JP4772485B2 - Scanning probe microscope - Google Patents

Description

  The present invention relates to a scanning probe microscope.

  A scanning probe microscope (SPM) is a scanning microscope that mechanically scans a mechanical probe to obtain information on the surface of a sample, and includes a scanning tunneling microscope (STM), an atomic force microscope (AFM), and a scanning type. It is a general term for a magnetic force microscope (MFM), a scanning capacitance microscope (SCaM), a scanning near-field light microscope (SNOM), a scanning thermal microscope (SThM), and the like.

  The scanning probe microscope raster-scans the mechanical probe and the sample relatively in the X and Y directions, obtains surface information of a desired sample region via the mechanical probe, and displays the mapping on the monitor TV.

  Among them, the AFM is the most widely used device. A cantilever with a mechanical probe at its free end, an optical displacement sensor that detects the displacement of the cantilever, and a mechanical probe and sample are scanned relatively. It has a scanner to do. The AFM can also perform manipulation of biological samples and observation and processing of samples other than biological samples.

  Recently, an AFM for observing a moving image of a living body that can observe the movement of a living biological sample in a liquid has attracted attention. In this AFM for biological moving image observation, the scanning time (time for acquiring one image) is 1 second or less, preferably 0.1 seconds or less at the latest. Considering that the scan time of the conventional AFM for living body is several minutes to several tens of minutes, the AFM for living body moving image observation has a very high scanning speed. The conventional AFM for living body is for observing a still image, whereas the AFM for observing a living body moving image is capable of observing a moving image.

  A living body AFM often employs a method (AC mode) that detects an interaction between sample probes from the vibration characteristics of a cantilever regardless of the scanning speed. This is because there is an advantage that the force acting between the sample and the probe can be kept weak compared to the normal mode.

  FIG. 1 is a block diagram illustrating a configuration example of a biomedical AFM. The configuration shown in FIG. 1 is for explaining the basic operation principle of the biological AFM, and does not show the difference between the conventional biological AFM and the biological moving image observation AFM.

  In FIG. 1, the stage 12 is water-repellent and can hold the liquid 14 by surface tension. A sample 9 held by the Y scanner 6, the X scanner 7, and the Z scanner 8 is disposed in the liquid 14. In other words, the Z scanner 8 also serves as a sample stage for holding the sample in the liquid. The Y scanner 6 is driven by the Y drive circuit 3 based on the Y scanning signal output from the controller 2 and scans the sample 9 in the Y direction. The X scanner 7 is driven by the X driving circuit 4 based on the X scanning signal output from the controller 2 and scans the sample 9 in the X direction. Further, the Z scanner 8 is driven by the Z drive circuit 5 based on the Z control signal output from the controller 2 to scan the sample 9 in the Z direction.

  A cantilever 10 having a probe at the free end is disposed in the liquid 14 so as to face the sample 9. The cantilever 10 is held by a holder 11 provided on the stage 12. The holder 11 is provided with a piezoelectric element 13 that receives the excitation signal from the controller 2 and mechanically vibrates the cantilever 10 with a predetermined amplitude and frequency.

  The stage 12 includes a transmission glass 16, and an objective lens 17 and an optical lever sensor 18 are disposed below the stage 12 in order to detect displacement of the cantilever 10 through the transmission glass 16. The optical lever sensor 18 is configured in the same manner as that disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-82037, and irradiates a converging laser beam 15 on the free end of the cantilever 10 via the objective lens 17. The displacement of the cantilever 10 is detected based on the spot position of the reflected light captured through the objective lens 17.

  The amplitude detection circuit 19 calculates the amplitude value of the displacement signal of the cantilever 10 output from the optical lever sensor 18 and outputs the calculated amplitude value of the cantilever 10 to the Z control circuit 20 as an amplitude signal. That is, the amplitude detection circuit 19 outputs a signal reflecting the vibration amplitude of the cantilever 10. The Z control circuit 20 controls the Z scanner 8 in the Z direction so that the amplitude signal output from the amplitude detection circuit 19 is kept constant.

