LIGHTING DEVICE

Abstract

A lighting device (1600) is disclosed. The lighting device comprises an array of optical elements (1620) and at least one radiation-emitting element (1630) configured to produce a structured light pattern (815, 1115, 1415) in conjunction with the array. An optical phase delay of each optical element of the radiation emitted by the at least one radiation-emitting element is configured such that the structured light pattern has a regular array of points. A method for manufacturing the lighting device is also disclosed.

Description

FIELD OF THE INVENTION

[0001] The present disclosure relates to the field of illumination devices for use in depth mapping applications, and more particularly relates to an illumination device for generating structured light patterns, such as dot patterns. BACKGROUND

[0002] Depth mapping of a scene, also known as 3-dimensional (3D) mapping, is commonly used by electronic devices such as smartphones, tablet devices, game consoles, and laptops.

[0003] In some examples, depth mapping of a scene may be used for security purposes, for example, to enable access to a resource on an electronic device or to unlock the electronic device based on 3D facial recognition. In some examples, electronic devices may also include image capture devices such as cameras, where a depth map of a scene may be used to enhance the image capture capabilities of the image capture devices.

[0004] Several depth mapping techniques are known. For example, stereo cameras can be used to determine a depth map of a scene based on differences between images captured by multiple cameras. Some depth mapping techniques may involve the illumination of a scene, where the properties of the illumination can be used to determine a depth map of the scene.

[0005] In some examples, structured light, e.g., a light pattern, may be used. Structured light may be projected onto a scene, and a pattern created in the scene by the projected structured light allows for distinguishing features of the scene depending on their distance from the structured light-emitting device. That is, an image of the structured light as projected onto a scene may be compared to a reference pattern, and disparities between the image and the reference pattern may be used to determine a depth map of the scene.

[0006] It is known that for a lighting device comprising a microlens array (MLA) with microlenses regularly arranged with a microlens pitch “d” and a plurality of radiation-emitting elements arranged on a common plane at a distance “d vm“ from the MLA, each radiation-emitting element being arranged to emit radiation with the wavelength “λ”, a particularly high-contrast structured light pattern can be achieved if: dVM=Nd22λ and where N is a positive integer.

[0007] The particularly high-contrast structured light pattern can be a regular dot pattern in which the dots are arranged at a defined distance and a defined size. However, to achieve such a high-contrast structured light pattern, the relationship between λ, d, d defined by Equation 1 must be maintained. vmand N must be maintained, which places physical limits on the design of such an illumination device. Furthermore, a relationship between the spacing and the size of the dots in the generated regular dot pattern is established, whereby a specific selection of the integer N can be used to select a spacing and thus also a corresponding dot size. Thus, an illumination device for generating a regular dot pattern designed with feature dimensions according to Equation 1 has a fixed relationship between dot sizes and dot spacing. Such a fixed relationship between dot size and dot spacing can limit the degrees of freedom in selecting the regular dot pattern.It is therefore desirable to provide an illumination device capable of generating structured light patterns suitable for use in depth mapping applications, the illumination device being capable of generating a high contrast pattern without being limited to meeting the requirements of Equation 1.

[0008] Furthermore, it is desirable that the pitch and spot size of a dot pattern generated with such an illumination device is not limited by a specific ratio between the pitch and the spot size.

[0009] Furthermore, it is also desirable that such a lighting device be suitable for use in electronic devices such as smartphones, smartwatches, tablet devices, game consoles and laptops, wherein the lighting device does not significantly increase the cost, complexity and / or size of the electronic devices.

[0010] It is therefore an object of at least one embodiment of at least one aspect of the present disclosure to eliminate or at least mitigate at least one of the above-mentioned deficiencies of the prior art. SUMMARY

[0011] The present disclosure relates to the field of illumination devices for use in depth mapping applications and methods for fabricating such illumination devices. More particularly, the present disclosure relates to an illumination device for generating structured light patterns, such as dot patterns.

[0012] According to a first aspect of the disclosure, a lighting device is provided, comprising: an array of optical elements; and at least one radiation-emitting element configured—in cooperation with the array—to generate a structured light pattern. An optical phase delay of each optical element of the radiation emitted by the at least one radiation-emitting element is configured such that the structured light pattern comprises a regular array of points.

[0013] Advantageously, by adjusting the optical phase retardation of each optical element, a high-contrast dot pattern can be generated wherein the dimensions of the illumination device do not follow the requirements of Equation 1. That is, by adjusting the optical phase retardation of each optical element, e.g., each individual optical element or a subset of optical elements, a relatively high-contrast dot pattern can be generated wherein a distance "D" between the at least one radiation-emitting element and the array of optical elements is not defined by Equation 1. Furthermore, a distance and a dot size of the pattern are not defined by a relationship that occurs when the distance "D" is defined by Equation 1, e.g., a high-contrast or "HC plane," as described in more detail below.

[0014] The array of optical elements may comprise a plurality of optical elements with different optical phase delays.

[0015] That is, each optical element or subset of optical elements can be configured to have different optical phase retardation properties, such that the array of optical elements comprises optical elements with different optical phase retardation properties. That is, in embodiments, the array of optical elements is not an array of optical elements all configured to have the same optical phase retardation properties.

[0016] Each optical element can have a microlens.

[0017] The array of optical elements can be a microlens array (MLA).

[0018] The optical phase retardation of each microlens may be defined at least in part by the thickness of the base portion of each microlens.

