CN117589083B - Method and device for precisely detecting structural surface shape of micro-optical element in situ - Google Patents
Method and device for precisely detecting structural surface shape of micro-optical element in situ Download PDFInfo
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- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
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Abstract
The invention provides a method for precisely detecting the structural surface shape of a micro-optical element in situ, which comprises the following steps: placing a white light interferometer on a first rotating shaft of a machine tool, and placing a workpiece on a second rotating shaft of the machine tool; adjusting the optical axis of the lens of the white light interferometer to coincide with the center of a second rotating shaft of the machine tool; processing the workpiece, and keeping the position of the workpiece on the second rotating shaft unchanged; the white light interferometer responds to a trigger signal sent by the machine tool, and shoots the structural surface type of the processed workpiece for a plurality of times according to a planned moving path; the structural surface shape includes a gentle structure and a steep structure. Also provided is an in-situ precision detection micro-optical element structure surface type device, comprising: the system comprises a machine tool, a white light interferometer, a splicing path planning and control system and graph splicing and synthesizing software. The invention can realize in-situ precise detection of the micro-optical element and better assist the high-precision processing of the micro-optical element.
Description
Technical Field
The invention relates to the technical field of in-situ measurement of microstructures manufactured by high-end equipment, in particular to a method and a device for in-situ precise detection of the structural surface type of a micro-optical element.
Background
In recent years, the miniaturization of optical instruments and the development of micro-system engineering are urgent to require the miniaturization of system structures and optical elements, and corresponding micro-optical concepts are proposed in the system structures and the optical elements, and mainly refer to optical surface microstructures with micrometer dimensions; micro-optical elements are widely used in various high-end equipment manufacturing scenarios; the processing difficulty is high, so that the method is one of the most advanced research directions internationally.
In the prior art, the micro-optical element is generally processed by adopting a photoetching and single-point diamond turning processing mode, a workpiece is required to be taken down for detection after processing, and the workpiece is installed on a machine tool for reprocessing if the workpiece is not required after detection. For example, the publication number is CN113340232A, a white light interferometry splicing measurement device and method of the surface profile of a tiny optical part is provided, a vibration isolation platform of the device is respectively provided with a Z-direction translation adjustment mechanism and a four-axis adjustment table, the Z-direction translation adjustment mechanism is provided with a white light interferometer with an interference microscope objective, the four-axis adjustment table is provided with a pitching turntable rotating around the Y direction, the pitching turntable is provided with a revolving turntable rotating around the Z direction, the revolving turntable is provided with a centering mechanism, the centering mechanism is provided with an elastic clamp for installing the optical part to be measured, and the axes of the pitching turntable and the revolving turntable are intersected at the center of the curvature radius of the optical part to be measured; when the device is used, the optical part to be tested needs to be installed in the elastic clamp. However, due to the small structural size of the micro-optical element, repeated installation and positioning accuracy is limited, and the micro-optical element can not be completely returned to the original position after being installed, so that repeated reworking can not be realized.
In view of the foregoing, there is a need for a device and a method for precisely detecting the structural surface shape of a micro-optical element in situ, so as to implement high-precision processing and measurement of the micro-optical element.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention provides a method and a device for precisely detecting the structural surface type of a micro-optical element in situ, so as to solve the technical problem that the micro-optical element can not be precisely detected in situ in the prior art.
The technical scheme adopted by the invention is as follows: in a first aspect, a method for precisely detecting a micro-optical element structure surface shape in situ is provided, which includes:
Placing a white light interferometer on a first rotating shaft of a machine tool, and placing a workpiece on a second rotating shaft of the machine tool;
adjusting the optical axis of the lens of the white light interferometer to coincide with the center of a second rotating shaft of the machine tool;
Processing the workpiece, and keeping the position of the workpiece on the second rotating shaft unchanged;
and the white light interferometer responds to a trigger signal sent by the machine tool, and shoots the structural surface type of the processed workpiece for a plurality of times according to the planned moving path.
Further, the structural surface shape includes a gentle structure and a steep structure.
