JPS63205606A - Projection lens - Google Patents

Abstract

PURPOSE:To shield X-rays and to permit magnification of a video by combining plastic lens barrels for shielding X-rays formed by incorporating plastic into an X-rays shielding material and a lens group combined with at least >=1 pieces of plastic lenses and glass elements. CONSTITUTION:Materials which shield the X-rays generated from a cathode ray tube 7 (simple substances of a lead compd., barium compd., strontium, titanium, zirconic acid compd., heavy metallic inorg. materials, etc., or mixed materials composed of several kinds thereof) are incorporated into the plastic so as to have <=0.5mR/Hr attenuation rate necessary for shielding the generated X-rays. The lens barrels 17-19 are manufactured by using such plastic. The plastic lenses 2, 4 and the glass lens 9 are combined with the lens barrels 17-19, by which the construction to shield the X-rays is obtd. The X-rays generated from the cathode ray tube is thereby shielded without using another shielding bodies and the macro-projection of the video of the cathode ray tube is permitted.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a projection lens used for shielding X-rays harmful to the human body generated from cathode ray tubes of video projectors, televisions, etc., and for enlarging and projecting images. It is related to.

Conventional technology In the past, high-precision optical lenses usually used a combination of a glass lens and a metal mirror, but in recent years plastic lenses have been developed with the aim of reducing weight and using plastic molding technology and plastic cutting technology. is being developed and put into practical use.

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 are emitted from the cathode ray tube. Occurs from the surface. glass lens.

In metal lens barrels, these X-rays are absorbed by the lens material glass and are not emitted to the front surface of the lens. In addition, X-rays passing through the outside of the glass lens were blocked by the metal lens barrel, and no X-rays leaked to the outside. However, projection lenses that use a combination of a plastic lens and a plastic lens barrel have the disadvantage that the plastic absorbs almost no X-rays, so the X-rays are not absorbed, are emitted to the front of the lens, and leak out of the lens barrel. are doing.

Therefore, for the purpose of shielding X-rays, the present applicant filed Japanese Patent Application No. 69-219708 (Japanese Unexamined Patent Publication No. 61-97617).
proposed a projection lens as shown in the following publication.

A conventional projection lens will be described below with reference to the drawings. FIG. 5 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 in the diagram
is a plastic lens barrel, and 2, 3.4 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-rays A, B, C, and D.

E is also emitted to the outside. Therefore, this X-ray must be shielded. 6 is a glass plate for X-rays B and C.

Although X-rays D and E can be blocked, X-rays A pass through the lens barrel 1 and leak to the outside. Reference numeral 6 denotes an X-ray shielding frame that shields X-rays A leaking from the lens barrel 1.

Reference numeral 8 denotes a back cover for shielding X-rays generated from the rear surface of the cathode ray tube 7.

As described above, in this conventional example, the glass plate 6 is mounted inside the lens barrel 1 to shield X-rays passing through the lenses 2, 3.4, and the shielding frame 6 and back cover 8 are used to shield the lens barrel. It is characterized by blocking X-rays leaking from 1.

FIG. 6 shows a second conventional example. In this example, 2.4 is a plastic lens, and 9 is a glass lens. X-rays that try to pass through these lenses can be blocked by the glass lens 9, but X-rays that pass outside the outer diameter of the glass lens 9
11iIA, , F, G cannot be shielded. Therefore, the inner diameter hole with a diameter slightly smaller than the outer diameter of the glass lens and the outer lens barrel 1
X made of iron plate finished with dimensions to be joined to the inner wall of 2
X-rays are shielded by a radiation shielding ring 10. In this case, as in the first example, the X-ray A passes through the outer lens barrel 12,
X-rays F and G are connected to a glass lens attachment fixing lip 16 that positions and attaches the glass lens 9 and the x#J shielding ring 1o, and
Since a gap is created between the glass lens 9 and the X-ray shielding ring 1o by the ray shielding ring fixing rib 16, leakage passes through this gap.

Therefore, as in the first example, the X-ray shielding iron frame 1 is placed outside the outer lens barrel 12.
4, an xfa shielding iron frame 13 is provided on the outside of the inner lens barrel 11,
These shielding iron frames 13 and 14 must shield the X-rays that have passed through the lens barrels 11 and 12.

Problems to be Solved by the Invention As mentioned above, when plastic is used for the lens barrel, there is a difference between using plastic for the lens barrel and materials that shield X-rays such as iron, lead, and zinc steel plates. The parallel X-rays of glass lens 9
However, it is not possible to shield oblique X-rays that are not parallel to the lens barrel and pass through the wall of the lens barrel 9. Therefore, in addition to the projection lens, the outer periphery of the lens barrel must be surrounded by X-ray shielding iron frames 13 and 14. Even so, the adhesion between the lens barrel and the shielding steel frame is poor, and a small gap is created from which X-rays leak. Therefore, it is necessary to stick lead tape or the like over the gap where the X-rays leak. Measures are being taken to prevent leaks. This requires metal press molds and parts costs, requires a large number of parts, and requires assembly man-hours, etc., which is costly.

