JPH08159917A - Continuous laser-intensity-monitoring apparatus - Google Patents

Abstract

PURPOSE: To provide a continuous laser-intensity-monitoring apparatus which has a wider measuring range while a good S/N ratio is maintained. CONSTITUTION: The continuous laser-intensity-monitoring apparatus is provided with a detector 7 which detects a laser beam, for monitoring, obtained by a laser beam which is output from a laser device 1. On the basis of data obtained by properly processing a signal which is detected by the detector 7, the intensity of the laser is monitored continuously. The monitoring apparatus is provided with a beam expander 5 which expands the beam diameter of the laser beam C for monitoring so as to form a parallel beam, a focusing lens 6 which condenses the parallel beam D, and a driving gear 12 which drives the focal position of the focusing lens 6 so as to be freely adjustable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser intensity continuous monitor for continuously monitoring the output intensity of laser light,
In particular, the present invention relates to a laser intensity continuous monitoring device provided with a means for changing the total energy amount of the laser light for monitoring incident on the light receiving portion of the detecting means.

[0002]

2. Description of the Related Art A continuous laser intensity monitor for continuously monitoring the output intensity of a laser has different measurement ranges, response speeds, displays, etc. depending on the type of detector used, but the operating principles are almost the same. Is. That is, the measurement range is selected according to the output of the pulse or continuous wave laser, the measurement and display are performed in the optimum measurement range, and the data processing is performed using a computer or the like.

Since there is usually only one detector used in the laser intensity continuous monitoring device, when switching the measurement range, the amplification factor of the amplifier is switched so that the detection signal of the detector becomes the full scale of the output of the device. It is done according to the system.

Further, the input / output linearity of the detector can be maintained within the maximum settable range.

For example, when the resolution of the device is several mv and the input / output linearity of the detector is 10 ² mv to 10 ^-3 mv, the number of detector outputs mv to 10 ^-3 mv is the measurement limit of the device. It becomes the following. Therefore, the output of the detector is amplified by an amplifier to obtain a measurable voltage of the device.

[0006]

However, since the input / output linearity of the detector is maintained within a predetermined range, laser output outside this range cannot be detected. Further, when the output of the detector is amplified by the amplifier, noise is amplified together with the signal, so that the S / N ratio is lowered.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a laser intensity continuous monitor device having a wider measurement range while maintaining a good S / N ratio.

[0008]

In order to solve the above-mentioned problems, a laser intensity continuous monitoring apparatus according to the present invention is provided.
As described in claim 1, a detection means for detecting the monitor laser light obtained by the laser light output from the laser device is provided, and the signal obtained by appropriately processing the signal detected by the detection means is converted into data obtained. In the laser intensity continuous monitoring device that continuously monitors the laser intensity based on
A means for changing the energy density when the monitor laser light is incident on the detection means is provided, and the means for changing the energy density is means for making the beam diameter of the monitor laser light into parallel light. And a condensing means for condensing the parallel laser beam for monitoring and a driving means for driving the focal position of the condensing means so as to be adjustable.

[0009]

According to the laser intensity continuous monitoring device having the above-mentioned structure, when the monitor laser light extracted from the laser light output from the laser device is incident on the detecting means, the monitor is incident on the light receiving portion of the detecting means. The total energy amount of the laser light for use (hereinafter referred to as energy density) is changed. That is, by controlling the amount of light incident on the detection surface of the detection means, it is possible to perform measurement in a wider range than the range that satisfies the input / output linearity of the detection means. The laser light of can also be measured without increasing noise by using the above-mentioned means for changing the energy density.

[0010]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 is a block diagram showing the configuration of an embodiment of a laser intensity continuous monitoring apparatus according to the present invention. This embodiment shows an example in which pulsed laser light is used as the laser light output from the laser device.

The laser intensity continuous monitor device includes a glass flat substrate 2 for branching a laser beam B from a main beam A output from a pulse laser device 1 as a laser device,
From the branched laser light B to the monitor laser light C
A glass flat substrate 3 for branching (hereinafter referred to as monitor light C), an attenuator 4 for controlling the intensity of the branched monitor light C, and a beam diameter of the monitor light C controlled to have a predetermined intensity are expanded. A beam expander 5 which is a means for making parallel light into a parallel light, and a focusing lens 6 which is a condensing means for condensing the monitor light D of the parallel light whose beam diameter is expanded.

Further, the continuous laser intensity monitoring device includes a detector 7 such as a photo sensor which is a detecting means arranged at the shortest focusing position of the focusing lens 6, and an amplifier for amplifying an output signal F from the detector 7. 8 and the amplified signal G
Is provided with a Hoxker integrator 9 which is a pulse / DC converter for converting the DC signal H into a DC signal H, and a computer 11 for inputting the DC signal through the computer interface 10 and the cable I to perform data processing.

Further, the continuous laser intensity monitor device adjusts the focus position of the focusing lens 6 along the optical axis so that the focus position of the monitor light E focused through the focusing lens 6 is changed within a required range. A drive device 1 such as an actuator, which is a drive means for driving in an adjustable manner.
2 and the drive unit 12 is connected to the computer 11 by GPIB.
It is connected via a cable K.

In the case of this embodiment, the detector 7 has a measurement range (input / output linearity) of, for example, three digits.

