JP2007047466A - Laser apparatus, method of modulating laser and laser microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely stabilize a laser beam at low cost even at a low emitting intensity without using such an optical component as a filter. <P>SOLUTION: A laser apparatus comprises: a laser light source; a laser modulator which modulates the intensity of the laser light emitted from the laser light source; a light quantity measurement part which measures the light quantity of the laser light; a variable amplifier part 27 which amplifies the light quantity signal S<SB>1</SB>measured with the light quantity measurement part; a control part 29 which controls the laser modulator on the basis of the light quantity signal S<SB>1</SB>amplified with the variable amplifier part 27; and an amplitude setting part 28 which so sets the amplitude S<SB>3</SB>of the variable amplifier part 27 that the amplified light quantity signal S<SB>2</SB>input to the control part 29 becomes a predetermined signal level according to the light quantity signal S<SB>1</SB>measured with the light quantity measurement part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laser device, a laser modulation method, and a laser microscope.

Conventionally, in order to stabilize the noise and fluctuation of laser light in a laser device, a part of the laser light including a plurality of wavelengths is branched by a beam splitter and the wavelength is selected by an exchangeable filter, and the laser having the selected wavelength is selected. A method is known in which light is detected by a photodetector and laser output and laser intensity modulation are performed based on the detected light quantity signal of the laser light (see, for example, Patent Document 1).
JP-A-11-231222

However, when changing the emission intensity of the laser light applied to the sample with a wide dynamic range, for example, 0.1% to 100%, it depends on the input resolution of the detection signal system that detects the laser light. There is an inconvenience that the fluctuation amount of the detectable signal is limited.
For example, even when the detector itself has a high resolution, when the detected light amount signal is converted into a digital signal by a 12-bit A / D converter, the A / D converter is used when the output intensity is 100%. When the gain is set so that the input range becomes 100%, the light amount signal having an intensity of 0.1% is converted into a 4LSB digital signal.

In this case, the signal of 1 LSB, which is the minimum unit of detection, is 25% of the signal having an intensity of 0.1%, and can only detect a change in the amount of light more than that, and can only detect a change in units of 25%. become. As a result, there is a problem that it is difficult to stably control the laser beam with high accuracy at a low emission intensity.
The above problem can be solved by increasing the resolution of all the components, but in that case, there is a problem that the cost becomes high.

  The present invention has been made in view of the above-described circumstances, and can use a laser apparatus that can stabilize laser light with high accuracy even at low emission intensity without using an optical component such as a filter, An object is to provide a laser modulation method and a laser microscope.

In order to achieve the above object, the present invention provides the following means.
The present invention relates to a laser light source, a laser modulation device that modulates the intensity of laser light emitted from the laser light source, a light amount measuring unit that measures the amount of laser light, and a light amount signal measured by the light amount measuring unit. A variable amplification unit, a control unit for controlling the laser modulation device based on the light amount signal amplified by the variable amplification unit, and an amplification input to the control unit according to the light amount signal measured by the light amount measurement unit Provided is a laser device including an amplification factor setting unit that sets an amplification factor of a variable amplification unit so that the light amount signal thus obtained has a predetermined signal level.

  According to the present invention, the light amount of the laser light whose intensity is modulated by the laser modulation device is measured by the light amount measurement unit, and the measured light amount signal is amplified by the variable amplification unit and then input to the control unit. In this case, the amplification factor of the variable amplification unit is set by the operation of the amplification factor setting unit so that the light amount signal input to the control unit has a predetermined signal level.

  In other words, when the measured light quantity is small, a large amplification factor is applied, and when the light quantity is large, a small amplification factor is applied, both of which are amplified so as to have the same signal level and then input to the control unit. Thus, even when the signal is fine, it is possible to close up the fluctuation and input it to the control unit to control the laser modulator. As a result, it is possible to emit laser light having a low emission intensity that is stabilized with high accuracy at a low cost without using an optical component such as a filter.

