CN101403728A - Phase distortion emendation method based on proximity correlation method in phased array ultrasonic detection - Google Patents

Abstract

During phased array ultrasonic detection, phase distortion among all passage signals occurs owning to the difference of assumed sound velocity and actual sound velocity, the non-uniformity of velocity in an object to be tested, the non-uniformity of all passage of a detection system, the natural phased error of the system and the like; the invention aims at providing a new method used for the corresponding phase correction of an ultrasonic phased array, in particular to an adjacent corresponding phase correction method; when the signal-to-noise ratio of an echo signal received by an array element is high, the precision of time delay evaluation can be effectively improved and the phase distortion among all the passage signals can be reduced; the adjacent corresponding phase correction method is based on the corresponding time delay evaluation between adjacent array elements and selects the echo signal of one array element in the array as a reference signal, and obtains the time delay quantity (phase difference) between two array element signals by the corresponding evaluation of the adjacent array element signals; and the time delay quantity between each array element and the reference array element is obtained by the gradual transmission and accumulative addition of adjacent array elements.

Description

In the phased array ultrasonic detection based on the phase aberration correction method of proximity correlation

Technical field

The present invention relates to ultrasonic phased array technology, especially the phase correction techniques of ultrasonic phase array.

Background technology

In phased array ultrasonic detection, the reasons such as heterogeneity of the inner velocity of sound of detected object, can cause and launch the phase deviation that focuses on each road signal in link and the collectiong focusing link in the phased array ultrasonic detection, thereby cause hyperchannel emission acoustic beam and receive acoustic beam and carry out phased signal after synthetic and distort, the amplitude and the signal to noise ratio (S/N ratio) of acoustic beam composite signal have been reduced, and making the acoustic beam composite signal beamwidth of focal spot increase, the spatial resolution of phased array ultrasonic detection and contrast resolving power all can be subjected to influence that acoustic beam distorts and variation.

The source of phase distortion mainly contains: the intrinsic phased error of the inconsistency of the unevenness of the velocity of sound, each passage of detection system and system etc. in the deviation between the supposition velocity of sound and the real velocity of sound, the object to be detected.

In optics,, introduced relevant function method for solving light along the phase differential problem that different travel paths causes.Relevant function method is a kind of maturation and widely used method, and it is effective important means at aspects such as inhibition random disturbance.Its rationale is the temporal correlation and the spatial coherence of signal.Spatial coherence is described the correlativity of signal at space difference place; Temporal correlation is described signal in difference correlativity or predictable contact constantly.In the phased array supersonic field, we use for reference relevant function method and obtain effective application aspect phase corrections.

Summary of the invention

Deal with problems: in phased array ultrasonic detection, because the deviation between the supposition velocity of sound and the real velocity of sound, the unevenness of the velocity of sound in the object to be detected, the phased error that the inconsistency of each passage of detection system and system are intrinsic etc., caused the phase distortion between each channel signal, the purpose of this invention is to provide the new method that a kind of ultrasonic phase array dependent phase is proofreaied and correct--contiguous dependent phase correction method, when the signal to noise ratio (S/N ratio) of the echoed signal that array element receives is higher, can effectively improve the precision that time delay is estimated, reduce the phase distortion between each channel signal.

Technical scheme: for realizing above purpose, the following technical scheme of the special proposition of the present invention:

In the correction of array echo signal, adopt the echoed signal of certain array element (on the limit or middle certain array element) to do the coherent reference signal.

Obtain two time delays (phase differential) between the array element signals by the relevant estimation between the adjacent array element signals, the time delay between each array element and the reference array element progressively transmits to add up by its adjacent array element and obtains.

Technique effect: theoretical analysis and experimental results show that under the lower situation of noise intensity (during signal to noise ratio snr＞12dB), the contiguous relevant evaluated error of estimating not produce substantially.

Embodiment

At first introduce the discrete form of related function, suppose that x (n) and y (n) are the finite energy signal, then the related function between them is defined as:

$R_{\mathrm{xy}}\left(m\right)=\underset{n=-\∞}{\overset{\∞}{\mathrm{\Σ}}}x\left(n\right)y(n+m)---\left(1\right)$

Suppose observable signal x (n) for the limit for length is arranged, and contain noise among the x (n) (suppose that useful signal is s (n), noise is u (n), x (n)=s (n)+u (n)), the auto-correlation of x (n) is so:

$R_x\left(m\right)=\frac{1}{N}\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}[s\left(n\right)+u\left(n\right)][s(n+m)+u(n+m)]=R_s\left(m\right)+R_{\mathrm{us}}\left(m\right)+R_{\mathrm{su}}\left(m\right)+R_u\left(m\right)---\left(2\right)$

Wherein, R _Us(m), R _Su(m) be the simple crosscorrelation of useful signal s and noise u, general noise u be at random and signal s should not have correlativity, so these two should be very little.R _u(m) be the auto-correlation of noise u, its energy mainly concentrates on the m=0 place, | m|＞0 o'clock, its decay is very fast.But less the time, the correlation function value of formula (2) is mainly by the auto-correlation of useful signal and the auto-correlation decision of noise for m.

In correlation-corrected, the time delay of two column signals (phase deviation) is to utilize the maximum value of two column signal cross correlation functions to estimate to obtain.But the existence of noise signal has produced influence for the estimated accuracy of time delay, i.e. R in the formula (2) _u(m) item size is the principal element that influences estimated accuracy.

In Ultrasonic Detection, the electrical noise in the piezoelectric chip is mainly caused by thermonoise, so suppose that the noise that each array element receives in the signal is incoherent substantially Gaussian distribution white noise, conforms to substantially with actual conditions.

Be estimated as the basis with the relevant time delay between the adjacent array element, the echoed signal of choosing an array element in the array is a reference signal, obtain two time delays (phase differential) between the array element signals by the relevant estimation between the adjacent array element signals, time delay between each array element and the reference array element progressively transmits to add up by its adjacent array element and obtains.Such as the array of one 16 array element, choose array element 1 and be reference array element, by contiguous correlation analysis, obtain the time delay d that array element 2 is followed between 1 _2-1, 3 follow the time delay d between 2 _3-2, 4 follow the time delay d between 3 _4-3... 16 follow the time delay d between 15 _16-15So, be in the phase correction of reference array element with array element 1, the time delay that other each array element need compensate is: array element 2 is d _2-1, array element 3 is d _2-1+ d _3-2... array element 16 is d _2-1+ d _3-2+ ...+d _16-15

When noise intensity is 0.15 when following, contiguous relevant estimate time delay that obtains and the time delay basically identical that adds in advance, promptly under the lower situation of noise intensity (during signal to noise ratio snr＞12dB), the contiguous relevant evaluated error of estimating not produce substantially.

Claims (2)

1, a kind of ultrasonic phase array transmitter, phase method of proofreading and correct is characterized in that: in the correction of array echo signal, adopt the echoed signal of certain array element (on the limit or certain middle array element) to do the coherent reference signal.

2, in the phased array ultrasonic detection as claimed in claim 1 based on the phase aberration correction method of proximity correlation, it is characterized in that: be estimated as the basis with the relevant time delay between the adjacent array element, the echoed signal of choosing an array element in the array is a reference signal, obtain two time delays (phase differential) between the array element signals by the relevant estimation between the adjacent array element signals, time delay between each array element and the reference array element progressively transmits to add up by its adjacent array element and obtains.