We present the results of research of autocollimating null-indicator in the angle measurement system intended for measuring angles between normals to faces of optical polygons or mirrors. The autocollimating null-indicator is considered with analog signal processing based on its digitization and center of mass estimation. We present the results of modeling and analyze the dependence of the sampling point number and signal-to-noise ratio on the accuracy of the signal center of mass determination. The results of experimental research of the system are presented.
Rotary optical encoders are widely used in all areas of industry, robotics and special equipment. The accurate measurement of their characteristics is a necessary task for their successful implementation. The report attempts to find a unified approach to determining the accuracy of rotary encoders. The proposed approach is based on statistics, on the reliability of the code, which characterizes the probability that the measured code corresponds to the specified code. To find the reliability of the code, it is necessary to measure angle of the turn using some goniometric device and compare the measured values with the codes of encoder. The report considers the laser dynamic goniometer for determining the error of absolute angle encoders, which allows measurements in a wide range of rotation rates with high accuracy. The measurement is performed at certain moments of time, depending on the electrical interface of the encoder. In the case of a parallel interface, the moments of time are determined by the moment when the code of the encoder changes. This data collection allows to get a General set of data. In the case of an encoder, where the sequential principle of reading the code, it is not possible to receive the General set in a wide range of rotation rates. The report analyzes the situation discussed above in detail. The report presents experimental data obtained on a laser dynamic goniometer and the results of calculating the reliability of the code.
Null-indicator (NI) is an optical device setting up a reference direction in space for high-precision angle measurements by means of dynamic goniometry. During continuous rotation of the optical object under test (e.g. optical polygon or gauge) together with the angular scale the NI registers moments when reflecting faces of the object are normal to the optical axis of the NI. At these moments NI yields electronic logical pulse which triggers the readout from the angular scale. Conventionally interferometric null-indicators were considered as the most accurate, though they have few significant drawbacks. The interferometric NI is very sensitive to the quality of the reflecting surface and other factors that may bring aberrations to the NI emitted wavefront. This makes the interferometric NI suitable only for laboratory applications with test objects of high quality. Recent development has shown that autocollimating NI with digital signal processing can reach the same level of random error as the interferometric one. But during testing of the experimental model of the autocollimating NI authors have encountered systematic error that needed additional study. The encountered error was related to the adjustment of certain element of the NI optical scheme and the object under test relatively to the axis of rotation. The report presents theoretical and experimental study of the influence of aforementioned factors on the accuracy of setting the reference direction by the autocollimating NI. Also authors give recommendations on the adjustment procedure of the dynamic goniometer utilizing autocollimating NI in order to reach required measurement accuracy.
We present the results of research of the angle measurement system for direction measurements. Development of the system is based on the dynamic goniometer, whose operation is defined by continuous rotation of the platform with the autocollimating null-indicator. The measurements of angles between mirrors are provided by the null-indicator and optical encoder. The results of the system calibration with the use of standard optical polygon are presented. The computer simulation of the calibration process was carried out, and requirements to optical elements alignment accuracy were estimated.
With high demand in performances, ring laser is proposed as an angular measuring transducer, due to its many considerable advantages compared to other means of angle’s measurement, since it’s based on the physical fundamentals, methods, equation/logarithms are developed and experimental work using high precision goniometer, this paper focus on reducing the instability, zero shift, the resolving power to as low as 0.05, the technique required to determine the output frequency within angle of periods in the RL output signals in an entire rotation (2π), The output characteristics instability of scale factor (K1) and zero shift (Ko ) was observed with time and the effect of instability on the rotational velocity of RL in regard to component error in measurement was minimized, the type of RL used proved to be the square type as different values based on CW and CCW was recorded.
It became necessary for proposing a remote non–contact method to measure angular positions and movement of an objects using Laser Dynamic Goniometer (LDG) as compared with the usual Photo-electrical autocollimators with narrow range of about 1deg. This article present analysis, errors as well as experimental results of using Laser Dynamic Goniometer to measure wide range with accuracy of approximately 0.1 arcs and a possibility of measuring constant angles with accuracy of 0.005 …0.1 arcs in the range of possible angles of 15…30degrees.
The report presents the results of experimental research of the angle measurement system intended for measuring angles between normal to some mirrors setting directions in the space. Dynamic mode of system operation is defined by continuous rotation of platform with the autocollimating null-indicator. The angle measurements are provided by the holographic optical encoder. The different ways of calibration of the system is considered in the report. The results of the system calibration with the chosen method are presented.
The report presents the results of experimental research of the angle measurement system intended for measuring angles
between normal to some mirrors setting directions in the space. Dynamic mode of system operation is defined by
continuous rotation of platform with the autocollimating null-indicator. The angle measurements are provided by the
holographic optical encoder.
The dynamic laser goniometer (LG) implementation for noncontact measurements of an object’s angular position is presented. One of the possible implementations involves determining the time dependence of the scanning mirror’s angular position. Another application is aimed at determining the oscillatory movement parameters on the test table. The results obtained in the course of the research show that the dynamic LG makes it possible to calibrate various kinds of test beds making angular oscillations or angular movement of arbitrary law.
