CN102589446A - High precision micro-displacement measurement apparatus and method - Google Patents

Abstract

The invention discloses a high precision micro-displacement measurement apparatus. The apparatus includes a housing; and a light source and gratings are successively arranged along an optical path in the housing, wherein the gratings are slidably installed in the housing along an optical axis direction. Besides, piezoelectric ceramics parts are also arranged; one sides of the piezoelectric ceramics parts are attached with the surfaces of the gratings; and the other sides of the piezoelectric ceramics parts are relatively fixed with the housing. Spacing between the gratings and a to-be-measured object can be adjusted by controlling shape variables of the piezoelectric ceramics parts themselves; therefore, light intensity change rates at all level directions can reach maximum values near the spacing, wherein the light intensity change rates are obtained by interferences of light beams directly reflected by the gratings and the light beam reflected by the reflecting surface of the to-be-measured object, so that the micro-displacement value of the to-be-measured object can be amplified by the light intensity variation. Compared with the current micro-displacement sensor, the provided micro-displacement measurement apparatus enables measurement precision to be improved.

Description

A high-precision micro-displacement measuring device and method

technical field

The invention relates to a high-precision micro-displacement measuring device and method, in particular to a piezoelectric ceramic-based micro-displacement measuring device and method for adjusting measurement accuracy.

Background technique

As an important part of the sensor field, the displacement sensor can be used to accurately measure the position and displacement changes of the measured object. It is mainly used to measure the displacement, thickness, vibration, distance, diameter and other geometric quantities of the object. It has broad application prospects in the military field.

In existing reports, displacement sensors are mainly divided into inductive displacement sensors, capacitive displacement sensors, photoelectric displacement sensors, ultrasonic displacement sensors, and Hall displacement sensors. Although there are many types, the displacement accuracy of the existing displacement sensors can only reach the nanometer level at the highest, so it plays a restrictive role in some aspects that require high-precision displacement measurement.

Fig. 1 is a micro-displacement sensor in the prior art, the object to be measured 1 is connected with the reflective surface 2, the light beam emitted by the light source 3 is reflected by the grating 4 and the reflective surface 2 respectively, and the two reflected light beams interfere, and the interference light beam The light intensity is detected by the photodetection device 5, and the distance between the object 1 and the grating 4 is changed by electrostatic attraction. When the distance between the two changes, correspondingly, the photodetection module 5 detects The light intensity information of the received coherent beam will also change accordingly, and the displacement of the object under test 1 can be calculated by analyzing the change of the light intensity information.

Contents of the invention

The invention proposes a high-precision micro-displacement measuring device aiming at the problem of low measurement accuracy existing in the micro-displacement sensor in the prior art.

A high-precision micro-displacement measuring device, including a housing, the housing is provided with a light source and a grating sequentially arranged along the optical path, the grating is slidably installed in the housing along the optical axis, and a piezoelectric ceramic component is also provided. One side of the piezoelectric ceramic component is attached to the surface of the grating, and the other side is relatively fixed to the shell.

With the micro-displacement measuring device with the above structure, after the beam emitted by the light source is reflected by the grating and the object to be measured, an interference beam is formed on the side of the grating facing the light source, and the piezoelectric ceramic component is driven by its own deformation and The connected grating moves along the optical axis to adjust the distance between the grating and the object to be measured. When the distance between the grating and the object to be measured is kept at a certain value, the small displacement of the object to be measured can cause the interference The light intensity change in each order direction of the beam is the largest, resulting in the largest light intensity difference. According to the light intensity difference, the small displacement of the object to be measured can be calculated, that is, the small displacement to be measured is passed through the light intensity. The difference is amplified, and a small displacement value can be obtained by detecting the value of the light intensity.

The piezoelectric ceramic component is an annular component whose center corresponds to the optical path and has two electrodes. The annular structure allows the light beam passing through the grating to pass without affecting the propagation of the light beam.

The micro-displacement measuring device is provided with: a piezoelectric ceramic drive module for driving deformation of piezoelectric ceramic components; a photoelectric detection module for detecting the light intensity of an interference beam, and the interference beam is a beam reflected by a grating and The light beam reflected by the object to be tested is formed by interference; it is used to control the signal processing module of the piezoelectric ceramic driving module according to the signal of the photoelectric detection module.

The two electrodes of the piezoelectric ceramic component are respectively connected to corresponding interfaces of the piezoelectric ceramic drive module.

