JP4659412B2 - Zoom lens and image projection apparatus having the same - Google Patents

Description

  The present invention relates to a zoom lens, and is suitable for a projection lens of a high-definition mobile liquid crystal projector, for example.

  Conventionally, various liquid crystal projectors (image projection apparatuses) that use a display element such as a liquid crystal to project an image formed on the display element onto a screen surface have been proposed.

  In particular, liquid crystal projectors are widely used in conferences and presentations as a device that can project an image of a personal computer or the like on a large screen.

  This liquid crystal projector is desired to be a so-called large-diameter telecentric optical system in which the pupil on the liquid crystal display device (reduction conjugate) side is at infinity because of the need for higher brightness of the device.

  In order to realize the above-mentioned conditions and a large-aperture / high-resolution projection lens (projection lens), a zoom lens that can correct various aberrations satisfactorily by arranging six lens groups under appropriate refractive power conditions. Lenses have been proposed (Patent Documents 1 and 2).

  In Patent Document 1, as projection lenses for a liquid crystal projector, an array of first to sixth lens groups having negative, positive, positive, negative, positive (or negative), and positive refractive powers in order from the magnification conjugate side (front). There has been proposed a 6-group zoom lens comprising six lens groups as a whole, and performing zooming by appropriately moving a predetermined lens group among them.

  On the other hand, in recent years, in order to place importance on portability and mobility, projector apparatuses are particularly required to be smaller and lighter.

As a projection lens having a simple configuration for realizing such needs, for example, a lens group having negative, positive, positive, and positive refractive powers in order from the magnification conjugate side is arranged. A zoom lens of a four-group zoom system in which the conjugate lens group is fixed has been proposed (Patent Document 3).
JP 2001-235679 A JP 2004-70306 A JP 2000-275519 A

  Proceeding with a multi-lens group of projection lenses works optically from the viewpoint of aberration correction, but generally the problem is that the configuration of the projection lens becomes complicated or heavy and difficult to manufacture. Will arise.

  Further, in the configuration of Patent Document 3 proposed as a simple configuration, since the lateral magnification of the variable power lens group is far apart from the same magnification, the focal position correcting lens that corrects the focal shift that occurs during zooming (during variable power). The amount of movement of the lens group is large, and the magnification ratio is reduced with the movement of the focal position correction lens group, so that the burden on the variable power lens group becomes large.

  In addition, when trying to realize a telecentric zoom lens suitable for a reduction conjugate side suitable for a liquid crystal projector, the positive refractive power increases for the entire lens group arranged on the reduction conjugate side from the stop, and the entire lens system is a retrofocus type. This increases the asymmetry of the entire lens system and makes it difficult to correct distortion and lateral chromatic aberration.

  The present invention is for a liquid crystal projector in which a high zoom ratio can be easily obtained while reducing the size of the entire lens system, and various aberrations associated with zooming are corrected well, and the entire screen has good optical performance. It is an object of the present invention to provide a suitable zoom lens and an image projection apparatus having the same.

The zoom lens of the present invention, turn towards after Ri by previous person, a first lens group having negative refractive power, a second lens group having a positive refractive power, a third lens group having positive refractive power, positive The second lens group moves from the front side to the rear side during zooming from the zoom position at the wide-angle end to the zoom position at the telephoto end, and has the third lens group. Are moved from the rear side to the front side while performing multiplication, respectively, and when the lateral magnification of the second lens group is β2w at the zoom position at the wide angle end,
1 <β2w <3
It is characterized by satisfying .

  According to the present invention, while reducing the size of the entire lens system, a high zoom ratio can be easily obtained, and various aberrations caused by zooming can be corrected well, and the liquid crystal projector has good optical performance over the entire screen. A zoom lens suitable for use can be achieved.

  FIG. 1 is a schematic diagram of a main part of an image projection apparatus (liquid crystal video projector) using a zoom lens according to a first embodiment of the present invention. FIG. 1A illustrates a state in which the zoom lens is at a wide-angle end zoom position. FIG. 5B shows the zoom lens in the zoom position at the telephoto end.

FIGS. 2A and 2B show the object distance (distance from the first lens group) of 1.8 m when the numerical value of Numerical Example 1 described later corresponding to Example 1 of the present invention is expressed in mm. is an aberration diagram at the wide-angle end (short focal length side) and the telephoto end (long focal length side) when the.

  FIG. 3 is a schematic diagram of a main part of an image projection apparatus using a zoom lens according to a second embodiment of the present invention. FIG. 3A is a diagram when the zoom lens is at the wide-angle end zoom position. Indicates when the zoom lens is at the zoom position at the telephoto end.

