JPH0528029B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an X-ray television camera device used in medical digital radiography, etc., and particularly relates to an X-ray television camera device using an image pickup tube having a blocking photoconductive film. It is something.

[Background of the invention]

Recently, new image pickup tubes have been used in the medical field, which previously relied on film, and the application of television cameras, which can obtain images instantly without the hassle of developing, is attracting attention and is being used in this field. Image pickup tubes are required to have a high dynamic range.

However, in an image pickup tube using a blocking type photoconductive film, the signal current tends to saturate at high illuminance, as shown in Figure 1, a typical example of its characteristics. It has the disadvantage that the signal current is unstable due to drift. In the figure, A shows the relationship between the amount of incident light and the signal current at a normal operating voltage of 50V.The saturation current is about 1.5μA, and the amount of incident light at that time is about _150lx , which is about 15 times more than the normal amount of light. It can be seen that the signal current saturates when

[Purpose of the invention]

The present invention was made in view of these circumstances, and its purpose is to enable efficient and stable operation even when high-intensity X-rays are incident in pulses as in digital radiography. An object of the present invention is to provide an X-ray television camera device.

[Summary of the invention]

In order to achieve such an objective, the present invention
Means is provided to increase the target voltage applied to the imaging tube in synchronization with the pulse-like rise of the X-ray dose, and to gradually lower the target voltage in response to a drop in the X-ray dose. Hereinafter, the present invention will be explained in detail using Examples.

[Embodiments of the invention]

FIG. 2 is a configuration diagram showing an embodiment of the present invention. In the figure, 1 is an X-ray device that generates X-rays;
2 is an image tube that converts X-rays that pass through an object (not shown) into a visible image; 3 is an image pickup tube equipped with a blocking photoconductive film that captures the optical image reproduced by the image tube 2; and 4 is an image pickup tube. 3 is the operating power supply, 5 is the image pickup tube 3
A signal processing device 6 is a target DC power source for processing the image signal obtained from the target image signal to obtain desired data.

Here, the voltage of the target DC power source 6 is variable, and the controller 7 controls the power source 6 in accordance with the timing of X-ray irradiation from the X-ray device 1 to change the target voltage. In other words, in digital radiography, it is necessary to irradiate a high amount of light in a pulsed manner, but in that case, the target voltage is set at As shown, a region without saturation characteristics is set in advance, and a high voltage is applied in synchronization with the irradiation timing of a high amount of light. For example, by doubling the target voltage to 100V, the saturation current also doubles as shown in FIG. 1, thereby doubling the amount of light used and producing more effective images. For example, in the case of the light amount indicated by A in FIG. 1, which conventionally became unstable and could not be used, it can be stably used in this embodiment. In addition, the third
In the figure, C indicates the signal current.

In the above configuration, if the increased voltage is suddenly lowered, the signal current may become unstable and the image may be temporarily interrupted. If such a situation is expected to occur, it is possible to stabilize the voltage by installing a 1-2 minute attenuation circuit and slowing down the voltage change only when the voltage drops, as shown by d in Figure 3. You can get the image.

〔Effect of the invention〕

As explained above, according to the present invention, the target voltage applied to the image pickup tube is increased in synchronization with the pulse-like rise of the X-ray dose, and the target voltage is gradually increased as the X-ray dose falls. By providing a lowering means, it becomes possible to operate stably even in a high light intensity region where conventional operation was unstable due to saturation characteristics. Furthermore, there is the advantage that efficient power consumption can be achieved by increasing the target voltage only when irradiating a high amount of light.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of saturation characteristics of an image pickup tube, FIG. 2 is a configuration diagram showing an embodiment of the present invention, and FIG. 3 is a waveform diagram for explaining its operation. 1... X-ray device, 2... Image tube, 3... Image pickup tube, 4... Operating power supply, 5... Signal processing device, 6
...DC power supply for target, 7...Controller.

Claims (1)

[Claims] 1. In an X-ray television camera device that has an X-ray generator and an image pickup tube equipped with a blocking photoconductive film that converts the X-rays transmitted through the subject into electrical signals, the amount of X-rays emitted from the X-ray generator is An X-ray television camera, characterized in that it is provided with means for increasing the target voltage applied to the image pickup tube in synchronization with pulse-like rises, and for gradually lowering the target voltage in response to a drop in the X-ray dose. Device.