Note: Descriptions are shown in the official language in which they were submitted.
~ ORIGIN OF ~HE _NVEN~ION
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7 BACKGROUND OF THE INVENTION
8 .
9 ~he use of a phased array transducer comprising a plural-
ity of adjac nt transducer elements ~or beam focusing i8 well
11 known in the ultrasonic~ imaging art as shown, for e~ample, in
12 U.S. Patent No.,3,936~791. The ~equen~ al. operation of indi~i-
13 dual ~ransducer elements or:groups of e1ements for be~m æc~nning
14 also is well known as shown, for example, in U.~. Patent No.
4,164,213. Al~o, ~ocusing means which incIude a æeparate tapped
16 ~del y line for eaoh element~of a transducer array are ~hown in
17 U.S. Patent No.~4,,116,229.~:~ The taps are changed ~or dynamically
focusing from minimum to maximum range a~ong the ~eam. Switohing
19~ ~of the taps occurs~during the ~ignal recep~ion period for genera-
~ion o~ switching transients which are potantially deleterious.
21 Alæo, a large number of re1a~ively expen~iYe tapp~d delay lines
22 are required for the beam ~ocusing and scanning operations pro-
23 vided by such prior art arrangement.
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1 SUMMARY OP THE INVENTION AND OBJECTS
2 .
3 An object o~ this invention is the provision o~ an im-
4 proved pulsed ultrasonic imaging system and method using elec-
~ tronic beam ~ocusing, scanning, and received signal processing
6 mean~ by means of which a high resolution real-time image of a
7 section of the interior of an object is obtained.
8 An object o~ this invention is the provision of a pulsed
9 ultrasonic imaging system o~ the forementioned type wherein a
relatively æmall number of fixed d~lay means are required for
beam ~ocusing and scanning of the section ~o be imaged.
12 An object of this invention iæ the provision of a pulsed
13 ultrasonic B-scan method and apparatus by means of which a well
14 focused real-t;me image of the entire section to be imaged i5
obtained using simpli~ied electronic foau~ing and scanning means.
16 Briefly, the above and other objects :.and advantages of
17 this invention are achieved by recurrent transmis~ion o~ ultra
18 sonic energy pulses into the object. An ultrasonic tran~duoer
19 array comprising a plurality o~ adjacent transducer elements
con~erts echo signals ~eceived from discontinuitie~ within the
21 ob~ect to equi~alent electrical signals. A range gated signal
22 processing meanc iB :responsi~e to electrical signal~ from tranc- 1,
23 ducer array elements produced by re~lected ultr2sonic waves re
24 ceived from within an~ one~of a plurality of contiguous range
zones wi~hin the cection o~ the object to be imag~d. The re-
2& ceived signal processor includeæ beam focusing and scanning means
27 :for focusing transducer array ~ements at the range zone at which
28 the proce~or is range gated and fo~ scanning the zones. The
29 resultant image line segment si~nal~ are supplied to a cathode
ray tube for Yisual display of the entire ima~ed section. A
32 digital converter may be uced fcr tempora~y ctorage o~ the
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1 line segment signals, from which converter entire video line sig-
2 nals may be obtained ~or display at a TV monitor.
3 The nature ~f the invention, together with othbr obj-ects,
4 features and advantages thereo~ will be more ~ully understood
from a consideration of the ~ollowing ,detailed description o~
6 certain embodiments thereof taken in connection with the '
7 accompanying drawings~
' 8 . . ,
9 . BRIEF DESCRIPTION OF THE DRAWINGS
11 In the drawings, wherein like re~erence charact~rs refer
12 to the same parts in the several views: '
13 Fig~ 1 is a block diagram showing an ultrasonic imaging
14 system embodying the present i~ventio,n;
Fig. 2 is a diag~am ~howing beam focusing of the trans-
16 ducer array at different range zones and time delay mean~
17 associated with each ~one;
18 ~ig. 3 is a graph showing the distribution o.~ time delay~
19 required for ~ocusing at the di~f~ren-t range 70ne3,
~ig. 4 is a timing diagram showing range gating of the
~1 receiver signal processor for operation at the different range .
