Optical device for detecting a light beam reflected on a distant target

description

The present invention relates to an optical device for detecting a light beam reflected at a long-range target, comprising a light source which is designed to emit the light beam in a predetermined direction onto the long-range target, a primary lens whose optical axis is substantially parallel to said predetermined direction and which is designed to focus the light beam reflected from a long distance target in a first focal point, and a detector unit for detecting focused light.

Such optical devices are used, for example, in laser measurement technology, in which a laser beam is emitted, reflected at a long-range target and its reflection is registered in a detector. The difference between the transmission time and the reception time can then be used to determine the distance to the long-term destination.

In order to register the light beam reflected from a remote target in a detector, the incident light beam is bundled. For this purpose, a so-called primary lens is arranged in the beam path of the light beam reflected from the far target, which lens focuses the light beam reflected from the far target onto a focal point in which the detector is arranged. Since long-range targets are far away in relation to the order of magnitude of the optical device, the beam directions of the emitted light beam and of the light beam that is reflected from the long-range target can be viewed as parallel.

A problem with such optical devices, however, is that the emitted light beam is reflected not only from the long-range target to be measured, but also from disruptive “close-up targets” in the air, such as dirt particles or insects. The light rays reflected by such interferences are registered by the detector and cause undesirable results or measurement errors.

It is known from the prior art to solve this problem by using the transit time of the light beam to determine which reflections originate from the close range, as described, for example, in WO 2016/173711 A1. Close-range reflections determined in this way can then be mathematically deleted from the overall result of the reflections. However, these computational solutions are particularly unsuitable for "multiple-time-around" capable laser scanners, in which several laser pulses are simultaneously on the path between the light source and the long-term target, which means that a direct assignment of results to running times is only possible to a limited extent.

The invention aims to provide a device which overcomes these problems and enables an improved surveying of long-range targets.

The invention provides an optical device of the aforementioned type, in which the detector unit is arranged such that the first focal point is between the primary lens and the detector unit, with an aperture within a normal to the optical axis cross-section of the light beam reflected from a distance between the first focal point and the detector unit is arranged.

The invention solves the problem of undesirably detected short-range targets in that the short-range sensitivity of the optical device is attenuated, and this is achieved by using a diaphragm which acts in a distance-selective manner between the first focal point and the detector unit. The spacing of the detector unit from the first focal point, for example at a predetermined distance of at least 100 μm, creates the additional path length required for the diaphragm according to the invention in the beam path of the light beam reflected from a distant target.

The diaphragm creates the possibility of masking out a higher proportion of near-target-reflected light compared to far-target-reflected light, in that the diaphragm is located in the area of ​​the focal points of the near-target-reflected light beams.

The invention thus creates a system that reflections from close range already / 19

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Patent office blocked in front of the detector, so that the result output by the detector has a higher weighting of light rays reflected from far targets to light rays reflected from near targets. Computational evaluations and processing of the detector output are therefore no longer required to prepare the measured value result.

The optical device according to the invention can be used in many areas of the prior art in which an active system performs the lighting and a detector records the lighting reflection, for example in the case of a camera with a light source for illuminating a scene. In these cases, the light source can be arranged in any desired vicinity of the primary lens.

Particularly preferably, however, the light source is arranged in the beam path in the beam path in front of the primary lens, viewed in the beam direction of the light beam reflected from a long distance target, and the diaphragm lies in that shadow of the light source that the light source casts in the light beam reflected from a long distance target. In laser measurement technology in particular, the light source is often arranged directly in front of the primary lens in order to couple its light beams as coaxially as possible into the beam path of the incident light beams, either by using a small deflecting mirror in the middle of the primary lens, via which a light source located on the side is coupled in. or by placing a small light source, such as a laser diode, directly in front of the primary lens. The light source inevitably blocks some of the total incident light at this position, including the desired long-range reflected light rays and the undesired short-range reflected light rays.

The invention takes advantage of this fact and positions the diaphragm in this shadow cast by the light source, but acting in a distance-selective manner between the first focal point and the detector unit. As a result, in comparison to the state of the art lens systems with a light source arranged in front of the primary lens, there is no decrease in usable light beams reflected from a long distance target, while the effect of reducing the close-up target reflection is retained in its entirety.

