CN1873377A - Laser encoder, displacement measurement method of using the laser encoder, and fabricating method of numerically controlled machine - Google Patents
Laser encoder, displacement measurement method of using the laser encoder, and fabricating method of numerically controlled machine Download PDFInfo
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- CN1873377A CN1873377A CNA2005100723571A CN200510072357A CN1873377A CN 1873377 A CN1873377 A CN 1873377A CN A2005100723571 A CNA2005100723571 A CN A2005100723571A CN 200510072357 A CN200510072357 A CN 200510072357A CN 1873377 A CN1873377 A CN 1873377A
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- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/36—Forming the light into pulses
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/347—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells using displacement encoding scales
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- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
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- G01D5/347—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells using displacement encoding scales
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- G01D5/34715—Scale reading or illumination devices
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/36—Forming the light into pulses
- G01D5/38—Forming the light into pulses by diffraction gratings
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Abstract
The invention discloses a laser coder. It includes one laser source, diffraction grating, polarization beam splitter prism, collimating lens, 1/4 wave plate, objective lens, coding disc, concave lens, cylindrical lens, and photo electricity receiver. The coding disc can rotate around center fixed rotating shaft. And its surface is the laser reflecting surface, and set three sets of information rail which is made up of banded unit. The invention also discloses the laser coder displacement measuring method and digital controlled machine tool processing method.
Description
(1) technical field
The present invention relates to a kind of measuring equipment that is used for accurate measured angular displacement, particularly a kind of incremental laser encoder based on CD (CD) technology can be applicable to various automation control area such as numerically-controlled machine, servomotor, various industrial machinery.
(2) background technology
In servomotor and CNC processing technology, need accurately measure the rotational angle of a rotation axis, so that be subjected to driven equipment that this rotation axis drives to produce the displacement of the lines or the angular displacement of one and this angle correspondence.Therefore, described rotational angle is measured accurately more, and the test of relevant devices and/or machining precision are also high more.
The incremental photoelectric encoder is widely used in all kinds of occasions.A typical incremental photoelectric encoder generally includes following five parts: light source, code-wheel, anti-dazzling screen, photodiode, and amplification/shaping (square wave) circuit.When code-wheel during with main axis rotation, code-wheel and anti-dazzling screen overlaid form Moire fringe, and the light that passes through is received by photodiode array, produces a plurality of shapes and is similar to sinusoidal waveform.Described circuit is similar to sinusoidal wave waveform transformation with these and becomes square-wave signal, and transfers to the subsequent conditioning circuit processing.
Accompanying drawing 1 of the present invention has provided a kind of synoptic diagram of typical rotary photoelectricity incremental encoder in the prior art.Fig. 1 shows a kind of typical scrambler in the prior art, and wherein number designation 11 is represented a light source, code-wheel of 12 expressions, mask of 13 expressions, photovoltaic array of 14 expressions, treatment circuit of 15 expressions.The light of outgoing passes code-wheel 12 and mask 13 in the light source 11, arrives photodiode array 14, and described photodiode array 14 changes the light signal that receives into electric signal, and described electric signal is delivered to thereafter treatment circuit 15.15 pairs of described electric signal of treatment circuit amplify and shaping (square waveization) is handled, and export a plurality of sawtooth wave, and its high and low level corresponds respectively to the light transmission part and the shading light part of code-wheel.
Prior art has developed some novel scramblers on the basis of above-mentioned typical scrambler.
Wherein, the diffraction type laser encoder is of paramount importance scrambler, and it can realize the resolution of micron even nanometer.The principle of this class scrambler is to utilize ± 1 order diffraction light beam that phase information is encoded.A kind of structure of scrambler of the type is disclosed in the U.S. Pat 5101102, this structure such as following shown in Figure 2.Among Fig. 2, grating dish of number designation 20 expressions, laser diode of 21 expressions, collimating mirror of 22 expressions, polarization prism of 23 expressions, 241,242 and 243 represent a quarter wave plate respectively, 251 and 252 represent a mirror respectively, 26 expression beam splitters (half-reflecting half mirror), and 271 and 272 represent a polarization sheet respectively, 281 and 282 represent an optical receiver respectively, and 291 and 292 represent a reverberator respectively.From figure, can clearly find out the trend and the processing procedure of light signal.
The problem of the disclosed technical scheme of this patent is, the optical device of use is more, and optical device is distributed in the code-wheel both sides, the debug process more complicated of two groups of symmetry light paths, and cost is very high.
The laser encoder of another kind of prior art is disclosed in the U.S. Pat 5825023.Fig. 3 shows the light channel structure of this scrambler.Among Fig. 3, laser diode of number designation 31 expressions, diffraction grating of 32 expressions, half-reflection and half-transmission sheet of 33 expressions, object lens of 34 expressions, one group of voice loop of 35 expressions, scale grating of 36 expressions, photo-detector of 37 expressions, code-wheel of 38 expressions.From figure, can clearly find out the trend and the processing procedure of light signal.This laser encoder is also referred to as automatic focus type laser encoder.It adopts three laser beams and a reflection-type code-wheel.Adopt a Liar three laser beam to be focused on the surface of a scale grating (scaling grating).
Described code-wheel is a kind of reflection-type code-wheel, and the discrepancy in elevation of its neighboring pixels is 1/4 wavelength of used laser.The information rail adjustment of code-wheel can accurately be controlled with the reflected signal of an interferometer.The scored area of reflection-type code-wheel is made up of two parts, therefore can critically control the direction of motion of code-wheel.The effect of the 3rd laser beam is to carry out automatic focus, and its light beam drops between above-mentioned two parts on the described reflection-type code-wheel.
The shortcoming of this laser encoder scheme is, when code-wheel during along with main axis rotation, the vibrations meeting exerts an influence to code-wheel and relevant light path inevitably.Because do not have the tracking servo device in the system, Nei Ce tracking light beam can jump to the scale zone, the outside of code-wheel sometimes, and the tracking light beam in the outside can jump to the inboard scale zone of code-wheel.For avoiding this abnormal beating, can only transfer the spacing of the scale zone, inside and outside both sides of code-wheel greatly, and can reduce the resolution of device so inevitably, do not reach the level of hope of 1.5 μ m.
(3) summary of the invention
At the deficiency of above-mentioned prior art, the invention discloses a kind of new laser encoder scheme and the application aspect displacement measurement and stepping machine tooling thereof.
Therefore, an object of the present invention is to provide a kind of laser encoder, adopt a discoid code-wheel, the core of this code-wheel is connected on the driving shaft, described driving shaft is vertical with card, adopt optical means, read the coded message of described code-wheel, and be presented at described information on the display or the processing of confession follow up device.Laser encoder provided by the present invention has adopted the structure of the single channel light more simple and direct than disclosed laser encoder in the U.S. Pat 5101102, adopts the tracking servo control technology simultaneously, the anti-vibration ability when having improved laser encoder work.
