CN104238110B - A kind of pre-compensation system of collimator tube wave front aberration based on adaptive optics - Google Patents

Abstract

A collimator wavefront aberration pre-compensation method based on adaptive optics, including: a collimator with a large aperture and a long focal length and an adaptive optics system; the collimator with a large aperture and a long focal length includes a mirror assembly and a window glass; an adaptive optics The optical system includes a light source assembly, a beam splitter, a first off-axis reflector, a second off-axis reflector, a third off-axis reflector, a wavefront detector, a wavefront corrector and a folding reflector; the present invention can real-time Detect the wavefront aberrations introduced to the large-aperture long-focus collimator due to factors such as processing and adjustment, temperature changes, temperature gradients, airflow disturbances, and platform vibrations, and can correct these wavefront aberrations in real time with high precision, and then Greatly improve the calibration accuracy and efficiency of the large-aperture long-focus collimator, greatly reduce the difficulty of developing the large-aperture long-focus collimator, and save a lot of test time and cost.

Description

A Collimator Wavefront Aberration Precompensation Device Based on Adaptive Optics

technical field

The invention relates to a collimator wavefront aberration precompensation device, in particular to a collimator wavefront aberration precompensation device based on adaptive optics, which belongs to the field of optical detection.

Background technique

The collimator is the most commonly used optical system calibration device, which can emit parallel light to simulate an infinitely distant target. High-precision collimators are usually an indispensable measurement benchmark for the adjustment and image quality inspection of infinite conjugate imaging optical systems such as photographic objectives and telescopic objectives. In the past, collimator tubes had smaller apertures, shorter focal lengths, smaller processing and adjustment errors, and were less affected by environmental factors such as temperature changes, temperature gradients, airflow disturbances, and platform vibrations. Compensation correction. With the increase of aperture and focal length, the impact of the above environmental factors on the collimator is also increasing, and the introduced wavefront aberration cannot be ignored.

At present, the collimator with large aperture and long focal length is usually tested in a vacuum state to avoid adverse effects on the collimator caused by factors such as airflow disturbance. In addition, high-precision temperature control, high-performance vibration isolation, and high-stable structural support for the collimator are required to avoid the surface shape error of the collimator itself and introduce wavefront aberration into the system, affecting the calibration accuracy. The traditional collimator with large aperture and long focal length has great limitations, mainly in:

1) The large-caliber and long-focus collimator has a great impact on the airflow disturbance, which requires vacuuming to eliminate it, and the vacuuming process is long, which affects the test progress and increases the test cost;

2) In the traditional scheme, it is usually necessary to place a window glass with high surface shape accuracy and good material uniformity at the exit of the collimator to achieve sealing. However, the difference in air pressure inside and outside during the vacuuming process will deform the window glass and introduce The new wavefront aberration affects the calibration accuracy of the collimator;

3) If the window glass is not used, it is generally necessary to connect the collimator to the vacuum tank, place the optical system to be inspected in the vacuum tank, and evacuate the collimator and the vacuum tank together, but the optical system to be inspected is in the vacuum tank In the middle, the installation and adjustment inspection is very inconvenient;

3) In the traditional scheme, it is difficult to eliminate the wavefront aberration introduced by factors such as vacuuming, temperature change, and platform vibration to the collimator, which affects the calibration accuracy of the collimator;

4) In the traditional scheme, it is difficult to monitor the wavefront aberration and calibration accuracy of the collimator in real time during the working process;

5) In the traditional scheme, to ensure high-precision temperature control, the ambient temperature must always be controlled within a certain range. If the ambient temperature changes greatly, it will take a long time to achieve temperature balance, which will reduce the calibration efficiency.

