CN101793909B - Novel grating accelerometer - Google Patents

Abstract

The embodiment of the invention provides a novel grating accelerometer, which can form multiple-beam interference between a grating gap and two reflectors by arranging a reflector on the bottom of a sensitive mass block and also arranging a reflector on the bottom of a grating. Therefore, by improving the optical structure of the accelerometer, the optical sensitivity is improved so as to improve the measuring accuracy of the accelerometer, reduce the requirement for the sensitivity of the mechanical structure of the accelerometer, be beneficial for improving the natural frequency and the impact resistance of the mechanical structure and reduce the processing difficulty of the accelerometer.

Description

A kind of novel grating accelerometer

Technical field

The present invention relates to the accelerometer field, relate in particular to a kind of novel grating accelerometer.

Background technology

At present, accelerometer is a kind of important mechanics sensor, has a wide range of applications at aspects such as traffic, military affairs, geographical detections, along with the application of optical means on measurement micrometric displacement and micro-acceleration, make the sensitivity of accelerometer break away from the restriction of electric capacity, be greatly improved.

In the prior art, grating accelerometer is based on light intensity type grating displacement sensor, its primary element is light source, grating sensing head and photo-electric conversion element, its principle of work is: when acceleration acts on the vibrating diaphragm of grating accelerometer, the chamber long hair is given birth to and is changed, thereby changes the inferior light intensity of detected level; Then by the test to light intensity, sense acceleration.Be illustrated in figure 1 as the implementation structure synoptic diagram of grating accelerometer in the prior art, among Fig. 1: on transparent substrates, make the conduction grating; Conductive film forms the phase sensitive grating as reflecting surface; When light beam incides on the conduction grating, conductive film and conduction grating reflect incident light respectively, and interference forms diffracted beam, the intensity of light beam and conductive film become sine or cosine relation with displacement with reference to broach, just can realize detection to micro-displacement or acceleration by this grating accelerometer.

But in the above-mentioned prior art constructions, because in space change, reflecting surface meeting run-off the straight or flexural deformation can have influence on the quality of diffraction pattern, thereby reduce the measuring accuracy of accelerometer; Simultaneously owing to need reach very high sensitivity, sensitivity requirement to physical construction is very high, causes the natural frequency of physical construction to reduce easily, has reduced the frequency range of test, also reduce the stability and the impact resistance of physical construction simultaneously, increased difficulty of processing.

Summary of the invention

The embodiment of the invention provides a kind of novel grating accelerometer, can improve the optical texture of accelerometer, improves optical sensitivity, thereby has improved the measuring accuracy of accelerometer; And reduced requirement to the sensitivity of accelerometer physical construction, help the natural frequency and the impact resistance of elevating gear structure, and then reduced the difficulty of processing of accelerometer.

The embodiment of the invention provides a kind of novel grating accelerometer, and the sensing head optical texture of described accelerometer partly comprises: responsive mass and grating, wherein:

Be provided with catoptron in described responsive mass bottom, and also be provided with catoptron, between described grating gap and two-layer catoptron, to form multiple-beam interference in described grating bottom.

Describedly also be provided with catoptron, specifically comprise in described grating bottom:

Increase the layer of metal film in the bottom of described grating, with described metallic film as time catoptron.

Described responsive mass adopts the beam with both ends fixed structure.

The catoptron that is provided with in described grating bottom adopts highly reflective material, to improve described acceleration measuring accuracy of measurement.

By the above-mentioned technical scheme that provides as can be seen, by being provided with catoptron, and also be provided with catoptron, just can between described grating gap and two-layer catoptron, form multiple-beam interference in described grating bottom in described responsive mass bottom.By improving the optical texture of accelerometer, improved optical sensitivity, thereby improved the measuring accuracy of accelerometer like this; And then reduced requirement to the sensitivity of accelerometer physical construction, and help the natural frequency and the impact resistance of elevating gear structure, reduced the difficulty of processing of accelerometer.

