Method for controlling an optical phase array, method for detecting an object using an optical phase array and optical system

Abstract

Method (500) for controlling an optical phase array (102), wherein the method (500) comprises the following steps: Reading (510) a measurement signal (116) representing an intensity distribution and / or a wavefront of a light signal (104) emitted by the optical phase array (102); Comparing (520) the measurement signal (116) with a reference signal to determine a deviation value (120) of a deviation between the measurement signal (116) and the reference signal;and generating (530) a control signal (124) to control the optical phase array (102) using the deviation value (120), wherein in the comparison step (520) the measurement 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 intensity distribution represented by the measurement signal (116) and the reference intensity distribution and / or between the wavefront represented by the measurement signal (116) and the reference wavefront as the deviation value (120).

Description

State of the art

[0001] The invention is based on a device or a method according to the species of the independent claims. The subject matter of the present invention is also a computer program.

[0002] In radar technology, groups of individual antennas with individual phase or amplitude control, so-called phase array antennas, are now state of the art. Phased array antennas can also be used in telecommunications, since they enable better performance, low weight, small installation space and flexible formation of an antenna profile.

[0003] In the optical wavelength range, especially in the infrared range, there is currently a great deal of 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) were developed, for example, within the framework of the SWEEPER program (SWEEPER = short-range, Wide Field-of-View Extremely Agile, Electronically Steered Photonic Emitter) by DARPA. Disclosure of Invention

[0004] Against this background, with the approach presented here, a method for controlling an optical phase array, a method for detecting an object using an optical phase array, a device that uses at least one of these methods, an optical system and finally a corresponding Computer program according to the main claims presented. Advantageous developments and improvements of the device specified in the independent claim are possible as a result of the measures listed in the dependent claims.

[0005] A method for driving an optical phased array is presented, the method comprising the following steps:

[0006] reading in a measurement signal which represents an intensity distribution and / or a wave front of a light signal emitted by the optical phase array;

[0007] 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

[0008] generating a control signal for driving the optical phased array using the offset value.

[0009] An optical phased array can be understood to mean an array of a plurality of individually controllable antenna elements for emitting light beams, with a specific radiation characteristic of the optical phased array being able to be realized by superimposing the light beams emitted by the antenna elements. The radiation characteristic can be changed solely by controlling the antenna elements, for example by changing an amplitude or phase setting of individual antenna elements, without the optical phase array having to be moved for this purpose. The optical phase array can be manufactured, for example, in a semiconductor technology process, for example based on silicon.

[0010] A measurement signal can be understood, for example, as a feedback signal coupled out of the light signal by means of a suitable optical device. For example, the measurement signal can also be a signal from a wave front sensor, also known as 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 as an electromagnetic signal in the visible light range. A reference signal can be understood, for example, as a target 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 control individual antenna elements of the optical phased array in such a way that the deviation is compensated for or corrected.

[0011] 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, if necessary, 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 development. The feedback can take place, 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, by modifying a phase distribution of individual antennas of the optical phase array.

[0012] For example, such a correction can take place using tabulated configurations or also actively using optimization algorithms, for example based on the Gerchberg-Saxton algorithm for diffractive phase elements or evolutionary algorithms. Alternatively, instead of actively correcting the phase elements, there is the possibility of compensating for the observed deviations from the ideal distribution on the basis of measurement results from a control loop in the data evaluation.

[0013] According to one embodiment, in the reading step, a signal can be read in as the measurement signal, which signal represents an intensity distribution of the light signal in a far field of the optical phase array. As a result, necessary corrections in a phase distribution of the optical phase array can be calculated particularly efficiently on the basis of a mathematical relationship between Fourier transformation and Fraunhofer diffraction.

[0014] According to a further embodiment, in the step of comparing, the measurement signal can be compared with a signal representing a reference intensity distribution as the reference signal in order 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 can represent a reference wavefront, wherein the measurement signal can be compared with the reference signal in order 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 precisely determined with relatively little computing effort.

