CN111929037A - Optical wedge compensator calibration system and calibration method thereof - Google Patents
Optical wedge compensator calibration system and calibration method thereof Download PDFInfo
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- CN111929037A CN111929037A CN202010800856.2A CN202010800856A CN111929037A CN 111929037 A CN111929037 A CN 111929037A CN 202010800856 A CN202010800856 A CN 202010800856A CN 111929037 A CN111929037 A CN 111929037A
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- G—PHYSICS
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- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/02—Testing optical properties
- G01M11/0242—Testing optical properties by measuring geometrical properties or aberrations
- G01M11/0271—Testing optical properties by measuring geometrical properties or aberrations by using interferometric methods
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/02—Testing optical properties
- G01M11/0242—Testing optical properties by measuring geometrical properties or aberrations
- G01M11/025—Testing optical properties by measuring geometrical properties or aberrations by determining the shape of the object to be tested
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Abstract
The invention provides an optical wedge compensator calibration system and a calibration method thereof, wherein the calibration method comprises the following steps: s1, designing an optical wedge compensator and a reflective CGH according to the parameters of the examined mirror; s2, placing the reflective CGH at the position of the detected mirror, and placing the spherical standard mirror between the interferometer and the reflective CGH; the light beam emitted by the interferometer is converged by the spherical standard lens and then enters the optical wedge compensator, is diffused by the optical wedge compensator and then reaches the reflective CGH, and is reflected back to the interferometer by the reflective CGH, so that the position and the system error of the optical wedge compensator are calibrated. According to the invention, an ideal aspheric surface is obtained by designing the reflective CGH to replace a detected mirror, so that divergent light passing through the optical wedge compensator can return in the original path after passing through the reflective CGH4 to realize zero position detection, thereby realizing accurate calibration of the position of the optical wedge compensator and solving the problem that the position of the optical wedge compensator is difficult to calibrate due to the fact that light is diverged after passing through the optical wedge compensator.
Description
Technical Field
The invention relates to the technical field of optical element detection, in particular to an optical wedge compensator calibration system and a calibration method thereof.
Background
With the development of astronomical optics, spatial optics needs aspheric optical elements with higher surface shape accuracy and larger caliber, and more strict requirements are provided for the optical processing means and processing accuracy of the aspheric optical elements, while optical detection is the premise and guarantee of optical processing, and high-accuracy optical processing needs the support of optical detection means with higher accuracy, so that the requirement on the detection accuracy of large-caliber convex aspheric optical elements is higher and higher.
The existing detection modes of the large-caliber convex aspherical mirror can be divided into a contour detection method and an interference detection method, the detection precision of the contour detection method is low, and the detection method is only suitable for detection in a grinding stage. For the polishing stage or the final measurement stage of the large-caliber convex aspherical mirror, an interference detection method is generally adopted. Interferometric detection methods can be further classified into non-null detection and null detection. The zero detection can be divided into a non-aberration method and a compensation detection method. The aberration-free method is only suitable for quadric surfaces, and a compensation detection method is generally adopted for the current space large-caliber high-order aspheric surface, namely, a Null lens compensator or a Computer Generated Hologram (CGH) compensator is utilized to generate the aspheric surface wavefront matched with the detected mirror so as to realize zero compensation interference detection. Because the reference surface of the Null lens compensator is an aspheric surface, a new compensator needs to be designed to detect the reference surface of the Null lens compensator, and it is difficult to manufacture the Null lens compensator for detecting the large-caliber convex aspheric reflector at present. The CGH compensator is limited by the existing CGH manufacturing process, and the manufactured caliber is limited, so that the CGH compensator can only be used for detecting a convex aspheric surface with a small caliber. Therefore, non-zero detection is adopted for detecting the large-caliber convex aspheric surface. The non-zero detection has wide applicability and can be suitable for various surface shapes.
