Large-view-field uniform pulse laser emission beam system

Abstract

The invention provides a large-view-field uniform pulse laser emission beam system. The large-view-field uniform pulse laser emission beam system comprises a laser emission light source used for generating a laser beam; the collimating lens is used for collimating the laser beams generated by the laser emission light source in the meridian direction; the micro lens array comprises a plurality of cylindrical mirror units and is used for expanding the straightened laser beams in the sagittal direction to obtain laser beams with preset light field energy distribution; wherein the surface type parameter of each cylindrical mirror unit in the micro-lens array is obtained based on the preset light field energy distribution and optical simulation software optimization. According to the invention, light field energy distribution with edge energy higher than center energy can be realized, the effect of the pulse laser emission beam system for a panoramic laser detection system is improved, customization of energy distribution of various special light fields can be realized, and the applicability is wide.

Description

Technical Field

[0001] The invention relates to the field of optoelectronic technology, and in particular to a large-field-of-view uniform pulse laser beam emitting system. Background Art

[0002] The working principle of panoramic laser detection is that the emitting light source outputs a narrow fan-shaped light beam which illuminates the space target to form a backscattered echo beam, which is focused into an anisotropic narrow light beam by the receiving optical system and then received by a one-dimensional planar photoelectric detector. After photoelectric conversion, subsequent data processing is performed.

[0003] However, in the panoramic laser detection system, the emitting light source mostly uses laser chips to achieve high-power output. Due to the unique elliptical spot and typical meridional Gaussian light intensity distribution of semiconductor laser chips, they are divergent in space. If they are not collimated and focused, the beam will diverge severely after a short transmission distance, and the energy utilization rate is very low. Moreover, the edge large field echo signal will be larger in size than the center area after being focused by the receiving optical system, resulting in damage to the edge beam energy or excessive size of the detector photosensitive surface. Summary of the invention

[0004] The embodiment of the present invention provides a large-field-of-view uniform pulse laser beam emitting system to solve the problem of providing a laser emitting system suitable for a panoramic laser detection system.

[0005] In a first aspect, an embodiment of the present invention provides a large-field-of-view uniform pulsed laser beam emitting system, comprising:

[0006] A laser emitting light source, used for generating a laser beam;

[0007] A collimating lens, used for collimating the laser beam generated by the laser emitting light source in the meridian direction;

[0008] The microlens array includes a plurality of cylindrical mirror units, which are used to expand the collimated laser beam in the sagittal direction to obtain a laser beam with a preset light field energy distribution; wherein the surface parameters of each cylindrical mirror unit in the microlens array are obtained based on the preset light field energy distribution and the optimization of optical simulation software.

[0009] In a possible implementation, the surface parameters include a curvature radius r and an asphericity coefficient K;

[0010] The curvature radius r and the asphericity coefficient K of each column mirror unit in the microlens array are obtained by optimizing the curvature radius r and the asphericity coefficient K based on the difference between the light field energy distribution of ray tracing in the simulated non-sequential mode by optical simulation software and the preset light field energy distribution.

[0011] In one possible implementation, the surface parameters include a subunit period;

[0012] The sub-unit period of the microlens array is determined based on the optical collimation calculation formula d=f*tan(θ), where d is the sub-unit period size, f is the sub-unit effective focal length, and θ is the half field of view.

[0013] In one possible implementation, the microlens array is made of glass, the subunit period is 0.3 mm, the subunit effective focal length is 0.26 mm, and the ratio of 0° center energy to ±30° edge energy of the expanded laser beam is 0.7:1.

[0014] In a possible implementation, the laser emission light source is four 905 nm laser chips connected in series horizontally with a period of 0.5 mm.

[0015] In a possible implementation, the microlens array is processed by a thermoforming method.

[0016] In a possible implementation, the microlens array is a convex lenticular lens array, a concave lenticular lens array, or an alternating convex-concave lenticular lens array.

[0017] In a possible implementation, a processing method of the microlens array is selected based on the surface type.

[0018] In a possible implementation, the microlens array is parallel to the chip end face of the laser emitting light source.

[0019] In a possible implementation, the collimating lens is a FAC aspheric lens.

