阅读说明：本技术 一种反射式点衍射干涉仪针孔对准装置和方法 (Pinhole alignment device and method for reflective point diffraction interferometer ) 是由 陈磊 崔鑫莹 郑东晖 朱文华 郑权 张正宇 陈佳 胡晨辉 于 2019-09-23 设计创作，主要内容包括：本发明公开了一种反射式点衍射干涉仪针孔对准装置和方法。该装置包括分光膜、斜入射反射式点衍射板、粗调光点接收屏、精调成像透镜、精调光斑接收屏、载频干涉图探测器。该对准方法分为以下四个步骤：根据粗调光点接收屏上光点的位置调整装置,使光斑透过点衍射板狭缝；根据精调光斑接收屏上光斑的大小调整系统光轴方向位置；找到光斑中针孔的像,并微调系统位置,将其移动至光斑中心；再次微调系统光轴方向位置,至光斑上出现干涉图样,此时光线已精确聚焦至针孔。本发明降低了目前斜入射反射式点衍射干涉仪对点难度,且准确度高、装置简单。(The invention discloses a pinhole alignment device and method for a reflective point diffraction interferometer. The device comprises a light splitting film, an oblique incidence reflection type point diffraction plate, a coarse adjustment light spot receiving screen, a fine adjustment imaging lens, a fine adjustment light spot receiving screen and a carrier frequency interference pattern detector. The alignment method comprises the following four steps: according to the position adjusting device for roughly adjusting the light spot on the light spot receiving screen, the light spot penetrates through the slit of the point diffraction plate; adjusting the position of the system in the direction of the optical axis according to the size of the light spot on the fine adjustment light spot receiving screen; finding out the image of the pinhole in the light spot, finely adjusting the position of the system, and moving the system to the center of the light spot; and fine-tuning the position of the system in the optical axis direction again until an interference pattern appears on the light spot, and at the moment, accurately focusing the light to the pinhole. The invention reduces the point aligning difficulty of the prior oblique incidence reflection type point diffraction interferometer, and has high accuracy and simple device.)

1. A pinhole alignment device of a reflection type point diffraction interferometer is characterized by comprising a light splitting film (1), an oblique incidence reflection type point diffraction plate (2) with a pinhole, a fine adjustment imaging lens (3), a fine adjustment light spot receiving screen (4), a coarse adjustment light spot receiving screen (5) and a carrier frequency interferogram detector (6), wherein the fine adjustment imaging lens (3) is arranged on the upper surface of the carrier frequency interferogram detector;

spherical waves to be measured are divided into two paths of converged light waves through a light splitting film (1) before focus convergence, wherein reflected light waves converge to a position on a coarse adjustment light spot receiving screen (5) conjugated with a pinhole of an oblique incidence reflection type point diffraction plate (2), transmitted light waves are divided into two paths of light waves from the front surface of the oblique incidence reflection type point diffraction plate (2) again, the light waves reflected from the front surface of the oblique incidence reflection type point diffraction plate (2) are used as test light for interference measurement, the light waves transmitted from the front surface of the oblique incidence reflection type point diffraction plate (2) are reflected by the rear surface and then returned along an original light path to converge to the position of the pinhole of the front surface of the oblique incidence reflection type point diffraction plate (2) and are divided into two paths of light waves again, wherein one path of light waves passes through the pinhole of the oblique incidence reflection type point diffraction plate (2) to be diffracted to form standard spherical waves which are used as reference light for interference measurement and finally, an interference pattern is formed on the carrier frequency interference detector (6), the other path of the interference pattern is reflected by the front surface of the oblique incidence reflection type point diffraction plate (2), then is transmitted from the rear surface of the oblique incidence reflection type point diffraction plate (2), passes through the fine adjustment imaging lens (3), and finally is imaged to the fine adjustment light spot receiving screen (4).

2. The pinhole alignment device of the reflective point-diffraction interferometer according to claim 1, wherein the beam-splitting film (1) forms an angle of 45 degrees with the main optical axis of the wavefront to be measured, the wavefront to be measured is divided into two parts, the transmitted light waves converge at the pinhole position in the oblique incidence reflective point diffraction plate (2), and a conjugate position which is in a fixed relationship with the pinhole position exists on the coarse adjustment light spot receiving screen (5), and the conjugate position is the position where the reflected light waves reflected by the beam-splitting film (1) of the wavefront to be measured converge.

