A contact micro-nano probe with online thermal drift compensation function

Abstract

The present invention discloses a contact micro-nano probe with an online thermal drift compensation function, comprising a probe housing with a cylindrical inner cavity; a microsphere probe is vertically fixed on the lower surface of an elastic spring, a beam splitter prism is fixed on the upper surface of the elastic spring, a laser and a right-angle prism are fixedly arranged on the lower cover of the probe housing, and the elastic spring is arranged on the hollow circular surface of the lower cover; the laser and the right-angle prism are respectively located on both sides of the beam splitter prism, so that the collimated light emitted horizontally by the laser is projected onto the beam splitter prism, the light reflected by the beam splitter prism is projected upward to a first position sensitive detector, the light transmitted by the beam splitter prism is projected onto the right-angle prism, and is reflected by the right-angle prism and projected upward to a second position sensitive detector; the second position sensitive detector is used to realize thermal drift measurement of the output light, thereby effectively improving thermal stability.

Description

Technical Field

[0001] The present invention belongs to the field of micro-nano measurement, and more specifically relates to a high-precision contact micro-nano probe used in a nanometer three-dimensional measuring machine. Background Art

[0002] With the development of ultra-precision processing and manufacturing technology, the demand for micro-nano detection is becoming increasingly urgent. The nano three-dimensional coordinate measuring machine is a typical equipment in the field of micro-nano detection, and the probe is a key component that affects its overall measurement accuracy. In the existing technology, the piezoelectric vibration probe has high precision, but the excitation structure composed of its internal piezoelectric driver has a complex processing process, and the overall manufacturing and maintenance of the probe is relatively difficult; the electromagnetic probe has high sensitivity and a large measurement range, but its accuracy is easily affected by strong external magnetic interference; the piezoresistive probe has a simple structure, but the sensor unit in the probe needs to be made through the MEMS etching process, which is relatively expensive.

[0003] In the invention patent specification with publication number CN102506725B, the applicant proposed a three-dimensional micro-nano contact scanning probe that uses an optical sensor for sensing. Compared with piezoelectric, electromagnetic and piezoresistive probes, it can achieve higher sensitivity and accuracy. However, the probe measurement unit contains four four-quadrant detectors and five dichroic prisms, with a complex structure and high difficulty in adjusting the optical path.

[0004] In the invention patent specification with publication number CN104457613A, the applicant proposed a three-dimensional micro-nano measurement probe. Through the setting of a double-layer suspension structure, only two four-quadrant photoelectric sensors are needed to complete the sensing function. The production cost is low, but the assembly process is relatively cumbersome, the probe has poor stability in the vertical direction, and low accuracy.

[0005] In the invention patent specification with publication number CN105783772B, the applicant proposed a single-sensor three-dimensional micro-nano contact trigger measurement probe, which uses a single optical sensor to sense the deflection of the probe. Without sacrificing accuracy, the probe structure is simplified, and its cost is low and installation and adjustment are convenient. However, in actual applications, the heat generated by the laser inside the probe causes serious drift of the emitted light, and the long-term measurement stability in industrial environments is poor. Summary of the Invention

[0006] The present invention aims to overcome the shortcomings of the above-mentioned prior art and provide a contact micro-nano probe with an online thermal drift compensation function. While ensuring high-precision and high-stability detection effects, it has the advantages of simple structure and low cost. It does not require a temperature sensor to compensate for the thermal drift error of the probe and improve the thermal stability of the probe.

