JP2017219630A - Projection zoom lens and projection-type image display device - Google Patents

Abstract

A novel projection zoom lens having a seven-lens-group configuration is realized. A projection zoom lens comprises, in order from the enlargement side to the reduction side, a first lens group 1G with negative refractive power, a second lens group 2G with positive refractive power, and a third lens group with negative refractive power. 3G, a fourth lens group 4G with positive refractive power, a fifth lens group 5G with positive refractive power, a sixth lens group 6G with negative or positive refractive power, and a seventh lens group 7G with positive refractive power. An aperture stop S is provided between the fourth lens group 4G and the fifth lens group 5G. During zooming, the second lens group 2G to the sixth lens group 6G move along the optical axis, resulting in the The distance between the first lens group 1G to the seventh lens group 7G changes, and the air-converted back focus at the d-line: Bf, the focal length of the entire system at the wide-angle end: fw, and the focal length of the entire system at the telephoto end: ft , the combined focal length of the first lens group: 1G_f satisfies the conditions (1) to (3). [Selection drawing] Fig. 1

Description

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

  In recent years, a “projection-type image display device” that enlarges a planar image and displays an image as a projection image has become widespread in recent years as a projector or the like used in a presentation at a conference or a home theater.

2. Description of the Related Art Conventionally, various projection zoom lenses for projecting a planar image to be displayed as a projection image with a variable magnification are known.
In recent years, the “projection distance” of the projector, that is, the distance between the projector main body and the display surface on which the projection image is displayed has been shortened, and a wide angle of view is also required for the projection zoom lens.

  As a lens system with a wide angle of view, a so-called negative lead type, that is, “a lens unit that has the negative refractive power of the most magnified lens group” is known, and it is composed of a relatively small lens group of 7 lens groups. As the negative lead type projection zoom lens, for example, those disclosed in Patent Documents 1 and 2 are known.

  It is an object of the present invention to realize a novel projection zoom lens having a seven lens group configuration.

The projection zoom lens according to the present invention is a projection zoom lens that projects a magnified planar image with a variable magnification, and in order from the magnification side to the reduction side, a first lens group having negative refractive power, A second lens group having a negative refractive power, a third lens group having a negative refractive power, a fourth lens group having a positive refractive power, a fifth lens group having a positive refractive power, and a negative or positive refractive power. A sixth lens group, a seventh lens group having a positive refractive power, an aperture stop between the fourth lens group and the fifth lens group, and from the second lens group during zooming. By moving up to the sixth lens group on the optical axis, the adjacent group interval of the first to seventh lens groups changes, and the back focus converted into air at the d-line: Bf, the entire system at the wide-angle end Focal length: fw at the telephoto end Focal length of the system: ft, combined focal length of the first lens group: 1G_f is, conditions:
(1) 2.0 <Bf / fw <5.0
(2) 1.5 <ft / fw <3.0
(3) -3.0 <1G_f / fw <-1.0
Satisfied.

  According to the present invention, a novel projection zoom lens having a seven-lens group configuration can be realized.

