JP4851146B2 - Two-group zoom projection lens and projection display device - Google Patents

Description

  The present invention relates to a two-group zoom projection lens mounted on a projection display device and the projection display device thereof, and more particularly to a projection lens used in a projector device employing a DMD (digital micromirror device) as a light valve. It is.

  In recent years, in addition to liquid crystal display devices, projection projector devices (projection display devices) using DMD display devices have become known. DMD controls the reflection direction of light from the light source using a highly reflective rectangular micro mirror that can change the inclination in the range of about 10 degrees or more according to the input video signal, Only the reflected light is focused on the screen, and the image can be projected. This is done, for example, by arranging millions or more of mirrors vertically and horizontally on a substrate and independently digitally controlling each mirror, and each mirror corresponds to one pixel in an image.

  In addition, unlike a liquid crystal display device, the DMD does not need to polarize the irradiation light, so there is little loss in the amount of light and it is excellent in terms of accuracy of gradation expression. Therefore, in a projection projector apparatus using DMD having such advantages, a projection lens having good lens characteristics is required so that a clear and highly accurate image can be obtained according to DMD. In order to meet these demands, a projection lens capable of correcting various aberrations at a wide angle of view has been proposed (see Patent Document 1).

JP 2004-240309 A

  As described above, a projection lens for a projection projector apparatus using a DMD needs to meet the characteristics and requirements of the projector. Accordingly, first, a high-performance and small-sized one is required, but it is naturally required that correction of various aberrations including chromatic aberration and distortion is also good at a wider angle of view. In particular, today, where high-definition color images are required, excellent chromatic aberration is required.

  The present invention has been made in view of the above circumstances. In a projection lens used in a projection projector apparatus using a DMD, a two-group zoom projection lens capable of satisfactorily correcting various aberrations with a small size and a wide angle of view. An object is to provide a display device.

The two-group zoom projection lens according to the present invention includes a first lens group having a negative refractive power and a second lens group having a positive refractive power in order from the magnification side, from the wide-angle end to the telephoto end. In zooming, the first lens group is configured to move continuously from the enlargement side toward the reduction side, and the second lens group moves continuously from the reduction side toward the enlargement side. In the two-group zoom projection lens configured as described above,
The second lens group includes, in order from the magnification side, a negative lens, a positive lens, a positive lens, a negative lens, and a positive lens.
The following conditional expressions (1) to (3) are satisfied.
(1) n _2i > 1.75
(2) 0.8 <D ₂ / f ₂ <1.2
(3) 0.6 <f _w / f ₂ <0.9
However,
n _2i : Refractive index with respect to d-line of the glass material constituting the negative lens in the second lens group (i is the lens number of the negative lens)
D ₂ : Full length of the second lens group f ₂ : Focal length of the second lens group f _w : Focal length at the wide angle end of the entire lens system Further, any of the negative lenses of the second lens group is on the reduction side. A meniscus lens having a concave surface is preferred.

The first lens group includes, in order from the magnifying side, a positive lens, a negative meniscus lens having a convex surface facing the magnifying side, a negative lens, and a positive lens, and satisfies the following conditional expression (4). It is preferable.
(4) 0.4 <f _w / | f ₁ | <0.7
However,
f ₁ : focal length of the first lens group

  The first lens group includes, in order from the magnifying side, a negative meniscus lens having a convex surface on the magnifying side, a negative lens, and a positive lens, and satisfies the conditional expression (4). It is preferable to make it.

  Furthermore, a projection display device according to the present invention includes a light source, a light valve, an illumination optical unit that guides a light beam from the light source to the light valve, and a two-group zoom projection lens according to the present invention. Is modulated by the light valve, and projected onto the screen by the two-group zoom projection lens.

  According to the two-group zoom projection lens of the present invention, the first lens group having a negative refractive power is disposed on the screen side to achieve a retrofocus type and achieve a wide angle.