Compared with the traditional nonzero-position compensator, the optical wedge used as the nonzero-position compensator for detecting the large-caliber convex aspheric surface has the unique advantages that: 1. the aberration of the off-axis part of the large-caliber convex aspheric surface is mainly astigmatism and coma aberration generally, and the optical wedge compensator can generate astigmatism and coma aberration and can well compensate the aberration of the off-axis part of the large-caliber convex aspheric surface; 2. the optical wedge compensator can be regarded as a parallel flat plate with a wedge angle, the manufacturing difficulty is low, the requirement on glass materials is not high, and the surface of the optical wedge compensator does not need to be coated with a film. However, the optical wedge compensator has the following disadvantages: the position of the optical wedge compensator is positioned in front of the focus of the converging light beam of the interferometer, and the light beam is diverged after passing through the optical wedge compensator and does not have the focus, so that the calibration of the optical wedge compensator is difficult, the surface shape accuracy of the large-caliber convex aspheric reflector detected by optical wedge compensation is low, the reliability is poor, and how to improve the calibration accuracy of the optical wedge compensator becomes the key for improving the surface shape accuracy of the large-caliber convex aspheric reflector detected by optical wedge compensation.
Disclosure of Invention
Aiming at the problem of difficult calibration of the optical wedge compensator, the invention provides an optical wedge compensator calibration system and a calibration method thereof, an ideal aspheric surface is obtained by designing a reflective CGH to replace a detected mirror, so that divergent light passing through the optical wedge compensator can return along the original path when reaching the reflective CGH, namely an ideal common-path detection light path is designed, zero position detection of a detection area of the reflective CGH is realized, and the specific position of the optical wedge compensator in actual detection and the system error of an optical wedge are obtained.
In order to achieve the purpose, the invention adopts the following specific technical scheme:
the invention provides an optical wedge compensator calibration system, which comprises an interferometer, a spherical standard mirror and a reflective CGH positioned at the position of a detected mirror, wherein the spherical standard mirror is positioned between the interferometer and the reflective CGH, a light beam emitted by the interferometer is converted into a spherical wave by the spherical standard mirror and then enters the optical wedge compensator, the spherical wave is diverged by the optical wedge compensator and then reaches the reflective CGH, and the spherical wave is reflected back to the interferometer by the reflective CGH, so that the position and the system error of the optical wedge compensator are calibrated.
Preferably, when the optical wedge compensator is not placed between the spherical standard mirror and the reflective CGH, the relative position between the interferometer and the reflective CGH is adjusted to minimize the defocusing amount of the detection wavefront of the interferometer, then the optical wedge compensator is placed between the spherical standard mirror and the reflective CGH, the position of the optical wedge compensator is adjusted to make the interference fringe measured by the interferometer be zero fringe or the detection wavefront be minimum, the position calibration of the optical wedge compensator is completed, and the interference wavefront of the optical wedge compensator at the position is taken as the system error of the optical wedge compensator.
Preferably, the optical wedge compensator calibration system further comprises an interferometer adjusting mechanism, and the interferometer is mounted on the interferometer adjusting mechanism.
Preferably, the optical wedge compensator calibration system further comprises an optical wedge compensator adjusting mechanism, and the optical wedge compensator is mounted on the optical wedge compensator adjusting mechanism.
Preferably, the optical wedge compensator calibration system further comprises a reflective CGH adjusting mechanism, and the reflective CGH is mounted on the reflective CGH adjusting mechanism.
The invention also provides a calibration method of the optical wedge compensator, which comprises the following steps:
s1, designing an optical wedge compensator and a reflective CGH according to the parameters of the examined mirror;
s2, placing the reflective CGH at the position of the detected mirror, and placing the spherical standard mirror between the interferometer and the reflective CGH; the light beam emitted by the interferometer is converted into a spherical surface wave by the spherical standard mirror and then enters the optical wedge compensator, the spherical surface wave is diffused by the optical wedge compensator and then reaches the reflective CGH, the reflective CGH is reflected back to the interferometer, and the position and the system error of the optical wedge compensator are calibrated.
Preferably, in step S2, calibrating the position and the system error of the optical wedge compensator specifically includes the following steps:
s201, when an optical wedge compensator is not arranged between the spherical standard mirror and the reflective CGH, adjusting the relative position between the interferometer and the reflective CGH to minimize the defocusing amount of the wavefront detected by the interferometer;
s202, the optical wedge compensator is placed between the spherical standard mirror and the reflective CGH, interference fringes measured by the interferometer are zero fringes or the detection wavefront is minimum by adjusting the position of the optical wedge compensator, the position is calibrated to be the position of the optical wedge compensator, and the interference wavefront of the optical wedge compensator at the position is obtained and used as the system error of the optical wedge compensator.