In the embodiment mentioned, the diaphragm preferably completely occupies the shadow mentioned in the cross section mentioned. This leads to a maximization of the light beams that are reflected near the target and which are blocked by the diaphragm, the light beams that are reflected at a long distance from being influenced by the diaphragm.

Particularly preferably, at least one further diaphragm is arranged within a further cross-section, normal to the optical axis, of the light beam reflected from a long distance target between the first focal point and the detector unit. This is particularly advantageous when diaphragms are used which are thin compared to the distance between the first focal point and the detector unit, for example disc-shaped diaphragms. If only a thin disc diaphragm is used, it can happen that light rays reflected close to the target cross the optical axis in front of or behind the diaphragm and are therefore perceived by the detector. The use of several diaphragms following one another along the optical axis minimizes this effect, so that the close-range sensitivity is further reduced.

If several diaphragms are used, it is advantageous if the diaphragms have different areas in cross-section and their area is greater, the further the respective diaphragm is spaced from the first focal point. As a result, the diaphragm shape can be adapted to the beam path of the light beam that is reflected from the far target, so that the detected portion of light reflected from the far target is not reduced. As a result, only light beams that are reflected close to the target are increasingly blocked.

The screen is preferably an opaque structure carried by a glass plate. This maximizes the proportion of usable light that is reflected from a long distance target, since the glass plate allows the light that is reflected from a long distance to pass unhindered in those areas in which the opaque structure is not incorporated into or onto the glass plate. In particular, no interfering webs or the like are required in order to position the diaphragm.

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The shape of the diaphragm itself can in principle be of any desired shape. It is preferably adapted to the shadow that the light source casts in the light beam reflected from the far target. In principle, diaphragms with a rectangular, pillow-shaped or oval cross-section are conceivable. The diaphragm is particularly preferably a round disk, since it is easy to manufacture and its effect can be modeled well for computational simulations.

The diaphragm can also be designed differently in the direction of the optical axis, for example, instead of having a disk shape, it is also in the shape of a rod or a cone, and again any cross-sections as described above can be used. The diaphragm is preferably a cone or a truncated cone which widens when viewed in the direction of the beam of the light beam reflected from a distant target. This corresponds, as it were, to a “continuum” of successive, infinitesimally thin disc diaphragms with progressively larger diameters, which increases the blocking of light rays reflected close to the target compared to discrete individual diaphragms or rod diaphragms.

In this embodiment, the opening angle of the cone is preferably adapted essentially to the beam path of the light beam reflected from a distant target. This achieves a particularly high yield of light that is reflected from a long distance target in the detector with a maximum reduction in the light that is reflected near the target.

Preferably, the diaphragm or that of the diaphragms closest to the first focal point is arranged at a distance of at least 100 μm from the first focal point. The adaptation of the distance to the first focal point enables flexible adjustment of the close-range sensitivity of the optical device, and the values ​​mentioned have proven to be a good compromise in practice.

In further advantageous embodiments, the diameter of the diaphragm 50 is 100%, preferably 80-100%, particularly preferably essentially 100%, of an image size B which is equal to GR * dj / ft, where G_R. is the beam diameter of an emitted light beam at a predetermined distance, dj is the distance from the diaphragm to the first focal point and ft is the distance from the primary lens to the first focal point.

In this way, the proportion of blocked light beams reflected close to the target and thus the attenuation of the near-range sensitivity of the device can be preset. For example, if the diameter of the aperture corresponds to 100% of the image size, the entire reflection of a nearby object is blocked, if it is less than 100%, only a fraction.

In order to achieve the distance required for the diaphragm between the first focal point and the detector unit, two different configurations can be selected.

In a first embodiment of the invention, the optical device comprises relay optics which are arranged between the first focal point and the detector unit and are designed to focus the light beam diverging from the first focal point on a second focal point is arranged substantially in the second focal point. In this embodiment, conventional detectors can be used, whereby the costs for the optical device can be kept low. The relay optics can also be used to arrange special optical filters such as an interference filter in the area between the lenses of the relay optics.

