CN204758926U - Expand and restraint collimation optical system - Google Patents

Abstract

The utility model discloses an expand and restraint collimation optical system and preparation method. Optical system include that preceding group transmission is expanded and restraint collimation group and expand with back group reflection and restraint collimation group, press the light incidence orientation, the transmission is expanded and is restrainted collimation group including a biconcave burden mirror, a biconvex direct position of telescope and two curved month direct position of telescopes, the curved phototropic incident direction of camber of two curved month direct position of telescopes, the reflection is expanded bundle collimation group and including two paraboloidal mirrors that have the same focus position, is small -bore paraboloidal mirror and heavy -calibre paraboloidal mirror in proper order, and the shape of face of heavy -calibre paraboloidal mirror is the off -axis concave surface. The utility model provides an expand the collimation system of restrainting, can expand and restraint for the arbitrary laser wavelength of broadband within range or white light laser provide the collimation, and not need any removal compensating unit. Its compact structure, it is small, expand and restraint that the multiplying power is big, the collimation performance is high, can be used to fields such as holographic imaging, optical test, laser radar.

Description

A Beam Expanding Collimation Optical System

technical field

The utility model relates to a compact wide-band high-magnification beam expansion collimation optical system.

Background technique

In many applications such as optical detection, spectral calibration, lidar, security, etc., it is necessary to shape the beam to emit the beam at a very small angle, so as to achieve long-distance transmission or optimal coupling of the beam. At present, the beam expansion and collimation of the optical system can be divided into two types, one is for the application and development of a single band of laser beam, and the corresponding beam expansion and collimation system has a transmission type, a reflection type and a combination of the two; the other is One is for the application of lasers at multiple wavelengths. This structure changes the distance between the eyepiece and the objective lens to adapt to different wavelengths while keeping the parameters of the optical components constant. The former type, because it is only applicable to a single wavelength, can easily meet the requirements of large magnification or variable magnification; the latter type, for lasers with multiple wavelengths, its large magnification beam expansion is not easy to achieve, and the distance between the eyepiece and the objective lens needs to be changed. Adaptation, that is, by designing a special adjustment mechanism or adding a spacer to meet the spacing requirements under different laser wavelengths, such as the document "Design of Multi-Wavelength Transmissive Beam Expander" (J. Infrared and Laser, vol37, No.7) A complex transmissive design is used to achieve beam expansion and collimation at three wavelengths. When adjusting the distance between the objective lens and the eyepiece, the system's spacing accuracy, parallelism and coaxiality will bring errors and affect the collimation performance. And with the application of continuous or white light lasers and some special applications, beam expanding and collimating optical systems suitable for continuous wavelength laser beams are required in a wide range of wavelengths, and this method of changing the pitch cannot be satisfied.

Contents of the invention

The utility model aims at the deficiencies in the prior art, and provides a wide-band high-magnification beam expansion collimation optical system, which can be applied to lasers with multiple wavelengths, without moving the lens to adjust the lens spacing to adapt to different wavelengths. Beam expander collimation has high-quality collimation performance and can achieve high optical transmittance. It is a compact wide-band high-magnification beam expander collimator optical system without a distance adjustment mechanism.

The technical solution to realize the purpose of this utility model is to provide a beam expansion collimation optical system, which includes a transmission beam expansion collimation group and a reflection beam expansion collimation group; according to the incident direction of light, the transmission beam expansion collimation group includes A beam expander group composed of a double concave negative mirror and a double convex positive mirror, a collimation group composed of the first meniscus positive mirror and the second meniscus positive mirror, the first and second meniscus positive mirrors The curvature of the mirror is bent to the incident direction of the light; the combined focal length of the beam expansion group is a negative value, the combined focal length of the collimation group is a positive value, and the magnification of the transmission beam expansion collimation group is the focal length of the collimation group and the focal length of the beam expansion group The absolute value of the ratio; the reflective beam expansion collimation group includes two parabolic mirrors with the same focal position, followed by a small-diameter parabolic mirror and a large-diameter parabolic mirror, and the surface shape of the large-diameter parabolic mirror is an off-axis concave surface, The beam expansion and collimation magnification of the reflective beam expansion and collimation group is the ratio of the vertex curvature radius of the large-diameter parabolic mirror to the vertex curvature radius of the small-diameter parabolic mirror.

