JP2013024965A - Variable power optical system for projection and projection type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable power optical system for projection providing a constant F number during variation in power, attaining miniaturization, providing a high telecentric property and a favorable projection image and favorably applied to movie theaters.SOLUTION: The variable power optical system for projection, in order from a magnification side, is disposed with: a first lens group G1 which is fixed during variation in power; a plurality of lens groups which move during variation in power; and a final lens group which is fixed during variation in power. The variable power optical system is telecentric on the reduction side. An aperture stop 3 is disposed in the final lens group and has a fixed number of apertures in the whole range of variation in power. At least a single lens is disposed in the magnification side of the aperture stop 3 in the final lens group. When Imφ is a maximum effective image circle diameter in the reduction side, fs is a composite focal length of lenses in the reduction side of the aperture stop 3, and exP is a distance from an imaging surface in the reduction side to a paraxial exit pupil position, the variable power optical system satisfies the following conditional expressions: (1) Imφ/fs<0.4 and (2) 30.0<|exP|/Imφ.

Description

  The present invention relates to a projection variable magnification optical system and a projection display device, and more particularly to a projection variable magnification optical system suitable for projection on a large screen in a movie theater or the like and a projection display device using the same. Is.

  2. Description of the Related Art Conventionally, projection projector apparatuses (projection display apparatuses) using light valves such as liquid crystal display elements and DMD (Digital Micromirror Device: registered trademark) have been widely used. In recent years, movie projectors and the like are also using such projection display devices that can project higher-definition images that can be applied to large screens. In the projection display device used for such a use, three light valves are provided for each primary color, the light flux from the light source is separated into the three primary colors by the color separation optical system, and each light valve passes through. Later, since a three-plate method of combining and projecting with a color combining optical system is adopted, it is required to have a long back focus and good telecentricity.

  Generally, the value obtained by dividing the projection distance by the screen width is called the slow ratio. The screen size and the distance from the screen to the projection room, that is, the projection distance varies from movie theater to movie theater. Therefore, in order to project an image having a size suitable for each movie theater, a lens corresponding to a slow ratio suitable for each movie is required. However, it is not a good idea to prepare them individually from the viewpoint of cost. In view of this, it is conceivable to use a variable magnification optical system to provide a wide range of possible slow ratios. As variable power optical systems for projection, for example, those described in Patent Documents 1 to 3 below are known.

  In many of the conventional projection variable magnification optical systems, the numerical aperture (hereinafter sometimes referred to as “F number”) changes during the magnification change. Normally, the telephoto side has a larger F-number than the wide side, so in such a variable magnification optical system, even in a movie theater of the same screen size, a movie with a large slow ratio will be darker. As a movie theater application, it is preferable that the F number is constant at the time of zooming. Therefore, the applicant of the present application is set in Patent Document 3 below so that the F number is constant at the time of zooming. A zoom lens for projection is proposed.

JP 2010-008797 A JP 2005-106948 A JP 2009-128683 A

  In recent years, demands for projection optical systems in the above fields have become strict. An image circle diameter suitable for movie theater use (hereinafter also referred to as the maximum effective image circle diameter) can be obtained. There has been a demand for achieving high telecentricity and obtaining a better projected image.

  The present invention has been made in view of such circumstances, and the F number is constant at the time of zooming, so that high telecentricity can be achieved while downsizing and a good projection image can be obtained. An object of the present invention is to provide a variable power optical system for projection and a projection display device suitable for use in a hall.

In order to achieve the above object, a variable power optical system for projection according to the present invention includes a first lens group that is disposed closest to the enlargement side and fixed at the time of zooming, and a zoom lens that is disposed closest to the reduction side. It consists essentially of a final lens group that is fixed at the time of zooming, and a plurality of lens groups that are arranged between the first lens group and the final lens group and move during zooming. The lens is telecentric, a stop is disposed in the final lens group, and the numerical aperture is set to be constant over the entire zoom range. At least one lens is arranged on the enlargement side of the stop in the final lens group. And the following conditional expressions (1) and (2) are satisfied.
Imφ / fs <0.4 (1)
30.0 <| exP | / Imφ (2)
However,
Imφ: Maximum effective image circle diameter on the reduction side fs: Combined focal length exP of the lens on the reduction side with respect to the stop exP: Imaging on the reduction side at the wide angle end when the reduction distance is the exit side Distance on the optical axis from the surface to the paraxial exit pupil position

In the projection variable magnification optical system according to the present invention, it is preferable that the following conditional expression (3) is satisfied.
0.7 <Ls / Lge (3)
However,
Ls: distance on the optical axis from the stop to the most reduction side lens surface Lge: distance on the optical axis from the most enlargement side lens surface to the most reduction side lens surface in the final lens group

In the projection variable magnification optical system according to the present invention, it is preferable that the following conditional expression (4) is satisfied.
1.8 <Bf / Imφ (4)
However,
Bf: Back focus on the reduction side of the entire system at the wide angle end (air conversion distance)

  In the zooming optical system for projection according to the present invention, it is preferable that the plurality of lens groups that move during zooming are substantially composed of two or three lens groups.

  In the variable power optical system for projection according to the present invention, for example, as a first aspect, the first lens group has a negative refractive power, the final lens group has a positive refractive power, Of the plurality of lens groups that move at this time, the most magnified lens group can have a negative refractive power.

When the projection variable magnification optical system according to the present invention adopts the first aspect, it is preferable that the following conditional expression (5) is satisfied.
1.5 <Bfn / fw (5)
However,
Bfn: Back focus on the reduction side of the entire system at the wide angle end (air equivalent distance)
fw: focal length of the entire system at the wide angle end

When the projection variable magnification optical system according to the present invention adopts the first aspect, it is preferable that the following conditional expression (6) is satisfied.
-10.0 <f1 / fw <-2.0 (6)
However,
f1: focal length of the first lens unit fw: focal length of the entire system at the wide-angle end

  Alternatively, in the variable power optical system for projection according to the present invention, for example, as a second aspect, the first lens group has a positive refractive power, the final lens group has a positive refractive power, A plurality of lens groups that move at the same time are, in order from the magnification side, substantially three lenses, a lens group having a negative refractive power, a lens group having a positive refractive power, and a lens group having a positive refractive power. It can comprise so that it may consist of a lens group.

When the projection variable magnification optical system according to the present invention adopts the second aspect, it is preferable that the following conditional expression (7) is satisfied.
1.3 <Bfp / fw (7)
However,
Bfp: Back focus on the reduction side of the entire system at the wide-angle end (air equivalent distance)
fw: focal length of the entire system at the wide angle end

When the projection variable magnification optical system according to the present invention adopts the second aspect, it is preferable that the following conditional expression (8) is satisfied.
Lp / Imφ <15.0 (8)
However,
Lp: Distance on the optical axis from the most magnified lens surface to the most demagnified lens surface at an infinite projection distance

  In the projection variable magnification optical system according to the present invention, it is preferable that all the lenses on the reduction side of the first lens group are constituted by a single lens.

  The projection variable magnification optical system according to the present invention is preferably configured to be a zoom lens by changing only the distance between the lens groups.

  In addition, when the projection variable magnification optical system according to the present invention is a zoom lens, focusing is performed on only a part of the first lens group including the lens disposed closest to the reduction side of the first lens group in the optical axis direction. It is preferable that the inner focus method is used.

  A projection display device according to the present invention is a projection variable power optical system that projects a light source, a light valve on which light from the light source is incident, and an optical image by light modulated by the light valve onto a screen. The projection variable magnification optical system of the present invention described above is provided.

  The zooming optical system for projection according to the present invention may be a zoom lens or a varifocal lens.

  The “enlarged side” means the projected side (screen side), and the screen side is also referred to as the enlarged side for the sake of convenience when performing reduced projection. On the other hand, the “reduction side” means the original image display area side (light valve side), and the light valve side is also referred to as the reduction side for the sake of convenience when performing reduced projection.

  In addition, the above-mentioned “consisting essentially of” and “consisting essentially of a lens group” are lenses and lens groups having substantially no power other than the lens group mentioned as a constituent element. It is intended that an optical element other than a lens such as a diaphragm or a cover glass may be included.

  Note that “the reduction side is telecentric” means that the bisector of the upper maximum ray and the lower maximum ray is parallel to the optical axis in the cross section of the light beam condensed at an arbitrary point on the reduction side image plane. Is not limited to the case where it is completely telecentric, that is, the case where the bisector is completely parallel to the optical axis, and includes cases where there are some errors. means. Here, the case where there is a slight error is a case where the inclination of the bisector with respect to the optical axis is within a range of ± 3 °.

  The “lens group” does not necessarily include a plurality of lenses but also includes a single lens.

  The “Imφ” can be obtained, for example, according to the specifications of the projection variable magnification optical system or the specifications of the apparatus in which the projection variable magnification optical system is mounted.

  The “single lens” means a single lens that is not joined.

  The zooming optical system for projection according to the present invention includes, in order from the magnification side, a first lens group that is fixed during zooming, a plurality of lens groups that move during zooming, and is fixed during zooming. The final lens group is arranged, the reduction side is telecentric, a stop is arranged in the final lens group, and the numerical aperture is set to be constant over the entire zoom range. In FIG. 3, at least one lens is disposed on the enlargement side of the stop, and is configured to satisfy a predetermined conditional expression.

  Therefore, according to the present invention, the numerical aperture can be kept constant over the entire range of zooming, high telecentricity can be achieved while achieving miniaturization, and a good projection image can be obtained. A suitable projection variable magnification optical system and projection display apparatus can be provided.

