JP4530259B2 - Zoom lens and projection display device using the same - Google Patents

Description

  The present invention relates to a zoom lens for image formation of a camera using an image pickup device such as a CCD or image pickup tube or a silver salt film, and further to a zoom lens for projection of a projection television, and more particularly to a projection display device using liquid crystal. The present invention relates to a projection zoom lens used and a projection display device using the same.

  As a conventional zoom lens, for example, a five-group configuration described in Patent Documents 1 and 2 is known. These are, in order from the object side, a negative first lens unit that is fixed and has a focusing function during zooming, for continuous zooming, and for correction of image plane movement caused by the continuous zooming, And a positive second lens group, a positive third lens group and a negative fourth lens group, and a fixed positive fifth lens group at the time of zooming, and further satisfies a predetermined conditional expression This is a zoom lens.

  Conventionally, this type of zoom lens is first required to have brightness in order to be compatible with a liquid crystal projector, and further to be compact in order to meet the demand for miniaturization of a projection display device. In addition, the reduction side of the projection lens is a substantially telecentric optical system for use in a projection lens that uses liquid crystal, and an optical system for color separation or color synthesis is inserted between the lens system and the image plane. Therefore, having an appropriate amount of back focus is also a prerequisite for this type of zoom lens.

  Further, in recent years, this type of zoom lens, as disclosed in Patent Documents 1 and 2, responds to a demand for projection from a distance close to a large screen in a projection display device. Many lenses have been proposed. For example, when projecting to a 100-inch size, there is one that assumes a projection distance of 2.5 to 3 m.

JP 2000-292701 A JP 2001-4919 A

  However, with the widespread use of projection display devices, the installation position is not necessarily limited between the audience and the screen. For example, the projector is suspended from the ceiling behind the audience and projected onto the screen over the audience's head. In some cases, the degree of freedom of the installation position is required. In such a case, a tele zoom lens having a long focal length is desirable rather than the zoom lens having a wide angle of view, and a projection distance of 5 to 10 m is assumed when projecting to a 100 inch size similar to the above. There is a demand for such a zoom lens with good optical performance.

  The present invention has been made in view of such circumstances, and a focal length in which various aberrations are favorably corrected, which is suitable for a projection display device using liquid crystal in a zoom lens having a five-group configuration with three-group movement. The object of the present invention is to provide a tele zoom lens having a long length. Another object of the present invention is to provide a projection display device using the zoom lens.

The zoom lens of the present invention includes, in order from the magnification side, a first lens group having a negative refractive power that performs fixed focusing during zooming;
Corrects the image plane movement caused by the continuous scaling and continuous scaling, mutually moved with a relationship, a second lens group having a positive refractive power, the third lens group and a negative refracting having a negative refractive power A fourth lens group having power;
Disposed and a fifth lens group having positive refractive power fixed during zooming Ri Na,
In the second lens group, the telephoto end position is positioned closer to the enlargement side than the zooming wide-angle end position, and in the fourth lens group, the telephoto end position is positioned closer to the reduction side than the zooming wide-angle end position. And
Furthermore, the following conditional expressions (1) to (4) are satisfied .
-2.2 <F ₁ /F<-1.2 (1)
0.6 <F ₂ /F≦0.923 (2)
-15.0 <F ₄ /F<-1.5 (3)
0.7 <F ₅ /F<1.2 (4)
However,
F: Focal length of the entire lens system at the wide-angle end (the conjugate point position on the enlargement side is infinite)
F ₁ : Focal length of the first lens group
F ₂ : focal length of the second lens group
F ₄ : Focal length of the fourth lens group
F ₅ : Focal length of the fifth lens group

  Furthermore, a projection display device of the present invention is characterized by comprising the above zoom lens as a light source, a light valve, and a projection lens for projecting an optical image by light modulated by the light valve onto a screen. is there.