[0019] Advantageously, a microlens array can be manufactured in which different microlenses of the array have different optical phase retardation properties based on the thickness of the base portion of each microlens. Advantageously, no additional components or materials are required to realize such a microlens array, compared to a prior art microlens array having a uniform distribution of identical microlenses.

[0020] The optical phase retardation of each microlens can be defined at least in part by the refractive index of each microlens.

[0021] Each microlens can be made of a material with a refractive index chosen to achieve the desired optical phase retardation.

[0022] The optical phase retardation of each microlens may be defined at least in part by the refractive index of a portion of the substrate on which each microlens is provided.

[0023] The optical phase retardation of each microlens can be defined, at least in part, by features such as materials, shapes, and dimensions, which can be chosen to impose a desired, localized phase retardation. For example, a substrate can be patterned with materials having different refractive indices, and an MLA can be formed over the pattern, forming an MLA in which different lenses have different optical phase retardation properties.

[0024] Each optical element can have a meta-lens.

[0025] The optical phase retardation of each meta-lens can be defined by the dimensions of one or more columns forming each meta-lens.

[0026] The optical phase retardation of each meta-lens can be defined by a relative rotation and / or shape of one or more mesas or fin-like structures forming each meta-lens.

[0027] The advantage is that no additional materials, such as materials with different refractive indices, are required to realize lenses with different optical phase retardation properties.

[0028] The array can be arranged at a first distance (d VM1) from the at least one radiation-emitting element, and wherein the optical phase delay of each optical element can be arranged such that the structured light pattern comprises a regular array of spots with a pitch and / or spot size that would be provided by a further illumination device, comprising: a further array of identical optical elements arranged at the same pitch (d) as the array of optical elements; wherein the further array of identical optical elements is arranged at a second pitch (d VM2 ) from a further at least one radiation-emitting element is arranged to emit radiation having the same wavelength (λ) as the radiation from the at least one radiation-emitting element, wherein the second distance (d VM2 ) from the first distance (d VM2) and wherein the further lighting device follows a first formula: DVM2=Nd22λ where N is an integer.

[0029] The first distance (d VM1 ) can follow a second formula: DVM1=Md22λ where M is an integer different from the integer N.

[0030] The first distance (d VM1 ) can be larger than the second distance (d VM2 ).

[0031] An optical phase delay of each optical element may correspond to a difference between: first optical path differences (OPD) with respect to an optical axis for each optical element of an array of optical elements at the first distance (d VM1 ) from the radiation-emitting illumination device; and second optical path differences (OPD2) with respect to the optical axis for each optical element of the array of optical elements at the second distance dVM2 from the radiation-emitting illumination device, wherein the second distance follows the second formula.

[0032] The at least one radiation-emitting element may comprise an array of surface emitters (vertical cavity surface emitting lasers, VCSELs). According to a second aspect of the disclosure, a method for manufacturing a lighting device is provided, the method comprising: establishing an optical phase delay of each optical element of an array of optical elements and arranging the array at a first distance (D VM1 ) of at least one radiation-emitting element, so that the at least one radiation-emitting element is arranged to generate, in cooperation with the array, a structured light pattern having a regular array of points.

[0033] Establishing an optical phase delay of each optical element may comprise: calculating first optical path differences (OPD1) with respect to an optical axis for each optical element of an array of optical elements at the first distance (d VM1 ) from the radiation-emitting illumination device; calculating second optical path differences (OPD2) with respect to the optical axis for each optical element of the array of optical elements at a second distance d vm2 from the radiation-emitting illumination device, wherein the second distance follows a first formula: DVM2=Nd22λ

[0034] Calculating the third optical path differences (ΔOPD) between the first and second optical path differences; and converting the third optical path differences (ΔOPD) into an optical phase delay of each optical element.

[0035] When each optical element comprises a microlens, converting the third optical path differences (ΔOPD) into the optical phase retardation of each optical element may comprise increasing the thickness of a base portion of each microlens.

[0036] If each optical element comprises a microlens, converting the third optical path difference (ΔOPD) into the optical phase retardation of each optical element may comprise selecting a refractive index of each microlens.

[0037] When each optical element comprises a microlens, converting the third optical path differences (ΔOPD) into the optical phase retardation of each optical element may comprise selecting a refractive index of a portion of a substrate on which each microlens is provided.

[0038] If each optical element comprises a meta-lens, converting the third optical path differences (ΔOPD) into the optical phase retardation of each optical element may comprise selecting the dimensions of one or more columns forming each meta-lens.

[0039] The optical phase delay of each optical element may be arranged such that a pitch and / or a spot size of the regular array of spots corresponds to a pitch and / or a spot size of an array of spots that would be generated by a further illumination device, comprising: a further array of identical optical elements arranged at the same pitch (d) as the array of optical elements; wherein the further array of identical optical elements is arranged at the second pitch (d vm2) from a further at least one radiation-emitting element is arranged to emit radiation having the same wavelength (λ) as the radiation from the at least one radiation-emitting element, wherein the second distance (d vm2 ) from the first distance (d vm1 ), and wherein the further lighting device follows the second formula.

