JPH05260267A - Drive control circuit for scanner mirror driving actuator - Google Patents

Abstract

PURPOSE:To provide a resonance type scanner drive control circuit which can increase the loop gain of only a low frequency area of a scanner control system and also can suppress the amplitude fluctuation of the scanner caused by the changes of the temperature and the attitude to prevent the complication of the system and to prevent the increase of the cost. CONSTITUTION:A drive control circuit consists of a drive signal generating circuit 9 which produces the sine wave drive signal and supplies this signal to an actuator 4 via a servo amplifier 11, an amplitude sensor 7 which detects the angle of deviation of a scanner mirror 3-1, a multiplier M which multiplies the result of addition/subtraction carried out between the detection signal of the sensor 7 and an amplitude command by the drive signal, an error amplifier circuit 10 which amplifies the result of the multiplier M, and an adder A-2 which adds the result of the circuit 10 to the drive circuit. Then a compensating circuit 13 is added between the multiplier M and the circuit 10 or the adder A-2 to compensate the gain characteristic of the low frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control circuit for a resonance type scanner used in an infrared imager, and more particularly, a compensation circuit is added to the amplitude control means to increase the loop gain for disturbance at low frequencies. The present invention relates to a drive control circuit for a resonance type scanner, which improves the accuracy of the above and suppresses the amplitude fluctuation of the scanner due to the change of the ambient temperature and the slow posture change.

[0002]

2. Description of the Related Art FIG. 7 is an illustration of an element array of an infrared detector. Most of the detectors used in the infrared imager are composed of a single element or linear array elements 1-1 to 1-n as shown. The size of one element is about 50 μm, and the elements are arranged at intervals of about 50 μm to form a linear array element. As will be described later, the scanner mirror in the scanner scans the linear array element in the vertical direction (V) and the horizontal direction (H) to obtain a two-dimensional image.

FIG. 8 is a block diagram of the essential parts of an infrared image device. As shown, the infrared energy from the background object OB is collected by the first infrared lens 2-1, collimated by the second infrared lens 2-2, and reflected by the scanner mirror 3-1 in the scanner 3. , And the infrared detectors 1-1 to 1-n converged by the third infrared lens 2-3.
Detected by.

FIG. 9 is a detailed view of the scanner shown in FIG. 8, which is an example of a resonance type scanner. 4 is an actuator,
5-1 and 5-2 are bearings, and 6 is a torsion spring. The actuator 4 is a motor, a solenoid or the like, and the torsion spring 6 is, for example, a torsion bar or a flexible pivot. The scanner mirror 3-1 is fixed to the torsion spring 6, and the torsion spring 6 is rotatably (amplitude) instructed by the bearings 5-1 and 5-2. A rotor 6-1 magnetically coupled to the actuator 4 at the tip of the torsion spring 6
Is provided, and the amplitude is changed by the change in the current applied to the actuator 4, whereby the twisting spring 6 is also changed, and the scanner mirror 3-1 is also changed. Then, the torsion spring 6 has a constant spring constant and a natural frequency determined by the mass, and if a sinusoidal vibration is applied from the outside corresponding to this natural frequency, the torsion spring 6 causes resonance. .. Therefore, if external vibration is applied according to this natural frequency, the scanner mechanism can be caused to resonate with a small external driving force, and the scanner mirror can be vibrated. The range of the amplitude of the scanner mirror is defined by the field of view of the background object.

FIG. 10 is a block diagram of amplitude control of the scanner mirror shown in FIG. The amplitude of the scanner mirror 3-1 is controlled by detecting the swing angle (maximum swing angle) information of the mirror by the amplitude detector 7 and feeding back the detection signal to the actuator 4. The detection signal of the amplitude detector 7 indicates the maximum swing angle, is added and subtracted with the amplitude command by the adder / subtractor A-1, and is multiplied by the sine wave drive signal from the drive signal generation source 9 by the multiplier M, , And these are added by the adder A-2 and amplified by the servo amplifier 11 and fed back to the actuator 4. The drive signal generation circuit generates a drive signal that secures the minimum swing angle of the mirror, and further, considering the influence of the disturbance detected by the amplitude detector 7, the actuator 4
Give feedback to.

FIG. 11 is an explanatory diagram of mechanical resonance characteristics of the scanner mirror. The vertical axis represents the degree of resonance, and the horizontal axis represents the vibration frequency applied to the actuator 4 from the drive signal generation circuit. The vertical axis represents the driving force of the mirror, and the place where the mechanical resonance point is maximum at a predetermined driving frequency is the maximum driving force for the scanner mirror. By the way, in the resonance type scanner, the amplitude of the mirror fluctuates due to the following factors.

