JP3371474B2 - Vibration optical element amplitude controller - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for an amplitude control device for a vibrating optical element.

[0002]

2. Description of the Related Art Conventional techniques relating to an amplitude control device for a vibrating optical element such as a resonant mirror that vibrates and emits an incident light beam are shown in FIGS. 8 and 9, for example. FIG. 8 shows that the sine wave output from the sine wave generation circuit 1 is amplified by the amplification circuit 2 whose amplification factor is variable and is amplified by an appropriate amplification factor. Is converted into a driving output by the mirror driving circuit 3 and emitted from the light source 4 and the resonant mirror 5
The light incident on was reflected while vibrating with an amplitude according to the vibration angle of the resonant mirror 5. The amplification factor of the amplification circuit 2 is controlled by the amplification factor control circuit 6, and the amplification factor control circuit 6 adjusts the amplification factor of the amplification circuit 2 so that the resonant mirror 5 vibrates as stably as possible according to a change in conditions such as temperature. I had decided.

FIG. 9 shows that the resonant mirror 5 is irradiated with spot light, the amplitude of the reflected wave is detected, and the amplitude is corrected based on the result. That is, the sine wave generation circuit 1
The sine wave output from is amplified by the amplification circuit 2 having a variable amplification rate, amplified by an appropriate amplification rate, and then converted into a drive output by the mirror drive circuit 3, and the resonant mirror 5 is oscillated and driven to generate spot light. The light incident on the resonant mirror 5 from the light source 4 was reflected while vibrating at an amplitude according to the vibration angle of the resonant mirror 5. The detectors 8 are arranged at both ends of the set amplitude of the reflected light, and the comparator circuit 9 receiving the output of the detector 8 outputs the signal intensity output to the CPU 10 in comparison with the set value, and the CPU 10 outputs the output of the comparator circuit 9. As a reference, the amplification circuit 2 is controlled to have an appropriate amplification factor. Since natural frequencies of these set values fluctuate due to changes in the environment such as temperature, means for correcting the natural frequencies are provided.

Of the above conventional techniques, the former is corrected by a predetermined amplification factor, but it is difficult to improve the precision of setting the amplification factor of the amplification circuit 2 which is predetermined with respect to a change in conditions. However, there is a problem in that the amplitude of the resonant mirror 5 does not exactly follow the control signal and the control accuracy is poor.

In the latter case, the detectors 8 for detecting the scanning end are arranged at both ends of the amplitude, and at least two detectors are required. And the amplitude setting is fixed,
If a plurality of amplitudes are to be changed and set, a plurality of detectors must be sequentially arranged, and there is a problem that the arrangement of members is complicated and the processing becomes complicated.

Japanese Patent Laid-Open No. 5-127109 (Patent Document 5) discloses an amplitude control device and control method for an oscillating optical element which solves these problems, can accurately control the amplitude of a resonant mirror, and can easily set a plurality of amplitudes. (Heihei 3-291723)
It is disclosed in the official gazette. As shown in FIG. 10, this technique uses a light source 4, a mask 12, a detector 13, and a timing circuit 14 to detect a time interval corresponding to the amplitude of a vibrating optical element, and a control unit 15 detects the detected time interval in advance. The correction is made by comparing with the reference time that has been obtained.

[0007]

However, Japanese Patent Laid-Open No. 5-12
The technique disclosed in Japanese Patent No. 7109 has a low responsiveness due to a time delay in the control system, it is difficult to accurately stabilize the amplitude of the vibrating optical element, and the temperature change, optical or electrical noise There was a problem that it was easily affected by disturbances such as.

In view of the above problems, the present invention provides a vibrating optical element that suppresses the effects of disturbance and delay of the control system, controls the amplitude of the resonant mirror accurately and stably, and can easily change and set the amplitude. It is an object to provide an amplitude control device.