Sectional drawing which shows the lens structure and light ray locus of the variable magnification optical system for projection which concerns on Example 1 of this invention. The figure which shows arrangement | positioning of a lens group in each position at the time of zooming, and a light ray locus | trajectory of the zooming optical system for projection which concerns on Example 1 of this invention. Sectional drawing which shows the lens structure and light ray locus | trajectory of the projection variable magnification optical system which concerns on Example 2 of this invention. The figure which shows arrangement | positioning of a lens group and a light ray locus | trajectory in each position at the time of zooming of the zooming optical system for projection which concerns on Example 2 of this invention. Sectional drawing which shows the lens structure and light ray locus of the variable magnification optical system for projection which concerns on Example 3 of this invention. FIG. 6 is a diagram showing the arrangement of lens groups and the ray trajectory at each position during zooming in the zooming optical system for projection according to Example 3 of the present invention. Sectional drawing which shows the lens structure and light ray locus of the variable magnification optical system for projection which concerns on Example 4 of this invention. FIG. 10 is a diagram showing the arrangement of lens groups and the ray trajectory at each position during zooming in the zooming optical system for projection according to Example 4 of the present invention. Sectional drawing which shows the lens structure and light ray locus of the variable magnification optical system for projection which concerns on Example 5 of this invention. The figure which shows arrangement | positioning of a lens group and a light ray locus | trajectory in each position at the time of zooming of the zooming optical system for projection which concerns on Example 5 of this invention. Sectional drawing which shows the lens structure and light ray locus of the variable magnification optical system for projection which concerns on Example 6 of this invention. The figure which shows arrangement | positioning of a lens group in each position at the time of zooming, and a light ray locus | trajectory of the zooming optical system for projection which concerns on Example 6 of this invention. Sectional drawing which shows the lens structure and light ray locus of the variable magnification optical system for projection which concerns on Example 7 of this invention. The figure which shows arrangement | positioning of a lens group and a light ray locus | trajectory in each position at the time of zooming of the zooming optical system for projection which concerns on Example 7 of this invention. Sectional drawing which shows the lens structure and light ray locus of the variable magnification optical system for projection which concerns on Example 8 of this invention. The figure which shows arrangement | positioning of a lens group and a light ray locus | trajectory in each position at the time of zooming of the zooming optical system for projection which concerns on Example 8 of this invention. Sectional drawing which shows the lens structure and light ray locus of the variable magnification optical system for projection which concerns on Example 9 of this invention. The figure which shows arrangement | positioning of a lens group in each position at the time of zooming, and a light ray locus | trajectory of the zooming optical system for projection which concerns on Example 9 of this invention. Sectional drawing which shows the lens structure and light ray locus of the variable magnification optical system for projection which concerns on Example 10 of this invention. The figure which shows arrangement | positioning of a lens group in each position at the time of zooming, and a light ray locus | trajectory of the zooming optical system for projection which concerns on Example 10 of this invention. Sectional drawing which shows the lens structure and light ray locus of the variable magnification optical system for projection which concerns on Example 11 of this invention. The figure which shows arrangement | positioning of a lens group in each position at the time of zooming, and a light ray locus | trajectory of the zooming optical system for projection which concerns on Example 11 of this invention. Sectional drawing which shows the lens structure and light ray locus of the variable magnification optical system for projection which concerns on Example 12 of this invention. The figure which shows arrangement | positioning of a lens group and a light ray locus | trajectory in each position at the time of zooming of the zooming optical system for projection which concerns on Example 12 of this invention. Sectional drawing which shows the lens structure and light ray locus of the variable magnification optical system for projection which concerns on Example 13 of this invention. The figure which shows arrangement | positioning of a lens group in each position at the time of zooming, and a light ray locus | trajectory of the zooming optical system for projection which concerns on Example 13 of this invention. Sectional drawing which shows the lens structure and light ray locus of the variable magnification optical system for projection which concerns on Example 14 of this invention. The figure which shows arrangement | positioning of a lens group and the light ray locus | trajectory in each position at the time of zooming of the zooming optical system for projection which concerns on Example 14 of this invention. FIG. 29A and FIG. 29B are diagrams for explaining shielding of unnecessary lower rays on the intermediate angle of view. Partial enlarged view for explaining shielding of unnecessary lower rays of intermediate angle of view FIGS. 31A to 31L are aberration diagrams of the projection variable magnification optical system according to Example 1 of the present invention. FIGS. 32A to 32L are diagrams showing aberrations of the variable magnification optical system for projection according to Example 2 of the present invention. 33A to 33L are aberration diagrams of the projection variable magnification optical system according to Example 3 of the present invention. 34 (A) to 34 (L) are graphs showing aberrations of the projection variable magnification optical system according to Example 4 of the present invention. 35 (A) to 35 (L) are graphs showing aberrations of the variable magnification optical system for projection according to Example 5 of the present invention. 36 (A) to 36 (L) are diagrams showing aberrations of the projection variable magnification optical system according to Example 6 of the present invention. FIGS. 37A to 37L are aberration diagrams of the projection variable-power optical system according to Example 7 of the present invention. 38 (A) to 38 (L) are graphs showing various aberrations of the projection variable magnification optical system according to Example 8 of the present invention. 39 (A) to 39 (L) are aberration diagrams of the projection variable magnification optical system according to Example 9 of the present invention. 40 (A) to 40 (L) are aberration diagrams of the projection variable-power optical system according to Example 10 of the present invention. 41 (A) to 41 (L) are graphs showing various aberrations of the projection variable magnification optical system according to Example 11 of the present invention. 42 (A) to 42 (L) are graphs showing aberrations of the projection variable magnification optical system according to Example 12 of the present invention. 43A to 43L are aberration diagrams of the variable magnification optical system for projection according to Example 13 of the present invention. 44 (A) to 44 (L) are aberration diagrams of the variable magnification optical system for projection according to Example 14 of the present invention. 1 is a schematic configuration diagram of a projection display device according to an embodiment of the present invention. Schematic configuration diagram of a projection display device according to another embodiment of the present invention

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, a variable power optical system for projection according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing a lens configuration at the wide-angle end of a projection variable-power optical system according to Embodiment 1 of the present invention, and FIG. 2 is a diagram when the projection variable-power optical system shown in FIG. 4 shows the movement positions of the lens units at the wide-angle end, the intermediate focal position, and the telephoto end. In FIG. 2, the moving direction of the moving lens group when changing from the wide-angle end to the intermediate focus position and from the intermediate focus position to the telephoto end is schematically shown by arrows between the positions. Both FIG. 1 and FIG. 2 also show the ray trajectories regarding the on-axis and outermost angle of view. FIGS. 3 to 28 are cross-sectional views showing other configuration examples according to the embodiment of the present invention, and correspond to projection variable magnification optical systems according to Examples 2 to 14 described later, respectively. Since the basic configuration is the same, the embodiment of the present invention will be described below mainly using the configuration example shown in FIGS. 1 and 2 as an example.

  The projection variable magnification optical system can be mounted on a projection display device for projecting a digital image used in a movie theater or the like. For example, projection for projecting image information displayed on a light valve onto a screen. It can be used as a lens. In FIG. 1 and FIG. 2, assuming that the left side of the drawing is the enlargement side and the right side is the reduction side and is mounted on a projection display device, glass blocks 2a and 2b such as color synthesis prisms (including filters) and the like. The image display surface 1 of the light valve located on the reduction side surface of the glass block 2b is also shown.

  In the projection display device, a light beam given image information on the image display surface 1 is incident on the projection variable optical system via the glass blocks 2a and 2b, and the paper surface is projected by the projection variable optical system. The image is enlarged and projected on a screen (not shown) arranged in the left direction.

  1 and 2 show an example in which the position of the reduction-side surface of the glass block 2b matches the position of the image display surface 1, but the present invention is not necessarily limited to this. 1 and 2 show only one image display surface 1, in the projection display device, the light flux from the light source is separated into three primary colors by a color separation optical system, and each of the primary colors is used. Alternatively, three light valves may be provided so that a full-color image can be displayed.

  The projection variable magnification optical system according to the present embodiment is arranged at the most enlargement side and fixed at the time of zooming, and is arranged at the most reduction side and fixed at the time of zooming. Only the last lens group, and a plurality of lens groups that are arranged between the first lens group G1 and the last lens group and move during zooming (hereinafter referred to as a zooming moving lens group). It has a lens group and is configured so that the reduction side is telecentric.

  For example, in the example shown in FIGS. 1 and 2, the first lens group G1, the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 are sequentially arranged from the enlargement side. Five lens groups are arranged. Among these, the three lens groups of the second lens group G2, the third lens group G3, and the fourth lens group G4 correspond to the moving lens group during zooming, and the fifth lens group G5 corresponds to the final lens group.

  In the example shown in FIGS. 1 and 2, the first lens group G1 is composed of six lenses (first lens L1 to sixth lens L6), and the second lens group G2 is 1 in the lenses constituting each lens group. The third lens group G3 is composed of one lens (eighth lens L8), and the fourth lens group G4 is composed of three lenses (ninth lens L9 to eleventh lens). L5), and the fifth lens group G5 includes a diaphragm 3 and seven lenses (a twelfth lens L12 to an eighteenth lens L18). However, the number of lenses constituting each lens group of the projection variable magnification optical system of the present invention is not necessarily limited to the examples shown in FIGS.

  The projection variable magnification optical system of the present embodiment has a diaphragm 3 disposed in the final lens group, and is set so that the numerical aperture is constant over the entire range of variable magnification. As the diaphragm 3, for example, a diaphragm that functions as an aperture diaphragm can be used.

  By disposing the diaphragm 3 on the reduction side with respect to all the lens groups that move at the time of zooming, even if the diaphragm 3 is a fixed diaphragm having a simple fixed aperture that does not change the diaphragm diameter, If the numerical aperture is constant and the projection magnification is the same, the image can be projected on the screen with the same brightness regardless of the projection distance. For example, it is effective when the projection distance is changed according to the size or shape of the indoor space of a movie theater or the like. Of course, a variable aperture having a variable aperture diameter can be used as the aperture 3.

