JP2000171702A - Projection lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a projection lens having the wide angle of view, a short projection distance, long back focus, large off-axis light quantity and telecentricity, and having little illuminance irregularity and little image distortion on a screen by specifying the constitution of a lens group. SOLUTION: This projection lens 20 is constituted by arraying a 1st lens group O, a diaphragm 400 and a 2nd lens group 300 in order from a large conjugate side to a small conjugate side. The 1st lens group O is provided with a 1A-th lens group 100 and a 1B-th lens group 200 in order from a long conjugate side to a short conjugate side and has positive refractive power as a whole. In such a case, the lens group 100 is constituted by arranging negative meniscus lenses 101 and 102, a biconcave lens 103 and a positive lens 104. In the lens group 200, one positive lens 201 is arranged. Furthermore, a combined lens 301, positive lenses 304 and 305 and an aspherical lens 306 are arranged in order from the long conjugate side to the short conjugate side in the lens group 300, which has a positive refractive index as a whole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a projection lens, and is suitably applied to, for example, a projection lens provided in a projection device of a projection display device.

[0002]

2. Description of the Related Art In recent years, projection display devices have become widespread. As one of such projection display devices, there is known a so-called rear projection type display device which performs display by projecting image light from a rear side of a transmission type screen.

The above-mentioned rear projection type projection display device is called a so-called three-panel type.
2. Description of the Related Art There is known a device having a two-dimensional image display element corresponding to three colors of red, green, and blue (R, G, B). In such a three-panel projection display device, for example, a light beam obtained by collimating light from a white light source with a reflector or the like is separated into three color light beams of red, green, and blue by a color separation mirror. The light beams of the three colors are red, green, and blue (R, G,
Light is input to each two-dimensional image display element (for example, LCD; Liquid Crystal Display) formed according to the video electric signal of B). The image light obtained on each of the two-dimensional image display elements corresponding to these red, green, and blue is color-combined into white by a color-combining optical system, and is enlarged and projected on a transmission screen through a projection lens. You.

Further, as another projection display device of the three-plate type, a light source emitting light of three colors of red, green and blue is used.
A collimated light beam from a light (LED or laser, etc.) enters each two-dimensional image display element formed in accordance with red, green, and blue (R, G, B) video electric signals, respectively. The image light obtained on each of the two-dimensional image display elements corresponding to these red, green, and blue (R, G, B) is synthesized into white by a color synthesis optical system, and transmitted through a projection lens. There is also known an image projected on a screen in an enlarged manner.

There is also known a so-called single-panel projection display device having one two-dimensional image display element. One of the single-panel systems is that light sources of three colors of red, green, and blue are emitted or passed in a time-division manner, and red, green, and blue (R, G, B) drive of each video electric signal is 1
2. Description of the Related Art There is known a system in which a two-dimensional image display element is used to perform enlarged projection on a transmission screen via a projection lens. In addition, red, green, and blue (R,
G, B) after forming three color filters
There is also known a method in which white light is incident on one two-dimensional image display element, and the light that has passed through the two-dimensional image display element is enlarged and projected on a transmission screen via a projection lens. Furthermore, the following single plate system is also known. This is because by entering white light into three dichroic mirrors distributed at minute angles, a luminous flux separated into three colors of red, green, and blue (R, G, B) is obtained for each angle, One of two
The light enters the two-dimensional image display element. On the two-dimensional image display device, red, green, and blue (R, G,
A set of three pixels corresponding to B) is collimated by a minute lens corresponding to each set, and the pixels for each color are driven by a video electric signal corresponding to each path. Then, the light incident on each of the pixels is enlarged and projected on a transmission screen through a projection lens.

Further, regarding the lens, a wide-angle lens for a single-lens reflex camera having a long back focus is used as a lens having the same configuration as the projection lens provided in each of the above-described projection display devices, taking into account the limitation of the quick return mirror and the like. Photo lens and CRT (Cathode Ray Tub
Many wide-angle projection lenses for projection televisions according to e) have also been proposed.

[0007]

In the configuration of the projection display device as described above, an optical element such as a dichroic prism or a dichroic mirror may be arranged as a color combining optical system. When a reflective two-dimensional image element is used, an optical element such as a polarizing beam splitter prism or a polarizing beam splitter mirror may be arranged. In such a case, a so-called back focus, which corresponds to the distance from the two-dimensional image display element to the rearmost end of the projection lens, must be secured longer.

Further, as a projection display device,
When an enlarged image is formed on the entire transmissive screen with one projection device, the projection distance (for example, the distance from the exit end of the projection lens to the transmissive screen via the mirror) is reduced in order to make the projection display device itself compact. It is necessary to shorten the beam length). For that purpose, it is necessary to obtain a large screen by widening the angle of the projection lens and increasing the divergence angle of the emitted light.

Further, in order to reduce color unevenness on a screen on which image light is projected, a reflection type two-dimensional image element such as a dichroic prism and a dichroic mirror used in a color synthesizing optical system is used. As for the polarizing beam splitter prism or the polarizing beam splitter mirror to be used, it is better that the light beam angle width hitting these coated surfaces is fixed. Therefore, it is necessary to have telecentricity so that the off-axis principal ray of the projection lens is perpendicular to the two-dimensional display element. Here, the projection lens is located at the optical axis passing through the center of the two-dimensional display element. On the other hand, the two-dimensional display element itself has a high contrast direction in only one direction, whereas the two-dimensional display element itself is symmetric. For this reason, it is necessary to make an angle to the light flux itself irradiated to the two-dimensional display element.

A two-dimensional image display element usually includes an LC.
Although a display device such as D is employed, since the LCD is driven by using the matrix electrodes, it is difficult to correct the distortion of the projection lens unlike the case of using a CRT. That is, in the case of a CRT, it is relatively easy to correct the distortion of the projection lens by using a raster shape correction function such as a pincushion distortion correction. Such a raster distortion correction is not usually performed in a display device to be performed. Given the circumstances above,
It is desirable that the distortion of the projection lens be as small as possible. However, this is an obstacle to widening the angle of the projection lens and obtaining a long back focus. In other words, it has been found that if telecentricity is given while ensuring a wide angle and a long back focus as the projection lens, the overall length of the lens or the diameter of the lens tends to increase.

A wide-angle photographic lens for a single-lens reflex camera or a projection lens for a projection television using a CRT has an insufficient back focus, and the incident angle and the exit angle of an off-axis light beam are tight. At present, the amount of light is small.

In recent years, a high-resolution lens has been demanded in response to the high definition of a light valve as a light source. Color shift of pixels due to chromatic aberration of magnification has become a problem.

