JPH06160708A - Projection lens and projection display device - Google Patents

Abstract

(57) [Abstract] [Purpose] The present invention relates to a projection lens having a wide aperture, a large aperture, and telecentricity, and a projection display device using this projection lens. Provided is a projection display device that displays a projection image of high image quality. [Structure] A first lens group G1 having negative power, a second lens group G2 having positive power, and a third lens group G3 having positive power including an aspherical surface having a weaker peripheral portion than a central portion in order from the screen side. Deploy. By arranging the third lens group G3 in the vicinity of the light valve, telecentricization and distortion aberration correction can be satisfactorily achieved without deteriorating the balance of various aberrations of the entire system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection lens for enlarging and projecting an optical image on a light valve onto a screen, and a projection type display device using this projection lens.

[0002]

2. Description of the Related Art In order to obtain a large-screen image, a method of forming an optical image according to an image signal on a light valve, irradiating the optical image with light, and enlarging and projecting it on a screen by a projection lens is better than before. Are known. Recently, attention has been paid to a projection display device that uses a liquid crystal display device as a light valve.

A schematic structure of a projection type display device using this liquid crystal display device is shown in FIG. The light emitted from the light source 1 passes through the liquid crystal display device 2 and enters the projection lens 3. The liquid crystal display device 2 includes an incident side polarization plate 4, a liquid crystal cell 5, and an emission side polarization plate 6. The liquid crystal cell 5 is one in which a twisted nematic liquid crystal 9 is sealed between two glass substrates 7 and 8, and matrix-shaped transparent electrodes are provided on the side surfaces of the liquid crystal layer of the glass substrates 7 and 8. The absorption axes of the incident-side polarization plate 4 and the emission-side polarization plate 6 are orthogonal to each other and form an angle of 45 ° with respect to the vertical scanning direction. When no voltage is applied to the transparent electrode, the linearly polarized light emitted from the incident side polarization plate is rotated by 90 ° in the liquid crystal cell 5 due to the optical rotatory power, so that the transmittance becomes maximum. When a voltage is applied, the optical rotatory power decreases according to the voltage, and the transmittance decreases. In this way, an optical image corresponding to the video signal is formed on the liquid crystal display device 2 as a change in transmittance, and this optical image is enlarged and projected on the screen 10 by the projection lens 3.

[0004]

The transmission efficiency of a liquid crystal display device for a light beam emitted from a light source is increased, and an optical image formed on the liquid crystal display device according to a video signal is displayed on a screen with high contrast. For projection, since the liquid crystal display device has a viewing angle dependency, a light beam incident on the liquid crystal display device at a certain angle must be used as a projection light beam. Therefore, in order to improve the uniformity of contrast, it is desirable that the projection lens has telecentricity so that the off-axis chief ray is parallel to the optical axis.

Further, since the liquid crystal display device is driven by using matrix electrodes, it is difficult to electrically correct the graphic distortion of the projected image. Therefore, the distortion of the projection lens needs to be as small as possible.

However, the above performance required for the projection lens makes it difficult to widen the angle of view of the projection lens which is required for downsizing the set size of the projection display device. .

In view of the above problems, the present invention provides a projection lens having a wide field angle, small distortion, telecentricity, and a large aperture, and excellent compactness and brightness using the projection lens. The present invention provides a projection display device that displays a high-quality projected image.

[0008]

To achieve this object, the first projection lens of the present invention irradiates light emitted from a light source to a light valve forming an optical image as a change in transmission efficiency according to a video signal. , A projection lens for transmitting and enlarging and projecting the optical image on the light valve onto the screen,
The first lens group having negative power, the second lens group having positive power, and the third lens group having positive power including an aspherical surface having weaker power in the peripheral portion than the central portion are provided in order from the screen side to provide telecentricity. I have.

The second projection lens of the present invention irradiates and transmits the light emitted from the light source to the light valve that forms an optical image as a change in transmission efficiency according to the image signal, and transmits the light image on the light valve. Is a projection lens for enlarging and projecting light onto a screen, and in order from the screen side, the first lens group having negative power, the second lens group having positive power, the dichroic prism, and the power of the peripheral portion weaker than that of the central portion. It has a positive power third lens group including a spherical surface, and has telecentricity.