Further, when detecting a gentle structure, the moving path and the photographing mode of the white light interferometer are as follows:
The white light interferometer moves along three linear displacement axes of the machine tool respectively, and an initial coordinate point of a moving path is (x 0,y0,z0); scanning the first horizontal structure region one by one in the transverse direction by using a white light interferometer, and respectively shooting from an initial coordinate point to a coordinate point (x n,y0,zn) until the first horizontal structure region is completely shot; translating the Y-axis coordinate according to the shooting moving step length, and scanning one by one in the transverse direction by using a white light interferometer until the second transverse area structure is completely shot; and moving the Y-axis coordinate for a plurality of times according to the shooting moving step length, and repeating the shooting process until the shooting of all the structures is completed.
Further, for a gentle structure, the planned moving path of the white light interferometer has coordinate points satisfying the following relationship:
The coordinate point is on the X-axis, and the Y-axis satisfies the following equation:
xn＝x0+n×tx
yn＝y0+n×ty
in the above formula, X 0 is an initial coordinate point on the X axis, Y 0 is an initial coordinate point on the Y axis, t x,ty is shooting moving step length in the X direction and the Y direction respectively, and the value range is determined according to the shooting view field range of the lens of the white light interferometer; n represents an nth coordinate point;
the coordinate point satisfies the following equation in the Z axis:
In the above-mentioned description of the invention, R is the curvature radius of a curved surface, k is a conic coefficient constant term, and a i is an aspheric higher-order coefficient.
Further, when detecting a steep structure, the moving path and the photographing mode of the white light interferometer are as follows:
The white light interferometer moves along two linear displacement axes and a first rotation axis of the machine tool respectively, an initial coordinate point of a moving path is (x 0,y0,z0,B0,C0), and after shooting of the initial coordinate point is completed, the white light interferometer moves to a next coordinate point (x 1,y0,z1,B1,C0) to shoot; shooting by moving the coordinate point for a plurality of times until the white light interferometer reaches the structure position (x n,y0,zn,Bn,C0) of the last transverse point; rotating the second rotating shaft by an angle, moving the white light interferometer to an initial position (x 0,y0,z0,B0,C1) for shooting, then moving to a next point coordinate (x 1',y0,z1',B1',C1) for shooting, and sequentially moving to a transverse final point position (x n',y0,zn',Bn',C1) for shooting in this way; and sequentially rotating the angles of the second rotating shafts until all the structures are shot.
Further, when a moving path of the white light interferometer is planned, a coordinate point is always generated along the normal direction of a curved surface center point in a shooting view field of the white light interferometer; and the optical axis of the lens of the white light interferometer is parallel to the normal direction of the region to be measured at each coordinate point, and the virtual focus of the lens of the white light interferometer is located on the surface of the region to be measured.
Further, for a steep structure, the planned moving path of the white light interferometer has coordinate points satisfying the following relationship:
The coordinate point is on the X axis, and the B axis satisfies the following equation:
Bn＝f′(x′n),x′n＝x0+n×tx
In the above formula, S is the distance between a point A 0 and a point B 0, a point A 0 is the virtual focus of the lens of the white light interferometer, a point B 0 is the rotation center of the rotation shaft of the B axis, θ is the included angle between the connecting line of A 0 and B 0 and the moving direction of the Z axis, t x is the shooting moving step length of the X direction, and the value range is determined according to the shooting view field range of the lens of the white light interferometer; n represents an nth coordinate point; x 0 is the initial coordinate point;
the coordinate point satisfies the following equation in the Z axis:
zn＝z0-2×f(x′n,0)+S×cos(θ)-S×cos(Bn+θ)
in the above equation, Z 0 is an initial coordinate point on the Z axis.
Further, the method further comprises the step of splicing the shot pictures, and fitting and analyzing the surface structure of the microstructure to be detected.
In a second aspect, an in-situ precision detection micro-optical element structure surface type device is provided, which is configured to implement the in-situ precision detection micro-optical element structure surface type method in the first aspect, and includes:
A machine tool comprising at least 3 linear displacement axes and at least 2 rotation axes;
the white light interferometer and the workpiece are respectively arranged on different rotating shafts;
The splicing path planning and control system is used for calculating a moving track coordinate point of the white light interferometer in the shooting process and controlling the white light interferometer to move and shoot according to the coordinate point; and
And the graph splicing and synthesizing software is used for splicing the shot pictures.
