CN103438805A - Refraction-amplifying optical displacement sensor - Google Patents

Abstract

The invention belongs to the technical field of optical displacement measurement and relates to a refraction-amplifying optical displacement sensor. In the prior art, a micro-force elastic element and a movable plane mirror are connected through a connecting rod, and the contact type measurement is low in measuring accuracy. The refraction-amplifying optical displacement sensor comprises a laser light source and a PSD, a refraction amplifying triple prism is arranged between the laser light source and the PSD, the optical axis of the laser light source is spatially perpendicular to the axis of the refraction amplifying triple prism, the incidence angle a for measuring light emitted by the laser light source to irradiate into the refraction amplifying triple prism is larger than or equal to 70 degrees and smaller than 90 degrees, and a light sensing face of the PSD is perpendicular to the measuring light emitted from the refraction amplifying triple prism. The displacement D to be tested is amplified a plurality of times by the refraction amplifying triple prism, so that the requirements for the resolution ratio of the PSD are obviously reduced, and the ordinary resolution ratio can meet the requirements. In a measuring process, the refraction-amplifying optical displacement sensor is not in contact with the surface of the micro-force elastic element to be tested, so that the reduction of the measuring accuracy caused by mechanical connection is avoided.

Description

Optical displacement sensor is amplified in refraction

Technical field

The present invention relates to a kind of refraction and amplify optical displacement sensor, small displacement is amplified and obtains the displacement value by light refraction, realize the high-acruracy survey of micro-nano displacement, simultaneously, do not require that used photo electric sensitive element has high resolving power, therefore, the characteristics that optical displacement sensor has low price when realizing high-acruracy survey are amplified in the present invention's refraction, belong to the optical displacement measurement technical field.

Technical background

Due to the microminaturization of engineering goods and parts, require MEMS (micro electro mechanical system) (MEMS) size small, by mechanical property, the kinetic characteristic of studying these micro mechanisms, can provide foundation for manufacturing good MEMS (micro electro mechanical system).Wherein, the friction and wear characteristic of understanding MEMS (micro electro mechanical system) is particularly important, prior art adopts micro-power flexible member to detect micro-friction, first adopt displacement measuring technology to measure the deflection of micro-power flexible member, then calculate micro-friction according to the deflection of micro-power flexible member and the relation of micro-friction.

Described displacement measuring technology is exactly but that displacement is converted to other measuring amount that definite relation is arranged with it.

The existing optical displacement measurement method that can measure micro-nano displacement is divided into interferometric method and diffraction approach two classes, and the device used is interferometer and diffractometer, but these apparatus structures are complicated, expensive, and measurement environment is required harsh.

In addition, adopt photo electric sensitive element also can realize the measurement of micro-nano displacement.For example, one piece of publication in " optics and engineering " the 4th the 2nd phase of volume, the article that is entitled as " the micro-displacement research based on PSD " discloses a kind of scheme of relevant micro-nano displacement measurement.The measurement mechanism that this scheme is used is by LASER Light Source, determine level crossing, moving level crossing, the PSD(position sensitive detector) composition such as, this scheme is according to the optical lever principle, by a connecting rod, micro-power flexible member and moving level crossing are coupled together, when elastic deformation occurs, micro-power flexible member surface deforms, cause that moving level crossing angle changes, measure light and determining level crossing, Multi reflection between moving level crossing, on PSD, obvious displacement occurs in hot spot, in this course, measurement mechanism not only changes angle to be converted into the change in location of hot spot on PSD, obtain displacement, and amplify.Detect the elastic deformation front and back occur by PSD, measure the change in location of light hot spot on PSD, by the relation of spot displacement amount and angle and the relation of angle and the surface deformation of micro-power flexible member, calculate the deflection on micro-power flexible member surface.Although that this measurement mechanism uses is not high-resolution PSD, but common resolution PSD, is that right, measuring accuracy is still higher.But, in this scheme, micro-power flexible member is connected by a connecting rod with moving level crossing, visible, this measurement scheme belongs to contact type measurement, and micro-power elastic element structure precision, contact type measurement will impact micro-power flexible member self stress deformation effect, can reduce measuring accuracy.

Summary of the invention

In order further to improve the measuring accuracy of micro-power deformation of elastic element, use the PSD of common resolution simultaneously, we have invented a kind of refraction and have amplified optical displacement sensor.

