JP2020106661A - Optical system for projection and projector - Google Patents

Abstract

To provide a compact ultra-wide angle optical system which can be zoomed.SOLUTION: An optical system 10 projecting a first image IM1 on a reduction side 2 to a magnification side 3 includes: a negative refractive power lens group G11 that is located on a most magnification side 3 and is fixed during zooming and focusing; a positive refractive power lens group G17 that is arranged on the most first image IM1 side and is fixed during zooming and focusing; and a plurality of intermediate lens groups GM that are arranged between the lens group G11 on the most magnification side 3 and the lens group G17 on the most first image IM1 side and move upon zooming and upon focusing. The plurality of intermediate lens groups GM is a positive refractive power first lens group G14 moving at least for focusing, and is arranged on the magnification side 3 of a diaphragm St via a positive refractive power second lens group G15 arranged adjacent to the magnification side 3 of the diaphragm St.SELECTED DRAWING: Figure 1

Description

The present invention relates to a projection optical system and a projector.

Japanese Patent Application Laid-Open No. 2004-187242 discloses a projection zoom lens that has a wide angle, secures an appropriate back focus, reduces the lens diameter on the reduction side, downsizes the device, and achieves good optical performance. It is described that the constant is facilitated. The projection zoom lens of Patent Document 1 includes, in order from the enlargement side, a negative first lens group that is fixed during zooming, an intermediate group that includes a plurality of lens groups that move during zooming, and a positive final lens that is fixed during zooming. It consists of groups, and the reduction side is non-telecentric. The lens group on the most magnification side and the lens group on the most reduction side of the intermediate group have positive refracting power, and move from the reduction side to the magnification side during zooming from the wide-angle end to the telephoto end. The final lens group includes two or more positive lenses and two or more negative lenses, and the positive lens is arranged on the most reduction side of the final lens group. A predetermined conditional expression regarding the focal length of the final lens group is satisfied.

International publication WO2014/076897

In a wide-angle lens that often requires a large screen size with a short projection distance, the change in screen size or the like with respect to the change in projection distance is large. For this reason, it is desired to control focusing to project a clear image. Particularly, in a wide-angle end, a simple mechanism is used in an ultra-wide-angle lens whose half angle of view is about 60 degrees or more. It is required to control focusing accurately.

One aspect of the present invention is an optical system for projecting a first image on the reduction side to the enlargement side, which is located on the most enlargement side and has a negative refractive power which is fixed during zooming and focusing. Of the lens group closest to the image side, and the lens group disposed closest to the first image side, which is fixed at the time of zooming and focusing, and is the lens group closest to the image side of positive refractive power, An optical system having a plurality of lens groups arranged between the lens group on the most magnification side and the lens group on the most image side, the plurality of intermediate lens groups including a lens group that moves during zooming and focusing. It is a system. The plurality of intermediate lens groups is a first lens group having a positive refracting power that moves at least for focusing, and has a positive refracting power arranged adjacent to the enlargement side of the diaphragm on the enlargement side of the diaphragm. The first lens group arranged via the second lens group of 1 and the third lens group arranged on the reduction side of the diaphragm.

This optical system has, as a basic configuration, a lens group on the most magnification side of negative refracting power from the magnification side, a first lens group of positive refracting power, a second lens group of positive refracting power, and a diaphragm. , And a third lens group and a lens group having a positive refractive power closest to the image side. This optical system as a whole includes a retrofocus type power arrangement in which negative power is arranged on the enlargement side and positive power is arranged on the reduction side, which is suitable for widening the angle, and further on the enlargement side of the diaphragm. By arranging lens groups of positive power at adjacent positions, the diaphragm can be downsized, whereby the lens diameters of the lens groups before and after the diaphragm can be reduced, and a relatively small and wide-angle optical system can be provided. Further, by disposing the positive first lens group that moves during focusing with the positive second lens group interposed between the stop and the diaphragm, the axial ray height of the light beam incident on the first lens group is arranged. And the off-axis chief ray height can be made substantially equal. By keeping the off-axis chief ray height low, the lens system that moves during focusing becomes smaller, which is advantageous for movement, and the same degree of correction is made for both on-axis and off-axis rays. You will have the ability.

Further, since the angle of the off-axis chief ray of the ray incident on the first lens group is a ray bent in a direction away from the optical axis as it goes toward the enlargement side, it is at a position where the off-axis chief ray height is relatively low. Even if it is incident at, the incident angle becomes large, and it becomes possible to suppress the aberration correction ability for the off-axis aberration from becoming excessively small. Further, since the second lens group and the first lens group both have positive power and share the effect of converging light rays emitted from the diaphragm as divergent light, No power needed. By weakening the power of the first lens group used as the focus group, it becomes possible to prevent the sensitivity to the variation of the position of the first lens group from becoming excessively high.

Therefore, it is possible to efficiently correct the entire light beam included in the light flux, and a sufficient focus correction function can be obtained by configuring the first lens group with a small number of lenses, typically one lens. Obtainable. In a wide-angle or ultra-wide-angle lens, it is possible to provide an optical system capable of accurately controlling focusing with a simple mechanism.

One example of the optical system is that the first lens group, the second lens group, and the third lens group disposed on the reduction side of the diaphragm move with negative power or extremely weak power for zooming. Further, the plurality of intermediate lens groups are arranged on the magnifying side of the first lens group in order from the magnifying side, and have a fifth lens group having a positive refractive power which moves during zooming and a zoom lens during zooming. And a fourth lens unit having a negative refractive power that moves to the second lens unit. In this optical system, the second lens unit and the third lens unit may be fixed.

The third lens group may include a first combination of lenses whose refractive powers are arranged adjacent to each other in the order of positive, negative, positive, negative, and positive from the magnification side. From the side, it may include a second combination of lenses having adjacent refractive powers negative, positive, negative, positive, negative, positive and positive. Aberration can be favorably corrected by adopting the arrangement of the refractive power having high symmetry.

The lens group on the most magnifying side is composed of four negative concave lens elements having a negative refractive power and a biconcave negative lens element arranged in order from the magnifying side. It may include one sub-lens group and a second sub-lens group composed of a biconvex positive lens and a biconcave negative lens. By configuring the group arranged on the most magnifying side with a large number of lenses having negative refractive power, it is possible to provide an optical system with a wider angle and excellent correction of aberrations.

