Patent Description:
The previous use of diffuser devices based on wet-chemically etched or lithographically manufactured diffusers has a high proportion of scattered or diffracted light due to the small structure sizes, which reduces the optical efficiency and limits the maximum achievable divergence angle and the uniformity of the intensity distribution. The resulting limited field of view and reduced resolution of these sensors do not allow sufficient functionality in the surrounding surveying of objects such as cars, robots, drones and the like. The necessary increase in the number of sensors is neither technically nor economically advantageous. In addition, when using the typical diffusers, it cannot be ensured that a diffraction of 0th order is generated with high intensity, which limits the laser safety of this optical solution and can lead to the expiration of the operating permit.

A diffuser device is known from <CIT>, for example. The designs described therein comprise a first lens array with a plurality of rotationally symmetric lenses on the entrance surface of a transparent substrate and a second lens array with a plurality of rotationally symmetric lenses on the opposite exit surface of the substrate. The light to be expanded can pass through the two lens arrays one after the other during operation of the diffuser device.

A device of the type mentioned above is known from <CIT>. The device is part of an illumination system for a microlithographic projection exposure apparatus. The device comprises three transparent substrates, which are spaced apart from one another. The first substrate comprises a first lens array having a plurality of cylindrical lenses and the second substrate comprises a second lens array having a plurality of cylindrical lenses. The lenses of the first lens array have cylinder axes extending in a first direction and the lenses of the second lens array have cylinder axes extending in a second direction perpendicular to the first direction.

A device for the homogenization of laser radiation is known from <CIT>. The device described therein comprises two transparent substrates, which are spaced apart from one another. The first substrate comprises a first lens array having a plurality of cylindrical lenses and the second substrate comprises a second lens array having a plurality of cylindrical lenses. The lenses of the first lens array and the lenses of the second lens array have cylinder axes extending in the same direction. The second substrate is movable relative to the first substrate.

The <CIT> discloses devices for converting laser radiation into laser radiation with an M profile. One of the devices described therein comprises three transparent substrates, which are spaced apart from one another. Each of the substrates comprises a lens array having a plurality of cylindrical lenses. The lenses of the lens arrays have cylinder axes extending in the same direction.

A device for the homogenization of laser radiation is known from <CIT>. The device described therein comprises three transparent substrates, which are spaced apart from one another. Each of the substrates comprises a lens array having a plurality of cylindrical lenses. The lenses of the lens arrays have cylinder axes extending in the same direction. The second and the third substrate are movable relative to each other.

The <CIT> discloses illumination devices for generating non-symmetric light beams used for signaling lights or warning lights for vehicles. One of the devices described therein comprises two transparent substrates, which are spaced apart from one another. The first substrate has a Fresnel lens with spherical Fresnel structures. The second substrate has two Fresnel lenses with cylindrical Fresnel structures. Thereby, Fresnel structures perpendicular to each other are arranged on the front side and the back side of the second substrate.

The problem underlying this invention is the creation of a diffuser device of the type mentioned above which can effectively expand light passing through it into a wide angular range. A distance measuring device with such a diffuser device and a LIDAR device with such a diffuser device shall be specified.

This is achieved by means of a diffuser device of the type mentioned at the beginning with the characteristic features of claim <NUM>, a device for measuring the distance of the type mentioned at the beginning with the characteristic features of claim <NUM> and a LIDAR device of the type mentioned at the beginning with the characteristic features of claim <NUM>. The subclaims concern preferred forms of the invention.

Claim <NUM> provides that the lenses of the first lens array and/or the lenses of the second lens array are aspherical, so that they deviate from the shape of a circular cylinder, wherein the lenses of the second lens array have a radius such that the light passing through the second lens array is widened in the first direction into an angular range of more than <NUM>°.

By forming the two lens arrays on different substrates, it can be ensured that the light distribution generated by the diffuser device is largely distortion-free. The substrates may be glass or plastic, for example, or may comprise glass or plastic. For example, the type and size of any distortion that may occur can be influenced by appropriately selecting the distance between the two substrates. Alternatively or additionally the type and size of distortion that may occur can be influenced by appropriately selecting the arrangement of the system rather than by appropriately selecting the distance between the two substrates. For example, to minimize pincushion distortion, a small angle diffuser substrate first followed by large angle diffuser substrate could be used. For example, to obtain a pattern with Barrel distortion, a large angle diffuser single side structured substrate first followed by small angle double side structured substrate could be used.

