JP2000275515A - Projection lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a projection lens which has a wide field angle, long back focus, and telecetricity with small aberrations by adjusting the focus by varying the interval between lens groups in a 1st lens group on the axis and satisfying specific conditional expressions. SOLUTION: This projection lens 20 has a 1st lens group 0, a diagragm 400, and a 2nd lens group 300 arrayed in order. The 1st lens group 0 has a (1A)th lens group 100 and a (1B)th lens group 200 and has positive refracting power on the whole. The 2nd lens group 300 has a positive refractive index on the whole. The on-axis lens group interval D1 between the 1st (1A)th lens group 100 and (1B)th lens group 200 is varied to make a focus adjustment accompanying variation in projection variation. The lens 20 meets conditional inequalities of 1.5<BF/F<3.0, 0.6<-F1A/F<1.4, 0.4<HF2/F2<0.73, 0.65<DS2/F<1.35, and 0.4<DS1/F1B<0.8. Neither F nor BF, etc. is explained here.

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 including a two-dimensional image display element (light valve) 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. And the luminous flux of the three colors is red,
Each two-dimensional image display element (for example, LCD; Liquid Cryst) formed in accordance with green and blue (R, G, B) video electric signals
al Display). 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 color. 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, if the projection lens is given telecentricity while securing a wide angle and a long back focus, 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 a high-definition light valve. However, with the high-resolution lens, magnification chromatic aberration around a screen is caused. Pixel color misregistration is becoming a problem.

In the case of a projection display device adopting a configuration in which an optical path is converted in a projection lens, as a focus adjustment method, for example, a focus position is obtained by adjusting a relative distance between the entire projection lens and a screen. It has been found that the use of the so-called whole feeding method is not appropriate because the center of the image on the screen is shifted. Therefore,
In such a projection display device, it is necessary to adopt a method for an appropriate focus adjustment other than the whole extension system.

Further, in the projection display device, the same projection lens can be used by adjusting the relative distance between the projection lens and the screen, even if the housings have different screen sizes. At this time, aberrations (for example, distortion and chromatic aberration of magnification) occur due to slight differences in the angle of each light beam condensed on the screen and manufacturing errors of the projection lens. Therefore, it is necessary to adjust such aberrations as much as possible. There is.

[0015]

In view of the above-mentioned problems, the present invention employs a method which is more advantageous than the whole extension system as a focus-adjustable projection lens, and provides a wide angle of view. It is another object of the present invention to provide a lens having a long back focus and telecentricity even in short-range projection, and further having small aberrations.

For this reason, the projection lens is configured as follows. That is, in order from the long conjugate side to the short conjugate side, the first lens group and the second lens group are arranged at a required interval before and after the stop. And the first
The lens group includes a first A lens group including at least one aspheric lens located on the longest conjugate side, at least one negative meniscus lens, and a first B lens including at least one positive lens. The second lens group includes a cemented lens composed of a biconcave lens and a positive lens from a side closest to the diaphragm to a side farthest from the stop, and at least one or more lenses. And a positive lens as a whole, and a positive refractive power as a whole. Then, by moving the axial lens unit interval between the first A lens unit and the first B lens unit in a direction that increases from a high projection magnification to a low projection magnification, the focus is adjusted by changing the projection magnification. And the focal length of the whole system when the projection magnification is the minimum is F,
The air-equivalent distance from the final 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 0.6 <−F1A / F <1.4 0.4 <HF2 / F2 <0, where DS2 is the distance of DS2 and the front principal point position of the second lens group is HF2. .73 0.65 <DS2 / F <1.35 0.4 <DS1 / F1B <0.8.

The projection lens of the present invention is also configured as follows. That is, in order from the long conjugate side to the short conjugate side, the first lens group and the second lens group are arranged at a required interval before and after the stop. The first lens group includes, from the long conjugate side to the short conjugate side, at least the aspheric lens which is located on the longest conjugate side and has a negative refractive power that increases from the optical axis center to the periphery thereof. A convex negative meniscus lens, a biconcave lens,
A first A lens group including a positive lens, and a first B lens group including at least one or more positive lenses, the second lens group having a positive refractive power as a whole;
The lens group includes a cemented lens composed of a biconcave lens and a positive lens, at least one or more positive lenses, and an aspherical lens from the side closest to the diaphragm to the side farthest from the stop.
It has a positive refractive power as a whole. Then, by moving the on-axis lens unit interval between the first A lens unit and the first B lens unit in a longer direction from a high projection magnification to a low projection magnification, focus adjustment is performed by changing the projection magnification. F, the focal length of the whole system when the projection magnification is the minimum, BF the air-equivalent distance from the last lens surface of the second lens unit to the small conjugate point, F1A the focal length of the first A lens unit, and the first B lens. The focal length of the group is F1
B, the focal length of the second lens group is F2, the distance from the last lens surface of the first lens group to the stop is DS1, the second is
1.5 <BF / F <3.0 0.6 <-F1A / F <1.40, where DS2 is the distance to the first lens surface of the lens group, and HF2 is the front principal point position of the second lens group. 0.4 <HF2 / F2 <0.73 0.65 <DS2 / F <1.35 0.4 <DS1 / F1B <0.8 The following conditional expression is satisfied.