A first projection display device of the present invention comprises a light source, a color separation optical means, a field lens, three light valves for forming an optical image as a change in transmission efficiency according to a video signal, and 3 The light emitted from the light source is separated into three primary color lights of blue, green and red by the color separation optical means, and the respective three primary color lights illuminate the corresponding light valves and are formed on the light valve. Each of the formed optical images is enlarged and projected on the screen by three projection lenses, and the above-mentioned first projection lens is used as the projection lens.

The second projection type display device of the present invention is
A light source, a color separation optical unit, a field lens, and an optical image are formed as a change in transmission efficiency according to a video signal.
Two light valves, a color synthesizing unit, and a projection lens are provided, and the light emitted from the light source is blue by the color separation optical unit.
The light is decomposed into three primary color lights of green and red, each of the three primary color lights irradiates a corresponding light valve, and the respective optical images formed on the light valve are combined into one by color combining means and then projected. The image is enlarged and projected on the screen by the lens, and the second projection lens is used as the color synthesizing unit and the projection lens.

[0012]

The first lens group and the second lens group of the projection lens of the present invention constitute a retrofocus type lens, and it is possible to achieve a wide angle of view without reducing the peripheral light quantity.
However, generally, when trying to reduce the F number with a wide-angle lens, off-axis aberrations such as distortion, astigmatism, and chromatic aberration of magnification tend to occur, and when trying to use telecentricity, the lens diameter increases and the overall lens system length increases. Prone.

Therefore, by disposing the third lens group having an aspherical surface in the vicinity of the liquid crystal display device, it is possible to favorably correct the off-axis aberration with almost no adverse effect on the compensation of the spherical aberration and the axial chromatic aberration. You can Further, the aspherical shape of the third lens group having the positive power makes it possible to favorably achieve telecentricity and especially distortion correction by making the power of the peripheral portion weaker than the power of the central portion. Further, as described above, since the third lens group arranged near the liquid crystal display device is telecentric, a compact structure can be achieved without increasing the lens diameter of the second lens group.

As is apparent from the above, the advantages of the projection lens of the present invention include a wide angle of view, a small distortion, a telecentric property, a large aperture, and the use of this projection lens. The projection type display device is excellent in compactness and can display a bright and high quality projected image.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

The construction of the first embodiment is shown in FIG. 1 and specific numerical values are shown in Table 1.

[0017]

[Table 1]

G1 is a first lens group, G2 is a second lens group, G3 is a third lens group, and L _i is an i-th lens. r _j is the radius of curvature of the j-th surface, d _j is the distance between the j-th surface and the next surface, n _i and ν _i are the refractive index and the Abbe number of the i-th lens at the e-line, respectively. f is the total focal length of the entire system, F
Is an F number, ω is a half angle of view on the screen side, and m is a magnification.

The first lens group G1 is, in order from the screen side, a first meniscus lens having a convex surface facing the screen side.
Lens L _1, second lens L ₂ of a negative meniscus lens having a convex surface directed toward the screen side, a third lens L ₃ of the negative meniscus lens having a convex surface directed toward the screen side, a second
The lens group G2 includes a fourth lens L _{4 which is} a positive meniscus lens having a concave surface facing the screen side, a fifth lens L _{5 which is} a biconcave lens, a sixth lens L _{6 which is} a positive meniscus lens having a concave surface facing the screen side, and a biconvex lens. is composed of a seventh lens L _7, the third lens group G3 is composed of the eighth lens L ₈ of the positive lens having a power is weak aspheric peripheral portion than in the center.

The aspherical shape of the eighth lens unit L ₈ is given by the following equation.

[0021]

[Equation 5]

Here, h is the height from the optical axis, S is the sag amount at the height h of the lens surface, κ _j is the conic constant, AD ′ _j ,
AD _j , AE _j , AF _j , and AG _j are third-order, fourth-order, and sixth-order, respectively.
These are the aspherical coefficients of the 8th, 10th, and 10th orders.

