Linear array projector for three-dimensional ranging system

Abstract

This invention discloses a linear array projector for a three-dimensional ranging system, comprising: a light source array, a lens, and a diffraction microlens array. The light source array includes multiple light sources for emitting light beams. These multiple light sources are arranged along a first direction. The lens is used to collimate the light beam. The diffraction microlens array diffracts the collimated light beam, thereby projecting an illumination pattern. The lens spacing of the diffraction microlens array relative to the first direction is greater than the lens spacing of the diffraction microlens array relative to a second direction. The illumination pattern is formed by overlapping multiple dot matrix patterns projected by the multiple light sources, and the illumination pattern includes multiple linear light patterns along the first direction.

Description

Technical Field

[0001] This invention relates to three-dimensional optical ranging, and more particularly to a linear array projector for a three-dimensional optical ranging system. Background Technology

[0002] Generally, three-dimensional optical distance measurement based on Time-of-Flight (ToF) technology typically relies on a flood illuminator and an image sensor to measure the distance to objects or shapes. However, due to the weak light energy of the flood illuminator, its effective projection distance is very short. Therefore, there is a need in the art for a pattern projector capable of providing high-energy illumination patterns and having a longer projection distance for optical distance measurement. Summary of the Invention

[0003] As described above, the present invention aims to provide a regular linear pattern projector for a three-dimensional optical ranging system. Embodiments of the present invention combine a light source array, lenses, and a diffractive microlens array to generate an illumination pattern with a regularly distributed linear light pattern. Embodiments of the present invention also overlap the dot matrix patterns generated by different light sources in the light source array to form an illumination pattern with multiple linear light patterns.

[0004] An embodiment of the present invention provides a linear array projector comprising: a light source array, a lens, and a diffraction microlens array. The light source array includes multiple light sources for emitting a light beam. The multiple light sources are arranged along a first direction. The lens is used to collimate the light beam. The diffraction microlens array is used to diffract the collimated light beam, thereby projecting an illumination pattern. The lens spacing of the diffraction microlens array relative to the first direction is greater than the lens spacing of the diffraction microlens array relative to a second direction. The illumination pattern is formed by overlapping multiple dot matrix patterns projected by the multiple light sources, and the illumination pattern includes multiple linear light patterns along the first direction.

[0005] An embodiment of the present invention provides an optical ranging system comprising: a flood illuminator, a linear array projector, and an image capturing device. The flood illuminator includes at least one light source and a diffuser, and is used to project a first illumination pattern. The linear array projector is used to project a second illumination pattern and includes: a light source array, a lens, and a diffractive microlens array. The light source array includes multiple light sources and is used to emit light beams. The multiple light sources are arranged along a first direction. The lens is used to collimate the light beam. The diffractive microlens array is used to diffract the collimated light beam, thereby projecting the second illumination pattern. The lens spacing of the diffractive microlens array relative to the first direction is greater than the lens spacing of the diffractive microlens array relative to a second direction. The second illumination pattern is formed by overlapping multiple dot matrix patterns projected by the multiple light sources, and the second illumination pattern includes multiple linear light patterns along the first direction. The image capturing device is used to capture the image reflected from the illumination patterns after they encounter an object. Attached Figure Description

[0006] Figure 1 This is a schematic diagram of the architecture of an optical ranging system according to an embodiment of the present invention;

[0007] Figure 2 This is a schematic diagram illustrating an embodiment of the dot matrix projector and floodlight illuminator of the present invention;

[0008] Figure 3 This is a detailed architecture diagram of the dot matrix projector according to an embodiment of the present invention;

[0009] Figures 4A-4E This is a schematic diagram illustrating how an embodiment of the present invention constructs a lighting pattern using overlapping dot matrix patterns;

[0010] Figures 5A-5E This is a schematic diagram illustrating how an embodiment of the present invention uses an interlaced dot matrix pattern to construct a lighting pattern;

[0011] Figures 6A-6B This is a schematic diagram illustrating how the layout of the light source array in different embodiments of the present invention affects the distribution of light spots in the lighting pattern;

[0012] Figure 7 This is a schematic diagram illustrating how the layout and staggered type of the light source array and microlens array in different embodiments of the present invention affect the distribution of light spots in the illumination pattern;

[0013] Figure 8 This is a detailed architecture diagram of the linear array projector according to an embodiment of the present invention;

[0014] Figure 9 This is a schematic diagram illustrating how a linear light pattern is generated according to an embodiment of the present invention;

[0015] Figure 10 This is a schematic diagram of the outline of the diffractive microlens array used in the linear array projector according to an embodiment of the present invention.

