JP2008243949A - Optical axis position detection device for pulsed laser light and optical axis position control device for pulsed laser light - Google Patents

Abstract

An optical axis fluctuation of a pulsed laser beam having a repetition rate of 10 kHz or less can be detected.
A two-dimensional position detecting element in which a light receiving surface for receiving pulsed laser light is formed as a resistance layer having a uniform resistance value, and when pulsed laser light is incident on the light receiving surface, a signal corresponding to the incident position is output. And a signal processing circuit that processes the signal output from the two-dimensional position detection element and outputs the incident position information of the pulsed laser light incident on the light receiving surface, and the signal processing circuit It has a peak hold circuit for storing the peak value of each signal waveform from the two-dimensional position detection element using a trigger signal synchronized with the output of the pulsed laser light incident on the surface.
[Selection] Figure 2

Description

  The present invention relates to an optical axis position detection device for pulsed laser light and an optical axis position control device for pulsed laser light, and more specifically, for correcting fluctuations in the optical axis of pulsed laser light, that is, spatial fluctuations. The present invention relates to an optical axis position detection device for pulse laser light and an optical axis position control device for pulse laser light suitable for use in the above.

  Conventionally, it has been recognized that it is important to detect fluctuations of the optical axis of pulsed laser light emitted from various pulse laser devices, that is, to detect spatial fluctuations and to suppress the fluctuations.

For example, in the laser system using the hollow fiber pulse compression technology, when the optical axis of the pulse laser beam emitted from the laser device fluctuates,
a. The hollow fiber incident end face is damaged by irradiation with pulsed laser light b. Fluctuates in the spectral broadening of the pulsed laser light after emission from the hollow fiber c. It has been pointed out that the problem that the power of the pulsed laser beam after emitting the hollow fiber fluctuates occurs.

In general, fluctuations in the optical axis of laser light in a laser system can be broadly classified into long-term fluctuations and short-term fluctuations.

  First, long-term fluctuations are fluctuations caused by contraction / expansion of optical elements, their supporting structures, optical benches, etc., mainly due to temperature changes in the surrounding environment, and generally slow fluctuations from several seconds to several hours. It is.

  On the other hand, short-term fluctuations are caused by atmospheric fluctuations, optical bench vibrations, and the like, and are fast fluctuations of about 1/100 second to 1 second.

Here, as a method for dealing with the above-mentioned long-term fluctuations and short-term fluctuations, a piezo drive mirror (a piezo drive mirror is a piezo actuator mounted on a mirror holder to give a slight displacement electrically to provide precision of the mirror. The PID circuit (the PID circuit is a control using an operational amplifier) based on the position information of the optical axis of the laser beam reflected by the position detection means and reflected by the control unit. It is one of the circuits, and consists of three arithmetic circuits: proportional, integral, and differential. A certain target value is set and each of the input signals (error from the target value) is set. The operation of the piezo drive mirror is fed using Click control to perform the position control of the piezoelectric driving mirror, techniques have been proposed to suppress the fluctuation of the position of the optical axis of the reflected laser beam by the piezoelectric driving mirror.

  When dealing with long-term fluctuations by the above method, for example, a CCD camera, a C-MOS camera, and a personal computer are used as the position detection means, and image information captured from the CCD camera, the C-MOS camera, or the like is used. It was analyzed by a personal computer and the position information of the optical axis of the laser beam reflected by the piezo drive mirror was obtained.

  However, the method using a CCD camera, a C-MOS camera, and a personal computer as the position detection means described above cannot follow short-term fluctuations.

  Therefore, when dealing with short-term fluctuations by the above method, a two-dimensional position detector comprising a two-dimensional position detecting device (PSD) and its signal processing circuit is used as the position detecting means. The laser beam reflected by the drive mirror is incident on the light receiving surface of the two-dimensional position detection element in the two-dimensional position detector, and the signal output from the two-dimensional position detection element by the incidence of the laser light is output by a signal processing circuit. The position information of the optical axis of the laser beam processed and reflected by the piezo drive mirror is obtained.

  That is, the two-dimensional position detector can detect the position with a very fast response speed of several tens of μs to 100 μs, so that it is possible to detect a change in the position of the optical axis of the laser beam due to a short-term change. Become.

  The two-dimensional position detector is composed of the two-dimensional position detection element and its signal processing circuit as described above. When light enters the two-dimensional position detection element, a current corresponding to the incident position of the light is generated. This current is processed by a signal processing circuit, and the incident position of the light is detected.

