Dot projector for 3D ranging systems

Abstract

This invention discloses a dot matrix projector for a three-dimensional ranging system, comprising: a light source array, a lens, and a diffraction unit. The light source array includes multiple light sources for emitting light beams. The lens is used to collimate the light beams. The diffraction unit is used to diffract the collimated light beams, thereby projecting an illumination pattern. The illumination pattern is formed by the overlapping of multiple dot matrix patterns projected by the light sources, or by the interleaving of multiple dot matrix patterns projected by the light sources.

Description

Technical Field

[0001] This invention relates to three-dimensional optical ranging, and more particularly to a dot matrix 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 object of the present invention is to provide a dot pattern projector for a three-dimensional optical ranging system. Embodiments of the present invention combine a light source array, lenses, and diffraction units to generate an illumination pattern composed of regular light dots. Furthermore, the dot patterns generated by different light sources in the light source array can be overlapped or interleaved to form the illumination pattern. According to various embodiments of the present invention, the diffraction unit can be implemented using a microlens array or diffractive optical elements. Because the present invention provides different pattern interleaving methods, it allows for a wide range of selection of the component parameters of the dot pattern projector, thereby providing flexibility in design and manufacturing.

[0004] One embodiment of the present invention provides a dot matrix projector, which includes: a light source array, a lens, and a diffraction unit. The light source array includes multiple light sources for emitting light beams. The lens is used to collimate the light beams. The diffraction unit is used to diffract the collimated light beams, thereby projecting an illumination pattern. The illumination pattern is formed by overlapping or interleaving multiple dot matrix patterns projected by the light sources.

[0005] An embodiment of the present invention provides an optical ranging system. The optical ranging system includes a flood illuminator, a dot matrix projector, and an image capturing device. The flood illuminator includes at least one light source and a diffuser for projecting a first illumination pattern. The dot matrix projector projects a second illumination pattern and includes: a light source array, a lens, and a diffraction unit. The light source array includes a plurality of light sources for emitting light beams. The lens is used to collimate the light beams. The diffraction unit is used to diffract the collimated light beams, thereby projecting the second illumination pattern, wherein the second illumination pattern is formed by the overlapping of multiple dot matrix patterns projected by the light sources, or by the interleaving of multiple dot matrix patterns projected by the light sources. The image capturing device is used to capture an image of the illumination pattern reflected by 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 invention illustrates how an embodiment of the invention constructs a lighting pattern using overlapping dot matrix patterns.

[0010] Figures 5A-5E This invention illustrates how an embodiment of the invention constructs a lighting pattern using an interlaced dot matrix 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] Symbol Explanation

[0014] 1 Optical ranging system

[0015] 10 substrate

[0016] 100 Dot Projector

[0017] 120 and 220 light source arrays

[0018] Light sources 120_1~120_4

[0019] 140 lens

[0020] 160 diffraction units

[0021] 260 diffuser

[0022] 200 floodlight

[0023] 300 Image Capture Device Detailed Implementation

[0024] 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.

[0025] 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.

[0026] 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 2Possible 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.

[0027] 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.

[0028] Figure 3 A 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 6AThe 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 can be vertical-cavity surface-emitting lasers (VCSELs), and there is an equal distance D_L between two adjacent light sources.

[0029] 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.

[0030] 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.

[0031] The distribution of light spots projected by light source 120_1-120_N can be determined based on various parameters. In one embodiment, it is assumed that in the dot pattern projected by a single light source, the fan-out angle between the zeroth-order diffracted light spot and the m-order diffracted light spot is θ. m Given that 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, the following relationship exists between these parameters:

[0032] D_M×sinθ m =mλ;

[0033] 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:

[0034]

[0035] 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.

[0036] Please refer to Figures 4A-4E To 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 2x2 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:

[0037]

[0038] (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.

[0039] In order for the bitmap patterns to overlap accurately, the following must be satisfied:

[0040] sinα=sinθ1;

[0041] 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 to satisfy sinα=sinθ, 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.

[0042] 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 5E 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:

[0043]

[0044] In order for the bitmap patterns to overlap accurately, the following must be satisfied:

[0045] N×sinα=sinθ

[0046] 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.

