JP3314618B2 - Moving mirror drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving mirror driving circuit for an interferometer used in a spectroscope or the like, and more particularly to a moving mirror driving circuit capable of preventing step-out at the start of driving.

[0002]

2. Description of the Related Art A conventional spectroscope using an interferometer emits white light into an interferometer, and interfering light, which is the output light of the interferometer, into the sample and detects the transmitted light, thereby obtaining a sample. Perform spectroscopic analysis.

FIG. 5 is a configuration block diagram showing an example of an inner interferometer portion of such a conventional spectroscope. In FIG. 5, 1 is a light source, 2 and 6 are lenses, 3 is a half mirror, 4 is a fixed mirror, 5 is a movable mirror, 7 is an optical fiber for guiding interference light to a sample (not shown), and 8 is a movable mirror drive. Means.

The output light of the light source 1 is incident on the half mirror 3 via the lens 2, and a part of the output light is reflected by the half mirror 3 and is transmitted to the fixed mirror 4, and the rest is transmitted through the half mirror 3 and is movable. 5 respectively.

The light reflected by the fixed mirror 4 and the movable mirror 5 is incident on the half mirror 3 again, becomes an interference light due to a difference in optical path between the two, and is incident on the optical fiber 7 via the lens 6.

At this time, the movable mirror 5 is driven by the movable mirror driving means 8 as shown by "a" in FIG. 5, thereby scanning the interference light generated by the half mirror 3.

FIG. 6 is a block diagram showing the construction of the moving mirror 5 and the moving mirror driving means 8 in detail. In FIG. 6, 5
5, the same reference numerals as those in FIG. 5 are attached, 9a and 9b are supporting leaf springs, 10 is a laser control circuit, 11 is a laser, 12
Is a four-divided photodetector, 13 is a moving mirror drive circuit, 14 is a coil, and 15 is a magnet.

The leaf springs 9a and 9b support the movable mirror 5 and are fixed to an interferometer main body (not shown) so as to be movable in the direction indicated by "A" in FIG.

The output light of the laser 11 is incident on the surface of the leaf spring 9b, and the reflected light is incident on the four-split photodetector 12. Further, the laser control circuit 10 controls the power of the output light of the laser 11 to be constant.

When the movable mirror 5 moves in the direction "A" in FIG. 6 in this state, the leaf springs 9a and 9b supporting the movable mirror 5 bend, and the optical axis of the light reflected from the leaf spring 9b moves. .

The quadrant photodetector 12 detects a change in the optical axis of the reflected light. That is, the four-split photodetector 12 has four photodetectors formed adjacent to each other, and detects the position of the movable mirror 5 by analyzing the distribution of the light intensity detected by the four photodetectors. be able to.

The change in the optical axis is input to the movable mirror drive circuit 13, and the movable mirror drive circuit 13 controls the drive current flowing through the coil 14 based on the change in the optical axis to control the position of the movable mirror 5. The coil 14 is fixed to the movable mirror 5 and moves the movable mirror 5 by a repulsive force with a magnet 15 installed adjacently.

FIG. 7 shows a conventional movable mirror driving circuit 13.
FIG. 3 is a configuration block diagram illustrating an example of the configuration. In FIG. 7, 16
Is a triangular wave generation circuit, 17 is a moving mirror position detection circuit, 18 is a subtractor, 19 is a control circuit, and 20 is a coil drive circuit.

The output of the triangular wave generation circuit 16 is connected to an addition input terminal of a subtractor 18, and the output of the moving mirror position detection circuit 17 is connected to a subtraction input terminal of the subtractor 18. Subtractor 1
The output of 8 is connected to the control circuit 19, and the output of the control circuit 19 is connected to the coil drive circuit 20. The output of the coil drive circuit 20 is connected to the coil 14 of FIG.

Here, the operation of the moving mirror driving circuit shown in FIG. 7 will be described with reference to FIG. FIG. 8 is a characteristic curve diagram showing a change in the drive current of the coil 14.

The position component of the moving mirror 5 output from the moving mirror position detecting circuit 17 is subtracted by a subtractor 18 from the triangular wave output from the triangular wave generating circuit 16. Therefore, a difference between the drive current and the current position is obtained.

