rus
Issue #3-4/2021
B.G.Turukhano, N.Turukhano, Yu.M.Lavrov, S.N.Khanov, V.V.Dobyrn, O.G.Ermolenko, L.A.Konstantinov, Е.F.Vilkov, I.V.Ladatko
Portable nano-holographic planmeter
Portable nano-holographic planmeter
DOI: 10.22184/1993-8578.2021.14.3-4.212.222
Portable NANO holographic plane meter refers to measuring technology, more precisely to the field of measuring and controlling the quality of optical surfaces, their deviation from a given surface shape, determining surface roughness, including super smooth surfaces, such as flat mirrors, polished substrates, etc. PNHPM leads to an increase in the measurement accuracy, removal of restrictions on the size of the surface, accelerate measurements in the wide temperature range.
Portable NANO holographic plane meter refers to measuring technology, more precisely to the field of measuring and controlling the quality of optical surfaces, their deviation from a given surface shape, determining surface roughness, including super smooth surfaces, such as flat mirrors, polished substrates, etc. PNHPM leads to an increase in the measurement accuracy, removal of restrictions on the size of the surface, accelerate measurements in the wide temperature range.
Теги: holographic length meter holographic plane meter surface roughness голографический длиномер голографический плоскомер шероховатость поверхности
INTRODUCTION
Portable nanoholographic planmeter is a holographic measuring system. It is designed for precision measurements in real time, processing and maintaining measurement results when working, both in autonomous mode and with automated measurement systems as a measuring and computing complex; this system is characterized by high reliability. Information on the magnitude of the deviation from flatness is displayed in digital tables and graphs. The PNHPm can be used in mechanical engineering, optical-mechanical industry, aircraft construction, in all high-tech industries, for calibration of industrial measuring standards, as well as in science and technology.
The design of the PNHPm device makes it possible to determine with a high nano accuracy deviation from flatness of the surface, remove the limit on the size of the measured surface and perform an accelerated measurement process with an increase in the operating temperature range. In the process of measurement there is no subjective human factor.
To control flatness of horizontally located surfaces, calibration rules are used (for example, the Ol-800 optic line [1], plates, flat glass plates, an interferometer, which has accuracy to 0.5 μm).
A device is known to determine the deviation from flatness of the surfaces, which includes an automatic collimator [2] as a measuring element and a mirror located on the measured surface with the possibility of moving along it.
The main disadvantage of this method is associated with a large size and weight of the autocollimator (9 kg) which needs to install it, as a rule, not on the surface to be measured so as to avoid distortions, due to which it is established, as a rule, not on the measured surface in order not to make distortion in this surface therefore the second-scale autocollimator scale and the mirror are installed on the measured surface. They are in the different coordinate systems (fixed and mobile) and do not depend on each other, therefore the transfer of information is carried out with a certain error due to changes in time and in space of their mutual locations.
MEASUREMENTS AND RESULTS
Laser interference measurements in the length ranges of 200 mm, 20 m and 1 km are carried out using helium-neon lasers providing high monochromatics, low rays and greater radiation intensity. In laser interferometry, the resolution in the meter range can be up to 0.1 μm / m and in proportion to the movement of the product. The error of the laser measuring measurement interferometers is no longer than the wavelength of the light (0.6 μm). Laser measurements are usually built according to the two-beam Michelson system, including a laser, a lightweight mirror and two reflectors, one of which is fixed, and the other is rigidly associated with the product. Reflected from the reference and object mirrors, light bundles are connected and interfered. At the output of the device, the number of interference bands is calculated using a photometric meter.
The disadvantage lacks of laser measurements is due to a relatively high sensitivity to external mechanical and temperature effects, which limits their application. The auto-collimation method is used to control deviations from straightness and flatness of surfaces with a large length (up to 40 ÷ 50 m).
The disadvantages of this method are due to insufficient accuracy of measurements associated with a subjective error in visual determination of the center of the collimated beam and combining it with the crossing of the brand, as well as the error, which can be caused by seismic fluctuations or vibration from technological equipment and construction equipment. The device is suitable only for measuring small changes in deviation from flatness and only for optical surfaces. Measurements of deviations from flatness are carried out manually by the operator. The device can define non-flatness of small surfaces.
The PNHPm allows to increase the accuracy of measurement of surface deviations from flatness, remove restrictions on the size of the measured surface and automate the measurement process, which substantially simplifies measurements.
