CN104237981A - Single ellipsoidal-surface beam expanding lens - Google Patents

Abstract

The invention discloses a single ellipsoidal beam expander lens, which is surrounded by two ellipsoidal surfaces, a vertical axis circular plane and a cylindrical side surface. The ellipsoidal lens is rotationally symmetrical about its central axis. Only one ellipsoidal lens can realize the beam expansion function, which greatly simplifies the structure of the beam expansion system and greatly improves the uniformity of the output beam spot. The beam expansion ratio of the ellipsoidal lens is 17.40, the maximum radius of the input beam is 5mm, and the maximum radius of the output beam is 87mm. The material of the ellipsoidal beam expander is SK2 glass with a refractive index equal to 1.600.

Description

A single ellipsoid beam expander lens

technical field

The present invention relates to an optical lens, in particular to a single ellipsoidal lens for beam expansion, the purpose of which is to input a parallel beam with a beam radius of r into a single ellipsoidal lens to output a parallel outgoing beam with a beam radius greater than R , R > r , without changing the plane wave characteristics of the light beam, and belongs to the field of optical design and application.

Background technique

In experiments related to light, it is often necessary to expand (reduce) the beam of light. The output beam of the laser is very thin, and the output beam must be expanded and collimated for more applications. The most commonly used beam expander systems are refractive systems, reflective systems, and catadioptric hybrid systems. Compared with the refraction system, the reflective beam expander system has no chromatic aberration, and is easy to realize large-aperture high-energy reflection, and is widely used in aerospace remote sensing and other fields. The structure of the refractive beam expander system is relatively simple, but when the zoom ratio is large, a large lens aperture is required, which significantly increases the spherical aberration, coma and other aberrations related to the aperture, which affects the collimation and uniformity of the beam. sex. Therefore, the refractive beam expander system is only used in the beam expander (beam shrinker) system that requires a small zoom ratio. This paper also mainly studies the refractive beam expander system, but this beam expander system is composed of a spherical surface, and its spherical aberration has nothing to do with the lens aperture, which is almost zero.

The traditional refractive beam expander system consists of at least two single lenses, so that the focal points of two single lenses with different focal lengths coincide, and the beam expander ratio is the ratio of the focal lengths of the two lenses. In order to increase the zoom ratio, not only the lens diameter needs to be increased, but also the number of lenses needs to be increased. However, these two methods will cause diffraction speckle fringes and affect the uniformity of the beam expansion (beam reduction) spot. The increase in the number of lenses also increases the difficulty of system assembly and debugging. According to the special optical refraction characteristics of the ellipsoid and the vector form of the law of refraction, this paper proposes to use a single ellipsoid lens as a beam expander or beam reducer, that is, only one ellipsoid lens can realize the beam expansion and contraction function of light, and When the aperture of the lens increases, the spherical aberration remains almost zero, which solves the problems affecting the difficulty of system adjustment and the unevenness of the exit spot.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the problems that the existing refractive beam expander system is composed of at least two lenses, the assembly and debugging are troublesome, and the outgoing light spots are not uniform. A kind of ellipsoidal lens that can realize the function of beam expansion with a single lens is proposed, that is, only one ellipsoidal lens can complete the beam expansion of light, which avoids the trouble of aligning the focus of two mirrors or multiple mirrors, and improves The uniformity of the expanded beam spot is improved.

The structure of the ellipsoidal lens of the present invention is shown in Figure 1. The ellipsoidal lens is surrounded by an ellipsoidal surface (1), an ellipsoidal surface (2), a vertical axis circular plane (3) and a side surface (4). The ellipsoidal surface The lens is rotationally symmetrical about its central axis; the parallel incident light beam with beam radius r is incident on the ellipsoidal surface (1) along the optical axis, and is refracted by the ellipsoidal surface (1) for the first time and irradiates on the ellipsoidal surface (2), and then After the second refraction by the ellipsoidal surface (2), it emerges parallel to the optical axis, and the radius of the outgoing beam is R, R>r, which realizes the expansion of the light beam; the reverse optical path is the contraction of the beam.

Preferably, the ellipsoid (1) should meet the requirements of the following formula:

(1)

in: , 0≤ h ≤5.75 mm, the maximum spherical aberration of this ellipsoid is on the order of 10 ^-15 mm, and the focal length in glass is 12 mm.

Preferably, the ellipsoid (2) should meet the requirements of the following formula:

(2)

in: , 0≤ h ≤95mm, the maximum spherical aberration of this ellipsoid is on the order of 10 ^-14 mm, and the focal length in glass is 209 mm.

Preferably, the inner and outer radii of the vertical axis circular plane (3) of the ellipsoidal lens are 5.75 mm and 95 mm respectively, and the position of the vertical axis circular plane is at x=6.86 mm; the side of the ellipsoidal lens ( 4) It is the part of a cylinder whose side is cut by the circular plane (3) and the ellipsoidal surface (2), and its bottom surface has a radius of 95 mm; The distance d = 221mm.

Preferably, the material of the ellipsoidal lens is SK2 glass with a refractive index of 1.60.

Preferably, the maximum beam radius incident on the aspheric surface (1) parallel to the optical axis is r _max =5mm.

