JPH02287886A - Image processor - Google Patents

Abstract

PURPOSE:To execute an edge emphasis processing without deteriorating an S/N ratio in a part of a motion in a screen by detecting the motion at every part of an image, determining a ratio of signals passing through two space frequency emphasis processing circuits in which degrees of space frequency emphasis are different in accordance therewith and adding these two signals. CONSTITUTION:A video signal is converted to a digital signal by an A/D converter 5, and sent to two space frequency emphasis processing circuits 9, 10, respectively. As for one space frequency emphasis processing circuit 9, its degree of space frequency emphasis is set strongly, and as for the other space frequency emphasis processing circuit 10, its degree is set weakly. In such a way, an image brought to strong edge emphasis processing and an image brought to weak edge emphasis processing pass through LUTs (look-up tables) 11, 12 and added by an adder 13. Therefore, by reducing the degree of edge emphasis of a part of a motion in a screen, and strengthening the degree of edge emphasis of a still part, a glaring sense of a noise part can be suppressed.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an image processing device that performs spatial frequency enhancement (edge enhancement) processing on images such as X-ray fluoroscopic images.

[Conventional technology]

2. Description of the Related Art Conventionally, spatial frequency enhancement processing has been performed on images such as X-ray fluoroscopic images in order to make them useful for actual medical diagnosis. This spatial frequency emphasis processing is performed, for example, by template processing in which a Laplace operator as shown in FIG. 5 is applied to each pixel of the entire screen.

[Problem to be solved by the invention]