In the above invention, the predetermined signal level is preferably 50% or more and 90% or less of the input dynamic range of the control unit.
More preferably, the predetermined signal level is about 80% of the input dynamic range of the control unit.

In the above invention, the amplification factor setting unit applies a negative offset to the light amount signal in accordance with the light amount signal measured by the light amount measurement unit, and then the amplified light amount signal input to the control unit. It is preferable to set the amplification factor of the variable amplification unit so that becomes a predetermined signal level.
This makes it possible to transmit the fluctuation of the light amount signal to the control unit with higher sensitivity for the laser light with low emission intensity, and to emit the stabilized laser light with higher accuracy. It becomes.

In the invention described above, a storage unit may be provided that stores the amplification factor set by the amplification factor setting unit in association with the light amount signal of the laser beam.
By doing so, the laser beam can be stabilized quickly and easily by reading the amplification factor from the storage unit without calculating the amplification factor each time the light amount signal varies.

In the above invention, the storage unit may store the amplification factor, the wavelength information of the laser light, and the emission intensity information in association with each other.
This makes it possible to quickly set the amplification factor when the wavelength and the emission intensity of the laser light are switched.

In the invention described above, a storage unit may be provided that stores the amplification factor and the offset amount set by the amplification factor setting unit in association with the light amount signal of the laser beam.
Further, the storage unit may store the amplification factor and the offset amount, the wavelength information of the laser beam, and the emission intensity information of the laser beam in association with each other.

  Further, in the above invention, a shutter unit that switches between passing and blocking of the laser beam between the light amount measuring unit and the sample is provided, and the shutter unit performs laser beam during the setting of the gain and the modulation of the laser intensity. Is preferably blocked. By doing so, the sample can be protected by preventing the sample from being irradiated with useless laser light during the setting of the amplification factor and the modulation of the laser intensity.

Moreover, this invention provides a laser microscope provided with one of the said laser apparatuses.
According to the present invention, a laser beam with low emission intensity can be stabilized with high accuracy and irradiated onto a sample, and a signal such as fine fluorescence emitted from the sample fluctuates due to fluctuations in the emission intensity of the laser beam. It is possible to perform observation with high accuracy.

The present invention also provides a laser modulation method for measuring the amount of laser light emitted from the laser light source, amplifying the measured light amount signal, and modulating the intensity of the laser light based on the amplified light amount signal. Provided is a laser modulation method for setting an amplification factor so that an amplified light amount signal has a predetermined signal level.
According to the present invention, since the measured light quantity signal is amplified so as to have a predetermined level, even when the emission intensity is low, the fluctuation of the laser beam is detected with high sensitivity and stabilized with high accuracy. Laser beam can be output.

In the above invention, the amplification factor setting unit performs amplification after applying a negative offset to the light amount signal in accordance with the light amount signal measured by the light amount measuring unit, and the amplified light amount signal has a predetermined signal level. It is preferable to set the amplification factor so that.
This makes it possible to transmit the fluctuation of the light amount signal to the control unit with higher sensitivity for the laser light with low emission intensity, and to emit the stabilized laser light with higher accuracy. It becomes.

  According to the present invention, there is an effect that laser light can be stabilized with high accuracy without using optical components such as a filter at low cost, particularly when the emission intensity is low.

A laser apparatus 1, a laser modulation method, and a laser microscope 2 according to an embodiment of the present invention will be described below with reference to FIGS.
A laser apparatus 1 according to this embodiment is used in a laser microscope 2 shown in FIG. The laser microscope 2 includes a laser light source device 3, an optical scanning device 4 that two-dimensionally scans the laser light L emitted from the laser light source device 3, and collects the scanned laser light L to form an intermediate image. A pupil projection lens 5 that forms an image, an imaging lens 6 that condenses the laser light L that forms an intermediate image to be substantially parallel light, and further condenses the laser light L that is condensed by the imaging lens 6. Then, the objective lens 8 that irradiates the sample A on the stage 7 and the fluorescence F that is generated in the sample A and returns through the objective lens 8, the imaging lens 6, the pupil projection lens 5, and the optical scanning device 4 are laser light. A dichroic mirror 9 that branches from L, a dichroic mirror 10 that further branches the branched fluorescence F for each wavelength, and a plurality of photodetectors 11 that respectively detect the branched fluorescence F are provided.

