JPS62252043A - Output fluorescent screen applying optical fiber plate - Google Patents

Abstract

PURPOSE:To reduce the uneven transmission efficiency of the phosphor radiation of individual photofibers, by making the incident surfaces in a curved surface for each optical fiber, and composing the interface between the phosphor material buried in the curved surface and the optical fiber, to act positively to the incident light from the phosphor material to the optical fiber when the center axis of the optical fibers acts as the optical axis. CONSTITUTION:While the end surfaces of the radiation of optical fiber plates are honed plainly and smoothly, the incident surface sides are processed to be concave at the phosphor layer 72 side, phosphors 72 are filled in the concaves, and a metallic pack layer 73 is formed at the surface. The electrons from a microchannel plate 6 penetrate through the metallic pack layer 73, and the lights generated by the electrons in the phosphor 72 are reflected to the optical fiber side. By giving a relation n1>n2, n2, between the refraction index of the phosphor material n1, that of the core 71c of the optical fiber 71, n2, and that of the clads 7ib, n2,, the interface between the phosphor layer 7 and the optical fiber 71 acts as a positive refraction surface to the light from the phosphor layer side when the central axis of the optical fibers 71 acts as the optical axis.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an output fluorescent surface using an optical fiber plate used in an image intensifier tube or the like.

(Prior Art) The basic configuration of an output fluorescent surface using a conventional optical fiber plate will be briefly explained.

FIG. 4 is an enlarged sectional view of an output fluorescent surface using a conventional optical fiber plate.

The optical fiber plate is made of tens of thousands of extremely thin optical fibers 71...71, and each optical fiber is bundled and fixed.

A single optical fiber consists of a core with a high refractive index and a cladding with a lower refractive index than the core.Both sides of the optical fiber plate are VF coated, and a phosphor is coated on one side. A layer 72 is formed. The phosphor layer 7
A well-known thin total bending layer (metal back N) 73 is formed on the upper surface of the metal back 2.

The light generated from the phosphor rN72 by electron bombardment is mainly sent to the optical fiber plate in the following manner.

■ One that reaches the end face of an optical fiber at a relatively small angle of incidence and enters directly.

■ Reflected by the metal back 1i73 and incident on the optical fiber plate.

When collimated light and Lambertian light of the same intensity are irradiated onto an optical fiber plate (with 72 and 73 separated using the apparatus shown in FIG. 4), the collimated light has a higher light transmittance.

With collimated light, 85% of the incident light reaches the output surface, whereas when Lambertian light is irradiated, only 60% reaches the output surface.

It is considered that the light emitted from the phosphor layer 72 or the light reflected by the metal bank layer 73 and incident on the optical fiber plate takes the form of incidence as the Lambertian light described above.

Therefore, it is reasonable to assume that about 40% of the light generated by the phosphor layer 72 does not reach the output surface.

Furthermore, the transmittance of each optical fiber forming the optical fiber plate also appears to vary with respect to Lambertian light.

This is because when light that enters the optical fiber at a relatively large angle of incidence is reflected by the cladding section, it is affected by variations in the refractive index of the cladding section and is output as a decrease in image quality.

Next, with an optical fiber plate having the shape shown in FIG. 4, not all of the fluorescence generated in the fluorescent layer 72 in front of a specific optical fiber, for example 71b, enters the optical fiber 71b, but the end face of the optical fiber 71b A relatively large amount of incident light is reflected.

In addition, some light is reflected by the metal back layer 73 and enters other optical fibers.

Such light will impair resolution of the output phosphor surface using the fiber optic plate.

(Problems to be Solved by the Invention) As described above, the output fluorescent surface using the conventional optical fiber plate suffers from variations in the transmission efficiency of the fluorescent light emitted by the individual optical fibers, and therefore the faithfulness of the image (image). There are problems with reproduction and resolution.

SUMMARY OF THE INVENTION An object of the present invention is to provide an output fluorescent surface using an optical fiber plate that can improve the dispersion of the transmission efficiency of fluorescent light emission and thus improve the faithful reproduction and resolution of images.

(Means for Solving the Problem) In order to achieve the above object, the present invention provides an output fluorescent surface using an optical fiber plate, in which the incident surface is curved for each optical fiber forming the optical fiber plate. ,
The interface between the fluorescent material embedded in the curved surface and the optical fiber has a positive effect on the end of the optical fiber that enters the optical fiber from the fluorescent material when the optical axis is the central axis of the optical fiber. It is composed of:

Usually, the refractive index of the fluorescent material is greater than the refractive index of the optical fiber, and the curved surface is concave.

Furthermore, by forming a thin layer of metal on the top surface of the fluorescent material, the transmission efficiency and resolution of fluorescent light emission can be further improved.

(Example) The present invention will be described in more detail below with reference to the drawings and the like.

FIG. 1 is a cross-sectional view of an image intensifier using an output fluorescent surface using an optical fiber plate according to the present invention.

An optical fiber plate 2 forming an entrance surface is provided on the front side of the vacuum vessel 4 of the image intensifier tube. A photocathode 3 is provided on this inner surface. Further, on the rear surface of the vacuum vessel 4 of the image intensifier tube, an output fluorescent surface 7 using an optical fiber plate according to the present invention is arranged.

An electron image of the photocathode 3 caused by light incident on the optical fiber plate 2 is formed on the incident surface of the microchannel plate 6 by a well-known electron optical system 5.

The electron image multiplied by the macrochannel plate 6 is further accelerated and excites the phosphor layer of the output phosphor surface 7, producing an image of enhanced light.

