JP2006162700A - Zoom lens system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens system having high accuracy at varying power and at focusing. <P>SOLUTION: The zoom lens system 5 includes a plurality of lens groups G1 to G7, and some groups G2 and G3 of the plurality of lens groups are synchronously shifted as one group at varying the power, and only the lens group G3 is shifted at the time of focusing. Some of the lens groups contributing to the variable power are only shifted at focusing, then, both the power varying accuracy and the focusing accuracy are attained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a zoom lens system having a plurality of lens groups.

  In a projection lens system that projects an image on a screen and a camera lens system that forms an image of an object on an imaging surface, a mechanism for focus adjustment is essential. As a focus adjustment mechanism, in addition to a mechanism that moves only the front lens group closest to the object side or the screen side, an inner focus system that performs focus adjustment by moving a lens group other than the front group is known. . Moving the lens group in front of the aperture to adjust the focus is called the inner focus method, and moving the lens group behind the aperture to adjust the focus is sometimes called the rear focus method. In the book, these are collectively referred to as the inner focus method.

The inner focus method has an advantage that the lens holding mechanism can be simplified because the lens length can be kept unchanged during focus adjustment. Furthermore, in the zoom lens system, the front group becomes larger as the angle becomes wider. However, if the inner focus method is used, it is not necessary to drive a large front group, so the load on the driving mechanism for focus adjustment can be reduced. It also has the merit that. For this reason, it is possible to perform focus adjustment at high speed, and there is also an advantage that the time required for autofocus can be shortened. For example, Patent Document 1 discloses a zoom lens that performs focusing by moving a second lens group following the first lens group closest to the object side.
JP 2002-131642 A JP 2004-309761 A

  However, if focusing is performed by moving the zoom lens, the zooming accuracy is lowered, and there is a possibility that a predetermined aberration correction capability cannot be obtained. On the other hand, when zooming is prioritized, focusing accuracy is insufficient, and in this case, a clear image may not be obtained. On the other hand, Patent Document 2 is configured to provide a focus group that does not move when zooming, divide the focus group into a plurality of lens groups, and move the rear lens group to perform inner focus. This method has an advantage of being easy to control while being an inner focus. However, among the plurality of lens groups constituting the lens system, there are many lens groups that do not contribute to zooming, and it is difficult to ensure aberration correction capability at the time of zooming.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an inner focus zoom lens system that can achieve both zooming accuracy and focusing accuracy. The inner focus method is used in camera lenses, but no example has been found in a projection zoom lens system that projects an image on a screen. Therefore, an object of the present invention is to provide a projection zoom lens system having a high aberration correction capability.

  For this reason, in the present invention, when a plurality of lens groups have a plurality of lens groups, and some of the plurality of lens groups move in a synchronized manner as a single group, Provides a zoom lens system in which some of the plurality of lens groups move independently, or only some of the plurality of lens groups move. In this zoom lens system, some of the plurality of lens groups that move synchronously as one group when zooming is handled as one lens group in the design of aberration correction for zooming. Therefore, the aberration correction performance at the time of zooming is ensured by the movement of some of the plurality of lens groups as a whole. When the focus is adjusted after zooming, some lens groups move independently, or only some lens groups of some lens groups move. The movement of the lens group for focus adjustment is very small, and is small compared to the movement of some of the plurality of lens groups as a whole when zooming. For this reason, even if some lens groups of some lens groups are moved, the relative positional accuracy of all of some lens groups in the plurality of lens groups constituting the zoom lens system Does not deteriorate so much. Therefore, it is possible to adjust the focus with high accuracy without substantially deteriorating the aberration correction accuracy for zooming.

  This zoom lens system moves when zooming a part of a plurality of lens groups including a lens group at the front end on the most object side or screen side, or a rear end lens on the opposite side. Including a configuration that moves only during focus adjustment. However, since the focus adjustment capability can be improved without degrading the zooming accuracy, the inner focus method is adopted without degrading the zooming accuracy by applying it to the internal lens group mainly responsible for zooming. The great effect that it can be obtained. Accordingly, it is desirable that some of the plurality of lens groups are internal lens groups of the lens system.

