Laser beam splitter

Abstract

The present application relates to a phase reference stripe laser beam splitter, which includes a diffraction optical element with a stripe pattern on its surface. The stripe pattern is composed of a plurality of single-period patterns arranged cyclically, and each single-period pattern includes a plurality of phase reference stripes and a plurality of phase modulation strips arranged alternately. For the same incident light, the phase delay of the output light of the phase modulation stripe relative to the output light of the phase reference stripe is (k+ρ)π, where k=±1,±3,±5,..., and the value range of ρ is [0.12,0.25] and [-0.25,-0.12]. The present application can provide a 1×N laser beam splitting element with high diffraction efficiency and low non-uniformity error.

Description

Technical Field

[0001] The present invention relates to the technical field of diffraction optics, and in particular to a laser beam splitter. Background Art

[0002] An important application of diffractive optical elements is laser beam splitting. Beam splitters convert a single laser beam into multiple beams (called sub-beams). These sub-beams can be arranged in either a regular or irregular pattern. Beam splitters are also known as array generators and are referred to variously in English, including beam splitters, fan-out elements, spots array generators, and multiple beam gratings.

[0003] Laser beam splitting components are used in many fields, such as laser material processing, optical communications, optical image processing, microelectronics, and microscopy. Specific examples include simultaneous multi-hole processing, high-speed laser texturing, and fiber coupling. Specific applications of laser drilling include tear-resistant cartons and metal films in the packaging industry, cigarette tipping paper, instant noodle meshes, liquid and gas discharge ducts, and pre-weakening of metal sheets in automotive airbags.

[0004] Beam splitting is a problem that is easy to describe but often difficult to implement, especially when high diffraction efficiency rather than low uniformity error is required. Many methods can be used to achieve beam splitting, including lens arrays, rectangular aperture gratings, Dammann gratings, the recently proposed circular Dammann grating, and diffractive optical elements with non-periodic structures, such as two-step, multi-step, or continuous structures.

[0005] When the input laser of a laser beam splitter is an arbitrary pattern, the laser beam splitter can clone the input pattern into multiple patterns with the same power density distribution, polarization state, and other characteristics. For example, when the input laser is a single line, a 1×7 laser beam splitter can convert the input single line laser into 7 lines, a 1×9 laser beam splitter can convert the single line into 9 lines, a 1×11 laser beam splitter can convert the single line into 11 lines, and a 1×13 laser beam splitter can convert the single line into 13 lines. Currently, laser beams are widely used for three-dimensional measurement. However, the laser beam splitters currently on the market still have problems such as low diffraction efficiency and large non-uniformity errors. In actual applications, these problems may lead to excessive heating of the device, excessive device size, increased measurement errors, and other problems.

[0006] Specifically, the geometric reconstruction of three-dimensional shapes is an important part of artificial intelligence and artificial vision. By projecting a narrow band of light onto a three-dimensional surface and accepting the resulting distorted illumination line from another angle, the three-dimensional shape of the object can be reconstructed. A faster and more versatile method is to project a pattern consisting of multiple stripes or arbitrary stripes, because this allows multiple samples to be obtained at the same time. From different angles, the pattern consisting of multiple stripes or arbitrary stripes will appear geometrically distorted due to the surface shape of the object. Although there are many other variations of structured light projection, the pattern of parallel stripes is widely used. The displacement of the stripes makes it possible to accurately retrieve the three-dimensional coordinates of any detail on the surface of the object.

[0007] Multi-line structured light with high diffraction efficiency and low non-uniformity error is crucial for various applications. If the non-uniformity error is too large, meaning there's a significant difference in brightness between the stripes, the light stripe signals received by the optical receiver may become oversaturated, increasing the position error perceived by the receiver. More seriously, the receiver may not receive signals from dark stripes. If the diffraction efficiency is low, the device requires a higher-power laser, which increases cost, energy consumption, and size. For handheld devices, this can also shorten the device's standby time.

[0008] Therefore, there is an urgent need for laser beam splitting solutions with high diffraction efficiency and small non-uniformity error. Summary of the Invention

[0009] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a laser beam splitting solution with high diffraction efficiency and small non-uniformity error.

[0010] To solve the above technical problems, the present invention provides a laser beam splitter, characterized in that it includes a diffractive optical element having a stripe pattern on its surface, wherein the stripe pattern is composed of a plurality of single-period patterns arranged cyclically, and each of the single-period patterns includes a plurality of phase reference strips and a plurality of phase modulation strips arranged alternately; the phase delay of the output light of the phase modulation strip relative to the output light of the phase reference strip is (k+ρ)π, where k=±1,±3,±5,..., and the value range of ρ is [0.12,0.25] and [-0.25,-0.12].

[0011] The laser beam splitter is a 1×7 beam splitter, wherein in the single-period pattern, the design positions of the dividing line between the phase reference strip and the phase modulation strip are, in order: 0, 0.2265625a, 0.6484375a, 0.875a, and a, where a is the width of the single-period pattern; wherein the deviation between the actual width of the phase reference strip and the phase modulation strip and the designed width is within ±1%, or the deviation between the actual position of any of the dividing lines and the designed position is within ±0.004a. That is, when the deviation between the actual position of the dividing line and the designed position is within the above range, it can be regarded as the manufacturing tolerance of the laser beam splitter and is covered by the protection scope of this application, and will not be further described below.