  More specifically, the two-dimensional position detection element is a photodiode, and its light receiving surface is a resistance layer having a uniform resistance value. When light enters the light receiving surface, the distance from the light incident position to the electrode The current is divided and output in inverse proportion to the signal, and the signal processing circuit performs arithmetic processing on the output current, and outputs a voltage linear with the incident position as position information of the incident position of light on the light receiving surface.

However, the two-dimensional position detector can be used in a laser system using a CW (continuous) laser, but cannot be used in a laser system using a repetitive pulse laser. .

  That is, when the pulse laser beam is incident on the two-dimensional position detection element, the signal waveform (before peak hold) as shown in FIG. 1 is output from the two-dimensional position detection element. There has been a problem that proper signal processing cannot be performed.

  In other words, the signal intensity of the signal output from the two-dimensional position detection element approaches zero in the time zone in which the laser light is not incident between the pulses, and the final stage in the signal processing circuit necessary for position detection The divider would not work.

  In addition, when using continuous light or using high repetition pulse laser light that can be regarded as continuous light sufficiently faster than the response speed of a two-dimensional position detector having a repetition rate of several tens of kHz or more, the above-described problem However, the above-described problems are caused by the pulsed laser beam having a repetition rate of 10 kHz or less.

The prior art that the applicant of the present application knows at the time of filing a patent is as described above and is not an invention related to a known literature, so there is no prior art information to be described.

  The present invention has been made in view of the various problems of the prior art as described above, and the object of the present invention is to change the optical axis of a pulsed laser beam having a repetition rate of 10 kHz or less. It is an object of the present invention to provide an optical axis position detection apparatus for pulsed laser light that can detect the above.

  Another object of the present invention is to provide an optical axis position control device for pulsed laser light that can suppress fluctuations in the optical axis of pulsed laser light that is repeatedly operated at a repetition rate of 10 kHz or less. To do.

  In order to achieve the above object, the pulse laser beam optical axis position detection apparatus according to the present invention uses a trigger signal synchronized with the output of the pulse laser beam to provide a peak value of each signal waveform from the two-dimensional position detection element. Is provided with a peak hold circuit.

  In order to achieve the above object, the optical axis position control device for pulsed laser light according to the present invention includes the optical axis position detection device for pulsed laser light according to the present invention for acquiring incident position information of the pulsed laser light. It is intended to be used.

That is, according to the first aspect of the present invention, the light-receiving surface that receives the pulsed laser light is formed as a resistance layer having a uniform resistance value, and when the pulsed laser light is incident on the light-receiving surface, A two-dimensional position detection element that outputs a corresponding signal, and a signal processing circuit that processes the signal output from the two-dimensional position detection element and outputs incident position information of the pulsed laser light incident on the light receiving surface. The signal processing circuit has a peak hold for storing a peak value of each signal waveform from the two-dimensional position detecting element using a trigger signal synchronized with the output of the pulse laser beam incident on the light receiving surface. It has a circuit.