  In such a configuration, upon receiving the excitation signal from the controller 2, the piezoelectric element 13 excites the cantilever 10 with a predetermined amplitude and a mechanical resonance frequency of the cantilever 10. The optical lever sensor 18 detects the amplitude of the cantilever 10, and the sample 9 held by the Z scanner 8 by the Z control circuit 20 and the Z drive circuit 5 is moved in the Z direction (sample 9) so that the vibration amplitude of the cantilever 10 becomes constant. Normal direction). At the same time, the Y drive circuit 3 drives the Y scanner 6 in the Y direction, and the X drive circuit 4 drives the X scanner 7 in the X direction, thereby scanning the sample 9 two-dimensionally. The output of the Z control circuit 20 at this time, that is, the applied voltage signal in the Z direction of the Z scanner 8 is acquired by the host computer 1 through the image data capturing unit 21, and the data is formed as an uneven signal on the sample surface. To do.

  A biological moving image observation AFM is characterized by a scanning method in the XY directions. Hereinafter, the difference in scanning method between the conventional AFM for living body and the AFM for living body moving image observation will be described.

  First, a conventional scanning method for a living body AFM will be described. 2 and 6 show the locus of XY scanning in the AFM. In FIG. 2 and FIG. 6, the number of scanning lines is drawn with little emphasis on visibility, but the actual number of scanning lines is generally about 128 to 512.

  FIG. 2 shows a general raster scan, and image data is acquired only in one direction (+ X direction). A scanning signal corresponding to this raster scanning is shown in FIG. In FIG. 3, the upper part shows the Y scanning signal, the interruption shows the X scanning signal, and the lower part shows the image data fetch command signal. Tf indicates the drawing cycle, which is equal to the reciprocal of the frame rate. The frame rate is the number of images drawn per second, and its unit is fps (frame per second). Ty is the time required for one raster scan, Tyu is the image acquisition time for one image (one frame), Tyd is the time to return from the drawing completion position to the next drawing reference position, Tx is the X scanning cycle, and Txu is X The moving time in the direction of acquiring scanning image data, Ts, indicates the time required to acquire image data in one X-scan.

  In this method, as shown in FIG. 3, observation is performed by repeating raster scanning continuously. This method is called continuous raster scanning and is characterized by Tf = Ty = Tyu + Tyd. Generally, Txu = Tx / 2, but as shown in FIG. 4, the moving speed may be different in the direction in which image data is acquired and in the opposite direction. Similarly, for Txu and Ts, as shown in FIG. 5, the scanning area may be larger than the drawing area (overscanning), and Txu = Ts is not always satisfied.

  FIG. 6 shows bidirectional raster scanning, which is a method for acquiring image data in both directions of Y scanning. Also in this case, image data is acquired only in one direction (+ X direction). FIG. 7 shows scanning signals corresponding to the raster scanning. In FIG. 7, the upper row shows the Y scanning signal, the interruption shows the X scanning signal, and the lower row shows the image data capture command signal. Also, Ty is the time required for one raster scan, Tyu = Tyd = Ty / 2 is the image acquisition time for one image (one frame), Tx is the X scan period, and Txu is the direction for acquiring the X scan image data. The moving time, Ts, indicates the time taken to acquire image data in one X scan.

  Even in this method, as shown in FIG. 7, raster scanning is continuously repeated for observation. This bidirectional raster scanning method does not require the time Tyd to return from the drawing completion position to the next drawing reference position, so that continuous observation can be performed at a slightly higher speed than the general raster scanning method.

  Next, a scanning method of the AFM for biological moving image observation will be briefly described. In the AFM for living body moving image observation, in addition to the above-described continuous raster scanning and continuous bidirectional raster scanning, a method called intermittent raster scanning which is not found in the conventional living body AFM is often used. This is a method that shortens the image acquisition time (capture time of one frame) in order to clearly capture the shape of the moving biological sample, and lowers the frame rate in order to reduce the volume of moving image data (capacity of the moving image file). Yes, suitable for long-term observation of moving biological samples.