[0012] The laser beam splitter is a 1×7 beam splitter, and in the single-period pattern, the normalized design positions of the boundary line between the phase reference strip and the phase modulation strip are as follows:

[0013] 0, 0.2109375, 0.6640625, 0.875, and 1;

[0014] 0, 0.21875, 0.65625, 0.875, and 1;

[0015] 0, 0.2265625, 0.6484375, 0.875, and 1;

[0016] 0, 0.234375, 0.640625, 0.875, and 1;

[0017] 0, 0.203125, 0.65625, 0.859375, and 1;

[0018] 0, 0.2109375, 0.6484375, 0.859375, and 1;

[0019] 0, 0.21875, 0.640625, 0.859375, and 1;

[0020] 0, 0.1953125, 0.6484375, 0.84375, and 1;

[0021] 0, 0.203125, 0.640625, 0.84375, and 1;

[0022] 0, 0.234375, 0.359375, 0.59375, and 1;

[0023] 0, 0.21875, 0.359375, 0.578125, and 1;

[0024] 0, 0.234375, 0.34375, 0.578125, and 1;

[0025] 0, 0.203125, 0.359375, 0.5625, and 1;

[0026] 0, 0.2109375, 0.3515625, 0.5625, and 1;

[0027] 0, 0.21875, 0.34375, 0.5625, and 1;

[0028] 0, 0.1953125, 0.3515625, 0.546875, and 1;

[0029] 0, 0.203125, 0.34375, 0.546875, and 1; or

[0030] 0, 0.2109375, 0.3359375, 0.546875, and 1;

[0031] The deviations between the actual widths of the phase reference strip and the phase modulation strip and the designed widths are both within ±1%, or the deviation between the actual position of any one of the dividing lines and the designed position is within ±0.004.

[0032] Among them, where k=1, the value range of ρ is [-0.222, -0.209].

[0033] In which, the laser beam splitter is a 1×9 beam splitter, wherein in the single-period pattern, the design positions of the dividing line between the phase reference strip and the phase modulation strip are: 0, 0.1953125a, 0.265625a, 0.453125a, 0.5234375a, 0.71875a and a, respectively, where a is the width of the single-period pattern; wherein the deviation between the actual width of the phase reference strip and the phase modulation strip and the designed width is within ±1%, or the deviation between the actual position of any one of the dividing lines and the designed position is within ±0.004a.

[0034] The laser beam splitter is a 1×9 beam splitter, and in the single-period pattern, the normalized design positions of the boundary line between the phase reference strip and the phase modulation strip are as follows:

[0035] 0, 0.1953125, 0.28125, 0.3203125, 0.5546875, 0.59375, 0.6796875, 0.875, and 1;

[0036] 0, 0.1953125, 0.2890625, 0.328125, 0.546875, 0.5859375, 0.6796875, 0.875, and 1;

[0037] 0, 0.171875, 0.25, 0.2890625, 0.5703125, 0.609375, 0.6875, 0.859375, and 1;

[0038] 0, 0.1796875, 0.2578125, 0.296875, 0.5625, 0.6015625, 0.6796875, 0.859375, and 1;

[0039] 0, 0.1796875, 0.265625, 0.3046875, 0.5546875, 0.59375, 0.6796875, 0.859375, and 1;

[0040] 0, 0.0390625, 0.1328125, 0.328125, 0.453125, 0.6484375, 0.7421875, 0.78125, and 1;

[0041] 0, 0.0390625, 0.125, 0.3203125, 0.4453125, 0.640625, 0.7265625, 0.765625, and 1;

[0042] 0, 0.0390625, 0.125, 0.3046875, 0.4453125, 0.625, 0.7109375, 0.75, and 1;

[0043] 0, 0.0390625, 0.1171875, 0.296875, 0.4375, 0.6171875, 0.6953125, 0.734375, and 1;

[0044] 0, 0.0390625, 0.1171875, 0.2890625, 0.4296875, 0.6015625, 0.6796875, 0.71875, and 1; or

[0045] 0, 0.1953125, 0.265625, 0.453125, 0.5234375, 0.71875, and 1;

[0046] The deviations between the actual widths of the phase reference strip and the phase modulation strip and the designed widths are both within ±1%, or the deviation between the actual position of any one of the dividing lines and the designed position is within ±0.004.

[0047] Where k=1, the value range of ρ is [-0.164, -0.158].

[0048] In which, the laser beam splitter is a 1×13 beam splitter, wherein in the single-period pattern, the design positions of the dividing line between the phase reference strip and the phase modulation strip are: 0, 0.1328125a, 0.2265625a, 0.3125a, 0.359375a, 0.4453125a, 0.5390625a, 0.671875a and a; wherein a is the width of the single-period pattern, k=1, the value range of ρ is [-0.145, -0.127], and the deviation between the actual width of the phase reference strip and the phase modulation strip and the designed width is within ±1%, or the deviation between the actual position of any one of the dividing lines and the designed position is within ±0.004a.

