JP2540498B2 - Automatic brightness adjustment device - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to automatic brightness adjustment of an X-ray television apparatus in which an image obtained by converting X-rays transmitted through a subject into light is captured by a television camera and displayed on a television. It relates to the device.

[Background of the Invention]

In the conventional device of this type, the brightness is often adjusted by changing only the tube voltage of the X-ray tube. In this case, since it is desirable to follow the change in the brightness of the television image as quickly as possible, the change rate of the tube voltage is generally increased. Therefore, when the TV luminance signal becomes appropriate, there is a delay in stopping the change in the tube voltage, which exceeds the appropriate value, and the tube voltage changes in the opposite direction this time in order to correct it. Then, this is repeated, and damping vibration occurs around the tube voltage that is the proper luminance of the television, and there is a problem that the television luminance causes hunting around the proper luminance.

[Object of the Invention]

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an automatic brightness adjustment device that can reduce the occurrence of hunting of TV brightness.

[Outline of Invention]

The TV brightness is considered to be proportional to the X-ray dose rate transmitted through the subject, and the transmitted X-ray dose rate is I = (KV) ^{3.5 to 4} x mA (I: transmitted X-ray dose rate, KV for a full-wave X-ray device). : Tube voltage value,
mA: tube current value). As can be seen from this example, in the X-ray apparatus, the transmitted X-ray dose rate changes more greatly when the tube voltage is changed than when the tube current is changed. Therefore, in the device of the present invention, it is assumed that there is always a response delay in automatic brightness adjustment, and the tube current change is used to correct the response delay in which hunting occurs, thereby achieving the above-mentioned object.

Example of Invention

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an example of an X-ray television set to which an automatic brightness adjusting device according to the present invention is applied, in which 1 is an AC power supply. After the low voltage AC from this power source 1 passes through the transformer 2,
It is rectified and smoothed through the rectifier 3 and the capacitor 4, converted into a constant voltage by the transistor 5, and converted into alternating current by the inverter 6. The alternating current from the inverter 6 is boosted by the high voltage transformer 7, rectified by the rectifier 8 and then applied to the X-ray tube 9, whereby X-rays are emitted from the X-ray tube 9. The X-rays transmitted through the subject 10 are converted into light by the II (image intensifier) 11, and this image is displayed on the monitor television 13 via the television camera 12.

The rectification and smoothing output by the rectifier 3 and the capacitor 4 are performed by the transistor 14, the inverter 15 and the transformer 16.
It is also given to the filament of the X-ray tube 9 via
The tube current of the X-ray tube 9 is changed by changing the voltage applied to the X-ray tube filament.

The device of the present invention, in such an X-ray television device,
TV image taken by camera 12, here monitor TV
A tube voltage automatic adjustment circuit 21 for changing the tube voltage of the X-ray tube 9 and a tube current automatic adjustment circuit 22 for changing the tube current of the X-ray tube 9 are provided for making the brightness of the monitor image by 13 constant.
And a brightness signal setting device 23 for setting an appropriate brightness signal of the television 13.

Here, the tube voltage automatic adjustment circuit 21 is an AND gate 21a,
21b, OR gate 21c, U / D (up / down) counter 2
It consists of 1d and D / A converter 21e. In addition, the tube current automatic adjustment circuit
22 is an inverter 22a, an AND gate 22b, a U / D (up
Down) Counter 22c and D / A converter 22d. Further, the brightness signal setting unit 23 is composed of three voltage comparators 23a to 23c. That is, the voltage comparators 23a to 23c determine the level (hereinafter, referred to as the brightness level) D of the brightness signal output in proportion to the brightness of the monitor image, and the voltage comparator 23a has the high brightness level D. 23b is appropriate, and 23c is low. OR gate 21c
Indicates that when the brightness level D is higher or lower than the comparison voltage A, C of the voltage comparators 23a, 23c (when it is out of the area between A and C), the output signal becomes high level and the U / D counter 21d counts. Start operation. In this case, the count speed of the counter 21d is determined by the clock CLK from the clock generator 24. The count output of the counter 21d is the D / A converter 21.
It is converted into an analog voltage by e and given to the base of the transistor 5, and the collector loss of the transistor 5 is changed to change the tube voltage of the X-ray tube 9. Since the brightness level D is lower than the comparison voltage A of the voltage comparator 23a, the voltage comparator 2
When the voltage is higher than the comparison voltage C of 3c, the counting operation of the U / D counter 21d is stopped, the change of the tube voltage is stopped and held at that voltage, and the tube current of the X-ray tube 9 is changed to U / D.
The counting operation of the D counter 22c starts. In this case, the count speed is also determined by the clock CLK. The count output of the counter 22c is converted into an analog voltage by the D / A converter 22d and given to the base of the transistor 14, the collector loss of the transistor 14 is changed, and the X-ray tube 9
And the tube current of the X-ray tube 9 is changed.

FIG. 2 is a diagram showing an example of the relationship between changes in the brightness level D after the operation of the device of the present invention is started and the comparison voltages A to C. As can be seen from this figure, after the start, the tube voltage is changed when the brightness level D exceeds the comparison voltage A, and the tube current is changed when they become equal.

When the brightness level D deviates from the region between the comparison voltages A and C, the U / D counter 22c is reset and returns to the value before the change.

In FIG. 1, 17 and 18 are capacitors, and V is a voltage source.

〔The invention's effect〕

As described above, according to the present invention, when the brightness signal becomes equal to the predetermined set value near the proper value, the tube voltage adjustment for greatly changing the transmission X-ray dose rate is switched to the tube current adjustment for small change, and hunting is performed. Since the change in the tube current is used for the correction of the response delay that occurs, it is possible to reduce the occurrence of the hunting of the TV brightness.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an example of an X-ray television set to which the device of the present invention is applied, and FIG. 2 is a diagram showing an example of the operation of the device of the present invention. 9 ... X-ray tube, 10 ... Subject, 11 ... I, I, 12 ... TV camera, 13 ... Monitor TV, 21 ... Automatic tube voltage adjustment circuit, 22 ... Automatic tube current adjustment circuit, 23 ...... Luminance signal setting device, D ...... Luminance signal level (luminance level).

Claims (1)

(57) [Claims] 1. A tube voltage of an X-ray tube according to a luminance signal of the television, in an X-ray television apparatus for capturing an image obtained by converting an X-ray transmitted through an object into light and displaying the image on a television. And a tube current automatic adjustment circuit for changing the tube current and a tube current automatic adjustment circuit, and a brightness signal setting device for setting the brightness signal of the television, the tube voltage automatic adjustment circuit, the brightness signal is the setting device If the result of the judgment by the setting device as to whether it is within the range of the predetermined level with respect to the proper level set in step 3 is outside the range of the predetermined level, the tube voltage adjusting operation is performed, The tube voltage adjusting operation is stopped when it is determined that the luminance signal is within the range of the predetermined level, and the tube voltage adjusting operation is stopped. Tube current adjustment Automatic brightness adjustment device, characterized in that to start the operation.