  FIG. 8 shows a scanning signal corresponding to intermittent raster scanning. In FIG. 8, Tf indicates the drawing cycle, which is equal to the reciprocal of the frame rate. The frame rate is the number of images drawn per second, and its unit is fps (frame per second). Further, Ty represents a time required for one raster scan, Tyu represents an image acquisition time for one image (one frame), and Tyd represents a time for returning from the drawing completion position to the next drawing reference position. As can be seen from FIG. 8, intermittent raster scanning is characterized by Tf> Ty = Tyu + Tyd, thereby suppressing the capacity of moving image data (capacity of moving image file).

  For example, when continuous scanning is performed with a raster scan time of 33 ms and a frame rate of 30 fps, if the observation is continued for 30 minutes, the number of images reaches 54,000. However, the number of images can be reduced to 1800 when intermittent raster scanning is performed with a time required for one raster scanning of 33 ms and a frame rate of 1 fps. In addition, since the relative scanning of the sample and the probe can be minimized, damage to the sample can be reduced. Thus, it can be said that intermittent raster scanning is a scanning method suitable for long-time observation.

  However, in intermittent raster scanning, as shown in FIG. 9, the X scanning signal behaves like a pulse signal (signal α) having a drawing period Tf, and the harmonic component of the pulse signal having the drawing period Tf becomes vibration noise. There is a defect that obstructs observation. Considering that the frame rate (number of images drawn per second, unit: fps (frame per second)) of the AFM for observing biological moving images is 1 to 30 fps, the harmonic component of this pulse signal is 1 Hz to 1 kHz. Will occur in almost all of the range. Even if the synthesis of the main body of the AFM for biological moving image observation is very high, at least one resonance frequency exists in the range of several Hz to several kHz as long as the mechanical device is composed of a large number of parts, and the pulse signal The harmonic component of this excites the resonance. That is, the pulse signal having the period Tf generates vibration noise.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a scanning probe microscope in which vibration noise generated in intermittent raster scanning is reduced.

In the present invention, image information is obtained by detecting a physical quantity generated between the probe and the surface of the sample while relatively scanning the probe and the sample with a probe having a sharp tip close to the sample. A scanning probe microscope that controls the raster scanning, and in accordance with an X scanning signal output from the scanning control unit, either the sample or the probe is moved in the X direction (raster scanning X scanning means for scanning in the scanning line direction), Y scanning means for scanning either the sample or the probe in the Y direction in accordance with a Y scanning signal output from the scanning control unit, and the X scanning. An image data acquisition unit that acquires image data in synchronization with the signal, and the scan control unit has a relationship of Tyu <1 / N between the image acquisition time Tyu [s] and the frame rate N [fps]. as intermittently It outputs a scanning signal, and characterized by continuously outputting the X scan signal having a constant amplitude value non-zero.

  According to the present invention, there is provided a scanning probe microscope in which vibration noise generated in intermittent raster scanning is reduced.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. The configuration of the scanning probe microscope in the following embodiment is the same as the conventional one shown in FIG. 1 in terms of hardware, and the scanning signal is different from the conventional one.

<First embodiment>
FIG. 10 shows a scanning signal in the scanning probe microscope according to the first embodiment of the present invention. In FIG. 10, Tf indicates a drawing cycle, which is equal to the reciprocal of the frame rate. Tyu indicates an image acquisition time, which is a time for drawing one image (one frame).

  The scanning of this embodiment is intermittent scanning, and there is a relationship of Tyu <1 / N between the image acquisition times Tyu and [s] and the frame rate N [fps]. The amplitude value of the Y scanning signal increases linearly only during the image acquisition time Tyu for acquiring the image data, and returns to almost 0 immediately after the acquisition of the image data. On the other hand, the amplitude value of the X scanning signal is always constant (≠ 0) and remains the amplitude value at the time of image data acquisition.

  For this reason, harmonic components such as pulse signals are eliminated from the X scanning signal, and generation of vibration noise is prevented. Therefore, the scanning probe microscope of the present embodiment can observe a moving organism in liquid with low noise.

  In the present embodiment, the amplitude value of the Y scanning signal returns to almost 0 immediately after the end of the acquisition of the image data. However, even if the amplitude value of the Y scanning signal decreases stepwise during the predetermined time after the end of the acquisition of the image data, it returns to about 0. Good.

