CN204495291U - A kind of filament diameter measurement mechanism based on double grating - Google Patents

Abstract

The utility model discloses a kind of filament diameter measurement mechanism based on double grating, comprise LASER Light Source, filtering system, filament, it is characterized in that, also comprise spatial filter, high dencity grating and imageing sensor, described LASER Light Source, filtering system, filament, spatial filter, high dencity grating and imageing sensor sequential, filament and high dencity grating form double grating system; Described spatial filter, high dencity grating, imageing sensor are all perpendicular to the optical axis at laser beam place; The optical axis of described filtering system and the optical axis coincidence at laser beam place.Benefit of the present utility model is: on the basis of an original diffractometry method, add high dencity grating, the characteristic making full use of high dencity grating segmentation and amplify, secondary amplification is carried out to a diffraction spectrum of filament, compared to a diffraction approach, measuring accuracy is higher, stability is better, measurement range is larger.

Description

A kind of filament diameter measurement mechanism based on double grating

Technical field

The utility model relates to a kind of proving installation, is specifically related to a kind of filament diameter measurement mechanism based on double grating.

Background technology

Diffraction grating is a kind of optical element that can carry out space periodic modulation to incident light wave amplitude and phase place, the dichroism powerful because of it and being used widely in thermometrically occasion.Along with the exquisiteness increasingly of modern manufacturing technique, the line number of grating can do larger and larger, and the ability of its amplification and segmentation is also more and more stronger, makes high dencity grating in high-precision thermometrically application in occupation of irreplaceable position.

The measurement of micron dimension filament diameter has the meaning of particular importance in laboratory study and micro machining technique, especially, in the industry of the different field products such as micromachine, bio-instruments, photoelectricity processing, weaving, many application requirements are measured accurately to micron dimension filament.Relative to measuring method that is mechanical or other contacts, measuring method based on the diffraction of light can overcome the deformation and the low shortcoming of precision that contact type measurement produces well, can measure accurately micron dimension filament, measuring error is also little, easily reaches the measurement requirement of various occasion.

The utility model utilizes the segmentation amplification characteristic of grating, the basis of a Measuring Diameter of Slim by Diffraction adds high density diffraction grating, there is re-diffraction, the diffraction spectra be amplified, effectively can improve the precision of measurement like this, increase the stability measured.

Utility model content

For solving the deficiencies in the prior art, break through the bottleneck that diffraction calibrates technology, the purpose of this utility model is, provides a kind of filament diameter measurement mechanism based on double grating, make full use of the segmentation amplification characteristic of high dencity grating, effectively improve the measuring accuracy that existing diffraction calibrates technology.

In order to realize above-mentioned target, the utility model adopts following technical scheme:

A kind of filament diameter measurement mechanism based on double grating, comprise LASER Light Source, filtering system, filament, it is characterized in that, also comprise spatial filter, high dencity grating and imageing sensor, described LASER Light Source, filtering system, filament, spatial filter, high dencity grating and imageing sensor sequential, filament and high dencity grating form double grating system; Described spatial filter, high dencity grating, imageing sensor are all perpendicular to the optical axis at laser beam place; The optical axis of described filtering system and the optical axis coincidence at laser beam place.

It is the parallel beam of λ that LASER Light Source produces wavelength, parallel beam is irradiated on filament and a diffraction occurs, spatial filter makes in diffraction spectra ± and the bright level of m level time passes through, and produce re-diffraction through high dencity grating, final diffraction spectrogram is gathered by imageing sensor.

Described filtering system is made up of a double lens 4f system and a small filter, and small filter is placed on twin-lens frequency plane.

Distance l between described filament and spatial filter ₀meet Fraunhofer diffraction condition, namely wherein a is filament diameter.

Usefulness of the present utility model is: on the basis of an original diffractometry method, add high dencity grating, the characteristic making full use of high dencity grating segmentation and amplify, secondary amplification is carried out to a diffraction spectrum of filament, compared to a diffraction approach, measuring accuracy is higher, stability is better, measurement range is larger.

Accompanying drawing explanation

Fig. 1 is the structural representation of the utility model based on the filament diameter pick-up unit of double grating.

Fig. 2 is the principle schematic of the utility model based on the filament diameter detection method of double grating.

The implication of Reference numeral in figure:

1-LASER Light Source, 2-filtering system, 3-filament, 4-spatial filter, 5-high dencity grating, 6-imageing sensor, 7-is through the Spectral structure of a filament diffraction, and 8-is through the Spectral structure of grating re-diffraction.

Embodiment

Below in conjunction with the drawings and specific embodiments, concrete introduction is done to the utility model.

The filament diameter pick-up unit based on double grating as shown in Figure 1, comprising: LASER Light Source 1, filtering system 2, filament 3, spatial filter 4, high dencity grating 5, imageing sensor 6, and wherein filament 3 and high dencity grating 5 constitute double grating system; Described spatial filter 4, high dencity grating 5, imageing sensor 6 are all perpendicular to the optical axis at laser beam place; The optical axis of described filtering system 2 and the optical axis coincidence at laser beam place.

Filtering system 2 is made up of double lens (4f) system and a small filter, and small filter is placed on twin-lens frequency plane.Distance l between filament 3 and spatial filter 4 ₀meet Fraunhofer diffraction condition, namely wherein a is filament diameter.Imageing sensor 6 is charge coupled cell CCD or the complementary metal oxide semiconductor (CMOS) CMOS of linear array or face battle array.