  According to the zoom lens of the present invention, various aberrations are favorably corrected by a five-group type in which the positive second lens group, the negative third lens group, and the negative fourth lens group are movable. It is possible to obtain a tele zoom lens with a long focal length that assumes a projection distance of 5 to 10 m when projecting to a size. Therefore, even when this zoom lens is used in a projection display device, the device can meet these demands.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a basic configuration of a zoom lens of Example 1 to be described later according to the present invention, and is a lens configuration diagram (WIDE) at a wide angle end and a lens configuration diagram (TELE) at a telephoto end. This lens will be described below as a representative of this embodiment.

That this zoom lens, the first lens group G ₁ having a negative refractive power for performing focusing in fixed during zooming, for continuous zooming, and correction of image plane movement caused by the continuous variable power Therefore, the second lens group G ₂ having a positive refractive power that moves relative to each other, the third lens group G ₃ having a negative refractive power, and the fourth lens group G ₄ having a negative refractive power, is disposed between the fifth lens group G ₅ is a relay lens having a positive refractive power fixed during the times from the enlargement side in the order formed by. Between the fifth lens group G ₅ and the liquid crystal display panel 1, more filters and low-pass filter for cutting infrared glass blocks 2 are arranged corresponding to the color combining optical system (color-separation optical system) . In the figure, X represents the optical axis.

The second lens group G ₂ is better the telephoto end position than at the wide-angle end position of the zooming is configured so as to be positioned on a larger scale side. The fourth lens group G ₄ is better at the telephoto end position than at the wide-angle end position of the zooming is configured to be positioned more reduction side.

Further, this zoom lens is configured to satisfy the following conditional expressions (1) to (4).
-2.2 <F ₁ /F<-1.2 (1)
0.6 <F ₂ /F<1.1 (2)
-15.0 <F ₄ /F<-1.5 (3)
0.7 <F ₅ /F<1.2 (4)
However,
F: Focal length of the entire lens system at the wide-angle end (the conjugate point position on the enlargement side is infinite)
F ₁ : Focal length F _{2 of} the first lens group G ₁ : Focal length of the second lens group G ₂ F ₄ : Focal length of the fourth lens group G ₄ F ₅ : Focal length of the fifth lens group G ₅

  The projection display device according to the present invention is a device including a light source, a light valve, and the above-described zoom lens according to the present invention. In this apparatus, the zoom lens according to the present invention functions as a projection lens for projecting an optical image of light modulated by a light valve onto a screen. For example, in the case of the liquid crystal video projector provided with the zoom lens shown in FIG. 1, a substantially parallel light beam is incident from a light source unit (not shown) on the right side of the paper, and carries image information displayed on the liquid crystal display panel 1. This light beam is enlarged and projected on a screen (not shown) in the left direction of the drawing by the zoom lens through the glass block 2. In general, in a liquid crystal video projector, a light beam from a light source is separated into three primary color lights of R, G, and B by a color separation optical system composed of a dichroic mirror and a lens array, and three liquid crystal display panels are provided for each primary color light. It is arranged so that a full color image can be displayed. The glass block 2 can be a dichroic prism that synthesizes the three primary color lights.

  Hereinafter, the operation and effect of the zoom lens according to the present embodiment and the projection display apparatus using the zoom lens will be described.

From the enlargement side in order, a first lens group G ₁ having a negative refractive power for performing focusing in fixed during zooming, for continuous zooming, and the correction of the image plane movement caused by the continuous variable power Therefore, the second lens group G ₂ having a positive refractive power and moves with a interrelated, the third lens group G ₃ and the fourth lens group G ₄ having a negative refractive power having a negative refractive power, variable the arrangement disposed between the fifth lens group G ₅ is a relay lens having a positive refractive power fixed during times, suitable for a projection display device using a liquid crystal, various aberrations are satisfactorily corrected A tele zoom lens having a long focal length can be obtained.

