JP6418482B2 - Projection zoom lens and projection-type image display device - Google Patents

Description

  The present invention relates to a projection zoom lens used as a projection lens for enlarging and projecting an image displayed on an image display element onto a projection surface such as a screen, and a projection type image display device equipped with the projection zoom lens. It is.

2. Description of the Related Art In recent years, a front projection type projector apparatus that projects an enlarged image on a screen in front of a projection type image display apparatus has been widely used for presentations in companies, education in schools, and home use.
An image display element that displays an image to be enlarged and projected on an “image display surface” is also called a “light valve”, but various types are known including a liquid crystal panel.
In recent years, a “micromirror device” typified by a digital micro-mirror device (hereinafter abbreviated as “DMD”) manufactured by Texas Instruments has attracted attention as a light valve. ing.
Of course, the projection zoom lens is preferably applicable to various light valves.
In the micromirror device (DMD), the micromirrors arrayed on the image display surface are selectively tilted to display an image.
Although there are various constraints, the micromirror device is advantageous for downsizing and high brightness, and has recently been widely spread.

In recent years, a zoom lens for projection has been required to be “high magnification and wide angle”. In addition, it is required to suppress performance fluctuations as much as possible during focusing.
As what meets such a request, those described in Patent Documents 1 and 2 are known.
In other words, the projection zoom lens described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2006-234893) has a negative, positive, positive, negative, positive, positive six lens group configuration, or negative, positive, positive, negative, It is a group structure with 7 lenses of positive, positive, and positive, and it is a method of focusing by moving a part of the first lens group at the time of focusing, and the aberration at the time of zooming is sufficiently suppressed. It has a lens group configuration as many as seven groups.
Further, the projection zoom lens described in Patent Document 2 (Japanese Patent Application Laid-Open No. 2010-160478) has a negative, positive, positive, positive, and positive five lens group configuration, and aberrations are sufficiently suppressed. The half angle of view: ωw remains at 38 ° at most.
In general, a “lens used for image projection” is different from a camera lens system in that “oblique light” is used as an imaging light beam.

In a photographing lens for a camera, a rotationally symmetric region with respect to the optical axis of the lens system is a photographing region, and in a photographing lens with a wide angle of view, a large photographing region around the lens optical axis is possible.
However, in a lens used for projecting an image, a projected image is formed by oblique rays, so that only a part of the “large area centered on the lens optical axis” can be used as an image projection area. .
For this reason, in order to increase the area of the projection surface on which the image is projected, it is necessary to widen the angle of the projection zoom lens.
Further, recently, there is a strong demand to reduce the projection distance of the projector device and “place the projector device closer to the projection surface”.
In order to realize a projection surface having a large area with such a close arrangement to the projection surface, further widening of the angle is desired for the projection zoom lens.

  The present invention has been made in view of the above-described circumstances, and has a five-lens group configuration for suppressing a variation in performance when the screen size is changed and focusing, and for projecting a wide angle of view. It aims to provide a zoom lens.

The projection zoom lens according to the present invention achieves the above-described object,
A projection zoom lens consisting of five groups constituting a projection optical system of an image display device that projects an image displayed on the surface of an image display element onto a projection surface and displays the enlarged image,
In order from the most magnified side,
A first lens group G1 having negative refractive power;
A second lens group G2 having a positive refractive power;
A third lens group G3 having a positive refractive power;
A fourth lens group G4 having a positive refractive power;
A fifth lens group G5 having a positive refractive power;
Consisting of
At the time of zooming from the short focus to the long focus, the interval between adjacent lens groups changes, the second lens group G2 moves to the reduction side, and the third lens group G3 and the fourth lens group G4. Moves to the enlargement side,
Focusing is performed by moving a part of the first lens group G1, and the first lens group G1 includes a negative group moving in the optical axis direction and a fixed negative group.
When focusing on a close side is moved to the partially enlarged side of the first lens group G1, a portion of the first lens group G1 upon focusing on a long distance side to the reduction side It is characterized by moving.

  According to the present invention, with a five-lens group configuration, by moving a part of the first lens group at the time of focusing, a wide angle of view is achieved, and the performance variation is effectively suppressed to be small. A zoom lens can be provided.

It is sectional drawing which shows the structure of the zoom lens for a projection of the Example (numerical example. The following is same) 1 which concerns on the 1st Embodiment of this invention. 3 is an aberration curve diagram of the projection zoom lens of Example 1. FIG. It is sectional drawing which shows the structure of the zoom lens for projection of Example 2 which concerns on the 2nd Embodiment of this invention. FIG. 6 is an aberration curve diagram of the projection zoom lens according to Example 2. It is sectional drawing which shows the structure of the zoom lens for projection of Example 3 which concerns on the 3rd Embodiment of this invention. 6 is an aberration curve diagram of the projection zoom lens of Example 3. FIG. It is sectional drawing which shows the structure of the zoom lens for projection of Example 4 which concerns on the 4th Embodiment of this invention. 6 is an aberration curve diagram of the projection zoom lens of Example 4. FIG. It is sectional drawing which shows the structure of the zoom lens for projection of Example 5 which concerns on the 5th Embodiment of this invention. FIG. 10 is an aberration curve diagram of the projection zoom lens according to Example 5. It is a schematic block diagram of the projector apparatus as a projection type image display apparatus concerning the 6th Embodiment of this invention.

