DE1548838C - Method for determining the spatial angular coordinates of an object in relation to the axis of a laser beam - Google Patents

Description

3 4

Solid angle co-ordinates of an object upon the excitation of the ultrasonic element 18, namely according to An adjustable delay device (nicftt without the transit time of the laser beam shown here). A mirror 22 is so obliquely angeprdschen the laser and the object in question, net that at a given one, to self-fluorescence must be taken into account. 5 of the B.uhinlaser $ tabes 20 sufficient pump size

According to an expedient embodiment of the rubirir concerning the greater part of the ypn the} Invention wire} the laser beam is deflected in pulses from beams emitted by the laser rod as; to sent that are at least as long as the Ah-this returns. In this way the duty is Steering time of the laser beam from the starting point to the laser beams prevented. That’s the optical one End point and back. In this way, as noph io, the return circle of the ruby laser steel can be locked. becomes apparent, in a particularly simple The delay period is chosen so that Show the solid angle coordinates of a counterpart that the line or the ultrasonic element ί.8 with to be determined. If a high voltage pulse occurs, actuate ^

According to yet another expedient embodiment, and an ultrasonic wave chirch that in her design the invention is also extended - for every 15 available medium at a point in time, As I know - the time lag between the equilibrium to which the overdevelopment of excited atoms send the impulses and the arrival of fier reflections within the laser rod or ruby laser rod animal impulses measured. As a result, it is possible to achieve a relatively maximum jiat. The natural radiation is nasty simply remove the bet ruby laser lab 2Q through the line "resp. hitting object from the receiving point cj? r? 9 the yitraschail element Iß to the mirror 22 ijjn, and reflected impulses can be determined. is influenced by the ultrasonic wave and

The invention is guided by means of Zeiphnupgen. JBecause of this, a state occurs which is called the explained in more detail below. Laser radiation at right angles to the mirror 22

F. i g. i shows schematically a rightet according to the invention. At this point a stajke sets in working arrangement; ? 5 positive feedback on the Rubinjas, shine,

Fig. 2 shows schematically the course of pines jgi according to which a very strong radiation discharge ileum occurring laser beam ·, * impact occurs. Dirrph periodic excitement of the ultras

p i g. 3 shows scherrjatically a spiral deflecting element 18 during the normal laser beam: th laser beam; generation can sgrnit a corresponding number

F i g. 4 show); the course of pines modulation signals 3 <? relatively strong impulses are received,
and Y °, n I ^m pul ^ser i> the reflection of pinem object Pas the operation of the optical scanning device

whose I ^ aumwinkeikoprdinateii to \> a- tion 12 underlying fundamental physjka-: voices are. } i ^s she principle is based on the fact that pin light beam after

The in F i g. 1 illustrated arrangement for determining traversal of a section with normal Delphi? ' Calculation of the solid angle coordinates of an object 35 gradients in the direction of the light distribution ζμΐη has ajs main components eipe ajs, taser to denote "'section of higher density hui is bundled standing "ultrasonic wave in a two-dimensional scanning device 12 for qptisphf refractive medium thus occurs a temporally changing rays, a laser switch 18, a Spnde- ii? her- sinusoidal pitch gradient axii, ζμίοίρρ of the telescope 14 μηιΐ a receiving station 16 rnit Light beam alternately on each side of the light receiving element 30. ^ ei the concerned one prupkkriotenfjl | c | ie hinciurcrigpletzt.
The arrangement accomplishes the deflection and scanning

of a laser beam, based on the axis of a qptidur-Gh, the already mentioned two-dimensional Ab ^ see §endeteleskpps, by means of yitraschajl, whereby tastvqrric3fitung 12 display yitr ^ sound scanner a part of the cell 12 given by the telescope's viewpoint is passed through, in the pin two-line siqnat Heaven is periodically illuminated. ler sgiraliger scanning beam is generated, as this,

