JPS60101177A - Image tube - Google Patents

Abstract

PURPOSE:To provide an image tube which is highly sensitive, has low afterimage characteristics and does not cause any deterioration of time response characteristics even during low intensity of illumination, by providing a specified phosphor on a fluorescent output screen. CONSTITUTION:A glass plate 11 provided with a photoelectric surface 12 and a fiber optics face plate 13 having a fluorescent screen 14 coated with a phosphor having an average particle size of 0.5-3.5mu and the formula of Ln2O2S:xTb (wherein 5X10<-5=x<=3X10<-2>g atom and Ln is at least one element selected from among La, Ga and Y) are arranged in such a manner that the photoelectric surface 12 and the fluorescent screen 14 are opposed to each other and hermetically sealed through holding fitments 15, 16 and an insulating ring 17. The inside thereof is kept under high vacuum to form an image tube 10.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an image tube, and more particularly to an image tube with improved afterimage characteristics.

[Technology of the Invention Fishing JFI] An image tube is an electron tube that has the V1 ability to intensify a weak light image into a bright light image.In recent years, it has become possible to connect an image tube as an optical amplifier to an image pickup tube and use it as a high-sensitivity television camera. Proposed.

Image tubes for such uses include a photocathode that converts an incident light image into an electron image, and a photocathode that converts an amplified electron image into an optical image.
A bipolar image tube with an Ii4 phosphor screen is commonly used.

Now, one type of Iil picture tube used as a television camera has a photoconductive surface made of Se-As-Te. This spectral sensitivity characteristic has a peak at approximately 450 nra, and is highly sensitive to blue light. However, this N
As the image tube coupled to the image tube, a blue-emitting phosphor Zn S :Aa (Pll) having an emission spectrum of about 450 nm is generally used for the output phosphor screen.

[Background Art Problem 1] A television camera that combines the above-mentioned image tube and m-picture tube has an effective sensitivity of about 10×8 when photographing in color compared to a conventional television camera. However, it became clear that it had a fatal drawback as a television camera: large afterimages. The above-mentioned ZnS:Δg phosphor is often used in cathode ray tubes, and the time for the brightness to decrease by 10% (10% attenuation time) is several tens of microseconds, and there is relatively little afterglow. However, it was found that this phosphor exhibits completely different behavior in terms of afterglow characteristics under minute currents than that of a cathode ray tube. That is, at stimulation current densities as low as several nanoamperes, an afterglow of 5 to 6% of the initial value was measured after 50 milliseconds of decay. For this reason, when used in an image tube whose operating current density is much lower than that of an polar ray tube, the above-mentioned value where the afterglow characteristics are noticeable in both the rise and decay of light emission is approximately twice the afterimage of the image pickup tube. However, in a combination of an image tube and an image pickup tube, the afterimage after 50 milliseconds is about 10%.This value increases even more when shooting under low illumination.

To improve afterglow characteristics, it is effective to some extent to add a very small amount of a substance such as N1 as a so-called killer, but
The drawback is that brightness is sacrificed.

Another phosphor with a short afterglow time is ZIIS: Tll.

Zn O: Zn, Y, S 1207: CQ, etc. were also considered, but due to insufficient brightness, they had no choice but to postpone their practical use.

[Object of the Invention] An object of the present invention is to provide an improved image tube that can obtain high output and whose time response characteristics do not deteriorate even when the image tube is in use.

[Summary of the Invention] The image tube according to the present invention has a general formula represented by the above formula,
Further, the output phosphor screen is formed of a phosphor having an average particle size of 0.5 to 3.5 microns.

Ln20. S: X T b (However, × is 5x10 ≦×≦3×10- and
is at least one element among La, Qa, and '/. ) That is, the response characteristics of the phosphor screen according to the present invention are the same even under low stimulation current as when under stimulation current normally used in cathode ray tubes. Moreover, the afterimage is, for example, 2 seconds after the stimulation stops.
J3 per millisecond is 1 to 2% or less, which is good.

As is well known, the emission spectrum and brightness of the Ln, O, S phosphors change as the amount of activation changes.

The present inventors took into consideration the spectral sensitivity characteristics of the photoconductive surface of the image pickup tube described above, and determined that L II! OLS: It has been found that a high image tube output can be obtained by setting the activation mx of the X Tb phosphor to 5x10≦X≦3xlO''.

Image tubes also require amplification of information that is concentrated in a small area, typically 10 to 30 millimeters in diameter.

Therefore, it goes without saying that the film formability of the output phosphor screen is a particularly important factor. Therefore, it is desirable that the particle size of the phosphor be as small as possible. However, the miniaturization of phosphor
This is undesirable because it causes a decrease in luminous efficiency. As a result of studies, the inventors of the present invention have found that an image tube composed of a phosphor having an average particle diameter of 0.5 to 3.5 microns has high output and excellent image quality.

[Embodiments of the invention] The present invention will be explained in detail below with reference to the drawings.

FIG. 1 shows a sectional view of an image tube 10 according to an embodiment of the present invention, in which a charging surface 12 is provided on a glass plate 11, and a fluorescent screen 14 is provided on a fiber optics face plate 13.
are formed, both plates 1 to 11.13 are arranged so that the photocathode 12 and the fluorescent screen 14 face each other, and the supporting metal fittings 15.16
and is airtightly delivered via an insulating ring body 11. The inside of the image tube is kept in a high vacuum.During operation, the photocathode is sealed and a voltage of around 10KV is applied to the phosphor screen. When an incident light image is formed on the photocathode, photoelectrons proportional to the incident light image are emitted from each part of the photocathode, and the photoelectrons are accelerated and impinge on the phosphor screen, stimulating it to emit light. A light image that is reproduced on the phosphor screen and is brighter than the incident light image is guided to the outside of the tube through the fiber Δbudics face plate.