Hereinafter, based on an embodiment of the present invention, a projection zoom lens and a projection type image display device according to the present invention will be described in detail with reference to the drawings.
The zoom lens of the present invention is a “projection zoom lens” as described above.
As described above, in the “projection zoom lens”, the imaging light beam is “oblique light”, and the projection zoom lens of the present invention also has “oblique light beam” as the projection light beam for forming the projection image. Is used.
FIGS. 1, 3, 5, 7, and 9 show cross-sectional configurations of the projection zoom lenses according to the first, second, third, fourth, and fifth embodiments of the present invention.
The zoom lenses of the first to fifth embodiments correspond to specific Examples 1 to 5 described later in this order.
In each of the above figures, the left side of each figure is the “enlargement side” and the right side is the “reduction side”. In order to avoid complications, the symbols are shared in these drawings.
In each of the drawings, reference numeral G1 indicates a first lens group, reference numeral G2 indicates a second lens group, reference numeral G3 indicates a third lens group, reference numeral G4 indicates a fourth lens group, and reference numeral G5 indicates a fifth lens group.

In other words, the projection zoom lens according to the embodiment shown in the above drawings has a five-lens group configuration in which the first to fifth lens groups G1 to G5 are arranged from the enlargement side toward the reduction side.
Further, in each of the above drawings, “Optical Device” (hereinafter abbreviated as “OD”) is shown as an image display element.
In each of these embodiments and examples, it is assumed that the light valve is “DMD, which is a micromirror device”. Of course, the light valve is not limited to this, but a liquid crystal display element, an LED element Etc.
In the above figures, the upper diagram shows “lens group arrangement at the wide-angle end (shown as wide angle in the drawing)”, and the lower diagram shows “lens group arrangement at the telephoto end (shown as telephoto in the drawing)”. .
Also, the broken line drawn between the upper and lower figures in these figures indicates the transition of the second lens group G2 to the fourth lens group G4 during zooming from the wide angle end to the telephoto end. The direction (or locus) is indicated, and the first lens group G1 and the fifth lens group G5 are fixed.
In the projection zoom lens whose embodiments are shown in the drawings, the first lens group G1 has negative refractive power, and the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G1. The lens group G5 has a positive refractive power.

During zooming from short focus to long focus, the distance between adjacent lens groups changes, the second lens group G2 moves to the reduction side, and the third lens group G3 and the fourth lens group G4 move to the enlargement side. Configured to move to.
Further, focusing is performed by moving a part of the first lens group G1, and the first lens group G1 includes a negative group that moves in the optical axis direction and a negative group that is fixed. During focusing, a part of the first lens group G1 moves to the enlargement side, and when focusing to the long distance side, a part of the first lens group G1 moves to the reduction side. ing.
Here, the “group” is defined as a group (block) that moves independently or a group (block) that does not move during zooming.
The first lens group G1 is divided into a fixed group (lumb) and a moving group (lumb) during focusing, but the first lens group does not move during zooming, and thus is regarded as one group. . Here, in the first lens group G1, the moving lens group is referred to as “first lens front group G1-1”, and the non-moving (fixed) lens group is referred to as “first lens rear group G1-2”. I will do it.
During focusing, the power of the first lens front group G1-1 that moves in the first lens group G1 is made stronger than the power of the first lens rear group G1-2 that does not move in the first lens group. In addition, it is possible to reduce the amount of focusing movement, and to effectively increase the optical performance by increasing the power to make the angle of view wider.

In order to satisfy such a condition, the negative lens group leading type is preferable, and it is desirable to move a part of the first lens group G1 which is the most magnified side. That is, the first lens rear group G1-2, which is a fixed group divided when the first lens group G1 is focused, and the first lens front group G1-1, which is a moving group, are both negative groups (negative refractive power). It is desirable that By setting the negative lens group first, there is an advantage that the chief ray height can be lowered and the effective lens diameter can be reduced. Therefore, it is possible to make the projection zoom lens with a wide angle of view compact.
The following conditional expression (1) defines the range of the first lens front group G1-1 that moves when the first lens group G1 is in focus and the first lens rear group G1-2 that is a fixed group. The conditions for optimizing chromatic aberration are shown.
(1) 0.1 <F1_m / F1_f <0.5
When focusing, when the focal length of the moving group G1-1 of the first lens group G1 is F1_m and the focal length of the fixed group G1-2 is F1_f, this conditional expression (1) This is a condition for optimizing the chromatic aberration correction in the zooming area and the focusing area. If the lower limit of conditional expression (1) is not reached, it is not desirable because axial chromatic aberration and lateral chromatic aberration become large. If the upper limit of conditional expression (1) is exceeded, axial chromatic aberration tends to be corrected, but lateral chromatic aberration does not increase. Undesirably because it grows.

At the time of image projection, a projection light beam (light beam by oblique rays) from the light valve side is guided from the fifth lens group G5 side to the first lens group G1 side.
At this time, since the first lens group G1 is negative, the divergence angle of the light beam from the fifth lens group G5 can be easily expanded by the first lens group G1.
Therefore, as described above, the jump angle of the light beam transferred from the second lens group G2 to the first lens group G1 can be kept small, and the divergence angle of the radiated light beam from the first lens group G1 can be increased reasonably.
In addition, there is an effect of suppressing performance deterioration due to the eccentricity of the lens at the time of manufacture.
The projection zoom lens according to the present invention can achieve even better performance by satisfying one or more of the following conditional expressions (2) to (4) in addition to the above-described configuration.
(2) 0.9 <| F1 | / Fw <1.3
(3) 8.0 <F5 / Fw <11.0
(4) 38 ° <ωw <45 °
In these conditions (2) to (4), the symbols of the parameters are as follows.