<Second embodiment>
FIG. 11 shows a scanning signal in the scanning probe microscope according to the second embodiment of the present invention. In FIG. 11, Tf indicates a drawing cycle, which is equal to the reciprocal of the frame rate. Tyu represents the image acquisition time.

  The scanning of this embodiment is intermittent scanning, and there is a relationship of Tyu <1 / N between the image acquisition times Tyu and [s] and the frame rate N [fps]. The amplitude value of the Y scanning signal increases linearly only during the image acquisition time Tyu for acquiring the image data, and returns to almost 0 immediately after the acquisition of the image data. On the other hand, the amplitude value of the X scanning signal increases linearly in a stepwise manner from almost 0 during a certain time Txs before the start of image data acquisition to become the amplitude value at the time of image data acquisition, and the image acquisition time Tyu. Is constant, and during a certain time Txe after the acquisition of the image data, the amplitude value at the time of acquisition of the image data decreases linearly in a stepwise manner to almost zero.

  The locus drawn by the peak value of the AM-modulated scanning waveform is a trapezoidal signal (signal β) as shown in FIG. For this reason, the harmonic component of the drawing period Tf is suppressed, and the generation of vibration noise is reduced. Therefore, the scanning probe microscope of the present embodiment can observe a moving organism in liquid with low noise. Further, since the driving of the X scanner 7 is intermittently stopped, fatigue of the X scanner 7, wear of the probe and adhesion of dirt, and damage to the sample are reduced.

  FIG. 13 shows an X scanning signal in a modification of the second embodiment. In the scanning of this modified example, the amplitude value of the X scanning signal increases in a sigmoidal shape in a stepwise manner from almost 0 during a certain time Txs before the start of image data acquisition, and the amplitude value at the time of image data acquisition It is constant during the image acquisition time Tyu, and gradually decreases from the amplitude value at the time of image data acquisition to an S-curve shape and becomes almost zero during a predetermined time Txe after the end of image data acquisition. .

  The locus drawn by the peak value of this AM-modulated scanning waveform is a trapezoidal signal (signal γ) with rounded corners. For this reason, the harmonic component of the drawing cycle Tf is better suppressed, and the generation of vibration noise is further reduced.

  In the present embodiment, the amplitude value of the Y scanning signal returns to almost zero immediately after the end of the acquisition of the image data, but in a stepwise manner, for example, during a predetermined time Txe after the end of the acquisition of the image data. It may decrease and return to almost zero.

<Third embodiment>
FIG. 14 shows the configuration of the scanning probe microscope of the third embodiment. In FIG. 14, members indicated by the same reference numerals as those shown in FIG. 1 are similar members. In other words, the apparatus of this embodiment differs from the apparatus of FIG. 1 in the Z control circuit 30 and the scanning signal. In the following, detailed description of the members already described with reference to FIG.

  In FIG. 14, the Z control circuit 30 controls the Z scanner 8 in the Z direction so as to keep the cantilever amplitude signal output from the amplitude detection circuit 19 constant. The controller 2 activates or deactivates the control function of the Z control circuit 30 according to the control ON / OFF command signal 31. When the control function is stopped, the Z control circuit 30 outputs a signal of the lowest level to the Z drive circuit 5, and the Z scanner 8 is in the minimum displacement state (the state where the probe of the sample 9 and the cantilever 10 are farthest apart). )become.

  FIG. 15 shows scanning signals of the scanning probe microscope of the third embodiment. In FIG. 15, Tf indicates a drawing cycle, which is equal to the reciprocal of the frame rate. Tyu represents the image acquisition time of one image (one frame). In this scanning, there is a relationship of Tf> Ty = Tyu + Tyd, similarly to the scanning signal shown in FIG. In other words, there is a relationship of Tyu <1 / N between the image acquisition time Tyu [s] and the frame rate N [fps]. Further, although the Y direction is intermittent scanning that moves only when image data is acquired, the X scan signal is continuously output without interruption even in a section where image data is not acquired. The amplitude value of the Y scanning signal increases linearly only during the image acquisition time Tyu for acquiring the image data, and returns to almost 0 immediately after the acquisition of the image data. On the other hand, the amplitude value of the X scanning signal is always constant (≠ 0) and remains the amplitude value at the time of image data acquisition.

