JPS58147616A - Device for observing pulse light repeated at high speed - Google Patents

Abstract

PURPOSE:To display streak images for many pulse light beams on the fluorescent surface of a streak tube simultaneously, by providing a sine wave oscillator generating a sine wave whose frequency is slightly different from the pulse light, and utilizing the output as a deflecting voltage. CONSTITUTION:The sine wave whose frequency is different from the pulse light by DELTAf is sent from the sine wave oscillator 7. In a mixer 8, the signal transmitted from a synchronous amplifier 5 is mixed with the sine wave sent from the sine wave oscillator 7. A low pass filter 9 passes a frequency region, which is lower than a frequency that is slightly higher than DELTAf, and the result is inputted to an input terminal 101 of a comparator 10. A potentiometer 103 is connected to an input terminal 102 of the comparator 10. When the input voltage at the input terminal 101 becomes larger than the input voltage at the input terminal 102, a pulse is sent from the comparator 10. A monostable multivibrator 11 is operated by the output of the comparator. A gate voltage is sent by a gate pulse generator 12. Said gate voltage is applied to a photoelectric surface 31 of the streak tube 3 and a microchannel plate 32.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high (2) rate repeating pulsed light observation device that uses a streak device to observe a pulsed light train that is repeatedly generated at high speed.

A streak device is used to observe high-speed pulsed light. First, the general configuration of this streak device will be briefly explained. The streak device is mainly composed of a streak tube having a photocathode, a deflection electrode, and a fluorescent surface. A deflection voltage for deflecting photoelectrons directed from the photocathode toward the fluorescent surface is supplied to the deflection electrode from a deflection power source. The pulsed light from the light source is split by an optical system, and one part is guided to the photocathode of the streak tube, and the other part is guided to a light receiving element provided with a trigger for starting the deflection power source.

Photoelectrons traveling from the photocathode to the fluorescent surface are deflected by a deflection electrode. The difference in the generation time of photoelectrons is converted into the distance on the fluorescent surface, and the density of photoelectrons is converted into the magnitude of the brightness of the fluorescent surface and displayed.

There is a desire to use such a streak device to display and observe two or more consecutive light emissions in a pulsed light train that is repeatedly generated at high speed on the lli surface. This is because if two or more pulsed lights can be displayed on one screen, changes between those pulsed lights can be compared.

The duration of the output pulse light of the dye laser and each light pulse of the light emission phenomenon that is excited by the output pulse light of the dye laser is extremely short, 1 to 1000 picoseconds. On the other hand, the repetition period of the output pulse light of the dye laser and the return period of the light emission phenomenon excited by this period are 5 to 12 nanoseconds. Therefore, the proportion of the light emitting portion during the repeated cycle is about 115 to 1/12000. If the time axis on the fluorescent surface is set so that two or more light emissions in such a pulsed light train appear consecutively on the fluorescent surface, the length on the fluorescent surface allotted to one light pulse will be extremely short. Become. The pulsed light train duty ratio is 1/100.
2 of the fluorescent surface where the effective length of the streak tube is 10 mm.
When a number of light pulses appear on the phosphor surface, the length on the phosphor surface allotted to one light pulse is only 0.11. In other words, only two light emissions are displayed at the expense of the temporal resolution of the streak image, and detailed comparison between the light pulses is not possible. The object of the present invention is to provide continuous (lj
An object of the present invention is to provide an observation device for high-speed repetitive pulsed light that can display streak images of J2 or more pulsed light without any interval or adjacently with a small interval. In order to achieve the above object, an observation device for high-speed repetitive pulsed light according to the present invention is provided on a charging surface.

a streak tube including a gate electrode, a deflection electrode, and a fluorescent surface; a first sine wave oscillator that generates a synchronized first sine wave; and a first sine wave oscillator that generates a synchronized first sine wave. and I with a slightly different frequency
a second sine wave oscillator that generates 82 sine waves;
a phase detector that detects a point in time when a certain phase relationship occurs between the sine wave of si and the second sine wave and generates a detection output; and a plurality of sine waves of the s It is comprised of a gate pulse generator that outputs a gate pulse that lasts for a period equal to or longer than a cycle, and connecting means that connects the gate pulse to the gate electrode of the streak tube and the output of the second sine wave oscillator to the deflection electrode. There is.

