JPS6224898B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an imaging device in which bias light is efficiently introduced and irradiated onto an imaging tube face plate from the bottom side of a stem.

In photoconductive image pickup tubes, afterimage characteristics are improved by irradiating a photoconductive film formed on a face plate with bias light. For this reason, various methods for uniformly and efficiently irradiating a photoconductive film with minute light have been studied. For example, by putting a light source inside the optical system,
Alternatively, there is one in which a light source is placed near the face plate of the image pickup tube. However, these methods have limited space in front of the image pickup tube, and cannot necessarily be generally applied. As a method that is not subject to spatial constraints, a light source is installed inside the stem pin insertion socket of the image pickup tube, and light is introduced into the image pickup tube from the bottom of the stem. A method has been proposed in which a photoconductive film is irradiated through a hole. However, in this method, the efficiency is extremely low depending on the distance between the light source and the hole in the electrode for light incidence, and in practical use, many problems occur, such as increased power consumption and increased heat output from the light source.

SUMMARY OF THE INVENTION An object of the present invention is to provide an imaging device that efficiently irradiates a photoconductive film with bias light introduced from the bottom surface of a stem, without the problems of the conventional bias light irradiation method.

In order to achieve the above object, in the present invention,
Traditionally, the electrode assembly of an electron gun has been held by providing parts that protrude in the radial direction from each electrode, and welding and fixing these parts to a glass rod placed outside the electrode assembly parallel to the tube axis. And the light incident on the inside of the glass rod in the axial direction from one end of the glass rod is
Focusing on the fact that the light is totally reflected inside the glass at the interface between the glass and the surrounding space and reaches the other end with low loss, we created a transparent glass rod that uses the light incident on the bottom of the stem to both hold the electrode structure and transmit light. Therefore, it was decided to efficiently guide light to the hole in the electrode, which has a hole for light incidence facing the photoconductive film. Since the photoconductive type image pickup tube scans with a low-speed electron beam, the potential difference between each electrode is relatively small, and a glass material suitable for light transmission can be selected relatively freely.

FIG. 1 is a diagram showing an embodiment of the present invention. 1 is a glass bulb, 1 _a is a stem, 1 _b is a stem pin, 2 is a first grating, 3 is a second grating, 4 is an accelerating electrode, 4 _a is a hole for light incidence, 5 is a transparent glass rod, 10 is a light source, 2
0 is the optical path. There is a face plate (not shown) facing the accelerating electrode 4, and a photoconductive film is formed on the inner surface (on the accelerating electrode side). The first grating 2, the second grating 3, and the accelerating electrode 4 each have a protrusion in the radial direction, and these protrusions are welded and fixed to the transparent glass rod 5 to hold the electrode structure of the electron gun. There is.
The light incident on the bottom of the stem _1a from the light source 10 is
The light is axially incident into the interior of the glass rod from the stem-side end surface of the transparent glass rod 5, and the refractive index of the glass is higher than the refractive index of the surrounding vacuum, and at a large incident angle, the light is incident on the glass rod surface (at the interface between the glass and the vacuum). The light that reaches this point is totally reflected, and since it repeats the total reflection and does not exit the glass rod, it reaches the vicinity of the light entrance hole _4a provided in the accelerating electrode 4 with low loss. If there were no glass rod 5, the illuminance on the light receiving surface is inversely proportional to the square of the distance from the light source when the distance is large relative to the _size of the light source. The illuminance from the light source 10 is extremely low, and it is impossible or extremely difficult to illuminate the entire surface of the photoconductive film further away from the hole due to restrictions on the electrode arrangement of the image pickup tube. On the other hand, if the present invention is implemented and both ends of the glass rod 5 are brought as close as possible to the hole _4a and the light source 10,
Since the optical loss during transmission within the glass rod is small, bias light irradiation can be applied to the photoconductive film using a practical low-power light source. Even if you decide to use the glass rod 5, as the distance between the end of the glass rod and the hole in the electrode or the light source increases, the effect of inserting the glass rod into the optical path will suddenly increase, as shown in Figure 2. descend. When the distance becomes four times or more the diameter of the glass rod, the effect of inserting the glass rod is virtually eliminated. Furthermore, in order to obtain appropriate bias irradiation with a low-power light source, a light bulb may be used in which a part of the bulb, for example, the head part, has a large glass thickness so as to have condensing lens characteristics. The light receiving surface illuminance distribution of this light bulb with a condensing lens approximates a Gaussian distribution, and between two points where the intensity decreases to 1/e of the value at the center is what is called 1/e.
Since most of the light energy is concentrated within the width e, the diameter of the glass rod 5 and the distance between its end and the light source are determined by the diameter of the glass rod 5 at the end position on the light source side. If the width is set to be 1/e or more of the illuminance distribution of the light source, light loss will be small. Note that in order to reduce light loss and increase usage efficiency, it is obvious that the hole _4a provided in the accelerating electrode, the transparent glass rod 5, and the light source 10 must be located on a straight line parallel to the axis of the image pickup tube. However, it is preferable that the shapes of both ends of the transparent glass rod 5 are convex toward the hole 4 _a provided in the electrode and convex toward the light source 10 , respectively. That is, if both ends of the transparent glass rod 5 are formed in this way, out of the light incident from the light source 10,
The rate of total reflection of light increases, and the light condensing ability to the hole also improves on the hole _4a side. Figure 3 shows the effect of making the end shape convex to the outside by contrasting the case where both ends of the glass rod 5 are flat in the left half A and the case where the end shape is convex outward in the right half B. FIG.

As explained above, according to the present invention, the light incident on the bottom surface of the stem from a low-power light source is efficiently guided to the photoconductive film provided on the face plate of the image pickup tube, thereby creating a bias that is effective for improving the afterimage characteristics of the image pickup tube. Since light can be applied and the same glass rod is used for both light transmission and holding the electrode structure, there is an advantage that there is almost no increase in manufacturing costs.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an example of the present invention, Figure 2 is a diagram showing changes in illuminance depending on the distance between the end of the glass rod and the electrode hole or light source, and Figure 3 is a diagram with the end of the glass rod convex outward. It is a figure explaining an effect. 1... Glass bulb, 1 _a ... Stem, 4...
Accelerating electrode, 4 _a ... hole for light incidence, 5 ... transparent glass rod, 10 ... light source.

Claims (1)

[Scope of Claims] 1. An electron gun consisting of a photoconductive film formed on the inner surface of one end of a cylindrical glass bulb, a plurality of electrodes coaxially held by a transparent glass rod, and an electron gun that holds the electron gun. , and a stem formed at the other end of the glass bulb for supplying power to the electron gun, and a light source disposed on the outer surface of the stem for irradiating the photoconductive film with bias light. In the imaging device, (a) a radially protruding portion provided on each of the plurality of electrodes is welded to the glass rod arranged parallel to the tube axis, so that the plurality of electrodes are spaced at a predetermined interval; (b) the light source is placed on an extension of the transparent glass rod, and (c) the electron gun is configured to allow light incident on the transparent glass rod from the light source to pass through to the photoconductive film side. (d) the shapes of both ends of the transparent glass rod are convex toward the hole provided in the electrode and convex toward the light source side, respectively, and the shape of both ends and the hole provided in the electrode are and (e) the distance to the light source is 4 times or less the diameter of the transparent glass rod, and (e) the illuminance distribution at the end of the transparent glass rod is l/
An imaging device characterized in that light from the light source is made incident through a condensing lens such that the width e is equal to or less than the diameter of the transparent glass rod.