Further, the calculator 11 is preliminarily inputted with data such as the diameter of the beam expander 5, the lens diameter of the focusing 6, the area of the light receiving portion of the detector 7, the moving amount of the focusing lens 6 and the like, and determines the intensity of the monitor light. Regardless, the drive of the drive device 12 is controlled so that the light amount satisfying the input / output linearity of the detector 7 is input to the detector.

Next, the operation will be described.

FIG. 3 is a graph showing the relationship between the output of the detector 7 and the corresponding energy density when the computer 12 processes the experimental results using the laser intensity continuous monitoring apparatus according to the present invention.

In the experiment, the intensity higher than the upper limit value of the input / output linearity of the detector 7 (in FIG. 3, the input / output linearity of the detector 7 is 3
In the case of a digit (10 ² to 10 ^-1 , a relative value), a laser beam having a constant intensity of 3 digits (10 ³ ) higher than that is irradiated to the laser intensity monitor device having the above-mentioned configuration to monitor. Here is an example.

First, the device drives the driving device 12 under the control of the computer 11 so that the focus of the focusing lens 6 becomes the long focus (state of x in FIG. 2) as shown in FIG. Move (see arrow s). Then, the focus position is finely adjusted to change the energy density of the monitor light E incident on the detector 7 so as to be set to the upper limit value of the input / output linearity of the detector 7.

For the purpose of experimentation, the intensity of the monitor light C is now attenuated by the attenuator 4 (the original measurement is free attenuation, and the attenuator is not necessary). It can be seen that by measuring the output of the detector 7 at the energy density, it is possible to measure up to the lower limit value of the input / output linearity of the detector 7.

When the lower limit of the input / output linearity of the detector 7 is measured, the focusing lens 6 is moved again (the state of y in FIG. 2, the actual input / output linearity portion of the detector 7 is satisfied). ), Increasing the energy density incident on the detector 7. Then, the upper limit value of the input / output linearity of the detector 7 is set again, and the measurement is performed by the procedure as described above.

When the measurement reaches the lower limit of the input / output linearity of the detector 7, the focusing lens 6 is moved again (state of z in FIG. 2) to increase the energy density incident on the detector 7. Then, the upper limit value of the input / output linearity of the detector 7 is set again, and the measurement is performed in the procedure as described above.

In this way, the focusing lens 6
The measurement is performed up to the lower limit value of the input / output linearity of the detector 7 in the state of z in FIG. As shown in FIG. 3, the range measured by the detector 7 is the range that satisfies the input / output linearity (black circle in FIG. 3), and the range that cannot be actually measured (10 ^{5
-10 2} , 10 ^-1 to 10 ^-4 ) can also be measured within a range that satisfies the input / output linearity, and the measurement result can be monitored by performing a calculation process by the computer 11 (white circle in FIG. 3). As a result, a dynamic measurement range (three times (9 digits) the input / output linearity (3 digits) of the detector 7) can be realized.

In the actual measurement, the optimum position of the focusing lens 6 in each of the x, y, and z regions obtained by the above-described experiment is stored in the computer 11, and the optimum position is sequentially determined by the detector output value. This is done by switching.

Further, for example, when the measurement limit of the apparatus is set to 10 ^-1 or less (10 ^-1 to 10 ^-4 ), conventionally, this portion was measured by increasing the amplification factor of the amplifier 8, but in this embodiment. According to the method, it is not necessary, and therefore the measurement can be performed without causing a decrease in the S / N ratio.

In the present embodiment, the focus position focused by the focusing lens is adjusted in order to change the energy density of the monitor light incident on the detector.
The present invention is not limited to this. For example, the same effect can be obtained even if the focus position of the focusing lens is fixed and the position of the detector is driven along the optical axis direction.

Although an example using pulsed laser light as the laser output light has been shown, the present invention is not limited to this, and continuous output laser light may be used, for example. In this case, a general A / D converter is used instead of the Hoxker integrator.

Further, although the glass flat substrate is used as the light separating means, the present invention is not limited to this.
For example, a beam splitter may be used.

[0030]

As described above, according to the laser power monitor device of the present invention, the S / N ratio is improved by providing the means for changing the energy density when the monitor laser light is incident on the detecting means. It is possible to realize a laser intensity continuous monitoring device having a good ratio and a wide measurement range.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing an embodiment of a laser intensity continuous monitoring apparatus according to the present invention.

FIG. 2 is a partially enlarged view showing a moving state of a focus in the laser intensity continuous monitoring device shown in FIG.

FIG. 3 is a graph showing an experimental result of a laser intensity continuous monitoring device according to the present invention.

[Explanation of symbols]

 1 pulse laser device 2 glass flat substrate 3 glass flat substrate 4 attenuator 5 beam expander 6 focusing lens 7 detector 8 amplifier 9 Hoxker integrator 10 computer interface 11 computer 12 driver A main beam B laser light CE monitor light F ~ H output signal I cable K GPIB cable

Claims (1)

[Claims] 1. A detection device for detecting a monitor laser beam obtained by a laser beam output from a laser device, and a laser intensity based on data obtained by appropriately processing a signal detected by the detection device. In the continuous laser intensity monitoring device for continuously monitoring, the means for changing the energy density when the monitor laser light is incident on the detection means is provided, and the means for changing the energy density is the monitor laser light. Means for expanding the beam diameter of the parallel light into parallel light, condensing means for condensing the parallel laser light for monitoring, and driving means for driving the focus position of the condensing means so as to be adjustable. A laser intensity continuous monitoring device comprising: