Compact high-precision pinhole phase shift point diffraction interference measurement device and method

Abstract

The invention discloses a compact high-precision pinhole phase shift point diffraction interference measurement device and method, and relates to the technical field of optical interference measurement, the compact high-precision pinhole phase shift point diffraction interference measurement device comprises a shell, the side wall of the shell is provided with a through hole, and the through hole is provided with a spherical lens; a diffracted light processing unit is obliquely mounted on the inner side wall of the upper end of the shell, a reflected light processing unit is obliquely mounted on the inner side wall of the lower end of the shell, and a unit to be tested is mounted outside the shell; the diffracted light processing unit emits to-be-tested light and reference light, the to-be-tested light irradiates a to-be-tested unit through the spherical lens, and the reference light and test light reflected by the to-be-tested unit irradiate the reflected light processing unit; and the diffracted light processing unit and the reflected light processing unit are electrically connected with the computer. According to the compact high-precision small hole phase shift point diffraction interference measuring device and method, high-precision absolute detection of the measured optical element is achieved, real-time visual monitoring can be achieved, and damage to human eyes during debugging is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of optical interference measurement, and in particular to a compact high-precision small-aperture phase-shift point diffraction interferometry measurement device and method. Background Art

[0002] With the development of major scientific projects such as aerospace, extreme ultraviolet lithography, and laser nuclear fusion, high-precision spherical optical components are widely used in many high-tech fields. Ultra-high processing precision requires ultra-high detection precision to match it. The current mainstream interference measurement devices are mainly Fizeau and Twyman-Green interferometers. Both interferometers use standard mirrors to generate reference light waves. Their detection accuracy is limited by the processing accuracy of the standard mirror and cannot meet the needs of ultra-precision surface detection. Point diffraction interferometer provides an excellent way for ultra-precision surface detection. This method does not require a standard mirror. It uses micron-level holes in the system to generate nearly ideal spherical waves. One part is used as reference light, and the other part is used as test light to detect the optical component to be tested. In theory, it can achieve nanometer or even sub-nanometer detection accuracy. At present, domestic research on point diffraction interferometers is still in the laboratory stage. There are four main factors that restrict the development of point diffraction interferometers into molding equipment: 1) Phase shift problem. Currently, conventional phase-shifting point diffraction interferometers mostly use large-load, high-precision piezoelectric ceramic phase shifters to move the test piece multiple times to introduce phase shift, and then use a multi-step phase shift algorithm to extract the phase, thereby obtaining the measured surface shape information. The larger the test piece, the higher the load capacity requirement for the piezoelectric ceramic phase shifter, and the corresponding piezoelectric ceramic phase shifter is more expensive. my country relies heavily on imports for large-load, high-precision piezoelectric ceramic phase shifters. Such piezoelectric ceramic phase shifters are expensive and have a long procurement cycle, which limits the development of my country's formed point diffraction equipment. Therefore, it is extremely necessary to develop a point diffraction interferometer that can be realized by relying on small-aperture, small-load piezoelectric ceramic phase shifters for phase shifting. 2) Conventional point diffraction interferometry optical paths are not conducive to instrumentation. Conventional point diffraction interferometry measurement systems generally divide the test light and reference light into two parts, upper and lower, and arrange the test light path and reference light path along two straight optical axes. Because the diffraction angle of the pinhole is very small, taking a 2μm pinhole as an example, its full diffraction angle is about 45°, so the angle between the test optical axis and the reference optical axis is also very small. Considering that the edge light of the diffracted beam is very weak and the full aperture is not utilized, the actual angle between the test optical axis and the reference optical axis can only reach within 20°, resulting in devices easily interfering with each other or blocking each other when arranging the optical path; the conventional optical path is too long and it is not easy to package the reference optical path and the diffraction front-end optical path into an integrated device; 3) Alignment of the reflected light spot of the DUT with the pinhole after diffraction. From the basic principle of point diffraction interferometry, it is known that the laser light emitted by the He-Ne laser produces a nearly ideal spherical wave after diffraction by the pinhole. After the diffracted light beam is transmitted to the surface of the DUT along the predetermined test optical axis, it will return along the original path carrying the surface shape information of the DUT and converge to the pinhole diffraction plate, forming a bright spot. Affected by the manual adjustment error of the DUT, the state of this light spot deviating from the center of the pinhole is uncertain. Only when this bright spot basically coincides with the center of the pinhole (i.e., aligned), can the central axis of the light beam reflected by the pinhole substrate basically coincide with the central axis of the reference optical path, that is, incident on the CCD image sensor along the predetermined test optical axis. Therefore, it is extremely necessary to realize visual monitoring of the alignment state of the reflected light spot of the DUT and the pinhole after diffraction. 4) Since the light beam diffracted by the pinhole is a divergent beam, it is only suitable for the detection of concave mirrors. If a spherical mirror is added in front to converge the light beam, forming a convergent beam or a parallel beam for detecting convex or flat surfaces, new spherical mirror errors will inevitably be introduced. Summary of the Invention