As the spring constant of the torsion spring 6 changes with temperature, the resonance frequency of the mechanical system supporting it also changes,
The mirror driving force changes due to the shift of the resonance point. In other words, the resonance point Q _MAX indicated by the solid line in the figure changes to the resonance point Q _T indicated by the dotted line due to a temperature change, and as is clear from the vertical axis, the mirror driving force decreases. As shown in FIG. 9, the torsion spring 6 includes the bearings 5-1 and 5-.
It is supported by 2, but the mirror driving force changes as the viscosity of this bearing changes with temperature.

By changing the posture of the scanner,
The unbalance moment of the mirror resonance mechanism also changes,
The driving force due to this changes. When the amplitude of the scanner mirror changes as described above, FIG.
As is clear from the above structure, since the mirror scans in the horizontal direction, the field of view of the infrared imaging device fluctuates as a result. This poses a problem in the operation of the apparatus, and therefore it is necessary to control the amplitude of the scanner mirror to be constant regardless of temperature and attitude.

12 to 15 show examples in which the above-mentioned problems are dealt with. FIG. 12 is a main part configuration diagram for explaining an example of a conventional technique, and FIG. 13 is a control circuit diagram thereof. FIG. 14 is a temperature control circuit diagram as another conventional example, and FIG. 15 is a control circuit as still another conventional example. In these figures, 4-1 and 4-2 are solenoid coils as actuators, 6 is a flexible pivot as a torsion spring, and 6-1 is a magnetic iron piece as a rotor fixed to the flexible pivot 6. 8-1 and 8-2 are frames. In this structure, the magnetic iron piece 6-1 vibrates due to the change in the magnetic field due to the solenoid coils 4-1 and 4-2, and the scanner mirror 3-1 vibrates.

In FIG. 13, 9 is a drive signal generating circuit,
Reference numeral 10 is an error amplifier circuit, and 11 is a servo amplifier. The error amplifier circuit 10 is connected between the multiplier A-1 and the adder A-2. Then, addition and subtraction are performed between the vibration angle detection signal from the amplitude detector 7 and the amplitude command, and further multiplication is performed with the sine wave drive signal. Solenoids 4-1 and 4
At -2, the diode causes only one side of the sine wave to flow through the coil. As described above, the circuit of FIG.
Solenoids 4-1 and 4 via 0 and servo amplifier 11
-Feedback to -2.

In FIG. 14, a heater H is wound around the frames 8-1 and 8-2 of FIG. 12, and the temperature control circuit shown in FIG. That is, a heater H consisting of a resistor is provided in the latter stage of the servo amplifier 11 of the circuit of FIG. 13, a mechanical part such as a scanner is heated by this heater, its temperature is detected by a temperature sensor S, and addition / subtraction is performed with a temperature command. To do. This temperature compensation is effective because the resonance degree changes with temperature as shown in FIG.

In FIG. 15, a drive frequency control circuit 12 having a scanner resonance frequency detector 12-1 is further provided in the circuit of FIG. In the graph of FIG. 11, in order to prevent the deviation of the resonance point due to the deviation of the driving frequency, the deviation of the resonance frequency is detected by the scanner resonance frequency detecting circuit 12-1, and the addition / subtraction with the driving frequency command is performed to multiply the multiplier A. -1
Add to.

Although the above measures have been taken conventionally,
These are summarized below. The gain of the error amplification circuit 10 is increased, the loop gain of the system is increased, and control can be performed with a smaller amplitude error (see FIG. 13). As a measure against the temperature change, the ambient temperature of the scanner mechanism is heated by a heater or electronically cooled to control it at a constant temperature (see FIG. 14).

As another measure against the change in temperature, the amplitude and frequency of the current supplied to the driving actuator of the scanner are controlled in response to the change in the resonant frequency of the scanner to compensate for the deviation of the resonant frequency (see FIG. 15). Furthermore, in processing, the processing accuracy of the scanner resonance drive input is improved to improve the concentricity of the mirror rotation axis,
The unbalance moment between the center of rotation and the center of gravity is reduced, or the unbalance moment is reduced by adjusting the mass balance of the mirror as a measure against posture changes.

[0015]

The above-mentioned conventional method has the following problems. In the above, if the gain is increased too much, the feedback becomes excessive, and as a result, the control system becomes unstable and hunting increases or oscillation occurs. Therefore, there is a limit to the increase in gain.

In the above, a temperature detection sensor, a heater for heating, an electronic cooler for cooling, a control circuit for these, etc. are required, and as a result, the system becomes complicated and power consumption increases. Also, there is no effect on posture change.
In the above, a resonance frequency sensor and its control circuit are newly required to control the amplitude and frequency of the current passed through the scanner driving actuator, which leads to a complicated system. Also, there is no effect on posture change.

