Interferometric displacement sensor for integration into machine tools and semiconductor lithography systems

Abstract

Interferometer (10) for the real-time measurement of absolute distances and/or relative position movements between a first and a second machine part, comprising a measurement unit (20) and a reflector unit (40). wherein the measurement unit (20) comprises a housing (21) with at least one wall made of heat-conducting material, wherein several measurement elements are arranged in the housing (21), wherein the measurement elements comprise: a laser source (22), a Peltier element (24) and a digital control (23) wherein the measurement elements are thermally coupled to the wall of the housing (21) made of heat-conducting material.

Claims

1. An optical length measuring system for measuring absolute distances and/or relative position movements between a first machine part and a second machine part, the optical length measuring system comprising an interferometer having an optoelectronic measurement unit and a reflector unit which includes at least one optical reflector; the optoelectronic measuring unit including a housing with at least one wall made of heat-conducting material, the heat-conducting material having a heat conductivity lambda value of more than 30 W/(m.Math.K) at 0 C., the housing having external dimensions of less than 75 mm75 mm200 mm, wherein several measurement elements are arranged in the housing, the measurement elements including a laser source, a Peltier element, and a digital control, wherein the measurement elements are arranged and thermally coupled directly to the at least one wall of the housing via a heat-conducting medium, the at least one wall being made of the heat-conducting material to facilitate cooling via convection, and the measurement elements including fibre-optic components and miniaturized digital electronics; and wherein the optoelectronic measurement unit includes a remote measurement head firmly connected to the first machine part, the remote measurement head being optically-coupled to the optoelectronic measurement unit via a light waveguide, and wherein the reflector unit is firmly connected to the second machine part.

2. The optical length measuring system according to claim 1, wherein the measurement elements comprise an interface board, a field programmable gate array (FPGA) board, a laser board and an optics board.

3. The optical length measuring system according to claim 1, wherein the heat-conducting material consists of one of the following materials or a combination thereof: aluminium, silver, copper.

4. The optical length measuring system according to claim 1, wherein the housing has external dimensions of less than 50 mm50 mm165 mm.

5. The optical length measuring system according to claim 1, wherein the housing has an enlarged surface, in particular cooling ribs, in at least a region, which promotes thermalization with the surrounding air masses.

6. The optical length measuring system according to claim 1, wherein the at least one optical reflector comprises at least three optical reflectors.

7. The optical length measuring system according to claim 1, wherein the digital control is configured to carry out a position determination of the reflector unit and/or a temperature and wavelength regulation.

8. The optical length measuring system according to claim 1, wherein the interferometer is provided with at least three measurement axes.

9. The interferometer according to claim 1, wherein a device is additionally provided for compensation of the variation in the refractive index of the air.

10. The optical length measuring system of claim 8, wherein the interferometer is provided with six measurement axes.

11. The optical length measuring system of claim 8, wherein the digital control is configured to determine a tilting, pitch, roll, yaw and a displacement between the first and second machine parts.

12. The optical length measuring system of claim 1, wherein the light waveguide is a fibre-optic cable.

13. The optical length measuring system of claim 1, wherein the remote head and reflector unit are configured to respectively send and reflect a beam of light therebetween.

Description

(1) Further advantageous embodiments are shown in the figures. The figures show:

(2) FIG. 1 a schematic representation of an interferometer according to the invention;

(3) FIG. 2 a closed top view of an embodiment example of the measurement unit according to the present invention;

(4) FIG. 3 an open top view of an embodiment example of the measurement unit according to the present invention;

(5) FIG. 4 a first embodiment example of an optical length measurement system for real-time measurement between a first and a second machine part and

(6) FIG. 5 a second embodiment example of an optical length measurement system for real-time measurement between a first, a second and a third machine part.

(7) FIG. 1 shows a schematic representation of an interferometer 10 according to the invention. The interferometer 10 comprises a measurement unit 20 as basic module and a reflector unit 40 remote therefrom. The measurement unit 20 consists of a housing 21, in which a laser source 22, a digital control 23 and a Peltier element 24 are accommodated. The laser source 22, the digital control 23 and the Peltier element 24 are thermally coupled to the inside of the wall of the housing 21, in that they are adhered to the housing by means of a heat-conducting foil.

