DE1039265B - Particle counting device - Google Patents

Description

GERMAN

The invention relates to particle counting devices, especially for estimating the dust content of an air sample.

Apparatus for making such an estimation have been proposed which Means such as B. Cathode ray tube light spot scanner included for sample scanning. That too proposed so-called »Wachtfleektechnik« is used to switch between the first (or last) Scanning a particle from the skin scan beam and other scans of the particle from both the Distinguish between main and wacht bundles or from the wacht bundle alone, with the normal scanning movements of the scanning beam are blocked when a particle is first (or last) "seen", after which, the scanning beam scans the particle to determine its nature or size, and then the scanning beam carries out its normal scanning movements again. The size of each Particles, from the information of the scans, the total number of particles from the number of blocks derived from normal scanning.

Although with such devices. Memory are dispensable, are liable to the use of the "watch fleece technique" sometimes have disadvantages. On the other hand, the "blocking spot technique" allows, if necessary, far more information about the nature or size of the particles in a sample than just about the Interaction of the scanning grid with the particles because, in the latter case, at most only the length of the line scans of a particle or the number of completely overlapped scan lines can be achieved. With certain particle shapes, even this information was not supplied correctly.

The invention aims at a particle counting device which has the desired properties of the Blocking spot scanning technology without the disadvantages of the "Wachtfleektechnik" has to switch between the first (or last) and. to distinguish other samples of a particle.

The invention therefore relates to a particle counting device, in which a sample is scanned by a scanning beam according to a rectilinear grid and in which means are provided for locking the bundle, which cause the normal Scanning movement of the beam is only stopped when a particle is scanned first (or last) will. It consists in the cyclical and the line scanning movement by a memory signal synchronizing storage devices for the line scan to distinguish between the first (or last) scan of the particle from the scan beam and other scans of the same Particles are present and these storage organs particle counting device

Applicant:

NV Philips' Gloeilampenfabrieken,
Eindhoven (Netherlands)

Representative: Dipl.-Ing. K. Lengner, patent attorney,
Hamburg 1, Mönckebergstr. 7th

Claimed priority:
Great Britain 23 March 1953 and 23 February 1954

Hugh Alexander Dell, Horley, Surrey (Great Britain), has been named as the inventor

are provided with a number of independent signal channels. from. which one carries a permanent signal, that the line scanning of the scanning beam triggers.

According to the invention, the line-to-line memory is of the cyclic type and has e.g. B. a magnetic pinching disc or drum with a first channel carrying a single continuously recorded signal which is used by means of a line synchronizing reading head to initiate or synchronize the line scanning of the scanning means, with a second recording channel, I. on which a scanning sync head records a signal when a particle is intercepted first (or last "), and with a third channel that works together with spatially separated recording and reading heads that record the interception of particles in a scan line or during them Signal canceling means are connected to the second and third channels in order to cancel the signals on these channels if necessary, and switching means are provided to switch the reading and recording heads on or off at appropriate moments.

The memory therefore has three tasks:

1. It causes the beginning of each line scan takes place with the recording means (disk, drum or the like) in a predetermined (angular) position;

2. It stores signals (hereinafter referred to as "particle signals"), all of the interceptions of particles in a scan line and, if present, deletes all of the previous ones Particle signals off;

809 658/130

i 039 265

3 4

3. If a new part of the output energy of the recording device is found when a line is scanned, a signal (in the form shown in FIG his records) recorded on the second channel, can and is described in more detail below,
and then about the same time as FIG. 5 The device and tasks of the further termination of this signal, the reading, switching, control and recording units mentioned illuminate recording and erasing heads al> excited, the normal from the operation of the device when scanning the sample is interrupted and the typical sample, part of which is particle shown in Fig. 2, is scanned. The normal palpation is. The middle of three adjacent scanning lines does not start again until after a signal appears, io are denoted _{by L 1} , L ₂ and L _3; the line L ₁ begins which indicates the end of the scan, and if the four particles A, B and C, the line L ₂ only the transmission of a scanning synchronizing signal particles B and C and the line L ₃ only the part of the scanning synchronizing head that is used as playback - check C.

