JP2008176261A - Zoom lens for projection and projection type display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens for projection which is suitable for a projector device using a DMD, which has high performance, which is compact, and which can achieve a wide angle of view and a high variable power ratio, without using a plurality of aspheric lenses. <P>SOLUTION: The zoom lens for projection includes a first group G<SB>1</SB>having negative refractive power, a second group G<SB>2</SB>having positive refractive power, a third group G<SB>3</SB>having positive refractive power and a fourth group G<SB>4</SB>having positive or negative refractive power, in order from a magnification side. At variable power from a wide-angle end to a telephoto end, the second group G<SB>2</SB>, the third group G<SB>3</SB>and the fourth group G<SB>4</SB>are moved to the magnification side, and the first group G<SB>1</SB>is slightly moved to a reduction side. A following conditional expression (1) is satisfied. (1) 0.95<frw/frt<1.05: Where frw is a composite focal length of the second group G<SB>2</SB>, the third group G<SB>3</SB>and the fourth group G<SB>4</SB>at the wide-angle end, and frt is a composite focal length of the second group G<SB>2</SB>, the third group G<SB>3</SB>and the fourth group G<SB>4</SB>at the telephoto end. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection zoom lens having a four-group configuration mounted on a projection display device and the like, and more particularly to image information from a light valve of a DMD (digital micromirror device) display device. The present invention relates to a projection zoom lens and a projection display device for enlarging and projecting a carried light beam on a screen.

  In recent years, a projection projector device (projection display device) using a DMD display device as a light valve has attracted attention.

  The DMD is formed by forming a highly reflective rectangular minute mirror (mirror element) on a silicon memory chip using a CMOS semiconductor technology, the inclination of which can be changed within a range of about 10 degrees or more by a video signal. The projection projector apparatus using this DMD controls the reflection direction of the light from the light source by changing the angle of the mirror element, and focuses only the desired reflected light on the screen to produce a desired image. Projection is made possible.

In this DMD, for example, millions or more of mirrors can be arranged vertically and horizontally on a substrate, and all these mirrors can be independently digitally controlled, so that each mirror corresponds to one pixel in an image. It will be.
Further, unlike the liquid crystal display device, the irradiation light does not need to be polarized, so there is little loss of light and it is excellent in terms of accuracy of gradation expression.

  As described above, the DMD display device has many advantages. However, in order to ensure the effectiveness of such advantages, a higher degree of demand is also made for the optical system mounted on the DMD display device. It is becoming. Further, there is an increasing demand for a portable projector having good portability for a projection projector apparatus using a DMD. However, it is necessary for an optical system to meet such a portability requirement. .

  By the way, there are many so-called time-division type projection projectors using DMD that constitute an illumination system without arranging a prism for color synthesis or separation of illumination light / projection light on the reduction side of the projection lens. It has been adopted. In this case, a space for arranging the prism and the like is not necessary, and the reduction side of the projection lens does not need to be telecentric. Therefore, the reduction side pupil is set at a position close to the panel, thereby further reducing the size of the lens. Is required. In addition, high image quality that matches the device resolution is required, but zooming with a wider angle of view and high zoom ratio is also required from the standpoint of installation.

  As a zoom lens system capable of satisfying the above-described requirements to some extent, for example, the one described in Patent Document 1 below is known.

JP 2004-271668 A JP 2006-078705 A Japanese Patent Application No. 2006-094052

The prior art described in Patent Document 1 can meet the above-described various requirements including a wide angle of view and a high zoom ratio. However, in order to maintain the aberration satisfactorily with the configuration described in Patent Document 1, it is necessary to arrange a plurality of aspheric lenses, as is clear from the examples.
For this reason, the burden of processing and assembling the optical system has increased, which has been a factor in increasing manufacturing costs.

  The prior art described in Patent Document 2 is a system in which the reduction side is telecentric, and is basically incompatible with the present invention in which downsizing is an important issue. The applicant of the present application has already disclosed a zoom lens for projection and a projection display device, which is a three-group zoom lens, but can achieve the same problem as the present invention to the JPO (Patent Document 3). reference).

  The present invention has been made in view of the above circumstances, and can achieve a wide angle of view, a high zoom ratio, and cost reduction without using a plurality of aspheric lenses, high performance, compact and bright, It is an object of the present invention to provide a projection zoom lens and a projection display apparatus suitable for a projection projector apparatus using a DMD.