FIG. 2 shows an example of the use of the image tube of the present invention.

The image tube 10 described above includes a fiber optics face plate 13 and a face plate 1- of the image pickup tube 20.
21 facing each other. The photoconductive surface provided on the face plate of this image pickup tube is about 4 mm as described above.
3e -As- with a peak of spectral sensitivity characteristics at 50 nm
Te is used.

FIG. 3 shows the afterglow characteristics of the image tube according to the present invention, where the vertical axis is the relative intensity of the image tube output, and the horizontal axis is the elapsed time after excitation is stopped. Curve A in FIG. 3 represents Y, 0 according to the present invention.
Curve 1 is the afterglow characteristic of an image tube using a 2S:Tb phosphor, and curve B is the afterglow characteristic of an image tube using a conventional zns:Ag phosphor.

As mentioned above, the afterglow characteristic of the output phosphor screen according to the present invention hardly changes by ->-1 depending on the stimulation current.

FIG. 4 shows the relationship between stimulation current density and 10% devaluation time.

Curves A, B, and C in Figure 4 are y, o, and s, respectively.
, Gd, 0. S: 1-b, La, O, S
: Corresponds to a saw output phosphor screen using Tb phosphor, and the curved line corresponds to a conventional output phosphor screen using ZIIS:Ag phosphor. As is clear from FIG. 4, the conventional example exhibits long afterglow characteristics in the normal operating current density region of the image tube (<-1x10-2 microA/Cl112), but the phosphor screen according to the present invention exhibits a low stimulation characteristic. No change is observed in the afterglow characteristics even with the current density. It can be seen that it has a practically sufficient afterglow characteristic as an output surface of an image tube combined with an image carrier. It also shows similar good rise characteristics.

Figure 5 shows Y, 0. S: Emission spectrum of the output phosphor screen according to the present invention using T'b phosphor as an example;
a) is rl-b activated mIfi for Y, 0.81 mol
o, o.

O1 gram atom, (b) 0.001 gram atom, and (C) 0.025 gram atom. The vertical axis is the relative intensity with each emission peak intensity set as 100. As is clear from the figure, the emission color changes from bluish-white to green due to m-degree quenching depending on the amount of Tb activation. These situations are similar even when the phosphor matrix is Gd, 02s, 1azo, or s.

FIG. 6 shows the spectral sensitivity characteristics of the photoconductive surface made of Se-As-Te.

Optical gain when combining the above-mentioned image pickup tube with the photoconductive surface and the image tube of the present invention, and L n, 0□S:x-r b
The relationship between the Tb activation amount of the phosphor is shown in FIG. 7. In FIG. 10, curves Δ, B, and C are Y20LS: x Tb, respectively.

GdLO,S: x Tb, La,O,S:
X Tb. As is clear from FIG. 7, the Tll activation amount is preferably 5x10≦X≦3x10.

FIG. 8 shows the relationship between the average particle diameter of the Y, O, S: T b phosphor and the image tube output according to the present invention. From the viewpoint of image quality, it is preferable to use as small a phosphor as possible, but as is clear from Figure 8, if the average particle size is less than 0.5 microns, the luminous efficiency will decrease as the particles become finer, leading to a decrease in image tube output. 1
0ri. On the other hand, if the average particle size exceeds 3.5 microns, the film forming properties of the phosphor screen deteriorate, resulting in low F resolution and significant deterioration in image quality. These trends are Gd2O,S: Tb, L
a20LS: It was exactly the same for the Tb phosphor. Therefore, in the present invention, the average particle size of the phosphor is 0.5 to 3.
．． A preferred range is 5 microns.

[Effects of the Invention] The image tube according to the present invention has high output and low afterimage, and the television camera of the present invention in which this image tube is combined with the image pickup tube has a sensitivity approximately 30 times that of the image pickup tube alone in black and white photography. , I was able to improve V by more than 10 times with color photography. In particular, it has become possible to capture images with unprecedentedly low afterimages under low illuminance.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of an image tube of one embodiment, Fig. 2 is a diagram of a television camera that combines an image tube and an image pickup tube, Fig. 3 is a diagram showing the afterglow characteristics of the image tube, and Fig. 4 Figure 5 shows the relationship between stimulation current density and 10% reduction time, Figure 5 shows the emission spectrum of the Y2O,S:T'b phosphor, and Figure 6 shows the relationship between the stimulation current density and the 10% reduction time. Figure 1 shows the spectral sensitivity characteristics of the surface, Figure 7 shows the relationship between the optical gain of the image tube and the -Ub activation amount, and Figure 8 shows the relationship between the -Ub activation amount and the Y
20□8+-1-17 is a diagram showing the relationship between the average particle diameter of the phosphor and the image tube output. 10... Image tube, 12... Photocathode, 14... Fluorescent screen, 20... Image pickup tube. Representative Patent Attorney Norichika Mado (other names) Figure 1 Figure 2 Figure 3 Direction C milliseconds Figure 4 Dentsusai and OtA/c monk 2F Figure 5 (C Non-Haricho ( 72'm) Fig. 6 Number table (In';m) Fig. 7 Pond row density diagram Fig. 8 Flat wood gusset (μ??1)

Claims (1)

[Claims] The general formula is represented by the above formula, and the average particle size is 0.5 to 3.
．． An image tube that uses 5 micron phosphor for the output phosphor screen. L n20. S: x T b (However, X is a 5x10≦X≦3×10-gram atom, and is at least one element of ln1.1Lla, Qd, or Y.)