JP2014219540A - Zoom lens for projection and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a new zoom lens for projection having a wide angle of view and high performance.SOLUTION: There is provided a zoom lens for projection used in an image display device that projects an image for projection displayed on an image display element on a projection target surface to enlarge and display the image, and having a four-lens-group configuration having first to fourth lens groups G1 to G4 arranged from the enlargement side to the reduction side, where the first lens group G1 has a negative, the second lens group G2 a negative, and the third lens group G3 a positive refractive power, respectively; and the fourth lens group G4 moves to the enlargement side in association with the variation of magnification from the wide angle end to the telephoto end.

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 image to be enlarged and projected on an “image 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 zoom lens can be applied to various light valves.

  In the micromirror device, the micromirrors arrayed on the image display surface are selectively tilted to display an image.

  When used as a light valve, the micromirror device has various restrictions, but is advantageous for downsizing and increasing the brightness of the projector apparatus, and has recently been widely used.

  In recent years, a zoom lens for projection has been required to be “high magnification and wide angle”.

The “lens used for image projection” is generally different from a photographic lens system for cameras in that “oblique light” is used as an imaging light beam.
In a photographing lens for a camera, a rotationally symmetric region with respect to the optical axis of the lens system is a photographing region, and in a photographing lens with a wide angle of view, a “large photographing region around the lens optical axis” is possible.

  In a lens used for projecting an image, a projected image is formed by oblique rays, so that a part of the “large area centered on the lens optical axis” can be used as an image projection area.

  For this reason, widening the angle of the projection zoom lens is indispensable for increasing the area of the projection surface onto which the image is projected.

  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.

Various projection zoom lenses composed of four lens groups are conventionally known.
Patent Document 1 discloses a projection zoom lens having a four lens group configuration in which four lens groups of negative, negative, positive, and positive are arranged from the enlargement side (screen side) to the reduction side (light valve side).

  The projection zoom lens described in Patent Document 1 has sufficiently suppressed aberrations, but the half angle of view at the wide-angle end is only 29 degrees, and it is difficult to say that it sufficiently meets recent demands. .

  In view of the above-described circumstances, an object of the present invention is to realize a novel projection zoom lens having a wide angle of view and high performance.

  The projection zoom lens according to the present invention is a projection zoom lens used in an image display device that projects and displays an image for projection displayed on an image display element on a projection surface. The first to fourth lens groups are sequentially arranged from the enlargement side to the reduction side, the first lens group has a negative refractive power, the second lens group has a negative refractive power, The third lens group has a positive refractive power, and the fourth lens group moves to the enlargement side upon zooming from the wide-angle end to the telephoto end.

  According to the present invention, a novel projection zoom lens having a wide angle of view and high performance can be realized.

3 is a cross-sectional view illustrating a configuration of a projection zoom lens according to Embodiment 1. FIG. 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. 10 is a cross-sectional view illustrating a configuration of a projection zoom lens according to Example 6. FIG. 10 is an aberration curve diagram of the projection zoom lens of Example 6. FIG. 10 is a cross-sectional view illustrating a configuration of a projection zoom lens according to Example 7. FIG. 10 is an aberration curve diagram of the projection zoom lens of Example 7. FIG. 10 is a cross-sectional view illustrating a configuration of a projection zoom lens according to Example 8. FIG. FIG. 10 is an aberration curve diagram of the projection zoom lens according to Example 8. 10 is a cross-sectional view illustrating a configuration of a projection zoom lens according to Example 9. FIG. 10 is an aberration curve diagram of the projection zoom lens of Example 9. FIG. 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.

The zoom lens of the present invention is a “projection zoom lens” as described above.
As described above, the “projection lens” uses “oblique light” as the imaging light beam, and the projection zoom lens of the present invention uses “oblique light beam” as the projection light beam for forming the projection image. It is done.

  1, 3, 5, 7, 7, 9, 11, 13, 15, and 17 show nine embodiments of the zoom lens for projection.

The projection zoom lenses according to these embodiments correspond to specific Examples 1 to 9 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”. The “enlargement side” is the side toward the projection surface such as a screen, and the “reduction side” is the side toward the image display element.