The zoom lens for projection according to the present invention includes, in order from the magnification side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a positive refractive power, and a positive or negative value. The second lens group, the third lens group, and the fourth lens group move to the enlargement side at the time of zooming from the wide-angle end to the telephoto end, and the following conditional expression ( It is characterized by satisfying 1).
0.95 <frw / frt <1.05 (1)
However,
frw: Composite focal length at the wide-angle end of the second, third and fourth lens groups frt: Composite focal length at the telephoto end of the second, third and fourth lens groups

Moreover, it is preferable that the following conditional expressions (2) and (3) are satisfied.
| M4 / f4 | <| M1 / f1 | <| M2 / f2 | <| M3 / f3 | (2)
0.4 <| M3 / f3 | <0.8 (3)
However,
Mn: Movement distance between the wide-angle end position and the telephoto end position of the nth lens group fn: Focal length of the nth lens group

Further, the following conditional expressions (4) and (5) may be satisfied instead of the conditional expressions (2) and (3).
| M4 / f4 | <| M2 / f2 | <| M1 / f1 | <| M3 / f3 | (4)
0.2 <| M3 / f3 | <0.6 (5)
However,
Mn: Movement distance between the wide-angle end position and the telephoto end position of the nth lens group fn: Focal length of the nth lens group

Moreover, it is preferable that the refractive index Nd with respect to d-line of the glass material constituting the lens having the strongest negative refractive power in the fourth lens group satisfies the following conditional expression (6).
Nd> 1.75 (6)

  In addition, it is preferable that a positive lens having a convex surface on the reduction side is disposed on the most reduction side of the fourth lens group.

  Further, it is preferable that a single aspheric lens is disposed in the fourth lens group.

  Furthermore, the projection display device of the present invention includes a light source, a light valve, an illumination optical unit that guides a light beam from the light source to the light valve, and any one of the above-described projection zoom lenses. The light beam is modulated by the light valve and projected onto the screen by the projection zoom lens.

  As described above, according to the projection zoom lens and the projection display apparatus of the present invention, the lens system has a four-group configuration, and the power and zoom function are appropriately distributed to each group. And a wide-angle system having a zoom ratio of about 1.6 times or more and a bright F-number of about 2.05 to 2.20 at the wide-angle end, with a good aberration balance. can do.

  Furthermore, by satisfying the predetermined conditional expression, various aberrations can be further improved while further reducing the size.

  When the conditional expression (1) is satisfied, the entire lens system can be approximately regarded as a retrofocus type two-group zoom lens, and a wide back angle and long back focus system can be obtained.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The projection zoom lens according to the embodiment shown in FIG. 1 (representing the state at the wide-angle end of Example 1 as a representative) is, in order from the magnification side, a first lens group G ₁ having negative refractive power, The zoom lens includes a second lens group G ₂ having a positive refractive power, a third lens group G ₃ having a positive refractive power, and a fourth lens group G ₄ having a positive or negative refractive power. The second lens group G ₂ , the third lens group G _3, and the fourth lens group G ₄ are moved to the enlargement side at the time of zooming, and a cover glass (filter part) 2 and DMD 1 are disposed at the subsequent stage. Arranged. In the figure, X represents the optical axis.

Here, the first lens group G ₁ includes, in order from the magnification side, a first lens L ₁ composed of a positive lens, a second lens L ₂ composed of a negative meniscus lens having a convex surface facing the magnification side, and a third lens composed of a negative lens. The lens L ₃ includes a fourth lens L _{4 made of} a positive lens having a convex surface facing the reduction side, and a fifth lens L ₅ made of a negative lens having a concave surface facing the magnification side. The fourth lens L ₄ and the fifth lens L ₅ are arranged so that the opposing surfaces are close to each other (Examples 1 to 4) or joined (Examples 5 to 8). If they are independent from each other, the degree of freedom in lens design is improved, and if they are joined together, optical adjustment (alignment adjustment) becomes easy.

The second lens group G ₂ is composed of a sixth lens L ₆ made of a single positive lens.
The third lens group G ₃ is composed of a seventh lens L ₇ made of a single positive lens.

Further, the fourth lens group G ₄ includes, in order from the enlargement side, an eighth lens L _{8 made of} a negative lens having a concave surface facing the reduction side, a ninth lens L _{9 made of} a negative lens having a concave surface facing the enlargement side, and consisting tenth lens _{L 10} and the eleventh lens _{L 11} formed of a positive lens having a convex surface facing the reduction side. Incidentally, in particular, an eleventh lens L _11, since the positive lens having a convex surface facing the reduction side, it is possible to promote the reduction side compact system.

  The lens configuration of each lens group is not limited to that having the above shape, and it is possible to increase or decrease one or more negative lenses or positive lenses.

Incidentally, only the eighth lens L ₈ among the respective lenses is an aspheric lens, its remaining is all being a spherical lens, the manufacturing cost can be achieved is not used a plurality of aspherical lenses . When one aspherical lens is used, it is possible to improve aberration correction efficiency by disposing it in the final lens group (fourth lens group G ₄ ).

