DE2023694A1 - Device for measuring light - Google Patents

Description

The invention relates to a device for measuring the optical density (blackening, light permeability etc.) of samples, measured values for the optical density are particularly in the graphic industry for a large Number of purposes needed. All previously known and in use facilities for such Measurements have certain disadvantages. For example, a commercially available apparatus uses a light source that is focused on an area of the film or copy material and the transmitted light is direct

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measured by standard light-sensitive tubes, jJiti The disadvantage of this device is that the output signal a linear function of the durchgolassenon Lightweight is 3 pounds. The optical density or uchwäraiin ,; iat however ala defines the logarithm of the / er-tiältuiosos the radiation intensity falling on the sample to the radiation intensity transmitted by the sample. One

further limitation of said device consists in that the output signal decreases with increasing optical density. This makes e3 difficult with high numbers the optical density a reading with sufficient Accuracy or with small loleranaen.

Another commercially available device uses a secondary electron multiplier (photomultiplier) for measuring the optical density of a sample. The photomultiplier is connected to a feedback circuit, around a constant current from the photomultiplier for all values of the light intensity falling on the photomultiplier au received. This is achieved by constantly varying the high voltage supply so that that the desired amperage is obtained. A measurement of the high voltage supply is provided from which then gives the value of the optical density.

This last-mentioned device also has

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various drawbacks. It is subject to gradual fluctuation (drift) and inaccuracies occur because of the high zero voltage at zero optical density. The output signal is proportional to the optical density of light and are therefore non-linear j oiipensationsschaitunjen required by a certain Photomultlplier au one with an optical measuring instrument provided to connect.

Compared to these devices with their above The device according to the invention has disadvantages a clear and surprising improvement of a uui <3 sample, the light reflected can make a measurement - for the optical density over the discharge curve öinti3 RJ-1 lied es * · - The;! O-Crlied is charged when a measurement is desired, up to a potential level, nas is higher than the aar supply of the various dynodes and the anode of the Photomul " tipliers required tensions. When unloading des RO-trii'e.des reaches the anode voltage of the Photoaultipler a predetermined level, a lot of the one Controls counter with clock input, which saves a numerical value to allow for a to give a digital reading of the measured optical density. The counter will stop when the falling curve the ^ J member has reached a noisy level

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Has. The tension you want is the one that is required is to the desired anode current for the optical Maintain density ITuLl. Am an important feature of the invention iet the use of a potential "floating", isolated voltage supply, which is between the cathode and the first dynode, to ensure a sufficient To generate voltage so that all electrons emitted by the cathode are captured and one in particular linearly working device receives, which works exactly and perfectly controllable in all operating areas.

An embodiment of the invention is described below explained in more detail with reference to the drawings.

Ii ¹ Ig. 1A and 1B together show the schematic circuit diagram of the device according to the invention.

Pig. 2 shows a voltage-discharge curve and serves to explain the mode of operation of the inventive - / - em Contraption.

Referring first to Figure 1 of the drawings, which is a block diagram of an apparatus according to the invention for the measurement of the photographic density shows. The entire circuit is designated as a whole with the reference number 10, a sample 12 is in the lower part of Fig. 1A

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indicated. It is illuminated by a light source 13 which is fed by a stabilized five volt voltage source. The light from the lamp is over guided a laser light guide 15, the light preferably a sample box 16 feeds. The sample box 16 is shown separately from the rest of the device, to indicate that it is mobile in order to examine its sample at any point. the Parts of the device not assigned to the sample 12 can be set up spatially remote from the sample. Therefore, the fiber optic path 15 is preferably of measurable length and extends from the electronic Part of the device for the actual sample. The distance can be a few centimeters or a half or whole meters or more. The device is thus sufficiently flexible that the operator can examine the sample 12 at a certain distance from the electronic part of the device. Of course the lamp 13 and its regulated voltage supply can also be arranged in the actual sample housing if so desired.

An additional Paser light guide indicated at 16 directs the reflected light from the sample 12 to a photomultiplier 17. Again, the spatial Distance between the sample 12 and the photomultiplier 17 due to the arrangement of the light guide 16 between the

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be and the tube 17 overcome.

