 20, where they are converted into a visible optical image and displayed on the output phosphor screen of the image intensifier 20. This displayed optical image is sent to a cine camera 22, a television camera 23 through an optical distributor 21, and
The optical image is transmitted to the photomultiplier tube 25 by the prism 24.
It will also be sent to Then, this photomultiplier tube 25 outputs an electric signal corresponding to the brightness of the optical image. This output is amplified by an amplifier 27, then shaped by a brightness level signal shaping circuit 28, and then provided to a differential amplifier 30. Since a reference signal for giving a desired brightness level preset by the appropriate brightness level setter 29 is input to the differential amplifier 30, the differential amplifier 30 adjusts the brightness level based on this reference signal. The output signals of the signal shaping circuit 28 are compared and a difference signal is output.

If the relay switching contact 31 is now switched to the A contact side, the difference signal will be sent to the power frequency synchronous pulse width modulation circuit 33. Then, this modulation circuit 33
pulse width modulates the power synchronization pulse as shown in FIG.
send to Upon receiving this pulse width modulated pulse, the lighting circuit 34 provides a corresponding output as shown in FIG. 3C to the light emitting element 34a. Therefore, the light emitting element 34a lights up with a brightness that corresponds to the output of the lighting circuit 34. This light is sent to the light receiving element PS through the light guide 35, and upon receiving this light, the light receiving element PS generates an electromotive force corresponding to the light. This electromotive force is applied to the bases of transistors 131 of the tetrode control units 4a and 5a, and these transistors 131 output an output as shown in FIG.
5a to the second grid. As a result, the tetrode tubes 4a and 5a are controlled by the bias voltage value (Fig. 3E) according to the signal given to the second grid, and the voltage between the cathode and the plate is controlled accordingly. become. That is, the voltage between the cathodes and the plates of the tetrode tubes 4a and 5a is controlled so as to give the X-rays a tube voltage that produces an image of the brightness set by the appropriate brightness level setting device 29.

Here, if the circuit shown in FIG. 2 is rewritten equivalently, it becomes as shown in FIG. 4a. That is, the transistor 121, rectifier circuit 118, and resistor 11 shown in FIG.
9. A switching circuit consisting of a capacitor 120 is connected to the switch S1, a second grid bias circuit consisting of a winding 126, a rectifier circuit 127a, a transistor 131, a resistor 132, and a capacitor 133 is connected to Eg2;
The first grid bias circuit consisting of resistor 128 and capacitor 129 corresponds to Eg1,
When a signal from the X-ray exposure timer 36 is given, the switch S1 is closed, and the tetrode tubes 4a,
5a becomes conductive and its internal voltage drop VT becomes the second
It will be determined by the grid bias voltage Eg2.

That is, as is well known in the tetrode tube, due to its characteristics, the plate current Ip, the first grid voltage
If Eg1 is constant, the internal voltage drop VT will depend on the second grid voltage Eg2. Therefore, by changing the second grid voltage Eg2, the internal voltage drop VT of the tetrode tube can be controlled. Therefore, the rectified output voltage of the high voltage rectifier circuit 3 is VHT, and the tube voltage applied to the X-ray tube 6 is
If VX, then Vx = VHT - 2VT. That is, by controlling the internal voltage drop of the tetrode tubes 4a and 5a, the tube voltage of the X-ray tube can be adjusted.
It will control Vx. The second grid voltage is connected to the negative power supply in series with Eg2 as shown in Figure 4b.
By connecting Eg2, the variable range can be shifted to the negative direction, and the adjustment range of the internal voltage drop can be made wider. As this negative power source -Eg2, for example, a circuit that adjusts a DC negative voltage obtained by a rectifier circuit to a target voltage using a Zener diode may be used, and this may be connected in series to Eg2.
Additionally, a surge absorption element (TNR) is connected between the cathode of the tetrode tube and the first and second grids to prevent excessive bias from being applied.

In this way, the tube voltage is controlled so that appropriate brightness is obtained, and the image intensifier 20
An image with appropriate brightness appears on the output phosphor screen.
This image is photographed by a television camera 23 and displayed on a monitor (not shown).

