Laser projection module based on microlens array

Abstract

This application discloses a laser projection module, which includes an illumination source and a microlens array. The microlens array includes multiple microlenses. In the working mode of projecting a dotted light field, the working distance D1 of the microlens array relative to the illumination source satisfies the following relationship: where N is a positive integer, preferably N≤5; λ is the wavelength of the light from the illumination source; α is a coefficient, 0<α≤1; and f is the focal length of the microlens. In this laser projection module, the working distance used for projecting a dotted light field further considers the influence of the microlens focal length. By appropriately selecting and optimizing the influence coefficient α of the microlens focal length, the light energy of the dotted light field generated at the corresponding working distance can be focused onto a significantly smaller spot, thereby greatly improving the contrast of the laser dotted light.

Description

TECHNICAL FIELD

[0001] The present application relates to three-dimensional sensing technology in general, and in particular to a laser projection module for a three-dimensional sensing device. BACKGROUND

[0002] There are three main types of optical three-dimensional sensing technology: binocular stereo vision, structured light technology and TOF (Time of Flying) technology. Different technologies have different performances and may be suitable for different application scenarios. In the consumer electronics field (e.g. mobile phones), the most widely used technologies at present are structured light technology and TOF technology. Both structured light technology and TOF technology need to be implemented based on a laser projection module capable of projecting a predetermined light field. Structured light technology requires a patterned light field to be projected, and TOF technology usually uses a flood light field, and can also use a patterned light field, such as a laser dot array.

[0003] Most existing laser dot array projection schemes form a collimated light beam from a VCSEL (Vertical Cavity Surface Emitting Laser) through a collimating lens to form a collimated light, and then diffract the collimated light through a DOE to form a dot array. However, this scheme needs a collimating lens to collimate the laser, and the system scheme is complex, the overall device is thick, and the cost is high. CN107429993B discloses a device for generating a laser dot array based on a microlens array, which simplifies the structure compared with the existing laser dot array projection scheme based on a diffractive optical element, and in particular significantly reduces the thickness of the device. However, this technology for generating structured light based on a microlens array is not perfect. SUMMARY

[0004] The object of the present application is to provide an optical waveguide device for diffractive display and a display device comprising the optical waveguide device, so as to at least partially overcome the deficiencies in the prior art.

[0005] According to an aspect of the present application, there is provided a laser projection module based on a microlens array, comprising an illumination light source and a first microlens array, the first microlens array comprising a plurality of first microlenses arranged in a first plane, the plurality of first microlenses being arranged in a first array with a first pitch P, wherein the laser projection module is configured to have a first working mode; in the first working mode, the first microlens array has a first working distance D1 relative to the illumination light source in a direction perpendicular to the first plane, and a dot array light field is projected on a target plane by modulation of light from the illumination light source through the first microlens array. The first working distance D1 satisfies the following relationship:

[0006]

[0007] Where N is a positive integer, preferably N≤5; λ is the wavelength of light from the illumination source; α is a first coefficient, 0<α≤1; and f is the focal length of the first microlens.

[0008] Advantageously, the first microlens has an aspherical surface and focal lengths f1 and f2 along two mutually perpendicular directions in the first plane, f = (f1 + f2) / 2.

[0009] Advantageously, the first array is a rectangular array, a parallelogram array, or a regular hexagonal array.

[0010] Advantageously, the lighting source includes a plurality of light-emitting points arranged in a second plane parallel to the first plane, and the plurality of light-emitting points are arranged in a light source array with a light source spacing W, the unit structure of the light source array being a similar polygon to the unit structure of the first array.

[0011] Advantageously, the first spacing P and the light source spacing W satisfy the following relationship: wW = pP, where w and p are positive integers with no common factors, preferably w = p = 1.

[0012] In some embodiments, the laser projection module is further configured to have a second operating mode; in the second operating mode, in a direction perpendicular to the first plane, the first microlens array has a second operating distance D2 relative to the illumination source, and the light from the illumination source is modulated by the first microlens array to project a uniform light field onto the target surface, wherein the second operating distance D2 satisfies the following relationship:

[0013]

[0014] Where M is a non-negative integer, β is the second coefficient, and 0.8≤β≤1.2.

[0015] Advantageously, the second working distance is less than the first working distance.

[0016] Advantageously, the laser projection module is configured such that at least one of the illumination source and the first microlens array is movable in a direction perpendicular to the first plane, such that the first microlens array switches between a first working distance and a second working distance relative to the illumination source.