“F1” represents the focal length of the first lens group G1, and “Fw” represents the focal length of the entire lens system.
“F5” represents the focal length of the fifth lens group G5, and “ωw” represents the half angle of view at the wide-angle end.
Conditional expression (2) relates to the axial chromatic aberration, particularly regarding the axial chromatic aberration on the telephoto side. When the value is below the lower limit, the power (1 / f) of the first lens group G1 becomes strong with respect to the focal length of the entire lens system, and the power balance is lost, so that axial chromatic aberration on the telephoto side becomes large. When the upper limit of conditional expression (2) is exceeded, the power (1 / f) of the first lens group G1 becomes weaker with respect to the focal length of the entire lens system, and astigmatism is in an improving direction. However, the spherical aberration tends to increase, which is not desirable because the aberration balance deteriorates.
Conditional expression (3) is a condition for proposing an optimum range for spherical aberration and astigmatism. If the lower limit of conditional expression (3) is not reached, the power of the fifth lens group G5 becomes strong, so that the tangential direction of spherical aberration and astigmatism becomes overexposed. On the other hand, when the upper limit of conditional expression (3) is exceeded, the power of the fifth lens group G5 becomes weak, and the tangential direction of spherical aberration and astigmatism becomes under. Therefore, it is desirable to be within the range of conditional expression (3).

Conditional expression (4) represents the first lens rear group G1-2, which is a negative group of the first lens group G1 at the time of focusing, which is negative / positive / positive / positive / positive in the five-group type of the present invention. This is a desirable half field angle range in the case of an optical system characterized in that the first lens front group G1-1, which is a negative group that is fixed and moved, is moved. Of course, if the number of lenses is increased, the amount of movement is increased, or the zoom ratio is reduced, it is possible even outside the range of conditional expression (4).
In the first lens group G1, it is desirable that the first lens front group G1-1 that moves during focusing and the first lens rear group G1-2 that does not move each include two or more lenses. If each group is composed of a single lens, a projection zoom with a wide angle (for example, an angle of view with a half angle of view exceeding 38 °) and a high zoom ratio (for example, 1.5 times or more), which is the subject of the present invention. When a lens is used, it is difficult to correct various aberrations that occur. In particular, since it becomes difficult to correct chromatic aberration and spherical aberration, it is desirable that each of the first lens group G1 has two or more moving groups and fixed groups at the time of focusing.
In the fifth lens group G5 of the present invention, the second lens group G2 and the fourth lens group G4 are a correction group, and the third lens group G3 is a zooming group. At the time of zooming from the wide-angle end to the telephoto end, the second lens group G2, which is a correction group, moves to the reduction side, and the third lens group G3, which is a zooming group, moves to the enlargement side, and is a correction group. The fourth lens group G4 is characterized by moving to the enlargement side. In the case of telephoto zoom, the correction group tends to move to the enlargement side when zooming from the wide-angle end to the telephoto end, but since the present invention is a wide-angle zoom, the second lens in the correction group The group G2 is characterized by moving slowly toward the reduction side.

The present invention is a wide-angle zoom projection system with a zoom ratio of approximately 1.5 times or more, but it goes without saying that the zoom ratio is also established when the zoom ratio is 1.5 times or less and 1.1 times.
Before giving a specific example of a zoom lens, a first embodiment (sixth embodiment) of a projector as a projection type image display apparatus according to the present invention will be briefly described with reference to FIG. .
This is an example in which a DMD 3 that is a micromirror device is employed as a light valve of the projector 1 that is the projection type image display device shown in FIG.
The projector 1 includes an illumination system 2, a DMD 3 that is a light valve, and a projection zoom lens 4.
As the projection zoom lens 4, the one described in any one of claims 1 to 9 according to the present invention, specifically, any one of Examples 1 to 5 can be used.
The “light of three colors RGB” is temporally separated from the illumination system 2 and irradiated to the DMD 3, and the tilt of the micromirror corresponding to each pixel is controlled at the timing when each color light is irradiated.
In this way, the “image to be projected” is displayed on the DMD 3, and the light whose intensity is modulated by the image is enlarged by the projection zoom lens 4 and enlarged and projected on the screen 5.

Although not shown, the illumination system 2 includes a light source, a condenser lens, an RGB color wheel, a mirror, and the like, and it is necessary to “ensure a certain extent”.
For this reason, it is necessary to increase the incident angle of the illumination light incident on the DMD 3 from the illumination system 2 to some extent.
Due to the above-described relationship between the space between the projection zoom lens 4 and the illumination system 2, it is necessary to secure the back focus of the projection zoom lens 4 to some extent.
The condenser lens, RGB color wheel and mirror constitute an “illumination optical system”.
In the zoom lenses according to Examples 1 to 5, when zooming from the wide-angle end to the telephoto end, the second lens group G2 gently moves to the reduction side, and the third to fourth lens groups G3 to G4 move to the enlargement side. Moving. Even during zooming, the back focus is secured sufficiently large.

Hereinafter, five specific examples of the projection zoom lens according to the present invention will be described.
The meanings of symbols in each embodiment are as follows.
F: Focal length of the entire optical system Fno: Numerical aperture R: Radius of curvature (“Paraxial radius of curvature” for aspheric surfaces)
D: Interplanar spacing Nd: Refractive index νd: Abbe number BF: Back focus The shape of the aspheric surface is specified by the well-known equation (5).

  In this equation (5), X is “displacement in the direction of the optical axis at the position of the height H from the optical axis with respect to the surface apex”, K is “conic coefficient”, C4, C6, C8, C10.・ ・ Is an aspherical coefficient.

[Example 1]
FIG. 1 is a view for explaining a projection zoom lens in Example 1 according to the first embodiment of the present invention.
The projection zoom lens according to Example 1 sequentially has a first lens group G1 having a negative refractive power and a positive refractive power sequentially from the enlargement side (left side in FIG. 1) to the reduction side (right side in FIG. 1). A second lens group G2 having a positive refractive power, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a positive refractive power. -It is a 5-group configuration of positive-positive-positive-positive.
As the light valve, an OD (abbreviation of Optical Device) is arranged, and the DMD described above is assumed.
During zooming from the wide-angle end to the telephoto end, the second lens group G2 moves gently toward the reduction side, and the third lens group G3 and the fourth lens group G4 move toward the enlargement side. At this time, the first lens group G1 and the fifth lens group G5 are fixed.
During focusing, focusing is performed by moving the first lens front group G1-1 in the first lens group G1 in the optical axis direction, but the first lens rear group G1-2 is fixed. .
The aperture stop AD is disposed between the third lens group G3 and the fourth lens group G4.

