Note: Descriptions are shown in the official language in which they were submitted.
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16-3-1979 1 PHA 20 798
"Multi-channel analyzer"
The present invention relates to a multi-
channel analyzer, particularl~ to a multi-channel x-ray
fluorescenc~e analyzer.
Such kind of analysing apparatus are described
in The Edase editor vol. 8 no.2, page 6-10. In an appa-
ratus as described a sample of material is struck by an
~-ray beam in known fashion and the radiation from the
sample resulting from x-ray excitation thereof, is col-
lected and analyzed. In another application a scanning
electron microscope (S~M) is utilized, in which an elec-
tron beam strikes a sample and the resulting radiation
from the sample is collected and anlyzed. According to
the prior art, such analysis of the resulting radiation
from the sample, involves feeding the signals or informa-
tion from the sample into a pre-amplifier of a known
multi-channel analyzer. The signals from the pre-ampli-
fier are then f'ed into an analog-to-digital converter
from which information is transferred to a comparator,
which generally comprises an upper range limit compara-
tor cmd a lower range limit comparator. These comparatorsserve to analyze the information received from the con-
verter and to de-termine and respond to those items of
information or signals whose intensit~ levels, which are
indicatlve of elements present in the materials of the
-
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16-3-1979 2 P~IA 20 798
sample, falls between the pre-established upper and lower
range limits for which the comparators are set. The signals
from the anaiog-to-digital converter are also fed into a
multi-channel memory, where the various:signals identifying
the elemental characteristics of the analyzed sample, are
stored.
The output signals from the comparators thus
those signals which fall within the pre-established range
defined by the comparators are fed into an event detector
10 which can be an "OR-gate" and pulse former and which regis-
ters the oc~urrence of the various signals from the compara-
tors. Signals or intelligence from the event detector are
fed into the output circuitry which in turn can be fed to
for example, a scanning electron microscope that constructs
15 an image of the analyzed sample area in accordance with the
incoming signals from the event detector.
The apparatus also includes a marker counter,
whose function it is to produce indices on the display and
locate them appropriately. The attributes can be, for exam-
20 ple, the image intensity, or brightness, the display grid,the display range scale, the width of the display window,
and, in spectrometry, the K.L. and M marks, as explained
below.
Information from the multi-channel memory is
25 fed into display drcuitry of the apparatus, which can be
the circuitry for a television display9 on which there can
be shown various information indicating the characteristics
of the sample, one such characteristic being the intensity,
or population, level of signals corresponding to a certain
30 energy or wavelength indicative of a particular chemical
element, e.g. iron, the intensi-ty being related to the
chemical content of this particular element in the sample.
In this particular type of application, wavelengthjenergy
information is stored in a number of sequential memory
35 channels of the multi-channel memory.
-In asmuch as particular energies, and, there-
fore, particular channels, relate to specific elements under
analysis, it is often desirable to identify these speci~ic
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3 PHA 20,798
energy channels, this being done by the prior art, as des-
cribed above, by using a comparator or counter-type circuit.
The present invention seeks to provide an
improved multi-channel analyzer system and is characterized
in that it contains
a) an analog-to-digital converter for receiving
incoming signals,
b) a multi-channel memory connected to the con-
verter,
c) an attribute memory bank comprising at least
one attribute memory and being connected to the multi-
channel memory,
d) a display circuitry connected to the attri-
bute memory bank and to said multi-channel memory,
e) a display device connected to the display
circuitry,
f) an output circuitry connected to ~he output
memory band, and
g) an output device for receiving and demon-
strating the signals from the output circuitry.
According to the invention, the specific energy
channels are depositories for signals or information from
the apparatus that operates on the specimen by radiation and
detection, such signals indicating various characteristics
of the specimen, e.g., the relative concentrations of the
elements present in the materials of the specimen.
While, as previously stated, the above prior
art apparatus employs comparator-or counter-type circuits
for identifying specific energy channels, the present
invention involves the software-controlled assignment of
attributes to discrete hardware memory channels, to allow
a synchronous real-time hardware response. The principle
of attribute memory involves pre-assigning markers, which
signify specific characteristics, or attributes, onto an
attribute memory bank that is not in an associated computer,
but, instead, is provided by dedicated hardware memory of
the multi-channel analyzer. The contents of the attribute
memory bank are configured by an associated computer cir-
.
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4 PHA 20,798
cuit but the attribute memory bank operates independentlyand asynchronously of the computer.
A multi-channel memory having, e.y., 1000 chan-
nels with 4 assignable attributes would provide a 1000 word
by 4 bit attribute memory bank.
