DE4429966C1 - High speed imaging for repetitive time variable processes - Google Patents

Abstract

A high speed camera system receives the generated image by a recording/playback system (3) via an optical switching unit (2) that is mechanically coupled (9). The sensing unit (1) can be laser based and generates a trigger signal (6) that is received by a synchronising module (5). The laser beam passes through an object mounted in a natrium vapour cell. The generated video signal (7) is transmitted to the synchronising unit to be combined with the trigger signal to produce half frame signals. For repetitive operation the time delay from frame to frame can be increased.

Description

The invention relates to a method and a Vorrich to observe fast, repetitive, space temporal processes.

They are systems for fast acquisition very quickly Processes in optical measurement technology as a framing camera known that allow image sequences with a temporal Chen distance between the individual images down to take about 10 µs (see brochure Kodak Ekta- Pro HS Motion Analyzer, Mod. 4540, Eastman Kodak Company 1993). This is done with the spatial resolution conventional video process quickly behind several images received and processed each other. The picture information nes are subdivided line by line and with a large number of data lines via fast analog-digital converters line by line in parallel to digital memory areas which are read out after the recording has been completed. This means that with a typical spatial resolution resolution of 512 × 512 pixels also 512 times the resolution wall for digitization, transmission and storage which must be operated as with standard Video processing with serial processing. The Repeti tion rate depends on the reading speed of the image  information on the individual permanent storage areas hand over. The total number of possible exposures however, depends on the size of this memory. To a long sequence of single with little storage space To be able to take pictures is to lower the elevation technical effort at the expense of spatial Resolution, e.g. B. only work with 256 × 256 pixels tet.

Furthermore, from US 4 970 597 a method for Ab formation of high-speed processes with a high speed camera known. Here, the repe high-speed processes using a Standard video camera, computer image processing hard goods, software and some additional components drawn. However, it is assumed that the be striking camera scans its image plane, d. H. that each Line of the output video image exactly that at the time contains existing image information at the point of scanning, which is not the case with CCD cameras. This is the procedure is restricted to certain cameras. With a predetermined time window is then at the beginning of each Line scan based on a trigger signal determines whether the process to be taken up within the repeated line. Upon confirmation, the relevant The last line saved. The scanning of the images will then repeated until at least in each line the process has been repeated. That can especially with high time resolution, d. H. at a very short trigger window, take a very long time. The Consideration of various phases of the process that still a corresponding multiple of the time required would not be explicitly provided.

From US 4,453,182 it is known when viewing a fast process an increased time resolution solution compared to that of a single video camera  to achieve that multiple video cameras in time division be used. A correspondingly short exposure to achieve the duration of the individual cameras this by means of a rotating prism or a ro exposed mirror successively.

The disadvantage is that the effort is proportional to the time resolution increases. The number of cameras and there also the requirements for the rotating mirror equipment but cannot be increased arbitrarily.

Finally, with that known from US 4,713,687 Procedure reached several temporal phases of a pre ganges separately on a screen. Herewith is an observation of a spatio-temporal process in parallel representation possible.

The disadvantage is that with a high technical effort no separation of recording and playback unit possible Lich and no standard video signals and no storage Security is provided.

This results in the task, a method and a Device for observing fast, repetitive, to create spatio-temporal processes, the low loading clearing times, high repetition rates and a high spatial resolution enables.

This task is done in a method of observation faster, repetitive, spatio-temporal processes solved the features of claim 1.

The advantages achieved with the invention are in particular special in that the dynamics of repeat in time the fast spatial structures are shown can. This is achieved through repetition and synchronize to the specified frame rate  control of the fast optical switching unit, with which the recording and playback unit exposes becomes. Exposure times and increments in the Ab groping of the time course can be done with little Effort down to the sub-microsecond range be lized, the image processing effort only corresponds to that of the normal video process. There are new uses for spacetime representation of fast optical phenomena that the possibilities of conventional methods in some Points like time resolution and better visuali sierbarkeit, surpass. It is advantageous if at repeated repetition of the processes within one Image the optical switching unit several times with the same Time delay is triggered. This makes it possible Lich, the exposure sequence inside a camera not just once, but in a pre-settable, to run the same number in each camera image. The prerequisite is that the number of repetitions of the operation in question within the possible exposure the number of preset more subject exposures not less. This addition achieves the advantage, especially with very short Shutter opening times extremely low amount of light falls on the recording and playback unit multiply the set number.

It is advantageous if the synchronization control unit as a shutter field change signal Control signal and a field change signal forms. Here it is advantageously possible with the closure control signal a shutter unit in the optical Control switching unit. With the field change signal is advantageously a switchable optical filter controlled in the optical switching unit that the even and the odd field of the video signal with different proportions of that of the measurement unit  emitted light exposed. With the field change signal it is achieved, two different proportions of the light emanating from the measuring unit, the not differentiate from the recording and playback unit that could be shown separately or saved chern.

The even and the odd field can be different spectral components or different polarizations components of the light are exposed.

It is advantageous that the trigger signals are off

• - synchronization signals of a modulation generator Ness
• - The beam by means of a repetition frequency detection unit and / or
• - acoustic vibrations of the processes by means of a Microphone unit

are formed in the measurement unit. This is it is possible to trigger the trigger signal in different ways and way in ignition processes, a propagation of light pulsing, space-time resolved spectroscopy, oscillato processes in burns and the like produce.

