JP3145134B2 - Deflection voltage application circuit for streak 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 circuit for applying a deflection voltage to a deflection electrode of a streak camera.

[0002]

2. Description of the Related Art A streak camera converts an incident light intensity into a change in luminance with respect to a position on a screen by converting incident light intensity into a position on a screen by converting the incident light into electrons and then passing the light between deflection electrodes and sweeping the light at high speed from above to below. Is measured as In order to perform a high-speed sweep, it is necessary to apply a voltage that changes at a high speed between the deflection electrodes, and this is performed by a deflection voltage application circuit. Generally, a step voltage obtained by switching of an avalanche transistor, a step recovery diode, a triode, a crytron, an FET, and the like is used as a basic deflection voltage, and further, a sweep speed is adjusted using a CR type filter or an RLC series type filter. That is, the inclination of the deflection voltage waveform is adjusted.

[0003]

However, if a CR type filter is used to adjust the sweep speed, a deflection voltage with poor linearity will result. That is, the step voltage is 0
Assuming that the voltage has changed from volts to V ₀ , the output voltage V (t) of the CR filter becomes V (t) = V ₀ (1−e ^{−t / CR} ) (1), and the voltage change rate dV ₀ / Dt is as follows: dV ₀ / dt = (V ₀ / CR) ・ e- ^{t / CR} (2) FIGS. 6A and 6B show equations (1) and (2), respectively.
These graphs show that the linearity is poor because the time change rate of the voltage approaches 0 as the voltage increases.

If an RLC series filter is used, the time change rate of the voltage has a peak (maximum value) due to the presence of L (inductance), and if a streak sweep is performed around the peak point of time. Thus, a deflection voltage having relatively good linearity can be generated. However, according to this filter, if the part with good linearity, that is, the part where the voltage time change rate has the maximum value, is moved to the center of the voltage amplitude, the undershoot and overshoot become large, and the streak image is fogged. Phenomenon appears.

[0005]

SUMMARY OF THE INVENTION The deflection voltage applying circuit of the present invention has been made in view of such a problem, and has a step voltage generating means for rapidly increasing an output voltage to a predetermined voltage by a trigger input. And a waveform shaping filter means for adjusting the slope of the voltage waveform output from the step voltage generating means while maintaining the left-right symmetry of the shaped voltage change rate. A Gaussian filter is desirable as the waveform shaping filter.

[0006]

When the step voltage output from the step voltage generating means passes through the waveform shaping filter means, the slope of the waveform becomes gentle. By adjusting the slope, the sweep speed can be adjusted. . Since the waveform shaping at this time is performed while maintaining the left-right symmetry of the voltage change rate after the shaping, the slope is always maximum at the center of the amplitude, and has excellent linearity.

[0007]

FIG. 1 is a block diagram showing an embodiment of the present invention. First, before starting the description of the deflection voltage application circuit 11, the streak camera 19 will be briefly described. When the light 25 is incident on the photocathode 22, electrons 26 corresponding to the light intensity of the incident light 25 are emitted from the photocathode 22. Electron 2
Numeral 6 is accelerated by an acceleration electrode (not shown), and is swept at high speed in the vertical direction by a deflection voltage when passing between the deflection electrodes 20 and 21. The swept electrons are multiplied by the micro channel plate 23 and converted into light on the phosphor screen 24. As a result, a change in light intensity that changes over time can be visually observed as a change in luminance in the vertical direction. In addition,
Meander lines, which are traveling wave type deflection plates, are employed for the deflection electrodes 20 and 21 of this embodiment. The traveling wave type deflection plate is designed such that the moving speed of the electrons and the phase speed of the deflection voltage transmitted through the deflection plate match. Sign 2
7, 28 are terminating resistors.

The deflection voltage applying circuit 11 includes a step voltage generating means 12, a waveform shaping filter 13, and a transformer 14.
5 and 66 are connected. Transmission lines 17 and 18 connected to the secondary output terminal of the transformer 14 are connected to deflection electrodes 20 and 21 of a streak camera 19.
Connecting each element with a transmission line has the advantage of not being restricted by the arrangement of each element. The step voltage generating means 12 is a switch circuit using an avalanche transistor. By applying a predetermined voltage to the terminal 121 and applying a trigger pulse to the terminal 122, a step voltage is output from the terminal 123. Reference numeral 124 indicates a charge line. This step voltage is applied to the waveform shaping filter 13 via the transmission line 15, and the time change rate of the voltage is changed. Here, the waveform shaping filter 1
A Gaussian filter 3 is used. Characteristic of the Gaussian filter is ideally a constant group delay with frequency, the attenuation A (dB) is, A (dB) = 3.010 ( f / f c) 2 However, f _c: Cut Expressed as off-frequency. FIG. 2 shows the frequency characteristic of the attenuation A.
Now, assuming that a step voltage having the waveform shown in FIG. 3A is output from the step voltage generating means 12, the waveform after passing through the waveform shaping filter 13 becomes as shown in FIG. The rate of change dV (t) / dt is as shown in FIG. The output voltage V (t) of the waveform shaping filter 13 and its time rate of change dV (t) / dt can be expressed as follows.

