JP2536997B2 - Solid strike camera - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a streak camera, and more particularly to a solid streak camera for measuring spatial intensity change by directly scanning pulsed light from a light source.

[0002]

2. Description of the Related Art A high-speed pulsed light measurement, which has been put into practical use at present and has the highest speed, includes a method of using a streak camera, which is used for measuring various high-speed light phenomena. High-speed pulsed light measurement with a streak camera will be briefly described with reference to FIG. The pulsed light P _L from the light source is incident on the slit 602, and the slit image of the pulsed light P _L is converged and imaged at a predetermined position on the photocathode 604 via the lens 603. Electrons are emitted on the photocathode 604 by the photoelectric effect of the pulsed light P _L. The electrons emitted from the photocathode 604 are accelerated by the mesh-shaped acceleration electrode 605 and converged by the convergent electron lens 611. The electrons converged by the converging electron lens 611 pass through the deflection field of the deflection plate 606 and form a streak image on the fluorescent screen 607. The deflecting plate 606 has a sweep voltage V _S generated from the trigger signal at the timing corresponding to the pulsed light by the sweep generator.
Are scanned and electrons passing through the deflection field of the deflection plate 606 are scanned (in this figure, scanning is performed from the top to the bottom). Therefore, the temporal intensity change of the pulsed light P _L is converted into the spatial intensity change in the scanning direction to form a streak image of the phosphor screen 607. This streak image is photographed by a still camera or a video camera (not shown), and the temporal intensity change of the pulsed light P _L is measured.

When measuring high-speed pulsed light with a streak camera, it is desirable that the image formed on the photocathode 604 formed by the input optical system is small in order to improve the time resolution, so the slit 602 is preferably thin. On the other hand, in order to increase the sensitivity, it is better that the light amount is large. Regarding this contradictory problem, in the invention described in "JP-A-62-50626",
Resolved by the same applicant. In the present invention, a glass rod is provided in the input optical system to increase the amount of light and equivalently pass through a narrow slit.

[0004]

In the above-described streak camera, when an attempt is made to obtain a measurement result by an electric signal, "light →
Since the conversion of "electron → light → electron" is performed, this is
Further simplification is considered. When the measurement light is directly scanned and converted into an electric signal, the device is significantly downsized and simplified, convenience such as portability is increased, and light in a wavelength region where photoelectric conversion is difficult (for example, infrared light). ) Will be able to measure. Further, in the measurement of the optical phenomenon, it is desirable to measure each wavelength in order to understand the phenomenon in detail. However, in the streak camera described above, it is necessary to prepare a streak camera for each wavelength, which is a large scale problem.

[0005]

In order to solve the above-mentioned problems, a solid streak camera of the present invention comprises an electro-optic crystal whose refractive index changes according to the strength of an electric field generated inside according to an applied voltage. A first means for causing pulsed light having a plurality of discrete wavelengths that have been incident to travel through the electro-optical crystal while changing the voltage applied to the electro-optical crystal with time, and scanning in a first direction; Second means for dispersing the scanned pulsed light in the first direction according to the wavelength (for example,
A prism, a diffraction grating, etc.), and third means for detecting the dispersed pulsed light according to the dispersed direction and reading the detection signal at the timing of the read pulse corresponding to the pulsed light. The “solid” of the solid streak camera means that the medium at the time of deflection is not a vacuum like the conventional streak camera but a solid substance such as an electro-optic crystal.

[0006]

In the solid-state streak camera of the present invention, the first means allows the incident pulsed light to pass through the electro-optic crystal whose refractive index or refractive index distribution changes with time, so that the incident pulsed light is In the scanning direction, the temporal intensity change of the pulsed light is converted into a spatial intensity change in the scanning direction. The scanned light is dispersed by the second means in the first direction according to the wavelength and its course is changed. Then, by the third means, the dispersed pulsed light is detected according to the dispersed direction, and is read as a detection signal corresponding to the pulsed light at the timing of the read pulse. Since the pulsed light is dispersed and the path changes depending on the wavelength, the detection signal has a component corresponding to each wavelength. As a result, a temporal intensity change corresponding to each wavelength of the pulsed light can be obtained.

[0007]

An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a solid-state streak camera according to a first embodiment of the present invention. This solid-state streak camera has a polarizer 102, an aperture 103, an optical deflector 104, and a Fourier transform lens 10 as an optical system of pulsed light detection means.
5, an image sensor 106, and a controller 121, a high voltage circuit 1 as a control system of the pulsed light detection means
Have 23. Further, it has a dispersion prism 107.

