Method for aligning the optical axis of a confocal probe with the axis of a spindle and rotary mechanism

Abstract

The application discloses a kind of for the adjustment device and method of confocal probe optical axis and main shaft rotation mechanism axis coaxial, device structure is: main shaft rotation mechanism is arranged on air floating marble vibration isolation platform, differential confocal probe is located above main shaft rotation mechanism;High-precision aligning and leveling workbench is installed on main shaft rotation mechanism;Standard reference hemisphere is placed on high-precision aligning and leveling workbench;Standard cubic spectrometer prism is placed directly above standard reference hemisphere;Full-automatic electronic internal focusing autocollimator is distributed in opposite sides of standard cubic spectrometer prism respectively;Full-automatic electronic internal focusing autocollimator realizes the fitting of the axis circle of main shaft rotation mechanism, and the axis precision calibration detection of main shaft rotation mechanism.The application has the advantages of high efficiency, good accuracy, and the method of assembling and adjusting is simple, and the coaxial precision is high.

Description

Technical Field

[0001] This invention belongs to the field of optomechanical assembly technology of large-aperture aspherical optical element surface shape accuracy detection device, and relates to an adjustment method for coaxiality between the optical axis of the confocal probe and the axis of the spindle rotation mechanism. Background Technology

[0002] Aspherical elements offer advantages such as aberration correction, improved image quality, expanded field of view, increased working distance, reduced light loss, shorter overall system length, and lighter system weight, resulting in high-quality image effects and superior optical properties. In the manufacturing process, aspherical surface shape rapid scanning and inspection devices are increasingly used to inspect the surface shape of aspherical elements. The differential confocal probe and spindle rotation mechanism are the core components of these devices. The differential confocal probe performs a two-dimensional scan of the aspherical sample placed on the high-speed spindle rotation mechanism to acquire the surface shape information of the aspherical sample being measured. (See...) Figure 1 The coaxial control accuracy of the differential confocal probe's optical axis with the axis of the high-speed rotating main shaft is particularly important. This is crucial because it determines whether the confocal probe can measure the vertex surface shape information of aspherical samples, thus affecting the overall surface shape information and detection accuracy of the aspherical sample being measured. However, due to design and manufacturing errors, as well as manual rough assembly of the differential confocal probe, it is difficult to ensure coaxiality between the differential confocal probe and the axis of the high-speed rotating main shaft. Consequently, during the measurement process, the differential confocal probe cannot scan the vertex surface shape information of the aspherical optical element placed on the high-speed rotating main shaft, resulting in missing surface shape information. This leads to a significant deviation in the matching benchmark between theoretical design data and detection data, increasing the difficulty of subsequent data processing of aspherical surface shape information and severely affecting the measurement accuracy of large-aperture optical element surface shape accuracy detection devices. Therefore, there is an urgent need for a method to calibrate the coaxiality of the confocal probe's optical axis with the axis of the rotating main shaft.

[0003] Regarding the calibration method of rotary table axis, scholars at home and abroad have proposed many new measurement methods. Published literature includes: "A new method for rotary table axis calibration based on conical fitting in 3D measurement system" published in Equipment Manufacturing Technology, "Two-axis rotary table calibration for structured light 3D measurement" published in the Journal of Shanghai Jiaotong University, and "Research on visual calibration method of pitch axis position" published in the Chinese Journal of Metrology. However, the axis calibration methods proposed in the above literature only measure the axis and cannot calibrate the spatial position of the axis.