Between the laser light source device 3 and the optical scanning device 4, a light amount detection device 12 for detecting the light amount of the laser light L emitted from the laser light source device 3 is provided. Further, a shutter 13 that opens and closes the optical path is provided between the light amount detection device 12 and the optical scanning device 4. As the shutter 13, a mechanical shutter, an electromagnetic shutter, an AOM (acousto-optic modulator: Acousto-Optic)
Modulator), EOM (Acousto-Optic Modulator) or MOM (Magneto-Optic Modulator)
Modulator) can be used.

  Further, the intensity of the laser light L emitted from the laser light source device 3 is controlled by the control unit 14 based on a detection signal from the light amount detection device 12. The control unit 14 also performs opening / closing control of the shutter 13.

The laser light source device 3 includes an argon laser light source 15 capable of simultaneously oscillating a plurality of laser beams L having wavelengths λ = 458 nm, 488 nm, and 514.5 nm, and a laser diode (LD) that oscillates a laser beam having a wavelength λ = 405 nm. 16 and AOTF (Acousto-Optic Tunable) for intensity modulation and wavelength switching of the laser light L emitted from the argon laser light source 15
Filter: acousto-optic variable wavelength filter) 17. The laser diode 16 can adjust its output itself by an output command signal from the control unit 14. The laser light L emitted from the argon laser light source 15 and the laser diode 16 is combined by a dichroic mirror 18. In the figure, reference numeral 19 denotes a mirror.

  The light quantity detection device 12 is disposed between the laser light source device 3 and the shutter 13, and a beam splitter 20 that branches a part of the laser light L emitted from the laser light source device 3 and combined by the dichroic mirror 18; A spectroscopic device 21 such as a prism that splits the laser beam L branched by the beam splitter 20 for each wavelength, and a photodetector 22 such as a photodiode that detects the intensity of the split laser beam L for each wavelength. ing.

The optical scanning device 4 is, for example, a so-called proximity galvanometer mirror in which two galvanometer mirrors (not shown) that are swung around two axes orthogonal to each other are arranged close to each other.
In the figure, reference numeral 23 is a mirror, reference numeral 24 is a confocal lens, reference numeral 25 is a confocal pinhole, and reference numeral 26 is a bandpass filter.

As shown in FIG. 2, the control unit 14 amplifies the light amount signal S ₁ of the laser light L input from the light detector 22 of the light amount detection device 12, and is amplified by the variable amplifier 27. and the light quantity signal S ₂ is the amplification factor setting unit 28 for setting the amplification factor S ₃ of the variable amplifier 27 such that the predetermined signal level, which is amplified by the amplification factor S ₃ set by the amplification factor setting unit 28 based on the light quantity signal _{S 2,} and a CPU29 for calculating the intensity modulation instruction signal _{S 4} to AOTF17.

The control unit 14 also has an input unit 30 for setting the emission intensity and wavelength of the laser beam L, the emission intensity and wavelength of the laser beam input by the input unit 30, and output command values to the AOTF 17 and the laser diode 16. a storage unit 31 is connected to the association with each and S _4. When the emission intensity and wavelength of the laser beam L are input from the input unit 30, the storage unit 31 is searched using the input emission intensity and wavelength as a key, and the output command value S to the corresponding AOTF 17 and laser diode 16. ₄ is read out.