  That is, the projection zoom lens according to each embodiment constitutes a projection optical system that projects the projection image displayed on the image display element onto the projection surface by the projection optical system and displays the enlarged image.

In order to avoid complications, the same reference numerals are used in the above drawings.
In each of the drawings, reference numeral G1 indicates a first lens group, reference numeral G2 indicates a second lens group, reference numeral G3 indicates a third lens group, and reference numeral G4 indicates a fourth lens group.

  That is, the projection zoom lens according to the embodiment shown in the above drawings has a four-lens group configuration in which the first lens group G1 to the fourth lens group G4 are sequentially arranged from the enlargement side toward the reduction side.

  An “aperture stop” is disposed below the third lens group G3.

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)”.

  In these drawings, “the arrow drawn between the upper and lower diagrams” indicates the second lens group G2 to the fourth lens group G4 during zooming from the wide-angle end to the telephoto end. Indicates the direction of transition.

  Regarding the lenses constituting each lens group, in the i-th lens group (i = 1 to 4), the j-th lens counted from the magnification side is represented by “Lij”.

In the projection zoom lens according to the embodiment shown in each of the drawings, both the first lens group G1 and the second lens group G2 have a negative refractive power, and the third lens group has a positive refractive power.
That is, in the first to fourth lens groups, the refractive power distribution of the first lens group G1 to the third lens group G3 is “negative / negative / positive”.

The refractive power of the fourth lens group G4 can be “positive or negative” as in a specific example described later.
At the time of zooming from the wide angle end to the telephoto end, the fourth lens group G4 moves to the enlargement side.

  By moving the fourth lens to the enlargement side, it is possible to reduce the “aberration fluctuation due to zooming”, and in particular, it is possible to reduce the fluctuation amount of the field curvature.

  The zoom lens for projection according to each embodiment described below satisfies the following condition (1).

(1) 34 degrees <ωw <50 degrees
Condition (1) defines the range of the half angle of view at the wide angle end.
That is, the half angle of view at the wide-angle end of the projection zoom lens according to the present invention is greater than 34 degrees and less than 50 degrees, and the zoom lens has a very wide angle of view.

  In order to satisfy such conditions, the negative lens group leading type is preferable.

  The projection zoom lens according to the present invention sets the refractive power distribution of the first lens group G1 to the third lens group G3 to “negative / negative / positive” and precedes the negative lens group (first and second lens groups). Yes.

  By setting the negative lens group in advance, the principal ray height can be further reduced, and the effective lens diameter can be reduced. Therefore, a wide-angle projection zoom lens can be realized in a compact manner.

  In addition, the “light beam jump angle” from the second lens group to the first lens group during image projection can be kept small.

  At the time of image projection, a projection light beam (light beam by oblique rays) from the light valve side is guided from the fourth lens group side to the first lens group 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 flux from the third lens group can be easily expanded by the second and first lens groups.

  Therefore, as described above, the jump angle of the light beam transferred from the second lens group G2 to the first lens group G1 can be kept small.

  For this reason, the divergence angle of the imaging light beam radiated 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.

  In the projection zoom lens according to the present invention, it is preferable that the second lens group moves to the reduction side and the third lens group moves to the enlargement side upon zooming from the wide-angle end to the telephoto end.

  Upon zooming from the wide-angle end to the telephoto end, the second lens group can “loosely and monotonously move toward the reduction side” or “move along a locus convex toward the reduction side”.

  In zooming from the wide-angle end to the telephoto end, when the third lens group moves to the enlargement side, it is preferable that the projection zoom lens satisfies the following condition (4) in addition to the above configuration.

(4) 1.0 <D3 / D4 <1.2
In the condition (4), “D3” and “D4” are the movement amounts of the third lens group G3 and the fourth lens group G4 at the time of zooming, respectively.

  Since the third lens group G3 and the fourth lens group G4 move in the same direction, the movement amounts D3 and D4 have the same sign.

