by means of visible radiation pulses onto visual objects in the surrounding environment

Abstract

This invention relates to a method for projecting a visual object (22) onto the surrounding environment (12) of a movable device (10), particularly a vehicle, comprising: - injecting an electromagnetic radiation pulse (32) in the visible spectrum into the surrounding environment (12), wherein the radiation pulse (32) has a temporal frequency distribution over its pulse duration (T2), which causes the pulse duration to shorten due to dispersion as it propagates in the surrounding environment (12). Furthermore, this invention relates to an apparatus for carrying out such a method and a vehicle including such an apparatus.

Description

Technical Field

[0001] The present invention relates to a method for projecting (virtual) visual objects into the surrounding environment, as well as an apparatus and a vehicle including means for performing such projection. Background Technology

[0002] Movable devices, especially vehicles, include visually perceptible signal systems in the form of lighting equipment, particularly for indicating planned driving maneuvers or potential hazards. In the prior art, there are methods that extend the possibility of projecting (virtual) objects into the surrounding environment.

[0003] Examples of solutions are disclosed in DE 10 2006 050 548 A1, DE 10 2006 050 546 A1, DE 10 2012024 494 A1 and DE 20 2016 004 062 U1.

[0004] What these solutions have in common is that the projected object or content may become difficult to identify, especially as the distance from the device increases. This is primarily due to the decrease in peak intensity with increasing distance from the projection unit, particularly due to increased divergence at greater distances from the projection device.

[0005] Due to safety requirements for projection devices that typically include laser beam sources, the power of the incident radiation cannot be arbitrarily increased. Refer to DIN EN 60825-1, which specifies the limits of the peak intensity or peak energy density of incident radiation that the human eye can be exposed to. Summary of the Invention

[0006] The present invention addresses the following objective: to provide a solution for projecting virtual visual objects into the surrounding environment in which the projected objects are well identifiable even as the distance from the projection device increases.

[0007] The task is solved by the technical solution according to the present invention. The present invention has several advantageous improvements.

[0008] This invention is based on the aforementioned understanding that the incident radiation power cannot be arbitrarily increased to comply with a given limit. However, according to the invention, the peak intensity or peak energy density limited by the limit is also related to the pulse duration of the incident radiation pulse. Therefore, a solution is proposed that achieves a larger pulse duration near the device (or radiation source) from which the projection is performed, thereby reducing the peak intensity or peak energy density within that range, and in particular, reducing it below a given limit. However, the pulse duration decreases with increasing distance.

[0009] This is achieved, in particular, in a way that at least partially compensates for the divergence effect that reduces peak intensity or peak energy density.

[0010] Then, the peak intensity or peak energy density decreases less drastically with increasing distance from the projecting device compared to the situation so far. Preferably, the peak intensity or peak energy density remains substantially at the same level as when initially projected into the surrounding environment (i.e., at a shorter distance from the projecting device).

[0011] Thus, it is possible to inject and maintain the highest possible peak intensity or peak energy density (but still below a given limit) until the projected radiation is incident on the surrounding environment. Because of the still high intensity at incidence, the radiation can still be reliably perceived by the human eye. In particular, the radiation can be perceived much better than the previously apparent intensity attenuation of the injected content when the pulse duration remains constant and the divergence increases with distance.

[0012] To compress the pulse duration accordingly during propagation, the present invention proposes to initially generate a frequency distribution within the incident radiation pulse that, under the influence of dispersion, results in a self-compression of the pulse during propagation in the surrounding environment. This frequency, or at least some of its components, is preferably slowed down or temporally compressed, thereby compressing the pulse duration. The generation of such a frequency distribution can be reliably achieved by means of a compactly constructed optical unit, thus the proposed solution can be implemented with minimal overall cost.

[0013] In particular, a method is proposed for projecting (virtual) visual objects (i.e., visually perceptible objects) into the surrounding environment of a movable device, especially a vehicle (and especially a motor vehicle, such as a passenger car, a truck, and / or a bus), the method comprising:

[0014] - An electromagnetic radiation pulse (especially a laser pulse) in the visible spectrum is injected into the surrounding environment, wherein the radiation pulse has a temporal frequency distribution over its pulse duration, which, upon entering (and especially propagating) the surrounding environment, causes the pulse duration to shorten due to dispersion (more precisely, upon propagation through the surrounding environment). The pulse duration therefore preferably shortens further with increasing distance from the device.

