The interference device for measuring the phase shift of light waves
(57) Abstract:Usage: in the field of measurement technology, namely in laser interferometry to measure the linear movement of various objects with high accuracy. The inventive device is an acousto-optic interferometer with an electronic measuring circuit implemented on the system phase-locked loop, which has a measuring and a reference input paths, each of which uses a delay line. 2 Il. The invention relates to the field of measuring equipment, namely, laser interferometry and can be used for measuring linear displacements of various objects (elements of machine tools, coordinate measuring machines, measuring robots and others) with high accuracy.To date for measuring linear displacement of already developed quite a large number of designs laser acousto-optic interferometers. In particular, a device for measuring phase shifts of light waves laser acousto-optic interferometer (analog) . This device consists of an optically coupled laser, mnogoopytnogo acoustooptics, deflecting wedge, similar elements of the interferometer base channel, a turning prism, biprism, the afocal optical focusing systems measuring, reference and basic channels, reflecting mirrors, three optical diaphragms, three focusing lenses, three photodetectors and electronic measuring systems,
For designs of laser interferometers, there is the concept of spatial period lPPthat means a moving object, resulting in phase shift 2 . In the above construction of the laser interferometer is the spatial period is not regulated and is a multiple of IPP=n/2, where is the wavelength of the laser radiation, n is the number of double strokes of the beam in the optical interferometer scheme.The essential advantage of the device described above is automatic compensation of errors introduced by the acoustooptic modulator and changes of the refractive index of air, through the creation of an additional reference channel.However, in this device there are two major shortcomings. The first is to limit the measurement accuracy, typical for phase measurement methods phase cdotu regulation of the spatial period lPPand, as a consequence, the need for additional conversion value of phase shift in the metric system when determining the actual movement of the object.The need to improve the accuracy of the measurements leads to the fact that the phase is a measure of transition to the frequency display of the phase shift. A known design of a laser interferometer with frequency indication of the phase shift  (similar), which is a way of measuring the phase shift of light waves, which contains optically coupled laser Michelson interferometer comprising a beam splitter, the measuring and the reference corner cube reflectors, dual optical valve, located in the reference channel of the interferometer modulator (e.g., acousto-optic cell), slit chart and PV, the emitter of ultrasonic waves, connected in series resonance amplifier and switch the oscillator.The disadvantages of this device include functionality associated with the inability of smooth adjustment of the spatial period lPPgenerated by the interferometer, as well as the insufficient accuracy of measurements, OGG common features is a device for implementing the method of measuring the phase shift of light waves  (prototype), which contains optically United monochromatic light source, an acousto-optic modulator (AOM) with one electrical input and spatially separated keywords. output optical flows, the collimator, the elements of the optical system of the interferometer reflecting the triple-prism, the photodetector is electrically connected to the first input of the phase detector of extreme values (PDAS), the first output of which is connected to the input of the pulse counter, and the output of the latter is the output of the entire device, and the second output is electrically connected to the generator input, managed code, and its output is connected as the second input PDAS, and with the electrical input of the AOM.This solution allows you to create a laser measuring system with a triangular function measuring conversion and managed spatial period.The disadvantage of this technical solution is the limit of measurement accuracy due to errors introduced by the acoustooptic modulator and instability axis of the directivity diagram of the radiation source.The present invention is aimed at achieving technical achiev="ptx2">The invention is directed to the achievement of the technical result, which is to improve the measurement accuracy when extending functionality.This result is achieved in that the proposed interference device for measuring the phase shift of light waves, containing optically United monochromatic light source, an acousto-optical modulator with one electrical input and three spatially separated keywords. optical flows, the collimator, the measuring path, consisting of series-connected optical and electrical channels, and the optical channel is implemented with a moving triple-prism scheme Mach-Zehnder interferometers in the first and one of the second keywords. optical flow, and the electrical channel consists of a generator, managed code, pulse meter, a photo detector, phase detector, the first output of which is connected to the input pulses, the output of the latter is the output of the device, and the second output of the phase detector is connected to the generator input, managed code, and its output is connected to the electrical input of the acousto-optical modulator is elektricheskogo channels, moreover, the optical channel is implemented by the circuit of the Mach-Zehnder interferometers, in which the spatial combined third and another part of the second keywords. optical flow, and electrical channel consists of serially connected photodetector and the first delay line, the output of which is connected to a second input of the phase detector, and measuring the tract entered the second delay line between the output of the photodetector and the first input of the phase detector.The proposed set of features was not previously known, and this result can only be achieved in this device.The construction and operation of the device, you receive the graphic material.In Fig. 1 shows a structural diagram of the interference device for measuring the phase shift of light waves; Fig. 