DD242089A1 - PROCESS FOR OPTICAL MODULATION WITH SHIFTING OF THE RADIATION - Google Patents

Abstract

Method for optical modulation with switching of the beam length, preferably for atomic absorption Spektralphotometermit with at least one radiator as a light source in which optionally a beam splitting and beam combination according to the selected mode, the radiation energy, controlled by a detection electronics, from the isochronous radiators to a receiver and light-dark signals are recorded in chronological order, characterized in that, depending on the selected mode at least two optical modulation devices with programmable switchable phase assignment ausfuehren a self-controlled movement for phase synchronization of the optical modulation devices. Furthermore, the invention includes a device for carrying out this method. Fig. 6

Description

Field of application of the invention

The invention is preferably applicable to optical modulation in an atomic absorption spectrophotometer to guide sample and reference beams, timed, in different modes to a receiver in different ways.

Characteristic of the known technical solutions

In spectrophotometers, despite improved techniques in light sources, optical assemblies, receivers, detection electronics, and despite the use of powerful computing technology, the need for dual beam devices has been preserved for a number of well known reasons.

In an atomic absorption spectrophotometer, the light of a line-emitting emitter and the light of a continuous spectrum emitting emitter in a predetermined signal nesting through a sample volume (sample beam) through and passed (reference beam) and mapped to a common receiver. The resulting by modulation light-dark signals are detected in a suitable manner and evaluated in a computer. In the known solutions, both the beam splitting and the beam combination are made either via rotating mirror-aperture systems or via semitransparent mirrors.

In PS-DS 2539184 an arrangement is described in which a beam splitter and a rotating sector disk are arranged in front of and a beam splitter for beam combination behind the sample volume.

Model IL 951 from Instrumentation Laboratory uses a beam splitter in front of the sample volume and a rotating mirror behind it.

In the Perkin Elmer Model 4000, two rotary mirrors are driven by a synchronous motor on a common axis, with a beam splitter in front of and behind the sample chamber.

The AAS3 developed by VEB Carl Zeiss Jena houses a rotating mirror driven by a synchronous motor in front of the sample volume and the beam splitter behind it. A disadvantage is in all cases a loss of reaching the receiver radiation power of line and broadband radiators up to 75%.

Furthermore, it is known, as described in PS-DD 65468, to drive modulation devices with a synchronous motor, wherein the evaluation signals are obtained by a plurality of sensors (eg, optocouplers) on additional control disks of the modulation device. Including the sensor adjustment, this means a great technical and economic effort.

Furthermore, modulation devices are known which are driven by a stepper motor. In the example (reference WP G 01 J / 2689537), a mirror-iris system for a two-beam photometer generates two optical signals "measurement" and "reference".

Here, the great technical and economic effort of several sensors and their adjustment is bypassed by the fact that the evaluation of the control pulses of the stepper, electronically adjustable delayed and synchronized by a sensor signal at the modulation mirror derived. With such a modulation device, however, a synchronous operation of two mirror systems, which can be switched over to different operating modes, is not possible.

It is also a circuit arrangement for the programmed control of several stepper drives known (document WP H 02 P / 2666715), are formed in particular for the purpose of positioning control pulses for one or more stepper drives by a revolving counter chain, which is resettable by an external signal, is clocked continuously by pulses and drives according to their counter reading addresses of a memory. The output signals of the memory are combined with selection signals in combination logic to drive signals for stepper drives. The solution disclosed in US Pat. No. 4,171,913 is the closest to the present invention description.

Object of the invention

The aim of the invention is to develop a method for optical modulation with switching of the beam paths and a device for carrying out the method with the least possible expense for a spectrophotometer, preferably for an atomic absorption spectrophotometer.

Essence of the invention

The object of the invention is to make the switching of the beam paths preferably in an atomic absorption spectrophotometer with a method and apparatus for carrying out the method so that an optimal light output at the receiver is achieved for different modes. The synchronization of two drives should be done by an electrical arrangement, so that a device-internal computer is freed from this task.