head works, it takes place. The line scanning movement of the electron beam

is sufficient that the recording means is brought about by the deflection device 8 when continuing with FIG

normal scanning in the same (angular) position is triggered by a pulse generated by a

as is when the scanning is interrupted, so that the first channel of the magnetic memory 9 by means of

Particle signals in the third channel is derived at the same distance from the playback head 10, which is in the

as the particles of this scan line following the mean are called "line sync head"

to be recorded. In this way, however, will become ao.

many new particles found in a scan line, and the memory 9 can be of any known type, despite possible and probable scan time differences, with sufficiently different for these particles, the recordable, magnetizable * surface provides three relatively accurate data on the Presence and the other recording channels and is set in rotation with a distribution of all particles in this line until it is substantially constant speed by a suitable motor used during the following scanning line. Has become simple, between new intercepts and, for the sake of security, the drum can be designed in such a way, repeated intercepts larger, from the preceding one, that it makes half a revolution for a complete moving line of particles to an uninterrupted line scan,
divorce. In this way there is a changed shape 30 If the light spot _{begins to scan the line L 1} under the "Wachtflecktechnik" instead of scanning the other prak- flow of the deflection device 8, there is no signal disadvantages from the recording device 6. until the light spot is a particle A

The invention is given on the basis of one in the drawing. Then a signal is sent to the pulse limiter

35 and former 7 supplied in more detail to the embodiment shown in the illustration, which has a suitably designed

purifies. deten, e.g. B. substantially rectangular pulse

Fig. 1 shows schematically, partly in a block diagram of the desired polarity, the switches S ₁ and S ₂

one form of dust particle counting device according to FIG. The switch S ₁ normally takes one

the invention; Position in which the impulse corresponds to a recording

Figure 2 is an illustration of the location of a particle head 11 communicated with the third channel

pattern; of the memory 9 is connected to this a das

Fig. 3 is a circuit diagram of a pulse limiting particle signal representing particles A to be recorded.

and-education unit; nen. In the initial position, the switch S _{2 is} in

Fig. 4 is a circuit diagram of a new signal - a position in which the pulse corresponds to the "new signal indicator; 45 indicator «12 is supplied, whose. Task in it

Fig. 5 shows signal waveforms; consists in determining whether the received pulse is a

Fig. 6 is a circuit diagram of a switching control unit showing first or repeated sampling of a particle.

and represents. As can be seen from the following, this is

Fig. 7 is a circuit of a pulse generator. achieved by that the input pulse from

In Fig. 1, the scanning means as a light spot 50 limiter 7 is compared with a signal that is shown scanner with a cathode ray tube 1. substantially simultaneously from reading head 13, which is provided with deflection means 2, to be received when receiving connected to the third channel, the tube drove the electron beam a straight line and z. B. at an angle of. 180 ° with the linear grid on the luminescent screen surface recording head 11 is arranged.
to be described. An optical system in the form of a 55 In the present case there is no reading head lens 3 can be used to take an image of the resulting signal 13, since the particle A is the first light spot of the same or different size particle to be intercepted on the first scanning line To focus on the Prol> e 4, and another so that the new signal indicator 12 of the switch control optics in the form of a lens 5 is used to ensure that the unit 14 and the pulse generator 15 supplies a pulse of light penetrating the sample to a photoelectric 60. When this pulse is received, the pick-up device 6 will drop. Assumed switch control unit 14 is effective and opens that the sample is a transparent plate, on switch S ₁ , S-, S ₉ with simultaneous separation of soft dust particles or the like. The recording head 11, the reading head 13 and are fixed, or a photographic rendition of the erase head 16; it also opens the switches of such a plate of the same or different 65 S ₃ and S ₄ , which is in positive or negative form with the line and image deflection device scales. The lines are connected, which the normal scanning playback can also lock on an opaque movements :. Next, it performs a signal surface to take place; In this case, the up to the signal path switch 17 and the scanning switch 18. receiving device is set up in such a way that the path switch 17 actuates the switch S ₂ and intercepts reflected light. 7 ° leads him to a position in which another signal from