[0009]

According to the present invention, a vibrating optical element for vibrating a light beam incident from a light source with a variable amplitude and emitting the vibrating optical element, driving means for driving the vibrating optical element, and driving the driving means. A sine wave generation circuit that generates a sine wave,
An amplification circuit that amplifies the sine wave with a variable amplification factor and outputs the amplified sine wave to the driving unit, a modulation unit that modulates a light beam emitted from the vibrating optical element in response to the vibration, and a modulation unit that modulates the light beam. Detecting means for detecting a light beam and outputting a detection signal, a time measuring means for measuring a time interval between the time points at which the detection signal has a predetermined intensity, and a gain factor for receiving a measurement value signal of the time interval. And an amplification factor control means for outputting an amplification factor control signal for controlling the
In the amplitude control device for a vibrating optical element that controls the amplitude by controlling the amplification factor, the amplification factor control means calculates an integrated value of a plurality of measurement values at the time intervals and outputs an integrated value signal. And a storage unit that stores a determination value corresponding to the amplitude and outputs a determination value signal, receives the integration value signal and the determination value signal, determines the magnitude relationship between the two, and determines the determination result. Based on the determination circuit, the amplification circuit outputs the amplification factor control signal to the amplification circuit.

The determining means stores the first, second, third and fourth determination values in descending order for each of the predetermined amplitudes, and the amplification factor control means stores the integrated value in the first to second order. When it is determined that it is between the determination value of 2 and the third determination value, when it is determined that the integrated value exceeds the first determination value so as to maintain the amplification factor, When it is determined that the integrated value is less than the fourth determination value so as to decrease the amplification factor, each outputs an amplification factor control signal to the amplification circuit to increase the amplification factor, When it is determined that the integrated value is between the first determination value and the second determination value, or between the third determination value and the fourth determination value, the amplification It is preferable not to output the amplification factor control signal for changing the ratio.

[0011]

When the light beam from the light source vibrates by the vibrating optical element, the time interval corresponding to its amplitude is measured. After integration of the time intervals, the amplification factor is variably controlled based on the determination result obtained by comparing with the preset determination value, and the amplitude of vibration of the vibrating optical element, that is, the scanning range of the light beam is controlled.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. As shown in the block diagram of FIG. 1, the light source 4 is a light source that emits a laser beam 11. Resonant mirror 5
Is an oscillating optical element that oscillates and emits the laser light 11 with a variable amplitude. The sine wave generation circuit 1 is a circuit for generating a sine wave having a resonance frequency of the resonant mirror 5, and an amplification circuit 2
Has a variable amplification factor and amplifies the sine wave to drive the mirror drive circuit 3
And a mirror drive circuit 3 are circuits for driving and vibrating the resonant mirror 5.

Laser light 1 reflected by the resonant mirror 5
A mask 12 is arranged on the optical path 1 of the laser light, and the light flux of the laser light 11 forms spot light on the mask 12 by a condenser lens (not shown). Mask 12
Is a blocking plate that blocks the laser light 11 that moves in one direction at the fixed position and allows the laser light 11 that moves in the opposite direction at the position to pass therethrough, and gives intensity modulation to the transmitted light.
The detector 13 is a photoelectric conversion element arranged at a position for receiving the laser beam 11 transmitted through the mask 12.

The clock circuit 14 receives the detection signal from the detector 13 and moves the laser beam 1 to the above-mentioned fixed position of the mask 12.
This is a circuit that measures the time interval from the time point when one spot light moves in a certain direction to the time point when it moves again in the same direction. The control unit 15 integrates the measurement values of the time intervals and outputs an amplification factor control signal for controlling the amplification factor of the amplification circuit based on the obtained integration value.

The control unit 15 calculates an integrated value of the measured values at a plurality of time intervals and outputs an integrated value signal,
The determination value corresponding to the reference time of the amplitude of the spot light 19 is stored, the determination value signal is output to the memory 17, the integrated value signal and the determination value signal are received, and the magnitude relationship between the two is determined.
The determination circuit 18 is configured to output an amplification factor control signal to the amplification circuit based on the determination result.