Next, a case will be described in which an X-ray image of the subject 19 is photographed by the cine camera 22 under automatic exposure control. In this case, the relay switching contact 18 is switched to the A contact side. Then, as shown in FIG. 5, when the rotation of the X-ray tube rotor node (not shown) starts, a trigger pulse is applied to the timer 36 via the gate circuit 39 to emit test X-rays for a predetermined period of time. Then, the timer 36 outputs a signal for a predetermined period of time, thereby turning on the tetrode tubes 4a and 5a. At the same time differential amplifier 1
7 amplifies the difference signal between the reference value output from the appropriate brightness level setter 29 and the detection output from the photomultiplier tube 25, which is output from the differential amplifier 30, and supplies the amplified signal to the servo motor 12. As a result, servo motor 1
2 is driven in response to an input signal, and the output side of the autotransformer 7 is adjusted. The X-ray tube voltage approaches the set value due to the output of the autotransformer 7 and the switching operations of the tetrode control units 4 and 5. If the shutter of the cine camera 22 is operated before the test X-rays are stopped, the X-ray exposure timer 36 is triggered again by the shutter synchronization signal. At the same time, the relay switching contact 31 is switched to the A contact side. Then, the X-ray exposure timer 36 outputs an output for a preset time, continuously drives the transistors 121 of the tetrode control units 4 and 5, and keeps the tetrode tubes 4a and 5a turned on in the same manner as described above. As a result, a tube voltage is applied to the X-ray tube 6 via the tetrode tubes 4a and 5a, so that the X-ray tube 6 emits X-rays. With this X-ray, the X-ray image of the subject 19 is transferred to the image intensifier 2.
0, and an X-ray image converted into an optical image appears on the output phosphor screen. This optical image is made incident on the cine camera 22 by the optical distributor 21 and photographed. On the other hand, since the light is also incident on the photomultiplier tube 25 via the prism 25, the output of the appropriate brightness level setting device 29 and the photomultiplier tube 25 for giving the preset appropriate brightness level as described above.
The internal voltage drop control of the tetrode tubes 4a, 5a is performed in accordance with the difference between the output of the tetrode tubes 4a and 5a, and the X-ray tube 6 is controlled so as to be provided with a tube voltage that provides appropriate brightness. Therefore, an optical image of appropriate brightness is incident on the cine camera 22 and photographed. When the predetermined time has elapsed, the timer 36 stops outputting, so the X-ray exposure stops and the imaging ends. Incidentally, voltage fluctuations in the three-phase power supply are appropriately adjusted by the servo motor 11 on the primary side of the autotransformer 7, so that the influence of power supply fluctuations is canceled out. Furthermore, by using, for example, a control circuit as shown in FIG. 6 as the servo control circuit 14, all operations of the apparatus shown in FIG. 1 can be automated.