In order to facilitate the assembly of the diaphragm, the diaphragm can be mounted on the relay optics in this embodiment, which is particularly easy with the aforementioned cone shape, since the cone or truncated cone has a sufficiently large base area for assembly. However, even in the case of disc-shaped diaphragms, it is advantageous to mount the diaphragm closest to the relay optics on the relay optics. Regardless of the shape of the faceplate, the faceplate can be glued to the relay optics, for example.

In the embodiment with relay optics, several relay optics can be used in cascade, which brings advantages in the construction of the optical device with it when the assembly of several panels in a row turns out to be difficult. Around

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Patent Office to realize this, the optical device comprises a first and a second relay optics, which are arranged between the first focal point and the detector unit,

Wherein the first relay optics is designed to focus the diverging from the first focal point from long-distance target reflected light beam on a second focal point, and the second relay optic is designed to focus the diverging from the second focal point from the long-range target reflected light beam on a third focal point to focus

Wherein said diaphragm is arranged between the first focal point and the first relay optics and said further diaphragm between the second focal point and the second relay optics, and

Wherein the detector unit is arranged essentially in the third focal point.

In a second embodiment of the invention, the detector unit is arranged in the area in which the light beam reflected from a long distance target diverges from the first focal point, the detector unit having a detection surface which extends over the entire cross section of the light beam reflected from a long distance target. In this embodiment, relay optics can be dispensed with, although a larger detection area is required for the detector unit than in the first embodiment. Large area detector units are more expensive, but the length of the optical device can be reduced.

In order to minimize the required detection area, the diaphragm can be mounted on the detector unit. Since the diaphragm is arranged at a predetermined distance from the first focal point, the detector surface can be kept smaller by mounting the detector unit on the diaphragm. In addition, the assembly of the panel is also simplified.

Preferably, the distance of the diaphragm from the first focal point and / or the area of ​​the diaphragm in the mentioned cross section and / or the position of the surface of the diaphragm in the mentioned cross section can be changed. This allows calibration and individual configuration of the diaphragm, whereby a single optical device can be adapted to different areas of use and applications.

Furthermore, the optical device preferably also comprises a motor for this purpose, which is designed to change the mentioned distance and / or the mentioned surface and / or the position of the surface of the diaphragm in the mentioned cross section. This allows an automatic calibration or configuration of the diaphragm even while the laser scanner is in operation. This is e.g. particularly favorable when the optical device is used in a laser scanner which is inaccessible during operation, for example in an unmanned aerial vehicle (UAV).

The invention is explained in more detail below with reference to the exemplary embodiments shown in the accompanying drawings. In the drawings show:

1 shows an optical device for laser distance measurement according to the prior art in a schematic side view;

FIG. 2 shows a diagram of the distance-dependent relative reception power of the device from FIG. 1; FIG.

3 shows a first embodiment of an optical device according to the invention for laser distance measurement with a pane diaphragm in a schematic side view;

FIG. 4 shows a diagram of the distance-dependent relative reception power of the device from FIG. 3; FIG.

[0040] FIG. 5 shows a second embodiment of the optical device according to the invention for laser distance measurement with two disk diaphragms in a schematic side view;

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<td>Figure 6</td><td>a diagram of the distance-dependent relative received power of the device of FIG. 5;</td>

<td>Figure 7</td><td>a third embodiment of the optical device according to the invention for laser distance measurement with a cone diaphragm in a schematic side view;</td>

<td>Figure 8</td><td>a diagram of the distance-dependent relative reception power of the device of FIG. 7;</td>

<td>Figure 9</td><td>a fourth embodiment of the optical device according to the invention for laser distance measurement with an oblique conical diaphragm in a schematic side view;</td>

<td>Figure 10</td><td>a fifth embodiment of the optical device according to the invention for laser distance measurement with a disk diaphragm and an offset light source in a schematic side view;</td>

<td>Figure 11</td><td>a sixth embodiment of the optical device according to the invention for laser distance measurement with cascaded relay optics; and</td>

<td>Figure 12</td><td>a seventh embodiment of the optical device according to the invention for laser distance measurement with a large-area detector unit.</td>

1 shows an optical device 1 according to the prior art. In this optical device 1, which is typically used for laser distance measurement, a light source 3 located centrally in front of a primary lens 2 emits a light beam 4.