Description of drawings

Fig. 1 is the implementation structure synoptic diagram of grating accelerometer in the prior art;

Fig. 2 is the structural representation of novel grating accelerometer that the embodiment of the invention provides;

Fig. 3 be in the embodiment of the invention reflectivity to the synoptic diagram of light intensity variable effect;

Fig. 4 is the relation curve synoptic diagram of reflectivity and acceleration measuring accuracy of measurement in the embodiment of the invention;

Fig. 5 is the one-level light intensity curve during different reflectivity in the embodiment of the invention.

Embodiment

The embodiment of the invention provides a kind of novel grating accelerometer, improve by optical texture traditional grating displacement sensor, be provided with catoptron in described responsive mass bottom, and also be provided with catoptron in described grating bottom, between described grating gap and two-layer catoptron, form multiple-beam interference.So just can improve the optical texture of accelerometer, improve optical sensitivity, thereby improve the measuring accuracy of accelerometer.

For better describing the embodiment of the invention, now in conjunction with the accompanying drawings specific embodiments of the invention are described, be illustrated in figure 2 as the structural representation of novel grating accelerometer that the embodiment of the invention provides, among Fig. 2:

The sensing head optical texture of grating accelerometer partly includes responsive mass and grating, and wherein: be provided with catoptron in described responsive mass bottom, be called upper reflector, this upper reflector is a completely reflecting mirror, and reflectivity is fixed; Simultaneously, also be provided with catoptron in described grating bottom, be called catoptron down, the reflectivity R of this catoptron is variable, in order to adjust the optical sensitivity of accelerometer; By above-mentioned setting, between described grating gap and two-layer catoptron, to form multiple-beam interference.

In the specific implementation process, the mode that catoptron is set in the grating bottom can be to increase the layer of metal film in the bottom of grating, as following catoptron, the metallic film here can be the conducting medium film of various reflectivity with this metallic film, for example silver foil film etc.; In addition, above-mentioned responsive mass can adopt the structural design of beam with both ends fixed.

Describe as follows to the course of work of the accelerometer of structure as shown in Figure 2 below: light source is from grating bottom incident, and light beam is behind the bottom reflection mirror, and a part of light is by optical grating reflection; Another part is the space process multipath reflection between following catoptron and upper reflector then; This two parts light is interfered again, forms the diffraction fringe of multilevel.According to the Film Optics theory, obtain easily the reflectivity of amplitude being respectively as 1 district among Fig. 2 and 2 districts:

${\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="HSA00000030665800011.png,HSA00000030665800012.png"\; state="\{\{state\}\}">r</figure-callout>}}_1=\frac{\sqrt{R}+\exp (-i{\mathrm{\&phi;}}_0)}{1+\sqrt{R}\exp (-i{\mathrm{\&phi;}}_0)}$

r ₂＝1

${\mathrm{\&phi;}}_0=\frac{4\mathrm{\&pi;}}{\mathrm{\&lambda;}}{d}_c$

Wherein, R is the reflectivity of the set following catoptron in grating bottom, and dc is long for the air chamber chamber, and λ is an optical source wavelength.

Light distribution with multilevel diffraction fringe is considered as stitching wide a of being respectively and b then, and grating constant is the stack of two grating diffration stripeds of d, and according to the physical optics principle, and obtaining stitching wide is that the distribution of amplitudes of grating on screen of d is for a, grating constant:

${\mathrm{<figure-callout\; id="1"\; label="E"\; filenames="HSA00000030665800011.png,HSA00000030665800012.png"\; state="\{\{state\}\}">E</figure-callout>}}_1^{\%}\left(p\right)=A\&CenterDot;\frac{\sqrt{R}+\exp (-i{\mathrm{\&phi;}}_0)}{1+\sqrt{R}\exp (-i{\mathrm{\&phi;}}_0)}\&CenterDot;\left(\frac{\sin \mathrm{\&alpha;}}{\mathrm{\&alpha;}}\right)\left(\frac{\sin \frac{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000030665800012.png,HSA00000030665800021.png"\; state="\{\{state\}\}">N</figure-callout>}}{2}\mathrm{\&delta;}}{\sin \frac{\mathrm{\&delta;}}{2}}\right)\exp \left[i(N-1)\frac{\mathrm{\&delta;}}{2}\right]$

And stitch the wide b that is, grating constant is that the distribution of amplitudes of grating on screen of d is:

