JPH11231253A - Directional control system for scanner driver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve actual accuracy of deflected position and linearity of the deflection by keeping advantageous generation of a directional control signal based on a triangular wave. SOLUTION: Information on an actually deflected position of a rotary mirror 3 and usable for a measurement value receiver is evaluated by coupling the measurement value receiver to a function generator 5 through a logical unit 13 to find a correction value for an exciting current, permitting to find a correction value by using a logical unit as an auxiliary means, and this correction value is used to exert an influence on a directional control frequency generated from the function generator 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a swing motor for driving a turning mirror which serves for the linear oscillating deflection of a light beam, and a swing motor which can be varied with respect to directional control frequency, frequency curve and amplitude. Having a direction control unit for powering the motor, a function generator coupled to the direction control unit, and a measurement receiver for obtaining a result of information about the deflection position of the turning mirror;
It relates to a direction control system for a scanner drive, in particular for a laser scanning microscope.

[0002]

2. Description of the Related Art In this technical field, an optical device having a scanning device (hereinafter referred to as a laser scanning microscope) is well known.
As the light source, a laser is used which, by nature, focuses the light on the screen, generally showing the light in one small spot along the ray path as a pixel. In this manner, almost all of the laser light is directed to this single target point.

In addition, the scanning device of such a device linearly deflects the light coming from the laser and the light reflected from the object surface, and also moves the light spots in the screen and in the object surface. Used for A raster scanning device whose direction is controlled in synchronization with the scanner outputs the resulting detector output signal as image information.

[0004] It is well known to deflect a light path by providing an electromechanically driven mirror for oscillating deflection of the light path so that the target point is moved in the direction of the axis to be designated as the X axis. is there. At this time, the mirror directs the laser beam to the second mirror driven in the same manner, and the second mirror causes the target point to move in the vertical axis direction, that is, the Y axis direction.

Next, the deflection in the X axis will be considered in more detail. Despite the small size of the deflecting mirror applied, and thus the low mass, in order to produce a fast and accurate movement of the mirror for good image linearity with a short imaging time, this type of scanning device requires There is always difficulty.
The reason for this is that the movement of the mirror and the ray path are subject to various disturbance effects based on the drive signal output from the direction control unit.
To a greater or lesser degree, it is to follow faithfully.
This is not enough for a high performance scanner, in which case
There is always a need to meet the demands of high scanning frequency and that the target point must maintain a constant speed throughout the deflection phase.

[0006] In order to maintain as linear a drive characteristic as possible for the deflecting mirror, a direction control signal having a triangular wave is produced in the direction control unit. The phase and amplitude of such a directional control signal form the basic premise that the deflection approximates the linear movement of the target point in time.

For the purpose of a consequent approximation of the triangular wave, a well-known state of the art uses harmonic analysis, ie a calculation with Fourier coefficients. Such a scanning device with an associated directional control unit is described, for example, in DE-OS 43 22 694.
It is described in. In this case, the directional control signal is made on the basis of two of the Fourier components, with the result of a relatively good approximation to a triangular wave. However, as a disadvantage, a directional control of the kind shown here does not reach satisfactory results, since both frequencies of the scanner are treated differently by amplitude and phase. This is the case even if additional harmonics of the fundamental frequency are used for further correction. In other words, the proposed solution of achieving the desired linearization is not suitable.

In the foregoing disclosure, two resonant scanners and one galvanometer scanner are planned for deflecting the laser beam in the X-axis, wherein the galvanometer scanner overlaps the DC swing operation with the resonant operation provided by the resonant scanner. Used for As is well known, the swing motion of a resonant scanner is furthermore due to the energy exchange, in particular between the movement of the mass of the mirror and the deflection of the elastic member (for example a spring) to which this mass is fixed.

