Optical: systems and elements – Lens – With support
Reexamination Certificate
2001-08-03
2003-09-02
Mack, Ricky (Department: 2873)
Optical: systems and elements
Lens
With support
C359S822000, C359S819000
Reexamination Certificate
active
06614605
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to an adjusting apparatus, in particular for a lens in an optoelectronic transmitting/receiving device, and a method for adjusting the adjusting apparatus.
In optoelectronic transmitting/receiving devices for communication via optical fiber networks, one of the main problems consists in providing an optical connection between an optical fiber that is coupled on in a connection opening and a transmitting/receiving component. In the case of a laser module used for a transmitting device, the divergent laser beam of a laser diode is imaged by one or more lenses onto the end face of an optical fiber in such a way as to obtain a maximum coupling-in efficiency of the laser power into the optical fiber. When monomode optical fibers are coupled on, this is achieved by a single lens or a lens pair imaging the so-called spot size of the laser onto the light entry opening of the optical fiber. When two lenses are used, an aspherical lens is preferably used as the first lens owing to the laser radiation beam angle, which is usually large. Furthermore, in the case of the two-lens configuration, a collimated beam is often sought between the two lenses because the distance between the lenses is then non-critical. However, in the case of two-lens configurations, it is likewise possible for the first lens to generate a greatly enlarged intermediate image which is reduced again to the light entry opening of the fiber by the second lens. Semiconductor lasers for optical wide-area transmission systems emit at wavelengths of 1.3 &mgr;m or 1.55 &mgr;m and have spot radii of the order of magnitude of 1 &mgr;m. Corresponding monomode optical fibers have spot radii of an order of magnitude of 5 &mgr;m. In order to attain a high coupling efficiency, the first lens typically has to be adjusted and fixed with an accuracy of ±0.5 &mgr;m in the x- and y-direction and of ±2 to 5 &mgr;m in the z-direction with regard to the laser chip. For reasons of long-term stability, the fixing is usually carried out either by AuSn soldering or by laser welding. In order that the lens carriers can be produced with acceptable tolerances or a welding distortion when fixing the lens carrier can be corrected, it is particularly advantageous if targeted readjustment of the lens carrier and thus of the lens position can be carried out by laser pulses. Instead of the lens coupling, the optical fiber can also be directly coupled to the laser. The fiber end face is often melted or etched for this purpose, thereby producing a suitable lens profile on the optical fiber itself. In this case, the (locally metallized) optical fiber can be fixed e.g. by soldering on the laser-adjustable carrier.
Adjusting apparatuses for lenses and methods for adjusting them in which laser-adjustable actuating elements or actuators are used are already known. These known configurations are based on the temperature gradient mechanism (TGM), in which a laser beam impinging on the surface of a sheet-metal part introduces into the material, by melting the material on the surface, shrinkage stresses distributed non-uniformly over the sheet-metal thickness. As a result, the sheet-metal part flexes when cooling in the direction of the incident laser beam. For an adjustment operation with single-sided accessibility for the laser beam, this results in that adjustment can be effected reliably and in a defined manner only in one direction, in other words a distance can only be lengthened or shortened as a result of the bending. Using so-called actuators, however, it is also possible to realize further directions of movement in the case of only single-sided accessibility of the laser beam. In this case, an actuator is understood to be a three-dimensional sheet-metal structure on which, by introducing shrinkage stresses at specific places, it is possible to initiate defined movements of the actuator in different directions.
Published, European Patent Application EP 0 373 225 A1 describes an optoelectronic semiconductor device in which an optoelectronic semiconductor component is retained by a carrier block and, at the same time, a lens holder is fixed on the carrier block, a lens positioned opposite the optoelectronic component being mounted into the lens holder. The lens holder is preformed in such a way that it deforms in a desirable manner as a result of local exposure to a laser beam and, consequently, the position of the lens can be altered with regard to the optoelectronic component.
Furthermore, U.S. Pat. No. 5,572,895 describes a method for reciprocal adjustment of two members of one or more actuators, the members being connected via a bridge. In this method, too, laser energy is fed to the actuators at suitable places in order to bring about a desired adjustment.
Finally, U.S. Pat. No. 6,030,114 discloses a laser-adjustable fuse switch in which, according to the same principle as explained above, a pre-bent contact connection of a bimetal strip can be adjusted for calibration purposes by application of a laser beam.
These known methods have the disadvantage, however, that they generally permit only an empirical procedure during the adjustment by application of a laser beam. Moreover, the adjusting apparatuses are generally configured in such a way that they allow only coarse adjustment or fine adjustment. In many cases, the adjustment also does not exhibit long-term stability owing to the stresses incorporated during the laser processing.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide an adjusting apparatus and a method for its adjustment that overcome the above-mentioned disadvantages of the prior art devices and methods of this general type, which make it possible to carry out more targeted adjustment, in particular by providing coarse adjustment and fine adjustment.
With the foregoing and other objects in view there is provided, in accordance with the invention, an adjusting apparatus containing a stationary base plate, a movable carrier plate, and a number of actuating elements each having a first end, a second end, and a form that can be altered by local application of radiation energy. Each of the actuating elements is connected to the stationary base plate at the first end and to the movable carrier plate at the second end.
In an adjusting apparatus according to the invention, a number of actuating elements whose form can be altered by local application of radiation energy, preferably in the form of laser radiation, are connected to the stationary base plate at one of their ends and to the movable carrier plate at their other end. An optical component to be adjusted, such as a lens, can be mounted onto the carrier plate. In this case, the adjusting apparatus may also be part of an optoelectronic transmitting/receiving device which has an optoelectronic component such as a laser diode or a semiconductor photodetector and a connection opening for an optical fiber, and in which a carrier which retains the optoelectronic component is mounted on stationary parts of the adjusting apparatus, in which case, in the mounted and adjusted state, the optoelectronic component is exactly aligned with the lens and the light entry opening of the optical fiber.
The invention makes it possible to dispose a plurality of actuating elements of different configurations between the base plate and the carrier plate, which actuating elements make it possible to set the different degrees of freedom of the adjustment and of the movement of the carrier plate independently of one another. In particular, the invention makes it possible to dispose a plurality of actuating elements relative to one another in such a way that they act with different transmission, so that one actuating element can be utilized for the coarse adjustment and the second actuating element can be utilized for the fine adjustment.
The individual actuating elements can have different configurations, some of which are known per se in the prior art. By way of example, in a particularly simple
Auracher Franz
Hamann Christoph
Hanebuth Henning
Wittmann Julius
Greenberg Laurence A.
Infineon - Technologies AG
Mack Ricky
Mayback Gregory L.
Stemer Werner H.
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