Further, according to the detection requirement, the working distance of the lens of the white light interferometer is increased and/or the size of the lens is reduced.
According to the technical scheme, the beneficial technical effects of the invention are as follows:
1. The in-situ precise detection of the gentle structure and the steep structure of the micro-optical element can be realized, and the high-precision processing of the micro-optical element can be better assisted;
2. the machine tool rotating shaft rotates to shoot and splice, so that the in-situ precise detection of the large-caliber high-steep micro-optical structure can be realized.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. Like elements or portions are generally identified by like reference numerals throughout the several figures. In the drawings, elements or portions thereof are not necessarily drawn to scale.
FIG. 1 is a schematic diagram of an in-situ precision detection device according to an embodiment of the present invention;
FIG. 2 is a schematic view of a micro-optical device structure according to an embodiment of the present invention;
FIG. 3 is a schematic view of a flat structure of a micro-optical device according to an embodiment of the present invention;
FIG. 4 is a schematic diagram showing the positions of a lens focus A0 and a rotation center B0 of a rotation B axis of a white light interferometer according to an embodiment of the present invention;
Fig. 5 is a schematic diagram of a lens position of a white light interferometer with a rotary B-axis 4 shooting structure according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of capturing positions 1, 2, and 3 of a steep structure of a micro-optical element according to an embodiment of the invention;
fig. 7 is a schematic diagram of capturing positions 4, 5, 6 of a steep structure of a micro-optical element according to an embodiment of the invention;
FIG. 8 is a schematic diagram of the photographing positions 7, 8, 9 of the steep structure of the micro-optical element according to an embodiment of the invention;
FIG. 9 is a schematic view showing a 3×3 image stitching process for rotating the B-axis of a steep structure of a micro-optical element according to an embodiment of the invention;
reference numerals:
1-X axis of lathe; 2-Y axis of lathe; 3-Z axis of lathe; 4-rotating the B shaft by a lathe; 41-white light interferometer, 411-white light interferometer lens; 42-knife holder knife; 43-the rotation center of the lathe B shaft; 5-turning the C shaft by a lathe; 51-a workpiece; 52-the center of the workpiece.
Detailed Description
Embodiments of the technical scheme of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are only for more clearly illustrating the technical aspects of the present invention, and thus are merely examples, and are not intended to limit the scope of the present invention.
It is noted that unless otherwise indicated, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this application belongs.
Examples
For ease of understanding, offline detection, online detection, and in-situ detection will be described first.
Offline detection: after the workpiece is machined, the workpiece is taken off the machine tool and detected beside the machine tool or in a detection chamber. The method is characterized in that the offline detection can only detect the result after processing, can not reflect the actual condition during processing, and can not continuously detect the change of the processing process.
And (3) online detection: i.e. the workpiece is simultaneously inspected during the machining process. The method is characterized by continuously detecting the change in the processing process and knowing the error distribution and development in the processing process; in-line detection is limited by some conditions in the process because it is performed during the process.
And (3) in-situ detection: after the workpiece is machined, the workpiece is detected under the condition that the workpiece is not dismounted on the machine tool. The method is characterized in that errors caused by positioning references during off-line detection, such as positioning reference displacement caused by manufacturing errors of the positioning references on a workpiece due to misalignment of the positioning references used during processing and the positioning references used during detection, can be avoided.
Aiming at the defects of the prior art, the embodiment provides a device for precisely detecting the structural surface type of a micro-optical element in situ, which comprises an ultra-precise machine tool, a white light interferometer, a splicing path planning and control system and graphic splicing and synthesizing software.
In this embodiment, for ease of understanding, the ultra-precise machine is exemplified by a lathe, and as shown in fig. 1, the machining axes of the ultra-precise machine include an X axis 1, a Y axis 2, a Z axis 3, a B axis 4, and a C axis 5. Wherein X, Y, Z shafts are high-precision linear displacement shafts, all adopt fully-constrained oil hydrostatic closed guide rails, and the motion precision is within 0.3 mu m; the B axis and the C axis are high-precision rotating shafts, and the position precision reaches +/-1 radian second.
