Patent ID: 12222480

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described.

FIGS.1to7illustrate seven examples of embodiments of the projection zoom lens of the present invention. In these figures, the left side of the figure is the “enlarged-side” and the right side is the “reduced-side”. The upper figure illustrated in the figure illustrates the lens arrangement at the wide-angle end and the lower figure illustrated in the figure illustrates the lens arrangement at the telephoto end.

Same reference numerals are used for items that are not likely to be confused inFIGS.1to7. That is, the reference numeral “group i” is represented by the reference numeral iG (i=1 to 5), and “aperture diaphragm” is represented by the reference numeral S. The reference numeral PR is used to designate a “color synthesis prism”. The reference numerals1a,1b, and1crepresent “first sub-lens group”, “second sub-lens group”, and “third sub-lens group”, respectively.

That is, the projection zoom lens according to the embodiment inFIGS.1to7is configured by arranging a first group1G, a second group2G, a third group3G, an aperture diaphragm S, a fourth group4G, and a fifth group5G in aforementioned order from the enlarged-side to the reduced-side. The first group G1includes a first sub-lens group1a, a second sub-lens group1b, a third sub-lens group1c, and these sub-lens groups are arranged in the aforementioned order from the enlarged-side to the reduced-side. The first group1G has a “negative refractive force”, and the second group2G to the fifth group5G all have “positive refractive force”. That is, the projection zoom lens is a “negative-lead type” as in the embodiment illustrated inFIGS.1to7. The first sub-lens group1ahas a “positive or negative refractive force”, and both the second sub-lens group1band the third sub-lens group1chave a “negative refractive force”. Hereinafter, a “positive refractive force” is expressed as “positive” or a “negative refractive force” is expressed as “negative”. Namely, for example, “a first group G1of a negative refractive force” is simply referred to as a “negative first group G1”, and “a first sub-lens group1aof a negative or positive refractive force” is simply referred to as a “negative or positive first sub-lens group1a”. The projection zoom lens is “telecentric on the reduced-side”. The first group1G which is configured by the first sub-lens group1a, the second sub-lens group1b, and the third sub-lens group1cforms a “focusing group”. The focusing group changes the spacing of a group adjacent to the first sub-lens group1ato the third sub-lens group1cwhen changing focus from an infinite distance to a near distance. The second group2G to the fifth group5G form a “zooming group”. At least the second group2G to the fourth group4G independently move to the enlarged-side when magnifying from the wide-angle end to a telephoto end, thereby performing a zooming.

Thus, the projection zoom lens of the present invention is a “negative lead-type” such that the “negative first group1G” is arranged on the enlarged-side and the “positive second group2G to the fifth group5G” are arranged on the reduced-side, and the reduced-side is a telecentric. This configuration can be used to easily achieve performance suitable for a projection zoom lens, such as a wide-angle of view, long back focus, and the like.

The “focusing group” includes three sub-lens groups1ato1c. By focusing by “changing the spacing of adjacent groups” of these three sub-lens groups, favorable focusing performance can be achieved in the short range, medium range, and long range. Further, the “zooming group” includes positive “second group2G to fifth group5G”. At least the second group2G to the fourth group4G independently move to the enlarged-side to perform “magnification from the wide-angle end to the telephoto end”, thereby achieving favorable optical performance over the entire zoom range. The fifth group5G can be moved during zooming or can remain at a fixed position as a fixed group.

InFIGS.1to7, the arrows drawn between the upper and lower figures indicate the movement of the first group G1to the fifth group G5during zooming from the wide-angle end to the telephoto end. In the embodiments illustrated inFIGS.1to7, the first group G1and the fifth group5G do not move during zooming. That is, the first group G1and the fifth group5G are “fixed groups”. The second group G2, the third group G3, and the fourth group G4move to the enlarged-side when zooming from the wide-angle end to the telephoto end, thereby changing the “interaction of the space between groups” in these groups G2to G4. In the examples illustrated inFIGS.1to7, when zooming from the wide-angle end to the telephoto end, the space between the second group G2and the third group G3is reduced, and the space between the third group G3and the fourth group G4is enlarged. When zooming from the wide-angle end to the telephoto end, the space between the first group G1and the second group G2is reduced and the space between the fourth group G4and the fifth group G5is enlarged, because the second group G2to the fourth group G4move to the “enlarged-side”. The fifth group5G, which is arranged on the most reduced-side, can sufficiently suppress the variation in telecentricity (main light angle) when magnifying by “fixing upon zooming”.