By constructing the first lens group G1 and the second lens group G2 as retrofocus type lenses, a wide angle of view can be achieved without a reduction in the amount of peripheral light, the projection distance is shortened, and the set is compact. Can be realized.

However, retrofocus lenses generally tend to cause off-axis aberrations such as distortion, astigmatism, and chromatic aberration of magnification, and when they are made to be telecentric and the F number is made small, these off-axis aberrations are improved. It is difficult to correct.

[0025] Therefore, the projection lens of the present invention is the third lens group G3 is provided in the vicinity of the liquid crystal display device, disposing the eighth lens L ₈ weak power in the peripheral portion than the central portion to the third lens group G3 is doing. Eighth lens L ₈ the can by a positive power to be telecentric without increasing the lens diameter of the second lens unit G2, in particular negative by weakening the power of the peripheral portion than the central portion It is possible to excellently correct distortion that tends to occur in the direction. Eighth lens L ₈
Is disposed in the vicinity of the liquid crystal display device, so that the above object can be achieved with almost no adverse effect on axial aberrations such as spherical aberration and axial chromatic aberration.

Further, in order to realize the desired characteristics of the projection lens of the present invention, it is necessary to satisfy the following conditions.

[0027]

[Equation 6]

[0028]

[Equation 7]

Here, f is a composite focal length of the entire projection lens system, f _G1 is a composite focal length of the first lens group G1, and d ₆ is an air gap between the first lens group G1 and the second lens group G2. is there.

The condition of (Equation 6) limits the combined focal length f _G1 of the first lens group _G1 to a certain range. When the value goes below the lower limit, it becomes difficult to set the distance d ₁₄ between the second lens group G2 and the third lens group G3 to a desired distance, and when trying to realize telecentricity, the lens diameter of the second lens group G2 becomes large. It is not preferable in terms of size reduction, weight reduction, and cost reduction. On the other hand, if the upper limit is exceeded, the load on the second lens group G2 and the third lens group G3 increases, and the first lens group G1
It becomes difficult to correct off-axis aberrations that occur in 1.

The condition of (Equation 7) is that the first lens group G1 and the second lens group G1
The distance d ₆ from the lens group G2 is limited to a certain range. When the value goes below the lower limit, it becomes difficult to set the distance d ₁₄ between the second lens group G2 and the third lens group G3 to a desired distance, and the load on the second lens group G2 or the third lens group G3 is made to be telecentric. However, if it is attempted to realize telecentricity by increasing the value of, it becomes difficult to correct off-axis aberrations in good balance. If the upper limit is exceeded, the total length of the projection lens becomes long, which causes a reduction in the amount of peripheral light.

An aberration diagram of the projection lens shown in (Table 1) is shown in (FIG. 2). In spherical aberration, the solid line is the e-line (54
Aberration at 6.07 nm, broken line is F line (486.1)
3 nm), and in astigmatism, the solid line shows the aberration in the sagittal direction, and the broken line shows the aberration in the meridional direction. As can be seen from (FIG. 2), the various aberrations are corrected in good balance. In particular, the distortion aberration is suppressed to within ± 0.1% by the effect of the aspherical surface of the third lens G1, and is corrected to such a degree that it can be practically ignored. The F number is as bright as 2.5 and the half angle of view is ω = 35.8 °, which is a wide angle of view. Also,
Telecentricity means that the angle between the chief ray and the optical axis is ±
The angle is within 0.5 °, and the uniformity of the projected image of the projection display device using the liquid crystal display device as the light valve can be realized.
Further, the aperture efficiency at the maximum angle of view is as high as 95% or more, and a sufficient peripheral light amount can be secured.

The projection lens of the present invention comprises the second lens group G2.
It is also possible to dispose a plane mirror between the second lens group G3 and the third lens group G3. This configuration is shown in (FIG. 3). M is a plane mirror, and P is a liquid crystal panel. By doing so (FIG. 3), the projection optical system of the projection display device can be made more compact. In this case, the third lens group G3
According to the effective display area of the liquid crystal panel P, the eighth lens L ₈ may be formed by cutting a part of its outer shape into, for example, a rectangular shape as indicated by the dotted line in FIG.

