JP2003005069A - Projection lens system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection lens system by which long back focus, a large off-axis light quantity and telecentricity are secured even in spite of a wide viewing angle and also short distance projection and also the various kinds of aberration including distortion aberration are reduced. SOLUTION: This projection lens system is provided with the first lens group G1 of negative refracting power and the second lens group G2 of positive refracting power in order from an enlarging side. A first lens L11 arranged on a most enlarging side possesses an aspherical surface in the first lens group. When the back focus at the time of air conversion is set as Bf, the focal distance of an entire lens system is set as (f), the air conversion rate of an interval between the first lens group and the second lens group is set as D12 and the focal distance of the first lens group is set as f1, the conditions of 4.0<Bf/f, 3.0<D12/f<5.0 and 1.0<|f1/f|<3.0 are satisfied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection lens system, for example, a spatial light modulator as a projection lens system for enlarging and projecting an image displayed on a display element such as a spatial light modulator at a fixed finite distance. A projection lens system having good telecentric performance with respect to a color synthesizing prism on the modulation element side, further having low distortion and excellent color characteristics,
In particular, the present invention relates to a projection lens system suitable for thinning and miniaturizing a projection display device.

[0002]

2. Description of the Related Art In recent years, projection display devices have become widespread. As one of such projection display devices, there is known a so-called rear projection type projection display device which performs display by projecting image light from the rear side of a transmissive screen.
In this type of rear projection type projection display device,
For example, a light beam obtained by collimating the light of a white light source with a reflector or the like is separated by a color separation mirror into three-color light beams of red, green, and blue. Then, the light fluxes of these three colors are red, green,
The light is incident on each spatial light modulation element or the like formed according to the blue image electric signal. The image lights obtained on the respective spatial light modulators corresponding to red, green, and blue are color-synthesized into white by a color synthesizing optical system, and enlarged and projected on a transmissive screen through a projection lens. It

Considering the limitations of the quick return mirror, a wide-angle photographic lens for a single-lens reflex camera with a long back focus and a wide-angle projection lens for a projection television using a CRT are used as lenses having the same structure. Proposed. Further, as a projection display device, a lens system forming a projection lens may have a structure in which the optical path is changed by 90 °, for example. This makes it possible to change the arrangement direction of the housing of the projection device in the projection display device and the installation direction of various optical elements from color separation to color combination inside the projection device. Further, the various optical elements described above can be miniaturized, and the projection display device can be miniaturized.

[0004]

In the configuration of the projection display device as described above, an optical element such as a dichroic prism or a dichroic mirror may be arranged as the color combining optical system. When using a reflective spatial light modulator or the like, an optical element such as a polarization beam splitter prism or a polarization beam splitter mirror may be arranged. In such a case, a so-called back focus, which corresponds to the distance from the spatial light modulator or the like to the rear end of the projection lens, must be secured long.

Further, as a projection display device,
When forming a magnified image on the entire transmissive screen, it is necessary to shorten the projection distance in order to downsize the projection display device itself. For that purpose, it is necessary to widen the angle of the projection lens and increase the divergence angle of the outgoing light on the magnifying side to obtain a large screen. In addition, in order to reduce color unevenness on the screen on which image light is projected, a polarized beam used when using a reflective spatial light modulator, such as a dichroic prism or dichroic mirror used in a color combining optical system. For a splitter prism, a polarization beam splitter mirror, or the like, it is preferable that the angular width of light rays that strikes these coated surfaces be constant over the entire area.
Therefore, it is necessary to have telecentricity so that the off-axis chief ray of the projection lens becomes perpendicular to the spatial light modulator or the like.

Further, as the spatial light modulator or the like, a normal LCD is used.
However, since the LCD is driven by using matrix electrodes, it is difficult to electrically correct the distortion of the projected image. Under such circumstances, it is desirable that the distortion of the projection lens is as small as possible. However, this is an obstacle to widening the angle of the projection lens and obtaining a long back focus. In other words, it was found that when the projection lens is provided with telecentricity after removing distortion, ensuring a wide angle and long back focus, it tends to increase the total lens length or the lens diameter. ing. Further, in a wide-angle photographic lens for a single-lens reflex camera or a projection lens for a projection television using a CRT, the back focus is insufficient, and the incident angle and the exit angle of the off-axis light beam are tight,
At present, there is no telecentricity and the amount of light is low.

Further, in recent years, a lens having a high resolution has been demanded in response to the high definition of a spatial light modulator or the like. With the higher resolution of the lens, the magnification in the peripheral portion of the screen is increased. Color shift of pixels due to chromatic aberration is becoming a problem. Further, in the projection display device, a desired magnified image may not be obtained on the screen due to manufacturing error of the projection lens or the projection device, and the projection magnification needs to be adjusted by the projection lens to adjust to the desired projection magnification. There is.