The PNHPm device is represented in Fig.1. It contains a measuring unit 1, comprising a probe 2, a cross-cutting hole platform 3, in which the measuring unit is installed. The probe has the possibility of touching the measured surface and moving in the plane perpendicular to the measured surface and along the measurement direction, and the platform is equipped with three supports A, B and C to install the device on the measured surface. As a measuring unit, a linear displacement sensor (holographic length meter, HLM) is used as a source of light, illuminating two diffraction gratings, one of which is measurable, rigidly related to the dipstick, and the other auxiliary, and photodetectors. Supports A, B, C are made of materials with a low temperature expansion coefficient and provide for a three-point platform installation to the surface. They are located in the vertices of the triangle in such a way that one of the sides of the triangle is parallel to one of the sides of the platform. In addition, the device comes complete with a test glass is attached to the device, which is necessary for its calibration (Fig.2).
HLM 1 is a precision measuring device with digital output of information and it has the measuring element in the form of a linear holographic diffraction lattice. The HLM uses the interface of two diffraction gratings 3 and 4 (Fig.3), of which one – measuring with a length, not less than the expected deviation from the flatness of the measured surface, and is rigidly connected to the probe 2 (Fig.1 and Fig.2), and the other auxiliary one is a small.
The use of raster conjugates of two holographic diffraction lattices forming combinational moire bands, for digital measurement of displacements by the method of a sequential account is based on the next phenomenon. If one lattice moves in its own plane perpendicular to its strokes, and the other is fixed in relation to the observer, then the moire stripes are also moved, and the number of bands that pass through any point of the raster field is equal to the number of strokes of the moving lattice, which have passed the same point. If one of the lattice are rigidly fixed to Fig.2 (Fig.1 and Fig.2) of the length, which must measure the deviation from the plane of the surface, and the other is still relative to it, then, counting the number of bands passing any fixed point, you can define a linear movement of mobile moving the probe, expressed in the number of periods of the diffraction lattice strokes. In this case, as can be seen from the tables, this period is 1 μm. In addition, in order to ensure a reversing count, the raster moire link must produce two signals shifted in the spatial phase by π / 2. Sinusoidal quadrature signals can be converted to rectangular signals (Fig.3). As a result, the measured movement is represented by a sequence of homogeneous pulses, and each pulse corresponds to the movement of the grille one step. The number of pulses is calculated by an electron reverse counter when they are illuminated by a light flux from the light source 1 contained in the measuring unit, interference combinational moire bands appear at the lattice outlet, resulting from the interference of the beams of various orders of diffraction of these gratings. Initially, an auxiliary lattice 4 is superimposed on the measuring lattice 3 (Fig.4), then the short lattice will be dispelled over the corner with the measuring lattice (vertical arrows (Fig.5) before receiving wide moire strips. The period of moire bands in the vertical direction are taken in 360°. Set one photodetector 1 and start moving the measuring lattice 3 to the right – left (horizontal arrows), moire bands will start shifting up and down and photodetectors will begin to read them.
To determine the displacement direction of the measuring lattice, a second photodetector is established to generate sinusoidal signals 2 in the field of moire bands with a shift by bands 90° relative to the first photodetector (as white squares 5 and 6 are installed, imitating photodetectors 1 and 2 (Fig.4).
Now, if you shift the measuring lattice, two photodetectors will begin to generate two sinusoids, shifted by 90°, that is, sinus and cosine. When offset in one direction, the offset will be at + 90°, and in another direction –90°. If the photodetectors 5 and 6 are connected in pairs, with a shift of 180° (which allows you to compensate for the constant component of the signal), then two sin and cos signals shifted at 90° are formed at the output of the photodetectors.
When receiving information about the sensor movement during reading, the sin and cos signals are converted to TTL signals (meander) if it requires CNC. The step and shape of the moire bands depends on the parameters of the lattices and on their mutual location. Basically, they are a family of straight lines. The movement of one of the grids rigidly related to the dipstream 2, relative to the second leads to the synchronous movement of the moire bands and in the case of the reverse to the synchronous reverse. It is possible to estimate the relationship between the movement of the measuring diffraction lattice along the measured surface and the movement of the moor band, i.e. determine the coefficient of optical reduction. In HLM, one fundamental property of the moire bands obtained as a result of raster hinge of two lattices is used, namely, it is a significant movement of a moving measuring lattice. Thus, there is a large-scale (enlarged) transformation of small movements of the measuring lattice into substantially large, proportional movements of the moire bands. It is this circumstance that allows you to install photodetectors in the field of moire bands, which have significantly large sizes than the movement of the measuring lattice. Photodetectors are installed in the aperture of the indicator lattice than and the size is determined. Movements of the moire bands are converted by photodetectors to electrical signals that are processed in the electronic logic control unit for HLM or in PC via the RS-232 interface in order to obtain digital information about the measured movement. In order to eliminate the temperature dependence, the Platform 3 (Fig.1) is made of quartz, probe 2 and supports 4 of the invar, and the tips of supports 4 of the sapphire. In addition, the HLM-30 string has the ability to calibrate in a large temperature range (about ± 10° C), which allows the device to operate at different temperature modes without loss of accuracy. The accuracy of the device when using the HLM-30 length, it reaches a resolution of 0.01 μM (Fig.6), and in the case of HLM-70 (measurement limit of 70 mm) (Fig.7) reaches 1 nm resolution.
