Patent Publication Number: US-2019178990-A1

Title: Optical set-up for a lidar system, lidar system and operating device

Description:
BACKGROUND INFORMATION 
     The present invention relates to an optical set-up for a LiDAR system, a LiDAR system as well as an operating device. The present invention relates in particular to an optical set-up for a LiDAR system for the optical detection of a field of view, in particular for an operating device, a vehicle or the like. The present invention furthermore relates to a LiDAR system for the optical detection of a field of view as such and in particular for an operating device, a vehicle or the like. The present invention furthermore provides a vehicle. 
     When using operating devices, vehicles and other machines and equipment, operating assistance systems or sensor systems for detecting the operational surroundings are increasingly utilized. Apart from radar-based systems or systems on the basis of ultrasound, light-based detection systems are also increasingly used, e.g., so-called LiDAR (light detection and ranging) systems. 
     Conventional LiDAR systems have a disadvantage in that in a coaxial arrangement, conventionally beam splitters are often used to separate the beam paths of the optical transmitter system and the optical receiver system. Due to their functional principle, these result in attenuations in radiation intensity both in the transmitting path, that is, when emitting primary light, as well as in the receiving path, that is, when receiving secondary light from the field of view, and thus reduce the sensitivity and accuracy of the detection process. 
     SUMMARY 
     The optical set-up according to the present invention may have the advantage that it is possible to do without the use of a beam splitter that attenuates the intensity of the radiation so that there are no resulting losses in intensity in the detection process. This increases the sensitivity and accuracy of the detection process and, according to the present invention, it may be achieved in that an optical set-up for a LiDAR system is provided for the optical detection of a field of view, in particular for an operating device, a vehicle or the like, in which on the one hand an optical receiver system and an optical transmitter system are developed at least on the field of view side (i) having essentially coaxial optical axes and (ii) a common optical deflection system and in which, on the other hand, an optical detector system is developed on the detector side which has means for directing light coming in—in particular from the field of view—directly via the optical deflection system onto a detector device. According to the present invention, the necessity of a beam splitter is eliminated because the optical detector system provided on the detector side has the ability and the corresponding means for directing, in direct cooperation with the optical deflection system, incident light, in particular from the field of view, via the optical deflection system onto the underlying detector device. 
     Preferred developments of the present invention are described herein. 
     In one advantageous development of the present invention, additional optical components, which may entail a corresponding loss, are eliminated in that the optical deflection system is designed and has means for directing light from the field of view directly onto the optical detector system. 
     An optical set-up that is particularly simple to control is achieved if, according to another development of the optical set-up of the present invention, the optical deflection system is designed to have a mirror, in particular a micromirror, that is able to be swiveled and/or oscillated in a one-dimensionally or two-dimensionally controllable manner. In this instance, a swiveling mirror is also to be understood as a mirror that is excitable to oscillations or to swiveling oscillatory motions. 
     Another advantageous development of the optical set-up of the present invention provides for the mirror or micromirror to be controllably swiveling and/or oscillating (i) in a first angular range for radiating primary light into the field of view and (ii) in a second angular range for directing secondary light from the field of view directly onto the optical detector system. 
     According to a preferred development of the present invention, a particularly compact construction of the optical set-up is achieved if the optical detector system is developed in direct spatial proximity of a detector element of the detector device. 
     Another development of the optical set-up in accordance with the present invention provides for the optical detector system to have a lens or form a lens, in particular in a hemispherical shape or in the shape of a combination of a perpendicular circular cylinder and a hemisphere on one face of the circular cylinder, the detector device or a sensor element of the detector device being situated on a side facing away from a convex side of the hemisphere. 
     Particularly low losses result in the optical set-up of the present invention if according to another advantageous specific development the optical detector system has or forms a material area embedding the optical detector device or a detector element of the detector device. In this case, boundary surfaces producing losses are avoided particularly effectively. 
     A particularly high degree of detection accuracy may be achieved if, according to another specific embodiment of the optical set-up of the present invention, the detector device or a sensor element of the detector device is situated essentially in the focal point or essentially in a focal plane of the optical detector system. 
