Diagonal optical interferometer ductilimeter metering method and device
The invention belongs to the length metering technical field.
With the small flexible or displacement of measurements by laser interferometry, be the most accurate method of length metering.What use at most in length metering is Michelson interferometer.This interferometer is a purpose with large scale (meter level range) metering generally, about 1/8 wavelength of resolution characteristic (about 80nm).Zhu He of Tsing-Hua University and Zhang Peilin have proposed little variable high sensitivity metering system in " laser system of dust resolution and the application in the material electroluminescent deformation is measured thereof " (the 10th the 8.9th phase of volume of " Chinese laser " nineteen eighty-three) literary composition, this system can reach the measurement resolution of dust.But this metering system circuit is complicated, and needs with expensive frequency stabilized laser.
The white Lip river of also available Fabry interferometer carries out length metering.The device that European patent EP-101-726-A provides, the energy measurement micro-displacement, but, only depend on the constant wide range that just can not carry out of interferometer spacing to measure because of the piezoelectric ceramics traverse is very little, be subjected to the influence of the physical change in the interferometer gap in measuring simultaneously.U.S. Pat-4172663, though also adopted multiple beam co-wavelength light beam to enter interferometer, but because it is measuring object with the light wavelength, its component properties, light path, machinery all design for reaching survey wavelength this purpose, thereby it can not be used for surveying the length variations amount.And the superfine people of Li Zhi is used for magnetostriction metering to the white Lip river of Fabry interferometer, because optical path difference is reduced to the 0.1mm level, has reduced the influence of physical change to measuring, and obtains the resolving power (" metal material research " 1984 year October the 40th page) of 3nm.Its shortcoming is: when the length variations value was grown up than half-wave, the sense data that moves that goes up figure from oscillography screen was difficult, when variation carry out becoming when very fast impossible.
The object of the present invention is to provide a kind of diagonal optical interferometer ductilimeter metering method and device, its energy range extension makes things convenient for reading.
Task of the present invention is finished as follows: an eyeglass of the white Lip river of Fabry interferometer, contact with determinand by the center measuring staff, and move with determinand; Another eyeglass is bonded at the free end of piezoelectric ceramics, and piezoelectric ceramics drives eyeglass and does scanning motion under the effect of scanning voltage.Adopt two bundles or the above light beam of two bundles, direct of travel when having a branch of light by the white Lip river of Fabry interferometer at least and telescopic displacement direction or interferometer normal direction have angle.The formation of this angle can be light beam normal incidence, and interferometer is tiltedly put; Can be that interferometer is just put, the light beam oblique incidence; And interferometer tiltedly puts, and light beam is got any direction.The optical path difference formula of the white Lip river of Fabry interferometer is:
Δ=2d·COSθ=kλ
Δ is the optical path difference between the transmitted light beam in the formula, and d is a distance between mirrors, and θ is the angle of cut of light beam and minute surface normal, and λ is an optical wavelength, and k is an interference level.Interference light intensity is for very big when k is integer.On the diagonal light beam, the interval of interference light maximum value, corresponding displacement is not δ d=λ/2, but greater than the value of λ/2; λ/2COS θ.Thereby on oscillogram, the normal incidence light beam is different with the peak separation of diagonal light beam, and their arrangement is as vernier caliper, normal incident light seems main scale, diagonal light seems vernier, according to the phase relation of they and scanning voltage waveform, can obtain the flexible or displacement variable of determinand.