The task is carried out in a device the procedure, d. H. to observe faster, repetition render, spatial-temporal processes, through the characteristics of Claim 8 solved.

It is particularly advantageous that through the introduction the optical switching unit in the beam and the control tion of the optical switching unit through the synchronization tion control unit a conventional recording and Playback unit by a conventional optical Switch unit is supplemented so that fast spatio-temporal processes recorded and for another  Evaluation can be displayed and saved. This reduces the effort required for one Observation of such processes is very essential.

It is advantageous that the synchronization unit from an exposure sequence control unit

• - The one via a video synchronization unit Video signal line for recording and playback unity leads, concerns,
• - The trigger unit on a trigger signal line leading to the test object unit is present,
• - Which is connected to an exposure preset unit
• - The on a shutter control signal line, which for optical switch unit leads, is present,

consists. This makes it possible to control the exposure tion by an electronic device. It is advantageous that the video synchronization unit is also present on a field change signal line. This makes it possible to determine whether that current field is even or odd.

It is advantageous that the video synchronization unit consists of a synchronization signal discriminator,

• - The one on the video signal line and the field change signal line is present and
• - The one over a vertical and a horizontal synchronous line with a first counter unit closed start line selection unit as well a second counter unit with connected end line selection unit is connected,
• - The horizontal sync line with the clock gears and the vertical sync line with the off release inputs of the meter is connected,
• - The output of the first counter unit being set gang and the output of the second counter unit an Oder gate, at the second entrance of which by the Exposure sequence control unit incoming image  end signal line is present at the reset input of a Most flip-flop unit is present, of which the exposure Ready signal line for exposure sequence control unit goes off.

This makes it possible to start and end the possible Exposure period within a camera image in Units of the line duration (64 µs for CCIR video signal) to select. The video synchronization unit delivers the beginning of the possible exposure period Exposure ready signal off, the reset when the period has expired or when the Exposure sequence control unit the preset Number of exposures.  

It is advantageous that the exposure preset unit consists

• - A third counter unit with one arranged Pre-selection unit for minimum number of delay steps and with an arranged pre-selection unit for maximum Number of delay steps at whose clock input the End of signal line is present, and its output with a multiplier with an arranged one Time resolution selector from which the delay default line to exposure sequence control unit leads, is connected.
• - an exposure time setting unit at which the exposure exposure time line is available for exposure sequence control unit leads,
• - A multiple exposure unit on which the Multiple exposure preset line is applied to Exposure sequence control unit leads.

This makes it possible to change the exposure time Number of multiple exposures, the delay step wide and the maximum and minimum number of delays steps. The exposure selector increases the delay time with each new camera image around the preset increment and puts it when the maximum value is exceeded, to the minimum value back.

It is advantageous that the exposure sequence control unit consists of

• - A clock generator, the output of which is a clock line tung leads,
• - a fourth counter unit
• - whose clock input is connected to the clock line,
• - At their preselection input, the delay specification is applied to the exposure control unit leads,
• - There is an und gate in front of their trigger input  whose first input is the digital trigger line from the trip unit and on its second one Input the exposure ready signal line from the video synchronization unit,
• - their output with the trigger input of a fifth Counter unit and with the setting input of a second Flip-flop unit is connected, at the output of which Lock control signal line is present,
• - the fifth counter unit,
• - whose clock input is connected to the clock line
• - at their preselection input the exposure time fork line and
• - At the trigger input, the output of the fourth count ler unit is arranged.
• - whose output with the clock input of a sixth Counter unit and with the reset input of the second flip-flop unit is connected
• - the sixth counter unit,
• - whose clock input with the output of the fifth Counter unit is connected,
• - whose preselection input with the multiple exposure pres cable line is connected
• - their trigger input with exposure ready shaft signal line is connected
• - Their output via the end of signal line with the Exposure control unit and the video synchronization tion unit is connected.

This makes it possible to have a preset number of exposure sequences consisting of

• - Waiting for the digital trigger signal to arrive
• - Activation of the shutter control signal line after Delay time expires
• - Deactivation of the shutter control signal line after Exposure time

to execute.  

It is advantageous that the trigger unit that with the Trigger signal line is connected to a digital trigger gersignal generated when the (analog) trigger signal or alternatively only its alternating voltage component adjustable threshold exceeds or falls below.

It is advantageous that the synchronization control unit consisting of the video synchronization unit and the exposure sequence control unit as one Plug-in card is formed in a computer unit is installed, with the exposure control unit as Program block is implemented as follows:

• a) call of the program block by an interrupt, when the exposure end signal line is activated,
• b) Increase the delay time or reset to the minimum value when the maximum value is reached and then output to the plug-in card.
• c) Output of the exposure time specification to the Plug-in card,
• d) Output the multiple exposure specification to the plug map.

This makes it possible to preset all exposure parameters and the control of the time sampling in very flexible way to adapt to changing requirements fit.

It is advantageous if the optical switching unit at least from an optical shutter unit, e.g. B. a mechanical modulator, electro-optical Modulator, acousto-optic modulator or the like, or from a correspondingly controllable Image intensifier unit is made via the shutter signal line is controlled. The selection of the Closure unit is to the respective measurement problem adapt.  