2~ Zones;
23 Fig. 5~, 5B and 5C diagrammatically show the spatial
24 for~a~'; of three different video ~rames obtained using three
dif~erent zone ~canning sequences; and
26 Fig. 6 is a block diagram 8imil2r to that of Pig. 1 ~ut
27 showing a portion of a modified form of this invention ~mploying
28 a digital scan converter.
29
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1 ¦ . DE~AILED DESCRIPTION
2 l
3 ¦ Re~erence now iæ made to Fig. l wherein there is shown
4 ¦ one embodiment of the novel ultrasonic imaging apparatus of the
5 ¦ present i~vention comprising a linear transducer array 10 which,
6 ¦ fo~ purposes o~ illustration, includes 64 adjacent t~ansducer
7 ¦ elements lO-l through 10-64. P~eferably, the array i~ provided
8 I with a cylindrical lens focusing means ll (see Fig. 2~ ~or beam
- g ¦ focusing in a plane normal to the plane of' the section 12 within
10 ¦ the object 14~to be imaged. With the illustrated arrangement~
11 ¦ the sect~ion 12 liea in the longitùdinal pLane of the transducer
12 ¦ array 10. ~he use of a cylindr~ical lens ~or such beam focusing
13¦ :is well known and requixes no further dPscription.
14 ¦ The transduoer ar~ay lO is included in a pulsed ultra~on-
1~ ~ic B-scan imaging system which also includes a transmitter com- .
16 prising a pulser:l6 which i8 supplied with recurrent timing .
~17 pulses ~rom a timing a~d control unit 18 .~or sn-of~ control there-
18 of, With the pulser turned on.a high frequc~cy energy pul~e i~
19 generated which is connected through transmit-reccive switch unit
20 to a switching matrix 22. ~i~e delay means 24, here compr~s-
21 ing seYen fixed ~i~nal dela~ elements 24-l through 24-7, axe In- i
: 22 cluded in the oonnection of seven o~ the transmit-r~ceive ;
23 switch~s 20-l thro~ugh~20-7, respectively, to the switGhing matrix
24 .2 ~ One transmit-receive switch 20-8 îs directly connected to
25 ~he ~witch matrix with no time delay means included in the inte~-
2:6 connection thereo~
271 The transduoer elemente lO-l~through 10-64 of the tran~-
28 ducer array are connected to the switching matrix 22 for connect-
29 ing sets o~ di~ferent numbers thereof to the pul5er 16. Timing
and control signals from timing and control unit 18 are ~upplied
31 to thc switohing matri~ 22 for eelectin~ a transducer element,
32 . . . .
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1 ¦ or group of adjacent elemenk~, to be activated during pulse ~rans~
2 ¦ mitting and receiving operations. The signal delay means 24,
3 ¦ for the delay of.transmitter signals supplied to the transducer
4 ¦ array, and o~ æignals received ~rom the array, provide for ~ocus-
5 ¦ ing of the beam at different depths within the section 12 o~ the
6 ¦ object 14, the depth at which the array is focused be;ng depend-
7 ¦ ent upon the delay elements 24-1 through 24-7 employed in the
8¦ connection of transducer elements to the pulsed B-scan trans-
9¦ mitter/receiver ~he axis o~ the beam is shi~-ted along ~he trans-
1~¦ ducer array 10 to a position dependent upon the transducer
11 ¦ element, or set of adjacent elements, employed during transmitting
12 and receivin~ operations. The functioning of the fixed delay
13 means 24 for beam focusing at dif~erent depth zones within the
14 section 12 to be imaged is described in greater de~ail hereinbelow
in ~he description o~ the receiving operation~ For pxesent
16 purposes, it will be understood that when the pulse transmitter
17 16 is turned on, a transduce~ element, or set of adjacent t~an~-
18 ducer element~ energized ~or puls0 generation o~ ultrasonic
waves which are focus~d at one o~ a pluralit~ o~ contiguous
range Zones within the section 12 to be imagedO The transducer
21 element, or ~et of elements, which is acti~ated ig shifted along :
22 the array, in the direction of double headed arrow 23, ~or sc~n-
23 ning each of the range zones.
