JP2001228434A - Electromagnetic drive type optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic drive type optical scanner which can hold the amplitude of light constantly with high accuracy against the temperature change. SOLUTION: The electromagnetic drive type optical scanner is equipped with a deviation detecting part 2 which detects the temperature deviation of the amplitude (scanning range) of a laser beam scanned by an optical scanning part 4 with a resonance type mirror oscillating in response to the feed of an AC signal with a fixed frequency based on the receiving time of the laser beam arriving at a prescribed position corresponding to the target amplitude, and an amplitude compensation part 3 which controls the intensity of the AC signal supplied to the resonance type mirror according to detection result of the deviation detecting part 2, and compensates the temperature deviation. Even if the resonance frequency of the resonance type mirror fluctuates by the temperature changes of the surrounding environment, etc., the amplitude of the laser beam thereby, is held constantly with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an electromagnetically driven optical scanning device that scans light using a resonance type mirror driven by using an electromagnetic force, and more particularly to an amplitude of light (scanning range) due to a change in temperature. The present invention relates to an electromagnetically driven optical scanning device capable of compensating for fluctuations in (1).

[0002]

2. Description of the Related Art As a resonance type mirror used in an electromagnetically driven optical scanning device, there is, for example, a semiconductor galvanometer mirror manufactured by using a micromachining technique previously proposed by the present applicant (for example, Japanese Patent Laid-Open No. 7-175005). And Japanese Patent Application Laid-Open No. 7-218857.

[0003] The basic configuration of this semiconductor galvanomirror will be briefly described. As shown in FIG. 14, the semiconductor galvanomirror has a torsion bar 102 and a movable plate 103 supported by the torsion bar 102 provided integrally with the silicon substrate 101 inside the silicon substrate 101. Is a flat coil 104 around
At a substantially center surrounded by the planar coil 104.
Are provided, and the silicon substrate 101 is placed on a frame-shaped insulating substrate 106. Then, the N pole and the S pole are opposed to the opposite side surface of the silicon substrate 101 so that the permanent magnet 107
Are arranged. Reference numeral 108 denotes an electrode terminal that is electrically connected to the plane coil 104.

This semiconductor galvanomirror has an electrode terminal 1
When an alternating current flows from 08 to the planar coil 104, an electromagnetic force acts on both ends of the movable plate 103 in accordance with Fleming's left-hand rule, and the movable plate 103 periodically swings around the torsion bar 102 in the direction of the arrow in the figure. Move. The frequency of the alternating current is set to the resonance frequency of the galvanometer mirror (for example, 1.5 k
Hz), the deflection angle of the movable plate 103 can be increased with a small input.

Therefore, the semiconductor galvanomirror can scan the laser beam by oscillating the movable plate 103 when the mirror 105 is irradiated with, for example, a laser beam, so that it can be widely applied to various optical devices.

The galvanomirror disclosed in Japanese Patent Application Laid-Open No. Hei 7-218857 is capable of electromagnetically coupling with the flat coil 104 below the movable plate 103 and detects the deflection angle of the movable plate 103 in addition to the above-described configuration. For detecting the deflection angle of the movable plate 103.

[0007] The mirror deflection angle of the semiconductor galvanometer mirror as described above is determined by the magnetic flux density and the coil current density. Until now, the control method of the mirror deflection angle has been performed by keeping the coil current constant.

[0008]

However, in a conventional electromagnetically driven optical scanning device using a resonance type mirror such as a semiconductor galvanometer mirror as described above, the resonance frequency changes due to the surrounding environment and the temperature change of itself. As a result, there is a drawback that the mirror deflection angle changes due to a deviation from the frequency of the alternating current flowing through the planar coil 104 (hereinafter referred to as the excitation frequency). That is, even if the excitation frequency is fixed, the mirror deflection angle changes due to the temperature change of the resonance frequency.

FIG. 15 is a diagram showing a frequency characteristic with respect to a mirror deflection angle in a general resonance type mirror. As shown by the solid line in FIG. 15, the mirror deflection angle at a certain temperature becomes maximum when the frequency of the alternating current flowing through the plane coil 104 matches the resonance frequency of the mirror, and decreases as the frequency deviates from the resonance point. It is known that the resonance frequency of this mirror shifts to a low frequency side or a high frequency side as shown by a broken line in FIG. 15 due to a temperature change of an ambient environment or the like. Is shown). Therefore, even if the excitation frequency is set so as to obtain a required deflection angle based on a certain temperature, and the excitation frequency is controlled to be constant, when the temperature of the surroundings changes, the mirror deflection angle also increases. It will fluctuate.

In an electromagnetically driven optical scanning device using such a resonance type mirror, the optical scanning range (hereinafter, referred to as amplitude) changes due to the fluctuation of the mirror deflection angle. In the case where the size and position of an object in a measurement area are detected by using such a method, it is difficult to realize a highly accurate detection operation.

The present invention has been made in view of the above points, and has as its object to provide an electromagnetically driven optical scanning device capable of maintaining a constant light amplitude with high accuracy with respect to a temperature change.

[0012]

In order to achieve the above object, an electromagnetically driven optical scanning device according to the present invention comprises a mirror and a coil mounted on the surface of a movable plate pivotally supported via a torsion bar. On the other hand, a resonance type having a magnetic field generating means for applying a magnetic field to a coil portion parallel to the axial direction of the torsion bar, and supplying an alternating current for driving the movable plate to the coil to swing the movable plate. In an electromagnetically driven optical scanning device that uses a mirror to irradiate the mirror with light emitted from a light source and scans the mirror, the amplitude of the scanning light reflected by the mirror is monitored, and the amplitude relative to a preset target amplitude is monitored. Deviation detecting means for detecting the deviation, and the magnitude of the AC current for driving the movable plate is determined based on the deviation detected by the deviation detecting means so that the amplitude of the scanning light substantially matches the target amplitude. Are those configured with an amplitude compensating means for settling.

In this configuration, the light emitted from the light source is reflected and scanned by the oscillating resonance type mirror, and the deviation representing the scanning range of the scanning light from the preset target amplitude is determined by the deviation detecting means. Is detected by In the amplitude compensating means, the magnitude of the AC current for driving the movable plate of the resonance type mirror is adjusted based on the deviation obtained by the deviation detecting means so that the amplitude of the scanning light substantially matches the target amplitude. . Thus, even if the resonance frequency of the resonance mirror fluctuates due to a temperature change in the surrounding environment or the like, the light amplitude can be kept constant with high accuracy.