If the eighth lens L ₈ of the third lens group G3 is a plastic lens, the weight can be reduced, and the aspherical surface and the outer shape can be easily processed by integral molding or the like.

For adjusting the focus of the projection lens of the present invention, it is preferable to fix the third lens group G3 and finely move the first lens group G1 and the second lens group G2 in the optical axis direction. Third lens group G
The lens No. 3 is arranged near the liquid crystal display device and has a long distance from the second lens group G2, so that focus adjustment can be performed with almost no deterioration in aberration balance. By doing so, in the case of the configuration in which the plane mirror M is arranged as shown in (FIG. 3), the lens barrel mechanism of the projection lens can be simplified.

Next, the configurations of the second and third embodiments are shown in (FIG. 4) and (FIG. 5), respectively, and specific numerical values are shown in (Table 2) and (Table 3). Aberration diagrams in each example are shown in (FIG. 6) and (FIG. 7), respectively. The symbols are the same as in the first embodiment.

[0037]

[Table 2]

[0038]

[Table 3]

The second embodiment has the same construction as that of the first embodiment, and the third embodiment is based on the first embodiment with the first lens group G1 in order from the screen side and the convex surface on the screen side. It is composed of a negative meniscus lens facing toward, a positive lens, and a negative meniscus lens having a convex surface facing toward the screen. Similar to the first embodiment, the second and third embodiments also have a wide field angle, a small F number, telecentricity, and various aberrations are well balanced.

The projection lens of the present invention can also be constructed by disposing a dichroic prism between the second lens group G2 and the third lens group G3. Specific values are shown in (Table 4) in the configuration of the fourth embodiment (FIG. 8). The symbols are the same as in the first embodiment.

[0041]

[Table 4]

A dichroic prism DP is arranged between the second lens group G2 and the third lens group G3, and the constructions of the first lens group G1, the second lens group G2 and the third lens group G3 are the same as those of the first embodiment. It is the same.

An aberration diagram of the projection lens shown in (Table 4) is shown in (FIG. 9). As can be seen from FIG. 9, various aberrations are corrected in a well-balanced manner. The F number is as bright as 2.5 and the half angle of view is ω = 35.8 °, which is a wide angle of view. Also,
Telecentricity means that the angle between the chief ray and the optical axis is ±
Within 0.5 °, the aperture efficiency at the maximum angle of view is 95.
%, Which is extremely high, and sufficient peripheral light quantity can be secured.

Similar to the first embodiment, the third lens group G3
If the eighth lens L ₈ is a plastic lens and the outer shape is, for example, a rectangular shape according to the effective display area of the liquid crystal display device, it is advantageous in reducing the size and weight and the cost.

Focus adjustment may be performed by fixing the dichroic prism DP and the third lens group G3, and finely moving the first lens group G1 and the second lens group G2 in the optical axis direction.

Next, the constitutions of the fifth and sixth embodiments are shown in FIG. 10 and FIG. 11, respectively, and concrete numerical values are shown in Table 5,
It shows in (Table 6). Aberration diagrams in each example are shown in (FIG. 12) and (FIG. 13), respectively. The symbols are the same as in the first embodiment.

[0047]

[Table 5]

[0048]

[Table 6]

The fifth embodiment has the same construction as the fourth embodiment, and the sixth embodiment is based on the fourth embodiment, in which the first lens group G1 is arranged in order from the screen side and the convex surface is arranged on the screen side. It is composed of a negative meniscus lens facing toward, a positive lens, and a negative meniscus lens having a convex surface facing toward the screen. Similar to the fourth embodiment, the fifth and sixth embodiments have a wide field angle, a small F number, telecentricity, and various aberrations are well balanced.

FIG. 14 shows the construction of an embodiment of the projection type display device according to the present invention, in which 11 is a light source, 15 is a color separation optical system, 16, 17 and 18 are field lenses, and
Reference numerals 9, 20, 21 are liquid crystal panels, and reference numerals 29, 30, 31 are projection lenses.

