JP2008090200A - Zoom lens and projection-type image display device - Google Patents

Abstract

A zoom lens suitable for a projector capable of projecting a large screen even in a narrow projection space and capable of freely changing the screen size, and a projection-type image display device using the zoom lens.
A zoom lens for enlarging and projecting from a primary image surface on the reduction side to a secondary image surface on the enlargement side, forms an intermediate image of the primary image surface, and at least at the time of zooming A first optical system L1 in which two or more groups move on the optical axis, and a second optical system L2 having at least one concave reflecting surface formed on the secondary image plane side with respect to the intermediate image. Each surface constituting the first optical system L1 and the second optical system L2 is formed of a rotationally symmetric surface with a common optical axis as a center, and light rays from the center of the primary image surface to the center of the secondary image surface are optical axes. , Then reflected by the concave reflecting surface, crosses the optical axis again and reaches the secondary image plane, and the following conditional expression (1) 0.5 <φ1 / φ2 <3
(2) 1 <AST / ASS <5
(3) | AST | / L12 <1
It is a zoom lens that satisfies
[Selection] Figure 1

Description

  The present invention relates to a zoom lens for enlarging and projecting from a primary image surface on the reduction side to a secondary image surface on the enlargement side, and a projection type image display apparatus having the zoom lens.

  High-definition projectors for conference presentations, home theaters using full HD (High Definition) or DVD (Digital Versatile Disk), so-called next-generation DVD, as represented by digital terrestrial broadcasting at home It is becoming popular.

  A zoom lens used in such a projector has a prism for color synthesis between a display element and a projection optical system, a polarization beam splitter (PBS) for separating polarization of light, a TIR (Total Internal reflection) for separating light beams, etc. A long back focus and a substantially telecentric configuration are required for the insertion. Therefore, a retrofocus type having negative and positive refractive power arrangements has been generally used.

Furthermore, [1] A large screen can be displayed in a narrow projection space, and it has a high zoom ratio and a function as an ultra-wide angle zoom lens that can freely expand and contract the screen.
[2] Decreasing the F value in order to project a brighter screen.
[3] A lens having high resolving power as the number of display pixels increases. It must also be low distortion.
[4] Telecentricity does not break even during zooming.
[5] To satisfy the above [1] to [4] and reduce the number of lens components and achieve a simple configuration in order to reduce the size and cost of the projector.
Are required as a zoom lens of a projector.

  As a wide-angle zoom lens having a substantially telecentric configuration suitable for a projector and having a half angle of view of about 40 degrees, there are five-component and six-component zoom lenses disclosed in Patent Documents 1 and 2 and the like.

  Patent Document 1 has five components of positive, negative, positive and positive from the object side, and three or more groups move at the time of zooming, so that the maximum half field angle is slightly less than 40 degrees, F / 1.8, zoom ratio A zoom lens of about 1.2 is achieved.

  Patent Document 2 has six components of negative positive positive positive negative from the object side, and at the time of zooming from the wide end to the tele end, four groups of 2 to 5 groups move to the object side, so that the half angle of view 30 A zoom lens with a zoom ratio of about -45 degrees, F / 2, around 0, and a zoom ratio of about 1.6-2.0 has been achieved.

  Although the application is mainly an imaging system, there is a super wide-angle zoom lens corresponding to 50 to 60 degrees in half angle of view.

  Patent Document 3 discloses a zoom lens having four components of positive, negative and positive from the object side and moving the four groups at the time of zooming to have a half angle of view of 60 degrees, F / 4.6, and a zoom ratio of about 2.0. Has achieved.

  Patent Document 4 has a zoom lens having four components of positive, negative, and positive from the object side and moving the four groups at the time of zooming, and a half angle of view of 50 degrees, F / 2.8, and a zoom ratio of about 2.2. Have achieved.

  Patent Document 5 uses three free-form reflecting surfaces to form an off-axial optical system, thereby achieving a zoom lens with a zoom ratio of about 20 that does not move the center of the screen even during zooming. (See FIG. 30).

