CN102865835B - Vernier slit type photoelectric auto-collimator - Google Patents

Abstract

The present invention provides that a kind of precision is high, the vernier slit type photoelectric auto-collimator of good reliability.This vernier slit type photoelectric auto-collimator, the line array CCD (6) being included in the monochromatic source (1) that main optical path sets gradually, many slits (2), spectroscope (3), collimator objective (4), rotating plane mirror (5) and arranging on spectroscope light splitting optical path, many slits (2) and line array CCD (6) conjugation; Described many slits (2) are made up of multiple parallel single slit, and each parallel single slit seam is wide all equal with kerf spacing; Using line array CCD as main scale, the picture of many slits (2) is as vernier scale, and vernier scale and main scale meet vernier Principle of sub-division.The present invention can be widely used in high-precision small-angle accuracy test, the small angle measurement etc. of catoptron sound state small angle error high-acruracy survey, angular displacement sensor Angle Calibration, optical flat cold working part.

Description

Vernier slit type photoelectric auto-collimator

Technical field

The present invention relates to a kind of high precision angular displacement detecting device, be specifically related to a kind of vernier slit type photoelectric auto-collimator.

Background technology

In precision measurement field of measuring techniques, photoelectric auto-collimator be widely used in small angle measurement, High-precision angle calibration, the flatness of guide rail, the fields of measurement such as flatness, revolving table position uncertainty of precision surface plate, be the conventional measuring equipment of department's indispensabilities such as machine-building, shipbuilding, Aero-Space, metrology and measurement, scientific research.Particularly in precision, Ultra-precision positioning, more there is irreplaceable effect.It both separately for engineering survey, can also can be used as the aiming in the optical metrological instruments such as transit, angular instrument, optical comparator and measurement component.

Because photoelectric auto-collimator essence is high-precision digital picture micrometric displacement detection system, change slit type and become the key element improving its precision.At present, slit type used in photoelectric auto-collimator mainly contains: crosshair, circular hole, the M shape/V-arrangement/graduation of N shape, single slit, grating etc.Crosshair, circular hole etc. have directly coordinated two-dimensional measurement with planar array detector, and be limited to the principle of work of face battle array device self, its measuring speed and precision all can be restricted.The main combination with single linear CCD of M shape/V-arrangement/N shape graticule realizes two-dimentional outer corner measurement, requires higher, and then affect measurement range and measuring accuracy to slit and line array CCD installation accuracy.According to single slit, then when single slit is as image, image-element is only seamed wide, is unfavorable for improving precision.The appearance of optical grating photoelectric self-collimator is a kind of exploration newly, and the displacement of the Moire fringe that the type autocollimator is produced by a pair optical grating pair obtains the angular displacement information of level crossing.Moire fringe displacement information is not only relevant with the pitch difference of the single grid line between optical grating pair, also relevant with the angle between optical grating pair, cause the installation of such autocollimator to grating higher, in addition the complicacy of Moire fringe itself, accurately to locate it, higher to later image processing requirements, Surveying Actual Precision and reliability are also restricted (if there is the error that explorer response or grating portray, impact will be even more serious).

Summary of the invention

For overcoming the deficiency that aforementioned background art exists, the present invention provides that a kind of precision is high, the vernier slit type photoelectric auto-collimator of good reliability.

Technical solution of the present invention is:

Vernier slit type photoelectric auto-collimator, the line array CCD (6) being included in the monochromatic source (1) that main optical path sets gradually, many slits (2), spectroscope (3), collimator objective (4), rotating plane mirror (5) and arranging on spectroscope light splitting optical path, many slits (2) and line array CCD (6) conjugation, the light that light source (1) sends by many slits (2), be reflected back spectroscope light splitting at plane mirror (5) after spectroscope transmission, images in line array CCD (6) place; Its special character is:

Described many slits (2) are made up of multiple parallel single slit, and each parallel single slit seam is wide all equal with kerf spacing; Using line array CCD as main scale, the picture of many slits (2) is as vernier scale, and vernier scale and main scale meet vernier Principle of sub-division.

Like this, when plane mirror (5) rotates a low-angle, many slits (can be referred to as " vernier slit ") image has certain displacement amount at line array CCD, the sub-pixed mapping displacement information after vernier segmentation is obtained by cursor principle, ccd output signal is changed through A/D, by mathematics transformational relation, positional information is converted to angular metric, thus can accurately angles of display change.