[0049] The diffractive optical element is a transmissive diffractive optical element, the depth d1 of the phase reference strip is 0, and the depth d2 of the phase modulation strip is:

[0050]

[0051] Wherein, λ is the wavelength of incident light, the diffractive optical elements are made of the same light-transmitting material, and n is the refractive index of the light-transmitting material.

[0052] The diffractive optical element is a transmissive diffractive optical element, which is made of a first light-transmitting material and a second light-transmitting material. The thickness of the phase reference strip is equal to the thickness of the phase modulation strip. The refractive index n1 of the first light-transmitting material and the refractive index n2 of the second light-transmitting material satisfy:

[0053]

[0054] Wherein, λ is the wavelength of incident light, and d is the thickness of the diffractive optical element.

[0055] Wherein, the diffractive optical element is a reflective diffractive optical element, and when the depth of the surface of the phase reference strip is 0, the depth d3 of the groove or protrusion of the phase modulation strip is:

[0056]

[0057] Wherein, λ is the wavelength of the incident light. When the depth d3 is positive, the phase modulation stripe is a stripe-shaped groove. When the depth d3 is negative, the phase modulation stripe is a stripe-shaped protrusion.

[0058] Compared with the prior art, this application has at least one of the following technical effects:

[0059] 1. The present application can provide a 1×N laser beam splitting element with high diffraction efficiency and low non-uniformity error.

[0060] 2. The present application can provide a 1×7 laser beam splitting element with high diffraction efficiency and low non-uniformity error.

[0061] 3. The present application can provide a 1×9 laser beam splitting element with high diffraction efficiency and low non-uniformity error.

[0062] 4. The present application can provide a 1×13 laser beam splitting element with high diffraction efficiency and low non-uniformity error. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 shows a single-period pattern of a stripe pattern of a diffractive optical element in one embodiment of the present application;

[0064] Figure 2a FIG4 shows a side view schematic diagram of a single-period pattern of a diffractive optical element in one embodiment of the present application;

[0065] Figure 2b A schematic side view of two continuously arranged single-periodic patterns of diffractive optical elements in one embodiment of the present application is shown;

[0066] Figure 3a A side view schematic diagram showing a single-period pattern in one embodiment of the present application shifted to the right by a certain distance is shown;

[0067] Figure 3b 1 shows a schematic top view of a single-period pattern after all turning points based on the design solution 3 in Table 1 are shifted to the right by 0.0125 in one embodiment of the present application;

[0068] Figure 4 A schematic diagram showing the variation of diffraction efficiency and non-uniformity error with ρ in a 1×7 beam splitting design.

[0069] Figure 5 A schematic diagram showing the variation of diffraction efficiency and non-uniformity error with ρ in a 1×9 beam splitting design;

[0070] Figure 6 A schematic diagram showing how the diffraction efficiency and non-uniformity error vary with ρ in a 1×13 beam splitting design. DETAILED DESCRIPTION

[0071] For a better understanding of the present application, various aspects of the present application will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely descriptions of exemplary embodiments of the present application and are not intended to limit the scope of the present application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0072] It should be noted that in this specification, the expressions of first, second, etc. are only used to distinguish one feature from another feature, and do not represent any limitation on the features. Therefore, without departing from the teaching of this application, the first subject discussed below can also be referred to as the second subject.

[0073] In the accompanying drawings, the thickness, size and shape of objects have been slightly exaggerated for ease of explanation. The accompanying drawings are only examples and are not drawn strictly to scale.

[0074] It should also be understood that the terms "comprises," "including," "having," "includes," and / or "comprising," when used in this specification, indicate the presence of the stated features, integers, steps, operations, elements, and / or parts, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, and / or combinations thereof. In addition, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire listed features rather than modifying the individual elements in the list. In addition, when describing embodiments of the present application, "may" is used to mean "one or more embodiments of the present application." And, the term "exemplary" is intended to refer to an example or illustration.

[0075] As used herein, the terms "substantially," "approximately," and similar terms are used as terms of approximation, not degree, and are intended to account for the inherent variations in measurements or calculations that would be recognized by those having ordinary skill in the art.

[0076] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which this application belongs. It should also be understood that terms (such as those defined in commonly used dictionaries) should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology and will not be interpreted in an idealized or overly formal sense unless expressly defined as such herein.

[0077] It should be noted that, unless there is any conflict, the embodiments and features in the embodiments of this application can be combined with each other.