JP 2004-054021 A JP 2005-292260 A JP 2005-106878 A Japanese Patent Laying-Open No. 2005-157097 JP 2004-295107 A

  However, the optical system shown in the conventional technique has the following problems. That is, while the optical systems disclosed in Patent Documents 1 and 2 are suitable for a projector, they are configured only by a refractive system, so that a further wide angle is maintained while maintaining an F value, a zoom ratio, and telecentricity. In this case, various aberrations such as field curvature, lateral chromatic aberration, and distortion are likely to deteriorate rapidly, and it becomes very difficult to obtain good optical performance, leading to an increase in diameter and overall lens length.

  The optical system disclosed in Patent Document 3 achieves an ultra-wide-angle zoom lens having a half angle of view of about 60 degrees, but has a large F value and is not a telecentric optical system. Is not suitable.

  The optical system disclosed in Patent Document 4 achieves a super wide-angle zoom lens with a half angle of view of about 50 degrees, and each aberration is appropriate while achieving a large aperture of about F / 2.8. It has been corrected. On the other hand, the telecentricity is greatly destroyed by zooming, and the lens group on the image plane side from the stop moves greatly during zooming and has a large positive refractive power. Since the value fluctuates greatly, the brightness is greatly affected. In addition, a large glass mold aspherical surface is used for the most magnified lens, which is difficult in terms of cost and is not suitable for a projector optical system.

  In the case of the projection optical system described in Patent Document 5, the optical block R is composed of an optical block R having three or more free-form surfaces and an optical block C having a zooming mechanism, and has an intermediate imaging surface in the optical block R. Thus, there is an advantage that the reflecting surface can be made small while widening the angle. On the other hand, the decentration aberration generated by decentering the reflecting surface is corrected by the remaining decentered reflecting surfaces, and at least three reflecting surfaces are required. Furthermore, the reflecting surface is not a rotationally symmetric structure, but is formed of a free-form surface, is very sensitive to surface accuracy and assembly system, and is difficult to manufacture, leading to a cost increase.

  In addition, since the stop is arranged on the exit side of the optical block C and the group having a zoom mechanism is formed between the stop and the display element surface, the F value fluctuation during zooming increases as the zoom ratio increases. Cheap. Although the zoom ratio of about 2 is achieved in the embodiment, the F value changes from F / 2.0 to F / 4.0 when zooming from the wide end to the tele end. Therefore, the brightness of the image display surface changes at the time of zooming, and a dark screen is generated particularly on the telephoto end side, which is not suitable for a projector. In the embodiment, the projection distance is about 1700 mm and the maximum is about 70 inches. When further widening the angle, each aberration may be greatly deteriorated.

  In view of the above-described conventional problems, the present invention provides a zoom lens suitable for a projector with a relatively simple configuration, for example, a half field angle of about 60 degrees, an F value of about 2.0, and a zoom ratio of about 1.5. This is the issue.

That is, the present invention is a projection optical system for enlarging and projecting from a primary image surface on the reduction side to a secondary image surface on the enlargement side, forming an intermediate image of the primary image surface, and at least at the time of zooming The two or more groups include a first optical system that moves on an optical axis, and a second optical system that has at least one concave reflecting surface formed on the secondary image plane side of the intermediate image, Each surface constituting the first optical system and the second optical system is constituted by a rotationally symmetric surface with a common optical axis as a center, and a light beam from the center of the primary image surface to the center of the secondary image surface is Crosses the optical axis, then reflects off the concave reflecting surface, crosses the optical axis again and reaches the secondary image plane, and the following conditional expression (1) 0.1 <φ1 / φ2 <3
(2) 1 <AST / ASS <5
(3) | AST | / L12 <1
Satisfying the above, for example, good optical performance can be obtained while the F value is around 2.3 and the zoom ratio is around 1.5 at a half angle of view of around 60 degrees.
Where φ1: refractive power of the first optical system φ2: refractive power of the second optical system | AST |: intermediate imaging position on the meridian plane in the first optical system | ASS |: spherical missing surface in the first optical system Intermediate imaging position at L12: Distance on the optical axis between the first optical system and the second optical system

  In order to solve the above-described problem, the projection type image display apparatus of the present invention includes a light source, a modulation unit that modulates light emitted from the light source based on a video signal, and a modulation unit described above. The zoom lens is provided for enlarging and projecting from the primary image surface on the side to the secondary image surface on the screen side.