Acta Photonica Sinica article number 1004-4213 (2008) 05-1020-3, date of publication is May 2008, titled "LCD Adaptive Optics Correction for Collimator Airflow Disturbance" introduces a method for collimator airflow The corrected liquid crystal adaptive optics system mainly carried out the liquid crystal adaptive optics system to correct the collimator airflow disturbance test. The scheme uses the Shack-Hartmann detector to detect the wavefront For the front aberration, the optical path is adjusted by the lens optical system, and the plane reflector is placed at the exit of the collimator to realize the return of the optical path. This technical solution preliminarily realizes the airflow disturbance correction of the collimator, but its disadvantage is that the wavefront detector can only detect the wavefront aberration of the collimator, but cannot detect the wavefront aberration of the adaptive optics system itself , has a large non-common optical path aberration, which affects the accuracy of wave correction and calibration; LCOS liquid crystal corrector can only correct linearly polarized light, and the energy utilization rate of natural light is lower than 50%; the correction of LCOS liquid crystal corrector The frequency is lower than 100Hz, and only low-frequency aberration correction can be performed; LCOS liquid crystal corrector has dispersion effect, and the applicable spectrum band is narrow (less than 50nm), so it cannot be used for white light correction; lens system has dispersion effect, and the optical path volume is large, so there is The lens surface reflects stray light and other limitations; the use of flat mirrors instead of window glass can only be used for the correction experiment of the adaptive optics system for the airflow, and cannot guarantee the normal correction work of the collimator at the same time, so it cannot be practically applied in engineering.

Contents of the invention

The technical problem of the present invention is: to overcome the deficiencies of the prior art, to provide a collimator wavefront aberration precompensation device based on adaptive optics, to overcome the current collimator with large diameter and long focal length based on the vacuum method The shortcomings of vacuuming effectively solve the influence of environmental factors such as temperature changes, temperature gradients, airflow disturbances, and platform vibrations on the calibration accuracy of large-aperture and long-focus collimators, and realize real-time detection and pre-compensation of wavefront aberrations. It saves a lot of test time and cost, and significantly improves the calibration performance.

The technical solution of the present invention is: a collimator wavefront aberration precompensation device based on adaptive optics, including: a large-aperture long-focus collimator and an adaptive optics system;

Large aperture and long focal length collimator including mirror assembly and window glass;

The adaptive optics system includes a light source assembly, a beam splitter, a first off-axis mirror, a second off-axis mirror, a third off-axis mirror, a wavefront detector, a wavefront corrector and a folding mirror;

The light source component is located at the focal point of the adaptive optics system; part of the light emitted by the light source component is transmitted through the beam splitter, and the other part is reflected by the beam splitter and reaches the second off-axis reflector, and the second off-axis reflector divides the beam splitter The reflected divergent light is reflected into quasi-parallel light and reaches the wavefront corrector;

The wavefront corrector performs wavefront correction on the quasi-parallel light reflected by the second off-axis reflector and then reflects it to the third off-axis reflector; the third off-axis reflector converges the calibrated quasi-parallel light reflected by the wavefront corrector on the The focus of the collimator enters the collimator;

The light incident on the collimator is reflected by the reflector assembly and becomes parallel light, and then reaches the window glass of the collimator. After the parallel light reaches the window glass of the collimator, part of the light is transmitted for the detection of the optical system, and the other part is passed through the window glass of the collimator. After being reflected by the window glass of the collimator, it passes through the mirror assembly, the third off-axis mirror, the wavefront corrector and the second off-axis mirror in turn against the incident light path, and then returns to the beam splitter;

Part of the light returning to the beam splitter is reflected by the beam splitter to the light source assembly, and the other part is transmitted by the beam splitter and reaches the first off-axis reflector, and becomes quasi-parallel light after being reflected by the first off-axis reflector. The parallel light enters the wavefront detector after being angled by the folding mirror;

The wavefront detector obtains the wavefront phase information of the incident light, and converts the wavefront phase information into the input voltage signal of the wavefront corrector. The wavefront corrector generates the corresponding surface shape according to the input voltage signal, and performs the wavefront aberration Correction to improve the wavefront accuracy of the output light from the collimator.

