A spectral confocal displacement sensor calibration method and device

Abstract

The present invention discloses a spectral confocal displacement sensor calibration method and device, which is used for calibrating the spectral confocal displacement sensor to be calibrated, including a laser interferometer, a movable slide, a laser interferometer reflector, a spectral confocal calibration plate, a movable slide controller, a host computer, and a spectral confocal displacement sensor controller. A measurement calibration model of the spectral confocal displacement sensor is established according to the wavelength of the collected displacement calibrated point to obtain a measured displacement value; multiple measurement experiments are performed to obtain a measured displacement value and a standard value, and an indication error is obtained according to the measured displacement value and the standard value obtained by experimental measurement, and the indication error is compensated to the measured displacement value to obtain a measured displacement value after compensation and calibration. The present invention not only greatly improves the accuracy of the spectral confocal displacement sensor, but also improves the calibration efficiency.

Description

Technical Field

[0001] The invention relates to a spectral confocal displacement sensor calibration method and device, belonging to the technical field of optical sensors. Background Art

[0002] The spectral confocal displacement sensor is a non-contact single-point compact optical displacement sensor based on the principle of spectral imaging. Compared with micro-displacement measuring instruments such as laser interferometers, capacitive micrometers and grating micrometers, the spectral confocal displacement sensor has technical advantages such as high measurement accuracy, fast detection speed and high system integration, and has become one of the important precision displacement measurement sensors in the field of advanced manufacturing. In addition to high-accuracy displacement measurement, the spectral confocal displacement sensor also has thickness measurement capabilities, so it has a wide range of applications in semiconductors, new energy batteries and precision instruments. At present, the accuracy of high-accuracy spectral confocal sensors has reached the sub-micron level. These increasingly improved technical indicators also put forward higher requirements on their calibration devices and calibration methods. However, there is still a lack of dedicated spectral confocal sensor calibration devices.

[0003] The spectral confocal displacement sensor mainly consists of two parts: the sensor optical probe and the sensor controller. The measurement principle of the spectral confocal displacement sensor is to use a specially designed dispersion objective lens to focus the complex light containing multiple wavelengths on the optical axis in an increasing or decreasing manner according to the wavelength, forming a series of continuous measurement points, and then the wavelength of the focused monochromatic light on the surface of the workpiece is detected by the spectrometer in the controller, and then converted into distance information, that is, a one-to-one correspondence is established between the different axial positions on the optical axis of the optical probe and the wavelength of the monochromatic light at the focus. However, due to the influence of factors such as the manufacturing tolerance of the positioning parts of optical elements and lenses, the wavelength information in the spectral confocal displacement sensor and the true value of the displacement cannot actually present a strict linear correspondence, which introduces nonlinear errors, that is, the wavelength information and the true value of the displacement are nonlinear. The traditional use of linear fitting measurement functions will bring large errors in the subsequent use of the sensor.

[0004] The current calibration methods of spectral confocal displacement sensors are often based on a few discrete data points, which makes it difficult to truly reflect the linearity of the spectral confocal displacement sensor over the full range. Moreover, due to the lack of dedicated calibration equipment, it leads to problems such as difficult installation, heavy workload, and low calibration efficiency. Summary of the invention

[0005] Purpose of the invention: In order to overcome the problems of low calibration efficiency and poor measurement accuracy of existing spectral confocal displacement sensors, the present invention provides a spectral confocal displacement sensor calibration device.

[0006] Technical solution: To achieve the above purpose, the technical solution adopted by the present invention is:

[0007] A spectral confocal displacement sensor calibration device is used for calibrating the spectral confocal displacement sensor to be calibrated, comprising a laser interferometer, a movable slide, a laser interferometer reflector, a spectral confocal calibration plate, a movable slide controller, a host computer, and a spectral confocal displacement sensor controller.

[0008] The spectral confocal calibration plate is installed on the workbench through a movable slide, and the laser interferometer reflector is fixed to the spectral confocal calibration plate. The movable slide is used for horizontal movement of the spectral confocal calibration plate on the workbench.