Furthermore, in the projection display device, even if the housings have different screen sizes, the same projection lens can be used by adjusting the projection distance between the projection lens and the screen. At this time, an aberration occurs due to a slight difference in the angle of each light beam focused on the screen, and it is necessary to adjust the aberration so that it is as small as possible.

Further, by providing the optical path changing means in the projection lens, as a projection display device, various optical elements from the arrangement direction of the housing of the projection device in the display device and from the color separation to the color combination inside the projection device. It is possible to change the installation direction of. Furthermore, the various optical elements described above can be miniaturized, and the projection display device can be miniaturized.

The present invention has been made in view of the above-mentioned problems, and employs a method which is more advantageous than the total payout method as a projection lens system capable of focus adjustment, and has a wide angle of view and a short angle. An object of the present invention is to provide a projection lens system that secures a long back focus, a large off-axis light amount, and telecentricity even in the case of distance projection, and that has various aberrations including distortion. Another object of the present invention is to provide a projection lens system capable of adjusting a change in projection magnification due to a manufacturing error to a desired magnification.

[0011]

In order to solve the above-mentioned problems, in the present invention, a first lens group having a negative refractive power and a first lens group having a positive refractive power are sequentially arranged from the enlargement side to the reduction side. In the first lens group, the first lens arranged on the most magnifying side has an aspherical surface, the back focus in air conversion is Bf, and the focal length of the entire lens system is f. When the air conversion value of the distance between the first lens group and the second lens group is D12 and the focal length of the first lens group is f1, 4.0 <Bf / f 3.0 <D12 / Provided is a projection lens system which satisfies the condition of f <5.0 1.0 <| f1 / f | <3.0.

According to a preferred embodiment of the present invention, the first
In the optical path between the lens group and the second lens group, optical path changing means is provided for changing the optical path of the light flux from the first lens group to the second lens group. Further, when the conjugate length is constant, the projection lens system is moved from the high magnification side to the low magnification side by moving the entire lens system to the enlargement side and reducing the air gap between the first lens group and the second lens group. It is preferable to change to the side. Further, when changing the projection distance to change the projection magnification, it is preferable to move the entire lens system and move part or all of the first lens group to perform focusing.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, in the projection lens system of the present invention, two groups of a first lens group having a negative refractive power and a second lens group having a positive refractive power are sequentially arranged from the screen side (enlargement side). It is configured. Then, by introducing an aspherical surface into the first lens that is arranged closest to the screen in the first lens group, a focusing method that is advantageous over the entire extension method is adopted, and a wide angle of view and a short distance are used. Even in projection, a long back focus, a large amount of off-axis light, and telecentricity can be secured, and a projection lens system with small aberrations including distortion can be realized. Furthermore, it is possible to realize a projection lens system capable of adjusting a change in projection magnification due to a manufacturing error to a desired magnification.

Further, in the projection lens system of the present invention, for changing the optical path of the light flux from the first lens group to the second lens group in the optical path between the first lens group and the second lens group. By providing the optical path changing means, it is possible to change the arrangement direction of the housing of the projection device in the projection display device and the installation direction of various optical elements in the projection device from color separation to color combination. Furthermore, various optical elements can be miniaturized, and the projection display device can be miniaturized.

In the projection lens system of the present invention, when the projection distance is changed to change the projection magnification, the entire lens system is moved and at the same time a part or all of the first lens group is moved to perform focusing. be able to. Further, when the conjugate length is constant, the projection magnification is reduced from the high magnification side by moving the entire lens system to the screen side (enlargement side) and reducing the air gap between the first lens group and the second lens group. It can be changed to double.

The projection lens system of the present invention satisfies the following conditional expressions (1) to (3). In the conditional expressions (1) to (3), Bf is the back focus at the time of air conversion, and f
Is the focal length of the entire lens system, D12 is the air-equivalent value of the distance between the first lens group and the second lens group, and f1 is the focal length of the first lens group.

4.0 <Bf / f (1) 3.0 <D12 / f <5.0 (2) 1.0 <| f1 / f | <3.0 (3)

Conditional expression (1) is a conditional expression for ensuring a sufficient back focus and shortening the focal length of the projection lens system, and the back focus Bf in air conversion and the focal length f of the entire lens system. It defines an appropriate range for the ratio. If the range of conditional expression (1) is exceeded, it is difficult to insert a color combining prism or a polarization beam splitter prism in the optical path between the projection lens system and the spatial light modulator or the like, which is inconvenient.