Based on above-mentioned basic technical scheme, the present invention has also carried out following optimization and has limited and improve:

The width of above-mentioned single slit is more than or equal to the line array CCD original image elemental size of 3 times.

If each parallel single slit seam is wide be d with kerf spacing, slit number is N, and line array CCD pixel dimension and image space-between are P _d, carried out M times of hardware subdivision to the ccd signal exported, then vernier scale and main scale meet following mathematical relation:

$(2N-1)\×d=[k\×(2N-1)-1]\×\frac{P_d}{M},$ Wherein, N=1,2,3, M=1,2,3, K=1,2,3 ...

The value of above-mentioned each parameter is preferably 2≤N≤50; 2≤k≤100; 1≤M≤20.

Above-mentioned light source specifically can adopt LED light source, LASER Light Source etc.

Want to obtain higher measuring accuracy, the focal length of collimator objective (4) can be longer, and the pixel number of line array CCD can be less, adopts corresponding vernier narrow slit structure can obtain higher precision.

The present invention has the following advantages:

The present invention is ingenious applies vernier Principle of sub-division, and this collimator is when debuging requirement and being lower, and can realize high-acruracy survey, reliability is high.The present invention can allow suitably to regulate the defocusing amount between line array CCD photosurface and optimum image plane.

The present invention can be widely used in high-precision small-angle accuracy test, the high-acruracy survey etc. of the verticality/flatness of the small angle measurement of catoptron sound state small angle error high-acruracy survey, angular displacement sensor Angle Calibration, optical flat cold working part, high precision table top or workpiece.

Accompanying drawing explanation

Fig. 1 is principle schematic of the present invention.

Fig. 2 is the mathematical relation schematic diagram between the present invention's line array CCD and vernier slit.

Embodiment

As shown in Figure 1, LED light source component (1), vernier slit (2), spectroscope (3), collimator objective (4), plane mirror (5), line array CCD (6) is included.On the focal plane that vernier slit (2) and line array CCD (6) are positioned at collimator objective (4) or near it.The bright vernier slit (2) of the illumination that LED light source component (1) sends, light collimates through collimator objective (4) and image in line array CCD (6) place after level crossing (5) reflection.When control plane catoptron (5) rotates a low-angle, vernier slit image has certain displacement amount at line array CCD, obtain the sub-pixed mapping displacement information after vernier segmentation by cursor principle, by mathematics transformational relation, positional information is converted to angular metric, and angles of display change in real time.

In Fig. 1, LED light source component adopts red-light LED light source.Line array CCD adopts single linear CCD, and single pixel dimension and image space-between are 7 μm, and single pixel dimension and image space-between also can be less; Equally with kerf spacing be all d when the seam of vernier slit (2) is wide, when vernier slit number is N, and single linear CCD pixel dimension and image space-between are P _d, using line array CCD as main scale, vernier slit (2) picture as vernier scale, when vernier slit (2) picture and line array CCD (6) between meet vernier Principle of sub-division time, when namely meeting following mathematical relation,

(2N-1) × d=[k × (2N-1)-1] × P _d, wherein N=1,2,3, K=1,2,3 ... (A)

The picture of vernier slit (2) is to line array CCD (6) unit pixel P _dachieve the error free segmentation meeting cursor principle, segmentation multiple is:

$f=\frac{1}{2N-1}---\left(B\right)$

Namely when vernier slit moves time, on vernier slit, the slit edges of correspondence position and the justified margin of line array CCD pixel, achieve sub-pixel subdivision, the whole pixel of the CCD that on vernier scale, the edge of first slit is corresponding, the error free sub-pixed mapping displacement of both sum reaction vernier slit chis.