The Laser · IQ is one-dimensional with the help of giries. 7 E i g. '2 shows. In this context, let the ultrasonic element 18 be controlled, one remarked that two AhlenkzeÜen, namely pipe for the sound horizontal direction generated in a modulation circuit 29 and one for. dip vertical ripple wave of suitable frequency is excited. In this 50 direction, we would know that it is possible in a suitable time to use only a single cell, the sequence and duration of which pulses are emitted by the laser 10. The ultra-a two-dimensional Ab-tastsfra, hi ran ^. If the sonic element or sonic control element 18 is used for the scanning cell 12, two ultrasonic cells are found in a laser feedback frame, so each cell becomes a sinusoidal shape between a laser rod 20 which, for example, generates a moving light spot. ^ earth both Ζρίΐρη can be ruby rod, and a total 'with signals of the same frequency, but with a Ptiar reflection causing end mirror 22 circular Yerlaufendpr scanning stralil. Other devices can also be used, such as pin rotary pieser scanning beam can be guided by a corresponding Mq.dur mirror pdpr a KerrzeUe, in the laser back latipn ^ on a spiral; The coupling space for the corresponding control modulation takes place in the cells $ \ ίϊφ which or a (^ circuit is included. A partial switch .tasikreises with a pin laser cavity. Furthermore, "is still" in a known frequency, the "lower" is than the ultrasound hall frequency. kurvet Block 29 is an annex in this connection

The pumping of the ruby laser rod 20 takes place with a corresponding modulation circuit, and by means of the pumping power source 26 / initially in front of the earth the block: 31 represents a supply source.

5 6

The spiral laser beam is more than half a mechanical telescopic movement,

Optical transmission embodied by a lens 17 shows the relevant target object or target within the

transmission system emitted through the transmission telescope 14. To keep the telescopic field of view. The telescopic movement

As a result, a mechanism executing movement through the telescope field of view is shown as block 36.

a given part of the sky illuminated. Asked by a 5; he moves both telescopes synchronously

located within the telescope field of view, dependence on tracking control signals in order to thereby

standing also as a target or object or target object, the telescopes in question are each related to the one in question

drawn object, such as a satellite, will aim an upcoming target.

Light signal is reflected, which with the help of the receiving In F i g. 2 is taken in space under a fixed winter telescope 16 and shown the laser scanning pattern occurring through an io kel; the be-photodetector formed light receiving element 30 meeting angle is referred to by points 1 to 4. The output pulses, which are matched by the photodetector 30 and which indicate the size of the telescope field of view, can then give a cathode. In Fig. 3 the course of a laser beam tube 32 is fed to the visual display, the scanning track is shown, whereby to simplify the display and in addition, the distance between the scanning line switching 35 and a computer system 34 can be fed to an electrical time setting, the distance between the scanning lines 35 and a computer system 34 is selected wide and the laser beam be as one. In these devices the time line is then shown instead of a line with a specific span between the relevant pulses measured width, as in an actual sensor, and furthermore the size of the solid angle of the implemented system to achieve a complete relevant object or target, based on the 20 field of view illumination during a scanning period of the axis of the transmitting telescope and thus based on which is the case. The in F i g. 3 illustrated laser beam axis of the emitted laser beam, calculated how the scanning track also runs only from the inside to this will be described in more detail below. outside, but not from the outside to the inside, as is the case with actual operation after the laser has been triggered by the trigger circuit. An Ab-33, the computer system 34 receives a pulse from the circular trajectory, through which it is modulation circuit 29 and thus receives a testimony to the fact that the laser beam is represented by the two-dimensional designation defining the time zero as well as the scanning device 12 or by two one-dimensional reference values Time measurement by receiving nale ultrasonic scanning devices is passed by from the corresponding target or object. In each case there are two ultrasound non-reflecting pulses. 30 waves generated at the same frequency f _s by 90 °