[0015] It is advantageous if, in the reading step, a signal is read in as the measurement signal whose phase distribution is essentially the same as a phase distribution of the light signal. As a result, inaccuracies when comparing the measurement signal with the reference signal can be kept as small as possible. A high degree of accuracy of the method can thus be guaranteed.

[0016] Furthermore, in the generating step, the control signal can be generated in order to correct the deviation. As a result, target specifications with regard to the light distribution emitted by the optical phase array can be met.

[0017] The approach described here also creates a method for detecting an object using an optical phase array, the method comprising the following steps: Reading in a measurement signal, which represents an intensity distribution and / or a wave front of a light signal emitted by the optical phase array, and a detector signal, which represents 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

[0018] Evaluate the detector signal using the deviation value to detect the object.

[0019] A detector signal can be understood to mean a signal generated by a detector device, such as a lidar or ladar sensor or some other optical sensor.

[0020] 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.

[0021] The approach presented here also creates a device that is designed to carry out, control or implement the steps of a variant of a method presented here in corresponding devices. The object on which the invention is based can also be achieved quickly and efficiently by this embodiment variant of the invention in the form of a device.

[0022] For this purpose, the device can have 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 in sensor signals from the sensor or for outputting data or control signals to the Have actuator and / or at least one communication interface for reading or outputting data that are embedded in a communication protocol. The arithmetic unit can be a signal processor, a microcontroller or the like, for example, while the storage unit can be a flash memory, an EPROM or a magnetic storage unit. The communication interface can be designed to read in or output data wirelessly and / or by wire, wherein a communication interface that can read in or output wire-bound data can, for example, read this data electrically or optically from a corresponding data transmission line or can output it to a corresponding data transmission line.

[0023] In the present case, a device can be understood to mean an electrical device that processes sensor signals and, depending thereon, outputs control and / or data signals. The device can have an interface that can be configured as hardware and / or software. In the case of a hardware design, 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 for the interfaces to be separate integrated circuits or to consist at least partially of discrete components. In the case of a software design, the interfaces can be software modules which are present, for example, on a microcontroller alongside other software modules.

[0024] In an advantageous embodiment, the device is used to control a vehicle. For this purpose, the device can, for example, access sensor signals such as acceleration, pressure, steering angle or surroundings sensor signals. The control is carried out 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: a phased optical 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.

[0025] The measuring device can be an optical sensor, for example.

[0026] According to one embodiment, the optical system can have an optical device for decoupling a feedback signal from the light signal. The optical device can be designed to direct the feedback signal to the measuring device. Accordingly, the measuring device can be designed to measure the intensity distribution and / or the wave front using the feedback signal. The optical device can be, for example, a beam splitter element, a lens element, in particular a converging lens, also known as a Fourier lens, a mirror element, a holographic element or another refractive, diffractive or reflective element or a combination of several optical components. For example, the optical device can be a Fraunhofer setup for observing a far-field intensity distribution of the optical phase array. This embodiment ensures that feedback is as precise as possible.

[0027] According to a further embodiment, the optical device can have at least one beam splitter element, at least one mirror element, at least one lens element or a combination of at least two of the elements mentioned. A beam splitter element can be understood to mean, for example, a beam splitter cube or a semi-transparent mirror. A lens element can be understood to mean, for example, a converging lens. In particular, the lens element can function as Fourier optics. With this embodiment, the optical device can be implemented inexpensively and with little effort.

[0028] 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 also advantageous used, especially when the program product or program is run on a computer or device.

[0029] Embodiments of the invention are shown in the drawings and explained in more detail in the following description. It shows:

[0030] figure 1 shows a schematic representation of an optical system according to an embodiment;

[0031] figure 2 shows a schematic representation of an optical system according to an embodiment;

[0032] figure 3 shows a schematic representation of how a Fraunhofer setup works for observing a far-field intensity distribution;

[0033] figure 4 shows a schematic representation of an optical device according to an embodiment;

[0034] figure 5 shows a flowchart of an embodiment of a method for driving an optical phased array; and

[0035] figure 6 shows a flow chart of an exemplary embodiment of a method for detecting an object using an optical phase array.

