JPS60105388A - Picture data interpolation device - Google Patents

Abstract

PURPOSE:To make it possible to smoothly interpolate by filtering and interpolating picture data so that the interpolation at the blank part between actual data is in an ideal distribution with a digital filter. CONSTITUTION:A picture memory 1 stores the picture obtained from an ultrasonic device. An interpolation point counter 2 detects and counts the interpolation points between picture elements by means of the actual data and in case of interpolation points, the actual data located just before are outputted to the rear stage side. A coefficient generator 4 receives the output information of an echo depth detector 3 and a counter 2 and for the data obtained from a memory 1, generates a correction coefficient to obtain the interpolation data. A digital filter 5 receives and operates the correction coefficient outputtedby a coefficient generator 4, thereby obtaining the ideal interpolation data at respective interpolation points from the data string given from a memory 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an image data interpolation device for interpolating image data of an ultrasonic diagnostic device or the like.

[Technical background of the invention]

For example, one of the ultrasonic diagnostic apparatuses used for medical diagnosis is a sector scan type ultrasonic diagnostic apparatus using an electronic scanning type ultrasonic probe (F-rope).

This device uses, for example, an array-type ultrasonic probe consisting of a plurality of ultrasonic transducer elements arranged in parallel, and for each ultrasonic transducer of this ultrasonic probe, By exciting each ultrasonic vibrating element by changing the excitation timing accordingly, the ultrasonic waves generated from each ultrasonic vibrating element interfere with each other to form an ultrasonic beam heading in the target direction. , the ultrasonic beam is made to perform sector scanning by electronically controlling the excitation timing.

In addition to the above ultrasonic diagnostic apparatus that performs sector scanning, there is also a mechanical sector scan system in which a single ultrasonic probe is scanned in sectors by a drive mechanism.

By the way, in such an ultrasound diagnostic apparatus, in order to display a fan-scan real-time tomographic image (real-time sector-scan tomographic image) on a television scanning monitor, echo signals obtained according to the transmission direction of the ultrasound beam are classified. The image data is written to the address of the pixel position corresponding to the ultrasonic raster direction of the frame memory that stores the image data as the original data of the echo signal on the ultrasonic raster of the monitor screen corresponding to the transmission direction, and the frame memory is written in accordance with the television scanning. Contents The entire horizontal direction, that is, the image is read out sequentially in the horizontal axis direction in accordance with the television scanning, and when the -scanning line is read out, the position is shifted in the vertical axis direction and read out again in the horizontal direction. Based on the incoming image data, linear interpolation processing is performed to fill in the pixels between ultrasound rusks. That is, the brightness levels of each image data at adjacent ultrasonic raster positions are connected with a straight line, and the data at each pixel position between these ultrasonic rasks is interpolated with a dinotal value corresponding to the level indicated by the intersection with this straight line. be.

Therefore, an image signal is sent to the monitor in which the blank space between each ultrasonic rask is filled with data obtained by linear interpolation based on the image data on the adjacent ultrasonic rask.
As a result, a dense ultrasound tomographic image can be obtained even if the number of ultrasound rasters (that is, corresponding to the number of ultrasound beams) is not sufficient. Sector scanning using the ultrasonic beam is performed continuously and repeatedly, and the data of the echo signals obtained one after another is stored in the frame memory and the position corresponding to the beam direction where the echo signal was obtained is updated with the old data. As the ultrasound progresses, a real-time ultrasound tomographic image is displayed on the monitor.

By the way, the interpolation process for pixels in the image data blank area between ultrasound rasters is performed by sequentially reading out the contents of pixels in the horizontal axis direction of the frame memory, and obtaining data by linear interpolation from the image data of adjacent ultrasound rasters. This was then used as interpolation data to fill in the blank space between the adjacent ultrasonic rusks, and this was used to perform -dimensional interpolation processing, digital-to-analog conversion, and a TV synchronization signal was added to create a composite video signal. Since the interpolated data is then fed to a television scanning monitor and displayed as an image, there is often a slight difference between the values of the interpolated data and the image data at the ultrasound raster positions on both sides, depending on the resolution of the digital data. Therefore, this causes a virtual image to be generated or an unnatural image to be displayed.

