PROCESS AND APPARATUS FOR MEASUREMENT OF PHYSICAL PARAMETERS OF MOVING MATTER BY MEANS OF COHERENT LIGHT SOURCE,BY HETERODYNE DETECTION OF LIGHT REFLECTED OR SCATTERED BY MOVING MATTER

Abstract: The light reflected or scattered by the moving matter is projected on identical path with the light of the coherent light source onto the surface of the photodetector in such a way that the scattered or reflected light reaches the surface of the photodetector after being reflected from the outcoupling element of the coherent light source operating in optimal regime of operation. The electrical signal appearing on the output of the photodetector is processed by the signal processing unit and in this way physical parameters of the moving matter are determined. In the apparatus according to the invention beamsplitter is positioned between the moving matter and the coherent light source and in the way of the light projected by the beamsplitter a photodetector is positioned, or beamsplitter is positioned between the coherent light source and photodetector and the moving matter is in the way of the light projected from the beamsplitter.

Description: PROCESS AND APPARATUS POR MEASUREMENT OP PHYSICAL R METERS OP MOVING MATTER BY MEMS OP COHERENT LIGHT SOURCE, BY METERODYΪΪΞ DETECTION OP LIGHT REFLECTED OR SCATTERED BY MOVING MATTER The present invention relates to process and apparatus for measuring physical parameters of moving matter by means of coherent light source by hetero¬ dyne detection of light scattered or reflected from the moving matter. The aforementioned physical parame¬ ters are the following: instantenous velocity of moving matter and quantities derived from it e.g. length of movement, acceleration, peripheral velocity, angular velocity, revolution per minute, frequency, etc., the average and variation of these quantities. Reflection or scattering power of moving matter its variation, surface distribution, and average value, etc. The an¬ gular dependence of the aforementioned quantities and quantities derived from it like straightness, curva- ture, etc. can be measured as well. It is known from the art that there are dif¬ ferent methods for non contact measurement of physi¬ cal parameters of moving matter. A significant group of these methods is based upon detection of scattered of reflected light from the natter and since coherent light sources (lasers) have come into being great pre¬ cision measurements of this kind are possible, namely making use of the interference ability of coherent light an accuracy of the order of the wavelength of light can be -achieved in length measurements. The in- terferometric measurement techniqque is applied among others in the US patent specification 3 796 493. OMPI he apparatus described in this patent spe cification is used for measurement of pitch of preci sion driving screws such as a lead screw. This task is performed by placing a corner cube reflector made of three parts onto a precision moving mechanism - a 5 slide. This slide is moved by the driving screw to b measured. " An optical code disk is rigidly in contact with the driving screw that gives a signal either o each revolution or for a certain angular turn. The measuring apparatus contains a laser, a partial refl 10 tor, two more reflectors and a detection system that is able to process the interference signal. The latt elements arr not moving. The principle of the measur ment is the following. Light radiated from the laser falls upon the partial reflector that projects part 15 of it onto the standing mirror that reflects it back through the partial mirror onto the detector. The' ot part of the laser light is projected by the partial reflector onto the corner cube reflector moved by th leas screw and from there it is projected onto a £0 standing mirror from where it is reflected back on the same path onto the partial reflector that projec it onto the detector where interference occurs. In case the number of- interference fringes is counted during a complete turn of the screw that is indicate 25 by the optical code disk and the accurate value of t laser frequency is known the pitch can be easily cal culated. The main advantage of this optical setup . is that even if the slide moved by the driving screv/ 30 makes a small angular displacement relative to the optical axis of the laser in the course of its move¬ ment, this displacement does not cause any errors becuase of the application of the corner cube reflec¬ tor. On the other hand disadvantageous is the great number of optical elements and the requirement that the relative position of the standing optical elements, of the laser and of the detector may not change during the course of the measurement because such a change the same kind of change in the interference as the movement initiated by the lead screw. Also the relative position of the elements of the corner cube reflector may not change. The maximum permitted mechanical insta¬ bility that. does not cause error in the measurement may not exceed half of the wavelength of the laser radiation. In the case of a He-Ne laser this upper error limit is about 0.3 micrometer. A different kind of measuring technique to measure physical