  The control ON / OFF command signal 31 is a rectangular signal and is switched in synchronization with the Y scanning signal. Accordingly, the control function of the Z control circuit 30 is activated or stopped in synchronization with the Y scanning signal. The control function of the Z control circuit 30 is stopped over the entire period in which image data is not acquired.

  This eliminates the harmonic component such as the pulse signal in the X scanning signal, and the generation of vibration noise due to the intermittent operation of the X scanning signal is completely prevented. Therefore, the scanning probe microscope of the present embodiment can observe a moving organism in liquid with low noise.

  Further, as shown in the waveform graph of the control ON / OFF command signal 31, the control function is OFF except when image data is acquired, that is, the probe of the sample 9 and the cantilever 10 is in the most separated state. As a result, the probe of the cantilever 10 and the sample 9 do not come into contact with each other except when image data is acquired, and wear of the probe and adhesion of dirt are kept to a minimum. In addition, damage to the sample is reduced.

  In the above description, the control function of the Z control circuit 30 is stopped in all the sections where image data is not acquired, but the control function of the Z control circuit 30 may be stopped in a part of the section where image data is not acquired. Good.

<Fourth embodiment>
FIG. 16 shows the configuration of the scanning probe microscope of the fourth embodiment. In FIG. 16, the members indicated by the same reference numerals as those shown in FIG. 1 are the same members. In other words, the apparatus of this embodiment differs from the apparatus of FIG. 1 in the Z control circuit 40 and the scanning signal. In the following, detailed description of the members already described with reference to FIG.

  The Z control circuit 40 controls the Z scanner 8 in the Z direction so as to keep the cantilever amplitude signal Vamp output from the amplitude detection circuit 19 constant. The Z control circuit 40 compares the control reference signal Vref supplied from the controller 2 with the amplitude signal Vamp of the cantilever, and controls the Z scanner 8 in the Z direction so that both signals coincide. In this embodiment, since the control reference signal Vref is characterized, the control reference signal Vref will be described in detail below.

  In the scanning probe microscope shown in the present embodiment, the cantilever 10 is brought into contact with the sample 9 in a state where the cantilever 10 is mechanically vibrated with a predetermined amplitude and a frequency near the resonance frequency. Then, control is performed so that the change in vibration amplitude of the cantilever 10 due to the interaction between the probe of the cantilever 10 and the sample 9 becomes constant. The control reference signal Vref is a signal indicating the target value of the change in the vibration amplitude of the cantilever 10 due to the interaction, and the target value is set by a force curve. First, the force curve will be described.

  FIG. 17A to FIG. 17C show the positional relationship between the cantilever 10 and the sample 9 shown in FIG.

  FIG. 17A shows a state where the probe of the cantilever 10 and the sample 9 are separated. Here, if the distance between the cantilever 10 and the sample 9 is Z, the vibration amplitude of the cantilever 10 excited by the piezoelectric element 13 is x0, and the probe length of the cantilever 10 is L, then Z> x0 + L.

  FIG. 17B shows a state in which the cantilever 10 and the sample 9 are brought closer to each other from the state of FIG. 17A and the probe of the cantilever 10 and the sample 9 start to contact each other. Here, Z = x0 + L holds, and Z at this time is set as Z0. That is, Z0 = x0 + L.

  FIG. 17C shows a state in which the cantilever 10 and the sample 9 are further brought closer to the state of FIG. 17B and the probe of the cantilever 10 and the sample 9 are appropriately brought into contact with each other. At this time, the vibration amplitude of the cantilever 10 decreases to xc. Here, Z = xc + L <x0 + L = Z0 holds.

  FIG. 18A is a graph showing a “relationship between the distance between the cantilever 10 and the sample 9 and the vibration amplitude of the cantilever 10”, which is called a force curve.