24 Re~lected ultra~onic ~aves ~rom discontinuities within the
2~ pul~e-in~onified object 14 are received by the transducer array
26 10 and converted to equi~alent electrical si~nals b~ the indivi-
27 dual transducer elements thereof. The output from one sr mo~e
28 of the transducer elements 10-1 through 10-64 is connect~d through
29 the transmit-receive æwitch means 20 to a summing amplifier 26.
The transmit-receive ~wi-tches ~0-1 through 20-8 simply .fl~ction
32 ¦ to i80l transmitted signal pul~es ~rom the inputs to the ~ummin~
~L5i5Z.~
1 amplifier. Obviously, preampli~ier~,;not shown, may be in¢luded
~ in the connections of the transmit-receive swit~hes to the
3 summing amplifie~ 26 for pre-ampli~ication of relatively low
4 level signals from the transducer elements.
I~ desired, operation o~ the system may be such that no
6 ~witching of the switching matrix 22 occurs between a pulse trans-
7 mission and associated pulse receiYing ~eration, in which case
8 it will be apparent that beam focusing and positioning is the
9 same during a single transmit-~eceive cycle o~ operation. Of,
10 course, di~f~rent sets o~ delay elements may be used during the
11 transmitting and associated receiving operations, if desired.
Sidelobe suppression, for example, may be enhanced by using
13 slightly dif~erent focal patterns in transmis~ion and reception.
14 For simplicity, however, operation using the same beam pattern
during a transmitting, receiving cylce of operation is describ~d.
16 With the present system, the output ~rom one or more trans
17 ducer elements is connected to the input t9 the ~umming ampli~
fie~ 26, during reoeiving operation. ~he output ~rom the ~umming
19 ampli~ier, which i~ related to a ~um of the i~puts, i~ supplied
to a time variable gain amplifier 28 having a gain characteristic
21 which ~arie~ as a function o~ time to compensate for los~ o~
22 signal amplitude as it traverse~ the tissue o~ the ~ubject 14.
23 In the illustrated arrangement the gain of the amplifier 28 is
24 varied in accordance with the QUtpUt from range gate and gain
function generator 3O. The range gate and gain functlon genera-
26 tor 3O simpl~ may comprise a ramp generator ~ith an output signal
27 which functions to increase the gain of the ampli~ier 28 in
28 proportion tolrange to o~set the losæ o~ signal caus~d by
29 acoustic absorption with}n the subject~ Start-stop operation of
the generator 3O is controlled ~y ~n output from the timing and
31 contr unit 18, Ihe range gate and gain ~unction generator
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1 ¦output when turned off, be~ore being tri~ered ~n5is ~uch as to
2 ¦disable operation of the amplifier 28, for receiver range gating.
3 With the illustrated arrangement, range gate operation of the
4 receiver at four contiguous range zones within the subje~t is pro-
~ vided, in the manner described belo~w. Db~iously, range gating
6 of the received signal at other loca-tions in the systam is
7 possible, the in~ention not being limited to any particular
8 gating means including the illustrated combination range gate
9 and gain function generator 30.
~he range g~ed signal from the time variable gain ampli-
11 ~ièr 28 is amplified by a variable gain ampli~ier 32, and the
12 ampli~ied output is detected py envelope detector 3~ comprising,
13 for example, a full wave rectifier followed by a low pass filter.