  In addition, the second lens group is divided into a front group and a rear group, and is configured symmetrically in the optical axis direction, with the concave surface of the negative lens in the front group facing the enlargement side and the concave surface of the negative lens in the rear group on the reduction side By setting the two concave surfaces in a lens arrangement in which the two concave surfaces are opposite to each other, various aberrations including chromatic aberration and distortion can be suppressed.

  Furthermore, by satisfying the predetermined conditional expressions (1) to (4), various aberrations can be further improved while reducing the size.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The two-unit zoom projection lens of the embodiment shown in FIG. 1 (representing the lens of Example 1 as a representative) is, in order from the magnification side, the first lens group G ₁ having negative refractive power, positive refractive power A second lens group G ₂ , a cover glass (filter part) 2, and DMD 1. In the figure, X represents the optical axis.

Here, the first lens group G ₁ includes a first lens L ₁ that is a positive lens in order from the magnification side, a second lens L ₂ that is a negative meniscus lens having a convex surface facing the magnification side, and a third lens that is a negative lens. to L ₃ and enlarged side is a positive lens with a convex surface and a fourth lens L _4. On the other hand, the second lens group G ₂ includes, in order from the magnification side, a fifth lens L ₅ is a negative lens having a convex surface facing the magnification _side, a sixth lens L ₆ is a positive _lens, a convex surface on the enlargement side positive The lens includes a seventh lens L ₇ that is a lens, an eighth lens L ₈ that is a negative lens with a convex surface facing the enlargement side, and a ninth lens L ₉ that is a positive lens.

Note that the first lens group G ₁ includes a first lens L ₁ composed of a negative meniscus lens having a convex surface facing the enlargement side in order from the enlargement side instead of the above configuration, a second lens L ₂ that is a negative lens, and a positive lens. the third lens L ₃ 3-lens configuration and may be made consisting of at.

Any negative lens in the second lens group G ₂ is configured to face the concave surface on the positive lens on the reduction side, provided with a pair of lenses made from these negative and positive lenses two pairs, the two pairs of lenses By arranging another positive lens between the pair, the occurrence of various aberrations can be suppressed. Further, since the two positive lenses of the second lens group G ₂ , the sixth lens L ₆ and the seventh lens L ₇ , have a refracting power as compared with the case where only one positive lens is disposed, various aberrations are obtained. Can be suppressed.

Moreover, two-group zoom projection lens of this embodiment, by moving the first lens group G ₁ and the second lens group G _2, and is configured to have a zoom function. Here, upon zooming from the wide-angle end to the telephoto end, the first lens group G ₁ is configured to move continuously toward the reduction side from the magnification side, a second lens group G ₂ is the reduction side It is comprised so that it may move continuously toward the expansion side.

  Next, the technical significance of the conditional expressions (1) to (4) will be described.

Condition (1) defines the refractive index of the negative lens in the second lens group G _2, by satisfying the conditional expression (1), it is possible to satisfactorily correct spherical aberration.

Condition (2) is for appropriately setting the power distribution of the second lens group G _2. When deviating from the range of the conditional expression (2), various aberrations, particularly spherical aberration, deteriorate.

Condition (3) is for setting by focusing on the second lens group G _2, the power distribution of the entire lens system properly. If the upper limit aberration increases occurring in the second lens group G _2, the whole lens system aberration correction becomes difficult. Meanwhile, since the distance falls below the lower limit and the first lens group G ₁ second lens group G ₂ becomes too large, the entire lens system compact becomes difficult.

Conditional expression (4) is for appropriately setting the power distribution of the entire lens system, focusing on the first lens group. If the upper limit aberration increases occurring in the first lens group G _1, the whole lens system aberration correction becomes difficult. Meanwhile, since the distance falls below the lower limit and the first lens group G ₁ second lens group G ₂ becomes too large, the entire lens system compact becomes difficult.

  Next, an embodiment of a projection display device according to the present invention will be briefly described. FIG. 9 is a schematic configuration diagram of a projection display apparatus according to the present embodiment.

