DESC:FIELD OF THE INVENTION
The present invention generally relates to a wind turbine. More particularly, the present invention relates to an automatic adjusting device, which is provided to be mounted on a rotor of a wind turbine for adjusting rotor blades of wind turbine.

BACKGROUND
The present invention relates to an automatic adjusting device, which is provided to be mounted on a rotor of a wind turbine according to the preamble of independent claim 1. Furthermore, the present invention relates to a wind turbine according to the preamble of independent claim 6. According to a third aspect, the present invention is directed to a method of automatically determining a defined pitch-adjustment of a rotor blade of a rotor of a wind turbine according to the preamble of independent claim 10.
Wind turbines generally comprise a nacelle incorporating a drive train and a rotor with one or more rotor blades. The nacelle is mounted on a tower. The rotor is connected to the drive train via a hub, on which the rotor blades are mounted. Different types of wind turbines are known in the art.
According to one type of wind turbines, which are known in the art, the rotor blades are adjustably mounted on the hub. This is realized by means of a pitch drive, said pitch drive being part of a pitch system. The pitch system, which is generally known in the prior art, participates in the control of the rotor speed to given set points. In general, the rotor speed is controlled by the load and by the pitch angle. By means of the pitch-drive, the rotor blades may be moved about a rotor blade axes into different pitch positions, said rotor blade axis extending in an axial direction of the rotor blade.
For adjusting the rotor blades in different positions and pitch-adjustments, in particular angular orientations, respectively, which generally represent different orientations of the rotor blades, the rotor comprises an adjusting device for determining a defined pitch-adjustment of the rotor blades.
A wrong orientation of the rotor blades can lead to energy losses and to unusual vibrations inside the drive train. Therefore it is necessary that the adjustment of the rotor blades and of the pitch-system, in particular the zero-degree-adjustment, is regularly checked and adjusted, in particular during an entry into service, during the maintenance of the wind turbine, after an exchange of a rotor blade and the like.
The required activities for checking the correct adjustment of the rotor blades are very complex and have to be performed manually since the hub incorporates, besides the pitch-drive for each rotor blade, also a number of different components, for example reinforcement devices, pitch bearings and the like. Furthermore the manual performance entails risks of mistakes caused by the service person. Therefore there is a need of providing a solution for automatically adjusting the rotor blade.
One of the prior art discloses a solution, which uses the weight and centrifugal forces of the rotor blades to control the rotor blade pitch. For this purpose a specific mechanical member has to be used which makes this known solution complex. Furthermore, it is not possible with this known solution to determine the zero-degree-position of the rotor blade for adjusting the rotor blade in this position.
Up to now it was necessary to perform such adjustment procedures manually by service people. The reason for this is the complexity of the interiority of the hub which incorporates a number of different components and elements. Therefore, current developments lead into the technical direction of providing manual and mechanical solutions.
To overcome the limitations discussed above and several others, the present invention pursues a different way, namely to use an optical system which is mounted on the rotor. It is the merit of the present invention that it overcomes the technical prejudice that due to the complexity only manual and mechanical solutions are applicable. The present invention found out that it is possible to use an optical system which is fixedly mounted on the rotor.

OBJECT OF THE INVENTION
Starting from the above mentioned state of the art, it is the object of the present invention to avoid the aforementioned drawbacks. In particular, it is the object of the present invention to provide an adjustment solution for automatically determining a defined pitch-adjustment of a rotor blade, in particular for determining the zero-degree-position of the rotor blade.
The object is solved according to the invention by the adjusting device with the features according to independent claim 1, which is first aspect of the invention, by the wind turbine with the features of independent claim 6, which is the second aspect of the invention, by the method of automatically determining a defined pitch-adjustment with the features of independent claim 10, which is the third aspect of the invention, as well as by the special use with the features of independent claim 15, which is the fourth aspect of the invention. Further features and details of the invention can be derived from the dependent claims, from the description as well as from the drawings. Therein, features and details which are described in connection with one aspect according to the invention apply with respect to their disclosure in their entirety also to the other aspects according to the invention, so that statements made with respect to one aspect also apply to their full extent to the other aspects and vice versa.
The underlying concept of the present invention is that a defined pitch-adjustment of the rotor blade of a rotor of a wind turbine can be automatically determined in a reliable and easy way. In particular, a specific angle-position of the rotor blade can be determined. According to a preferred embodiment, the zero-degree position of the rotor blade can be determined. However, the present invention is not limited to this specific embodiment. Furthermore the present invention can be used to determine a specific pitch-angle-offset, such that a control system can perform a precise adjustment between a real position, for example a real airfoil chord, and a target position, for example the target position of the airfoil chord.

