JPH11231218A - Zoom lens for projection and projector device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens for projection which has a small chromatic difference of magnification and a simple composition and is suitable for a high resolution liquid crystal projector device. SOLUTION: Since light beams of each wavelength can be made incident on a projection lens 10 after corrections have been made suitable for the light beams of each wavelength so that chromatic difference of magnification is not generated on the side of an auxiliary lens 11 by providing auxiliary lenses 11R and 11B arranged individually on the side of the light sources of each color light beam in addition to the projection lens 10 which is a common configuration to the light beams of each color arranged on the side of a screen 9, it is possible to provide a projection use zoom lens 1 having a very high image- forming performance with a very simple configuration. Therefore, the use of the zoom lens for projection in accordance with this invention makes it possible to fully correspond to higher resolution of light valve in future as an output device of a personal computer, and further makes it possible to provide a compact and light projector device 8 at an inexpensive cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection zoom lens of a projector for enlarging and projecting an image displayed by a light valve on a screen, and more particularly to a projection zoom lens suitable for a liquid crystal color projector. .

[0002]

2. Description of the Related Art FIG. 13 shows a schematic configuration of a general three-panel type liquid crystal projector. A projector 8 capable of enlarging and projecting an image on a screen or the like generally includes a projection zoom lens 1 for projecting an image supplied from an incident side toward a screen, and an image forming apparatus for supplying an image to the projection zoom lens 1. 7 is provided. In the case of a liquid crystal projector device, a liquid crystal panel is employed as a light valve of the image forming apparatus 7. In the projector device 8 shown in FIG. 13, a white light source 6 and light emitted from the light source 6 are color-separated. And dichroic mirrors 5R and 5G, and liquid crystal panels 3B, 3G and 3R which are transmission type display media (light valves) for forming images of respective colors separated into red, green and blue. The projection image formed by the liquid crystal panels 3B, 3G, and 3R is guided to the dichroic prism 2 by the reflection mirror 4, is subjected to color synthesis, and then enters the projection lens 1. Then, the images displayed on each of the liquid crystal light valves 3B, 3G and 3R are enlarged and combined to form an image on the screen 9.

[0003]

A projection (projection) zoom lens used in such a liquid crystal projector is as follows.
A long back focus is required to insert the dichroic prism 2, and the dichroic prism has a large dependence on the incident angle due to spectral characteristics, so that the configuration on the liquid crystal panel side must be a telecentric light beam. Further, the present invention is not limited to the above-described three-plate image forming apparatus.
When a liquid crystal light valve is used, the viewing angle of the liquid crystal panel is not so large, and the angle dependence of image quality is large. Therefore, it is desirable that the incident side of the projection lens be telecentric.

Further, in recent years, such a liquid crystal projector has been frequently used as a display device of a computer, and the color shift of a projected image is severely restricted. For example, a high performance such that chromatic aberration is within one pixel of the liquid crystal is obtained. Required for projection lenses. In addition, the display adapter of the personal computer is changed from the conventional VGA to the SV
Since the resolution is increased to GA or XGA, the allowable value of chromatic aberration tends to be more severe. In order to reduce the color shift, it is necessary to add an achromatic lens, so that the number of components of the projection lens increases, and therefore, the projection lens becomes large, heavy and expensive. Also, when the number of components of the projection lens increases, it becomes difficult to obtain a bright and large image, so it is necessary to employ a lens having a large aperture and a high transmittance, and the projection lens is further larger, heavier, and It will be expensive.

[0005] On the other hand, there is a strong demand for a projector device which is small and can be easily used as an output device of a personal computer, and which can be supplied at low cost.
And as the performance of such a projector device, sufficient performance as an output device of the computer as described above,
Needless to say, it is particularly required that a bright and large image without color shift be obtained at a short distance.

Accordingly, it is an object of the present invention to provide a projection zoom lens capable of projecting an image having very small color shift with a small number of components, and a projector apparatus using the same. It is another object of the present invention to provide a light-weight, compact, low-cost projection zoom lens and projector having sufficient imaging performance as an output device such as a personal computer.