Further, in the above-mentioned electromagnetically driven optical scanning device, the deviation detecting means detects a scanning light reaching a predetermined position corresponding to the target amplitude, and a light receiving state of the light receiving portion. A deviation detecting unit that determines a deviation of the amplitude of the scanning light from the target amplitude, and outputs a control signal instructing compensation of the deviation to the amplitude compensating unit;
May be provided.

In this configuration, the deviation of the amplitude of the scanning light from the target amplitude is determined by the deviation detecting unit based on the light receiving state of the light receiving unit. Further, regarding the electromagnetically driven optical scanning device, based on the light receiving state of the light receiving unit, it is determined whether the light source is in a non-light emitting state or the amplitude of the scanning light has not reached the vicinity of the target amplitude. It is preferable that a small-amplitude detecting means for judging and outputting a control signal for increasing the amplitude of the scanning light to the amplitude compensating means be provided.

In such a configuration, when the light source is in a non-lighting state or when the amplitude of the scanning light does not reach the vicinity of the target amplitude at the time of starting the apparatus, the state is small based on the light receiving state of the light receiving unit. Judgment is made by the amplitude detecting means, and control for increasing the amplitude of the scanning light is performed.

In one embodiment of the above-described electromagnetically driven optical scanning device, the light receiving section is provided for at least one end of a scanning range when it is assumed that the amplitude of the scanning light substantially matches the target amplitude. Detecting the light that is actually scanned, the deviation detecting unit measures the duration of the state in which the light is detected by the light receiving unit, and sets a value corresponding to the measured duration and the target amplitude. The deviation of the amplitude of the scanning light may be determined based on the result of the comparison. Specifically, the light receiving unit, a reflector provided near at least one end of the scanning range, a photo sensor that receives the scanning light reflected by the reflector and outputs a light receiving signal,
May be provided.

In this configuration, when the light emitted from the light source and reflected by the resonance type mirror reaches the fixed mirror provided at a predetermined position corresponding to the target amplitude, the light is further reflected by the fixed mirror and is then reflected by the photo sensor. Is received at. The photo sensor generates a light receiving signal when receiving the scanning light, and the light receiving signal is sent to the deviation detecting unit.

In another aspect of the above-described electromagnetically driven optical scanning device, the light receiving unit may include a central portion excluding both ends of a scanning range when it is assumed that the amplitude of the scanning light substantially matches the target amplitude. , Detecting the light that is actually scanned,
The deviation detection unit measures the duration of a state in which no light is detected by the light receiving unit, and based on a comparison result between the measured duration and a set value corresponding to the target amplitude, the scanning light. May be determined. Specifically, the light receiving section receives a retroreflector provided at a central portion excluding both ends of the scanning range and the scanning light retroreflected by the retroreflector in the vicinity of the resonant mirror. And a photo sensor that outputs a light receiving signal.

In this configuration, when the light emitted from the light source and reflected by the resonance mirror reaches the retroreflector provided at the center except for the both ends of the scanning range, the light is further retroreflected by the retroreflector. Later, the light is received by the photo sensor.
On the other hand, the scanning light that has reached both ends of the scanning range is not retroreflected, and is not received by the photo sensor near the resonant mirror. Therefore, the deviation detecting section determines the deviation of the amplitude of the scanning light based on the duration of the state where the reflected light is not detected by the light receiving section.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of the electromagnetically driven optical scanning device according to the first embodiment.

In FIG. 1, the present electromagnetically driven optical scanning device detects, for example, the amplitude (scanning range) of a laser beam scanned by the optical scanning unit 4 based on a photosensor output signal from the light receiving unit 4. And a driving state of the optical scanning unit 4 according to the detection results of the small amplitude detecting unit 1 and the deviation detecting unit 2 as the small amplitude detecting unit and the deviation detecting unit 2, respectively. And an amplitude compensator 3 as an amplitude compensator for controlling and compensating for the amplitude of the laser beam.

The small amplitude detector 1 has, for example, a first counter 11, a first comparator 12, and an OR circuit 13. The first counter 11 counts up by a clock signal CLK from the crystal oscillator 10 and counts the count value C1.
Is output to the first comparator 12. The above crystal oscillator 10
Generates a clock signal CLK having a constant cycle T _CLK (frequency f _CLK = 1 / T _CLK ) and generates the clock signal C
LK is sent to the first counter 11, the deviation detection unit 2 and the amplitude compensation unit 3, respectively.

The first comparator 12 compares the count value C1 of the first counter 11 with a preset value E1,
When the count value C1 reaches the set value E1 (C1 = E
In 1), the high-level output signal is sent to the OR circuit 13 and the amplitude compensator 3. The setting value E1 will be described later. The OR circuit 13 performs a logical OR operation on the output signal of the first comparator 12 and the photosensor output signal sent from the light receiving unit 5 to output a signal for resetting the count value C1 of the first counter 11 to 0. Upon receiving the output signal from the OR circuit 13, the first counter 11 is reset.

The deviation detecting unit 2 includes, for example, a second counter 2
1, a second comparator 22 and a delay pulse generating circuit 23. The second counter 21 enters an enabled state (a state in which counting up is permitted) in response to a photosensor output signal sent from the light receiving unit 5, and is counted up by a clock signal CLK from the crystal oscillator 10. The value C2 is output to the second comparator 22. The second comparator 22 compares the magnitude relationship between the count value C2 of the second counter 21 and a preset set value E2, and sends an output signal corresponding to the comparison result to the amplitude compensator 3. The set value E2 and the output signal of the second comparator 22 will be described later.

The delay pulse generating circuit 23 includes the crystal oscillator 1
In synchronization with the clock signal CLK from 0, a delay pulse signal DP2 that rises, for example, two clocks after the fall of the photosensor output signal is generated, and the delay pulse signal DP2 is output to the second counter 21. Upon receiving the delay pulse signal DP2, the count value C2 of the second counter 21 is reset.

The amplitude compensator 3 includes, for example, a third counter 3
1, an OR circuit 32, AND circuits 33 and 34, and a delay pulse generating circuit 35. The third counter 31 is OR
The count value is counted up by the output signal from the circuit 32, and is counted down by the output signal from the AND circuit 34, and the drive current set value corresponding to the count value is sent to the optical scanning unit 4. The OR circuit 32 performs a logical OR operation on the output signal of the first comparator 12 of the small amplitude detector 1 and the output signal of the AND circuit 33, and outputs a signal for counting up the third counter 31.

