JP2001350094A - Optical system, projection optical system, image projection device having the same, and imaging device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] When combined with a cross dichroic prism, the entire zoom lens can be made very small, and even when combined with a color combining prism other than the cross dichroic prism and having a longer optical path length, the cross dichroic prism can be used. Provided is a zoom lens capable of realizing almost the same size as that in the case of the combination. SOLUTION: From an enlargement conjugate side, a first lens group I having a negative refractive power, a second lens group II having a positive refractive power, a third lens group III having a positive refractive power, and a fourth lens having a negative refractive power. A six-group zoom lens including a group IV, a fifth lens group V having a positive or negative refractive power, and a sixth lens group VI having a positive refractive power, wherein the focal length at the wide-angle end of the entire zoom lens system is fw, and the second lens The focal length of the group
When f2, 0.02 <fw / f2 <0.6 is satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system suitable for a projection lens for enlarging and projecting a liquid crystal image or the like used in a liquid crystal projector or the like, having a compact structure and excellent optical characteristics. .

[0002]

2. Description of the Related Art Conventionally, light from three transmission type liquid crystal panels (image forming elements) for each color light of RGB is color-combined by a cross dichroic prism (color synthesizing means) and enlarged and projected on a screen. Various projection lenses for liquid crystal projectors have been proposed in Japanese Patent Application Laid-Open No. H11-95098.

The projection lenses disclosed in the first to eighth embodiments of the above publication include, in order from the enlargement conjugate side (screen side), a first lens unit having a negative refractive power and a second lens group having a positive refractive power. Lens group, third lens group with negative refractive power, fourth lens group with positive refractive power
A four-group configuration including lens groups, wherein the second lens group and the third lens group are moved in the optical axis direction during zooming, and the third lens group is further divided into front and rear groups during zooming. The zoom lens is configured to perform zooming by moving in a direction other than the lens group closest to the enlargement conjugate side and the lens group closest to the reduction conjugate side (liquid crystal panel side) in the optical axis direction. ing.

[0004]

In recent years, liquid crystal projectors have been required to be further miniaturized and improved in brightness, and the projection lenses used therein have also been required to be smaller and larger in diameter. I have. The projection lens disclosed in the above publication has an F-number of about 2.3, and if the diameter is further increased while keeping the configuration disclosed in the above publication, the degree of freedom in lens design becomes insufficient. There have been problems such as a decrease in the size and an increase in the size of the entire lens.

Although the cross dichroic prism shown in FIG. 19 of the above publication is very small, it is very difficult to manufacture and join the prism. Therefore, in order to reduce the manufacturing cost of the color combining prism, a method in which the dichroic mirror layers do not intersect inside the prism has been studied as a new color combining method.

When the zoom lens according to the present invention is combined with a cross dichroic prism, the overall length can be extremely reduced, and even when combined with a prism of a color synthesis type other than the cross dichroic prism, which has a longer prism optical path length, the entire system can be used. It is an object of the present invention to provide an optical system which can realize almost the same size as a conventional system using a cross dichroic prism without increasing the size.

[0007]

In the optical system according to the present invention, the whole system is constituted by at least six optical components having optical power, and at least four of the at least six optical components are used when zooming. The first optical component that moves and is closest to the enlargement conjugate side is an optical system having a negative optical power, and the first optical component is a biconvex lens and a negative negative convex component on the enlargement conjugate side in order from the enlargement conjugate side. It is characterized by having a meniscus lens, a negative lens, and a positive lens having a stronger power on the enlargement conjugate side than on the reduction conjugate side.

In the optical system according to the present invention, the entire system is constituted by at least six optical components having optical power.
At least four of the at least six optical components move during zooming, and the first optical component closest to the magnification conjugate side is an optical system having a negative optical power, and the at least six optical components are The second of the second from the expanded conjugate side
The optical component includes a positive lens in order from the enlargement conjugate side, and a negative lens having a stronger power on the enlargement conjugate side than the reduction conjugate side.

In the optical system according to the third aspect, the entire system is constituted by at least six optical components having optical power.
At least four of the at least six optical components move during zooming, and the first optical component closest to the magnification conjugate side is an optical system having a negative optical power, and the at least six optical components are Of which the third third from the expanded conjugate side
The optical component is characterized by comprising one positive lens.

In the optical system according to the present invention, the entire system is constituted by at least six optical components having optical power.
At least four of the at least six optical components move during zooming, and the first optical component closest to the magnification conjugate side is an optical system having negative optical power, and the wide-angle end of the entire optical system Where fw is the focal length of the second optical component and f2 is the focal length of the second optical component of the at least six optical components from the magnification conjugate side, and 0.02 <fw / f2 <0.6- (1). Features.

The optical system according to claim 5 is the optical system according to claim 4, wherein, of the at least six optical components, a third third optical component from the enlargement conjugate side comprises one positive lens. It is characterized by:

An optical system according to a sixth aspect is the optical system according to any one of the third to fifth aspects, wherein, of the at least six optical components, a second second optical component from an enlargement conjugate side is an optical system. It is characterized by including a positive lens from the conjugate side and a negative lens having stronger power on the enlargement conjugate side than on the reduction conjugate side.

An optical system according to a seventh aspect is the optical system according to any one of the second to sixth aspects, wherein the first optical component closest to the enlargement conjugate side of the at least six optical components is an optical component on the enlargement conjugate side. , A bi-convex lens, a negative meniscus lens convex on the enlargement conjugate side, a negative lens, and a positive lens having stronger power on the enlargement conjugate side than on the reduction conjugate side.

An optical system according to an eighth aspect is the optical system according to any one of the second to sixth aspects, wherein the first optical component closest to the enlargement conjugate side of the at least six optical components is an optical system on the enlargement conjugate side. , A bi-convex lens, a negative meniscus lens convex on the enlargement conjugate side, and a negative lens having strong power on the enlargement conjugate side.

An optical system according to a ninth aspect is the optical system according to any one of the first to eighth aspects, wherein the entire optical system has a first optical component having a negative refractive power, a positive optical component, and a positive optical component. A second optical component having a positive refractive power, a third optical component having a positive refractive power, a fourth optical component having a negative refractive power, a fifth optical component having a positive or negative refractive power, and a sixth optical component having a positive refractive power. It has six optical components.

An optical system according to a tenth aspect is the optical system according to any one of the first to ninth aspects, wherein the focal length of the first optical component closest to the enlargement conjugate side among the at least six optical components is f1. When the focal length at the wide-angle end of the entire optical system is fw, -1 <fw / f1 <-0.3- (2) is satisfied.

The optical system according to claim 11 is the optical system according to claims 1 to 10
The optical system according to any one of the preceding claims, wherein the at least 6
When the focal length of the third optical component third from the magnification conjugate side among the three optical components is f3, and the focal length at the wide-angle end of the entire optical system is fw, 0.45 <fw / f3 <1.3. ―It is characterized by satisfying (3).

The optical system of claim 12 is the optical system of claims 1 to 11
The optical system according to any one of the preceding claims, wherein the at least 6
When the focal length of the fourth optical component fourth from the magnification conjugate side among the two optical components is f4, and the focal length at the wide-angle end of the entire optical system is fw, −0.9 <fw / f4 <−0. .1-(4) is satisfied.

