A CGH alignment method

Abstract

The application relates to the technical field of optical detection, and particularly provides a CGH alignment method, and the alignment process comprises the following steps: decomposing alignment errors of two CGHs into interval errors, tilt errors and eccentric errors; providing detection light through an interferometer, and a shaping unit is used for switching a spherical standard mirror or a plane standard mirror to a transmission light path of the detection light; according to the sensitivity of different error components to different wavefronts, matching the detection light of the corresponding wavefront for each error component, and setting different alignment areas on the two CGHs; for each error component, the shaping unit is controlled to shape the detection light into corresponding wavefront detection light, the corresponding wavefront detection light is used for irradiating the corresponding alignment areas on the two CGHs, and the relative poses of the two CGHs are adjusted according to the interference fringes of the corresponding alignment areas, so that the error component is suppressed. The application realizes high-precision alignment of the interval, tilt and eccentricity of the CGH.

Description

Technical Field

[0001] This invention belongs to the field of optical detection technology, and particularly relates to a CGH alignment method. Background Technology

[0002] With the rapid growth in demand for aerospace and astronomical observation, and the continuous expansion of application scenarios, the performance requirements of large-scale optoelectronic imaging equipment are becoming increasingly stringent. The number of optical components is increasing, their surface shapes are becoming more complex, and the wavefront accuracy requirements of optical systems are rising. These demands pose unprecedented challenges to the assembly and adjustment technology of optical systems. Among these challenges, detection accuracy is a prerequisite for ensuring manufacturing accuracy. Faced with increasingly complex optical components, traditional single compensation devices often struggle to meet the demands of high-precision detection.

[0003] To address this challenge, the dual CGH (computational hologram) null-compensation detection method is considered an effective approach. This method utilizes two CGH devices to achieve the detection and alignment of multiple elements in complex optical systems. However, the precise control of the relative positions of multiple CGH devices during detection, especially the relative positions between two CGH devices, has a crucial impact on detection accuracy. Therefore, achieving high-precision alignment between the two CGH devices will significantly improve both detection and alignment accuracy.

[0004] Existing dual-CGH alignment methods use circular grating moiré fringes for CGH alignment. This method involves designing four sets of circular gratings etched at the same positions around the main CGH, distributed at the four corners of a square. The grating line frequencies of two circular gratings at the same position on different CGH elements are very similar, and their overlap produces moiré fringes. When the two CGH elements are fitted together, the alignment is determined by observing the changes in the four sets of circular grating moiré fringes. This method relies on visual observation of the moiré fringes, resulting in large observation errors and low efficiency; in fact, when the positions of the two CGHs are significantly different, moiré fringes may not even be obtained. This method has significant limitations and cannot achieve high-precision alignment between dual CGHs. Summary of the Invention

[0005] In view of this, the present invention aims to provide a CGH alignment method that achieves switching between plane wave and spherical wave by changing different standard mirrors, and designs different CGH alignment areas to achieve high-precision alignment of the interval, tilt, and eccentricity of the two CGHs.

[0006] To achieve the above objectives, the technical solution created by this invention is implemented as follows:

[0007] This invention provides a CGH alignment method for aligning at least two CGHs, the at least two CGHs including a first CGH and a second CGH, the alignment process of the first CGH and the second CGH including:

[0008] The alignment error of the first CGH and the second CGH is decomposed into error components of different forms;

[0009] The probe light is provided by an interferometer, and a shaping unit is set in the transmission optical path of the probe light. The shaping unit is used to shape the probe light into probe light with different wavefronts.

[0010] Based on the sensitivity of different error components to different wavefronts, a corresponding wavefront probe light is matched for each error component;

[0011] Different alignment areas are set on the first CGH and the second CGH according to the paired error components and the probe light of the corresponding wavefront;

[0012] For any error component, the control shaping unit shapes the probe light into a wavefront probe light paired with the error component, uses the wavefront probe light paired with the error component to illuminate the corresponding alignment areas on the first CGH and the second CGH, and adjusts the relative pose of the first CGH and the second CGH according to the interference fringes of the corresponding alignment areas to suppress the error component.