In this optical system, the radius of curvature Rs1 of the reduction side surface of the biconcave negative lens of the first sub-lens group and the curvature radius Rs2 of the enlargement side surface of the biconvex positive lens of the second sub-lens group May satisfy the following condition (1).
0.8<Rs1/Rs2<1.2 (1)

The focal length pfs2 of the biconvex positive lens and the focal length nfs2 of the biconcave negative lens of the second sub-lens group may satisfy the following condition (2).
−1.2<pfs2/nfs2≦−0.8 (2)

The focal length fs1 of the first sub-lens group, the focal length fs2 of the second sub-lens group, and the focal length fw at the wide-angle end of the optical system satisfy the following conditions (3) and (4). Good.
-1.6<fs1/fw<-1.0 (3)
0<|fs1/fs2|<0.1 (4)

The curvature Rs22 of the reduction side surface of the biconvex positive lens and the curvature Rs23 of the expansion side surface of the biconcave negative lens in the second sub lens group may satisfy the following condition (5).
0.8<Rs22/Rs23<1.2 (5)

Another aspect of the present invention is a projector including the optical system described above and an image forming device arranged on the reduction side.

FIG. 3 is a diagram illustrating an example of an optical system and a device including the optical system. The figure which shows lens data. The figure which shows aspherical surface data. The figure which shows various numerical values including the space before and behind each group which moves by zooming. The figure which shows various aberrations at a wide-angle end. The figure which shows various aberrations at a telephoto end. The figure which shows an example of a different optical system and the apparatus containing an optical system. FIG. 8 is a diagram showing lens data of the optical system shown in FIG. 7. FIG. 8 is a diagram showing aspherical surface data of the optical system shown in FIG. 7. FIG. 8 is a diagram showing various numerical values including the front and rear intervals of each group that moves during zooming of the optical system shown in FIG. 7. FIG. 8 is a diagram showing various aberrations at the wide-angle end of the optical system shown in FIG. 7. FIG. 8 is a diagram showing various aberrations at the telephoto end of the optical system shown in FIG. 7.

The present invention will be further described with reference to the drawings. FIG. 1 shows an apparatus including an optical system (optical system) according to an embodiment of the present invention. An example of the apparatus is a projector 100, which includes an optical system 10 and a light modulator (light valve) 5 arranged on the reduction side 2. The optical system 10 for a projector outputs an image (image) IM1 of the image plane 5a of the light modulator 5 from the enlargement side 3 as projection light 19 and projects (projects) it onto a screen or a wall surface (not shown) to produce an enlarged image. To re-image. The light valve 5 may be an LCD, a digital mirror device (DMD), an organic EL or the like as long as it can form an image, and may be a single plate type or a system that forms an image of each color. The light valve 5 may be a light emitting type or an illumination type. In the case of the illumination type, the projector 100 may further include an illumination optical system (not shown). The screen may be a wall surface, a whiteboard, or the like, and the projector 100 may be a front projector or a rear projector including a screen.

The optical system 10 is a projection optical system having a zoom function, as shown in FIG. 1A showing the arrangement at the wide-angle end and FIG. 1B showing the arrangement at the telephoto end. The optical system 10 is composed of 7 groups and 22 lenses. Specifically, the optical system 10 is located on the most magnification side 3 and is fixed at the time of zooming and focusing. The lens group G11 on the most magnification side of the negative refracting power and the first lens group on the most reduction side 2 are provided. And a lens group G17 arranged closest to the image IM1 and having a positive refractive power, which is the closest to the image side (the lens group closest to the reduction side) G17, which is fixed during zooming and focusing. The optical system 10 includes an intermediate lens group GM composed of a plurality of lens groups G12 to G16 between the lens groups G11 and G17 fixed to the most enlargement side 3 and the reduction side 2. The intermediate lens group (intermediate lens group) GM includes a lens group that moves during zooming and focusing. The intermediate lens group (GM) includes a plurality of lens groups and is a first lens group G14 having a positive refractive power that moves at least for focusing, and has a positive refractive power on the enlargement side 3 of the diaphragm St. It includes a first lens group G14 arranged via a second lens group G15, and a third lens group G16 arranged on the reduction side 2 of the diaphragm St and having a negative refractive power. The first lens group G14 and the second lens group G15 are adjacent to the enlargement side of the diaphragm St, that is, the first lens group G14 sandwiches only the second lens group G15 and the enlargement side of the diaphragm St. It is located in.

The intermediate lens group GM of this example is a lens group of a positive refractive power (fifth lens group in the intermediate lens group GM) G12 that is arranged in order from the enlargement side 3 and that moves during zooming. A negative refractive power lens group (fourth lens group in the intermediate lens group GM) G13 that moves during zooming, and a positive refractive power lens group (in the intermediate lens group GM) that moves for focusing. Of the first lens group G14, a lens group of positive refractive power (second lens group in the intermediate lens group GM) G15, and a negative lens group of negative refractive power arranged on the reduction side across the diaphragm St. And a lens group (third lens group in the intermediate lens group GM) G16.

That is, the intermediate lens group GM is provided on the magnifying side 3 of the first lens group G14 in order from the magnifying side 3 and the fifth lens group G12 of positive refractive power which moves during zooming and zooming. And a fourth lens group G13 having a negative refractive power which moves at the time of, and the second lens group G15 and the third lens group G16 are fixed. A fourth lens group G13 having a negative refractive power is arranged on the enlargement side of the first lens group G14, and the distance between the fourth lens group G13 on the enlargement side of the first lens group G14 during zooming ( The air gap) changes.

In this optical system 10, a lens group G14 having a positive refractive power, which moves for focusing, is arranged on the enlargement side 3 of the diaphragm St via a lens group G15 having a positive refractive power, and the diaphragm St is reduced. The lens unit G16 having a negative refractive power is arranged on the side 2. The optical system 10 has, as a whole, a negative-positive-negative-positive-positive-negative-positive seven-group configuration, and when a stop is included, negative-positive-negative-positive-positive-stop-negative-positive. It is composed.