Another object of the present invention is to provide a kind of displacement detector, adopt above-mentioned laser encoder of the present invention, read and the corresponding coded data of the anglec of rotation of a laser code dish with optical instrument, these coded datas are converted to relevant angular displacement data of rotation with the driving shaft of laser code dish, or further these angular displacement data are converted to a relevant displacement of the lines amount or another angular displacement of rotation with the driving shaft of this code-wheel again.
Another purpose of the present invention is to provide a kind of stepping job operation, adopted above-mentioned laser encoder of the present invention to measure relative position between workpiece to be machined and the processing machine, the stepping amount of processing machine is controlled by a stepping rotating shaft, described stepping rotating shaft is positioned at the center of a laser code dish of the present invention and perpendicular with the card of this code-wheel, and perhaps described stepping axle directly or indirectly links to each other with the rotating shaft that is positioned at described laser code disk center; Adopt optical means to read the coded message of this scrambler, and come the rotation of the described stepping rotating shaft of servocontrol, and then drive machining tool and carry out stepping and process with these information.
Specifically, according to an aspect of the present invention, the invention discloses a kind of laser encoder, comprising:
A) LASER Light Source is used to send Ray Of Light, and directive also passes a diffraction light coral;
B) above-mentioned diffraction grating is used to accept the light of described light source ejaculation and allow that described light passes, and produces diffracted beam;
C) polarization splitting prism is used to make light from described diffraction grating to be linear polarizationization and penetrates along original direction; This polarization splitting prism also will be reflexed to concavees lens by the light that a collimation lens returns;
D) above-mentioned collimation lens makes the polarization linearly polarized light collimationization ejaculation from described polarization splitting prism; And the light that allows to return from a quarter wave plate passes and projects described polarization splitting prism;
E) above-mentioned quarter wave plate makes the polarization linearly polarized light from described collimation lens change the ovalization polarized light into; And the elliptically polarized light that allows to return from object lens passes, and it changed into linearly polarized light when passing and projects on the described collimation lens;
F) above-mentioned object lens allow to pass through also described light focusing to a code-wheel from the light of above-mentioned quarter wave plate;
G) above-mentioned code-wheel, comprise a basic unit and a reflection horizon, can be around a fixing rotating shaft rotation, its surface is for reflecting the reflecting surface of described laser, and this surperficial part is for being focused the code area of described code-wheel from the light of above-mentioned object lens; Described code area for round three of described rotation center apart from one another by the concentric information rail of opening (track), wherein each information rail is made up of a plurality of striped cell that are spaced apart from each other, described striped cell is boss or the pit areas that forms in the code-wheel surface working, and other regional differences in height on described boss or pit areas and code-wheel surface are 1/4 value after the refractive index modifications of described basic unit of used optical maser wavelength;
H) above-mentioned concavees lens, allow to return by described collimation lens, pass and cylindrical lens of directive through the light of the reflection of described polarization splitting prism;
I) above-mentioned cylindrical lens allows to pass through from the light of above-mentioned concavees lens, throws and focuses on the photelectric receiver;
J) above-mentioned photelectric receiver comprises at least one photoelectricity receiving element, is used to receive the light from above-mentioned cylindrical lens, changes described light into electric signal, and described electric signal is counted.
Described code-wheel comprises a basic unit and a reflection horizon at least by the order of layer.In addition, outside the reflection horizon, also can comprise a protective seam and a label layer.Described basic unit can be a layer of polycarbonate, and as the basis of code-wheel, its thickness should be enough to make each layer processing and fabricating successfully thereon thereafter; Described reflection horizon can be an aluminium coated, and its thickness should be able to make described laser be reflected with predetermined reflection; The effect of described protective seam is from the back-protective reflection horizon, and its thickness for example can be more than tens microns; Described label layer can be for example print, be used to represent aspects for information about such as product and trade mark, its material and thickness are not limit, only otherwise influencing code-wheel integrally moves and get final product.For example,, as adopt laser encoder of the present invention, also can not establish label layer on its code-wheel for the numerically-controlled machine process equipment of a practicality.
Described photoelectricity receiving element can be a photodiode; Therefore, described photelectric receiver comprises at least one photodiode, for example comprises 6 photodiodes described below, and these 6 photodiodes are formed a photodiode array.This photodiode array for example can be a photodiode array in the servomechanism installation of laser encoder of the present invention.
Coded message is integrated on three information rails of code-wheel, and it is three concentric circles that radius is ascending of symmetry that these three information rails are with the center of circle of code-wheel, and wherein each information rail is made up of a plurality of striped cell separated from one another.Described a plurality of striped cell can be to adopt method such as etching to process on the card of code-wheel, and these zones are lower relatively than other zone, so can claim that they are that (pit) distinguished in the hole.Comparatively speaking, the smooth zone outside these holes is called as bank district (land).Three diffracted beams shine respectively on these three information rails.Relevant linear polarization diffraction light is focused on the code-wheel, exactly, is focused on basically on described three information rails.The light that the light of reflected back and other regional reflex from code-wheel are returned on the striped cell since phasic difference 180 degree mutually therefore cancel each other.In this case, total intensity of reflected light is compared with the situation that does not have illumination to be mapped to striped cell, and intensity can descend.In the realization, light is every through a striped cell, and catoptrical intensity will descend once.The strength degradation of this pulsating is handled and counted, just can know the increment of the rotational displacement of the rotating shaft that drives code-wheel.
Can on the outermost in described three information rails and the most inboard two information rails, a striped cell bigger with the area of other striped cell be set respectively, other bigger striped cell in block district on the more same information rail promptly respectively is set.The position of the bigger striped cell of these two areas is set, makes two 1 order diffraction light beams can shine this two special striped cell simultaneously, this moment, catoptrical intensity can be lower than the intensity of reflected light at other striped cell place.Described rotating shaft is whenever circled, and two 1 order diffraction light beams can shine these two special striped cell once, can measure the rotation week number of rotating shaft with counter whereby.
Information rail (track) is gone up except that the bigger mark zone of above-mentioned two areas (shape district, zero-bit for example recited above hole), and the width in other shape districts, hole (pit) is identical.The length in the shape district, hole on the different information rails not simultaneously, the resolution of scrambler is also correspondingly different.
Introduce reading of zero signal below
When two-beam from two when luminous point E and F project the zero-bit district, its intensity of reflected light can be respectively a little less than the intensity of reflected light when projecting other common hole district, so the total reflective light intensity of the two also can be than a little less than the common hole district.With this phenomenon effectively the scanning number of turns of luminous point make metering.That is to say that along with the rotation of code-wheel, each two declines from luminous point total reflected light intensity can be understood that code-wheel makes a circle again.
Can adopt the technology of preparation CD and these block code areas of the code-wheel that technology prepares laser encoder of the present invention.Usually, fairly simple method is to form pit areas in described code-wheel surface working, and the etch amount of this method is less, than being easier to reach higher processing precision.