By satisfying the condition (4), it is possible to easily maintain high performance in the “total zoom range from the wide angle short to the telephoto end” with a zoom ratio of 1.45 times or more.
Outside the range of condition (4), fluctuations in various aberrations, particularly on the telephoto side, tend to increase during zooming.

  In the zoom lens for projection according to the present invention, it is preferable that the first lens group is fixed when zooming from the wide-angle end to the telephoto end.

  As described above, when the first lens group G1 is fixed at the time of zooming, the outer shape of the projection zoom lens provided in the image forming apparatus does not change.

  Therefore, there is an advantage that “decentering of the lens group” is less likely to occur compared to the type in which the first lens group moves during zooming.

  The movement of the first lens group to the fourth lens group as described above accompanying zooming makes it possible to reduce the fluctuation amount of various aberrations, especially the fluctuation amount of coma aberration accompanying zooming.

  In addition to the above-described configuration, the projection zoom lens according to the present invention can achieve even better performance by satisfying one or more of the following conditions (2) and (3).

(2) | F3 | <| F4 |
(3) 0.9 <F3-4w / F3-4t <1.1.

  The meanings of the parameter symbols in the conditions (2) and (3) are as follows.

  “F3” is the focal length of the third lens group, and “F4” is the focal length of the fourth lens group.

  “F3-4w” is “the combined focal length of the third lens group and the fourth lens group” at the wide angle end, and “F3-4t” is the “combined focal length of the third lens group and the fourth lens group at the telephoto end”. Is.

  Condition (2) defines the magnitude relationship between the absolute values of the focal lengths F3 and F4.

  When the condition (2) is not satisfied, it is difficult to balance the power distribution of the entire projection zoom lens system, and various aberrations are likely to increase.

  By satisfying the condition (2), it is easy to balance the power distribution of the entire system, and it is easy to correct various aberrations.

  When the upper limit of condition (3) is exceeded, the “difference in the combined focal length of the third lens group and the fourth lens group” becomes large during zooming, and spherical aberration and axial chromatic aberration tend to become large during zooming.

  Also, astigmatism at the telephoto end tends to increase.

  When the lower limit of condition (3) is exceeded, coma at the telephoto end tends to increase.

  By satisfying the condition (3), it is possible to suppress an increase in astigmatism and coma at the telephoto end, and to effectively suppress variations in spherical aberration and axial chromatic aberration during zooming.

The refractive power of the fourth lens group G4 is preferably “smallest in absolute value” among all the lens groups.
If the refractive power of the fourth lens group is larger than the refractive power of the other lens groups in absolute value, it becomes difficult to balance the power distribution of the entire system, which tends to increase various aberrations.

  In zooming from the wide-angle end to the telephoto end, when the second lens group G2 moves to the reduction side, it is preferable that the movement of the second lens group G2 to the reduction side is “slow”.

  In this case, it is preferable that the third lens group G3 and the fourth lens group G4 move “individually” to the enlargement side.

  By making the movement of the second lens group G2 to the fourth lens group G4 as described above, it is easy to suppress aberration fluctuations during zooming, and a high-performance projection zoom lens can be realized.

  In particular, when the first lens group is fixed, compactness can be improved.

  When zooming from the wide-angle end to the telephoto end, if the third lens group G3 and the fourth lens group G4 are moved to the enlargement side, it is easy to ensure the back focus even during zooming.

  Therefore, it is easy to use a micromirror device such as DMD as a light valve of a projection zoom lens.

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

  The image display apparatus includes a light source, an image display element, an illumination optical system, and a projection optical system.

  The “light source” emits light for forming an enlarged image projected on the projection surface.

  The “image display element” displays an image for projection.

  The “illumination optical system” illuminates the image display element with light emitted from a light source.

  The “projection optical system” is irradiated with a projection light beam that is irradiated by the illumination optical system and modulated by the projection image displayed on the image display element, and projects an enlarged image of the projection image onto the projection surface.

  The projector apparatus 1 shown in FIG. 19 is an example in which a DMD that is a micromirror device is employed as the light valve 3.