[0036] In the following description of favorable exemplary embodiments of the present invention, the same or similar reference symbols are used for the elements which are shown in the various figures and have a similar effect, with a repeated description of these elements being dispensed with.

[0037] figure 1 shows a schematic representation of an optical system 100 according to one embodiment. Shown is a block diagram for detecting a deviation of an optical phased array 102 emitted light signal 104 from an ideal ray. The optical system 100 includes a first block 106 from a transmission unit in the form of the optical phased array 102 , OPA for short, and a receiving unit in the form of a measuring device 108 for measuring an intensity distribution or, additionally or alternatively, a wave front of the light signal 104 , such as using a Fresnel lens, and a second block containing a device 112 for electronic signal processing and control of the optical phase array 102 represented.

[0038] The device 112 includes a reading unit 114 to read in one of the measuring device 108 generated measurement signal 116 , which is the intensity distribution or the wave front of the light signal 104 represented. The reading unit 114 conducts the measurement signal 116 to a comparison unit 118 further, which is designed to the measurement signal 116 compared to a reference signal. The comparison unit generates the result of the comparison 118 a deviation value 120 , showing a deviation between the measurement signal 116 and the reference signal, i. H. between an actual value and a target 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 array102 is realized. According to one embodiment, the comparison unit is 118 formed 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 use the deviation value 120 a control signal 124 for driving the optical phased array 102 to generate and to the optical phase array 102 transferred to.

[0039] 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 the light signal 104 into a useful light signal 128 , which represents a specific useful light distribution, and a feedback signal 130 for the control circuit for controlling the optical phased array 102 to share, with the feedback signal 130 through the optical device 126 on the measuring device 108 is steered. The measuring device is corresponding 108 designed to the measurement signal 116 using the feedback signal 130 to create. In particular, the optical device 126 formed 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 is equivalent to.

[0040] figure 2 shows a schematic representation of an optical system 100 according to one embodiment. The optical system 100 essentially corresponds to the above based on figure 1 described optical system. Shown is a block diagram of optical phased array beam profile deviation detection 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 transmitter and receiver unit, the optical subsystem for signal monitoring and an electronic control circuit for signal generation and control. The detector device 200 is designed to capture one of a scenery 202 reflected portion 204 that of the optical phased array 102 emitted light signal 104 , more precisely by splitting the light signal 104 by means of the optical device 126 received useful light signal 128 , to detect. Here, the detector device generates 200 a the scenery 202 representative detector signal 206 and sends it to an evaluation unit 208 the device 112 , which also contains the deviation value 120 from the comparison unit 118 receives. The evaluation unit 208 is trained to recognize the scene 202 the detector signal 206 using the deviation value 120 evaluate.

[0041] figure 3 shows a schematic representation of how a Fraunhofer structure works 300 for the observation of a far-field intensity distribution, as for example from the previous reference to the figure 1 and figure 2 described measuring device can be measured. the inside figure 3 structure shown shows, for example, a basic structure previously based on the figure 1 and figure 2 described optical device. The Fraunhofer structure 300 includes a diffractive structure 302 to bend a beam of light 304 . The bending structure 302 is at a distance d from a Fourier lens 306 arranged with the focal length f. A focal plane 308 the Fourier lens 306 is indicated by a vertical line.