Laser encoder further aspect according to the present invention, the code area of described code-wheel is lower than other zone of code-wheel, if when not having other medium from air to the information rail, its difference in height should be 1/4 of used optical maser wavelength.
If related light medium is suitable, when two polarization components of medium equated, described ovalization polarized light just became circularly polarized light.
Laser encoder further aspect according to the present invention, described laser encoder also comprises a servomechanism installation, be used to check focusing error and/or the tracking error situation of light beam on code-wheel, according to this focusing error situation object lens are adjusted, so that realization is to the correction of focusing error and/or tracking error.Laser encoder of the present invention is formed a light-source system with LASER Light Source and diffraction grating.Penetrate the diffraction light of a plurality of orders of diffraction time from this light-source system, the solution of the present invention adopts is 0 order diffraction light and is distributed in two 1 grade of these 0 order diffraction light both sides (promptly ± 1 grade) diffracted beam.
Specifically, described servomechanism installation comprises a tracking coil and a focusing coil at least.The tracking coil can carry out servocontrol to object lens according to one first composite signal of some photodiode signal in the described photodiode array, makes described first composite signal be returned to 0, makes light beam not break away from relevant information rail; Described focusing coil can carry out servocontrol to object lens according to one second composite signal different with above-mentioned first composite signal in the photodiode array, makes described second composite signal be returned to 0, and light beam is focused on the surface of code-wheel.
Wherein, described first composite signal and second composite signal are respectively the signals that is combined into after through the computing that simply adds deduct by described several photodiode signals, the computing of being adopted that adds deduct should make first composite signal of gained reflect the tracking state of described light beam preferably, and makes second composite signal of gained reflect the state of aggregation of described light beam preferably.
Perhaps, described servomechanism installation can comprise a photodiode array, a prime amplifier, a proportional plus integral plus derivative controller, a driver and a voice coil motor; Described photodiode array can comprise 6 photodiodes, is used to receive relevant photosignal, and described photosignal is successively through being handled accordingly behind described prime amplifier, proportional plus integral plus derivative controller, driver and the voice coil motor; Described voice coil motor comprises a tracking coil and a focusing coil, described tracking coil carries out servocontrol according to the signal E of one the 5th photodiode in the described photodiode array and the difference feedback signal TE (TE=E-F) of one the 6th photodiode signal F, object lens are made adjustment, make TE be returned to 0, make light beam not break away from relevant information rail; The feedback signal FE=(A+C)-(B+D) of described focusing coil after according to one first photodiode A, the second photodiode B, the 3rd photodiode C and the 4th photodiode D signal combination carries out servocontrol, object lens 6 are made adjustment, make FE be returned to 0, light beam is focused on the code-wheel.
Laser encoder further aspect according to the present invention also can adjust the position of described LASER Light Source and the direction of illumination of emergent light, so that light focusing is on described code-wheel.But, comparatively speaking, adjust the control of the easier realization of object lens to light beam.
According to another aspect of the present invention, the invention discloses a kind of displacement measurement method, adopt the aforesaid laser encoder of the present invention, comprising:
A) light that sends of LASER Light Source projects on the code-wheel after through described diffraction grating, polarization splitting prism, collimation lens, quarter wave plate, object lens;
B) being provided with three on described code-wheel is the information rail of axle with the core, each information rail is made up of a plurality of striped cell that are spaced apart from each other, described band shape is boss or the dimple-shaped zone that forms in the code-wheel surface working, and other regional difference in height on described boss or dimple-shaped zone and code-wheel surface should make the light that returns from described boss or dimple-shaped regional reflex and differ 180 degree from the light that other regional reflex on code-wheel surface is returned in phase place; Code-wheel is subjected to the irradiation from the light of described object lens in rotary course, and the light reflected back and pass described object lens;
C) light that returns from described object lens arrives described polarization splitting prism through described quarter wave plate, described collimation lens, and reflexed to described concavees lens by described polarization splitting prism, and, project on the described photelectric receiver through described concavees lens, cylindrical lens;
D) described photelectric receiver changes the light signal that is received into electric signal, and described electric signal is counted, and described count value is represented the rotation angle displacement of the axle of described driving code-wheel rotation.
Described displacement measurement method for example can be with laser encoder of the present invention with a kind of servomotor associated working, with laser encoder as the built-in position feedback unit of servomotor.Positional information by the output servo motor rotor is used for the position probing relevant with servomotor.
Alleged displacement measurement in the measuring method of the present invention had both comprised angle displacement measurement, also comprised the measurement of the displacement of the lines amount relevant with the rotation angle displacement of the driving shaft that drives described laser code disc spins.
The environment medium that is moved in the displacement measurement method of the present invention is generally air, also can be sealed other medium (for example other gas), perhaps is vacuum.
According to a further aspect of above-mentioned displacement measurement method,, can obtain the shift value of another driver part of directly or indirectly linking to each other with above-mentioned rotating shaft according to measured above-mentioned value of angular displacement.Described this shift value can be angular displacement or displacement of the lines.
According to a further aspect of the invention, the invention also discloses a kind of numerically-controlled machine job operation, be used to process a workpiece, adopt laser encoder of the present invention to measure and control the motion of numerically-controlled machine.Described job operation comprises the Processing Curve of determining earlier a machining tool (as the cutter of lathe) according to processing request, this Processing Curve is changed into the corner data of rotating shaft of the code-wheel of laser encoder of the present invention again, it is characterized in that comprising:
A) light that sends of LASER Light Source projects on the code-wheel after through described diffraction grating, polarization splitting prism, collimation lens, quarter wave plate, object lens;
B) being provided with three on described code-wheel is the information rail of axle with the core, each dwelling rail is made up of a plurality of striped cell that are spaced apart from each other, described band shape is boss or the dimple-shaped zone that forms in the code-wheel surface working, and other regional difference in height on described boss or dimple-shaped zone and code-wheel surface should make the light that returns from described boss or dimple-shaped regional reflex and differ 180 degree from the light that other regional reflex on code-wheel surface is returned in phase place; Code-wheel is subjected to the irradiation from the light of described object lens in rotary course, and the light reflected back and pass described object lens;
C) light that returns from described object lens arrives described polarization splitting prism through described quarter wave plate, described collimation lens, and reflexed to described concavees lens by described polarization splitting prism, and, project on the described photelectric receiver through described concavees lens, cylindrical lens;
D) described photelectric receiver changes the light signal that is received into electric signal, and described electric signal is counted, and described count value is represented the rotation angle displacement of the axle of described driving code-wheel rotation;
(e) the rotation angle shift value with gained carries out negative feedback, and a main control unit of input numerically-controlled machine drives described rotating shaft or a driver part that is associated with this rotating shaft is processed described workpiece to be processed according to processing request.