The white light interferometer 41 is arranged on the B axis of the ultra-precise lathe, and can rotate 360 degrees around the B axis; the B axis is arranged on the Z axis, and the white light interferometer can perform linear motion along the Z axis. In a specific embodiment, the selection of the white light interferometer is not limited and may be implemented in any manner achievable in the prior art. The lens of the white light interferometer is detachable, and different multiplying power lenses can be selected according to the outline dimension characteristics of the microstructure.
The splicing path planning and control system selects an industrial personal computer matched with the ultra-precise lathe as a carrier, and the splicing path planning is mainly used for calculating a moving track coordinate point of the white light interferometer in the shooting process and can be realized through a processing software coordinate point calculation function matched with the ultra-precise lathe; and the white light interferometer is controlled to move and shoot according to the coordinate points.
The graph splicing and synthesizing software is used for splicing the shot pictures; the implementation is not limited and may be implemented in any way possible in the prior art.
The device for precisely detecting the structural surface type of the micro-optical element in-situ processing has the following working principle:
Moving the lens focus of the white light interferometer to the position of a workpiece 51 (the workpiece is a micro-optical element which needs to be processed and detected), and planning a splicing path according to the structural shape of the workpiece to be detected; then the white light interferometer relies on high-precision motion axes of the ultra-precise lathe, each axis moves according to the planned path point, and stops when the axes move to a preset position, a trigger signal is sent to the white light interferometer, a shooting signal of the white light interferometer is triggered, after single shooting is completed, the white light interferometer is fed back to a lathe moving signal, and each axis moves to the next position according to the planned path point to continue shooting; and finally, splicing the shot pictures, and carrying out fitting analysis to obtain the surface structure of the microstructure to be measured.
In some embodiments, the later white light interference system needs to splice the photographed pictures, so when two adjacent pictures are photographed, the pictures need to have a superposition position, and the superposition ratio is determined according to the structural appearance characteristics.
For micro-optical elements, the structural surface type can be mainly divided into a gentle structural surface type and a steep structural surface type. For the two different structural surface types, different path planning methods are adopted by the splicing path planning and control system respectively. In this embodiment, when the slope of the microstructure edge of the micro-optical element is less than or equal to 15 °, defining such a structural surface as a gentle structure; when the slope of the microstructure edge of the micro-optical element is larger than 15 degrees, the structural surface shape is defined as a steep structure.
Processing and in-situ precision detection of a gentle structure of a micro-optical element, comprising:
1. Placing a small white light interferometer 41 on a five-axis single-point diamond lathe rotation B axis 4 as shown in FIG. 1;
2. The optical axis of the lens of the white light interferometer 41 is adjusted to coincide with the center of the rotating C-axis 5 of the lathe, and the coordinate 1 is recorded;
3. Placing a workpiece on a lathe rotary C shaft 5;
4. Rotating the lathe to rotate the B shaft 4, aligning the cutter 42 with the rotation center of the workpiece 51, recording the coordinates 2, and processing the workpiece;
5. The lathe rotates the B shaft 4, rotates and moves to the position of the coordinate 1, adjusts the white light interferometer 41 to a proper position, enables the edge of the processed workpiece structure 51 to appear in the lens, and generates interference light spots, and records the coordinate 3;
6. Setting the movement step length of a lathe according to the size of the shot view field of the selected lens, then programming, starting from the starting point coordinate 3, gradually moving the step length distance, and then shooting. As shown in fig. 2, the lens of the white light interferometer 41 is located at the position 1, then photographing is performed, a trigger signal is sent to the lathe after photographing, the lathe moves to the position 2 for photographing again, and the lathe moves to the position 3 for photographing after photographing. Each photographing has an overlapping area for later picture splicing calculation;
7. After the transverse splicing is completed, the lathe Y-axis 2 is moved according to the shooting moving step length, and the shooting of the moving Y-axis has the same overlapping area. Repeating the step 6, photographing at the positions 4, 5, 6, 7, 8 and 9 respectively in sequence, finally obtaining 9 data as shown in figure 3, and then calculating and splicing the data according to the overlapping area;
8. And inputting theoretical structural parameters, and calculating the three-dimensional point cloud. Then generating the combined data into an actual measurement three-dimensional point cloud with the same format; and then, calculating the difference value of the two three-dimensional point clouds to obtain structural face type errors or other required data.