According to the above configuration, a plurality of consecutive pulsed lights can be displayed continuously without the intervals between (5) and (4) parts where no pulsed light exists, so that the object of the present invention can be completely achieved.

Hereinafter, the operating principle of the apparatus of the present invention will be explained first, and then the embodiments will be explained in detail.

The sine wave output from the first sine wave oscillator that generates the first sine wave in synchronization with the high-speed repetitive pulsed light input to the photocathode of the streak tube is f1=A sin ω4t, a sine wave whose frequency is slightly different from that of the pulsed light. The second wave generating wave
The second sine wave output from the sine wave oscillator is f2=Bsin
ωbt and Hata.

The phase detector detects the first sine wave fr = A sinω
It detects the point in time when a certain phase relationship occurs between at and the second sine wave f2 =Bsin a+b, and sends out a detection output.

This phase detector includes a mixer for mixing the first sine wave and the second sine wave, a low-pass filter for extracting the low-frequency component from the output of the mixer, and a low-pass filter for extracting the low-frequency component from the output of the mixer. It can be composed of a level detector that detects the output level of the device.

(6) The output f'-r, X f2 of the mixer that mixes the first sine wave and the second sine wave is given by the following equation.

f' =AxBsin ωa t −5in ωb t
= (AxB/2) (cos(ωa-ωb)t-c
os (ωa + ωb) t) Since ωa and ωb are only slightly different, ωa - ωb is small, and ωa + ωb#2
Good as ωa. The composite wave f' is ωa + ωb and ωa − ωb
Since it passes through a low-pass filter with a cutoff frequency between f' - (AXB/2) cos (ωa - ωb) t
only passes through. This is a so-called beat wave.

The output of this low-pass filter f' = (AxB/2) cos(ωa-ωb)
By detecting with a level detector that t has reached a predetermined level, it is possible to detect the point in time when a certain phase relationship occurs between ωa and 05. The constant phase (ωa-ωb)t to be detected will be described in detail later using an example. In short, f1 = Asinωat represents the phase of the photoelectron flow in the optical pulse and the stream caused by it.
In order to make this photoelectron flow correspond sequentially to the deflection electric field, the phase at the start of the sweep of the second sine wave Bs1nωbt used to generate the deflection electric field is made to have a certain correspondence to the phase of fl =A sinωat.

The gate pulse generator receives the detection output of the phase detector and outputs a gate pulse that lasts for a period longer than a plurality of cycles of the output of the first sine wave oscillator.

This gate pulse is applied to the gate electrode of the streak tube via the connection means. .

The pulse width of this gate pulse corresponds to the entire period including a plurality of pulsed lights intended to appear as a streak image on the fluorescent surface of the streak tube.

The gate electrode of the streak tube allows the photoelectron flow to pass toward the phosphor surface only while this gate pulse is applied.

The output sine wave B sinωbt of the second sine wave oscillator is connected to the deflection electrode of the streak tube by a connecting means. During the period in which the gate pulse is applied to the gate electrode of the streak tube, the sine wave B sinωb
The vicinity where t becomes zero is used to generate a deflection electric field.

Each time this deflection electric field is generated, a photoelectron flow caused by the optical pulse portion passes through the deflection electrode portion and appears sequentially on the fluorescent surface.

Pulse light period 2π/ωa and deflection electric field period 2π/ωb
Since the images are slightly different from each other, the streak images of each pulsed light appear on the fluorescent surface with slight shifts in sequence, so they do not overlap.

Furthermore, the period! ! 2π (1/ωa-1/ωb) is equal to or slightly larger than the width of the pulsed light. Furthermore, a streak image appears on the fluorescent surface only during the period when the output pulse of the phase detector is applied to the gate electrode.

It is desirable that the streak image of the optical pulse that first appears after the gate electrode of the streak tube is in a state of allowing passage of the photoelectron flow is located at one end of the fluorescent surface of the streak tube on the sweep start side. This condition is based on the phase of the pulsed light (actually it is necessary to take into account the delay time until it reaches the deflection electrode, but it can be considered that it has a certain correspondence with the phase of the first sine wave) and the polarization ( 9) (8) Determined by the relationship with the phase of the second sine wave which is the output of the second sine wave oscillator that determines the self-position.