[0017] In other embodiments, the laser projection module may further include a second microlens array, the second microlens array including a plurality of second microlenses arranged in a first plane, the plurality of second microlenses being arranged in a second array with a second spacing P', wherein the laser projection module is further configured to have a second operating mode; in the second operating mode, light from the illumination source is modulated by the second microlens array to project a uniform light field onto the target surface.

[0018] Advantageously, the second spacing P' satisfies the following relationship:

[0019]

[0020] Where M' is a non-negative integer; f' is the focal length of the second microlens; α' is the third coefficient, 0 < α' ≤ 1; β' is the fourth coefficient, 0.8 ≤ β' ≤ 1.2.

[0021] Advantageously, in the first operating mode, the illumination source is positioned directly opposite the first microlens array; in the second operating mode, the illumination source is positioned directly opposite the second microlens array.

[0022] Advantageously, the laser projection module is configured such that the illumination source can move parallel to the first plane relative to the first microlens array and the second microlens array.

[0023] In the laser projection module according to an embodiment of the present invention, the working distance from the microlens array to the illumination source in the working mode for projecting a dot matrix light field further considers the influence of the microlens focal length. By appropriately selecting and optimizing the influence coefficient α of the microlens focal length, the light energy of the dot matrix light field generated at the corresponding working distance can be focused onto a significantly smaller dot spot, thereby greatly improving the contrast of the laser dot matrix. Attached Figure Description

[0024] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0025] Figure 1 This is a schematic diagram of a laser projection module according to Embodiment 1 of the present invention;

[0026] Figure 2 For use Figure 1 A schematic diagram of an example of the microlens array and light source array of the laser projection module shown;

[0027] Figure 3 It shows the basis Figure 1 The simulation diagram of a single light spot in the dot matrix light field obtained by the laser projection module for different values ​​of parameter α.

[0028] Figure 4 It shows Figure 3 The diagrams of the lattice light fields obtained when α = 0 and α = 0.9 in the example shown;

[0029] Figure 5 , Figure 6 and Figure 7 The following are examples of different parameter conditions based on Figure 1 The simulation diagram of a single light spot in the dot matrix light field obtained by simulating different values ​​of parameter α of the laser projection module shown.

[0030] Figure 8 This is a schematic diagram of the laser projection module according to Embodiment 2 of the present invention;

[0031] Figure 9 It shows the basis Figure 8 Simulation diagrams of the dot matrix light field and uniform light field obtained by the laser projection module shown.

[0032] Figure 10 A schematic diagram of a laser projection module according to Embodiment 3 of the present invention; and

[0033] Figure 11 for Figure 10 A schematic diagram of a variant of the laser projection module shown. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. For ease of description, only the parts relevant to the invention are shown in the drawings. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0035] This application is based on the following discovery: In the apparatus for generating a laser dot matrix disclosed in CN107429993B, the relationship between the lens spacing of the microlens array, the distance from the microlens array to the light source, and the wavelength is strictly defined; however, experiments show that under this strictly defined relationship, the contrast of the laser dot matrix is ​​not optimal; further research revealed that the contrast of the laser dot matrix is ​​also affected by the focal length of the microlenses in the microlens array. Based on these findings, improvements have been made to the laser dot matrix projection device based on a microlens array, proposing a new structural relationship to effectively improve the dot matrix contrast. The following will describe the specific embodiments with reference to the accompanying drawings.

[0036] Figure 1 This is a schematic diagram of a laser projection module according to Embodiment 1 of the present invention. Figure 1As shown, the laser projection module 10 includes an illumination source 11 and a microlens array 12. The illumination source 11 may include a single light-emitting point or multiple light-emitting points. Figure 1 In the example shown, the illumination source 11 includes a plurality of light-emitting points 11a. The microlens array 12 includes elements arranged on a plane ( Figure 1 Multiple microlenses 12a in the xy plane shown are arranged in an array at a predetermined pitch P (see...). Figure 2 (Arrays 12A and 12B are shown). According to this embodiment, the laser projection module 10 is configured to operate with a projection array light field. Specifically, in the operation mode of the projection array light field, in the direction perpendicular to the xy plane (i.e., Figure 1 In the z-direction (as shown), the microlens array 12 has a working distance D1 relative to the illumination source 11, such that light from the illumination source 11 is modulated by the microlens array 12 and projected onto the target surface 20 to form a dotted light field LF. According to an embodiment of the present invention, in the working mode of projecting the dotted light field, this working distance D1 satisfies the following relationship:

[0037]

[0038] Where N is a positive integer, preferably N≤5; λ is the wavelength of light from the illumination source 11 (i.e., the working wavelength of the laser projection module); α is a coefficient, and 0<α≤1; f is the focal length of the microlens 12a.