[0013]

In order to solve the above problems, the present invention provides a projection lens having a wide angle of view, a long back focus with a short projection distance, a large amount of off-axis light, and telecentricity. It is another object of the present invention to reduce illuminance unevenness, image distortion, and the like on a projection screen as much as possible, and to obtain as small a chromatic aberration of magnification as possible.

For this reason, as the projection lens, it is assumed that the first lens group and the second lens group are arranged in order from the long conjugate side to the short conjugate side and at a required interval before and after the stop. The first lens group includes, from the long conjugate side to the short conjugate side, a first A lens group including an aspheric lens located on the longest conjugate side, at least one or more negative meniscus lens, and at least a positive lens group. A first B lens group including a lens, the second lens group including a biconcave lens and a positive lens from the side closest to the stop; At least one or more positive lenses and an aspherical lens are provided so as to have a positive refractive power as a whole.

As a projection lens, a first lens group and a second lens group are arranged in order from a long conjugate side to a short conjugate side, and at a required interval before and after the stop. The first lens group includes, from a long conjugate side to a short conjugate side, a first A lens group including an aspheric lens located on the longest conjugate side and at least one or more negative meniscus lens. A first B lens group including a positive lens; and a second lens group including a cemented lens including a biconcave lens and a positive lens from the side closest to the stop. , At least one or more positive lenses and an aspheric lens are configured to have a positive refractive power as a whole. Then, the combined focal length of the whole system is F, the air-equivalent distance from the last lens surface of the second lens group to the small conjugate point when the projection magnification is the largest is BF, and the focal length of the first A lens group is F1A, the focal length of the first B lens group is F1B, the focal length of the second lens group is F2, the distance from the last lens surface of the first lens group to the diaphragm is DS1, and the distance from the diaphragm to the first lens surface of the second lens group is F1A. Distance of DS2,
Assuming that the front principal point position of the second lens group is HF2, 1.5 <BF / F <3.0 0.9 <-F1A / F <3.5 0.35 <HF2 / F2 <0.65 0.65 <DS2 / F <1.35 0.21 <DS1 / F1B <0.66.

As a projection lens, a first lens unit and a second lens unit are arranged in order from a long conjugate side to a short conjugate side and a required distance before and after the stop. The first lens group includes, from the long conjugate side to the short conjugate side, an aspheric lens located on the longest conjugate side, a negative meniscus lens convex on the long conjugate side, and a biconcave lens or a convex lens on the long conjugate side. 3 with meniscus lens
A first A lens group including three groups and a first B lens group including at least a positive lens are provided so as to have a positive refractive power as a whole, and the second lens group is arranged from the side closest to the diaphragm. And a cemented lens composed of a biconcave lens and a positive lens, at least one or more positive lenses, and an aspherical lens are provided so as to have a positive refractive power as a whole.

According to the above configuration, a long back focus and a short projection distance are secured, and the conditions for obtaining a projection lens that maintains telecentricity are satisfied.
In addition, the size of the entire lens system can be appropriately suppressed, and various aberrations can be easily corrected.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a projection lens according to an embodiment of the present invention will be described. The projection lens of the present embodiment will be described as being provided in a projection device of a rear projection type projection display device employing an LCD as a two-dimensional image display element.

The following description will be made in the following order. 1. Configuration of projection display device 1-1. Overall configuration 1-2. Internal configuration of projection device (first example) 1-3. Internal configuration of projection device (second example) 1-4. 1. Internal configuration of projection device (third example) Configuration of projection lens 2-1. Lens arrangement structure 2-2. Conditional expression 2-3. Numerical embodiments, etc.

1. Configuration of projection display device 1-1. Overall Configuration First, the overall configuration of a projection display device that can be configured by mounting a projection device including the projection lens of the present embodiment will be described.

FIG. 1 is an internal side view showing an example of the overall configuration of such a projection display device. In the projection display device 500 shown in this figure, a bent mirror 504 is provided on the back surface of the cabinet 501, and a transmissive screen 21 is provided on the front surface of the cabinet 501. The bent mirror 504 is
It is attached at an angle at which image light projected from the projection device 502 described below can be reflected and projected on the screen 504.

The projection device 502 is installed in the cabinet 501 as shown in FIG. In the cabinet 503 of the projection device 502, optical components such as a light source, a dichroic mirror, a liquid crystal panel block, and a dichroic prism (a light combining element), which will be described later, are arranged, and a light flux as image light is obtained by these operations. The luminous flux as image light obtained here is projected by the projection lens 20 and emitted as projection light 600.

In the projection display device 500 having such a structure, the projection light 600 is emitted upward from the projection lens 20 so as to be applied to the bending mirror 504. Then, the projection light 600 emitted from the projection lens 20 has its optical path bent by the bending mirror 504 and is irradiated on the screen 21. On the screen 21, an enlarged image obtained by the projection light projected from the projection lens 20 is displayed. For example, the viewer views the display image by looking at the screen 21 from a direction opposite to the direction where the projection lens 20 is arranged.

The projection display device to which the present invention can be applied is not limited to the configuration shown in FIG. 1. For example, the projection display device may be installed in a cabinet of the projection display device. May be changed as appropriate depending on the optical path changing direction of the projection lens.

1-2. Internal Configuration of Projection Apparatus (First Example) Next, the internal configuration of the projection apparatus 502 shown in FIG. 1 will be described with reference to FIG. FIG. 2 conceptually shows an internal structure as a first example of a projection device 502 on which the projection lens of the present embodiment can be mounted. Here, a part other than the screen 21 forms the projection device 502.

As a projection device 502 shown in FIG. 2, a lamp 1 as a light source, such as a metal halide lamp, is disposed at a focal position of a reflector 2 (parabolic mirror). Light emitted from the lamp 1 is reflected by the reflector 2, collimated so as to be substantially parallel to the optical axis, and emitted from the opening of the reflector 2. Of the light emitted from the opening of the reflector 2, unnecessary light in the infrared region and the ultraviolet region is reflected by the IR-UV cut filter 3.
As a result, only light rays effective for display are guided to various optical elements arranged at the subsequent stage.

In the subsequent stage of the IR-UV cut filter 3,
Subsequent to the multi-lens array 4, a multi-lens array 5 is provided. In this case, the multi-lens array 4 is a state in which a plurality of convex lenses having a similar outer shape equal to the aspect ratio of the effective aperture of each liquid crystal panel block, which is a light modulating means, are shifted in phase by, for example, ２. And has a flat shape arranged in a houndstooth check pattern. The multi-lens array 5 is of a plano-convex type in which a plurality of convex lenses 5a are formed on the side of the multi-lens array 4 facing the convex lenses. By arranging the multi-lens array 4 and the multi-lens array 5, I
The luminous flux passing through the R-UV cut filter 3 is efficiently
In addition, the light is uniformly applied to an effective opening of a liquid crystal panel block described later.