When the gentle structure is subjected to in-situ precision detection, the white light interferometer only moves along the X, Y, Z axis. And (3) planning a moving path of the white light interferometer, wherein an initial coordinate point is (x 0,y0,z0), moving to the next point (x 1,y0,z1) for shooting after shooting is completed, scanning one by one according to the transverse direction according to the caliber of the structure to be detected and the shooting view field of the lens of the white light interferometer until the shooting (x n,y0,zn) position is reached, and completing all shooting of the transverse structure area. The Y-axis is then translated again, moved to the (x 0,y1,z0 ') position, moved to the next point (x 1,y1,z1') in the manner described above, and also moved until the entire swatter of the present lateral zone structure is completed. The Y-axis is moved in turn until the entire structure is photographed.
For a gentle structure, the planned moving path of the white light interferometer has the following relation of each coordinate point:
The coordinate point is on the X-axis and the Y-axis satisfies the following equation:
xn＝x0+n×tx
yn＝y0+n×ty
In the above formula, X 0 is an initial coordinate point on the X axis, Y 0 is an initial coordinate point on the Y axis, t x,ty is shooting moving step length in the X direction and the Y direction respectively, and the value range is determined according to the shooting view field range of the lens of the white light interferometer; n represents the nth coordinate point.
The coordinate point satisfies the following equation in the Z axis:
In the above equation, z=f (x n,yn) is an aspheric equation, from which the three-dimensional point cloud coordinates of the curved surface can be calculated, in which equation, R is the curvature radius of a curved surface, k is a conic coefficient constant term, and a i is an aspheric higher-order coefficient.
Processing and in-situ precision detection of a steep structure of a micro-optical element, comprising:
1. Placing the white light interferometer 41 on the five-axis single-point diamond lathe rotation B axis 4 as in fig. 1;
2. Finding the rotation center B 0 coordinate of the rotation B shaft 4 of the single-point diamond lathe and the focus A 0 coordinate of the lens of the white light interferometer 41, wherein 52 in FIG. 4 is the center position of the workpiece, namely the position overlapped with the focus of the lens of the white light interferometer;
3. the optical axis of the lens of the white light interferometer 41 is adjusted to coincide with the center of the rotating C-axis 5 of the lathe, and the coordinate 1 is recorded;
4. placing a workpiece on a lathe rotary C shaft 5;
5. rotating the lathe to rotate the B shaft 4, aligning the cutter 42 with the rotation center of the workpiece 51, recording the coordinates 2, and processing the structural surface to be detected of the workpiece;
6. The lathe rotates the B axis 4, rotates and moves to the position of the coordinate 1, then moves the lathe Z axis 3, aligns the lens of the white light interferometer 41 to the processed structure 51, and moves the lathe Z axis 3 slightly until the interference fringes are called, wherein the focus A 0 of the lens of the white light interferometer 41 just falls on the structure. Recording the coordinates 4 (X 0,Y0,Z0,B0) at this time;
7. Because of the large angle of construction, the white light interferometer 41 cannot take a picture of a structure with a large slope, and the lathe rotation B axis 4 needs to be rotated by a certain angle and then taken. According to the coordinate of the focal point A 0 of the lens of the white light interferometer 41 obtained in the step 2 and the coordinate of the rotation center B 0 of the single-point diamond lathe rotation B axis 4, and combining the curvature surface type of the measured piece and the coordinate 4 obtained in the step 6, calculating the axial coordinate value of the machine tool X, Y, Z, B corresponding to each region of the measured piece, so that the optical axis of the lens of the white light interferometer 41 always follows the normal direction of the measured region, and the focal point A 0 of the lens of the white light interferometer 41 always falls on the measured piece;
8. The lathe rotates the B shaft 4 to rotate a certain angle, simultaneously moves along with the X, Z shaft, calculates the moving position of the area to be measured according to the step 7, and sequentially shoots the pictures of the position 1, the position 2 and the position 3 when the interferometer lens shoots as shown in the figure 5, as shown in the figure 6;
9. Returning to the original position 1, the lathe is rotated by 60 degrees to rotate the C-axis 5, and positions 4, 5 and 6 are photographed in sequence according to the steps 7 and 8 as shown in fig. 7, and positions 7,8 and 9 are photographed as shown in fig. 8. Finally, 3×3 photos are taken as shown in fig. 9, and then spliced and combined;
10. And inputting theoretical structural parameters, and calculating the three-dimensional point cloud. And then generating the measured three-dimensional point cloud with the same format from the combined data. And then, calculating the difference value of the two three-dimensional point clouds to obtain structural face type errors or other required data.
