DE102004018106B4 - High-precision optical position detector for galvanometer rotary screens - Google Patents

Abstract

High-precision optical position detector for galvanometer rotary drives for precise and reproducible deflection of laser beams by means of mirrors or similar elements, comprising a diaphragm (6) connected to the drive (2), a radiation source (9) and at least two radiation detectors (11) Aperture (6) depending on the current position, the beam path between the source (9) and detectors (11) influenced or interrupts, continue
- The diaphragm (6) coaxially between the radiation source (9) and radiation detectors (11) is arranged, wherein the diaphragm (6) has a cylindrical sleeve shape (6) with a plurality of circumferentially formed windows (7) and the radiation source (9) in the sleeve interior extends,
- As well as with the radiation source (9) connected to a radiation-conducting and-scattering rod or finger (10) extends into the interior of the cylinder sleeve (6) which emits scattered radiation rotationally symmetrical uniformly distributed and has a lateral scattered light optimizing surface structure.

Description

The The invention relates to a high precision optical position detector for galvanometer rotary actuators for precise and reproducible deflection of laser beams by means of mirrors or the like elements, comprising one connected to the drive Aperture, a radiation source and at least two radiation detectors, the aperture depending on the current position between the beam path Source and detectors affected or interrupted, according to claim 1.

For laser scan heads and There mirrors used galvanometer drives are used. For such Drives an exact position detection is necessary. The precision must be in the range of μrad lie and it is the position detection device itself no or just a little inertia exhibit. Furthermore, care is taken in such arrangements to bear that the measuring device has sufficient electromagnetic compatibility owns or even emits no appreciable interference radiation.

Galvanometer scanner are highly dynamic rotary actuators for optical applications that a motor part and a high-precision position detector. The engine part is based on solutions of the prior art z. B. on the so-called moving magnet technology. As mentioned above, is prevalent Field of application of such galvanometer scanners the fast and precise positioning from mirrors to laser beam deflection.

Regarding the Position detector systems are optical arrangements, but also capacitive solutions Previously known with butterfly disc ceramic. In an optical Sensor is z. B. from a combination of a butterfly aperture disc, light-emitting Diodes and photodiodes assumed, the latter in special Segmentation are arranged.

at the position detectors, the task is solved, the respective angular position of the rotationally moving drive element to capture, so that the desired highly dynamic control of the drive with suitable electronic Funds can be done.

The US 6426 635 B1 shows a galvanometer position detector on a capacitive basis, where a cylinder arrangement is presented there and a tubular signal plate is provided which has a plurality of symmetrically equally distributed sensitive surfaces. The position detection is now carried out under consideration of changing dielectric conditions when performing a rotational movement.

With respect to the prior art optical position detectors is for example on the EP 0 140 574 A1 or the GB 2 005 407 A1 referenced, the latter comprising an optical encoder.

In the EP 1 295 090 B1 there is described a position detector for a scanning device comprising a movable light shield, at least two light detectors disposed behind the light shield and coverable by the light shield as it moves with different coverage dimensions, and at least one light source for emitting light to the light detectors ,

Out is the different overlap dimensions the position of the light shield can be determined. According to this solution of the prior art Furthermore, a reflector is provided in front of the light shield is arranged, wherein the light source for emitting light in such a way is arranged that the light emanating from her to the reflector and then from the reflector in the direction of the light detectors a deflection takes place. The light source itself is laterally of the light detectors arranged adjacent to these.

The light shield according to EP 1 295 090 B1 has a butterfly shape and is therefore not completely rotationally symmetric with the result of undesired moments of inertia, especially in a reversal of motion of the actual drive connected to the light shield. Furthermore, in the position detector training according to EP 1 295 090 B1 Care must be taken to ensure that radiation energy from the light source does not reach the adjacent detectors in an undesired manner, but only via the virtual detour with the aid of the reflector designed as a cap. The fact that the reflector of the prior art must have a certain minimum distance from the light shield, inevitably results in an undesirable increase in the installation space in such photodetectors. Further difficulties exist in the desirable integration of signal preprocessing electronics within the detector housing.