[0004] In summary, in order to improve the coaxiality accuracy between the optical axis of the differential confocal probe and the axis of the main spindle rotary motion mechanism, it is necessary to develop a method for making the optical axis of the differential confocal probe and the axis of the main spindle rotary motion mechanism coaxial. Summary of the Invention

[0005] (I) Purpose of the Invention

[0006] The purpose of this invention is to solve the problem of coaxial accuracy between the optical axis of the differential confocal probe and the axis of the main shaft rotation mechanism of the aspherical optical element under test, and to eliminate the error of missing vertex surface shape information of the aspherical optical element placed on the high-speed rotation mechanism of the main shaft by scanning the optical axis of the differential confocal probe. This invention proposes a method for achieving coaxiality between the optical axis of the differential confocal probe and the axis of the main shaft rotation mechanism, which is simple to operate, allows for rapid adjustment of the spatial pose of the confocal probe, and achieves high-precision coaxiality between the optical axis of the differential confocal probe and the axis of the main shaft rotation mechanism of the aspherical optical element under test, thereby improving the detection accuracy of the rapid scanning and detection device for aspherical surface shapes.

[0007] (II) Technical Solution

[0008] To solve the above-mentioned technical problems, the present invention provides an adjustment device for coaxiality between the optical axis of a confocal probe and the axis of the spindle rotation mechanism, comprising: a differential confocal probe 1, a spindle rotation mechanism 2, an air-float marble vibration isolation platform 3, a standard cubic beam splitter prism 4, a fully automatic electronic internal focusing autocollimator 5, a standard reference hemisphere 6, and a high-precision self-aligning and leveling worktable 7.

[0009] The spindle rotation mechanism 2 is arranged on the air-floating marble vibration isolation platform 3, and the differential confocal probe 1 is located above the spindle rotation mechanism 2; the high-precision self-aligning and leveling worktable 7 is installed on the spindle rotation mechanism 2; the standard reference hemisphere 6 is placed on the high-precision self-aligning and leveling worktable 7; the standard cubic beam splitter prism 4 is placed directly above the standard reference hemisphere 6; the fully automatic electronic internal focusing autocollimator 5 is distributed on opposite sides of the standard cubic beam splitter prism 4; the fully automatic electronic internal focusing autocollimator 5 realizes the fitting of the axis of the spindle rotation mechanism 2 and calibrates and detects the axis accuracy of the spindle rotation mechanism 2.

[0010] The calibration device also includes a standard flat crystal 8, which is installed on the mechanical end face of the differential confocal probe 1 to make the pitch direction of the differential confocal probe 1 coincide with that of the axis of the spindle rotation mechanism 2.

[0011] The present invention also provides a method for calibrating the optical axis of a confocal probe to be coaxial with the axis of the spindle rotation mechanism, comprising the following steps:

[0012] Step 1: Set up the spindle rotation mechanism 2, calibrate the rotation axis, and adjust the optical path. Mount the high-precision self-aligning and leveling worktable 7 on the spindle rotation mechanism 2, and place the standard reference hemisphere 6 on the high-precision self-aligning and leveling worktable 7. Set the focal length of the fully automatic electronic internal focusing autocollimator 5 to infinity (+∞). Adjust the spatial position of the standard cubic beam splitter prism 4 and the fully automatic electronic internal focusing autocollimator 5 so that the cross reticle of the fully automatic electronic internal focusing autocollimator 5 passes through the plane of the standard cubic beam splitter prism 4 and the standard reference hemisphere 6, and the cross reticle reflected image enters the field of view of the fully automatic electronic internal focusing autocollimator 5.

[0013] Step 2: Rotate the spindle rotation mechanism 2 and measure the center of the circular motion of the crosshair reflection image center through the fully automatic electronic internal focusing autocollimator 5; adjust the tilt of the high-precision self-aligning and leveling table 7 so that the center of the crosshair reflection image center observed by the fully automatic electronic internal focusing autocollimator 5 does not move in the circular motion.