[0078] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0079] According to one embodiment of the present application, a laser beam splitter is provided, which includes a diffractive optical element having a periodic strip pattern, wherein each period of the strip pattern includes multiple phase reference strips and multiple phase modulation strips, and the phase reference strips can serve as a reference for phase modulation. For example, a certain configuration can be used to make the phase delay of the output light of the phase modulation strip relative to the output light of the phase reference strip be (k+ρ)π. In one example, by setting a suitable thickness for the phase reference strip, the phase of the output light (e.g., the output light) of the phase reference strip is completely consistent with the phase of the incident light, that is, the phase reference strip can be regarded as not modulating the incident light, and therefore can also be referred to as a zero phase difference strip. However, it should be noted that the zero phase difference strip is only a special case. In fact, the phase of the output light of the phase reference strip can have a constant phase difference with the incident light. For example, the phase reference strip can be configured to cause the incident light to be emitted after a phase delay of φ0, and the phase modulation strip causes the incident light to be emitted after a phase delay of φ0+(k+ρ)π. The phase delay φ0 can be regarded as the reference phase. For a transmissive diffractive optical element, since the thickness of the transmissive diffractive optical element corresponding to the phase reference strip is constant, φ0 is also constant. When the laser is incident vertically, the phase reference strip of the transmissive diffractive optical element delays the phase of the incident light. Where d is the thickness of the transmissive diffractive optical element at the phase reference strip, n is the refractive index of the material at the phase reference strip, and λ is the wavelength of the incident light. For reflective diffractive optical elements, due to half-wave loss, incident light will be delayed or advanced by half a wavelength when reflected from both the phase reference strip and the phase modulation strip.

[0080] Furthermore, in the above embodiment, k = ±1, ±3, ±5, ..., ρ = ±0.12 to 0.25. That is, the value range of ρ is [0.12, 0.25] and [-0.25, -0.12]. When k is a positive integer, ρ can be positive or negative; similarly, when k is a negative integer, ρ can be positive or negative. The optimal value of ρ varies under different stripe pattern designs, and its optimal value can be obtained through scalar or strict vector diffraction formula simulation. Figure 1 FIG1 shows a single periodic pattern of a stripe pattern of a diffractive optical element in an embodiment of the present application. Part (a) shows a single periodic pattern at a top view angle, and part (b) shows a single periodic pattern at a side view angle. Figure 1As shown, in this embodiment, the phase reference strips and the phase modulation strips are arranged alternately, and the boundary positions between the phase reference strips and the phase modulation strips in a single cycle are: 0, 0.2265625a, 0.6484375a, 0.875a and a, where a is the width of a single cycle of the strip pattern. The first segment defined by the above-mentioned dividing line, that is, the segment from 0 to 0.2265625a, is the phase modulation strip. Figure 1 The white area in part (a) of . Accordingly, Figure 1 The black area in part (a) corresponds to the phase reference strip. Generally speaking, the strip pattern of the laser beam splitter can include tens, hundreds or even thousands of periods. The diffraction optical element of this embodiment can split the linear laser (such as line structured light) into 1×7 beams, that is, when the incident light is a single linear laser, the outgoing light is 7 parallel linear lasers. Based on the single-period pattern of this embodiment, the inventors conducted actual tests on the diffraction optical element. When the value of ρ is -0.222 to -0.209, the non-uniformity error of the diffraction optical element is 6.1%, and the diffraction efficiency is 82%. It can be seen that the laser beam splitter design of this embodiment can obtain very excellent diffraction efficiency, while also having excellent non-uniformity error performance.

[0081] Furthermore, in some other embodiments of the present application, a variety of other single-cycle patterns are provided to achieve 1×7 splitting. Table 1 shows 18 single-cycle pattern design schemes for 1×7 splitting in the present application. Among them, the design scheme provided in the first embodiment is Design 3 in Table 1. The turning point in Table 1 is the dividing line between the phase reference strip and the phase modulation strip. The values recorded in the turning point items in Table 1 are normalized values, that is, the values recorded in the turning point items in Table 1 are: the turning point positions assuming that the width of the single-cycle pattern is 1. Similarly, the value recorded in the minimum width item between the two turning points is also a normalized value, that is, the minimum width between the two turning points assuming that the width of the single-cycle pattern is 1. Furthermore, Figure 4 The diagram shows the diffraction efficiency and non-uniformity error of the 1×7 beam splitting design as a function of ρ. Figure 4 It can be seen from the figure that for the 1×7 beam splitting design, when the value range of ρ is [-0.222, -0.209], the diffractive optical element has better diffraction efficiency and non-uniformity error.

[0082] Table 1

[0083]

[0084]

[0085]

[0086] Furthermore, in some embodiments of the present application, the phase reference stripes and the phase modulation stripes in the stripe pattern can be realized by providing stripe-shaped grooves on the surface of the diffractive optical element. Figure 2a A side view schematically shows a single-period pattern of a diffractive optical element in one embodiment of the present application. Figure 2b FIG2 shows a schematic side view of two single-period patterns of continuously arranged diffractive optical elements in one embodiment of the present application. Figure 2a and Figure 2b In this embodiment, the surface of the diffractive optical element has a plurality of strip-shaped grooves, which correspond to the phase modulation strips. The strip-shaped platform areas formed between the grooves are phase reference strips. Furthermore, in this embodiment, the depth d1 of the phase reference strips of the diffractive optical element is 0;

[0087] The depth d2 of the phase modulation strip is:

[0088]

[0089] Where λ is the wavelength of the incident light, n is the refractive index of the light-transmitting material constituting the diffractive optical element, and k = ±1, ±3, ±5, ... Herein, the depth of a stripe of a diffractive optical element can be understood as the depth of a groove formed by processing the element surface (e.g., photolithography or etching). When the depth is a negative number, the corresponding stripe can be understood as a boss.