  In the present embodiment, glass is generally used as the lens material, but plastic can also be used if various conditions such as heat resistance and temperature conditions are met. In particular, the use of plastic in the aspheric lens is advantageous in terms of manufacturability and cost reduction.

  Here, the aspherical surface in the present embodiment is represented by the following aspherical expression.

In the zoom lens for projection according to the present embodiment, the second lens group G ₂ , the third lens group G _3, and the fourth lens group G ₄ are all on the magnification side at the time of zooming from the wide angle side to the telephoto side. Go to, whereas, first lens group G ₁ has a configuration that moves slightly reduction side. It is also possible to fix the first lens group G ₁ at the time of zooming.

The projection zoom lens according to the present embodiment is configured not only to satisfy the following conditional expression (1) but also to satisfy the following conditional expressions (2) and (3).
0.95 <frw / frt <1.05 (1)
| M4 / f4 | <| M1 / f1 | <| M2 / f2 | <| M3 / f3 | (2)
0.4 <| M3 / f3 | <0.8 (3)
However,
frw: Composite focal length at the wide angle end of the second lens group G ₂ , the third lens group G ₃ and the fourth lens group G ₄ frt: the second lens group G ₂ , the third lens group G ₃ and the fourth lens group combined focal length Mn at the telephoto end of the G _4: moving distance fn the wide-angle end position and the telephoto end position of the n lens unit is a focal length of the n lens unit

Further, the following conditional expressions (4) and (5) may be satisfied instead of the conditional expressions (2) and (3).
| M4 / f4 | <| M2 / f2 | <| M1 / f1 | <| M3 / f3 | (4)
0.2 <| M3 / f3 | <0.6 (5)
However,
Mn: Movement distance between the wide-angle end position and the telephoto end position of the nth lens group fn: Focal length of the nth lens group

Also, the fourth lens group G _4, the refractive index Nd is configured to satisfy the conditional expression (6) below with respect to the d-line of glass material which negative refractive power constitute the strongest lenses.
Nd> 1.75 (6)

Here, the technical significance of the conditional expressions (1) to (6) described above will be described.
Conditional expressions (1) to (5) are for appropriately setting the variable magnification sharing of each lens unit at the time of variable magnification.

By satisfying the conditional expression (1), the first lens group G ₁ and a front group, seen as a group after collectively the second lens group G _2, the third lens group G ₃ and the fourth lens group G ₄ In this case, the entire lens system can be approximately regarded as a retrofocus type two-group zoom lens.
In this way, by configuring the type close to the retrofocus type two-group zoom lens, it is possible to meet the demand for a long back focus with a wide angle of view.

  On the other hand, in the case where the lens is configured to be a type approximate to the retrofocus type two-group zoom lens, if the F-number is reduced to make a bright lens system, the lens outer diameter of the rear group tends to increase. Yes, it causes an increase in the size of the lens system.

Accordingly, the conditional expression (2), (3) or (4), the refractive power of each lens constituting the so, the second lens group G ₂ and the third lens group G ₃ which moves during zooming satisfies (5) By adjusting the distribution to be appropriate, it is possible to construct a practical compact size while achieving a brightness of about F2.05-2.20 at the wide-angle end.

  Therefore, satisfying all of these conditional expressions (1), (2) and (3), or (1), (4) and (5) is suitable for the brightness while making a bright lens system. This is desirable for obtaining the effect of correcting aberrations and suppressing the enlargement of the lens system.

Further, the conditional expression (6) defines the refractive index with respect to the d-line of the glass material constituting the lens having the strongest negative refractive power (the ninth lens L _{9 in} each embodiment) in the fourth lens group G ₄ . It defines the range for improving spherical aberration and chromatic aberration. That is, if the lower limit of conditional expression (6) is not reached, it is difficult to correct spherical aberration and chromatic aberration.

  Next, an embodiment of a projection display device according to the present invention will be briefly described. FIG. 49 is a schematic configuration diagram of a projection display apparatus according to this embodiment.

  As shown in FIG. 49, the light beam emitted from the light source 101 passes through a rod integrator 102 for uniformizing the light amount distribution of the light beam in a cross section perpendicular to the optical axis, and thereafter, the three primary color light ( R, G, and B) are selectively converted in time series to the DMD 103. In this DMD 103, modulation switching to the color light is performed according to the change of the color of the incident light, and the projection light appropriately modulated by the DMD 103 enters the projection zoom lens 104, and finally the screen. 105 is reached.