[0013] Preferably, the first CGH and the second CGH are respectively mounted on two six-degree-of-freedom adjustment frames, and the pose adjustment of the first CGH and the second CGH is realized through the six-degree-of-freedom adjustment frames.

[0014] Preferably, the different error components include: interval error, tilt error and eccentricity error.

[0015] Preferably, a tilt alignment region and an eccentric alignment region are respectively provided on the first CGH and the second CGH, and an interval alignment region is also provided on the first CGH.

[0016] Preferably, the shaping unit is used to switch the spherical standard mirror or the plane standard mirror to the transmission optical path of the probe light.

[0017] Preferably, the process for suppressing interval errors includes:

[0018] The probe light is processed into a spherical wave using a spherical standard mirror. The spherical wave is phase-modulated through the spaced alignment region of the first CGH and incident on the second CGH. The phase-modulated spherical wave is symmetrically reflected back to the interferometer along the normal of the center point of the second CGH for interference, and the wavefront map of the spaced alignment region is obtained. The spaced error between the first CGH and the second CGH is calculated based on the PV value of the wavefront map of the spaced alignment region. The first CGH and the second CGH are adjusted according to the spaced error.

[0019] Preferably, the tilt error suppression process includes:

[0020] The probe light is processed into a plane wave by a plane standard mirror. The plane wave is phase-modulated by the tilt alignment area of ​​the first CGH and incident on the tilt alignment area of ​​the second CGH. The phase-modulated plane wave is reflected back to the interferometer by the tilt alignment area of ​​the second CGH along the original incident light path for interference. The relative tilt of the first CGH and the second CGH is adjusted until the tilt alignment area of ​​the second CGH shows zero fringes.

[0021] Preferably, the process for suppressing eccentricity error includes:

[0022] The probe light is processed into a spherical wave by a spherical standard mirror. The spherical wave is phase-modulated by the eccentric alignment region of the first CGH. The phase-modulated plane wave is reflected back to the interferometer by the eccentric alignment region of the second CGH along the original incident light path. The relative eccentricity of the first CGH and the second CGH is adjusted until the tilted eccentric alignment region of the second CGH shows zero fringes.

[0023] Preferably, the first CGH further includes a main region, and the interval alignment region, tilt alignment region and eccentric alignment region of the first CGH are concentric rings, which are nested in sequence around the outer periphery of the main region;

[0024] The second CGH also includes a main region. The tilt alignment region and the eccentric alignment region of the second CGH are concentric rings and are nested in sequence around the outer periphery of the main region.

[0025] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0026] This invention decomposes the alignment error between CGHs and utilizes the physical characteristics of spherical waves (sensitive to defocusing and eccentricity) and plane waves (sensitive to tilt) to design a dedicated alignment region for the CGH. It transforms the calculation of three types of deviations—interval, tilt, and eccentricity—into intuitive and quantitatively measurable interference fringe information. The error state is determined by the wavefront image PV value and interference fringes. Pose adjustment achieves a PV value close to 0 and a zero-fringe state, thus suppressing the three types of deviations. This invention, through the core operation of changing the standard mirror in front of the interferometer, can complete the detection and correction of all types of deviations on the same hardware platform without introducing additional complex optical paths or devices. It has the advantages of simple operation and high adjustment accuracy, completely solving the drawbacks of traditional methods that determine the error state by observing changes in moiré fringes with the naked eye.

[0027] The alignment method of the present invention is not limited to the alignment of two CGHs, but can be extended to multi-CGH systems or other complex optical assembly scenarios that require high-precision coaxial adjustment. Attached Figure Description

[0028] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0029] Figure 1 This is a flowchart of the CGH alignment method provided according to an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of the region division of the first CGH and the second CGH according to an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the optical path for adjusting the interval between the first CGH and the second CGH according to an embodiment of the present invention;

[0032] Figure 4 This is a schematic diagram of the tilt adjustment optical path of the first CGH and the second CGH provided according to an embodiment of the present invention;

[0033] Figure 5 This is a schematic diagram of the eccentric adjustment optical path of the first CGH and the second CGH provided according to an embodiment of the present invention;

[0034] Figure 6 This is a schematic diagram of interference fringes before the first CGH and the second CGH are eccentrically adjusted, according to an embodiment of the present invention.