The AND circuit 33 outputs a high-level output signal output from the second comparator 22 of the deviation detector 2 when the count value C2 has not reached the set value E2 (C2 <E2), An AND operation is performed on the delayed pulse signal DP3 output from the pulse generation circuit 35 and the result of the AND operation is transmitted to the OR circuit 32. The AND circuit 34 outputs the count value C2 from the second comparator 22 of the deviation detection unit 2 to the set value E2.
(C2> E2) and the delayed pulse signal DP3 output from the delayed pulse generation circuit 35, and the third counter 31 is counted down. Output a signal.

The delay pulse generating circuit 35 includes the crystal oscillator 1
In synchronization with the clock signal CLK from 0, a delay pulse signal DP3 that rises, for example, one clock after the fall of the photosensor output signal is generated, and the delay pulse signal DP3 is output to the AND circuits 33 and 34, respectively.

The optical scanning unit 4 is a known optical scanning device configured to scan a laser beam with a desired amplitude using a resonance type mirror. FIG. 2 is a block diagram illustrating an example of a functional configuration of the optical scanning unit 4 and the light receiving unit 5.

In the configuration example of FIG. 2, the optical scanning unit 4 includes an optical system 41 having a resonance type mirror, a driving unit 42 for driving the optical system 41 in accordance with a driving current set value sent from the amplitude compensating unit 3, and Having.

The optical system 41 is, for example, as shown in FIG.
It has a laser light source 41A and a semiconductor galvanometer mirror 41B, and each component is arranged at a predetermined position. The laser light source 41A is a general light source that generates laser light of a required wavelength, and is arranged so that the generated laser light is irradiated near the center of the mirror surface of the semiconductor galvanometer mirror 41B. The semiconductor galvanomirror 41B has, for example, a configuration as shown in FIG. 14 described above, and the movable plate 103 on which the mirror 105 is formed swings in accordance with an alternating current supplied from the driving unit 42 and flowing through the planar coil 104. Swings at an angle θ. Thereby, the laser light from the laser light source 41A is
The light is incident on the mirror 105 and reflected, and is scanned in a linear direction within a range of an angle 2θ around the reflection point.
The amplitude of the laser light indicates the scanning range of the laser light corresponding to the angle 2θ as shown in the figure.

The light receiving section 5 has a fixed mirror 51 and a photo sensor 52, for example, as shown in FIG. 3, and each component is arranged at a predetermined position. When the amplitude of the laser beam reaches a predetermined required amplitude, the fixed mirror 51
It is provided at a position where a laser beam passing through one end (near the maximum amplitude) of the scanning range can be reflected. The fixed mirror 51 has a mirror surface sufficiently wider than the beam diameter of the laser light, and is controlled so that the laser light is not scanned beyond the fixed mirror 51 as described later. Photo sensor 52
Is disposed at a position capable of receiving the laser beam reflected by the fixed mirror 51, generates a photosensor output signal whose level changes in accordance with the incidence of the laser beam, and outputs the photosensor output signal to the small-amplitude detection unit 1. , To the deviation detecting section 2 and the amplitude compensating section 3, respectively.

The drive section 42 (FIG. 2) has, for example, a D / A converter 42A and a drive current control circuit 42B. The D / A converter 42A converts the drive current set value transmitted from the amplitude compensator 3 from a digital signal to an analog signal. The drive current control circuit 42B is a circuit that generates an AC current for driving the semiconductor galvanomirror 41B of the optical system 41 and adjusts the magnitude of the AC current according to a drive current set value from the D / A converter 42A. .
The frequency of the alternating current output from the drive current control circuit 42B to the semiconductor galvanometer mirror 41B is controlled to be constant at the excitation frequency as shown in FIG. Shall be.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG. In FIG. 4, when the power of the apparatus is turned on, first, in step 10 (indicated by S10 in the figure, the same applies hereinafter), the drive current set value set in the third counter 31 is initialized to 0. You. Next, at step 20, the clock signal CLK is output from the crystal oscillator 10 and the count-up operation of the first counter 11 is started at the same time when the first and second counters 11 and 21 are reset. Thereby, in step 30,
The count value C1 of the first counter 11 is incremented by +1.

Then, in step 40, it is determined whether or not a laser beam has entered the photosensor 52 of the light receiving section 5. Immediately after the power is turned on, the output signal from the photo sensor 52 is not generated, so that the counting operation of the second counter 21 of the deviation detection unit 2 is not started. Therefore,
Until the laser light is incident on the photo sensor 52, control according to the count value C1 of the first counter 11 is performed.

If it is determined that no laser light is incident on the photo sensor 52, the process proceeds to step 50, where the first comparator 1
In 2, it is determined whether or not the count value C1 of the first counter 11 has reached the set value E1. This set value E1
Is set to a count value corresponding to, for example, about 1.5 times the resonance cycle of the semiconductor galvanometer mirror 41B, and the count value C1 of the first counter 11 is set to a set value E1.
Is reached, it is determined that the laser light is in a non-lighting state or that the scanning amplitude of the laser light is insufficient. In this case, the process proceeds to step 60. On the other hand, if the count value C1 has not reached the set value E1, the process returns to step 30 and the above processing is repeated.

In step 60, a process for increasing the drive current set value is performed. Specifically, a high-level output signal is output from the first comparator 12, and the output signal is sent to the OR circuit 32 of the amplitude compensator 3. The OR circuit 32 receives the input of the high-level signal from the first comparator 12 and changes the output signal to the high level, and the third counter 31
Sent to The third counter 31 receives the high-level output signal from the OR circuit 32, counts up, and sends the drive current set value whose level is increased by one to the optical scanning unit 4. Thereby, the magnitude of the driving current supplied to the semiconductor galvanomirror 41B of the optical scanning unit 4 increases by one level, and the driving state is adjusted so that the amplitude of the laser light increases.

In the optical scanning section 4, as shown in step 70, it is determined whether or not the drive current set value from the amplitude compensation section 3 has reached a preset maximum value. Specifically, the drive current set value is, for example, 0 to 2
Considering the case of taking a value such as 55, the drive current has the following relationship.

(Drive current) ∝ (reference voltage of D / A converter) × (drive current set value [0 to 255]) /
When the 256 drive current set value reaches the maximum value 255, the drive current becomes the maximum level determined according to the reference voltage of the D / A converter 42A. The reference voltage that determines the maximum level of the drive current is the semiconductor galvanometer mirror 41B
Is set in accordance with the maximum drive current level that does not destroy.

