JPH10134390A - Laser beam controller and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize laser power control by a small-scale and inexpensive system structure. SOLUTION: A photodetector 13 detects the intensity of an incident laser beam from a laser light source 11 through a polarizer 12, and supplies it to a noise eater circuit 14. The noise eater circuit 14 computes the displacement of the laser beam intensity from the photodetector 13, determines in a feedforwarding manner the correction quantity of the polarizer 12 according to the displacement, and supplies a control signal for that correction quantity to a motor driving part 15 for rotating the polarizer. This driving part 15 is driven in accordance with the control signal from the noise eater circuit 14, and rotates the polarizer 12. A managing part 17 for the rotary angle and position of the polarizer controls the motor driving part 15 for rotating the polarizer, and limits its rotary angle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser light control device and method, for example, a laser light control device and method for stably controlling the output of laser light emitted from a laser light source.

[0002]

2. Description of the Related Art As a method of controlling laser output power, a control method using an AOM (acoustooptic modulator) modulator and an EOM (electrooptic modulater) modulator has been effective.

FIG. 6 shows a configuration example of a conventional servo system. The set level output unit 1 generates and outputs a signal of a predetermined reference level. Error detector 2
Inputs a signal supplied from the set level output unit 1 and a signal supplied from a displacement detector 6 described later, detects a difference therebetween, and outputs the difference. The error amplifier 3 amplifies and outputs a signal from the error detector 2. The drive unit 4 outputs a control signal according to the level of the output signal from the error amplifier 3 and controls the control target 5. Further, the displacement detector 6 detects an absolute displacement amount of the control target 5 and outputs a corresponding detection signal.

As described above, in the conventional servo system, a signal of a level corresponding to the absolute displacement amount of the control
, And operates to make the displacement amount of the control target 5 constant. Therefore, in the conventional method, the absolute displacement amount of the control target 5 always depends on the output of the drive unit 4, and in order to keep the displacement amount of the control target 5 constant, the drive unit 4 Is always required.

[0005]

SUMMARY OF THE INVENTION However, AOM
As a drawback when using the modulator, a large power loss is raised, and there is a problem that is not preferable from the viewpoint of output efficiency. Further, the EOM modulator has no problem in terms of power loss, but has a problem that the scale of the system configuration becomes large because high voltage driving is required.

In the conventional servo system, a constant drive amount of the drive unit 4 to the control target 5 is always required.

The present invention has been made in view of such a situation, and it is an object of the present invention to control a laser output efficiently and with high accuracy with a simple device.

[0008]

According to a first aspect of the present invention, there is provided a laser light control device comprising: a laser light amount adjusting means for passing an arbitrary variable component of laser light emitted from a laser light source; and a laser light amount adjusting means. And a control unit that controls the laser light amount adjusting unit according to the output of the laser light detecting unit.

According to a sixth aspect of the present invention, there is provided a laser light control device for controlling a light quantity of a laser light emitted from a laser light source, a driving means for rotating and driving the variable light element, and detecting a laser light passing through the variable light element. And a control means for controlling the driving means so as to rotate the photon according to the output of the laser light detecting means.

According to another aspect of the present invention, there is provided a laser light control method for detecting a laser light emitted from a laser light source, comparing the detected value with a reference output value, obtaining a control signal corresponding to the comparison value, and converting the control signal into a control signal. Based on the control, control is performed such that an arbitrary variable component of the laser light emitted from the laser light source is passed.

In the laser light control device according to the first aspect, the laser light amount adjusting means passes an arbitrary variable component of the laser light emitted from the laser light source, and the laser light detecting means includes the laser light amount adjusting means. The control means controls the laser light amount adjusting means according to the output of the laser light detecting means.

In the laser light control device according to the sixth aspect, the variable element adjusts the amount of laser light emitted from the laser light source, the driving means drives the variable element to rotate, and the laser light detecting means includes: Detects the laser light that has passed through the variable,
The control means controls the driving means to rotate the photon according to the output of the laser light detecting means.

In the laser light control method according to the present invention, the laser light emitted from the laser light source is detected, the detected value is compared with a reference output value, and a control signal corresponding to the comparison value is obtained. Is controlled so that an arbitrary variable component of the laser light emitted from the laser light source passes.