That is, in FIG. 6, Ry0-S is the differential amplifier 1
This is an input opening/closing relay switch installed on the output side of Tr1, and Tr1 operates using the signal given through this switch Ry0-S as a base input.
NPN type transistor, Tr2 is also a switch
It is a PNP type transistor that operates with the signal given via Ry0-S as the base input. Therefore, if the base input is positive, transistor Tr1
is turned on, and if it is negative, the transistor Tr2 is turned on. Ry1 is the coil of the first relay connected between the collector of transistor Tr1 and the power supply bus, and Ry2 is the coil of the second relay connected between the collector side of transistor Tr2 and the power supply bus. The coil is energized by turning on the transistor connected to it. NG1 is a two-input NAND gate which receives the collector potentials of the transistors Tr1 and Tr2 as input, and detects the ON operation of the transistors Tr1 and Tr2. FF1 is this nand gate NG
JK flip-flop operated by the output of 1,
FF2 is set by the output of NAND gate NG1, and is an X-ray exposure stop signal from an X-ray controller (not shown) that sets X-ray exposure conditions and controls exposure.
R- is reset by XRO and gives the Q output terminal output to the X-ray controller as an X-ray exposure command.
The S flip-flop, FF3, is set by the Q output terminal output of the JK flip-flop FF1, is reset by the X-ray exposure stop signal XRO, and sends the Q output terminal output to the X-ray controller as an X-ray exposure preparation completion signal. R-S flip-flop, which gives
Ry3 is a coil for operating the switch 18 operated by the Q output terminal output of the R-S flip-flop FF2, Ry4 is a coil for operating the relay switching contact 31 operated by the Q output terminal output of the R-S flip-flop FF3, SW is a pushbutton switch for generating a ready signal indicating readiness,
FF0 is set by this ready signal, and X
R-S reset by radiation exposure stop signal XRO
The flip-flop Ry0 is a coil that is operated by the Q output terminal output of the R-S flip-flop FF0 to operate the switch Ry0-S of the input switching relay. PA is a power amplifier that amplifies the output of the differential amplifier 17, PG is a pulse generator, and CP is a pulse generator that amplifies the output of the power amplifier PA.
Chopper chopping with PG output pulse,
Ry1-S is a switch of the first relay which is closed when the coil Ry1 of the first relay is energized and supplies the output of the chopper CP to the normal rotation side terminal of the servo motor 12, and Ry2-S is a switch of the second relay. relay coil
A second terminal that is closed when Ry2 is energized and supplies the output of the stopper CP to the reverse side terminal of the servo motor 12.
This is a relay switch.

The operation of the servo control circuit 14 having such a configuration will be explained. First, press the push button switch SW to start. As a result, the ready signal shown in FIG. 7a is output, and the R-S flip-flop FF0
is applied to the set terminal of As a result, R-S
Flip-flop FF0 is set and outputs the signal shown in FIG. 7b from its Q output terminal. As a result, the coil Ry0 of the input opening/closing switch is energized, and the input opening/closing switch Ry0-S is closed.
Therefore, the output of the differential amplifier 17 is the transistor
Applied to the bases of Tr1 and Tr2. In the initial state, the R-S flip-flops FF2 and FF3 have been reset by the previous X-ray exposure stop signal XRO, so the relay coils Ry3 and Ry4 are both deenergized, so the switch 18 and the relay switching contact 31 are all switched to the B contact on the normally closed side, and therefore only the tube voltage manual control system using the conductive voltage manual setting device 15 operates. The potentiometer 16 is configured to be varied in conjunction with the set position of the output voltage adjustment slider 10 of the autotransformer 7, and the level of the negative potential is adjusted by the potentiometer 16. , this negative potential and tube voltage manual setting device 15
The addition voltage of positive potential for setting from differential amplifier 1
7 is input. Therefore, if the output of the differential amplifier 17 is positive, the transistor Tr1 is turned on, the coil Ry1 of the first relay is energized, and the switch Ry1 of the first relay which opens and closes the normal rotation side terminal of the servo motor 12 is activated. -S closes. The output of the differential amplifier 17 is added to the power amplifier PA to amplify it, and this amplified output is chopped by the chopper CP and then sent to the closed first relay switch Ry1-S. Since the voltage is input to the normal rotation side input terminal of the servo motor 12 through the servo motor 12, the servo motor 12 rotates in the normal direction, and moves and adjusts the output voltage adjustment slider 10 of the autotransformer 7 in a direction to increase the output.

