A light beam splitting parallel output device

Abstract

The application relates to a light beam splitting parallel output device, which comprises a diffraction splitting element, a flat optical window sheet and a focusing optical element arranged in sequence along an optical axis; the optical window sheet has an incident surface and an exit surface, and the incident surface and the exit surface are both coated with a reflective layer; in the incident surface, a light-transmitting region is formed in a central region of the reflective layer corresponding to the optical axis; in the exit surface, a plurality of light-transmitting regions are formed in the reflective layer, and the number of the light-transmitting regions in the exit surface is the same as the splitting number N of the diffraction splitting element; and the interval of sub-beams emitted from the exit surface is an even multiple of a coating distance parameter. The application can shorten the axial interval between the diffraction splitting element and the focusing lens under the premise of ensuring the beam quality (such as the parallelism of the sub-beams) of each sub-beam, thereby helping the light beam splitting parallel output device to realize miniaturization.

Description

Technical Field

[0001] This invention relates to the field of optical device technology, and more specifically, to a beam splitting and parallel output device. Background Technology

[0002] A diffractive beam splitter (DOE) is a typical diffractive optical element that splits an incident laser beam into multiple sub-beams. These sub-beams are projected onto a working plane, enabling various applications such as laser scribing, laser cutting, and laser drilling. For example, in solar cell manufacturing, multiple sub-beams can be projected at equal intervals onto a working plane for mass laser scribing of solar cells; in liquid crystal display (LCD) manufacturing, multiple sub-beams can be projected at equal intervals onto a working plane for mass laser cutting of LCDs; furthermore, diffractive beam splitters can also be used to output multiple sub-beams for mass laser drilling of cigarette filters. In addition to these applications, diffractive beam splitters can also be used for laser power monitoring to achieve beam sampling; they can also be used in 3D sensing technology (e.g., for 3D sensing in Kinect); and they can also be used in skin treatment and cosmetic procedures.

[0003] In existing technologies, the output sub-beams of diffraction beam splitters typically have an angle. Other sub-beams, except the zeroth-order sub-beam, are projected obliquely onto the working plane. Therefore, a crucial parameter of a diffraction beam splitter is the angular spacing of the emitted laser beams after diffraction. For example, if the adjacent angular spacing is 20 mrad (milliradians), then at a working distance of 1000 mm (millimeters), the distance between two adjacent emitted laser beams is approximately 20 mm; while at a working distance of 1500 mm, the distance is approximately 30 mm. It can be seen that under this output method, the distance between the various laser sub-beams on the workpiece surface increases with the working distance. In some applications, to ensure that the spacing of each sub-beam on the working plane meets design requirements, the distance between the diffraction beam splitter and the working plane must be accurate, which places high demands on the assembly precision of the optical path system. However, the laser output device and the working plane are usually two independent devices, and the assembly precision required to assemble them together is sometimes difficult to achieve. More seriously, when sub-beams other than the zeroth-order sub-beam are projected obliquely onto the working plane, it will be impossible to obtain a hole or machining section perpendicular to the workpiece surface when using such sub-beams for machining (such as drilling), making it difficult to meet the usage requirements of actual application scenarios.

[0004] To overcome the above problems, a type of equally spaced beam splitting output device has emerged on the market, which combines diffraction beam splitting elements with focusing lenses. Equally spaced beam splitting output means that each sub-beam is output in parallel after beam splitting. Figure 1A schematic diagram of the optical path of a typical equally spaced beam splitter output device is shown. (Reference) Figure 1 A focusing lens 3 (where f is the focal length of the focusing lens 3) can be placed at a focal length f behind the diffraction beam splitter 1. This focusing lens 3 can focus each sub-beam output from the diffraction beam splitter 1 at a given distance, thereby converting the individual sub-beams output at equal angles into multiple sub-beams parallel to the optical axis. The spacing between the parallel sub-beams is not affected by the position of the working plane, reducing the difficulty of setting up the laser output device and the working plane. Furthermore, since each sub-beam can be projected perpendicularly onto the working plane, it can have a higher quality projected spot compared to beams projected at an angle, thereby improving the accuracy of laser processing (or laser treatment). On the other hand, the distance between the focusing lens and the diffraction beam splitter is usually much smaller than the distance from the diffraction beam splitter to the working plane. Therefore, the focusing lens and the diffraction beam splitter can be assembled in an optical bracket (e.g., a lens barrel) to facilitate the use of the beam splitter.

[0005] Theoretically, as long as the distance between the focusing lens and the diffraction beam splitter is equal to the lens focal length, the emitted sub-beams will be parallel. The distance between the emitted sub-beams of the diffraction beam splitter depends only on the working distance (or lens focal length) and the angle between the emitted beams. The angle between the emitted beams is independent of the distance between the diffraction element and the lens (i.e., the lens focal length). Therefore, theoretically, the choice of distance between the focusing lens and the diffraction beam splitter (i.e., the choice of lens focal length) has no effect on the angle of the emitted beam. However, due to limitations in actual manufacturing processes, the distance between the focusing lens and the diffraction beam splitter (i.e., the axial distance between the diffraction beam splitter and the focusing lens; axial distance refers to the distance along the optical axis) cannot be infinitely reduced. In other words, if the distance between the focusing lens and the diffraction beam splitter is too small, the parallelism of the output sub-beams or the spot quality of the sub-beams themselves will be significantly degraded. Specifically, when the axial distance between the focusing lens and the diffraction beam splitter decreases, the focusing lens needs a larger numerical aperture. However, there are limits to how large numerical apertures can be achieved; in practical manufacturing, lenses with excessively large numerical apertures cannot be produced. Even if a large numerical aperture lens could be manufactured, it would suffer from excessive aberrations (increasing the numerical aperture often leads to an increase in all six aberrations). Excessive aberrations would cause distortion in the emitted sub-beam, making it difficult to meet the requirements of practical applications. Furthermore, a larger numerical aperture also shortens the depth of focus of the focusing lens, significantly increasing the requirements for its assembly precision and thus increasing assembly deviations. On the other hand, the reduced axial distance between the focusing lens and the diffraction beam splitter also necessitates a larger diffraction angle for the diffraction beam splitter. When the diffraction angle is too large, the actual manufacturing precision of the diffraction beam splitter itself becomes difficult to meet requirements, resulting in uncontrollable distortion of the emitted sub-beam.