Preferably, in step S1, the design of the optical wedge compensator specifically includes the following steps:
s101, performing subaperture planning according to parameters of a detected mirror to be detected, and calculating the deviation of the aperture of each circle of the detected mirror;
s102, calculating parameters of the optical wedge compensator according to the deviation of the aperture of each circle of the detected mirror, and obtaining the optical wedge compensator through ZEMAX software simulation design.
Preferably, in step S1, the design of the reflective CGH includes the design of the detection region and the design of the alignment region; wherein the content of the first and second substances,
the detection area is designed as follows:
the optical wedge compensator is placed between the spherical standard mirror and the reflective CGH, the detected mirror is replaced by a Zernike surface in ZEMAX software, the detection wavefront of the interferometer is zero by changing the Zernike coefficient, and the Zernike coefficient at the moment is used as the surface shape of the detection area of the reflective CGH;
the design of the alignment area is as follows:
removing an optical wedge compensator between the spherical standard mirror and the reflective CGH, changing a Zernike coefficient to enable the detection wavefront of the interferometer to be zero, and taking the Zernike coefficient at the moment as the surface shape of an alignment area of the reflective CGH; and the number of the first and second groups,
and according to the relation between the calibers and the positions of the alignment area and the detection area, the CGH is carved on the glass substrate to form the reflective CGH.
Preferably, after step S2, the method further includes the following steps:
and S3, replacing the reflective CGH with the inspected mirror to finish the surface shape precision detection of the inspected mirror.
The invention can obtain the following technical effects:
1. the precise calibration of the optical wedge compensator is realized through the reflective CGH, so that the problem that the optical wedge compensator is difficult to calibrate is solved;
2. the design precision of the CGH is high, other auxiliary calibration modes such as a laser tracker and the like are not needed, the calibration precision of the optical wedge compensator can be improved, and the operation error is reduced;
3. the reflective CGH only needs to design a detection area and an alignment area, and does not need to design a reference area, so that the design of the CGH is easier.
Drawings
FIG. 1 is a schematic diagram of an optical wedge compensator calibration system according to one embodiment of the present invention;
FIG. 2 is a schematic diagram of a surface shape accuracy detection system according to an embodiment of the present invention;
FIG. 3 is a flow chart illustrating a calibration method of an optical wedge compensator according to an embodiment of the present invention.
Wherein the reference numerals include: interferometer 1, spherical standard mirror 2, optical wedge compensator 3, reflective CGH4, inspected mirror 8, interferometer adjusting mechanism 5, optical wedge compensator adjusting mechanism 6, CGH adjusting mechanism 7 and inspected mirror adjusting mechanism 9.
Detailed Description
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same reference numerals are used for the same blocks. In the case of the same reference numerals, their names and functions are also the same. Therefore, detailed description thereof will not be repeated.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not to be construed as limiting the invention.
The invention provides a calibration system and a calibration method of an optical wedge compensator, which are used for realizing calibration of the optical wedge compensator, wherein the calibration method is realized based on the calibration system. The invention aims to achieve the aim of improving the surface shape precision detection precision of the large-caliber convex aspheric mirror by accurately calibrating the position of the optical wedge compensator and removing the system error introduced by the optical wedge compensator.
The optical wedge compensator calibration system and the calibration method corresponding to the optical wedge compensator calibration system provided by the embodiment of the invention will be described in detail below with reference to the accompanying drawings.
FIG. 1 illustrates the structure of an optical wedge compensator calibration system according to one embodiment of the present invention.
As shown in fig. 1, an optical wedge compensator calibration system provided in an embodiment of the present invention includes: the interferometer comprises an interferometer 1, a spherical standard mirror 2 and a reflective CGH4, wherein the reflective CGH4 is arranged at the position of a detected mirror, and the spherical standard mirror 2 is arranged at the position between the interferometer 1 and the reflective CGH 4. Interferometer 1 and spherical etalon 2 are located on one side of wedge compensator 3 and reflective CGH4 is located on the other side of wedge compensator 3.
The optical path of the optical wedge compensator calibration system is as follows: light beams emitted by the interferometer 1 are incident to the spherical standard mirror 2, are converted into spherical waves by the spherical standard mirror 2, are incident to the optical wedge compensator 3, are dispersed by the optical wedge compensator 3 to reach the reflective CGH4, and are reflected back to the interferometer 1 by the reflective CGH 4.