  Accordingly, in the present invention, the light beam from the center of the primary image surface to the center of the secondary image surface intersects the optical axis of the first optical system, and is then reflected by the concave reflecting surface, and again the optical axis. By tracing the optical path that reaches the secondary image plane intersecting with the second optical system, for example, the light that forms an image on the secondary image plane from the first optical system arranged in a substantially horizontal direction is upward (or downward) by the second optical system. To output.

  According to the present invention as described above, a zoom lens suitable for a projector having a large half angle of view, F value, and zoom ratio can be provided, a large screen can be projected even in a narrow projection space, and freely. It is possible to provide a zoom lens suitable for a projection type image display device capable of changing the screen size and a projection type image display device using the zoom lens.

  The best mode for carrying out a zoom lens and a projection-type image display device of the present invention will be described below with reference to the accompanying drawings.

  That is, the zoom lens according to the present embodiment is a projection optical system that performs enlarged projection from the primary image surface on the reduction side to the secondary image surface on the enlargement side, and forms an intermediate image of the primary image surface, At the time of zooming, at least two or more groups include a first optical system that moves on an optical axis, and a second optical system that forms the secondary image surface by the intermediate image. A light beam from the center to the center of the secondary image plane intersects the optical axis, is further reflected by the concave reflecting surface, and crosses the optical axis again to reach the secondary image plane. To summarize the image formation relationship, the first optical system forms an intermediate image of the primary image plane, and then forms a pupil as convergent light by the concave reflecting surface, and then forms an image as the secondary image plane. ing.

The intermediate image of the first optical system is disposed between the first optical system and the second optical system, and the following conditional expression (1) 0.5 <φ1 / φ2 <3
(2) 1 <AST / ASS <5
(3) | AST | / L12 <1
By satisfying the above, good optical performance can be obtained.
Where φ1: refractive power of the first optical system φ2: refractive power of the second optical system | AST |: intermediate imaging position on the meridian plane in the first optical system | ASS |: spherical missing surface in the first optical system Intermediate imaging position at L12: Distance on the optical axis between the first optical system and the second optical system

  Conditional expression (1) is the ratio of the refractive power φ1 of the first optical system and the refractive power φ2 of the second optical system. When the ratio is below the lower limit, the curvature of the concave reflecting surface becomes very large. The aberration generated on the concave reflecting surface becomes very large. When the upper limit is exceeded, since the refractive power of the first optical system is large, it is difficult to correct aberrations on the concave reflecting surface.

Conditional expression (2) calculates the ratio of the image positions of the intermediate image on the meridian plane (or meridional plane: the cross section including the principal ray and the optical axis) and the spherical surface (or the sagittal plane: a plane perpendicular to the meridian plane). It is a thing. As shown in FIG. 31, when the concave reflection surface of the second optical system is A and the curvature radius is r, the meridional section has the curvature radius r regardless of h. On the other hand, rcos θ is obtained at the spherical surface, and the light beam incident on the spherical surface has a different refractive power due to h.

  In order for the light beams incident on the cross sections described above to form an image at the same position on the secondary image plane, the image forming positions on the cross sections of the intermediate image must be at different positions. In addition, since the light beam incident on the spherical surface is incident on a surface having a smaller radius of curvature at θ> 0 than the light beam incident on the meridian surface, the light beam is closer to the second optical system side than the imaging position on the meridian surface. There is a need.

  Therefore, the conditional expression (2) defines an appropriate range of each of the imaging positions described above. When the lower limit is not satisfied, that is, the imaging position of the spherical surface is smaller than the imaging position of the meridian plane. When positioned on the first optical system side, it is difficult to form images at the same position on the secondary image plane. When the upper limit is exceeded, the image formation positions on the meridian plane and the spherical surface are separated, so that it is difficult to simultaneously form images on the secondary image plane.

  Conditional expression (3) is a ratio between an arbitrary imaging position on the meridian plane and the distance on the optical axis of the first optical system and the second optical system.

  In the present invention, the first optical system is of a type having an intermediate image, and forms an image after exiting the first optical system and reaching the second optical system. And smaller than the distance on the optical axis of the second optical system.

  When the field curvature generated in the first optical system is imaged on the plane of the secondary image plane by the reflecting surface of the second optical system, reducing the curvature amount of the first optical system as much as possible reduces the optical performance. Desirable for good.