In the present embodiment, the light source 3 is a mirror which emits light provided by a further unit, for example laser light, in a predetermined direction Rt which is essentially parallel to the optical axis A of the primary lens 2. Alternatively, the light source 2 can also be directly a light-generating laser diode, lamp or the like.

When the emitted light beam 4 is reflected from a long-range target (not shown), the long-range target-reflected light beam 5 always falls essentially in the direction R opposite to the emission direction Rj₂ parallel to the optical axis A on the primary lens 2, which is due to the large distance between the long-term target and the primary lens 2 in relation to the size of the primary lens 2.

The primary lens 2 is designed in such a way, for example by selecting a corresponding radius of curvature, that it focuses the light beam 5 reflected from a distant target in a first focal point Ft. For this purpose, the primary lens 2 can be designed, for example, as a convex lens 2 or as another optical element which is able to bundle incident light rays.

To detect the light beam 5 reflected from a long distance target, a detector 6 is located in the first focal point F ^ The detector 6 is, for example, an avalanche photodiode ("avalanche photodiode", APD), which is used as a highly sensitive photodiode and thus the light beam 5 reflected from a long distance target is also low Can detect light output.

Fig. 1 also shows a near-target-reflected light beam 7, which was reflected by an undesired near-target, for example an air pollution, an insect or the like. The light beam 7 reflected near the target is incident on the primary lens 2 at an angle to the optical axis A, which is due to the small distance between the near target and the primary lens 2 in relation to the size of the primary lens 2.

Under near-target-reflected light beams 7 are understood to mean those light beams which were emitted by the light source 4 and reflected by a near-target which is at a distance of preferably less than 500 m, particularly preferably less than 100 m, very particularly preferably less than 30 m , from the primary lens 2. In contrast to this, light rays 5 reflected from a long distance target are understood to mean those light rays which are emitted by the light source 4

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Patent Office sent out and reflected from long-range targets outside of these distances.

As a result of the inclined direction of incidence of the light beam 7 reflected at close range onto the primary lens 2, it is generally not focused on the focal point Ft. Depending on the angle of incidence and the position of incidence on the primary lens 2, the near-target-reflected light beam 7 is projected onto the detector 6, which registers its presence and thus outputs a “false” measurement result, ie one that is not correlated with the long-range target to be detected.

2 shows an amplitude curve 8 typical for the optical device 1, the relative received power registered by the detector 6 in [dB] on the ordinate and the target distance in [m] on the abscissa. It can be seen that the reception sensitivity of the device 1 has a maximum precisely in that close range of approx. 5 m in which measurement results from disruptive close-up targets are undesirable.

FIG. 3 shows a first embodiment of an optical device 9 according to the invention, wherein reference symbols used in relation to FIG. 1 stand for the same components. In particular, the angular relationships of the emitted, far-target-reflected and near-target-reflected light beams 4, 5, 7 are the same, but the detector 6 assumes a different position, as will be explained below.

In the embodiment of FIG. 3, a relay optic 10 is arranged such that the first focal point Ft lies between the primary lens 2 and the relay optic 10, ie the relay optic 10 is in the R direction₂ of the far-target-reflected light beam 5 arranged behind the first focal point F1.

The relay optics 10 is designed to direct the light beam 5 diverging from the first focal point Ft, which is reflected from the long-range target, onto a second focal point F₂ to focus in which the detector 6 is located in the optical device 9. The relay optics 10 can be designed, for example, as a convex lens, as two composite convex lenses 11 as shown in FIG. 3, or as two plano-convex lenses 12 as shown in FIG. 7. If relay optics 10 with two lenses 11, 12 are used, a filter, for example an interference filter, can also be used between the two lenses 11, 12.

In order to block light rays 7 reflected close to the target, a diaphragm 13 is within a cross section Q! Which is normal to the optical axis A! of the light beam 5 reflected from a distant target is arranged between the first focal point Ft and the relay optics 10. The screen 13 is opaque and preferably has no holes.