[0003] The purpose of the present invention is to provide a compact high-precision small-aperture phase-shift point diffraction interferometry measurement device and method to solve the problems listed in the background technology.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions: The present invention provides a compact high-precision small-aperture phase-shift point diffraction interferometry measurement device, comprising: The invention comprises a shell, wherein a through hole is formed on a side wall of the shell, and a spherical lens is mounted on the through hole; A diffraction light processing unit is obliquely mounted on the inner side wall of the upper end of the housing, a reflection light processing unit is obliquely mounted on the inner side wall of the lower end of the housing, a unit to be tested is mounted on the outside of the housing, and a cooling fan is also mounted on the side wall of the housing; The diffraction light processing unit emits a test light and a reference light, the test light passes through the spherical lens and is irradiated onto the unit to be tested, and the reference light and the test light reflected by the unit to be tested are both irradiated back to the reflected light processing unit; The diffraction light processing unit and the reflected light processing unit are both electrically connected to a computer.

[0005] Preferably, the diffraction light processing unit includes a He-Ne laser, a beam expansion and collimation system, a microscope objective lens, a diffraction aperture and a rear-end photosensitive array; The He-Ne laser is installed obliquely on the inner side wall of one end of the housing, and the laser light emitted by the He-Ne laser passes through the beam expansion and collimation system, the microscope objective lens, the diffraction aperture and the rear photosensitive array in sequence. The beam expansion and collimation system, the microscope objective lens, the diffraction aperture and the rear photosensitive array are all installed obliquely on the inner side wall of the housing; Furthermore, the He-Ne laser, the beam expansion and collimation system, the microscope objective lens, the diffraction aperture and the rear-end photosensitive array are all located on the same axis.

[0006] Preferably, a piezoelectric ceramic phase shifter is installed on the diffraction aperture, and the piezoelectric ceramic phase shifter drives the diffraction aperture to move with the same step length to generate phase shift.

[0007] Preferably, the reflected light processing unit includes a reflector, a collimator, an imaging lens and a CCD image sensor, wherein the reflector is parallel to the inner side wall of the housing, the CCD image sensor is arranged obliquely on the inner side wall of the lower end of the housing, and the imaging lens and the collimator are sequentially mounted between the CCD image sensor and the reflector; The reflecting mirror, the collimating mirror, the imaging lens and the CCD image sensor are all arranged in sequence on the same axis.

[0008] Preferably, the rear-end photosensitive array is bonded to the substrate of the diffraction aperture, and the rear-end photosensitive array is electrically connected to the computer.

[0009] Preferably, the CCD image sensor is electrically connected to the computer.

[0010] Preferably, the unit to be tested comprises an optical element to be tested and a six-dimensional adjustment frame, one end of the optical element to be tested faces the spherical lens, and the other end of the optical element to be tested is fixedly mounted on the six-dimensional adjustment frame.

[0011] Preferably, the optical element to be tested includes a concave mirror, a convex mirror or a plane mirror.