14 The detector 34 output, which iæ related to the envelope o~ the
-15 broad band high frequency signal ~rom the amplifier 32, is ~hown
16 supplied tQ an ultrasonic image display device 36 comprising a
17 cathode ray -tube. Generally, a compression ampli.fier, not ~hown,
18 is includad in the connection of th~ de-tector output ~ignal to
19 the cathode ray tube 36 ~or matching -the detected signal with
characteristics of the cathode ray tube for proper display o~
21 the entire æignal range~ The detector output iæ applied as an I
22 input to the control grld o~ the cathode ray tube for intensity, ,
23 ~-axis, control of the electron beam thereof~
24 For the illustrated B-scan display, cathod~ ray tube beam
deflection in the X or horizontal, direction is proportional to
26 the position of the ultrasonic beam across the array sc~nning
27 path. An X-axi~ generator 389 *riggered by synchronizing and
28 control signals from the timing and control unit l8 provides a
29 step function signal output which is supplied to the horizontal
deflection sy~tem of the cathode ray tube 36 for shifting the
31 trace on the cathode ~ay tube in accordance with the position of
32 the ultrasonic beam axis o~ the transducer array lO.
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1 Vertical, or Y-axis, de~lection of the cathode ray tube
2 is provided by a ramp generator 4O which is triggered by an
~ output ~rom the timing and control unit 18 at a selected time
4 period following transmitter operation. The r~mp generator 4O
output is supplied to the vertical deflection ~ystem of the cath-
6 ode ray tube ~6 ~or vertical scanning o~ the trace. ~5 mentioned
7 above, a plurality of contiguous range zones are employed such
8 that a plurality of individual signal trace segments are required
9 for production o~ a complete video scanning linen In the illus-
trated arrangement, ~our such range zones are employed~ As
Il will become apparent, a comple~te high resolution B-scan ultrasonic
12 im~ge of the body part lying within the section 12 o~ the body
13 part is provided at the face o~ the cathode ray -tube 36 by display
14 of the,plurality o~ video line segments obtained ~rom e~ch of
the range zones within the section 12.
16 In Figo 2 ~ to which re~erence now is made, the transducer
17 array lO and attached cylindrical lens 11 are ~hown in contact
18 with the objec-t 14, such as ~oft tissue o~ a body. The ~action
19 12 to be imaged is shown divided into a plurality of range zones~
and~for purposes of illustration, ~our range zones identified as
21 zone 1 through zone 4 are depicted. The zones may be of ~ual
22 or unequal width (ile. range) as desired, wi~h the number o~
23 range zones employed depending, among other things, upon de~ired
24 resolution through the entire range o~ operation. As describ~d
above, the ~ignal ~elay unit 24 compriseS a SPt of ~even delay
26 means 24-1 through 24-7 and, during opera-tion, sets of individual
27 delay means , here ranging in number ~rom zero to æeven, are
28 employed ~or focusing at the di~erent ran~e ~ones~ For operation
29 in zone 1, th0 switching matrix 22 simply ~unction~ to connect
a selected one o* the ~ixty-four transducer elements directly to
31 ~ summing smplifier 26 through trsnsmit-receive switch 20-8
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1 without passage of the signal through any o~ the delay eleme"ts,
2 The diagram o* Fig. 2, under the h~adin~ "DELAYS hMPLOYED" in-
3 dicates that no delay is employed for ZONE 1 operation. In ~ig.
4 2, one line is shown leading from a single transducer element,
here element 10-18, to the ~ONE 1 section of the diagram to
6 illustrate the fact that ~or operation at ZONE 1 the transducer
7 elements are operated singly (in sets of one). It ~urther will
8 be understood ~hat during ZONE 1 operation the receiver is range
9 gated for processing signals receiYed from the operative trans-
~0 ducer element only during the time reflected signals are received
11 from within the zone.
12 In ra~ge zone 1, immediately adjacent the transducer13 arra~, beæt resolution is obtained using single transducer ~lement3.
