Autofocus and particle sensor device and corresponding method, as well as camera and particle sensor system

Abstract

Combined autofocus and particle sensor device (1a; 1b; 1c), comprising: an optical emitter device (2) which is configured to emit at least one measuring laser beam (L) into an environment of the combined autofocus and particle sensor device (1a; 1b; 1c); a detector device (3) which is configured to detect the at least one measuring laser beam (L) scattered by particles or objects (6) in the vicinity of the combined autofocus and particle sensor device (1a; 1b; 1c) and to output a corresponding measuring signal; and an evaluation unit (4) which is designed to use the measurement signal: a. to determine at least one measurement parameter relating to the particles (6) in the vicinity of the combined autofocus and particle sensor device (1a; 1b; 1c) in a first operating mode; and b. in a second operating mode to generate a control signal to adjust the focus of an external camera (5), wherein the evaluation device (4) is further configured to use different filters for evaluating the measurement signal in the first operating mode and in the second operating mode.

Description

[0001] The present invention relates to a combined autofocus and particle sensor device. The invention further relates to a combined camera and particle sensor system. Finally, the invention relates to a combined autofocus and particle measurement method. Specifically, the invention relates to combined autofocus and particle sensor devices and corresponding measurement methods for use in mobile devices, particularly smartphones. State of the art

[0002] In many large cities with high traffic volumes or in industrial areas, air pollution, particularly due to suspended particulate matter, can become problematic. To measure exceedances of limit values ​​or to identify specific problem areas, public institutes or scientific research facilities conduct measurements to determine particle pollution. However, there is also increasing demand in the private sector for options to determine particle pollution locally. This creates a need for portable, miniaturized sensors to detect particle pollution.

[0003] Particle load can be determined, for example, based on optical measurements. An example optical particle sensor is known from WO 2017 / 198699 A1. A laser sensor module has multiple lasers that emit measuring laser beams that are reflected by particles in the vicinity of the particle sensor. Using a self-mixing interference (SMI) method, the properties of the particles in the vicinity of the particle sensor can be determined. An SMI method means that the reflected measuring laser beams interfere with the emitted measuring laser beams, with the interference leading to changes in the optical and electrical properties of the laser. The precise determination of these changes allows conclusions to be drawn about the properties of the particles.

[0004] Another exemplary optical particle sensor for detecting particle densities of small particles with particle sizes in the range between 0.05 µm and 10 µm is known from WO 2018 / 104153 A1.

[0005] Furthermore, a laser sensor for multi-parameter detection is known from US 2018 / 0 224 368 A1. US 2007 / 0091295 A1 relates to a self-mixing laser sensor. DE 698 12 928 T2 discloses a method for determining particles in a liquid sample.

[0006] Portable devices such as smartphones typically include cameras for capturing images and videos, in addition to optical sensors. While the camera's focus was traditionally set manually, most modern cameras, and especially cameras on portable devices such as smartphones, tablets, or notebooks, have autofocus (AF), i.e., a technology that automatically focuses on a subject. A distinction is made between active autofocus and passive autofocus. Active autofocus emits electromagnetic radiation, such as ultrasound or an auxiliary light, while passive autofocus uses only the light emitted or reflected by the subject.

[0007] Passive autofocus systems incorporate edge contrast measurement, which varies the focal length of the lens and maximizes the brightness gradient at contour edges. Other passive methods include phase detection, line sensors, and cross sensors.

[0008] Active autofocus systems employ time-of-flight methods, in which the distance to an object is determined based on the time of flight of ultrasonic waves or laser beams reflected from the object. An AF assist lamp can be used to enable passive methods, such as contrast measurement or phase detection, even in poorly lit situations.

[0009] For various sensor functions, especially for determining particle properties, and for an autofocus function of a camera, several sensors are typically required, which represents a high overall effort and can lead to space problems in the wearable devices. Disclosure of the invention

[0010] The invention provides a combined autofocus and particle sensor device having the features of claim 1, a combined camera and particle sensor system having the features of claim 7 and a combined autofocus and particle measuring method having the features of claim 9.

[0011] Preferred embodiments are the subject of the respective subclaims.