[0012] Preferably, the six-dimensional adjustment frame has the functions of X, Y, and Z three-dimensional translation, tilt and pitch around the Z axis, and rotation around the Z axis; during testing, the test piece is rotated equally around the Z axis within 360° i times, the i is a multiple of four, we get i Test surface of the optical element to be tested Wx , y ~ W i x , y , to obtain iThe average value of the test data Wx , y ,use Wx , y minus Wx , y That is, the errors of the added spherical lens and the diffraction reference wave surface itself are separated from the surface shape information obtained by multiple rotations, and the high-precision absolute surface shape of the optical component to be tested is detected.

[0013] A measurement method for a compact high-precision small-aperture phase-shift point diffraction interferometry device comprises the following steps: Step 1: After the front-end optical path calibration is completed, the CCD image sensor can collect a bright circular light spot 1, which is the reference light. The optical component to be tested is placed at its curvature radius. The tilt and pitch directions of the five-dimensional adjustment frame are adjusted so that the light spot 2 corresponding to the test light converges to a point and falls on the back-end photosensitive array. The generated optical signal is converted into an electrical signal and sent to the computer's host monitoring software; Step 2: Monitor the position of the second light spot displayed on the computer and continue to adjust the optical element to be tested in the tilt and pitch directions until the second light spot is located in the hollow area of the rear photosensitive array, completing the rough alignment of the front optical path and the diffraction aperture; Step 3: The alignment between the back-end optical path and the diffraction pinhole is collected in real time by a CCD image sensor in the back-end optical path and monitored in real time by a connected computer. The two-dimensional position of the second light spot on the plane where the pinhole is located is adjusted until interference fringes are observed on the computer. Step 4: Continue to adjust the X and Y directions of the optical element to be tested so that the center of the interference fringe ring is located in the center of the interference area for subsequent adjustments; Step 5: Adjust the Z-axis direction of the optical element to be tested so that the number of interference fringe rings is minimized, and the alignment of the rear optical path and the diffraction aperture is completed; Step 6: Operate the piezoelectric ceramic phase shifter to move the corresponding step length. At this time, the CCD image sensor obtains multiple interference fringe images with different phases. The collected images are processed online by a computer to obtain the surface shape information of the optical component to be tested.

[0014] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention has a compact structure, a simple principle, low cost and convenient operation. The size of the device is reduced by phase shifting the pinhole and using a turning optical path, while also ensuring high-precision measurement. At the same time, a photosensitivity component for indicating the position of the reflected light spot of the tested piece is added to the rear end of the pinhole, so that real-time visual monitoring of the alignment between the reflected light spot of the optical element to be tested and the center of the diffraction pinhole can be achieved, which not only improves the alignment accuracy but also reduces the damage to the human eye during debugging. Furthermore, adding or replacing different spherical lenses at the output end of the test light path can realize surface shape detection of various optical elements to be tested, such as convex, concave and flat surfaces, and further combined with multiple rotation detection of the tested piece, high-precision absolute detection of the tested optical element can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will be further described below with reference to the accompanying drawings.

[0016] Figure 1 This is a schematic diagram of concave mirror detection in a compact, high-precision, small-aperture phase-shift point diffraction interferometry device according to the present invention; Figure 2 This is a schematic diagram of a convex mirror detection device for a compact, high-precision, small-aperture phase-shift point diffraction interferometry measurement device according to the present invention; Figure 3 This is a schematic diagram of a plane mirror detection device for a compact, high-precision, small-aperture phase-shift point diffraction interferometry measurement device according to the present invention; Figure 4 A schematic side view of the rear-end photosensitive array of the present invention; Figure 5 It is a three-dimensional schematic diagram of the back-end photosensitive array of the present invention.