[0009] The laser interferometer, the spectral confocal calibration plate, and the spectral confocal displacement sensor to be calibrated are installed on a workbench, and the laser interferometer, the laser interferometer reflector, the spectral confocal calibration plate, the spectral confocal calibration plate, and the spectral confocal displacement sensor to be calibrated are arranged in sequence along the laser interferometer emission light path.

[0010] The movable slide controller is connected to the movable slide, the spectral confocal displacement sensor controller is connected to the spectral confocal displacement sensor to be calibrated, and the host computer is respectively connected to the laser interferometer, the movable slide controller, and the spectral confocal displacement sensor controller.

[0011] Preferably: it also includes an environmental compensation sensor, and the environmental compensation sensor is used for light compensation of the laser interferometer.

[0012] Preferably, the normal line of the spectral confocal calibration plate is parallel to the optical axis of the laser interferometer.

[0013] Preferably, the optical axis of the laser interferometer is coaxial with the optical axis of the spectral confocal displacement sensor to be calibrated.

[0014] Preferably, the movable slide comprises a motor, a bracket, a screw, and a threaded slider, wherein the motor and the bracket are mounted on a workbench, the screw is mounted on the bracket via a bearing, the threaded slider is threadedly connected to the screw, and the threaded slider is slidably connected to the bracket. The spectral confocal calibration plate is fixedly mounted on the threaded slider.

[0015] Preferably, the spectral confocal calibration plate is a thin plate, and both surfaces of the thin plate are smooth and parallel.

[0016] A spectral confocal displacement sensor calibration method, using the spectral confocal displacement sensor calibration device, comprises the following steps:

[0017] Step 1: Start the laser interferometer to emit laser and start the spectral confocal displacement sensor to be calibrated.

[0018] Step 2: The host computer controls the movement of the moving stage through the moving stage controller, and the moving stage controls the movement of the spectral confocal calibration plate. The laser emitted by the laser interferometer is reflected back by the laser interferometer reflector, and the distance the laser interferometer reflector moves back and forth is measured as the standard value of the calibration point; the light source emitted by the spectral confocal displacement sensor to be calibrated is irradiated on the spectral confocal calibration plate, and when the light is focused on the spectral confocal calibration plate, the wavelength corresponding to the spectral confocal calibration point on the spectral confocal calibration plate is measured.

[0019] Step 3: When the spectral confocal calibration plate moves within the measuring range of the spectral confocal displacement sensor to be calibrated, the host computer records the wavelengths corresponding to different displacement calibration points, and the laser interferometer records the standard values ​​of the corresponding calibration points.

[0020] Step 4: Establish a measurement calibration model of the spectral confocal displacement sensor according to the wavelength of the collected displacement calibration point, and obtain the measured displacement value through the measurement calibration model.

[0021] Step 5, perform multiple measurement experiments to obtain measured displacement values ​​and standard values, obtain indication errors based on the measured displacement values ​​and standard values ​​obtained by experimental measurement, and compensate the indication errors to the measured displacement values ​​to obtain compensated and calibrated measured displacement values.

[0022] Preferably: the measurement calibration model is:

[0023]

[0024]

[0025] ;

[0026] ;

[0027] ;

[0028] in, Indicates the measured displacement value, represents the wavelength, represents the number of displacement calibration points, represents the measurement calibration factor of one, represents the measurement calibration factor of two, Indicates the measurement calibration factor three, represents the measurement calibration constant, Indicates The wavelength of the displacement calibration point, Indicates The displacement is calibrated at a point.

[0029] Preferably, the measured displacement value after compensation calibration is:

[0030] = ;

[0031] in, Represents the measured displacement value after compensation calibration, Indicates the measured displacement value, Indicates indication error.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The spectral confocal displacement sensor of the present invention has high displacement value measurement accuracy and high calibration efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the structure of the spectral confocal displacement sensor calibration device. DETAILED DESCRIPTION

[0035] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0036] The principle of the spectral confocal displacement sensor is to use a complex light source, whose emitted light is gathered by a dispersive lens group through a beam splitter. Within the measurement range, the axial dispersion of the objective lens is used to spectrally encode the distance. The light of different wavelengths will focus on different positions of the optical axis. The designed dispersive objective lens will ideally focus the light wavelength. It corresponds to the axial dispersion shift d one by one, and the two are linearly related.