[0007]

In a conventional projection lens, achromatism is performed by combining lenses having different powers in units such as lens groups. On the other hand, the present invention focuses on the fact that an image for each color is formed in a three-plate type projector device or the like, and is of such an extent that the chromatic aberration of magnification can be corrected for the luminous flux of each color but does not affect the imaging performance. Achromatism is performed by inserting power correction lenses individually, greatly reducing the load for correcting chromatic aberration on the projection lens side. That is, the projection zoom lens of the present invention is a zoom lens for projection of a color image in which the incident side is telecentric, and is capable of zooming a plurality of components common to the red, green, and blue light beams arranged on the screen side. A projection lens and an auxiliary lens arranged on the side of the red or blue light source.

It is a matter of course that an auxiliary lens may be provided so as to correct a light beam of another color based on a light beam of red or blue. With reference to the green light flux, which is the central region of visible light, the auxiliary lens having a power sufficient to correct the chromatic aberration of magnification is provided for the red, blue or both light fluxes, so that the magnification can be maintained without affecting the imaging performance. Correction of chromatic aberration is possible. By the auxiliary lens, a light beam that has already been corrected for each color so as to reduce color shift to the projection lens can be incident. Therefore, since there is no need to strictly correct the chromatic aberration of magnification in the projection lens, it is possible to project a clear image with very little color shift by using a small number of constituent lenses. For this reason, it is possible to provide a compact and lightweight projection zoom lens that can obtain a bright image. In addition, expensive lenses such as a glass lens having a high refractive index and a glass lens having anomalous dispersion conventionally used for correcting lateral chromatic aberration in a projection lens are not required. Therefore, a projector device including the projection zoom lens of the present invention and an image forming apparatus such as a liquid crystal panel capable of supplying each of the red, green, and blue projection images to the incident side of the projection zoom lens is provided. In addition, a clear image without color shift can be projected, and sufficient imaging performance as an output device such as a personal computer can be exhibited. And it can be supplied at low cost as a light and compact projector device.

Such a projection zoom lens according to the present invention can of course be applied to a three-lens type projector, but if the projector is a one-lens type projector using a dichroic mirror or a dichroic prism, the projection lens is You only need one. In a projector device using a dichroic prism capable of synthesizing a projection image into one, a projection lens is arranged on the screen side of the dichroic prism, and a correction lens is arranged on the image forming apparatus side of each light beam of the dichroic prism. It is possible. Therefore, the projection zoom lens of the present invention can be introduced in an arrangement in which a thin auxiliary lens is newly added to the image forming apparatus side of the dichroic prism and hardly affects the basic configuration of the projector apparatus. .

It is desirable that the auxiliary lens used in the projection zoom lens of the present invention has a very weak power that does not affect the imaging performance, so that a single auxiliary lens is sufficient. Therefore, even if a combination of a projection lens and an auxiliary lens is used, it is only necessary to add a single lens having low power, and it can be realized with a simpler configuration than a conventional projection lens.

Further, since the auxiliary lens is arranged at a position close to the liquid crystal panel, it is possible to use a lens made of the same material as the liquid crystal panel, that is, a plastic lens. Further, the surface accuracy is comparable to that of the liquid crystal panel, and there is no problem. Even a lens having a surface accuracy of one-tenth, one-hundredths or less of the lens used in the conventional projection zoom lens has sufficient performance. Can demonstrate. Therefore, even if the auxiliary lens is additionally provided, there is no effect on the cost, the arrangement of the projection zoom lens, and the like, and the configuration of the projection lens can be simplified as described later, so that the accompanying effect can be maximized. .

As described above, since the chromatic aberration is corrected by the correction lens, the number of components of the projection lens can be reduced, and the total number of projection lenses is equal to or smaller than that of the conventional projection lens. It is possible to provide a projection zoom lens having a higher imaging performance, in particular, a high correction capability of lateral chromatic aberration. As a projection lens, in order from the screen side, a first lens group having a single negative refractive power;
A second lens group having a single refractive power and a third lens group having a negative refractive power; and a fourth lens group having a positive refractive power. Sufficient imaging performance can be obtained with a simple configuration that enables zooming by moving the lens group. Further, the fourth lens group is divided into a front group on the screen side and a rear group on the entrance side, and the imaging performance is improved by controlling the distance between the front group and the rear group during zooming. it can. The performance can also be improved by making the screen side of the first lens group aspherical. In particular, since the projection zoom lens of the present invention has a configuration in which the number of components is small and a bright image can be obtained, it is possible to use a lot of plastic lenses, which can reduce the cost and can easily connect the lens by introducing an aspherical surface. Image performance can be improved.

