JP2002357771A - Wide angle zoom lens and projection type display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfactorily correct various aberrations even when a viewing angle is about 70 degrees in very close range by composing a wide angle zoom lens of a 1A-th negative lens group and a 1B-th lens group, carrying out focusing by moving the two lens groups relatively to each other, and regulating power distribution of the two lens groups within an appropriate relative range. SOLUTION: The first negative lens group G1 for carrying out focusing by fixed variable power, a second positive lens group G2 , a third positive lens group G3 and a negative fourth lens group G4 which are moved relatively to each other for the correction of continuous variable power and image surface movement, and a fifth positive lens group G5 of the fixing by the fixed variable power are arranged in order from the magnification side. The first lens group G1 consists of the 1A-th negative lens group G1 A and a first negative lens group G1 B, and the focusing depends on relative movement of the two lens groups. An expression: 0.4<;f1 /f1 A<;1.0 is satisfied, wherein f1 A is the focal distance of the 1A-th lens group, and f is the focal distance of the entire lens system at a wide-angle end.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens for imaging an image sensor such as a CCD or an image pickup tube or a camera using a silver halide film or the like, and further relates to a zoom lens for projection of a projection type television. The present invention relates to a wide-angle zoom lens used in a projection display device using the light valve of the above, and a projection display device using the same.

[0002]

2. Description of the Related Art As a conventional zoom lens, for example, a negative first lens group having a fixed focusing function at the time of zooming, which is described in Japanese Patent Application Laid-Open No. 5-297276, is used. There is known a positive second lens group having a magnification function, a negative third lens group for correcting the movement of the image plane due to zooming, and a fixed positive fourth lens group.

However, most of them are small C
It is designed for use in an imaging device such as a CD. Therefore, in order to use these lenses as a projection lens of a projection display device using liquid crystal, it is necessary to increase the size of the lens on which the image to be projected is formed on the reduction side. Becomes quite large. In addition, when used in a projection lens, distortion is often insufficiently corrected in the prior art.

[0004] Also, as for the projection lens of a device using a liquid crystal, it is desirable that the reduction side of the projection lens be an almost telecentric optical system in consideration of the illumination system. No such consideration has been made. Furthermore, even if an attempt is made to insert an optical system for color separation or color synthesis between the lens system and the image plane, there are few systems provided with a back focus that allows such an attempt.

To solve such a problem, a negative first lens unit having a fixed focusing function at the time of zooming, and a correction of an image plane movement caused by continuous zooming and by the continuous zooming. Therefore, the second lens unit includes a positive second lens unit, a positive third lens unit, a negative fourth lens unit, and a fixed positive fifth lens unit which are fixed at the time of zooming. Japanese Patent Application Laid-Open
A zoom lens described in JP-A-10-268193 is known.

[0006]

However, in recent years, there has been a demand for a projection type display device to project from a distance close to a large screen by using a wider-angle projection lens. The above-described Japanese Patent Application Laid-Open No. 10-268193 discloses a zoom lens that achieves compactness of the lens system with respect to the reduction side size, an appropriate back focus amount, and approximately telecentricity on the reduction side. However, the angle of view is 23 to 25 degrees, and it cannot be said that such a demand has been sufficiently satisfied. In recent years, there has been a strong demand for miniaturization of projection display devices, and further miniaturization of projection lenses has been required.

[0007] In view of such circumstances, the present applicant has filed a patent application.
A five-group zoom lens disclosed in the specification of 2000-339955 is disclosed.

This zoom lens is of a five-group type in which a second lens group and a third lens group having a positive refractive power and a fourth lens group having a negative refractive power are movable. By setting the focal length and the like in an appropriate range, it is possible to reduce the aberration variation due to zooming while widening the angle of view compared to the related art. In addition, the lens system can be made compact with respect to the size of the reduction side, the light rays in the tangential plane on the reduction side are made substantially uniform with respect to the optical axis, and a color combining optical system or the like is inserted at a predetermined position. Since a suitable back focus amount can be obtained, a projection display device using this zoom lens can be a compact device with a wide angle of view and well corrected aberration.

However, recent projection type display devices are required to be used in various projection environments, and there are many demands to increase the projection size even in a small space projection environment. In order to satisfy the above, further widening of the angle of the zoom lens is required.
In the five-group zoom lens described in the above specification, the angle of view at the wide-angle end is about 60 degrees, which is considered to be somewhat wide. Therefore, there is a problem that it is difficult to correct the tilt of the image plane.

