JPH02115828A - Lenticular lens for back projection type projection television - Google Patents

Abstract

PURPOSE:To increase the vertical visual field angle while reducing a decrease in screen gain by forming many spherical projections or recessed surfaces and linear parts which are arrayed uniformly and vertically at a ratio within a constant range on an incidence- side lenticular or projection surface. CONSTITUTION:Many spherical projections 11a which are arranged uniformly at the rate within the constant range at the right angles to the pitch direction of black stripes formed on a projection side are formed on the incidence side of the lenticular lens 1 of the back projection type projection television. Expressions I and II hold for the ratio P of the radius H2 of the external edge of a spherical surface 11a and the distance H1 from the center of the spherical surface to the external edge of an adjacent spherical surface and the center angle theta of the spherical surface 11a respectively. Nearly parallel light which is incident on the lenticular lens 11 from a Fresnel sheet is diffused by the projections 11a and the orientation angle is increased even vertically to project the light from a projection surface, thereby increasing the vertical visual field angle of the whole screen.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a so-called rear projection type projection television in which an image of a projection tube is projected from the back of the screen and the projected image is viewed from the front of the screen. Regarding the lenticular lens.

[Technical background of the invention and its problems] Conventionally, in rear projection type projection televisions, in order to make a somewhat bright image visible even from an oblique direction in front of the screen, the projected light is diffused by the screen.
A predetermined viewing angle is obtained.

FIG. 6 is a diagram showing the basic configuration of the rear projection type projection television as described above, and in the figure, 3 is a CRT.
An ear projection device consisting of a projection tube, a projection lens, etc.; 4 a screen consisting of a Fresnel sheet 41 disposed on the side of the projection device 3 and a lenticular lens 42 disposed on the exit surface side of this Fresnel sheet 41; .

A Fresnel lens 4 is provided on the exit surface of the Fresnel sheet 41.
1a is formed, and a large number of lenticular lenses 42a are formed on the entrance surface of the lenticular lens 42, and the pitch direction is the horizontal direction of the screen (perpendicular to the drawing). The light passes through the Fresnel sheet 41 and the lenticular lens 42 and is emitted to the front of the screen 4.

At this time, the projected light from the projection device 3 is macroscopically converged into parallel light by the Fresnel lens 41a formed on the output surface of the Fresnel sheet 41, and the lenticular lens 4
The light emitted from the lenticular lens 42 is diffused in the horizontal direction by the lenticular lens 42a formed on the incident surface of the lens 2, and the horizontal direction angle of the light emitted from the lenticular lens 42 is expanded. This expands the horizontal viewing angle seen from the front of the screen 4.

On the other hand, in the vertical direction, the lenticular lens 42
The viewing angle is expanded by adding a diffusing agent to diffuse the projected light.

However, when the amount of the diffusing agent is increased, the light transmittance is lowered and the screen gain is lowered, the contrast is lowered, and the projected image is blurred, resulting in a decrease in resolution. Furthermore, if the amount of diffusing agent is small, the brightness in the vertical direction will vary greatly depending on the angle, and bright bands of light (hot bands) will appear in the horizontal direction of the screen, degrading the quality of the image.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a lenticular lens for a rear projection television that increases the viewing angle in the vertical direction while minimizing the decrease in screen gain.

[Summary of the invention]

The present invention provides a lenticular lens for a rear projection television, in which a large number of spherical protrusions or a large number of concave surfaces and linear portions are formed on the lenticule on the incident side or on the exit surface in a vertical direction at a ratio within a certain range. , this protrusion or concave surface causes vertical diffusion.

〔Example〕

FIG. 1 is a perspective view of a lenticular lens according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken perpendicularly from the incident side to the exit side in FIG. Note that FIG. 1 is a view seen from the incidence side on the Fresnel sheet side, and shows a part of the lenticular lens cut away.

The lenticular lenses 11 are formed on the incident side of the lenticular lens 1 and arranged with the horizontal direction of the screen as the pitch direction, and the lenticular lenses 11 are formed on the exit surface side.
Protrusions 12 are formed horizontally at the same pitch,
A black stripe 12a is formed on the surface of the protrusion 12 by printing or the like.

The width of the black stripe 12a is the pinch width (D)
The output surface 13 is formed in the gap between each black stripe 12a, the surface of which is projected outward.

