JP2016109810A - Projection lens and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel fixed-focus projection lens configured to adjust focus in accordance with a projection distance.SOLUTION: A projection lens is for projecting an image displayed on an image display element to a projection surface to present a magnified view of the image and is capable of adjusting focus in accordance with a projection distance. The projection lens includes, in order from a magnification side to the image display element side, a first lens group G1 having positive or negative refractive power close to zero, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having positive refractive power, where an aperture stop (Stop) is located in the fifth lens group G5. When adjusting focus, the first lens group G1 and the fifth lens group G5 are stationary, while two or more groups of the second through fourth lens groups G2-G4 move. An effective lens diameter MDi of a lens with the largest effective lens diameter in an i-th lens group (i is 1 through 5) satisfies a magnitude relation expressed as: MD5<MD2<MD3≤MD4<MD1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a projection lens and an image display device.

  In recent years, image display devices that project an image displayed on an image display element as an enlarged image on a projection surface have been widely used for presentations in companies, education in schools, and home use.

  Hereinafter, the image display element is also referred to as “light valve”, the projection surface is also referred to as “screen”, and the image display device is also referred to as “projector”.

  Various types of projection lenses for forming an image displayed on the image display element on the screen are also known, but one type is “a type that performs a focusing operation according to the projection distance with a fixed focus”. Are known (Patent Documents 1 to 3).

  This invention makes it a subject to implement | achieve the novel projection lens of the type which performs a focusing operation | movement according to a projection distance with a fixed focus.

A projection lens according to the present invention is a projection lens that projects an image displayed on an image display element onto a projection surface to display the enlarged image, and can be focused according to a projection distance. A first lens group having a refractive power close to 0 in a positive or negative direction, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power sequentially toward the side. A fifth lens group having a positive refractive power, an aperture stop in the fifth lens group, and the first lens group and the fifth lens group are fixed at the time of focusing; When two or more of the fourth lens groups move and the effective lens diameter of the lens having the largest effective lens system in the i-th lens group (i = 1 to 5) is MDi, these are magnitude relationships:
MD5 <MD2 <MD3 <MD4 <MD1
Satisfied.

  According to the present invention, a novel projection lens of a type that performs a focusing operation in accordance with the projection distance with a fixed focus can be realized.

3 is a cross-sectional view illustrating a configuration of a projection lens of Example 1. FIG. FIG. 6 is a cross-sectional view showing the movement of a group of projection lenses in Example 1. FIG. 3 is an aberration curve diagram of the projection lens of Example 1. FIG. 6 is a cross-sectional view illustrating a configuration of a projection lens of Example 2. FIG. 6 is a cross-sectional view showing the movement of a group of projection lenses in Example 2. 6 is an aberration curve diagram of the projection lens of Example 2. FIG. FIG. 6 is a cross-sectional view illustrating a configuration of a projection lens of Example 3. FIG. 6 is a cross-sectional view showing the movement of a group of projection lenses in Example 3. FIG. 6 is an aberration curve diagram of the projection lens of Example 3. 10 is a cross-sectional view illustrating a configuration of a projection lens of Example 4. FIG. FIG. 10 is a cross-sectional view showing the movement of a group of projection lenses in Example 4. FIG. 6 is an aberration curve diagram of the projection lens of Example 4. 6 is a cross-sectional view illustrating a configuration of a projection lens of Example 5. FIG. FIG. 10 is a cross-sectional view showing the movement of a group of projection lenses in Example 5. FIG. 10 is an aberration curve diagram of the projection lens of Example 5. It is a schematic block diagram of an example of the projector apparatus as an image display apparatus. It is a schematic block diagram of another example of the projector apparatus as an image display apparatus.

  Hereinafter, embodiments will be described.

  5, FIG. 7, FIG. 7, FIG. 10, and FIG. 13 show five embodiments of projection lenses.

The projection lenses of these embodiments correspond to specific Examples 1 to 5 described later in this order.
In each of the above figures, the left side of the figure is the “enlargement side (screen side)” and the right side is the “reduction side (image display element side)”. In order to avoid complications, the symbols are shared in these drawings.
In each of the drawings, reference numeral G1 indicates a first lens group, reference numeral G2 indicates a second lens group, reference numeral G3 indicates a third lens group, reference numeral G4 indicates a fourth lens group, and reference numeral G5 indicates a fifth lens group.

  Reference numeral Stop denotes an aperture stop.