[0006] One solution to the aberration problem of focusing lenses is to use an equivalent spherical Fresnel lens instead. Compared to traditional focusing lenses, spherical Fresnel lenses can solve the problem of manufacturing focusing lenses with large numerical apertures; however, they still suffer from significant spherical aberration. Excessive spherical aberration prevents the acquisition of parallel output sub-beams. Specifically, when the outermost large-angle sub-beams are output parallel to the optical axis, the inner small-angle sub-beams diverge from the optical axis. Figure 2 A schematic diagram of an equidistant beam splitting output device based on a spherical Fresnel lens is shown, in which the inner beam diverges, wherein the spherical Fresnel lens 4 replaces the [missing information - likely a specific element or component]. Figure 1 The focusing lens 3 and the diffraction beam splitter 1 are not in the middle. Figure 2 (as shown in the image); while when the innermost small-angle sub-beam is output parallel to the optical axis, the outer large-angle sub-beam and the optical axis converge at an angle (as shown in the image). Figure 3 A schematic diagram of an equidistant beam splitting output device based on a spherical Fresnel lens is shown, in which the outer beam converges, wherein the spherical Fresnel lens 4 replaces the outer beam. Figure 1 The focusing lens 3 and the diffraction beam splitter 1 are not in the middle. Figure 3 (As shown in the image). In other words, for a spherical Fresnel lens, due to its large spherical aberration, it is difficult to ensure that the inner and outer sub-beams maintain parallel output at the same time.

[0007] Figure 3 A schematic diagram of an equidistant beam splitting output device based on a spherical Fresnel lens, showing the outer beam converging in a converging state, is shown.

[0008] In summary, the aforementioned challenges in manufacturing and assembling the focusing lens and diffraction beam splitter elements result in a still relatively large size for beam splitting and parallel output devices. On the other hand, the market demand for miniaturization of optical devices is constantly increasing. Therefore, there is an urgent need for a method that can shorten the axial distance between the diffraction beam splitter elements and the focusing lens while ensuring the beam quality (e.g., sub-beam parallelism) of each sub-beam. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of the prior art and provide a solution that can shorten the axial distance between the diffraction beam splitter and the focusing lens while ensuring the beam quality (e.g., the parallelism of the sub-beams) of each sub-beam.

[0010] To solve the above-mentioned technical problems, the present invention provides a beam splitting and parallel output device, comprising: a diffraction beam splitting element and a focusing optical element arranged sequentially along the optical axis; characterized in that a plate-shaped optical window is further disposed between the diffraction beam splitting element and the focusing optical element, the optical window having an incident surface and an exit surface, and both the incident surface and the exit surface are coated with a reflective layer; on the incident surface, a light-transmitting region is formed in the reflective layer corresponding to the central region of the optical axis; on the exit surface, a plurality of light-transmitting regions are formed in the reflective layer, the number of light-transmitting regions on the exit surface being the same as the number N of beam splitting of the diffraction beam splitting element; and light exits from the exit surface. The spacing between the sub-beams is an even multiple of the coating distance parameter, and the size of a single light-transmitting region is 1 to 1.05 times the coating distance parameter; the coating distance parameter is 1.12 to 1.52 times the laser spot diameter; on the emitting surface, the light-transmitting regions are located in the following coordinate region: (2k-1)dp / 2 to (2k+1)dp / 2; where dp is the coating distance parameter, and the spacing between adjacent light-transmitting regions is an even multiple of the coating distance parameter; and when the number of beams N is even, k takes a value among non-zero integers; when the number of beams N is odd, k is 0 or takes a value among integers with an absolute value greater than 2, and the spacing between adjacent light-transmitting regions is an even multiple of the coating distance parameter.

[0011] Among the multiple diffraction sub-beams emitted by the diffraction beam splitter, there are at least first diffraction level sub-beams and second diffraction level sub-beams. The first diffraction level sub-beams and the second diffraction level sub-beams exchange positions after being reflected by the optical window. The position exchange is as follows: the position of the sub-beam that was originally closer to the optical axis changes to the position that is farther from the optical axis, and the position of the sub-beam that was originally farther from the optical axis changes to the position that is closer to the optical axis.

[0012] Wherein, the diffraction angle of the first diffraction-level sub-beam is smaller than that of the second diffraction-level sub-beam, and the region of the optical window plate coated with the reflective layer and its light-transmitting region cause the first diffraction-level sub-beam to be reflected more times within the optical window plate than the second diffraction-level sub-beam, thereby causing the first diffraction-level sub-beam and the second diffraction-level sub-beam to interchange positions after being reflected by the optical window plate.

[0013] Wherein, the diffraction half-angle of the first diffraction level sub-beam is greater than 6 degrees, and the difference between the diffraction half-angle of the first diffraction level sub-beam and the diffraction half-angle of the second diffraction level sub-beam is at least 2.5 degrees or at least 15% of the diffraction half-angle of the second diffraction level sub-beam.

[0014] Wherein, the diffraction half-angle of the sub-beam of the first diffraction level is more than 1.5 times the diffraction half-angle of the sub-beam of the second diffraction level.

[0015] Wherein, the focusing optical element is a focusing lens; or the focusing optical element is a spherical Fresnel lens equivalent to a focusing lens.

[0016] The focusing optical element is a hyperboloid lens, and the surface height function of the hyperboloid lens is:

[0017]

[0018] Where r represents the distance from any position of the hyperboloid lens to the center of the lens, n represents the refractive index of the hyperboloid lens material, and f represents the distance between the diffraction beam splitter and one side of the hyperboloid lens plane, with the hyperboloid side facing the diffraction beam splitter.

[0019] The focusing optical element is an aberration-corrected Fresnel lens, and the surface height function of the aberration-corrected Fresnel lens is:

[0020]

[0021] Where r represents the distance from any position of the hyperboloid lens to the lens center, n represents the refractive index of the hyperboloid lens material, and f represents the distance between the diffraction beam splitter and the aberration-correcting Fresnel lens; the function rem(A,B) represents the remainder when A is divided by B; where rem(A,B) = A - fix(A / B) * B, fix() represents rounding to 0, λ represents the wavelength of the laser, and l is any positive integer. When l = 1, the maximum depth of the Fresnel lens microstructure is minimized.

[0022] The thickness of the optical window is 7.5mm to 10mm; the spacing between the sub-beams emitted from the optical window is 4mm to 6mm.

[0023] The beam splitting parallel output device is a 1x4 or 1x5 beam splitting device;

[0024] In the 1x4 beam splitter, the sub-beams emitted by the diffraction beam splitter element include a 0th-order diffraction sub-beam, ±1st-order diffraction sub-beams, and ±2nd-order diffraction sub-beams. The 0th-order diffraction sub-beam is blocked by the reflective layer on the exit surface of the optical window. The ±1st-order diffraction sub-beams are reflected four times within the optical window before exiting, and the ±2nd-order diffraction sub-beams are reflected twice within the optical window before exiting.

[0025] In the 1x5 beam splitter, the sub-beams emitted by the diffraction beam splitter element include a 0th-order diffraction sub-beam, ±1st-order diffraction sub-beams, and ±2nd-order diffraction sub-beams. The 0th-order diffraction sub-beam is emitted directly from the emission surface of the optical window, the ±1st-order diffraction sub-beams are emitted after being reflected 6 times within the optical window, and the ±2nd-order diffraction sub-beams are emitted after being reflected 2 times within the optical window.