As described above, focusing is performed by changing the “spacing of adjacent groups” of the first sub-lens group1aor the third sub-lens group1cthat constitutes the focusing group. In this case, the focusing from infinity (long range) to near distance (short range) can be performed by setting the first sub-lens group1ato be negative, fixing the second sub-lens group1b, and moving the first sub-lens group1aand the third sub-lens group1cto the enlarged-side. When focusing is performed as described above, a focal length of the first sub-lens group1ais f1a(<0), a focal length of the third sub-lens group1cis f1c(<0), and a focal length of the entire system at the wide-angle end is fw, preferably satisfying the following conditional formulae:
−30<f1a/fw<−5  (1)
−30<f1c/fw<−4  (2)
If the negative second sub-lens group1bis fixed and the first sub-lens group1aand the third sub-lens group1care moved, a “different role” can be provided to the first sub-lens group1aand the third sub-lens group1c. Therefore, the functionality and convenience by using these first and third sub-lens groups as independent adjustment mechanisms can be improved.

Moving the first sub-lens group1ais effective for “field curvature correction on mainly around the peripheral portion”, and moving the third sub-lens group1cis effective for “defocusing adjustment from a center to the peripheral portion”. When the upper limit of the conditional formula (1) is exceeded, the negative force of the first sub-lens group1abecomes excessive, and the focus sensitivity of the center portion becomes high. Therefore, the focus of the center portion is easily changed when the field curvature correction of the peripheral portion is performed. When the lower limit of the conditional formula (1) is exceeded, the negative force of the first sub-lens group1abecomes too small, thereby being disadvantageous to the correction of aberrations at low or medium resolutions.

When the upper limit of the conditional formula (2) is exceeded, the negative force of the third sub-lens group1cbecomes excessive, and the aberration change tends to become large in accordance with focusing. When the lower limit of the conditional formula (2) is exceeded, the negative force of the third sub-lens group1cbecomes underpowered, resulting in “the amount of movement of the third sub-lens group1cat the time of focusing becomes large”, so that the overall length of the projection zoom lens is likely to be excessive.

The fifth group5G may include “a plurality of lenses containing one or more positive lenses”. The fifth group5G may be preferably configured by having a most reduced lens to be a positive lens. When a focal length of the positive lens is f5, the Abbe number of the lens material is νd5, and a focal length of the entire system at the wide-angle end is fw, preferably satisfying the following conditional formulae:
0.1<fw/f5<0.3  (3)
νd5<26  (4)
By satisfying the conditional formulae (3) and (4), both the corrections of frame aberration and chromatic aberration can be achieved.

When the upper limit of the conditional formula (3) is exceeded, the refractive force of the entire systems is relatively weakened with respect to the refractive force of the “positive lens at the most reduced-side”. Therefore, the achievement of the telecentricity on the reduction side tends to be difficult, and the total length of the lens is likely to be excessive. When the lower limit of the conditional formula (3) is exceeded, the refractive force of the entire system is relatively excessive with respect to the refractive force of the “positive lens at the most reduced-side” and thus various aberrations including frame aberrations tend to be over corrected. When the upper limit of conditional formula (4) is exceeded, favorable correction of chromatic aberration is likely to be difficult.

The second group2G included in the zooming group has a “positive refractive force” but can include “one or more negative lenses” in addition to the positive lens. Thus, when the second group2G includes “a positive lens and one or more negative lenses”, it is preferable for the following condition formulae to be satisfied:
5<νd2p−νd2n<15  (5)
νd2n<25  (6)
In the conditional formulae (5) and (6), “νd2p” is the “Abbe number relative to d-line of positive lens material of the lens on the most reduced-side” among the positive and negative lenses included in the second group2G. In addition, “νd2n” is the “Abbe number relative to d-line of negative lens material of the lens on the most reduced-side”.

Conditional formula (5) regulates the “difference between Abbe numbers relative to the d-line between the negative lens on the most reduced-side and the positive lens on the most reduced-side” in the second group2G. Accordingly, the negative lens is assumed to be “higher dispersion”. Therefore, when adjusting “the difference of the Abbe numbers between the negative lens and the positive lens” is in an appropriate range, a favorable chromatic aberration correction effect can be obtained. If the lower limit of the conditional formula (5) is exceeded, the difference of the Abbe numbers between the “two lenses of positive and negative” becomes small, and there will be insufficient correction of chromatic aberration. If the upper limit of conditional formula (5) is exceeded, the difference of Abbe number is excessive, and excessive correction of aberration is likely to occur.

