JP6229364B2 - Projection zoom lens and image display device - Google Patents

Description

  The present invention relates to a projection zoom lens and an image display device.

  The image display device can be implemented as a projector device.

  In recent years, a front projection type projector device that projects an enlarged image on a screen in front of the device has been widely used for presentations in companies, education in schools, and home use.

  An image display element that displays an enlarged projection image on a “display surface” is also called a “light valve”, but various types are known including a liquid crystal panel.

  In recent years, “micromirror devices” typified by digital micromirror devices (DMD) manufactured by Texas Instruments have attracted attention as light valves.

  It is preferable that the projection optical system for projecting and displaying the projection image displayed on the display surface of the image display element on the projection surface such as a screen has a scaling function.

  Of course, it is preferable that the projection zoom lens having such a zoom function is applicable to various light valves.

  In consideration of compactness and the simplicity of a displacement mechanism for displacing each lens group during zooming, the projection zoom lens is preferably configured with as few lens groups as possible.

  2. Description of the Related Art Conventionally, as a projection zoom lens configured with a small number of lens groups, those having a three-lens group configuration disclosed in Patent Documents 1 and 2 are known.

  The projection zoom lenses described in Patent Documents 1 and 2 have negative, positive, and positive refractive power distribution from the enlargement side (screen side) to the reduction side (light valve side).

  An object of the present invention is to provide a projection zoom lens having a new three-lens group configuration having negative, negative, and positive refractive power distribution from the enlargement side to the reduction side.

The projection zoom lens according to the present invention constitutes a projection optical system of an image display device that projects a projection image displayed on an image display element onto a projection surface as an enlarged image of the projection image, and displays the enlarged image. A projection zoom lens having a first lens group having a negative refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power in order from the enlargement side to the reduction side , Ri Na an aperture stop in the third lens group, the first lens group is composed of three or less lenses and the refractive power, the first to third lens in groups, in absolute value The largest half angle of view at the wide-angle end: ωw
Condition: (4) 38 degrees <ωw
Satisfied.

  According to the present invention, it is possible to provide a novel projection zoom lens having the number of constituent lens groups as small as three and having an unprecedented refractive power distribution.

3 is a cross-sectional view illustrating a configuration of a projection zoom lens according to Embodiment 1. 3 is an aberration curve diagram of the projection zoom lens of Example 1. FIG. 6 is a cross-sectional view illustrating a configuration of a projection zoom lens according to Example 2. FIG. FIG. 6 is an aberration curve diagram of the projection zoom lens according to Example 2. 6 is a cross-sectional view illustrating a configuration of a projection zoom lens according to Example 3. FIG. 6 is an aberration curve diagram of the projection zoom lens of Example 3. FIG. 6 is a cross-sectional view illustrating a configuration of a projection zoom lens according to Example 4. FIG. 6 is an aberration curve diagram of the projection zoom lens of Example 4. FIG. 10 is a cross-sectional view illustrating a configuration of a projection zoom lens according to Example 5. FIG. FIG. 10 is an aberration curve diagram of the projection zoom lens according to Example 5. It is a schematic block diagram of the projector apparatus as an image display apparatus.

  Hereinafter, embodiments for carrying out the invention will be described.

  In the “projection zoom lens” of the present invention, “oblique light beam” is used as a projection light beam for forming a projected image.

  5, FIG. 3, FIG. 5, FIG. 7, and FIG. 9 show five embodiments of the projection zoom lens.

The zoom lenses according to these embodiments correspond to specific Examples 1 to 5 described later in this order.
In each of the above figures, the left side of the figure is the “enlargement side” and the right side is the “reduction side”. In order to avoid complications, the symbols are shared in these drawings.
In each of the above drawings, the first lens group, the second lens group, and the third lens group are indicated by reference numerals G1 to G3 in this order, respectively.

  In other words, the projection zoom lens according to the embodiment shown in the above drawings has a three-lens group configuration in which the first lens group G1 to the third lens group G3 are sequentially arranged from the enlargement side to the reduction side.

