JPH0545603A - Resonance type scan - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a resonance type scanner, and an object thereof is to provide a resonance type scanner capable of keeping the amplitude of a scanner mirror highly stable with a simple structure. [Structure] A mechanical scanner including an actuator 1, a scanner mirror 2, and a torsion spring 3 is driven by an AC signal near the resonance frequency of the system, and the scanner mirror 2
In the resonance type scanner in which the amplitude of the detector is controlled to be constant, the detection units 6a and 6b independently detect the vibration position of the scanner mirror 2, and the vibration detection unit 7 corresponds to the difference between the detection outputs of the detection units 6a and 6b. Scanner mirror 2 based on signal
Form a detection signal D corresponding to the amplitude of This allows
The fluctuations that appear the same in the detection units 6a and 6b due to fluctuations in the ambient temperature and the like are canceled, and the amplitude of the scanner mirror is controlled with high stability. Preferably, the detectors 6a and 6b are provided so that their characteristic changes with respect to temperature are substantially the same and are close to each other.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to resonant scanners,
More specifically, the present invention relates to a resonance scanner that drives a mechanical scanner including an actuator, a scanner mirror, and a torsion spring with an AC signal near the resonance frequency of the system, and controls the amplitude of the scanner mirror to be constant.

This type of resonant scanner is indispensable for a two-dimensional infrared image pickup device. However, if the amplitude of the scanner mirror fluctuates due to fluctuations in the surrounding environment such as temperature, the field of view of the imaging device will fluctuate, which is extremely inconvenient. Therefore, it is desired to provide a resonance type scanner in which the amplitude of the scanner mirror is kept highly stable.

[0003]

2. Description of the Related Art FIG. 5 is a diagram showing a configuration of a conventional resonance type scanner. FIG. 5A is a block diagram of the resonance type scanner.
FIG. 5B is a plan view of the scanner mirror portion.
In FIG. 5A, 1 is an actuator, 11 is a coil (stator), 12 is a rotor, 2 is a scanner mirror, 2b is a chopper flag, 3 is a torsion spring such as a torsion bar or a flex pivot, and 4 is an actuator drive. Section, 5'is an error detection section, 6 is a photocoupler, 61
Is a light emitting diode, 62 is a phototransistor, and 8 is an AC signal source.

Assuming that the inertial mass of the scanner mirror 2 is M, the friction coefficient is b, and the spring constant is C, the amplitude x when a certain force is applied to the scanner mirror 2 is approximately x = x ₀ e ^-bt. It is given by ^{/ 2M} sin (ω ₀ t + φ). ω ₀ is the resonance frequency (C / M) ^{1/2 of the system} , and the friction coefficient b is assumed to be sufficiently small. Since this is a damped vibration, the vibration of the scanner mirror 2 eventually stops. Therefore, when an external force of F = Asin ωt is applied to the scanner mirror 2 by the actuator 1, a resonance response (resonance) is obtained when approximately ω = ω ₀ , and the amplitude x of the scanner mirror 2 becomes extremely large and constant. Become.
The amplitude x of the scanner mirror 2 at this time is approximately given by x = (AM / bω ₀ ) sinω ₀ t. However, since the actual friction coefficient b and the like are not constant, the maximum amplitude (AM / bω ₀ ) of the scanner mirror 2 also changes accordingly. Therefore, conventionally, the fluctuation of the maximum amplitude (AM / bω ₀ ) is detected by the photocoupler 6, and the error signal E is detected according to the detected error signal E.
The actuator drive unit 4 was controlled so that

In FIG. 5B, the maximum amplitude of such a scanner mirror 2 is about ± 10 degrees in swing angle. Conventionally, when the swing angle of the scanner mirror 2 is +6 to 8 degrees. The single photo coupler 6 is provided at a position where the chopper flag 2b does not block the optical path. Therefore, the output PH of the photocoupler 6 becomes HIGH level when the swing angle of the scanner mirror 2 exceeds +6 to 8 degrees, and L when it returns to +6 to 8 degrees from the maximum swing angle.
It reaches the OW level. That is, the output P of this photo coupler 6
H is a signal for detecting the time when the scanner mirror 2 is near a predetermined maximum swing angle.