In optical displacement sensor is amplified in the present invention's refraction, LASER Light Source 1 and PSD9 are arranged, it is characterized in that, as shown in Figure 1 and Figure 2, refraction is amplified prism 6 on the reflected light path between LASER Light Source 1 and PSD9, LASER Light Source 1 optical axis is vertical with refraction amplification prism 6 axial spaces, the incident angle a that prism 6 is amplified in the measurement light incident refraction that LASER Light Source 1 is sent is more than or equal to 70 °, is less than 90 °, and the PSD9 light-sensitive surface is vertical with the measurement light that amplifies prism 6 outgoing from refraction.

Its technique effect of the present invention is, the measurement illumination of LASER Light Source 1 emission is mapped to micro-power flexible member surface 5, be reflected and amplify with incident angle a incident refraction a minute surface of prism 6, amplified after prism 6 reflects the light-sensitive surface that shines PSD9 by refraction, obtain thus a positional information.After micro-power flexible member generation elastic deformation, micro-power flexible member surface 5 is subjected to displacement D, and as shown in Figure 1, measurement light is reflected and amplifies with identical incident angle a incident refraction the same minute surface of prism 6, and still, incidence point has moved a distance L ₁, as shown in Figure 2, amplified after prism 6 reflects the light-sensitive surface that shines PSD9 by refraction, still, point of irradiation has moved a distance h ₃, obtain thus another positional information, obtain distance h by the signal processing unit after PSD9 ₃value.In above-mentioned measuring process, due to the generation of described displacement D, cause the reflection measurement light with respect to the original optical path translation distance h ₁, this measurement light has been refracted after the incident minute surface refraction of amplifying prism 6 with respect to the original optical path translation distance h ₂, when incident angle a is greater than 70 °, distance h ₂much larger than distance h ₁, as h ₂/ h ₁can reach 43, as shown in Figure 3, amplify from refraction after the outgoing minute surface refraction of prism 6 with respect to original optical path translation distance h although measure light ₃be less than distance h ₂, still, the two differs very little.In addition, micro-power flexible member surface 5 occurs displacement D and described distance h ₁there is corresponding relation, like this just can be by obtained distance h ₃value convert and to obtain the value of the displacement D that value is extremely small, although the value of displacement D is in micro-nano magnitude,, because being refracted, this displacement D amplifies prism 6 amplification several times, therefore requirement to the resolution of PSD9 obviously reduces, and has common resolution and gets final product.Due in measuring process, the present invention's refraction amplify optical displacement sensor with by surface 5 noncontacts of micrometer power flexible member, the decline of the measuring accuracy that causes because of mechanical connection can not occur.

The accompanying drawing explanation

Fig. 1 is that optical displacement sensor general structure schematic diagram is amplified in the present invention's refraction, and this figure doubles as Figure of abstract.Fig. 2 measures light to amplify the light path schematic diagram of the refraction amplification prism in optical displacement sensor by the present invention's refraction.Fig. 3 amplifies incident angle a and the enlargement factor h of prism for measuring light incident refraction ₂/ h ₁graph of relation.Fig. 4 reflects for the measurement light incident of propagating in prism is amplified in refraction incident angle c and the minification h that amplifies prism outgoing minute surface ₃/ h ₂graph of relation.Thereby Fig. 5 be measure light incident refraction amplify the prism hot spot be stretched in one direction, afterwards launching spot correct the prism hot spot with the perpendicular direction of the direction that is stretched before on again be stretched and obtain the situation schematic diagram of correcting.Fig. 6 is the situation schematic diagram of the measurement light incident PSD after light spot shape is corrected.