If the drive current set value has not reached the maximum value (0 to 254), the process returns to step 20 and the above series of processes is repeated. On the other hand, if the drive current set value has reached the maximum value (255), the process proceeds to step 80, and after the drive current set value is changed from the maximum value to the 0 level, the process returns to step 20 to return to the above series of processing. Is repeated. Thereby, for example, when the laser light source 41A is in a non-lighting state, even if the drive current setting value is continuously increased, it is possible to avoid supplying a large drive current that breaks the semiconductor galvanometer mirror 41B. Become.

If it is determined in step 40 that the laser light has been incident on the photosensor 52, the process proceeds to step 90, where the incident time of the laser light on the photosensor 52 is measured.

Specifically, a high-level photosensor output signal is generated by the incidence of the laser beam on the photosensor 52, and the photosensor output signal is supplied to the OR circuit 13, the second counter 21, and the delay pulse generation circuit 23. , 35 respectively.

The count value C1 of the first counter 11 is set to the set value E1 (because the output signal of the photosensor goes high at each resonance cycle of the semiconductor galvanometer mirror 41B when the laser beam enters the photosensor 52). (Set to about 1.5 times the resonance period). Therefore, after the laser light is incident on the photo sensor 52, the control according to the count value C1 of the first counter 11 as described above is interrupted, and the control according to the count value C2 of the second counter 21 is performed. Will be performed.

The second counter 21 receives the high level photo sensor output signal and switches to the enabled state.
The count-up operation is continued according to the clock signal CLK from the crystal oscillator 10, and the count-up operation is continued while the output signal of the photosensor remains at the high level, and the count value C 2 is sent to the second comparator 22. Therefore, the count value C2 of the second counter 21 corresponds to the incident time of the laser beam on the photo sensor 52.

In each of the delay pulse generating circuits 23 and 35, the falling of the photosensor output signal is detected in synchronization with the clock signal CLK from the crystal oscillator 10, and the falling of the photosensor output signal is delayed by two clocks from the falling. The rising delay pulse signal DP2 is output from the delay pulse generation circuit 23, and the delay pulse signal DP3 rising with a delay of one clock is output from the delay pulse generation circuit 35.

FIG. 5 is a diagram showing an example of the signal waveform of the photosensor output signal and the delay pulse signals DP2 and DP3 together with the locus (upper stage) of the laser light reflected by the fixed mirror 51.

As shown in FIG. 5, when the laser beam to be scanned reaches the fixed mirror 51 (point [1]), the output signal of the photo sensor goes high. Then, while the laser light is scanned from [1] to [2] on the fixed mirror 51, the photosensor output signal is at a high level, and the time required during this period is n counts (counts synchronized with the clock signal CLK). (Corresponding to the count value C2 of the second counter 21)
_Is n · T _CLK .

When the laser beam reaches the point [2] and the output signal of the photosensor changes to a low level, the falling edges are detected by the delay pulse generation circuits 23 and 35, respectively, and one count delay from the falling edge. The (n + 1 count) rising delayed pulse signal DP3 is generated by the delayed pulse generating circuit 35 and is delayed by two counts (n
The delayed pulse signal DP2 which rises (+2 counts) is generated by the delayed pulse generation circuit 23.

More specifically, the n-count may be set by formulating the scanning distance L _S of the laser beam on the fixed mirror 51 between the n-counts as follows. That is,
The one-side scanning angle when the scanning light has the maximum amplitude is θ _max [d
eg], and the distance from the semiconductor galvanometer mirror 41B to the fixed mirror 51 is R [m] (see FIG. 3), the one-sided amplitude S [m] of the scanning light can be expressed by the following equation (1). .

S = R · sin θ _max (1) Further, the resonance period of the semiconductor galvanomirror 41B is set to T _R [s
ec], the scan angle α [deg] when the clock cycle T _CLK [sec] is counted n can be expressed by the following equation (2).

Α = 360 · n · T _CLK / T _R (2) Further, the scanning distance L _S of the laser beam on the fixed mirror 51
Can be expressed by the following equation (3) using the one-sided amplitude S and the scanning angle α in the above equations (1) and (2).

L _S = S−S · cos (α / 2) = S {1−cos (α / 2)} = R · sin θ _max · {1−cos (180 · n · T _CLK / T _R )} (3) Accordingly, assuming that the length of the fixed mirror 51 in the scanning direction is W [m], the setting of the n-count may be set so as to satisfy the following expression (4).

R · sin θ_max・ ｛1-cos (180 ・ n ・ T_CLK/ T_R)｝ <W ... (4) As an example of specific numerical values, a semiconductor galvanomirror
Distance R from the base 41B to the fixed mirror 51 = 0.1 m, one side
Side scan angle θ_max= 20deg, clock cycle T_{CL K}= 1μ
s, resonance period T_R= 670 μs, n counts
When the default setting is 50, the above equation (3) is used.
The scanning distance L of the laser beam on the fixed mirror 51_S=
Calculated as 0.94 mm. In such a setting, fixed
The length W of the mirror 51 in the scanning direction may be several mm.
And Note that a relatively small fixed mirror 51 is used.
The only thing that can be done is the movement of the scanning light on both sides of the amplitude.
Is relatively slow.

Next, at step 100, the second comparator 2
In 2, the count value C2 corresponding to the laser beam incident time of the photo sensor 52 is compared with the set value E2. The set value E2 is set corresponding to the laser light incident time of the photo sensor 52 when the amplitude of the laser light reaches a predetermined required amplitude. Therefore, when the count value C2 is equal to the set value E2 (C2 = E2
In 2), it is determined that the required amplitude is obtained, and when the count value C2 is smaller than the set value E2 (C2 <E
In 2), it is determined that the amplitude of the laser beam is insufficient,
When the count value C2 is larger than the set value E2 (C2>
In E2), it is determined that the amplitude of the laser beam is too large.

The deviation of the amplitude of the laser beam due to the temperature change can be quantitatively obtained based on the difference between the count value C2 and the set value E2 in the same manner as in the case of the above-mentioned equation (1). It is possible to perform compensation in accordance with the deviation amount obtained in a typical manner. However, in the present embodiment, it is determined that only the amplitude of the laser beam is larger or smaller than the target value, and the operation of the amplitude compensator 3 is switched according to the determination result, thereby simplifying the compensation operation. I made it.

More specifically, when it is determined that the amplitude of the laser light is insufficient (C2 <E2), the high-level output signal is output from the second comparator 22 to the AND circuit 33 of the amplitude compensator 3.
Sent to On the other hand, when it is determined that the amplitude of the laser light is too large (C2> E2), the high-level output signal is output from the second comparing unit 22 to the AND circuit 3 of the amplitude compensating unit 3.
4 The delay pulse signal DP3 from the delay pulse generation circuit 35 is input to each of the AND circuits 33 and 34, and when both the output signal from the second comparator 22 and the delay pulse signal DP3 become high level. , High-level output signals are output from the AND circuits 33 and 34.