[0012] According to a first aspect, the invention accordingly relates to a combined autofocus and particle sensor device comprising an optical emitter device, a detector device, and an evaluation device. The optical emitter device is configured to emit at least one measuring laser beam into the environment of the combined autofocus and particle sensor device. The detector device detects the at least one measuring laser beam scattered by particles or objects in the environment of the combined autofocus and particle sensor device and outputs a corresponding measurement signal. The evaluation device is configured to determine at least one measured variable relating to the particles in the environment of the combined autofocus and particle sensor device using the measurement signal in a first operating mode and to generate a control signal for adjusting the focus of an external camera in a second operating mode.

[0013] According to a second aspect, the invention relates to a combined camera and particle sensor system, comprising a camera and a combined autofocus and particle sensor device, which is designed to adjust the focus of the camera using the control signal.

[0014] According to a third aspect, the invention relates to a combined autofocus and particle measurement method, wherein at least one measuring laser beam is emitted, the at least one measuring laser beam scattered by particles or objects is detected, and a corresponding measurement signal is output. In a first method mode, a measurement variable relating to the particles is determined using the measurement signal, and in a second method mode, a control signal for adjusting the focus of a camera is generated using the measurement signal. Advantages of the invention

[0015] The device according to the invention can be used both for an autofocus function and as a particle sensor. The two operating modes or methods (autofocus mode or method and particle sensor mode or method) can be used or carried out either independently of one another, i.e. one after the other, or simultaneously. Since only a single, common optical emitter device and a corresponding detector device are necessary for both functions, the combined autofocus and particle sensor device can be designed to be very compact, thus reducing the required installation space, which is particularly advantageous for portable devices such as smartphones. By dispensing with multiple independent sensors, manufacturing costs are further reduced.

[0016] According to a preferred embodiment of the combined autofocus and particle sensor device, the measuring principle of the detector device is based on a self-mixing interference (SMI) method, i.e., the at least one emitted measuring laser beam interferes with the corresponding scattered measuring laser beam. The measurement signal can be generated based on a photocurrent from photodiodes of the detector device.

[0017] According to a preferred development of the combined autofocus and particle sensor device, the evaluation device is configured to calculate the distance of an object from the combined autofocus and particle sensor device in the second operating mode using the measurement signal and to generate the control signal as a function of the calculated distance. Particularly when using an SMI method, the distance can be determined very quickly and precisely, thus eliminating the need for time-consuming focus adjustment, for example, by means of edge contrast measurement, where multiple test images must be generated until the optimal focus is achieved.

[0018] According to a further development of the combined autofocus and particle sensor device, the evaluation device is designed to calculate, in the second operating mode, a speed value and / or a direction of movement of an object in the environment of the autofocus and particle sensor device using the measurement signal and, depending on the calculated speed value and / or the calculated direction of movement of the object, to predict a setting of the focus of the external camera at a future point in time and to generate the control signal accordingly.According to a further development, the current distance of the object from the autofocus and particle sensor device can be measured using the measurement signal, and the distance of the object from the autofocus and particle sensor device at at least one future point in time can be predicted using the calculated velocity and / or the calculated direction of movement. More generally, the trajectory of the object can be calculated so that the focus can always be on the object, with the control signal being generated accordingly.

[0019] The optical emitter device of the combined autofocus and particle sensor device can emit any number of measuring laser beams. In particular, the emitter device can also emit only a single measuring laser beam. However, it is preferred that the optical emitter device emits a plurality of measuring laser beams, i.e., at least two measuring laser beams. In particular, the optical emitter device can be configured to emit at least three measuring laser beams in different spatial directions. Assuming a homogeneous particle stream, using at least three measuring laser beams allows the projections of vectorial particle properties, such as a velocity or acceleration of the particles in the particle stream, onto the different spatial directions to be determined. Since the spatial directions differ, the vectorial particle properties can be fully reconstructed.When using four or more measuring laser beams, certain redundancies occur, which means that additional plausibility checks can be carried out to improve the reliability of the results.

[0020] According to a preferred development of the autofocus and particle sensor device, the optical emitter device is designed to emit a plurality of measuring laser beams, wherein in an energy-saving mode the optical emitter device emits only a subset of the measuring laser beams and / or wherein in the energy-saving mode the detector device detects only a subset of the scattered measuring laser beams and outputs the measurement signal. The energy-saving mode can be used both in the first operating mode, i.e., in the particle sensor mode, and in the second operating mode, i.e., in the autofocus mode, but can also be used for both operating modes. According to some embodiments, the energy-saving mode can always be executed in the first operating mode or always in the second operating mode.