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

  As the projection zoom lens 4, the one described in any one of claims 1 to 9, specifically, any one of Examples 1 to 9 is used.

  The illumination system 2 includes a light source 21, a condenser lens CL, an RGB color wheel CW, and a mirror M, and it is necessary to “ensure a certain amount of space” in which the illumination system 2 is disposed.

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, the back focus of the projection zoom lens 4 needs to be ensured to “a certain size”.

  Light from the light source 21 is incident on the RGB color wheel CW through the condenser lens CL.

  The RGB color wheel CW rotates and sequentially separates the transmitted light into R (red), G (green), and blue (B). That is, the RGB three colors of light are sequentially separated in time.

  The “light of three colors RGB” is temporally separated from the illumination system 2 and irradiated to the DMD 3, and the tilt of the micromirror corresponding to each pixel is controlled at the timing when each color light is irradiated.

  In this way, the “projection image” is displayed on the DMD 3, and the light whose intensity is modulated by the projection image is magnified by the projection zoom lens 4 and magnified and projected onto the screen 5.

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

In the zoom lenses of Examples 1 to 9, the third lens group G3 and the fourth lens group G4 move 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.

  Nine specific examples of the projection zoom lens according to the present invention will be described below.

  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 “displacement in the direction of the optical axis at the position of the height H from the optical axis with respect to the surface vertex”, K is the “conical coefficient”, C4, C6, C8, C10. “Aspheric coefficient”.

"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 L24.

  The third lens group G3 is composed of two lenses L31 and L32.

  The fourth lens group G4 includes four lenses L41 to L44.

  As described above, a DMD is assumed as the light valve, and the DMD has a cover glass CG.

  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 and the fourth lens group G4 move to the enlargement side.

  The first lens group G1 is fixed during zooming.

  The first lens group G1 is a negative group, and includes a positive meniscus lens L11 having a convex surface on the enlargement side, a negative meniscus lens L12 having a convex surface on the enlargement side, and a meniscus lens L13.

  The meniscus lens L13 is a meniscus lens having a small thickness deviation ratio that is concave on the reduction side and the peripheral portion of the lens is bent on the reduction side.

  The second lens group G2 is a negative group, and includes a biconvex lens L21, a biconcave lens L22, a biconcave lens L23, and a biconvex lens L24.

  The biconvex lens L21 and the biconcave lens L22 are cemented.

The third lens group G3 is a positive group and includes two positive lenses L31 and L32.
The fourth lens group G4 is a negative group, and includes a negative meniscus lens L41 that is convex on the enlargement side, a biconvex lens L42, a negative meniscus lens L43 that is concave on the enlargement side, and a biconvex lens L44.

  The negative meniscus lens L41 and the biconvex lens L42 are cemented.

  In the description of Examples 1 to 9, “biconvex lens” is a positive lens form, and “biconcave lens” is a negative lens form.

  The focal length: F range, F number, half angle of view at the wide angle end: ωw of the entire system in Example 1 are as follows.

F = 16.3 to 24.4 mm, Fno = 2.55 to 3.33, ωw = 35.7 °
The data of Example 1 is shown in Table 1.

  In Table 1, “S (surface number)” is the surface number counted from the enlarged side, the surface of the aperture stop (surface number: 18 in the table), the surface of the cover glass CG (surface number in the table: 26). 27).

  “INF” in the table indicates that the radius of curvature is infinite. Furthermore, “*” indicates that the surface with this symbol is “aspherical surface”.

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

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

  S6, S13, and S18 of “D column” in Table 1 represent “lens group intervals that change upon zooming”.

  Table 3 shows the distance between the lens groups when the projection distance is 2000 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.
The upper part of FIG. 2 shows the aberration at “wide-angle end (displayed as wide angle)”, the middle part shows “intermediate focal length (displayed as intermediate)”, and the lower part shows aberration at “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 9 below.

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

  As shown in FIG. 3, the first lens group G1 includes lenses L11 to L13, and the second lens group G2 includes lenses L21 to L24.

  The third lens group G3 is composed of two lenses L31 and L32.

  The fourth lens group G4 includes four lenses L41 to L44.