Further, in the projection zoom lens of the present invention, the focal length fe of the projection lens at the e-line (546.1 nm) and the wavelength of the projection lens at 610 nm or 460 n are used.
It is desirable that the focal length fc of m and the focal length fch of the auxiliary lens at a wavelength of 610 nm or 460 nm satisfy the following expression.

250 <| (fc−fe) × fch | <1000 (1) Focal length of a projection lens having a wavelength of 546.1 nm corresponding to a green light flux (hereinafter, G light) in a central region of visible light fe
And a light beam of another color (wavelength 610 nm is a red light beam (hereinafter referred to as R light), and wavelength 460 nm is a blue light beam (hereinafter B light beam).
The absolute value of the product of the difference between the focal length fc of the projection lens and the focal length fc of the auxiliary lens at a wavelength corresponding to (light)) is (1)
When the value is below the lower limit of the expression, it becomes difficult to correct the chromatic aberration of magnification at the telephoto end, and the effect of the auxiliary lens as an imaging lens appears, which affects the imaging performance of the projection lens. On the other hand, when the value exceeds the upper limit of the expression (1), the performance as the auxiliary lens is insufficient, and the effect of removing the chromatic aberration of magnification cannot be obtained, and the chromatic aberration of magnification at the wide angle end cannot be removed.

Further, in the projection lens according to the present invention, it is desirable that the focal length f1 of the first lens unit and the focal length f2 of the second lens unit of the projection lens satisfy the following expression.

-2.5 <(f1 / f2) <-0.5 (2) Ratio of the focal length f1 of the first lens unit of the projection lens to the focal length f2 of the second lens unit When the value is below the lower limit of the expression (2), curvature of field is apt to occur, and the imaging performance on the projection lens side deteriorates, so that chromatic aberration of magnification occurs over the entire range from the wide-angle end to the telephoto end. On the other hand, when the value exceeds the upper limit of the expression (2), the back focus of the projection lens cannot be long, so that it is difficult to obtain the performance as a telecentric optical system, and distortion tends to occur.

[0017]

[First Embodiment] FIG. 1 shows an optical system of a projector using a projection zoom lens 1 according to a first embodiment of the present invention. FIG. 2 shows the position of each lens of the projection zoom lens 1 of the present example at the wide-angle end (a) in a state of enlarged display, the telephoto end (c) in a standard state, and the intermediate state (b). Is shown. The overall configuration of the exemplified projector 8 is the same as that described with reference to FIG. 13, and a portion related to the projection zoom lens in the optical system is extracted and shown in FIG. In the projector device 8 shown in the figure, light from a light source (not shown) is split into red, green, and blue light, and each of the liquid crystal panels 3R, 3G, and 3R as image forming devices.
And is synthesized by the dichroic prism 2 and further projected on the screen 9 by the projection zoom lens 1. In this way, a color image in which the images formed on the liquid crystal panels 3R, 3G, and 3R are combined is formed on the screen 9. The projection zoom lens 1 of this example is arranged on a projection lens 10 common to each of the light fluxes R, G, and B arranged on the screen 9 of the dichroic prism 2 and on the red R light source side of the dichroic prism 2. Auxiliary lens 11R and an auxiliary lens 11B disposed on the blue G light source side of the dichroic prism 2.

The projection lens 10 of the projection zoom lens 1 of this embodiment has four lens groups G1 to G from the screen 9 side.
It is composed of eight lenses L11 to L44 grouped into four, and detailed data of each lens is as shown below. The first lens group G1 disposed closest to the screen 9 is a lens group having a negative refractive power. In this example, the first lens group G1 has a single negative meniscus lens L11 convex on the screen 9 side. Has become. The position of the first lens group G1 is not moved during zooming.

Next, a second lens group G for zooming is arranged.
Reference numeral 2 denotes a lens group having a positive refractive power. In this example,
It has one biconvex positive lens L21. The second lens group G2 for zooming moves on the optical axis from the entrance side to the opposite side of the screen 9 from the wide-angle end to the telephoto end, and a projection image of a predetermined magnification is displayed on the screen. You can get it. Third lens group G following this
Reference numeral 3 denotes a correction lens group that moves along the optical axis during zooming, and employs a lens group having a negative refractive power. The projection zoom lens 1 of this example is configured by a combination of a positive lens L31 convex on the screen side and a negative lens L32 biconcave.