[0015] Radiation pulses can be generated using known radiation sources, particularly laser beam sources. Ultrashort laser pulses may be involved, but these pulses are altered after or during their generation, as further explained below, to produce a frequency distribution. Radiation pulses can follow each other at high frequencies so that they are perceived by the human eye as a constant beam or a constant projection and / or incident object. To project and thus map a desired object onto the surrounding environment, the radiation pulses can interact with suitable units (e.g., with an optical mask) in a conventional manner. However, it is also possible to make the laser pulse, or the pulsed laser beam formed therefrom, movable (i.e., capable of variable orientation), so that an object can be generated, arguably, by means of a moving (pulsed) laser beam, by drawing onto the surrounding environment. Any other methods in the prior art can also be used, as disclosed, particularly in the prior known publications cited at the beginning.

[0016] In a manner known per se, a radiation pulse (which may also be referred to as an optical pulse and / or a laser pulse) may comprise a certain spectrum or a certain bandwidth of electromagnetic waves with different frequencies. In other words, a radiation pulse may comprise a wave packet at the location of electromagnetic radiation. The radiation pulse may first be generated by a radiation source as an optical pulse having a wave packet in which the individual waves have the same phase. In particular, bandwidth-limited or Fourier-limited pulses may be involved, which have a small, preferably minimal, possible pulse duration for the wavelength spectrum they encompass. This generated pulse, present within the device, can be guided through an optical unit of the type described below to subsequently experience or generate a desired frequency distribution. Thus, within the scope of this disclosure, referring to an initially or initially generated radiation pulse, the pulse radiation may in particular be Fourier-limited, wherein a radiation pulse having a temporal frequency distribution (which is preferably generated subsequently or on the basis of an initially generated Fourier-limited pulse) may be referred to as a radiation pulse incident on the surrounding environment.

[0017] Movable devices can be understood in particular as devices with their own drive systems. For example, industrial robots can also be included.

[0018] According to a preferred variation, the temporal frequency distribution is configured such that the high-frequency components (within the wavelength spectrum of the radiation pulse) precede the low-frequency components (within the proposed wavelength spectrum) in time. As mentioned, the radiation pulse can consist of electromagnetic waves with individual frequencies, each having a certain bandwidth. The high-frequency components can be frequency components exceeding the intermediate or average frequency. The low-frequency components can be components below the intermediate or average frequency. Other thresholds for dividing the components can also be preset. It is not necessary for all high-frequency components to precede all low-frequency components in time. However, preferably, the temporal frequency distribution is configured such that at least some, and preferably the majority, high-frequency components precede at least some, and preferably the majority, low-frequency components in time.

[0019] It has been shown that, in the context of propagation in the surrounding environment and the dispersive effects of the air typically present there, this temporal frequency distribution results in the high-frequency component being slowed down more strongly than the low-frequency component. This leads to temporal compression, or in other words, pulse temporal compression, thereby shortening the pulse duration and increasing the peak intensity.

[0020] In particular, a preferred variation is configured such that the radiation pulse is negatively chirped. This term, known in the art, can be understood in particular as the temporal frequency distribution occurring in the manner described above, i.e., the high-frequency component precedes the low-frequency component in time. To provide a correspondingly negatively chirped radiation pulse, there are optical elements, such as anomalous dispersive media, such as so-called chirped mirrors, through which the initially generated, and especially Fourier-limited, pulse can be guided. In this way, the desired temporal frequency distribution can be provided with minimal cost.

[0021] An improved scheme is configured such that the radiation pulse is generated based on the distance to the area of ​​the surrounding environment to which the object should be projected. This specifically relates to the frequency distribution of the radiation pulse. Thus, the initially generated radiation pulse (whose frequency distribution is later set by a defined dispersion in the optical unit) can be generated in a conventional manner as a Fourier-limited radiation pulse and, in particular, a laser pulse. But at least the subsequent frequency distribution can be determined according to the distance, such that the incident radiation pulse is generated accordingly, either distance-dependent or distance-dependent.