The Processing Curve of a described machining tool (as the cutter of lathe) refers to the relative machining path of machining tool with respect to workpiece to be processed.The corner data of the rotating shaft of described code-wheel refer to the setting with respect to the processing aspect the corner of described rotating shaft done according to processing request, for example with respect to the setting of process time and/or processing worker tool displacement amount.
We call the PA signal to two that the come from diffraction grating 1 order diffraction signals that separate, and 0 order diffraction signal between two PA signals is called the PB signal.
Described light source is a LASER Light Source.Preferably, described light source can be a lasing fluorescence diode.Adopt LASER Light Source can improve the precision of displacement measurement and/or digital control processing.
It is similar that three beams of the present invention detects the used three light beams design of light beam design and CD, also is the both sides that two 1 order diffraction light beams (from luminous point) branch is listed in 0 order diffraction light beam (pipper).
Adopting object lens to focus the laser beam into a plurality of of code-wheel is processed on the information track of cheating shape.A two-way prism in the polarization splitting prism will reflex to from the light of reflected back on the code-wheel on the described photo-detector diode array.
A zone line of described photo-detector diode array can be used for inspection center's luminous point information, and detects relevant to luminous point (satellite spot) information with two zones that are positioned at these zone line both sides.
In numerically-controlled machine job operation of the present invention, for example can be that laser encoder of the present invention is carried out position sampling as a kind of detection feedback element of driving shaft of numerically-controlled machine, convert the angular metric of its rotation to pulse signal, the main control unit that offers servo-drive system is realized position servo control.
Laser encoder of the present invention, the displacement measurement method that adopts this laser encoder and numerically-controlled machine job operation are with respect to the advantage of prior art; the accuracy that adopts servo techniques to protect signal to obtain; manufacturing to code-wheel requires to decrease, and has correspondingly reduced the manufacturing cost of code-wheel.Simultaneously, the light channel structure that is adopted is comparatively compact, and other parts can be fixed after the light channel structure adjustment is finished except that object lens, therefore in use guarantees its precision easily.
(4) description of drawings
The present invention adopts following synoptic diagram to introduce background technology of the present invention and laser encoder of the present invention and the application aspect displacement measurement and numerically-controlled machine processing thereof.Wherein:
Fig. 1 is the typical rotary optical incremental encoder of a prior art synoptic diagram;
Fig. 2 is a kind of laser incremental encoder synoptic diagram of prior art;
Fig. 3 is the index path of prior art automatic focus laser encoder;
Fig. 4 is the light path synoptic diagram of laser encoder of the present invention;
Fig. 5 is information rail (track) synoptic diagram of laser code dish of the present invention;
Fig. 6 is the synoptic diagram of the code-wheel of laser encoder of the present invention;
Fig. 7 is a synoptic diagram of photelectric receiver in the laser code dish of the present invention;
Synoptic diagram when Fig. 8 is n=1 on the information rail of laser beam irradiation in code-wheel;
Synoptic diagram when Fig. 9 is n=2 on the information rail of laser beam irradiation in code-wheel;
The synoptic diagram of the code-wheel when Figure 10 is n=2;
Figure 11 shows the frequency characteristic of signal PA and PB;
Figure 12 is the synoptic diagram of tracking servo ring and focus servo loop; Figure 13 carries out the synoptic diagram that displacement measurement and numerically-controlled machine add formula for adopting laser encoder of the present invention.
(5) embodiment
Fig. 1 to Fig. 3 has correspondingly introduced some aspects of background technology of the present invention; Fig. 4 to Figure 11 has introduced the various aspects of apparatus and method of the present invention.
Fig. 4 shows the light path of laser encoder of the present invention.Among the figure, LASER Light Source of number designation 1 expression, diffraction grating of 2 expressions, polarization splitting prism of 3 expressions, collimation lens of 4 expressions, quarter wave plate of 5 expressions, object lens of 6 expressions, code-wheel of 7 expressions, concavees lens of 8 expressions, cylindrical lens of 9 expressions, photodiode array of 10 expressions, 7A represents a tracking coil, and 7B represents a focusing coil.As shown in the figure, the light that comes from diffraction grating (2) is focused on the code-wheel 7 after through polarization splitting prism 3, collimation lens 4, quarter wave plate 5, object lens 6, be reflected from code-wheel 7 again, behind described object lens 6, quarter wave plate 5, collimation lens 4, get back to polarization splitting prism 3, and be polarized Amici prism 3 reflections, through being focused on the photelectric receiver 10 behind concavees lens 8, the cylindrical lens 9.Described photelectric receiver 10 can be a kind of photodiode array that is used for sensed light signal.
Specifically, the laser encoder shown in Fig. 4 comprises:
A) LASER Light Source 1 is used to send Ray Of Light, and directive also passes diffraction light coral 2;
B) above-mentioned diffraction grating 2 is used to accept the light of described light source ejaculation and allow that described light passes, and produces diffracted beam;
C) polarization splitting prism (PBS) 3 is used to make light from described diffraction grating 2 to be linear polarizationization and penetrates along original direction; This polarization splitting prism 3 also will be reflexed to concavees lens 8 by the light that a collimation lens 4 returns;
D) above-mentioned collimation lens 4 makes the polarization linearly polarized light collimationization ejaculation from described polarization splitting prism 3; And the light that allows to return from a quarter wave plate 5 passes and projects described polarization splitting prism 3;
E) above-mentioned quarter wave plate 5 makes the polarization linearly polarized light from described collimation lens 4 change the ovalization polarized light into; And the elliptically polarized light that allows to return from object lens 6 passes, and it changed into linearly polarized light when passing and projects on the described collimation lens 4;
F) above-mentioned object lens 6 allow to pass through also described light focusing to a code-wheel 7 from the light of above-mentioned quarter wave plate 5;
G) above-mentioned code-wheel 7 can be around a fixing rotating shaft rotation, and its surface is for reflecting the reflecting surface of described laser, and this surperficial part is for being focused the code area of described code-wheel 7 from the light of above-mentioned object lens 6; Described code area for round three of described rotation center apart from one another by the concentric information rail of opening (track), wherein each information rail is made up of a plurality of striped cell that are spaced apart from each other, described striped cell is boss or the pit areas that forms in the code-wheel surface working, and other regional differences in height on described boss or pit areas and code-wheel surface are that the conversion back is 1/4 of used optical maser wavelength under the environment medium;
H) above-mentioned concavees lens 8, allow 4 that return by described collimation lens, pass and cylindrical lens 9 of directive through the light of the reflection of described polarization splitting prism 3;
I) above-mentioned cylindrical lens 9 allows to pass through from the light of above-mentioned concavees lens 8, throws and focuses on the photelectric receiver 10;
J) above-mentioned photelectric receiver 10 receives the light from above-mentioned cylindrical lens 9, changes described light into electric signal, and described electric signal is counted.