     For a quick and accurate response of a LiDAR system in accordance with an example embodiment of the present invention, it is necessary that conditions are such that only small deflection ranges are required for the underlying optical deflection system. 
     Thus, one preferred specific embodiment of the optical set-up of the present invention provides for the detector device or a sensor element of the detector device and an element providing a primary light, in particular a light source, to be situated in direct spatial proximity of one another and/or lie in a plane essentially perpendicular to detector-side optical axes of the optical transmitter system and/or the optical receiver system. 
     For a precise illumination of the field of view and a detection of light from the field of view, according to an advantageous development of the optical set-up of the present invention, an optical aperture system may be developed, which is situated in front of the optical deflection system on the field of view side and which is designed and has means to direct primary light from the optical deflection system into the field of view and to direct light from the field of view onto the optical deflection system. 
     The present invention further relates to a LiDAR system for the optical detection of a field of view, in particular for a or as part of an operating device, a vehicle and the like, an optical set-up of the present invention being developed and used in accordance with the present invention. 
     According to another aspect of the present invention, an operating device is also provided, in particular a vehicle or the like, which is designed to include a LiDAR system of the present invention for the optical detection of a field of view. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Specific embodiments of the present invention are described in detail with reference to the figures. 
         FIG. 1  is a block diagram, which shows schematically a specific embodiment of the optical set-up of the present invention in connection with a specific embodiment of a LiDAR system of the present invention. 
         FIG. 2  shows in a schematic block diagram another specific embodiment of a LiDAR system of the present invention using an alternative development of the optical set-up of the invention. 
         FIGS. 4 through 5  show another specific embodiment of the optical set-up of the present invention in a LiDAR system and its representational characteristics. 
         FIGS. 6 through 8  show in a schematic and sectional lateral view specific embodiments of the optical set-up of the present invention with different possibilities of producing and providing primary light. 
         FIGS. 9 through 12  show in a schematic and sectional lateral view various optical detector systems as well as their representational behavior, which may be used in specific embodiments of the optical set-up of the present invention. 
         FIGS. 13 through 16  show graphs that illustrate various representational characteristics of specific embodiments of the optical set-up of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS 
     Exemplary embodiments of the present invention are described in detail below with reference to  FIGS. 1 through 16 . Identical and equivalent elements and components as well as elements and components that act in an identical or equivalent manner are designated with the same reference symbols. The designated elements and components are not described in detail in every case of their occurrence. 
     The represented features and further characteristics may be isolated from one another in any desired form and may be combined with one another as desired, without departing from the essence of the invention. 
     In the form of a schematic block diagram,  FIG. 1  shows a specific embodiment of LiDAR system  1  of the present invention using a specific embodiment of the optical set-up  10  of the present invention. 
     LiDAR system  1  according to  FIG. 1  has an optical transmitter system  60 , which is fed by a light source  65 , e.g. in the form of a laser, and emits primary light  57 —possibly after passing through a beam-shaping optical system  66 —into a field of view  50  for detecting and/or investigating an object  52  located there. 
     According to  FIG. 1 , LiDAR system  1  furthermore has an optical receiver system  30 , which receives light, and in particular light reflected by object  52  in field of view  50 , as secondary light  58  via an objective lens  34  as primary optical system and transmits it via an optical detector system  35  as secondary optical system to a detector device  20 . 
     Light source  65  and detector device  20  are controlled via control lines  42  and  41  by a control and evaluation unit  40 . 
     In  FIG. 1 , the common field of view-side optical deflection system  32  and the detector-side optical detector system  35  are represented schematically. 
     As part of primary optical system  34 , optical deflection system  62 , which may also be called an objective lens and which functions in connection with optical transmitter system  60  as an emitting objective projection lens, is designed to receive primary light  57  and to direct it into field of view  50  including object  52 . 
     In connection with optical receiver system  30 , the common field of view-side optical deflection system  62  works together with optical detector system  35  as secondary optical system in such a way that the secondary light  58  received from field of view  50  is directed onto optical detector system  35  in a direct manner, that is, without interposition of a beam splitter, in order thus to reach detector device  20  without interposition of additional optical components. Primary optical system  34  acts in connection with optical receiver system  30  as a receiving objective projection lens. 
