JPH09145998A - Projection lens and liquid crystal projector using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection lens which can have aberrations such as distortion and a chromatic aberration reduced over the entire projection image surface and can be increased in resolution. SOLUTION: Lenses L1-L6 composed of single lenses are arranged in order from the side of a projection surface, and the lens L1 is a biconvex lens, the lens L2 is a positive meniscus lens which has its projection surface on the projection surface side, and the lens L3 is a negative meniscus lens having its convex surface on the projection surface side. Further, the lenses L4 and L5 are cemented together into one body to form a negative meniscus lens which has its convex surface on the image plane side on the whole, the lens L6 is a biconvex positive lens and this is such a projection lens that the refractive indexes of the respective lenses and the Abbe numbers to a (d) line, and the lens arrangement are determined according to the focal length of the projection lens and the positive-negative balance of aberrations generated by the lenses L1-L6, and the lenses arranged on inner sides are smaller in Abbe number.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection lens for enlarging and projecting an image projected on a panel onto a screen, and more particularly to a projection lens used in a liquid crystal projector or the like which requires high resolution. Furthermore, it relates to a liquid crystal projector using the projection lens.

[0002]

2. Description of the Related Art In a liquid crystal projector, a light beam emitted from a light source is converted into red (R) light by a dichroic mirror.
The light is split into three primary colors, green (G) and blue (B), and is incident on the liquid crystal panel corresponding to each color. The light fluxes transmitted through the respective liquid crystal panels are again color-synthesized by the dichroic mirror and enlarged and projected on the screen by the projection lens.
As a projection lens used in such a liquid crystal projector, a lens called retrofocus in which the distance (back focus) between the projection lens and the liquid crystal panel is longer than the focal length is used. The reason why back focus is required is to secure a space for disposing a dichroic mirror for color combination between the projection lens and the liquid crystal panel.
If the focal length is increased, wide-angle projection cannot be performed, and the projection distance must be increased to obtain a large screen. Therefore, the back focus is large and the focal length of the projection lens is small. Is used. In general, the retrofocus lens has a lens structure in which the concave lens and the convex lens have a refractive power distribution in order from the screen side.

[0003]

Generally, in a projection lens used in a liquid crystal projector or the like in which an image projected on a panel is enlarged and projected on a screen, an F number (lens or lens) indicating the brightness of an optical system is used. It is desirable to make the reciprocal of the aperture ratio of the reflecting mirror as small as possible, and to have a lens configuration in which aberrations such as distortion, astigmatism, and chromatic aberration of magnification are favorably corrected over the entire projection screen. However, in a projection lens such as a retrofocus lens configuration used in a conventional liquid crystal projector or the like, if an attempt is made to sufficiently correct aberrations such as distortion, astigmatism, and chromatic aberration, it is attempted to obtain a high resolution. However, there is a problem that the number of lenses increases and the cost increases. In addition, since the distortion aberration is about 2 to 3% in each of the maximum images, for example, in a case where a plurality of liquid crystal projectors are arranged and the images projected from the respective liquid crystal projectors are overlapped to obtain a brighter image, the projections are different. There is a problem that the displayed images cannot be completely overlapped.

An object of the present invention is to solve the above problems, to reduce the aberrations such as distortion, astigmatism, and chromatic aberration over the entire projected image with a constitution in which the number of lenses is small, and the resolution is high. It is to provide a projection lens that can be used. Further, it is to provide a liquid crystal projector using the projection lens.

[0005]

The projection lens according to the present invention comprises:
First to sixth lenses, each of which is a single lens, are sequentially arranged from the projection surface side, the first lens is a biconvex lens, and the second lens is a positive meniscus whose convex surface faces the projection surface side. A lens, the third lens is a negative meniscus lens having a convex surface directed toward the projection surface, and the fourth and fifth lenses are integrally joined to each other, and a negative meniscus lens having a convex surface directed toward the image plane side as a whole , The sixth lens is a biconvex positive lens, and has a focal length of the projection lens and the first lens.
A projection lens in which the refractive index of each lens, the Abbe number for the d-line, and the lens arrangement are determined according to the positive / negative balance of the aberrations generated in the sixth lens, wherein the Abbe number is arranged inside It is characterized in that it is smaller than the lens used.

In this case, when the radius of curvature of each lens of the first to sixth lenses is represented by r1 to r11 from the projection surface side and the lens thickness / air distance is represented by d1 to d10 from the projection surface side. When the focal length of the projection lens is 100 mm, the refractive indices n1 to n6 of the first to sixth lenses, the Abbe numbers ν1 to ν6 with respect to the d line, the radii of curvature r1 to r11, the lens thickness / air distance d1 to d10 may be given under the following conditions.