Conditional expression (2) is a conditional expression for maintaining a good air gap along the optical axis between the first lens group and the second lens group, and is the same as the first lens group and the second lens group. An appropriate range is defined for the ratio between the air-converted value D12 of the interval of and the focal length f of the entire lens system. When the value exceeds the upper limit of conditional expression (2), it is possible to secure a sufficient air space for providing the optical path changing means, but it is disadvantageous because the total lens length becomes too large. On the other hand, when the value goes below the lower limit of conditional expression (2), it is not possible to secure the air space necessary for providing the optical path changing means.

Conditional expression (3) is a conditional expression for properly suppressing the size of the entire lens system and maintaining good back focus and optical performance. The conditional expression (3) is the focal length f1 of the first lens group and the entire lens system. An appropriate range is defined for the ratio with the focal length f. If the upper limit of conditional expression (3) is exceeded, the retrofocus type structure becomes weak, which makes it difficult to maintain a long back focus, which is inconvenient. When the value goes below the lower limit of conditional expression (3), a long back focus can be obtained, but the occurrence of astigmatism and distortion increases, which is difficult to correct, which is inconvenient.

As in the projection lens system of the present invention, the first lens unit having a negative refractive power and the second lens unit having a positive refractive power are sequentially arranged from the screen side.
The so-called retrofocus type having a two-group structure including a lens group is advantageous for securing a long back focus and widening the angle, and is suitable as a projection lens system used in a projection display device, but it has a negative distortion. This is a big problem that the occurrence is large and the correction is difficult. Therefore, in the projection lens system of the present invention, an aspherical surface should be introduced into the first lens group of the two-group configuration consisting of the first lens group having negative refractive power and the second lens group having positive refractive power in order from the screen side. Thus, it is possible to favorably correct the negative distortion aberration.

In particular, introducing an aspherical surface into the lens closer to the screen side is more effective in correcting distortion. In addition, the size of the lens in the radial direction should be smaller than the diameter of the conventional lens that corrects distortion by disposing a lens unit having positive refracting power on the screen side of the first lens unit having negative refracting power. Therefore, the lens system can be downsized. As will be described later, an example in which an aspherical surface is introduced into the screen side surface of the first lens arranged closest to the screen side of the first lens group as an example having a high effect of correcting distortion in each of the embodiments of the present invention. Is shown.

Further, in the projection display device, the positional relationship between the screen and the spatial light modulator or the like is generally fixed, and the distance in the optical axis direction is set mechanically in order to obtain a projection image at a desired magnification on the screen. It is difficult to change to. Therefore, in the present invention, when the projection image of the desired magnification cannot be obtained on the screen due to the manufacturing error of the projection lens system or the projection display device, the conjugate length is kept constant, that is, the screen and the spatial light modulator are By moving the entire lens system to the enlargement side (screen side) while keeping the distance constant, by changing the air gap between the first lens group having negative refractive power and the second lens group having positive refractive power, It is possible to obtain a desired enlargement magnification while maintaining good optical performance. As described below, the above-described scaling is possible in all the embodiments of the present invention.

Furthermore, in the projection display device, even if the housings have different screen sizes, the same projection lens system can be used by adjusting the projection distance between the projection lens system and the screen. At this time, an aberration occurs due to a slight difference in the angle of each light beam focused on the screen, and it is necessary to adjust the aberration so that it is as small as possible. In the present invention, when the projection distance is changed and the magnification is changed, the entire lens system is moved, and at the same time, a part or all of the first lens unit having a negative refractive power is moved to perform focusing, thereby improving the optical performance. You can change the enlargement ratio while keeping it at.

As will be described later, in the first and second embodiments of the present invention, the entire lens system is moved along the optical axis, and the first lens and the second lens of the first lens group having negative refractive power are used. By changing the air distance between the lens and the air distance between the first lens group having a negative refractive power and the second lens group having a positive refractive power,
Focusing is done. On the other hand, in the third embodiment,
Focusing is performed by moving the entire lens system along the optical axis and changing the distance between the first lens and the second lens of the first lens group having a negative refractive power.

Further, in general, by providing an optical path changing means in the projection lens system, as a projection display device, the direction in which the housing of the projection device is arranged in the display device,
It is possible to change the installation direction of various optical elements from color separation to color combination inside the projection device. Further, the various optical elements described above can be miniaturized, and the projection display device can be miniaturized. Also in the present invention, the first lens group having negative refractive power and the second lens group having positive refractive power
By providing an optical path changing means between the lens group and the lens group, as a projection display device, the disposition direction of the housing of the projection device in the display device and the installation direction of various optical elements from color separation to color synthesis inside the projection device. It is possible to change. Further, it becomes possible to miniaturize the above various optical elements, and it is possible to miniaturize the projection display device.