     The provision of an optical aperture system  70  on the field of view side is optional and advantageous for a suitable emission of the primary light  57  and for the bundling reception of the secondary light  58 . 
     Detector device  20  may be developed having one or more sensor elements  22 . 
     Optical set-up  10  is designed for a LiDAR system  1  for the optical detection of a field of view  50 , in particular for an operating device, a vehicle or the like, and is developed having an optical transmitter system  60  for emitting a transmit light signal into field of view  50 , a detector device  20  and an optical receiver system  30  for optically projecting field of view  50  onto detector device  20 . 
     Optical receiver system  30  and optical transmitter system  60  are designed on the field of view side (i) so as to have essentially coaxial optical axes, and they have a common optical deflection system  62 . 
     Optical receiver system  30  has a secondary optical system  35  on the detector side, which is designed and comprises means for directing light coming in from the field of view  50  via optical deflection system  62  onto detector device  20 . 
     In optical set-up  10 , optical transmitter system  60  is generally designed and has an arrangement for emitting primary light  57  into field of view  50 . 
     Furthermore, in optical set-up  10 , optical receiver system  30  is designed and has an arrangement for optically projecting field of view  50  onto detector device  20 . 
       FIG. 2  shows in a similar way as  FIG. 1  another specific embodiment of a LiDAR system  1  using an alternative development of the optical set-up  10  of the present invention. 
     The components provided in the specific embodiment shown in  FIG. 2  correspond essentially to the components shown in  FIG. 1 . In  FIG. 2 , however, emphasis is placed on (a) the spatial proximity between optical detector system  35  as secondary optical system of optical receiver system  30  with respect to detector device  20  and sensor elements  22  on the one hand and, on the other hand, (b) the direct spatial proximity of the beam paths of optical transmitter system  60  and optical receiver system  30  and in particular the direct spatial proximity of detector device  20  having sensor elements  22  with respect to light source  65  as element  67  providing primary light  57 . 
       FIG. 3  shows a more concrete specific embodiment of LiDAR system  1  of the present invention using a specific embodiment of the optical set-up  10  of the present invention. 
     This specific embodiment implements the basic principle shown in  FIGS. 1 and 2  more concretely. Detector device  20  including a sensor element  22  together with a light source  65  or generally together with an element  67  providing a primary light  57  are situated in or on a common substrate  25 , which defines detector plane  24 . 
     For this purpose, sensor element  22  and element  67  providing the primary light  57  are situated in direct spatial proximity to one another. This has the consequence that optical deflection system  62 , e.g., in the form of a micromirror  63  that is able to swivel or oscillate in a controllable manner, only has to be swiveled about directly adjacent angular ranges and/or about angular ranges of small dimension in order thereby to illuminate field of view  50  including the object  52  situated therein—possibly mediated by optical aperture system  70 —with primary light  57  and/or to direct secondary light  58  from field of view  50  onto detector device  20  including sensor element  22 . 
     For this purpose, optical detector system  35  has the form of a lens  36  including a hemispherical segment  37  and a cylindrical segment  38  having a common axis of symmetry  39 . Hemispherical segment  37  is attached directly—e.g., as a single piece of material—on the face or surface of the cylindrical segment facing away from detector device  20 . 
     The differently marked beams for secondary light  58  correspond to different distances  71  between optical aperture system  70  and object  52 . 
     In specific embodiments without optical aperture system  70 , the distance  71  between object  52  in field of view  50  and optical deflection system  62  is consequential. 
     In  FIG. 3 , the beam of secondary light  58  designated by reference numeral  72 - 1  comes from a near object  52  of field of view  50 , whereas the beam of secondary light  58  designated by  72 - 3  comes from a more remote object  52  of field of view  50 . For traversing a greater distance, secondary light  58  requires more time, within which mirror  63  of the optical deflection system swivels by a greater angle. Beam  72 - 3  is thus deflected to a greater degree than beam  72 - 1 . 
     Optical deflection system  62  and particularly its mirror  63  have a first angular range  64 - 1 , which is used to project secondary light  58  from field of view  50  onto detector device  20 , and a second angular range  64 - 2 , which is used to distribute primary light  57  from element  67  providing primary light  57  into field of view  50 . 