According to a second aspect of the present invention, a light receiving surface comprising a two-dimensional plane of an XY orthogonal coordinate system is provided, and when a pulse laser beam emitted from a pulse laser device is incident on the light receiving surface, the pulse According to the incident position of the laser beam, currents I _X1 and I _X2 are output as signals from the electrodes arranged on opposite sides in the X axis direction of the light receiving surface, respectively, and are opposed in the Y axis direction of the light receiving surface. using a two-dimensional position detecting element and a current I _Y1 and the current I _Y2 is output as a signal, respectively, and a current I _Y1 and the current I _Y2 output from the two-dimensional position detection element from each electrode disposed in side , subtracts the current _{I Y2} from the current _{I Y1,} a first subtracter for outputting a signal _I Y1 _{-I Y2,} the current _{I Y1} output from the two-dimensional position detecting element Using the flow _{I Y2,} current _{I Y1} and adds the current _{I Y2,} the signal _I Y1 ₊ a first adder for outputting the _{I Y2,} current output from the two-dimensional position detecting element _{I X1} and the current I using the _X2, it subtracts the current _{I X2} from the current _{I X1,} a second subtracter for outputting a signal _I X1 _{-I X2,} the current _{I X1} and the current _{I X2} output from the two-dimensional position detecting element _Is used to add the current I _X1 and the current I _X2 and output a signal I _X1 + I _X2 and a trigger signal synchronized with the output of the pulse laser beam from the pulse laser device A first peak hold circuit for storing and outputting a signal I _Y1p -I _Y2p which is a peak value of a signal waveform of the signal I _Y1 -I _Y2 output from the first subtractor; and a pulse by the pulse laser device A second signal I _Y1p + I _Y2p which is a peak value of the signal waveform of the signal I _Y1 + I _Y2 output from the first adder is stored and output using a trigger signal synchronized with the output of the laser beam. And the peak value of the signal waveform of the signal I _X1 -I _X2 output from the second subtractor using a trigger signal synchronized with the output of the pulse laser beam from the pulse laser device. Output from the second adder using a third peak hold circuit that stores and outputs the signals I _X1p -I _X2p and a trigger signal synchronized with the output of the pulse laser beam from the pulse laser device a fourth peak hold circuit configured to store the signal _I X1p _{+ I X2p} is the peak value of the signal waveform of the signal _I X1 _{+ I X2,} the first The signal _I Y1p _{-I Y2P} output from Kuhorudo circuit divided by the signal _I Y1p _{+ I Y2p} output from the second peak hold circuit, an operation result of該除calculation _{Y = I Y1p -I Y2p / I} Y1p + I _Y2p is output as the incident position information of the pulsed laser light incident on the light receiving surface, and the signal I _X1p -I _X2p output from the third peak hold circuit is the fourth peak hold. _Divide by the signal I _X1p + I _X2p output from the circuit, and output X = I _X1p −I _X2p / I _X1p + I _X2p as the calculation result of the division as the incident position information of the pulse laser beam incident on the light receiving surface And a calculation result Y obtained by the first divider is incident on the light receiving surface of the two-dimensional position detection element. Represents the Y coordinate value in the XY orthogonal coordinate system of the incident position of the pulse laser beam, and the calculation result X obtained by the second divider is the result of the pulse laser beam incident on the light receiving surface of the two-dimensional position detection element. The X coordinate value in the XY orthogonal coordinate system of the incident position is shown.

  According to a third aspect of the present invention, the light receiving surface for receiving the pulsed laser light is formed as a resistance layer having a uniform resistance value. When the pulsed laser light is incident on the light receiving surface, A two-dimensional position detection element that outputs an analog signal corresponding to the analog signal, an analog / digital converter that converts the analog signal output from the two-dimensional position detection element into a digital signal, and an output from the analog / digital converter Signal processing means for processing the received digital signal and outputting a digital signal indicating the incident position information of the pulsed laser light incident on the light receiving surface, and the signal processing means is incident on the light receiving surface. Peak hold means for storing the peak value of each signal waveform from the two-dimensional position detection element using a trigger signal synchronized with the output of the pulse laser beam It is obtained by way has.

  According to a fourth aspect of the present invention, there is provided an optical axis position control device for controlling a position of an optical axis in a pulse laser light optical axis position control device for controlling a position of an optical axis of the pulse laser light. The reflected drive mirror and the pulse laser beam reflected by the drive mirror are received to detect the incident position of the pulse laser beam, and the detection result is output as incident position information of the pulse laser beam incident on the light receiving surface. And a PID circuit for controlling the drive mirror based on the incident position information output from the optical axis position detecting device for the pulse laser beam. It is made to have.

  According to a fifth aspect of the present invention, there is provided an optical axis position control device for a pulse laser beam that controls the position of the optical axis of the pulse laser beam. A reflecting drive mirror and a pulse laser beam reflected by the drive mirror are detected to detect an incident position of the pulse laser beam, and the detection result indicates incident position information of the pulse laser beam incident on the light receiving surface. 4. The digital signal for controlling the drive mirror based on the invention according to claim 3 outputted as a digital signal and the digital signal indicating the incident position information outputted from the optical axis position detecting device of the pulse laser beam. Generating and outputting a PID control means, and a digital signal outputted from the PID control means is converted into an analog signal and outputted to the drive mirror That is obtained to have a digital / analog converter.

  According to a sixth aspect of the present invention, in the invention according to the fourth or fifth aspect of the present invention, the drive mirror is a piezo drive mirror or a voice coil drive mirror. It is intended to be.

  Since the present invention is configured as described above, the present invention has an excellent effect that it is possible to detect the fluctuation of the optical axis of the pulsed laser beam having a repetition rate of 10 kHz or less.

  In addition, since the present invention is configured as described above, it has an excellent effect that it is possible to suppress fluctuations in the optical axis of pulsed laser light that is repeatedly operated at a repetition rate of 10 kHz or less.