The optical system of claim 13 is the optical system of claims 1 to 12
The optical system according to any one of the preceding claims, wherein the at least 6
When the focal length of the fifth fifth optical component from the magnification conjugate side of the two optical components is f5, and the focal length at the wide-angle end of the entire optical system is fw, −0.15 <fw / f5 <0. 35-(5) is satisfied.

The optical system according to claim 14 is the optical system according to claims 1 to 13
The optical system according to any one of the preceding claims, wherein the at least 6
When the focal length of the sixth optical component that is the sixth from the magnification conjugate side among the two optical components is f6 and the focal length at the wide-angle end of the entire optical system is fw, 0.2 <fw / f6 <0.8 ―It is characterized by satisfying (6).

The optical system according to claim 15 is the optical system according to claims 1 to 14
5. The optical system according to claim 1, wherein the optical components at both ends of the optical system are fixed with respect to the reduction-side conjugate point during zooming.

The optical system according to claim 16 is the optical system according to claims 1 to 15
The optical system according to claim 1, wherein the second optical component and the fifth optical component that are the second and fifth optical components from the magnification conjugate side of the at least six optical components are integrated when zooming. It is characterized by moving to.

The optical system of claim 17 is the optical system of claims 1 to 16
The optical system according to claim 1, wherein the second, third, and fourth optical components are the second, third, fourth, and fifth optical components from the magnification conjugate side of the at least six optical components.
The optical component and the fifth optical component are all characterized in that they move from the reduction conjugate side to the enlargement conjugate side when zooming from the wide-angle end to the telephoto end.

The optical system of claim 18 is the optical system of claims 1 to 17
The optical system according to any one of the preceding claims, wherein the at least 6
The fourth optical component, which is the fourth optical component from the enlargement conjugate side, has one negative lens having stronger power on the reduction conjugate side than on the enlargement conjugate side.

The optical system of claim 19 is the optical system of claims 1 to 18
The optical system according to any one of the preceding claims, wherein the at least 6
The fifth optical component, which is the fifth optical component from the enlargement conjugate side, is a negative lens having stronger power on the enlargement conjugate side than the reduction conjugate side and a positive lens having stronger power on the reduction conjugate side, in order from the enlargement conjugate side. The lens is characterized in that a positive lens having a strong power is provided on the reduction conjugate side.

The optical system according to claim 20 is the optical system according to claims 1 to 19
The optical system according to any one of the preceding claims, wherein the at least 6
The sixth optical component, which is the sixth optical component from the enlargement conjugate side, has one positive lens having stronger power on the enlargement conjugate side than on the reduction conjugate side.

The optical system according to claim 21 is the optical system according to claims 1 to 20.
7. The optical system according to claim 1, wherein a focus adjustment is performed by moving a first optical component closest to the enlargement conjugate side among the at least six optical components in an optical axis direction.

The optical system according to claim 22 is the optical system according to claims 1 to 21.
The optical system according to claim 1, wherein when the conjugate point on the magnification side is at infinity from the optical system, the at least 6
The air-equivalent length between the surface of the optical component closest to the reduction conjugate side and the conjugate point on the reduction side of the optical component closest to the reduction side is b
f, when the focal length at the wide angle end of the entire optical system is fw, 0.8 <bf / fw- (7) is satisfied.

An optical system according to a twenty-third aspect is the optical system according to any one of the first to twenty-second aspects, wherein the second, third, fourth, and fifth optical systems of the at least six optical components from the magnification conjugate side. The components are the second optical component, the third optical component, the fourth optical component,
The fifth optical component, the second at the time of zooming from the wide-angle end to the telephoto end
The moving amount of the optical component is M2, the moving amount of the third optical component when zooming from the wide-angle end to the telephoto end is M3, the moving amount of the fourth optical component when zooming from the wide-angle end to the telephoto end is M4, When the moving amount of the fifth optical component at the time of zooming from the wide-angle end to the telephoto end is M5, 1.3 <M2 / M3 <1− (8) 0.4 <M4 / M3 <1− (9) 0.4 <M5 / 23. The method according to claim 1, wherein M3 <1− (10) is satisfied.
The optical system according to item 1.

The optical system according to claim 24 is the optical system according to claims 1 to 23.
The optical system according to any one of the preceding claims, wherein the at least 6
When the first optical component, the second optical component, the third optical component, the fourth optical component, the fifth optical component, and the sixth optical component of the two optical components in order from the enlargement conjugate side, from the wide-angle end to the telephoto end Upon zooming, the distance between the first optical component and the second optical component decreases, the distance between the second optical component and the third optical component decreases,
The distance between the third optical component and the fourth optical component increases,
The distance between the optical component and the sixth optical component is increased.

The optical system according to claim 25 is the optical system according to claims 1 to 24
The optical system according to any one of the above, wherein the focal length at the wide-angle end of the entire optical system is fw, and the distance between the reduction-side conjugate point and the reduction-side pupil position at the wide-angle end is tkw, | fw / tkw | <0.25− (11)

A projection optical system according to a twenty-sixth aspect has color synthesizing means for synthesizing light of different colors from a plurality of image forming elements, and emits light from the plurality of image forming elements onto a projection surface. In the projection optical system for projection, the air conversion length between the projection optical system and the image forming element when the conjugate point on the enlargement side is at infinity from the projection optical system is bf, and the air conversion length of the color combining prism is When ppath, 1.2 <bf / ppath <2.1-(12) is satisfied.

A projection optical system according to a twenty-seventh aspect is the projection optical system according to the twenty-sixth aspect, wherein 1.2 <bf / ppath <1.5- (13) is satisfied.

In the projection optical system according to claim 28, the backing lecture 26 or
27. The projection optical system according to item 27, wherein the color combining means includes two or more prisms, and has two dichroic mirror layers that reflect light having different wavelength ranges from each other. Are characterized in that they do not intersect inside the color synthesizing means.

A projection optical system according to a twenty-ninth aspect is the projection optical system according to the twenty-eighth aspect, wherein the color synthesizing means has a prism having a surface that functions as a total reflection surface and a transmission surface on the most exit side, Further, when the prism disposed between the two dichroic mirror layers is cut along a plane in the color synthesis direction, the cross-sectional view is formed of four or more line segments, and the outer surface of the surface where the dichroic mirror layer is not formed is formed. At least one of the inflection points in the cross-sectional view is characterized in that it exists inside the prism from a line connecting both ends of the line in the cross-sectional view of the surface on which the two dichroic mirror layers are formed.

A projection optical system according to claim 30 is the projection optical system according to claim 28 or
30. The projection optical system according to claim 29, wherein the color synthesizing unit has a prism having a surface that functions as a total reflection surface and a transmission surface on the most exit side, and the prism disposed between the two dichroic mirror layers. Is cut by a plane in the color synthesis direction, the outer shape of the cross-sectional view is formed by four or more line segments, and at least one of the inner angles of the outer shape of the cross-sectional view is an angle exceeding 180 degrees.

The projection optical system according to the thirty-first aspect is characterized in that,
30.A projection optical system according to any one of the preceding claims, wherein the color synthesizing means is constituted by four or more prisms, and has a prism having a surface that functions as a total reflection surface and a transmission surface on the most exit side. It has two dichroic mirror layers that reflect light having different wavelength ranges from each other, and a plurality of prisms are arranged between the two dichroic mirror layers.