In the utility model, the magnification of the transmission beam expansion and collimation group is 2x to 10x; the magnification of the reflection beam expansion and collimation group is 8x to 30x.

The optical system provided by the utility model is composed of a transmission beam expansion collimation group and a reflection beam expansion collimation group, and its principle is as follows:

The transmission beam expander collimation group realizes small magnification beam expansion of light, and adopts double concave mirror-biconvex and meniscus mirror-meniscus mirror. Due to the relatively small beam expansion, the aberrations are mainly spherical aberration and chromatic aberration. Spherical aberration correction is realized by optimizing the surface shape, and chromatic aberration correction of wide-band wavelengths is realized by selecting a suitable combination of glass materials. The reflective beam expander group is composed of two off-axis parabolic mirrors, and adopts an elliptical concentric structure to achieve beam expansion at small angles and large magnifications. The light output by the transmitted beam expander and collimator group enters the small-diameter off-axis parabolic mirror, and then reflects to the large-diameter off-axis parabolic mirror to achieve a larger ratio of beam expansion.

The transmission beam expansion and collimation group of the beam expansion and collimation optical system of the utility model is composed of four lenses, and generally realizes beam expansion and collimation less than 10 times. The first two mirrors form a mirror beam expander group. The first mirror is biconcave, using materials with relatively high dispersion and high refractive index; the second mirror is biconvex, using materials with low refractive index and low dispersion performance. Their combined focal length is negative; the latter two form a collimation group, both of which are meniscus positive mirrors, and their curvatures are bent toward the incident direction of the light beam. The selection of the two lenses is opposite to that of the first two, that is, the first The first meniscus positive mirror is made of materials with low refractive index and low dispersion performance, and the second meniscus positive mirror is made of materials with relatively high dispersion and relatively high refractive index. The initial focal length and material selection are determined according to the following formulas (1), (2) and (3):

;

in, is the beam expansion and collimation magnification of the lens beam expansion and collimation group, is the focal length of the expanded beam group, is the focal length of the collimation group, and are the focal length of the double-concave negative mirror in the beam expander group and its material Abbe number, respectively, and are the focal length of the biconvex positive mirror in the beam expander group and the Abbe number of its material, respectively. Similarly, the material selection of the lenses in the collimation group is also obtained according to formulas (1), (2) and (3).

The beam expansion and collimation group in the utility model adopts two parabolic mirrors at the same focal point, which can realize beam expansion and collimation of more than 10x. The off-axis folding of the optical path through the parabolic mirror can reduce the structural length of the optical system. One of the focal points of the two parabolic mirrors is at the same position, forming an elliptical concentric structure, which can correct several aberrations other than field curvature, such as spherical aberration, coma, astigmatism, etc. The small-diameter parabolic mirror and the large-diameter parabolic mirror have the same focus position, that is, the ellipses on both sides are concentric structures. Its vertex curvature ratio is the beam expander collimation ratio of the group , namely formula (4):

(4);

in, is the radius of curvature of the vertex of the small-diameter parabolic mirror, is the radius of curvature of the vertex of the large-aperture parabolic mirror. After the combination of the current transmission beam expansion collimation group and the rear reflection beam expansion collimation group, the formed beam expansion collimation magnification ratio is formula (5):

(5);

As a result, a beam expansion and collimation ratio of more than 30 times can be formed, and even a beam expansion and collimation ratio of more than 200 times can be achieved. After the two are combined, the remaining aberrations can be corrected by mutual compensation. For example, the remaining advanced spherical aberration of the front transmission group can be corrected in the reflection group, and the remaining field curvature in the reflection group can be compensated in the transmission group. Due to the off-axis reentrant optical path, the volume of the system can be reduced, and the transmission beam expansion and collimation group can be placed in the off-axis space, so that the transmission beam expansion and collimation group does not need to occupy extra space, thus making the system more compact.