parameters of moving.matter is.the he¬ terodyne detection of light reflected or scattered from the matter. The essence of it is the following. In case light with frequency "f" falls upon matter moving with velocity "v"-then the frequency of the reflected or scattered light changes because of the Doppler effect in the frame of reference relative to that the matter moves with velocity "v" and in that the light source and the light detector-are in rest. In case the qtical axis of the projected and the reflected or scattered light are coincident, then where "c" is the velocity of light and " f » is the angle between the direction of the velocity of the moving mat¬ ter and that of the light projected onto the matter. OMPI WIPO - 4 - In case part of the light beam co ing dire ly from the coherent light source and the scattered or reflected light from the moving matter (that is different in frequency) are allowed to interfere on the surface of the detector in such a way that the t lights are spatially coherent - i.e. the phase diffe rence over the whole surface area of the detector is c stant - then as a result of the interference the two lights will amplify or attenuate each other with frequencyAf = (f - f) on the surface of the detect In this way an electrical signal is produced on the output of the detector with frequency f that is re lated to the velocity of the moving matter by the relation This is a well known description ofthe optical heter dyne technique and its applications can be ound amo others e.g. in the books Chu:"Laser Light Scattering and Kallard: "Exploring Laser-Light". - The " difficulties with, the 'optical hetero¬ dyne measuring technique are caused by the requireme of spatial coherence of the two lights on the surfac of the detector that has been achieved by the follow ing methods. 1/ The setup corresponds to a conventional Michelson interferometer in that one of the mirrors is replaced by the moving matter. In this arrangemen the other mirror must be set and held in a fixed pos tion relative to the source optical elements and de- tector with an accuracy in the order of the waveleng of light during the complete course of measurement. 2/ On the principle of operation of laser - Doppler - anemometers: at the point of cross sec¬ tion of two coherent light beams with different direc¬ tions the frequency of reflected or scattered light from the moving matter into two different directions changes differently because of the different angles relative to the direction of velocity of the moving matter. As the beams reaching the surface of the de¬ tector ariving from the area of cross section of the two beams are of different frequency but fulfilling the requirement of spatial coherence there ore they interfere. The spatial cohrerence is assured by the fact that the two light beams with different frequency arrive from the same point in space in identical paths . at the surface of the detector. The disadvantage of this method is that the condition of spatial coherence is fulfilled only for a small volume in space. There¬ fore this method has been mainly used for measurement of velocity of moving media, e.g. liquids, gases, etc. A very interesting optical heterodyne tech- nique is used in the US patent 3 790 284. The appara- ' tus disclosed in " this patent makes measuring of stisLght- ness and roll possible. The simplest example of this invention con¬ sists of a laser that radiates light with two frequen- cies f, and f 2 ,-two polarizers, two partial reflectors, a Wollaston prism that is fixed to the moving slide of the apparatus, two " stationary mirrors positioned at given angles relative to each other and the optical axis, an auxiliary mirror, tw photodetectors and a reversible counter. The principle of operation of the apparatus is the following: The light with two frequencies radia- OMPI < IPO ted by the laser passes through the polarizers and in this way the plane of polarization of the light com¬ ponent with frequency f, will be perpendicular to tha of f ? . After that the partial reflector splits the be and part of it falls upon a reference detector, where by means of interference It can be detected by the heterodyne method. The frequency output of this photo detector is (fp-f-,) that is transmitted to one of the inputs of the reversible counter. The other part of t beam from the partial reflector falls through another partial reflector onto a Y/ollaston prism that separat the f-, and f p frequency beams because of their orthog nal polarization, and the two beams propagate at diff rent paths. The two beams are projected onto a pair o mirrors positioned at given angles relative to each other and the optical axis, from which they are ' refle ed back onto the Wollaston prism where they are re-- combined. ' art of this recombined beam falls upon th measuring " photodetector after being partially reflec- ted by the second partial reflector and completely reflected by an auxiliary mirror, on the surface of which the light interferes and the heterodyne signal is transmitted to the other input of the reversible counter. In case of the Y/ollaston prism is not moving the output of this photodetector is (fp-f.,) as well. On the other