Among the focusing group (the first group1G) configured by the first sub-lens group1ato the third sub-lens group1c, the lens at the most enlarged-side (the lens arranged closest to the enlarged-side in the first sub-lens group1a) has two aspherical surfaces, and the following condition formula is preferably satisfied:
−0.5<(L11R1−L11R2)/(L11R1+L11R2)<−0.1  (7)
“L11R1” in the conditional formula (7) is the radius of curvature of the paraxial axis of the enlarged-side in the two-aspherical surface lens of the first sub-lens group1a, and “L11R2” is the paraxial radius of curvature of the reduced-side. Satisfying the conditional formula (7) allows favorable correction of a distortion aberration and a frame aberration. When the upper limit of the conditional formula (7) is exceeded, the correction effect of the distortion aberration becomes smaller, and when the lower limit is exceeded, the correction effect of the frame aberration becomes smaller. Among the focusing group configured by the first sub-lens group1aor the third sub-lens group1c, the lens arranged at the most enlarged-side is preferably “both sides are aspheric surfaces, concave on the enlarged-side in the paraxial region and convex on the enlarged-side in the peripheral region”. In order to correct the frame aberration and the field curvature, the shape of the peripheral portion of the lens arranged on the most enlarged-side is of convex shape on the enlarged-side, and the peripheral light is bent toward the optical axis. In contrast, when the shape at the enlarged-side in the central portion is formed to be concave, it is possible to prevent the surface angle of the peripheral portion from being too large while maintaining the power of the peripheral portion, thereby improving the moldability of the lens surface. In addition, both sides of the lens may be “concave to the enlarged-side” in the extreme peripheral area.

When the focal length of the focusing group (the first group1G) is fg1, the focal length of the second group2G in the zooming group is fg2, and the focal length of the entire system at the wide-angle end is fw, the following conditional formulae is preferably satisfied:
−2.5<fg1/fw<−1.5  (8)
5<fg2/fw<12  (9)
The focal length “fg1” is the “focal length when focusing at infinity”. By satisfying these conditional formulae (8) and (9), miniaturization of the lens can be achieved while maintaining the back focus of the projection zoom lens for a long time. When the parameter of the conditional formula (8) is large (or small), the negative refractive force of the first group1G increases (or decreases). When the upper limit of the conditional formula (8) is exceeded, excessive correction of aberration is likely to occur. In addition, when the lower limit is exceeded, securing long back focus is likely to be difficult. When the parameters of the conditional formula (9) are large (or small), the refractive force of the zooming group (2G to5G) decreases (or increases). When the upper limit of the conditional formula (9) is exceeded, the amount of movement of the zooming group at the time of magnification increases as the positive refractive force decreases, so that the total length of the lens tends to be long. When the lower limit of the conditional formula (9) is exceeded, the positive refractive force becomes excessive, and excessive correction of aberration is likely to occur.

The third sub-lens group1ccan have “a plurality of lenses including a negative lens”. When the Abbe number of the negative lens material on the most reduced-side is “νd1c”, the following conditional formula is preferably satisfied:
νd1c>70  (10)
“Low dispersion glass satisfying conditional formula (10)” is used as the “most reduced negative lens” to be moved during focusing, thereby allowing favorable chromatic aberration correction over the entire focusing range.

The embodiments illustrated inFIGS.1to6indicate the preferred configuration of the first sub-lens group1a, the second sub-lens group1b, and the third sub-lens group1cthat constitute the focusing group. That is, as in the embodiments illustrated inFIGS.1to6, the first sub-lens group1aand the second sub-lens group1bare both configured by “one negative lens,” and the third sub-lens group1ccan be “a configuration including three lenses arranged with a negative lens, a negative lens, and a positive lens from the enlarged-side”.

Alternatively, as in the embodiment illustrated inFIG.7, the first sub-lens group1ain the first group1G may be configured by one negative lens, the second sub-lens group1bmay be configured by two negative lenses, and the third sub-lens group1cmay be configured by one negative lens and one positive lens in this order from the enlarged-side.

In Example 1 and Example 7, which will be described later, the first sub-lens group1aof both Examples 1 and 7 have the same lens. In Example 1 and Example 7, the lens configurations of the second sub-lens group1band the third sub-lens group1care different, and each lens in the second group G2to the fifth group5G is different. As described above, two or more types of projection zoom lenses having different focal lengths can be achieved by sharing the first sub-lens group1aand changing the “configuration of the second sub-lens group and the other sub-lens groups”. In other words, when developing two or more types of projection zoom lenses, by sharing the first sub-lens group1a, the initial investment cost of the development can be reduced. As described above, the fifth group5G can be configured by a plurality of lenses including one or more lenses having positive refractive force, but the fifth group5G may also be configured using “only one positive lens”.

By using the projection zoom lens as described above, a novel projection device can be configured that can change the size of the projecting image without being hindered by the distance from the projected surface.

EXAMPLES

Hereinafter, specific examples of a projection zoom lens are given below. Examples 1 to 7 described below are, in this order, examples of the embodiments illustrated inFIGS.1to7.