The first lens group G1 of the projection zoom lens according to the first exemplary embodiment includes a negative lens L11 including a negative meniscus lens having a convex surface directed toward the enlargement side sequentially from the enlargement side to the reduction side, and the lens center portion on the enlargement side. A negative lens L12 composed of a negative meniscus lens that is bent toward the reduction side and has a small thickness deviation ratio, a negative lens L13 composed of a negative meniscus lens with a convex surface directed toward the enlargement side, and a reduction side A positive lens L14 composed of a biconvex lens with a convex surface having a larger curvature than the surface on the enlargement side, a negative lens L15 composed of a negative meniscus lens with a convex surface facing the magnification side, and a curvature larger than that on the enlargement side on the reduction side. A negative lens L16 made of a biconcave lens is disposed on the concave surface.
In this first lens group G1, aspheric surfaces are formed on both surfaces of the negative lens L12.
Of the first lens group G1, the negative lens L11, the negative lens L12, and the negative lens L13 constitute a first lens front group G1-1 that has negative refractive power and moves together during focusing. ing.
In addition, in the first lens group G1, the positive lens L14, the negative lens L15, and the negative lens L16 have negative refractive power, and constitute a fixed first lens rear group G1-2 at the time of focusing. doing.

The second lens group G2 comprises solely a positive lens L21 consisting of a positive meniscus lens with the convex surface facing the enlargement side. The third lens G3 includes a positive lens L31 composed of a positive meniscus lens having a convex surface facing the enlargement side, a positive lens L32 composed of a biconvex lens having a convex surface having a larger curvature than the reduction side on the magnification side, and a concave surface facing the magnification side. A negative lens L33 made of a negative meniscus lens facing the lens is disposed. These two lenses, the positive lens L32 and the negative lens L33, are bonded in close contact with each other to form a cemented lens. The fourth lens group G4 includes a negative lens L41 made of a biconcave lens having a concave surface having a larger curvature than the reduction side on the enlargement side, and a positive lens L42 made of a biconvex lens having a convex surface having a larger curvature on the enlargement side than the reduction side. A positive lens L43 composed of a biconvex lens having a convex surface having a larger curvature than the enlargement side is disposed on the reduction side.
The two lenses of the negative lens L41 and the positive lens L42 are bonded in close contact with each other to form a cemented lens.
Moreover, aspherical surfaces are formed on both surfaces of the positive lens L43.
In the fifth lens group G5, only a positive lens L51 including a planoconvex lens having a convex surface directed toward the enlargement side is disposed.

On the reduction side of the fifth lens group G5, an OD made of DMD, for example, is arranged as an image display element.
The range of the focal length F, the F number Fno, and the half angle of view ωw at the wide angle end in Example 1 are as follows.
F = 12.6 to 18.3 mm, Fno = 2.58 to 3.04, ωw = 43.0 °
The data of Example 1 is shown in Table 1 below.

In Table 1, the surface number is the surface number counted from the enlargement side, and includes the surface of the aperture stop AD (surface number: 21 in the table). OD represents an optical device.
“INF” in the table indicates that the radius of curvature is infinite. Further, “*” (asterisk) indicates that the surface to which this symbol is attached, that is, the third surface, the fourth surface, the 25th surface and the 26th surface are “aspherical surfaces”.
These matters are the same in each of the following embodiments.

"Aspherical data"
The aspherical data in the above equation (5) is shown in Table 2 below.
In the aspheric coefficient, “En” represents “power of 10”, that is, “× 10 ⁿ ”, for example, “E-05” represents “× 10 ⁻⁵ ”.

  In Table 1, D13, D15, D20, and D26 represent variable intervals of the lens group that change during zooming. Bf represents back focus. The distance between the lens groups when the projection distance is 1550 mm is shown in Table 3 below for the wide-angle end, the middle, and the telephoto end.

"Parameter values for each conditional expression"
In the case of Example 1, values corresponding to the conditional expressions (1) to (4) are as shown in Table 4 below, which satisfy the conditional expressions (1) to (4), respectively.

FIG. 2 shows aberration diagrams of Example 1.
The upper part of the left side of FIG. 2 shows the aberration at the “wide-angle end (indicated as wide angle)”, the middle part at “intermediate focal length (indicated as intermediate)”, and the lower part at “telephoto end (indicated as telephoto)”. In addition, the upper right graph shows aberration diagrams corresponding to 40 inches at the wide angle end, and the lower right graph shows aberration diagrams corresponding to 300 inches at the wide angle end. As described above, focusing is performed by moving G1-1 in the optical axis direction.
In the aberration diagrams at each stage, the left diagram is “spherical aberration”, the middle diagram is “astigmatism”, and the right diagram is “distortion aberration”.
R, G, and B in the “spherical aberration” diagram represent wavelengths: R = 625 nm, G = 550 nm, and B = 460 nm, respectively.
In the “astigmatism” diagram, “T” indicates tangential and “S” indicates sagittal rays.
Astigmatism and distortion are shown for a wavelength of 550 nm.
These indications in the aberration diagrams are the same in the aberration diagrams of Examples 2 to 5 below.
It goes without saying that even if the screen size is changed, the fluctuation in performance is small and the optical performance is good.