The principle of operation of the device is as follows. Initially, the device is calibrated using the reference plate 6 (Fig.2). In this case, platform 3 is installed, on support tips 4 and measuring unit 1 with probe 2 are mounted on the surface of the reference plate 6. The control unit is set to the "Calibration" position and the HLM is set to zero; as a result the kcal calibration coefficient is automatically accounted by the control unit. The instrument readings during all stages of measurements will automatically take this value into account. Moreover, kcal>0, if the surface of the reference plate is convex, and kcal<0, if its surface is concave. Next, after calibration, the platform 3 and HLM-1 with the probe 2 is transferred to the measured surface and switch to the measurement of the deviation from surface flatness. The control unit is set to the "Measurement" position and the testimony of HLM is set. After that, the surface measurement can be started. The measurement of the deviation from the surface flatness is based on the principle of measurement of the deviation from the surface flatness during measurements in various directions of this surface (for example, x and y). To do this, associate an orthogonal coordinate system with the measured XOY surface and determine the origin of coordinates. The wheel triangle can be on the measuring line, parallel to the direction OX or respectively, OY, and HLM-1 should be located in the middle of this category by fixing in hole 2. In this case, the ABBE errors will be minimal. Move the side line of the platform parallel to the sides along the selected direction of movement OX or OY, through equal selected intervals associated with a specific task. In this particular case, the interval was chosen equal to half the sides AB. As guides along which you need to move platform 3, you can use a ruler or a laser beam, etc.
After each movement, the carriage stops and the digital values from the electronic HLM unit are read-out. In the memory of the computer, the digital values of the hix height of the sensor are recorded in this direction OX. The same actions are carried out for all other lines parallel to the OX axis, covering the entire measured surface through the necessary intervals. In the memory of the computer, the digital values of the hiy sensor heights are recorded in the OY direction and for all other lines parallel to the OY axis.
The program for measured values builds a deviation from surface flatness within XOY in three coordinates X, Y, Z.
Moreover, the design of the device is that there are no restrictions on the number of measurement points, thereby large-scale the measured surface. The HLM-30/100/200 device was awarded a certificate of approval of the type of measuring instruments in 2018 [3].
Fig.7and Fig.8 show HLM-30 and HLM-70. In Fig.8, a range of changes to the deviation from the surface flatness ranging from -0.08 to +1.2 μm, determined with a resolution of 0.01 μm, and in Fig.9 there is a detailed cross section of deviation from non-flatness of the surface in the measurement direction along axis OX. The same section can be obtained along the OY axis. The intervals through which measurements were carried out were equal to half the length of the AB category, i.e. distance from one of the supports located on the sides, to the HLM probe.
Currently, HLM measuring length up to 200 mm [4] and with a measurement accuracy of vertical from ± 0.05 to ± 0.2 μm and a resolution of 10 nm to 1 nm.
The measuring node does not change its position relative to the platform support points. Moreover, its installation in the middle of the base AB, i.e. symmetrically relative to the supports, allows you to maintain the same accuracy in each measurement.
In Fig.8, a pattern of the deviation distribution from the flatness of the measured surface is given, and in Fig.9 the deviation from the flatness scanned in one of the cross section of this surface.
