阅读说明：本技术 基于短相干光源干涉仪的大行程光程匹配装置及实验方法 (Short coherent light source interferometer-based long-stroke optical path matching device and experimental method ) 是由 马骏 于逸凡 朱日宏 李建欣 苗新宇 魏聪 于 2020-04-30 设计创作，主要内容包括：本发明公开了一种基于短相干光源干涉仪的大行程光程匹配装置及实验方法,使用短相干光源可以消除光学元件前后表面反射形成的杂散光的特性,进行高精度的测量,但是只有当两支光接近零光程位置时才能干涉,此时需要对两只光进行补偿。本发明利用多组角锥棱镜通过一定的几何排列方式形成角锥阵列,在自由空间里,将其作为干涉仪的延迟线来匹配大行程光程,补偿参考光和测试光的相位差。本发明克服了大口径干涉仪干涉腔腔长难改变以及长腔长难匹配等问题,亦可通过光纤环形器,在光波导中补偿参考光和测试光的相位差。本发明设计的装置条纹对比度高,适用于多种口径,干涉腔长的干涉仪。(The invention discloses a short coherent light source interferometer-based large-stroke optical path matching device and an experimental method. The invention utilizes a plurality of sets of pyramid prisms to form a pyramid array in a certain geometric arrangement mode, and in a free space, the pyramid array is used as a delay line of an interferometer to match a long-stroke optical path so as to compensate the phase difference of reference light and test light. The invention overcomes the problems that the cavity length of the interference cavity of the large-caliber interferometer is difficult to change, the long cavity length is difficult to match and the like, and can also compensate the phase difference of the reference light and the test light in the optical waveguide through the optical fiber circulator. The device designed by the invention has high fringe contrast and is suitable for interferometers with various calibers and interference cavity lengths.)

1. A long-stroke optical path matching device based on a short coherent light source interferometer is characterized by comprising a light source module, an interference module and an imaging module; the light source module comprises a short coherent laser (1), a first polarization maintaining fiber (2-1), an optical fiber collimator (3), a polarizer (4), a half-wave plate (5), a reflector (6), a polarization splitting prism (7), a first quarter-wave plate (8-1), a second quarter-wave plate (8-2), a pyramid prism (9), a large-stroke optical path matching module (10), an optical fiber coupler (11), a second polarization maintaining fiber (2-2), an optical fiber matching sleeve (12) and a third polarization maintaining fiber (2-3); the interference system comprises a beam splitter prism (13), a collimating lens (14), a reference mirror (15) and a to-be-detected mirror (16); the imaging module comprises an imaging lens (17), a third quarter-wave plate (8-3) and a polarization CCD camera (18);

the optical fiber collimator (3), the polarizer (4), the half-wave plate (5) and the reflector (6) are sequentially arranged on a first light path, the reflector (6), the polarization beam splitter prism (7) and the long-stroke optical path matching module (10) are sequentially arranged on a second light path, the pyramid prism (9), the first quarter-wave plate (8-1), the polarization beam splitter prism (7) and the optical fiber coupler (11) are sequentially arranged on a third light path, the beam splitter prism (13), the collimating lens (14), the reference mirror (15) and the mirror to be detected (16) are sequentially arranged on a fourth light path, and the polarization CCD camera (18), the third quarter-wave plate (8-3), the imaging lens (17) and the beam splitter prism (13) are sequentially arranged on a fifth light path;