[0022] In particular, the duration of the incident radiation pulse (i.e., a pulse with a temporal frequency distribution) can be selected based on the distance. Specifically, the incident radiation pulse can be selected such that it is stretched in time with varying intensity depending on the distance (generally, the greater the distance, the greater the temporal stretch). For example, this variable stretching can be achieved using an LCD (liquid crystal display) based pulse shaper or by adapting the reflection number on a chirped reflective or transmissive layer (such as a chirped mirror).

[0023] A suitable pulse shaper (or pulse modulator) is available. The pulse can then be spatially decomposed via an optical grid. Each spectral component is preferably mapped onto an LCD, where a spatial phase orientation is applied at the pixels of the LCD, such that different spectral components acquire different phase delays through refractive index modulation. A temporal phase orientation, corresponding to chirp, can then be applied via subsequent spectral-spatial combining.

[0024] When adapting the number of reflections, a defined dispersion or a defined amount of dispersion can be applied to each reflection using, for example, a chirped mirror mentioned above. The pulse here collects the spectral phase through the material of the mirror (or the pulse phase can be composed of or defined by the corresponding chirp fraction). This phase can also correspond to the temporal phase within a time period.

[0025] Generally, temporal stretching can be performed such that, when incident on the surrounding environment (i.e., at a defined distance), a desired reduction in pulse duration occurs, meaning the incident pulse has a pulse duration reduced in a desired manner. This can be achieved by starting with propagation in air with defined characteristics (e.g., defined temperature and / or humidity) and by calculating, for example, the shortened pulse duration due to expected dispersion. Such calculations may include solving the Helmholtz equation for determining nonlinear propagation.

[0026] As already mentioned, according to a variation, a radiation pulse can be first generated (e.g., within the device) with an initial pulse duration, and then a frequency distribution and a stretching of the initial pulse duration to the initially injected pulse duration can be generated. This can also be done within the device and / or radiation source. A pulse with the corresponding stretching of the frequency distribution can then be injected into the surrounding environment and propagates in the direction of the incident region. With increased propagation in the surrounding environment, the pulse duration is advantageously shortened. Alternatively, a pulse with a frequency distribution having a stretched pulse duration can be directly generated and injected, which is then correspondingly shortened in time.

[0027] Due to the initial extended pulse duration, the peak intensity is selectively reduced, especially near vehicles equipped with projection devices. This improves operational safety and reduces the risk of injury to personnel in the surrounding environment. However, the progressively decreasing pulse duration ensures that sufficient peak intensity remains present when incident on the surrounding environment, thus providing reliable visibility there.

[0028] In particular, it can be configured such that the pulse duration incident on the surrounding environment is closer to the initially generated pulse duration than the initially injected pulse duration (after the temporal stretching and generation of the frequency distribution). In other words, the temporal stretching can therefore be largely reversed during propagation in the surrounding environment. In particular, this can be done such that the pulse duration incident on the surrounding environment substantially corresponds to the initially generated pulse duration, and especially to the pulse duration in the Fourier limit. Alternatively, the pulse duration can deviate from the mentioned pulse duration by no more than 10% or 20%. If the chirped pulse is directly generated and injected, the pulse duration can be reduced such that it is reduced compared to the initially injected pulse duration. The pulse duration can then be closer to the pulse duration corresponding to the (fictitious or theoretical) pulse duration of the injected pulse if the pulse does not have a direct frequency distribution, i.e., the frequency distribution is generated after the initial generation.

[0029] The present invention also relates to an apparatus for projecting visual objects into the surrounding environment. The apparatus has at least one radiation source configured to project electromagnetic radiation pulses (especially laser pulses) within the visible spectrum into the surrounding environment. The radiation pulses have a frequency distribution over their pulse duration (i.e., a frequency distribution over time), which, upon impact with the surrounding environment, causes the pulse duration to shorten due to dispersion. The apparatus itself need not be movable, but can be, for example, arranged at the location of a movable apparatus as a projection device.