  Therefore, it is possible to obtain good optical performance by making the amount of field curvature of the first optical system smaller than the distance on the optical axis of the first optical system and the second optical system as in conditional expression (3). It becomes. When the value is below the lower limit, an image is formed between the concave reflecting surface and the secondary image surface, so that the image cannot be formed on the secondary image surface.

  Further, by setting at least one concave reflecting surface constituting the second optical system to be a rotationally symmetric aspherical surface, it is possible to obtain even better optical performance. Here, the expression of the aspherical surface is the following formula 1.

However,
Z: Sag amount of aspheric surface h: Height perpendicular to optical axis c: Curvature of paraxial K: Conic constant Ai: i-th order aspheric coefficient.

In the zoom lens according to the present embodiment, the concave reflecting surface is a rotationally symmetric aspheric surface, and satisfies the following conditional expression (4).
(4) K <1

  Conditional expression (4) defines an appropriate range for the shape of the concave reflecting surface. When the upper limit is exceeded, an image cannot be formed on the secondary image plane with low distortion unless the first optical system has a wide angle. Further, as h increases, it becomes larger than the paraxial curvature. That is, the aberration generation amount increases in both the first optical system and the second optical system, so that it is impossible to correct the aberration. Therefore, by setting the range defined by conditional expression (4), it is possible to suppress the amount of aberration generated in the second optical system.

  Further, with regard to focusing at the time of changing the projection distance, an adjustment mechanism is provided in the first optical system as in the case of zooming, and the entire first optical system or at least one group of light of the first optical system is provided. By performing the movement on the axis, it becomes possible without moving the concave reflecting surface, which is mechanically difficult.

  The projection-type image display apparatus according to the present embodiment includes a light source, a modulation unit that modulates and outputs light emitted from the light source based on a video signal, and a screen side from a primary image plane on the modulation unit side. A zoom lens for enlarging and projecting to the secondary image plane, wherein the zoom lens forms an intermediate image of the primary image plane, and at the time of zooming, at least two or more groups move on the optical axis. A first optical system, and a second optical system having one or more concave reflecting surfaces for forming the intermediate image on the secondary image plane, from the center of the primary image plane to the center of the secondary image plane. The incident light beam crosses the optical axis of the first optical system, is further reflected by the concave reflecting surface, and crosses the optical axis again to reach the secondary image surface.

  In particular, since the projection type image display apparatus of the present embodiment projects an image formed by the modulation means on the screen using the zoom lens described above, it can project a large screen even in a narrow projection space. While making it possible to freely change the size of the projection screen, it is possible to display a magnified image that is bright and has high resolution and low distortion.

  Since the zoom lens according to the present embodiment includes a rotationally symmetric optical system, the position of the screen can be easily achieved by moving the display element on a plane perpendicular to the optical axis.

  In addition, since the pupil of the second optical system with respect to the secondary image plane of the intermediate image is formed between the second optical system and the screen, the degree of freedom in routing the optical path in the cabinet is increased, and the second It becomes possible to provide a shielding portion having an opening at the pupil position where the light beam is most narrowed between the optical system and the screen, and it becomes easy to take the dust prevention measures and the stray light measures of the zoom lens of this embodiment.

  Therefore, the zoom lens according to the present embodiment has the above-described configuration, so that it is possible to easily obtain an ultra wide angle and good optical performance with a relatively simple configuration.

  In addition, the projection type image display apparatus using the zoom lens according to the present embodiment also provides an apparatus with high image quality and low distortion optical performance that can project a large screen even in a narrow projection space with a relatively simple configuration. it can.

  Hereinafter, embodiments and numerical examples of the zoom lens and the projection type image display apparatus according to the present embodiment will be described with reference to the drawings and tables. In the following embodiments, an example in which the three groups constituting the first optical system move during zooming is taken as an example, but the present invention can also be applied to a configuration in which two groups move during zooming.

  (Form of Example 1)

  FIG. 1 is an optical path diagram of the first embodiment. P is a display element as modulation means, and light emitted from a light source (not shown) is modulated by the display element P based on the video signal to form a primary image plane. As the display element P, a reflective or transmissive dot matrix liquid crystal panel, a digital micromirror device (DMD), or the like can be used. Also, PP in the figure indicates a polarization beam splitter (PBS), a color synthesis prism that synthesizes RGB video signals, a TIR (Total Internal Reflector) prism, and the like. The figure consists of three positions from the top: wide end, middle and tele end.