As shown in Figure 4, described servomechanism installation comprises a tracking coil 7A and a focusing coil 7B, described tracking coil 7A carries out servocontrol according to one the 5th photodiode E among the described photodiode array 11a and the difference feedback signal TE (TE=E-F) of one the 6th photodiode F signal, direction to object lens 6 is made adjustment, make TE be returned to 0, make light beam not break away from relevant information rail; The feedback signal FE=(A+C)-(B+D) of described focusing coil 7B after according to photodiode A, B, C and D signal combination carries out servocontrol, made adjustment in the position of object lens 6, makes FE be returned to 0, and light beam is focused on the code-wheel.
As shown in Figure 12, laser encoder further aspect according to the present invention, this laser encoder also can comprise a servomechanism installation, this servomechanism installation comprises a photodiode array 11a (this photodiode array 11a also is the ingredient of described photelectric receiver simultaneously), a prime amplifier 11b, a proportional plus integral plus derivative controller 11c, a driver 11d, a voice coil motor (VCM) 11e; Described photodiode array 11a comprises 6 photodiodes again, be used to receive relevant photosignal, described photosignal passes through described prime amplifier 11b successively, proportional plus integral plus derivative controller 11c, handled accordingly behind driver 11d and the voice coil motor 11e, described voice coil motor 11e comprises a tracking coil (7A) and a focusing coil (7B), described tracking coil (7A) carries out servocontrol according to the difference feedback signal TE (TE=E-F) of photodiode E and F signal, direction to object lens 6 is made adjustment, make TE be returned to 0, make light beam not break away from relevant information rail; The feedback signal FE=(A+C)-(B+D) of described focusing coil (7B) after according to photodiode A, B, C and D signal combination carries out servocontrol, made adjustment in the position of object lens 6, makes FE be returned to 0, and light beam is focused on the code-wheel.
The code-wheel 7 of laser encoder of the present invention has been shown among Fig. 5, wherein has been provided with information rail 7a, 7b and the 7c of three concentric annular from inside to outside, wherein every information rail is made up of a plurality of striped cell with different on every side separated from one another.More preferential mode is, adopts this area etching method commonly used to process the striped cell of hole shape, and wherein striped cell is than hanging down 1/4 wavelength around it.
In practice, on code-wheel, film if desired, then need to consider the variation of light path, correspondingly to making correction the degree of depth of described striped cell.
Introduce the code-wheel of laser encoder of the present invention below in conjunction with Fig. 6, and how to determine the degree of depth that the hole is distinguished according to the plated film of code-wheel.
Fig. 6 is the cross sectional representation of the code-wheel of laser encoder of the present invention.Scrambler among the figure comprises 4 layers, i.e. transparent base layer, reflection horizon, protective seam and label layer.Transparent base layer can be made of polycarbonate, and thickness can be about 1.2mm; The reflection horizon can be spattered aluminium technology by vacuum evaporation of aluminum or negative electrode and prepare, and thickness can be 50-100nm; Protective seam can be 6 to 7 microns acrylate layer; The effect of label layer is to add commercial mark thereon, and its material and thickness are not had strict requirement, only otherwise the operate as normal that influences described code-wheel gets final product.Laser beam is by transparent polycarbonate bottom incident, and hole district (Pit) degree of depth is approximately 0.1um, and 0.5um is wide.The refractive index of transparent base layer can be 1.55 ± 0.10.
Introduce the degree of depth in the information rail Zhong Keng district that how to determine code-wheel or the height in bank district below.
Get near bank district and when regional when laser beam, all reflected light all are same-phases.When laser beam is got near hole district and when regional, from cheating the reflected light increase that the zone obtains
Phase shift, this can cause will offsetting from hole regional reflex light the reflected light of near zone.At this moment this just mean from the total intensity of CD reflection light and will significantly reduce.So distance between the bank district is distinguished in the hole, under the situation that does not change medium refraction index, should be optical maser wavelength
In practice, as adopting aluminum gallium arsenide GaAlAs laser diode, its aerial wavelength X is 780nm, and this moment is because also exist polycarbonate basic unit in the middle of information rail and the air medium.When laser beam incident behind layer of polycarbonate because refraction index changing, the refractive index n 2=1.55 of layer of polycarbonate, so effective wavelength is 780nm/1.55=503nm, and the degree of depth in hole district should calculate
Therefore in practice, the degree of depth in hole district will be through the correction of dielectric layer refractive index.Importantly, the degree of depth of gained should make from the light of hole district or bank district reflected back and compare with the light that other regional reflex from code-wheel is returned, and differs 180 degree on phase place.
What send from semiconductor laser is that wavelength X is the oval-shaped linearly polarized light with certain angle of divergence of 780nm.Form circularly polarized light through polarization splitting prism 3 with quarter wave plate 5 (linearly polarized light of optical axis and incident becomes 45 ' angle) back, by focusing on the code-wheel 7 by object lens 6 again behind the collimating mirror 4.The circularly polarized light that reflects from the card of code-wheel 7 passes object lens 6, once more by quarter wave plate 5 formed with perpendicular to former catoptrical linearly polarized light.At this moment, the emerging ray polarized light at incident ray polarized light direction upper deflecting 90 ', the laser beam of this moment is no longer by polarization splitting prism 3, but reflexes on the photelectric receiver 10 by polarization splitting prism 3.
The block of information of code-wheel 7 is positioned at the comparatively middle zone of inclined to one side code-disc 7.For example, can adopt the CD of a 120mm as the laser code dish.When adopting such laser code dish, three information rails can be set in diameter is to locate between the 50mm to 116mm.
Preferred scheme is: the width in the shape district, hole of three information rail 7a, 7b and 7c all is 0.5 μ m.When adopting the laser of 780nm wavelength, the hole is aforesaid 0.13 μ m deeply.
Fig. 7 shows 6 photodiodes in the photelectric receiver 10 that adopts laser encoder of the present invention, is used for receiving photosignal.Wherein, two photodiode E and F are respectively applied for reception from the information rail 7a of both sides and reflected signal and the tracking error signal TE from luminous point (satellite spots) of 7c, wherein TE is set at the difference of E and two photosignals that photodiode received of F, i.e. TE=E-F; Wherein this reflected signal is represented with PA, i.e. PA=E+F; Other four photodiode A, B, C and D are used to detect main beam, obtain focus error signal FE and PB signal; Wherein, four photodiode A, B, C and D between E and the F are used to receive the reflected light signal from the intermediate information rail, i.e. PB=A+B+C+D.In the reality, the position of each photodiode can not be to be close to as shown in Figure 6, but the distance that can scatter.
For making laser encoder of the present invention have better anti-shake performance, can adopt a servocontrol ring that it is carried out out of focus and/or the correction that leaves the right or normal track, that is to say, carry out tracking servo and focus servo control.
Because for the influence of code-wheel, there is error in system on focus direction and tracking direction when the off-centre of main shaft and rotation, the permissible error value is to decide according to optically read principle and institute's canned data type.