As will be described later, in the first embodiment of the present invention, a mirror (planar mirror) is adopted as the optical path changing means, and the optical path is changed by 90 °. In the case of the optical path changing means using a mirror, as compared with the case of the optical path changing means using a prism, since the medium is air, the optical path is shortened and the total lens length can be shortened, and the loss of the light quantity due to the internal absorption of the prism is reduced. It is possible to avoid it. A metal mirror can be used as the mirror. Furthermore, when using either the P wave or the S wave in the projection lens system, it is possible to use a mirror or the like using a dielectric film that reflects the P wave or the S wave. On the other hand, the second embodiment shows a structure in which a prism is adopted as the optical path changing means and the optical path is changed by 120 °. In the case of the optical path changing means using a prism, compared with the case of the optical path changing means using a mirror, since the medium is glass (optical material), the optical path can be lengthened,
It is possible to increase the optical path changing angle. The third
The embodiment shows a structure that does not employ the optical path changing means.

[0028]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In each embodiment, the projection lens system of the present invention is composed of, in order from the screen side (enlargement side), a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power. ing. Then, in the first lens group G1, the screen side surface of the first lens L11 disposed closest to the screen side is formed in an aspherical shape.

In each embodiment, the height of the aspherical surface in the direction perpendicular to the optical axis is y, and the aspherical surface extends along the optical axis from the tangent plane at the apex of the aspherical surface to the position on the aspherical surface at the height y. The distance (sag amount) is z, the radius of curvature of the vertex is r,
When the conical coefficient is κ and the aspherical coefficient of _{order n} is C _n , it is expressed by the following mathematical expression (a).

[0030]

## EQU1 ## z = (y ² / r) / {1+ (1-κ · y ² /
r ² ) ^1/2 } + C ₄ · y ⁴ + C ₆ · y ⁶ + C ₈ · y ⁸ (a) In each of the examples, the aspherical lens surface is marked with * on the right side of the surface number. is doing.

[First Embodiment] FIG. 1 is a view showing the lens arrangement of a projection lens system according to the first embodiment of the present invention.
In the projection lens system of Example 1, the first lens group G1
Is, in order from the screen side, a negative meniscus lens L11 having an aspherical convex surface facing the screen side, a biconcave lens L12, a negative meniscus lens L13 having a convex surface facing the screen side, and a negative surface having a concave surface facing the screen side. It is composed of a cemented lens (L14, L15) formed by bonding a meniscus lens L14 and a positive meniscus lens L15 having a concave surface facing the screen side.

The second lens group G2 includes, in order from the screen side, a negative meniscus lens L having a convex surface facing the screen side.
21 and a biconvex lens L22 with a convex surface having a strong curvature facing the screen side, a cemented lens (L21,
L22), an aperture stop AS, and a cemented lens (L23, L24) formed by bonding a biconvex lens L23 having a convex surface having a weak curvature toward the screen side and a biconcave lens L24 having a concave surface having a strong curvature toward the screen side. , A biconvex lens L25 having a convex surface having a weak curvature toward the screen side, a biconcave lens L26 having a concave surface having a weak curvature toward the screen side, and a biconvex lens L27 having a convex surface having a strong curvature toward the screen side.
A cemented lens (L26, L27) made by bonding with
And a biconvex lens L28 having a convex surface with a strong curvature facing the screen side.

In the first embodiment, the first lens group G1
A mirror (flat mirror) M as an optical path changing unit is arranged in the optical path between the second lens group G2 and the second lens group G2 to change the optical path by 90 °. Further, on the reduction side of the second lens group G2, that is, in the optical path between the second lens group G2 and the spatial light modulator, a plurality of prisms as a color combining optical system are arranged. Further, the entire lens system is moved along the optical axis, and the air gap (d2) between the first lens L11 and the second lens L12 of the first lens group G1 and the first lens group G1 and the second lens group G2 are Focusing is performed by changing the air space (d9) of the above. Further, while moving the entire lens system to the screen side, the first lens group G
The zooming is performed by changing the air gap (d9) between the first lens group G2 and the second lens group G2.

The following table (1) lists the values of specifications of the projection lens system according to the first example of the present invention. In the overall specifications of Table (1), f is the focal length of the projection lens system, FNO
Represents the F number, ω represents the half angle of view, and Bf represents the back focus when converted into air. In addition, table (1)
In the lens specifications, the first column is the number of the surface from the screen side, r in the second column is the radius of curvature of each surface (vertex curvature radius in the case of an aspherical surface), and d in the third column is The distance from one surface to the next surface, n in the fourth column is the refractive index for the e-line (λ = 546.07 nm), which is the reference wavelength, and ν in the fifth column is the Abbe number. 1.0 is omitted. In the following tables (2) and (3), the above notations are the same.

