JP2001124988A - Projection lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain projection lens which has high optical performance, while keeping its cost low by reducing the number of lenses constituting the whole system in comparison to conventional lenses. SOLUTION: This projection lens has a wide-angle and long-back focus and also has aberrations which are corrected with ease, even if the number of lenses is reduced by satisfying conditional expressions (1) to (5).

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.

Further, from the viewpoint of cost, it is preferable that the cost of the projection lens itself is also reduced. For this purpose, for example, reducing the number of lenses constituting the projection lens is considered as one measure. Can be

[0014]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a projection lens having the highest possible optical performance even with a small number of lenses. . That is, the angle of view is wide,
In addition, even in short-range projection, a long back focus and telecentricity can be obtained, and further, aberrations with small aberrations can be obtained.

Therefore, the projection lens is configured as follows. That is, as the projection lens of the present invention, the first lens group, the stop, and the second lens group are arranged in order from the long conjugate side to the short conjugate side. The first lens group includes an aspheric lens located on the longest conjugate side and at least one positive lens, and has a positive refractive power as a whole. The second lens group includes at least one set. And a positive refractive power as a whole. At the same time, the focal length of the entire system is F, the air-equivalent distance from the final lens surface of the second lens group to a small conjugate point at a predetermined projection magnification is BF, the focal length of the second lens group is F2, Assuming that the position of the front principal point of the two lens units is HF2, the following conditional expression is satisfied: 1.87 <BF / F 0.22 <HF2 / F2 <0.57.

The projection lens of the present invention is also configured as follows. That is, the first lens group, the stop, and the second lens group are arranged in order from the long conjugate side to the short conjugate side. The first lens group includes a meniscus lens having a convex shape on the long conjugate side and at least one positive lens, and has a positive refractive power as a whole. The second lens group includes at least one set of affixed lenses. A lens and an aspherical lens are provided so as to have a positive refractive power as a whole.
At the same time, the focal length of the entire system is F, the air-equivalent distance from the final lens surface of the second lens group at a predetermined projection magnification to a small conjugate point is BF, the focal length of the second lens group is F2, Assuming that the front principal point position of the second lens group is HF2, the following conditional expression is satisfied: 1.87 <BF / F 0.22 <HF2 / F2 <0.57.

The projection lens of the present invention is also configured as follows. That is, the first lens group, the stop, and the second lens group are arranged in order from the long conjugate side to the short conjugate side. The first lens group is composed of two groups including an aspherical lens located on the longest conjugate side and a positive lens, and has a positive refractive power as a whole. A pair of laminated lens and aspherical lens
It consists of three groups and has a positive refractive power. At the same time, the focal length of the entire system is F, the air-equivalent distance from the final lens surface of the second lens group at a predetermined projection magnification to a small conjugate point is BF, and the focal length of the second lens group is F
2. Assuming that the front principal point position of the second lens group is HF2, the following conditional expression is satisfied: 1.87 <BF / F 0.22 <HF2 / F2 <0.57.

Further, the projection lens of the present invention is configured as follows. That is, the first lens group, the stop, and the second lens group are arranged in order from the long conjugate side to the short conjugate side. The first lens group is composed of two groups, an aspherical lens and a positive lens located on the longest conjugate side, and has a positive refractive power as a whole. The second lens group is located closest to the stop. Positive refraction as a whole, consisting of an aspherical lens and a cemented lens arranged in two groups and three lenses, or an aspherical lens, a positive lens and a cemented lens arranged closest to the stop, and three groups. Made to have power. At the same time, the focal length of the whole system is F, the air-equivalent distance from the final lens surface of the second lens group at a predetermined projection magnification to a small conjugate point is BF, the focal length of the second lens group is F2,
Assuming that the front principal point position of the second lens group is HF2, the following conditional expression is satisfied: 1.87 <BF / F 0.22 <HF2 / F2 <0.57.

The projection lens of the present invention is also configured as follows. The first lens group, the stop, and the second lens group are arranged in order from the long conjugate side to the short conjugate side. The first lens group includes two groups of an aspherical lens and a positive lens on the longest conjugate side, or three groups of three aspherical lenses and a negative meniscus lens and a positive lens on the longest conjugate side. The second lens group includes a set of cemented lenses and an aspherical lens disposed on the shortest conjugate side, and has three positive lens elements. It is made to have. At the same time, the focal length of the entire system is F, the air-equivalent distance from the final lens surface of the second lens group to a small conjugate point at a predetermined projection magnification is BF, the focal length of the second lens group is F2, Assuming that the position of the front principal point of the two lens units is HF2, the following conditional expression is satisfied: 1.87 <BF / F 0.22 <HF2 / F2 <0.57.