A projection optical system according to a thirty-second aspect is the projection optical system according to any one of the twenty-eighth to thirty-first aspects, wherein the color synthesizing means sequentially forms an optically smooth surface from a light emission side. A first prism having three or more surfaces, and two optically smooth surfaces
A second prism having at least three optically smooth surfaces, a third prism having at least three optically smooth surfaces, and a fourth prism having at least two optically smooth surfaces. Second
A dichroic mirror layer that reflects the first color light is provided on one or both of the opposing surfaces of the prism, and a dichroic mirror layer that reflects the second color light on one or both of the surfaces where the third prism and the fourth prism face each other. It is characterized by having.

A projection optical system according to a thirty-third aspect is the projection optical system according to any one of the twenty-eighth to thirty-second aspects, wherein the color synthesizing means sequentially forms an optically smooth surface from a light emitting side. A first prism having three or more surfaces, one of the three or more surfaces having a surface serving as a transmission surface and a total reflection surface, and a second prism having two or more optically smooth surfaces. A third prism having three or more optically smooth surfaces, and a fourth prism having two or more optically smooth surfaces,
A dichroic mirror layer for reflecting the first color light is provided on one or both surfaces of the prism and the second prism facing each other, and the second color light is reflected on one or both surfaces of the third prism and the fourth prism. It is characterized by having a dichroic mirror layer.

A projection optical system according to a thirty-fourth aspect is the projection optical system according to any one of the twenty-sixth to thirty-fourth aspects, wherein the entire system is constituted by at least six optical components having optical power. At least four of the six optical components move during zooming, and the first optical component closest to the magnification conjugate side has a negative engineering power.

According to a thirty-fifth aspect of the present invention, the projection optical system has color synthesizing means for synthesizing lights of different colors from the plurality of image forming elements, and the light from the plurality of image forming elements is projected onto the projection surface. 26. Any one of claims 1 to 25 as a projection optical system for projecting.
In the projection optical system using the optical system according to claim, bf, the air conversion length between the projection optical system and the image forming element when the conjugate point on the enlargement side is at infinity from the projection optical system, the color synthesis When the air conversion length of the prism is ppath, 1.2 <bf / ppath <2.1 is satisfied.

A projection optical system according to a thirty-sixth aspect is the projection optical system according to the thirty-fifth aspect, wherein 1.2 <bf / ppath <1.5 is satisfied.

An image projection apparatus according to a thirty-seventh aspect has the optical system according to any one of the first to twenty-fifth aspects, and is formed by an image forming element disposed at a conjugate point on the reduction side using the optical system. It is characterized in that the projected image is enlarged and projected.

According to a thirty-eighth aspect of the present invention, there is provided the image projecting apparatus according to the twenty-sixth aspect
37. The projection optical system according to any one of claims 36 to 36, wherein an image formed by an image forming element disposed at a conjugate point on the reduction side is enlarged and projected using the projection optical system. .

The image projection apparatus according to claim 39,
40. The image projection device according to claim 38, wherein the image forming element comprises a liquid crystal display element.

The image pickup apparatus according to claim 40 is the first or second embodiment.
5. An image of an object is projected onto a photoconductor at a conjugate point on the reduction side by using the optical system according to any one of 5.

[0047]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the optical system according to the present invention will be described with reference to the drawings. In this embodiment, the optical system of the present invention is used as a projection optical system of a liquid crystal projector. However, the optical system of the present invention is not limited to a projection optical system used for a liquid crystal projector or the like, and there may be various other embodiments. Here, features common to all embodiments when the optical system of the present invention is applied to a projection optical system will be described.

The zoom lens (optical system) in this embodiment is
As shown in FIGS. 1 to 8, from the enlargement conjugate side (the screen side in the projection optical system of the projector, the object side in the imaging optical system of the camera) to the reduction conjugate side (the image forming element side in the projection optical system of the projector, the imaging of the camera). In the optical system, the first lens group (first optical component) I having a negative refractive power I,
Second lens group (second optical component) II having positive refractive power, third lens group (third optical component) III having positive refractive power, fourth lens group (fourth optical component) IV having negative refractive power IV , A fifth lens group (fifth optical component) V having a positive or negative refractive power, a sixth lens group (sixth optical component) VI having a positive refractive power, and six lens groups. Each lens group (optical component) is composed of only a lens in the present embodiment. However, the present invention is not limited to a lens but may include other optical elements such as a mirror.

The first lens unit is arranged in order from the magnification conjugate side.
It consists of a biconvex lens, a negative meniscus lens convex on the enlargement conjugate side, a biconcave lens, a positive meniscus lens convex on the enlargement conjugate side, or a biconvex lens, a negative meniscus lens convex on the enlargement conjugate side and having strong power on the enlargement conjugate side. It is composed of a negative lens. The reason why the positive lenses are arranged on the enlargement conjugate side and the reduction conjugate side of the first lens group is that distortion is mainly corrected by the enlargement conjugate side positive lens, and chromatic aberration is corrected by the reduction conjugate side positive lens. is there. The correction of distortion is easier when the height of the off-axis chief ray is higher because the location where the light flux corresponding to each image height passes is different.In the correction of chromatic aberration, especially for the correction of lateral chromatic aberration, It is preferable to perform chromatic aberration correction at a position where the height of the outer principal ray is low because occurrence of high-order chromatic aberration of magnification is small. The negative lens desirably has the above shape in order to disperse the negative refractive power of each surface and reduce the occurrence of higher-order distortion, coma, and astigmatism.

The second lens group is composed of a biconvex lens in order from the enlargement conjugate side and a negative meniscus lens convex to the reduction conjugate side. The lens surface of the second group which is closest to the reduction conjugate side corrects the distortion generated by the negative lens of the first group, and the air lens in the second lens group which is closest to the enlargement conjugate side of the first group. The astigmatism which largely occurs on the lens surface on the reduction conjugate side of the positive lens is corrected.

The third lens group is composed of one biconvex lens having a strong power on the magnification conjugate side. One biconvex lens of the third lens group makes the incident angle and the exit angle of each of the luminous fluxes around the pupil of the on-axis image height to each lens surface substantially equal, and the third group produces spherical aberration. In order to minimize the shape, the power of the lens surface on the enlargement conjugate side is stronger than the power of the lens surface on the reduction conjugate side.

The fourth lens group is composed of one negative lens having a strong power on the reduction conjugate side. The fourth lens group has the above shape in order to reduce the spherical aberration generated in the fourth lens group.

The fifth lens group is arranged in order from the magnification conjugate side.
A biconcave lens having strong power on the enlargement conjugate side, a positive lens having strong power on the reduction conjugate side, and a positive lens having strong power on the reduction conjugate side, the biconcave lens and the positive lens on the enlargement conjugate side Are joined. Arranging the negative lens on the magnifying conjugate side of the fifth lens group is to jump up the light beam with the negative lens, obtain a long back focus, and perform chromatic aberration correction at a low height of the off-axis principal ray, This is to suppress the occurrence of higher-order chromatic aberration of magnification. The two positive lenses have a shape in which the lens surface on the reduction conjugate side has a stronger power than the lens surface on the opposite side in order to disperse the refraction of on-axis and off-axis light beams.

The sixth lens group is composed of one positive lens having a strong power on the magnification conjugate side. By giving a strong power to the enlargement conjugate side, the distance between the combined principal plane of the fifth lens group and the point where the light ray of the sixth lens group is actually refracted from the first lens group is increased from the optical axis. Since it can be increased in some places, the combined refracting power can be weakened in the peripheral optical path, and the pincushion type distortion can be reduced on the screen side.