SUMMARY OF THE INVENTION
According to the first aspect of the present invention, an adjusting device is provided, said adjusting device being provided to be mounted on a rotor of a wind turbine, which rotor comprises a hub and at least one rotor blade, said rotor blade, by means of a pitch-drive, being adjustably mounted on the hub to be moved in different pitch positions for rotation, said adjusting device comprising a device for automatically determining a defined pitch-adjustment of the rotor blade, in particular for determining the zero-degree-position of the rotor blade. The adjusting device is characterized in the device for determining a defined pitch-adjustment comprises an optical system, said optical system comprising a reflection element being adapted for being mounted on the rotor blade, in particular for being mounted on the rotor blade at a position indicating the zero-degree-position of the rotor blade, and an emitter/receiver-device being adapted for being mounted on the hub, said emitter/receiver-device being further adapted for emitting light signals and for receiving light signals being reflected from the reflection element.
The present invention is preferably directed to such types of wind turbines which use a pitch-system for adjusting the rotor blades in different positions of rotation. The adjusting device according to the first aspect of the invention is provided to be mounted on a rotor of a wind turbine. This means that in the operating condition the adjusting device is mounted, preferably fixedly mounted, on the rotor. This rotor comprises a hub and at least one rotor blade, preferably three rotor blades. However, the present invention is not limited to a specific number of rotor blades. Each rotor blade is adjustably mounted on the hub by means of or via a pitch-drive, such that each rotor blade can be moved in different pitch positions for rotation. The adjusting device is not limited to be used with specific embodiments of wind turbines. In particular, the adjusting device can be used in connection with a wind turbine according to the second aspect of the present invention which is described in more detail further below.
In particular, the pitch-drive is part of a pitch-system. The pitch-system, which per se is known in the prior art, controls the rotor speed to given set points, which are denoted as well as pitch positions for rotation in the present patent application. By means of the pitch-system different pitch angles or pitch adjustments of the rotor blades which are set to a defined rotor blade angle, can be adjusted. Preferably, each rotor blade has its own pitch-drive consisting of a drive member. The present invention is not limited to specific types of drive members. For example, the drive member can be an electrical motor, a hydraulic drive, or the like. Preferably, the required set points for the rotor blade position are transmitted to the pitch system from a control device which, for example, might be a central control system. In particular the pitch-drive of each rotor blade is located inside the hub. The hub connects the rotor blades with the drive train of the wind turbine, which is generally located inside a nacelle.
According to the present invention the adjusting device comprises a device for automatically determining a defined pitch adjustment of the rotor blade. The rotor blade may be adjustable in different adjustment positions by means of said adjusting device. In such a case the pitch drive of the rotor blade may be part of the adjusting device as well. In any case it is at least the purpose of the adjusting device that defined pitch-adjustments of the rotor blade can be determined in accordance with the description of the underlying concept disclosed further above. According to a preferred embodiment, it is the purpose of the adjusting device to determine the zero-degree-position of the rotor blade.
According to the present invention, the adjusting device is configured in a very specific way such that it is now possible to perform the pitch adjustment of the rotor blades automatically. For this purpose the device for determining a defined pitch-adjustment comprises an optical system, said optical system comprising a reflection element and an emitter/receiver-device for emitting/receiving light signals. However, as mentioned further above, due to technical prejudice no idea or concept existed so far to incorporate an optical system into the rotor of a wind turbine for automatically determining defined positions of the rotor blade. Moreover the different components of the optical system have to be arranged on the rotor in a very specific manner.
According to the present invention the reflection element of the optical system is adapted to be mounted on the rotor blade. This means that in the operating condition the reflection element is mounted on the rotor blade. According to a preferred embodiment the reflection element is adapted to be mounted or is mounted on the rotor blade root.
In a preferred embodiment the adjusting device is adapted for determining the zero-degree-position of the rotor blade, wherein the reflection element is adapted to be mounted on the rotor blade at a position indicating the zero-degree-position of the rotor blade. Furthermore the optical system comprises an emitter/receiver-device, said device being adapted for being mounted on the hub. Preferably the device is adapted for being mounted inside the hub. This means that in the operating condition the emitter/receiver-device is mounted on/inside the hub. According to a preferred embodiment the emitter/receiver-device is adapted to be mounted, or is mounted on the hub base body. Nevertheless it is also applicable that the device is adapted for being mounted outside the hub.
Preferred embodiments of the optical system are described in more detail further below.
The adjusting device according to the present invention has a number of advantages. It is possible that the adjusting device can be preassembled when the wind turbine and its components are manufactured. Nevertheless it is also easy to upgrade existing wind turbines with such an adjusting device.