According to the present invention, by arranging the lens arrangement according to each of the above constitutions and satisfying the conditional expressions, the number of lenses is reduced, the angle of view is high, and the back focus is long. A short projection distance is secured,
In addition, a condition for obtaining a projection lens that maintains telecentricity is satisfied.

[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. 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 the description is 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, first, the light source /
In the spatial modulation unit 30, [the lamp 1R for red, the reflector 2R for red] [the lamp 1G for green, the reflector 2G for green] [the lamp 1B for blue, the reflector 2B for blue]
Are arranged according to the positional relationship shown in the figure. The lights collimated and emitted from the lamps and reflectors for the respective colors pass through a red time-division spatial modulation element 51R, a green time-division spatial modulation element 51G, and a blue time-division spatial modulation element 51B, respectively. The red light beam R, the green light beam G, and the blue light beam B are respectively transferred to the dichroic mirror unit 5.
0 is emitted.

Here, the time division spatial light modulating element 51 for red
The R, green time-division spatial modulation element 51G, and the blue time-division spatial modulation element 51B perform an operation corresponding to the image display in the plane sequential of each color of RGB. That is, for example, within one frame period, when the red time-division spatial modulation element 51R transmits light, the green time-division spatial modulation element 51R
The G and blue time-division spatial modulation elements 51B are configured not to transmit light. For example, at a predetermined timing thereafter, the light is transmitted through the green time-division spatial modulation element 51G and the red time-division spatial modulation element is used. Light is not transmitted through the 51R and blue time-division spatial modulation element 51B. At the subsequent predetermined timing, light is transmitted through the blue time-division spatial modulation element 51B,
The red time-division spatial modulation element 51R and the green time-division spatial modulation element 51G are controlled so as not to transmit light. By repeating such a time-divisional spatial modulation operation for each RGB for each frame, the light source / spatial modulator 3
From 0, the respective light beams of RGB are emitted alternately in a certain short fixed cycle. By such an operation, as an image finally projected on the screen 21, images of respective colors of RGB are alternately displayed in a short cycle.
This can be viewed as a full-color image (white light) in which the three colors B are combined.

As described above, the dichroic mirror unit 50 on which the light of each color emitted from the time division spatial modulation element 51R for red, the time division spatial modulation element 51G for green, and the time division spatial modulation element 51B for blue enters , Dichroic mirrors 50a and 50b arranged in a position as shown in FIG.
It has.

Here, the time-division spatial modulation element 51R for red color
The light flux R emitted from is reflected by the dichroic mirror 50a and enters the integrator 52. The light beam G emitted from the green time-division spatial modulation element 51G passes through the dichroic mirrors 50a and 50b and enters the integrator 52. The light beam B emitted from the blue time-division spatial modulation element 51B is reflected by the dichroic mirror 50b and enters the integrator 52.

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 polarization beam splitter 54 is reflected on the PBS-coated surface in the polarization 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.

FIG. 6 shows another example of a projection display device as a fourth example. In the configuration shown in FIG. 6, the light source / spatial modulator 3 is different from the configuration shown in FIG.
A light source / spatial modulator 30B is provided instead of 0. In FIG. 6, the same parts as those in FIG.

In the light source / spatial modulator 30B shown in FIG. 6, the light collimated by the lamp 1 and the reflector 2 is time-division red light arranged so that three light beams are superimposed along the optical axis direction. The light is emitted to the spatial modulation element 51R, the blue time-division spatial modulation element 51B, and the green time-division spatial modulation element 51G. The emitted light is made incident on the integrator 52.

Even in this configuration, the time-division spatial light modulating element 51R for red, the time-division spatial light-modulating element 51G for green, and the time-division spatial light-modulating element 51B for blue correspond to the image display by the plane sequential method of each color of RGB. Thus, the transmission and non-transmission timings of the light are controlled. Therefore, also in this case,
From the spatial modulation section 30B, the luminous flux of each color of RGB is emitted alternately in a short time.

FIG. 7 shows still another example of the projection display device as the fourth example. In the projection display device shown in FIG. 7A, the light source / spatial modulator 30 is replaced with the light source / spatial modulator 30 in the configuration shown in FIG.
C is provided. In FIG. 7, the same parts as those in FIG.

The light source / spatial modulator 30C shown in FIG.
, A lamp 1, a reflector 2, and a time-division spatial modulation panel 40 are provided. The light collimated by the lamp 1 and the reflector 2 passes through the time-division spatial modulation board 40 and thereafter enters the integrator 52.