Amplification factor setting unit 28, for example, a reference signal generator 32 for outputting a reference signal S ₀ representing the signal level as a target, amplified by the reference signal S ₀ and the variable amplifier 27 from the reference signal generator 32 a differentiator 33 for calculating a difference between the light quantity signal _{S 2,} is constituted by said CPU 29. CPU29 is the difference signal S ₅ from the differentiator 33 and determines whether a zero (or less than a predetermined value), if not zero, and changes the amplification factor S ₃ (e.g., incremented by a predetermined value), the zero If it is (or less than a predetermined value), so that the writing in the memory 31 a gain S ₃ at that time in association with the emission intensity and wavelength of the laser beam L.
Here, the target signal level is preferably in the range of about 50 to 80% of the input dynamic range of the control unit 14, and more preferably about 80%. In the present embodiment, by setting the value of 80% as a signal level as a reference signal S _0.

In the figure, reference numeral 34 is A / D converter for converting the difference signal _{S 5} into a digital signal, reference numeral 35 is a D / A converter for converting the output from the CPU29 into an analog signal. After amplification factor S ₃ is once set, as long as the emission intensity and the wavelength of the laser light source device 3 is not changed, the amplification factor S ₃ of the variable amplifier 27 is adapted to be fixed to that value.

In the present embodiment, the work for setting the amplification factor S ₃ of the variable amplifier 27 is adapted to be performed in a state that blocks the light path by the shutter 13.
That is, when the sample A is irradiated with the laser beam L, a raster scan method is adopted in which two galvanometer mirrors are reciprocally swung to irradiate in one direction, and as shown in FIG. It is common to irradiate only the area where the moving speed is stable (area surrounded by the solid line B). In this case, the shutter 13 is operated during the movement of the galvano mirror in the other direction and between the lines in the return direction so that the sample A is not irradiated with the laser beam L.
Therefore, in the present embodiment, the gain setting operation of the variable amplifier 27 is performed during the return operation of the galvanometer mirror (during the operation indicated by the broken line in the drawing).

The operation of the laser apparatus 1 and the laser microscope 2 according to the present embodiment configured as described above will be described below.
According to the present embodiment, when the emission intensity and wavelength of the laser light L are set from the input unit 30, the control unit 14 searches the storage unit 31 and outputs an output command value S to the AOTF 17 and the laser diode 16. ₄ is read out. Then, the control unit 14 reads the output command value S ₄ and outputs the AOTF17 and laser diode 16, the emission intensity and wavelength corresponding to the output command value S ₄ from an argon laser light source 15 and laser diode 16 of the laser beam L Let it emit.

  In the present embodiment, for example, the laser beam L having a wavelength of 514.5 nm is set to be emitted from the argon laser light source 15. Accordingly, the laser light L having two types of wavelengths is emitted from the laser diode 16 together with the laser light L having a wavelength of 405 nm.

At this time, the control unit 14 starts an amplification factor setting operation for the variable amplifier 27. The control unit 14, the amplification factor setting operation, so as not to vary the output command value S ₄ to AOTF17 and laser diode 16 from the control unit 14, sets off the feedback. In the following, since the work for the argon laser light source 15 and the work for the laser diode 16 are the same, only the laser light source 15 will be described.

Then, as described above, while the shutter 13 is closed, the laser light L emitted from the laser light source 15 is branched by the beam splitter 20, split by the spectroscopic device 21, and detected by the photodetector 22. .
The light amount signal S ₁ of the laser light L from the laser light source 15 detected by the light detector 22 is amplified by being input to the variable amplifier 27. In the initial state, the amplification factor S ₃ of the variable amplifier 27 is set to a very small value (e.g., zero). Then, the amplified light quantity signal S _2, by being inputted to the differentiator 33, is compared with a reference signal S _0. Difference signal _{S 5} output from the differentiator 33 is inputted to the CPU 29 are digitized in the A / D converter 34, the difference signal _{S 5} whether zero (less than a predetermined value) is determined at CPU 29.