[0007] The present invention adopts the following technical solutions to solve the technical problems:

[0008] The contact-type micro-nano probe with online thermal drift compensation function of the present invention is characterized by:

[0009] The probe housing is formed by setting an upper cover and a lower cover at the top and bottom ends of the cylindrical vertical tube respectively, forming a probe housing with a cylindrical inner cavity, and the lower cover is an annular end cover with a hollow circular surface;

[0010] A probe unit includes a microsphere probe vertically fixed at the center of the lower surface of an elastic spring, a beam splitter prism fixed at the center of the upper surface of the elastic spring, a laser and a right-angle prism fixed on the upper end surface of a lower cover, and the elastic spring disposed on the hollow circular surface of the lower cover; the laser and the right-angle prism are located on either side of the beam splitter prism, so that collimated light emitted horizontally by the laser is projected onto the beam splitter prism, and reflected light from the beam splitter prism is projected upward; and transmitted light from the beam splitter prism is projected onto the right-angle prism and reflected by the right-angle prism and projected upward.

[0011] The sensing unit includes a first position-sensitive detector and a second position-sensitive detector fixedly arranged on the lower end surface of the upper cover. The reflected light formed in the beam splitter prism is projected onto the first position-sensitive detector, and the reflected light from the right-angle prism is projected onto the second position-sensitive detector. The second position-sensitive detector is used to measure the thermal drift of the output light.

[0012] The contact micro-nano probe with online thermal drift compensation function of the present invention is also characterized in that: a laser fixing seat and a beam splitter prism fixing seat are integrally arranged on the lower cover, the laser is fixedly arranged in the laser fixing seat, and the beam splitter prism is fixedly arranged in the beam splitter prism fixing seat.

[0013] The contact micro-nano probe with online thermal drift compensation function of the present invention is also characterized in that the distance d1 between the center of the reflective surface of the beam splitter prism and the detection surface of the first position sensitive detector is set to:

[0014] d1=d2+d3

[0015] in:

[0016] d2 represents the distance between the center of the reflective surface of the beam splitter and the center of the reflective surface of the right-angle prism;

[0017] d3 represents the distance between the center of the reflecting surface of the right-angle prism and the detection surface of the second position sensitive detector;

[0018] The contact micro-nano probe with the thermal drift online compensation function of the present invention is also characterized in that the thermal drift online compensation method is set as follows:

[0019] The voltage signal change value Δv of the second position sensitive detector caused by the thermal drift of the microsphere probe is calculated by formula (1): 21, Δv 22 , Δv 23 , Δv 24 :

[0020]

[0021] in:

[0022] v 21 、v 22 、v 23 、v 24 is the four-quadrant initial voltage signal of the second position sensitive detector;

[0023] v 21 '、v 22 '、v 23 '、v 24 ' is the four-quadrant voltage signal output by the second position sensitive detector after the microsphere probe produces thermal drift;

[0024] The displacements x, y, and z of the microsphere probe in two mutually perpendicular directions in the horizontal plane and in the vertical direction after thermal drift compensation are calculated by formula (2):

[0025]

[0026] in:

[0027] v 11 '、v 12 '、v 13 '、v 14 ' is the four-quadrant voltage signal output by the first position sensitive detector after the microsphere probe produces thermal drift;

[0028] k x1 、k y1 and k z1 It is the proportional coefficient obtained by probe calibration, which refers to the proportional coefficient between the displacement of the stylus ball measured by the first position sensitive detector in two mutually perpendicular directions in the horizontal plane and in the vertical direction, and the output four-quadrant voltage signal of the first position sensitive detector.

[0029] The contact micro-nano probe with online thermal drift compensation function of the present invention is also characterized in that: the proportional coefficient k x1 、k y1 、k z1 Calculated by formula (3):

[0030]

[0031] in:

[0032] ΔV X11 , ΔVX12 , ΔV X13 , ΔV X14 It is the change value of the four-quadrant voltage signal output by the first position sensitive detector after the measuring ball produces a fixed displacement S in the X direction;

[0033] ΔV Y11 , ΔV Y12 , ΔV Y13 , ΔV Y14 It is the change value of the four-quadrant voltage signal output by the first position sensitive detector after the measuring ball produces a fixed displacement S in the Y direction;

[0034] ΔV Z11 , ΔV Z12 , ΔV Z13 , ΔV Z14 It is the change value of the four-quadrant voltage signal output by the first position sensitive detector after the measuring ball produces a fixed displacement S in the Z direction;

[0035] Probe calibration process: Use the electric displacement platform to move along the X, Y, and Z directions and touch the probe ball, so that the probe ball produces a fixed displacement S, and record the corresponding four voltage output changes. Use formula (3) to calculate the proportional coefficient k x1 、k y1 、k z1 value.