FIG. 7B shows the time-division spatial modulation panel 40.
Is shown from the front. As you can see from this figure,
The time-division spatial modulation panel 40 has a red dichroic filter 4 that transmits a red component in the form shown in the figure, for example.
1R, a blue dichroic filter 41B transmitting a blue component, and a green dichroic filter 41G transmitting a green component are provided. Then, the mounting is performed in the projection display device so as to rotate about the rotation shaft 42. Further, the positional relationship with the light source unit including the lamp 1 and the reflector 2 is defined so that the range of the light flux emitted from the light source unit indicated by a broken line in FIG. 7B is covered by the dichroic filter portion of each color. Is done.

In this configuration, by rotating the time-division spatial modulation panel 40 in a predetermined direction at a predetermined rotation cycle, a light beam transmitted from the light source unit through the time-division spatial modulation panel 40 is:
RGB colors are obtained in a time-division manner. That is, the light beams of the respective colors RGB are emitted alternately in a short cycle in accordance with the frame sequential method.

The transmission type light valve (liquid crystal panel block) provided in the structure shown in the first to third examples is, for example, an STN (Super Twisted Nem).
atic) A liquid crystal display element, a ferroelectric liquid crystal display element, a polymer dispersion type liquid crystal display element and the like can be adopted. Also,
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. Moreover,
A reflection type liquid crystal element such as a grating light valve having a structure whose shape or state is changed by an electric field can also be given.

The projection device according to the present embodiment has been described with reference to four examples (two modifications are shown as a fourth example). However, these are merely examples, and the present invention is not limited to the example. There are various other possible internal configurations of the projection display device on which the projection lens of the form described above can be mounted.

[0061] 2. Lens A so-called retrofocus type lens system is adopted 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. 8 and 9. Let me explain briefly.

The lens L1 shown in FIG. 8A has a positive refractive power. FIG. 8A shows that, when the object is at the infinite position, the focal position of the normal lens having a positive refractive power is located at a focal length on the short conjugate side from the principal point. 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. 8C has a negative refractive power. FIG. 8C shows that the lens having a negative refractive power has a long focal length on the conjugate side from the principal point when the object is at the infinite position.

Therefore, as shown in FIG. 8D, 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 a long conjugate side by a front lens L2 having a negative refractive power (which may be regarded as a lens group), and a 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. 9 shows the relationship between the stop position and the telecentricity of the principal ray in a retrofocus type lens system. As shown in FIG. 9A, 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. 9B, 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.

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, and this is effective in correcting off-axis aberrations such as astigmatism 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 fifth embodiments to be described hereinafter 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 fifth embodiments is given, and the shape of each lens, the distance between the lenses, and the like are represented by numerical embodiments described later. I do. In FIGS. 10 to 14 described below, reference numerals r1 to r15 (r13) indicate lens surface numbers, and d1 to d14.
Reference numerals shown up to (d12) indicate a lens surface interval and a lens interval (lens thickness) on the principal ray axis. The reference numerals L1 to L6 (L5) assigned to the lenses are lens numbers assigned to the lenses themselves in the order of arrangement from the long conjugate side to the short conjugate side. .

First, the lens arrangement structure of the projection lens 20 according to the first embodiment will be described. FIG.
FIG. 3 is a lens cross-sectional view conceptually showing a lens arrangement structure of the projection lens 20 according to the first embodiment. In these figures, the left side of the figures is the screen 21 side (long conjugate side), and the right side is the light valve and photosynthesis element side (short conjugate side). The photosynthesis element 60 includes, for example, each of the photosynthesis elements (19, 19A,
19B) and the polarization beam splitter 54 shown in FIGS. 5 to 7.
To the light valve shown in FIG.
(GB liquid crystal display panel block).

As the projection lens 20 of the first embodiment, as shown in FIG. 10, a first lens group 100, a diaphragm 300, and a second lens group 200 are sequentially arranged from the long conjugate side to the short conjugate side. It consists of

In this case, the first lens group 100 sequentially includes the aspherical lens 101 from the long conjugate side to the short conjugate side.
And a positive lens 102 are arranged.
It has a positive refractive power. Here, both surfaces of the aspheric lens 101 as the meniscus lens located on the longest conjugate side have aspheric surfaces according to the aspheric coefficient in the numerical embodiment described later. Further, the aspheric lens 101 is configured such that the negative refractive power increases from the center of the optical axis to the periphery thereof. The positive lens 102 is disposed so as to be in contact with the diaphragm 300, as can be seen from the numerical embodiments described later.