Due to the cylindrical lens design, the expansion can be optimized separately for two different directions.

It may be provided that the lenses of the first lens array are arranged side by side in the second direction and the lenses of the second lens array are arranged side by side in the first direction. The crossed arrangement of the cylindrical lenses of the first and second arrays allows the expansion for two perpendicular directions to be optimized separately. For example, a different expansion can be selected for a horizontal direction than in the vertical direction perpendicular to it.

It is possible that the first lens array is located on the entrance surface or on the exit surface of the first substrate or the second substrate. Alternatively or additionally, it may be provided that the second lens array is arranged on the entrance surface or on the exit surface of the first substrate or the second substrate.

It is possible that the diffuser device comprises a third lens array, and/or a fourth lens array, which is or are also arranged on the first substrate and/or the second substrate. For example, one or both substrates can be provided with two lens arrays. The increase in the number of lens arrays increases the design possibilities with regard to the light distribution to be generated.

It may be provided that the diffuser device comprises a lens arranged on the first substrate and/or on the second substrate, in particular on its exit surface, or arranged on a separate third substrate. The light passing through the diffuser device can be additionally widened by a lens of this type, for example a diffusing lens. As an alternative to an additional lens, an additional lens array with a corresponding function can also be considered.

It may be provided that the diffuser device comprises a collimator lens or a collimator lens array in the front of the diffuser device. The collimator lens can also be integrated or combined into the first or the second substrate.

It is possible that the lenses of the first lens array and/or the lenses of the second lens array are refractive or diffractive or holographic lenses. Alternatively, the lenses can also be gradient index lenses.

It may be provided that the lenses of the first lens array and/or the lenses of the second lens array have a positive or negative refractive power. It is also possible to provide the lenses of one of the lens arrays with a positive refractive power and the lenses of another of the lens arrays with a negative refractive power.

It is possible that the lenses of the first lens array and/or the lenses of the second lens array are arranged regularly or irregularly. For example, the lenses of one of the lens arrays may have mutually different dimensions or radii.

It may be provided that the lenses of the first lens array and/or the lenses of the second lens array are asymmetrically shaped, in particular in such a way that between the lenses there is partly a step-like offset. Lenses with an asymmetric shape can influence the light passing through the diffusion device so that the far field profile becomes asymmetrical.

Due to the asymmetry of the lenses, the left edges of the lenses have a different design than the right edges of the lenses, so that a step-like offset can occur at least partially between adjacent lenses. In order to reduce this effect, it is possible to provide that the lenses of a lens array on the entrance surface of one of the substrates are asymmetrically shaped, wherein prisms or one common prism are arranged on the exit surface of this substrate. In this case the lenses can have the same SAG values at the left and right lens aperture positions, which ensures a continuous transition from each lens to the adjacent lens. It should be noted that SAG values are also called Sagitta values or Z values of the lens surface. Such a measure can largely prevent the step-like offset between adjacent lenses. The production of the lens array can be simplified by largely avoiding the step-like offset.

Alternatively, it may be provided that the lenses of a lens array on the entrance surface of one of the substrates are asymmetrically shaped wherein one common prism is arranged on the entrance surface of this substrate. In this case there is no offset between adjacent lenses.

Alternatively, it may be provided that the lenses of a lens array on the entrance surface of one of the substrates are symmetrically shaped, wherein the lenses of a lens array on the exit surface of this substrate are asymmetrically shaped. In this case it is possible to obtain an total efficiency of about <NUM>% without preliminary collimation and with a minimum step-like offset between the lenses on the exit surface. The SAG values in this case can be different.

It may be provided that the center distances of the lenses of the first lens array from the center distances of the lenses of the second lens array are different, in particular wherein the center distances of the lenses of the first lens array are larger than the center distances of the lenses of the second lens array. This allows the center distances or the dimensions, especially the widths, of the lenses to be optimized specifically for the two different directions of light distribution.