Further, the projection lens of the present invention is configured as follows. That is, in order from the long conjugate side to the short conjugate side, the first lens group and the second lens group are arranged at a required interval before and after the stop. The first lens group extends at least from the long conjugate side to the short conjugate side,
An aspheric lens having a negative refractive power decreasing from the optical axis center to its periphery on the longest conjugate side, a negative meniscus lens having a convex shape on the long conjugate side, a biconcave lens, and a positive lens A first lens unit having at least one positive lens, and a first lens unit having at least one positive lens. The first lens unit has a positive refractive power as a whole. From the side farther away from the camera, 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, and have a positive refractive power as a whole. On this,
By moving the on-axis lens unit interval between the first A lens unit and the first B lens unit in a direction that increases from a high projection magnification to a low projection magnification, the focus is adjusted by changing the projection magnification, and the projection magnification is adjusted. Is the focal length of the entire system when F is the minimum, F is the air-equivalent distance from the final lens surface of the second lens group to the small conjugate point, F1A is the focal length of the first A lens group, and F1A is the focal length of the first B lens group. F1B, 2nd
The focal length of the lens group is F2, the distance from the last lens surface of the first lens group to the stop is DS1, the distance from the stop to the first lens surface of the second lens group is DS2, the front principal point position of the second lens group. HF2, 1.5 <BF / F <3.0 0.6 <-F1A / F <1.4 0.4 <HF2 / F2 <0.73 0.65 <DS2 / F <1.350 .4 <DS1 / F1B <0.8.

Further, the projection lens of the present invention is configured as follows. That is, in order from the long conjugate side to the short conjugate side, the first lens group and the second lens group are arranged at a required interval before and after the stop. The first lens group includes, from the long conjugate side to the short conjugate side, at least the aspheric lens that is located at the longest conjugate side and has a negative refractive power that decreases from the optical axis center to the periphery thereof. A first A lens group including a negative meniscus lens having a convex shape, a biconcave lens, and a first B lens group including at least one or more positive lenses, and has a positive refractive power as a whole. The second lens group is
From the side closest to the stop to the side farthest away, a cemented lens composed of a biconcave lens and a positive lens, at least one positive lens, and an aspherical lens are provided, and have a positive refractive power as a whole. Then, by moving the on-axis lens group interval between the first A lens group and the first B lens group in a direction that increases from a high projection magnification to a low projection magnification, focus adjustment is performed by changing the projection magnification. In addition, the focal length of the entire system when the projection magnification is the minimum is F,
The air-equivalent distance from the final 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 0.6 <−F1A / F <1.4 0.4 <HF2 / F2 <0, where DS2 is the distance of DS2 and the front principal point position of the second lens group is HF2. 0.73 0.65 <DS2 / F <1.35 0.4 <DS1 / F1B <0.8

According to the above configuration, the distance between the on-axis lens groups of the first A lens group and the first B lens group is moved in a direction of increasing from a high projection magnification to a low projection magnification, thereby adjusting the focus by changing the projection magnification. To be done. That is, a mechanism for adjusting the focal point is provided on the front side (long conjugate side) of the lens system. By satisfying each conditional expression with the lens arrangement according to the above configuration, a short projection distance is secured while maintaining a high angle of view and a long back focus, and telecentricity is maintained. The conditions for obtaining a projection lens are satisfied. In addition, correction of various aberrations is easily performed.

[0021]

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. Internal configuration of projection device (third example) 1-5. 1. Internal configuration of projection device (fourth example) Lens 3. Configuration of projection lens 3-1. Arrangement structure of lens 3-2. Conditional expression 3-3. Focus adjustment 3-4. 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.

FIGS. 1A and 1B are a side view and a front view showing an example of the overall configuration of such a projection display device. In the projection display device 500 shown in these figures, a bent mirror 504 is provided on the back surface of the cabinet 501, and the cabinet 5
The transmission screen 21 is provided on the front surface of the screen 01. The bending mirror 504 is connected to a projection device 502 described below.
Is mounted at an angle such that it can reflect image light projected from the screen and project it on the screen 504.

The projection device 502 is installed in the cabinet 501 as shown in FIG. In an optical unit 503 of the projection device 502, optical components such as a light source, a dichroic mirror, a liquid crystal panel block (light valve), and a dichroic prism (a photosynthetic element), which will be described later, are arranged. Luminous flux. 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. For example, in consideration of miniaturization of the projection display device, etc., the projection device 50
2, a configuration is also known in which a mirror is provided in the optical path to convert the optical path of the light beam. However, as the present invention, the configuration for converting the optical path in the projection device 502 in this manner is or is not adopted. It does not matter if it is not done.

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. In the present embodiment, as shown in FIG. 1, the structure of the projection display device is as follows.
Bend mirror 5 between projection lens 20 and screen 21
Although the optical path is converted by providing the optical path 04, the bent mirror 504 in FIG. 2 is not shown here for the sake of convenience mainly in describing the internal configuration of 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 pass through the respective condenser lenses 8, 11, and 17 respectively.
Through the liquid crystal panel blocks 9, 12, and 18 for each color.
(Corresponding to a light valve). Each of the liquid crystal panel blocks 9, 12, and 18 of each color is provided with a liquid crystal panel, and is provided with an incident-side polarizing plate for aligning the polarization direction of light incident on the front stage of the liquid crystal panel in a predetermined direction. 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 incident-side polarizers in each of the liquid crystal panel blocks 9, 12, and 18 are arranged so as to transmit a plane of parallel polarization in the plane of FIG. Each of the liquid crystal panels constituting the liquid crystal panel blocks 9, 12, 18 is, for example, a TN (Twisted Nematic) type, and operates in a so-called normally white type, for example. It is arranged to transmit polarized light perpendicular to the plane of the paper.

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 the light onto, for example, a transmission type screen 21.