The second lens group 200 is arranged in order from the long conjugate side to the short conjugate side.
1. A three-group configuration in which an aspheric lens 204 is arranged is adopted. The cemented lens 201 includes a meniscus lens 202 having a negative refractive power and a positive lens 203 having a positive refractive power, which are arranged from the long conjugate side to the short conjugate side.
Are bonded together. With such a configuration, the second lens group 200 has a positive refractive index as a whole. The aspheric lens 204 in the second lens group 200 also has an aspheric coefficient according to a numerical embodiment described later. Further, as can be said for the second and third embodiments, the longest lens interval in the entire system of the projection lens 20 is set to be in the first lens group. That is, the longest lens interval in the entire system is the axial air interval that is the interval (d2) between the aspherical lens 101 and the positive lens 102.

In the present specification, the “final lens surface” or “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 lens group 100 shown in FIG. 10, the “final lens surface” of the first lens group 100 is the lens surface (r4) on the short conjugate side of the positive lens 104, The “first lens surface” of the first lens group 100 is the lens surface (r1) on the long conjugate side of the aspheric lens 101.

FIG. 11 is a sectional view showing a lens arrangement of a projection lens 20 according to a second embodiment. In this figure, the same parts as those in FIG. 10 are denoted by the same reference numerals, and the description of the parts having the same contents will be omitted. The projection lens 20 according to the second embodiment shown in FIG.
At 00, a three-group, four-element configuration in which an aspheric lens 205, a positive lens 204, and a cemented lens 201 are arranged in order from the long conjugate side to the short conjugate side is adopted. Have. In this case, the aspherical lens 205 in the second lens group 200 has a shape in which both surfaces are convex to the short conjugate side.

FIG. 12 is a sectional view showing a lens arrangement of a projection lens 20 according to the third embodiment. The arrangement structure of the projection lens 20 according to the third embodiment shown in FIG. 12 is the same as that of the second embodiment shown in FIG. The description of is omitted here. However,
In this case, as can be seen from the numerical embodiments described later, the positive lens 102 and the aperture 300 are not in a state of contact but are arranged at a predetermined axial air interval that is considered to be close. ing. This applies to the fourth and fifth embodiments described below.

The lens sectional view shown in FIG. 13 shows the lens arrangement structure of the projection lens 20 as the fourth embodiment, and the same parts as those in FIGS. Is omitted. The projection lens 20 according to the fourth embodiment shown in FIG.
At 00, a three-group three-element configuration in which an aspheric lens 101, a meniscus lens 103 having a negative refractive power, and a positive lens 102 are arranged in order from the long conjugate side to the short conjugate side is adopted. It has a positive refractive power. The second lens group 200 has the same lens arrangement structure as the second lens group 200 of the first embodiment shown in FIG.

FIG. 14 is a sectional view showing a lens arrangement of a projection lens 20 according to a fifth embodiment. The arrangement structure of the projection lens 20 according to the fourth embodiment shown in FIG. 14 is the same as that of the third embodiment shown in FIG. The description of is omitted here.

3-2. Conditional Expression The projection lens 20 according to the first to fifth embodiments having the above-described configuration satisfies the following conditional expressions (1) to (5).

The focal length of the entire system is F, the air equivalent distance from the final lens surface of the second lens group 200 at a predetermined projection magnification to a small conjugate point is BF, the focal length of the second lens group 200 is F2, Assuming that the front principal point position of the lens group 200 is HF2, 1.87 <BF / F (1) 0.22 <HF2 / F2 <0.57 (2)

The Abbe number of a lens having a positive refractive power (positive lens 203) in the cemented lens 201 of the second lens group 200 is νP, and the negative refractive power of the lens 201 in the second lens group 200 is Assuming that the Abbe number of the lens (the meniscus lens 202) is νN, 55.0 <νP (3) νN <30.0 (4)

Further, assuming that the longest surface interval in the first lens group 100 is t1G and the focal length of the lens having a positive refractive power closest to the stop in the first lens group 100 is F1P, 0.41 <t1G / F1P <0.84 (5)

Next, each of the above conditional expressions will be described.
For example, as can be seen from the configurations shown in FIGS. 2 to 7, 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, so that a long back focus is required. 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) indicates that the position of the stop 300 and the second
This is a condition for telecentricity of the lens group 200. In general, rays that pass through the front focal point of the lens become parallel rays after passing through the lens. In the case of the projection lens 20 of the present embodiment, if a stop is set near the front focal point of the second lens group 200, the principal ray emitted to the short conjugate side becomes close to a parallel ray, and it can be understood that telecentricity can be realized. I have. In other words, the best telecentricity is obtained when the position of the front principal point of the second lens group 200 from the stop 300 matches the focal length F2 of the second lens group 200. Conditional expression (2) defines this.
By the way, if the telecentricity is lost, the symmetry of the upper ray and the lower ray is also lost, so depending on the angle characteristics when transmitting or reflecting through the coating film of the prism or mirror for color synthesis and polarizing beam splitter, the The intensity differs depending on the wavelength, which causes 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 (2), the telecentricity cannot be secured unless the refractive power of the second lens group 200 is weakened, and the telecentricity is intentionally maintained in a state where the upper limit of the conditional expression (2) is exceeded. If so, the back focus will be shortened. vice versa,
If the lower limit of conditional expression (2) is exceeded, the refracting power of the second lens group 200 will increase, and accordingly, the first A lens group 1
Since the refracting power of 00 must also be increased, it is difficult to correct off-axis aberrations and the lens diameter is undesirably large.