It is possible that the lenses of the first lens array have such a radius that the light passing through the first lens array is widened in the second direction into an angular range of more than <NUM>°, in particular into an angular range of more than <NUM>°, preferably into an angular range of more than <NUM>°, for example into an angular range of about <NUM>°, and/or in that the lenses of the second lens array have a radius such that the light passing through the second lens array is widened in the first direction into an angular range of about <NUM>°. For example, an angular range of <NUM>° is suitable for the horizontal direction of a LIDAR device of a motor vehicle, whereas an angular range of approximately <NUM>° is suitable for the vertical direction of a LIDAR device of a motor vehicle.

It is possible that the lenses of the first lens array have a radius of less than <NUM>, in particular a radius of less than <NUM>, preferably a radius of less than <NUM>, for example a radius of about <NUM>, and/or in that the lenses of the second lens array have a radius of less than <NUM>, in particular a radius of less than <NUM>, preferably a radius of less than <NUM>, for example a radius of about <NUM>,<NUM>. For example, the first lens array can be made of fused silica glass. The lenses of the first lens array can have a center distance or pitch of <NUM> and a conical constant of -<NUM>. Additionally, the second lens array can be made of S-TIH53 glass. The lenses of the second lens array can have a center distance or pitch of <NUM> and a conical constant of -<NUM>.

Preferably the radius of the lenses of the first lens array is larger by a factor between <NUM> and <NUM> than the radius of the lenses of the second lens array.

In particular, it may be provided that the distance between the first lens array and the second lens array is unequal to the focal length of the lenses of the second lens array or unequal to the focal length of the lenses of the second lens array in the direction of propagation of the light.

For the spatial measurement and positioning of stationary and mobile objects, the use of laser light sources enables a combined temporally and spatially resolved measurement. The combination of a laser light source, a diffuser device and a 1D or 2D detector unit can simultaneously evaluate a defined field of view. The use of a diffuser device serves to adapt the illumination field to the field of view of the detector unit. The temporal resolution is determined by the illumination duration and the frequency of the measurement repetitions. The spatial resolution is determined by the illumination of a contiguous surface of a sphere segment, whose equidistant distance to the laser light source and to the detector unit allows a temporally resolved spatial distance measurement. A diffuser device has the task of transforming the incident laser beam onto the angular space of a sphere segment of the illumination field or onto the plane surface or of creating such an angular or space light intensity distribution that corrects the aberrations of the detector system and thus illuminating the field of view of the detector unit. The variety of possible laser light sources such as a diode, a VCSEL, a DPSSL, a fiber laser or an SLD results in a dependence of the illumination quality and its applicability on the beam quality M<NUM> and the beam parameter product BPP of the respective source. In order to be able to use arbitrary sources, the diffuser device can be designed so that the exit angle of the diffuser device exceeds the entrance angle formed by the divergence of the laser light source and a possible tilting angle of the optical axis of the laser light source by a multiple. In order to achieve a defined distribution of the illumination power over the angular space, refractive surfaces of the diffuser device can be selected with a defined deviation from a spherical or circular cylindrical segment, resulting in a uniform power distribution over the entire angular space. The combination of several refractive surfaces of this type with different apertures or different center distances of the refractive surfaces, respectively, additionally allows a superposition of the refractive deflection of the light with a diffractive pattern structure resulting from the superposition of plane waves with different tilting angles to the different refractive lens segments. The resulting light distribution correlates with the wavelength of the light and is spatially and temporally stable. In addition, it has a defined, very low modulation structure which, in combination with the detector unit and a calibration procedure, leads to an additional improvement in the detection stability and resolution of the unit.

The diffuser device can consist of one or more components that either simultaneously span the angular space or separately generate the angles in the horizontal and vertical directions.

The combination of refractive lens arrays with different apertures or different center distances of the lenses, respectively offers for the first time the possibility to generate large illumination angles and at the same time to constructively superimpose the diffractive power component into the homogeneous illumination and detection quality. In particular, the additional use of optical glasses with a refractive index ><NUM> opens up the possibility of realizing divergence angles ><NUM>°. The use of aspherical surfaces, especially surfaces deviating from a circular cylindrical shape, additionally offers the possibility of deflecting more light at large angles, whereby the detection unit enables almost the same detection quality and resolution in all spatial directions.