3. The pinhole alignment device of the reflective point-diffraction interferometer of claim 1, wherein the light waves transmitted by the front surface of the oblique-incidence reflective point-diffraction plate (2) are reflected by the rear surface and converged to a pinhole position, and part of the light is reflected and transmitted from the rear surface of the oblique-incidence reflective point-diffraction plate (2), i.e. the light illuminates a pinhole and is finally imaged to the fine-tuning spot receiving screen (4) through the fine-tuning imaging lens (3), and the convergence condition of the light in the oblique-incidence reflective point-diffraction plate (2) is reflected through the image of the pinhole.

4. The pinhole alignment device of the reflective point-diffraction interferometer according to claim 2, wherein the conjugate position of the pinhole on the oblique incidence reflective point-diffraction plate (2) is at the intersection point of the coarse light spot receiving screen (5) and the optical axis of the spherical wave reflected by the spectroscopic film (1), and the distance d from the coarse light spot receiving screen (5) to the spectroscopic film (1) is as follows:

wherein l is the distance from the oblique incidence reflection type point diffraction plate (2) to the light splitting film (1), h is the thickness of the oblique incidence reflection type point diffraction plate (2), and theta₁Is the working angle of the oblique incidence reflection type point diffraction plate (2)And n is the refractive index of the oblique incidence reflection type point diffraction plate (2).

5. The pinhole alignment device of the reflective point-diffraction interferometer of claim 3, wherein the fine-tuning imaging lens (3) has a shift Δ Y from the primary optical axis in the Y-direction, wherein the Y-direction is vertical to the primary optical axis, the X-direction is horizontal to the primary optical axis, and the shift Δ Y is as follows:

wherein, theta₁The working angle of the oblique incidence reflection type point diffraction plate (2), n is the refractive index of the oblique incidence reflection type point diffraction plate (2), and h is the thickness of the oblique incidence reflection type point diffraction plate (2).

6. A reflective point-diffraction interferometer pinhole alignment method based on the reflective point-diffraction interferometer pinhole alignment apparatus of claim 1, wherein the reflective point-diffraction interferometer pinhole alignment apparatus is used for alignment and interferometric measurement, an interferometric optical path is integrated on an adjustment frame with five-dimensional adjustment function, and the adjustment steps are as follows:

step 1, adjusting the pitching inclination of the system to change an elliptical light spot on a coarse adjustment light spot receiving screen (5) into a perfect circle;

step 2, adjusting the directions of an X axis and a Y axis of the system to enable the light spots to move to the reference position of the fine adjustment light spot receiving screen (4), wherein the Z axis is perpendicular to the main light axis, the X axis is the horizontal direction perpendicular to the main light axis, and the Y axis is the vertical direction perpendicular to the main light axis;

step 3, adjusting the Z-axis direction of the system to reduce the light spot at the reference position until a circular light spot appears on the fine-tuning light spot receiving screen (4);

step 4, observing the image on the fine adjustment light spot receiving screen (4), finding the image of the pinhole, fine adjusting the X-axis direction and the Y-axis direction of the system, and moving the image of the pinhole to the center of the circular light spot;

step 5, fine-tuning the Z-axis direction of the system again to enlarge the image of the pinhole relative to the circular facula until a low-frequency interference pattern appears on the fine-tuning facula receiving screen (4), wherein the low-frequency interference pattern represents that light rays are converged to the pinhole and the accurate alignment of the pinhole is completed;

step 6, the carrier frequency interference pattern detector (6) obtains a carrier frequency interference pattern containing the spherical wave superposition of transverse dislocation and longitudinal dislocation; and restoring the wavefront phase by using the interferogram, carrying out Fourier transform on the interferogram, taking the +1 or-1 level sidelobe, and then carrying out Fourier inverse transformation to restore the wavefront phase.

Technical Field

The invention belongs to the technical field of optical interference measuring instruments, and particularly relates to a pinhole alignment device and method for a reflection type point diffraction interferometer.

Background

In the transient wave-front detection technology, the point diffraction interferometer is widely applied, and ideal spherical waves generated by diffraction of a pinhole are used as reference waves, so that errors of a common interferometer caused by reference surfaces are eliminated.

