A coaxial sighting system

Abstract

The application provides a coaxial aiming system for target point positioning and aiming of a picosecond terminal optical path of inertial confinement fusion (ICF), which is composed of a projection mirror, a window, a main mirror, a secondary mirror, a lens group, a cylindrical mirror and a CCD detector, and each optical element is coaxial; the system multiplexes the projection mirror and the window in the picosecond terminal optical path, and does not need to additionally increase a target chamber flange window; the cylindrical mirror is used to correct the astigmatism aberration introduced by the large-angle inclined projection mirror; considering that the projection mirror needs to change the angle to accurately guide the position change of the laser landing point, under the illumination light source with the wavelength of 590nm±7.5nm and the working wavelength of 1053nm, the projection mirror is optimized for different use angles, and the high imaging resolution requirement can be realized; the coaxial two-mirror structure is adopted, and the structure is compact and small in size. In addition, the Cassegrain structure composed of the main mirror, the secondary mirror and the lens group and the cylindrical mirror are independently designed, and the later assembly and adjustment is facilitated.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of optical technology, and particularly relates to a coaxial aiming system. BACKGROUND

[0002] Inertial confinement fusion (ICF) is an important method to realize nuclear fusion reaction, and has extremely important applications in new energy exploration, military defense and physical research. ICF uses high-power laser beams to uniformly irradiate a target pellet composed of thermonuclear fuel, and compresses the target pellet in a very short time to achieve fast ignition. During the target shooting process, the aiming and positioning of the target point have high requirements, which directly affect the target shooting efficiency.

[0003] In the picosecond terminal optical path, the picosecond pulse laser finally passes through a projection mirror and is incident into a target chamber cone cavity to realize target shooting. The existing picosecond cone bottom aiming scheme adds a moving-in and moving-out beam splitter in the picosecond optical path, occupies a target chamber flange resource, and uses a Cassegrain system + off-axis parabolic mirror to aim at the cone bottom. This scheme needs to move in and move out the beam splitter and the off-axis parabolic mirror, and the cost of the beam splitter assembly is high, and the off-axis parabolic mirror cannot be focused. Therefore, a new cone bottom aiming scheme is needed, which can realize high imaging resolution and save target chamber flange resources. SUMMARY

[0004] The purpose of the application is to provide a coaxial aiming system for target positioning and aiming of the picosecond terminal optical path of inertial confinement fusion (ICF), which has high resolution and can save target chamber flange resources.

[0005] To achieve the above purpose, the design is realized by the following technical means:

[0006] A coaxial aiming system is placed behind a projection mirror and a window to realize coaxial illumination and imaging. The system multiplexes part of the picosecond terminal system optical path and does not need to use additional flanges. The multiplexed optical path includes a projection mirror placed at a large angle and a window. The coaxial aiming system includes a projection mirror, a window, a main mirror, a secondary mirror, a lens group composed of two lenses with a spatial interval, a cylindrical mirror and a CCD detector. The light beam passes through the projection mirror and the window in sequence, is reflected by the main mirror and the secondary mirror twice, passes through the lens group and the cylindrical mirror, and finally realizes imaging of the target point of the picosecond terminal system on the CCD detector.

[0007] The projection mirror, the window, the main mirror, the secondary mirror, the lens group and the cylindrical mirror are coaxial;

[0008] The projection mirror is arranged at a large angle with the optical axis, and the large-angle inclined projection mirror introduces a large astigmatism, so the influence of the inclined projection mirror needs to be considered. The design uses a cylindrical mirror to correct the astigmatism introduced by the large-angle inclined projection mirror.

[0009] The projection mirror and the window are optical elements already existing in the picosecond terminal system optical path.

[0010] The illumination uses an LED with a spectral width of 15nm and a main wavelength of 590nm and a 1053nm laser.

[0011] Further, the main mirror is an aspheric mirror with a conic coefficient.

[0012] Further, the aspheric surface equation satisfies the following equation:

[0013]

[0014] Wherein, z(r, theta) is the sag of the optical surface, r is the radius of the meridian section circle, theta is the direction angle, c is the curvature, and k is the conic coefficient.

