Optical scanner and method for detecting objects in a surveillance area

Abstract

Optical scanner for detecting objects in a monitored area with a light transmitter (10) for emitting a pulsed transmission beam (30) into the monitoring area (90), with a detector (50) for detecting light pulses (40) reflected from an object (A, B) in the monitoring area (90), with a two-axis micromechanical beam deflection device (20) via which the transmitting beam (30) is directed into the monitoring area (90), wherein a direction of the transmitting beam (30) is variable with the beam deflection device (20) in a first direction (θ) and in a second direction (φ), and with a control and evaluation unit (60) for controlling the light emitter (30) and the micromechanical beam deflection device (20), for evaluating light pulses (40) detected by the detector (50) at an angular position (θ, φ) of the transmitting beam (30) and for determining a distance (d) of an object (B) corresponding to this angular position (θ, φ) of the transmitting beam (30) from a transit time of the detected light pulses (40), wherein a detection beam path, through which light (40) reflected from the monitoring area (90) reaches the detector (50), runs over the beam deflection device (20) and wherein an optical axis (38) of a beam path of the transmitting beam and an optical axis (58) of the detection beam path of the reflected light (40) are partially coaxial, characterized by that the light emitter (10) is arranged in an opening of a receiving lens (78).

Description

[0001] The present invention relates, in a first aspect, to an optical scanner according to the preamble of claim 1 and, in a second aspect, to a method for detecting objects in a monitoring area according to the preamble of claim 13.

[0002] An optical scanner of this type for detecting objects in a monitoring area comprises the following components: a light transmitter for emitting a pulsed beam into the monitoring area, a detector for detecting light pulses reflected back from an object in the monitoring area, a two-axis micromechanical beam deflection device through which the beam is directed into the monitoring area, wherein the direction of the beam can be varied in a first direction and in a second direction by means of the beam deflection device, and a control and evaluation unit for controlling the light transmitter and the micromechanical beam deflection device, for evaluating light pulses detected by the detector at a given angular position of the beam, and for determining the distance of an object corresponding to this angular position of the beam from the travel time of the detected light pulses.

[0003] In a generic method for detecting objects in a monitoring area, the following process steps are carried out: a pulsed transmitting beam is emitted into a monitoring area via a two-axis micromechanical beam deflection device, wherein the transmitting beam is scanned over the monitoring area in two coordinate directions using the beam deflection device, light pulses reflected back from an object in the monitoring area are detected, a transit time of the detected light pulses is determined, and from a transit time of light pulses detected in one direction of transmission of the transmitting beam, a distance to an object corresponding to that direction is determined.

[0004] Examples of devices and methods of this type are described in EP 3933442 A1.

[0005] To detect the light reflected back from the monitored area as effectively as possible, lenses and / or concave mirrors are used as receiving optics in devices of this type. Such setups require a comparatively large installation space, which makes the use of these scanners difficult or impossible for some applications. Furthermore, the scanned angular ranges necessitate receiving optics with a relatively large numerical aperture.

[0006] US 2020 / 0249324A1 relates to a LIDAR system with at least one processor configured to control at least one light source to project light in the direction of a field of view and receiving first signals from at least one first sensor that are related to the light projected by the at least one light source and reflected by an object in the field of view, wherein the light incident on the at least one first sensor has the form of a light spot with an outer boundary.The processor can be configured to receive second signals from at least one second sensor, which are associated with light noise, wherein the at least one second sensor is located outside the outer boundary; determine an indicator for the magnitude of the light noise based on the second signals received from the at least one second sensor; and determine the first signals received from the at least one first sensor and a distance to the object based on the indicator.

[0007] DE 10 2016 200 109 A1 relates to a device for detecting objects in a detection area, comprising a radiation device for emitting an electromagnetic scanning beam into at least a part of the detection area, a device for modulating the scanning beam, a detection device for detecting reflected radiation from at least a part of the detection area, and a device for evaluating the time behavior of the detected reflected radiation as a function of the modulation of the scanning beam. In order to use the most powerful laser possible as a light source without endangering eye safety and the general safety of persons, the invention provides that the radiation device includes a radiation source that irradiates a scattering device, which scatters the radiation at least partially into the detection area.

[0008] DE 10 2011 005 277 A1 relates to a handheld laser distance measuring device with at least one laser unit designed to determine a first distance using a laser beam in a first relative direction. It is proposed that the laser unit be designed to determine at least a second distance concurrently using a laser beam in at least a second relative direction that differs from the first.

[0009] One object of the present invention can be considered to be to provide an optical scanner and a method for detecting objects in a monitoring area, which can be implemented in a space-saving manner without significant loss in optical performance data.

[0010] This problem is solved by the optical scanner having the features of claim 1 and by the method having the features of claim 13.

[0011] The optical scanner of the type described above is further developed according to the invention in that a detection beam path, through which light reflected from the monitoring area reaches the detector, runs through the beam deflection device and that an optical axis of a beam path of the transmitting beam and an optical axis of the detection beam path of reflected light run partially coaxially.

[0012] The method of the type described above is further developed according to the invention in that light reflected from the monitoring area is directed to the detector via the beam deflection device, and that an optical axis of a beam path of the transmitting beam and an optical axis of the detection beam path of reflected light are partially coaxial.

[0013] A significant advantage of the invention is that the orientation of the detection beam path changes with the respective position of the beam deflection device. Measures to increase the numerical aperture of the detection beam path, which are necessary when dealing with a comparatively large angular range to be scanned but a spatially unchanging detection beam path, can then be omitted.

[0014] Advantageous embodiments of the optical scanner according to the invention are explained below, particularly in connection with the dependent claims and the figures.