In other words, let us consider the case where an image data string as shown by black circles in FIG. 1 is interpolated. In the figure, the black circles are the pixels at the ultrasonic raster positions, the white circles are the pixel positions of the blank areas, and the vertical axis is image data corresponding to brightness. As shown in Figure 1, the image data at adjacent ultrasonic raster positions (black circles in the figure) are connected by a straight line, and the interpolated data for the pixel position that is the blank area between the pixel positions of the image data is the interpolated data at the pixel position. The level of the straight line (d) is assigned to the level of the straight line in ) is divided by the number of blank pixels existing between these pixels, and interpolated data is obtained by giving a difference to each pixel for each obtained portion, so at this time,
Interpolated data is not quantized for amounts smaller than its minimum resolution, Δ2.

Therefore, even if there is actually a slight difference within 32 in the data value to be interpolated, it will not be reflected in the data value, and as a result, only a change in steps of Δ2 will be given, and the interpolation data will be interpolated. When an image is displayed using the image data after the interpolation, it will not only look unnatural, but also cause glare because the peaks tend to be steep due to linear interpolation.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image data interpolation device that can display more natural images.

[Summary of the invention]

That is, in order to achieve the above-mentioned object, the present invention solves the problem that, when there is blank data to be interpolated mixed with data forming an image in data for each pixel position of a given image, the data for each pixel position is interpolation detection means for receiving the data and detecting an interpolation point between data for image formation, counting the number of times the interpolation point has been detected during this period, and outputting the latest received data for image formation; The data X11 K'2 r... of the latest plural line segments of the data output from the interpolation detection means has a data storage capacity equal to the number of interpolation points existing between the image forming data.
A data holding unit that holds xn uses the correction coefficient a given to these multiple sets of data...''!+aB to calculate in -・a2 al for the data X l r X 2 + ''' XI +an-a3 a2X
22 +a4as xs +-+an -84a3 xn-2
+an-as a2xn-.

2 + discharge...lL3 a2 al The weighting function of the in/4' pulse response of the ideal filter set in advance is the correction coefficient adan・
・・a2. 1J, and a coefficient generating means for reading out and outputting a correction coefficient corresponding to the value of the number of times of interpolation point detection. Interpolation is performed using a digital filter to obtain an ideal distribution.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

In other words, in order to display an image obtained by an ultrasound sector scan more naturally on a television scanning monitor, it is necessary to It is necessary to fill in the blank parts with some interpolated data. Ideally, it is desirable to interpolate the original echo information using a smooth, continuous, and vibration-free function as shown in FIG. This FIG. 2 is an ideal example of interpolation, where black circles are actual data and white circles are interpolated data.

The present invention aims to increase resolution and improve image quality by performing processing to improve azimuth resolution, and then performing smoothing to obtain an interpolated image close to the ideal shape as shown in Figure 2. It is.

In other words, the resolution of images in ultrasonic devices can be roughly divided into two types: distance resolution and azimuth resolution.

Among these, the distance resolution is the resolution in the direction in which the ultrasonic waves propagate, and this is approximately determined by the pulse width of the ultrasonic waves that are radiated in a cylindrical manner.

On the other hand, the relative resolution is the resolution within a cross section perpendicular to the propagation direction of the ultrasonic wave, and this is roughly determined by the beam thickness of the transmitted ultrasonic wave and the receiving directivity of the receiving ultrasonic transducer. The thickness of the transmitted ultrasonic beam is determined by the directivity of the transmitting ultrasonic transducer; in other words, the azimuth resolution is determined by the directivity of the transmitting ultrasonic transducer and the receiving ultrasonic transducer. It is safe to say that it will be done.

All of these are determined by the unique conditions of the ultrasonic device, but if we also focus on azimuth resolution, the ultrasonic signal is a sound wave, so it spreads, and in the subject, it spreads at a high frequency. There is a tendency for the area components to be attenuated, and this has a negative effect on the azimuth direction.

Therefore, by correcting this, it is possible to improve the lateral resolution of the already obtained ultrasound image.