The fourth lens group on the most incident side of the projection lens 10 of the projection zoom lens 1 is a lens group having a positive refractive power as a whole, and a biconcave negative lens L41 forming a doublet from the screen side. And a biconvex positive lens L42
And a positive lens L43 convex on the incident side and a positive lens L44 convex on the screen side.

Further, the projection zoom lens 1 of the present embodiment
As the auxiliary lens 11, a positive lens 11R convex on the incident side with a weak power on the R light side is disposed so as to be almost in close contact with the surface of the dichroic prism 2, and a negative lens 11B on the incident side with a weak power on the B light side. Are similarly arranged. No auxiliary lens is provided on the G light side. As described above, the auxiliary lenses 11R and 11B are provided with different curvatures suitable for the respective wavelengths, so that the correction appropriate for the wavelengths is performed and the chromatic aberration of magnification is generated in the projection lens 10 beforehand. I try to prevent it.

The projection zoom lens 1 of this embodiment as described above.
The projection zoom lens 1 in which the projection lens 10 is composed of four negative-positive-negative-positive lens groups and is a retrofocus type combination, so that a long back focus can be secured and the entrance side is telecentric It has become. Therefore, as described above, the projection zoom lens is suitable for the projector 8 using a dichroic prism or a liquid crystal panel as a light valve. Further, in the projection zoom lens 1 of the present example, a large angle of view is obtained because the lens group G1 having a negative refractive power is provided in front of the screen side, and a small and large image with excellent wide-angle performance is projected. It is a zoom lens that can be used.

Further, in the projection zoom lens 1 of the present embodiment, since the auxiliary lenses 11R and 11B of low power are provided to correct the chromatic aberration of magnification, in the projection lens 10, the first lens group G1 and the The second lens group G2 is a single lens unit, and no combination of a plurality of lenses having different powers or a combination of a plurality of lenses forming a doublet is used for achromatism.
In addition, the third lens group G3 does not employ a doublet for achromatization. Therefore, the projection lens 1
0 is realized by a minimum configuration of eight pieces,
It is possible to realize a projection zoom lens 1 that has a sufficient wide-angle performance while being compact, and is brighter and has a smaller F-number. For this reason, it is possible to provide a small-sized projector device 8 that can project a large bright image with a short projection distance by using the projection zoom lens 1 of the present example.

Further, in the projection zoom lens 1 of this embodiment, the focal length fe of the G light having a wavelength of 546.1 nm of the projection lens 10 and the R distance of the 610 nm wavelength of the projection lens 10 are set.
By making the focal length fc of the light or the B light having a wavelength of 460 nm and the focal length fch of the auxiliary lens 11R or 11B satisfy the following expression, the auxiliary lens 11 can sufficiently correct the chromatic aberration of magnification, and The projection zoom lens 1 having good imaging performance without affecting the imaging performance is selected.

250 <| (fc−fe) × fch | <1000 (1) Further, the focal length f1 of the first lens group G1 of the projection lens 10 and the focal length of the second lens group G2 of the second lens group. f2 satisfies the following expression so that a projection zoom lens with good aberration correction is selected.

−2.5 <(f1 / f2) <− 0.5 (2) In the lens data shown below, ri is the radius of curvature of each lens surface arranged in order from the screen side, and di is the screen The distance between the lens surfaces arranged in order from the side, ni is the refractive index (d) of each lens arranged in order from the screen side.
Line) and νi indicate the Abbe number (d line) of each lens arranged in order from the screen side. Further, in the projection zoom lens 1 of the present example, the stop S is provided on the incident side of the second lens group G2, and the distance between the stop S and the lens surfaces on both sides is also described. The same applies to the lens data of each embodiment described below. In addition, INF in the data indicates the surface of the stop and the prism, and the unit of the length is described in mm unless otherwise specified.