[0030] Furthermore, the present invention also relates to a vehicle, particularly a motor vehicle, and especially a passenger car or freight car, that includes such a device.

[0031] The apparatus can generally be configured to implement and / or provide the method according to any aspect described herein. To this end, the apparatus may include any additional features and measures to provide all states, steps, interactions, and effects described in the context of the method. In particular, all interpretations and modifications of the method features may also be applied to apparatus features with the same wording or set within apparatus features with the same wording. Attached Figure Description

[0032] Embodiments of the present invention will now be explained with reference to the accompanying schematic diagrams. The same reference numerals may be used throughout the drawings for features of the same function or type.

[0033] Figure 1 A vehicle is illustrated in a schematic, highly simplified diagram, which includes a device according to an embodiment of the invention, wherein the device implements a method according to an embodiment of the invention.

[0034] Figure 2 It shows Figure 1 A detailed view of the device and, in particular, its radiation source.

[0035] Figure 3 A flowchart of a method implemented by the apparatus in the previous figures is shown. Detailed Implementation

[0036] exist Figure 1 The image shows vehicle 10, which is a motor vehicle and, exemplarily, a bus used for transporting passengers. The view shown corresponds to a side view of vehicle 10, where the wheels 11 shown belong to the front axle (in...). Figure 1 The left wheel (11) and the rear axle ( Figure 1 (Right wheel 11).

[0037] Vehicle 10 is situated within an surrounding environment 12, which is substantially represented by a driving lane. Vehicle 10 has a projection device 14 on its observer-facing side for projecting visual objects into the surrounding environment. The projection device 14 includes a radiation source 16 and optionally includes a distance sensor 18.

[0038] The distance sensor 18 can be constructed based on any common distance measurement principle. In particular, it relates to an optical distance sensor 18, which performs distance measurements, for example, using laser triangulation. Alternatively, a radar-based distance sensor 18 can also be used. The sensor axis A is indicated by a dashed line, along which the distance sensor 18 can detect the distance to the surrounding environment 12. Currently, the sensor axis A can be slightly tilted in the observer's direction. The distance sensor 18 can be used to detect the distance between the device 14 and slopes, the height of the edge of the driveway, and especially the height of the sidewalk or the surface of the driveway, which can also vary according to the vehicle load.

[0039] A radiation cone 20 is shown for the radiation source 16. This radiation cone is a virtual feature, which should indicate the region into which the radiation source 16 can direct radiation. Figure 1 In an exemplary case, a circle is mapped onto the surface of the driving lane as object 22. For example, the circle may contain warning indications (e.g., "Stop"), arrows indicating planned steering maneuvers, or other indications to other road users. The surrounding environment area 24 is delineated with dashed lines, and the distance to this surrounding environment area can be measured using distance sensor 18, and the visual object 22 is incident on this surrounding environment area.

[0040] Radiation source 16 can be manually activated. However, radiation source can also be automatically activated by a control device of vehicle 10 that is not shown separately, such as when parked at a bus stop or when flashing signal lights.

[0041] exist Figure 2 In the diagram, radiation source 16 is shown in a schematic cross-sectional view, revealing its internal components. First, laser source 26 is visible. This laser source generates (preferably high-frequency) visible laser pulses 28, one of which is exemplarily shown. This laser pulse is an initially generated Fourier-limited laser pulse 28 with a particularly short pulse duration T1.

[0042] The radiation source 16 also includes an optical unit 30 through which the laser pulse 28 is guided. The optical unit 30 is a chirped mirror with anomalous dispersion behavior. Such a component is known in the prior art. By means of such a chirped mirror 30, the pulse duration T1 of the pulse 28 can be stretched, thereby producing an incident pulse 32 with a stretched pulse duration 12 and a temporal frequency distribution.

[0043] More precisely, it can be seen that the initially generated laser pulse 28 has a relatively short pulse duration T1. The laser pulse 32, stretched by the chirped mirror 30 and subsequently injected into the surrounding environment, has an increased pulse duration T2. ​​As has been shown above, chirped pulses can also be generated and injected directly.