[0017] Explanation of the accompanying symbols: 1. He-Ne laser; 2. Beam expansion and collimation system; 3. Microscope objective lens; 4. Piezoelectric ceramic phase shifter; 5. Diffraction aperture; 6. Back-end photosensitive array; 7. Spherical lens; 8. Optical element to be tested; 9. Six-dimensional adjustment frame; 10. Reflector; 11. Collimating lens; 12. Imaging lens; 13. CCD image sensor; 14. Computer; 15. Housing. DETAILED DESCRIPTION

[0018] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0019] like Figure 1-Figure 5 As shown, a compact high-precision small-aperture phase-shift point diffraction interferometry device and method comprises: a housing 15, a through hole is formed in the side wall of the housing 15, and a spherical lens 7 is mounted on the through hole. The parameters of the spherical lens 7 can be increased, decreased or replaced according to the different optical elements to be tested; A diffraction light processing unit is installed obliquely on the inner side wall of the upper end of the housing 15, and a reflection light processing unit is installed obliquely on the inner side wall of the lower end of the housing 15. The unit to be tested is installed outside the housing 15. A cooling fan is also installed on the side wall of the housing 15 to reduce the temperature inside the housing and reduce the heat generated by various components inside the housing. The diffraction light processing unit emits the test light and the reference light, the test light passes through the spherical lens 7 and is irradiated onto the unit to be tested, and the reference light and the test light reflected by the unit to be tested are both irradiated back to the reflected light processing unit; The diffraction light processing unit and the reflected light processing unit are both electrically connected to the computer 14 .

[0020] Specifically, the diffraction light processing unit includes a He-Ne laser 1, a beam expansion and collimation system 2, a microscope objective 3, a diffraction aperture 5 and a rear-end photosensitive array 6; The He-Ne laser 1 is installed obliquely on the inner side wall of one end of the housing 15. The laser light emitted by the He-Ne laser 1 passes through the beam expansion and collimation system 2, the microscope objective lens 3, the diffraction aperture 5 and the rear photosensitive array 6 in sequence. The beam expansion and collimation system 2, the microscope objective lens 3, the diffraction aperture 5 and the rear photosensitive array 6 are all installed obliquely on the inner side wall of the housing 15. Furthermore, the He-Ne laser 1, the beam expansion and collimation system 2, the microscope objective lens 3, the diffraction aperture 5 and the rear-end photosensitive array 6 are all located on the same axis.

[0021] Specifically, a piezoelectric ceramic phase shifter 4 is installed on the diffraction aperture 5, and the piezoelectric ceramic phase shifter 4 drives the diffraction aperture 5 to move the same step size to produce phase shift, thereby obtaining a set of interference images with different phase shift amounts for restoring the surface shape to be measured; the CCD image sensor 13 is electrically connected to the computer 14, and the CCD image sensor 13 can collect multiple interference images with different phases and be received by the CCD image sensor 13.

[0022] Specifically, the reflected light processing unit includes a reflector 10, a collimator 11, an imaging lens 12, and a CCD image sensor 13. The reflector 10 is parallel to the inner side wall of the housing 15. The CCD image sensor 13 is arranged obliquely on the inner side wall of the lower end of the housing 15. The imaging lens 12 and the collimator 11 are sequentially installed between the CCD image sensor 13 and the reflector 10. The reflector 10, the collimating mirror 11, the imaging lens 12 and the CCD image sensor 13 are sequentially arranged on the same axis; Furthermore, a cooling plate and a temperature sensor are installed on the outer surface of the CCD image sensor 13. Through the PID controller, the CCD image sensor 13 is kept in a suitable temperature range to ensure measurement accuracy.

[0023] like Figure 4-Figure 5 As shown, the rear photosensitive array 6 is bonded to the substrate of the diffraction pinhole 5, and the rear photosensitive array 6 is electrically connected to the computer 14, so that the diffraction pinhole is located in the central hollow area of the photosensitive array with holes. The test light reaches the surface of the optical element to be tested and is reflected, carrying the surface shape information of the optical element to be tested back to the rear surface of the diffraction pinhole. The reflected test light hits the rear photosensitive array, and the upper computer software of the computer (14) will display the light spot deviation position. The position of the optical element to be tested is adjusted so that the reflected light spot hits the hollow area of the photosensitive array, indicating that the preliminary light spot is preliminarily aligned with the pinhole. Furthermore, the back-end photosensitive array is composed of 988 photosensitive units, of which 912 photosensitive units are arranged in the four quadrants of the rectangular circuit board in a rectangular array, and 76 photosensitive units are arranged in the center line of the rectangular circuit board in a cross array. The maximum horizontal and vertical detection distances are both 50 mm, and the spacing between single photosensitive units does not exceed 0.7 mm. The diffraction holes are embedded in the hollow area of the two circuit boards. The hollow circle in the center of the circuit board allows the laser to emit a nearly ideal spherical wave through the diffraction holes without being blocked by the photosensitive array; when the reflected light spot of the test piece hits the photosensitive array, the spatial position of the light spot in the cross area can be obtained through the computer host visual monitoring software, and then the light spot can be further adjusted according to the distance between the photosensitive unit and the center of the diffraction hole; so that the number of interference fringe rings observed on the computer is the least, that is, the optimal alignment state, and interference fringe collection can be performed at this time.