(8) Via three outlets in the front end of the housing 21, three measurement beams S1, S2 and S3 can be directed from the measurement 20 onto the reflector unit 40. The beams reflected from there are detected by the measurement unit 20 and evaluated via the digital control 23 in real time.

(9) This makes it possible to record relative movements and/or absolute distances between the measurement module 20 and the reflector unit 40 in real time.

(10) FIG. 2 shows a closed top view of an embodiment example of the measurement unit 20 according to the present invention. The housing 21 has cooling ribs 31 which are arranged on the long side of the housing 21. On the front end of the housing 21 three sensor outputs 30.1, 30.2 and 30.3 are arranged, via which the measurement beams can be coupled out of the measurement unit and the reflected radiation detected.

(11) FIG. 3 shows an open top view of an embodiment example of the measurement unit 20 according to the present invention. The housing 21 has the cooling ribs 31 and the sensor outputs 30.1, 30.2 and 30.3 as in FIG. 2. Furthermore, an optical board 33 as well as a laser board 22 (with Peltier elementnot shown separately) can be recognized in the housing 21. In addition, a digital control is shown as FPGA 23, which is arranged over an interface board 34. A contact with the wall of the housing is produced for the digital control 23 via a heat-conducting foil 32.

(12) By the use of miniaturized electronic and optical components it is possible to reduce the size of the housing to below 50 mm50 mm165 mm (breadthheightlength). The heat-producing components (DFB-Laser 22, FPGA 23, Peltier element) are here thermally coupled to the housing 21 and the housing 21 itself is used as a heat sink (cooling via convection). Besides the named cuboid form, this design also allows other construction forms with comparable construction volumes (e.g. flatter design for use in control cabinets etc.)

(13) FIG. 4 shows a first embodiment example of an optical length measurement system for real-time measurement between a first machine part 51 and a second machine part 52. The two machine parts 51, 52 are movable against one another via running slides in the direction of the arrow A. Movement errors such as pitch and yaw can occur along the arrow B. A measurement unit 20 is firmly screwed to the first machine part 51. The measurement unit directs three measurement beams S1, S2 and S3, onto a reflector unit 40 which is firmly connected to the second machine part 52. Due to the distance between the three measurement points and the reflector unit 40 it is possible to measure both a position change between the first machine part 51 and the second machine part 52 along the axis A, and also movement errors along the axis B. This measurement can take place in incremental manner (measurement of the relative movement) and also in absolute manner (measurement of the absolute distance or the absolute tilt angle).

(14) FIG. 5 shows a second embodiment example of an optical length measurement system for real-time measurement between a first machine part 51, a second machine part 52 and a third machine part 53. The two machine parts 51, 52 are movable with respect to one another via running slides in the direction of the arrow A. The two machine parts 53, 52 are movable with respect to one another via running slides in the direction of the arrow C. A measurement unit 20 is connected to two fibre-coupled measurement heads 28.1 and 28.2 via optical waveguides 29. The measurement head 28.1 is attached to the first machine part 51 and aligned with a reflector unit 40.1 on the second machine part 52. The measurement head 28.2 is attached to the third machine part 53 and aligned with a reflector unit 40.2 on the second machine part 52. The measurement unit 20 is remotely accommodated in a control cabinet (not shown).

(15) When the slides are moved in directions A and C, the remote measurement heads 28.1 and 28.2 now measure the relative movement or the absolute distances between the first 51 and second 52 or the second 52 and third 53 machine parts. The glass fibre 29 allows a connection of the measurement unit 20 in a remote spacethis can be situated more than 1,000 m away from the measurement heads 28.1 and 28.2.

(16) In this way an interferometer has been provided for the real-time measurement of absolute distances and/or relative position movements between a first and a second machine part, as well as an optical length measurement system for measuring absolute distances and/or relative position movements between a first and a second machine part, which avoids the disadvantages of the state of the art.

LIST OF REFERENCE NUMBERS

(17) 10 Interferometer 20 Measurement unit/basic module 21 Housing 22 Laser source 23 Digital control 24 Peltier element 25 Voltage regulator module 26 Device for compensation of the variation in the refractive index of the air 27 AD/DA converter 28 Remote (fibre-coupled) measurement head 29 Light waveguide 30 Sensor output 31 Cooling ribs 32 Heat-conducting foil 33 Optical board 34 Interface board 40 Reflector unit 50 Machine part 51 First machine part 52 Second machine part 53 Third machine part