  In addition, the projection variable magnification optical system according to the present embodiment is configured such that at least one lens is disposed on the enlargement side of the stop 3 in the final lens group. By disposing at least one lens that is fixed at the time of zooming in the final lens group on the magnification side from the stop 3, it becomes easy to satisfactorily correct curvature of field in the entire zooming range.

  Further, by providing the lens holding member disposed in the final lens group on the enlargement side with respect to the stop 3 to have an aperture function, the lower unnecessary light beam at the intermediate angle of view is reduced in the wide angle end and the zooming region from the wide angle end. It becomes possible to shield, and it becomes easy to improve the telecentricity. This will be described with reference to FIGS. 29A, 29B, and 30. FIG.

  FIG. 29A shows a lens cross-sectional view and a ray trajectory at the wide-angle end of the projection variable magnification optical system shown in FIG. In FIG. 29A, the upper side beam 4Aw of the on-axis marginal, the lower side beam 4Bw of the on-axis marginal, the upper side beam 5Aw of the intermediate field angle, the lower side beams 5Bw and 5Cw of the intermediate field angle, and the upper side beam 6Aw of the maximum field angle. The lower ray 6Bw of the maximum field angle is shown.

  FIG. 29B shows a lens cross section and a ray locus at the telephoto end of the projection variable magnification optical system shown in FIG. FIG. 29B shows an axial upper marginal ray 4At, an axial marginal lower ray 4Bt, an intermediate angle of view upper ray 5At, an intermediate angle of view lower ray 5Bt, a maximum angle of view upper ray 6At, and a maximum. A lower ray 6Bt of the angle of view is shown. Note that in FIG. 29B, some symbols are omitted to avoid complication of the drawing.

  In the example shown in FIGS. 29A and 29B, the lens arranged on the enlargement side of the stop 3 in the final lens group is the twelfth lens L12. FIG. 30 is a partially enlarged view of the vicinity of the twelfth lens L12 in FIG. However, in FIG. 30, illustration of light rays having the maximum angle of view is omitted. In FIG. 30, a holding member 7 for the twelfth lens L12 is additionally shown.

  As shown in FIG. 30, by providing the holding member 7 of the twelfth lens L12 with an opening function, the lowermost ray of the intermediate angle of view can be set to the lower ray 5Cw indicated by the thick line in FIG. . The holding member 7 only needs to have an opening function capable of blocking unnecessary light having an intermediate angle of view, and the shape thereof is not limited to that shown in FIG.

  If the holding member 7 of the twelfth lens L12 does not have an opening function, the lowermost ray of the intermediate angle of view becomes the lower ray 5Bw indicated by the dotted line in FIG. 30, and the lower ray of the intermediate angle of view. However, the lens system passes through the lens system more than necessary, and the telecentricity at the intermediate angle of view deteriorates.

  It is preferable to shield unnecessary rays that deteriorate the telecentricity and off-axis optical performance to such an extent that there is no practical problem. However, when trying to shield such unnecessary rays with respect to the lower ray of the intermediate angle of view, as can be seen from FIGS. 29A and 29B, on the reduction side of the stop 3, it is below the on-axis marginal. Since the side light beam passes through a position farther from the optical axis than the off-axis lower light beam, the lower light beam at the intermediate angle of view cannot be blocked on the reduction side from the stop 3. In addition, in the lens on the enlargement side from the zoom moving lens group, the lower ray of the maximum field angle at the telephoto end and the wide angle end passes through a position farther from the optical axis than the lower ray of the intermediate angle of view. For example, even if the holding member of the lens on the magnification side of the moving lens group at the time of zooming is provided with an aperture function to shield unwanted rays, the luminous flux with the maximum field angle at the telephoto end and the wide angle end and the intermediate image near the wide angle end It is difficult to improve the telecentricity for both the angular luminous flux, and the difficulty increases as the zoom ratio increases.

  As described above, by arranging a lens in the final lens group on the enlargement side with respect to the diaphragm 3 and providing the holding member of this lens with an opening function, it is possible to improve aberration correction and improve telecentricity. it can. Although it is possible to dispose only the light-shielding member having the aperture function without disposing the lens in the final lens group on the magnification side from the stop 3, it is better to dispose the lens as in this embodiment. In addition to improving aberration correction and telecentricity, space can be used efficiently, which is advantageous for further miniaturization.

Furthermore, the projection variable magnification optical system of the present embodiment is configured to satisfy the following conditional expressions (1) and (2).
Imφ / fs <0.4 (1)
30.0 <| exP | / Imφ (2)
However,
Imφ: Maximum effective image circle diameter on the reduction side fs: Combined focal length exP of the lens on the reduction side with respect to the stop exP: Imaging on the reduction side at the wide angle end when the reduction distance is the exit side Distance on the optical axis from the surface to the paraxial exit pupil position

  Conditional expression (1) defines the relationship between the maximum effective image circle diameter, so-called image circle size, and the combined focal length of the lens on the reduction side of the stop 3. If the upper limit of conditional expression (1) is exceeded, the lens diameter on the enlargement side of the first lens group G1 will increase. By configuring so as to satisfy the conditional expression (1), it is possible to reduce the size while obtaining a desired size of the image circle.

  Conditional expression (2) relates to the exit pupil position and the size of the image circle. By configuring so as to satisfy the conditional expression (2), it is possible to ensure telecentricity while obtaining a desired image circle size.

  In addition, it is preferable that the projection variable magnification optical system according to the present embodiment further has the following configurations as appropriate. In addition, as a preferable aspect, it may have one of the structures described below, or may have any combination.

  The first lens group G1 may have a negative refractive power. The first lens group G1 that is the most magnified lens group is a negative lead type optical system that is a negative lens group, which is advantageous for widening the angle.

  Alternatively, the first lens group G1 may have a positive refractive power. By using a positive lead type optical system in which the first lens group G1, which is the most magnified lens group, is a positive lens group, it is easy to obtain a high zoom ratio.

  Since the final lens group is the lens group on the most demagnifying side, it preferably has a positive refractive power so that the diameter of the lens group located on the magnifying side does not increase.

  The configuration of the moving lens unit at the time of zooming can be selected as appropriate. For example, the moving lens unit can be configured to include two or three lens units. If the moving lens unit at the time of zooming is composed of two or three lens units, it becomes easy to suppress both the enlargement of the entire system and aberration fluctuations at the time of zooming.

  For example, as the first aspect of the projection variable magnification optical system, the first lens group G1 has a negative refractive power, the final lens group has a positive refractive power, The lens unit on the most enlarged side can be configured to have a negative refractive power. By adopting such an aspect, it is easy to obtain an enlargement lens diameter in an appropriate size and obtain a high zoom ratio while obtaining a wide angle of view.

  When the configuration of the first aspect is adopted and the moving lens unit at the time of zooming is composed of two lens groups in which a negative lens group and a positive lens group are arranged in order from the magnification side, In addition to the above-described effect obtained by the aspect, an effect that the size can be further easily reduced can be obtained.

  When the configuration of the first aspect is adopted and the zooming moving lens unit is composed of three lens units in which a negative lens unit, a positive lens unit, and a positive lens unit are arranged in order from the magnification side. In addition to the above-described effect obtained by the first aspect, it is possible to obtain an effect that it becomes easier to correct the field curvature in the entire zooming range.

When the configuration of the first aspect is adopted, it is preferable that one or both of the following conditional expressions (5) and (6) are satisfied.
1.5 <Bfn / fw (5)
-10.0 <f1 / fw <-2.0 (6)
However,
Bfn: Back focus on the reduction side of the entire system at the wide angle end (air equivalent distance)
fw: focal length of the entire system at the wide angle end f1: focal length of the first lens unit

  Conditional expression (5) defines the value of the ratio of the back focus of the entire system to the focal length of the entire system at the wide-angle end in the negative lead type optical system, and is a beam splitter, cross dichroic prism, TIR. It is possible to secure an appropriate space for inserting a glass block or the like as color synthesizing means such as a prism. That is, if the lower limit of conditional expression (5) is not reached, it is difficult to ensure a long back focus, and it becomes difficult to insert a glass block or the like as a color synthesizing unit on the reduction side of the lens system.

  Conditional expression (6) defines the power of the first lens group G1 in the negative lead type optical system. If the lower limit of conditional expression (6) is not reached, the outer diameter of the lens on the enlargement side becomes large, making it difficult to widen the angle, and it becomes difficult to ensure a long back focus. It becomes difficult to insert a glass block or the like. Exceeding the upper limit of conditional expression (6) makes it difficult to correct curvature of field and distortion.

  As a second aspect of the zooming optical system for projection, the first lens group G1 has a positive refractive power, the final lens group has a positive refractive power, and the zooming moving lens group is on the magnification side. In order from the lens group having a negative refractive power, a lens group having a positive refractive power, and a lens group having a positive refractive power. Can do. With such a positive lead type lens configuration, it becomes easy to obtain a high zoom ratio. In addition, by changing the moving group at the time of zooming from the enlargement side in order of negative, positive, and positive refractive power arrangement, the variation in aberrations at the time of zooming compared to the negative, negative, and positive refractive power arrangement, In particular, it becomes easy to suppress variations in spherical aberration.

