CN101403730A - Phase distortion emendation method based on combination 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 a combined corresponding phase correction method; when noise signal intensity is different, the precision of the time delay evaluation can be effectively improved and the phase distortion among all the passage signals can be reduced; and the combined corresponding phase comprehensively uses the adjacent corresponding method and the integrated corresponding method comprehensively to carry out corresponding analysis to all array elements and reference signals, thus obtaining the time delay quantity of each array element corresponding to the reference signal.

Description

In the phased array ultrasonic detection based on the phase aberration correction method of combination 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 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 has caused the phase distortion between each channel signal.Phase correction based on contiguous correlation analysis is very little to estimated bias under the little situation of signal noise intensity, but the estimated bias under the big situation of noise intensity is strengthened; And the phase correction of lump correlation analysis fine to the estimated bias control under the big situation of signal intensity worsens under the less situation of noise intensity on the contrary.The purpose of this invention is to provide new method--the lump dependent phase correction method that a kind of ultrasonic phase array dependent phase is proofreaied and correct, under the noise signal strength different situations, 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, earlier signal noise is carried out power Spectral Estimation, judge noise intensity, it is relevant to determine to be suitable for contiguous relevant still lump as criterion.

If adopt contiguous correlation-corrected method, then adopt the echoed signal of certain array element (on the limit or certain middle 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.

If adopt lump correlation-corrected method, then the signal that receives with all array elements directly superposes sum as reference signal, and each array element and reference signal are done correlation analysis, try to achieve the time delay of each array element with respect to reference signal.

Technique effect: theoretical analysis is with to experimental results show that employing strong based on the contiguous dependent phase associating dependent phase correction method applicability relevant with lump, and the antinoise interference performance is strong, can be effectively in the evaluated error of different noise intensity control time delay.

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.

In the correction of array echo signal, adopt the direct stack sum of proofreading and correct preceding whole array element signals to do reference signal, each array element and reference signal are done correlation analysis, try to achieve the time delay of each array element with respect to reference signal.

Claims (2)

1, a kind of method of ultrasonic phase array phase correction is characterized in that: in the correction of array echo signal, earlier the echoed signal noise intensity is carried out power Spectral Estimation, then carry out correlation analysis phase place is proofreaied and correct.

2, in the phased array ultrasonic detection as claimed in claim 1 based on the phase aberration correction method of combination correlation, it is characterized in that: selecting according to signal noise intensity is that the signal that echoed signal or all array element with certain array element in the array receive directly superposes sum as reference signal, each array element and reference signal are done correlation analysis, try to achieve the time delay of each array element with respect to reference signal.