Device for cleaning an optical element of a camera system

Abstract

Device (1) for cleaning an optical element (3) of a camera system (2), wherein the device (1) comprises at least one ultrasonic transducer (5) arranged on the optical element (3) for acting on the optical element (3) with ultrasonic waves (7), characterized in that a frequency of the ultrasonic waves (7) generated by means of the at least one ultrasonic transducer (5) is set such that an excitation frequency is adapted to the natural frequency of a deposit (12) on the optical element (3).

Description

[0001] The invention relates to a device for cleaning an optical element of a camera system, in particular for a camera system of a vehicle.

[0002] Vehicles today increasingly include assistance systems that support the driver when driving the vehicle. Such assistance systems also typically include a camera system arranged on the exterior of the vehicle for optically detecting and recording the vehicle's surroundings. The installation location of the camera system depends particularly on the intended assistance function. Camera systems for reversing aids are generally arranged in the area of ​​the rear of the vehicle or the rear window. For so-called surround view systems, additional camera systems are typically arranged in the side area of ​​the vehicle, for example, below the vehicle's side mirrors. The image recorded by the camera systems can usually be shown to the vehicle user on a display in the vehicle cabin.

[0003] Camera systems located on the exterior of the vehicle can become dirty while driving, for example due to contaminants such as rain, snow, salt or dust, which limits or prevents the assistance systems from functioning.

[0004] To protect the optical devices from contamination and external weather influences, the camera systems are therefore typically designed with a cleaning device and / or the camera systems are installed in a flap and can be folded out or extended manually or automatically as required.

[0005] DE 42 17 559 A1 relates to a device for keeping the exposed surface of an optical imaging system or radar system clean, wherein a ring- or tube-like, piezoelectrically excitable resonator device is provided which is coupled to the exposed surface in the form of an optical element or protective window and via which the element or protective window can be excited to bending vibrations in the ultrasonic frequency range.

[0006] From DE 28 09 748 A1 a device for cleaning a surface of an optical component, such as an infrared camera, with a cleaning fluid and an ultrasonic transducer that can be activated for a cleaning process is known.

[0007] DE 10 2005 021 671 A1 discloses a device for cleaning a lens surface of a camera.

[0008] However, the state-of-the-art solutions for preventing or removing deposits are only partially effective. Problems are particularly caused by deposits such as salts or soil deposits, which, due to interfacial effects (i.e., surface adhesion), permanently adhere to the optical elements of camera systems and cannot be removed with conventional cleaning solutions. In this case, the adhering material can often only be removed by manual cleaning and using aggressive cleaning fluids.

[0009] In the future, it is desirable for camera-based assistance systems to be able to operate at higher vehicle speeds, for example, to provide warning functions across the entire vehicle's operating range. However, at higher speeds, the camera systems and their optical components become dirty even faster, requiring frequent cleaning of the camera lenses during operation, which limits the availability of the assistance function.

[0010] Against this background, the object of the invention is to provide a solution that enables simple and effective cleaning of a camera system.

[0011] This object is achieved by a device having the features of claim 1. Advantageous embodiments and further developments are the subject of subclaims, whereby combinations and further developments of individual features are also conceivable.

[0012] A key concept of the invention is to prevent and / or remove deposits or contamination on optical elements of camera systems, in particular on an outer lens or an optically transparent cover, by means of ultrasonic waves coupled into the optical element. By subjecting the optical element to ultrasound, improved cleaning can be achieved in an advantageous manner compared to previously known cleaning solutions, in particular by altering the interface effects described above.

[0013] The solution according to the invention can prevent the adhesion of deposits to optical elements, particularly during travel. Furthermore, already adhering contaminants can be caused to slide off. This is achieved in particular by liquefying the adhering material by subjecting the optical element to ultrasound in the interface region. The introduced ultrasonic energy preferably covers the entire surface of the optical element and can also be transmitted over longer distances. As a further advantage over known solutions, this can reduce the energy required to clean the optical element.

[0014] For the purposes of the invention, deposits can be understood as any type of contamination that can accumulate on the optical element of the camera system, particularly during vehicle operation. This includes, in particular, moist deposits such as water, snow, and ice, as well as salt or soil deposits.

