High-stability laser detection device for atomic force microscope

Abstract

The invention relates to a high-stability laser detection device for an atomic force microscope, which comprises a camera obscura, and a focusing adjusting mechanism, a light spot vertical adjusting mechanism and a light spot horizontal adjusting mechanism which are arranged in the camera obscura, and is characterized in that a micro-cantilever is arranged in a fixing groove at the bottom of the camera obscura; the camera obscura is a cube; the focusing adjusting mechanism can drive the laser to move along the first side face of the camera obscura, the light spot vertical adjusting mechanism can drive the triangular reflector to move along the first side face of the camera obscura, the triangular reflector is perpendicular to the bottom plate and forms a 45-degree included angle with the first side face, and laser emitted by the laser is parallel to the first side face and can irradiate the triangular reflector. Reflected light of the triangular reflector is perpendicular to the side surface I; the light spot horizontal adjusting mechanism can drive the dichroscope to move along the second side face of the camera obscura, the second side face is perpendicular to the first side face, the included angle between the dichroscope and the bottom plate is 45 degrees, reflected light rays of the triangular reflector are reflected to the micro-cantilever through the dichroscope to form light spots, and the reflected light rays of the dichroscope are perpendicular to the bottom plate.

Description

Technical Field

[0001] The invention belongs to the technical field of scanning probe microscopy, and in particular relates to a high-stability laser detection device for an atomic force microscope. Background Art

[0002] Cantilever atomic force microscope (AFM) can obtain the surface morphology and multiple physical properties of various samples in the atmosphere, solution and vacuum environment. It studies the surface structure and properties of materials by detecting the extremely weak atomic interaction force between the surface of the sample to be tested and a miniature force sensitive element. A pair of micro cantilevers that are extremely sensitive to weak forces are fixed at one end, and the tiny needle tip at the other end is close to the sample. The needle tip interacts with the sample, and the force will cause the micro cantilever to deform or change its motion state. In order to detect the deformation and motion state of the micro cantilever, a laser detection device is generally used. The laser beam is focused and hits the micro cantilever, and then reflected to the position sensitive detector (PSD). During scanning, due to the atomic interaction force between the sample surface and the cantilever tip, the micro cantilever will bend and deform with the sample surface morphology, and the position of the reflected light spot will change accordingly. The light spot position is then converted into an electrical signal through the PSD for acquisition, and the sample surface morphology information can be obtained.

[0003] In atomic force microscopy, the stability of the laser detection device is a key factor in determining the resolution of AFM, which mainly includes the incident light path adjustment and PSD adjustment. Incident light path adjustment is to adjust the optical path length from the laser to the probe and the position of the laser spot on the probe microcantilever. The former is to adjust the incident light path length to match the focal length of the laser so that the focal plane of the laser coincides with the microcantilever, thereby minimizing the laser spot; the latter is to be able to adjust the spot position to the front end of the microcantilever midline to obtain the best reflection spot shape and the highest sensitivity. PSD adjustment is to ensure that the reflection spot hits the center of the PSD.

[0004] At present, in terms of adjusting the incident light path, the position of the spot formed by the laser irradiating the micro-cantilever is adjusted by adjusting the position of the laser. The distance from the laser to the micro-cantilever can only be determined when the laser is fixed, which will greatly reduce the stability of the laser detection device. When adjusting the laser position, the laser angle changes slightly due to vibration, etc., and the spot hitting the micro-cantilever will move greatly due to the optical lever. The spot reflected on the PSD will also move, resulting in insufficient stability.

[0005] When the position of the laser is moved, the focal length of the laser cannot be adjusted accordingly, so that the light spot on the cantilever cannot be adjusted to the minimum. It is possible that the diameter of the light spot will be larger than the width of the micro-cantilever and diffraction will occur, causing the light spot on the PSD to scatter, thus affecting the resolution. Summary of the invention

[0006] In view of the above problems, the present invention provides a high-stability laser detection device for an atomic force microscope, comprising a dark box and a focus adjustment mechanism, a light spot vertical adjustment mechanism and a light spot horizontal adjustment mechanism in the dark box, wherein the micro cantilever is arranged in a fixed groove at the bottom of the dark box; the dark box is a cube;

[0007] The focusing adjustment mechanism can drive the laser to move along the side of the dark box, and the spot vertical adjustment mechanism can drive the triangular reflector to move along the side of the dark box. The triangular reflector is perpendicular to the bottom plate and forms an angle of 45 degrees with the side. The laser emitted by the laser is parallel to the side and the bottom plate of the dark box, and can be irradiated onto the triangular reflector. The reflected light of the triangular reflector is perpendicular to the side and the bottom plate of the dark box.