hand if the slide moves parallel to the optical axis the frequency of the light falling upon the measuring detector changes because of the Doppler shift but the difference of the two frequencies is unchanged. In case the slide moves perpendicular to the axis during the course of its motion then the vel city components of the Wollaston prism are different into the directions of propagation of the f-, and £„ frequency light beams emerging from it, therefore they will be different for each one of the pair of reflectors. Thus the Doppler shift is different for the lights with frequency £-, and f p and so the frequency of the outp_ut of the measuring photodetector will be different. The reversible counter stores the difference of impulse numbers coming from the two detectors that will charac¬ terize the straightness of the measured path. Main advantage of this apparatus from optical point of view is that by using light with two frequency components and heterodyne detection errors caused by small movements of optical elements (except of reflect¬ ing mirrors) cancel and no error in measurement occurs from this reason. On the other hand a disadvantage is the great number of optical elements including some extraordinary optical elements as well. Also strict stability of potision in time is still required for the reflecting mirrors. Prom the aforementioned examples it is clear that both the interferometric and the heterodyne measuring technique have been used for measuring parameters of moving matter with great difficulties. In case the moving matter has been a rigid body than some auxiliary equip- ent has had to be fastened to it, and in case it is a moving medium then it has been possible to perform a measurement only in a small volume, and in most cases complicated and precise optical systems were needed. Part of these difficulties are elmina ed by US patent 3 -958881 but it raises new problems as well. This patent discloses a setup in which the light scatter¬ ed back from the moving matter is Dassing through the outcoupling element of the laser into the laser wher it is amplified, heterodyned with the original laser light and in this way the laser radiates a light mod lated with a frequency corresponding to the differen frequency. This setup makes measurement in principle anywhere along the laser beam possible and does not require auxiliary equipment. Its disadvantage origi¬ nates from the fact that the laser by character oper tes in a small bandwidth i f ι aser ) and w k-i-O- this bandwidth amplification of the active medium tends to zero because of saturation. Taking into account the small transmittance of the outcoupling element - gene rally a few percent - and the quality factor of the laser resonator that is close to bot less then one e for 0 frequency diference a significant loss of light occurs by feeding the scattered light back into the laser. Because of the frequency dependence of the quality- factor losses increase by increasing the frequency difference f. In conclusion the bandwidth Λ flτa ΩOΩ r V , limits the theoretically measurable velocit _Af-, *C y / laser max ^ 2f . cos bacuse in case Λf ^ι a ser " kke laser does not transm the light with the shifted frequency at all. T e loss of intensity makes the use of this method impossible in case of small backscattered inte sities. The simplest way of increasing of intensity could be achieved by using higher power lasers. The apparatus working on the basis of the above mentioned principle almost always contain COp lasers. The losse could be decreased only by operating the laser in a non optimal regime, e.g. by lowering the reflection c efficient of the outcoupling element that increases the efficiency of feeding the light back into the laser and at the same time the active medium is not saturated; on the other hand in this way the intensity of the laser is lower therefore the signal - to - noise ratio is ..not improved. This has.been experimentally verified also by N.M.- Doyle, Y/.D. Berber and M.B. White in a paper: "Use of an Oscillating Laser as a Heterodyne Receiver Preamplifier" (IEEE Jorunal of Quantum Electronics QE-3, 479, 1976). The purpose of the present invention is the simultaneous elimination of the difficulties mentioned above and describe a process and apparatus that makes measurement of physical parameters of moving natter by opirical heterodyne technique possible. The problem to be solved by the invention there¬ fore can be summarized in the following: process and apparatus are needed by which physical parameters of moving matter can be measured in a non contact way using coherent light source in such a way that adjustment and stability in the order of the wavelength of light are not needed and the position of measurement is not re¬ stricted to a small volume, Furthermore it should make measurement possible in case of small scattered light intensities, the maximum measurable velocity should not be limited by the laser and it should be as ε ple as possible. The basis of the present invention is the fact that the problems listed above can be easily solved if instead of the well known methods the scattered or reflect- ed light from the moving matter is projected