JP2009020189A - Zoom lens and image projection apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens having good optical performance over the entire projection distance from the near to the far, in which the variation in the distance of field curvature is corrected with a simple and inexpensive configuration.
A zoom lens having a negative first group, a positive second group, and a positive third group in order from the enlargement side, and at the time of zooming, the first group and the second group The first group has a first subunit having a negative refractive power and a second subunit having a negative refractive power in order from the enlargement side, and from a long distance to a short distance. During focusing, the first subunit moves to the reduction side and the second subunit moves to the enlargement side.
[Selection] Figure 1

Description

  The present invention relates to a zoom lens, and more particularly to a projection lens for a projector.

  In recent years, the resolution of liquid crystal projectors used in home theaters and presentations has been increasing, and projectors using liquid crystal panels with high resolution have begun to be released. Along with this, the resolution of projection lenses for projectors is also increasing.

  Since a projection lens for a projector requires a wide angle and a long back focus, conventionally, the lens group on the most screen side is often the focus group in a retro-focus type configuration. In such a configuration, since the focus group is moved at the time of focusing (focal length adjustment), optical performance such as curvature of field mainly has changed.

  In order to reduce the change in curvature of field due to focusing, in Patent Document 1, the first lens group is placed in front of the zoom lens including the negative first lens group and the positive second lens group from the magnification conjugate side. The group is divided into a group and a rear group, and the front group and the rear group are independently fed forward.

  In Patent Documents 2 and 3, in a negative-positive-negative-positive four-group zoom lens, the first lens group is divided into a first refractive power group A and a negative refractive power group 1B, of which the first lens group B Focusing is done by moving only.

In Patent Document 4, in a negative, positive, positive, and positive five-group zoom lens, the first lens group is divided into a first refractive power group A and a negative refractive power group 1B, and these are moved. Focusing is performed. However, there is no disclosure about how the first group A and the group 1B move during focusing.
Japanese Patent Laid-Open No. 61-116315 (Japanese Patent Publication No. 03-003205) Japanese Patent Laid-Open No. 02-296208 (Japanese Patent Registration No. 2862272) Japanese Patent Application Laid-Open No. 07-261084 (Japanese Patent Registration No. 3318883) JP 2002-357777 A

  As an image projected by a future image projection apparatus such as a projector becomes higher in definition, it is necessary to more strictly correct (reduce) aberration fluctuations (mainly field curvature) during focusing.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a zoom lens having a small variation in field curvature during focusing.

In order to solve the above-described problem, the zoom lens of the present application includes a first lens unit having a negative refractive power, which is disposed closest to the enlargement side, and a first lens unit having a positive refractive power which is disposed adjacent to the first lens unit. A zoom lens including a second lens unit and a third lens unit having a positive refractive power disposed on the reduction side with respect to the second lens unit, and the first lens unit and the first lens unit when zooming The first lens unit has a negative refractive power first subunit composed of one or more negative lenses in order from the enlargement side, and two negative lenses. And a second subunit having a negative refractive power including one positive lens, and the distance between the first subunit and the second subunit is determined when focusing from a long distance to a short distance. When narrowed The second subunit has moved to the enlargement side, the outer diameter of the lens arranged on the most enlargement side of the second subunit is φ1BS, and the outer diameter of the lens arranged on the most reduction side of the second subunit is When the diameter is φ1BI,
0.8 <φ1BS / φ1BI <1.2 (1)
It is characterized by satisfying.

  The zoom lens according to another aspect of the present invention includes a first lens unit having a negative refractive power disposed on the most enlarged side, and a second lens unit having a positive refractive power disposed adjacent to the first lens unit. A zoom lens including a third lens unit having a positive refractive power and disposed on the reduction side of the second lens unit, wherein the first lens unit and the second lens unit at the time of zooming The first lens unit has, in order from the enlargement side, a first subunit having a negative refractive power composed of one or more negative lenses, one negative lens, and one sheet. And a second subunit having a negative refractive power composed of a lens having a smaller outer diameter than a lens having the smallest outer diameter among the lenses included in the second lens unit, Distance to distance Upon focusing from, the first subunit and the second subunit and the second subunit with spacing is narrowed for is thus being moved to the magnification side.

  The zoom lens according to another aspect of the present invention includes a first lens unit having a negative refractive power disposed on the most enlarged side, and a second lens unit having a positive refractive power disposed adjacent to the first lens unit. A zoom lens including a third lens unit having a positive refractive power and disposed on the reduction side of the second lens unit, wherein the first lens unit and the second lens unit at the time of zooming The first lens unit has a negative refractive power first subunit composed of one or more negative lenses, two negative lenses, and one lens in order from the magnification side. The second subunit having a negative refractive power composed of a positive lens is used, and the distance between the first subunit and the second subunit is narrowed during focusing from a long distance to a short distance. With 2 subunit is characterized by moving the magnification side.

  The zoom lens according to another aspect of the present invention includes a first lens unit having a negative refractive power disposed on the most enlarged side, and a second lens unit having a positive refractive power disposed adjacent to the first lens unit. A zoom lens including a third lens unit having a positive refractive power and disposed on the reduction side of the second lens unit, wherein the first lens unit and the second lens unit at the time of zooming The first lens unit has a first subunit having a negative refractive power and a second subunit having a negative refractive power in order from the magnification side, and from a long distance In focusing at a short distance, the first subunit moves to the reduction side, and the second subunit moves to the enlargement side.