As shown in FIG. 3, as is customary in laser measurement technology, the light source 3 is arranged centrally in front of the primary lens 2 in its beam path, viewed in the beam direction of the light beam 5 reflected from a distance. The beam path of the light beam 5 reflected from a long distance target is understood here to mean that region which is traversed by the light beam 5 reflected from a long distance target.

Due to the fact that the light source 3 is arranged in the beam path in front of the primary lens 2, the light source 3 casts a shadow S in the light beam 5 reflected from a distant target. Already by the arrangement of the light source 3 in front of the primary lens 2 and the shadow S caused by it thus a reduction in the amount of light that can be received by the detector 6 in terms of distant target-reflected light. In order not to further impair the performance of the optical device 9 for detecting light reflected from a distant target, the diaphragm 13 lies in the said shadow S of the light source 3.

In the exemplary embodiment of FIG. 3, the diaphragm 13 is a disk, that is to say it has a small thickness in the beam direction R₂ of the light beam 5 reflected from a long distance target is seen. The shape of the disk in the cross section Qi can be arbitrary, for example rectangular, circular or oval, or it can also be adapted to the shape of the shadow S of the light source 3 and thus to it itself. If the light source 3 casts a round shadow S in cross section Q, for example_1; so the shape of the diaphragm 13 in cross section Q! be round.

The area χ_Ί the diaphragm 13 in the cross section Qi is, for example, 0.1-50%, preferably 0.5-25%, particularly preferably 1-10%, of the said cross-section Qt of the remote target

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Patent Office inflected light beam 5 and can in principle be selected independently of the shadow S. Alternatively, the area χ_Ί of the diaphragm 13 in the cross section Qi can be adapted to the shadow S cast by the light source 3, for example in such a way that the diaphragm 13 covers the shadow S in the cross section Q! completely occupies. Alternatively, the area Xj of the diaphragm 3 in the cross section Qi can also have a predetermined ratio to the shadow S and, for example, occupy 50% of the shadow S.

In a further embodiment, the diameter of the diaphragm 13 can also be adapted to the size of the image occurring in the cross-section Qi of that focal spot that results on an extended close-up target located at a predetermined distance R from the primary lens 2 if the beam diameter and the beam expansion of the emitted light beam 4 over the distance R are taken into account.

In order to completely hide the reflection of a near target located at the distance R, the diameter of the diaphragm 13 corresponds to at least one image size B with

B = G_R.* d₁/ f₁,

Where G_R. the beam diameter of the emitted light beam 4 at the predetermined distance R, ie the distance from the diaphragm 13 to the first focal point Ft and L the distance from the primary lens 2 to the first focal point Ft. This results from the lens equation for a thin primary lens 2. The diameter of the diaphragm 13 can also be 50-100% or 80-100% of the image size B mentioned, in order to block only a predetermined proportion of light that is reflected close to the target.

If the diaphragm 13 is implemented as a disk, it can be, for example, a small plate carried by webs and thus introduced between the primary lens 2 and the relay optics 10. Alternatively, the screen 13 can be an opaque structure carried by a glass plate, which is, for example, etched into the glass plate or glued onto it.

The purpose of the diaphragm 13 is to block light beams 7 reflected close to the target, as shown in FIG. 3. Light beams 7 reflected close to the target cross the optical axis A as a rule between the first focal point Ft and the relay optics 10, so that they hit the diaphragm 13 and are thus blocked. As described above, the light beams 5 reflected from a long distance target are not impaired by this arrangement of the diaphragm 13, since the diaphragm 13 is arranged in the shadow S of the light source 3.

4 shows the effect of the diaphragm 13 in detail. Analogously to FIG. 2, in FIG. 4 the relative received power in [dB] is plotted on the ordinate and the target distance in [m] is plotted on the abscissa. For reference, the typical amplitude curve 8 of the optical device 1 according to the prior art of FIG. 1 is also shown in FIG. 4.