[0015] The terms transmitting beam and transmitting light beam are used synonymously in this application.

[0016] Semiconductor light sources, especially semiconductor lasers, particularly in the infrared range, are typically used as light emitters. Light emitters in the visible and ultraviolet ranges can also be used. Semiconductor detectors, such as CCD, CMOS, and SPAD detectors, are generally used as detectors.

[0017] In principle, the beam deflection device can include means for diffracting beam deflection. However, the term beam deflection is intended to refer specifically to specular deflection.

[0018] In principle, the biaxial micromechanical beam deflection device can be formed by two uniaxial micromechanical mirrors. The term "micromechanical mirror" refers in particular to MEMS (Micro-Electro-Mechanical Systems) mirrors. Preferably, the biaxial micromechanical beam deflection device can be implemented by a single biaxial micromechanical mirror.

[0019] In principle, it is possible for the first and second axes of the beam deflection device to not be oriented perpendicular to each other. However, for the purpose of setting a specific orientation of the beam deflection device, it is preferable for the first and second axes to be perpendicular to each other. The angular coordinates of the beam deflection device can then be advantageously changed independently of each other.

[0020] In principle, it is possible for the first and second axes of the beam deflection device not to intersect. However, it is advantageous if the first and second axes of the beam deflection device do intersect. Preferably, the point of intersection can be located at a mirror surface.

[0021] The emitted beam of the light source can, in principle, travel at any angle relative to the axes of the beam deflection device. However, for controlling the operating parameters, designs are preferred in which the emitted beam of the light source is coaxial or parallel to an axis of the beam deflection device.

[0022] The beam deflection device can be controllable, and the control and evaluation unit can be configured to control the beam deflection device. The control and evaluation unit can also be configured to read out the instantaneous angular position of the beam deflection device. In principle, control signals applied to the beam deflection device, i.e., to the micromechanical mirror(s), can be interpreted as signals indicating the current angular positions of the beam deflection device. Preferably, however, the micromechanical beam deflection device has internal position sensors that each output an instantaneous angular position for the two axes of the beam deflection device. The instantaneous angular positions of the beam deflection device can also be referred to as actual angular positions. Such internal position sensors can be implemented with piezoelectric sensors that are mechanically coupled to the mirror surfaces to be deflected.

[0023] The pivoting of the beam deflection device about at least one axis or about both axes can be operated quasi-statically, periodically and / or resonantly oscillating.

[0024] The transmitted light beam can be pivoted by the beam deflection device about the first axis and / or the second axis over an angular stroke of 30°, in particular 40°, and most preferably 50° or more. The larger the overall accessible angular range, the larger the numerical aperture of the receiving optics should be if the detection beam path does not pass through the beam deflection device.

[0025] In principle, the movement of the beam deflection device around the first axis does not need to be synchronized with the movement of the beam deflection device around the second axis. However, for numerous applications, especially those where it is crucial to clearly define the direction in which the transmitted beam is emitted at any given time, it is preferable for the movement of the beam deflection device around the first axis to be synchronized with that around the second axis. Examples of such applications include those described below using a pilot laser for the optical display of information on an object within the monitored area.

[0026] If the ratio of the beam deflection device's oscillation frequency around the first axis to its oscillation frequency around the second axis is such that the trajectory of points illuminated in the monitored area coincides with itself after a certain number of oscillation cycles around either the first or the second axis, then the ratio of the beam deflection device's oscillation frequencies is said to be commensurate. If this is not the case, meaning the trajectory of points illuminated in the monitored area never coincides with itself, then the ratio of the beam deflection device's oscillation frequency around the first axis to its oscillation frequency around the second axis is said to be non-commensurate. In this case, the monitored area is scanned at an arbitrarily high density.However, this high sampling density may only be achieved after long measurement times.

[0027] In practice, for synchronized operation, a certain integer and therefore commensurable ratio of the oscillation frequency of the beam deflection device around the first axis to the oscillation frequency of the beam deflection device around the second axis will usually be chosen, whereby the monitoring area is scanned sufficiently densely in a sufficiently short time.

[0028] Depending on the measurement task, the ratio of the oscillation frequency of the beam deflection device about the first axis to the oscillation frequency of the beam deflection device about the second axis can, in principle, be freely chosen. For example, the oscillation frequency of the beam deflection device about the first axis can be 10 to 100 times greater than the oscillation frequency of the beam deflection device about the second axis, or vice versa.

[0029] In preferred variants, the vibration frequency at which the beam deflection device oscillates around the first axis during operation is of the same order of magnitude as the vibration frequency at which the beam deflection device oscillates around the second axis during operation.

[0030] For example, the oscillation frequency at which the beam deflection device oscillates around the first axis during operation can advantageously differ from the oscillation frequency at which the beam deflection device oscillates around the second axis during operation by less than 20%, preferably by less than 10%, and most preferably by less than 5%. The trajectories that an illuminated point traces in a plane perpendicular to the transmission direction within the monitored area then correspond to Lissajous figures. The closer together the temporally successive paths of these Lissajous figures are, the less the two oscillation frequencies differ.

[0031] Preferably, a beam deflection device, in particular a biaxial micromechanical mirror, is used in which the resonant frequency of an oscillation about the first axis is equal to or at least similar to the resonant frequency of an oscillation of the beam deflection device about the second axis. However, it is also possible for these two resonant frequencies to be different.

[0032] The vibrational degrees of freedom of a biaxial mirror are at least weakly coupled mechanically, so that the biaxial mirror as a complete mechanical system can have at least two resonance frequencies.