It is a figure for demonstrating Example 1 of the zoom lens for projection. It is a figure for demonstrating Example 2 of the zoom lens for projection. It is a figure for demonstrating Example 3 of the zoom lens for projection. It is a figure for demonstrating Example 4 of the zoom lens for projection. It is a figure for demonstrating Example 5 of the zoom lens for projection. It is a figure for demonstrating Example 6 of the zoom lens for projection. It is a figure for demonstrating Example 7 of the zoom lens for projection. FIG. 3 is a diagram illustrating data of a projection zoom lens according to Example 1. FIG. 4 is a diagram illustrating various parameters of the projection zoom lens according to the first exemplary embodiment. 6 is a diagram illustrating data of a projection zoom lens according to Example 2. FIG. 6 is a diagram illustrating various parameters of a projection zoom lens according to Embodiment 2. FIG. 6 is a diagram illustrating data of a projection zoom lens according to Example 3. FIG. 6 is a diagram illustrating various parameters of a projection zoom lens according to Example 3. FIG. FIG. 6 is a diagram illustrating data of a projection zoom lens according to Example 4. FIG. 6 is a diagram illustrating various parameters of a projection zoom lens according to Example 4. FIG. 10 is a diagram illustrating data of a projection zoom lens according to Example 5. FIG. 10 is a diagram illustrating various parameters of a projection zoom lens according to Example 5. FIG. 10 is a diagram illustrating data of a projection zoom lens according to Example 6. FIG. 10 is a diagram illustrating various parameters of a projection zoom lens according to Example 6. FIG. 10 is a diagram illustrating data of a projection zoom lens according to Example 7. FIG. 10 is a diagram illustrating various parameters of a projection zoom lens according to Example 7. FIG. 3 is an aberration diagram at the wide-angle end of the projection zoom lens according to Example 1; FIG. 4 is an aberration diagram at the telephoto end of the projection zoom lens according to Example 1; FIG. 6 is an aberration diagram at a wide-angle end of the projection zoom lens according to Example 2. FIG. 6 is an aberration diagram at the telephoto end of the projection zoom lens according to Example 2; FIG. 10 is an aberration diagram at a wide-angle end of the projection zoom lens according to Example 3; FIG. 10 is an aberration diagram at a telephoto end of the projection zoom lens according to Example 3; FIG. 10 is an aberration diagram at a wide-angle end of the projection zoom lens according to Example 4; FIG. 10 is an aberration diagram at a telephoto end of the projection zoom lens according to Example 4; FIG. 10 is an aberration diagram at a wide-angle end of the projection zoom lens according to Example 5; FIG. 10 is an aberration diagram at a telephoto end of the projection zoom lens according to Example 5; FIG. 10 is an aberration diagram at a wide-angle end of the projection zoom lens according to Example 6; 10 is an aberration diagram at a telephoto end of a projection zoom lens in Example 6. FIG. 10 is an aberration diagram at a wide-angle end of the projection zoom lens according to Example 7. FIG. FIG. 10 is an aberration diagram at a telephoto end of the projection zoom lens according to Example 7; It is a figure which shows two examples of embodiment of the image display apparatus for projection.

Hereinafter, embodiments will be described.
1 to 7 show seven examples of the embodiment of the projection zoom lens. These seven embodiments correspond to Examples 1 to 7 described later in the order shown.
1 to 7, the upper diagram shows the lens arrangement at the “wide-angle end”, and the lower diagram shows the lens arrangement at the “telephoto end”.
In these figures, the left side of the figure is the “enlarged side”, that is, the side on which the projected image is projected, and the right side of the figure is the reduced side, ie, the “side on which the planar image is displayed”.
In order to avoid complications, the symbols are shared in these drawings.
1 to 7, “1G” is the first lens group, “2G” is the second lens group, “3G” is the third lens group, “4G” is the fourth lens group, and “5G” is the fifth lens. “6G” represents a sixth lens group, and “7G” represents a seventh lens group.
In the embodiment shown in FIG. 1 to FIG. 7, a “projection zoom lens used in a three-plate projector using three liquid crystal panels for displaying three primary color images” is assumed. The composition prism is shown. “S” indicates an aperture stop, “OI” indicates an image display surface, that is, a panel surface of a liquid crystal panel, and is also referred to as “planar image OI” in the following.

The first lens group 1G has “negative refractive power”, the second lens group 2G has “positive refractive power”, and the third lens group 3G has “negative refractive power”.
The fourth lens group 4G and the fifth lens group 5G both have “positive refractive power”, the sixth lens group 6G has “negative or positive refractive power”, and the seventh lens group 7G has “positive power”. Refracting power ".
That is, the projection zoom lens according to each embodiment shown in FIGS. 1 to 7 is a projection zoom lens that projects a planar image OI with a variable magnification.
The projection zoom lens includes a first lens group 1G having a negative refractive power, a second lens group 2G having a positive refractive power, and a third lens group having a negative refractive power in order from the enlargement side to the reduction side. 3G, fourth lens group 4G having positive refractive power, fifth lens group 5G having positive refractive power, sixth lens group 6G having negative or positive refractive power, and seventh lens group having positive refractive power 7G, and an aperture stop S is provided between the fourth lens group 4G and the fifth lens group 5G.