Since the delay pulse signal DP3 becomes high level after the laser beam is no longer incident on the photosensor 52 as shown in FIG. 5, the count operation of the second counter 21 is stopped. On the way, AND circuits 33 and 3
4 does not output a high-level output signal, and after the determination of the laser light incident time on the photosensor 52 is completed, amplitude deviation compensation is performed.

When a high-level output signal is output from the AND circuit 33, the output signal is input to the OR circuit 32, and a high-level output signal is output from the OR circuit 32. Based on the output signal from the OR circuit 32, the third counter 31 is counted up in the same manner as in the case of step 60 described above, and the drive current set value whose level is increased by one is sent to the optical scanning unit 4. Thereby, the magnitude of the driving current supplied to the semiconductor galvanomirror 41B of the optical scanning unit 4 increases by one level, and the driving state is adjusted so that the amplitude of the laser light increases. Then, the process proceeds to the above-described step 70 and the same processing is performed.

On the other hand, when a high-level output signal is output from the AND circuit 34, the output signal is output to the third counter 31.
Then, as shown in step 110, the third counter 31 counts down, and the drive current set value whose level is reduced by one is sent to the optical scanning unit 4. As a result, the magnitude of the drive current supplied to the semiconductor galvanomirror 41B of the optical scanning unit 4 is reduced by one level, and the drive state is adjusted such that the amplitude of the laser light is reduced. Then, the process proceeds to step 20 described above, and the same processing is repeated. In step 100, the count value C
Even when it is determined that 2 is the same as the set value E2, the process returns to step 20 described above and the same processing is repeated.

As described above, according to the first embodiment,
The scanning state of the laser beam in the optical scanning unit 4 is monitored to detect a deviation of the amplitude, and the magnitude of the drive current of the semiconductor galvanometer mirror 41B is controlled according to the detection result. The amplitude of the laser beam can be kept constant with high accuracy even when the temperature changes. This is particularly useful when detecting the size and position of an object in a measurement area using an optical scanning device. Specifically, for example, application to an area sensor, a shape measuring instrument, a laser microscope, a barcode scanner, a laser printer, or the like is effective. However, the application of the present invention is not limited to the above, and can be widely applied to various optical devices.

In the first embodiment, the laser light to be scanned is reflected by the fixed mirror 51 and received by the photo sensor 52. However, for example, a photo sensor is provided at the position of the fixed mirror. Alternatively, the scanned laser beam may be directly received by the photo sensor.

Next, a second embodiment according to the present invention will be described. FIG. 6 is a perspective view illustrating an appearance of an electromagnetically driven optical scanning device according to the second embodiment. Also, FIG.
FIG. 7 is a block diagram illustrating a configuration of the electromagnetically driven optical scanning device in FIG. 6. The same parts as those in the configuration of the first embodiment are denoted by the same reference numerals.

As shown in the figure, the electromagnetically driven optical scanning device according to the second embodiment includes an optical scanning unit 4 in a sensor unit.
The scanning light emitted from the light source is retroreflected by the reflection section 53, and the reflected light is received by the photo sensor 52 in the sensor unit. Specifically, when the configuration of the second embodiment is different from the configuration of the first embodiment, a reflecting portion 53 is provided instead of the fixed mirror 51 that reflects the scanning light, and the scanning origin detecting means is used. The difference is that the scanning origin detecting unit 6 is provided in the sensor unit. The configuration of the second embodiment other than the above is basically the same as the configuration of the first embodiment.

The reflection section 53 is composed of, for example, a support 53A and a retroreflection plate 53B. Retroreflective plate 53B
Is a general member having a reflective surface such that most of the reflected light is due to retroreflection, and is mounted at a predetermined position on the surface of the support 53A facing the sensor unit. The scanning light retroreflected by the retroreflective plate 53B is received by the photosensor 52 disposed near the optical scanning unit 4 in the sensor unit. The photosensor 52 and the reflecting section 53 constitute a light receiving section 5 '. In addition,
Retroreflection refers to reflection in which reflected light selectively returns in a direction substantially along the optical path of incident light over a wide incident angle.

The scanning origin detecting section 6 comprises, for example, a delay signal generating circuit 61 and an origin detecting circuit 62. As shown in FIG. 8, for example, the delay signal generating circuit 61 includes a low-pass filter configured using a resistor 61A and a capacitor 61B, and a comparator 61C that determines the level of a signal that has passed through the low-pass filter. In the delay signal generating circuit 61, the rising and falling of the scanning frequency clock signal sent from the optical scanning unit 4 is dulled by a low-pass filter, and the binary signal is divided by the comparator 61C, thereby delaying the scanning frequency clock signal. A signal is generated. The above-described scanning frequency clock signal is a signal corresponding to the frequency of the drive signal for driving the semiconductor galvanomirror 41B of the optical scanning unit 4, and is a clock signal indicating a scanning frequency close to the resonance frequency of the semiconductor galvanomirror 41B.

For example, as shown in FIG. 9, the origin detecting circuit 62 includes inverters 62A and 62C and an AND circuit 62B.
It is composed of In the origin detecting circuit 62, the scanning delay signal from the delay signal generating circuit 61 and the photo sensor 5
The output signal from 2 is inverted by the inverter 62A and the AND operation is performed by the AND circuit 62B, and the operation result is inverted by the inverter 62C. This inverter 62
As described later, the output signal of C is a signal indicating only a break on the scanning origin side among breaks of the reflected light generated at the upper end portion and the lower end portion of the reflection section 53, respectively. A signal indicating a light-receiving waveform on the scanning origin side output from the scanning origin detection unit 6 is sent to the small amplitude detection unit 1 to enable the first counter 11 and, via the inverter 6A, to the deviation detection unit 2 Are sent to the second counter 21 and the delay pulse generation circuit 23, and the delay pulse generation circuit 35 of the amplitude compensator 3. Inverter 6
The signal inverted at A corresponds to the photosensor output signal in the case of the first embodiment.

Next, the operation of the second embodiment will be described. In the present apparatus, as shown in FIG. 6 described above, the direction of the laser beam when the semiconductor galvanometer mirror 41B of the optical scanning unit 4 is stopped is angularly positioned at the center of the retroreflective plate 53B with respect to the scanning direction. It is assumed that the arrangement of the sensor unit and the reflection unit 53 is set in advance so as to be located. Here, the deflection angle (scanning angle) of the semiconductor galvanometer mirror 41B is set to θ, and when the laser beam reaches one end (the lower end in FIG. 6) of the scanning range, the scanning origin (0 °) is set. angle theta _max when reached in 6 upper end)
And

In the above setting, when the laser light source 41A of the light scanning section 4 is turned off and the semiconductor galvanomirror 41B is stopped, the photo sensor 52 does not receive reflected light. The output signal level becomes a low level as shown in the upper part of FIG.