  In addition, an image projection apparatus according to the present invention includes a light modulation element and the zoom lens that projects a light beam emitted from the light modulation element onto a projection surface.

  According to the present invention, it is possible to reduce the fluctuation of the curvature of field during focusing with a simple configuration, and a zoom lens having good optical performance over the entire projection distance from close to far, and an image using the zoom lens. A projection device can be obtained.

  This embodiment describes a zoom lens suitable for use as a zoom lens, mainly as a projection lens for a projector. In particular, it is a zoom lens that can reduce the change in field curvature that occurs during focusing (focus adjustment, focal length adjustment) (to reduce the amount of change), and can withstand higher image definition in the future. A zoom lens is described.

  First, projectors (image projection apparatus, image projection apparatus, and liquid crystal projector) will be briefly described. Main projector components include a light source, a light modulation element (image forming element) such as a liquid crystal panel, an illumination optical system that illuminates the light modulation element with a light beam emitted from the light source, and a light beam emitted from the light modulation element (image light). ) On a projection surface such as a screen (image projection). Of course, a dichroic mirror, a dichroic prism, a polarizing beam splitter, a polarizing plate, a retardation plate (1/2 retardation plate, 1/4 retardation plate) and the like are also required depending on the projector type.

  In the present embodiment, a projection lens for image projection that projects light emitted from a light modulation element onto a projection surface in such a projector (image projection apparatus) will be described. This projection lens is required to have a long back focus, high telecentricity on the reduction side (reduction conjugate side, light modulation element side), and the like. Furthermore, as described above, there is a need for a zoom lens that has a small variation in field curvature during focusing (focus adjustment).

  In view of this, the present embodiment aims to provide a zoom lens in which the variation in field curvature during focusing is small.

  Hereinafter, Examples 1, 2, and 3 that achieve these objects will be described in detail with reference to the drawings.

  FIG. 1 shows a cross-sectional view of the first embodiment. The zoom lens (projection lens) of Example 1 is a zoom lens having a six-group configuration including first to sixth groups in order from the magnification side (magnification conjugate side, projection surface side, paper left side). Here, the first group (first lens unit) G1 having a negative refractive power is a lens unit that does not move for zooming but moves during focusing (focus adjustment). The second group (second lens unit) G2 disposed adjacent to the first group has a positive refractive power, and the third group third group (third lens) disposed adjacent to the second group. (Unit) G3 also has a positive refractive power. Further, the fourth group (fourth lens unit) G4 arranged adjacent to the third group has a negative refractive power and the fifth group (fifth lens unit) arranged adjacent to the fourth group. G5 has a positive refractive power. These second to fifth groups move to the enlargement side during zooming from the wide end (wide angle end) to the tele end (telephoto end). The sixth lens unit (sixth lens unit) G6 having positive refractive power does not move for zooming. These first to sixth groups are arranged adjacent to each other, and the distance between the two adjacent lens groups (lens units) is changed with zooming. In particular, zooming is performed by changing the distance between the first group (first lens unit) and the second group (second lens unit) (and the distance between the second group and the third group).

  The first group (first lens unit) G1 includes a first refractive index A first group (first subunit) G1A and a negative refractive power first group B (second subunit) G1B. The first group A is composed of one negative lens (which may be composed of two or more negative lenses, but is preferably composed of only negative lenses). More specifically, it is composed of a single negative meniscus lens 1 convex on the magnification conjugate side. The first group B includes two negative lenses and one positive lens, and the two negative lenses are arranged on the enlargement side with respect to one positive lens. More specifically, in order from the magnification conjugate side, compared to the negative meniscus lens 2 convex to the magnification conjugate side, the negative lens 3 having a stronger power on the magnification side surface, compared to the magnification side surface. The positive lens 4 has a strong power on the reduction side surface. Here, the comparison of the power (refractive power, optical power) on both surfaces of the lens means that the power is stronger when the reciprocal of the absolute value of the focal length of both surfaces is larger.

  The first A group G1A moves from the enlargement side to the reduction side as the enlargement side conjugate point changes (focusing, focus adjustment) from the far side (far, infinity) to the near side (near, close) The first B group G1B moves from the reduced conjugate side to the enlarged conjugate side. That is, when focusing from the long-distance side to the short-distance side, the first A group and the first B group move in the direction of narrowing (shrinking) each other (in the direction of approaching each other). In the first embodiment, the movement amount in the optical axis direction of the first A (first subunit) group G1A is half the movement amount in the optical axis direction of the first B group (second subunit) G1B ( It is configured using a cam ring (not shown).

  The second group (second lens unit) G2 having positive refractive power is disposed on the magnification conjugate side from the stop SP because the off-axis principal ray PL1 between the first group and the second group is the optical axis CL1. This is to make them almost parallel. By disposing the stop at such a position, the movement of the first axis B in the first B group G1B, which has the largest amount of movement in the optical axis direction during focusing, can reduce the height of the off-axis principal ray in the first B group. We try to reduce changes. The aperture stop SP is disposed on the third group (the rear side (reduction side) of the third lens unit) and is moved together with the third group at the time of zooming.