The control circuit 19 controls the coil drive circuit 20 to control the drive current applied to the coil 14 so that the difference becomes zero.

FIG. 8A shows a waveform indicating a control target, and FIG. 8B shows a change in drive current when driving is started at the timing "a" in FIG. By controlling the drive current as described above, it can be seen that the control target is sequentially followed from the drive start.

[0019]

However, "A" in FIG.
If the drive is started at the timing of (1), the control target is followed, but if the drive is started at the timing "B" in FIG. 8, for example, the control target is not followed as shown in (c) of FIG. There was a problem that it might be in a state. Accordingly, an object of the present invention is to realize a moving mirror driving circuit capable of preventing step-out at the start of driving.

[0020]

According to a first aspect of the present invention, a triangular wave, which is a control target, is generated in a moving mirror driving circuit for driving a moving mirror constituting an interferometer. A drive start control circuit that controls the waveform of the triangular wave at the start of driving the triangular wave generation circuit and the movable mirror,
A moving mirror position detecting circuit for detecting a current position of the moving mirror; a subtractor for calculating a difference between outputs of the driving start control circuit and the moving mirror position detecting circuit; and a coil driving circuit for setting the difference to zero. And a control circuit for controlling a drive current applied to the coil using the control circuit.

According to a second aspect of the present invention, at the start of driving of the movable mirror, the DC voltage component of the triangular wave is set to “0 V” from the vicinity of the positive power supply voltage or the negative power supply voltage. And a control circuit at the start of driving for controlling so as to gradually change to "."

In order to achieve the above object, according to a third aspect of the present invention, in the first aspect of the present invention, the gain of the internal amplifier is gradually changed from "0" to "1" at the start of driving of the movable mirror. A drive control circuit for controlling the amplitude of the triangular wave is provided.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration block diagram showing one embodiment of a moving mirror driving circuit according to the present invention.

In FIG. 1, reference numerals 16, 17, 18, 19 and 20 denote the same reference numerals as in FIG. 7, reference numeral 21 denotes a drive start control circuit, 100 denotes an output signal of the triangular wave generation circuit 16,
01 is an output signal of the control circuit 21 at the start of driving.

The output of the triangular wave generation circuit 16 is connected to a control circuit 21 at the start of driving, and the output of the control circuit 21 at the start of driving is connected to an addition input terminal of the subtracter 18.

The output of the moving mirror position detection circuit 17 is
8, the output of the subtractor 18 is connected to the control circuit 19, and the output of the control circuit 19 is connected to the coil drive circuit 20.

The operation of the embodiment shown in FIG. 1 will be described with reference to FIGS. FIG. 2 shows a driving start control circuit 2
FIG. 3 is a circuit diagram showing an example of the control circuit 21 shown in FIG.
FIG. 6 is a timing chart for explaining the operation of FIG.

In FIG. 2, reference numerals 100 and 101 denote the same reference numerals as in FIG. 1, 22 denotes an adder, 23 denotes a switch circuit, 24 and 26 denote resistors, 25 denotes a capacitor, and 27 denotes a transistor.

One end of the switch circuit 23 is connected to one end of a resistor 24, and the other end of the resistor 24 is connected to one end of a resistor 26 and one end of a capacitor 25.

The other end of the resistor 26 is connected to the base of the transistor 27, and the collector of the transistor 27 is connected to the adder 2
2 is connected to one input terminal. An output signal 100 is input to the other input terminal of the adder 22, and an output of the adder 22 is output as an output signal 101.

The other end of the switch circuit 23 is connected to a positive voltage source "+ V", and the other end of the capacitor 25 and the emitter of the transistor 27 are connected to a negative voltage source "-V".

Before the start of driving, the switch circuit 23 is turned "ON" by a control circuit (not shown), so that the transistor 27 is also turned "ON", and the collector voltage of the transistor 27 is the voltage of the negative voltage source. -V ".

When driving is started, the switch circuit 23 is turned off by a control circuit (not shown), and the capacitance 2
5 is charged into the resistor 26 and the transistor 2
7 discharges.