  In FIG. 18A, the vertical axis represents the vibration amplitude of the cantilever 10, and the horizontal axis represents the distance between the cantilever 10 and the sample 9. As shown in this graph, when the cantilever 10 and the sample 9 are brought close to each other, the vibration amplitude of the cantilever 10 is a constant value x0 until the distance between the cantilever 10 and the sample 9 becomes Z0. When the distance becomes smaller than Z0 (when the probe of the cantilever 10 and the sample 9 are brought into contact with each other), the vibration amplitude of the cantilever 10 becomes smaller than x0.

  Here, xc is set as the target value of the change in the vibration amplitude of the cantilever 10 in the control. xc is the vibration amplitude of the cantilever 10 in a state where the probe of the cantilever 10 and the sample 9 are in proper contact with each other, and is generally about 70% to 95% of x0. At this time, if the sensor sensitivity of the optical lever sensor 18 is set to S [nm / V], “the magnitude (voltage value) of the amplitude signal Vamp of the cantilever output from the amplitude detection circuit 19”, “the cantilever 10 and the sample 9”. The relationship of “distance to” is the graph shown in FIG. 18B. That is, when the vibration amplitude of the cantilever 10 is x0, the magnitude (voltage value) of the cantilever amplitude signal Vamp is x0 / S, and when the vibration amplitude of the cantilever 10 is xc, the magnitude (voltage value) of the cantilever amplitude signal Vamp is xc / S.

  Next, the control reference signal Vref will be described.

  In the above description, the target value of the change in the vibration amplitude of the cantilever 10 due to the interaction is set as xc. That is, the target value of the magnitude (voltage value) of the amplitude signal Vamp of the cantilever is xc / S. Since the Z control circuit 40 compares the control reference signal Vref and the amplitude signal Vamp of the cantilever and performs control so that both signals coincide with each other, the control reference signal Vref of the control reference signal Vref is set to a desired value (xc). The magnitude (voltage value) may be set to xc / S.

  By the way, in the conventional scanning probe microscope, the control reference signal is a constant value (DC signal), and therefore the voltage value xc / S continues to be output. On the other hand, in the scanning probe microscope of the present embodiment, the value of the control reference signal Vref is changed as appropriate.

  FIG. 19 shows the control reference signal Vref and the XY scanning signal in the scanning probe microscope of the present embodiment. As shown in FIG. 19, the control reference signal Vref is a signal that increases and decreases in synchronization with the Y scanning signal, and repeatedly takes two values of xn / S and xc / S alternately. Here, xn / S> xc / S. The control reference signal Vref may be a rectangular signal that switches in synchronization with the Y scanning signal, but is preferably a trapezoidal signal that switches gently in synchronization with the Y scanning signal. In the case of a rectangular signal, the control reference signal Vref takes a large value (xn / S) in all the sections in which image data is not acquired, and in the case of a trapezoidal signal, the control reference signal Vref is a section in which no image data is acquired. Some take large values (xn / S). Here, as shown in FIG. 18A, xn is a value larger than the fundamental vibration amplitude x0 of the cantilever 10, and the cantilever 10 does not actually vibrate at this vibration amplitude. That is, even if this target value (xn / S) is output to the control reference signal Vref, the Z control circuit 40 cannot perform control, and the displacement of the Z scanner 8 is minimum (search for the sample 9 and the cantilever 10). The needle is in the most distant state). This is the same state as when the control function is stopped in the third embodiment.

  The control reference signal Vref takes the value of xc / S when acquiring image data as in the conventional scanning probe microscope, and becomes the value of xn / S when not acquiring image data. In other words, the control function is activated when acquiring image data, and the control function is stopped when image data is not acquired, and the probe of the sample 9 and the cantilever 10 is in the most distant state. Become. Further, switching from xc / S to xn / S is performed gradually over time Tie. Furthermore, switching from xn / S to xc / S is also performed gradually over time Tis. Tie and Tis may be the same value.