  And, by fixing the lens groups at both ends of the plurality of lens groups, the merit as the inner focus method, that is, the lens holding property is improved, the load of autofocus is reduced, and the speed can be increased. The benefits can be obtained. In the case of the inner focus method, a method called a floating method in which other lens groups move at the same time may be employed in order to compensate for aberration correction performance that decreases due to the movement of the internal lens for focus adjustment. . In the present invention, this method can also be adopted. However, in the present invention, when zooming, a part of a plurality of lens groups move synchronously as one lens group, and at the time of focus adjustment, only a part of the plurality of lens groups moves. Thus, there is little deterioration in aberration correction performance in focus adjustment. Therefore, sufficient aberration correction performance can be obtained without adopting a complicated system until the other lens groups are moved together when performing focus adjustment.

  As described above, the zoom lens system of the present invention is a system having both accuracy at the time of zooming and accuracy at the time of focus adjustment. Therefore, an optical apparatus having the zoom lens system of the present invention and an image processing apparatus that inputs or outputs an image via the zoom lens system can perform zooming, and obtains a clear image when zooming (magnification). Or can be output.

  The present invention is also a method for controlling a zoom lens system having a plurality of lens groups, wherein a plurality of lens groups that are part of the plurality of lens groups are moved synchronously as one group in order to change the magnification. And a control method comprising: moving a part of the plurality of lens groups independently or moving only a part of the plurality of lens groups to adjust the focus. Furthermore, the present invention is a control mechanism of a zoom lens system having a plurality of lens groups, and a plurality of lens groups that are part of the plurality of lens groups are moved synchronously as one group in order to change the magnification. And a control mechanism having means and means for moving some of the plurality of lens groups independently or only of some of the plurality of lens groups for focus adjustment.

  The zoom lens system of the present invention can be applied to a projection zoom lens that projects projection light from an image generation device that generates light by modulating light onto a screen. For example, in order from the screen 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 having a positive refractive power. In the zoom lens system of seven groups, the fifth lens group having a negative refractive power, the sixth lens group having a positive refractive power, and the seventh lens group having a positive refractive power The second lens group and the third lens group constitute part of a plurality of lens groups that move as one lens group when zooming, and only the third lens group is used for focus adjustment. The moving inner focus method can be adopted.

  In this projection zoom lens system, the first lens and the seventh lens group at both ends are fixed, the fourth and fifth lens groups are moved, and the second and third lenses are moved as one group. Zooming is performed, and the third lens group is moved to perform focusing. For this reason, the zoom lens system for projection according to the present invention can improve the accuracy of zooming (magnification) and focusing, respectively. Therefore, since the yield in the manufacturing process of the zoom lens system can be improved, even if the mechanism for controlling the lens group is somewhat complicated, the cost increase can be absorbed sufficiently, and the total cost is not increased. The zoom lens system of the invention can be provided.

  Accordingly, the projector apparatus having the projection zoom lens system of the present invention and the image generation apparatus such as the DMD or the liquid crystal panel can perform zooming, and can clearly display the image at the time of zooming.

In the zoom lens system for projection, it is desirable that the combined focal length f1 of the first lens group and the total focal length fw at the wide angle end of the zoom lens system satisfy the following condition (A).
0.5 <| f1 / fw | <1.5 (A)

  If the upper limit of this condition (A) is exceeded, the negative power of the first lens group becomes too weak, making it difficult to correct coma and making it difficult to ensure good optical characteristics. Further, when the lower limit of the condition (A) is exceeded, the negative power of the first lens group becomes too strong, and it becomes difficult to correct spherical aberration and coma aberration, and it is difficult to ensure good optical characteristics.

It is desirable that the combined focal length f6 of the sixth lens group and the overall focal length fw at the wide angle end of the zoom lens system satisfy the following condition (B).
2.0 <f6 / fw <3.5 (B)

  If the upper limit of this condition (B) is exceeded, the power of the sixth lens group becomes too weak, the overall length becomes long, and it is difficult to achieve both downsizing and aberration correction. If the lower limit of the condition (B) is exceeded, the power of the sixth lens group becomes too strong, making it difficult to correct aberrations. Therefore, by satisfying the condition (B), it is possible to provide a projection zoom lens that is compact and has better imaging performance.