[0039] In some implementations, the microlens 12a can have an aspherical surface shape, thereby having different focal lengths f1 and f2 in two mutually perpendicular directions in the xy plane. For example, in the xz plane, the microlens 12a has a focal length f1; in the yz plane, the microlens 12a has a focal length f2. In the above case, in the laser projection module according to an embodiment of the present invention, the focal length f of the microlens 12a in the above relationship can be taken as follows: f = (f1 + f2) / 2.

[0040] For illustrative purposes only, Figure 2 Different arrangements of the microlens array and light source array that can be used in the laser projection module 10 are shown. Figure 2 The top left corner shows a microlens array 12 in the form of a rectangular array 12A, and the bottom right corner shows a microlens array 12 in the form of a regular hexagonal array 12B. Besides... Figure 2 In addition to the form shown, the microlens array that can be used in this invention can also be, for example, a parallelogram array.

[0041] According to an embodiment of the present invention, the illumination source 11 may include a plurality of light-emitting points 11a. Preferably, the plurality of light-emitting points 11a are arranged in a light source array in another plane parallel to the plane containing the microlens array 12, for example...Figure 2 The right-hand diagram shows arrays 11A and 11B, where the unit cell structures (lattices) of the light source arrays 11A and 11B are respectively... Figure 2 The unit structures of the rectangular microlens array 12A and the regular hexagonal microlens array 12B shown on the left are similar polygons. More preferably, the spacing P of the microlenses 12a in the microlens array 12 and the spacing W between the light-emitting points in the illumination source (i.e., the light source spacing) satisfy the following relationship:

[0042] wW=pP

[0043] Where w and p are positive integers with no common factors, preferably w = p = 1.

[0044] To illustrate the technical effect of the laser projection module according to embodiments of the present invention in improving the contrast of the laser dot matrix, simulation calculation data examples will be given below.

[0045] (Data Example 1)

[0046] Data Example 1 is based on Figure 1 The laser projection module 10 shown is simulated for different values ​​of parameter α to calculate the distribution of the dot matrix light field. In Data Example 1, the operating wavelength λ = 940 nm; both the illumination source 11 and the microlens array 12 are rectangular arrays, where P = W = 39 μm, f = 40 μm; N = 2, and α is selected as 11 points with equal intervals between 0 and 1; the pattern of a single point spot in the dot matrix light field obtained through simulation calculation is shown below. Figure 3 As shown. Figure 3 As shown, when α is 0.8, 0.9, and 1, the diameter of a single spot is the minimum of 2 pixels. Therefore, the optimal value is the intermediate α = 0.9. It can be seen that compared to the spot diameter of 9 pixels when α = 0, when α is between 0.8 and 1, the light energy of the laser dot field generated at the corresponding working distance D1 is focused onto a significantly smaller spot, thus greatly improving the contrast of the laser dot matrix. To see this effect more clearly and intuitively, Figure 4 The diagram further shows the lattice light field obtained when α = 0 and α = 0.9 in Data Example 1.

[0047] According to embodiments of the present invention, the optimal value of the coefficient α used to determine the working distance D1 between the microlens array 12 and the illumination source 11 in the laser projection module varies depending on various parameters of the laser projection module. Those skilled in the art, after reading this application, can determine the optimal value of coefficient α and the corresponding working distance through simulation or experimentation based on specific applications. For ease of understanding, examples 2-4 of simulation calculations for different values ​​of α under different parameter conditions are further provided below.

[0048] (Data Example 2)

[0049] In Example 2, the operating wavelength λ = 940 nm; both the illumination source 11 and the microlens array 12 are rectangular arrays, where P = 30 μm, W = 30 μm, and N = 2; the focal length f of the microlens 12a is selected as 30 μm, 50 μm, and 70 μm, and α is selected as 7 equally spaced points between 0 and 1.2; the pattern of a single point spot in the lattice light field obtained through simulation calculation is shown in... Figure 5 As shown in the image.

