JPS6062788A - X-ray television device having video memory - Google Patents

Abstract

PURPOSE:To obtain a display picture having an equivalent luminance to that of a position to be checked by extracting only a video signal at a specific region of a picture based on a synchronizing signal separated from the video signal to utilize effectively the resolution of an A/D converter. CONSTITUTION:A video signal Vin from a television camera is fed to the A/D converter 13 via a video amplifier 12, an output of the video amplifier 12 is branched and fed to a peak detection circuit at the same time, where a peak value of the entire reion or a specific region of a picture is detected at a point P. The peak value is given to the A/D converter 13 as a reference voltage value of the A/D conversion, where a digital output value depending on the input level is obtained. Thus, any maximum value of the video level is matched to the full scale of the A/D converter 13 and uniform luminance is obtained on the entire picture.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention is used in the field of video memory devices for X-ray television.

Original F! A relates to an X-ray television apparatus having a video memory, and specifically relates to control of a reference voltage of an A/D converter provided in front of the video memory.

(b) Conventional technology A still image of the examined body part obtained by X-ray exposure is stored in memory, and when necessary, the saved image can be retrieved without having to be exposed to X-rays again. X-ray television equipment with video memory, capable of displaying on a TVK monitor, is widely used.

This device A/D converts the image (video) signal from the TV right camera and stores the digital signal in the video memory. Since the reference voltage or scale of the converter is fixed, the resolution of A/D conversion cannot be used effectively for too small analog inputs, and on the other hand, for too large analog inputs, it will overscale and correct conversion will not be performed. There is a problem that it cannot be done.

This means that the image will be displayed on the monitor TV in a manner different from the actual brightness distribution of the examined area, which may lead to misdiagnosis. Even when there is an excessive change in
An object of the present invention is to provide an X-ray television apparatus that can effectively utilize the resolution of a /D converter and display an image having a brightness equivalent to that of a region to be examined.

) Configuration The above purpose is video amplifier, A/D converter, video memo! J, a peak-to-peak circuit comprising a series circuit of a D/A converter and a monitor TV, connecting the output branch of the video amplifier to the reference voltage control terminal of the A/D converter, and having at least one switch between them; This is achieved by inserting a detection circuit, arranging a timing generation circuit to capture only the video signal in a specific area of the screen based on the synchronization signal separated from the video signal, and controlling the timing of the switch using the output of this circuit. can.

(e) Example A preferred embodiment of the present invention will be explained based on the drawings.

FIG. 1 is a schematic block diagram showing one embodiment. Vi
This is an analog video signal from a nuTV camera. 11 is a synchronization signal separation circuit, 12 is a video amplifier, and 13 is an A/D
Converter, 14, video memory, 15-digit D/A converter, 1
6 is a monitor TV, 17 is a buffer, an 18-digit sample/hold circuit, a 20-digit timing generation circuit, and a 21-digit set circuit.

Figure 2 shows the effective screen of the TV monitor.
It is illustrated as a specific area.

Video signal Vinff from TV left camera, video amplifier 1
2 to the A/D converter 13, and at the same time, the output of the video amplifier 12 is branched and sent to the peak detection circuit, where the peak value in the entire area of the image or in the specified area is detected at point P. Detected in This peak value is used as a reference voltage value for A/D conversion, and the signal is given to the A/D converter 13. In this way, by varying the A/D conversion level, the A/D
Depending on the input level of the converter 13, a digital output value is obtained, and any maximum value of the video level can be matched with the full scale of the A/D converter 13.

In the illustrated embodiment, the switch SWI is a peak detection switch, and is closed during scanning according to a specific area (shaded area) in FIG. 2, starting from point B,
It repeatedly opens and closes on the way and ends up with 0 points. The switch SW2 is a peak value reset switch, and the charge stored in the capacitor C is discharged by this switch. The timing is done before scanning the specific area. switch S
W3 is a peak value holding switch for transferring the peak value to the sample and hold circuit 18, and is closed after scanning a specific area. In addition, 21 set circuits, switch SW1
．． SW2. This is a circuit for setting the time constant during operation of SW3.

As another embodiment, the video amplifier 12 and the A/D converter 1
3, and the amplification factor of the amplifier is controlled by the peak detection value. In this case, the reference voltage of the A/D converter 13 is fixed to a constant value.

(f) Effects The present invention has the advantage that uniform brightness can be obtained over the entire image regardless of changes in the video signal level, and the resolution or accuracy of the A/D converter is improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing an effective screen of a monitor TV. 12 is a video amplifier, 13 is an A/D converter, 18 is a sample hold circuit, and 20 is a timing generation circuit.

Claims (1)

[Claims] In an X-ray television device having a series circuit of a video amplifier, an A/D converter, a video memory, a D/A converter, and a monitor TV, the output branch of the video amplifier is connected to the reference voltage control terminal of the A/D converter. A peak detection circuit having at least one switch is inserted between the peak detection circuit and a timing generation circuit for capturing only the video signal in a specific area of the screen based on the synchronization signal separated from the video signal. An X-ray television apparatus having a video memory, characterized in that the switching device is timing-controlled by the output.