Another device for position measurement is in the WO 98/54548 A1 proposed. This apparatus consists essentially of a rotating cylinder, in whose surface a mask is integrated, which alternately has light-transmitting and -undurchlässige strips. The mask thus moves along with the hollow cylinder. A light source inside the rotating cylinder emits light via a collimating lens on the mask. A detector array mounted on the outside of the rotating cylinder receives the mask out through the mask urgent rays of light.

In the EP 0 874 224 B1 it is an optical incremental encoder, as it is in many forms, eg. B. in the control of printers or the like application.

According to the local Doctrine should be the recognition of the direction of rotation of the incremental wheel thereby possible that as a light receiver provided photodiodes are arranged so that they each have at most one of the breakthroughs fed to the increment wheel light and they can not simultaneously have a brightness maximum that to them the breakthroughs supplied Detecting light of the light source.

The Detection of emanating from the incremental light radiation through the attached photodiodes is characterized by a best possible association of the Distance and the width of the openings of the incremental referred optimized for the angular position of the radiation detectors.

The DE 41 13 720 A1 discloses a forked light barrier comprising a rotatably mounted optical fiber into which light is fed by a stationary light emitter. The light guide is arranged centrally with a stationary pot-shaped body of lichtleitendem material and is surrounded by a cylinder having wall passages. At the upper edge of the body, a garland of equal sized oblique surfaces is arranged. At the bottom of the body corresponding photo elements are provided to the inclined surfaces. Each photo element is assigned a specific angular position of the light guide.

The Detection of the emitted light, which by the in the cylinder attached wall outlets is thus carried out by a first on the oblique surfaces of the body ring and subsequently along the side surfaces of the cup-shaped body out Direction of the light to the photo elements. This represents a relative complicated and complicated Construction with respect to the light detection is.

According to the teaching of the JP 62 133 314 A it is a position detector in which a diaphragm is provided, which is arranged coaxially between the radiation source and radiation detectors, wherein the diaphragm has a cylindrical sleeve shape with a peripheral window. The radiation source is shown as a finger-like structure in the sleeve interior.

The radiation detectors are realized by a cylindrical photodetector body. It can be concluded that with the help of the Positonsdetektors the JP 62 133 314 A only an integral determination of the radiation energy is possible, which occurs through the peripheral window of the diaphragm. A use for controlling high-precision galvanometer rotary actuators therefore excludes.

Out The above, it is therefore an object of the invention, an advanced High precision optical position detector for galvanometer rotary actuators for precise and reproducible deflection of laser beams by means of mirrors or the like elements, comprising one connected to the drive Aperture, one radiation source and at least two radiation detectors specify the aperture, depending on the current position, the beam path influences or interrupts between source and detectors.

By the novel position detector, it should be possible, the length of Shorten galvanometer rotary actuators. Continue to worry to carry that the appropriate units preassembled and are interchangeable, d. H. be manufactured in a cost effective way can.

The solution The object of the invention is achieved with a high-precision optical Position detector for Galvanometer rotary actuators according to the feature combination according to claim 1, wherein the dependent claims expedient refinements and developments represent.

It It is proposed to provide an optical finger which is rotationally symmetrical essentially uniformly distributed scattered radiation emitted by a corresponding emission device, for. B. a light-emitting Diode is provided.

at an embodiment the invention is at the journal of the rotating element, for. B. Galvanometric drive magnet a windowed cylinder sleeve fixed, which acts as a movable aperture in a position change, wherein the light path between the scattered light finger and preferably rotationally symmetrical arranged radiation detectors is interrupted.

at An embodiment of the invention are for radiation bundling still cylindrical lenses in front of the radiation detectors z. B. as Photoreceiver diodes are formed, arranged. The receiver diodes can open a radiation-transmissive Material, eg. B. also be arranged a sleeve, wherein here also a monolithic or a hybrid training provided is. The main advantage here is the thermal Coupling through the sleeve material, so that an undesirable Drift at temperature changes can be prevented.