The conditional expressions (3) and (4) define the Abbe number as a lens material. The conditional expression (3) particularly indicates the condition of the Abbe number of the positive lens of the cemented lens 201 having a strong refractive power. Exceeding the ranges represented by the conditional expressions (3) and (4) causes the chromatic aberration of magnification to increase, and the corners of the projection screen are likely to be colored.

Conditional expression (5) is used to make the off-axis ray emitted from the first lens group 100 incident on the second lens group 200 with a good balance.
Is the condition. In a normal retrofocus type projection lens, a long conjugate side has a negative refractive power and a short conjugate side has a positive refractive power across the stop. However, the projection lens 20 of the present embodiment has the first lens group 1
In the first lens group 100, the lens group that is located on the conjugate side longer than the positive lens 102 closest to the diaphragm 300 at the 00
The conjugate side closest to 0 and shorter than the positive lens 102 is the rear group of the retrofocus type. By doing so, the off-axis rays emitted from the first lens group can be made to enter the second lens group in a well-balanced manner, so that the size of the entire lens system, the back focus, and the optical performance can be kept good. If the upper limit of conditional expression (5) is exceeded, the overall length of the lens will increase, and accordingly the outer diameter of the first lens group 100 will increase. In addition, when the focal length of the first lens group 100 having the closest refractive power to the lens having the closest refractive power becomes small, the angle of the off-axis ray incident on the second lens group 200 becomes sharp, and it is difficult to correct aberration. Become. If the lower limit of conditional expression (5) is exceeded, the refracting power of each lens of the first lens group 100 becomes strong, and in particular, aberration of light rays passing through the periphery occurs, making it difficult to correct.

3-3. Numerical Embodiments, etc. Numerical embodiments as the projection lens 20 of the first to fifth embodiments are shown in FIGS. 15 to 19, respectively. In each of FIGS. 15 to 19A, i is the surface number (lens surface number) of the lens surface counted from the long conjugate side, which is represented by r1 to r15 (r
It corresponds to the lens surface indicated by the reference numeral 13). 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.
F in each of FIGS. 5A to 19A indicates the focal length of the projection lens, and Fno indicates the F number. In addition, the left column of each drawing (a) in FIGS.
, An optical element corresponding to the lens surface number is described together with the lens number indicated as L1L6 (L5).

The surface shape (aspheric surface coefficient) as an aspheric surface shown in each of FIGS. 15 to 19B is an orthogonal coordinate system (Z) in which the center of the surface is the origin and the optical axis direction is Z. X, Y,
In Z), r is the central radius of curvature, K is the conic constant, A
4, A6, A8, and A10 are the fourth, sixth, eighth,
When a 10th order aspheric coefficient is used,

(Equation 1) Is represented by the following equation.

FIG. 20 shows a numerical example satisfying the above-described conditional expressions (1) to (5) in the first to fifth embodiments.

Further, according to each of FIGS. 21 to 25, the first
13 shows spherical aberration, astigmatism, and distortion of the projection lens 20 of the fifth to fifth embodiments. In order to obtain the results shown in the various aberration diagrams shown in these drawings, although not shown in the numerical embodiments, the light combining element 19 (shown in FIGS. 19A,
19B) or as a polarizing beam splitter 54, a parallel plane plate having a center plane spacing of 36 mm (refractive index n = 1.51633, Abbe number ν = 64.0) is used for the calculation. However, the numerical value of such a color combining prism is
It does not affect the configuration of the projection lens as the present invention.

The actual structure of the projection lens according to the first to fifth embodiments is not limited to those shown in FIGS. 10 to 14, but includes the conditional expressions described above. As long as the various conditions described above are satisfied, the number of lenses forming each lens group may be changed. 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. The present invention is not limited to this, and can be applied to, for example, wide-angle photographic lenses for single-lens reflex cameras, industrial cameras, electrophotography, etc., and projection lenses for projection televisions using CRTs. You.