As a group configuration of the lens groups, the negative lens group is disposed closest to the enlargement conjugate side and the positive lens group is disposed closest to the reduction conjugate side. This is for realizing a shorter focal length and obtaining a large projection image at a short projection distance. Further, the positive lens group on the reduction conjugate side is required to be telecentric with respect to the reduction conjugate plane. The second, third, fourth, and fifth lens groups are second, third,
When the four or five lens groups are combined, they have a positive refractive power as a whole, and at each focal length position, while changing the distance between the lens groups so as to minimize each aberration,
During zooming from the wide-angle end to the telephoto end, the lens moves from the reduction conjugate side to the enlargement conjugate side.

In this embodiment, two types of color combining prisms are assumed. The first is a color combining prism shown in FIG. This prism is composed of four prisms, a dichroic mirror layer for reflecting the first color light is formed on the 7B surface of the prism 7, and a dichroic mirror layer for reflecting the second color light is formed on the 9B surface of the prism 9. ing. The first color light and the second color light are configured to reflect light in different wavelength ranges, and
It is configured to be able to combine colors. Image forming element 1
1, 12, and 13 perform image formation corresponding to three primary colors. Compared with a conventional color separation prism composed of three prisms used in a video camera or the like using three CCDs, by forming a prism sandwiched between two dichroic mirror layers by two prisms,
The optical path length of the prism is shortened. Compared to the conventional cross dichroic prism, this prism does not have two types of dichroic mirror layers intersecting, so the angular accuracy of the prism constituting the color combining prism may be low, and the prism at the time of joining the prisms Since the accuracy can be reduced, a projection optical system with extremely low manufacturing cost can be realized.

Second, the cross dichroic prism CSP2 in FIG. 34 is composed of four prisms 14, 15, 1
6 and 17, the two types of dichroic mirror layers DM1 and DM2 intersect inside the prism. Therefore, the color combining prism has an advantage that the shortest prism optical path length can be obtained. For this reason, there is an advantage that the back focus of the projection lens PJL can be short, and the design of the projection lens PJL is easy.

Next, each conditional expression will be described. Conditional expression (1) restricts the focal length of the entire system at the wide-angle end of the zoom lens and the focal length of the second lens group. In a region exceeding the lower limit of conditional expression (1), the conditional expression (1) is satisfied. Since the positive power becomes weaker, the off-axis light beam spreads on the magnification conjugate side with respect to the second lens unit, and the effective diameter of the first lens unit increases, which is not good. In a region exceeding the upper limit value of the conditional expression (1), the positive power of the second lens unit becomes too strong, so that the combined principal point of the second and subsequent lens units moves to the enlargement conjugate side, and in the entire system. In order to realize a short focal length, the first lens group must be moved to the enlargement conjugate side, which is not good because the total length of the lens increases.

Conditional expression (2) restricts the focal length of the entire system at the wide-angle end of the zoom lens and the focal length of the first lens unit. In the region exceeding the lower limit of conditional expression (2),
This is not good because the negative power of the first lens group becomes too strong and the curvature of field becomes excessive. In a region exceeding the upper limit value of the conditional expression (2), the negative power of the first lens unit becomes too weak, so that it is difficult to realize a short focal length in the entire system, and the projection distance for obtaining a large screen image becomes short. It is not good because it becomes big.

Conditional expression (3) restricts the focal length of the entire system at the wide-angle end of the zoom lens and the focal length of the third lens group. In the region exceeding the lower limit value of conditional expression (3),
Since the positive power of the third lens group becomes weaker, the off-axis light beam spreads on the enlargement conjugate side than the third lens group, which is not good because the effective diameter of the first lens group increases. In a region exceeding the upper limit value of the conditional expression (3), the positive power of the third lens unit becomes too strong, and a large spherical aberration is generated in the third lens unit, which is not good.

Conditional expression (4) restricts the focal length of the entire system at the wide-angle end of the zoom lens and the focal length of the fourth lens unit. In the region exceeding the lower limit of conditional expression (4),
Since the negative power of the fourth lens group becomes too strong, the curvature of field becomes excessive, which is not good. In a region exceeding the upper limit value of the conditional expression (4), the negative power of the fourth lens group becomes too weak, so that the fourth lens group cannot sufficiently jump up on-axis marginal rays, and has a sufficient back focus. It's not good because it can't be taken.

Conditional expression (5) restricts the focal length of the entire system at the wide-angle end of the zoom lens and the focal length of the fifth lens group. In the region exceeding the lower limit of conditional expression (5),
Since the negative power of the fifth lens group becomes stronger, telecentricity with respect to the image plane on the reduction conjugate side is lost.
Not good. In a region exceeding the upper limit value of the conditional expression (5), the positive power of the fifth lens unit becomes too strong, so that the back focus cannot be sufficiently obtained.

The conditional expression (6) restricts the focal length of the entire system at the wide-angle end of the zoom lens and the focal length of the sixth lens group. In the region exceeding the lower limit value of the conditional expression (6),
Since the positive power of the sixth lens group becomes weak, the telecentricity with respect to the image plane on the reduction conjugate side is lost.
Not good. In a region exceeding the upper limit value of the conditional expression (6), the positive power of the fifth lens group becomes too strong, so that the telecentricity with respect to the image plane on the reduction conjugate side is lost and the back focus cannot be sufficiently obtained. Absent.

Conditional expression (7) restricts the ratio of the focal length of the entire system at the wide-angle end of the zoom lens to the ratio of the back focus on the reduction conjugate side when the conjugate point on the enlargement conjugate side is at infinity in the left direction on the paper. The back focus indicates a value obtained by converting the prism into air. In a region exceeding the lower limit value of the conditional expression (7), a space for disposing the color synthesizing prism cannot be sufficiently obtained, which is not good.

Conditional expression (8) restricts the ratio of the amount of movement of the second lens unit to the amount of movement of the third lens unit during zooming from the wide-angle end to the telephoto end. In the region exceeding the lower limit, the amount of movement of the second lens group toward the enlargement conjugate side during zooming from the wide-angle end to the telephoto end decreases. As a result, the amount of movement of the combined principal point after the second lens group Is reduced, and a large zoom ratio cannot be obtained.
In a region exceeding the upper limit value of the conditional expression (8), the amount of movement of the second lens unit becomes too large, and the entire lens length becomes large.

Conditional expression (9) restricts the ratio of the amount of movement of the fourth lens unit to the amount of movement of the third lens unit upon zooming from the wide-angle end to the telephoto end. In a region exceeding the lower limit, the amount of movement of the fourth lens unit toward the enlargement conjugate side during zooming from the wide-angle end to the telephoto end decreases. It is not good because it is not possible to get large. In a region exceeding the upper limit value of the conditional expression (9), the amount of movement of the fourth lens unit becomes too large, and the entire lens length becomes large.

Conditional expression (10) restricts the ratio of the amount of movement of the fifth lens unit to the amount of movement of the third lens unit upon zooming from the wide-angle end to the telephoto end. In a region exceeding the lower limit, the amount of movement of the fifth lens unit to the enlargement conjugate side during zooming from the wide-angle end to the telephoto end decreases. As a result, the amount of movement of the combined principal point after the second lens unit Is reduced, and a large zoom ratio cannot be obtained. In a region exceeding the upper limit value of the conditional expression (10), the amount of movement of the fifth lens unit becomes too large, and the overall length of the lens becomes large.