It is advantageous that the optical switching unit is little very well

• - A switchable optical filter that over half image change signal line is driven and
• - the one behind the switchable optical filter, driven by the shutter control signal line optical shutter unit exists and in addition
• - An attached in front of the switchable optical filter Lens system can contain.

This makes it possible to be in the even and odd Fields of the video signal the recording and re dispensing unit with different, through the switchable Filter selected proportions of that of the measurement object to expose emitted light, e.g. B. with ver different spectral components or different polarities station components.

It is advantageous if the recording and playback unit from at least one video camera unit, e.g. B. a CCD camera. It is advantageous that the Video camera not by tampering with the camera must be changed. Rather, you can take pictures any suitable for the respective measurement problem Video cameras are used.

It is advantageous if a on the video camera unit Monitor unit, a video recorder unit and / or one Image processing unit with an over an RGB signal line connected color monitor unit arranged is. Which configuration to choose depends on that respective measurement problem. Can be used for permanent storage normal video recorders whose Storage medium has a large capacity and price is cheap. For quantitative evaluation you can if any, with the camera unit used  compatible commercial image processing systems to be used. Through this it is also possible to a false color in an originally monochrome image Displayed on an RGB (red-green-blue) color monitor to make, in particular by the switchable optical filter recorded difference Lichen light components shown in different colors can be.

It is advantageous if the measurement object unit at least has a trigger signal generating unit which consists of

• - A modulation generator unit that is electrically connected is connected to the test object,
• an optical repetition frequency detection unit, e.g. B. a photodiode to which from the beam via Beam splitter coupled out part of the intensity will, and / or
• - A microphone unit, the acoustic vibrations of the object to be measured,

consists. This makes it possible in a simple manner Way, adapted to the measurement problem, from the measurement object prepare the respective trigger signal themselves.

It is advantageous if the measurement object unit from one Laser unit with the electrically connected Modulation generator unit, one in the laser beam ordered test object and the one from the test object exiting beam arranged repetitions frequency detection unit exists. This is it possible, time-resolved laser spectroscopic measurements perform both with a modulated laser beam and the image acquisition towards this modulation synchronize, or the measurement object a laser beam suspend constant intensity and capture the image to any oscillations that may occur in the test object predetermined frequency to synchronize.

The invention is described below in one embodiment example explained in more detail. Show it:

Fig. 1 is a block diagram of a device according to the invention more rapidly for observation, of repeating, of spatial and temporal processes,

FIG. 2a, b and c are block diagrams of trigger signal generating units of an apparatus shown in FIG. 1,

Fig. 2d is a block diagram of a Meßobjekteinheit a device according to Fig. 1,

Fig. 2e is a block diagram of a laser unit according to a Meßobjekteinheit Fig. 2d,

Fig. 2f is a schematic block diagram of a measurement object in a Meßobjekteinheit according to Fig. 2d,

Fig. 3 is a schematic block diagram of an optical switching device of a Vorrich processing shown in FIG. 1,

Fig. 4 is a schematic block diagram of a recording and reproducing unit of a device according to FIG. 1,

FIG. 5a is a block diagram of a synchronizing device of a control unit 1 according to Fig.

Fig. 5b is a block diagram of a Videosynchroni sationseinheit a synchronization control unit of FIG. 5a,

Fig. 5c is a block diagram of an exposure bias unit of a synchronization control unit of FIG. 5a,

FIG. 5d shows a block diagram of an exposure sequence of a Synchronistions control unit control unit according to Fig. 5a,

FIGS. 6a and b show a detailed illustration of a Vorrich tung Monitoring faster, the spatio-temporal 1 repeat operations as shown in FIG. With FIGS. 1, 2a, 2b, 2c, 2d, 2e, 2f, 3, 4, and 5a- d,

Fig. 7a through 7r images of an observation of spatial and temporal processes in sodium vapor,

Fig. 8 course of the spot centers in the time course of Fig. 7a to 7r and

FIG. 9 shows an exposure process over time in a device according to FIGS. 6a and b in a schematic representation.

In order to represent spatio-temporal processes in measurement processes, the temporal course of which can no longer be seen with the naked eye, in the form of a real-time slow motion so slow that not only the temporal sequence is recognizable, but also without a noticeable time delay between measurement and Representation occurs, an optical switching unit 2 is arranged in a beam 4 , which is emitted by a measurement object unit 1 and is directed at a recording and reproducing unit 3 (cf. FIG. 1). If necessary, the optical switching unit 2 can be attached directly to the recording and reproducing unit 3 with mechanical connecting elements 9 . The optical switching unit is connected to a synchronization control unit 5 via a shutter control signal line 8 . From the synchronization control unit 5 , a trigger signal line 6 leads to the measurement unit 1 and a video signal line 7 to the recording and playback unit 3 .