In the present invention, a memory channel is
identified as a member of a small group of channels repre-
senting a specific elemental energy peak width, wherein one
or more of the channels of the group are located in the
multi-channel memory of the computer (i.e., a first multi-
channel memory) and others of the channels of the group are
located in one or more further multi-channel memories that
are, as stated above, located not in an associated computer, -
but, instead, are in a separate attribute memory bank, with
the operation of the memory or memories of the attribute
memory bank being configured by the associated computer cir~
cuit and operating independently and asynchronously of the ~;
computer. The difficulty to detect associated multiple
peaks in the non-contiguous channels are overcome with the
apparatus according to the present invention.
An advantage of the present invention is that
its employment of a multi-channel analyzer attribute memory
provides unlimited flexibility in detecting associated
multiple peaks in the non-contiguous channels. The present
25 invention is also usable as a single channel analyzer. In ~
a preferred embodiment of the invention the display cir- ~;
cuitry of the analyzer apparatus comprises
a) means for producing a maximum si~nal value
(Nmax) to be fit to a signal truncator,
b) a frequency ratioer connected to the trun-
cator and to a system frequency clock,
c) a first gate connected to the frequency ~-
ratioer for receiving a display synchronizing signal F,
d) a counter connected to the first gate, said
counter receiving signals (Nchannel)to be monitored,
e) a zero detector connected to the counter,
and
f) a second gate connected to the zero de-
.
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16-3-1979 5 PHA 20 7g8
tector and to the first gate for receiving a television
synchronizing signal TF from the first ga-te the second gate
providing an output signal z modulating the display device.
Brief description of the drawings.
Fig. 1 is a schematic block diagram of a cir-
cuit in the prior art for processing spectral data, using
a comparator-type circuit as described.
Fig. 2 is a schematic block diagram of an
apparatus according to the present invention, employing a
lO multi-channel memory and an attribute memory bank providing
- non-contiguous memory channels.
~igure 3 is a schematic representation of digi-
tal means of the display circuitry according to a preferred
embodiment of the present invention.
Figure 4 is a schematic depiction of a vertical
television raster representing scan timing data.
Figure 5 is a schematic representation of analog
means for achieving a vertical television raster output
spectrum.
Flgure 6 is a schematic representation of
digital neans for achieving horizontal television raster
output spectrum.
Figure 7 is a schematic representation-of
analog means according to another embodiment of the present
25 invention, for achieving horizontal television raster~
In fig. 1 an x-ray detector 11, a pre--amplifier
12, an analog-digital converter 14, an upper limit compara-
tor 16, a lower limit comparator 18, a multi-channel memory
20, an evcnt detcctor 22, an output circuitry 24, a scan-
30 ning electron microscope 25, a marker counter 26 a displaycircuitry 28 and a display 29 are listed and interconnected
as described above in accordance with prior art.
The preferred embodimen-t of fig. 2 is related
to an x-ray spectameter but can be used in other types of
35 a~alysator appara~us as well. Signals generated by an x-ray
detector 52 in response to radiation emanating from an
~-ray impinged sample, not shown but previously de~scribed,
the signal populatlon and makeup thus, the energy of the
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- 16-3-1979 6 PHA 20 798
signal which is dictated by the energy and wavelength of the
emanated radiation, indicate various characteristics of the
sample, e.g. the identities of the elements present in the
sample material and their relative concentrations. These
signals are transferred, preferably, to a pre-amplifier 54,
whose output is then fed into an analog-to-digital converter
56.
The digital data from the a.d. converter 56
are fed into a multi-channel memory 64 and further into an
lO attribute memory bank 58, which can comprise one or more
attribute memory components 60, 62, etc. The output of the
multi-channel analyzer is fed into a display circuitly 66,
to which a television display 67 maintained to equal or ex-
ceed somewhat the value of the highest peak of the informa-
15 tion being collected. The means comprises apparatus toachieve a display of line G on the television display screen
the contents of a particular channel, N, are placed in a
count-down counter whose content is rnonitored. At time t2
the counter is counted down by a clock F and simultaneously
20 the Z mode of the tube is brightened. When the contents of
the counter are zero (at t3) the brightness modulation is
switched off. To ensure the correct operation, the follow-
ing parameters are employed:
f~ Nmax
~ T histogram
g N max g a
- N channel
f
T histogram = T scan x k
Where f is the clock frequency,
N max is the vertical scale maximum value,
T historgrarn is the time to display a line of maximum
amplitude,
T scan is the sweep or scan time of display (e.g.
ty-t1 ),
T bright is the bright time (e.g. t3-t2),
N channel is the content of the particular channel
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16-3-1979 7 PHA 20 798
that is displayed, and
k is the proportion o~ the t~tal vertical sweep used
for full vertical scale.~
In accordance with the present invention, when
S a certain threshold value is exceeded by any channel of the
display, the maximum full scale Nmax, is constantly varied
to ~ollow the level or contents of the highest level chan-
nel. In this situation, logic memory. Further, the attribute
memory bank can be such as to provide reserve bits to which
10 other attributes can be assigned, thus permitting the as-
signment of such attributes being done by software changes
instead of hardware changes. In prior art mode of analysing
commonly re~erred to as the fixed vertical scaling mode,
the vertical amplitude of the signals is established at some
15 predetermined level and the ~ata are collected and fed into
the display apparatus, it sometimes occurring that certain
respective pea~s of various components of the spectrum ex-
ceed this pre-established level and are not registered in
the visual display.