There are many light points between the ground. Also, after assembling the projection lens, X-rays must be measured and leakage locations must be found, so the size and shape of the X-ray shielding iron frame cannot be made perfect from the beginning and must be revised repeatedly. There was a problem.

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.

Means for Solving the Problems The present invention provides a material (
The above-mentioned
It is contained so as to have the attenuation rate necessary to shield the line,
A lens barrel is manufactured using the plastic, and a plastic lens and a glass lens are combined in the lens barrel to provide a structure for shielding X-rays.

According to the present invention, it is possible to provide a projection lens configured to block 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.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of an embodiment of the present invention.

In the figure, reference numeral 17 denotes an inner lens barrel, which fixes the plastic lens 2 and the glass lens 9 in predetermined positions.

Reference numeral 18 denotes an outer lens barrel for positioning and fixing the plastic lens 4. Reference numeral 19 denotes a lens barrel for attaching and fixing the cathode ray tube 7 and the lens.

These inner tubes 17. Outer barrel 18. The lens mounting barrel 19 is an X-ray shielding plastic barrel that shields X-rays from exiting the projection lens in the structure of the X-ray shielding projection lens of the present invention. This inner lens barrel 17. Outer barrel 18. The plastic material used for the lens mounting barrel 19 is made of materials that shield X, [1, such as lead compounds, barium compounds, strontium, titanium, zirconate, Zinc 2 alloy (pb-
8n) Other heavy metals, metals, inorganic substances, mixtures thereof, composite substances, etc. are mixed into plastic so as to have the necessary X-ray attenuation rate to shield the X-rays generated by the cathode ray tube. It has a sealed structure that covers at least the entire front surface of the cathode ray tube 7 and prevents X-rays generated from the cathode ray tube 7 from leaking from the projection lens.

In the case of a video projector-TV, the X-rays generated when high voltage is applied to the cathode ray tube are Although the high voltage applied varies, it is usually 46 to +ekV. The amount of X-rays generated at that time is 1600μA
, 2000 μA.

Looking at the current value of 2500 μA and the voltage value of 42 to 4 ekV, T in Figure 2 20 shows that the higher the current value, the more leakage of X-rays as shown in the L line, and the higher the voltage, the more leakage of X-rays. is large. Therefore, the lens barrel 17°18.19GC example in Fig. 1, u
10% i'xm shielding material PbO.

The results of investigating the amount of X-ray leakage by containing 20% and 30% (1
The wall thickness of the lens barrels 7, 18, and 19 was 2.5+m t ), as shown in Fig. 2, 22, 23, and 24. Here, 22 contains 10% Pb0, 23 contains 20% pbo, and 24 contains 30% PbO, and the amount of X-ray leakage will be 0.5 m R/Hr or less if the PbO content is 20% or more. (However, P
Even with b010% content, the current value is 1600 μA and the voltage is 43
kv or less, it is 0.5 mR/Hr).

Incidentally, 20 is the data when the lens is not attached, and 21 is the data when the conventional lens barrel shown in FIG. 6 is used, and it is clear from these data that an X-ray shielding iron frame is required.

Therefore, in order to reduce the amount of X-ray leakage to 0.5 mR/Hr or less, the X-ray attenuation rate of the plastic containing the X-ray shielding material is investigated and the X-ray shielding plastic material is selected based on the relationship between the amount of leakage and the attenuation rate. All you have to do is choose. Figure 3 shows experimental data on the relationship between the X-ray attenuation rate and the amount of leakage.
(inner tube 17 is 2.5 mm thick and outer tube 18 is 2.5 mm thick), the leakage amount is 0.5 m, and the attenuation rate of R/Hr is:
Under the current/voltage of 1500/IA/451CV of 25, the point of 28 is 0.16 or less, 26 (D2000/IJA/
Under 45kVO current/voltage, the point 29 is 0.098 or less, and under 27, 2500μA/45kVO current/voltage, the point 3o is 0.09 or less. Based on the relationship between the amount of leakage of X-rays and the attenuation rate, various xa shielding materials (B a S O4tB a Z 03 r S
r CO3, Z n , P b S n alloy, other heavy metals, metals, inorganic substances, or complex mixtures thereof, etc.) in various proportions x11i! The attenuation rate of the shielding plastic material is measured for various wall thicknesses, and an attenuation curve depending on the X-ray shielding material content and wall thickness is created, for example, as shown in FIG. 4, and is used in a video projector-television. Depending on the voltage and current values generated by various cathode ray tubes,
Make material selection. For example, 45 kV, 2500/
In the case of JA, as shown in Figure 3, the plastic containing an X-ray shielding material, that is, the lens barrel, has an attenuation rate of 0.09 or less at the intersection point 3o of the 0.5mR/Hr leakage line and the 2500zlA/45kV attenuation curve. If the wall thickness of the inner and outer barrels is 5 sam, the material (Pb020%) has an attenuation rate of 0.09 or less on the 5 m thickness line in Figure 4.
(Zn50%), (B a SO450%), (PbO
1o%/B a S O4 40%χ (pb-3n alloy 3
0%), (Pb030%), etc. can be used. In addition, materials with a lower attenuation rate than these materials, i.e. (P b,
z r O320%) (PbTiO320%), (Zn
30%), (PbO10%), (B a Z r O3
20%), (S r CO3 20%), etc., the wall thickness of the lens barrel should be selected so that it is below the dot plate that intersects with the line of the attenuation factor of 0.09. For example, P b T 10320%
In this case, the wall thickness should be 6.6 trm or more, and in the case of 30% Zn, the wall thickness should be 8 trm or more. Furthermore, even if the wall thickness can only be 5 m or less due to the design, it is sufficient to select an M-shielding material that is equal to or less than the intersection of the attenuation factors of 0.09 or less on the designed wall thickness line.