[0008] The light spot horizontal adjustment mechanism can drive the dichroic mirror to move along the side 2 of the dark box. The side 2 is perpendicular to the side 1. The dichroic mirror and the bottom plate form an angle of 45 degrees. The reflected light of the triangular reflector is reflected by the dichroic mirror to the micro-cantilever to form a light spot. The reflected light of the dichroic mirror is perpendicular to the bottom plate.

[0009] The present invention arranges a triangular reflector and a dichroic mirror on the laser propagation path, so that the laser is reflected twice by the two lenses and finally irradiates the micro-cantilever arranged on the bottom plate of the dark box to form a light spot. The focus adjustment mechanism adjusts the position of the laser movement, thereby adjusting the optical path length from the laser to the micro-cantilever to match the laser focal length and adjust the size of the light spot to obtain the best quality reflected light spot. The light spot vertical adjustment mechanism adjusts the position of the triangular reflector, and the laser reflection point also moves with the triangular reflector, so that the laser light path reflected by the triangular reflector moves with the reflection point. The light spot horizontal adjustment mechanism adjusts the position of the dichroic mirror and cooperates with the position of the triangular reflector to accurately hit the micro-cantilever below. The present invention can not only adjust the focus light spot, but also adjust the light path through the focus adjustment mechanism, the light spot vertical adjustment mechanism and the light spot horizontal adjustment mechanism, thereby improving the stability of the light path.

[0010] Optionally, the dark box includes four side surfaces, a bottom plate and a removable top cover, which are side surface one, side surface two, side surface three and side surface four in clockwise direction;

[0011] A hollow fixing groove is provided on the bottom plate for placing the probe holder. The micro cantilever is arranged on the probe holder, and the fixing groove is located below the light spot level adjustment mechanism. A through hole is provided on the top cover so that the microscope objective lens extends into the dark box through the through hole, and the microscope objective lens is located directly above the tip of the micro cantilever.

[0012] Optionally, the focusing adjustment mechanism includes a first displacement stage, a first fixed seat and a laser, one side of the first displacement stage is fixed on side one, and the other side faces the inside of the dark box and is connected to the first fixed seat, and the first fixed seat supports and fixes the laser; a first displacement knob is provided on the side of the first displacement stage facing side four, and the first displacement knob passes through side four, so as to control the movement of the first fixed seat outside the dark box.

[0013] Further optionally, the first fixed seat includes a first connecting plate and a fixing ring connected to each other, the first connecting plate is connected to the moving part of the first translation stage, the fixing ring faces the inside of the dark box, the central axis of the fixing ring is horizontal, the laser is horizontally arranged and inserted into the fixing ring, and moves with the first fixed seat.

[0014] Optionally, the light spot vertical adjustment mechanism includes a second displacement stage, a second fixed seat and a triangular reflector, one side of the second displacement stage is fixed on side one, and the other side faces the inside of the dark box and is connected to the second fixed seat, and the second fixed seat supports and fixes the triangular reflector; a second displacement knob is provided on the side of the second displacement stage facing side two, and the second displacement knob passes through side two, so as to control the movement of the second fixed seat outside the dark box.

[0015] Further optionally, the second fixing seat includes a second connecting plate and a fixing bracket connected to each other, and the second connecting plate is connected to the moving part of the second translation stage;

[0016] The fixed support includes an upper triangular plate and a lower vertical plate, both of which are perpendicular to the second connecting plate, one right-angled side of the triangular plate is connected to the second connecting plate, and the other right-angled side is connected to the top edge of the vertical plate; one side edge of the vertical plate is connected to the second connecting plate, the side edge on the opposite side faces the inside of the dark box, and the bottom edge is parallel to the bottom plate; the triangular reflector is pasted inside the fixed support and moves with the second fixed seat.

[0017] Further optionally, the triangular reflector is placed vertically, with the top and bottom surfaces being two right triangles respectively, and the three side surfaces being squares; the top surface of the triangular reflector is glued to the lower surface of the triangle plate, and the two mutually perpendicular side surfaces of the triangular reflector are glued to the side surfaces of the second connecting plate and the vertical plate facing the inside of the fixed bracket respectively, so that the triangular reflector is stably fixed in the fixed bracket.