Claim <NUM> provides that the diffuser device is a diffuser device in accordance with the invention.

Simultaneous spatial distance measurement (TOF LIDAR) with laser light is an essential component of future autonomous mobility. The use of quasi-simultaneous scanning solutions is classified by all users only as an interim solution and does not offer sufficient spatial and temporal resolution. The optical or mechanical deflection of lines has the additional disadvantage that the line detectors can only be used to a limited extent and that the superimposition of light lines and the imaging onto the line sensor is only possible in a limited solid angle with limited resolution. The proposed diffuser devices can be combined with any laser light source to cover automotive, transportation, consumer ID and machine vision applications.

Further features and advantages of this invention are clearly illustrated by the following description of preferred embodiments of the invention with reference to the enclosed illustrations.

In the figures the same or functionally the same parts are provided with the same reference signs. In some of the figures cartesian coordinate systems are drawn for better orientation.

The embodiment of a diffuser device shown in <FIG> comprises a transparent substrate <NUM> having a first lens array <NUM> on an entrance face <NUM> and a second lens array <NUM> on an exit face <NUM> opposite the entrance face <NUM>. The lenses <NUM>, <NUM> of the lens arrays <NUM>, <NUM> are each designed as cylindrical lenses.

The lenses <NUM> of the first lens array having <NUM> cylindrical axes extending in a first direction x, the lenses <NUM> of the second lens array having <NUM> cylindrical axes extending in a second direction y perpendicular to the first direction x. The lenses <NUM> of the first lens array <NUM> are arranged next to each other in the second direction y (see <FIG>) and the lenses <NUM> of the second lens array <NUM> are arranged next to each other in the first direction x (see <FIG>).

The entrance surface <NUM> and the exit surface <NUM> are opposite to each other in a third direction z, which is perpendicular to the first and second directions x, y. In the position of use of the diffuser device, light passes through the substrate <NUM> in the z-direction.

The lenses <NUM> of the first lens array <NUM> and the lenses <NUM> of the second lens array <NUM> are concave cylindrical lenses. It is possible to use convex lenses instead of concave lenses for the first and/or second lens array <NUM>, <NUM>.

The lenses <NUM> of the first lens array <NUM> and the lenses <NUM> of the second lens array <NUM> are aspherical, so that they deviate from the shape of a circular cylinder.

The lenses <NUM> of the first lens array <NUM> have such a radius that the light passing through the first lens array <NUM> is widened in the second direction into a first angular range <NUM> of about <NUM>°, for example (see the far field in <FIG>).

Furthermore, the lenses <NUM> of the second lens array <NUM> have such a radius that the light passing through the second lens array <NUM> is widened in the first direction into an angular range <NUM> of about <NUM>°, for example (see the far field in <FIG>). For example, the radius could be about <NUM>. In addition, the conical constant, which is a measure of the size of the aspheric formation of the lenses, can have a size of <NUM>.

Such a light distribution can be advantageously used for a LIDAR device where the angular range <NUM> of about <NUM>° can correspond to the horizontal direction of the light distribution and the angular range <NUM> of about <NUM>° can correspond to the vertical direction of the light distribution.

In particular, it may be provided that the distance between the first lens array <NUM> and the second lens array <NUM> in the z direction is not equal to the focal length of the lenses <NUM> of the second lens array <NUM>.

Furthermore, the width of the lenses <NUM> of the first lens array <NUM> in the y-direction is greater than the width of the lenses <NUM> of the second lens array <NUM> in the x-direction. Accordingly, the center distance of the lenses <NUM> of the first lens arrays <NUM> in the y-direction is greater than the center distance of the lenses <NUM> of the second lens array <NUM> in the x-direction.

The lenses <NUM>, <NUM> of the first and second lens arrays <NUM>, <NUM> are shown in the figures as refractive lenses. There is, however, a possibility that other optical elements, such as diffractive elements, reflective elements or holographic elements, may be used as cylindrical lenses instead of refractive lenses. Alternatively, the lenses can also be gradient index lenses.

The diffuser device can be supplied with light from a laser light source or an LED light source. Examples of this are multi-mode laser light sources or small mode laser light sources with M<NUM> greater than about <NUM>. In the case of a single-mode laser light source, no continuous distribution occurs in the far field, but a large number of point intensity distributions.