[Example 2]
FIG. 3 is a diagram for explaining a projection zoom lens in Example 2 according to the second embodiment of the present invention.
The projection zoom lens of Example 2 has, in order from the enlargement side (left side in FIG. 3) to the reduction side (right side in FIG. 3), a first lens group G1 having negative refractive power, and positive refractive power. A second lens group G2, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a positive refractive power are arranged, so-called negative-positive. -Positive-positive-positive five-group configuration.
As the light valve, an OD (abbreviation of Optical Device) is arranged, and the DMD described above is assumed.
During zooming from the wide-angle end to the telephoto end, the second lens group G2 moves gently toward the reduction side, and the third lens group G3 and the fourth lens group G4 move toward the enlargement side. At this time, the first lens group G1 and the fifth lens group G5 are fixed.
During focusing, focusing is performed by moving the first lens front group G1-1 in the first lens group G1 in the optical axis direction, but the first lens rear group G1-2 is fixed. .

The aperture stop AD is disposed between the third lens group G3 and the fourth lens group G4.
The first lens group G1 of the projection zoom lens according to the second embodiment includes a negative lens L11 including a negative meniscus lens having a convex surface directed toward the enlargement side sequentially from the enlargement side to the reduction side, and the lens center portion on the enlargement side. A negative lens L12 composed of a negative meniscus lens that is bent toward the reduction side and has a small thickness deviation ratio, a negative lens L13 composed of a negative meniscus lens with a convex surface directed toward the enlargement side, and a reduction side A positive lens L14 composed of a biconvex lens with a convex surface having a larger curvature than the surface on the enlargement side, a negative lens L15 composed of a negative meniscus lens with a convex surface facing the magnification side, and a curvature larger than that on the enlargement side on the reduction side. A negative lens L16 made of a biconcave lens having a concave surface is disposed.
In this first lens group G1, aspheric surfaces are formed on both surfaces of the negative lens L12.
Of the first lens group G1, the negative lens L11, the negative lens L12, and the negative lens L13 constitute a first lens front group G1-1 that has negative refractive power and moves together during focusing. ing.

In addition, in the first lens group G1, the positive lens L14, the negative lens L15, and the negative lens L16 have negative refractive power, and constitute a fixed first lens rear group G1-2 at the time of focusing. doing.
The second lens group G2 comprises solely a positive lens L21 consisting of a positive meniscus lens with the convex surface facing the enlargement side. The third lens G3 includes a positive lens L31 composed of a positive meniscus lens having a convex surface facing the enlargement side, a positive lens L32 composed of a biconvex lens having a convex surface having a larger curvature than the reduction side on the magnification side, and a concave surface facing the magnification side. A negative lens L33 made of a negative meniscus lens facing the lens is disposed. These two lenses, the positive lens L32 and the negative lens L33, are bonded in close contact with each other to form a cemented lens. The fourth lens group G4 includes a negative lens L41 made of a biconcave lens having a concave surface having a larger curvature than the reduction side on the enlargement side, and a positive lens L42 made of a biconvex lens having a convex surface having a larger curvature on the enlargement side than the reduction side. A positive lens L43 composed of a biconvex lens having a convex surface having a larger curvature than the enlargement side is disposed on the reduction side.
The two lenses of the negative lens L41 and the positive lens L42 are bonded in close contact with each other to form a cemented lens.
Moreover, aspherical surfaces are formed on both surfaces of the positive lens L43.
In the fifth lens group G5, only a positive lens L51 including a planoconvex lens having a convex surface directed toward the enlargement side is disposed.

On the reduction side of the fifth lens group G5, an OD made of DMD, for example, is arranged as an image display element.
The range of the focal length F, the F number Fno, and the half angle of view ωw at the wide angle end in Example 2 are as follows.
F = 13.4 to 19.4 mm, Fno = 2.58 to 3.04, ωw = 41.2 °
The data of Example 2 is shown in Table 5 below.

"Aspherical data"
The aspherical data in the above equation (5) is shown in Table 6 below.

  In Table 5, D13, D15, D20, and D26 represent variable intervals of the lens group that change during zooming. Bf represents back focus. The distance between the lens groups when the projection distance is 1650 mm is shown in Table 7 below for the wide-angle end, the middle, and the telephoto end.

"Parameter values for each conditional expression"
In the case of Example 2, the values corresponding to the conditional expressions (1) to (4) are as shown in Table 8 below, which satisfy the conditional expressions (1) to (4), respectively.

FIG. 4 shows aberration diagrams of Example 2.
It goes without saying that even if the screen size is changed, the fluctuation in performance is small and the optical performance is good.

Example 3
FIG. 5 is a view for explaining a projection zoom lens in Example 3 according to the third embodiment of the present invention.
The projection zoom lens of Example 3 sequentially has a first lens group G1 having negative refractive power and a positive refractive power from the enlargement side (left side in FIG. 5) to the reduction side (right side in FIG. 5). A second lens group G2, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a positive refractive power are arranged, so-called negative-positive. -Positive-positive-positive five-group configuration.
As the light valve, an OD (abbreviation of Optical Device) is arranged, and the DMD described above is assumed.
During zooming from the wide-angle end to the telephoto end, the second lens group G2 moves gently toward the reduction side, and the third lens group G3 and the fourth lens group G4 move toward the enlargement side. At this time, the first lens group G1 and the fifth lens group G5 are fixed.
During focusing, focusing is performed by moving the first lens front group G1-1 in the first lens group G1 in the optical axis direction, but the first lens rear group G1-2 is fixed. .

