JP2658208B2 - Laser output monitor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device that is mounted on a laser device and monitors its output power.

<Prior Art> In general, a device for monitoring a laser output uses a beam splitter to guide a part of the output light of the laser device to an optical sensor, and uses a calculation formula or the like based on a predetermined calibration curve to convert the sensor output. To convert it to laser output power and display it on a display or the like. This conversion is usually performed by a microcomputer, and the above-described calculation formula and its constants are stored in a ROM. Before shipping the device, the calculation formulas and constants to be stored in the ROM are set as a reference power meter outside the device, and the measured value of the laser output power by the power meter and the output of this monitor device are used. It is recorded and determined by obtaining a calibration curve based on these.

<Problems to be Solved by the Invention> According to the conventional techniques as described above, the calibration procedure of the apparatus,
In other words, there is a problem that procedures such as offline collection of calibration data using a power meter, derivation of a calibration curve based on the data, and further writing of the results to a ROM including a link to a main program are complicated. .

In addition, constants and calculation formulas once written in ROM are
It is virtually impossible to change on the user side.
However, in the case of an excimer laser or the like in which the optical system is easily changed, there is a case where re-calibration is actually required due to, for example, a change in the beam incident position on the optical sensor for monitoring. Conventional devices cannot cope. In particular, when the measured value of the laser output monitoring device is fed back to the laser device to perform power control for stabilizing the output or the like, the necessity of re-calibration increases.

An object of the present invention is to solve such a problem.

<Means for Solving the Problems> In order to achieve the above object, according to the present invention, in a computer system for converting an optical sensor output into a laser output measurement value, a nonvolatile RAM for storing information for the conversion is provided.
Is provided, and the information can be rewritten, thereby enabling re-calibration.

As one means for rewriting the information in the nonvolatile RAM, an input circuit for inputting measurement value information of the output light of the laser device by an external standard power meter is provided in the computer system, and the computer system is provided with a laser. A command for causing the device to oscillate in a plurality of output states is issued, and the optical sensor output in each output state and the input signal from the input circuit are respectively taken in, and the above-described conversion based on the taken in data is performed. Means for determining the information to be used and incorporating a program for changing the contents of the nonvolatile RAM.

As another means for rewriting information in the nonvolatile RAM, the nonvolatile RA is stored in the computer system.
A key input device for changing the content of M or a connection means thereof is provided, and a computer system is provided with an interpreter for interpreting and executing information in the non-volatile RAM at the time of conversion to the measured value, or It is also possible to adopt a means of incorporating a compiler which translates the information when inputting it from the key input device and stores it in the nonvolatile RAM.

The information for converting the optical sensor output into the measured value is a coefficient representing the calibration curve, a calculation formula including a constant, or only the coefficient or the constant in the calculation formula, or the optical sensor output and the measured value. , Or a combination of a plurality of these tables.

<Operation> With the above configuration, the calibration operation is executed online by the program of the computer system, and the information based on the correct calibration curve is automatically stored, or
By operating the key input device based on off-line calibration data collection, information for conversion to measured values can be arbitrarily changed.

<Example> An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the embodiment of the present invention.

The laser device includes a laser chamber 1 that performs laser oscillation, a laser drive control circuit 2 that supplies an excitation signal to the laser chamber 1, and the like, and a part of the output laser light is monitored by a beam splitter 3 to monitor a laser output. The light is guided to the optical sensor 41 of the device 4.

The laser output monitoring device 4 includes an optical sensor 41, an optical output measuring circuit 42 for inputting its output, and a microcomputer system.

The microcomputer system includes an MPU 43, a ROM 44 in which a program described later is written, and an A / D converter described later.
RAM 45 with an area for storing data from 47 and a working area, nonvolatile storage of calibration curve coefficients, etc.
A / D converter 4 for digitizing the output from RAM 46, optical output measuring circuit 42, and standard power meter 5 placed outside
7, Display 48 that displays the calculated laser output measurement result
And an input / output interface 49 for connection to an external device, and these are connected to each other by a bus line. The input stage of the A / D converter 47 is provided with an input signal switching circuit (not shown) such as a multiplexer.