The mirror assembly includes one or two aspheric mirrors, or one or two aspheric mirrors and one or two folding mirrors.

The light source component is a single light source or a component composed of a light source and a target.

The surface reflectance of the window glass located inside the collimator is less than 1%, and the reflectance of the surface located outside the collimator is 20% to 50%; the surface shape accuracy of the surface located outside the collimator is better than λ/50rms, The λ is the wavelength of the incident light.

The wavefront detector is a Shaker-Hartmann wavefront detector, and the wavefront detection accuracy is better than λ/50rms.

The wavefront corrector is a MEMS deformable mirror, and the wavefront correction accuracy is better than λ/20rms.

The wavefront corrector and the wavefront detector satisfy the object-image relationship, and the effective apertures of the two match.

The advantage of the present invention compared with prior art is:

(1) The wavefront detector of the present invention can detect the wavefront aberration of the entire optical system including the collimator and the adaptive optics system, and can eliminate the non-common optical path between the wavefront detection branch and the light source illumination branch Aberration, which improves the correction accuracy of the wavefront aberration and the calibration accuracy of the collimator; the wavefront detector described in the existing literature can only detect the wavefront aberration of the collimator, and cannot detect the adaptive optics system Its own wavefront aberration has a large non-common optical path aberration, which affects the accuracy of wave correction and calibration;

(2) The wavefront corrector of the present invention adopts MEMS deformable mirror, which has high utilization rate of light energy (above 95%), high correction frequency (above 1000Hz), no dispersion effect, wide correction spectrum (full optical spectrum), etc. Advantages: The scheme described in the existing literature uses LCOS liquid crystal correctors, which can only correct linearly polarized light. The energy utilization rate of natural light is lower than 50%, and the correction frequency is lower than 100Hz. Only low-frequency aberrations can be corrected. Dispersion effect, narrow applicable spectrum (less than 50nm), cannot be used for white light correction, so it has great limitations;

(3) The adaptive optics system of the present invention adopts an off-axis reflective optical system, which has the advantages of no dispersion effect, compact structure, and no lens surface reflection stray light; the scheme described in the existing literature adopts a lens system, which has dispersion effects, The volume of the optical path is large, and there are limitations such as reflection of stray light on the lens surface;

(4) The adaptive optics system of the present invention can compensate and correct various wavefront aberrations introduced by various factors such as processing and adjustment, temperature changes, temperature gradients, airflow disturbances, and platform vibrations to the large-aperture long-focus collimator; The schemes described in the existing literature can only be used for compensation and correction of wavefront aberrations introduced by low-frequency airflow disturbances, and are helpless for wavefront aberrations introduced by high-frequency airflow disturbances or other factors;

(5) The present invention optimizes the design of the window glass of the flat light tube, which not only ensures the high-precision detection and compensation correction of the wavefront aberration by the adaptive optics system, but also ensures the normal calibration work of the collimator; The above scheme uses a plane reflector to replace the window glass, which can only be used for the correction experiment of the airflow by the adaptive optics system, and cannot guarantee the normal correction work of the collimator at the same time, and cannot be practically applied in engineering;

(6) The present invention uses an adaptive optical system to compensate and correct various wavefront aberrations introduced by factors such as processing and adjustment, temperature changes, temperature gradients, airflow disturbances, and platform vibrations to the large-aperture long-focus collimator in real time. It eliminates the vacuuming, temperature balance, debugging, vibration attenuation and other links of the large-aperture long-focus collimator, greatly reduces the temperature control requirements and processing and adjustment difficulties of the large-aperture long-focus collimator, and saves a lot of test time and cost. , and significantly improved the calibration accuracy;

(7) The present invention realizes the real-time detection and pre-compensation of wavefront aberrations in the working process, and can also generate known beams that meet special wavefront requirements to meet special detection requirements, which significantly improves the long focal length of large apertures. Calibration performance of collimators.

Description of drawings

FIG. 1 is a schematic diagram of a large-aperture collimator and an adaptive optics system of the present invention.

detailed description

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings.