In the present invention, filtering processing is performed using a digital filter based on actual data to obtain ideal interpolated data at interpolation points, and smoothing is performed on these data if necessary to obtain image data close to the ideal. .

Figure 3 shows an example of the image data sequence with improved azimuth resolution, and Figure 4 shows the image data sequence after smoothing. It can be seen that

An embodiment of the present invention using this principle will be described below.

FIG. 5 is a block diagram showing the configuration of this device.

In the figure, reference numeral 1 denotes an image memory having a capacity of at least one frame for storing an ultrasonic image obtained from a sector scan type ultrasonic device (not shown).

generate address information corresponding to the position of the ultrasonic beam in an ultrasonic rask address generator, and control the ultrasonic device so that the ultrasonic beam direction is set in advance for each address in accordance with this address; A write address generator (not shown) that receives the output of the ultrasonic rask address generator and generates a write address for the image memory 1 corresponds to the transmitting direction of the ultrasonic beam. All the addresses of the image memory 1 are generated and the image data is stored in the memory specified by the address of the image memory 1.

Further, the readout of the image memory 1 is carried out by a readout address generator (not shown) at a speed corresponding to the television scanning, and by sequentially switching and specifying the address of the image memory 1 so that the horizontal and vertical scanning is the same as the television scanning. .

Reference numeral 2 denotes an interpolation point counter, which receives the image data read out from the image memory 1 and calculates the number of blank pixels in the image data between adjacent ultrasonic rasks (receiving the ultrasonic data). If the data is zero, the data value will be zero, so if the data is zero, it is a blank pixel). Interpolation point data is stored in advance, and the data is read out by specifying the address using the output address of the read address generator, thereby calculating interpolation points and the number of interpolation points between pixels (vixels) based on the actual data, and performing interpolation. If it is a point, the immediately preceding actual data is output to the subsequent stage.

Reference numeral 3 denotes an echo depth detector that detects the depth position at the time of ultrasonic echo detection in the image data read out from the image memory 1, and calculates the depth from the TV display position and applies a filter function to improve the azimuth resolution. Used as a depth/grammeter. Specifically, it is constructed of, for example, a memory, and depth information is written in an address corresponding to each pixel position in the image memory 1, and the depth information is read out from the address corresponding to the output address of the read address generator.

4 is a coefficient generator that generates a filter function for improving azimuth resolution and obtaining ideal interpolation data, which receives information output from the echo depth detector 3 and interpolation point number counter 2 and generates a coefficient from the image memory 1. The interpolation point position,
It generates correction coefficients to obtain ideal interpolation data corresponding to the number of interpolation points and echo depth.

5 is a digital filter that receives the correction coefficients output from the coefficient generator 4, performs calculations using these correction coefficients, and obtains ideal interpolation data at each interpolation point from the data string given from the image memory 1. be.

6 is a buffer that temporarily holds the output data of the digital filter 5, and 7 is a D/A converter that converts the data provided through the buffer 6 into all analog signals.

FIG. 6 shows a detailed block diagram of the main parts of this device.

2 is an interpolation point counter, which receives data sequentially read out for each pixel from the image memory 1 in accordance with television scanning;
The content of the data (for example, at a pixel position where no ultrasonic echo data is stored, the data is 0'',
Interpolation point detector 2 detects whether or not it is an interpolation point position by indicating a data value other than "O" if ultrasonic echo data is stored.This interpolation point detector 2 detects an interpolation point. While generating an output, a counter 22 and a multiplexer 2 count the detection output to obtain the number of interpolation points.
3. Consists of a latch 24 that holds the output of this Malp-Glexer 23, and temporarily holds it every time it receives the output of the 24-digit multiplexer 23, and the multiplexer 23 is connected to the interpolation point number detector 21, which generates an interpolation point detection output. When this happens, the output of the latch 24 is selected, and when the interpolation point detection output cannot be obtained, the output read from the image memory 1 is selected and given to the latch 24.

4 is a coefficient generator, and this coefficient generator 4 has n read-only memories (for example, P-ROM) 4- for the maximum number of interpolation points.
2 to 4-n, each of which stores interpolation coefficients that provide an ideal interpolation data distribution according to the number of interpolation points and the position of the interpolation points. Output.

