JPH0486583A - Frame correlation circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a frame correlation circuit used in a digital scan converter (hereinafter referred to as DSC) in an ultrasonic diagnostic apparatus, a radar, a fish finder, or the like.

[Conventional technology]

In an ultrasonic diagnostic apparatus, a DSC is provided between an ultrasonic transmitting/receiving circuit and a monitor. 200SC is a device for converting image data obtained asynchronously with a television signal into a television signal, and is mainly composed of memory.

The DSC performs a frame correlation process that calculates the correlation for each image frame. This frame correlation processing averages the obtained images for each frame to reduce noise that causes flickering on the screen.

FIG. 2 shows a frame correlation circuit in a conventional DSC. In the case of the conventional device, it is the ROM1 that operates as the frame correlation circuit. In the ROMI, newly input data y is entered into the upper 8 bits of the address of the ROMI. On the other hand, 1 stored in the image memory 2
By inputting the previous frame data yi-+ to the lower 8 bits of the ROMI address, the output zi is
zi -a "iI+b'"/I-+ is obtained. This output data Zi is stored at the address in the image memory 2 where the data y, .

Here, in the conventional algorithm for creating the contents of ROM1, if address A is 16 bits and data D is 8 bits, then B=A/256 (rounded down), and the upper 8 bits of B near address correspond to data y1.C=A -BX256 C Near address lower 8 bits correspond to data y, -1 D=a-B+b-C. The purpose of conventional frame correlation processing is to remove noise, and the values of a and b are fixed.

As a result, ROMI constitutes a linear low-pass filter.

[Problem to be solved by the invention]

In an ultrasonic diagnostic apparatus, an amplification valve and the like in a cardiac B-mode image move at a fairly high speed, and there are flickering noises caused by speckles and side lobes in the heart chamber. This noise can be reduced by setting the coefficients a and b equally to ro and 5J and performing averaging processing as in the conventional device. However, in this way the coefficients a, b
If they are set equally, the image of an amplifying valve or the like that moves at a fairly high speed as mentioned above will be blurred.

On the other hand, if we want to clearly display this amplification valve, we can change a to "
1'', and b must be set to approximately r□.

In this way, the further you try to reduce noise, the more the low-pass is similarly applied to fast-moving parts of the image, resulting in blurred images. On the other hand, if you try to clearly display fast-moving parts, it becomes impossible to reduce noise.

An object of the present invention is to provide a frame correlation circuit that can reduce noise and clearly display fast-moving parts.

[Means to solve the problem]

The frame correlation circuit according to the present invention averages the obtained images for each frame and removes noise, and multiplies input frame data and previous frame data by respective coefficients. Correlation calculation data output means for outputting the added data is provided.

The correlation calculation data output means is configured so that its coefficient value is changed depending on the magnitude of input data.

[Effect]

In the present invention, coefficients used when performing correlation calculations are changed according to human data. That is, when the amplitude of input data is small, this input data can be determined to be noise, and therefore, as in the conventional case, coefficients that can reduce this noise are selected. Also, if the amplitude of the input data is large,
Since it can be determined that the signal has some meaning, in this case, a coefficient is selected that emphasizes the input data without taking an average with the previous data. Further, for input data having a level intermediate between noise and a signal having some meaning, the coefficient is set to a value intermediate between the case of noise reduction and the case of emphasizing human input data.

With this, for example, the B of the heart in an ultrasound diagnostic device can be
In the mode image, the image of the valve moving very quickly is clearly displayed, and the noise level is sufficiently correlated with the frame, so there is no flickering on the screen.

〔Example〕

FIG. 1 is a schematic block diagram of an ultrasonic diagnostic apparatus employing a frame correlation circuit according to an embodiment of the present invention.