[0021] According to a preferred development of the combined autofocus and particle sensor device, the measured variable relating to the particles comprises one or more of reflection amplitudes, Doppler shifts, particle velocity magnitudes, particle spacings, particle movement directions, particle sizes, particle distributions, particle size distributions, particle densities, and reflectivity. The measured variable relating to the particles can thus comprise any optically detectable properties of the particles.

[0022] According to the invention, the evaluation device is designed to use different filters to evaluate the measurement signal in the first operating mode and the second operating mode. In particular, different bandwidths can be filtered and used in a fast Fourier transformation.

[0023] According to a preferred development of the combined autofocus and particle sensor device, the optical emitter device comprises at least one laser diode. Alternatively or additionally, the detector device can comprise at least one photodiode. The laser diode can be a VCSEL (vertical cavity surface emitting laser). This is understood to mean a light-emitting diode in which the light is emitted perpendicular to the plane of the semiconductor chip. The at least one photodiode can be integrated into a corresponding laser diode.

[0024] According to a preferred development of the combined camera and particle sensor system, the optical emitter device of the combined autofocus and particle sensor device is designed to emit the at least one measuring laser beam into an environmental area of ​​the combined autofocus and particle sensor device, which at least partially overlaps with a detection area of ​​the camera.

[0025] According to a preferred development of the combined autofocus and particle measurement method, in the second method mode, a distance of an object is calculated using the measurement signal and the control signal is generated as a function of the calculated distance.

[0026] According to a further development of the combined autofocus and particle measurement method, in the second method mode, a velocity and / or direction of movement of an object is calculated using the measurement signal. Depending on the calculated velocity and / or direction of movement of the object, a camera focus setting at a future time is predicted. The control signal is generated accordingly.

[0027] According to a preferred embodiment of the combined autofocus and particle measurement method, a plurality of measuring laser beams are emitted, with only a subset of the measuring laser beams being emitted in an energy-saving mode. Alternatively or additionally, only a subset of the scattered measuring laser beams can be detected in the energy-saving mode, and the corresponding measurement signal can be output.

[0028] According to a preferred development of the combined autofocus and particle measurement method, the measured variable relating to the particles comprises one or more of reflection amplitudes, Doppler shifts, particle velocity magnitudes, particle distances, particle movement directions, particle sizes, particle distributions, particle size distributions, particle densities and a reflectivity.

[0029] According to the invention, different filters are used to evaluate the measurement signal in the first process mode and in the second process mode. Short description of the drawings

[0030] They show: Fig. 1 is a schematic block diagram of a combined autofocus and particle sensor device according to an embodiment of the invention; Fig. 2 a schematic oblique view of a combined autofocus and particle sensor device according to another embodiment of the invention; Fig. 3 is a schematic block diagram illustrating the particle sensor function of the combined autofocus and particle sensor device; Fig. 4 a schematic block diagram explaining the autofocus setting; Fig. 5 is a schematic block diagram of a combined autofocus and particle sensor device according to another embodiment of the invention; and Fig. 6 a schematic flow diagram of a combined autofocus and particle measurement procedure.

[0031] In all figures, identical or functionally equivalent elements and devices are provided with the same reference numerals. The numbering of process steps serves the purpose of clarity and is generally not intended to imply a specific chronological order. In particular, several process steps can be performed simultaneously. Description of the embodiments

[0032] Fig. 1 shows a schematic block diagram of a combined autofocus particle sensor device 1a according to a first embodiment of the invention. This device comprises an optical emitter device 2, a detector device 3, and an evaluation device 4. The optical emitter device 2 preferably comprises a plurality of laser diodes designed as VCSELs, which emit corresponding measuring laser beams L. Through optimized beam shaping, the evaluable distance range can be maximized and the desired resolution achieved. When using a plurality of laser diodes, the measuring laser beams are preferably emitted in different spatial directions using suitable lens and / or mirror devices. The detector device 3 comprises photodiodes, wherein the number of photodiodes corresponds to the number of laser diodes. The photodiodes are preferably integrated into the laser diodes.The emitted measuring laser beams L are reflected by an object 6, for example, a user's hand, or by particles 6, such as dust particles, in the vicinity of the autofocus and particle sensor device 1 and detected by the photodiodes. The object or particles 6 can be static or moving.

[0033] The evaluation device 4 includes a self-mixing interference analysis function, which detects the interference of the emitted and reflected measuring laser beams L. In particular, a photocurrent of the photodiodes can be measured and output as a measurement signal.