[0018] Optionally, the light spot level adjustment mechanism includes a third displacement stage, a third fixed seat and a dichroic mirror, one side of the third displacement stage is fixed on the side surface two, and the other side faces the inside of the dark box and is connected to the third fixed seat, and the third fixed seat supports and fixes the dichroic mirror; a third displacement knob is provided on the side of the third displacement stage facing the side surface three, and the third displacement knob passes through the side surface three, and can control the movement of the third fixed seat outside the dark box.

[0019] Further optionally, the third fixed seat is connected to the moving part of the third translation stage, and a first inclined block is provided on a side of the third fixed seat facing the dark box, and a top surface of the first inclined block is perpendicular to the second side surface and is inclined at 45 degrees to the horizontal plane;

[0020] The side of the dichroic mirror that receives the reflected light from the triangular reflector is receiving surface one, which is inclined downward. The part of receiving surface one close to the third fixed seat is attached to the top surface of the first inclined block, so that receiving surface one is 45 degrees to the horizontal plane and moves with the third fixed seat.

[0021] Optionally, the dark box also includes a detector adjustment mechanism, which includes a fourth displacement stage, a fixed frame and a position sensitive detector (PSD). One side of the fourth displacement stage is fixed on side four, and the other side faces the interior of the dark box and is connected to the fixed frame. The position sensitive detector is placed inside the fixed frame, and the light receiving window of the position sensitive detector faces side two.

[0022] Optionally, the dark box also includes a reflection adjustment mechanism, which includes a fifth displacement stage, a fourth fixed seat and a plane reflector. One side of the fifth displacement stage is fixed on the side three, and the other side faces the inside of the dark box and is connected to the fourth fixed seat. The fourth fixed seat supports and fixes the plane reflector. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the high-stability laser detection device for atomic force microscope;

[0024] Figure 2 is an explosion schematic diagram of the laser detection device;

[0025] Figure 3 is a schematic diagram of a second fixing seat;

[0026] Figure 4 is a schematic diagram of a third fixing seat;

[0027] Figure 5 is a schematic diagram of a fourth fixing seat;

[0028] Figure 6 A schematic diagram of a fixing frame for fixing a position sensitive detector;

[0029] Figure 7 is a schematic diagram of a fixed slot;

[0030] Figure 8 is a schematic diagram of the bottom surface of the sheet metal part;

[0031] Fig. 9 is a schematic diagram of a probe holder;

[0032] Fig.10 is a schematic diagram of the micro cantilever at the front end of the probe holder;

[0033] Fig.11 Schematic diagram of the relationship between the microcantilever and the light spot position under the microscope.

[0034] In the accompanying drawings, 1-dark box, 2-micro cantilever, 3-fixed groove, 4-laser, 5-side one, 6-side two, 7-side three, 8-side four, 9-triangular reflector, 10-bottom plate, 11-dichroic mirror, 12-top cover, 13-probe holder, 14-microscope objective lens, 15-first displacement stage, 16-second displacement stage, 17-third displacement stage, 18-fourth displacement stage, 19-fifth displacement stage, 20-first fixed seat, 21-second fixed seat, 22-first inclined block , 23-second inclined block, 24-first displacement knob, 25-second displacement knob, 26-third displacement knob, 27-fourth displacement knob, 28-fifth displacement knob, 29-sixth displacement knob, 30-fixing ring, 31-triangular plate, 32-vertical plate, 33-fourth fixed seat, 34-position sensitive detector, 35-fixing frame, 36-light receiving window, 37-plane reflector, 38-sheet metal, 39-fixing plate, 40-spring sheet, 41-third fixed seat. DETAILED DESCRIPTION

[0035] This embodiment provides a high-stability laser detection device for an atomic force microscope, such as Figure 1-Figure 11 As shown, it includes a dark box 1 and a focus adjustment mechanism, a light spot vertical adjustment mechanism and a light spot horizontal adjustment mechanism in the dark box 1, and a micro cantilever 2 is arranged in a fixed groove 3 at the bottom of the dark box 1; the dark box 1 is a cube;

[0036] The focusing adjustment mechanism can drive the laser 4 to move along the side 5 of the dark box 1, and the light spot vertical adjustment mechanism can drive the triangular reflector 9 to move along the side 5 of the dark box 1. The triangular reflector 9 is perpendicular to the bottom plate 10 and forms an angle of 45 degrees with the side 5. The laser light emitted by the laser 4 is parallel to the side 5 and the bottom plate 10 of the dark box 1, and can be irradiated onto the triangular reflector 9. The reflected light of the triangular reflector 9 is perpendicular to the side 5 and parallel to the bottom plate 10 of the dark box 1.