[0050] like Figure 5 As shown, for the different values ​​of f (30μm, 50μm, and 70μm), the diameter of a single light spot reaches its minimum when α = 1, which is 3 pixels, 4 pixels, and 5 pixels respectively. It can be seen that under the above parameter conditions, α = 1 is the optimal value. Figure 3 Similarly, it can be seen that compared with the diameter of the spot when α=0 (13 pixels, 20 pixels and 29 pixels respectively), when α is 1, the light energy of the lattice light field generated at the corresponding working distance D1 is focused onto a significantly smaller spot, which is beneficial to improving the contrast of the laser lattice.

[0051] (Data Example 3)

[0052] In Example 3, the operating wavelength λ = 940 nm; both the illumination source 11 and the microlens array 12 are rectangular arrays, where P = 50 μm, W = 50 μm, and N = 2; the focal length f of the microlens 12a is selected as 30 μm, 50 μm, and 70 μm, and α is selected as 7 equally spaced points between 0 and 1.2; the pattern of a single point spot in the lattice light field obtained through simulation calculation is shown in... Figure 6 As shown in the image.

[0053] like Figure 6 As shown, for the different values ​​of f (30μm, 50μm, and 70μm), the diameter of a single light spot basically reaches its minimum when α = 0.8, which is 2 pixels, 2 pixels, and 3 pixels respectively. It can be seen that under the above parameter conditions, α = 0.8 can be considered the optimal value. Figure 3 and Figure 5 Similarly, it can be seen that compared with the diameter of the spot when α=0 (6 pixels, 12 pixels and 17 pixels respectively), when α is 0.8, the light energy of the lattice light field generated at the corresponding working distance D1 is focused onto a significantly smaller spot, which is beneficial to improving the contrast of the laser lattice.

[0054] (Data Example 4)

[0055] In Example 4, the operating wavelength λ = 940 nm; both the illumination source 11 and the microlens array 12 are rectangular arrays, where P = 70 μm, W = 70 μm, and N = 2; the focal length f of the microlens 12a is selected as 30 μm, 50 μm, and 70 μm, and α is selected as 7 equally spaced points between 0 and 1.2; the pattern of a single point spot in the lattice light field obtained through simulation calculation is shown in... Figure 7 As shown in the image.

[0056] like Figure 7 As shown, for f = 30μm, when α takes values ​​of 0, 0.2, 0.4, and 0.6, the diameter of a single spot is the minimum of 2 pixels. In this case, the intermediate value α = 0.3 is the optimal value. Similarly, for f = 50μm, when α takes values ​​of 0.2, 0.4, and 0.6, the diameter of a single spot is the minimum of 2 pixels. In this case, the intermediate value α = 0.4 is the optimal value. For f = 70μm, when α takes values ​​of 0.4, 0.6, and 0.8, the diameter of a single spot is the minimum of 2 pixels. In this case, α = 0.6 is the optimal value. Figure 3 and Figure 5 The results are slightly different. Figure 7 This more clearly shows that the optimal value of the coefficient α used to determine the working distance D1 may differ under different parameter conditions. However, compared to Figure 3 and Figure 5 Similar to the example shown, from Figure 7 As can be seen, when f is 50μm, compared to the diameter of the spot (4 pixels) when α = 0, when α is 0.4, the light energy of the lattice light field generated at the corresponding working distance D1 is focused onto the spot reduced to half its size; when f is 70μm, compared to the diameter of the spot (6 pixels) when α = 0, when α is 0.6, the light energy of the lattice light field generated at the corresponding working distance D1 is focused onto the spot reduced to one-third its size. Both of these factors contribute to improving the contrast of the laser lattice.

[0057] Figure 8 This is a schematic diagram of a laser projection module according to Embodiment 2 of the present invention. Figure 8 The laser projection module 10' shown is Figure 1 The laser projection module 10 shown has essentially the same structure and operating mode, namely: both laser projection module 10 and laser projection module 10' include an illumination source 11 and a microlens array 12. The microlens array 12 includes multiple microlenses 12a arranged in an array in a plane. When the microlens array 12 is at a working distance D1 relative to the illumination source 11, the laser projection module is in the working mode of projecting a dotted light field to project a dotted light field LF onto the target surface 20 (see...). Figure 1 The working distance D1 satisfies the following relationship:

[0058]

[0059] Where N is a positive integer, preferably N≤5; λ is the wavelength of light from illumination source 11; α is a coefficient, 0<α≤1; and f is the focal length of microlens 12a.