The adjusting device according to the present invention is preferably suitable for an automatic zero-degree-setup of the pitch-system of a wind turbine. In such a case the reflection element is mounted to the rotor blade in the exact zero-degree-position. The emitter/receiver-device is mounted on a hub in a corresponding, defined position. When the rotor blade is positioned in its zero-degree position, light signals which have been emitted from the emitter/receiver-device in the direction of the reflection element get reflected at the reflection element back in the direction of the emitter/receiver-device. Therefore, when the emitter/receiver-device receives light signals which have been reflected by the reflector element, the rotor blade is positioned in its zero-degree-position.
Therefore, by means of the emitter/receiver-device which is mounted on the hub and by means of the reflection element which is mounted on the rotor blade, the zero-degree position of the rotor blade or the reaching of this position can be automatically determined.
According to a preferred embodiment, the optical system is a reflection-light-barrier. A reflection-light-barrier comprises an emitter and a receiver, which are jointly mounted, in particular in parallel, in one single housing. Light signals which are emitted from the emitter are reflected back from a receiving element being opposite to said emitter. The reflected light signals are received by the receiver.
Preferably, the reflection element is a retro-reflection element. A retro-reflection element is a device or comprises a surface that reflects light signals back to its source with a minimum of scattering.
Preferably, the emitter/receiver-device comprises an emitter for emitting light signals. This emitter comprises at least one light source. The present invention is not limited to specific types of light sources. For example, the light source can be a light emitting diode (LED), an organic light emitting diode (OLED) or a laser diode.
Preferably, the emitter/receiver-device comprises at least one receiver for receiving light signals. This receiver is adapted for detecting reflected light signals. The present invention is not limited to specific types of receivers. For example, the receiver can be a photodiode, a phototransistor, a light dependent resistor or a CCD-sensor.
According to a preferred embodiment, a control device is provided which controls the adjusting device. For example the control device can be provided for controlling the adjusting device only. In such a case the control device may be part of the adjusting device. According to a different embodiment, the control device can be part of or can be the central control system of the wind turbine. In such a case the adjusting device may comprise an interface to said control device in order to establish a communication link between the adjusting device and the control system. The communication link might be a bi-directional communication link. Via said interface and said communication link, data can be or are exchanged between the control device and the adjusting device.
The control device may incorporate a routine or sub-routine, by means of which the rotor blade can be moved within the respective pitch-range, until the optical system detects that the desired pitch-position of the rotor blade has been reached. The control device may transmit the required set points for the rotor blade position as well. Preferably, each rotor blade is controlled separately and independently. The control device may be configured to control the pitch-drive of each rotor blade as well.
The use of such a control device supports the automatic adjustment of the rotor blade in a defined position in accordance with the description of the underlying concept disclosed further above, in particular in the zero-degree-position. Via said control device the pitch-drive of the rotor blade may be actuated, which means that the rotor blade is moved, until the control device gets the information from the sender/receiver-device of the optical system, that light signals that have been emitted from the emitter have been reflected from the reflection element and have been received by the receiver. Once the receiver has received or detected the reflected light signals, which means that the rotor blade has reached the desired position, the receiver may transmit a piece of information to the control device that the desired position has been reached. Inside the control device, this piece of information can be stored as a respective offset.
According to a second aspect of the invention a wind turbine is provided. The wind turbine comprises a nacelle which incorporates a drive train. The drive train transmits and converts the rotor speed to the generator. Therefore, the wind turbine comprises a rotor being connected to said drive train, said rotor comprising a hub and at least one rotor blade, preferably three rotor blades, said at least one rotor blade, by means of a pitch-drive, being adjustably mounted on the hub to be moved in different pitch positions for rotation about a blade axis which extends in an axial direction of the rotor blade, and an adjusting device comprising a device for automatically determining a defined pitch-adjustment of the rotor blade in accordance with the description of the underlying concept disclosed further above, in particular for determining the zero-degree-position of the rotor blade. The wind turbine is characterized in that the device for determining a defined pitch-adjustment comprises an optical system, said optical system comprising a reflection element being mounted on the rotor blade, in particular being mounted on the rotor blade in accordance with the description of the underlying concept disclosed further above, in particular at a position indicating the zero-degree-position of the rotor blade, and an emitter/receiver-device being mounted on, in particular inside or outside, the hub, said emitter/receiver-device being further adapted for emitting light signals and for receiving light signals being reflected from the reflection element. Preferably the wind turbine comprises an adjusting device according to the first aspect of the invention, which is described further above. With regard to the configuration and the function of the wind turbine, full reference is also made to the general description and to the description of the adjusting device according to the first aspect of the invention as disclosed above.