Furthermore, in the lens system in which the zooming movement amount Δd2 of the second lens group, that is, the second lens group moves together with the third lens group, the second lens group and the third lens group. It is desirable that the zoom movement amount Δd2 and the overall focal length fw at the wide-angle end of the zoom lens system satisfy the following condition (C).
0.1 <Δd2 / fw <0.25 (C)

  If the upper limit of the condition (C) is exceeded, the powers of the second lens group and the third lens group become too weak and the overall length becomes long, making it difficult to achieve both downsizing and aberration correction. If the lower limit of the condition (C) is exceeded, the powers of the second lens group and the third lens group become strong, making it difficult to correct aberrations.

Further, the movement amount Δd2 of the second lens group and the combined focal length f23 of the second lens group and the third lens group that move during zooming as a group satisfy the following condition (D). It is desirable to satisfy.
Δd2 / f23 <0.07 (D)
When the upper limit of the condition (D) is exceeded, the focus performance is degraded.

Furthermore, it is desirable that the zooming movement amount Δd2 of the second lens group and the focal length f3 of the third lens group that moves during focusing satisfy the following condition (E).
Δd2 / f3 <0.035 (E)
When the upper limit of the condition (E) is exceeded, the focus performance is degraded.

  These conditions (A) to (E) are a zoom lens system of seven groups of negative-positive-positive-positive-negative-positive-positive in order from the screen side, and the third lens group performs focus adjustment. Therefore, it is a condition suitable for providing a zoom lens system having both a focus adjustment function and an aberration correction function in the moving inner focus lens. That is, in the present invention, in order from the screen 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 lens A fourth lens group having a refractive power, a fifth lens group having a negative refractive power, a sixth lens group having a positive refractive power, and a seventh lens group having a positive refractive power; A projection zoom lens system that projects projection light from a generation device onto a screen.When zooming, the lens groups at both ends are fixed, the other lens groups are moved, and when adjusting the focus, A zoom lens system in which only three lens groups move is provided. The seven-group zoom lens system preferably satisfies at least one of the above conditions (A) to (E).

(First embodiment)
FIG. 1 shows an outline of a projector apparatus centering on a zoom lens system according to the present invention. The projector 1 projects an image on an external screen 9, and is combined with an LCD 2 that is an image generation device (light valve) that modulates light to generate an image, and a prism 3 that color-synthesizes the image. And a zoom lens system 5 for projecting the projected light onto the screen 9. Although the image generation apparatus may be of a self-luminous type, in many cases, the amount of light is insufficient for projection, and therefore, the image generation apparatus is provided with a light source that is not shown in FIG.

  The zoom lens system 5 includes 16 lenses L11 to L71 grouped into seven lens groups G1 to G7 in order from the screen 9 side. The zoom lens system 5 further includes a control mechanism 10 that controls the movement of these lens groups G1 to G7. The control mechanism 10 moves to change the magnification of the lens groups G2 to G6 excluding the lens groups G1 and G7 at both ends of the plurality of lens groups G1 to G7 constituting the lens system 5. It has. The zooming moving mechanism 11 moves some of the plurality of lens groups G2 and G3 synchronously as one group (lens group G23) when zooming. Further, the control mechanism 10 moves only the third lens group G3 out of some of the plurality of lens groups G2 and G3 that are moved synchronously as one group for zooming in order to adjust the focus. A moving mechanism 12 for adjusting the focus is provided. The control mechanism 10 further includes stepping motors 13 and 14 that drive the moving mechanisms 11 and 12 and a control unit 15 that controls the motors 13 and 14. As shown in FIG. 2, the control unit 15 moves the lens groups G2 to G6 with a predetermined relationship for zooming, and at this time, the lens groups G2 and G3 are moved synchronously as one group. In order to adjust the focus, step 16 and step 17 for moving only the lens group G3 are sequentially performed so that an image with a desired variable magnification is clearly displayed on the screen 9.