Between the multi-lens array 5 and the effective aperture of the liquid crystal panel block, the luminous flux from the lamp 1 is changed to red, green,
Dichroic mirrors 6 and 10 are arranged to separate blue light. In the example shown in this figure, first, the red light beam R is reflected by the dichroic mirror 6, and the green light beam G and the blue light beam B are transmitted. The traveling direction of the red light beam R reflected by the dichroic mirror 6 is turned by 90 ° by the mirror 7 and the red liquid crystal panel block 9
Is led to the condenser lens 8 in front of.

On the other hand, the green and blue luminous fluxes G and B transmitted through the dichroic mirror 6 are
Will be separated by That is, the green light flux G
Is reflected and bent in the traveling direction by 90 °, and guided to the condenser lens 11 in front of the liquid crystal panel 12 for green. Then, the blue light beam B passes through the dichroic mirror 10 and proceeds straight, and is guided to the condenser lens 17 in front of the blue liquid crystal panel 18 via the relay lens 13, the mirror 14, the inversion relay lens 15, and the mirror 16.

In this manner, the red, green, and blue luminous fluxes R, G, and B are supplied to the respective condenser lenses 8, 11, and 17 respectively.
Through the liquid crystal panel blocks 9, 12, and 18 for each color.
Is incident on. The liquid crystal panel blocks 9 and 1 of these colors
In Nos. 2 and 18, a liquid crystal panel is provided, and an incident-side polarizing plate for aligning the polarization direction of light incident on the front stage of the liquid crystal panel in a certain direction is provided. A so-called analyzer that transmits only light having a predetermined polarization plane of the emitted light is disposed at the subsequent stage of the liquid crystal panel, and the intensity of the light is modulated by a voltage of a circuit for driving the liquid crystal.

Generally, dichroic mirrors 6, 10
In order to make effective use of the above characteristics, the reflection and transmission characteristics of the P polarization plane are used. Therefore, the above-mentioned incident side polarizing plate in each of the liquid crystal panel blocks 9, 12, 18 is arranged so as to transmit a plane of parallel polarization in the plane of FIG. Each liquid crystal panel constituting the liquid crystal panel blocks 9, 12, 18 is, for example, of the TN type, and its operation is of, for example, a normally white type, and the analyzer is perpendicular to the plane of FIG. It is arranged to transmit polarized light.

Then, the liquid crystal panel blocks 9, 12, 1
The light flux of each color light-modulated by 8 is incident on each surface shown in a light combining element (cross dichroic prism) 19. This photosynthetic element is formed by combining reflection films 19a and 19b with a prism having a predetermined shape. The red light flux R in the photosynthesis element 19 is reflected by the reflection film 19.
a, and the blue light flux B is reflected by the reflection film 19b and is incident on the projection lens 20. The green light flux G is incident on the projection lens 20 so as to go straight through the light combining element 19 and pass therethrough. As a result, the light beams R, G, and B are incident on the projection lens 20 in a state of being combined into one light beam.

The projection lens 20 converts the light beam incident from the light combining element 19 into projection light, and projects it on, for example, a transmission type screen 21. In the present embodiment, actually, after the optical path is changed by 90 ° in the projection lens 20, the light is reflected by the bending mirror 504 provided in the projection display device, and then the light beam is projected onto the screen 21. Will be

1-3. Internal Configuration of Projection Apparatus (Second Example) FIG. 3 conceptually shows an internal structure as a second example of a projection apparatus 502 on which the projection lens 20 of the present embodiment can be mounted. In this figure, the same parts as those in FIG.

In this case, the light beam B is reflected by the dichroic mirror 6A at the subsequent stage of the multi-lens array 5, and the light beam R and the light beam G are passed. The light beam B reflected by the dichroic mirror 6A is reflected by the mirror 7A, and further reflected by the condenser lens 8A.
, And after being light-modulated through the liquid crystal panel block 9A for blue, the light enters the photosynthesis element 19A from the illustrated direction.

The light beam R and the light beam G that have passed through the dichroic mirror 6A are combined with the subsequent dichroic mirror 10A.
Is incident on. In this case, the dichroic mirror 10A
Then, the light beam R is reflected and the light beam G is allowed to pass. The light beam R reflected by the dichroic mirror 10A passes through the condenser lens 11A, is light-modulated via the liquid crystal panel block 12A for red light, and then enters the light combining element 19A from the illustrated direction.
The light beam G that has passed through the dichroic mirror 10A is converted into a relay lens 13A, a mirror 14A, and a reversing relay lens 1.
5A, condenser lens 17A via mirror 16A
To reach. Then, after passing through the condenser lens 17A and being light-modulated through the liquid crystal panel block 18A for green, the light is incident on the photosynthesizing element 19A from the illustrated direction.

The light combining element 19A is also formed by combining prisms of a predetermined shape with reflection films 19A-a and 19A-b. Of the light beams of the respective colors incident on the photosynthesis element 19A, the light beam B is reflected by the reflection films 19A-b and is incident on the projection lens 20, and the light beam G is reflected by the reflection films 19A-a and is projected on the projection lens 20A. Is incident on. The light beam R passes through the light combining element 19A so as to go straight on and enters the projection lens 20. As a result, the light beams R, G, and B are combined into one light beam and incident on the projection lens 20.

1-4. Internal Configuration of Projection Apparatus (Third Example) FIG. 4 conceptually shows an internal structure as a third example of a projection display apparatus on which the projection lens of the present embodiment can be mounted. In this figure, the same parts as those in FIGS. 2 and 3 are denoted by the same reference numerals, and description thereof will be omitted.

In this case, the dichroic mirror 6B
Reflects the light flux G, and passes the light flux R and the light flux B. The light beam G reflected by the dichroic mirror 6B is reflected by the mirror 7B and the condenser lens 8
B, after passing through the liquid crystal panel block 9B for green, the light is incident on the photosynthesis element 19B from the illustrated direction.