[0037] The light spot horizontal adjustment mechanism can drive the dichroic mirror 11 to move along the side 2 6 of the dark box 1. The side 2 6 is perpendicular to the side 1 5. The dichroic mirror 11 and the base plate 10 form an angle of 45 degrees. The reflected light of the triangular reflector 9 is reflected by the dichroic mirror 11 onto the micro-cantilever 2 to form a light spot. The reflected light of the dichroic mirror 11 is perpendicular to the base plate 10.

[0038] Optionally, the dark box 1 includes four side surfaces, a bottom plate 10 and a removable top cover 12, which are side surface 1 5, side surface 2 6, side surface 3 7 and side surface 4 8 in clockwise direction, side surface 1 5 is parallel to side surface 3 7, and side surface 2 6 is parallel to side surface 4 8;

[0039] A hollow fixing groove 3 is provided on the bottom plate 10 for placing a probe holder 13. The micro-cantilever 2 is arranged on the probe holder 13, and the fixing groove 3 is located below the light spot level adjustment mechanism; the top cover 12 is connected to the tops of the four side surfaces by screws, and the top cover 12 is provided with a through hole so that a microscope objective lens 14 can extend into the dark box 1 through the through hole. The microscope objective lens 14 is located directly above the tip of the micro-cantilever 2 to observe the size and position of the light spot on the micro-cantilever 2, as well as the sample surface, for selecting the scanning area.

[0040] The side surface and the bottom plate 10 of the dark box 1 may be formed in one piece, or may be connected to each other by screws.

[0041] Optionally, the focusing adjustment mechanism includes a first displacement stage 15, a first fixed seat 20 and a laser 4, one side of the first displacement stage 15 is fixed on the side surface 5, and the other side faces the inside of the dark box 1 and is fixedly connected to the first fixed seat 20, and the first fixed seat 20 supports and fixes the laser 4; a first displacement knob 24 is provided on the side of the first displacement stage 15 facing the side surface 8, and the first displacement knob 24 passes through the side surface 8, and can control the movement of the first fixed seat 20 outside the dark box 1.

[0042] Further optionally, the first translation stage 15 is a conventional one-dimensional translation stage, and its horizontal translation knob is the first translation knob 24 .

[0043] Further optionally, the first fixed seat 20 includes a first connecting plate and a fixing ring 30 connected to each other, the first connecting plate is connected to the moving part of the first translation stage 15, the fixing ring 30 faces the inside of the dark box 1, the central axis of the fixing ring 30 is horizontal, the laser 4 is horizontally arranged and inserted into the fixing ring 30, and moves with the first fixed seat 20.

[0044] The first displacement knob 24 adjusts the front-to-back position of the laser 4 (ie, the horizontal distance from the triangular reflector 9 ) by adjusting the optical path length from the laser 4 to the micro-cantilever 2 to match the laser focal length.

[0045] Optionally, the light spot vertical adjustment mechanism includes a second displacement stage 16, a second fixed seat 21 and a triangular reflector 9, one side of the second displacement stage 16 is fixed on the side surface 1 5, and the other side faces the inside of the dark box 1 and is fixedly connected to the second fixed seat 21, and the second fixed seat 21 supports and fixes the triangular reflector 9; a second displacement knob 25 is provided on the side of the second displacement stage 16 facing the side surface 2 6, and the second displacement knob 25 passes through the side surface 2 6, and can control the movement of the second fixed seat 21 outside the dark box 1.

[0046] Further optionally, the second translation stage 16 is also a conventional one-dimensional translation stage, and its horizontal translation knob is the second translation knob 25 .

[0047] Further optionally, the second fixing seat 21 includes a second connecting plate and a fixing bracket connected to each other, and the second connecting plate is connected to the moving part of the second translation stage 16;

[0048] The fixed support includes an upper triangular plate 31 and a lower vertical plate 32, both of which are perpendicular to the second connecting plate, a right-angled side of the triangular plate 31 is connected to the second connecting plate, and the other right-angled side is connected to the top edge of the vertical plate 32; one side edge of the vertical plate 32 is connected to the second connecting plate, the side edge on the opposite side faces the interior of the dark box 1, and the bottom edge is parallel to the bottom plate 10; the triangular reflector 9 is pasted inside the fixed support and moves with the second fixed seat 21.

[0049] Further optionally, the triangular reflector 9 is placed vertically, with the top and bottom surfaces being two right triangles respectively, and the three side surfaces being squares; the top surface of the triangular reflector 9 is glued to the lower surface of the triangle plate 31, and the two mutually perpendicular side surfaces of the triangular reflector 9 are glued to the side surfaces of the second connecting plate and the vertical plate 32 facing the inside of the fixed bracket respectively, so that the triangular reflector 9 is stably fixed in the fixed bracket.