[0060] The laser projection module 10' differs from the laser projection module 10 in that it is also configured to operate in a mode that projects a uniform light field. In this mode, the microlens array 12 has a working distance D2 relative to the illumination source 11, such that the light from the illumination source 11 is modulated by the microlens array 12 and projected onto the target surface to form a uniform light field. The working distance D2 satisfies the following relationship:

[0061]

[0062] Where M is a non-negative integer, β is a coefficient, and 0.8≤β≤1.2.

[0063] In the above relation It can be regarded as This term ensures that the working distance D2 is as far away from the working distance D1 as possible (when N takes different integer values, D1 can take values ​​that are basically equal to...). (different values ​​for the interval), so that the microlens array 12 can play a better role in dispersing and homogenizing the light from the illumination source 11, and realize the projection of the uniform light field.

[0064] For illustrative purposes only, Figure 9 It shows the basis Figure 8 Examples of simulation diagrams of the dot matrix light field and uniform light field obtained by the laser projection module 10' shown.

[0065] Preferably, such as Figure 8 As shown, in the laser projection module 10', the working distance D2 is smaller than the working distance D1 to avoid increasing the thickness of the module.

[0066] exist Figure 8In the example shown, the microlens array 12 is depicted as being movable along a plane perpendicular to the plane in which the microlens array 12 is located, thereby switching between a working distance D1 for projecting a dotted light field and a working distance D2 for projecting a uniform light field relative to the illumination source 11. This can be achieved, for example, by configuring a linear motor or other electromagnetic actuation mechanism in the laser projection module 10' for driving the movement of the microlens array 12, or even by providing the microlens array 12 with a manual actuation and limiting structure. It should be understood that the laser projection module 10' according to this embodiment is not limited to moving the microlens array 12, and can also be configured to switch the working distance by moving the illumination source 11 or by moving both the illumination source 11 and the microlens array 12, thereby achieving a switching of the working mode.

[0067] Figure 10 This is a schematic diagram of a laser projection module according to Embodiment 3 of the present invention. Figure 10 The laser projection module 10 shown includes an illumination source 11' and two microlens arrays, namely a first microlens array 12 and a second microlens array 12'. The first microlens array 12 and the illumination source 11' have the same structure and relationship as the microlens array and illumination source in the laser projection module 10 of the present invention. In particular, they have a working distance D1 for projecting a dot matrix light source. For details, please refer to the above description, which will not be repeated here.

[0068] like Figure 10 As shown, the second microlens array 12' includes a plurality of microlenses 12'a arranged in the same plane as the first microlens array 12. The plurality of microlenses 12'a are arranged in an array with a predetermined spacing P', which is different from the arrangement spacing P of the microlenses 12a in the first microlens array 12, so that the light from the illumination source 11' is modulated by the second microlens array 12' and projected onto the target surface to form a uniform light field.

[0069] Preferably, the spacing P' in the second microlens array 12' satisfies the following relationship:

[0070]

[0071] Where M' is a non-negative integer; f' is the focal length of the second microlens 12'a; α' is a coefficient, 0 < α' ≤ 1; β' is a coefficient, 0.8 ≤ β' ≤ 1.2.

[0072] exist Figure 10In the example shown, the illumination source 11' has two light source groups corresponding to the first microlens array 12 and the second microlens array 12', respectively, and the two light source groups are shown with different light source spacings W and W' to cooperate with different microlens arrays to achieve better lattice light field and uniform light field. In some implementations, the first microlens array and the second microlens array can have different array forms, such as rectangular arrays and regular hexagonal arrays, respectively.

[0073] It should be understood that the above is merely exemplary and not limiting. For example, the illumination source 11' may correspond to two microlens arrays having a uniform light source configuration, such as having the same array form and / or the same light source spacing.

[0074] Figure 11 for Figure 10 A schematic diagram of a variant of the laser projection module shown. Figure 11 The laser projection module 10” shown has the same characteristics as... Figure 10 The laser projection module 10” shown has a basically the same structure, except that the laser projection module 10”' is configured such that the illumination source 11 can move parallel to the plane in relation to the first microlens array 12 and the second microlens array 12', so that in the working mode of projecting a dotted light field, the illumination source 11 faces the first microlens array 12, while in the working mode of projecting a uniform light field, the illumination source 11 faces the second microlens array 12'.