  FIG. 2 shows details of the projection optical system portion of FIG. The first optical system L1 is composed of six groups I to VI from the secondary image plane side. When zooming from the wide end to the tele end, the II, III, and V groups are located on the secondary image plane side. Moving. Here, the I, IV, VI groups and the concave reflecting surface of the second optical system are fixed during zooming.

Table 1 shows the composite focal length f, half angle of view ω, and F value of Example 1. Here, the combined focal length means that the refractive power of the first optical system is φ1, the refractive power of the second optical system is φ2, the intermediate image side principal point position of the first optical system, and the concave reflection that constitutes the second optical system. If the combined refractive power is φ when the distance to the surface is Δ, 1 / f = φ = φ1 + φ2-Δ · φ1 · φ2
It is expressed. By zooming from the wide end to the tele end, the F value is F / 2.00 to F / 2.05, the half angle of view is 53 degrees to 43.9 degrees, and the zoom ratio is 1.37 times. Here, the zoom ratio is the ratio of the combined focal length of the wide end and the tele end.

  Table 2 shows lens data of Example 1. The surface numbers are assigned so as to increase from the secondary image surface (projection image side) to the primary image surface (display element side) as S1, S2, S3,. The surface number of the stop and the surface number on which the aspherical surface is arranged can be seen on the right side of the surface number, and the aspherical data is shown in Table 3. The locations marked as variable in the interval column are the intervals that change when scaling, and are shown in Table 4. In the column of curvature radius, INFINITY indicates that the surface is a plane, and the refractive index (ne) and the Abbe number (νe) are numerical values at the e-line (546.1 nm).

  3 to 5 are longitudinal aberration diagrams of the first embodiment. From the left, spherical aberration, field curvature, and distortion are illustrated. The solid line is 546.07 nm, the broken line is 620 nm, and the one-dot chain line is 460 nm. 3 is the wide end, FIG. 4 is the middle, and FIG. 5 is the tele end. Here, looking at the spherical aberration diagrams at the wide end, the middle end, and the tele end, the main wavelength of 546.07 nm is not focused on the optical axis, but the center of the display element actually used is the screen center. There is no problem because the focus is set in the vicinity (see Table 5).

  6 to 8 are lateral aberration diagrams of Example 1. FIG. The solid line is 546.07 nm, the broken line is 620 nm, and the one-dot chain line is 460 nm. 6 is the wide end, FIG. 7 is the middle, and FIG. 8 is the tele end. The scale is set at 12.5 μm.

  FIG. 9 shows an example of a projection type image display apparatus using the first embodiment. In the figure, the projection state at the wide end is shown, and the projector is suspended from the ceiling. Here, P is a display element, PP is a color combining prism, L1 is a first optical system, M1 is a plane mirror for bending an optical path, and L2 is a second optical system. The light beam emitted from the display element P follows the color separation prism PP, the first optical system L1, the bending mirror M1, and the second optical system L2 in this order, and reaches the screen surface S.

  A portion indicated by A in the drawing is dust-proof glass, which not only prevents dust from the outside, but also has a function not to accidentally touch the second optical system L2. If a transparent glass substrate is mainly used and both surfaces are coated with an antireflection film, an image can be projected without affecting the image quality. In addition, since the dust-proof glass is disposed near the pupil formed between the concave reflecting surface and the secondary image plane, which are the second optical system, the optical system can be made compact.

  Here, Table 5 shows the vertical × horizontal dimensions, the dot size, and the like of the display elements used in this figure. In Example 1, the distance between the secondary image surface and the concave reflecting surface is 1700 mm. However, when the display element shown in Table 5 is used, the screen size on the secondary image surface side is 110 inches at the wide end. It becomes 95 inches at the middle and 80 inches at the telephoto end.

  FIG. 10 is a view of FIG. 9 viewed from below. Here, light valves such as a light source and an illumination optical system are omitted. In the figure, the device is projected from the ceiling, but it may of course be projected from the floor or from the side.