[0007]

[Table 2] A liquid crystal projector of the present invention is characterized by including at least one of the projection lenses described above, and a liquid crystal panel being arranged at a back focus position of the projection lens.

In this case, an optical member may be arranged between the projection lens and the liquid crystal panel.

<Operation> In the present invention configured as described above, the refractive index of each lens is determined according to the focal length of the projection lens and the positive / negative balance of the aberrations generated in the first to sixth lenses. The Abbe number and the lens arrangement for the d-line and the d-line are determined, and aberrations such as distortion, astigmatism, and chromatic aberration are sufficiently corrected. In particular, in the lens configuration as in the present invention, it has been experimentally shown that chromatic aberration can be more effectively corrected in a state in which the Abbe numbers of the first to sixth lenses are set to be smaller for the lenses arranged inside. Has been obtained.

In the liquid crystal projector of the present invention,
Since the projection lens having the above-described action is used, for example, in a case where a plurality of liquid crystal projectors are arranged and the images projected from each of them are overlapped to obtain a brighter image, Can be completely overlapped.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing the outline of a projection lens according to an embodiment of the present invention.

The projection lens of this embodiment is composed of six single lenses, that is, lenses L1 to L1 arranged in order from the projection surface side.
It is composed of L6. The lens L1 is a biconvex lens,
The lens L2 is a positive meniscus lens whose convex surface faces the projection surface side, and the lens L3 is a negative meniscus lens whose convex surface faces the projection surface side. The lenses 4 and 5 are integrally joined together to form a negative meniscus lens with the convex surface facing the incident surface side as a whole. The lens 6 is a biconvex positive lens. In the figure,
r1 to r11 are radii of curvature of the lens surfaces of the lenses L1 to L6, n1 to n6 are refractive indices of the lenses L1 to L6, and d1 to d10.
Indicates the lens thickness and air distance.

In this projection lens, the focal length of the projection lens and the aberrations generated in the lenses L1 to L6 are positive.
The negative balance determines the refractive index of each lens, the Abbe number for the d-line, and the lens arrangement. Here, the positive / negative balance of aberration means, for example, the lens L1.
Let L6 be the first to eleventh surfaces in order from the projection surface side, the first surface + 0.73, the second surface + 0.4
3, ..., 5th surface -0.73, 6th surface -2.75, ...
This is the positive / negative balance of spherical aberration, and the aberration is canceled by this balance.

In the projection lens having the above construction,
For example, the refractive indices n1 to n6 of the lenses L1 to L6 and the Abbe numbers ν1 to ν6 for the d-line (wavelength 587.6 nm) are given under the following conditions, and the focal length of the projection lens and the positive / negative of the aberration of each lens are given. Lens L1 according to the balance of
When the radius of curvature of L6, the lens thickness and the air gap are determined, aberrations such as spherical aberration, astigmatism, distortion and chromatic aberration can be favorably corrected over the entire projected image.

[0016]

[Table 3] Below, as specific examples, the optimum values of the radius of curvature of each lens and the lens thickness and the air gap when the focal length f is 100 mm and the focal length f is 338.2 mm are listed.

<Example 1> The focal length f is 338.2 m.
m, F number 4.0, back focus bf 23
When the maximum image height H is 3.9 mm and the maximum image height H is 65 mm, the optimum values of the radii of curvature of the lenses L1 to L6 and the lens thickness / air distance are as shown in the table below.

[0018]

[Table 4] The spherical aberration, astigmatism, and distortion in this case are shown in FIGS. 2 (a) to 2 (c), respectively. As can be seen from FIG. 2, the spherical aberration, astigmatism, and distortion are smaller under the conditions in the above table.
Further, in the chromatic aberration correction, more effective correction is obtained in a state where the Abbe number of each lens is set to be smaller for the lens arranged inside, as in the present embodiment.

<Embodiment 2> Focal length f is 100 mm, F
Number 4.0, back focus bf 69.8m
m and the maximum image height H is 20 mm, the lenses L1 to L
The optimum values of the radius of curvature of 6, the lens thickness and the air space are set as shown in the following table.

[0020]

[Table 5] The spherical aberration, astigmatism, distortion, and chromatic aberration in this case are also smaller than those in the case of <Example 1> described above.

FIG. 3 shows an example of a liquid crystal projector using the projection lens of the present invention described above.

In FIG. 3, 100 is a projection lens having the structure shown in FIG. 1, 101 is a light source, 102a to 102c are mirrors, 103 is a filter, 104a to 104d are dichroic mirrors, and 105a to 105c are liquid crystal panels.