[0009] Apart from the above-described arrangement in which a plurality of separate scanners are each driven at a single resonance frequency inside the scanning device, it is possible to drive a single scanner at a plurality of resonance frequencies. Are known. In this example, U
S-PAT 4859846 describes the operation of one scanner, which operates with one mirror and creates a plurality of resonance frequencies for this scanner by means of a suitable directional control system. The resonance scanner system is also important in this direction control system. This solution is also suitable for eliminating the drawback that the actual deflection position of the position given by the direction control signal is upset by various disturbing influences, for example, the influence of external temperature or the amount of influence on material conditions. Absent.

[0010]

Accordingly, the present invention provides
Further forming a direction control system for driving a scanner of the kind described above, so as to maintain the advantageous generation of the direction control signal based on the triangular wave and to improve the accuracy of the actual deflection position and the linearity of the deflection. To do so.

[0011]

According to the invention, this object is achieved by coupling a measurement receiver to a function generator through a logic unit for finding a correction value for the excitation current.

This makes it possible to evaluate the information available to the measured value receiver concerning the actual deflection position of the turning mirror and to find correction values with the aid of a logic unit. It can also be used to influence the directional control frequency emitted by the function generator so that deviations are reduced or completely eliminated. In so far, a control of the scanning operation is performed through the solution according to the invention, which controls the deviation of the actual deflection position of the mirror from the position given by the directional control frequency and provides further control of the turning mirror. The excitation current is changed accordingly.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In one advantageous embodiment of the invention,
It is proposed to couple at least one signal output of the function generator to an additional signal output of the logic unit for the purpose of transmitting a reference signal and a comparison signal. This also allows the use of a directional control frequency in the logic unit, which is based on the actual deflection of the mirror or on the comparison of the mirror's response frequency to the directional control frequency.

The logic unit incorporates a first calculation circuit for converting information about the deflection position of the turning mirror into the amplitude and phase of the scan driver in relation to a plurality of direction control frequencies. The results can be displayed in the form of a Bode plot.

Further, in the logical unit, the series y = 4
/ Π + [k ₁ sin (x + ψ ₁ ) −k ₂ sin (3x + ψ ₂ )
_{^{/ 3 2 + k 3 sin (}} 5x + ψ 3) / 5 2 - k 1 for Fourier frequency in + ···] ··· k _n and [psi ₁ · ·
A second calculation circuit has been incorporated to find the value of ψ _n . However, from k ₁ to k _n is the correction factor, x is is the phase angle deflection angle, and the [psi ₁ to [psi _n. This calculation circuit makes it possible to analyze the response behavior of the deflecting mirror by means of harmonics and determine the Fourier coefficients k ₁ to k _n . In this case, the response frequency is decomposed into a sum of pure swings (harmonic swings) and a fixed part.

In addition, the logic unit incorporates a third calculation circuit to standardize the directional control function which has been modified from a comparison between the actually achieved deflection position and the desired deflection position. In this case, standardization of the directional control function corrected based on the correction value derived from this comparison is performed. Furthermore, in the case of a small phase error, the coefficient is from k1 to, for example, k5, and in the case of a large phase error, the deviation Δψ ₁
To Δ 例 え ば_5, for example, is switched to the direction control function.

The directional control instructions calculated and corrected in the logic unit taking into account the correction values are arranged in a suitable data set and further directed to a function generator, where they are first stored. By taking into account the correction values for this first resonance frequency up to, for example, the fifth resonance frequency, a highly accurate correction of the direction control frequency is ensured.

In another preferred embodiment of the invention, an analog-to-digital converter is used in the signal path between the measurement receiver and the logic unit, and in a signal path between the function generator and the direction control unit. It is planned to prepare a digital-to-analog converter for powering the swing drive. The analog-to-digital converter may include a digital signal processor. This converts the analog signal provided by the measurement receiver into a digital signal required by the logic unit and, accordingly, the analog signal for preparing the direction control unit of the digital frequency signal provided by the function generator Conversion to is guaranteed.