  During zooming, the second lens group 2G to the sixth lens group 6G move on the optical axis to change the adjacent group spacing of the first lens group 1G to the seventh lens group 7G.

  The first lens group 1G and the seventh lens group 7G are fixed groups with respect to zooming, and are fixed during zooming.

The projection zoom lens according to the present invention has a back focus converted to air at the d-line: Bf, a focal length of the entire system at the wide-angle end: fw, a focal length of the entire system at the telephoto end: ft, and the composition of the first lens group. Focal length: 1G_f, condition:
(1) 2.0 <Bf / fw <5.0
(2) 1.5 <ft / fw <3.0
(3) -3.0 <1G_f / fw <-1.0
Satisfied.

“Back focus” is defined as “the distance between the final surface of the lens system and the image plane” as is well known. The projection zoom lens according to the present invention projects a planar image as an enlarged image, and the planar image and the projected enlarged image are in a “conjugate relationship”.
In this specification, based on this conjugate relationship, an enlarged image is considered as an object plane and a planar image as an image plane. Therefore, “back focus” in this specification is the distance between the lens surface on the most reduction side of the projection zoom lens and the “planar image”.
Back focus: Bf is determined by the “d-line refractive index” in the region other than air on the optical path between the most reduced lens surface of the projection zoom lens and the planar image OI. It is a value converted into air.

  When the optical path between the most reduced lens surface and the planar image OI is “air only”, the refractive index of air is 1, so the back focus: Bf is the most reduced lens surface and the planar image OI. Is equal to the optical path length (L).

  In each of the embodiments described with reference to FIGS. 1 to 7, as described above, the color combining prism PR is provided on the optical path between the lens surface closest to the reduction side and the planar image OI. When the refractive index with respect to the d-line of the material of the color synthesis prism PR is Nd and the thickness is D, the back focus is extended by “D (1-1 / Nd)” due to the presence of the color synthesis prism PR. In this case, “back focus converted to air in the d-line” is “L + D (1-1 / Nd)”.

  Hereinafter, back focus: Bf converted to air in the d line regardless of the presence or absence of the color combining prism PR is also simply referred to as “back focus: Bf”.

Condition (1) is a condition for setting an appropriate range of “ratio between back focus: Bf and focal length at wide angle end: fw”.
When the back focus: Bf increases and the focal length: fw decreases, the parameter (Bf / fw) of the condition (1) increases. Conversely, when the back focus: Bf decreases and the focal length: fw increases, the parameter (Bf / fw) of the condition (1) decreases.
When the color synthesizing prism PR is used, “back focus converted to air at the d line: Bf” needs to have a certain size in order to arrange the color synthesizing prism PR.
Recently, “DMD (digital mirror device)” has been widely used as an image display element for displaying a planar image. In this case, a “color” between the planar image and the lens surface on the most reduction side is used. There is no need to provide a “combination prism”. However, since the illumination optical system for illuminating the DMD is close to the optical axis of the projection zoom lens, a certain amount of back focus is still required.
When the lower limit value of the condition (1) is exceeded, the back focus: Bf becomes small, and it is difficult to secure the required distance between the lens surface on the most reduction side and the planar image.
Further, the focal length: fw becomes relatively large, and the positive refractive power of the projection zoom lens becomes small, so that it is difficult to realize a wide angle of view.
When the upper limit value of the condition (1) is exceeded, the focal length: fw becomes small, and the positive refractive power of the projection zoom lens becomes excessive, and it is difficult to correct various aberrations.
By satisfying the condition (1), it is possible to realize an appropriately sized back focus and an appropriate field angle and aberration correction.