The light flux R and the light flux B that have passed through the dichroic mirror 6B are incident on the dichroic mirror 10B, so that the light flux R is reflected and the light flux B passes. The light beam R reflected by the dichroic mirror 10B is incident on the photosynthesis element 19B from the illustrated direction via the condenser lens 11B and the liquid crystal panel block 12B for red. Dichroic mirror 1
The light beam B that has passed through 0B is incident on the photosynthesis element 19B from the illustrated direction through the relay lens 13B, the mirror 14B, the inversion relay lens 15B, the mirror 16B, the condenser lens 17B, and the liquid crystal panel block 18B for blue. Is done.

The light combining element 19B is also formed by combining prisms of a predetermined shape with reflection films 19B-a and 19B-b. Here, of the light beams of each color that have entered the light combining element 19B, the light beam G is the reflection film 19B-a.
The light beam B is reflected by the reflection film 19B-b, and the light beam R passes through the photosynthetic element 19B so as to go straight, and is incident on the projection lens 20 as one light beam. .

Although the projection apparatus according to the present embodiment has been described above with reference to three examples, these are merely examples, and the internal configuration of a projection display apparatus on which the projection lens according to the present embodiment can be mounted is described. Is variously conceivable. For example, the projection devices of the above three examples are 2
It employs a so-called transmissive structure in which light is transmitted through a three-dimensional image display element (liquid crystal panel block), but the length of the prism (photosynthesis element) between the lens and the liquid crystal panel block (light valve) is the same. If so, the projection lens according to the present embodiment adopts a configuration in which light modulated by the two-dimensional image display element (liquid crystal panel block) is reflected so as to be incident on the projection lens. It is also possible to apply to.

2. Configuration of projection lens 2-1. Lens Arrangement Structure Subsequently, a lens arrangement structure of the projection lens according to the present embodiment will be described. The projection lens according to the first to tenth embodiments described below is a projection lens 20 in the projection display device shown in FIGS.
It is adopted as. Note that, here, mainly the description of the lens arrangement structure as each of the first to tenth embodiments is given, and the shape of each lens, the distance between the lenses, and the like are represented by numerical embodiments described later. And

First, the lens arrangement structure of the projection lens 20 according to the first embodiment will be described. FIG.
FIG. 2 is a lens cross-sectional view conceptually showing a lens arrangement structure of a projection lens 20 according to the first embodiment. In these figures, the left side of the figures is the screen 21 side (large conjugate side), and the right side is the liquid crystal panel block and photosynthesis element side (small conjugate side). Also, the photosynthetic element 60
Are the respective light combining elements (19, 1) shown in FIGS.
9A and 19B) conceptually showing the light valve 7
Numeral 0 conceptually shows the RGB color liquid crystal display panel block shown in FIGS.

As shown in FIG. 5, the projection lens 20 according to the first embodiment has a first lens group 0, a diaphragm 400, and a second lens group 3 from the large conjugate side to the small conjugate side.
00 are arranged in order.

In this case, the first lens group 0 includes a first A lens group 100 and a first B lens group 200 in order from the long (large) conjugate side to the short (small) conjugate side, and as a whole, has positive refraction. Have power. In this case, the first A lens group 100 includes, in order from the large conjugate side to the small conjugate side, a negative meniscus lens 101, a negative meniscus lens 102, a biconcave lens 103, and a positive lens 104.
Is arranged. Here, both surfaces of the negative meniscus lens 101 located on the longest conjugate side have an aspheric surface according to an aspheric coefficient in a numerical embodiment described later. In the first B lens group 200, one positive lens 201 is arranged.

The second lens group 300 is composed of the cemented lens 30 in order from the long conjugate side to the short conjugate side.
1, a positive lens 304, a positive lens 305, and an aspheric lens 306 are arranged. Laminated lens 301
Is constructed by bonding together a biconcave lens 302 and a positive lens 303 arranged from the long conjugate side to the short conjugate side. With such a configuration, the second lens group 300
Has a positive refractive index as a whole. Also, as can be said for each of the following embodiments, the longest on-axis air spacing on the long conjugate side and the short conjugate side, based on the position of the diaphragm 400, It is made to be in the closest position.

In this specification, the "final lens surface" or the "first lens surface" may be used to specify a lens surface in one lens group. The “final lens surface” refers to the lens surface closest to the short conjugate side in the lens group, and the “first lens surface” refers to the lens surface closest to the long conjugate side in the lens group. Say. As a specific example, in the case of the first A lens group 100 shown in FIG.
Is the lens surface (r8) on the short conjugate side of the positive lens 104, and the "first lens surface" of the first A lens group 100 is the lens surface (r1) on the long conjugate side of the meniscus lens 101. ).

FIGS. 6 and 7 show lens arrangement structures of the projection lens 20 according to the second and third embodiments, respectively. The arrangement structure of the projection lens 20 according to the second and third embodiments shown in FIGS. 6 and 7 is the same as that of the first embodiment shown in FIG. The description of each part is omitted here.

The lens sectional views of FIGS. 8 and 9 show the lens arrangement structure of the projection lens 20 according to the fourth and fifth embodiments, respectively. The description is omitted by attaching reference numerals. In the projection lenses 20 of the fourth and fifth embodiments shown in FIGS. 8 and 9, as the lens arrangement structure of the second lens group 300, the cemented lens 301 is sequentially arranged from the long conjugate side to the short conjugate side. , Aspheric lens 306, positive lens 3
04, a positive lens 305 is arranged.

The lens sectional views shown in FIGS. 10A and 10B show the lens arrangement structure of the projection lens 20 as the sixth embodiment, and the same parts as in FIGS. Description is omitted. In the projection lens 20 shown in this figure, the first A lens group 100 is composed of three lenses: a negative meniscus lens 101, a negative meniscus lens 102, and a biconcave lens 103. That is, the positive lens 104 that has been included in the first A lens group 100 of the projection lens 20 illustrated in FIGS. 5 to 9 is omitted. The second lens group 300 includes the fourth and fifth lenses.
Similarly to the embodiment (FIGS. 8 and 9), the cemented lens 301 and the cemented lens 301 are sequentially arranged from the long conjugate side to the short conjugate side.
Aspheric lens 306, positive lens 304, positive lens 305
Is arranged.

11 and 12 show the lens arrangement structure of the projection lens 20 according to the seventh and eighth embodiments, respectively. In these drawings, the same parts as those in FIGS. 5 to 10 are denoted by the same reference numerals, and description thereof is omitted. In the projection lenses 20 of the seventh and eighth embodiments shown in FIGS. 11 and 12, the second lens group 30
As a lens arrangement structure of 0, the cemented lens 301 and the positive lens 30 are sequentially arranged from the long conjugate side to the short conjugate side.
4. An aspheric lens 306 and a positive lens 305 are arranged. That is, in the seventh and eighth embodiments, the second
The aspheric lens 306 in the lens group 300 is a positive lens 3
04 and the positive lens 305. As in the sixth embodiment (FIG. 10), the first A lens group 100 includes three lenses: a negative meniscus lens 101, a negative meniscus lens 102, and a biconcave lens 103.