Embodiment

In optical displacement sensor is amplified in the present invention's refraction, LASER Light Source 1 and PSD9 are arranged, as shown in Figure 1 and Figure 2.After LASER Light Source 1, refraction coaxially settles pinhole filter 2, collimation lens 3, aperture diaphragm 4 before amplifying prism 6 successively.Eliminate because of the optical element in airborne dust, LASER Light Source 1 and measure trimmed book body scattered light to measuring the interference of light by pinhole filter 2.Collimation lens 3 makes measurement light have predetermined angular with respect to the light path axis, becomes satisfactory collimated light.By aperture diaphragm 4 filtering parasitic lights contract measurement light beam diameter.Measurement illumination now is mapped to micro-power flexible member surface 5 and is reflected.Refraction is amplified prism 6 between LASER Light Source 1 and PSD9, and is positioned on measurement reflection of light light path.LASER Light Source 1 optical axis is vertical with refraction amplification prism 6 axial spaces, and it is vertical but non-intersect that prism 6 axis are amplified in the measurement light optical axis after this mark sheet is reflected by micro-power flexible member surface 5 now and refraction.The incident angle a that the measurement light that LASER Light Source 1 is sent is amplified prism 6 by the rear incident refraction of 5 reflection of micro-power flexible member surface is more than or equal to 70 °, is less than 90 °.Amplify on the light path between prism 6 and PSD9 and be mounted with successively hot spot rectification prism 7, optical filter 8 in refraction.Geometric parameter, optical parametric that hot spot is corrected prism 7 are identical with refraction amplification prism 6; The axis that hot spot is corrected prism 7 is vertical with the axis of refraction amplification prism 6; It is identical with incident minute surface, the outgoing minute surface of refraction amplification prism 6 that hot spot is corrected prism 7.Optical filter 8 is complementary with measurement light, and the most of parasitic light in light is measured in filtering.The PSD9 light-sensitive surface is vertical with the measurement light that amplifies prism 6 outgoing from refraction.

The measurement light that LASER Light Source 1 is sent is incident collimation lens 3 after pinhole filter 2 filtering, dwindle beam diameter by aperture diaphragm 4 again after collimation, measurement illumination now is mapped to micro-power flexible member surface 5, after reflection, prism 6 is amplified in the incident refraction, the measurement light that amplifies prism 6 outgoing from refraction carries out the light spot shape rectification by hot spot rectification prism 7, approach circular, to meet the requirement of PSD to the launching spot shape, measure the most of parasitic light in light by optical filter 8 filterings, finally project on the PSD9 light-sensitive surface.

When micro-power flexible member surface 5 is subjected to displacement D, cause the reflection measurement light with respect to the original optical path translation distance h ₁, displacement D is converted into the parallel distance h of reflection measurement light ₁, its pass is:

h ₁=2Dcosβ，

In formula, β is for measuring the incident angle on the micro-power flexible member of light incident surface 5.

When micro-power flexible member surface 5 is subjected to displacement D, by the incidence point of measurement light on the incident minute surface of refraction amplification prism 6 of micro-power flexible member surface 5 reflections, with respect to original optical path, moved a distance L ₁, measure light and be refracted after the incident minute surface refraction of amplifying prism 6 with respect to the original optical path translation distance h ₂, following relation is arranged:

h ₁=L ₁cosa，

And h ₂=L ₁cosb,

In formula, b amplifies the refraction angle of the incident minute surface of prism 6 for measuring light by refraction.

The refractive index that prism 6 is amplified in refraction is n, and relational expression is arranged:

$\sin b=\frac{\sin a}{n}.$

The enlargement factor h of prism 6 is amplified in refraction ₂/ h ₁for:

$\frac{h_2}{h_1}=\frac{\sqrt{n^2-{\sin }^{2}a}}{n\cos a}.$

As shown in Figure 3, along with the increase of incident angle a, enlargement factor h ₂/ h ₁increase gradually, when incident angle a reaches more than 70 °, enlargement factor h ₂/ h ₁increase in the scope of 2～43 times, regulate incident angle a and can control enlargement factor h ₂/ h ₁.

In like manner known, when measuring light and amplify the outgoing minute surface outgoing of prism 6 from refraction, with respect to the distance of original optical path translation, be distance h ₃, and distance h ₃be less than distance h ₂, known accordingly, refraction is amplified prism 6 and is also had minification h ₃/ h ₂:

$\frac{h_3}{{\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="HDA0000368420330000011.png,HDA0000368420330000022.png"\; state="\{\{state\}\}">h</figure-callout>}}_2}=\frac{\sqrt{{1-\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="HDA0000368420330000011.png,HDA0000368420330000022.png"\; state="\{\{state\}\}">n</figure-callout>}}^2{\sin }^{2}c}}{\cos c},$

In formula, c amplifies the incident angle of the outgoing minute surface of prism 6 for measuring light by refraction.

As shown in Figure 4, along with the increase of incident angle c, minification h ₃/ h ₂reduce gradually, when incident angle c is below 20 ° the time, minification h ₃/ h ₂more than 0.9, in fact, due to h ₃, h ₂the two differs very little, and it is very little that the multiple of refraction amplification prism 6 dwindles effect.