14 In the course of a complete scanning cycle~ during which the
entire section 12 is scanned, ever~ transduoer element o~ the ar
16 ray will have been indi~.idually operated to provide a line ~eg-
17 ment in~ormation ~ignal fo~ each transducer element in ZONE 1.
18 In the Fig. 1 arrangement, the line segment ~ignal~ are supplied
lg to the cathode ray tube 36 a~ they are produced for real-time
imaging thereat. With sixty-four tranæducer elements in the
21 array, a total of sixty-~our line segments per zone are obtained ;
~2 u~ing the illustrated apparatus in the above de~cribed mannerO .
23 ~n ~ig. 2, the beam directional patter~ for ZONE 1 cperation,
24 provided b~ actiYation o~ a single transducer element9 is identi-
~ied by reference numeral 44, and the beam axis duri~g actlva-
26 tion o~ said transducer elèment, here element }0-~8 is identified
27 by reference numeral 46
28
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1 Signal delay elements included in signal delay unit 24
2 are employed for electronic beam focusing within range zones 2,
3 3 and 4~ For operation in ZONE 4, for example, which zone is
4 farthest ~rom the transducer array 10, sets of ~ teen transducer
elements are employed. together with all seven of the delay means
6 24-1 through 24-7. The time delays provided by slements 24-1
7 through 24-7 increase as the reference numeral suffix increases;
8 with a minimum time delay being pro~ided by delay means 24-1
9 and a maximum time delay being provided by delay means 2~-7. In
Fig..3, a plot of the time delays emplo~ed ~or ~he delay means
11 24-1 through 24-7 is shown.
12 For beam focusing at range Z~NE 4, shown in Fig. 2, the
13 outer-most transducer elements employed for focusing along beam
14 axis 46, here transducer elements 10-11 and 10-25, are directly
connec~ed by the switching matrix 22 to the transmit-receive
16 switch 20-8 without delay. Transducer element 10-18 at the beam.
17 axis 46 is connected by the switching matrix to the delay means
18 24-7 ~or maximum delay o~ transmitted and received slgnals. As
19 is well undcrstood, beam fo~usîng i~ provided ~y use of progress-
ively larger time delays in going from the outer most transducer
21 elements to the center transducer element of the set employed.
Z In Fig~ 2, wherein the set of transducer elements 10-11 through
?3 10-2~ is u~ed for focusing at 50NE 4 along beam axis 46, trans-
24 ducer elements 10-17 and 10-19 a~e connec~ed th.rough time delay
element 24-6 to the summing ampllfier 26. Similarl~, other pairs
26 o~ transducer elements, including elements 10-16 and 10-2p,
27 elements 10-15 and 10-21, elements 10--14 and 10-22, elements
28 10-13 and 10-23 and elements 10-12 and 10-24 are c~nnected throug
29 time del~y elements 24-5, 24~4, 24-3, 24-2 and 24-1, respectively
to the input of summing amplifier 26. During operation, differcn
32 ¦ sete o$ teen transducer element~ are connected by the ~witohi~
1~ l
1 matrlx 22 for scanning ran~e ~ONE 4 while focusing thereat, As-
2 jacent opposite ends of the transducer array the beam is formed
3 using fewer transducer elements with a corresponding degradation
4 in imaging thereat. With the illust~ated arrangement, for each
range zone, including range ZONE 4, sixty~fou~ range gated line
6 segment signals are obtained, which signals are processed b~ the
7 recei~er for display at the cathode ray tube 36, In Fig. 2
8 focused ultra~onic beams 48-2, 48~3 and 48-4 for focusing at
9 points 50-2, 50-3 and 50-4 at range zones 2, 3 and 4, respective-
ly, along beam ax;s 46, are shown, together with associated waYe-
11 ~ronts 52-2, 52-3 and 52-4.
12 From an examination o`~ Fig. 2, it will be seen that a
13 set o~ ~ewer transducer elements~ and associated delay elements
14 ~re used for operation at range zone 3 than ~nge zon 4. Simila
ly, the set of transdu~er elements for ~ocusing at range zone 2 .
