CN110793756A - An optical correction device for monitoring the optical axis of a reflecting telescope based on polarization beam splitting - Google Patents

Abstract

The invention discloses an optical correction device for monitoring an optical axis of a reflecting telescope based on polarization beam splitting. The device comprises an optical fiber light source, a collimating lens, a beam splitter prism, a polarization beam splitter prism, a first parallel plate, a quarter wave plate, a pyramid prism, a second parallel plate, a converging lens and a detector; in the process of the optical correction telescope system, a polarization beam splitter prism, a quarter wave plate and a pyramid prism are adopted to generate two collinear light beams with opposite directions, so that the high-precision registration of the optical axis of the optical correction telescope system and the normal of an auxiliary standard plane mirror is realized. The device is a relative test, and solves the problem of test precision caused by artificial interpretation errors, test environments and the like in the conventional absolute test optical axis. In addition, the reference optical axis and the test optical axis share a light path, so that the test precision and the light correction efficiency are greatly improved without being influenced by vibration in the test process.

Description

An optical correction device for monitoring the optical axis of a reflecting telescope based on polarization beam splitting

technical field

The invention belongs to the field of optical testing and optical adjustment, and relates to an optical calibration device for monitoring the optical axis of a reflective telescope based on polarization splitting, which is particularly suitable for the optical calibration process of a reflective telescope system. Registration and real-time monitoring of plane mirror normals. It is also suitable for the processing of large-diameter aspherical mirrors, and the registration of laser emission and reception.

Background technique

The reflective space optical camera loads such as lidar and laser altimeter have higher and higher requirements for the optical axis pointing of the reflective telescope system in the optical load. For the pointing test, the registration accuracy requirements are getting higher and higher. In the optical assembly process, the most important thing is to collinearly register the optical axis of the optically calibrated space reflection telescope system with the normal line of the auxiliary large-aperture standard plane mirror. There are two main traditional solutions: the first one is to control the perpendicularity between the optical axis of the main mirror and the back of the main mirror, which is strictly controlled during the processing of the main mirror of the telescope. It is collinear with the normal line of the auxiliary large-aperture plane mirror and used as optical axis registration. This method depends on processing and has low precision, so it is difficult to give accurate optical axis pointing. The second is to use the theodolite to align the optical axis of the telescope system, then rotate the theodolite 180°, and adjust the auxiliary large-caliber standard plane mirror so that its normal line coincides with the optical axis of the theodolite. This will introduce a variety of errors when establishing a benchmark. The error, the zero position error of adjusting the theodolite level, the rotation error introduced by rotating the theodolite, etc., the process is cumbersome, the repeatability is not high, and it is difficult to realize the real-time monitoring of the optical axis in the optical calibration process.

Therefore, in the process of optical calibration of the reflecting telescope system, how to improve the registration accuracy of the optical axis of the reflecting telescope system being optically calibrated and the normal collinear optical axis of the auxiliary large-aperture plane mirror, eliminate the human error and environmental error of the test, and achieve high Repeated test accuracy and real-time monitoring in the process of optical calibration are problems that need to be solved in the field of optical testing and optical calibration.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a kind of optical correction device based on polarization beam splitting monitoring of the optical axis of a reflecting telescope. This device is shown in accompanying drawing 1, and the test optical path diagram in the process of optical correction of large-diameter reflecting telescope system, as shown in the accompanying drawing 2, the specific steps of the test method are as follows:

Step 1: The device self-checks before testing. The optical fiber light source 1 is turned on, and the outgoing light from the optical fiber located at the focal plane of the collimating lens 2 emits parallel light through the collimating lens 2, and reaches the polarizing beam splitting prism 4 through the beam splitter prism 3, and is divided into two linearly polarized P light and S light. Once the reference beam is transmitted through the polarizing beam splitter prism 4, it passes through the quarter-wave plate 6 to become circularly polarized light, and then passes through the corner cube prism 7 and returns to the original path, and passes through the quarter-wave plate 6 for the second time to become The linearly polarized S light reaches the beam splitting surface of 45° in the polarizing beam splitting prism 4, and the linearly polarized S light exits at an angle of 90° with the original optical axis, reaching the surface of the second parallel plate 8, and the reflected part of the beam is reflected by the polarizing beam splitting prism 4 , passing through the quarter-wave plate 6 for the third time, becoming circularly polarized light, and then passing through the corner cube prism 7 and returning to the original path, passing through the quarter-wave plate 6 for the fourth time, becoming linearly polarized P light, transmitting After passing through the polarizing beam splitting prism 4 , it is reflected by the beam splitting prism 3 and reaches the converging lens 9 , and is imaged on the detector 10 . The reference beam 2 passes through the 45° beam splitting surface in the polarizing beam splitting prism 4, and the linearly polarized S light exits at an angle of 90° with the original optical axis, and reaches the surface of the No. 1 parallel plate 5. The beam splitting prism 3 reflects and reaches the condensing lens 9 to be imaged on the detector 10 . Comparing the centroid positions of the two reference beams on the detector 10, when the combined error of the two centroid positions is less than the optical axis pointing accuracy requirement of the optically calibrated reflective telescope system, the self-checking of the device is completed. This spot is the reference spot, and the centroid of the reference spot is (x ₀ , y ₀ ).