  4A and 4B show aberrations at the wide-angle end and the telephoto end when the object distance is 1.8 m when the numerical value of Numerical Example 2 described later corresponding to Example 2 of the present invention is expressed in mm. FIG.

  FIG. 5 is a schematic diagram of a main part of an image projection apparatus using a zoom lens according to a third embodiment of the present invention. FIG. 5A shows the zoom lens at the wide-angle end zoom position. Indicates when the zoom lens is at the zoom position at the telephoto end.

  6A and 6B show aberrations at the wide-angle end and the telephoto end when the object distance is 2.1 m when the numerical value of Numerical Example 3 described later corresponding to Example 3 of the present invention is expressed in mm. FIG.

  FIG. 7 is a schematic diagram of a main part of an image projection apparatus using a zoom lens according to a fourth embodiment of the present invention. FIG. 7A is a diagram when the zoom lens is at the wide-angle end zoom position. Indicates when the zoom lens is at the zoom position at the telephoto end.

  8A and 8B show aberrations at the wide-angle end and the telephoto end when the object distance is 2.1 m when the numerical value of numerical example 4 described later corresponding to the fourth example of the present invention is expressed in mm. FIG.

  FIG. 9 is a schematic diagram of a main part of an image projection apparatus using a zoom lens according to a fifth embodiment of the present invention. FIG. 9A shows the zoom lens in the zoom position at the wide-angle end. Indicates when the zoom lens is at the zoom position at the telephoto end.

  FIGS. 10A and 10B show aberrations at the wide-angle end and the telephoto end when the object distance is 2.1 m when the numerical value of Numerical Example 5 described later corresponding to Example 5 of the present invention is expressed in mm. FIG.

  In the image projection apparatuses according to the first to fifth embodiments shown in FIGS. 1, 3, 5, 7, and 9, an original image (projected image) of an LCD is displayed on a screen surface S using a zoom lens (projection lens, projection lens) PL. The state of the enlarged projection is shown above.

  S is a screen surface (projection surface), and LCD is an original image (projected image) such as a liquid crystal panel (liquid crystal display element). The screen surface S and the original image LCD have a conjugate relationship. Generally, the screen surface S has a longer conjugate point (first conjugate point) on the enlarged side (front), and the original image LCD has a shorter distance. The conjugate point (second conjugate point) corresponds to the reduction side (back). When the zoom lens is used as a photographing system, the screen surface S side is the object side, and the original image LCD side is the image side.

  GB is a glass block provided for optical design corresponding to a color synthesis prism, a polarizing filter, a color filter, and the like.

  The zoom lens PL is attached to a liquid crystal video projector main body (not shown) via a connecting member (not shown). The liquid crystal display element LCD side after the glass block GB is included in the projector body.

  L1 is a first lens group having a negative refractive power, L2 is a second lens group having a positive refractive power, L3 is a third lens group having a positive refractive power, and L4 is a fourth lens group having a positive refractive power.

  In each embodiment, the second lens unit L2 is moved backward and the third lens unit L3 is moved forward as indicated by an arrow during zooming (magnification) from the wide-angle end to the telephoto end zoom position.

The first lens group L1, the fourth lens unit L4 does not move because the zooming.

  The focusing is performed by moving the first lens unit L1 in Examples 1 and 3 of FIGS. 1 and 5, and the second lens unit L2 in Examples 2, 4, and 5 of FIGS. 3, 7, and 9. It is moved.

  The focusing may be performed by moving the display panel LCD.

  SP is an aperture stop, and in Examples 1 and 2 of FIGS. 1 and 3, it is arranged on the rear side of the tenth surface from the front to the rear.

  In Example 3-5 of FIG.5, FIG.7, FIG.9, it arrange | positions from the front to the back on the 8th surface.

  Each lens surface is provided with a multilayer coating for antireflection.

  In the aberration diagrams of FIGS. 2, 4, 6, 8, and 10, G indicates an aberration at a wavelength of 550 nm, R indicates a wavelength at 610 nm, B indicates an aberration at a wavelength of 460 nm, ΔS (sagittal image plane tilt), ΔM (meridional). Both image plane tilts indicate aberrations at a wavelength of 550 nm. F is an F number. ω is a half angle of view.

  In each embodiment, a wide lead angle and a long back focus can be easily obtained by a negative lead type zoom lens configuration preceded by a lens unit having a negative refractive power.