[0033] Advantageously, the beam deflection device, in particular a biaxial micromechanical mirror, is operated oscillating about both axes at frequencies close to at least one resonant frequency of the beam deflection device. Typical resonant frequencies of a biaxial mirror are 2 to 3 kHz.

[0034] Advantageously, the vibration frequency at which the beam deflection device, in particular a biaxial micromechanical mirror, oscillates about the first axis during operation, and / or the vibration frequency at which the beam deflection device oscillates about the second axis during operation, differs only by up to 10%, preferably only by up to 5%, and particularly preferably only by up to 2%, from the resonance frequency for the axis in question or from a resonance frequency of the overall mechanical system of the biaxial beam deflection unit.

[0035] Tests have shown that the vibration of the beam deflection device is particularly stable under these operating parameters. Further improvements in operational stability are possible if the beam deflection device is located and operated in a vacuum. This allows for good decoupling from both temperature fluctuations and externally introduced mechanical disturbances.

[0036] For a good signal-to-noise ratio, it is important to direct as much of the light reflected from the monitored area as possible onto the detector. From this perspective, it is preferable to have light-collecting optics to focus the light reflected from the monitored area onto the detector. For example, the light-collecting optics can include at least one converging lens, at least one concave mirror, at least one Fresnel lens, and / or at least one holographic lens.

[0037] In principle, a detector with only a single detector segment is sufficient. However, it can be preferable to have multiple detector segments that can be read separately. If only the detection signal of those detector segments where the signal exceeds a defined threshold is considered, a better signal-to-noise ratio can be achieved compared to evaluating all segments.

[0038] An aperture of the detection beam path can be provided in particular by an aperture of the beam deflection device.

[0039] In a further particularly preferred embodiment of the optical scanner according to the invention, the light emitter and the detector are housed in a transmitting and receiving assembly in which the optical axis of the beam path of the transmitting light beam and the optical axis of the detection beam path are partially coaxial.

[0040] The combining of the transmit and detection beam paths can be achieved using at least one beam splitter. For example, a semi-transparent mirror can be used, through which the transmit beam is coupled onto a coaxial portion of the transmit and detection beam paths and directed towards the monitored area.

[0041] Alternatively, a semi-transparent mirror can be provided, via which light pulses reflected from the monitoring area are coupled out from the coaxial part of the transmitting beam path and the detection beam path and directed towards the detector.

[0042] In principle, the semi-transparent mirror can act as a polarization beam splitter. In this case, suitable measures must be taken to polarize, for example, the transmitting beam. Particularly preferably, the semi-transparent mirror is a neutral beam splitter with a splitting ratio greater than 60:40, more preferably greater than 70:30, and most preferably greater than 75:25, wherein the larger portion is coupled into or out of the detection beam path.

[0043] According to the invention, the light emitter is arranged in an opening of a receiving lens. Preferably, the opening in which the light emitter is arranged lies on the optical axis of the receiving lens.

[0044] Further improvements in the signal-to-noise ratio are possible if the amount of stray light entering the detection beam path is minimized. From this perspective, it is preferable to have a plate opaque to the transmitted light for optical separation of the transmitting beam path and the detection beam path; this plate can, for example, be positioned between the light source and the detector.

[0045] In another preferred embodiment, the opaque plate is integrally formed with a plastic molded part in which the light emitter, the detector, and / or the beam deflection device are housed. This offers advantages in the assembly of the optical scanner. The light-collecting optics can also be housed within the plastic molded part or formed by the plastic molded part, for example, as a converging lens.

[0046] In another preferred embodiment, the control and evaluation unit is set up for clocked operation, wherein at least one measurement of an object distance is carried out per clock cycle and wherein the results of the at least one distance measurement for each clock cycle are stored in an image memory together with an angular position of the beam deflection device read out at the respective time.

[0047] A corresponding preferred variant of the method according to the invention is characterized in that the optical scanner is operated in a clocked manner, that at least one measurement of an object distance is carried out per clock cycle, and that the results of the at least one distance measurement for each clock cycle are stored in an image memory together with an angular position of the beam deflection device read out at the respective time.

[0048] Synchronized pivoting of the beam deflection device around its first and second axes is not absolutely necessary for clocked operation if the actual angular positions of the beam deflection device can be read out.

[0049] Preferably, several distance measurements, for example five to ten, are carried out per cycle, and an average of the object distances determined from the distance measurements is calculated and stored.

[0050] In a further preferred embodiment of the optical scanner according to the invention, the control and evaluation unit is configured to reduce, in order to examine a section of the monitoring area, an angular stroke over which the beam deflection device is pivoted back and forth about a first axis, compared to a maximum possible angular stroke about a first axis, and / or to reduce an angular stroke over which the beam deflection device is pivoted back and forth about the second axis, compared to a maximum possible angular stroke about the second axis.

[0051] A corresponding variant of the method according to the invention is characterized in that, for examining a section of the monitoring area, an angular stroke over which the beam deflection device is pivoted back and forth about a first axis is reduced compared to a maximum possible angular stroke about the first axis and / or that an angular stroke over which the beam deflection device is pivoted back and forth about a second axis is reduced compared to a maximum possible angular stroke about the second axis.

[0052] These variants offer particularly versatile applications compared to the state of the art, and the available measurement modes are significantly expanded.

[0053] Preferably, a first interval of the angles over which the beam deflection device is pivoted about the first axis is at least partially smaller than the maximum possible angular stroke of the beam deflection device about the first axis, and a second interval of the angles over which the beam deflection device is pivoted about the second axis is at least partially smaller than the maximum possible angular stroke of the beam deflection device about the second axis. Furthermore, a position of the first interval within the maximum possible angular stroke about the first axis and a position of the second interval within the maximum possible angular stroke about the second axis can be set.