  An “aperture stop” is arranged in the third lens group G3.

  The following symbols are attached to the lenses in each lens group. That is, in the i-th lens group (i = 1 to 3), the j-th lens counted from the magnification side is represented by “Lij”.

Further, in each of the above drawings, the symbol CG indicates “a cover glass of an image display element (light valve)”.
In these embodiments and examples, “DMD as a micromirror device” is assumed as the light valve, but of course, the light valve is not limited to this.

  In the above figures, the upper diagram shows “lens group arrangement at the wide angle end (indicated as wide angle)”, and the lower diagram shows “lens group arrangement at the telephoto end (indicated as telephoto)”.

  Also, the arrows drawn between the upper and lower figures in these figures indicate the displacement of the second lens group G2 and the third lens group G3 during zooming from the wide-angle end to the telephoto end. Indicates direction.

  In the projection zoom lens according to the embodiment shown in each of the above drawings, both the first lens group G1 and the second lens group G2 have “negative refractive power”.

The third lens group G3 has “positive refractive power”.
That is, the refractive power distribution of the first lens group G1, the second lens group G2, and the third lens group G3 is “negative / negative / positive”.

  Hereinafter, the “lens group having a negative refractive power” is also referred to as a “negative group”, and the “lens group having a positive refractive power” is also referred to as a “positive group”.

  As described above, the projection zoom lens according to the present invention is a negative lens group leading type of “negative / negative / positive” from the enlargement side toward the reduction side.

  By setting the negative lens group in advance, the chief ray height can be made lower and the effective lens diameter can be made smaller. Therefore, a wide-angle projection zoom lens can be realized in a compact manner.

  In addition, it is possible to keep the “light beam jump angle” from the second lens group to the first lens group small during image projection.

  At the time of image projection, a projected light beam (light beam by oblique rays) from the light valve side is guided from the third lens group G3 side to the first lens group G1 side.

  At this time, since the first lens group G1 and the second lens group G2 are both negative, the divergence angle of the light beam from the third lens group G3 can be easily expanded by the second and first lens groups.

  Accordingly, the jump angle of the light beam transferred from the second lens group G1 to the first lens group G1 can be suppressed small, and the “divergence angle of the radiated light beam” from the first lens group G1 can be increased without difficulty.

  In addition, there is an effect of suppressing performance deterioration due to the eccentricity of the lens at the time of manufacture.

The projection zoom lens according to the present invention satisfies (4) among the following conditions (1) to (4) together with the above-described configuration, but at least one of the conditions (1) to (3) together with the condition (4). Is preferably satisfied.

(1) 0.10 <f1 / f2 <0.25
(2) 1.5 <| f1 | / Fw <2.1
(3) 1.9 <f3 / Fw <2.7
(4) 38 degrees <ωw.

  The meanings of the parameter symbols in these conditions (1) to (4) are as follows.

  “F1” is the focal length (<0) of the first lens group, “f2” is the focal length (<0) of the second lens group, and “f3” is the focal length (> of the third lens group). 0).

  “Fw” is a focal length at the wide-angle end of the entire lens system, and “ωw” is a half angle of view at the wide-angle end.

  Condition (1) is an effective condition for realizing “wide field angle and good aberration correction” at the wide-angle end, and particularly effective for good correction of astigmatism and curvature of field.

  When the upper limit of the condition (1) is exceeded, the refractive power (= 1 / f1) of the first lens group becomes “relatively small in absolute value” with respect to the refractive power of the second lens group, and the field curvature is large. Easy to be.

When the lower limit of condition (1) is exceeded, the refractive power of the first lens group becomes “relatively large in absolute value” with respect to the refractive power of the second lens group (= 1 / f2), and the astigmatic difference is large. Easy to be.
When the condition (1) is satisfied, an optimum solution for astigmatism correction can be obtained, and an increase in field curvature can be effectively suppressed.
In the zoom lens for projection according to the present invention, the refractive power distribution “negative / negative / positive” of the first lens unit to the third lens unit easily satisfies the condition (1).