During zooming, the two lens groups L2 and L3 move independently while changing their mutual distance. When zooming from the wide-angle end to the telephoto end zoom position, the moving lens groups L2 and L3 all have a multiplication effect. is doing.

  When the zoom lens of each embodiment is used as a projector, that is, with respect to image formation from the rear to the front, all the lens groups that move during zooming have a demagnifying action.

  The second and third lens groups L2 and L3 both exhibit a multiplying action, share the zoom ratio, and reduce the magnification burden of the third lens group L3, which is a zoom lens group. ing.

  In the zoom lens of each embodiment, when the distance between the object images changes, the first lens unit L1 or the second lens unit L2 is moved on the optical axis to adjust the focus, thereby realizing a simple zoom lens structure. .

  In each embodiment, the first lens unit L1 on the most conjugate side (front side) and the fourth lens unit L4 on the reduction conjugate side (back side) are fixed with respect to the reduction conjugate surface during zooming. As a result, the entire lens length remains unchanged in the entire zoom range, the robustness of the projection lens unit is ensured, and the lens group with a large outer diameter is fixed during zooming, so there is little change in weight balance and it works favorably on the holding mechanism surface. Like to do.

  The second lens unit L2 moves from the enlargement conjugate side (front side) to the reduction conjugate side (rear side) during zooming from the wide-angle end to the telephoto end zoom position, and the third lens unit L3 moves to the reduction conjugate side ( By moving from the rear side) to the magnification conjugate side (front side), both have a multiplication effect, and the burden on the variable power lens unit L3 is reduced.

  The third lens unit L3, which is the main variable power lens unit, includes at least two positive lenses and at least one negative lens. The third lens unit L3 is a lens unit for securing a zoom ratio (magnification ratio), and a lens configuration is selected so that there is no large aberration variation even if the lateral magnification changes due to the movement of this lens unit. Yes. Therefore, the third lens unit L3 uses at least two positive lenses to share the positive refractive power to reduce the occurrence of aberrations, and at least one negative lens to sufficiently generate the aberrations generated by the positive lens. The lens configuration can be adjusted.

  As a result, aberration fluctuations during zooming are reduced.

  Also, good imaging performance is ensured by using at least one aspherical surface as the aberration correction means. The lens having the aspherical surface can be realized lighter and easier if it is formed by molding plastic. With respect to the arrangement of the aspheric surfaces, it is preferable to arrange one or more on the front side and the rear side across the aperture stop.

  Further, it is desirable that the aspherical surface provided on the front side across the aperture stop is the surface of the negative lens, and the aspherical surface provided on the rear side is the surface of the positive lens. As a result, the asymmetrical aberration (coma aberration / distortion aberration) caused by the so-called retrofocus type refractive power arrangement in which the front side has a negative refractive power and the rear side has a positive refractive power across the aperture stop is corrected well. .

  As the aspherical shape for correcting the aberration, the aspherical shape provided on the front side across the aperture stop is provided on the concave surface, and the negative refractive power becomes weaker (weaker) from the optical axis to the periphery. The shape and the aspherical shape provided on the rear side are preferably provided on the convex surface so that the positive refractive power becomes weaker (weaker) from the optical axis to the periphery.

  In order to reduce lateral chromatic aberration that is difficult to correct as a feature of a zoom lens at the wide-angle end of a retrofocus type, at least one glass lens having an Abbe number of 80 or more is provided.

  The first lens unit L1 includes two or more negative lenses.

  The second lens unit L2 is composed of one positive lens to realize a lighter and simpler projection lens. In relation to this, the fourth lens unit L4 on the rearmost side also requires a positive refractive power in order to realize telecentric performance. However, the fourth lens unit L4 is configured by a single positive lens to further reduce the weight.

  Further, in some cases, the rearmost fourth lens unit L4 can be used as a lens unit for back focus adjustment. For this reason, it is preferable that the fourth lens unit L4 is composed of one positive lens.

At the zoom position at the wide-angle end, the lateral magnifications of the second lens group and the third lens group are β _2W and β _3W , respectively, and the focal length of the lens group disposed behind the aperture stop is f _r , L is the distance from the aperture stop to the front principal point position of the lens unit disposed behind, and the lateral magnifications at the wide-angle end and the telephoto end of the second lens unit L2 are β _2W and β _2T , respectively. When
1 <β _2W <3 (1)
−1.3 <β _3W <−0.8 (2)
0.75 <L / f _r <1.1 (3)
0.88 <β _2T / β _2W <1.20 (4)
Is satisfied.