[0054] Advantageously, for example, a first solid angle area can be measured in a first process phase and a second solid angle area, which is smaller than the first solid angle area and is contained within the first solid angle area, can be measured in a second process phase.

[0055] Specifically, in the first procedural phase, the first interval can be set to a first value and the second interval to a first value, and in a second procedural phase, the first interval can be set to a second value and the second interval to a second value, where the second value of the first interval is smaller than its first value and the second value of the second interval is smaller than its first value.

[0056] These method variations make it possible, for example, to quickly scan the monitored area and, in effect, first determine where an object is located within that area. In the second phase of the process, the area where an object was found in the first phase can then be examined in more detail. Preferably, the rate at which the light pulses are emitted remains constant. The smaller area is then scanned in the second phase with a correspondingly higher spatial resolution.

[0057] For a single deflection axis of the micromechanical beam deflection device, for example a micromechanical mirror, the following applies to the angular resolution W: W=R / (Δθ*f)

[0058] With: Δθ Stroke of angle θ, Amplitude of angle R Rate, at which the light pulses are emitted, f Oscillation frequency of the mirror

[0059] The angular resolution W is therefore inversely proportional to the amplitude Δθ of the mirror's oscillation. At the same rate R at which the light pulses are emitted and the same oscillation frequency f of the mirror, the angular resolution thus increases when the amplitude Δθ is reduced. For example, with two axes, halving the angular displacement for both axes results in a resolution four times greater.

[0060] Alternatively or additionally, the oscillation frequency at which the micromechanical mirror is operated and / or the measurement duration can be adjusted depending on the interval over which the micromechanical mirror oscillates back and forth. The spatial resolution is also influenced by the parameters of the micromechanical mirror's oscillation frequency and the measurement duration.

[0061] Preferably, the rate at which the light pulses are emitted is kept constant and, in particular, at the maximum possible value.

[0062] The first value of the first interval can be the maximum possible angular stroke around the first axis with the beam deflection device and / or the first value of the second interval can be the maximum possible angular stroke around the second axis with the beam deflection device.

[0063] The second value of the first interval and / or its position within the maximum possible angular stroke around the first axis and / or the second value of the second interval and / or its position within the maximum possible angular stroke around the second axis can preferably be set depending on measurement data from the optical scanner obtained in the first process phase.

[0064] In a further advantageous embodiment of the optical scanner according to the invention, at least one pilot laser emitting in the visible range is provided and the control and evaluation unit is configured to control the pilot laser for optically displaying information on an object in the monitoring area by repeatedly illuminating selected locations on the object.

[0065] Compared to the state of the art, these measures offer advantages in terms of user experience. They also open up new operating possibilities and make the operation of the optical scanner simpler and therefore safer. The pilot laser can also preferably be a semiconductor laser.

[0066] Generally, it is sufficient for the pilot laser to emit at a single wavelength in the visible spectrum. However, it is also possible to use pilot lasers that, preferably with variable control, emit at multiple wavelengths in the visible spectrum. This allows symbols of different colors to be displayed on an object within the monitored area.

[0067] The light source and the pilot laser can also be implemented using one and the same laser emitting light in the visible range. In this case, time-of-flight measurements may be temporarily unavailable for the times or time intervals when the laser is operated by the control and evaluation unit in its function as a pilot laser to optically display information on an object within the monitored area.

[0068] In principle, the transmitted light beam and the transmitting beam path of the pilot laser can diverge in the monitored area. Preferably, an optical axis of a transmitting beam path of the pilot laser is at least partially collinear with an optical axis of the light source. For example, a transmitting beam path of the pilot laser can be collinear with the transmitted light beam in the monitored area. In particular, the light from the pilot laser can be coupled into the transmitting beam path of the light source using a beam splitter.

[0069] The light from the pilot laser can be directed into the monitoring area via the beam deflection device or via another swiveling, in particular micromechanical, mirror that can be controlled separately.

[0070] Preferably, the control and evaluation unit is configured to display symbols, in particular characters, numbers and / or graphic symbols, on an object in the monitored area by appropriately controlling the pilot laser over time.

[0071] For example, to visually display information on an object within the monitored area, selected locations on the object can be repeatedly illuminated with a pilot laser emitting in the visible spectrum. The pilot laser can be controlled at appropriate times for this purpose.

[0072] For example, to project a point onto an object, the pilot laser must be briefly activated to emit light whenever the beam deflection device aligns it with that point. This corresponds to the principle of a stroboscope.

[0073] To achieve a continuous image for the human eye, the frequency at which the same point on the object in the monitoring area is illuminated by the pilot laser should be higher than the flicker fusion frequency for the human eye. The flicker fusion frequency for the human eye is a few tens of Hz.

[0074] More complex objects or symbols can then be composed of individual points to be illuminated.

[0075] Particularly advantageous is the ability to signal areas on the object within the monitoring area to a user using the pilot laser, which are then monitored by the optical scanner for control via user gestures, especially with one of the user's hands.

[0076] Alternatively or additionally, the pilot laser can be used to signal areas on the object where the optical scanner's measurement data deviates from the expected values ​​stored for that object. This can indicate, for example, the quality and / or quantity of a deviation from an expected value.

[0077] Finally, it is also possible to use the pilot laser to display measurement data from the optical scanner, which is currently being obtained for an object in the monitoring area, onto the object itself.

[0078] Alternatively or additionally, in further advantageous variants, one or more of the following information can be displayed on an object: one or more boundaries of a currently detected angular range in the monitoring area, a center of a currently detected angular range in the monitoring area.