  Hereinafter, an example of an embodiment of an optical axis position detection device for pulse laser light and an optical axis position control device for pulse laser light according to the present invention will be described in detail with reference to the accompanying drawings.

First, FIG. 2 is a block diagram illustrating an example of an embodiment of an optical axis position detection device for pulsed laser light according to the present invention.

  An optical axis position detection device (hereinafter simply referred to as “optical axis position detection device”) 10 of the pulse laser beam according to the present invention 10 is a pulse laser device (not shown) that has a repetition rate of 10 kHz or less. The two-dimensional position detecting element 12 is formed of a photodiode that receives the pulse laser beam emitted from the two-dimensional position detecting element 12 and is formed as a resistance layer having a uniform resistance value. Subtractors 14a and 14b for subtracting signals, adders 16a and 16b for adding signals output from the two-dimensional position detecting element 12, and a trigger signal synchronized with the output of the pulse laser beam from the pulse laser device. The peak values of the signal waveforms of the signals output from the subtracters 14a and 14b and the adders 16a and 16b are stored and output. Peak hold circuits 18a, 18b, 18c, and 18d, a divider 20a that divides the peak value output from the peak hold circuit 18a and the peak value output from the peak hold circuit 18b, and the peak hold circuit 18c. The divider 20b divides the peak value and the peak value output from the peak hold circuit 18d.

More specifically, although the two-dimensional position detecting element 12 is a known element, the two-dimensional position detecting element 12 has a rectangular light receiving surface made up of a two-dimensional plane of an XY orthogonal coordinate system, and the pulse laser beam emitted from the pulse laser device on the light receiving surface. , The current I _X1 and the current I _X2 are output as signals from the electrodes respectively arranged on opposite sides in the X-axis direction of the light-receiving surface according to the incident position of the pulse laser beam, and the Y-axis of the light-receiving surface A current I _Y1 and a current I _Y2 are output as signals from the electrodes disposed on opposite sides in the direction, respectively.

The current I _Y1 and the current I _Y2 output from the two-dimensional position detection element 12 are subtracted by the subtractor 14a, and a signal I _Y1 -I _Y2 is output from the subtractor 14a.

Further, the current I _Y1 and the current I _Y2 output from the two-dimensional position detection element 12 are added by the adder 16a, and a signal I _Y1 + I _Y2 is output from the adder 16a.

On the other hand, the current I _X1 and the current I _X2 output from the two-dimensional position detection element 12 are subtracted by the subtractor 14b, and the signal I _X1 -I _X2 is output from the subtractor 14b.

Further, the current I _X1 and the current I _X2 output from the two-dimensional position detection element 12 are added by the adder 16b, and a signal I _X1 + I _X2 is output from the adder 16b.

Then, the signal I which is the peak value of the signal waveform of the signals I _Y1 -I _Y2 output from the subtractor 14a using the trigger signal synchronized with the output of the pulse laser beam from the pulse laser device by the peak hold circuit 18a. _Y1p- I _Y2p is stored and output.

Similarly, the signal I which is the peak value of the signal waveform of the signal I _Y1 + I _Y2 output from the adder 16a using the trigger signal synchronized with the output of the pulse laser beam from the pulse laser device by the peak hold circuit 18b. _Y1p + I _Y2p is saved and output.

Further, the signal I which is the peak value of the signal waveform of the signal I _X1 -I _X2 output from the subtractor 14 b using the trigger signal synchronized with the output of the pulse laser beam from the pulse laser device by the peak hold circuit 18 c. _X1p- I _X2p is stored and output.

Similarly, the signal I which is the peak value of the signal waveform of the signal I _X1 + I _X2 output from the adder 16b by using the trigger signal synchronized with the output of the pulse laser beam from the pulse laser device by the peak hold circuit 18d. _X1p + I _X2p is stored and output.

The divider 20a divides the signal I _Y1p −I _Y2p output from the peak hold circuit 18a by the signal I _Y1p + I _Y2p output from the peak hold circuit 18b, and Y = I _Y1p −I _Y2p / I _Y1p + I _Y2p is acquired.

Further, the divider 20b divides the signal I _X1p −I _X2p output from the peak hold circuit 18c by the signal I _X1p + I _X2p output from the peak hold circuit 18d, and X = I _X1p −I which is the calculation result. _X2p / I _X1p + I _X2p is acquired.