[0024] Specifically, the unit to be tested includes an optical element to be tested 8 and a six-dimensional adjustment frame 9, one end of the optical element to be tested 8 faces the spherical lens 7, and the other end of the optical element to be tested 8 is fixedly mounted on the six-dimensional adjustment frame 9, which is used to provide surface shape information to be tested. By adding or replacing different spherical lenses, different optical elements can be adapted for detection.

[0025] Specifically, the optical element 8 to be tested includes a concave mirror, a convex mirror or a plane mirror.

[0026] During operation, the laser light emitted by the He-Ne laser passes through the beam expansion and collimation system, the microscope objective lens and the diffraction pinhole in sequence to generate a nearly ideal spherical wave, which is divided into the test light and the reference light; the reference light passes through the reflector, the collimator lens and the imaging lens in sequence and is received by the CCD image sensor; the test light reaches the surface of the optical element to be tested and is reflected. The test light carrying the surface information of the optical element to be tested returns along the original path, reaches the diffraction pinhole substrate, is reflected by the surface of the rear-end photosensitive array to the reflector and then turns to the reference light path. During this period, the test light and the reference light interfere with each other, and the interference image is finally collected by the CCD image sensor and received by the computer.

[0027] Specifically, the six-dimensional adjustment frame 9 has the functions of X, Y, and Z three-dimensional translation, tilt and pitch around the Z axis, and rotation around the Z axis; during testing, the test piece is rotated equally around the Z axis within 360°. i times, the i is a multiple of four, we get i Test surface of the optical element to be tested W 1 x , y - W i x , y , to obtain i The average value of the test data Wx , y ,use W 1 x , y minus Wx , y That is, the errors of the added spherical lens and the diffraction reference wave surface itself are separated from the surface shape information obtained by multiple rotations, and the high-precision absolute surface shape of the optical component to be tested is detected.

[0028] A measurement method for a compact high-precision small-aperture phase-shift point diffraction interferometry device comprises the following steps: Step 1: After the front-end optical path calibration is completed, the CCD image sensor 13 can collect a bright circular light spot 1, which is the reference light. The optical element 8 to be tested is placed at its curvature radius, and the tilt and pitch directions of the five-dimensional adjustment frame are adjusted so that the light spot 2 corresponding to the test light converges to a point and falls on the rear-end photosensitive array 6. The generated optical signal is converted into an electrical signal and transmitted to the host monitoring software of the computer 14; Step 2: Monitor the position of the second light spot displayed on the computer 14 and continue to adjust the optical element 8 to be tested in the tilt and pitch directions until the second light spot is located in the hollow area of the rear photosensitive array 6, completing the rough alignment of the front optical path and the diffraction aperture; Step 3: The alignment between the rear optical path and the diffraction aperture is collected in real time by the CCD image sensor 13 of the rear optical path and monitored in real time by the computer 14 connected thereto, and the two-dimensional position of the second light spot on the plane where the aperture is located is adjusted until interference fringes are observed on the computer 14; Step 4: Continue adjusting the X and Y directions of the optical element to be tested 8 so that the center of the interference fringe ring is located at the center of the interference area for subsequent adjustment; Step 5: Adjust the Z-axis direction of the optical element to be tested 8 so that the number of interference fringe rings is minimized, and the alignment of the rear optical path and the diffraction aperture is completed; Step 6: Operate the piezoelectric ceramic phase shifter 4 to move the corresponding step length. At this time, the CCD image sensor 13 obtains multiple interference fringe images with different phases. The collected images are processed online by the computer 14 to obtain the surface shape information of the optical element 8 to be tested.