[0036] Compared with the existing technology, the beneficial effects of the present invention are embodied in:

[0037] 1. The optical path structure of the present invention is simple, and only a beam splitter prism and a right-angle prism are used to realize the micro-nano-level measurement function of the trigger probe. Without using a temperature sensing device, the probe has the function of thermal drift compensation, thereby improving its thermal stability.

[0038] 2. This invention adopts a split design, dividing the probe into a probe unit and a sensing unit, which simplifies assembly. The probe's microsphere probe and elastic spring are consumable materials. They are assembled together on the probe's lower cover to form the probe unit. In the event of damage, only the probe unit needs to be replaced, eliminating the need to repair the entire probe, effectively reducing maintenance difficulty.

[0039] 3. The present invention adopts an integrated mechanical structure, which significantly reduces the number of machined parts required for the probe. Only the probe upper cover, cylindrical barrel and probe lower cover are required. Compared with piezoelectric, electromagnetic and piezoresistive probes, the present invention has a simple structure, low manufacturing and maintenance costs, and is more practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of the internal structure of the present invention;

[0041] Figure 2 Schematic diagram of the measuring optical path of the present invention;

[0042] Figure 3 It is a schematic diagram of the external structure of the present invention;

[0043] Figure 4 This is a schematic diagram of the installation of the elastic mechanism and prism in the present invention;

[0044] Figure 5 This is a schematic diagram of the installation of the position sensitive detector in the present invention;

[0045] Figure 6 This is a schematic diagram of the horizontal X-axis measurement principle of the present invention;

[0046] Figure 7 This is a schematic diagram of the horizontal Y-axis measurement principle of the present invention;

[0047] Figure 8 It is a schematic diagram of the vertical measurement principle of the present invention;

[0048] Figure 9 This is a schematic diagram of the thermal drift compensation principle of the present invention;

[0049] Figure 10 This is a schematic diagram of the dimensions of the optical path and optical arm of the present invention;

[0050] Numbers in the figure: 1 probe upper cover, 2 first position sensitive detector, 3 second position sensitive detector, 4 cylindrical body, 5 right-angle prism, 6 probe lower cover, 6a right-angle prism fixing seat, 6b laser fixing seat, 7 elastic spring, 8 microsphere probe, 9 laser, 10 spectroscopic prism. DETAILED DESCRIPTION

[0051] The contact micro-nano probe with online thermal drift compensation function in this embodiment includes:

[0052] like Figure 1 and Figure 3 As shown: the probe shell is provided with an upper cover 1 and a lower cover 6 at the top and bottom ends of the cylindrical vertical tube 4 respectively, forming a probe shell with a cylindrical inner cavity. The lower cover 6 is an annular end cover with a hollow circular surface. The diameter of the probe shell is 49 mm and the height is 57 mm.

[0053] like Figure 1 、 Figure 2 and Figure 4As shown: a probe unit, which includes a microsphere probe 8 fixed vertically at the center of the lower surface of the elastic spring 7 by gluing, a dichroic prism 10 fixed at the center of the upper surface of the elastic spring 7 by gluing, a laser 9 and a right-angle prism 5 fixedly arranged on the upper end surface of the lower cover 6, and the elastic spring 7 is arranged at the hollow circular surface of the lower cover 6; the laser 9 and the right-angle prism 5 are located on both sides of the dichroic prism 10, so that the collimated light emitted horizontally by the laser 9 is projected onto the dichroic prism 10, and the reflected light of the dichroic prism 10 is projected upward, and the transmitted light of the dichroic prism 10 is projected onto the right-angle prism 5 and reflected by the right-angle prism 5 and projected upward.