  Condition (2) is “the focal length of the first lens unit: the optimum range of f1” at the wide-angle end of the entire lens system.

If the range of the condition (2) is exceeded, the balance between the focal length f1 of the first lens group and the focal length Fw at the wide-angle end of the entire lens system tends to be lost.
In the three-lens group configuration like the projection zoom lens of the present invention, the “aberration correction burden” of the first lens group is large even if the focal length of the first lens group is too small or too large.

  It is particularly desirable for correction of “field curvature and axial chromatic aberration” to be within the range of condition (2).

  By satisfying the condition (2), “aberration correction by the first lens group” at the time of zooming can be optimized, and the remaining of various aberrations including curvature of field and chromatic aberration can be effectively avoided.

Condition (3) is a condition for improving various aberrations in the entire zooming range.
In the projection zoom lens according to the present invention, the second lens group can be an “aberration correction group”, and the third lens group can be a “variable magnification group”.

Since the third lens group is provided with an “aperture stop”, it affects all aberrations.
Among these, the influence on spherical aberration and coma is great.

  When the parameter of the condition (3) becomes large (or small), the positive refractive power of the third lens group becomes relatively small (or large) with respect to the refractive power at the wide angle end of the entire lens system.

  When the upper limit or lower limit of the condition (3) is exceeded, “spherical aberration and coma aberration are likely to occur” easily.

  By satisfying the condition (3), it is possible to effectively suppress the occurrence of various aberrations, particularly spherical aberration and coma aberration.

Condition (4) defines the “half-angle range” at the wide-angle end.
As described above, the “projection zoom lens” of the present invention uses the “oblique light beam” as the projection light beam for forming the projected image.

  For this reason, the projection image is formed by oblique rays and can be used as an image projection area in a part of the “axis target area centered on the lens optical axis”.

  For this reason, in order to increase the area of the projection surface on which an image is projected, it is necessary to widen the angle of the projection zoom lens.

  Further, recently, there is a strong demand to reduce the projection distance of the projector device and “place the projector device closer to the projection surface”.

  In order to realize a projection surface having a large area with such a close arrangement to the projection surface, further widening of the angle is desired for the projection zoom lens.

  A “projection zoom lens having a half angle of view larger than 38 degrees at the wide angle end” that satisfies the condition (4) has a very wide angle of view.

  In each of the projection zoom lenses according to the embodiments shown in the above drawings, the first lens group G1 which is “the most magnified lens group at the time of zooming” is fixed.

  At the time of zooming, the second lens group G2 and the third lens group G3 move.

  That is, upon zooming from the wide-angle end to the telephoto end, the second lens group G2 moves to the reduction side, and the third lens group G3 moves to the enlargement side.

  In Examples 1 to 5, the refractive power of the first lens group G1 is the largest in “absolute value”.

  These configurations are preferable in a projection zoom lens having negative, negative, and positive refractive power distribution.

The number of lenses constituting the first lens group is preferably three or less.
Since a lens having a large lens diameter is used for the first lens group, the size of the first lens group is likely to increase when the number of constituents of the first lens group is four or more.

  Further, the weight of the first lens group also becomes heavy, and there is a risk that decentration may occur due to the weight of the first lens group.

  The first lens group preferably has at least one aspheric lens.

  By disposing at least one aspheric lens in the first lens group, distortion can be effectively reduced.

  Before giving a specific example of a projection zoom lens, a projector apparatus will be briefly described as an embodiment of an image display apparatus with reference to FIG.

  The projector apparatus 1 shown in FIG. 11 is an example in which a DMD that is a micromirror device is employed as the light valve 3. Of course, the light valve is not limited to this.

  The projector device 1 includes an illumination system 2, a DMD 3 that is a light valve, and a projection zoom lens 4 that is a projection optical system.