Example 1

Example 1 is an example illustrated inFIG.1, and its configuration is as described above. The data of Example 1 is illustrated inFIG.8. InFIG.8, the “surface number” in the left column represents the number of the plane containing the aperture from the projected surface on the enlarged-side to the image display surface on the reduced-side. The surface (plane) number “0” is a “projected surface”, and the surface (plane) number “IMG” is an “image display surface”. The surface (plane) numbers “40 and 41” are “prismatic surfaces of color synthesis prism PR”.

The “virtual plane” is set to make it easier to see the “change of space between planes due to zooming” and the “change of space between planes due to focusing” of the projection zoom lens. That is, surface number “1” and surface number “14” in the surface numbers inFIG.8are virtual planes. In this way, the space between the surface number including the virtual plane “0” to the surface number “IMG” is set to “d (d0to dIMG)” as illustrated in the figure. Throughout all embodiments, the “unit of quantity having a dimension of length” is “mm” unless otherwise indicated.

InFIG.8, the “R” column indicates the radius of curvature of each surface number including “virtual plane and aperture plane” (or “paraxial curvature radius” for aspheric surfaces). The “Nd and νd” is the “refractive index and Abbe number with respect to d line” of the material of the lens.

In the surface number, “surface (plane) marked with an asterisk” is an aspherical surface. In the following Examples, aspheric surfaces are represented by the following well known formulae:
Z=(h2/R)/[1+√(1−(1+k)(h/R)2]+ΣAi·hi(i=1 to 20)
In this formula, “Z” is the aspheric mass, “R” is the paraxial curvature radius, “h” is the distance from the optical axis at the aspheric surface, “K” is the conical constant, and “Ai (i=1 to 20)” is the first-to-twentieth order aspheric coefficient.
[Data of Aspheric Surface]

FIG.9indicates data of the aspheric surfaces of the projection zoom lens in Example 1. For example, “2.320884E-02” means “2.320884E-02×10−2” in the aspherical data indicated inFIG.9. The same applies to the following other Examples.

InFIG.10, “optical data” at the wide-angle end (Wide), the middle focal length (Middle), and the telephoto end (Tele) of the projection zoom lens in Example 1 are illustrated. The “optical data” includes a focal length “f”, a field angle “ω (degrees)”, a maximum object height “Ymax”, a F number “Fno”, a total length “TL”, and an air-converted back focus “BF (in air)”.

FIG.11indicates the focal length of each group in Example 1. In this figure, “f” is the focal length of each group, and the first group1G to the fifth group5G are indicated as G1to G5. In addition, G1a, G1b, and G1crefers to the first sub-lens group1a, the second sub-lens group1b, and the third sub-lens group1c, respectively. “First surface” is the surface number on the most enlarged-side among these groups.

FIG.12Aindicates the wide-angle end (Wide), the middle focal length (Middle), and the telephoto end (Tele) due to the change of plane spacing in accordance of zooming. Zooming is achieved by moving the second group G2to the fourth group G4, so that the plane spacings such as 15, 20, 23, and 39 change.FIG.12Bindicates the short range, medium range, and long range due to the change of plane spacing according to focusing. The “short range” is a lens arrangement of the focusing group when focusing to the short range in the group arrangement at the wide-angle end. The “long range” is a lens arrangement of the focusing group when focusing infinitely in the group arrangement at the telephoto end. The “medium range” is the lens arrangement of the focusing group at the middle focal length. This arrangement is a “reference arrangement” and each sub-lens group in the focusing group is not displaced by the aforementioned “virtual plane (surface numbers “1” and “14” in Example 1)”.

In focusing, the spacing of the first sub-lens group1a, the second sub-lens group1b, and the third sub-lens group1cin the first group1G changes. Therefore, the plane spacings “d0, d1, d4, d7, and d14” change. The “medium range” in focusing is the “reference state of focusing” in which the focusing is not performed. In this state, the plane spacings “d1, d4, d7, and d14” are all 0. In this case, the value of the plane spacing “d0” is the same as “d0” inFIG.12A.

In the “short range”, the projection zoom lens is a group arrangement of the wide-angle end, d0becomes 59 mm, and the first sub-lens group1amoves to the enlarged-side so that the d1becomes −0.0317 mm. This value equals the increment of plane spacing d4as +0.0317 mm. Similarly, the third sub-lens group1cmoves to the enlarged-side so that the plane spacing d7becomes −0.0709 mm. This value equals an increment of the plane spacing d14as +0.0709 mm.