The lens groups G15 and G16, which are arranged on the reduction side 2 of the intermediate lens group GM with the diaphragm St interposed therebetween, are fixed lens groups that do not move during zooming and focusing. Therefore, the optical system 10 of the present example includes a fixed lens group GF1 on the magnifying side, which is composed of a lens group G11 having a fixed negative refractive power, which is sequentially arranged from the magnifying side 3, and a wide-angle end to a telephoto end. A lens group G12 having a positive refractive power, which moves to the reduction side 2 during zooming, a lens group G13 having a negative refractive power, which moves to the reduction side 2 during zooming, and a lens group G13 during focusing. It includes a lens group G14 having a positive refractive power and a fixed lens group GF2 on the reduction side 2 of the positive refractive power which does not move as a whole during zooming and focusing. Therefore, it can be said that the optical system 10 as a whole has a lens configuration of five groups of negative-positive-negative-positive-positive. The fixed lens group GF2 on the most reduction side 2 includes a lens group G15 having a positive refractive power arranged on the enlargement side 3 and a lens group G16 having a negative refractive power arranged on the reduction side 2 with the diaphragm St interposed therebetween. And a lens group G17 having a positive refractive power. The refractive power of the lens group (G16+G17) arranged on the reduction side 2 of the stop St is a positive refractive power as a whole.

Whichever configuration is referred to, the optical system 10 is a lens group having a negative lead retrofocus type power arrangement in which a lens group having a negative refractive power is arranged on the magnification side, and the magnification side 3 has a wide angle. The lens structure is easy to make, and the reduction side 2 is telecentric or telecentric-like, so that it is easy to secure a long back focus. Further, a diaphragm St is arranged on the reduction side 2, a lens group G14 having a positive refractive power and a lens group G15 having a positive refractive power are arranged on the enlargement side 3 with the diaphragm St interposed therebetween, and a negative refraction is made on the reduction side 2. A lens group G16 for power and a lens group G17 for positive refracting power are arranged. In this lens arrangement, a lens group G16 having a negative refractive power and a lens group G17 having a positive refractive power are arranged on the reduction side 2 of the diaphragm St to condense the light flux at a relatively short distance, while on the expansion side 3 The lens groups G14 and G15 having a positive refractive power can gradually spread the light flux over a relatively long distance. Therefore, the lens diameter can be reduced before and after the stop St, and aberrations can be favorably corrected by disposing a plurality of small lenses.

On the other hand, in the lens group G14 disposed on the enlargement side 3 of the diaphragm St via the lens group G15 having a positive refractive power, the axial ray height (LHx) 7x with respect to the optical axis 7 and the off-axis chief ray height ( LHy)7y can be made substantially equal. In the lens group G14, the on-axis chief ray height 7x and the off-axis chief ray height 7y are incident at substantially the same position, so that the off-axis chief ray height 7y is suppressed to a low value, and the lenses forming the lens group G14 for focusing are small in size. It becomes advantageous for movement. Further, since it has the same correction ability for both on-axis and off-axis rays, it is possible to efficiently correct the entire ray (entire luminous flux). On the other hand, if the off-axis chief ray height 7y is too low, the balance of the correction capability for off-axis rays is lost and it is necessary to bring the lens group G14 closer to the reduction side. In that case, it is necessary to increase the positive refractive power. As a result, aberrations are overcorrected for axial rays, and the imbalance is increased. On the other hand, if the off-axis chief ray height 7y is too high, it is necessary to move the lens away from the diaphragm St, which increases the lens diameter.

In this example, the focusing lens group G14 is realized by a single-lens positive meniscus lens L12 having a convex surface on the magnification side 3, and the surface S22 on the magnification side 3 and the surface on the reduction side 2 of this lens L12. Both of S23 are aspherical surfaces to ensure the aberration correction capability during focusing and to simplify the mechanism for focusing. The on-axis ray height 7x and the off-axis chief ray height 7y are almost equal in the vicinity of any of the surfaces S22 and S23 of the focusing lens L12, and are, for example, within ±30%, and more preferably within ±20%. Alternatively, they may be substantially equal inside the lens.

That is, the ratio of the on-axis ray height (LHx) 7x and the off-axis chief ray height (LHy) 7y on the surface S23 on the incident side (reduction side) 2 of the lens L12 may satisfy the following condition (0). ..
0.7<|LHx/LHy|<1.3 (0)

The off-axis chief ray height 7y is located at a relatively high position, and if positive power is applied to this position, the off-axis chief ray has an effect of correcting distortion and lateral chromatic aberration. The closer to the enlargement side 3, the greater the correction effect but the larger the lens L12. The lower limit of condition (0) may be 0.8 or 0.85. The upper limit of condition (0) may be 1.2 or 1.15.

Further, during zooming, it is preferable that the air distance on the enlargement side of the focusing lens group (first lens group) G14 varies. As for the rays emitted from the magnification side to the lens group G14, the axial rays are emitted from the lens group G14 in a state where the upper and lower rays (marginal rays) defining the axial ray height are almost parallel, and are off-axis as they go toward the enlargement side. The light ray enters the lens group (fourth lens group) G13 at an angle with respect to the optical axis so as to be separated from the optical axis. Therefore, since the air gap on the enlargement side of the lens group G14 changes, the light rays incident on the lens group G13 have a stronger influence on off-axis light rays before and after zooming than on-axis light rays. With the above configuration, by performing the focusing with the lens group G14, it becomes possible to more effectively correct the off-axis aberration in which the aberration easily varies due to zooming of the wide-angle optical system.

FIG. 2 shows data of the lenses L1 to L22 of the projection optical system 10. The lens data includes the number (S) of each element (each lens surface in the case of a lens), the radius of curvature R (mm), the distance D (interval, mm) between the surfaces of each element, and the refractive index nd (d line). ), and Abbe number νd (d line). FIG. 3 shows the surface number of the aspherical surface in the surface of each element and the aspherical surface data. The aspherical surface is represented by the coefficient R shown in FIG. 2 and FIG. 3 where X is the coordinate in the optical axis direction, Y is the coordinate in the direction perpendicular to the optical axis, the traveling direction of light is positive, and R is the paraxial radius of curvature. It is expressed by the following equation using the coefficients K and A4 to A14. Note that “en” means “10 to the nth power”. The same applies to each of the following examples.
^{X = (1 / R) Y} 2 / [1+ {1- (1 + K) (1 / R) 2 Y 2} 1/2]
+A4Y ⁴ +A6Y ⁶ +A8Y ⁸ +A10Y ¹⁰ +A12Y ¹² +A14Y ¹⁴

In the optical system 10 shown in FIGS. 1 and 2, the lens group G14, which is the first lens group disposed on the reduction side 2 of the lens groups forming the intermediate lens group GM, moves only for focusing, The lens group G15, which is the lens group of, and the lens group G16, which is the third lens group, are the fifth lens group that is fixed (does not move during focusing and zooming) and that are arranged in order from the enlargement side 3. The lens group G12 and the lens group G13, which is the fourth lens group, move during zooming.