2 is a graphic explanation of the process of formation of the functions of measuring conversion for different values of the spatial period lPP.The proposed device (Fig. 1) consists of the following elements: a monochromatic light source (laser) 1, acousto-optic modulator (AOM) 2, the collimator 3, reflecting the triple prism 4, the measuring path, consisting of about the CLASS="ptx2">Optical channel 5 measurement circuit includes mirrors 9, 11 and beam splitter cube 10.Electrical channel 6 measurement circuit includes a photodetector 12, the delay line 13, the phase detector 14, the pulse counter 15, the controlled oscillator code (GUK) 16.Optical channel 7 of the reference path includes a beam-splitting cubes 17, 18 and mirror 19, 20.Electrical channel 8 control path includes a photodetector 21, the delay line 22.The proposed device operates as follows.The laser beam 1 is directed to AOM 2, after which it is distributed on the first E (+1), zero (E (0) and minus first E (-1) diffraction order output spectrum. The collimator 3 output order is sent to the measuring circuit in the form of parallel rays.The first order modulation E (+1) extends to triple-prism 4, is returned into the optical channel 4, beam splitter cube 10 combined spatial and interferes with the zero order diffraction E (0) at the output of the photodetector 12.Optical channel 7 anchor tract collected under the scheme of the interferometer of Mach-Zehnder interferometers based on two beam-splitting cubesat and interfere at the input of the photodetector 21.Optical heterodyning in the plane of the important aspect of keywords. optical flow leads to the outputs of the photodetectors 12 and 21 of the measuring and reference frequency signals. These signals pass through the delay lines 13 and 22 receive the time delays t1, t2and act accordingly on the first (test) and second (reference) inputs of phase detector 14.When moving triple-prism 4 to the first input of phase detector 14 is formed by the sequence information of the logical pulse, which is fed to the input of the pulse counter 15. At the output of the pulse counter 15 produces a digital code corresponding total phase signal.On the second output of the phase detector 14 is formed of the digital code input to the input unit GUK 16. The output frequency signal of the latter is fed to the electrical input of the AOM 2.In this device, the function measuring the conversion of the phase detector is a ramp with a negative slope (symmetric triangular function). This kind of function measuring conversion is quite common, allowing you to exclude from the conversion process neulasta.As one of the variants of the algorithms of the phase detector may be next. The phase difference between the input frequency signal is converted into a digital code N. If the output of the digital combination of N corresponds to two extreme values (N= 0 when =0 or N=Nmaxwhen =2 ), then the first output information is formed logical pulse.The essence of the operation of the device is as follows.1. Studies show that the value of the spatial period lPPfor the measuring circuit bases of the reference channel is defined by the formula:
IPP=(1+2k), (1) ,
K- gross ratio control loop measuring circuits;
the time delay of propagation of ultrasonic waves in the acousto-optic modulator;
the wavelength of the radiation source.The introduction of the reference channel leads to the fact that the value in the formula (1) is determined by the difference of the delays in the measuring and reference channels =t=t2-t1. . By adjusting the value of t due to a change in t1and/or t2you, ultimately, to control the spatial period.Using modern electronic database you can change t with a little of the VA signal delay can be different, on the basis of ultrasonic, electromagnetic delay lines, based on the RC-elements, on the basis of electronic devices (timers).2. The errors inherent in the laser acousto-optical measuring systems, include the following:
the error caused by the presence of the reflected acoustic wave in the modulator and slow fluctuations of the velocity of propagation of acoustic waves in AOM due to temperature changes svetoslava;
the uncertainty due to instability of the axis of the directivity diagram of the radiation source.The use of diagrams with two paths inteferometry (test and reference) allows the parasitic phase raids that occur in both channels, to compensate for each other. As a result, these errors can be completely excluded from the conversion process measurement data, which increases the measurement accuracy.Schematically, generator, managed code can be built on the basis of the well-studied diagrams of the frequency synthesizer or a two stage scheme: d / a Converter + a voltage controlled oscillator, = controlled oscillator code.Thus, the proposed device is. is using delay lines in the measuring circuit provides the additional ability to control the spatial period. The interference device for measuring the phase shift of light waves, containing optically United monochromatic light source, an acousto-optical modulator with one electrical input and three spatially separated keywords. optical flows, the collimator, the measuring path, consisting of series-connected optical and electrical channels, and the optical channel is implemented with a moving triple-prism scheme Mach-Zehnder interferometers in the first and one of the second keywords. optical flow, and the electrical channel consists of a generator, managed code, pulse meter, a photo detector, phase detector, a first output of which is connected to the input of the pulse counter, the yield of the latter is an output device, and the second output of the phase detector is connected to the generator input, managed code, and its output is connected to the electrical input of the acousto-optic modulator, characterized in that the device additionally introduced the reference tract, consisting of EME Mach-Zehnder interferometers, in which spatial combined third and another part of the second keywords. optical flow, and electrical channel consists of serially connected photodetector and the first delay line, the output of which is connected to a second input of the phase detector, and measuring the tract entered the second delay line between the output of the photodetector and the first input of the phase detector.
