JP2013019985A - 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, having an appropriate back focus, allowing wide angle easily, having a high variable power ratio, suppressing size increase of an entire system, having a constant F number at variable power and telecentric configuration at a reduction side, and enabling excellent projection image.SOLUTION: The variable power optical system comprises: a first lens group G1 being positive, arranged closest to a magnification side, and fixed when varying power; a final lens group being positive, arranged closest to a reduction side, and fixed when varying power; and a plurality of lens groups arranged between the first lens group G1 and the final lens group, and configured to move when varying power. The reduction side is set to be telecentric. A diaphragm is arranged in the final lens group, and a numerical aperture in whole range of the variable power is constant. A predetermined conditional expression is satisfied regarding an internal transmittance at wavelength 440 nm and 460 nm at each lens, center thickness of each lens, back focus of the entire system, variable power ratio, total lens thickness, and maximum effective image circle diameter at the reduction side.

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 a variable power optical system for projection, for example, the one described in Patent Document 1 below is known.

  However, in many of the conventional variable magnification optical systems for projection, the numerical aperture (hereinafter sometimes referred to as “F number”) changes during magnification. 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. For cinema applications, it is preferable that the F number is constant during zooming, and the following Patent Document 2 proposes a projection zoom lens set so that the F number is constant during zooming. ing.

Japanese Patent No. 3382696 JP 2009-128683 A

  By the way, in order to increase the width of the slow ratio, it is desirable that the variable magnification optical system has a high variable magnification ratio. In a conventional projection zoom lens, if an image circle diameter suitable for cinema use (hereinafter also referred to as the maximum effective image circle diameter) is achieved while achieving the above zoom ratio and the above-mentioned demand, There arises a problem that the performance is deteriorated and the optical system is enlarged.

  On the other hand, if the lens system has exactly the same specifications and performance at the wide-angle end, the higher the zoom ratio, the greater the number of lenses required to maintain good performance in the entire zoom range. However, as the number of lenses increases, it becomes more difficult to keep the transmittance of the entire system high. In order to obtain a good projection image, it is preferable that the lens system has high uniformity of transmittance in the visible range. In particular, a projection lens for movie theaters is required to have a high transmittance value and a high uniformity in a wavelength range of about 400 to 700 nm. It is possible to achieve a highly uniform transmittance by applying a coating with characteristics that allow the uniformity of the transmittance in the entire lens system, but to increase the transmittance value itself. Therefore, it is necessary to use a material having a high internal transmittance. In general, an optical material used for a lens has a lower internal transmittance at a shorter wavelength side in a wavelength range of about 400 to 700 nm.

  The present invention has been made in view of the above circumstances, has an appropriate back focus, is easy to widen the angle, and has a large zoom ratio. It is an object of the present invention to provide a projection variable-power optical system and a projection display device in which the F number is constant, the reduction side is telecentric, and a good projection image can be obtained.

In order to achieve the above object, a projection variable magnification optical system according to the present invention includes a first lens group having a positive refractive power that is disposed closest to the enlargement side and fixed at the time of zooming, and is most reduced. A final lens group having a positive refractive power that is disposed on the side and fixed during zooming, and a plurality of lenses that are disposed between the first lens group and the final lens group and that move during zooming And 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. (1) and (2) are satisfied.
L / Imφ <15.0 (2)
However,
k: Number of lenses included in the entire system T440i: Internal transmittance when the thickness of the i-th lens material from the magnification side is 10 mm at a wavelength of 440 nm Di: Center thickness of the i-th lens from the magnification side Bfw: At the wide-angle end Back focus on the reduced side of the entire system (air equivalent distance)
T460i: Internal transmittance Zr when the thickness of the i-th lens material from the magnifying side is 10 mm at a wavelength of 460 nm: Zoom ratio L at the telephoto end with respect to the wide-angle end L: From the lens surface on the most magnifying side when the projection distance is infinite Distance Imφ on the optical axis to the lens surface closest to the reduction side: Maximum effective image circle diameter on the reduction side

In the projection variable magnification optical system according to the present invention, it is preferable that any one of the following conditional expressions (3) to (7) or any combination is satisfied.
enPt / ft + ft / Bft <4.0 (4)
1.3 <Bfw / fw <3.0 (5)
30.0 <| exP | / Imφ (6)
1.6 <Zr <3.0 (7)
However,
Ndi: Refractive index at the d-line of the i-th lens from the magnification side νdi: Abbe number enPt at the d-line of the i-th lens from the magnification side enPt: Telephoto end at an infinite projection distance when the magnification side is the incident side Distance on the optical axis from the most magnified lens surface to the entrance pupil position in FIG. 5: focal length of the entire system at the telephoto end Bft: back focus on the reduction side of the entire system at the telephoto end (air equivalent distance)
fw: focal length of the entire system at the wide-angle end exP: distance on the optical axis from the reduction-side image plane at the wide-angle end to the paraxial exit pupil position when the projection distance is infinite when the reduction side is the exit side

  Further, in the projection variable magnification optical system according to the present invention, the plurality of lens groups that move during zooming can be configured to substantially consist of three lens groups.