The reflection type point diffraction interferometer features that its substrate is a parallel plate with a light splitting film plated in a rectangular slit on its front surface, a light shielding film with an elliptical pinhole on its back surface, and a high-reflectivity film and an anti-reflection film on its back surface. The spherical wave to be measured is partially directly reflected on the rectangular slit to be used as the test wavefront, the rest part of the spherical wave is transmitted from the slit and then reflected by the high-reflection film, and the spherical wave is converged and diffracted at the pinhole to generate the ideal divergent spherical wave which is used as the reference wavefront. Compared with a common synchronous phase-shifting point diffraction interferometer, the reflection type point diffraction interferometer has the advantages of high precision, low cost and the like. However, in the pinhole alignment process of the reflective point diffraction interferometer, the light condition in the point diffraction plate cannot be observed, and an effective auxiliary alignment tool and method are not available, so that the process is difficult to complete, and usually a great deal of experience accumulation is required.

Disclosure of Invention

The invention aims to provide a pinhole alignment device and a pinhole alignment method for a reflective point diffraction interferometer, which are convenient to operate and high in alignment precision.

The technical solution for realizing the invention is as follows: a pinhole alignment device of a reflection type point diffraction interferometer comprises a light splitting film, an oblique incidence reflection type point diffraction plate with a pinhole, a fine adjustment imaging lens, a fine adjustment light spot receiving screen, a coarse adjustment light spot receiving screen and a carrier frequency interferogram detector, wherein the fine adjustment imaging lens is arranged on the upper surface of the reflection type point diffraction plate;

the spherical wave to be measured is divided into two paths of converged light waves through a light splitting film before the focus is converged, wherein the reflected light wave is converged to a position on a coarse adjustment light spot receiving screen, which is conjugated with a pinhole of an oblique incidence reflection type point diffraction plate, the transmitted light wave is divided into two paths of light waves from the front surface of the oblique incidence reflection type point diffraction plate again, the light wave reflected from the front surface of the oblique incidence reflection type point diffraction plate is used as test light for interference measurement, the light wave transmitted from the front surface of the oblique incidence reflection type point diffraction plate is reflected by a rear surface and then returns along an original light path to be converged to the pinhole position of the front surface of the oblique incidence reflection type point diffraction plate and is divided into two paths of light waves again, wherein one path of light waves is diffracted through the pinhole of the oblique incidence reflection type point diffraction plate to form a standard spherical wave which is used as reference light for interference measurement, and finally, and the other path of light is reflected by the front surface of the oblique incidence reflection type point diffraction plate, then is transmitted from the rear surface of the oblique incidence reflection type point diffraction plate, passes through the fine adjustment imaging lens and finally is imaged to the fine adjustment light spot receiving screen.

Furthermore, the beam splitting film and the main optical axis of the wavefront to be measured form an included angle of 45 degrees, the wavefront to be measured is divided into two parts, the transmitted light wave is converged at the pinhole position in the oblique incidence reflection type point diffraction plate, a conjugate position which forms a fixed relation with the pinhole position exists on the coarse adjustment light spot receiving screen, and the conjugate position is the position where the reflected light wave reflected by the beam splitting film of the wavefront to be measured is converged.

Furthermore, after the light wave transmitted by the front surface of the oblique incidence reflection type point diffraction plate is reflected by the rear surface and converged to the position of the pinhole, part of the light is reflected and then transmitted from the rear surface of the oblique incidence reflection type point diffraction plate, namely, after the light illuminates the pinhole, the light is finally imaged to the fine adjustment light spot receiving screen through the fine adjustment imaging lens, and the convergence condition of the light in the oblique incidence reflection type point diffraction plate is reflected through the image of the pinhole.

Furthermore, the conjugate position of the pinhole on the oblique incidence reflective point diffraction plate is at the intersection point of the coarse adjustment light spot receiving screen and the optical axis of the spherical wave reflected by the light splitting film, and the distance d from the coarse adjustment light spot receiving screen to the light splitting film is as follows:

wherein l is the distance from the oblique incidence reflection type point diffraction plate to the light splitting film, h is the thickness of the oblique incidence reflection type point diffraction plate, and theta₁Is the working angle of the oblique incidence reflection type point diffraction plate, and n is the refractive index of the oblique incidence reflection type point diffraction plate.

Further, a shift amount Δ Y in the Y direction exists between the optical axis of the fine imaging lens and the main optical axis, where the Y axis direction is a vertical direction perpendicular to the main optical axis, the X axis is a horizontal direction perpendicular to the main optical axis, and the shift amount Δ Y is as follows:

wherein, theta₁The working angle of the oblique incidence reflection type point diffraction plate is shown, n is the refractive index of the oblique incidence reflection type point diffraction plate, and h is the thickness of the oblique incidence reflection type point diffraction plate.