[0015] Further, the rear surface of the cylindrical mirror is a cylindrical surface with a generatrix in the x direction, and the cylindrical equation is:

[0016] y = 2r0z

[0017] Wherein, z is the sag of the optical surface, and r0 is the curvature radius of the near-axis part of the curved surface.

[0018] Further, the two lenses of the lens group are made of two kinds of glass materials, namely, crown glass and flint glass.

[0019] Further, the secondary mirror and the lens group are spherical mirrors.

[0020] The above technical scheme conceived by the present application achieves the following beneficial effects:

[0021] (1) The coaxial aiming system multiplexes the existing optical path of the picosecond terminal system, does not need to use additional flanges, and saves the scarce flange resources in the target chamber.

[0022] (2) The coaxial aiming system considers that the projection mirror needs to change the angle to accurately guide the position change of the laser falling point, and under the illumination light source of the LED with a wavelength of 590nm and a spectral width of 15nm and the working wavelength of 1053nm, the different use angles of the projection mirror are optimized, and high imaging resolution requirements can be achieved.

[0023] (3) The coaxial aiming system of the present invention takes into account the influence of a large-angle tilted projection mirror, which introduces significant astigmatism. The astigmatism introduced by the large-angle tilted projection mirror is corrected by adding a cylindrical mirror.

[0024] (4) The coaxial aiming system of the present invention adopts a coaxial two-reflector structure, which effectively utilizes the system space, shortens the system length, and makes the entire optical system compact and small in size.

[0025] (5) In the coaxial aiming system of the present invention, when the projection mirror and cylindrical mirror are removed from the optical path, the Cassegrain structure composed of the primary mirror, secondary mirror and lens group is independent, and its image quality can reach the near diffraction limit, which is convenient for subsequent offline system assembly and adjustment. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the optical path of a coaxial aiming system according to the present invention;

[0027] Figure 2 This is a schematic diagram of the modulation transfer function of a coaxial aiming system with a working wavelength of 590nm (spectral width of 15nm) when the target point falls at the center position.

[0028] Figure 3 This is a schematic diagram of the modulation transfer function of a coaxial aiming system of the present invention when the target point falls at the center position and the working wavelength is 1053nm;

[0029] In the diagram: 1. Projection mirror; 2. Glass window; 3. Primary mirror; 4. Secondary mirror; 5. Lens group; 6. Cylindrical mirror; 7. CCD detector. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but this should not be construed as limiting the scope of protection of the present invention.

[0031] like Figure 1 As shown, the present invention provides a coaxial aiming system, including a projection mirror 1, a window 2, a primary mirror 3, a secondary mirror 4, a lens group 5 consisting of two lenses, a cylindrical mirror 6, and a CCD detector 7; the projection mirror 1, window 2, primary mirror 3, secondary mirror 4, lens group 5, cylindrical mirror 6, and CCD detector 7 share the same optical axis.

[0032] The projection mirror 1 and window 2 are already optical components in the optical path of the picosecond terminal system. The coaxial aiming system of the present invention reuses the projection mirror 1 and window 2 to avoid the use of additional flange resources.

[0033] The primary mirror 3 uses a conical surface to correct spherical aberration; its aspherical equation is:

[0034]

[0035] Wherein, z(r, theta) is the sag of the optical surface, r is the radius of the meridional plane cross section circle, theta is the direction angle, c is the curvature, and k is the conic coefficient;

[0036] The sub-reflector 4 is in the shape of a convex surface, is designed as a spherical mirror, can effectively reduce manufacturing difficulty and manufacturing cost, and is used for receiving light reflected by the main reflector and reflecting;

[0037] The lens group 5 is composed of two lenses, adopts two kinds of glass materials, namely, crown glass and flint glass, the chromatic aberration introduced by the two kinds of materials is opposite in sign, and the chromatic aberration introduced by the projection reflector can be corrected;

[0038] The cylindrical mirror 6 is mainly used for correcting the astigmatism introduced by the projection reflector with a large angle of inclination;

[0039] The present application considers the change of the laser falling point position introduced by the change of the azimuth angle of the projection reflector, and is optimized for different use angles of the projection reflector, when the target point falls in any position in a sphere with a diameter of phi 25mm, high imaging resolution can be realized;

[0040] The illumination light source of the present application is an LED with a main wavelength of 590nm and a spectral width of 7.5nm, and the wavelength of 1053nm is also considered, and the coaxial aiming system of the present application has high imaging resolution under the two working wavelengths.