The projection zoom lens according to the present invention will be further described below using specific examples.
<Example 1>
FIG. 1 shows a schematic configuration of a projection zoom lens (wide-angle end) according to the first embodiment. In this projection zoom lens, in order from the magnification side, a first lens group G ₁ having a negative refractive power, a second lens group G ₂ having a positive refractive power, and a third lens group G ₃ having a positive refractive power. , And a fourth lens group G ₄ having a positive or negative refractive power, and the second lens group G ₂ , the third lens group G _3, and the fourth lens group G ₄ at the time of zooming from the wide angle end to the telephoto end The cover glass (filter part) 2 and DMD 1 are disposed in the subsequent stage. In the figure, X represents the optical axis.

Here, in order from the magnification side, the first lens group G ₁ includes a first lens L ₁ composed of a positive meniscus lens having a convex surface facing the magnification side, and a second lens L ₂ composed of a negative meniscus lens having a convex surface facing the magnification side. And a third lens L ₃ , a fourth lens L _{4 made} of a biconvex lens, and a fifth lens L ₅ made of a biconcave lens. Note that the fourth lens L ₄ and the fifth lens L ₅ are disposed so that their opposing surfaces are close to each other via a gap.

  The radius of curvature R (mm) of each lens surface of this zoom lens for projection, the center thickness of each lens, and the air space between each lens (hereinafter collectively referred to as the axial upper surface distance) D (mm), Table 1 shows values of the refractive index N and the Abbe number ν in the d-line. The numbers in the table represent the order from the enlargement side (the same applies to Tables 3, 5, 7, 9, 11, 13, and 15 below). Further, the upper part of Table 1 shows values of focal length f (mm), back focus Bfw (mm), FNo, and angle of view 2ω (degrees) (Tables 3, 5, 7, 9, below). The same in 11, 13, 15).

  In the numerical values in Table 1, the three numerical values are described step by step, the leftmost numerical value indicates the wide-angle end value, the central numerical value indicates the intermediate position value, and the rightmost numerical value indicates the telephoto value. The end values are shown (same in Tables 3, 5, 7, 9, 11, 13, 15 below).

Further, the eighth surfaces of the lens L ₈ (fifteenth surface and the surface No. 16) is a respective aspheric Table 2, for each of these aspheric surfaces, each constant K of the aspheric expression, A ₃ shows the value of ~A _20.

Moreover, according to the projection zoom lens of Example 1, as shown in Tables 1 and 17, all of the conditional expressions (1) to (3) and (6) are satisfied (fourth lens group G _4). in the medium, the refractive index Nd9 = 1.805 of the strongest negative power glass material of the ninth lens _{L 9).}

  FIG. 2 shows a lens movement locus at the time of zooming in the projection zoom lens according to the first embodiment.

  Further, FIG. 11 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration at each of the wide-angle end, the intermediate position, and the telephoto end of the projection zoom lens of Example 1, and FIGS. 14 are lateral aberration diagrams with respect to light having a wavelength of 546.07 nm at the wide-angle end, the intermediate position, and the telephoto end, respectively. The astigmatism diagram shows aberrations for the sagittal image surface and the tangential image surface (the same applies to FIGS. 15, 19, 23, 27, 37, 41, and 45 below).

  As is apparent from these aberration diagrams, according to the projection zoom lens of Example 1, each aberration can be corrected extremely well.

  In addition, according to the projection zoom lens of Example 1, the zoom ratio can be made 1.59 times or more and nearly 1.6 times while the optical performance is good. Also, the angle of view 2ω at the wide-angle end can be as wide as 67.2 degrees.

<Example 2>
FIG. 3 shows a schematic configuration of the zoom lens for projection according to the second embodiment. The lens configuration of the projection zoom lens according to Example 2 is substantially the same as that of Example 1, and a duplicate description is omitted.

Table 3 shows the values of the radius of curvature R (mm) of each lens surface of the projection zoom lens, the axial top surface distance D (mm) of each lens, and the refractive index N and the Abbe number ν at the d-line of each lens.
Further, the eighth surfaces of the lens L ₈ (fifteenth surface and the surface No. 16) is a respective aspheric Table 4, for each of these aspheric surfaces, each constant K of the aspheric expression, A ₃ shows the value of ~A _20.

Further, according to the projection zoom lens of Example 2, as shown in Tables 3 and 17, all of the conditional expressions (1) to (3) and (6) are satisfied (fourth lens group G _4). in the medium, the refractive index Nd9 = 1.805 of the strongest negative power glass material of the ninth lens _{L 9).}

  FIG. 4 shows the lens movement locus at the time of zooming in the projection zoom lens according to the second embodiment.

