JPS6343475A - X-rays screening projecting lens - Google Patents

Abstract

PURPOSE:To screen X-rays which occurs from a cathode ray tube without using another screening body by making a lens barrel with plastics which is made to include X-rays screening materials in order to hold an attenuation factor necessary to screen the Xrays. CONSTITUTION:Plastic materials used for a cathode ray tube lens barrel 11 includes the materials which screen X-rays, heavy metal, inorganic materials, such as a lead compound, a barium compound, a strontium compound, etc., so as to screen the X-rays which occurs from the cathode ray tube 7. For example, the at tenuation factor of the X-rays in case of mixing the lead com pound PbO at 40% with the plastics is improved much more than the attenuation factor of the X-rays in case of using only plastics and moreover improved more than the characteristic of the materials of a glass lens. Even in case of mixing the barium compound at 40% with the plastics, the attenuation factor of the X-rays is improved much more than that obtained by using only plastics as materials.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to video projectors - X-rays used for shielding harmful X-rays emitted by cathode ray tubes such as televisions and enlarging images. This invention relates to a shielding projection lens.

Conventional technology In the past, glass lenses were mostly used for high-precision optical lenses, but in recent years, plastic lenses have been developed for the purpose of weight reduction and have been put into practical use using plastic molding and cutting techniques. ing.

Plastic lenses are rapidly being adopted for projection lenses that require high-precision, large-diameter lenses.

This type of lens is mostly used in video projectors, but if the video projector malfunctions and high voltage is applied to the cathode ray tube, X-rays that would not normally be emitted will be transmitted to the cathode ray tube. Generated from the light emitting surface. With a projection lens that uses a glass lens, these X-rays are absorbed by the lens material glass and are not emitted to the front of the lens, but with a projection lens that uses a plastic lens, the plastic absorbs almost no X-rays. It has the disadvantage that X-rays are emitted to the front surface of the lens. Therefore, for the purpose of shielding X-rays, the present applicant proposed a projection lens as shown in Japanese Patent Application No. 69-219708 filed earlier. A conventional projection lens will be described below with reference to the drawings.

FIG. 4 is a cross-sectional view of a first example of a conventional projection lens composed of three lenses, all of which are plastic lenses.

1 is a lens barrel made of a resin molded product, and 2, 3, and 4 are plastic lenses. Reference numeral 7 denotes a cathode ray tube, and the image projected thereon is projected onto a screen (not shown) via a projection lens. Similarly, X-ray A.

B, C, D, and E are also emitted to the outside. Therefore, this X-ray must be shielded.

A glass plate 6 can block X-rays B, C, D, and E, but X-rays A pass through the lens barrel 1 and leak to the outside. Reference numeral 6 is an X-ray shielding frame that shields X-rays A leaking from the lens barrel 1.

8 is a back cover for shielding X-rays generated from the rear surface of the cathode ray tube. As described above, this conventional example is characterized in that a glass plate is mounted inside the lens barrel to block X-rays passing through the lens, and a shielding frame blocks X-rays leaking from the lens barrel. FIG. 6 shows a second conventional example.

1 is a lens barrel, 2 and 4 are plastic lenses, and 9 is a glass lens. In this example, X-rays passing through the glass lens 9 can be blocked;
X-rays passing through 11 cannot be blocked.

Therefore, X-rays are shielded by the X-ray shielding ring 10, which has an inner diameter hole slightly smaller than the outer diameter of the glass lens and is dimensioned to be joined to the inner wall of the lens barrel 1. Even in this case 1
As in the example, X-rays A pass through the lens barrel, and X-rays F and G leak through the thickness of the lip that positions the glass lens 9 and the X@shielding ring 10.

Therefore, it must be shielded by the X-ray shielding frame 6 as in the first example.

Problems to be Solved by the Invention As described above, when plastic is used for the lens barrel 1, unlike materials that shield X-rays such as iron, lead, and zinc steel plates, parallel X-rays inside the lens barrel can be shielded. cannot block the X-rays passing through the lens barrel wall. Therefore, in addition to the projection lens, the outer periphery must be surrounded by an X-ray shielding frame or the like. Even so, the contact between the lens barrel and the shielding frame has poor adhesion, and lead tape or other material is pasted thereon to prevent leakage of X-rays.

This has many problems, such as the cost of metal press molds and parts, and the large number of parts, which requires more man-hours for assembly. In addition, since the X-rays must be measured after the projection lens is assembled to find the leakage location, the size and shape of the X-ray shielding frame cannot be made perfect from the beginning and has to be repeatedly corrected. There is.

The present invention eliminates the drawbacks of plastic lenses and plastic lens barrels as described above, and provides a projection lens having an X-ray shielding effect.

The only way to solve the problem is to use materials (lead compounds,
Barium compounds, strontium compounds.