[0042] figure 4 shows a schematic representation of an optical device 126 according to one embodiment. With the optical setup 126 it can be the above based on the figure 1 to figureAct 3 described optical device. An exemplary schematic setup for monitoring the intensity distribution in the far field of the optical phase array is shown 102 , also called the far-field intensity distribution. The optical device 126 is according to this embodiment according to the above with reference to FIG figure 3 described principle implemented as a Fraunhofer structure for performing an optical Fourier transformation. This includes the optical device 126 for example a beam splitter element 400 for dividing the from the optical phased array 102 emitted light signal 104 into the feedback signal 130 and the useful light signal 128 with the corresponding useful light distribution. Opposite the beam splitter element 400 is a mirror element 402 arranged, which is designed to the feedback signal 130 on a lens element 404 , here a Fourier lens. The lens element 404 is designed to use the feedback signal 130 on the detector device 200 , located in the back focal plane of the lens element 404 located to steer.

[0043] The following is an example of a structure for controlling the optical phased array 102 via far-field measurements based on figure 4 described again in other words.

[0044] 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. The use of the mirror element is optional 402 , which can be flat or designed as a free-form surface in order to compensate for differences in the optical path length and to obtain the phase reference for the interference pattern as far as possible. The far-field distribution is generated using a Fourier lens as the lens element 404 on the detector device 200 . The position of the useful light distribution is determined, for example, using a camera. According to the displacement theorem, lateral shifts occur, for example, by readjusting the phase array 102 with a linear phase component, since denotes the Fourier transform.

[0045] figure 5 shows a flow chart of an embodiment of a method 500 for driving an optical phased array. The procedure 500 can, for example, in connection with a previously based on the figure 1 to figure 4 described device are carried out. Here, in one step 510 read in the measurement signal generated by the measurement 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 wave front 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 offset value.

[0046] figure 6 shows a flow chart of an embodiment of a method 600 for detecting an object using an optical phased array. The procedure 600 can, for example, in connection with a previously based on the figure 1 to figure 4 described device are carried out. Here, in one step 610 the measurement signal generated by the measuring device of the optical system and the detector signal generated by the detector device are read in. Depending on the exemplary embodiment, the measurement signal represents an intensity distribution, in particular a far-field intensity distribution, or a wave front 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 evaluates the detector signal using the deviation value to detect the object.

[0047] Below are various embodiments of the approach presented here based on the figure 1 to figure 6 summarized again in other words.

[0048] 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 transparent mirror, a beam splitter cube or a diffractive or holographic element. Here, however, attention should be paid to maintaining a relative phase distribution in order to reduce the phase distribution being influenced by the decoupling. The maintenance 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 is for example in the figure 3 and figure 4, an optical Fourier transform for observing far-field intensity distribution in a back focal plane of the Fourier lens 404 realized. Instead of a classic refractive lens, a diffractive or holographic element or a microlens array can also be used as the lens element 404 be used. For example, the use of a microlens array opens up further possibilities for measuring the wave fronts and determining the deviation from the target specification, for example using a Shack-Hartmann sensor.

[0049] According to a further exemplary embodiment, reflections on the optics of the optical system 100 occur, used. On the one hand, it should be ensured that the reflections match the phase distribution of the emitted light signal 104 maintain. On the other hand, it should be ensured that the reflections do not fall directly on the phase array 102 , but on the detector device next to it 200 meeting. The detector device 200 can be implemented, for example, as a detector array.

[0050] The advantage of measuring the far-field intensity is the mathematical relationship between Fourier transformation and Fraunhofer diffraction. Based on the previously described Fraunhofer structure for a far-field measurement, a necessary correction in the phase distribution can be calculated with relatively little effort and, for example, the phase distribution can be optimized using a suitable algorithm. For example, a lateral offset of an optical target distribution, ie the optical beam in the far field, compared to a target state is detected by the control circuit proposed here and corrected by an additional linear phase component. When the wave front is determined directly, 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.

[0051] According to a further embodiment, the optical system comprises 100 additionally a detector component, for example in the form of the detector device 200 , to compensate for a determined deviation between the target and actual distribution in a data evaluation on the detector side.

[0052] An important difference to typical Fraunhofer setups for diffractive optical elements is the comparatively large divergence and the combination of the phase of the very likely curved wave fronts of the individual emitters and the induced phase distribution of the phase array 102 .