The amplitude curve 14 shows the reception sensitivity of the optical device 9 of FIG. 3 with the diaphragm 13 between the first focal point Ft and the relay optics 6. The diaphragm 13 is at a distance di (FIG. 3) from the first focal point Ft arranged. At this distance di, light rays 5, for example, are refracted by the primary lens 2 and are reflected by close-up targets which are located at a distance of 8 m in front of the primary lens 2. This causes a minimum Mt of the amplitude curve 14 for the target distance of 8 m. The shape and relative depth of the minimum Mt is dependent on the shape and size of the surface Xj of the diaphragm 13 in the cross section Qi and can be determined experimentally through experiments or through simulations .

FIG. 5 shows a variant of the optical device 9 from FIG. 3, in which, in addition to the diaphragm 13, a further diaphragm 15 within a further cross-section Q normal to the optical axis A₂ of the light beam 5 reflected from the far target is arranged between the first focal point Ft and the relay optics 10. The further diaphragm 15 is at a distance d₂ from the first focal point Ft, the distances dj and d₂ are different.

The further diaphragm 15 can be made structurally exactly the same as the diaphragm 13, for example in each case as a disk, and also like the diaphragm 13, for example as a plate with Ste

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Patent Office gene or as an opaque structure supported by a glass plate. The diaphragm 13 and the further diaphragm 15 can also have the respective cross section Qi, Q₂ have the same or a different shape, for example circular, oval or rectangular.

The areas x_1; x₂ the diaphragm 13 and the further diaphragm 15 can in the respective cross-section Qi, Q₂ be the same size. Alternatively, as shown in FIG. 5, the diaphragms have different areas x in cross section_1; x₂ on, with its area χ_Ί, x₂ The closer the respective diaphragm 13, 15 is to the relay optics 10, the larger it is. The size of the respective area x preferably follows_1; x₂ the beam path of the light beam 5 reflected from a distant target between the first focal point Ft and the relay optics 10, so that the ratio between distance d_1; d₂ and area x_1; x₂ in cross section Q_1; Q₂ is constant, ie dj / xj = d₂/ x₂.

The diaphragm 13 closest to the first focal point Ft is arranged at a distance of at least 100 μm from the first focal point Ft in order to ensure that the light beam 5 reflected from a far target is not blocked by the diaphragm 13. This also applies to the embodiment of FIG. 3.

6 shows, analogously to FIGS. 2 and 4, the relative received power in [dB] on the ordinate and the target distance in [m] on the abscissa, wherein in addition to the amplitude curve 16 of the optical device 9 from FIG. 5 shows the amplitude curve 8 of the optical device 1 from FIG. 1 for reference.

In the example of FIGS. 5 and 6, the distance dj of the diaphragm 13 was chosen such that it corresponds to a target distance of 5 m, and the distance d₂ such that it corresponds to a target distance of 15 m. This causes two minima M₂, M₃ of the amplitude curve 16 for the target distances of 5 m and 15 m.

7 shows a further variant of the optical device 9 from FIG. 3, in which, instead of a disk-shaped diaphragm 13, a diaphragm 17 in the shape of a truncated cone is arranged between the first focal point Ft and the relay optics 10. The shape of the diaphragm 15 widens in the beam direction R here₂ of the distant target-reflected light beam 5 and could also be designed as a cone shape. Alternatively, a non-expanding rod shape could also be used instead of the cone or truncated cone shape.

The opening angle (cone apex angle) of the cone or truncated cone shape of the diaphragm 17 can in principle be selected as desired. In the exemplary embodiment in FIG. 7, the opening angle was adapted to the beam path of the light beam 5 reflected from a distant target.

The conical diaphragm 17 of FIG. 7 is thus arranged not only within a cross section, but directly within a continuum of cross sections Q, of the light beam 5 reflected from a distant target between the first focal point Ft and the relay optics 10. In this sense, the diaphragm 17 can be defined in the form of a cone or truncated cone in that it is within cross-sections Q, between a first cross-section Q! at a distance dj from the first focal point Ft and a last cross-section Q₂ at a distance d₂ from the first focal point Ft.