[0014] Step 3: The focal length of the fully automatic electronic internal focusing autocollimator 5 is set at the center of the standard reference hemisphere 6. The standard reference hemisphere 6 is translated so that the crosshair reticle is reflected by the center of the standard reference hemisphere 6 and enters the field of view of the fully automatic electronic internal focusing autocollimator 5. The main spindle rotation mechanism 2 is rotated to measure the center of the circular motion of the crosshair reflection image center through the fully automatic electronic internal focusing autocollimator 5. The translation of the high-precision self-aligning and leveling stage 7 is adjusted so that the center of the crosshair reflection image observed by the fully automatic electronic internal focusing autocollimator 5 does not move in the circular motion. This position is calibrated as the position of the main spindle rotation axis (x1, y1).

[0015] Step 4: Construct a coaxial optical path between the differential confocal probe 1 and the main spindle rotation mechanism 2. Place the standard flat crystal 8 tightly against the mechanical reference end face of the differential confocal probe 1. Set the focal length of the fully automatic electronic internal focusing autocollimators 5 on the left and right sides of the standard cubic beam splitter prism 4 at infinity (+∞). Adjust the position of the left fully automatic electronic internal focusing autocollimator 5 so that the reference crosshair of the left fully automatic electronic internal focusing autocollimator 5 is aligned to (x1, y1). Observe the autocollimated image of the crosshair through the standard flat crystal using the left fully automatic electronic internal focusing autocollimator 5. Adjust the tilt of the differential confocal probe 1 so that the crosshair of the autocollimated image observed by the fully automatic electronic internal focusing autocollimator 5 is aligned to (x1, y1). Remove the standard flat crystal 8 and the standard cubic beam splitter prism 4.

[0016] Step 5: Make a slight translation adjustment to the differential confocal probe 1. When the displacement information of the differential confocal probe 1 is at its minimum or the energy information is at its maximum, the confocal probe adjustment is complete.

[0017] Step 6: Secure the differential confocal probe 1. After securing, remove the standard reference hemisphere 6. Adjustment complete.

[0018] (III) Beneficial Effects

[0019] The above-mentioned technical solution provides a method for aligning the optical axis of the confocal probe with the axis of the spindle rotation mechanism, which offers several advantages, including the following:

[0020] (1) This invention utilizes a standard reference hemisphere and a fully automatic electronic internal focusing autocollimator to replace trial and error in completing the coaxiality of the optical axis of the differential confocal probe with the axis of the main shaft rotation mechanism. Compared with trial and error, it has the advantages of high efficiency and good accuracy.

[0021] (2) The present invention utilizes a standard reference hemisphere and a fully automatic electronic internal focusing autocollimator to accurately calibrate the spatial position of the axis of the spindle rotation mechanism;

[0022] (3) The assembly and adjustment method used in this invention is simple and has high coaxial accuracy;

[0023] (4) The present invention adopts the method of coaxiality between the optical axis of the differential confocal probe and the axis of the main shaft rotation mechanism, which lays the foundation for achieving high precision surface shape detection of the aspherical detection device. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the differential confocal probe and spindle rotation mechanism in a large-aperture optical element surface shape accuracy detection device, which is the object of this invention.

[0025] Figure 2 This is a schematic diagram of the calibration and adjustment of the rotation axis of the main spindle rotation mechanism.

[0026] Figure 3 This is a schematic diagram of the pitch adjustment of the confocal probe and the axis of the spindle rotation mechanism.

[0027] Figure 4 This is a schematic diagram showing the alignment of the confocal probe with the axis of the spindle rotation mechanism.

[0028] In the figure: 1. Differential confocal probe; 2. Spindle rotation mechanism; 3. Air-float marble vibration isolation platform; 4. Standard cubic beam splitter prism; 5. Fully automatic electronic internal focusing autocollimator; 6. Standard reference hemisphere; 7. High-precision self-aligning and leveling worktable; 8. Standard flat crystal. Detailed Implementation

[0029] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0030] To address the problem of accurate alignment between the optical axis of the differential confocal probe and the axis of the high-speed rotation mechanism of the main shaft in a certain aspherical optical element testing device, this embodiment provides a high-precision alignment and reasonable and feasible solution to ensure that the optical axis of the differential confocal probe scans the vertex surface information of the aspherical optical element under test.