[0014]

FIG. 1 is a block diagram showing a configuration example of an embodiment of a laser output power control system (noise eater system) to which a control device of the present invention is applied. The laser light source 11 emits laser light. Polarizer 1
2 (laser light quantity adjusting means, variable element) outputs an arbitrary polarization of the laser light. The photodetector 13 (laser light detecting means) detects the laser light emitted from the laser light source 11 through the polarizer 12, and outputs a signal corresponding to the level of the detected laser light.

The noise eater circuit 14 (control means) outputs driving information such as a driving direction and a driving amount based on a signal supplied from the photodetector 13 and an internal set level. The polarizer rotation motor drive unit 15 supplies a predetermined control signal to the polarizer rotation motor 16 (drive means) according to the drive information input from the noise eater circuit 14. The polarizer rotation motor 16 is configured by a stepping motor, rotates the polarizer 12 according to a control signal from the polarizer rotation motor drive unit 15, and displays a position signal indicating how much the polarizer rotation motor 16 is rotating. Is output.

As means for restricting the rotation angle of the polarizer to be within a predetermined range, a polarizer rotation angle position management unit 17 is provided. Polarizer rotation angle position management unit 1
The control unit 7 controls the polarizer rotation motor drive unit 15 based on the position signal output from the polarizer rotation motor 16 so that the rotation angle of the polarizer 12 falls within a range of 0 to 45 degrees.

FIG. 2 shows the rotation angle of the polarizer 12 and the laser output power detected by the photodetector 13 (hereinafter referred to as the laser output power).
(Referred to as laser output detection power as appropriate). The horizontal axis represents the rotation angle of the polarizer 12, and the vertical axis represents the laser output power.

As shown in FIG. 1, when the polarizer rotation angle is in the range of 0 ° to 45 °, the laser output power has a monotonically increasing relationship, but when it exceeds 45 °, the laser output power decreases conversely. Would. Therefore, it is necessary to limit the rotation angle to 0 to 45 degrees in order to stabilize the servo system. For this reason, the polarizer rotation angle position management unit 1
Reference numeral 7 receives a position signal output from the polarizer rotation motor 16, manages the rotation angle position of the polarizer 12, and controls the polarizer rotation motor drive unit 15.

As a result, the rotation angle of the polarizer 12 becomes 45
It is possible to prevent the servo from oscillating more than once and to stabilize the system.

FIG. 3 is a block diagram showing a detailed configuration example of the noise eater circuit 14. As shown in FIG. A / D converter 21
Converts the signal supplied from the photodetector 13 into digital data. The laser output setting section 22 (laser output setting means) outputs data corresponding to a predetermined output level of the laser light source 11. Power error detector 2
3 (arithmetic means) detects a difference (power error amount) between the output data of the A / D converter 21 and the output data of the laser output setting unit 22, outputs its absolute value, and outputs its polarity information. .

As means for converting the output of the power error amount detector 23 into a signal for controlling the polarizer rotation motor driving unit 15, a power error amount / correction rotation angle conversion block 24 includes:
A correction rotation angle / drive time conversion block 25 (signal conversion means) is provided.

The power error / correction rotation angle conversion block 24 outputs from the power error amount detector 23 the correction rotation angle of the polarizer 12 that is optimal for bringing the laser output power value closer to the laser output set value. Data and A / D
Photodetector 13 output from converter 21
Is determined from data corresponding to the detected laser output power, and the corresponding data is output.

Correction rotation angle / drive time conversion block 25
Converts the data corresponding to the corrected rotation angle amount from the power error amount / corrected rotation angle conversion block 24 into the drive time of the polarizer rotation motor drive unit 15 in FIG. The data (correction amount information) corresponding to the drive time is transmitted to the polarizer rotation motor drive unit 15 in FIG. 1 together with the data (polarity information) corresponding to the polarizer correction direction detected by the power error amount detector 23. Supplied.

As shown in FIG. 2, the laser output detection power and the corrected rotation angle have a correlation, and are supplied from the power error amount detector 23 by the power error amount / corrected rotation angle conversion block 24. Based on the data corresponding to the detected power error amount and the data corresponding to the laser output detection power of the photodetector 13 supplied from the A / D converter 21, the optimum polarization for bringing the laser output power value closer to the laser output set value. The correction rotation angle of the child 12 is determined.