[0079] Alternatively or additionally, in further advantageous variants, one or more of the following status information of the optical scanner can be displayed on an object: clock rate, rate at which light pulses are emitted, oscillation frequency of the beam deflection device for one or both axes, angular stroke of the beam deflection device for one or both axes.

[0080] The object on which the information is displayed in the monitored area does not necessarily have to be the object that is primarily intended to be detected. For example, a user can hold a sheet of paper into the monitored area to visualize the current limits of a detected angular range.

[0081] The optical scanner according to the invention is particularly preferably configured for carrying out the methods according to the invention. This applies in particular to the control and evaluation unit and the components controlled and / or read out by it, i.e. the control of the transmitter, the micromechanical mirror, the pilot laser, the reading out of the actual angular position positions of the micromechanical mirror and the reading out and evaluation of the signals from the detector.

[0082] Further advantages and properties of the optical scanner and methods according to the invention are explained below in connection with the figures. These show: Fig. 1: a schematic side view of an optical scanner not according to the invention in a typical measurement situation; Fig. 2: A schematic partial view from above of the optical scanner Fig. 1; Fig. 3: a schematic side view of an embodiment of an optical scanner not according to the invention in a typical measurement situation; Fig. 4: a schematic view of a surveillance area and a section thereof; Fig. 5: a schematic view of a section of the monitoring area to illustrate variants of the method according to the invention; Fig. 6: a schematic view of a further section of the monitoring area to illustrate variants of the method according to the invention; Fig. 7: a schematic representation of an example of a coaxial transmitting and receiving unit (not part of the invention); and Fig. 8: a schematic representation of an example of a coaxial transmitting and receiving unit according to the invention.

[0083] Identical and equivalent components are usually marked with the same reference symbols in the figures.

[0084] The in Fig. One schematically represented optical scanner 100 first has a light transmitter 10 for emitting a pulsed transmitting light beam 30 into a monitoring area 90. Furthermore, a detector 50 is provided for detecting light pulses 40 that are reflected back from an object A, B in the monitoring area 90.

[0085] A micromechanical beam deflection device 20 is then provided, through which the transmitted light beam 30 is guided into the monitoring area 90. In the illustrated embodiment, the beam deflection device 20 is a two-axis micromechanical mirror that can be pivoted about a first axis 21 and a second axis 22. In the illustrated example, the first axis 21 intersects the second axis 22 at a right angle. The first axis 21 is parallel to the y-axis of a coordinate system 11, and the second axis 22 is collinear with the z-axis of this coordinate system 11. In the example shown, Fig. 1 and Fig. In the embodiment shown in Figure 2, the light transmitter 10 is mounted such that the transmission direction 30 is coaxial with the z-axis.

[0086] By pivoting the mirror 20 about the first axis 21, an angle θ of the transmitted light beam relative to the z-axis is varied. This is in Fig. Figure 1 shows three transmitting beams 31, 32, 33 at different times, each aligned at a different angle θ relative to the z-axis. Furthermore, by pivoting the mirror 20 about the second axis 22, the angle φ of the transmitted light beam relative to the x-axis is varied. This is shown in Fig. Figure 2 shows where the transmitting beams 31 and 33 are depicted.

[0087] The angle φ by which the transmitted light beam 33 is rotated relative to the x-axis of the coordinate system 11 can be called the azimuthal angle φ, see Fig. 2. The angle θ by which the transmitting beam 31, 32, 33 is tilted relative to the z-axis of the coordinate system 11 can be called the polar angle θ. An angular interval by which the mirror 20 can be pivoted about the first axis 21 is given in Fig. Figure 1 is illustrated with the double arrow Δθ. An angular interval by which the mirror 20 can be pivoted about the second axis 22 is shown in Figure 1. Fig. 2 illustrated with the double arrow Δφ.

[0088] Finally, according to the invention, the optical scanner 100 comprises a control and evaluation unit 60 for controlling the light transmitter 10 and for determining the transit time of the light pulses detected by the detector 50 and for determining the object distance of an object A, B relative to the optical scanner 100 based on the transit time of light pulses detected at a specific angular position θ, φ of the transmitted light beam 30. In the example shown, the control and evaluation unit 60 is configured to read out an angular position θ, φ of the micromechanical mirror 20. The control and evaluation unit 60 can, for example, be implemented by a programmable microcontroller or a comparable component, such as an FPGA.

[0089] Fig. Figure 2 shows the optical scanner 100. Fig. 1 in a schematic view from above, i.e., in the direction of the negative z-axis of coordinate system 11. The transmitting beams 31 and 33 are shown, which assume different angles φ relative to the x-axis. The coordinate system 11 in Fig. 2 corresponds to that of the Fig. 1. An example is shown in Fig. 2 also a distance d to object B.

[0090] To optically separate the transmitting and receiving sides, a non-transparent plate 54 is provided, which is arranged between the light transmitter 10 and the light detector 50. This plate 54 serves to prevent, as far as possible, stray light from the transmitting side from reaching the detector 50.

[0091] To focus light 40, which is reflected back from the monitoring area 90, a converging lens 52 is provided, which focuses the reflected light 40 onto the detector 50.

[0092] Finally, the optical scanner has 100 Fig. 1. A pilot laser 12 is present, which emits in the visible range and is coupled into the transmitting beam path via a beam splitter 14, for example, a color splitter or a dichroic beam splitter. The beam path of the pilot laser 12 is collinear with the beam path of the transmitting light 30 in the monitoring area 90. The pilot laser 12 serves to optically display symbols, for example, letters or numbers, on objects in the monitoring area. This is used in connection with Fig. 5 explained in more detail.