Compared with the prior art, the utility model has the beneficial effects of:

1. The beam expansion and collimation system provided by the utility model can realize large-magnification beam expansion and collimation of wide-band light beams without setting element adjustment mechanisms or aberration compensation components. The realization method proposed by the utility model can not only be applied to the visible and near-infrared bands, but also applicable to other bands, such as ultraviolet, medium-wave and long-wave infrared bands.

2. The wide-band and high-magnification compact beam expansion collimation system provided by the utility model can provide beam expansion and collimation for any laser wavelength or white light laser within the wide-band range without any moving compensation parts, and the structure is compact. Small in size, large in beam expansion magnification, and high in collimation performance, it can be used in holographic imaging, optical testing, laser radar, etc.

Description of drawings

Fig. 1 is a schematic structural diagram of a wide-band high-magnification beam expansion collimation optical system provided by an embodiment of the present invention;

Figure 2 is a wavefront diagram at 632.8nm for a wide-band high-magnification beam expansion collimation optical system provided by the embodiment of the present invention;

Figure 3 is a wavefront diagram at 1064nm for a wide-band high-magnification beam expansion collimation optical system provided by an embodiment of the present invention;

Fig. 4 is the MTF curve diagram of the outgoing light beam of a wide-band high-magnification beam expansion collimation optical system provided by the embodiment of the present invention after being imaged by a 200mm ideal lens;

Fig. 5 is a schematic structural diagram of a wide-band high-magnification beam expansion collimation optical system provided by another embodiment of the present invention;

In the figure, 1, a double-concave negative lens; 2, a double-convex positive lens; 3, the first meniscus lens; 4, the second meniscus lens; 5, a small-diameter parabolic mirror; 6, a large-diameter parabolic mirror.

Detailed ways

The technical solution of the utility model will be further elaborated below in conjunction with the accompanying drawings and embodiments.

Example 1:

The design requirements of the beam expanding and collimating optical system to be processed in this embodiment: the incident light beam is 1.5mm, the divergence angle is 22mrad, and the beam expanding and collimating of 33x is realized. The applicable wavelength range is 488nm～1064m.

Referring to accompanying drawing 1, it is a kind of optical system structure schematic diagram that is used for broadband high-magnification beam expansion collimation that the present embodiment provides; It comprises transmission beam expansion collimation group and reflection beam expansion collimation group; Described transmission expansion collimation group The beam collimation group, according to the incident direction of the light, includes a beam expansion group composed of a double concave negative mirror 1 and a double convex positive mirror 2, and is composed of the first meniscus positive mirror 3 and the second meniscus positive mirror 4 The collimation group; the combined focal length of the beam expansion group is negative, the curvature of the two meniscus positive mirrors is bent to the light incident direction, the combined focal length of the collimation group is positive, and the magnification of the transmission beam expansion collimation group is the collimation group The absolute value of the ratio of the focal length to the focal length of the beam expander group; the reflective beam expander collimation group includes two parabolic mirrors with the same focal position, which are the small-diameter parabolic mirror 5 and the large-diameter parabolic mirror 6 in turn, and the surface of the large-diameter parabolic mirror The shape is an off-axis concave surface, and the surface shape of the small-diameter parabolic mirror is an off-axis convex surface. The beam expansion collimation magnification of the rear group is the ratio of the vertex radius of curvature of the large-diameter parabolic mirror 6 to the vertex radius of curvature of the small-diameter parabolic mirror 5.

The flow chart of specific steps for preparing a wide-band high-magnification beam expansion collimation optical system in this embodiment, the steps are as follows:

1. According to the design requirements of the beam expansion collimation optical system to be processed, such as volume, wavelength range, beam expansion collimation magnification or input and output angles, etc., allocate the transmission beam expansion collimation group and the reflection beam expansion collimation group Beam expansion and collimation magnification, so that the beam expansion magnification of the front transmission beam expansion collimation group is between 2x and 10x, and the magnification of the rear reflection beam expansion collimation group is above 8x to achieve the required beam expansion and collimation magnification.