[0090] When k=1, the diffraction optical element can have a smaller thickness, so the material cost is lower. At this time, if ρ takes a negative number, that is, ρ takes a value in the range [-0.25,-0.12], it is only necessary to etch a strip-shaped groove with a smaller depth on the surface of the plate-shaped transparent material to obtain the required strip pattern for realizing the laser beam splitting function. Due to the small etching depth, the above design concept has many advantages such as low process cost and high production efficiency. In this embodiment, the incident light enters the translucent diffraction optical element, and after being modulated by the diffraction optical element, it is emitted from the other surface of the diffraction optical element. In other words, this embodiment adopts a transmissive diffraction optical element. The above-mentioned transmissive diffraction optical element can be applied to any single-period pattern design scheme listed in Table 1.

[0091] Furthermore, in some other embodiments of the present application, a reflective diffraction optical element may be used. The reflective diffraction optical element may also have a plurality of strip-shaped grooves and strip-shaped bosses located between the grooves, thereby forming an optical path difference, thereby achieving the desired phase modulation. In this embodiment, since the incident light beam will not penetrate the diffraction optical element, the thickness of the diffraction optical element itself may not be restricted, but the phase reference strip (the light reflected by the strip has no phase difference with the incident light) is achieved by adjusting the distance between the diffraction optical element and the incident light source. As for the phase modulation strip, there is a specific thickness difference between it and the phase reference strip, thereby achieving the desired phase difference. Specifically, when the surface of the phase reference strip (referring to the reflecting surface) is 0, the groove or boss depth d3 of the phase modulation strip is:

[0092]

[0093] Wherein, λ is the wavelength of incident light, k = ±1, ±3, ±5, ..., ρ = ±0.12 to 0.25.

[0094] When the depth d3 is positive, the phase modulation strip is a stripe-shaped groove, and when the depth d3 is negative, the phase modulation strip is a stripe-shaped protrusion.

[0095] It should be noted that the above-mentioned reflective diffractive optical element can be applied to any single-period pattern design scheme listed in Table 1.

[0096] Furthermore, in some other embodiments of the present application, the transmissive diffractive optical element can also use different refractive indices to achieve phase modulation. Since different refractive index materials are used to realize the phase reference strips and the phase modulation strips, the transmissive diffractive optical element can have no height difference. Assuming that the refractive index of the transparent material of the phase reference strips is n1 and the refractive index of the transparent material of the phase modulation strips is n2, then:

[0097]

[0098] Wherein, λ is the wavelength of incident light, d is the thickness of the diffractive optical element, and k = ±1, ±3, ±5, ...

[0099] It should be noted that the above-mentioned reflective diffractive optical element can be applied to any single-period pattern design scheme listed in Table 1.

[0100] Each laser beam splitter in the above embodiment is used to achieve 1×7 beam splitting, but the present application is not limited to this. By designing a new stripe pattern, 1×9 beam splitting, 1×13 beam splitting, and more beam splitting can also be achieved. Table 2 shows 11 single-cycle pattern design schemes for 1×9 beam splitting in this application. Among them, design scheme 11 is the preferred scheme, and the preferred value range of ρ is [-0.164, -0.158]. Further, Figure 5 The diagram shows the diffraction efficiency and non-uniformity error of the 1×9 beam splitting design as a function of ρ. Figure 5 It can be seen from the figure that for the 1×9 beam splitting design, when the value range of ρ is [-0.164, -0.158], the diffractive optical element has better diffraction efficiency and non-uniformity error.

[0101] Table 2

[0102]

[0103]

[0104]

[0105]

[0106] Table 3 shows a single-period pattern design scheme for 1×13 beam splitting in this application. In this design scheme, the preferred value range of ρ is [-0.145, -0.127]. Figure 6 The diagram shows the variation of diffraction efficiency and non-uniformity error with ρ in the 1×13 beam splitting design. Figure 6 It can be seen from the figure that for the 1×13 beam splitting design, when the value range of ρ is [-0.145, -0.127], the diffractive optical element has better diffraction efficiency and non-uniformity error.

[0107] Table 3

[0108]

[0109] Any of the single-periodic patterns in Tables 2 and 3 can be combined with the aforementioned transmissive or reflective diffractive optical elements. A transmissive diffractive optical element can be made of a single light-transmitting material, with different thicknesses (also understood as groove depths) used to create the phase reference and phase modulation strips. Alternatively, the diffractive optical element can have a uniform thickness (i.e., no grooves) and use light-transmitting materials with different refractive indices to create the phase reference and phase modulation strips. Specific thickness and refractive index setting methods can be found in the previous section and will not be detailed here.