When adopting laser encoder of the present invention, for realizing measuring preferably and processing effect, wish that the franchise of laser beam on focus direction is about 1um, radially the franchise of tracking direction is about 0.1um.So little tolerance deviation obviously can not rely on the way that improves mechanical precision to realize merely, and the servo-drive system of guaranteeing the correct tracking target information of luminous point rail must be set in system.Focus servo and tracking servo have been adopted in this programme.
In the focus servo loop, Ddisc represents the distance of desired code-wheel to object lens.Because code-wheel fluctuates periodically up and down during rotation, actual range will change; Dol has reflected because main spot moves the variable in distance that causes.
In the tracking servo ring, two positions that the Ddisc representative is desired from luminous point.Because periodically swinging can appear in code-wheel when rotated, two physical locations that drop on the target information rail from luminous point are also changing.Reflect because two variations of moving the luminous point cause from luminous point at random with parameter Dol with respect to position on the information rail of both sides.
Adopt the common Astigmatism methord type of focusing, to produce a focus error signal (FE).The luminous point that projects photodiode array (A, B, C, D, E and F) is along with the size of code-wheel defocusing amount is changing shape.With the FE signal is the difference of oblique both sums of four-quadrant photodiode, that is: FE=(A+C)-(B+D).Actual conditions show that this amount has reflected the state of aggregation of light beam on code-wheel more accurately.
If code-wheel is too near apart from object lens, FE＞0 then;
If code-wheel is in the focusing range, FE=0;
If code-wheel is too far away apart from object lens, FE＜0.
Near focusing range, the FE approximately linear can provide and well feed back signal to servo loop.
Can adopt 3 tracking modes that a tracking error signal (TE) is provided, focus on three signals of coding on the card by detection, the distribution of these three points is centres of main spot (central spot) information that mediates rail, and two from luminous point be distributed in both sides information rail slightly outside, referring to Fig. 4.
When main spot was positioned at intermediate information rail central, two were departed from separately information rail central authorities a little from luminous point, equidistantly distribute the both sides in main spot.Corresponding two signals equate in the photodiode array in the photelectric receiver 10, and the difference of signal E and F is TE=E-F=0.When main spot departed from intermediate information rail central a little, two Strength Changes from luminous point caused the E signal of photodiode to increase, and the F signal reduces TE＞0 simultaneously; Opposite, when main spot departed from intermediate information rail central round about a little, two Strength Changes from luminous point caused the E signal of photodiode to reduce, and the F signal increases simultaneously, TE＜0;
Near the tracking range of signal, the TE approximately linear can provide and well feed back signal to servo loop.
According to the static gain requirement, behind the model of having selected photodiode 11a, prime amplifier 11b and driver 11d and voice coil motor 11e, can adopt proportion integration differentiation control to proofread and correct (pid correction) means as phase compensation and adjustment servo gain.
Further specify laser encoder of the present invention and some technical characteristics in displacement measurement method and numerically-controlled machine job operation thereof below.
When laser encoder of the present invention is set, need make suitable selection to its frequency of operation, the relevant performance parameter of device can change with the frequency of operation of device.Figure 11 shows laser encoder of the present invention when work, the characteristic that inner signal PA and PB become with frequency.
Experiment shows that the amplitude A of reflected light electric signal (perhaps intensity) does not become with frequency basically in low-frequency range, and the raising with frequency reduces when high frequency.For apparatus and method of the present invention, the frequency f 1 that signal intensity begins to descend is about 196kHz, and the frequency f 2 during 2/3 amplitude is about 720kHz.Therefore, if signal frequency response during greater than 196kHz, should be proofreaied and correct the output of signal according to the frequency characteristic of signal, in order to determine the threshold value of zero signal.
Scrambler disclosed in this invention is the same with conventional incremental encoder, has light source, sensing receiving-member (as photodiode) and the code-wheel with circle of information rail equally.But compared with the prior art scrambler of the present invention still has a great difference:
1. sensing principle is different from conventional scrambler.Do not adopt directly to receive the photosignal mode, and adopted the reflected light mode that receives based on the coding card of CD technology;
2. reading principle is based on the laser diffraction basis.Laser has been used as light source, has replaced common LED source;
3. the design of code-wheel: can be with the discoid body that is similar to the CD dish as code-wheel, this will make the overall cost of scrambler descend;
4. light path element all is packaged together except object lens, and is compact and low-cost, and overall cost is reduced.
The technique effect of laser code dish of the present invention can embody from the improvement of the resolution measurement index of code-wheel diagonal displacement.
The resolution of code-wheel of the present invention had both depended on the size of coding information on disk rail diameter, also depended on the length of hole (pit) and step (land).
Because the design reasons of light path, main spot is fixed from the distance between the luminous point with two, therefore can determine the resolution of device by the diameter of cheating the length of distinguishing (pit area) He An district (land area) and information rail.
In general, for making the phase differential that 90 degree are arranged between signal PA and the PB, need to satisfy:
2×D
2＝(2n-1)×(L
pit+L
land) (1)
Wherein: n be illustrated in one the spot scan cycle Nei Keng district or the number of times that repeats of bank district, promptly one section camber line between main spot (central laser spot) and adjacent two among the luminous point one the quantity of luminous point of process.In the reality, because middle main spot is basic identical with two diameters from luminous point and code-wheel that are positioned at the main spot both sides, so described three information rails are three camber lines that paste very closely, can be approx main spot and adjacent camber line between luminous point be considered as in the information rail described three information rails one section.D2 represent main spot and both sides from the distance between the luminous point, Lpit represents to cheat section length, Lland represents the bank section length.
Device resolution is to be decided by following method.In practice, can set the equal in length in He An district, hole district, i.e. Lpit=Lland=L, the hole is distinguished or the length in bank district is; So,
The selection of the length in He An district, hole district should be bigger than the diameter of middle laser spot.Correspondingly, the resolution of code-wheel is
Promptly
Wherein, D is the diameter of used coding information on disk rail.Because the spacing of three relevant information rails is far smaller than the diameter of information rail (for example when the diameter of middle information rail is 80mm or 120mm, spacing between two adjacent information rails for example can be 1.6 μ m), therefore can think approx that the true footpath of these three information rails is identical.
State on the information rail of laser beam irradiation in code-wheel has been shown among Fig. 8, n=1 wherein, when promptly main spot dropped on hole district, adjacent one was dropped in the adjacent hole district from luminous point, is not crossed over other hole district between the two.Among Fig. 7,3 bullets represent to drop on after light is by the diffraction grating in the light-source system three luminous points on the code-wheel.Hole groove on the black rectangular block presentation code dish.
