JP3381497B2 - Projection lens device and rear projection type image display device using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection-type image display device, and in particular, it provides a bright image with excellent focusing performance even at the periphery of the screen, uses inexpensive glass material, and has a wide angle of view with a short projection distance. And a projection-type image display device excellent in cost performance using the same.

[0002]

2. Description of the Related Art In recent years, a television set as a home image display device has become larger in size with the horizontally wide screen. There are two types of home-use image display devices, a direct view type using a cathode ray tube and a so-called projection type in which an image on a small projection tube of about 7 inches is enlarged and projected on a screen by a projection lens. Due to compactness and weight restrictions, projection-type image display devices have become the mainstream for screen sizes exceeding 37 inches.

Initially, this projection-type image display device was inferior to the direct-view type in screen brightness and focus performance.
However, in recent years, due to improvements in the performance of individual components such as the projection lens, screen, and projection tube, the screen brightness,
Focusing performance is approaching that of the direct-view type.

In the process of improving the performance of the projection type image display device, the projection lens device, which is a key device, is
Various technological developments have been made. First, as a first step, in order to obtain a screen brightness equal to or higher than that of the direct-view type, as disclosed in the publication of US Pat. No. 4,682,862, it is attempted to reduce the F value by using a lot of plastic aspherical lenses. Came.

Next, as a second step, a projection lens device was developed which simultaneously realizes improvement of screen brightness and improvement of focus performance. As this projection lens device,
As disclosed in Japanese Patent Laid-Open No. 3-137610, there is an example in which a plastic aspherical lens and a doublet glass lens are used. As a result, in the current projection type television receiver, a projection lens of about f / 1.1 is used, and the brightness and focus performance of a level that is practically no problem are secured in the entire screen.

As a third step, and nowadays, a projection lens device with a short projection distance and a wide angle of view that can realize a compact set is becoming the mainstream of development. As a document disclosing a specific technique for realizing a projection lens device with a wide angle of view and the actual projection lens device without deteriorating the screen brightness, especially the brightness of the peripheral portion of the screen and the focusing performance, Japanese Patent Application Laid-Open No. Hei 4 (1998) -5608 publication is mentioned. Hereinafter, it will be referred to as the first related art.

The first prior art disclosed herein is 6
By combining plastic aspherical lenses and glass lenses in a group of projection lens devices,
The above-mentioned problems are solved. Furthermore, the glass lens shares almost all the positive refracting power of the projection lens device,
Since the plastic aspherical lens has almost no structure, fluctuations in focus performance due to temperature changes peculiar to the plastic aspherical lens are reduced.

In the first prior art, the shape of the fluorescent surface of the projection tube is provided with a curvature so as to be convex toward the electron gun side. As a result, the normal of the fluorescent surface in the peripheral area of the screen is
The projection lens device is configured to face the entrance pupil, and more image light can be taken in compared to a flat fluorescent surface, so there is no practical problem even if the angle of view is widened. It is possible to obtain the peripheral light amount of.

Further, the lens of the sixth lens group (hereinafter referred to as the sixth lens group)
Although the field curvature is corrected by a group lens), the projection tube fluorescent surface has a curvature so that it is convex toward the electron gun side, thereby reducing the amount of field curvature generation itself.
The focus performance around the screen is improved.

Further, as a technical document disclosing a wide-angle projection lens device realizing a better focus performance without lowering the brightness of the peripheral portion of the screen, and a specific technique for realizing the same. , US Pat.
Publication No. 540 is cited. Hereinafter, it will be referred to as a second conventional technique.

In this second conventional technique, a projection lens having a structure of 5 groups and 6 elements is disclosed, and the shape of the fluorescent surface of the projection tube, which is an object point, has a curvature so that it is convex toward the electron gun side. The aspherical surface has an inflection point such that the curvature of the peripheral portion becomes smaller than the curvature near the optical axis. This allows
Both high-precision correction of field curvature and astigmatism are achieved, and good focusing performance and sufficient peripheral light quantity are secured around the screen screen.

Further, in this projection lens device, the lenses of the third lens group (hereinafter referred to as the third group lens), which share most of the refracting power of the entire lens system, are made up of a concave lens of high dispersion glass and a low dispersion glass. As a configuration obtained by pasting convex lenses, chromatic aberration is corrected and a large aperture ratio (F value of 0.
96) and high focusing performance.

On the other hand, the deterioration of the focus performance due to the temperature change and the humidity change, which is a problem peculiar to the plastic lens, is caused by the lens of the first lens group (hereinafter, referred to as the first lens group) and the lens of the second lens group (hereinafter, By combining the second group lens), it is possible to cancel the deterioration of the focusing performance that occurs in each lens.