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 flux R and the light flux G passing through the dichroic mirror 6A are combined with the dichroic mirror 10A at the subsequent stage.
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 beam R and the light beam B that have passed through the dichroic mirror 6B are incident on the dichroic mirror 10B, so that the light beam R is reflected and the light beam 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. .

1-5. Internal Configuration of Projection Apparatus (Fourth Example) Next, FIG. 5 shows an internal structure of a projection display apparatus according to the present embodiment as a fourth example. This fourth example has a structure employing a reflection type light valve. On the other hand, in the configurations of the first to third examples described above, a transmission type light valve is employed. That is, a liquid crystal panel block ([9, 12, 18] [9A, 12A, 18] that forms a two-dimensional image by transmitting incident light.
A] [9B, 12B, 18B]) were provided as transmission light valves.

In the configuration shown in FIG. 5, a blue light emitting diode unit (blue LED unit) 51B and a red LE
The D unit 51R and the green LED unit 51G are arranged in a positional relationship as shown in the figure, and the dichroic mirror unit 50 is arranged on the optical path of each LED unit.
The dichroic mirror unit 50 includes dichroic mirrors 50a and 50b arranged in a position as shown in the figure.

Here, the light beam emitted from the blue LED unit 51B is reflected by the dichroic mirror 50b.
The light enters the integrator 52. The light beam emitted from the red LED unit 51R is reflected by the dichroic mirror 5R.
The light is reflected by Oa and enters the integrator 52. Green L
The light beam emitted from the ED unit 51G passes through the dichroic mirrors 50a and 50b, and passes through the integrator 52.
Incident on.

The integrator 52 corresponds to the multi-lens arrays 4 and 5 shown in FIGS. Each of the RGB light beams (white light) incident on the integrator 52 is split by each lens of the integrator. Each split light beam is refracted by the condenser lens 53 in the direction of the light valve. A polarizing plate 56 is provided downstream of the condenser lens 53. In this polarizing plate 56, only the light of the S-wave oscillation direction is transmitted and made incident on the polarizing beam splitter 54. At this time, the light is illuminated so that all the luminous fluxes as S waves overlap the light valve 55. In addition, besides the method of providing the polarizing plate 56, PBS
(Polarization Beam Splitter) and a polarization conversion means using a half-wave plate may be used to make a light beam of only S wave without absorption of P wave.

The light beam incident on the polarizing beam splitter 54 is reflected on the PBS-coated surface in the polarizing beam splitter 54 to illuminate the light valve 55. Light valve 5
At 5, a two-dimensional image is formed by the image signal, and the incident light is reflected as an image converted into a P wave. Then, the light enters the polarization beam splitter 54 again, passes through the PBS coated surface, and is enlarged and projected on the screen 21 by the projection lens 20. Here, the LED units for each of the RGB colors (51
R, 51G, 51B) and the light valve 55,
An image is displayed in a plane sequence of each color of RGB. For example, when the red LED unit 51R is lit, R (red)
The two-dimensional image of R is formed by the image signal of (1), and the image of R is projected on the screen 21. G (green), B
(Blue) is similarly lit, and the driving by this cycle is performed in a short time. Thus, apparently, the respective colors of RGB are combined and recognized as white light.

The transmission type light valve (liquid crystal panel block) provided in the structure shown in the first to third examples is, for example, STN (Super Twisted Nemati).
c) A liquid crystal display device, a ferroelectric liquid crystal display device, a polymer dispersed type liquid crystal display device, or the like can be employed. The driving method includes simple matrix driving or active matrix driving. On the other hand, as the reflection type light valve shown in the fourth example, for example, a driving electrode or a driving active element is provided on a glass substrate or a silicon substrate, and a liquid crystal of TN (Twisted Nematic) mode, a ferroelectric A reflective liquid crystal element for driving a liquid crystal, a polymer dispersed liquid crystal, or the like can be employed. It is also conceivable to employ a reflective liquid crystal element that applies a voltage to the liquid crystal by irradiating light through a photoconductive film. Further, a reflective liquid crystal element such as a grating light valve having a structure whose shape or state is changed by an electric field can be used.

The projection device according to the present embodiment has been described above with reference to four examples. However, these are merely examples, and the internal configuration of the projection display device on which the projection lens according to the present embodiment can be mounted is described. Is variously conceivable.

2. Lens A so-called retrofocus type lens system is employed as the projection lens 20 of the present embodiment described below. Here, the principle of the retrofocus lens will be described with reference to FIGS. Let me explain briefly.

The lens L1 shown in FIG. 6A has a positive refractive power. FIG. 6A shows that a normal lens having a positive refractive power has a focal position at a small conjugate focal distance from the principal point when the object is at an infinite position. In contrast, FIG.
As shown in (b), when the object point is near, the focal position becomes longer.

On the other hand, the lens L2 shown in FIG. 6C has a negative refractive power. FIG. 6C shows that the lens having a negative refractive power has a large conjugate focal length from the principal point when the object is at the infinite position.

Therefore, as shown in FIG. 6D, a retrofocus type lens system is formed by combining a lens having the above-described characteristics and having a positive refractive power with a lens having a negative refractive power. Can be formed.
In such a retrofocus type, an image is formed at a short distance on the large conjugate side using a front lens L2 having a negative refractive power (which may be regarded as a lens group), and the positive refractive power behind the lens L2. The lens L1 (which may be regarded as a lens group) having an image has an object point as an object point, so that a long back focus is obtained.