The aperture stop AD is disposed between the third lens group G3 and the fourth lens group G4.
The first lens group G1 of the projection zoom lens according to Example 3 includes a negative lens L11 including a negative meniscus lens having a convex surface directed toward the enlargement side sequentially from the enlargement side to the reduction side, and the lens center portion on the enlargement side. A negative lens L12 composed of a negative meniscus lens that is bent toward the reduction side and has a small thickness deviation ratio and a biconcave lens with a concave surface having a larger curvature than the surface on the magnification side toward the reduction side. A negative lens L13, a positive lens L14 composed of a biconvex lens having a convex surface having a larger curvature than the surface on the magnification side on the reduction side, a negative lens L15 composed of a negative meniscus lens having a convex surface on the magnification side, and magnification on the reduction side And a negative lens L16 made of a biconcave lens having a concave surface having a larger curvature than the side surface.
In this first lens group G1, aspheric surfaces are formed on both surfaces of the negative lens L12.
Of the first lens group G1, the negative lens L11, the negative lens L12, and the negative lens L13 constitute a first lens front group G1-1 that has negative refractive power and moves together during focusing. ing.

In addition, in the first lens group G1, the positive lens L14, the negative lens L15, and the negative lens L16 have negative refractive power, and constitute a fixed first lens rear group G1-2 at the time of focusing. doing. The negative lens L13 in the third embodiment is a biconcave lens, whereas the negative lens L13 in the first and second embodiments is a negative meniscus lens.
The second lens group G2 comprises solely a positive lens L21 consisting of a positive meniscus lens with the convex surface facing the enlargement side.
The third lens G3 includes a positive lens L31 composed of a positive meniscus lens having a convex surface facing the enlargement side, a positive lens L32 composed of a biconvex lens having a convex surface having a larger curvature than the reduction side on the magnification side, and a concave surface facing the magnification side. A negative lens L33 made of a negative meniscus lens facing the lens is disposed. These two lenses, the positive lens L32 and the negative lens L33, are bonded in close contact with each other to form a cemented lens. The fourth lens group G4 includes a negative lens L41 made of a biconcave lens having a concave surface having a larger curvature than the reduction side on the enlargement side, and a positive lens L42 made of a biconvex lens having a convex surface having a larger curvature on the enlargement side than the reduction side. A positive lens L43 composed of a biconvex lens having a convex surface having a larger curvature than the enlargement side is disposed on the reduction side.
The two lenses of the negative lens L41 and the positive lens L42 are bonded in close contact with each other to form a cemented lens.

Moreover, aspherical surfaces are formed on both surfaces of the positive lens L43.
In the fifth lens group G5, only a positive lens L51 including a planoconvex lens having a convex surface directed toward the enlargement side is disposed.
On the reduction side of the fifth lens group G5, an OD made of DMD, for example, is disposed as an image display element.
The range of the focal length F, the F number Fno, and the half angle of view ωw at the wide-angle end in Example 3 are as follows.
F = 13.8 to 20.0 mm, Fno = 2.58 to 3.04, ωw = 40.4 °
The data of Example 3 is shown in Table 9 below.

"Aspherical data"
The aspherical data in the above equation (5) is shown in Table 10 below.

  In Table 9, D13, D15, D20, and D26 represent variable intervals of the lens group that change during zooming. Bf represents back focus. The distance between the lens groups when the projection distance is 1700 mm is shown in Table 11 below for the wide-angle end, the middle, and the telephoto end.

"Parameter values for each conditional expression"
In the case of Example 3, values corresponding to the conditional expressions (1) to (4) are as shown in the following Table 12, which respectively satisfy the conditional expressions (1) to (4).

FIG. 6 shows aberration diagrams of Example 3.
It goes without saying that even if the screen size is changed, the fluctuation in performance is small and the optical performance is good.

Example 4
FIG. 7 is a view for explaining a projection zoom lens in Example 4 according to the fourth embodiment of the present invention.
The projection zoom lens of Example 4 has, in order from the enlargement side (left side in FIG. 7) to the reduction side (right side in FIG. 7), a first lens group G1 having negative refractive power, and positive refractive power. A second lens group G2, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a positive refractive power are arranged, so-called negative-positive. -Positive-positive-positive five-group configuration.
As the light valve, an OD (abbreviation of Optical Device) is arranged, and the DMD described above is assumed.
During zooming from the wide-angle end to the telephoto end, the second lens group G2 moves gently toward the reduction side, and the third lens group G3 and the fourth lens group G4 move toward the enlargement side. At this time, the first lens group G1 and the fifth lens group G5 are fixed.
During focusing, focusing is performed by moving the first lens front group G1-1 in the first lens group G1 in the optical axis direction, but the first lens rear group G1-2 is fixed. .

The aperture stop AD is disposed between the third lens group G3 and the fourth lens group G4.
The first lens group G1 of the projection zoom lens according to Example 4 includes a negative lens L11 including a negative meniscus lens having a convex surface directed toward the enlargement side sequentially from the enlargement side to the reduction side, and the lens center portion on the enlargement side. A negative lens L12 composed of a negative meniscus lens that is bent toward the reduction side and has a small thickness deviation ratio, and a negative surface composed of a biconcave lens with a concave surface having a larger curvature than the surface on the enlargement side directed toward the reduction side. A lens L13, a positive lens L14 made of a biconvex lens having a convex surface with a larger curvature than the surface on the enlargement side, a negative lens L15 made of a negative meniscus lens having a convex surface on the enlargement side, and a reduction side on the enlargement side And a negative lens L16 made of a biconcave lens having a concave surface having a larger curvature than that of the first lens surface.
In this first lens group G1, aspheric surfaces are formed on both surfaces of the negative lens L12.
Of the first lens group G1, the negative lens L11, the negative lens L12, and the negative lens L13 constitute a first lens front group G1-1 that has negative refractive power and moves together during focusing. ing.