It can be seen from the foregoing that by the Fiber light guides 15 and 16 great freedom in the spatial arrangement of the device is given relative to the sample, the length of the light guide in a large area can be freely selected.

A common arrangement for the sample chamber 16 is to have a suitable housing a certain distance from the sample 12 so that the light from the lamp 13 travels through the sample 12 at a precisely defined distance. Also from the light guide ¹ 16 received, reflected light passes through the same route. The sample housing 16 preferably has a push button switch 18 which, when actuated, triggers the operation of the apparatus shown in FIG. 1 to obtain a measurement of the optical density.

As for the position connected to the photomultiplier tube 17, it can be seen that the light guide directs the light onto the cathode of the tube 17. The tube contains a number of dynodes that have a multiplying effect cause. The light hitting the cathode releases a few electrons that are directed towards the first dynode marked 17a are running. The first dynode responds to the impact of the electrons by

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it in turn emits electrons, whereby a certain 'amplification is achieved. This process repeats itself, .and when the signal arrives at the anode 17b, it has been amplified a million times. Through this you get a sufficient signal strength, which in the'üb-. ri; -eti circuit can be processed. How it works a photomultiplier is assumed to be generally known, so it is only shown in abbreviated form here will. .

Of particular importance in the arrangement shown in Fig. 1A is the use of an insulated, "Schwiame'p.üen ¹¹ voltage supply between cathode and dynode, which is denoted by the reference numeral- 19. The normal voltage supply for the dynodes is indicated at 20 , respectively. the voltage source 19 is located between the cathode 1VC and the first dynode 17a. preferably, it is precisely regulated and stabilized, and the output voltage of the "floating" power source 19 is pre-μ to ^ sweise be controlled accurately, so that a linear working method ' The dynode 17a is obtained. The secondary emission or the multiplication factor of the dynode in question is very well linear if the preferred arrangement described here is used.

The main voltage source 20 is in turn the Lines 21 and 22 and the switch 13 are connected.

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When this switch is actuated, sufficient voltage is generated to charge a capacitor 25. The capacitor 25 can be regulated to a small extent by a parallel connected, th capacitor 23, and he lies in parallel with an adjustment resistor 24. It can be seen that the low voltage side. of the capacitor 25 is directly earthed.

As shown in Figure 1A, the tube 17 contains a number of additional dynodes, generally designated 17d are designated. The dynodes are in series with points of increasing potential of a voltage divider circuit connected, which is indicated generally at 26. The resistors forming the voltage divider are preferred equal, so that the voltages on the various dynodes increase in equal steps. For example the voltage drop across each of the resistors of the voltage divider 26 can be 100 Y to achieve the optimum potential difference of the various dynodes.

From the foregoing it will be seen that the tube is connected to circuitry which is very general can be referred to as an RC element. The RC element generates the voltages required to operate the tube 17. This applies to all amplifier stages of the tube 17 with the exception of the first dynode 17a, the one with the cathode 17c connected directly via the voltage source 19 lat,

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which is always one required for linear work Maintains dynode voltage.

The reference symbol 29 denotes a reference current generator which is adjustable to generate a current of a certain strength through a resistor 29. The resistance 29 is connected to a voltage measuring amplifier 30 (level detector amplifier). When the amplifier is 30 indicates a certain potential level, he presses one Kipp-Multivibrator 31 (one shot multivibrator, Schmidt-Irigger), to generate a signal in a line 32. The strength of the from the tube 17 to the resistor 29 and The current flowing to the voltage measuring amplifier 30 controls the amplifier 30. To understand this mode of operation reference is made to FIG. This shows the charge curve of the RO element, which essentially consists of the capacitor 25 exists. The part of the curve labeled 33 shows the charging of the capacitor. 34 designated the optimal charging voltage of the capacitor 25, which is related to the terminal voltage of the voltage source 20 is. The charging of the capacitor 25 apparently continues as long as the push button switch 18 'is depressed remain. When the switch 18 is released, the capacitor 25 begins to discharge. This point is at 35 in the voltage curve of Pig. 2 included. At 36 is the beginning of the exponential discharge curve is

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net, which describes the behavior of the Rfl-GliedejB connected in parallel to the tube 17.