When the configuration of the second aspect is adopted, it is preferable that one or both of the following conditional expressions (7) and (8) are satisfied.
1.3 <Bfp / fw (7)
Lp / Imφ <15.0 (8)
However,
Bfp: Back focus on the reduction side of the entire system at the wide-angle end (air equivalent distance)
fw: focal length Lp of the entire system at the wide angle end: distance on the optical axis from the most enlarged lens surface to the most reduced lens surface at the projection distance infinity Imφ: maximum effective image circle diameter on the reduced side

  Conditional expression (7) defines the ratio of the ratio of the back focus of the entire system to the focal length of the entire system at the wide-angle end in a positive lead type optical system, and includes a beam splitter, a cross dichroic prism, and TIR. It is possible to secure an appropriate space for inserting a glass block or the like as color synthesizing means such as a prism. That is, if the lower limit of conditional expression (7) is not reached, it is difficult to ensure a long back focus, and it becomes difficult to insert a glass block or the like as a color synthesizing means on the reduction side of the lens system.

  Conditional expression (8) is a positive lead type optical system in which the size of the image circle and the distance on the optical axis from the most enlargement side lens surface to the most reduction side lens surface at the projection distance infinity (hereinafter, The total thickness of the lens). If the upper limit of conditional expression (8) is exceeded, the desired image circle size cannot be obtained, and it is difficult to provide a function necessary as a projection variable magnification optical system for applications such as movie theaters to which the present invention is intended. Or the total lens thickness is too large.

  In addition, the projection variable magnification optical system according to the present embodiment is not limited to adopting the first aspect and the second aspect described above, and even when adopting another structure, the structure described below is appropriately selected. It is preferable to have it.

The variable power optical system for projection according to the present embodiment preferably satisfies any one of the following conditional expressions (3), (4), and (9), or any combination.
0.7 <Ls / Lge (3)
1.8 <Bf / Imφ (4)
1.4 <Zr (9)
However,
Ls: Distance on the optical axis from the stop to the most demagnifying lens surface Lge: Distance on the optical axis from the most magnified lens surface to the most demagnifying lens surface in the final lens group Bf: Entire system at the wide-angle end Back focus (air equivalent distance)
Imφ: Maximum effective image circle diameter on the reduction side Zr: Zoom ratio of the telephoto end to the wide angle end

  Conditional expression (3) defines the position of the stop 3 in the optical axis direction in the final lens group. If the lower limit of conditional expression (3) is not reached, the total length of the lens system becomes long and the lens system becomes large.

  Conditional expression (4) relates to the ratio between the back focus and the size of the image circle. If the lower limit of conditional expression (4) is not reached, a glass block or the like as a color synthesizing means such as a beam splitter, a cross dichroic prism, or a TIR prism is provided on the reduction side of the lens system while obtaining a desired image circle size. It is difficult to secure an appropriate space for insertion.

  Conditional expression (9) defines the zoom ratio. If the lower limit of conditional expression (9) is not reached, a high zoom ratio cannot be obtained, the range that can be used as a zooming optical system for projection becomes narrow, and the cost merit is reduced. It cannot be said that it is suitable as a projection variable magnification optical system for such applications.

Moreover, it is more preferable that the following conditional expressions (1-1) to (9-1) are satisfied instead of the conditional expressions (1) to (9) described above.
Imφ / fs <0.37 (1-1)
35.0 <| exP | / Imφ (2-1)
0.8 <Ls / Lge (3-1)
2.2 <Bf / Imφ (4-1)
2.0 <Bfn / fw (5-1)
−7.0 <f1 / fw <−2.3 (6-1)
1.5 <Bfp / fw (7-1)
Lp / Imφ <12.0 (8-1)
1.5 <Zr (9-1)

  In the projection variable magnification optical system according to the present embodiment, it is preferable that all the lenses on the reduction side of the first lens group are constituted by single lenses instead of cemented lenses. On the reduction side of the first lens group, there are many portions where the on-axis light beam and off-axis light beam overlap, so that when the projection variable magnification optical system is mounted on the projection display device and used in combination with a high-output light source, However, there is a possibility that the bonding agent for bonding the lens may be significantly deteriorated and deteriorated, resulting in a decrease in lens performance. However, by not using the bonding lens, it is possible to avoid the occurrence of such a problem. In order to avoid the occurrence of such a problem as much as possible, it is more preferable that all the lenses in the entire system are constituted by a single lens instead of a cemented lens.

  In the variable power optical system for projection according to the present embodiment, as in the example shown in FIG. 1, it is possible to employ a configuration without using an aspheric surface in which each lens surface is a spherical surface. This is advantageous in terms of cost. Of course, the projection variable magnification optical system of the present embodiment can be configured to use an aspherical surface, and in this case, aberration correction can be performed more satisfactorily.

  Further, the projection variable magnification optical system of the present embodiment may be configured to be a zoom lens by changing only the distance between the lens groups. In other words, the zoom lens may be converted to the varifocal lens or the varifocal lens to the zoom lens by changing only the distance between the lens groups. According to such a configuration, it can be used for different focus type devices with a minimum change in the mechanism structure, and the cost merit can be increased.

  When the projection variable magnification optical system is a zoom lens, focusing when the projection distance changes is part of the first lens group G1 including the lens arranged closest to the reduction side of the first lens group G1. It is preferable to adopt an inner focus method in which only the lens is moved in the optical axis direction.

  For example, in the example shown in FIG. 21, focusing is performed by integrally moving the third lens L3 and the fourth lens L4, which are the first and second lenses from the reduction side of the first lens group G1, in the optical axis direction. Is possible. By adopting the inner focus method, it is not necessary to drive the enlargement side lens having a large diameter and a large weight, so that the load on the drive mechanism can be reduced and the entire lens thickness can be kept constant during focusing.

  In the variable power optical system for projection according to the present invention, focusing can be performed by moving the entire first lens group G1 or a part other than the reduction side, or other than the first lens group G1. It is also possible to move by moving all or part of the lens group.

  The projection variable magnification optical system that is the object of the present invention is preferably an optical system having an F number smaller than 3.0 in the entire variable magnification range. Further, in the variable power optical system for projection targeted by the present invention, it is preferable that distortion (distortion aberration) is suppressed to about 2% or less in the entire variable power range.

  Next, an embodiment of a projection display apparatus according to the present invention will be described with reference to FIGS. 45 and 46. FIG. 45 is a schematic configuration diagram showing a part of a projection display apparatus according to an embodiment of the present invention, and FIG. 46 is a schematic configuration diagram showing a part of a projection display apparatus according to another embodiment of the present invention. It is.

  The projection display device shown in FIG. 45 includes reflective display elements 11a to 11c as light valves corresponding to each color light, dichroic mirrors 12 and 13 for color separation, and a cross dichroic prism 14 for color composition. The illumination optical system 10 includes a total reflection mirror 18 for deflecting the optical path and polarization separation prisms 15a to 15c. Note that a light source (not shown) is disposed in front of the dichroic mirror 12.

  White light from the light source is decomposed into three colored light beams (G light, B light, and R light) by the dichroic mirrors 12 and 13. The separated color light beams pass through the polarization separation prisms 15a to 15c, enter the corresponding reflective display elements 11a to 11c, are light-modulated, and are color-combined by the cross dichroic prism 14, and then the above-mentioned. The incident light enters the projection variable magnification optical system 19 according to the embodiment. The optical image by the incident light is projected on a screen (not shown) by the projection variable magnification optical system 19.

  On the other hand, a projection display apparatus according to another embodiment shown in FIG. 46 includes reflective display elements 21a to 21c as light valves corresponding to each color light, and TIR (Total Internal Reflection) for color separation and color synthesis. An illumination optical system 20 having prisms 24 a to 24 c and a polarization separation prism 25 is provided. Note that a light source (not shown) is disposed in front of the polarization separation prism 25.

  The white light from the light source passes through the polarization separation prism 25 and is then decomposed into three color light beams (G light, B light, and R light) by the TIR prisms 24a to 24c. The separated color light beams are incident on the corresponding reflective display elements 21a to 21c to be light-modulated, proceed again in the opposite directions through the TIR prisms 24a to 24c, and are color-synthesized, and then transmitted through the polarization separation prism 25. Then, the light enters the projection variable magnification optical system 29 according to the above-described embodiment. An optical image by the incident light is projected on a screen (not shown) by the projection variable magnification optical system 29.

  In addition, as the reflective display elements 11a to 11c and 21a to 21c, for example, a reflective liquid crystal display element, DMD, or the like can be used. 45 and 46 show an example in which a reflective display element is used as a light valve. However, the light valve provided in the projection display device of the present invention is not limited to this, and a transmissive liquid crystal display element, etc. A transmissive display element may be used.

  Next, specific examples of the projection variable magnification optical system according to the present invention will be described. Among Examples 1 to 14 described below, Examples 1 to 10 are negative lead type optical systems in which the first lens group has negative refractive power, and Examples 11 to 14 are positive for the first lens group. This is a positive lead type optical system having refractive power. Moreover, Examples 1-8 and 11-14 are 5 group structures, and Example 9, 10 is a 4 group structure.

  Although Examples 1 to 14 described below are configured as varifocal lenses, Examples 5, 9, and 11 can be zoomed by changing only the distance between lens groups, as will be described later as modified examples. It is configured to be used as a lens. When Examples 1 to 14 are used as varifocal lenses, focusing at the time of zooming or when the projection distance is changed is performed by an entire payout system in which the entire system is integrally moved in the optical axis direction. .

<Example 1>
FIG. 1 and FIG. 2 show the lens configuration and ray trajectory at the wide-angle end of the projection variable magnification optical system of Example 1, respectively, the arrangement of lens groups and ray trajectory at each position during zooming. The configurations shown in FIGS. 1 and 2 are those when the reduction ratio is −0.002 times. Since the detailed description of FIGS. 1 and 2 is as described above, a part of the overlapping description is omitted here.