In addition, in the first lens group G1, the positive lens L14, the negative lens L15, and the negative lens L16 have negative refractive power, and constitute a fixed first lens rear group G1-2 at the time of focusing. doing. The difference is that the negative lens L13 in the fourth embodiment is a biconcave lens, whereas the negative lens L13 in the first and second embodiments is a negative meniscus lens.
The second lens group G2 comprises solely a positive lens L21 consisting of a positive meniscus lens with the convex surface facing the enlargement side.
The third lens G3 includes a positive lens L31 composed of a positive meniscus lens having a convex surface facing the enlargement side, a positive lens L32 composed of a biconvex lens having a convex surface having a larger curvature than the reduction side on the magnification side, and a concave surface facing the magnification side. A negative lens L33 made of a negative meniscus lens facing the lens is disposed. These two lenses, the positive lens L32 and the negative lens L33, are bonded in close contact with each other to form a cemented lens. The fourth lens group G4 includes a negative lens L41 made of a biconcave lens having a concave surface having a larger curvature than the reduction side on the enlargement side, and a positive lens L42 made of a biconvex lens having a convex surface having a larger curvature on the enlargement side than the reduction side. A positive lens L43 composed of a biconvex lens having a convex surface having a larger curvature than the enlargement side is disposed on the reduction side.
The two lenses of the negative lens L41 and the positive lens L42 are bonded in close contact with each other to form a cemented lens.

Moreover, aspherical surfaces are formed on both surfaces of the positive lens L43.
In the fifth lens group G5, only a positive lens L51 including a planoconvex lens having a convex surface directed toward the enlargement side is disposed.
On the reduction side of the fifth lens group G5, an OD made of DMD, for example, is disposed as an image display element.
The range of the focal length F, the F number Fno, and the half angle of view ωw at the wide angle end in Example 4 are as follows.
F = 14.6 to 21.1 mm, Fno = 2.58 to 3.04, ωw = 38.9 °
The data of Example 4 is shown in Table 13 below.

"Aspherical data"
The aspherical data in the above equation (5) is shown in Table 14 below.

  In Table 13, D13, D15, D20, and D26 represent variable intervals of the lens group that change during zooming. Bf represents back focus. The distance between the lens groups when the projection distance is 1800 mm is shown in Table 15 below for the wide-angle end, the middle, and the telephoto end.

"Parameter values for each conditional expression"
In the case of Example 4, the values corresponding to the conditional expressions (1) to (4) are as shown in Table 16 below, which satisfy the conditional expressions (1) to (4), respectively.

FIG. 8 shows aberration diagrams of Example 4.
It goes without saying that even if the screen size is changed, the fluctuation in performance is small and the optical performance is good.

Example 5
FIG. 9 is a view for explaining a projection zoom lens in Example 5 according to the fifth embodiment of the present invention.
The projection zoom lens of Example 5 has a first lens group G1 having a negative refractive power and a positive refractive power sequentially from the enlargement side (left side in FIG. 9) to the reduction side (right side in FIG. 9). A second lens group G2, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a positive refractive power are arranged, so-called negative-positive. -Positive-positive-positive five-group configuration.
As the light valve, an OD (abbreviation of Optical Device) is arranged, and the DMD described above is assumed.
During zooming from the wide-angle end to the telephoto end, the second lens group G2 moves gently toward the reduction side, and the third lens group G3 and the fourth lens group G4 move toward the enlargement side. At this time, the first lens group G1 and the fifth lens group G5 are fixed.
During focusing, focusing is performed by moving the first lens front group G1-1 in the first lens group G1 in the optical axis direction, but the first lens rear group G1-2 is fixed. .
The aperture stop AD is disposed between the third lens group G3 and the fourth lens group G4.

The first lens group G1 of the projection zoom lens according to Example 5 includes a negative lens L11 including a negative meniscus lens having a convex surface directed toward the enlargement side sequentially from the enlargement side to the reduction side, and the lens center portion on the enlargement side. A negative lens L12 composed of a negative meniscus lens that is bent toward the reduction side and has a small thickness deviation ratio, and a negative surface composed of a biconcave lens with a concave surface having a larger curvature than the surface on the enlargement side directed toward the reduction side. A lens L13, a positive lens L14 composed of a biconvex lens having a convex surface having a larger curvature than the surface on the enlargement side on the reduction side, a negative lens L15 made of a plano-concave lens having a concave surface on the reduction side, and a reduction side on the enlargement side And a negative lens L16 made of a biconcave lens having a concave surface having a larger curvature than the surface.
In this first lens group G1, aspheric surfaces are formed on both surfaces of the negative lens L12.
Of the first lens group G1, the negative lens L11, the negative lens L12, and the negative lens L13 constitute a first lens front group G1-1 that has negative refractive power and moves together during focusing. ing.
In addition, in the first lens group G1, the positive lens L14, the negative lens L15, and the negative lens L16 have negative refractive power, and constitute a fixed first lens rear group G1-2 at the time of focusing. doing. The difference is that the negative lens L13 in the fifth embodiment is a biconcave lens, whereas the negative lens L13 in the first and second embodiments is a negative meniscus lens.

The second lens group G2 comprises solely a positive lens L21 consisting of a positive meniscus lens with the convex surface facing the enlargement side.
The third lens G3 includes a positive lens L31 composed of a positive meniscus lens having a convex surface facing the enlargement side, a positive lens L32 composed of a biconvex lens having a convex surface having a larger curvature than the reduction side on the magnification side, and a concave surface facing the magnification side. A negative lens L33 made of a negative meniscus lens facing the lens is disposed. These two lenses, the positive lens L32 and the negative lens L33, are bonded in close contact with each other to form a cemented lens. The fourth lens group G4 includes a negative lens L41 made of a biconcave lens having a concave surface having a larger curvature than the reduction side on the enlargement side, and a positive lens L42 made of a biconvex lens having a convex surface having a larger curvature on the enlargement side than the reduction side. A positive lens L43 composed of a biconvex lens having a convex surface having a larger curvature than the enlargement side is disposed on the reduction side.
The two lenses of the negative lens L41 and the positive lens L42 are bonded in close contact with each other to form a cemented lens.
Moreover, aspherical surfaces are formed on both surfaces of the positive lens L43.