The first cross section Q! does not coincide with the first focal point Ft, but is spaced a minimum distance di from it, in order to ensure that the light beam 5 reflected from a distant target is not blocked by the diaphragm 17. The first cross section Q! lies, for example, at a distance di of 100 μm from the first focal point F ^

The embodiment of FIG. 7 is not subject to any restrictions with regard to the variants explained for FIGS. 3 and 5. For example, two diaphragms 17 in the shape of a cone or truncated cone can be used, these can be mounted by means of webs or formed as opaque structures supported by (thick) glass plates. If the diaphragm 17 is designed as a cone or truncated cone, it is advisable to mount the diaphragm 17 on the relay optics 10. For this purpose, for example, the base of the cone or truncated cone of the diaphragm 17 can be glued to the relay optics 10, which for this purpose can preferably be flat on the side of the diaphragm 17.

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In the same way, however, the disk-shaped diaphragm 13, 15 of FIGS. 3 and 5 closest to the relay optics 10 could also be mounted directly on the relay optics 10, for example by gluing it on.

8 shows, analogously to FIGS. 2, 4 and 6, the amplitude curve 18 of the optical device 9 from FIG. 7, the relative received power in [dB] on the ordinate and the target distance in [dB] on the abscissa. m] is plotted and the amplitude curve 8 of the optical device 1 of FIG. 1 is shown for reference.

It can be seen from the amplitude curve 18 that, in contrast to the amplitude curves 14 and 16 of FIGS. 2 and 4, the conical or frustoconical diaphragm 17 of FIG. 9 no longer forms discrete minima, but an essentially continuous minimum at the level of -90 dB.

9 and 10 show further embodiments according to which the light source 3 is arranged decentrally in front of the primary lens 2 (FIG. 9) or not at all in front of the primary lens 2 (FIG. 10).

From FIG. 9 it can be seen that a light source 2 arranged asymmetrically with respect to the optical axis A casts an asymmetrical shadow S. If a diaphragm 19 is arranged here in the shadow S of the light source 3, its shape is adapted to the shadow S accordingly. For this purpose, a diaphragm 19 can be used, which is designed as an oval disk arranged asymmetrically about the optical axis A or as an oblique cone or oblique truncated cone, as shown in FIG. 9. In such embodiments, the reception sensitivity of the device 9 for light beams 5 reflected from a remote target is not impaired by the diaphragm 19 if this is arranged in the shadow S. However, the diaphragm 19 blocks at least a portion of the light beams 7 reflected close to the target, so that the close-range sensitivity of the optical device 9 is reduced.

10 shows an embodiment in which the light source 3 is arranged next to the primary lens 2 and not in front of it. Due to the offset of the light source 3 with respect to the primary axis A, light beams reflected close to the target do not fall parallel to the optical axis A. In order to compensate for this effect, the diaphragm 13 can be arranged eccentrically with respect to the primary lens 2 in order to block a larger proportion of light beams 7 reflected close to the target, as shown schematically in FIG. 10 shown.

It can be seen immediately that no shadow S is cast by the light source 3 in this embodiment. If, however, the diaphragm is arranged in the same way as in FIG. 3, apart from the above-explained effect of the eccentrically incident light rays 7 reflected close to the target, surprisingly essentially the same amplitude curve 14 is achieved as in the embodiments of FIGS. 3 and 4, in which the diaphragm 13 forms the shadow S completely occupied Qt in cross section. This is due to the fact that the light beams 5 reflected from a long distance target are not blocked this time by the light source 3, but by the diaphragm 13.

Instead of the disk shape of the diaphragm 13 of FIG. 10, any other diaphragm shape as described above for FIGS would be arranged.

11 shows an embodiment in which a plurality of relay optics 10, 20 are arranged in a cascade, so that a separate aperture 13, 15 can be provided for each relay optics 10, 20.

In this embodiment, the first relay optics 10 focuses the light beam 5 diverging from the first focal point Ft from the long-range target, onto a second focal point F₂, and the second relay optics 20 focuses the one from the second focal point F₂ from diverging long-range target-reflected light beam 5 onto a third focal point F₃, wherein the detector unit 6 is essentially in the third focal point F₃ is arranged, resulting in the cascade arrangement.