  In the projection variable magnification optical system according to the present invention, the plurality of lens groups that move during zooming have a positive refractive index with the second lens group having a negative refractive index from the magnification side. It is preferable to include a third lens group and a fourth lens group having a positive refractive index.

  In the variable power optical system for projection 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 arranged closest to the reduction side of the first lens group in the optical axis direction. It is preferable to be configured so as to be performed by an inner focus method of moving to the position.

  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.

  Note that the phrase “consisting essentially of” and “substantially consisting of two or three lens groups” substantially has power other than the lens groups mentioned as the constituent elements. It means that there are no lenses or lens groups, and those having optical elements other than lenses such as a diaphragm and a cover glass.

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

  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 “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 having a positive refractive power that is fixed during zooming, a plurality of lens groups that move during zooming, A final lens group having a positive refractive power that is fixed at the time of magnification is arranged, the reduction side is telecentric, a diaphragm is arranged in the final lens group, and the numerical aperture is constant over the entire range of zooming And is configured to satisfy a predetermined conditional expression. As a result, it is easy to widen the angle, and while maintaining an appropriate back focus, it is possible to have a high zoom ratio while suppressing an increase in the size of the entire system. The brightness of the projection screen can be made constant, and for example, a projection variable magnification optical system suitable for a movie theater can be provided.

  In particular, the variable power optical system for projection according to the present invention is configured to satisfy the conditional expression (1) in consideration of the transmittance on the short wavelength side of the lens material in addition to the back focus and the variable power ratio. Therefore, the transmittance characteristic of the entire lens system can be made suitable while ensuring an appropriate length of back focus and a high zoom ratio, and a good projected image can be obtained. In addition, since the variable power optical system for projection according to the present invention is configured to satisfy the conditional expression (2) regarding the length of the lens system in the optical axis direction and the image circle diameter, the enlargement of the lens system is suppressed. However, for example, an image circle diameter suitable for movie theater use can be secured.

  In addition, since the projection display apparatus according to the present invention includes the projection variable magnification optical system according to the present invention, it is easy to project at a wide angle, and a large variable magnification ratio can be obtained without extremely increasing the size of the apparatus. It has a high versatility and can obtain a good projection image over the entire range of zooming, and can be suitable for, for example, movie theater use.

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. 9A to 9L are aberration diagrams of the variable power optical system for projection according to Example 1 of the present invention. FIGS. 10A to 10L are diagrams showing aberrations of the variable magnification optical system for projection according to Example 2 of the present invention. FIGS. 11A to 11L are graphs showing aberrations of the projection variable magnification optical system according to Example 3 of the present invention. 12A to 12L are aberration diagrams of the projection variable magnification optical system according to Example 4 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 on the on-axis and off-axis. In the following, embodiments of the present invention will be described with the configuration examples shown in FIGS. 1 and 2 as representative examples.

  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 this embodiment includes a first lens group G1 having a positive refractive power that is disposed on the most magnification side and fixed at the time of magnification change, and is disposed on the most reduction side and varies. A final lens group having a positive refractive power fixed at the time of magnification, and a plurality of lens groups (hereinafter referred to as a variable lens) disposed between the first lens group G1 and the final lens group and moving at the time of zooming. Only the double-moving lens group) as a substantial lens group, and the reduction side is configured to be telecentric.

  In this way, by making the first lens group G1 closest to the enlargement side a positive lens group, it is easy to increase the magnification.

  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.

  If the number of moving lens groups at the time of zooming of the zooming optical system for projection according to the present invention is configured by three lens groups, it is easy to suppress both the enlargement of the entire system and the aberration fluctuation at the time of zooming. It becomes.