The liquid crystal panels 19, 20 and 21 are each composed of an incident side polarization plate, a liquid crystal cell using twisted nematic liquid crystal, and an emission side polarization plate. In addition, the projection lenses 29, 3
0 and 31 are those shown in (FIG. 1) and (Table 1), respectively, and are flat mirrors between the first and second lens groups 26, 27 and 28 and the third lens groups 22, 23 and 24. 25 are arranged.

The light emitted from the light source 11 is separated into three colors of blue, green and red by the color separation optical system 15 composed of three dichroic mirrors 12, 13 and 14, and the three colors of light correspond to each other. Field lens 16, 17, 18
And illuminates the liquid crystal panels 19, 20 and 21. The optical image on the liquid crystal panel 19, 20, 21 is the projection lens 2
It is enlarged and projected on a screen (not shown) by 9, 30, 31.

The internal structure of the cabinet of the projection display apparatus of the present invention is shown in FIG. A screen 42 is arranged on the upper front side of the cabinet 41, and a projector 43 is arranged on the lower rear side.
Are arranged. The configuration of the projector 43 is the same as that shown in (FIG. 6). The light emitted from the projector 43 passes through the plane mirrors 44 and 45 to form a projected image on the screen 42.

The structures shown in FIGS. 14 and 15 can be made compact by using the projection lenses 29, 30, 31 shown in FIG.
A high-resolution projected image can be displayed. Furthermore, the projection lens 2
Since 9, 30, and 31 have telecentricity, even when the liquid crystal panels 19, 20, and 21 have viewing angle dependence, it is possible to display a projected image with excellent uniformity of contrast.

In general, a liquid crystal panel using twisted nematic liquid crystal can display a projected image with a higher contrast when the incident angle of an incident light beam is slightly inclined rather than 0 °. When the F number of the illumination optical system including the light source 11, the color separation optical system 15, and the field lenses 16, 17, and 18 is larger than the F numbers of the projection lenses 29, 30, and 31, the optical axis of the illumination optical system is set to Projection lens 29,3
When the liquid crystal panels 19, 20 and 21 are arranged so as to be slightly inclined with respect to the optical axes of 0 and 31, and the light that is obliquely illuminated is used as the projection image, a high-contrast projection image can be displayed without impairing the brightness. Since the projection lens of the present invention has a large F number of 2.5, it is possible to realize high brightness and high contrast without any practical problems.

FIG. 16 shows the construction of another embodiment of the projection type display device according to the present invention, in which 51 is a light source, 55 is a color separation optical system, 58, 59 and 60 are field lenses.
Reference numerals 61, 62 and 63 are liquid crystal panels, and 69 is a projection lens.

The liquid crystal panels 61, 62 and 63 are composed of an incident side polarization plate, a liquid crystal cell using twisted nematic liquid crystal, and an emission side polarization plate. The projection lens 69 is basically the one shown in (FIG. 8) and (Table 4).
It is composed of one third lens group 64, 65, 66, a color combining optical system 67 composed of one dichroic prism, and one first and second lens group 68.

The light emitted from the light source 51 is divided into blue, green and red by a color separation optical system 55 composed of three dichroic mirrors 52, 53 and 54 and plane mirrors 56 and 57.
The color lights are separated into three colors, and the lights of the three colors are transmitted through the corresponding field lenses 58, 59 and 60, and the liquid crystal panels 61 and 6
Irradiate 2,63. The optical images on the liquid crystal panels 61, 62 and 63 are combined into one by the projection lens 69 and then enlarged and projected onto a screen (not shown).

The configuration shown in FIG. 16 also has a projection lens 69.
By using the one shown in FIG. 8 (FIG. 8), a compact structure can be achieved, and a bright and high-resolution projected image can be displayed. In addition, the first and second lens groups 68 of the projection lens 69
Since it can be one, it is possible to further reduce the weight. Further, since the projection lens 69 has telecentricity, it is possible to display a projected image with excellent contrast uniformity even when the liquid crystal panels 61, 62, 63 have viewing angle dependence.