FIG. 6 is an operation timing chart of the conventional resonance type scanner. When the scanner mirror 2 is vibrating at a predetermined (set) amplitude A, the output of the photocoupler 6 is PH.
_A , and a signal P obtained by pulse-shaping this with a predetermined threshold th
Results in a signal P _A of pulse width T _A. However, if the amplitude of the scanner mirror 2 increases to B for some reason, the output of the photocoupler 6 becomes PH _B , and the pulse-shaped signal P becomes a signal P _B having a pulse width T _B. As described above, the pulse signals P _A and P _B have pulse widths T _A and T _B corresponding to the respective maximum amplitudes of the scanner mirror 2, and by comparing these with the reference signal R having a predetermined pulse width, An error signal E for keeping the amplitude of the scanner mirror 2 constant can be fed back to the actuator drive unit 4.

However, for example, when the ambient temperature of the photocoupler 6 rises, the dark current of the phototransistor 62 increases, so that the output PH of the photocoupler 6 increases in the overall signal level like the signal PH _C. Moreover, the field of view of such a photocoupler 6 has a certain spread, and
Since the light blocking characteristic of the chopper flag 2b is not sharp, the increase of the dark current of the phototransistor 62 also affects the transient portion of the output PH of the photocoupler 6. Therefore, the pulse-shaped signal P becomes a signal P _C having a pulse width T _C , whereby the scanner mirror 2
Will change the maximum amplitude of.

FIG. 7 is a diagram showing an example of a constant amplitude control of a conventional resonance type scanner. In the figure, 100 is a resonance type scanner unit, 101 is a temperature sensitive element such as a thermistor, 102 is a temperature comparison unit, and 103 is a drive unit. Reference numeral 104 denotes a temperature control element such as a Peltier element. Conventionally, the error signal T _E is formed by comparing the detected temperature T _{H of the} temperature sensitive element 101 with the set temperature T ₀ , whereby the driving unit 103 controls the ambient temperature of the resonant scanner unit 100 to be constant. Was there. But,
This causes the system to be complicated, and power consumption and weight to be increased.

FIG. 8 is a diagram showing another example of the amplitude constant control of the conventional resonance type scanner. In the figure, 201 and 202 are lenses, 203 and 204 are slits, 205 is a light emitting element, and 206 is a light receiving element. .. According to this method, the light beam incident on the light receiving element 206 is sufficiently narrowed and the light blocking characteristic of the slit 204 is extremely sharp. Therefore, the output PH of the photocoupler 6 is similar to the signal PH _A. It has a very sharp transient part. Therefore,
Even if the output level of the photocoupler 6 rises like the signal PH _C due to the rise of the ambient temperature, the transient portion thereof is hardly affected, and therefore the field of view of the resonant scanner hardly changes. However, such an increase in the lens system and the slits not only complicates the system and increases the weight, but also makes it difficult to manufacture and adjust the optical system.

[0010]

As described above, there is no conventional resonance type scanner that can keep the amplitude of the scanner mirror highly stable with a simple structure. An object of the present invention is to provide a resonance type scanner which can keep the amplitude of a scanner mirror highly stable with a simple structure.

[0011]

The above problems can be solved by the structure shown in FIG. That is, the resonant scanner of the present invention is
The actuator 1, the scanner mirror 2, the torsion spring 3, the actuator drive unit 4 that drives the actuator 1 with an AC signal near the resonance frequency of these systems, a detection signal D corresponding to the amplitude of the scanner mirror 2, and a predetermined signal. R
In the resonance type scanner provided with the error detection unit 5 which feeds back the error signal E for keeping the amplitude constant to the actuator drive unit 4 by comparing with, a plurality of detection units for detecting the vibration position of the scanner mirror 2. 6a and 6b, and a vibration detector 7 that forms a detection signal D corresponding to the amplitude of the scanner mirror 2 based on a signal corresponding to the difference between the detection outputs of the detectors 6a and 6b.