A possible embodiment of the measurement object unit 1 is shown in Fig. 2d. A laser unit 11.1 is connected via a modulation signal line 13 to a modulation generator unit 12 , from which the trigger signal line 6 originates. The laser 11.1 emits a laser beam which is guided through a measurement object 11.2 . In the test object 11.2 , as FIG. 2f shows, a sodium vapor cell 11.2.1 is used, in which there is also nitrogen with a partial pressure of 100 mbar as a buffer gas. Magneto-optical effects in the formation of structures are examined. Helmholtz coils 11.2.2 are therefore placed around the sodium vapor cell 11.2.1 for each spatial direction, with which the magnetic field locally present in the sodium vapor cell can be defined in a defined manner for all spatial directions by controlling the Helmholtz coils with precision current sources. The particle density of the sodium is adjusted by changing the cell temperature. In front of the sodium vapor cell 11.2.1 surrounded by Helmholtz coils 11.2.2 there is a lens system 11.2.3 and behind it, for part of the measurements, a feedback mirror 11.2.3 'is positioned. The laser beam 4 'passed through this test object 11.2 thus constructed leaves it as an optical beam 4 , which passes through a repetition frequency detection unit 12 ' and leaves the test unit 1 . From the repetition frequency detection unit 12 'goes a trigger signal line 6 '. The laser unit 11.1 itself consists of an arrangement of the dye laser element 11.1.1 one after the other, which generates a laser beam 14 through an optical modulation element 11 . 1st 2 , a beam shaping unit ( spatial filter) 11.1.3 and a polarization unit 11.1.4 passes through so as to leave the laser unit 11.1 as a laser beam 4 '. For the generation of a trigger signal 60 , 60 ', 60 '', a trigger signal generation unit 12 is formed, as is also shown in FIGS. 2a, 2b and 2c.

In Fig. 2a, the laser unit 11.1 and the Modula tion generator unit 12 are connected via the modulation signal line 13. Due to the repetitive switching on and off of the laser or a modulation of its intensity, there is a forced repetition, the trigger signal 60 is then given by the corresponding synchronizing signal of the modulation generator 12 . Of course, it is also conceivable to modulate other parameters of a measurement in this way and to synchronize the measurement with them.

In Fig. 2b, a situation is shown in which no repetition is specified, ie the test object is kept under constant time conditions, but the test object 11 shows oscillatory behavior by itself. In the case of such self-repetition, part of the intensity is taken from the beam 4 'with a beam splitter 14 and a small, characteristic spatial area is selected with an aperture and imaged on a photodetector, which thus acts as a repetition frequency detection unit 13 .

In Fig. 2c shows a situation, in which the, is running in the measurement object 11 to be observed accompanied operation of acoustic vibrations of which can be assumed to run in synchronism with the spatial-temporal behavior. Such a situation can e.g. B. occur in combustion processes. Through the microphone unit 12 '', these noises are picked up by the measurement object and converted into the corresponding trigger signal 60 ''. This makes it possible to investigate the cause of the noise in question.

The optical switching unit 2 can be realized by a shutter unit 23 which is connected to the shutter signal line 8 . A lens system 21 is positioned in front of the closure unit 23 in the beam 4 . Between the lens system 21 and the shutter unit 23 , a switchable optical filter 22 can be positioned, which is connected to the field change signal line 8 '. Acoustic-optical modulators can be used as the closure unit 23 . The principle of the acousto-optical modulators is based on the diffraction of a light wave incident on a crystal at a refractive index grating, which is generated by an ultrasound wave running in the crystal, which in turn is coupled into the crystal by a piezoelectric transmitter. The scope of delivery of an acousto-optical modulator includes a corresponding driver device for controlling the piezoelectric transmitter. The beam deflected by the grating is considered. If the piezoelectric transmitter is not activated, there is no grating and no diffraction takes place. By switching the driver off and on, the relevant beam can also be switched on and off.

The switchable optical filter has the function here a polarization filter and is replaced by an electro optical modulator realized. This causes by the transverse or longitudinal electro-optical Effect a polarization rotation depending on an applied voltage.

As shown in FIG. 4, the recording and playback unit 3 consists of at least one camera unit 31 . It is particularly advantageous that any video camera suitable for the respective measurement problem, e.g. B. a CCD camera can be used. It is possible that the switchable shutter unit 23 is connected directly to the camera unit 31 . It is also possible that the shutter unit 23 is installed in the camera unit 31 and thus becomes an integrated part of the video camera. These two options are particularly useful when an electronic image intensifier is used as a shutter unit. To the camera unit 31 , a monitor unit 32 is ruled out. Well-known Videomoni gates can be used, such as those used for. B. can be used to play other records. A video recorder unit 33 is also connected to the camera unit 31 and is used for the permanent storage of recorded images. It is particularly advantageous that the storage medium of the video recorder has a very large storage capacity and is extremely inexpensive. In addition, an image processing unit 34 is connected to the camera unit 31 , with which a quantitative evaluation of the recorded images can be carried out and which enables the display of false color representations via an RGB (red-green-blue) signal line 35 on a color monitor 36 .

It is particularly advantageous that in particular the partial components of the measurement unit 1 , the optical switching unit 2 and the recording and playback unit 3 are already available in many institutions, in particular in research and development facilities which deal with specific measurement problems. This enables a very cost-effective implementation of the device and method according to the invention, since only the synchronization control unit 5 needs to be purchased.

In FIG. 5, the synchronization control unit in detail is shown. It consists of an exposure sequence control unit 54 , which is connected via an exposure ready signal line to a video synchronization unit 51 , to which the video signal line 7 leads. A digital trigger signal line 56 connects the exposure sequence control unit to a trigger unit 52 , to which the trigger signal line 6 leads. An exposure setting unit 53 is setting circuit via a delay line 57 setting, an exposure time 58, a multiple exposure bias line 59 'and a picture sending signal line 59 connected to the exposure sequence control unit.