[0047] 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.

[0048] 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:

[0049] or

[0050]

[0051] 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:

[0052] as well as

[0053]

[0054] 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:

[0055] N 2 ×(2|m H |+1)×(2|m V |+1).

[0056] In N=1, m H =±33 and mV 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.

[0057] Figure 6A and Figure 6B The 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.

[0058] In summary, embodiments of the present invention provide a dot matrix projector for a three-dimensional optical ranging system. The dot matrix projector of the present invention can be used in conjunction with a floodlight illuminator in an optical ranging system to provide a high-energy illumination pattern and a long projection distance. Both the diffuser of the floodlight illuminator and the diffraction unit of the dot matrix projector can be implemented using the same type of optical elements (e.g., both microlens arrays, or both diffraction optical units), 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 to overlap or interleave, enabling a wider range of selection for the component parameters of the dot matrix projector, significantly improving design and manufacturing flexibility.

[0059] 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 dot pattern projector, comprising: A light source array, comprising multiple light sources for emitting light beams; Lenses are used to collimate light beams; and A diffraction unit is used to diffract the beam of light directly behind the light source, thereby projecting an illumination pattern. This illumination pattern is composed of overlapping or interlaced dot patterns projected by the light sources. in, The diffraction unit includes a microlens array, wherein if the wavelength of the light beam emitted by the light sources is λ, the fan-out angle between the zero-order diffracted spot and the m-order diffracted spot in the lattice pattern produced by the light sources is θ. m And if the element spacing or lens spacing of the diffraction unit is D_M, then: D_M×sinθ m =mλ.

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

3. The dot matrix projector as claimed in claim 1, wherein the distance between adjacent light sources among the light sources is fixed.

4. The dot matrix projector as claimed in claim 1, wherein the light source is regularly distributed or hexagonally distributed in the light source array.

5. The dot matrix projector of claim 1, wherein the distance between the light source array and the optical center of the lens is equal to the equivalent focal length of the lens.

6. The dot matrix projector as claimed in claim 1, wherein if the distance between two adjacent light sources is D_L, the effective focal length of the lens is D_EFL, and the collimated beam of a light source not on the optical axis of the lens has an offset angle of α from the optical axis, then:

7. The dot matrix projector as claimed in claim 1, wherein if the illumination pattern is composed of overlapping dot matrix patterns projected by different light sources, and the collimated beam of a light source not on the optical axis of the lens has an offset angle of α with the optical axis, and the fan-out angle between the zero-order diffracted light spot and the first-order diffracted light spot in the dot matrix pattern generated by the light source is θ1, then: sinα=sinθ1.

8. The dot matrix projector as claimed in claim 1, wherein if the illumination pattern is composed of dot matrix patterns projected by different light sources in an alternating manner, and the collimated beam of a light source not on the optical axis of the lens has an offset angle of α between it and the optical axis, and the fan-out angle between the zero-order diffracted light spot and the first-order diffracted light spot in the dot matrix pattern generated by the light source is θ1, then: N×sinα=sinθ1.

9. An optical ranging system, comprising: A floodlight illuminator comprising at least one light source and a diffuser for projecting a first lighting pattern; A dot matrix projector for projecting a second lighting pattern includes: A light source array, comprising multiple light sources for emitting light beams; Lenses are used to collimate light beams; and A diffraction unit is used to diffract the beam of light directly behind the source, thereby projecting the second illumination pattern. This second illumination pattern is composed of overlapping or interlaced dot matrix patterns projected by the light sources. The diffraction unit includes a microlens array, wherein if the wavelength of the light beam emitted by the light sources is λ, the fan-out angle between the zero-order diffracted spot and the m-order diffracted spot in the lattice pattern produced by the light sources is θ. m And if the element spacing or lens spacing of the diffraction unit is D_M, then: D_M×sinθ m =mλ; An image capturing device is used to capture images of the reflections of objects on the lighting patterns.

10. The optical ranging system of claim 9, wherein both the diffuser and the diffraction unit are microlens arrays.

Images