When the laser light source 41A is turned on while the semiconductor galvanometer mirror 41B remains stopped, the retroreflective plate 2
The laser beam reflected by B is continuously received by the photo sensor 52, and the output signal level of the photo sensor 52 becomes a high level as shown in the middle part of FIG.

Further, when the drive of the semiconductor galvanometer mirror 41B is started and the scanning amplitude of the laser beam is increased,
The output signal level of the photo sensor 52 has a waveform that changes to a low level once every half cycle of the semiconductor galvanomirror 41B as shown in the lower part of FIG. This is due to the fact that the scanning of the laser beam deviates from both ends of the retroreflective plate 53B and is not retroreflected, and the photosensor 52 stops receiving the reflected light.

It is known that the timing at which the light-receiving waveform of the photo sensor 52 becomes low level varies according to the relationship between the scanning frequency (drive frequency) and the resonance frequency of the semiconductor galvanometer mirror 41B. Specifically, FIG.
As shown in (A) to (C), when the semiconductor galvanomirror 41B is driven at a frequency higher than the resonance frequency, when the scanning frequency clock signal is at a low level, the output of the photosensor 52 is at a low level. On the other hand, when the semiconductor galvanomirror 41B is driven at a frequency lower than the resonance frequency, when the scanning frequency clock signal is at a high level, the output of the photosensor 52 is at a low level.

In the present embodiment, as will be described later, a method for compensating the scanning amplitude when the laser beam reaches the scanning origin side is employed. Therefore, the low-level output of the photo sensor 52 is set to the scanning origin side (0 ° side). ) Or the opposite side (θ
_It must be determined based on the scanning frequency clock signal whether or not this occurred on the _max side). However, if the relationship between the output level of the photosensor 52 and the scanning frequency clock signal fluctuates as described above, it becomes difficult to determine the scanning origin side.

Therefore, in the present apparatus, a delay signal generating circuit 61 as shown in FIG.
Using the scanning delay signal and the output level of the photo sensor 52, the origin detecting circuit 62 as shown in FIG.
The light receiving waveform on the scanning origin side is detected.

More specifically, when the scanning frequency clock signal sent from the optical scanning unit 4 passes through the low-pass filter of the delay signal generating circuit 61, a signal having a dull waveform as shown in FIG. Then, the level is determined by the comparator 61C of the delay signal generating section 61, whereby a scanning delay signal having a waveform as shown in FIG. It is desirable that the amount of delay in the delay signal generation circuit 61 be about 1/4 cycle of the scanning frequency clock signal. The origin detecting circuit 62 determines the scanning origin side when both the scanning delay signal and the photosensor output signal become high level as described above, and determines the light receiving waveform on the scanning origin side as shown in FIG. Is output. Note that the signal waveform in FIG. 11F shows a waveform corresponding to a case where the drive frequency is higher than the resonance frequency.

When the scanning origin detection processing is performed as described above, the control for keeping the amplitude of the laser beam at a predetermined constant value by using the scanning origin side received light waveform output from the scanning origin detecting section 6 is performed. Done.

FIG. 12 is a flowchart showing a specific amplitude compensation operation in the second embodiment. In FIG. 12, first, at step 210, the first to third counters 1
The count values C1 to C3 of 1, 1, 31 are reset, respectively. Then, in step 220, whether the retroreflected light of the laser light is received by the photo sensor 52,
That is, it is determined whether or not the output level of the scanning origin detecting unit 6 is at a high level. If it is determined that the reflected light is received, the count value C1 of the first counter 11 is incremented by +1 according to the clock signal CLK from the crystal oscillator 10 in step 230.
Go to 0.

In step 240, the count value C1 of the first counter 11 in the first comparator 12 is set to the set value E1.
Is determined. This set value E1 is the same as in the first embodiment. When the count value C1 of the first counter 11 has reached the set value E1, it is determined that the laser light is turned on and the amplitude of the laser light is insufficient, and the process proceeds to step 250. On the other hand, if the count value C1 has not reached the set value E1, the process returns to step 220 and the above processing is repeated.

In step 250, the count value C1 of the first counter 11 is reset. At the same time, in step 260, a process of increasing the amplitude of the laser beam is performed. Specifically, a high-level output signal is output from the first comparator 12, and the output signal is sent to the OR circuit 32 of the amplitude compensator 3. The OR circuit 32 receives a high-level signal from the first comparator 12 and sends a high-level output signal to the third counter 31. The third counter 31 receives the high-level output signal from the OR circuit 32 and counts up. When the drive current set value increases by one level, the magnitude of the drive current supplied to the semiconductor galvanomirror 41B becomes one. Increase by the level,
The amplitude of the scanning light increases.

If it is determined in step 220 that no reflected light is received, the process proceeds to step 270, where the time when the light reception waveform on the scanning origin side is at low level is measured. Specifically, in step 270,
Since the output signal from the inverter 6A goes high every resonance cycle of the semiconductor galvanomirror 41B, the count value C1 of the first counter 11 is reset before reaching the set value E1. At the same time, step 28
At 0, the second counter 21 that has received the high-level output signal from the inverter 6A switches to the enable state, and switches to + according to the clock signal CLK from the crystal oscillator 10.
It is incremented by one. Then, in step 290, it is determined whether or not the retroreflected light of the laser beam is received by the photo sensor 52. If it is determined that the reflected light is received, the process proceeds to step 300. on the other hand,
If it is determined that no reflected light is received, step 28
Returning to 0, the above operation is repeated. When the laser light source 41A is not turned on, it is determined in step 290 that there is no light reception. Therefore, the operations of steps 280 and 290 are repeated until the laser light source 41A is turned on.

The principle of the time measurement performed in steps 270 to 290 is that the relationship between the high level and the low level of the photosensor output signal in the case of the first embodiment shown in FIG. 5 is inverted. In the same way. Here, FIG. 13 shows the present embodiment corresponding to FIG. 5, and the description thereof is omitted.