According to the invention, an ideal aspheric surface is obtained by designing the reflective CGH4 to replace a detected mirror, so that divergent light passing through the optical wedge compensator 3 can return to the interferometer 1 along the original path after reaching the reflective CGH4, namely, an ideal common-path detection light path is designed to realize zero position detection of a detection area of the reflective CGH4, thereby obtaining the specific position and system error of the optical wedge compensator 3 in actual detection, realizing calibration of the position of the optical wedge compensator 3, and solving the problems that light rays are diverged after passing through the optical wedge compensator 3 and the position of the optical wedge compensator 3 is difficult to calibrate.
The calibration process of the position of the optical wedge compensator 3 is as follows: when the optical wedge compensator calibration system is not placed in the optical wedge compensator 3 (i.e. before the optical wedge compensator 3 is placed between the spherical standard mirror 2 and the reflective CGH 4), the relative position between the interferometer 1 and the reflective CGH4 is adjusted to minimize the POWER value (i.e. defocus) of the interferometer 1, the positions of the fixed interferometer 1 and the reflective CGH4 are not moved any more, then the optical wedge compensator 3 is placed in the optical wedge compensator calibration system (i.e. the optical wedge compensator 3 is placed between the spherical standard mirror 2 and the reflective CGH 4), the position of the optical wedge compensator 3 is adjusted to make the interference fringe measured by the interferometer 1 be zero fringe or the detection wavefront be minimum, and the position where the interference fringe measured by the interferometer 1 is zero or the detection wavefront is minimum is taken as the ideal position of the optical wedge compensator 3, so as to complete the position calibration of the optical wedge compensator 3. The interference wavefront of the optical wedge compensator 3 at the ideal position is obtained and taken as the system error of the optical wedge compensator 3, and after the system error of the optical wedge compensator 3 is removed, the surface shape detection precision of the detected mirror can be improved.
In some embodiments of the present invention, the optical wedge compensator calibration system further includes an interferometer adjusting mechanism 5, an optical wedge compensator adjusting mechanism 6, and a CGH adjusting mechanism 7, wherein the interferometer 1 is installed on the interferometer adjusting mechanism 5, the position of the interferometer 1 is adjusted by the interferometer adjusting mechanism 5, the optical wedge compensator 3 is installed on the optical wedge compensator adjusting mechanism 6, the position of the optical wedge compensator 3 is adjusted by the optical wedge compensator adjusting mechanism 6, the reflective CGH4 is installed on the CGH adjusting mechanism 7, and the position of the reflective CGH4 is adjusted by the CGH adjusting mechanism 7.
Fig. 2 is a structure of a surface shape accuracy detection system according to an embodiment of the present invention.
As shown in fig. 2, after the position of the optical wedge compensator 3 is calibrated, the reflective CGH4 and the CGH adjustment mechanism 7 are replaced with the examined mirror 8 and the examined mirror adjustment mechanism 9, and the other optical elements are not changed, so that the interferometer 1, the spherical standard mirror 2, the optical wedge compensator 3, the interferometer adjustment mechanism 5, the optical wedge compensator adjustment mechanism 6, and the examined mirror adjustment mechanism 9 constitute a surface shape accuracy detection system of the examined mirror 8, thereby realizing surface shape accuracy detection of the examined mirror 8.
The interferometer adjusting mechanism 5, the optical wedge compensator adjusting mechanism 6, the CGH adjusting mechanism 7, and the detected mirror adjusting mechanism 9 are all of the prior art, and therefore, they are not described herein again.
The above details explain the structure and the working principle of the calibration system of the optical wedge compensator provided by the present invention. Corresponding to the optical wedge compensator calibration system, the invention also provides a method for calibrating the optical wedge compensator by using the optical wedge compensator calibration system.
FIG. 3 shows a flow chart of a calibration method of an optical wedge compensator according to an embodiment of the present invention.
As shown in fig. 3, the calibration method of the optical wedge compensator provided in the embodiment of the present invention includes the following steps:
s1, designing the optical wedge compensator and the reflective CGH according to the parameters of the examined mirror.
The specific designs of the wedge compensator and the reflective CGH are described in detail below, respectively.
Optical wedge compensator
The design of the optical wedge compensator specifically comprises the following steps:
s101, sub-aperture planning is carried out according to parameters of the detected mirror, and deviation of each circle of sub-apertures of the detected mirror is calculated.