If the difference signal _{S 5} non-zero (or less than a predetermined value) in the CPU 29, the gain _{S 3} is incremented gain _{S 3} of the variable amplifier 27 is rewritten in the CPU 29, the work is repeated. Then, when the difference signal S ₅ is determined to be zero (or less than a predetermined value), the amplification factor S ₃ at that time, in association with the wavelength and the emission intensity information of the laser beam L that is emitted at that time It is written in the storage unit 31. In this state, the control unit 14 sets feedback to on. Thus, the output command value _{S 4} to AOTF17 and laser diode 16 is adjusted based on the detected intensity signal _{S 1.}

In this case, according to the laser device 1, the laser modulation method, and the laser microscope 2 according to the present embodiment, the light amount input to the differentiator 33 regardless of the emission intensity of the laser light L emitted from the laser light source device 3. since the signal level of the signal S ₂ is amplified so as to be equal in signal level, in particular, when the emission intensity of the laser beam L is low, to increase the detection sensitivity of the change, to perform good correction operation There is an advantage that you can.

Specifically, in the example as described above, when the emission intensity of the laser beam L is 0.1% so that 80% of the signal level, the gain S ₃ is set to about 800. As a result, the amplified light quantity signal _{S 2} becomes a signal 3276LSB the A / D converter, therefore, it is possible to detect the variation of 0.03% in the intensity signal _{S 2.}
Therefore, according to the laser apparatus 1, the laser modulation method, and the laser microscope 2 according to the present embodiment, the AOTF 17 and the laser light L can be stabilized with high accuracy even when the emission intensity of the laser light L is low. it is possible to adjust the output command value S ₄ to the laser diode 16.

  Then, according to the laser microscope 2 according to the present embodiment, as described above, the laser light L can be stabilized with high accuracy at any emission intensity from low emission intensity to high emission intensity. Therefore, it is possible to prevent the light amount of the very fine fluorescence F emitted from the light from fluctuating due to the intensity fluctuation of the laser light L, and to obtain an accurate observation result. In particular, there is an advantage that proper observation can be performed by adjusting the emission intensity of the laser light L so as not to fluctuate even if a temperature drift of the optical component due to a change in environmental temperature occurs.

Further, according to the laser microscope 2 according to the present embodiment, since the amplification factor setting operation is performed with the shutter 13 closed, the laser beam L unnecessary for observation is irradiated on the sample A during the operation. It is possible to prevent the occurrence of inconvenience such as fading of the sample A.
The amplification factor setting operation may be performed by setting the photodetector 22 as a multi-division photodiode, providing a plurality of amplification factor setting units 28 in parallel for a plurality of wavelengths, or performing a single amplification factor. The setting unit 28 may perform time division while switching the AOTF 17 and the laser diode 16.

In the present embodiment, the amplification factor S ₃ of the variable amplifier 27, it is assumed that automatically search to be set when the emission intensity and wavelength of the laser beam L is switched, alternatively, by switching between the laser beam emitting intensity and wavelength of the L, for example, working to obtain an amplification factor S ₃ by switching to the exit intensity of 0.1% to 100% of the laser beam L in increments of 0.1% pre Place, gain S ₃ obtained may be stored in the storage unit 31 together with the radiation intensity and wavelength information of the laser beam L to. During actual observation, the storage unit 31 is searched based on the emission intensity and wavelength information of the laser light L input from the input unit 30, and the amplification factor stored corresponding to the emission intensity and wavelength is stored. setting the variable amplifier 27 to S _3. By doing in this way, in addition to the above effect, it is not necessary to perform the amplification factor setting operation every time the wavelength or the emission intensity of the laser beam L is changed, and the laser beam L can be quickly emitted immediately after the start of the emission of the laser beam L. There is an advantage that the emission intensity can be stabilized with high accuracy.

Further, the variable amplifier 27 used in the present embodiment may be constituted by an integrator. In this case, the amplification factor S ₃ is managed by the time accumulating a charge in the integrator.
Also, the laser light source device 3 has been described by taking the argon laser light source 15 and the laser diode 16 as an example, but instead of this, the laser light L in the wavelength range from ultraviolet to near infrared, continuous output or femtosecond units. Any gas laser, solid state laser, or dye laser capable of pulse output may be used. Further, as a modulation element for modulating the emission intensity of the laser light L, EOM or MOM may be used instead of the AOTF 17.