  The illumination system 2 includes a light source 21, a condenser lens CL, an RGB color wheel CW, and a mirror M.

  The light source 21 emits light that illuminates the projection image displayed on the light valve 3.

  The condenser lens CL, the RGB color wheel CW, and the mirror M constitute an “illumination optical system”.

As the projection zoom lens 4, one described in any one of claims 1 to 8 , specifically, any one of Examples 1 to 5 described later is used.

  The illumination system 2 irradiates the display surface of the DMD 3 with “R (red), G (green), and B (blue) light of three colors” separated in time.

  Then, the inclination of the “micromirror corresponding to each pixel” on the display surface is controlled at the timing when each color light of RGB is irradiated on the display surface.

  In this way, the “projection image to be projected” is displayed on the display surface of the DMD 3.

  The projection image displayed on the display surface of the DMD 3 is projected as an enlarged image on the screen 5 that is the projection surface by the projection zoom lens 4 that is a projection optical system, and is enlarged and displayed.

  That is, the projection zoom lens receives a projection light beam modulated by the projection image, and projects an enlarged image of the projection image on the screen 5.

  The illumination system 2 including the light source 21, the condenser lens CL, the RGB color wheel CW, and the mirror M needs to “ensure a certain amount of space” for arranging the illumination system 2.

For this reason, it is necessary to increase the incident angle of the illumination light incident on the DMD 3 from the illumination system 2 to some extent.
Due to the above-described relationship between the space between the projection zoom lens 4 and the illumination system 2, it is necessary to secure the back focus of the projection zoom lens 4 to some extent.

In the projection zoom lenses of Examples 1 to 5 described later, the third lens G3 moves to the enlargement side upon zooming from the wide angle end to the telephoto end.
Accordingly, a sufficiently large back focus is ensured even during zooming.

  That is, the projector device 1 whose embodiment is shown in FIG. 11 illuminates the image display element 3 with the light source 21, the image display element 3 that displays the projection image to be projected, and the light emitted from the light source 21. Illumination optical systems CL, CW, and M, and a projection optical system that receives a projection light beam irradiated by the illumination optical system and modulated by the projection image, and projects an “enlarged image of the projection image” on the projection surface 5 The projection zoom lens according to any one of claims 1 to 11 is used as a projection optical system.

  Hereinafter, five specific examples of the projection zoom lens according to the present invention will be described.

  The meanings of symbols in each embodiment are as follows.

F: Focal length of the entire optical system
Fno: Numerical aperture
R: radius of curvature (“paraxial radius of curvature” for aspheric surfaces)
D: Surface spacing
Nd: Refractive index
νd: Abbe number
BF: Back focus.

  The aspherical surface is represented by the following well-known expression.

^{X = (H 2 / R)} / [1+ {1-K (H / r) 2} 1/2]
+ C4 · H ⁴ + C6 · H ⁶ + C8 · H ⁸ + C10 · H ¹⁰ +.

  In this equation, X is “height from the optical axis with respect to the surface apex: displacement in the optical axis direction at the position of H”, K is “conic coefficient”, C4, C6, C8, C10. Is the aspheric coefficient.

  In the following, for the “meniscus lens”, a convex or concave side and whether the refractive power is positive or negative are specified.

  Therefore, for example, “a negative meniscus lens having a convex surface on the enlargement side” is referred to as “a negative lens convex on the enlargement side”.

  The “biconvex lens” is one of positive lens forms, and the “biconcave lens” is one of negative lens forms.

  In Examples 1 to 5 described below, the first lens group G1 is fixed during zooming.

"Example 1"
The projection zoom lens of Example 1 is shown in FIG.

  As shown in FIG. 1, the first lens group G1 includes lenses L11 to L13, and the second lens group G2 includes lenses L21 to L25.

  The third lens group G3 includes lenses L31 to L36.

  As described above, a DMD is assumed as the light valve, and the DMD has a cover glass CG. This also applies to the following Examples 2 to 5.