Conditional expression (11) restricts the absolute value of the ratio between the focal length at the wide-angle end and the pupil position on the reduction conjugate side at the wide-angle end. In the region exceeding the upper limit of conditional expression (11),
It is not good because the telecentricity with respect to an image forming element such as a liquid crystal panel deteriorates. When a liquid crystal panel whose contrast changes in accordance with the incident angle of light is used as an image forming element, if the telecentricity is deteriorated, contrast unevenness occurs in a display screen. Further, since the angle of incidence of the color combining prism with respect to the dichroic mirror layer differs between the central part and the peripheral part of the image forming element, the cutoff wavelength of light shifts and color unevenness occurs.

Conditional expression (12) shows that the back focus on the reduction conjugate side when the conjugate point on the enlargement conjugate side at the wide-angle end of the zoom lens is located at infinity on the left side of the paper, and the optical path of the color combining prism when converted to air. This is a conditional expression limited to the length, and adapted to Examples 4 to 7. In a region exceeding the lower limit value of the conditional expression (12), the distance between the color synthesizing prism and the image forming element such as the liquid crystal panel is not sufficiently long, so that it is difficult to dispose the exit-side polarizing plate or the liquid crystal panel or the exit side. It is not good because the polarizing plate cannot be sufficiently cooled. In a region exceeding the upper limit of conditional expression (12), the distance between the color combining prism and the image forming element such as a liquid crystal panel and the distance between the color combining prism and the projection lens are unnecessarily increased, and the overall length of the lens is increased. Not good because it comes.

More preferably, when Expression (13) is satisfied,
Optical characteristics are further improved.

The first to fifth embodiments will be described below. The symbols in the examples are ri, the radius of curvature of the i-th lens surface from the enlargement conjugate side, and i + 1 from the enlargement conjugate side.
The surface distance between the second lens surfaces is di, the refractive index at the d-line of the i-th lens from the magnification conjugate side is ni, and the refractive index is i from the magnification conjugate side.
Let the Abbe number of the second lens be νi. CSP indicates a dummy glass corresponding to a color combining prism, and FP indicates a focal plane on which an image forming element such as a liquid crystal panel is arranged.
In the aberration diagrams, e is e-line, F is F-line, C is C-line.
A line, g represents a g line, M represents a meridional surface, and S represents a sagittal surface. The aberration diagram of lateral chromatic aberration is based on the e line.

(First Embodiment) FIG. 1 is a sectional view of a lens according to a first embodiment of the present invention, and FIGS. 9, 10, and 11 are aberration diagrams of the zoom lens according to the first embodiment at the wide-angle end, an intermediate position, and a telephoto end. Numerical Example 1 shows design values of the first embodiment. The design example in FIG. 1 is 0.7 inches (effective display range 14.336 mm × 10.
752 mm) for projecting a liquid crystal. The projection size is 100 inches at the wide-angle end of 4 m. The design example of FIG. 1 is a projection lens designed for the color combining prism CSP1 composed of four prisms shown in FIG.

The F-number is 1.7 at the wide-angle end and 2 at the telephoto end.
This is a very bright projection lens. The zoom ratio is 1.3.

(Second Embodiment) FIG. 2 is a sectional view of a lens according to a second embodiment of the present invention, and FIGS. 12, 13, and 14 are aberration diagrams of the zoom lens according to the second embodiment at the wide-angle end, the intermediate position, and the telephoto end. Numerical example 2 shows design values of the second example. The design example of FIG. 2 is also 0.7 inches (effective display range 14.336 mm X 1
It is a projection lens for projecting a 0.752 mm) liquid crystal. The projection size is 100 inches at the wide-angle end of 3.6 m.

The F-number is 1.7 at the wide-angle end and 2 at the telephoto end.
This is a very bright projection lens. The zoom ratio is 1.3. The design example of FIG. 2 is also a projection lens designed for the color combining prism CSP1 composed of four prisms shown in FIG. Although the configuration is almost the same as that of the embodiment of FIG. 1, the focal length range is shifted to the short focal length side so that a larger screen image can be obtained at the same projection distance as compared with the embodiment of FIG. is there. The overall lens length and the front lens effective diameter are slightly larger than those in the first embodiment for widening the angle.

(Third Embodiment) FIG. 3 is a sectional view of a lens according to a third embodiment of the present invention, and FIGS. 15, 16, and 17 are aberration diagrams of the zoom lens according to the third embodiment at the wide-angle end, an intermediate position, and a telephoto end. Numerical Example 3 shows design values of the third example. The design example in FIG. 3 is also 0.7 inches (effective display range 14.336 mm X 1
It is a projection lens for projecting a 0.752 mm) liquid crystal. The projection size is 100 inches at the wide-angle end of 4 m.

The F number is 2 at the wide-angle end and 2.2 at the telephoto end.
And a bright projection lens. The zoom ratio is 1.2 times.
The design example in FIG. 3 is also a projection lens designed for the color combining prism CSP1 including the four prisms shown in FIG. The configuration is almost the same as that of the embodiment of FIG.
F-number is darkened from F1.7 to F2, and the zoom ratio is 1.
This is a design example in which the specification is reduced from 3 times to 1.2 times to reduce the size. The total lens length of Example 1 (distance from the vertex of the lens surface closest to the enlargement conjugate side to the conjugate point of the reduction conjugate side) of 131.7 mm and the total lens length of Example 2 13
In contrast to 9.813 mm, the total lens length of Example 3 is 11
It is extremely small at 6.487 mm.

(Fourth Embodiment) FIG. 4 is a sectional view of a lens according to a fourth embodiment of the present invention, and FIGS. 18, 19 and 20 are aberration diagrams of the zoom lens according to the fourth embodiment at the wide-angle end, at the intermediate position, and at the telephoto end. Numerical Example 4 shows design values of the fourth example. The design example of FIG. 4 is 0.9 inches (effective display range 18.432 mm X 1
This is a projection lens for projecting a 3.824 mm) liquid crystal. The projection size is 100 inches at the wide-angle end of 3.6 m.

The F-number is 1.7 at the wide-angle end and 2 at the telephoto end.
This is a very bright projection lens. The zoom ratio is 1.3. The design example in FIG. 4 is a projection lens designed for the cross dichroic prism CSP2 shown in FIG.
Although the lens configuration is the same as that of the embodiment of FIGS. 1 to 3, the value obtained by dividing the back focus by the focal length at the wide-angle end is smaller than that of the first to third embodiments. Considering the size, it is extremely small.

(Fifth Embodiment) FIG. 5 is a sectional view of a lens according to a fifth embodiment of the present invention, and FIGS. 21, 22, and 23 are aberration diagrams of the zoom lens according to the fifth embodiment at the wide-angle end, the intermediate position, and the telephoto end. Numerical example 5 shows design values of the fifth example. The design example of FIG. 5 is also 0.9 inches (effective display range 18.432 mm X 1
This is a projection lens for projecting a 3.824 mm) liquid crystal. The projection size is 100 inches at the wide-angle end of 3.6 m.

The F-number is 1.7 at the wide-angle end and 2 at the telephoto end.
This is a very bright projection lens. The zoom ratio is 1.3. 5 is also a projection lens designed for the cross dichroic prism CSP2 shown in FIG.
The configuration is almost the same as that of the embodiment of FIG.
By moving the second lens group II and the fifth lens group V integrally, the number of cam grooves of the lens barrel (not shown) can be reduced by one, so that the cost can be reduced.