[0035]

[Table 1] (Overall specifications) f = 12.53 FNO = 2.93 ω = 40.09 Bf = 52.35 (Lens specifications) Surface number rd ν 1 * 5000.000 8.00 1.49290 57.1 (L11) 2 331.058 (d2 = variable) 3 -1543.299 3.00 1.61520 58.7 (L12) 4 42.178 22.50 5 94.147 3.00 1.61520 58.7 (L13) 6 25.843 8.00 7 -44.983 3.00 1.80811 46.5 (L14) 8 -380.525 6.00 1.76167 27.5 (L15) 9 -51.938 (d9 = variable) 10 73.183 2.00 1.77621 49.6 (L21) 11 27.256 6.00 1.72538 34.7 (L22) 12 -267.261 2.90 13 ∞ 21.80 (aperture diaphragm AS) 14 86.512 6.50 1.49845 81.6 (L23) 15 -20.994 2.00 1.80811 46.5 (L24) 16 56.494 4.00 17 60.747 10.00 1.48915 70.2 (L25) 18 -28.021 2.90 19 -227.657 2.00 1.77621 49.6 (L26) 20 31.799 10.50 1.49845 81.6 (L27) 21 -54.947 3.40 22 46.651 8.00 1.48915 70.2 (L28) 23 -133.128 (d23 = Variable) 24 ∞ 35.50 1.51872 64.1 25 ∞ 23.00 1.84668 24.0 26 ∞ 1.66 27 ∞ 2.70 1.51872 64.1 28 ∞ (aspherical surface coefficient) 1 surface κ = 1.0000 C ₄ = 2.7105 × 10 ⁻⁶ C ₆ = −7.4595 × 10 ⁻¹⁰ C ₈ = 2.0675 × 10 ^-13 (Surface spacing during zooming) Reference value Projection magnification 73.21 71.89 70.57 d2 6.00 6.00 6.00 d9 50.33 48.00 45.76 d23 8.84 9.44 10.05 (Surface spacing during focusing) Reference value Projection magnification 48.17 71.89 83.75 d2 6.40 6.00 5.90 d9 47.10 48.00 48.80 d23 9.77 9.44 9.21 (Value corresponding to conditional expression) (1) Bf / f = 4.18 (2) D12 / f = 3.83 (3) | f1 / f | = 1.95

2 to 6 are various aberration diagrams of the first embodiment. That is, FIG. 2 shows a projection magnification of 7 which is the reference projection magnification.
Aberration diagrams at 1.89 times are shown in FIG.
FIG. 4 is a diagram showing various aberrations when the projection magnification is 83.75 times, FIG. 5 is a diagram showing various aberrations when the projection magnification is 73.21 times, and FIG. 6 is a diagram when the projection magnification is 70.57 times. The various aberration diagrams of are shown respectively.

In each aberration diagram, NA is the numerical aperture on the spatial light modulator side, Y is the image height of the spatial light modulator, e is the e line (λ = 546.07 nm), and C is the C line (λ). = 656.
28 nm) and F shows the F line (λ = 486.13 nm), respectively. In the aberration diagram showing astigmatism, the solid line shows the sagittal image plane and the broken line shows the meridional image plane. The above notations are the same in the subsequent aberration diagrams 8 to 12 and the aberration diagrams 14 to 18. As is apparent from each aberration diagram, in the first example, it is found that various aberrations are well corrected in the state of the reference value, the state of zooming, and the state of focusing.

[Second Embodiment] FIG. 7 is a view showing the lens arrangement of a projection lens system according to the second embodiment of the present invention.
In the projection lens system of Example 2, the first lens group G1
Are, in order from the screen side, a negative meniscus lens L11 having an aspherical convex surface facing the screen side, a negative meniscus lens L12 having a convex surface facing the screen side, and a negative meniscus lens L13 having a convex surface facing the screen side. It is composed of a biconcave lens L14 and a cemented lens (L14, L15) formed by laminating a positive meniscus lens L15 having a convex surface facing the screen side.

The second lens group G2 includes, in order from the screen side, a negative meniscus lens L having a convex surface facing the screen side.
21 and a biconvex lens L22 with a convex surface having a strong curvature facing the screen side, a cemented lens (L21,
L22), an aperture stop AS, and a cemented lens (L23, L24) formed by bonding a biconvex lens L23 having a convex surface having a weak curvature toward the screen side and a biconcave lens L24 having a concave surface having a strong curvature toward the screen side. , A biconvex lens L25 having a convex surface having a weak curvature toward the screen side, a biconcave lens L26 having a concave surface having a weak curvature toward the screen side, and a biconvex lens L27 having a convex surface having a strong curvature toward the screen side.
A cemented lens (L26, L27) made by bonding with
And a biconvex lens L28 having a convex surface with a strong curvature facing the screen side.