[0029] Example 1

[0030] like Figure 1 As shown in the figure, an embodiment of testing a concave mirror is shown. Taking a 2μm diffraction pinhole as an example, its full diffraction angle is about 45°. A diffraction range of 22° is taken to cover the test optical path. The angles between the test light and the reference light and the central axis of the diffracted beam are both 11°. Without adding the spherical lens 7, the numerical aperture NA of the tested concave mirror should be ≤ sin11°. To comply with usage habits, the entire optical path is rotated 11° clockwise so that the test optical axis is emitted horizontally and perpendicular to the vertical surface of the shell. The tested object is arranged along the test optical axis O1, and the center of the pinhole is substantially coincident with the center of curvature of the vertex of the tested object.

[0031] Example 2

[0032] like Figure 2 As shown, this is an embodiment of detecting a convex mirror. A spherical lens is added to the test light path so that the light beams emitted from the pinhole intersect at one point after passing through the spherical lens. The detection can be achieved by adjusting the curvature center of the convex mirror to coincide with the intersection point after the spherical lens.

[0033] Example 3

[0034] like Figure 3 As shown in the figure, an embodiment of plane mirror detection is used. Taking a 2μm diffraction aperture as an example, its full diffraction angle is about 45°. A diffraction range of 22° is taken to cover the test light path. A spherical lens with a diameter of D=60 and a focal length of 150mm is selected for light path collimation. The focus of the spherical lens coincides with the diffraction aperture, and the output parallel light is directly incident on the plane mirror to be tested. At this time, the aperture of the plane mirror to be tested shall not exceed 60mm.

[0035] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0036] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A compact high-precision small-aperture phase-shift point diffraction interferometry device, characterized in that: It comprises a shell (15), a side wall of the shell (15) is provided with a through hole, a spherical lens (7) is mounted on the through hole, and a cooling fan is also mounted on the side wall of the shell (15); A diffraction light processing unit is obliquely mounted on the inner side wall of the upper end of the housing (15), a reflection light processing unit is obliquely mounted on the inner side wall of the lower end of the housing (15), and a unit to be tested is mounted on the outside of the housing (15); The diffraction light processing unit emits the light to be tested and the reference light, the light to be tested passes through the spherical lens (7) and is irradiated onto the unit to be tested, and the reference light and the test light reflected by the unit to be tested are both irradiated back to the reflected light processing unit; The diffraction light processing unit and the reflected light processing unit are both electrically connected to a computer (14).

2. A compact high-precision pinhole phase-shift point diffraction interferometry device according to claim 1, characterized in that: The diffraction light processing unit includes a He-Ne laser (1), a beam expansion and collimation system (2), a microscope objective lens (3), a diffraction aperture (5) and a rear-end photosensitive array (6); The He-Ne laser (1) is installed obliquely on the inner side wall of one end of the housing (15); the laser light emitted by the He-Ne laser (1) passes through the beam expansion and collimation system (2), the microscope objective lens (3), the diffraction pinhole (5) and the rear photosensitive array (6) in sequence; the beam expansion and collimation system (2), the microscope objective lens (3), the diffraction pinhole (5) and the rear photosensitive array (6) are all installed obliquely on the inner side wall of the housing (15); Furthermore, the He-Ne laser (1), the beam expansion and collimation system (2), the microscope objective lens (3), the diffraction aperture (5) and the rear-end photosensitive array (6) are all located on the same axis.

3. The compact high-precision small-aperture phase-shift point diffraction interferometry device according to claim 2, characterized in that: A piezoelectric ceramic phase shifter (4) is mounted on the diffraction aperture (5), and the piezoelectric ceramic phase shifter (4) drives the diffraction aperture (5) to move with the same step length to generate phase shift.