The laser drive control circuit 2 is connected to the input / output interface 49, and the keyboard 6 can be connected as necessary.

The standard power meter 5 is a power meter that is precisely adjusted, and can measure and output the power of the input laser light.
The output laser light from the laser chamber 1 is installed so as to be directly input, and the output is taken into the microcomputer system through the AD converter 47.

A measurement program and a calibration program are written in the ROM 44, and either one can be selected by operating the keyboard 6 or the like. In the ROM 44, a calculation equation of a predetermined order for converting the data from the optical output measurement circuit 42 into a measurement value is written in advance. One or more of them are not written as specific numerical values, and are in a blank state, for example.

FIG. 2 is a flowchart showing the contents of the measurement program written in the ROM 44. This program is selected at the time of normal measurement.

In this measurement program, only the output from the optical output measurement circuit 42 is transmitted through the A / D converter 47 at a predetermined cycle.
It is incorporated into M45, and every time it is incorporated, the coefficients and constants in the non-volatile RAM 46 are inserted into the above-described formula in the ROM 44, and the acquired data is substituted into a measured value. It is displayed on the display 48 every moment.

FIG. 3 is a flowchart showing the contents of a calibration program written in the ROM 44. This program is selected when calibrating the apparatus. In this case, a standard power meter 5 is installed and the output light of the laser chamber 1 is measured. , And its output to an AD converter 47.

In this calibration program, after performing initial settings such as data clear in the RAM 45, first, a command is issued to the laser drive control circuit 2 of the laser device to excite the laser chamber 1 under a plurality of oscillation conditions. The digitized data of the output of the optical power measurement circuit 42 and the output of the standard power meter 5 in the output state under each condition are sequentially stored in the RAM 45 as a pair.

That is, for example, n combinations of the laser power supply voltage and the oscillation frequency are set in advance, and
Laser oscillation is sequentially performed under the combination conditions up to the first, and at each oscillation, the optical output measurement circuit 42
And the output of the external standard power meter 5 are AD
By using the converter 47 in a time-sharing manner, each of them is digitized and incorporated. The control of the laser oscillation may be performed directly by the microcomputer system in the laser output monitor device 4, or if the microcomputer is provided in the laser drive control circuit 2, coordination with the microcomputer is also possible. You may go to.

When the n data pairs are stored in the RAM 45 by the above operation, the coefficients and the like of the above-described formula are calculated using the data pair group by, for example, the least square method. The curve obtained by inserting the calculated coefficients and the like into the calculation formula represents a correct calibration curve relating the current incident light intensity to the optical sensor 41 and the actual laser output light intensity. The coefficients and the like thus obtained are stored in the nonvolatile RAM 46.
The coefficients and the like previously stored and transmitted are discarded, and the calibration operation ends.

FIG. 4 is a flowchart showing a main part of the contents of a calibration program according to another embodiment of the present invention, and shows a portion corresponding to the portion A in the embodiment shown in FIG.

In this embodiment, for example, a plurality of calculation expressions y = f (x), y = g (x), and y = h (x) having different orders are written in the ROM 44 in advance. deep.

Then, after the n data pairs described above are obtained,
The coefficients and the like of the respective calculation formulas are determined based on the least square method using these. Next, the most practical calculation formula is selected from the calculation formulas whose coefficients and the like have been determined. That is, the n sets of calibration data in the RAM 45 are substituted into the equations into which the coefficients and the like are inserted, and, for example, the equation with the smallest error is selected. Then, it is determined whether or not the selected expression can be converted within a predetermined allowable error range, and if so, the identification symbol corresponding to the expression and the coefficient of the expression are stored in a nonvolatile manner. This is stored in the RAM 46 and the calibration is completed.

If the above determination is out of the range, a calibration table is automatically created from the n data pairs, the calibration table is stored in the nonvolatile RAM 46, and the calibration is completed.