Next, a laser device 1, a laser modulation method, and a laser microscope 2 according to a second embodiment of the present invention will be described with reference to FIG.
The laser device 1, the laser modulation method, and the laser microscope 2 according to the present embodiment are different from the laser device 1, the laser modulation method, and the laser microscope 2 according to the first embodiment in the configuration of the amplification factor setting unit 50. In the description of the present embodiment, portions having the same configuration as those of the laser device 1, the laser modulation method, and the laser microscope 2 according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In this embodiment, the amplification factor setting unit 50, as shown in FIG. 4, and an adder 51 for adding the offset value S ₆ in front of the variable amplifier 27. Further, with respect to the reference signal generating unit 32, CPU 29 is adapted to be able to adjust the reference signal _{S 7.}

Specifically, the amplification factor setting operation in the present embodiment is performed according to the following procedure.
First, the first, in the same way as the laser device 1 according to the first embodiment, searches for a gain S ₃ of the variable amplifier 27, the amplification factor S ₃ which is searched temporarily sets. That is, as the reference signal _{S 7,} and sets 80% of the input range of the A / D converter 34, the amplification factor _{S 3} the amplified light quantity signal _{S 2} is 80% of the signal level inputted to the CPU29 tentative Is set.

Second, the amplification factor _{S 3} of the variable amplifier 27, fixed to the amplification factor _{S 3} which is provisionally set, as the reference signal _{S 7,} 50% or less of the value of the input range of the A / D converter 34, for example, Set 10%. At this point, since the amplified intensity signal S ₂ is set to 80% of the input range of the A / D converter 34, the output from the differentiator 33 has a negative value. Therefore, CPU 29 until the output of the differentiator 33 becomes zero, decrements the offset value _{S 6} to be input to the adder 51. When the difference signal S ₅ output from the differentiator 33 becomes zero, the offset value S ₆ at that time is stored in the storage unit 31.

Third, to secure the offset value _{S 6} to be input to the adder 51, as the reference signal _{S 7,} 20 to 80% of the value of the input range of the A / D converter 34, for example, 50% is set. Then, the same amplification factor setting operation as in the first embodiment is performed again. That is, the amplification factor S ₃ which is temporarily set in the above, will further incremented, when the output of the differentiator 33 when is zero CPU29 determines, records the amplification factor S ₃ at that time in the memory 31 And set feedback on.

According to the laser device 1, the laser modulation method, and the laser microscope 2 according to the present embodiment configured as described above, the negative offset value S ₆ is set to the detected light amount signal S ₁ , thereby further increasing the value. can be set amplification factor S ₃ and will, in particular, in the case emission intensity of the laser beam L is low, detection of a variation in the intensity of the laser light L with high sensitivity, can be transmitted to the CPU 29. Therefore, it is possible to detect the fluctuation in the intensity of the finer laser beam L and easily stabilize it.

In the present embodiment, the case where the offset value S ₆ and the amplification factor S ₃ are automatically searched and set has been described, but instead, the intensity and wavelength of the laser light L are previously determined prior to observation. The offset value S ₆ and the amplification factor S ₃ may be measured in association with and stored in the storage unit 31. By doing so, the offset value S ₆ and the amplification factor S ₃ can be set as soon as the wavelength and the emission intensity of the laser beam L are specified from the input unit 30. The output intensity can be quickly stabilized.

FIG. 5 shows an example of the relationship between the setting of the amplification factor S ₃ , the image acquisition and the update of the output command value S ₄ , and the opening / closing operation of the shutter 13.
According to this figure, when the emission intensity and wavelength of the laser beam L are set and the process is started, first, amplification factor setting work is performed for all wavelengths used. Next, the feedback (FB) is set to OFF, the shutter 13 is opened, laser scanning for one screen is performed, and then the shutter 13 is closed. In this state, feedback is set to ON, the output command value S ₄ for all wavelengths are used has been updated, then updated and closing the image acquisition and output command value S ₄ of the shutter 13 is repeated.

