JPH08129637A - Digital image processor - Google Patents

Abstract

(57) [Abstract] [Purpose] An easy-to-see display image in which gradation conversion characteristics (contrast, brightness) do not change suddenly due to image movement is obtained. [Structure] A motion detecting means including a frame memory 8 and a motion detector 9 is provided. Motion detector 9
Compares the current image data with the previous image data stored in the frame memory 8 to detect the motion of the image. The LUT control circuit 7 receives the signal from the motion detector 9, stops the setting of the lookup table 2 performed according to the output of the maximum value detection circuit 5 and the minimum value detection circuit 6, and the gradation conversion characteristic (window) is Don't change.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital image processing apparatus for digitally processing a video signal such as a medical X-ray image, and particularly controls the gradation of an image displayed on a television monitor in an X-ray television system. The present invention relates to a digital image processing device.

[0002]

2. Description of the Related Art Conventionally, an X-ray television system irradiates an object with X-rays from an X-ray tube and transmits X-rays through the object.
The X-ray image intensifier is irradiated with a line, and an X-ray TV camera is coupled to the X-ray image intensifier to obtain a video signal of an X-ray transmission image, which is displayed as a perspective image on a TV monitor device. , Useful for medical diagnosis. In digital radiography,
This video signal is digitized and recorded, and subjected to various kinds of processing, or returned to an analog video signal and displayed on a TV monitor device or the like. Usually, this digital X-ray imaging apparatus is provided with an automatic gradation processing function, detects the maximum value and the minimum value in one image of digitized image data (pixel value data), and The window is controlled so that the pixel value within the range between the maximum value and the minimum value is expanded to 0% to 100% (from the black level to the white level) of the display gradation, and the gradation is converted.

[0003]

However, in the conventional digital X-ray imaging apparatus, there is a problem that the display image becomes difficult to see depending on the observation site due to the automatic gradation processing function. For example, in fluoroscopic image diagnosis of the stomach, the pixel value changes abruptly due to the inflow (filling) of the contrast medium into the region of interest and the postural change due to the movement of the contrast medium in the stomach. The gradation conversion characteristics that change corresponding to the value change abruptly. Therefore, a sudden change in display gradation causes a sudden change in the contrast and brightness of the display image, which makes the image hard for an observer to see and restless.

In view of the above, the present invention relates to a case where a large image change is caused by a rapid filling of a contrast agent, a change in body position, etc.
In the case of a normal image that does not change the gradation conversion characteristics and does not cause a large image change, it corresponds to the maximum value and the minimum value of the image data for each of a large number of images sequentially obtained for each frame. A digital image processing device with an improved automatic gradation processing function that changes the gradation conversion characteristics to eliminate sudden changes in the contrast and brightness of the displayed image and makes the displayed image easier to see. The purpose is to provide.

[0005]

In order to achieve the above object, a digital image processing apparatus of the present invention detects a motion of an image by comparing a current video signal and a previous video signal for each pixel. A motion detecting means for controlling the gradation converting means for changing the gradation converting characteristic of the digital video signal according to the detected value is provided. The motion detection means is a frame memory that stores previous image data,
It is composed of a motion detector that compares the image read from the frame memory with the current video signal for each pixel to detect the motion of the image.

[0006]

The operation of the present invention is as follows. The motion detecting means detects the movement of the image by comparing the current video signal with the previous video signal stored in the frame memory for each pixel. When the image at the time of changing the body position is moving rapidly due to the rapid filling of the contrast agent, the image is largely moved, so that the pixel value between the current image and the previous image greatly changes. The motion detecting means detects the movement from the change of the pixel value, and controls the gradation conversion characteristic in accordance with the maximum value and the minimum value in the image of each digital video signal for each image. The gradation processing function is stopped so that the gradation conversion characteristic does not change.

As a result, the gradation conversion characteristic of the gradation control means for controlling the gradation conversion characteristic even when a sudden image movement occurs
Since the gradation conversion characteristic before the movement of the image does not change and does not change, a sudden change in the contrast and brightness of the display image does not occur. On the other hand, for a normal image with a small change in the image, the gradation control means sets the gradation corresponding to the maximum value and the minimum value of the image data for each of a large number of images sequentially obtained for each frame. By changing the characteristics and giving an appropriate gradation conversion characteristic to the image, a display image with an appropriate gradation can be obtained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG. A video signal as original image data such as an X-ray image signal obtained from an X-ray TV system is converted into digital image data by the A / D converter 1. This image data is sent to the D / A converter 3 via the look-up table 2 and is returned to the analog video signal.
It is sent to the V monitor device 4 and displayed. The lookup table 2 functions as a gradation converter that converts input image data (pixel value), which is a kind of input / output converter, into a value suitable for display and outputs the converted value. As shown in FIG. 2, the conversion characteristic (input / output characteristic) expands a certain width (window) W into 0% to 100% of the output (from the black level to the white level of the display image). There is. The gradation conversion characteristic is represented by the window W and its center C.