A reflective point diffraction interferometer pinhole alignment method based on the reflective point diffraction interferometer pinhole alignment device is characterized in that the reflective point diffraction interferometer pinhole alignment device is aligned and subjected to interference measurement, an interference optical path is integrated on an adjusting frame with a five-dimensional adjusting function, and the adjusting steps are as follows:

step 1, adjusting the pitching inclination of a system to change an elliptical light spot on a coarse adjustment light spot receiving screen into a perfect circle;

step 2, adjusting the directions of an X axis and a Y axis of the system to enable the light spots to move to the reference position of the fine-tuning light spot receiving screen, wherein the Z axis is perpendicular to the main light axis, the X axis is the horizontal direction perpendicular to the main light axis, and the Y axis is the vertical direction perpendicular to the main light axis;

step 3, adjusting the Z-axis direction of the system to reduce the light spot at the reference position until a circular light spot appears on the fine-tuning light spot receiving screen;

step 4, observing the image on the fine adjustment light spot receiving screen, finding the image of the pinhole, fine adjusting the X and Y axis directions of the system, and moving the image of the pinhole to the center of the circular light spot;

step 5, fine-tuning the Z-axis direction of the system again to enlarge the image of the pinhole relative to the circular light spot until a low-frequency interference pattern appears on the fine-tuning light spot receiving screen, wherein the low-frequency interference pattern represents that light rays are converged to the pinhole, and the accurate alignment of the pinhole is completed;

step 6, the carrier frequency interference pattern detector obtains a carrier frequency interference pattern comprising spherical wave superposition with transverse dislocation and longitudinal dislocation; and restoring the wavefront phase by using the interferogram, carrying out Fourier transform on the interferogram, taking the +1 or-1 level sidelobe, and then carrying out Fourier inverse transformation to restore the wavefront phase.

Compared with the prior art, the invention has the following remarkable advantages: (1) the alignment difficulty of the pinhole is greatly reduced, and auxiliary information of alignment is provided for an operator; (2) the alignment precision is improved, and therefore the contrast of the carrier frequency interference pattern is improved.

Drawings

FIG. 1 is a schematic diagram showing the structure and coordinate axis directions of a vacuum alignment apparatus for a reflective point-diffraction interferometer according to the present invention.

Fig. 2 is a schematic diagram of the conjugate position of the pin hole on the coarse tuning spot receiving screen according to the present invention.

Fig. 3 is a schematic diagram illustrating an offset between an optical axis and a main optical axis of the fine-tuning imaging lens according to the present invention.

Fig. 4 is a schematic view of an oblique incidence reflective point diffraction plate on which the present invention is based, wherein (a) is a front view and (b) is a sectional view.

FIG. 5 is a flow chart of a pinhole alignment method of the present invention.

FIG. 6 is a schematic diagram of a five-dimensional adjusting frame according to the present invention.

Detailed Description

The invention relates to a pinhole alignment device of a reflective point diffraction interferometer, which quickly adjusts a test light focus to the position of a pinhole of a reflective point diffraction plate to realize the quick alignment of the reflective point diffraction interferometer, and comprises a light splitting film 1, an oblique incidence reflective point diffraction plate 2 with a pinhole, a fine adjustment imaging lens 3, a fine adjustment light spot receiving screen 4, a coarse adjustment light spot receiving screen 5 and a carrier frequency interference pattern detector 6, wherein the oblique incidence reflective point diffraction plate is provided with a pinhole;

spherical wave to be measured is divided into two paths of converged light waves through a light splitting film 1 before focus convergence, wherein reflected light waves converge to a position on a coarse adjustment light spot receiving screen 5 conjugated with a pinhole of an oblique incidence reflection type point diffraction plate 2, transmitted light waves are divided into two paths of light waves again from the front surface of the oblique incidence reflection type point diffraction plate 2, the light waves reflected from the front surface of the oblique incidence reflection type point diffraction plate 2 are used as test light for interference measurement, the light waves transmitted from the front surface of the oblique incidence reflection type point diffraction plate 2 are reflected by a rear surface and then returned along an original light path to converge to the pinhole position of the front surface of the oblique incidence reflection type point diffraction plate 2 and are divided into two paths of light waves again, wherein one path of light waves passes through the pinhole of the oblique incidence reflection type point diffraction plate 2 to be diffracted to form standard spherical wave which is used as reference light for interference measurement and finally interferes with the test light for interference measurement, and, and the other path of light is reflected by the front surface of the oblique incidence reflection type point diffraction plate 2, then is transmitted from the rear surface of the oblique incidence reflection type point diffraction plate 2, passes through the fine adjustment imaging lens 3, and finally is imaged to a fine adjustment light spot receiving screen 4.

