JPH09281403A - Microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microscope using a piezoelectric actuator which is always controlled at the optimum speed of response. SOLUTION: When a command value for driving the piezoelectric actuator is outputted by a command part 21, the amplitude of a step input is obtained from a difference between the command value of a previous time and that of a present time. Then, an optimum control gain (P(proportion) gain and I(integral) gain) for the amplitude of the step input at this time is read out by the amplitude of the step input from a look-up table 226. The controlled variable of the piezoelectric actuator where the optimum speed of response is obtained by a PI control operation considering the control deviation of the difference between a relative distance between a revolver and a stage and the command value of a commanding means by using the control gain is calculated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microscope in which the relative distance between a sample observation lens and a stage is controlled by the displacement of a piezoelectric actuator.

[0002]

2. Description of the Related Art Recently, scanning laser microscopes among microscopes include a revolver equipped with a stage and an objective lens.
m or sub-μm order positioning is required,
Further, in order to shorten the image capturing time, it is necessary to displace the stage and the revolver at high speed, and a piezoelectric actuator having a large generating force and a high response has been used.

Since the piezoelectric actuator used for such positioning is non-linear with respect to the input voltage and has a hysteresis characteristic, it is necessary to correct these linearly and eliminate the hysteresis.
For this reason, closed loop control is adopted, and control means therefor is used.

Conventionally, as such control means, I (integral) control, PI (proportional / integral) control, PID
In some cases, (proportional, integral, differential) control is adopted, and the results of these calculations are amplified by a high-voltage amplifier to generate a drive signal for the piezoelectric actuator.

Japanese Patent Laid-Open No. 6-138395 discloses an example of a microscope having a piezoelectric actuator as a conventional drive source. As shown in FIG. 7, it has a sensor unit 202 for detecting the relative distance between the revolver 200 of the microscope and the stage 201, and it is in accordance with the deviation between the relative distance detected by the sensor unit 202 and the movement target command value. The control amount of the piezoelectric actuator 203 is calculated, and the control amount is amplified by a high voltage amplifier to obtain the piezoelectric actuator 20.
By controlling 3, the revolver 200 and the stage 201
I am trying to perform positioning between and.

In this case, in calculating the control amount of the piezoelectric actuator 203, first, the command value is set to r and the sensor unit 20 is operated.
Assuming that the relative distance between the revolver 200 and the stage 201 detected in 2 is x, the control deviation e of the displacement amount is calculated from the difference from the command value r by the equation (1).

E = r−x (1) Further, based on the control deviation e obtained from the equation (1),
The proportional-plus-integral control calculation is executed by the equation (2) to obtain the piezoelectric actuator control amount v.

V = Kp ^* e + Ki ^* ∫edt (2) Here, KP: proportional gain, Ki: integral gain, and the piezoelectric actuator control amount v calculated in this manner is the piezoelectric actuator control amount v. The piezoelectric actuator 203 is sent to the actuator 203 and is controlled to position the revolver 200 and the stage 201.

[0009]

By the way, in such a configuration, the control gains of the proportional gain and the integral gain are fixedly used, and these control gains are used as fixed values for the calculation.

Therefore, a command value of one amplitude can be set as an optimum control gain, but a control gain that is optimum may not be optimum for other command values of different amplitudes. is there.

For example, for a scanning laser microscope having a full stroke of 100 μm and a resolution of 0.1 μm, when the driving of the piezoelectric actuator 203 is controlled by the control gain de PI control optimized with a command value of 10 μm, an input command is given. When a command value as large as 100 μm is given, the control gain is not appropriate, and therefore an overshoot as shown in FIG. 8 occurs. Since it takes time to calm this state, the piezoelectric actuator 2
The settling time of 03 takes a long time. On the contrary, the resolution of the scanning laser microscope is 0.1
When a small command value of about μm is given, the deviation e is small. Therefore, in the equation (2), if the control gain when the deviation e is 100 μm is used as it is, the control amount v becomes small, and FIG. As shown in the figure, it takes a long time to rise, and the settling time of the piezoelectric actuator 103 is also long.