Next, the mask 12 will be described in detail. As shown in FIG. 2, the mask 12 is composed of a blocking portion 22 and a transmitting portion 23 provided in the central portion of the transparent plate 21. Boundaries 24 a and 24 b between the blocking portion 22 and the transmitting portion 23 are provided in a direction perpendicular to the scanning direction of the spot light 19. Blocking portion 22 between the boundary 24a and the boundary 24b
Corresponds to the amplitude of the spot light 19 to be controlled. Different amplitudes can be accommodated by masks having different widths of the blocking portion 22 between the boundaries 24a and 24b.

The operation of the sine generation circuit 1 which will be described below oscillates a sine wave having the resonance frequency of the resonant mirror 5, and the sine wave output from the sine generation circuit 1 is amplified by the amplification circuit 2 with an appropriate amplification factor. Input to the mirror drive circuit 3. The mirror drive circuit 3 inputs an output suitable for driving the resonant mirror 5 to the resonant mirror 5, and the resonant mirror 5 is oscillated by a sine wave at a resonance frequency. The laser light 11 is reflected while vibrating with an amplitude according to the vibration angle of the resonant mirror 5. The laser light 11 is condensed to become spot light 19.

The spot light 19 is incident on the mask 12 and vibrates on the mask 12 while reciprocating in the horizontal direction between the positions a1 and a2 of the transmitting portion 23 while crossing the boundaries 24a and 24b of the mask 12. The spot light 19 is transmitted at the position a1 of the transmitting portion 23 outside the boundary 24a, is not transmitted at the position a3 of the blocking portion 22 inside the boundary 24a, and is beyond the position a2 of the transmitting portion 23 outside the boundary 24b. Re-transparent. Each time the spot light 19 crosses the boundaries 24a and 24b, transmission and blocking are repeated, and the transmitted light is detected by the detector 1
It is incident on 3.

Therefore, the intensity of the laser light 11 which passes through the mask 12 is such that the spot light 19 is at the boundaries 24a and 24b.
The intensity of the detection signal is repeated each time the intensity exceeds, and the magnitude of the detection signal output from the detector 13 upon reception of the transmitted light varies depending on the position of the spot light moving on the mask 12. Figure 3
As shown in the time t-detection signal intensity I relationship, the detection signal intensity I is 0 when the spot light 19 is illuminating the blocking portion 22, and the spot light 19 illuminates the transmitting portion 23. The detected signal strength I is I ₁ when the power is on. The detection signal intensity I changes each time the spot light 19 crosses the boundaries 24a and 24b. By providing the reference intensity I ₀ , it is possible to measure the time interval at which the detection signal intensity I becomes I ₁ , that is, the time interval at which the light beam crosses the blocking unit 22. Information on the time interval is output from the time counting circuit 14 to the integrating circuit 16.

Upon receipt of the information on the time interval from the time counting circuit 14, the integrating circuit 16 integrates the time interval a predetermined number of times to obtain the integrated time, and the integrated value is set to the judgment value preset and stored by the judging circuit 17. Based on the judgment.

This processing in the control unit 15 will be described with reference to the flowchart shown in FIG. The process starts in step 1, and the integrated value is cleared in step 2. In step 3, the time value of the time interval is input from the time counting circuit 14, and in step 4, the integrated value is calculated. The integrated value is repeatedly obtained by a predetermined specified number of times according to the equation 1. I _{n + 1} = I _n − (I _n × w) + (T × w) (1) where I _{n + 1} : (n + 1) integrated value I _n : n integrated value T : (N + 1) th time interval w detected: weighting coefficient