The object is achieved by a method according to the preamble of the main claim according to the invention by the features of the characterizing part of the main claim and by an apparatus for performing the method according to claim 6. Preferred developments are described in the subclaims.

The inputs and outputs of the circuit elements described in the device for carrying out the method are preferably designed as multi-channel inputs and outputs in the circuit implementation.

The programmable memory supplies according to the clock frequency at the counter and synchronous to the count of the counter at least three signals of different frequency, the average value of which differs depending on the necessary control frequencies of the stepper drives. The output signals of the Phasenauswerteschaltung and the signals for timing the counter, which changes the Impulsverkürzerstufe with time shift in the phase position and the pulse length are linked in the selection logic. Thereby, two signals are supplied to the control frequencies for the two stepper drives in such a way that, controlled by the result of the comparison in the phase evaluation, depending on whether

Whether the respective sensor supplies a signal leading or lagging the reference phase signal, the corresponding stepper drive runs with a control frequency reduced or increased to the average frequency until a sufficient phase match is achieved. Subsequently, the selection logic, which forms a common synchronization signal from the signals of the phase evaluation circuit for both drive systems, informs the computer of the device that the synchronous operation of both systems has been achieved.

In the phase evaluation circuit set forth in claim 9, the D and R input of the third D flip-flop, which is triggered by the respective sensor signal, only Η-potential when the corresponding stepper drive should remain defined depending on the selected mode.

The inventive solution enables the realization of a low-cost atomic absorption spectrophotometer with high physical performance. Optionally, the analytically required operating modes of two-beam and single-beam operation, in each case in variations, as well as the emission mode are possible with absorption. The losses of radiant power are significantly reduced compared to the prior art, so that an optimal radiant power reaches the receiver. The modulation devices used in the solution according to the invention, including stepper motor, can be manufactured easily and without great economic outlay. The effort to adjust both modulation devices and the required detection electronics is low, since each modulation device with associated sensor can be mounted in a defined energized stepper motor in a device and the evaluation signals supplied by the programmable memory are synchronous to the signals for the desired phase position and thus to the concurrent drive systems ,

embodiment

The proposed invention will be explained in more detail below with reference to schematic drawings. Show it:

Fig. 1: beam path schematically

Fig. 2: Assignment of the rotating mirror in the various drive modes

Fig. 3: sector discs

Fig. 4: Signal sequence perperiod for the operating modes

5: Timing diagram for the operating mode two-beam operation with background correction (DB-BC)

Fig. 6: Inventive Schaltung arrangement in an overview

Fig. 7: Inventive phase evaluation circuit for a modulation device

Fig. 8: Signal representation for phase evaluation circuit

Fig. 9: Input signals of the evaluation logic, shown as an example

Fig. 10: Example of the programmable memory in a RAM variant

Fig. 1 shows schematically the optical structure of a photometer, in which the proposal according to the invention is included. The light from line emitter 1 or broadband emitter 2 is guided symmetrically over the mirrors 3 and 4 onto the rotating mirror 5. According to FIG. 2, the rotating mirror 5 has two reflective (22) and two transmitting (23) sectors per revolution, with which the beam splitting into the sample beam 12 and comparison beam 13 takes place. Upon reflection on the rotating mirror 5, the sample beam is formed

12 of 1 and the reference beam 13 of FIG. 2, the sample beam 12 of FIG. 2 and the reference beam 13 of FIG. 1. The sample beam 12 passes through the mirror 14 and the reference beam 13 via the rotary mirror 16, which is designed as a sector mirror Transmission of the sample beam 12 as well as reflection on the reflective sector 26, the comparison beam

13 via the mirror 19,20 into the monochromator 21 passes.

Per period, which corresponds to half a rotation of the rotating mirrors 5 and 16, depending on the mode, a maximum of 4 different signals are present. By variable assignment of the rotating mirror 5 and 16 to each other different modes are possible.

In all operating modes, the full radiation power reaches the monochromator 21. In addition, in all operating modes, except for DB-BC, it is possible to combine two signals of the same type in analog form before they are taken over by the computer.