A mirror 102a is arranged in the traveling direction of the light beam from the light source 100, and a filter 103, dichroic mirrors 104a and 102c, a liquid crystal panel 105c, and a mirror 102d are sequentially arranged in the traveling direction of the light beam reflected by the mirror 102a. It is arranged. The dichroic mirror 104a reflects the R light and transmits the G and B lights.
The dichroic mirror 104b reflects B light and transmits G light.

A mirror 102b is arranged in the traveling direction of the light beam (R light) reflected by the dichroic mirror 104a, and the liquid crystal panel 105a, the dichroic mirror 104c, is arranged in the traveling direction of the light beam reflected by the mirror 102b. 1
04d, the projection lens 100 is arranged. A liquid crystal panel 105b and the dichroic mirror 104c are arranged in the traveling direction of the light beam (B light) reflected by the dichroic mirror 104b.
In 4c, the R light is transmitted, the B light is reflected, and these light fluxes are combined.

The luminous flux reflected by the mirror 102c (G
The dichroic mirror 104d is arranged in the traveling direction of (light), and the R and G lights from the dichroic mirror 104c are transmitted through the dichroic mirror 104d and the G light is reflected to combine these light fluxes. Done.

In the above liquid crystal projector, the liquid crystal panels 105 to 105c are arranged at the back focus position of the projection lens 100, and the liquid crystal panels 105 to 1 are arranged.
The R, B, G images respectively projected on 05c are enlarged and projected on a screen (not shown).

The above-mentioned liquid crystal projector has R, B, G images projected on three transmissive liquid crystal panels, respectively.
The images are color-synthesized, and the color-synthesized image is projected by one projection lens. For example, three R, B, G images respectively projected on three reflective liquid crystal panels are displayed. It is also possible to adopt a configuration in which projection is performed by each of the two projection lenses.

[0028]

Since the present invention is constructed as described above, it has the following effects.

According to the present invention, aberrations such as distortion, astigmatism, and chromatic aberration are sufficiently corrected, so that a projection lens having a high resolution over the entire projection screen is provided. There is an effect that can be. Further, since the structure is composed of 6 elements in 5 groups, there is an effect that the number of lenses can be reduced.

According to the third and fourth aspects, since the projection lens having the above-mentioned action is used,
In addition to providing a high-resolution image, it is possible to arrange a plurality of liquid crystal projectors and superimpose the images projected from each of them to obtain a brighter image.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an outline of a projection lens according to an embodiment of the present invention.

FIG. 2 is a diagram showing each aberration in the projection lens shown in FIG. 1, where (a) shows spherical aberration, (b) shows astigmatism, and (c) shows distortion.

3 is a configuration diagram showing an outline of a liquid crystal projector to which the projection lens shown in FIG. 1 is applied.

[Explanation of symbols]

 L1 to L6 lens d1 to d10 lens thickness / air gap n1 to n11 refractive index r1 to r11 radius of curvature 100 projection lens 101 light source 102a to 102c mirror 103 filter 104a to 104d dichroic mirror 105a to 105c liquid crystal panel

Claims (4)

[Claims] 1. First to sixth lenses, each of which is a single lens, are sequentially arranged from the projection surface side, the first lens is a biconvex lens, and the second lens is a convex surface on the projection surface side. Positive meniscus lens, the third lens is a negative meniscus lens whose convex surface faces the projection surface side, and the fourth and fifth lenses are integrally joined so that the convex surface faces the image surface side as a whole. The negative meniscus lens and the sixth lens are biconvex positive lenses, and the refraction of each lens is adjusted according to the focal length of the projection lens and the positive / negative balance of the aberrations generated in the first to sixth lenses. A projection lens in which the Abbe number and the lens arrangement for the ratio and the d-line are determined, wherein the Abbe number is smaller for the lens arranged on the inner side. 2. The projection lens according to claim 1, wherein the radius of curvature of each of the first to sixth lenses is represented by r1 to r11 from the projection surface side, and the lens thickness / air distance is the projection surface side. From d1 to d10, the refractive indexes n1 to n6 of the first to sixth lenses, the Abbe numbers ν1 to ν6 with respect to the d line, and the radii of curvature r1 to The projection lens is characterized in that r11, lens thickness and air distances d1 to d10 are given under the following conditions. [Table 1] 3. A liquid crystal projector comprising at least one projection lens according to claim 1 or 2, wherein a liquid crystal panel is arranged at a back focus position of the projection lens. 4. The liquid crystal projector according to claim 3, wherein an optical member is arranged between the projection lens and the liquid crystal panel.