2. The initial focal length and material selection are determined according to the following formulas (1), (2) and (3):

;

in, is the beam expansion and collimation magnification of the lens beam expansion and collimation group, is the focal length of the expanded beam group, is the focal length of the collimation group, and are the focal length of the double-concave negative mirror in the beam expander group and its material Abbe number, respectively, and are the focal length of the biconvex positive mirror in the beam expander group and the Abbe number of its material, respectively. Similarly, the material selection of the lenses in the collimation group is also obtained according to formulas (1), (2) and (3).

Use the optical simulation software Zemax or CodeV to perform chromatic aberration correction, spherical aberration optimization, and focal length selection on the beam expander group composed of the first two mirrors and the collimation group composed of the rear two mirrors in the lens beam expander collimation group, and then combine the beam expander group and collimation group for comprehensive aberration correction.

3. Optimizing the curvature, spacing or off-axis amount of the rear reflective beam expander collimation group; the ratio of the curvature of the vertices of the two parabolic mirrors is the beam expander collimation ratio of the group , namely formula (4):

(4);

in, is the radius of curvature of the vertex of the small-diameter parabolic mirror, is the radius of curvature of the vertex of the large-aperture parabolic mirror.

4. Combine the transmission beam expansion collimation group and the reflection diffusion collimation group. After the current transmission beam expansion collimation group and the rear reflection beam expansion collimation group are combined, the formed beam expansion collimation ratio is formula (5):

(5);

The aberration and collimation performance of the system are generally optimized, and various parameters of the system are obtained.

Judging whether the obtained results meet the requirements, if the mirror processing difficulty or volume size limit cannot meet the expected requirements, then adjust the two groups of magnifications according to the method of step 1, return to step 2 and redesign to balance the system horizontally and vertically size; otherwise, go to step 5.

5. Under the conditions that the beam expander collimation performance and processing technology requirements can be met, the system processing, assembly and testing are carried out to obtain a beam expander collimation optical system.

According to the above implementation steps, the specific parameters obtained are shown in Table 1.

Table 1

.

In the embodiment of the utility model, the transmission beam expansion collimation group is placed in the space left by the off-axis oblique reflection of the reflection beam expansion collimation group, which makes the whole system more compact. The length of the entire optical system is 85 mm, and the width is 65 mm.

In this embodiment, the lens in the front transmission beam expander collimation group, the negative mirror 1 is in front, and the positive lenticular mirror 2 is behind, and the negative mirror 1 and the positive lenticular mirror 2 form a negative lens group. Negative mirror 1 uses flint glass ZF2 with high dispersion and high refractive index, and positive lenticular mirror 2 uses crown glass K9 with low refractive index and low dispersion. Mirror 3 and mirror 4 constitute a positive mirror group, both of which are in the form of a positive meniscus, and the curvature is bent toward the light incident direction, and the two mirrors are respectively K9 and ZF2.

In this embodiment, the reflecting mirror 5 of the rear group adopts a convex paraboloid surface shape, and the off-axis distance is 6 mm. The parabolic mirror 4 samples a concave paraboloid surface shape, and the off-axis distance is 40 mm. The focal positions of the two parabolic mirrors coincide.

According to the current technology, the beam expanding and collimating optical system given by the utility model can transmit more than 90% of the incident beam with a divergence angle of 22mrad in the 488nm-1064nm band, and the divergence angle of the outgoing beam obtained after collimation and expansion is less than 0.7mrad , the beam expansion magnification is 33x.

Referring to accompanying drawing 2, the wavefront diagram of the central field of view and the edge divergence field of view at 632.8nm is given in this embodiment, wherein, (a) the picture is the PV value, (b) the picture is the RMS value; it can be seen from the figure It is found that the PV value is 0.093 wavelength and the RMS value is 0.02 wavelength at 0 field of view, and the PV value is 0.086 wavelength and RMS value is 0.020 wavelength at the edge field of view.