As shown in Figure 1, it is a schematic diagram of a large-aperture collimator and an adaptive optics system of the present invention. It can be seen from Figure 1 that a collimator wavefront aberration precompensation device based on adaptive optics provided by the present invention includes: Aperture long focal length collimator and adaptive optics system;

The large diameter and long focal length collimator includes a parallel light assembly 10 and a window glass 11. The light aperture of the collimator is greater than 1.5m and the focal length is greater than 30m; the parallel light assembly 10 includes one or two aspheric mirrors, Or include one or two aspheric mirrors and one or two folding mirrors, the reflectance of the surface of the window glass 11 located inside the collimator is less than 1%, and the reflectance of the surface located outside the collimator is 20% ~50%, the surface shape accuracy of the surface located outside the collimator is better than λ/50rms, where λ is the wavelength of the incident light.

The adaptive optics system includes a light source assembly 4, a beam splitter 5, a first off-axis mirror 3, a second off-axis mirror 6, a third off-axis mirror 9, a wavefront detector 1, a wavefront corrector 7 and Refracting mirror 2; the light source component 4 is generally a single light source or a component composed of a light source and a target, and the wavefront detector 1 is a Shack-Hartmann wavefront with a wavefront detection accuracy better than λ/50rms detector;

The light source assembly 4 is located at the focal point of the adaptive optics system; part of the light emitted by the light source assembly 4 is transmitted through the beam splitter 5, and the other part is reflected by the beam splitter 5 and reaches the second off-axis mirror 6, and the second off-axis reflection The divergent light reflected by the beam splitter 5 is reflected by the mirror 6 into a quasi-parallel light and reaches the wavefront corrector 7; the single reflection of the off-axis mirror surface has a reflectivity of more than 99%, and the beam splitter 5 has 50% reflectivity and 50% transmittance.

The wavefront corrector 7 performs wavefront correction on the quasi-parallel light reflected by the second off-axis reflector 6 and then reflects it to the third off-axis reflector 9; The quasi-parallel light converges at the focal point 8 of the collimator and then enters the collimator; the wavefront corrector 7 is a MEMS deformable mirror with a wavefront correction accuracy better than λ/20rms;

The light incident on the parallel light pipe is reflected by the parallel light component 10 and becomes parallel light, and then reaches the parallel light window glass 11. After the parallel light reaches the parallel light window glass 11, part of the light is transmitted for the detection of the optical system, and the other part is paralleled. After being reflected by the light window glass 11, it passes through the parallel light assembly 10, the third off-axis mirror 9, the wavefront corrector 7 and the second off-axis mirror 6 in turn against the incident light path, and then returns to the beam splitter 5;

Part of the light returning to the beam splitter 5 is reflected by the beam splitter 5 to the light source assembly 4, and the other part is transmitted by the beam splitter 5 and reaches the first off-axis reflector 3, and is reflected by the first off-axis reflector 3 to become quasi-parallel light, the quasi-parallel light enters the wavefront detector 1 after being angle-refracted by the folding mirror 2;

The wavefront detector 1 obtains the wavefront phase information of the incident light, and converts the wavefront phase information into the input voltage signal of the wavefront corrector 7, and the wavefront corrector 7 generates a corresponding surface shape according to the input voltage signal to perform wavefront Aberration correction improves the wavefront accuracy of the light output from the collimator (better than λ/14rms). The wavefront corrector 7 and the wavefront detector 1 satisfy the object-image relationship, and the effective apertures of the two match.

The technical scheme of the present invention can shorten the calibration preparation time (traditional solutions include vacuuming, temperature stabilization, etc.) of large-diameter and long-focus collimators from the current 8-12 hours to within 30 minutes; The wavefront accuracy of light is improved from below λ/10rms to above λ/14rms.

The invention can be used for real-time correction of aberrations of large-diameter and long-focus collimator tubes with a clear aperture of more than 1.5 m and a focal length of more than 30 m, and can significantly improve the calibration accuracy and calibration efficiency of the large-diameter long-focus collimator tube.