Condition (2) is a condition for determining the ratio of the focal lengths at the wide-angle end and the telephoto end: ft / fw, that is, “an appropriate range of the so-called zoom ratio”. That is, in the above-described configuration of the projection zoom lens according to the present invention, satisfactory optical performance can be realized in the “zoom ratio range” of the condition (2) by satisfying the conditions (1) and (3).
Condition (3) is a condition for setting an appropriate range of the focal length: 1G_f of the first lens group 1G having negative refractive power and the focal length: fw at the wide angle end: 1G_f / fw.
The “negative focal length: 1G_f” of the first lens group 1G having a negative refractive power has a larger negative refractive power as its absolute value is smaller, which is advantageous for “widening the angle” of the projection zoom lens. Astigmatism, curvature of field, etc. are likely to occur greatly.
Further, when the focal length: fw of the entire system at the wide angle end is large, “refractive power as a projection zoom lens” is small, and it is difficult to achieve a wide angle of view. Therefore, it becomes difficult to correct various aberrations.
If the magnitude of the focal length: 1G_f with respect to the focal length: fw of the entire system at the wide-angle end exceeds the lower limit value of the condition (3), it becomes difficult to correct various aberrations such as astigmatism and field curvature. Conversely, when the upper limit is exceeded, it becomes difficult to achieve a wide angle of view.

The first lens group of the projection zoom lens according to the present invention preferably includes at least two “lenses having a negative refractive power with a convex surface facing the enlargement side”.
In each of the embodiments shown in FIGS. 1 to 7, the first lens group 1G has two or more “lenses having negative refractive power with a convex surface facing the enlargement side”. Hereinafter, the “lens having negative refractive power” is simply referred to as “negative lens”. Similarly, a “lens having a positive refractive power” is called a “positive lens”.
The first lens group has “negative refracting power”, but if these negative refracting powers are realized by a plurality of negative lenses, the negative refracting power required for the first lens group is shared by the plurality of negative lenses. The divergence angle of the light beam transmitted from the reduction side to the enlargement side can be smoothly increased to easily realize a wide angle of view, and the enlargement side lens surface of two or more negative lenses can be By making the convex surface on the enlargement side, it becomes easy to correct distortion.

The projection zoom lens according to the present invention has the following conditions in addition to the above conditions (1), (2), and (3):
(4) 1.5 <2G_f / fw <5.0
(5) -4.5 <3G_f / fw <-1.0
It is preferable to satisfy at least one of the following.
In the conditions (4) and (5), fw is “the focal length of the entire system at the wide-angle end (> 0)” as described above, and 2G_f is “the combined focal length of the second lens group (> 0)”, 3G_f Represents “combined focal length (<0) of the third lens group”.
Condition (4) is a condition for setting “a suitable range for the refractive power of the entire system” of the refractive power of the second lens group. Condition (5) is a condition for setting the “refractive power of the entire system” of the third lens group. This is a condition for setting a “preferable range for refractive power”.
When the lower limit value of the condition (4) is exceeded, the positive refractive power of the second lens group becomes large, and it is possible to correct distortion aberration generated in the first lens group. Correction is likely to be difficult. When the upper limit is exceeded, the positive refractive power of the second lens group becomes small and aberrations such as field curvature and astigmatism can be corrected, but it is difficult to correct distortion when the field angle is widened. It is easy to become.
If the lower limit of condition (5) is exceeded, aberrations such as astigmatism and curvature of field can be corrected, but it is easy to cause “insufficient negative refractive power on the telephoto side”. When the upper limit is exceeded, correction of various aberrations such as astigmatism and distortion tends to be difficult.
Satisfying the conditions (4) and (5) facilitates “realization of good optical performance” within the zoom ratio range specified by the condition (2).
By satisfying at least one of the conditions (4) and (5) together with the conditions (1) to (3), the effects of these conditions can be obtained. However, together with the conditions (1) to (3), the conditions Needless to say, it is most preferable to satisfy (4) and (5).
The second lens group has “positive refracting power”, but by including one or more “lens having negative refracting power” among the lenses constituting the second lens group, “2G_f” in the condition (4) is satisfied. "Is easy to adjust to" satisfy condition (4) ".

  Further, by configuring the third lens group with “only one lens having negative refractive power”, the lens configuration can be simplified.