The lens group G11 of the lens group closest to the expansion side 3 is composed of seven lenses L1 to L7 arranged in order from the expansion side 3. The lens L1 on the most magnifying side 3 is a negative meniscus lens convex to the magnifying side 3, and the lens L2 is a biconcave negative lens near the optical axis 7, but as a whole, a negative meniscus convex to the magnifying side 3 is used. The lens L3 is a negative meniscus lens convex to the magnification side 3, the lens L4 is a negative meniscus lens convex to the magnification side 3, the lens L5 is a biconcave negative lens, and the lens L6 is It is a biconvex positive lens, and the lens L7 is a biconcave negative lens. By constructing the preceding four lenses L1 to L4 by a lens having a negative refractive power concave on the reduction side 2, a large number of negative lenses can be compactly arranged, and a negative lens having a large aperture on the most magnifying side 3 The group can be arranged compactly.

The lens group G11 is composed of these negative meniscus lenses L1 to L4 and a biconcave negative lens L5. The first sublens group G11-1 has a negative refracting power, and the biconvex positive lens L6 and It may be defined as a combination with the second sub-lens group G11-2 constituted by the biconcave negative lens L7, and the lens group G11 arranged on the most magnifying side has a large negative power of six lenses. By constructing the lens and the one lens having a positive power, it is possible to provide the optical system 10 having a wider angle and capable of favorably correcting the aberration.

The radius of curvature Rs1 of the surface S10 on the reduction side 2 of the biconcave negative lens L5 of the first sub-lens group G11-1 and the curvature of the surface S11 on the enlargement side of the biconvex positive lens L6 of the second sub-lens group G11-1. The radius Rs2 may satisfy the following condition (1).
0.8<Rs1/Rs2<1.2 (1)

Both surfaces S10 and S11 are curved surfaces on the enlargement side 3, and both surfaces can be arranged close to each other when the radius of curvature of both surfaces satisfies the condition (1), and at S10 which is a concave surface and S11 which is a convex surface, Aberrations can be better corrected by canceling out the aberrations by giving almost the same amount of effect to the surface curvature and the distortion aberration.

The focal length pfs2 of the biconvex positive lens L6 and the focal length nfs2 of the biconcave negative lens L7 of the second sub lens group G11-2 may satisfy the following condition (2).
−1.2<pfs2/nfs2≦−0.8 (2)
The condition (2) indicates that the focal lengths of the both lenses have opposite signs and that the absolute values thereof are close to each other, and that the cemented lens is a combination in which the cementing is removed for high luminance. If the radius of curvature of the cemented surface of the cemented lens is small, or if the diameter of the cemented lens is large, there is a possibility that the cemented surface cannot be stably maintained due to a temperature rise due to the passage of a high-luminance light beam. In the second sub-lens group G11-2, the positive lens L6 and the negative lens L7 have the same field curvature and decentering sensitivity with opposite signs, and their absolute values are substantially the same, so that aberration correction can be performed in a well-balanced manner. If the absolute values of the powers of these lenses are far apart, differences in these aberrations/efficacies also occur and the balance is lost.

The focal length fs1 of the first sub-lens group G11-1, the focal length fs2 of the second sub-lens group G11-2, and the focal length fw at the wide-angle end of the optical system 10 have the following conditions (3) and ( 4) may be satisfied.
-1.6<fs1/fw<-1.0 (3)
0<|fs1/fs2|<0.1 (4)

In the lens group G1 on the most magnifying side 3 having negative power as a whole, the power of the first sub-lens group G11-1 made up of a large number of negative lenses is increased to some extent with respect to the total power of the optical system 10. It is desirable to sufficiently weaken the power of the second sub-lens group G11-2 having the combination of positive and negative powers subsequent thereto. To widen the angle, a plurality of lenses having a strong negative power are required on the front side (enlargement side) 3 of the optical system 10, and the second sub-lens group G11-2 which receives the rays of light does not increase the power so much to widen the angle. The optical system 10 suitable for

The curvature Rs22 of the reduction side 2 surface S12 of the biconvex positive lens L6 of the second sub-lens group G11-2 and the curvature Rs23 of the expansion side 3 surface S13 of the biconcave negative lens L7 are the following conditions ( 5) may be satisfied.
0.8<Rs22/Rs23<1.2 (5)
The condition (5) indicates that the opposite surfaces S12 and S13 have close radii of curvature, and also indicates that the cemented lens is a combination in which the cemented lens is peeled off for high brightness. By arranging surfaces of opposite signs, which have close radii of curvature, close to each other, it becomes possible to correct aberrations in a well-balanced manner.

Further, the optical path lengths of the lenses L2 to L4 of the first sub-lens group G11-1, that is, the distance (optical path length) from the surface S3 of the lens L2 closest to the enlargement side 3 to the surface S8 of the lens L4 closest to the reduction side 2. The following condition (6) may be satisfied between the LL 24 and the distance (optical path length) LLA from the enlargement side surface S1 of the lens L1 closest to the enlargement side 3 to the stop St1.
0<LL24/LLA≦0.2 (6)
The entire optical system 10 can be shortened.

The lens group that is the second lens group from the magnifying side 3 and that is the lens group (fifth lens group) G12 that is the most magnifying side 3 of the intermediate lens group GM is a lens group having a two-element configuration or a three-element configuration that has positive power as a whole Is a lens group that moves to the reduction side 2 when zooming from the wide-angle end to the telephoto end. The lens group G12 of this example includes a biconvex positive lens L8 arranged in order from the enlargement side 3, a positive meniscus lens L9 convex to the reduction side 2, and a negative meniscus lens L10 convex to the reduction side 2. The lenses L9 and L10 constitute a cemented lens B11 having a positive power as a whole.

The third lens group from the magnifying side 3 and the lens group (fourth lens group) G13 next to the intermediate lens group GM is a lens group having a single negative power as a whole. It is a lens group that moves to the reduction side 2 when zooming to the edge. The lens group G13 of this example is a single-lens configuration of a biconcave negative lens L11.