  When zooming from the wide-angle end to the telephoto end, the second lens group G2 moves to the reduction side, and the third lens group G3 moves to the enlargement side.

  The first lens group G1 is a negative group, a negative lens L11 that is convex on the magnifying side, a meniscus lens L12 that is concave on the magnifying side and the peripheral portion of the lens is bent to the reducing side, and has a small thickness ratio, and is convex on the magnifying side It is composed of a negative lens L13.

The second lens group G2 is a negative group, and includes a biconvex lens L21, a biconcave lens L22, a positive lens L23 convex to the reduction side, a biconcave lens L24, and a biconvex lens L25.
The lens L23 and the lens L24 are cemented.

The third lens group G3 is a positive group, and includes a biconvex lens L31, a positive lens L32 convex on the enlargement side, a negative lens L33 convex on the enlargement side, a biconvex lens L34, a negative lens L35 convex on the reduction side, and a biconvex lens L36. Has been.
The lens L33 and the lens L34 are cemented.

  An “aperture stop” is disposed on the reduction side of the positive lens L32.

  The focal length: F range, numerical aperture, and half angle of view at the wide-angle end: ωw of Example 1 are as follows.

F = 13.0 to 15.5 mm, Fno = 2.55 to 2.89, ωw = 42.1 °
The data of Example 1 is shown in Table 1.

  In Table 1, “S” is “surface number”, which is the number of the surface counted from the enlarged side, the surface of the aperture stop (surface number: 20 in the table), the surface of the cover glass CG (surface number in the table). : 28, 29).

  In the table, “INF” indicates that the radius of curvature is infinite, and “*” indicates that the surface to which this symbol is attached is “aspherical”.

  These matters are the same in each of the following embodiments.

"Aspherical data"
The aspherical data is shown in Table 2.

In the notation of Table 2, for example, “6.68101E-21” represents “6.68101 × 10 ⁻²¹ ”. The same applies to the following.

  In Table 1, S6 and S15 represent lens group intervals that change during zooming.

  Table 3 shows the distance between the lens groups when the projection distance is 1600 mm for the wide-angle end, the middle, and the telephoto end.

"Parameter values for each condition"
Table 4 shows parameter values of the conditions (1) to (4).

FIG. 2 shows aberration diagrams of Example 1.
2 shows the aberration at the “wide-angle end (displayed as wide angle)”, the middle shows the aberration at “intermediate focal length (displayed as intermediate)”, and the lower shows the aberration at the “telephoto end (displayed as telephoto)”.

  In the aberration diagrams at each stage, the left diagram is “spherical aberration”, the middle diagram is “astigmatism”, and the right diagram is “distortion aberration”.

R, G, and B in the “spherical aberration” diagram represent wavelengths: R = 625 nm, G = 550 nm, and B = 460 nm, respectively.
In the “astigmatism” diagram, “T” indicates tangential and “S” indicates sagittal rays.

  Astigmatism and distortion are shown for a wavelength of 550 nm.

  These indications in the aberration diagrams are the same in the aberration diagrams of Examples 2 to 5 below.

"Example 2"
The projection zoom lens of Example 2 is shown in FIG.

  As shown in FIG. 3, the first lens group G1 is composed of lenses L11 to L13, and the second lens group G2 is composed of lenses L21 to L25.

  The third lens group G3 includes lenses L31 to L36.

  When zooming from the wide-angle end to the telephoto end, the second lens group G2 moves to the reduction side, and the third lens group G3 moves to the enlargement side.

  The first lens group G1 is a negative group, a negative lens L11 that is convex on the magnifying side, a meniscus lens L12 that is concave on the magnifying side and the peripheral portion of the lens is bent to the reducing side, and has a small thickness ratio, and is convex on the magnifying side It is composed of a negative lens L13.