The above example has been explained, but when the voltage and current values are different from this case (46kV/2000/JA).

43kV/1500/jA, and various other types), it goes without saying that the X-rays generated by the voltage and current applied to the cathode ray tube can be shielded by appropriately combining the wall thickness of the lens barrel and the attenuation rate of the X-ray shielding material. stomach.

In addition, the content rate and attenuation rate of the X-ray shielding material listed in the examples are just examples; there are many other shielding materials, and depending on the purpose of use, various shielding materials may be included in the plastic to create an attenuation curve and leakage amount. It is important to create and use relationships.

As shown in Fig. 1, the plastic lenses 2 and 4 and the glass lens 9 are each held by a lip made of an X-ray shielding material and integrally formed with the plastic lens barrel, and configured to create a gap between the lenses and the lens barrel. Therefore, the transmitted Xa like X@H is blocked by the rib. The X-ray operator is shielded by a glass lens.

Further, X@A is shielded by the wall surface of the outer lens barrel 18.

Note that the lens mounting barrel 19 is fixed to the cathode ray tube side with screws (not shown), and the outer barrel 18 is fixed to the cathode ray tube side with a screw (not shown).
The inner barrel 17 is partially inserted into the outer barrel 18 and fixed using a fixing part 20 and screws (not shown).

Effects of the Invention As is clear from the above description, the present invention can reliably prevent leakage of X-rays by manufacturing and assembling a lens barrel from a glass lens and a plastic material mixed with an X-ray shielding material. Unlike conventional lenses, there is no need to separately install expensive x'fm shielding flat glass or metal rings just for X-ray shielding, or use iron frames or lead tape for X-ray shielding. It has achieved the purpose of line shielding. Therefore, the structure is simple, the number of parts is reduced, the assembly time is short, and it can be manufactured at low cost.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a projection lens according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of a projection lens according to an embodiment of the present invention.
A characteristic diagram showing an example of the measurement results of the amount of X-ray leakage depending on the amount of X-ray leakage and the mixing ratio of the xIw shielding material. Figure 3 is a characteristic diagram showing the relationship between the attenuation rate of the mixing ratio of the xm shielding material and the amount of leakage. The figure is a characteristic diagram showing an example of the measurement results of the X-ray attenuation curve depending on the mixing ratio and wall thickness when various X-ray shielding materials are mixed.
figure. FIG. 6 is a sectional view of each conventional projection lens. 2, 4...Plastic lens, 7...
・Cathode ray tube, 9...Glass lens, 17, 18
．． 19...Plastic lens barrel mixed with X-ray shielding material. Name of agent: Patent attorney Toshio Nakao and one other person?

Claims (4)

[Claims] (1) Consists of an X-ray-shielding plastic lens barrel made of plastic containing an X-ray-shielding material, and a lens group consisting of a combination of at least one plastic lens and a glass element, which blocks X-rays generated from a cathode-ray tube. A plastic mirror containing an X-ray shielding material that shields X-rays and has an X-ray attenuation rate such that the amount of X-rays generated from the cathode ray tube leaking from the lens barrel is 0.5 mR/Hr or less. A projection lens using a tube. (2) The projection lens according to claim 1, wherein the X-ray shielding plastic lens barrel covers at least the entire front surface of the cathode ray tube, and has a structure that prevents X-rays generated from the cathode ray tube from leaking from the projection lens. (3) Measure the X-ray attenuation rate of a composite material for a plastic lens barrel manufactured by mixing different X-ray shielding materials with plastic at a predetermined ratio, and project it against the amount of X-rays generated by the cathode ray tube. A projection lens according to claim 1 or 2, which uses an X-ray shielding composite material selected from an X-ray shielding composite material having an X-ray attenuation rate such that X-rays leaking from the lens are 0.5 mR/Hr or less. . (4) When the lens barrel is made of plastic material mixed with X-ray shielding material, the amount of X-rays leaking from the projection lens is 0.5 m.
The projection lens according to claim 1 or 2, wherein the wall thickness of the lens barrel is set to be R/Hr or less.