  1 and 2 has a negative, positive, and positive power array in order from the enlargement side. By configuring in this way, aberration at the time of zooming is achieved. It is easy to suppress the fluctuation of the spherical aberration, particularly the fluctuation of the spherical aberration. When the entire system is composed of 5 groups and the power array is positive, negative, positive, positive, positive in order from the magnification side, from wide-angle lens system to telephoto lens system with long back focus and large zoom ratio Can be easily realized.

In the example shown in FIG. 1 and FIG. 2, the first lens group G1 is composed of four lenses (first lens L1 to fourth lens L4), and the second lens group G2 is 3 lenses. The third lens group G3 includes two lenses (eighth lens L8 and ninth lens L9), and the fourth lens group G4 includes one lens. The fifth lens group G5 includes a diaphragm 3 and eight lenses (an eleventh lens L11 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

  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.

Further, the projection variable magnification optical system of the present embodiment is configured to satisfy the following conditional expressions (1) and (2).
L / Imφ <15.0 (2)
However,
k: Number of lenses included in the entire system T440i: Internal transmittance when the thickness of the i-th lens material from the magnification side is 10 mm at a wavelength of 440 nm Di: Center thickness of the i-th lens from the magnification side Bfw: At the wide-angle end Back focus on the reduced side of the entire system (air equivalent distance)
T460i: Internal transmittance Zr when the thickness of the i-th lens material from the magnifying side is 10 mm at a wavelength of 460 nm: Zoom ratio L at the telephoto end with respect to the wide-angle end L: From the lens surface on the most magnifying side when the projection distance is infinite Distance Imφ on the optical axis to the lens surface closest to the reduction side: Maximum effective image circle diameter on the reduction side

  Conditional expression (1) is obtained by multiplying the average value of the two terms relating to the internal transmittance and the back focus at a wavelength of 440 nm and a wavelength of 460 nm of each lens constituting the entire system by a zoom ratio. ing. If the lower limit of conditional expression (1) is surpassed, the transmittance of the entire system on the short wavelength side in the wavelength range of 400 to 700 nm is lowered, an appropriate length of back focus cannot be obtained, and a high zoom ratio is obtained. At least one defect that cannot be obtained will occur.

  More specifically, if the transmittance on the short wavelength side is low in the wavelength range of 400 to 700 nm, not only the transmittance value itself is lowered due to the general characteristics of the optical material, but also the wavelength range of 400 to 700 nm. In this case, the uniformity of the transmittance at the time is also lowered, and it becomes difficult to obtain a good projected image. If a back focus having an appropriate length cannot be obtained, it is impossible to secure an appropriate space for inserting a glass block or the like as a color composition unit such as a beam splitter, a cross dichroic prism, or a TIR prism. If the desired high zoom ratio is not obtained, the versatility is low, and it is difficult to provide a function necessary as a projection zoom optical system for a movie theater or the like intended by the present invention. .

  In a lens system having exactly the same specifications and performance at the wide-angle end, a higher zoom ratio requires a larger number of lenses in order to keep the performance in the entire zooming range better. However, the transmittance of the entire system becomes lower as the number of lenses increases. By satisfying the conditional expression (1), it is possible to obtain an appropriate length of back focus and a high zoom ratio while obtaining a good projection image with a favorable transmittance characteristic of the entire system.

  Conditional expression (2) is the maximum effective image circle diameter, so-called image circle size, and the distance on the optical axis from the most magnified lens surface to the most demagnifying lens surface (hereinafter, the lens) when the projection distance is infinity. The total thickness)). If the upper limit of conditional expression (2) is exceeded, the desired image circle size cannot be obtained, and it is difficult to provide a function required 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, 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.

It is preferable that the projection variable magnification optical system of the present embodiment satisfies any one of the following conditional expressions (3) to (7) or any combination.
enPt / ft + ft / Bft <4.0 (4)
1.3 <Bfw / fw <3.0 (5)
30.0 <| exP | / Imφ (6)
1.6 <Zr <3.0 (7)
However,
k: Number of lenses of the entire system Ndi: Refractive index νdi of the i-th lens from the magnification side νdi: Abbe number Di of the i-th lens from the magnification side Di: Center of the i-th lens from the magnification side Thickness Bfw: Back focus on the reduction side of the entire system at the wide angle end (air equivalent distance)
Zr: magnification ratio enPt at the telephoto end with respect to the wide angle end: distance ft on the optical axis from the lens surface on the most magnified side at the telephoto end at the infinite projection distance to the entrance pupil position when the magnification side is the entrance side : Focal length of the entire system at the telephoto end Bft: Back focus on the reduction side of the entire system at the telephoto end (air equivalent distance)
fw: focal length of the entire system at the wide-angle end exP: distance on the optical axis from the reduction-side image plane at the wide-angle end to the paraxial exit pupil position when the projection distance is infinite when the reduction side is the exit side Imφ: Maximum effective image circle diameter on the reduction side