[0015] According to the invention, at least one ultrasonic oscillator is arranged on the at least one optical element of the camera system. The ultrasonic oscillator is designed in particular to generate and emit ultrasonic waves and serves to apply ultrasonic waves to the optical element. For this purpose, the at least one ultrasonic oscillator is preferably arranged on the optical element in such a way that it is mechanically coupled to the optical element directly or at least via a suitable sound conductor, in order to enable direct transmission of the ultrasonic waves generated by the ultrasonic oscillator to the body of the optical element or at least to its outer surface.

[0016] The ultrasonic transducer can, for example, be arranged on a circuit board within the camera system, in particular on a circuit board containing image acquisition and / or image analysis electronics. The ultrasonic transducer can also be positioned such that it is in contact with a lens of the imaging system, in particular the back of the lens. This minimizes the effort required for the proposed cleaning solution, both in terms of additional mechanical or electronic components and in terms of power consumption.

[0017] Within the scope of the invention, the optical element of the camera system can be, for example, a lens or another optical beam-shaping or beam-steering element of an imaging system of the camera system. The imaging system refers, in particular, to a lens of the camera system.

[0018] Furthermore, the optical element of the camera system can also be an optically transparent cover glass, i.e. an element without a direct beam shaping or beam steering function, which is arranged, for example, in a light incidence opening of the camera system and protects a downstream imaging system of the camera system from external environmental influences.

[0019] In any case, the optical element is preferably an external closure element, i.e. the element which closes off an imaging system of the camera system from the external environment or the detection area and is thus directly exposed to weather influences and contamination.

[0020] According to a preferred embodiment of the device according to the invention, the ultrasonic oscillator arranged on the optical element is a piezoelectric ultrasonic resonator.

[0021] Within the scope of the invention, the ultrasonic oscillator is preferably arranged in a region of the optical element that is not relevant to the detection function of the camera system. Particularly when the optical element is a lens or a cover glass of an imaging system of the camera system, the ultrasonic oscillator is preferably arranged at the edge of the optical element and preferably outside the detection range or viewing angle of the camera system. The region that is not relevant to the detection function is understood to mean, in particular, a region of the optical element through which radiation passes exclusively that is not detected by the camera system, for example, by means of a photosensitive image recording element.

[0022] The ultrasonic transducer is preferably powered by a periodic voltage. The ultrasonic transducer can be connected, in particular, via a suitable signal line to a PWM (pulse width modulation) output of a microcontroller. It is particularly possible to use the PWM output of an existing microcontroller or one used for other functions of the camera system. Furthermore, the ultrasonic transducer can also be connected, via a suitable signal line, to an LVDS channel (low voltage differential backchannel) of the camera system, which primarily serves to transmit the image data acquired by the camera system.

[0023] The device according to the invention can further comprise means which are designed to detect contamination of the optical element and which are further designed to control the ultrasonic oscillator depending on this detection of contamination, i.e. in particular when contamination of the optical element is detected. The means can be, for example, an image processing system which detects contamination directly in the camera image. Furthermore, they can be means which serve to measure the attenuation of the amplitude of the ultrasonic waves generated by the ultrasonic oscillator. Based on the attenuation, i.e. based on the return measurement signal, the coverage density of the adhering material on the optical element can be deduced. Furthermore, the return measurement signal can be used as a control variable for the generation of the ultrasonic waves, i.e.The frequency and / or amplitude setting of the ultrasonic waves can be controlled depending on the back measurement of the amplitude attenuation.

[0024] Further advantages and optional embodiments of the invention will become apparent from the following description and the drawings. Exemplary embodiments are illustrated in simplified form in the drawings and explained in more detail in the following description.

[0025] The single figure shows a preferred embodiment of the device 1 according to the invention for cleaning an optical element of a camera system 2.

[0026] In the case shown, the optical element is a lens 3 of the camera system 2, in particular the outer lens 3 of an imaging system 4 of the camera system 2.

[0027] The camera system 2 can, for example, be a camera system 2 that is arranged in the front, side or rear area of ​​a vehicle and serves to capture image data from the vehicle environment for one or more assistance systems.