In the second embodiment, the first lens group G1
A prism P as an optical path changing unit is arranged in the optical path between the second lens group G2 and the second lens group G2 to change the optical path by 120 °. Further, as in the first embodiment, a plurality of prisms as a color combining optical system are provided on the reduction side of the second lens group G2, that is, in the optical path between the second lens group G2 and the spatial light modulator. Are arranged. Further, as in the first embodiment, while moving the entire lens system along the optical axis,
The first lens L11 and the second lens L1 of the first lens group G1
2 and the air gap (d2) and the first lens group G1 and the second
Focusing is performed by changing the air gap (d9) from the lens group G2. Further, similarly to the first embodiment,
Zooming is performed by moving the entire lens system to the screen side and changing the air gap (d9) between the first lens group G1 and the second lens group G2. Next table (2)
The values of specifications of the projection lens system according to Example 2 of the present invention are listed below.

[0041]

[Table 2] (Overall specifications) f = 12.38 FNO = 2.91 ω = 40.97 Bf = 54.31 (lens specifications) Surface number rd ν 1 * -5193.789 9.00 1.49290 57.1 (L11) 2 121.677 (d2 = variable) 3 807.816 3.00 1.65141 53.0 (L12) 4 74.148 17.50 5 61.357 3.00 1.61520 58.7 (L13) 6 24.608 9.20 7 -170.584 3.00 1.77621 49.6 (L14) 8 25.717 10.00 1.72733 29.2 (L15) 9 224.817 (d9) = Variable) 10 ∞ 50.50 1.51872 64.1 (P) 11 ∞ 4.00 12 45.790 2.00 1.77621 49.6 (L21) 13 17.611 5.00 1.59667 35.3 (L22) 14 -430.954 2.90 15 ∞ 20.30 (Aperture stop AS) 16 105.725 5.50 1.48915 70.2 (L23) 17 -49.089 2.00 1.80811 46.5 (L24) 18 54.686 4.00 19 58.982 10.00 1.49845 81.6 (L25) 20 -31.590 2.90 21 -607.242 2.00 1.77621 49.6 (L26) 22 30.825 11.00 1.49845 81.6 (L27) 23 -63.371 3.40 24 43.897 10.00 1.49845 81.6 (L28) 25 -399.180 (d25 = variable ) 26 ∞ 35.50 1.51872 64.1 27 ∞ 23.00 1.84668 24.0 28 ∞ 2.50 29 ∞ 2.70 1.51872 64.1 30 ∞ (aspherical coefficient) One surface κ = 1.0000 C ₄ = 2.7143 × 10 ^-6 C ₆ = −7.4345 × 10 ^-10 C ₈ = 2.0710 × 10 ^-13 (Surface spacing when changing magnification) Reference value Projection magnification 73.36 71.99 70.67 d2 5.00 5.00 5.00 d9 7.87 6.00 4.21 d25 8.38 9.00 9.62 (Surface spacing during focusing) Reference value Projection magnification 48.48 71.99 94.16 d2 5.70 5.00 4.80 d9 5.60 6.00 6.80 d25 9.22 9.00 8.69 (Value corresponding to conditional expression) (1) Bf / f = 4.39 (2) D12 / f = 3.46 (3) | f1 / f | = 2.07

8 to 12 are various aberration diagrams of the second embodiment. That is, FIG. 8 is a diagram showing various aberrations when the projection magnification is 71.99 times, which is the reference projection magnification, and FIG.
Fig. 10 shows various aberration diagrams at 8 times, Fig. 10 shows various aberration diagrams at projection magnification of 94.16 times, Fig. 11 shows various aberration diagrams at projection magnification of 73.36 times, and Fig. 12 shows projection magnification of 70.67 times. The various aberration diagrams at the time are shown respectively. As is clear from each aberration diagram, in the second example, as in the first example, various aberrations are satisfactorily corrected in the state of the reference value, the state of zooming, and the state of focusing. You can see that

[Third Embodiment] FIG. 13 is a view showing the lens arrangement of a projection lens system according to the third embodiment of the present invention. In the projection lens system of the third example, the first lens group G1 includes, in order from the screen side, a negative meniscus lens L11 having an aspherical convex surface facing the screen side and a concave surface having a weak curvature facing the screen side. Concave lens L12,
Negative meniscus lens L13 with convex surface facing the screen
And a biconcave lens L14 having a concave surface having a weak curvature facing the screen side and a biconvex lens L15 having a convex surface having a strong curvature facing the screen side are cemented together (L1
4, L15).