[0035] Figure 7 This is a schematic diagram of interference fringes after the first CGH and the second CGH are eccentrically adjusted according to an embodiment of the present invention.

[0036] The reference numerals in the figures include:

[0037] Interferometer 1, Interferometer adjustment frame 2, Spherical standard mirror 31, Plane standard mirror 32, First CGH 4, First six-degree-of-freedom adjustment frame 5, Second CGH 6, Second six-degree-of-freedom adjustment frame 7. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and do not constitute a limitation thereof. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the invention. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, some operations related to the invention are not shown or described in the specification. This is to avoid obscuring the core parts of the invention with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; the relevant operations can be fully understood based on the description in the specification and general technical knowledge in the art.

[0039] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined to form various implementations. Furthermore, the order of the steps or actions in the method description can be changed or adjusted in a manner readily apparent to those skilled in the art. Therefore, the various orders in the specification and drawings are merely for the clear description of a particular embodiment and do not imply a mandatory order, unless otherwise stated that a particular order must be followed.

[0040] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0041] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0042] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0043] Please see Figure 1 In one embodiment of the present invention, a CGH alignment method is provided. This method is used to align at least two CGHs (computational holograms) in a system. During the alignment process, two CGHs can be aligned sequentially, and the aligned CGH is used as a reference to continue aligning all other CGHs. The alignment process for any two CGHs is the same. Specifically, an arbitrary first CGH and a second CGH are selected as examples to describe the alignment process between CGHs. The alignment process includes:

[0044] The alignment error of the first CGH and the second CGH is decomposed into error components of different forms;

[0045] The probe light is provided by an interferometer, and a shaping unit is set in the transmission optical path of the probe light. The shaping unit is used to shape the probe light into probe light with different wavefronts.

[0046] Based on the sensitivity of different error components to different wavefronts, a corresponding wavefront probe light is matched for each error component;

[0047] Different alignment areas are set on the first CGH and the second CGH according to the paired error components and the probe light of the corresponding wavefront;

[0048] For any error component, the control shaping unit shapes the probe light into a wavefront probe light paired with the error component, uses the wavefront probe light paired with the error component to illuminate the corresponding alignment areas on the first CGH and the second CGH, and adjusts the relative pose of the first CGH and the second CGH according to the interference fringes of the corresponding alignment areas to suppress the error component.

[0049] First, based on the alignment requirements between the two CGHs, the alignment errors of the first CGH and the second CGH are decomposed into different error components, specifically: interval error, tilt error, and eccentricity error. Among them, the interval error refers to the difference between the actual distance and the design distance between the first CGH and the second CGH; the tilt error refers to the relative tilt angle between the first CGH and the second CGH; and the eccentricity error refers to the spatial offset between the center point of the first CGH and the center point of the second CGH.

[0050] Because spherical wavefronts are highly sensitive to the lateral offset of the measured wavefront center relative to the optical axis (i.e., eccentricity error), this error is characterized as a linearly changing phase gradient in the interferogram, facilitating direct calculation. Plane wavefronts, on the other hand, provide an absolutely flat phase reference, which is extremely sensitive to the overall tilt of the measured wavefront (i.e., tilt error). These errors are directly converted into tilt or regular bending of the interference fringes, facilitating intuitive observation and quantitative analysis. Therefore, this invention proposes that during the dual CGH alignment process, the spherical and plane waves emitted by the interferometer are switched by switching between spherical and plane standard mirrors. Different forms of error components are paired with their suitable wavefront forms; that is, the wavefront of the probe light is selected during the correction of each error component, and corresponding CGH alignment areas are set for different forms of wavefronts and error components.