Further, FIG. 15 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration at each of the wide-angle end, the intermediate position, and the telephoto end of the projection zoom lens of Example 2, and FIGS. 18 are lateral aberration diagrams with respect to light having a wavelength of 546.07 nm at the wide-angle end, the intermediate position, and the telephoto end, respectively.
As is apparent from these aberration diagrams, according to the projection zoom lens of Example 2, each aberration can be corrected extremely well.

  Further, according to the projection zoom lens of Example 2, it is possible to make the zoom ratio 1.59 times or more and close to 1.6 times while improving the optical performance. Also, the angle of view 2ω at the wide-angle end can be as wide as 67.0 degrees.

<Example 3>
FIG. 5 shows a schematic configuration of the projection zoom lens according to the third embodiment. The lens configuration of the projection zoom lens according to Example 3 is substantially the same as that of Example 1, and a duplicate description is omitted.

Table 5 shows values of the radius of curvature R (mm) of each lens surface of this projection zoom lens, the distance D (mm) between the axial top surfaces of each lens, and the refractive index N and Abbe number ν of each lens at the d-line.
Further, the eighth surfaces of the lens L ₈ (fifteenth surface and the surface No. 16) is a respective aspheric in Table 6, for each of these aspheric surfaces, each constant K of the aspheric expression, A ₃ shows the value of ~A _20.

Further, according to the projection zoom lens of Example 3, as shown in Tables 5 and 17, all of conditional expressions (1) to (3) and (6) are satisfied (fourth lens group G _4). in the medium, the refractive index Nd9 = 1.805 of the strongest negative power glass material of the ninth lens _{L 9).}

  FIG. 6 shows the lens movement locus during zooming in the projection zoom lens of Example 3.

Further, FIG. 19 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration at each of the wide-angle end, the intermediate position, and the telephoto end of the projection zoom lens of Example 3, and FIGS. 22 is a lateral aberration diagram with respect to light having a wavelength of 546.07 nm, at the wide-angle end, the intermediate position, and the telephoto end, respectively.
As is clear from these aberration diagrams, according to the projection zoom lens of Example 3, each aberration can be corrected extremely well.

  Further, according to the projection zoom lens of Example 3, the zoom ratio can be made 1.59 times or more and nearly 1.6 times while the optical performance is good. Also, the angle of view 2ω at the wide-angle end can be as wide as 67.2 degrees.

<Example 4>
FIG. 7 shows a schematic configuration of the projection zoom lens according to the fourth embodiment. The lens configuration of the projection zoom lens according to Example 4 is substantially the same as that of Example 1, and a duplicate description is omitted.

Table 7 shows values of the radius of curvature R (mm) of each lens surface of this projection zoom lens, the axial top surface distance D (mm) of each lens, and the refractive index N and Abbe number ν of each lens at the d-line.
Further, the surfaces of the eighth lens L ₈ (fifteenth surface and the surface No. 16) is a respective aspheric in Table 8, for each of these aspheric surfaces, each constant K of the aspheric expression, A ₃ shows the value of ~A _20.

Further, according to the projection zoom lens of Example 4, as shown in Tables 7 and 17, all of conditional expressions (1) to (3) and (6) are satisfied (fourth lens group G _4). in the medium, the refractive index Nd9 = 1.805 of the strongest negative power glass material of the ninth lens _{L 9).}

  FIG. 8 shows a lens movement locus during zooming in the projection zoom lens of Example 4.

Further, FIG. 23 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration at the wide-angle end, the intermediate position, and the telephoto end of the projection zoom lens of Example 4, and FIGS. 26 is a lateral aberration diagram with respect to light having a wavelength of 546.07 nm, at the wide-angle end, the intermediate position, and the telephoto end, respectively.
As is apparent from these aberration diagrams, according to the projection zoom lens of Example 4, each aberration can be corrected extremely well.

  Further, according to the projection zoom lens of Example 4, the zoom ratio can be set to 1.59 times or more and close to 1.6 times while the optical performance is good. Also, the angle of view 2ω at the wide-angle end can be as wide as 67.2 degrees.

<Example 5>
FIG. 9 shows a schematic configuration of the projection zoom lens according to the fifth embodiment. The lens configuration of the projection zoom lens according to Example 5 is substantially the same as that of Example 1, and a duplicate description is omitted. The fourth lens L ₄ and the fifth lens L ₅ are different from those of the above-described embodiments in that they are configured as cemented lenses.

Table 9 shows values of the radius of curvature R (mm) of each lens surface of the projection zoom lens, the axial top surface distance D (mm) of each lens, and the refractive index N and Abbe number ν of each lens at the d-line.
Further, the eighth surfaces of the lens L ₈ (14th surface and the 15th surface) is the respective aspheric, the table 10, for each of these aspheric surfaces, each constant K of the aspheric expression, A ₃ shows the value of ~A _20.