For example, when the diameter D of the information rail of the inboard of the block of information in the code-wheel was 50mm, D2=20um, and n=1 (see figure 7) according to formula (2) and (3), cheated section length accordingly and are
And corresponding resolution is
Another example, for obtaining higher resolution, can design main spot and cross over hole district two or more on the same information rail (or bank district) from spot scan cycle of light that the spacing of luminous point is crossed over more than 1 or 1, that is, the resolution of code-wheel also can correspondingly change.
N=2 has been shown among Fig. 9 (promptly when main spot drops on hole district on the information rail, an adjacent hole of dropping on another information rail from luminous point is distinguished, also has hole district between the two, be to have crossed over two hole districts between the two) time, laser spot is radiated at the state on the information rail of code-wheel.
In the embodiment shown in Fig. 8, n=2, according to formula (2) and (3), corresponding hole length is
And corresponding resolution
Therefore, the n value strengthens the resolution that has improved laser code dish of the present invention.
Certainly, in this case the shape in zero signal (index signal) district should be following Fig. 9 reflected like that.In Fig. 9, not resembling among Fig. 5, the zero signal district on the information rail of both sides, do not separated two striped cell of arranging but lay respectively at for an adjacent row's striped cell.
The invention also discloses the displacement measurement method and the numerically-controlled machine job operation that adopt above-mentioned laser encoder.
Can be according to the present invention the step-by-step counting of scrambler gained during the rotation of the code-wheel of laser encoder, obtain the rotation angle displacement of code-wheel.
In addition, also can be according to the as above value of angular displacement of gained, to the value of angular displacement of the rotation of another device or the displacement of the lines value of translation, perhaps one of this device shift value of describing with the array in the above space of two dimension is measured.Its method is characterised in that, with the rotating shaft and the device interlock to be measured of a described displacement of the code-wheel of laser encoder of the present invention, according to the interaction relation of the two and the angular displacement of code-wheel of the present invention, extrapolates the displacement of this device.
An example realizing numerically-controlled machine job operation of the present invention is, make the rotating shaft of code-wheel of laser encoder of the present invention and the drive unit interlock of numerically-controlled machine, according to the Processing Curve of the interaction relation and the drive unit of the angular displacement of code-wheel of the present invention and described numerically-controlled machine of the two, come the motion of the described numerically-controlled machine of FEEDBACK CONTROL, realize high-precision processing.
Referring to Figure 13, Figure 13 carries out the synoptic diagram that displacement measurement and numerically-controlled machine add formula for adopting laser encoder of the present invention.Among the figure, laser encoder of the present invention of number designation 131 expressions; The main control unit of a numerically-controlled machine of 132 expressions; Speed control of 133 expressions; Current controller of 134 expressions; Telegon of 135 expressions; (PCC) power of 136 expressions is accepted the order of current controller and the feedback information of scrambler and is compared computing, drives follow-up 136; AC servo motor of 137 expressions; Current measurement circuit of 138 expressions; Rotary transformer of 139 expressions; Gear case of 140 expressions; Platen of 141 expressions.This numerically-controlled machine is when work, the current actual value of the supplying electric current controller 134 that records with the rotor-position of AC servo motor 137, by current measurement circuit 138, by rotary transformer 139 measure the speed actual value of feed speed controller 133, and four amounts such as displacement actual value of the supply numerically-controlled machine main control unit 132 that is recorded by laser encoder 131 of the present invention are carried out negative feedback, be fed on the main control unit of numerically-controlled machine, the work of numerically-controlled machine is controlled.In device shown in Figure 13, the angle of rotation of the driving shaft of 131 pairs of numerically-controlled machines of laser encoder carries out displacement sampling, and this angle of rotation conversion of signals is become pulse signal, offers the servocontrol that the main control unit 132 of described numerically-controlled machine carries out displacement.The task of displacement control is accurately to be controlled the position of each coordinate axis on the numerically-controlled machine by described main control unit 132.A kind of way of realization of described device is, laser encoder of the present invention is installed on the platen as displacement transducer, mechanical shift is converted to digit pulse, and these pulse values are delivered to the position position measurement interface of main control unit, count by counter.Sample to the feedback signal of this displacement actual value in computer cycle tail ground in the described main control unit 132, and the result that this sampling feedback value and poor benefit program are exported is compared, and obtains a site error value.This site error value through a software gain adjust after, be transferred to a digital to analog converter, thereby, drive worktable and move to the direction that reduces site error for servomechanism installation provides control voltage.
The applicant has exemplarily provided three types of technology scheme of the present invention in the above.Those of ordinary skills are not difficult according to foregoing, and the relation between laser code dish of the present invention and described displacement measurement method and the numerically-controlled machine job operation is made rational popularization.
Claims (8)
1, a kind of laser encoder comprises:
A) LASER Light Source (1) is used to send Ray Of Light, and directive also passes a diffraction light coral (2);
B) an above-mentioned diffraction grating (2) is used to accept the light of described LASER Light Source ejaculation and allow that described light passes, and produces diffracted beam;
C) polarization splitting prism (3) is used to make light from described diffraction grating (2) to be linear polarizationization and penetrates along original direction; This polarization splitting prism (3) also will be reflexed to concavees lens (8) by the light that a collimation lens (4) returns;
D) an above-mentioned collimation lens (4) makes the polarization linearly polarized light collimationization ejaculation from described polarization splitting prism (3); And the light that allows to return from a quarter wave plate (5) passes and projects described polarization splitting prism (3);
E) an above-mentioned quarter wave plate (5) makes the polarization linearly polarized light from described collimation lens (4) change the ovalization polarized light into; And the elliptically polarized light that allows to return from object lens (6) passes, and it changed into linearly polarized light when passing and projects on the described collimation lens (4);
F) above-mentioned object lens (6), allow from the light of above-mentioned quarter wave plate (5) by and described irradiate light and focus on a code-wheel (7);
G) an above-mentioned code-wheel (7) can be around a fixing rotating shaft rotation, and its surface is for reflecting the reflecting surface of described laser, and this surperficial part is for being focused the code area of described code-wheel (7) from the light of above-mentioned object lens (6); Described code area for round three of described rotation center apart from one another by the concentric information rail of opening, wherein each information rail is made up of a plurality of striped cell that are spaced apart from each other, described striped cell is boss or the pit areas that forms in code-wheel (7) surface working, and other regional differences in height on described boss or pit areas and code-wheel surface should make the light that returns from described boss or dimple-shaped regional reflex and differ 180 from the light that other regional reflex on code-wheel surface is returned in phase place to be spent;
H) above-mentioned concavees lens (8), allow to return by described collimation lens (4), pass and cylindrical lens of directive through the light of the reflection of described polarization splitting prism (3);
I) an above-mentioned cylindrical lens (9) allows to pass through from the light of above-mentioned concavees lens (8), throws and focuses on the photelectric receiver (10);
J) an above-mentioned photelectric receiver (10) comprises at least one photoelectricity receiving element, is used for receiving the light from above-mentioned cylindrical lens (9), and changes the light signal that is received into electric signal, and described electric signal is counted.