In the case of the configuration shown in FIG. 16 also, since the F number of the projection lens is 2.5, which is a large aperture, the light source 51, the color separation optical system 55, the plane mirrors 56 and 57, and the field lens 58. , 59, 60 are arranged so that the optical axis of the illumination optical system is slightly tilted with respect to the optical axis of the projection lens 69, and the liquid crystal panels 61, 62, 63 are provided with a projection image of the light illuminated obliquely. If used, a high-contrast projected image can be displayed without impairing the brightness.

In each of the projection display devices of this embodiment, the liquid crystal display device using twisted nematic liquid crystal is used as the light valve. However, other types of liquid crystal display devices and those using electro-optic crystal are used. Any transmissive type that forms an optical image as a change in characteristics can be used as a light valve.

[0062]

As described above, according to the present invention, it is possible to provide a projection lens having a wide angle of view, a small distortion, a telecentric property, and a large aperture. Also,
By using this projection lens, it is possible to provide a projection type display device which is excellent in compactness, is bright, and displays a projection image of high quality, and is extremely effective.

[Brief description of drawings]

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

FIG. 2 is an aberration diagram in the first example of the projection lens of the present invention.

FIG. 3 is a schematic configuration diagram showing an arrangement example of a projection lens of the present invention.

FIG. 4 is a sectional configuration diagram of a projection lens according to a second embodiment of the present invention.

FIG. 5 is a sectional configuration diagram of a projection lens according to a third embodiment of the present invention.

FIG. 6 is an aberration diagram in the second example of the projection lens of the present invention.

FIG. 7 is an aberration diagram of a projection lens according to a third embodiment of the present invention.

FIG. 8 is a sectional configuration diagram of a projection lens according to a fourth embodiment of the present invention.

FIG. 9 is an aberration diagram of a projection lens according to a fourth embodiment of the present invention.

FIG. 10 is a sectional configuration diagram of a projection lens according to a fifth embodiment of the present invention.

FIG. 11 is a sectional configuration diagram of a projection lens according to a sixth embodiment of the present invention.

FIG. 12 is an aberration diagram of a projection lens according to a fifth example of the present invention.

FIG. 13 is an aberration diagram in the sixth example of the projection lens of the present invention.

FIG. 14 is a perspective view showing a configuration of a projector of the projection display device of the present invention.

FIG. 15 is a side cross-sectional configuration diagram showing a configuration of an optical system in a cabinet of the projection display apparatus of the present invention.

FIG. 16 is a schematic configuration diagram showing a configuration of a projector of another projection display device of the present invention.

FIG. 17 is a schematic configuration diagram of a conventional projection display device.

[Explanation of symbols]

 11, 51 Light source 15, 55 Color separation optical system 19, 20, 21, 61, 62, 63 Liquid crystal panel 29, 30, 31, 69 Projection lens

Claims (26)