[0016] Figure 11A This is a schematic diagram of an illumination pattern generated by a single light source in an embodiment of the present invention;

[0017] Figure 11B This is a schematic diagram of an illumination pattern generated by multiple light sources arranged along the same direction in an embodiment of the present invention.

[0018] Symbol Explanation

[0019] 1 Optical ranging system

[0020] 10 substrate

[0021] 100 Dot Projector

[0022] 120, 220, 420 light source arrays

[0023] Light sources 120_1~120_4 and 420_1~420_4

[0024] 140 and 440 lenses

[0025] 160 diffraction units

[0026] 260 diffuser

[0027] 200 floodlight

[0028] 300 Image Capture Device

[0029] 400 linear array projector

[0030] 460° diffraction microlens array Detailed Implementation

[0031] Numerous specific details are described below to provide the reader with a thorough understanding of embodiments of the invention. However, those skilled in the art will understand how the invention can be implemented in the absence of one or more specific details, or using other methods, elements, or materials. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring the core concepts of the invention.

[0032] The phrase "an embodiment" in this specification means that a particular feature, structure, or characteristic described in that embodiment may be included in at least one embodiment of the invention. Therefore, the phrase "in an embodiment" appearing throughout this specification does not necessarily refer to the same embodiment. Furthermore, the aforementioned particular features, structures, or characteristics may be combined in any suitable form in one or more embodiments.

[0033] Please refer to Figure 1 This figure illustrates the architecture of an optical ranging system 1 according to an embodiment of the present invention. As shown, the optical ranging system 1 includes a dot pattern projector 100, a flood illuminator 200, and an image capturing device 300. Both the dot pattern projector 100 and the flood illuminator 200 are used to project high-energy illumination patterns onto objects within the field of view (FOV) of the image capturing device 300. In different embodiments of the present invention, the dot pattern projector 100 and the flood illuminator 200 may project different types of illumination patterns sequentially or simultaneously. Figure 2 Possible configurations of the dot projector 100 and the floodlight 200 are illustrated. As shown, the dot projector 100 (which includes a light source 120, a collimating lens 140, and a diffraction unit 160, and is used to project a dot illumination pattern) and the floodlight 200 (which includes a light source 220 and a diffraction unit 260, and projects a floodlight illumination pattern) share the same substrate. The dot projector 100 and the floodlight 200 may use their own independent diffraction units 160 and 260, both of which are disposed on the same common substrate 10. The diffraction unit 160 of the dot projector 100 can be a microlens array (MLA) or a diffractive optical unit (DOE) disposed on the common substrate 10. The diffraction unit 260 of the floodlight 200 can also be a microlens array or an optical diffraction unit disposed on the common substrate 10. Arranging two different diffraction units adjacent to each other on the same substrate has the advantage of reducing manufacturing complexity. Furthermore, the etching or mold reversal of the dot projector 100 and the floodlight illuminator 200 can be performed simultaneously, which will reduce costs and assembly time.

[0034] The image capturing device 300 may include (but is not limited to) a focusing lens, a filter, and an image sensor (e.g., a complementary metal-oxide-semiconductor (CMOS) image sensor or a charge-coupled device (CCD) image sensor). The image capturing device 300 is used to capture an image of an illumination pattern reflected by an object. Based on the image captured by the image capturing device 300, the depth information of the object can be calculated.

[0035] Figure 3A schematic diagram of a dot matrix projector 100 according to an embodiment of the present invention is shown. As shown, the dot matrix projector 100 includes a light source array 120, a lens 140, and a diffraction unit 160. The light source array 120 is used to emit a light beam and includes multiple light sources 120_1-120_N, wherein the light sources 120_1-120_N are arranged in an array. In different embodiments of the present invention, the light sources 120_1-120_N may be... Figure 6A The distribution shown is either regularly distributed or hexagonally distributed. Note that the number of light sources 120_1-120_N in the illustration is for illustrative purposes only; depending on the requirements, the light source array 120 in other embodiments of the present invention may contain more or fewer light sources. Furthermore, in a preferred embodiment, light sources 120_1-120_N may be vertical-cavity surface-emitting lasers (VCSELs), and there is an equal distance D_L between two adjacent light sources.