Next, at step 300, the second comparator 2
In 2, the count value C2 corresponding to the time when the light reception waveform on the scanning origin side is at the low level is compared with the set value E2. This set value E2 is the same as in the first embodiment. When the count value C2 is the same as the set value E2 (C2 = E2), it is determined that the required amplitude is obtained. When the count value C2 is smaller than the set value E2 (C2 <E2), the amplitude is determined. Is determined to be insufficient,
When the count value C2 is larger than the set value E2 (C2>
In E2), it is determined that the amplitude is too large.

If it is determined that the amplitude of the scanning light is insufficient (C2 <E2), the process proceeds to step 310, where the high-level output signal is sent from the second comparing unit 22 to the AN of the amplitude compensating unit 3.
It is sent to the D circuit 33. On the other hand, if it is determined that the amplitude of the scanning light is too large (C2> E2), the process proceeds to step 320, where the high-level output signal is output to the second comparing unit 2
2 to the AND circuit 34 of the amplitude compensator 3. Each A
The delay pulse signal DP3 from the delay pulse generation circuit 35 is input to the ND circuits 33 and 34, respectively. When both the output signal from the second comparator 22 and the delay pulse signal DP3 become high level, A high-level output signal is output from each of the AND circuits 33 and 34.

When a high-level output signal is output from the AND circuit 33, the output signal is input to the OR circuit 32, and a high-level signal is output from the OR circuit 32.
Thereby, the third counter 31 is counted up,
The driving state is adjusted such that the magnitude of the driving current supplied to the semiconductor galvanometer mirror 41B increases by one level, and the scanning amplitude of the laser beam increases. Then, after the count value C2 of the second counter 21 is reset in step 330, the process proceeds to step 220, and the same processing is repeated.

On the other hand, when a high-level signal is output from the AND circuit 34, the third counter 31 counts down, and the magnitude of the drive current supplied to the semiconductor galvanomirror 41B decreases by one level. The driving state is adjusted so that the amplitude of light becomes small. Then, after the count value C2 of the second counter 21 is reset in step 330, the process proceeds to step 220, and the same processing is repeated. If it is determined in step 300 that the count value C2 is the same as the set value E2, the process proceeds to step 330.

Steps 210 to 3 as described above
By repeating a series of processes of 30, the laser beam can be stably scanned at a predetermined amplitude (target amplitude).

As described above, according to the second embodiment, when it is assumed that the amplitude of the scanning light substantially coincides with the target amplitude, the retroreflective plate 53B is made to correspond to the central portion excluding both ends of the scanning range. By arranging and measuring the duration when the photo sensor 52 stops receiving the retroreflected light,
The deviation of the amplitude of the laser beam can be detected, and the same effect as in the first embodiment can be obtained.

In the second embodiment described above, the configuration is described in which the retroreflective plate is disposed at the center portion excluding both ends with respect to the scanning range of the scanning light. It is also possible to arrange the retroreflectors only at both ends and to prevent the scanning light from being retroreflected at the center. In this case, since the output signal level of the photo sensor 52 is inverted, the first
It is possible to apply the same concept as in the embodiment.

In the first and second embodiments, the case where the small amplitude detecting section 1, the deviation detecting section 2, and the amplitude compensating section 3 have a digital circuit configuration has been described. However, the present invention is not limited to this. For example, you may make it comprise using an analog circuit.

[0090]

As described above, in the electromagnetically driven optical scanning device according to the present invention, the temperature deviation of the amplitude of the light scanned by the resonance type mirror is detected by the deviation detecting means, and the resonance is detected based on the detected deviation. By adjusting the magnitude of the alternating current for driving the movable plate of the mold mirror, the amplitude of the scanning light can be kept constant with high accuracy even when the temperature changes in the surrounding environment or the like. This makes it possible to realize various optical devices that accurately detect, for example, the size, position, and the like of an object in a measurement area, using the optical scanning device.

Further, a small amplitude detecting means for judging that the light source is not turned on or the amplitude of the scanning light has not reached the vicinity of the target amplitude is provided, so that the light source can be turned off or the apparatus can be started up. It is possible to automatically control the amplitude of the scanning light from time to time.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an electromagnetically driven optical scanning device according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating an example of a functional configuration of a light scanning unit and a light receiving unit according to the first embodiment.

FIG. 3 is a diagram illustrating a configuration example of an optical system and a light receiving unit according to the first embodiment.

FIG. 4 is a flowchart illustrating an operation of the first embodiment.

FIG. 5 is a diagram showing an example of each signal waveform of a photosensor output signal and a delay pulse signal in the first embodiment.

FIG. 6 is a perspective view showing an appearance of a second embodiment according to the present invention.

FIG. 7 is a block diagram showing a configuration of the second embodiment.

FIG. 8 is a diagram illustrating a configuration example of a delay signal generation circuit according to the second embodiment;

FIG. 9 is a diagram illustrating a configuration example of an origin detection circuit according to the second embodiment;

FIG. 10 is a diagram for explaining an operation at the time of starting the device in the second embodiment.

FIG. 11 is a diagram illustrating an operation of detecting a scanning origin in the second embodiment.

FIG. 12 is a flowchart showing a specific operation of the second embodiment.

FIG. 13 is a diagram showing an example of each signal waveform of a photosensor output signal and a delay pulse signal in the second embodiment.

FIG. 14 is an exploded view showing a configuration example of a known semiconductor galvanomirror.

FIG. 15 is a diagram illustrating a specific example of a frequency characteristic of a mirror deflection angle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Small amplitude detection part 2 ... Deviation detection part 3 ... Amplitude compensation part 4 ... Optical scanning part 5 ... Light receiving part 6 ... Scanning origin detection part 10 ... Crystal oscillator 11, 21, 31 ... Counter 12, 22 ... Comparator 13 , 32 ... OR circuit 23, 35 ... delay pulse generating circuit 33, 34 ... AND circuit 41 ... optical system 41A ... laser light source 41B ... semiconductor galvanometer mirror 42 ... drive unit 42A ... D / A converter 42B ... drive current control circuit 51 ... Fixed mirror 52 ... Photo sensor 53 ... Reflection part 53B ... Retroreflection plate 61 ... Delay signal generation circuit 62 ... Origin detection circuit

Claims (15)