[0091]

As described above, the following effects can be obtained as the projection lens of the present invention. First, claim 1 (corresponding to the first to fifth embodiments), claim 5 (corresponding to the first to fifth embodiments), and claim 10 (corresponding to the first and third embodiments) Claim 15 (second and third)
According to the invention described in claim 21 (corresponding to the first and fourth embodiments), the number of lenses forming the entire system of the projection lens is reduced as compared with the related art, thereby increasing the cost. It is possible to obtain high optical performance while suppressing it. That is, as the optical characteristics, a long back focus can be obtained, and the focal length of the entire projection lens system (total length of the lens system) can be shortened. This also allows the projection display device including the projection lens of the present invention to be downsized. 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, telecentricity between the aperture and the second lens group can be ensured to prevent color unevenness and intensity unevenness appearing on the screen of the projected image.

Further, claim 4, claim 9, claim 14,
According to the nineteenth and twenty-third aspects of the present invention, the chromatic aberration of magnification is suppressed by defining the Abbe number of the lens material for the cemented lens constituting the second lens group, and the corners of the projection screen are hardly colored. To be.

Further, claim 8, claim 13, and claim 1
According to the eighth and twenty-fifth aspects of the present invention, the first lens group is configured so that off-axis rays emitted from the first lens group enter the second lens group with a good balance. Aberration correction can be easily performed without making the angle of the off-axis light beam incident on the optical axis sharp. This leads to the effect that color shift around the screen can be suppressed even if the resolution of the lens is increased with the increase in the resolution of the light valve (liquid crystal panel), for example.

Further, claim 2, claim 6, claim 11,
The invention according to claim 16 and claim 22, the invention according to claim 3, claim 7, claim 12, claim 17 and claim 23, the invention according to claim 20 and claim 27, and the claim. By defining the lens arrangement or lens shape as in the invention described in Item 24, various variations can be obtained as the projection lens of the present invention, and the degree of freedom to select a lens structure suitable for actual use conditions and the like. And the enhancement of the optical characteristics of the projection lens described above can be enhanced.

[Brief description of the drawings]

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

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

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

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

FIG. 5 is a 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 a diagram showing a configuration (another example of the fourth example) of a projection display device provided with a projection lens according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating a configuration (still another example of the fourth example) of a projection display device including a projection lens according to an embodiment of the present invention.

FIG. 8 is an explanatory diagram illustrating the principle of a retrofocus lens.

FIG. 9 is an explanatory diagram illustrating a relationship between a stop position and telecentricity of a principal ray.

FIG. 10 is a lens cross-sectional view showing a structural example of a projection lens as the first embodiment.

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

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

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

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

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

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

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

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

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

FIG. 20 is a diagram showing numerical values corresponding to conditional expressions (1) to (5) in each of the first to fifth embodiments.

FIG. 21 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the first embodiment.

FIG. 22 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the second embodiment.

FIG. 23 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the third embodiment.

FIG. 24 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of the projection lens as the fourth embodiment.

FIG. 25 is an aberration diagram showing a spherical aberration, an astigmatism, and a distortion of a projection lens as a fifth embodiment.

[Explanation of symbols]

1 (1R, 1G, 1B) lamp, 2 (2R, 2G, 2)
B) Reflector, 3IR-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 LCD panel block, 10, 10A, 10B Dichroic mirror,
11, 11A, 11B Condenser lens, 12, 1
2A, 12B Liquid crystal panel block, 13, 13A, 1
3B relay lens, 14, 14A, 14B mirror,
15, 15A, 15B Inverting relay lens, 16, 1
6A, 16B mirror, 17, 17A, 17B condenser lens, 18, 18A, 18B liquid crystal panel block, 19, 19A, 19B photosynthesis element, 19a, 1
9b, 19A-a, 19A-b, 19B-a, 19B-
b reflective film 20 projection lens, 21 screen, 3
0, 30A, 30B light source / spatial modulator, 40 time-division spatial modulator, 41R, 41G, 41B dichroic filters (red, green, blue), 50 dichroic mirror, 50a, 50b dichroic mirror, 51R,
51G, 51B time-division spatial modulation element (for red, green, blue), 52 integrator, 53 condenser lens, 54 polarization beam splitter, 55 light valve, 56 polarizing plate, 55R, 55G, 55B light valve, 60 photosynthesis element , 70 light valve, 1
00 first lens group, 101 aspherical lens, 102
Positive lens, 103 meniscus lens, 200 second lens group, 201 bonded lens, 202 meniscus lens, 203 positive lens, 204 aspheric lens, 2
05 aspheric lens, 300 aperture, 500 projection display device, 501 cabinet, 502 projection device, 503 optical unit, 504 screen,
504 bent mirror, 600 projected light

Claims (27)