[0040] The above summary is intended to be exemplary and not limiting. The disclosure includes one or more corresponding aspects, embodiments, or features in isolation or in various combinations, whether or not specifically recited (including claimed) in that combination or in isolation. It is to be understood that features defined above in accordance with any aspect of the present disclosure or below with respect to a particular embodiment of the disclosure may be used, either alone or in combination with another defined feature, in another aspect or embodiment, or to form another aspect or embodiment of the disclosure. SHORT DESCRIPTION OF THE DRAWINGS:

[0041] These and other aspects of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings in which: Fig. 1 shows a configuration of radiation-emitting elements and a microlens array and a resulting structured light pattern, illustrating a functional principle of prior art lighting devices; Fig. Figure 2 shows several structured light patterns comprising arrays of points corresponding to different HC levels and representing a further example of the operating principle of prior art lighting devices; Fig. Figure 3 is a diagram illustrating the relationship between the number of dots and the size of the dots of a structured light pattern produced with prior art lighting devices; Fig. Figure 4 shows a representation of the optical path differences for a configuration consisting of a radiation-emitting element and a microlens array; Fig. Figure 5 shows a further illustration of the optical path differences for configurations of radiation-emitting elements and microlens arrays arranged on different HC levels; Fig. 6 is an example of a step of calculating an optical path difference in a first method of designing a lighting device according to an embodiment of the disclosure; Fig. 7 a further step in the first procedure of Fig. 6 shows a method for designing a lighting device according to the disclosure; Fig. 8 shows a structured light pattern produced by a lighting device arranged according to the method described in Fig. 6 and Fig. 7; Fig. 9 shows an example of a step for calculating an optical path difference in a second method for designing a lighting device according to another embodiment of the disclosure; Fig. 10 a further step in the second procedure of Fig. 9 shows a method for designing a lighting device according to another embodiment of the disclosure; Fig. 11 shows a resulting structured light pattern of a lighting device produced according to the method described in Fig. 9 and Fig. 10; Fig. 12 shows an example of a step for calculating an optical path difference in a third method for designing a lighting device according to another embodiment of the disclosure; Fig. 13 a further step in the third procedure of the Fig. 12 shows a method for designing a lighting device according to another embodiment of the disclosure; Fig. 14 shows a structured light pattern resulting from a lighting device arranged according to the method described in the Fig. 12 and Fig. 13; Fig. 15 shows cross-sections of arrays of optical elements, wherein an optical phase retardation of each optical element is configured according to an embodiment of the disclosure; and Fig. 16 shows an example of a lighting device according to an embodiment of the disclosure. DETAILED DESCRIPTION OF THE DRAWINGS

[0042] Fig. 1 shows a configuration of radiation-emitting elements 105, 110 and a microlens array 115 as well as a resulting structured light pattern, which illustrates a functional principle of prior art lighting devices.

[0043] A first radiation-emitting element 105 emits radiation that impinges on the microlens array 115 to generate a dot pattern 120. That is, a single first radiation-emitting element 105 generates the entire Fig. 1 dot pattern shown 120.

[0044] A second radiation-emitting element 110 also emits radiation, which impinges on the microlens array 115. The second radiation-emitting element 110 is separated from the first radiation-emitting element 110 by a distance "d." The microlenses of the microlens array 115 are also separated by the distance "d."

[0045] That is, the spacing of the microlens array 115 corresponds to the spacing of the radiation-emitting elements 105, 110.

[0046] A distance d vm between the radiation-emitting elements 105, 110 and the microlens array 115 is defined by equation 1, where N is an integer and λ is a wavelength of the radiation emitted by the radiation-emitting elements 105, 110.

[0047] In the example, if an angle between the second radiation-emitting element 110 and an optical axis 'z' of the microlens of the microlens array 115 in front of the second radiation-emitting element 110 is equal to a diffraction angle of the microlens array 115, a second dot pattern is generated that exactly overlaps the first dot pattern 120. Thus, a plurality of radiation-emitting elements separated by a distance corresponding to the spacing of a microlens array and located at a distance from the MLA defined by Equation 1 can be used to generate a high-contrast dot pattern.

[0048] This means that in the example of Fig. 1 the radiation from each radiation-emitting element 105, 110 impinges on each lens of the microlens array with substantially the same phase, so that the radiation from the lenses interferes constructively to produce the high-contrast dot pattern. A precise arrangement of the distance d vm between the radiation-emitting elements 105, 110 and the microlens array 115 relative to the distance d of the microlens array 115 and the radiation-emitting elements 105, 110 is required to ensure that constructive interference takes place to produce the required high-contrast dot pattern.

[0049] Fig. Figure 1 also shows a depth profile of the microlens array 115, wherein the microlens array comprises lenses arranged at a submillimeter pitch. For illustrative purposes, the depth has been normalized to a range of 0 to 1, and the dimensions of the square-pitch microlens array are between "+A" and "-A" millimeters in the x and y directions.

[0050] As described above, the distance d vm partially defined by the integer N. Each instance of N corresponds to a plane and can be referred to as a high-contrast plane or “HC plane.” That is, a plane with a distance of 1xd vm can be called the “HC1 plane”, a plane with a distance of 2xd vm as “HC2 level”, and so on.

[0051] It is known that the dot size and dot pitch of the generated dot pattern depend on N, e.g. on the respective HC level.

[0052] In Fig. 2, for example, several structured light patterns are shown which have arrays of points corresponding to different HC levels, which is another example of the operating principle of prior art lighting devices.

[0053] The examples in Fig. 2 correspond to a central portion of a dot pattern projected by a square-pattern microlens array at a distance of one meter.