, go up corresponding interference level at normal incidence light beam (interferometer is just put) and be changed to Δ K when being Δ d when to be measured
0, corresponding interference level is changed to Δ K on the diagonal light beam
1, represent their integer and fraction part respectively with upper right footmark i and d;
| Δ K
<math><msup><mi></mi><msub><mi>i</mi></msup><mi>0</mi></msub></math> -ΔK
<math><msup><mi></mi><msub><mi>i</mi></msup><mi>1</mi></msub></math> |<1 scope, for certain Δ
Have:
The COS θ of molecule often can ignore as 1 in the formula.Can be by this formula only by Δ K
<math><msup><mi></mi><msub><mi>d</mi></msup><mi>0</mi></msub></math> With Δ K
<math><msup><mi></mi><msub><mi>d</mi></msup><mi>1</mi></msub></math> Calculate Δ K
<math><msup><mi></mi><msub><mi>i</mi></msup><mi>0</mi></msub></math> Numerical value, thereby obtain quantity to be measured.In practical operation, measure the magnitude of voltage on pairing each piezoelectric ceramics of interference light maximum value earlier, determine its elongation by the elongation of piezoelectric ceramics and the funtcional relationship of voltage, calculate Δ K by following formula again
0If | Δ K
<math><msup><mi></mi><msub><mi>i</mi></msup><mi>0</mi></msub></math> -ΔK
<math><msup><mi></mi><msub><mi>i</mi></msup><mi>1</mi></msub></math> | surpassed 1, can judge Δ K with the normal length metering method
0The interval, to determine its super integer.When interferometer is tiltedly put, when the direct of travel of incident beam was consistent with the normal direction of interferometer, the variation of interferometer spacing d was than the little factor COS θ of the telescopic displacement value that causes variation, at reading with calculate Δ K
<math><msup><mi></mi><msub><mi>i</mi></msup><mi>0</mi></msub></math> Mathematical relation on, just the same with the method for above-mentioned oblique incident ray.When two light beams, an incident angle is 0, another incident angle is suitable θ, when entering an interferometer simultaneously, two angular separations are not 0 light beam, peak separation difference on oscillogram according to the phase relation between they and scanning voltage waveform, can obtain the flexible or displacement variable of determinand.
The present invention can make in the quick measurement, and range reaches 50
More than, resolving power can reach 2
Do not measured the time effects of object variation, can the timesharing reading.Apparatus of the present invention are simple in structure, and are easy to operate, and cost is low.The fast precise measurement that can be used for small flexible or displacement.As: the electricity of material causes, magnetostriction measurement, macromolecule monocrystal condensation measurement etc.
Below in conjunction with accompanying drawing the present invention is further described.
Accompanying drawing is the synoptic diagram of a kind of embodiment of the present invention.
Referring to accompanying drawing, parallel spring guide rail [3] provides a small translation guide rail.It makes the mobile maintenance of the center measuring staff [15] that is connected in above it and contact [2] thereof accurate parallel.The contact [2] of center measuring staff [15] contacts with determinand, in succession three eyeglasses of the white Lip river of Fabry interferometer [6,7,8] of lower end.When determinand was flexible, center measuring staff [15] drove three eyeglass motions.Other three eyeglasses of the white Lip river of Fabry interferometer [6,7,8] are bonded at respectively on three piezoelectric ceramic tubes [5].About 0.1 0.3mm of the spacing of interferometer.Interferometer [8] is tiltedly put, and its normal and telescopic displacement direction have angle; Two other is just put, and its normal and telescopic displacement angular separation are 0.The inwall ground connection of piezoelectric ceramic tube [5], outer wall connect the scanning output (replacing voltage generator with oscillograph here) of oscillograph [10].The output of photoelectric tube [9] connects oscillograph [10] and amplifier [11].Catoptron (or beam splitter) [14] is sent into each interferometer to a laser of launching from common non-frequency stabilized He-Ne laser [4], when wherein having the placement of two catoptrons can make light beam enter interferometer [6,8] and the telescopic displacement direction angle is arranged.The photosignal of interferometer [6] is shown that by oscillograph the photosignal of interferometer [7.8] is input to digital voltmeter [12] as read instruction after amplifier [11] amplifies, and voltage table is write down the piezoelectric ceramics voltage of photoimpact due in.These voltage values are delivered to data handling system through interface [13] and are handled, record or demonstration measurement result.