[0034] The evaluation device 4 operates in two operating modes, which can be selected, for example, based on user input. In a first operating mode, or particle sensor mode, the measurement signal is evaluated to determine a measured variable relating to the particles in the environment of the combined autofocus and particle sensor device 1. In the second operating mode, a control signal for adjusting the focus of an external camera 5 is generated and output.

[0035] When evaluating the measurement signal by the evaluation device 4, several processing steps can be carried out, in particular downsampling (decimation) to change the frequency range, a fast Fourier transformation (FFT), a binning step to combine several pixel values, and particle or object detection to detect the presence of a particle or object 6. The specifically used parameters depend on the operating mode, ie, for example, different frequency ranges are taken into account for the FFT using respective filters.

[0036] In each operating mode, the optical emitter device 2 and the detector device 3 can be controlled accordingly by the evaluation device 4. In particular, the laser diodes of the emitter device 2 can be operated in a first phase, wherein the drive current of the laser diodes is modulated in order to achieve a desired resolution, which enables faster object detection. Upon modulation of the current, a Doppler shift occurs, and the evaluation device 4 can determine the distance of the objects or particles 6 based on the measurement signal. The laser diodes of the emitter device 2 can continue to be operated in a second phase, wherein the drive current of the laser diodes is constant or static, i.e., not modulated. Based on occurring Doppler shifts, the speed of the objects or particles 6 can be determined, or the residence time can be determined, i.e.,the time during which the object or particle 6 remains within the detection range of the respective measuring laser beam L. For each measuring laser beam L, a scalar velocity or velocity component of the objects or particles 6 can be determined, and the vectorial velocity of the objects or particles 6 can be calculated by the evaluation device 4 based on the respective velocity components. The vectorial velocity of the objects or particles 6 thus includes both the absolute value of the velocity of the objects or particles 6 and the direction of movement of the objects or particles 6.

[0037] In the first operating mode or particle sensor mode, the evaluation device 4 uses the evaluated measurement signal to determine particle estimates for the number of particles per volume, i.e., a particle number density. Based on the particle estimates for the number of particles per volume, the evaluation device 4 then calculates a particle load. In particular, the evaluation device 4 can calculate the corresponding particle load based on the particle estimates for the number of particles per volume and with the aid of a model that maps the distribution of the sizes or diameters of the dust particles and the distribution of the mass or density of the dust particles. For example, PMx values ​​can be calculated, whereby only particles up to a certain diameter x are taken into account, such as coarse dust, fine dust, and / or ultrafine dust values.

[0038] In the second operating mode, or autofocus mode, the evaluation device 4 generates the control signal for adjusting the focus of the external camera 5. As soon as the evaluation device 4 detects an object 6, the distance and optionally the speed of the object 6 are determined as described above. The control signal is generated depending on the calculated distance. Additionally, a trajectory can be calculated based on the speed of the object 6, so that the autofocus is automatically adjusted and the camera 5 thus remains focused on the object 6.

[0039] The combined autofocus and particle sensor device 1a can be operated sequentially in the first operating mode or in the second operating mode. However, it is also possible for the evaluation device 4 to evaluate the measurement signal in parallel in both operating modes, so that both the particle sensing and the generation of the control signal are carried out simultaneously.

[0040] Furthermore, the combined autofocus and particle sensor device 1a can be operated in a power-saving mode, wherein at least one of the laser diodes of the optical emitter device 2 is deactivated. Alternatively or additionally, the detector device 3 can detect only a subset of the scattered measuring laser beams L and output the measurement signal accordingly.

[0041] The camera 5 and the combined autofocus and particle sensor device 1 form a combined camera and particle sensor system.

[0042] Fig. Figure 2 shows a schematic oblique view of a combined autofocus and particle sensor device 1b according to a second embodiment of the invention. Accordingly, the optical emitter device comprises three laser diodes 71, 72, 73, which emit laser beams L1, L2, L3 substantially perpendicular to the surface of a common substrate 74. These laser beams are deflected in different spatial directions by a deflection device 76 arranged on a carrier 75 and exit through an opening 77 of the carrier 75. The deflection device 76 can comprise lenses or mirror elements. Regarding the further components and the functional principle of the combined autofocus and particle sensor device 1b, reference can be made to the first embodiment described above.