onto the photodetector on a path identical with the patch of the coherent light source. Namely in this case the direct and the scattered or reflected light seem to origina from identical light sources. The coherent light sou that is preferably a laser possesses at least one outcoupling element that is capable to transmit and reflect the light, and the light beam radiated from the laser - by the operation principle of the laser follows every motion of the outcoupling element. So if the outcoupling element " of the coherent light sou is used to reflect the light reflected or scattered from the moving matter then the condition of spatial coherence is automatically fulfilled. As the back- scattered light is not fed back into the laser there fore it can he operated in its optimal regime - opti mal outcoupling element, saturated active medium - - and the part of the backscattered light that is spat ally coherent can be projected completely ττithout lo on a path identical with that of the laser beam onto the surface of the photodetector. At the same time the maximum measurable difference frequency is not limited by the narrow bandwidth of the laser but by the bandwidth ofthe photodetector (P) that may reach 10 9 Hz. The maximum measurable veloci r 'ty is v / * • c max 2f . cos^ in this way may reach very high values. The pre sent Intention on one hand relates to a process to me sure physical parameters of moving matter by means of coherent light source, by heterodyne de ection of light scattered or reflected from the moving matte in such a way that the light from the coherent light source is projected-onto the moving matter either di rectly or through optical imaging element characterized by that that the reflected or scattered light from the coherent light source are projected on identical paths onto the surface of the photodetector in such a way, that the scattered or reflected light is projected onto the surface of the photodetector by being reflect¬ ed from the outcoupling element of the coherent light source operating in an optimal regime, and by process¬ ing the output signal of the photodetector physical parameters of the moving matter are determined. On the. other hand the invention relates to an apparatus to measure physical parameters of moving matter that posesses coherent light source, photodetec¬ tor with connected signal processor unit, characterized by that, that a beam splitter is positioned beτween the coherent. light source and the moving matter and a photodetector is positioned in the way of the beam pro¬ jected from the beam splitter, or a beam splitter is positioned between the coherent light source and the , photodetector and the moving matter is positioned in the way of the beam projected from the beam splitter. A more detailed describtion of the invention is given on the basis of the drawings which show a few embodiments and application examples of the inven- tion. On the drawings (schematic views) Pig. 1 is an example of an embodiment of the present invention which shows an arrangement for deter¬ mination of angular or peripherical velocity of a rotating cylinder; Pig. 2 is a modified arrangement used for measuring sur- . face characteristics of a moving rough surface; Pig. 3 shows an embodiment of the invention in that more then one beam are projected onto the movi matter that makes measurement of spatial motio of the moving matter possible; In Pig. 1 the light beam 15 from the cohere light source 11 - preferably a laser falls through the outcoupling element 19 upon beam-splitter 20 - a parti reflesfcor in our example. Reflected by beamsplitter 20 part of the light beam 17 falls upon the photodetecto 12 - that is preferably a PIN diode,. Through beamsplit ter 20 and optical imaging element 14 - that is a lens in the example - the other part of the light beam 18 falls upon moving matter 10 - that is a rotating cy¬ linder in the example. Reflected or scattered light 16 from the moving matter 10 through optical imaging element 14 and " beam-splitter 20 falls upon the outcoup ling element 19 of laser 11 and is reflected. This reflected light 21 is reflected again b beamsplitter 20 falls upon the surface of photodetec- tor 12 where it interferes with part of beam 17 thus on the output of photodetector 12 an electrical signal with frequency appears corresponding to the difference frequency. This electrical signal is processed by signal process ing unit 13. With the apparatus shown in Pig. 1 e.g. the revolution per second of the rotating cylinder "n" can be determined, "v" is the peripherical velocity- of the cylinder. As for the revolution per second "n" v - -. holds where "r" is the radius of the rotating cylin¬ der, if the frequency "f" of the direct light 15 of the laser 11 and "r" and "7"" are known then the revolution per second can be determined by n = A t 4f . r o 1? . cos^ The value of f is related to cc by. ~f = 90 - cc and the angle cc can be easily measured. Important advantage of-the process and apparatus in this embodiment is that Λf can be measured within a fraction of the time of a complete revolution of the cylinder. In this way the instante- nous value of the revolution per second and its fluc- tuation