In the fifth lens group G5, only a positive lens L51 including a planoconvex lens having a convex surface directed toward the enlargement side is disposed.
On the reduction side of the fifth lens group G5, an OD made of DMD, for example, is disposed as an image display element.
The range of the focal length F, the F number Fno, and the half angle of view ωw at the wide angle end in Example 5 are as follows.
F = 14.8 to 21.4 mm, Fno = 2.58 to 3.04, ωw = 38.4 °
The data of Example 5 are shown in Table 17 below.

"Aspherical data"
The aspherical data in the above equation (5) is shown in Table 18 below.

  In Table 17, D13, D15, D20, and D26 represent variable intervals of the lens group that change during zooming. Bf represents back focus. The distance between the lens groups when the projection distance is 1900 mm is shown in Table 19 below for the wide-angle end, the middle, and the telephoto end.

"Parameter values for each conditional expression"
In the case of Example 5, values corresponding to the conditional expressions (1) to (4) are as shown in Table 20 below, which satisfy the conditional expressions (1) to (4), respectively.

FIG. 10 shows aberration diagrams of Example 5.
It goes without saying that even if the screen size is changed, the fluctuation in performance is small and the optical performance is good.

As shown in the aberration diagrams of Examples 1 to 5, in any of the projection zoom lenses of each example, various aberrations are corrected at a high level, and spherical aberration, astigmatism, field curvature, lateral chromatic aberration, and distortion are corrected. Aberrations are also sufficiently corrected.
Further, as shown in Examples 1 to 5, during focusing, the first lens rear group to which the first lens group is fixed and the first lens front group that moves (both have negative refractive power). By dividing the focusing into a fixed group and a moving group, there is an effect of suppressing the occurrence of eccentricity with respect to the weight of the lens. Further, as shown in FIGS. 2, 4, 6, 8, and 10, it is needless to say that the variation in aberration during focusing can be reduced by dividing the first lens group into a fixed group and a moving group.
In addition, by moving a part of the first lens group at the time of focusing in the five lens group configuration and fixing a part thereof, the screen size is changed, and fluctuations in performance when focused are kept small. A projection zoom lens that achieves a wide angle (for example, a half angle of view exceeding 48 °) and approximately 1.5 times or more is realized.

G1 1st lens group G2 2nd lens group G3 3rd lens group G4 4th lens group G5 5th lens group AD Aperture stop OD Optical device

JP 2006-234893 A JP 2010-160478 A

Claims (10)

A projection zoom lens consisting of five groups constituting a projection optical system of an image display device that projects an image displayed on the surface of an image display element onto a projection surface and displays the enlarged image,
In order from the most magnified side,
A first lens group G1 having negative refractive power;
A second lens group G2 having a positive refractive power;
A third lens group G3 having a positive refractive power;
A fourth lens group G4 having a positive refractive power;
A fifth lens group G5 having a positive refractive power;
Consisting of
At the time of zooming from the short focus to the long focus, the interval between adjacent lens groups changes, the second lens group G2 moves to the reduction side, and the third lens group G3 and the fourth lens group G4. Moves to the enlargement side,
Focusing is performed by moving a part of the first lens group G1, and the first lens group G1 includes a negative group moving in the optical axis direction and a fixed negative group.
When focusing on a close side is moved to the partially enlarged side of the first lens group G1, a portion of the first lens group G1 upon focusing on a long distance side to the reduction side A zoom lens for projection characterized by moving.   2. The projection zoom lens according to claim 1, wherein when focusing, the absolute values of the respective powers of the moving negative group and the fixed negative group of the first lens group G <b> 1 (reciprocal of focal length (1) / | F |), the zoom lens for projection is characterized in that the power of the moving group is larger.   The projection zoom lens according to claim 1, wherein focusing is performed by moving a lens group closest to the enlargement side. 2. The projection zoom lens according to claim 1, wherein when focusing, the focal length of the moving group of the first lens group G1 is F1_m, and the focal length of the fixed group is F1_f. ):
(1) 0.1 <F1_m / F1_f <0.5
Projection zoom lens characterized by satisfying In the projection zoom lens according to any one of claims 1 to 4,
When the focal length of the first lens group G1 is F1, and the focal length at the wide angle end of the entire lens system is Fw, the following conditional expression (2):
(2) 0.9 <| F1 | / Fw <1.3
Projection zoom lens characterized by satisfying In the projection zoom lens according to any one of claims 1 to 5,
The projection zoom lens according to claim 1, wherein the moving group and the fixed group of the first lens group G1 at the time of focusing are each composed of two or more lenses. The projection zoom lens according to any one of claims 1 to 6,
During zooming from short focus to long focus, the second lens group G2 moves to the reduction side, the third lens group G3 moves to the enlargement side, and the fourth lens group G4 moves to the enlargement side. A zoom lens for projection. The projection zoom lens according to any one of claims 1 to 7,
When the focal length of the fifth lens group G5 is F5 and the focal length at the wide-angle end of the entire lens system is Fw, the following conditional expression (3):
(3) 8.0 <F5 / Fw <11.0
Projection zoom lens characterized by satisfying The projection zoom lens according to any one of claims 1 to 8,
With the half angle of view at the wide angle end as ωw, the following conditional expression (4):
(4) 38 ° <ωw <45 °
Projection zoom lens characterized by satisfying A light source;
An image display element for displaying an image to be projected;
An illumination optical system that illuminates the image display element with light emitted from the light source;
A projection optical system that is irradiated with the illumination optical system and is incident with a projection light beam modulated by an image displayed on the image display element, and projects an enlarged image of the image on the projection surface; and
An image display apparatus using the projection zoom lens according to claim 1 as the projection optical system.

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