Lens data iridini vi1: 103.587 10.00 1.71736 29.50 Lens L11 2: 28.697 D2 3: 65.150 4.80 1.72916 54.67 Lens L21 4: -81.448 0.20 5: INF D5 Aperture S 6: 62.453 3.50 1.84666 23.78 Lens L31 7 : 218.722 14.90 8: -57.895 2.00 1.78590 43.93 Lens L32 9: 54.256 D9 10: -55.451 2.40 1.84666 23.78 Lens L41 11: 56.907 10.10 1.56384 60.83 Lens L42 12: -36.757 0.20 13: 231.976 6.60 1.67003 47.20 Lens L43 14: -74.886 0.20 15: 57.964 7.10 1.67003 47.20 Lens L44 16: 18608.827 17: INF 33.00 1.51680 64.20 Prism 18: INF 19R: INF 1.00 1.51680 64.20 Auxiliary lens 11R 19G: INF 19B: INF 1.00 1.51680 64.20 Auxiliary lens 11B 20R: -1600 20B: 850 Zoom status f D2 D5 D9 FNo. Wide-angle end 37.38 41.36 0.80 10.31 2.50 Intermediate 43.0 35.05 9.22 8.20 2.70 Telephoto end 48.7 35.05 18.31 4.11 2.90 Focal length at 546.1 nm (fe) 37.40 Focal length other than auxiliary lens with 610 nm wavelength (fc1) 37.55 Auxiliary lens with 610 nm wavelength 3101.3 Focal length (fc2) other than the auxiliary lens having a wavelength of 460 nm (fc2) 37.13 Focal length of the auxiliary lens having a wavelength of 460 nm (fch2) -1620.8 Focal length (f1) of the first lens group G1- 58.15 Focal length (f2) of second lens group G2 50.12 (1) Equation (fc1-fe) × fch1 = 465.2 for 610 nm (fc2-fe) × fch2 = 437.6 for 460 nm (2) f1 / f2 = −1.16, and the projection zoom lens satisfies the above conditions.

The lens interval D2 is a numerical value when an image is formed at a position 2.4 m from the front end of the lens, and is the same in the following embodiments.

FIG. 3 shows the spherical aberration, astigmatism, and distortion at the wide-angle end (a), the middle (b), and the telephoto end (c) of the projection zoom lens of this embodiment, respectively.
In the spherical aberration diagram, the R light (620.0 nm) is indicated by a broken line,
G light (546.1 nm) is converted to a solid line and B light (460.0 nm).
nm) indicates the aberration of each wavelength by a dashed line, and the astigmatism diagram shows a tangential ray (T) and a sagittal ray (S). The astigmatism and the distortion show the image height with respect to the vertical axis. Further, FIG. 4 shows the chromatic aberration of magnification at the wide-angle end (a), the middle (b), and the telephoto end (c) of the projection zoom lens of this example.
The chromatic aberration of magnification (horizontal chromatic aberration) of light (dashed line) and B light (dotted line) is shown on the basis of G light (solid line), and the image height is shown on the vertical axis. The same applies to the following embodiments.

The projection zoom lens of this embodiment has a short focal length range of 37.4 to 48.7 and an F-number of 2.0.
It is a bright lens of 5-2.9. Further, the chromatic aberration of magnification in each of the wide-angle end state, the intermediate state, and the telephoto end state is within an extremely small range. In addition, the spherical aberration, astigmatism, and distortion in each state are sufficiently small and have no practical problems, and the projection zoom lens of this example has good imaging performance. As described above, in the projection zoom lens 1 of the present embodiment, the correction lenses 11R and 11B are installed upstream of the dichroic prism 2 so as to correct the R light and the B light, respectively. You do not need to do this. Therefore, a projection zoom lens having a small chromatic aberration of magnification and good imaging performance is obtained despite being a low-cost type of projection lens having an eight-element configuration, and a high-resolution image with little pixel color shift is obtained on a screen. This is a projection zoom lens that can be formed.
In addition, since chromatic aberration can be corrected with a small number of lenses, a zoom lens for projection is provided that has various advantages obtained by reducing the number of lenses as described above, such as being small, lightweight, bright, and improving wide-angle performance. can do.

Embodiment 2 FIG. 5 shows a projector 8 using a projection zoom lens 1 according to Embodiment 2 of the present invention.
The optical system is extracted and shown. FIG. 6 shows the positions of the respective lenses at the wide-angle end (a), the telephoto end (c) as a standard state, and the intermediate state (b). In addition,
In the following embodiments, the same parts as those in the above embodiments are denoted by the same reference numerals, and description thereof will be omitted. The projection zoom lens 1 of the present embodiment also has a projection lens 10 arranged on the screen 9 side of the dichroic prism 2 and an auxiliary lens 11 arranged on the light source side of the dichroic prism 2.
In this example, the auxiliary lens 1 for R light is provided.
Only 1R is installed. The projection lens 10 includes eight lenses L11 to L44 grouped into four lens groups G1 to G4 in the same manner as described above, and the fourth lens group G4 includes a front group G41 and a rear group G42. And can be moved independently on the optical axis during zooming. For this reason, when displaying an image including the intermediate region from the wide-angle end to the telephoto end, an image can be formed using an appropriate portion of each lens group, so that aberration and field curvature can be further improved. . In particular, in the projection zoom lens 1 of this example, since the chromatic aberration of magnification of the B light can be suppressed and the performance can be improved, sufficient chromatic aberration of magnification can be corrected even if the correction lens for the B light is omitted. 1
As 1, one sheet for R light is arranged.