Before the on-site precise detection of the steep structure is carried out, the height of the cutter processing is possibly different from the height of the lens of the white light interferometer, and the lens of the white light interferometer is enabled to be overlapped with the optical axis adjustment of the piece to be detected by moving the white light interferometer on the Y axis. When the steep structure is subjected to in-situ precise detection, the white light interferometer needs to move along the X, Z, B-axis, and meanwhile, the lathe rotation C-axis also moves in a matched manner. When a moving path of the white light interferometer is planned, coordinate points are generated along the normal direction of the curved surface center point in the field of view shot by the white light interferometer all the time, the optical axis of the lens of the white light interferometer is parallel to the normal direction of the area to be measured at each coordinate point, and the virtual focus of the lens of the white light interferometer falls on the surface of the area to be measured. The planned moving path of the white light interferometer has an initial coordinate point (x 0,y0,z0,B0,C0), the optical axis of the lens of the white light interferometer at the position is parallel to the normal direction of the area to be measured, and the virtual focus of the lens of the white light interferometer falls on the surface of the area to be measured (generally, the point takes the position of 0 slope of the topmost end or bottommost end of the surface to be measured). After shooting is completed, the white light interferometer is directly moved to the next coordinate point (x 1,y0,z1,B1,C0) according to the calculated track coordinate point, at the moment, the optical axis of the lens of the white light interferometer is parallel to the normal direction of the area to be detected, and the virtual focus of the lens of the white light interferometer still falls on the surface of the area to be detected. And moving in sequence in this way, and moving the coordinate point for multiple times to reach the structure position (x n,y0,zn,Bn,C0) of the last transverse point by the white light interferometer. After the transverse shooting is completed, the Y axis does not move, but the lathe rotates the C axis by an angle (for example, 15 degrees, 30 degrees, 45 degrees, 60 degrees and 90 degrees), a specific angle is selected according to the shooting area of the structure to be detected and the view field shooting area of the lens of the white light interferometer, then the lathe moves to an initial position (x 0,y0,z0,B0,C1) according to the mode, the optical axis of the lens of the white light interferometer at the same position is parallel to the normal direction of the area to be detected, and the virtual focus of the lens of the white light interferometer falls on the surface of the area to be detected. After this position shooting is completed, it moves directly to the next point coordinate (x 1',y0,z1',B1',C1) according to the trajectory calculation, and in this way moves to the laterally final point position (x n',y0,zn',Bn',C1) in turn. And C-axis angles are sequentially rotated according to the mode until all the structures are shot. Specifically, the rotation angle is related to the interval angle of the C axis, for example, if the interval angle of the C axis is 45 degrees, the shooting angle is 0, 45, 90, 135 degrees; if the C interval angle is 30 degrees, the shooting angles are 0, 30, 60, 120 and 150 degrees.
For steep structures, the planned white light interferometer movement path has coordinate points (x n,y0,zn,Bn,C0) satisfying the following relationship:
During detection, the Y axis does not move, the position of the coordinate point on the Y axis is the initial Y 0 position, Y 0 =0, and the moving path track meets the following three-dimensional curved surface coordinate equation:
In this equation, the number of times the equation, R is the curvature radius of a curved surface, x is a coordinate point, k is a conic coefficient constant term, a i is an aspheric higher-order coefficient,
The white light interferometer transversely moves according to the X axis to perform equal step length t x movement, the coordinate of the next point is (X 1,y0,z1,B1,C0),Y0 is unchanged in position, C 0 is unchanged, the coordinate point is on the X axis, and the B axis meets the following equation:
Bn＝f′(x′n),x′n＝x0+n×tx
In the above formula, S is the distance between the point a 0 and the point B 0, the point a 0 is the virtual focus of the lens of the white light interferometer, the coordinate of a 0 is (X A0,YA0,ZA0), the point B 0 is the rotation center of the B-axis rotation shaft, the coordinate point of B 0 is (X B0,YB0,ZB0), the point a 0 and the point B 0 are on the same plane, that is, Y A0＝YB0 =0, θ is the included angle between the connecting line of a 0 and B 0 and the moving direction of the Z axis, t x is the shooting moving step length of the X direction, and the value range is determined according to the shooting field range of the lens of the white light interferometer; n represents an nth coordinate point; x 0 is the initial coordinate point on the X-axis.