of the pickup device 6 is fed to the scanning switch 18, and the scanning switch 18 actuates the switch S _{6 of} the F-direction changing unit 19 to make this unit effective, whereby the light spot generated by electron beams scans the particle in the F-direction. At the moment the particle is encountered, the pulse generator 15 transmits a signal to the scan sync record reading head 20 through the switch • S * ₈ to have the head 20 record a signal on the second channel. The unit 15 also transmits a signal to the synchronizing switch 21, and this switch changes the position of the switch S ₈ so that signals originating from the head 20 - which acts as a reading head - immediately after the scanning of both the switch control unit 14 and the signal path switch 17 via switch Jv ₇ , which was moved to the open position by sampling switch 18 when it was initially energized.

Since the particle A is small, a slight deflection of the scanning light spot will sweep the spot across the particle until it is "seen" by the pickup device C , which then sends a signal to the scanning switch 18 so that this switch is reset and in this way the scan is ended and. the switch ^ ₇ closes.

It will be understood that the time delay between the scanning of particle A and the end of its scanning depends on the size of the particle, and during this period the magnetic storage drum will have rotated through a certain angle, which is less or more than one revolution can. It is only necessary that normal scanning begins when the drum is in the same angular position as when it was first started! of particle A, and this is caused by the scan sync signal recorded on the second channel. When the drum reaches this position, the scanning synchronizing head 20, which acts as a. Playback head acts, a pulse via the switch S ₇ to the switch control unit 14 and to the signal path switch 17. The unit 14 is then set again, whereby the switches S ₁ , S ₅ , 6 * 9 are closed and the switches S ₅ , S _{4 are} opened so that normal scanning can continue. The path switch 17 is also set anew, whereby the switch ^ _{2 is} actuated, which feeds any new signal originating from the limiter 7 to the new signal indicator 12. Furthermore, the pulse originating from the scanning synchronizing head 20 is fed to the synchronizing switch 21 in order to reset it, whereby the switch S _e in is moved to the position in which the head can receive a new recording signal from the pulse generator 15 when it encounters the next particle. Since the switch S _{9 is} closed, the erasing head 16 cooperating with the second channel cancels the second channel scanning synchronization signal, as a result of which this channel is free for further use.

The units 12, 14, 15, 17, 18 and 21 and the switches operated by them thus resume their initial position and the first channel of the storage unit carries a record of the particle A in a position along the channel from its beginning corresponding to the position of particle A in the first scan line.

The whole sequence of the aforementioned actions is repeated when particles B, C and D are hit first in line L ₁ , so that at the end of the first, line, the third channel of the memory carries a record of these intercepts correctly spatially separated, the The total length of this recording corresponds to the distance between the recording head 11 and the reading head 13, which two distances are measured along the channel path. In this device, at the beginning of the scanning of the line L ₂ (due to the line synchronizing signal coming from the head 10 cooperating with the first channel), the beginning of the recording of the line L ₁ cooperates with the reading head 13, so that to the extent that As the scanning of the line L ₂ progresses, the reading head 13 supplies signals corresponding to the scans of the particles in the line L ₁ . In this way a form of the watch spot technique is achieved so that in the case of a particle A which does not overlap the line L ₂ , the new signal indicator 12 receives a signal from the head 13 but no signal from the limiter 7 when the scanning beam is in the Line L _{2 reaches} a position which corresponds to the position of particle A in line L _1. This signal from the head 13 does not actuate the new signal indicator 12, so normal scanning takes place until the particle /? is found. At this moment the new signal indicator 12 receives a signal from the limiter 7 (second interception of the particle B) and almost simultaneously a signal from the head 13 (first interception of the particle). When such signals are received by the new signal indicator 12, it does not take effect so normal scanning continues, in this case to the end of line L ₂ , with no further scans since particle D does not extend into line L ₂ .