The The configuration described above can also be used as a linear arrangement concentrically guided sleeves designed to linear changes in position in this way capture. In this application case, a displacement movement of the cylinder sleeve cover executed.

in the Difference to the prior art is no longer from laterally adjacent Light source and radiation detector and light shield with in front of the shield located reflector, but rather on a panel parked coaxially between the radiation source and radiation detectors is, wherein the diaphragm, the aforementioned cylindrical sleeve shape having circumferentially formed windows and the radiation source as a finger or radiation-conducting rod in the sleeve interior extends. The rod or finger emits scattered radiation and has a lateral scattered light optimizing surface structure, manufactured z. B. by etching or laser engraving, on.

Next the embodiment, after which on a cone-shaped End of the drive axle, the cylinder sleeve is fastened, there is in extension of the inventive idea, the possibility of the pin-shaped end the drive itself as a hollow cylinder with corresponding windows train. This can be done for example by turning and milling.

At the front end of the arrangement of pin and sleeve, in oriented substantially perpendicular to the drive axis, is a support plate provided which the actual radiation source or an arrangement from several radiation sources.

Of the photoconductive rod or fingers is z. B. from a doped, photoconductive material. For example, here is an acrylic material used.

The Radiation detectors can thermally coupled to be located on a common substrate. Here it is conceivable to arrange the radiation detectors on a sleeve carrier or integrate into it, wherein the sleeve carrier with the substantially perpendicular to the drive axis oriented carrier plate, for example by a snap-in attachment is connected.

Of the Sleeve bearer with the radiation detectors, the cylinder sleeve and the radiation-conducting and scattering rod or fingers can form a concentric arrangement as a structural unit.

Between Aperture and radiation detectors may be provided with a lens arrangement be, with these, as mentioned, For example, has cylindrical lenses.

The Arrangement of support plate, Sleeve carrier and / or Radiation detectors, radiation source and rod is preferred as replaceable unit executed and preparable in this way.

The support plate For example, as a circuit board assemblies for electronic Signal processing have.

With the carrier plate can over it In addition, at least one further printed circuit board sandwiched be, this circuit board means for electronic calibration having the arrangement.

The Calibration data and / or calibration algorithms can be found in a memory are stored, which is arranged on the circuit board.

The exchangeable assembly of carrier plate, Sleeve carrier and / or Radiation detectors, radiation source and rod are inserted into a housing capsule. and mountable, wherein the housing capsule with the rest Drive assembly, z. B. connected by force and / or positive engagement becomes.

The Radiation detectors of the arrangement may be as surface photodiodes or else be designed as a CCD line or matrix arrangement.

If z. B. for reasons the resolution required, there is a possibility through the cylinder sleeve one with changed Replace window structure by disassembling accordingly and mounting on the cone-shaped End of the drive axle is made.

With the above explained Position detector arrangement creates an almost completely rotationally symmetric Solution, which form relative to the diaphragm in cylindrical sleeves, if necessary, can be balanced in a simple manner. In the motion reversal points of the drive remain the mass moment of inertia limited, so that the dynamics of the drive itself is not limited.

at the coaxial or concentric design of the position detector results in a further advantage a shortening of the length and so that the total space of one with the position detector according to the invention provided galvanometer rotary drive.

by virtue of the arrangement of the radiation detectors on a sleeve carrier is it is possible keep the temperature level of the detectors constant.