[0054] A first structured light pattern 205 comprises a regular array of points. In this example, the gap between the microlens array and the array of radiation-emitting elements is approximately 1.3 millimeters and corresponds to the HC1 plane. The first structured light pattern 205 can therefore be referred to as an HC1 pattern.

[0055] A second structured light pattern 210 has a regular array of dots. In this example, the gap between the microlens array and the array of radiation-emitting elements is approximately 2.7 millimeters and corresponds to the HC2 plane. The second structured light pattern 210 can therefore be referred to as an HC2 pattern. The dots of the HC2 pattern are smaller than the dots of the HC1 pattern.

[0056] A third structured light pattern 210 has a regular array of points. In this example, the gap between the microlens array and the array of radiation-emitting elements is approximately 5.3 millimeters and corresponds to the HC4 plane. The third structured light pattern 215 can therefore be referred to as an HC4 pattern. The points of the HC4 patterns are smaller and arranged at a finer pitch than the points of the HC1 and HC2 patterns.

[0057] This means that the different dot sizes and spacing in the examples of Fig. 2 are due to the distances between the emitter and the microlens array, where in each example the distance between the emitter and the microlens array follows equation 1. This principle is explained with reference to Fig. 3 is explained in more detail.

[0058] Fig. Figure 3 shows a diagram illustrating the relationship between the number of dots and the size of the dots of a structured light pattern produced with prior art lighting devices.

[0059] In the example, the graph shows an approximate spot diameter as a function of the number of spots within a specific field of view (FOV), which in the example shown is approximately 60° x 50°. It goes without saying that the data presented in the graph is for illustrative purposes only.

[0060] Each point in the diagram represents a different combination of microlens array spacing and HC plane, e.g. a different distance d vm It can be seen that a size of the points is approximately inversely proportional to a number of points within a given FOV.

[0061] The diagram also shows that for square microlens arrays, the HC2 plane provides the smallest spot diameter for a given number of points within the FOV.

[0062] It can be seen that structured light patterns with combinations of point number and point size, represented by the shaded area 305, cannot be achieved for lighting devices that follow Equation 1. Fig. 4 shows a representation of the optical path differences (OPD) for a configuration consisting of a radiation-emitting element 405 and a microlens array 410.

[0063] The radiation-emitting element 405 is located at a distance d vm from the microlens array 410 and emits radiation directly toward the microlens array 410 along the "z" axis. A distance between the radiation-emitting element 405 and each lens of the microlens array 410 can be calculated and expressed as OPD compared to the distance d vm on the axis. The OPD is expressed as a modulo of the wavelength λ. Thus, 0 and 1 mean the same phase. An example of the OPD of an HC1 plane is also shown in Fig. 4 shown.

[0064] The various HCN planes exhibit OPD patterns, so that constructive interference occurs at the output of the microlens array, forming dots in specific directions or angles. These OPD patterns are different in each HC plane. The respective OPD pattern determines the number of dots in the dot pattern. The pattern is closely related to the vmThis phenomenon is described in Fig. 5, which shows OPD representations for configurations of radiation-emitting elements and microlens arrays arranged in different HC planes. For example, a first OPD representation 505 corresponds to an HC1 plane, e.g., N=1, a second OPD representation 510 corresponds to an HC2 plane, and a third OPD representation 515 corresponds to an HC4 plane.

[0065] As described in more detail below, embodiments of the disclosure relate to modifying the microlens array such that, for any selected distance between the emitter and the microlens array, the radiation emitted by the at least one radiation-emitting element toward the microlens array undergoes an OPD that produces a desired number of spots and / or spots at a desired spacing.

[0066] Fig. 6 shows an example of a step for calculating an OPD in a method for designing a lighting device according to an embodiment of the disclosure.

[0067] For example, a lighting device with a microlens array located at a distance d vm , hereinafter referred to as the first distance d VM1 denoted, of at least one radiation-emitting illumination device and is arranged such that equation 1 is followed, may be arranged such that normally an HC2 pattern is generated, e.g. N=2, thereby forming a first structured light pattern 205. For such an illumination device, a first OPD 605 may be calculated. However, it may be desirable for a pattern having a number of points that generally correspond to an HC4 pattern, e.g. a third structured light pattern 215, to be generated without the first distance d VM1to change. A second OPD 610 can be calculated, wherein the second OPD 610 corresponds to a desired HC4 plane, e.g., an OPD when the distance is set to a second distance d vm2 should be increased so that N=4.

[0068] A difference between the first OPD 605 and the second OPD 610 can be calculated to generate a third OPD 615. The third optical path difference 615 can be converted into an optical phase delay for each optical element, as described in more detail below. The method of Fig. 6 is in Fig. 7, which illustrates a method for designing the illumination device, is explained in more detail. A profile 705 of a microlens array is shown, with the microlens array illustrating lenses with a pitch of less than one millimeter. For the purposes of the example, the depth was normalized to a range from 0 to 1.

[0069] Also shown is a first dot pattern 710 that the microlens array can produce when it is at the first distance d VM1 of at least one radiation-emitting element, which in this example is approximately 2.7 millimeters. The first dot pattern 710 is an HC2 pattern.

