Moving a nonlinear crystal or a saturable absorber in two dimensions

Abstract

A device for moving a nonlinear crystal or a saturable absorber in two dimensions includes a first and a second piezo unit, each having a corresponding carrier, piezo driver, and carriage moveable by the piezo driver at incremental steps along a linear path with respect to the carrier between a first and a second end location, in which the linear paths of the first piezo unit and the second piezo unit are orthogonal. The nonlinear crystal/saturable absorber is fastenable on the carriage of the first piezo unit and the carrier of the first piezo unit is fastened on the carriage of the second piezo unit. The device further includes stops that define the carriage end locations, an end location detection configured to detect the carriages at their respective end locations, and a counting unit configured to count the steps covered during the moving of the carriage.

Claims

1. A device for moving a nonlinear crystal or a saturable absorber in two dimensions, the device comprising: a first piezo positioning unit comprising a first carrier, a first piezo driver, and a first carriage moveable by the first piezo driver at incremental steps along a first linear path with respect to the first carrier between a first end location and a second end location; a second piezo positioning unit comprising a second carrier, a second piezo driver, and a second carriage moveable by the second piezo driver at incremental steps along a second linear path with respect to the second carrier between a third end location and a fourth end location, the second linear path being orthogonal to the first linear path, wherein the nonlinear crystal or the saturable absorber is fastenable to the first carriage of the first piezo positioning unit and wherein the first carrier of the first piezo positioning unit is fastened to the second carriage of the second piezo positioning unit; a plurality of stops, wherein each stop of the plurality of stops defines a different corresponding end location of the first through fourth end locations; a detector comprising an electrical voltage unit electrically coupled to the plurality of stops, wherein the detector is operable to detect the first carriage at the first end location and at the second end location and is operable to detect the second carriage at the third end location and at the fourth end location; a counting unit operable to count a number of incremental steps covered by the movement of the first carriage along the first linear path and operable to count a number of incremental steps covered by the movement of the second carriage along the second linear path; and a contact element arranged on the first carriage of the first piezo positioning unit, wherein the contact element is operable to touch each stop of the plurality of stops, and wherein the plurality of stops are configured as a single stop element that is fixed to the second carrier.

2. The device of claim 1, comprising a control unit coupled to the counting unit, the control unit comprising an analysis unit, wherein the analysis unit is operable to: calculate a distance of each incremental step along the first linear path from a length of the first linear path between the first end location and the second end location and from the number of incremental steps covered by the movement of the first carriage along the first linear path; and calculate a distance of each incremental step along the second linear path from a length of the second linear path between the third end location and the fourth end location and from the number of incremental steps covered by the movement of the second carriage along the second linear path.

3. The device of claim 1, wherein the plurality of stops are configured as a single monolithic stop element.

4. A method for determining the length of an incremental step of the first carriage and the second carriage of the device of claim 1, the method comprising: detecting the first end location and the second end location of the first carriage by a first electric signal and a second electric signal when the contact element of the first carriage electrically contacts a first stop of the plurality of stops and a second stop of the plurality of stops, respectively; counting, by a counting unit of the device, a first number of incremental steps covered by movement of the first carriage along the first linear path from the first end location to the second end location; detecting a third end location and a fourth end location of the second carriage by a third electric signal and a fourth electric signal when the contact element electrically contacts a third stop of the plurality of stops and a fourth stop of the plurality of stops, respectively; counting, by the counting unit, a second number of incremental steps covered by movement of the second carriage along the second linear path from the third end location to the fourth end location; dividing a distance between the first end location and the second end location by the first number of incremental steps to provide a distance covered by each incremental step along the first linear path; and dividing a distance between the third end location and the fourth end location by the second number of incremental steps to provide a distance covered by each incremental step along the second linear path.

5. The method of claim 4, wherein the first carriage is positioned at the first stop arranged at the first end location, the second carriage is positioned at the third stop arranged at the third end location, the method further comprising: moving the first carriage by the first piezo driver from the first end location to the second stop at the second end location; and moving the second carriage by the second piezo driver from the third end location to the fourth stop at the fourth end location.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic that illustrates a perspective view of an example of a device for moving a crystal or a saturable absorber in two dimensions.

(2) FIG. 2 is a schematic that illustrates an example of a circuit diagram of a control unit that is electrically connected to the exemplary moving device of FIG. 1.

(3) FIG. 3 is a schematic that illustrates a perspective view of an example of a device for moving a crystal, in which the device includes a crystal holder.

(4) FIG. 4 is a schematic that illustrates the moving device of FIG. 1 with a carriage moved into a left end location.

(5) FIG. 5 is a schematic that illustrates the moving device of FIG. 1 with a carriage moved into a right end location.

(6) FIG. 6 is a schematic that illustrates the moving device of FIG. 1 with a carriage moved into an upper end location.

(7) FIG. 7 is a schematic that illustrates the moving device of FIG. 1 with a carriage moved into a lower end location.

DETAILED DESCRIPTION

(8) FIGS. 1 and 2 are schematics that illustrate a moving device 1 for moving a nonlinear crystal 2. The moving device 1 has a first piezo positioning unit 3 and a second piezo positioning unit 4, each of which has a respective linear moving paths or moving directions 5, 6. The moving paths/directions 5, 6 are arranged orthogonally in relation to one another.