In step 5, it is checked whether or not the specified number of times has been integrated. After the specified number of times is integrated, the process proceeds to step 6, and if not, steps 3 and 4 are repeated until the specified number of times is reached. In step 6, whether or not the integrated value is larger than the judgment value j3 is checked. If the integrated value is larger than the judgment value j3, the process proceeds to step 7, and if not, the process proceeds to step 12. In step 7, it is checked whether the integrated value is larger than the judgment value j2. If the integrated value is larger than the judgment value j2, the process proceeds to step 8,
If not, go to step 11. In step 8, it is checked whether the integrated value is larger than the judgment value j1 and the integrated value is judged to be the judgment value j.
If it is larger than 1, the process proceeds to step 9, and if not, the process proceeds to step 10. In step 9, it is determined that the integrated value is within the range r1 and stored. In step 10, it is determined that the integrated value is within the range r2 and stored. In step 11, it is determined that the integrated value is within the range r3 and stored. At step 12, it is checked whether the integrated value is larger than the judgment value j4,
If the integrated value is larger than the judgment value j4, the process proceeds to step 13, and if not, the process proceeds to step 14. In step 13, it is determined that the integrated value is within the range r4 and stored. In step 14, it is determined that the integrated value is within the range r5, and it is stored.

The above judgment values j1, j2, j3, j4 and j5 are as shown in FIG.
It is set as follows. The judgment value j1 is the lower limit of the range r1 and the upper limit of the range r2, the judgment value j2 is the lower limit of the range r2 and the upper limit of the range r3, the judgment value j3 is the lower limit of the range r3 and the upper limit of range r4, and the judgment value j4 is the lower limit of the range r4. And range r
It is a value for determining the upper limit of 5.

The range r3 is a normal amplitude range, the range r1 is an excessive amplitude range, and the range r5 is an excessive amplitude range. In addition, the range r2 is out of the normal range but not excessively large, and the range r4 is out of the normal range but not too small. Immediately controlling each of them causes excessive control so that the dead zone for stopping the control. Is the range.

Then, the decision circuit 18 determines that the integrated value is in the range r.
When it is determined to be 3, the amplification factor is maintained,
The amplification factor control signal is amplified so that the amplification factor is decreased when it is determined that the integrated value is in the range r1, and the amplification factor is increased when it is determined that the integrated value is in the range r5. When output to the circuit and the integrated value is determined to be in the range r2 or the range r4, the amplification factor control signal is not changed.

The amplification circuit 2 increases or decreases the amplification factor based on the amplification factor control signal from the determination circuit 18, and amplifies the output of the sine wave generation circuit 1 with an appropriate amplification factor. The mirror drive circuit 3 drives the resonant mirror 5 based on the corrected amplification factor, and the resonant mirror 5 vibrates with an accurate amplitude. The amplitude of the resonant mirror 5 is accurately maintained by performing the control every predetermined time.

In this embodiment, a mask that blocks light is used, but it is also possible to use a mask configured to reflect light or to give light a modulation other than intensity. Although a mask that transmits light at both ends of the amplitude is shown in FIG. 2, the blocking portion and the transmitting portion may be arranged in reverse. According to the present embodiment, the amplitude can be changed by changing the judgment value and the mask. According to the present embodiment, the amplitude is directly detected and the latest measured value is weighted and compared with the integrated value obtained by integrating the time intervals, so that the influence of disturbance is small. Moreover, since the dead zone is set, there is no excessive control.

Next, the second embodiment will be described with reference to FIGS.
Will be described. The mask 25 is a linear scale in which engraved lines are arranged in a row in the transmissive part 26 at a constant period, and the engraved part forms the reflective part 27. The spot light 19 moves so as to cross the line of markings arranged in a row. When the spot light 19 oscillates with an amplitude between the positions c1 and c2, as shown in FIG. 7, the detection signals d1 and d are generated at the times corresponding to the positions c1 and c2.
2 occurs. In addition, transmission and reflection are alternately repeated in the engraved line forming the reflection part 27 and the transmissive part between the engraved lines. When the reference intensities I ₀₁ and I ₀₂ are provided and the intensity detection signal between them is output, the scanning signal e corresponding to the engraved line is obtained. Scanning signal e
Is used to form a scan clock signal for inputting image information, for example. The integrated value of the time interval is calculated from the detection signals d1 and d2, compared with a predetermined judgment value, and the amplification factor control signal is output to the amplification circuit to control the amplitude.