Various methods are available for focusing, that is, “focusing”. In focusing, “the entire first lens group or one or more lenses included in the first lens group” moves in the optical axis direction. By doing so, the focusing mechanism can be simplified.
Further, the seventh lens group having a positive refractive power can be constituted by “one positive lens”. In each of the embodiments shown in FIGS. 1 to 7, the seventh lens group 7G is composed of “only one positive lens”, and the seventh lens group is composed of one positive lens. The configuration of the projection zoom lens can be simplified.

The projection zoom lens according to the present invention can be used in a projection type image display apparatus that displays a planar image displayed on an image display element with a variable magnification.
Specific examples of the projection zoom lens will be described below.
"Example 1"
In Example 1, the lens configuration is shown in FIG.
The data of the projection zoom lens of Example 1 is shown in FIG.
In FIG. 8, “i” in the uppermost column is a parameter representing a surface (the lens surface and the surface of the aperture stop S, the surface of the color combining prism PR) counted from the enlargement side, and “IMG” is a plane image. The surface to be displayed.
“R” is a radius of curvature, “D” is a surface interval, “j” is a parameter representing a lens counted from the magnification side, and “PR” is a color composition prism. “N” is the refractive index of the d-line, and “ν” is the Abbe number. The same applies to the second to seventh embodiments.

FIG. 9 shows various parameters of the projection zoom lens of Example 1.
9A shows the focal length at the wide-angle end, the intermediate focal length (shown as intermediate), and the telephoto end. (B) is the surface interval at the wide-angle end, the middle, and the telephoto end of the portion of the surface interval “variable” in the data shown in FIG. 8, and (c) is the value of the parameter (1) to (5) ( Conditional expressions (1) to (5) are shown).

  (D) shows a surface interval between adjacent lens groups of the first lens group 1G to the seventh lens group 7G at the wide angle end (WIDE), the intermediate focal length (MEAN), and the telephoto end (TELE). (E) is the focal length at the wide angle end: fw, the focal length at the telephoto end: ft, the back focus converted to air at the d-line: Bf, the combined focal length of the first lens group 1G: 1G_f, and the second lens group 2G. The combined focal length: 2G_f and the combined focal length of the third lens group 3G: 3G_f are shown.

  The same applies to Examples 2 and below.

"Example 2"
In Example 2, the lens configuration is shown in FIG.
The data of the projection zoom lens of Example 2 is shown in FIG.
FIG. 11 shows various parameters of the zoom lens for projection according to the second embodiment, following FIG.

"Example 3"
In Example 3, the lens configuration is shown in FIG.
Data of the projection zoom lens of Example 3 is shown in FIG.
FIG. 13 shows various parameters of the zoom lens for projection according to the third embodiment, following FIG.

Example 4
In Example 4, the lens configuration is shown in FIG.
Data of the projection zoom lens of Example 4 is shown in FIG.
FIG. 15 shows various parameters of the zoom lens for projection according to the fourth embodiment, following FIG.

"Example 5"
In Example 5, the lens configuration is shown in FIG.
Data of the projection zoom lens of Example 5 is shown in FIG.
FIG. 17 shows various parameters of the zoom lens for projection according to the fifth embodiment, following FIG.

"Example 6"
In Example 6, the lens configuration is shown in FIG.
Data of the projection zoom lens of Example 6 is shown in FIG.
In FIG. 19, various parameters of the projection zoom lens of Example 6 are shown in FIG.

"Example 7"
In Example 7, the lens configuration is shown in FIG.
Data of the projection zoom lens of Example 7 is shown in FIG.
FIG. 21 shows various parameters of the zoom lens for projection according to the seventh embodiment, following FIG.

The range of fluctuation of the half angle of view accompanying zooming is as follows.
Example 1 36.1 degrees to 20.0 degrees
Example 2 36.1 degrees to 20.0 degrees
Example 3 40.1 degrees to 26.4 degrees
Example 4 36.1 degrees to 20.0 degrees
Example 5 41.5 degrees to 26.0 degrees
Example 6 36.1 degrees to 20.0 degrees
Example 7 33.6 degrees to 14.9 degrees
Among Examples 1 to 7, in Examples 1, 2, 3, 5, 6, and 7, the sixth lens group G6 has negative refractive power, and in Example 4, the sixth lens group G6 has Has positive refractive power.