The look-up table 2 is a kind of input / output converter and is usually composed of a RAM or the like. RAM
Address is specified by the input value, and the output value corresponding to the input value is written in each address. Arbitrary gradation conversion characteristics can be obtained by changing the value written in each address. The digital image data output from the A / D converter 1 is input to the maximum value detection circuit 5 and the minimum value detection circuit 6, and the maximum value and the minimum value in one image are detected and the LUT control is performed. Sent to circuit 7. In the LUT control circuit 7, the window W and the center C are calculated from the maximum value and the minimum value, and those values are set in the lookup table 2 (the values are written to the respective addresses of the RAM configuring the lookup table 2). .

As a result, an appropriate gradation conversion characteristic corresponding to the maximum value and the minimum value of each image data, that is, a window is set.

The above-described configuration and operation are no different from those of the conventional image processing apparatus of this type. The digital image data output from the A / D converter 1 is also input to the frame memory 8 and the motion detector 9 which constitute the motion detecting means provided by the present invention. The frame memory 8 stores the current image data and delays it by one frame.

The motion detector 9 compares, for each pixel, the current image data output from the A / D converter 1 and the previous image data read one frame before read from the frame memory 8. The motion of the image is detected from the signal.

The detection of the difference signal is a method of setting a motion detection range effective for detecting the motion of an image other than the region of interest and obtaining the sum of absolute values of difference values in a plurality of pixels within the motion detection range. Alternatively, a method of obtaining the difference in the total sum of pixel values of the entire image may be used. When the difference value between the current image and the previous image obtained in this way is larger than a predetermined value, the motion detector 9 indicates that the image is moving due to postural change, rapid filling of the contrast agent, or the like. LUT
A control signal is sent to the control circuit 7 to stop the automatic gradation control function so as not to change the gradation conversion characteristic, that is, the window. As a result, since the window is held in the window before the movement of the image, there is no sudden change in the contrast or brightness of the display image due to a sudden change in gradation.

Therefore, the LUT control circuit 7 does not change the gradation conversion characteristics according to the maximum value and the minimum value detected when the image is moving due to body position conversion, rapid filling of the contrast agent, etc. The gradation conversion characteristics are substantially the same as the gradation conversion characteristics before the movement of the image, and it is possible to display an image with stable contrast and brightness without a sudden change of the screen. In the embodiment, the control function of the gradation conversion characteristic of the LUT control circuit is stopped in response to the output of the motion detector, and the gradation conversion characteristic before the movement of the image is retained. You may make it switch to the preset gradation conversion characteristic which brightness does not change suddenly.

[0015]

As described above with reference to the embodiments, according to the digital image processing apparatus of the present invention, the motion detecting means for detecting the movement of the image is provided so that the maximum value and the minimum value of one image can be detected. Correspondingly, the automatic gradation function that changes the gradation conversion characteristics is controlled, and the automatic gradation function is disabled when motion of the image is detected. If there is no sudden change in the gradation characteristics due to the movement of the image due to such things as there is no movement of the image, the gradation conversion characteristics corresponding to the maximum and minimum values of the image are given for each frame. The gradation conversion characteristic, that is, the window can be dynamically set. As a result, it is possible to always obtain a high-quality image having contrast and brightness that are easy for a doctor or the like to see.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a graph showing gradation characteristics.

[Explanation of symbols]

1: A / D converter 2: Look-up table 3: D / A converter 4: TV monitor device 5: Maximum value detection circuit 6: Minimum value detection circuit 7: LUT control circuit 8: Frame memory 9: Motion detector

─────────────────────────────────────────────────── ───Continued from the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H04N 7/18 L

Claims (1)

[Claims] 1. An A / D conversion means for converting a current video signal into a digital signal, a gradation conversion means for converting the gradation of the A / D-converted digital video signal, and one of the digital video signals. Means for detecting a maximum value and a minimum value in each image, and a gradation conversion control means for controlling the gradation conversion characteristic in the gradation conversion means in accordance with the detected maximum value and minimum value. In a digital image processing apparatus comprising: a motion detecting means for comparing the current digital video signal with a previous digital video signal to detect a motion of an image, and the motion detecting means of the gradation converting means. A digital image processing device characterized in that a control function of gradation conversion characteristics is stopped.