  In other words, the projection lens shown in each of the above embodiments has a five-lens group configuration in which the first lens group G1 to the fifth lens group G5 are arranged sequentially from the enlargement side to the reduction side.

  The reference numerals of the lenses constituting the first lens group G1 to the fifth lens group G5 are determined as follows.

  That is, in the lenses constituting the i-th lens group Gi, the code of the j-th lens counted from the magnification side is “Lij”.

In the embodiments shown in the drawings, the first lens group G1 is composed of two lenses L11 and L12, and the second lens group G2 is composed of three lenses L21, L22, and L23.
The third lens group G3 is composed of one lens L31, the fourth lens group G4 is composed of one lens L41, and the fifth lens group G5 is composed of five lenses L51 to L55.

Further, in each of the above drawings, the symbol CG indicates “a cover glass of an image display element (light valve)”.
In the embodiments and examples described below, “DMD as a micromirror device” is assumed as the light valve, but of course, the light valve is not limited to DMD.

  The “image display surface” of the image display element is in close contact with the “right surface in the drawing” of the cover glass CG shown in the above drawings. The image displayed on the image display surface is projected on the screen by the projection lens and enlarged.

  2, 5, 8, 11, and 14 are diagrams for explaining focusing in the projection lens according to the embodiment shown in FIGS. 1, 4, 7, 10, and 13.

  In FIG. 1, FIG. 4, FIG. 7, FIG. 10 and FIG. 13, "medium distance" means that the projection distance, that is, the distance from the projection lens to the projection surface (screen) is the "reference distance". To do.

  2, 5, 8, 11, and 14, the “upper view” shows the lens group arrangement at the “short distance” in which the projection distance to the screen is shorter than the intermediate distance, and the “lower view”. Indicates the lens group arrangement at a “far distance” in which the projection distance is longer than the middle distance.

  In these figures, “broken line shown between the upper and lower figures” represents the state of movement of the lens group when focusing from a short distance to a long distance.

  The first lens group G1 has “refractive power close to 0 with positive or negative”. That is, the refractive power of the first lens group G1 can be “positive or negative”, but the refractive power is close to zero.

  In other words, the first lens group G1 is “substantially afocal”.

  The second lens group G2 has “negative refractive power”, and the third lens group G3 to the fifth lens group G5 all have “positive refractive power”.

When the effective lens diameter of the “lens with the largest effective lens diameter” is MDi in the i-th lens group (i = 1 to 5), these are the magnitude relationships:
MD5 <MD2 <MD3 <MD4 <MD1
Is satisfied.

  The fifth lens group G5 is composed of five lenses L51 to L55. Of the fifth lens group G5, as shown in the figure, the lens L51 has the largest effective lens diameter.

  The second lens group G2 includes three lenses L21 to L23. As shown in the drawing, the lens L21 has the largest effective lens diameter in the second lens group G2.

  Since the third lens group G3 is composed of one lens L31, the lens L31 has the largest effective lens diameter in the third lens group G3.

  Since the fourth lens group G4 is also composed of one lens L41, the lens L41 has the largest effective lens diameter in the fourth lens group G4.

  The first lens group G1 is composed of two lenses L11 and L12, and the lens L11 has the largest effective lens diameter in the first lens group G1 as shown in the figure.

  The “effective lens diameter” mentioned above means a normal “effective lens diameter” measured by placing a pinhole on the optical axis.

  In the projection lens of the present invention, as described above, the first lens group has “refractive power close to 0 with positive or negative” and is substantially afocal.

  In this way, by effectively making the first lens group G1 afocal, it is possible to effectively correct “Petzval sum, distortion, and lateral chromatic aberration”.

  In focusing, the first lens group G1 and the fifth lens group G5 are fixed, and two or more of the second lens group G2 to the fourth lens group G4 are moved.

  That is, the focusing operation is performed by so-called “floating focus”, and even if the projection distance changes, it is possible to suppress “field curvature and astigmatism fluctuations” to be small.

Further, in the i-th lens group (i = 1 to 5), the effective lens diameter of the lens having the largest effective lens system is expressed by the relationship in magnitude of MDi.
MD5 <MD2 <MD3 <MD4 <MD1
It's like that.

  When the magnitude relationship of MDi is set in this way, the “peripheral light amount ratio” can be increased, and a bright image can be realized up to the periphery of the enlarged projected image.

  In the embodiment being described, the MDi satisfies the above magnitude relationship, so that a good correction of chromatic aberration can be realized.

