A method for self-calibration of optical probe head accuracy based on point self-focusing principle

Abstract

The present invention discloses a method for self-calibration of the precision of an optical probe probe based on the point self-focusing principle. The method equips the optical probe probe with a differential confocal module, and utilizes the high-precision characteristics of the differential confocal module to make the position of the focal point of the objective lens strictly correspond to the center position of the self-focusing sensor. The method can be used in the installation and adjustment stage of the optical probe probe, and can also be used in the periodic calibration stage of the optical probe probe. The differential confocal module included in the method can be used to calibrate the correspondence between the position of the focal point of the objective lens and the center position of the self-focusing sensor, ensuring that the focal point of the objective lens is on the surface of the object to be measured, and the reflected laser spot is also focused on the center of the self-focusing sensor. The method of the present invention can be used in the installation and adjustment stage of the optical probe probe, and can also be used in the periodic calibration stage of the optical probe probe. It helps to ensure the measurement accuracy of the optical probe probe. The method of the present invention has a wide range of uses, and is particularly suitable for calibration of the focusing accuracy of the optical probe probe.

Description

Technical Field

[0001] The invention relates to the field of precision measurement, and in particular to a precision self-calibration method for an optical probe probe based on the point self-focusing principle. Background Art

[0002] The geometric accuracy measurement of micro-complex parts is a global problem. This is mainly because the depth and width of the grooves of micro-complex parts are relatively large. Due to the limitation of the size of the probe ball, the traditional contact measurement method cannot detect the bottom of the groove, that is, it cannot measure the geometric characteristics of the complete groove. Optical measurement methods are also unable to effectively obtain bottom data due to edge occlusion and surface inclination. With the development of optical measurement technology, optical probe probes with smaller "probe" sizes have gradually entered the field of vision of researchers. Among them, optical probe probes based on the point self-focusing principle have been widely used due to their simple measurement principles and high measurement efficiency. Focus accuracy is the most important factor determining the measurement accuracy of optical probe probes based on the point self-focusing principle. Research on the accuracy self-calibration method of optical probe probes based on the point self-focusing principle plays a vital role in improving the measurement accuracy of optical probe probes. Summary of the invention

[0003] The purpose of the present invention is to improve the focusing accuracy of an optical probe probe based on the point self-focusing principle, and to propose a method for self-calibration of the accuracy of an optical probe probe based on the point self-focusing principle. The method equips the optical probe probe with a differential confocal module, and utilizes the high-precision characteristics of the differential confocal module to make the position of the objective lens focus strictly correspond to the center position of the self-focusing sensor. The method can be used in the installation and adjustment stage of the optical probe probe, and can also be used in the regular calibration stage of the optical probe probe.

[0004] The above purpose is achieved through the following technical solutions:

[0005] The optical probe probe based on the point self-focusing principle of the optical probe probe precision self-calibration method includes an illumination light source, a laser light source, a first lens, a second lens, a self-focusing sensor, a CCD camera, a first beam splitter, a second beam splitter, a z-axis controller, a z-axis moving platform, an objective lens, a z-axis grating, a differential confocal module, a first reflector, a second reflector, a third reflector and a fourth reflector. The differential confocal module includes a third lens, a third beam splitter, a first aperture, a second aperture, a first photodetector, a second photodetector and a differential light intensity signal processing module; the laser beam emitted by the laser light source is reflected by the second reflector, transmitted through the first beam splitter, and then reflected by the second beam splitter. After being focused by the objective lens, it irradiates the surface of the object to be measured. The light reflected back to the objective lens is collimated, and a part of the light is focused by the first lens onto the self-focusing sensor after being reflected by the second beam splitter and the first beam splitter. Another part of the light is reflected by the second beam splitter, transmitted through the first beam splitter, and then reflected by the fourth reflector and the third reflector to irradiate the inside of the differential confocal module; the position of the focal point of the objective lens corresponds to the center position of the self-focusing sensor, that is, when the laser beam is focused on the surface of the object to be measured, the reflected laser beam can also be focused by the first lens to the center of the self-focusing sensor; the differential confocal module is used to calibrate the correspondence between the position of the focal point of the objective lens and the center position of the self-focusing sensor; the white light beam emitted by the illumination light source is reflected by the first reflector, transmitted through the first beam splitter, and then reflected by the second beam splitter, and after being focused by the objective lens, it irradiates the surface of the object to be measured. The light reflected back to the objective lens is collimated and then transmitted through the second beam splitter, and is focused by the second lens onto the CCD camera; the CCD camera is used to monitor the real-time information of the surface of the object to be measured; when the objective lens does not focus the laser beam on the surface of the object to be measured, the first lens will not focus the laser beam on the center of the self-focusing sensor, and the self-focusing sensor will send the generated deviation signal to the z-axis controller, thereby controlling the z-axis moving platform to move along the moving direction of the probe, so that the position of the objective lens focus and the center position of the self-focusing sensor are balanced again; the z-axis grating is used to record the displacement of the probe movement.