[0050] The three sides of the triangular reflector 9 are pasted in the fixing bracket, which greatly improves the stability of the triangular reflector 9 compared to the conventional triangular reflector 9 with one side fixed. Even if the triangular reflector 9 moves with the second connecting plate, the relative position of the triangular reflector 9 and the second connecting plate can be ensured to be stable. Since the micro cantilever 2 is at the bottom of the dark box 1, the overall optical path is close to the bottom plate 10, and the position of the light received by the triangular reflector 9 is also relatively low. Therefore, the triangular plate 31 is above the vertical plate 32, which can fix the triangular reflector 9 without hindering the triangular reflector 9 from receiving light.

[0051] The second displacement knob 25 adjusts the front-rear position of the triangular reflector 9 so as to irradiate the light reflected by the triangular reflector 9 onto the dichroic mirror 11 .

[0052] Optionally, the light spot level adjustment mechanism includes a third displacement stage 17, a third fixed seat 41 and a dichroic mirror 11, one side of the third displacement stage 17 is fixed on the side surface 2 6, and the other side faces the inside of the dark box 1 and is fixedly connected to the third fixed seat, and the third fixed seat supports and fixes the dichroic mirror 11; a third displacement knob 26 is provided on the side of the third displacement stage 17 facing the side surface 3 7, and the third displacement knob 26 passes through the side surface 3 7, and can control the movement of the third fixed seat outside the dark box 1.

[0053] Further optionally, the third displacement stage 17 is a conventional one-dimensional displacement stage, and its horizontal displacement knob is the third displacement knob 26 .

[0054] Further optionally, the third fixed seat is connected to the moving part of the third displacement stage 17, and a first inclined block 22 is provided on the side of the third fixed seat facing the dark box 1, and the top surface of the first inclined block 22 is perpendicular to the side surface 26 and is inclined at 45 degrees to the horizontal plane;

[0055] The side of the dichroic mirror 11 that receives the reflected light from the triangular reflector 9 is the receiving surface 1, which is inclined downward, and the portion of the receiving surface 1 close to the third fixed seat is attached to the top surface of the first inclined block 22, so that the receiving surface 1 is 45 degrees to the horizontal plane and moves with the third fixed seat. The dichroic mirror 11 is perpendicular to the side 2 6, and the side of the dichroic mirror 11 close to the side 1 5 is higher than the side close to the side 3 7.

[0056] The third displacement knob 26 adjusts the front and rear positions of the dichroic mirror 11 (i.e., the horizontal distance from the triangular reflector 9), so that the laser reflection point also moves along with the dichroic mirror 11, thereby making the laser light path reflected by the dichroic mirror 11 move along with the reflection point. After being reflected by the dichroic mirror 11, the laser is irradiated onto the micro-cantilever 2.

[0057] In the present invention, the reflection band of the dichroic mirror 11 is 575-725nm, and the transmission band is 400-530nm, while the wavelength of the laser is 650nm, which is within the reflection band range, so most of the laser will be reflected on the receiving surface 1 of the dichroic mirror 11 and transmitted to the micro-cantilever 2, and only a small part will pass through the dichroic mirror 11. When using an optical microscope to observe the laser spot and sample surface on the micro-cantilever 2, a large part of the 575-725nm light will be filtered out by the dichroic mirror 11, so that the brightness of the laser spot in the optical microscope screen is weakened, so that the spot of the micro-cantilever 2 and the sample surface can be clearly observed at the same time. Most of the existing AFM optical microscopes add a short-pass filter to reduce the brightness of the laser spot in the observation screen. The present invention uses a dichroic mirror 11, which not only plays the role of taking over the transfer light path in the laser propagation path, but also reduces the brightness of the spot by blocking some wavelengths of light.

[0058] By adjusting the focus adjustment mechanism, the optical path length between the laser 4 and the micro-cantilever 2 is changed. The spot size can be observed in the microscope and the spot can be adjusted to the minimum. By adjusting the vertical adjustment mechanism of the spot, the spot finally hit on the micro-cantilever 2 moves in a direction parallel to the micro-cantilever 2. By adjusting the horizontal adjustment mechanism of the spot, the spot finally hit on the micro-cantilever 2 moves in a direction perpendicular to the micro-cantilever 2. The position of the spot can be observed through the microscope objective 14, and the spot is adjusted to the end of the center line of the micro-cantilever 2 (that is, the needle tip of the micro-cantilever 2, and the spot cannot exceed the cantilever). At this point, the best quality reflection spot can be obtained. The displacement knobs of the first displacement stage 15, the second displacement stage 16, and the third displacement stage 17 can all be locked. After obtaining the best reflection spot, the three displacement stages are locked, so that the rigidity of the mechanical structure is greatly improved.