  Further, the arrangement of the lenses in the first B group G1B is such that the negative meniscus lens 2 is convex on the enlargement side, the negative lens 3 is stronger on the enlargement side than the reduction side, and is stronger on the reduction side than the enlargement side. The positive lens 4 has power. The reason for this arrangement is to keep the angle of the off-axis principal ray PL1 substantially parallel to the optical axis CL1 in the first B group G1B.

  The first A group G1A is composed of a single negative meniscus lens 1 convex on the magnification conjugate side in order to reduce the occurrence of coma and astigmatism (field curvature) (field curvature). It is.

  Further, when the first A group G1A is focused from a long distance to a short distance, the height of the off-axis principal ray from the optical axis during focusing in the first A group G1A is changed. This is to reduce the size.

  In order to reduce the change in field curvature during focusing, the angle of the off-axis principal ray PL1 between the first group G1 and the second group G2 with respect to the optical axis CL1 is substantially parallel and within the first B group G1B. The angle of the off-axis principal ray PL1 to the optical axis CL1 is also substantially parallel.

  Further, since the off-axis light beam is converged toward the magnification conjugate side by the lens 4, the effective diameter of the lenses 2, 3, 4 of the first B group G 1 B is consequently larger than the effective diameter of the lens 5 of the second group. Get smaller. For this reason, the lens outer diameter of the first B group G1B is smaller than the outer diameter of the lens 5 of the second group G2.

  The reason why the negative lens on the most enlargement side of the first B group G1B is an aspherical lens is to satisfactorily correct distortion. If it is the second lens from the magnifying side, even if an inexpensive plastic aspheric lens is used, there is no risk of scratches and the off-axis principal ray is high from the optical axis, so off-axis aberrations A high effect can be obtained in the correction.

  In Example 1, the off-axis principal ray PL1 is made substantially parallel to the optical axis CL1 by the lens 5 in the second group and the lens 4 on the most reducing side in the first B group, and the off-axis light beam diameter is directed toward the enlargement side. Narrow down. Furthermore, the first B group G1B arranged at a position where the off-axis chief rays are substantially parallel is moved to the enlargement conjugate side during focusing from a long distance to a short distance. With this configuration, it is possible to provide a zoom lens with a small change in field curvature during focusing. Further, the reason why the first A group G1A is moved to the reduction conjugate side is to correct a slight change in field curvature when the first A group G1A is fixed.

  The first A group G1A is moved independently of the first B group G1B so that the height of the off-axis chief ray in the first A group G1A having a large angle with respect to the optical axis of the off-axis chief ray PL1 hardly occurs. ing.

  Next, aberration diagrams of Example 1 are shown in FIGS. Each figure is described below.

  FIG. 2 shows spherical aberration, astigmatism (field curvature), and distortion at the wide end when the distance from the front end of the lens of the first numerical embodiment of the present invention to the magnification conjugate point is 1.2 m.

  FIG. 3 shows spherical aberration, astigmatism (field curvature), and distortion aberration at the telephoto end when the distance from the lens front end to the magnification conjugate point in the first numerical example of the present invention is 1.2 m.

  FIG. 4 shows spherical aberration, astigmatism (curvature of field), and distortion at the wide end when the distance from the front end of the lens according to Numerical Example 1 of the present invention to the magnification conjugate point is 2.1 m.

  FIG. 5 shows spherical aberration, astigmatism (field curvature), and distortion aberration at the telephoto end when the distance from the lens front end to the magnification conjugate point in the first numerical example of the present invention is 2.1 m.

  FIG. 6 shows spherical aberration, astigmatism (field curvature), and distortion at the wide end when the distance from the lens front end to the magnification conjugate point is 9 m in Numerical Example 1 of the present invention.

  FIG. 7 shows spherical aberration, astigmatism (field curvature), and distortion aberration at the telephoto end when the distance from the lens front end to the magnification conjugate point is 9 m according to Numerical Example 1 of the present invention.

  In the astigmatism diagram, the dotted line indicates the meridional image plane, and the solid line indicates the sagittal image plane.

  Even if the distance from the enlargement side conjugate point to the surface on the most enlargement conjugate side of the lens changes from 1.2 m to 9 m, the change in field curvature is kept small. More specifically, in accordance with the change in spherical aberration due to the change in the distance from the front end of the lens to the magnification conjugate point, 1.2 m is slightly under the standard distance 2.1 m, and 9 m is slightly less than the standard distance 2.1 m. I'm trying to make it over. In this way, the movement amount is set so that the image surface becomes flat by balancing the spherical aberration and the curvature of field.

  FIG. 8 shows a cross-sectional view of the second embodiment. The points not particularly described are the same as those in the first embodiment.

  The zoom lens of Example 2 includes, in order from the magnification conjugate side, a first group G1 having a negative refractive power, a second group G2 having a positive refractive power, a third group G3 having a positive refractive power, a fourth group G4 having a negative refractive power, The lens unit includes a fifth group G5 having positive refractive power and a sixth group G6 having positive refractive power. These first to sixth groups are arranged adjacent to each other.