The present invention has been made in view of such circumstances, and has a long back focus, and a light beam in the tangential plane on the reduction side is substantially uniform with respect to the optical axis, but the size of the light on the reduction side is small. It has a compact configuration, and various aberrations, particularly the tilt of the image plane, are favorably corrected.
It is an object of the present invention to provide a wide-angle zoom lens having a degree of view that is wider than that of the related art. Another object of the present invention is to provide a projection display device using the zoom lens.

[0011]

A wide-angle zoom lens according to the present invention includes, in order from the magnification side, a first lens unit having a negative refractive power for performing fixed focusing during zooming, and a continuous zooming lens. Therefore, the second lens group having a positive refractive power, the third lens group having a positive refractive power, and the negative refractive power, which move relative to each other, are corrected for correcting the image plane movement caused by the continuous zooming. And a fifth lens group having a fixed positive refractive power at the time of zooming, wherein the first lens group is fixed at the time of zooming in order from the magnification side. A first A lens group having a negative refractive power and a first B lens group having a negative refractive power, which are mutually movable for performing focusing, are arranged, and the following conditional expressions (1) to (5) ) Is satisfied.

(1) 1.5 <f ₂ /f<4.0 (2) 2.0 <f ₃ /f<5.0 (3) 1.5 <f ₅ /f<3.0 (4) _{) -1.8 <f 1 /f<-0.9 (5} ) 0.4 <f 1 / f 1A <1.0 f: the entire lens system at the wide angle end focal length f _1: the first lens group focal length f _2: the two lens groups focal length f _3: the focal point of the third lens group distances f _5: fifth lens group having a focal length f _1A: focal length of the 1A lens group

It is preferable that the lens closest to the enlargement side of the first B lens group is a lens having a concave surface facing the enlargement side. Further, it is preferable that at the time of zooming, the distance between the second lens group and the third lens group is narrowed toward the telephoto end.

Further, a projection type display apparatus according to the present invention is characterized in that any one of the above-mentioned wide-angle zoom lenses is mounted and an image displayed on a light valve is projected on a screen.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a basic configuration of a wide-angle zoom lens according to a first embodiment of the present invention described later, and is a lens configuration diagram (WIDE) at a wide-angle end. This lens will be described below as a representative of the present embodiment.

[0016] That is, the lens includes a first lens group G ₁ having a negative refractive power for performing focusing in fixed during zooming, for continuous zooming, and the image plane movement caused by the continuous variable power In order to correct the above, a second lens group G ₂ having a positive refractive power, a third lens group G ₃ having a positive refractive power, and a fourth lens group G ₄ having a negative refractive power move in relation to each other. , made a fifth lens group G ₅ having a positive refractive power fixed during zooming from the magnification side are arranged in this order. The first lens group G ₁ is composed of a first lens group G _1B having a first 1A lens group G _1A and negative refractive power having a negative refractive power, focusing these two lens groups are moved to each other This is done by:

The lens closest to the enlargement side (the fifth lens L ₅ in FIG. 1) of the first B lens group G _1B is a lens having a negative refractive power with the concave surface facing the enlargement side. In addition, the fifth
Between the lens group G ₅ and the image plane 1, the glass block 2 filter or a low pass filter further corresponding to the color combining optical system (color-separation optical system) for cutting infrared rays are arranged. In the figure, X represents the optical axis.

The said first lens group _{G 1} has a focusing function in fixed during zooming, the second, third, and fourth groups each lens of _{G 2,} G 3, _{G 4} is with interrelated By moving, it has a function of correcting continuous magnification and correcting an image plane movement caused by the continuous magnification. Note fifth lens group G ₅ is fixed relay lens during zooming. In addition,
Wherein said second lens group G ₂ during zooming third lens group G
₃ is configured to be narrower toward the telephoto end.