[0014]

There are some problems to be solved in the projection lens device having the six-group structure according to the first prior art described above.

First, the first problem is a problem caused by the lens structure. In the projection lens device, a third group lens having a weak negative refractive power on the screen side of a lens of the fourth lens group (hereinafter referred to as a fourth group lens) that shares most of the positive refractive power of the entire lens system. Are arranged. The third group lens corrects spherical aberration and coma.

Therefore, the entrance pupil position of the entire lens system moves from the center of the fourth lens group to the screen side. As a result, if an attempt is made to further widen the angle of view (shortening the projection distance) with the lens configuration described above, distortion,
It becomes difficult to correct astigmatism.

A second problem is that in this lens configuration, the F value of the projection lens device is reduced (enlargement of aperture ratio).
And, when trying to obtain a sufficient peripheral light amount ratio, the apertures of the first lens group, the second lens group and the third lens group become large,
Production cost increases.

Further, in the aberration correction of the projection lens device, the correction share of each lens group is as follows.

The first lens group is a meniscus spherical lens having a positive refractive power, and corrects spherical aberration and coma.

The second lens group is a meniscus-shaped plastic aspherical lens having a weak positive refractive power, and corrects spherical aberration and coma.

The third lens group is a spherical lens having a weak diverging effect and corrects spherical aberration and coma.

The fourth group lens is a biconvex glass spherical lens having a strong light condensing effect.

Further, the lens of the fifth lens group (hereinafter referred to as the fifth lens group) is a meniscus-shaped plastic aspherical lens having a weak positive refractive power, and corrects astigmatism, distortion and coma. .

The sixth lens group has a concave surface facing the screen, has a negative refracting power together with the cooling liquid (A), and is configured to correct the field curvature.

Of these, the second group lens and the fifth group lens are plastic aspherical lenses, and both have a meniscus shape having a weak positive refractive power. In this way, the plastic lens is made to have almost no refracting power to reduce the fluctuation of the focus performance due to the temperature change peculiar to the plastic aspherical lens.

As described above, the plastic aspherical lens using the first prior art has a third problem that the lens shape that can be taken is limited and the aberration correction capability cannot be fully utilized.

Further, there is a fourth problem that the cost is high because four glass lenses are included.

Furthermore, since the fifth lens group has a small amount of aspherical surface, the sixth lens group is a glass lens, and the lens surface on the screen side is a spherical surface, the correction of astigmatism and the correction of field curvature are not compatible. Therefore, the fifth problem is correction of astigmatism in the peripheral portion of the screen.

The problem to be solved by the projection lens device having a structure of 5 groups and 6 elements according to the second prior art is cost reduction.

There are the following two factors that increase the cost of this projection lens device.

The first factor of cost increase is the shape of the fluorescent surface of the projection tube. At present, the mainstream of the fluorescent surface shape of projection tubes is spherical fluorescent surfaces, but when this projection lens device is applied, it is necessary to make the fluorescent surface shape aspherical, and the projection tube is a special specification, so it is a set. Will increase the cost.

The second factor of cost increase is that this projection lens realizes a large aperture ratio (F value of 0.96) and corrects chromatic aberration well, so that the third lens group has a large aperture and high dispersion. The doublet lens is a combination of a concave lens and a large-diameter low-dispersion convex lens.

Generally, the cost of optical glass is higher as the refractive index is higher and the dispersion is smaller. In the second conventional technique, the optical glass used for the third lens group of the projection lens disclosed in Example 1 is SF11 for high dispersion glass and SK16 for low dispersion glass. The price of these optical glasses is S when the standard (1.0) is SK5, which is a typical optical glass used for projection lenses.
F11 is (2.3) and SK16 is (2.1), which is more than double.

Therefore, an object of the present invention is to solve the problems of the above-mentioned conventional projection lens apparatus, use inexpensive optical glass, and have excellent focusing performance up to the periphery of the screen, and a bright image can be obtained. A wide-angle projection lens device with a short distance and a projection-type image display device using the projection lens device with excellent cost performance are provided.

[0035]

In order to achieve the above object, the projection lens device of the present invention uses the following technical means.

First, the first problem and the second problem of the first prior art.
In order to solve the above problem, most of the positive refracting power of the entire lens system is shared by a glass lens (hereinafter referred to as a glass power lens). At this time, on the screen side of the lens group including the glass power lens, a lens having a negative refractive power is not arranged, but a plastic aspherical lens having a weak positive refractive power is arranged near the optical axis. As a result, the entrance pupil does not move from the glass power lens to the screen side, so that the first problem can be solved and a projection lens device with a wide angle of view can be realized.

Further, since the image light flux passing through the lens group including the glass power lens is converged and is incident on the lens group located on the screen side, the aperture of each of these lenses can be made as small as possible. Can solve problems.

