The telescope structure of the 1.2-meter laser ranging system of the Yunnan Observatory is a ground-level telescope. When the Gaussian beam is emitted at full aperture,
the position and occlusion of the mainmirror and submirror prevents the center energy
of the beam from being emitted. According to the high energy of the Gaussian beam
center, this paper is based on the free-form surface optics to shaping the Gaussian beam
into a large-caliber ring beam, which increases the energy of the emitted beam and increases the photon echo detection intensity.
Free-form surface beam shaping is a new beam shaping method that is different
from traditional beam shaping. It has high design freedom and flexible spatial distribution. The beam shaping of free-form surface shaping system not only simplifies the
structure of the optical system, but also effectively controls it. Beam, to achieve any
beam shape.
The focus of this paper is on the core problem of free-form surface design - the
free-form surface design method, in order to establish an efficient and accurate freeform surface design theory, and design an accurate optical design for the 1.2-meter
laser ranging system. The transmitted beam is shaped into a ring beam. Aiming at the
shortcomings of existing traditional optical system beam shaping methods, this paper
proposes an accurate design system for free-form surface beam shaping system and establishes a free-form surface model. Firstly, based on the study of traditional optics,
based on the characteristics of geometric optics, a cone lens is used to realize the generation of a hole beam and a hole-shaped beam of a specific shape of a given size.
However, the spot size of the beam shaping by the cone lens cannot be changed, and the
laser emission energy is limited in the case where the existing system is already fixed,
and the highest utilization of energy cannot be achieved.
In order to achieve the maximum utilization of laser energy, the paper then reconstructs and models the freeform surface shape by tracking the light trace based on the
optimization idea. The method comprises two steps. The first step is to establish an energy conservation relationship between the incident surface and the target surface, and
obtain a free curved surface shape by the correspondence between the actual range of the required light on the target surface and the actual incident light spot size. Coordinate
function. The second step is based on the nonsequential ray tracing method, and the
evaluation function is constructed by the total energy of the ring beam shaped by the
freeform surface optics, and the performance of the freeform surface shaping system
is further optimized. After obtaining a continuous freeform surface shape, the effectiveness of the freeform optical system was verified by simulation data analysis. The
laser beam quality with freeform shaping is better than the previous laser beam shaping system, and the freeform optical system has high design freedom and applicability,
providing an effective optical solution for complex laser beam shaping.
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