In a preferred embodiment, the adjusting device also comprises a ruler for indicating a defined pitch-adjustment of the rotor blade, said ruler being mounted on the rotor blade. In particular this ruler, which is generally known in the prior art, precisely indicates an angular position of the rotor blade, in particular the zero-degree-position of the rotor blade. Preferably, the reflection element of the optical system of the adjusting device is mounted on the rotor blade in the zero-degree-position indicated by the ruler. Such a ruler is a good backup device for the case that the reflection element on the rotor blade gets lost, and vice versa.
According to yet another preferred embodiment of the present invention, at least one reinforcing element is mounted inside the hub. In order to allow light signals being transmitted between the emitter/receiver-device and the reflection element inside the hub without interruption, the reinforcing element preferably comprises an aperture, said aperture being adapted to allow light signals to pass through the reinforcement element from the emitter/receiver-device to the reflection element, and vice versa.
In a preferred embodiment, the emitter/receiver-device which is mounted on the hub, preferably on the hub base body is protected by a protection element, preferably by a protection element against kicks.
According to a third aspect of the present invention a method is provided, said method being a method of automatically determining a defined pitch-adjustment of a rotor blade of a rotor of a wind turbine in accordance with the description of the underlying concept disclosed further above, in particular of determining the zero-degree-position of the rotor blade, said rotor blade being, by means of a pitch-drive, adjustably mounted on a hub of said rotor such that the rotor blade can be moved in different pitch positions for rotation, whereby a defined pitch-adjustment of the rotor blade, in particular the zero-degree-position of the rotor blade, is determined by use of an adjusting device comprising a device for determining a defined pitch-adjustment of the rotor blade. This method is characterized by the following steps:
a) by means of an optical system, which is part of the device for determining a defined pitch-adjustment, and which comprises an emitter/receiver-device, light signals are emitted from an emitter of said emitter/receiver-device and are transmitted into the direction of a reflection element of said optical system, which is mounted on the rotor blade;
b) by means of said pitch-drive the rotor blade is moved until the rotor blade is positioned in the defined pitch-adjustment, in which the light signals are reflected from the reflection element back to the emitter/receiver-device;
c) the reflected light signals are received by a receiver of said emitter/receiver-device and get further processed and/or evaluated.
With regard to the function and to the procedure of the method, full reference is also made to the general description and to the description of the first and second aspects as disclosed further above. In particular the method is performed by use of a wind turbine according to the second aspect of the present invention.
In a preferred embodiment, the adjustment devices, as well as the pitch-drive are controlled by a control system, preferably by a common control system. With this regard full reference is made to the disclosure of the control device in connection with the first aspect of the present invention.
Preferably, the offset of the rotor blade into the defined pitch-adjustment is transmitted to the control system and gets preferably stored therein. With this regard full reference is made to the disclosure of the control device in connection with the first aspect of the present invention.
According to a preferred embodiment, the automatic determination of the defined pitch-adjustment of the rotor blade is repeated in predefined time intervals, or it is performed during a specific working procedure or maintenance procedure. It is not unusual that a pitch movement of the rotor blade is performed in defined time intervals. Or the automatic determination of the defined pitch-adjustment can be performed in parallel to the pitch bearing movement for the purpose of lubrication. The automatic determination of the defined pitch-adjustment according to the present invention may take place during such a pitch movement.
According to the fourth aspect of the present invention, an optical system, comprising a reflection element and an emitter/receiver-device, said emitter/receiver-device being adapted for emitting light signals and for receiving light signals being reflected from the reflection element, is used for automatically determining a defined pitch-adjustment of a rotor blade of a rotor of a wind turbine in accordance with the description of the underlying concept disclosed further above, in particular the zero-degree-position of the rotor blade. Or an adjusting device according to the first aspect of the present invention, or a wind turbine according to the second aspect of the present invention, or a method according to third aspect of the present invention is used for automatically determining a defined pitch-adjustment of a rotor blade of a rotor of a wind turbine in accordance with the description of the underlying concept disclosed further above, in particular the zero-degree-position of the rotor blade.
The present invention according to its four aspects has a number of advantages. First of all, any energy losses due to a false position of the rotor blades can be avoided. Furthermore, any undesired stresses can be avoided by means of a reduction of vibrations which might arise to a false position of the rotor blades. A faulty zero-degree-orientation caused by a manual procedure can be avoided as well. The working time during a maintenance procedure can be reduced.
The invention will now be explained in more detail with respect to exemplary embodiments with reference to the enclosed drawings, wherein the foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing figures.