[0054] like Figure 2 and Figure 5 The sensor unit shown in the figure includes a first position-sensitive detector 2 and a second position-sensitive detector 3 fixedly mounted on the lower end surface of the upper cover 1. Light reflected from the beam splitter prism 10 is projected onto the first position-sensitive detector 2, while light reflected from the right-angle prism 5 is projected onto the second position-sensitive detector 3. The second position-sensitive detector 3 is used to measure thermal drift of the emitted light. The sensing element of the probe in this invention is a position-sensitive detector, which can be replaced by a four-quadrant detector. The light source is a semiconductor laser, or a light-emitting diode.

[0055] In specific implementation, the corresponding technical measures also include:

[0056] like Figure 4 As shown: a laser fixing seat 6a and a beam splitter prism fixing seat 6b are integrally arranged on the lower cover 6, the laser 9 is fixedly arranged in the laser fixing seat 6a, and the beam splitter prism 5 is fixedly arranged in the beam splitter prism fixing seat 6b.

[0057] like Figure 10 As shown: the distance d1 between the center of the reflecting surface of the beam splitter prism 10 and the detecting surface of the first position sensitive detector 2 is set:

[0058] d1=d2+d3

[0059] in:

[0060] d2 represents the distance between the center of the reflecting surface of the beam splitter prism 10 and the center of the reflecting surface of the right-angle prism 5;

[0061] d3 represents the distance between the center of the reflecting surface of the right-angle prism 5 and the detecting surface of the second position sensitive detector 3;

[0062] In this embodiment, d1, d2 and d3 are set to 43.5 mm, 16 mm and 27.5 mm respectively.

[0063] like Figure 9 、 10As shown, laser 9 is affected by a combination of ambient temperature fluctuations, self-heating, and thermal deformation of the laser mount 6b structure, causing its emitted light to undergo angular deflection. This simultaneously changes the positions of the light spots on the photosensitive surfaces of the first and second position-sensitive detectors 2 and 3. Because d1 is equal to the sum of d2 and d3, and the size of the beam splitter prism is much smaller than the size of the optical arm of the transmission light path, the linear translation of the transmitted light is almost negligible. Therefore, the signal current changes of the first and second position-sensitive detectors 2 and 3 due to thermal drift are consistent, and the four voltage signals obtained by converting the current signals also change in a consistent manner. When thermal drift occurs during the probe triggering process, the four voltage outputs of the first and second position-sensitive detectors 2 and 3 are all affected by the thermal drift, and in this embodiment, the degree of impact is the same.

[0064] Based on the above setting, when the probe produces thermal drift during the triggering process, the first position sensitive detector 2, in addition to sensing the thermal drift of the probe, also senses the displacement distance of the microsphere compared to the second position sensitive detector 3. The four output voltages of the first position sensitive detector 2 are subtracted from the four voltage change values ​​of the second position sensitive detector 3. By correcting the four output voltages of the first position sensitive detector 2, the thermal compensation function can be realized online.

[0065] Set the thermal drift online compensation method as follows:

[0066] The voltage signal change value Δv of the second position sensitive detector 3 caused by the thermal drift of the microsphere probe is calculated by formula (1): 21 , Δv 22 , Δv 23 , Δv 24 :

[0067]

[0068] in:

[0069] v 21 、v 22 、v 23 、v 24 is the four-quadrant initial voltage signal of the second position sensitive detector 3;

[0070] v 21 '、v 22 '、v 23 '、v 24 ' is the four-quadrant voltage signal output by the second position sensitive detector 3 after the microsphere probe generates thermal drift;

[0071] The displacements x, y, and z of the microsphere probe in two mutually perpendicular directions in the horizontal plane and in the vertical direction after thermal drift compensation are calculated by formula (2):

[0072]

[0073] in:

[0074] v 11 '、v 12 '、v 13 '、v 14 ' is the four-quadrant voltage signal output by the first position sensitive detector 2 after the microsphere probe generates thermal drift;

[0075] k x1 、k y1 and k z1 It is the proportional coefficient obtained by probe calibration, and refers to the proportional coefficient between the displacement of the measuring ball measured by the first position sensitive detector 2 in two mutually perpendicular directions in the horizontal plane and the vertical direction and the output four-quadrant voltage signal of the first position sensitive detector 2.