[0006] The laser beam entering the differential confocal module is converged by the third lens, and a part of the light is reflected by the third beam splitter, and after passing through the first aperture, it is irradiated onto the first photodetector behind the focal plane. The other part of the light is transmitted through the third beam splitter, and after passing through the second aperture, it is irradiated onto the second photodetector in front of the focal plane. Light intensity signals are generated on the first photodetector and the second photodetector, namely, the post-focus light intensity response curve and the pre-focus light intensity response curve. After the two parts of the signal are processed by the differential light intensity signal processing module, a differential light intensity response curve is obtained. The differential light intensity curve has the characteristic of strictly crossing the zero point, so its zero position has a better correspondence with the position of the objective lens focus, that is, when the objective lens focus is on the surface of the object to be measured, the differential signal output is zero. At the same time, the differential light intensity curve within the measurement range of the optical probe probe has very good linearity.

[0007] When assembling the optical probe, follow the steps below:

[0008] Step 1: The objective lens of the optical probe probe performs scanning measurement along the moving direction of the probe within the full measurement range;

[0009] Step 2: The differential confocal module collects and processes data to obtain a differential light intensity response curve;

[0010] Step 3: Determine that the object to be measured is located on the focal plane of the objective lens according to the zero point of the differential light intensity response curve;

[0011] Step 4: Adjust the spatial position of the autofocus sensor until the output signal of the autofocus sensor is zero;

[0012] Step 5: The self-focusing sensor is fixedly installed inside the optical probe head. At this time, the zero point position of the differential light intensity response curve, the position of the objective lens focus and the position of the center of the self-focusing sensor correspond to each other.

[0013] For regular calibration, follow the steps below:

[0014] Step 6: The objective lens of the optical probe probe performs scanning measurement along the moving direction of the probe within the full measurement range;

[0015] Step 7: The differential confocal module collects and processes data to obtain a differential light intensity response curve;

[0016] Step 8: Determine that the object to be measured is located on the focal plane of the objective lens according to the zero point of the differential light intensity response curve;

[0017] Step 9: Record the output data of the autofocus sensor and the output data of the z-axis grating;

[0018] Step 10: In the linear region of the self-focusing sensor, the output data of the z-axis grating is matched with the output data of the self-focusing sensor to complete the precision self-calibration of the optical probe head.

[0019] The present invention has the following characteristics and beneficial effects:

[0020] The differential confocal module included in the method of the present invention can be used to calibrate the corresponding relationship between the position of the objective lens focus and the center position of the self-focusing sensor, ensuring that the objective lens focus is on the surface of the object to be measured, and the reflected laser spot is also focused on the center of the self-focusing sensor. The method of the present invention can be used in the installation and adjustment stage of the optical probe probe, and can also be used in the regular calibration stage of the optical probe probe. It helps to ensure the measurement accuracy of the optical probe probe.

[0021] The method of the invention has wide applications, and is particularly suitable for calibrating the focusing accuracy of an optical probe probe. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the structure of the optical probe head based on the point self-focusing principle.

[0023] Figure 2 Schematic diagram of the differential confocal module structure.

[0024] Figure 3 Schematic diagram of the differential light intensity response curve.

[0025] Figure 4 Schematic diagram of the calibration focus system.

[0026] Markings in the figure: 1-illumination light source; 2-laser light source; 3-first lens; 4-self-focusing sensor; 5-CCD camera; 6-second lens; 7-second spectroscope; 8-z-axis controller; 9-z-axis moving platform; 10-probe moving direction; 11-objective lens; 12-z-axis grating; 13-first spectroscope; 14-third reflector; 15-differential confocal module; 16-fourth reflector; 17-first reflector; 18-second reflector; 19-measured object; 20-laser beam entering the differential confocal module; 21-third lens; 22-first aperture; 23-first photodetector; 24-third spectroscope; 25-second aperture; 26-second photodetector; 27-differential light intensity signal processing module, 28-pre-focus light intensity response curve; 29-post-focus light intensity response curve; 30-differential light intensity response curve. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. However, this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