The second lens group G2 is composed of a biconvex lens L21 having a convex surface having a weak curvature facing the screen side and a negative meniscus lens L22 having a concave surface facing the screen side, which are cemented in order from the screen side. ，
L22), an aperture stop AS, a cemented lens (L23, L24) formed by bonding a biconcave lens L23 having a concave surface with a weak curvature toward the screen side and a positive meniscus lens L24 having a convex surface toward the screen side, and a screen. Cemented lens (L25, L26) formed by bonding a negative meniscus lens L25 having a convex surface facing toward the side and a biconvex lens L26 having a convex surface having a strong curvature facing toward the screen side, and a concave lens having a weak curvature facing toward the screen side. The concave lens L27 and the biconvex lens L28 with the convex surface having a strong curvature facing the screen side.
A cemented lens (L27, L28) made by bonding with
And a biconvex lens L29 having a convex surface with a strong curvature facing the screen side, and a negative meniscus lens L210 having a concave surface facing the screen side.

In the third embodiment, unlike the first and second embodiments, the optical path changing means is not arranged in the optical path between the first lens group G1 and the second lens group G2. . However, as in the first and second examples, the color combining optical system is provided on the reduction side of the second lens group G2, that is, in the optical path between the second lens group G2 and the spatial light modulator. Are arranged as a plurality of prisms. Further, unlike the first and second embodiments, the entire lens system is moved along the optical axis, and the air gap (d2) between the first lens L11 and the second lens L12 of the first lens group G1. Focusing is performed by changing. Further, similarly to the first and second examples, by moving the entire lens system to the screen side and changing the air gap (d9) between the first lens group G1 and the second lens group G2, I am changing the magnification. The following table (3)
The values of specifications of the projection lens system according to the third example of the present invention are listed.

[0046]

[Table 3] (Overall specifications) f = 12.37 FNO = 3.24 ω = 40.44 Bf = 52.27 (lens specifications) Surface number rd n ν 1 * 435.529 6.00 1.49290 57.1 (L11) 2 55.697 (d2 = variable) 3 -1260.152 3.00 1.51872 64.1 (L12) 4 52.205 29.94 5 179.961 3.00 1.62287 60.2 (L13) 6 43.973 9.99 7 -108.989 2.00 1.69978 55.6 (L14) 8 75.159 8.00 1.72733 29.2 (L15) 9 -166.003 (L15) d9 = variable) 10 73.795 5.00 1.59903 35.5 (L21) 11 -23.025 1.20 1.77621 49.6 (L22) 12 -77.804 2.90 13 ∞ 20.30 (aperture diaphragm AS) 14 -152.862 2.00 1.80085 45.3 (L23) 15 37.482 4.50 1.48914 70.4 (L24) 16 90.114 4.00 17 49.649 2.00 1.77621 49.6 (L25) 18 41.021 8.00 1.49845 81.6 (L26) 19 -41.285 2.80 20 -389.673 2.00 1.80401 42.2 (L27) 21 34.438 9.00 1.49845 81.6 (L28) 22 -53.185 3.40 23 54.098 6.00 1.49845 81.6 ( L29) 24 -97.648 2.30 25 -53.319 6.0 0 1.48914 70.4 (L210) 26 -60.618 (d26 = variable) 27 ∞ 35.50 1.51872 64.1 28 ∞ 23.00 1.84668 24.0 29 ∞ 2.50 30 ∞ 2.70 1.51872 64.1 31 ∞ (aspherical coefficient) 1 surface κ = 1.0000 C ₄ = 2 .4042 × 10 ⁻⁶ C ₆ = −5.7580 × 10 ⁻¹⁰ C ₈ = 1.8996 × 10 ⁻¹³ (surface spacing during zooming) Reference value Projection magnification 73.37 72.05 70.77 d2 9.70 9.70 9.70 d9 52.37 50.00 47.72 d26 6.37 6.92 7.47 (surface spacing during focusing) Reference value Projection magnification 48.36 72.05 83.89 d2 10.50 9.70 9.50 d9 50.00 50.00 50.00 d26 7.00 6.92 6.90 (Value corresponding to conditional expression) (1) Bf / f = 4.22 (2) D12 /F=4.04 (3) | f1 / f | = 2.07

14 to 18 are aberration diagrams of the third embodiment. That is, FIG. 14 is a diagram showing various aberrations when the projection magnification is 72.05, which is the reference projection magnification, and FIG.
FIG. 16 is a diagram showing various aberrations at 8.36 times, and FIG. 16 shows a projection magnification of 83.8.
FIG. 17 shows various aberration diagrams at 9 ×, FIG. 17 shows various aberration diagrams at projection magnification of 73.37 ×, and FIG. 18 shows various aberration diagrams at projection magnification of 70.77 ×. As is clear from the aberration diagrams, in the third example, as in the first example and the second example, various aberrations are observed in the reference value state, the zoomed state, and the focusing state. It can be seen that is corrected well.