When considering echo depth, correction coefficient data including coefficient multiplication for resolution correction corresponding to echo depth? Let me remember it.

5 is a digital filter, and at least n shift registers 51-1. 51-n are connected in series, and the output data of the latch 24 of the interpolation point counter 2 is given to these latches 51-1 to 51-n. Further, the digital filter 5 is an adder 5.
2-J, 52-2. -52-m, 54-J,
54-, multiplier 53-1゜53-2.53-2.・
...63-t, the adder 52-1 adds the output of the latch 24 and the output of the final stage shift register 51-n, and the adder 52-2 adds the output of the first stage and n-1. The configuration is such that the outputs of the shift registers 51-1+57-n-1 of the second stage are added together so that the amount of addition is digitized. Further, addition is not performed to the shift register 51-C at the center position.

Multiplier 53-1.53-2. ...53-1-1 is provided corresponding to each adder 52'-1# to 52-m, and 53-1 is called 52-J, and 53-2 is called 52-2. In addition, 53-1 has the output of 4-1 of the read-only 4-1.4-2e to 4-n, and 53-2 has the output of 4-2. Corresponding correction coefficient outputs are provided, and these are multiplied and output. The multiplier 53-6 uses a read-only memo 9 for the output data of the central shift register 51-e.
Correction is performed by multiplying the correction coefficient data read from 4-n. Further, the adder 54-1 is a multiplier 53-1, 53-2
54-2 adds the output of a multiplier 53-30 (not shown) and the output of the adder 54-1. Further, the adder 54- is used to add the output of the multiplier 53-t and the output of the adder 54-k-1.

Next, the operation of this device having the above configuration will be explained. For example, the number of ultrasonic rasters of the ultrasonic device (not shown) used is 1.
Assuming 28 lines, this ultrasonic device will generate raster directions from 1 to 128 in order from a means (not shown) for generating an ultrasonic raster address that determines the ultrasonic raster direction necessary to perform a sector scan by starting the device. The address is repeatedly generated at a predetermined timing. These sequentially output addresses are output to an ultrasonic transceiver and a writing address generator (not shown) in the ultrasonic device, so that the ultrasonic transceiver is directed in the same direction as the ultrasonic raster set in advance corresponding to each address. The ultrasound probe for ultrasound transmission and reception is controlled so that the ultrasound beam transmission and reception directions are as follows. The ultrasonic reception signal, that is, the echo signal thus obtained is given to an A/D converter, where it is converted into a digital value and becomes image data.

On the other hand, when the write address generator receives an address output, it sequentially corresponds to the address in the ultrasonic raster direction corresponding to this address in the depth direction (the depth direction in the diagnostic part of the subject) according to the propagation time of the echo signal. update the address and output it.

Address output and A/D of this write address generator
The output of the converter (image data) is sent to image memory 1,
The image memory 1 stores image data at the address specified by the address output. Therefore, the image memory 1 contains image data corresponding to the echo signal level from each depth position caused by the ultrasound beam at a position corresponding to the transmission direction and depth of the ultrasound beam on the memory corresponding to one screen's worth of pixels. will be remembered as.

Since the ultrasonic raster address generator updates the addresses sequentially, the ultrasonic beam is scanned in a fan shape, and the image data obtained corresponding to this is stored in the image memory l. Therefore, image data of a tomographic image obtained by fan-shaped scanning of an ultrasonic beam is stored on the image memory 1.

The image data in the image memory 1 is stored at a position specified by an output address of a read address generator (not shown) that sequentially generates read addresses at timings corresponding to television scanning and in a sweep direction matching the television scanning. The object is read out in accordance with a read timing signal (not shown) for read timing, and is output to the interpolation point counter 2. The image data on the image memory 1 is stored at pixel positions corresponding to the direction of the ultrasound beam, and when this is displayed as a TV image, the image data exists only at the position relative to the direction in which the ultrasound echo signal was received. , the image of the ultrasonic echo signal is displayed only at that position.

