System for shaping and focusing laser radiation with fibre optic output to remote object

Abstract

FIELD: electronic engineering.SUBSTANCE: invention relates to optical-electronic instrumentation for generating and directing laser radiation to a remote object. The system for forming and focusing laser radiation from an emitter with a fibre-optic output onto a remote object includes an emitter with a fibre-optic output, a two-lens system for forming radiation of a given directional pattern, a device for focusing radiation onto a remote object, with the end of the fibre-optic output core located in the focal plane of the radiation formation system. The absolute value of the focal length of the first negative lens from the end is less than the focal length of the second positive lens from the end, and the ratio of the values of their focal lengths and the rear focal segment are reduced, and the air gap between the lenses is increased in accordance with the ratios: 1≥|f'1| / f'2≥0,6, l1=K1⋅f'eff., l2=K2⋅f'eff., where: where |f' 1| is the absolute value of the focal length of the first negative lens from the end; f'2 is the focal length of the second positive lens from the end; l1 is the back focal length; f'eff. is the effective focal length of the formation system; l2 is the air gap between the lenses; coefficients K1= 0.57-0.35 and K2= 0.17-0.27.EFFECT: increase in the diffraction quality of radiation.1 cl, 2 dwg

Description

[0001] The invention relates to optical-electronic instrument making and can be used in the development of laser systems for the formation and focusing of laser radiation on a remote object.

[0002] A system for forming and focusing laser radiation on a target is known [1], including four fiber emitters with fiber optic leads, four systems for forming laser radiation in the form of short-focus collimators, four rotating flat mirrors directed at the target, installed behind the collimator of each emitter, two-fold beam expanders with a mechanism for longitudinal movement of the eyepiece.

[0003] When using this system for generating and directing radiation to a target, the following are significant disadvantages: a wide beam pattern of laser radiation due to the short focal length of the collimator (~250 mm), low radiation density on the target due to the lack of focusing of the radiation at a given range and a wide beam pattern of the emitter, a significant size of the radiation spot on the target, and low axial radiation intensity on a remote object.

[0004] A system for forming and focusing laser radiation on a target is known [2], including a system for forming laser radiation with a short-focus collimator in the form of an aspherical lens, a system for forming the required directional pattern of laser radiation from an emitter in a mirror telescope with off-axis parabolic mirrors in the form of a concave primary and convex secondary mirrors, a device for focusing laser radiation on a remote object, carried out by longitudinal movement of the aspherical lens of the collimator.

[0005] When using the known method of forming and focusing radiation on an object, the following are significant disadvantages: high radiation loads on the optical elements of the collimator and the secondary mirror of the telescopic system due to their close location to the end of the radiating body of the emitter, causing thermal deformations of the optical surfaces of the optical elements and deteriorating the radiation pattern; low radiation density on the object due to the wide radiation pattern of the emitter; the complexity and high cost of manufacturing aspherical optics for the collimator and telescopic system; the complexity of adjusting off-axis parabolic mirrors.

[0006] The closest in technical essence to the proposed one is a system for forming and focusing laser radiation from an emitter with a fiber-optic output onto a remote object [3], including an emitter with a fiber-optic output, a radiation formation system, a device for focusing radiation onto a remote object, the end of the fiber-optic output core is located in the focal plane of the radiation formation system.

[0007] The disadvantages of this system include: the significant length of the radiation generation system, the considerable size of the radiation spot on the target, which is determined by the effective focal length of the generation system, and the low radiation density on the remote object.

[0008] The objective of the invention is to create a compact optical system for forming and focusing laser radiation with a fiber optic output to a remote object, effectively forming diffraction-quality radiation.