FIGS. 13 and 14 are sectional views of the projection lens 20 according to the ninth and tenth embodiments, respectively.
1 shows a lens arrangement structure. Also in these figures, the same parts as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted. Projection lens 2 of ninth and tenth embodiments
As shown in FIGS. 13 and 14, a positive lens 307 is added to the second lens group 300 as 0. Then, the second lens group 300 is configured by arranging a cemented lens 301, an aspheric lens 306, a positive lens 304, a positive lens 305, and a positive lens 307 in order from the long conjugate side to the short conjugate side. Also in this case, the first
The A lens group 100 is described in the sixth embodiment (FIG. 1).
As in the case of 0), it is composed of three lenses: a negative meniscus lens 101, a negative meniscus lens 102, and a biconcave lens 103.

Note that the first to first data shown in FIGS.
0, the aspherical lens 30 in the second lens group 300 which is a feature of the present invention.
The shape of No. 6 will be specifically shown later by numerical embodiments.

2-2. Conditional Expressions In the projection lens 20 according to the first to tenth embodiments having the above configuration, the following conditional expressions (1) to (1)
0) is satisfied.

The combined focal length of the entire system is F, the second lens group 3
BF is the air-equivalent distance from the final lens surface of No. 00 to the small conjugate point, F1A is the focal length of the first A lens group 100,
The focal length of the first B lens group 200 is F1B, the focal length of the second lens group 300 is F2, the distance from the last lens surface of the first lens group 0 to the aperture is DS1, and the first lens of the second lens group 300 from the aperture is 1.5 <BF / F <3.0 (1) 0.9 <-F1A / F <3.5, where DS2 is the distance to the surface and HF2 is the front principal point of the second lens group 300. (2) 0.35 <HF2 / F2 <0.65 (3) 0.65 <DS2 / F <1.35 (4) 0.21 <DS1 / F1B <0. 66 (5) Also, 2.0 <F1B / F <6.3 (6)

RA1 is the radius of curvature of the long conjugate side of the aspheric lens 306 in the second lens group 300, and RA2 is the radius of curvature of the short conjugate side of the aspheric lens 306 in the second lens group 300. 0.0 ... (7) 0.0 <RA2 ... (8)

The positive lenses (304, 305, 307) in the second lens group 300 have Abbe numbers of ν2P
67 <ν2P (9)

Also, among the positive lenses provided in the second lens group 300, for the lens having the strongest positive refractive power, the Abbe number of the positive lens is ν2PMAX, and 67 <ν2PMAX (10)

Next, the above-mentioned conditional expressions will be described.
For example, as can be seen from the configurations shown in FIGS. 2 to 5, as the projection lens of the projection display device, it is necessary to use an optical element such as a dichroic mirror or a dichroic prism for color synthesis. is necessary. Further, for example, when the purpose is to reduce the size of the projection display device, that is, to reduce the size of the housing, in order to obtain a large screen with a wide projection angle at a short projection distance, the entire projection lens system is required. It is necessary to shorten the focal length. Therefore, in the present embodiment, by satisfying the conditional expression (1), two conditions of a long back focus and a short focal length of the entire projection lens system are achieved.

Conditional expression (2) is for keeping the size of the entire lens system, the back focus and the optical performance favorable. In the projection lens of the present embodiment, the first A lens group 100 forms a retrofocus type front group having a negative refractive power, and the first B lens group 200 and the second lens group 3
00 forms a rear group of a trofocus type having a positive refractive power. Therefore, when the value exceeds the upper limit of conditional expression (2),
It becomes difficult to maintain a long back focus because the retrofocus type configuration becomes weak. In order to intentionally increase the back focus under the condition exceeding the upper limit of the conditional expression (2), the principal points of the first A lens group 100 and the first B lens group 200 to the second lens group 300 must be determined. It is necessary to increase the interval, so that the overall length of the lens becomes longer. As a result, the outer diameter of the first lens group 0 becomes larger, and the number of lenses required to constitute the first A lens group 100 increases. Not preferred. If the lower limit of conditional expression (2) is exceeded, the negative refracting power of the first A lens group 100 becomes too strong, so that the field curvature becomes excessive, and large barrel-shaped distortion occurs on the short conjugate side. Problem arises.

The conditional expressions (3) and (4) show that the stop 400 and the second
A condition regarding telecentricity of the lens group 300 is defined. -In general, rays passing through the front focal point of the lens become parallel rays after passing through the lens. In the case of the projection lens of the present embodiment, if the stop 400 is set near the front focal point of the second lens group 300, the principal ray emitted to the short conjugate side becomes closer to a parallel ray, and telecentricity is realized. it can. That is, the telecentricity is best when the sum of DS2 and HF2 is equal to F2. By the way, if the telecentricity is lost, the symmetry of the upper ray and the lower ray is also lost, so depending on the angle characteristic when transmitting or reflecting through the coating film of the prism or mirror for color synthesis and polarizing beam splitter, it depends on the wavelength. The light beams have different intensities, which may cause unevenness due to color and intensity on the screen of the projected image. Here, when the value exceeds the upper limit of the conditional expression (3), the telecentricity cannot be secured unless the refraction of the second lens group 300 is weakened, and the telecentricity is intentionally maintained in a state where the upper limit of the conditional expression (3) is exceeded. If so, the back focus will be shortened. Conversely, if the lower limit of conditional expression (3) is exceeded, the refracting power of the second lens group 300 will become strong, and accordingly, the first lens unit 300 will have the first lens unit.
Since the refractive power of the lens group 100 must be increased, it is difficult to correct off-axis aberrations and the lens diameter is large, which is not preferable. When the value exceeds the upper limit of the conditional expression (4), the refractive power of the second lens group 300 becomes strong, and accordingly, the refractive power of the first A lens group 100 must also be made strong. It becomes difficult or the diameter of the lens becomes large. If the lower limit of conditional expression (4) is exceeded, the telecentricity cannot be ensured unless the refractive power of the second lens group 300 is weakened, or the balance of the retrofocus type refractive power is lost, and the back focus is shortened. .