Furthermore, the beam splitting film 1 and the main optical axis of the wavefront to be measured form an included angle of 45 degrees, the wavefront to be measured is divided into two parts, the transmitted light wave is converged at the pinhole position in the oblique incidence reflection type point diffraction plate 2, a conjugate position which forms a fixed relation with the pinhole position exists on the coarse adjustment light spot receiving screen 5, and the conjugate position is the position where the reflected light wave reflected by the beam splitting film 1 of the wavefront to be measured is converged.

Further, after the light wave transmitted by the front surface of the oblique incidence reflection type point diffraction plate 2 is reflected by the rear surface and converged to the pinhole position, part of the light is reflected and then transmitted from the rear surface of the oblique incidence reflection type point diffraction plate 2, namely, after the light illuminates the pinhole, the light is finally imaged to the fine adjustment light spot receiving screen 4 through the fine adjustment imaging lens 3, and the convergence condition of the light in the oblique incidence reflection type point diffraction plate 2 is reflected through the image of the pinhole.

Further, the conjugate position of the pinhole on the oblique incidence reflective point diffraction plate 2 is at the intersection point of the coarse adjustment light spot receiving screen 5 and the optical axis of the spherical wave reflected by the spectroscopic film 1, and the distance d from the coarse adjustment light spot receiving screen 5 to the spectroscopic film 1 is as follows:

wherein l is the distance from the oblique incidence reflection type point diffraction plate 2 to the light splitting film 1, h is the thickness of the oblique incidence reflection type point diffraction plate 2, and theta₁Is the working angle of the oblique incidence reflective point diffraction plate 2, and n is the refractive index of the oblique incidence reflective point diffraction plate 2.

Further, a shift Δ Y exists between the optical axis of the fine-tuning imaging lens 3 and the main optical axis in the Y direction, where the Y direction is a vertical direction perpendicular to the main optical axis, the X direction is a horizontal direction perpendicular to the main optical axis, and specifically, as shown in the coordinate system in fig. 1, the shift Δ Y is as follows:

wherein, theta₁Is the working angle of the oblique incidence reflection type point diffraction plate 2, n is the refractive index of the oblique incidence reflection type point diffraction plate 2, and h is the thickness of the oblique incidence reflection type point diffraction plate 2.

A reflective point diffraction interferometer pinhole alignment method based on the reflective point diffraction interferometer pinhole alignment device is characterized in that the reflective point diffraction interferometer pinhole alignment device is aligned and subjected to interference measurement, an interference light path is integrated on an adjusting frame with a five-dimensional adjusting function, the structure and a directional diagram of the adjusting frame are shown in figure 6, and the adjusting steps are as follows:

step 1, adjusting the pitching inclination of the system to change the elliptic light spots on the rough adjusting light spot receiving screen 5 into a perfect circle;

step 2, adjusting the directions of an X axis and a Y axis of the system to enable the light spots to move to the reference position of the fine adjustment light spot receiving screen 4, wherein the Z axis is perpendicular to the main light axis, the X axis is the horizontal direction perpendicular to the main light axis, and the Y axis is the vertical direction perpendicular to the main light axis;

step 3, adjusting the Z-axis direction of the system to reduce the light spot at the reference position until a circular light spot appears on the fine-tuning light spot receiving screen 4;

step 4, observing the image on the fine adjustment light spot receiving screen 4, finding the image of the pinhole, fine adjusting the X and Y axis directions of the system, and moving the image of the pinhole to the center of the circular light spot;

step 5, fine-tuning the Z-axis direction of the system again to enlarge the image of the pinhole relative to the circular light spot until a low-frequency interference pattern appears on the fine-tuning light spot receiving screen 4, wherein the low-frequency interference pattern represents that light rays are converged to the pinhole, and the accurate alignment of the pinhole is completed;

step 6, the carrier frequency interference pattern detector 6 obtains a carrier frequency interference pattern containing spherical wave superposition of transverse dislocation and longitudinal dislocation; and restoring the wavefront phase by using the interferogram, carrying out Fourier transform on the interferogram, taking the +1 or-1 level sidelobe, and then carrying out Fourier inverse transformation to restore the wavefront phase.

The invention is described in further detail below with reference to the figures and the embodiments.