[0059] Optionally, the dark box 1 further includes a detector adjustment mechanism, which includes a fourth displacement stage 18, a fixing frame 35 and a position sensitive detector 34 (PSD), one side of the fourth displacement stage 18 is fixed on the side surface 48, and the other side faces the inside of the dark box 1 and is fixedly connected to the fixing frame 35, the position sensitive detector 34 is placed inside the fixing frame 35, and the light receiving window 36 of the position sensitive detector 34 faces the side surface 26;

[0060] The fourth displacement stage 18 is a conventional two-dimensional displacement stage, and its horizontal displacement knob is the fourth displacement knob 27, which faces the side three 7 and passes through the side three 7. The vertical displacement knob is the fifth displacement knob 28, which faces the top cover 12 and passes through the top cover 12 vertically upward, and can control the movement of the fixed frame 35 outside the dark box 1.

[0061] Further optionally, the fixing frame 35 includes a third connecting plate and a fixing shell which are connected to each other, the third connecting plate is connected to the moving part of the fourth displacement stage 18, the fixing shell can cover the outer side surface of the position sensitive detector 34, and then the position sensitive detector 34 is fixed on the third connecting plate, and the light receiving window 36 of the position sensitive detector 34 is exposed from the fixing shell.

[0062] The fourth displacement stage 18 drives the position sensitive detector 34 to move on a two-dimensional vertical plane parallel to the side surface 28 through its own moving part, and adjusts the position of the PSD so that the reflected light of the micro-cantilever 2 spot hits the center of the PSD light receiving window 36. The laser is incident on the micro-cantilever, and enters the PSD light receiving window 36 after being reflected by the micro-cantilever and a plane mirror. The PSD can detect the coordinate position of the laser spot relative to the center of the PSD (i.e., the center of the window), and output two electrical signals. The voltages of the two electrical signals respectively represent the horizontal coordinate and the vertical coordinate of the spot with the PSD as the origin. The two electrical signals are connected to the controller, so that the control system can obtain the spot position information and obtain the tilt degree of the micro-cantilever by calculation.

[0063] When the micro-cantilever is tilted by force, the light path reflected by the micro-cantilever will also tilt, causing the position of the light spot on the PSD to change, and the voltage of the two electrical signals output by the PSD will also change. The controller will also obtain the change in the light spot position and calculate the tilt of the micro-cantilever as the input signal of the controller feedback system. The above PSD detection method is the prior art.

[0064] Optionally, the dark box 1 further includes a reflection adjustment mechanism, which includes a fifth displacement stage 19, a fourth fixed seat 33 and a plane reflector 37, one side of the fifth displacement stage 19 is fixed on the side surface 3 7, and the other side faces the inside of the dark box 1 and is fixedly connected to the fourth fixed seat, and the fourth fixed seat supports and fixes the plane reflector 37;

[0065] The fifth displacement stage 19 is a conventional one-dimensional displacement stage, and its vertical displacement knob is the sixth displacement knob 29 . The sixth displacement knob 29 is vertically upward and passes through the top cover 12 , and can control the movement of the fourth fixed seat outside the dark box 1 .

[0066] Further optionally, the fourth fixed seat is connected to the moving part of the fifth displacement stage 19, and a second inclined block 23 is provided on the side of the fourth fixed seat facing the dark box 1, and the top surface of the second inclined block 23 is perpendicular to the side surface 7 and is inclined at 30 degrees to the horizontal plane;

[0067] The side of the plane reflector 37 that receives the reflected light of the micro cantilever 2 is the receiving surface 2, which is tilted downward, and the part of the receiving surface 2 close to the fourth fixing seat is attached to the top surface of the second inclined block 23, so that the receiving surface 2 is 30 degrees with the horizontal plane and moves with the fourth fixing seat. The plane reflector 37 is perpendicular to the side surface 3 7, and the side of the plane reflector 37 close to the side surface 4 8 is higher than the side close to the side surface 2 6.