Since these phase differences appear as the output of the low-pass filter, it is sufficient to determine the detection level of a level detector that detects the output level of the low-pass filter of the phase detector. The detection level at which this phase should be detected can be calculated from any delay time, deflection sensitivity of the streak tube, and amplitude of the second sine wave applied to the deflection electrode. However, in reality (or ultimately) it is easier to adjust the detection level of the level detector included in the phase detector while observing the streak image.

Next, a more detailed explanation will be given with reference to Examples.

FIG. 1 is a block diagram showing an embodiment of a pulsed light observation device according to the present invention.

The dye laser oscillator 1 is a light source that repeatedly emits light at high speed. This dye laser oscillator 1 is capable of emitting laser light with a pulse width of 5 picoseconds at an arbitrary repetition period in the frequency range of 80 to 200 MHz (17).

The anti-transparent mirror 2 forming the beam splitter has the above-mentioned (10
) The output light of the dye laser oscillation B1 is branched into two streams.

One of the branched pulsed laser beams is made incident on the charging surface 31 of the streak tube 3 through an optical system consisting of a reflecting mirror, a slit lens, an optical path length variable device 20, and the like. A first sine wave oscillator that generates a first sine wave that is synchronized with the high-speed repetitive pulse light manually applied to the photocathode 31 of the streak tube 3 is connected to the beam splitter and the PIN photodiode 4.
．． It consists of a tuned amplifier 5.

The other of the branched pulsed laser beams is made incident on the PIN photodiode 4 of the first sine wave oscillator. PIN photodiode 4 is a charging element with extremely fast response speed.
Outputs a pulsed current in response to the incidence of pulsed laser light. The output of the PIN photodiode 4 is connected to a tuned amplifier 5.

The tuned amplifier 5 can operate at any frequency in the range of 80 to 200 MHz as a center frequency. The center frequency is set equal to the oscillation frequency of the dye laser, and the tuned amplifier 5 sends out a first sine wave synchronized with the repetition frequency of the output pulse of the PIN photodiode 4. The frequency counter 6 counts and displays the frequency of the first sine wave sent out by the tuned amplifier 5.

The sine wave oscillation B7 forms a second sine wave oscillator that generates a second sine wave having a slightly different frequency from the pulsed light. The sine wave oscillator 7 is an oscillator that can send out a sine wave of any frequency within the frequency range of 80 to 200 MH2.

A phase detector detects a point in time when a fixed phase relationship occurs between the output of the first sine wave oscillator and the output of the second sine wave oscillator, and generates a detection signal.

This phase detector includes a mixer 8 that mixes the output of the first sine wave oscillator and the output of the second sine wave oscillator, and a low-pass filter that extracts the low frequency component from the output of the mixer 8. 9, and a level detector 10 for detecting the output level of the low-pass filter 9.

An example will be described below in which the dye laser oscillator l emits pulsed light at a frequency of 100 MHz.

Since the dye laser oscillation 'al sends out pulsed light at a frequency of 100 MHz, the frequency of the dye laser oscillation 'al is 100 MHz from the tuned amplifier 5.
A first sine wave of Hz is transmitted, and the frequency counter 6 displays 100 MHz.

The operator reads the 100 MHz display on the frequency counter 6 and turns the sine wave oscillator 7 to (100+Δf) MHz (Δf
Adjust to send out the second sine wave of <<100).

The mixer 8 outputs the output of the first sine wave oscillator, that is, the first sine wave f, (100 MH2) sent out by the tuned amplifier 5 and the second sine wave f2 (100 MH2) sent out by the second sine wave oscillator 7.
0+Δf) MHz and mix f=f.

A composite wave of X f2 is sent out.

f=fl xf2 = A 5in (2X108π)t X B sin (2X 108tt + 2 πΔ
f) -AxB/2 (cos2 nΔft-co
s (4X 108n + 2 rtΔf)t) An example of the configuration of the mixer 8 is shown in FIG. The mixer 8 is composed of a ring modulator, and a first
The second sine wave f which is the output of the second sine wave oscillator is input from the terminal (13) (12) 82.
2 is input, and the synthesized wave shown in the previous example is output from the terminal 83.