~6 inoludes fewer transducer elements and aB~ociated delay~ ~han the
17 set for operation at range zone 3. In the illustrated arrangemen-
18 operation at range zones 3 and 2s include the use of ~1 and 7
19 transducer elements, and 5 and 3 delay means, respectively. It
will be ~een, then, that at least ~ome of the delay m~ans 24-1
21 through 24-7 are employed for focusing at a pluralit~ of differen I
22 range zones. In the particular arr~ngemPnt, delay means 24 1
23 is used ~or ~ocusing at zones 3 and 4, delay m~ans 24-2 is u~ed
24 for focusing at ~ones 2 and 4, dela~ means 24~3 is used for $ocus
2~ ing at zones 3 and 4, delay msans 24-4 is used for focusing at
26 zones 2, 3 and 4, dela~ means 24~5 is u~ed ~or focusing at zones
27 2, 3 and 4~ and delay means 24 6 is used for ~ocusing at zones
28 3 and 4.
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1 Once the number o~ transducer elementæ to be included in
2 each set ther~of ~or operation at the different zones îs deter-
8 mined,in a manner explained below, the delays required ~or focus-
4 ing at the various focal points 50-2, 50-3, 50-4 within the re-
spective range zones may be calculated. In Fig, 3, to which
6 re~erence again is made, a plot of the calculated delay times ~or
7 focusing at ~ocal points 50-2, 50-3 and 50-4 is shown. From the
8 plot it will be seen that the delay times are grouped along the
9 time delay axis. Knowing the desired accuracy at the frequency
10 of th~ highest expected return, the required accuracy of the time
11 delays employed may be de~ermined. For example only, for O~l
12 wa~elength accuracy at a frequency of about 15 MHz, t~me delays
13 within an accuracy o~ approximately ~ 6u7 n sec are rfequired.
14 Consequently, any group of deIay times ~alling within a range o~
13.4 n sec may be satisfied ~y use sf a single delay means. Ub-
16 viously, the possible grouping will depend upon physical dimen-
I7 sions o~ the array in addition to the operating frequency ana
18 accuracy desired. In Fig, 3, seven sets o* time delays,^~ncluding
19 one set of one delay provide the necffAfssary delays ~or focusing
20 at all four range zone~. l
21 With the illustrated invention, a ~ingle ~can line seg- If
22 ment is obtained from one of the four range zones ~or each tranæ-
23 mit-receive cy~le of operation. One sequence o~ transmitter
24 and receiver gating operation which may be ~ollowed in scanning
the image is shown in the timing diagram of ~i~. 4 to which
26 figure reference now is made. There, reeurrent tranæmitter pulses
27 Tl~ T2, T3,- ~4 and T5 are shown ~ollowed, in time, by range gat-
28 ing of the receiver for operation at range zones 1, 2, 37 4 andl,
29 respectively. When the æystem employs four r~nge zones, and
sixty-four scan line segments are o~tained for each z~ne, a total
31 of 256 ~can line segments are obtained~ and displayed in the
32 ~our~e of a complete scanning cycle. . .
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1 It will be understood that the invention is not limited .
2 to any particular scanning sequence. This may be illus.trated by
3 re~erence to Figs. 5A, 5B and 5C o~ the drawing showing th~ee
different scanning orders out of a substantially infinite number
6 of possible sequences. In the drawings, the four line segments
6 forming a single line are shown with gaps therebetween for ea~e
7 in identifying the same. In practice, no such gaps exi~t, and
8 the segments ~orming one line are contiguous. The order in which
9 the line segments are obtained, and displa~ed, are identi~ied
IU by underlined numbers 1 through ~9 only some o~ which are
11 illustrated. In Fig. 5A it will be seen that all four line
12 segments of a single line are consecutively obtained and displayed
13 be~ore stepping the beam axis to an adjacent position. For this
14 operation, rec~iver range gating operation of the typ~ illustrated
in Fig. 4 would be employed.