[0012]

In the resonance type scanner of the present invention, the detection unit 6
a and 6b independently detect the vibration position of the scanner mirror 2 with respect to the portions where the vibration phase of the scanner mirror 2 is different, and the vibration detecting unit 7 detects the detecting positions 6a and 6b.
The detection signal D corresponding to the amplitude of the scanner mirror 2 is formed based on the signal corresponding to the difference in the detection output of the. In this way, by providing a plurality of systems of detection units 6a and 6b, even if the ambient temperature or the like changes, the variation that appears in the output PH ₂ of the detection unit 6a also appears in the output PH ₁ of the detection unit 6b. Therefore, by obtaining the signal corresponding to the difference between the two signals PH ₁ and PH ₂ , it is possible to always cancel the variation.

Preferably, the plurality of detectors 6a, 6b are
The characteristic changes with respect to temperature are substantially the same, and they are provided close to each other. As a result, the effect of cancellation is significantly improved.

[0014]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. 2A and 2B are diagrams showing the configuration of the resonance type scanner of the first embodiment. FIG. 2A is a block diagram of the resonance type scanner, and FIG. 2B is a plan view of the scanner mirror portion. In FIG. 2A, 1 is an actuator such as a motor or solenoid, 11 is a coil (stator),
Reference numeral 12 is a rotor, 2 is a scanner mirror, 2a and 2b are chopper flags, 3 is a torsion spring such as a torsion bar or a flex pivot, 4 is an actuator drive section, 5 is an error detection section, 51 is a subtractor, and 6a and 6b are A photocoupler, 7 is a vibration detector, 71 and 72 are pulse shaping circuits, 7
3 is a flip-flop (FF), 74 is a counter, and 8 is an AC signal source.

The flip-flop 73 is a photo coupler 6.
b is set at the rising edge of the signal P ₁ obtained by pulse-shaping the output signal PH ₁ and the output signal P of the photocoupler 6a is set.
Reset of H ₂ at the rising edge of the pulse shaping signal P _2. The counter 74 counts the clock signal CLK in the section where the output signal T of the flip-flop 73 is HIGH level, and outputs the count value D. And
The error detection unit 5 obtains the difference between the count value D and the predetermined set value R, and returns the obtained error signal E to the actuator drive unit 4 as a control signal for reducing the error signal E.

In FIG. 2B, in the first embodiment,
When the oscillation angle of the scanner mirror 2 is +6 to 8 degrees, the photo coupler 6a is provided at a position where the chopper flag 2a does not block the optical path, and when the oscillation angle of the scanner mirror 2 is approximately +0 degrees, The photocoupler 6b is provided at a position where the chopper flag 2b does not block the optical path.

FIG. 3 is an operation timing chart of the resonance type scanner of the first embodiment, which shows the output PH _{1 of the} photocoupler 6b.
Is H when the swing angle of the scanner mirror 2 exceeds approximately 0 degrees.
It becomes the IGH level, and when it returns to approximately 0 degrees from the maximum swing angle again, it becomes the LOW level. On the other hand, photo coupler 6
The output PH _{2 of a} has a swing angle of the scanner mirror 2 of +6 to 8
The level becomes HIGH when the angle exceeds the limit, and becomes LOW when the angle returns from +6 to 8 degrees from the maximum swing angle. The signals obtained by pulse-shaping these signals PH ₁ and PH ₂ with the threshold value th are signals P ₁ and P ₂ , respectively.

Therefore, when a signal corresponding to the temporal difference between these signals P ₁ and P ₂ is obtained, a signal T having a pulse width T _A is obtained.
Is obtained. By the way, this signal T is HI when the swing angle of the scanner mirror 2 reaches from 0 degree to +6 to 8 degrees each time.
This is a GH level signal, and its pulse width T _A has a relationship in which it decreases as the maximum amplitude of the scanner mirror 2 increases, and conversely increases as the maximum amplitude of the scanner mirror 2 decreases. Therefore, feedback is applied to the actuator drive unit 4 so that the pulse width T _{A of the} signal T becomes constant.