       FIGS. 4 and 5  show schematically the projection relations in a specific embodiment of a LiDAR system  1  with a specific embodiment of the optical set-up  10  from  FIG. 3  including the distance-dependency, for a one-dimensionally moved optical deflection system  62  respectively one the right side and for a two-dimensionally moved optical deflection system respectively on the left side.  FIG. 4  provides a simple top view, while  FIG. 5  provides an exploded view. 
       FIGS. 4 and 5  show the path of secondary light  58  in relation to lenses  36  and detector device  20  having thin sensor elements  22 . The figures show the location  74  of the laser aperture and the beam position  75  after bundling or collimating. 
       FIGS. 6 through 8  show different specific embodiments of the optical set-up  10  of the present invention with a focus on the different implementations of the generation of primary light  57 . 
     In the specific embodiment shown in  FIG. 6 , the element  67  producing primary light  57  is formed by a light source  65  itself, for example a laser light source, a laser diode or the like. 
     In the specific embodiment shown in  FIG. 7 , an external light source  65  is used, which produces primary light  57  and directs it onto a mirror element as the element  67  in substrate  25  providing the primary light  57 . 
     In the specific embodiment shown in  FIG. 8 , the element  67  providing primary light  57  is a through hole in substrate  25 , the actual light source  65  being located on its backside or the side facing away from detector device  20 . 
       FIGS. 9 through 12  schematically show projection relations in different specific embodiments of the optical set-up  10  of the present invention. Graphs are shown in each instance, on the abscissa of which a specific distance measure is represented, while the ordinate, as a function thereof, shows the beam position of secondary light  58  on sensor elements  22  of a detector device  20  behind optical detector system  35 . 
     Indications are also provided for a small distance  72 - 1 , an intermediate distance  72 - 2  and a large distance  72 - 3  of object  52  in field of view  50 . 
       FIGS. 9 and 12  respectively show in schematic fashion an optical detector system  35  having two lenses  36  and the projection relations that obtain in each case. 
       FIGS. 10 and 11  show a set-up having only one lens  36  for the construction of optical detector system  35 . 
       FIGS. 13 and 14  show in the form of graphs the relative light outputs in optical detector systems having one lens  36  and having two lenses  36 , which occur on the respective sensor element  22 , as a function of the distance of object  52 . 
       FIGS. 15 and 16  respectively show the relative output on sensor element  22  of detector device  20  as a function of the distance of the hole, which is plotted on the abscissa, using the code for small distances  72 - 1 , intermediate distances  72 - 2  and great distances  72 - 3  from object  52  in field of view  50 . 
     These and further features and characteristics of the present invention are explained in more detail below: 
     Conventional LiDAR architectures  1  often use coaxial arrangements of transmitter path  60  and receiver path  30 . The transmitter itself is made up, e.g., of a modulated laser diode as light source  65 . In the simplest case, e.g., brief pulses of a high to very high peak output are generated. Detector device  29  has a single or several AP diodes (avalanche photo diode) as sensor element  22 . PIN diodes are also popular. Silicon and germanium diodes are less expensive than diodes made of compound semiconductors (e.g., InGaAs), but only allow for a less efficient detection of radiation of wavelengths of more than approx. 900 nm. 
     In the coaxial arrangement, conventionally a beam splitter is often required, which deflects the laser output for example at a ratio of 1:1 (50%) in different directions. I.e., the transmit beam passes through an optional optical system and the beam splitter before being deflected by a deflection unit  62  in the direction toward field of view (FOV)  50 , in which the distance, the presence or the reflective characteristics of an object  52  assumed to exist there are to be measured. 
     The direction of object  52  as target may be determined by the position of deflection unit  62 . Depending on the specific embodiment, a further optical system is provided. The beam reflected by object  52  follows as secondary light  58  the same path as primary light  57  in the transmit path  60 . This is the case when deflection unit  62  moved only negligibly during the measurement. This condition is generally fulfilled. 
     The conventionally utilized beam splitter deflects a portion of the receive beam onto a receiver, a further optical system being possibly required. 