The negative lens L11 that constitutes the fourth lens group G13 is a lens that is adjacent to the first lens group G14 that moves during focusing on the enlargement side. With the above structure, the first lens group G14 having a positive refractive power relaxes in the opposite direction the ray angle of the off-axis ray refracted in the direction approaching the optical axis toward the enlargement side. It is possible to suppress the height of the off-axis chief ray when the light emitted from G14 is incident on the lens group on the enlargement side from becoming too low.

Further, since the negative lens 11 is a biconcave lens, the negative refracting power can be shared by each surface, and the refraction angle of the light beam on each surface can be reduced, so that the occurrence of aberration can be suppressed. ..

The third to fourth lens group on the magnifying side, and the lens group (first lens group) G14 next to the intermediate lens group GM is a lens group having a single positive power as a whole, and is used for zooming. It is a lens group that does not move but moves during focusing. The lens group G14 of the present example is a single-lens configuration of a positive meniscus lens L12 having a convex surface on the enlargement side 3.

The third to fifth lens group on the magnifying side, and the lens group (second lens group) G15 next to the intermediate lens group GM is a two-lens group having a positive power as a whole, and is a fixed lens. It is a group. The lens group G15 of this example has a two-lens configuration including a negative meniscus lens L13 that is convex toward the enlargement side 3 and a biconvex positive lens L14 that are arranged in order from the enlargement side 3.

The lens group G16 arranged with the diaphragm St interposed therebetween is the third to sixth lens group on the enlargement side, and is the lens group (third lens group) G16 on the most reduction side 2 of the intermediate lens group GM. The lens group G16 is a fixed lens group, which is a lens group of 6 or 7 lenses having negative power as a whole. The entire lens group G16 may have negative power or very weak positive power. For example, the focal length fr3 of the lens group G16 may satisfy the following condition (7) with respect to the focal length fw at the wide angle end of the optical system 10.
0<fw/fr3<0.001 (7)

Specifically, the lens group G16 of this example includes a biconcave negative lens L15, a biconvex positive lens L16, a biconcave negative lens L17, and a biconvex positive lens, which are arranged in order from the enlargement side 3. It is composed of a lens L18, a biconcave negative lens L19, a biconvex positive lens L20, and a biconvex positive lens L21, and the negative lens L19 and the positive lens L20 are convex lenses on the reduction side as a whole. It constitutes B12.

The lens group G16 includes a first combination (lens arrangement) AR1 including lenses arranged adjacent to each other in the order of positive power, negative power, positive power, negative power, and positive power from the enlargement side 3. The lens arrangement AR1 includes a biconvex positive lens L16, a biconcave negative lens L17, a biconvex positive lens L18, a biconcave negative lens L19, and a biconvex positive lens L20. This lens arrangement AR1 is a biconvex positive lens arranged on the reduction side 2 of the stop St in order to correct aberrations that are likely to occur in a negative lead retrofocus type wide-angle lens and tend to cause a problem in a high-definition optical system. Before and after the lens L18, the arrangement of the positive lens L16 and the negative lens L17 as an achromatic lens and the symmetrical arrangement of the negative lens L19 and the positive lens L20 are included, and each aberration mainly including chromatic aberration is corrected. Further, by providing a negative-positive arrangement on the reduction side 2, positive (under) distortion aberration is generated by the incidence of the off-axis ray while the principal ray height is high and the incident angle is large, and the diaphragm St is generated. More negative (over) distortion aberration occurring on the enlargement side 3 can be offset.

The center of the arrangement AR1 is composed of a biconvex positive lens L18. The upper ray of the off-axis ray bounced up by the negative lens L17 is returned to the optical axis side to suppress the divergence of the luminous flux and suppress the enlargement of the optical element 5 on the image side (reduction side) 2 and to the upper side with respect to the principal ray. Aberration due to asymmetry by reducing the angle difference between the light beam and the lower light beam, for example, negative (over) tangential astigmatism for canceling positive (under) tangential astigmatism that occurs on the magnification side, It can be generated and corrected. Further, by disposing this positive lens L18, the power of the lens group G16 having two negative and positive combinations (positive lens L16 and negative lens L17, negative lens L19 and positive lens L20) in which the combined power inclines to the negative is obtained. It can be weakened.

The lens group G16 includes a second combination (lens arrangement) AR2 including lenses arranged adjacent to each other in the order of negative, positive, negative, positive, negative, positive and positive refractive powers from the enlargement side 3. The lens arrangement AR2 includes a biconcave negative lens L15, a biconvex positive lens L16, a biconcave negative lens L17, a biconvex positive lens L18, a biconcave negative lens L19, and a biconvex positive lens. L20 and a biconvex positive lens L21 are included. The convergent light converged on the reduction side 2 of the aperture stop St is diverged to make substantially parallel light incident on the facing surfaces of the positive lens L16 and the negative lens L17. Further, the difference between the angles of the upper ray and the lower ray with respect to the principal ray is reduced, and the aberration due to asymmetry, for example, the negative (over) for canceling the positive (under) tangential astigmatism that occurs on the enlargement side. It can be corrected by generating tangential astigmatism.

The lens L15 on the most magnifying side 3 of the lens group G16 is a biconcave negative lens. By making the surface of the magnifying side 3 concave, the marginal rays that have stood too far (particularly the lower rays) are laid down to reduce the difference in angle between the chief ray and the upper and lower rays, and the bundle of marginal rays that are substantially parallel By diverging strongly due to the concave surface of the surface on the reduction side having a small curvature, it is possible to widen while correcting the distortion of the light rays that have been converged for passing through the diaphragm.

By providing the lens L21 having a positive power on the most reduction side 2 of the lens group G16, it is possible to suppress the spread of the emission angle of the marginal rays due to the concave side surface of the reduction side 2 of the expansion lens L20. .. Further, even if the lens group G16 is configured to move as in the following examples, it is arranged on the reduction side 2 by the lens L21 having a positive power with respect to the change in the distance from the image plane 5a. It is possible to suppress the fluctuation of the incident position of the marginal ray on the lens. Therefore, it is possible to suppress the enlargement of the lens on the reduction side 2.

The lens surface S39 on the reduction side 2 of the lens L20 having the second positive power from the reduction side 2 of the lens group G16 may be a concave surface. Since the emission angle of the peripheral light rays of the emitted light rays is widened, the light flux can be diverged and emitted without increasing the negative power of the cemented lens B12, and the positive power of the lens L21 arranged on the reduction side 2 can be increased. Can be set relatively weakly. Therefore, aberration correction becomes easy.