Detailed data of each lens is as shown below.

Lens data iridini vi1: 80.338 2.00 1.67003 47.20 Lens L11 2: 32.260 D2 3: 53.072 4.80 1.58913 61.25 Lens L21 4: -85.750 1.20 5: INF D5 Aperture S 6: 33.484 4.20 1.80518 25.46 Lens L31 7 : 103.223 6.70 8: 95.702 2.00 1.76182 26.61 Lens L32 9: 22.895 D9 10: -19.747 2.00 1.84666 23.78 Lens L41 11: 75.960 10.70 1.62041 60.34 Lens L42 12: -25.966 D12 13: -2531.677 6.30 1.74950 35.04 Lens L43 14: -60.454 0.20 15: 66.821 7.00 1.67003 47.20 Lens L44 16: -356.185 17: INF 33.00 1.51680 64.20 Prism 18: INF 19R: INF 1.00 1.51680 64.20 Auxiliary lens 11R 19G: INF 19B: INF 20R: -5700 Zoom state f D2 D5 D9 D12 FNo . Wide-angle end 37.36 49.20 0.80 10.20 0.80 2.50 Intermediate 43.0 39.50 7.75 9.83 3.92 2.66 Telephoto end 48.7 31.76 17.87 6.85 4.53 2.82 Focal length at 546.1 nm (fe) 37.31 Focal length other than auxiliary lens with 610 nm wavelength (fc1) 37.36 Wavelength Focal length of the auxiliary lens of 610 nm (fch1) 11048.5 Focal length of the first lens group G1 (f1) -81.41 Focal length of the second lens group G2 (f2) 56.15 The equation (1) for 610 nm is (fc1- fe) × fch1 = 552.4 Expression (2) is f1 / f2 = −1.50, and the lens satisfies the above-described condition.

FIG. 7 shows the spherical aberration, astigmatism and distortion at the wide-angle end (a), the middle (b) and the telephoto end (c) of the projection zoom lens of this embodiment, respectively.
FIG. 8 shows the chromatic aberration of magnification in each state. The projection zoom lens according to the present embodiment also has a simple and low-cost configuration in which the projection lens 10 includes eight lenses, but the chromatic aberration of magnification falls within a very narrow range, and chromatic aberration of magnification is extremely excellently removed. It turns out that it is a zoom lens. The values of the aberrations shown in FIG. 7 are even better than those in the first embodiment at the wide-angle end, the middle position, and the telephoto end, respectively, and provide a projection zoom lens having excellent imaging performance. You can see that.

Further, the range of the focal length is 37.36-4.
Since it is a lens as short as 8.7 and an F-number as bright as 2.5 to 2.82, it is small and lightweight, has no color shift, and can project a bright high-resolution image suitable for computer output. A zoom lens can be provided.

Third Embodiment FIG. 9 shows a projector 8 using a projection zoom lens 1 according to a third embodiment of the present invention.
The optical system is extracted and shown. FIG. 10 shows the positions of the respective lenses at the wide-angle end (a), the telephoto end (c) as a standard state, and the intermediate state (b). The projection zoom lens 1 of this example also includes an auxiliary lens 11 arranged on the light source side of the dichroic prism 2 in addition to the projection lens 10, and only the auxiliary lens 11R for R light is installed. Also, the projection lens 10 has a 4
The fourth lens group G4 is composed of eight lenses L11 to L44 grouped into one lens group G1 to G4, and the fourth lens group G4 is similar to the above-described projection zoom lens.
41 and a rear group G42. Further, the projection zoom lens of the present example includes a first lens group G1.
Lens L11 and the lens L21 of the second lens group G2
As a plastic lens.
Of the lens L11 of the lens group G1 on the screen side (R
1) is made aspherical.