  The calculation result Y acquired by the divider 20a indicates the Y coordinate value in the XY orthogonal coordinate system of the incident position of the pulsed laser light incident on the light receiving surface of the two-dimensional position detection element 12, and is acquired by the divider 20b. The calculated result X indicates the X coordinate value in the XY orthogonal coordinate system of the incident position of the pulsed laser light incident on the light receiving surface of the two-dimensional position detection element 12.

The light incident on the light receiving surface of the two-dimensional position detection element 12 is calculated by the arithmetic processing using the current I _X1 , the current I _X2 , the current I _Y1 , and the current I _Y2 output from the two-dimensional position detection element 12. Since the method for obtaining the XY coordinate value of the incident position is a known method, detailed description thereof is omitted.

In the above configuration, in the optical axis position detection device 10, the peak hold circuits 18a, 18b, 18c, and 18d are provided in the previous stage of the dividers 20a and 20b, so that the output is synchronized with the output of the pulse laser light of the pulse laser device. The peak value of each signal waveform from the two-dimensional position detection element 12 can be stored using the trigger signal that has been removed, and can be output to the dividers 20a and 20b.

  That is, the signal waveform (after the peak hold) shown in FIG. 1 is a signal waveform after the peak hold circuit 18a, 18b, 18c, 18d holds the peak value and stores the peak value, and the next pulse enters. Until the signal strength is maintained.

  For this reason, even in the time zone in which the laser beam is not incident between the pulses, the final-stage dividers 20a and 20b in the signal processing circuit necessary for position detection can be made to function.

The optical axis position detection device 10 described above is a signal processing circuit located at the subsequent stage of the two-dimensional position detection element 12, that is, subtracters 14a, 14b, adders 16a, 16b, peak hold circuits 18a, 18b, 18c, Although the case where 18d and the dividers 20a and 20b are constructed by analog circuits has been described, it is needless to say that the present invention is not limited to this.

  That is, when the signal processing circuit located at the subsequent stage of the two-dimensional position detection element 12 is constructed by a digital circuit, the analog signal output from the two-dimensional position detection element 12 is converted to an analog / digital (A / D) converter. It can be converted into a digital signal using a computer, loaded into a computer, and peak value detection and addition / subtraction / division can all be realized by processing by a software program.

Next, an example of an embodiment of an optical axis position control device for pulsed laser light according to the present invention will be described.

  FIG. 3 shows a laser system using an optical axis position control device for pulsed laser light according to the present invention (hereinafter simply referred to as “optical axis position control device” as appropriate) provided with the optical axis position detection device 10 described above. An example of a block configuration explanatory diagram is shown.

  This laser system 100 is a system that can be used when pulse laser light is incident on a hollow fiber in order to generate high-intensity femtosecond laser light by hollow fiber pulse compression.

  Such a laser system 100 is reflected by a titanium sapphire laser device 102 having a repetition rate of 1 kHz as a pulse laser device, a total reflection mirror 104 that reflects pulse laser light emitted from the titanium sapphire laser device 102, and a total reflection mirror 104. A piezo drive mirror 106 that reflects the pulse laser beam, a beam splitter 108 that divides the pulse laser beam reflected by the piezo drive mirror 106 into two optical paths, and a pulse laser beam in one of the optical paths branched by the beam splitter 108. , The total reflection mirror 112 that reflects the pulse laser light in the other optical path branched by the beam splitter 108, and the light of the pulse laser light reflected by the piezo drive mirror 106. The optical axis position detection device 10 arranged so that the pulse laser beam reflected by the total reflection mirror 112 serving as a position detection means for detecting the position information of the two-dimensional position detection element 12 is incident on the light receiving surface of the two-dimensional position detection element 12; And a PID circuit 114 for inputting outputs from the dividers 20a and 20b of the shaft position detecting device 10.

  Here, a trigger signal, which is a synchronization signal for synchronizing with the output of the pulse laser beam from the titanium sapphire laser device 102, is input from the titanium sapphire laser device 102 to the optical axis position detection device 10.

  In the laser system 100, the optical axis position detection device 10, the piezo drive mirror 106, and the PID circuit 114 constitute an optical axis position control device for pulsed laser light according to the present invention.

In the above-described configuration, in the laser system 100 described above, the pulsed laser light emitted from the titanium sapphire laser device 102 is reflected by the piezo drive mirror 106 via the total reflection mirror 104 and is split into two optical paths by the beam splitter 108. Branch off.

  Then, the pulse laser beam of one of the two optical paths branched by the beam splitter 108 enters the hollow fiber 110.