  FIG. 3 shows the lens configuration of the zoom lens system 5. FIG. 3A shows the arrangement of the lenses at the wide-angle end that is in an enlarged display state, and FIG. 3B shows the arrangement of the lenses at the telephoto end that is in a standard state. The zoom lens system 5 includes seven lens groups G1 to G7 of negative-positive-positive-positive-positive-negative-positive-positive refractive power in order from the screen 9, and is a retrofocus type as a whole. The image input side of the LCD 2 that is an image generation device is telecentric, and the image generated by the LCD 2 can be projected clearly.

  First, the first lens group G1 on the screen 9 side is a lens group having a negative refractive power as a whole, and a positive meniscus lens L11 convex from the screen side (front) to the screen 9 side, A negative meniscus lens L12 convex on the screen 9 side, a negative meniscus lens L13 similarly convex on the screen side, and a biconcave negative lens L14 are included.

  The second lens group G2 is a lens group having a positive refracting power as a whole, and includes a single positive meniscus lens L21 that is concave on the screen 9 side. During zooming, the second lens group G2 and the third lens group G3 move as a single lens group G23 in synchronization. However, during focus adjustment (focusing), the second lens group G2 Does not move, and only the third lens group G3 moves. The third lens group G3 is a lens group having a positive refractive power as a whole, and is composed of a negative meniscus lens L31 convex on the screen side forming a doublet and a positive biconvex lens L32.

  The fourth lens group G4 is a lens group having a positive refractive power as a whole, and has a single-lens configuration on the screen 9 side. The fifth lens group G5 is a lens group having a negative refractive power as a whole across the stop S, and forms a doublet, a concave positive meniscus lens L51 on the screen 9 side and a biconcave negative lens. L52.

  The sixth lens group G6 is a lens group having a positive refractive power as a whole, a positive lens L61 having a substantially flat screen 9 side, a double concave negative lens L62 forming a doublet, and a double convex positive lens L63. And a concave positive meniscus lens L64 on the screen 9 side and a biconvex positive lens L65.

  The seventh lens group G7 closest to the LCD 2 is a lens group having a positive refractive power as a whole, and is composed of a single lens having a positive meniscus lens L71 convex on the screen 9 side. The zoom lens system 5 is composed of 16 lenses L11 to L71.

  As shown in FIG. 3, when zooming from the wide-angle end to the telephoto end, in the zoom lens system 5 of the present example, the first lens group G1 and the seventh lens group G7 are fixed. As described above, the second lens group G2 moves together with the third lens group G3 toward the screen 9 during zooming (magnification). Furthermore, the fourth lens group G4, the fifth lens group, and the sixth lens group also move to the screen 9 side at a predetermined ratio.

  When focusing, an inner focus method is employed in which the second lens group G2 does not move and only the third lens group G3 is moved back and forth to perform focusing.

  On the other hand, in the lens system 5 of this example, the second lens group G2 and the third lens group G3 move together as a lens group G23 during zooming.

  In the lens data shown below, Rdy is the radius of curvature (mm) of each lens arranged in order from the screen side, Thi is the distance (mm) between the lens surfaces arranged in order from the screen side, and nd is from the screen side. The refractive index (d line) of each lens arranged in order, vd indicates the Abbe number (d line) of each lens arranged in order from the screen side. INFINITY and FLAT indicate planes.

  Further, the distances changed by zooming are the distance d2 between the first lens group G1 and the second lens G2, the distance d3 between the second lens group G2 and the third lens group G3, and the third lens, respectively. A distance d4 between the group G3 and the fourth lens group G4, a distance d5 between the fourth lens group G4 and the fifth lens group G5, a distance d6 between the fifth lens group G5 and the sixth lens group G6, The distance d7 between the sixth lens group G6 and the seventh lens group G7 is set. The diaphragm S is disposed on the screen side of the fifth lens group G5 and moves together with the fifth lens group G5. Therefore, the distance d5 indicates the distance between the fourth lens group G4 and the diaphragm S. Yes. Further, the values are shown when the distance between the screen side surface of the lens L11 closest to the screen and the screen 9 is 2850 mm. The same applies to the other embodiments.