In order to realize a tele zoom lens, it is necessary to increase the negative refractive power as compared with a standard zoom lens. However, would change the power balance between the first lens group G ₁ and the fixed fifth lens group G ₅ for performing focus Therefore, a large risk of the optical performance deterioration. For good optical performance, it is desirable to change the balance of power to solve the movable group G ₂ ~G _4. However, also in the moving groups G _{2 to} G ₄ , it is not desirable in terms of optical performance to make the refractive power of the negative lens group too strong or suppress the refractive power of the positive lens group too much. Therefore, the zoom lens according to the present embodiment, the negative refractive power is shared by the two groups of the third lens group G ₃ and the fourth lens group G _4, to have no refractive power each group is too strong It is configured.

Since the first lens group G ₁ is that by diverging light rays having a negative refractive power, of the movement group G ₂ ~G _4, the second lens group G ₂ and the group having a positive refractive power, it is desirable to share the negative refractive power in the third lens group G ₃ and the fourth lens group G _4. In this manner, a tele zoom lens can be realized by moving the three groups G _{2 to} G ₄ in relation to each other.

Further, the zoom lens according to the present embodiment, the second lens group G ₂ is located in a more enlarged side toward the telephoto end position than at the wide-angle end position of the zooming, the fourth lens group G ₄ is a wide-angle end position of zooming It is preferable that the telephoto end position is located on the reduction side as compared with FIG. Further, the second lens group G ₂ moves from the wide angle end to move to the expanded side during zooming to the telephoto end, the fourth lens group G ₄ is the reduction side during zooming to the telephoto end from the wide-angle end It is preferable to configure so as to.

That is, the light Tabadaka of the axial ray in the second lens group G _2, since increases in towards the telephoto side than the wide angle side, the second lens group G ₂ is the direction of the telephoto end position than at the wide-angle end position of the zooming the mutual arrangement located on a larger scale side, it is possible to reduce the diameter of the second lens group G _2.

Further, with regard fourth lens group G _4, the configuration found the following telephoto end position than at the wide-angle end position of the zoom position to a more reduction side, the first lens group G ₁ and the second lens group G ₂ of the lens diameter This can contribute to downsizing. In the zoom lens according to the present embodiment, the aperture position of the imaginary principal ray of the off-axis intersects the optical axis, highly dependent on the refractive power of the fifth lens group G _5, its position about the third lens at the wide-angle end present in the vicinity of the group _{G 3} and the fourth lens group _{G 4.} For example, in the embodiment to be described later, it is present in the middle of the third lens group G ₃ and the fourth lens group G _4. If, the fourth lens group G _4, a structure in which the direction of the telephoto end position than at the wide-angle end position of the zoom position more enlarged side, when located on the enlargement side of the stop position of the virtual, both negative refractive The third lens group G ₃ and the fourth lens group G ₄ having power will jump up the light beam. In this case, since it is possible to reduce the brightness and while ensuring the peripheral light amount of the first lens group G ₁ and the second lens group G ₂ lens diameter at the telephoto end becomes very difficult, the fourth lens group G ₄ Is configured to move toward the reduction side upon zooming from the wide-angle end to the telephoto end, and it is preferable to make the lens diameters of the groups G ₁ and G ₂ compact.

Next, the condition for (1), the negative refractive power of the first lens group G ₁ to exceed the lower limit is weakened, F No. Or becomes difficult aberration correction lens with a small amount of movement increases with cause aberration fluctuations of the first lens group G ₁ by focusing may become violent. Also when a negative refractive power exceeds the upper limit is strengthened, by the first lens group G ₁ too thrown up on-axis ray becomes particularly difficult to correct aberrations such as distortion aberration and spherical aberration.

Further, the conditional expression for (2) is the amount of movement of the second lens group G ₂ with zooming the positive refractive power of the second lens group G ₂ exceeds the upper limit weakened becomes large lens size increases End up. The aberration correction becomes difficult when the positive refractive power of the second lens group G ₂ than the lower limit becomes stronger.