${\mathrm{<figure-callout\; id="2"\; label="E"\; filenames="HSA00000030665800012.png,HSA00000030665800021.png"\; state="\{\{state\}\}">E</figure-callout>}}_2^{\%}\left(p\right)=A\&CenterDot;\left(\frac{\sin \mathrm{\&beta;}}{\mathrm{\&beta;}}\right)\left(\frac{\sin \frac{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000030665800012.png,HSA00000030665800021.png"\; state="\{\{state\}\}">N</figure-callout>}}{2}\mathrm{\&delta;}}{\sin \frac{\mathrm{\&delta;}}{2}}\right)\exp \left[i(N-1)\frac{\mathrm{\&delta;}}{2}\right]$

In the following formula:

$\mathrm{\&alpha;}=\frac{\mathrm{\&pi;}}{\mathrm{\&lambda;}}\&CenterDot;a\&CenterDot;\sin \mathrm{\&theta;}$

$\mathrm{\&beta;}=\frac{\mathrm{\&pi;}}{\mathrm{\&lambda;}}\&CenterDot;b\&CenterDot;\sin \mathrm{\&theta;}$

$\mathrm{\&delta;}=\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}d\&CenterDot;\sin \mathrm{\&theta;}$

θ wherein is an angle of diffraction.

Again above-mentioned diffraction light is carried out the amplitude stack, obtains total light amplitude and distribute:

$E^{\%}\left(p\right)=A\left(\frac{\sin \frac{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000030665800012.png,HSA00000030665800021.png"\; state="\{\{state\}\}">N</figure-callout>}}{2}\mathrm{\&sigma;}}{\sin \frac{\mathrm{\&sigma;}}{2}}\right)\exp \left[i(N-1)\frac{\mathrm{\&sigma;}}{2}\right]\frac{1}{(1+R+2\sqrt{R}\cos {\mathrm{\&phi;}}_0)}\&CenterDot;$

$[-i\sin {\mathrm{\&phi;}}_0(1-R)\frac{\sin \mathrm{\&alpha;}}{\mathrm{\&alpha;}}+(2\sqrt{R}+\cos {\mathrm{\&phi;}}_0+R\cos {\mathrm{\&phi;}}_0)\frac{\sin \mathrm{\&alpha;}}{\mathrm{\&alpha;}}$

$+(1+R+2\sqrt{R}\cos {\mathrm{\&phi;}}_0)\frac{\sin \mathrm{\&beta;}}{\underset{\&OverBar;}{\mathrm{\&beta;}}}]$

And the light distribution expression formula is:

$I=A^2{\left(\frac{\sin \frac{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000030665800012.png,HSA00000030665800021.png"\; state="\{\{state\}\}">N</figure-callout>}}{2}\mathrm{\&sigma;}}{\sin \frac{\mathrm{\&sigma;}}{2}}\right)}^2\frac{1}{{(1+R+2\sqrt{R}\cos {\mathrm{\&phi;}}_0)}^2}\{{\left[\sin {\mathrm{\&phi;}}_0(1-R)\frac{\sin \mathrm{\&alpha;}}{\mathrm{\&alpha;}}\right]}^2$

$+{[(2\sqrt{R}+\cos {\mathrm{\&phi;}}_0+R\cos {\mathrm{\&phi;}}_0)\frac{\sin \mathrm{\&alpha;}}{\mathrm{\&alpha;}}+(1+R+2\sqrt{R}\cos {\mathrm{\&phi;}}_0)\frac{\sin \mathrm{\&beta;}}{\mathrm{\&beta;}}]}^2\}$

When grating grid facewidth degree is that two of grating constant d/for the moment, the light distribution expression formula can be reduced to:

$I\left(m\right)=\frac{1}{2}{\left(\frac{\sin \left(\frac{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="HSA00000030665800012.png,HSA00000030665800021.png"\; state="\{\{state\}\}">m</figure-callout>}}{2}\mathrm{\&pi;}\right)}{\frac{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="HSA00000030665800012.png,HSA00000030665800021.png"\; state="\{\{state\}\}">m</figure-callout>}}{2}\mathrm{\&pi;}}\right)}^2[1+{(-1)}^m\cos \left(2{\tan }^{-1}\left(\frac{1-\sqrt{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="HSA00000030665800011.png,HSA00000030665800012.png"\; state="\{\{state\}\}">R</figure-callout>}}}{1+\sqrt{R}}\tan \frac{{\mathrm{\&phi;}}_0}{2}\right)\right)]$

Wherein, m is that the order of diffraction is inferior.