S and θ are calculated as follows:
The coordinate point x n、Bn can be calculated by the formula;
the coordinate point satisfies the following equation in the Z axis:
zn＝z0-2×f(x′n,0)+S×cos(θ)-S×cos(Bn+θ)
in the above equation, Z 0 is an initial coordinate point on the Z axis.
For the above technical solution, in some embodiments, a motion axis with higher precision may be selected, and the detection environment is thermostatically controlled, so that measurement errors caused by motion position errors due to low motion axis precision or environmental temperature runout can be avoided.
In some embodiments, the working distance of the lens of the white light interferometer can be properly increased and the size of the lens can be properly reduced according to the requirements, so that the risk that the working distance is too short or the size of the lens is too large to touch a workpiece to be detected in the rotation process of the B axis of the white light interferometer can be avoided, and the detection angle is not limited by the lens of the white light interferometer any more.
For the in-situ precision detection micro-optical element structure surface type device, the splicing algorithm of the graph splicing and synthesizing software is divided into two forms: a smooth detection structure, namely a white light interference system only moves along a X, Y axis, only position information is needed to be recorded, and photographed pictures are spliced by combining a photographing overlapping area. In addition, the steep structure is detected, the white light interferometer is limited in angle of the measurement structure due to the limitation of the numerical aperture of the lens, shooting of the large-slope structure is realized by rotating the rotating B shaft of the lathe and the rotating C shaft of the lathe during measurement of the steep structure, and the large-slope structure is formed by splicing the angle B, C of the position X, Y, Z and the information of the overlapping area.
By the technical scheme provided by the embodiment, the in-situ precise detection of the gentle structure and the steep structure of the micro-optical element can be realized, and the high-precision processing of the micro-optical element can be better assisted; particularly, the in-situ precise detection of the large-caliber high-steep micro-optical structure can be realized by rotating and shooting and splicing the machine tool rotating shaft. Specifically, by adopting the ultra-precise lathe, the caliber can be measured to 350mm, and the steepness can be detected to obtain a hemisphere with a slope close to 90 degrees; the detection precision can reach 0.1um.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention, and are intended to be included within the scope of the appended claims and description.
Claims (8)
1. A method for precisely detecting the structural surface shape of a micro-optical element in situ, which is characterized by comprising the following steps:
Placing a white light interferometer on a first rotating shaft of a machine tool, and placing a workpiece on a second rotating shaft of the machine tool;
adjusting the optical axis of the lens of the white light interferometer to coincide with the center of a second rotating shaft of the machine tool;
Processing the workpiece, and keeping the position of the workpiece on the second rotating shaft unchanged;
the white light interferometer responds to a trigger signal sent by the machine tool, and shoots the structural surface type of the processed workpiece for a plurality of times according to a planned moving path; the structural surface shape comprises a steep structure;
When detecting a steep structure, the moving path and shooting mode of the white light interferometer are as follows: the white light interferometer moves along two linear displacement axes and a first rotation axis of the machine tool respectively, an initial coordinate point of a moving path is (x 0,y0,z0,B0,C0), and after shooting of the initial coordinate point is completed, the white light interferometer moves to a next coordinate point (x 1,y0,z1,B1,C0) to shoot; shooting by moving the coordinate point for a plurality of times until the white light interferometer reaches the structure position (x n,y0,zn,Bn,C0) of the last transverse point; rotating the second rotating shaft by an angle, moving the white light interferometer to an initial position (x 0,y0,z0,B0,C1) for shooting, then moving to a next point coordinate (x 1',y0,z1',B1',C1) for shooting, and sequentially moving to a transverse final point position (x n',y0,zn',Bn',C1) for shooting in this way; sequentially rotating the angles of the second rotating shafts until all the structures are shot;
for a steep structure, the planned moving path of the white light interferometer has coordinate points satisfying the following relation:
The coordinate point is on the X axis, and the B axis satisfies the following equation:
Bn＝f′(x′n),x′n＝x0+n×tx
In the above formula, S is the distance between a point A 0 and a point B 0, a point A 0 is the virtual focus of the lens of the white light interferometer, a point B 0 is the rotation center of the rotation shaft of the B axis, θ is the included angle between the connecting line of A 0 and B 0 and the moving direction of the Z axis, t x is the shooting moving step length of the X direction, and the value range is determined according to the shooting view field range of the lens of the white light interferometer; n represents an nth coordinate point; x 0 is the initial coordinate point;
the coordinate point satisfies the following equation in the Z axis:
zn＝z0-2×f(x′n,0)+S×cos(θ)-S×cos(Bn+θ)
In the above equation, Z 0 is an initial coordinate point on the Z axis, R is the curvature radius of a curved surface, x is a coordinate point, k is a conic coefficient constant term, and a i is an aspheric higher-order coefficient.