However, in the past, edge enhancement processing was performed by applying a --like weight to the entire screen, so if there was a moving part of the screen, this processing was also performed on the moving part of the screen, and as a result, S/N where the noise part was noticeable
There was a problem that the ratio of the image was poor. That is, moving parts in the screen are blurred, and the signal level is lower than that of stationary parts. In contrast, the noise level is the same for both stationary and moving parts. Therefore, the moving portion has a worse S//N ratio than the stationary portion. If edge enhancement processing is applied to this moving part with a poor S/N ratio in the same way as a static part, the negative layer S/N ratio will be poor, and the noise part will be even more pronounced and the glare will be emphasized. The present invention proposes an image processing device that can perform edge enhancement processing without deteriorating the S/N ratio in moving parts of the screen and making noise parts less noticeable. purpose.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes two spatial frequency emphasizing processing circuits having different degrees of spatial frequency emphasis, and an image processing device having two spatial frequency emphasizing circuits with different degrees of spatial frequency emphasis. A circuit that detects movement for each part of the
A circuit that determines the ratio of the signals that have passed through the two spatial frequency emphasis processing circuits and adds the two signals (fAi can be obtained). [Operation] Movement is detected for each part of the image, and the two The proportion of the signal that has passed through the spatial frequency emphasis processing circuit is determined, and the two signals are added.The two spatial frequency emphasis processing circuits are set to have different degrees of spatial frequency emphasis.Therefore, the screen In the static parts, strong spatial frequency emphasis is applied and the image becomes a shape, and in the moving parts, weak spatial frequency emphasis is applied, or it becomes a shape. This results in an image that is not distorted, and the noise in that part of the image is made less noticeable. [Example] Next, an example of the present invention will be explained with reference to the drawings. , X-ray tube]
The ray passes through the subject 2 and enters the image intensifier 3, where it is converted into a transmitted X-ray image or an optical image, and then the T
It is converted into a video signal by the V right camera. This video signal (analog signal) is converted into a digital signal by the A/D converter 5 and sent to two spatial frequency emphasis processing circuits 9 and 10, respectively. This spatial frequency emphasizing processing circuit 9.10 includes a template 1, which applies a Laplace operator as shown in FIG. 5 to each pixel of the entire screen.
One of the spatial frequency emphasizing processing circuits 9 is set to have a strong degree of spatial frequency emphasizing, and the spatial frequency emphasizing circuit of the curved direction 0 is set to a weak degree. It is set. In this way, the image that has undergone strong edge enhancement processing and the image that has undergone weak edge enhancement processing are stored in LUT (lookup table) 1,
・1 Added by adder 13 via 12. L U T'
1], 1.2 is composed of, for example, a RAM, and functions as an input/output converter that converts and outputs the input signal value for each pixel, and its input/output conversion characteristics are shown in Figure 2. Various characteristics can be selected as shown below. That is, when the value of the input signal is I and the value of the output signal is O, for example, ○=k This coefficient 1 (is selected for each pixel by the signal from the motion detection circuit i\l. Therefore, the component with strong edge enhancement and the component with weak edge enhancement are mixed while selecting the ratio jπ for each pixel. In order to control this ratio, a frame memory 6, a subtracter 7, and a motion detection circuit 8 are stored.In other words, frame memory 0 stores the image one frame before. One elephant is stored, and the value of each pixel of this one image and the current image (direction of each pixel of the elephant) are subtracted for each corresponding pixel in the subtracter 7. The output of the subtractor 7 is almost zero in parts where there is movement, but it becomes a large output in parts with movement.The motion detection circuit 8 detects the magnitude of the movement according to the magnitude of the signal output from the subtracter 7 for each pixel. In this way, the image represented by the video signal output from adder ]3 is a signal with a strong degree of edge emphasis for pixels with no movement. This results in an image with a high proportion of signal components, and a high proportion of signal components with weak edge enhancement or no edge enhancement at pixels with movement.This video signal is converted to an analog signal by D/A converter]4. After the conversion, the image is sent to the monitor W15 and displayed as an X-ray transmission image with the degree of edge enhancement adjusted for each part of the image according to the amount of movement as described above. The video signal input to the emphasis processing circuit 9.10 may be one that has passed through a recursive filter 16 (not shown with a dotted line). In the modified example shown in Fig. 3, this recursive filter is constructed using the frame memory 6.The current image 1 and
The image of the previous frame stored in the frame memory 6 is added by the adder 19 through the LUTs 17 and 18, and is stored again in the frame memory 6. By repeating this process for each frame, the image is subjected to recursive filter processing. The resulting image is formed in the frame memory 6. LUT
17. The degree of remaining one phenomenon is determined by setting the input/output conversion characteristics in 18. The image of the current frame and the image subjected to recursive filter processing are input to the subtracter 7,
Since subtraction is performed between these, the subtracter 7 outputs a large output for moving pixels, and an almost zero output for pixels that do not move. In the modification shown in FIG. 4, recursive filter processing is further controlled for each pixel so that recursive filter processing is not performed on moving pixels. That is, the output signal of the motion detection circuit 8 causes the LUT 20 to
．． The input/output conversion characteristics of 21 are transferred to the controller 1, and the output image from one adder and the image of the current frame are added by the adder 22. An image is obtained with recursive filter processing applied to each pixel. This makes it possible to reduce the effect of afterimages in moving parts and prevent the image from trailing. [Effects of the Invention] According to the image processing device of the present invention, it is possible to reduce the degree of edge emphasis in moving parts of the screen and increase the degree of edge emphasis in static parts, thereby reducing the glare in noise parts. It is possible to obtain an image in which the details are easily seen by suppressing the noise and by strongly emphasizing edges in still parts.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
Graphs showing input/output conversion characteristics in the UT, FIGS. 3 and 4 are block diagrams showing modified examples, and FIG. 5 is a diagram showing a Laplace operator. 1...X-ray tube, 2...limb analysis, 3...image intensifier, 4...TV camera, 5...A/D
Converter, 6... Frame memory, 7... Subtractor, 8... Motion detection circuit, 9.10... Spatial frequency emphasis processing circuit, 1 1 , 12 , 17 , 18
, 20, 21... L U "I'"
, 13.19.22... Adder, 14... D/A converter, 15... Monitor device.

Claims (1)

[Claims] (1) Two spatial frequency emphasis processing circuits with different degrees of spatial frequency emphasis, a circuit that detects movement for each part of the image, and a circuit that passes through the above two spatial frequency emphasis processing circuits according to the detected movement. An image processing device comprising: a circuit that determines a signal ratio and adds the two signals.