Light distribution expression formula according to following formula, the following catoptron of design different reflectivity is illustrated in figure 3 as in the embodiment of the invention reflectivity to the synoptic diagram of light intensity variable effect, among Fig. 3: from top to bottom, be respectively reflectivity R and be 0.9,0.7,0.2 and 0 o'clock light intensity curve; As seen from Figure 3, reflectivity is high more, and light intensity curve is precipitous more, and the sensitivity of accelerometer is just high more.

Be illustrated in figure 4 as the relation curve synoptic diagram of reflectivity and acceleration measuring accuracy of measurement in the embodiment of the invention, by among Fig. 4 as can be known: at reflectivity is the measuring accuracy that 0.8 measuring accuracy and reflectivity are at 0 o'clock, improve nearly 20 times, increased the precision of accelerometer measures greatly.

By the optical texture of the described accelerometer of the foregoing description, just can improve optical sensitivity, thereby improve the measuring accuracy of accelerometer; And then reduced requirement to the sensitivity of accelerometer physical construction, and help the natural frequency and the impact resistance of elevating gear structure, reduced the difficulty of processing of accelerometer.

For instance, come above-mentioned novel grating accelerometer is verified that in this instantiation: adopt JDW-3 type laser instrument as light source, luminous power is 5mw, and wavelength is 635nm, by constant current driven below with concrete operational instances; It is 10 microns grating that grating adopts two sheet gration constants, and sheet gration bottom evaporation one deck semi-transparent metals film as under catoptron; The moving part of accelerometer is replaced by the catoptron that is fixed on the fine adjustment stage; The degree of regulation of fine adjustment stage is 0.2667 μ m/V; Utilize the distance between this fine adjustment stage accommodation reflex mirror and the grating, utilize the OPHIR light power meter one-level light intensity to be tested record data; According to the light intensity data that records, light intensity curve is drawn, the one-level light intensity curve when obtaining different reflectivity, as shown in Figure 5.

By above-mentioned experimentation, observed the significant change phenomenon that the one-level light intensity produces along with the long change in chamber, but because the influence of vibration, light intensity curve has certain fluctuation.Change curve from Fig. 5 is as can be known: reflectivity R is respectively 0 and 0.5 light intensity curve as can be seen, when reflectivity is 0.5, light intensity curve than reflectivity be 0 o'clock more precipitous, thereby improved the sensitivity of sensor optics structure, and then improved the measuring accuracy of accelerometer, verified the correctness of the described novel grating accelerometer of the embodiment of the invention.

In sum, the embodiment of the invention can be improved the optical texture of accelerometer, improves optical sensitivity, thereby has improved the measuring accuracy of accelerometer; And then reduced requirement to the sensitivity of accelerometer physical construction, and help the natural frequency and the impact resistance of elevating gear structure, reduced the difficulty of processing of accelerometer.

The above; only for the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, and anyly is familiar with those skilled in the art in the technical scope that the present invention discloses; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection domain of claims.

Claims (4)

1. a novel grating accelerometer is characterized in that, the sensing head optical texture of described accelerometer partly comprises: responsive mass and grating, wherein:

Be provided with catoptron in described responsive mass bottom, and also be provided with catoptron, between described grating gap and two-layer catoptron, to form multiple-beam interference in described grating bottom.

2. accelerometer as claimed in claim 1 is characterized in that, describedly also is provided with catoptron in described grating bottom, specifically comprises:

Increase the layer of metal film in the bottom of described grating, with described metallic film as catoptron.

3. accelerometer as claimed in claim 1 is characterized in that, described responsive mass adopts the beam with both ends fixed structure.

4. as one of them described accelerometer of claim 1-3, it is characterized in that the catoptron that is provided with in described grating bottom adopts highly reflective material, to improve described acceleration measuring accuracy of measurement.

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