[0036] Lens 140 is used to collimate the light beam emitted from light source array 120. Preferably, the distance between the light source array 120 and the optical center of lens 140 is equal to the effective focal length D_EFL of lens 140. Accordingly, the light beam passing through lens 140 can be more focused, resulting in smaller and higher contrast of the light spots in the illumination pattern projected by dot projector 100. Furthermore, diffraction unit 160 is used to diffract the light beam, thereby projecting an illumination pattern with regularly distributed light spots (such as...). Figure 3 (As shown). In various embodiments of the present invention, the diffraction unit 160 may be a diffraction optical element or a microlens array.

[0037] Additionally, the floodlight 200 may include a light source and a diffuser, and uses a diffractive optical element or a microlens array as the diffuser. In one embodiment, if a diffractive optical element is used as a diffraction unit 160 in the dot projector 100, the floodlight 200 will also use a diffractive optical element as its diffuser. On the other hand, if a microlens array is used as a diffraction unit 160 in the dot projector 100, the floodlight 200 will also use a microlens array as its diffuser. When a microlens array is used as a diffraction unit 160, the microlens array 160 includes a plurality of plano-convex microlenses. Furthermore, the lens spacing between adjacent unit lenses in the microlens array 160 is D_M. When a diffractive optical element is used as a diffraction unit 160, the unit spacing between adjacent optical units in the diffractive optical element 160 is D_E. In a preferred embodiment, the lens spacing D_M of the microlens array 160 or the unit spacing D_E of the diffractive optical element 160 can be greater than 10 μm, which is relatively easy to manufacture.

[0038] The distribution of light spots projected by light source 120_1-120_N can be determined based on various parameters. In one embodiment, assuming that the fan-out angle between the zero-order diffracted light spot and the m-order diffracted light spot in the dot pattern projected by a single light source is θm, and the wavelength of the light beam emitted by this light source is λ, and the lens spacing of the microlens array 160 is D_M, then these parameters will have the following relationship:

[0039] D_M×sinθ m =mλ;

[0040] Where m is the diffraction order. And according to the above formula, the fan-out angle θ1 between the zeroth-order diffracted point and the first-order diffracted point of the lattice pattern is:

[0041]

[0042] In addition, such as Figure 3 As shown, compared to the dot matrix pattern (pattern A) projected by the light source 120_1 located on the optical axis of lens 140, the dot matrix pattern (pattern B) projected by the light source 120_2 not located on the optical axis of lens 140 will be translated in the vertical direction. In various embodiments of the present invention, the illumination pattern projected by the dot matrix projector 100 is substantially formed by overlapping or interleaving the dot matrix patterns projected by different light sources.

[0043] Please refer to Figures 4A-4ETo further understand the embodiments of the present invention, how different dot matrix patterns generated by different light sources are superimposed to form an illumination pattern. In this embodiment, the light source array 120 is a 2×2 array composed of light sources 120_1 to 120_4. Figure 4B and Figure 4C The dot matrix patterns produced by light sources 120_1 to 120_2, located on the optical axis of lens 140, are shown respectively. Figure 4D and Figure 4E The dot matrix patterns produced by light sources 120_3 to 120_4, which are not on the optical axis of lens 140, are then drawn respectively. The collimated beams of light sources 120_3 to 120_4 will have a deviation angle α between themselves and the optical axis of lens 140, and this deviation angle α can be determined in the following way:

[0044]

[0045] (D_L is the distance between two adjacent light sources; D_EFL is the effective focal length of lens 140). Therefore, compared with the dot pattern projected by light sources 120_1 to 120_2, the dot pattern projected by light sources 120_3 to 120_4 will be translated in the vertical direction.