[0053] If an embodiment includes an "and / or" link between a first feature and a second feature, this should be read in such a way that the embodiment according to one embodiment includes both the first feature and the second feature and according to a further embodiment either only that having the first feature or only the second feature.

Claims

[1] Procedure ( 500 ) for controlling an optical phase array ( 102 ), wherein the procedure ( 500 ) includes the following steps: Read ( 510 ) of a measurement signal ( 116 ), which represents an intensity distribution and / or a wavefront of one of the optical phase arrays ( 102 ) emitted light signal ( 104 ) represents; Compare ( 520 ) of the measurement signal ( 116 ) with a reference signal to determine a deviation value ( 120 ) a deviation between the measurement signal ( 116 ) and the reference signal; and Generate ( 530 ) of a control signal ( 124 ) to control the optical phase array ( 102 ) using the deviation value ( 120 ). [2] Procedure ( 500 ) according to claim 1, wherein in the reading step ( 510 ) a signal as the measurement signal ( 116) is read in, which shows an intensity distribution of the light signal ( 104 ) in a far field of the optical phase array ( 102 ) represents. [3] Procedure ( 500 ) according to one of the preceding claims, wherein in the step of comparison ( 520 ) the measurement signal ( 116 ) is compared with a signal representing a reference intensity distribution and / or a reference wavefront as the reference signal in order to detect a lateral offset between the signal produced by the measurement signal ( 116 ) represented intensity distribution and the reference intensity distribution and / or between the intensity distribution represented by the measurement signal ( 116 ) represented wavefront and the reference wavefront as the deviation value ( 120 to determine. [4] Procedure ( 500 ) according to one of the preceding claims, wherein in the reading step ( 510 ) a signal as the measurement signal ( 116) is read in, whose phase distribution is essentially the same as the phase distribution of the light signal ( 104 ) is. [5] 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. [6] Procedure ( 600 ) for recognizing an object ( 202 ) using an optical phase array ( 102 ), wherein the procedure ( 600 ) includes the following steps: Read ( 610 ) of a measurement signal ( 116 ), which represents an intensity distribution and / or a wavefront of one of the optical phase arrays ( 102 ) emitted light signal ( 104 ) represents, and a detector signal ( 206 ), which is through the object ( 202 ) reflected portion ( 204 ) of the light signal ( 104 ) represents; Compare ( 620) of the measurement signal ( 116 ) with a reference signal to determine a deviation value ( 120 ) a deviation between the measurement signal ( 116 ) and the reference signal; and Evaluate ( 630 ) of the detector signal ( 206 ) using the deviation value ( 120 ), to the object ( 202 ) to recognize. [7] Device ( 112 ) with units ( 114 , 118 , 122 ; 208 ), who are trained to carry out the procedure ( 500 ) according to any one of claims 1 to 5 and / or the method ( 600 ) to execute and / or control according to claim 6. [8] Optical system ( 100 ) with the following characteristics: an optical phase array ( 102 ) to emit a light signal ( 104 ); a measuring device ( 108 ) to measure an intensity distribution and / or a wavefront of the light signal ( 104); and a device ( 112 ) according to claim 7. [9] Optical system ( 100 ) according to claim 8, with an optical device ( 126 ) to extract a feedback signal ( 130 ) from the light signal ( 104 ), wherein the optical device ( 126 ) is designed to process the feedback signal ( 130 ) on the measuring device ( 108 ) to steer, whereby the measuring device ( 108 ) is designed to control the intensity distribution and / or the wavefront using the feedback signal ( 130 ) to eat. [10] 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 ) exhibits. [11] Computer program trained to perform the procedure ( 500) according to any one of claims 1 to 5 and / or the method ( 600 ) to execute and / or control according to claim 6. [12] Machine-readable storage medium on which the computer program according to claim 11 is stored.

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