More specifically, if the upper limit of the
vertical scale is set at a given value A, and analytical
x-ray fluorescence of a sample is carried out in a fashion
familiar to the art, as the analysis is continued, informa
tion is continuously fed into the display device (e.g. a
25 television display) as a result of which? at a certain time,
the measure of the intensity of a constituent material of
the sample is at a level C and at a subsequent time, such
intensity is at a level B, with the intensity level there- -
after reaching, and subsequently exceeding, level A. Con-
30 sequently, the peak portion of a first sample component
(which can be the intensity of, e.g. iron in the sample) endsup off the display while a second sample component (which
can represent the intensity of e.g. nickel in the sample)
remains fully within the display viewing field, this ob-
35 viously being an undesirable result due to the inabilit~to gauage the pea~ of the ~irst sample component.
According to the present invention the upper
limit of the range of the vertica] scale is initially set
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16-3-1979 8 PHA 20 798
. ..
at pre-set fixed value and when this value is reached by
the highest data point, the upper limit of the ~ertical
scale range is then continuously maintaine~ at a level that
is at least equal to and preferably exceeds somewhat, the
5 highest peak value of the data, such that there is a dynamic
adjustment of the upper limit of the vertical scale, there-
by énsuring tha-t all of the data are displayed and permit-
ting the relatively low values on the vertical range to be
maintained for a period of time and thus enabling reading
10 and comparison of these lower values for a larger projcction
of the examination time than is available wi-th the previously
described prior art techniques. Specifically, as the inten-
sity, i.e. the vertical scale reading of the highest peak
of the data displayed (i.e. the peak for display component
15 corresponding to the first sample component increases dur-
ing the eæamination of the samp~e, the extent of the ver-
tical range increases commensurately. As mentioned above,
the visual display can be achieved with a television dis-
play, using either a vert~ical television raster in which
20 historgram lines are provided by the television scan line,
i.e. the display comprises one or more vertical bars or
lines or a horizontal television raster.
In fig. 3, where the display is produced by a
vertical television raster, two successivellines G and H
25 are shown with t1 designating the beginning of the scan for
line G, t2 designating the starting time of the histo=gram
being produced, t3 designating the stopping time of the
histogram, and t4 the start of the flyback. At t6 the histo-
gram H is begun to be written with such writing stopping
30 at t7 and t8 designating the start of the flyback. The
starting times of the histogram, t29 t6~ t1o are alway9 the
same and the respective finishing times of the his~ograms
t3, t7, t11 being determined by the contents of the com-
ponents or channels being displayed at those particular tim-
35 es.
~ eferring to figure 4, there is describeddigital means for modulating the vertical televisio~ raster
according to the present invention, where the upper range
.
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16-3-1979 g P~ 20 798
limit of the display is continuously.
The output of a first attribute memory 60 of
the bank 5~ is fed into the display circuitry 66 (it being
possible to feed into the display circuitry 66 the output o~
more than one attribute memory bank). The output of the first
attribute memory 60 can provide one or more indices to the
display circuitry, such as, for example~ the brightness of
a portion of interest of the display, energy range markers,
peak centroid identifiers, or ~-axis modulation bits for
lO windo~ annunciation. Where other attribute memories address
the disp]ay circuitry 66, other indices can be provided by
them to the display device, such indices appearing on the
display screen and being usable for reference purposes or
for other purposes.
The output of a second attribute memory 62 is
fed into the output circuitry 68 which can drive a scanning
electron microscope (S.~.M.) display 69 to enhance an image
of the inspected sample. This is a single-channel analysis,
in principle.
By employing the present apparatus, the attri-
butes or indices, that are desired for the output and dis-
play devices can be provided to them by simultaneous opera-
tion with the provision thereto of the information from the
multi-channel memory instead of the prior art technique of
25 employing separate processing steps for providing the attri-
butes or indices to the output and display devices. The
present invention provides a simpler and less expensive
apparatus by virtue of the possibility of omitting the
comparator (16, 18 of Fig. 1) and the necessary there still
30 applies the equatlon
f Nmax
T histogram
and, since T histogram is a constant, the frequency f is
directly proportional to Nma~.