The second lens group G2 is a negative group, and includes a biconvex lens L21, a biconcave lens L22, a positive lens L23 convex to the reduction side, a biconcave lens L24, and a biconvex lens L25.
The lens L23 and the lens L24 are cemented.

  The third lens group G3 is a positive group, and includes a biconvex lens L31, a positive lens L32 convex on the enlargement side, a negative lens L33 convex on the enlargement side, a biconvex lens L34, a negative lens L35 convex on the reduction side, and a biconvex lens L36. Has been.

  The lens L33 and the lens L34 are cemented.

  An “aperture stop” is disposed on the reduction side of the positive lens L32.

  In Example 2, the focal length of the entire system: the range of F, the numerical aperture, and the half angle of view at the wide-angle end: ωw are as follows.

F = 13.0 to 15.5 mm, Fno = 2.55 to 2.89, ωw = 42.1 °
The data of Example 2 is shown in Table 5.

"Aspherical data"
Table 6 shows the aspherical data.

  Table 7 shows the distance between the lens groups when the projection distance is 1600 mm for the wide-angle end, the middle, and the telephoto end.

"Parameter values for each condition"
Table 8 shows parameter values of the conditions (1) to (4).

  FIG. 4 is an aberration diagram of Example 2 according to FIG.

"Example 3"
The projection zoom lens of Example 3 is the one shown in FIG.

  As shown in FIG. 5, the first lens group G1 includes lenses L11 to L13, and the second lens group G2 includes lenses L21 to L25.

  The third lens group G3 includes lenses L31 to L36.

  When zooming from the wide-angle end to the telephoto end, the second lens group G2 moves to the reduction side, and the third lens group G3 moves to the enlargement side.

  The first lens group G1 is a negative group, a negative lens L11 that is convex on the enlargement side, a concave lens on the enlargement side, and the lens peripheral portion is inflected to the reduction side. It is composed of a negative lens L13.

  The second lens group G2 is a negative group, and includes a biconvex lens L21, a negative lens L22 concave on the reduction side, a positive lens L23 convex on the reduction side, a biconcave lens L24, and a positive lens L25 convex on the enlargement side.

  The lens L23 and the lens L24 are cemented.

  The third lens group G3 is a positive group, and includes a biconvex lens L31, a positive lens L32 convex on the enlargement side, a biconcave lens L33, a biconvex lens L34, a negative lens L35 convex on the reduction side, and a biconvex lens L36.

  The lens L33 and the lens L34 are cemented.

  An “aperture stop” is disposed on the reduction side of the positive lens L32.

  In Example 3, the focal length of the entire system: the range of F, the numerical aperture, and the half angle of view at the wide-angle end: ωw are as follows.

F = 12.2 to 14.5 mm, Fno = 2.55 to 2.89, ωw = 43.8 °
The data of Example 3 is shown in Table 9.

"Aspherical data"
Table 10 shows the aspheric data.

  Table 11 shows the distance between the lens groups when the projection distance is 1500 mm for the wide-angle end, the middle, and the telephoto end.

"Parameter values for each condition"
Table 12 shows parameter values of the conditions (1) to (4).

  FIG. 6 is an aberration diagram of Example 3 according to FIG.

Example 4
The projection zoom lens of Example 4 is shown in FIG.

  As shown in FIG. 7, the first lens group G1 is composed of lenses L11 to L13, and the second lens group G2 is composed of lenses L21 to L25.

  The third lens group G3 includes lenses L31 to L36.

  When zooming from the wide-angle end to the telephoto end, the second lens group G2 moves to the reduction side, and the third lens group G3 moves to the enlargement side.

  The first lens group G1 is a negative group, and includes a negative lens L11 that is convex on the enlargement side, a meniscus lens L12 that is convex on the enlargement side and has a small thickness deviation ratio, and a negative lens L13 that is convex on the enlargement side.

  The second lens group G2 is a negative group, and includes a biconvex lens L21, a biconcave lens L22, a positive lens L23 convex to the reduction side, a biconcave lens L24, and a biconvex lens L25.

