Patent ID: 12204094

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG.1shows, in schematic form, a MEMS system according to a specific example embodiment of the present invention.

In detail,FIG.1shows a MEMS system1. MEMS system1includes a reference generator2that produces a reference signal S1. In addition, MEMS system1includes a linear controller3that produces a control signal MS for controlling a deflecting unit6. Control signal MS for deflecting unit6is transmitted to this unit. Deflecting unit6includes, for the deflecting of a light beam incident on deflecting unit6, a drive unit6afor one or more micromirrors6beach of which is movable about a respective axis or about two axes, and that are then in particular periodically moved corresponding to control signal MS in order to correspondingly deflect a light beam.

In addition, a measuring unit9that measures a position of micromirror or micromirrors6bis connected to deflecting unit6. On the basis of the measured position, using a deviation measuring unit10a current deviation of a controlled variable of deflecting unit6(i.e., here the controlled variable for controlling the position of micromirror6b) from a specified target variable is ascertained on the basis of reference signal S1. This deviation is then in turn transmitted to both a repetitive controller7and to linear controller3.

In addition, MEMS system1includes two anti-windup devices4a,4bthat are configured parallel to linear controller3. In addition, a Smith predictor5is configured parallel to the input and output of linear controller3. Linear controller3is used for the controlling and stabilization of micromirror6bin a continuous frequency controlling band, or controlling range, that is as large as possible. Here, linear controller3is first correspondingly configured neglecting the dead time of the controlled system of MEMS system1. MEMS system1shown inFIG.1has a control path that includes the movable axis or axes of micromirror6b, measuring unit9for determining position, and (not shown inFIG.1) an analog-digital/digital-analog converter, including analog filters. Smith predictor5is used in turn for the dynamic compensation of controlling errors that result from the neglecting of the dead time. Anti-windup devices4a,4bare used in turn to limit integrators of linear controller3in the case in which controlled variables for deflecting unit6are calculated or requested outside specified limits. In addition, using repetitive controller7, occurrent controlling errors are compensated periodically, i.e., over at least one preceding period.

Reference signal S1 provided by reference generator2is, inFIG.1, a wave-shaped, bandwidth-limited signal. Using signal S1, the image point of an image provided by a projection device (not shown here) is then projected with different speeds for the different axes of micromirror6b. As a result, it is necessary to adapt or subsequently control the brightness of the image point. The wave-shaped, bandwidth-limited reference signal S1 can here be limited to a few, for example five, fundamental harmonic frequencies of a base signal, for example a rectangular or sinusoidal signal, with which an excitation of deflecting unit6, in particular of micromirror6b, is to take place. In this way, a reliable controlling out of deviations is enabled. In particular, reference signal S1 can be made up of finitely many fundamental harmonics of a sawtooth signal. The fundamental harmonics can be selected such that they lie within the controlling range, or control interval, of linear controller3. Using repetitive controller7, a compensation is achieved of dead times that result from the analog-digital conversion. For this purpose, repetitive controller7has a storage device7ain which the controlling error is stored over at least one excitation period of the reference signal, or of micromirror6b, from which future controlling errors and corresponding controlled variables can be derived. Periodic disturbances can in this way be efficiently controlled out, even if for example mirror resonance frequencies of micromirror11change.

FIG.2shows a MEMS system according to a specific example embodiment of the present invention.

FIG.2shows a MEMS system1having a linear controller3and a deflecting unit6. A sawtooth-shaped periodic reference signal S1 is supplied to linear controller3, which then provides a corresponding periodic adjusting signal MS for deflecting unit6. Based on the measured controlled variable of deflecting unit6, via a measuring unit9and a corresponding deviation measuring unit10, linear controller3then controls deflecting unit6on the basis of the comparison with periodic reference signal S1, and produces the corresponding periodic adjusting signal MS for deflecting unit6.

The overall deviation MSA is stored in a storage unit7a. Storage unit7astores not only the current deviation of the current period of reference signal S1, but also the deviation over at least one earlier period. Storage unit7aprovides this information to an image processing device8bof a projection device8that includes an image providing device8afor providing an image. Image processing device8breceives as information, on the one hand, for example a sinusoidal high-frequency signal S2 on one axis, and receives signal S1 on the other axis. Image processing device8bnow ascertains a two-dimensional image having a corresponding pixel function p for each pixel to be projected, taking into account the deviation, and forms the pixel function p via a projector8cfor the projection of the image. In other words, image processing device8btakes into account not only the two reference signals S1, S2 for representing the image, but also takes into account the measured deviations MSA at at least one different point in time. Here, controlling errors of a deflecting unit6, in particular of a micromirror6b, which are periodic in a certain time window, are used to correct projected image contents so that a consistency is enabled between the controlling of deflecting unit6, in particular a micromirror position, and the image contents to be projected, even if controlling errors continuously change.

As stated above, reference signals S1, S2 are used to control deflecting unit6about different axes. The movement of micromirror6bof deflecting unit6can take place with different speeds about different axes, corresponding to different periods of the respective reference signal S1, S2. Image processing device8bin turn uses these signals S1, S2 to determine that pixel in the image to be projected that is to be represented at a particular time by projector8cof projection device8. Storage unit7ais fashioned in particular as a ring memory, preferably for the “lower” axis, which stores, over a period, the measured deviation between a reference position of micromirror6bof deflecting unit6and the actual position of micromirror6b. Under the assumption that this deviation between two temporally successive periods is equal, this deviation is used to correct reference signal S2 of image processing device8b, and thus of the image to be projected.

In addition, the method described in relation toFIG.1and the method described in relation toFIG.2can be combined with one another, which further improves the precision of the controlling of deflecting unit6and of image processing unit8b. Storage unit7acan be used here both by repetitive controller7and by image processing device8b.

FIG.3schematically shows a method according to a specific example embodiment of the present invention.

In detail,FIG.3shows a method for operating a MEMS system having at least one projection unit for providing an image via at least one light beam, and a deflecting unit for the two-dimensional deflection of the at least one light beam.

The method includes the following steps:

In a step T1, there takes place a driving of the deflecting unit using at least one reference signal, so that the deflecting unit periodically deflects a light beam at least two-dimensionally.

In a further step T2, there takes place a measurement of at least a controlled variable of the deflecting unit that corresponds to a position of the deflected light beam.

In a further step T3there takes place an ascertaining of a current deviation of the at least one controlled variable from a target variable that corresponds to a target position of the light beam.

In a further step T4there takes place a calculation of at least one compensating variable based on the ascertained deviation.

In a further step T5, there takes place a controlling of the deflecting unit with regard to the deflection and/or of the projection unit with regard to the image provision, based on the calculated at least one compensating variable for reducing the deviation of the light beam from the target position, the at least one compensating variable being additionally calculated on the basis of an earlier deviation in at least one earlier period, for the controlling of the deflecting unit.

In sum, at least one of the specific embodiments of the present invention has at least one of the following advantages:controlling over a large controlling rangehigher precision in the representation of imagesgreater flexibilitycompensation of dead times

Although the present invention has been described on the basis of preferred exemplary embodiments, it is not limited thereto, but can be modified in many ways.