In the projection lens device of the present invention, the refractive power near the optical axis of the plastic aspherical lens is set to 30% or less of that of the glass power lens in order to reduce the deterioration of focus performance with respect to changes in temperature and humidity. Further, the correction of the aberration depending on the aperture is performed by the aspherical shape of the portion (the peripheral portion of the lens) separated from the optical axis. Fluctuations due to temperature and humidity changes in the local refracting power obtained by the aspherical shape of the peripheral portion of the lens are offset by combining a plurality of plastic aspherical lenses, which affects aberration correction. Without the lens shape can be determined, the third
Can solve the problem of.

Further, since the plastic aspherical lens having a large amount of aspherical surface can be frequently used by the above-mentioned technical means, the number of glass lenses can be reduced and the fourth problem can be solved.

In order to solve the fifth problem, a lens having a negative refracting power with a concave surface facing the screen is provided at the position closest to the projection tube which is the image light source, and the lens surface on the screen side of this lens is provided. Astigmatism reduces the astigmatism around the screen. Furthermore, in the lens arranged on the screen side of this lens, the shape of the lens surface on the projection tube side is convex on the projection tube side near the optical axis, and concave on the projection tube side in the peripheral portion. Astigmatism around the screen can be reduced with higher accuracy.

In order to realize the cost reduction which is the problem of the projection lens having the structure of the second conventional technique, the following two means are used.

The first means is to make the fluorescent surface of the projection tube applied to the projection lens device a spherical fluorescent surface. If the fluorescent surface of the 5-group 6-element projection lens disclosed in Example 1 of the second prior art is changed to a spherical surface as it is, the concave lens emission of the fifth group from the object point in the peripheral portion of the screen on the fluorescent surface. Since the optical path length to the surface is different between the spherical (sagittal) surface and the meridional (meridional) surface, astigmatism occurs at the peripheral portion of the screen, resulting in a large difference in focus performance between the sagittal direction and the meridional direction. This tendency is particularly remarkable in the peripheral portion of 90% or more of the screen corner.

Therefore, in the present invention, the lens surface on the screen side of the lens having negative refracting power of the sixth lens group is closer to the peripheral portion of the screen on the fluorescent surface than the object point near the optical axis of the lens. The difference in optical path length between the sagittal surface and the meridional surface is reduced by forming the lens area (divergence effect) in the lens area through which the image light flux passes. further,
In the lens arranged on the screen side of the lens having the negative refractive power, the shape of the lens surface on the projection tube side is convex toward the projection tube near the optical axis, and concave on the projection tube side in the peripheral portion. With such a shape, the difference in optical path length can be further reduced, and astigmatism around the screen can be significantly reduced.

The second means is to change the third lens group to inexpensive optical glass.

Therefore, the correction of chromatic aberration is realized by the high-dispersion plastic concave lens and the inexpensive low-dispersion glass convex lens.

Further, as shown in FIG. 6, the main wavelength 545 nm component of the emission spectrum of the phosphor is shown in at least one of the lenses constituting the projection lens device (see FIG. 6 for a general green phosphor). It is also effective to reduce the chromatic aberration itself by providing a filter that cuts spurious components other than those showing the emission spectrum).

Further, in order to realize a large aperture, the above-mentioned highly-dispersed plastic concave lens is made to have a strong aspherical shape, and aberrations are corrected with higher accuracy.

[0048]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 is a sectional view showing a main part of a lens of a projection lens device as an embodiment of the present invention. In FIG. 1, P ₁ is a fluorescent surface of a projection tube (CRT), 8 is a projection tube panel, 7 is a cooling liquid, 6 is a sixth lens group, 5 is a fifth lens group, 4 is a fourth lens group, and 3 is a third lens group. The fourth group lens, 2 is the second group lens, and 1 is the first group lens. The first lens group through the fifth lens group are assembled in the inner lens barrel 9 and fixed to the outer lens barrel 10 with fixing screws 12. Further, the outer lens barrel 10 is screwed and fixed to the bracket 11 via the fixing plate 13. The image on the projection tube fluorescent surface P ₁ , which is the object surface, is enlarged and projected on the screen 14.

In the embodiment of the present invention, the focal length of the sixth lens group is calculated by including the projection tube panel 8, the cooling liquid 7, and the fluorescent surface P ₁ .

FIG. 2 is a diagram showing the configuration of a projection lens device as one embodiment of the present invention and the result of ray tracing. Table 1 shows specific lens data. FIG. 3 is a diagram showing a configuration of a projection lens device as another embodiment of the present invention and a result of ray tracing. Table 7 shows concrete lens data. Figure 4
3 is a diagram showing the same configuration of the embodiment as in FIG. 1 and the result of ray tracing, and Table 10 shows concrete lens data. In the configuration of the projection lens device shown in FIGS. 2 to 4, the lens barrel and other structural parts are omitted for convenience of description.