[0026] Compared with the prior art, this application has at least one of the following technical effects:

[0027] 1. This application can shorten the axial distance between the diffraction beam splitter and the focusing lens while ensuring the beam quality (e.g., the parallelism of the sub-beams) of each sub-beam, thereby helping to miniaturize the beam splitting and parallel output device.

[0028] 2. In some embodiments of this application, by inserting an optical window with a reflective film attached at a specific position, the required diffraction angle (referring to the parallel light spacing required to meet design requirements) of the output beam of the DOE is reduced, the manufacturing difficulty of the DOE is reduced, thereby helping to improve the beam quality of the output beam.

[0029] 3. In some embodiments of this application, by inserting an optical window with a reflective film attached at a specific position, the numerical aperture required by the focusing lens (referring to the parallel light spacing required to meet the design requirements) is reduced, the manufacturing difficulty of the focusing lens is reduced, and thus helps to improve the beam quality of the output beam.

[0030] 4. In some embodiments of this application, the sub-beams of the first and second diffraction levels are interchanged after reflection by the optical window. This design allows the sub-beams with higher initial energy to undergo more reflections, helping to achieve a more balanced energy distribution between the different levels of sub-beams. Because the output parallel beam has a more balanced energy, this design is well-suited for laser processing of arrayed devices (e.g., multiple chips arrayed on the same wafer surface).

[0031] 5. In some embodiments of this application, a hyperboloid lens or an aberration-correcting Fresnel lens is provided in the beam splitting parallel output device, which can better compensate for the angular error of the output sub-beam, thereby improving the parallelism of the output sub-beam.

[0032] 6. In some embodiments of this application, the special design of the optical window can make the beam splitting and parallel output device more robust. For example, even when there are certain device assembly errors (such as errors caused by the assembly process of the optical window with the DOE and focusing optical elements), the output sub-beams can still maintain good parallelism, and each sub-beam still has good beam quality and energy utilization. Attached Figure Description

[0033] Figure 1 A schematic diagram of the optical path of a typical equally spaced beam splitter output device is shown.

[0034] Figure 2 A schematic diagram is shown of an equidistant beam splitting output device based on a spherical Fresnel lens, in which the inner beam diverges.

[0035] Figure 3 A schematic diagram of an equidistant beam splitting output device based on a spherical Fresnel lens is shown, showing the outer beam in a converging state;

[0036] Figure 4 A schematic diagram of the optical path of a 1x2 beam splitter parallel output device according to one embodiment of this application is shown;

[0037] Figure 5 This paper shows a schematic diagram of the optical path of a 1x3 beam splitter parallel output device according to one embodiment of the present application;

[0038] Figure 6 A comparative schematic diagram of the optical field amplitude distribution of four outgoing sub-beams at a distance of 100 mm is shown, obtained by angular spectrum simulation of a 1x4 equally spaced beam splitter output device based on a traditional scheme; where the solid line and the dashed line represent the optical field amplitude distribution of the sub-beams when the position of the focusing optical element has zero error and a deviation of 0.1 mm, respectively;

[0039] Figure 7 A comparative schematic diagram of the optical field amplitude distribution of four outgoing sub-beams at a distance of 100 mm is shown, obtained by angular spectrum simulation of a 1x4 equally spaced beam splitting output device based on an embodiment of this application; wherein the solid line and the dashed line represent the optical field amplitude distribution of the sub-beams when the position of the focusing optical element has zero error and a deviation of 0.1 mm, respectively;

[0040] Figure 8 This invention provides a schematic diagram of the optical path of a 1x4 equally spaced beam splitter output device according to an embodiment of the present application.

[0041] Figure 9 The graph shows the beam energy variation with beam energy in a single-mode laser application scenario. The horizontal axis represents the coefficient obtained by dividing the beam energy diameter by the laser spot diameter, i.e., the multiple of the beam energy diameter to the laser spot diameter. The vertical axis represents the laser energy contained within the beam energy diameter, i.e., the proportion of energy within the beam energy diameter (i.e., the proportion relative to the total energy of the laser beam). Detailed Implementation

[0042] To better understand this application, various aspects of this application will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely illustrative of exemplary embodiments of this application and are not intended to limit the scope of this 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.

[0043] It should be noted that in this specification, the terms "first," "second," etc., are used only to distinguish one feature from another and do not imply any limitation on the features. Therefore, without departing from the teachings of this application, the first subject discussed below may also be referred to as the second subject.

[0044] In the accompanying drawings, the thickness, size, and shape of the objects have been slightly exaggerated for ease of illustration. The drawings are for illustrative purposes only and are not drawn to scale.

[0045] It should also be understood that the terms "comprising," "including," "having," "containing," and / or "comprising," when used in this specification, indicate the presence of the stated features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or combinations thereof. Furthermore, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire listed feature, not individual elements in the list. Additionally, when describing embodiments of this application, the word "may" is used to mean "one or more embodiments of this application." And the term "exemplary" is intended to refer to an example or illustration.

[0046] As used herein, the terms “basically,” “approximately,” and similar terms are used as terms of approximation rather than terms of degree, and are intended to describe inherent biases in measured or calculated values ​​that will be recognized by those skilled in the art.

[0047] Unless otherwise specified, all terms used herein (including technical terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms (e.g., those defined in common dictionaries) shall be interpreted as having the meaning consistent with their meaning in the context of the relevant art and shall not be interpreted in an idealized or overly formal sense unless expressly so specified herein.

[0048] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0049] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0050] According to one embodiment of this application, a beam splitting parallel output device is provided. In this device, by adding an optical window with an attached reflective layer, the manufacturing difficulty of the diffraction beam splitting element and the focusing lens is reduced, thereby shortening the axial distance between the diffraction beam splitting element and the focusing lens while ensuring the parallelism of each sub-beam.

[0051] Specifically Figure 4 A schematic diagram of the optical path of a 1x2 beam splitter parallel output device according to one embodiment of this application is shown. Figure 5 A schematic diagram of the optical path of a 1x3 beam splitter parallel output device according to one embodiment of this application is shown. (Refer to reference...) Figure 4 and Figure 5 The beam splitting and parallel output device may include a diffraction beam splitting element 1, an optical window 2, and a focusing optical element arranged sequentially along the optical axis. Figure 4 and Figure 5 The focusing optical elements are all spherical Fresnel lenses 4). The optical window 2 has an incident surface facing the diffraction beam splitter 1 and an exit surface facing the focusing optical element. Both the incident and exit surfaces are coated with a reflective layer. In some embodiments, the reflective layer may be continuous and have several circular light-transmitting areas at several specific locations. In other embodiments, the reflective layer may be striped, with strip-shaped light-transmitting areas at several specific locations between adjacent reflective layers. The number and specific locations of the light-transmitting areas are determined by a series of parameters, which will be further described below in conjunction with embodiments.