  The variable power optical system for projection of Example 1 includes, in order from the magnification side, a first lens group G1 having a negative refractive power, a second lens group G2 having a negative refractive power, and a first lens group having a positive refractive power. This is a five-group configuration in which a three-lens group G3, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a positive refractive power are arranged, and the reduction side is telecentric. On the reduction side of the lens group G5, glass blocks 2a and 2b such as an image display surface 1 of a light valve composed of a reflective liquid crystal display panel and a color synthesis prism (including filters such as an infrared cut filter and a low-pass filter) are disposed. Has been.

  At the time of zooming, the first lens group G1 and the fifth lens group G5 are fixed, the second lens group G2, the third lens group G3, and the fourth lens group G4 are movable. It is represented. Further, the numerical aperture is set to be constant over the entire range of zooming.

  The first lens group G1, in order from the magnifying side, a first lens L1 made of a positive meniscus lens having a convex surface on the magnifying side, a second lens L2 made of a negative meniscus lens having a concave surface on the reducing side, A third lens L3 made of a negative meniscus lens having a concave surface facing the reduction side, a fourth lens L4 made of a biconcave lens, a fifth lens L5 made of a negative meniscus lens having a convex surface facing the enlargement side, and a biconvex lens And a sixth lens L6. The fifth lens L5 and the sixth lens L6 are cemented.

  The second lens group G2 includes a seventh lens L7 made of a biconcave lens. The third lens group G3 includes an eighth lens L8 made of a positive meniscus lens having a convex surface directed toward the reduction side. The fourth lens group G4 includes, in order from the magnifying side, a ninth lens L9 made of a biconvex lens, a tenth lens L10 made of a negative meniscus lens having a convex surface facing the magnifying side, and an eleventh lens L11 made of a biconvex lens. It is composed of

  The fifth lens group G5 has, in order from the magnifying side, a twelfth lens L12 made of a negative meniscus lens having a convex surface directed toward the magnifying side, an aperture (including an aperture and a variable aperture) 3, and a convex surface directed toward the magnifying side. A thirteenth lens L13 made of a positive meniscus lens, a fourteenth lens L14 made of a negative meniscus lens having a convex surface facing the enlargement side, a fifteenth lens L15 made of a biconvex lens, and a sixteenth lens L16 made of a biconcave lens The 17th lens L17 which consists of a biconvex lens, and the 18th lens L18 which consists of a biconvex lens.

  The variable power optical system for projection according to the first exemplary embodiment includes a single lens in which all the lenses on the reduction side of the first lens group G1 are not cemented. Moreover, since all the lens surfaces are spherical and no aspherical surface is used, this is advantageous in terms of cost.

  The upper table of Table 1 shows basic lens data of the projection variable magnification optical system of Example 1. Table 1 also shows the diaphragm 3 and the glass blocks 2a and 2b. In Table 1, in the column of Si, i-th (i = 1) when the surface number is given to the component so that the surface on the enlargement side of the component on the most enlargement side is first and increases sequentially toward the reduction side. 2, 3, ...). The Ri column indicates the radius of curvature of the i-th surface, and the Di column indicates the surface spacing on the optical axis Z between the i-th surface and the i + 1-th surface. Further, in the column of Ndj, the d-line (wavelength 587.6 nm) of the j-th (j = 1, 2, 3,. The νdj column indicates the Abbe number of the j-th component with respect to the d-line.

  However, the sign of the radius of curvature is positive when the surface shape is convex on the enlargement side and negative when the surface shape is convex on the reduction side. The distance between the first lens group G1 and the second lens group G2, the distance between the second lens group G2 and the third lens group G3, the distance between the third lens group G3 and the fourth lens group G4, and the fourth lens group G4 and the fifth lens group G4. The interval of the lens group G5 is a variable interval that changes at the time of zooming, and (variable 1), (variable 2), (variable 3), and (variable 4) are entered in the columns corresponding to these intervals, respectively. Yes.

  The lower table of Table 1 shows the focal length of the entire system at the wide-angle end, the intermediate focal position, and the telephoto end, and the values of the variable intervals (variable 1), (variable 2), (variable 3), and (variable 4). . Further, at the top of Table 1, the F number Fno. Of the projection variable magnification optical system of Example 1 is shown. And a full angle of view 2ω.

  The data in Table 1 are values when the focal length of the entire projection variable magnification optical system at the wide angle end is normalized to 10.0. In Table 1, numerical values rounded by a predetermined digit are shown.

  31A to 31D respectively show spherical aberration, astigmatism, distortion (distortion aberration), and chromatic aberration of magnification (chromatic aberration of magnification) of the projection variable magnification optical system of Example 1 at the wide-angle end. An aberration diagram is shown. 31E to 31H show the spherical aberration, astigmatism, distortion (distortion aberration), and chromatic aberration of magnification (chromatic aberration of magnification) of the projection variable magnification optical system of Example 1 at the intermediate focal position, respectively. Each aberration diagram is shown. 31 (I) to 31 (L), respectively, the spherical aberration, astigmatism, distortion (distortion aberration), and lateral chromatic aberration (chromatic aberration of magnification) of the projection variable magnification optical system of Example 1 at the telephoto end. An aberration diagram is shown.

  The aberration diagrams in FIGS. 31A to 31L are based on the d-line, but in the spherical aberration diagram, the F-line (wavelength wavelength 486.1 nm) and the C-line (wavelength 656.3 nm). ) Also shows aberrations, and the lateral chromatic aberration diagram shows aberrations related to the F-line and C-line. In the astigmatism diagram, aberrations in the sagittal direction and the tangential direction are indicated by a solid line and a broken line, respectively. F described above the vertical axis of the spherical aberration diagram indicates the F number, and ω described above the vertical axis of the other aberration diagrams indicates the half angle of view. The aberration diagrams in FIGS. 31A to 31L are obtained when the reduction magnification is −0.002 times.

  The symbols, meanings, and description methods of the lens configuration diagram, lens group arrangement diagram, table, and aberration diagram of Example 1 described above are basically the same for the following Examples 2 to 14 unless otherwise specified. is there. In addition, the lens configuration diagram, the lens group arrangement diagram, and the aberration diagram of Example 1 described above are those when the reduction magnification is −0.002 times, and the basic lens data is standardized with a focal length of 10.0. The same applies to the following Examples 2 to 14.

<Example 2>
FIGS. 3 and 4 show the lens configuration and ray trajectory at the wide-angle end of the projection variable magnification optical system of Example 2, respectively, and the arrangement of the lens groups and ray trajectories at each position during zooming. The projection variable magnification optical system according to Example 2 has substantially the same configuration as the projection variable magnification optical system according to Example 1, but the fifth lens L5 of the first lens group G1 is formed of a biconcave lens. The point is that the eighth lens L8 of the third lens group G3 is a biconvex lens, the tenth lens L10 of the fourth lens group G4 is a biconcave lens, and the twelfth lens L12 of the fifth lens group G5 is a biconcave lens. This is different in that the thirteenth lens L13 of the fifth lens group G5 is composed of a biconvex lens.

  F-number Fno. Of the variable power optical system for projection of Example 2. The total field angle 2ω is shown at the top of Table 2, the basic lens data is shown in the upper table of Table 2, and the focal length of the entire system at the wide angle end, the intermediate focal position, the telephoto end, and the value of each variable interval are shown. The results are shown in the lower table of Table 2. FIGS. 32A to 32L show aberration diagrams of the variable power optical system for projection according to Example 2. FIG.

<Example 3>
FIG. 5 and FIG. 6 show the lens configuration and ray trajectory at the wide angle end of the projection variable magnification optical system of Example 3, respectively, the arrangement of the lens groups and the ray trajectory at each position during zooming. The variable power optical system for projection according to Example 3 has substantially the same configuration as the variable power optical system for projection according to Example 1, but the fourth lens L4 of the first lens group G1 is flat on the enlargement side. The fifth lens L5 of the first lens group G1 is a biconcave lens, the eighth lens L8 of the third lens group G3 is a biconvex lens, and the fourth lens group G4 is the fourth lens group G4. The tenth lens L10 is formed of a biconcave lens, the twelfth lens L12 of the fifth lens group G5 is formed of a planoconcave lens with the plane facing the enlargement side, and the aperture stop 3 is provided on the reduction side surface of the thirteenth lens L13. Are different.

  F-number Fno. Of the variable power optical system for projection of Example 3. And the total angle of view 2ω are shown at the top of Table 3, the basic lens data is shown in the upper table of Table 3, and the focal length of the entire system at the wide angle end, the intermediate focal position, the telephoto end, and the value of each variable interval The results are shown in the lower table of Table 3, respectively. In addition, FIGS. 33A to 33L show aberration diagrams of the projection variable magnification optical system of Example 3, respectively.

<Example 4>
FIG. 7 and FIG. 8 show the lens configuration and the ray trajectory at the wide-angle end of the projection variable magnification optical system of Example 4, respectively, the arrangement of the lens groups and the ray trajectory at each position during zooming. The projection variable optical system according to Example 4 has substantially the same configuration as the projection variable optical system according to Example 1, but the eleventh lens L11 of the fourth lens group G4 is convex on the enlargement side. It is different in that it is composed of a positive meniscus lens facing.

  F-number Fno. Of the variable power optical system for projection of Example 4. The total field angle 2ω is shown at the top of Table 4, the basic lens data is shown in the upper table of Table 4, the focal length of the entire system at the wide angle end, the intermediate focal position, the telephoto end, and the values of each variable interval. The results are shown in the lower table of Table 4, respectively. Further, FIGS. 34A to 34L show aberration diagrams of the variable power optical system for projection according to Example 4, respectively.