[0043] Fig. Figure 3 shows a schematic block diagram explaining the particle sensor function of the combined autofocus and particle sensor device 1a. Accordingly, this device emits at least one measuring laser beam L, which is reflected by particles 6. As described above, the autofocus and particle sensor device 1 determines at least one measured variable related to the particles 6, which is output to a host processor 8 for further processing.

[0044] Fig. Figure 4 shows a schematic block diagram to explain the setting of the autofocus of the camera 5. The camera comprises an autofocus processor 53 and an autofocus motor 52, as well as a lens 51. The control signal generated by the evaluation device 4 of the combined autofocus and particle sensor device 1a is transmitted to the autofocus processor 53, which controls the autofocus motor 52 such that the lens 51 is correctly focused according to the control signal.

[0045] Fig. 5 shows a schematic block diagram of a combined autofocus and particle sensor device 1c according to a third embodiment of the invention. In addition to the laser diodes described above, the optical emitter device 2 comprises a laser drive 21, which adjusts the drive current of the laser diodes. An LF modulation control unit 22 controls the laser drive 21 in the first phase described above, wherein the drive current of the laser diodes is modulated. The modulation occurs at low frequency (LF). A static laser control unit 23 controls the laser drive 21 in the second phase described above, i.e., at a constant drive current without modulation. Furthermore, the detector device 3 comprises a photo front-end device 31, which measures the photocurrent of the photodiodes of the detector device 3. A signal processing device 41 of the evaluation device 4 is designed to further process the photocurrent.For this purpose, the signal processing device 41 comprises an autofocus-specific first signal processing unit 411, a split second signal processing unit 412, and a particle sensor-specific third signal processing unit 413. The first signal processing unit 411 and the third signal processing unit 413 can comprise filters that are specifically designed for the respective operating modes, while the second signal processing unit 412 can be used to evaluate the photocurrent in both the first operating mode and the second operating mode. The split functionality of the second signal processing unit 412 allows the complexity of the combined autofocus and particle sensor device 1 to be reduced compared to individual sensors. The LF modulation control unit 22, the static laser control unit 23, and the signal processing device 41 can be controlled via a host interface 42 of the evaluation device 4.

[0046] Fig. Figure 6 shows a schematic flow diagram of a combined autofocus and particle measurement method. The method can be implemented using an autofocus and particle sensor device described above. In particular, all functionalities described above can also be applied to the method, and conversely, the method steps described below can be implemented using one of the autofocus and particle sensor devices described above.

[0047] In a first method step S1, at least one measuring laser beam L is emitted. Preferably, several measuring laser beams L and preferably at least three measuring laser beams are emitted in different spatial directions.

[0048] In a second method step S2, the at least one measuring laser beam L, which has been scattered by particles or objects 6, is detected. A corresponding measurement signal is generated and output using a self-mixing interference method.

[0049] In a method step S3, it is determined whether the method should be performed in a first method mode or in a second method mode. The first method mode corresponds to the above-described first operating mode of the combined autofocus and particle sensor device, and the second method mode corresponds to the above-described second operating mode of the combined autofocus and particle sensor device.

[0050] In the first method mode, at least one measured variable relating to the particles in the environment of the combined autofocus and particle sensor device is determined in a further method step S4. In particular, as described in more detail above, the velocity, distance, number of particles per volume, or particle load can be calculated and output.

[0051] In the second method mode, a control signal for adjusting the focus of a camera 5 is generated in a further method step S5. The control signal is determined taking into account a calculated distance and a calculated speed of an object 6, which are calculated based on the measurement signal.

[0052] However, the invention is not limited to the embodiment shown. In particular, it is possible to perform method steps S4 and S5 in parallel, ie, to simultaneously determine a measured variable relating to the particles 6 and generate the control signal for adjusting the focus of the camera 5. Furthermore, it is possible to reduce the number of channels in a power-saving mode, ie, to deactivate individual laser diodes of the optical emitter device 2.