During the scan of line L ₂ , the memory has rotated half a revolution, and at the end of the scan of line L ₂ , the third channel record of line L _{1 has} been erased by the erase head 16, which is with both this channel and the second channel collaborates.

At the end of the scanning of line L ₂ , the third channel of the memory carries signals representing the second scans of particles B and C for comparison with signals occurring _{in line L 3.}

In the example shown, only the particle C overlaps the line L ₃ , so that the scanning of this line will proceed from end to end without the light spot being locked, and at the end of the line the signals in the third channel of the memory, which the scans in line L ₂ is deleted and only the scan of particle C in line L ₃ remains for use during the next scan line.

It is evident from the above that each time the light spot is locked in order to scan a particle, the F-direction changing unit is actuated, the measured size of the scanned particle e.g. B. a function is proportional to the time during which the unit is actuated, or a potential that changes with the F-Rich, device deflection. The latter case is shown schematically by the resistor 23 at which a potential occurs when a capacitor, the charge of which corresponds to the extent of the scanning, is discharged at the end of the scanning. At the end of the scan, the switch S _{e is returned} to the position in which the F-direction changing unit is blocked (the lower position in FIG. 1), and the transition potential generated at the resistor 22 becomes known to a pulse level analyzer and counter 23

Form fed. In this way, as the scanning of the pattern progresses, one becomes Pulse series with any time distribution and with different amplitudes fed to the analyzer 23, who can give an analysis of the series of impulses in any way. The impulses can z. B. divided into any number of groups, so that both individual counts of particles of each group as well as a total count of all particles can take place. The latter Counting can, if desired, simply depend on the number of actuations of the switch control unit 14 are routed ali.

Suitable switching arrangements, which are given, for example, only for the limiting unit 7, the various switch units and the pulse generator 15, will now be described with reference to FIGS. 3, 4, 5, 6 and 7.

Limiter unit

A suitable circuit for the limiter unit is shown in Fig. 3 and can be a cathode-coupled double triode 24 a, 24 ?; contain. The signals of the imaging device 6 are pressed the control grid of the triode 24, and the anode is connected via a resistor 25 to the control grid of the triode 24 b; this grid is connected via a resistor 26 to a negative potential source. The anodes of the triodes are connected to a positive supply voltage line via load resistors 27 and 28, and the circuit values are set so that a certain amplitude exceeding pulses substantially rectangular and constant amplitude pulses at the anode of the triode 24 b Ergel> s.

If it is assumed that the potential at the output of the recording device increases when the Scanning beam encounters a particle, and. falls when it leaves the particle, the limiter 7 deliver a positive pulse which is substantially rectangular and the length of which is the length of the particle in the direction of the line scan.

New signal indicator

The positive pulses coming from the limiter 7 are, as described above, fed to the new signal indicator 2, which also receives signals from the reading head 13 connected to the third channel of the memory. The new signal indicator 12 can be of the form shown in the circuit diagram of FIG. In this circuit, the signal from the limiter 7, after differentiating in the normal way, is _{fed to the anode of the diode F 1} , the cathode of which is connected to the control grid of the triode F ₂ acting as a pulse inverter. Signals occurring at the anode of the tube V., are fed to the control grid of the tube F ₃ , with which the tube F ₄ forms a bistable multivibrator. The anode of tube F ₃ is connected to the control grid of tube F ₄ , the anode of tube F ₄ to the control grid of tube F ₃ in the usual manner. The differentiated input signal is also fed to the catching grid of the tube F ₄ , and the control grid of this tube is connected to a negative supply voltage line via a resistor 29 which is bridged _{by a triode F 5.} The anode of tube F ₅ is therefore coupled to the control grid of tube F ₄ and its cathode is connected to the negative supply voltage line. The particle signal generated by the reading head, which appears as a positive signal of substantially rectangular waveform, is fed to _{the control grid of the tube F 5.}

The operation of this circuit is as follows: at the beginning the tube F _{3 is} conductive and the tube F ₄ is made non-conductive at its control grid; tube F ₅ is non-conductive by connecting its control grid to a negative bias line

xo (-HT ₂ in Figure 4).