[0031] like Figure 1 The diagram shows a differential confocal probe and a spindle rotation mechanism in a large-aperture optical element surface shape accuracy testing device. The device includes a differential confocal probe 1, a spindle rotation mechanism 2, and an air-float marble vibration isolation platform 3. The spindle rotation mechanism 2 is arranged on the air-float marble vibration isolation platform 3, and the differential confocal probe 1 is located above the spindle rotation mechanism 2.

[0032] like Figure 2 The diagram shows the axis calibration and adjustment of the main spindle rotation mechanism, which includes a standard cubic beam splitter prism 4, a fully automatic electronic internal focusing autocollimator 5, a standard reference hemisphere 6, and a high-precision self-aligning and leveling table 7. The high-precision self-aligning and leveling table 7 is mounted on the main spindle rotation mechanism 2. The standard reference hemisphere 6 is placed on the high-precision self-aligning and leveling table 7. The standard cubic beam splitter prism 4 is placed directly above the standard reference hemisphere 6. The fully automatic electronic internal focusing autocollimators 5 are distributed on opposite sides of the standard cubic beam splitter prism 4.

[0033] The fully automatic electronic internal focusing autocollimator 5 can fit the axis of the spindle rotation mechanism 2 by circling, and can calibrate and test the accuracy of the axis of the spindle rotation mechanism 2.

[0034] The standard reference hemisphere 6 has the same external dimensions as a standard optical hemisphere. The surface of the standard reference hemisphere 6 is coated with an anti-reflective film, and the surface profile accuracy is better than 1 / 30λ, where λ is 0.6328μm. The plane of the standard reference hemisphere 6 is coated with a reflective film, thereby achieving the coincidence of the rotation of the optical components and the main shaft rotation mechanism 2.

[0035] The high-precision self-aligning and leveling worktable 6 enables precise adjustment of translation (±3mm) and pitch (±0.5°); it works in conjunction with the spindle rotation mechanism 2 to detect the center and pitch level accuracy of the workpiece.

[0036] like Figure 3 The diagram shows a schematic of the pitch adjustment of the confocal probe and the axis of the spindle rotation mechanism. The diagram shows a standard flat crystal 8. The surface of the standard flat crystal 8 is coated with a reflective film, and the parallelism difference between the two sides is better than 5″. It is installed on the mechanical end face of the differential confocal probe 1, thereby realizing that the pitch direction of the differential confocal probe 1 and the axis of the spindle rotation mechanism 2 are coincident.

[0037] Based on the above-mentioned detection device, this embodiment also provides a method for calibrating the coaxiality of the optical axis of the confocal probe and the axis of the spindle rotation mechanism, including the following steps:

[0038] Step 1: Set up the spindle rotation mechanism 2, calibrate the rotation axis, and adjust the optical path. Mount the high-precision self-aligning and leveling worktable 7 on the spindle rotation mechanism 2, and place the standard reference hemisphere 6 on the high-precision self-aligning and leveling worktable 7. Set the focal length of the fully automatic electronic internal focusing autocollimator 5 to infinity (+∞). Adjust the spatial position of the standard cubic beam splitter prism 4 and the fully automatic electronic internal focusing autocollimator 5 so that the cross reticle of the fully automatic electronic internal focusing autocollimator 5 passes through the plane of the standard cubic beam splitter prism 4 and the standard reference hemisphere 6, and the cross reticle reflected image enters the field of view of the fully automatic electronic internal focusing autocollimator 5.

[0039] Step 2: Rotate the spindle rotation mechanism 2 and measure the center of the circular motion of the crosshair reflection image center through the fully automatic electronic internal focusing autocollimator 5; adjust the tilt of the high-precision self-aligning and leveling table 7 so that the center of the crosshair reflection image center observed by the fully automatic electronic internal focusing autocollimator 5 does not move in the circular motion.