The lens group G17 on the most reduction side 2 in the optical system 10 is a fixed positive power lens group, and in this example, it is a single biconvex positive lens L22. The fixed lens group G17 is an image forming lens for the image plane 5, and its power is adjusted so that the image side (reduction side) 2 is substantially telecentric.

FIG. 4 shows various numerical values at the time of zooming of the optical system 10. Distances (distances) D14, D19, and D21 indicate changes in the distance between the lens groups G12 and G13 that move during zooming and the lens groups before and after, and the distance D23 indicates the amount of operation that the lens group G14 moves during focusing. Is shown as a short distance (0.78 m), a middle distance (1.24 m), and a long distance (6.40 m) to the projected screen.

The optical system 10 is a projection lens having a zoom ratio of 1.06 and a half angle of view of about 60 degrees and an ultra wide angle. The F number is as small as 2.4 and bright, and the total length is relatively about 260 mm. It is a compact projector lens system.

The numerical values of this optical system are as follows.
Focal length (fw) of optical system at wide-angle end: 6.731 mm
Focal length of lens group G11 (lenses L1 to L7, fixed group GF1): -9.783 mm
Focal length of sub lens group G11-1 (fs1): -9.782 mm
Focal length (fs2) of sub lens group G11-2: 197.588 mm
Focal length of lens L6 (pfs2): 35.451 mm
Focal length of lens L7 (nfs2): -36.184 mm
Focal length of lens group G12 (lenses L8 to L10, zoom group): 46.760 mm
Focal length of lens group G13 (lens L11, zoom group): -121.989 mm
Focal length of lens group G14 (lens L12, focus group): 98.568 mm
Focal length of lens group G15 (lenses L13 to L14, fixed group): 48.001 mm
Focal length of lens group G16 (lenses L15 to L21, fixed group): -93.196 mm
Focal length of lens group G17 (lens L22, fixed group): 40.371 mm
Focal length of lens group GF2 (lenses L13 to L22, fixed group): 32.900 mm
Focal length of lens group GR (lens L15 to lens L22, fixed group): 28.588 mm
Optical path length (LL24) of lenses L2 to L4: 27.703 mm
Optical path length (LLA) from lens L1 to stop St1: 184.043 mm
Condition (0) (LHx(7.856)/LHy(7.800)): 1.01
Condition (1) (Rs1/Rs2:(R10/R11)): 1.008
Condition (2) (pfs2/nfs2): -0.980
Condition (3) (fs1/fw): −1.453
Condition (4) (|fs1/fs2|): -0.05
Condition (5) (Rs22/Rs23:(R12/R13)): 1.107
Condition (6) (LL24/LLA): 0.151

5A to 5C show spherical aberration, astigmatism, and distortion at the wide angle end of the optical system 10. 6A to 6C show spherical aberration, astigmatism, and distortion at the telephoto end of the optical system 10. Spherical aberration indicates a wavelength of 680 nm (long dashed line), a wavelength of 620 nm (solid line), a wavelength of 550 nm (short dashed line), a wavelength of 460 nm (dashed line), and a wavelength of 430 nm (dashed line). A tangential ray T and a sagittal ray S are shown.

As described above, in the projection optical system 10, it is possible to provide the optical system 10 in which the above-described conditions (0) to (6) are satisfied and the various aberrations at the wide-angle end and the telephoto end are well corrected.

FIG. 7 shows a different optical system 10. The optical system 10 is a projection optical system having a zoom function, as shown in FIG. 7A showing the arrangement at the wide-angle end and FIG. 7B showing the arrangement at the telephoto end. The optical system 10 is composed of 7 groups and 22 lenses, is located on the most magnifying side 3 and is fixed at the time of zooming and focusing. , A lens group arranged on the side of the first image IM1 closest to the reduction side 2 and fixed during zooming and focusing, and having a positive refractive power that is closest to the image side (the lens group closest to the reduction side). Lens group) G17. The optical system 10 includes an intermediate lens group GM composed of a plurality of lens groups G12 to G16 between the lens groups G11 and G17 fixed to the most enlargement side 3 and the reduction side 2. The intermediate lens group GM includes a lens group that moves during zooming and focusing.

The intermediate lens group GM of this example includes a lens group G12 having a positive refractive power fixed in zooming and focusing and a negative lens group fixed in zooming and focusing, which are sequentially arranged from the enlargement side 3. A lens group G13 having a refractive power, a lens group having a positive refractive power (first lens group in the intermediate lens group GM) G14 that moves for zooming and focusing, and a positive lens group that moves during zooming and focusing. A lens group having a refractive power (second lens group in the intermediate lens group GM) G15 and a lens group having a weak positive refractive power (middle lens) that moves on zooming and is disposed on the reduction side with the stop St interposed. The third lens group G16 in the lens group GM is included.

In this optical system 10, the lens group G14 having a positive refractive power that moves for focusing is disposed on the enlargement side 3 of the diaphragm St via the lens group G15 having a positive refractive power, and the diaphragm St is reduced. The lens unit G16 having a weak positive refractive power that satisfies the condition (7) is arranged on the side 2. Further, the optical system 10 has a seven-group configuration of negative-positive-negative-positive-positive-positive-positive as a whole, and including a diaphragm, negative-positive-negative-positive-positive-aperture-positive- It has a positive composition.

The lens groups G12 and G13 arranged on the enlargement side 3 of the intermediate lens group GM are fixed lens groups that do not move during zooming and focusing. Therefore, the optical system 10 of this example includes a fixed lens group GF1 on the magnifying side, which is composed of lens groups G11, G12, and G13 with fixed negative refractive power, which are arranged in order from the magnifying side 3, and a wide-angle end. Lens group G14 having a positive refractive power that moves to the magnifying side 3 when zooming to the telephoto end, a lens group G15 that has a positive refractive power that moves to the magnifying side 3 during zooming, and A lens group G16 having a positive refracting power that moves to the enlargement side 3 at this time and a fixed lens group GF2 on the reduction side 2 having a positive refracting power that does not move during zooming and focusing are included. .. The lens groups G14 and G15 are lens groups that move even during focusing (F). Therefore, it can be said that the optical system 10 has a lens configuration of five groups of negative-positive-positive-positive-positive.

