DE102016216711A1 - A method for driving an optical phase array, method for detecting an object by means of an optical phase array and optical system - Google Patents

Abstract

The invention relates to a method for driving an optical phase array (102). In this case, a measurement signal (116) is read in which represents an intensity distribution and / or a wavefront of a light signal (104) emitted by the optical phase array (102). The measuring signal (116) is compared with a reference signal in a further method step in order to determine a deviation value (120) of a deviation between the measuring signal (116) and the reference signal. Finally, using the deviation value (120), a control signal (124) for driving the optical phase array (102) is generated.

Description

State of the art

The invention is based on a device or a method according to the preamble of the independent claims. The subject of the present invention is also a computer program.

In radar technology, groupings of individual antennas with individual phase or amplitude control, so-called phase array antennas, are now state of the art. Phase-array antennas can also be used in telecommunications since they allow better performance, low weight, small installation space and flexible shaping of an antenna profile.

In the field of optical wavelengths, especially in the infrared range, there is currently great research interest in the implementation of optical phase arrays with integrated photonic elements. Possible approaches for the production of optical phase arrays with CMOS processes (CMOS = complementary metal-oxide-semiconductor) or SOI processes (SOI = silicon on insulator) have been described, for example, in the context of the SWEEPER program (SWEEPER = short-range, Wide Field-of-View Extremely Agile, Electronically Steered Photonic Emitter) of DARPA.

Disclosure of the invention

Against this background, with the approach presented here, a method for driving an optical phase array, a method for detecting an object by means of an optical phase array, furthermore a device which uses at least one of these methods, an optical system and finally a corresponding one Computer program presented according to the main claims. The measures listed in the dependent claims advantageous refinements and improvements of the independent claim device are possible.

A method for driving an optical phase array is presented, the method comprising the following steps:

Reading a measurement signal representing an intensity distribution and / or a wavefront of a light signal emitted by the optical phase array;

Comparing the measurement signal with a reference signal to determine a deviation value of a deviation between the measurement signal and the reference signal; and

Generating a control signal for driving the optical phase array using the deviation value.

An optical phase array can be understood to mean an array of a plurality of individually controllable antenna elements for emitting light beams, wherein a specific emission characteristic of the optical phase array can be realized by superposing the light beams emitted by the antenna elements. The emission characteristic can be changed solely by controlling the antenna elements, for example by changing an amplitude or phase adjustment of individual antenna elements, without the need for movement of the optical phase array. The optical phase array can be produced, for example, in a process of semiconductor technology, for example based on silicon.

For example, a measurement signal can be understood as a feedback signal coupled out of the light signal by means of a suitable optical device. For example, the measurement signal may also be a signal from a wavefront sensor, also called a Shack-Hartmann sensor. The measurement signal can also represent a signal generated by means of an optical Fourier transformation. A light signal can be understood to mean an electromagnetic signal in the range of visible light. A reference signal can be understood, for example, to be a nominal value of a beam profile of the optical phase array. Depending on the embodiment, the intensity distribution can be an intensity distribution in a near or far field of the optical phase array. For example, the control signal can be generated in order to drive individual antenna elements of the optical phase array in such a way that the deviation is compensated or corrected.

The approach presented here is based on the knowledge that a beam profile or a phase distribution of an optical phase array can be directly monitored and optionally actively corrected via suitable feedback. This makes it possible to counteract fluctuations in the beam profile or the phase distribution, for example due to environmental influences or operational heat generation. The feedback can be done, for example, via far field measurements to determine a far field intensity distribution or, additionally or alternatively, via a wavefront measurement. This has the advantage that the emitted light distribution can be effectively monitored during operation and can be corrected, for example, via a modification of a phase distribution of individual antennas of the optical phase array.

For example, such a correction can be carried out using tabulated configurations or else actively by optimization algorithms, for example based on the Gerchberg-Saxton algorithm for diffractive phase elements or evolutionary algorithms. Alternatively, instead of active correction of the phase elements, it is possible to compensate for the observed deviations from the ideal distribution on the basis of measurement results of a control loop in the data evaluation.

According to one embodiment, in the reading-in step, a signal representing an intensity distribution of the light signal in a far field of the optical phase array can be read in as the measurement signal. As a result, necessary corrections in a phase distribution of the optical phase array can be calculated particularly efficiently due to a mathematical relationship between Fourier transformation and Fraunhofer diffraction.