  (Form of Example 2)

  FIG. 11 is an optical path diagram of the second embodiment. P is a display element as modulation means, and light emitted from a light source (not shown) is modulated by the display element P based on the video signal to form a primary image plane. As the display element P, a reflective or transmissive dot matrix liquid crystal panel, a digital micromirror device (DMD), or the like can be used. Also, PP in the figure indicates a polarization beam splitter (PBS), a color synthesis prism that synthesizes RGB video signals, a TIR (Total Internal Reflector) prism, and the like. The figure consists of three positions from the top: wide end, middle and tele end.

  FIG. 12 shows details of the projection optical system portion of FIG. The first optical system L1 is composed of six groups I to VI from the secondary image plane side, and the II, III, IV, and V groups are secondary image planes during zooming from the wide end to the tele end. Move to the side. Here, the I and VI groups and the concave reflecting surface of the second optical system are fixed during zooming.

Table 6 shows the combined focal length f, half angle of view ω, and F value of Example 2. Here, the combined focal length means that the refractive power of the first optical system is φ1, the refractive power of the second optical system is φ2, the intermediate image side principal point position of the first optical system, and the concave surface constituting the second optical system. If the combined refractive power is φ when the distance to the reflecting surface is Δ, 1 / f = φ = φ1 + φ2-Δ · φ1 · φ2
It is expressed. By zooming from the wide end to the tele end, the F value is F / 2.50 to F / 2.71, the half angle of view is 55 degrees to 37.6 degrees, and the zoom ratio is 1.80 times. Here, the zoom ratio is the ratio of the combined focal length of the wide end and the tele end.

  Table 7 shows lens data of Example 1. The surface numbers are assigned so as to increase from the secondary image surface (projection image side) to the primary image surface (display element side) as S1, S2, S3,. The surface number of the stop and the surface number on which the aspherical surface is arranged can be seen on the right side of the surface number, and the aspherical data is shown in Table 8. The locations marked as variable in the interval column are the intervals that change when scaling, and are shown in Table 9. In the column of curvature radius, INFINITY indicates that the surface is a plane, and the refractive index (ne) and the Abbe number (νe) are numerical values at the e-line (546.1 nm).

  FIGS. 13 to 15 are longitudinal aberration diagrams of Example 1, and spherical aberration, field curvature, and distortion are shown from the left. The solid line is 546.07 nm, the broken line is 620 nm, and the one-dot chain line is 460 nm. 13 is the wide end, FIG. 14 is the middle, and FIG. 15 is the tele end. Here, looking at the spherical aberration diagrams at the wide end, the middle end, and the tele end, the main wavelength of 546.07 nm is not focused on the optical axis, but the center of the display element actually used is the screen center. (See Table 10), there is no problem because the focus is set.

  16 to 18 are lateral aberration diagrams of Example 2. FIG. The solid line is 546.07 nm, the broken line is 620 nm, and the one-dot chain line is 460 nm. 16 is the wide end, FIG. 17 is the middle, and FIG. 18 is the tele end. One scale is set to 12.5 μm.

  As the image display device of the second embodiment, the one shown in FIG. 9 can be considered. For example, when the display pixel size shown in Table 10 is used, the projection distance is 1700 mm, the wide end is 110 inches, the middle is 80 inches, and the tele end is 60. Inches.

  (Form of Example 3)

  FIG. 19 is an optical path diagram of the third embodiment. P is an image display element as a modulation means, and light emitted from a light source (not shown) is modulated by the display element P based on a video signal to form a primary image plane. As the display element P, a reflective or transmissive dot matrix liquid crystal panel, a digital micromirror device (DMD), or the like can be used. Also, PP in the figure indicates a polarization beam splitter (PBS), a color synthesis prism that synthesizes RGB video signals, a TIR (Total Internal Reflector) prism, and the like. The figure consists of three positions from the top: wide end, middle and tele end.

  FIG. 20 shows details of the projection optical system portion of FIG. The first optical system L1 is composed of six groups I to VI from the secondary image plane side, and the II, III, IV, and V groups are secondary image planes during zooming from the wide end to the tele end. Move to the side. Here, the I and VI groups and the concave reflecting surface of the second optical system are fixed during zooming.