can be determined. Adjusting = 90 , runout of the rotating cylinder in the direction of light beam 15 can be determined as well. In " case cc = 0, cos/ = 1 and so v = Λf v ~ 2cf Integrating velocity "v" over the time "T" of a complete revolution the value of runout is received namely Note that because of possible surface roughness of the cylinder during the course of runout measurement unwanted highfrequency wavepackets may appear on the output of photodetector 12 that can falsificate the measurement., These high frequency components can be easily filtered if the signal processing unit 13 con¬ tains an appropriate low pass filter. In Pig. 2 the light beam 15 from the coher light source 11 - preferably a laser falls on the beamsplitter 20 - a partial reflector in our example Prom the beamsplitter a part of the light beam 17 falls directly upon the photodetector 12. The other part of the light beam 18 is projected through the optical imaging element 14 - a lens in our example - on the moving matter 10 - ' a moving rough surface in o example. The scattered or reflected light 16 from th moving matter passing through the optical imaging el ment 14 is reflected by the beam splitter 20 and the outcoupling element 19 of laser 11, and this reflect light 21 by beamsplitter 20 " is projected on the sur¬ face of the photodetector where it interferes with part of beam 17 * In this way on the output of the ph detector 12 an electrical signal with frequency 4* = (f . ≥L-. cos ) appears corresponding to the difference frequency. This electrical signal is processed b" signal proces unit 13. With the apparatus shown in Pig. 2 size "s" of surface elements of the moving matter 10 perpendi lar to the .direction of light beam 18 and also the d tribution of the size of these elements can be deter mined. Namely from the surface of the matter 10 movi in a way described above light is reflected onto the photodetector 12 In case the surface element interse ing the light beam 18 is perpendicular to said light beam. Prom this perpendicular surface element for a tine period t v s . s±n'p arrives the reflected light beam with frequency O >__ > onto the photodetector 12 on the output of which electrical signal with frequency λt = (f . ~ . cos 3 ) lasts also for a time period "t". In the equations used in the above example "v" is the velocity of the moving matter 10, " " is the angle between the directions of light beam 18 and the motion of moving matter 10. When a surface element of the moving matter 10 perpendicular to light beam 18 leaves the spot illuminated by light beam 18 then the continuous electrical signal from the output of photo¬ detector 12 with frequency "Δ " is terminated, i.e. from photodetector 12 wavetrains-with final lengths are transmitted to the signal processing unit 13. In case the signal processing unit 13 mea¬ sures the value of frequency " J\£", the lengths of wavetrains "t" and the angle y" is known then the size of single surface elements can be determined by s = ■s 2f In this way for a surface moving by arbitrary velocity relative to the apparatus the surface structure can be examined and the size distribution of the surface elements can be determined. The smallest resolvable element size is in the range of the wavelength of the light. In Pig. 3 the coherent light source 11 is a laser the direct light 15 of which falls on beamsplitter 20. Through beamsplitter 20 part 17 of the light beam is projected onto the photodetector 12. The beamsplit¬ ter 20 in our example consists of two beam splitting elements 22. The beam splitting elements 22 are favcur- ably partial reflectors. The other parts 18 of the light beam using the beam splitting elements 22 are projected through the optical imaging elements 14 - in our example lenses - onto the moving matter 10. In this way light beams 23 and 24 illuminate the surface of the moving matter 10 from two diffe¬ rent directions. The scattered or reflected light 1 from the moving matter 10 passes through optical im ing elements 14 and falls upon the beamsplitter 20, the beam splitting elements 22 project it onto the outcoupling element 19 of the coherent light source 11, from the outcoupling element it is reflected .ba and this reflected light 21 through beamsplitter 20 Is projected onto the photosensitive surface of the photodetector 12, where it interferes with part of light beam 17. In this way on the output of photo¬ detector 12 the sum of electrical signals with .two frequencies appear " ^i " aEd "Δ ^ " ' , f 1 = (f . - =~ . cos f ) where v-^ is the magnitude of the velocity of the point of the moving matter 10 illumirsed by light beam 23; ≥ is the magnitude of the velocity of the point of the moving matter 10 illuminated by light beam 24JJ^ is the angle between the direction of velocity of the point illuminated by light beam 23 and the direction of light beam 23; f 2 is the angle between the direction of velocity of the point illu ted by light beam 24 and the direction of light bea Prom the equations above the velocity components into the direction of light beams 23 and 24 of the moving matter 10 can be determined, because the signal processing unit 13 can- separate the elect- rical signals with