[0110] It should be noted that in this application, the stripe pattern of the diffractive optical element can be manufactured using semiconductor processes, such as photolithography or etching. The manufacturing error of the actual position of the turning point of the single-period pattern compared to the designed position can be much less than 1%. When the manufacturing error is less than 1%, the beam splitter still has high diffraction efficiency and the non-uniformity error can be controlled within a reasonable range. Taking the 1×9 beam splitter corresponding to the 11th design in Table 2 as an example, when the error of the first turning point (turning point 0.1953125) is -1% (the -1% here refers to -1% of the width of the strip determined by the turning point, which will not be repeated below), its diffraction efficiency increases from 77.7% to 78.2%, and its non-uniformity error increases from 2.8% to 7.5% (this non-uniformity error is still less than 10% and is within a reasonable range). When the error of the first turning point is +1%, its diffraction efficiency decreases from 77.7% to 77.2%, and its non-uniformity error increases from 2.8% to 9.5% (this non-uniformity error is still less than 10% and is within a reasonable range). For another example, taking the 1×9 beam splitter corresponding to the 11th design in Table 2, when the error of the last turning point (i.e., turning point 1) is -1%, its diffraction efficiency decreases from 77.7% to 77.2%, and its non-uniformity error increases from 2.8% to 7.7%. When the error of the last turning point is +1%, its diffraction efficiency increases from 77.7% to 78.1%, and its non-uniformity error increases from 2.8% to 12.1%. In summary, for any of the single-period pattern designs for the beam splitters in Tables 1, 2, and 3, if the manufacturing error of the turning point position (i.e., the boundary between the phase reference stripe and the phase modulation stripe) is within ±1%, the actual product can be considered to meet the basic requirements of the design. Of course, when semiconductor processes such as photolithography or etching are used to manufacture the stripe pattern of a diffractive optical element, the manufacturing error can actually be far less than ±1%, thereby achieving the optimal performance of the corresponding design.

[0111] In general, the design schemes listed in Tables 1, 2, and 3 are theoretically ideal. In actual laser beam splitters, a certain degree of error in the single-cycle pattern is permitted, but this error should be limited to a certain range. Preferably, the manufacturing error of the laser beam splitter should satisfy the following requirements: 1) the deviation between the actual width of the phase reference stripe and the phase modulation stripe and the designed width is within ±1%, or 2) the deviation between the actual position of any one of the dividing lines (i.e., turning points) and the designed position is within ±0.004a. Where a is the single-cycle width. When the positions of the turning points are expressed as normalized values, a = 1. Therefore, condition 2) can be written as the deviation between the actual position of any one of the dividing lines (i.e., turning points) and the designed position is within ±0.004. The designed width is the width of the phase reference stripe or the phase modulation stripe, determined by the designed position of the dividing line; the actual width is the width of the phase reference stripe or the phase modulation stripe in the actual laser beam splitter. As long as any one of the above conditions 1) and 2) is met, the manufacturing error of the laser beam splitter is deemed to be within a reasonable range and is covered by the protection scope of this application.

[0112] Among the multiple design solutions shown in Tables 1, 2, and 3, Design 3 was the best for a 1×7 beamsplitter, with a non-uniformity error of 6.1% and a diffraction efficiency of 82%. For a 1×9 beamsplitter, Design 11 was the best solution, with a non-uniformity error of 2.8% and a diffraction efficiency of 77.7%. For a 1×13 beamsplitter, the design solution in Table 3 achieved a non-uniformity error of 11% and a diffraction efficiency of 80%.

[0113] It should be noted that in this application, the description of the turning point positions in Tables 1, 2, and 3 for the same design solution is not unique. Because the stripe pattern of the diffractive optical element is arranged periodically, shifting a single periodic pattern to the right or left will not affect the actual performance of the stripe pattern. Figure 3a FIG2 shows a side view of a single-period pattern in an embodiment of the present application shifted to the right by a certain distance. Figure 3a , the single-period pattern shifts to the right (or left), that is, all the turning points of the single-period pattern shift to the right (or left) as a whole, which will not affect the structure of the entire stripe pattern itself, and therefore will not affect the actual performance of the stripe pattern. For example, Figure 3b The diagram shows a schematic top view of a single-period pattern after all turning points of the design solution 3 in Table 1 are shifted to the right by 0.0125 in one embodiment of the present application. Figure 3bFor Design 3 in Table 1, if its starting point is shifted to the right by 0.0125, the rightmost black area moves to the leftmost. After the rightward shift of 0.0125, the turning points of the single-period pattern can be expressed as: 0, 0.0125, 0.2390625, 0.6609375, 0.8875, 1 (normalized, assuming the width of the single-period pattern is 1). If the starting point of Design 3 in Table 1 is shifted to the left by 0.6484375, the turning points of the single-period pattern can be expressed as: 0, 0.2265625, 0.3515625, 0.578125, 1 (normalized, assuming the width of the single-period pattern is 1). The above-mentioned turning point combinations of the single-period pattern obtained by rightward or leftward shift are merely modified expressions of the same design solution and are essentially equivalent to the turning point combinations recorded in Table 1, Table 2, or Table 3. In other words, the design solutions represented by the turning point combinations recorded in Table 1, Table 2 or Table 3 should be considered to cover various deformed turning point combinations obtained by shifting the turning point combinations recorded in the above tables to the left or right.