The projection lens device of the embodiment of the present invention displays a 5.3 inch raster on the projection tube fluorescent surface P ₁ .
It is constructed so as to obtain the best performance when it is enlarged and projected on a screen to 60 inches. The half angle of view of the projection lens is 36 degrees, which realizes a high angle of view, and a sufficiently compact set can be realized even in a projection television apparatus having one folding mirror 15 as shown in FIG.

Specific lens data that can be taken by the projection lens device according to the present invention are shown in Tables 1 to 10, which should be referred to.

Next, how to read the lens data will be described based on Table 1. Table 1 shows data separately for a spherical system that mainly handles a lens region near the optical axis and an aspherical system for the outer peripheral portion thereof.

First, the screen has an infinite radius of curvature (that is, a plane), and the surface S of the first lens group 1 from the screen.
The distance on the optical axis to ₁ (plane spacing) is 1042.6 mm,
It is shown that the refractive index of the medium in the meantime is 1.0. The radius of curvature of the lens surface S ₁ is 91.403 mm
(The center of curvature is on the image generation source side), and the lens surface S
Distance between ₁ and S _{2 on} the optical axis (plane spacing) is 8.874 mm
It is shown that the refractive index of the medium in the meantime is 1.49334. Thereafter, in the same manner, finally, the radius of curvature of the fluorescent surface P ₁ of the projection tube panel 8 is 350 mm, the thickness of the projection tube panel on the optical axis is 11.49 mm, and the refractive index is 1.56.
232 is shown. The surfaces S ₁ and S ₂ of the first group lens 1, the surfaces S ₃ and S ₄ of the second group lens 2, the surfaces S ₇ and S ₈ of the fourth group lens 4, and the surfaces S ₉ and S of the fifth group lens 5. _10th , 6th
An aspherical coefficient is shown for the surface S ₁₁ of the group lens.

Here, the aspherical surface coefficient is a coefficient when the lens surface shape is expressed by the following equation.

[0056]

[Equation 1]

Here, Z (r) is the radial direction of the lens, where Z (r) is the optical axis direction from the screen to the image generation source, as shown in FIGS. Represents the height of the lens surface when is taken as the r-axis. r represents the distance in the radial direction, and RD represents the radius of curvature. Therefore, CC, AE, AF, AG, AH
If each coefficient such as is given, the height of the lens surface (hereinafter referred to as sag amount), that is, the shape is determined according to the above equation.

FIG. 8 is an explanatory view of the aspherical surface As (r). By substituting each value into the above-mentioned aspherical surface term, the lens surface Ss (r) of only the spherical system becomes (As (r) -Ss. (R))
A lens surface that is deviated only by this is obtained. This ratio (As
The larger the absolute value of (r) / Ss (r), the stronger the degree of aspherical surface.

The above is how to read the data shown in Table 1. Tables 2 to 10 show data corresponding to other examples, but the reading is the same.

Next, the operation of each lens group of the projection lens device of the present invention will be described.

As shown in FIGS. 2, 3 and 4, the first group lens 1 has a concave peripheral portion, and from the object point A on the axis to the image light flux (upper limit ray RAY1, lower limit ray RAY2). Corrects spherical aberration and coma aberration from the object point B at the peripheral portion of the screen to the image light flux (upper limit ray RAY3, lower limit ray RAY4). In the vicinity of the place where the upper limit ray RAY3 passes, it has an aspherical shape that is concave toward the screen side (the lens peripheral part away from the optical axis of the screen side lens surface). Further, also in the vicinity of the place where the lower limit ray RAY4 passes, if the position where the principal ray (not shown) passes is used as a reference, it has an aspherical shape that locally becomes concave on the screen side.

In order to correct astigmatism and coma, the second lens group 2 has a lens peripheral portion on the screen side, which is away from the optical axis of the screen side lens surface, as shown in FIGS. 2, 3 and 4. It has an aspherical shape that is convex to. Also,
When this lens is combined with the first lens group 1,
Since the negative refracting power based on the peripheral lens shape (concave) of the first lens group 1 and the positive refracting power based on the peripheral lens shape (convex) of the second lens cancel each other, both lenses are made of plastic. Even in the case of a molded product, it is possible to suppress deterioration of the focus performance of the projection lens device that occurs due to changes in temperature and amount of moisture absorption.

The third lens group 3 is made of glass in order to reduce the drift of the focusing performance due to the temperature change, and has a positive refractive power as large as possible. In the embodiment, SK5, which is an inexpensive optical glass, is used to reduce the manufacturing cost of the projection lens.