  Next, the technical meaning of each conditional expression described above will be described.

  Conditional expression (1) prescribes the lateral magnification of the second lens unit L2, and if the lower limit is exceeded, the burden of the zoom ratio that the third lens unit L3 for zooming increases increases, and the upper limit If the value is exceeded, it is difficult to correct spherical aberration and coma with a good balance.

  Conditional expression (2) defines the lateral magnification of the third lens group, which is a lens group for zooming, and the focal position shift during zooming (zooming) is large no matter which of the condition range is exceeded. Therefore, the necessary movement amount of the second lens unit L2, which is a lens unit for correcting the focal position, is not preferable.

  Conditional expression (3) is for ensuring telecentric performance.

  If the configuration is outside the range of the conditional expression (3), good telecentric performance cannot be obtained, and when used in a liquid crystal projector or the like, peripheral illuminance drop or in-screen color unevenness occurs, which is not preferable.

  By restricting the zooming effect by the second lens unit L2 within the range of the above conditional expression (4), all the projection distances and zooms from the wide-angle end to the telephoto end can be achieved even when the second lens unit L2 is focused. For zooming to a position, the amount of focal movement is suppressed within a certain focal depth range.

  More preferably, the numerical ranges of the conditional expressions (1) to (4) are set as follows.

1.3 <β _2W <2.9 (1a)
−1.3 <β _3W <−0.85 (2a)
0.85 <L / f _r <1.1 (3a)
0.95 <β _2T / β _2W <1.20 (4a)
Next, features of the zoom lens of each embodiment will be described.

  In Example 1 of FIG. 1, the first lens unit L1 has a three-lens configuration of negative, negative, and negative lenses in order from the front side to the rear side.

  The front lens diameter is set small by setting the apparent pupil position to the front side by configuring the first lens unit L1 entirely with a negative lens.

  Further, the second negative lens from the front side is a lens made of a plastic material having both aspheric surfaces, and efficiently corrects distortion and the like.

  The second lens unit L2 has a multiplication function while correcting the focal position shift accompanying the movement of the third lens unit L3 to be kept behind, and reduces the magnification burden that the third lens unit L3 earns. Yes.

  The third lens unit L3 may play a role as a main variable power lens unit. In this embodiment, the third lens unit L3 is the largest in the constituent lens units as a positive, negative, positive, and positive lens in order from the front side to the rear side. Consists of lens elements. In particular, the positive lens located at the rearmost side has both aspheric surfaces formed by molding a plastic material, and mainly corrects distortion aberration, curvature of field, and the like. In this embodiment, the temperature drift characteristic at the time of environmental change is canceled between the positive lens made of this plastic material and the negative lens made of the plastic material in the first lens unit L1.

  The fourth lens unit L4 has a single positive lens configuration, and mainly has a refraction action that makes the angle of the off-axis chief ray parallel to the optical axis, and the combined refraction of the first to third lens units L1 to L3. The effect is that the force can be set small. As the glass type of the lenses constituting the fourth lens unit L4, the trade name s-al14 (Ohara Inc.) is applied.

  Desirably, if a glass material satisfying the following equation is selected, a correction surface for a wide-range chromatic aberration of magnification is effective.

That νd the Abbe number of the single positive lens material of the fourth lens unit L4, a partial fraction ratio θ _{g ·} F, d-line, F-line, the refractive index for the C line and _{n d, n F, n c} ,

When
0 <θ _{g · F} − (0.6438−0.001682νd)
To be satisfied.

  According to the present embodiment, a zoom lens that achieves a zoom ratio of about 1.5 times with a simple mechanism despite the large aperture of F value of 1.7 is realized.

  The second embodiment is different from the first embodiment in that the focus adjustment is performed by the second lens group, except that the zoom ratio of the second lens group L2 hardly changes during zooming. In FIG. 5, the detailed description is omitted because it is the same.

  According to the present embodiment, a zoom lens that secures a zoom ratio of about 1.45 times with a simple mechanism despite the F value of 1.7 is realized.

  In the third exemplary embodiment, the first lens unit L1 has two negative and negative lenses in order from the front side to the rear side. The front lens diameter is set small by setting the apparent pupil position forward by designing the interior of the first lens unit L1 entirely with a negative lens. Further, the first lens from the front side is a lens having both aspheric surfaces formed by molding a glass material, and efficiently corrects distortion.