[0051] Specifically, such as Figure 2 As shown, based on the detection requirements of interval error, tilt error, and eccentricity error, both the first and second CGHs are divided into: a main region, a tilt alignment region, and an eccentric alignment region. An additional interval alignment region is designed on the first CGH. The main region is circular, while the interval, tilt, and eccentric alignment regions are concentric rings. The interval, tilt, and eccentric alignment regions of the first CGH are nested sequentially around the outer periphery of the main region. Similarly, the tilt and eccentric alignment regions of the second CGH are nested sequentially around the outer periphery of the main region. There may also be unetched areas outside the eccentric alignment region of the second CGH. The specific division of the alignment regions can be achieved using traditional methods.

[0052] like Figure 3As shown, for the detection of interval error, the focal point of interferometer 1 is used as the intermediate calibration value. By adjusting the distances between the first CGH4, the second CGH6 and the focal point of interferometer 1, the interval between the first CGH4 and the second CGH6 can be indirectly determined to eliminate the interval error. The optical frame required for alignment includes: interferometer 1, interferometer adjustment frame 2, shaping unit, first CGH4, first six-degree-of-freedom adjustment frame 5, second CGH6 and second six-degree-of-freedom adjustment frame 7. Interferometer 1 is a laser interferometer used to provide probe light and receive the reflected echoes processed by the first CGH4 and the second CGH6, and perform interference to obtain interference fringes. Interferometer 1 is mounted on interferometer adjustment frame 2, which allows adjustment of the position and orientation of interferometer 1. A shaping unit is provided on the transmission optical path of the probe light provided by interferometer 1. The shaping unit is used to shape the probe light into different wavefront probe lights required for detecting different error components. In this embodiment of the invention, the shaping unit includes a spherical standard mirror 31 and a planar standard mirror 32. When detecting different error components, either the spherical standard mirror 31 or the planar standard mirror 32 can be placed in the optical path to achieve wavefront shaping of the probe light. The switching between the spherical standard mirror 31 and the planar standard mirror 32 can be designed as a manual replacement of the standard mirror, or a mechanical structure can be designed to switch the standard mirror in the optical path. After the probe light is shaped by the shaping unit, it is first transmitted through the first CGH4, undergoes phase modulation through a specific alignment area on the first CGH4, and is reflected by the specific alignment area of ​​the second CGH6 when it illuminates it. The reflected light then enters the interferometer 1 along the original incident light path for interference. The first CGH4 and the second CGH6 are respectively mounted on the first six-degree-of-freedom adjustment frame 5 and the second six-degree-of-freedom adjustment frame 7. The positions and attitudes of the first CGH4 and the second CGH6 can be adjusted through the first six-degree-of-freedom adjustment frame 5 and the second six-degree-of-freedom adjustment frame 7 to eliminate alignment errors and achieve high-precision alignment.

[0053] Specifically, in the process of detecting the interval error, the interferometer 1 is first preheated for 30 minutes and its accuracy is calibrated. Then, the spherical standard mirror 31 is inserted into the optical path so that the focal point of the interferometer 1 can be used as a reference for calibration. First, the interferometer 1 emits a probe light, which is shaped into a spherical wavefront by the spherical standard mirror 31. The spherical wavefront illuminates the interval alignment area of ​​the first CGH4. The interval alignment area of ​​the first CGH4 is a transmission area. The spherical wave undergoes phase modulation through the interval alignment area of ​​the first CGH4 and is incident on the front surface of the second CGH6. The spherical wavefront is reflected by the front surface of the second CGH6 and, according to the law of reflection, is symmetrically reflected back to the interferometer along the normal of the center point of the second CGH6 to interfere with the reference light, thus obtaining the wavefront map of the interval alignment area of ​​the first CGH4. The interval error of the first CGH4 and the second CGH6 is calculated based on the PV value of the interval alignment area wavefront map. The first CGH4 and the second CGH6 are adjusted according to the interval error so that the interval error approaches 0 or meets the preset requirements. The formula for calculating the interval error between the first CGH4 and the second CGH6 is:

[0054] ;

[0055] in, For interval error, This represents the wavefront change caused by axial position deviation, i.e., the PV value resulting from defocusing (power). , Where is the focal length and D is the diameter of the incident pupil. The axial position deviation can be calculated from the positive or negative defocus value, and the interval error guides the adjustment of the interval between the first CGH4 and the second CGH6.