Further, the conditional expression for the (3), the negative refractive power of the fourth lens group G ₄ exceeds the upper limit becomes stronger, the amount of aberration is increased, it becomes difficult to correct aberrations. Further, the negative refractive power of the fourth lens group G ₄ than the lower limit is weakened, the amount of movement becomes excessively large at the time of zooming of the fourth lens group G _4, the lens system compact becomes difficult. In particular, when the fourth lens group G ₄ is configured such that the telephoto end position is located on the reduction side as compared with the zoom wide-angle end position, this increase in the amount of movement is similar to that of the fourth lens group G ₄ . becomes increased air gap between the fifth lens group G _5, is very large impact on the total lens length.

Also, one of the two negative lens groups G ₃ and G _{4 in} the moving groups G _{2 to} G ₄ having a strong refractive power and the other having a weak refractive power means that the lens group having a weak refractive power moves. The amount will increase, making it difficult to make compact. If an attempt is made to compact the lens forcibly, the burden on zooming and aberration correction to other groups increases, and as a result, aberration correction becomes difficult. It is preferable that the two negative lens groups G ₃ and G ₄ share negative refractive power in a well-balanced manner to diverge the light beam gently.

Further, the conditional expression for (4), when the positive refractive power of the fifth lens group G ₅ than the lower limit becomes stronger, the back focus is short and it is difficult to the reduction side in the state of substantially telecentric . By satisfying this lower limit value, the zoom lens can ensure a predetermined back focus, and a dichroic prism for color synthesis necessary for projecting a color image can be inserted at the position of the glass block 2. It becomes possible. On the other hand, the upper limit, greater too long back focus the positive refractive power of the fifth lens group G ₅ is weakened, the size including the lens back is increased. Further axial ray height in the fifth lens group G ₅ becomes difficult becomes too aberration correction lower.

  Note that the zoom lens of the present invention is not limited to a use mode as a projection lens of a projection display device using a transmissive liquid crystal display panel, but is a projection lens or DMD of a device using a reflective liquid crystal display panel. It can also be used as a projection lens for devices using other light modulation means, etc. In addition, it has a zoom function used for imaging means such as CCDs and image pickup tubes, as well as cameras using silver halide films, etc. It can also be used as an imaging lens.

  Further, the projection display device is configured so that the zoom lens according to the present invention and another lens having a wide angle of view or a lens suitable for a standard projection distance can be selectively exchanged and mounted. As a result, the degree of freedom of the installation location of the apparatus can be increased.

  Hereinafter, each example will be specifically described using data. The zoom lens according to the present invention is not limited to the following embodiments, and for example, the number and shape of the lenses constituting each lens group can be appropriately selected.

<Example 1>
As described above, the zoom lens according to Example 1 is configured as shown in FIG. That in order from the lens magnification side, a first lens group G ₁ is from a biconcave lens having a surface with a stronger curvature directed onto the first lens L ₁ and the reduction side consisting of a biconvex lens having a surface with a stronger curvature directed onto the enlargement side A cemented lens with the second lens L ₂ , a third lens L ₃ composed of a biconcave lens having a strong curvature surface facing the reduction side, and a fourth lens L ₄ composed of a positive meniscus lens facing the convex surface toward the magnification side Thus, the second lens group G ₂ includes a fifth lens L _{5 made of} a biconvex lens having a strong curvature surface facing the reduction side, and a sixth lens L _{6 made of a} biconvex lens having a strong curvature surface directed to the enlargement side. becomes, the third lens group G ₃ is composed of a cemented lens of an eighth lens L ₈ made of a biconcave lens having a surface with a stronger curvature and seventh lens L ₇ made of a biconvex lens of double-sided same curvature to the reduction side, the fourth lens group _{G 4} is, both A cemented lens of a tenth lens L ₁₀ made from ninth lens L ₉ and a positive meniscus lens having a convex surface facing the magnification side which is a biconcave lens having the same curvature, the fifth lens group G ₅ is stronger curvature the magnification side An eleventh lens L ₁₁ composed of a biconcave lens facing the surface of the lens, a twelfth lens L ₁₂ composed of a positive meniscus lens having a convex surface facing the reduction side, and a thirteenth lens composed of a biconvex lens facing the surface of strong curvature toward the magnification side. L ₁₃ includes a fourteenth lens L _{14 made of} a plano-convex lens having a convex surface directed toward the enlargement side.