Further, according to the projection zoom lens of Example 5, as shown in Tables 9 and 17, all of conditional expressions (1) to (3) and (6) are satisfied (fourth lens group G _4). in the medium, the refractive index Nd9 = 1.805 of the strongest negative power glass material of the ninth lens _{L 9).}

  FIG. 10 shows a lens movement locus during zooming in the projection zoom lens of Example 5.

FIG. 27 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration at the wide-angle end, the intermediate position, and the telephoto end of the projection zoom lens according to Example 5, and FIGS. 30 are lateral aberration diagrams with respect to light having a wavelength of 546.07 nm at the wide-angle end, the intermediate position, and the telephoto end, respectively.
As is apparent from these aberration diagrams, according to the projection zoom lens of Example 5, each aberration can be corrected extremely well.

  Further, according to the projection zoom lens of Example 5, the zoom ratio can be made 1.59 times or more and nearly 1.6 times while the optical performance is good. Also, the angle of view 2ω at the wide-angle end can be as wide as 67.4 degrees.

<Example 6>
FIG. 31 shows a schematic configuration of the zoom lens for projection according to the sixth embodiment. The lens configuration of the projection zoom lens according to Example 6 is substantially the same as that of Example 1, and a duplicate description is omitted. The fourth lens L ₄ and the fifth lens L ₅ are the same as those in the fifth embodiment described above in that they are configured as cemented lenses.

Table 11 shows the radius of curvature R (mm) of each lens surface of this zoom lens for projection, the distance D (mm) between the axial top surfaces of each lens, and the refractive index N and Abbe number ν for each lens d-line.
Further, the surfaces of the eighth lens L ₈ and (fourteenth surface and fifteenth surface) is set to each aspherical surface, the table 12, for each of these aspheric surfaces, each constant K of the aspheric expression, A ₃ shows the value of ~A _16.

Further, according to the projection zoom lens of Example 6, as shown in Tables 11 and 17, all of conditional expressions (1) to (3) and (6) are satisfied (fourth lens group G _4). in the medium, the refractive index Nd9 = 1.847 of the strongest negative power glass material of the ninth lens _{L 9).}

  FIG. 32 shows a lens movement locus during zooming in the projection zoom lens of Example 6.

Further, FIG. 37 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration at the wide-angle end, the intermediate position, and the telephoto end of the projection zoom lens of Example 6, and FIGS. 40 is a lateral aberration diagram with respect to light having a wavelength of 546.07 nm, at the wide-angle end, the intermediate position, and the telephoto end, respectively.
As is apparent from these aberration diagrams, according to the projection zoom lens of Example 6, each aberration can be corrected extremely well.

  Further, according to the projection zoom lens of Example 6, the zoom ratio can be set to 1.59 times or more and close to 1.6 times with good optical performance. Also, the angle of view 2ω at the wide-angle end can be as wide as 67.4 degrees.

<Example 7>
FIG. 33 shows a schematic configuration of the zoom lens for projection according to the seventh embodiment. The lens configuration of the projection zoom lens according to Example 7 is substantially the same as that of Example 1, and a duplicate description is omitted. The fourth lens L ₄ and the fifth lens L ₅ are the same as those in the fifth embodiment described above in that they are configured as cemented lenses.

Table 13 shows the values of the radius of curvature R (mm) of each lens surface of the projection zoom lens, the axial top surface distance D (mm) of each lens, and the refractive index N and Abbe number ν of each lens at the d-line.
Further, the eighth surfaces of the lens L ₈ (14th surface and the 15th surface) is the respective aspheric, the table 14, for each of these aspheric surfaces, each constant K of the aspheric expression, A ₃ shows the value of ~A _16.

Further, according to the projection zoom lens of Example 7, as shown in Tables 13 and 17, all the conditional expressions (1) and (4) to (6) are satisfied (fourth lens group G _4). in the medium, the refractive index Nd9 = 1.847 of the strongest negative power glass material of the ninth lens _{L 9).}

  FIG. 34 shows the lens movement locus at the time of zooming in the projection zoom lens of the seventh embodiment.

41 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration at the wide-angle end, the intermediate position, and the telephoto end of the projection zoom lens according to Example 7, and FIGS. 44 are lateral aberration diagrams with respect to light having a wavelength of 546.07 nm at the wide-angle end, the intermediate position, and the telephoto end, respectively.
As is apparent from these aberration diagrams, according to the projection zoom lens of Example 7, it is possible to correct each aberration very well.