  Further, in the projection zoom lenses of Examples 1 to 7, in order to perform focusing from infinity to a finite distance, the entire system of the first lens group 1G (Examples 2, 5, and 7) or the first lens group 1G is used. One or more included lenses (Examples 1, 3, 4, and 6) are moved in the optical axis direction.

FIG. 22 is an aberration diagram at the wide-angle end of the projection zoom lens according to Example 1.
FIG. 23 is an aberration diagram at the telephoto end of the projection zoom lens according to Example 1.
FIG. 24 is an aberration diagram at the wide-angle end of the projection zoom lens according to Example 2.
FIG. 25 shows aberration diagrams at the telephoto end of the projection zoom lens of Example 2. FIG.
FIG. 26 is an aberration diagram at the wide-angle end of the projection zoom lens according to Example 3.
FIG. 27 shows aberration diagrams at the telephoto end of the projection zoom lens according to Example 3.
FIG. 28 shows aberration diagrams at the wide-angle end of the projection zoom lens according to Example 4.
FIG. 29 is an aberration diagram at the telephoto end of the projection zoom lens in Example 4.
FIG. 30 is an aberration diagram at the wide-angle end of the projection zoom lens according to Example 5.
FIG. 31 is an aberration diagram at the telephoto end of the projection zoom lens in Example 5.
FIG. 32 is an aberration diagram at the wide-angle end of the projection zoom lens according to Example 6.
FIG. 33 shows aberration diagrams at the telephoto end of the projection zoom lens according to Example 6.
FIG. 34 is an aberration diagram at the wide-angle end of the projection zoom lens according to Example 7.
FIG. 35 shows aberration diagrams at the telephoto end of the projection zoom lens according to Example 7.
Each of these aberration diagrams is calculated using the “projection image displayed on the enlargement side as the object plane” and the position of the “planar image” on the reduction side as the image plane as described above.
“Y” in the aberration diagram is the maximum image height, “½ of the diagonal length of the planar image OI”, and “14.6 mm” through Examples 1 to 7. In the coma aberration diagram, 0H to 1H are values obtained by standardizing 14.6 mm as 1H and 0 mm as 0H.

  In each aberration diagram, the left diagram shows spherical aberration, astigmatism, and distortion, and the right diagram shows coma. In the spherical aberration and coma aberration diagrams, “R” represents red light having a wavelength of 620 nm, “G” represents green light having a wavelength of 540 nm, and “B” represents blue light having a wavelength of 460 nm. Further, astigmatism and distortion are related to the green light.

In astigmatism, “T” indicates tangential, and “S” indicates sagittal.
As is apparent from each aberration diagram, in each of the examples, good performance is realized at both the wide-angle end and the telephoto end.

Hereinafter, two embodiments of the projection type image display apparatus will be described with reference to FIG.
Each of the projection type image display apparatuses shown in FIG. 36 is a projector, and is hereinafter referred to as projectors PR1 and PR2. In order to avoid complication, the projection type zoom lens is indicated by “reference numeral 4”.
The projector PR1 shown in FIG. 36A is a three-plate projector using a liquid crystal panel, and three liquid crystal panels PR, PG, and PB are used as shown. A “red component image of the projection image” is displayed on the liquid crystal panel PR, and this image is illuminated with red illumination light having a wavelength of 620 nm emitted from the illumination device LR. The red illumination light is intensity-modulated by the red component image displayed on the liquid crystal panel LR and enters the color combining prism PR.

  The “green component image of the projected image” is displayed on the liquid crystal panel PG, and this image is illuminated with green illumination light having a wavelength of 540 nm emitted from the illumination device LG. The green illumination light is intensity-modulated by the green component image displayed on the liquid crystal panel LG and enters the color combining prism PR.