Ccd output signal is changed through A/D, is digital signal by analog-signal transitions, when the A/D change over clock signal adopted be the M of CCD integral time doubly, namely M times of hardware subdivision has been carried out to the ccd signal exported; Suppose that the original pixel number of CCD is N _c, the pixel number of output then becomes MN _c, when adopting this divided method, the width of single slit is more preferably greater than 3 times of original Pixel sizes.In this case, when meeting vernier Principle of sub-division between the picture and line array CCD (6) of vernier slit (2), when namely meeting following mathematical relation,

wherein, N=1,2,3, M=1,2,3, K=1,2,3 ... (C)

The picture of vernier slit (2) is to the unit pixel after line array CCD (6) segmentation achieve the error free segmentation meeting cursor principle, segmentation multiple is:

$f=\frac{1}{2N-1}---\left(D\right)$

Namely when vernier slit moves time, the justified margin of the slit edges of correspondence position and the line array CCD pixel after segmenting on vernier slit, achieve sub-pixel subdivision, the whole pixel of the CCD after the segmentation that on vernier scale, the edge of first slit is corresponding, the error free sub-pixed mapping displacement of both sum reaction vernier slit chis.

If the focal length of collimator objective (4) is f, when the distance of many slit image movements is S, when tested level crossing (5) rotates θ, according to autocollimation principle, have: S=ftan2 θ.If select the focal distance f=300mm of collimator objective (4), the single pixel dimension of line array CCD is 7 μm, and the effective resolution of single pixel is: $\mathrm{\θ}=\frac{1}{2}\arctan \left(\frac{S}{f}\right)=\frac{1}{2}\arctan \left(\frac{7}{300\×1000}\right)\≈{2.4}^{\′\′}.$ Actual measuring accuracy is often lower than 2.4 ", by adopting four narrow slit structures (getting N=4) meeting above-mentioned condition (A), when getting k=5, namely single slit of vernier slit and kerf spacing are can realize line array CCD individual Image segmentation precision, the subdivision accuracy that now can reach is: if carry out M=4 to Output Signal of Linear CCD's doubly to segment, the effective resolution of the single pixel after segmentation is:

$\mathrm{\θ}=\frac{1}{2}\arctan \left(\frac{S}{f}\right)=\frac{1}{2}\arctan \left(\frac{7}{300\×1000\×4}\right)\≈{0.6}^{\′\′},$ When four narrow slit structures (getting N=4) get k=20, namely single slit of vernier slit and kerf spacing are can realize the line array CCD after segmentation individual Image segmentation precision, the subdivision accuracy that now can reach is: mathematical relation schematic diagram between line array CCD and vernier slit as shown in Figure 2.

Want to obtain higher measuring accuracy, the focal length of collimator objective (4) can be longer, and the pixel number of line array CCD can be less, adopts corresponding vernier narrow slit structure can obtain higher precision.

The present invention can be widely used in high-precision small-angle accuracy test, the high-acruracy survey etc. of the verticality/flatness of the small angle measurement of catoptron sound state small angle error high-acruracy survey, angular displacement sensor Angle Calibration, optical flat cold working part, high precision table top or workpiece.

Claims (5)

1. vernier slit type photoelectric auto-collimator, the line array CCD (6) being included in the monochromatic source (1) that main optical path sets gradually, many slits (2), spectroscope (3), collimator objective (4), rotating plane mirror (5) and arranging on spectroscope light splitting optical path, many slits (2) and line array CCD (6) conjugation, the light that light source (1) sends by many slits (2), be reflected back spectroscope light splitting at plane mirror (5) after spectroscope transmission, images in line array CCD (6) place; It is characterized in that:

Described many slits (2) are made up of multiple parallel single slit, and each parallel single slit seam is wide is d with kerf spacing; Using line array CCD as main scale, the picture of many slits (2) is as vernier scale, and vernier scale and main scale meet vernier Principle of sub-division.

2. vernier slit type photoelectric auto-collimator according to claim 1, is characterized in that: the width of described single slit is more than or equal to the line array CCD original image elemental size of 3 times.

3. vernier slit type photoelectric auto-collimator according to claim 1, is characterized in that: establish that each parallel single slit seam is wide is d with kerf spacing, and slit number is N, and line array CCD pixel dimension and image space-between are P _d, carried out M times of hardware subdivision to the ccd signal exported, then vernier scale and main scale meet following mathematical relation:

wherein, N=1,2,3, M=1,2,3, K=1,2,3 ...

4. vernier slit type photoelectric auto-collimator according to claim 3, is characterized in that: the value of each parameter is 2≤N≤50; 2≤k≤100; 1≤M≤20.

5. vernier slit type photoelectric auto-collimator according to claim 4, is characterized in that: described light source is LED light source or LASER Light Source.