In the projection lens in each of the embodiments being described, the fifth lens group G5 is “the most important lens group that affects all aberrations other than distortion”.
In order to achieve high definition, particularly to reduce chromatic aberration, it is preferable that the fifth lens group has at least one pair of cemented lenses.
The lenses L52 and L53 are cemented with each form of the projection lens. Of course, the arrangement of the cemented lens in the fifth lens group in this way does not limit the configuration of the projection lens of the present invention.

  In the projection lens according to each of the embodiments being described, the magnitude relationship of the MDi is the same as the magnitude relationship of the outer shape of the lens providing the DMi.

  As shown in each figure, the outer diameter of the lens L12 in the first lens group G1 is substantially the same as the outer diameter of the lenses L31 and L41 of the third lens group G3 and the fourth lens group G4.

  The lenses L12 to L41 have a “substantially symmetric lens structure”.

  With such a “substantially symmetric lens configuration”, the occurrence of chromatic aberration can be kept small.

  That is, the chromatic aberration of magnification that cannot be corrected by the fifth lens group G5 can be corrected by the entire lens system by making the lenses L12 to L41 “substantially symmetrical” as described above.

  In the projection lens of the present invention, the aperture stop is arranged “in the fifth lens group which is the lens group closest to the reduction side”.

  When the DMD is used as the light valve, it is necessary to reduce the outer diameter of the lens group on the reduction side of the projection lens in consideration of the arrangement relationship between the illumination optical system and the projection lens.

  By disposing the aperture stop in the fifth lens group closest to the reduction side, the outer diameter of the fifth lens group can be effectively reduced.

  The projection lens of the present invention also has a focal length of the entire system: F, a focal length of the first lens group: f1, a focal length of the second lens group: f2, a focal length of the third lens group: f3, and a fourth lens. It is preferable that the focal length of the group: f4 and the focal length of the fifth lens group: f5 satisfy the following conditions (1) to (5).

(1) -0.02 <F / f1 <0.25
(2) −2.5 <f2 / F <−0.5
(3) 5.5 <f3 / F <7.5
(4) 5.5 <f4 / F <7.5
(5) 1.9 <f5 / F <3.9
As described above, the refractive power of the first lens group can be positive or negative, but the refractive power is close to 0 and is “substantially afocal”.

  Condition (1) gives a suitable range of “substantially afocal” for the first lens group.

  By satisfying the condition (1), it becomes possible to optimally correct various aberrations.

  Outside the range of condition (1), “sagittal coma and field curvature” tends to be particularly large.

  Condition (2) is an optimum condition for minimizing the change in aberration when the projection distance is changed. When the lower limit or the upper limit of condition (2) is exceeded, the “astigmatism difference” accompanies the change in the projection distance. "Is easy to grow.

  Condition (3) is an optimum condition for minimizing the change in aberration associated with the change in the projection distance. When the lower limit or upper limit of the condition (3) is exceeded, the “chromatic aberration and spherical aberration” is accompanied by the change in the projection distance. Easy to grow.

  Condition (4) is the optimum condition for spherical aberration. If the lower limit of condition (4) is exceeded, a large difference between the green wavelength and the red wavelength is likely to occur due to the spherical aberration in the high aperture portion.

  If the upper limit of the condition (4) is exceeded, the “shift between the green wavelength and the blue wavelength” tends to occur greatly due to the spherical aberration in the high aperture portion.

  Condition (5) is the optimum condition for minimizing axial chromatic aberration and astigmatism. If the lower limit or upper limit of condition (5) is exceeded, axial chromatic aberration tends to increase and astigmatism also increases greatly. It's easy to do.

  All the lenses constituting the first lens group are preferably formed of “d-line refractive index: glass material having nd of 1.9 or more”.

  By forming all the lenses constituting the first lens group with high refractive glass having “d-line refractive index: nd of 1.9 or more”, the first lens group, and thus the projection lens, can be made compact.

  The projection lens of the present invention can also be configured so that “the third lens group is fixed and the second lens group and the fourth lens group move in the same direction” during focusing.

In the focusing operation, fixing the third lens group and “moving the second lens group and the fourth lens group in the same direction” is a focusing method suitable for floating focus.
If the second lens group and the fourth lens group are moved in different directions during focusing, the lateral chromatic aberration, coma aberration, and astigmatism are likely to change in different directions.

  In the projection lens of each embodiment described above, the second lens group G2 plays a role of correcting coma and astigmatism generated in the fifth lens group G5.

  In other words, when the second lens group G2 is moved during focusing when the projection distance is changed, it is possible to satisfactorily correct coma and astigmatism generated in the fifth lens group G5. .