As shown in FIGS. 2, 3 and 4, the fourth lens group 4 has a meniscus shape whose central portion is concave toward the screen side or a biconcave lens shape (Examples in Tables 6 and 7). so,
The lens peripheral portion has an aspherical shape which is a meniscus shape concave on the screen side.

An image light flux (upper limit ray RA
For Y1 and lower ray RAY2), spherical aberration correction is performed with a concave shape in the lens peripheral portion, and by using a high-dispersion material with an Abbe number of 45 or less, chromatic aberration is reduced in combination with the third lens group 3. is doing.

On the other hand, the fourth group lens 4 of the present invention has a meniscus shape having a concave center on the screen side as described above, or a biconcave lens shape (Examples in Tables 6 and 7) and has a lens periphery. Since the portion has an aspherical shape that is a concave meniscus shape on the screen side, the lens has a uniform thickness as a whole, and even if a plastic material such as PC (polycarbonate) having poor fluidity during molding is used. , High shape accuracy can be obtained.

As shown in FIGS. 2, 3 and 4, the fifth group lens 5 is a high-order coma generated by the image light flux (upper limit ray RAY3, lower limit ray RAY4) from the object point B in the peripheral portion of the screen. In order to correct the aberration, the vicinity of the place where the lower limit ray RAY4 passes has an aspherical shape that is concave on the projection tube side (the shape of the peripheral portion of the lens surface on the projection tube side that is the image generation source). . Further, also in the vicinity of the place where the upper limit ray RAY3 passes, if the position where the principal ray (not shown) passes is used as a reference, it has an aspherical shape that is locally concave on the screen side.

Therefore, the lens surface of the lens on the projection tube side has an aspherical shape in which the vicinity of the optical axis is convex on the projection tube side and the peripheral portion is concave on the projection tube side. Further, the refracting power is made as small as possible in order to suppress the deterioration of the focusing performance of the projection lens caused by the change of the temperature and the amount of moisture absorption as much as possible.

The sixth lens group 6 corrects the curvature of field together with the fluorescent surface P ₁ . Further, unlike Conventional Example 2, since the fluorescent surface P ₁ is a spherical fluorescent surface, the aspherical surface shape of the screen side lens surface of the sixth group lens 6 is as shown in FIGS. 2, 3, and 4. Compared with the refractive power near the optical axis, the image light flux (upper limit ray RAY3, lower limit ray RA) from the object point B in the peripheral portion of the screen
Astigmatism is also corrected at the same time as a shape in which the refracting power is weakened in the region where Y4) passes.

FIG. 9 shows a function obtained by quadratic differentiation of the function representing the aspherical surface shape of the sixth group lens 6 on the screen side,
It is a graph of the values obtained by substituting the distance r from the optical axis. On the lens surfaces of the above-mentioned first conventional technique (conventional example 1) and second conventional technique (conventional example 2), the number increases monotonically from the optical axis of the lens to the peripheral portion. From this, it can be seen that the refracting action of the lens monotonically increases from the vicinity of the optical axis to the peripheral portion. On the other hand, in the embodiment of the present invention, the value obtained in the same manner has an inflection point as in the case of Example 8 or exceeds 70% of the effective diameter as in Examples 9 and 10. It decreases with . As a result, the refraction of the lens from the vicinity of the optical axis to the periphery,
You can see that it became stronger and then weaker.

10 and 11 show how the aspherical shape of the lens surface on the screen side of the sixth lens group 6 is away from the lens surface Ss (r) of the spherical system only. The horizontal axis of each figure is a relative value of the distance r to the lens effective diameter, and the vertical axis of FIG. 10 is A.
The difference between s (r) and Ss (r), and the vertical axis in FIG. 11 is the difference between As (r) and Ss (r) in each lens data normalized by the maximum value. First conventional technology (in the figure,
Compared with the conventional example 1), the embodiment of the present invention uses As (r) and S
The difference in s (r) is as small as 1/2 or less, the peripheral portion of the sixth lens group 6 does not become thick, and the thickness is uniform, so that good moldability can be obtained.

Next, using the above-described projection lens device according to the present invention, a 5.33 inch raster is projected on the fluorescent surface of the projection tube, and the MTF is enlarged and projected (60 inches) on the screen. (Modulation Tr
FIGS. 12 to 21 show the evaluation results of the focus performance by the transfer function.

Here, FIG. 12 is a characteristic diagram corresponding to Table 1, FIG. 13 is a characteristic diagram corresponding to Table 2, and FIG. 14 is a characteristic diagram corresponding to Table 3. Hereinafter, similarly, FIG. Is Table 10
It is a characteristic diagram corresponding to. As the evaluation frequency, the case where 300 TV lines are taken as white and black stripe signals on the screen is shown. As shown in FIGS. 12 to 21, according to this configuration, a good MTF characteristic can be obtained.