FIG. 7 shows the relationship between the stop position and the telecentricity of the principal ray in a retrofocus type lens system. As shown in FIG. 7A, when an object is located at an infinite position, parallel rays enter the lens and converge at a focal point. Conversely, when there is an object point at the focal position, a parallel light beam is emitted from the lens. Here, as shown in FIG. 7B, it is assumed that the principal ray is a ray passing through the center of the stop. If the stop position is set at the front focal position of the lens group after the stop under this condition, the emitted light becomes a parallel light, and the telecentricity of the principal light can be realized.

The following can be said about the focus adjustment as a retrofocus type lens system.
As shown in FIG. 8A, when the object is at a short distance from the infinity position, the back focus of the entire lens system becomes long. In this case, the entire lens is moved as shown in FIG. 8B. Te-Focusing on a fixed position is performed. Such a focus adjustment is referred to herein as an “entire feeding method”.

At this time, in the retrofocus type lens system, the image of the front lens (lens group) having a negative refractive power becomes closer as the object point becomes closer. Therefore, the back focus of the rear lens (lens group) is also long. Here, the back focus of the entire system can be kept constant by always placing the image of the front lens and the front lens (lens group) viewed from the rear lens (lens group) at a fixed position. Therefore, in a case where a plurality of lens groups are further arranged in the front lens group, when the projection distance changes, the distance between the lens groups forming the front lens group is changed to change the image position of the front group. -By making it constant, it is possible to adjust the focus without moving the back focus of the entire system.

This principle is applied to the projection lens of the present embodiment described below. That is, focus adjustment is performed by changing the distance between the lens groups in the front lens group in the entire lens system, instead of using the method of the whole extension system in adjusting the focus. According to such a method, for example, when the distance between one lens group in the entire lens system is changed within a certain screen size range, the distance between the lens groups in the front lens group in the entire lens system is changed. Will change the interval,
Since the focus adjustment can be performed at the same time, the positions of the entire lens and the light valve do not change. In addition, since the focus adjustment mechanism is provided on the front side in the entire lens system, the mechanism for holding the lens is simplified, and the working efficiency when actually assembling and adjusting the projection lens is improved.

As will be described later, the projection lens of this embodiment includes a front lens group (front group: first lens group) and a rear lens group (rear group: second lens) in the lens system. Each of the groups has a structure in which an aspherical lens having a required aspherical shape is arranged. Here, conditions for using an aspherical surface as a lens will be briefly described.

When an aspheric lens is used as the negative lens of the front group, the shape is such that the negative power (negative refractive power) becomes weaker as the distance from the optical axis increases. When an aspheric lens is used as the positive lens in the rear group, the shape is such that the positive power (positive refractive power) becomes weaker as the distance from the optical axis increases.
On the other hand, when an aspheric lens is used as the negative lens in the rear group, the shape is such that the negative power (negative refractive power) becomes weaker as the distance from the optical axis increases. At this time, it is preferable to use the aspherical portion as the aspherical lens on a surface where the height of the off-axis light beam from the optical axis is as high as possible. As a result, the amount of overlap between light beams having different image heights is reduced, which is effective in correcting off-axis aberrations such as critical aberration and distortion. The use of an aspherical portion on an axially or off-axis overlapping surface is effective in correcting spherical aberration, coma, and the like.

3. Configuration of projection lens 3-1. Lens Arrangement Structure Subsequently, the lens arrangement structure of the projection lens according to the present embodiment will be described with reference to FIGS. Projection lenses according to the first to tenth embodiments to be described below are employed as the projection lens 20 in the projection display device shown in FIGS. Note that, here, mainly the description of the lens arrangement structure as each of the first to tenth embodiments will be given, and the shape of each lens, the distance between the lenses, and the like will be represented by numerical embodiments described later. I do. In FIGS. 9 to 18 described later, reference numerals r1 to r23 (r21) indicate lens surface numbers, and d1 to d22 (d
The reference numerals up to 20) indicate the lens surface interval and the lens interval (lens thickness) on the principal ray axis.

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 light valve and photosynthesis element side (small conjugate side). The photosynthesis element 60 is, for example, each of the photosynthesis elements (19, 19A, 1) shown in FIGS.
9B) and the polarization beam splitter 54 shown in FIG. 5. The light valve 70 is a light valve shown in FIGS. 2 to 5 (in FIGS. 2 to 4, an RGB color liquid crystal display). Panel block).

As shown in FIG. 9, the projection lens 20 according to the first embodiment has a first lens group 0, an aperture 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 a long (large) conjugate side to a short (small) conjugate side, and as a whole, has positive refraction. Have power. In this case, the first A lens group 100 includes an aspheric lens 101 and a negative meniscus lens 1 in order from a large conjugate side to a small conjugate side.
02, a biconcave lens 103, and a positive lens 104 are arranged. Here, both surfaces of the aspheric lens 101 located on the longest conjugate side have aspheric surfaces according to the aspheric coefficient in the numerical embodiment described later. Further, both the aspherical lens 101 and the negative meniscus lens 102 have long convex shapes on the conjugate side. 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. The aspheric lens 306 in the second lens group 300 also has an aspheric coefficient according to a numerical embodiment described later. 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 the present 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 short conjugate side lens surface (r8) of the positive lens 104, and the "first lens surface" of the first A lens group 100 is the long conjugate side lens surface of the aspherical lens 101 ( r1).

The lens sectional views of FIGS. 10 and 11 show the lens arrangement structure of the projection lens 20 according to the second and third embodiments, respectively. These FIGS. 10 and 11
Projection lens 20 as second and third embodiments shown in FIG.
Is the same as that of the first embodiment shown in FIG. 9, the same components are denoted by the same reference numerals, and description of each part is omitted here.