  On the other hand, the pulse laser beam in the other of the two optical paths branched by the beam splitter 108 is incident on the light receiving surface of the two-dimensional position detection element 12 in the optical axis position detection device 10 via the total reflection mirror 112. The optical axis position detection apparatus 10 outputs the XY coordinate value of the incident position of the pulsed laser light incident on the light receiving surface of the two-dimensional position detecting element 12 to the PID circuit 114 as the positional information of the optical axis of the pulsed laser light. .

  The details of the operation of the optical axis position detection apparatus 10 are as described above, and thus detailed description thereof is omitted.

  The PID circuit 114 feedback-controls the drive operation of the piezo drive mirror 106 based on the position information of the optical axis of the pulse laser beam detected and output by the optical axis position detection device 10 to control the position of the piezo drive mirror. And the fluctuation of the position of the optical axis of the pulse laser beam reflected by the piezo drive mirror 106 is suppressed.

Accordingly, in the laser system 100, the final stage dividers 20a and 20b in the signal processing circuit necessary for position detection in the optical axis position detection device 10 are provided even in a time zone in which the laser light is not incident between pulses. As a result, the fluctuation of the position of the optical axis of the pulsed laser beam reflected by the piezo drive mirror 106 can be reliably suppressed.

For this reason, in the laser system 100,
a. It is possible to prevent the incident end face of the hollow fiber from being damaged by the irradiation of the pulse laser beam. B. It is possible to suppress fluctuations in the spectral broadening of the pulsed laser light after emission from the hollow fiber. C. An excellent effect is obtained that the fluctuation of the power of the pulsed laser light after emitting the hollow fiber can be suppressed.

The laser system 100 described above is synchronized with the output of the pulse laser beam output from the titanium sapphire laser device 102 as position detection means for detecting the position information of the optical axis of the pulse laser beam reflected by the piezo drive mirror 106. Unlike the conventional technique described in “Background Art” only in that it includes an optical axis position detection device 10 that operates by inputting the trigger signal, based on the position information of the detected optical axis of the pulsed laser light, The technique of feedback control of the driving operation of the piezo drive mirror 106 using the PID circuit 114 to suppress the fluctuation of the optical axis position of the pulsed laser light is the same as the conventional technique.

Here, FIGS. 4A and 4B show an example of the results of an experiment performed using the laser system 100. FIG.

  In this experiment, a known two-dimensional position detection device is arranged in place of the hollow fiber 110, and the fluctuation of the optical axis of the pulsed laser light to be incident on the hollow fiber 110 is measured by this two-dimensional position detection device. Ah.

  FIG. 4A shows a distribution of measured optical axis positions when feedback control of the piezo drive mirror 106 using the optical axis position detection device 10 is not performed.

  On the other hand, FIG. 4B shows a distribution of measured optical axis positions when feedback control of the piezo drive mirror 106 is performed using the optical axis position detection device 10.

  As shown in FIGS. 4A and 4B, when the above feedback control is not performed, a fluctuation range of approximately 150 μm is observed, but when the above feedback control is performed, The fluctuation range was suppressed to +/− 4 μm (1 μm by RMS).

Here, when frequency analysis is performed on the data shown in FIGS. 4A and 4B by using Allan variance, a graph shown in FIG. 5 is obtained.

  As is clear from FIG. 5, by performing feedback control, fluctuation components up to approximately 100 Hz (0.01 seconds or more in the integration time in FIG. 5) were suppressed.

Note that the laser system 100 described above includes signal processing circuits located downstream of the two-dimensional position detection element 12, that is, subtracters 14a and 14b, adders 16a and 16b, peak hold circuits 18a, 18b, 18c, and 18d, and division. Although the example using the optical axis position detection device 10 in which the devices 20a and 20b are constructed by analog circuits is shown, the two-dimensional position detection element 12 is used instead of the optical axis position detection device 10 in which the signal processing circuit is constructed by an analog circuit. Of course, an optical axis position detecting device in which a signal processing circuit located in the subsequent stage is constructed by a digital circuit may be used.

  In this case, the PID control executed by the PID circuit 114 is also performed by controlling the software program on the computer without providing the PID circuit 114, and the digital signal output from the computer after the PID control is executed. A digital / analog (D / A) converter converts the signal into an analog signal, and the piezo drive mirror 106 may be set to be feedback-controlled by the converted analog signal.

Further, the above-described embodiment may be modified as shown in (1) to (4) described below.