[0052] Optical windows in existing technologies are mainly used to separate two environments, such as separating the interior and exterior of an instrument, isolating the internal and external parts to protect internal components. Windows do not change the optical magnification; they only affect the optical path length. When selecting a window, factors such as material properties, transmittance, scattering, wavefront distortion, corrosion resistance, thermal shock resistance, and damage threshold must be considered. In this embodiment, the inherent characteristics of the optical window are utilized by depositing a reflective layer on a specific area of ​​the window, which is then used in a beam splitting and parallel output device. Specifically, the optical window with the reflective layer can be inserted between the diffraction beam splitter and the focusing lens to shorten the axial distance between them while ensuring the parallelism of each sub-beam and the quality of the beam spot.

[0053] The following explanation uses a 1x4 splitter application scenario as an example.

[0054] Example 1

[0055] Figure 8This diagram illustrates the optical path of a 1x4 equally spaced beam splitting output device according to an embodiment of this application. 1x4 beam splitting involves dividing a laser beam into four parallel output sub-beams. In one example, assuming a laser beam energy diameter of 2.7 mm, the four sub-lasers after splitting need to be emitted in parallel with a spacing of approximately 10 mm. It should be noted that the definition of the laser beam energy diameter here is not based on the traditional laser spot diameter, but rather on a laser parameter determined based on energy utilization for ease of description in this embodiment. If a 99% energy utilization rate is required for the laser beam, then the beam energy diameter defined in this embodiment is the diameter of the circle encompassing 99% of the laser energy in a single laser beam. In contrast, the traditional laser spot diameter is determined as the power density decreases to 1 / e... 2 The beam energy diameter is defined as follows. In this embodiment, the coating distance parameter of the optical window is directly related to the position of the reflective layer and the position of the light-transmitting area of ​​the optical window, which will be described in detail below.

[0056] In this embodiment, the axial length of the beam splitter parallel output device is limited to 10 mm. Considering the thickness of the diffraction beam splitter element and the lens, this embodiment uses a flat optical material with a thickness of approximately 8 mm. Without loss of generality, this embodiment uses flat fused silica to fabricate the optical window.

[0057] Specifically, the length of the fused silica plate can be the laser beam energy diameter plus the distance between the two outermost sub-beams. Assuming a laser beam energy diameter of 2.7 mm, the length of the fused silica plate is generally not less than 32.7 mm. For one-dimensional beam splitting, the width of the fused silica plate should not be less than the diameter of the laser spot to avoid laser energy loss. It should be noted that the length and width of the fused silica plate refer to the length and width of its surface (i.e., the incident or exit surface), while the dimension along the optical axis is the thickness of the fused silica plate. In this embodiment, the plate length should be greater than 13d. spot (d spot The diameter of the laser beam energy (which will be described in further detail below) is 35.1 mm.

[0058] Without loss of generality, in this embodiment, the fused silica plate is 8 mm thick and is a square plate with a length and width equal to or greater than 35.1 mm. The fused silica plate is located close to the diffraction beam splitter. After the laser beam exits from the diffraction beam splitter, it is split into four beams, which enter the fused silica plate from the center of the left side (i.e., from the incident surface). Therefore, a non-reflective layer region with a diameter approximately equal to the incident beam energy diameter is left at the center of the left side of the fused silica plate, while the remaining areas are coated with a reflective layer. After the four sub-beams are split by the diffraction beam splitter, they enter the fused silica plate and undergo multiple reflections. The two outer laser beams (commonly referred to as ±2nd order diffraction beams in the industry) exit from the top and bottom exit ports of the fused silica plate, while the two inner laser beams (commonly referred to as ±1st order diffraction beams in the industry) exit from the two middle exit ports of the fused silica plate. The design needs to prevent the two outer laser beams from exiting through the inner windows. Assuming the half-angle of the outermost sub-beam is α, according to the law, the angle of refraction of this sub-beam after entering the transmission material is α / n, where n is the refractive index of the fused silica. The distance the sub-beam travels in the vertical direction after being reflected twice in the plate is...

[0059]

[0060] In the formula d plate This is the thickness of the plate. This distance must be greater than twice the diameter of the laser beam to allow for the inner sub-beam to exit, i.e.

[0061]

[0062] In the formula d spot The diameter is the energy of the laser beam.

[0063]

[0064] α > 27.1deg

[0065] That is, the diffraction beam splitting angle of the diffraction beam splitting element must be greater than 54.2 degrees. At this time, the numerical aperture of the focusing lens is 0.46.

[0066] The full angle of diffraction beam splitting of the above-mentioned diffraction beam splitting element and the numerical aperture of the focusing lens are both within the existing processing capabilities, which can ensure that the tolerance of the actual processed products is within the tolerable range.

[0067] In contrast, if a traditional beam-splitting parallel output device is used (see reference...) Figure 1If the diffraction beam splitter has a diffraction half-angle of 56.3 degrees and a total diffraction angle spacing of 112.6 degrees, then the numerical aperture of the focusing lens needs to reach 0.83. Given the current manufacturing capabilities of diffractive optical elements, manufacturing a diffraction beam splitter with a full diffraction angle of 112.6 degrees is extremely difficult, and manufacturing a focusing lens with a numerical aperture of 0.83 is also very challenging. Compared to the ideal values ​​of the design, the parallelism of the output sub-beams and the spot quality of the sub-beams themselves in the actual product of this traditional beam-splitting parallel output device will be significantly degraded, making it difficult to meet the application requirements of various industries.

[0068] Furthermore, in this embodiment, it is assumed that the four sub-beams after beam splitting are required to be emitted in parallel with a spacing of approximately 10 mm. Therefore, taking the center position of the plate in the vertical direction as 0, the four sub-beams after beam splitting are required to be emitted at positions of approximately ±5 mm and ±15 mm.

[0069] Therefore, the center coordinates of the reflection positions of the two outer sub-beams are:

[0070]

[0071] In the formula, m represents the 1st, 3rd, and 5th reflections, i.e., m = 1, 3, 5. The calculated value is y = d. spot 3D spot and 5D spot mm, i.e., y = 2.7, 8.1, 13.5 mm.

[0072] The center of the window for the first and third reflections is y = 2d. spot mm, that is, 5.4 mm, which is the value when m = 2 in formula (2).

[0073] Based on this calculation, the four sub-beams after beam splitting will be emitted in parallel with a spacing of 10.8 mm, meaning the four beams will be emitted in a 4d... spot Parallel projection at intervals. The plate length should be greater than 13d. spot That is, 35.1mm.

[0074] Therefore, the coordinates of the region on the exiting surface without a reflective layer (i.e., the transmission region) are: 5.4 ± 1.35.