[0044] The temporal frequency distribution is also represented by the further spaced-apart troughs of the incident pulse 32. Here, along the schematically shown time axis t (or observed along the pulse duration T2), the high-frequency component HA (especially within the blue light spectrum) precedes the low-frequency component NA of the light spectrum in time. The latter, in particular, can be located within the red spectrum.

[0045] The pulse 32, stretched in time in this way (e.g., within the radiation cone 20), propagates through the surrounding environment and the air present there. Due to the relationship described above, the pulse 32 is here compressed in time. When incident on the surrounding environment region 24, the correspondingly compressed pulse 33 has a reduced pulse duration T3 compared to the initially incident (stretched) pulse duration T2. ​​This pulse duration can substantially correspond to the initially generated pulse duration T1. Therefore, the pulse 33 incident on the surrounding environment 24 can also correspond to the Fourier-limited pulse 28.

[0046] exist Figure 3The described process is illustrated again with the aid of a method diagram. In step S1, a pulse 28 with a reduced, and particularly Fourier-limited, pulse duration T1 is initially generated. In step S2, the initially generated pulse 28 is guided through a chirped mirror 30. Thus, in step S3, the pulse 32 is stretched in time (i.e., has an increased pulse duration T2) and has the described frequency distribution. In step S4, the injected and stretched pulse 32 propagates through the surrounding environment and undergoes self-compression of dispersion. In step S5, the pulse is incident in the surrounding environment 24, where, due to self-compression, the pulse again approaches and preferably also has the initially generated pulse duration T1.

[0047] It goes without saying that the pulses 28, 32, and 33 described separately here can also be considered as single pulses or unique pulses whose state (especially pulse duration and frequency distribution) varies.

[0048] As described in the general description section, the duration T2 of the initially incident pulse can be varied based on the distance measured using sensor 18, and in particular selected according to that distance. This can be done to make the self-compression during propagation sufficient to obtain a pulse 33 that is sufficiently compressed in the surrounding environment, and in particular, to make its pulse duration T3 close to the initially generated pulse duration T1.

[0049] Therefore, any of the optical units mentioned above, especially the pulse shaper mentioned above, can be attached to or alternatively attached to the chirped mirror 30.

[0050] Subsequently, the physical cohesion on which the proposed method is based was explained once again using the formula.

[0051] The peak intensity I of a highly coherent light source (such as laser source 26 used here) can be described by the following equation (1):

[0052]

[0053] Here, E p The pulse energy is based on equation (3) below, where σ is a constant envelope parameter, ω is the beam diameter, and τ is the pulse duration. Peak intensity is measured in W / m².

[0054] By multiplying by the repetition rate f in Hz rep The peak energy density ρ(2) was obtained:

[0055]

[0056] The peak energy density is expressed in J / m².

[0057] The pulse energy can be determined as follows, where P represents the power in watts (3):

[0058]

[0059] In particular, as illustrated in equations (1) and (2), the peak intensity I or peak energy density ρ decreases quadratically with increasing beam diameter ω. However, the increase in beam diameter is always due to the divergence effect during propagation in the surrounding environment.

[0060] The resulting automatic attenuation of peak intensity I causes visibility to the human eye to decrease with increasing distance from laser source 26.

[0061] The present invention addresses this problem by varying the pulse duration τ in relation to distance, and in particular by reducing the pulse duration as the distance to the radiation source 26 increases, as described above.

[0062] Because the pulse duration τ is relatively high near the radiation source due to time stretching (see...). Figure 2 In T2), so as illustrated from equations (1) and (2), the peak intensity I or peak energy density ρ is selectively reduced there. Thus, the limits that should be observed for health reasons can be adhered to. And with increasing distance and selectively reduced during this pulse duration τ (see... Figure 2 In T3), the peak intensity I or peak energy density ρ is increased, thereby ensuring visibility when incident on the surrounding environment.