At this time, the potentiometer 16 is also varied in conjunction with the movement of the output voltage adjusting slider 10. Therefore, if the potentiometer 16 is set to move in the negative potential direction at this time, the negative potential will increase as the adjustment progresses, so the added value with the positive set potential from the tube voltage manual setting device 15 will increase as the adjustment progresses. approaches zero, and when it reaches approximately zero, the transistor Tr1 is turned off. Therefore, the coil Ry1 of the first relay is deenergized and its switch Ry1-
S is also opened and the servo motor 12 stops. Conversely, when the output of the differential amplifier 17 is negative, the transistor Tr2 is turned on, the coil Ry2 of the second relay is energized, and its switch Ry2-S is closed, thereby causing the servo motor to Since the input from the chopper CP is given to the reverse side input terminal of the servo motor 12, the servo motor 12 starts reverse rotation. As a result, the output voltage adjusting slider 10 of the autotransformer 7 is moved and adjusted in the direction in which the output decreases, and the potentiometer 16 is also moved in the direction of zero potential, so the output of the potentiometer 16 is adjusted. The sum of the set values of and the manual tube voltage setting device 15 approaches zero. When the value reaches approximately zero, the transistor Tr2 is turned off and the coil Ry2 of the second relay is deenergized. This causes the switch Ry2-S to open and the servo motor 12 to stop. With the above steps, adjustment of the output side of the autotransformer 7 to obtain the desired tube voltage is completed. When the transistors Tr1 and Tr2 are turned on, the collector potential of the turned-on transistor decreases, so the NAND gate NG1, which receives these collector potentials as input, generates an "H" level output as shown in Figure 7c. . FF1, FF2, which takes the output of this NAND gate NG1 as input,
Since all of FF3 operate at negative logic, they are not operated. When the tube voltage setting is completed and both transistors Tr1 and Tr2 are turned off, the NAND gate NG1 input becomes "H" and returns to the "L" level output again, so the falling signal causes R- The S flip-flop FF2 is set and the Q output terminal goes high as shown in Figure 7d.
Level output is output. At the same time, the JK flip-flop FF1 is also triggered, and the output shown in FIG. 7e is output from its Q output terminal. Therefore, the coil Ry3 of the third relay is energized, and this Ry3
The switch 18 is switched to the A contact (normally open). As a result, the signal from the photomultiplier tube 25 is input to the input of the differential amplifier 17. At this time, the output from the Q output terminal of the R-S flip-flop FF2 is given to the trigger pulse generation circuit 37 as an X-ray exposure preparation command, thereby activating the trigger pulse generation circuit 37 and starting the rotation of the X-ray tube rotor node. Then, at the point in time when the rotation of the X-ray tube rotor node is started, a trigger pulse is applied to the timer 36 via the gate circuit 39 to emit test X-rays for a predetermined period of time. Then, this timer 36
A signal is output for a predetermined period of time, thereby turning on the tetrode tubes 4a and 5a. At the same time, the differential amplifier 17 amplifies the difference signal between the reference value output from the differential amplifier 30 and the detection output of the photomultiplier tube 25 and supplies it to the servo motor 12 . As a result, the servo motor 12 is driven in accordance with the input signal, and the output side of the autotransformer 7 is adjusted. At this time, either transistor Tr1 or Tr2 is turned on or off again to form a NAND gate as shown in Figure 7c.
Since the output level from NG1 changes, at the second falling edge, the Q output falling signal of FF1 causes FF3 to change.
is set, and an "H" level signal is output from the Q output terminal. The X-ray tube voltage approaches the set value by the output of the autotransformer 7 and the control operations of the tetrode control units 4 and 5. And, by the Q output terminal output of this FF3,
If the shutter of the cine camera 22 is operated before the test X-rays are stopped, the X-ray exposure timer 36 is triggered again by the shutter synchronization signal.
Coil Ry4 of the fourth relay is energized by the Q output terminal output of FF3, and relay switching contact 31 is switched to the A contact side. Then, this X-ray exposure timer 36 outputs an output for a preset time, and the transistors 12 of the tetrode control units 4 and 5
1 continues to be driven, and the tetrode tubes 4a and 5a continue to be turned on in the same manner as described above. As a result, a tube voltage is applied to the X-ray tube 6 via the tetrode tubes 4a and 5a, so that the X-ray tube 6 emits X-rays. The X-rays cause an X-ray image of the subject 19 to enter the image intensifier 20, and an X-ray image converted into an optical image appears on the output fluorescent surface thereof. This optical image is made incident on the cine camera 22 by the optical distributor 21 and photographed. On the other hand, since the light is also incident on the photomultiplier tube 25 via the prism 25, the output of the appropriate brightness level setter 29 and the output of this photomultiplier tube 25 are used to provide a preset appropriate brightness level as described above. The internal voltage drop control of the tetrode tubes 4a, 5a is performed according to the difference between the two, and the X-ray tube 6 is controlled to be provided with a tube voltage that provides appropriate brightness. Therefore, an optical image of appropriate brightness is incident on the cine camera 22 and photographed. When the predetermined time has elapsed, the timer 36
stops the output, so the X-ray exposure stops and the imaging ends. Shooting stop signal output at this time
FF0, FF2, FF3 are reset by XRO,
Therefore, Ry2 and Ry4 are deactivated. As a result, 18 and 31 are brought to the B contact side, and Ry0-S is also opened, completing the entire operation. Incidentally, voltage fluctuations in the three-phase power supply are appropriately adjusted by the servo motor 11 on the primary side of the autotransformer 7, so that the influence of power supply fluctuations is canceled out. As described above, fully automatic operation is possible.