BRIEF DESCRIPTION OF THE INVENTION
Figure 1 shows a depiction of a wind turbine; and
Figure 2 shows a section of a depiction of the rotor of a wind turbine.

DETAILED DESCRIPTION OF THE INVENTION
Reference is made to Figure 1 and Figure 2 which disclose the construction of a wind turbine and a section of rotor of a wind turbine.
Figure 1 of the present invention shows a wind turbine (10) with a tower (12) and a nacelle (11). Nacelle (11) is rotatable mounted on the tower (12). Nacelle (11) incorporates a drive train (not shown), said drive train being connected to a rotor (13). Rotor (13) comprises three rotor blades (14) which are mounted to a hub (15). Hub (15) of rotor (13) is connected to a drive shaft of the drive train.The rotor blades (14) are adjustably mounted on the hub (15). This is realized by means of pitch drives (16), said pitch drives (16) being part of a pitch system. The pitch system controls the rotor speed to given set points. By means of pitch-drives (16), the rotor blades (14) may be moved about a rotor blade axes into different pitch positions, said rotor blade axis extending in an axial direction of the rotor blades (14). Each rotor blade (14) is connected to the hub (15) via its pitch-drive (16).
Figure 2 of the present invention depicts the pitch drive (16) of each rotor blade (14), which is connected to hub (15) via a pitch bearing (17). Wind turbine (10) comprises a control system (18) which is schematically depicted in Figure 2.In order to automatically determine a defined pitch-adjustment of the rotor blade (14), in particular to automatically determine the zero-degree-position of the rotor blade, the rotor (13) comprises an adjusting device (20) comprising a device for determining the defined pitch-adjustment of the rotor blade (14). This device comprises an optical system with a number of different components. One component is a reflection element (21) which is mounted on the rotor blade (14), in particular on the rotor blade root (14a).
The adjusting device (20) may further comprise a ruler (22) as an optional member for indicating a defined pitch-adjustment of the rotor blade (14), said ruler(22) being mounted on the rotor blade (14) as well. This ruler (22) indicates the zero-degree-position of the rotor blade (14). The reflection element (21) of the optical system of the adjusting device (20) is mounted on the rotor blade (14) in the zero-degree-position indicated by the ruler (22). In general, such a ruler (22) is used for manually adjusting the rotor blade (14). In any case the ruler (22) is a good backup element for the case that the reflection element (21) gets lost from the rotor blade (14), and vice versa.
Furthermore the optical system comprises an emitter/receiver-device (23), which is mounted on the hub (15) via a fixing device (19). As shown in Figure 2, the emitter/receiving-device (23) is mounted inside hub (15) on the hub base body (15a). The emitter/receiver-device (23)is protected by a protection element (not shown), preferably by a protection element against kicks.
The emitter/receiver-device (23) comprises an emitter (24) which has a light source, particularly a laser diode, for emitting light signals. Furthermore, the emitter/receiver-device (23) comprise a receiver (25), in particular a photo diode, which is capable of receiving light signals. At least one reinforcing element (not shown) is mounted inside the hub (15). In order to allow light signals being transmitted between the emitter/receiver-device (23) and the reflection element (21) inside the hub (15) without interruption, the reinforcing element comprises an aperture, said aperture being adapted to allow light signals to pass through the reinforcement element from the emitter/receiver-device (23) to the reflection element (21), and vice versa.
The adjusting device (20) according to the present invention is suitable for an automatic zero-degree-setup of the rotor blade (14). When the rotor blade (14) is positioned in its zero-degree position, light signals which have been emitted from the emitter (24) in the direction of the reflection element (21), which is depicted by arrow (26) in Figure 2, get reflected back at the reflection element (21) in the direction of the receiver (25), which is depicted by arrow (27) in Figure 2. Therefore, when the emitter/receiver-device (23) receives light signals which have been reflected from the reflector element (21), the rotor blade (14) is positioned in its zero-degree-position.
The control system (18) of the wind turbine (10) is connected to the emitter/receiver-device (23) via a communication link (28). Furthermore, control system (18) is connected to the pitch-drive (16) via a communication link (29).The control system (18) incorporates a routine or sub-routine, by means of which the rotor blade (14) can be moved within the respective pitch-range, until the optical system detects that the desired pitch-position of the rotor blade (14) has been reached. The control system (18) transmits the required set points for the rotor blade position to the pitch-drive (16) via communication link (29). By means of said control system (18) the pitch-drive (16) of the rotor blade (14) is actuated, which means that the rotor blade (14) is moved, until the control system (18) gets the information from the sender/receiver-device (23) of the optical system via communication link (28), that light signals that have been emitted from the emitter(24) have been reflected from the reflection element (21) and have been received by the receiver (25). Once the receiver (25) has received or detected the reflected light signals as depicted by arrow (27), which means that the rotor blade (14) has reached the desired position, the receiver (25) transmits a piece of information to the control system (18) via communication link (28), that the desired position has been reached. Inside the control system (18), this piece of information can be stored as a respective offset. The adjustment device (20) which is incorporated in the rotor (13) of wind turbine (10) allows that the zero-degree-position of the rotor blade (14) can be automatically determined and checked.