The contents not described in detail in the present invention belong to the well-known technology of those skilled in the art.

Claims (7)

1. A collimator wavefront aberration precompensation device based on adaptive optics, characterized in that it comprises: a collimator with a large aperture and a long focal length and an adaptive optics system; The collimator with large aperture and long focal length includes a collimator (10) and a window glass (11); The adaptive optics system includes a light source assembly (4), a beam splitter (5), a first off-axis reflector (3), a second off-axis reflector (6), a third off-axis reflector (9), a wavefront A detector (1), a wavefront corrector (7) and a folding mirror (2); The light source assembly (4) is located at the focal point of the adaptive optics system; part of the light emitted by the light source assembly (4) is transmitted through the beam splitter (5), and the other part is reflected by the beam splitter (5) to achieve the second off-axis reflection Mirror (6), the second off-axis mirror (6) reflects the divergent light reflected by the beam splitter (5) into quasi-parallel light and reaches the wavefront corrector (7); The wavefront corrector (7) performs wavefront correction on the quasi-parallel light reflected by the second off-axis reflector (6) and then reflects it to the third off-axis reflector (9); the third off-axis reflector (9) converts the wave The calibrated quasi-parallel light reflected by the front corrector (7) converges at the focus (8) of the collimator and then enters the collimator; The light incident on the collimator is reflected by the parallel light component (10) to become parallel light and then reaches the window glass (11) of the collimator. After the parallel light reaches the window glass (11) of the collimator, part of the light is transmitted for use in The detection of the optical system is carried out, and the other part is reflected by the window glass (11) of the collimator and passes through the parallel light component (10), the third off-axis mirror (9), and the wavefront corrector (7) in sequence against the incident light path and the second off-axis reflector (6) and then return to the beam splitter (5); Part of the light returning to the beam splitter (5) is reflected by the beam splitter (5) to the light source assembly (4), and the other part is transmitted by the beam splitter (5) and reaches the first off-axis reflector (3), and passes through the second An off-axis reflector (3) becomes quasi-parallel light after reflection, and the quasi-parallel light enters the wavefront detector (1) after undergoing an angle deflection by the folding reflector (2); The wavefront detector (1) obtains the wavefront phase information of the incident light, and converts the wavefront phase information into the input voltage signal of the wavefront corrector (7), and the wavefront corrector (7) generates corresponding The surface shape is used to correct the wavefront aberration and improve the wavefront accuracy of the output light from the collimator. 2. A collimator wavefront aberration precompensation device based on adaptive optics according to claim 1, characterized in that: the parallel light component (10) comprises one or two aspheric mirrors, or Includes one or two aspheric mirrors and one or two folding mirrors. 3. A collimator wavefront aberration precompensation device based on adaptive optics according to claim 1, characterized in that: the light source component (4) is a single light source or a component composed of a light source and a target. 4. A collimator wavefront aberration precompensation device based on adaptive optics according to claim 1, characterized in that: the surface reflectivity of the window glass (11) inside the collimator is less than 1% , the reflectivity of the surface outside the collimator is 20% to 50%; the surface shape accuracy of the surface outside the collimator is better than λ/50rms, where λ is the wavelength of the incident light. 5. A collimator wavefront aberration precompensation device based on adaptive optics according to claim 1, characterized in that: the wavefront detector (1) is a Shaker-Hartmann wavefront detector device, the wavefront detection accuracy is better than λ/50rms. 6. A collimator wavefront aberration precompensation device based on adaptive optics according to claim 1, characterized in that: the wavefront corrector (7) is a MEMS deformable mirror, and the wavefront correction accuracy is excellent at λ/20rms. 7. A collimator wavefront aberration precompensation device based on adaptive optics according to claim 1, characterized in that: the wavefront corrector (7) and the wavefront detector (1) meet the object image relationship, and the effective calibers of the two match.