Referring to accompanying drawing 3, the wavefront diagram of the central field of view and the edge divergence field of view at 1064nm is given in this embodiment, wherein, (a) the picture is the PV value, (b) the picture is the RMS value; it can be seen from the figure , at 0 field of view, the PV value is 0.078 wavelength, the RMS value is 0.14 wavelength, and at the edge field of view, the PV value is 0.091 wavelength, and the RMS value is 0.015 wavelength.

Referring to FIG. 4 , it is a modulation transfer function (MTF) curve after focusing and imaging the beam expander collimation system provided by this embodiment with a 200mm ideal lens. As can be seen from Fig. 5, under the incidence of 22mrad divergence angle, through the beam expansion and collimation of the optical system of the present utility model, and then manage the imaging of the ideal lens, the MTF obtained is close to the diffraction limit, which can illustrate that the beam expansion and collimation optical system of the present utility model has Good beam expander quasi-performance.

Example 2

Referring to accompanying drawing 5, this embodiment provides a schematic structural diagram of a wide-band high-magnification beam expansion collimation optical system; this embodiment uses the same transmission and diffusion collimation group as in Embodiment 1, and the reflection beam expansion A small diameter concave parabolic mirror is used.

The small-diameter concave parabolic mirror 5 in the present embodiment has the same apex curvature value as that of the convex parabolic mirror in embodiment 1, and the sign is opposite, that is, the radius of curvature of the element 5 in Table 1 is changed to -20.1. Since the use of a small concave parabolic mirror will form an intermediate real focal point, the overall length of the system will become longer, while when using the small-diameter convex parabolic mirror in Embodiment 1, a virtual focal point will be formed, and the length will be shortened. When the small-diameter concave parabolic mirror in this embodiment is in use, the off-axis direction is opposite to that of the small-diameter convex parabolic mirror in Embodiment 1, that is, the off-axis distance is -6mm.

In this embodiment, after the light beam incident on the small concave reflector, it will first converge to a point, which is the common focus of the parabolic mirror 5 and the parabolic mirror 6 . The converged light beam diverges and is incident on a large-diameter paraboloid to achieve collimation.

The performance index of the beam expander collimation system involved in this embodiment is consistent with that of Embodiment 1.

The beam expander collimation system of the utility model can realize large-magnification beam expander collimation of a wide-band beam without setting an element adjustment mechanism or an aberration compensation component. The realization method proposed by the utility model can not only be applied to the visible and near-infrared bands, but also applicable to other bands, such as ultraviolet, medium-wave and long-wave infrared bands.

Claims (2)

1. A beam expanding collimating optical system, comprising: the device comprises a transmission beam expanding collimation group and a reflection beam expanding collimation group; according to the incident direction of light rays, the transmission beam expanding collimation group comprises a beam expanding group consisting of a biconcave negative lens (1) and a biconvex positive lens (2), and a collimation group consisting of a first meniscus positive lens (3) and a second meniscus positive lens (4), wherein the curvatures of the first meniscus positive lens and the second meniscus positive lens are both bent towards the incident direction of the light rays; the combined focal length of the expanded beam grouping is a negative value, the combined focal length of the collimation grouping is a positive value, and the multiplying power of the transmission expanded beam collimation group is the absolute value of the ratio of the focal length of the collimation grouping to the focal length of the expanded beam grouping; the reflection beam expanding collimation group comprises two parabolic mirrors with the same focus position, a small-caliber parabolic mirror (5) and a large-caliber parabolic mirror (6) in sequence, the surface shape of the large-caliber parabolic mirror is an off-axis concave surface, and the beam expanding collimation magnification of the reflection beam expanding collimation group is the ratio of the vertex curvature radius of the large-caliber parabolic mirror (6) to the vertex curvature radius of the small-caliber parabolic mirror (5).

2. The beam expanding collimating optical system of claim 1, wherein: the multiplying power of the transmission beam expanding collimation group is 2 x-10 x; the multiplying power of the reflection beam expanding collimation group is 8 x-30 x.