Conditional expression (5) indicates that the off-axis rays emitted from the first A-lens group 100 should be converted into the second rays with a good balance.
The first B lens group 2 for making the light enter the lens group 300
00 condition. If the upper limit of conditional expression (5) is exceeded, the overall lens length will increase, and accordingly the outer diameter of the first A lens group 100 will increase. Also, the first B lens group 20
When the focal length of 0 is small, the angle of the off-axis ray incident on the second lens group 300 becomes sharp, so that it becomes difficult to correct the aberration. If the lower limit of conditional expression (5) is exceeded, the first condition will be satisfied.
Since the refractive power of each lens of the A lens group 100 becomes strong,
In particular, aberrations of light rays passing through the periphery occur, making correction difficult.

Conditional expression (6) is used to form an image formed from the first A lens group 100 and formed on the long conjugate side at a long distance on the short conjugate side, and to provide the second lens with a good balance of off-axis rays. First B lens group 2 for entering the lens group 300
00 condition. If the upper limit of conditional expression (6) is exceeded, the overall length of the lens will increase.
The outer diameter of 0 becomes large. When the focal length of the first B lens group 200 decreases, the second lens group 300
The angle of an off-axis ray incident on the lens becomes sharp, and it becomes difficult to correct aberration. If the lower limit of conditional expression (6) is exceeded, the first condition will be satisfied.
Since the refractive power of each lens of the A lens group 100 becomes strong,
In particular, aberrations occur in light rays passing through the periphery, making correction difficult.

Conditional expressions (7) and (8) are satisfied by the second lens unit 30.
This defines the shape of the aspheric lens 306 in the middle.

Condition (9) defines the Abbe number of the lens material for the positive lens constituting the second lens group 300. When the value exceeds the range represented by the conditional expression (9), the chromatic aberration of magnification increases, and the corners of the projection screen are easily colored.

The conditional expression (10) restricts the Abbe number of the positive lens having the strongest refracting power among the positive lenses constituting the second lens group 300, which have a particularly strong influence. When the value exceeds the range represented by the conditional expression (10), the chromatic aberration of magnification also increases, and the corners of the projection screen easily become colored.

2-3. Numerical Embodiments, etc. Numerical embodiments as the projection lens 20 of the first to tenth embodiments are shown in FIGS. In each of FIGS. 15 to 24A, i is the surface number (lens surface number) of the lens surface counted from the long conjugate side, which is indicated by r1 to r22 in FIGS. Corresponding to the surface. R indicates the radius of curvature of the lens surface corresponding to each lens surface number i. D indicates the lens surface interval corresponding to each lens surface number i, ND indicates the refractive index of the lens corresponding to each lens surface number i, and VD indicates the Abbe number of the lens corresponding to each lens surface number i. FIG.
24, F indicates the focal length of the projection lens, Fno indicates the F number, and M indicates the projection magnification.

The surface shape as an aspheric surface shown in each of FIGS. 15 to 24B is an orthogonal coordinate system (X, Y, Z) with the center of the surface as the origin and the optical axis direction as Z. )
r is the central radius of curvature, K is the conic constant, A4, A6, A8,
When A10 is a fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficient, respectively,

(Equation 1) Is represented by the following equation.

FIG. 25 shows a numerical example satisfying the above-mentioned conditional expressions (1) to (11) in the first to tenth embodiments.

Further, according to each of FIGS. 26 to 35, the first
13 shows spherical aberration, astigmatism, and distortion of the projection lens 20 according to the tenth to tenth embodiments. In order to obtain the results shown in the various aberration diagrams shown in these drawings, although not shown in the numerical embodiments, the light combining element 19 (shown in FIGS. 19
A, 19B), the center plane spacing is 36 mm (refractive index n =
The calculation is performed with a parallel flat plate having 1.51633 and Abbe number ν = 64.0). However, the numerical values relating to such a color combining prism do not affect the configuration of the projection lens as the present invention.

The actual structure of the projection lens according to the first to tenth embodiments is not limited to those shown in FIGS. 5 to 14, but satisfies the conditional expressions described above. As long as it is possible, the number of lenses forming each lens group may be changed. In the above embodiment, the projection lens of the present invention is described as being provided in a projection device using a liquid crystal panel as a two-dimensional image display element in a rear projection type projection display device. However, the present invention can be applied to, for example, wide-angle photographic lenses for single-lens reflex cameras, industrial cameras, electrophotography, and the like, and projection lenses for projection televisions using a CRT.

[0073]

As described above, the following effects can be obtained as the projection lens of the present invention. First, according to the present invention, a long back focus can be obtained, and the focal length of the entire projection lens system (total length of the lens system) can be shortened. In addition, it is possible to avoid an increase in the number of lenses and an increase in the size of the lens system, and to suppress curvature of field and barrel-shaped distortion on the short conjugate side. In addition, it is possible to secure telecentricity between the diaphragm and the second lens group, and to prevent color unevenness and intensity unevenness appearing on the screen of the projected image. Further, since the first B lens group is configured to make the off-axis light rays emitted from the first A lens group enter the second lens group with a good balance, the off-axis light rays entering the second lens group 300 The aberration can be easily corrected without making the angle too tight. This leads to the effect that color shift around the screen can be suppressed even if the resolution of the lens is increased with the increase in the resolution of the light valve (liquid crystal panel), for example.

Further, claims 2, 13, and 24 are provided.
According to the invention described in (1), an image emitted from the first A lens group and formed on the long conjugate side is formed at a long distance on the short conjugate side, and off-axis rays are incident on the second lens group with a good balance. Becomes possible, which facilitates aberration correction.

Further, claim 7, claim 18, and claim 29
According to the invention described in (1), the shape of the aspherical lens in the second lens group can be defined so as not to hinder the effects of the present invention.

Further, claims 10 and 11 and claims 21 and
2. As in the invention according to claims 32 and 33, the second
By defining the Abbe number of the lens material for the positive lens constituting the lens group, the chromatic aberration of magnification is suppressed, and the corners of the projection screen are hardly colored.

Further, claims 3, 4, 5, 6, 8, 9,
Claims 14, 15, 16, 17, 19, 20 and Claim 2
By defining the lens arrangement or lens shape as in the inventions described in 5, 26, 27, 28, 30, and 31, various variations can be obtained as the projection lens of the present invention, and The degree of freedom to select a suitable lens structure is obtained accordingly, and the enhancement of the optical characteristics of the projection lens described above can be enhanced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an overall configuration of a projection display device including a projection lens according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration (first example) of a projection display device including a projection lens according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a configuration (second example) of a projection display device including a projection lens according to an embodiment of the present invention.

FIG. 4 is a diagram showing a configuration (third example) of a projection display device provided with a projection lens according to an embodiment of the present invention.