     Aspects of the conventional constellation are:
         Only the interesting section of FOV  50  is projected onto the receiver. This preselection reduces the noise output on the receiver resulting from interference sources (brake lights, headlights, sunlight).   The deflection unit directs the receive beam always onto the same spot on the detector. As a result, it is possible to design the detector to be very small (single diode) or to use a better receiving diode (InGaAs).   The beam splitter deflects a portion of the transmit output into the housing instead of directing it onto the target. As a result, a higher transmit output must be provided for the transmitter. The deflected beam may interfere with the receiver.   The receive output is also reduced by the beam splitter. This is a critical point since the receive output is normally very low and a further reduction is very disadvantageous for the system behavior.       

     In a system having a separated constellation, by contrast, the target direction must be determined either by the deflection unit or by the receiver. If the appearance angle of the target is determined or specified by the position of the deflection unit, a single large photo diode suffices in principle, onto which the entire FOV is projected. This approach has the disadvantage that a lot of ambient light is directed onto the detector. Alternatively, the receiver may be constructed from a photodiode array or a photodiode linear array. The FOV is thereby divided into parts and a single photodiode is illuminated only by a part of the FOV and thus is illuminated only by a portion of the ambient light. 
     Aspects of this way of proceeding are:
         The optical receive paths and transmit paths may be implemented independently of one another, according to their individual requirements, and no compromise is necessary.   A very large receiver diode array is required. For this reason, it cannot be produced cost-effectively from compound semiconductors. This prevents the use of large eye-safe wavelengths. Such an array also requires a great amount of electrical energy, which requires expensive cooling measures.       

     It is an objective of the present invention to make a beam splitter superfluous in a coaxial LiDAR system  1 . The system offers the mentioned advantages of a conventional coaxial system without its disadvantages. Moreover, large and expensive detectors become superfluous. 
     A main feature of the present invention focuses the receive pulse output issuing from a micromirror  63  onto a small area or point in a plane  24 . 
     The separation of transmit path  60  and receive path  30  is assumed by an optical deflection system  62  and in particular by a rapidly oscillating micromirror  63 . The beam of secondary light  58  is focused further by an optical detector system  35 , which is located directly in front of detector device  20 . 
     In particular, the transmitter unit, e.g. in the sense of an element  67  providing the primary light  57 , and the receiver unit, e.g., in the sense of detector device  20  having a sensor element  22 , are situated in very close proximity to each other. 
     Advantages of the present invention are:
         No beam splitter is required. As a result, no receive output is lost. The full transmit output is emitted.   A single small photodiode or a photodiode linear array or a photodiode array may be used in detector device  20 .   The possibility of being able to make do with one single receiving diode (InGaAs) allows for the use of large eye-safe wavelengths, e.g. in the range of approximately 1,550 nm, in economical fashion.   A large receiver array may be omitted.   In a suitable design of optical detector system  35 , an optical zero-meter signal may be provided.   A lens  36  of optical detector system  35  may be applied directly onto the detector in a very space saving manner.       

     The basic principle is shown in  FIG. 3  for example. 
     Components of the present invention may be configured on a plane  24 , called the detector plane. This plane may be flat or vaulted. Either a printed circuit board (PCB) or a semiconductor chip are possible. 
     A brief laser pulse is emitted from a small surface on the detector plane. The laser beam is directed via a deflection unit  62  onto a point or an object  52  in field of view or FOV  50 . 
     Additional optical aperture systems  70  are possible. 
     The light output reflected or diffusely scattered by object  52  is collimated by optical aperture system  70  and is again directed onto optical deflection system  62  as deflection unit. 
     Deflection unit  62  is a mirror  63  oscillating in a plane for example. 
     During the pulse propagation time from mirror  63  to object  52  and back, the mirror position changed slightly since mirror  63  oscillates continuously and rapidly. As a result, the receive pulse is projected onto a location on detector plane  24  that differs from the emitter area. A small distance of object  52  results in a slight deflection of the receive beam, beam  72 - 1  in  FIG. 3 . A greater distance of object  52  results in a stronger deflection, beam  72 - 3  in  FIG. 3 . 