16 In the Fig. 5B scanning s~quence, an sn-kire rangc zone
17 is beam scanned, be~ore range gating to an adjacent range zone.
18 In the illustrated pattern, the range zonas l, ~, 3 and 4 are
19 sequentially scanned.
~0 If desired, a substantially ran~om scanning order may bs
21 employed such as illustrated in Fig. 5C. After all 256 line .
22 segments are obtained and displayed~ the sequence is repeated.
23 With any sequence o~ op~ration it is a ~imple matter to synchroniz
24 display of the line segment with the receiver gating and beam
po~ition.
26 The number of transducer elements to be included in each
27 set thereof for ~ocusing at the dîf~erent ~ange zones may be
28 dete~mined by calculating resolution within each range zone
29 using different numbers of adjacent transducer elements în the ~et
31
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1 The set which provides the best lateral resolution ~or the depth
2 of the zone would then be used. In the illustrated arrangement
3 only sets which include an odd number of transducer elements are
4 employed such that the be2m axis extends from the cen-ter o~ a
transducer element. Obviously, a system using an even number o~
6 transducer elements may be u~ed wherein the beam axis e~tends
7 from a point between adjacent transducer elements. Also, by
8 using both odd and even numbers of transducers in the sets
9 thereof the number of lines obtainable is substantially doubled,
without an increase in the number of transducer elements included
11 in the array.
~2 The invention having been described in detail in accord-
13 ance with requirem~nts o~ the Patent Statutes, various other
14 changes and modifications wilI suggest themselves to those
skilled in this art. For example, it will be apparent that the
16 display at the ~ace o~ the cathode ray tube 36 ma~ be conv~rt~d
17 by scan converter means responsive to such display to ~ignals
18 which may be employed by a conventional television type monitor
19 or display. In another modi~ication of the invention ~hown in
~ig. 6, the electrical line segment signals`~rom the en~elope
21 detector 34 are supplied to a digital scan eonverter 60 for
22 conversion to a composite video signal which may be di~played at
23 a conventional television monitor ~2. Digital scan conver~ers
24 for such use are well known and o~ten include a gray ~cale genera-
tor for ~neration of multibit digital si~nals which are temporar-
26 ily stored in a read-write memory. Timin~ s;gnal~ from timing
27 and control means l8~ also are supplied to the di~ital æcan con-
28 verter for control thereof. Complete Yideo l}nes are read out
29 of the digital ~can conver.er for display at the monitor 62.
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1 Since sixty-four lines of video information are provided using
2 the sixty-four element array, each line may be replicated eight
3 times, if desired, to produce a ~12 line display. ~lso, instead
4 of simple replication, the signal~ for each synthetically
generated scan line may be interpolated by appropriate mixing of
6 si~nals from two adjacent actual scan lines. Such details of
7 signal processing for furnishing a more pleasing presentation
8 are well known and form no part o~ the present invention. It
g will be understood, however, that temporary storage o~ line seg-
ment signals required for digital ~can conversion does not pre-
11 clude real-time imaging by the system.
12 Other change~, as mentioned a~ove, include the use of .
13 di~ferent delay mean3 for associated transmitting and receiving
14 operations ~or different beam focusing actisn. Also, it will be
15 apparent that the invention i8 not limited to the use o~ Your
16 range ~ones. A sy~tem and method embodying the pre6ent invention
17 employing eight rang~ zones has been built and tested~ Addition-
12 ally the sy~tem may employ range zone6 of dif:~erent size, i~
19 desired, w;th the ~ize o~ each ~one being dependent upon the
desired resolution throughout the full depth Q~ the section to be
~1 imaged. It is intended that the abo~e and other such ch~nge~
22 and m~difications shall fall within the.spirit and scope of the
23 invention de~ined in the app~nded claims.
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