  The third lens unit L3 may play a role as a main variable power lens unit. In the present embodiment, the third lens unit L3 is the most positive, negative, positive, positive lens in order from the front side to the rear side in the constituent lens units. It consists of many lens elements. In particular, for the positive lens located at the rearmost side, a lens having both aspheric surfaces formed by molding a glass material is used, and distortion, field curvature, etc. are mainly corrected efficiently.

  Since the other points are the same as those of the first embodiment, detailed description thereof is omitted.

  According to the present embodiment, a zoom lens that secures a zoom ratio of about 1.25 times with a simple mechanism despite the large aperture of F value of 1.5 is realized.

  In Example 4, the first lens unit L1 has a two-lens configuration of negative and negative lenses in order from the front side to the rear side. By making the first lens arranged on the most front side a negative lens, the apparent pupil position is set on the front side, and the front lens diameter is set small.

  The first lens uses a special low-dispersion glass product name s-FPL51 (Ohara Co., Ltd.) with an Abbe number of 80 or more. Furthermore, both surfaces are aspherical, and the lateral chromatic aberration and distortion are efficiently achieved. Etc. are corrected.

  In particular, the rear concave surface of this aspherical surface has an aspherical shape in which the negative refractive power becomes gentle (weak) as it goes to the lens periphery. Aberrations are corrected efficiently.

  The third lens unit L3 may play a role as a main variable power lens unit. In this embodiment, the third lens unit L3 is the largest in the constituent lens units as positive, negative, positive, and positive lenses in order from the front side to the rear side. Consists of lens elements. In particular, with respect to the most positive lens located on the rearmost side, both surfaces formed by molding a glass material are aspherical lenses, and mainly correct distortion and field curvature.

  In particular, the convex surface on the rear side of this aspherical shape has an aspherical shape in which the positive refracting power becomes looser as it goes to the periphery of the lens, thereby correcting distortion, curvature of field, etc. is doing.

Since other points are the same as those of the third embodiment, detailed description thereof is omitted.
According to the present embodiment, a zoom lens that secures a zoom ratio of about 1.25 times with a simple mechanism despite the large aperture of F value of 1.5 is realized.

  In the fifth embodiment, since the third lens unit L3 operates at a magnification equal to or less than −0.9 at the zoom position at the wide-angle end, movement of the second lens unit L2 for focal position correction is performed. Has an inflection point near the wide-angle end.

Since other points are the same as those of the fourth embodiment, detailed description thereof is omitted.
According to the present embodiment, a zoom lens that secures a zoom ratio of about 1.25 times with a simple mechanism despite the large aperture of F value of 1.5 is realized.

  A lens group having a small refractive power, a converter lens, or the like may be disposed on the object side of the first lens group or / and on the image side of the fourth lens group.

Numerical examples 1 to 5 respectively corresponding to the zoom lenses of Examples 1 to 5 are shown below. In each numerical example, i indicates the order of the optical surfaces from the enlarged surface (front side), ri is the radius of curvature of the i-th optical surface (i-th surface), and di is the i-th surface and the i-th surface + 1 surface. , Ni and νi represent the refractive index and Abbe number of the material of the i-th optical member with respect to the d-line, respectively. f is a focal length, and FNO is an F number. ω is a half angle of view.
The two rearmost surfaces of Numerical Examples 1 to 5 are surfaces constituting a glass block GB conceived for a color separation prism, a face plate, various filters, and the like.

Further, when k is an eccentricity, A, B, C, D, and E are aspherical coefficients, and the displacement in the optical axis direction at the position of the height h from the optical axis is x with respect to the surface vertex, the aspherical surface The shape is
x = (h ² / r) / [1+ [1- (1 + k) (h / R) ² ] ^1/2 ]
+ Ah ⁴ + Bh ⁶ + Ch ⁸ + Dh ¹⁰ + Eh ¹²
Is displayed. Where r is the paraxial radius of curvature.

Incidentally, for example, "e-Z" means ^{"10 -Z".}

  Table 1 shows the relationship between the above-mentioned conditional expressions 1 to 4 and various numerical values in the numerical examples 1 to 5.