<FIG> shows that the far field of the light emitted by the diffuser device exhibits comparatively strong cushion distortion.

In order to produce less distortion in the far field, two separate substrates <NUM>, <NUM> are provided for the embodiment according to <FIG>, which are separated from each other by an air gap <NUM>. The air gap <NUM> separates the substrates <NUM>, <NUM> in z-direction from each other.

In the embodiment according to <FIG>, a first lens array <NUM> is arranged on the entrance surface <NUM> of the first substrate <NUM>, which has lenses <NUM> designed as cylindrical lenses. Furthermore, a second lens array <NUM> is arranged on the entrance surface <NUM> of the second substrate <NUM> and has lenses <NUM> designed as cylindrical lenses.

The lenses <NUM>, <NUM> of the embodiment according to <FIG>can be designed like the lenses <NUM>, <NUM> of the embodiment according to <FIG>.

In particular, the lenses <NUM> of the first lens array have <NUM> cylindrical axes extending in the first direction x, wherein the lenses <NUM> of the second lens array have <NUM> cylindrical axes extending in the second direction y. The lenses <NUM> of the first lens array <NUM> are arranged next to each other in the second direction y (see <FIG>) and the lenses <NUM> of the second lens array <NUM> are arranged next to each other in the first direction x (see <FIG>).

Furthermore, the lenses <NUM> of the first lens array <NUM> have such a radius that the light passing through the first lens array <NUM> is expanded in the second direction y into a angular range <NUM> of about <NUM>°, for example (see the far field in <FIG>).

Furthermore, the lenses <NUM> of the second lens array <NUM> have such a radius that the light passing through the second lens array <NUM> is expanded in the first direction x into an angular range <NUM> of about <NUM>°, for example (see the far field in <FIG>). For example, the radius could be about <NUM>,<NUM>. In addition, the conical constant, which is a measure of the size of the aspheric formation of the lenses, can have a size of <NUM>.

<FIG> shows that the far field of the light emitted by the diffusion device according to <FIG> shows only a comparatively low cushion distortion, whereby the reduction of the cushion distortion is also caused by the use of two substrates for the lens arrays <NUM>, <NUM>.

In contrast to the embodiment according to <FIG>, the embodiment according to <FIG> provides, in addition to the two lens arrays <NUM>, <NUM>, a third lens array <NUM>, which is arranged on the exit surface <NUM> of the first substrate <NUM>. The third lens array <NUM>, like the first lens array <NUM>, has <NUM> convex lenses designed as cylindrical lenses.

It should be noted at this point that all lens arrays <NUM>, <NUM>, <NUM> can have either concave or convex lenses <NUM>, <NUM>, <NUM>.

<FIG> shows that the far field of the light emanating from the diffuser device according to <FIG> shows only a comparatively low ton distortion. In particular, the type and size of distortion can be influenced by selecting the appropriate distance between the substrates <NUM>, <NUM>.

It is possible that in addition to the first and third lens arrays <NUM>, <NUM> on the first substrate <NUM>, two lens arrays may also be provided on the second substrate <NUM>, namely the second lens array <NUM> shown on the entrance surface <NUM> and a fourth lens array not shown on the exit surface <NUM> of the second substrate <NUM>. Alternatively, two lens arrays may also be provided on the second substrate <NUM> and only one lens array on the first substrate <NUM>.

The third embodiment according to <FIG> is similar to the second embodiment according to <FIG>. However, in the third embodiment, the second lens array <NUM> with lenses <NUM> having such a radius that they expand the light passing through the second lens array <NUM> in the second direction y into an angular range <NUM> of, for example, approximately <NUM>° is provided on the entrance surface of the first substrate <NUM> left in the z-direction and in <FIG>, respectively.

Furthermore, in the third embodiment the first lens array <NUM> with lenses <NUM> is provided on the entrance surface <NUM> of the second substrate <NUM> and the third lens array <NUM> with lenses <NUM> is provided on the exit surface <NUM> of the second substrate <NUM>. Lenses <NUM>, <NUM> have such a radius that they expand the light passing through the first and third lens arrays <NUM>, <NUM> in the first direction x into an angular range <NUM> of about <NUM>°, for example.