The low-pass filter 9 is a low-pass filter that passes components in a frequency range slightly lower than the roaring frequency than the frequency Δf. Therefore, the low-pass filter 9 uses the output wave of the mixer 8 as f' =
(AXB/2) Only cos2gΔr-t is allowed to pass.

The output terminal of the low-pass filter 9 is connected to one input 101 of a comparator 10 constituting a level detector, and the sine wave f' is input to the input terminal 101 of the comparator. Comparator 1
The other input end 102 of the 0 is connected to the sliding end of a 1 meter 103. The comparator lO has a voltage input to the input terminal 101 that is thicker than a voltage input to the input terminal 102 (
Sends a pulse when

The output terminal of the comparator IO is connected to the input terminal of the monostable multi-bi break 11.

The monostable multivibrator 11 is activated at the rising edge of the output pulse of the comparator 11, and is turned off after a certain period of time (14). This fixed time will be described later.

The gate pulse generator 12 sends out a gate voltage when the output of the monostable multi-bi break is in the on state.

The output of the gate pulse generator 12 is connected to the photocathode 31 of the streak tube 3 and the output end electrode of the microchannel plate 32 via a capacitor 13.

When the gate voltage is generated, -800 volts is applied to the photocathode 31, and +900 volts is applied to the output end side electrode of the microchannel plate 32.
A voltage of volts is applied respectively. The $2 sine wave output from the sine wave oscillator 7 is amplified by the drive amplifier 14 and applied to the deflection electrode 33 of the streak tube 3. The amplitude of the sine wave applied to this deflection electrode 33 is 1150 volts from -575 volts to +575 volts, which is +100 volts.
Volts to -100 volts are used for the sweep.

A photocathode 31 is formed on the inner wall of the entrance surface of the airtight container 30 of the streak tube 3, and a fluorescent surface 34 is formed on the other inner wall.
is formed.

(15) A mesh electrode 35 between them. Focusing electrode 36. Aperture electrode 37. Deflection electrode 33. Microchannel plates 32 are arranged in sequence. Micro channel 71/7
'L/-) 32 input end side electrode and aperture electrode 3
7 is grounded. Power supply 21 and dividing resistors 22 and 23
.

24, potentials of 14,000 volts are applied to the photocathode 31, -4,200 volts to the mesh electrode, and 14,500 volts to the focusing electrode. The fluorescent surface 34 is connected to the output end electrode of the microchannel plate 32 by a power supply 25.
A potential higher than 0 volts is applied.

When no gate voltage is applied by the gate pulse generator 12, photoelectrons cannot pass through the mesh electrode 35. Further, at this time, since no multiplied electrons are emitted from the microchannel plate 32, the fluorescent surface 34 is kept in a dark state.

When a gate voltage is applied by a gate pulse generator, photoelectrons from the fluorescent surface 31 are accelerated by the potential of the mesh electrode 35. The accelerated photoelectrons are focused on the aperture of the aperture electrode 37 by the electron lens formed by the focusing electrode 36 and enter the region between the two electrode plates of the deflection electrode 33. Here, when a voltage is applied to the deflection electrode 33, the photoelectrons are deflected. In this example, the deflection voltage is +10
The incident position of photoelectrons is designed to move from the upper end of the microchannel plate 32 to the lower end when changing from 0 volts to -100 volts. Photoelectrons incident on the microchannel plate 32 are multiplied and incident on the fluorescent surface 34, forming a streak image. Fluorescent surface 34
The effective distance in the streak tube sweep direction is 10 m.

Next, the conditions for making the first streak image of continuous pulsed light appear near the upper end of the fluorescent surface 34 and the reason why they are successively spaced at appropriate intervals and do not overlap will be explained with reference to the drawings.

In FIG. 3, (A) shows the optical output of the dye laser oscillator l. Let this frequency be 100MHz. The first sine wave (B) tuned to this output has the same < 100
It is MHz. The oscillation frequency is 100.5MH in the same figure (C).
2 shows the output waveform of the second sine wave oscillator 7 of No. 2.

In the same figure (D), the gate pulse generator 12 sends out (17
) (It)J shows the gate drive voltage waveform.