[0028] According to the invention, at least one ultrasonic transducer 5 is arranged on the lens 3, in this case in an edge region of the lens 3 and thus in an area not relevant to the detection function of the camera system 2. The area of ​​the lens 3 not relevant to the detection function is characterized in this case in particular by the fact that it lies outside the detection range or outside the viewing angle 6 of the camera system 2.

[0029] The ultrasonic oscillator 5 is mechanically coupled to the lens 3 for the direct transmission of ultrasonic waves 7 to the lens body and for exposing the outer surface 8 of the lens 3 to ultrasonic waves 7. The outer surface 8 of the lens 3 is, in particular, the surface or side of the lens 3 that, when the lens 3 is arranged in the imaging system 4, faces the vehicle's surroundings and is thus directly exposed to weather influences and contamination during driving.

[0030] The ultrasonic oscillator 5 can be a so-called ultrasonic resonator or sound transducer. The most common ultrasonic oscillators 5 are piezoelectric and magnetostrictive oscillators, which convert high-frequency electrical currents into mechanical vibrations. Piezoelectric oscillators essentially consist of an arrangement of piezoelectric ceramics and corresponding mechanical components that form a resonator and adapt the vibrations to the object being sounded. To achieve sufficiently high power, several oscillators can also be connected together in a group.

[0031] The control of the ultrasonic oscillator 5, in particular the control or regulation of the ultrasonic waves 7 generated by the at least one ultrasonic oscillator 5, can be carried out within the scope of the invention by means of a high-frequency electrical operating voltage, which is provided, for example, via an ultrasonic generator connected to the at least one ultrasonic oscillator. In this case, the frequency, amplitude, and power of the ultrasonic waves 7 generated by the ultrasonic oscillator 5 and transmitted to the lens 3 can be adjusted via the operating voltage.

[0032] In the illustrated case, the ultrasonic oscillator 5 is connected via a signal line 9 to a PWM output 10 of a microcontroller 11. The microcontroller 11 can be a microcontroller 11 that is also used for other purposes or control functions in the camera system 2. The voltage of the PWM output 10 thus allows the ultrasonic waves 7 generated by the ultrasonic oscillator 5 to be adjusted or controlled in a cost-effective and simple manner, in particular by means of a pulsed signal voltage of, for example, 1 MHz.

[0033] According to the invention, the device 1 serves to prevent and remove deposits 12, in particular on the outer side 8 of the lens 3 or an optical element of the imaging system 4 of the camera system 2. The deposits 12 can be, for example, contaminants such as water, snow, ice and moist earth deposits. The prevention or removal of these deposits 12 is achieved by coupling the ultrasonic waves 7 into the optical element, whereby a change in the interface effects, in particular the surface adhesion, between the outer surface 8 of the optical element and the respective components of the deposits 12 is achieved. By subjecting the optical element to ultrasound, in particular a liquefaction and thus a detachment of the adhering material takes place in the interface regions.The introduced ultrasonic energy can pass over the entire surface 8 of the optical element and can also be transmitted over greater distances.

[0034] The mode structure of the ultrasonic waves 7 generated by means of the at least one ultrasonic oscillator 5 can in particular be set such that surface waves with high amplitude are generated at least on the outer surface 8 of the optical element. The amplitude of the coupled waves can in particular be set such that the adhesion forces typically occurring of adhering materials are overcome. Furthermore, the amplitude can be set so strong that a phase transition is generated in the adhering material, i.e. that a change in the state of aggregation or modification from crystalline to amorphous is achieved, which subsequently leads to the flowing away or detachment of the material or deposits 12 from the surface 8.

[0035] Furthermore, according to the invention, the frequency of the ultrasonic waves 7 generated by the at least one ultrasonic oscillator 5 is adjusted such that a good coupling of the ultrasonic waves 7 to deposits 12 on the outer surface 8 of the optical element is achieved. According to the invention, the good coupling of the ultrasonic waves 7 is understood to mean an adjustment of the ultrasonic oscillator 5 such that the excitation frequency, ie, the generated frequency of the ultrasonic waves 7, is adapted to the natural frequency of the deposits 12.