Table 11 shows the composite focal length f, half angle of view ω, and F value of Example 1. Here, the combined focal length means that the refractive power of the first optical system is φ1, the refractive power of the second optical system is φ2, the intermediate image side principal point position of the first optical system, and the concave surface constituting the second optical system. If the combined refractive power is φ when the distance to the reflecting surface is Δ, 1 / f = φ = φ1 + φ2-Δ · φ1 · φ2
It is expressed. By zooming from the wide end to the tele end, the F value is F / 2.40 to F / 2.51, the half angle of view is 65.1 degrees to 57.0 degrees, and the zoom ratio is 1.35 times. Here, the zoom ratio is the ratio of the combined focal length of the wide end and the tele end.

  Table 12 shows lens data of Example 3. The surface numbers are assigned so as to increase from the secondary image surface (projection image side) to the primary image surface (display element side) as S1, S2, S3,. The surface number of the stop and the surface number on which the aspherical surface is arranged are shown on the right side of the surface number, and the aspherical data are shown in Table 13. Locations marked as variable in the interval column are intervals that change during zooming, and are shown in Table 14. In the column of curvature radius, INFINITY indicates that the surface is a plane, and the refractive index (ne) and the Abbe number (νe) are numerical values at the e-line (546.1 nm).

  FIGS. 21 to 23 are longitudinal aberration diagrams of Example 3, which are spherical aberration, curvature of field, and distortion from the left. The solid line is 546.07 nm, the broken line is 620 nm, and the one-dot chain line is 460 nm. 21 is the wide end, FIG. 22 is the middle, and FIG. 23 is the tele end. Here, looking at the spherical aberration diagrams at the wide end, the middle end, and the tele end, the focus position on the optical axis does not match the main wavelength of 546.07 nm, but the screen of the display element actually used There is no problem because the focus is set at the center (see Table 15).

  24 to 26 are lateral aberration diagrams of Example 3. FIG. The solid line is 546.07 nm, the broken line is 620 nm, and the one-dot chain line is 460 nm. 24 is the wide end, FIG. 25 is the middle, and FIG. 26 is the tele end. One scale is set to 9.5 μm.

  FIG. 27 shows an example of a projection type image display apparatus using the third embodiment. The light beam emitted from the display element P follows the color separation prism PP, the first optical system L1, the bending mirror M1, the second optical system L2, and the bending mirror M2, and reaches the transmission screen S having a Fresnel shape. Since the zoom lens of the present invention projects off the optical axis during image display, the projection screen position shifts in the optical axis direction at the time of zooming from the wide end to the tele end. At the time of zooming from the wide end to the tele end, the projection screen position can be made constant by changing the vertical distance between the center of the display element and the optical axis.

  Table 15 shows the display element size used in FIG. 27 and the display element center positions at the wide end and the tele end. In this example, a rear projection television is assumed. The screen size at the wide end is 52.8 inches, and at the tele end is 38.4 inches. The depth is 330 mm, which is no problem even when compared with a conventional rear projection television. Further, here, since the optical unit is bent immediately after the screen, there is no projecting portion below the screen in terms of design.

  FIG. 28 is a top view of the state at the wide end in FIG. Of course, in the third embodiment, a projection method as shown in FIG. 9 is also possible, and in this case, the screen vertical direction can be freely changed.

  FIG. 29 shows a TV distortion diagram on the image display surface of FIG. The thick line of the outer frame is the screen size at the wide end. The upper row is the wide end and the lower row is the tele end.

  Table 16 lists the conditional expressions (1) to (4) of Examples 1 to 3 of the present invention, and Table 17 lists the numerical values as the basis.

  Thus, by satisfying the conditional expression, the half angle of view is a super wide angle of about 60 degrees and the F value is about 2.3, and the zoom ratio is 1.5 with high resolution and low distortion. It becomes possible to obtain the front and rear zoom lenses with a relatively easy configuration.

  In addition, the specific shapes and numerical values of the respective parts shown in the above-described embodiments and examples are merely examples of the implementation performed in carrying out the present invention, and thereby the technical scope of the present invention. Should not be interpreted in a limited way.

  A projection-type image display device that uses transmissive, reflective liquid crystal, or DMD (digital micromirror device) as a display element, can project a large screen even in a narrow projection space, and can freely change the display screen size. It can also be applied to a front projection type projector capable of realizing the above, or a rear projection type projection television.

