JPS6037637B2 - Laser output setting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser output setting device for making the laser output of a Caesar oscillator match a set value and maintaining the stabilized output.

Conventionally known laser output setting methods include stabilizing the discharge current of a laser discharge tube using a constant current circuit, and setting this current value to a desired value using a setting dial.

However, since there are various factors that cause the laser output to fluctuate in addition to the discharge current, it is not possible to set and stably maintain the laser output simply by setting the discharge current to a constant value. In addition to fluctuations in the discharge current, the causes of fluctuations in laser output include changes in the spacing and head angle of the resonator mirrors due to thermal and mechanical factors, changes in the pressure and flow rate of the laser medium gas, deterioration of the resonator mirrors, and the discharge tube. These include fluctuations in water cooling temperature and water flow rate.

The present invention also addresses such fluctuation factors in laser output.
By detecting the laser output and feedback controlling the discharge current based on the signal, the laser output setting can be stabilized. That is, if the laser output is controlled by such a control system, the above-mentioned various fluctuation factors will be suppressed or absorbed by this feedback control system.In the laser output setting device of the present invention, the laser output detection signal An appropriate stabilizing element for stabilizing the control system is introduced between the operation signal obtained by comparing the output setting signal and the discharge current, which is the manipulated variable, to automatically set the laser output and stabilize the output. In addition, a current limiting circuit is provided to ensure safe operation of this feedback control system.

In this way, the purpose of the present invention is to automatically follow and stabilize the laser output to a set value for a laser resonator whose output is not constant due to various fluctuation factors, and to ensure safe operation of the control system. The object of the present invention is to provide a laser output setting device that ensures the following.

The present invention will be explained below according to the drawings.

FIG. 1 is a diagram showing the basic configuration of a laser output setting device according to the present invention, and the mathematical expressions in the diagram represent the transfer functions of each block.

A part P3 (S) of the output 2 from the laser tube 1 enters the output detector 4, and the detected output P4 (S) is transmitted to the output converter 5.
can be converted to a voltage signal at This detection signal Po(S) is applied to the setting signal Ps(S) from the output setting section 7 in the subtracter 6.
) is compared and subtracted to form operating signals P, (S).
This operation signal P, (S) is input to the operation unit 8, and after being converted into a discharge current P2 (S), which is the operation amount, the laser tube 1
control. The control section in Figure 1 is rough.

The transfer function of each block is shown using the ras operator S, where Q and 6 are the time constants of the power meter 4 and the operation unit 8, respectively, and A, B, C, and D are the characteristics of each block. It is a constant of the transfer function determined based on The reason why there is a time delay between the power meter 4 and the output converter 5 is that a slow-response device such as a thermocouple is used to detect the power of, for example, a C02 laser or a YAG laser. Also, the reason why the operation signal P, (S) has a first-order delay element A6/S+6 between the manipulated variable P2 (S) is to stabilize the operation of this control system, as is well-known as a standard of servo systems. It's for a reason. The specific numerical value of the transfer function of this control system is determined experimentally from the characteristics of the power meter used, the laser output characteristics with respect to the discharge current, the characteristics of the elements of the electronic circuit system, etc.

FIG. 2 is a block diagram of the circuit system of the laser output setting side calendar according to the present invention.

It is easy to determine a practical electronic circuit system by inverse Labrasian transformation of the transfer function shown in FIG. 1, and since the method and specific circuit can already be realized using current technology, their description will be omitted.

For example, the output conversion section 5 in FIG. 1 is the differentiating circuit 9 and the adding circuit 10' in FIG.
1 and the current conversion circuit 12.

The output of the power meter 4 is differentiated by a differentiating circuit 9, and the output is added to the output of the power meter 4 by an adding circuit 10.

The meaning of these signal additions will be explained with reference to FIG. In FIG. 3, the output a of the power meter 4 shows a slow exponential rise, so if the system is operated with this signal alone, the response of the system will be poor. Therefore, the differential signal b and the output a
By using the signal c obtained by adding , the time constant for reaching a steady state is shortened as shown in the figure. This addition signal is compared with the output of the output setting section 7 in the subtraction circuit 6, and inputted to the integration circuit 11 as the subtraction signal.

The output of the integrating circuit 11 is converted into a discharge current value as a manipulated variable in a current conversion circuit 12 to control the laser oscillator 1. The output of the output setting unit 7 also controls the current limiter 13 to prevent the system from operating normally and the discharge current to increase abnormally due to a failure or deterioration of the power meter or failure of each control block. ing. The limited current of the current limiter 13 is transmitted to the laser discharge tube in the laser oscillator 1 via the current conversion circuit 12. FIG. 4 is a diagram showing the operation of the current limiter.

The machine axis is the discharge current i, and the vertical axis is the laser output W. Straight line b is a control current straight line determined from this power characteristic, and the restricted area is the lower right area of straight line b. When normal feedback control is performed, if the laser output for current i is W, then the limiting current is current i2 determined from the intersection of DC b and W. In this way, the laser output setting device of the present invention corrects the first-order delay of the power detector in order to stabilize the control system and perform fast-response control. A first-order delay is also set, and a current limiter is also installed to maintain system safety in the event of a failure of the control system or laser oscillator.

Therefore, if the laser oscillation conditions and environmental conditions (temperature, vibration) are within normal ranges, the laser output can be automatically set to a desired value and a highly stable laser output can be maintained. The laser output setting device of the present invention can be applied not only to gas lasers but also to solid state lasers such as YAG lasers.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of the laser output setting device according to the present invention, FIG. 2 is a block diagram of the circuit system of the laser output device according to the present invention, FIG. 3 is an explanatory diagram of the operation of the output converter, and FIG. FIG. 4 is an operational diagram of the current limiter. 1: laser oscillator, 2: laser output, 4: power meter, 9: differentiation circuit, 10: addition circuit, 6: subtraction circuit, 11: integration circuit, 12: current conversion circuit, 13: current limiter. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. A power meter that detects laser output, a differentiation circuit that differentiates the output of this power meter, an addition circuit that adds the output of the power meter and the output of the power meter, an output setting section, and this output. It consists of a subtraction circuit that subtracts the output of the adder circuit from the output of the setting section, an integration circuit that integrates the output of this subtraction circuit, a current conversion circuit that converts the output of this integration circuit into a current, and a laser oscillator. A laser output setting device characterized by being capable of making the output match a set value and stabilizing the laser output. 2. Laser output according to claim 1, characterized in that it has a current limiter that limits the discharge current of the laser oscillator according to the output of the output setting section, and guarantees the safety of the laser oscillator and the electronic circuit system. Setting device.