Device for measuring deviations from straightness

 

(57) Abstract:

The invention relates to measuring equipment, namely, laser interferometry, and can be used to control the deviations of the form. The technical result is greater accuracy and a wider range of measurements. The result is achieved that the device comprises a source of monochromatic radiation and optically associated angular reflector mounted on the carriage, an acoustic modulator, the collimator and the photodetector, between the input of the photodetector and the electrical input acoustic modulator cascaded system-locked loop and a delay line with a variable delay value. 1 Il.

The invention relates to measuring equipment, namely, laser interferometry, and can be used to control deviations form guide elements of machine tools and measuring instruments.

A device for controlling the straightness /1/ (analog), which consists of a monochromatic source, the collimator, the beam splitting unit, triple-prism mounted on the measuring carriage, diaphragm, acoustic modulator emitter and the ultrasonic generator display.

The disadvantage of this device is to limit the measuring range defined by the periodicity of the static characteristics of the device. The maximum value of the measuring range does not exceed the length of the ultrasonic wave

A device for measuring deviations from straightness /2/ (analog), which contains a monochromatic light source and optically associated with the collimator, the beam splitting unit, triple-prism, mounted on a measuring carriage, acoustic modulator emitter and the ultrasonic frequency generator, the afocal optical system and located in its focus two of the photodetector is electrically connected to the outputs of the two phase detectors, the second inputs of the detectors associated with the generator output ultrasonic frequency, the outputs of the detectors associated with the computing and display devices.

This device allows you to increase the measurement accuracy by eliminating the component of the error determined by the instability of the chart axis direction of the light source. But the measurement range is also less than the ultrasonic wavelength L, which is a disadvantage and limits the scope of primetrust for the implementation of the method of measuring the displacement of the object /3/ (prototype), which contains a monochromatic light source, a collimator, a beam splitter, shaper radiation, the measuring reflector, the reference reflector, the optical wedge, bounding the aperture, sitemodule, optical system, three of the photodetector, three narrow-band amplifier, fotometricheskoe device, two meter frequency electronic generator and key.

This device allows the measurement of the spatial displacement with high accuracy due to the formation of acoustoelectronic feedback (AOC) and the frequency display input lateral movement. However, measurement accuracy is a function of measurement range and improved accuracy of measurement requires a reduction of the measurement range. This measuring device is a significant disadvantage and limits its use.

The invention is directed to the achievement of the technical result, which is to improve the accuracy and extend the range.

This result is achieved in that the proposed device for measuring deviations from straightness contains a monochromatic light source and optically coupled what od collimator, a sensor with electrical outlet, between the output of the photodetector and the electrical input acoustic modulator cascaded system phase-locked loop and a delay line with a variable delay value.

Obtained a new quality from this set of features previously was not known and can only be achieved in this device.

The drawing shows a diagram of the proposed measuring device.

The device includes a monochromatic light source (laser) 1, mirror 2, the triple-prism 3, the sliding carriage 4, the acoustic modulator (AOM) 5, system 6, the collimator 7, the photodetector 8, the system phase-locked loop (PLL) 9, a line with a variable delay value signal (hereinafter delay line) 10.

The device operates as follows.

The laser light 1 is reflected from mirror 2, sent to triple-prism 3, mounted on a movable carriage 4.

Reflected from triple-prism 3, the laser beam passes through the AOM 5, where dirigeret three diffraction order E(+1), E(0) and E(-1). Collimator 7 there are two diffraction order E(+1) and E(0), spatial owls is nick keywords. optical flow leads to the appearance at the output of the photodetector 8 electric signal U1= U1mcos(2fmt +a1) This signal is fed to the input of PLL 9. The output frequency signal of the PLL 9 should the delay line 10, after which enters the electrical input of the AOM 5.

The operation of the device is as follows.

The functionality of the system PLL enable to implement this mode of operation, in which for a particular frequency range of the phase change modulator AOMcan be compensated for by changes in the phase delay lines Cin accordance with the expression

AOM+C= 0 (1)

The first component of formula (1) is determined by the offset of the laser beam relative to the system, and the expression for it can be written in the following form:

< / BR>
where LAOMchanging the distance between the laser beam and a system modulator;

vSVthe velocity distribution of ultrasonic waves.

This device before electrical input acousto-optic modulator is used, the delay line. The feature of her work is that the phase characteristic isC() depends on the frequency of the signal /4/

C() =o+C() = to-2K (3)

whereo= toon the belt component, which defines the different phase shifts for the individual spectral components of the frequency signal;

To the proportionality coefficient that depends on the internal properties of the delay line.

Equation of expression (2) and the variable component of the expression (3), we get

< / BR>
After simplifying the expression (4) This expression shows that between changes in the frequency and displacement of the laser beam there is a linear relationship.

Thus, the accuracy improvement is achieved by eliminating the nonlinear components in the expression between the output frequency and offset of the laser beam. Range expansion is implemented by changing the value of the proportionality coefficient K.

As a line with variable signal delay can be used as an electronic device, and a separate discrete elements.

As electronic devices can be used in filters (active or passive), phase-frequency characteristic which is in a certain range is a linear or quasi-linear) function of /4/.

In discrete elements with variable signal delay often use the physical phenomenon of dispersion of elastic is RSNA the delay line can be created by ultrasonic waves, and surface acoustic waves in smokeproof. In the first case, as Zvukovaya can be applied to plates of steel, aluminum and magnetic alloys, fused quartz and other materials. For the second case are typically used plates of quartz, lithium niobate /4, 5, 6/.

Sources of information used in the preparation of the description:

1. A. S. N 1464037 (USSR), class. G 01 B 11/00. Acousto-optical device for measuring deviations from linearity. Telesetsky C. I. Ignatov S. A. Yakovlev N. A. //Publ. in B. I. -1989, N 9. (similar).

2. A. S. N 1717957 (USSR), class. G 01 B 11/26. Device for measuring deviations from linearity. Telesetsky C. I. Yakovlev N. A. //Publ. in B. I. 1992, N 9. (similar).

3. A. S. N 1765691 (USSR), class. G 01 B 11/26. A method of measuring the displacement of the object. Telesetsky C. I. Yakovlev N. A. //Publ. in B. I. 1992, N 36. (prototype).

4. Baskakov, S. I. Radio circuits and signals: Textbook. for universities on special. "Radiotekh. -2nd ed. Rev. and additional M High. SHK. 1988 448 S.

5. Electronics: Encyclopedic dictionary. /CH. edit Century, Kolesnikov,) Owls. encyclopedia, 1991. 688 S.

6. A receiving device. /Under the editorship of Professor A. P. Zhukovsky, Uch. ed-E.-M. "Higher school", 1989. 342 C.

Ostrowski associated angular reflector, mounted on the carriage, acousto-optical modulator with optical and electrical inputs, a collimator, a sensor with electrical outlet, characterized in that between the output of the photodetector and the electrical input of the acousto-optic modulator cascaded system phase-locked loop and a delay line with a variable delay value.

 

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