(Sixth Embodiment) FIG. 6 is a sectional view of a lens according to a sixth embodiment of the present invention. FIGS. 24, 25 and 26 show aberration diagrams of the zoom lens according to the sixth embodiment at the wide-angle end, at the intermediate position, and at the telephoto end. Numerical Example 6 shows design values of the sixth example. The design example of FIG. 6 is also 0.9 inches (effective display range 18.432 mm X 1
This is a projection lens for projecting a 3.824 mm) liquid crystal. The projection size is 100 inches at the wide-angle end of 4 m.

The F-number is 2 at the wide-angle end and 2.2 at the telephoto end.
And a bright projection lens. The zoom ratio is 1.2 times.
6 is also a projection lens designed for the cross dichroic prism CSP2 shown in FIG. Compared to Examples 4 and 5, the projection distance at the wide-angle end of 100 inches was increased, and the F-number at the wide-angle end was increased from F1.7 to F
The size is reduced to 2, and the size is reduced. The total lens length of the fourth embodiment is 149.611 mm,
In Example 6, the total lens length was reduced to 131.619 mm, compared to 151.595 mm in Example 5.

(Seventh Embodiment) FIG. 7 is a sectional view of a lens according to a seventh embodiment of the present invention. FIGS. 27, 28 and 29 show aberration diagrams of the zoom lens according to the seventh embodiment at the wide-angle end, at the intermediate position, and at the telephoto end. Numerical example 7 shows design values of the seventh example.

The design example shown in FIG. 7 is a projection lens for projecting a 0.7-inch (effective display area 14.336 × 10.752 mm) liquid crystal. The projection size is 100 inches at the wide-angle end of 4 m.

The design example of FIG. 7 is also a projection lens designed for the cross dichroic prism CSP2 as shown in FIG.

The F-number is 2 at the wide-angle end and 2.1 at the telephoto end.
5 is a bright projection lens. The zoom ratio is 1.2 times. The lens configuration is different from the first to sixth embodiments in the configuration of the first lens group. The biconvex lens, the negative meniscus lens convex on the enlargement conjugate side, and the negative lens having strong power on the enlargement conjugate side are arranged in order from the enlargement conjugate side. The difference is that it is composed of a lens. Compared with Examples 1 to 6, the prism optical path length was shorter, and the F-number, the projection distance, and the zoom ratio were also down-specified, so that the number of lenses in the first group could be reduced by one. The total lens length is 106.559 mm, which is the shortest in the embodiment of the present invention.

(Eighth Embodiment) FIG. 8 is a sectional view of a lens according to an eighth embodiment of the present invention. FIGS. 30, 31, and 32 are aberration diagrams of the zoom lens according to the eighth embodiment at the wide-angle end, the intermediate position, and the telephoto end. Numerical example 8 shows design values of the eighth example. 8 is 0.9 inches (effective display area 18.432 × 13.8).
24) A projection lens for projecting the liquid crystal. The projection size is 100 inches at the wide-angle end of 3.6 m.

The F-number is 1.7 at the wide-angle end and 2 at the telephoto end.
This is a very bright projection lens. The zoom ratio is 1.3. The design example in FIG. 8 is a projection lens designed for the cross dichroic prism CSP2 shown in FIG.
The present invention has substantially the same configuration as that of the fourth embodiment, except that the fifth lens group is composed of a weak negative lens group.
The total lens length is 149.804 mm.

[0090]

[Outside 1]

[0091]

[Outside 2]

[0092]

[Outside 3]

[0093]

[Outside 4]

[0094]

[Outside 5]

[0095]

[Outside 6]

[0096]

[Outside 7]

[0097]

[Outside 8]

Hereinafter, conditional expressions (1) to (13) in each embodiment will be described.
Shows the value of

[0099]

[Table 1]

As described above, the first to eighth embodiments correspond to the three-plate system in which three image forming elements (liquid crystal panel, original) are often used in a liquid crystal projector or the like. FIG. 35 is a schematic diagram of a three-panel liquid crystal display, in which a liquid crystal panel 35 (reduction conjugate side) is provided in a liquid crystal projector 31.
There are three images, and the red, green and blue images formed by the three images are synthesized by the color synthesis prism 2 and projected on a screen 4 (enlargement conjugate side) through a zoom lens (optical system). Of course, this may be a single-panel type. In the case of a single-panel type, since there is only one liquid crystal panel, a color combining prism is not required. Further, the optical system of the present invention is not limited to a liquid crystal projector, and may be used for various imaging devices such as a digital camera, a silver halide camera, and a video camera. FIG. 36 is a schematic diagram when used in a camera. An image of an object 39 (magnification conjugate side) is formed on a photoconductor 37 (reduction conjugate side) in the camera body 36 through a zoom lens 38.

As described above, the optical system of the present invention can be used not only for a liquid crystal projector but also for an imaging device.

[0102]

According to the present invention, the F number is extremely bright, from 1.7 to 2, for synthesizing three liquid crystals and projecting the same on a screen. Good performance and a small projection lens can be realized.

If the present invention is applied to a liquid crystal projector using a cross dichroic prism, an unprecedented small liquid crystal projector can be realized. Further, if the projection lens of the present invention is applied to a color synthesis prism of a type in which two types of dichroic mirror layers do not intersect, it is possible to suppress an increase in the overall length of the lens due to an increase in the optical path length of the prism, which makes manufacturing extremely easy. Thus, a liquid crystal projector with low manufacturing cost can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view of a zoom lens according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a zoom lens according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a zoom lens according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a zoom lens according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a zoom lens according to a fifth embodiment of the present invention.

FIG. 6 is a sectional view of a zoom lens according to a sixth embodiment of the present invention.

FIG. 7 is a sectional view of a zoom lens according to a seventh embodiment of the present invention.

FIG. 8 is a sectional view of a zoom lens according to Embodiment 8 of the present invention;

FIG. 9 is an aberration diagram at a wide-angle end of the zoom lens according to the first embodiment of the present invention.

FIG. 10 is an aberration diagram of an intermediate position of the zoom lens according to the first embodiment of the present invention.

FIG. 11 is an aberration diagram at a telephoto end of a zoom lens according to Embodiment 1 of the present invention.

FIG. 12 is an aberration diagram at a wide-angle end of a zoom lens according to a second embodiment of the present invention.

FIG. 13 is an aberration diagram at an intermediate position of the zoom lens according to Embodiment 2 of the present invention;

FIG. 14 is an aberration diagram at a telephoto end of a zoom lens according to Embodiment 2 of the present invention;

FIG. 15 is an aberration diagram at a wide-angle end of a zoom lens according to Embodiment 3 of the present invention;

FIG. 16 is an aberration diagram at an intermediate position of the zoom lens according to Embodiment 3 of the present invention.

FIG. 17 is an aberration diagram at a telephoto end of a zoom lens according to Embodiment 3 of the present invention;

FIG. 18 is an aberration diagram at a wide-angle end of a zoom lens according to a fourth embodiment of the present invention.

FIG. 19 is an aberration diagram at an intermediate position of the zoom lens according to Embodiment 4 of the present invention.

FIG. 20 is an aberration diagram at a telephoto end of a zoom lens according to Embodiment 4 of the present invention;

FIG. 21 is an aberration diagram at a wide-angle end of a zoom lens according to Embodiment 5 of the present invention;

FIG. 22 is an aberration diagram at an intermediate position of the zoom lens according to Embodiment 5 of the present invention.