[0074]

[Table 1]

[0075]

[Table 2]

[0076]

[Table 3]

[0077]

[Table 4]

[0078]

[Table 5]

[0079]

[Table 6]

[0080]

[Table 7]

[0081]

[Table 8]

[0082]

[Table 9]

[0083]

[Table 10]

Regarding the examples of the present invention shown in Tables 1 to 10, the focal length of the entire projection lens device is f ₀ , the first
The focal lengths of the group lens 1, the second group lens 2, the third group lens 3, the fourth group lens 4, the fifth group lens 5, and the sixth group lens 6 are f ₁ , f ₂ , f ₃ , When f ₄ , f ₅ , and f ₆ are set, the relationships shown in Table 11 are established. That is, 0.24 <f ₀ / f ₁ <0.34 0.0 <f ₀ / f ₂ <0.18 0.78 <f ₀ / f ₃ <0.91 −0.20 <f ₀ / f ₄ <a _{-0.0 0.0 <f 0 / f 5} <0.21 -0.61 <f 0 / f 6 <-0.55. In this embodiment, most of the positive refracting power of the entire projection lens device is shared by the third lens group, which is a glass lens, to reduce the temperature drift of the focusing performance.

Next, the shape of the lens surface will be described.
The first lens group 1 screen side lens surface S _1, the image generation source side lens surface S ₈ of the fourth lens 4, the image generation source side lens surface S ₁₀ of the fifth lens 5, the screen of the sixth lens 6 The following can be said about the aspherical shape of the side lens surface S ₁₁ . This will be described below with reference to FIG.

In FIG. 8, as described above, the height (sag amount) of the lens surface when the optical axis direction from the screen to the image generation source is the Z axis and the radial direction of the lens is the r axis is Ss (r), C for spherical system, that is, RD only
Letting As (r) be the case of substituting each aspherical surface coefficient such as C, AE, AF, AG, and AH into the above equation 1, substituting the value of the lens effective radius for r, the degree of aspherical surface (As / Ss
Absolute value of) can be obtained.

Screen-side lens surface S of the first group lens 1
The ratio of As to Ss of ₁ has a relationship of −0.1 <(As / Ss) as shown in Table 13.

Further, as shown in Table 13, the ratio of As and Ss of the image-generation-source-side lens surface S _{8 of} the fourth lens group 4 is −21.2 <(As / Ss). .

When the distance (surface spacing) between the first lens group 1 and the second lens group 2 on the optical axis is L ₁₂ , the ratio to the focal length f ₀ of the entire projection lens apparatus is in the screen. The relation of L ₁₂ / (f ₀ <0.25) is established as shown in Table 14 in relation to the light amount in the region. Below this range, the peripheral light amount ratio in the middle area of the screen decreases.

On the optical axis between the first group lens 1 and the second group lens 2, the distance (surface spacing) L ₁₂ between the second group lens 2 and the third group lens 3 The ratio of the distance (surface spacing) L ₂₃ is determined by the balance of aberration correction, and as shown in Table 14, the relationship of 1.3 <(L ₁₂ / L ₂₃ ) is established. Below this range, good focusing performance cannot be obtained.

The screen side lens surface S of the third lens group 3.
The relationship of | Ra ₃ | <| Rb ₃ | holds between the absolute value of the curvature radius Ra ₃ of ₅ and the absolute value of the curvature radius Rb ₃ of the image-generation-source-side lens surface S ₆ of the third lens group 3. This is to reduce spherical aberration and coma that occur in the third lens group 3.

The screen side lens surface S of the fourth lens unit 4.
A relationship of | Ra ₄ | <| Rb ₄ | holds between the absolute value of the radius of curvature Ra ₄ of ₇ and the absolute value of the radius of curvature Rb ₄ of the image generation source side lens surface S ₈ of the fourth group lens 4. This is to balance the reduction of the positive refractive power contribution to the third lens group 3 and the correction of chromatic aberration and spherical aberration. In addition, the fourth group lens 4 has an Abbe number of 4
Chromatic aberration can be reduced by using a material of 5 or less.

The features have been described above based on the lens data of the projection lens device as the embodiment of the present invention.

In this embodiment, the aspherical surface used up to the 10th-order aspherical coefficient AH has been described.
It goes without saying that the present invention also includes a configuration in which higher-order coefficients higher than the second order are included.