Further, this zoom lens is configured to satisfy the following conditional expressions (1) to (5). _{(1) 1.5 <f 2 /f<4.0} (2) 2.0 <f 3 /f<5.0 (3) 1.5 <f 5 /f<3.0 (4) -1 _{.8 <f 1 /f<-0.9 (5)} 0.4 <f 1 / f 1A <1.0 f: the focal point of the entire lens system at the wide-angle end length f _1: the focal length f of the first lens group _2: a second focal length of the lens unit f _3: the third focal point of the lens group distances f ₅ a focal length f _1A of the fifth lens group is a focal length of the 1A lens group

A projection type image display device according to the present invention is a device including a light source, a light valve, and the above-described wide-angle zoom lens according to the present invention. In this device, the zoom lens according to the present invention functions as a projection lens for projecting an optical image based on light modulated by the light valve on a screen. For example, in the case of a liquid crystal video projector provided with the wide-angle zoom lens shown in FIG. 1, a substantially parallel light beam is incident from a light source unit (not shown) on the right side of the drawing, and the image is formed on an image plane 1 of a light valve such as a liquid crystal display panel. This light beam carrying the projected image information is enlarged and projected by the zoom lens through the glass block 2 onto a screen (not shown) on the left side of the drawing. In addition,
Although only one imaging plane 1 is shown in FIG. 1, in a liquid crystal video projector, a light beam from a light source is generally converted into three primary colors of R, G, and B by a color separation optical system including a dichroic mirror and a lens array. The liquid crystal is separated into light and three liquid crystal display panels are arranged for each primary color light so that a full-color image can be displayed. The glass block 2 can be a dichroic prism that combines the three primary colors.

The operation and effect of the wide-angle zoom lens according to the present embodiment and the projection display device using the same will be described below.

First, continuous zooming of this zoom lens and
To correct the image plane movement caused by the continuous zooming,
Second lens group G having a refractive power of₂, A third lens with positive refractive power
Group G ₃, The fourth lens group G having a negative refractive power₄Group of three
Zumi by moving in a relationship
Aberration fluctuations due to ringing can be reduced. Again
For a given lens group, the power is above the conditional expression (1)-
By being configured to satisfy (4), predetermined
Lens group movement distance is short
The overall length is compact, and various aberrations are well corrected.
A zoom lens can be obtained.

Furthermore, from the distance between the second lens group G ₂ and the third lens group G ₃ is configured to be narrower toward the telephoto end side, it is possible to reduce the moving distance required for zooming, the total lens The system can be made more compact.

By the way, the first lens group G ₁ has a focusing function, but if the first lens group G ₁ overall during focusing moves integrally with,
It is difficult to obtain an angle of view of about 60 degrees or more. This is 6
This is because if the angle of view is set to about 0 degrees or more, it becomes difficult to satisfactorily correct various aberrations, particularly the inclination of the image plane. Thus, in the embodiment, the first lens group G ₁
Is composed of a first A lens group G _1A having a negative refractive power and a first lens group G _1B having a negative refractive power, and focusing is performed by moving these two lens groups relative to each other. This makes it possible to satisfactorily correct various aberrations even when the angle of view is as close as about 70 degrees.

Next, the technical significance of each conditional expression will be described. As for the conditional expression (1), the upper limit
When the positive power of the lens group G ₂ is weakened, the moving amount accompanying the magnification is large next to the lens size increases. The aberration correction becomes difficult when the positive power of the second lens group G ₂ than the lower limit becomes stronger.

[0026] The conditional expression (2), when the positive power of the third lens group G ₃ exceeds the upper limit is weakened, the moving amount accompanying the magnification increases becomes large lens size.
The aberration correction becomes difficult when the positive power of the third lens group G ₃ than the lower limit becomes stronger.

[0027] The conditional expression (3), the positive power of the fifth lens group G ₅ than the lower limit becomes stronger, the back focus is short and it is difficult to the reduction side in the state of substantially telecentric . By satisfying the lower limit, the zoom lens can secure a predetermined back focus, and a dichroic prism for color synthesis necessary for projecting a color image can be inserted at the position of the glass block 2. It becomes possible. On the other hand, the upper limit, greater too long back focus the positive power of the fifth lens group G ₅ is weakened, the size including the lens back is increased. Further the fifth lens group _{G 5}
In this case, the on-axis ray height becomes too low, and it becomes difficult to correct aberration.

[0028] The conditional expression for (4), the negative power of the first lens group G ₁ to exceed the lower limit is weakened, becomes difficult to correct aberration lens with a small F value, the first lens group by focusing G ₍₁₎ The movement amount of the whole increases, and the aberration fluctuation becomes severe. Also when a negative power exceeds the upper limit is strengthened, by the first lens group G ₁ too thrown up on-axis ray becomes particularly difficult to correct aberrations such as distortion aberration and spherical aberration.