As a result, the position of the revolver 200 may not be settled by the time the image is captured by the microscope, and if the image is captured in this state, the captured image may be distorted.

Further, the revolver 200 in a state where the stage 201 is displaced by 100 μm of full stroke, for example.
Since the clearance L between the objective lens and the sample on the stage 201 is about several μm, there is a possibility that the objective lens may collide with the sample due to the occurrence of overshoot and the sample may be damaged. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a microscope using a piezoelectric actuator that can always be controlled with an optimum response speed.

[0014]

According to the first aspect of the present invention,
In a microscope in which a relative distance between a sample observing lens and a stage is controlled by displacement of a piezoelectric actuator, a command means for outputting a command value for driving the piezoelectric actuator, and a command value of the command means in advance And a control gain storage means for storing the optimum control gain, and an optimum control gain corresponding to the command value of the command means is read from the control gain storage means and applied to a predetermined control calculation to control the piezoelectric actuator. And a driving means for driving the piezoelectric actuator according to the control amount output from the computing means.

According to a second aspect of the present invention, in the first aspect, the control gain storage means has an amplitude of a step input obtained from a difference between a previous command value and a current command value by the command means, and the step. The optimum control gain according to the input amplitude is stored.

The invention according to claim 3 is the invention according to claim 1 or 2, wherein the computing means is the difference between the relative distance between the sample observation lens and the stage and the command value of the command means, and The control amount of the piezoelectric actuator is calculated by the optimum control gain read from the control gain storage means.

As a result, according to the present invention, since the optimum control gain according to the command value of the command means can be applied to calculate the control amount of the piezoelectric actuator, the piezoelectric actuator can always be operated at the optimum response speed. It can be controlled, and driven parts such as a sample observation lens and a stage can be settled in the shortest time.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a scanning laser microscope as an example to which the present invention can be applied. In the figure,
The scanning laser microscope 101 includes a laser light source 102, a scanning optical system 104, an objective lens 105, and a confocal optical system 10.
6, the stage 108. Laser light source 10
The laser light emitted from the laser beam 2 passes through the beam splitter 103 and enters the scanning optical system 104.

The scanning optical system 104 is composed of two optical deflectors for two-dimensionally scanning a laser beam. The laser light is deflected in the X direction by the first optical deflector,
It is deflected in the Y direction by the second optical deflector. In this way, the laser light is two-dimensionally deflected within a plane perpendicular to the optical axis, and scanning is controlled by a command from the computer 114 via the controller box 110.

This laser light is condensed on the sample 107 by the objective lens 105 to form a minute spot. This minute spot moves two-dimensionally on the sample 107 in accordance with the movement of the optical deflector, similarly to the raster scanning of the TV.

The laser beam reflected from the sample 107 returns in the reverse direction of the incident optical path and is reflected by the beam splitter 103. The reflected light enters the confocal optical system 106 and a confocal image is obtained. The confocal optical system 106 includes a photodetector such as a photomultiplier that converts reflected light into an electric signal,
It is composed of a pinhole arranged in front of the photodetector and at a position conjugate with the focus position of the objective lens 105.

The image signal from the confocal optical system 106 is sent to the image memory 111 of the controller box 110 and displayed on the display 115 as a luminance image of the sample. The image is updated every time an XY scan is performed.

Since the confocal optical system 106 removes information other than the focus position by the pinhole, a tomographic image can be obtained when the sample 107 is a transparent object such as a biological specimen. Further, by moving the stage 108 in the optical axis direction each time the XY scanning is completed, continuous tomographic images can be obtained.

The movement of the sample 107 in the optical axis direction is performed by moving the stage 108 in the optical axis direction by the Z drive circuit 113. The control of the stage 108 is
This is performed by the computer 114 via the Z drive circuit 113.