[0095]

[Table 11]

[0096]

[Table 12]

[0097]

[Table 13]

[0098]

[Table 14]

[0099]

EFFECTS OF THE INVENTION According to the present invention, (1) the concave lens is not arranged on the screen side of the third lens group, which has most of the positive refracting power of the entire projection lens system, so that the angle of view can be widened. Distortion and astigmatism can be corrected, and both high focus and wide angle of view can be achieved.

(2) a third lens group having a positive refractive power,
Since the concave lens is not arranged between the first group lens closest to the screen side, the light rays focused on the peripheral portion of the screen do not diverge during this period. Therefore, the ray height can be lowered,
A good peripheral light amount ratio can be realized.

(3) Most of the positive refracting power of the entire lens system for projection is shared by the third lens group, and temperature and temperature are controlled by the combination of the local aspherical shapes of the first lens group and the second lens group. It is possible to reduce the deterioration of the focus performance due to the fluctuation of the moisture absorption amount.

(4) As the sixth group lens, a lens having a negative refractive power with a concave surface facing the screen is provided at a position closest to the projection tube which is the image light source, and the lens surface on the screen side of this lens is used as a lens. The optical path length difference between the sagittal surface and the meridional surface is reduced by making the lens refractive power weaker in the area where the image light flux from the object point in the peripheral area of the screen passes through than in the vicinity of the optical axis of Make it smaller.

Further, in the lens arranged on the screen side of the lens having the negative refractive power, the shape of the lens surface on the projection tube side is convex toward the projection tube side in the vicinity of the optical axis, and in the peripheral portion, The concave shape on the side of the projection tube makes it possible to further reduce the optical path length difference and more accurately correct astigmatism around the screen.

(5) The cost of the projection lens apparatus as a whole is reduced by using an inexpensive low-dispersion glass convex lens as the third lens group. Further, in order to correct the chromatic aberration, the fourth group lens is made as a high dispersion plastic concave lens and is combined with the third group lens.

Further, by providing a filter for cutting spurious components other than the main wavelength component of the emission spectrum of the phosphor in at least one lens constituting the projection lens device, the chromatic aberration itself is reduced. is doing.

(6) Further, in order to realize a large aperture, the above-mentioned fourth lens group is made of a high-dispersion plastic concave lens, and its shape is made to be a strong aspherical shape, so that the aberration can be corrected with high precision.

If the projection lens device described above is used,
It is possible to realize a compact rear projection display device that can obtain a bright, high-focus image over the entire area of the screen.

If the projection lens device of the present invention is applied,
Between the distance (projection distance) L (mm) from the lens side of the lens closest to the screen on the screen side of the first group lens to the transmissive screen and the diagonal effective size M (inch) of the transmissive screen. , 17.3 <(L / M) <17.6, and a compact set can be realized.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a projection lens device as an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a projection lens device as an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a projection lens device as an embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a projection lens device as an embodiment of the present invention.

FIG. 5 is a cross-sectional view in the screen vertical direction showing a main part of a rear projection type image display device as a projection type image device.

FIG. 6 is an emission spectrum characteristic diagram of a green phosphor.

FIG. 7 is an explanatory diagram used for explaining the definition of a lens shape.

FIG. 8 is an explanatory diagram used to describe the definition of a lens shape.

FIG. 9 is a characteristic diagram showing characteristics of a lens shape.

FIG. 10 is a characteristic diagram showing characteristics of a lens shape.

FIG. 11 is a characteristic diagram showing characteristics of a lens shape.

FIG. 12 is an MTF characteristic diagram of the projection lens device of Table 1 shown as an example of the present invention.

FIG. 13 is an MTF characteristic diagram of the projection lens device of Table 2 shown as an example of the present invention.

FIG. 14 is an MTF characteristic diagram of the projection lens device of Table 3 shown as an example of the present invention.

FIG. 15 is an MTF characteristic diagram of the projection lens device of Table 4 shown as an example of the present invention.

16 is an MTF characteristic diagram of the projection lens device of Table 5 shown as an example of the present invention. FIG.

FIG. 17 is an MTF characteristic diagram of the projection lens device of Table 6 shown as an example of the present invention.

FIG. 18 is an MTF characteristic diagram of the projection lens device of Table 7 shown as an example of the present invention.

FIG. 19 is an MTF characteristic diagram of the projection lens device of Table 8 shown as an example of the present invention.

FIG. 20 is an MTF characteristic diagram of the projection lens device of Table 9 shown as an example of the present invention.

FIG. 21 is an MTF characteristic diagram of the projection lens device of Table 10 shown as an example of the present invention.