  A DMD is assumed as the light valve, and the DMD has a cover glass CG.

  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 and the fourth lens group G4 move to the enlargement side.

  The first lens group G1 is a negative group, and includes a negative meniscus lens L11 having a convex surface on the enlargement side, a negative meniscus lens L12 having a convex surface on the enlargement side, and a meniscus lens L13.

  The meniscus lens L13 is a meniscus lens having a small thickness deviation ratio that is concave on the reduction side and the peripheral portion of the lens is bent on the reduction side.

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

  The biconcave lens L23 and the biconvex lens L24 are cemented.

The third lens group G3 is a positive group and includes two positive lenses L31 and L32.
The fourth lens group G4 is a negative group, and includes a negative meniscus lens L41 that is convex on the enlargement side, a biconvex lens L42, a negative meniscus lens L43 that is concave on the enlargement side, and a biconvex lens L44.

  The negative meniscus lens L41 and the biconvex lens L42 are cemented.

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

F = 13.1 to 19.6 mm, Fno = 2.55 to 3.34, ωw = 41.9 °
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 set to 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 similar 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 L24.

  The third lens group G3 is composed of two lenses L31 and L32.

  The fourth lens group G4 includes four lenses L41 to L44.

  A DMD is assumed as the light valve, and the DMD has a cover glass CG.

  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 and the fourth lens group G4 move to the enlargement side.

  The first lens group G1 is a negative group, and includes a negative meniscus lens L11 having a convex surface on the enlargement side, a negative meniscus lens L12 having a convex surface on the enlargement side, and a meniscus lens L13.

  The meniscus lens L13 is a meniscus lens having a small thickness deviation ratio that is concave on the reduction side and the peripheral portion of the lens is bent on the reduction side.

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

  The biconcave lens L23 and the biconvex lens L24 are cemented.

The third lens group G3 is a positive group and includes two positive lenses L31 and L32.
The fourth lens group G4 is a negative group, and includes a negative meniscus lens L41 that is convex on the enlargement side, a biconvex lens L42, a negative meniscus lens L43 that is concave on the enlargement side, and a biconvex lens L44.

  The negative meniscus lens L41 and the biconvex lens L42 are cemented.

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

F = 11.5 to 17.2 mm, Fno = 2.56 to 3.34, ωw = 45.5 °
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 1400 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 similar 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 L24.

  The third lens group G3 is composed of two lenses L31 and L32.

  The fourth lens group G4 includes four lenses L41 to L44.

  A DMD is assumed as the light valve, and the DMD has a cover glass CG.

  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 and the fourth lens group G4 move to the enlargement side.

  The first lens group G1 is a negative group, and includes a negative meniscus lens L11 having a convex surface on the enlargement side, a negative meniscus lens L12 having a convex surface on the enlargement side, and a meniscus lens L13.

  The meniscus lens L13 is a meniscus lens having a small thickness deviation ratio that is concave on the reduction side and the peripheral portion of the lens is bent on the reduction side.

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

  The biconcave lens L23 and the biconvex lens L24 are cemented.

The third lens group G3 is a positive group and includes two positive lenses L31 and L32.
The fourth lens group G4 is a negative group, and includes a negative meniscus lens L41 that is convex on the enlargement side, a biconvex lens L42, a negative meniscus lens L43 that is concave on the enlargement side, and a biconvex lens L44.

  The negative meniscus lens L41 and the biconvex lens L42 are cemented.

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

F = 10.3 to 15.4 mm, Fno = 2.56 to 3.34, ωw = 48.6 °
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 1250 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 shows aberration diagrams of Example 4 according 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 L12, and the second lens group G2 includes lenses L21 to L24.

  The third lens group G3 is composed of two lenses L31 and L32.

  The fourth lens group G4 includes four lenses L41 to L44.

  A DMD is assumed as the light valve, and the DMD has a cover glass CG.

  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 and the fourth lens group G4 move to the enlargement side.

  The first lens group G1 is a negative group, and includes a negative meniscus lens L11 and a meniscus lens L12 having a convex surface facing the enlargement side.