  For zooming from the wide end (wide angle end) to the tele end (telephoto end), the first group (first lens unit) G1 and the sixth group (sixth lens unit) G6 do not move. In zooming from the wide end (wide angle end) to the tele end (telephoto end), the second group (second lens unit) G2, the third group (third lens unit) G3, and the fourth group (Fourth lens unit) G4 and fifth group (fifth lens unit) G5 are moved to the enlargement side.

  The first group G1 is composed of a negative first refractive power first group A (first subunit) G1A composed of a single negative lens, and a negative refractive power first group B (second subunit) G1B. ing. The first group A includes a single negative meniscus lens 1 that is convex on the magnification conjugate side. The first group B includes two negative lenses and one positive lens. More specifically, in order from the magnification conjugate side, the negative meniscus lens 2 convex to the magnification conjugate side, the negative lens 3 having a stronger power on the magnification conjugate side surface than the surface on the magnification conjugate side, and the surface on the magnification conjugate side The positive lens 4 has a stronger power on the reduction conjugate side surface.

  The first A group G1A moves from the reduced conjugate side to the enlarged conjugate side in accordance with the change of the enlarged side conjugate point from the long distance side to the short distance side, and the first B group G1B moves from the reduced conjugate side to the enlarged conjugate side. Move to, and focus. In the second embodiment, on the optical axis with a cam ring (not shown) or the like so that the moving amount at the time of focusing of the first group A G1A becomes 20% of the moving amount at the time of focusing of the first group B G1B. It is configured to move.

  In the second embodiment, as described above, the first A group G1A and the first B group G1B are set to a movement amount of 20% with respect to the movement amount of both G1B when focusing from a long distance to a short distance. As a result, the change in the height of the off-axis principal ray in the first A group can be reduced as compared with the conventional focus method in which the lenses 1 to 4 are moved together during focusing. As a result, it is possible to reduce the change in field curvature aberration during focusing.

  The first A group G1A preferably has a negative meniscus lens shape with a convex surface facing the magnification conjugate side in order to reduce the occurrence of coma and astigmatism (field curvature, field curvature). The first B group G1B is configured such that a change in height from the optical axis of the off-axis principal ray PL1 in the first B group G1B is reduced. Specifically, a negative meniscus lens 2 having a convex surface facing the magnification conjugate side from the magnification conjugate side, a negative lens 3 having strong power on the magnification conjugate side, and a positive lens 4 having strong power on the reduction conjugate side are arranged in this order. Has been.

  Next, aberration diagrams of Example 2 are shown in FIGS. Each figure is described below.

  FIG. 9 shows spherical aberration, astigmatism (field curvature), and distortion at the wide end when the distance from the lens front end to the magnification conjugate point is 1.2 m according to Numerical Example 2 of the present invention.

  FIG. 10 shows spherical aberration, astigmatism (field curvature), and distortion aberration at the telephoto end when the distance from the lens front end to the magnification conjugate point is 1.2 m according to Numerical Example 2 of the present invention.

  FIG. 11 shows spherical aberration, astigmatism (field curvature), and distortion at the wide end when the distance from the lens front end to the magnification conjugate point is 2.1 m according to Numerical Example 2 of the present invention.

  FIG. 12 shows spherical aberration, astigmatism (field curvature), and distortion aberration at the telephoto end when the distance from the lens front end to the magnification conjugate point in the second numerical example of the present invention is 2.1 m.

  FIG. 13 shows spherical aberration, astigmatism (field curvature), and distortion aberration at the wide end when the distance from the lens front end to the magnification conjugate point is 9 m in Numerical Example 2 of the present invention.

  FIG. 14 shows spherical aberration, astigmatism (field curvature), and distortion at the telephoto end when the distance from the lens front end to the magnification conjugate point is 9 m according to Numerical Example 2 of the present invention.

  Even if the distance from the enlargement side conjugate point to the surface on the most enlargement conjugate side of the lens changes from 1.2 m to 9 m, the change in field curvature is kept small.

As a comparison, in the configuration of Numerical Example 1, when the focusing is performed by integrating the lenses 1 to 4, the wide distances when the distance from the front end of the lens to the magnification side conjugate point is 1.2 m, 2.1 m, and 9 m are shown. FIG. 15 to FIG. 20 show aberration diagrams (spherical aberration, astigmatism (field curvature), distortion) at the end and tele end. 15 to 20 are diagrams respectively described below.

  FIG. 15 shows a case where the distance from the front end of the lens to the magnification conjugate point is 1.2 m when the first A group and the first B group (lenses 1 to 4) are integrated in the first numerical embodiment of the present invention. Spherical aberration, field curvature, and distortion are shown at the wide end.

  FIG. 16 shows a case where the distance from the front end of the lens to the magnification conjugate point is 1.2 m when the first A group and the first B group (lenses 1 to 4) are focused together in Numerical Example 1 of the present invention. , Shows spherical aberration, curvature of field, and distortion at the tele end.

  FIG. 17 shows a case where the distance from the front end of the lens to the magnification conjugate point is 2.1 m when the first A group and the first B group (lenses 1 to 4) are focused together in Numerical Example 1 of the present invention. Spherical aberration, field curvature, and distortion are shown at the wide end.

  FIG. 18 shows a case where the distance from the front end of the lens to the magnification conjugate point is 2.1 m when the first A group and the first B group (lenses 1 to 4) are focused together in Numerical Example 1 of the present invention. , Shows spherical aberration, curvature of field, and distortion at the tele end.

