JP2542466B2 - 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 solid streak camera for measuring spatial intensity change by directly scanning pulsed light from a light source.

[0002]

2. Description of the Related Art Phenomena involving absorption and emission of light in a substance are one of the fundamental natural phenomena due to the transition of quantum states in the substance. It is the theme. High-speed pulsed light is a transient phenomenon of absorption and emission of this light, and its measurement technique is very important for understanding this basic physical phenomenon. Among the high-speed pulsed light measurements, the fastest one that is currently in practical use is the method using a streak camera.

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.

[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. However, when the measurement light is directly scanned, there is a problem that the scanning width for the focused spot of the pulsed light is smaller and the resolution is lower than that of the above-described streak camera.

In view of the above-mentioned problems, the present invention is to provide a solid streak camera having a high resolution, which has a configuration in which the measuring light is directly converted into an electric signal.

[0006]

The solid streak camera of the present invention is a pulsed light that scans pulsed light at a timing corresponding to the pulsed light from a light source, focuses the light on an image sensor, detects the light, and outputs the light as a detection signal. It is characterized by having a detecting means and a calculating means for calculating from the detection signal based on the shape of the focused spot on the image sensor to calculate the time waveform of the pulsed light from the light source.

[0007]

The pulsed light from the light source is focused on the image sensor by the pulsed light detection means and scanned. And
The temporal intensity change of the pulsed light is converted from the image sensor into a spatial intensity change in the scanning direction and output as a detection signal. This detection signal includes a component of a condensed spot shape on the image sensor, and this component is removed by the calculating means, so that a time waveform of the pulsed light with higher resolution can be obtained.

[0008]

Embodiments of the present invention will be described with reference to FIGS. FIG. 1 shows a solid-state streak camera according to an 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, the output of the image sensor 106 has an arithmetic unit (arithmetic means) 130.

The polarizer 102 is a pulsed light P _L from a light source.
To linearly polarized light, and the aperture 103 uses the polarizer 10
Only the light of a predetermined size out of the light passing through 2 is passed. 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. FIG. 2 is a so-called double prism type, in which two prism-shaped crystals are laminated by inverting their optical axes. 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.
FIG. 3 shows a so-called quadruple electrode type, which has a sweep voltage V as shown in FIG.
_S is applied to deflect the incident light.

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 image sensor 106 converts the light condensed by the Fourier transform lens 105 into an electric signal, and outputs this electric signal as a detection signal V _OUT according to the read pulse V _READ .
An array element of InSb or Ge is 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. The arithmetic device 130 samples the detection signal V _OUT from the image sensor 106, converts it into a digital value, performs deconvolution processing, and displays it on the waveform display device 132.

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

[0013] First, the incident pulse light P _L in a state in which the sweep voltage is applied to V _S state or a constant voltage is not applied sweep voltage V _S to the optical deflector 104, an image sensor 106
An image is formed on the upper surface to form a focused spot. The detection signal V _{OUT at} this time is a signal representing the shape of the focused spot, and this detection signal V _OUT is stored in the arithmetic unit 130 as the point spread function h (x).

Next, the sweep voltage V _S is applied to the optical deflector 104 and scanning is performed to measure the temporal intensity change of the pulsed light P _L. The operation at this time will be described in detail as follows.

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
The light is collected by the image sensor 106 and is focused 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 as shown in FIG. 4A, and the time waveform of the pulsed light P _L as shown in FIG. 4B is deflected by the optical deflector 104 and The spatial waveform as shown in (c) is imaged on the image sensor 106. In this way, the temporal intensity change of the pulsed light is converted into the spatial intensity change. The pulsed light P _L deflected by the optical deflector 104 is reflected by the image sensor 106 on the focused spot.
Is detected by the detection element of. The detection signal V _OUT is read and output at the timing of the read pulse V _READ . Then, it is sampled by the arithmetic unit 130.

When a lithium niobate crystal is used as the optical deflector 104, the deflection angle θ _d is expressed by the following equation (Equation 1).

[0017]

[Equation 1]

The number of decomposition points N on the image sensor 106 is expressed by the following equation (Equation 2).

