JPS60100346A - Projection type cathode ray tube - Google Patents

Abstract

PURPOSE:To improve the rate of beam-condensing of lens units by making intensity distribution of light distribution at a emission point in a fluorescent screen different in the central portion from that in the circumference portion when introducing the light emitted from a projection type cathode ray tube into projection lens units. CONSTITUTION:A projection type television set 1, in which pictures from the monochrome cathode ray tubes 2-4 with blue, green and red color are enlarged and projected on a front picture screen 6 by means of projection lens units 5, is formed to obtain color pictures. And when introducing the light emitted from respective cathode ray tubes 2-4 into the lens units 5, the intensity distribution of light distribution on a fluorescent screen 8 is selected to match to the introducing angle of luminous flux which is determined by the geometrical position relationship between the point on the fluorescent screen 8 and the lens units 5, for example, the most part of luminous flux in the area over 20 deg. of the angle of divergence is set to converge within the area of 20 deg.. Thus, it is possible to make the rate of beam-condensing of the lens units 5 large and to improve the brightness of the pictures.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention enlarges and projects an image projected on a fluorescent surface onto a video screen in front of it through a projection lens placed opposite to the fluorescent surface. The present invention relates to a projection type cathode ray tube.

[Prior art]

For television sets that use shadow mask color cathode ray tubes, which are currently in widespread use, it is thought that the screen size that can be obtained is limited to about 30-40 mm, mainly due to their structural constraints. ing. For this reason, a projection television set (1) as shown in Figure 1 was developed as a means of receiving television images on a larger screen size, and is now becoming popular.

Such a projection television set (1) uses two small monochrome cathode ray tubes with a screen size of about 5 to 8 to realize monochrome images of B (blue), G (green), and R (red), respectively.
) , +3) , +4) In other words, the monochromatic image from the projection cathode ray tube is enlarged and projected onto the video screen (6) in front of the projection lens unit (5).
) You can get a large-screen color image on the screen.

The size of the video screen (6) is generally about 40 to 70, so small monochrome cathode ray tubes F21 and +31 are used.
, +4) are projected on the video screen (6) with an area enlarged approximately 50 to 100 times. Therefore, in the projection television set (1), how a sufficiently bright projected image can be realized on the video screen (6) is an important point in terms of performance. For this reason, the cathode for projection? Improvements in the 1f41 ti phosphor, application of cathode ray 7 Hz t1q structure capable of high-load operation, and improvements to the video screen (6) and projection lens unit (5) are continuing.

However, in projection television (7) (1), one of the major factors hindering the improvement of the brightness of the projected image is the monochromatic cathode ray tube for projection (21, (31, (41) There is a low condensing efficiency when light is taken into the lens unit (5).This problem will be explained in detail in Figure 2.1.!11.

Figure 2 shows the projection lens unit (5), which is the image projection part of the projection television set (1), and the monochrome IXA tubes (2+, +3+, +4+) arranged in front of it.
FIG. Monochrome printing for projection 4fA thin tube f2)
, [31, +41 consists of a vacuum envelope (10) and an electron gun (not shown) inserted inside the vacuum envelope (10). A phosphor layer (8) is formed on the inner surface of the face plate (7) that constitutes a part of the envelope (101). Electron 4k 10th: A metal back film (9) made of aluminum (At) evaporation film as a light reflecting film is formed to constitute a fluorescent surface (11). Back membrane (6)
The phosphor layer (8) is excited by the energy of an electron beam emitted from an electron gun (not shown) disposed opposite to each other on the side inner surface, and a phosphor surface emission output is obtained.

A projection lens unit (5) is disposed close to the front of the face plate (7) of such monochromatic cathode ray tubes f2), [31, +41. This projection lens unit (5) is usually configured as a compound lens that incorporates about 3 to 8 optical lenses (G) in a lens barrel (121). An example of a lens is shown below.In the case of such a projection lens unit (5), compared to the face plate size of monochromatic cathode ray tubes (2+, +3) and +41, due to aberration problems, cost and space ffl. It is difficult to choose a lens aperture that is too large.For this reason, the fluorescent surface (l
The useful angle of capture when light emitted from υ is captured into the full projection lens unit (5) is very limited.

For example, in the case of emission at the center of the fluorescent surface 01), the optically useful outermost optical path range is denoted by (lO). At the light emitting point, the angle (θl
) varies slightly depending on the configuration of the projection lens unit (5), but is approximately in the range of ±15° to ±20°. That is, θ1=±15° to 20°.

Similarly, in the case of light emission around the fluorescent surface (11), the optically useful range of the outermost optical path is indicated by C1h'). Also, the angles (02) and (θ3) formed by the optically useful outermost optical path (ne) with respect to the normal to the fluorescent surface (IIJ) at the light emitting point are approximately (θ angle is 15° or 20°, (θ3) becomes 25° to 30°.