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It is clear that the tube 17 is brought to a ringing tone by applying the appropriate voltages to the various JBLektvoden ^ doi * tube. The application of an overvoltage has koine special effect on the operation * If the voltage of the capacitor sucked by AEEN voltage divider 26 wirdj works Röhr © on and supplies an output current sura SpannungeraeBverstarlcai? .-O ₀ Depending on the setting of the Reieffenzstroraciuelle 28 and the value of resistor 23 erreioht the input voltage at Meßveretärker 50 the predetermined level _P is ig designated at 3 ₀ 2 37 ₀ Beira detecting flieses predetermined SpannungsiniY <9au8 iffl Teretärkes? 30 responds to the multivibrator 31 and forms a pulse in the line 32, the further processing of which in the following is based on! 1B will be explained in the eiazeloen »

Wisäei? A line is provided on FIG. 1A which leads to a differential amplifier 40 which is connected to a further tilting multivibrator 41 (one shot multivibrator). This multivibrator generates a pulse in a line 42 to be described later. The differential amplifier is supplied with an input voltage from a reference voltage source marked 43.

i
Voltage source 43. 2u Ibeachtoa is the connection of the

line 39 with the obea bosotatsbenen RC-GIied “¥ ie er ^

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iniiorlioh. the HO element is charged and discharged exponentially, as shown in FIG. The line 39 is connected to the Ilochspaunungsseite of the HO element, and then the voltage in the line 39 drops in the form shown in FIG. The Differentialveri3t ^; irl: m. ' 40 works when the voltage in line 39 üeii iu Fi;. 2 reached point 38.

!. In fol (- be endon settings IleßverstäL'la .- 3Ü UUD 40 considered the measuring amplifier 40 Gu _t; i: ornuete circuit is set so that a pulse, It: called "olsenden Leoeimpuls is generated If, the YGroot '^ ntitTO voltage at the dynodes corresponds to that which only requires the generation of an anode current from a sample 12 with an optical density Hull. In other words, if the sample 12 shown in Pig. IA has the optical density Hull and If the photo multiplier tube 17 is continuously operated with the anode current which corresponds to the current from the reference current source 28, a certain dynode voltage would be established. This is the voltage given by the point 38 of the discharge curve according to FIG at the optical density results in zero, and thus the voltage level at which the read pulse is generated.

Wenu a sample with a different from Hull

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optical density is measured, is a higher dynode voltage required to create an anode e-torah, which corresponds to the current from the reference current source 28. This tension is at 37 in 1? 2 indicated * If the Dynode voltage drops to this value, is in the Line 32 generates a start pulse by the voltage stress amplifier 40 controls the pulse generator 31.

In the following, Pig «1B is considered« The start pulse arrives on line 32, to which an electronic Gate 48 (gate) is connected. The gate 48 pulses from an oscillator 50 with fixed Speed fed «At d @ i? preferred execution Rungeform is dl © X pulse rate 4000 Hertz «Of course any other suitable pulse frequency can also be selected. In any case, the Impuls® of the Oscillator or clockwork 50 the input signal sum £ or 48 represent.

The clockwork pulses from the oscillator 50 are fed through the gate 46 to a counter 51 . Dies® fence

kaö.e 1st fait another »counting decade 52 and this again connected to a third count decade 54. The exit the third counting decade is at a fourth counting stage connected, which is labeled 55. While Qftle first If there are three counting levels, the last counting level only needs to be a counter with four counting values.

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Since an optical density reading of 4 »00 one Change in light intensity of 10 000? 1, it is obviously not necessary to adjust the counting area of counting stage 55 to extend to a full decade.

Each of the four above-mentioned counting levels is with connected to an ITull detector 56. The zero detector 56 gives an input to gate 58 to close it. This means that once the gate 58 has started has to pass clockwork pulse Q from the oscillator 50 to the first counting stage 51, the device counts ceaselessly continues until the zero detector does a zero count in each of the four counting levels. At this point the lor 48 is closed and the original one The idle state is restored.