The assembly of rod, sleeve carrier with radiation detectors and optionally lens assembly and carrier plate manufacturing side assembled and adjusted without great effort as preferred part of a housing enclosure. Since both the radiation source and the radiation detectors are electrically and mechanically contacted with the carrier plate and as a sandwich arrangement further wiring carriers, in particular printed circuit boards can be provided in the housing encapsulation, it is possible to perform the signal preprocessing within the detector, including a detector-specific calibration or the possibility of analog Digital conversion of the measurement signals heard.

The Invention is based on an embodiment and be explained in more detail with the aid of a figure.

The FIG. 1 shows a principle longitudinal section illustration of a Detector end of a galvanometer rotary actuator.

A cone 1 of the moving magnet drive 2 is from a warehouse 3 taken in a bearing block 4 located.

At the front end 5 of the pin 1 is a diaphragm in cylindrical sleeve shape (cylinder sleeve 6 ) attached.

Distributed on the circumference has the cylinder sleeve 6 window 7 , which have a structure adapted depending on the application in terms of length, width or shape.

During a movement of the drive 2 and the pin 1 This movement is applied to the cylinder sleeve 6 transmitted with the consequence of a change in position of the windows 7 ,

In this embodiment, it is assumed that the cylinder sleeve 6 as a discrete component with the end of the pin 1 to connect. Alternatively, it is also possible to form a hollow cylinder section by means of a blind hole in the front end of the pin. By milling then in this section windows or slots analogous to those of the cylinder sleeve 6 be introduced.

At the front end of the arrangement of pins 1 and cylinder sleeve 6 , oriented substantially perpendicular to the drive axis, is a carrier plate 8th provided which the radiation source 9 receives.

The radiation source 9 can for example be designed as a light-emitting diode, wherein the emitted wavelength is to be matched to the selectivity of the radiation receiver.

With the radiation source 9 optically operatively connected is a radiation-conducting and scattering rod or finger 10 provided in the interior of the cylinder sleeve 6 protrudes.

In one embodiment, the cylinder sleeve 6 so far to the attachment end of the rod or finger 10 introduced that the leakage of an undesirable scattered light can be effectively prevented.

The radiation detectors 11 can z. B. in the form of a hybrid discretely on a sleeve carrier 12 be fixed, which in turn with the support plate 8th communicates.

Alternatively it is possible to use the radiation detectors 11 as z. B. thin-film photoelements on a radiation-permeable sleeve carrier 12 to separate, in the sense of a monolithic detector training.

The carrier plate 8th can assemblies, eg. B. electronic circuits, for signal processing.

According to the illustration of the embodiment are with the support plate 8th PCBs 13 and 14 sort of a sandwich.

These circuit boards 13 and 14 take on further electronic components for signal preprocessing and / or calibration of the photodetector array. There is also the possibility here of making a signal conversion analog / digital by arranging corresponding electronic means.

The assembly of carrier plate 8th , the circuit boards 13 and 14 as well as on the carrier plate 8th located elements is in a Gehäusekaspel 15 accommodated, which z. B. by means of a mounting flange 16 can be connected to the drive.

For the purpose of radiation bundling are between the cylinder sleeve 6 and the radiation detectors 11 cylindrical lenses 17 provided, which also on the carrier plate 8th be fixed.

The in the housing capsule 15 preassembled unit of carrier plate 8th and the elements located there can be pushed from right to left as shown in the figure and then using the aforementioned mounting flange 16 be attached.

In the case of a necessary replacement of elements due to malfunction may replace the housing capsule 15 be made with the components therein, without consuming a variety of electrical or mechanical contacts or Ver must be solved.