The lens sectional views of FIGS. 12 and 13 show the lens arrangement structure of the projection lens 20 according to the fourth and fifth embodiments, respectively, and the same parts as in FIGS. The description is omitted by attaching reference numerals. In the projection lenses 20 of the fourth and fifth embodiments shown in FIGS. 12 and 13, 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. , An aspheric lens 306,
A positive lens 304 and a positive lens 305 are arranged.

The lens cross-sectional view shown in FIG. 14 shows the lens arrangement structure of the projection lens 20 as the sixth embodiment, and the same parts as those in FIGS. Is omitted. Projection lens 20 shown in FIG.
Then, the first A lens group 100 includes an aspheric lens 101,
It comprises three lenses, a negative meniscus lens 102 and a biconcave lens 103. That is, the positive lens 104 which has been included in the first A lens group 100 of the projection lens 20 shown in FIGS. 9 to 13 has been omitted. In addition,
Similarly to the fourth and fifth embodiments (FIGS. 12 and 16), the second lens group 300 includes a cemented lens 301, an aspheric lens 306, and a positive lens in order from the long conjugate side to the short conjugate side. 304, a positive lens 305 is arranged.

FIGS. 15 and 16 show the lens arrangement of the projection lens 20 according to the seventh and eighth embodiments, respectively. In these figures, the same parts as those in FIGS. 9 to 14 are denoted by the same reference numerals, and description thereof will be omitted. In the projection lenses 20 of the seventh and eighth embodiments shown in FIGS. 15 and 16, 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. Regarding the first A lens group 100, similarly to the sixth embodiment (FIG. 14), the aspherical lens 101, the negative meniscus lens 10
2. It is composed of three lenses, biconcave lens 103.

17 and 18 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 FIGS. 9 to 16 are denoted by the same reference numerals and description thereof will be omitted. As the projection lens 20 of the ninth and tenth embodiments, as shown in FIGS.
A positive lens 307 is added in the second lens group 300. Then, the second lens group 300 sequentially moves from the long conjugate side to the short conjugate side,
1. Aspheric lens 306, positive lens 304, positive lens 3
05, the positive lens 307 is arranged. Also in this case, the first A lens group 100 is constituted by three lenses of an aspherical lens 101, a negative meniscus lens 102, and a biconcave lens 103, as in the sixth embodiment (FIG. 14).

Then, the first to the first shown in FIGS.
In the projection lens 20 according to the tenth embodiment, the first A lens group 1 is used for focus adjustment with a change in projection magnification.
The distance on the optical axis (inter-axial lens group interval) between 00 and the first B lens group 200 is changed. That is, the lens surface interval shown as the variable interval D1 in FIGS. 9 to 18 is varied. At this time, in the configuration of the projection lens 20 according to the first to tenth embodiments, the first A lens group 100 and the first B lens group 20 are used.
The on-axis lens group interval of 0 (variable interval D1) is moved so as to change in a long direction from a high projection magnification to a low projection magnification. Here, the first A lens group 100 and the first
When changing the on-axis lens group interval of the B lens group 200, the second lens group 30
The distance to zero is not changed.

3-2. 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.

When the projection magnification is minimum (projection distance is infinity), the focal length of the entire system is F, the air conversion distance from the last lens surface of the second lens group 300 to a small conjugate point is BF, and the focal length of the first A lens group 100 is F1A focal length, first B lens group 20
0 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 stop is DS1, and the distance from the stop 400 to the first lens surface of the second lens group 300 is Distance DS2, second lens group 300
1.5 <BF / F <3.0 (1) 0.6 <−F1A / F <1 where HF2 is the front principal point position (distance from the first lens surface of the second lens group) 0.4 (2) 0.4 <HF2 / F2 <0.73 (3) 0.65 <DS2 / F <1.35 (4) 0.4 <DS1 / F1B < 0.8 ... (5)

Further, 1.63 <F1B / F <2.62 (6)

Also, let RA1 be the radius of curvature of the long conjugate side of the aspheric lens 306 in the second lens group 300, and RA2 be 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 lens (304, 305, 307) in the second lens group 300 has its Abbe number set to ν2P
67 <ν2P (9)

Further, 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 distance between 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 preferable to increase the overall length of the lens, and accordingly, the outer diameter of the first lens group 0 increases, or the number of lenses required to configure the first A lens group 100 increases. Absent. If the lower limit value of the conditional expression (2) is exceeded, the negative refractive 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.

Conditional expressions (3) and (4) indicate 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 broken, the symmetry of the upper ray and the lower ray is also lost, so depending on the angle characteristics 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 refractive power 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 increase, and accordingly the first lens unit 300
Since the refractive power of the lens group 100 must also 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 be made strong. Or the diameter of the lens increases. If the lower limit of conditional expression (4) is exceeded, telecentricity cannot be secured 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 light rays emitted from the first A lens group 100 should be converted into the second light 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 make the off-axis light rays in the second balance with good balance. 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.

The conditional expressions (7) and (8) satisfy the condition of the second lens unit 30.
This defines the shape of the aspheric lens 306 in the middle.

The conditional expression (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 are particularly influential. 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. 19 to 28, respectively. 19A to FIG. 28A, i is the surface number (lens surface number) of the lens surface counted from the long conjugate side, which is represented by r1 to r23 (r
This corresponds to the lens surface indicated by the reference numeral up to 21). R indicates the radius of curvature of the lens surface corresponding to each lens surface number i. D is a lens surface interval corresponding to each lens surface number i, ND is a refractive index of a lens having a wavelength of 587.56 mm corresponding to each lens surface number m, and VD is an Abbe of a lens corresponding to each lens surface number i. Indicates a number. FIG.
9 to 28, F in the margin of each drawing (a) indicates the focal length of the projection lens, and Fno indicates the F number. Also, 2
w indicates the angle of view.