In the “long range”, the projection zoom lens is arranged in a group of the telephoto end. The plane spacing d0between the projected surface (surface number: 0) and the virtual surface (surface number: 1) expands to d0=595 mm, and the first sub-lens group1amoves to the reduced-side to d1=0.0183 mm. This value equals to the reduced amount of plane spacing d4: −0.0183. Similarly, the third sub-lens group1cmoves to the reduced-side, and the plane spacing: d7becomes d7=+0.0339 mm. This value equals to the plane spacing corresponding to the virtual surface of surface number 14, such as, the reduced amount of d14=−0.00339 mm.

FIG.13Aindicates the “wide-angle end and telephoto end” of the “spacing between adjacent groups” of the first group1G, the second group2G, the third group3G, the fourth group4G, and the fifth group5G associated with zooming. Furthermore,FIG.13Bindicates the “wide-angle end and telephoto end” of the changes in the plane spacing of the first sub-lens group1a, the second sub-lens group1b, and the third sub-lens group1c, and also indicates the “wide-angle end and telephoto end” of the changes in the plane spacing between the third sub-lens group1cand the second group2G.

FIG.14indicates the values of each parameter of the conditional formulae (1) to (10) for the projection zoom lens of Example 1. The projection zoom lens of Example 1 satisfies the conditional formulae (1) to (10).FIG.15indicates an aberration figure of the projection zoom lens of Example 1.FIG.15Ais an aberration figure at the wide-angle end andFIG.15Bis an aberration figure at the telephoto end. The solid lines in the astigmatism figure represent Sagittal rays and the dashed lines represent meridional rays. As illustrated in each aberration figure, Example 1 exhibits excellent performance.

Example 2

Example 2 is an example illustrated inFIG.2, and the configuration is as described above. The data of Example 2 is illustrated inFIG.16in a similar manner as inFIG.8illustrating the data of Example 1. InFIG.16, the surface number “0” is a “projected plane” and the surface number “IMG” is an “image display plane”. InFIG.16, virtual planes (surface numbers “1” and “14”) are also set to facilitate viewing of “a change in plane spacing caused by zooming” and “a change in plane spacing caused by focusing” of the projection zoom lens.

The plane spacing between the surface number including the virtual plane “0” and the surface number “IMG” is set as the plane spacing “d (d0to dIMG)” as illustrated in the figures. The surface numbers 40 and 41 are “prismatic surfaces of color synthesis prism PR”.
[Data of Aspheric Surface]

FIG.17indicates data of the aspheric surfaces of the projection zoom lens of Example 2.

InFIG.18, “optical data” at the wide-angle end (Wide), the middle focal length (Middle), and the telephoto end (Tele) of the projection zoom lens in Example 2 are illustrated in a similar manner as inFIG.10. InFIG.19, the focal length of each group in Example 2 is illustrated in a similar manner as inFIG.11.

FIG.20Aindicates the wide-angle end (Wide), the middle focal length (Middle), and the telephoto end (Tele) due to the change of plane spacing according to zooming.FIG.20Bindicates the short range, medium range, and long range due to the change of plane spacing according to focusing.FIG.21Aindicates the “wide-angle end and telephoto end” of the spacing between adjacent groups of the first group1G, the second group2G, the third group3G, the fourth group4G, and the fifth group5G according to zooming.FIG.21Bindicates the “short range and long range” of the changes in spacing, according to focusing, of the first sub-lens group1a, the second sub-lens group1b, and the third sub-lens group1c; and of the changes in plane spacing, according to focusing, of the third sub-lens group1cand the second group2G.

FIG.22indicates the values of each parameter of the conditional formulae (1) to (10) for the projection zoom lens of Example 2. The projection zoom lens of Example 2 satisfies the conditional formulae (1) to (10).FIG.23indicates an aberration figure of the projection zoom lens of Example 2, in a similar manner as illustrated inFIG.15.

As illustrated in each aberration figure, Example 2 exhibits excellent performance.

Example 3

Example 3 is an example illustrated inFIG.3, and the configuration is as described above. The data of Example 3 is indicated inFIG.24in a similar manner as illustrated inFIG.8. InFIG.24, the surface number “0” is a “projected plane” and the surface number “IMG” is an “image display plane”. In the same manner as Examples 1 and 2, Example 3 includes virtual planes (surface numbers “1” and “15”). The plane spacing between the surface number including the virtual plane “0” and the surface number “IMG” is set as the plane spacing “d (d0to dIMG)” as illustrated in the figures. The surface numbers “42 and 43” are “prismatic surfaces of color synthesis prism PR”. Furthermore, the plane numbers “44 and 45” are cover glass planes provided on the image display of the image display device.

[Data of Aspheric Surface]

FIG.25indicates data of the aspheric surfaces of the projection zoom lens of Example 3.