Further, in this zoom lens, the second lens group G ₂ and the third lens group G ₃ are both moved to the expanded side from the wide-angle end during zooming to the telephoto end, the fourth lens group G ₄ is a wide-angle end Moves to the reduction side when zooming from to the telephoto end.

  The radius of curvature R of each lens surface in Example 1 (standardized with the focal length in the infinite state of the conjugate point on the enlargement side at the wide angle end as 1; the same in the following tables), the center thickness of each lens Table 1 shows the air spacing D between the lenses (normalized with the same focal length as the radius of curvature R; the same in the following tables), the refractive index N and the Abbe number ν of each lens at the d-line. Show. In Table 1 and Tables 3, 5, and 7 to be described later, the numbers corresponding to the symbols R, D, N, and ν are sequentially increased from the enlargement side.

Also in Table 2, the wide-angle end in the first embodiment (zoom ratio 1.00), the distance of the intermediate position (zoom ratio 1.25), and the telephoto end (zoom ratio 1.50) the first lens group G ₁ in the second lens group G ₂ D ₇ (variable 1), a distance D ₁₁ (variable 2) between the second lens group G ₂ and the third lens group G ₃ , a distance D ₁₄ (variable 3) between the third lens group G ₃ and the fourth lens group G ₄ , and The distance D ₁₇ (variable 4) between the fourth lens group G ₄ and the fifth lens group G ₅ , the reduction magnification at the wide-angle end, the focal length F _{1 of} the first lens group G ₁ , and the focal point of the second lens group G ₂ distance _{F 2,} shows a focal length _{F 5} of the focal length _{F 4} and the fifth lens group _{G 5} of the fourth lens group _{G 4.}

  FIG. 3 shows various aberrations (spherical aberration, astigmatism, distortion, and the like) at the wide angle end (WIDE) at the reduction magnification of −0.0098 and intermediate (MIDDLE) and telephoto end (TELE) at the same conjugate length. It is an aberration diagram showing lateral chromatic aberration). 3 to 6, the astigmatism diagrams show aberrations with respect to the sagittal image surface and the tangential image surface, and the respective chromatic aberration diagrams show aberrations with respect to the d-line.

  As is clear from FIG. 3 and Tables 1 and 2 above, the zoom lens of Example 1 satisfies all of the conditional expressions (1) to (4), and good aberration correction is performed over the entire zoom region. It is a compact tele zoom lens that achieves an appropriate back focus amount and substantially telecentricity on the reduction side.

<Example 2>
The zoom lens according to Example 2 is configured as shown in FIG. 2 and is substantially the same as that of Example 1. The main difference from the first embodiment, the first lens group G ₁ is in order from the magnification side, a first lens L ₁ made of a plano-convex lens having a convex surface on the enlargement _side, facing a surface with a stronger curvature directed onto the reduction side A second lens L _{2 made of} a biconcave lens, a third lens L _{3 made of} a biconcave lens having a strong curvature surface facing the enlargement side, and a fourth lens L _{4 made of a} biconvex lens having a strong curvature surface directed to the enlargement side It is the point which consists of. Table 3 shows the curvature radius R of each lens surface, the center thickness of each lens and the air gap D between each lens, the refractive index N and the Abbe number ν of each lens at the d-line in Example 2.