List of Reference Numerals

10 Wind turbine
11 Nacelle
12 Tower
13 Rotor
14 Rotor blade
14a Rotor blade root
15 Hub
15a Hub base body
16 Pitch drive
17 Pitch bearing
18 Control system
19 Fixing device
20 Adjusting device
21 Reflection element
22 Ruler
23 Emitter/receiver-device
24 Emitter
25 Receiver
26 Emitted light signals
27 Reflected light signals
28 Communication link
29 Communication link

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles described herein can be applied to other embodiments without departing from the spirit or scope of the invention. Thus, it is to be understood that the description and drawings presented herein represent a presently preferred embodiment of the invention and are therefore representative of the subject matter which is broadly contemplated by the present invention. It is further understood that the scope of the present invention fully encompasses other embodiments that may become obvious to those skilled in the art and that the scope of the present invention is accordingly not limited.
,CLAIMS:We claim:

1. An adjusting device (20), said adjusting device (20) being provided to be mounted on a rotor (13) of a wind turbine (19), which rotor (13) comprises a hub (15) and at least one rotor blade (14), said rotor blade (14), by means of a pitch-drive (16), being adjustably mounted on the hub (15) to be moved in different pitch positions for rotation, said adjusting device (20) comprising a device for automatically determining a defined pitch-adjustment of the rotor blade (14), in particular for determining the zero-degree-position of the rotor blade (14), characterized in that the device for determining a defined pitch-adjustment comprises an optical system, said optical system comprising a reflection element (21) being adapted for being mounted on the rotor blade (14), in particular for being mounted on the rotor blade (14) at a position indicating the zero-degree-position of the rotor blade (14), and an emitter/receiver-device (23) being adapted for being mounted on the hub (15), said emitter/receiver-device (23) being further adapted for emitting (26) light signals and for receiving (27) light signals being reflected from the reflection element (21).

2. The adjusting device according to claim 1, characterized in that the optical system is a reflection-light-barrier.

3. The adjusting device according to claim 1 or 2, characterized in that the reflection element (21) is a retro-reflection element.

4. The adjusting device according to anyone of claims 1 to 3, characterized in that the emitter/receiver-device (23) comprises an emitter (24) for emitting light signals, said emitter (24) comprising at least one light source, in particular a light emitting diode (LED), an organic light emitting diode (OLED) or a laser diode, and/or that the emitter/receiver-device (23) comprises at least one receiver (25) for receiving light signals, said receiver (25) being adapted for detecting reflected light signals, in particular said receiver (25) being a photodiode, a phototransistor, a light dependent resistor or a CCD-sensor.

5. The adjusting device according to anyone of claims 1 to 4, characterized in that the adjusting device (20) comprises a control device or that the adjusting device (20) comprises an interface to a control device.