CONCLUSIONS
The advantages of this PNHPm:
increase of the measurement accuracy. The accuracy of the measuring lattice is given by the formula: (0.02 + 0.4L / 1000) μm, where L is the length of the measurement in mm,
acceleration of the measurement process,
increase of the limit of measured deviations from flatness,
reduction of the dimensions of the platform and the measuring node, the content of a small number of optical-mechanical nodes,
fixation of the measuring node in the platform hole relative to the poverty points,
platforms 3 and supports with tips 4 with low temperature dependence,
removal of restrictions on the size of the measured surface, both from small and from large values (i.e., expanding the range of the measured surface,
the measured deviation of the surface from the surface flatness H = ± 15 mm, which is associated with the characteristics of the measuring length of HLM-30,
ability to automate the measurement process,
device weighs no more than 300 g,
increase of the working temperature range,
time of one measurement cycle is minimal, because memorization and data processing is automatically controlled by the control unit or on the computer,
possibility to measure not only horizontal surfaces,
reduction of the weight of the measuring unit. ■
Declaration of Competing Interest. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Portable nanoholographic planmeter is a holographic measuring system. It is designed for precision measurements in real time, processing and maintaining measurement results when working, both in autonomous mode and with automated measurement systems as a measuring and computing complex; this system is characterized by high reliability. Information on the magnitude of the deviation from flatness is displayed in digital tables and graphs. The PNHPm can be used in mechanical engineering, optical-mechanical industry, aircraft construction, in all high-tech industries, for calibration of industrial measuring standards, as well as in science and technology.
The design of the PNHPm device makes it possible to determine with a high nano accuracy deviation from flatness of the surface, remove the limit on the size of the measured surface and perform an accelerated measurement process with an increase in the operating temperature range. In the process of measurement there is no subjective human factor.
To control flatness of horizontally located surfaces, calibration rules are used (for example, the Ol-800 optic line [1], plates, flat glass plates, an interferometer, which has accuracy to 0.5 μm).
A device is known to determine the deviation from flatness of the surfaces, which includes an automatic collimator [2] as a measuring element and a mirror located on the measured surface with the possibility of moving along it.
The main disadvantage of this method is associated with a large size and weight of the autocollimator (9 kg) which needs to install it, as a rule, not on the surface to be measured so as to avoid distortions, due to which it is established, as a rule, not on the measured surface in order not to make distortion in this surface therefore the second-scale autocollimator scale and the mirror are installed on the measured surface. They are in the different coordinate systems (fixed and mobile) and do not depend on each other, therefore the transfer of information is carried out with a certain error due to changes in time and in space of their mutual locations.
MEASUREMENTS AND RESULTS
Laser interference measurements in the length ranges of 200 mm, 20 m and 1 km are carried out using helium-neon lasers providing high monochromatics, low rays and greater radiation intensity. In laser interferometry, the resolution in the meter range can be up to 0.1 μm / m and in proportion to the movement of the product. The error of the laser measuring measurement interferometers is no longer than the wavelength of the light (0.6 μm). Laser measurements are usually built according to the two-beam Michelson system, including a laser, a lightweight mirror and two reflectors, one of which is fixed, and the other is rigidly associated with the product. Reflected from the reference and object mirrors, light bundles are connected and interfered. At the output of the device, the number of interference bands is calculated using a photometric meter.
The disadvantage lacks of laser measurements is due to a relatively high sensitivity to external mechanical and temperature effects, which limits their application. The auto-collimation method is used to control deviations from straightness and flatness of surfaces with a large length (up to 40 ÷ 50 m).
The disadvantages of this method are due to insufficient accuracy of measurements associated with a subjective error in visual determination of the center of the collimated beam and combining it with the crossing of the brand, as well as the error, which can be caused by seismic fluctuations or vibration from technological equipment and construction equipment. The device is suitable only for measuring small changes in deviation from flatness and only for optical surfaces. Measurements of deviations from flatness are carried out manually by the operator. The device can define non-flatness of small surfaces.
The PNHPm allows to increase the accuracy of measurement of surface deviations from flatness, remove restrictions on the size of the measured surface and automate the measurement process, which substantially simplifies measurements.
The PNHPm device is represented in Fig.1. It contains a measuring unit 1, comprising a probe 2, a cross-cutting hole platform 3, in which the measuring unit is installed. The probe has the possibility of touching the measured surface and moving in the plane perpendicular to the measured surface and along the measurement direction, and the platform is equipped with three supports A, B and C to install the device on the measured surface. As a measuring unit, a linear displacement sensor (holographic length meter, HLM) is used as a source of light, illuminating two diffraction gratings, one of which is measurable, rigidly related to the dipstick, and the other auxiliary, and photodetectors. Supports A, B, C are made of materials with a low temperature expansion coefficient and provide for a three-point platform installation to the surface. They are located in the vertices of the triangle in such a way that one of the sides of the triangle is parallel to one of the sides of the platform. In addition, the device comes complete with a test glass is attached to the device, which is necessary for its calibration (Fig.2).
