CN200986441Y

CN200986441Y - Dual-grating displacement sensor

Info

Publication number: CN200986441Y
Application number: CN 200620163346
Authority: CN
Inventors: 刘晓军; 陈晓辉
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2006-12-01
Filing date: 2006-12-01
Publication date: 2007-12-05
Anticipated expiration: 2016-12-01

Abstract

The utility model discloses a double grating displacement transducer. The utility model comprises a displacement unit; a displacement guide unit; a signal processing circuit; a laser, a double grating unit and a photoelectric receiver, which are arranged on a same ray path. The double grating unit consists of a movable grating and a fixed grating. Grating lines and planes of the fixed grating and movable grating are parallel. The movable grating is fixed on the displacement unit. The displacement unit and the displacement guide unit compose a translational motion pair; and the direction of movement of the translational motion pair is normal to the grating lines and parallel with the grating planes. Laser beams transmitted by the laser are transmitted to the double grating unit, and double grating interference occurs. The photoelectric receiver is used to receive the produced interference fringe, and transfer produced electrical signal to the signal processing circuit. By adopting the device, better interference fringe characteristics and fringe voltage signal can be obtained than single grating displacement transducers; the utility model is proper to adopt higher subdivision and to get higher resolution. As long as the movable grating moves in a consistent way, considerable displacement range can be achieved. The measuring range is as wide as 20mm, and the resolution is as high as 0.01 um.

Description

A kind of double-raster displacement sensor

Technical field

The utility model belongs to the measurement mechanism technical field, relates to a kind of displacement transducer of interfering based on double grating.

Background technology

At present the method for Displacement Measurement has a lot, such as utilizing the moire fringe displacement sensor, and Centigrade scale, milscale, tenthousandth micrometer, and the single-grating interferometer on the present market etc.But there are some problems in they.

The General Principle of single-grating interferometer is: laser vertical incides diffraction grating, forms+1 grade and-1 grade of two bundle diffraction light behind a diffraction; Adopt two catoptrons and an Amici prism that this two bundles diffraction light is converged to produce and interfere, form interference fringe; When grating moves, cause the striped corresponding mobile; Counting and segmentation by interference fringe can obtain pattern displacement.Owing to exist two catoptrons and Amici prism to realize that diffraction light converges the requirement of interference, cause the single-grating interferometer volume ratio huger, adjust inconvenient; And the moire fringe displacement sensor adopts the big grating of pitch, resolving power to be difficult to improve.

Summary of the invention

The purpose of this utility model is to provide a kind of double-raster displacement sensor, and this displacement transducer has the resolution height, range is big, simple in structure, convenient adjusts and the little characteristics of volume.

A kind of double-raster displacement sensor that the utility model provides, it comprises displacement unit, displacement pilot unit and signal processing circuit, and is positioned at laser instrument, double grating unit and photelectric receiver on the same light path; The double grating unit is by moving grating and decide optical grating constitution, it is parallel respectively with the grid plane with the grid line of moving grating to decide grating, moving grating is fixed on the displacement unit, and displacement unit and pilot unit are formed the rectilinear motion pair, and its direction of motion is perpendicular to grid line and be parallel to the grid plane; The laser beam incident that laser instrument sends to double grating unit generation double grating is interfered, and photelectric receiver is used to receive the interference fringe of generation, and with the electric signal that produces send that signal processing circuit is amplified to, sensing, segmentation and counting.

The present invention is a kind of displacement transducer of interfering based on double grating, when measurand promotes displacement unit when the displacement pilot unit is subjected to displacement, move the grating movement therewith, and relatively move, thereby make the double grating interference fringe produce corresponding moving with deciding the grating generation.When two gratings relatively move a pitch d, the then mobile one-period of interference fringe, the also mobile one-period of sine voltage signal that converts to by photelectric receiver.If choose the grating of 1000 lines/mm, then pitch d is that 0.001mm is 1um, and the one-period number of sine voltage signal is represented the displacement of 1um at this moment.If adopt 80 segmentation offset of sinusoidal voltage signals further to segment, then can further improve resolution to about 0.01um.In fact, because this kind principle of interference can obtain than better interference effect of monochromatic light grid and striped voltage signal, be fit to take higher segmentation to reach higher resolution.In addition, as long as high conformity in the moving grating moving process should be able to be realized sizable displacement range.Measurement range of the present utility model can reach 20mm, and resolving power reaches about 0.01um.

Description of drawings

Fig. 1 is a double grating principle of interference synoptic diagram;

Fig. 2 is the double-raster displacement sensor structural representation.

Embodiment

The present invention interferes by optical grating diffraction and forms the interference fringe feature corresponding with the grating cycle, and the reception by interferometric fringe signal and analyze and realize the high precision and large measuring range displacement measurement.The present invention is further detailed explanation below in conjunction with accompanying drawing.