[0046] In order for the bitmap patterns to overlap accurately, the following must be satisfied:

[0047] sinα=sinθ1;

[0048] That is, the deviation angle α between the collimated beam of the light source and the optical axis must be the same as the fan-out angle θ1 between the zero-order diffracted light point and the first-order diffracted light point. If the light source spacing D_L, the effective focal length D_EFL, and the lens spacing D_M (when the diffracting unit 160 is a microlens array) or the unit spacing D_E (if the diffracting unit 160 is a diffracting optical unit) are well controlled, and sin α=sin θ is satisfied, then the dot pattern can be translated exactly by one unit dot distance D_P (i.e., the distance between adjacent light points in the dot pattern) in the vertical or horizontal direction, thus forming an overlapping illumination pattern.

[0049] Please see Figures 5A-5E To further understand the embodiments of the present invention, how different dot matrix patterns generated by different light sources constitute an illumination pattern in an interlaced manner. In this embodiment, the light source array 120 is a 2×2 array composed of light sources 120_1 to 120_4. Figure 5B and Figure 5C The dot matrix patterns produced by light sources 120_1 to 120_2, located on the optical axis of lens 140, are shown respectively. Figure 5D and Figure 5EThe dot matrix patterns produced by light sources 120_3 to 120_4, which are not on the optical axis of lens 140, are then drawn respectively. The collimated beams of light sources 120_3 to 120_4 will have a deviation angle α between themselves and the optical axis of lens 140, and this deviation angle α can be determined in the following way:

[0050]

[0051] In order for the bitmap patterns to overlap accurately, the following must be satisfied:

[0052] N×sinα=sinθ;

[0053] The interleaving coefficient N determines how the lattice patterns interleave. When N is 1, the lattice patterns will be offset by a unit dot spacing D_P in the vertical or horizontal direction, thus forming a pattern like... Figure 4A The overlapping lighting pattern shown. When N is 2, the dot pattern will be offset by a dot spacing D_P of 1 / 2 unit in the vertical or horizontal direction, thus forming a pattern like... Figure 5A The interlaced lighting pattern is shown. When N is 3, the dot matrix pattern will be offset by 1 / 3 unit of dot spacing D_P in the vertical or horizontal direction, thus forming an interlaced lighting pattern.

[0054] In summary, the lens spacing D_M of the diffraction unit 160 (when the diffraction unit 160 is a microlens array) or the unit spacing D_E of the diffraction unit 160 (when the diffraction unit 160 is a diffractive optical unit) determines the fan-out angle θ, which affects the distribution of light spots (e.g., light spot density) in the dot pattern projected by a single light source. Furthermore, the light source spacing D_L and the effective focal length D_EFL of the lens 140 determine the fan-out angle θ, which affects the offset between the dot patterns.

[0055] Assuming the effective focal length D_EFL is 2mm and the light source spacing is 30μm, the lens spacing D_M (if the diffraction unit 160 is a microlens array) or the unit spacing D_E (if the diffraction unit 160 is a diffraction optical unit) of the diffraction unit 160 can be determined by the following formula:

[0056] or

[0057]

[0058] Therefore, the lens spacing D_M or element spacing D_E of the diffraction element 160 is approximately 62.7 μm when N = 1 (i.e., overlapping type) and approximately 31.3 μm when N = 2 (i.e., staggered type). Furthermore, to achieve an illumination pattern sufficient to cover a 60° (horizontal) × 40° (vertical) field of interest (FOI), the size of the illumination pattern can be determined as follows:

[0059] as well as

[0060]

[0061] Where, θ mH For (60° / 2), θ mV The value is (40° / 2). Therefore, in an overlapping lighting pattern (N=1), the horizontal diffraction order m is... H The diffraction order in the vertical direction is ±33, m. V The value is ±22. In an interleaved lighting pattern (N=2), the horizontal diffraction order m is... H The diffraction order in the vertical direction is ±16, m. V The value is ±11. Therefore, the total number of light spots in the lighting pattern can be determined by the following formula:

[0062] N 2 ×(2|m H |+1)×(2|m V |+1).

[0063] In N=1, m H =±33 and m V With N=±22, the total number of light spots will be around 3015, while with N=2 and m H =±16 and m V With a value of ±11, the total number of light spots will be around 3036. This demonstrates that by adjusting the interlacing coefficient N and the lens spacing D_M (or unit spacing D_M), a similar number of light spots can be provided within a fixed FOI. Therefore, this invention significantly improves the design and manufacturing flexibility of the diffraction unit 160.