  In FIG. 19, in the first numerical example of the present invention, when the focusing is performed by integrating the first group A and the first group B (lenses 1 to 4), the wide distance when the distance from the lens front end to the magnification conjugate point is 9 m. Spherical aberration, field curvature, and distortion are shown at the edges.

  In FIG. 20, in the first numerical example of the present invention, when the focusing is performed by integrating the first group A and the first group B (lenses 1 to 4), the telephoto when the distance from the lens front end to the magnification conjugate point is 9 m is shown. Spherical aberration, field curvature, and distortion are shown at the edges.

  As can be seen from FIG. 15 to FIG. 20, when focusing is performed with the lenses 1 to 4 integrated, the field curvature is over 9 m at 1.2 m with respect to the reference distance 2.1 m. Then it becomes under. Also, spherical aberration is under 1.2m and over 9m with respect to the reference distance 2.1m, so there is a shift in the focus position near and around the optical axis, and the focus is adjusted near the optical axis. The surrounding area will be blurred.

  FIG. 21 is a cross-sectional view of the third embodiment. The points not particularly described are the same as those in the first embodiment.

The zoom lens of Example 3 includes, in order from the magnification conjugate side, a first group GG1 having a negative refractive power, a second group GG2 having a positive refractive power, a third group GG3 having a positive refractive power, and a fourth group GG4 having a negative refractive power. The lens unit includes a fifth group GG5 having a positive refractive power and a sixth group GG6 having a positive refractive power. These first to sixth groups are arranged adjacent to each other,
For zooming from the wide end (wide angle end) to the tele end (telephoto end), the first group (first lens unit) GG1 and the sixth group (sixth lens unit) GG6 do not move. In zooming from the wide end (wide angle end) to the tele end (telephoto end), the second group (second lens unit) GG2, the third group (third lens unit) GG3, and the fourth group (Fourth lens unit) GG4 and fifth group (fifth lens unit) GG5 are moved to the enlargement side.

  The first group GG1 is composed of a negative first refractive power first group A (first subunit) GG1A composed of one negative lens and a negative refractive power first group B (second subunit) GG1B. ing. The first group A includes a single negative meniscus lens 21 that is convex on the magnification conjugate side. The first group B includes two negative lenses and one positive lens. More specifically, the first group B includes, in order from the enlargement side, a negative meniscus lens 22 that is convex on the enlargement side, a negative lens 23 that has stronger power on the enlargement side surface than the reduction side surface, and an enlargement side surface. And a positive lens 24 having a stronger power on the reduction side surface.

  The first A group GG1A is fixed and the first B group GG1B is moved from the reduced conjugate side to the enlarged conjugate side in accordance with the change (focusing) of the enlarged side conjugate point from the long distance side to the short distance side.

  In the third embodiment, at the time of focusing, only the first B group GG1B is moved from the reduction conjugate side to the enlargement conjugate, thereby making it possible to reduce the change in field curvature with respect to the conjugate point change on the enlargement conjugate side. With a simple configuration, a so-called floating effect can be obtained.

  When the distance from the front end of the lens to the magnification conjugate point changes, the conventional focusing method in which the lenses 21 to 24 are extended to the magnification conjugate side with respect to the change of the magnification side conjugate point from the long distance to the short distance, the first group GG1. Moves on the optical axis. As a result, the height of the off-axis principal ray from the optical axis in the concave lens 21 closest to the magnification conjugate side changes greatly. Therefore, when the first group GG1 moves to the reduction conjugate side and the conjugate point on the magnification conjugate side is far, the height of the off-axis principal ray in the concave lens 21 from the optical axis becomes small. On the other hand, when the first conjugate group GG1 is extended to the magnification conjugate side and the conjugate point on the magnification conjugate side is close, the height of the off-axis principal ray in the concave lens 21 from the optical axis increases. For this reason, when the magnification conjugate point is far, the off-axis chief ray passes through a place where the power of the concave lens 21 is weak, so that the field curvature is under, and when the magnification conjugate point is close, the concave lens 21 is. Since the off-axis chief ray passes through where the power of is strong, the field curvature is over.

  In Example 3, the first group B includes, in order from the magnification side, a negative meniscus lens 22 convex on the magnification side, a negative lens 23 having a relatively strong absolute value of the power on the magnification side with respect to the surface on the reduction side, The positive lens 24 is configured such that the absolute value of the power of the reduction side surface is relatively strong with respect to the enlargement side surface. In focusing with this configuration, even if only the first B group GG1B is moved in the optical axis direction, the first A group GG1A remains fixed, so the change in the height of the off-axis principal ray in the first A group GG1A is reduced. be able to. The off-axis principal ray passing through the first B group GG1B is configured not to have a large angle with respect to the optical axis.

  Next, aberration diagrams of Example 2 are shown in FIGS. Each figure is described below.

  FIG. 22 shows spherical aberration, astigmatism (field curvature), and distortion at the wide end when the distance from the lens front end to the magnification conjugate point is 1.2 m according to Numerical Example 3 of the present invention.

  FIG. 23 shows spherical aberration, astigmatism (field curvature), and distortion aberration at the telephoto end when the distance from the front end of the lens to the magnification conjugate point in Numerical Example 3 of the present invention is 1.2 m.