The surface shape as an aspheric surface shown in each of FIGS. 19 to 28 (b) is a rectangular 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.

Further, FIGS. 19 to 28 show diagrams (c),
The lens surface intervals corresponding to three predetermined projection magnifications are shown. D1 is the last lens surface of the first A lens group 100,
This is the lens surface distance between the first lens surfaces of the first B lens group 200, and D2 is the surface distance between the short conjugate side of the photosynthetic element 60 and the incident surface of the light valve 70. The specific positions of D1 and D2 in each embodiment are respectively shown in FIG.
18 to FIG.

FIG. 29 shows a numerical example satisfying the conditional expressions (1) to (10) described above in the first to tenth embodiments.

Further, according to each of FIGS. 30 to 59, the first
13 shows spherical aberration, astigmatism, and distortion of the projection lens 20 according to the tenth to tenth embodiments. Here, the first
For each of the tenth to tenth embodiments, spherical aberration, astigmatism, and distortion corresponding to each projection magnification corresponding to each diagram (c) in FIGS. 19 to 28 are shown. 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. 19A, 1
9B) or as the polarizing beam splitter 54, the center plane spacing is 36 mm (refractive index n = 1.51633, Abbe number ν)
= 64.0) is calculated.
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. 12 to 18, but may be any of the focus adjustment methods described above. As long as the conditional expression is satisfied, the number of lenses forming each lens group may be changed. The adjustment according to the present invention can simultaneously correct the aberration error of the lens, but can also be used for correcting various aberrations caused by the manufacturing error of the projection lens. In the above embodiment, the projection lens of the present invention has been described as being provided in the projection device using the liquid crystal panel and the light valve as the two-dimensional image display element in the rear projection type display device. It is not limited to this, for example,
It is also applicable to wide-angle photographic lenses for single-lens reflex cameras, industrial cameras, electrophotography, etc., and projection lenses for projection televisions using CRTs.

[0094]

As described above, the following effects can be obtained as the projection lens of the present invention. First, claim 1, claim 13 (corresponding to the first embodiment), claim 18 (corresponding to the second to fifth embodiments), and claim 2
According to the invention described in 3 (corresponding to the sixth to tenth embodiments), the distance between the on-axis lens groups of the first A lens group and the first B lens group is moved according to the projection magnification, so that each projection magnification can be changed. After the focus is adjusted, a long back focus can be obtained, and the focal length (total length of the lens system) of the entire projection lens system can be shortened. Thus, the size of the projection display device including the projection lens of the present invention can be reduced. 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.

The focus adjustment according to the present invention employs a method of moving the front lens group in the lens system. For this reason, a projection device including the projection lens according to the present invention is, for example, actually a projection device. It is only necessary to provide a mechanism for operating the lens tip projecting from the lens. Therefore, a mechanism for adjustment is easy to configure, and at the time of adjustment, there is no need to disassemble the housing of the apparatus. Further, in the focus adjustment for moving the front group in the lens system, the performance as an optical system is maintained even when the projection magnification changes, so that the present invention is commonly applied to projection display devices corresponding to different screen sizes. The projection device provided with the projection lens can be adopted.

Further, claim 3, claim 14, and claim 1
According to the ninth and twenty-fourth aspects of the present invention, an image formed 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 light rays are well balanced in the second lens. It is possible to make the light incident on the group, which facilitates aberration correction.

According to the present invention, 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 11 and 12 and claims 16 and 1
7, the chromatic aberration of magnification is suppressed by defining the Abbe number of the lens material for the positive lens constituting the second lens group, as in the invention described in claims 21, 22, and 32, 33. The colors are hardly colored at the corners of the projection screen.

Further, claims 2, 4, 5, 6, 8, 9,
10, claim 15, claim 20, claim 25, 26, 2
By defining the lens arrangement or lens shape as in the inventions described in 7, 28, 30, and 31, various variations can be obtained as the projection lens of the present invention, and a lens structure suitable for actual use conditions and the like. Can be selected, and the improvement 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 diagram showing a configuration (fourth example) of a projection display device provided with a projection lens according to an embodiment of the present invention.

FIG. 6 is an explanatory diagram showing the principle of a retrofocus lens.

FIG. 7 is an explanatory diagram showing a relationship between a stop position and telecentricity of a principal ray.

FIG. 8 is an explanatory diagram for explaining a focus adjustment technique.

FIG. 9 is a lens cross-sectional view illustrating a configuration example of a projection lens as the first embodiment.

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

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

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

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

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

FIG. 15 is a lens cross-sectional view illustrating a configuration example of a projection lens as a seventh embodiment.

FIG. 16 is a lens cross-sectional view illustrating a configuration example of a projection lens as an eighth embodiment.

FIG. 17 is a lens cross-sectional view illustrating a configuration example of a projection lens as a ninth embodiment.

FIG. 18 is a lens cross-sectional view illustrating a configuration example of a projection lens as a tenth embodiment.

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

FIG. 20 is a diagram illustrating a numerical embodiment of a projection lens as a second embodiment.

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

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

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

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

FIG. 25 is a diagram illustrating a numerical embodiment of a projection lens as a seventh embodiment.

FIG. 26 is a diagram showing a numerical embodiment of a projection lens as an eighth embodiment.

FIG. 27 is a diagram illustrating a numerical embodiment of a projection lens as a ninth embodiment;

FIG. 28 is a diagram showing a numerical embodiment of a projection lens as a tenth embodiment.