  The lens L23 and the lens L24 are cemented.

  The third lens group G3 is a positive group, and includes a biconvex lens L31, a positive lens L32 convex on the enlargement side, a negative lens L33 convex on the enlargement side, a biconvex lens L34, a negative lens L35 convex on the reduction side, and a biconvex lens L36. Has been.

  The lens L33 and the lens L34 are cemented.

  An “aperture stop” is disposed on the reduction side of the positive lens L32.

  In Example 4, the focal length of the entire system: the range of F, the numerical aperture, and the half field angle at the wide-angle end: ωw are as follows.

F = 13.7 to 16.4 mm, Fno = 2.55 to 2.89, ωw = 40.4 °
The data of Example 4 is shown in Table 13.

"Aspherical data"
Table 14 shows the aspheric data.

  Table 15 shows the distance between the lens groups when the projection distance is 1700 mm, at the wide-angle end, the middle, and the telephoto end.

"Parameter values for each condition"
Table 16 shows parameter values of the conditions (1) to (4).

  FIG. 8 is an aberration diagram of Example 4 similar to FIG.

"Example 5"
The projection zoom lens of Example 5 is shown in FIG.

  As shown in FIG. 9, the first lens group G1 includes lenses L11 to L13, and the second lens group G2 includes lenses L21 to L25.

  The third lens group G3 includes lenses L31 to L36.

  When zooming from the wide-angle end to the telephoto end, the second lens group G2 moves to the reduction side, and the third lens group G3 moves to the enlargement side.

  The first lens group G1 is a negative group, and includes a negative lens L11 that is convex on the enlargement side, a meniscus lens L12 that is convex on the enlargement side and has a small thickness deviation ratio, and a negative lens L13 that is convex on the enlargement side.

The second lens group G2 is a negative group, and includes a biconvex lens L21, a biconcave lens L22, a positive lens L23 convex to the reduction side, a biconcave lens L24, and a biconvex lens L25.
The lens L23 and the lens L24 are cemented.

The third lens group G3 is a positive group, and includes a biconvex lens L31, a positive lens L32 convex on the enlargement side, a negative lens L33 convex on the enlargement side, a biconvex lens L34, a negative lens L35 convex on the reduction side, and a biconvex lens L36. Has been.
The lens L33 and the lens L34 are cemented.

  An “aperture stop” is disposed on the reduction side of the positive lens L32.

  In Example 5, the focal length of the entire system: the range of F, the numerical aperture, and the half angle of view at the wide-angle end: ωw are as follows.

F = 14.6 to 17.9 mm, Fno = 2.55 to 2.89, ωw = 38.9 °
The data of Example 5 is shown in Table 17.

"Aspherical data"
Table 18 shows the aspheric data.

  The distance between the lens groups when the projection distance is 1800 mm is shown in Table 19 for the wide-angle end, the middle, and the telephoto end.

"Parameter values for each condition"
Table 20 shows parameter values of the conditions (1) to (4).

  FIG. 10 is an aberration diagram of Example 5 following FIG.

  As shown in each aberration diagram, in each example, various aberrations are corrected at a high level. That is, spherical aberration, astigmatism, curvature of field, lateral chromatic aberration, and distortion are sufficiently corrected.

  As shown in Examples 1 to 5, the first lens group G1 is composed of three lenses.

  As the first lens group, a lens having a large lens diameter is used, but the first lens group can be reduced in weight by using three first lens groups as in the embodiment.

  This weight reduction can suppress the eccentricity of the lens due to its own weight.

In addition, it is possible to effectively reduce distortion by arranging at least one aspheric lens in the first lens group.
In Examples 1 to 5, the distortion aberration can be positively corrected, but this is nothing but the result of disposing an aspheric lens in the first lens group.

  The first lens group G1 has “an astigmatism and distortion correction effect”.

  In Examples 1 to 5, the first lens group G1 has “the most enlargement side surface is convex on the enlargement side, and the most reduction surface is concave”.