[0070] The third OPD 615 can be converted into an optical phase delay for each optical element of the microlens array. In the example of the Fig. 7, the optical phase retardation is realized by increasing the thickness of each element of the microlens array in accordance with the third OPD 615. In one example, additional material may be added to each optical element of the microlens array by altering a base layer of the individual lenses. In other examples, the optical phase retardation of each optical element of the microlens array may be altered by adjusting the refractive index of the substrate on which the microlens array is formed. A material thickness 715 to be added to each optical element is depicted. By adding the material thickness 715 to the design of each element of the microlens array with the initial profile 705, a microlens array can be provided that creates a second dot pattern 720 while being at the first distance d VM1 of which at least one radiation-emitting element remains.

[0071] The second dot pattern 720 has dots that are substantially the same size as the dots of the first dot pattern 710, but with a spacing corresponding to the spacing of an HC4 pattern. Therefore, the second dot pattern 720 has four times the number of dots as the first dot pattern 710.

[0072] That is, starting from an initial design for an illumination device that would produce an HC2 pattern, an optical phase retardation of each lens of the microlens array was adjusted by adding additional material to each optical element of the microlens such that, in a resulting design for the illumination device, the illumination device is configured to produce a dot pattern with a pitch corresponding to an HC4 pattern. The distance between the microlens array and at least one radiation-emitting element is the same in the original design and the resulting design.

[0073] Fig. Figure 8 shows a resulting structured light pattern of a lighting device which is designed according to the Fig. 6 and Fig. 7. The HC2 pattern 805 of the original design is shown, which in the example is at a first distance d VM1 of 2.7 millimeters between the microlens array and the at least one radiation-emitting element. Also shown is an HC4 pattern 810 that would result if the first distance were increased to a second distance dvm2 of 5.3 millimeters, wherein the HC4 pattern has smaller dots arranged at a finer pitch.

[0074] Finally, a third pattern 815 is shown, which is generated by the resulting illumination device after the optical phase delay of each element of the MLA has been adjusted as described above. The third pattern 815 has dots that are substantially the same size as the dots of the first dot pattern 810, since the dot diameter varies with the first distance d vm1that has not been changed. The third pattern 815 has points arranged at a distance corresponding to the distance of the HC4 pattern 810.

[0075] Advantageously, the above-described adjustment of the optical phase delay enables a cost-effective illumination device configured to generate the third pattern 815. Alternative means for generating such a pattern may require the implementation of four sections of radiation-emitting elements or the division of the MLA into four relatively shifted sections, which incurs costs and increases complexity.

[0076] Fig. 9 shows an example of a step for calculating an OPD in another method for designing a lighting device according to another embodiment of the disclosure.

[0077] For example, an illumination device with a microlens array at a distance of 2 millimeters from at least one radiation-emitting illumination device. It is clear that the distance of 2 millimeters was chosen as an example, and other distances can be selected. In particular, the distance of 2 millimeters does not correspond to an HC plane, ie, it is not a distance d vm according to equation 1. For such a lighting device, a first OPD 905 can be calculated.

[0078] However, it may be desirable to generate a point pattern that generally corresponds to an HC2 pattern, e.g., a second structured light pattern 210, without changing the 2-millimeter spacing. A second OPD 910 may be calculated, wherein the second OPD 910 corresponds to a desired HC2 plane, e.g., an OPD when the spacing is set to a second distance d vm2should be changed so that N=2.

[0079] A difference between the first OPD 905 and the second OPD 910 can be calculated to obtain a third OPD 915. The third optical path difference 915 can be converted into an optical phase delay of each optical element, as described in more detail below. The method of Fig. 9 is in Fig. 10, which illustrates a method for designing the illumination device. Shown is a profile 1005 of a microlens array, wherein the microlens array, for example, comprises lenses arranged at a submillimeter depth. For the purposes of the example, the depth has been normalized to a range from 0 to 1. Also shown is a first pattern 1010 that the microlens array can produce when arranged at a distance from a radiation-emitting element, which in the described example is 2 millimeters.

[0080] The third OPD 915 can be converted into an optical phase delay for each optical element of the microlens array. In the example of the Fig. 10, the optical phase retardation is realized by increasing the thickness of each element of the microlens array in accordance with the third OPD 915. In one example, additional material may be added to each optical element of the microlens array by altering a base layer of the individual lenses. In other examples, the optical phase retardation of each optical element of the microlens array may be altered by adjusting a refractive index of the substrate on which the microlens array is formed. A material thickness 1015 added to each optical element is illustrated. By adding the material thickness 1015 to the design of each element of the microlens array with the original profile 705, a microlens array can be provided that creates a dot pattern 1020 while remaining at a distance of 2 millimeters from the radiation-emitting element.

[0081] The second dot pattern 720 has dots with a spacing corresponding to the spacing of an HC2 pattern.

[0082] That is, starting from an initial design for an illumination device that would not produce a dot pattern, the optical phase retardation of each lens of the microlens array was adjusted by adding additional material to each optical element of the microlens such that, in a resulting design for the illumination device, the illumination device is configured to produce a dot pattern with a pitch corresponding to an HC2 pattern. The distance between the microlens array and the radiation-emitting element is the same in the original design and the resulting design.

[0083] Fig. Figure 11 shows a structured light pattern resulting from a lighting device arranged according to the method described in Fig. 9 and Fig. 10 presented first procedure was designed.

[0084] Shown is the pattern 1105 of the original design, which in the example is based on a distance of 2 millimeters between the microlens array and the radiation-emitting element. An HC2 pattern 1110, which would result if the distance were increased to a distance dvm2 of approximately 2.7 millimeters, is also shown. Finally, a third pattern 1115 is shown, the third pattern 1115 being generated by the resulting illumination device after the optical phase retardation of each element of the MLA has been adjusted as described above. The third pattern 1115 has dots arranged at a distance corresponding to the distance of the HC2 pattern 1110. The dots of the third pattern 1115 are slightly larger than the dots of the HC2 pattern 1110 because the dot diameter is linked to the 2-millimeter distance, which was not changed.