In the above, the number of man-hours required for processing each component and the number of man-hours required for adjustment at the time of assembly are increased, resulting in an increase in cost. Also, there is no effect on temperature change. An object of the present invention is to increase the loop gain only in the low frequency region of the scanner control system in the amplitude control of the resonance type scanner, so that it is possible to suppress the amplitude fluctuation of the scanner due to the temperature change and the attitude change. It is an object of the present invention to provide a drive control circuit of a resonance type scanner that prevents the system from becoming complicated and does not increase the cost.

[0018]

FIG. 1 is a block diagram showing the principle of the present invention. As shown in the figure, in the present invention, the compensation circuit 13 is provided between the multiplier M and the error amplifier 10. By increasing the loop gain only in the low frequency region of the scanner control system using the compensating circuit 13, it is possible to suppress the amplitude variation of the scanner due to the temperature change and the attitude change, and as a result, it is possible to prevent the system from becoming complicated. However, the cost increase can be suppressed.

[0019]

In the present invention, paying attention to the fact that the fluctuation of the amplitude due to the temperature change is slow, the response to the temperature change is increased by increasing the gain at a low frequency without being urged, and as a result, It corresponds to slow changes. That is, in the present invention, a compensation circuit as will be described later is provided, and control is performed so as to increase the servo gain at a low frequency so as to cope with temperature changes.

[0020]

FIG. 2 is an example of a compensation circuit (compensation circuit I), and FIG. 4 is a Bode diagram of this compensation circuit I. As shown in FIG. 2, the compensation circuit I is a circuit including a resistor R and a capacitor C, and is connected between the multiplier M and the error amplifier 10. Therefore, the output of the compensation circuit I is amplified by the error amplification circuit 10. Further, the graph of FIG. 4 shows the transfer function of the compensation circuit I, and the transfer function G of the compensation circuit I can be expressed by G = (1 + T ₂ ) / (1+ (T ₂ / α) S). Here, the resistance ratio α = R ₁ / (R ₁ + R ₂ ),
The time constant T ₂ = R ₂ · C. The solid line in FIG. 4 is a graph of this transfer function.

FIG. 3 shows another example of the compensation circuit (compensation circuit II). This compensating circuit is connected to the preceding stage of the error amplifying circuit 10, or the error amplifying circuit itself is configured by the present compensating circuit II. As shown in the figure, the operational amplifier OP is provided, but when it is connected to the previous stage of the error amplifier circuit 10, amplification by the operational amplifier OP is not necessary. On the other hand, the error amplification circuit 10
When it is used instead of, it needs to be amplified by the operational amplifier OP. Then, the transfer function G ′ of this compensation circuit II
Is G ′ = G ₁ (1 + T ₂ ′ S) / (1+ (T ₂ ′ / α ′) S). Here, time constant T ₂ '= C · R ₂ ', gain G ₁ =
R ₀ / R ₁ ′, resistance ratio α = R ₀ / (R ₀ + R ₂ ′).

In FIG. 4, the vertical axis represents the gain and the horizontal axis represents the angular frequency. The solid line shows the gain characteristic of only the compensation circuit I, and the dotted line shows the gain characteristic corrected by the compensation circuit I and the error amplification circuit. As described above, this gain characteristic shows the transfer function G. Furthermore, the alternate long and short dash line shows the phase characteristic. Therefore, the dotted line shows the compensation characteristics of the actual circuit.

As shown by the solid line, the gain is reduced at high frequencies and the phase is delayed at angular frequencies in the range of α / T ₂ to 1 / T ₂ . Therefore, the time constant T ₂ and the resistance ratio α are appropriately selected, the compensation circuit I is connected, and the gain in the attenuated high frequency region is set to the error amplification circuit 10.
If it is compensated by, the gain in the low frequency region can be increased as shown by the dotted line. Although the Bode diagram of the compensation circuit II is not shown, the compensation circuit II can further increase the low frequency gain.

FIG. 5 is an open loop Bode diagram of the scanner control system when the compensation circuit I is connected to the scanner control system. In the gain characteristic, the solid line is the case where the compensation circuit I is present, and the dotted line is the case where it is not. Also, in the phase characteristics,
The solid line shows the case where the compensation circuit I is present, and the dotted line does not. As is clear from comparison with the dotted line, connecting the compensating circuit I makes it possible to increase the gain characteristic in the low frequency region without affecting the gain characteristic and the phase characteristic in the high frequency region.

Therefore, the error can be reduced (the amplitude fluctuation can be reduced) by increasing the gain with respect to the low frequency, that is, the slow influence such as the temperature change. The compensating circuits I and II described above can easily suppress the amplitude fluctuation due to the change of the ambient temperature of the scanner and the slow attitude change, and as a result, the system is not complicated and the cost is not increased. It can be seen that the phase characteristic is delayed as compared with the dotted line.