The movement of the stage 108 will be described with reference to FIG. FIG. 2 shows a detailed configuration of the stage 108 of the scanning laser microscope 101. In the figure, 1 is a microscope body, and this microscope body 1
A revolver 2 is provided.

The revolver 2 is provided with a plurality of objective lenses 105 having different magnifications as a sample observation lens. Further, the microscope main body 1 is provided with a coarse operation mechanism section 4. The rough motion mechanism section 4 has a fixed side power transmission mechanism storage box 41 and a movable side power transmission mechanism storage box 42, and the movable side power transmission mechanism storage box 42 of the microscope body 1 is operated by operating a focusing handle (not shown). It is movable in the optical axis direction, that is, in the Z direction in the figure.

A bearing 5 for linear movement is installed in the movable-side power transmission mechanism storage box 42 of the rough motion mechanism section 4 as described above.
The stage supporting member 6 is provided via the above, and the stage 108 is attached to the stage supporting member 6.

A sample 107 is placed on the stage 108, and a movable side power transmission mechanism storage box 42 provided via a bearing 5 together with the stage support member 6.
However, it is further movable in the Z direction.

Further, the movable side power transmission mechanism storage box 42 is provided with a fine operation mechanism section 9. This fine movement mechanism section 9
Has a piezoelectric actuator 91, and drives the stage support member 6 in the optical axis direction by changing the protrusion amount of the movable piece of the piezoelectric actuator 91 in accordance with the voltage value applied to the piezoelectric actuator 91. I'm trying to control.

Further, the microscope body 1 is provided with a sensor section 10. The sensor unit 10 detects a relative distance between the revolver 2 and the stage 108. FIG.
Is a specific example of the sensor circuit 112 and the Z drive circuit 113 in FIG. In the figure, reference numeral 21 denotes a command unit, which is a command unit 2
1 outputs a command value for driving the piezoelectric actuator 91.

The command unit 21 includes a control unit 22.
Are connected. The control unit 22 includes a CPU 221 and A
/ D converters 222 and 223, D / A converter 22
4, memory 225 and lookup table 226.

Here, the A / D converter 222 digitally converts the command value given from the command unit 21, and
The A / D converter 223 digitally converts signals corresponding to the relative distance between the revolver 2 and the stage 108, which is fed back from the sensor unit 10 to be described later, and gives the signals to the CPU 221.

The memory 225 stores the previous command value and the current command value by the command unit 21. The lookup table 226 is a command value for driving the piezoelectric actuator 91, and the step input amplitude for displacing the stage by a certain amount, that is, the step obtained from the difference between the command value of this time from the command unit 21 and the command value of the previous time. It stores the input amplitude and optimum control gains (here, P (proportional) gain and I (integral) gain) according to the amplitude of the step input. In this case, the amplitude of these step inputs and the optimum control gain according to the amplitude of the step inputs are stored as execution data obtained by operating the drive circuit in advance or data obtained by simulation by a computer or the like. are doing.

Then, the CPU 221 considers the signals digitally converted by the A / D converters 222 and 223, the read data from the memory 225 and the look-up table 226, and the voltage value corresponding to the appropriate control amount of the piezoelectric actuator 91. Is calculated, and this voltage value is analog-converted by the D / A converter 224 and output.

A high-voltage amplifier 23 is connected to the control unit 22, and the piezoelectric actuator 91 described above is connected to the output side of the high-voltage amplifier 23. The stage 108 is driven by the amount of displacement of the piezoelectric actuator 91.

Further, the relative distance between the revolver 2 and the stage 108 detected by the above-mentioned sensor unit 10 is
Feedback is provided to the control unit 22 via the sensor amplifier 24.

Next, the operation of the embodiment configured as described above will be described. Now, when the positioning control is started, the flowchart shown in FIG. 4 is executed. First, in step 301, the previous command value of the command unit 21 is read from the memory 225, and the CPU 22 and the command value of this time are read.
Give to 1. In step 302, the CPU 221 calculates the amplitude of the step input from the difference between the current command value and the previous command value.