     The deflection depends on the oscillation frequency of mirror  63 , on distance  71  between object  52  and mirror  63 , on the distance between detector plane  24  and mirror  63  and possibly on the aperture. 
     Without further measures, the receive beam projected onto detector plane  24  would describe a line of possible projection locations, depending on object distance  71 . 
     The receive beam of secondary light  58  must be directed onto a sensor element  22 . If the above-mentioned parameters are selected for a great deflection, then the projected beam would become very long and require large detectors. In the opposite case, i.e. when selecting the parameters for small deflections, reflections on near objects  52  would have the result that the receive beam would again strike the emitter surface and could not be detected. 
     A remedy is provided by the introduction of an optical detector system  35 , which is mounted in front of or directly on the detector module as detector device  20 . 
       FIG. 3  shows a lens  36  having a hemispherical lens part  37  and a cylindrical substructure or pedestal  28 . 
       FIG. 3  shows a sectional view of an axis symmetrical lens  36 . 
     Other geometries and specific embodiments of optical detector system  35  are possible. 
     If lens  36  is implemented accordingly, all incident beams are directed onto a very small area regardless of the corresponding object distances  71 . The selection of the FOV section together with the associated reduction of the ambient light intensity is thus effected by micromirror  63 . 
       FIG. 4  shows the top view onto detector plane  24 .  FIG. 5  complements  FIG. 4  with an exploded view. The individual elements from  FIG. 5  stacked one on top of the other result in the representation in  FIG. 4 . The further elucidation refers to  FIG. 5  from top to bottom.
     (1) The right side respectively represents the case of a mirror  63  that oscillates in only one plane; a one-dimensional or 1D case. The left sides concern the case of a mirror  63  that moves also in an orthogonal direction and that deflects the beam from the plane at y=0; two-dimensional or 2D case. The 1D case is approximately also given when the vertical frequency is selected to be much smaller than the horizontal frequency.   (2) The laser aperture is at the center. Various specific embodiments of the same are explained later.   (3) The representation of the beam movement is the totality of all possible projection locations of the received laser beam. Depending on the distance of object  52 , the receive beam is deflected to a greater or lesser extent. The legend on the right side itemizes the distance information by using reference numerals  72 - 1 ,  72 - 2 ,  72 - 3  for small, average and great distances, respectively.
       In the case of a one-dimensional deflection of mirror  63 , no deflection occurs in the y direction. In the two-dimensional case, a deflection will also occur in the orthogonal direction (left).   This representation shows the beam positions uninfluenced by the lens.   
       (4) Two specific embodiments of lenses  36  are shown. On the left is the dome-shaped lens  36  already explain in  FIG. 3 , on the right is a lens  36  of similar shape but more extended in the y direction. The left lens  36  is able to compensate also for the vertical deflection by 2D mirror  63 . A wider lens  63  could make the collimation more independent of an erroneous adjustment.   (5) Receive beam position  75  following collimation is ideally point-shaped, regardless of object distance  71 .   (6) The detector area is shaped and dimensioned in such a way that all receive beams are focused on it regardless of object distance  71 .   

     Laser Aperture 
     In the specific embodiment shown in  FIG. 6 , the laser aperture is formed by a laser module that is integrated in detector plane  24  as light source  65 . 
     The laser may be mounted as an external component on substrate  25  (PCB/semiconductor material, “die”, “chip”) and wired on substrate  25 . 
     It is possible for the wiring to occur directly on substrate  25 . The laser may be worked out directly from the semiconductor material. In this instance, however, a high degree of electromagnetic interference (EMV, EMI) may be caused by high-energy switching elements on detector plane  24 . 
     According to  FIG. 7 , the aperture may be made of a mirrored surface on substrate  25 , which is irradiated by a laser  65 . 
     According to  FIG. 8 , substrate  25  may be provided with an opening or a hole at the location of the aperture, which the laser beam penetrates from the back side. 
     In this case and in the case of  FIG. 7 , the EMV problem is circumvented by a possible great distance between laser  65  and sensor element  22 . 
     Simulation results are presented in the following. 
     Beam Path 
       FIGS. 9 through 12  show the simulated beam path for individual rays (ray tracing). All rays are emitted by a deflection unit  62  assumed to be point-shaped (right). The object distance  71  is represented as  72 - 1  close,  72 - 2  average,  72 - 3  distant. 