[0019] And now, the photocoupler 6b, the temperature of 6a rises, the signal level of the output signal PH _1, PH ₂ rises as indicated by a dotted line in FIG, each signal PH _1, PH
The transient parts of ₂ are also affected respectively, but these effects appear substantially the same for the photocouplers 6b and 6a. Therefore, if a signal corresponding to the time difference between the signals P ₁ and P ₂ obtained by pulse-shaping them is obtained. , After all T _A = T _C
Therefore, the fluctuation due to temperature can be canceled at any time. The method of obtaining the signal corresponding to the difference between the output signals of the photocouplers 6b and 6a is not limited to the above.

FIG. 4 is a diagram showing the configuration of the resonance type scanner of the second embodiment. FIG. 4A is a block diagram of the resonance type scanner, and FIG. 4B is a plan view of the scanner mirror portion. is there. In FIG. 4A, 6c is a detection element, and inside thereof, photocouplers _6c1 and _6c2 having substantially the same characteristic changes with respect to temperature are provided close to each other.

In FIG. 4B, in the second embodiment,
When the oscillation angle of the scanner mirror 2 is +6 to 8 degrees, the photocoupler 6 _c1 is provided at a position where the chopper flag 2b does not block the optical path, and the oscillation angle of the scanner mirror 2 is approximately +0 degrees. The photocoupler 6 _c2 is provided at a position where the chopper flag 2b does not block the optical path. Then, the photocoupler 6 _c2 outputs the signal PH ₁ ,
The photocoupler 6 _c1 outputs the signal PH ₂ .

Therefore, also in this case, the amplitude constant control of the scanner mirror 2 can be performed with high accuracy by the same method as in the first embodiment, and in the case of the second embodiment, the photocouplers 6 _c1 and 6 _{c1 are used} .
_Since the temperature characteristics and temperature environment of _c2 can be made the same, the effect of cancellation is significantly improved. The amplitude variation of the resonant scanner with respect to the temperature change is about ± 20% in the conventional configuration of FIG. 5, and about ± 3% in the configuration of FIG.
In the configuration of FIG. 8, it was about ± 1%. On the other hand, in the configuration of FIG. 2 of the first embodiment, about ± 3% was obtained. Further improvement can be achieved with the configuration of FIG. 4 of the second embodiment.

[0023]

As described above, according to the present invention, a plurality of detecting portions 6a, 6 for detecting the vibration position of the scanner mirror 2 are provided.
b, and a vibration detector 7 that forms a detection signal D corresponding to the amplitude of the scanner mirror 2 based on a signal corresponding to the difference between the detection outputs of the detectors 6a and 6b. Therefore, highly accurate amplitude constant control of the scanner mirror can be realized without complicating the system and without increasing power consumption and weight.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a configuration of a resonance type scanner of a first embodiment.

FIG. 3 is an operation timing chart of the resonance type scanner of the first embodiment.

FIG. 4 is a diagram showing a configuration of a resonance type scanner of a second embodiment.

FIG. 5 is a diagram showing a configuration of a conventional resonant scanner.

FIG. 6 is an operation timing chart of a conventional resonance type scanner.

FIG. 7 is a diagram showing an example of amplitude constant control of a conventional resonant scanner.

FIG. 8 is a diagram showing another example of amplitude constant control of a conventional resonant scanner.

[Explanation of symbols]

 1 Actuator 2 Scanner Mirror 3 Torsion Spring 4 Actuator Drive Unit 5 Error Detection Unit 6a, 6b Detection Unit 7 Vibration Detection Unit

Claims (2)

[Claims] 1. An actuator (1), a scanner mirror (2), a torsion spring (3), and an actuator drive section (4) for driving the actuator (1) with an AC signal near the resonance frequency of these systems. , Scanner mirrors (2)
The error detection unit (5) for feeding back the error signal (E) for keeping the amplitude constant by comparing the detection signal (D) corresponding to the amplitude of the predetermined signal (R) to the actuator drive unit (4). ) And a plurality of detection units (6a, 6b) for detecting the vibration position of the scanner mirror (2) and a signal corresponding to the difference between the detection outputs of the detection units (6a, 6b). And a vibration detector (7) that forms a detection signal (D) corresponding to the amplitude of the scanner mirror (2). 2. The resonance type scanner according to claim 1, wherein the plurality of detection units (6a, 6b) have substantially the same characteristic changes with respect to temperature and are provided close to each other.