Now, if the time point when the phases of the first sine wave f1 and the second sine wave completely match is set as the reference time point (to), then f' and '1+ f2 when t seconds have passed from that point are expressed by the following formulas, respectively. is given by

f' = coslOπt fH= sin (200X 10 πt) f2 =
sin (201X 10 πt)The above f,,
When a time point when a 90 degree phase difference occurs between f2 is detected and the gate pulse is connected to the gate electrode of the streak tube, the gate of the streak tube opens and photoelectrons first reach the deflection electrode 33 of the streak tube. The group is fluorescent surface 3
It is assumed that the adjustment is made so that it is brought closer to the upper end of 4.

In the vicinity of the optical pulse (0) shown in FIG. 3(A), the f,...
Assuming that a predetermined phase difference occurs between f2, a gate pulse (D) that lasts 100 ns appears from this point (precisely speaking, just before that). And this gate pulse (D
) is caused to contribute to the deflection (118).

The fluorescent surface 34 is swept when the phase of f2 is from 19° to 9°.
It is between 1710° and 189°.

Note that the time point when changing from 1710 to 1890 is in the middle of successive photoelectron current pulses, and since there is no photoelectron current pulse in the region of the deflection electrode 33, no image appears on the fluorescent surface 34 due to this sweeping.

The sweep time of the fluorescent surface is from 9.95 nanoseconds for one period of f2 (
9950 picoseconds) x (180/3600)
= 500 picoseconds, and the sweep speed is 10ml1/5
00 picoseconds - 20ao + every nanosecond.

Next, referring to Figure 14, fl and f near the optical pulse (0)
The relationship between the two will be explained.

This figure exaggerates the time axes of other waveforms near the phase zero of the first sine wave to facilitate understanding of the phase relationship between the phase zero point of the first sine wave and the second sine wave. This is what is shown.

Photoelectron current pulse I (0) caused by light pulse (0)
The moment when the beam enters the deflection region of the deflection electrode 33 (this point in time will be referred to as tr as the second reference point in time).

), it is assumed that the phase of the first sine wave is zero. Note that by adjusting the optical path length from the dye laser oscillator 1 to the photocathode 31 using the optical path variable device 20, the photoelectrons can be made to reach the region of the deflection electrode 33 at an arbitrary phase point of fl.

At this time, the second sine wave is advanced by a predetermined angle δ (180-9=171) degrees than the first sine wave. The phase detector detects just before this and generates the gamer pulse G.

The voltage applied to the deflection electrode by the second sine wave at the second reference time r is +100V. This causes the photoelectron current pulse (0) to be deflected to correspond to the uppermost side of the fluorescent surface.

At the moment when the next photoelectron current pulse I (1) enters the deflection region of the deflection electrode 33 (after 10 nanoseconds from the reference time tr, the phase of the first sine wave is zero), the second sine wave From the sine wave of δ (180-9= 171 > + 1.8
It will be in a state that has advanced by a degree. And the deflection voltage for I (1) is lower than that for I (0) and I
The image (1) appears below the image (0) on the fluorescent surface. The above 1.8 degrees is 10nsX (1,8/360
) = 0.05ns = 1mm above the fluorescent surface at 50ps
corresponds to

At the same moment when the next photoelectron current pulse I (2) enters the deflection region of the deflection electrode 33 (20n from the reference time tr)
After s has elapsed, the second sine wave becomes δ(180-9=171)+I:
It will be in a state where it has advanced by 8x2 degrees. and! The deflection voltage for (2) is 1 lower than that for (1) l
The image (2) appears below the image of the fluorescent surface kl (1).

Generally speaking, at the moment when the i-th photoelectron current pulse I(i) enters the deflection region of the deflection electrode 33 (after i x 1Ons have passed from the reference time tr, the phase of the first sine wave is zero), the The second sine wave is δ(180-9=1
71) The state is advanced by −1,8×i degrees. And I
The deflection voltage for I(i-1) is lower than that for I(i-1), and the image of l(i) is 1(i-1) on the fluorescent surface.
appears below the statue.

1(0) and 1(11) are shown in FIG. 3 (CG), and the waveform diagram of the M2 sine wave corresponding to these is shown in the same figure (H(21) (20)).