[0076] In this embodiment, the first position sensitive detector 2 and the second position sensitive detector 3 both adopt a two-dimensional PSD (model S5990-01) produced by Hamamatsu (HAMAMATSU) of Japan, whose rise time is about 1 microsecond, so the dynamic response of thermal drift compensation is relatively fast.

[0077] In this embodiment, the proportionality coefficient k x1 、k y1 、k z1 Calculated by formula (3):

[0078]

[0079] in:

[0080] ΔV X11 , ΔV X12 , ΔV X13 , ΔV X14 It is the change value of the four-quadrant voltage signal output by the first position sensitive detector 2 after the measuring ball generates a fixed displacement S in the X direction;

[0081] ΔV Y11 , ΔV Y12 , ΔV Y13 , ΔV Y14 It is the change value of the four-quadrant voltage signal output by the first position sensitive detector 2 after the measuring ball produces a fixed displacement S in the Y direction;

[0082] ΔV Z11 , ΔV Z12 , ΔV Z13 , ΔV Z14 It is the change value of the four-quadrant voltage signal output by the first position sensitive detector 2 after the measuring ball produces a fixed displacement S in the Z direction;

[0083] Probe calibration process: Use the electric displacement platform to move along the X, Y, and Z directions and touch the probe ball, so that the probe ball produces a fixed displacement S, and record the corresponding four voltage output changes. Use formula (3) to calculate the proportional coefficient k x1 、k y1 、k z1 value.

[0084] The principle of horizontal displacement sensing of the probe is as follows:

[0085] like Figure 6 and Figure 7 As shown in FIG, when the microsphere probe 8 is subjected to a horizontal touch force, the elastic spring 7 and the dichroic prism 10 are laterally offset, the outgoing light beam from the laser 9 is deflected by the reflected light formed in the dichroic prism 10, and the position of the light spot on the photosensitive surface of the first position sensitive detector 2 changes, resulting in a change in the magnitude of the current signal output by the position sensitive detector. The current signals output by the four quadrants are converted into voltage signals using a current / voltage conversion circuit, and the change in the light spot position is converted into a displacement signal output according to formula (2).

[0086] The vertical displacement sensing principle of the probe is set as follows:

[0087] like Figure 8 As shown, when microsphere probe 8 is touched vertically, it drives elastic spring 7 and dichroic prism 10 to shift vertically. The outgoing light beam from laser 9, reflected by dichroic prism 10, shifts horizontally, and the position of the light spot on the photosensitive surface of first position-sensitive detector 2 changes. The current signals output from the four quadrants are converted into voltage signals using a current / voltage conversion circuit. The change in light spot position is converted into a displacement signal output according to equation (2).

Claims

1. A contact micro-nano probe with online thermal drift compensation function, characterized by include: The probe housing is provided with an upper cover (1) and a lower cover (6) at the top and bottom ends of a cylindrical vertical cylinder (4) respectively, forming a probe housing having a cylindrical inner cavity, wherein the lower cover (6) is an annular end cover having a hollow circular surface; A probe unit comprises a microsphere probe (8) fixed vertically at the center of the lower surface of an elastic spring (7), a beam splitter prism (10) fixed at the center of the upper surface of the elastic spring (7), a laser (9) and a right-angle prism (5) fixedly arranged on the upper end surface of a lower cover (6), and the elastic spring (7) arranged at the hollow circular surface of the lower cover (6); the laser (9) and the right-angle prism (5) are respectively located on both sides of the beam splitter prism (10), so that the collimated light emitted horizontally by the laser (9) is projected onto the beam splitter prism (10), and the reflected light of the beam splitter prism (10) is projected upward, and the transmitted light of the beam splitter prism (10) is projected onto the right-angle prism (5) and reflected by the right-angle prism (5) and projected upward; The sensing unit comprises a first position sensitive detector (2) and a second position sensitive detector (3) fixedly arranged on the lower end surface of the upper cover (1); the reflected light formed in the beam splitter prism (10) is projected onto the first position sensitive detector (2); the reflected light from the right-angle prism (5) is projected onto the second position sensitive detector (3); and the second position sensitive detector (3) is used to realize the thermal drift measurement of the output light.