HLM 1 is a precision measuring device with digital output of information and it has the measuring element in the form of a linear holographic diffraction lattice. The HLM uses the interface of two diffraction gratings 3 and 4 (Fig.3), of which one – measuring with a length, not less than the expected deviation from the flatness of the measured surface, and is rigidly connected to the probe 2 (Fig.1 and Fig.2), and the other auxiliary one is a small.
The use of raster conjugates of two holographic diffraction lattices forming combinational moire bands, for digital measurement of displacements by the method of a sequential account is based on the next phenomenon. If one lattice moves in its own plane perpendicular to its strokes, and the other is fixed in relation to the observer, then the moire stripes are also moved, and the number of bands that pass through any point of the raster field is equal to the number of strokes of the moving lattice, which have passed the same point. If one of the lattice are rigidly fixed to Fig.2 (Fig.1 and Fig.2) of the length, which must measure the deviation from the plane of the surface, and the other is still relative to it, then, counting the number of bands passing any fixed point, you can define a linear movement of mobile moving the probe, expressed in the number of periods of the diffraction lattice strokes. In this case, as can be seen from the tables, this period is 1 μm. In addition, in order to ensure a reversing count, the raster moire link must produce two signals shifted in the spatial phase by π / 2. Sinusoidal quadrature signals can be converted to rectangular signals (Fig.3). As a result, the measured movement is represented by a sequence of homogeneous pulses, and each pulse corresponds to the movement of the grille one step. The number of pulses is calculated by an electron reverse counter when they are illuminated by a light flux from the light source 1 contained in the measuring unit, interference combinational moire bands appear at the lattice outlet, resulting from the interference of the beams of various orders of diffraction of these gratings. Initially, an auxiliary lattice 4 is superimposed on the measuring lattice 3 (Fig.4), then the short lattice will be dispelled over the corner with the measuring lattice (vertical arrows (Fig.5) before receiving wide moire strips. The period of moire bands in the vertical direction are taken in 360°. Set one photodetector 1 and start moving the measuring lattice 3 to the right – left (horizontal arrows), moire bands will start shifting up and down and photodetectors will begin to read them.
To determine the displacement direction of the measuring lattice, a second photodetector is established to generate sinusoidal signals 2 in the field of moire bands with a shift by bands 90° relative to the first photodetector (as white squares 5 and 6 are installed, imitating photodetectors 1 and 2 (Fig.4).
Now, if you shift the measuring lattice, two photodetectors will begin to generate two sinusoids, shifted by 90°, that is, sinus and cosine. When offset in one direction, the offset will be at + 90°, and in another direction –90°. If the photodetectors 5 and 6 are connected in pairs, with a shift of 180° (which allows you to compensate for the constant component of the signal), then two sin and cos signals shifted at 90° are formed at the output of the photodetectors.
When receiving information about the sensor movement during reading, the sin and cos signals are converted to TTL signals (meander) if it requires CNC. The step and shape of the moire bands depends on the parameters of the lattices and on their mutual location. Basically, they are a family of straight lines. The movement of one of the grids rigidly related to the dipstream 2, relative to the second leads to the synchronous movement of the moire bands and in the case of the reverse to the synchronous reverse. It is possible to estimate the relationship between the movement of the measuring diffraction lattice along the measured surface and the movement of the moor band, i.e. determine the coefficient of optical reduction. In HLM, one fundamental property of the moire bands obtained as a result of raster hinge of two lattices is used, namely, it is a significant movement of a moving measuring lattice. Thus, there is a large-scale (enlarged) transformation of small movements of the measuring lattice into substantially large, proportional movements of the moire bands. It is this circumstance that allows you to install photodetectors in the field of moire bands, which have significantly large sizes than the movement of the measuring lattice. Photodetectors are installed in the aperture of the indicator lattice than and the size is determined. Movements of the moire bands are converted by photodetectors to electrical signals that are processed in the electronic logic control unit for HLM or in PC via the RS-232 interface in order to obtain digital information about the measured movement. In order to eliminate the temperature dependence, the Platform 3 (Fig.1) is made of quartz, probe 2 and supports 4 of the invar, and the tips of supports 4 of the sapphire. In addition, the HLM-30 string has the ability to calibrate in a large temperature range (about ± 10° C), which allows the device to operate at different temperature modes without loss of accuracy. The accuracy of the device when using the HLM-30 length, it reaches a resolution of 0.01 μM (Fig.6), and in the case of HLM-70 (measurement limit of 70 mm) (Fig.7) reaches 1 nm resolution.