[0040] Step 3: The focal length of the fully automatic electronic internal focusing autocollimator 5 is set at the center of the standard reference hemisphere 6. The standard reference hemisphere 6 is translated so that the crosshair reticle is reflected by the center of the standard reference hemisphere 6 and enters the field of view of the fully automatic electronic internal focusing autocollimator 5. The main spindle rotation mechanism 2 is rotated to measure the center of the circular motion of the crosshair reflection image center through the fully automatic electronic internal focusing autocollimator 5. The translation of the high-precision self-aligning and leveling stage 7 is adjusted so that the center of the crosshair reflection image observed by the fully automatic electronic internal focusing autocollimator 5 does not move in the circular motion. This position is calibrated as the position of the main spindle rotation axis (x1, y1).

[0041] Step 4: Construct a coaxial optical path between the differential confocal probe 1 and the main spindle rotation mechanism 2. Place the standard flat crystal 8 tightly against the mechanical reference end face of the differential confocal probe 1. Set the focal length of the fully automatic electronic internal focusing autocollimators 5 on the left and right sides of the standard cubic beam splitter prism 4 at infinity (+∞). Adjust the position of the left fully automatic electronic internal focusing autocollimator 5 so that the reference crosshair of the left fully automatic electronic internal focusing autocollimator 5 is aligned to (x1, y1). Observe the autocollimated image of the crosshair through the standard flat crystal using the left fully automatic electronic internal focusing autocollimator 5. Adjust the tilt of the differential confocal probe 1 so that the crosshair of the autocollimated image observed by the fully automatic electronic internal focusing autocollimator 5 is aligned to (x1, y1). Remove the standard flat crystal 8 and the standard cubic beam splitter prism 4.

[0042] Step 5: Make a slight translation adjustment to the differential confocal probe 1. When the displacement information of the differential confocal probe 1 is at its minimum or the energy information is at its maximum, the confocal probe adjustment is complete.

[0043] Step 6: Secure the differential confocal probe 1. After securing, remove the standard reference hemisphere 6. Adjustment complete.