  The “blue component image of the projected image” is displayed on the liquid crystal panel PB, and this image is illuminated with blue illumination light having a wavelength of 460 nm emitted from the illumination device LB. The blue illumination light is intensity-modulated by the blue component image displayed on the liquid crystal panel LB and enters the color combining prism PR. The liquid crystal panels PR, PG, PB, the illumination devices LR, LG, LB and the like are controlled by the control unit CT.

  In this way, the respective color lights incident on the color combining prism are combined by the color combining prism, incident on the projection zoom lens 4, and enlarged and projected on the screen S as a color image.

  As the projection zoom lens 4, any one of claims 1 to 8 can be used. Specifically, the projection zoom lens 4 is one according to any of the first to seventh embodiments described above in combination with the color synthesis prism PR. Can be suitably used.

A projector PR2 shown in FIG. 36B is an example in which DMD3 is employed as an image display element that displays a planar image.
The projector PR2 includes an illumination system 2, a DMD 3 that is an image display element, and a projection zoom lens 4.

  As the projection zoom lens 4, the lens described in any one of claims 1 to 8, specifically, any one of Examples 1 to 7 can be used. Since the projector PR2 does not use the color synthesizing prism PR, the back focus: Bf is equal to “the optical path length between the lens surface closest to the reduction side and the planar image on the DMD 3”.

  The “lights of the three colors R, G, and B” are temporally separated from the illumination system 2 and irradiated onto the display surface of the DMD 3, and at the timing when each color light is irradiated, “a minute mirror corresponding to each pixel ( Control the "tilt of the micromirror".

  In this way, the “planar image to be projected” is displayed on the display surface of the DMD 3, and the light whose intensity is modulated by the planar image is imaged on the screen S by the projection zoom lens 4. Magnified projection.

  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” for arranging the light source 21.

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 lens 4 and the illumination system 2, it is necessary to secure the back focus of the projection lens 4 to some extent. The mirror M is used to secure the incident angle of the illumination light, and for projection The zoom lens 4 ensures the necessary back focus.
The condenser lens CL, the RGB color wheel CW, and the mirror M constitute an “illumination optical system”. A “control unit” that controls the illumination optical system, the light source 21, and the like is not shown in FIG.

As described above, according to the present invention, the following projection zoom lens and projection type image display apparatus can be realized.
[1]
A projection zoom lens for projecting a planar image (OI) with a variable magnification, and in order from the magnification side to the reduction side, a first lens group (1G) having a negative refractive power, a positive refractive power A second lens group (2G) having negative refractive power, a third lens group (3G) having negative refractive power, a fourth lens group (4G) having positive refractive power, and a fifth lens group (5G having positive refractive power) ), A sixth lens group (6G) having negative or positive refractive power, a seventh lens group (7G) having positive refractive power, and a fourth lens group (4G) and a fifth lens group (5G). Between the second lens group (2G) and the sixth lens group (6G) during zooming, the first lens group (1G) or The group interval of the seventh lens group (7G) changes, and the back focal length converted to air in the d-line Carcass: Bf, the focal length of the entire system at the wide angle end: fw, the focal length of the entire system at the telephoto end: ft, combined focal length of the first lens group: 1G_f is, conditions:
(1) 2.0 <Bf / fw <5.0
(2) 1.5 <ft / fw <3.0
(3) -3.0 <1G_f / fw <-1.0
Zoom lens for projection satisfying the above (Examples 1 to 7).

[2]
The projection zoom lens according to [1], wherein the first lens group (1G) includes at least two lenses having negative refractive power with a convex surface facing the enlargement side (Examples 1 to 7).
[3]
The projection zoom lens according to [1] or [2], wherein the combined focal length of the second lens group (2G) is 2G_f, and the focal length of the entire system at the wide angle end is fw.
(4) 1.5 <2G_f / fw <5.0
Zoom lens for projection satisfying the above (Examples 1 to 7).
[4]
[3] The projection zoom lens according to [3], wherein the second lens group (2G) includes at least one lens having negative refractive power (Examples 1 to 7).

[5]
The projection zoom lens according to any one of [1] to [4], wherein the combined focal length of the third lens group (3G) is 3G_f, and the focal length of the entire system at the wide angle end is fw.
(5) -4.5 <3G_f / fw <-1.0
Zoom lens for projection satisfying the above (Examples 1 to 7).