1

spigot

2

Moving magnet drive

3

camp

4

bearing block

5

frontal End of the pin

6

cylinder sleeve

7

window

8th

support plate

9

radiation source

10

Rod or fingers

11

radiation detectors

12

sleeve carrier

13 14

PCBs

15

housing capsule

16

mounting flange

17

cylindrical lens

Claims (17)

High-precision optical position detector for galvanometer rotary drives for precise and reproducible deflection of laser beams by means of mirrors or similar elements, comprising one with the drive ( 2 ) connected aperture ( 6 ), a radiation source ( 9 ), and at least two radiation detectors ( 11 ), whereby the diaphragm ( 6 ) depending on the current position the beam path between source ( 9 ) and detectors ( 11 ) influences or interrupts, furthermore - the diaphragm ( 6 ) coaxial between radiation source ( 9 ) and radiation detectors ( 11 ), wherein the diaphragm ( 6 ) a cylindrical sleeve shape ( 6 ) with several peripheral windows ( 7 ) and the radiation source ( 9 ) extends into the sleeve interior, - as well as with the radiation source ( 9 ) connected a radiation-conducting and-scattering rod or finger ( 10 ) in the interior of the cylinder sleeve ( 6 ), which emits scattered radiation in a rotationally symmetrical and uniform manner and has a surface structure that optimizes the lateral scattered light. Position detector according to claim 1, characterized in that at a pin-shaped end of the drive axle ( 5 ) the cylinder sleeve ( 6 ) is attached. Position detector according to claim 2, characterized in that at the front end of the arrangement of pins ( 1 ) and sleeve ( 6 ), oriented substantially perpendicular to the drive axis, a carrier plate ( 8th ) is provided, which the radiation source ( 9 ). Position detector according to one of the preceding claims, characterized in that the light-conducting rod or finger ( 10 ) consists of a doped, photoconductive material. Position detector according to one of the preceding claims, characterized in that the radiation detectors ( 11 ) are thermally coupled on a common substrate. Position detector according to claim 5, characterized in that the radiation detectors ( 11 ) on a sleeve carrier ( 12 ) are arranged or integrated in these, wherein the sleeve carrier ( 12 ) with the substantially perpendicular to the drive axis oriented carrier plate ( 8th ) connected is. Position detector according to claim 6, characterized in that the sleeve carrier ( 12 ) with the radiation detectors ( 11 ), the cylinder sleeve ( 6 ) and the radiation-conducting and scattering rod or finger ( 10 ) forms a concentric arrangement. Position detector according to one of the preceding claims, characterized in that between aperture ( 6 ) and radiation detectors ( 11 ) A lens arrangement is provided. Position detector according to claim 8, characterized in that the lens arrangement cylindrical lenses ( 17 ) having. Position detector according to one of the preceding claims, characterized in that the radiation source ( 9 ) consists of at least one light emitting diode. Position detector according to claim 6, characterized in that the arrangement of carrier plate ( 8th ), Sleeve carriers ( 12 ) and / or radiation detectors ( 11 ), Radiation source ( 9 ) and rod or finger ( 10 ) is designed as a replaceable unit. Position detector according to claim 11, characterized in that the carrier plate ( 8th ) Has assemblies for electronic signal processing. Position detector according to claim 11 or 12, characterized in that with the carrier plate ( 8th ) at least one printed circuit board ( 13 ; 14 ) is sandwiched, said circuit board ( 13 ; 14 ) Comprises means for electronic calibration of the device. Position detector according to claim 13, characterized in that the calibration data and / or calibration algorithms are stored in a memory which on the circuit board ( 13 ; 14 ) is arranged. Position detector according to claim 11, characterized in that the exchangeable assembly of support plate ( 8th ), Sleeve carriers ( 12 ) and / or radiation detectors ( 11 ), Radiation source ( 9 ) and staff ( 10 ) in a housing capsule ( 15 ) can be inserted and mounted, wherein the housing capsule ( 15 ) is connectable to the rest of the drive assembly. Position detector according to one of the preceding claims, characterized in that the radiation detectors ( 11 ) are designed as surface photodiodes or as CCD line or matrix arrangement. Position detector according to claim 2, characterized in that the cylinder sleeve ( 6 ) by such a changed window structure interchangeable at the pin-shaped end of the drive axle ( 5 ) is attached.