The planning of the aperture of the detected mirror needs to satisfy the following conditions:
(1) an overlapping area is formed between the sub-apertures, and the overlapping proportion of 30% is ensured between the inner ring sub-aperture and the outer ring sub-aperture;
(2) the wedge angle of the optical wedge compensator is within 10 degrees;
(3) the area of the sub-aperture region is enlarged as much as possible on the basis of ensuring the first two conditions, thereby reducing the number of required sub-apertures.
S102, calculating parameters of the optical wedge compensator according to the deviation of each circle of sub-aperture of the detected mirror, and obtaining the optical wedge compensator through ZEMAX software simulation design.
And calculating the deviation of each circle of sub-aperture according to the convex aspheric parameters (aspheric aperture, vertex curvature radius, quadric constant, high-order term coefficient and the like) of the examined lens, and determining the specific position of the sub-aperture needing optical wedge compensation. If the examined lens has more than one circle of sub-aperture needing compensation, the deviation amount of the sub-aperture of two adjacent circles is analyzed to determine whether an optical wedge compensator can be used. And inputting the deviation of each circle of sub-aperture into ZEMAX software to obtain parameters of the optical wedge compensator, and designing the optical wedge compensator meeting the shape requirement of the detected mirror surface through simulation of the ZEMAX software.
Two, reflection type CGH
The design of the reflective CGH comprises the design of a detection area and the design of an alignment area, wherein the detection area is used for calibrating the system error of the optical wedge compensator and the specific position of the optical wedge compensator in a wedge compensator calibration system, and the alignment area is used for aligning with the interferometer to ensure that the reflective CGH is in the correct position during calibration.
The detection area is designed as follows:
the optical wedge compensator is placed between the spherical standard mirror and the reflective CGH, the detected mirror is replaced by a Zernike surface in ZEMAX software, the detection wavefront of the interferometer is zero by changing the Zernike coefficient, and the Zernike coefficient at the moment is the surface shape of the detection area of the reflective CGH.
The design of the alignment area is as follows:
and removing the optical wedge compensator between the spherical standard mirror and the reflective CGH, and changing the Zernike coefficient to enable the detection wavefront of the interferometer to be zero, wherein the Zernike coefficient at the moment is the surface shape of the alignment area of the reflective CGH.
After the design of the detection area and the alignment area is finished, the CGH is carved on the glass substrate according to the caliber and position relation of the alignment area and the detection area to form the reflective CGH.
It should be noted that, when designing the CGH, the stripe-drawing density of the CGH should be controlled to be about 3 μm, the detection area of the reflective CGH is slightly larger than the effective area of the actual detection, and the overall design caliber of the reflective CGH is less than or equal to 140 mm.
The reflective CGH only needs to design the alignment area and the detection area, and does not need to design the reference area, so that the reflective CGH is easier to design.
S2, placing the reflective CGH at the position of the detected mirror, and placing the spherical standard mirror between the interferometer and the reflective CGH; the light beam emitted by the interferometer is converged by the spherical standard lens and then enters the optical wedge compensator, is diffused by the optical wedge compensator and then reaches the reflective CGH, and is reflected back to the interferometer by the reflective CGH, so that the position and the system error of the optical wedge compensator are calibrated.
Through the design of the reflective CGH, an ideal aspheric surface is obtained, the reflective CGH is placed at the position of a detected mirror to replace the detected mirror, so that a light beam diffused by the optical wedge compensator can return along the original path when reaching the reflective CGH to form a common-path detection light path, zero position detection of a detection area of the reflective CGH is realized, and the position and system error of the optical wedge compensator in actual detection are obtained.
The method for calibrating the position and the system error of the optical wedge compensator specifically comprises the following steps:
s201, when an optical wedge compensator is not placed between the spherical standard mirror and the reflective CGH, adjusting the relative position between the interferometer and the reflective CGH to enable the defocusing amount of the wave front detected by the interferometer to be minimum.
And adjusting the position between the reflective CGH and the interferometer by adopting a CGH adjusting mechanism and an interferometer adjusting mechanism through the alignment area of the reflective CGH.