Whichever configuration is referred to, the present optical system 10 is also a lens group having a negative focus retrofocus type power arrangement in which a lens group having negative refractive power is arranged on the magnification side, The lens configuration is easy to make a wide angle, and the reduction side 2 is telecentric or telecentric-like to easily secure a long back focus. Further, the diaphragm St is arranged on the reduction side 2, and the lens group G14 having a positive refractive power and the lens group G15 having a positive refractive power are arranged on the enlargement side 3 with the diaphragm St interposed therebetween. In this lens arrangement, similarly to the optical system described above, by disposing the lens groups G14 and G15 having a positive refractive power on the enlargement side 3, the lens diameter can be reduced before and after the diaphragm St, and a small lens can be obtained. Aberrations can be favorably corrected by arranging a plurality of them.

Further, in the lens group G14 disposed on the enlargement side 3 of the diaphragm St via the lens group G15 having a positive refractive power, the axial ray height (LHx) 7x with respect to the optical axis 7 and the off-axis chief ray height ( LHy)7y can be made substantially equal. Therefore, in the lens group G14, it is possible to reduce the size of the lens forming the lens group G14 that is incident at a position where the on-axis ray height 7x and the off-axis chief ray height 7y are substantially equal to each other and moves even during focusing. In this example, the focusing lens group G14 is realized by a single-lens positive meniscus lens L12 having a convex surface on the magnification side 3, and the surface S22 on the magnification side 3 and the surface on the reduction side 2 of this lens L12. Both of S23 are aspherical surfaces to ensure the aberration correction capability during focusing and to simplify the mechanism for focusing. The on-axis ray height (LHx) 7x and the off-axis chief ray height (LHy) 7y may satisfy the condition (0) as described above.

FIG. 8 shows data of the lenses L1 to L22 of the projection optical system 10. Further, FIG. 9 shows the surface number of the aspherical surface in the surface of each element and the aspherical surface data. The lens configuration of the optical system 10 shown in FIG. 7 is basically the same as that of the optical system shown in FIG. 1, and the description of the common parts will be omitted.

The lens group G11 of the lens group closest to the magnification side 3 is composed of seven lenses L1 to L7 arranged in order from the magnification side 3, and includes the optical system 10 shown in FIG. 1 and the respective lenses L1 to L7. The basic configuration is common. The lens group G11 is composed of the negative meniscus lenses L1 to L4 and the biconcave negative lens L5, and has a first sub-lens group G11-1 having a negative refractive power, a biconvex positive lens L6, and It is also the same as that it may be defined as a combination with the second sub-lens group G11-2 constituted by the biconcave negative lens L7.

The lens group G12 that is the second lens group from the magnifying side 3 and is included in the fixed lens group GF1 on the magnifying side 3 is a lens group having a two-element configuration or a three-element configuration with positive power as a whole. The lens group G12 of this example includes a biconvex positive lens L8 arranged in order from the enlargement side 3, a positive meniscus lens L9 convex to the reduction side 2, and a negative meniscus lens L10 convex to the reduction side. The lenses L9 and L10 form a cemented lens B11 having a positive power as a whole. The lens group G13, which is the third lens group from the magnifying side 3 and is included in the fixed lens group GF1 on the magnifying side 3, has a biconcave negative lens L11.

The third to fourth lens groups on the magnification side, and the first lens group G14 of the intermediate lens group GM is a lens group having a single positive power as a whole, and is a lens group that moves during zooming and focusing. Is. The lens group G14 of the present example is a single-lens configuration of a positive meniscus lens L12 having a convex surface on the enlargement side 3.

The second lens group G15 of the intermediate lens group GM, which is the third to fifth lens group on the magnifying side, is a two-lens group having a positive power as a whole, and is a lens group that moves during zooming and focusing. Is. The lens group G15 of this example has a two-lens configuration including a negative meniscus lens L13 that is convex toward the enlargement side 3 and a biconvex positive lens L14 that are arranged in order from the enlargement side 3.

The lens group G16 arranged with the stop St interposed therebetween is the third to sixth lens group on the enlargement side, and is the lens group (second lens group) G16 on the most reduction side 2 of the intermediate lens group GM. The lens group G16 is a lens group composed of 6 or 7 elements having a weak positive power as a whole, and is a lens group which moves during zooming. Specifically, in order from the enlargement side 3, a biconcave negative lens L15, a biconvex positive lens L16, a biconcave negative lens L17, a biconvex positive lens L18, and a biconcave negative lens L19. It is composed of a positive meniscus lens L20 having a convex surface on the magnifying side 3 and a biconvex positive lens L21. The negative lens L19 and the positive meniscus lens L20 collectively form a biconcave cemented lens B12.

The lens group G16 includes a first combination (lens arrangement) AR1 including lenses arranged adjacent to each other in the order of positive power, negative power, positive power, negative power, and positive power from the enlargement side 3. Further, the lens group G16 includes a second combination (lens arrangement) AR2 including lenses arranged adjacent to each other in the order of refractive power from the expansion side 3 to negative, positive, negative, positive, negative, positive, and positive. ..

FIG. 10 shows various numerical values when the optical system 10 is magnified (zoomed). The distances (distances) D21, D23, and D27 represent changes in the distance between the lens groups G14 and G15 that move during zooming and the lens groups before and after the lens group G15, when the distance to the projection screen is a short distance (0.78 m). Showing. In addition, the operation amounts of the lens groups G14 and G15 that are moved during focusing are shown as a short distance (0.78 m), a middle distance (1.24 m), and a long distance (6.40 m) to the projection screen. ing.

This optical system 10 is a projection lens with a zoom ratio of 1.07 times and a half angle of view of 60 degrees or more and an ultra wide angle. The F number is as small as 2.4 and bright, and the total length is 250 mm or less and compact. It is a projector lens system.