the output end of a short coherent laser (1) is connected with one end of a first polarization maintaining fiber (2-1), the other end of the first polarization maintaining fiber (2-1) is connected with an optical fiber collimator (3), emergent light is ensured to be spatially collimated light, the collimated light sequentially passes through a polarizer (4) and a half-wave plate (5) to generate linearly polarized light, the linearly polarized light is refracted by a reflector (6) and enters a polarization beam splitter prism (7), the linearly polarized light is decomposed into first transmitted light and first reflected light through the polarization beam splitter prism (7), the first transmitted light is p light, and the first reflected light is s light; the s light is converted into circularly polarized light in the opposite direction through the first quarter-wave plate (8-1), is reflected by the pyramid prism (9), and when passing through the first quarter-wave plate (8-1) again, the circularly polarized light is converted into linearly polarized light again; the p light is converted into circular polarized light with opposite directions through the second quarter-wave plate (8-2), is reflected by the long-stroke optical path matching module (10), and is converted into linear polarized light again after passing through the second quarter-wave plate (8-2) again; originally, s light reflected by a polarization beam splitter prism (7) is changed into first p light, transmitted p light is changed into first s light, at the moment, the first p light and the first s light are converged on the polarization beam splitter prism (7), enter an optical fiber coupler (11) and are coupled to enter a second polarization maintaining optical fiber (2-2), the second polarization maintaining optical fiber (2-2) is connected with a third polarization maintaining optical fiber (2-3) through an optical fiber matching sleeve (12), and the converged and coupled light enters an interference module; the coupling light is decomposed into second transmission light and second reflection light through the light splitting prism (13), the second transmission light is collimated through the collimating lens (14), the reflection light is converged through the rear surface of the reference mirror (15) and the front surface of the mirror (16) to be detected and is decomposed into third reflection light and third transmission light through the light splitting prism (13), the third reflection light enters the imaging module, firstly passes through the imaging lens (17), then passes through the third quarter wave plate (8-3), and finally is imaged on the target surface of the polarization CCD camera (18).

2. The short coherent light source interferometer-based long-stroke optical path matching device of claim 1, wherein: the fast axis directions of the first quarter wave plate (8-1), the second quarter wave plate (8-2) and the third quarter wave plate (8-3) form 45 degrees with the optical axis.

3. The short coherent light source interferometer-based long-stroke optical path matching device of claim 1, wherein: the long-stroke optical path matching module (10) is a pyramid array, and an optical path is folded through a pyramid, and the array on one side is moved, so that any optical path between 0 and 5m can be obtained in a tiny space, and the cavity length of 0 to 5m is matched.

4. The short coherent light source interferometer-based long-stroke optical path matching device of claim 1, wherein: the pyramid array comprises 9 one-inch pyramid prisms and 1 half-inch pyramid prism, wherein 5 one-inch pyramid prisms ensure that the center heights are consistent and are transversely arranged into a group; 4 one inch pyramids and half inch pyramids guarantee that the center height is unanimous in addition, and transverse arrangement is a set of, and two sets of array pyramids face is opposite and parallel, and the pyramid center has certain offset, lets the incident light beat in pyramid prism non-center department, utilizes the parallel characteristic of pyramid prism emergent light and incident light, turns over the light path.

5. The short coherent light source interferometer-based long-stroke optical path matching device of claim 1, wherein: the large-stroke optical path matching module (10) is a polarization-maintaining optical fiber circulator, and optical paths are freely selected in the optical waveguide to match different cavity lengths under different calibers.

6. An experimental method based on the short coherent light source interferometer-based long-stroke optical path matching device of any one of claims 1 to 5, characterized by comprising the following steps:

step one, opening a short coherent laser (1), connecting a first polarization maintaining fiber (2-1) into a collimator (3), sequentially adjusting the positions of a polarizer (4), a half-wave plate (5) and a reflector (6), and coupling spatial collimated light into a second polarization maintaining fiber (2-2) by adjusting an optical fiber coupler (11);

measuring and recording the distance L between the rear surface of the reference mirror (15) and the front surface of the mirror (16) to be measured, and moving the long-stroke optical path matching module (10) to a position near the optical path difference L of the first transmitted light and the first reflected light through the translation stage;

step three, controlling the polarization CCD camera (18) and the translation stage simultaneously through the computer, setting the translation stage to move in a fixed step length, acquiring the acquired image through the polarization CCD camera (18) after each movement, and reading and storing the gray value of one point;

observing gray values, wherein the gray values are zero optical path positions when mutation occurs and are also optical path matching optimal positions;

and step five, moving the translation stage to a target position, acquiring a short coherent interference fringe pattern through a polarization CCD camera (18), and calculating by using a four-step phase-shifting algorithm.

