JP3276418B2 - Image tube equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image tube for converting an optical image received at an entrance window into a photoelectron image by a photocathode and reproducing the optical image at an exit window. The present invention relates to an image tube device provided with means for cooling.

[0002]

2. Description of the Related Art In an image tube, a photocathode is formed inside an entrance window, and an optical image incident on the entrance window is converted into a photoelectron image by an external photoelectric effect of the photocathode. The photoelectron image is accelerated and imaged by an electron lens system, then multiplied by an electron multiplier, enters a phosphor screen formed inside the exit window, and is reproduced as an optical image.

In such an image tube, the photocathode emits thermoelectrons by heat even when no light is incident. These thermoelectrons become thermal noise and cause deterioration of the S / N ratio of the image tube. As a method for suppressing such emission of thermoelectrons, there is a means for cooling an image tube, particularly a photocathode.

FIG. 7 shows a conventional general cooling means.
This cooling means encloses the entire image tube 1 in a cylindrical housing 2 to evacuate the space between the two, and a plurality of Peltier elements 3 are arranged such that a heat absorbing portion is on the image tube 1 side and a heat radiating portion. Is arranged between the outer surface of the side wall of the image tube 1 and the inner surface of the side wall of the housing 2 so that the side of the housing 2 is located on the side of the housing 2. In such a configuration, when a voltage is applied to the Peltier element 3, the temperature of the heat absorbing portion becomes low, the side wall portion of the image tube 1 is cooled, and as a result, the photocathode (not shown) inside the entrance window 4 is cooled. You.

[0005] As a conventional photocathode cooling means, there is known an apparatus as shown in FIG.
0930). This photocathode cooling device 5 includes two annular metal plates 5c and 5d having translucent windows 5a and 5b attached to the central opening, and a plurality of metal plates 5c and 5d arranged between these metal plates 5c and 5d. And a heat absorbing portion of the Peltier element 5e is in contact with one metal plate 5d.
When a voltage is applied to the Peltier element 5e, the temperature of the window 5b of the metal plate 5d becomes low. Therefore, by attaching the window 5b in a state where the window 5b is in contact with the entrance window 4 of the image tube 1, the photoelectric inside the entrance window 4 can be obtained. Surface 6 is cooled.

[0006]

The above two prior arts can both cool the photocathode 6, but the former, that is, the means for surrounding the entire image tube 1 with the housing 2, cools the entire image tube 1. Therefore, there is a problem that the efficiency is low.

On the other hand, in the photocathode cooling device 5 shown in FIG.
Since the low-temperature window 5b is in contact with the entrance window 4 of the image tube 1, the window 5b is cooled down to the exit window 7 through the side wall of the image tube 1, and dew condensation may occur on the surface of the exit window 7. Also,
Since most of the image tube 1 is exposed to the atmosphere, there is a problem that the photocathode 6 is not sufficiently cooled by external heat.

The present invention has been made in view of such circumstances, and an image tube capable of effectively cooling a photocathode of an image tube to improve the S / N ratio and preventing the occurrence of dew condensation. It is intended to provide a device.

[0009]

In order to achieve the above object, according to the present invention, there is provided an image tube having a photocathode inside an entrance window, and the image tube is provided at a predetermined interval. A housing in which a housing entrance window is arranged at a position facing the entrance window of the image tube;
A peltier element for cooling the photocathode of the image tube, wherein a radiating portion of the peltier element is fixed to a predetermined portion of the housing adjacent to the housing entrance window, and the peltier element is located near the photocathode of the image tube. By fixing the heat absorbing portion, the image tube is supported on the housing, and the inside of the housing is evacuated.

The image tube apparatus according to the second aspect of the present invention further comprises a temperature detecting means for detecting the temperature of the photocathode of the image tube, and responds to the temperature of the photocathode detected by the temperature detecting means. And controlling the Peltier element.

[0011]

As described above, since the heat absorbing portion of the Peltier element is fixed near the photocathode, the photocathode can be efficiently cooled. Further, since the image tube is supported only by the Peltier element in a vacuum in the housing, it is not affected by external heat, and the cooling effect by the Peltier element does not decrease.

Further, since the heat radiation portion of the Peltier element is fixed to the housing, the temperature of the housing surface is increased,
As a result, dew condensation on the housing entrance window and exit window is prevented.