<Example 5>
FIG. 9 and FIG. 10 show the lens configuration and ray trajectory at the wide angle end of the projection variable magnification optical system of Example 5, respectively, the arrangement of the lens groups and the ray trajectory at each position during zooming. The projection variable optical system according to Example 5 has substantially the same configuration as the projection variable optical system according to Example 1, but the fourth lens L4 of the first lens group G1 is flat on the enlargement side. The fifth lens L5 is a biconcave lens, the eighth lens L8 of the third lens group G3 is a biconvex lens, and the tenth lens L10 of the fourth lens group G4 is both The difference is that the lens is made of a concave lens, and the twelfth lens L12 of the fifth lens group G5 is made of a plano-concave lens with the plane facing the enlargement side.

  F-number Fno. Of the variable power optical system for projection of Example 5. And the total angle of view 2ω are shown at the top of Table 5, basic lens data is shown in the upper table of Table 5, the focal length of the entire system at the wide angle end, the intermediate focus position, the telephoto end, and the values of each variable interval. The results are shown in the lower table of Table 5, respectively. FIGS. 35A to 35L show aberration diagrams of the projection variable magnification optical system of Example 5. FIGS.

<Example 6>
FIGS. 11 and 12 show the lens configuration and the ray trajectory at the wide-angle end of the projection variable magnification optical system of Example 6, respectively, the arrangement of the lens groups and the ray trajectory at each position during zooming. In the variable power optical system for projection according to Example 6, the sign of the refractive power of each lens group of the first lens group G1 to the fifth lens group G5, the fixed group at the time of zooming, and the moving group are described in Example 1. Although the configuration is the same as that of the projection variable magnification optical system, the lens configuration of each lens unit is different from that of the first embodiment as described below.

  The first lens group G1 includes, in order from the magnification side, a first lens L1 composed of a biconvex lens, a second lens L2 composed of a negative meniscus lens having a concave surface facing the reduction side, and a negative lens facing the concave surface toward the reduction side. The lens includes a third lens L3 made of a meniscus lens, a fourth lens L4 made of a biconcave lens, a fifth lens L5 made of a biconcave lens, and a sixth lens L6 made of a biconvex lens. The fifth lens L5 and the sixth lens L6 are cemented.

  The second lens group G2 includes a seventh lens L7 made of a biconcave lens. The third lens group G3 includes an eighth lens L8 made of a biconvex lens. The fourth lens group G4 includes, in order from the magnification side, a ninth lens L9 made of a biconvex lens, a tenth lens L10 made of a biconcave lens, and an eleventh lens L11 made of a biconvex lens.

  The fifth lens group G5 includes, in order from the magnifying side, a twelfth lens L12 made of a biconcave lens, a thirteenth lens L13 made of a positive meniscus lens having a convex surface facing the magnifying side, and a reduction-side surface of the thirteenth lens L13. 3 (including an aperture and a variable aperture), a 14th lens L14 made of a biconvex lens, a 15th lens L15 made of a biconcave lens, a 16th lens L16 made of a biconvex lens, and a biconvex lens. The 17th lens L17 and the 18th lens L18 which consists of a plano-convex lens which orient | assigned the plane to the reduction side are comprised.

  The variable power optical system for projection of Example 6 is composed of a single lens in which all the lenses on the reduction side of the first lens group G1 are not cemented. Moreover, since all the lens surfaces are spherical and no aspherical surface is used, this is advantageous in terms of cost.

  F-number Fno. Of the variable power optical system for projection of Example 6. And the total angle of view 2ω are shown at the top of Table 10, basic lens data is shown in the upper table of Table 6, and the focal length of the entire system at the wide angle end, the intermediate focal position, the telephoto end, and the values of each variable interval are shown. The results are shown in the lower table of Table 6, respectively. FIGS. 36A to 36L show aberration diagrams of the projection variable magnification optical system of Example 6. FIGS.

<Example 7>
FIG. 13 and FIG. 14 show the lens configuration and ray trajectory at the wide angle end of the projection variable magnification optical system of Example 7, respectively, the arrangement of the lens groups and the ray trajectory at each position during zooming. The projection variable magnification optical system according to Example 7 has substantially the same configuration as the projection variable magnification optical system according to Example 6, but the fifth lens L5 of the first lens group G1 is convex on the enlargement side. The lens is composed of a negative meniscus lens facing the lens, the eighth lens L8 of the third lens group G3 is composed of a positive meniscus lens having a concave surface facing the enlargement side, and the thirteenth lens L13 of the fifth lens group G5 is composed of a biconvex lens. The point is that the fourteenth lens L14 is a negative meniscus lens having a convex surface facing the enlargement side, the fifteenth lens L15 is a biconvex lens, the sixteenth lens L16 is a biconcave lens, and the eighteenth lens L18 is a biconvex lens This is different in that the diaphragm 3 is provided between the twelfth lens L12 and the thirteenth lens L13.

  F-number Fno. Of the variable power optical system for projection of Example 7. And the total angle of view 2ω are shown at the top of Table 7, the basic lens data is shown in the upper table of Table 7, the focal length of the entire system at the wide angle end, the intermediate focal position, the telephoto end, and the values of each variable interval. The results are shown in the lower table of Table 7, respectively. FIGS. 37A to 37L show aberration diagrams of the projection variable magnification optical system of Example 7. FIGS.

<Example 8>
FIGS. 15 and 16 show the lens configuration and ray trajectory at the wide-angle end of the projection variable magnification optical system of Example 8, respectively, the arrangement of the lens groups and the ray trajectory at each position during zooming. In the variable power optical system for projection according to Example 8, the sign of the refractive power of each lens group of the first lens group G1 to the fifth lens group G5, the fixed group at the time of zooming, and the moving group are described in Example 1. Although the configuration is the same as that of the projection variable magnification optical system, the lens configuration of each lens unit is different from that of the first embodiment as described below.

  The first lens group G1, in order from the magnifying side, a first lens L1 made of a positive meniscus lens having a convex surface on the magnifying side, a second lens L2 made of a negative meniscus lens having a concave surface on the reducing side, The lens includes a third lens L3 made of a plano-concave lens having a concave surface facing the reduction side, a fourth lens L4 made of a biconcave lens, and a fifth lens L5 made of a biconvex lens.

  The second lens group G2 includes, in order from the enlargement side, a sixth lens L6 made of a biconcave lens and a seventh lens L7 made of a positive meniscus lens having a convex surface facing the reduction side. The third lens group G3 includes, in order from the enlargement side, an eighth lens L8 made of a negative meniscus lens having a convex surface directed toward the reduction side, and a ninth lens L9 made of a biconvex lens. The fourth lens group G4 includes, in order from the magnification side, a tenth lens L10 made of a negative meniscus lens having a convex surface directed toward the magnification side, and an eleventh lens L11 made of a biconvex lens.

  The fifth lens group G5 has, in order from the magnifying side, a twelfth lens L12 made of a positive meniscus lens having a convex surface directed toward the magnifying side, an aperture (including an aperture and a variable aperture) 3, and a convex surface directed toward the magnifying side. A thirteenth lens L13 composed of a negative meniscus lens, a fourteenth lens L14 composed of a biconcave lens, a fifteenth lens L15 composed of a biconvex lens, a sixteenth lens L16 composed of a biconvex lens, and a seventeenth lens L17 composed of a biconvex lens. It consists of and.

  The projection variable magnification optical system of Example 8 is composed of a single lens in which all the lenses are not cemented. Moreover, since all the lens surfaces are spherical and no aspherical surface is used, this is advantageous in terms of cost.

  F-number Fno. Of the variable magnification optical system for projection according to the eighth embodiment. And the total angle of view 2ω are shown at the top of Table 8, the basic lens data is shown in the upper table of Table 8, the focal length of the entire system at the wide angle end, the intermediate focus position, the telephoto end, and the values of each variable interval. The results are shown in the lower table of Table 8, respectively. FIGS. 38A to 38L show aberration diagrams of the projection variable magnification optical system of Example 8. FIGS.

<Example 9>
FIGS. 17 and 18 show the lens configuration and the ray trajectory at the wide-angle end of the projection variable magnification optical system of Example 9, respectively, the arrangement of the lens groups and the ray trajectory at each position during zooming. The projection variable magnification optical system according to Example 9 has, in order from the enlargement side, a first lens group G1 having a negative refractive power, a second lens group G2 having a negative refractive power, and a positive refractive power. The third lens group G3 and a fourth lens group G4 having a positive refractive power are arranged in a four-group configuration, the reduction side is telecentric, and the fourth lens group G4 has a reflective liquid crystal on the reduction side. Glass blocks 2a and 2b such as a light valve image display surface 1 including a display panel and a color synthesis prism (including filters such as an infrared cut filter and a low-pass filter) are disposed.

  At the time of zooming, the first lens group G1 and the fourth lens group G4 are fixed, the second lens group G2 and the third lens group G3 are movable, and the movable mode is shown in FIG. Further, the numerical aperture is set to be constant over the entire range of zooming.

  The first lens group G1 includes, in order from the magnifying side, a first lens L1 made of a plano-convex lens having a convex surface on the magnifying side, a second lens L2 made of a negative meniscus lens having a concave surface on the reducing side, and a biconcave lens. The third lens L3 and the fourth lens L4, a fifth lens L5 made of a negative meniscus lens having a concave surface facing the reduction side, and a sixth lens L6 made of a biconvex lens. The fifth lens L5 and the sixth lens L6 are cemented.

  The second lens group G2 includes, in order from the enlargement side, a seventh lens L7 made of a negative meniscus lens having a convex surface facing the reduction side, and an eighth lens L8 made of a positive meniscus lens having a convex surface facing the reduction side. Has been. The third lens group G3 includes, in order from the enlargement side, a ninth lens L9 made of a positive meniscus lens having a convex surface facing the reduction side, and a tenth lens L10 made of a negative meniscus lens having a convex surface facing the reduction side, It is composed of an eleventh lens L11 made of a biconvex lens.