  FIG. 24 shows spherical aberration, astigmatism (field curvature), and distortion at the wide end when the distance from the lens front end to the magnification conjugate point in the third numerical example of the present invention is 2.1 m.

  FIG. 25 shows spherical aberration, astigmatism (field curvature), and distortion at the telephoto end when the distance from the lens front end to the magnification conjugate point is 2.1 m according to Numerical Example 3 of the present invention.

  FIG. 26 shows spherical aberration, astigmatism (field curvature), and distortion at the wide end when the distance from the lens front end to the magnification conjugate point is 9 m in Numerical Example 3 of the present invention.

  FIG. 27 shows spherical aberration, astigmatism (field curvature), and distortion aberration at the telephoto end when the distance from the lens front end to the magnification conjugate point is 9 m in Numerical Example 3 of the present invention.

  Even if the distance from the enlargement side conjugate point to the surface on the most enlargement conjugate side of the lens changes from 1.2 m to 9 m, the change in field curvature is kept small.

As a comparison, in the configuration of Numerical Example 3, when the focusing is performed with the lenses 1 to 4 integrated, the wide distance when the distance from the front end of the lens to the enlargement side conjugate point is 1.2 m, 2.1 m, and 9 m. FIG. 28 to FIG. 33 show aberration diagrams (spherical aberration, astigmatism (field curvature), distortion) at the end and tele end.

  FIG. 28 shows spherical aberration at the wide end when the distance from the front end of the lens to the magnification conjugate point is 1.2 m when focusing is performed with the first group A and the first group B integrated in Numerical Example 3 of the present invention. , Shows astigmatism (field curvature) distortion.

  FIG. 29 shows spherical aberration at the telephoto end when the distance from the front end of the lens to the magnification conjugate point is 1.2 m when focusing is performed by integrating the first A group and the first B group in Numerical Example 3 of the present invention. Astigmatism (field curvature) and distortion are shown.

  FIG. 30 shows spherical aberration at the wide end when the distance from the front end of the lens to the magnification conjugate point is 2.1 m in the third numerical example of the present invention when focusing is performed with the first group A and the first group B integrated. Astigmatism (field curvature) and distortion are shown.

  FIG. 31 shows spherical aberration at the telephoto end when the distance from the front end of the lens to the magnification conjugate point is 2.1 m when focusing is performed with the first group A and the first group B integrated in Numerical Example 3 of the present invention. Astigmatism (field curvature) and distortion are shown.

  FIG. 32 shows spherical aberration at the wide end in the third numerical example of the present invention when the distance from the lens front end to the magnification conjugate point is 9 m when focusing is performed with the first group A and the first group B integrated. Point aberration (field curvature) and distortion are shown.

  FIG. 33 shows spherical aberration at the telephoto end when the distance from the front end of the lens to the magnification conjugate point is 9 m when focusing is performed with the first group A and the first group B integrated in Numerical Example 3 of the present invention. Point aberration (field curvature) and distortion are shown.

  When focusing is performed with the lenses 1 to 4 integrated, the curvature of field is over at a reference distance of 2.1 m, over at 2 m, under at 9 m, and spherical aberration under at 1.2 m, 9 m. Then it is over. For this reason, there is a shift between the focus positions near and around the optical axis, and the periphery is blurred when focusing near the optical axis.

  Specific lens data of Examples 1, 2, and 3 are shown below. Example 1 is Numerical Example 1, Example 2 is Numerical Example 2, and Example 3 is Numerical Example 3. In each numerical example, i indicates the order of the optical surfaces from the magnification conjugate side (left side of the paper), Ri is the radius of curvature of the i-th optical surface, and di is between the i-th surface and the i + 1-th surface. The inter-surface distances, ni, and vi respectively indicate the refractive index and Abbe number of the i-th optical member with respect to the d-line.

Further, when K is a conic constant and B, C, D, E, and F are aspherical coefficients, the displacement in the optical axis direction at the position of the height h from the optical axis is set to x with reference to the surface vertex. When the aspheric shape is
^{x = (y 2 / R)} / [1+ {1- (1 + K) (y 2 / R 2)} 1/2] + By 4 + Cy 6 + Dy 8 + Ey 10 + Fy 12
Can be expressed as

  The first, second, and third embodiments have been described above. The conditional expressions satisfied by these embodiments will be described below.

The lens outer diameter on the most magnifying side (magnifying conjugate side) of the first B group (second subunit) is φ1BS, and the lens outer diameter on the most reducing side (reducing conjugate side) of the first B group (second subunit) is φ1BI. The following conditional expression is satisfied.
0.8 <φ1BS / φ1BI <1.2 (1)
Conditional expression (1) limits the ratio of the outer diameter of the lens on the most magnification conjugate side and the outer diameter of the lens on the most reduction conjugate side of the first group B (second subunit). In a region exceeding the lower limit value and the upper limit value of conditional expression (1), the angle of the off-axis principal ray in the first B group with respect to the optical axis becomes large. Since the change of becomes large, it is not preferable.

More preferably, 0.9 <φ1BS / φ1BI <1.1 (1a)
It is still better to satisfy.