In the operation of the digital means as
sho~n in fig. 4 for vertical television raster, the value
Nmax of the highest level information channel is fed into
a p~ogrammable frequency ratioing device 72 via a truncator
.
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16-3-1979 10 PHA 20 798
74, which frequency ratioing device can be a digital diffe-
rential analyzer, binary rate multiplier, or any other digi-
tal device available in the art. Device 72 ensures to pro-
duce a frequency propor-tional to Nmax and inversely propor-
tional to T histogram. While it is preferred that the valueof N be truncated to reduce high frequency problems, this is
not essenti~
The~'threshold value for the count (vertical
axis) is preset into a data register 76. In the case of
10 spectrum coliection (i.e. dynamic data coilection), each
time an event occurs in any channel (horizontal axis) the
count magnitude is fed into a further data register 78, this
data then being compared with the threshold value stored in
the past data register 76 by means of a digital comparator
15 80. A logic circuitry element 82 then will cause the con-
tents of data register 78 to be shifted into the first data
register 76, when the data value in the further data regis-
ter 78 exceeds the value of the first data register 75. Thus
when the threshold value is exceeded, the last data value
20 stored in the first data register 76 is the Nmax value.
Generally, the value of NmaX at the end of the last -tele-
vision frame is fed into frequency ratioer 72 via truncator
74 and this value will be used to scale the following tele-
vision frame. ~n the case of a spectrum which had been pre-
25 viously collected and stored, N x is generated using thecircuitry as shown in fig. l~ 5 but then the channel data
values are compared only once, that being when the memory
is loaded from the storage.
A s~stem clock frequency, Fs is also fed into
30 the frequency ratioer 72. The output frequency f, from the
frequency ratioer is then proportional to Nmax, such output
frequency being fed into a gate 86, to which a television
synchronizing signal is fed. The output of gate 86 is used
to count down the contents of counter 88, into which the ver-
35 tical scale value, Nchannel has been preset. The contents ofcounter are fed into detect zero means 90, whose output is
fed into another gate 92. The -television synchronizing sig~
nal is also fed into gate 92, the output of which pro~ides
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16-3-1979 11 PHA 20 798
Z modulation.
In the operation of the apparatus~ the counter
88 is preset'with a Nchannel value at time t1? t5, tg~ etc.
(Figure 4) or at least some time between t3 and t6, t7 and
tlo etc. Then, at time t2, t6, t10 gate 86 is opened by the
television synchronizing pulse, causing -the frequency f (fi-
gure 4), to start counting down counter 88. Simultaneously,
the television synchronizing pulse opens gate 92, allowing
the output of the zero detection means to provide a Z modu-
10 lation. When counter 88 is at zero value, this occurring att3, t7, t11, etc., then Z modulation will then automatically
disappear since this is produced only when the zero detec-
tion means output does no-t represent zero. Thus, in bullding
each TV frame, frequency ratioer 72 is loaded once per
15 frame at the ~eginning of the rrame and counter 88 is preset
once per line.
To achieve vertical television ras-ter modula
tion in the analog mode, according to the present invention
(Figure 5), the value Nmax is truncated by truncator 100
20 (where truncation is desired, same being preferred but not
required) and is converted by digital-to analog converter
102 into a D.C. voltage which is used as an initial condi-
tion in an analog integration circuit 104 whose input is a
voltage corrresponding to Nchannel, a television synchroni-
25 zing signal being fed into the analog integratlon circuit104. The ou-tput of the integrator 104 is logically clamped
to produce a Z modulation signal.
The integrator run down is started at t2, t6,
t10 etc., by the television synchronizing pulse and reaches
30 zero level at t3, t7, t11, etc. This circuit is the analog
equivalent of the circuit in figure 4.
To achieve horizontal television raster accor-
ding to the present invention, where this is desired to be
achieved by digital means, information is transferred from
35 a multi-channel analyzer memory 110 (figure 6) to a display
memory 112, the contents of each channel being divided by
kN by digital means 114, thus normalizing the value of
each channel to a rnaximum vertical scale value of N
max
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16-3-1979 12 PHA 20 7g8
.
Such digital means can comprise a computer, microprocessor
or hardwire digital arithmetic circuitry.
'Such horizontal television raster can be achie~
ved by analog means according to a further embodiment of
this invention, with a multi-channel analyzer 120 (figure
7), from which information is transferred to a digital-to-
analog converter 122, from which converter information is
fed into a voltage divider 124 to which VN is fed, the
max
lO output of which voltage divider is then transferred to the
analog shift register array 126 with the output therefrom
being fed to a display devlce~
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