7. The experimental method of the short coherent light source interferometer-based long-stroke optical path matching device according to claim 6, wherein: collimated light generates linear polarized light through the polarizer (4) and the half-wave plate (5), s light and p light with the same light intensity are generated after the collimated light passes through the polarization splitting prism (7) through the rotation of the half-wave plate (5), and the s light and the p light are coupled to polarization maintaining optical fibers through the optical fiber coupler (11) and enter the interference module.

8. The experimental method of the short coherent light source interferometer-based long-stroke optical path matching device according to claim 6, wherein: in the first step, the coherence length of the short coherent laser (1) is 0.5 mm.

9. The experimental method of the short coherent light source interferometer-based long-stroke optical path matching device according to claim 6, wherein: the large-stroke optical path matching module (10) is arranged on the translation stage.

Technical Field

The invention belongs to a light source interference phase shifting technology, and particularly relates to a long-stroke optical path matching device based on a short coherent light source interferometer and an experimental method.

Background

In the twenty-first century, optics is the development of society, and the production of new industries injects vitality. Planar and spherical optical elements are widely used in various fields, especially aerospace, astronomy, military, medical, etc., as the most common optical elements in optical systems. High-end optical devices, represented by large-aperture mirrors and micro-spheres, present significant challenges to the fabrication of optical elements and the integration of optical systems. For the processing of optical elements, the traditional surface shape detection method comprises a knife edge method, a Hartmann sensor method, a Ruikang busy method, a subaperture splicing method, a pentaprism scanning method and the like. The methods have the defects that the to-be-measured piece is damaged or subjective experience is used as a judgment standard, and the methods are not digital, so that the accuracy is very poor. The interferometer as a non-contact measuring device has become an important and common means for measuring physical quantities such as surface shape, refractive index change and the like by introducing a phase shift technology in a communication theory.

In the short-coherent light source module, because the self-coherent length of the short-coherent light source is short, the two light beams can interfere to generate interference fringes only when approaching the zero optical path position. Because the interferometer has certain interval between standard mirror and the piece that awaits measuring when measuring, consequently the light source position needs carry out optical path matching through certain mode, adopts the pyramid to carry out the folding of optical path in the experiment. The pyramid prism has three perpendicular right-angle surfaces, the incident light forms total reflection on the three right-angle surfaces and keeps returning in the original direction, and the reflected light is always parallel to the incident light no matter what the incident angle is. The pyramid prism has high reflection efficiency, and ideally, the pyramid prism can return incident light in high efficiency in the original direction, and the incident position of the pyramid prism is changed to enable the incident light and the reflected light to generate certain transverse and longitudinal deviation.

When the large-aperture plane mirror is detected, as the aperture is increased, pushing the to-be-detected mirror to change the cavity length becomes a difficult thing and destroys the stability of the cavity, and at the moment, the optical path difference of two short coherent lights of the light source module is changed to match the cavity length, so that the workload can be reduced. The measurement of some specific optical element physical quantities, such as the radius of curvature of the spherical element, requires a long interferometric cavity length, and it is also a challenge to match the cavity length in a highly integrated light source module. Therefore, the problem can be effectively solved by adding the long-stroke optical path matching module to one of the two short coherent lights.

Disclosure of Invention

The invention aims to provide a matching device and an experimental method based on a short coherent light source interferometer long-stroke optical path, which can accurately match any interference cavity length of 0-5m in a highly integrated light source module in a short time and can acquire an interference pattern without other stray fringes in a polarization CCD camera.

The technical solution for realizing the purpose of the invention is as follows: a long-stroke optical path matching device based on a short coherent light source interferometer comprises a light source module, an interference module and an imaging module; the light source module comprises a short coherent laser, a first polarization maintaining fiber, an optical fiber collimator, a polarizer, a half-wave plate, a reflector, a polarization splitting prism, a first quarter-wave plate, a second quarter-wave plate, a pyramid prism, a long-stroke optical path matching module, an optical fiber coupler, a second polarization maintaining fiber, an optical fiber matching sleeve and a third polarization maintaining fiber; the interference system comprises a beam splitter prism, a collimating lens, a reference mirror and a mirror to be measured; the imaging module comprises an imaging lens, a third quarter-wave plate and a polarization CCD camera;