4. The compact high-precision small-aperture phase-shift point diffraction interferometry device according to claim 1, characterized in that: The reflected light processing unit comprises a reflector (10), a collimator (11), an imaging lens (12) and a CCD image sensor (13); the reflector (10) is parallel to the inner side wall of the housing (15); the CCD image sensor (13) is arranged obliquely on the inner side wall of the lower end of the housing (15); the imaging lens (12) and the collimator (11) are sequentially mounted between the CCD image sensor (13) and the middle portion of the reflector (10); The reflector (10), the collimating mirror (11), the imaging lens (12), and the CCD image sensor (13) are all arranged in sequence on the same axis.

5. The compact high-precision small-aperture phase-shift point diffraction interferometry device according to claim 2, characterized in that: The rear-end photosensitive array (6) is bonded to the substrate of the diffraction aperture (5), and the rear-end photosensitive array (6) is electrically connected to the computer (14).

6. The compact high-precision pinhole phase-shift point diffraction interferometry device according to claim 4, characterized in that: The CCD image sensor (13) is electrically connected to the computer (14).

7. The compact high-precision pinhole phase-shift point diffraction interferometry device according to claim 1, characterized in that: The unit to be tested comprises an optical element to be tested (8) and a six-dimensional adjustment frame (9), one end of the optical element to be tested (8) faces the spherical lens (7), and the other end of the optical element to be tested (8) is fixedly mounted on the six-dimensional adjustment frame (9).

8. The compact high-precision pinhole phase-shift point diffraction interferometry device according to claim 7, characterized in that: The optical element (8) to be tested includes a concave mirror, a convex mirror or a plane mirror.

9. The compact high-precision small-aperture phase-shift point diffraction interferometry device according to claim 7, characterized in that: The six-dimensional adjustment frame (9) has the functions of X, Y, and Z three-dimensional translation, tilting and pitching around the Z axis, and rotating around the Z axis; during testing, the tested piece is rotated equally around the Z axis within 360 degrees. i times, the i is a multiple of four, we get i Test surface of the optical element to be tested W 1( x , y )~ W i ( x , y ), and obtain i The average value of the test data W ( x , y ),use W 1( x , y )minus W ( x , y ) That is, the errors of the added spherical lens and the diffraction reference wave surface itself are separated from the surface shape information obtained by multiple rotations, and the high-precision absolute surface shape of the optical component to be tested is detected.

10. The measurement method of a compact high-precision small-aperture phase-shift point diffraction interferometry device according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1: After the front-end optical path calibration is completed, the CCD image sensor (13) can collect a bright circular light spot 1, which is the reference light. The optical element to be tested (8) is placed at its curvature radius, and the tilt and pitch directions of the five-dimensional adjustment frame are adjusted so that the light spot 2 corresponding to the test light converges at one point and falls on the rear-end photosensitive array (6). The generated light signal is converted into an electrical signal and reaches the host monitoring software of the computer (14); Step 2: monitor the position of the second light spot displayed on the computer (14) and continue to adjust the optical element to be tested (8) in the tilt and pitch directions until the second light spot is located in the hollow area of the rear photosensitive array (6), completing the rough alignment of the front optical path and the diffraction aperture; Step 3: The alignment between the rear optical path and the diffraction pinhole is collected in real time by a CCD image sensor (13) of the rear optical path and monitored in real time by a computer (14) connected thereto, and the two-dimensional position of the second light spot on the plane where the pinhole is located is adjusted until interference fringes are observed on the computer (14); Step 4: Continue adjusting the X and Y directions of the optical element to be tested (8) so that the center of the interference fringe ring is located at the center of the interference area for subsequent adjustment; Step 5: Adjust the Z-axis direction of the optical element to be tested (8) so that the number of interference fringe rings is minimized, and the alignment of the rear end optical path and the diffraction aperture is completed; Step 6: Operate the piezoelectric ceramic phase shifter (4) to move the corresponding step length. At this time, the CCD image sensor (13) obtains multiple interference fringe images with different phases. The collected images are processed online by the computer (14) to obtain the surface shape information of the optical element to be tested (8).

Images