Looking at how it works the first time a particle is scanned, the positive pulse generated by the differentiator, which is the leading edge of the particle, passes through tube F ₁ and makes tube F ₂ conductive, causing a negative pulse from the anode of that tube is fed to the control grid of the tube F _3. The tube F ₃ becomes non-conductive as a result, and the multivibrator tips over into its other stable position in which the tube F _{4 is} conductive, since it is open both on its control grid and on its catching grid. When the negative pulse occurs, which is generated by the differentiator representing the trailing edge of the particle, it can _{not influence the control grid of tube F 2} because of the rectifier tube F ₁ , but it occurs at the catch grid of tube F ₄ , which limits the anode current, whereby the multivibrator tips over into its first stable position. Thereafter, the entire emission current of the tube flows momentarily to the screen grid, the potential of which has a negative pulse which is fed to the switch control unit 14 and the pulse generator 15.

When considering the operation of the indicator, e.g. B. during the second interception of the particle B (line. L ₂ ) and assuming that the signal originating from the reading head 13 occurs, the control grid of the tube F ₃ becomes positive, so that the tube V _{5 is} completely conductive and the potential of the control grid of the tube V ₁ , reduced. If the positive pulse of the differentiated signal coming from the limiter 7 is _{fed to the tube F 2} and the corresponding negative pulse is fed to the tube F ₃ , the mutivibrator cannot tilt because the control grid of the tube F _{4 is} inevitably kept at a very low potential . In this way, when the negative pulse of the differentiated signal is applied to the trap gate of the tube F ₄ , no signal will appear at the control grid and no output power will be applied to the switch control unit 14 or the pulse generator 15.

5 shows (in pairs) the waveforms of the signals generated by the limiter 7 (after differentiation) and by the reading head 13 for different types of particles. The waveforms shown at (α) represent the first intercept of a particle. And those at (b), (c), (d) and (e) show the intercepts following the first for different particle shapes that overlap two or more scan lines . The waveforms at (b) arise when a particle of greater length with substantially parallel sides which is beveled in the direction of the line scan is found, and at (c) when such a particle is beveled in the opposite direction; at (d) and (e) the waveforms are shown when a tapered particle is found, at (d) the sides diverge in the direction of the image scan, and at (e) they converge in the same direction. With (/) only the reading head signal is available (e.g. if the memory unit causes a signal _{in line L 2,}

Claims (7)