The video synchronization unit 51 is composed as shown in FIG. Represents 5b, from a synchronization signal discriminator 51.1, a counter unit 51.3 with start line code unit 51.2, a counter unit 51.5 with Endzeilenvorwahleinheit 51.4, a flip-flop unit 51.6 and an OR gate 51.7 together.

At the synchronization signal discriminator 51.1 the video signal line 7 arrives and the field change signal line 8 'starts. Via a vertical and a horizontal synchronizing line, the synchronization signal discriminator 51.1 is connected to both the first counter unit 51.3 and the second counter unit 51.5 , the horizontal synchronizing line 51.8 being connected to the clock inputs and the vertical synchronizing line 51.9 to the triggering inputs of the counters. The output of the first counter unit 51.3 is connected to the set input and the output of the second counter unit 51.5 is connected to the reset input of the flip-flop unit 51.6 via the OR gate 51.7 , at the second input of which the picture end signal line 59 is present. The exposure ready signal line 55 goes from the output of the flip-flop unit 51.6 .

A possible implementation of the exposure specification unit 53 is shown in FIG. 5c. From an exposure time setting unit 53.6 leads the exposure time line 58 directly away, likewise leads from a multiple exposure setting unit 53.7 directly to the multiple exposure setting line 39 '. The delay line 57 is connected to a multiplier unit 53.5 with a time resolution preselection unit 53.4 . The multiplier unit 53.3 is connected to a counter unit 53.3 with a preselection unit for a minimum number of delay steps 53.1 and a preselection unit for a maximum number of delay steps 53.2 , at whose clock input the end of signal line ( 59 ) is present.

In FIG. 5d shows a possible embodiment of an exposure sequence controller 54 is shown. A clock generator unit 54.1 is connected to a clock line 54.5 at the clock inputs of a counter unit 54.2 and a counter unit 54.3 . The delay input line 57 leads to the preselection input of the counter unit 54.2 , an und gate 54.6 is connected to its trigger input, the digital trigger line 56 leads to its first input and the exposure ready signal line 55 leads to its second input. The output of the counter unit 54.2 leads to the trigger input of the counter unit 54.3 and to the set input of a flip-flop unit 54.4 . The exposure time line 58 leads to the preselection input of the counter unit 54.3 , its trigger input is connected to the output of the counter unit 54.2 . The output of the counter unit 54.3 leads to the clock input of a counter unit 54.7 and to the reset input of the flip-flop unit 54.4 . From the output of flip-flop unit 54.4 the shutter control signal line goes from the eighth The multiple exposure preset line 59 'leads to the preselection input of the counter unit 54.7 , its trigger input is connected to the exposure ready signal line 55 . The end of signal line 59 leads from the output of the counter unit 54.7 .

The mode of operation of the device for observing rapid, repetitive, spatio-temporal processes, which the method according to the invention realizes and how it results from the illustrated exemplary embodiments, is explained below in particular with reference to FIGS. 6a, 6b, 7 and 8.

Through the sodium vapor cell as a measurement object passes the laser beam 14 , which is a dye laser beam with visible light in the vicinity of the sodium D1 line (wavelength 589.6 nm). As long as the laser beam 14 does not interact with the sodium vapor, it has a Gaussian beam profile with a diameter of at least 50 microns and a divergence angle of at most 20 mrad. When interacting with the sodium vapor, the beam can split into two parts with different circular polarization directions, between the axes of which there is an angle of up to 50 mrad; measurements with the additional feedback mirror can result in more complicated patterns, usually hexagonal or ring-shaped structures, the beam is then less divergent and has a diameter of at most 1 mm.

Because of the small opening angle of the beam 4 emanating from the measurement object 1 , a commercially available acousto-optical modulator is used as the optical shutter unit 23 . In the switched-on state, this deflects the incoming beam 4 by an angle of 24 mrad (1st diffraction order). The camera unit 31 is set up in the axis of this deflected beam 4 .

The light passing straight through the modulator (0. Diffraction order) is dimmed.

In front of the shutter unit 23 , a small portion of the light is branched off from the beam 4 and imaged on a displaceable pinhole, behind which a photo detector is attached, which measures the time course of intensity in a small area of the structure to be examined and thus initially an estimate enables the necessary temporal resolution and later provides the trigger signal 60 .

In order to implement a polarization-discriminating measurement, a quarter-wave plate and an electro-optical modulator are additionally used as a switchable optical filter 22 , the latter being operated here as a polarization-rotating element and allowing a distinction to be made between left and right circular polarized light.

The camera unit 31 is a commercially available black and white video camera as used for measurement purposes. The video signal 70 is displayed on the monitor unit 32 , which is a black and white analog monitor, and recorded with the video recorder unit. An image processing card 34 with an RGB color monitor 36 is used for storage on a ′ 486 microcomputer and for displaying still images and converting them into false color images.

The synchronization control unit uses a commercial integrated circuit (LM1881) to extract from the video signal a vertical synchronizing signal 71 and a horizontal synchronizing signal (see lines 51.8 and 51.9 ) and the information as to whether the current field comprises the even or the odd lines. The position and the duration of the (maximum) active area (exposure ready signal 72 ) within the 20 ms long image spacing can be set in units of the line duration of 64 microseconds, for example to allow adaptation to an internal electronic shutter. The active area ends when the preset number of exposures has been made. Within the synchronization control unit, the trigger unit (trigger unit) 52 generates the digital trigger signal 61 from an analog input signal 60 , which, within the active window, triggers the exposure sequence. The usual setting options (AC / DC triggering, positive / negative edge) are available.