The reference numerals 57, 58 and 59 denote the three memories described with the mentioned counting decades. The output of each memory leads to a converter that converts from binary conditional decimal to decimal Display converts. The converters bind with 60, 61 and

i
62 designated. Each deciraal converter is marked with an ^f

ι
suitable reading device, such as a Uixie tube, which are designated with 63, 64 and 65. The read pulse supplied in line 42 of the circuit described in Pig, IB © read pulse is supplied to memories 57, 58 and 59. When this pulse .flies different memory

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activated, the counting values generally contained in the counting stages i> 2, p «| - and ρ 3 are fed to the reading devices via the decimal converter. These provide a visible rope for the operator, and awar in the preferred decimal representation, in which the optical density is always specified, Ke are therefore the starter pulse in the device shown in Pig, 1B. The reading impnls are used to provide a visual indication of the desired sea result.

The erfissäuags calibrated aia ^ ii in Pig. 2 shown or compressed duroh, calibration device 24 »

is calibrated or the resistance 24 «The

e 36 is stretched of resistance in the

& be heard about it _? that, as mentioned above, the definition of the optical density is a logarithmic puncture, the decrease in the charge of the capacitor and in particular the _{curve shown in Mg 0} 2 has an exponential course Exponetrically all curve progression results in the conversion of the measured values for the optical density into the desired digital display. can practice the absolute values of optical thought? a very large area of for example = spielsweiae '10 OOOsi vasiiereöp what an extraordinary

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represents great ilealism. The device according to the invention, however, has such large measured value variations by changing the voltage at the photamultiplier 17 in a ratio of less than 4s 1. Furthermore, the device never operates linearly. As mentioned above, that part of the Pnotomultiplierröhre 17 _f which reinforces the weakest iji.-nale, connected to a floating voltage source Lo, which ensures that this stage always receives an IUr linear mode of operation sufficient voltage.

iJine another way to calibrate the device, bosteut in a setting of the oscillator 50. With A reading is taken of a given sample 12 of known optical density and the digital display is on the display means 63 »64 and 65, if the display is too high, the oscillator frequency is reduced and took another reading, slurred the Anseiße au is low, the oscillator is accelerated and watched the digital display again. In this way it is very easy to get a calibration that remains constant for any time.

i) The device according to the invention is characterized in particular by good reproducibility of the VLeQ results. Furthermore, the device comes essentially without complicated compensation circuits or the like,

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from the curve shown in Fig. 2 to that mentioned above Adjust definition of optical density. As a result, the device operates with great reliability over long periods of time, and there are no problems whatsoever with the device starting up or warming up, as is the case with the previously known devices. Most of the devices known to date will be preferably operated in continuous 24-hour operation so that the device at as constant an oil temperature as possible is working. The device according to the invention is essentially immune to changes in properties of the individual switching components due to temperature changes.

Numerous changes and refinements of the described embodiment are within the scope of the invention possible. For example, the one shown in Pig * 1B could be Display part of the device can be changed, depending on the number of digits of the counter result or the desired Form of the numerical value to be read. Furthermore, the device can be modified to include compensating devices for reciprocity errors, as they are generally known in the graphic arts industry. In short, the reciprocity error is based on the fact that the integral of the light intensity generated during a Time interval impinges on a photographic medium, compared to another a different Blackening. This can happen even though the

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integral light intensity "in both photographisohen
Media can be the same. The reciprocity factor is
an adjustment factor which can be specified for the individual case by calibrating the device according to the invention. The calibration is effected by changing the pulse frequency of the oscillator 50 or by setting it
the calibration circuit 24 according to Pig. IA. In both cases, the reciprocity factor is taken into account and the device operates normally . ■

The device according to the invention enables deviations in the optical density to be detected in a very routine manner. This means that if a filter is used which shifts the display by a certain value, for example 0.50, then this! Factor in
the measured value display is taken into account by simple arithmetic.