FIG. 6 is a block diagram of the essential portions of an infrared image device to which the present invention is applied. As mentioned above, the infrared energy from the background object OB is collected by the first lens 2-1 and
Are made parallel by the lens 2-2, converged by the third and fourth lenses, and converted from an optical signal to an electric signal by the infrared detection device 14. The electric signal is amplified by the amplifier 15, imaged by the video circuit 16, and displayed on the monitor television 17.

[0027]

As described above, according to the present invention,
In the resonance type scanner used for the infrared imaging apparatus, it is possible to suppress the amplitude fluctuation due to the change of the ambient temperature and the attitude of the scanner to be small without complicating the system and increasing the cost. That is, in the conventional method shown in FIG. 13, the amplitude variation of the resonance type scanner with respect to the temperature change and the posture change is about ± 20% when no measures are taken, and the conventional method shown in FIGS. 14 and 15 is ± 5%. %Met. In the present invention, the amplitude fluctuation could be suppressed to ± 5% or less.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is an example (compensation circuit I) of a compensation circuit of the present invention.

FIG. 3 is another example (compensation circuit II) of the compensation circuit of the present invention.

4 is a Bode diagram of the compensation circuit I of FIG.

5 is an open loop Bode diagram of the scanner control system when the compensation circuit of FIG. 2 is connected to the scanner control system.

FIG. 6 is a configuration diagram of a main part of an infrared image device to which the present invention is applied.

FIG. 7 is an explanatory diagram of an element array of an infrared detector.

FIG. 8 is a configuration diagram of a main part of an infrared image device.

FIG. 9 is a detailed view of the scanner shown in FIG.

10 is a block diagram of amplitude control of the scanner mirror shown in FIG.

FIG. 11 is an explanatory diagram of resonance characteristics of a scanner mirror.

FIG. 12 is a main part configuration diagram illustrating an example of a conventional technique.

FIG. 13 is a control circuit diagram of the configuration of FIG.

FIG. 14 is a temperature control circuit diagram as another conventional example.

FIG. 15 is a control circuit as still another example of the related art.

[Explanation of symbols]

 1-1 to 1-n ... Infrared detector 2-1 to 2-3 ... Infrared lens 3 ... Scanner 3-1 ... Scanner mirror 4 ... Actuator 5-1 and 5-2 ... Bearing 6 ... Torsion spring 6- 1 ... Rotor 7 ... Amplitude detector 8-1, 8-2 ... Frame 9 ... Drive signal generation circuit 10 ... Error amplification circuit 11 ... Servo amplifier 12 ... Drive frequency control circuit 13 ... Compensation circuit

Claims (4)

[Claims] 1. A drive control circuit for an actuator for driving a scanner mirror in a resonance type scanner of an infrared image device, the drive signal generating a sine wave drive signal supplied to the actuator (4) via a servo amplifier (11). A generation circuit (9), an amplitude detector (7) for detecting a swing angle of the scanner mirror (3-1), a detection signal of the amplitude detector and an addition / subtraction result of an amplitude command, and the drive signal are multiplied. And a multiplier (M) for amplifying the result of the multiplier, and an adder (A-2) for adding the result of the error amplifier and the drive signal. In the drive control circuit of the mirror driving actuator, a compensating circuit (13) for compensating for gain characteristics at low frequencies is provided between the multiplier and the error amplifying circuit. -Drive control circuit for drive actuator. 2. A drive control circuit for an actuator for driving a scanner mirror in a resonance type scanner of an infrared image device, wherein a drive signal for generating a sine wave drive signal supplied to the actuator (4) through a servo amplifier (11). A generation circuit (9), an amplitude detector (7) for detecting a swing angle of the scanner mirror (3-1), a detection signal of the amplitude detector and an addition / subtraction result of an amplitude command, and the drive signal are multiplied. And a multiplier (M) for amplifying the result of the multiplier, and an adder (A-2) for adding the result of the error amplifier and the drive signal. In the drive control circuit of the mirror driving actuator, a compensating circuit (13) for compensating the gain characteristic at a low frequency is provided between the multiplier and the adder. Actuator drive control circuit. 3. The compensating circuit comprises a first resistor (R ₁ ) and a second resistor (R ₁ ).
Of the resistor (R ₂ ) and the capacitor (C) are connected in series, the input side is connected between the first resistor and the capacitor, and a common connection point of the first and second resistors. The drive control circuit according to claim 1, wherein an output side is connected between (P) and the capacitor. 4. The compensation circuit comprises an operational amplifier (OP), one input side of the operational amplifier is connected to the input side through a resistor, and the output side of the operational amplifier and the input side are fed back by a resistor and a capacitance. The drive control circuit according to claim 2, which is configured to be connected.