That is, 15≦θ2≦20° and 25≦θ3≦306.

Therefore, the angle at which the light emitted from the fluorescent surface (11) is introduced into the projection lens unit (5) and the range in which the luminous flux is utilized differ greatly between the center and the peripheral portion of the fluorescent surface (11).

Figure 3 shows the fluorescent surface (
11) shows the light intensity distribution of light emission from the phosphor layer (8) when the phosphor layer (8) is excited by an electron beam, and in this case, the phosphor layer (8) Since it is almost a perfect diffusion surface, it follows LAMBERT's law. A diagram showing the relative luminescence intensity with respect to the divergence angle at this time is shown in FIG. In this way, when the phosphor layer (8) is close to a completely diffusing surface, the phosphor layer (8) emits light from the phosphor surface by the projection lens unit (5).
) will be described below.

In Fig. 3, the minute light-emitting surface at part (5) in the phosphor layer (8) of the phosphor surface (11) is designated as ΔS, and its direction tilted by θ with respect to the normal line of this part is designated as ΔS. The brightness of the point is Lθ
, if Iθ is the luminous intensity in the θ direction when observed from a sufficiently far distance compared to ΔS, then 1θ=/Lθ−cosods==LθIIcosθ・Δ
S......(■).

Further, when the light emitting surface is a completely diffusing surface, L is constant regardless of the angle and can be expressed as Lθ=L=const...-(II).

Now, the perfectly diffused light plane ΔS in such (6) section
Let Φθ be the luminous flux that is emitted into a cone with an apex angle of 2θ in front, then Φθ=flldω=/2′rdtpfθ16sinθ
dθ...(2) OO. Substituting (1) and (11) into 011) gives Φ0=2yrLISfθsinθ−eolIθdo=w
LΔ5sin'θ...contract). Therefore, the total luminous flux Φ emitted forward than ΔS
T is obtained by substituting θ=2 into equation (IV) and ΦT=>mar Lli
s ・River... (~r).

Therefore, if the light beam emitted from ΔS in part (6) of FIG. ,
becomes.

Figure 4 shows the relationship between the angle of capture of light emitted from monochromatic @polar rays into the projection lens unit (5) and the condensing rate. For type television sets, the fluorescent surface is +111? If the capture angle of the light emitted from the projection lens unit (5) in the center case is 01=±20', the light collection rate is only 12%.

Also, the situation around the fluorescent surface q11 is θ2=15°, θ3
= 306, the ratio of the luminous flux within this solid angle to the total luminous flux is approximately 18%, but in the case of the periphery of the fluorescent surface (1j), only a small portion of this luminous flux actually occurs. Since the light cannot be taken into the projection lens Enit (5), the light collection rate is extremely small. Therefore, in the case of a conventional projection television set, less than 10% of the luminous flux emitted from the fluorescent surface (II) is utilized, and nearly 90% of the luminous flux remains. does not contribute to the brightness of the screen image.

[Summary of the invention]

This invention improves the conventional projection television (7).
This was developed in view of the poor light condensing efficiency when incorporating monochromatic cathode ray light emission into the projection lens unit for projection in K. To provide a projection type cathode ray tube that can make the projected image on the screen of a projection type television set extremely bright.

[Embodiments of the invention]

Hereinafter, an embodiment of the present invention will be described with reference to FIG. The main point of this invention is that it is extremely difficult to increase θ in order to improve the light collection rate due to the constraints mentioned above.
) In contrast, the aim is to concentrate the luminous flux as much as possible and feed it in. In this case, as mentioned above, the angle at which the luminous flux is taken into the projection lens unit (5) and the usage range of the luminous flux are different between the center and the periphery of the fluorescent surface +Ill, so ideally the fluorescent Face t
From the center to the periphery of the phosphor surface (11), the phosphor surface (11) gradually increases in accordance with the take-in angle determined by the geometrical position between the point on the phosphor surface (11) and the projection lens unit (5).
) It is necessary to change each point Qj self light strength 1 no upper cloth.

Figure 6 iJ Distribution of light emission from the phosphor layer (8) when the phosphor layer (8) in the center of the phosphor surface 011 of the projection type monochromatic cathode ray tube according to the present invention is excited by an electron beam. It shows an example of light intensity distribution. In this case, the divergence angle is 20
Since a considerable part of the luminous flux in the area with a divergence angle of 20° or more is concentrated in an area with a divergence angle of 20° or more, the apparent light condensing rate of the projection lens unit (5) increases, and each angle within a divergence angle of 20° The luminous intensity of the fluorescent surface in the direction shown in Fig. 3 has been greatly improved compared to the conventional fluorescent surface (11) which is close to a completely diffused surface, and the projection lens unit (5) allows the projection lens unit (5) to (6) The brightness of the image projected at the center of the screen can also be significantly improved. FIG. 5(G) shows the relative emission intensity with respect to the divergence angle in the case as shown in FIG. 6.