  As shown in FIG. 9, the light beam emitted from the light source 101 is selectively converted into each of the three primary color lights (R, G, B) in time series by a color wheel (not shown), and the illumination optical system 102 The DMD 103 is irradiated with a uniform light amount distribution in a cross section perpendicular to the optical axis of the light beam. In this DMD 103, modulation switching to the color light is performed according to the change of the color of the incident light, and the projection light appropriately modulated by the DMD 103 enters the second group zoom projection lens 104, and finally The screen 105 is reached.

  Note that the projection display apparatus shown in FIG. 9 shows one embodiment of the present invention, and various modifications can be made. For example, instead of providing a single-plate DMD, the RGB colors may be modulated simultaneously by three DMDs corresponding to each color light. In this case, a color separation / combination prism (not shown) is disposed between the second group zoom projection lens 104 and the DMD 103.

  Hereinafter, the second group zoom projection lens of the present invention will be further described with reference to specific examples.

<Example 1>
A schematic configuration of a two-group zoom projection lens according to Example 1 is shown in FIG. The 2-group zoom projection lens includes, in order from the magnification side, a first lens group G ₁ having a negative refractive power, and by disposing the second lens group G ₂ having a positive refractive power.

Here, the first lens group G ₁ is, in order from the magnifying side, a first lens L ₁ that is a biconvex lens, a second lens L ₂ that is a negative meniscus lens having a convex surface facing the magnifying side, and a third lens that is a biconcave lens. and a fourth lens L ₄ is a positive meniscus lens having a convex surface directed toward the lens L ₃ and the magnification side. On the other hand, the second lens group G ₂ is directed from the enlargement side, the fifth lens L ₅ formed of a negative meniscus lens having a convex surface facing the magnification _side, a sixth lens L ₆ is a biconvex _lens, a convex surface on the enlargement side A seventh lens L _{7 made of} a positive meniscus lens, an eighth lens L _{8 made of} a negative meniscus lens having a convex surface facing the enlargement side, and a ninth lens L ₉ being a biconvex lens.

The fifth lens _{L 5} and the eighth lens _{L 8} of the second lens group _{G 2} is adapted to the concave to the configuration for the sixth lens _{L 6} and the ninth lens _{L 9} respectively, and the fifth lens _{L 5} By disposing the seventh lens L ₇ between the sixth lens L ₆ and each lens pair composed of the eighth lens L ₈ and the ninth lens L ₉ , the occurrence of various aberrations can be suppressed. Yes. Further, by arranging the adjacent two positive lenses of the sixth lens L ₆ and the seventh lens L ₇ of the second lens group G _2, the positive refractive power is distributed, occurrence of various aberrations is suppressed It has become so.

  The radius of curvature R (mm) of each lens surface of this two-group zoom projection lens, the center thickness of each lens, and the air spacing between the lenses (hereinafter collectively referred to as the axial upper surface spacing) D (mm), each lens Table 1 shows the values of the refractive index N and the Abbe number ν for the d-line. The numbers in the table represent the order from the enlargement side. In the middle part of Table 1, the focal length f, the back focus distance bf, FNo. The value of the angle of view 2ω is shown.

Further, according to the two-group zoom projection lens of Example 1, as shown in the lower part of Table 1, the conditional expressions (1) to (4) are satisfied. Note that (distance from the surface of the first lens L ₁ on the object side to the image-side surface of the last lens: hereinafter the same) the total length of the lens system is a 77.9Mm.

  FIG. 2 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration of the two-group zoom projection lens of Example 1. In the astigmatism diagram, aberrations with respect to the sagittal image surface and the tangential image surface are shown. In these aberration diagrams, h represents the image height.

  As is clear from these aberration diagrams, according to the two-group zoom projection lens of Example 1, each aberration, particularly lateral chromatic aberration, can be corrected extremely well.

<Example 2>
FIG. 3 shows a schematic configuration of the two-group zoom projection lens according to the second embodiment. In the present embodiment, descriptions overlapping with those in the first embodiment are omitted.

  The lens configuration and operational effects of the two-group zoom projection lens according to Example 2 are substantially the same as those of Example 1.