  Further, according to the projection zoom lens of Example 7, the zoom ratio can be 1.59 times or more and nearly 1.6 times while the optical performance is good. Also, the angle of view 2ω at the wide-angle end can be as wide as 67.4 degrees.

<Example 8>
FIG. 35 shows a schematic configuration of the zoom lens for projection according to the eighth embodiment. The lens configuration of the projection zoom lens according to Example 8 is substantially the same as that of Example 1, and a duplicate description is omitted. The fourth lens L ₄ and the fifth lens L ₅ are the same as those in the fifth embodiment described above in that they are configured as cemented lenses.

Table 15 shows the values of the radius of curvature R (mm) of each lens surface of the projection zoom lens, the axial top surface distance D (mm) of each lens, and the refractive index N and Abbe number ν of each lens at the d-line.
Further, the surfaces of the eighth lens L ₈ (14th surface and the 15th surface) is the respective aspheric, the table 16, for each of these aspheric surfaces, each constant K of the aspheric expression, A ₃ shows the value of ~A _16.

Further, according to the zoom lens for projection of Example 8, as shown in Tables 15 and 17, all the conditional expressions (1) and (4) to (6) are satisfied (fourth lens group G _4). in the medium, the refractive index Nd9 = 1.847 of the strongest negative power glass material of the ninth lens _{L 9).}

  FIG. 36 shows the lens movement locus during zooming in the projection zoom lens of Example 8. FIG.

FIG. 45 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration at the wide-angle end, the intermediate position, and the telephoto end of the projection zoom lens according to Example 8, and FIGS. 48 are lateral aberration diagrams with respect to light having a wavelength of 546.07 nm at the wide-angle end, the intermediate position, and the telephoto end, respectively.
As is clear from these aberration diagrams, according to the zoom lens for projection of Example 8, each aberration can be corrected extremely well.

  Further, according to the projection zoom lens of Example 8, it is possible to make the zoom ratio 1.59 times or more and close to 1.6 times while improving the optical performance. Also, the angle of view 2ω at the wide-angle end can be as wide as 67.4 degrees.

1 is a schematic diagram showing the configuration of a projection zoom lens according to Example 1 of the present invention. FIG. FIG. 3 is a schematic diagram illustrating a lens movement locus during zooming in the projection zoom lens according to the first exemplary embodiment. Schematic showing the configuration of a projection zoom lens according to Example 2 of the present invention. Schematic showing the lens movement locus at the time of zooming in the projection zoom lens of Example 2 Schematic showing the configuration of a projection zoom lens according to Example 3 of the present invention. Schematic showing the lens movement locus at the time of zooming in the projection zoom lens of Example 3 Schematic showing the configuration of a projection zoom lens according to Example 4 of the present invention. Schematic showing the lens movement locus at the time of zooming in the projection zoom lens of Example 4 Schematic showing the configuration of a projection zoom lens according to Example 5 of the present invention. FIG. 7 is a schematic diagram illustrating a lens movement locus during zooming in the projection zoom lens according to the fifth exemplary embodiment. Aberration diagram showing various aberrations (spherical aberration, astigmatism, distortion and lateral chromatic aberration) of the projection zoom lens of Example 1. Aberration diagram showing lateral aberration at the wide-angle end of the projection zoom lens of Example 1. FIG. Aberration diagram showing lateral aberration at the intermediate position of the projection zoom lens of Example 1. FIG. Aberration diagram showing lateral aberration at the telephoto end of the projection zoom lens of Example 1. FIG. Aberration diagrams showing various aberrations (spherical aberration, astigmatism, distortion, and lateral chromatic aberration) of the projection zoom lens of Example 2. FIG. Aberration diagram showing lateral aberration at the wide-angle end of the projection zoom lens of Example 2. FIG. Aberration diagram showing lateral aberration at the intermediate position of the projection zoom lens of Example 2 Aberration diagram showing lateral aberration at the telephoto end of the projection zoom lens of Example 2 Aberration diagram showing various aberrations (spherical aberration, astigmatism, distortion, and lateral chromatic aberration) of the projection zoom lens of Example 3 Aberration diagram showing lateral aberration at the wide-angle end of the projection zoom lens of Example 3 Aberration diagram showing lateral aberration at the intermediate position of the projection zoom lens of Example 3 Aberration diagram showing lateral aberration at the telephoto end of the projection zoom lens of Example 3 Aberration diagrams showing various aberrations (spherical aberration, astigmatism, distortion, and lateral chromatic aberration) of the projection zoom lens of Example 4 Aberration diagram showing lateral aberration at the wide-angle end of the projection zoom lens in Example 4 Aberration diagram showing lateral aberration at the intermediate position of the projection zoom lens of Example 4 Aberration diagram showing lateral aberration at the telephoto end of the projection zoom lens of Example 4 Aberration diagrams showing various aberrations (spherical aberration, astigmatism, distortion, and lateral chromatic aberration) of the projection zoom lens of Example 5 Aberration diagram showing lateral aberration at the wide-angle end of the zoom lens for projection according to the fifth embodiment. Aberration diagram showing lateral aberration at the intermediate position of the projection zoom lens of Example 5 Aberration diagram showing lateral aberration at the telephoto end of the projection zoom lens of Example 5 Schematic showing the configuration of a projection zoom lens according to Example 6 of the present invention. Schematic showing the lens movement locus at the time of zooming in the projection zoom lens of Example 6 Schematic showing the configuration of a projection zoom lens according to Example 7 of the present invention. Schematic showing the lens movement locus at the time of zooming in the projection zoom lens of Example 7 Schematic showing the configuration of a projection zoom lens according to Example 8 of the present invention. Schematic showing the lens movement locus at the time of zooming in the projection zoom lens of Example 8 Aberration diagrams showing various aberrations (spherical aberration, astigmatism, distortion, and lateral chromatic aberration) of the projection zoom lens of Example 6. Aberration diagram showing lateral aberration at the wide-angle end of the projection zoom lens in Example 6 Aberration diagram showing lateral aberration at the intermediate position of the projection zoom lens of Example 6 Aberration diagram showing lateral aberration at the telephoto end of the projection zoom lens of Example 6 Aberration diagram showing various aberrations (spherical aberration, astigmatism, distortion and lateral chromatic aberration) of the projection zoom lens of Example 7 Aberration diagram showing lateral aberration at the wide-angle end of the projection zoom lens in Example 7. Aberration diagram showing lateral aberration at the intermediate position of the projection zoom lens of Example 7 Aberration diagram showing lateral aberration at the telephoto end of the projection zoom lens in Example 7 Aberration diagram showing various aberrations (spherical aberration, astigmatism, distortion and lateral chromatic aberration) of the projection zoom lens of Example 8 Aberration diagram showing lateral aberration at the wide-angle end of the zoom lens for projection according to the eighth embodiment. Aberration diagram showing lateral aberration at the intermediate position of the projection zoom lens of Example 8 Aberration diagram showing lateral aberration at the telephoto end of the zoom lens for projection according to the eighth embodiment. 1 is a schematic configuration diagram of a projection display device according to an embodiment of the present invention.