[Claims] 1. A first lens group, a stop, and a second lens group are arranged in this order from a long conjugate side to a short conjugate side, and the first lens group is an aspheric lens located on the longest conjugate side. And at least one positive lens, so that the second lens group has a positive refractive power as a whole. The second lens group includes at least one set of a cemented lens and an aspheric lens, and In addition to having a positive refractive power, the focal length of the entire system is F, the air-equivalent distance from the final lens surface of the second lens group at a predetermined projection magnification to a small conjugate point is BF, The focal length of the lens group is F2,
A projection lens characterized by satisfying the following conditional expression: 1.87 <BF / F 0.22 <HF2 / F2 <0.57, where HF2 is the front principal point position of the lens group. 2. The projection lens according to claim 1, wherein the aspherical lens of the first lens group has a negative refractive power that increases from the center of the optical axis to the periphery. 3. The positive lens of the first lens group is disposed so as to be in contact with the stop or at a predetermined distance that is considered to be close to the stop. The projection lens according to claim 1, wherein: 4. The cemented lens in the second lens group is formed by combining a lens having a negative refractive power and a positive lens having a positive refractive power in order from a long conjugate side to a short conjugate side. In addition, the Abbe number of a lens having a positive refractive power in the cemented lens of the second lens group is νP, and the Abbe number of a lens having a negative refractive power in the cemented lens of the second lens group is νN, The projection lens according to claim 1, wherein the following conditional expression is satisfied: 55.0 <νPνN <30.0. 5. A first lens group, a stop, and a second lens group are arranged in this order from a long conjugate side to a short conjugate side, and the first lens group has a meniscus lens convex to the long conjugate side. Including at least one positive lens,
The second lens group has at least one set of a cemented lens and an aspherical lens as a whole, and has a positive refractive power as a whole. The distance is F, the air-equivalent distance from the last lens surface of the second lens group to the small conjugate point at the predetermined projection magnification is BF, the focal length of the second lens group is F2, and the second
A projection lens characterized by satisfying the following conditional expression: 1.87 <BF / F 0.22 <HF2 / F2 <0.57, where HF2 is the front principal point position of the lens group. 6. The method according to claim 5, wherein the meniscus lens of the first lens group is an aspherical lens and has a negative refractive power that increases from the optical axis center to the periphery. The projection lens as described. 7. The positive lens of the first lens group is disposed so as to be in contact with the stop or at a predetermined distance that is considered to be close to the stop. The projection lens according to claim 5, wherein: 8. The longest lens interval in the entire system is made to exist after the aspherical lens assumed to be in the first lens unit, and the longest surface interval in the first lens unit is set. Is defined as t1G and the focal length of a lens having a positive refractive power closest to the stop in the first lens group is defined as F1P, and the following conditional expression is satisfied: 0.41 <t1G / F1P <0.84. A projection lens according to claim 5. 9. The cemented lens in the second lens group is composed of a combination of a lens having a negative refractive power and a positive lens having a positive refractive power arranged in order from a long conjugate side to a short conjugate side. In addition, the Abbe number of the lens having a positive refractive power of the cemented lens of the second lens group is νP, and the Abbe number of the lens having a negative refractive power of the cemented lens of the second lens group is νN. The projection lens according to claim 5, wherein the following conditional expression is satisfied: 0.0 <νPνN <30.0. 10. A first lens group, a stop, and a second lens group are arranged in this order from a long conjugate side to a short conjugate side, and the first lens group is an aspheric lens located on the longest conjugate side. The second lens group is composed of a set of a cemented lens and an aspherical lens. , The focal length of the entire system being F, the air-equivalent distance from the last lens surface of the second lens group to a small conjugate point at a predetermined projection magnification being BF, The focal length of the lens group is F2,
A projection lens characterized by satisfying the following conditional expression: 1.87 <BF / F 0.22 <HF2 / F2 <0.57, where HF2 is the front principal point position of the lens group. 11. The aspheric lens of the first lens group,
11. The projection lens according to claim 10, wherein the negative refractive power increases from the optical axis center to the periphery. 12. The positive lens of the first lens group is disposed so as to be in contact with the stop or at a predetermined distance that is considered to be close to the stop. The projection lens according to claim 10, wherein: 13. The longest lens interval in the whole system is made to exist between the aspherical lens and the positive lens of the first lens group, and the longest surface interval in the first lens group is t1G, 11. The lens system according to claim 10, wherein a focal length of a lens having a positive refractive power closest to the stop in the first lens unit is F1P, and a conditional expression of 0.41 <t1G / F1P <0.84 is satisfied. The projection lens according to 1. 