FIG. 23 is an aberration diagram at a telephoto end of a zoom lens according to Embodiment 5 of the present invention;

FIG. 24 is an aberration diagram at a wide-angle end of a zoom lens according to Embodiment 6 of the present invention;

FIG. 25 is an aberration diagram at an intermediate position of the zoom lens according to Embodiment 6 of the present invention;

FIG. 26 is an aberration diagram at a telephoto end of a zoom lens according to Embodiment 6 of the present invention;

FIG. 27 is an aberration diagram at a wide-angle end of a zoom lens according to Embodiment 7 of the present invention;

FIG. 28 is an aberration diagram at an intermediate position of the zoom lens according to Embodiment 7 of the present invention;

FIG. 29 is an aberration diagram at a telephoto end of a zoom lens according to Embodiment 7 of the present invention;

FIG. 30 is an aberration diagram at a wide-angle end of a zoom lens according to Embodiment 8 of the present invention;

FIG. 31 is an aberration diagram at an intermediate position of the zoom lens according to Embodiment 8 of the present invention;

FIG. 32 is an aberration diagram at a telephoto end of a zoom lens according to Embodiment 8 of the present invention;

FIG. 33 is a sectional view of a zoom lens and a color combining prism according to the first embodiment of the present invention.

FIG. 34 is a cross-sectional view of a cross dichroic prism combined with the projection lens of the present invention.

FIG. 35 is a schematic diagram when the present invention is applied to a liquid crystal projector.

FIG. 36 is a schematic diagram when the present invention is applied to a camera.

[Explanation of symbols]

 I First lens group II Second lens group III Third lens group IV Fourth lens group V Fifth lens group VI Sixth lens group FP Focal plane CSP Color synthesis prism CSP1 Color synthesis prism composed of four prisms CSP2 Cross dichroic prism

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 5/74 H04N 5/74 A 9/31 9/31 CF term (reference) 2H087 KA06 KA07 KA07 MA12 PA10 PA11 PA18 PB11 PB12 QA02 QA07 QA14 QA22 QA26 QA34 QA41 QA45 RA36 RA41 SA57 SA63 SA64 SA65 SA66 SA72 SB05 SB13 SB22 SB32 SB44 5C022 AB66 AC54 5C058 AA06 BA05 BA25 EA12 EA26 5C060 BA04 BA09 BB13 BC05 HC05 HC01 HC01

Claims (40)