[0037]

[0038] But in fact, due to factors such as lens optical errors and signal processing errors, the wavelength The relationship between the displacement d is not linear, but nonlinear. In this case, the traditional use of linear fitting measurement function will bring large errors in the subsequent use of the sensor.

[0039] In view of the above problems, this embodiment provides a spectral confocal displacement sensor calibration method, using the spectral confocal displacement sensor calibration device, including the following steps:

[0040] Step 1, start the laser interferometer 1 to emit laser, and start the spectral confocal displacement sensor 5 to be calibrated. The laser emitted by the laser interferometer 1 is reflected back by the laser interferometer reflector 3, and the distance between the laser interferometer reflector 3 and the laser interferometer 1 is measured.

[0041] Step 2: The host computer 8 controls the moving slide 2 to work through the moving slide controller 7, and the moving slide 2 controls the movement of the spectral confocal calibration plate 4. The laser emitted by the laser interferometer 1 is reflected back by the laser interferometer reflector 3, and the distance of the laser interferometer reflector 3 moving forward and backward is measured as the standard value of the calibration point; the light source emitted by the spectral confocal displacement sensor 5 to be calibrated is irradiated on the spectral confocal calibration plate 4, and when the light is focused on the spectral confocal calibration plate 4, the wavelength corresponding to the calibration point of the spectral confocal calibration plate 4 is measured.

[0042] Step 3, when the spectral confocal calibration plate 4 moves within the measuring range of the spectral confocal displacement sensor 5 to be calibrated, the host computer 8 records the wavelengths corresponding to different displacement calibration points, and the laser interferometer 1 records the standard values ​​of the corresponding calibration points.

[0043] Step 4: Establish a measurement calibration model of the spectral confocal displacement sensor 5 according to the wavelength of the collected displacement calibration point. Obtain the measured displacement value through the measurement calibration model.

[0044] In order to solve the problem that the use of linear fitting measurement function will bring large errors in the subsequent use of the sensor, we establish a measurement calibration model of the spectral confocal displacement sensor 5 based on the wavelength of the collected displacement calibration point, so that the wavelength can form an accurate corresponding relationship with the displacement.

[0045] During calibration, the displacement calibration point is The corresponding wavelength value collected by the spectral confocal displacement sensor is .

[0046] Assume the measurement function is , is a piecewise function, and In each small area The above is a cubic polynomial, that is:

[0047]

[0048] That is:

[0049]

[0050] In this way, there are 4 undetermined coefficients in each small interval, and there are n small intervals in total, so there are 4n parameters that need to be determined, and therefore 4n conditional constraints are also required to solve these 4n parameters.

[0051] Although it is a piecewise function, the curve should be smooth and continuous, that is, The second-order derivative is continuous on the interval and at each node The continuity condition should be met:

[0052]

[0053] This gives us 3n-3 conditions, plus This constraint condition has n+1 conditions, totaling 4n-2 conditions. Two more conditions are added, that is, the second-order derivatives of the two endpoints are 0:

[0054]

[0055] With these conditions, we can solve the measurement equation .

[0056] The measurement calibration model is thus:

[0057]

[0058]

[0059] ;

[0060] ;

[0061] ;

[0062] in, Indicates the measured displacement value, represents the wavelength, represents the number of displacement calibration points, represents the measurement calibration factor of one, represents the measurement calibration factor of two, Indicates the measurement calibration factor three, represents the measurement calibration constant, Indicates The wavelength of the displacement calibration point, Indicates The displacement is calibrated at a point.

[0063] Put the measurement equation The calibration is completed by bringing in the controller of the spectral confocal displacement sensor.

[0064] Step 5, perform multiple measurement experiments to obtain measured displacement values ​​and standard values, obtain indication errors based on the measured displacement values ​​and standard values ​​obtained by experimental measurement, and compensate the indication errors to the measured displacement values ​​to obtain compensated and calibrated measured displacement values.

[0065] The measured displacement value after the compensation calibration is:

[0066] = .

[0067] in, Represents the measured displacement value after compensation calibration, Indicates the measured displacement value, Indicates indication error.