[0041] The coaxial aiming system of the present application considers the offline installation and adjustment of the system in the later stage, the Cassegrain structure composed of the main reflector, the sub-reflector and the lens group is an independent structure, the image quality of which can reach near-diffraction limit, and the aberration of the projection reflector is completely corrected by the cylindrical mirror.

[0042] The index of the coaxial aiming system of the present application is shown in Table 1.

[0043] Table 1

[0044] Index name Index parameter Wavelength 590 nm (spectrum width 15 nm), 1053 nm Field of view ± 10 mm Working distance 2300 mm Imaging resolution ≤ 10 μm

[0045] The surface shape parameters of each element are shown in Table 2.

[0046] Table 2

[0047]

[0048] The modulation transfer function curves corresponding to different wavelengths when the target point falls in the central position are shown in Figure 2 and Figure 3The modulation transfer function curves of each field of view are close to the diffraction limit, when the working wavelength is 590nm±7.5nm in the visible light band, in the range of the central field of view (±10mm) of the object, the MTF is greater than 0.2 at the cut-off frequency of 140lp / mm, and the object resolution can reach 8.9μm, when the working wavelength is 1053nm, in the range of the central field of view (±10mm) of the object, the MTF is greater than 0.2 at the cut-off frequency of 80lp / mm, and the object resolution can reach 15.6μm.

[0049] The coaxial aiming system designed by the application considers the target point position adjustment (in a ball of Φ25mm) caused by the azimuth change of the projection mirror, and the imaging resolution corresponding to the target points falling in different positions is shown in Table 3, and can all meet the requirement of the imaging resolution of the system.

[0050] Table 3

[0051]

[0052] In summary, the coaxial aiming system designed by the application can be used to realize the aiming of the target point of the cone target. The system multiplexes the existing projection mirror and window optical path of the picosecond terminal system, and does not need to use an extra flange; the system considers the change of the laser falling point position caused by the angle change of the projection mirror, and can realize the requirement of high imaging resolution under the wavelength of 590nm, the spectral width of 15nm of the LED and the working wavelength of 1053nm; the system considers the influence of the large-angle inclined projection mirror, and corrects the astigmatism introduced by the large-angle inclined projection mirror by the cylindrical mirror. The system adopts the coaxial two-reflection structure, effectively utilizes the system space, shortens the system length, makes the whole optical system structure compact, and has a small volume. The coaxial two-reflection and lens group of the system are independently designed, which is convenient for offline installation and adjustment, and the cylindrical mirror is only used to correct the astigmatism introduced by the projection mirror.

Claims

1. A coaxial sighting system for target point positioning and sighting of an inertial confinement nuclear fusion picosecond terminal system, comprising a projection mirror (1) and a window (2), characterized in that, The coaxial sighting system comprises a main reflector (3), a secondary reflector (4), a lens group (5) composed of two lenses with air interval, a cylindrical mirror (6) and a CCD detector (7) placed in sequence along the optical path on the same optical axis; the projection mirror (1) is placed at an angle with the optical axis; the light beam passes through the projection mirror (1) and the window (2) in sequence, is reflected twice by the main reflector (3) and the secondary reflector (4), is transmitted through the lens group (5) and the cylindrical mirror (6), and finally realizes imaging of the target point of the picosecond terminal system on the CCD detector (7).

2. A collimating system according to claim 1, wherein The main reflector (3) is a non-spherical surface with a conical coefficient.

3. A collimating system according to claim 1, wherein The front surface of the cylindrical mirror (6) is a plane, and the rear surface is a cylindrical surface.

4. A collimating system according to claim 1, wherein The lens group (5) is composed of two lenses made of crown glass and flint glass respectively.

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