Since the position of the spherical standard mirror is fixed, adjusting the position between the reflective CGH and the interferometer actually adjusts the position of the interferometer and the position of the reflective CGH relative to the spherical standard mirror. More specifically, the position of the reflective CGH relative to the spherical standard mirror is adjusted by the CGH adjusting mechanism, and the position of the interferometer relative to the spherical standard mirror is adjusted by the interferometer adjusting mechanism.
S202, placing an optical wedge compensator between the spherical standard mirror and the reflective CGH, enabling interference fringes measured by the interferometer to be zero fringes or the detected wavefront to be minimum by adjusting the position of the optical wedge compensator, calibrating the position as the position of the optical wedge compensator, and obtaining the interference wavefront of the optical wedge compensator at the position as the system error of the optical wedge compensator.
After the reflective CGH and the interferometer are aligned, the positions of the reflective CGH and the interferometer are fixed, the position of the optical wedge compensator is adjusted through an optical wedge compensator adjusting mechanism (both the manufacturing error of the optical wedge and the non-uniformity of the refractive index of the material are within a design allowable range), the number of interference fringes measured by the interferometer is zero or the detection wavefront is minimum, the position is an ideal position of the optical wedge compensator, the position of the optical wedge compensator is accurately calibrated, the interference wavefront of the interferometer at the ideal position is obtained, the interference wavefront is the system error of the optical wedge compensator, and the surface shape detection precision of the detected mirror can be improved by removing the system error of the optical wedge compensator.
Due to the fact that the design accuracy of the reflective CGH is high, after the optical wedge compensator is calibrated through the reflective CGH, other auxiliary calibration modes (such as a laser tracker) are not needed for calibration, the calibration accuracy of the optical wedge compensator can be improved, and operation errors are reduced.
In an embodiment of the present invention, after step S2, the method further includes the following steps:
and S3, replacing the reflective CGH with the inspected mirror to finish the surface shape precision detection of the inspected mirror.
After the position of the optical wedge compensator is calibrated, the reflective CGH is replaced by the inspected mirror, and the surface shape precision detection of the inspected mirror is realized.
The surface shape precision detection process of the examined mirror is as follows: the interferometer emits light beams which are irradiated on the spherical standard mirror and then converted into spherical waves, the spherical waves are irradiated on the detected mirror after passing through the optical wedge compensator and then reflected by the detected mirror, the spherical waves return to the interferometer after passing through the optical wedge compensator and the spherical standard mirror again, and the wave fronts reflected by the detected mirror are superposed with the reference wave front light reflected by the reference surface of the spherical standard mirror to form interference fringes; and adjusting the positions of the interferometer and/or the optical wedge compensator or/and the examined mirror until the number of interference fringes is zero to obtain the surface shape information of each subaperture of the examined mirror.
In another embodiment of the present invention, after step S3, the method further includes the following steps:
and S4, analyzing the detection result and judging whether the precision requirement is met.
In the process of detecting the surface shape accuracy of the examined lens, the surface shape accuracy of the examined lens is influenced by many factors, such as: surface shape precision error of the reflective CGH substrate, design and processing errors of the reflective CGH, adjustment errors of the reflective CGH and the optical wedge compensator, system errors of the interferometer, environmental vibration and the like. Therefore, it is necessary to perform precision analysis on the detection result to determine whether the precision requirement is satisfied.
The invention adopts a multi-step method to separate the system error of the optical wedge compensator and the system error of the interferometer, analyzes the influence of the adjusting error of each adjusting mechanism on the detection result, and makes the adjusting error of each adjusting mechanism within the minimum error range allowed by the optical wedge compensation detection, so as to improve the detection precision of the optical wedge compensation detection method, and make the detection precision of the method better than 1/100 lambda (RMS value, lambda is 632.8nm), thereby meeting the requirement of precisely detecting the large-caliber large-deviation convex aspheric reflector.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
The above embodiments of the present invention should not be construed as limiting the scope of the present invention. Any other corresponding changes and modifications made according to the technical idea of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. The optical wedge compensator calibration system comprises an interferometer and a spherical standard mirror, and is characterized by further comprising a reflective CGH located at the position of a detected mirror, wherein the spherical standard mirror is located between the interferometer and the reflective CGH, a light beam emitted by the interferometer is converted into a spherical wave through the spherical standard mirror and then enters the optical wedge compensator, the spherical wave is diverged by the optical wedge compensator and then reaches the reflective CGH, and the spherical wave is reflected back to the interferometer through the reflective CGH, so that the position and the system error of the optical wedge compensator are calibrated.