  The second lens group can be fixed during focusing.

  In this case, it is preferable to move the third lens group and the fourth lens group in opposite directions during focusing.

In this case, the positional relationship between the first lens group and the second lens group is fixed. At this time, the combined focal length f12 of the first lens group and the second lens group is a condition:
(6) −2.5 <f12 / F <−0.5
Is preferably satisfied.

  In the case of fixing the second lens group, “optimum correction of various aberrations” becomes possible by satisfying the condition (6).

  In the case where the condition (1) is satisfied while the second lens group is moved, the “projection capable of performing proper focusing” is compared to the case where the condition (6) is satisfied while the second lens group is fixed. The distance can be increased.

  When the second lens group is fixed and the condition (6) is satisfied, the projection distance at which proper focusing can be performed is slightly shortened. However, since the second lens group is fixed, the “mechanism for performing the focusing operation”. Can be simplified.

  An image display device (projector) according to the present invention includes a light source, an image display element that displays an image to be projected, an illumination optical system that illuminates the image display element with light emitted from the light source, and the illumination optical system. A projection optical system that receives a projection light beam irradiated by a system and modulated by an image displayed on the image display element, and projects an enlarged image of the image on a projection surface.

  The projection lens according to any one of claims 1 to 5 is used as the projection optical system.

  With reference to FIG. 16, one embodiment of the projector will be described.

  The projector 1 shown in FIG. 16 is an example in which a DMD (digital micromirror device manufactured by Texas Instruments), which is a micromirror device, is employed as the light valve 3.

  The projector 1 includes an illumination system 2, a DMD 3 that is a light valve, and a projection lens 4.

  As the projection lens 4, the lens described in any one of claims 1 to 5, specifically, any one of Examples 1 to 5 described later is used.

  The “light of three colors RGB” is temporally separated from the illumination system 2 and irradiated to the DMD 3, and the tilt of the micromirror corresponding to each pixel is controlled at the timing when each color light is irradiated.

  In this way, the “image to be projected” is displayed on the DMD 3, and the light whose intensity is modulated by the image is projected and displayed as an enlarged image on the screen S that is the projection surface by the projection lens 4. .

  The illumination system 2 includes a light source 21, a condenser lens CL, an RGB color wheel CW, and a mirror M, and it is necessary to “ensure a certain amount of space” for arranging the light source 21.

For this reason, it is necessary to increase the incident angle of the illumination light incident on the DMD 3 from the illumination system 2 to some extent.
Due to the above-described relationship between the space between the projection lens 4 and the illumination system 2, it is necessary to secure the back focus of the projection lens 4 to some extent.

  The condenser lens CL, the RGB color wheel CW and the mirror M constitute an “illumination optical system”.

  FIG. 17 shows another embodiment of the projector.

  An optical path separating means 5 such as a half prism is provided between the projection lens 4 and the light valve 3 so that a part of the light from the screen S side is separated to the image pickup device 6 side.

  The imaging element 6 is disposed at a position optically equivalent to the light valve 3 and has a conjugate relationship with the screen S.

  In this way, the image on the screen S can be picked up by the image sensor 6 receiving light.

  In all the embodiments described below, “DMD” is assumed as the light valve, but the light valve is not limited to the DMD.

  Hereinafter, five specific examples of the projection zoom lens according to the present invention will be described.

  The meanings of symbols in each embodiment are as follows.

F: Focal length of the entire optical system
Fno: Numerical aperture
R: radius of curvature (“paraxial radius of curvature” for aspheric surfaces)
D: Surface spacing
Nd: Refractive index
Vd: Abbe number
BF: Back focus.

  The aspheric shape is represented by the following well-known expression.

^{X = (H 2 / R)} / [1+ {1-K (H / r) 2} 1/2]
+ C4 · H ⁴ + C6 · H ⁶ + C8 · H ⁸ + C10 · H ¹⁰ +.

  In this equation, X is “displacement in the direction of the optical axis at the position of the height H from the optical axis with respect to the surface vertex”, K is the “conical coefficient”, C4, C6, C8, C10. Aspheric coefficient.

  The lenses constituting the projection lenses of Examples 1 to 5 are as shown in FIGS. 1, 4, 7, 10, and 13.

  That is, the first lens group G1 includes lenses L11 and L12, and the second lens group G2 includes lenses L21 to L23.

  The third lens group G3 includes a lens L31, and the fourth lens group G4 includes a lens L41. The fifth lens group G5 includes lenses L51 to L55.