Table 4 shows the distance D ₈ between the first lens group G ₁ and the second lens group G _{2 at} the wide angle end (zoom ratio 1.00), the intermediate position (zoom ratio 1.25), and the telephoto end (zoom ratio 1.50) in the second embodiment. (Variable 1), distance D ₁₂ (variable 2) between the second lens group G ₂ and the third lens group G ₃ , distance D ₁₅ (variable 3) between the third lens group G ₃ and the fourth lens group G ₄ , and the first The distance D ₁₈ (variable 4) between the fourth lens group G ₄ and the fifth lens group G ₅ , the reduction magnification at the wide angle end, the focal length F _{1 of} the first lens group G ₁ , and the focal length of the second lens group G ₂ F _2, shows a focal length _{F 5} of the focal length _{F 4} and the fifth lens group _{G 5} of the fourth lens group _{G 4.}

  FIG. 4 shows various aberrations (spherical aberration, astigmatism, distortion and distortion) at the wide angle end (WIDE) at the reduction magnification of −0.0098 and intermediate (MIDDLE) and telephoto end (TELE) at the same conjugate length. It is an aberration diagram showing lateral chromatic aberration). As is clear from FIG. 4 and Tables 3 and 4 above, the zoom lens of Example 2 satisfies all the conditional expressions (1) to (4), and good aberration correction is performed over the entire zoom region. It is a compact tele zoom lens that achieves an appropriate back focus amount and substantially telecentricity on the reduction side.

<Example 3>
The zoom lens according to Example 3 is configured as shown in FIG. 7 and is substantially the same as that of Example 1. The main difference from Example 1 is that the first lens group G ₁ is a first lens L _{1 made of} a positive meniscus lens having a convex surface on the enlargement side in order from the enlargement side, and a plano-concave lens having a flat surface on the enlargement side. The second lens L ₂ is composed of a cemented lens of a third lens L ₃ composed of a biconcave lens having a strong curvature surface facing the magnification side and a fourth lens L ₄ composed of a plano-convex lens having a convex surface facing the magnification side. Is a point. Table 5 shows the curvature radius R of each lens surface, the center thickness of each lens and the air gap D between each lens, the refractive index N and the Abbe number ν of each lens at the d-line in Example 3.

Table 6 shows the distance D ₇ between the first lens group G ₁ and the second lens group G _{2 at} the wide angle end (zoom ratio 1.00), the intermediate position (zoom ratio 1.20), and the telephoto end (zoom ratio 1.40) in Example 3. (Variable 1), distance D ₁₁ (variable 2) between the second lens group G ₂ and the third lens group G ₃ , distance D ₁₄ (variable 3) between the third lens group G ₃ and the fourth lens group G ₄ , and the first The distance D ₁₇ (variable 4) between the fourth lens group G ₄ and the fifth lens group G ₅ , the reduction magnification at the wide-angle end, the focal length F _{1 of} the first lens group G ₁ , and the focal length of the second lens group G ₂ F _2, shows a focal length _{F 5} of the focal length _{F 4} and the fifth lens group _{G 5} of the fourth lens group _{G 4.}

  FIG. 5 shows various aberrations (spherical aberration, astigmatism, distortion, and the like) at the wide angle end (WIDE) at the reduction magnification of −0.0098 and intermediate (MIDDLE) and telephoto end (TELE) at the same conjugate length. It is an aberration diagram showing lateral chromatic aberration). As is apparent from FIG. 5 and Tables 5 and 6 above, the zoom lens of Example 3 satisfies all of the conditional expressions (1) to (4), and good aberration correction is performed over the entire zoom region. It is a compact tele zoom lens that achieves an appropriate back focus amount and substantially telecentricity on the reduction side.

<Example 4>
The zoom lens according to Example 4 is configured as shown in FIG. 8 and is substantially the same as that of Example 1. The main difference from Example 1 is that any lens group of the first lens group G ₁ to the fifth lens group G ₅ does not include a cemented lens. Table 7 shows the curvature radius R of each lens surface, the center thickness of each lens and the air gap D between each lens, the refractive index N and the Abbe number ν of each lens at the d-line in Example 4.