The exposure presetting unit 53 allows the selection of an amount Δt of the time step by which a time delay is increased from picture to picture (values: 100 ns, 200 ns, 500 ns..., 50 µs, 100 µs) and the minimum and maximum time delay each between 0 and 999 of these time steps. When the preset number of exposures have been made and both fields of a frame are exposed, the time delay is increased by the time step; if the maximum time delay is reached, the minimum time delay is set again. The counter units 51.3 and 51.5 can be stopped during operation in order to be able to examine the behavior at a specific point in time. Furthermore, the exposure preset unit allows the exposure time to be preset in 1 to 99 time steps, which can be selected from the same values as the delay time steps, and the preselection of up to 99 times the multiple exposure.

The exposure sequence control unit 54 realizes the delay time 82 and the exposure time, the delay time 82 and the exposure time 80 with fast counter units 54.2 and 54.3 , which are clocked simultaneously with a free-running clock 81 of 10 MHz. Before the exposure signal 72 was formed from the video signal 70 and the digital trigger signal 61 was derived from the trigger threshold of the analog trigger signal 60 . Since all the fast digital operations shown in FIG. 9 are synchronized to the already mentioned central clock of 10 MHz, the jitter, ie the triggering inaccuracy of the exposure sequence, is only due to the period of the quartz oscillator. It may take a maximum of 100 ns until the actual counting process of the counter units begins after triggering the trigger signal 61 . A delay of 600 ns (6 clock periods, 10 MHz) with a pulse width of 200 ns (2 clock periods) is selected in FIG. 9. A jitter of 100 ns remains even if longer delay times are selected. Due to the different gate delays, the minimum delay between the arrival of the trigger signal 61 and the switching on of the exposure pulse 80 is approximately 100 ns.

By means of a corresponding logical combination of the ready-to-illuminate signal 72 , the digital trigger signal 61 and the clock 81 , the following sequence is achieved:

• The counter unit 54.2 (delay counter) is started on the next clock edge after the arrival of the information that after the start of the predetermined exposure period of a new image a repetition of the process to be observed occurs;
• - After counter unit 54.2 has expired, the output for the exposure pulse is switched on and counter unit 54.3 (exposure counter) is started;
• - After counter unit 54.3 has expired, the output for the exposure pulse is switched off and counter unit 54.7 (multiple exposure counter) is counted down by one step;
• - As long as the counter unit 54.7 has not yet expired, the next trigger signal 61 is waited for and the sequence runs again;
• - After expiry of the counter unit 54.7 , the exposure-ready signal 72 is reset and the signal for incrementing or resetting the exposure preselection unit 53 is given.

With the device thus realized, one can Achieve a slow motion factor of up to 400,000, d. H. in the full output at a time interval of 40 ms pictures correspond to a time interval of the amount Δt of 100 ns in the process examined.

In the FIG. 7a. . . 7r shows a selection of individual recordings of a beam splitting process, which were recorded when the laser beam 14 was switched on repeatedly. The individual images are recorded with a minimum delay increment of the amount Δt of 100 ns between successive images. By appropriate wiring of the modulation generator 12 , in that the trigger signal 60 500 ns was given before triggering the modulation signal 13 , the immediate switch-on time was also observed. At first you can only see a spot whose light is circularly polarized. In the timing of Fig. 7a, this first light is the zero of the time t = 0, associated with. The intensity of this spot increases monotonously over a further 500 ns ( FIG. 7b). At t = 600 ns ( FIG. 7c), another spot can be seen that is circularly polarized in opposite directions. The intensity of the second spot increases more than that of the first component during the following period. After 1 ms ( Fig. 7g) a rotation of the two spots can be determined clockwise. As can be seen from FIG. 7j, this continues during the next microseconds, the intensity ratio of the spots barely changing. When the stationary position is reached after approx. 8 ms ( Fig. 7r), a rotation angle of 150 ° has been exceeded.

In Fig. 8 the movement is summarized during the first 10 ms after turning on the laser. The time-resolved observation of such behavior enables the investigation and identification of various cooperating mechanisms whose effects on the direction of the splitting on the one hand and their typical time constants on the other hand are known, which would only be possible on the basis of stationary behavior.

Observation depends essentially on the resolving power pending. The resolving power of a representation driving is the measure of the smallest distance between two in Space and / or time of neighboring observation values or Objects to be observed by an observation or Measuring device registered with certainty with certainty can be.

By the inventive method and the device are used to obtain a good temporal resolution in short exposure times with a high Repetition rate realized and for representation for the Consideration prepared by the human eye since whose low temporal resolving power is one direct observation of fast optical phenomena not allowed.

The spatial information is also displayed in such a way that the human eye can know it. When realizing the representation, the visualizability is ensured by the selection of a sufficiently large screen 32 so that the (relative) resolution specified by the camera 31 is available to the eye without loss.