The advantages of this optical system are: 1. Compared with the prior art, the beam expander system provided by the present invention has only one lens, which saves the trouble of assembling and debugging multiple lenses. 2 . The outgoing beam can be enlarged by 17.40 times without changing the plane wave characteristics of the beam.

Description of drawings

Fig. 1 is the two-dimensional structure schematic diagram of the ellipsoid beam expander lens embodiment of the present invention;

Fig. 2 is the three-dimensional structure schematic diagram of the ellipsoid beam expander lens embodiment of the present invention;

Fig. 3 is the two-dimensional simulation diagram of the beam expansion process of the ellipsoidal beam expander lens embodiment of the present invention;

Fig. 4 is the three-dimensional analog diagram of the beam expansion process of a single ellipsoidal beam expander lens of the present invention;

Figure 5 is a three-dimensional simulation illustration of the beam expansion process of a single ellipsoidal beam expander lens when the incident light rays are in the same plane;

Fig. 6 is a schematic diagram of the light intensity distribution on the vertical axis plane at x =250 mm of the embodiment of the ellipsoidal beam expander lens of the present invention;

The reference signs are as follows:

d in accompanying drawing 1 is the distance between the apex of the ellipsoid (1) and the apex of the ellipsoid (2).

Detailed ways

According to the structure of the ellipsoidal lens shown in Figure 1, an ellipsoidal lens with a beam expansion rate of 17.40 times is designed, and the lens length (the distance from the apex of the ellipsoidal surface (1) to the apex of the ellipsoidal surface (2)) is d = 221 mm and a height of 95 mm, the material of the ellipsoidal lens is SK2 glass with a refractive index equal to 1.60.

The light only passes through the two ellipsoidal surfaces of the lens, and the ellipsoidal surface (1) is given by the equation

decision, where: , 0≤ h ≤5.75mm, the maximum spherical aberration of this ellipsoid is on the order of 10 ^-15 mm, and the focal length in glass is 12 mm.

The ellipsoid (2) is given by the equation decision, where: , 0≤ h ≤95mm, the maximum spherical aberration of this ellipsoid is on the order of 10 ^-14 mm, and the focal length in glass is 209 mm.

Make the foci of the ellipsoid (1) and the ellipsoid (2) coincide in the glass, then the distance between the apex of the ellipsoid (1) and the vertex of the ellipsoid (2) is 221 mm.

The inner and outer radii of the vertical axis circular plane of the ellipsoidal lens are 5.75 mm and 95 mm respectively, and the position of the vertical axis circular plane is at x=6.86 mm; For the sectional part, the radius of the bottom surface of the cylinder is 95 mm; the side surface of the lens and the plane of the ring are only used to connect two ellipsoidal surfaces, not the working surface.

The incident beam parallel to the optical axis with a maximum beam radius of r _max =5mm is incident on the ellipsoidal surface (1), refracted by the ellipsoidal surface (1) for the first time, reaches the ellipsoidal surface (2), and then passes through the ellipsoidal surface (2) After the second refraction, it exits parallel to the optical axis, and the maximum outgoing beam radius is 87 mm.

Assuming that the incident wave is a plane wave, and the light intensity is uniformly distributed in the vertical axis direction, then the outgoing wave is also a plane wave, and the light intensity of the outgoing wave is also uniformly distributed in the vertical axis plane. the

Claims (6)

1. A single ellipsoidal lens for beam expansion, characterized in that: the ellipsoidal lens is surrounded by an ellipsoidal surface (1), an ellipsoidal surface (2), a vertical ring plane (3) and a side surface (4) , the ellipsoidal lens is rotationally symmetrical about its central axis; the parallel incident light beam with beam radius r is incident on the ellipsoidal surface (1) along the optical axis, and is irradiated to the ellipsoidal surface (1) after the first refraction by the ellipsoidal surface (1) 2) above, after the second refraction by the ellipsoidal surface (2), it exits parallel to the optical axis, and the radius of the outgoing beam is R , R > r , to realize the expansion of the light beam; the reverse optical path is the contraction of the beam. 2. A single ellipsoid lens for beam expansion according to claim 1, characterized in that: the ellipsoid (1) should meet the requirements of the following formula: (1) in: , 0 ≤ h ≤ 5.75 mm. 3. A single ellipsoid lens for beam expansion according to claim 1, characterized in that: the ellipsoid (2) should meet the requirements of the following formula: (2) in: , 0 ≤ h ≤ 95 mm. 4. A single ellipsoidal lens for beam expansion according to claim 1, characterized in that: the inner and outer radii of the vertical axis circular plane (3) of the ellipsoidal lens are 5.75 mm and 95 mm respectively, The position of the vertical axis circular plane is at x=6.86 mm; the side surface (4) of the ellipsoidal lens is a part of a cylindrical side cut by the ellipsoidal surface (2) and the circular plane (3), and the radius of the bottom surface is 95 mm; the distance d from the vertex of the ellipsoidal surface (1) to the vertex of the ellipsoidal surface (2) of the ellipsoidal lens is 221 mm. 5. A single ellipsoidal lens for beam expansion as claimed in claim 1, characterized in that: the material of the ellipsoidal lens is SK2 glass with a refractive index of 1.60. 6. A single ellipsoidal lens for beam expansion according to claim 1, characterized in that: the maximum beam radius incident on the ellipsoidal surface (1) parallel to the optical axis is r _max =5 mm.