Further, most characteristic condition in the present embodiment (5) defines the ratio of the power of the 1A lens group G _1A with respect to the first lens group G ₁ total power exceeds the lower limit If the ratio of the power of the first A lens group G _1A becomes too small, the amount of movement must be increased, so that the height of the incident light beam incident on the first lens group G ₁ changes greatly, resulting in distortion and image tilt. It becomes difficult to correct these and other aberrations in a well-balanced manner. On the other hand, exceeding the upper limit, the first A lens group G
_If the ratio of the power of _1A becomes too large, the ratio of the power of the first B lens group G _1B becomes relatively small, and the amount of movement of the first B lens group G _1B must be increased, thus correcting various aberrations. Becomes difficult.

[0030]

Embodiments Each embodiment will be specifically described below using data.

<Embodiment 1> The wide-angle zoom lens according to Embodiment 1 is configured as shown in FIG. 1 as described above. That is, this lens is the first lens in order from the magnifying side.
The A lens group G _1A is made up of four single lenses L _{1 to} L ₄ , and the first B lens group G _1B is made up of a single biconcave lens L
Consists _{of 5,} the second lens group _{G 2} is composed of one cemented lens and a single two lenses _L 6 ~L _9, the third lens group _{G 3,} two lenses alone _L 10 _{~L 11} Consisting of
The fourth lens group _{G 4} is two lenses _L 12 ~L alone
Made up of _13, the fifth lens group _{G 5} is composed of one cemented lens and a single two lenses _L 14 _{~L 17.}

In the first embodiment, the radius of curvature R of each lens surface (standardized with the focal length at the wide-angle end being 1; the same applies to the following tables), the center thickness of each lens, and the air gap between each lens Table 1 shows D (normalized by the same focal length as the radius of curvature R; the same applies to each of the following tables), the refractive index N of each lens at d-line, and Abbe number ν. Table 1 and Tables 2 to be described later.
In 4, the numbers corresponding to the symbols R, D, N, and ν are sequentially increased from the enlargement side.

The wide-angle end (WIDE; 1.00 times), the middle (MIDDLE; 1.18 times), and the telephoto end (TELE: 1.times.).
The 1A lens group at 43-fold) _{G 1A} and 1B-th lens group _{G 1 B} distance _{D 8} (variable 1), the 1B lens group _{G 1B} and the second lens group _{G 2} a distance _{D 1 0} (variable 2), Distance D ₁₇ between second lens group G ₂ and third lens group G ₃ (variable 3), distance D ₂₁ between third lens group G ₃ and fourth lens group G ₄ (variable 4), and fourth lens group G ₄ When it is shown in the lower part of Table 1 magnification at a distance _{D 25} (variable 5) and close of the fifth lens group _{G 5.}

Note that the lower part of Table 1 shows the intervals of the variables 1 to 5 at each magnification, divided into infinity (upper part) and closest (lower part). Table 5 below shows numerical values corresponding to the conditional expressions (1) to (5) in Example 1.

[0035]

[Table 1]

FIGS. 3, 4 and 5 show the wide-angle end (WIDE) and the middle (MIDD) of the wide-angle zoom lens according to the first embodiment.
FIG. 9 is an aberration diagram showing various aberrations (spherical aberration, astigmatism, distortion, and lateral chromatic aberration) at the time of closest setting at the telephoto end (TELE). Note that FIG.
5 to 5 and FIGS. 6 to 14 below, each astigmatism diagram shows aberration with respect to the sagittal image plane and the tangential image plane, and each chromatic aberration of magnification diagram shows aberration with respect to d-line.

As is clear from FIGS. 3 to 5 and Table 5 below, according to the wide-angle zoom lens of the first embodiment, excellent aberration correction is performed over the entire zoom range even at the closest setting, and the reduction side size is reduced. That the back focus can be set to an appropriate size, and that the light beam in the tangential plane on the reduction side is substantially parallel and symmetric with respect to the optical axis. In addition, it is possible to obtain a lens having a wider angle of view at the wide angle end, that is, an angle of view 2ω = 68.6 degrees compared with the related art.