  As described above, in the present embodiment, there is a relationship of Tf> Ty = Tyu + Tyd similarly to the scanning signal shown in FIG. In other words, there is a relationship of Tyu <1 / N between the image acquisition time Tyu [s] and the frame rate N [fps]. Further, although the Y direction is intermittent scanning that moves only when image data is acquired, the X scan signal is continuously output without interruption even in a section where image data is not acquired. The amplitude value of the Y scanning signal increases linearly only during the image acquisition time Tyu for acquiring the image data, and returns to almost 0 immediately after the acquisition of the image data. On the other hand, the amplitude value of the X scanning signal is always constant (≠ 0) and remains the amplitude value at the time of image data acquisition.

  This eliminates the harmonic component such as the pulse signal in the X scanning signal, and the generation of vibration noise due to the intermittent operation of the X scanning signal is completely prevented. Therefore, the scanning probe microscope of the present embodiment can observe a moving organism in liquid with low noise.

  Furthermore, in this embodiment, since the control reference signal Vref is a trapezoidal signal in which two values are gently switched, in addition to the advantages of the third embodiment, the switching operation between the control function and the stop is gently performed. Done. This leads to improved control stability.

  FIG. 20 shows a control reference signal Vref and an XY scanning signal in a modification of the fourth embodiment. The control reference signal Vref is an S-shaped trapezoidal signal that smoothly switches between two values of xn / S and xc / S. According to this, the switching operation between the operation and stop of the control function is smoothly performed. This leads to improved control stability.

  The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to these embodiments, and various modifications and changes can be made without departing from the scope of the present invention. Also good.

  For example, as shown in FIG. 21, the X scanning signal may be changed to a waveform obtained by squashing the edges of the triangular wave. In this case, overscanning (Txu> Ts) that takes a scanning area larger than the drawing area is required, but the harmonic component generated by the X scanning signal itself is reduced. As a result, vibration noise is further reduced.

  As another example, as shown in FIG. 22, the Y scanning signal may be returned using all the sections in which image data is not acquired. That is, Tyd = Tf−Tyu. In this way, the harmonic component of the Y scanning signal is also reduced, and vibration noise is further reduced.

  Furthermore, in this embodiment, the vibration amplitude of the cantilever is controlled to be a predetermined value, but this is also effective for a scanning probe microscope that controls the vibration frequency and phase of the cantilever.

It is a block diagram which shows the example of 1 structure of AFM for biological bodies. A general raster scanning locus is shown. FIG. 3 shows a scanning signal corresponding to the raster scanning shown in FIG. The X scanning signals having different moving speeds in the image data acquisition direction and the opposite direction are shown. An X scan signal and an image data fetch command signal in overscan are shown. The locus of bidirectional raster scanning is shown. 7 shows scanning signals corresponding to the raster scanning shown in FIG. A scanning signal corresponding to intermittent raster scanning is shown. FIG. 9 shows a locus drawn by the X scanning signal and the peak value of the scanning waveform shown in FIG. The scanning signal in the scanning probe microscope of 1st embodiment of this invention is shown. The scanning signal in the scanning probe microscope of 2nd embodiment of this invention is shown. 11 shows a locus drawn by the X scanning signal and the peak value of the scanning waveform shown in FIG. The locus | trajectory which the X scanning signal and the peak value of the scanning waveform in the modification of 2nd embodiment of this invention draw is shown. The structure of the scanning probe microscope of 3rd embodiment is shown. The scanning signal of the scanning probe microscope of 3rd embodiment is shown. The structure of the scanning probe microscope of 4th embodiment is shown. The cantilever probe shown in FIG. 16 is separated from the sample. FIG. 17A shows a state in which the cantilever and the sample are brought close to each other from the state of FIG. The cantilever and the sample are brought closer to each other from the state of FIG. 17B, and the cantilever probe and the sample are in proper contact with each other. The graph (force curve) which shows the relationship between the distance of a cantilever and a sample, and the vibration amplitude of a cantilever is shown. The relationship between the distance between the cantilever and the sample and the magnitude (voltage value) of the amplitude signal of the cantilever is shown. The control reference signal and XY scanning signal in the scanning probe microscope of 4th embodiment are shown. The control reference signal and XY scanning signal in the modification of 4th Embodiment are shown. The other X scanning signal applicable to 1st embodiment-4th embodiment is shown. The other Y scanning signal applicable to 1st embodiment-4th embodiment is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Host computer, 2 ... Controller, 3 ... Y drive circuit, 4 ... X drive circuit, 5 ... Z drive circuit, 6 ... Y scanner, 7 ... X scanner, 8 ... Z scanner, 9 ... Sample, 10 ... Cantilever, DESCRIPTION OF SYMBOLS 11 ... Holder, 12 ... Stage, 13 ... Piezoelectric element, 14 ... Liquid, 15 ... Laser light, 16 ... Transmission glass, 17 ... Objective lens, 18 ... Sensor, 19 ... Amplitude detection circuit, 20 ... Z control circuit, 21 ... Image data fetch section, 30 ... Z control circuit, 31 ... Control ON / OFF command signal, 40 ... Z control circuit.