[0064] Figure 6A and Figure 6B Different layouts of the light source array 120 and their corresponding lighting patterns are illustrated in the embodiments of the present invention. As shown in the figure, the distribution of light spots in the lighting pattern retains the light source layout pattern in the light source array 120. Figure 7 The illumination patterns obtained by different light source layouts, different microlens array unit lens layouts, and different interlacing types are illustrated.

[0065] In addition to the dot matrix projector described above, in some embodiments of the present invention, a linear array projector is also used to generate illumination patterns for three-dimensional ranging. Please refer to... Figure 8 The figure illustrates a line pattern projector 400, which can be used to project an illumination pattern composed of multiple linear light patterns. As shown, the line pattern projector 400 includes a light source array 420, a lens 440, and a diffractive microlens array 460. The light source array 420 is used to emit a light beam and includes multiple light sources 420_1 to 420_4 arranged in a line. Note that the number of light sources included in the light source array 420 may vary depending on different requirements. In various embodiments of the invention, a single light source array may have more or fewer light sources. Preferably, each of the light sources 420_1 to 420_4 may be a vertical-cavity surface-emitting laser (VCSEL), and there is an equal spacing between two adjacent light sources. The lens 440 is used to collimate the light beam emitted by the light source array 420. Preferably, the distance between the optical centers of the light source array 420 and the lens 440 may be equal to the effective focal length of the lens 440. Lens 440 allows the light beam to be more focused, resulting in finer, clearer line patterns and higher contrast in the illumination pattern projected by the linear projector 400. Figure 9 As shown, light sources 420_1 to 420_4 in the light source array 420 can produce dot matrix patterns. These dot matrix patterns can be overlapped in the horizontal direction to form an illumination pattern with multiple linear light patterns.

[0066] As described above, the illumination pattern of the linear array projector 400 is generated by slightly shifting the dot matrix pattern projected by the light sources 420_1 to 420_4 in the horizontal direction. To achieve this, the diffraction MLA 460 has, for example... Figure 10The profile shown is illustrated. In one embodiment, the lens spacing (center-to-center distance) of the diffractive MLA 460 relative to the horizontal direction can be 60 μm, the lens spacing of the diffractive MLA 460 relative to the vertical direction can be 20 μm, the maximum sag height of the diffractive MLA 460 on the convex surface of the lens can be approximately 33.69 μm, and the maximum slope of the diffractive MLA 460 can be approximately 73 degrees. In the above embodiment, the light sources 420_1 to 420_4 are arranged horizontally, and the lens spacing of the diffractive MLA 460 in the horizontal direction is greater than the lens spacing in the vertical direction, so that the dot pattern projected by the light sources 420_1 to 420_4 can be slightly offset in the horizontal direction and overlap in the horizontal direction, so as to ultimately form multiple line patterns in the horizontal direction.

[0067] Figure 11A The illumination pattern produced by a single light source is illustrated. As mentioned earlier, the lens spacing of the diffractive MLA 460 is wider in the horizontal direction. Therefore, the fan-out angle of the dot pattern in the horizontal direction is smaller, resulting in a smaller offset of the dot pattern in the horizontal direction. Figure 11B This diagram illustrates the lighting pattern produced by light sources arranged horizontally. Because the light sources are arranged horizontally, the dot matrix pattern exhibits greater overlap in the horizontal direction.

[0068] In some embodiments, light sources 420_1 to 420_4 can be arranged vertically, and the lens spacing of the diffractive MLA 460 in the vertical direction is wider than the lens spacing of the diffractive MLA 460 in the horizontal direction. This causes the dot matrix patterns projected by light sources 420_1 to 420_4 to be slightly offset in the vertical direction, and thus overlap in the vertical direction, ultimately forming multiple linear light patterns in the vertical direction. In some embodiments of the present invention, light sources 420_1 to 420_4 can be arranged along a first direction, and the lens spacing of the diffractive MLA 460 in this first direction is wider than the lens spacing of the diffractive MLA 460 in a second direction. This causes the dot matrix patterns projected by light sources 420_1 to 420_4 to be slightly offset in this first direction, and thus overlap in this first direction, ultimately forming multiple linear light patterns in this first direction.