Explanation of symbols

L ₁ ~L ₁₁ lens G ₁ ~G ₄ lens group X optical axes 1,103 DMD
2 Cover glass (filter part)
101 Light source 102 Rod integrator 104 Zoom lens for projection 105 Screen

Claims (7)

In order from the magnification side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive or negative refractive power, And the second lens group, the third lens group, and the fourth lens group move to the enlargement side upon zooming from the wide-angle end to the telephoto end, and satisfy the following conditional expression (1): Zoom lens for projection.
0.95 <frw / frt <1.05 (1)
However,
frw: Composite focal length at the wide-angle end of the second, third and fourth lens groups frt: Composite focal length at the telephoto end of the second, third and fourth lens groups 2. The projection zoom lens according to claim 1, wherein the following conditional expressions (2) and (3) are satisfied.
| M4 / f4 | <| M1 / f1 | <| M2 / f2 | <| M3 / f3 | (2)
0.4 <| M3 / f3 | <0.8 (3)
However,
Mn: Movement distance between the wide-angle end position and the telephoto end position of the nth lens group fn: Focal length of the nth lens group 2. The projection zoom lens according to claim 1, wherein the following conditional expressions (4) and (5) are satisfied.
| M4 / f4 | <| M2 / f2 | <| M1 / f1 | <| M3 / f3 | (4)
0.2 <| M3 / f3 | <0.6 (5)
However,
Mn: Movement distance between the wide-angle end position and the telephoto end position of the nth lens group fn: Focal length of the nth lens group The refractive index Nd with respect to d-line of the glass material constituting the lens having the strongest negative refracting power in the fourth lens group satisfies the following conditional expression (6): The projection zoom lens according to claim 1.
Nd> 1.75 (6)   5. The projection zoom lens according to claim 1, wherein a positive lens having a convex surface facing the reduction side is disposed on the most reduction side of the fourth lens group.   6. The projection zoom lens according to claim 1, wherein one aspherical lens is disposed in the fourth lens group. 7. A light source, a light valve, an illumination optical unit that guides a light beam from the light source to the light valve, and the projection zoom lens according to any one of claims 1 to 6, and the light beam from the light source A projection display device that modulates light with the light valve and projects the light onto a screen with the projection zoom lens.

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