  The meniscus lens L12 is a meniscus lens having a small thickness deviation ratio that is concave on the reduction side and the peripheral portion of the lens is bent on the reduction side.

  The second lens group G2 is a negative group, and includes a biconvex lens L21, a biconcave lens L22, a biconcave lens L23, and a biconvex lens L24.

  The biconvex lens L21 and the biconcave lens L22 are cemented.

The third lens group G3 is a positive group and includes two positive lenses L31 and L32.
The fourth lens group G4 is a negative group, and includes a biconcave lens L41, a biconvex lens L42, a negative meniscus lens L43 concave on the enlargement side, and a biconvex lens L44.

  The negative meniscus lens L41 and the biconvex lens L42 are cemented.

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

F = 11.4 to 17.1 mm, Fno = 2.56 to 3.34, ωw = 45.7 °
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 1400 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 similar to FIG.

"Example 6"
The projection zoom lens of Example 6 is the one shown in FIG.

  As shown in FIG. 11, the first lens group G1 includes lenses L11 to L13, and the second lens group G2 includes lenses L21 to L24.

  The third lens group G3 is composed of two lenses L31 and L32.

  The fourth lens group G4 includes four lenses L41 to L44.

  A DMD is assumed as the light valve, and the DMD has a cover glass CG.

  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 and the fourth lens group G4 move to the enlargement side.

  The first lens group G1 is a negative group, and includes a negative meniscus lens L11 having a convex surface on the enlargement side, a negative meniscus lens L12 having a convex surface on the enlargement side, and a meniscus lens L13.

  The meniscus lens L13 is a meniscus lens that is concave on the reduction side and the peripheral portion of the lens is bent on the reduction side.

  The second lens group G2 is a negative group, and includes a biconvex lens L21, a biconcave lens L22, a biconcave lens L23, and a biconvex lens L24.

  The biconvex lens L21 and the biconcave lens L22 are cemented.

The third lens group G3 is a positive group and includes two positive lenses L31 and L32.
The fourth lens group G4 is a positive group, and includes a biconcave lens L41, a biconvex lens L42, a negative meniscus lens L43 concave on the enlargement side, and a biconvex lens L44.

  The negative meniscus lens L41 and the biconvex lens L42 are cemented.

  In Example 6, the focal length of the entire system: the range of F, the F number, and the half angle of view at the wide-angle end: ωw are as follows.

F = 14.7-22.1 mm, Fno = 2.55-3.34, ωw = 38.5 °
The data of Example 6 is shown in Table 21.

"Aspherical data"
Table 22 shows the aspherical data.

  Table 23 shows the distance between the lens groups when the projection distance is 1800 mm for the wide-angle end, the middle, and the telephoto end.

"Parameter values for each condition"
Table 24 shows the parameter values of the conditions (1) to (4).

  FIG. 12 is an aberration diagram of Example 6 similar to FIG.

"Example 7"
The projection zoom lens of Example 7 is shown in FIG.

  As shown in FIG. 13, the first lens group G1 includes lenses L11 to L13, and the second lens group G2 includes lenses L21 to L24.

  The third lens group G3 is composed of two lenses L31 and L32.

  The fourth lens group G4 includes four lenses L41 to L44.

  A DMD is assumed as the light valve, and the DMD has a cover glass CG.

  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 and the fourth lens group G4 move to the enlargement side.

  The first lens group G1 is a negative group, and includes a negative meniscus lens L11 having a convex surface on the enlargement side, a negative meniscus lens L12 having a convex surface on the enlargement side, and a meniscus lens L13.

  The meniscus lens L13 is a meniscus lens that is concave on the reduction side and the peripheral portion of the lens is bent on the reduction side.

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

  The positive lens L21 convex on the enlargement side and the negative meniscus lens L22 convex on the enlargement side are cemented.

The third lens group G3 is a positive group and includes two positive lenses L31 and L32.
The fourth lens group G4 is a positive group, and includes a biconcave lens L41, a biconvex lens L42, a negative meniscus lens L43 concave on the enlargement side, and a biconvex lens L44.