[0028] like Figure 1As shown, the optical probe probe based on the point self-focusing principle includes an illumination light source 1, a laser light source 2, a first lens 3, a second lens 6, a self-focusing sensor 4, a CCD camera 5, a first beam splitter 13, a second beam splitter 7, a z-axis controller 8, a z-axis moving platform 9, an objective lens 11, a z-axis grating 12, a differential confocal module 15, a first reflector 17, a second reflector 18, a third reflector 14 and a fourth reflector 16; the laser beam emitted by the laser light source 2 is reflected by the second reflector 18, transmits through the first beam splitter 13, is reflected by the second beam splitter 7, is focused by the objective lens 11, and irradiates the surface of the object to be measured 19. The light reflected back to the objective lens 11 is collimated, and a part of the light is focused by the first lens 3 onto the self-focusing sensor 4 after being reflected by the second beam splitter 7 and the first beam splitter 13. Another part of the light is reflected by the second beam splitter 7, and is transmitted through the first beam splitter 13, and then is reflected by the fourth reflector 16 and the third reflector 14, and is irradiated to the inside of the differential confocal module 15; the position of the focus of the objective lens 11 corresponds to the center position of the self-focusing sensor 4, that is, when the laser beam is focused on the surface of the object to be measured 19, the reflected laser beam can also be focused by the first lens 3 to the center of the self-focusing sensor 4; the differential confocal module 15 is used to calibrate the correspondence between the position of the focus of the objective lens 11 and the center position of the self-focusing sensor 4; the white light beam emitted by the illumination light source 1 is reflected by the first reflector 17, and is transmitted through the first beam splitter 13, and then is reflected by the second beam splitter 7, and after being focused by the objective lens 11, it is irradiated to the surface of the object to be measured 19. The light reflected back to the objective lens 11 is collimated and then transmitted through the second beam splitter 7, and is focused by the second lens 6 onto the CCD camera 5; the CCD camera 5 is used to monitor the real-time information of the surface of the object 19 to be measured; when the objective lens 11 does not focus the laser beam onto the surface of the object 19 to be measured, the first lens 13 will not focus the laser beam onto the center of the self-focusing sensor 4, and the self-focusing sensor 4 will send the generated deviation signal to the z-axis controller 8, thereby controlling the z-axis moving platform 9 to move along the probe moving direction 10, so that the position of the focus of the objective lens 11 and the center position of the self-focusing sensor 4 are balanced again; the z-axis grating 12 is used to record the displacement of the probe movement.

[0029] like Figure 2As shown, the laser beam 20 entering the differential confocal module 15 is converged by the third lens 21, and a part of the light is reflected by the third beam splitter 24, passes through the first aperture 22, and irradiates the first photodetector 23 behind the focal plane. The other part of the light is transmitted through the third beam splitter 24, passes through the second aperture 25, and irradiates the second photodetector 26 in front of the focal plane. Light intensity signals are generated on the first photodetector 23 and the second photodetector 26, namely, the post-focus light intensity response curve 29 and the pre-focus light intensity response curve 28. After the two parts of the signal are processed by the differential light intensity signal processing module 27, a differential light intensity response curve 30 is obtained. The differential light intensity curve 30 has a strict zero-crossing characteristic, so its zero position has a better corresponding relationship with the position of the focus of the objective lens 11, that is, when the focus of the objective lens 11 is on the surface of the object 19 to be measured, the differential signal output is zero. At the same time, the differential light intensity curve 30 within the measurement range of the optical probe probe has very good linearity.

[0030] When assembling the optical probe, follow the steps below:

[0031] Step 1: The objective lens 11 of the optical probe probe performs scanning measurement along the moving direction of the probe within the full measurement range;

[0032] Step 2: The differential confocal module 15 collects and processes data to obtain a differential light intensity response curve 30;

[0033] Step 3: Determine that the object 19 is located on the focal plane of the objective lens 11 according to the zero point of the differential light intensity response curve 30;

[0034] Step 4: Adjust the spatial position of the autofocus sensor 4 until the output signal of the autofocus sensor 4 is zero;

[0035] Step 5: The autofocus sensor 4 is fixedly installed inside the optical probe head. At this time, the zero point position of the differential light intensity response curve 30, the position of the focus of the objective lens 11 and the position of the center of the autofocus sensor 4 correspond to each other.

[0036] For regular calibration, follow the steps below:

[0037] Step 6: The objective lens 11 of the optical probe probe performs scanning measurement along the moving direction of the probe within the full measurement range;

[0038] Step 7: The differential confocal module 15 collects and processes data to obtain a differential light intensity response curve 30;

[0039] Step 8: Determine that the object 19 is located on the focal plane of the objective lens 11 according to the zero point of the differential light intensity response curve 30;

[0040] Step nine: record the output data of the self-focusing sensor 4 and the output data of the z-axis grating 12;

[0041] Step 10: In the linear region of the self-focusing sensor 4, the output data of the z-axis grating 12 is matched with the output data of the self-focusing sensor 4 to complete the precision self-calibration of the optical probe head.