Step 2: Test beam 1 and reference beam 1 are in the same optical path. The outgoing light from the optical fiber located at the focal plane of the collimating lens 2 is collimated by the collimating lens 2 into parallel light, passes through the beam splitting prism 3 and reaches the polarizing beam splitting prism 4, and is divided into two beams of linearly polarized P light and S light. The first test beam is the linearly polarized P light that directly passes through the polarizing beam splitter prism 4, passes through the quarter-wave plate 6, becomes circularly polarized light, and then passes through the corner cube prism 7, and then returns to the original path, and the second time passes through a quarter of the light. The first wave plate 6 becomes linearly polarized S light and reaches the 45° beam splitting surface of the polarizing beam splitting prism 4. The linearly polarized S light exits at an angle of 90° with the original optical axis, and transmits through the second parallel plate 8 to reach the On the optical axis reference prism 11 of the optical correction reflective telescope system, the optical correction device is adjusted as a whole, so that the direction of the light beam is basically collinear with the normal line of the optical axis reference prism of the optical correction telescope system, returns, and is reflected by the polarization beam splitting prism 4 , passing through the quarter-wave plate 6 for the third time, becoming circularly polarized light, and then passing through the corner cube prism 7 and returning to the original path, passing through the quarter-wave plate 6 for the fourth time, becoming linearly polarized P light, transmitting After the polarizing beam splitting prism 4, it is reflected by the beam splitting prism 3 to reach the converging lens 9, imaged on the detector 10, and the device is adjusted again so that the centroid of the returned spot is consistent with the centroid of the reference spot, and the spot centroid of the test beam 1 (x ₁ , y _{1 )} ).

Step 3: Test beam 2 and reference beam 2 share the same optical path. The outgoing light from the fiber at the focal plane of the collimating lens 2 emits parallel light through the collimating lens 2, passes through the beam splitting prism 3 and reaches the polarizing beam splitting prism 4, and is divided into two beams of linearly polarized P light and S light. After being reflected by the 45° beam-splitting surface of the polarizing beam splitting prism 4, the linearly polarized S light emerges at an angle of 90° with the original optical axis, and is transmitted through the No. The large-caliber standard plane mirror of the optical correction, so that its normal line is collinear with the beam direction, returns to the original path, is reflected by the polarizing beam splitting prism 4, and is reflected by the beam splitting prism 3 to reach the converging lens 9, and image it on the detector 10. Adjust the device again. , so that the centroid of the returned light spot is consistent with the centroid of the reference light spot, and the centroid of the light spot of the test beam 2 (x ₂ , y ₂ ).

Step 4: After steps 1 to 3, the optical axis registration of the optical axis of the optically calibrated reflective telescope system and the normal of the auxiliary large-aperture plane mirror is completed. At this time, the orientation of the device is adjusted. At this time, the spot positions of the test beam 1 and the test beam 2 on the detector 10 move at the same time, and the position of the reference spot remains unchanged, so that the three spots do not overlap. At this time, by calculating the relationship between the centroids of the three light spots in real time, the drift of the optical axis of the reflected telescope system to be calibrated and the normal line of the auxiliary large-aperture plane mirror 12 can be obtained. The calculation formula is as follows:

When the optical axis of the optically calibrated telescope is collinear with the normal line of the auxiliary large-aperture standard plane mirror, θ _x =0, θ _y =0.

The characteristics and beneficial effects of the present invention are mainly reflected in the following aspects: (1) the test beam and the reference beam of the device share the same optical path, which is not affected by the test environment, and the test repeatability is high; (2) the device is the test beam and the reference beam. The relative measurement between the reference beams, and the use of the detector to obtain the centroid of the light spot, the difference between the centroids of the light spot is calculated, the artificial reading error is eliminated, and the optical axis registration is realized with high precision; (3) The device can be used in the entire reflection type. In real-time monitoring during the optical calibration of the telescope system, in addition to monitoring the relative position changes, it can also monitor whether the optical axis of the calibrated reflecting telescope system has changed or the auxiliary large-aperture plane mirror has changed. (4) The optical correction device of the present invention is not only suitable for the field of optical correction of reflective telescope systems, but also for the processing of large-diameter aspherical mirrors, and the registration of laser emission and reception.