With the timing of the emitters 1 and 2 is given by energy gain and improvement of the signal-to-noise ratio.

The rotating mirrors 5 and 16 are controlled by stepper drives 8 and 17, respectively. In each case on the sensor 9 or 18 detects the current position of the respective rotary mirror. Fig. 2 shows the position of the rotating mirrors 5 and 16 in the various modes at the time when the light 24 is on the rotating mirror 5 in the center of the reflective sector 22. It can be seen how the rotating mirror 16 is varied to the light 25 in the phase position.

Fig. 3 shows the sector discs 6 and 7 for detecting the dark signals.

4, the signal sequence is summarized for different operating modes.

5 shows by way of example the timing diagram of the optical signals for the operating mode DB-BC.

In Fig. 6, the inventive circuit arrangement is shown in an overview. It consists of a rotating counter 27 with, for example, 10 bits, which is reset by a signal · E1 before starting the stepper drives 8,17 and then via the input E 2 with a pulse train for starting the stepper drives from a small frequency to f _T rises, is clocked. The outputs of counter 27 drive 10 bits of address inputs of programmable memory 28.

Other address inputs can be driven by input signals, which are shown together in Fig. 6 as E3, to switch the mode. According to the count in the counter 27 of the programmable memory 28 provides at its outputs at least 3 signals of different frequencies for a stepper drive. The middle of three frequencies is used when the stepper 8 is synchronized. The other frequencies reduce a lead or lag by one step per revolution of the counter 27. For the second stepper drive 17, the same signal outputs, optionally with an additional switching signal for both modulation devices, can be used. However, it is also possible to use 3 other output signals of the programmable memory 28 for this purpose.

The 3 output signals of the programmable memory 28 for a system are combined in the selection logic 29 with the output signals of the phase evaluation circuit 30 so that a selection takes place, depending on the result of the phase evaluation, between the desired phase signal 34 and 35 and the sensor signal 37 and 36 respectively. The respective resulting signal of each system is used in the selection logic as a gate signal for the obtained in the pulse shortening with a time shift 31 from the frequency f _T signal ff, which then controls the respective stepper drive 8 and 17 respectively. The stepper drives 8,17 drive the rotating mirror aperture system 33 and the rotating mirror 16, with the help of the sensors 9,18, the sensor signals 37,36 are formed, which contain the information about the actual phase position of the respective modulation device.

The desired phase signals 34, 35 can be obtained from two further output signals of the programmable memory 28. If the desired phase position is to remain unchanged for a modulation device, an output signal of the counter 27 can be used directly as a desired phase signal 34.

In response to the mode signals E3, the target phase signal 52 in the phase shifter 32 may be changed in phase. The output signal A1, which is formed in the selection logic 29 from the output signals of the Phasenauswerteschaltung 30, reports the computer of the device synchronous operation of both rotary mirror systems 33,16.

With A2, all signals for the evaluation of the present in electrical form optical measurement signal in the analog and digital data acquisition are summarized. In Fig. 6 is not shown that the counter 27 can be set when it outputs an overflow pulse. With this determination of the counter area on the counter 27, this is brought into conformity with the modulation period of the modulation means at a certain frequency f _T. After resetting the counter 27, the remaining area can be used during startup of the stepper drives 8, 17.

7 shows the phase evaluation circuit according to the invention for a system. It consists of three D flip-flops 38,39,40, a mono-flop 41 which is triggered by an L / H edge of the control signal 37, and an AND gate 42. The D-type flip-flops 38 and 39 are turned on the L / H edge of the reference phase signal 34 is triggered. The D flip-flop 40 is held in the reset state by a mode signal E 3 when a mode is selected in which the corresponding stepper 8,17 does not stop. If one of the modulation devices is to stop in a defined manner, the corresponding input signal E3 receives Potential potential and the next L / H edge of the sensor signal 37, 36 triggers the D flip-flop 40 to H, whereby the output signal A6 with its L enters the selection logic 29 closes and the corresponding stepper 8,17 stops.