[0069] Similar to the dot projector 100, the linear projector 400 can be used in conjunction with the flood illuminator 200 in an optical ranging system to project patterns onto objects for the image capturing device 300 to acquire depth information. Furthermore, the linear projector 400 and the flood illuminator 200 can share the same substrate. The linear projector 400 and the flood illuminator 200 can use separate diffraction units 460 and 260, respectively, all disposed on the shared substrate. That is, the diffraction MLA 460 (a microlens array) of the linear projector 400 is disposed on the same substrate as the diffraction unit 260 (also a microlens array) of the flood illuminator 200. Sharing the same substrate and arranging the two diffraction units adjacently reduces the complexity of the manufacturing process. This allows the etching or mold flipping of the linear projector 400 and the flood illuminator 200 to be completed simultaneously, thereby reducing costs and assembly time.

[0070] In summary, embodiments of the present invention provide a dot matrix projector and a linear array projector, intended for use in three-dimensional optical ranging systems. The dot matrix projector or linear array projector of the present invention can be used in conjunction with a floodlight illuminator in an optical ranging system to provide a high-power illumination pattern and a considerably long projection distance. The diffuser of the floodlight illuminator, and the diffraction unit of the dot matrix projector or linear array projector, can all be implemented using the same type of optical elements (e.g., MLAs or DOEs), thereby simplifying the manufacturing of the optical ranging system. Furthermore, embodiments of the present invention allow the dot matrix patterns generated by different light sources in the light source array to overlap or interleave, enabling a wider range of adjustment for the component parameters of the dot matrix projector. This effectively improves the design and manufacturing flexibility of the dot matrix projector. Moreover, since the linear light pattern in the illumination pattern generated by the linear array projector is produced by the offset and overlap of the dot matrix patterns, the brightness uniformity of the linear illumination pattern can be better improved.

[0071] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made in accordance with the claims of the present invention should be included within the scope of the present invention.

Claims

1. A linear array projector, comprising: A light source array comprising multiple light sources for emitting light beams, wherein the multiple light sources are arranged along a first direction; Lenses are used to collimate light beams; and A diffractive microlens array is used to diffract a straight-back beam of light to project an illumination pattern, wherein the lens pitch of the diffractive microlens array relative to the first direction is greater than the lens pitch of the diffractive microlens array relative to the second direction. in, The lighting pattern is formed by overlapping dot matrix patterns projected by the multiple light sources, and the lighting pattern includes multiple linear light patterns along the first direction.

2. The linear array projector of claim 1, wherein each of the light sources is a vertical-cavity surface-emitting laser (VCSEL).

3. The linear array projector as claimed in claim 1, wherein the distance between adjacent light sources among the plurality of light sources is fixed.

4. The linear array projector as claimed in claim 1, wherein the maximum sag height of the diffractive microlens array is approximately 33.69 μm, and the maximum slope of the diffractive microlens array is approximately 73 degrees.

5. The linear projector of claim 1, wherein the first direction is perpendicular to the second direction.

6. The linear array projector as claimed in claim 1, wherein the first direction is a horizontal direction and the second direction is a vertical direction.

7. An optical ranging system, comprising: A floodlight illuminator comprising at least one light source and a diffuser for projecting a first lighting pattern; A linear array projector for projecting a second illumination pattern includes: A light source array comprising multiple light sources for emitting light beams, wherein the multiple light sources are arranged along a first direction; Lenses are used to collimate light beams; and A diffractive microlens array is used to diffract the aligned beam of light, thereby projecting the second illumination pattern. The lens pitch of the diffractive microlens array relative to the first direction is greater than the lens pitch of the diffractive microlens array relative to the second direction. The second illumination pattern is formed by overlapping dot matrix patterns projected by the multiple light sources, and the second illumination pattern includes multiple linear light patterns along the first direction; An image capturing device is used to capture images of the reflections of objects on the lighting patterns.

8. The optical ranging system of claim 7, wherein the diffuser is a microlens array.

9. The optical ranging system of claim 7, wherein the diffuser is a diffractive optical element.

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