This ultrasonic diagnostic device includes a diagnostic device main body 10 and a probe 11 connected to the diagnostic device main body 10. The probe 11 is composed of, for example, a plurality of micro vibrators. The apparatus main body 10 includes an ultrasonic transmitting/receiving circuit 12 connected to a probe 11, a DSC 13, a monitor 14, and a control section 15. Further, an A/D conversion circuit 16 is provided between the ultrasonic transmitter/receiver circuit 12 and the DSC 13 to convert an analog signal into a digital signal, and an A/D conversion circuit 16 is provided between the DSC 13 and the monitor 14 to convert the digital signal into an analog signal. A D/A conversion circuit 17 for conversion is provided.

The ultrasonic transmitting/receiving circuit 12 includes a high-frequency pulse oscillator for transmitting an ultrasonic beam, an amplifier for amplifying reflected echoes, a detection circuit, etc., and is configured to obtain a B-mode tomographic image signal. In addition, the DSC 13 includes a panzer memory, an image memory, a video signal mixer, etc.
This is a circuit for converting image data obtained by the ultrasonic transmitting/receiving circuit 12 into a television signal. Also this DS
A frame correlation circuit is configured in C13. DSC1
The signal obtained in step 3 is converted into an analog signal via the D/A conversion circuit 17 and displayed on the monitor 14.

As shown in FIG. 2, the DSC 13 is provided with an image memory 2 and a ROM 1 constituting a frame correlation circuit.

The ROMI uses the input data y and the data y8-1 of the previous frame as addresses, and outputs data Zi obtained by performing correlation processing from these data to the image memory 2. The contents of this ROMI are created using the following algorithm.

That is, the address is A (16 bits) and the data is D (8 bits). Then, B = A / 256 (rounded down) The upper 8 bits of the B near address correspond to the input data y, C = l - BX256 The lower 8 bits of the C near address correspond to the data y of the previous frame
, -1. At this time, (2) If the B and C are simultaneously less than d (for example, rlo, +), they can be determined to be noise, so the output data D is as follows: D=a+・B+b+・C a+ =b,=0. 5. Also, if B and C are simultaneously greater than or equal to d and less than e (end), these can be judged to be intermediate between noise and tomographic data, so the output data D is D=az ・B4-bZ
・C a2 =0.75 bz =0.25. Furthermore, ■If either B or C is greater than or equal to f (fee), it can be determined that these are tomographic data, so the output data D is D=a= ・[3+b, ・c a= =1.0. Let bz = 0.

In this way, depending on the amplitude of the input data, the coefficient a
, b as appropriate, noise with small amplitude can be sufficiently reduced by performing frame correlation processing. Therefore, flickering of images on the monitor is suppressed. On the other hand, for objects that move very quickly, such as heart valves in a B-mode image, the frame correlation process does not function, and the image does not become blurred. therefore,
A clear image can be obtained.

In the embodiment described above, the correlation processing coefficients are changed in three stages, but by dividing the coefficients into even more fine stages, fine-grained handling can be achieved.

Further, in the above embodiment, the frame correlation circuit of the present invention is applied to a DSC of an ultrasonic diagnostic apparatus, but it can be similarly applied to a receiver of a radar apparatus, a fish finder, etc., for example.

〔Effect of the invention〕

As described above, the present invention can sufficiently reduce speckle noise on the monitor and unnecessary noise due to side lobes, while reducing the noise for fast-moving objects. Images can be made clearer.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram of an ultrasonic diagnostic apparatus employing an embodiment of the present invention, and FIG. 2 is a block diagram showing a part of the DSC. 1...ROM, 2...image memory, 13...DS
C. Patent applicant: Shimadzu Corporation, factory representative: Yukio Ono

Claims (1)

[Claims] (1) A frame correlation circuit that takes the average of each frame of the obtained image and removes noise, and outputs data obtained by multiplying the input frame data and the previous frame data by respective coefficients and adding them. A frame correlation circuit, comprising: a correlation calculation data output means, the coefficient value of the correlation calculation data output means being changed according to the magnitude of input data.