The principle of operation of the device is as follows. Initially, the device is calibrated using the reference plate 6 (Fig.2). In this case, platform 3 is installed, on support tips 4 and measuring unit 1 with probe 2 are mounted on the surface of the reference plate 6. The control unit is set to the "Calibration" position and the HLM is set to zero; as a result the kcal calibration coefficient is automatically accounted by the control unit. The instrument readings during all stages of measurements will automatically take this value into account. Moreover, kcal>0, if the surface of the reference plate is convex, and kcal<0, if its surface is concave. Next, after calibration, the platform 3 and HLM-1 with the probe 2 is transferred to the measured surface and switch to the measurement of the deviation from surface flatness. The control unit is set to the "Measurement" position and the testimony of HLM is set. After that, the surface measurement can be started. The measurement of the deviation from the surface flatness is based on the principle of measurement of the deviation from the surface flatness during measurements in various directions of this surface (for example, x and y). To do this, associate an orthogonal coordinate system with the measured XOY surface and determine the origin of coordinates. The wheel triangle can be on the measuring line, parallel to the direction OX or respectively, OY, and HLM-1 should be located in the middle of this category by fixing in hole 2. In this case, the ABBE errors will be minimal. Move the side line of the platform parallel to the sides along the selected direction of movement OX or OY, through equal selected intervals associated with a specific task. In this particular case, the interval was chosen equal to half the sides AB. As guides along which you need to move platform 3, you can use a ruler or a laser beam, etc.
After each movement, the carriage stops and the digital values from the electronic HLM unit are read-out. In the memory of the computer, the digital values of the hix height of the sensor are recorded in this direction OX. The same actions are carried out for all other lines parallel to the OX axis, covering the entire measured surface through the necessary intervals. In the memory of the computer, the digital values of the hiy sensor heights are recorded in the OY direction and for all other lines parallel to the OY axis.
The program for measured values builds a deviation from surface flatness within XOY in three coordinates X, Y, Z.
Moreover, the design of the device is that there are no restrictions on the number of measurement points, thereby large-scale the measured surface. The HLM-30/100/200 device was awarded a certificate of approval of the type of measuring instruments in 2018 [3].
Fig.7and Fig.8 show HLM-30 and HLM-70. In Fig.8, a range of changes to the deviation from the surface flatness ranging from -0.08 to +1.2 μm, determined with a resolution of 0.01 μm, and in Fig.9 there is a detailed cross section of deviation from non-flatness of the surface in the measurement direction along axis OX. The same section can be obtained along the OY axis. The intervals through which measurements were carried out were equal to half the length of the AB category, i.e. distance from one of the supports located on the sides, to the HLM probe.
Currently, HLM measuring length up to 200 mm [4] and with a measurement accuracy of vertical from ± 0.05 to ± 0.2 μm and a resolution of 10 nm to 1 nm.
The measuring node does not change its position relative to the platform support points. Moreover, its installation in the middle of the base AB, i.e. symmetrically relative to the supports, allows you to maintain the same accuracy in each measurement.
In Fig.8, a pattern of the deviation distribution from the flatness of the measured surface is given, and in Fig.9 the deviation from the flatness scanned in one of the cross section of this surface.
CONCLUSIONS
The advantages of this PNHPm:
increase of the measurement accuracy. The accuracy of the measuring lattice is given by the formula: (0.02 + 0.4L / 1000) μm, where L is the length of the measurement in mm,
acceleration of the measurement process,
increase of the limit of measured deviations from flatness,
reduction of the dimensions of the platform and the measuring node, the content of a small number of optical-mechanical nodes,
fixation of the measuring node in the platform hole relative to the poverty points,
platforms 3 and supports with tips 4 with low temperature dependence,
removal of restrictions on the size of the measured surface, both from small and from large values (i.e., expanding the range of the measured surface,
the measured deviation of the surface from the surface flatness H = ± 15 mm, which is associated with the characteristics of the measuring length of HLM-30,
ability to automate the measurement process,
device weighs no more than 300 g,
increase of the working temperature range,
time of one measurement cycle is minimal, because memorization and data processing is automatically controlled by the control unit or on the computer,
possibility to measure not only horizontal surfaces,
reduction of the weight of the measuring unit. ■
Declaration of Competing Interest. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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