(9) The first piezo positioning unit 3 includes a first carrier 7, a first piezo drive 7a, and a first carriage 8, in which the first carriage 8 is movable with respect to the first carrier 7 step-by-step in the first moving direction 5 between two end locations along the first moving path by the first piezo drive 7a. The second piezo positioning unit 4 includes a second carrier 9, a second piezo drive 9a, and a second carriage 10, in which the second carriage 10 is movable with respect to the second carrier 9 step-by-step in the second moving direction 6 between two end locations along the second moving path by the second piezo drive 9a. The second carrier 9 is fastened on a base body 11 of the moving device 1.

(10) The first carrier 7 is fastened on the second carriage 10 so that the crystal 2 arranged on the first carriage 8 can be moved into different positions in a two-dimensional plane spanned by the two moving directions 5, 6 by way of the superposition of the moving motions of the two carriages 8, 10 (see, e.g., the positions and/or end locations shown in FIGS. 4 to 7 and described herein).

(11) The moving device 1 also includes, for each of the first piezo positioning unit 3 and the second piezo positioning unit 4, stops 12, 13, 14, 15 arranged in each case on the two end locations of the different positioning units. The stops 12, 13, 14, 15 jointly form a stop element 16 designed as a monolithic frame. If a contact element 17 formed on the first carriage 8 touches one of the stops 12, 13, 14, 15, a circuit may be closed by a voltage unit 21 resulting in the generation of an “end location detection” signal (e.g., a signal that indicates the contact element 17 of the first carriage 8 touches the stop element 16 at one of the stops 12, 13, 14, 15). The voltage unit 21 applies an electrical potential between the carriage 8 and the stops 12, 13, 14, 15 and/or between the contact element 17 and the stops 12, 13, 14, 15. A determination as to whether it is the left or right (or upper or lower) stop 12, 13, 14, 15 that is contacted by the contact element 17 of the first carriage 8 may be made when it is known in which moving direction 5, 6 the first carriage 8 was previously moved in each case. That is, the same detection signal is obtained in the different moving directions 5, 6 as a result of the one-piece stop element 16. The stop element 16 and/or the frame having the stops 12, 13, 14, 15 is formed on the base body 11. The contact element 17 and the two piezo positioning units 3, 4 are shown in a middle position in FIG. 1.

(12) The moving device 1 also includes a control unit 22 having a first and a second counting unit 18, 19 for counting the steps covered in each case during the moving of the first or second carriage 8, 10, respectively, and an analysis unit 20 for calculating the incremental steps along the moving paths and the number of the counted steps. The moving device 1 enables, in some implementations, simple, rapid and accurate determination of the incremental steps of the individual piezo positioning units 3, 4 without complex position measurement systems. The counting units 18, 19 are arranged in the control unit 22 and count the steps of the carriages 8, 10 by an analysis of the driving signal 23.

(13) As shown in FIG. 3, a crystal holder 24 is fastened on the carriage 8 of the moving device 1 to hold a nonlinear (e.g., laser) crystal. Alternatively to the nonlinear crystal 2, a holder for the saturable absorber, such as a SESAM, can also be arranged on the carriage 8 in the moving devices 1 of FIGS. 1 and 3-7.

(14) An example of a method for determining the respective incremental steps will be explained in greater detail with reference to FIGS. 4 to 7.

(15) The first carriage 8 and/or the contact element 17 of the first carriage 8 is shown in four different end locations in FIGS. 4 to 7. In each case, the first carriage 8 is moved accordingly with respect to the first carrier 7 and the second carriage 10 is moved with respect to the second carrier 9 or the base body 11. In detail, FIG. 4 shows a left end location of the first carriage 8 and/or the contact element 17 formed thereon, FIG. 5 shows a right end location of the first carriage 8 and/or the contact element 17 formed thereon, FIG. 6 shows an upper end location of the first carriage 8 and/or the contact element 17 formed thereon, and FIG. 7 shows a lower end location or end location position of the first carriage 8 and/or the contact element 17 formed thereon.

(16) As an example, to determine the incremental step of the first carriage 8 in the first moving direction 5, during the step-by-step moving of the first carriage 8 from a first, upper end location (see, e.g., FIG. 6) into a second, lower end location (see, e.g., FIG. 7), the steps covered are counted, and subsequently the length of a previously known moving path, which is delimited by the distance of the two end locations, is divided by the number of the counted steps, to obtain the length of each incremental step as the result of the division. The second carriage 10 can be moved in a similar manner. That is, the second carriage 10 may be moved from a first, left end location (see, e.g., FIG. 4) into a second, right end location (see, e.g., FIG. 5), where the steps covered in this example are counted to determine the length of each incremental step of the second carriage 10. In each case, the total length of the first moving path and the total length of the second moving path is required to count the steps. As shown in the examples of FIGS. 6 and 7, the first carriage 8 is positioned before commencing the step-by-step moving at the one stop 14 arranged at the upper end location and subsequently moved completely along the linear moving path up to the other stop 15 arranged at the second, lower end location. In this example, the two end locations of the carriage 8 and/or the contact element 17 are detected by the end location detectors provided at the stops 14, 15.

(17) The stop element 16 and/or the frame can fundamentally delimit the moving paths of the carriages 8, 10 so that the piezo drives 7a, 9a do not extend up into their respective end positions, but instead the respective carriages 8, 10 are stopped beforehand at the stops 12, 13, 14, 15 of the stop element 16. Reliable positioning of the nonlinear crystal 2 can be ensured by such delimiting of the moving paths.

(18) A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other implementations are within the scope of the following claims.