This is the ultrasonic raster on the TV image, but as mentioned above, the ultrasonic beam is only transmitted and received in 128 directions within a predetermined angular range by fan-shaped scanning, so the ultrasonic raster as shown in Figure 8 is As viewed from the position of the sonic probe P, blank pixels with no echo signal are created between the ultrasonic tests 5 (between the ultrasonic beam positions).

Therefore, since the tomographic image becomes coarser as it goes in the depth direction, normally, for a pixel at a pixel position on the frame memory 4 where there is no image data of an echo signal, a pixel at an adjacent ultrasonic 2 star position via this pixel is Interpolation data is collected and interpolated using linear interpolation based on the image data.

When the image data read out from the image memory 1 as described above is received, the interpolation point number counter 2 calculates the image data of the pixel position between adjacent ultrasonic rusks, that is, the number of blank pixels based on this image data. is detected, and in the blank area, an interpolation point detection output indicating that the interpolation point is located is generated and counted. Furthermore, when there is no interpolation point detection output, the image data is latched and output, and when there is an interpolation point detection output, this latched image data is output again.

That is, assuming that the interpolation point counter 2 has a configuration as shown in FIG. It is detected whether it is a point or not. If it is an interpolation point, an interpolation point detection output is generated.

Assume now that the image data has, for example, an 8-bit configuration, and that pixels other than those at the ultrasonic raster position have data values of zero because there is no echo signal.

When reading in the television scanning direction, if it is initialized at the start position of each line in each line direction,
Since the output data from the image memory 1 is zero until the pixel at the outermost ultrasonic raster position is read out in each row direction, a data string containing only zeros is sequentially input to the interpolation point counter 2. . During this period, the interpolation point number counter 2 generates an interpolation point detection output for each pixel data output from the interpolation detector 21 and the image memory 7, and outputs the interpolation point detection output to the counter 2.
Give to 2. The counter 22 counts this, and the interpolation point detection output is also given to the multiplexer 23.
Multiplexer 23 selects the output of latch 24, receives it, and supplies it to latch 24. Therefore, at this point, the content held by the latch 24 is always zero. Every time the latch 24 outputs data, the data is sent to the shift register 5 NO 1 in the upper stage of the digital filter 5 and held.
The old data held until now is sent to the subsequent shift register. When the data of the pixels of the outermost ultrasonic rusk position are read out from the image memory 1, the interpolation point detector 21 does not generate an interpolation point detection output.
The count value of the counter 22 is cleared when there is no output of 1 and only the read timing signal of the image memory 1 is generated, but the count value is always given to the coefficient generator 4.

As a result, the coefficient generator 4 stores data corresponding to the given count value in each read-only memory 4-J, 4-2 . ~
4-n, the corresponding multiplier "53-1.~5"
3-1 K is given, but each latch 24° shift register 5
1-1. Since the contents held by 51-n are zero, the outputs of each multiplier 53-1 to 53-t are zero. Therefore, the addition output to the adder 54- becomes zero.

In this way, in readout in the television scanning direction, each row direction is initialized at each leading position. Since the output data from the memory 1 is zero, a data string containing only zeros is sequentially input to the complementary point counter 2. Therefore, during that time, the interpolation point detector 21 generates a detection output for each pixel-by-pixel data output from the image memory 1, and the counter 22 counts this.

When the data of the pixel at the outermost ultrasonic rask position is read out from the image memory 1, the interpolation point detector 21 does not generate an output, so there is no output from the interpolation point detector 21 and only the readout timing signal of the image memory J By clearing the counter 22 when this occurs, the number of interpolation points between the time when the data of the pixel at the ultrasonic rask position is injected and that point is determined.

Furthermore, data is read out from the image memory 1, and data of some (for example, three) blank pixels continues.
It is assumed that the data of the pixel at the next ultrasonic rask position is read out.

During this time, since three zero data are output, the count value of the counter 2 is successively counted up to N1"N211.113".

This count value is calculated for each read-only memory 4-1, 4-2. ~
4-n, and the data at the address corresponding to the given count value is sent from each memory as a correction coefficient to the multiplier 53-1. .about.53-6, where the corresponding adders 52-1. ~ and the output of latch5NOC.