[0063] List of reference numerals

[0064] 10. Vehicles (equipment)

[0065] 11 (Vehicle) Wheels

[0066] 12 Surrounding Environment

[0067] 14 (Projection) Device

[0068] 16 Radiation Sources

[0069] 18 Distance Sensor

[0070] 20 Radial Conical Part

[0071] 22 Virtual visual objects

[0072] 24 Surrounding environment area

[0073] 26 laser sources

[0074] 28. Initially generated pulse

[0075] 30 optical units (chirped mirrors)

[0076] 32 The initial pulse

[0077] 33 Pulses incident on the surrounding environment

[0078] T1 Initial pulse duration

[0079] T2 Initial pulse duration

[0080] T3 is the duration of the incident pulse in the surrounding environment.

[0081] NA low-frequency share

[0082] HA High Frequency Share

[0083] A. Sensor axis of the distance sensor

[0084] t Timeline.

Claims

1. A method for projecting a visual object (22) onto the surrounding environment (12) of a movable device (10), comprising: - By means of a radiation source (16), an electromagnetic radiation pulse (32) in the visible spectrum range is injected into the surrounding environment (12), wherein, The electromagnetic radiation pulse (32) has a temporal frequency distribution over its initial pulse duration (T2), which, when propagating in the surrounding environment (12), causes the pulse duration to shorten due to dispersion. The electromagnetic radiation pulse (32) is generated based on the distance between the radiation source (16) and the surrounding environment area (24) onto which the visual object (22) should be projected. in, The initial pulse duration (T2) of the corresponding electromagnetic radiation pulse (32) and the initial temporal stretch of the frequency distribution therefrom are generated according to the distance. or, First, the electromagnetic radiation pulses (32) are generated with an initial pulse duration (T1). Then, the frequency distribution is generated by stretching the initial pulse duration (T1) to the initially incident pulse duration (T2). The initially incident pulse duration (T2) is then shortened again to the pulse duration (T3) incident on the surrounding environment region (24) as the propagation in the surrounding environment increases. The greater the distance, the greater the time stretch, which causes the peak intensity or peak energy density near the radiation source (16) to drop below a given limit, and the desired pulse duration to decrease at the distance.

2. The method according to claim 1, Its features are, The frequency distribution is performed such that the high-frequency component (HA) precedes the low-frequency component (NA) in time.

3. The method according to claim 1 or 2, Its features are, The electromagnetic radiation pulse (32) is negatively chirped.

4. The method according to claim 1 or 2, Its features are: - The distance between the radiation source (16) and the surrounding environment area (24) is detected using at least one distance sensor (18).

5. The method according to claim 1 or 2, Its features are, The pulse duration (T3) when incident on the surrounding environment area (24) is closer to the initial pulse duration (T1) than the initial pulse duration (T2).

6. The method according to any one of claims 1 to 2, characterized in that, The movable device (10) is a vehicle.

7. A device (14) for projecting a visual object (22) into a surrounding environment (12), having at least one radiation source (16) configured to inject electromagnetic radiation pulses (32) in the visible spectrum into the surrounding environment (12), wherein, The electromagnetic radiation pulse (32) has a frequency distribution over its initial pulse duration (T2), which, upon entering the surrounding environment (12), causes the pulse duration to shorten due to dispersion. The electromagnetic radiation pulse (32) is generated based on the distance between the radiation source (16) and the surrounding environment area (24) onto which the visual object (22) should be projected. in, The initial pulse duration (T2) of the corresponding electromagnetic radiation pulse (32) and the initial temporal stretch of the frequency distribution therefrom are generated according to the distance. or, First, the electromagnetic radiation pulses (32) are generated with an initial pulse duration (T1). Then, the frequency distribution is generated by stretching the initial pulse duration (T1) to the initially incident pulse duration (T2). The initially incident pulse duration (T2) is then shortened again to the pulse duration (T3) incident on the surrounding environment region (24) as the propagation in the surrounding environment increases. The greater the distance, the greater the time stretch, which causes the peak intensity or peak energy density near the radiation source (16) to drop below a given limit, and the desired pulse duration to decrease at the distance.

8. A vehicle (10) comprising the device (14) according to claim 7.

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