  The negative meniscus lens L41 and the biconvex lens L42 are cemented.

  In Example 7, the focal length of the entire system: the range of F, the F number, and the half angle of view at the wide angle end: ωw are as follows.

F = 13.1 to 19.6 mm, Fno = 2.55 to 3.34, ωw = 41.8 °
The data of Example 7 is shown in Table 25.

"Aspherical data"
Table 26 shows the aspherical data.

  Table 27 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 28 shows parameter values of the conditions (1) to (4).

  FIG. 14 is an aberration diagram of Example 7 similar to FIG.

"Example 8"
The projection zoom lens of Example 8 is shown in FIG.

  As shown in FIG. 15, the first lens group G1 includes lenses L11 to L13, and the second lens group G2 includes lenses L21 to L24.

  The third lens group G3 is composed of two lenses L31 and L32.

  The fourth lens group G4 includes four lenses L41 to L44.

  A DMD is assumed as the light valve, and the DMD has a cover glass CG.

  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 and the fourth lens group G4 move to the enlargement side.

  The first lens group G1 is a negative group, and includes a negative meniscus lens L11 having a convex surface on the enlargement side, a negative meniscus lens L12 having a convex surface on the enlargement side, and a meniscus lens L13.

  The meniscus lens L13 is a meniscus lens that is concave on the reduction side and the peripheral portion of the lens is bent on the reduction side.

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

  The positive lens L21 convex on the enlargement side and the negative meniscus lens L22 convex on the enlargement side are cemented.

The third lens group G3 is a positive group and includes two positive lenses L31 and L32.
The fourth lens group G4 is a positive group, and includes a biconcave lens L41, a biconvex lens L42, a negative meniscus lens L43 concave on the enlargement side, and a biconvex lens L44.

  The negative meniscus lens L41 and the biconvex lens L42 are cemented.

  In Example 8, the focal length of the entire system: the range of F, the F number, and the half angle of view at the wide angle end: ωw are as follows.

F = 11.5 to 17.2 mm, Fno = 2.55 to 3.34, ωw = 45.5 °
The data of Example 8 is shown in Table 29.

"Aspherical data"
Table 30 shows the aspherical data.

  Table 31 shows the distance between the lens groups when the projection distance is 1400 mm for the wide-angle end, the intermediate end, and the telephoto end.

"Parameter values for each condition"
Table 32 shows parameter values of the conditions (1) to (4).

  FIG. 16 is an aberration diagram of Example 8 similar to FIG.

"Example 9"
The projection zoom lens of Example 9 is shown in FIG.

  As shown in FIG. 17, the first lens group G1 includes lenses L11 to L13, and the second lens group G2 includes lenses L21 to L24.

  The third lens group G3 is composed of two lenses L31 and L32.

  The fourth lens group G4 includes four lenses L41 to L44.

  As described above, a DMD is assumed as the light valve, and the DMD has a cover glass CG.

  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 and the fourth lens group G4 move to the enlargement side.

  The first lens group G1 is a negative group, and includes a negative meniscus lens L11 having a convex surface on the enlargement side, a negative meniscus lens L12 having a convex surface on the enlargement side, and a meniscus lens L13.

  The meniscus lens L13 is a meniscus lens that is concave on the reduction side and the peripheral portion of the lens is bent on the reduction side.

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

  A positive lens L21 convex on the enlargement side and a negative meniscus lens L22 convex on the enlargement side are cemented.

The third lens group G3 is a positive group and includes two positive lenses L31 and L32.
The fourth lens group G4 is a positive group, and includes a biconcave lens L41, a biconvex lens L42, a negative meniscus lens L43 concave on the enlargement side, and a biconvex lens L44.

  The negative meniscus lens L41 and the biconvex lens L42 are cemented.

  The focal length of the entire system in Example 9: F range, F number, and half angle of view at the wide angle end: ωw are as follows.

F = 10.7 to 16.0 mm, Fno = 2.55 to 3.34, ωw = 47.5 °
The data of Example 9 is shown in Table 33.

"Aspherical data"
Table 34 shows the aspherical data.