Second Embodiment A zoom lens according to a second embodiment has substantially the same configuration as that of the first embodiment. Table 2 shows the radius of curvature R of each lens surface, the center thickness of each lens, the air gap D between the lenses, the refractive index N at d-line of each lens, and the Abbe number ν in Example 2.

Also, the wide-angle end (WIDE; 1.00 times), the middle (MIDDLE; 1.18 times), and the telephoto end (TELE; 1.times.).
The 1A lens group at 43-fold) _{G 1A} and 1B-th lens group _{G 1 B} distance _{D 8} (variable 1), the 1B lens group _{G 1B} and the second lens group _{G 2} a distance _{D 1 0} (variable 2), Distance D ₁₇ between second lens group G ₂ and third lens group G ₃ (variable 3), distance D ₂₁ between third lens group G ₃ and fourth lens group G ₄ (variable 4), and fourth lens group G ₄ When it is shown in the lower part of Table 1 magnification at a distance _{D 25} (variable 5) and close of the fifth lens group _{G 5.}

The lower part of Table 2 shows the intervals of the variables 1 to 5 at each magnification, divided into infinity (upper part) and closest parts (lower part). Table 5 below shows numerical values corresponding to the conditional expressions (1) to (5) in Example 2.

[0041]

[Table 2]

FIGS. 6, 7 and 8 show the wide-angle end (WIDE) and the middle (MIDD) of the wide-angle zoom lens according to the second embodiment.
FIG. 9 is an aberration diagram showing various aberrations (spherical aberration, astigmatism, distortion, and lateral chromatic aberration) at the time of closest setting at the telephoto end (TELE).

As is clear from FIGS. 6 to 8 and Table 5 below, according to the wide-angle zoom lens of the second embodiment, excellent aberration correction is performed over the entire zoom area even at the closest setting, and the reduction side size is reduced. That the back focus can be set to an appropriate size, and that the light beam in the tangential plane on the reduction side is substantially parallel and symmetric with respect to the optical axis. In addition, a lens having a wider angle of view than the conventional lens having an angle of view of 2ω = 68.8 degrees at the wide angle end can be obtained.

<Embodiment 3> FIG. 2 shows Embodiment 3 according to the present invention.
1 shows the basic configuration of the zoom lens of FIG. 1 and is a lens configuration diagram (WIDE) at the wide-angle end.

The zoom lens according to the third embodiment is actually
Although the configuration is substantially the same as that of the first embodiment,
Group G_1AIs a single three lens L₁~ L₃From
The first B lens group G_1BBut one cemented lens (biconcave
Lens and biconvex lens) L ₄, L₅Consisting of
Group G₂Is a single three lens L₆~ L₈From
The third lens group G₃But one cemented lens L₉, L
₁₀The fourth lens group G₄But one cemented lens
L₁₁, L₁₂The fifth lens group G₅But one
A cemented lens and a single lens L₁₃~ L₁₆From
You.

In the third embodiment, the radius of curvature R of each lens surface, the center thickness of each lens and the air gap D between each lens, the refractive index N of each lens at d-line, and the Abbe number ν
Are shown in Table 3.

Also, the wide-angle end (WIDE; 1.00 times), the middle (MIDDLE; 1.06 times) and the telephoto end (TELE; 1.times.).
10 ×), a distance D ₆ between the _{first A} lens group G _1A and the first B lens group G _{1 B} (variable 1), a distance D ₉ between the first B lens group G _1B and the second lens group G ₂ (variable 2), The distance D ₁₅ between the second lens group G ₂ and the third lens group G ₃ (variable 3), the third
The lower part of Table 3 shows the distance D ₁₈ (variable 4) between the lens group G ₃ and the fourth lens group G ₄ , the distance D ₂₁ (variable 5) between the fourth lens group G ₄ and the fifth lens group G ₅ , and the close-up magnification. Shown in

The lower part of Table 3 shows the intervals of the variable numbers 1 to 5 at each magnification, divided into infinity (upper part) and closest parts (lower part). Table 5 below shows numerical values corresponding to the conditional expressions (1) to (5) in Example 3.

[0049]

[Table 3]

FIGS. 9, 10 and 11 show the third embodiment.
Wide-angle zoom lens of wide angle end (WIDE), middle (MI
FIG. 9 is an aberration diagram showing various aberrations (spherical aberration, astigmatism, distortion, and lateral chromatic aberration) at the time of closest setting at the telephoto end (TELE).