  Conditional expression (3) is obtained by multiplying a term relating to the refractive index, Abbe number, and back focus of each lens constituting the entire system by a zoom ratio. In a lens system having exactly the same specifications and performance at the wide-angle end, a higher zoom ratio requires a larger number of lenses in order to keep the performance in the entire zooming range better. Also, the higher the refractive index of the lens material, the more useful for aberration correction. Furthermore, it may be effective to use a material having a high refractive index and high dispersion for correcting chromatic aberration.

  However, the transmittance of the entire system becomes lower as the number of lenses increases. In general, the higher the refractive index, the higher the refractive index and the higher the dispersion, the worse the internal transmittance characteristics.

  If the lower limit of conditional expression (3) is not reached, an appropriate length of back focus is obtained in which the transmittance value of the entire system decreases and the uniformity of the transmittance in the wavelength range of 400 to 700 nm decreases. There will be at least one problem of not being able to obtain a high zoom ratio. By satisfying the conditional expression (3), it is possible to achieve a suitable back focal length and a high zoom ratio while obtaining a good projected image with a favorable transmittance characteristic of the entire system.

  Conditional expression (4) relates to the entrance pupil position and the back focus. When the upper limit of conditional expression (4) is exceeded, the distance from the most magnified lens surface to the entrance pupil position becomes longer, the enlarged lens diameter of the first lens group G1 becomes larger, or an appropriate back focus is obtained. I can't get it.

  Conditional expression (5) relates to the ratio between the back focus and the focal length at the wide-angle end. Conditional expression (5) makes it possible to secure an appropriate space for inserting a glass block or the like as a color synthesis means such as a beam splitter, a cross dichroic prism, or a TIR prism while obtaining a desired focal length. It is. That is, if the lower limit of conditional expression (5) is not reached, it will be difficult to insert a glass block or the like as a color composition means on the reduction side of the lens system. If the upper limit of conditional expression (5) is exceeded, the total lens length becomes long, and the lens system becomes large.

  Conditional expression (6) relates to the exit pupil position and the size of the image circle. If the lower limit of conditional expression (6) is not reached, it is difficult to ensure telecentricity while obtaining the desired image circle size.

  Conditional expression (7) defines the zoom ratio. If the lower limit of conditional expression (7) 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. If the upper limit of conditional expression (7) is exceeded, the projection variable magnification optical system has a magnification ratio larger than that required, and the total lens length becomes long. As a result, the lens system becomes large.

From the above circumstances, it is more preferable that the following conditional expressions (1-1) to (8-1) are satisfied instead of the conditional expressions (1) to (8).
L / Imφ <12.0 (2-1)
enPt / ft + ft / Bft <3.7 (4-1)
1.4 <Bfw / fw <2.0 (5-1)
35.0 <| exP | / Imφ (6-1)
1.7 <Zr <2.5 (7-1)

  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 is changed is part of the first lens group G1 including the lens arranged closest to the reduction side of the first lens group 1. 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. 1, focusing can be performed by moving the two lenses L4 and L5 closest to the reduction side of the first lens group G1 in the optical axis direction. 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. FIG. 13 is a schematic configuration diagram showing a part of a projection display apparatus according to an embodiment of the present invention, and FIG. 14 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. 13 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. 14 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. 13 and 14 show an example in which a reflective liquid crystal display element is used as a light valve. However, the light valve provided in the projection display apparatus of the present invention is not limited to this, and a transmissive liquid crystal display element or the like. Alternatively, 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. Examples 1 to 4 described below are configured as varifocal lenses, but Example 1 can be used as a zoom lens by changing only the distance between lens groups, as will be described later as a modified example. It is configured. When Examples 1 to 4 are used as varifocal lenses, focusing when 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 positive 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 includes, in order from the magnification side, a first lens L1 made of a negative meniscus lens having a concave surface facing the reduction side, a second lens L2 made of a plano-convex lens having a convex surface facing the magnification side, and the magnification side The third lens L3 is composed of a positive meniscus lens having a convex surface facing the surface, and the fourth lens L4 is composed of a biconvex lens.