Description of drawings

Fig. 1 is the schematic diagram that the device of the present invention is used for optical calibration;

Fig. 2 is the schematic diagram of the optical correction step of the device of the present invention: wherein Figure (1) is a schematic diagram of the optical correction step 1 of the device itself, Figure (2) is a schematic diagram of the optical correction step 2 of the device itself, and Figure (3) is the optical calibration of the device itself. Figure (4) is a schematic diagram of step 4 of optical calibration of the device itself, and Figure (5) is a schematic diagram of step 5 of optical calibration of the device itself.

Detailed ways

Embodiments of the patented method will be described in detail below with reference to the accompanying drawings.

The main components used in the present invention are described:

Fiber light source 1: couple the 633nm wavelength laser to the output of a single-mode fiber with a core diameter of 10um.

Collimating lens 2: Sampling Edmund company model #36-165 molded aspherical lens, diameter 12.5mm, focal length 10mm.

Beamsplitter 3: Sampling Thorlab's model BS016, a beam-splitting cube with a diameter of 20mm, material quartz, a quarter wavelength of the transmitted wavefront @633nm, and a beam splitting ratio of 50:50.

Polarizing beam splitter prism 4: Sampling Thorlab's model is PBS202, a polarizing beam splitter cube with an aperture of 20mm, material SF1, a quarter wavelength of the transmitted wavefront @633nm, and a polarization beam splitting ratio of 1000:1.

No. 1 parallel plate 5, No. 2 parallel plate 8: customized components, diameter 30mm, material quartz, parallelism of front and rear sides is better than 3 seconds, transmission wavefront RMS value is better than 1/15 wavelength@633nm, close to polarizing beam splitter prism 4 One side is coated, its reflectivity is 30%@633nm, and the other side is coated with anti-reflection coating, 98%@633nm.

Quarter-wave plate 6: The sampling Thorlab formula model is WPMQ05M-633, a quarter-wave plate with an aperture of one-half inch, and one-tenth of the wavelength of the transmitted wavefront @633nm.

Corner prism 7: Sampling Thorlab company model PS975-A, diameter 25.4mm, anti-reflection grinding 350-700nm, surface shape accuracy better than one-tenth wavelength@633nm, material quartz, angle deviation between incident and outgoing rays is better than 3 second.

Convergence lens 9: a laser-grade aspherical lens with a model number of 39-560 from Edmund, a diameter of 25.4 mm, and a focal length of 50.8 mm.

Detector 10: Sampling a small scientific research COMS sensor with a pixel size of 3.45um×3.45um and a pixel size of 2448×2048 from Thorlab.

The specific steps of the installation and calibration of the device of the present invention are as follows, such as accompanying drawing 2:

1) Using the photoelectric autocollimator 16, align the No. 1 parallel plate 5, and adjust the photoelectric autocollimator 16, so that the cross line returned by the No. 1 parallel plate 5 is in the center of the photoelectric autocollimator, and the polarizing beam splitter prism 4 makes The reticle near the side surface of the second parallel plate 8 is overlapped with the return of the first parallel plate, and then the second parallel plate 8 is installed so that the returned reticle coincides with the previous two reticles, as shown in the attached drawings. 2(1);

2) Move the photoelectric autocollimator 16, and adjust the focus of the photoelectric autocollimator 16 in a direction approximately 90 degrees from the original, so that it is aligned with the polarizing beam splitter prism 4, and the returned cross line is in the center of the photoelectric autocollimator 16, and fine-tune it The photoelectric autocollimator 16 and the polarizing beam splitter prism 4 make the reticle of the reference beam 1 and the reference beam 2 coincide, and then install the quarter-wave plate 6 and the corner cube prism 7, as shown in Figure 2 (2) ;

3) Install the beam splitting prism 3 so that the autocollimator cross line it returns and 2) coincide, as shown in accompanying drawing 2 (3);

4) Install the converging prism 9 and the detector 10, so that the cross line in 3) is reflected by the beam splitter prism 3 and enters the center of the detector, as shown in accompanying drawing 2(4);

5) Install the optical fiber light source 1 and the collimating lens 2 so that the reference beam 1 and the reference beam 2 spot on the detector 10 are in the center of the detector, that is, the self-optical calibration of the device is completed, as shown in accompanying drawing 2 (5). Show.