[Explanation of symbols]

1 ... 1st group lens, 2 ... 2nd group lens, 3 ... 3rd group lens, 4 ... 4th group lens, 5 ... 5th group lens, 6 ... 6th group lens, 7 ... Coolant, 8 ... Projection Tube panel, 9 ... Inner lens barrel, 10 ... Outer lens barrel, 11 ... Bracket, 12 ... Fixing screw, 13 ... Fixing plate, 14 ... Screen, 15 ... Optical path folding mirror, 16 ... Screen, 17 ... Projection lens device, 18 ... Bracket, 20 ... Image luminous flux, 21 ... Housing, P ₁ ... Fluorescent surface, A ... Object point on optical axis, B ... Object point around screen.

─────────────────────────────────────────────────── ─── Continued Front Page (72) Takahiko Yoshida, Inventor Takahiko Yoshida, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Ltd.Hitachi, Ltd. Address Stock Company Hitachi, Ltd. Information & Video Division (56) Reference JP-A-4-362908 (JP, A) JP-A-1-263611 (JP, A) JP-A-6-208054 (JP, A) JP 4-121704 (JP, A) JP-A-4-258912 (JP, A) JP-A-62-94811 (JP, A) JP-A-63-169610 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) G02B 13/18 G02B 13/16

Claims (6)

(57) [Claims] 1. A projection lens device for enlarging and projecting an original image displayed on an image generation source onto a screen, wherein a meniscus having positive refractive power and having a central portion convex toward the screen in order from the screen side. A first lens group including at least one lens, a second lens group including a lens having a positive refractive power, and a central portion having a convex lens surface on the image generation source side, and a second lens group having a positive refractive power. The third lens group that includes the lens that it has, the fourth lens group that has a negative refractive power and that has a concave lens surface on the screen side, and the positive lens that has a positive refractive power A fifth lens group including a lens having a convex lens surface on the source side and a sixth lens group including a lens having a concave lens surface on the screen side and having a negative refracting power are arranged, and the following conditions are set. Lens device for projection characterized by satisfying 0.24 <f0 / f1 <0.35 0.0 <f0 / f2 <0.18 0.78 <f0 / f3 <0.91 −0.20 <f0 / f4 <0.0 0.0 <f0 /F5<0.21 −0.61 <f0 / f6 <−0.55 where f0: focal length of the entire projection lens device f1: focal length of the first lens group f2: focal length of the second lens group f3: focal length of third lens group f4: focal length of fourth lens group f5: focal length of fifth lens group f6: focal length of sixth lens group 2. In the third lens group, the radius of curvature Ra3 of the lens surface having the strongest positive refractive power on the screen side and the radius of curvature Rb3 of the lens surface on the image generation source side are: The projection lens device according to claim 1, wherein the projection lens device has a relationship of Ra3 | <| Rb3 |. 3. A projection tube is used as the image generation source, and the sixth lens group is provided with a lens having a negative refractive power having a lens surface having a concave surface facing the screen, and for cooling the projection tube. 3. The cooling liquid and the fluorescent surface glass of the projection tube are used, and the center of curvature of the fluorescent surface glass exists on the screen side.
The projection lens device according to. 4. A projection lens device for enlarging and projecting an original image displayed on an image generation source onto a screen, wherein a central portion is convex with respect to the screen in order from the screen side,
A first lens group including a lens having a concave lens surface at a peripheral portion, and a second lens group including a lens having a lens surface having a convex central portion with respect to an image generation source and a concave peripheral portion. , A third lens group including a lens having a positive refracting power, a fourth lens group including a lens having a negative refracting power and a concave lens surface on the screen side, a positive refracting power, and a center A fifth part including at least one lens having a lens surface whose portion is convex toward the image generation source side and whose peripheral portion is concave.
A projection lens device comprising: a lens group; and a sixth lens group, which includes a negative lens having a concave lens surface on the screen side, and satisfies the following conditions. 0.24 <f0 / f1 <0.35 0.0 <f0 / f2 <0.18 0.78 <f0 / f3 <0.91 −0.20 <f0 / f4 <0.0 0.0 <f0 /F5<0.21 −0.61 <f0 / f6 <−0.55 where f0: focal length of the entire projection lens device f1: focal length of the first lens group f2: focal length of the second lens group f3: focal length of third lens group f4: focal length of fourth lens group f5: focal length of fifth lens group f6: focal length of sixth lens group 5. A projection tube is used as the image generation source, the sixth lens group has a lens having a negative refracting power having a concave surface on the screen side, a cooling liquid for cooling the projection tube, and The projection lens device according to claim 4, wherein the projection lens is configured by using a fluorescent surface glass of a projection tube, and a center of curvature of the fluorescent surface glass is present on the screen side. 6. The lens of the first lens group, the second lens group, the fourth lens group, the fifth lens group, and the sixth lens group, wherein at least one surface is an aspherical surface. Or the projection lens device according to item 5.