[0075] The regions are -5.4±1.35, 16.2±1.35, and -16.2±1.35. The regions of 5.4±1.35 and -5.4±1.35 are for the inner ±1st order sub-beam emission, while the regions of 16.2±1.35 and -16.2±1.35 are for the outer ±2nd order sub-beam emission. The reflective layer must be coated on the emission surface at coordinates of 2.7±1.35, 8.1±1.35, and 13.5±1.35, and symmetrically below at -2.7±1.35, -8.1±1.35, and -13.5±1.35. All coordinates for the reflective layer are in mm.

[0076] Example 2

[0077] When the sub-beam exits the flat plate without reflection, the distance it travels in the vertical direction is...

[0078]

[0079] The ±1st order sub-beam needs to be moved 5mm in the vertical direction. When d plate When the beam width is 8mm, the diffraction angle α required for the sub-beam to move 5mm in the vertical direction (perpendicular to the optical axis) is 46.6 degrees. Considering the great difficulty in manufacturing a DOE with a diffraction half-angle of 46.6 degrees, in this embodiment, it is proposed to have the ±1st order sub-beams reflected twice before being emitted.

[0080] After the sub-beam is reflected twice in the flat plate, the distance it travels vertically at the exit is...

[0081]

[0082] When d plate =8mm, the diffraction angle required for the sub-beam to move 5mm in the vertical direction is α = 10.4 degrees. It can be seen that reflecting the ±1st order sub-beam twice before re-emerging greatly reduces the required diffraction angle.

[0083] After the sub-beam is reflected four times in the flat plate, the distance it travels vertically at the exit is...

[0084]

[0085] The ±2-level sub-beam needs to be moved 15mm in the vertical direction. When d plate =8mm, the diffraction angle required for the sub-beam to move 15mm in the vertical direction is α = 17 degrees.

[0086] In this embodiment, the ±1st order sub-beam is reflected twice in the plate, and the ±2nd order sub-beam is reflected four times in the plate. The diffraction half-angle of the ±1st order sub-beam is 10.4 degrees, and the diffraction half-angle of the ±2nd order sub-beam is 17 degrees, meaning the full angle of the diffraction beam splitter is 34 degrees. At this point, the numerical aperture of the focusing lens is 0.29.

[0087] In this embodiment, the ±2nd order sub-beam needs to avoid the ±1st order sub-beam during the first and third reflections. The positions of the ±2nd order sub-beam during the first and third reflections are tan(17 / 1.45)×8=1.66mm and tan(17 / 1.45)×8×5=8.3mm, respectively. The exit position of the ±1st order sub-beam is ±5±1.35mm. It can be seen that the exit of the ±1st order sub-beam does not affect the reflection of the ±2nd order sub-beam.

[0088] In this embodiment, the positions of the ±1st order sub-beam and the ±2nd order sub-beam are actually interchanged. To avoid confusion, the sub-beam output after DOE diffraction is called the diffracted sub-beam, and the sub-beam output after passing through the optical window is called the outgoing sub-beam. The ±1st order diffracted sub-beam is converted into the ±2nd order outgoing sub-beam after reflection by the optical window, and the ±2nd order diffracted sub-beam is converted into the ±1st order outgoing sub-beam after reflection by the optical window.

[0089] In this embodiment, for ease of description, the two diffraction orders are referred to as the first diffraction order (e.g., ±1 order) and the second diffraction order (e.g., ±2 order). The diffraction angle of the sub-beam of the first diffraction order is smaller than that of the sub-beam of the second diffraction order. The reflective layer-coated area and the light-transmitting area of ​​the optical window plate cause the first diffraction order sub-beam to undergo more reflections within the optical window plate than the second diffraction order sub-beam, thereby causing the first and second diffraction order sub-beams to interchange positions after reflection by the optical window plate. Generally, the lower-order diffraction sub-beams of a diffractive optical element (DOE) (i.e., those closer to the optical axis and with smaller diffraction angles) have higher energy, while the higher-order diffraction sub-beams (i.e., those further from the optical axis and with larger diffraction angles) have relatively lower energy. In this embodiment, the first diffraction order is configured with more reflections, and the second diffraction order is configured with fewer reflections. This not only helps to better stagger the two sub-beams of different orders but also helps to make the energy of the sub-beams of different orders more balanced. Because energy loss may occur during reflection, and the more reflections there are, the greater the energy loss, arranging more reflections for sub-beams with higher initial energy helps to achieve a more balanced energy distribution between different levels of sub-beams. It should be noted that although energy loss may occur during reflection, this loss is tolerable compared to the excessively large diffraction angle of the DOE and the excessively large numerical aperture of the focusing optics. Therefore, the overall benefits brought by the improvements of this invention are still very significant.

[0090] The previous section used a 1x4 beam splitter as an example to introduce the beam splitter parallel output device in this application when the number of output sub-beams is even. The following section will use a 1x5 beam splitter as an example to introduce the beam splitter parallel output device in this application when the number of output sub-beams is odd.

[0091] Example 3

[0092] In a 1x5 beam splitting application scenario, the laser beam energy diameter is 2.7 mm, and the four sub-beams are emitted in parallel with a spacing of approximately 10 mm. It should be noted that the definition of the laser beam energy diameter here is not based on the traditional laser spot diameter, but rather on a laser parameter determined based on energy utilization for ease of description in this invention. If a 99% energy utilization rate is required for the laser beam, then the beam energy diameter defined in this invention is the diameter of the circle encompassing 99% of the laser energy within a single laser beam.

[0093] In this embodiment, it is assumed that the axial length of the beam splitter parallel output device is limited to 10 mm. Considering the thickness of the diffraction beam splitter element and the lens, this embodiment uses a flat optical material with a thickness of approximately 8 mm. Without loss of generality, this embodiment uses flat fused silica to fabricate the optical window.

[0094] Specifically, the length of the fused silica plate can be the laser beam energy diameter plus the distance between the two outermost sub-beams. Assuming a laser beam energy diameter of 2.7 mm, the length of the fused silica plate is generally not less than 42.7 mm. For one-dimensional beam splitting, the width of the fused silica plate should not be less than the diameter of the laser spot to avoid laser energy loss. It should be noted that the length and width of the fused silica plate refer to the length and width of its surface (incident or exit surface), and the dimension along the optical axis is its thickness. In this embodiment, the plate length should be greater than 17d. spot (d spot The diameter of the laser beam energy (which will be described in further detail below) is 45.9 mm.