[0075] It should be understood that, in other implementations, the laser projection module 10”' can also be configured to switch the above-mentioned operating modes by moving the microlens array or both the microlens array and the illumination source.

[0076] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A laser projection module based on a microlens array, comprising: an illumination light source; and a first microlens array comprising a plurality of first microlenses arranged in a first plane, the plurality of first microlenses being arranged in a first array with a first pitch P, wherein the laser projection module is configured to have a first working mode; in the first working mode, the first microlens array has a first working distance D1 relative to the illumination light source in a direction perpendicular to the first plane, and a light from the illumination light source is modulated by the first microlens array to project a dot array light field on a target plane, wherein the first working distance D1 satisfies the following relationship: the first microlens has an aspheric surface profile and has focal lengths f1 and f2 along two mutually perpendicular directions in the first plane, respectively, and f = (f1 + f2) / 2. where N is a positive integer; λ is the wavelength of light from the illumination light source; f is the focal length of the first microlens; a is a first coefficient, and the first coefficient a is selected from a range of 0 < a < 1 such that: the distance of the first microlens array relative to the illumination light source is the point spot diameter in the dot matrix light field projected at the first working distance D1 is reduced compared to the point spot diameter in the dot matrix light field projected when the distance of the first microlens array relative to the illumination light source is 2. The laser projection module of claim 1, wherein, N≤5。 3. The laser projection module of claim 1, wherein, the first array is a rectangular array, a parallelogram array, or a regular hexagonal array.

4. The laser projection module of claim 1, wherein, the illumination light source comprises a plurality of light emitting points arranged in a second plane, the second plane being parallel to the first plane, and the plurality of light emitting points are arranged in a light source array with a light source pitch W, a unit structure of the light source array is a similar polygon to a unit structure of the first array.

5. The laser projection module of claim 1, wherein, the first pitch P and the light source pitch W satisfy the following relationship:

6. The laser projection module of claim 5, wherein, wW = pP where w and p are positive integers without common factors. w = p = 1.

7. The laser projection module of claim 6, wherein, the illumination light source comprises a plurality of light emitting points arranged in a second plane, the second plane being parallel to the first plane, and the plurality of light emitting points are arranged in a light source array with a light source pitch W, a unit structure of the light source array is a similar polygon to a unit structure of the first array.

8. The laser projection module of claim 4, wherein, the first pitch P and the light source pitch W satisfy the following relationship:

9. The laser projection module of claim 8, wherein, wW = pP where w and p are positive integers without common factors. w = p = 1.

10. The laser projection module of claim 9, wherein, the laser projection module is further configured to have a second working mode; in the second working mode, the first microlens array has a second working distance D2 relative to the illumination light source in the direction perpendicular to the first plane, and a light from the illumination light source is modulated by the first microlens array to project a uniform light field on the target plane, 11. The laser projection module of any one of claims 1-10, wherein, wherein the second working distance D2 satisfies the following relationship: where M is a non-negative integer, and β is a second coefficient, 0.8 ≤ β ≤ 1.

2. the second working distance is smaller than the first working distance.

12. The laser projection module of claim 11, wherein, the laser projection module is configured such that at least one of the illumination light source and the first microlens array is movable along a direction perpendicular to the first plane, so as to switch the first microlens array relative to the illumination light source between the first working distance and the second working distance.

13. The laser projection module of claim 11, wherein, 14.The laser projection module of any one of claims 1-10, further comprising: a second microlens array comprising a plurality of second microlenses arranged in a first plane, the plurality of second microlenses being arranged in a second array with a second pitch P’, ​ The laser projection module is further configured to have a second working mode; in the second working mode, light from the illumination light source is modulated by the second microlens array to project a uniform light field on the target surface.

15. The laser projection module of claim 14, wherein, The second interval P' satisfies the following relationship: wherein D1 is the first working distance; M' is a non-negative integer; f' is the focal length of the second microlens; a' is a third coefficient, 0 16. The laser projection module of claim 14, wherein, In the first working mode, the illumination light source is opposite to the first microlens array; in the second working mode, the illumination light source is opposite to the second microlens array.

17. The laser projection module of claim 16, wherein, The laser projection module is configured such that the illumination light source can move parallel to the first plane relative to the first microlens array and the second microlens array.

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