As shown in Figure 1, laser beam incident earlier through last optical grating diffraction, produces+1 during to two blocks of gratings of parallel placement, 0 and 1 order diffraction light, their respectively again through after an optical grating diffraction, produce respectively (+1 ,+1), (+1,0), (+1 ,-1), (0 ,+1), (0,0), (0 ,-1) and (1 ,+1), (1,0), (1 ,-1).Suitably adjust the position relation between grating, then (+1,0) and (0 ,+1), (+1 ,-1) and (1 ,+1) and (1,0) and (0 ,-1) all can interfere respectively, obtain interference fringe.Select-1 order diffraction light of+1 order diffraction light, note is done (+1 ,-1), selection-1 order diffraction light+1 order diffraction light, note is done (1 ,+1), and they coincide with on the film viewing screen, then produce light and dark interference fringe.When two gratings take place can to produce moving of interference fringe perpendicular to the relatively moving of groove direction, promptly light intensity periodically changes, and this light signal is converted into periodic electric signal through photelectric receiver.

Displacement transducer of the present invention designs based on above-mentioned principle of work, and it comprises double grating interference system and signal processing circuit two parts, and its structure as shown in Figure 2.

The double grating interference system comprises laser instrument 1, moving grating 2, decides grating 3, photelectric receiver 4 and displacement unit 5, displacement pilot unit 7.Wherein, laser instrument 1, moving grating 2, decide grating 3 and photelectric receiver 4 composition double grating optical interference circuits.Move grating 2 and decide grating 3 formation double grating unit, grid plane of the two and grid line direction are all parallel to each other.Decide on the base that grating 3 can be fixed on displacement transducer, moving grating 2 is fixed on the displacement unit 5, moving grating 2 can be with displacement unit 5 in the guiding lower edge of displacement pilot unit 7 perpendicular to grid line and be parallel to the direction motion on grid plane.The moving grating 2 of the laser beam incident that laser instrument 1 sends is interfered with the double grating unit generation double grating of deciding grating 3 compositions, produces interference fringe, and photelectric receiver 4 receives interference fringe, and sends the electric signal of generation to signal processing circuit 8.

During displacement measurement, measurand 6 promotes displacement unit 5 and moves along displacement pilot unit 7, and moving grating 2 moves thereupon, and relatively moves with deciding grating 3 generations, and this moment, interference fringe produced corresponding mobile, and photelectric receiver 4 is accepted this interferometric fringe signal.When moving grating 2 when deciding grating 3 and move a pitch d, the interference fringe one-period that relatively moves, the change in electric one-period that photelectric receiver 4 produces.

In order to reduce horizontal volume, laser instrument 1 can vertically be placed, and at this moment, can thereunder place catoptron 9, and effect is the light beam that vertical light beam is become level.

Displacement unit 5 and displacement pilot unit 7 are used for guaranteeing moving direction and the consistance in moving that moving grating is correct.Wherein displacement unit 5 and displacement pilot unit 7 can adopt multiple mode to realize.A kind of mode is to adopt round guide and linear motion bearing to realize.Two linear motion bearing component movement pairs on round guide and the bracing frame, thus make round guide do rectilinear motion in strict accordance with the direction of linear motion bearing.Also can adopt sheet spring linkage to realize, promptly form sheet spring guide rail as the displacement pilot unit, connect two free-ended movable blocks of spring, as displacement unit by two parallel plate springs.Also can adopt V-way pair, rolling guide-rail pairs to wait in addition and realize displacement unit 5 and displacement pilot unit 7.

Signal processing circuit 8 is connected with photelectric receiver 4, is used for that the electric signal corresponding with interferometric fringe signal to photelectric receiver 4 output amplifies, sensing, segmentation, counting.In signal processing circuit, contraposition differs the two-way sinusoidal electric signals of 90 degree, handles forming square-wave signal on the one hand by shaping, is used for hardware four subdivision and count and sensing; Find the solution fraction part after four subdivision and count by A/D conversion and software segmentation on the other hand, further improve the resolution of system,, then finally can make resolution improve 80 times if adopt software 20 segmentations.Can adopt the digital display circuit that result's numeral of measuring is shown at last.

Claims

1, a kind of double-raster displacement sensor is characterized in that, it comprises displacement unit (5), displacement pilot unit (7) and signal processing circuit (8), and is positioned at laser instrument (1), double grating unit and photelectric receiver (4) on the same light path;

The double grating unit is by moving grating (2) and decide grating (3) formation, it is parallel respectively with the grid plane with the grid line of moving grating (2) to decide grating (3), moving grating (2) is fixed on the displacement unit (5), displacement unit (5) is formed the rectilinear motion pair with displacement pilot unit (7), and its direction of motion is perpendicular to grid line and be parallel to the grid plane;

The laser beam incident that laser instrument (1) sends to double grating unit generation double grating is interfered, and photelectric receiver (4) is used to the interference fringe accepting to produce, and with the electric signal that produces send that signal processing circuit (8) is amplified to, sensing, segmentation and counting.

2, double-raster displacement sensor according to claim 1 is characterized in that: displacement unit (5) is respectively round guide and linear motion bearing with displacement pilot unit (7).