[0042] The above description of the disclosed implementation cases enables professionals and technicians in the field to implement or use the present invention, and various modifications to the implementation cases are obvious to professionals and technicians in the field. The general principles defined herein can be embodied in other implementation cases without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the implementation cases shown in the present method, but requires the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A method for self-calibrating the precision of an optical probe probe based on the point self-focusing principle, wherein the optical probe probe implementing the method comprises an illumination light source, a laser light source, a first lens, a second lens, a self-focusing sensor, a CCD camera, a first beam splitter, a second beam splitter, a z-axis controller, a z-axis moving platform, an objective lens, a z-axis grating, a differential confocal module, a first reflector, a second reflector, a third reflector and a fourth reflector; wherein the differential confocal module comprises a third lens, a third beam splitter, a first aperture, a second aperture, a first photodetector, a second photodetector and a differential light intensity signal processing module; a laser beam emitted by the laser light source is reflected by the second reflector, transmitted through the first beam splitter, then reflected by the second beam splitter, and irradiated onto the surface of the object to be measured after being focused by the objective lens; the light reflected back to the objective lens is collimated, and a part of the light is focused by the first lens onto the self-focusing The sensor; another part of the light is reflected by the second beam splitter, and is transmitted through the first beam splitter, and then is reflected by the fourth reflector and the third reflector, and is irradiated to the inside of the differential confocal module; the position of the focal point of the objective lens corresponds to the center position of the self-focusing sensor, that is, when the laser beam is focused on the surface of the object to be measured, the reflected laser beam can also be focused by the first lens to the center of the self-focusing sensor; the differential confocal module is used to calibrate the correspondence between the position of the focal point of the objective lens and the center position of the self-focusing sensor; the white light beam emitted by the illumination light source is reflected by the first reflector, and is transmitted through the first beam splitter, and then is reflected by the second beam splitter, and after being focused by the objective lens, it is irradiated to the surface of the object to be measured; the light reflected back to the objective lens is collimated and then transmitted through the second beam splitter, and is focused by the second lens onto the CCD camera; the CCD camera is used to monitor the real-time information of the surface of the object to be measured; the z-axis grating is used to record the displacement of the probe; Features: When assembling the optical probe, follow the steps below: Step 1: The objective lens of the optical probe probe performs scanning measurement along the moving direction of the probe within the full measurement range; Step 2: The differential confocal module collects and processes data to obtain a differential light intensity response curve; Step 3: Determine that the object to be measured is located on the focal plane of the objective lens according to the zero point of the differential light intensity response curve; Step 4: Adjust the spatial position of the autofocus sensor until the output signal of the autofocus sensor is zero; Step 5: The self-focusing sensor is fixedly installed inside the optical probe head. At this time, the zero point position of the differential light intensity response curve, the position of the objective lens focus and the position of the center of the self-focusing sensor correspond to each other; For regular calibration, follow the steps below: Step 6: The objective lens of the optical probe probe performs scanning measurement along the moving direction of the probe within the full measurement range; Step 7: The differential confocal module collects and processes data to obtain a differential light intensity response curve; Step 8: Determine that the object to be measured is located on the focal plane of the objective lens according to the zero point of the differential light intensity response curve; Step 9: Record the output data of the autofocus sensor and the output data of the z-axis grating; Step 10: In the linear region of the self-focusing sensor, the output data of the z-axis grating is matched with the output data of the self-focusing sensor to complete the precision self-calibration of the optical probe head.

2. The optical probe probe precision self-calibration method based on the point self-focusing principle according to claim 1 is characterized in that: The laser beam entering the differential confocal module is converged by the third lens, and a part of the light is reflected by the third beam splitter, passes through the first aperture, and irradiates the first photodetector behind the focal plane; the other part of the light is transmitted through the third beam splitter, passes through the second aperture, and irradiates the second photodetector in front of the focal plane; light intensity signals are generated on the first photodetector and the second photodetector, namely, the post-focus light intensity response curve and the pre-focus light intensity response curve; the two parts of the signal are processed by the differential light intensity signal processing module to obtain a differential light intensity response curve; the differential light intensity curve has a strict zero-crossing characteristic, so the zero position has a corresponding relationship with the position of the objective lens focus, that is, when the objective lens focus is on the surface of the object to be measured, the differential signal output is zero; at the same time, the differential light intensity curve within the measurement range of the optical probe probe has very good linearity.

3. The optical probe probe precision self-calibration method based on the point self-focusing principle according to claim 1 is characterized in that: When the objective lens does not focus the laser beam onto the surface of the object being measured, the first lens will not focus the laser beam onto the center of the self-focusing sensor. The self-focusing sensor will send the generated deviation signal to the z-axis controller, thereby controlling the z-axis moving platform to move along the moving direction of the probe, so that the position of the objective lens focus and the center position of the self-focusing sensor are balanced again.

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