[0009] The stated problem is solved in that in a known system for forming and focusing laser radiation with a fiber optic output onto a remote object, including an emitter with a fiber optic output, a two-lens system for forming radiation of a given directional pattern, a device for focusing radiation onto a remote object, with the end of the core of the fiber optic output located in the focal plane of the radiation forming system, the absolute value of the focal length of the first negative lens from the end is less than the focal length of the second positive lens from the end and the ratio of the values ​​of their focal lengths and the back focal segment are reduced, and the air gap between the lenses is increased in accordance with the relationships:

[0010] 1≥|f'1| / f'2≥0.6,

[0011] l1=K1⋅f' эф. ,

[0012] l2=K2⋅f' эф., Where

[0013] where |f'1| is the absolute value of the focal length of the first negative lens from the end;

[0014] f'2 - focal length of the second positive lens from the end;

[0015] l1- posterior focal segment;

[0016] f' эф. - effective focal length of the formation system;

[0017] l2- air gap between lenses;

[0018] coefficients K1=0.57-0.35 and K2=0.17-0.27.

[0019] Fig. 1 shows the basic optical diagram of the prototype, Fig. 2 shows the basic optical diagram for implementing the proposed system, where: 1 - laser with fiber optic output; 2 - end face of the fiber optic output core; 3 - two-lens radiation generation system; 3(1) - first negative lens from the end face; 3(2) - second positive lens from the end face; 4 - focusing device.

[0020] The laser with fiber optic output 1 is designed to generate laser radiation transmitted through the fiber optic output, through the end of the core of which 2, the laser beam emerges.

[0021] The beam-forming system 3 is designed as a telephoto lens and is intended to generate radiation with a given directional pattern and to construct an image of the end face of the fiber optic output 2 on a remote object. The beam-forming system is a two-lens system: the first lens from end face 3(1) is negative, and the second lens from end face 3(2) is positive.

[0022] The end of the core of the fiber optic output 2 is located in the plane of the objects of the telephoto lens 3. When the end of the core of the fiber optic output is located in the focal plane of the telephoto lens, a beam focused to infinity and focused to a specified distance when it moves away from the telephoto lens emerges through it.

[0023] Focusing device 4 is designed to aim and focus laser radiation on a remote object.

[0024] The system for forming and focusing laser radiation with fiber optic output to a remote object operates as follows.

[0025] The end face of the core of the fiber optic output 2 is located in the plane of the objects of the telephoto lens 3. The distant object is located in the image space of the telephoto lens 3.

[0026] When a control command is given to supply power to laser 1, the laser begins to generate coherent electromagnetic waves transmitted through the fiber optic lead, the end of the core of which 2 is the radiation source, from which divergent powerful laser radiation emerges.

[0027] The output divergent laser radiation of the emitter, emanating from the end face of the core of the fiber optic output 2, passes the first negative lens from the end face 3(1), further expanding the laser beam, hits the second positive lens of the shaping system and, passing it, forms radiation of the required directional pattern close to the diffraction quality, and is focused at infinity when the end face of the core of the fiber optic output is located in the focal plane of the telephoto lens. When the end face of the core of the fiber optic output 2 is moved relative to the telephoto lens or the telephoto lens or one of its lenses relative to the end face of the core of the fiber optic output, focusing device 4 performs aiming and focusing to a specified distance where the remote object is located.Since the end face of the fiber optic output 2 is located in the plane of the object of the telephoto lens 3, and the system is focused on a distant object, the end face of the fiber optic output of the emitter and the distant object are conjugated, and the telephoto lens creates an image of the end face of the fiber optic output 2, where the laser radiation of emitter 1 emerges, onto the distant object. The radiation of emitter 1 will then be focused on the distant object.

[0028] In this case, the absolute value of the focal length of the first negative lens from the end is less than the focal length of the second positive lens from the end, and the ratio of the values ​​of their focal lengths and the back focal segment are reduced, and the air gap between the lenses is increased in accordance with the ratios:

[0029] l≥|f'| / f'2≥0.6,

[0030] l1= K1⋅f' эф. ,

[0031] l2= K2⋅f' эф. , Where:

[0032] where |f'1| is the absolute value of the focal length of the first negative lens from the end;

[0033] f'2 - focal length of the second positive lens from the end;

[0034] l1- posterior focal segment;

[0035] f' эф. - effective focal length of the formation system;

[0036] l2- air gap between lenses;

[0037] coefficients K1=0.57-0.35 and K2=0.17-0.27.