[0056] like Figure 4As shown, during the tilt error detection process, the plane standard mirror 32 is inserted into the optical path, and the interferometer 1 emits a probe light. The probe light is shaped into a plane wavefront by the plane standard mirror 32. The plane wavefront illuminates the tilt alignment area of ​​the first CGH4, which is the transmission area. After phase modulation by the tilt alignment area of ​​the first CGH4, the plane wavefront continues to be transmitted to the tilt alignment area of ​​the second CGH6, which is the reflection area. The tilt alignment area of ​​the second CGH6 reflects the plane wavefront back to the interferometer 1 for interference (i.e., it passes through the first CGH4 and the plane standard mirror 32 sequentially along the original optical path before entering the interferometer 1). The interferometer obtains the interference fringes corresponding to the tilt alignment area of ​​the second CGH6. The pose of the second CGH6 is adjusted by the second six-degree-of-freedom adjustment frame 7, and the relative tilt angle of the first CGH4 and the second CGH6 is adjusted until the interference fringes corresponding to the tilt alignment area of ​​the second CGH6 appear as zero fringes, thus completing the tilt alignment of the first CGH4 and the second CGH6.

[0057] like Figure 5 As shown, during the detection of eccentricity error, the spherical standard mirror 31 is inserted into the optical path, and the interferometer 1 emits a probe light. The probe light is shaped into a spherical wavefront by the spherical standard mirror 31. The spherical wavefront illuminates the eccentric alignment area of ​​the first CGH4, which is a transmission area. After phase modulation by the eccentric alignment area of ​​the first CGH4, the plane wavefront continues to be transmitted to the eccentric alignment area of ​​the second CGH6, which is a reflection area. The eccentric alignment area of ​​the second CGH6 reflects the spherical wavefront back to the interferometer 1 for interference. The interferometer obtains the interference fringes corresponding to the eccentric alignment area of ​​the second CGH6. The pose of the second CGH6 is adjusted by the second six-degree-of-freedom adjustment frame 7, and the relative deviation between the center points of the first CGH4 and the second CGH6 is adjusted until the interference fringes corresponding to the eccentric alignment area of ​​the second CGH6 appear as zero fringes. Then, the eccentric alignment of the first CGH4 and the second CGH6 is completed.

[0058] At this point, the alignment of the first CGH4 and the second CGH6 is complete. If there are other CGHs in the system that need adjustment, the first CGH4 or the second CGH6 can be used as a reference to form a CGH pair with another CGH, and the adjustment can be performed according to the above method until all CGHs are aligned. It should be noted that after a CGH has been adjusted and aligned, when using it as a reference to adjust other CGHs, the position and spatial orientation of the reference CGH must remain unchanged.

[0059] The alignment scheme of this invention has been experimentally verified, such as... Figure 6 and 7The diagram shows the interference fringes after eccentric adjustment of the first CGH4 and the second CGH6, respectively. The following data were obtained experimentally:

[0060] For two CGH4 and CGH6, both with a diameter of 300 mm, the method first uses an alignment region to adjust the interval between CGH4 and CGH6, achieving a positioning accuracy better than 0.5 micrometers. Then, using a tilt alignment region, the tilt of CGH4 and CGH6 is adjusted, achieving a relative tilt accuracy better than 0.01 degrees. Finally, using an eccentric alignment region, the eccentricity of CGH4 and CGH6 is adjusted, achieving a relative eccentricity accuracy better than 0.01 millimeters. This invention achieves alignment between CGHs, meeting high detection accuracy requirements; the alignment accuracy is far superior to existing technical solutions.

[0061] In summary, the above description is merely a preferred embodiment of this specification and is not intended to limit the scope of protection of this specification. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this specification should be included within the scope of protection of this specification.