[0114] In this application, the turning point location data for each design scheme in Tables 1, 2, and 3 was derived using a simulated annealing algorithm, using a computer to search and optimize within a large data space. Generally speaking, product non-uniformity errors are very sensitive to the design location of the turning point; even small deviations can lead to a dramatic increase in non-uniformity errors. Therefore, finding the appropriate turning point location is one of the main design challenges of a 1×N laser beam splitter. This article does not provide a detailed description of the simulated annealing algorithm and the corresponding turning point location search and optimization methods.

[0115] In this application, the value of the single-period width a affects the diffraction angle of the emitted light. The non-uniformity errors recorded in Tables 1, 2, and 3 are the best data that can be achieved within the diffraction angle range commonly used in existing applications of laser beam splitters. When the value of the single-period width a changes, the diffraction angle changes accordingly, which may lead to a certain decline in the performance of the non-uniformity error. However, in general, under the premise of a certain diffraction angle, the various design schemes recorded in Tables 1, 2, and 3 are preferred schemes for 1×7, 1×9, or 1×13 laser beam splitters. Under these preferred schemes, excellent diffraction efficiency and relatively excellent non-uniformity error data can be obtained simultaneously.

[0116] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention and are intended to be encompassed by the claims of the present invention.

Claims

1. A laser beam splitter, characterized in that: A diffractive optical element having a stripe pattern on its surface, wherein the stripe pattern is composed of a plurality of single-period patterns arranged cyclically, and each of the single-period patterns includes a plurality of phase reference stripes and a plurality of phase modulation stripes arranged alternately; for the same incident light, the phase delay of the output light of the phase modulation stripes relative to the output light of the phase reference stripes is (k+ρ)π, where k = ±1, ±3, ±5, ..., and the value range of ρ is [0.12, 0.25] and [-0.25, -0.12]; In which, the laser beam splitter is a 1×7 beam splitter, wherein in the single-cycle pattern, the design positions of the dividing line between the phase reference strip and the phase modulation strip are: 0, 0.2265625a, 0.6484375a, 0.875a and a, respectively, where a is the width of the single-cycle pattern; wherein the deviation between the actual width of the phase reference strip and the phase modulation strip and the designed width is within ±1%, or the deviation between the actual position of any one of the dividing lines and the designed position is within ±0.004a.

2. A laser beam splitter, characterized in that: A diffractive optical element having a stripe pattern on its surface, wherein the stripe pattern is composed of a plurality of single-period patterns arranged cyclically, and each of the single-period patterns includes a plurality of phase reference stripes and a plurality of phase modulation stripes arranged alternately; for the same incident light, the phase delay of the output light of the phase modulation stripes relative to the output light of the phase reference stripes is (k+ρ)π, where k = ±1, ±3, ±5, ..., and the value range of ρ is [0.12, 0.25] and [-0.25, -0.12]; The laser beam splitter is a 1×7 beam splitter, and in the single-period pattern, the normalized design positions of the boundary line between the phase reference strip and the phase modulation strip are as follows: 0, 0.2109375, 0.6640625, 0.875, and 1; 0, 0.21875, 0.65625, 0.875, and 1; 0, 0.234375, 0.640625, 0.875, and 1; 0, 0.203125, 0.65625, 0.859375, and 1; 0, 0.2109375, 0.6484375, 0.859375, and 1; 0, 0.21875, 0.640625, 0.859375, and 1; 0, 0.1953125, 0.6484375, 0.84375, and 1; 0, 0.203125, 0.640625, 0.84375, and 1; 0, 0.234375, 0.359375, 0.59375, and 1; 0, 0.21875, 0.359375, 0.578125, and 1; 0, 0.234375, 0.34375, 0.578125, and 1; 0, 0.203125, 0.359375, 0.5625, and 1; 0, 0.2109375, 0.3515625, 0.5625, and 1; 0, 0.21875, 0.34375, 0.5625, and 1; 0, 0.1953125, 0.3515625, 0.546875, and 1; 0, 0.203125, 0.34375, 0.546875, and 1; or 0, 0.2109375, 0.3359375, 0.546875, and 1; The deviation between the actual width of the phase reference strip and the phase modulation strip and the designed width is within ±1%, or the deviation between the actual position of any one of the dividing lines and the designed position is within ±0.004, where k=1 and the value range of ρ is [-0.222, -0.209].

3. A laser beam splitter, characterized in that: A diffractive optical element having a stripe pattern on its surface, wherein the stripe pattern is composed of a plurality of single-period patterns arranged cyclically, and each of the single-period patterns includes a plurality of phase reference stripes and a plurality of phase modulation stripes arranged alternately; for the same incident light, the phase delay of the output light of the phase modulation stripes relative to the output light of the phase reference stripes is (k+ρ)π, where k = ±1, ±3, ±5, ..., and the value range of ρ is [0.12, 0.25] and [-0.25, -0.12]; In which, the laser beam splitter is a 1×9 beam splitter, wherein in the single-period pattern, the design positions of the dividing line between the phase reference strip and the phase modulation strip are: 0, 0.1953125a, 0.265625a, 0.453125a, 0.5234375a, 0.71875a and a, respectively, where a is the width of the single-period pattern; wherein the deviation between the actual width of the phase reference strip and the phase modulation strip and the designed width is within ±1%, or the deviation between the actual position of any one of the dividing lines and the designed position is within ±0.004a.

