DE102004018106A1 - High accuracy optical position detector for dynamic laser beam scanner mirror drives has light source feeding light guide rod coaxial with cylindrical screen with windows - Google Patents

Abstract

A high accuracy optical position detector for dynamic laser beam deflection mirror drives (2) has a light source feeding a light guide rod (10) inside a coaxial exchangeable cylindrical shell screen (6) with windows (7) controlling interruption of the beam to the detector (11) thermally mounted on a similar substrate.

Description

The The invention relates to a high precision optical position detector for dynamic Drives, especially for a precise one 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 the preamble of 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 e.g. 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 technology is e.g. from a combination of a butterfly aperture, 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-PS 6,426,635 shows a galvanometer position detector on capacitive Base, where a cylinder assembly is presented there and a tubular signal plate is provided, which has a plurality of symmetrically equally distributed sensitive surfaces having. The position detection is now changing in consideration of changing dielectric ratios at execution made 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 generic 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.

From the above, it is therefore an object of the invention to provide a further developed high-precision optical position detector for dynamic drives, in particular for a precise and reproducible deflection of laser beams by means of mirrors or the like elements comprising a indicating the aperture associated with the drive, a radiation source, and at least two radiation detectors, the aperture depending on the instantaneous position influencing or interrupting the beam path between the source and the detectors.

By the novel position detector, it should be possible, the length of Shorten galvanometer rotary actuators as a preferred application. Farther is for that Ensure that the corresponding units are preassembled and are interchangeable, i. be manufactured in a cost effective way can.

The solution The object of the invention is achieved with an optical position detector according to the combination of features according to claim 1, wherein the dependent claims at least expedient embodiments and represent further education.

Accordingly, lies the basic idea of the invention is to provide an optical finger which rotationally symmetric essentially uniformly distributed scattered radiation emitted by a corresponding emitter, e.g. a light emitting diode is provided.

at an embodiment of the invention is at the journal of the rotating element, e.g. magnets the galvanometric drive fixed a windowed cylinder sleeve, the at a position change acts as a movable diaphragm, the light path between the Stray light fingers and preferably rotationally symmetrically arranged radiation detectors is interrupted.

at An embodiment of the invention are for radiation bundling still cylindrical lenses in front of the radiation detectors, e.g. as photoreceptor diodes are formed, arranged. The receiver diodes can open a radiation-transmissive Material, e.g. also a sleeve be arranged, here also a monolithic or a Hybrid training is provided. As a significant advantage here results in the thermal coupling through the sleeve material, so that a 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.

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.

With the radiation source (s) is then connected to the radiation-conducting and scattering rod or fingers provided, which in the interior of the cylinder sleeve extends.

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.

In addition, at least one further printed circuit board can be connected to the carrier plate in a sandwich-like manner, this printed circuit board having means for electronic calibration of the arrangement has.

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

Of the photoconductive rod or fingers consists e.g. from a doped, photoconductive material. For example, here is an acrylic material used.

Of the Staff can over it In addition, a lateral scattering light optimizing surface structure, made e.g. by etching or by laser engraving.

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, e.g. connected by force and / or positive connection becomes.

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

If e.g. 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 can without manufacturing side huge Effort as preferred part of a housing encapsulation mounted and adjusted become. Because both the radiation source and the radiation detectors electrically and mechanically contacted with the carrier plate and as a sandwich arrangement further wiring carrier, in particular printed circuit boards in the housing enclosure can be provided Is it possible, to perform the signal preprocessing within the detector, including also a detector specific calibration or the possibility the analog-to-digital conversion heard the measurement signals.

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 visually 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 For example, in the form of a hybrid arrangement, they can be discreetly placed 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 eg thin-film photoelements on a radiation-permeable sleeve carrier 12 to separate, in the sense of a monolithic detector training.

The carrier plate 8th may have assemblies, such as 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 housed, which, for example, with the help 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 having to be solved in a complex manner a variety of electrical or mechanical contacts or connections.

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 (19)

High-precision optical position detector for dynamic drives, in particular for a precise and reproducible deflection of laser beams by means of mirrors or similar elements, comprising an aperture connected to the drive, a radiation source and at least two radiation detectors, the aperture depending on the current position, the beam path between source and Detectors influenced or interrupted, characterized in that the diaphragm is arranged coaxially between the radiation source and radiation detectors, wherein the diaphragm has a cylindrical sleeve shape with peripheral windows and the radiation source extends into the sleeve interior. Position detector according to claim 1, characterized in that that the drive is designed as a galvanometer rotary drive, being on a cone-shaped End of the drive axle attached to the cylinder sleeve or the pin-shaped end itself is designed as a hollow cylinder. Position detector according to Claim 2, characterized that at the front end of the arrangement of pin and sleeve, in oriented substantially perpendicular to the drive axis, a support plate is provided, which receives the radiation source. Position detector according to claim 3, characterized that connected to the radiation source is a radiation-conducting and-scattering rod or finger extends into the interior of the cylinder sleeve. Position detector according to one of the preceding claims, characterized in that the radiation detectors thermally coupled are located on a common substrate. Position detector according to Claim 5, characterized that the radiation detectors are arranged on a sleeve carrier or in this are integrated, with the sleeve carrier with the carrier plate oriented substantially perpendicular to the drive axis connected is. Position detector according to Claim 6, characterized that the sleeve carrier with the radiation detectors, the cylinder sleeve and the radiation-conducting and scattering rod or finger forms a concentric arrangement. Position detector according to one of the preceding Claims, characterized in that between the aperture and radiation detectors a Lens arrangement is provided. Position detector according to claim 8, characterized in that the lens arrangement has cylindrical lenses. Position detector according to one of the preceding Claims, characterized in that the radiation source of at least a light emitting diode. Position detector according to Claim 6, characterized that the arrangement of carrier plate, Sleeve carrier and / or Radiation detectors, radiation source and rod or finger as a replaceable unit is executed. Position detector according to Claim 11, characterized that the carrier plate Assemblies for having an electronic signal processing. Position detector according to claim 11 or 12, characterized characterized in that with the carrier plate at least a circuit board is sandwiched, said circuit board Having means for electronic calibration of the arrangement. Position detector according to Claim 13, characterized that the calibration data and / or calibration algorithms in a memory are stored, which is arranged on the circuit board is. Position detector according to claim 4, characterized in that that the rod consists of a doped, light-conducting material. Position detector according to Claim 15, characterized that the rod has a lateral scattering light optimizing surface structure having. Position detector according to Claim 11, characterized that the interchangeable assembly of carrier plate, sleeve carrier and / or Radiation detectors, radiation source and rod in a housing capsule can be inserted and mounted, wherein the housing capsule with the remaining drive assembly connectable is. Position detector according to one of the preceding Claims, characterized in that the radiation detectors as surface photodiodes or formed as a CCD line or matrix arrangement. Position detector according to Claim 2, characterized that the cylinder sleeve by having one with changed Window structure replaceable at the pin-shaped end of the drive axle is attached.