The total magnification K that prism 6 is amplified in refraction is:

$K=\frac{h_3}{h_1}=\frac{\sqrt{n^2-{\sin }^{2}a}}{n\cos a}\frac{\sqrt{1-{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="HDA0000368420330000011.png,HDA0000368420330000022.png"\; state="\{\{state\}\}">n</figure-callout>}}^2{\sin }^{2}c}}{\cos c}.$

Increase incident angle a, reduce incident angle c, just can realize the amplification of 2～40 times, realize thus linear amplification of optics of displacement measurement.

Measure light beam cross-section shape approximate circle, suppose that this approximate circle is:

x ²+y ²=R ²。

Amplification in view of refraction amplification prism 6, after a branch of measurement light amplifies prism 6 by refraction, can be exaggerated K doubly as the x direction of principal axis of beam cross section approximate circle or y direction of principal axis in certain direction, as be exaggerated K at the y direction of principal axis doubly, so, amplifying the rear beam cross section approximate circle of prism 6 by refraction becomes:

$\frac{x^2}{R^2}+\frac{y^2}{K^2{R}^2}=1.$

Visible, beam cross-section shape becomes an ellipse, as shown in Figure 5, project hot spot on the PSD light-sensitive surface by distorted, and the hot spot that PSD requires light-sensitive surface to receive should be circular.For this reason, the present invention adds hot spot rectification prism 7 after prism 6 is amplified in refraction.Geometric parameter, the optical parametric of correcting prism 7 due to hot spot are identical with refraction amplification prism 6, there is identical incident minute surface, outgoing minute surface, but, the axis that hot spot is corrected prism 7 is vertical with the axis of refraction amplification prism 6, so, after the measurement light of refraction amplification prism 6 outgoing is corrected prism 7 by hot spot, can be exaggerated K doubly in another direction, as be exaggerated K at the x direction of principal axis doubly, be exaggerated K doubly at the y direction of principal axis, so, the beam cross section approximate circle from 7 outgoing of hot spot rectification prism becomes:

$\frac{x^2}{K^2{R}^2}+\frac{y^2}{K^2{R}^2}=1.$

As shown in Figure 5, Figure 6, to become radius be K for measurement light beam cross-section shape now ²r ²circle, meet the requirement of PSD to the sensitization light spot shape.

Refraction is amplified prism 6 and is corrected a prism amplification system of prism 7 compositions with hot spot, in optical displacement sensor is amplified in the present invention's refraction, can configure n such prism amplification system, can realize the K of optical displacement ⁿdoubly amplify.

Claims (4)

1. optical displacement sensor is amplified in a refraction, comprise LASER Light Source (1) and PSD(9), it is characterized in that, refraction amplify prism (6) be positioned at LASER Light Source (1) and PSD(9) between reflected light path on, LASER Light Source (1) optical axis is vertical with refraction amplification prism (6) axial space, the incident angle a that prism (6) is amplified in the measurement light incident refraction that LASER Light Source (1) is sent is more than or equal to 70 °, is less than 90 °, and PSD(9) light-sensitive surface is vertical with the measurement light that amplifies prism (6) outgoing from refraction.

2. optical displacement sensor is amplified in refraction according to claim 1, it is characterized in that, LASER Light Source (1) afterwards, refraction amplifies prism (6) and coaxially settles successively before pinhole filter (2), collimation lens (3), aperture diaphragm (4).

3. optical displacement sensor is amplified in refraction according to claim 1, it is characterized in that, is mounted with hot spot rectification prism (7) at refraction amplification prism (6) and on the light path PSD(9); Geometric parameter, optical parametric that hot spot is corrected prism (7) are identical with refraction amplification prism (6); The axis that hot spot is corrected prism (7) is vertical with the axis of refraction amplification prism (6); It is identical with incident minute surface, the outgoing minute surface of refraction amplification prism (6) that hot spot is corrected prism (7).

4. optical displacement sensor is amplified in refraction according to claim 3, it is characterized in that, refraction is amplified prism (6) and is formed a prism amplification system with hot spot rectification prism (7), n such prism amplification system can be configured in optical displacement sensor is amplified in the present invention's refraction, the K of optical displacement can be realized ⁿdoubly amplify.

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