FIG. 29 is a diagram showing numerical values corresponding to conditional expressions (1) to (10) in each of the first to tenth embodiments.

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

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

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

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

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

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

FIG. 36 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the third embodiment.

FIG. 37 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the third embodiment.

FIG. 38 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the third embodiment.

FIG. 39 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the fourth embodiment.

FIG. 40 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the fourth embodiment.

FIG. 41 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of a projection lens as a fourth embodiment.

FIG. 42 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the fifth embodiment.

FIG. 43 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the fifth embodiment.

FIG. 44 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the fifth embodiment.

FIG. 45 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the sixth embodiment.

FIG. 46 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the sixth embodiment.

FIG. 47 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the sixth embodiment.

FIG. 48 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the seventh embodiment.

FIG. 49 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the seventh embodiment.

FIG. 50 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the seventh embodiment.

FIG. 51 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of a projection lens as an eighth embodiment.

FIG. 52 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the eighth embodiment.

FIG. 53 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of a projection lens as an eighth embodiment.

FIG. 54 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of a projection lens as a ninth embodiment.

FIG. 55 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of a projection lens as a ninth embodiment.

FIG. 56 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of a projection lens as a ninth embodiment.

FIG. 57 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of a projection lens as a tenth embodiment.

FIG. 58 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of a projection lens as a tenth embodiment.

FIG. 59 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of a projection lens as a 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, 50 dichroic mirror, 50a,
50b dichroic mirror, 51R, 51G, 51
B LED unit, 52 integrator, 53 condenser lens, 54 polarizing beam splitter, 55
Light valve, 56 polarizing plate, 55R, 55G, 55B
Light valve, 60 photosynthesis element, 70 light valve, 0 first lens group, 100 1A lens group, 10
1 aspherical lens, 102 meniscus lens, 103
Biconcave lens, 104 positive lens, 200 second A lens group, 201 positive lens, 300 second lens group, 30
1 laminated 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, 503 optical unit, 504 screen, 504 bent mirror, 600 projection light