The ultrasonic scanning device 12 in which one are out of phase with each other. As above, modulation takes place in two directions, must be carried out with Si, the scanning in question takes place on inputs of sufficiently high amplitude controlled in succession, whereby one inward and one inward are achieved so that the required field coverages are achieved within the boundaries of the part by means of the amplitude mode head field of view 35 lation of the sound pressure in both waves with one. The course of the spiral scanning beam is generated at a lower frequency f _m. Accordingly, it follows from the center outwards and each point in the spiral can then, unambiguously expressed, reverse back to the center. The laser is, namely 1. through the period of time-10 is then pumped and controlled to a one-point zero of the amplitude in the modulation cycle, umpteen pulse of constant intensity of such duration 40 2. through the two frequencies, namely through to emit that which is equal to or a little longer than the scanning frequency and by the modulation frequency, the duration of one cycle of the beam scanning modulation and 3. by the maximum deflection angle,
frequency. The synchronization of the firing This is expediently carried out in that each at Nullablenkposition the beam scanning modulation point on the current outward spiral by R tion cycle is performed by one in the modulation (telescopic axle distance angle) and synchronizing contained Θ (azimuth circuit 29 45, and position) is determined as shown in FIG. 3 is shown in such a way that the laser beam is spiraling outwards and as this works out mathematically below and is pressed again during the scanning period:
returns inside. Is the target or R = 2f tR
the object within the field of view of the transmitting 50 _{UQ (} j ^m °
telescope, the emitted laser beam hits the Θ = 2 π f
objective in question on two occasions, once currency ^si '
rend of spiraling outward and once those contained in the equations above during spiraling inward. Individual characters have the following meaning:
Reception of the two reflected signals or Im- 55 ",,. ,,,. ,,,,
pulse and measurement of the time between these ^R o = the maximum deflection angle of the two signals or pulses corresponding to the azimuth and radial angle,
Radial position of the target in question, these are the fm = modulation frequency
Solid angle coordinates, based on the axis of the (typical value 1000 Hz),
Telescope and thus related to the axis of the out- 60 / _s = sampling frequency (typical value 100 kHz),
transmitted laser beam, regardless of the distance _t = time span from R = 0 (zero amplitude clearly determined. By measuring the time position in the modulation cycle) to the radial span from time zero to receipt of the target's position,
the signals or impulses indicate the distance

65 These relationships are shown in FIG. 4 shown in the

win the signal. the course of the modulation frequency signal and of

The information can be corrected as often as the impulses shown by one of the in

how the laser is operated in pulses. The target located in the position indicated in FIG.

have been caught. In the target position B , the emitted laser beam strikes the target or object in question twice, since it spirals outwards and inwards. As a result, a received signal trace is generated as shown in FIG. 4 is shown.

If the modulation frequency f _m and the time span Δ t (time span between the received pulses) are known for the received signal, the value for t can be calculated from the following relationship:

and accordingly, R and Θ can be expressed as follows:

= R ₀ (If _m At)

To determine R and Θ it is only necessary to measure Δ t; this variable is independent of the distance of the target or object from the measuring arrangement under consideration.

Furthermore, since it is only a time difference measurement between the received pulses, it is one Optics with high image quality are not required. This allows the use of a collection system with large aperture possible, increasing the likelihood of recognizing a target or object is increased and / or the distance still permitting operation of the arrangement under consideration is enlarged. The ultrasonic scanning device 12

ίο can work continuously during operation, the laser 10 operating in pulse mode for angle measurement synchronously with the zero point amplitude works on the modulation envelope. As stated above, in addition to measurement the length of time between emission of a laser beam and reception of the two pulses from the one in question A distance measurement is carried out on the coming target or object. In such a procedure it is then necessary to calculate the total time between

To measure ao solution of the laser pulse and reception of the first reflected pulse in the photodetector 30 and subtract the time period t from this size, which represents the time period from the zero point amplitude of the spiral scanning path. This relationship can be written as follows:

_ "Speed of light ._

Distance = ^Ξ (total time - /).

In calculating the time t in the above mathematical expressions, it is assumed that the destination is fixed. A target movement within the time interval between the outward run and the inward run of the laser beam spiral must be taken into account with regard to the accuracy of the measurement. The change in the period of time Δt which is expected when observing a moving target object in comparison with a stationary target object depends on the speed of the target object in question, on the distance and on the system modulus frequency.

Since a complete telescope field illumination is required, the system modulation frequency depends on the selected scanning frequency, on the laser beam scattering and on the number of resolvable elements required within the telescope field of view. Assuming that laser beam scattering occurs for, say, 90 seconds, 5: 1 reduction optics and a 30 minute telescopic field of view are used, complete illumination coverage could be achieved with 50 circular scans (30 minutes / 18 seconds = units = 50 circles ); therefore the modulation frequency does not need to be higher than V _{100 of} the sampling frequency if complete field illumination is to take place without overlap. That is, if the sampling frequency is 50OkHz, the modulation frequency should be 5kHz or less.