The polarizer 102 is a pulsed light P _L from the light source.
Is converted into linearly polarized light having a predetermined polarization direction, and the aperture 103 allows only light having a predetermined diameter to pass through the polarizer 102. The optical deflector 104 changes the direction of incident light according to the magnitude of the sweep voltage V _S. As the optical deflector 104, one having a structure as shown in FIGS. 2 to 3 using a crystal having electro-optical properties is used. The optical deflector shown in FIG. 2 is of a so-called double prism type, and is formed by laminating two prism-shaped crystals with their optical axes reversed. When a sweep voltage V _S is applied in the vertical direction of this double prism type optical deflector, the direction of incident light is bent at an angle proportional to the voltage. The optical deflector of FIG. 3 is a so-called quadruple electrode type, and applies a sweep voltage V _S to deflect incident light as shown in the figure. The polarization direction of the linearly polarized light output from the polarizer 102 is determined according to the direction of the optical principal axis of the electro-optic crystal of the optical deflector 104. Then, the polarizer 102, the aperture 103, and the optical deflector 10
4, and the high-voltage circuit 123 in the light deflection means (first means)
Is configured.

The Fourier transform lens 105 is the optical deflector 1
The light that has passed through 04 is condensed and Fourier-transformed on the image sensor 106 to form a far-field image. The dispersion prism 107 wavelength-disperses the light passing through the Fourier transform lens 105 in a direction substantially the same as the deflection direction of the optical deflector 104, and changes its path according to the wavelength. That is, the position of focusing is changed according to the wavelength. In this case, the path of the light of the short wavelength λ ₂ is bent more than that of the light of the long wavelength λ ₁ , and the light is condensed in the lower part of the figure. Image sensor 1
Reference numeral 06 denotes a one-dimensional image sensor, which is provided at a position where the light whose path is bent by the dispersion prism 107 is condensed, in parallel to the wavelength dispersion direction. The image sensor 106 converts into an electric signal for each condensing position, and outputs this electric signal as a detection signal V _OUT according to the read pulse V _READ . The image sensor 106 includes
An array element of InSb or Ge is also used for receiving infrared light.

The controller 121 generates a sweep pulse V _SWEEP and a read pulse V _READ from the trigger signal V _TRIG synchronized with the pulsed light P _L from the light source and outputs them to the high voltage circuit 123 and the image sensor 106, respectively. The high-voltage circuit 123 is composed of a klytron element, an avalanche transistor, etc., and generates a high voltage for driving the optical deflector 104, that is, a sweep voltage V _S from the sweep pulse V _SWEEP and outputs it to the optical deflector 104.

Next, the operation of this solid-state streak camera will be described.

The pulsed light P _L from the light source is _generated by the polarizer 102.
Is converted into linearly polarized light by, and only light of a predetermined size passes through the aperture 103 and enters the optical deflector 104. The pulsed light P _L incident on the optical deflector 104 is reflected by the optical deflector 10
The path is bent by 4, and the Fourier transform lens 105
Is collected at. Then, after being wavelength-dispersed by the dispersion prism 107, they are converged on the image sensor 106 to form an image. On the other hand, the trigger signal V _TRIG is input to the controller 121, and the sweep pulse V _SEEP , the read pulse V _READ, and the high-voltage circuit 123 output the sweep voltage V _S at the timing corresponding to the pulsed light P _L from the light source.

The sweep voltage V _S has a time waveform having a predetermined sweep time τs as shown in FIG. 4A, and the pulsed light P _L has a wavelength λ ₁ (solid line) and a wavelength λ ₂ (dotted line). 4 has a time waveform as shown in FIG.
Spatial waveforms such as the solid line and the dotted line in FIG. 4C are obtained on the image sensor 106. Thus, the temporal intensity change of the pulsed light is converted into a spatial intensity change corresponding to the wavelength, and the pulsed light P _L is detected by the detection element of the image sensor 106 on the focused spot. Detection signal V
_OUT is read and output at the timing of the read pulse V _READ . FIG. 5 shows that the wavelength λ ₁ and the wavelength λ ₂ are 755
nm, 532 nm detection signal V _OUT actually obtained
It shows the waveform of. The detection signal V _OUT has a wavelength λ
₁ has a component of temporal intensity change corresponding to light of wavelength λ ₂ and from this, temporal intensity change is obtained for each of light of wavelength λ ₁ and wavelength λ ₂ , and one streak camera can measure You can measure.

In particular, this embodiment using an image sensor has few effective detectors in the infrared region, and is very effective for measurement in such a wavelength region.

FIG. 6 shows the configuration of the second embodiment. This solid-state streak camera is characterized in that a diffraction grating 108 is used in place of the dispersion prism 107 of the above-described embodiment, and an image sensor 106 is provided so as to avoid the position where the 0th-order diffracted light of the diffraction grating 108 is condensed. .
The diffraction grating 108 changes the position where light is condensed according to the wavelength, and has the same function as the dispersion prism 107 of the embodiment. Saturation of the image sensor is avoided by preventing the image sensor 106 from receiving the 0th order diffracted light.
Also in the second embodiment, a temporal intensity change for each of a plurality of wavelengths can be obtained by the same operation as that of the first embodiment.