[0036] The frequency of the ultrasonic waves 7 generated by the at least one ultrasonic oscillator 5 can further be adjusted and varied within the scope of the invention such that a resonant coupling of the ultrasonic waves 7 to the deposits 12 on the outer surface 8 of the optical element is achieved. In this case, an acoustic surface wave can preferably be generated that propagates only in two dimensions on the interface of the optical element. In particular, the excitation frequency is adapted to the natural frequency of the deposits such that the surface waves can propagate within and above the geometric surface of the optical element, i.e., orthogonally to the normal vector of the surface 8.

[0037] The device 1 according to the invention can also be designed with means for back-measuring the attenuation of the amplitude of the generated ultrasonic waves 7. Based on the attenuation, i.e., based on the back-measurement signal, the coverage density of the adhering deposits 12 can be determined. Furthermore, the back-measurement signal can be used as a control variable for the generation of the ultrasonic waves 7, i.e., the frequency and / or amplitude setting of the ultrasonic waves 7 can be controlled depending on the back-measurement of the amplitude attenuation.

[0038] The device 5 according to the invention can in particular also be designed with a plurality of ultrasonic generators, ie with two or more ultrasonic generators connected to the at least one ultrasonic oscillator 5. The plurality of ultrasonic generators can be connected to the same ultrasonic oscillator(s) 5 (resonators), or each ultrasonic oscillator 5 can be connected to only one ultrasonic generator.

[0039] In an embodiment of the device according to the invention with multiple ultrasonic generators, these can be operated in such a way that a superposition of the ultrasonic waves 7 emitted by the at least one ultrasonic oscillator 5 and thus a local increase in the oscillation amplitude is achieved, in particular on the outer surface 8 of the optical element and in particular in such a way that, under resonance conditions, the energy is transferred to the adhesion or deposits 12. The increase in the oscillation amplitude leads to improved removal of the adhering material. The constructive interference of multiple resonators leads to an increase in amplitude. For this purpose, it is necessary to coordinate the frequencies and the phase position of the individual resonators so that the constructive interference occurs on a well-defined partial surface of the optical element.

[0040] Furthermore, when the device 1 according to the invention is configured with multiple ultrasonic generators, these can be operated in such a way that the phases of the ultrasonic waves 7 emitted by the at least one ultrasonic oscillator 5 are varied. This allows the location of the local increase in the oscillation amplitude to be varied. In particular, in conjunction with the described increase in the oscillation amplitude, this achieves improved removal of the adhering material across the entire affected surface 8. List of designations 1 device 2 camera system 3 lenses 4 Imaging system 5 ultrasonic transducers 6 viewing angles 7 ultrasonic waves 8 outer surface 9 Signal line 10 PWM output 11 microcontrollers 12 deposits

Claims

[1] Device (1) for cleaning an optical element (3) of a camera system (2), wherein the device (1) comprises at least one ultrasonic oscillator (5) arranged on the optical element (3) for subjecting the optical element (3) to ultrasonic waves (7), characterized by that a frequency of the ultrasonic waves (7) generated by means of the at least one ultrasonic oscillator (5) is set such that an excitation frequency is adapted to the natural frequency of a deposit (12) on the optical element (3). [2] Device (1) according to claim 1, characterized by that the optical element (3) is a lens (3) of an imaging system (4) of the camera system (2). [3] Device (1) according to claim 1, characterized by that the optical element (3) is an optically transparent cover glass of the camera system (2). [4] Device (1) according to one of the preceding claims, characterized bythat the ultrasonic surge oscillator (5) is a piezoelectric ultrasonic resonator. [5] Device (1) according to one of the preceding claims, characterized by that the ultrasonic oscillator (5) is arranged in an area of ​​the optical element (3) which is not relevant for a detection function of the camera system (2). [6] Device (1) according to one of the preceding claims, characterized by that the ultrasonic oscillator (5) is operated via a periodic voltage. [7] Device (1) according to one of the preceding claims, characterized by that the ultrasonic oscillator (5) is connected via a signal line (9) to a PWM output (10) of a microcontroller (11) of the camera system (2). [8] Device (1) according to one of the preceding claims, characterized by that the ultrasonic oscillator (5) is connected to an LVDS channel of the camera system (2) via a signal line (9). [9] Device (1) according to one of the preceding claims comprising means designed to - to detect contamination of the optical element (3) and - to control the ultrasonic oscillator (5) depending on detected contamination. [10] Vehicle camera comprising a device (1) according to any one of the preceding claims.

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