As is clear from FIGS. 9 to 11 and Table 5 below, according to the wide-angle zoom lens of the third embodiment, excellent aberration correction is performed over the entire zoom area even at the closest setting, and the reduction side size is reduced. That the back focus can be set to an appropriate size, and that the light beam in the tangential plane on the reduction side is substantially parallel and symmetric with respect to the optical axis. In addition, a lens having a wider angle of view than the conventional lens having an angle of view of 2ω = 68.0 degrees at the wide angle end can be obtained.

Fourth Embodiment A zoom lens according to a fourth embodiment has substantially the same configuration as that of the zoom lens according to the third embodiment. Table 4 shows the radius of curvature R of each lens surface, the center thickness of each lens, the air gap D between the lenses, the refractive index N at d-line of each lens, and the Abbe number ν in Example 3.

Also, the wide-angle end (WIDE; 1.00 times), the middle (MIDDLE; 1.06 times) and the telephoto end (TELE: 1.X).
10 ×), a distance D ₆ between the _{first A} lens group G _1A and the first B lens group G _{1 B} (variable 1), a distance D ₉ between the first B lens group G _1B and the second lens group G ₂ (variable 2), The distance D ₁₅ between the second lens group G ₂ and the third lens group G ₃ (variable 3), the third
The lower part of Table 4 shows the distance D ₁₈ (variable 4) between the lens group G ₃ and the fourth lens group G ₄ , the distance D ₂₁ (variable 5) between the fourth lens group G ₄ and the fifth lens group G ₅ , and the close-up magnification. Shown in

The lower part of Table 4 shows the intervals of the variables 1 to 5 at each magnification, divided into infinity (upper part) and closest parts (lower part). Table 5 below shows numerical values corresponding to the conditional expressions (1) to (5) in Example 4.

[0055]

[Table 4]

FIGS. 12, 13 and 14 show the wide-angle end (WIDE) and the middle (M) of the wide-angle zoom lens according to the fourth embodiment.
FIG. 9 is an aberration diagram showing various aberrations (spherical aberration, astigmatism, distortion, and lateral chromatic aberration) at the time of closest setting at the telephoto end (TELE) and at the telephoto end (TELE).

As is clear from FIGS. 12 to 14 and Table 5 below, according to the wide-angle zoom lens of the fourth embodiment, excellent aberration correction is performed over the entire zoom range even at the closest setting, and the reduction side size is reduced. The size of the light beam can be made compact, the back focus can be set to an appropriate size, and the light beam in the tangential plane on the reduction side is substantially parallel and symmetric with respect to the optical axis. In addition, it is possible to obtain a lens having a wider angle of view than the related art, in which the angle of view 2ω = 67.8 degrees at the wide angle end.

[0058]

[Table 5]

The zoom lens according to the present invention is not limited to the above-described embodiment, but may be variously modified. For example, the number of lenses constituting each lens group and the radius of curvature of each lens may be changed. R and the lens interval (or lens thickness) D can be changed as appropriate.

In the above embodiment, the lens of the present invention is used as a projection lens of a projection display device using a transmission type liquid crystal display panel. However, the usage of the zoom lens of the present invention is not limited to this. Projection lens or DM of a device using a reflective liquid crystal display panel
It can be used as a projection lens or the like of an apparatus using other light modulation means such as D, and a zoom function used for imaging means such as a CCD and an imaging tube, and a camera using a silver halide film or the like. Can also be used as an imaging lens having

[0061]

As described in the foregoing, according to the wide-angle zoom lens of the present invention, the first lens group G _1, the first having a first 1A lens group G _1A and negative refractive power having a negative refractive power
Consisted B lens group G _1B, focusing is to perform by moving the two lens groups to each other, further, by defining the power distribution of the two lens groups in an appropriate range, image It is possible to satisfactorily correct various aberrations even when the angle is as close as about 70 degrees.

Further, the second lens group and the third lens group having a positive refractive power and the fourth lens group having a negative refractive power are of a movable five-group type. Since the range is set to an appropriate range as described above, it is possible to reduce aberration fluctuations due to zooming while widening the angle of view. In addition, the lens system can be made compact with respect to the size of the reduction side, the light rays in the tangential plane on the reduction side are made substantially uniform with respect to the optical axis, and a color combining optical system or the like is inserted at a predetermined position. An appropriate back focus amount can be obtained.