Based on the filament diameter detection method of the filament diameter measurement mechanism of double grating, comprise the steps:

1), before the start of the measurement, take off the filament 3 in Fig. 1 measurement mechanism, spatial filter 4 and high dencity grating 5, standard diffraction part is placed on the position of filament 3, open LASER Light Source 1, make it by standard diffraction part generation diffraction, the level time spacing of corresponding diffraction spectra measured by imageing sensor 6, calculates the distance of standard diffraction part and imageing sensor 6 according to the parameter of diffraction spectra and standard diffraction part, and namely the position of filament 3 is to the distance l of imageing sensor 6 ₃.

Wherein, standard diffraction part can be master grating, standard slit or standard filament etc. can produce the standard component of diffraction.Distance between standard diffraction part to imageing sensor 6 is calculated by the diffraction law of these standard diffraction parts, the diffraction formula of master grating, standard slit and standard filament is dsin θ=k λ, wherein d is corresponding grating constant, slit width or filament diameter, and λ is wavelength for master grating, x' is the distance that the bright level of kth level time arrives diffraction spectra center, be the dark level of the kth level time distance to diffraction spectra center for standard slit and standard filament x', just can calculate the distance l between standard diffraction part to imageing sensor according to d, k, λ and x', the standard diffraction part of other types then uses corresponding diffraction equation to calculate.

When calculating the level time spacing of diffraction spectra, for the imageing sensor of linear array, directly carry out noise reduction, filtering to the one dimension spectrum measured, the crest finding diffraction spectra distribute or wave trough position are to calculate the secondary pixel distance of the order of diffraction; The imageing sensor of face battle array is then carry out the process such as Threshold segmentation, target detection to the two dimensional image collected, and finds the coordinate points of each grade time in diffraction spectra, thus calculates the pixel distance of each grade time.Each grade spacing is then the product of the physical size of the single pixel of its pixel distance and sensor.

2), use with 1) identical method, standard diffraction part is placed on the position at device middle-high density grating 5 place, calculates by the method measuring diffraction spectra the distance l that high dencity grating 5 arrives imageing sensor 6 ₂, also can obtain the distance l between surveyed filament to high dencity grating thus ₁=l ₃-l ₂.

3) high dencity grating 5 being, d by surveyed filament 3, spatial filter 4 and grating coefficient puts back to the original place in measurement mechanism, as shown in the beam-pointing in Fig. 2, a diffraction is there is in the light beam that LASER Light Source produces through filament, adjustment spatial filter, make to only have in the diffraction spectra of filament ± the bright level time of m level time can pass through, form the Spectral structure 7 through a filament diffraction, the bright level of this two levels time is time again through grating generation re-diffraction, and final Diffraction fringe distribution is as shown in Figure 2 through the Spectral structure 8 of grating re-diffraction.Final diffraction spectra is gathered by imageing sensor, calculates the bright level of+m level secondary+n level through the optical grating diffraction spectrum of filament diffraction and the secondary distance 2x between the-n level of optical grating diffraction is composed of the bright level of-m level of filament diffraction by the method for image procossing.

4), according to m, n, d, l ₁, l ₂, 2x and light source wavelength X just can according to equation $x=l_1\tan \left(\mathrm{atc}\sin \frac{\mathrm{\λ}{\mathrm{\α}}_m}{\mathrm{\πa}}\right)+l_2\tan \left[\arcsin (\frac{\mathrm{\λ}{\mathrm{\α}}_m}{\mathrm{\πa}}+\frac{\mathrm{n\λ}}{d})\right]$ Solve the diameter obtaining filament, wherein α _mfor the bright level of the m level time position of filament diffraction, its numerical value equals m the positive number solution of equation α=tan α, and the non-zero disaggregation of this equation is { α=1.43 π, 2.459 π, 3.470 π, 4.479 π ....When utilizing this equation to calculate filament diameter a, the method for the numerical evaluation such as dichotomy or process of iteration is used to solve.

More than show and describe ultimate principle of the present utility model, principal character and advantage.The technician of the industry should understand, and above-described embodiment does not limit the utility model in any form, the technical scheme that the mode that all employings are equal to replacement or equivalent transformation obtains, and all drops in protection domain of the present utility model.

Claims (4)

1. the filament diameter measurement mechanism based on double grating, comprise LASER Light Source, filtering system, filament, it is characterized in that, also comprise spatial filter, high dencity grating and imageing sensor, described LASER Light Source, filtering system, filament, spatial filter, high dencity grating and imageing sensor sequential, filament and high dencity grating form double grating system; Described spatial filter, high dencity grating, imageing sensor are all perpendicular to the optical axis at laser beam place; The optical axis of described filtering system and the optical axis coincidence at laser beam place.

2. a kind of filament diameter measurement mechanism based on double grating according to claim 1, it is characterized in that: it is the parallel beam of λ that LASER Light Source produces wavelength, parallel beam is irradiated on filament and a diffraction occurs, spatial filter makes in diffraction spectra ± and the bright level of m level time passes through, produce re-diffraction through high dencity grating again, final diffraction spectrogram is gathered by imageing sensor.

3. a kind of filament diameter measurement mechanism based on double grating according to claim 1, is characterized in that: described filtering system is made up of a double lens 4f system and a small filter, and small filter is placed on twin-lens frequency plane.

4. a kind of filament diameter measurement mechanism based on double grating according to claim 2, is characterized in that: the distance l between described filament and spatial filter ₀meet Fraunhofer diffraction condition, namely wherein a is filament diameter.