     The representations of  FIGS. 11 and 12  show that all rays are focused onto a small area. The principle may be extended to a greater number of lenses  26 , which decreases the size of the focal points. 
       FIGS. 9 through 12  thus show simulated beam paths for a single-lens configuration— FIGS. 9 and 12 —and for a two-lens configuration— FIGS. 10 and 11 . 
       FIGS. 9 and 10  show that the beams of secondary light  58  emanate from a point-shaped deflection unit  62  (right) and strike detector plane  24  (left). 
       FIGS. 11 and 12  show lens  26  in detail for a one-lens and respectively for a two-lens configuration. 
     Parameters
         distance between mirror  63  and detector plane  24 : 3 cm or 5 cm for one lens and two lenses  36  respectively   aperture diameter=100 μm,
           lens diameter=(1.25 mm and 0.35 mm respectively)   
           pedestal height=0.9 mm and 0.3 mm respectively)   mirror oscillation frequency=30 kHz   Lens material: polycarbonate at n=1.6       

     Discussion of Minimum Range 
       FIGS. 13 and 14  show the output striking the sensor surface as a function of the object distance  71 . The represented values refer to the output emanating from mirror  63 . The output missing at 100% is deflected by spherical lens  37  in the event of an angle of incidence that is too low. Receive beams for very close objects  52  are not sufficiently deflected by mirror  63  and again strike the laser aperture, while somewhat more distant objects  52  produce beams that strike lens  36  at a very low angle and are attenuated as a result. 
     Incident beams always have a certain extension. Very close targets  52  also produce a very strong backscatter signal. For these reasons, in a real case, it will be possible to detect even very close objects  52 . 
     Furthermore, very strong receive signals may override the detector. In this case, an attenuation of the receive signal would even be advantageous. 
     Lens Shape 
     Dome-shaped and pill-shaped lenses  37  with pedestal  38  are shown. 
     The concrete specific embodiment of optical detector system  35  may be adapted to the particular application. The main point for this purpose is that the optical detector system  35  focuses if possible all incident beams of secondary light  58  on one or multiple areas that are as small as possible, as point-shaped as possible. 
     Possible specific embodiments of the optical detector system are inter alia:
         A plano-convex lens  37  having a pedestal  38  is possible.   So far, maximally one lens  36  and one sensor element  22  per side were shown. The expansion of the number of lenses and detectors in the x direction in  FIG. 4  (micro-lens array/detector linear array) is possible.   Figure respectively showed only one lens  36  above the aperture. An arrangement of lenses in one direction possibly suffices. In this case, it would only be possible to evaluate the oscillatory motion of deflection unit  62  in one direction.   A holographic element would accomplish the deflection without a curved surface.   An asymmetrically shaped element could improve the blind minimum range by offering in the area of the opening a smaller angle with respect to the incident beam.       

     Detector Output 
     In  FIGS. 15 and 16 , the output incident on detector plane  24  is plotted as a function of the distance from the opening, for the case of a single lens  36  (left) and for two lenses  36  (right). Again, output is seemingly lost for very close objects  52 . The output for objects  52  further removed may be distributed on the detector surface nearly at will by adapting the lens geometry. 
     In the case of  FIG. 15  for a single lens  36 , the entire output is distributed on an area of approx. 600 μm diameter. 
     In the case of  FIG. 16  for two lenses  236 , two detectors of 200 μm diameter are required. 
     An expansion to more than two lenses  36  is possible. 
     Increase of the Pulse Succession Frequency 
       FIG. 13  indicates that beams from very distant objects  52  are attenuated and are no longer directed onto detector device  20 . This may be a very useful effect. For conventional LiDAR systems must wait before initiating a new scan (=emission of a laser beam) until the receive pulses from very distant objects  52 , which are actually located beyond the specified maximum distance, have also been received. 
     In a LiDAR system  1  of the present invention, beams from very distant objects  52  would be directed onto a point in detector plane  24  at which no sensor element  22  exists. Thus a higher pulse succession frequency would be possible, and the system dynamics could be increased.