Lens data (No. 1)
No. Rdy Thi nd vd
1 128.20500 10.83 1.83500 42.98 Lens L11
2 502.57800 0.32
3 89.67700 2.50 1.62041 60.34 Lens L12
4 46.62600 12.86
5 234.02700 2.50 1.83500 42.98 Lens L13
6 64.27900 14.14
7 -99.64500 2.50 1.83500 42.98 Lens L14
8 133.44800 d2 (variable)
9 -1151.39900 6.82 1.80518 25.46 Lens L21
10 -117.26800 d3 (fixed)
11 -3577.44400 2.50 1.84666 23.78 Lens L31
12 51.72100 17.89 1.80610 33.27 Lens L32
13 -161.77900 d4 (variable)
14 77.72000 8.76 1.72342 37.99 Lens L41
15 -277.26600 16.77
16 FLAT d5 (variable) Aperture S
17 -99.22800 6.06 1.84666 23.78 Lens L51
18 -28.12700 2.92 1.83400 37.34 Lens L52
19 80.78900 d6 (variable)
20 13571.72500 6.16 1.48749 70.44 Lens L61
21 -43.58800 2.43
22 -34.16600 2.62 1.84666 23.78 Lens L62
23 129.87400 8.64 1.48749 70.44 Lens L63
24 -59.71200 0.25
25 -428.95400 7.42 1.49700 81.61 Lens L64
26 -66.23 300 0.25
27 1189.29200 11.87 1.49700 81.61 Lens L65
28 -54.55700 d7 (variable)
29 98.22200 7.25 1.80518 25.46 Lens L71
30 1195.39700 1.56
31 FLAT 62.20 1.51680 64.20 Prism 3

The distance (mm) between the lens groups is as follows.
Wide-angle end Medium Telephoto end d2 15.07 12.80 11.21
d3 10.00 10.00 10.00
d4 28.20 18.98 6.03
d5 14.91 20.00 27.34
d6 12.05 9.21 5.10
d7 0.50 9.74 21.04

The focal length (mm) of each lens group is as follows.
fw (total focal length at the wide-angle end): 35.702
ft (total focal length at the telephoto end): 49.601
Magnification: 1.39
Back focus: 94.05
Half angle of view: 30.30
f1 (focal length of the first lens group G1): −38.17
f23 (the combined focal length of the second lens group G2 and the third lens group G3): 103.59
f2 (focal length of second lens group G2 (zoom component of lens group G23)): 160.35
f3 (focal length of the third lens group G3 (focus component of the lens group G23)): 250.00
f6 (synthetic focal length of the sixth lens group G6): 91.508
Δd2 (zooming movement amount of the second lens group G2 (lens group G23)): 3.86

Therefore, the conditions defined in the above formulas (A) to (E) are as follows.
Condition (A) (| f1 / fw |): 1.069
Condition (B) (f6 / fw): 2.563
Condition (C) (Δd2 / fw): 0.108
Condition (D) (Δd2 / f23): 0.037
Condition (E) (Δd2 / f3): 0.015

  Therefore, the zoom lens system 5 of the present example satisfies the conditions (A) to (E), and the power of the first lens group and the power of the sixth lens group are set in appropriate ranges. As shown in FIGS. 4 to 7, good aberration correction performance is obtained in the range from the wide-angle end to the telephoto end. Also, the focus adjustment ability is high. For this reason, the zoom lens system 5 of the present example is a wide-angle lens having a half angle of view of 30 ° or more, and has a high magnification of 1.39 and a back focus of 94.05, which is sufficiently long. High optical performance can be obtained from the wide-angle end to the telephoto end.

  FIG. 4 shows spherical aberration, astigmatism and distortion at the wide-angle end of the projection zoom lens 5. FIG. 5 shows spherical aberration, astigmatism and distortion at the telephoto end. Further, in FIGS. 6 and 7, spherical aberration (unit: mm) at the wide-angle end and the telephoto end is shown by lateral aberration diagrams. The spherical aberration indicates values at respective wavelengths of 620.0 nm (dashed line), 550.0 nm (solid line), and 450.0 nm (dashed line). In the astigmatism and lateral aberration diagrams, the aberrations of the tangential ray (T) and the sagittal ray (S) are shown, respectively.