FIELD: measurement technology.
SUBSTANCE: device for measuring linear sizes has additional counter, two subtracters, two decoders and AND-OR gate. Output of amplitude selector is connected with inputs of first and second permanent storages through additional counter. Outputs of permanent storages are connected with first inputs of first and second subtracters. The second inputs and outputs of subtracters are connected with output of unit for counting marks and with first inputs of first and second decoders. Outputs of decoders are connected with first and second inputs of AND-OR gate. The third input and output of AND-OR gate are connected correspondingly with output of unit for counting number of marks and with first input of indicator.
EFFECT: reduced influence of error of object installation; improved precision of measurement.
FIELD: device providing receiving of information on condition of object's surface.
SUBSTANCE: device can be used for inspecting surfaces of objects at tunnel and atomic-power modes of operation in scanning probe microscope. Power probe for scanning probe microscope has quartz crystal vibrator provided with needle fixed at surface of one arm of quartz vibrator due to chemical bond between needle and surface. There are variants of the device where thread-shaped crystals are used as needles and nanotubes. Thread-shaped crystals can be made of carbon, metal, semiconductor and isolator. Needles can be also fixed at external surface of arm of quartz vibrator as well as its edge and side surfaces. Needles can be arranges as in parallel to axis of symmetry of quartz vibrator and in perpendicular to its axis. According to one more variant, needle can be fixed at random angle to axis of plane of one arm of quartz vibrator. In some cases surface of arm of quartz vibrator can used for fixing several needles of different lengths.
EFFECT: improved sensitivity of probe; widened operational capabilities.
12 cl, 6 dwg
FIELD: measuring arrangements.
SUBSTANCE: device comprises unmovable base provided with the first cantilever, two carriages provided with drives controllable with a computer, pickup of linear movements, arrangement for mounting blade and first measuring channel connected with the computer. The first carriage is mounted on the unmovable base and is made for permitting movement parallel to the X-axis. The first measuring passage is defined by the optoelectronic head and units secured to the unmovable base, third carriage provided with an actuator controlled by a computer and pickup of linear displacements, second measuring channel, first and scone markers of the blade with actuating members controlled by a computer, arrangement setting the blade mounted on the first carriage and made for permitting rigid orientation of the blade in the vertical plane, second and third carriages arranged on the first and second cantilevers, respectively, and made for permitting movement parallel to the Z-axis, first and second markers of the blade, fiber optic heads of the first and second measuring channels arranged on the second and third carriages from the both sides of the study blade. The objectives of the fiber optic heads are mounted for permitting triangulation link of the photodetector with the sourced through the blade surface of the blade to be tested.
EFFECT: enhanced efficiency.
6 cl, 7 dwg
FIELD: measurement of object shape.
SUBSTANCE: the device has two luminous radiating systems located relative to the measured surfaces of the object, each of them forms luminous lines at the preset sections of the object, a photoreceiver with an objective lens and a computer unit, whose input an objective lens and a computer unit, whose input is connected to the output of the photoreceiver. The photoreceiver is made in the form of a matrix and is optically coupled to each luminous radiating system. In addition, the device has mirrors located relative to the measured surfaces of the object at an acute angle to its surface and is optically coupled to the photo-receiver through the objective lens, whose optical axis is positioned in the plane of symmetry.
EFFECT: enhanced accuracy of measurement, capacity and simplified construction of the device.
6 cl, 2 dwg
FIELD: woodworking industry, particularly for measuring moving timber thickness.
SUBSTANCE: device comprises conveyer for feeding timber material to be adjusted to obtain predetermined timber thickness, thickness measuring means, processing unit to determine insufficient timber thickness, means to distinguish above timber from another ones. Thickness measuring means determines timber thickness in several points during conveyance thereof on the base of main output signals generated by displacement transducers. Displacement transducers are located in several locations along timber width. If timber has several parts of a given length with thicknesses deviated from tolerance band for predetermined value in conveyance direction one can come to conclusion that timber has insufficient thickness.