  The second lens group G2, in order from the magnifying side, includes a fifth lens L5 made of a negative meniscus lens having a convex surface facing the magnifying side, a sixth lens L6 made of a biconcave lens, and a positive lens having a convex surface facing the magnifying side. The seventh lens L7 is a meniscus lens. 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 with 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 the magnification side The lens is composed of a sixteenth lens L16 made of a negative meniscus lens having a convex surface facing the first lens, 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 1 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.

  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, the surface number column indicates the surface numbers when the surface numbers are assigned to the components 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. The R column shows the radius of curvature of each surface, and the D column shows the spacing between adjacent surfaces on the optical axis Z.

  In the Ndi column of the basic lens data, the d-line (wavelength 587...) Of the i-th (j = 1, 2, 3,...) Component that sequentially increases toward the reduction side with the most magnified component as the first. 6 nm), and the column of νdi indicates the Abbe number of the i-th component with respect to the d-line. The column of T440i shows the internal transmittance when the material of the i-th component has a thickness of 10 mm at a wavelength of 440 nm, and the column of T460i shows the thickness of the material of the i-th component at a wavelength of 460 nm. The internal transmittance at 10 mm is shown.

  However, in the basic lens data, 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. Further, 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. The interval of the fifth 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. doing.

  In the lower table of Table 1, 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 (variable 1), (variable 2), (variable 3), and (variable 4) are shown. Show. 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.

  9A to 9D respectively show spherical aberration, astigmatism, distortion (distortion aberration), and chromatic aberration of magnification (chromatic aberration of magnification) of the variable magnification optical system for projection of Example 1 at the wide-angle end. An aberration diagram is shown. FIGS. 9E to 9H show 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 intermediate focal position, respectively. Each aberration diagram is shown. 9 (I) to 9 (L) 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 telephoto end. An aberration diagram is shown.

The aberration diagrams in FIGS. 9A to 9L 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. 9A to 9L 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 4 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 4.

<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 first lens group G1, in order from the magnifying side, a first lens L1 made of a negative meniscus lens having a convex surface facing the magnifying side, a second lens L2 made of a positive meniscus lens having a convex surface facing the magnifying side, The third lens L3 is a biconvex lens.

  The second lens group G2, in order from the magnifying side, is a fourth lens L4 made of a negative meniscus lens having a convex surface on the magnifying side, a fifth lens L5 made of a biconcave lens, and a positive lens having a convex surface on the magnifying side. The sixth lens L6 is a meniscus lens. The third lens group G3 includes, in order from the magnifying side, a seventh lens L7 made of a negative meniscus lens having a convex surface facing the magnifying 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 having a convex surface on the enlargement side The fifteenth lens L15 is a meniscus lens, the sixteenth lens L16 is a biconvex lens, and the seventeenth lens L17 is a biconvex lens.

  The variable power optical system for projection according to the second embodiment has substantially the same configuration as the variable power optical system for projection according to the first embodiment. However, the first lens group G1 is composed of four lenses in Example 1, but is composed of three lenses in Example 2. Further, regarding the fifth lens group G5, the lens configuration of the fourth lens from the enlargement side (the fourteenth lens L14 in Example 1 and the thirteenth lens L13 in Example 2) is different.

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. 10A to 10L show aberration diagrams of the projection variable magnification optical system of 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 projection variable optical system according to Example 3 has substantially the same configuration as the projection variable optical system according to Example 2, but the lens configuration is different only for the fifth lens group G5. The fifth lens group G5 is configured by eight lenses in the second embodiment, and is configured by nine lenses in the third embodiment. The detailed lens configuration of the fifth lens group G5 is shown below.

  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 positive meniscus lens having a convex surface on the reduction side, and a negative having a convex surface on the reduction side A fifteenth lens L15 made of a meniscus lens, a sixteenth lens L16 made of a positive meniscus lens having a convex surface facing the enlargement side, a seventeenth lens L17 made of a biconvex lens, and an eighteenth lens L18 made of a biconvex lens. It is configured.

  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. FIGS. 11A to 11L show aberration diagrams of the projection variable magnification optical system of Example 3. FIG.

<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 3, but the lens configurations of the first lens group G1 and the fifth lens group G5 are the same. Different.

  Specifically, in the first lens group G1 of Example 4, the second lens L2 of the first lens group G1 is a biconvex lens, and the third lens L3 of the first lens group G1 has a convex surface facing the enlargement side. This is different from the first lens group G1 of Example 3 in that it is composed of a positive meniscus lens. The fifth lens group G5 includes, in order from the magnification 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 magnification side, and an aperture (aperture and 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 biconvex, and a fifteenth lens made of biconcave lens. The lens includes a lens L15, 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 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. FIGS. 12A to 12L show aberration diagrams of the variable power optical system for projection according to Example 4. FIG.