Claims

[1] Combined autofocus and particle sensor device (1a; 1b; 1c), comprising: an optical emitter device (2) which is designed to emit at least one measuring laser beam (L) into an environment of the combined autofocus and particle sensor device (1a; 1b; 1c); a detector device (3) which is designed to detect the at least one measuring laser beam (L) scattered by particles or objects (6) in the environment of the combined autofocus and particle sensor device (1a; 1b; 1c) and to output a corresponding measuring signal; and an evaluation device (4) which is designed to use the measurement signal: a. in a first operating mode, to determine at least one measured variable relating to the particles (6) in the environment of the combined autofocus and particle sensor device (1a; 1b; 1c); and b. in a second operating mode, to generate a control signal for adjusting a focus of an external camera (5), wherein the evaluation device (4) is further designed to use different filters for evaluating the measurement signal in the first operating mode and in the second operating mode. [2] Combined autofocus and particle sensor device (1a; 1b; 1c) according to claim 1, wherein the evaluation device (4) is designed to calculate a distance of an object (6) from the combined autofocus and particle sensor device (1a; 1b; 1c) in the second operating mode using the measurement signal and to generate the control signal as a function of the calculated distance. [3] Combined autofocus and particle sensor device (1a; 1b; 1c) according to claim 1 or 2, wherein the evaluation device (4) is designed to calculate, in the second operating mode, using the measurement signal, a speed value and / or a direction of movement of an object (6) in the environment of the autofocus and particle sensor device (1a; 1b; 1c) and, depending on the calculated speed value and / or the calculated direction of movement, to predict an adjustment of the focus of the external camera (5) at a future point in time and to generate the control signal accordingly. [4] Combined autofocus and particle sensor device (1a; 1b; 1c) according to one of the preceding claims, wherein the optical emitter device (2) is designed to emit a plurality of measuring laser beams (L), wherein in an energy-saving mode the optical emitter device (2) is designed to emit only a subset of the measuring laser beams (L) and / or wherein the detector device (3) is designed in the energy-saving mode to detect only a subset of the scattered measuring laser beams (L) and to output the measuring signal. [5] Combined autofocus and particle sensor device (1a; 1b; 1c) according to one of the preceding claims, wherein the measured variable relating to the particles (6) comprises at least one of reflection amplitudes, Doppler shifts, particle velocity magnitudes, particle spacings, particle movement directions, particle sizes, particle distributions, particle size distributions, particle densities and a reflectivity. [6] Combined autofocus and particle sensor device (1a; 1b; 1c) according to one of the preceding claims, wherein the optical emitter device (2) comprises at least one laser diode, in particular a VCSEL, and the detector device (3) comprises at least one photodiode, in particular a photodiode integrated into the at least one laser diode. [7] Combined camera and particle sensor system, comprising a camera (5) and a combined autofocus and particle sensor device (1a; 1b; 1c) according to one of the preceding claims, which is designed to adjust the focus of the camera (5) using the control signal. [8] Combined camera and particle sensor system according to claim 7, wherein the optical emitter device (2) of the combined autofocus and particle sensor device (1a; 1b; 1c) is designed to emit the at least one measuring laser beam (L) into an environmental area of ​​the combined autofocus and particle sensor device (1a; 1b; 1c), which at least partially overlaps with a detection area of ​​the camera (5). [9] Combined autofocus and particle measurement method, with the steps: Emitting (S1) at least one measuring laser beam (L); and Detecting (S2) the at least one measuring laser beam (L) scattered by particles or objects (6) and outputting a corresponding measuring signal; wherein in a first method mode at least one measurement variable relating to the particles (6) is determined using the measurement signal (S4); wherein in a second method mode, a control signal for adjusting a focus of a camera (5) is generated (S5) using the measurement signal; and whereby different filters are used to evaluate the measurement signal in the first process mode and in the second process mode. [10] Combined autofocus and particle measuring method according to claim 9, wherein in the second method mode a distance of an object (6) is calculated using the measurement signal and the control signal is generated as a function of the calculated distance. [11] Combined autofocus and particle measuring method according to one of claims 9 or 10, wherein in the second method mode, a speed value and / or a direction of movement of an object (6) is calculated using the measurement signal and, depending on the calculated speed value and / or the calculated direction of movement, an adjustment of the focus of the camera (5) at a future time is predicted and the control signal is generated accordingly. [12] Combined autofocus and particle measuring method according to one of claims 9 to 11, wherein a plurality of measuring laser beams (L) are emitted, wherein in an energy saving mode only a subset of the measuring laser beams (L) is emitted and / or wherein in the energy saving mode only a subset of the scattered measuring laser beams (L) is detected and the corresponding measuring signal is output. [13] Combined autofocus and particle measuring method according to one of claims 9 to 12, wherein the measured variable with respect to the particles (6) comprises at least one of reflection amplitudes, Doppler shifts, particle velocity magnitudes, particle spacings, particle movement directions, particle sizes, particle distributions, particle size distributions, particle densities and a reflectivity.

Images