As described above, the projection zoom lens according to the present invention uses the auxiliary lens 11 to
The number of components can be reduced, and furthermore, it is not necessary to configure each group with two lenses for achromatism or to adopt a doublet type lens. Therefore, the material of the lens can be freely selected, and it is possible to further reduce the cost by adopting a plastic lens for a lens having a large aperture such as the first and second lens groups as in this example. it can. Further, by adopting a plastic lens, it is easy to make the lens surface aspherical, so that the cost can be reduced and the imaging performance of the projection zoom lens can be improved.

The detailed data of each lens is as shown below.

Lens data iridini vi 1: 72.770 2.00 1.49140 57.82 Lens L11 2: 26.840 D2 3: 45.998 10.00 1.49140 57.82 Lens L21 4: -78.539 0.20 5: INF D5 Aperture S 6: 31.882 5.10 1.84666 23.78 Lens L31 7 : 161.000 1.20 8: 134.695 6.00 1.76182 26.61 Lens L32 9: 21.745 D9 10: -18.813 2.00 1.84666 23.78 Lens L41 11: 96.720 9.60 1.62041 60.34 Lens L42 12: -24.788 D12 13: -926.987 6.30 1.74950 35.04 Lens L43 14: -67.514 0.20 15: 57.817 7.80 1.67003 47.20 Lens L44 16: -310.538 17: INF 33.00 1.51680 64.20 Prism 18: INF 19R: INF 1.00 1.51680 64.20 Auxiliary lens 11R 19G: INF 19B: INF 20R: -5700 Zoom state f D2 D5 D9 D12 FNo . Wide-angle end 37.40 52.81 0.80 13.82 0.80 2.50 Intermediate 43.0 42.43 10.57 11.54 3.70 2.66 Telephoto end 48.7 34.21 23.07 7.62 3.34 2.83 Aspherical surface count of surface 1 (lens L11) K = 0.000000 A = 0.972391 × 10 ^-6 , B = 0.190336 × 10 ⁻⁸ C = −0.367785 × 10 ⁻¹¹ , D = 0.340506 × 10 ⁻¹⁴ However, the aspheric surface formula is as follows.

X = (y ² / r) / [1+ {1- (1 + K) (y ² / r ² )} ^1/2 ] + Ay ⁴ + By ⁶ + Cy ⁸ + Dy ¹⁰ (3) Wavelength 546.1 nm 37.405 Focal length of non-auxiliary lens with wavelength of 610 nm (fc1) 37.446 Focal length of auxiliary lens with wavelength of 610 nm (fch1) 11400 Focal length of first lens group G1 (f1) -87.46 Second The focal length (f2) of the lens group G2 is (f2) 60.41 (1) is (fc1-fe) × fch1 = 467.4 for 610 nm, (2) is f1 / f2 = −1.45, which satisfies the above-mentioned condition. Lens.

FIG. 11 shows the spherical aberration, astigmatism, and distortion at the wide-angle end (a), the middle (b), and the telephoto end (c) of the projection zoom lens of the present example, respectively. 2 shows the chromatic aberration of magnification in the state of FIG. The projection zoom lens of this example is also a simple and low-cost configuration using eight projection lenses 10 and further using a lot of plastic lenses, but the chromatic aberration of magnification is contained in a very narrow range and color deviation is extremely small. This is a projection zoom lens. Further, the values of the aberrations shown in FIG. 11 are practically sufficiently good values at the wide-angle end, the middle position, and the telephoto end, respectively, and it is considered that the projection zoom lens has excellent imaging performance. Recognize.

Further, the projection zoom lens of this embodiment also has a short focal length range of 37.40 to 48.7 and an F-number of 2.
It is a bright lens of 5 to 2.83.

[0043]

As described above, the projection zoom lens of the present invention is provided with a projection lens having a configuration common to the light beams of the respective colors provided on the screen side and individually provided on the light source side of the light beams of the respective colors. An auxiliary lens is provided, so that it can enter the projection lens after performing a correction suitable for a light flux of each wavelength so that lateral chromatic aberration does not occur on the auxiliary lens side. Therefore, the projection lens has no burden of chromatic aberration correction, and can achieve high imaging performance with an extremely simple and simple configuration. Therefore, by using the projection zoom lens of the present invention, it is possible to remove magnification chromatic aberration corresponding to high resolution while having a simple configuration with a small number of components. A compatible projection zoom lens can be provided. Therefore, by using the projection zoom lens of the present invention, a light valve of an image forming apparatus such as a liquid crystal as an output device of a personal computer can sufficiently cope with high resolution in the future. A projector device that can be supplied at low cost can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a projection zoom lens according to a first embodiment of the present invention.