[Claims] 1. A magnetic field generating means for providing a mirror and a coil on a surface of a movable plate pivotally supported via a torsion bar while applying a magnetic field to a coil portion parallel to an axial direction of the torsion bar. Using a resonance type mirror having a structure in which an alternating current for driving a movable plate is supplied to the coil to swing the movable plate, and light emitted from a light source is irradiated on the mirror to perform scanning. In the electromagnetically driven optical scanning device, a deviation detection unit that monitors the amplitude of the scanning light reflected by the mirror and detects a deviation from a preset target amplitude, based on the deviation detected by the deviation detection unit, And an amplitude compensating means for adjusting the magnitude of the alternating current for driving the movable plate so that the amplitude of the scanning light substantially matches the target amplitude.査 apparatus. 2. A light receiving section for detecting the scanning light reaching a predetermined position corresponding to the target amplitude, the deviation detecting means; and a scanning light for the target amplitude based on a light receiving state of the light receiving section. 2. An electromagnetically driven optical scanning device according to claim 1, further comprising: a deviation detecting unit that determines a deviation of the amplitude of the signal and outputs a control signal for instructing compensation of the deviation to the amplitude compensating means. . And determining whether the light source is in a non-light emitting state or the amplitude of the scanning light has not reached near the target amplitude based on a light receiving state of the light receiving unit. 3. The electromagnetically driven optical scanning device according to claim 2, further comprising: a small amplitude detection unit that outputs a control signal for increasing the amplitude to the amplitude compensation unit. 4. The light receiving section detects light that is actually scanned in the vicinity of at least one end of a scanning range when it is assumed that the amplitude of the scanning light substantially matches the target amplitude, The deviation detecting unit measures the duration of a state in which light is detected by the light receiving unit, and, based on a comparison result of the measured duration and a set value corresponding to the target amplitude, detects a deviation of the scanning light. 4. The electromagnetically driven optical scanning device according to claim 2, wherein a deviation of the amplitude is determined. 5. A light receiving unit comprising: a reflector provided near at least one end of the scanning range; a photo sensor for receiving the scanning light reflected by the reflector and outputting a light receiving signal; The electromagnetically driven optical scanning device according to claim 4, comprising: 6. A retroreflector provided near at least one end of the scanning range, and the scanning light retroreflected by the retroreflector is received near the resonant mirror. 5. The electromagnetically driven optical scanning device according to claim 4, further comprising: a photosensor that outputs a light receiving signal. 7. A counter which is activated by a light receiving signal from the light receiving unit and counts up in accordance with a clock signal having a fixed period, and a setting corresponding to the count value of the counter and the target amplitude. Comparing with the value, when the count value is greater than the set value, determine that the amplitude of the scanning light is greater than the target amplitude, generate a control signal to reduce the amplitude of the scanning light, When the count value is smaller than the set value, a comparator that determines that the amplitude of the scanning light is smaller than the target amplitude and generates a control signal that increases the amplitude of the scanning light, And a delay pulse generation circuit that generates a pulse signal for resetting the counter after a predetermined time has elapsed from the fall of the light receiving signal from the device. Electromagnetically actuating optical scanning apparatus according to any one of claims 4-6. 8. The amplitude compensator receives a control signal output from the deviation detector and increases the amplitude of the scanning light, counts up, and receives a control signal that decreases the amplitude of the scanning light. A counter that counts down and outputs a drive current set value that indicates the magnitude of the AC current corresponding to the count value; and resets the counter after a predetermined time has elapsed from the fall of the light receiving signal from the light receiving unit. The electromagnetically driven optical scanning device according to any one of claims 4 to 7, further comprising a delay pulse generation circuit that generates a pulse signal. 9. A small-amplitude detecting means for counting up according to a clock signal having a constant cycle, comparing a count value of the counter with a set value corresponding to a resonance cycle of the resonance-type mirror, A comparator for generating a control signal for increasing the amplitude of the scanning light when the count value exceeds the set value; receiving a light receiving signal from the light receiving unit or a control signal from the comparator to reset the counter; 5. A reset circuit for generating a reset signal.
An electromagnetically driven optical scanning device according to any one of Items 1 to 8, 10. The light receiving unit detects light to be actually scanned for a central portion excluding both ends of a scanning range when it is assumed that the amplitude of the scanning light substantially matches the target amplitude, The deviation detection unit measures the duration of a state in which no light is detected by the light receiving unit, and based on a comparison result between the measured duration and a set value corresponding to the target amplitude, the scanning light. The electromagnetically driven optical scanning device according to claim 2 or 3, wherein a deviation of the amplitude of the optical scanning is determined. 11. The light receiving section receives a retroreflector provided at a central portion of the scanning range excluding both ends, and receives the scanning light retroreflected by the retroreflector near the resonance mirror. The electromagnetically driven optical scanning device according to claim 10, further comprising: a photosensor that outputs a received light signal. 12. An origin of a periodic optical scan is specified based on a change in a light receiving state of the photosensor generated in response to light from the light source being scanned at one end of a scanning range. 12. The electromagnetically driven optical scanning device according to claim 11, further comprising scanning origin detection means for outputting a light receiving signal corresponding to the scanning origin. 13. The deviation detecting section is activated by a signal obtained by inverting a light receiving signal from the scanning origin detecting means,
A counter that counts up according to a clock signal having a fixed period; and compares a count value of the counter with a set value corresponding to the target amplitude, and when the count value is larger than the set value, the amplitude of the scanning light. Determines that the amplitude is larger than the target amplitude, generates a control signal to reduce the amplitude of the scanning light, when the count value is smaller than the set value, the amplitude of the scanning light is smaller than the target amplitude Judging that it is small, a comparator that generates a control signal to increase the amplitude of the scanning light, and after a predetermined time has elapsed from the fall of the inverted signal of the light receiving signal from the scanning origin detection means, 13. The electromagnetically driven optical scanning device according to claim 12, further comprising: a delay pulse generation circuit that generates a pulse signal for resetting the counter. 14. The amplitude compensating means counts up in response to a control signal output from the deviation detecting section for increasing the amplitude of the scanning light, and receives a control signal for decreasing the amplitude of the scanning light in response to the control signal. A counter that counts down and outputs a drive current set value that instructs the magnitude of the AC current corresponding to the count value; and a predetermined time elapses from a fall of a signal obtained by inverting a light receiving signal from the scanning origin detection unit. 14. The electromagnetically driven optical scanning device according to claim 12, further comprising: a delay pulse generation circuit that generates a pulse signal for resetting the counter after performing the operation. 15. A counter which is activated in response to a light receiving signal from said scanning origin detecting means and counts up in accordance with a clock signal having a fixed period, and wherein said small amplitude detecting means counts up in accordance with a clock signal having a predetermined period. A comparator that compares a set value according to a resonance cycle of the mold mirror and, when the count value exceeds the set value, generates a control signal that increases the amplitude of the scanning light; and And a reset circuit that receives a control signal from the comparator or a signal obtained by inverting the light receiving signal of the above and generates a signal for resetting the counter. An electromagnetically driven optical scanning device according to claim 1.