  The fourth lens group G4 has, in order from the magnifying side, a twelfth lens L12 made of a biconcave lens, a diaphragm (including an aperture and a variable diaphragm) 3, a thirteenth lens L13 made of a biconvex lens, and a concave surface facing the reduction side. A fourteenth lens L14 made of a negative meniscus lens, a fifteenth lens L15 made of a biconvex lens, a sixteenth lens L16 made of a biconcave lens, a seventeenth lens L17 made of a biconvex lens, and an eighteenth lens made of a biconvex lens. L18.

  The projection variable magnification optical system of Example 9 is composed of a single lens in which all the lenses on the reduction side of the first lens group G1 are not cemented. Moreover, since all the lens surfaces are spherical and no aspherical surface is used, this is advantageous in terms of cost.

  F-number Fno. Of the variable power optical system for projection of Example 9. The total field angle 2ω is shown at the top of Table 9, the basic lens data is shown in the upper table of Table 9, and the focal length of the entire system at the wide angle end, the intermediate focal position, the telephoto end, and the value of each variable interval are shown. The results are shown in the lower table of Table 9, respectively. FIGS. 39A to 39L show aberration diagrams of the projection variable magnification optical system of Example 9.

<Example 10>
FIGS. 19 and 20 show the lens configuration and the ray trajectory at the wide-angle end of the projection variable magnification optical system of Example 10, respectively, the arrangement of the lens groups and the ray trajectory at each position during zooming. The variable power optical system for projection according to Example 10 has substantially the same configuration as the variable power optical system for projection according to Example 9, but the first lens L1 of the first lens group G1 is more than a biconvex lens. Is different.

  F-number Fno. Of the variable power optical system for projection of Example 10. The total angle of view 2ω is shown at the top of Table 10, the basic lens data is shown in the upper table of Table 10, the focal length of the entire system at the wide angle end, the intermediate focus position, the telephoto end, and the value of each variable interval. The results are shown in the lower table of Table 10, respectively. FIGS. 40A to 40L show aberration diagrams of the projection variable magnification optical system of Example 10. FIG.

<Example 11>
FIG. 21 and FIG. 22 show the lens configuration and ray trajectory at the wide angle end of the projection variable magnification optical system of Example 11, respectively, the arrangement of the lens groups and the ray trajectory at each position during zooming. The projection variable magnification optical system according to Example 11 has, in order from the magnification side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive power. The third lens group G3, the fourth lens group G4 having a positive refractive power, and the fifth lens group G5 having a positive refractive power are arranged in a five-group configuration, and the reduction side is telecentric. On the reduction side of the five lens group G5, there are glass blocks 2a and 2b such as an image display surface 1 of a light valve composed of a reflective liquid crystal display panel and the like, and a color synthesis prism (including filters such as an infrared cut filter and a low-pass filter). Has been placed.

  At the time of zooming, the first lens group G1 and the fifth lens group G5 are fixed, the second lens group G2, the third lens group G3, and the fourth lens group G4 are movable. It is represented. Further, the numerical aperture is set to be constant over the entire range of zooming.

  The first lens group G1 includes, in order from the enlargement side, a first lens L1 made of a negative meniscus lens having a convex surface on the enlargement side, a second lens L2 made of a plano-convex lens having a flat surface on the reduction side, and an enlargement side. It is composed of a third lens L3 made of a positive meniscus lens having a convex surface and a fourth lens L4 made of a biconvex lens.

  The second lens group G2 includes, in order from the magnifying side, a fifth lens L5 made of a negative meniscus lens having a convex surface on the magnifying side, a sixth lens L6 made of a biconcave lens, and a positive meniscus lens having a convex surface on the magnifying side. And a seventh lens L7.

  The third lens group G3 includes, in order from the magnification side, an eighth lens L8 made of a negative meniscus lens having a convex surface facing the magnification side, and a ninth lens L9 made of a biconvex lens. The fourth lens group G4 includes a tenth lens L10 made of a biconvex lens.

  The fifth lens group G5 includes, in order from the magnifying side, an eleventh lens L11 made of a biconcave lens, a twelfth lens L12 made of a positive meniscus lens having a convex surface facing the magnifying side, and an aperture (including an aperture and a variable aperture) 3 A thirteenth lens L13 made of a biconcave lens, a fourteenth lens L14 made of a plano-convex lens having a convex surface on the reduction side, a fifteenth lens L15 made of a negative meniscus lens having a convex surface on the reduction side, and on the enlargement side The lens includes a sixteenth lens L16 made of a negative meniscus lens having a convex surface, a seventeenth lens L17 made of a biconvex lens, and an eighteenth lens L18 made of a biconvex lens.

  The projection variable magnification optical system of Example 11 is composed of a single lens in which all the lenses are not cemented. Moreover, since all the lens surfaces are spherical and no aspherical surface is used, this is advantageous in terms of cost.

  F-number Fno. Of the variable power optical system for projection of Example 11 And the total angle of view 2ω are shown at the top of Table 11, basic lens data is shown in the upper table of Table 11, and the focal length of the entire system at the wide angle end, the intermediate focal position, the telephoto end, and the values of each variable interval are shown. The results are shown in the lower table of Table 11, respectively. In addition, FIGS. 41A to 41L show aberration diagrams of the projection variable magnification optical system of Example 11, respectively.

<Example 12>
FIG. 23 and FIG. 24 show the lens configuration and ray trajectory at the wide-angle end of the projection variable magnification optical system of Example 12, respectively, the arrangement of the lens groups and the ray trajectory at each position during zooming. The variable power optical system for projection according to Example 12 is the same as in Example 11 regarding the sign of the refractive power of each lens group of the first lens group G1 to the fifth lens group G5, the fixed group at the time of zooming, and the moving group. Although the configuration is the same as that of the projection variable magnification optical system, the lens configuration of each lens group is different from that of Example 11 as described below.

  The first lens group G1 includes, in order from the magnification side, a first lens L1 composed of a negative meniscus lens having a convex surface facing the magnification side, a second lens L2 composed of a positive meniscus lens having a convex surface facing the magnification side, and a biconvex lens. And a third lens L3.

  The second lens group G2 includes, in order from the magnifying side, a fourth lens L4 made of a negative meniscus lens having a convex surface facing the magnifying side, a fifth lens L5 made of a biconcave lens, and a positive meniscus lens having a convex surface facing the magnifying side. And a sixth lens L6.

  The third lens group G3 includes, in order from the magnification side, a seventh lens L7 made of a negative meniscus lens having a convex surface facing the magnification side, and an eighth lens L8 made of a biconvex lens. The fourth lens group G4 includes a ninth lens L9 made of a biconvex lens.

  The fifth lens group G5 includes, in order from the magnifying side, a tenth lens L10 made of a biconcave lens, an eleventh lens L11 made of a positive meniscus lens having a convex surface facing the magnifying side, and an aperture (including an aperture and a variable aperture) 3 A twelfth lens L12 made of a biconcave lens, a thirteenth lens L13 made of a biconvex lens, a fourteenth lens L14 made of a negative meniscus lens having a convex surface on the reduction side, and a negative meniscus lens having a convex surface on the magnification side And a sixteenth lens L16 made of a biconvex lens, and a seventeenth lens L17 made of a biconvex lens.

  The projection variable magnification optical system of Example 12 is composed of a single lens in which all the lenses are not cemented. Moreover, since all the lens surfaces are spherical and no aspherical surface is used, this is advantageous in terms of cost.

  F-number Fno. Of the variable power optical system for projection of Example 12. And the total field angle 2ω are shown at the top of Table 12, basic lens data is shown in the upper table of Table 12, and the focal length of the entire system at the wide-angle end, the intermediate focal position, the telephoto end, and the value of each variable interval are shown. The results are shown in the lower table of Table 12, respectively. FIGS. 42A to 42L show aberration diagrams of the projection variable magnification optical system of Example 12. FIGS.

<Example 13>
FIGS. 25 and 26 show the lens configuration and light ray locus at the wide angle end of the projection variable magnification optical system of Example 13, respectively, the arrangement of the lens groups and the light ray locus at each position during magnification. The projection variable optical system according to Example 13 has substantially the same configuration as the projection variable optical system according to Example 12, but the fourteenth lens L14 of the fifth lens group G5 is convex on the reduction side. A point consisting of a positive meniscus lens facing the lens, a point consisting of a fifteenth lens L15 consisting of a negative meniscus lens having a convex surface facing the reduction side, a point consisting of a negative meniscus lens facing the convex surface facing the magnification side, a fifth lens The difference is that the lens group G5 further includes an eighteenth lens L18 made of a biconvex lens disposed on the most reduction side.

  The fifth lens group G5 of the variable power optical system for projection according to Example 13 includes, in order from the magnifying side, a tenth lens L10 made of a biconcave lens and an eleventh lens L11 made of a positive meniscus lens having a convex surface facing the magnifying side. A diaphragm (including an aperture and a variable diaphragm) 3, a twelfth lens L12 made of a biconcave lens, a thirteenth lens L13 made of a biconvex lens, and a fourteenth lens L14 made of a negative meniscus lens having a convex surface facing the reduction side. And a fifteenth lens L15 made of a negative meniscus lens having a convex surface facing the enlargement side, a sixteenth lens L16 made of a biconvex lens, and a seventeenth lens L17 made of a biconvex lens.

  F-number Fno. Of the variable power optical system for projection of Example 13 And the total field angle 2ω are shown at the top of Table 13, basic lens data is shown in the upper table of Table 13, and the focal length of the entire system at the wide angle end, the intermediate focal position, the telephoto end, and the values of the variable intervals are shown. The results are shown in the lower table of Table 13, respectively. In addition, FIGS. 43A to 43L show aberration diagrams of the zooming optical system for projection according to Example 13, respectively.