Claims (5)

1. The utility model provides a light school device of reflection telescope optical axis monitoring based on polarization beam split, includes fiber light source (1), collimating lens (2), beam splitter prism (3), polarization beam splitter prism (4), parallel flat board (5), quarter wave plate (6), pyramid prism (7), parallel flat board (8) No. two, convergent lens (9), detector (10), its characterized in that:

the optical fiber emergent point of the optical fiber light source (1) is positioned on the focal plane of the collimating lens (2), parallel light collimated by the collimating lens (2) reaches the polarization beam splitter prism (4) through the beam splitter prism (3) and is divided into two beams of test light of linear polarization P light and S light:

the first beam of test light is linearly polarized light P generated by the transmission polarization beam splitter prism (4) and passes through the quarter wave plate (a)6) The light beam is changed into circularly polarized light, the circularly polarized light returns through a pyramid prism (7) and then returns to the original path, the linearly polarized light passes through a quarter wave plate (6) for the second time and is changed into linearly polarized light S, the linearly polarized light S reaches a 45-degree splitting surface in a polarization splitting prism (4) and is emitted out in a direction forming an included angle of 90 degrees with the original optical axis, the linearly polarized light S is transmitted through a second parallel flat plate (8) and reaches an optical axis reference prism of an optical correction telescope system, the orientation of the optical correction device is integrally adjusted, the direction of the light beam is collinear with the normal of the reference prism of the optical correction telescope system, the original path returns, the light beam is reflected through the polarization splitting prism (4), the light beam returns through the quarter wave plate (6) for the third time and is changed into circularly polarized light, the original path returns through the pyramid prism (7), the light beam returns through the quarter wave plate (6) for the fourth time and is changed into linearly polarized, imaging onto a detector (10) and recording the spot centroid (x) on the detector₁,y₁)；

The second beam of test light is linearly polarized S light generated by reflection of a 45-degree light splitting surface in a polarizing beam splitter PBS (4), the linearly polarized S light is emitted in a direction forming an included angle of 90 degrees with the original optical axis, is transmitted through a first parallel flat plate (5) and reaches a large-caliber standard plane mirror for auxiliary light calibration, the large-caliber standard plane mirror for auxiliary light calibration is adjusted to enable the normal line of the large-caliber standard plane mirror to be collinear with the direction of the light beam, the light beam returns to the original path, is reflected by the polarizing beam splitter prism (4), is reflected by the light splitter prism (3) to reach a convergent lens (9), is imaged on a detector (10), and the light spot centroid (x) on the detector is recorded₂,y₂)；

In addition, when the first beam of test light enters the second parallel flat plate (8), the first beam of test light is divided into two beams, the first beam of test light is transmitted, the first beam of reference light is reflected, and the path of the later propagation is consistent with that of the first beam of test light. When the second beam of test light is incident on the first parallel flat plate (5), the second beam of test light is divided into two beams, the second beam of test light is transmitted and reflected, the reference beam II is reflected, and the rear propagation path is consistent with the second beam of test light. The first beam of test light and the second beam of test light are coincided on the detector and are the result of the light correction of the detector, and the centroid of the light spot is (x)₀,y₀). The focal length of the converging lens (9) is f', so that the optical axis of the optically corrected telescope system and the auxiliary optical axis can be obtainedTwo-dimensional angle theta of normal line of large-caliber standard plane mirror_xOff angle in the horizontal direction, theta_yDeclination angle in pitch direction:

when the optical axis of the optically corrected telescope system is collinear with the normal of the auxiliary large-caliber standard plane mirror, theta_x＝0，θ_y＝0。

2. The optical correction device for the optical axis monitoring of the reflection telescope based on the polarization beam splitting as claimed in claim 1, wherein: the optical fiber light source (1) is a single-mode optical fiber output with the wavelength of 633 nm.

3. The optical correction device for the optical axis monitoring of the reflection telescope based on the polarization beam splitting as claimed in claim 1, wherein: no. one parallel plate (5), No. two parallel plate (8) be transmission quartz material, the depth of parallelism of front and back two sides is superior to 3 seconds, and transmission wavefront RMS value is superior to 1/15 wavelength @633nm, and the plane that is close to polarization beam splitter PBS (4) one side plates the reflecting film, and its reflectivity is 30% @633nm, and antireflection coating is plated to the other side, 98% @633 nm.

4. The optical correction device for the optical axis monitoring of the reflection telescope based on the polarization beam splitting as claimed in claim 1, wherein: the pyramid prism (7) is made of quartz, and the angle deviation of incident light and emergent light is better than 3 seconds.

5. The optical correction device for the optical axis monitoring of the reflection telescope based on the polarization beam splitting as claimed in claim 1, wherein: the detector (10) is a commercial CMOS detector with 2048 × 2048 pixels and the pixel size of 3.45um × 3.45 um.

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