According to a further embodiment, in the step of comparing, the measurement signal may be compared with a signal representing a reference intensity distribution as the reference signal to determine a lateral offset between the intensity distribution represented by the measurement signal and the reference intensity distribution. Additionally or alternatively, the reference signal may represent a reference wavefront, wherein the measurement signal may be compared with the reference signal to determine a lateral offset between the wavefront represented by the measurement signal and the reference wavefront as the deviation value. As a result, the deviation value can be determined precisely with relatively little computational effort.

It is advantageous if, in the reading-in step, a signal is read in as the measurement signal whose phase distribution is substantially equal to a phase distribution of the light signal. As a result, inaccuracies in comparing the measurement signal with the reference signal can be kept as low as possible. Thus, a high accuracy of the method can be ensured.

Furthermore, in the step of generating, the control signal may be generated to correct the deviation. As a result, targets can be met with respect to the light distribution emitted by the optical phase array.

The approach described here also provides a method for detecting an object by means of an optical phase array, the method comprising the following steps:
Reading a measurement signal representing an intensity distribution and / or a wavefront of a light signal emitted by the optical phase array, and a detector signal representing a portion of the light signal reflected by the object;
Comparing the measurement signal with a reference signal to determine a deviation value of a deviation between the measurement signal and the reference signal; and

Evaluate the detector signal using the deviation value to detect the object.

A detector signal may be understood to be a signal generated by a detector device, such as a lidar or ladar sensor or another optical sensor.

These methods can be implemented, for example, in software or hardware or in a mixed form of software and hardware, for example in a control unit.

The approach presented here also creates a device that is designed to perform the steps of a variant of a method presented here in appropriate facilities to drive or implement. Also by this embodiment of the invention in the form of a device, the object underlying the invention can be solved quickly and efficiently.

For this purpose, the device may comprise at least one computing unit for processing signals or data, at least one memory unit for storing signals or data, at least one interface to a sensor or an actuator for reading sensor signals from the sensor or for outputting data or control signals to the sensor Actuator and / or at least one communication interface for reading or outputting data embedded in a communication protocol. The arithmetic unit may be, for example, a signal processor, a microcontroller or the like, wherein the memory unit may be a flash memory, an EPROM or a magnetic memory unit. The communication interface can be designed to read or output data wirelessly and / or by line, wherein a communication interface which can read or output line-bound data, for example, electrically or optically read this data from a corresponding data transmission line or output in a corresponding data transmission line.

In the present case, a device can be understood as meaning an electrical device which processes sensor signals and outputs control and / or data signals in dependence thereon. The device may have an interface, which may be formed in hardware and / or software. In the case of a hardware-based embodiment, the interfaces can be part of a so-called system ASIC, for example, which contains a wide variety of functions of the device. However, it is also possible that the interfaces are their own integrated circuits or at least partially consist of discrete components. In a software training, the interfaces may be software modules that are present, for example, on a microcontroller in addition to other software modules.

In an advantageous embodiment, the device is used to control a vehicle. For this purpose, the device can access, for example, sensor signals such as acceleration, pressure, steering angle or environmental sensor signals. The control takes place via actuators such as brake or steering actuators or an engine control unit of the vehicle. In addition, the approach described here creates an optical system with the following features:
an optical phase array for emitting a light signal;
a measuring device for measuring an intensity distribution and / or a wavefront of the light signal of the light signal; and
a device according to a preceding embodiment.

The measuring device may be, for example, an optical sensor.

According to one embodiment, the optical system may comprise an optical device for coupling out a feedback signal from the light signal. The optical device may be configured to direct the feedback signal to the measuring device. Accordingly, the measuring device can be designed to measure the intensity distribution and / or the wavefront using the feedback signal. The optical device can be, for example, a beam splitter element, a lens element, in particular a collecting lens, also called a Fourier lens, a mirror element, a holographic element or another refractive, diffractive or reflective element or a combination of a plurality of optical components. For example, the optical device may be a Fraunhofer structure for observing a far field intensity distribution of the optical phase array. By this embodiment, the most accurate feedback can be ensured.

According to a further embodiment, the optical device may comprise at least one beam splitter element, at least one mirror element, at least one lens element or a combination of at least two of said elements. A beam splitter element may, for example, be understood as a beam splitter cube or a semitransparent mirror. By a lens element can be understood, for example, a convex lens. In particular, the lens element can function as Fourier optics. By this embodiment, the optical device can be realized inexpensively and with little effort.

Also of advantage is a computer program product or computer program with program code which can be stored on a machine-readable carrier or storage medium such as a semiconductor memory, a hard disk memory or an optical memory and for carrying out, implementing and / or controlling the steps of the method according to one of the embodiments described above is used, especially when the program product or program is executed on a computer or a device.