In the measurement program in this embodiment, non-volatile
If a calibration table is created in the RAM 46, the calibration table is used.If there is no calibration table, the display table 48 is calculated using a calculation formula in the ROM 44 corresponding to the identification code and a coefficient in the nonvolatile RAM 46.
Calculate the measured value to be displayed in.

According to the above embodiment, the calibration method for converting the light detection value of the optical sensor 41 into laser power is not fixed, and the most appropriate method is automatically selected, and more accurate calibration can be performed.

In each of the above embodiments, the signal from the standard power meter 5 is directly taken into the laser output monitor 4 through the A / D converter 47. Computer can be interposed. In this case, the calculation of the coefficients and the like in the calibration curve can be executed by the intervening computer.

In each of the embodiments described above, an example in which a series of calibration operations are automatically performed online has been described. However, a configuration may be adopted in which calibration data is sampled offline and a calibration curve is obtained by a human.

That is, for calibration, a standard power meter 5 is installed as in the previous embodiment, but the output is an A / D converter.
Not introduced in 47. Then, the laser chamber 1 is oscillated in various output states, and each time the measurer reads and records the display value of the standard power meter 5 and the display value of the laser output monitor device 4. Then, the measurer determines an appropriate calibration curve based on the record, and calculates an equation representing the calibration curve,
The input is made from the keyboard 6. Then, this equation is stored in the nonvolatile RAM 46.

In this case, any of the following methods can be adopted.

One is an interprinter method, in which a keyboard 6 is used.
Is stored in the non-volatile RAM 46, and when the measurement value is calculated by the measurement program, the calculation formula in the non-volatile RAM 46 is interpreted by the interprinter in the ROM 44 and the calculation is executed.

The other one is a compiler system. A compiler for converting a calculation formula input from the keyboard 6 into executable software is provided in the ROM 44, and is used as a subroutine for calculating a measurement program at the time of inputting the calculation formula. Compile and store in the non-volatile RAM 46. Then, the subroutine is called when the measurement value is calculated.

In this embodiment, although data for calibration and determination of a calibration curve are performed off-line, calibration with high flexibility is always possible.

<Effects of the Invention> As described above, according to the present invention, information for converting the output of the optical sensor for monitoring into the output power of the laser device is stored in the nonvolatile RAM, and the nonvolatile RAM Since the information inside the device can be easily rewritten, the user can easily re-calibrate the device if necessary.

In addition, the work of the initial calibration at the time of shipping the device can be omitted, since the printing of the calibration curve into the conventional ROM or the like can be omitted.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the calibration of the embodiment of the present invention, FIG. 2 is a flowchart showing the contents of a measurement program written in the ROM 44, and FIG. It is a flowchart shown. FIG. 4 is a flowchart showing a main part of the contents of a calibration program according to another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Laser chamber 2 ... Laser drive control circuit 3 ... Beam splitter 4 ... Laser output monitoring device 41 ... Optical sensor 42 ... Optical output measurement circuit 43 ... MPU 44 ... ROM 45 ... RAM 46 ... … Non-volatile RAM 47… A / D converter 48… Display 49… I / O interface 5… Standard power meter 6… Keyboard

Claims (1)

(57) [Claims] An optical sensor is attached to a laser device, receives a part of output light from the laser device extracted by a beam splitter by an optical sensor, incorporates the output of the optical sensor into a computer system, and measures the intensity of the laser output. A device that converts and outputs a value, in the computer system, a nonvolatile RAM that stores information for the conversion,
An input circuit for inputting a signal from an external standard power meter capable of directly inputting output light from the laser device and outputting its intensity information is provided, and the computer system outputs the laser device to a plurality of outputs. A command for oscillating in the state is issued, and the output of the optical sensor in each output state and the input signal from the input circuit are respectively taken, and the information for the conversion is obtained based on the taken data. A laser output monitoring device comprising a program for determining and updating the content of the nonvolatile RAM.