Further, when the focal length of the first group (first lens unit) is f1, and the focal length of the first group B (second subunit) is f1B, the following conditional expression is satisfied.
0.2 <f1 / f1B <0.8 (2)
Conditional expression (2) limits the ratio of the focal lengths of the first group and the first group B. In the region exceeding the lower limit of the conditional expression (2), the focal length of the first B group becomes too large (refractive power becomes too weak), so that the amount of movement during focusing of the first B group becomes too large, and the entire lens (Especially, the first group) becomes large. Further, in the region exceeding the upper limit value of the conditional expression (2), the power of the first B group becomes too strong, so the off-axis chief ray angle in the first B group diverges with respect to the magnification side (magnification conjugate side). This is not preferable because the change in field curvature due to the movement of the first B group in the optical axis direction becomes large.

More preferably,
0.3 <f1 / f1B <0.7 (2a)
0.45 <f1 / f1B <0.6 (2b)
It is still better to satisfy.

  Table 1 shows the values of conditional expressions (1) and (2) in Examples 1, 2, and 3 respectively.

  These conditional expressions (1) and (2) are not essential for the present invention, and these conditional expressions can provide a more preferable zoom lens (projection lens for an image projection apparatus). This is a conditional expression for obtaining the effect.

  In addition, all of Examples 1, 2, and 3 are zoom lenses having a six-group configuration, but this is not a limitation. For example, the fifth group (fifth lens unit) and the sixth group (sixth lens unit) on the reduction side with respect to the fourth group (fourth lens unit) are omitted, and a four-group configuration (from the enlargement side, negative positive / negative) , Negative, positive, positive, etc.). Of course, the sixth group (sixth lens unit) on the reduction side with respect to the fifth group (fifth lens unit) is omitted, and a five-group configuration (from the enlargement side, negative / positive / positive / positive / negative / positive / positive / positive / negative / positive / positive / negative). Justice).

  In Examples 1, 2, and 3, the first group (first lens unit) is composed of a first A group (first subunit) and a first B group (second subunit). Not limited to this, it may have a third subunit.

  In the first, second, and third embodiments, the first group A (first subunit) is composed of one negative lens. However, the present invention is not limited to this. As described above, the first group A (first subunit) is composed of one or more negative lenses. It only has to be configured. That is, the first group A may be composed of two negative lenses or three negative lenses. Similarly, the first group B (second subunit) includes two negative lenses and one positive lens, but this is not a limitation. For example, two negative lenses may be replaced with two or more negative lenses, or one positive lens may be replaced with one or more positive lenses.

  Further, the first, second, and third embodiments may arbitrarily combine the features of each other. For example, the manner of movement of the first group A (first subunit) and the group 1B (second subunit) in the first group (first lens unit) is arbitrarily changed in the first, second and third embodiments. It doesn't matter.

  In this embodiment, a zoom lens, particularly a zoom lens suitable for use as a projection lens for a projector that projects an image onto a projection surface has been described. However, a camera or the like (video camera, surveillance camera, etc.) You may apply to observation apparatuses, such as an apparatus and binoculars. When applied to a camera or the like, the zoom lens guides image light emitted from a subject (enlargement side conjugate surface) to a photoelectric conversion element (reduction side conjugate surface) such as a CCD.

Sectional view of Numerical Example 1 Aberration diagram at the wide end 1.2 m in Numerical Example 1. Aberration diagram at the telephoto end 1.2 m in Numerical Example 1. Aberration diagram at the wide end 2.1 m in Numerical Example 1. Aberration diagram at the telephoto end 2.1 m according to Numerical Example 1. Aberration diagram at the wide end 9 m in Numerical Example 1. Aberration diagram at the telephoto end 9 m of Numerical Example 1. Sectional view of Numerical Example 2 Aberration diagram at the wide end 1.2 m in Numerical Example 2. Aberration diagram at the telephoto end 1.2 m in Numerical Example 2. Aberration diagram at the wide end 2.1 m in Numerical Example 2. Aberration diagram at the telephoto end 2.1 m according to Numerical Example 2. Aberration diagram at the wide end 9 m in Numerical Example 2. Aberration diagram at the telephoto end 9 m in Numerical Example 2. Aberration diagram at the wide end 1.2 m in Numerical Example 1 (G1 to 4 integrated focus) Aberration diagram at the telephoto end 1.2 m in Numerical Example 1 (G1-4 integrated focus) Aberration diagram at the wide end 2.1 m in Numerical Example 1 (G1-4 integrated focus) Aberration diagram at the telephoto end 2.1 m of Numerical Example 1 (G1-4 integrated focus) Aberration diagram at the wide end 9 m of Numerical Example 1 (G1-4 integrated focus) Aberration diagram at the telephoto end 9m of Numerical Example 1 (G1-4 integrated focus) Sectional view of Numerical Example 3 Aberration diagram at the wide end 1.2 m in Numerical Example 3. Aberration diagram of Numerical Example 3 at a telephoto end of 1.2 m Aberration diagram at the wide end 2.1 m in Numerical Example 3. Aberration diagram at the telephoto end 2.1 m in Numerical Example 3 Aberration diagram at the wide end 9 m in Numerical Example 3. Aberration diagram at telephoto end 9 m in Numerical Example 3 Aberration diagram at the wide end 1.2 m in Numerical Example 3 (G1-4 integrated focus) Aberration diagram at the telephoto end 1.2 m in Numerical Example 3 (G1-4 integrated focus) Aberration diagram at the wide end 2.1 m in Numerical Example 3 (G1-4 integrated focus) Aberration diagram at the telephoto end 2.1 m in Numerical Example 3 (G1-4 integrated focus) Aberration diagram at the wide end 9 m in Numerical Example 3 (G1-4 integrated focus) Aberration diagram at the telephoto end 9m in Numerical Example 3 (G1-4 integrated focus)