[0062] The systems, apparatuses, modules, or units described in one or more of the above embodiments may be implemented by a computer chip or entity, or by a product having a certain function. A typical implementation device is a computer. Specifically, a computer may be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smartphone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or any combination of these devices.

[0063] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0064] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

Claims

1. A method of CGH alignment for aligning at least two CGHs, the at least two CGHs comprising a first CGH and a second CGH, characterized in that, The alignment process of the first CGH and the second CGH comprises: decomposing the alignment error of the first CGH and the second CGH into different-form error components; providing probe light by an interferometer, and arranging a shaping unit on the transmission light path of the probe light, the shaping unit being used for shaping the probe light into probe light of different wavefronts; matching the probe light of the corresponding wavefront for each error component according to the sensitivity of different-form error components to different wavefronts; arranging different alignment areas on the first CGH and the second CGH according to the matched error components and the corresponding wavefronts of the probe light; for any error component, controlling the shaping unit to shape the probe light into the wavefront probe light matched with the error component, irradiating the corresponding alignment area on the first CGH and the second CGH with the wavefront probe light matched with the error component, and adjusting the relative pose of the first CGH and the second CGH according to the interference fringes of the corresponding alignment area to suppress the error component.

2. The CGH alignment method of claim 1, wherein, The first CGH and the second CGH are respectively mounted on two six-degree-of-freedom adjustment frames, and the pose adjustment of the first CGH and the second CGH is realized by the six-degree-of-freedom adjustment frames.

3. The CGH alignment method of claim 1, wherein, The different-form error components comprise interval error, tilt error and eccentric error.

4. The CGH alignment method of claim 3, wherein, Tilt alignment areas and eccentric alignment areas are respectively arranged on the first CGH and the second CGH, and the first CGH is further provided with an interval alignment area.

5. The CGH alignment method of claim 4, wherein, The shaping unit is used for switching a spherical standard mirror or a planar standard mirror to the transmission light path of the probe light.

6. The CGH alignment method of claim 5, wherein, The suppression process of the interval error comprises: the probe light is processed into a spherical wave by the spherical standard mirror, the spherical wave is phase-modulated by the interval alignment area of the first CGH, and is incident to the second CGH, the phase-modulated spherical wave is symmetrically reflected back to the interferometer along the normal line of the center point of the second CGH to interfere, an interval alignment area wavefront graph is obtained, the interval error of the first CGH and the second CGH is calculated according to the PV value of the interval alignment area wavefront graph, and the first CGH and the second CGH are adjusted according to the interval error.

7. The CGH alignment method of claim 5, wherein, The suppression process of the tilt error comprises: the probe light is processed into a planar wave by the planar standard mirror, the planar wave is phase-modulated by the tilt alignment area of the first CGH, and is incident to the tilt alignment area of the second CGH, the phase-modulated planar wave is reflected back to the interferometer along the original incident light path by the tilt alignment area of the second CGH to interfere, and the relative tilt of the first CGH and the second CGH is adjusted until the tilt alignment area of the second CGH shows zero fringes.

8. The CGH alignment method of claim 5, wherein, The suppression process of the eccentric error comprises: the probe light is processed into a spherical wave by the spherical standard mirror, the spherical wave is phase-modulated by the eccentric alignment area of the first CGH, and the phase-modulated planar wave is reflected back to the interferometer along the original incident light path by the eccentric alignment area of the second CGH to interfere, and the relative eccentricity of the first CGH and the second CGH is adjusted until the tilt eccentric alignment area of the second CGH shows zero fringes.

9. The CGH alignment method of claim 4, wherein, The first CGH further comprises a main area, and the interval alignment area, the tilt alignment area and the eccentric alignment area of the first CGH are concentric circular rings and are nested in the outer periphery of the main area in sequence. The second CGH further comprises a main area, the tilt alignment area and the eccentric alignment area of the second CGH are concentric circular rings, and are nested in the outer periphery of the main area in sequence.

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