  In the zoom lens system 5 of this example, when zooming, the second lens group G2 and the third lens group G3 are moved as one lens group in synchronization, and when zooming, the zoom lens system 5 is similar to the zooming. The method of moving only a part of the third lens group G3 of the lens group that contributes to the above is adopted. Therefore, it is not necessary to move the second lens group G2 that greatly contributes to zooming for focus adjustment. Even if the third lens group G3 is moved for focus adjustment, the influence of zooming on the aberration correction performance is not affected. The focus adjustment performance at the time of zooming can be sufficiently secured. For this reason, since the zoom lens system 5 of this example moves only a part of the lens group that contributes to zooming when performing focus adjustment, it is possible to achieve both zooming accuracy and focus adjustment accuracy. It is a lens system that can. Accordingly, as shown in FIGS. 4 to 7, each aberration of the zoom lens system 5 of the present example is corrected well at each zooming, and the projection with good performance that hardly shows the influence of coma aberration. It has become a zoom lens. As described above, the projection zoom lens 5 of this example is a projection zoom lens with high imaging performance from the wide-angle end to the telephoto end. By adopting this zoom lens system, a bright image is projected with high resolution. The projector 1 that can be provided can be provided.

(Second embodiment)
FIG. 8 shows a lens configuration of a different zoom lens system 6 of the present invention. FIG. 8A shows the arrangement of the lenses at the wide-angle end that is in a magnified display state, and FIG. 8B shows the arrangement of the lenses at the telephoto end that is in a standard state. The zoom lens system 6 includes seven lens groups G1 to G7 having negative-positive-positive-positive-positive-negative-positive-positive refractive power in order from the screen 9 side, and is a retrofocus type as a whole. The image input side of the LCD 2 that is an image generation device is telecentric, and the image generated by the LCD 2 can be projected clearly.

  The total number of lenses constituting this lens system 6 is 16, the number of lenses constituting each of the lens groups G1 to G7 is not different from the above example, and the basic shape of each lens is Although there is a slight difference such that the lens L61 closest to the screen 9 in the sixth lens group G6 is a positive meniscus lens L61 that is slightly concave on the screen side, it is almost the same as the above lens system.

  In the lens system 6 of this example, as shown in FIG. 8, when zooming from the wide angle end to the telephoto end, the first lens group G1 and the seventh lens group G7 are fixed, and the other lens groups are: Each of the second lens group G2 and the third lens group G3 is moved to the screen 9 side at a predetermined ratio. Therefore, in the lens system 6 of this example, the second lens group G2 and the third lens group G3 do not move as one lens group during zooming, but move at their respective ratios. When focusing, an inner focus method is employed in which only the third lens group G3 is moved forward and backward to perform focusing.

Lens data (No. 2)
No. Rdy Thi nd vd
1 117.634 10.46 1.83500 42.98 Lens L11
2 388.607 0.25
3 81.323 2.50 1.62041 60.34 Lens L12
4 44.359 11.95
5 173.625 2.50 1.83500 42.98 Lens L13
6 56.328 14.72
7 -88.502 2.50 1.83500 42.98 Lens L14
8 158.109 d2 (variable)
9 -288.432 5.54 1.80518 25.46 Lens L21
10 -107.189 d3 (variable)
11 751.116 2.50 1.84666 23.78 Lens L31
12 50.116 17.37 1.80610 33.27 Lens L32
13 -139.608 d4 (variable)
14 82.177 7.95 1.72342 37.99 Lens L41
15 -221.570 13.19
16 FLAT d5 (variable) Aperture S
17 -100.213 6.13 1.84666 23.78 Lens L51
18 -28.647 2.70 1.83400 37.34 Lens L52
19 79.609 d6 (variable)
20 -719.588 6.08 1.48749 70.44 Lens L61
21 -45.003 2.45
22 -34.917 2.50 1.84666 23.78 Lens L62
23 131.765 8.26 1.48749 70.44 Lens L63
24 -59.921 0.25
25 -601.595 7.71 1.49700 81.61 Lens L64
26 -63.807 0.25
27 1058.612 11.42 1.49700 81.61 Lens L65
28 -55.451 d7 (variable)
29 95.439 6.90 1.80518 25.46 Lens L71
30 606.798 25.00
31 INFINITY 62.20 1.51680 64.20 Prism 3
32 INFINITY