For spatial-temporal observation / representation, a functional principle is implemented here that combines high temporal and spatial resolution. As in particular the Fig. 7a,. . . , 7r show, a suitable form of documentation of spatio-temporal behavior is offered here, which makes the behavior visible precisely in the resolution limits of the human eye.

Claims (23)

1. Procedure for the observation of fast, repetitive, spatio-temporal processes in which

• - An optical beam ( 4 ) is emitted by a measurement object unit ( 1 ),
• - The optical beam ( 4 ) is interrupted by an optical switching unit ( 2 ),
• at least one trigger signal ( 6 ) is generated in the measurement object unit ( 1 ) with the beam ( 4 ),
• - A recording and playback unit ( 3 ) takes pictures from the beam ( 4 ) and generates a video signal ( 7 ) and
• - A synchronization control unit ( 5 ) receives the trigger signal ( 6 ) and the video signal ( 7 ) and forms a shutter / field change signal ( 8 ), by which the optical switching unit ( 2 ) is then triggered,
• - If after the beginning of a possible exposure period of a new image given by the recording and reproduction unit ( 3 ) a re petition of the process to be recorded ( 40 a,... 40 r) occurs and
• - An from picture to picture by an amount (Δt) he increased time delay between the occurrence of the respective process ( 40 a,... 40 r) and the triggering of the optical switching unit ( 2 ) is inserted.

2. The method according to claim 1, characterized in that with repeated repetition of the processes ( 40 a,... 40 r) within the predetermined exposure period, the optical switching unit ( 2 ) is triggered several times with the same time delay. 3. The method according to claim 1 or 2, characterized in that the synchronization control unit ( 5 ) as a shutter field change signal forms a shutter control signal ( 80 ) and a field change signal ( 80 '). 4. The method according to any one of claims 1 to 3, characterized in that a shutter unit ( 23 ) in the optical switching unit ( 2 ) is controlled with the shutter control signal ( 80 ). 5. The method according to any one of claims 1 to 4, characterized in that with the field change signal ( 80 ') switchable optical filter ( 22 ) in the optical switching unit is controlled so that the even and the odd field of the video signal ( 70 ) with different Portions of the light emitted by the measuring unit ( 1 ) are exposed. 6. The method according to claim 5, characterized in that the even and the odd field of the video signal ( 70 ) with different spectral components or different polarization components of the light are exposed. 7. The method according to any one of claims 1 to 6, characterized in that the trigger signals ( 6 )

• - A synchronization signal output of a modulation unit ( 12 ),
• - The beam ( 4 ) by means of a repetition frequency detection unit ( 12 ') and / or
• - Acoustic vibrations of the processes ( 40 a,... 40 r) by means of a microphone unit ( 12 '') in the test object unit ( 1 ).

8. A device for observing fast, repetitive, spatio-temporal processes for carrying out the method according to one of claims 1 to 7, comprising

• a measuring object unit ( 1 ) and a recording and reproducing unit ( 3 ) which are connected to one another by a beam ( 4 ),
• - An optical switching unit ( 2 ) which is arranged in the beam ( 4 ), and
• - A synchronization control unit ( 5 ) which is connected to the optical switching unit ( 2 ) and is connected both to the measurement unit ( 1 ) and to the recording and playback unit ( 3 ).

9. The device according to claim 8, characterized in that the synchronization control unit ( 5 ) from an exposure sequence control unit ( 54 )

• - which is connected via a video synchronization unit ( 51 ) to a video signal line ( 7 ) leading to the recording and playback unit ( 3 ),
• - which is connected via a trigger unit ( 52 ) to a trigger signal line ( 6 ') which leads to the test object unit ( 1 ),
• - Which is connected to an exposure preset unit ( 53 ), and
• - Which is applied to a shutter control signal line ( 8 ) leading to the optical switching unit ( 2 ).

10. The device according to claim 8 to 9, characterized in that the video synchronization unit ( 51 ) on a field change signal line ( 8 '), which if just leads to the optical switching unit, is present. 11. The device according to one of claims 8 to 10, characterized in that the video synchronization unit ( 51 ) consists of a synchronization signal nal discriminator ( 51.1 ),

• - The on the video signal line ( 7 ) and the field alternating signal line ( 81 ) is present and
• - which is connected via a vertical and a horizontal sync line both to a first counter unit ( 51.3 ) with connected start line preselection unit ( 51.2 ) and to a second counter unit ( 51.5 ) with connected end line preselection unit ( 51.4 ),
• - The horizontal synchronizing line ( 51.8 ) with the clock inputs and the vertical synchronizing line ( 51.9 ) with the triggering inputs of the meters is connected,
• - the output of said first counter unit (51.3) at the set input and the output of said second counter unit (51.5) via an OR gate (51.7) to the sen second input of the incoming of the exposure sequence control unit (54) forming signal line (59) is applied, at the reset input of a first flip-flop unit ( 51.6 ), from which the exposure ready signal line ( 55 ) goes to the exposure sequence control unit ( 54 ).

12. The apparatus according to claim 8 to 11, characterized in that the exposure preset unit ( 53 ) be from

• - A third counter unit ( 53.3 ) with an arranged pre-selection unit for the minimum number of delay steps ( 53.1 ) and with an arranged pre- selection unit for the maximum number of delay steps ( 53.2 ), at whose clock input the end of the signal line ( 59 ) is present, and whose output with a multiplier ( 53.5 ) is connected to an arranged time resolution selection unit ( 53.4 ), from which the delay preset line ( 57 ) leads to the exposure sequence control unit ( 54 );
• - an exposure time setting unit ( 53.6 ) on which the exposure time setting line ( 58 ) is applied, which leads to the exposure sequence control unit ( 54 );
• - A multiple exposure control unit ( 53.7 ) on which the multiple exposure control line ( 59 ') is located, which leads to the exposure sequence control unit ( 54 ).