[0085] The example of Fig. 9 to 11 apply to a lighting device featuring a single radiation-emitting element. In embodiments of the lighting device having a plurality of radiation-emitting elements, a central portion 920 of the third OPD 915 may be arranged periodically.

[0086] Advantageously, the above-described adjustment of the optical phase delay enables a cost-effective illumination device which is configured such that the dot pattern 1020 can be generated with any distance between the at least one radiation-emitting element and the microlens array. Fig. 12 shows an example of a step for calculating an OPD in another method for designing a lighting device according to another embodiment of the disclosure.

[0087] For example, an illumination device with a microlens array with a pitch d vm , hereinafter referred to as the first distance d VM1 denoted, by at least one radiation-emitting illumination device and arranged to follow equation 1, arranged to normally generate an HC4 pattern, e.g., N=4, thereby generating a first structured light pattern 205. For such an illumination device, a first OPD 1205 may be calculated. However, it may be desirable to generate a pattern that generally corresponds to an HC2 pattern, e.g., a second structured light pattern 210, without changing the first distance d VM1 to change. A second OPD 1210 may be calculated, wherein the second OPD 1210 corresponds to a desired HC2 plane, e.g., an OPD when the distance is set to a second distance d vm2 should be increased so that N=2.

[0088] A difference between the first OPD 1205 and the second OPD 1210 can be calculated to obtain a third OPD 1215. The third optical path difference 1215 can be converted into an optical phase delay of each optical element, as described in more detail below.

[0089] The procedure from Fig. 12 will be in Fig. 13, which illustrates a method for designing the illumination device. Shown is a profile 1305 of a microlens array, wherein the microlens array comprises, by way of example, lenses with a pitch in the submillimeter range. For the purposes of the example, the depth has been normalized to a range from 0 to 1. Also shown is a first dot pattern 1310 that the microlens array can generate when positioned at the first pitch d VM1of at least one radiation-emitting element, which in the example is approximately 5.3 millimeters. The first dot pattern 1310 is an HC4 pattern.

[0090] The third OPD 1215 can be converted into an optical phase delay for each optical element of the microlens array. In the example of the Fig. 13, the optical phase retardation is realized by increasing the thickness of each element of the microlens array in accordance with the third OPD 1315. In one example, additional material may be added to each optical element of the microlens array by altering a base layer of the individual lenses. In other examples, the optical phase retardation of each optical element of the microlens array may be altered by adjusting a refractive index of the substrate on which the microlens array is formed. A material thickness 1315 added to each optical element is illustrated. By adding the material thickness 1315 to the design of each element of the microlens array with the initial profile 1305, a microlens array can be provided that creates a second dot pattern 1320 while being at the first distance d vm1 of which at least one radiation-emitting element remains.

[0091] The second dot pattern 1320 has dots that are substantially the same size as the dots of the first dot pattern 1310, but with a spacing corresponding to the spacing of an HC2 pattern. Therefore, the second dot pattern 1320 has one-quarter the number of dots of the first dot pattern 1310.

[0092] That is, starting from an initial design for an illumination device that would produce an HC4 pattern, an optical phase retardation of each lens of the microlens array was adjusted by adding additional material to each optical element of the microlens such that, in a resulting design for the illumination device, the illumination device is configured to produce a dot pattern with a pitch corresponding to an HC2 pattern. The distance between the microlens array and at least one radiation-emitting element is the same in the original design and the resulting design.

[0093] Fig. Figure 14 shows a structured light pattern resulting from a lighting device arranged according to the method described in Fig. 12 and Fig. 13 presented first procedure was designed.

[0094] Shown is the HC4 pattern 1405 of the original design, which in the example is placed at a first distance d vm1 of approximately 5.3 millimeters between the microlens array and the at least one radiation-emitting element. An HC2 pattern 1410 that would be generated if the first distance were reduced to a second distance dvm2 of approximately 2.6 millimeters is also shown, wherein the HC2 pattern includes smaller dots arranged at a finer pitch.

[0095] Finally, a third pattern 1415 is shown, which is generated by the resulting illumination device after the optical phase delay of each element of the MLA has been adjusted as described above. The third pattern 1415 has dots that are substantially the same size as the dots of the first dot pattern 1410, since the dot diameter varies with the first distance d VM1that has not been changed. The third pattern 1415 has points arranged at a distance corresponding to the distance of the HC2 pattern 1410.

[0096] Fig. 15 shows cross-sections of arrays of optical elements wherein an optical phase retardation of each optical element is configured according to an embodiment of the disclosure.

[0097] In a first example, a first array of optical elements 1505 is a microlens array comprising a plurality of microlenses. For illustrative purposes only, the first array of optical elements 1505 is depicted as having seven microlenses in cross-section, although it is understood that in practical implementations, a microlens array may have more or fewer than seven microlenses in cross-section. The first array of optical elements 1505 includes a substrate 1510. Each optical element is formed on the substrate 1510, and each optical element includes a base portion 1520 and a lens portion 1525. It will be appreciated that the base portion 1520 of each optical element may differ in thickness from other base portions 1520 of other optical elements formed on the substrate 1510.