Claims (7)

Scanning probe that obtains image information by detecting the physical quantity generated between the probe surface and the sample surface while relatively scanning the probe and the sample with the probe having a sharp tip close to the sample. A microscope,
A scanning control unit for controlling the raster scanning;
X scanning means for scanning either the sample or the probe in the X direction that is the scanning line direction of the raster scanning in accordance with an X scanning signal output from the scanning control unit;
Y scanning means for scanning either the sample or the probe in the Y direction according to a Y scanning signal output from the scanning control unit;
An image data acquisition unit that acquires image data in synchronization with the Y scanning signal,
The scanning control unit intermittently outputs a Y scanning signal so that the image acquisition time Tyu [s] and the frame rate N [fps] have a relationship of Tyu <1 / N, and a constant amplitude value that is not 0 scanning probe microscope characterized by continuously outputting the X scan signal with. A liquid stage for holding the liquid;
A sample stage for holding the sample in a liquid;
A cantilever having the probe at the free end;
A cantilever holder for holding the cantilever in the liquid;
Vibration means for vibrating the cantilever near its mechanical resonance frequency;
A vibration state detection means for detecting a vibration state of the cantilever by irradiating a convergent light focused on the free end of the cantilever, and outputting a signal reflecting the vibration state;
Z fine movement means for finely moving either the cantilever holder or the sample stage in the Z direction;
Z control means for controlling the Z fine movement means based on the output signal of the vibration state detection means;
Control function control means for operating or stopping the control function of the Z control means in synchronization with the Y scanning signal, and other than the image acquisition time, the control function control means is a function of the Z control means. The scanning probe microscope according to claim 1, wherein the control function is stopped.   The scanning probe microscope according to claim 2, wherein the vibration state detection means includes amplitude detection means for detecting the vibration amplitude of the cantilever, and outputs a signal reflecting the vibration amplitude. A liquid stage for holding the liquid;
A sample stage for holding the sample in a liquid;
A cantilever having the probe at the free end;
A cantilever holder for holding the cantilever in the liquid;
Vibration means for vibrating the cantilever near its mechanical resonance frequency;
A vibration state detection means for detecting a vibration state of the cantilever by irradiating a convergent light focused on the free end of the cantilever, and outputting a signal reflecting the vibration state;
Z fine movement means for finely moving either the cantilever holder or the sample stage in the Z direction;
A reference signal generating means for outputting a reference signal indicating a desired vibration state of the cantilever holder;
A Z control means for comparing the output signal of the vibration state detection means with the reference signal and controlling the Z fine movement means so that they match,
The scanning probe microscope according to claim 1, wherein the reference signal is a signal that repeatedly takes at least two values in synchronization with the Y scanning signal.   5. The scanning probe microscope according to claim 4, wherein the vibration state detection means includes amplitude detection means for detecting the vibration amplitude of the cantilever, and outputs a signal reflecting the vibration amplitude.   The reference signal is a substantially rectangular signal that repeatedly takes two values of large and small, takes a small value during the image acquisition time, and takes a large value during part or all of the time other than the image acquisition time. The scanning probe microscope according to claim 5, wherein the scanning probe microscope is characterized.   The reference signal is a substantially trapezoidal signal that repeatedly takes two values, large and small, and changes gradually, takes a small value during the image acquisition time, and part or all of the time other than the image acquisition time The scanning probe microscope according to claim 5, wherein the scanning probe microscope takes a large value.

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