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Claims (1)

Claims Optical density device Bum Measen, characterized by means for displaying the optical density of a Prob® by linking an exponential function with zero optical density and the optical density of the sample. 2. Priority for measuring the optical density an unknown sample by. facilities 2 to measure the optical density, .Equipment for linking the measured value with a Exponential function, and means for displaying the result obtained therefrom. 3, device for "measuring the optical density of an unknown" sample by means of a photomul \; iplierrcJhre, checked by devices for Aufreoiiterhaitfeß © iöer constant span between the cathode £ 17 ©) and 4 @ f first »Djöoäe (17a) tier PhotoajultipliaETÖhjee (17 ) on © iaesa W®1. * 'der ausEetoht that the or st «.. dynode essentially all of the cathode absorbed electrons. 4. Apparatus sum Hessen the optical density of an unbe.canned sample, geke η η ζ e 1 ch η et iiarch facilities sum generation of an exponential function, facilities for assigning a first point of the exponential function to a volumetric or reference value of the optical Density and facilities for assignment »-: .en cities two th α point of the exponential function to tier ■ unknown optical density of the sample. TO 5. Device for displaying the optical density of an unnamed sample, characterized by a clockwork or a pulse generator to generate of impulses to be stored in a register and by setting up the register in such a way that that this the pulses from the pulse generator stores during a 2-time interval which the optical density of the unknown sample is assigned. 6. gate direction according to claim 1, characterized by the following institutions: a) insane switching devices to form an exponential running conversion signal for the logarithm of the optical density; 009851/1318 b) second switching devices for plaguing a point . · On the exponential signal corresponding to the optical density of the sample; o) third switching devices for setting a further one Point on the exponential signal corresponding to an arbitrary reference value of the optical density; '' d) fourth switching devices for converting the part located between W the two specified points of the exponential signal in a measuring display for the optical density * 7 «Device according to claim 1, S β & θ .η η % β ic-hB et by the following devices! a) A first switching device, which after an exponential function works; £ b) a second switching device for entering a Sig * - nals in the first switching device in dependency from the optical. Density of the sample}. - c) third notices that. exit first switching device is connected, ssurn testify one of the optical density of the sample. Conversion according to the exponential iCucve © αϊ? · *: Ν speaking signal; ϊ • - 3 -009851/1318 bad omäW d) digital connected to the third switching device Display means for displaying the optical diodes the sample. 8, device according to claim 2, g β k βn η ζ e i ο h η e t through the following facilities $ a) A numerical digital display device; b) a pulse generator connected to the display device for generating a train of pulses; c) Control switching devices for controlling the number of pulses supplied by the pulse generator of the display device for influencing the display, the control device being controlled by the measuring device for the optical density of an unknown sample in such a way that the total number of pulses supplied by the pulse generator has the optical density the unknown sample is linked. \ 9. The apparatus of claim 3, wherein the photoraultiplier tube has further synods in addition to the first dynod, characterized by the following facilities: a) A voltage source (20) for generating an operating voltage do the additional dynodes (17d) of the (17); 008851/1318 '■ BATHROOM to) an output circuit connected to the Photomultipli® carrot (17) generating a signal _g which is a measured value for a & as a function of the optical density of the unknown sample (12) falling on the photoraultiplier tube (17); c) display device the iß dependence of dea on The output circuit generates a signal that is an Aasoige. the optical density üe'C VLUbelmnn ^ m 'SvabQ . 10. The device according to claim 5 _S g β ke κ ß - draws, through following® a) An electric oö © e aleictucmtsöhas for (4 ^) sv / i ~ sch the ItopulsgensratoE ¹ (50) uad the register j b) Schalteinriohtungea (2B ₀ 30, 31) sum generating a start pulse, dee the supply of pulses from the IsapölegQüemtoi? (50) isms register controls $ c) an da® Magister aisg @ sohl © s @ © a © display means (63 » 64, 65), d) Schaltiaittel. (4O ₉ 41 _s 43) to generate a control signal to control ά®Έ ! © gistei ?: such ₉ öaß eia signal Ia digital construction © Haag aß ctiß Aaseigesaic- = tel e) and öin® measuring device (15 - 17) f'i * ul & optlsc.is density of an unknown J? i7 © foe ₃ die e..