JPH05217526A - Photomultiplier - Google Patents

Abstract

PURPOSE:To reduce the image distortion by forming a recessed plane having a curvature determined on the basis of the electron image focus plane of a lens on the fluorescent surface supporting side of a glass substrate, and forming a projection surface having a curvature determined so that a visible light image forms a planary imaginary image, viewed from an output side, on a visible light image output side. CONSTITUTION:Since an image focus plane due to an electronic lens is obtained by the simulation using CAD, the degree of freedom of the curvature of the image focus plane is increased, and the preparation of an output image having little strain is facilitated by a glass substrate having a curved recessed surface. Further, since the radiation plane of the substrate is formed to a proper projection surface through the lens calculation, the visible output light beam can be made parallel. For example, the plane faced to the electron orbit due to the electron lens of a glass substrate 28g is formed to a recessed surface, and a fluorescent body 28f is formed, and the plane for outputting the visible light beam is formed to a projecting plane. Accordingly, the image focus plane can be obtained by the electron lens without using a fiber plane or a special collimating lens, and the light image free from distortion as a whole can be obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is used in the field of image sensors. The present invention relates to a photomultiplier tube which outputs a visible light image by accelerating photoelectrons emitted from a photocathode of an input surface by an electron lens to form an image on the output phosphor screen, and particularly to supporting the output phosphor screen. It relates to an improved glass substrate.

[0002]

2. Description of the Related Art FIG. 4 shows a general X-ray photomultiplier tube (XI
It is a schematic longitudinal cross-sectional view of I). Such XII converts X-rays incident from the incident window 12w into visible rays by the input surface 12i, and then converts them into photoelectrons, which are accelerated and converged by the acceleration electrode 14 and the anode 16, that is, those electrodes. 14 and 16 play the role of an electronic lens and output surface 18
The image is formed on the phosphor layer (surface) of the above, and the output surface fluoresces and outputs visible light. Further, the output visible light is converted into tandem light (parallel light) by the collimator lens 20, and is condensed and used by an image pickup device such as a TV camera or a cine camera (not shown). In addition, 10 is a vacuum envelope.

Of these, focusing on the electron lens formed by the acceleration electrode 14 and the anode 16 and the output surface 18, the output surface 18 is a glass substrate having a flat input / output surface as shown in FIG. 5, which is also a single plate of optical glass. Alternatively, it is composed of a laminated composite plate 18g. As a result, the phosphor layer (surface) 18f
Is also supported as a flat surface.

As a few examples, as shown in FIG. 6, a phosphor layer 18 'is provided.
A glass substrate is used which is composed of a fiber plate 18′g having a concave surface on the f-support side.

In the case of a glass substrate 18g having a flat entrance / exit surface as shown in FIG. 5, the electron image forming surface is made as close to the flat surface as possible by devising the electrode shape and applied voltage. There is also an example in which the scattered light is suppressed by increasing the thickness of the glass to improve the contrast (Jitsuko Sho 59-3316).
No. 1).

[0006]

In the case of the structure shown in FIG. 5, the input surface 1 having a concave surface as shown in FIG.
The electrons emitted from 2i must be imaged on a flat surface, and even if it is corrected by a large number of electrodes, the output phosphor screen 1
Distortion tends to remain in the image formed on 8.

In the case of the structure shown in FIG. 6, the distortion due to the electron lens is advantageous, but since the fiber plate is used, a. Resolution limitation by fiber fiber thickness, b. Yield reduction due to clogging of fiber fibers, c. There is a problem such as an increase in unit cost due to the use of fiber plates. Incidentally, the design of the collimator lens 20 shown in FIG. 4 becomes very complicated if the glass substrate is replaced with a glass substrate having the same shape without using the fiber.

The object of the present invention is to significantly reduce the distortion caused by an electronic lens without using a fiber plate as a substrate for supporting an output phosphor screen and without using a special collimating lens for a tandem spatial distance. The object is to provide a photomultiplier tube capable of outputting a good visible light image with little distortion as a whole.