InFIG.26, “optical data” at the wide-angle end (Wide), the middle focal length (Middle), and the telephoto end (Tele) of the projection zoom lens in Example 3 are illustrated in a similar manner as inFIG.10. InFIG.27, the focal length of each group in Example 3 is illustrated in a similar manner as inFIG.11.

FIG.28Aindicates the wide-angle end (Wide), the middle focal length (Middle), and the telephoto end (Tele) due to the change of plane spacing in accordance of zooming. Zooming is achieved by moving the second group G2to the fourth group G4, so that the plane spacings such as 15, 20, 23, and 39 change. The change in plane “d0” between a target surface (surface number “0”) and a virtual surface “1” is constant.FIG.28Bindicates the short range, medium range, and long range due to the change of plane spacing according to focusing. Focusing is achieved by moving the spacing of planes in the first sub-lens group1a, the second sub-lens group1b, and the third sub-lens group1cin the first group1G. Therefore, the plane spacings such as d0, d1, d4, and d14change.FIG.29Aindicates the “wide-angle end and telephoto end” of the spacing between adjacent groups of the first group1G, the second group2G, the third group3G, the fourth group4G, and the fifth group5G according to zooming.FIG.29Bindicates the “short range and long range” of the changes in spacing, according to focusing, of the first sub-lens group1a, the second sub-lens group1b, and the third sub-lens group1c; and of the changes in plane spacing, according to focusing, of the third sub-lens group1cand the second group2G.

FIG.30indicates the values of each parameter of the conditional formulae (1) to (10) for the projection zoom lens of Example 3. The projection zoom lens of Example 3 satisfies the conditional formulae (1) to (10).FIG.31indicates the aberration figure of the projection zoom lens of Example 3 as illustrated in a similar manner as inFIG.15.

As illustrated in each aberration figure, Example 3 exhibits excellent performance.

Example 4

Example 4 is an example illustrated inFIG.4, and the configuration is as described above. The data of Example 4 is indicated inFIG.32in a similar manner as illustrated inFIG.8. InFIG.32, the surface number “0” is a “projected plane” and the surface number “IMG” is an “image display plane”. In the same manner as Examples 1 to 3, Example 4 includes virtual planes (surface numbers “1” and “14”). The plane spacing between the surface number including the virtual plane “0” and the surface number “IMG” is set as the plane spacing “d (d0to dIMG)” as illustrated in the figures. The surface numbers “35 and 36” are “prismatic surfaces of color synthesis prism PR”. Furthermore, the plane numbers “37 and 38” are cover glass planes provided on the image display of the image display device.

[Data of Aspheric Surface]

FIG.33indicates data of the aspheric surfaces of the projection zoom lens of Example 4.

InFIG.34, “optical data” at the wide-angle end (Wide), the middle focal length (Middle), and the telephoto end (Tele) of the projection zoom lens in Example 4 are illustrated in a similar manner as inFIG.10. InFIG.35, the focal length of each group in Example 4 is illustrated in a similar manner as inFIG.11.

FIG.36Aindicates the wide-angle end (Wide), the middle focal length (Middle), and the telephoto end (Tele) due to the change of plane spacing according to zooming. Zooming is achieved by moving the second group G2to the fourth group G4, so that the plane spacings such as 15, 18, 21, and 32 change. The change in plane spacing “d0” between a target surface (surface number “0”) and a virtual surface “1” is constant (153 mm).FIG.36Bindicates the short range, medium range, and long range due to the change of plane spacing according to focusing. Focusing is achieved by moving the spacing of planes in the first sub-lens group1a, the second sub-lens group1b, and the third sub-lens group1cin the first group1G. Therefore, the plane spacings such as d0, d1, d4, d7, and d14change.FIG.37Aindicates “wide-angle end and telephoto end” of the spacing between adjacent groups of the first group1G, the second group2G, the third group3G, the fourth group4G, and the fifth group5G according to zooming, in a similar manner as inFIG.13.

FIG.37Bindicates the “short range and long range” of the changes in spacing, associated with focusing, of the first sub-lens group1a, the second sub-lens group1b, and the third sub-lens group1c; and of the changes in plane spacing, associated with focusing, of the third sub-lens group1cand the second group2G.

FIG.38indicates the values of each parameter of the conditional formulae (1) to (10) for the projection zoom lens of Example 4. The projection zoom lens of Example 4 satisfies the conditional formulae (1) to (10).FIG.39depicts the aberration figure of the projection zoom lens of Example 4 in a similar manner as inFIG.15.

As illustrated in each aberration figure, Example 4 exhibits excellent performance.