FIG. 7 shows the configuration of the third embodiment. This embodiment has different wavelengths λa, λb, λc.
This measuring light is introduced into the solid streak camera of the first embodiment. The optical fibers 150a, b, c guide the respective measurement lights, and the collimator lens 109 converts the light from the optical fibers 150a, b, c into parallel light P _L. Also in this embodiment, a temporal intensity change can be obtained for each of the wavelengths λa, λb and λc by the same operation as that of the first embodiment. This embodiment has an advantage that an optical fiber is used, and a complicated optical system for guiding the measurement light can be omitted.

FIG. 8 shows the configuration of the fourth embodiment. This embodiment is the first to measure optical property changes.
The embodiment is applied.

The material 301 to be measured is a material that absorbs the monitor light due to a change in physical properties caused by the pump light when the pump light (wavelength λ ₁ ) and the coherent monitor light (wavelength λ ₂ ) are simultaneously incident. Dichroic mirror 302
The pump light is transmitted and the monitor light is reflected and given to the material to be measured 301 in the same optical path. The modulation element 303 is made of an electro-optic crystal and transmits monitor light when a voltage is applied. The pulse generation circuit 310 applies a voltage to the modulation element 303 when there is a trigger signal V _TRIG . Modulation element 303
The pulse generation circuit 310 constitutes a switch that transmits the monitor light when the trigger signal V _TRIG is present.

The pump light has a sweep time τs as shown in FIG.
(A) has a waveform, and when this is incident on the measured material 301, the transmittance of the measured material 301 for the monitor light changes as shown by the solid line in FIG. 9 (b) (the dotted line indicates that there is no pump light). When). On the other hand, the monitor light is given to the measured material 301 in synchronization with the trigger signal V _TRIG , and the measured material 30
The monitor light transmitted through 1 changes as shown by the solid line in FIG. 9C (dotted line when there is no pump light).

The light P _L transmitted through the material 301 to be measured is
The pump light having the waveform of FIG. 9A and the monitor light of the solid line of FIG. 9C are combined, and the change in physical properties cannot be measured unless the intensities at those wavelengths are measured. Here, the light P _L transmitted through the measured material 301 has the same intensity change with time as the pump light (wavelength λ ₁ ) and the monitor light (wavelength λ ₂ ) in the same operation as in the first embodiment. . In particular, since it is possible to know the transient changes in the pump light and the monitor light at the same time, it is possible to know the transient changes in the physical properties of the measured material 301 in detail.

The present invention is not limited to the above-mentioned embodiment, but various modifications are possible.

In the first and second embodiments described above, two different
However, it is possible to easily obtain a temporal intensity change for each of a plurality of wavelengths of three or more by making the size of the image sensor sufficient.

An address type image sensor may be used as the image sensor 106. In particular,
In the second embodiment, it may be possible to measure the total light intensity by modifying it so that it also receives the 0th-order light. As described above, according to the solid-state streak camera of the present invention, the incident pulsed light is dispersed according to the wavelength, and is read out as a detection signal corresponding to the pulsed light at the timing of the read pulse, so that the wavelength of the pulsed light is adjusted according to each wavelength. Since the temporal intensity change can be obtained, one streak camera can measure the temporal intensity changes of a plurality of wavelengths.

Further, in the above-mentioned third and fourth embodiments,
Although the application of the first embodiment is shown, the second embodiment can be applied in the same manner.

[0025]

As described above, according to the solid streak camera of the present invention, incident pulsed light is dispersed according to wavelength,
By reading out as a detection signal corresponding to the pulsed light at the timing of the read pulse, a temporal intensity change corresponding to each wavelength of the pulsed light can be obtained, so that one streak camera can detect the temporal intensity change of a plurality of wavelengths. Can be measured.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment.

FIG. 2 is a diagram showing an example of an optical deflector.

FIG. 3 is a diagram showing an example of an optical deflector.

FIG. 4 is a waveform diagram of each part.

FIG. 5 is a waveform diagram of a detection signal.

FIG. 6 is a configuration diagram of a second embodiment.

FIG. 7 is a configuration diagram of a third embodiment.

FIG. 8 is a configuration diagram of a fourth embodiment.

FIG. 9 is a waveform diagram of pump light, monitor light, and the like.

FIG. 10 is a configuration diagram of a conventional example.

Claims (1)

(57) [Claims] 1. Internally generated in response to an applied voltage
Equipped with an electro-optic crystal whose refractive index changes according to the strength of the electric field
The voltage applied to the electro-optic crystal should not change over time.
The incident pulsed light with multiple discrete wavelengths.
First means for moving in the electro-optic crystal to scan in a first direction; and the scanned pulsed light in the first direction depending on the wavelength.
Solid comprising second means for dispersing, a third means for reading the timing of the read pulse by detecting the detection signal in response to said pulsed light dispersed in the dispersed direction corresponding to said pulsed light Streak camera.