[Claims] 1. A projection lens for irradiating and transmitting light emitted from a light source to a light valve forming an optical image as a change in transmission efficiency according to a video signal, and enlarging and projecting the optical image on the light valve on a screen. In addition, a first lens group having negative power, a second lens group having positive power, and a third lens group having positive power including an aspherical surface having a weaker peripheral portion than the central portion are arranged in order from the screen side. A projection lens having a telecentric property. 2. The projection lens according to claim 1, which satisfies the following conditions. [Equation 1] [Equation 2] Here, f is a composite focal length of the entire system, f _G1 is a composite focal length of the first lens group, and d ₆ is an air gap between the first lens group and the second lens group. 3. The first lens group comprises, in order from the screen side, a positive meniscus lens having a convex surface facing the screen side, a negative meniscus lens having a convex surface facing the screen side, and a negative meniscus lens having a convex surface facing the screen side. The projection lens according to claim 1, wherein: 4. The first lens group comprises, in order from the screen side, a negative meniscus lens having a convex surface facing the screen side, a positive lens, and a negative meniscus lens having a convex surface facing the screen side. Item 1. The projection lens according to item 1. 5. The projection according to claim 1, wherein the second lens group comprises, in order from the screen side, a positive lens, a biconcave lens, a positive meniscus lens having a concave surface facing the screen, and a biconvex lens. lens. 6. The projection lens according to claim 1, wherein the third lens group is arranged near the light valve. 7. The projection lens according to claim 1, wherein the third lens group is a plastic lens. 8. The projection lens according to claim 1, wherein the third lens group has a rectangular outer shape. 9. The projection lens according to claim 1, wherein a plane mirror is arranged between the second lens group and the third lens group. 10. The projection lens according to claim 1, wherein the third lens group is fixed, and the focus adjustment is performed by moving the first lens group and the second lens group in the optical axis direction. . 11. A projection lens for irradiating and transmitting light emitted from a light source to a light valve that forms an optical image as a change in transmission efficiency according to a video signal, and magnifying and projecting the optical image on the light valve onto a screen. In addition, from the screen side, in order from the screen side, the first lens group having negative power, the second lens group having positive power, the dichroic prism, and the third lens having positive power including an aspherical surface having weaker power in the peripheral portion than in the central portion.
A projection lens comprising a lens group and having telecentricity. 12. The projection lens according to claim 11, which satisfies the following conditions. [Equation 3] [Equation 4] Here, f is a composite focal length of the entire system, f _G1 is a composite focal length of the first lens group, and d ₆ is an air gap between the first lens group and the second lens group. 13. The first lens group comprises, in order from the screen side,
The projection lens according to claim 11, comprising a positive meniscus lens having a convex surface facing the screen side, a negative meniscus lens having a convex surface facing the screen side, and a negative meniscus lens having a convex surface facing the screen side. 14. The first lens group comprises, in order from the screen side,
The projection lens according to claim 11, comprising a negative meniscus lens having a convex surface facing the screen side, a positive lens, and a negative meniscus lens having a convex surface facing the screen side. 15. The second lens group, in order from the screen side,
The projection lens according to claim 11, comprising a positive lens, a biconcave lens, a positive meniscus lens having a concave surface facing the screen, and a biconvex lens. 16. The projection lens according to claim 11, wherein the third lens group is arranged near the light valve. 17. The projection lens according to claim 11, wherein the third lens group is a plastic lens. 18. The projection lens according to claim 11, wherein the third lens group has a rectangular outer shape. 19. The focus adjustment is performed by fixing the third lens group and the dichroic prism and moving the first lens group and the second lens group in the optical axis direction. Projection lens. 20. A light source, a color separation optical means, a field lens, three light valves that form an optical image as a change in transmission efficiency according to a video signal, and three projection lenses. The emitted light is decomposed into the three primary color lights of blue, green and red by the color separation optical means,
The primary color light illuminates the corresponding light valve,
The projection display device according to claim 1, wherein each optical image formed on the light valve is enlarged and projected on a screen by the three projection lenses, and the projection lens according to claim 1 is used as the projection lens. 21. The projection display device according to claim 20, wherein the illumination optical system including the light source, the color separation optical means and the field lens is configured to illuminate the light valve obliquely. 22. The projection display device according to claim 20, wherein the light valve is a liquid crystal display device. 23. A light source, a color separation optical means, a field lens, three light valves for forming an optical image as a change in transmission efficiency according to a video signal, a color synthesizing means, and a projection lens. The light emitted from the light source is separated into three primary color lights of blue, green and red by the color separation optical means,
The light of each of the three primary colors illuminates the corresponding light valve, and the respective optical images formed on the light valve are combined into one by the color combining means, and then enlarged on the screen by the projection lens. A projection display device, comprising: the projection lens according to claim 11, which is projected and used as the color synthesizing means and the projection lens. 24. The projection display device according to claim 23, wherein the projection lens includes one first lens group, one second lens group, and three third lens groups. 25. The projection display apparatus according to claim 23, wherein an illumination optical system including a light source, a color separation optical means, and a field lens is configured to illuminate the light valve obliquely. 26. The projection display device according to claim 23, wherein the light valve is a liquid crystal display device.