[0020] The embodiment of the present invention provides a large-field-of-view uniform pulsed laser beam emission system, which utilizes the characteristics of the micro lenses of each sub-unit of the microlens array to scatter parallel light beams into a certain angle range and form a special energy distribution within a certain angle range, and uses optical simulation software to optimize the surface parameters of the microlens array by taking the light field energy distribution as the optimization target, which can improve the edge light beam energy and reduce the center energy, and compensate for the weak edge echo signal at the receiving end, thereby balancing the edge and center energy, and realizing a light field energy distribution in which the edge energy is higher than the center energy, thereby improving the effect of the pulsed laser emission beam system for the panoramic laser detection system, and being able to realize the customization of various special light field energy distributions, and having a wide range of applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0022] Figure 1 It is a schematic diagram of the structure of a large-field-of-view uniform pulsed laser beam emitting system provided by an embodiment of the present invention;

[0023] Figure 2A It is a schematic diagram of incident beam expansion of a parallel light beam provided by an embodiment of the present invention;

[0024] Figure 2B is a schematic diagram of beam expansion with angled incidence provided by an embodiment of the present invention;

[0025] Figure 3 This is a ray tracing effect diagram after beam expansion provided by an embodiment of the present invention;

[0026] Figure 4A is a far-field light energy distribution diagram after beam expansion provided by an embodiment of the present invention;

[0027] Figure 4B is a light field distribution diagram of a specific ratio provided by another embodiment of the present invention;

[0028] Figure 4C is a light field distribution diagram of a specific ratio provided by another embodiment of the present invention;

[0029] Figure 5A is a cross-sectional schematic diagram of a convex lenticular lens array provided by an embodiment of the present invention;

[0030] Figure 5B is a cross-sectional schematic diagram of a concave cylindrical lens array provided by an embodiment of the present invention;

[0031] Figure 5C It is a cross-sectional schematic diagram of a concave-convex alternating lenticular lens array provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to enable people in the technical field to better understand the present solution, the technical solution in the embodiment of the present solution will be clearly described below in conjunction with the drawings in the embodiment of the present solution. Obviously, the described embodiment is an embodiment of a part of the present solution, not all of the embodiments. Based on the embodiments in the present solution, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present solution.

[0033] The term "including" and any other variations in the specification and claims of this solution and the above drawings mean "including but not limited to", and is intended to cover non-exclusive inclusions and is not limited to the examples listed in the text. In addition, the terms "first" and "second" are used to distinguish different objects, not to describe a specific order.

[0034] The following is a detailed description of the implementation of the present invention in conjunction with the specific drawings:

[0035] Figure 1 A schematic diagram of the structure of a large field of view uniform pulsed laser beam emitting system provided by an embodiment of the present invention. Figure 1 , the large field of view uniform pulsed laser beam emission system includes:

[0036] A laser emitting light source 11, used to generate a laser beam;

[0037] A collimating lens 12, used for collimating the laser beam generated by the laser emitting light source in the meridian direction;

[0038] The microlens array 13 includes a plurality of cylindrical mirror units, which are used to expand the collimated laser beam in the sagittal direction to obtain a laser beam with a preset light field energy distribution; wherein the surface parameters of each cylindrical mirror unit in the microlens array are obtained based on the preset light field energy distribution and optimized by optical simulation software.

[0039] In this embodiment, the specific structure of the entire system can be as follows: Figure 1 As shown, 11 is a laser chip, 12 is a collimating lens, 13 is a microlens array, 14 is a metal tube shell, 15 is a driving circuit, and 16 is a ceramic carrier.

[0040] In the pulse laser detection system, the emitting light source mostly uses 905nm laser chips in series to achieve high-power output. Due to the unique elliptical spot and typical meridional Gaussian light intensity distribution of the semiconductor laser chip, it is divergent in space. If it is not collimated and focused, the light beam diverges severely after a short transmission distance, and the energy utilization rate is very low. Therefore, in the laser detection system, it is necessary to compress the light source in the meridional direction to increase the light power density. In addition, due to the particularity of laser detection, it is necessary to realize 360° full-field laser emission and reception, so the emitting light source is required to meet the 60° (6 groups), 90° (4 groups), and 120° (3 groups) light field energy uniform distribution.

[0041] The main ways to homogenize semiconductor laser beams include aspheric lens groups, microlens arrays, compound eye lenses, binary optical elements, etc. These methods can shape Gaussian beams into flat-top beams. Among them, microlens arrays not only have the same functions as traditional lenses, converging, diverging, integrating, and evenly distributing beams, but also have the characteristics of high integration, refractive and diffractive mixing, etc.