For this reason, as shown in FIG. 3A, the collector voltage of the transistor 27 gradually rises, and finally reaches "0 V". Since this waveform and the output signal 100 which is a triangular wave shown in FIG. 3B are added by the adder 22, the output voltage 101 has a waveform as shown in FIG.

The waveform shown in FIG. 3C is a triangular wave whose DC voltage component gradually rises from the vicinity of the negative power supply voltage "-V" and finally becomes "0".

That is, since the waveform as shown in FIG. 3 (c) is the control target, the drive current that has been turned to the negative side is applied to the coil 14 at the start of driving, and thereafter gradually returns to the normal drive current. , It becomes easier to follow the control target.

Further, since the drive start time control circuit 21 operates in synchronization with the drive start timing, it is possible to prevent a step-out state due to a difference in timing shown by "a" or "b" in FIG. .

As a result, by controlling the triangular wave, which is the control target of the moving mirror drive circuit, by the drive start time control circuit 21, it is possible to prevent step-out at the start of drive.

In the embodiment shown in FIG. 1 and the like, the control target at the start of driving is a triangular wave whose DC voltage component gradually rises from near the negative power supply voltage "-V" to "0 V". May be a triangular wave gradually falling from near the positive power supply voltage “+ V” to “0 V”.

The drive start control circuit 21 has an internal amplifier, and gradually increases the amplification factor of the internal amplifier from "0" to "1" so that the output signal of the triangular wave generation circuit 16 can be controlled. As shown in FIG. 4, the waveform may be controlled so that the amplitude of the triangular wave gradually increases from zero.

In this case, since the amplitude of the triangular wave, which is the control reference, gradually increases, no large drive current is applied to the coil 14 immediately, so that step-out at the start of drive can be prevented.

[0042]

As is apparent from the above description,
According to the present invention, the following effects can be obtained. By controlling the triangular wave, which is the control target of the moving mirror drive circuit, by the drive start control circuit, it is possible to realize a movable mirror drive circuit capable of preventing step-out at the start of drive.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram showing one embodiment of a moving mirror driving circuit according to the present invention.

FIG. 2 is a circuit diagram showing an example of a drive start control circuit.

FIG. 3 is a timing chart for explaining the operation of a drive start control circuit.

FIG. 4 is a characteristic curve diagram showing another output example of the drive start control circuit.

FIG. 5 is a configuration block diagram illustrating an example of an interferometer portion of a conventional spectroscope.

FIG. 6 is a configuration block diagram showing details of a moving mirror and a moving mirror driving unit.

FIG. 7 is a configuration block diagram illustrating an example of a conventional moving mirror driving circuit.

FIG. 8 is a waveform showing a control target and a drive current.

[Explanation of symbols]

 Reference Signs List 1 light source 2, 6 lens 3 half mirror 4 fixed mirror 5 moving mirror 7 optical fiber 8 moving mirror driving means 9a, 9b leaf spring 10 laser control circuit 11 laser 12 quadrant photodetector 13 moving mirror driving circuit 14 coil 15 magnet 16 Triangular wave generation circuit 17 Moving mirror position detection circuit 18 Subtractor 19 Control circuit 20 Coil drive circuit 21 Drive start control circuit 22 Adder 23 Switch circuit 24, 26 Resistance 25 Capacity 27 Transistor 100, 101 Output signal

Claims (3)

(57) [Claims] 1. A moving mirror driving circuit for driving a moving mirror constituting an interferometer, comprising: a triangular wave generating circuit for generating a triangular wave as a control target; and a drive start control for controlling a waveform of the triangular wave when the moving mirror starts driving. A circuit, a moving mirror position detecting circuit for detecting a current position of the moving mirror, a subtractor for calculating a difference between outputs of the driving start control circuit and the moving mirror position detecting circuit, and such that the difference becomes zero. A driving circuit for controlling a driving current applied to the coil using the coil driving circuit. 2. When the driving of the movable mirror is started, the DC voltage component of the triangular wave is set to "0"
2. A driving start-time control circuit for performing control so as to gradually change to V ".
A moving mirror driving circuit as described in the above. 3. A driving start control circuit for gradually changing an amplification factor of an internal amplifier from "0" to "1" at the start of driving of a movable mirror and controlling the amplitude of the triangular wave. The moving mirror driving circuit according to claim 1.