FIG. 2 shows an enlarged sectional view of the output fluorescent surface using this optical fiber plate. FIG. 3 is an enlarged cross-sectional view showing a portion of the fluorescent surface of the embodiment related to one optical fiber.

A fiber optic plate is made up of tens of thousands of optical fibers.
The output end face is polished smooth, and the input face side is processed into a concave shape (a spherical surface with a substantially radius r) on the fluorescent layer 72 side, as shown in FIG.

Forming concave holes in the core plate of an optical fiber can be accomplished by using an optical fiber plate having a core plate that can be selectively etched with an acid or alkaline solution.

A phosphor 72 is filled in this recess and a thin metal layer is formed on the surface thereof to form a metal bank layer 73. As is well known, this metal back layer 73 transmits electrons from the microchannel plate 6 and reflects light generated within the phosphor 72 by the electrons toward the optical fiber side.

In this example, the phosphor layer 72 was formed of a fluorescent material with a refractive index n1=2.2, and an optical fiber plate with a smaller refractive index was used.

The refractive index of the core portion 71c of the optical fiber 71 is n2=1.8
, the refractive index n2' of the cladding part 71d of the optical fiber 71=
t, 5.

In this way, nl>n2. Given the relationship n2', the interface between the phosphor layer 72 and the optical fiber 71 is the same as the optical fiber 71.
When the central axis of the phosphor N72 is set as the optical axis, it moves as a positive refracting surface with respect to light from the phosphor N72 side.

Compared to the conventional phosphor formed on a smooth flat surface, more light emitted from the phosphor is captured into the optical fiber, and the number of times it is reflected by the cladding can be reduced. can.

Therefore, the light can be propagated within the optical fiber without being influenced by the difference in reflectance at the internal reflection surface of the cladding part, and absorption is also reduced.

The reason why less light is reflected on the surface of the optical fiber can be explained as follows.

By making the incident end face of the optical fiber 71 concave, the incident angle of most of the light emitted from the phosphor layer 72 becomes smaller than when the incident end face is flat as in the conventional case. The number of components incident perpendicularly to the plane increases.

Therefore, the amount of light that is totally reflected at the incident interface is significantly smaller than that in the conventional case, and the light is effectively guided into the optical fiber.

(Effects of the Invention) As explained in detail above, the present invention provides an output fluorescent surface using an optical fiber plate, in which the incident surface is curved for each optical fiber forming the optical fiber plate.
The interface between the fluorescent material embedded in the curved surface and the optical fiber has a positive effect on the light entering the optical fiber from the fluorescent material when the optical axis is the central axis of the optical fiber. It is composed of

Therefore, it serves to collect fluorescent light emitted from various directions into the optical fiber, and the rays of the collected emitted light have a smaller angle with respect to the optical axis of the optical fiber, and as a result, the rays of the collected emitted light have a smaller angle with respect to the optical axis of the optical fiber. The number of reflections is reduced, and variations in the transmission efficiency of fluorescent light emitted by individual optical fibers due to variations in reflectance on the reflective surface are reduced, resulting in faithful reproduction of images.

The refractive index of the fluorescent material is usually greater than the refractive index of the optical fiber, and the curved surface is concave.

Furthermore, by forming a thin layer of metal on the top surface of the fluorescent material, a so-called metal back metal layer, the light emitted from the phosphor between this layer and the concave surface of the optical fiber is transferred to the metal back. Due to the metal layer and the concave surface, most of the light is sent into the corresponding optical fiber, and there is almost no possibility that the light will enter other optical fibers.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of an image intensifier using an output fluorescent surface using an optical fiber plate 1 according to the present invention. FIG. 2 is an enlarged cross-sectional view of an output fluorescent surface using an optical fiber plate according to the present invention. FIG. 3 is an enlarged cross-sectional view showing a portion of the fluorescent surface of the embodiment related to one optical fiber. FIG. 4 is a cross-sectional view showing an example of an output fluorescent surface using a conventional optical fiber plate. 2... Optical fiber plate 3 forming an incident surface...
Photocathode 4... Vacuum vessel 5... Electron optical system 6... Micro channel plate 7... Output fluorescent surface 71 using optical fiber plate.
... Optical fiber 72 ... Phosphor layer 73 ... Metal back layer Patent applicant Hamamatsu Photonics Co., Ltd. Agent Patent attorney Inoro Mizoka) Figure

Claims (3)

[Claims] (1) In the output fluorescent surface using an optical fiber plate, the entrance surface is curved for each optical fiber forming the optical fiber plate, and the interface between the fluorescent material embedded in the curved surface and the optical fiber. Output fluorescent light using an optical fiber plate, characterized in that the optical fiber plate is configured to have a positive effect on light incident on the optical fiber from the fluorescent material when the central axis of the optical fiber is the optical axis. surface. (2) An output fluorescent surface using an optical fiber plate according to claim 1, wherein the refractive index of the fluorescent material is greater than the refractive index of the optical fiber and the curved surface is concave. (3) In the output fluorescent surface using an optical fiber plate, the entrance surface is curved for each optical fiber forming the optical fiber plate, and the interface between the fluorescent material embedded in the curved surface and the optical fiber. has a positive effect on light incident on the optical fiber from the fluorescent material when the optical axis is the central axis of the optical fiber, and further a thin metal layer is formed on the upper surface of the fluorescent material. An output fluorescent surface using an optical fiber plate, characterized in that the output fluorescent surface is configured with an optical fiber plate.