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. It shows:

1 a schematic representation of an optical system according to an embodiment;

2 a schematic representation of an optical system according to an embodiment;

3 a schematic representation of an operation of a Fraunhofer structure for the observation of a far field intensity distribution;

4 a schematic representation of an optical device according to an embodiment;

5 a flowchart of an embodiment of a method for driving an optical phase array; and

6 a flowchart of an embodiment of a method for detecting an object by means of an optical phase array.

In the following description of favorable embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and similar acting, with a repeated description of these elements is omitted.

1 shows a schematic representation of an optical system 100 according to an embodiment. Shown is a block diagram for detecting a deviation of one of an optical phase array 102 emitted light signal 104 from an ideal ray. The optical system 100 includes a first block 106 from a transmitting unit in the form of the optical phase array 102 , short OPA, and a receiving unit in the form of a measuring device 108 for measuring an intensity distribution or, additionally or alternatively, a wavefront of the light signal 104 , using a Fresnel lens, for example, and a second block comprising a device 112 for electronic signal processing and control of the optical phase array 102 represents.

The device 112 includes a read-in unit 114 for reading in one of the measuring device 108 generated measuring signal 116 , the intensity distribution or the wavefront of the light signal 104 represents. The reading unit 114 conducts the measuring signal 116 to a comparison unit 118 Next, which is adapted to the measurement signal 116 to compare with a reference signal. As a result of comparison, the comparison unit generates 118 a deviation value 120 , which is a deviation between the measurement signal 116 and represents the reference signal, ie between an actual value and a desired value of the output signal 104 of the optical system 100 , The comparison unit 118 sends the deviation value 120 to a generating unit 122 For example, as an electronic component for controlling a phase profile of the optical phase array 102 is realized. According to one embodiment, the comparison unit 118 trained to the deviation value 120 using an algorithm in the context of a correction method to correct the deviation. The generating unit 122 is designed to be using the deviation value 120 a control signal 124 for driving the optical phase array 102 and to the optical phase array 102 transferred to.

According to this embodiment, the optical system 100 with an optical device 126 executed, also called optical subsystem. The optical device 126 is designed to receive the light signal 104 in a Nutzlichtsignal 128 , which represents a specific useful light distribution, and a feedback signal 130 for the control loop for controlling the optical phase array 102 to share, with the feedback signal 130 through the optical device 126 on the measuring device 108 is steered. Accordingly, the measuring device 108 trained to the measurement signal 116 using the feedback signal 130 to create. In particular, the optical device 126 trained to the feedback signal 130 such from the light signal 104 decouple that a phase distribution of the measurement signal 116 essentially a phase distribution of the light signal 104 equivalent.

2 shows a schematic representation of an optical system 100 according to an embodiment. The optical system 100 essentially corresponds to the above with reference to 1 described optical system. Shown is a block diagram of a detection of a deviation of the beam profile of the optical phase array 102 and a corresponding correction in an object recognition and detector evaluation of an optional detector device 200 of the optical system 100 , such as a lidar sensor. The optical system 100 includes the transmitting and receiving unit, the optical subsystem for signal monitoring and an electronic control circuit for signal generation and control. The detector device 200 is designed to be one of a scenery 202 reflected proportion 204 of that optical phase array 102 emitted light signal 104 , more precisely, by splitting the light signal 104 by means of the optical device 126 received Nutzlichtsignals 128 to detect. In this case, the detector device generates 200 a the scenery 202 representing detector signal 206 and sends this to an evaluation unit 208 the device 112 and the deviation value 120 from the comparison unit 118 receives. The evaluation unit 208 is trained to recognize the scenery 202 the detector signal 206 using the deviation value 120 evaluate.

3 shows a schematic representation of an operation of a Fraunhofer structure 300 for the observation of a far-field intensity distribution, as described, for example, by the above with reference to 1 and 2 described measuring device can be measured. The in 3 structure shown, for example, shows a basic structure of the above with reference to the 1 and 2 described optical device. The Fraunhofer structure 300 includes a diffractive structure 302 for diffracting a light beam 304 , The diffractive structure 302 is at a distance d to a Fourier lens 306 arranged with the focal length f. A focal plane 308 the Fourier lens 306 is indicated by a vertical line.