More preferably, the logic unit, the function generator, the analog-to-digital converter and the digital-to-digital converter
An analog converter is in each case coupled to the cycle generator. This passes the response frequency information supplied by the measurement receiver to the logic unit, the modified directional control command to the function generator, and the synchronous directional control command for the next scanning process. It becomes possible.

As a swing motor, a galvanic drive unit is incorporated. Thereby, a definitive swing operation obtained by the exciting current of the turning mirror can be realized. The measurement value receiver incorporates a capacitive angle measurement system. The angle measurement system is incorporated so as to be used to determine the position value of the turning mirror in both scanning directions, ie for the forward and backward movement of the galvanic drive. As a result, the two-way position value is directed to the input of the logic unit through the digital signal processor, and thus can be realized in only one direction with about half the image formation time compared to the scanning process,
That is, the forward travel and the backward travel of the scanner operation can be realized, and the small deviation that still exists may be the same between the forward travel and the backward travel.

Next, the present invention will be described in more detail with reference to an embodiment and the accompanying drawings.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the embodiment shown in FIG. 1, a scanner 1 has a galvanic drive 2, a revolving mirror 3 coupled to the galvanic drive 2 through a mechanical connection 9, and a control input of the galvanic drive 2. A directional control unit 4 having an output in connection with the section, as well as a capacitive goniometer 7 used to search for a mirror position that varies with phase, is provided. Furthermore, there is a function generator 5 connected to the signal input of the digital signal processor 6 via a signal path 16, wherein the output of the signal processor 6 is connected to the signal path 1.
7 to the command input of the direction control unit 4. The first output of the capacitive angle measuring system 7 is an adjustment path 8
To the control input of the direction control unit 4.

The direction control unit 4 is designed such that it supplies the galvanic drive 2 with an excitation current, which is variable with respect to its frequency, swing configuration and amplitude. The function generator 5 can emit a plurality of different frequencies, these frequencies being individually selected and through a signal path 16, a digital signal processor 6 and a signal path 17 in the direction control unit 4 in the galvanic drive. It is designed to be able to imprint the control voltage for two. In this case, a composite triangular voltage (FIG. 2) including only the frequencies that can be processed by the galvanic driver 2
And FIG. 3) is based on the control voltage. As a specific example, in the function generator 5, 4
Take an example where two different frequencies are ready to ring.

In operating this arrangement, in each case the fundamental frequency and all harmonics call up a response which can be changed by the associated amplification and phase shift, which response represents the deflection position of the turning mirror 3 which is correspondingly changed. Since each deflection position corresponds to one position of the laser beam in the process of passing through the row scanned in the X direction, the galvanic drive 2 operates at the frequency of the excitation current or the frequency contained in the control voltage. Each is transmitted to the turning mirror 3 through the mechanical connection 9. By way of example, in each step 12
00 deflection positions are scanned, and each of these deflection positions is assigned one image point on the object plane.

The deflection position taken in each case by the turning mirror 3 corresponds to the position value indicated by the capacitive angling system 7, which value is sent back to the directional control unit 4 via the adjustment path 8, where: As soon as there is a deviation between the target and actual mirror position from the set or ideally desired deflection position, the direction control signal for the subsequent direction control of the galvanic drive 2 is modified. Used for These steps are performed with well-known adjustments.

Next, in order to be able to achieve a very short image forming time, in particular in the range of less than one second, a highly accurate deflection of the turning mirror 3 based on the course of the control voltage is ensured. The synthesized triangular voltage, which is enabled and starts the scanning operation, has a very wide
It is problematic to match the amplitude and the phase. This means that the transfer coefficient of the directional control function for the response operation is as close to the value 1 as possible, thereby limiting the deviation between the directional control function and the response operation to a minimum, for example, ≦ 0.5 pixels. . To achieve this, the directional control system described so far, based on the adjustment of the directional control frequency, according to the invention, has one logical unit 1
3 and the command input of this logic unit is divided into a signal path 12 and a second digital signal processor 1.
1 and a signal path 10 through a capacitive goniometer 7
Are connected to the second output unit. The output of logic unit 13 is connected via signal path 14 to the direction control input of function generator 5. In order to transfer the reference signal and the comparison signal from the function generator 5 to the logic unit 13, there is another connection between the function generator 5 and the logic unit 13 via a signal path 15. In addition, a cycle generator 18 is incorporated, which is connected to the second digital signal processor 11 via signal path 19, to the logic unit 13 via signal path 20, to the function generator 5 via signal path 24 and via signal path 21. Each is connected to a first digital signal processor 6.