  The curvature radius R (mm) of each lens surface of this two-group zoom projection lens, the center thickness of each lens and the air space D (mm) between each lens, the refractive index N and the Abbe number ν at the d-line of each lens Values are shown in Table 2. The numbers in the table represent the order from the enlargement side. In the middle part of Table 2, the focal length f, the back focus distance bf, FNo. The value of the angle of view 2ω is shown.

  Moreover, according to the two-group zoom projection lens of Example 2, as shown in the lower part of Table 2, the conditional expressions (1) to (4) are satisfied. The total length of the lens system is 76.3 mm.

  FIG. 4 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration of the two-group zoom projection lens of Example 2. In the astigmatism diagram, aberrations with respect to the sagittal image surface and the tangential image surface are shown. In these aberration diagrams, h represents the image height.

  As is clear from these aberration diagrams, according to the two-group zoom projection lens of Example 2, it is possible to very well correct each aberration, particularly the lateral chromatic aberration.

<Example 3>
A schematic configuration of a two-group zoom projection lens according to Example 3 is shown in FIG. In the present embodiment, descriptions overlapping with those in the first embodiment are omitted.

The lens configuration of the two-group zoom projection lens according to Example 3 is different from that of Example 1 in both the first lens group G ₁ and the second lens group G ₂ . Specifically, as a first difference, the fourth lens L ₄ of the first lens group G ₁ is a biconvex lens, and the third lens L ₃ and the fourth lens L ₄ are cemented lenses. Is different. As the second difference, the eighth lens L ₈ of the second lens group G ₂ is a plano-concave lens having a concave surface directed toward the reduction side, also differs in that the ninth lens L ₉ is a biconvex lens ing.

  The operational effects of this embodiment are substantially the same as those of the first embodiment.

  The curvature radius R (mm) of each lens surface of this two-group zoom projection lens, the center thickness of each lens and the air space D (mm) between each lens, the refractive index N and the Abbe number ν at the d-line of each lens Values are shown in Table 3. The numbers in the table represent the order from the enlargement side. In the middle part of Table 3, the focal length f, the back focus distance bf, FNo. The value of the angle of view 2ω is shown.

  Further, according to the two-group zoom projection lens of Example 3, as shown in the lower part of Table 3, the conditional expressions (1) to (4) are satisfied. The total length of the lens system is 60.3 mm.

  FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration of the two-group zoom projection lens of Example 3. In the astigmatism diagram, aberrations with respect to the sagittal image surface and the tangential image surface are shown. In these aberration diagrams, h represents the image height.

  As is clear from these aberration diagrams, according to the two-group zoom projection lens of Example 3, each aberration, particularly lateral chromatic aberration, can be corrected extremely well.

<Example 4>
FIG. 7 shows a schematic configuration of a two-group zoom projection lens according to Example 4. In the present embodiment, descriptions overlapping with those in the first embodiment are omitted.

Lens configuration of two-group zoom projection lens according to Example 4, when compared with those of Example 1, the configuration of the first lens group G ₁ is different. In particular, the number of lenses of the first lens group G _1, whereas the one in Example 1 is a four lenses, that of this embodiment is a three-element configuration. Here a specific configuration of the first lens group G ₁ is composed, in order from the magnification side, a first lens L ₁ of a negative meniscus lens having a convex surface facing the magnification _side, a second lens L ₂ and a biconvex lens is a biconcave lens and a third lens _{L 3} is.

  The operational effects of this embodiment are substantially the same as those of the first embodiment.

  The curvature radius R (mm) of each lens surface of this two-group zoom projection lens, the center thickness of each lens and the air space D (mm) between each lens, the refractive index N and the Abbe number ν at the d-line of each lens Values are shown in Table 4. The numbers in the table represent the order from the enlargement side. In the middle part of Table 4, the focal length f, the back focus distance bf, FNo. The value of the angle of view 2ω is shown.