14. The cemented lens in the second lens group is composed of a combination of a meniscus lens having a negative refractive power and a positive lens having a positive refractive power arranged in order from a long conjugate side to a short conjugate side. In addition, the Abbe number of the lens having a positive refractive power of the cemented lens of the second lens group is νP, and the Abbe number of the lens having a negative refractive power of the cemented lens of the second lens group is νN, The projection lens according to claim 10, wherein the following conditional expression is satisfied: 55.0 <νPνN <30.0. 15. A first lens group, a stop, and a second lens group are arranged in this order from a long conjugate side to a short conjugate side, and the first lens group is an aspheric lens located on the longest conjugate side. And a positive lens as a whole, having a positive refractive power as a whole. The second lens group includes an aspherical lens disposed closest to the diaphragm and a cemented lens in two groups. Or, it is composed of an aspherical lens, a positive lens, and a cemented lens, which are arranged closest to the stop, and has four lenses in three groups, and has a positive refractive power as a whole. The distance is F, the air-equivalent distance from the last lens surface of the second lens group to the small conjugate point at the predetermined projection magnification is BF, the focal length of the second lens group is F2, and the second
A projection lens characterized by satisfying the following conditional expression: 1.87 <BF / F 0.22 <HF2 / F2 <0.57, where HF2 is the front principal point position of the lens group. 16. The aspheric lens of the first lens group,
16. The projection lens according to claim 15, wherein the negative refractive power increases from the optical axis center to the periphery. 17. The positive lens of the first lens group is disposed so as to be in contact with the stop or at a predetermined distance that is considered to be close to the stop. The projection lens according to claim 15, wherein: 18. The longest lens interval in the whole system is made to exist between the aspherical lens and the positive lens of the first lens group, and the longest lens interval in the first lens group is set to t1G. And wherein the focal length of a lens having a positive refractive power closest to the stop in the first lens group is F1P, and a conditional expression of 0.41 <t1G / F1P <0.84 is satisfied. 15. The projection lens according to 15. 19. The cemented lens in the second lens group is composed of a combination of a meniscus lens having a negative refractive power and a positive lens having a positive refractive power arranged in order from a long conjugate side to a short conjugate side. In addition, the Abbe number of the lens having a positive refractive power of the cemented lens of the second lens group is νP, and the Abbe number of the lens having a negative refractive power of the cemented lens of the second lens group is νN, The projection lens according to claim 15, wherein the following conditional expression is satisfied: 55.0 <νPνN <30.0. 20. The projection lens according to claim 15, wherein the aspheric lens in the second lens group has a convex shape on both short conjugate sides. 21. A first lens group, a stop, and a second lens group are arranged in order from a long conjugate side to a short conjugate side, and the first lens group is an aspheric lens located on the longest conjugate side. And two groups of positive lenses, or an aspheric lens located on the longest conjugate side, a negative meniscus lens, and three groups of three positive lenses, and as a whole have a positive refractive power, The second lens group is composed of a group of three cemented lenses and an aspherical lens disposed on the shortest conjugate side, and has a positive refractive power as a whole. The distance is F, the air-equivalent distance from the last lens surface of the second lens group to the small conjugate point at the predetermined projection magnification is BF, the focal length of the second lens group is F2, and the second
A projection lens characterized by satisfying the following conditional expression: 1.87 <BF / F 0.22 <HF2 / F2 <0.57, where HF2 is the front principal point position of the lens group. 22. The aspheric lens of the first lens group,
22. The projection lens according to claim 21, wherein the negative refractive power increases from the optical axis center to the periphery. 23. The positive lens of the first lens group is disposed so as to be in contact with the stop or at a predetermined distance that is considered to be close to the stop. The projection lens according to claim 21, wherein: 24. The projection lens according to claim 21, wherein a longest lens interval in the entire system is set between the stop and the second lens group. 25. The longest lens interval in the entire system is made to exist between the aspherical lens and the positive lens of the first lens group, and the longest surface interval in the first lens group is t1G. And wherein the focal length of a lens having a positive refractive power closest to the stop in the first lens group is F1P, and a conditional expression of 0.41 <t1G / F1P <0.84 is satisfied. 22. The projection lens according to 21. 26. The cemented lens in the second lens group is composed of a combination of a meniscus lens having a negative refractive power and a positive lens having a positive refractive power arranged in order from a long conjugate side to a short conjugate side. In addition, the Abbe number of the lens having a positive refractive power of the cemented lens of the second lens group is νP, and the Abbe number of the lens having a negative refractive power of the cemented lens of the second lens group is νN, The projection lens according to claim 21, wherein the following conditional expression is satisfied: 55.0 <νPνN <30.0. 27. The projection lens according to claim 21, wherein the aspherical lens in the second lens group has a shape as a biconvex lens.