the optical fiber collimator, the polarizer, the half-wave plate and the reflector are sequentially arranged on a first light path, the reflector, the polarization beam splitter prism and the long-stroke optical path matching module are sequentially arranged on a second light path, the pyramid prism, the first quarter-wave plate, the polarization beam splitter prism and the optical fiber coupler are sequentially arranged on a third light path, the beam splitter prism, the collimating lens, the reference mirror and the mirror to be detected are sequentially arranged on a fourth light path, and the polarization CCD camera, the third quarter-wave plate, the imaging lens and the beam splitter prism are sequentially arranged on a fifth light path;

the output end of the short coherent laser is connected with one end of a first polarization maintaining fiber, the other end of the first polarization maintaining fiber is connected into an optical fiber collimator, the emergent light is ensured to be space collimated light, the collimated light sequentially passes through a polarizer and a half-wave plate to generate linear polarization light, the linear polarization light enters a polarization splitting prism through a reflection mirror to turn a light path, the linear polarization light is decomposed into first transmission light and first reflection light through the polarization splitting prism, the first transmission light is p light, and the first reflection light is s light; the s light is converted into circularly polarized light with the opposite direction through the first quarter-wave plate, is reflected by the pyramid prism, and is converted into linearly polarized light again when passing through the first quarter-wave plate again; the p light is converted into circularly polarized light with opposite directions through the second quarter-wave plate, is reflected by the long-stroke optical path matching module, and is converted into linearly polarized light again after passing through the second quarter-wave plate again; the s light reflected by the polarization beam splitter prism is changed into first p light, the transmitted p light is changed into first s light, at the moment, the first p light and the first s light are converged on the polarization beam splitter prism, enter the optical fiber coupler and are coupled to enter a second polarization maintaining optical fiber, the second polarization maintaining optical fiber is connected with a third polarization maintaining optical fiber through an optical fiber matching sleeve, and the converged and coupled light enters the interference module; the coupling light is decomposed into second transmission light and second reflection light through the beam splitter prism, the second transmission light is collimated through the collimating lens, the reflection light passing through the rear surface of the reference mirror and the reflection light passing through the front surface of the mirror to be detected are converged and decomposed into third reflection light and third transmission light through the beam splitter prism, the third reflection light enters the imaging module, firstly passes through the imaging lens and then passes through the third quarter-wave plate, and finally images are formed on the target surface of the polarization CCD camera.

An experimental method of a matching device based on a short coherent light source interferometer large-stroke optical path comprises the following steps:

opening a short coherent laser, connecting a first polarization maintaining fiber into a collimator, sequentially adjusting the positions of a polarizer, a half-wave plate and a reflector, and coupling spatial collimated light into a second polarization maintaining fiber by adjusting an optical fiber coupler;

measuring and recording the distance L between the rear surface of the reference mirror and the front surface of the mirror to be measured, and moving the large-stroke optical path matching module to a position near the optical path difference L of the first transmitted light and the first reflected light through the translation stage;

step three, controlling the polarization CCD camera and the translation stage simultaneously through a computer, setting the translation stage to move in a fixed step length, acquiring an acquired image through the polarization CCD camera after each movement, and reading and storing a gray value of one point;

observing gray values, wherein the gray values are zero optical path positions when mutation occurs and are also optical path matching optimal positions;

and step five, moving the translation stage to a target position, acquiring a short coherent interference fringe pattern through a polarization CCD camera, and calculating by using a four-step phase-shifting algorithm.

Compared with the prior art, the invention has the remarkable advantages that:

(1) the length of the cavity of the interferometer does not need to be changed by pushing the lens to be measured, and the optical path difference of the two light beams is only needed to be adjusted in the light source module; (2) by adding the long-stroke optical path matching module, a large optical path can be obtained in a very small space, so that the light source module becomes highly integrated; (3) the short coherent light source is adopted, so that the influence of the miscellaneous fringes formed by the optical elements in the system on the measurement result is avoided, and the problem of the noise of the traditional interferometer system is solved; (4) the light source module has free optical path regulating quantity of 0-5m, so that one light source can be suitable for interferometers with various calibers and cavity lengths, and the monotonous pattern that one light source of the traditional interferometer is only suitable for one interference module is broken;

drawings

FIG. 1 is a light path diagram of a long-stroke optical path matching device based on a short coherent light source interferometer.