Numerical example 1
f: 14.0mm to 20.8mm FNO: 1.74 to 2.04 ω: 38.57 ° to 28.25 °
R dn ν
1 24.625 1.70 1.854 23.8
2 18.139 2.37
3 () 1.50 1.532 55.8
4 () 9.60
5 -32.957 1.50 1.748 44.8
6 54.327 ()
7 61.736 4.12 1.734 28.5
8 -58.889 ()
9 31.211 4.01 1.810 40.9
10 -316.955 18.42
11 -15.586 1.10 1.854 23.9
12 249.328 0.20
13 56.372 7.49 1.518 64.1
14 -16.900 0.75
15 () 3.34 1.532 55.8
16 () ()

17 41.666 4.33 1.699 55.5
18 -235.774 4.05
19 inf. 29.20 1.518 64.1
20 inf. 3.26
Group interval data
WT
d 6 1.86 4.06
d 8 27.11 7.71
d16 0.60 17.81
Aspheric data
(1 / r) k ABCD
3 4.593e-002 7.993e-001 -2.120e-005 6.817e-008 1.227e-010 4.360e-013
E
-4.915e-015
(1 / r) k ABCD
4 7.589e-002 -2.824e-001 -2.944e-005 8.476e-008 -5.653e-010 1.301e-011
E
-4.451e-014
(1 / r) k ABCD
15 -3.819e-003 4.342e + 002 3.930e-006 -1.668e-008 -1.340e-010 -1.569e-013
E
0.000e000
(1 / r) k ABCD
16 -2.082e-002 7.964e-002 9.159e-006 3.967e-008 -6.118e-010 4.156e-012
E
-1.419e-014
Numerical example 2
f: 14.4mm to 20.9mm FNO: 1.74 to 2.11 ω: 37.78 ° to 28.15 °
R dn ν
1 23.206 1.70 1.854 23.8
2 17.547 3.08
3 () 1.50 1.532 55.8
4 () 11.43
5 -34.323 1.50 1.699 55.5
6 49.415 ()
7 56.583 4.60 1.704 30.1
8 -68.463 ()
9 32.297 3.21 1.790 44.2
10 -203.225 19.54
11 -15.722 1.10 1.854 23.9
12 705.401 0.20
13 65.246 7.17 1.566 60.7
14 -17.741 0.75
15 () 3.38 1.532 55.8
16 () ()

17 39.206 4.21 1.699 55.5
18 -1037.518 4.05
19 inf. 29.20 1.518 64.1
20 inf. 3.38
Intergroup data
WT
d 6 1.20 3.44
d 8 24.85 6.93
d16 0.60 16.27
Aspheric data
(1 / r) k ABCD
3 4.476e-002 7.993e-001 -2.120e-005 6.817e-008 1.227e-0104.360e-013
E
-5.353e-015
(1 / r) k ABCD
4 7.455e-002 -2.824e-001 -2.944e-005 8.476e-008-5.653e-010 1.301e-011
E
-5.160e-014
(1 / r) k ABCD
15 -3.760e-003 4.342e + 002 3.930e-006 -1.668e-008 -1.340e-010 -1.569e-013
E
0.000e000
(1 / r) k ABCD
16 -1.931e-002 3.085e-001 9.225e-006 4.343e-008 -6.307e-010 3.927e-012
E
-1.253e-014
Numerical Example 3
f: 17.0mm to 21.1mm FNO: 1.54 to 1.91 ω: 29.10 ° to 24.17 °
R dn ν
1 () 1.50 1.585 59.4
2 () 11.76
3 -23.490 1.50 1.766 40.1
4 40.837 ()
5 53.977 4.38 1.811 33.3
6 -40.375 ()
7 35.950 5.53 1.776 49.6
8 -176.515 20.39
9 -17.085 1.10 1.854 23.9
10 -5428.849 0.20
11 81.439 7.82 1.699 55.5
12 -21.220 0.75
13 () 4.19 1.585 59.4
14 ( )( )
15 39.496 4.51 1.716 53.9
16 1931.328 4.05

17 inf. 23.00 1.518 64.1
18 inf.6.04
Intergroup data
WT
d 4 1.58 1.95
d 6 17.74 8.10
d14 4.26 13.54
Aspheric data
(1 / r) k ABCD
1 4.238e-002 7.993e-001 -2.120e-005 6.817e-008 1.227e-010 4.360e-013
E
-2.787e-015
(1 / r) k ABCD
2 7.817e-002 -2.824e-001 -2.944e-005 8.476e-008 -5.653e-010 1.301e-011
E
-3.227e-014
(1 / r) k ABCD
13 -3.378e-003 -4.342e + 002 3.930e-006 -1.668e-008 -1.340e-010 -1.569e-013
E
0.000e + 000
(1 / r) k ABCD
14 -1.474e-002 2.397e + 000 8.559e-006 9.616e-009 -2.750e-010 1.110e-012
E
-3.036e-015
Numerical Example 4
f: 17.0mm to 21.1mm FNO: 1.54 to 1.91 ω: 29.10 ° to 24.12 °
R dn ν
1 () 1.50 1.498 81.5
2 () 11.73
3 -25.375 1.50 1.810 40.9
4 40.289 ()
5 49.849 4.10 1.811 33.3
6 -43.299 ()
7 38.522 3.92 1.776 49.6
8 -152.356 20.18
9 -17.536 1.10 1.854 23.9
10 504.102 0.20
11 78.395 8.10 1.661 50.9
12 -20.883 0.75
13 () 3.42 1.585 59.4
14 ( )( )
15 42.125 4.57 1.699 55.5
16 1951.130 4.05