  (1) In the above-described embodiment, the piezo drive mirror is used to change the optical axis of the pulse laser beam. However, the present invention is not limited to this, and instead of the piezo drive mirror, For example, a voice coil drive mirror or the like may be used.

  (2) In the above-described embodiment, the case where the present invention is used for suppressing the fluctuation of the optical axis of the pulse laser beam in the hollow fiber pulse compression has been described, but it is needless to say that the present invention is not limited to this. For example, you may use this invention for suppression of the fluctuation | variation of the optical axis of the pulse laser beam in laser processing.

  (3) In the above-described embodiment, the two-dimensional position detection element is provided with a rectangular light receiving surface composed of a two-dimensional plane of the XY orthogonal coordinate system, but the shape of the light receiving surface is limited to a rectangular shape. Needless to say, any shape such as a square shape can be appropriately selected.

  (4) The above-described embodiment and the modifications shown in (1) to (3) above may be used in appropriate combination.

  The present invention can be used for laser processing using pulsed laser light, spatial light communication, energy transmission, optical measurement, and the like.

FIG. 1 is a waveform diagram for explaining the prior art and the present invention. FIG. 2 is a block diagram illustrating an example of an embodiment of an optical axis position detection apparatus for pulsed laser light according to the present invention. FIG. 3 is a block diagram illustrating an example of a laser system using the optical axis position control device for pulsed laser light according to the present invention. 4 (a) and 4 (b) show an example of the results of an experiment conducted using a laser system using the optical axis position control device for pulsed laser light according to the present invention, and FIG. 4 (a) shows the light according to the present invention. FIG. 4B is a graph showing a distribution of measured optical axis positions when feedback control of the piezo drive mirror using the axial position detection apparatus is not performed, and FIG. 4B is an optical axis position detection apparatus according to the present invention. 6 is a graph showing a distribution of measured optical axis positions when feedback control of a piezo drive mirror is performed using the sq. FIG. 5 is a graph showing the results of frequency analysis performed on the data shown in FIGS. 4A and 4B using Allan variance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical axis position detection apparatus 12 Two-dimensional position detection element 14a, 14b Subtractor 16a, 16b Adder 18a, 18b, 18c, 18d Peak hold circuit 20a, 20b Divider 100 Laser system 102 Titanium sapphire laser apparatus 104 Total reflection mirror 106 Piezo drive mirror 108 Beam splitter 110 Hollow fiber 112 Total reflection mirror 114 PID circuit

Claims (6)