[0098] Thus, the optical phase retardation of each microlens can be selected by selecting the thickness of the respective base portion 1520. With reference to the embodiments described above, by adding a specific material thickness to the base portion of each optical element of a microlens array, a microlens array can be provided that effectively creates a desired OPD relative to at least one radiation-emitting element.

[0099] In a second example, a second array of optical elements 1530 is a microlens array comprising a plurality of microlenses. Again, for illustrative purposes only, the second array of optical elements 1530 is shown as having seven microlenses in cross-section, although it is understood that in practical implementations, a microlens array may have more or fewer than seven microlenses in cross-section. The second array of optical elements 1530 includes a substrate 1535. Each optical element is formed on the substrate 1535, and each optical element includes a base portion 1540 and a lens portion 1545. Each optical element is formed over a respective portion 1550 of the substrate, wherein a refractive index of the respective portion 1550 of the substrate on which each microlens is provided can be selected to define the optical phase retardation of each optical element.Each respective section may be deposited as a layer, e.g., as a thin film, on the substrate 1535 or formed in another manner.

[0100] In a third example, a third array of optical elements 1560 is a microlens array comprising a plurality of microlenses. In this example, each optical element is formed from a material having a refractive index selected to define the optical phase retardation of each optical element. That is, different lenses in the third array may be formed from different materials, with the different materials having different refractive indices.

[0101] Moreover, in further embodiments, the techniques in any or all of the first, second, and / or third examples may be combined.

[0102] In a fourth example, a fourth array of optical elements 1590 is an array of metalenses 1595a-e. For illustrative purposes only, the fourth array of optical elements 1590 is depicted as having five metalenses in cross-section, although it is understood that in practical implementations, an array of metalenses may have more or fewer than five metalenses in cross-section.

[0103] In the fourth example, the optical phase retardation of each metalens is defined by the dimensions and / or shape and / or orientation of one or more columns, fins, mesas, or fin-like columns that form each metalens. For cylindrical columns, the optical phase retardation of each metalens can be defined, for example, by the dimensions, such as the diameter of each column.

[0104] For fin-like columns, the optical phase retardation of each meta-lens can be defined by a relative rotation of the columns. In general, the characteristics of each meta-lens can be selected to achieve a desired phase retardation.

[0105] Fig. 16 shows an example of a lighting device 1600 for illumination according to an embodiment of the disclosure. The example lighting device 1600 includes a first substrate 1605. The substrate 1605 may be, for example, a printed circuit board (PCB) or a silicon substrate.

[0106] The lighting device 1600 also includes a spacer 1610. The spacer 1610 is mounted on the first substrate 1605. The spacer 1610 holds a second substrate 1615 at a specific distance from the first substrate 1605. The second substrate can be, for example, a glass substrate. The second substrate 1615 is transparent to the wavelengths of the radiation emitted by the plurality of radiation-emitting elements 1630.

[0107] An array of optical elements 1620 is located on the second substrate 1615. The array of optical elements 1620 may, for example, be a microlens array 1620. In other examples, the array of optical elements 1620 may be a metalens array. The array of optical elements 1620 may be formed, for example, by a replication process, nanoimprinting, or by otherwise applying or gluing the array 1620 to the second substrate 1615.

[0108] A third substrate 1625 is mounted on the first substrate 1605. A plurality of radiation-emitting elements 1630 are formed on the third substrate 1625. In some embodiments, the plurality of radiation-emitting elements 1630 are VCSELs. The plurality of radiation-emitting elements 1630 can be arranged as a regular array of radiation-emitting elements 1630, e.g., in a grid pattern.

[0109] The plurality of radiation-emitting elements 1630 are configured to generate a structured light pattern in cooperation with the array of optical elements 1620. An optical phase delay of each optical element 1620 of the radiation emitted by the plurality of radiation-emitting elements 1630 is configured such that the structured light pattern comprises a regular array of points.

[0110] Although the disclosure has been described in terms of preferred embodiments as set forth above, it is to be understood that these embodiments are illustrative only, and that the claims are not limited to these embodiments. Those skilled in the art may, in light of the disclosure, make modifications and alternatives that fall within the scope of the appended claims. Any feature disclosed or illustrated in the present description may be incorporated into any embodiment, either alone or in a suitable combination with any other feature disclosed or illustrated herein. LIST OF REFERENCE SYMBOLS 105 first radiation-emitting element 110 second radiation-emitting element 115 microlens array 205 first structured light pattern 210 second structured light pattern 215 third structured light pattern 305 shaded area 405 radiation-emitting element 410 microlens array 505 first OPD representation 510 second OPD display 515 third OPD representation 605 first OPD 610 second OPD 615 third OPD 705 initial profile 710 first dot pattern 715 thickness 720 second dot pattern 805 HC2 pattern 810 HC4 pattern 815 third pattern 905 first OPD 910 second OPD 915 third OPD 920 central section 1005 Profile 1010 first pattern 1015 Thickness 50 1020 dot pattern 1105 patterns 1110 HC2 pattern 1115 third pattern 1205 first OPD 1210 second OPD 1215 third OPD 1305 Profile 1310 first dot pattern 1320 second dot pattern 1315 third OPD 1405 HC4 pattern 1410 HC2 pattern 1415 third pattern 1505 optical elements 1510 Substrat 1520 base section 1525 lens section 1530 optical elements 1535 Substrat 1540 base section 1545 lens section 1550 corresponding section 1560 optical elements 1590 optical elements 1595a Meta lens 1595b Meta-Lens 1595c Meta lens 1595d Meta lens 1595a Meta lens 1595e Meta lens 1595f Meta lens 1600 lighting device 1605 first substrate 1610 spacers 1615 second substrate 1620 optical elements 1625 third substrate 1630 radiation-emitting elements