Thus, the projection display device using the zoom lens of the present invention can be a compact device having a wide angle of view and well corrected aberration.

[Brief description of the drawings]

FIG. 1 is a lens configuration diagram of a zoom lens according to a first embodiment at a wide-angle end.

FIG. 2 is a lens configuration diagram at a wide-angle end of a zoom lens according to a third embodiment.

FIG. 3 is a view showing a wide-angle end (closest) of the zoom lens according to the first embodiment;
Each aberration diagram in

FIGS. 4A and 4B are aberration diagrams in the middle (closest) of the zoom lens according to the first embodiment.

FIG. 5 is a telephoto end (closest) of the zoom lens according to the first embodiment;
Each aberration diagram in

FIG. 6 illustrates a wide-angle end (closest) of the zoom lens according to the second embodiment.
Each aberration diagram in

FIGS. 7A and 7B are aberration diagrams in the middle (closest) of the zoom lens according to Example 2. FIGS.

FIG. 8 is a telephoto end (closest) of the zoom lens according to the second embodiment;
Each aberration diagram in

FIG. 9 is a view illustrating a wide-angle end (closest) of a zoom lens according to a third embodiment;
Each aberration diagram in

FIG. 10 shows a middle (closest) position of the zoom lens according to the third embodiment.
Each aberration diagram in

FIG. 11 is an aberration diagram at a telephoto end (closest) of a zoom lens according to a third embodiment;

FIG. 12 is each aberration diagram at the wide-angle end (closest) of the zoom lens according to Example 4;

FIG. 13 shows the middle (closest) position of the zoom lens according to Example 4;
Each aberration diagram in

FIG. 14 is each aberration diagram at the telephoto end (closest) of the zoom lens according to Example 4;

[Explanation of symbols]

G _{1 to} G ₅ , G _1A , G _1B lens groups L _{1 to} L ₁₇ lenses Radius of curvature such as R _{1 to} R ₃₄ lenses D _{1 to} D ₃₃ Surface spacing (thickness) such as lenses X Optical axis 1 Image plane 2 Glass block

Continued on front page F term (reference) 2H087 KA01 KA06 KA07 MA05 MA12 MA18 NA02 PA15 PA19 PB17 QA02 QA06 QA12 QA22 QA26 QA34 QA41 QA45 SA41 SA44 SA46 SA49 SA53 SA55 SA63 SA64 SA65 SA72 SA76 SB06 SB15 SB09 SB33 SB45 5H09 SB11 BA11 BA23 EA01 EA02 EA12

Claims (4)

[Claims] 1. A first lens group having a negative refractive power for performing fixed focusing during zooming in order from an enlargement side, and an image plane movement caused by continuous zooming and caused by the continuous zooming. The second lens group having a positive refractive power, which moves in relation to each other, and the third lens group having a positive refractive power
A lens group and a fourth lens group having a negative refractive power, and a fifth lens group having a fixed positive refractive power at the time of zooming. In order, it is fixed at the time of zooming, and can move each other for focusing.
A wide-angle zoom comprising a first A lens group having a negative refractive power and a first B lens group having a negative refractive power arranged to satisfy the following conditional expressions (1) to (5). lens. _{(1) 1.5 <f 2 /f<4.0} (2) 2.0 <f 3 /f<5.0 (3) 1.5 <f 5 /f<3.0 (4) -1 _{.8 <f 1 /f<-0.9 (5)} 0.4 <f 1 / f 1A <1.0 f: the focal point of the entire lens system at the wide-angle end length f _1: the focal length f of the first lens group _2: a second focal length of the lens unit f _3: the third focal point of the lens group distances f ₅ a focal length f _1A of the fifth lens group is a focal length of the 1A lens group 2. The wide-angle zoom lens according to claim 1, wherein a lens closest to the enlargement side of the first B lens group is a lens having a concave surface facing the enlargement side. 3. The zoom lens according to claim 1, wherein at the time of zooming, the distance between said second lens group and said third lens group becomes narrower toward the telephoto end.
Or the wide-angle zoom lens according to 2. 4. A projection type display device comprising the wide-angle zoom lens according to claim 1, wherein an image displayed on a light valve is projected on a screen.