Figure 5 (A) is a schematic diagram of the streak image appearing on the fluorescent surface. Figure 5 (B) shows the photoelectron flow pulse
Indicates the correspondence with

In the device according to the present invention, a second sine wave oscillator that generates a sine wave having a frequency slightly different from that of the pulsed light is provided, and the second sine wave output from this oscillator is used as a deflection voltage. Streak images corresponding to a large number of pulsed lights can be displayed at once on a surface. That is, in the apparatus according to the present invention, a plurality of streak images of optical pulses of an optical pulse train with a small duty ratio can be displayed in close proximity to each other on the fluorescent surface of the streak tube without lowering the resolution. It became possible to compare.

The duration of the luminescence that is the object of observation is expected to vary depending on the woodcutter. However, this problem can be solved by arbitrarily adjusting the distance between the streak images by changing the frequency of the second sine wave to a91.

The device according to the present invention is provided with a gate pulse generator that receives the detection output (22) of the phase detector and outputs a gate pulse that lasts for a period (necessary time) longer than a plurality of cycles of the output of the first sine wave oscillator. , the device is designed to operate substantially only during the period when this gate voltage is generated. Therefore, outside this period, the thermionic current is multiplied and the fluorescent surface 3
4 and emit light, raising the level of the background of the fluorescent surface. Therefore, the streak image can be observed in extremely good condition.

Various modifications can be made to the embodiments described in detail above within the scope of the present invention.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a waveform observation device for continuous repeating pulsed light according to the present invention. Figure w42 is a circuit diagram showing an example of the configuration of a mixer used in the device. Figure $3 is a waveform diagram C for explaining the operation of the circuit No. 11. - FIG. 4 is a waveform diagram for explaining the phase relationship near the second reference time point. FIG. 5 is an explanatory diagram showing the correspondence between the streak image appearing on the fluorescent surface and the photoelectron current pulse I. It is a graph. ■... Dye laser oscillator 2... Anti-transparent mirror (beam splitter) 3... Streak tube 30... Airtight container 31... Photocathode 32...
Microchannelzolate 33...deflection electrode
34... Fluorescent surface 35... Network electrode 36...
Focusing electrode 37...Aperture electrode 4...PIN photodiode 5...Tuned amplifier 6...Frequency counter 7...(2nd) Sine wave oscillator 8...Mixer 9...Low frequency Filter 10... Comparator 11... Monostable multivibrator (23) 12... Gate pulse generator Patent applicant Hamamatsu Telehi Co., Ltd. Agent Patent attorney Hisashi Inoro (25) (24)

Claims (3)

[Claims] (1) A streak tube including a photocathode, a gate electrode, a deflection electrode, and a fluorescent surface, and an Ill sine wave oscillator that generates a first sine wave synchronized with high-speed repetitive pulse light input to the photocathode of the streak tube. and a second sine wave oscillator that generates a second sine wave having a frequency slightly different from that of the pulsed light, and a point at which a certain phase relationship occurs between the first sine wave and the second sine wave. a phase detector that detects and generates a detection output; a gate pulse generator that receives the detection output of the phase detector and outputs a gate pulse that lasts for a period longer than a plurality of cycles of the first sine wave; and the gate l1lIjI! of high-speed repetitive pulsed light consisting of connecting means for connecting the pulse to the gate electrode of the streak tube and the output of the second sine wave oscillator to the deflection electrode. Device. (1) (2) The first sine wave oscillator that generates the first sine wave that is synchronized with the high-speed repetitive pulsed light input to the photocathode of the streak tube generates the first sine wave that is synchronized with the high-speed repetitive pulsed light input to the photocathode of the streak tube. Claim 1, comprising: a beam splitter for splitting and taking out a part of the beam; a light-receiving element for converting the branched output of the beam splitter; and a tuned amplifier synchronized with the output of the light-receiving element. An observation device for high-speed repetitive pulsed light. (3) The phase detector includes a mixer that mixes the first sine wave and the second sine wave, a low-pass filter that extracts the low frequency component from the output of the mixer, and the 2. An observation device for high-speed repetitive pulsed light according to claim 1, comprising a level detector for detecting the output level of a low-pass filter.