Further, when the temperature of the photocathode is detected and the Peltier element is controlled based on the detected value,
The temperature of the photocathode can be kept constant, thereby stabilizing the spectral sensitivity characteristics.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows an image tube apparatus according to the present invention, in which reference numeral 10 denotes an image tube. The image tube 10 is of a conventionally known type and has a substantially cylindrical shape. One end of the image tube 10 (the left end in FIG. 1) serves as an entrance window 11 for an optical image, and a photocathode 12 is formed inside the window. In addition, image tube 1
The other end of 0 is an emission window 13, inside which a phosphor screen (not shown) is formed.

The image tube 10 is coaxially accommodated in a cylindrical housing 14 at a predetermined interval. The housing 14 is composed of a cup-shaped main body 15 made of glass and an annular end plate 16 made of metal, preferably copper, having a high thermal conductivity attached to the open end of the cup-shaped main body 15. A glass housing entrance window 17 is attached to the center opening of the end plate 16 and is arranged to face the entrance window 11 of the image tube 10. An air-cooled or water-cooled radiator plate 18 is attached to the outer surface of the end plate 16.

The space between the end plate 16 and the cup-shaped main body 15 and the space between the end plate 16 and the housing entrance window 17 are hermetically connected, and the housing 14 has a closed structure. However, since it is difficult to directly couple the glass and copper, between the end plate 16 and the cup-shaped main body 15 or the housing entrance window 17, as shown in FIGS.
r), a plurality of metals such as nickel (Ni), copper (Cu) and indium (In) are desirably interposed.

A copper outward flange 19 is provided on an outer peripheral portion of the image tube 10 adjacent to the entrance window 11, and an annular copper plate 20 is fixed to the flange 19. When the image tube 10 is arranged at a predetermined position in the housing 14, the annular copper plate 20 is arranged to face the end plate 16 of the housing 14. As shown in FIG. 2, a plurality of (eight in this embodiment) Peltier elements 21 are arranged at equal intervals in the circumferential direction between the end plate 16 of the housing 14 and the annular copper plate 20. Radiator 21 of each Peltier element 21
a is fixed to the end plate 16 of the housing 14,
b is fixed to the annular copper plate 20. Therefore, image tube 1
0 is supported by the Peltier element 21 with respect to the housing 14.

The Peltier device 21 is connected to an electrode 22 provided through the cup-shaped body 15 via a lead wire 23 having a low thermal conductivity. This Peltier element electrode 2
A temperature controller 24 outside the housing 14 is connected to 2. A temperature detector 25 such as a platinum temperature sensor is attached to the annular copper plate 20. The temperature detector 25 detects the temperature of the annular copper plate 20, and can calculate the temperature of the photocathode 12 from the detected value. The value detected by the temperature detector 25 is input to the temperature controller 24 via the lead wire 26 and the electrode 27 having low thermal conductivity. The temperature controller 24 controls the voltage applied to the Peltier element 21 in accordance with the detected value, so that the temperature of the heat absorbing portion 21b can be controlled.

Reference numeral 28 denotes a chip tube, and the image tube 1
After the housing 14 is housed in the housing 14 and the end plate 16 is attached, the air in the housing 14 is evacuated to a vacuum. When the pressure in the housing 14 is reduced to a desired value, the tip tube 28 is closed using a burner or the like. Reference numeral 29 denotes a getter for absorbing the residual gas after the interior of the housing 14 is evacuated to maintain the degree of vacuum.

Reference numeral 30 denotes an electrode mounted through the cup-shaped main body 15 for applying a voltage to the image tube 10 or extracting a signal from the image tube 10. These electrodes 30 are connected to the image tube 10 by leads 31 having low thermal conductivity.

In the above configuration, the optical image is transmitted through the housing entrance window 17 to the entrance window 11 of the image tube 10.
Is converted into a photoelectron image by the photocathode 12 inside the entrance window 11, and the photoelectron image is multiplied in the image tube 10 and reproduced as an optical image on the phosphor screen. The reconstructed image is output through the emission window 13 of the image tube 10 and the housing emission window 32 opposed thereto.

The Peltier device 21 is a temperature controller 24
, The heat of the photocathode 12 is absorbed. That is, the heat absorbing portion 21 b of the Peltier element 21 is
Then, the heat of the photoelectric surface 12 is absorbed through the annular copper plate 20, and the heat is released from the heat radiating portion 21a to the heat radiating plate 18 attached to the end plate 16. Since the image tube 10 is supported only by the Peltier element 21 in a vacuum in the housing 14, the photocathode 12 is efficiently cooled without being affected by external heat. As a result, when the outside air temperature is 20 ° C. and the temperature of the water-cooled radiator plate is constant at 20 ° C., the temperature of the photocathode 12 is −
The temperature could be lowered to 40 ° C. In the conventional configuration shown in FIG. 8, it was possible to lower the temperature only to −20 ° C. under the same conditions. Of course, the cooling temperature varies depending on the heat capacity of the Peltier element 21, the heat radiating plate 18, the housing 14, and the like.