また、実施例４の２群ズーム投影レンズによれば、表４の下段に示すように、条件式（１）〜（４）は満足されている。そして、レンズ系の全長は５６．５ｍｍとされている。

Further, according to the two-group zoom projection lens of Example 4, as shown in the lower part of Table 4, the conditional expressions (1) to (4) are satisfied. The total length of the lens system is 56.5 mm.

  FIG. 8 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration of the two-group zoom projection lens of Example 4. In the astigmatism diagram, aberrations with respect to the sagittal image surface and the tangential image surface are shown. In these aberration diagrams, h represents the image height.

  As is clear from these aberration diagrams, according to the two-group zoom projection lens of Example 4, each aberration, particularly lateral chromatic aberration, can be corrected extremely well.

1 is a schematic diagram showing the configuration of a two-group zoom projection lens according to Example 1 of the present invention. FIG. Aberration diagram showing various aberrations (spherical aberration, astigmatism, distortion and lateral chromatic aberration) of the two-group zoom projection lens of Example 1 Schematic showing the configuration of a two-group zoom projection lens according to Example 2 of the present invention. Aberration diagram showing various aberrations (spherical aberration, astigmatism, distortion and lateral chromatic aberration) of the two-group zoom projection lens of Example 2 Schematic showing the configuration of a two-group zoom projection lens according to Example 3 of the present invention. Aberration diagrams showing various aberrations (spherical aberration, astigmatism, distortion, and lateral chromatic aberration) of the second group zoom projection lens of Example 3 Schematic showing the configuration of a two-group zoom projection lens according to Example 4 of the present invention. Aberration diagram showing various aberrations (spherical aberration, astigmatism, distortion and lateral chromatic aberration) of the two-group zoom projection lens of Example 4 Schematic configuration diagram of a projection display device using the two-group zoom projection lens of the present invention

Explanation of symbols

L _{1 to} L ₉ lens G _{1 to} G ₂ lens group X optical axis 1, 103 DMD
2 Cover glass (filter part)
101 Light source 102 Illumination optical system 104 2 group zoom projection lens 105 Screen

Claims (5)

A first lens group having a negative refractive power and a second lens group having a positive refractive power are disposed in order from the magnifying side, and the first lens group at the time of zooming from the wide angle end to the telephoto end. Is configured to continuously move from the enlargement side toward the reduction side, and the second lens group is configured to continuously move from the reduction side toward the enlargement side. In
The second lens group includes, in order from the magnification side, a negative lens, a positive lens, a positive lens, a negative lens, and a positive lens.
A two-group zoom projection lens characterized by satisfying the following conditional expressions (1) to (3).
(1) n _2i > 1.75
(2) 0.8 <D ₂ / f ₂ <1.2
(3) 0.6 <f _w / f ₂ <0.9
However,
n _2i : Refractive index with respect to d-line of the glass material constituting the negative lens in the second lens group (i is the lens number of the negative lens)
D ₂ : Full length of the second lens group f ₂ : Focal length of the second lens group f _w : Focal length at the wide angle end of the entire lens system   2. The two-unit zoom projection lens according to claim 1, wherein each of the negative lenses of the second lens unit is a meniscus lens having a concave surface directed toward the reduction side. The first lens group includes, in order from the magnifying side, a positive lens, a negative meniscus lens having a convex surface facing the magnifying side, a negative lens, and a positive lens, and satisfies the following conditional expression (4): The two-group zoom projection lens according to claim 1 or 2, characterized in that:
(4) 0.4 <f _w / | f ₁ | <0.7
However,
f ₁ : focal length of the first lens group The first lens group includes, in order from the magnification side, a negative meniscus lens having a convex surface on the magnification side, a negative lens, and a positive lens, and satisfies the following conditional expression (4). The two-group zoom projection lens according to claim 1 or 2.
(4) 0.4 <f _w / | f ₁ | <0.7
However,
f ₁ : focal length of the first lens group   A light source, a light valve, an illumination optical unit that guides a light beam from the light source to the light valve, and a two-group zoom projection lens according to any one of claims 1 to 4, wherein the light beam from the light source Is projected on a screen by the two-group zoom projection lens.

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