Before starting a specific scanning operation, for example in a laser scanning microscope, the entire directional control system is checked for system errors, so that highly accurate deflection of the turning mirror 3 is possible depending on the planned frequency. Correction in consideration of the system error is first possible by the above connection arrangement. For the purpose of the course indicated as this correction, one after the other, all of the 42 frequencies provided by the function generator 5 are called up and the scanning process is started with these frequencies. In this case, the digital signal processors 6, 11, the function generator 5 and the logic unit 13 are synchronized by the cycle generator 18. The response introduced by the logic unit 13 is evaluated and analyzed in the form of a Bode diagram, where for each frequency of the Fourier coefficients it is possible to search for the transfer coefficient added to the phase angle. Based on the searched phase angle and transfer coefficient, synthesis of the directional control function is possible for a wide range of scanning frequencies (1/64 Hz... To 600 Hz). Used with the directional control frequency of the capacitive angle measurement system 7 for the modified directional control frequency of The data set for the oscillation of the triangular wave synthesized in this way is filed in the function generator 5, from which it can be called up periodically. In this way, a data set that takes into account the nature of the scanning system is made available as a result of a correction step in the function generator 5.
This data set determines how the scanning operation should be steered to maintain the desired highly accurate periodic deflection.

By the possible correct scanning operation here and by evaluating the response through the capacitive goniometer 7 for each of the 1200 deflection points of the laser beam, the same as in the correction step described above. , The deviation from the ideal deflection position is found, from which the modified direction control commands are obtained and filed in the function generator. From here, periodically and in accordance with the cycle frequency provided by the cycle generator, testing and further processing of the modified directional control data set are performed to achieve a highly accurate scan position.

FIG. 3 shows the uncorrected control voltage for a specific system in the form of a composite triangular voltage for a scanning process having an imaging time of 0.75 seconds. In this case, the length z indicates the measured amount of the row scanned in the X direction. In addition, a triangular wave 22 for the direction control voltage and a triangular wave 23 for the response operation should be recognized. Obviously, the triangular wave 23 does not have its zero crossing point at z / 2, ie the turning mirror 3 and the laser beam deflected thereby do not exactly follow the directional control voltage provided by the triangular wave 22.

FIG. 2 shows the situation after the correction has been made. The triangular wave 23 of the response action is smoothed, especially near the inversion point on the side, and now has its zero crossing point exactly at z / 2.

The connection arrangement according to the invention makes it possible to realize a composite triangular voltage with a high mirror symmetry and consequently a two-way scanning with high accuracy requirements.

[Brief description of the drawings]

FIG. 1 is a connection diagram of a direction control system according to the present invention.

FIG. 2 is a corrected control voltage change diagram in which an image forming time is less than 1 second.

FIG. 3 is an uncorrected control voltage change diagram in which the image forming time is less than 1 second.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Scanner 2 Galvanic drive part 3 Rotating mirror 4 Direction control unit 5 Function generator 6 Digital signal processor 7 Capacitive angle measurement system 8 Adjustment path 9 Mechanical connection part 10 Signal path 11 Second digital signal processor 12 Signal path 13 Logical unit 14 signal path 15 signal path 16 signal path 17 signal path 18 cycle generator 19 signal path 20 signal path 21 signal path 22 triangular wave 23 triangular wave 24 signal path