[0095] Without loss of generality, in this embodiment, the fused silica plate is 8 mm thick and is a square plate with a length and width equal to or greater than 45.9 mm. The fused silica plate is located close to the diffraction beam splitter. After the laser beam exits from the diffraction beam splitter, it is split into 5 beams, which enter the fused silica plate from the center of the left side (i.e., from the incident surface). Therefore, a non-reflective layer region with a diameter approximately equal to the energy diameter of the incident beam is left at the center of the left side of the fused silica plate, and the remaining positions are coated with a reflective layer. After the 5 sub-beams are split by the diffraction beam splitter and enter the fused silica plate, they undergo multiple reflections. The outermost two laser beams (commonly referred to as ±2nd order diffraction beams in the industry) exit from the upper and lower exit ports of the fused silica plate, the inner two laser beams (commonly referred to as ±1st order diffraction beams in the industry) exit from the inner two exit ports of the fused silica plate, and the central laser beam (commonly referred to as 0th order diffraction beam in the industry) exits from the exit port at the very center of the fused silica plate. The design needs to prevent the two outer laser beams from escaping through the inner window. Assuming the half-angle of the outermost sub-beam is α, according to the law, the angle of refraction of this sub-beam after entering the transmission material is α / n, where n is the refractive index of the fused silica. The distance the sub-beam travels vertically after being reflected twice in the plate is...

[0096]

[0097] In the formula d plate This is the thickness of the plate. This distance must be greater than 2.5 times the diameter of the laser beam to allow for the inner sub-beam to exit, i.e.

[0098]

[0099] In the formula d spot The diameter is the energy of the laser beam.

[0100]

[0101] α > 33.3deg

[0102] That is, the diffraction beam splitting angle of the diffraction beam splitting element must be greater than 66.6 degrees. At this time, the numerical aperture of the focusing lens is 0.54.

[0103] The full angle of diffraction beam splitting of the above-mentioned diffraction beam splitting element and the numerical aperture of the focusing lens are both within the existing processing capabilities, which can ensure that the tolerance of the actual processed products is within the tolerable range.

[0104] In contrast, if a traditional beam-splitting parallel output device is used (see reference...) Figure 1 If the diffraction beam splitter has a diffraction half-angle of 63.4 degrees and a total diffraction angle spacing of 126.9 degrees, then the numerical aperture of the focusing lens needs to reach 0.89. Given the current manufacturing capabilities of diffractive optical elements, manufacturing a diffraction beam splitter with a full diffraction angle of 126.9 degrees is extremely difficult, and manufacturing a focusing lens with a numerical aperture of 0.89 is also very challenging. Compared to the ideal values ​​of the design, the actual product of this traditional beam-splitting parallel output device will show significant deterioration in the parallelism of the output sub-beams and the spot quality of the sub-beams themselves, making it difficult to meet the application requirements of various industries.

[0105] The center coordinates of the reflection positions of the two outer sub-beams are:

[0106]

[0107] In the formula, m represents the 1st, 3rd, and 5th reflections, i.e., m = 1, 3, 5. The calculated value is y = d. spot 3D spot and 5D spot mm, i.e., y = 2.7, 8.1, 13.5 mm.

[0108] The center of the window for the first and third reflections is y = 2d. spot mm, which is 5.4 mm, or the value when m = 2.

[0109] Based on this calculation, the five sub-beams after beam splitting are actually emitted in parallel with a spacing of 10.8 mm, meaning the five beams after beam splitting emit in a 4d... spot Parallel projection spacing. The plate length should be greater than 17d. spot That is, 45.9mm.

[0110] Therefore, the coordinates of the unreflective areas on the exit surface are: 0±1.35, 10.8±1.35, -10.8±1.35, 21.6±1.35, and -21.6±1.35. The 0±1.35 area is used for the central 0th-order sub-beam exit, the 10.8±1.35 and -10.8±1.35 areas are used for the inner ±1st-order sub-beam exit, and the 21.6±1.35 and 21.6±1.35 areas are used for the outer ±2nd-order sub-beam exit. The other areas of the exit surface are coated with a reflective layer. All coordinates for the reflective layer are in mm.

[0111] Example 4

[0112] The following is another embodiment of a 1x5 beam splitter parallel output device.

[0113] Assuming the subbeam exits directly from the flat plate without reflection, the distance it travels in the vertical direction is...

[0114]

[0115] The ±1st order sub-beam needs to be moved 10mm in the vertical direction. When d plate =8mm, the diffraction angle required for the sub-beam to move 10mm in the vertical direction is α = 74.8 degrees. Considering the extreme difficulty in manufacturing a DOE with a diffraction half-angle of 74.8 degrees, this embodiment proposes to have the ±1st order sub-beams reflected twice before being emitted.

[0116] After the sub-beam is reflected twice in the flat plate, the distance it travels vertically at the exit is...

[0117]

[0118] When d plate =8mm, the diffraction angle required for the sub-beam to move 10mm in the vertical direction is α = 20.4 degrees. It can be seen that reflecting the ±1st order sub-beam twice before re-emerging greatly reduces the required diffraction angle.

[0119] After the sub-beam is reflected four times in the flat plate, the distance it travels vertically at the exit is...

[0120]

[0121] The ±2-level sub-beam needs to be moved 20mm in the vertical direction. When d plate =8mm, the diffraction angle required for the sub-beam to move 20mm vertically is α = 22.6 degrees. This angle is close to the angle of the ±1st order sub-beam (20.4 degrees), which is unfavorable for avoidance between sub-beams. Therefore, consider having the ±2nd order sub-beams reflect 6 times before exiting. The distance the sub-beam moves vertically at the exit point after reflecting 6 times in the plate is:

[0122]

[0123] The ±2-level sub-beam needs to be moved 20mm in the vertical direction. When d plate =8mm, the diffraction angle required for the sub-beam to move 20mm in the vertical direction is α = 15.9 degrees.

[0124] In this embodiment, the ±1st-order sub-beam is reflected twice in the plate, and the ±2nd-order sub-beam is reflected six times. The diffraction half-angle of the ±1st-order sub-beam is 20.4 degrees, and the diffraction half-angle of the ±2nd-order sub-beam is 15.9 degrees. That is, for the actual diffraction element, the ±1st-order and ±2nd-order sub-beams are interchanged. To avoid confusion, we refer to the final outer light as the ±2nd-order sub-beam. On the other hand, the full angle of the diffraction beam splitter element, after recalculation, is 40.8 degrees. At this time, the numerical aperture of the focusing lens is 0.35.

[0125] The ±2nd order sub-beam needs to avoid the ±1st order sub-beam during the first and third reflections. The positions of the ±2nd order sub-beam during the third and fifth reflections are tan(15.9 / 1.45)×8×5=7.75mm and tan(15.9 / 1.45)×8×9=13.9mm, respectively. The exit position of the ±1st order sub-beam is ±10±1.35mm. It can be seen that the exit of the ±1st order sub-beam does not affect the reflection of the ±2nd order sub-beam.