2. The optical wedge compensator calibration system according to claim 1, wherein when the optical wedge compensator is not placed between the spherical standard mirror and the reflective CGH, the relative position between the interferometer and the reflective CGH is adjusted to minimize the defocus amount of the wavefront detected by the interferometer, then the optical wedge compensator is placed between the spherical standard mirror and the reflective CGH, the position of the optical wedge compensator is adjusted to minimize the interference fringes measured by the interferometer or the detection wavefront, the position calibration of the optical wedge compensator is completed, and the interference wavefront of the optical wedge compensator at the position is taken as the system error of the optical wedge compensator.
3. The optical wedge compensator calibration system of claim 1 further comprising an interferometer adjustment mechanism, the interferometer being mounted on the interferometer adjustment mechanism.
4. The optical wedge compensator calibration system according to claim 1, further comprising an optical wedge compensator adjustment mechanism, wherein said optical wedge compensator is mounted on said optical wedge compensator adjustment mechanism.
5. The optical wedge compensator calibration system as claimed in claim 1 further comprising a reflective CGH adjustment mechanism, said reflective CGH mounted on said reflective CGH adjustment mechanism.
6. A calibration method of an optical wedge compensator is characterized by comprising the following steps:
s1, designing an optical wedge compensator and a reflective CGH according to the parameters of the examined mirror;
s2, placing the reflective CGH at the position of the detected mirror, and placing a spherical standard mirror between the interferometer and the reflective CGH; the light beam emitted by the interferometer is converted into a spherical surface wave by the spherical standard mirror and then enters the optical wedge compensator, the spherical surface wave is diverged by the optical wedge compensator and then reaches the reflective CGH, the reflective CGH reflects the spherical surface wave back to the interferometer, and the position and the system error of the optical wedge compensator are calibrated.
7. The method for calibrating an optical wedge compensator according to claim 6, wherein calibrating the position and the system error of the optical wedge compensator in step S2 specifically comprises the following steps:
s201, when an optical wedge compensator is not placed between the spherical standard mirror and the reflective CGH, adjusting the relative position between the interferometer and the reflective CGH to enable the defocusing amount of the wavefront detected by the interferometer to be minimum;
s202, placing the optical wedge compensator between the spherical standard mirror and the reflective CGH, enabling the interference fringe measured by the interferometer to be zero fringe or the detection wavefront to be minimum by adjusting the position of the optical wedge compensator, calibrating the position as the position of the optical wedge compensator, and obtaining the interference wavefront of the optical wedge compensator at the position as the system error of the optical wedge compensator.
8. The method for calibrating an optical wedge compensator according to claim 6, wherein in step S1, the design of the optical wedge compensator specifically comprises the following steps:
s101, performing subaperture planning according to parameters of a detected mirror to be detected, and calculating the deviation of the subaperture of each circle of the detected mirror;
s102, calculating structural parameters of the optical wedge compensator according to the deviation of each circle of sub-aperture of the detected mirror, and obtaining the optical wedge compensator through ZEMAX software simulation design.
9. The method for calibrating an optical wedge compensator according to claim 6, wherein in step S1, the design of the reflective CGH comprises the design of the detection region and the design of the alignment region; wherein the content of the first and second substances,
the detection area is designed as follows:
placing the optical wedge compensator between the spherical standard mirror and the reflective CGH, changing the detected mirror into a Zernike surface in ZEMAX software, changing a Zernike coefficient to enable the detection wavefront of the interferometer to be zero, and taking the Zernike coefficient at the moment as the surface shape of the detection area of the reflective CGH;
the design of the alignment area is as follows:
removing an optical wedge compensator between the spherical standard mirror and the reflective CGH, changing a Zernike coefficient to enable the detection wavefront of the interferometer to be zero, and taking the Zernike coefficient at the moment as the surface shape of an alignment area of the reflective CGH; and the number of the first and second groups,
and according to the relation between the calibers and the positions of the alignment area and the detection area, describing a CGH on the glass substrate to form the reflective CGH.
10. The method for calibrating an optical wedge compensator according to any one of claims 6-9, further comprising the following steps after step S2:
and S3, replacing the reflective CGH with the inspected mirror to finish the surface shape precision detection of the inspected mirror.
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