[0009]

The above-mentioned object is to provide a photomultiplier tube for outputting a visible light image by accelerating photoelectrons emitted from a photocathode of an input surface by an electron lens to form an image on an output fluorescent screen. In the above, the fluorescent surface supporting side of the glass substrate supporting the output fluorescent surface is formed into a concave surface, while the visible light image output side is formed into a convex surface, and the curvature of the concave surface is based on the electron image forming surface by the electron lens. And the curvature of the convex surface is determined so that the concave visible light image by the fluorescent surface arranged along the electron image plane forms a plane virtual image when viewed from the output side.

[0010]

Since the image plane formed by the electron lens is obtained by the simulation using CAD, the degree of freedom of the curvature of the image plane becomes high, and the glass substrate having such a concave concave surface produces an output image with little distortion. Will be easier. In addition, since the exit surface of such a glass substrate is formed as an optimal convex surface by lens calculation, the visible output light beam becomes a parallel light beam equivalent to that shown in FIG. 5, and a special collimating lens is not required, and it is the same as before. Optical lens is used.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the image formed on the phosphor layer 28f by the electron lens reproduces the image formed by the phosphor and emits light to become an optical image. The subsequent principle will be described with reference to FIG.

In FIG. 2, the optical image is represented by curves A, F and G. This curve is a spherical surface, a hyperboloid of revolution, an elliptic surface, etc. depending on the design of the electron lens, but here it is a spherical surface. Point A
The light emitted from the light source has a locus indicated by A → B → C or A → D → E. However, points B and D are arbitrary points on the convex side surface limited by the critical angle of the glass substrate 28g (refractive index η). When viewed from the position O side, the apparent position of the point A is H.

Similarly, the apparent positions of the points F and G are I and J.
become. At this time, if the convex surface curvature of the glass substrate is designed based on the refractive index η so that the points H, I, and J are on the same plane, the output light can be handled optically equivalent to the case of FIG.

If the thickness of the glass substrate is determined based on the principle of the prior invention (Japanese Utility Model Publication No. 59-33161), the effect of the invention can be obtained.

Further, in the glass substrate (basically a convex lens) as in the present invention, blurring due to chromatic aberration is feared.
In the case of XII, since it can be regarded as monochromatic light, there is no problem.

Further, the glass substrate constituting the output surface according to the present invention is composed of a plurality of glass substrates 28g1 and 10g (vacuum envelope) having the same refractive index as illustrated in FIG.
It may be composed of 8 g 2, and they may be bonded together by a colorless and transparent adhesive having the same refractive index.

Alternatively, a plurality of glass substrates having different refractive indexes may be bonded to each other and designed so as to exert the effects of the present invention as a whole.

[0018]

[Effect] As described above, without using a defective fiber plate or a special collimating lens, a glass substrate having a curved surface on which the image plane formed by the electron lens coincides can be easily obtained. Since the exit surface can also be formed into an appropriate convex surface by lens calculation, the distortion due to the electron lens can be significantly reduced, and a good optical image with little distortion can be obtained as a whole of XII.

[0019]

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a main part of an output surface showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a function and effect of the output surface.

FIG. 3 is an explanatory diagram of a main part of an output surface showing another embodiment.

FIG. 4 is a schematic vertical sectional view of a general X-ray photomultiplier tube.

FIG. 5 is a configuration diagram of an output surface according to a conventional example.

FIG. 6 is a configuration diagram of an output surface according to another conventional example.

[Explanation of symbols]

 10 Enclosure 14 Accelerating Electrode 16 Anode Electrode 18 Output Surface 18f Output Phosphor Layer (Surface) 18g Glass Substrate 20 Collimating Optical Lens 28g Glass Substrate

Claims (1)

[Claims] 1. Photoelectrons emitted from the photocathode of the input surface are accelerated by an electron lens to form an image on the output fluorescent screen,
In a photomultiplier tube that outputs a visible light image, the fluorescent screen supporting side of the glass substrate that supports the output fluorescent screen is a concave surface,
On the other hand, the visible light image output side is formed into a convex surface,
The curvature of the concave surface is determined based on the electron image plane formed by the electron lens, and the curvature of the convex surface is a plane virtual image of the concave visible light image formed by the fluorescent surface arranged along the electron image plane when viewed from the output side. A photomultiplier tube, characterized in that it has been determined to form