EFFECT: reduce time of thickness determination, increased quality thereof.
5 cl, 8 dwg
FIELD: measurement technology; instrument engineering.
SUBSTANCE: device has bed, movable mechanism of movable carriage, optical units of basic and vernier dial of measuring rule, photo-element unit disposed onto movable carriage, mechanism for moving optical units relatively movable carriage, device for counting optical lines of basic and vernier dials of measuring rule, line coincidence unit of basic and vernier dials, difference signal determination unit, correction memory unit. The latter has corrections relatively standard depending on number of line of measuring rule of basic and vernier dials introduced through algebraic adding unit into measuring rule basic and vernier dial number of lines counters and units of determining précised linear value of lines of basic and vernier dials. Basic and vernier dials of measuring rule are reduced relatively minimal interval of length of 0, 5 mm 10 to 40 times by means of photographing.
EFFECT: improved precision of measurement of linear distances.
3 cl, 3 dwg
FIELD: the invention refers to measuring technique.
SUBSTANCE: the mode of measuring the form of an object includes formation of a light line on the surface of the object with the aid of the light-emitting system lying in the preset cross-section of the object, getting the image of the light line, its processing and definition of the coordinates of the profile of the cross-section of the object. AT that collateral light lines are formed on the surface by turns with the aid of two light-emitting systems illuminating the surface in preset cross-section of the object at different angles in its every point, images of light lines are received. On each of them sites are revealed. A resultant image is compiled out of the images of the indicated sites. According to this resultant image the coordinates of the profile of the cross-section of the object are determined. The arrangement for measuring the form of the object has a light-emitting system optically connected with a photoreceiver and a computing unit. It also has one additional light-emitting system optically connected with a photoreceiver and a commuting unit connected with its input to the computing unit, and with its output - with every light-emitting system. Optical axles of light-emitting system are placed in one plane and located to each other at an angle equal 5-800.
EFFECT: the invention increases accuracy of measuring by way of excluding the distortions of the zone of influence on the results of measuring.
13 cl, 5 dwg
FIELD: the invention refers to measuring technique particularly to devices for linear measurements and may be used in machine-tool construction.
SUBSTANCE: the arrangement has a bed, a movable mechanism of a mobile carriage, a main and a nonius scale of a measuring ruler, optical units of a main and a nonius scale of a measuring ruler, a unit of photo , elements, units of coincidence of the stated number of the mark of the main and the nonius scale and exact linear meaning of the stated number of the mark of the main and the nonius scale, a stop unit of the mobile carriage, a unit of algebraical summation, a correction memory unit. At that the main and the nonius scales of the measuring ruler are reduced relatively to the minimum interval of length of 0,5 mm with the aid of photographing in 10 and 40 times.
EFFECT: the invention provides increased accuracy at measuring linear distance.
11 cl, 3 dwg
FIELD: measurement technology.
SUBSTANCE: according to method of contact-free optical measurement the object is placed between laser radiation source and photoreceiver. Power of laser radiation P is measured and compared with preset level of power P0 . Laser radiation is optically scanned into beam of parallel rays at the area where object finds its place and size of object is found from size of shade of object onto photoreceiver while correcting time of exposure from value of difference (P0-P). Device for realizing the method has laser, beam-splitting plate, short-focused cylindrical lens, output cylindrical lens, collimating lens, CCD, data processing unit, photoreceiving threshold unit.
EFFECT: improved precision of measurement.
5 cl, 1 dwg
FIELD: measuring engineering.
SUBSTANCE: method comprises setting the article to be controlled on the movable traverse gear having two extent of freedom, illuminating the surface of the article by light, receiving the light reflected from the surface of the article with the use of a photodetector, moving the article parallel to the X-axis, determining coordinates of the light spots on the photodetectors of the current values of the heights of the article shape, locking the position of the table, scanning the main section of the article shape, comparing it with the reference one , and determining the quality of the article shape. The main section is scanned by moving the article parallel to the Y-axis, when the traverse gear is in a position determined from the formula proposed. The device comprises unmovable horizontal base, vertical cantilever secured to the base, unit for measuring the article shape mounted on the vertical cantilever, two carriages that define a traverse gear and provided with the individual drives controlled by a computer, and pickup of linear movements. The first carriage moves parallel to the X-axis, and the second carriage is mounted on the first one and moves parallel Y-axis.
EFFECT: improved quality of control.
4 cl, 4 dwg