Explanation of symbols

SP Aperture G1 First Group (First Lens Unit)
G2 second group (second lens unit)
G3 third group (third lens unit)
G4 4th group (4th lens unit)
G5 5th group (5th lens unit)
G6 6th group (6th lens unit)
G1A Group 1A (first subunit)
G1B Group 1B (second subunit)
PL1 off-axis chief ray CL1 optical axis

Claims (10)

A first lens unit having a negative refractive power, arranged on the most enlarged side,
A second lens unit having a positive refractive power, disposed adjacent to the first lens unit;
A third lens unit having a positive refractive power and disposed on the reduction side of the second lens unit;
A zoom lens including
During zooming, the distance between the first lens unit and the second lens unit is changed,
The first lens unit includes, in order from the enlargement side, a first subunit having a negative refractive power composed of one or more negative lenses, one negative lens, and one positive lens. It is composed of a second subunit having a negative refractive power composed of a lens having a smaller outer diameter than a lens having the smallest outer diameter among the lenses included in the lens unit,
A zoom lens characterized in that, during focusing from a long distance to a short distance, the distance between the first subunit and the second subunit is reduced and the second subunit moves to the enlargement side. A first lens unit having a negative refractive power, arranged on the most enlarged side,
A second lens unit having a positive refractive power, disposed adjacent to the first lens unit;
A third lens unit having a positive refractive power and disposed on the reduction side of the second lens unit;
A zoom lens including
During zooming, the distance between the first lens unit and the second lens unit is changed,
The first lens unit is, in order from the enlargement side, a first subunit having a negative refractive power composed of one or more negative lenses, a negative lens composed of two negative lenses, and one positive lens. It consists of a second subunit of refractive power,
A zoom lens characterized in that, during focusing from a long distance to a short distance, the distance between the first subunit and the second subunit is reduced and the second subunit moves to the enlargement side. A first lens unit having a negative refractive power, arranged on the most enlarged side,
A second lens unit having a positive refractive power, disposed adjacent to the first lens unit;
A third lens unit having a positive refractive power and disposed on the reduction side of the second lens unit;
A zoom lens including
During zooming, the distance between the first lens unit and the second lens unit is changed,
The first lens unit includes a first subunit having a negative refractive power and a second subunit having a negative refractive power in order from the magnification side.
The zoom lens, wherein the first subunit moves to the reduction side and the second subunit moves to the enlargement side during focusing from a long distance to a short distance. A first lens unit having a negative refractive power, arranged on the most enlarged side,
A second lens unit having a positive refractive power, disposed adjacent to the first lens unit;
A third lens unit having a positive refractive power and disposed on the reduction side of the second lens unit;
A zoom lens including
During zooming, the distance between the first lens unit and the second lens unit is changed,
The first lens unit has a negative refractive power including, in order from the magnification side, a first subunit having a negative refractive power composed of one or more negative lenses, two negative lenses, and one positive lens. Of the second subunit,
During focusing from a long distance to a short distance, the distance between the first subunit and the second subunit is reduced and the second subunit is moved to the enlargement side,
When the outer diameter of the lens arranged on the most enlargement side of the second subunit is φ1BS and the outer diameter of the lens arranged on the most reduction side of the second subunit is φ1BI,
0.8 <φ1BS / φ1BI <1.2
A zoom lens characterized by satisfying   5. The zoom lens according to claim 1, wherein the first subunit moves to a reduction side during focusing from a long distance to a short distance. When the outer diameter of the lens arranged on the most enlargement side of the second subunit is φ1BS and the outer diameter of the lens arranged on the most reduction side of the second subunit is φ1BI,
0.8 <φ1BS / φ1BI <1.2
The zoom lens according to claim 1, wherein the zoom lens satisfies the following. The first subunit is composed of one negative meniscus lens convex on the enlargement side in order from the enlargement side,
In order from the magnification side, the second subunit is a negative meniscus lens convex on the magnification side, a negative lens having a stronger power on the magnification side than on the magnification side, and a surface on the reduction side than the magnification side The zoom lens according to claim 1, wherein the zoom lens includes a positive lens having strong power. When the focal length of the first lens unit is f1, and the focal length of the second subunit is f1B,
0.2 <f1 / f1B <0.8
The zoom lens according to claim 1, wherein: In order from the magnification conjugate side, the first lens unit having a negative refractive power, the second lens unit having a positive refractive power, the third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, A fifth lens unit having a refractive power of 6 and a sixth lens unit having a positive refractive power,
9. The zoom lens according to claim 1, wherein the second, third, fourth, and fifth lens units move in the optical axis direction during zooming. A light modulation element;
An image projection apparatus comprising: the zoom lens according to claim 1, which projects a light beam emitted from the light modulation element onto a projection surface.

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