[0068] This embodiment also provides a spectral confocal displacement sensor calibration device, which is combined with a spectral confocal displacement sensor calibration method and is used to calibrate the spectral confocal displacement sensor 5 to be calibrated. Figure 1 As shown, it includes a laser interferometer 1, a movable slide 2, a laser interferometer reflector 3, a spectral confocal calibration plate 4, a movable slide controller 7, a host computer 8, and a spectral confocal displacement sensor controller 9.

[0069] The spectral confocal calibration plate 4 is installed on the workbench through the movable slide 2, and the laser interferometer reflector 3 is fixed to the spectral confocal calibration plate 4. The movable slide 2 is used for the horizontal movement of the spectral confocal calibration plate 4 on the workbench. The spectral confocal calibration plate 4 is a thin plate, and the two sides of the thin plate are smooth and parallel, and need to have a high degree of parallelism. The material is generally ceramic. The movable slide 2 adopts a precision movable slide. The spectral confocal calibration plate 4 is installed on the movable slide 2, and the movable slide is controlled by the host computer 8, and can realize automatic one-dimensional movement.

[0070] The laser interferometer 1, the spectral confocal calibration plate 4, and the spectral confocal displacement sensor 5 to be calibrated are installed on a workbench, and the laser interferometer 1, the laser interferometer reflector 3, the spectral confocal calibration plate 4, the spectral confocal calibration plate 4, and the spectral confocal displacement sensor 5 to be calibrated are arranged in sequence along the emission light path of the laser interferometer 1. One side of the spectral confocal calibration plate 4 is fixed to the laser interferometer reflector 3 of the laser interferometer 1, and the laser interferometer 1 is set up in the same section to measure the displacement of the spectral confocal calibration plate 4. The spectral confocal displacement sensor 5 to be calibrated is set up on the other side of the spectral confocal calibration plate 4 and adjusted to a suitable position to ensure that the optical axis of the laser interferometer 1 is as coaxial as possible with the optical axis of the spectral confocal displacement sensor 5 to be calibrated. In addition, it is also necessary to ensure that the normal of the spectral confocal calibration plate 4 is as parallel as possible to the optical axis of the laser interferometer 1.

[0071] The movable slide controller 7 is connected to the movable slide 2, the spectral confocal displacement sensor controller 9 is connected to the spectral confocal displacement sensor 5 to be calibrated, and the host computer 8 is connected to the laser interferometer 1, the movable slide controller 7, and the spectral confocal displacement sensor controller 9 respectively.

[0072] It also includes an environment compensation sensor 6 , which is used for light compensation of the laser interferometer 1 .

[0073] The movable slide 2 includes a motor, a bracket, a screw, and a threaded slider. The motor and the bracket are mounted on a workbench. The screw is mounted on the bracket through a bearing. The threaded slider is threadedly connected to the screw, and the threaded slider is slidably connected to the bracket. The spectral confocal calibration plate 4 is fixedly mounted on the threaded slider.

[0074] When the spectral confocal calibration plate moves within the measurement range of the spectral confocal displacement sensor being calibrated, the host computer records the wavelengths corresponding to different positions. At the same time, the laser interferometer records the standard value of the corresponding calibrated point.

[0075] If the calibrated spectral confocal displacement sensor already has a displacement output function, the measured displacement value can be compared and calculated with the standard value to obtain the indication error, and then the calibrated spectral confocal displacement sensor can be compensated. In this way, a spectral confocal displacement sensor with higher measurement accuracy can be obtained.

[0076] The spectral confocal displacement sensor calibration method and device of this embodiment can greatly improve the accuracy and calibration efficiency of the spectral confocal displacement sensor.