different "-4^" and "A ± 2 " frequ¬ encies, Y/ith this method not only the one component of the velocity of the moving matter corresponding to a certain direction can be determined but- oth the magnitude and the direction of the velocity of the motion , can be -measured. In case a beamsplitter which illuminates with at least three not co-planer light beams the moving matter is used then the magnitude and direction of three dimensional motion can be de¬ termined, if the light beams illuminate the same spot of the moving matter. If the moving matter can be con¬ sidered a rigid body and the light beams illuminate different spots, translational motion in space can be examined. With an analysis of the heterodyne signal In case of simultaneous translation and rotation the individual components of motion can be separated. If the moving matter can not be considered as a rigid body using several beams, relative motion of certain points of the matter can be examined. The smallest measurable volume within which the parameters of motion can not be resolved is in the range of the wavelength of light. In certain applications, when the surface of the movin^g matter is reflecting no imaging elements are necessary. It is worth to note that it has not been en- tioned and it is not mentioned in the claims as well only where it is of decisive importance that the light intensity may significantly change while passing through or being reflected by certain optical elements, and other reflections - not mentioned in this descrip¬ tion - may occur..] These effects are of secondary im tance and do not concern the essence of the inventi They can be considered as constant loss factors. An example is considered on the basis of Pig. 2 about the error in case a plane-parallel plate is used fo beamsplitter 20 that reflects 10 % the incident lig and transmits the rest. All the other elements are sidered to be ideal and only the reflected or -scatt light 16 is considered. Only 10 % of the reflected or scattered light 16 from the moving matter 10 is reflected by beamsplitter 20 towards the outcouplin element 19 of the coherent light source 11, the res passes through beamsplitter 20 and is radiated Into free space. An almost total reflection occurs on th outcoupling element 19 of the coherent light source 11 and 90 % of the light 21 reflected from the out¬ coupling element 19 passes through beamsplitter 20 and -falls upon the surface of photodetector 12. Tha means that only 9 % of the scattered of reflected light 16 reaches the photodetector 12. Prom beamspl ter 20, 10 % of the light 21 reflected from outcoup ing element 19 may get back through the imaging ele ment 14 onto the moving matter 10. This Is only 1 % of the original reflected or scattered light. Even if this light could reach by some total reflection photodetector 12 and interfere on its surface - wit a different heterodyne frequency - this signal woul be negligable to the original signal because as it has to pass the same path it may produce a signal with maximum amplitude 1 % relative to the useful light, that is negligable. OM The advantages of the process and apparatus described in the present invention can be summarized in the following. It makes possible measurement of physical . parameters of moving matter using a coherent light source by heterodyne detection of light scattered or reflected by the moving matter in such a way that ' b^ nature of the method it does not require adjustment and stability with interferometric accuracy the illu- inating beam must only hit the moving matter. In case only one beam is projected onto the moving matter than the position of measurement can be anywhere along this beam within the limit of sensitivi¬ ty of the apparatus. In case if there is a mean to follo\ the motion of moving matter on its course of motion or its -motion is limited to a region where it is conti¬ nuously illuminated by the beam or beams than thespa- tial dimensions of the volume of measurement are limit- ed only by the limits of sensitivity. Measurements of the parameters of the moving matter with the method described in the " invention are of non contact nature and in general do not require attaching any optical element or elements ot the moving matter to be examined. Because the operational frequency of the coherent light source is high therefore measurements can provide instantaneous values of the parameters mea¬ sured (e.g. in case of a He-Ne laser when thevelocity ofthe moving matter parallel v/ith light beam radiated is 1 mm/sec then the frequency of the photodetector signal is about 3 kHz). - 20 - As the process described in this inventi can- be realized with low power lasers as well e.g. He-Ne or semiconductor lasers, that may cost a fra tion of the price of a CO p laser and the realizati does not require fine mechanical elements, its rea zation is cheaper than that of the previously know methods. In conclusion the process .described here provides the accuracy of the previous interferomet and heterodyne methods of measurement and at the sa time it extends the range of possible applications and realization of the process and apparatus disclo in this invention can be very easily realized.