In this figure, made the update of the output command value S ₄ for each laser beam scanning of one screen, it is also possible to update the output command value S ₄ each time one line scanning. By doing in this way, the emitted intensity of the laser beam L can be stabilized more accurately.

1 is an overall configuration diagram showing a laser microscope according to a first embodiment of the present invention. It is a block diagram which shows the amplification factor setting part with which the control part of the laser microscope of FIG. 1 is equipped. It is a schematic diagram which shows the relationship between the scanning range of the laser beam by the laser microscope of FIG. 1, and the irradiation range of the laser beam to a sample. It is a block diagram which shows the gain setting part provided in the control part of the laser microscope which concerns on the 2nd Embodiment of this invention. 2 is a flowchart showing a relationship between irradiation of a sample with laser light by the laser microscope of FIG. 1, output intensity update, and shutter on / off.

Explanation of symbols

L laser light S ₁ light quantity signal S ₂ amplified light quantity signal S ₃ gain S ₆ offset value (offset)
DESCRIPTION OF SYMBOLS 1 Laser apparatus 2 Laser microscope 12 Light quantity detection apparatus (light quantity measurement part)
13 Shutter (shutter part)
15 Argon laser light source (laser light source)
16 Laser diode (laser light source)
17 AOTF (Laser Modulator)
27 Variable amplification unit 28, 50 Gain setting unit 29 CPU (control unit)
31 Memory unit

Claims (12)

A laser light source;
A laser modulation device for modulating the intensity of the laser light emitted from the laser light source;
A light amount measuring unit for measuring the amount of laser light;
A variable amplification unit for amplifying the light amount signal measured by the light amount measurement unit;
A control unit for controlling the laser modulation device based on the light amount signal amplified by the variable amplification unit;
An amplification factor setting unit for setting the amplification factor of the variable amplification unit so that the amplified light amount signal input to the control unit has a predetermined signal level according to the light amount signal measured by the light amount measurement unit; Laser apparatus provided.   The laser apparatus according to claim 1, wherein the predetermined signal level is 50% or more and 90% or less of an input dynamic range of the control unit.   The laser apparatus according to claim 2, wherein the predetermined signal level is about 80% of an input dynamic range of the control unit.   The amplification factor setting unit applies a negative offset to the light amount signal according to the light amount signal measured by the light amount measuring unit, and then the amplified light amount signal input to the control unit has a predetermined signal level. The laser device according to claim 1, wherein the amplification factor of the variable amplification unit is set as described above.   5. The laser device according to claim 1, further comprising a storage unit configured to store the amplification factor set by the amplification factor setting unit in association with a light amount signal of laser light.   The laser device according to claim 5, wherein the storage unit stores the amplification factor, the wavelength information of the laser beam, and the emission intensity information of the laser beam in association with each other.   The laser apparatus according to claim 4, further comprising a storage unit that stores the amplification factor and the offset amount set by the amplification factor setting unit in association with a light amount signal of laser light.   The laser apparatus according to claim 7, wherein the storage unit stores the amplification factor and offset amount, wavelength information of laser light, and emission intensity information of laser light in association with each other. A shutter unit that switches between passing and blocking of laser light between the light amount measuring unit and the sample,
9. The laser device according to claim 1, wherein the shutter unit blocks laser light during setting of an amplification factor and modulation of laser intensity.   A laser microscope provided with the laser apparatus according to claim 1. Measure the amount of laser light emitted from the laser light source,
Amplifies the measured light signal,
A laser modulation method for modulating the intensity of laser light based on an amplified light quantity signal,
A laser modulation method for setting an amplification factor so that an amplified light quantity signal has a predetermined signal level.   The amplification factor setting unit amplifies after applying a negative offset to the light amount signal according to the light amount signal measured by the light amount measuring unit, and the amplification factor so that the amplified light amount signal becomes a predetermined signal level. The laser modulation method according to claim 11, wherein:

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