[0048]

As described above, according to the present invention, it is possible to realize a projection lens system having a wide angle, a short projection distance, a long back focus, and good telecentricity. In particular, it is possible to realize a projection lens system capable of performing high-contrast projection in a projection device using a liquid crystal panel, and having small aberrations such as distortion, and capable of changing the optical path inside. it can.
Then, for example, when the projection display device is configured by applying the projection lens including the optical path changing means of the present invention to a projection device using a spatial light modulator, etc., a thin and small device with a small depth and the like. And good image quality is expected.

Further, by moving each lens group along the optical axis direction to perform focus adjustment (focusing),
A good display image can be obtained. In other words, it is possible to easily perform the focus adjustment work without causing the phenomenon that the center of the image on the screen shifts as in the case of adopting the so-called total extension type focusing. A good display image can be obtained even when the projection lens system of the present invention is adopted. Also, by moving each lens group along the optical axis direction to change the magnification, it is possible to absorb the influence of manufacturing errors of the projection lens system and the projection display device, and reduce the cost of the display device. Also, the adjustment work time can be shortened.

[Brief description of drawings]

FIG. 1 is a diagram showing a lens configuration of a projection lens system according to Example 1 of the present invention.

FIG. 2 is a diagram showing various aberration diagrams at a projection magnification of 71.89 times which is a reference projection magnification in the first example.

FIG. 3 is a diagram showing various aberration diagrams at a projection magnification of 48.17 times in the first example.

FIG. 4 is a diagram showing various aberration diagrams at a projection magnification of 83.75 times in the first example.

FIG. 5 is a diagram showing various aberration diagrams when the projection magnification is 73.21 times in the first example.

FIG. 6 is a diagram showing various aberration diagrams when the projection magnification is 70.57 times in the first example.

FIG. 7 is a diagram showing a lens configuration of a projection lens system according to Example 2 of the present invention.

FIG. 8 is a diagram showing various aberration diagrams at a projection magnification of 71.99 times which is a reference projection magnification in the second example.

FIG. 9 is a diagram showing various types of aberration at a projection magnification of 48.48 times in the second example.

FIG. 10 is a diagram showing various aberration diagrams at a projection magnification of 94.16 times in the second example.

FIG. 11 is a diagram showing various aberration diagrams when the projection magnification is 73.36 times in the second example.

FIG. 12 is a diagram showing various aberration diagrams when the projection magnification is 70.67 times in the second example.

FIG. 13 is a diagram showing a lens configuration of a projection lens system according to Example 3 of the present invention.

FIG. 14 is a diagram showing various aberration diagrams at a projection magnification of 72.05, which is the reference projection magnification in the third example.

FIG. 15 is a diagram showing various aberrations when the projection magnification is 48.36 times in the third example.

FIG. 16 is a diagram showing various aberration diagrams when the projection magnification is 83.89 times in the third example.

FIG. 17 is a diagram showing various aberration diagrams when the projection magnification is 73.37 times in the third example.

FIG. 18 is a diagram showing various aberration diagrams when the projection magnification is 70.77 times in the third example.

[Explanation of symbols]

G1 first lens group G2 Second lens group M mirror P prism AS aperture stop Li each lens

Continued front page    F-term (reference) 2H087 KA06 LA03 MA09 MA15 NA02                       PA09 PA10 PA16 PB13 PB15                       QA02 QA03 QA07 QA17 QA19                       QA22 QA26 QA34 QA37 QA41                       QA45 QA46 RA05 RA12 RA13                       RA32 RA36 RA41 RA42 SA07                       SA09 SA62 SA63 SB06 SB11                       TA03

Claims (4)

[Claims] 1. A first lens group having a negative refracting power and a second lens group having a positive refracting power are provided in this order from the enlargement side to the reduction side, and the first lens group has the largest enlargement. The first lens arranged on the side has an aspherical surface, the back focus in air conversion is Bf, the focal length of the entire lens system is f, and the distance between the first lens group and the second lens group is When the air conversion value is D12 and the focal length of the first lens group is f1, 4.0 <Bf / f 3.0 <D12 / f <5.0 1.0 <| f1 / f | <3 A projection lens system characterized by satisfying the condition of 0.0. 2. An optical path changing means for changing an optical path of a light beam from the first lens group to the second lens group in an optical path between the first lens group and the second lens group. The projection lens system according to claim 1, wherein the projection lens system is provided. 3. When the conjugate length is constant, the first lens group and the second lens group are moved while moving the entire lens system to the enlargement side.
3. The projection lens system according to claim 1, wherein the projection magnification is changed from the high magnification side to the low magnification side by reducing the air space between the lens group and the lens group. 4. When the projection distance is changed to change the projection magnification, the entire lens system is moved and at the same time a part or all of the first lens group is moved to perform focusing. The projection lens system according to any one of 3 above.