17 inf. 23.00 1.518 64.1
18 inf. 8.52
Intergroup data
WT
d 4 1.45 1.84
d 6 19.16 9.38
d14 2.84 12.23
Aspheric data
(1 / r) k ABCD
1 4.454e-002 7.993e-001 -2.120e-005 6.817e-008 1.227e-010 4.360e-013
E
-3.420e-015
(1 / r) k ABCD
2 8.266e-002 -2.824e-001 -2.944e-005 8.476e-008 -5.653e-010 1.301e-011
E
-2.663e-014
(1 / r) k ABCD
13 -3.283e-003 4.342e + 002 3.930e-006 -1.668e-008 -1.340e-010 -1.569e-013
E
0.000e + 000
(1 / r) k ABCD
14 -1.819e-002 3.396e + 000 8.090e-006 9.793e-009 -2.717e-010 9.330e-013
E
-2.362e-015
Numerical Example 5
f: 17.0mm to 21.1mm FNO: 1.54 to 1.91 ω: 29.06 ° to 24.15 °
rd nd Vd
1 () 1.50 1.498 81.5
2 () 10.05
3 -27.440 1.50 1.810 40.9
4 32.131 ()
5 43.389 4.23 1.811 33.3
6 -44.120 ()
7 33.698 3.77 1.776 49.6
8 -425.823 17.42
9 -18.213 1.10 1.854 23.9
10 310.689 0.20
11 69.633 6.77 1.661 50.9
12 -20.768 0.75
13 () 3.44 1.585 59.4
14 ( )( )
15 40.954 3.42 1.699 55.5
16 1710.457 4.05

17 inf. 23.00 1.518 64.1
18 inf. 6.61
Intergroup data
WT
d 4 2.24 2.27
d 6 17.77 8.74
d14 4.83 13.82
Aspheric data
(1 / r) k ABCD
1 4.634e-002 7.993e-001 -2.120e-005 6.817e-008 1.227e-010 4.360e-013
E
-2.691e-015
(1 / r) k ABCD
2 8.394e-002 -2.824e-001 -2.944e-005 8.476e-008 -5.653e-0101.301e-011
E
-1.950e-014
(1 / r) k ABCD
13 -3.500e-003 4.342e + 002 3.930e-006 -1.668e-008 -1.340e-010 -1.569e-013
E
0.000e + 000
(1 / r) k ABCD
14 -1.895e-002 1.864e + 000 1.097e-005 -3.098e-009 -8.515e-011 2.039e-013
E
-1.950e-015

  FIG. 11 is a schematic view of a main part of an embodiment of the image projection apparatus of the present invention.

In this figure, the zoom lens described above is applied to a three-plate color liquid crystal projector, and image information of a plurality of color lights based on a plurality of liquid crystal display elements (display units) is synthesized through a color synthesizing unit, and the projection lens is used on the screen surface. Fig. 2 shows an image projection apparatus for enlarging and projecting. In FIG. 11, a color liquid crystal projector 1 synthesizes RGB color light from three liquid crystal panels 5B, 5G, and 5G of R, G, and B into one optical path by a prism 2 as a color synthesizing unit. Projection is performed on a screen 4 using a projection lens 3 composed of

  FIG. 12 is a schematic view of the main part of an embodiment of the optical apparatus of the present invention.

  In the present embodiment, an example in which the above-described zoom lens is used as an imaging lens in an optical apparatus including an imaging device such as a video camera, a film camera, or a digital camera is shown.

  In FIG. 12, the image of the subject 9 is formed on the photoconductor 7 by the photographing lens 8 to obtain image information.

  As described above, according to each of the embodiments, a zoom lens suitable for a liquid crystal projector having good optical performance over the entire screen, by properly correcting various aberrations associated with zooming while reducing the size of the entire lens system. Can be achieved.

