CN2084604U - Precision detector for surveyor's rod grating - Google Patents

Abstract

The utility model relates to an accuracy detector for surveyor's rod grating belonging to the technical field of the grating digital display. The utility model is characterized in that two rod gratings with the same grating pitch are formed into a pair face to face. The two rod gratings move towards an X direction and a Y direction through a photodetector, measure the light-intensity variation of the moire fringe image, output data via a digital indicator, and obtain the marking line error of each rod grating via the data processing. The utility model has the advantages of high precision, high measuring accuracy free from the limit of the measured rod grating accuracy, good repetitiveness, low cost, strong practicability, convenient operation and use, etc.

Description

Precision detector for surveyor's rod grating

The present invention is a kind of scale grating instrument for testing precision, belongs to long grating digital readout technical field, is applicable to the detection to scale grating line precision.

In the last few years, the grating digital readout technology had become the application foundation of China's novel lathe design and old machine reformation.But still lack complete grating quality testing means and the method for testing of a cover so far.

At present, the detection of scale grating precision is to adopt and standard length method relatively.Mostly standard length is based on optical maser wavelength or high precision scale grating.During measurement, need that tested scale grating is assembled into complete pattern displacement and pass puzzled device, and be positioned on the straight line with the datum length device.The two counts length relatively separately to same shift length, and difference is obtained in pointwise or segmentation, promptly is the error profile of tested scale grating line.This detection method has its advantage on absolute dimension is measured, but is subjected to certain restriction on using:

1, control requires very harsh to environmental baseline.Require that as laser instrument stable temperature control (in ± 0.2 ℃) is arranged.

2, the instrument cost is higher, needs expensive laser length measurement system or high-precision grating displacement sensor.

3, the precision of rectilinear motion of the installation of tested scale grating and detecting instrument worktable influences accuracy of detection.Adjustment during detection need be spent the long time, operation inconvenience.

The objective of the invention is to simplify testing conditions, improve detection efficiency, reduce the detecting instrument cost, avoid the deficiency of existing detecting instrument, and propose a kind of scale grating instrument for testing precision.

Purpose of the present invention can reach by following measure: adopt two scale grating face one sides with identical pitch opposed be combined into right, the corresponding both sides of dividing across the scale grating pair of luminous and receiving element in the photodetector, make X, Y to moving by detector with respect to the scale grating pair, the light intensity of measuring its Moire fringe image changes, carry out mould/number conversion, counting, decoding and show output by the photosignal of digital indicator, draw the groove error of every scale grating through data processing the detector input.

Form an inspected-unit with three scale gratings, make up in twos three times, read three groups of data, row and difference then can be obtained the error profile of every scale grating line from computing again.If when the scale grating of known error distribution is arranged, then only need carry out a multiple measurement to detected scale grating.

Description of drawings:

Fig. 1 is a schematic diagram of the present invention

Fig. 2 is the figure of syntagmatic in twos of three scale gratings

Fig. 3 is a digital display frame of reference block scheme

Fig. 4 is the pick-up unit structural drawing

Fig. 5 is the measured precision curve comparison diagram of the present invention and laser grating check meter

Wherein: a figure is the test data of laser grating detector, and sampled point is spaced apart 20 millimeters.

B figure is detection data of the present invention, and sampled point is spaced apart 7.5 millimeters.

The present invention is further detailed in conjunction with the accompanying drawings below:

1, measuring principle

With scale grating 1 and opposed the fitting tightly together of 2 one sides of scale grating, adjust the small angle of cut between the two grid line, on the chi face, form the Moire fringe band (as Fig. 1) that a light and shade changes.By the light-emitting component on the detector 4 and photosensitive receiving element 5(such as Fig. 4) receive the bright dark Changing Pattern in this striped edge with big or small.

The Moire fringe width is determined by formula (1)

$B=P_1{P}_2\sqrt{{{\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="912142073\_DRIMG1.png"\; state="\{\{state\}\}">P</figure-callout>}}_1}^2+{{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="912142073\_DRIMG1.png"\; state="\{\{state\}\}">P</figure-callout>}}_2}^2+2P_1{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="912142073\_DRIMG1.png"\; state="\{\{state\}\}">P</figure-callout>}}_2\cos \mathrm{\&theta;}}----\left(1\right)$

P in the formula ₁And P ₂Be the pitch of scale grating 1,2, θ is the angle of cut of two scale grating grid lines.Constant as θ, then B is according to P ₁, P ₂Change and change.If

P ₁＝P ₀＋△P ₁（2）

P ₂＝P ₀＋△P ₂（3）

With formula (2) and formula (3) substitution formula (1) computing, after the simplification:

B＝［（P ₀＋ΔP ₁＋ΔP ₂） ²－P ₀（ΔP ₁＋ΔP ₂）－（ΔP ₁＋ΔP ₂） ²＋ΔP ₁ΔP ₂］／

（4）

If satisfy condition

P ₀θ ²－（△P ₁＋△P ₂）≈0 （5）

P ₀＞＞（△P ₁＋△P ₂） （6）

Then B can use the following formula approximate representation:

B＝ (P ₀＋△P ₁＋△P ₂)/(θ) ＝B _o＋△B （7）

For scale grating pair any position B _iGeneral formula

B _i＝ (P ₀＋△P _1i＋△P _2i)/(θ) ＝B _o＋△B _i（8）

l＝1，2，3，…n

△ B _iCan record B _iAlso can measure.If only survey B ₁With △ B _i, then

$\frac{{\mathrm{\&Delta;B}}_i}{{\mathrm{<figure-callout\; id="1"\; label="B"\; filenames="912142073\_DRIMG1.png"\; state="\{\{state\}\}">B</figure-callout>}}_1}=\frac{{\mathrm{\&Delta;P}}_{1i}+{\mathrm{\&Delta;P}}_{2i}}{P_0+{\mathrm{\&Delta;P}}_{11}+{\mathrm{\&Delta;P}}_{21}}\&ap;\frac{{\mathrm{\&Delta;P}}_{\mathrm{li}}+{\mathrm{\&Delta;P}}_{2i}}{P_0}----\left(9\right)$

Because P ₀For known, C _iCan obtain.Then have

△P _1i＋△P _2i＝C _iP ₀（10）

Because the variation of bandwidth is decided by the variation of pitch, thereby formula (10) is the fundamental formular that detects scale grating line error.

2, measuring process

Detector 6 or scale grating pair 1,2X measure △ B1 to relatively moving, and detector 6 with respect to scale grating pair 1,2Y to traverse measurement B value (as Fig. 4).

The simulating signal of photosensitive receiving element 5 is input to amplifier 8 simultaneously with the d. c. voltage signal of manual balanced potentiometer 7, to decoding monitor 10, provides and detected value (as Fig. 3) behind A/D analog to digital conversion circuit 9.

3, error separating

Unit under test by three scale gratings are formed as shown in Figure 2, carries out 1-2,1-3, and 2-3 makes up in twos.After the measurement, obtain following result by formula (10).

△P _1i＋△P _2i＝C ^〔1〕 _iP ₀（11）

△P _1i＋△P _3i＝C ^〔2〕 _iP ₀（12）

△P _2i＋△P _3i＝C ^〔3〕 _iP ₀（13）

Solve by formula (11), (12), (13):

△P _1i＝ (C ^（2） _i+C ⁽¹⁾ _i-C ⁽³⁾ _i)/2 P ₀（14）

△P _2i＝ (C ^（2） _i+C ⁽¹⁾ _i-C ⁽³⁾ _i)/2 P ₀（15）

△P _3i＝ (C ^（2） _i+C ⁽³⁾ _i-C ⁽³⁾ _i)/2 P ₀（16）

Formula (14), (15), (16) are the groove error profile of scale grating 1,2,3.

Compared with the prior art the present invention has following advantage:

(1), accuracy of detection of the present invention is subjected to environmental influence little, its degree of accuracy is not subjected to the restriction of tested scale grating precision, the instrument good reproducibility, 1m reaches ± 0.5 μ m with interior precision.

(2), detection technique is not only simple, directly perceived, and can isolate the error that grating ruling error and the distortion of chi base cause.

(3), detecting instrument is cheap, practical, be convenient to operation, use.

Claims (3)

1, a kind of scale grating instrument for testing precision that comprises photodetector and digital indicator, it is characterized in that two scale grating face one sides with identical pitch opposed be combined into right, the corresponding both sides of dividing across the scale grating pair of luminous and receiving element in the photodetector, making X, Y by detector with respect to the scale grating pair changes to the light intensity of its Moire fringe image of traverse measurement, digital indicator shows output, draws the groove error of every mark root chi grating through data processing.

2, scale grating instrument for testing precision as claimed in claim 1, it is characterized in that forming unit under test by three scale gratings, opposed in twos combination is three times respectively, and light intensity variation, the digital indicator of being measured three groups of Moire fringe images by photodetector show three groups of data of output.

3, scale grating instrument for testing precision as claimed in claim 1, it is characterized in that the scale grating that distributes by known error and the opposed combination of tested scale grating once, the light intensity of measuring its Moire fringe image to photodetector changes, and digital indicator shows output data.

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