FIG. 4 is a graph for explaining an example of a conversion algorithm used when the power error amount / correction rotation angle conversion block 24 converts the power error amount into a polarizer correction rotation angle. And the power error amount. The vertical axis represents the laser output set value P _set and the laser output detection power P _det , and the horizontal axis represents the corrected rotation angle of the polarizer 12.

In FIG. 4, the laser output setting power P
_Assuming that the difference between the _set and the laser output detection power P _det (power error amount) is ΔP, the rotation angle to be corrected (corrected rotation angle) ΔΦ is the difference ΔP and the laser output set power P
It turns out to be a function of _set . Therefore, from the value of the difference ΔP and the laser output setting power P _{The set,} the correction rotation angle ΔΦ
Can be estimated, and the estimated corrected rotation angle Δ
The control signal corresponding to Φ is converted into the drive time of the polarizer rotation motor drive unit 15 as described later, and is supplied to the polarizer rotation motor drive unit 15 in a feed-forward manner every time the laser output power is detected. . As a result, the polarizer rotation motor drive unit 15 rotates the polarizer 12 according to the control signal, and controls the laser output power detected by the photodetector 13 to approach the laser output power set value output by the laser output setting unit 22. .

That is, the corrected rotation angle amount output from the power error amount / correction rotation angle conversion block 24 is supplied to the correction rotation angle / drive time conversion block 25, and the drive of the polarizer rotation motor drive unit 15 in FIG. It is converted to time and output as correction amount information. Also, a power error detector 2
At 3, the direction for correcting the polarizer is detected and output as polarity information. This polarity information is calculated based on the corrected rotation angle /
Along with the correction amount information output from the drive time conversion block 25, the correction amount information is supplied to the polarizer rotation motor drive unit 15. Thereby, the driving direction of the polarizer rotation motor 16 is determined.

This control method is common to the control method based on the two information of the detection error amount and the polarity, as in the case of the normal servo method. Since the absolute angular position is held by using the stepping motor for the rotation of No. 12, the correction amount depends only on the power error amount. That is, the polarizer rotation motor 16 is driven in a feed-forward manner by the angle estimated by the correction amount conversion table only when the laser output power is sampled and detected by the A / D converter 21 and a power error ΔP occurs. If the value of the power error ΔP is 0, the polarizer rotation motor driving unit 1
5 is not driven, and the rotation angle of the polarizer 12 is maintained as it is.

As described above, the drive information (drive direction, drive amount) is supplied from the noise eater circuit 14 to the polarizer rotation motor drive unit 15 only when a power error occurs, so that the reliability as a servo system is improved. Can be enhanced.

FIG. 5 shows a sequence of a series of processes performed by the noise eater circuit 14. That is, at time T1, the laser output power value is sampled and detected by the A / D converter 21, then at time T2, the power error amount and its polarity are detected by the power error amount detector 23, and at time T3. The power error amount / correction rotation angle conversion block 24 converts the power error amount into a correction rotation angle amount of the polarizer 12. Next, at time T4, in the correction rotation angle / drive time conversion block, the correction rotation angle amount of the polarizer 12 is converted into the drive time of the polarizer rotation motor 16 by the polarizer rotation motor drive unit 15. Then, a similar sequence is continuously and repeatedly executed. Thereby, the polarizer 12 can be adjusted to an angle at which a desired laser output power can be obtained.

As described above, since the laser output power is controlled by using the polarizer, control with higher power efficiency can be performed as compared with a conventional control system using an AOM device. Further, a small-scale and inexpensive system can be configured as compared with a control system using an EOM device.

Further, as described above, by combining the control by the continuous feed-forward method and the driving of the stepping motor, the motor can be driven only when a power error occurs. Reliability can be improved.

Further, by using the conversion algorithm in the power error amount / correction rotation angle conversion block 24, it becomes possible to perform control suitable for the system.

In the above-described embodiment, the control method for detecting the amount of error between the set value and the detected value and performing the correction sequence continuously in a feedforward manner in accordance with the estimation of the amount of error is the laser power. The present invention can be applied not only to the control system but also to other fields. Further, the method of responding to the system by the power error amount / correction rotation angle conversion block 24 is not limited to the control method using the rotation of the polarizer as the control target, and may be applied to a system using another control target. it can.