[0042] After the edge large field of view echo signal is focused by the receiving optical system, its spot size will be larger than that of the central area, resulting in damage to the edge beam energy or excessive size of the detector photosensitive surface. In this regard, the applicant has found that a special light field energy distribution can be designed to increase the edge beam energy and reduce the center energy, thereby compensating for the weak edge echo signal at the receiving end and balancing the edge and center energy.

[0043] In semiconductor laser light sources, the active area of ​​a 905nm laser chip is generally 200μm*10μm (sagittal*meridian direction). Compared with commonly used optical collimation systems, it has significant point light source characteristics. Therefore, it is usually used to collimate parallel light, thereby achieving efficient use of light energy. In some special usage contexts, light energy is required to cover a specific field of view, such as the field of panoramic laser fuses. According to demand, the laser light source covers 60° and 90° in the sagittal direction. The point source characteristics of the light source are not easy to be evenly scattered within a specific angle range. When a beam of parallel light or light with a certain divergence angle is incident on the microlens array, due to the principle of light refraction, the parallel light beam will be scattered by the sub-unit microlenses within a certain angle range and form a special energy distribution within a certain angle range. For example Figure 2A and Figure 2B As shown in the figure, when a beam of parallel light or light with a divergent angle is incident on the microlens array, due to the principle of light refraction, the parallel light beam will be scattered by the sub-unit microlenses within a certain angle range and form a special energy distribution within a certain angle range. Therefore, based on the preset light field energy distribution, a model of the microlens array can be constructed in the optical simulation software, multiple groups of surface parameters can be simulated, and based on the difference between the simulated light field energy distribution and the preset light field energy distribution, the surface parameters can be selected and adjusted to obtain the surface parameters that meet the preset light field energy distribution.

[0044] The embodiment of the present invention utilizes the characteristics that the tiny lenses of each sub-unit of the microlens array scatter parallel light beams into a certain angle range and form a special energy distribution within a certain angle range, and uses optical simulation software to optimize the surface parameters of the microlens array by taking the light field energy distribution as the optimization target, which can improve the edge light beam energy and reduce the center energy, and compensate for the weak edge echo signal at the receiving end, thereby balancing the edge and center energy, and realizing a light field energy distribution in which the edge energy is higher than the center energy, thereby improving the effect of the pulse laser emission beam system for the panoramic laser detection system, and can realize the customization of various special light field energy distributions, and has a wide range of applicability.

[0045] In a possible implementation, the surface parameters include a curvature radius r and an asphericity coefficient K;

[0046] The curvature radius r and the asphericity coefficient K of each column mirror unit in the microlens array are obtained by optimizing the curvature radius r and the asphericity coefficient K based on the difference between the light field energy distribution of ray tracing in the simulated non-sequential mode by optical simulation software and the preset light field energy distribution.

[0047] In this embodiment, ZEMAX optical simulation software can be used to establish a preliminary model of the sub-unit surface type, including parameters such as external dimensions, radius of curvature, and aspheric coefficient K value, so that the input light beam is approximated as a parallel light beam; by setting optimization parameters and different weights (here different weights can be considered as different proportions of field of view angles), the energy distribution under different field of view angles can be optimized to determine the spatial distribution of the sub-unit aspheric surface type (x, y). Optical tracing is established in the simulation non-sequential mode, and an actual light source model is established. After a large number of ray tracings, the far-field light field distribution is obtained. The center is 0°, and the edge angle can be set according to user needs, such as 20°, 30°, etc. Taking the convex cylindrical lens array as an example, the ray tracing effect after beam expansion is as follows. Figure 3 shown.

[0048] In one possible implementation, the surface parameters include a subunit period;

[0049] The sub-unit period of the microlens array is determined based on the optical collimation calculation formula d=f*tan(θ), where d is the sub-unit period size, f is the sub-unit effective focal length, and θ is the half field of view.

[0050] In this embodiment, the incident light beam in the actual light field space generally has a certain divergence angle. When the light beam is transmitted to the microlens array subunit, if the subunit size is much larger than the light beam size, the light beam cannot be approximated as a parallel light beam, and the Gaussian performance of the Gaussian light beam after being collimated by a single lens still exists, which cannot meet the requirements of beam expansion with a larger field of view angle, and the center energy is the highest, which cannot meet the requirements. If the subunit size is much smaller than the spot size, it can be considered that the light beam is approximately parallel light, and the beam expansion effect is achieved after the light beam is refracted. The smaller the subunit size, the smaller the light beam is divided, and the more uniform the light field energy is. However, due to the difficulty of process processing, the subunit period is generally at the level of several hundred microns.