Fig. 2 is a schematic view of a pyramid array.

Fig. 3 is a schematic diagram of a polarization maintaining fiber circulator.

Fig. 4 is a schematic diagram of a delay line scanning process, in which the position of the abrupt change of the gray level value is the successful position of the optical path difference matching.

Detailed Description

The invention is described in further detail below with reference to the attached drawing

Referring to fig. 1, a long-stroke optical path matching device based on a short coherent light source interferometer includes a light source module, an interference module, and an imaging module. The light source module comprises a short coherent laser 1, a first polarization maintaining fiber 2-1, an optical fiber collimator 3, a polarizer 4, a half-wave plate 5, a reflector 6, a polarization splitting prism 7, a first quarter-wave plate 8-1, a second quarter-wave plate 8-2, a pyramid prism 9, a large-stroke optical path matching module 10, an optical fiber coupler 11, a second polarization maintaining fiber 2-2, an optical fiber matching sleeve 12 and a third polarization maintaining fiber 2-3; the interference system comprises a beam splitter prism 13, a collimating lens 14, a reference mirror 15 and a to-be-detected mirror 16; the imaging module comprises an imaging lens 17, a third quarter-wave plate 8-3 and a polarization CCD camera 18.

The optical fiber collimator 3, the polarizer 4, the half-wave plate 5 and the reflector 6 are sequentially arranged on a first light path, the reflector 6, the polarization splitting prism 7 and the long-stroke optical path matching module 10 are sequentially arranged on a second light path, the pyramid prism 9, the first quarter-wave plate 8-1, the polarization splitting prism 7 and the optical fiber coupler 11 are sequentially arranged on a third light path, the splitting prism 13, the collimating lens 14, the reference mirror 15 and the mirror 16 to be detected are sequentially arranged on a fourth light path, and the polarization CCD camera 18, the third quarter-wave plate 8-3, the imaging lens 17 and the splitting prism 13 are sequentially arranged on a fifth light path.

The output end of the short coherent laser 1 is connected with one end of a first polarization maintaining fiber 2-1, the other end of the first polarization maintaining fiber 2-1 is connected with an optical fiber collimator 3, the emergent light is ensured to be space collimated light, the collimated light sequentially passes through a polarizer 4 and a half-wave plate 5 to generate linearly polarized light, the linearly polarized light is refracted by a reflector 6 and enters a polarization beam splitter prism 7, the linearly polarized light is decomposed into first transmission light and first reflection light through the polarization beam splitter prism 7, the first transmission light is p light, and the first reflection light is s light; the s light is converted into circularly polarized light in the opposite direction through the first quarter-wave plate 8-1, is reflected by the pyramid prism 9, and when passing through the first quarter-wave plate 8-1 again, the circularly polarized light is converted into linearly polarized light again; the p light is converted into circularly polarized light with opposite directions through the second quarter-wave plate 8-2, is reflected by the long-stroke optical path matching module 10, and is converted into linearly polarized light again after passing through the second quarter-wave plate 8-2 again; originally, the s light reflected by the polarization beam splitter prism 7 is changed into first p light, the transmitted p light is changed into first s light, at the moment, the first p light and the first s light are converged on the polarization beam splitter prism 7, enter the optical fiber coupler 11 and are coupled to enter the second polarization maintaining optical fiber 2-2, the second polarization maintaining optical fiber 2-2 is connected with the third polarization maintaining optical fiber 2-3 through the optical fiber matching sleeve 12, and the converged and coupled light enters the interference module; the coupling light is decomposed into second transmission light and second reflection light through the beam splitter prism 13, the second transmission light is collimated through the collimating lens 14, the reflection light passing through the rear surface of the reference mirror 15 and the reflection light passing through the front surface of the mirror 16 to be measured are converged and decomposed into third reflection light and third transmission light through the beam splitter prism 13, the third reflection light enters the imaging module, passes through the imaging lens 17 and the third quarter-wave plate 8-3, and finally is imaged on the target surface of the polarization CCD camera 18.