In the high-precision micro-displacement measuring device of the present invention, both the photoelectric detection module and the piezoelectric ceramic driving module are connected to the signal processing module, and the signal processing module changes the deformation of the piezoelectric ceramic component by controlling the piezoelectric ceramic driving module on the one hand, and the other On the one hand, it is used to receive the information collected by the photoelectric detection module. The signal processing module analyzes the information fed back by the photoelectric detection module and the distance between the grating and the object to be measured, and controls the piezoelectric ceramic drive module to drive the piezoelectric ceramic to adjust the grating and reflection. The distance between the surfaces applies a modulation signal of a certain frequency and amplitude to the piezoelectric ceramics at the same time, and the displacement of the measured surface can be accurately obtained by applying lock-in amplification to the detection signal.

The present invention also provides a high-precision micro-displacement measurement method, comprising the following steps:

(1) The light beam emitted by the light source passes through the grating and is projected onto the reflective surface of the object to be measured;

(2) The diffracted beam reflected by the grating interferes with the diffracted beam of the same order generated by the grating reflected by the reflective surface;

(3) Use the modulation voltage to drive the piezoelectric ceramic components to generate phase modulation signals, and perform phase-locked amplification processing on the light intensity signal of the interference beam detected by the detector to calculate the displacement of the object to be measured.

The key of the method of the present invention is that, before starting the measurement, the piezoelectric ceramics itself deforms to drive the grating connected to it to move axially until the initial distance between the grating and the reflective surface of the object to be measured is an odd number of λ/8 times, λ is the wavelength of the light beam emitted by the light source, because the light intensity of each order of the interference beam will change with the distance between the grating and the emitting surface of the object to be measured, such as the light intensity expression of the first-order diffracted light The formula is: I=(4I _in /π ² )×sin ² (2πd/λ), where I _in and λ are the light intensity and wavelength of the light beam emitted by the light source, and d is the distance between the grating and the reflective surface of the object to be measured , and the change of the intensity I of the first-order diffracted light to the distance d can be expressed as:

$<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; /</span><span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; 8</span>}\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; \&pi;\&lambda;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; \&pi;d</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>$

When d is an odd multiple of λ/8, is the maximum, that is, the rate of change of the detected light intensity is the largest, so that the small displacement is amplified by the change of light intensity, and the small displacement can be indirectly measured by measuring the light intensity.

In the present invention, a piezoelectric ceramic component is arranged between the shell and the grating, and the distance between the grating and the reflective surface of the object to be measured is adjusted by controlling the deformation of the piezoelectric ceramic itself. When the distance is controlled at a certain fixed value, the measured The unit displacement of the object can lead to the largest change in light intensity in each order direction of the interference beam. By detecting the change in light intensity and performing lock-in amplification processing on the detection signal, the displacement of the measured surface can be accurately obtained. Compared with the micro-displacement sensor in the prior art, the invention improves the measurement sensitivity.

Description of drawings

Fig. 1 is a schematic structural diagram of a micro-displacement sensor in the prior art;

Fig. 2 is the structural representation of micro-displacement measuring device of the present invention;

Fig. 3 is a schematic structural view of the piezoelectric ceramic component of the present invention.

Detailed ways

An embodiment of the present invention will be described below with reference to the accompanying drawings.

Figure 2 is a structural schematic diagram of a high-precision micro-displacement measuring device of the present invention, including a housing 6, which is provided with a light source 3 and a grating 4 sequentially arranged along the optical path, and the grating 4 is slidably installed on the housing 6 along the optical axis direction Inside, there is also a piezoelectric ceramic component 7 , one side of the piezoelectric ceramic component 7 is attached to the surface of the grating 4 , and the other side is relatively fixed to the housing 6 .

As shown in FIG. 3 , the piezoelectric ceramic component 7 is ring-shaped, and the middle part is a light-transmitting hole to allow the light beam emitted by the light source to pass through.

Quartz glass 8 is arranged on the surface of the grating 4 facing the light source 3, and the piezoelectric ceramic component 7 applies voltage to the two electrodes of the piezoelectric ceramic component 7 through the piezoelectric ceramic drive module 9 connected to it to control the piezoelectric ceramic component. The amount of deformation of the component 7; when the light beam from the light source 3 is incident on the grating 4, a part of the light is directly reflected by the grating 4; the other part is irradiated to the reflective surface 2 through the gap of the grating 4 and then reflected back. Interference occurs on one side of the interference beam to form an interference beam. A photodetection module 5 is arranged on each order direction of the interference beam to detect the light intensity of the interference beam and transmit the detected light intensity information to the signal processing unit connected to it. module 10 , the signal processing module 10 simultaneously controls the piezoelectric ceramic driving module 9 and indirectly controls the deformation of the piezoelectric ceramic component 7 .