4 shows a schematic representation of an optical device 126 according to an embodiment. In the optical device 126 it may be the preceding one based on the 1 to 3 act described optical device. Shown is an exemplary schematic structure for monitoring the intensity distribution in the far field of the optical phase array 102 , also called far-field intensity distribution. The optical device 126 is according to this embodiment in accordance with the foregoing with reference to 3 described principle realized as a Fraunhofer structure for performing an optical Fourier transform. For this purpose, the optical device includes 126 for example, a beam splitter element 400 for dividing that of the optical phase array 102 emitted light signal 104 in the feedback signal 130 and the Nutzlichtsignal 128 with the corresponding useful light distribution. Opposite the beam splitter element 400 is a mirror element 402 arranged, which is adapted to the feedback signal 130 on a lens element 404 , here a Fourier lens, to steer. The lens element 404 is designed to receive the feedback signal 130 on the detector device 200 located in the back focal plane of the lens element 404 is to steer.

Hereinafter, an embodiment of a structure for controlling the optical phase array 102 via far field measurements based on 4 again described in other words.

die Fourier-Transformierte bezeichnet.The optical phase array 102 is an optical component, such as the beam splitter element 400 , downstream, which is part of the emitted light 104 decoupled from the beam path. Optionally, the use of the mirror element 402 , which may be flat or formed as a free-form surface to compensate for differences in the optical path length and to obtain the phase reference for the interference pattern as far as possible. The generation of the far field distribution takes place by means of a Fourier lens as a lens element 404 on the detector device 200 , The position of the useful light distribution is determined, for example, by means of a camera. Lateral shifts occur according to the shift rate, for example by readjustment of the phase array 102 with a linear phase component, since

called the Fourier transform.

5 shows a flowchart of an embodiment of a method 500 for driving an optical phase array. The procedure 500 For example, in connection with a preceding on the basis of 1 to 4 described device are performed. This is done in one step 510 read in the measurement signal generated by the measuring device of the optical system. Depending on the exemplary embodiment, the measurement signal represents an intensity distribution, in particular a far field intensity distribution, or a wavefront of the light emitted by the optical phase array. In one step 520 the measurement signal is compared with the reference signal to determine the deviation value. Finally, in one step 530 generates the control signal using the deviation value.

6 shows a flowchart of an embodiment of a method 600 for recognizing an object by means of an optical phase array. The procedure 600 For example, in connection with a preceding on the basis of 1 to 4 described device are performed. This is done in one step 610 read in the measurement signal generated by the measuring device of the optical system and the detector signal generated by the detector device. Depending on the exemplary embodiment, the measurement signal represents an intensity distribution, in particular a far field intensity distribution, or a wavefront of the light emitted by the optical phase array. In one step 620 the measurement signal is compared with the reference signal to determine the deviation value. Finally, in one step 630 the detector signal is evaluated using the deviation value to detect the object.

Hereinafter, various embodiments of the approach presented here on the basis of 1 to 6 summarized again in other words.

According to one embodiment, a portion of the phase array 102 emitted light 104 by means of the beam splitter element 400 , such as a transmissive mirror, a beam splitter cube or a diffractive or holographic element, deflected. In this case, however, care should be taken to maintain a relative phase distribution in order to reduce an influence on the phase distribution by the decoupling. The preservation of the relative phase distribution is achieved, for example, by using the mirror element 402 allows. Depending on the aperture and divergence of the emitted light 104 is according to an embodiment by means of a Fraunhofer structure, as for example in the 3 and 4 4 is an optical Fourier transform for observing the far-field intensity distribution in a back focal plane of the Fourier lens 404 realized. Instead of a classical refractive lens may also be a diffractive or holographic element or a microlens array as a lens element 404 be used. For example, the use of a microlens array results in further possibilities for measuring the wavefronts and determining the deviation from the target, for example by means of a Shack-Hartmann sensor.

According to a further embodiment reflections are made to optics of the optical system 100 occur, used. For this purpose, it should be ensured on the one hand, that the reflections the phase distribution of the emitted light signal 104 maintained. Second, it should be ensured that the reflections are not directly to the phase array 102 , but on the adjacent detector device 200 to meet. The detector device 200 can be realized for example as a detector array.

The advantage of measuring the far-field intensity is the mathematical relationship between Fourier transformation and Fraunhofer diffraction. Thus, based on the above-described Fraunhofer structure for a far-field measurement, a required correction in the phase distribution can be determined mathematically with relatively little effort and, for example, the phase distribution can be optimized by means of a suitable algorithm. By way of example, a lateral offset of an optical target distribution, that is to say the optical beam in the far field, with respect to a desired state is detected by the control loop proposed here and corrected by an additional linear phase component. In the direct determination of the wavefront, for example by means of a Hartmann-Shack sensor, for example, there is also a local correction of the phase distribution in the optical phase array 102 to correct the measured local wavefront deviations.