Claims: WHAT IS CLAIMED IS: 1. Process for measuring physical parameters of moving matter (10) by means of coherent light source (11) by heterodyne detection of scattered or reflected s light. (16) from moving matter (10) in which light (15) of coherent light source (11) is projected either di¬ rectly or thorugh optical imaging system (14) onto moving matter (10) c h a r a c t e r i z e d " b y projecting reflected or scattered light (16) from mov¬ ing matter (10) and light (15) from coherent light source (11) onto the surface of photodetector (12) on optically identical paths in such a way that scattered or reflected light (16) reaches the surface of photo¬ detector (12) by being reflected from outcoupling ele¬ ment (19) of coherent light source (11) operating in optimum regime of operation and determining the phy¬ sical parameters of moving matter (10) by means of processing the electrical signal appearing on the out¬ put of photodetector (12) by signal processing unit (13). 2. Process according to claim 1 c h-a r a..c - t e r i z e d b y dividing light (15) from the coherent light source into at least two parts and pro¬ jecting one part (17) of the light directly to photo¬ detector (12) and the other part (18) of the light either directly or through optical imaging element (14) onto moving matter (10), then projecting scattered or reflected light (16) from moving matter (10) onto out¬ coupling element (19) of coherent light source (11) by beam splitting element (20) and leading reflected light (21) from outcoupling element (19) by beam splitting element (20) onto the surface ' of photodetec¬ tor (12). 3. Process according to claim 1 or 2 to measure directional characteristics of physical para meters of moving matter (10) c h a r a c t e r i z e b y dividing light (15) from coherent light source (11) into several parts, projecting part (17) of the light beam directly onto photodetector (12) while projecting other parts (18) of the light beam either directly or through optical imaging elements (14) at different agnles either to identical or different points of moving matter (10), projecting reflected o scattered light (16) from movin matter (10) either directly or through optical imaging elements (14) by beam splitting element (20) to outcoupling elemen (19) of coherent light source (11) from where pro ec ing reflected light (21) by beamsplitter (20) onto t surface of photodetector (12). 4. Apparatus for measuring physical para¬ meters of moving matter (10) which comprises of co- herent light source (11), photodetector (12), signal processing unit (13) connected to photodetector (12) c h a r a c t e r i z e d i n t hat beamsplitter (20) is disposed between moving matter (10) and cohe rent light source (11), photodetector (12) is positio er £.- ed in the way of light projecte ' from beamsplitter (20), or beamsplitter (20) is positioned between coh rent light source (11) and photodetector (12) while moving matter (10) is " in the way of light projected fro beamsplitter (20). 5. Apparatus according to claim 4 c h a r t e r i z e d i n that beamsplitter (20) is posi tioned between coherent light source (11) and photo¬ detector (12) and moving matter (10) is positioned - 23 - in the way of the light directly projected by beam¬ splitter (20) from light (15) of coherent light source (11), while in given case optical imaging element (14) is positioned between beamsplitter (20) and moving matter (10), (Pig. 2). 6. Apparatus according to claim 4 c h a r a c - t e r i z e d b y beamsplitter (20) and in given case optical imaging element (14) positioned between coherent light source (11) and moving matter (10) and by photodetector (12) positioned in the way of the light that is directly projected from light (15) of the cohe¬ rent light source and of light (16) that is reflected or scattered by moving matter (10) and reflected by outcoupling element (19) of coherent light source (II) and projected by beam-splitter (20), (Pig. 1). 7. Apparatus according to claim 4 to determine direction dependency of physical parameters of moving matter (10) c h a r a c t e r i z e d b a beam¬ splitter (20) consisting of at least two, possibly integrated beam splitting elements (22) is positioned between coherent light source (11) and photodetector (12), furthermore by one or more optical imaging ele¬ ments positioned between beam splitting elements (22), 8. Apparatus according to any of claims 4-7 c h a r a c t e r i z e d i n that the coherent light source (11) is a He-Ne or a semiconductor laser.

Inventors: ENGARD F, PECZELI I, RICHTER P
Applicants: BUDAPESTI MUESZAKI EGYETEM, ENGARD F, MTA KOEZPONTI FIZ KUTATO INTEZ, NOVEX FOREIGN TRADE CO LTD, PECZELI I, RICHTER P, BUDAPESTI MUSZAKI EGYETEM, MTA KOEZPONTI FIZIKAI KUTATO INTEZETE, NOVEX TALALMANYFEJLESZTO ES ERTEKESITO KUELKERESKEDELMI
Application year: 1981
Main classification: G01P3
IPC codes: G01B11, G01P3, G01P15