[0051] In this embodiment, in order to improve the uniformity of light field energy distribution and reduce the difficulty of process processing, the microlens subunit period is designed to be 0.3mm, and the light beam irradiated on the microlens subunit surface can be approximately considered as a parallel light beam. According to the optical collimation calculation formula d=f*tan(θ), d can be considered as the subunit period size, f is the subunit effective focal length, and f is related to the material refractive index n.

[0052] In one possible implementation, the microlens array is made of glass, the subunit period is 0.3 mm, the subunit effective focal length is 0.26 mm, and the ratio of 0° center energy to ±30° edge energy of the expanded laser beam is 0.7:1.

[0053] In this embodiment, according to the formula, when the sub-unit period is d=0.3mm and the half field of view θ=30°, f=0.26mm is obtained by calculation, the material of the microlens array is set to glass, and the microlens array surface parameters are obtained after ray tracing under non-sequential conditions using optical simulation software, so as to achieve a uniform beam output with an energy ratio of 0° and 30° in the far field of 0.7:1, which meets the use requirements.

[0054] The beam divergence angle test equipment is used to test the energy distribution of the light field after beam expansion, and the Figure 4A The far-field light energy distribution diagram is shown. According to user needs, the surface parameters can be designed to achieve Figure 4B , Figure 4C The specific scale light field distribution is shown.

[0055] In a possible implementation, the laser emission light source is four 905 nm laser chips connected in series horizontally with a period of 0.5 mm.

[0056] In this embodiment, the emitting light source of the present invention uses four 905nm laser chips packaged in series horizontally to achieve high peak power output with a period of 0.5mm. Photolithography technology is used to produce high-precision pad patterns on the surface of the ceramic carrier with an accuracy of up to 1μm. The pads are used to accurately position the tube core, which is sintered on the carrier. The relative position error between the tube core and the carrier is controlled within ±5μm, thereby improving the beam compression accuracy in the meridian direction.

[0057] In a possible implementation, the microlens array is processed by a thermoforming method.

[0058] In this embodiment, when the material is low-melting-point glass, a microlens array is obtained by hot forming, which can meet the high reliability requirements of military use environment, power environment, etc., and a high-precision alloy mold needs to be made, and the microlens array is produced by six-dimensional high-precision free-form surface machining. The advantage of this method is that a layer of soft material is prepared on the surface of the alloy mold, and the soft material surface shape can be adjusted in real time according to the surface shape design to achieve high precision requirements.

[0059] In a possible implementation, the microlens array is a convex lenticular lens array, a concave lenticular lens array, or an alternating convex-concave lenticular lens array.

[0060] In this embodiment, the cross section of the convex cylindrical lens array is as follows: Figure 5A As shown, the cross section of the concave cylindrical mirror array is as follows Figure 5B As shown, the cross section of the concave-convex alternating cylindrical lens array is as follows Figure 5C shown.

[0061] In a possible implementation, a processing method of the microlens array is selected based on the surface type.

[0062] In this embodiment, the conventional microlens array processing methods include mechanical processing, hot forming, heat reflow, nanoimprinting, etc. Among them, the mechanical processing method adopts cold processing to produce, which is limited by the processing accuracy of the machine tool. The periodic size of the microlens array subunit is relatively large, generally above 0.5mm, with large processing errors and low surface accuracy; the hot reflow method and nanoimprinting method require the production of specific masks and are produced by semiconductor processing technology. The finished product materials are mostly plastic materials, which do not meet the high reliability requirements of military use; the process processing requires real-time parameter monitoring and adjustment of process parameters; the accuracy is low, and there are strict requirements on the subunit surface and arrow height; the processing cycle is long and does not meet the actual use requirements. The adaptability of each processing method and each surface type can be compared through experiments, and the processing method and surface type can be combined to obtain the microlens array that best meets the requirements.

[0063] In a possible implementation, the microlens array is parallel to the chip end face of the laser emitting light source.

[0064] In this embodiment, the microlens array is bonded to the metal tube shell by ultraviolet glue for rapid curing. Since the microlens array is insensitive to the arc divergence angle, distance from the chip, etc., it is sufficient to ensure that it is parallel to the chip end face during the debugging process.