[0019]

[Equation 2]

[0020] Substituting the actual value represented by the deflection angle theta _d of equation (1) in the following equation (3), the deflection angle theta _d
Is 10 mrad.

[0021]

(Equation 3)

When k = 1, w = 2 mm and λ = 1 μm, the number N of decomposition points is 20, which is considerably small. This is because the focused spot on the image sensor has a certain spread. _{Assuming that} the waveform of the detection signal V _OUT is f (x) and the waveform of the temporal intensity change of the true pulsed light is g (x), the above-mentioned point spread function h (x) is used to express these relationships as follows. It is expressed by (Equation 4).

[0023]

[Equation 4]

These relationships are called convolution, and are schematically shown in FIG. 5 (however, the noise component is ignored). In this way, the waveform f (x) of the detection signal V _OUT is obtained by the point spread function h (x).
Becomes dull, and the resolution is greatly reduced compared to the true waveform g (x). Detection signal V _OUT
The waveform f (x) obtained by sampling M points at and converting it to a digital value is expressed by the following equation (Equation 5) using g (x) and h (x).

[0025]

(Equation 5)

If expressed by simultaneous equations, the following equation (Equation 6) is obtained.

[0027]

(Equation 6)

In the arithmetic unit 130, the point spread function h
The above equation (Equation 6) is solved from (x) and the waveform f (x) obtained by sampling the detection signal V _OUT to obtain the waveform g _i (sampling value) of the temporal intensity change of the true pulsed light. The calculation is being performed. There are various methods for this calculation (numerical analysis), but the Gauss-Seidel method is used as an example. This operation is expressed by the following equation (Equation 7),
The solution is given by the convergence of the iterative solution g _i ^(k) . This calculation is performed in the flowchart of FIG.

[0029]

(Equation 7)

Normally, in the Gauss-Seidel method, an appropriate value is substituted for an initial value (in this case, the 0th iterative solution g _i ⁽⁰⁾ ) and the processing is started. In the case of this embodiment, f (x) is g
By utilizing the fact that it is close to (x), the convergence time is shortened by substituting the sampling value f _i of the detection signal V _OUT into the 0th iterative solution g _i ⁽⁰⁾ , and real-time processing is performed. In this way, the sampling value g _i of the temporal intensity change of the true pulsed light is obtained, and the decomposition score of the temporal intensity change is greatly improved.

The present invention is not limited to this embodiment, and the following modifications are possible.

For example, as a numerical analysis method, Gauss
Instead of the Seidel method, other numerical analysis methods such as the Jacobi method can be used. Further, the sampling value f _i of the detection signal V _OUT is substituted for the ^0th iterative solution g _i ⁽⁰⁾ ,
Instead of the sampling value f _i , another appropriate value may be substituted.

[0033]

As described above, according to the solid-state streak camera of the present invention, since the focusing spot shape component is removed from the detection signal including the focusing spot shape component by the calculating means, the resolution of the time waveform of the pulsed light is reduced. Can be made higher, and the temporal change of the pulsed light can be measured more accurately.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

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

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

FIG. 4 is a diagram showing a relationship between a time waveform of a sweep voltage, a time waveform of pulsed light, and a spatial waveform of pulsed light.

FIG. 5 is a waveform f (x) of a detection signal V _OUT , a waveform g (x) of a temporal intensity change of true pulsed light, and a point spread function h.
The figure which shows the relationship of (x).

FIG. 6 is a waveform g (x) of the temporal intensity change of the true pulsed light
The flowchart which calculates.

FIG. 7 is a configuration diagram of a conventional example.

[Explanation of symbols]

104 ... Optical deflector, 105 ... Fourier transform lens, 10
6 ... Image sensor, 130 ... Arithmetic device, P _L ... Pulsed light, V _OUT ... Detection signal

Claims (1)

(57) [Claims] 1. A pulsed light detection means for scanning the pulsed light at a timing corresponding to the pulsed light from a light source, condensing it on an image sensor to detect it, and outputting it as a detection signal, and condensing light on the image sensor. A solid-state streak camera, comprising: a calculation unit that calculates from the detection signal based on a spot shape to calculate a time waveform of pulsed light from the light source.