The specific measurement steps are as follows: first, turn on the light source 3, and the light beam emitted by the light source 3 passes through the quartz glass 8, the grating 4, and the piezoelectric ceramic component 7 in sequence, and then is projected onto the reflective surface 2 of the object under test 1, and the piezoelectric beam is controlled by the signal processing module 10. The ceramic drive module 9 is used to adjust the voltage applied by the piezoelectric ceramic drive module 9 to the two electrodes of the piezoelectric ceramic component 7, to change the deformation of the piezoelectric ceramic component 7, and to drive the grating 4 to move along the optical axis, so that The distance between the grating 4 and the reflective surface 2 of the object to be measured 1 is λ/8, where λ is the wavelength of the light beam emitted by the light source, and record the light intensity value of the first-order diffracted light of the interference beam detected by the photoelectric detection module 5 at this time, and then adjust The position of the object to be measured 1, so that it produces a small displacement along the optical axis, and record the light intensity value of the first-order diffracted light of the interference beam again. Through phase-locked amplification and differential processing, higher measurement accuracy can be obtained. By comparing before and after The light intensity value twice can be calculated to obtain the tiny displacement value to be measured.

The grating 4 used in the embodiment of the present invention is made of metal with a period of 2 μm; the present invention uses a ceramic-glass bonding process to combine the metal grating on the quartz glass 8 with piezoelectric ceramics to make a sensitive component for measurement. Specifically, it is realized by the following contents: firstly, a metal thin film of chromium Cr is plated on one side of the quartz glass 8, and a metal grating is fabricated by electron beam exposure. Then, the grating 4 and the piezoelectric ceramic part 7 are combined into an integral part by a bonding process. The reflective surface 2 is a plane reflective surface with a certain reflectivity.

The light source 3 adopted in the embodiment of the present invention is a vertical cavity surface-emitting laser with a power of 1mW and a wavelength of 850nm, driven by a constant power circuit; the photodetector device 5 adopts a photodiode, and the minimum detectable photocurrent is 0.1nA, and the response sensitivity 0.6A/W. The present invention uses piezoelectric ceramic components to change the distance between the grating and the object to be measured, so that when the distance takes a certain value, the change rate of light intensity is the largest, and detects the small displacement caused by the object to be measured near this value. The change amount of light intensity, the micro-displacement measuring device and method of the present invention improve the detection accuracy.

Claims (4)

1. high-precision micro displacement measurement mechanism; Comprise shell (6); Be provided with light source (3) and the grating (4) arranged successively along light path in the shell (6), it is characterized in that: described grating (4) slidably is installed in the shell (6) along optical axis direction, also is provided with piezoelectric ceramic part (7); The surface of these piezoelectric ceramic part (7) one sides and described grating (4) fits, opposite side and shell (6) relative fixed.

2. high-precision micro displacement measurement mechanism according to claim 1 is characterized in that, described piezoelectric ceramic part (7) is the center annular element corresponding with light path and has two electrodes.

3. high-precision micro displacement measurement mechanism according to claim 1 is characterized in that, is provided with:

Be used to drive the Piezoelectric Ceramic module (9) of piezoelectric ceramic part (7) deformation;

Be used to detect the photodetection module (5) of interfering beam light intensity, described interfering beam is for to interfere formation by grating (4) beam reflected with by determinand (1) beam reflected;

Be used for controlling the signal processing module (10) of Piezoelectric Ceramic module (9) according to the signal of photodetection module (5).

4. a high-precision micro displacement measuring method is characterized in that, may further comprise the steps:

(1) the light source outgoing beam is through projecting the reflecting surface of determinand behind the grating;

(2) interfered through time diffracted beam at the same level that grating produces by the diffracted beam of optical grating reflection and the face reflection that is reflected;

(3) utilize modulation voltage to drive piezoelectric ceramic part and produce a position phase modulation signal, the light intensity signal of the interfering beam that detector is surveyed advances the displacement that the horizontal lock processing and amplifying calculates determinand.

Images