  The upper table of Table 5 shows values corresponding to the conditional expressions (1) to (7) of Examples 1 to 4. In the lower table of Table 14, values related to the conditional expressions of Examples 1 to 4 are shown. 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. Π440, Π460, and ΠNν in the lower table of Table 14 are described below the lower table. As shown in Table 5, the projection variable magnification optical systems of Examples 1 to 4 satisfy all the conditional expressions (1) to (7).

  In Examples 1 to 4 described above, the reduction side is telecentric, has a long 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 it has a small zoom ratio and a large zoom ratio of 1.90 to 2.01, fluctuations in aberrations during zooming are suppressed, and each optical aberration is well corrected to achieve high optical performance. It is what you have.

<Modification of Example 1>
The first embodiment is configured to be a zoom lens by changing only the distance between the lens groups. Table 6 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 1 as a zoom lens by changing only the distance between the lens groups in Table 6. The distance of each variable interval is shown. When the modified example of Example 1 is used as a zoom lens, focusing when the projection distance varies is performed by moving the third lens L3 and the fourth lens L4 of the first lens group G1 in the optical axis direction. An inner focus method is adopted. In Table 6, 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 (12)

A first lens unit having a positive refractive power arranged at the most enlargement side and fixed at the time of zooming, and a positive lens having a positive refractive power arranged at the most reduction side and fixed at the time of zooming It is substantially composed of a final lens group and a plurality of lens groups that are arranged between the first lens group and the final 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,
A zooming optical system for projection, which satisfies the following conditional expressions (1) and (2).
L / Imφ <15.0 (2)
However,
k: Number of lenses included in the entire system T440i: Internal transmittance when the thickness of the i-th lens material from the magnification side is 10 mm at a wavelength of 440 nm Di: Center thickness of the i-th lens from the magnification side Bfw: At the wide-angle end Back focus on the reduced side of the entire system (air equivalent distance)
T460i: Internal transmittance Zr when the thickness of the i-th lens material from the magnifying side is 10 mm at a wavelength of 460 nm: Zoom ratio L at the telephoto end with respect to the wide-angle end L: From the lens surface on the most magnifying side when the projection distance is infinite Distance Imφ on the optical axis to the lens surface closest to the reduction side: Maximum effective image circle diameter on the reduction side 2. The projection variable magnification optical system according to claim 1, wherein the following conditional expression (3) is satisfied.
However,
Ndi: Refractive index at the d-line of the i-th lens from the magnification side νdi: Abbe number at the d-line of the i-th lens from the magnification side The projection variable magnification optical system according to claim 1, wherein the following conditional expression (4) is satisfied.
enPt / ft + ft / Bft <4.0 (4)
However,
enPt: Distance on the optical axis from the most magnified lens surface to the entrance pupil position at the telephoto end at the telephoto end when the projection distance is infinity when the magnification side is the entrance side ft: Focal length Bft of the entire system at the telephoto end: Back focus on the reduction side of the entire system at the telephoto end (air equivalent distance) The variable power optical system for projection according to any one of claims 1 to 3, wherein the following conditional expression (5) is satisfied.
1.3 <Bfw / fw <3.0 (5)
fw: focal length of the entire system at the wide angle end   5. The projection variable magnification optical system according to claim 1, wherein the plurality of lens groups that move during zooming are substantially composed of three lens groups. 6.   The plurality of lens groups that move during zooming are, from the magnification side, a second lens group having a negative refractive index, a third lens group having a positive refractive index, and a fourth lens having a positive refractive index. 6. The variable power optical system for projection according to claim 1, comprising a group. The projection variable power optical system according to claim 1, wherein the following conditional expression (6) is satisfied.
30.0 <| exP | / Imφ (6)
However,
exP: Distance on the optical axis from the image plane on the reduction side to the paraxial exit pupil position at the wide angle end when the projection distance is infinity when the reduction side is the exit side   8. 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. 9.   9. The projection variable magnification optical system according to claim 1, wherein the zoom lens is configured to be a zoom lens by changing only an interval between the lens groups. 10.   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. 10. The projection variable magnification optical system according to claim 1, wherein the projection variable magnification optical system is configured to perform the focus method. 11. The projection variable magnification optical system according to claim 1, wherein the following conditional expression (7) is satisfied.
1.6 <Zr <3.0 (7)   The light source, a light valve on 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.