[6]
[5] The projection zoom lens according to [5], wherein the third lens group (3G) includes only one lens having negative refractive power (Examples 1 to 7).

[7]
The projection zoom lens according to any one of [1] to [6],
A zoom lens for projection in which the entire first lens group (1G) or at least one lens included in the first lens group moves in the optical axis direction during focusing (Examples 1 to 7).
[8]
The projection zoom lens according to any one of [1] to [7], wherein the seventh lens group (7G) includes only one lens having a positive refractive power. Lens (Examples 1-7).

[9]
A projection-type image display device (PR1, PR2) that magnifies and displays a planar image displayed on the image display elements (PR, PG, PB, 3) with a variable magnification, and expands the planar image with a variable magnification. A projection type image display apparatus using the projection zoom lens described in any one of [1] to [7] as a projection zoom lens (4) to be projected (FIG. 36).

The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments described above, and the invention described in the claims unless otherwise specified in the above description. Various modifications and changes are possible within the scope of the above.
The effects described in the embodiments of the present invention are merely a list of suitable effects resulting from the invention, and the effects of the present invention are not limited to those described in the embodiments.

1G first lens group
2G second lens group
3G third lens group
4G 4th lens group
S Aperture stop
5G 5th lens group
6G 6th lens group
7G 7th lens group
PR color composite concave prism
OI plane image

JP 2011-28123 A JP 2008-275713 A

Claims (9)

A projection zoom lens that magnifies and projects a planar image at a variable magnification, and in order from the magnification side to the reduction side, a first lens group having a negative refractive power and a second lens group having a positive refractive power A third lens group having negative refractive power, a fourth lens group having positive refractive power, a fifth lens group having positive refractive power, a sixth lens group having negative or positive refractive power, and positive refraction A seventh lens group having power, and having an aperture stop between the fourth lens group and the fifth lens group;
During zooming, the distance from the second lens group to the sixth lens group moves on the optical axis, so that the group interval of the first to seventh lens groups changes,
The back focus converted to air at the d-line: Bf, the focal length of the entire system at the wide-angle end: fw, the focal length of the entire system at the telephoto end: ft, and the combined focal length of the first lens group: 1G_f.
(1) 2.0 <Bf / fw <5.0
(2) 1.5 <ft / fw <3.0
(3) -3.0 <1G_f / fw <-1.0
Projection zoom lens that satisfies the requirements. The projection zoom lens according to claim 1,
A projection zoom lens, wherein the first lens group includes at least two lenses having a negative refractive power with a convex surface facing the enlargement side. The projection zoom lens according to claim 1 or 2,
The combined focal length of the second lens group: 2G_f and the focal length of the entire system at the wide angle end: fw are the conditions:
(4) 1.5 <2G_f / fw <5.0
Projection zoom lens that satisfies the requirements. A projection zoom lens according to any one of claims 1 to 3,
The projection zoom lens, wherein the second lens group includes at least one lens having negative refractive power. The projection zoom lens according to any one of claims 1 to 4,
The combined focal length of the third lens group: 3G_f and the focal length of the entire system at the wide angle end: fw are the conditions:
(5) -4.5 <3G_f / fw <-1.0
Projection zoom lens that satisfies the requirements. A projection zoom lens according to any one of claims 1 to 5,
A projection zoom lens in which the third lens group is composed of only one lens having negative refractive power. A projection zoom lens according to any one of claims 1 to 6,
A zoom lens for projection in which the entire system of the first lens group or at least one lens included in the first lens group moves in the optical axis direction during focusing. A projection zoom lens according to any one of claims 1 to 7,
The projection zoom lens, wherein the seventh lens group is composed of only one lens having a positive refractive power. A projection-type image display device that displays the planar image displayed on the image display element with a variable magnification and a projection display,
9. A projection type image display apparatus using the projection zoom lens according to claim 1, as a projection zoom lens for enlarging and projecting a planar image at a variable magnification.

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