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The diaphragms are arranged here in such a way that said diaphragm 13 between the first focal point Ft and the first relay optics 10 and said further diaphragm 15 between the second focal point F₂ and the second relay optics 20 is arranged. The distances d_1; d₂ of the diaphragms 13, 15 from the respectively closest focal points F_1; F.₂ can be selected in such a way that the diaphragms 13, 15 suppress light rays 7 reflected close to the target from different target distances in front of the primary lens 2.

Disc, conical or truncated cone diaphragms can be used in all embodiments. However, disc diaphragms are preferred and the diameter of the diaphragms can vary from the respective distance di, i.e.₂ the diaphragm 13, 15 to the closest focal point F in each case_1; F.₂ be made dependent.

It goes without saying that the cascade shape shown can also be expanded in that, instead of two relay optics 10, 20 each with a cover 13, 15, more than two relay optics each with a cover 13 are used. In addition, it is possible to use more than one diaphragm for at least one of the relay optics 10, 20.

The various relay optics 10, 20 can be configured identically or differently, for example one with convex lenses as in FIG. 3 and the other with plano-convex lenses as in FIG. 7, and / or with different focal lengths .

FIG. 12 shows a variant of the optical device 1 from FIG. 3, in which no relay optics 10 are used. Instead, the detector unit 6 is arranged in the area in which the light beam 5 reflected from a long distance target diverges from the first focal point Ft, the detector unit 6 having a detection surface that extends over the entire cross section of the light beam 5 reflected from a long distance target and thus has a larger detection surface than that Detector unit 6 of the embodiment of FIG. 3.

When the diaphragm 13 is mounted directly on the detector unit 6, the distance between the first focal point Ft and the detector unit 6 can be reduced substantially to the distance dj between the first focal point Ft and the diaphragm 13. In principle, however, the detector unit 6 can also be spaced apart from the diaphragm 13. The embodiment of FIG. 11 with a large-area detector unit is generally also suitable for diaphragms 13 with a conical or conical shape. Truncated cone shape as shown in Figs.

In all the embodiments mentioned, the distance di of the diaphragm 13, 15, 17, 19 from the first focal point Ft and / or the area x_1; x₂ the diaphragm 13, 15, 17, 19 in said cross-section Q_1; Q₂ and / or the position of the surface x_1; x₂ the diaphragm 13, 15, 17, 19 in said cross-section Q_1; Q₂ be changeable, for example by the diaphragm 13, 15, 17, 19 along the optical axis A - or normal to this - is arranged to be manually displaceable.

If a disc screen is used, it can be composed, for example, of several sickle-shaped lamellae, which can increase or decrease the area of ​​the disc screen by a rotary movement.

Conical or truncated cone apertures can be designed with a variable opening angle, or telescopic rods can alternatively be used, which also changes the area of ​​the aperture in the respective cross-section Q, depending on the state of telescoping.

Instead of manually, the diaphragm 13, 15, 17, 19 can also be moved by a motor, the said distance d_1; d₂, the named area x_1; x₂ or the named position changed.

In all the embodiments mentioned, the diaphragm 13, 15, 17, 19 can leave the outer edge of the cross-section Q, free, so that the entire area Xt of the diaphragm 13, 15, 17, 19 lies within the said cross-section Q i. The diaphragm 13, 15, 17, 19 can be arranged at a predetermined minimum distance from the outline of the cross section Q 1. Alternatively, the diaphragm 13, 15, 17, 19 can also protrude laterally from the outside into the cross section Q 1. In

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AT 520 307 B1 2019-03-15 Austrian

Patent Office of these variants leaves the diaphragm 13, 15, 17, 19 free, for example at least 50%, preferably at least 70%, particularly preferably at least 90%, of the outline of the cross section Q. The diaphragm 13, 15, 17, 19 can furthermore be arranged without holes and / or in such a way that it intersects the optical axis A.

Generally speaking, the diaphragm 13, 15, 17, 19 is arranged and / or designed in such a way that it blocks a greater proportion of light rays 7 reflected close to the target than light rays 5 reflected from far away.

The invention is accordingly not limited to the illustrated embodiments, but includes all variants, modifications and combinations thereof that fall within the scope of the attached claims.