A light-receiving surface that receives the pulsed laser light is formed as a resistance layer having a uniform resistance value, and when the pulsed laser light is incident on the light-receiving surface, a two-dimensional position detection element that outputs a signal corresponding to the incident position;
A signal processing circuit that processes a signal output from the two-dimensional position detection element and outputs incident position information of a pulsed laser beam incident on the light receiving surface;
The signal processing circuit includes a peak hold circuit that stores a peak value of each signal waveform from the two-dimensional position detection element using a trigger signal synchronized with the output of the pulsed laser light incident on the light receiving surface. An optical axis position detection apparatus for pulsed laser light. A light-receiving surface comprising a two-dimensional plane of an XY orthogonal coordinate system, and when the pulse laser beam emitted from the pulse laser device is incident on the light-receiving surface, in the X-axis direction of the light-receiving surface according to the incident position of the pulse laser light The current I _X1 and the current I _X2 are output as signals from the electrodes arranged on the opposite sides, respectively, and the currents I _Y1 and I I are respectively output from the electrodes arranged on the opposite sides in the Y-axis direction of the light receiving surface. A two-dimensional position detection element from which _Y2 is output as a signal;
Using the current _{I Y1} and the current _{I Y2} output from the two-dimensional position detecting element, it subtracts the current _{I Y2} from the current _{I Y1,} a first subtracter for outputting a signal _I Y1 _{-I Y2,}
Using the current _{I Y1} and the current _{I Y2} output from the two-dimensional position detecting element, the sum of the current _{I Y1} and the current _{I Y2,} a first adder which outputs a signal _I Y1 _{+ I Y2,}
Using the current _{I X1} and the current _{I X2} output from the two-dimensional position detecting element, it subtracts the current _{I X2} from the current _{I X1,} a second subtracter for outputting a signal _I X1 _{-I X2,}
Using the current _{I X1} and the current _{I X2} output from the two-dimensional position detecting element, the sum of the currents _{I X1} and the current _{I X2,} a second adder for outputting a signal _I X1 _{+ I X2,}
A signal I _Y1p -I _Y2p which is a peak value of the signal waveform of the signals I _Y1 -I _Y2 output from the first subtractor using a trigger signal synchronized with the output of the pulse laser beam by the pulse laser device. A first peak hold circuit for storing and outputting
A signal I _Y1p + I _Y2p which is a peak value of the signal waveform of the signal I _Y1 + I _Y2 output from the first adder is stored using a trigger signal synchronized with the output of the pulse laser beam from the pulse laser device. A second peak hold circuit that outputs the
A signal I _X1p -I _X2p which is a peak value of a signal waveform of the signals I _X1 -I _X2 output from the second subtractor using a trigger signal synchronized with the output of the pulse laser beam by the pulse laser device. A third peak hold circuit for storing and outputting
The signal I _X1p + I _X2p which is the peak value of the signal waveform of the signal I _X1 + I _X2 output from the second adder is stored using a trigger signal synchronized with the output of the pulse laser beam from the pulse laser device. And a fourth peak hold circuit that outputs
The signal I _Y1p −I _Y2p output from the first peak hold circuit is divided by the signal I _Y1p + I _Y2p output from the second peak hold circuit, and Y = I _Y1p − A first divider that outputs I _Y2p / I _Y1p + I _Y2p as incident position information of a pulsed laser beam incident on the light receiving surface;
The signal I _X1p −I _X2p output from the third peak hold circuit is divided by the signal I _X1p + I _X2p output from the fourth peak hold circuit, and X = I _X1p − A second divider that outputs I _X2p / I _X1p + I _X2p as incident position information of the pulsed laser light incident on the light receiving surface;
The calculation result Y obtained by the first divider indicates the Y coordinate value in the XY orthogonal coordinate system of the incident position of the pulsed laser light incident on the light receiving surface of the two-dimensional position detection element, and the second division. The calculation result X acquired by the detector indicates the X coordinate value in the XY orthogonal coordinate system of the incident position of the pulse laser beam incident on the light receiving surface of the two-dimensional position detection element. Position detection device. A light-receiving surface that receives pulsed laser light is formed as a resistance layer having a uniform resistance value, and when pulsed laser light is incident on the light-receiving surface, a two-dimensional position detection element that outputs an analog signal corresponding to the incident position;
An analog / digital converter that converts an analog signal output from the two-dimensional position detection element into a digital signal and outputs the digital signal;
Signal processing means for processing a digital signal output from the analog / digital converter and outputting a digital signal indicating incident position information of the pulsed laser light incident on the light receiving surface;
The signal processing means includes peak hold means for storing a peak value of each signal waveform from the two-dimensional position detection element using a trigger signal synchronized with the output of the pulsed laser light incident on the light receiving surface. An optical axis position detection apparatus for pulsed laser light. In the optical axis position control device for the pulse laser beam that controls the position of the optical axis of the pulse laser beam,
A drive mirror that reflects the target pulse laser beam for controlling the position of the optical axis;
The pulse laser beam reflected by the drive mirror is received, the incident position of the pulse laser beam is detected, and the detection result is output as incident position information of the pulse laser beam incident on the light receiving surface. Item 3. An optical axis position detection device for pulsed laser light according to any one of items 2;
An optical axis position control apparatus for pulsed laser light, comprising: a PID circuit that controls the drive mirror based on the incident position information output from the optical axis position detection apparatus for the pulsed laser light. In the optical axis position control device for the pulse laser beam that controls the position of the optical axis of the pulse laser beam,
A drive mirror that reflects the target pulse laser beam for controlling the position of the optical axis;
The pulse laser beam reflected by the drive mirror is received, the incident position of the pulse laser beam is detected, and the detection result is output as a digital signal indicating the incident position information of the pulse laser beam incident on the light receiving surface. Item 3. An optical axis position detection device for pulsed laser light according to Item 3,
PID control means for generating and outputting a digital signal for controlling the drive mirror based on a digital signal indicating the incident position information output from the optical axis position detection device of the pulse laser beam;
An optical axis position control device for pulsed laser light, comprising: a digital / analog converter that converts a digital signal output from the PID control means into an analog signal and outputs the analog signal to the drive mirror. In the optical-axis position control apparatus of the pulse laser beam of any one of Claim 4 or Claim 5,
The drive mirror is a piezo drive mirror or a voice coil drive mirror. An optical axis position control device for pulsed laser light.

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