CN104898284A - Aspheric extender lens - Google Patents

Abstract

The invention relates to an aspheric beam expander, the aspheric beam expander is a solid lens surrounded by an aspheric surface and a columnar side, the aspheric surface is an ellipsoid, and when the ellipsoid is placed vertically, it satisfies The equation is: The beam expander of the invention can obtain an elliptical light spot and can realize asymmetric illumination. The beam expander of the present invention has good universality to light beams of different wavelengths, and can effectively reduce light loss and improve brightness when performing speckle measurement on an asymmetric object.

Description

An aspheric beam expander

technical field

The invention relates to an optical lens, in particular to an aspheric beam expander.

Background technique

The beam expander has the advantages of increasing the beam width, increasing the light-passing area, and facilitating observation and measurement. It is widely used in optical systems or experiments such as laser collimation, electronic speckle interferometry, and Fresnel holography. Spherical beam expanders are widely used due to their low process requirements, simple processing, and easy realization, and basically meet the requirements of experiments and scientific research. With the development of electronic speckle interferometry technology and digital holographic detection technology, the requirements for the quality of the wavefront formed by the laser through the beam expander are further improved, especially for the measurement of irregular objects or in the three-dimensional measurement of large dislocation electronic speckle, asymmetric Illumination, so the traditional spherical beam expander can no longer meet the requirements of image quality and asymmetry. Compared with spherical mirrors, aspheric mirrors have the advantage of low spherical aberration and can improve the quality of light waves. Therefore, many precision measurements and scientific research are based on the production and development of aspheric mirrors.

Contents of the invention

Aiming at the problems existing in the prior art, the invention provides an aspheric beam expander.

In order to solve the above technical problems, the technical solution of the present invention is:

An aspheric beam expander is a solid lens surrounded by an aspheric surface and a cylindrical side surface, the aspherical surface is an ellipsoidal surface, and when the ellipsoidal surface is placed vertically, the equation satisfied is:

Preferably, the aspheric beam expander is made of BK7 glass.

Preferably, the radius of curvature of the apex of the aspheric surface along the x-axis is 3mm.

Preferably, the radius of curvature of the apex of the aspheric surface along the y-axis is 6mm.

Preferably, the aspheric beam expander can reshape parallel beam expansion into an elliptical light spot.

The application of the aspherical beam expander in the asymmetric illumination of the three-dimensional electronic speckle interferometer.

The beneficial technical effect of the present invention is:

1. The beam expander of the present invention can obtain an elliptical light spot and realize asymmetrical illumination.

2. The beam expander of the present invention has good universality for beams of different wavelengths.

3. The beam expander of the present invention can effectively reduce light loss and improve brightness when performing speckle measurement on an asymmetric object.

Description of drawings

Fig. 1 is the front view structure schematic diagram of the present invention;

Fig. 2 is the top view of the present invention;

Fig. 3 is the optical refraction surface under the non-paraxial situation of lens;

Fig. 4 is the optical refraction surface under the paraxial situation of lens;

Fig. 5 is the schematic diagram of vertical ellipsoid in coordinate axis;

Fig. 6 is a schematic diagram of an ellipse on a yoz plane;

Fig. 7 shows the diffused image of parallel light beams observed on the plane at 800mm after passing through the aspheric beam expander calculated by simulation.

Among them, 1. Aspherical surface, 2. Side surface.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

As shown in FIG. 1 and FIG. 2 , an aspheric beam expander is a solid lens surrounded by an aspheric surface 1 and a cylindrical side surface 2 , and the aspheric surface 1 is an ellipsoidal surface.

The aspheric beam expander is made of BK7 glass (also known as K9 glass, refractive index n=1.51680).

The lens is made of BK7 glass with a semi-major axis of 2mm, a semi-minor axis of 1.5mm, and a thickness of 2mm. In order to obtain the vertical ellipsoid shown in Figure 5 and Figure 6, using the rotation characteristics of the Biconic surface, the radius of curvature at the vertex D along the x-axis direction is designed to be 3mm, that is, c=3mm, and the conic value of the ellipse in the yoz plane is 1. Let a=3mm at the same time. Then the radius of curvature of the vertex along the y-axis R ₀ =a·(1+k)=6mm; the intercept of the y-axis of the ellipsoid Then the surface equation that the designed ellipsoid satisfies is Substituting the lens size into the surface equation, the maximum thickness of the curved surface in the x-axis direction is about 0.354mm, and the maximum thickness of the curved surface in the y-axis direction is about 0.41mm.

