CN104142498A - Novel beam expander of coherent wind lidar - Google Patents

Abstract

The invention relates to a novel beam expander of a coherent wind lidar, and belongs to the field of lidar atmosphere detection. The novel beam expander comprises an input lens (1) and an output lens (2). The input lens (1) is a plano-concave lens, wherein the front surface of the plano-concave lens is a concave spherical surface, and the rear surface of the plano-concave lens is a plane. The output lens (2) is a plano-convex lens, wherein the front surface of the plano-convex lens is a plane, and the rear surface of the plano-convex lens is a convex spherical surface. Incident lasers are diverged and expanded by the input lens (1) to reach the output lens (2), collimation and divergence angle compression are carried out on the laser beam through the output lens (2), and the laser beam is emitted out with the laser emitting angle approximating that of parallel lasers. Compared with an existing beam expander, the novel beam expander has the advantages that the combination of the one plano-concave lens and the one plano-convex lens is adopted, laser energy losses are reduced, and the laser energy utilization efficiency and the collimation effect are improved; an optical system of the beam expander is small in size, simple in structure, high in laser energy utilization efficiency, high in stability and low in cost, and the problem that the existing beam expander is large in lens number, complex in structure, large in laser energy loss and the like is solved.

Description

A kind of novel relevant anemometry laser radar beam expander

Technical field

The present invention relates to a kind of novel relevant anemometry laser radar beam expander, belong to laser radar detection atmosphere field.

Technical background

The research of variation, the weather forecast etc. of the transmitting of atmospheric wind to atmospheric physics, airport wind field, spacecraft and operation, temperature, humidity has material impact.Coherent wind laser radar is a kind of novel survey wind means, utilize Doppler's principle, heterodyne detection technology, adopt laser as probe source, to the pulse of atmosphere Emission Lasers, receive the backscatter signal of atmosphere (particulate and atmospheric molecule), carry out Wind Speed Inversion by analyzing the radially Doppler shift of Emission Lasers, its time, spatial resolution are high, the air speed error that detection obtains is little, has higher maneuverability.

Beam expander is the important component part of coherent wind laser radar, and its performance has determined the detection accuracy of laser radar.Beam expander is the lens subassembly that can change laser beam diameter and the angle of divergence.The laser beam of sending from laser instrument has certain angle of divergence, makes laser beam become collimation (parallel) light beam by the adjusting of beam expander, could utilize focus lamp to obtain tiny high power density hot spot; Can change beam diameter for use in different optical instrumentations by beam expander.

In coherent wind laser radar, for the needs of detected with high accuracy, in system aperture, need to obtain coherent signal as much as possible, the larger beam diameter of transmitting ratio is to atmosphere, in order to reduce telescopical design difficulty of processing, cutting down cost, need between laser instrument and telescope, add beam expander, laser beam is carried out to pre-beam-expanding collimation.The backscatter signal of atmosphere (particulate and atmospheric molecule) is larger by the beam diameter after telescope, in order to coordinate other optical device, as coupling mechanism, need to after telescope, add contracting bundle device (beam expander inversion), reduce beam diameter.

Existing beam expander eyeglass number is more, structure is more complicated and optical energy loss is serious.

Summary of the invention

The object of the invention is the defect more for existing beam expander eyeglass number, structure is more complicated and optical energy loss is serious, propose a kind of novel relevant anemometry laser radar beam expander, finally obtain a kind of volume compact, the coherent wind laser radar beam expander that simple in structure, optical energy loss is few.

The object of the invention is to be achieved through the following technical solutions.

A kind of novel relevant anemometry laser radar beam expander, is characterized in that: comprise 1 input mirror and 1 outgoing mirror; Arrival outgoing mirror is dispersed, expanded to incident light through input mirror, and through outgoing mirror, to beam collimation, the compression angle of divergence, rising angle is similar to parallel light emergence.

Described input mirror is that front surface is the plano-concave lens that concave spherical surface, rear surface are plane;

Described outgoing mirror is that front surface is the plano-convex lens that plane, rear surface are protruding sphere.

Beneficial effect:

Contrast existing beam expander, the present invention adopts 1 plano-concave lens and 1 plano-convex lens combination, has reduced optical energy loss, has improved the efficiency of light energy utilization and collimation effect; Make this beam expander optical system volume little, simple in structure, the efficiency of light energy utilization is high, and stability is high, and cost is low, has solved the problems such as existing beam expander eyeglass number is more, structure is more complicated, optical energy loss is serious.

Brief description of the drawings

Fig. 1 is the structural representation that the novel relevant Laser Measuring wind and thunder in the present invention reaches beam expander;

Fig. 2 is the principle schematic that the novel relevant Laser Measuring wind and thunder in the present invention reaches beam expander;

Fig. 3 is the index path that the novel relevant Laser Measuring wind and thunder in the present invention reaches beam expander;

Fig. 4 is modulation transfer function (MTF) curve map that the novel relevant Laser Measuring wind and thunder in the present invention reaches beam expander;

Fig. 5 is the wavefront difference figure that the novel relevant Laser Measuring wind and thunder in the present invention reaches beam expander;

Reference numeral: 1-input mirror, 2-outgoing mirror.

Embodiment

Introduce in detail the present invention below in conjunction with the drawings and the specific embodiments.

As shown in Figure 1, the novel relevant anemometry laser radar beam expander of one of the present invention is made up of as outgoing mirror 2 as input mirror 1 and a plano-convex lens a plano-concave lens, and the light of laser instrument transmitting is compressed to the angle of divergence, collimator and extender, reduce optical energy loss, improved the utilization factor of laser.This beam expander optical system volume is little, simple in structure, and the efficiency of light energy utilization is high, and stability is high, and cost is low.

Be illustrated in figure 2 the fundamental diagram of beam expander, can find out that beam expander generally includes an input negative lens and an output positive lens.Input mirror sends a virtual focus light beam to outgoing mirror, and two lens are empty confocal arrangement.Input mirror focuses on (virtual focus) on front focal plane by the laser beam of incident, new ω ' with a tight waist ₀with angle of divergence θ ' be

${{\mathrm{\ω}}_0}^{\′}=\frac{f_1\mathrm{\λ}}{\mathrm{\π}{\mathrm{\ω}}_0}---\left(1\right)$

${\mathrm{\θ}}^{\′}=\frac{2\mathrm{\λ}}{\mathrm{\π}{{\mathrm{\ω}}_0}^{\′}}---\left(2\right)$

$\mathrm{\ω}\left(l\right)={\mathrm{\ω}}_0\sqrt{1+{\left(\frac{\mathrm{l\λ}}{\mathrm{\π}{\mathrm{\ω}}_0^2}\right)}^2}---\left(3\right)$

In formula, λ is laser wavelength of incidence, and ω (l) is incoming laser beam beam radius on incident mirror, and l is the incident laser distance with incident mirror with a tight waist, f ₁the focal length of input mirror, ω ₀the with a tight waist of incident beam.Because ω ₀' drop on the back focal plane of outgoing mirror, and the focal distance f of outgoing mirror ₂be greater than the focal length of inputting mirror, Gaussian beam will be collimated by beam expanding lens.Collimation multiplying power is as follows:

$T=\frac{\mathrm{\θ}}{{\mathrm{\θ}}^{\′\′}}=T_1\sqrt{1+{\left(\frac{\mathrm{l\λ}}{\mathrm{\π}{\mathrm{\ω}}_0^2}\right)}^2}---\left(4\right)$

T in formula ₁=f ₂/ f ₁, θ is the angle of divergence of incident beam.After beam expanding lens, ω with a tight waist ₀" and angle of divergence θ " is

${{\mathrm{\ω}}_0}^{\′\′}=\frac{\mathrm{\λ}}{\mathrm{\π}{{\mathrm{\ω}}_0}^{\′}}{f}_2---\left(5\right)$

${\mathrm{\θ}}^{\′\′}=\frac{\mathrm{\θ}}{T}---\left(6\right)$

(1) formula substitution (5) is obtained

ω ₀″＝T ₁ω(l) (7)

From (4) to (7) formula can find out, expand multiplying power and collimation multiplying power not only with the relating to parameters of beam expander, also relevant with the position of parameters of laser beam and expander lens.The function of beam expander is to reduce the angle of divergence of laser beam, and then makes laser focused hot spot less.

General requirement according to coherent wind laser radar: the multiple that expands of beam expander is 4 times, the bore of incident light is 3.5mm, the bore of emergent light is 14mm, the angle of divergence is about 0.3085 ° (half-angle), wavefront difference is less than 1/4 λ, adopt the material of infrared band, comprise 1 plano-concave lens (1) and 1 plano-convex lens (2), the light of laser instrument transmitting is expanded, the compression angle of divergence, rising angle is similar to parallel light emergence, the length of controlling beam expander is no more than 50mm, the edge of each lens leaves the fitting allowance of about 2mm, beam expander systematic parameter is as shown in table 1, beam expander index path as shown in Figure 3.This beam expander have volume little, simple in structure, be conducive to Design of Mechanical Structure, without features such as internal focal point, optical energy loss are few.

Table 1 beam expander systematic parameter

Expand greatly the optical system of multiple, general modulation transfer function and the wavefront difference of adopting evaluated, modulation transfer function (MTF) is the main method of evaluating optical system, as shown in Figure 4, modulation transfer function curve has shown the sagitta of arc (S) of each visual field (0 °, 0.216 °, ± 0.3085 °) and the modulation transfer function curve of meridian (T) face and diffraction limit (TS DIFF.LIMIT) curve coincides, and illustrates that aberration control obtains fine.

Wavefront difference as shown in Figure 5, is 0.0016 wavelength left and right at the wavefront difference root mean square of 0 visual field and 1 visual field (unit: milliradian mrad), much smaller than 1/4 wavelength, meets the designing requirement of coherent wind laser radar system.

Above-described specific descriptions; object, technical scheme and beneficial effect to invention further describe; institute is understood that; the foregoing is only specific embodiments of the invention; be used for explaining the present invention, the protection domain being not intended to limit the present invention, within the spirit and principles in the present invention all; any amendment of making, be equal to replacement, improvement etc., within protection scope of the present invention all should be included in.

Claims (2)

1. a novel relevant anemometry laser radar beam expander, is characterized in that, comprises an input mirror 1 and an outgoing mirror 2; Arrival outgoing mirror is dispersed, expanded to incident light through input mirror 1, and through outgoing mirror 2, to beam collimation, the compression angle of divergence, rising angle is similar to parallel light emergence.

2. the novel relevant anemometry laser radar beam expander of one according to claim 1, is characterized in that, described input mirror 1 for front surface be the plano-concave lens that concave spherical surface, rear surface are plane; Described outgoing mirror 2 for front surface be the plano-convex lens that plane, rear surface are protruding sphere.