It is possible to calculate the effects on the system accuracy resulting from a movement of a target object by assuming a speed and a distance. Assuming that a target object is moving at a speed of 150 mph. moved at a distance of 1500 km, it can be shown that the duration of one time second corresponds to an arc angle of about 0.264 °. Assuming that the object in question is located on an axis that would result in the greatest error in At with respect to a stationary target object, with an output pulse with a modulation frequency of 5 kHz the target object would be about 0.2 arc seconds ahead Return of the modulation scan to the axial position. Therefore, the second received pulse reflected from the target object in question would occur earlier, on the order of 20 nanoseconds, regardless of the direction of movement, than would be expected if a stationary target object were assumed. On the other hand, if the target object is shifted off the axis, the target movement between the illumination provided by the outward spiral and the inward spiral is less than in the case of the on-axis setting, and therefore a change in Δ t is related on an assumed fixed target object, would be less; however, the second reflected pulse would occur at an earlier or later point in time, depending on the direction of movement of the target object in question. In either case, the angular displacement of a moving target is less than the system resolution.

Instead of a pulsed laser can also

a continuous laser can be used. In this case it is then necessary to use the Ambiguity in the successively received pulses due to an additional circuit compensate and thus determine the received pulse train. For example, every Beam modulation cycle a reference mark can be generated, or it can be between successive Time intervals lying in pulses are used to eliminate the ambiguity. Such Methods are already known in themselves.

209 548/105

By using the lens 17 constituting an optical transmission system in the manner that the telescope angle field of view corresponds to the sound cell angle, the absolute system resolution would change increase in proportion to the deflection angle achieved. For example, the sound cell deflection angle would be increase from 1 to 5 °, the smallest angle of resolution would be reduced by a factor of 5. This means that with a 1 ° sound cell and a 30-minute telescope field of view every minute of the sound cell angle would correspond to 30 seconds of the actual field of view, while with a 5 ° sound cell would correspond to 6 seconds of the actual field of view every minute. Is the Sonic cell deflection half a minute, so would be the angular position of the outward running Laser beam is 3 arc seconds.

The resolving power is further increased in that a time measurement is used to measure the angle which is one of the most inherently accurate measurements.

In addition, a greater evaluation capability is achieved by the arrangement described, which is based on corresponding signal-to-noise level ratios. If the laser pulse is scattered and not concentrated, and if the telescope field of view is covered during scanning, the received Signal of the same duration as the transmitted pulse. This enables a better evaluation using integration procedures. The duration of the scanning of the respective target object corresponding pulses, which are much shorter in duration, from the scanning arrangement described here are received, but have a lot due to the higher energy density of the laser beam higher amplitude.

With regard to the telescope used for signal or pulse pick-up, it should be noted that this Telescope can be omitted when using beam deflection optics in the transmitting telescope. Further the laser beam does not need to be passed through a telescope, but can do the respective Scan the target object surface even without such a telescope. In this case, the transmitting telescope is also dispensable. The field of view would be changed if the transmitting telescope were omitted; at this Modification is then required, however, a receiving telescope. In a corresponding way it would be possible to modify the described arrangement in such a way that by using an axis shift signal Formed error signal a beam control takes place, in connection with the synchronization and modulation circuit 29. In this way the laser beam in question is returned, so that the entire emitted laser beam pulse is applied to the target object in question. Such a practice is of great value for satellite communications. When the beam control is carried out, the controlled laser 10 emits a train of pulses, the frequency of which the frequency of the control signals of the one-dimensional ultrasonic cell or the laser blanking element 18 corresponds to, for example 100 kHz, specifically for one corresponding to the laser pumping duration Period of z. B. 2 ms. The two-dimensional scanning device 12 is also operated at a constant sound power level driven with a frequency of 100 kHz possessing signal, whereby a circular Scanning results and the deflection angle of the laser beam is the angle between the axis of the Telescope 14 and that of the target object. Accordingly, the target object becomes circular at each Scanning with the laser operated in pulses at the appropriate time for the purpose of illuminating the Target object divided. The laser blanking element 18 and the ultrasonic scanning cell are synchronized to to ensure that the controlled laser pulses each serving for a circular scan are below a suitable scanning azimuth angle.