  In addition, according to the present invention, it is possible to achieve a zoom lens suitable for an optical apparatus such as a video camera, a film camera, or a digital camera that forms image information on an imaging means surface such as a film or a CCD.

Schematic view of main parts of the image projection apparatus according to the first embodiment. Aberration diagram of Numerical Example 1 Schematic view of main parts of an image projection apparatus according to Embodiment 2. Aberration diagram of Numerical Example 2 Schematic view of main parts of an image projection apparatus according to Embodiment 3. Aberration diagram of Numerical Example 3 Schematic view of main parts of an image projection apparatus according to Embodiment 4. Aberration diagram of Numerical Example 4 Schematic view of main parts of an image projection apparatus according to Embodiment 5. Aberration diagram of Numerical Example 5 Schematic diagram of essential parts when the image projection apparatus of the present invention is applied to a color liquid crystal projector. Schematic diagram of the main part of an embodiment of the optical apparatus of the present invention

Explanation of symbols

L1 1st lens group L2 2nd lens group L3 3rd lens group L4 4th lens group ST Aperture stop LCD Liquid crystal display device (image plane)
GB glass block (color synthesis prism)
ΔS Sagittal image plane tilt ΔM Meridional image plane tilt 1 Liquid crystal projector 2 Color composition means 3 Projection lens 4 Screen 5 (5B, 5G, 5R) Liquid crystal panel 6 Imaging device 7 Imaging means 8 Shooting lens 9 Subject

Claims (15)

Turn towards after Ri by previous person, fourth having a negative first lens group having a refractive power, a second lens group having a positive refractive power, a third lens group having positive refractive power, positive refractive power When zooming from the wide-angle end zoom position to the telephoto end zoom position, the second lens group moves from the front side to the rear side, and the third lens group moves from the rear side to the front side. When the lateral magnification of the second lens group is β2w at the zoom position at the wide angle end,
1 <β2w <3
A zoom lens characterized by satisfying In the zoom position of the wide-angle end, when the lateral magnification of the third lens group and β 3w, - 1.3 <β3w < -0.8
The zoom lens according to claim 1, wherein: The zoom lens according to claim 1 or 2, wherein focus adjustment is performed by moving the first lens group or the second lens group on an optical axis. The first lens group and the fourth lens group any one of the zoom lens according to claim 1 to 3, characterized in that it is fixed relative to the rear of the conjugate plane. The third lens group includes at least two positive lenses, one or more of any one of the zoom lens of claims 1 to 4, characterized in that it is constructed from a negative lens. Has an aperture stop, and the focal distance f _r of the lens groups are arranged from the opening aperture in the _rear, the distance from the aperture stop to the principal point of the front side of the lens group disposed behind L and when,
0.75 <L / fr <1.1
Any one of the zoom lens of claims 1 to 5, characterized by satisfying. The zoom lens according to any one of claims 1 to 6 , wherein the zoom lens has an aperture stop, and each of the front and rear lens groups sandwiching the aperture stop has an aspheric surface. . 2. An aperture stop, wherein at least one negative lens on the front side and at least one positive lens on the rear side across the aperture stop have an aspherical surface. The zoom lens according to any one of 7 to 7 . An aperture stop is provided, and at least one concave surface of the lens unit on the front side across the aperture stop has an aspherical shape in which the negative refractive power decreases from the optical axis toward the periphery, at least one convex lens group, any one of the zoom lens of claims 1 to 8, characterized in that the optical axis is a non-spherical shape in which a positive refractive power becomes weaker toward the peripheral portion. The zoom lens according to any one of claims 1 to 9 , wherein the zoom lens has at least one glass having an Abbe number of 80 or more. The zoom lens according to any one of claims 1 to 10 , wherein the second lens group includes one positive lens. The zoom lens according to any one of claims 1 to 11 , wherein the fourth lens group includes a single positive lens. When the lateral magnification and beta 2t in Nozomu distal end of the second lens group,
0.88 <β2t / β2w <1.20
Any one of the zoom lens of claims 1 to 12, characterized by satisfying. The fourth lens group is composed of a single positive lens, the Abbe number of the material of the positive lens is νd, the partial fraction ratios are θg · F, d-line, F-line, C-line refractive indices nd, nf, nc,

When
0 <θg · F− (0.6438−0.001682νd)
Any one of the zoom lens of claims 1 to 13, characterized by satisfying. And any one of the zoom lens of claims 1 14, and a display unit for forming an original image, a projection apparatus an original image formed by the display unit, characterized in that projected onto the screen by the zoom lens .