[0038] While maintaining the effective focal length of the formation system, reducing the back focal length leads to an increase in the air gap between the lenses, and when certain conditions are met for the ratios of the focal lengths of the lenses and the air gaps, the length of the formation system will decrease, and the diffraction quality of the output laser radiation will be maintained.

[0039] By satisfying certain conditions for the ratios of the focal lengths of the lenses and air gaps while maintaining the length of the telephoto lens, its focal length increases, thereby reducing the divergence of the output radiation of the emitter, reducing the size of the focused radiation on a distant object and increasing the radiation density on the object.

[0040] The diameter of the output radiation at a remote object is equivalent to the geometric size of the image of the end face of the fiber optic output core at a remote object, constructed by a telephoto lens:

[0041] D=d⋅L / f эф. , where D is the diameter of the fiber core image or the diameter of the output radiation at a distance L, d is the diameter of the fiber core, f эф. - effective focal length of the optical system of a telephoto lens.

[0042] The actual size of this image is slightly larger due to blurring, which is determined by the aberrations of the system and its resolution. However, the longer the effective focal length of a telephoto lens's optical system, the smaller the image size of the optical fiber core at distance L, and naturally, the smaller the size of the focused radiation on a distant object and the higher the radiation density on the object.

[0043] In the proposed system for generating and focusing laser radiation with a fiber optic output to a remote object, the fulfillment of certain conditions for the ratios of the focal lengths of the lenses and air gaps while maintaining the focal length of the telephoto lens allows:

[0044] - reduce the length of the forming system;

[0045] - to create a compact optical system for forming and focusing laser radiation on a remote object, effectively forming diffraction-quality radiation;

[0046] while maintaining the length of the telephoto lens, it allows:

[0047] - increase its focal length, thereby forming radiation with a narrower directional pattern and reducing the divergence of the emitter's output radiation, leading to a decrease in the size of the focused radiation on a distant object and an increase in the radiation density on the object.

[0048] Currently, the company has developed, manufactured, assembled, and is successfully testing the proposed system for generating and focusing laser radiation with a fiber optic output to a remote object.

[0049] Sources of information:

[0050] 1. Sprangle, Phillip & Ting, A. & Penano, JR & Fischer, Richard & Hafizi, Bahman. (2008). Incoherent Combining of High-Power Fiber Lasers for Directed-Energy Applications. 2.25.

[0051] 2. Patent RU 2699944, published 09.11.2019, bulletin. No. 26, IPC: G01S 17 / 88 (2019.05), F41G 3 / 22 (2019.05).

[0052] 3. Patent RU 2814149, IPC: G01S 17 / 88; publication date: 02 / 22 / 2024 - prototype.

Claims

A system for generating and focusing laser radiation from an emitter with a fiber optic output onto a remote object, comprising an emitter with a fiber optic output, a two-lens system for generating radiation of a given directional pattern, a device for focusing radiation onto a remote object, with the end of the core of the fiber optic output located in the focal plane of the radiation generation system, characterized in that the absolute value of the focal length of the first negative lens from the end is less than the focal length of the second positive lens from the end and the ratio of the values ​​of their focal lengths and the back focal segment are reduced, and the air gap between the lenses is increased in accordance with the relationships: 1≥|f'1| / f'2≥0.6, l l =K1⋅f' эф. , l2= K2⋅f' эф. , Where: where |f'1| is the absolute value of the focal length of the first negative lens from the end; f'2 - focal length of the second positive lens from the end; l1 - posterior focal segment; f' эф. - effective focal length of the formation system; l2 - air gap between lenses; coefficients K1=0.57-0.35 and K2=0.17-0.27.

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