Claims

[1] Lighting device (1600) comprising: an array of optical elements (1620); at least one radiation-emitting element (1630) configured to generate a structured light pattern (815, 1115, 1415) in cooperation with the array; wherein an optical phase delay of each optical element of the radiation emitted by the at least one radiation-emitting element is arranged such that the structured light pattern comprises a regular array of points. [2] The lighting device (1600) of claim 1, wherein the array of optical elements (1620) comprises a plurality of optical elements having a different optical phase delay from one another. [3] The lighting device (1600) of claim 1 or 2, wherein each optical element comprises a microlens. [4] Lighting device (1600) according to claim 3, wherein the optical phase retardation of each microlens is defined at least in part by: a thickness of a base portion of each microlens; a refractive index of each microlens; and / or a refractive index of a portion of a substrate on which each microlens is provided. [5] The lighting device (1600) of claim 1 or 2, wherein each optical element comprises a meta-lens. [6] The illumination device (1600) of claim 5, wherein the optical phase delay of each meta-lens is defined by at least one of the following features: Dimensions of one or more columns forming each meta-lens; and / or a relative rotation and / or shape of one or more mesas or fin-like structures forming each meta-lens. [7] Lighting device (1600) according to one of claims 1 to 6, wherein the array is arranged at a first distance (d VM1) of the at least one radiation-emitting element (1630) and wherein the optical phase delay of each optical element is arranged such that the structured light pattern (815, 1115, 1415) comprises a regular array of points with a spacing and / or point size that would be provided by another illumination device, comprising: a further array of identical optical elements arranged at the same pitch (d) as the array of optical elements; wherein the further array of identical optical elements is arranged at a second distance (d VM2 ) from a further at least one radiation-emitting element is arranged to emit radiation having the same wavelength (λ) as the radiation from the at least one radiation-emitting element, wherein the second distance (d VM2 ) from the first distance (d VM2 ) differs; and wherein the further lighting device follows a first formula: DVM2=Nd22λ where N is an integer. [8] Lighting device (1600) according to one of claims 7, wherein the first distance (d VM1 ) follows a second formula: Dvm1=Md22λ where M is an integer different from the integer N. [9] Lighting device according to claim 7 or 8, wherein the first distance (d VM1 ) is greater than the second distance (d VM2 ). [10] The lighting device (1600) according to any one of claims 7 to 9, wherein an optical phase delay of each optical element corresponds to a difference between: first optical path differences (OPD) with respect to an optical axis for each optical element of an array of optical elements at the first distance (d VM1 ) from the radiation-emitting lighting device; and second optical path differences (OPD2) with respect to the optical axis for each optical element of the array of optical elements at the second distance d VM2 from the radiation-emitting illumination device, wherein the second distance follows the second formula. [11] Lighting device (1600) according to one of the preceding claims, wherein the at least one radiation-emitting element (1630) comprises an array of surface emitters (VCSEL). [12] A method of manufacturing a lighting device (1600), the method comprising: Establishing an optical phase delay of each optical element of an array of optical elements (1620) and arranging the array at a first distance (D VM1) of at least one radiation-emitting element, so that the at least one radiation-emitting element is arranged to generate, in cooperation with the array, a structured light pattern (815, 1115, 1415) having a regular array of points. [13] The method of claim 12, wherein establishing an optical phase delay of each optical element comprises: Calculating first optical path differences (OPD1) with respect to an optical axis for each optical element of an array of optical elements at the first distance (d VM1 ) from the radiation-emitting lighting device; Calculating second optical path differences (OPD2) with respect to the optical axis for each optical element of the array of optical elements at a second distance d VM2 from the radiation-emitting illumination device, wherein the second distance follows a first formula: Dvm2=Nd22λ Calculating the third optical path differences (ΔOPD) between the first and second optical path differences; and Converting the third optical path differences (ΔOPD) into an optical phase delay of each optical element. [14] The method of claim 13, wherein converting the third optical path differences (ΔOPD) into the optical phase delay of each optical element comprises: if each optical element comprises a microlens, at least one of: Increasing the thickness of a base portion of each microlens; Selecting a refractive index of each microlens; and / or selecting a refractive index of a portion of a substrate on which each microlens is provided; or, if each optical element has a meta-lens, Selecting the dimensions of one or more columns forming each meta-lens and / or a relative rotation and / or shape of one or more mesas or fin-like structures forming each meta-lens. [15] A method according to claim 14, wherein the optical phase delay of each optical element is arranged such that a pitch and / or a spot size of the regular array of spots corresponds to a pitch and / or a spot size of an array of spots that would be generated by another illumination device, comprising: a further array of identical optical elements arranged at the same pitch (d) as the array of optical elements; wherein the further array of identical optical elements is arranged at the second distance (d VM2) from a further at least one radiation-emitting element is arranged to emit radiation having the same wavelength (λ) as the radiation from the at least one radiation-emitting element, wherein the second distance (d VM2 ) from the first distance (d VM1 ), and wherein the further lighting device follows the second formula.

Images