2, laser encoder as claimed in claim 1, also comprise a servomechanism installation, this servomechanism installation comprises a tracking coil (7A) and a focusing coil (7B), described tracking coil (7A) carries out servocontrol according to the difference feedback signal TE=E-F of one the 5th photodiode (E) in the described photodiode array (11a) and one the 6th photodiode (F) signal, direction to object lens 6 is made adjustment, and makes TE be returned to 0, makes light beam not break away from relevant information rail; The feedback signal FE=(A+C)-(B+D) of described focusing coil (7B) after according to photodiode A, B, C and D signal combination carries out servocontrol, made adjustment in the position of object lens 6, makes FE be returned to 0, and light beam is focused on the code-wheel.
3, laser encoder as claimed in claim 1 also comprises a servomechanism installation, this servomechanism installation comprises a photodiode array (11a), a prime amplifier (11b), a proportional plus integral plus derivative controller (11c), a driver (11d), a voice coil motor (11e); Described photodiode array (11a) comprises 6 photodiodes again, be used to receive relevant photosignal, described photosignal is handled after passing through described prime amplifier (11b), proportional plus integral plus derivative controller (11c), driver (11d) and voice coil motor (11e) successively accordingly; Described voice coil motor 11e comprises a tracking coil (7A) and a focusing coil (7B), described tracking coil (7A) carries out servocontrol according to the difference feedback signal TE=E-F of one the 5th photodiode (E) in the described photodiode array (11a) and one the 6th photodiode (F) signal, direction to object lens (6) is made adjustment, make described difference feedback signal TE be returned to 0, make light beam not break away from relevant information rail; The feedback signal FE=(A+C)-(B+D) of described focusing coil (7B) after according to photodiode A, B, C and D signal combination carries out servocontrol, make adjustment in position to object lens (6), make the feedback signal FE after the combination be returned to 0, light beam is focused on the code-wheel.
4, a kind of displacement measurement method adopts claim 1 or 2 described code-wheels, wherein:
(1) light that sends of LASER Light Source (1) projects on the code-wheel (7) after through described diffraction grating (2), polarization splitting prism (3), collimation lens (4), quarter wave plate (5), object lens (6);
(2) being provided with three on described code-wheel (7) is the information rail of axle with the core, each information rail is made up of a plurality of striped cell that are spaced apart from each other, described band shape is boss or the dimple-shaped zone that forms in code-wheel (7) surface working, and other regional difference in height on described boss or dimple-shaped zone and code-wheel (7) surface should make the light that returns from described boss or dimple-shaped regional reflex and differ 180 degree from the light that other regional reflex on code-wheel surface is returned in phase place; Code-wheel is subjected to the irradiation from the light of described object lens (6) in rotary course, and the light reflected back and pass described object lens (6);
(3) light that returns from described object lens (6) arrives described polarization splitting prism (3) through described quarter wave plate (5), described collimation lens (4), and reflexed to described concavees lens (8) by described polarization splitting prism (3), and, project on the described photelectric receiver (10) through described concavees lens (8), cylindrical lens (9);
(4) described photelectric receiver (10) changes the light signal that is received into electric signal, and described electric signal is counted, and described count value is represented the rotation angle displacement of the axle of described driving code-wheel (7) rotation.
5, method as claimed in claim 4, wherein adopt a servomechanism installation to check focusing error and/or the tracking error situation of light beam on code-wheel (7), and according to this focusing error and/or tracking error situation object lens are adjusted, laser beam is focused on the information rail of described code-wheel.
6, the method described in claim 4 according to measured above-mentioned value of angular displacement, obtains the shift value of another driver part of directly or indirectly linking to each other with above-mentioned rotating shaft.
7, the method described in claim 5 according to measured above-mentioned value of angular displacement, obtains the shift value of another driver part of directly or indirectly linking to each other with above-mentioned rotating shaft.
8, a kind of numerically-controlled machine job operation is processed a workpiece with a numerically-controlled machine, and adopts laser encoder as claimed in claim 1 or 2 to measure and control the motion of numerically-controlled machine; Described job operation comprises the Processing Curve of determining earlier a machining tool according to processing request, this Processing Curve is changed into the corner array of rotating shaft of the code-wheel of laser encoder of the present invention again, it is characterized in that comprising:
A) light that sends of LASER Light Source (1) projects on the code-wheel (7) after through described diffraction grating (2), polarization splitting prism (3), collimation lens (4), quarter wave plate (5), object lens (6);
B) being provided with three on described code-wheel (7) is the information rail of axle with the core, each information rail is made up of a plurality of striped cell that are spaced apart from each other, described band shape is boss or the dimple-shaped zone that forms in the code-wheel surface working, and other regional difference in height on described boss or dimple-shaped zone and code-wheel surface should make the light that returns from described boss or dimple-shaped regional reflex and differ 180 degree from the light that other regional reflex on code-wheel surface is returned in phase place; Code-wheel (7) is subjected to the irradiation from the light of described object lens (6) in rotary course, and the light reflected back and pass described object lens (6);
C) light that returns from described object lens (6) arrives described polarization splitting prism (3) through described quarter wave plate (5), described collimation lens (4), and reflexed to described concavees lens (8) by described polarization splitting prism (3), and, project on the described photelectric receiver (1 0) through described concavees lens (8), cylindrical lens (9);
D) described photelectric receiver (10) changes the light signal that is received into electric signal, and described electric signal is counted, and described count value is represented the rotation angle displacement of the axle of described driving code-wheel (7) rotation;
E) the rotation angle shift value with gained carries out negative feedback, and a main control unit (132) of input numerically-controlled machine drives described rotating shaft or a driver part that is associated with this rotating shaft is processed described workpiece to be processed according to processing request.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2005100723571A CN100538278C (en) | 2005-05-31 | 2005-05-31 | Laser encoder adopts the displacement measurement method and the numerically-controlled machine job operation of this laser encoder |
| DE200610024179 DE102006024179A1 (en) | 2005-05-31 | 2006-05-23 | Angle encoder has laser source split into three beams and focussed on reflecting coding disc with quarter wave deep impressed pattern on marking rings |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2005100723571A CN100538278C (en) | 2005-05-31 | 2005-05-31 | Laser encoder adopts the displacement measurement method and the numerically-controlled machine job operation of this laser encoder |
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| CN1873377A true CN1873377A (en) | 2006-12-06 |
| CN100538278C CN100538278C (en) | 2009-09-09 |
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| CNB2005100723571A Active CN100538278C (en) | 2005-05-31 | 2005-05-31 | Laser encoder adopts the displacement measurement method and the numerically-controlled machine job operation of this laser encoder |
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| CN (1) | CN100538278C (en) |
| DE (1) | DE102006024179A1 (en) |
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| Publication number | Publication date |
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| CN100538278C (en) | 2009-09-09 |
| DE102006024179A1 (en) | 2007-01-04 |
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