2. The contact micro-nano probe with online thermal drift compensation function according to claim 1, characterized in that: A laser fixing seat (6a) and a beam splitter prism fixing seat (6b) are integrally arranged on the lower cover (6); the laser (9) is fixedly arranged in the laser fixing seat (6a); and the beam splitter prism (10) is fixedly arranged in the beam splitter prism fixing seat (6b).

3. The contact micro-nano probe with online thermal drift compensation function according to claim 1, characterized in that: The distance d1 between the center of the reflection surface of the beam splitter prism (10) and the detection surface of the first position sensitive detector (2) is set to: d1=d2+d3 Wherein: d2 represents the distance between the center of the reflection surface of the beam splitter prism (10) and the center of the reflection surface of the right-angle prism (5); d3 represents the distance between the center of the reflection surface of the right-angle prism (5) and the detection surface of the second position sensitive detector (3).

4. The contact micro-nano probe with online thermal drift compensation function according to claim 1, characterized in that: Set the thermal drift online compensation method as follows: The voltage signal change value Δv of the second position sensitive detector (3) caused by the thermal drift of the microsphere probe is calculated by formula (1): 21 , Δv 22 , Δv 23 , Δv 24 : Where: v 21 、v 22 、v 23 、v 24 is the four-quadrant initial voltage signal of the second position sensitive detector (3); v 21 '、v 22 '、v 23 '、v 24 ' is the four-quadrant voltage signal output by the second position sensitive detector (3) after the microsphere probe generates thermal drift; The displacements x, y, and z of the microsphere probe in two mutually perpendicular directions in the horizontal plane and in the vertical direction after thermal drift compensation are calculated by formula (2): Where: v 11 '、v 12 '、v 13 '、v 14 ' is the four-quadrant voltage signal output by the first position sensitive detector (2) after the microsphere probe generates thermal drift; k x1 、k y1 and k z1 The proportionality coefficient is obtained by measuring head calibration, and refers to the proportionality coefficient between the displacement of the measuring ball measured by the first position sensitive detector (2) and the output four-quadrant voltage signal of the first position sensitive detector (2) in two mutually perpendicular directions and the vertical direction in the horizontal plane.

5. The contact micro-nano probe with online thermal drift compensation function according to claim 4, characterized in that: The proportionality coefficient k x1 、k y1 、k z1 Calculated by formula (3): in: ΔV X11 , ΔV X12 , ΔV X13 , ΔV X14 It is the change value of the four-quadrant voltage signal output by the first position sensitive detector after the measuring ball produces a fixed displacement S in the X direction; ΔV Y11 , ΔV Y12 , ΔV Y13 , ΔV Y14 It is the change value of the four-quadrant voltage signal output by the first position sensitive detector after the measuring ball produces a fixed displacement S in the Y direction; ΔV Z11 , ΔV Z12 , ΔV Z13 , ΔV Z14 It is the change value of the four-quadrant voltage signal output by the first position sensitive detector after the measuring ball produces a fixed displacement S in the Z direction; Probe calibration process: Use the electric displacement platform to move along the X, Y, and Z directions and touch the probe ball, so that the probe ball produces a fixed displacement S, and record the corresponding four voltage output changes. Use formula (3) to calculate the proportional coefficient k x1 、k y1 、k z1 value.

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