[0068] The fifth translation stage 19 drives the plane reflector 37 to move through its moving part. The receiving surface of the plane reflector 37 receives the light reflected by the micro cantilever 2 and then reflects it to the center of the light receiving window 36 of the position sensitive detector 34, so as to facilitate detection by the position sensitive detector 34.

[0069] Optionally, the central axis of the fixing groove 3 is parallel to the side 1 5, the front end of the central axis points to the side 2 8, and the rear end points to the side 2 6; the micro-cantilever 2 is arranged on the lower surface of the front end of the probe holder 13, and the probe holder 13 protrudes forward, the probe holder 13 is snapped into the fixing groove 3, the probe holder 13 does not completely cover the fixing groove 3, and a part of the front end of the fixing groove 3 is left, so that the micro-cantilever 2 is exposed in the vacant part of the front end of the fixing groove 3, and the light reflected by the dichroic mirror 11 can be vertically irradiated onto the micro-cantilever 2;

[0070] The angle between the micro-cantilever 2 and the horizontal plane is 15 degrees, and the angle between the reflected light of the light spot of the micro-cantilever 2 and the vertical plane is 30 degrees. The reflected light of the micro-cantilever 2 is irradiated onto the receiving surface 2 of the plane reflector 37 (the receiving surface 2 is 30 degrees to the horizontal plane), and then reflected by the plane reflector 37 to the center of the PSD light receiving window 36.

[0071] Further optionally, a sheet metal part 38 is provided above the probe frame 13 for fastening the probe frame 13; a fixing plate 39 is provided above the sheet metal part 38, the fixing plate 39 is connected to the bottom plate 10 by screws, and the fixing plate 39 presses the sheet metal part 38 against the upper surface of the probe frame 13;

[0072] The sheet metal part 38 is provided with a plurality of hollow positions, each of which is connected to a downwardly inclined spring sheet 40 , and the spring sheet 40 extends downwardly out of the hollow position in a natural state.

[0073] The probe holder 13 (a conventional probe holder) is snapped into the fixing groove 3, the sheet metal 38 is placed on the upper surface of the probe holder 13, and the spring sheet 40 in a natural state contacts the upper surface of the probe holder 13, the fixing plate 39 presses the sheet metal 38 downward from above the sheet metal 38, and at the same time the fixing plate 39 is connected to the base plate 10, the spring sheet 40 is pressed to fill (cover) the hollow position upward, and the probe holder 13 is pressed by the spring sheet 40, thereby fixing the initial position of the micro cantilever 2.

[0074] The present invention adopts several lockable translation stages to adjust and fix the laser emitted by the laser 4, and can finely adjust the laser spot size, while greatly improving the stability of the laser 4; when adjusting the laser spot position, the angle at which the laser hits the micro-cantilever 2 does not change, so that the angle of the reflected light path remains unchanged, so that the position of the spot hitting the PSD is almost unchanged, so that only fine-tuning is required for subsequent adjustment of the PSD; three mechanisms for adjusting the laser spot size, horizontal position, and vertical position are respectively fixed on the side walls, which reduces the load of each translation stage, removes coupling, and greatly improves the mechanical rigidity.

Claims

1. A high-stability laser detection device for an atomic force microscope, characterized in that: It includes a dark box and a focus adjustment mechanism, a light spot vertical adjustment mechanism and a light spot horizontal adjustment mechanism in the dark box, and the micro cantilever is arranged in a fixed groove at the bottom of the dark box; the dark box is a cube; The focusing adjustment mechanism can drive the laser to move along the side of the dark box, and the spot vertical adjustment mechanism can drive the triangular reflector to move along the side of the dark box. The triangular reflector is perpendicular to the bottom plate and forms an angle of 45 degrees with the side. The laser emitted by the laser is parallel to the side and the bottom plate of the dark box, and can be irradiated onto the triangular reflector. The reflected light of the triangular reflector is perpendicular to the side and the bottom plate of the dark box. The light spot horizontal adjustment mechanism can drive the dichroic mirror to move along the side 2 of the dark box. The side 2 is perpendicular to the side 1. The dichroic mirror and the bottom plate form an angle of 45 degrees. The reflected light of the triangular reflector is reflected by the dichroic mirror to the micro-cantilever to form a light spot. The reflected light of the dichroic mirror is perpendicular to the bottom plate.

2. The high stability laser detection device according to claim 1, characterized in that: The dark box comprises four side surfaces, a bottom plate and a removable top cover, which are side surface one, side surface two, side surface three and side surface four in clockwise direction; A hollow fixing groove is provided on the bottom plate for placing the probe holder. The micro cantilever is arranged on the probe holder, and the fixing groove is located below the light spot level adjustment mechanism. A through hole is provided on the top cover so that the microscope objective lens extends into the dark box through the through hole, and the microscope objective lens is located directly above the tip of the micro cantilever.