1 sheet of drawings

Claims (5)

1 2 The arrangement in question is also used to: process an object by means of a laser beam, but not to locate an object. 1. A method for determining the space angle. It is also known as a COLIDAR system of an object in relation to 5 known positioning systems (»Radio Mentor«, 4, 1962, the axis of a spiral deflected around the axis- S. 304, 305) known to abt a laser beam spirally Laser beam, marked thereby. This well-known positioning system is then used e t that the laser beam spirals from one to determine the distance of an object, Starting point to an end point and on the - but not to it - the solid angle coordinates of the same Web is deflected back and the time to measure the object hitting it. distance between the two from the object In connection with the above-mentioned reflected pulses is measured. th COLIDAR system, it is also known (»Defense 2. The method as claimed in claim 1, characterized in that the technical monthly bulletins 59, 1962, No. 2, p. 79), the indicates that the laser beam is pulses away from an object from a measuring arrangement is sent, which are at least as long as 15 to be measured in that the transit time is determined, the the duration of the deflection of the laser beam from the initial point to the emission of a light pulse to seepoint to the end point and back. ner return to the measuring arrangement passes. Included 3. The method according to claim 2, whereby the distance and the angle of the target are intended indicates that, moreover, what is known is automatically determined for a laser, as in itself - The time interval between the end of this, however, means that the axis of one ends in this the impulses and the arrival of the sem context to be used telescope reflected pulses is measured. is to be directed at the object in question. The solid angle coordinates of the object in question relative to the axis of the telescope, however, with the help of the 25 considered known system cannot be measured. For the automatic tracking of targets, The invention relates to a method for a device known (USA.-Patent Determination of the solid angle coordinates of a Ge 3 046 332), in which a real image of the respective object in relation to the axis of a spiral 3 ° target on the collector electrode of an optoelectronic the axis of the deflected laser beam. niche converter is mapped. The one in question In connection with the determination of the Win converter, it has deflection plates at which a deflection position of a body it is already known steering voltage is applied, due to which the (U.S. Patent 3,242,796) which is electronically scanned from an image mentioned for. on the body used for the measurement in question - in this way one obtains an electrical image that Outgoing light is not mechanically characteristic for the essential properties of the angular scanning devices of the above-mentioned image. The picture in question will men, but scanned with the help of a non-mechanical spiral. From the phase position of the Ultrasonic light deflection system. Those obtained in this case when scanning the image in question required optical receiving device is 40 pulses with respect to the phase position of the relatively complicated in structure and scanning control voltage used becomes a laborious. corresponding control voltage for the target tracking It is also known that laser devices can be used for target tracking. About the determination to use rays that are emitted by two injection lasers of solid angle coordinates of the target with respect to opposite conductivity types, but the light emanating from the target is also the. The two injection lasers are not known in this context,
A conically shaped block is attached that finally there is already a scanning device with two alternately occurring radiation lobes, known in one application (US Pat. No. 2,855,521), with a certain area overlapping radiation lobes which give a spiral scanning of one to be scanned. In what way is done with such a target 50 field from the inside to the outside and back. Tracking arrangement, the solid angle coordinates of the spatial angle coordinates of a laser beam can be determined via the use of a laser beam to affect the object in relation to the axis of the mood, is not known in this object in relation to the axis of the laser beam context. (However, IBM Techni- is nothing in this context either becal Disclosure Bulletin, Vol. 6, No. 4 September 55 knows. 1963, p. 62). In connection with optical the invention, the object is to provide a It is already known to radar systems (»Procee way to show how the dings of the IEEE ”, January 1963, p. 213), impulse spatial angle coordinates of an object in relation to use powered high-power lasers. In to be determined on the axis of a laser beam how such radar systems can do the space 60. angular coordinates of an object in relation to solved the above-indicated task at the axis of the laser beam used in each case for a method of the type mentioned agree, is in the relevant composition according to the fact that the laser beam spirally However, this is not known. shaped from a starting point to an end point An arrangement is also known (»Electro-65 and is deflected back on the same path and sneeze «, October 5, 1962, pp. 39 to 43), in which the time interval between the two is from an ultra-object reflected pulses are measured in a laser feedback cavity, sound control for generating pulses takes place. The invention has the advantage that the