[0065] In a possible implementation, the collimating lens is a FAC aspheric lens.

[0066] In this embodiment, the emitting light source outputs an elliptical light spot and then passes through a FAC lens in the meridian direction for fast axis compression to achieve high-density energy output; the FAC lens is bonded to the metal tube shell by UV glue for rapid curing; the laser light source uses a FAC aspheric lens in the meridian direction to collimate the beam to achieve 1.0° angle compression, thereby increasing the field of view light power density

[0067] As can be seen from the above, for the field of laser detection, this patent designs a high peak power output pulse laser. The arc loss direction design adopts an aspherical surface microlens array to achieve 60° light field coverage. The energy ratio of the center beam and the edge beam is 0.7:1, which increases the edge ratio of the field of view, reduces the difficulty of optical design of the laser detection receiving end, and realizes panoramic detection through the arrangement of the laser array. Finally, three different surface microlenses are analyzed, all of which can achieve fan-shaped beam output with a specific field of view angle in the arc sagittal direction of the emitting light source and high uniform energy distribution.

[0068] The beneficial effects of the present invention include:

[0069] 1. The microlens array group is composed of multiple sub-unit cylindrical mirrors, and the unit size is small, ≤0.3mm. The unit size of the microlens array on the market is generally around 1mm, resulting in poor uniformity of the light field after beam expansion;

[0070] 2. In order to compensate for the weak edge echo signal, that is, to balance the energy distribution of the center and edge light, a microlens array is designed in the present invention, so that the energy ratio of the far field center and the 30° energy after beam expansion is 0.7:1.

[0071] 3. Three types of microlens arrays are designed, and the appropriate type can be selected according to the microlens processing method. The microlens array beam expansion system design is insensitive to the number of emitting light source chips, divergence angle, spot diameter, distance, etc., and has a small size and low assembly precision requirements.

[0072] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A large field of view uniform pulsed laser beam emission system, characterized in that: include: A laser emitting light source, used for generating a laser beam; A collimating lens, used for collimating the laser beam generated by the laser emitting light source in the meridian direction; A microlens array includes a plurality of cylindrical mirror units, which are used to expand the collimated laser beam in the sagittal direction to obtain a laser beam with a preset light field energy distribution; wherein the surface parameters of each cylindrical mirror unit in the microlens array are optimized based on the preset light field energy distribution and optical simulation software.

2. The large field of view uniform pulse laser beam emission system as claimed in claim 1, characterized in that: The surface parameters include the curvature radius r and the asphericity coefficient K; The curvature radius r and the asphericity coefficient K of each column mirror unit in the microlens array are obtained by optimizing the curvature radius r and the asphericity coefficient K based on the difference between the light field energy distribution of ray tracing in the simulation non-sequential mode by optical simulation software and the preset light field energy distribution.

3. The large field of view uniform pulse laser beam emission system as claimed in claim 1, characterized in that: The surface parameters include subunit period; The sub-unit period of the microlens array is determined based on the optical collimation calculation formula d=f*tan(θ), where d is the sub-unit period size, f is the sub-unit effective focal length, and θ is the half field of view.

4. The large field of view uniform pulse laser beam emission system as claimed in claim 1, characterized in that: The microlens array is made of glass, the subunit period is 0.3 mm, the subunit effective focal length is 0.26 mm, and the ratio of 0° center energy to ±30° edge energy of the expanded laser beam is 0.7:

1.

5. The large field of view uniform pulse laser beam emission system as claimed in claim 4, characterized in that: The laser emission light source is four 905nm laser chips connected in series horizontally, with a period of 0.5mm.

6. The large field of view uniform pulse laser beam emission system as claimed in claim 4, characterized in that: The microlens array is processed by a thermal forming method.

7. The large field of view uniform pulse laser beam emission system as claimed in claim 1, characterized in that: The microlens array is a convex cylindrical lens array, a concave cylindrical lens array or an alternating concave and convex cylindrical lens array.

8. The large field of view uniform pulse laser beam emitting system as claimed in claim 7, characterized in that: The processing method of the microlens array is selected based on the surface type.

9. The large field of view uniform pulse laser beam emission system as claimed in claim 1, characterized in that: The microlens array is parallel to the chip end face of the laser emitting light source.

10. The large field of view uniform pulse laser beam emitting system according to claim 1, characterized in that: The collimating lens is a FAC aspheric lens.

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