[0093] In an alternative embodiment, the pilot laser and the light emitter can also be implemented by one and the same laser emitting in the visible range. In this case, the beam splitter 14 is not necessary.

[0094] The light emitter 10, the micromechanical mirror 20, and the detector 50 can be contained within a molded plastic part (not shown here), to which the plate 54 may also be molded. It is also possible that the lens 52 is contained within or formed by the molded plastic part.

[0095] The components of the optical scanner 100 are made of Fig. 1 are enclosed in a housing 18 which has a window 19 transparent to the transmitting light 30 and the light of the pilot laser 12.

[0096] During measurement operation, the mirror 20 and thus the transmitted light beam is pivoted around both the first axis 21 and the second axis 22 to scan an angular range in the monitoring area 90.

[0097] The in Fig. The embodiment of an optical scanner 200 shown in Figure 3 (not part of the invention) differs from that of the Fig. 1 and Fig. 2 essentially by the fact that the detection beam path also passes over the micromechanical mirror 20. The mirror 20 therefore limits the numerical aperture of the detection beam path. From this perspective, it is advantageous for this embodiment to use micromechanical mirrors 20 with the largest possible area. The transmitter 10 and the detector 50 are in the example of the Fig. 3 housed in a transmitting and receiving unit 70, in which the transmitting beam path is at least partially collinear with the detection beam path. Examples of such transmitting and receiving units 71, 72 show the Fig. 7 and Fig. 8.

[0098] Fig. Figure 4 shows a maximum detectable angle range 80 in the monitoring area 90, which is given on the one hand by a maximum possible angle stroke Δθmax of the mirror 20 in the θ-coordinate and on the other hand by a maximum possible angle stroke Δφmax of the mirror 20 in the φ-coordinate.

[0099] Fig. Figure 4 also shows a reduced angular range 84, which lies within the maximum detectable angular range 80. Within this reduced angular range 84, the angle θ can be varied in the interval Δθ between the values ​​θ1 and θ2. The angle φ can be varied in the interval Δφ between the values ​​φ1 and φ2. The size of the interval Δθ and its position within the interval Δθmax, i.e., the values ​​θ1 and θ2, can be selected based on measurement results obtained in a first process phase. The same applies to the size of the interval Δφ and its position within the interval Δφmax, i.e., the values ​​φ1 and φ2. For example, an object that was detected in the first process phase and is to be measured more precisely in the second process phase may be located in the range 84. The rate at which the light pulses are emitted is preferably not changed in the second process phase, in which only the reduced area 84 is sampled.This means that the reduced area 84 is scanned with increased spatial resolution compared to the maximum detectable area.

[0100] Fig. Figure 5 shows a section of the maximum detectable angular range 80 over a partial range of approximately 5° of the maximum angular range Δφmax of the azimuthal angle φ. The transmitted beam 30 can be pivoted over the angular range Δθmax using the mirror 20. Three trajectories 81, 82, and 83 are shown as examples, each indicating the position over which the transmitted light beam is moved by pivoting the mirror about its first axis 21 (variation of the angle θ) and second axis 22 (variation of the angle φ). In the example shown, the three trajectories 81, 82, and 83 may correspond to successive periods of the oscillation of the mirror 20 about the second axis 22, i.e., the oscillation in the φ coordinate. This means that in synchronized operation and with equal intervals between the subsequent periods of oscillation of the mirror 20 in the φ-coordinate, the trajectory returns to the first trajectory 81 after four further periods. An example is shown in Fig. Figure 5 shows an angular interval of 1° of the azimuthal angle. This shows that the spatial resolution is approximately 1 / 6°.

[0101] Finally, in Fig. Figure 5 shows three points 91, 92, and 93, which are intended to be points illuminated by the pilot laser 12 at the moment the light beam passes through them. When, after the corresponding number of periods of oscillation of the mirror 20 in the φ coordinate (here, for example, after six rotations), the trajectory again meets point 91, the pilot laser 12 must be reactivated so that point 91 is illuminated again. For a continuous optical representation to be created for the human eye, the frequency at which one and the same point, for example, point 91, is repeatedly illuminated must be higher than the flicker fusion frequency of the human eye, typically higher than a few tens of Hz. If letters, characters, or symbols are to be displayed, these can be composed of individual points.For this operation, in which 12 symbols are to be displayed on an object using the pilot laser, the movement of the mirror 20 in the φ coordinate should be synchronized with that in the θ coordinate.

[0102] Fig. Figure 6 shows another section 84 of the maximum detectable angular range 80 with an object C located at the displayed angular coordinates. If, for example, scanning object C reveals a deviation from the expected position at position 88, this position 88 can be signaled to a user by the pilot laser 12.

[0103] Exemplary embodiments of transmitting and receiving units, as used in the exemplary embodiment of the optical scanner 200 of the Fig. 3 can be used in connection with the Fig. 7 and Fig. 8 explained.

[0104] In Fig. Figure 7 is a schematic example of a transmitting and receiving unit 71 (not part of the invention). There, the transmitting light beam 30 of the transmitter 10 is coupled into the beam path via a semi-transparent mirror 74. In the transmitting beam path, downstream from the semi-transparent mirror 74, an optical axis 38 of the transmitting beam path runs collinearly with an optical axis 58 of the detection beam path. To focus light 40 reflected from the monitoring area, which is coupled into the Fig. 7 and Fig. 8 not shown mirrors 20 (see Fig. 3) a lens 76 is present, through which the optical axis of the detection beam path 58 of the detection beam path is determined.