[0044] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for calibrating the coaxiality of the optical axis of a confocal probe and the axis of the spindle rotation mechanism, characterized in that, The calibration is performed using a calibration device comprising: a differential confocal probe (1), a spindle rotation mechanism (2), an air-float marble vibration isolation platform (3), a standard cubic beam splitter (4), a fully automatic electronic internal focusing autocollimator (5), a standard reference hemisphere (6), and a high-precision self-aligning and leveling table (7); the spindle rotation mechanism (2) is arranged on the air-float marble vibration isolation platform (3), and the differential confocal probe (1) is located above the spindle rotation mechanism (2); the high-precision self-aligning and leveling table (7) is installed on the spindle rotation mechanism (2); the standard reference hemisphere (6) Placed on a high-precision self-aligning and leveling worktable (7); a standard cubic beam splitter (4) is placed directly above a standard reference hemisphere (6); fully automatic electronic internal focusing autocollimators (5) are distributed on opposite sides of the standard cubic beam splitter (4); the fully automatic electronic internal focusing autocollimators (5) achieve the fitting of the axis of the main shaft rotation mechanism (2) and calibrate and test the axis accuracy of the main shaft rotation mechanism (2); the standard reference hemisphere (6) has the same external dimensions as a standard optical hemisphere; the surface of the standard reference hemisphere (6) is coated with an anti-reflection film, and the surface profile accuracy is better than 1 / 30. , The standard reference hemisphere (6) is coated with a reflective film to achieve the coincidence of the optical component and the rotation of the main shaft rotation mechanism (2); the incident optical axis and the output optical axis of the standard cubic beam splitter (4) are deflected by an angle of 90°±5", thereby achieving the folding of the optical axis; the high-precision self-aligning and leveling table (7) achieves precise adjustment of translation ±3mm and pitch ±0.5°; in conjunction with the main shaft rotation mechanism (2), it achieves the detection of the center and pitch level accuracy of the detection optical component; the calibration device also includes: a standard flat crystal (8), which is installed on the mechanical end face of the differential confocal probe (1) to achieve the coincidence of the pitch direction of the differential confocal probe (1) and the axis of the main shaft rotation mechanism (2); the surface of the standard flat crystal (8) is coated with a reflective film, and the parallel difference between the two sides is better than 5″; The calibration method includes the following steps: Step 1: Set up the spindle rotation mechanism (2) and calibrate the optical path. Install the high-precision self-aligning and leveling worktable (7) on the spindle rotation mechanism (2) and place the standard reference hemisphere (6) on the high-precision self-aligning and leveling worktable (7). Set the focal length of the fully automatic electronic internal focusing autocollimator (5) to infinity (+∞). Adjust the spatial position of the standard cubic beam splitter (4) and the fully automatic electronic internal focusing autocollimator (5) so that the cross reticle of the fully automatic electronic internal focusing autocollimator (5) passes through the plane of the standard cubic beam splitter (4) and the standard reference hemisphere (6) and the cross reticle reflected image enters the field of view of the fully automatic electronic internal focusing autocollimator (5). Step 2: Rotate the spindle rotation mechanism (2) and measure the center of the circular motion of the cross-shaped reflective image center through the fully automatic electronic internal focusing autocollimator (5); adjust the tilt of the high-precision self-aligning and leveling table (7) so that the center of the cross-shaped reflective image observed by the fully automatic electronic internal focusing autocollimator (5) does not move in the circular motion. Step 3: Set the focal length of the fully automatic electronic internal focusing autocollimator (5) at the center of the standard reference hemisphere (6), translate the standard reference hemisphere (6) so that the cross reticle is reflected by the center of the standard reference hemisphere (6) and enters the field of view of the fully automatic electronic internal focusing autocollimator (5); rotate the main spindle rotation mechanism (2) and measure the center of the circular motion of the center of the cross reticle reflection image through the fully automatic electronic internal focusing autocollimator (5); adjust the translation of the high-precision centering and leveling stage (7) so that the center of the cross reticle reflection image observed by the fully automatic electronic internal focusing autocollimator (5) does not move in the circular motion, and mark this position, which is the position of the main spindle rotation axis (x1, y1). Step 4: Construct a coaxial optical path between the differential confocal probe (1) and the main shaft rotation mechanism (2), and place the standard flat crystal (8) tightly against the mechanical reference end face of the differential confocal probe (1); set the focal length of the fully automatic electronic internal focusing autocollimator (5) on the left and right sides of the standard cubic beam splitter (4) to infinity (+∞), and adjust the position of the left fully automatic electronic internal focusing autocollimator (5) so that the reference crosshair of the left fully automatic electronic internal focusing autocollimator (5) is adjusted to (x1, y1); observe the autocollimated image of the crosshair through the standard flat crystal through the left fully automatic electronic internal focusing autocollimator (5); adjust the tilt of the differential confocal probe (1) so that the crosshair autocollimated image observed by the fully automatic electronic internal focusing autocollimator (5) is adjusted to (x1, y1); remove the standard flat crystal (8) and the standard cubic beam splitter (4); Step 5: Make a slight translation adjustment to the differential confocal probe (1). When the displacement information of the differential confocal probe (1) is at its minimum or the energy information is at its maximum, the confocal probe adjustment is complete. Step 6: Fix the differential confocal probe (1). After fixing, remove the standard reference hemisphere (6) and the adjustment is complete.

2. An application of the calibration method for coaxiality between the optical axis of the confocal probe and the axis of the spindle rotation mechanism as described in claim 1 in the field of optomechanical assembly technology of a large-aperture aspherical optical element surface shape accuracy detection device.

Images