FIG. 5 is a graph showing the relationship between the temperature of the photocathode 12 and the number of thermoelectrons in the dark (dark count). From this figure, it can be seen that the lower the temperature of the photocathode 12, the lower the generation of thermoelectrons. When the generation of thermoelectrons is suppressed, thermal noise is reduced and the S / N ratio is improved.

The heat absorbed from the photocathode 12 is radiated from the heat radiating portion 21a of the Peltier element 21 via the end plate 16 to the heat radiating plate, and a part of the heat is transmitted to the glass-like main body 15 of the housing. The temperature of the housing exit window 32 can be equal to or higher than the outside air temperature. Therefore, dew condensation does not occur on the surface of the housing exit window 32. Since the heat from the Peltier element 21 is also transmitted to the housing entrance window 17, dew condensation on the housing entrance window 17 is also prevented. still,
Under the above conditions, the temperature of the housing entrance window 17 is 23
° C, and the temperature of the housing exit window 32 was 20 ° C.

Further, since the temperature controller 24 can control the voltage applied to the Peltier element 21 based on the detection value from the temperature detector 25, the temperature of the photocathode 12 can be maintained constant. Figure 6 shows the image tube 1
5 is a graph showing a spectral sensitivity characteristic of 0, and shows a case where the temperature of the photocathode 12 is −25 ° C. and a case where it is + 25 ° C. From this figure, it can be seen that when the temperature of the photocathode 12 changes, the spectral sensitivity characteristics also change.
By keeping the temperature of the photocathode 12 constant, the spectral sensitivity characteristics can be stabilized.

[0027]

As described above, according to the present invention, the temperature of the photocathode of the image tube can be sufficiently lowered, and the generation of thermoelectrons from the photocathode can be suppressed. The S / N ratio of the image tube can be improved.

Further, since the heat absorbing portion of the Peltier element is fixed in the vicinity of the photocathode and the image tube is arranged in the vacuum heat insulating structure of the housing, the cooling efficiency is extremely high, and the energy consumption can be reduced.

On the other hand, according to the present invention, since a part of the heat radiation from the Peltier element is used to increase the temperatures of the exit window and the entrance window of the housing, dew condensation is prevented on the surfaces of these windows. be able to.

Further, since the temperature of the photocathode can be kept constant by controlling the Peltier element, the spectral sensitivity characteristics of the image tube are stabilized, and the performance of the image tube is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an image tube device according to the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is an enlarged view of a portion A in FIG. 1;

FIG. 4 is an enlarged view of a portion B in FIG. 1;

FIG. 5 is a graph showing the relationship between the temperature of the photocathode and the number of thermoelectrons in the dark.

FIG. 6 is a graph showing spectral sensitivity characteristics of the image tube when the temperature of the photocathode is different.

FIG. 7 is a cross-sectional view showing a conventional structure for cooling a photocathode of an image tube.

FIG. 8 is a cross-sectional view showing another conventional structure for cooling a photocathode of an image tube.

[Explanation of symbols]

10 image tube, 11 entrance window, 12 photocathode, 13
... Emission window, 14 ... Housing, 15 ... Cup body, 1
6 ... end plate, 17 ... housing entrance window, 18 ... radiator plate, 1
9: flange, 20: annular copper plate, 21: Peltier element,
21a: heat dissipating section, 21b: heat absorbing section, 24: temperature controller, 25: temperature detector, 32: housing exit window.

────────────────────────────────────────────────── ─── of the front page continued (72) inventor Suzuki, Hideki 1 Hamamatsu Photonics in the Corporation of Hamamatsu, Shizuoka Prefecture Ichino-cho address 1126 (58) investigated the field (Int.Cl. ^7, DB name) H01J 31/50

Claims (2)

(57) [Claims] 1. An image tube having a photocathode inside an entrance window, a housing entrance window surrounding the image tube at a predetermined interval, and a housing entrance window at a position facing the entrance window of the image tube. And a peltier element for cooling the photocathode of the image tube, wherein a radiator of the peltier element is fixed to a predetermined portion of the housing adjacent to the housing entrance window. Fixing the heat absorbing portion of the Peltier element near the entrance window of the image tube to support the image tube with respect to the housing and evacuate the interior of the housing. Tube equipment. 2. The apparatus according to claim 1, further comprising a temperature detector for detecting a temperature of the photocathode of the image tube, and controlling the Peltier element in accordance with the temperature of the photocathode detected by the temperature detector. The image tube device according to claim 1, wherein