Boots – shoes – and leggings
Reexamination Certificate
2000-12-01
2002-10-29
Pihulic, Daniel T. (Department: 3662)
Boots, shoes, and leggings
Reexamination Certificate
active
06471389
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a dynamic delay curve generator. More particularly, the present invention relates a dynamic delay curve generator for an ultrasonic imaging system.
2. Description of Related Art
Most ultrasonic imaging systems (for example, ultrasonic scanners for medical use) use a transducer array to transform an image to data points. The transducer array consists of a plurality of transducer elements arranged to lie on a straight line or an arc. When a target object is scanned by an ultrasonic scanner, a beam of ultrasound is sent to a particular target point. On hitting the target point, the ultrasound is reflected. Since distances from the target point to each transducer element are different, each transducer element will not receive the echo signal from the target point at the same time. Hence, the reflected signals received by each transducer element must be suitably delayed before combining to form a response signal. The single response signal represents the sum of all ultrasonic energy reflected from the target point.
Each transducer element can be defined as a channel. For example, a transducer array having M transducer elements can be regarded as having M channels. In general, the dynamic delay curve of each transducer element corresponding to the reflected sound beam received can be represented by the following formula:
Δ
t
=
D
(
x
,
θ
,
R
0
)
=
-
x
sin
θ
V
+
(
x
cos
θ
)
2
V
2
R
0
where, &Dgr;t is the weighted delay parameter, for controlling the delay after a response signal is received by a transducer element, x is the position of each transducer element, &thgr; is the beam steering angle, defined as the angle subtended by the line joining the beam reflection point to the center of the transducer array and the vertical center line of the transducer array, V is the speed of the beam, and R
0
is the distance from the beam reflecting point to the central point of the transducer array.
FIG. 1
is a graph showing the dynamic delay curve of a transducer element (channel) within an ultrasonic imaging system. As shown in
FIG. 1
, the beam control angle &thgr; is fixed. According to the dynamic delay curve formula, the delay parameter &Dgr;t of a transducer element (corresponding to a particular position x) varies with distance R only. Here, distance R can be represented the number of N delay cycles.
FIG. 2
shows a portion of the beamformer circuit in a conventional ultrasonic imaging system. The beamformer circuit includes a delay generator
20
that corresponds with a transducer or a channel (CH#1), a memory unit
24
, an internally plugged circuit
26
, an adder
28
and a parameter decoder
22
. As shown in
FIG. 2
, delay generator
20
generates a coarse-tune delay control signal
23
and a fine-tune delay control signal
25
to memory unit
24
and internally plugged circuit
26
according to the output parameters from parameter decoder
22
. Control signals
23
and
25
control the delay of response signals received by the transducer element. In other words, coarse-tune control signal
23
and fine-tune control signal
25
are the signals produced by the delay generator
20
after an internal computation using digital dynamic delay weighted parameter K (as shown in FIG.
1
).
FIG. 3
is a flow chart showing the steps in generating the dynamic delay curve of a conventional ultrasonic imaging system. Conventionally, a dynamic delay curve is produced using a delay generator like the one shown in FIG.
2
. By generating digital delay weighted parameter K that corresponds to a particular transducer element, delay of the response signal received by the said transducer element can be controlled. As shown in
FIG. 3
, the first step S
30
is to define A=N
0
+1−&phgr;; j=1; &Dgr;N=1, where
φ
=
x
2
cos
2
θ
C
2
T
R
Δ
t
0
,
T
R
T
R
is sampling cycle, &Dgr;t
0
is fine resolution cycle. In step S
32
, the condition if A≦0 is checked. If A≦0 is true, step S
34
is executed setting A=A+j−&phgr;; &Dgr;N=&Dgr;N+1 followed by executing step S
32
again. If A≦0 is false, step S
36
is executed setting A=A+N0+&Dgr;N; j=j+1 followed by executing step S
34
. In addition, when A≦0 is true, step S
35
is also executed setting off the calculation of K=K+1. The currently obtained delay weighted parameter K is used for controlling the delay of the response signal received by the transducer element. Hence, according to the dynamic delay curve generation method for a conventional ultrasonic imaging system, a dynamic delay curve corresponding to the transducer element is obtained.
For a conventional dynamic delay current generator (for example, the delay generator shown in FIG.
2
), the system must provide 120 Mhz clock if an output result is needed for every 40 MHz. In other words, a conventional beamformer design needs to have two groups of clock signals (40 MHz and 120 MHz). The first group (40 MHz) serves as signals for general signal sampling. The second group (120 MHz) is used for generating the dynamic delay curve of delay generator
20
. However, having two groups of different clock signals in a system not only will increase system complexity, but will also lead to system instability.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide a dynamic delay curve generation method in an ultrasonic imaging system. The ultrasonic imaging system includes a transducer array that comprises of a plurality of transducer elements. Each transducer element corresponds to a position x. The angle between a line joining a beam reflection point to the center of the transducer array and the vertical centerline of the transducer array is defined to be &thgr;; the sampling cycle is defined to be T
R
; fine resolution cycle is defined to be &Dgr;t
0
; and, beam speed is defined to be V. The ultrasonic imaging system also includes a parameter decoder. The dynamic delay curve generation method that corresponds to each transducer element includes at least the following steps: (1) obtaining three initial values of K
0
, N
0
and &phgr;
1
from the parameter decoder, where
φ
1
=
1
-
x
2
cos
2
θ
N
0
V
2
T
R
Δ
t
0
;
(2) defining A=N
0
+&phgr;
1
, B=1+N
0
, C=&phgr;
1
, D=0, E=0, K=K
0
; (3) executing B=B+1, D=B+E, E=C+2; (4) judging if A≦0, and if A≦0 is false, execute step (5), on the contrary, if A≦0 is true, execute step (6); (5) executing A=A+C and then executing step (3) again; and (6) executing A=A+D, C=C+1 and at the same time executing K=K+1, where the delay weighted parameter K is used for controlling the delay of response signal received by each transducer element, finally executing step (3) again.
This invention also provides a dynamic delay curve generator in an ultrasonic imaging system. The ultrasonic imaging system includes a transducer array that having a plurality of transducer elements. Each transducer element corresponds to a position x. The angle between a line joining a beam reflection point to the center of the transducer array and the vertical centerline of the transducer array is defined to be &thgr;; the sampling cycle is defined to be T
R
; fine resolution cycle is defined to be &Dgr;t
0
; and, beam speed is defined to be V. The ultrasonic imaging system further includes a parameter decoder for providing three initial values K
0
, N
0
and &phgr;
1
, where K
0
is the initial delay weighted parameter, N
0
is the initial delay cycle number and
φ
1
=
1
-
x
2
cos
2
θ
N
0
V
2
T
R
Δ
t
0
.
The dynamic delay curve generator includes at least a
Gau Yow-Ling
Hu Chen-Hua
Liao Chen-Nan
Chung-Shan Institute of Science and Technology
J.C. Patents
Pihulic Daniel T.
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