Table 8 shows the distance D ₈ between the first lens group G ₁ and the second lens group G _{2 at} the wide angle end (zoom ratio 1.00), the intermediate position (zoom ratio 1.20), and the telephoto end (zoom ratio 1.40) in Example 4. (Variable 1), distance D ₁₂ (variable 2) between the second lens group G ₂ and the third lens group G ₃ , distance D ₁₆ (variable 3) between the third lens group G ₃ and the fourth lens group G ₄ , and the first The distance D ₂₀ (variable 4) between the fourth lens group G ₄ and the fifth lens group G ₅ , the reduction magnification at the wide-angle end, the focal length F _{1 of} the first lens group G ₁ , and the focal length of the second lens group G ₂ F _2, shows a focal length _{F 5} of the focal length _{F 4} and the fifth lens group _{G 5} of the fourth lens group _{G 4.}

  FIG. 6 shows various aberrations (spherical aberration, astigmatism, distortion, and distortion) at the wide angle end (WIDE) at the reduction magnification of −0.0098 and the intermediate (MIDDLE) and telephoto end (TELE) at the same conjugate length. It is an aberration diagram showing lateral chromatic aberration). As is clear from FIG. 6 and Tables 7 and 8 above, the zoom lens of Example 4 satisfies all of the conditional expressions (1) to (4), and good aberration correction is performed over the entire zoom region. It is a compact tele zoom lens that achieves an appropriate back focus amount and substantially telecentricity on the reduction side.

FIG. 3 is a lens configuration diagram at the wide-angle end and a telephoto end of the zoom lens according to the first embodiment. FIG. 5 is a lens configuration diagram of the zoom lens according to Example 2 at the wide-angle end and the telephoto end. Each aberration diagram of the zoom lens according to Example 1 Each aberration diagram of the zoom lens according to Example 2 Each aberration diagram of the zoom lens according to Example 3 Each aberration diagram of the zoom lens according to Example 4 FIG. 6 is a lens configuration diagram at the wide-angle end and the telephoto end of a zoom lens according to Example 3; FIG. 6 is a lens configuration diagram at the wide-angle end and a telephoto end of a zoom lens according to Example 4;

Explanation of symbols

G ₁ ~G ₅ lens group L ₁ ~L ₁₃ lens R ₁ to R of curvature such as ₂₈ lens surface radius D ₁ to D ₂₇ lens spacing (lens thickness)
X Optical axis 1 LCD panel 2 Glass block

Claims (2)

In order from the magnification side, a first lens group having negative refractive power that performs fixed focusing at the time of zooming;
Corrects the image plane movement caused by the continuous scaling and continuous scaling, mutually moved with a relationship, a second lens group having a positive refractive power, the third lens group and a negative refracting having a negative refractive power A fourth lens group having power;
Disposed and a fifth lens group having positive refractive power fixed during zooming Ri Na,
In the second lens group, the telephoto end position is positioned closer to the enlargement side than the zooming wide-angle end position, and in the fourth lens group, the telephoto end position is positioned closer to the reduction side than the zooming wide-angle end position. And
Furthermore, the zoom lens characterized by satisfying the following conditional expressions (1) to (4).
-2.2 <F ₁ /F<-1.2 (1)
0.6 <F ₂ /F≦0.923 (2)
-15.0 <F ₄ /F<-1.5 (3)
0.7 <F ₅ /F<1.2 (4)
However,
F: Focal length of the entire lens system at the wide-angle end (the conjugate point position on the enlargement side is infinite)
F ₁ : Focal length of the first lens group
F ₂ : focal length of the second lens group
F ₄ : Focal length of the fourth lens group
F ₅ : Focal length of the fifth lens group Light source, a projection display apparatus comprising the light valves, and claim 1 Symbol placement of the zoom lens and projection lens for projection of the optical image on the screen according to the light modulated by the light valve.

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