In Figure 8, the time lags of the reference phase signal 34 and the sensor signal 37 in the phase position at forward 53, at synchronous 54 and at caster 55 of the rotating mirror-aperture system 33 and the associated output signals A3 with H at forward, A4 with H at Synchronous operation and A5 with H at follow-up of the sensor signal 37 shown to illustrate the function of the phase evaluation circuit shown in Figure 7. The phase position is evaluated as synchronous when the triggering L / H edge of the desired phase signal 34 in the time of At of the triggered by the L / H edge of the sensor signal 37 mono-flop

41 is located. In this case, the D flip-flop 39 is triggered to L signal, so that at its negated output Η signal is applied. The sensor signal 53 is in its phase position so that both D flip-flops are triggered to H and thus by the AND gate

42 formed signal A3 in advance Η signal leads. The sensor signal 55, which arises in a lag compared to the reference phase signal 34, causes the D flip-flop 38 is triggered to L signal and thus applied to its negated output and to A5 a Η signal.

FIG. 9 shows by way of example the input signals of the selection logic. In addition to operating mode signals E3 and the pulse-shortened and time-shifted counter clock ff, both as in FIG. 6, 3 signals for each step drive 8 or 17 are respectively provided by the programmed memory 28. In synchronized operation of the rotating mirror shutter system 33, the phase evaluation circuit 30 supplies the signal A4 with Η level, whereby the signal f ₃₀ , which has a constant frequency with H pulses of a length, which = 1 / fr, in the selection logic 29 is selected as a gate signal for Tf, so that the stepper drive 8 with a constant frequency corresponding to that of f ₃₀ , is driven. The symbol f ₃₀ is to be understood in such a way that the step drive performs 30 steps in one modulation period.

If there is no synchronous operation, 29 or 31 steps should be carried out in the time corresponding to a modulation period, depending on whether the sensor signal 37 is in the lead or lag with respect to the reference phase signal. When forwarding the signal A3 of the Phasenauswerteschaltung 30 provides a Η level and thus selects in the selection logic 29 f ₂ g as a gate signal for ff and at caster A5 delivers a Η level and selects f ₃₁ .

For each revolution of the counter 27, the forward or follower of the stepper drive 8 can be corrected by the rotating mirror shutter system 33 by a whole step. In order to achieve a much better synchronization, the well-energized stepper motor of the stepper drive 8 is mounted in a device with the rotating mirror shutter system 33. The same applies to the step drive 17 with the non-designated connections as to the step drive 8.

In Fig. 10, the programmable memory is shown in a RAM variant. The output signals of the counter 27, which is not shown here, are combined to an internal address bus 43 and control the address inputs of, for example, 4 RAM 44,45,46,47.

The data in outputs of each RAM are connected to the outputs of a tri-state output driver 48, 49 and the D inputs of a circuit of commonly clocked D flip-flops 50, 51.

The 44-47 programming data, separately for each mode of operation, is provided by the instrument computer via the data inputs E 6, while the corresponding RAM 44 ~ 47 and drivers 48, 49 are provided by Chip Select E4 and Write E 5 input signals are controlled, and the counter 27 is clocked after a reset in the rhythm of programming. It is always possible to program 2 RAM with 4-bit data width at the same time if E 6 8-bit are available as data inputs.

Switching to the respective RAM 44-47 is done by E4. After programming, all RAM 44-47 are activated by E4. By removing E 5, RAM 44-47 is switched to read and drivers 48, 49 are switched to passive. During the run of the drives, which has already been described in the embodiments of FIGS. 6-9, depending on the state of the counter 27 are at the outputs of the RAM 44-47 and thus at the inputs of 50,51 to the information at Clocks of 50.51 at their outputs as signals f ₂ g, f ₃₀ , f ₃ i are used for each drive, as a reference phase signal 35 and as signals for evaluation A2 in the analog and digital Meßwertverarbeitung.

In FIG. 10, only 2 drivers 48, 49 and 2 circuits of commonly clocked D flip-flops 50, 51 are shown in simplified form. Is used to clock 50, 51 uses the signal f _T with the reverse for clocking the counter 27 edge, in this case, the pulse compression with a time shift of 31 can be omitted.