3. The high stability laser detection device according to claim 2, characterized in that: The focus adjustment mechanism comprises a first displacement stage, a first fixing seat and a laser, one side of the first displacement stage is fixed on the first side, and the other side faces the inside of the dark box and is connected to the first fixing seat, and the first fixing seat supports and fixes the laser; A first displacement knob is provided on a side of the first displacement platform facing the side surface four. The first displacement knob passes through the side surface four and can control the movement of the first fixing seat outside the dark box.

4. The high stability laser detection device according to claim 3, characterized in that: The first fixed seat includes a first connecting plate and a fixing ring which are connected to each other. The first connecting plate is connected to the moving part of the first translation stage. The fixing ring faces the inside of the dark box. The central axis of the fixing ring is horizontal. The laser is horizontally arranged and inserted into the fixing ring to move with the first fixed seat.

5. The high stability laser detection device according to claim 2, characterized in that: The light spot vertical adjustment mechanism includes a second displacement stage, a second fixed seat and a triangular reflector. One side of the second displacement stage is fixed on the side surface one, and the other side faces the inside of the dark box and is connected to the second fixed seat. The second fixed seat supports and fixes the triangular reflector. A second displacement knob is provided on the side of the second displacement stage facing the side surface two. The second displacement knob passes through the side surface two and can control the movement of the second fixed seat outside the dark box.

6. The high stability laser detection device according to claim 5, characterized in that: The second fixing seat comprises a second connecting plate and a fixing bracket connected to each other, and the second connecting plate is connected to the moving part of the second translation stage; The fixing bracket includes an upper triangular plate and a lower vertical plate, the triangular plate and the vertical plate are both perpendicular to the second connecting plate, one right-angle side of the triangular plate is connected to the second connecting plate, and the other right-angle side is connected to the top edge of the vertical plate; one side edge of the vertical plate is connected to the second connecting plate, the side edge on the opposite side faces the inside of the dark box, and the bottom edge is parallel to the bottom plate; the triangular reflector is pasted inside the fixing bracket and moves with the second fixing seat; The triangular reflector is placed vertically, with the top and bottom surfaces being two right triangles respectively, and the three side surfaces being squares; the top surface of the triangular reflector is glued to the lower surface of the triangle plate, and the two mutually perpendicular side surfaces of the triangular reflector are correspondingly glued to the side surfaces of the second connecting plate and the vertical plate facing the inside of the fixed bracket, so that the triangular reflector is stably fixed in the fixed bracket.

7. The high stability laser detection device according to claim 2, characterized in that: The light spot level adjustment mechanism includes a third displacement stage, a third fixed seat and a dichroic mirror. One side of the third displacement stage is fixed on the second side, and the other side faces the inside of the dark box and is connected to the third fixed seat. The third fixed seat supports and fixes the dichroic mirror. A third displacement knob is provided on the side of the third displacement stage facing the third side. The third displacement knob passes through the third side and can control the movement of the third fixed seat outside the dark box.

8. The high stability laser detection device according to claim 7, characterized in that: The third fixed seat is connected to the moving part of the third translation stage, and a first inclined block is provided on the side of the third fixed seat facing the dark box, and the top surface of the first inclined block is perpendicular to the second side surface and is inclined at 45 degrees to the horizontal plane; The side of the dichroic mirror that receives the reflected light from the triangular reflector is receiving surface one, which is inclined downward. The part of receiving surface one close to the third fixed seat is attached to the top surface of the first inclined block, so that receiving surface one is 45 degrees to the horizontal plane and moves with the third fixed seat.

9. The high stability laser detection device according to claim 2, characterized in that: The dark box also includes a detector adjustment mechanism, which includes a fourth displacement platform, a fixed frame and a position sensitive detector. One side of the fourth displacement platform is fixed on the side surface four, and the other side faces the inside of the dark box and is connected to the fixed frame. The position sensitive detector is placed inside the fixed frame, and the light receiving window of the position sensitive detector faces the side surface two.

10. The high stability laser detection device according to claim 2, characterized in that: The dark box also includes a reflection adjustment mechanism, which includes a fifth displacement stage, a fourth fixed seat and a plane reflector. One side of the fifth displacement stage is fixed on the side surface three, and the other side faces the inside of the dark box and is connected to the fourth fixed seat. The fourth fixed seat supports and fixes the plane reflector.

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