  Table 35 shows the distance between the lens groups when the projection distance is 1300 mm for the wide-angle end, the middle, and the telephoto end.

"Parameter values for each condition"
Table 36 shows parameter values of the conditions (1) to (4).

  FIG. 18 is an aberration diagram of Example 9 similar to FIG.

  As shown in the aberration diagrams, in the projection zoom lenses according to the respective embodiments, various aberrations are corrected at a high level, and spherical aberration, astigmatism, curvature of field, lateral chromatic aberration, and distortion are sufficiently corrected.

  As shown in Examples 1 to 9, the first lens group G1 includes two or three lenses.

  A lens having a large lens diameter is used for the first lens group G1, but the first lens group can be reduced in weight by setting the number of the first lens group to two or three as in the embodiment.

This weight reduction can suppress the eccentricity of the lens due to its own weight.
In Examples 1 to 9, the first lens group G1 is provided with “a correction effect for astigmatism and distortion”.

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

  In any of the projection zoom lenses of Examples 1 to 9, 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.

  In the projection zoom lens of each embodiment, the first lens group G1 is a focus group, the second lens group G2 is a compensator (aberration correction group), and the third lens group is a zooming group.

  The projection zoom lens according to the present invention has a “wide angle of view” in which the half angle of view at the wide angle end is larger than 34 degrees, and the fourth lens group G4 is moved to the enlargement side when zooming to the telephoto end. Yes.

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

G1 first lens group
G2 second lens group
G3 Third lens group
G4 4th lens group

JP 2012-189971 A

Claims (11)

A projection zoom lens used in an image display device for projecting and projecting a projection image displayed on an image display element onto a projection surface,
In the four lens group configuration, the first to fourth lens groups are sequentially arranged from the enlargement side to the reduction side,
The first lens group has negative refractive power,
The second lens group has negative refractive power,
The third lens group has a positive refractive power,
A zoom lens for projection, wherein the fourth lens unit moves to the enlargement side upon zooming from the wide-angle end to the telephoto end. The projection zoom lens according to claim 1,
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 claim 1,
The zoom for projection, wherein the second lens unit moves slowly and monotonously toward the reduction side or moves along a locus convex toward the reduction side upon zooming from the wide-angle end to the telephoto end. lens. The projection zoom lens according to any one of claims 1 to 3,
When zooming from the wide-angle end to the telephoto end, the third lens unit moves to the enlargement side,
The amount of movement of the third lens group: D3 and the amount of movement of the fourth lens group: D4 during zooming are as follows:
(4) 1.0 <D3 / D4 <1.2
Projection zoom lens characterized by satisfying The projection zoom lens according to any one of claims 1 to 4,
A projection zoom lens, wherein the first lens unit is fixed during zooming from the wide-angle end to the telephoto end. The projection zoom lens according to any one of claims 1 to 5,
The focal length of the third lens group is F3, and the focal length of the fourth lens group is F4.
(2) | F3 | <| F4 |
Projection zoom lens characterized by satisfying The projection zoom lens according to any one of claims 1 to 6,
The combined focal length of the third lens group and the fourth lens group at the wide angle end: F3-4w, and the combined focal length of the third lens group and the fourth lens group at the telephoto end: F3-4t are:
(3) 0.9 <F3-4w / F3-4t <1.1
Projection zoom lens characterized by satisfying The projection zoom lens according to any one of claims 1 to 7,
A projection zoom lens characterized in that the refractive index of the fourth lens group is the smallest in absolute value among all the lens groups. The projection zoom lens according to any one of claims 1 to 8,
When zooming from the wide-angle end to the telephoto end, the second lens group gently moves to the reduction side, and the third lens group and the fourth lens group individually move to the enlargement side. . The projection zoom lens according to any one of claims 1 to 9,
Half angle of view at wide-angle end: ωw, conditions:
(1) 34 degrees <ωw <50 degrees
Projection zoom lens characterized by satisfying A light source;
An image display element for displaying an image for projection;
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 a projection image displayed on the image display element, 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 10 as the projection optical system.

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