In the CPU 221, step 303 is executed.
Then, the optimum control gain (P (proportional) gain KP and I (integral) gain KI) corresponding to the amplitude of the step input calculated in step 302 from the lookup table 226
And at step 304, the sensor unit 10
Revolver 2 and stage 108 which are fed back more
A / D converter 22 outputs a signal according to the relative distance between
It is digitally converted by 3 and captured.

Then, in step 305, the control deviation e is calculated from the above equation (1), and the optimum control amount v of the piezoelectric actuator 91 is calculated by the PI control calculation shown in equation (2). Then, the voltage value corresponding to the control amount v is set to the D / A converter 224.
Is converted to analog and output.

Further, the analog-converted output of the D / A converter 224 is amplified by the high-voltage amplifier 23 and given to the piezoelectric actuator 91, which causes the piezoelectric actuator 91 to generate a voltage value corresponding to the control amount v from the control section 22. Is displaced by, and the stage 108 is driven by a corresponding amount.

Then, in step 307, the memory 225
Update the previous command value of this time with this command value, and
Returning to 01, the above operation is repeated. With such a configuration, for example, with respect to a scanning laser microscope having a full stroke of 100 μm and a resolution of 0.1 μm, a step input of 100 μm is given as a current command value from a state where the previous command value is 0 μm. In such a case, the difference between the current command value and the previous command value becomes 100 μm.

However, in this case, the lookup table 22 is set for the amplitude of the step input having a difference of 100 μm.
From 6, the optimum control gain (P (proportional) gain and I (integral) gain) corresponding to the amplitude of the step input is read out, and the PI control calculation using this optimum control gain is C
Since it is executed by the PU 221, the control amount for the piezoelectric actuator 91 is such that an optimum response speed can be obtained, and as a result, overshoot does not occur as shown in FIG. It becomes possible to realize an operation that is sufficiently shorter than the image capture time.

If a step input of 1 μm is newly given as the current command value from this state,
Since the previous command value was 100 μm, the difference between these is -9
It becomes 9 μm. Then, also in this case, the lookup table 2 is set for the amplitude of the step input having the difference of −99 μm.
Since the optimum control gain corresponding to the amplitude of this step input is read from 26, control of the piezoelectric actuator 91 such that the optimum response speed is obtained by the PI control calculation in the CPU 221 using the optimum control gain. The quantity will be calculated.

Here, even for the difference of −99 μm, the control amount of the piezoelectric actuator 91 is calculated again because the characteristics of the piezoelectric actuator 91 are different between rising and falling, and therefore, depending on the sign (+ or −) of the difference. This is because it is necessary to change the control gain.

On the other hand, on the contrary, when a small command value of about 0.1 μm, which is the resolution of the scanning laser microscope, is given, the look-up table 226 is applied to the small step input amplitude at this time. Accordingly, by reading out the optimum control gain, the control amount of the piezoelectric actuator 91 such that the optimum response speed is obtained by the PI control calculation in the CPU 221 is calculated.
As shown in FIG. 6, it is possible to quickly rise to the target value, and the settling time of the stage 108 can be significantly shortened.

Therefore, in this way, when the command value for driving the piezoelectric actuator 91 is output from the command unit 21, the step input amplitude is obtained from the difference between the previous command value and the current command value. , The optimum control gain (P (proportional) gain and I (integral) gain) for the step input amplitude at this time is read from the look-up table 226 based on the step input amplitude, and this control gain is used. , PI considering the control deviation e of the difference between the relative distance between the revolver and the stage and the command value of the command means.
Since the control calculation makes it possible to calculate the control amount of the piezoelectric actuator 91 that obtains the optimum response speed, the piezoelectric actuator can always be controlled at the optimum response speed, whereby the stage 108 is settled in the shortest time. Therefore, it is possible to significantly reduce the image capturing time.