[Claims] 1. A system comprising at least six optical components having optical power, wherein at least four of the at least six optical components move during zooming, and the first optical component is closest to the magnification conjugate side. The component is an optical system having negative optical power, and the first optical component is, in order from the enlargement conjugate side, a biconvex lens, a negative meniscus lens convex to the enlargement conjugate side, a negative lens, and a reduction conjugate side. An optical system characterized by having a positive lens having strong power on the enlargement conjugate side. 2. The first optical system, which is constituted by at least six optical components having optical power, wherein at least four of the at least six optical components move during zooming and are closest to the magnification conjugate side. An optical system whose component has negative optical power, of the at least six optical components, the second second optical component from the enlargement conjugate side, in order from the enlargement conjugate side, has a ratio between the positive lens and the reduction conjugate side. An optical system comprising a negative lens having strong power on the enlargement conjugate side. 3. A first optical system having at least six optical components having optical power, wherein at least four of the at least six optical components move at the time of zooming and are closest to the magnification conjugate side. An optical system in which the component has a negative optical power, wherein the third optical component, which is the third optical component from the magnification conjugate side, of the at least six optical components comprises one positive lens. . 4. A first optical system having at least six optical components having optical power, wherein at least four of the at least six optical components move during zooming, and the first optical component is closest to the enlargement conjugate side. The component is an optical system having a negative optical power, and the focal length at the wide-angle end of the entire optical system is fw, and the focal length of the second second optical component from the magnification conjugate side of the at least six optical components Where f2 is satisfied, and 0.02 <fw / f2 <0.6 is satisfied. 5. The optical system according to claim 4, wherein a third third optical component from the enlargement conjugate side of said at least six optical components comprises one positive lens. 6. A second optical component, which is second from the enlargement conjugate side, of the at least six optical components, has a negative power having a stronger power on the enlargement conjugate side than on the positive lens and the reduction conjugate side from the enlargement conjugate side. The optical system according to claim 3, further comprising a lens. 7. The first optical component closest to the enlargement conjugate side among the at least six optical components is, in order from the enlargement conjugate side,
7. A biconvex lens, a negative meniscus lens convex on the enlargement conjugate side, a negative lens, and a positive lens having stronger power on the enlargement conjugate side than on the reduction conjugate side. Optical system. 8. The first optical component closest to the enlargement conjugate side among the at least six optical components is, in order from the enlargement conjugate side,
7. The optical system according to claim 2, further comprising a biconvex lens, a negative meniscus lens convex on the enlargement conjugate side, and a negative lens having strong power on the enlargement conjugate side. 9. The entire optical system includes, in order from the magnification conjugate side, a first optical component having a negative refractive power, a second optical component having a positive refractive power, a third optical component having a positive refractive power, and a negative refractive power. A fourth optical component of
9. The optical system according to claim 1, comprising six optical components: a fifth optical component having a positive or negative refractive power and a sixth optical component having a positive refractive power. 10. When the focal length of the first optical component closest to the enlargement conjugate side among the at least six optical components is f1 and the focal length at the wide-angle end of the entire optical system is fw, -1 <fw / 10. The optical system according to claim 1, wherein f1 <-0.3 is satisfied. 11. The focal length of a third third optical component from the enlargement conjugate side among the at least six optical components is f3,
11. The lens system according to claim 1, wherein 0.45 <fw / f3 <1.3 is satisfied when the focal length at the wide-angle end of the entire optical system is fw.
The optical system according to the item. 12. A focal length of a fourth fourth optical component from an enlargement conjugate side among the at least six optical components is f4,
12. The optical system according to claim 1, wherein when the focal length at the wide-angle end of the entire optical system is fw, -0.9 <fw / f4 <-0.1 is satisfied.
The optical system according to the item. 13. The focal length of a fifth fifth optical component from the enlargement conjugate side among the at least six optical components is f5,
13. The optical system according to claim 1, wherein, when the focal length at the wide-angle end of the entire optical system is fw, -0.15 <fw / f5 <0.35 is satisfied.
The optical system according to the item. 14. A focal length of a sixth sixth optical component from an enlargement conjugate side among the at least six optical components is f6,
14. The lens system according to claim 1, wherein 0.2 <fw / f6 <0.8 is satisfied when the focal length at the wide-angle end of the entire optical system is fw.
The optical system according to the item. 15. The optical system according to claim 1, wherein the optical components at both ends of the optical system are fixed with respect to the reduction-side conjugate point during zooming. 16. The second optical component and the fifth optical component, which are the second and fifth optical components from the enlargement conjugate side, of the at least six optical components, move together during zooming. The optical system according to claim 1. 17. The second, third, fourth, and fifth optical components that are the second, third, fourth, and fifth optical components from the magnification conjugate side of the at least six optical components are 2. A zoom lens system according to claim 1, wherein when zooming from the wide-angle end to the telephoto end, the zoom lens moves from the reduction conjugate side to the enlargement conjugate side.
17. The optical system according to any one of items 16 to 16. 18. A fourth optical component, which is the fourth optical component from the enlargement conjugate side among the at least six optical components, has one negative lens having a stronger power on the reduction conjugate side than on the enlargement conjugate side. The optical system according to any one of claims 1 to 17, wherein 19. A fifth lens component, which is a fifth optical component from the enlargement conjugate side among the at least six optical components, is a negative lens having stronger power on the enlargement conjugate side than on the reduction conjugate side in order from the enlargement conjugate side. 19. The optical system according to claim 1, further comprising a positive lens having a strong power on the conjugate side and a positive lens having a strong power on the reduction conjugate side. 20. The sixth optical component, which is the sixth optical component from the enlargement conjugate side among the at least six optical components, has one positive lens having a stronger power on the enlargement conjugate side than on the reduction conjugate side. 20. Any one of claims 1 to 19, characterized in that:
The optical system according to the item. 21. A first optical component closest to the enlargement conjugate side among the at least six optical components is moved in an optical axis direction,
3. The focus adjustment is performed.
0. The optical system according to any one of the preceding items. 22. When the conjugate point on the enlargement side is at infinity from the optical system, the most conjugate side of the at least six optical components and the most conjugate point on the reduction side are connected with the conjugate point on the reduction side. 23, wherein 0.8 <bf / fw is satisfied, where bf is the air-equivalent length and fw is the focal length at the wide-angle end of the entire optical system.
The optical system according to the item. 23. The second, third, fourth, and fifth optical components of the at least six optical components from the magnification conjugate side as a second optical component, a third optical component, a fifth optical component, The amount of movement of the second optical component at the time of zooming from the wide-angle end to the telephoto end is M2, the amount of movement of the third optical component at the time of zooming from the wide-angle end to the telephoto end is M3, and the amount of change is M3 from the wide-angle end to the telephoto end. When the moving amount of the fourth optical component at the time of magnification is M4 and the moving amount of the fifth optical component at the time of zooming from the wide-angle end to the telephoto end is M5, 1.3 <M2 / M3 <10.4 <M4 / M3 < 23. The method according to claim 1, wherein 1 0.4 <M5 / M3 <1 is satisfied.
The optical system according to item 1. 24. A first optical component, a second optical component, a third optical component,
When the optical component, the fourth optical component, the fifth optical component, and the sixth optical component are used, at the time of zooming from the wide-angle end to the telephoto end, the distance between the first optical component and the second optical component decreases, and The distance between the second optical component and the third optical component decreases, and the third optical component and the fourth optical component
The distance between the optical components increases, and the distance between the fifth optical component and the sixth optical component increases.
7. The optical system according to claim 1. 25. The focal length at the wide-angle end of the entire optical system is fw, and the distance between the reduction-side conjugate point and the reduction-side pupil position at the wide-angle end is tkw.
The optical system according to any one of claims 1 to 24, wherein | fw / tkw | <0.25 is satisfied. 26. A projection optical system comprising a color synthesizing unit for synthesizing lights of different colors from a plurality of image forming elements, and projecting light from the plurality of image forming elements onto a projection surface. When the air conversion length between the projection optical system and the image forming element when the conjugate point on the enlargement side is at infinity from the projection optical system is bf, and the air conversion length of the color combining prism is ppath, 1.2 < A projection optical system which satisfies bf / ppath <2.1. 27. The projection optical system according to claim 26, wherein 1.2 <bf / ppath <1.5 is satisfied. 28. The color synthesizing means comprises two or more prisms, and has two dichroic mirror layers that reflect light having different wavelength ranges from each other, and the two dichroic mirror layers are the color synthesizing layers. 28. A projection optical system according to claim 26 or 27, wherein the projection optical system does not intersect inside the means. 29. The color synthesizing means has a prism having a surface that functions as a total reflection surface and a transmission surface on the most exit side, and further includes a prism disposed between the two dichroic mirror layers in a color synthesis direction. When cut along a plane, the cross-sectional view outline is formed by four or more line segments, and at least one of the bending points in the cross-sectional view of the surface on which the dichroic mirror layer is not formed is formed by the two dichroic mirror layers. 29. The projection optical system according to claim 28, wherein the projection optical system exists inside the prism with respect to a line segment connecting both ends of the line segment in the cross-sectional view of the surface. 30. The color synthesizing means includes a prism having a surface that functions as a total reflection surface and a transmission surface on the most exit side, and further includes a prism disposed between the two dichroic mirror layers in a color synthesis direction. 30. The sectional view according to claim 28 or 29, wherein when cut in a plane, the cross-sectional outline is formed by four or more line segments, and at least one of the inner angles of the cross-sectional outline is an angle exceeding 180 degrees. Projection optics. 31. The color synthesizing means is constituted by four or more prisms, has a prism having a surface that functions as a total reflection surface and a transmission surface on the most exit side, and reflects light having different wavelength ranges from each other. 31. The projection optical system according to claim 28, further comprising two dichroic mirror layers, wherein a plurality of prisms are arranged between the two dichroic mirror layers. 32. The color combining means includes, in order from the light emission side, a first prism having three or more optically smooth surfaces and a second prism having two or more optically smooth surfaces. A third prism having three or more optically smooth surfaces, and a fourth prism having two or more optically smooth surfaces, one of the opposing surfaces of the first and second prisms Alternatively, a dichroic mirror layer that reflects the first color light is provided on both sides, and a dichroic mirror layer that reflects the second color light is provided on one or both surfaces of the third prism and the fourth prism facing each other. Claim 2
32. The projection optical system according to any one of items 8 to 31. 33. The color synthesizing means includes, in order from the light emission side, at least three optically smooth surfaces, and one of the three or more surfaces has a transmission surface and a total reflection surface. A first prism having a dual-purpose surface, a second prism having two or more optically smooth surfaces, and a third prism having three or more optically smooth surfaces.
A prism, and a fourth prism having two or more optically smooth surfaces, and a dichroic mirror layer that reflects the first color light on one or both of the opposing surfaces of the first prism and the second prism. 33. The projection optical system according to claim 28, further comprising: a dichroic mirror layer that reflects the second color light on one or both surfaces of the third and fourth prisms facing each other. 34. The whole system is constituted by at least six optical components having optical power, wherein at least four of the at least six optical components move during zooming,
The first optical component closest to the magnification conjugate side has a negative engineering power.
The projection optical system according to item 1. 35. A projection optical system comprising a color synthesizing unit for synthesizing light of different colors from a plurality of image forming elements, and projecting the light from the plurality of image forming elements onto a projection surface. Item 25. In the projection optical system using the optical system according to any one of Items 1 to 25, an air conversion between the projection optical system and the image forming element when the enlargement side conjugate point is at infinity from the projection optical system. The projection optical system satisfies 1.2 <bf / ppath <2.1, where bf is the length and ppath is the air conversion length of the color combining prism. 36. The projection optical system according to claim 35, wherein 1.2 <bf / ppath <1.5 is satisfied. 37. An optical system according to claim 1, wherein an image formed by an image forming element arranged at a conjugate point on a reduction side is enlarged and projected by using the optical system. An image projection device characterized by the above-mentioned. 38. An image forming apparatus comprising: the projection optical system according to claim 26; and using the projection optical system to form an image formed by an image forming element disposed at a conjugate point on a reduction side. An image projection device for performing enlarged projection. 39. The image forming device according to claim 37, wherein the image forming device comprises a liquid crystal display device.
Item. 40. An image pickup apparatus using the optical system according to claim 1 to project an image of an object onto a photoconductor at a conjugate point on a reduction side.