FIG. 5 is a lens cross-sectional view illustrating a configuration example of a projection lens as the first embodiment.

FIG. 6 is a lens cross-sectional view illustrating a structural example of a projection lens as a second embodiment.

FIG. 7 is a lens cross-sectional view illustrating a configuration example of a projection lens as a third embodiment.

FIG. 8 is a lens cross-sectional view illustrating a structural example of a projection lens as a fourth embodiment.

FIG. 9 is a lens cross-sectional view illustrating a structural example of a projection lens as a fifth embodiment.

FIG. 10 is a lens cross-sectional view illustrating a configuration example of a projection lens as a sixth embodiment.

FIG. 11 is a lens cross-sectional view illustrating a structural example of a projection lens as a seventh embodiment.

FIG. 12 is a lens cross-sectional view illustrating a configuration example of a projection lens as an eighth embodiment.

FIG. 13 is a lens cross-sectional view illustrating a configuration example of a projection lens as a ninth embodiment.

FIG. 14 is a lens cross-sectional view illustrating a configuration example of a projection lens as a tenth embodiment.

FIG. 15 is a diagram showing a numerical embodiment of the projection lens as the first embodiment.

FIG. 16 is a diagram showing a numerical embodiment of a projection lens as a second embodiment.

FIG. 17 is a diagram showing a numerical embodiment of a projection lens as a third embodiment.

FIG. 18 is a diagram showing a numerical embodiment of a projection lens as a fourth embodiment.

FIG. 19 is a diagram showing a numerical embodiment of a projection lens as a fifth embodiment.

FIG. 20 is a diagram showing a numerical embodiment of a projection lens as a sixth embodiment.

FIG. 21 is a diagram showing a numerical embodiment of a projection lens as a seventh embodiment.

FIG. 22 is a diagram showing a numerical embodiment of a projection lens as an eighth embodiment.

FIG. 23 is a diagram showing a numerical embodiment of a projection lens as a ninth embodiment.

FIG. 24 is a diagram showing a numerical embodiment of a projection lens as a tenth embodiment.

FIG. 25 is a diagram showing numerical values corresponding to conditional expressions (1) to (10) in each of the first to tenth embodiments.

FIG. 26 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the first embodiment.

FIG. 27 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the second embodiment.

FIG. 28 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the third embodiment.

FIG. 29 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the fourth embodiment.

FIG. 30 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the fifth embodiment.

FIG. 31 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the sixth embodiment.

FIG. 32 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the seventh embodiment.

FIG. 33 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of a projection lens as an eighth embodiment.

FIG. 34 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of a projection lens as a ninth embodiment.

FIG. 35 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the tenth embodiment.

[Explanation of symbols]

1 lamp, 2 reflector, 3 IR-UV cut filter, 4,5 multi-lens array, 6,6A, 6B
Dichroic mirror, 7,7A, 7B mirror,
8, 8A, 8B Condenser lens, 9, 9A, 9B
Liquid crystal panel block, 10, 10A, 10B dichroic mirror, 11, 11A, 11B condenser lens, 12, 12A, 12B Liquid crystal panel block, 1
3, 13A, 13B relay lens, 14, 14A, 1
4B mirror, 15, 15A, 15B Inverting relay lens, 16, 16A, 16B mirror, 17, 17A,
17B Condenser lens, 18, 18A, 18B
Liquid crystal panel block, 19, 19A, 19B Photosynthesis element, 19a, 19b, 19A-a, 19A-b, 19B
-A, 19B-b Reflective film 20 Projection lens, 21
Screen, 60 photosynthesis element, 70 light valve, 0
1st lens group, 100 1A lens group, 101, 1
02 meniscus lens, 103 biconcave lens, 104
Positive lens, 200 2A lens group, 201 positive lens, 300 second lens group, 301 bonded lens,
302 biconcave lens, 303 positive lens, 304 positive lens, positive lens 305, aspheric lens 306, positive lens 307, 400 aperture, 500 projection display device, 501 cabinet, 502 projection device, 50
3 cabinet, 504 screen, 504 bent mirror, 600 projected light

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H087 KA06 LA03 LA24 NA02 PA08 PA09 PA18 PB09 PB10 QA02 QA03 QA07 QA17 QA19 QA22 QA26 QA34 QA41 QA45 QA46 RA05 RA12 RA13 RA26 RA32 RA41 RA43 RA48 TA01 TA02 TA03

Claims (33)