The report presents the results of analysis of the angle measurement system intended for measuring angles between some directions set in the space by reflectors. Dynamic mode of system operation is defined by continuous rotation of platform with the autocollimating null-indicator. The angle measurements are provided by the ring laser or the holographic optical encoder.
At the present time, there is a need for effective metrological control of the functional parameters of the modern rotary encoders due to their increased production level. This metrological control has to be carried out with high accuracy and high speed of operation. One of the most effective ways of solving this task is the use of dynamic goniometer (DG) jointly with an optical angle encoder and/or ring laser. The article deals with the principles of DG construction and considers the methods and results of DG investigation for the rotary encoder calibration as well as the elimination procedure of various types of DG uncertainties. The article shows that application of the proposed procedure allows to reduce the level of DG uncertainty to 0.2 arcsec, which ensures the uncertainty value of the rotary encoder metrological control by the means of DG to within 0.05 arcsec in a wide range of angular velocities.
The report presents results of implementation of the dynamic laser goniometer in the mode of non-contact measurements
of an object’s angular position. One of obtained results is connected with determination of the time dependence of the
scanning mirror angular position. Another kind of implementation result is determination of parameters of a test table
oscillatory movement. The obtained results shows that the use of the LG makes it possible to calibrate various kinds of
test-beds making angular oscillations or angular movement of some other law.
Due to the increase in production of the angle transducers characterized by high accuracy and high speed of operation , there arises a need for metrological control of their function parameters. This challenge can be successfully met involving the dynamic goniometer systems (DG), which consist of the optical angle encoder (OAE) or the ring laser (RL) .
The dynamic laser goniometer systems , the scale of which is produced by the ring laser, can be successfully used for calibration of the angle encoders. The ring laser operating in the mode of the angle measurement during its rotation has a number of undeniable advantages, such as high degree of uniformity and potential accuracy. However, alongside with the advantages it has several limitations, such as the measurement error increase at low rotation velocity values and instability of the angular scale factor . Integrating the ring laser and the optical angle sensor, the angular scale of which is characterized by a considerably lower uniformity, but a greater degree of stability, provides for the studying of the metrological characteristics of the dynamic goniometer, expansion of the range or its angular operation velocity and its operation in static mode. The articles covers the issues of constructing the dynamic goniometer for calibration of angle encoders as well as the methods and results of its studies.
The results of analysis and experimental investigation of a laser goniometer (LG), working in the mode of the noncontact measurement of an object’s angular position, are presented. The important feature of this approach is the very wide range of high-accuracy measurements. In this case, the LG, characterized by the accuracy of ∼0.1 arc sec, has big advantages in comparison to photoelectrical autocollimators which have a rather narrow range of measured angular positions. Our results indicate that the use of a laser dynamic goniometer makes it possible to measure constant angles with an accuracy of 0.05 to 0.1 arc sec in the range of possible angles of 15 to 20 deg. If the measured angle is varying, the residual measurement error contains an additional component, which is equal to ∼0.2 arc sec, induced by the nonflatness of the optical polygon’s faces and by the problems with statistical averaging of the measurement results.
Now more and more digital optical rotary encoders with a serial output code are widely adopted. In this regard there is a
need of an assessment of precision characteristics of such converters.
As means of calibration and checking of such sensors the dynamic laser goniometer with the ring laser as a reference
angular sensor is used.
In the report the technique of an estimation of precision characteristics of angular optical encoders with a serial output
code is considered.
The report presents results of analysis and experimental research of the laser goniometer in the mode of operation – noncontact
measurements of an object’s angular position. An important feature of this mode is an extremely large range of
measurement with high accuracy. With the usual resolution of about 0,1 arcs the laser goniometer has in this mode of
operation an essential advantage against photo-electric autocollimators with their rather small measuring range. Obtained
results confirm that the laser dynamic goniometer using in the mode of non-contact measurement of an object’s angular
position can be characterized by the range of angle measurements up to 15…20 deg and accuracy of constant angles on
the level 0,05…0,1 arcs. The error of angles changing in time has additional components on the level of 0,2 arcs
connected with influence of optical polygon face unflatness and difficulties of use the statistical averaging of
The report describes the laser goniometer intended for calibration of a circular optical encoders. This is one of the most perspective systems based on the rotating ring laser. This system provides the calibration of every line of optical encoder even if number of lines achieves one hundred thousands or more. The system operates in fully automate mode and calibration procedure takes very small time. The accuracy of calibration is on the level of 0,1 arcs. The rotation rate range is up to 5...10 revolutions per second. The important feature of the system is ability to measure dynamic error of optical encoder. The schematic of the system, analysis of errors, examples of implementation are considered in the report. The important part of the report is devoted to metrological support of calibration of an optical encoders. The angle standard based on the ring laser and the holographic optical encoder with systematic error on the level of 0,01 arcs is described also in the report.