ü dta i'ctmit- «5 - ■" ■ .Ana get /%%% pt "■ ' ■ - - ORfGfNAt means (28, 30, 31) for generating the start pulse and to the switching device (40, 41 »43) ■ ss-um generating the control pulse is connected. 11, device according to claim 3 with a light source for illuminating the sample with an adjustable amount of light, marked duroh facilities (16) for supplying the light from the sample to the Cathode (IYc) of the photomultiplier tube (17). · 12. Device according to Aaeprueh 3, g e k β ti η draws by the following linrichtuBgeai a) Mne adjustable light source (13, 14) » b) fiber light guide (15) swiscbaa of the light source (13) up to a point close to the unscanned sample (12); , c) further fiber light guides; (16) »wipe ^ o the sample (12) to the photomultiplier tube (17) f where the light head a transmission veElüafc of known value have to make other variations of the on the photomultiplier tube falling light except through the 1? robe to switch off caused changes " 13. Torriohtung according to claim Z ₉ gek eu η draws the following Blnriohtungeat 009851/1318
ORIGINAL BATHROOM * a) Bin housing for the measuring device for the optical j Density of the unknown sample and for the connected device for generating a digital display value for the optical density, b) a movable sample measuring head connected to the housing (16)} c) "Devices in the sample measuring head (16). for detecting of the light coming from the unknown sample (12) j c) Connection means between the probe head and the Housing for transferring the measured value into the housing. 14 · Device according to claim 2, characterized by the following institutions: a) A photomultiplier tube with a cathode, at least two synods and one anode; b) Means of guiding the light from the unknown ™ sample (12) for photomultiplier tube (17) » c) an RC circuit (25 »26), which runs in parallel with the Photooultlplierröhre (17) is switched and at least one dynode of the tube is supplied with voltage; d) a voltage source (20) for charging the RC-ßliedes to a certain potential; e) Means for discharging the RC-Glledes after an exponential Function; ■ 0 0 9 8_5 1/1318 BAD ORIGHNAL ΛΓ f) a first and a second potential measuring amplifier (30, 40) controlled by the discharge of the Rö-Glieda be and the match of tension with one of the optical density of the unknown sample or a reference potential assigned to a reference value determine; g) means controlled by the potential measuring amplifiers for Generation of digital signals for controlling digital display means as a function of the optical Density of unknown sample » 15. The device according to claim 2, characterized by the following devices! a) A photomultiplier tube (17) with a cathode (I7ö) ^ at least two dynodes (17a, 17d) and one anode (17t)) j b) a voltage source for supplying at least one photoinultipliarrotube dynodesj c) one remote from the photoraultiplier tube (17) in, sample measuring head to be placed near the sample to be measured (16) j d) means for supplying the unknown sample through the sample tube head to the PbotomttlMpU er tube; e) control means for triggering the operation of the photo 009851/1318 $ 3 multiplier tube by producing a power supply for the photomultiplier tube. .16, device according to claim 2, characterized by the following devices: a) A photomultiplier tube (17) with at least two Dynodes (17a, 17d); b) means for supplying dynode voltage to the photomultiplier tube} o) switching means (25, 26) aura changing the dynode voltage according to an exponential function with time} d) a source (50) for clockwork pulses; β) a display register connected to the pulse source; f) switching means (28, 30, 31, 40, 41, 43) for controlling the Number of pulses in the register in such a way that the exponential change of the dynode voltage at the photoraultiiplier tube with the pulse frequency in such a way linked! is that in the display register a display the optical density appears. 17. The apparatus of claim 3 ^; geke η η - a e i c h η ejt by means of generating »a lynoden-I f voltage at the photomultiplier tube (17), which has an exponential Has passage of time. Q09 & SW1-318
BAD Ola & i Ij. Device according to claim 17 »β e k e η η a -ß i η et through bodies (23t 24) to change ' the jeacliwindi,; icelt of the exponential decay. 1_ · ί. Device according to Anapruch U, £ -e k β η η ε ei cn no t through adjustable HC elements (23, 24). 4J "0, device according to claim 5, thereby cg" a Ti-U ":: - I η <? t that the frequency did adjust the pulse ^ u - ": n? rators {..) , uai- a correction of the 3 Ue :: iprocit.- csf.'higher optical density can be achieved. - 10 - 009851/1318 BAD ORIGFNAl,