FIG. 2 is a diagram showing the arrangement of the lens of the projection zoom lens shown in FIG. 1 at each of a wide-angle end (a), a telephoto end (c), and an intermediate state (b).

FIG. 3 is a diagram illustrating various aberrations of the lens according to Example 1, illustrating aberrations at a wide-angle end (a), a telephoto end (c), and an intermediate state (b).

FIG. 4 is a diagram illustrating chromatic aberration of magnification of the lens of Example 1, showing aberrations at each of a wide-angle end (a), a telephoto end (c), and an intermediate state (b).

FIG. 5 is a diagram illustrating a configuration of a projection zoom lens according to a second embodiment of the present invention.

FIG. 6 is a diagram showing the arrangement of the lens of the projection zoom lens shown in FIG. 5 at each of a wide-angle end (a), a telephoto end (c), and an intermediate state (b).

FIG. 7 is a diagram illustrating various aberrations of the lens according to Example 2, illustrating aberrations at a wide-angle end (a), a telephoto end (c), and an intermediate state (b).

FIG. 8 is a diagram showing chromatic aberration of magnification of the lens of Example 2, showing aberrations at each of a wide-angle end (a), a telephoto end (c), and an intermediate state (b).

FIG. 9 is a diagram illustrating a configuration of a projection zoom lens according to a third embodiment of the present invention.

10 is a diagram showing the arrangement of the lens of the projection zoom lens shown in FIG. 9 at each of a wide-angle end (a), a telephoto end (c), and an intermediate state (b).

FIG. 11 is a diagram illustrating various aberrations of the lens of Example 3, illustrating aberrations at each of a wide-angle end (a), a telephoto end (c), and an intermediate state (b).

FIG. 12 is a diagram illustrating chromatic aberration of magnification of the lens according to the third embodiment, showing aberrations at each of a wide-angle end (a), a telephoto end (c), and an intermediate state (b).

FIG. 13 is a diagram illustrating a configuration example of a liquid crystal projector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Projection zoom lens 2 Dichroic prism 3 Liquid crystal panel 4 Reflection mirror 5 Dichroic mirror 6 Light source 7 Image forming device 8 Projector device 9 Screen 10 Projection lens 11 Auxiliary lenses G1 to G4 Lens group L11 to L44.

Claims (10)

[Claims] 1. A zoom lens for projecting a color image having a telecentric entrance side, comprising a plurality of zoomable projection lenses common to the red, green and blue light beams arranged on a screen side. Alternatively, a projection zoom lens having an auxiliary lens disposed on a blue light source side. 2. The projection zoom lens according to claim 1, wherein the auxiliary lens for red and the auxiliary lens for blue having different curvatures are arranged on the side of the red and blue light sources, respectively. 3. The projection zoom lens according to claim 1, wherein the auxiliary lens is a single lens. 4. The projection lens according to claim 1,
In order from the screen side, a first lens group having a single refractive power and a second lens group having a single refractive power and a third lens group having a negative refractive power. Of the fourth power of
A zoom lens for projection, comprising: a lens group; and zooming is possible by moving the second and third lens groups. 5. The zoom lens system according to claim 4, wherein the fourth lens group includes a front group on a screen side and a rear group on an incident side, and controls an interval between the front group and the rear group during zooming. A projection zoom lens, characterized in that it is possible. 6. The projection zoom lens according to claim 4, wherein a screen side of the first lens group is aspherical. 7. The projection lens according to claim 1, wherein a focal length fe of the projection lens at a wavelength of 546.1 nm, a focal length fc of the projection lens at a wavelength of 610 nm or 460 nm,
A focal length fch of a wavelength of 610 nm or 460 nm of the auxiliary lens satisfies the following expression. 250 <| (fc−fe) × fch | <1000 8. The projection system according to claim 4, wherein a focal length f1 of the first lens unit and a focal length f2 of the second lens unit of the projection lens satisfy the following expression. Zoom lens. −2.5 <(f1 / f2) <− 0.5 9. A projection zoom lens according to claim 1, further comprising: an image forming apparatus capable of supplying projection images of red, green, and blue to an incident side of the projection zoom lens. Characteristic projector device. 10. The dichroic prism according to claim 9, further comprising a dichroic prism capable of synthesizing the projection images into one, wherein the projection lens is disposed on a screen side of the dichroic prism. A projector device, which is disposed on the image forming apparatus side.