[0126] Furthermore, in the above embodiments, the focusing lens in the beam splitting and parallel output device can be replaced by an equivalent spherical Fresnel lens. Since the fabrication process of a spherical Fresnel lens can suppress some types of aberrations to a certain extent, it helps to further improve the spot quality of the output parallel sub-beam.

[0127] Furthermore, in the above embodiments, the focusing lens in the beam splitting and parallel output device can also be replaced by an aberration-correcting hyperboloid lens. Compared to using a focusing lens, the aberration-correcting hyperboloid lens can further suppress spherical aberration, thereby further improving the parallelism of the output parallel sub-beams. Specifically, the surface height function of the aberration-correcting hyperboloid lens is:

[0128]

[0129] Where r represents the distance from any position of the hyperboloid lens to the center of the lens, n represents the refractive index of the hyperboloid lens material, and f represents the distance between the diffraction beam splitter and one side of the hyperboloid lens plane, with the hyperboloid side facing the diffraction beam splitter.

[0130] Furthermore, in some embodiments, the aberration-correcting lens can be replaced by an equivalent Fresnel lens. The surface height function of the aberration-correcting Fresnel lens is...

[0131]

[0132] Where r represents the distance from any position of the hyperboloid lens to the lens center, n represents the refractive index of the hyperboloid lens material, and f represents the distance between the diffraction beam splitter and the aberration-correcting Fresnel lens; the function rem(A,B) represents the remainder when A is divided by B; where rem(A,B) = A - fix(A / B) * B, fix() represents rounding to 0, λ represents the wavelength of the laser, and l is any positive integer. When l = 1, the maximum depth of the Fresnel lens microstructure is minimized.

[0133] Compared to the solution using a focusing lens, this embodiment helps to further improve the spot quality of the output parallel sub-beam, and can also further improve the parallelism of the output parallel sub-beam.

[0134] The inventors employed a rigorous angular spectrum method for simulation to analyze the impact of installation errors on the parallelism of the sub-beam output. For a conventional beam splitting and parallel output device without an optical window, it was assumed that an aberration-corrected Fresnel lens was used as the focusing optical element (i.e., an aberration-corrected Fresnel lens was used instead of a focusing lens). This aberration-corrected Fresnel lens had a radius of 10 mm and a focal length of 10 mm, with the diffraction beam splitting element located at the front focal plane of the aberration-corrected Fresnel lens. When the installation error was 0%, the angle between the four sub-beams and the optical axis was 0, meaning the four sub-beams were output in parallel, and the distance between any two adjacent sub-beams at a distance of 10 mm was 5 mm. When the installation error was 0.1 mm, the angles between the inner two sub-beams and the optical axis were ±0.11 degrees, and the angles between the outer two sub-beams and the optical axis were ±0.23 degrees. At a distance of 10 mm, the deviations of the four sub-beams from the design values ​​were 0.04, 0.02, -0.02, and -0.04 mm, respectively.

[0135] Figure 6 The figure shows the optical field amplitude distribution of the four outgoing sub-beams at a distance of 100 mm when no reflection-transmission window is used, no positional error is present, and there is a 0.1 mm positional error between the diffraction beam splitter and the focusing optics. The horizontal axis represents position in mm, and the vertical axis represents the laser power density distribution.

[0136] Figure 7 The figure shows the optical field amplitude distribution of the four outgoing sub-beams at a distance of 100 mm, with and without positional error when using a reflective-transmitting window, and with a positional error of 0.1 mm between the diffraction beam splitter and the focusing optics. The horizontal axis represents position in mm, and the vertical axis represents the laser power density distribution. (Reference) Figure 7 In the beam splitting and parallel output device of this application, which incorporates an optical window coated with a reflective layer, an aberration-corrected Fresnel lens is used as the focusing optical element. This aberration-corrected Fresnel lens has a focal length of 32.6 mm. When the installation error is 0.1 mm, the angle between the two inner sub-beams and the optical axis remains almost unchanged, and they are still output in parallel. At a distance of 10 mm, the deviation of the four adjacent sub-beams from the design value is almost zero. It can be seen that the parallelism of the output sub-beams is significantly improved after incorporating the optical window coated with a reflective layer.

[0137] The beam energy diameter defined in the above embodiments is the diameter of the circle encompassing 99% of the laser energy in a laser beam. In applications with lower requirements for laser utilization, the beam energy diameter can also be defined according to other percentages of laser energy. For example, the beam energy diameter can be the diameter of the circle encompassing A% of the laser energy in a laser beam, where A can be a value within a certain range according to actual needs. For example, 90≤A≤99. The coating distance parameter of the optical window can be equal to the beam energy diameter. Generally speaking, the coating distance parameter is 1.12 to 1.52 times the laser spot diameter (note that in the prior art, the aperture of the optical element configured for the laser beam is usually 2.5 times the laser spot diameter, which is significantly different from this invention). The spacing between sub-beams (referring to the spacing between the beam centers of sub-beams) is an even multiple of the coating distance parameter, and the size of a single transparent area (the diameter of a circular transparent area, or the width of a single transparent stripe area of ​​a striped transparent area) is 1 to 1.05 times the coating distance parameter. In actual manufacturing, appropriately enlarging the size of the light-transmitting area, for example, by setting it to 1.05 times the determined coating distance parameter, will help overcome assembly errors. For instance, when there is an assembly error between the actual installation configuration of the optical window and the design position, since the size of the light-transmitting area is set to 1.05 times the determined coating distance parameter, as long as the error is controlled, the beam energy required by the design can still pass through the light-transmitting area, thereby ensuring the beam quality of the output parallel light.

[0138] Furthermore, Figure 9 The graph shows the beam energy as a function of beam energy in a single-mode laser application scenario. The horizontal axis represents the coefficient obtained by dividing the beam energy diameter by the laser spot diameter, i.e., the ratio of the beam energy diameter to the laser spot diameter. The vertical axis represents the laser energy contained within the beam energy diameter, i.e., the proportion of energy within the beam energy diameter (i.e., the proportion relative to the total energy of the laser beam). (Reference) Figure 9When the beam energy diameter is approximately 1.12 times the laser spot diameter, the laser energy contained within that beam energy diameter is approximately 0.9, meaning the energy percentage is approximately 90%. When the beam energy diameter is approximately 1.52 times the laser spot diameter, the laser energy contained within that beam energy diameter is approximately 0.99, meaning the energy percentage is approximately 99%. Here, the laser spot diameter is defined as 1 / e of the power density at its highest point at the center. 2 At this point, the laser spot diameter contains 86.5% of the total laser energy.