[0105] In the exemplary embodiment of a transmitting and receiving unit 72 according to the invention, which is in Fig.As shown in Figure 8, the transmitter 10 is arranged in an axial recess of a receiving lens 78 such that the optical axis 38 of the transmitting beam path runs downstream of the transmitter 10 coaxially with the optical axis 58 of the detection beam path.

[0106] The present invention introduces a novel optical scanner characterized by a simple design and diverse application possibilities. Reference symbol list 10 light transmitters 12 pilot lasers 14 beam splitters, dichroic beam splitters 18 cases 19 windows in housing, transparent for transmitted light 30 and reflected light 40 20 biaxial beam deflection devices, biaxial micromechanical mirrors 21 first axis of rotation of the micromechanical mirror 20, parallel to the y-axis 22 second axis of rotation of the micromechanical mirror 20, collinear to the z-axis 30 Transmitting beam, transmitting light, transmitting light beam 31 Transmitting beam at a first time t1 in angular position θ1, φ1 32 Transmitting beam at a second time t2 in angular position θ2, φ2 33 Transmitting beam at a third time t3 in angular position θ3, φ3 38 Transmitting beam path, optical axis of the transmitting beam path 40 light pulses reflected from object A, B / reflected light 30 50 Detector 52 lens 54 Dividing plate 58 Detection beam path, optical axis of the detection beam path 60 Control and evaluation unit 70 coaxial transmit and receive unit 71 First embodiment of a coaxial transmitting and receiving unit 72 Second embodiment of a coaxial transmitting and receiving unit 74 Beam splitters, neutral beam splitters 76 Converging lens 78 Converging lens with axial opening for receiving the light source 10 80° maximum detectable angle range in the monitoring area 90° 81 First trajectory of the transmitting beam in the angular range 80 82 second trajectory of the transmitting beam in the angular range 80 83 third trajectory of the transmitting beam in the angular range 80 84 Section of the maximum detectable angle range 80 85 Section of the maximum detectable angle range 80 88 Information optically displayed on an object C in the monitoring area 90 with pilot laser 90 Monitoring area 91 first point illuminated with the pilot laser 12 on an object 92 second point illuminated by the pilot laser 12 on an object 93 third point illuminated by the pilot laser 12 on an object 100 optical scanners 200 optical scanners according to the invention An object within the monitored area B Object in the monitored area C Object in the monitored area d Distance of object B to the optical scanner 100 x x-axis y y-axis z z-axis φ Azimuthal angle of the transmitting beam 31 relative to the x-axis Δφ Stroke, variation or interval of the azimuthal angle φ Δφmax maximum stroke of the azimuthal angle φ φ1 first boundary of the interval Δφ φ2 second limit of the interval Δφ φ1 Azimuthal angle of the transmitting beam 31 φ2 Azimuthal angle of the transmitting beam 32 φ3 Azimuthal angle of the transmitting beam 33 θ Polar angle of the transmitted beam relative to the z-axis Δθ Hub, variation or interval of the polar angle θ Δθmax maximum range of the polar angle θ θ1 first limit of the interval Δθ θ2 second limit of the interval Δθ θ1 Polar angle of the transmitting beam 31 θ2 Polar angle of the transmitting beam 32 θ3 Polar angle of the transmitting beam 33

Claims

[1] Optical scanner for detecting objects in a monitored area with a light transmitter (10) for emitting a pulsed transmission beam (30) into the monitoring area (90), with a detector (50) for detecting light pulses (40) reflected from an object (A, B) in the monitoring area (90), with a two-axis micromechanical beam deflection device (20) via which the transmitting beam (30) is directed into the monitoring area (90), wherein a direction of the transmitting beam (30) is variable with the beam deflection device (20) in a first direction (θ) and in a second direction (φ), and with a control and evaluation unit (60) for controlling the light emitter (30) and the micromechanical beam deflection device (20), for evaluating light pulses (40) detected by the detector (50) at an angular position (θ, φ) of the transmitting beam (30) and for determining a distance (d) of an object (B) corresponding to this angular position (θ, φ) of the transmitting beam (30) from a transit time of the detected light pulses (40), wherein a detection beam path, through which light (40) reflected from the monitoring area (90) reaches the detector (50), runs over the beam deflection device (20) and wherein an optical axis (38) of a beam path of the transmitting beam and an optical axis (58) of the detection beam path of the reflected light (40) are partially coaxial, characterized by , that the light emitter (10) is arranged in an opening of a receiving lens (78). [2] Optical scanner according to claim 1, characterized by , that the beam deflection device (20) is controllable and that the control and evaluation unit (60) is set up to control the beam deflection device (20). [3] Optical scanner according to claim 1 or 2, characterized by , that the control and evaluation unit (60) is configured to read out an instantaneous angular position (θ, φ) of the beam deflection device (20). [4] Optical scanner according to any one of claims 1 to 3, characterized by , that an aperture of the detection beam path is given by an aperture of the beam deflection device (20). [5] Optical scanner according to any one of claims 1 to 4, characterized by, that the light emitter (10) and the detector (50) are housed in a transmitting and receiving assembly (70; 71; 72) in which the optical axis (38) of the beam path of the transmitting beam and the optical axis (58) of the detection beam path are partially coaxial. [6] Optical scanner according to any one of claims 1 to 5, characterized by , that a semi-transparent mirror is present, via which light pulses (40) reflected from the monitoring area (90) are coupled out from the coaxial part of the transmitting beam path and the detection beam path and directed towards the detector (50). [7] Optical scanner according to claim 6, characterized by that the semi-transparent mirror is a polarization beam splitter. [8] Optical scanner according to claim 6, characterized by, that the semi-transparent mirror (74) is a neutral beam splitter with a division ratio greater than 60:40, preferably greater than 70:30 and particularly preferably greater than 75:

25. [9] Optical scanner according to any one of claims 1 to 8, characterized by , that the opening in which the light emitter (10) is arranged lies on the optical axis (58) of the receiving lens (78). [10] Optical scanner according to any one of claims 1 to 9, characterized by , that the control and evaluation unit (60) is set up for clocked operation, wherein at least one measurement of an object distance (d) is performed per cycle and that the results of at least one distance measurement for each cycle are stored in an image memory together with an angular position (θ, φ) of the beam deflection device (20) read out at the respective time. [11] Optical scanner according to any one of claims 1 to 10, characterized by , that at least one pilot laser (12) emitting in the visible range is present and that the control and evaluation unit (60) is set up to control the pilot laser (12) for optically displaying information on an object in the monitoring area for repeatedly illuminating selected locations (91, 92, 93) on the object. [12] Optical scanner according to claim 11, characterized by , that the transmitting beam path of the pilot laser (12) in the monitoring area (70) is collinear with the transmitting beam (31, 32, 33). [13] Methods for detecting objects in a surveillance area, in which a pulsed transmitting beam (30) is emitted into a monitoring area (90) via a two-axis micromechanical beam deflection device (20), in which the transmitting beam (30) is scanned with the beam deflection device (20) in two coordinate directions (θ, φ) over the monitoring area (90), where light pulses (40) reflected from an object (A, B) in the monitoring area (90) are detected, in which a transit time of the detected light pulses (40) is determined and in which a distance (d) of an object (B) belonging to a direction (θ, φ) of transmission (30) is determined from a transit time of light pulses (40) that are detected in a direction (θ, φ) of transmission (30), wherein light (40) reflected from the monitoring area (90) is directed via the beam deflection device (20) to the detector (50) and wherein an optical axis (38) of a beam path of the transmitting beam and an optical axis (58) of the detection beam path of the reflected light (40) are partially coaxial, characterized by , that the light emitter (10) is arranged in an opening of a receiving lens (78). [14] Method according to claim 13, characterized by , that the optical scanner (100, 200) is operated in a clocked mode, that at least one measurement of an object distance (d) is performed per cycle and that the results of at least one distance measurement for each cycle are stored in an image memory together with an angular position (θ, φ) of the beam deflection device (20) read out at the respective time. [15] Method according to claim 13 or 14, characterized by that several distance measurements are carried out per cycle and that an average of the object distances determined from the distance measurements is calculated and stored. [16] Method according to any one of claims 13 to 15, characterized by , that to examine a section (84) of the surveillance area (80) • an angular stroke (Δθ) over which the beam deflection device (20) is pivoted back and forth about a first axis (21) is reduced compared to a maximum possible angular stroke (Δθmax) about the first axis (21), and / or • an angular stroke (Δφ) over which the beam deflection device (20) is pivoted back and forth about a second axis (22) is reduced compared to a maximum possible angular stroke (Δφmax) about the second axis (22). [17] Method according to claim 16, characterized by , that a first interval of the angles (Δθ) over which the beam deflection device (20) is pivoted about the first axis (21) is at least phase-wise smaller than a maximum possible angular stroke (Δθmax) of the beam deflection device (20) about the first axis (21) and that a second interval of the angles (Δφ) over which the beam deflection device (20) is pivoted about the second axis (22) is at least phase-wise smaller than a maximum possible angular stroke (Δφmax) of the beam deflection device (20) about the second axis (22) and that a position of the first interval (Δθ) is set within the maximum possible angular stroke (Δθmax) around the first axis (21) and that a position of the second interval (Δφ) is set within the maximum possible angular stroke (Δφmax) around the second axis (22). [18] Method according to claim 16 or 17, characterized by , that in a first process phase a first solid angle area (80) is measured and in a second process phase a second solid angle area (84) is measured, which is smaller than the first solid angle area (80) and is contained in the first solid angle area (84). [19] Method according to any one of claims 16 to 18, characterized by , that in a first procedural phase the first interval is set to a first value (Δθmax) and the second interval is set to a first value (Δφmax) and that in a second procedural phase the first interval is set to a second value (Δθ) and the second interval is set to a second value (Δφ), where the second value (Δθ) of the first interval is smaller than its first value (Δθmax) and the second value (Δφ) of the second interval is smaller than its first value (Δφmax). [20] Method according to any one of claims 16 to 19, characterized by , that the first value of the first interval is the maximum possible angular stroke (Δθmax) about the first axis (21) with the beam deflection device (20) and / or that the first value of the second interval is the maximum possible angular stroke (Δφmax) around the second axis (22) with the beam deflection device (20). [21] Method according to any one of claims 16 to 20, characterized by , that the second value of the first interval (Δθ) and / or its position within the maximum possible angular displacement (Δθmax) around the first axis (21) and / or the second value of the second interval (Δφ) and / or its position within the maximum possible angular displacement (Δφmax) around the second axis (22) are set depending on measurement data from the optical scanner (100, 200) obtained in the first process phase. [22] Method according to any one of claims 13 to 21, characterized by , that the rate at which the light pulses are emitted is kept constant and, in particular, at a maximum possible value. [23] Method according to any one of claims 13 to 22, characterized by, that to optically display information on an object (C) in the monitoring area (90), selected locations on the object (C) are repeatedly illuminated with a pilot laser (12) emitting in the visible range. [24] Method according to claim 23, characterized by , that a frequency at which points on the object (A) in the monitoring area are illuminated with the pilot laser (12) is greater than the flicker fusion frequency for the human eye.

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