[0029]

As described above, according to the present invention, the light beam emitted from the vibrating optical element is made incident on the mask, and the time interval of the light amount change periodically generated at both ends of the mask is controlled.
Since the amplitude of the vibrating optical element is directly monitored, the amplitude can be detected with high accuracy. The amplitude is detected as a time interval, and the time interval is weighted to the latest value and integrated, and compared with the determination value, so that it is less affected by disturbance. Further, since the judgment value is set in advance including the dead zone and the comparison judgment is performed, the influence of the delay of the control system is suppressed, and the control with a high degree of stability can be performed without causing excessive control. The members can be easily arranged with a simple configuration, and the determination value can be changed and set for each predetermined amplitude to change and control the amplitude.

[Brief description of drawings]

FIG. 1 is a block diagram of an amplitude control device for a vibrating optical element according to a first embodiment.

FIG. 2 is a plan view of a mask used in the first embodiment.

FIG. 3 is a time-detection output intensity diagram in the first embodiment.

FIG. 4 is a flowchart of amplitude control in the first embodiment.

FIG. 5 is a diagram showing setting of judgment values in the first embodiment.

FIG. 6 is a plan view of a mask used in the second embodiment.

FIG. 7 is a time-detection output intensity diagram in the second embodiment.

FIG. 8 is a block diagram of a conventional amplitude control device for a vibrating optical element.

FIG. 9 is a block diagram of a conventional amplitude control device for an oscillating optical element.

FIG. 10 is a block diagram of a conventional amplitude control device for a vibrating optical element.

[Explanation of symbols]

1 ... Sine wave generator 2 ... Amplifying circuit 3 ... Mirror drive circuit 4 ... Light source 5 ... Resonant mirror 6 ... Amplification factor control circuit 11 ... Laser light 12 ... Mask 13 ... Detector 14 ... Measuring circuit 15 ... Control unit 16 ... Integration circuit 17 ... Memory 18 ... Determination circuit 19 ... Spot light 21 ... Transparent plate 22 ··· Blocking unit 23 ... Transparent part 24a, 24b ... Boundary

Claims (2)

(57) [Claims] 1. A vibrating optical element that vibrates and emits a light beam incident from a light source with a variable amplitude, driving means for driving the vibrating optical element, and sinusoidal wave generation for generating a sinusoidal wave for driving the driving means. A circuit, an amplifier circuit that amplifies the sine wave with a variable amplification factor and outputs the amplified sine wave to the driving unit, a modulating unit that modulates a light beam emitted from the vibrating optical element in response to the vibration, and the modulating unit. Detecting the light beam modulated by, detecting means for outputting a detection signal, time measuring means for measuring the time interval between the time points when the detection signal has a predetermined intensity, and receiving the measurement value signal of the time interval, In an amplitude control device for an oscillating optical element, which comprises an amplification factor control means for outputting an amplification factor control signal for controlling the amplification factor to the amplification circuit, and which controls the amplitude by controlling the amplification factor, Increase The width ratio control means calculates an integrated value of a plurality of measurement values of the time intervals, outputs an integrated value signal, and a storage means which stores a determination value corresponding to the amplitude and outputs a determination value signal. And a determination means that receives the integrated value signal and the determination value signal, determines a magnitude relationship between the two, and outputs the amplification factor control signal to the amplification circuit based on the determination result. Amplitude control device for optical elements. 2. The determination means, for each predetermined amplitude,
The first, second, third, and fourth determination values are stored in descending order, and the amplification factor control means determines that the integrated value is between the second determination value and the third determination value. When it is determined that the integrated value exceeds the first determination value, the integrated value is decreased so as to maintain the amplification rate. When it is determined that the amplification factor is less than the determination value, the amplification factor control signals are output to the amplification circuit so as to increase the amplification factor, and the integrated value is the first determination value and the second determination value. Or when it is determined that it is between the third determination value and the fourth determination value, the amplification factor control signal for changing the amplification factor is not output. Item 2. An amplitude control device for an oscillating optical element according to Item 1.