Heavy metal inorganic materials, etc.) are contained in plastic to have the attenuation rate necessary to shield the generated X-rays, a lens barrel is manufactured using the plastic, and a plastic lens and a glass lens are combined in the lens barrel. Due to this,
It is characterized by having a structure that shields the wires.

According to the present invention, it is possible to provide an X-ray shielding projection lens configured to shield X-rays generated from a cathode ray tube without using a separate shield and to enlarge and project an image of the cathode ray tube. can.

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of an embodiment of the present invention. Reference numeral 11 denotes an X-ray shielding plastic lens barrel that shields X-rays from exiting the projection lens in the structure of the X-ray shielding projection lens of the present invention. The plastic material used for this lens barrel 11 is a material that shields X-rays, such as lead compounds, barium compounds, strontheim compounds, and other heavy metals, in order to shield X-rays generated from the cathode ray tube.

A plastic material mixed with an inorganic material or the like is used so as to have an X-ray attenuation rate necessary to shield the X-rays generated from the cathode ray tube.

In the case of a video projector-television, an X-ray shielding material at least similar to conventional iron plates or bad lead steel plates is required to shield the X-rays generated when high voltage is applied to the cathode ray tube. Among the X-ray shielding materials, for example, 13 lead compounds such as Pb
When 40% of O is mixed into plastic, the X-ray attenuation rate has the characteristics shown in 13 in Figure 2.
Glass lens material 5K with linear attenuation rate significantly improved from 12
The X-ray attenuation rate is improved compared to characteristic 15 of -5. Furthermore, the X-ray attenuation rate 14 when 40'% of barium compound B a S O 4 is mixed into plastic is also close to that of glass lens material 5K-5, but slightly worse. However, the X-ray attenuation rate is significantly improved over the X-ray attenuation rate of 12 for plastic alone.

This material was molded into an actual lens barrel, attached to a cathode ray tube, and the amount of leakage of X-rays generated from the cathode ray tube was investigated (the experiment was carried out in 2
．． 6), for example, PbO4o
Although it varies depending on the amount of X-rays generated in the case of a person, as shown in Figure 3, the characteristics 17 of the lens barrel made only of plastic and the characteristics 18 of the plastic lens barrel mixed with PbO indicate that the leakage of X-rays is o, 18-
Significantly improved to 0.2 mR/Hr, safety standard 0.5
m R/Hr or less.

As shown in this example, when PbO is mixed at 40%, it is possible to achieve the same X-ray attenuation rate and leakage as glass, but other X-ray shielding materials such as lead compounds, barium, and strontheim compounds may also be used. Similarly, it is necessary to determine the mixing ratio by examining the X-ray attenuation rate and the amount of X-ray leakage.

In addition, in order to completely block X-rays from a cathode-ray tube as a projection lens, the structure of the lens barrel made by mixing the above-mentioned X-ray-shielding material must be constructed so as to cover the entire front and side surfaces of the cathode-ray tube from which X-rays leak. It is important to.

Therefore, as shown in Fig. 1, the plastic lenses 2 and 4 and the glass lens 9 are held in the X-ray shielding lens barrel 11 by a lip made of X-ray shielding material and integrally formed with the lens barrel, creating a gap between the lenses and the lens barrel. By doing so, the ribs block transmitted X-rays such as X-rays H.

The X-ray technician is shielded by a glass lens. The X-rays A are blocked by the outer wall of the lens barrel 11. The X-rays J are X-rays that leak directly without passing through the lens, but are blocked by the wall surface to which the cathode ray tube 7 of the lens barrel is attached. As before, the rear surface of the cathode ray tube 7 is shielded from pX-rays by an iron frame 8.

Effects of the Invention As is clear from the above explanation, the present invention is similar to conventional lenses in which leakage of X-rays is prevented by manufacturing and combining a lens barrel with a glass lens and a plastic material mixed with an X-ray shielding material. Achieves the purpose of X-ray shielding with a simple configuration without installing expensive flat glass or metal rings for X-ray shielding, or using iron frames or lead tape for X-ray shielding. are doing. Therefore, the structure is simple, the number of parts is reduced, assembly time is short, and manufacturing is possible at low cost.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of an X-ray shielding projection lens according to an embodiment of the present invention, Figs. 2 and 3 are graphs showing its effects in comparison with a conventional example, and Figs. 4 and 6 respectively. FIG. 2 is a cross-sectional view of a conventional projection lens. 2.4...Plastic lens, 7...
・Cathode ray tube, 9...Glass lens, 11...
...Lens barrel. Name of agent: Patent attorney Toshio Nakao and 1 other person
2 Figure o S 10 I
sz. Sometimes (−

Claims (1)

[Claims] An X-ray shielding lens barrel is manufactured by mixing plastic with a material that shields X-rays so that it has an X-ray attenuation rate necessary to shield the X-rays generated by the cathode ray tube, and the X-ray shielding lens barrel and the plastic are mixed. An X-ray shielding projection lens constructed by combining a lens and a glass lens.