That is, when the image data at the ultrasonic rask position is input manually, the interpolation point detector 21 detects that it is not an interpolation point and switches the multiplexer 23 to the image memory 1 side. Therefore,
Image data from the image memory 1 is sent via the multiplexer 23 to the latch 24 and latched there. This latched image data is transferred to the adder 52-1 and the shift register 51 at the next reading timing of the image memory 1.
-1, and at this point, the image data read out from the image memory 1 becomes zero because it becomes the interpolation point position. Therefore, the counter 22 becomes 1'', and the multiplexer 23 selects the output data of the latch 24 and supplies it again to the latch 24 to hold it.

The adder 52-1 that receives the output data of the latch 24 adds this data to the output data (zero) of the final stage shift register 51-n and provides the result to the multiplier 53-1. Data obtained by multiplying the output data of the latch 24 by a correction coefficient is given to the next stage adder 54-1. In addition, other adders 52-2. Although addition is also performed in the shift register 51-2.

Since .about.51-n-1 is zero, only the output of adder 53-1 is output from adder 54-1. ~After 54-k/'F
y sent to Noah 6.

Similarly, the image data read out at the next read timing of the image memory 1 becomes zero.

Therefore, the counter 22 becomes 1'', and the multiplexer 23 selects the output data of the latch 24 and supplies it again to the latch 24 to hold it.

The adder 52-1 that receives the output data of the latch 24 adds the output data (zero) of the final stage shift register 51-n to this data and provides it to the multiplier 53-1.
3-1 supplies data obtained by multiplying the output data of the latch 24 by a correction coefficient to the next stage adder 54-1.

At this time, the data in the shift register 51-1 is transferred to the latch 24.
The old data held in this shift register 51-1 is replaced by the output data from the shift register 51-1.
-2.

Therefore, the adder 52-2 is connected to this shift register 51-1.
The old data output from the shift register 51-n-1 is added to the data (zero) output from the shift register 51-n-1, and this added value is sent to the multiplier 53-2, where the correction coefficient value output from the memory 4-2 is calculated. Multiplied. Each multiplier 53-1. The outputs of 53-t to 53-t are added together through adders 54-1, 54-2, and 54-k, and output to the buffer 6.

In this way, when the image data output from the image memory 1 is zero, the data held in the latch 24 is read in again.
, if the image data is other than zero, this image data is captured and held in the latch 24. Then, each time image data from the image memory 1 is read, the subsequent shift register 51-1. ~51-n.

Therefore, until the image data of the next ultrasonic rask position arrives, the image data of the previous ultrasonic rask position is held and the shift register 51-1. ~51-n are shifted to the later stage side.

In addition, each adder 52-1, 52-2... adds each pair of data from the outer frame to the inner frame of the n-stage shift registers 5j-1 to 51-n, and adds data in pairs according to the interpolation point position. After multiplying by the coefficients, the sum of these is used as the interpolation data of the interpolation point. Therefore, by appropriately selecting the correction coefficient value, it is possible to obtain ideal interpolation data corresponding to the position of each interpolation point.

That is, to realize a digital filter with given characteristics, first find an impulse response or transfer function that approximately satisfies the design conditions, and then construct a digital circuit to realize them. A digital filter with a finite impulse response is inherently stable, and can also have ideal linear phase characteristics.

On the other hand, if the impulse response continues indefinitely, the transfer equation must be expressed as a rational equation in order to realize the circuit. This type of stable filter may or may not have a linear phase characteristic. Although there is a direct method of designing a digital filter from the beginning, a method of designing an existing analog filter based on SZ conversion is also effective. Since an analog filter can be expressed by a differential equation in the time domain, it is converted into a digital filter by differential differentiation, and the S domain is divided into two.
can be mapped to a region. However, since this method does not accurately map the left half plane of the S plane onto the unit circle of two planes, stability and frequency characteristics are not preserved, and this method is rarely used in practice.

However, an SZ conversion method that satisfies the above conditions has been developed, and the research results of analog filters are now being utilized in digital filters.

Here, also in the case of digital filters, high-pass, band-pass, and band-elimination filters can be obtained by suitably frequency converting a low-pass filter.