[0035]

According to the laser light control device of the present invention, the laser light amount adjusting means allows an arbitrary variable component of the laser light emitted from the laser light source to pass therethrough, and the laser light detecting means controls the laser light. The laser light adjusted by the light amount adjusting means is detected, and the control means controls the laser light amount adjusting means in accordance with the output of the laser light detecting means. Only the motor can be driven to control the control object, and the reliability of the control can be improved. .

According to the laser light control device of the sixth aspect, the variable element adjusts the amount of laser light emitted from the laser light source, the driving means drives the variable element to rotate, and the laser light detecting means controls the laser light. Detecting the laser light that has passed through the photon, and the control means controls the driving means to rotate the photon according to the output of the laser light detecting means. The motor can be driven to control the control target only when the error occurs, and the reliability of the control can be improved.

According to the laser light control method of the present invention, the laser light emitted from the laser light source is detected, the detected value is compared with the reference output value, and a control signal corresponding to the comparison value is obtained. Since it is controlled to pass any variable light component of the laser light emitted from the laser light source based on the signal, by combining with a stepping motor, the motor is driven only when a difference occurs, and the control target Can be controlled, and the reliability of the control can be increased.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of an embodiment of a noise eater system to which a control device of the present invention is applied.

FIG. 2 is a graph showing a correlation between a rotation angle of a polarizer and laser output power.

FIG. 3 is a block diagram illustrating a detailed configuration example of a noise eater circuit 14 of FIG. 1;

FIG. 4 is a graph showing a correlation between a corrected rotation angle and a power error amount.

FIG. 5 is a diagram showing a system sequence.

FIG. 6 is a block diagram illustrating a configuration of an example of a conventional servo system.

[Explanation of symbols]

1 set level output section, 2 error detector, 3 error amplifier, 4 drive section, 5 controlled object, 6 displacement detector, 11 laser device, 12 polarizer, 13 photodetector, 14 noise eater circuit, 15 polarizer rotation motor drive section , 16 polarizer rotation motor, 17 polarizer rotation angle position management unit, 21 A / D converter, 22 laser output setting unit, 23 power error detector, 24 power error / correction rotation angle conversion block, 25 correction rotation angle / Driving time conversion block

Claims (9)

[Claims] 1. A laser light amount adjusting means for passing an arbitrary variable component of laser light emitted from a laser light source; a laser light detecting means for detecting the laser light adjusted by the laser light amount adjusting means; Control means for controlling the laser light amount adjusting means in accordance with the output of the light detecting means. 2. The control means includes: a laser output setting means for setting a reference output value of laser light; and a difference between a reference output value from the laser output setting means and an output value of the laser light detection means. 2. The laser light control device according to claim 1, further comprising: an operation unit; and a signal conversion unit that outputs a signal for controlling the laser light amount adjustment unit based on an output value of the operation unit. 3. 3. The laser light control device according to claim 2, wherein said signal conversion means has a table for converting an output value of said calculation means into said control signal. 4. A laser light amount adjusting means, comprising:
The laser light control device according to claim 1, further comprising: a driving unit configured to rotationally drive the variable element. 5. The laser light control device according to claim 4, wherein said driving means is a stepping motor. 6. A variable element for adjusting the amount of laser light emitted from a laser light source, driving means for rotating and driving the variable element, laser light detecting means for detecting laser light passing through the variable element, Control means for controlling said driving means so as to rotate said variable element according to the output of said laser light detecting means. 7. The control means includes: a laser output setting means for setting a reference output value of laser light; and detecting a difference between a reference output value from the laser output setting means and an output value of the laser light detection means. 7. The laser light control device according to claim 6, further comprising: a calculating unit that performs a control signal corresponding to a rotation angle of the photon based on an output value of the calculating unit. . 8. A laser beam emitted from a laser light source is detected, the detected value is compared with a reference output value, a control signal corresponding to the comparison value is obtained, and the laser beam is emitted from the laser light source based on the control signal. A laser light control method, characterized in that control is performed so that an arbitrary variable component of the laser light is transmitted. 9. The laser light control method according to claim 8, wherein a variable is used to pass the arbitrary variable component.