4. A laser beam splitter, characterized in that: A diffractive optical element having a stripe pattern on its surface, wherein the stripe pattern is composed of a plurality of single-period patterns arranged cyclically, and each of the single-period patterns includes a plurality of phase reference stripes and a plurality of phase modulation stripes arranged alternately; for the same incident light, the phase delay of the output light of the phase modulation stripes relative to the output light of the phase reference stripes is (k+ρ)π, where k = ±1, ±3, ±5, ..., and the value range of ρ is [0.12, 0.25] and [-0.25, -0.12]; The laser beam splitter is a 1×9 beam splitter, and in the single-period pattern, the normalized design positions of the boundary line between the phase reference strip and the phase modulation strip are as follows: 0, 0.1953125, 0.28125, 0.3203125, 0.5546875, 0.59375, 0.6796875, 0.875, and 1; 0, 0.1953125, 0.2890625, 0.328125, 0.546875, 0.5859375, 0.6796875, 0.875, and 1; 0, 0.171875, 0.25, 0.2890625, 0.5703125, 0.609375, 0.6875, 0.859375, and 1; 0, 0.1796875, 0.2578125, 0.296875, 0.5625, 0.6015625, 0.6796875, 0.859375, and 1; 0, 0.1796875, 0.265625, 0.3046875, 0.5546875, 0.59375, 0.6796875, 0.859375, and 1; 0, 0.0390625, 0.1328125, 0.328125, 0.453125, 0.6484375, 0.7421875, 0.78125, and 1; 0, 0.0390625, 0.125, 0.3203125, 0.4453125, 0.640625, 0.7265625, 0.765625, and 1; 0, 0.0390625, 0.125, 0.3046875, 0.4453125, 0.625, 0.7109375, 0.75, and 1; 0, 0.0390625, 0.1171875, 0.296875, 0.4375, 0.6171875, 0.6953125, 0.734375, and 1; or 0, 0.0390625, 0.1171875, 0.2890625, 0.4296875, 0.6015625, 0.6796875, 0.71875, and 1; The deviation between the actual width of the phase reference strip and the phase modulation strip and the designed width is within ±1%, or the deviation between the actual position of any one of the dividing lines and the designed position is within ±0.004, where k=1 and the value range of ρ is [-0.164, -0.158].

5. A laser beam splitter, characterized in that: A diffractive optical element having a stripe pattern on its surface, wherein the stripe pattern is composed of a plurality of single-period patterns arranged cyclically, and each of the single-period patterns includes a plurality of phase reference stripes and a plurality of phase modulation stripes arranged alternately; for the same incident light, the phase delay of the output light of the phase modulation stripes relative to the output light of the phase reference stripes is (k+ρ)π, where k = ±1, ±3, ±5, ..., and the value range of ρ is [0.12, 0.25] and [-0.25, -0.12]; In which, the laser beam splitter is a 1×13 beam splitter, wherein in the single-period pattern, the design positions of the dividing line between the phase reference strip and the phase modulation strip are: 0, 0.1328125a, 0.2265625a, 0.3125a, 0.359375a, 0.4453125a, 0.5390625a, 0.671875a and a; wherein a is the width of the single-period pattern, k=1, the value range of ρ is [-0.145, -0.127], and the deviation between the actual width of the phase reference strip and the phase modulation strip and the designed width is within ±1%, or the deviation between the actual position of any one of the dividing lines and the designed position is within ±0.004a.

6. The laser beam splitter according to any one of claims 1 to 5, characterized in that: The diffractive optical element is a transmissive diffractive optical element, and the depth d1 of the phase reference strip is 0; The depth d2 of the phase modulation strip is: Wherein, λ is the wavelength of incident light, the diffractive optical elements are made of the same light-transmitting material, and n is the refractive index of the light-transmitting material.

7. The laser beam splitter according to any one of claims 1 to 5, characterized in that: The diffractive optical element is a transmissive diffractive optical element, and is made of a first light-transmitting material and a second light-transmitting material. The thickness of the phase reference strip is equal to the thickness of the phase modulation strip. The refractive index n1 of the first light-transmitting material and the refractive index n2 of the second light-transmitting material satisfy: Wherein, λ is the wavelength of incident light, and d is the thickness of the diffractive optical element.

8. The laser beam splitter according to any one of claims 1 to 5, characterized in that: The diffractive optical element is a reflective diffractive optical element. When the depth of the surface of the phase reference strip is 0, the depth d3 of the groove or protrusion of the phase modulation strip is: Wherein, λ is the wavelength of the incident light. When the depth d3 is positive, the phase modulation stripe is a stripe-shaped groove. When the depth d3 is negative, the phase modulation stripe is a stripe-shaped protrusion.

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