Similarly, FIG. 7 shows the fluorescent surface 0 in the case of this invention.
) shows an example of the light intensity distribution of light emitted from the phosphor layer (8) when the phosphor layer (8) in the peripheral area is excited by an electron beam. In this case, the part of the luminous flux in the area where the divergence angle is 30 or more is between 15° and 30°.
Since the light is concentrated in the area within ', the apparent light collection rate of the projection lens unit (5) increases, and the intensity of fluorescent surface emission in each angular direction within the divergence angle of 15° to 30° also increases. , the projection lens unit (5) and the video screen (6).
) The brightness of the image projected on the periphery of the screen can also be significantly improved. FIG. 5M shows the relative emission intensity with respect to the divergence angle of 71' for the case as shown in FIG.

Note that the light emitting surface light distribution intensity distribution at the famous point of yB light tl+i (Ill
As a concrete method for J
0532 ``Cathode ray tube face plate structure for suppressing +: l'-) and low and method for suppressing the same'' is very suggestive. i.e. faceplay
) It has been suggested that the light emitting surface light intensity distribution can be changed by forming an optical interference film between +71 and the phosphor layer (8).

[The fruits of invention]

As described above, according to the present invention, in a projection television set, when capturing the projection cathode ray tube or the lamp emission into the projection lens unit, the geometry between the point of the fluorescent surface and the projection lens unit is adjusted. The light intensity distribution of the emitted light at each point on the fluorescent surface is optimized according to the angle of capture of the luminous flux determined by the relationship between flffi and the utilization of that luminous flux, and the apparent light condensing of the projection lens unit is optimized. As a result, the brightness of the projected image on the video screen can be significantly improved, making it possible to provide a high-quality projection television set.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the structure of a projection television set, Figure 2 is a cross-sectional diagram of a projection lens unit and a monochromatic cathode ray for projection disposed in front of it, and Figure 3 is a conventional projection type cathode. A diagram showing the light intensity distribution of the fluorescent surface of a capillary tube, Figure 4 is a diagram showing the relationship between the direction of light emission into the projection lens unit and the light collection rate, and Figure 5 is a diagram showing the divergence of the fluorescent surface light emission. A diagram showing the relative luminous intensity with respect to angle, FIG. 6 is a diagram showing the light intensity distribution at the center of the fluorescent surface of the projection type cathode capillary according to the present invention, and FIG. 7 is a diagram showing the periphery of the fluorescent surface in the case of the present invention. FIG. 3 is a diagram showing a partial light intensity distribution. (1)...Projection television set, (2+,
+31, [41...B (1 color), G (green), R
(Red) emitting monochromatic cathode ray tube, (5)...projection lens unit), (ll...l!!A!-image screen, (
7)... Face plate, (8)... Fluorescent layer,
(9)...Metal back film, uO)...Vacuum envelope, (111...fluorescence m1, (121...lens barrel). Note that the numbers in the first round are the same or equivalent. Shows the S minute. Agent Masuo Oiwa 1st IQi+ Figure 3 Figure 4 θ (degrees) Figure 5 Figure 6 Pe Figure 71a Just ° Left Sleeve Author (self-motivated) 59 9 21 Showa Year Month 1] Patent Director-General of the Agency2, Name of the invention Projection Cathode Ray Tube3, amend h Relationship with the case 1.1 Address of applicant No. 2, 1E12-3, JL, F-Yo IJI-ku, Tokyo Name ( 6 (1, 1) Mitsubishi Electric Corporation Representative Hitoshi Katayama 4, Agent address 11 Suga, 2-2-3 Marunouchi, 1'JJ-ku, Chiyo, Tokyo - 1 Den I 5 of the specification subject to amendment "Scope of Claims" column. 6 Contents of Amendment A, Part 1 (1) The scope of claims is amended as shown in the attached sheet. In a projection cathode ray tube that enlarges and projects an image projected on a light surface 1 onto a video screen in front via a projection lens placed opposite to the fluorescent surface, the light intensity distribution of light emitting points on the fluorescent surface is described. LLj so that it is included in chemical formula 1
A projection type cathode ray tube characterized by the following features: ”

Claims (1)

[Claims] (1) In a projection cathode ray tube that enlarges and projects an image projected on a fluorescent surface onto a video screen in front via a projection lens placed opposite to the fluorescent surface, the emission of the fluorescent surface is turned on. A projection type cathode ray tube characterized in that the light intensity distribution is different between the central part and the peripheral part of the fluorescent blood.