[Claims] 1. A first lens group and a second lens group are arranged in order from a long conjugate side to a short conjugate side with a required interval before and after the stop, and the first lens group has a long conjugate side. 1A comprising an aspherical lens located on the longest conjugate side from the side to the short conjugate side, and at least one or more negative meniscus lenses.
A second lens group including a first lens group including at least a positive lens so as to have a positive refractive power as a whole; A projection lens comprising a cemented lens made of a lens, at least one or more positive lenses, and an aspheric lens, and having a positive refractive power as a whole. 2. The projection lens according to claim 1, wherein the first B lens group satisfies the following conditional expression: 2.0 <F1B / F <6.3. 3. The longest on-axis air spacing is closer to the iris on the conjugate side longer than the throttle, and the longest on-axis air spacing is closer to the iris on the conjugate side shorter than the throttle. The projection lens according to claim 1, wherein the projection lens is present. 4. The aspheric lens in the second lens group,
2. The projection lens according to claim 1, wherein the projection lens has a shape that is convex toward the short conjugate side so that negative refractive power increases from the optical axis to the periphery. 3. 5. The aspherical lens in the second lens group,
2. The projection lens according to claim 1, wherein the projection lens has a shape that is convex toward the long conjugate side so that negative refractive power increases from the optical axis to the periphery. 3. 6. The aspheric lens in the second lens group,
2. The projection lens according to claim 1, wherein the projection lens has a biconcave shape so that the negative refractive power increases from the optical axis to the periphery. 7. The aspheric lens in the second lens group,
It has a shape in which the negative refractive power becomes stronger from the optical axis to the periphery. The radius of curvature of the long conjugate side of the aspheric lens in the second lens group is RA1, and the radius of curvature of the short conjugate side of the aspheric lens in the second lens group is RA1. The projection lens according to claim 1, wherein a conditional expression of RA1 <0.0 0.0 <RA2 is satisfied, where RA2 is a radius of curvature. 8. The aspheric lens in the second lens group,
2. The optical system according to claim 1, wherein the second lens unit is arranged on a conjugate side shorter than the cemented lens in the second lens unit and has a shape in which negative refractive power increases from the optical axis to the periphery. The projection lens according to 1. 9. The method according to claim 1, wherein at least two positive lenses are provided in the second lens group, and the aspherical lens in the second lens group is disposed between the two positive lenses. The projection lens according to claim 1. 10. The projection lens according to claim 1, wherein the positive lens in the second lens group satisfies a conditional expression of 67 <ν2P, where Abbe number of the positive lens is ν2P. 11. The lens having the strongest positive refractive power among the positive lenses provided in the second lens group has the Abbe number of the lens having the strongest positive refractive power set to ν2PMA.
2. The projection lens according to claim 1, wherein X satisfies the following conditional expression: 67 <ν2PMAX. 12. A first lens group and a second lens group are arranged in order from a long conjugate side to a short conjugate side with a required space before and after the stop, and the first lens group has a long conjugate side. 1A comprising an aspherical lens located on the longest conjugate side from the side to the short conjugate side, and at least one or more negative meniscus lenses.
A second lens group including a first lens group including at least a positive lens so as to have a positive refractive power as a whole; It has a cemented lens composed of lenses, at least one or more positive lenses, and an aspherical lens, and has a positive refractive power as a whole. When the magnification is large, the air conversion distance from the last lens surface of the second lens group to the small conjugate point is BF, and the focal length of the first A lens group is F1.
A, the focal length of the first B lens group is F1B, the focal length of the second lens group is F2, the distance from the last lens surface of the first lens group to the diaphragm is DS1, and the distance from the diaphragm to the first lens surface of the second lens group is 1.5 <BF / F <3.0 0.9 <-F1A / F <3.5 0.35 <HF2 / F2 <0, where DS2 is the distance of DS2 and the front principal point position of the second lens group is HF2. 0.65 <DS2 / F <1.35 0.21 <DS1 / F1B <0.66 A projection lens characterized by satisfying the following conditional expression: 13. The projection lens according to claim 12, wherein the first B lens group satisfies the following conditional expression: 2.0 <F1B / F <6.3. 14. The longest on-axis air gap exists on the conjugate side longer than the throttle, and the longest on-axis air gap on the conjugate side shorter than the throttle becomes closest to the throttle. 13. A projection lens according to claim 12, wherein it is present. 15. The aspheric lens in the second lens group has a shape that is convex to the short conjugate side, so that negative refractive power increases from the optical axis to the periphery. The projection lens according to claim 12, wherein 16. The aspheric lens in the second lens group has a shape that is convex toward a long conjugate side so that negative refractive power increases from the optical axis to the periphery. The projection lens according to claim 12, wherein 17. The optical system according to claim 12, wherein the aspheric lens in the second lens group has a biconcave shape so that the negative refractive power increases from the optical axis to the periphery. The projection lens according to 1. 18. The aspheric lens in the second lens group has a shape in which negative refractive power increases from the optical axis to the periphery, and has a long radius of curvature on the long conjugate side of the aspheric lens in the second lens group. 14. The conditional expression: RA1 <0.00.0 <RA2, where RA1 is RA1 and the radius of curvature of the short conjugate side of the aspherical lens in the second lens group is RA2. Projection lens. 19. The aspheric lens in the second lens group is arranged on a conjugate side shorter than the cemented lens in the second lens group, and has a strong negative refractive power from the optical axis to the periphery. 13. The projection lens according to claim 12, wherein the projection lens has a shape. 20. The second lens group, wherein at least two positive lenses are provided, and the aspherical lens in the second lens group is disposed between the two positive lenses. The projection lens according to claim 12. 21. The projection lens according to claim 12, wherein the positive lens in the second lens group satisfies a conditional expression of 67 <ν2P, where Abbe number of the positive lens is ν2P. 22. Among the positive lenses provided in the second lens group, the lens having the strongest positive refractive power has an Abbe number of the lens having the strongest positive refractive power of ν2PMA.
13. The projection lens according to claim 12, wherein X satisfies the following conditional expression: 67 <ν2PMAX. 23. A first lens group and a second lens group are arranged in order from a long conjugate side to a short conjugate side and at a predetermined interval before and after the stop, and the first lens group has a long conjugate side. From the side to the short conjugate side, from a group of three elements including an aspheric lens on the longest conjugate side, a negative meniscus lens convex on the long conjugate side, and a biconcave lens or a meniscus lens convex on the long conjugate side. A first A lens group having a positive refractive power and a first B lens group having at least a positive lens. The second lens group has a positive refractive power as a whole. A projection lens comprising a cemented lens composed of a concave lens and a positive lens, at least one or more positive lenses, and an aspheric lens, and having a positive refractive power as a whole. 24. The projection lens according to claim 23, wherein the first B lens group satisfies the following conditional expression: 2.0 <F1B / F <6.3. 25. On the conjugate side longer than the throttle, the longest axial air gap exists at the position closest to the throttle, and on the conjugate side shorter than the throttle, the longest axial air gap is at the position closest to the throttle. The projection lens according to claim 23, wherein the projection lens is present. 26. The aspheric lens in the second lens group has a shape that is convex to a short conjugate side so that negative refractive power increases from the optical axis to the periphery. The projection lens according to claim 23, wherein 27. The aspheric lens in the second lens group has a shape convex to the long conjugate side, so that negative refractive power increases from the optical axis to the periphery. The projection lens according to claim 23, wherein 28. The aspherical lens in the second lens group has a biconcave shape so that negative refractive power increases from the optical axis to the periphery. The projection lens according to 1. 29. The aspheric lens in the second lens group has a shape in which negative refractive power increases from the optical axis to the periphery, and has a long radius of curvature on the long conjugate side of the aspheric lens in the second lens group. 24. A conditional expression of RA1 <0.00.0 <RA2, where RA1 is RA1 and a radius of curvature of the short conjugate side of the aspherical lens in the second lens group is RA2. Projection lens. 30. The aspheric lens in the second lens group is disposed on a conjugate side shorter than the cemented lens in the second lens group, and has a strong negative refractive power from the optical axis to the periphery. The projection lens according to claim 23, wherein the projection lens has a shape of: 31. The second lens group, wherein at least two positive lenses are provided, and the aspheric lens in the second lens group is disposed between the two positive lenses. A projection lens according to claim 23. 32. The projection lens according to claim 23, wherein the positive lens in the second lens group satisfies a conditional expression of 67 <ν2P, where Abbe number of the positive lens is ν2P. 33. Among the positive lenses provided in the second lens group, the lens having the strongest positive refractive power has an Abbe number of the lens having the strongest positive refractive power of ν2PMA.
The projection lens according to claim 23, wherein X satisfies the following conditional expression: 67 <ν2PMAX.