Fundamentals of Beam Expander Design

Different optical systems have different deflection capabilities for light beams. In physics, the ability of an optical system to deflect a light beam is called the optical power. The optical power is equal to the difference between the convergence degree of the image beam and the object beam convergence, commonly used letters To represent. focal power of refracting surface Among them, n' is the refractive index of the image space, n is the refractive index of the object space, R is the spherical radius, f' is the focal length of the image space, and f is the focal length of the object space. The power equation above is general for any optical system. Under the paraxial condition, the deflection power of the focal power to the light satisfies the paraxial ray tracing formula (PRTE). Consider the optical refraction surface in the non-paraxial case as shown in Fig. 3. In the figure, a ray is incident on the refracting surface at height y and refracted. At the intersection of the ray and the refracting surface, the normal of the surface and a straight line parallel to the optical axis are drawn, and they are all represented by dotted lines. The figure also marks the angle between the light and the optical axis (U and U'), the incident angle and refraction angle of the light (I and I'), and the curvature C of the refraction surface (C=1/R). If the intersection point is moved down close to the optical axis, Figure 3 will evolve into the paraxial situation shown in Figure 4.

According to the mathematical relationship, in Figure 4, -α=y/R, then the angle α can be expressed as

α＝-y/R＝-y C (1)

The relationship between the angles in Figure 4 is

$\left\{\begin{array}{c}\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; u</span>}\\ \mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; u</span>}}^{<span\; class="notranslate">\; \&prime;</span>}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

In the paraxial condition, the Snell formula is expressed as

ni=n'i' (3)

Substituting formula (2) into formula (3), we have

n(-α+u)=n'(-α+u')

n'u'=nu-nα+n'α

n'u'=nu+(n'-n)α (4)

Substitute formula (1) into formula (4) to get

n'u'=nu-y[(n'-n)C] (5)

Equation (5) is called the curved paraxial ray tracing equation (PRTE), where, is the optical power of a single refractive surface. It can be known from formula (5), The larger the value of , the stronger the light deflection ability. Therefore, changing the radius of curvature of the refraction surface can change the deflection direction of the light, thereby realizing the shaping of the circular light spot.

As shown in Figure 7, the software simulation results show that the new beam expander can realize aspherical and non-uniform beam expansion, and can expand the beam of parallel light with a diameter of 2mm and a wavelength of 632.8nm at 800mm to form an elliptical spot of 280mm×140mm , and has good universality for beams of different wavelengths.

Although the specific implementation of the present invention has been described above in conjunction with the accompanying drawings, it does not limit the scope of protection of the invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, those skilled in the art do not need to pay creative work Various modifications or variations that can be made are still within the protection scope of the present invention.

Claims (6)

1. an aspheric surface beam expanding lens, is characterized in that: described aspheric surface beam expanding lens is the solid lens surrounded by aspheric surface and column side, and described aspheric surface is ellipsoid, and when described ellipsoid is for vertically placing, satisfied equation is:

2. according to the aspheric surface beam expanding lens in claim 1, it is characterized in that: described aspheric surface beam expanding lens is made up of BK7 glass.

3. according to the aspheric surface beam expanding lens in claim 2, it is characterized in that: described aspheric summit is 3mm along the radius-of-curvature of x-axis.

4. according to the aspheric surface beam expanding lens in claim 3, it is characterized in that: described aspheric summit is 6mm along the radius-of-curvature of y-axis.

5., according to the arbitrary described aspheric surface beam expanding lens of claim 4, it is characterized in that: directional light can expand and be shaped as oval hot spot by described aspheric surface beam expanding lens.

6. according to the application of the arbitrary described aspheric surface beam expanding lens of claim 1-5 in three-dimensional electronic speckle interferometer asymmetric lighting.