6. A wind turbine (10), said wind turbine(10) comprising a nacelle (11) which incorporates a drive train, a rotor (13) being connected to said drive train, said rotor (13) comprising a hub (15) and at least one rotor blade (14), said rotor blade (14), by means of a pitch-drive (16), being adjustably mounted on the hub (15) to be moved in different pitch positions for rotation about a blade axis which extends in an axial direction of the rotor blade (14), and an adjusting device (20) comprising a device for automatically determining a defined pitch-adjustment of the rotor blade (14), in particular for determining the zero-degree-position of the rotor blade (14), characterized in that the device for determining a defined pitch-adjustment comprises an optical system, said optical system comprising a reflection element (21) being mounted on the rotor blade (14), in particular being mounted on the rotor blade (14) at a position indicating the zero-degree-position of the rotor blade (14), and an emitter/receiver-device (23) being mounted on the hub (15), said emitter/receiver-device (23) being further adapted for emitting light signals and for receiving light signals being reflected from the reflection element (21).

7. The wind turbine according to claim 6, characterized in that the adjusting device (20) is configured according to anyone of claims 2 to 5.

8. The wind turbine according to claim 6 or 7, characterized in that the adjusting device (20) comprises a ruler (22) for indicating a defined pitch-adjustment of the rotor blade (14), said ruler (22) being mounted on the rotor blade (14), and that the reflection element (21) is mounted on the rotor blade (14) in the zero-degree-position indicated by the ruler (22).

9. The wind turbine according to anyone of claims 6 to 8, characterized in that at least one reinforcing element is mounted inside the hub (15), said reinforcing element comprising an aperture, said aperture being adapted to allow light signals to pass through the reinforcement element from the emitter/receiver-device (23) to the reflection element (21), and vice versa.

10. A method of automatically determining a defined pitch-adjustment of a rotor blade (14) of a rotor (13) of a wind turbine (10), in particular of determining the zero-degree-position of the rotor blade (14), said rotor blade (14) being, by means of a pitch-drive (16), adjustably mounted on a hub (15) of said rotor (13) such that the rotor blade (14) can be moved in different pitch positions for rotation, whereby a defined pitch-adjustment of the rotor blade (14), in particular the zero-degree-position of the rotor blade (14), is determined by use of an adjusting device (20) comprising a device for determining a defined pitch-adjustment of the rotor blade (14), said method being characterized by the following steps:
a) by means of an optical system,which is part of the device for determining a defined pitch-adjustment, and which comprises an emitter/receiver-device (23), light signals are emitted (26) from an emitter (24) of said emitter/receiver-device (23) and are transmitted into the direction of a reflection element(21) of said optical system, which is mounted on the rotor blade (14);
b) by means of said pitch-drive (16) the rotor blade (14) is moved until the rotor blade (14) is positioned in the defined pitch-adjustment, in which the light signals are reflected (27) from the reflection element (21) back to the emitter/receiver-device (23);
c) the reflected (27) light signals are received by a receiver (25) of said emitter/receiver-device (23) an get further processed and/or evaluated.

11. The method according to claim 10, characterized in that the method is performed by use of a wind turbine (10) according to anyone of claims 6 to 9.

12. The method according to claim 10 or 11, characterized in that the adjusting device (20) and/or the pitch-drive (16) is controlled by a control system (18).

13. The method according to claim 12, characterized in that the offset of the rotor blade (14) into the defined pitch-adjustment is transmitted to the control system (18) and gets preferably stored therein.

14. The method according to anyone of claims 10 to 13, characterized in that the automatic determination of the defined pitch-adjustment of the rotor blade (14) is repeated in predefined time intervals.

15. Use of an optical system, comprising a reflection element (21) and an emitter/receiver-device (23), said emitter/receiver-device (23) being adapted for emitting (26) light signals and for receiving (27) light signals being reflected from the reflection element (21), for automatically determining a defined pitch-adjustment of a rotor blade (14) of a rotor (13) of a wind turbine (10) , in particular the zero-degree-position of the rotor blade (14), or use of an adjusting device (20) according to anyone of claims 1 to 7, or of a wind turbine (10) according to anyone of claims 8 to 11, or of a method according to anyone of claims 12 to 14 for automatically determining a defined pitch-adjustment of a rotor blade (14) of a rotor (13) of a wind turbine (10), in particular the zero-degree-position of the rotor blade (14).