The distance (mm) between the lens groups is as follows.
Wide-angle end Middle Telephoto end d2 12.62 11.00 7.40
d3 10.59 7.84 10.00
d4 37.56 30.39 16.44
d5 15.62 20.24 27.98
d6 12.02 9.15 5.34
d7 0.50 10.29 21.75

The focal length of each lens group is as follows.
fw (total focal length at the wide-angle end): 35.708
ft (total focal length at the telephoto end): 49.609
Magnification: 1.39
Back focus: 94.07
Half angle of view: 30.04
f1 (combined focal length of the first lens group): −37.62
f23 (combined focal length of the second lens group G2 and the third lens group G3): 96.77
f2 (focal length of second lens group G2 (zoom component of lens group G23)): 207.28
f3 (focal length of the third lens group G3 (focus component of the lens group G23)): 164.80
f6 (synthetic focal length of the sixth lens group): 90.806
Δd2 (zooming amount of lens group G2): 5.22

Therefore, the conditions defined in the above formulas (A) to (E) are as follows.
Condition (A) (| f1 / fw |): 1.054
Condition (B) (f6 / fw): 2.543
Condition (C) (Δd2 / fw): 0.146
Condition (D) (Δd2 / f23): 0.054
Condition (E) (Δd2 / f3): 0.032

  Accordingly, the zoom lens system 6 of the present example satisfies the conditions (A) to (E), and the power of the first lens group and the power of the sixth lens group are set in appropriate ranges. As shown in FIGS. 9 to 12, good aberration correction performance is obtained in the range from the wide-angle end to the telephoto end. Also, the focus adjustment ability is high. For this reason, the zoom lens system 6 of the present example is a wide-angle lens having a half angle of view of 30 ° or more, and has a high magnification of 1.39 and a sufficiently long back focus of 94.07. High optical performance can be obtained from the wide-angle end to the telephoto end.

  The zoom lens system 6 of this example moves the second lens group G2 and the third lens group G3 independently when zooming, and moves only the third lens group G3 during focus adjustment. This is a seven-group zoom lens system employing an inner focus system. Accordingly, it is possible to adjust the focus without moving the second lens group G2 that has a large influence on the zooming even though it is an inner focus system, and the zooming has little influence on the aberration correction performance. A sufficient focus adjustment performance can be secured. Therefore, the lens system can achieve both the accuracy of zooming and the accuracy of focus adjustment. Further, by setting the parameters so as to satisfy the above conditions (A) to (E), as shown in FIGS. 9 to 12, each aberration is well corrected at each zooming. A lens can be provided. Therefore, by employing this zoom lens system, it is possible to provide the projector 1 that can project a bright image with high resolution.

  In each of the above examples, the description is based on a projector using an LCD as an image generation device, but the present invention is also applied to a DLP projector using a DMD as an image generation device (light valve). be able to. Furthermore, the present invention can also be applied to a rear projector device in which a screen is integrated. In addition to projector-type optical equipment that projects images and has a light valve as an image processing device, it is also possible to use an imaging system such as a still camera or a television camera that has an image processing device that acquires an image such as an image sensor. The present invention can also be applied to an optical apparatus.

It is a figure which shows schematic structure of the projector apparatus which concerns on this invention. It is a flowchart which shows the control method of a zoom lens system. It is a figure which shows the structure of the zoom lens system shown in FIG. 1, and is a figure which shows arrangement | positioning of the lens in each state of a wide angle end (a) and a telephoto end (b). FIG. 4 is a longitudinal aberration diagram of the zoom lens system shown in FIG. 3 and shows aberrations at the wide-angle end. FIG. 4 is a longitudinal aberration diagram of the zoom lens system shown in FIG. 3 and shows aberrations at the telephoto end. FIG. 4 is a lateral aberration diagram of the zoom lens system shown in FIG. 3 and shows aberrations at the wide-angle end. FIG. 4 is a lateral aberration diagram of the zoom lens system shown in FIG. 3 and shows aberrations at the telephoto end. It is a figure which shows the structure of the different example of the zoom lens system of this invention, and is a figure which shows arrangement | positioning of the lens in each state of a wide angle end (a) and a telephoto end (b). FIG. 9 is a longitudinal aberration diagram of the zoom lens system shown in FIG. 8 and shows aberrations at the wide-angle end. FIG. 9 is a longitudinal aberration diagram of the zoom lens system shown in FIG. 8 and shows aberrations at the telephoto end. FIG. 9 is a lateral aberration diagram of the zoom lens system shown in FIG. 8 and shows aberrations at the wide-angle end. FIG. 9 is a lateral aberration diagram of the zoom lens system shown in FIG. 8 and shows aberrations at the telephoto end.