In the above embodiment, the PI (proportional / integral) control is described, but other than this, for example,
P (proportional) control, I (integral) control, and PID (proportional / integral / derivative) control may be adopted. Further, in the above-described embodiment, the stage 108 side is the driven part, but the revolver 3 side is also the driven part. Further, in the above-described embodiment, the look-up table 226 in the control unit 22 stores the amplitude of the step input and the optimum control gain corresponding to the amplitude of the step input as a table. Instead of the up table 226, a card-shaped storage medium such as a removable IC card may be used.

In the above-described embodiment, the scanning laser microscope has been described as an example, but a lens for observing the sample is provided like an ordinary optical microscope or an ultrasonic microscope, and this lens and the sample are mounted. Any stage can be applied as long as the relative distance between the stage and the stage can be controlled by the displacement of the piezoelectric actuator.

[0049]

As described above, according to the present invention, the control amount of the piezoelectric actuator can be calculated by applying the optimum control gain according to the command value of the command means.
The piezoelectric actuator can always be controlled at the optimum response speed, which allows the driven parts such as the revolver and the stage to be settled in the shortest time, and the image acquisition time can be greatly shortened.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a scanning laser microscope applied to an embodiment of the present invention.

FIG. 2 is a diagram showing a detailed configuration of a stage portion of a scanning laser microscope applied to one embodiment.

FIG. 3 is a diagram showing a piezoelectric actuator drive circuit according to an embodiment.

FIG. 4 is a flowchart for explaining the operation of the embodiment;

FIG. 5 is a diagram for explaining the operation of the embodiment.

FIG. 6 is a diagram for explaining the operation of the embodiment.

FIG. 7 is a schematic configuration diagram showing an example of a conventional scanning laser microscope.

FIG. 8 is a diagram for explaining the operation of a conventional scanning laser microscope.

FIG. 9 is a diagram for explaining the operation of a conventional scanning laser microscope.

[Explanation of symbols]

 101 ... Scanning laser microscope, 102 ... Laser light source, 103 ... Beam splitter, 104 ... Scanning optical system, 105 ... Objective lens, 106 ... Confocal optical system, 107 ... Sample, 108 ... Stage, 109 ..., 110 ... Controller box , 111 ... Image memory, 112 ... Sensor circuit, 113 ... Z drive circuit, 114 ... Computer, 115 ... Display, 1 ... Microscope body, 2 ... Revolver, 4 ... Coarse operation mechanism section, 41 ... Fixed side power transmission mechanism storage Box, 42 ... Movable side power transmission mechanism storage box, 5 ... Bearing, 6 ... Stage support member, 9 ... Fine movement mechanism section, 91 ... Piezoelectric actuator, 10 ... Sensor section, 21 ... Command section, 22 ... Control section, 221 ... CPU, 222, 223 ... A / D converter, 224 ... D / A converter, 225 ... Memory, 2 26 ... Look-up table, 23 ... High-voltage amplifier, 24 ... Sensor amplifier.

Claims (3)

[Claims] 1. A microscope in which a relative distance between a sample observation lens and a stage is controlled by displacement of a piezoelectric actuator, and command means for outputting a command value for driving the piezoelectric actuator, and the command means in advance. Control gain storage means for storing the optimum control gain according to the command value of, and the optimum control gain according to the command value of the command means is read from the control gain storage means, applied to a predetermined control calculation, A microscope comprising: a calculation unit that calculates the control amount of the piezoelectric actuator; and a drive unit that drives the piezoelectric actuator according to the control amount output from the calculation unit. 2. The control gain storage means stores an amplitude of a step input obtained from a difference between a previous command value and a current command value by the command means, and an optimum control gain according to the amplitude of the step input. The microscope according to claim 1, wherein 3. The calculation means controls the piezoelectric actuator by the difference between the relative distance between the sample observation lens and the stage and the command value of the command means, and the optimum control gain read from the control gain storage means. The microscope according to claim 1 or 2, wherein an amount is calculated.