2 is an optical path diagram of Example 1. FIG. FIG. 2 is a detailed view of a projection optical system portion of Example 1. FIG. 6 is a longitudinal aberration diagram (wide end) of Example 1. FIG. 4 is a longitudinal aberration diagram (middle) of Example 1. FIG. 4 is a longitudinal aberration diagram (tele end) of Example 1. FIG. 4 is a lateral aberration diagram (wide end) of Example 1. FIG. 4 is a lateral aberration diagram (middle) of Example 1. FIG. 6 is a lateral aberration diagram (tele end) of Example 1. It is a figure which shows an example of the projection type image display apparatus which uses Example 1. FIG. It is the figure which looked at FIG. 9 from the bottom. 6 is an optical path diagram of Example 2. FIG. FIG. 6 is a detailed view of a projection optical system portion of Example 2. FIG. 6 is a longitudinal aberration diagram (wide end) of Example 2. FIG. 6 is a longitudinal aberration diagram (middle) of Example 2. FIG. 5 is a longitudinal aberration diagram (tele end) of Example 2. FIG. 6 is a lateral aberration diagram (wide end) of Example 2. FIG. 6 is a lateral aberration diagram (middle) of Example 2. FIG. 5 is a lateral aberration diagram (tele end) of Example 2. FIG. 6 is an optical path diagram of Example 3. FIG. 6 is a detailed view of a projection optical system portion of Example 3. FIG. 6 is a longitudinal aberration diagram (wide end) of Example 3. FIG. 6 is a longitudinal aberration diagram (middle) of Example 3. FIG. 6 is a longitudinal aberration diagram (tele end) of Example 3. FIG. 6 is a lateral aberration diagram (wide end) of Example 3. FIG. 6 is a lateral aberration diagram (middle) of Example 3. FIG. 5 is a lateral aberration diagram (tele end) of Example 3. FIG. 10 is a diagram illustrating an example of a projection-type image display device using Example 3. It is the figure which looked at the state at the time of the wide end of FIG. 27 from the top. It is TV distortion figure in the image display surface of FIG. It is a schematic diagram explaining a prior art example. It is a schematic diagram explaining a meridian surface and a spherical notch surface.

Explanation of symbols

  L1 ... first optical system, L2 ... second optical system, P display element (primary image plane), PP / color combining prism, S ... screen (secondary image plane)

Claims (5)

A zoom lens for enlarging and projecting from a primary image surface on the reduction side to a secondary image surface on the enlargement side,
Forming an intermediate image of the primary image plane, and at the time of zooming, at least two groups move on the optical axis;
A second optical system having at least one concave reflecting surface formed on the secondary image plane side of the intermediate image,
Each surface constituting the first optical system and the second optical system is composed of a rotationally symmetric surface with a common optical axis as a center, and a light beam extending from the center of the primary image surface to the center of the secondary image surface. Crosses the optical axis, then reflects off the concave reflecting surface, crosses the optical axis again and reaches the secondary image plane, and the following conditional expression (1) 0.1 <φ1 / φ2 <3
(2) 1 <AST / ASS <5
(3) | AST | / L12 <1
A zoom lens characterized by satisfying
Where φ1: refractive power of the first optical system φ2: refractive power of the second optical system | AST |: intermediate imaging position on the meridian plane in the first optical system | ASS |: spherical missing surface in the first optical system Intermediate imaging position at L12: Distance on the optical axis between the first optical system and the second optical system The concave reflecting surface is formed of a rotationally symmetric aspheric surface, and the following conditional expression (4) K <1
The zoom lens according to claim 1, wherein:
However,
K: Conic constant The zoom lens according to claim 1, wherein when the projection distance is changed, focusing is performed by moving the entire first optical system or at least one group of the first optical system on an optical axis. A light source;
Modulation means for modulating and outputting the light emitted from the light source based on a video signal;
A zoom lens for enlarging and projecting from the primary image surface on the modulation means side to the secondary image surface on the screen side,
The projection type image display apparatus characterized by using the zoom lens according to any one of claims 1 to 3 as the zoom lens. The projection type image display device according to claim 4, wherein the projection image position is changed by moving the display element in a plane perpendicular to the optical axis at the time of zooming.

Images