A causal discrete-time linear system is called a digital filter. The input/output relationship of a digital filter is defined by the impulse response (h(n)), where the impulse response value h (n) is 0'; In contrast, when h(n)iii:0, a linear system defined by the impulse response (h(n)) is called an FIR filter, and N is the duration of the impulse response. The 2-conversion of the impulse response of the FIR filter is H(z)=h(0)+h(1)z-"i...+h(N-
1) z−(N−”) , , (2) and the Fourier transform is expressed as n=Q. H(1) is periodic with a period of 2π as follows.

H((-1)=H(ω+2πm), m=o, ±1.±
2. −−− −−・(4) Below, this H←) is FIR
This is called the frequency response of the filter.

Now, the frequency response H) is expressed as H(1) = ±l H@+) l a ”” −(5)
I will express it as Here, θ) represents the phase, which is first required to satisfy a specific functional relationship, and accordingly, the sign is selected so as to satisfy Equation (5). For example, a desirable property of an FIR filter is that the phase characteristic as a function of ω sometimes becomes θ←);-αω (6). Here, α is a constant called a phase lag, and an FIR filter having this property is called a summer-type linear phase filter. Impulse response (
When the value of h(n)) is not 0 for at least two or more n, that is, when (h(n)) is neither an identity sequence of 0 nor an impulse. , that FIR filter is meaningful (non-tri
vial).

An FIR filter with a linear phase has a symmetrical impulse response as shown below, and the phase delay α is uniquely defined by the duration N.

Prove this. Now, the impulse response (h(n))
Assume that the FIR74 router with has a summer type linear phase characteristic. From the above equations (3), (5), and (6), the following two equations can be derived.

By taking the ratio of these two equations, we get n=O, so from this we get n:Q n=Q. This formula can be written as from the addition formula for trigonometric functions. Since this is in the form of a Fourier series, if a solution exists, it is unique. Therefore, if equation (7) does not hold, then h(n)30 for all n, or if α is a positive integer, h for all n other than n=α.
(n) Must be thirty. Thus, equation (7) must be satisfied for the FIR filter to be meaningful. At this time, in order for equation Q'4 to hold true for all ω, equation (8) must be satisfied.

Equation (8) shows that the impulse response of the FIR filter having summer type linear phase characteristics is symmetrical about n=(N-1)/2.

Generally, an FIR filter whose phase characteristic is determined by the frequency response expressed by equation (6), which is the above-mentioned linear relational expression, is called a filter having a linear phase characteristic, but since the image is bilaterally symmetrical, a linear phase is preferable.

Therefore, the present invention uses an FIR filter.

In this device, the digital filter 5 is ym=Σh(k
) x (n-k) - - - α4 = 1 A filter is used. Here - is the filter output, x(
n-k) is the input image data, and when formula (to) is expanded, 'Im= a t4 (''' (aB(a s (Xt
+x, )+X2 +xn-1)+xa+xn -z
)...)+Xyu+x,) ・・・・・・・・・a421
+1 (Note that ayu, aB, and al are correction coefficients) When this is further expanded, +aH...alalaljc.

ym=Σh (k) aB al・・・・・・・・・
By applying a correction coefficient aAy...' S+6g p a 1 to each impulse response kl+ to h1, an output value ym that has the desired ideal distribution can be obtained. By setting, it becomes possible to obtain interpolated data with distributions as shown in FIGS. 2 and 4. The circuit shown in FIG. 6 is a combination that calculates this relational expression, and the correction coefficient is read-only memory IJ4-7. ...4-n in advance.

Further, it is also possible to improve the azimuth resolution by setting a correction coefficient in consideration of the echo depth, reading out the corresponding correction coefficient in accordance with the echo depth and the interpolation point position, and correcting it.

The image data after interpolation processing sent to buffer 6 is "/A"
The converter 7 converts the signal into an analog signal, adds a synchronization signal, etc., and then sends it to a monitor (not shown) to display it as an image.

Note that since this can be known in advance from the pixel position in a portion outside the scanning area of the sector scan, it goes without saying that it is set in advance not to perform interpolation in this area.