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 is the longest. A first A lens group including at least one or more negative meniscus lens on the conjugate side, and a first B lens group including at least one or more positive lens, The second lens group has a cemented lens composed of a biconcave lens and a positive lens, from the side closest to the diaphragm to the side farthest from the stop, at least one positive lens, After having an aspheric lens and having a positive refracting power as a whole, the axial lens group interval between the first A lens group and the first B lens group increases from a high projection magnification to a low projection magnification. By moving in the direction, the focus is adjusted by changing the projection magnification, the focal length of the entire system when the projection magnification is minimum is F, and from the last lens surface of the second lens group to a small conjugate point. , The focal length of the first A lens group is F1A, the focal length of the first B lens group is F1B, and the focal length of the second
2. The distance from the last lens surface of the first lens group to the stop is DS1, the distance from the stop to the first lens surface of the second lens group is DS2, and the front principal point position of the second lens group is HF2. 5 <BF / F <3.0 0.6 <-F1A / F <1.4 0.4 <HF2 / F2 <0.73 0.65 <DS2 / F <1.35 0.4 <DS1 / F1B <0.8 A projection lens characterized by satisfying the following conditional expression: 2. The first A lens group includes an aspheric lens from a long conjugate side to a short conjugate side,
The projection lens according to claim 1, wherein a meniscus lens having a convex shape on the long conjugate side and a biconcave lens or a meniscus lens having a convex shape on the long conjugate side are arranged. 3. The projection lens according to claim 1, wherein the first B lens group satisfies the following conditional expression: 1.63 <F1B / F <2.62. 4. The longest on-axis air gap is closer to the iris on the conjugate side longer than the throttle, and the longest on-axis air gap 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. 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 a short 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 shape that is convex toward the long conjugate side so that negative refractive power increases from the optical axis to the periphery. 3. 7. 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 negative refractive power increases from the optical axis to the periphery. 3. 8. 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, and has a radius of curvature RA1 on the long conjugate side of the aspheric lens in the second lens group and a radius of curvature on the short conjugate side of the aspheric lens in the second lens group. 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. 9. The aspherical lens in the second lens group,
It is arranged on the shortest conjugate side closest to the cemented lens in the second lens group, and has a shape in which negative refractive power increases from the optical axis to the periphery. The projection lens according to claim 1. 10. 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. 11. 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. 12. The positive lens having the strongest positive refractive power among the positive lenses provided in the second lens group has an Abbe number of the positive lens having the strongest positive refractive power of ν2PM.
The projection lens according to claim 1, wherein AX satisfies the following conditional expression: 67 <ν2PMAX. 13. 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. From the side to the short conjugate side, at least, an aspherical lens that is located on the longest conjugate side and has a large negative refractive power from the center of the optical axis to the periphery thereof, and a negative meniscus lens having a convex shape on the long conjugate side, A first A lens group including a concave lens and a positive lens, and a 1B lens group including at least one or more positive lenses
A second lens group having a positive refractive power as a whole; and a cemented lens comprising a biconcave lens and a positive lens, from the side closest to the diaphragm to the side farthest from the stop, and at least one lens. It has at least one positive lens and an aspherical lens and has a positive refractive power as a whole, and further increases the axial lens group interval between the first A lens group and the first B lens group with a high projection magnification. By moving the lens in the direction in which the projection magnification becomes longer from the lower magnification to the lower, the focal length is adjusted by changing the projection magnification, the focal length of the entire system when the projection magnification is minimum is F, and the final distance of the second lens group is The air-equivalent distance from the lens surface to the small conjugate point is BF, the focal length of the first A lens group is F1A, the focal length of the first B lens group is F1B, and the focal length of the second lens group is F.
2. The distance from the last lens surface of the first lens group to the stop is DS1, the distance from the stop to the first lens surface of the second lens group is DS2, and the front principal point position of the second lens group is HF2. 5 <BF / F <3.0 0.6 <-F1A / F <1.4 0.4 <HF2 / F2 <0.73 0.65 <DS2 / F <1.35 0.4 <DS1 / F1B <0.8 A projection lens characterized by satisfying the following conditional expression: 14. The projection lens according to claim 13, wherein the first B lens group satisfies the following conditional expression: 1.63 <F1B / F <2.62. 15. The longest on-axis air gap exists at a position closest to the throttle toward the conjugate side longer than the throttle, and the longest on-axis air gap at the conjugate side shorter than the throttle becomes closest to the throttle. 14. The projection lens according to claim 13, wherein the projection lens is present. 16. The projection lens according to claim 13, 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. 17. The positive lens having the strongest positive refractive power among the positive lenses provided in the second lens group has an Abbe number of the positive lens having the strongest positive refractive power of ν2PM.
The projection lens according to claim 13, wherein AX satisfies the following conditional expression: 67 <ν2PMAX. 18. 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. From the side to the short conjugate side, at least, an aspherical lens that is located on the longest conjugate side and has a low negative refractive power from the center of the optical axis to the periphery thereof, and a negative meniscus lens having a convex shape on the long conjugate side, A first A lens group including a concave lens and a positive lens, and a 1B lens group including at least one or more positive lenses
A second lens group having a positive refractive power as a whole; and a cemented lens comprising a biconcave lens and a positive lens, from the side closest to the diaphragm to the side farthest from the stop, and at least one lens. It has at least one positive lens and an aspherical lens and has a positive refractive power as a whole, and further increases the axial lens group interval between the first A lens group and the first B lens group with a high projection magnification. By moving the lens in the direction in which the projection magnification becomes longer from the lower magnification to the lower, the focal length is adjusted by changing the projection magnification, the focal length of the entire system when the projection magnification is minimum is F, and the final distance of the second lens group is The air-equivalent distance from the lens surface to the small conjugate point is BF, the focal length of the first A lens group is F1A, the focal length of the first B lens group is F1B, and the focal length of the second lens group is F.
2. The distance from the last lens surface of the first lens group to the stop is DS1, the distance from the stop to the first lens surface of the second lens group is DS2, and the front principal point position of the second lens group is HF2. 5 <BF / F <3.0 0.6 <-F1A / F <1.4 0.4 <HF2 / F2 <0.73 0.65 <DS2 / F <1.35 0.4 <DS1 / F1B <0.8 A projection lens characterized by satisfying the following conditional expression: 19. The projection lens according to claim 18, wherein the first B lens group satisfies the following conditional expression: 1.63 <F1B / F <2.62. 20. On the conjugate side longer than the throttle, the longest on-axis air gap exists at the position closest to the throttle, and on the conjugate side shorter than the throttle, the longest on-axis air gap is at the position closest to the throttle. 19. The projection lens according to claim 18, wherein it is present. 21. The projection lens according to claim 18, 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 positive lens having the strongest positive refractive power of ν2PM.
19. The projection lens according to claim 18, wherein AX 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, at least, an aspheric lens that is located on the longest conjugate side and has a negative refractive power that decreases from the optical axis center to the periphery thereof, and a negative meniscus lens that is convex toward the long conjugate side. A first A lens group including a concave lens, and a first B lens group including at least one or more positive lenses so that the second lens group has a positive refractive power as a whole. From the side closest to the diaphragm to the side farthest from the stop, a cemented lens composed of a biconcave lens and a positive lens, at least one or more positive lenses, and an aspherical lens, having a positive refractive power as a whole. In addition, by moving the on-axis lens group interval between the first A lens group and the first B lens group in a direction that increases from a high projection magnification to a low projection magnification, focus adjustment by changing the projection magnification is performed. F is the focal length of the entire system when the projection magnification is the minimum, BF is the air-equivalent distance from the last lens surface of the second lens unit to the small conjugate point, F1A is the focal length of the first A lens unit, The focal length of the 1B lens group is F1B, and the focal length of the second lens group is F
2. The distance from the last lens surface of the first lens group to the stop is DS1, the distance from the stop to the first lens surface of the second lens group is DS2, and the front principal point position of the second lens group is HF2. 5 <BF / F <3.0 0.6 <-F1A / F <1.4 0.4 <HF2 / F2 <0.73 0.65 <DS2 / F <1.35 0.4 <DS1 / F1B <0.8 A projection lens characterized by satisfying the following conditional expression: 24. The projection lens according to claim 23, wherein the first B lens group satisfies the following conditional expression: 1.63 <F1B / F <2.62. 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 the short conjugate side so that the negative refractive power increases from the optical axis to the periphery. 24. The projection lens according to claim 23, wherein: 27. The aspherical lens in the second lens group has a shape that is convex toward the long conjugate side so that negative refractive power is increased from the optical axis to the periphery. 24. 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. 24. The projection lens according to 23. 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 aspherical lens in the second lens group is disposed on the shortest conjugate side closest to the cemented lens in the second lens group, and has a negative value from the optical axis to the periphery. 24. The projection lens according to claim 23, wherein the projection lens has a shape having a high refractive power. 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 positive lens having the strongest positive refractive power of ν2PM.
24. The projection lens according to claim 23, wherein AX satisfies the following conditional expression: 67 <ν2PMAX.