Claims (10)

claims: 1. A method for optical modulation with switching of the beam paths, preferably for atomic absorption spectrophotometer with at least one radiator as a light source in which either a beam splitting and beam combination according to the selected mode of operation, the radiant energy, controlled by a detection electronics, from the isochronous radiators reaches a receiver and light-dark signals are detected in chronological order, characterized in that, depending on the selected mode at least two optical modulation devices with programmable switchable phase assignment perform a self-controlled movement for phase synchronization of the optical modulation devices. 2. The method according to claim 1, characterized in that the position of the detected in a period zero signals is varied depending on the selected mode and that per period several signals of the same kind are summarized before the digital Meßwertverarbeitung. 3. The method according to claim 1, characterized in that, depending on the selected operating mode, the controlled movement of the optical modulation means takes place as a synchronous movement. 4. The method according to claim 1, characterized in that, depending on the selected operating mode, the controlled movement of the optical modulation means is such a movement, wherein at least one optical modulation device is brought into a preferably defined stop position and at least one further optical modulation device performs uniform motion. 5. The method according to claims 1 to 4, characterized in that an actual phase position of each optical modulation device is determined and compared with reference information provided by the operating mode phase assignment of the optical modulation means that from the phase comparison control signals for changing the phase position of each optical Modulation device are obtained and that at the same time depending on the phase assignment in phase synchronization of the optical modulation devices mutually effective evaluation signals for the Meßwertverarbeitung be obtained. 6. Apparatus for carrying out the method according to claims 1 to 5, characterized in that an externally resettable and clocked counter is provided, which on the output side is connected to the inputs of a programmable memory, preferably a RAM and a first input of a Phasenauswerteschaltung, in that signals for selecting the operating modes are present at a further input of the programmable memory, that signals for the measured value processing are present at a first output of the programmable memory, that a second output of the programmable memory, which supplies a reference phase signal, is connected to a first input of a phase changeover device is at whose second input the signals for the selection of the modes abut that further outputs of the programmable memory are connected to inputs of a selection logic in that at a second input of the phase evaluation circuit, the output signal e of the phase switching device, the output signals of a first and at least one second sensor for detecting the phase position of the optical modulation devices abut at a third and at least one fourth input that the selection logic on the input side with the outputs of the Phasenauswerteschaltung, the output of a Impulsverkürzerstufe with time shift and the signals for the choice of the operating modes in connection is that abut at a first output of the selection logic of the phase synchronization of the moving optical modulation devices depending valid evaluation signals for the Meßwertverarbeitung that more outputs of the selection logic with step control inputs of at least two stepper drives in conjunction and that with the stepper drives rotary mirror are mechanically connected, which are in optical communication with the sensors for detecting the phase position of the optical modulation means. 7. Apparatus according to claim 6, characterized in that the sensors are preferably designed as optoelectronic reflection couplers. 8. Apparatus according to claim 6, characterized in that the desired phase signals applied to an output of the programmable memory and an output of the externally resettable and clocked counter. 9. Apparatus according to claim 6, characterized in that the Phasenauswerteschaltung per optical modulation device of a mono-flop, a first, second and third flip-flop, preferably D flip-flops, and an AND gate is that at the D input of the first flip-flop , At the input of the monoflop and at the T input of the third flip-flop each abut the control signals that abut at the T inputs of the first and second flip-flop each of the desired phase signals that at the D and the R input of the third flip-flop a signal to choose the operating modes is that the output of the mono-flop with the D input of the second flip-flop is in communication, that the Q output of the first flip-flop with a first input of the AND gate and the Q output of the second flip-flop with a second Input of the AND gate is in communication that applied to the output of the AND gate sync signals that rest at the Q output of the first flip-flop tracking signals that at the Q output of the second Flip-flop sync signals abut that rest on the Q output of the third flip-flop tracking signals, and that applied to the output of the AND gate evaluation signals. 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