  By doing so, an effect of “reducing fluctuations in field curvature and distortion” at the time of zooming can be obtained.

  As described above, in any of the projection zoom lenses of Examples 1 to 5, the first lens group G1 is fixed when zooming from the wide-angle end to the telephoto end.

  Then, the second lens group G2 moves to the reduction side, and the third lens group G3 moves to the enlargement side.

  By doing so, fluctuations in various aberrations during zooming can be reduced.

  In addition, the “half angle of view at the wide angle end: ωw” of the projection zoom lenses of Examples 1 to 5 exceeds 38 degrees.

  That is, the half angle of view: ωw is 42.1 degrees, 42.1 degrees, 43.8 degrees, 40.4 degrees, and 38.9 degrees in claims 1 to 5, respectively.

  As described above, as a projection zoom lens having a three-lens group configuration, those described in Patent Documents 1 and 2 are known as having a negative, positive, and positive refractive power distribution.

  The projection zoom lenses described in Patent Documents 1 and 2 have good performance because the aberration during zooming is sufficiently suppressed.

  However, the projection zoom lens described in Patent Document 1 has a half angle of view of 29 degrees at the wide angle end.

  In addition, the projection zoom lens described in Patent Document 2 has a half angle of view at the wide angle end of only 38 degrees.

  The projection zoom lens according to the present invention employs “negative / negative / positive” refractive power distribution, and can realize “a large half angle of view exceeding 38 degrees” at the wide-angle end as in the first to fifth embodiments.

G1 first lens group
G2 second lens group
G3 Third lens group

Japanese Patent No. 5152854 Japanese Patent No. 4601430

Claims (9)

A projection zoom lens that constitutes a projection optical system of an image display device that projects a projection image displayed on an image display element onto a projection surface as an enlarged image of the projection image and displays the enlarged image,
In order from the enlargement side to the reduction side, a first lens unit having a negative refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power are provided, and an aperture is formed in the third lens group. Ri name by arranging the aperture,
The first lens group is composed of three or less lenses, and its refractive power is the largest in absolute value among the first to third lens groups,
Half angle of view at wide-angle end: ωw, conditions:
(4) 38 degrees <ωw
Projection zoom lens that satisfies the requirements. The projection zoom lens according to claim 1,
The focal length of the first lens group is f1, and the focal length of the second lens group is f2.
(1) 0.10 <f1 / f2 <0.25
Projection zoom lens characterized by satisfying The projection zoom lens according to claim 1 or 2,
The focal length of the first lens group: f1, the focal length of the wide-angle end of the entire lens system: Fw, the conditions:
(2) 1.5 <| f1 | / Fw <2.1
Projection zoom lens characterized by satisfying The projection zoom lens according to any one of claims 1 to 3,
The focal length of the third lens group is f3, and the focal length of the wide-angle end of the entire lens system is Fw.
(3) 1.9 <f3 / Fw <2.7
Projection zoom lens characterized by satisfying The projection zoom lens according to any one of claims 1 to 4,
A zoom lens for projection, wherein a lens group on the most magnified side is fixed at the time of zooming. The projection zoom lens according to claim 5.
A projection zoom lens, wherein the second lens group and the third lens group move during zooming. The projection zoom lens according to claim 6.
A zoom lens for projection, wherein when zooming from the wide-angle end to the telephoto end, the second lens group moves to the reduction side and the third lens group moves to the enlargement side. The projection zoom lens according to any one of claims 1 to 7,
A projection zoom lens , wherein the first lens group includes at least one aspherical lens. A light source;
An image display element for displaying a projection image to be projected;
An illumination optical system that illuminates the image display element with light emitted from the light source;
A projection optical system that is irradiated with the illumination optical system and receives a projection light beam modulated by the projection image, and projects an enlarged image of the projection image on a projection surface;
An image display apparatus using the projection zoom lens according to any one of claims 1 to 8 as the projection optical system.

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