V (t) = V∞ ｛ ^1/2 + (1 / π ^1/2 )
_{Ert (0.8491ω c t) ω c} = 2πf c Ert (x): error function dV (t) /dt=0.4791V∞ω _c · EXP
[(0.8491ω _c t) ^2] As can be seen from FIG. 3 (b), it is possible to get a good waveform linearity in the central portion of the voltage change.

FIG. 4 shows a specific configuration of a Gaussian filter. Approximate solutions have been obtained so as to meet the theoretical formulas described above. If the values of C _n and L _{n + 1} are determined based on the approximate solutions, almost theoretical characteristics can be obtained. When a Gaussian filter is actually designed with a cutoff frequency of 35.9 MHz, C ₁ = 22 pF and L ₂ = 0.18 μm
H, C ₃ = 148 pF (third-order filter). FIG.
Shows the change of the voltage waveform by the actually designed Gaussian filter. Curve A shows the waveform before passing, and curve B shows the waveform after passing. The curve B shows that the linearity at the center of the voltage level is good, and that no undershoot or overshoot occurs at the front and rear ends of the change.

The voltage that has passed through the waveform shaping filter 13 is
The waveform is input to the primary side of the transformer 14 via the transmission line 16 and two waveforms having a phase difference of 180 degrees are obtained from the secondary side output terminal. These two waveforms are shown in transmission lines 17 and 18
And push-pull sweep is performed. Unlike the one-sided sweep, the push-pull sweep does not have a potential variation between the deflection plates, so that the deterioration of the spatial resolution during the streak sweep can be minimized. Between the transformer 14 and the deflection electrodes 20 and 21,
Since there is no noise source such as a semiconductor element, no jitter occurs between the two waveforms. If the loss due to the transformer 14 is ignored, the sum of the input voltage and the output voltage becomes equal. Therefore, if the turns ratio of the primary side and the secondary side is 1: 1, the output voltage of each becomes 1/2 times the input voltage, but the turn ratios are 1: 2 and 1: 2. 3. If you do something like
A large voltage can be obtained. This is the transformer 14
The same applies to the case where a transmission line type is used.

The deflection voltage thus generated is applied to the deflection electrodes 20 and 21. In general, the traveling wave type deflection plate itself is a transmission line having a uniform characteristic impedance. Therefore, if impedance matching with the transformer 14 is performed, there is no power loss and no waveform distortion due to a reflected wave. That is, the input waveform is stored, and therefore, the streak sweep speed determined by the waveform shaping filter 13 can be obtained with good reproducibility. In this embodiment, a Gaussian filter is used as the waveform shaping filter 13, but other filters may be used as long as they are Gaussian filters. Examples of the Gaussian filter include a Bessel filter and a linear phase filter with an equiripple error in addition to the Gaussian filter.

[0013]

As described above, according to the deflection voltage applying circuit of the present invention, since the waveform shaping filter is performed while maintaining the left-right symmetry of the voltage change rate after shaping, the slope is always the amplitude. It has the greatest linearity at the center of the

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a diagram illustrating a frequency characteristic of an attenuation amount of a Gaussian filter.

FIG. 3 is a diagram showing characteristics of a waveform shaping filter 13;

FIG. 4 is a circuit diagram showing a specific configuration of a Gaussian filter.

FIG. 5 is a diagram showing specific input / output waveforms of a Gaussian filter.

FIG. 6 is a diagram showing characteristics of a conventional circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Deflection voltage application circuit 12 ... Step voltage generation circuit 13 ... Waveform shaping filter 14 ... Transformer 15-18 ... Transmission line 19 ... Streak camera 20, 21 ... Deflection electrode

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yui Koishi 1126-1, Nomachi, Hamamatsu-shi, Shizuoka Prefecture Inside Hamamatsu Photonics Co., Ltd. (56) References JP-A-3-41324 (JP, A) Full-scale Sho-61 35465 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 43/30

Claims (4)

(57) [Claims] 1. A step voltage generating means for steeply increasing an output voltage to a predetermined voltage by a trigger input, and a bilateral symmetry of a voltage change rate after shaping by adjusting a slope of a voltage waveform output from the step voltage generating means. And a deflection voltage applying circuit for a streak camera, comprising: 2. The deflection voltage applying circuit according to claim 1, wherein the Gaussian type waveform shaping filter circuit is a Gaussian filter. 3. A step voltage generating means for steeply increasing an output voltage to a predetermined voltage by a trigger input, and a bilateral symmetry of a voltage change rate after shaping by adjusting a slope of a voltage waveform output from the step voltage generating means. And a waveform shaping filter means for adjusting while holding the voltage, and a deflection voltage applying circuit for a streak camera, comprising: a transformer for converting an output voltage of the waveform shaping filter means into two voltages having phases different by 180 degrees. 4. The deflection voltage application circuit according to claim 3, wherein said waveform shaping filter means is a Gaussian filter.