Example 5

Example 5 is an example illustrated inFIG.5, and the configuration is as described above. The data of Example 5 is indicated inFIG.40in a similar manner as illustrated inFIG.8. InFIG.40, the surface number “0” is a “projected plane” and the surface number “IMG” is an “image display plane”. In the same manner as Examples 1 to 4, Example 5 includes virtual planes (surface numbers “1” and “14”). The plane spacing between the surface number including the virtual plane “0” and the surface number “IMG” is set as the plane spacing “d (d0to dIMG)” as illustrated in the figures. The surface numbers “42 and 43” are “prismatic surfaces of color synthesis prism PR”. Furthermore, the plane numbers “44 and 45” are cover glass planes provided on the image display of the image display device.

[Data of Aspheric Surface]

FIG.41indicates data of the aspheric surfaces of the projection zoom lens of Example 5.

InFIG.42, “optical data” at the wide-angle end (Wide), the middle focal length (Middle), and the telephoto end (Tele) of the projection zoom lens in Example 5 are illustrated in a similar manner as inFIG.10. InFIG.43, the focal length of each group in Example 5 is illustrated in a similar manner as inFIG.11.

FIG.44Aindicates the wide-angle end (Wide), the middle focal length (Middle), and the telephoto end (Tele) due to the change of plane spacing according to zooming. Zooming is achieved by moving the second group G2to the fourth group G4, so that the plane spacings such as 15, 20, 23, and 39 change. The change in plane spacing “d0” between a target surface (surface number “0”) and a virtual surface “1” is constant (148 mm).FIG.44Bindicates the short range, medium range, and long range due to the change of plane spacing according to focusing. Focusing is achieved by moving the spacing of planes in the first sub-lens group1a, the second sub-lens group1b, and the third sub-lens group1cin the first group1G. Therefore, the plane spacings such as d0, d1, d4, d7, and d14change.FIG.45Aindicates “wide-angle end and telephoto end” of the spacing between adjacent groups of the first group1G, the second group2G, the third group3G, the fourth group4G, and the fifth group5G according to zooming, in a similar manner as inFIG.13.

FIG.45Bindicates the “short range and long range” of the changes in spacing, associated with focusing, of the first sub-lens group1a, the second sub-lens group1b, and the third sub-lens group1c; and of the changes in plane spacing, associated with focusing, of the third sub-lens group1cand the second group2G.

FIG.46indicates the values of each parameter of the conditional formulae (1) to (10) for the projection zoom lens of Example 5. The projection zoom lens of Example 5 satisfies the conditional formulae (1) to (10).FIG.47indicates the aberration figure of the projection zoom lens of Example 5 in a similar manner as inFIG.15.

As shown in each aberration figure, Example 5 exhibits excellent performance.

Example 6

Example 6 is an example illustrated inFIG.6, and the configuration is as described above. The data of Example 6 is indicated inFIG.48in a similar manner as illustrated inFIG.8. InFIG.48, the surface number “0” is a “projected plane” and the surface number “IMG” is an “image display plane”. In the same manner as Examples 1 to 5, Example 6 includes virtual planes (surface numbers “1” and “14”). The plane spacing between the surface number including the virtual plane “0” and the surface number “IMG” is set as the plane spacing “d (d0to dIMG)” as illustrated in the figures. The surface numbers “42 and 43” are “prismatic surfaces of color synthesis prism PR”. Furthermore, the plane numbers “44 and 45” are cover glass planes provided on the image display of the image display device.

[Data of Aspheric Surface]

FIG.49indicates data of the aspheric surfaces of the projection zoom lens of Example 6.

InFIG.50, “optical data” at the wide-angle end (Wide), the middle focal length (Middle), and the telephoto end (Tele) of the projection zoom lens in Example 6 are illustrated in a similar manner as inFIG.10. InFIG.51, the focal length of each group in Example 6 is illustrated in a similar manner as inFIG.11.

FIG.52Aindicates the wide-angle end (Wide), the middle focal length (Middle), and the telephoto end (Tele) due to the change of plane spacing according to zooming. Zooming is achieved by moving the second group G2to the fourth group G4, so that the plane spacings such as 15, 20, 23, and 39 change. The change in plane spacing “d0” between a target surface (surface number “0”) and a virtual surface “1” is constant (148 mm).FIG.52Bindicates the short range, medium range, and long range due to the change of plane spacing according to focusing. Focusing is achieved by moving the spacing of planes in the first sub-lens group1a, the second sub-lens group1b, and the third sub-lens group1cin the first group1G. Therefore, the plane spacings such as d0, d1, d4, d7, and d14change.FIG.53Aindicates “wide-angle end and telephoto end” of the spacing between adjacent groups of the first group1G, the second group2G, the third group3G, the fourth group4G, and the fifth group5G according to zooming, in a similar manner as inFIG.13.