In the above operation, with reference to fig. 1, 2 and 3, the long-stroke optical path matching module 10 may be a pyramid array formed by a plurality of pyramids in a certain geometric arrangement. When the delay line is matched, one side of the pyramid array is fixed at one end, the other side of the pyramid array is placed on the translation table, the central heights of the pyramid array and the translation table are consistent, but the pyramid array and the translation table are staggered from the central height of the whole system by a small distance, light can enter the pyramid array from the outer side of the pyramid as far as possible, and if the light impinges on the edge or the central part, great loss can be caused.

The pyramid array comprises 9 one-inch pyramid prisms and 1 half-inch pyramid prism, wherein 5 one-inch pyramid prisms ensure that the center heights are consistent and are transversely arranged into a group; 4 one inch pyramids and half inch pyramids guarantee that the center height is unanimous in addition, and transverse arrangement is a set of, and two sets of array pyramids face is opposite and parallel, and the pyramid center has certain offset, lets the incident light beat in pyramid prism non-center department, utilizes the parallel characteristic of pyramid prism emergent light and incident light, turns over the light path.

The long-stroke optical path matching module 10 is a polarization maintaining fiber circulator, and optical paths are freely selected in an optical waveguide to match different cavity lengths under different calibers.

An experimental method of a large-stroke optical path matching device based on a short coherent light source interferometer comprises the following steps:

step one, opening a short coherent laser 1, connecting a first polarization maintaining fiber 2-1 into a collimator 3, sequentially adjusting the positions of a polarizer 4, a half-wave plate 5 and a reflector 6, and coupling spatial collimated light into a second polarization maintaining fiber 2-2 by adjusting an optical fiber coupler 11.

And step two, measuring and recording the distance L between the rear surface of the reference mirror 15 and the front surface of the mirror to be measured 16, and moving the pyramid array to the position near the optical path difference L of the first transmitted light and the first reflected light through the translation stage.

And step three, simultaneously controlling the polarization CCD camera 18 and the translation stage through the computer, setting the translation stage to move in a fixed step length, acquiring the acquired image through the polarization CCD camera 18 after each movement, and reading and storing the gray value of one point.

And step four, observing gray values, and when sudden change occurs, determining the gray values to be the zero optical path position and also the optimal optical path matching position, as shown in FIG. 4.

And step five, moving the translation stage to a target position, acquiring a short coherent interference fringe pattern through the polarization CCD camera 18, and calculating by using a four-step phase-shifting algorithm.

When the polarization maintaining optical fiber circulator is used as the large-stroke optical path matching module 10, the optical signal can be controlled by selecting the input port and the output port to match the cavity length of the interference cavity. The specific steps are that firstly, the length of the recording cavity is measured, the optical path is selected in the optical waveguide, and the CCD camera is observed, if the optical path is not matched with the optical waveguide, the camera displays a blank, and when the optical path is matched with the optical waveguide, the camera displays clear interference fringes with high contrast.

The pyramid array is used as the interferometer delay line to match the long-stroke optical path, when the phase difference of the reference light and the test light is compensated, the structure is simple, the stability is high, the large optical path can be obtained in a tiny space, and the integration level of the light source module is improved; when the polarization-maintaining optical fiber circulator is used as a delay line, the optical path is selected from the optical waveguide, and both the optical path and the optical path can obtain the free optical path regulating quantity of 0-5m, so that the cavity length of the interferometer does not need to be changed by pushing a lens to be measured, and one light source module is suitable for interferometers with various calibers and cavity lengths.

In summary, the invention realizes the matching of the length of the interference cavity by adding the angle cone array or the optical fiber circulator as the long-stroke optical path matching module in the light source module. Compared with the traditional method for pushing the mirror to be measured or the reference mirror, the method improves the working efficiency and ensures the precision of the measurement result.