In addition, Fig. 7 shows the state of change in the signal of ~ in the circuit of Fig. 6 in the form of a time chart.In this way, this device uses the actual data in the tomographic image data obtained by the ultrasonic device. Since the interpolation of the blank space in between is performed using a digital filter, filtering is performed to obtain an ideal distribution, smooth interpolation can be performed, and since it is a digital filter, it can be It becomes possible to perform smoothing to remove the sense of discontinuity in the sound wave image and to improve the azimuth resolution.

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, but can be implemented with appropriate modifications within the scope of the gist thereof. Although we have shown an example where it is applied to a device, it can also be applied to a linear scanning method as shown in Figure 9, where there is a blank pixel between image data and interpolation is performed for this pixel. In some cases, this interpolation method can be applied as is, and the digital filter can also be applied in various ways, such as being able to be realized using software processing by a computer or other arithmetic devices.

〔Effect of the invention〕

As described in detail above, the present invention provides a method for receiving the data for each pixel position when there is blank data to be interpolated mixed with the data forming the image in the data for each pixel position of the given image. interpolation detection means for detecting an interpolation point of data between data for image formation, counting the number of times the interpolation point is detected during this period, and outputting all of the latest received data for image formation; It has a data storage capacity at least equal to the number of interpolation points existing between the image forming data, and the latest plural coarse fraction data X1+X2*...Xmf of the data output by the interpolation detection means, data to be retained , the data
l 1) C21"' X B+a?-"' IL48
s! ++-2+ IL! L...hs&zXm-1+
&! L 0. '2 2 2 83! Lgllll! , a digital filter that outputs the data obtained by this calculation every time the data for each pixel position is given, and an ideal filter that is set in advance for each number of interpolation points. The weighting function of the ini4 pulse response is the correction coefficient aBt...a211L1
and a coefficient generating means for reading out and outputting a correction coefficient corresponding to the value of the number of times of interpolation point detection. Since the interpolation of the blank space is filtered and interpolated using a digital filter to obtain an ideal distribution, smooth interpolation can be performed.Also, since it is a digital filter, ultrasonic It is possible to provide an image data interpolation device having features such as smoothing that removes a sense of discontinuity in an image and improving azimuth resolution.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an example of data interpolation using linear interpolation, Fig. 2 is a diagram showing an example of ideal data interpolation, Fig. 3 is a diagram showing an example of data interpolation aimed at improving azimuth resolution, and Fig. 4 is a diagram showing an example of data interpolation using linear interpolation.
The figure shows an example of the smoothing of FIG. 3, FIG. 5 is a block diagram showing an embodiment of the present invention, FIG. FIG. 8 is a diagram for explaining the situation in which interpolation points are generated by fan-shaped scanning, and FIG. 9 is a diagram showing linear scanning. 1... Image memory, 2... Interpolation point counter, 3...
・Echo depth detector, 4...Coefficient generator, 5...Digital filter, 6...Buffer, 7...''/A
i converter, 21... interpolation point detector, 22... counter, 23... multiplexer, 24... latch, 51
-1°~51-n...Shift register, 52-1.5
2-2.54-1. ~54-k...Adder, 53-1
．． 53-2. ...53-t... Multiplier. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 5 Figure 6

Claims (1)

[Scope of Claims] When there is blank data to be interpolated mixed with the data forming the image in the data for each pixel position of the given image, the data for each pixel position is received and the image is an interpolation detection means for detecting an interpolation point of data between data for forming an image, counting the number of times of detection of the interpolation point during this period, and outputting the latest received data for forming an image; Data xi r
+... Data holding □ section that holds the data, correction coefficient l given to these multiple sets of data,...a2+a
Using I, for the data xl r x21 ""n, an -I JalXl + an-Ja2X212 + aias
+ayu...-& 31L g The weighting function of the impulse response of the filter and the ideal filter, which is set in advance and corresponds to each number of interpolation points, is the correction coefficient ILn, . . .
t2. 1. An image data interpolation device comprising: coefficient generating means for reading out and outputting a correction coefficient stored as al and corresponding to the value of the number of times of interpolation point detection.