13. The apparatus of claim 8 to 12, characterized in that the exposure sequence control unit ( 54 ) consists of

• - a clock generator ( 54.1 ), the output of which leads to a clock line ( 54.5 ),
• - a fourth counter unit ( 54.2 )
• - whose clock input is connected to the clock line ( 54.5 ),
• - At the preselection input of the delay line ( 57 ) is applied, which leads to the exposure unit ( 53 ),
• - Before their trigger input is an und gate ( 54.6 ), on the first input of which the digital trigger line ( 56 ) from the trigger unit ( 52 ) and on the second input of the ready signal line ( 55 ) from the video synchronization unit ( 51 ) leads,
• - whose output is connected to the trigger input of a fifth counter unit ( 54.3 ) and to the set input of a second flip-flop unit ( 54.4 ), at whose output the shutter control signal line ( 8 ) is applied,
• - the fifth counter unit ( 54.3 ),
• - whose clock input is connected to the clock line ( 54.5 ),
• - At the preselection input, the exposure time preset line ( 58 ) and
• the output of the fourth counter unit ( 54.2 ) is arranged at the trigger input thereof,
• - The output of which is connected to the clock input of a sixth counter unit ( 54.7 ) and to the reset input of the second flip-flop unit ( 54.4 )
• - the sixth counter unit ( 54.7 ),
• - whose clock input is connected to the output of the fifth counter unit ( 54.3 ),
• - whose preselection input is connected to the multiple exposure presetting line ( 59 ′),
• - whose trigger input is connected to the exposure-ready signal line ( 55 ),
• - The output of which is connected via the end of image signal line ( 59 ) to the exposure setting unit ( 53 ) and the video synchronization unit ( 51 ).

14. Device according to one of claims 8 to 13, characterized in that the trigger unit ( 52 ) which is connected to the trigger signal line ( 6 ) generates a digital trigger signal ( 56 ); if the (analog) trigger signal ( 60 , 60 ', 60 '') or alternatively only its AC voltage component exceeds or falls below an adjustable threshold value. 15. Device according to one of claims 8 to 14, characterized in that the synchronization unit ( 5 ) consisting of the video synchronization unit ( 51 ) and the exposure sequence control unit ( 54 ) is designed as a plug-in card which is installed in a computer unit , the exposure preset unit ( 53 ) being implemented as a program module as follows:

• a) call of the program block by an interrupt when the exposure end signal line ( 59 ) is activated,
• b) increasing the delay time specification or resetting to the minimum value when the maximum value is reached and then outputting it to the plug-in card ( 57 ),
• c) outputting the exposure time specification ( 58 ) to the plug-in card,
• d) Output the multiple exposure default ( 59 ') to the plug-in card.

16. The device according to one of claims 8 to 15, characterized in that the optical switching unit ( 2 ) at least from an optical shutter unit ( 23 ), for. B. a mechanical modulator, electro-optical modulator, acousto-optical modulator or the like, or also consists of a corresponding to controllable image intensifier unit, which is controlled via the shutter signal line ( 8 ). 17. The device according to one of claims 8 to 16, characterized in that the optical switching unit ( 2 ) at least from

• - A switchable optical filter ( 22 ) which is controlled via the field change signal line ( 8 ') and
• - The behind the switchable optical filter ( 22 ), through the shutter control signal line ( 8 ) driven optical shutter unit ( 23 ) and additionally
• - Before the switchable optical filter ( 22 ) brought lens system ( 21 ) may contain.

18. Device according to one of claims 8 to 17, characterized in that the recording and playback unit from at least one video camera unit ( 31 ), for. B. a CCD camera. 19. The device according to one of claims 8 to 18, characterized in that on the video camera unit ( 31 )

• - a monitor unit ( 32 ),
• - A video recorder unit ( 33 ) and / or
• - An image processing unit ( 34 ) with a color monitor unit ( 36 ) connected via an RGB signal line ( 35 )

is arranged. 20. Device according to one of claims 8 to 19, characterized in that in the measurement unit ( 1 ) at least one trigger signal generating unit ( 12 , 12 ', 12 '') is present, which consists of

• a modulation generator unit ( 12 ) which is electrically connected to the measurement object ( 11 ),
• - An optical repetition frequency detection unit ( 12 '), for. B. a photodiode to which part of the intensity is coupled out of the beam ( 4 ) via a beam splitter ( 13 '), and / or
• - A microphone unit ( 12 ''), the acoustic vibrations from the measurement object ( 11 ) receives,

consists. 21. The device according to one of claims 8 to 20, characterized in that the measurement object unit ( 1 ) from a laser unit ( 11.1 ) with the electrically conductively connected modulation generator unit ( 12 ), a measurement object ( 11.2 ) arranged in the laser beam ( 4 ') and the repetition frequency detection unit ( 12 ') arranged in the beam ( 4 ) emerging from the measurement object ( 11.2 ).