According to a further embodiment, the optical system comprises 100 in addition, a detector component, such as in the form of the detector device 200 in order to compensate for a determined deviation between desired and actual distribution in a data evaluation on the detector side.

An important difference to typical Fraunhofer structures for diffractive optical elements consists in the comparatively large divergence and the combination of the phase of the very likely curved wavefronts of the individual emitters and the induced phase distribution of the phase array 102 ,

If an exemplary embodiment comprises a "and / or" link between a first feature and a second feature, then this is to be read so that the embodiment according to one embodiment, both the first feature and the second feature and according to another embodiment either only first feature or only the second feature.

Claims (12)

Procedure ( 500 ) for driving an optical phase array ( 102 ), the process ( 500 ) includes the following steps: reading in ( 510 ) of a measuring signal ( 116 ) having an intensity distribution and / or a wavefront of one of the optical phase array ( 102 ) emitted light signal ( 104 represents; To compare ( 520 ) of the measuring signal ( 116 ) with a reference signal to obtain a deviation value ( 120 ) a deviation between the measuring signal ( 116 ) and the reference signal; and generating ( 530 ) of a control signal ( 124 ) for driving the optical phase array ( 102 ) using the deviation value ( 120 ). Procedure ( 500 ) according to claim 1, wherein in the step of reading ( 510 ) a signal as the measuring signal ( 116 ) is read, the intensity distribution of the light signal ( 104 ) in a far field of the optical phase array ( 102 ). Procedure ( 500 ) according to one of the preceding claims, wherein in the step of comparing ( 520 ) the measuring signal ( 116 ) is compared with a signal representing a reference intensity distribution and / or a reference wavefront as the reference signal in order to determine a lateral offset between the signal detected by the measurement signal ( 116 ) intensity distribution and the reference intensity distribution and / or between by the measuring signal ( 116 ) and the reference wavefront represented as the deviation value (FIG. 120 ) to investigate. Procedure ( 500 ) according to one of the preceding claims, wherein in the reading-in step ( 510 ) a signal as the measuring signal ( 116 ) whose phase distribution is substantially equal to a phase distribution of the light signal ( 104 ). Procedure ( 500 ) according to one of the preceding claims, wherein in the step of generating ( 530 ) the control signal ( 124 ) is generated to correct the deviation. Procedure ( 600 ) for recognizing an object ( 202 ) by means of an optical phase array ( 102 ), the process ( 600 ) includes the following steps: reading in ( 610 ) of a measuring signal ( 116 ) having an intensity distribution and / or a wavefront of one of the optical phase array ( 102 ) emitted light signal ( 104 ) and a detector signal ( 206 ), the one through the object ( 202 ) reflected proportion ( 204 ) of the light signal ( 104 represents; To compare ( 620 ) of the measuring signal ( 116 ) with a reference signal to obtain a deviation value ( 120 ) a deviation between the measuring signal ( 116 ) and the reference signal; and evaluation ( 630 ) of the detector signal ( 206 ) using the deviation value ( 120 ) to the object ( 202 ) to recognize. Contraption ( 112 ) with units ( 114 . 118 . 122 ; 208 ), which are adapted to the process ( 500 ) according to one of claims 1 to 5 and / or the method ( 600 ) according to claim 6 execute and / or to control. Optical system ( 100 ) having the following features: an optical phase array ( 102 ) for emitting a light signal ( 104 ); a measuring device ( 108 ) for measuring an intensity distribution and / or a wavefront of the light signal ( 104 ); and a device ( 112 ) according to claim 7. Optical system ( 100 ) according to claim 8, comprising an optical device ( 126 ) for coupling out a feedback signal ( 130 ) from the light signal ( 104 ), the optical device ( 126 ) is adapted to the feedback signal ( 130 ) on the measuring device ( 108 ), the measuring device ( 108 ) is adapted to the intensity distribution and / or the wavefront using the feedback signal ( 130 ) to eat. Optical system ( 100 ) according to claim 9, wherein the optical device ( 126 ) at least one beam splitter element ( 400 ) and / or at least one mirror element ( 402 ) and / or at least one lens element ( 404 ) having. Computer program that is adapted to the procedure ( 500 ) according to one of claims 1 to 5 and / or the method ( 600 ) according to claim 6 execute and / or to control. A machine readable storage medium storing the computer program of claim 11.

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