"Effect" In this way, an autotransformer that controls the input voltage of the high-pressure generator, and a tetrode that is provided between the high-pressure generator and the X-ray tube and controls the output of the high-pressure generator given to the X-ray tube. a tetrode control unit comprising a tube, a circuit for controlling a first grid bias of the tetrode tube, and a circuit for controlling a second grid bias of the tetrode tube; a circuit for detecting the intensity of an X-ray image produced by the X-ray tube; It is composed of a circuit that supplies a difference signal between the detection signal and a preset value to the autotransformer at the initial stage of X-ray exposure, and to the tetrode control unit after a predetermined period of time has elapsed. At the initial stage of X-ray exposure, the luminance control is performed using the difference signal to control the output of the autotransformer so that the luminance reaches the set value, and after a predetermined time elapses, the output of the autotransformer is controlled.
By adjusting the tube voltage by controlling the internal voltage drop of the tetrode tube by grid bias adjustment according to the difference signal, the set value can be achieved.In addition to being able to perform quick brightness control, the second grid bias By adding a negative power supply to the second grid bias circuit that performs voltage control and making it possible to lower the second grid bias voltage to the voltage of this negative power supply, the control range for the internal voltage drop of the tetrode tube is widened. It is possible to provide an X-ray control device having excellent features such as:

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a circuit diagram showing details of the tetrode control unit, and FIG. 3 is a time chart for explaining the second grid bias voltage control of the tetrode tube.
Figure 4a is a diagram showing an equivalent circuit of the circuit in Figure 2;
Figure b is a diagram showing an example of widening the internal drop adjustment range, Figure 5 is a time chart for automatic exposure control of a cine camera, and Figure 6 is an example of the servo control circuit 14 for full automation. , Figure 7 is the time chart. 1... High pressure generator, 4, 5... Tetrode control unit, 4a, 5a... Tetrode tube, 6...
X-ray tube, 7... autotransformer, 10... output voltage adjustment slider, 12... servo motor, 20...
...Image intensifier, 25...Photomultiplier tube, 29...Appropriate brightness level setter, 30...
...Differential amplifier.

Claims (1)

[Claims] 1. An autotransformer that adjusts the input voltage to a high-voltage generator that generates a high voltage to be applied to the X-ray tube, and a series connection between the X-ray tube and the output side of the high-voltage generator. a first grid bias circuit for controlling the bias voltage of the first grid to make the tetrode conductive during X-ray irradiation, and a second grid bias circuit for controlling the internal voltage drop of the tetrode tube. a tetrode tube control unit comprising a second grid bias circuit for controlling the bias voltage of the tetrode tube, a circuit for detecting the brightness of the optically converted image of the X-ray image by the X-ray tube, and a detection signal from the detection circuit and a preset A comparison circuit is used to output the difference signal from the comparison circuit, and the output signal from the comparison circuit is used to control the autotransformer until a predetermined period of time elapses from the start of rotation of the anode of the X-ray tube. a switching means for supplying the signal as a control signal to the tetrode tube control unit after the predetermined time has elapsed; and a switching means for supplying the output signal of the comparison circuit to the switching means for the predetermined time. An X-ray control device characterized by comprising: a time limit means for appropriately setting the time limit. 2. The X-ray control device according to claim 1, wherein in the second grid bias circuit, a predetermined negative voltage is applied to the second grid bias voltage output from the second grid bias circuit for correction. .