which corresponds to the first scan of particle A in line L1). In each of these cases (b) to (/), the switch control unit 14 is not supplied with a signal, either because the reading head signal is on the multivibrator. that has hindered the setting or has brought it back into the position in which it does not respond to the negative rear edge pulse of the differentiated signal from the limiter 7. IO switch control unit As described above, the new signal indicator only sends out a pulse when a particle is first scanned, and this pulse is fed to the switch control unit 14 to be described and to the pulse generator 15 to be described later. A suitable circuit for the switch controller is shown in FIG. This unit can advantageously contain a cathode-coupled double triode F6, V7 which forms a bistable multivibrator. The anode of tube V6 is connected to the control grid of tube F7, the anode of tube F7 is connected to the control grid of tube V6. The two control grids are connected to a negative supply voltage line via grid discharge resistors. and the anodes are each connected to a positive supply voltage line via load resistors. Negative signals from the new signal indicator 12 are fed to the control grid of tube Ve, which is initially conductive, while tube V1 is non-conductive. The multivibrator can be brought into its stable initial position by the negative signals fed to the control grid of the tube V1. these signals are taken from the scanning synchronizing head 21. At 7, νά \ $ \ χ of a negative pulse from the new signal indicator 12, a negative pulse occurs at the anode of the tube V1, which is able to open the switches S1, S%, S ^ and S-. Since these switches are shown schematically as mechanical switches, the anode circuit of the tube V1 contains a multiple contact relay 30, the contacts of which form the aforementioned switches. It will be evident, however, that such mechanical switches can be replaced by electronic switches; in this case the relay is of course not used. The signal path switch 17 is fed to the signal path switch 17, as mentioned above, in order to move the switch 5 * 2 into the position in which the limiter 7 taken from the Signals are fed to the sampling switch 18, which in turn actuates the switch .J6 and opens the switch S1. Both the signal path switch and the sampling switch can be of exactly the same type as the aforementioned switch control unit, so that further description of these parts is unnecessary. The synchronization switch 21, whose. Position set by a pulse originating from the pulse generator 15 and. readjusted from a signal from the scanning synchronizing head 20 may also include the same circle as that shown in FIG. Pulse generator A suitable circuit for the pulse generator is shown in FIG. It can advantageously contain a cathode-coupled double triode V8, V9, the anode of the tube V8 being connected to the control grid of the tube V9 via a capacitor F. The control grid is connected to ground via a resistor R, and the time constant CR has a suitable value. Negative input pulses taken from the new indicator 12 are applied to the biased control grid of the tube F8. In the initial position, tube F8 is conductive and tube F9 is non-conductive. When a negative pulse is received at the control grid of the tube F8, this tube becomes non-conductive and the tube F8 becomes conductive, as a result of which the potential at the anode of the tube F9 drops. After one through the time constant of. CR-induced time delay, the tubes F8, F9 forming a monostable multivibrator return to their initial position, so that a substantially rectangular pulse of the desired duration occurs at the anode of the tube F9. This pulse is fed to the scanning synchronizing head 21 whenever a particle is first intercepted to record a signal in the second channel which, as described above, is present to synchronize the action of the scanning means with the rotation of the storage drum. It is clear that the invention is not restricted to the devices described with reference to the block diagram of FIG. 4, since the magnetic storage device can be replaced by any other device which fulfills the same objects. It can e.g. The storage device may be of an electronic type. Furthermore, the invention is not limited to the simple scanning of the particles, as described above. Such a scan can be of any other suitable or arbitrary form. Such other types of scanning can be applied using more than one scanning spot. These devices can be provided with other receiving means 6, since more than one of these means may be required. However, such modifications are obvious to a person skilled in the art. It goes without saying that the invention is not limited to the particular switching arrangements mentioned above and. that practical circumstances adapted modifications are possible. Pa τ ε ν τ α ν s ρ r π c η ε: 1. Particle counter device, in which a sample by a, scanning beam according to a rectilinear grid is scanned and in which means for blocking the bundle are provided, which have the effect that the normal scanning movement of the bundle is only stopped if when a particle is scanned first (or last), characterized in that cyclically working and the line scanning movement by a memory signal synchronizing storage elements for the line scan to distinguish between the first (or last) scan of the particle from the scan beam and other scans of the same particle are present and these storage organs with a Number of independent signal channels are provided, one of which carries a permanent signal that the line scanning of the scanning beam triggers. 2. Particle counter device according to claim 1, characterized in that the second of the Signal channels Particle signals carries all 809 63 & / 130 Scans of scan bundles that correspond to particles on a scan line. 3. Particle counter device according to claim 1 or 2, characterized by means for recording the particle signals on the second signal channel when scanning a line and means for reading the signals while scanning the following line. 4. Particle counter device according to claim 1 or 2, characterized in that a scanning synchronization signal from a third signal channel each time the scanning bundle meets a new particle can be stored. 5. particle counter device according to claim 4, characterized in that means for both Recording as well as reading the scanning Synchronizing signal in said third channel and means for canceling said signal are present after reading. 6. Particle counter device according to claim 5, characterized by means for blocking the Reading, recording and erasing heads after scanning has taken place and after the corresponding one has been sent Scanning synchronizing signal from said reading means. 7. Particle counter device according to claim 1 or one of the following, characterized in that that the line storage members contain a magnetic recording disk or drum. Legacy Patents Considered:
German patents 918 054, 919 268, 929 822. 1 sheet of drawings © 809 638/130 9.58