[0077] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A spectral confocal displacement sensor calibration method, characterized in that: A spectral confocal displacement sensor calibration device is used to calibrate a spectral confocal displacement sensor (5) to be calibrated. The spectral confocal displacement sensor calibration device comprises a laser interferometer (1), a movable slide (2), a laser interferometer reflector (3), a spectral confocal calibration plate (4), a movable slide controller (7), a host computer (8), and a spectral confocal displacement sensor controller (9); The spectral confocal calibration plate (4) is mounted on a workbench via a movable slide (2), and the laser interferometer reflector (3) is fixed to the spectral confocal calibration plate (4), and the movable slide (2) is used for horizontal movement of the spectral confocal calibration plate (4) on the workbench; The laser interferometer (1), the spectral confocal calibration plate (4), and the spectral confocal displacement sensor (5) to be calibrated are mounted on a workbench, and the laser interferometer (1), the laser interferometer reflector (3), the spectral confocal calibration plate (4), the spectral confocal calibration plate (4), and the spectral confocal displacement sensor (5) to be calibrated are arranged in sequence along an emission light path of the laser interferometer (1); The movable slide controller (7) is connected to the movable slide (2), the spectral confocal displacement sensor controller (9) is connected to the spectral confocal displacement sensor (5) to be calibrated, and the host computer (8) is respectively connected to the laser interferometer (1), the movable slide controller (7), and the spectral confocal displacement sensor controller (9); The following steps are involved: Step 1, start the laser interferometer (1) to emit laser, and start the spectral confocal displacement sensor (5) to be calibrated; Step 2, the upper computer (8) controls the mobile slide (2) to work through the mobile slide controller (7), and the mobile slide (2) controls the movement of the spectral confocal calibration plate (4); the laser emitted by the laser interferometer (1) is reflected back by the laser interferometer reflector (3), and the distance moved forward and backward by the laser interferometer reflector (3) is measured as the standard value of the calibration point; the light source emitted by the spectral confocal displacement sensor (5) to be calibrated is irradiated on the spectral confocal calibration plate (4), and when the light is focused on the spectral confocal calibration plate (4), the wavelength corresponding to the calibration point of the spectral confocal calibration plate (4) is measured; Step 3, when the spectral confocal calibration plate (4) moves within the measurement range of the spectral confocal displacement sensor (5) to be calibrated, the host computer (8) records the wavelengths corresponding to different displacement calibration points, and the laser interferometer (1) records the standard values ​​of the corresponding calibration points; Step 4, establishing a measurement calibration model of the spectral confocal displacement sensor (5) according to the wavelength of the collected displacement calibration point; obtaining the measured displacement value by measuring the calibration model; The measurement calibration model is: ; ; ; in, Indicates the measured displacement value, represents the wavelength, represents the number of displacement calibration points, represents the measurement calibration factor of one, represents the measurement calibration factor of two, Indicates the measurement calibration factor three, represents the measurement calibration constant, Indicates The wavelength of the displacement calibration point, Indicates displacement calibration point; Step 5, performing multiple measurement experiments to obtain measured displacement values ​​and standard values, obtaining indication errors according to the measured displacement values ​​and standard values ​​obtained by experimental measurement, and compensating the indication errors to the measured displacement values ​​to obtain compensated and calibrated measured displacement values; The measured displacement value after the compensation calibration is: = ； in, Represents the measured displacement value after compensation calibration, Indicates the measured displacement value, Indicates indication error.

2. The spectral confocal displacement sensor calibration method according to claim 1, characterized in that: It also includes an environmental compensation sensor (6), wherein the environmental compensation sensor (6) is used for light compensation of the laser interferometer (1).

3. The spectral confocal displacement sensor calibration method according to claim 2, characterized in that: The normal line of the spectral confocal calibration plate (4) is parallel to the optical axis of the laser interferometer (1).

4. The spectral confocal displacement sensor calibration method according to claim 3, characterized in that: The optical axis of the laser interferometer (1) is coaxial with the optical axis of the spectral confocal displacement sensor (5) to be calibrated.

5. The spectral confocal displacement sensor calibration method according to claim 4, characterized in that: The movable slide (2) comprises a motor, a bracket, a screw and a threaded slider, wherein the motor and the bracket are mounted on a workbench, the screw is mounted on the bracket via a bearing, the threaded slider is threadedly connected to the screw, and the threaded slider is slidably connected to the bracket; the spectral confocal calibration plate (4) is fixedly mounted on the threaded slider.

6. The spectral confocal displacement sensor calibration method according to claim 5, characterized in that: The spectral confocal calibration plate (4) is a thin plate, and the two surfaces of the thin plate are smooth and parallel.

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