Also for such an embodiment of the diffuser device, the choice of the distance between the substrates <NUM>, <NUM> together with the focal length or radius of the lenses <NUM> of the first lens array <NUM> and the focal length or radius of the lenses <NUM> of the third lens array <NUM> can influence the type and size of the distortion.

The fourth embodiment according to <FIG> is similar to the first embodiment according to <FIG>, but the fourth embodiment has a large cylindrical lens <NUM> on the exit surface of the second substrate <NUM> in the z-direction and <FIG> on the right, respectively. The large cylindrical lens <NUM> is designed as a concave cylindrical lens whose cylindrical axis extends in the second direction y like that of the lenses <NUM> of the second lens array <NUM>.

Instead of the large cylindrical lens <NUM>, a collimating lens array with small cylindrical lenses may also be used (not shown).

In the design shown in <FIG>, the large cylindrical lens <NUM> is integrated into the second substrate <NUM> or arranged on its exit surface <NUM>. However, it is also possible to provide a (not shown) third substrate on which the large cylindrical lens <NUM> is formed. This third substrate is then arranged in particular in the z-direction behind the second substrate <NUM> or in <FIG> to the right of the second substrate <NUM>.

The embodiment of a diffuser device shown in <FIG> comprises a transparent substrate having a first lens array <NUM> on an entrance face <NUM> and a third lens array <NUM> on an exit face <NUM> opposite the entrance face <NUM>. The lenses <NUM>, <NUM> of the lens arrays <NUM>, <NUM> are each designed as cylindrical lenses. The diffuser device comprises a collimator lens which is integrated into the entrance face <NUM> of the substrate.

The embodiment of a diffuser device shown in <FIG> comprises a transparent substrate having a first lens array <NUM> on an entrance face <NUM> The lenses <NUM> of the lens array <NUM> on the entrance surface <NUM> of the substrate are asymmetrically shaped wherein one common prism <NUM> is arranged on the entrance surface <NUM> of this substrate. In this case there is no offset between adjacent lenses <NUM>.

The embodiment of a diffuser device shown in <FIG> comprises a transparent substrate having a first lens array <NUM> on an entrance face <NUM> The lenses <NUM> of the lens array <NUM> on the entrance surface <NUM> of the substrate are asymmetrically shaped wherein one common prism <NUM> is arranged on the exit surface <NUM> of this substrate. In this case the lenses <NUM> have the same SAG values at the left and right lens aperture positions.

Claim 1:
Diffuser device comprising a first lens array (<NUM>) having a plurality of cylindrical lenses (<NUM>) and a second lens array (<NUM>) having a plurality of cylindrical lenses (<NUM>) through which light passes successively during operation of the diffuser device, wherein the lenses (<NUM>) of the first lens array (<NUM>) have cylinder axes extending in a first direction (x) and the lenses (<NUM>) of the second lens array (<NUM>) have cylinder axes extending in a second direction (y) perpendicular to the first direction (x), the diffuser device comprises a first transparent substrate (<NUM>) having an entrance surface (<NUM>) and an exit surface (<NUM>) and a second transparent substrate (<NUM>) having an entrance surface (<NUM>) and an exit surface (<NUM>), wherein the first lens array (<NUM>) is disposed on the first substrate (<NUM>) and the second lens array (<NUM>) is disposed on the second substrate (<NUM>), or wherein the second lens array (<NUM>) is disposed on the first substrate (<NUM>) and the first lens array (<NUM>) is disposed on the second substrate (<NUM>), and wherein the first substrate (<NUM>) and the second substrate (<NUM>) are spaced apart from one another, in particular an air gap (<NUM>) being arranged between the first substrate (<NUM>) and the second substrate (<NUM>), characterized in that the lenses (<NUM>) of the first lens array (<NUM>) and/or the lenses (<NUM>) of the second lens array (<NUM>) are aspherical, so that they deviate from the shape of a circular cylinder, wherein the lenses (<NUM>) of the second lens array (<NUM>) have a radius such that the light passing through the second lens array (<NUM>) is widened in the first direction (x) into an angular range (<NUM>) of more than <NUM>°.