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Sebastian Titre D-35043 Marburg Rentmeister Strasse 37

Claims (13)

[Claims] 1. A swing motor for driving a turning mirror which serves for linear oscillation deflection of a light beam and for feeding the swing motor with an exciting current which can be varied with respect to directional control frequency, frequency curve and amplitude. Scanner drive, in particular for a laser scanning microscope, comprising a directional control unit, a function generator coupled to the directional control unit, and a measurement receiver for obtaining the result of the information about the deflection position of the pivoting mirror. The direction control system according to claim 1, wherein the measurement receiver receives a function generator (5) through a logic unit (13) to find a correction value for the excitation current.
Direction control system for a scanner drive, characterized in that it is coupled to 2. A signal input added to the logic unit (13) via a signal path (15) for transmitting a reference signal and a comparison signal, at least one signal output of the function generator (5). The directional control system for a scanner drive according to claim 1, wherein the directional control system is coupled to a unit. 3. In a logic unit (13), a first calculation circuit for converting information on the deflection position of the turning mirror (3) into amplitude and phase of the scanner (1) is associated with a plurality of direction control frequencies. 3. The direction control system for a scanner drive according to claim 1, wherein the direction control system is incorporated as a part. 4. A series in a logical unit (13).
y = 4 / π [k ₁ sin (x + ψ ₁ ) −k ₂ sin (3x + ψ ₂ ) / 3
² + k ₃ sin (5x + ψ ₃ ) / 5 ² − +...] (However,
from k ₁ to k _n is the correction factor, x is the deflection angle, and k ₁ for Fourier frequency in is the phase angle) from [psi ₁ to ψ _n ··· k _n and [psi ₁ · · · [psi 4. The direction control system for a scanner drive according to claim 1, wherein a second calculation circuit for finding the value of _n is incorporated. 5. In a logic unit (13), a third calculation circuit is incorporated for modeling a modified directional control function from a comparison between the actually achieved deflection position and the desired deflection position, In this case, a modified directional control function is modeled on the basis of the correction values derived from this comparison, and in the case of small phase errors the coefficients k ₁ to k ₅ for example and / or the individual function values are and in the case of large phase errors from the deviation [Delta] [phi] ₁ is, for example, up to [Delta] [phi] _5, characterized in that it is switched to the direction control function, the direction control for the scanner drive unit according to one of the claims 1-4 system. 6. The direction control system for a scanner driver according to claim 3, wherein the result of the first calculation circuit is displayed in a Bode diagram. 7. The directional control frequency, wherein the third calculation circuit can be used for the direction control frequency through a circuit component for finding a correction value for the first harmonic resonance frequency to the twentieth harmonic resonance frequency. A direction control system for a scanner driver according to claim 5. 8. A power supply for an analog-to-digital converter in a signal path between the measured value receiver and the logic unit (13) and a power supply for a swing motor in a signal path between the function generator and the direction control unit. A directional control system for a scanner drive according to one of the preceding claims, characterized in that a digital-to-analog converter is incorporated for the purpose. 9. The direction control system for a scanner drive according to claim 8, wherein the analog-to-digital converter is a digital signal processor. 10. The logic unit (13), the function generator (5), the analog-to-digital converter and the digital-to-analog converter are each provided with a cycle generator (1).
A directional control system for a scanner drive according to claim 8, characterized in that it is coupled to (8). 11. A directional control system for a scanner drive according to claim 1, wherein a galvanic drive (2) is used as a swing motor. 12. The method according to claim 1, wherein a capacitive angle measuring system is used as the measured value receiver.
A direction control system for a scanner driver according to any one of claims 11 to 11. 13. Capacitive goniometer system (7) is designed for ascertaining the position value of the turning mirror in the bidirectional scanning direction, that is, for advancing and retracting the galvanic drive (2), and in two directions. The direction control system for a scanner drive according to claim 12, characterized in that the position value is directed via a digital signal processor (11) to an input of a logic unit (5).