A large number of spherical protrusions 11a are formed on the surface of the lenticule 11, which are arranged on average in a certain range of ratios in the vertical direction, and substantially parallel light entering the lenticule 11 (incidence surface) from a Fresnel sheet (not shown) is formed on the surface of the lenticular 11. is the protrusion 11a
The light is diffused by the microscopic refraction effect of the light, and is emitted from the output surface 13 in this diffused state.

In this way, the light from the output surface 13 is diffused by the protrusion 11a, so that the directivity angle is increased in the vertical direction as well, and the viewing angle of the entire screen in the vertical direction is expanded.

As an example, as shown in FIG. 2, when the distance from the center of the protrusion 11at to the outer edge of the adjacent protrusion 11a2 is Ht, the radius of the outer edge of the protrusion 11a is H2, and the central angle is θ, as shown in FIG. , H2/H1=0. 417 θ = 30°.

FIG. 3 is a diagram showing the vertical light distribution characteristics of the lenticular lens of the example in comparison with a conventional lenticular lens and one in which the above value H2/Ht +θ is changed. is a conventional lenticular lens without protrusions, and curve &'ib is H2/HI=1
, θ=30' (Lenticular lens with D-shaped protrusions formed; curve C shows the screen gain characteristics of the lenticular lens of Example.

As can be seen from the figure, in curve a, the 1/2 value angle (
α angle), 1/3 value angle (β angle) and 1/10 value angle are all small. In addition, in curve A, the α angle is 16°8°, the β angle is 20.7°, and the 1/1o value angle is 30.8°, which are sufficiently large, but the peak gain is 37% lower than that of curve a. , the brightness decreases significantly. However, in curve C, the α angle is 11.6°, the β angle is 15.3°, and the 1/IO value angle is 26.
At 5°, the peak gain is also suppressed to a drop of about 15% of curve a.

In this way, according to the lenticular lens of the example,
It can be seen that the vertical viewing angle is expanded while reducing the peak gain.

A major feature of the present invention is that it utilizes surface diffusion on protrusions (concave surfaces), and simply increasing the content of the diffusing agent causes light reflection loss and does not provide the above performance.

In the above embodiment, the protrusion 11a is formed on the lenticular lens 11, but as shown in FIG.
A similar effect can be obtained by forming. Note that this concave surface 1
1a', the above H,, H2, θ
is as shown in the figure.

Furthermore, although the intervals between the protrusions 11a are made random in the horizontal direction, the protrusions or concave surfaces may be formed at regular intervals in the horizontal direction as shown in FIG.

Further, the protrusion 11a or the concave surface 11a' may be formed on the exit surface 13 of the lenticular lens.

In addition, in the lenticular lens of the present invention, each of the above values H2/H1, θ is 0.2≦1 (27H1≦0.7 15°≦θ≦45°, then α Make a hot hand with an angle of 11° or more and a β angle of 14° or more (1/1
A wide viewing angle in the vertical direction can be achieved by setting the decimal angle to 25° or more.

〔Effect of the invention〕

As explained above, according to the lenticular lens of the present invention, a large number of spherical protrusions or a large number of concave surfaces are formed on the lenticule on the incident side or on the exit surface in a vertical direction at a ratio within a certain range, and the protrusions are Alternatively, since vertical diffusion is performed by the concave surface, a wide viewing angle in the vertical direction can be realized while minimizing a decrease in screen gain.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a lenticular lens according to an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view of FIG. 1, and FIG. , FIG. 4 is a diagram showing a cross section of a lenticular lens according to another embodiment, FIG. 5 is a diagram showing an example of the arrangement of protrusions or concave surfaces, and FIG. 6 is a diagram showing the configuration of a rear projection type projection television according to the present invention. It is. ■...Lenticular lens, 11...Lenticular 11a...Protrusion, lla'...Concave surface, 13...
...Emission surface. Figure Figure Figure Figure 5

Claims (1)

[Claims] A rear projection type projection television in which the gap between the black stripes formed on the front side is used as the exit surface of the projected light, and a large number of lenticules arranged in a direction parallel to the pitch direction of the black stripes are formed on the back side. In the lenticular lens, a large number of spherical protrusions or a large number of concave surfaces and straight portions are formed on the lenticular or exit surface at a ratio within a certain range on average in a direction perpendicular to the pitch direction of the black stripes; A back surface characterized in that the ratio of the radius of the outer edge to the distance from the center of the spherical surface to the outer edge of an adjacent spherical surface and the central angle of the spherical surface satisfy the following conditions (a) and (b). Lenticular lens for projection television. (a) 0.2≦P≦0.7 (b) 15°≦θ≦45° where P is the above ratio and θ is the above central angle.