[0139] In some embodiments of this application, the sub-beams emitted from the diffractive optical element do not interchange positions within the optical window. Assuming the diffractive optical element has sub-beams of a first diffraction order and a second diffraction order, and the half-angle of the first diffraction order is greater than the half-angle of the second diffraction order, then the half-angle of the first diffraction order sub-beam is more than 1.5 times that of the second diffraction order sub-beam. Further, in some embodiments of this application, the half-angle of the first diffraction order sub-beam emitted from the diffractive optical element is greater than 6 degrees. Here, the first diffraction order is the diffraction order with the smallest diffraction angle other than the zeroth order diffraction beam. When its half-angle is greater than 6 degrees, it helps the sub-beam to cross the transmission region of the second diffraction sub-beam during reflection, thereby avoiding beam mixing and reducing energy loss of the first diffraction order sub-beam.

[0140] In some embodiments of this application, the sub-beams emitted from the diffractive optical element undergo positional interchange within the optical window. Assuming the diffractive optical element has sub-beams of a first diffraction order and a second diffraction order, and the half-angle of the first diffraction order is greater than the half-angle of the second diffraction order, then the difference between the half-angle of the first diffraction order sub-beam and the half-angle of the second diffraction order sub-beam is at least 2.5 degrees (e.g., in embodiments 2 and 4) or at least 15% of the half-angle of the second diffraction order sub-beam. Further, in some embodiments of this application, the half-angle of the first diffraction order sub-beam emitted from the diffractive optical element is greater than 6 degrees. Here, the first diffraction order is the diffraction order with the smallest diffraction angle other than the zeroth order diffraction beam. When its half-angle is greater than 6 degrees, it helps the sub-beam to cross the transmission region of the second diffraction sub-beam during reflection, thereby avoiding beam mixing and reducing energy loss of the first diffraction order sub-beam.

[0141] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand 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 all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A parallel light beam splitting device comprising: A diffraction beam splitter and a focusing optical element are arranged sequentially along an optical axis; characterized in that a flat optical window is further provided between the diffraction beam splitter and the focusing optical element, the optical window having an incident surface and an exit surface, and both the incident surface and the exit surface are coated with a reflective layer. On the incident surface, the reflective layer has a light-transmitting area in the central region corresponding to the optical axis; On the exiting surface, the reflective layer has multiple light-transmitting regions, and the number of light-transmitting regions on the exiting surface is the same as the number of beams N of the diffraction beam splitting element; the spacing between the sub-beams emitted from the exiting surface is an even multiple of the coating distance parameter, and the size of a single light-transmitting region is 1 to 1.05 times the coating distance parameter; On the exiting surface, the light-transmitting area is located in the following coordinate region: (2k-1)dp / 2 to (2k+1)dp / 2; Wherein, dp is the coating distance parameter, which is 1.12 to 1.52 times the diameter of the laser spot, and the spacing between adjacent light-transmitting areas is an even multiple of the coating distance parameter; Furthermore, when the number of beams N is even, k takes a value among non-zero integers; when the number of beams N is odd, k is 0 or takes a value among integers with an absolute value greater than 2, and the spacing between adjacent light-transmitting areas is an even multiple of the coating distance parameter.

2. The beam splitting parallel output device according to claim 1, wherein, The diffraction beam splitter emits multiple diffraction sub-beams, including at least a first diffraction level sub-beam and a second diffraction level sub-beam. The first diffraction level sub-beam and the second diffraction level sub-beam exchange positions after being reflected by the optical window. The position exchange is as follows: the position of the sub-beam that was originally closer to the optical axis changes to the position that is farther from the optical axis, and the position of the sub-beam that was originally farther from the optical axis changes to the position that is closer to the optical axis.

3. The beam splitting parallel output device according to claim 2, wherein, The diffraction angle of the first diffraction-level sub-beam is smaller than that of the second diffraction-level sub-beam. The reflective layer coated area and the light-transmitting area of ​​the optical window plate cause the first diffraction-level sub-beam to be reflected more times within the optical window plate than the second diffraction-level sub-beam, thereby causing the first diffraction-level sub-beam and the second diffraction-level sub-beam to interchange positions after being reflected by the optical window plate.

4. The beam splitting parallel output device according to claim 3, wherein, The diffraction half-angle of the first diffraction level sub-beam is greater than 6 degrees, and the difference between the diffraction half-angle of the first diffraction level sub-beam and the diffraction half-angle of the second diffraction level sub-beam is at least 2.5 degrees or at least 15% of the diffraction half-angle of the second diffraction level sub-beam.

5. The beam splitting parallel output device according to claim 3, wherein, The half-angle of the sub-beam of the first diffraction order is more than 1.5 times that of the half-angle of the sub-beam of the second diffraction order.

6. The beam splitting parallel output device according to claim 1, wherein, The focusing optical element is a focusing lens; or the focusing optical element is a spherical Fresnel lens that is equivalent to a focusing lens.

7. The beam splitting parallel output device according to claim 1, wherein, The focusing optical element is a hyperboloid lens, and the surface height function of the hyperboloid lens is: Where r represents the distance from any position of the hyperboloid lens to the center of the lens, n represents the refractive index of the hyperboloid lens material, and f represents the distance between the diffraction beam splitter and one side of the hyperboloid lens plane, with the hyperboloid side facing the diffraction beam splitter.

8. The beam splitting parallel output device according to claim 1, wherein, The focusing optical element is an aberration-corrected Fresnel lens, and the surface height function of the aberration-corrected Fresnel lens is: Where r represents the distance from any position of the hyperboloid lens to the center of the lens, n represents the refractive index of the hyperboloid lens material, f represents the distance between the diffraction beam splitter and the aberration-free Fresnel lens; the function rem(A,B) represents the remainder when A is divided by B; where rem(A,B)=A-fix(A / B)*B, fix() means rounding to 0, λ represents the wavelength of the laser, and l is any positive integer.

9. The beam splitting parallel output device according to claim 1, wherein, The thickness of the optical window is 7.5mm to 10mm; the spacing between the sub-beams emitted from the optical window is 4mm to 6mm.

10. The beam splitting parallel output device according to claim 2, wherein, The beam splitting parallel output device is a 1x4 or 1x5 beam splitting device; In the 1x4 beam splitter, the sub-beams emitted by the diffraction beam splitter element include a 0th-order diffraction sub-beam, ±1st-order diffraction sub-beams, and ±2nd-order diffraction sub-beams. The 0th-order diffraction sub-beam is blocked by the reflective layer on the exit surface of the optical window. The ±1st-order diffraction sub-beams are reflected four times within the optical window before exiting, and the ±2nd-order diffraction sub-beams are reflected twice within the optical window before exiting. In the 1x5 beam splitter, the sub-beams emitted by the diffraction beam splitter element include a 0th-order diffraction sub-beam, ±1st-order diffraction sub-beams, and ±2nd-order diffraction sub-beams. The 0th-order diffraction sub-beam is emitted directly from the emission surface of the optical window, the ±1st-order diffraction sub-beams are emitted after being reflected 6 times within the optical window, and the ±2nd-order diffraction sub-beams are emitted after being reflected 2 times within the optical window.

Images