The numerical values of this optical system are as follows.
Focal length (fw) of optical system at wide-angle end: 6.636 mm
Focal length of fixed group GF1 (lenses L1 to L11): -18.234 mm
Focal length of lens group G11 (lenses L1 to L7): -8.3316 mm
Focal length (fs1) of sub lens group G11-1: -8.555 mm
Focal length (fs2) of sub lens group G11-2: 121.477 mm
Focal length of lens L6 (pfs2): 32.219 mm
Focal length (nfs2) of lens L7: -32.723 mm
Focal length of lens group G12 (lenses L8 to L10): 39.925 mm
Focal length of lens group G13 (lens L11): −84.963 mm
Focal length of lens group G14 (lens L12, focus and zoom group): 85.035 mm
Focal length of lens group G15 (lenses L13 to L14, focus and zoom group): 76.296 mm
Focal length of lens group G16 (lenses L15 to L21, zoom group, fr3): 10170.598 mm
Focal length of lens group G17 (lens L22, fixed group GF2): 43.935 mm
Focal length of lens group GR (lenses L15 to L22): 30.027 mm
Optical path length (LL24) of lenses L2 to L4: 27.975 mm
Optical path length (LLA) from lens L1 to diaphragm St1: 175.082 mm
Condition (0) (LHx(7.434)/LHy(8.419)): 0.88
Condition (1) (Rs1/Rs2:(R10/R11)): 1.098
Condition (2) (pfs2/nfs2): -0.985
Condition (3) (fs1/fw): -1.289
Condition (4) (|fs1/fs2|): -0.070
Condition (5) (Rs22/Rs23:(R12/R13)): 1.099
Condition (6) (LL24/LLA): 0.160
Condition (7) (fw/fr3): 0.0007

11A to 11C show spherical aberration, astigmatism, and distortion at the wide-angle end of the optical system 10. 12A to 12C show spherical aberration, astigmatism, and distortion at the telephoto end of the optical system 10. As described above, also in this projection optical system 10, it is possible to provide the optical system 10 that satisfies the above-described conditions (0) to (7) and that the various aberrations at the wide-angle end and the telephoto end are excellently corrected. Further, in the ultra wide-angle optical system (lens system) 10 whose half angle of view exceeds 60 degrees at the wide-angle end, focusing can be realized by moving one or three lenses having a small diameter. Therefore, the mechanical load at the time of focusing can be reduced, and the compact optical system 10 can be provided. Further, as shown in the aberration diagrams, these optical systems 10 also have good aberration correction during zooming and focusing, and as a projection optical system, they are capable of zooming and are compact, but have good aberration correction. It is possible to provide the projection optical system 10 capable of projecting the captured image and the projector 100 including the projection optical system 10.

10 optical system, 100 projector

Claims (18)

An optical system for projecting the first image on the reduction side to the enlargement side,
The lens group on the most magnification side of the negative refracting power, which is located on the most magnification side and is fixed during zooming and focusing,
A lens group disposed closest to the first image side, which is fixed during zooming and focusing, and has a positive refractive power and is closest to the image side;
A plurality of lens groups arranged between the most magnifying side lens group and the most image side lens group, and a plurality of intermediate lens groups including a lens group that moves during zooming and focusing; Have,
The plurality of intermediate lens groups is a first lens group having a positive refractive power that moves at least for focusing, and a positive lens group disposed adjacent to the expansion side of the diaphragm on the expansion side of the diaphragm. A first lens group arranged via a second lens group having a refractive power,
An optical system including a third lens group arranged on the reduction side of the diaphragm. In claim 1,
An optical system in which the first lens group and the second lens group are arranged adjacent to each other on the enlargement side of the diaphragm. In claim 1 or 2,
The third lens group is an optical system in which the negative refractive power or the focal length fr3 satisfies the following condition with respect to the focal length fw at the wide angle end of the optical system.
0<fw/fr3<0.001 In any one of Claim 1 thru|or 3,
An optical system in which the plurality of intermediate lens groups include a fourth lens group having a negative refractive power and arranged adjacent to the expansion side of the first lens group. In claim 4,
An optical system in which the distance between the fourth lens group and the first lens group changes during zooming. In any one of Claim 1 thru|or 5,
An optical system in which the first lens group, the second lens group, and the third lens group move for zooming. In any one of Claim 1 thru|or 5,
The plurality of intermediate lens groups include a fifth lens group having a positive refractive power and arranged on the magnifying side of the fourth lens group, and the fourth lens group and the fifth lens group during zooming. An optical system in which the group moves. In any one of Claim 1 thru|or 7,
The first lens group is an optical system including one lens. In any one of claims 1 to 8,
The third lens group is an optical system including a first combination of lenses that are adjacently arranged in order of positive, negative, positive, negative, and positive refractive powers from the magnification side. In any one of claims 1 to 9,
The said 3rd lens group is an optical system containing the 2nd combination which consists of the lens by which refractive power was negatively, positively, negatively, positively, negatively, positively, and adjacently arranged in order from the expansion side. In any one of Claim 1 thru|or 10,
The lens group on the most magnifying side has a negative refracting power composed of four lenses having negative refractive power concave on the reduction side and biconcave negative lenses arranged in order from the magnifying power side. A first sub-lens group,
An optical system including a second sub-lens group composed of a biconvex positive lens and a biconcave negative lens. In claim 11,
The radius of curvature Rs1 of the reduction side surface of the biconcave negative lens of the first sub-lens group and the curvature radius Rs2 of the enlargement side surface of the biconvex positive lens of the second sub-lens group An optical system that meets the following conditions.
0.8<Rs1/Rs2<1.2 In Claim 11 or 12,
An optical system in which a focal length pfs2 of the biconvex positive lens and a focal length nfs2 of the biconcave negative lens of the second sub-lens group satisfy the following conditions.
−1.2<pfs2/nfs2≦−0.8 In any one of Claim 11 thru|or 13,
An optical system in which the focal length fs1 of the first sub-lens group, the focal length fs2 of the second sub-lens group, and the focal length fw at the wide-angle end of the optical system satisfy the following conditions.
-1.6<fs1/fw<-1.0
0<|fs1/fs2|<0.1 In any one of Claim 11 thru|or 14,
An optical system in which the curvature Rs22 of the reduction side surface of the biconvex positive lens and the curvature Rs23 of the expansion side surface of the biconcave negative lens of the second sub-lens group satisfy the following conditions.
0.8<Rs22/Rs23<1.2 In any one of Claim 1 thru|or 15,
An optical system in which the ratio of the on-axis ray height LHx and the off-axis chief ray height LHy on the most reduction side surface of the first lens group satisfies the following condition.
0.7<|LHx/LHy|<1.3 In any one of Claim 1 thru|or 16,
An optical system, wherein the first image is an intermediate image, and has a relay lens group that forms the first image. An optical system according to any one of claims 1 to 17,
A projector having an image forming device arranged on the reduction side.

Images