2. The method for in-situ precision detection of micro-optical element structure surface type according to claim 1, wherein when a moving path of a white light interferometer is planned, a coordinate point is always generated along a normal direction of a curved surface center point in a shooting view field of the white light interferometer; and the optical axis of the lens of the white light interferometer is parallel to the normal direction of the region to be measured at each coordinate point, and the virtual focus of the lens of the white light interferometer is located on the surface of the region to be measured.
3. The in-situ precision detection micro-optic element structure surface type method of claim 1, wherein the structure surface type further comprises a gentle structure.
4. The method for in-situ precision detection of micro-optical element structure surface type according to claim 3, wherein the moving path and shooting mode of the white light interferometer when detecting the gentle structure are as follows:
The white light interferometer moves along three linear displacement axes of the machine tool respectively, and an initial coordinate point of a moving path is (x 0,y0,z0);
scanning the first horizontal structure region one by one in the transverse direction by using a white light interferometer, and respectively shooting from an initial coordinate point to a coordinate point (x n,y0,zn) until the first horizontal structure region is completely shot;
translating the Y-axis coordinate according to the shooting moving step length, and scanning one by one in the transverse direction by using a white light interferometer until the second transverse area structure is completely shot;
And moving the Y-axis coordinate for a plurality of times according to the shooting moving step length, and repeating the shooting process until the shooting of all the structures is completed.
5. The method for in-situ precision detection of micro-optical element structure surface type according to claim 4, wherein for a gentle structure, the planned white light interferometer moving path has a coordinate point satisfying the following relationship:
The coordinate point is on the X-axis, and the Y-axis satisfies the following equation:
xn＝x0+n×tx
yn＝y0+n×ty
in the above formula, X 0 is an initial coordinate point on the X axis, Y 0 is an initial coordinate point on the Y axis, t x,ty is shooting moving step length in the X direction and the Y direction respectively, and the value range is determined according to the shooting view field range of the lens of the white light interferometer; n represents an nth coordinate point;
the coordinate point satisfies the following equation in the Z axis:
In the above-mentioned description of the invention, R is the curvature radius of a curved surface, k is a conic coefficient constant term, and a i is an aspheric higher-order coefficient.
6. The method for in-situ precision detection of micro-optical element structure surface type according to claim 1, further comprising the steps of splicing the shot pictures, and fitting and analyzing the surface structure of the microstructure to be detected.
7. An in-situ precision detection micro-optical element structure surface type device, characterized in that it is used for implementing the in-situ precision detection micro-optical element structure surface type method according to any one of claims 1-6, and comprises:
A machine tool comprising at least 3 linear displacement axes and at least 2 rotation axes;
the white light interferometer and the workpiece are respectively arranged on different rotating shafts;
The splicing path planning and control system is used for calculating a moving track coordinate point of the white light interferometer in the shooting process and controlling the white light interferometer to move and shoot according to the coordinate point; and
And the graph splicing and synthesizing software is used for splicing the shot pictures.
8. The in-situ precision detection micro-optical element structure surface type device according to claim 7, wherein the lens working distance of the white light interferometer is increased and/or the lens size is reduced according to the detection requirement.
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