Explanation of symbols

1 Projector 2 LCD
5, 6 Zoom lens system 9 Screen 10 Control mechanism

Claims (15)

  A plurality of lens groups, and some of the plurality of lens groups move synchronously as a single group when zooming, and when the focus is adjusted, A zoom lens system in which a lens group is independent or only a part of the plurality of lens groups is moved.   2. The zoom lens system according to claim 1, wherein the some of the plurality of lens groups are lens groups inside the zoom lens system.   The zoom lens system according to claim 2, wherein lens groups at both ends of the plurality of lens groups are fixed.   4. The zoom lens system according to claim 1, wherein the zoom lens system is a projection zoom lens that projects projection light from the image generation device onto a screen. 5. The first lens group having a negative refractive power, the second lens group having a positive refractive power, the third lens group having a positive refractive power, and a positive refractive power in order from the screen side. A fourth lens group, a fifth lens group having a negative refractive power, a sixth lens group having a positive refractive power, and a seventh lens group having a positive refractive power,
The second lens group and the third lens group constitute the part of the plurality of lens groups;
A zoom lens system in which only the third lens group moves during the focus adjustment. In order from the screen 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 having a positive refractive power And a fifth lens group having a negative refractive power, a sixth lens group having a positive refractive power, and a seventh lens group having a positive refractive power. A projection zoom lens system for projecting onto a screen,
A zoom lens system in which the lens groups at both ends are fixed and the other lens groups are moved when zooming, and only the third lens group is moved during focus adjustment. 7. The zoom lens system according to claim 5, wherein the combined focal length f1 of the first lens group and the total focal length fw at the wide-angle end of the zoom lens system satisfy the following condition.
0.5 <| f1 / fw | <1.5 The zoom lens system according to claim 5 or 6, wherein the combined focal length f6 of the sixth lens group and the total focal length fw at the wide-angle end of the zoom lens system satisfy the following condition.
2.0 <f6 / fw <3.5 7. The zoom lens system according to claim 5, wherein an amount of magnification change Δd <b> 2 of the second lens group and an overall focal length fw at the wide-angle end of the zoom lens system satisfy the following condition.
0.1 <Δd2 / fw <0.25 The zoom lens according to claim 5 or 6, wherein the zoom lens moving amount Δd2 and the combined focal length f23 of the second lens group and the third lens group satisfy the following condition: system.
Δd2 / f23 <0.07 7. The zoom lens system according to claim 5, wherein the zooming movement amount Δd <b> 2 of the second lens unit and the combined focal length f <b> 3 of the focus adjustment of the third lens unit satisfy the following condition.
Δd2 / f3 <0.035   A projector apparatus comprising the zoom lens system according to claim 4 and the image generation apparatus.   4. An optical apparatus comprising: the zoom lens system according to claim 1; and an image processing apparatus that inputs or outputs an image via the zoom lens system. A method of controlling a zoom lens system having a plurality of lens groups,
A plurality of lens groups that are part of the plurality of lens groups are moved synchronously as one group in order to change magnification,
And a step of moving the some lens groups independently or only some lens groups of the some lens groups to adjust the focus. A control mechanism of a zoom lens system having a plurality of lens groups,
Means for moving a plurality of lens groups of a part of the plurality of lens groups synchronously as one group in order to change magnification;
A control mechanism having means for moving the partial lens groups independently or only a partial lens group of the partial lens groups for focus adjustment.

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