<Example 14>
FIGS. 27 and 28 show the lens configuration and ray trajectory at the wide-angle end of the projection variable magnification optical system of Example 14, respectively, the arrangement of the lens groups and the ray trajectory at each position during zooming. The projection variable optical system according to Example 14 has substantially the same configuration as the projection variable optical system according to Example 13, but the second lens L2 of the first lens group G1 is a biconvex lens. The third lens L3 is different from the fifth lens group G5 in that the third lens L3 is composed of a positive meniscus lens having a convex surface facing the enlargement side.

  The fifth lens group G5 includes, in order from the magnifying side, a tenth lens L10 made of a biconcave lens, an eleventh lens L11 made of a positive meniscus lens having a convex surface facing the magnifying side, and an aperture (including an aperture and a variable aperture) 3 A twelfth lens L12 made of a negative meniscus lens having a convex surface facing the enlargement side, a thirteenth lens L13 made of a biconcave lens, a fourteenth lens L14 made of a biconvex lens, and a fifteenth lens L15 made of a biconcave lens, The lens includes a sixteenth lens L16 made of a biconvex lens, a seventeenth lens L17 made of a positive meniscus lens having a convex surface facing the reduction side, and an eighteenth lens L18 made of a biconvex lens.

  F-number Fno. Of the variable power optical system for projection of Example 14 And the total field angle 2ω are shown at the top of Table 14, basic lens data is shown in the upper table of Table 14, and the focal length of the entire system at the wide angle end, the intermediate focal position, the telephoto end, and the values of each variable interval are shown. The results are shown in the lower table of Table 14, respectively. FIGS. 44A to 44L show aberration diagrams of the projection variable magnification optical system of Example 14, respectively.

  Table 15 shows values related to the values corresponding to the conditional expressions (1) to (9) of Examples 1 to 14. The sign of exP is negative when the paraxial exit pupil position is on the enlargement side with respect to the reduction-side image plane, and is positive when the paraxial exit pupil position is on the reduction side. As shown in Table 15, the projection variable magnification optical systems of Examples 1 to 10 satisfy all conditional expressions (1) to (6) and (9), and the projection variable magnifications of Examples 11 to 14 are used. The optical system satisfies all conditional expressions (1) to (4) and (7) to (9).

  In Examples 1 to 14 described above, the reduction side is telecentric, has a sufficient back focus, does not employ an aspheric surface, and has an F number of about 2.5 over the entire zoom range from the wide angle end to the telephoto end. Although the zoom ratio is as small as 1.5 to 2.0, fluctuations in aberrations during zooming are suppressed, and each optical aberration is corrected well, resulting in high optical performance. It is what has.

<Modification of Example 5>
The fifth embodiment is configured to be a zoom lens by changing only the distance between the lens groups. Table 16 shows the focal length of the entire system at the wide-angle end, the intermediate focal position, and the telephoto end when the projection distance is infinite when using Example 5 as a zoom lens by changing only the distance between the lens groups in Table 16. The distance of each variable interval is shown. When the modified example of the fifth embodiment is used as a zoom lens, the cemented lens in which the fifth lens L5 and the sixth lens L6 of the first lens group G1 are cemented is used as the optical axis for focusing when the projection distance varies. An inner focus method is adopted, which is performed by moving in the direction. In Table 16, the surface interval that changes during the focusing, that is, the interval between the fourth lens L4 and the fifth lens L5 is shown as D8.

<Modification of Example 9>
The ninth embodiment is also configured to be a zoom lens by changing only the distance between the lens groups. Table 17 shows the total focal length at the wide-angle end, the intermediate focal position, and the telephoto end when the projection distance is infinite when using Example 9 as a zoom lens by changing only the distance between the lens groups in Table 17. The distance of each variable interval is shown. When the modified example of the ninth embodiment is used as a zoom lens, the cemented lens in which the fifth lens L5 and the sixth lens L6 of the first lens group G1 are cemented is used as the optical axis for focusing when the projection distance varies. An inner focus method is adopted, which is performed by moving in the direction. In Table 17, the surface interval that changes during the focusing, that is, the interval between the fourth lens L4 and the fifth lens L5 is shown as D8.

<Modification of Example 11>
The eleventh embodiment is also configured to be a zoom lens by changing only the distance between the lens groups. Table 18 shows the focal length of the entire system at the wide-angle end, the intermediate focal position, and the telephoto end when the projection distance is infinite when using Example 11 as a zoom lens by changing only the distance between the lens groups in Table 18. The distance of each variable interval is shown. When the modified example of Example 11 is used as a zoom lens, the third lens L3 and the fourth lens L4 of the first lens group G1 are moved together in the optical axis direction for focusing when the projection distance varies. The inner focus method is used. In Table 18, the surface interval that changes during the focusing, that is, the interval between the second lens L2 and the third lens L3 is shown as D4.

  As described above, the present invention has been described with reference to the embodiments and examples. However, the projection variable magnification optical system according to the present invention is not limited to the above examples, and various modifications can be made. For example, the radius of curvature, the surface interval, the refractive index, and the Abbe number of each lens can be appropriately changed.

  Further, the projection display device of the present invention is not limited to the above configuration, and for example, the light valve used and the optical member used for light beam separation or light beam synthesis are not limited to the above configuration, Various modifications can be made.

DESCRIPTION OF SYMBOLS 1 Image display surface 2a, 2b Glass block 3 Aperture 10, 20 Illumination optical system 11a-11c, 21a-21c Reflective display element 12, 13 Dichroic mirror 14 Cross dichroic prism 15a-15c, 25 Polarization separation prism 18 Total reflection mirror 19 , 29 Variable magnification optical system for projection 24a to 24c TIR prism G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group G5 Fifth lens group Z Optical axis

Claims (15)

A first lens group arranged closest to the enlargement side and fixed during zooming; a final lens group arranged closest to the reduction side and fixed during zooming; the first lens group; It is substantially composed of a plurality of lens groups that are arranged between the last lens group and move during zooming,
The reduction side is telecentric,
A diaphragm is disposed in the final lens group, and the numerical aperture is set to be constant over the entire range of zooming,
In the final lens group, at least one lens is disposed on the enlargement side from the stop,
A zooming optical system for projection, which satisfies the following conditional expressions (1) and (2).
Imφ / fs <0.4 (1)
30.0 <| exP | / Imφ (2)
However,
Imφ: Maximum effective image circle diameter on the reduction side fs: Composite focal length exP of the lens closer to the reduction side than the stop exP: Reduction side connection at the wide-angle end when the reduction distance is the exit side Distance on the optical axis from the image plane to the paraxial exit pupil position 2. The projection variable magnification optical system according to claim 1, wherein the following conditional expression (3) is satisfied.
0.7 <Ls / Lge (3)
However,
Ls: distance on the optical axis from the stop to the most reduction side lens surface Lge: distance on the optical axis from the most enlargement side lens surface to the most reduction side lens surface in the final lens group The projection variable magnification optical system according to claim 1, wherein the following conditional expression (4) is satisfied.
1.8 <Bf / Imφ (4)
However,
Bf: Back focus on the reduction side of the entire system at the wide angle end (air conversion distance)   The variable power optical system for projection according to any one of claims 1 to 3, wherein the plurality of lens groups that move during zooming are substantially composed of two or three lens groups. system.   The first lens group has a negative refracting power, the final lens group has a positive refracting power, and the most magnified lens group among the plurality of lens groups that move during zooming is negative. The projection variable power optical system according to claim 1, having a refractive power. 6. The projection variable magnification optical system according to claim 5, wherein the following conditional expression (5) is satisfied.
1.5 <Bfn / fw (5)
However,
Bfn: Back focus on the reduction side of the entire system at the wide angle end (air equivalent distance)
fw: focal length of the entire system at the wide angle end The projection variable magnification optical system according to claim 5 or 6, wherein the following conditional expression (6) is satisfied.
-10.0 <f1 / fw <-2.0 (6)
However,
f1: Focal length of the first lens group fw: focal length of the entire system at the wide angle end The first lens group has a positive refractive power, the final lens group has a positive refractive power;
The plurality of lens groups that move during zooming are, in order from the magnification side, a lens group having a negative refractive power, a lens group having a positive refractive power, and a lens group having a positive refractive power. 5. The projection variable-power optical system according to claim 1, comprising substantially three lens groups. 9. The projection variable magnification optical system according to claim 8, wherein the following conditional expression (7) is satisfied.
1.3 <Bfp / fw (7)
However,
Bfp: Back focus on the reduction side of the entire system at the wide-angle end (air equivalent distance)
fw: focal length of the entire system at the wide angle end The variable power optical system for projection according to claim 8 or 9, wherein the following conditional expression (8) is satisfied.
Lp / Imφ <15.0 (8)
However,
Lp: Distance on the optical axis from the most magnified lens surface to the most demagnified lens surface at an infinite projection distance   11. The variable power optical system for projection according to claim 1, wherein all lenses on the reduction side of the first lens group are configured by a single lens.   The variable power optical system for projection according to any one of claims 1 to 11, wherein a zoom lens is configured by changing only an interval between lens groups.   When the projection variable magnification optical system is a zoom lens, focusing is an inner that moves only a part of the first lens group including the lens arranged closest to the reduction side of the first lens group in the optical axis direction. The projection variable power optical system according to any one of claims 1 to 12, wherein the projection variable power optical system is configured to perform the focus method. The variable power optical system for projection according to claim 1, wherein the following conditional expression (9) is satisfied.
1.4 <Zr (9)
However,
Zr: zoom ratio of telephoto end to wide angle end   The light source, a light valve into which light from the light source is incident, and a projection variable power optical system that projects an optical image by light modulated by the light valve onto a screen. A projection display device comprising the projection variable magnification optical system according to claim 1.