FIG.53Bindicates the “short range and long range” of the changes in spacing, associated with focusing, of the first sub-lens group1a, the second sub-lens group1b, and the third sub-lens group1c; and of the changes in plane spacing, associated with focusing, of the third sub-lens group1cand the second group2G.

FIG.54indicates the values of each parameter of the conditional formulae (1) to (10) for the projection zoom lens of Example 6. The projection zoom lens of Example 6 satisfies the conditional formulae (1) to (10).FIG.55indicates the aberration figure of the projection zoom lens of Example 6 in a similar manner as inFIG.15.

As shown in each aberration figure, Example 6 exhibits excellent performance.

Example 7

Example 7 is an example illustrated inFIG.7, and the configuration is as described above. The data of Example 7 is indicated inFIG.56in a similar manner as illustrated inFIG.8. InFIG.56, the surface number “0” is a “projected plane” and the surface number “IMG” is an “image display plane”. In the same manner as Examples 1 to 6, Example 7 includes virtual planes (surface numbers “1” and “14”). The plane spacing between the surface number including the virtual plane “0” and the surface number “IMG” is set as the plane spacing “d (d0to dIMG)” as illustrated in the figures. The surface numbers “42 and 43” are “prismatic surfaces of color synthesis prism PR”.

[Data of Aspheric Surface]

FIG.57indicates data of the aspheric surfaces of the projection zoom lens of Example 7.

InFIG.58, “optical data” at the wide-angle end (Wide), the middle focal length (Middle), and the telephoto end (Tele) of the projection zoom lens in Example 7 are illustrated in a similar manner as inFIG.10. InFIG.59, the focal length of each group in Example 7 is illustrated in a similar manner as inFIG.11.

FIG.60Aindicates the wide-angle end (Wide), the middle focal length (Middle), and the telephoto end (Tele) due to the change of plane spacing according to zooming. Zooming is achieved by moving the second group G2to the fourth group G4, so that the plane spacings such as 15, 20, 23, and 39 change. The change in plane spacing “d0” between a target surface (surface number “0”) and a virtual surface “1” is constant (148 mm).FIG.60Bindicates the short range, medium range, and long range due to the change of plane spacing according to focusing. Focusing is achieved by moving the spacing of planes in the first sub-lens group1a, the second sub-lens group1b, and the third sub-lens group1cin the first group1G. Therefore, the plane spacings such as d0, d1, d4, d7, and d14change.FIG.61Aindicates “wide-angle end and telephoto end” of the spacing between adjacent groups of the first group1G, the second group2G, the third group3G, the fourth group4G, and the fifth group5G according to zooming, in a similar manner as inFIG.13.

FIG.61Bindicates the “short range and long range” of the changes in spacing, associated with focusing, of the first sub-lens group1a, the second sub-lens group1b, and the third sub-lens group1c; and of the changes in plane spacing, associated with focusing, of the third sub-lens group1cand the second group2G.

FIG.62indicates the values of each parameter of the conditional formulae (1) to (10) for the projection zoom lens of Example 7. The projection zoom lens of Example 7 satisfies the conditional formulae (1) to (10).FIG.63indicates the aberration figure of the projection zoom lens of Example 7 in a similar manner as inFIG.15.

As illustrated in each aberration figure, Example 6 exhibits excellent performance.

Hereinafter, one embodiment of a projector using the projection zoom lens of the present invention will be described with reference toFIG.64.

FIG.64schematically illustrates one embodiment of a projector. Inside a casing1of the projector body, a projection zoom lens PZL, image generator device ISR, ISB, and ISG using the “image display devices” such as a liquid crystal panel, and a color synthesis prism PR are loaded.

The image generator device ISR displays a “red component image” of the color image to be projected on the image display surface of the image display device, generates “red component image light LR”, and emits it toward the color synthesis prism PR.

The image generator device ISG displays a “green component image” of the color image on the image display surface of the image display device, generates “green component image light LG”, and emits it toward the color synthesis prism PR.

The image generator ISB displays a “blue component image” of a color image on the image display surface of the image display device, generates “blue component image light LB”, and emits it toward the color synthesis prism PR.

The color synthesis prism PR synthesizes red component image light LR, green component image light LG, and blue component image light LB to be “color image light IML” to be transmitted into the projection zoom lens PZL.

The projection zoom lens PZL emits incoming color image light IML toward a screen as the projection image forming light PRL.

As the projection zoom lens PZL, the zoom lenses described above, such as Examples 1 to 7, can be used. Although preferred embodiments of the invention have been described above, the invention is not limited to the specific embodiments described above, and various modifications and alterations can be made within the scope of the claimed invention, unless otherwise specified in the above-described description. The effects described in the embodiments of the present invention are merely listed in the list of preferred effects arising from the invention, and the effects of the invention are not limited to those described in the embodiments.