  The aperture stop Stop is disposed “between the lenses L51 and L52 of the fifth lens group G5” in the first and second embodiments, and “the lenses L53 and L54 of the fifth lens group” in the third to fifth embodiments. It is arranged “between”.

"Example 1"
The projection zoom lens of Example 1 is shown in FIG.

  The movement of the lens group when the projection distance from the projection lens to the screen changes from “short distance to long distance” is shown by a broken line in FIG.

  At the time of focusing, the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed, and the first lens group G2 and the fourth lens group G4 move to the reduction side in the optical axis direction.

  The focal length: F, F number, and half angle of view at short distance: ωw of the entire system in Example 1 are as follows.

F = 14.7 mm, Fno = 1.71, ωw = 30.6 °
The data of Example 1 is shown in Table 1.

  In Table 1, the leftmost column of the table represents “surface number (the surface number counted from the enlargement side includes“ aperture stop surface ”)”.

  “CG” represents a cover glass of DMD which is a light valve.

  In the table, “INF” indicates that the radius of curvature is infinite, and the symbol “*” indicates that the surface to which this symbol is attached is “aspherical surface”.

  These matters are the same in each of the following embodiments.

"Aspherical data"
The aspherical data is shown in Table 2.

In Table 2, for example, “s6” means “surface with surface number 6”. The same applies to the following. In the notation of aspheric data, for example, “2.332648E-15” means “2.326648 × 10 ⁻¹⁵ ”. The same applies to the following.

  In Table 1, D5, D11, D14, and D17 are “lens group intervals” that change upon zooming. D0 represents the distance from the screen side surface of the lens L11 to the screen.

`` Lens group interval ''
Table 3 shows the lens group spacing.

"Condition Parameter Values"
Table 4 shows parameter values of the conditions (1) to (5).

FIG. 3 shows aberration diagrams of Example 1.
The upper part of FIG. 3 shows the aberration in a state where the projection distance is 1800 mm (medium distance), the middle part is the projection distance: 1117 mm (near distance), and the lower part is the projection distance: 4084 mm (far distance).

  That is, the projection lens of Example 1 can be focused on an arbitrary projection distance between these short distances and long distances.

  In the aberration diagrams at each stage, the left diagram is “spherical aberration”, the middle diagram is “astigmatism”, and the right diagram is “distortion aberration”.

R, G, and B in the “spherical aberration” diagram represent wavelengths: R = 625 nm, G = 550 nm, and B = 460 nm, respectively.
In the “astigmatism” diagram, “T” indicates tangential and “S” indicates sagittal rays.

  Astigmatism and distortion are shown for a wavelength of 550 nm.

  These indications in the aberration diagrams are the same in the aberration diagrams of Examples 2 to 5 below.

  As shown in FIG. 3, even when the projection lens of Example 1 is focused by changing the projection distance, the variation in performance is small and good optical performance is obtained.

"Example 2"
The projection zoom lens of Example 2 is shown in FIG.

  The movement of the lens group when the projection distance changes from a short distance to a long distance is shown by a broken line in FIG.

  During focusing, the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed, and the second lens group G2 and the fourth lens group G4 move to the reduction side in the optical axis direction.

  In Example 2, the focal length of the entire system: F range, F number, and half angle of view at short distance: ωw are as follows.

F = 14.7 mm, Fno = 1.71, ωw = 30.5 °
The data of Example 2 is shown in Table 5.

"Aspherical data"
Table 6 shows the aspherical data.

`` Lens group interval ''
Table 7 shows the lens group spacing.

"Condition Parameter Values"
Table 8 shows parameter values of the conditions (1) to (5).

  FIG. 6 shows aberration diagrams of Example 2 according to FIG.

  The upper part of FIG. 6 shows the aberration in the state where the projection distance is 1800 mm (medium distance), the middle part is the projection distance: 1116 mm (near distance), and the lower part is the projection distance: 4047 mm (far distance).

  That is, the projection lens of Example 2 can focus on an arbitrary projection distance between these short distances and long distances.

"Example 3"
The projection zoom lens of Example 3 is the one shown in FIG.

  The movement of the lens group when the projection distance changes from the short distance side to the long distance is shown by a broken line in FIG.

  At the time of focusing, the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed, and the first lens group G2 and the fourth lens group G4 move to the reduction side in the optical axis direction.

  In Example 3, the focal length of the entire system: F range, F number, and half angle of view at short distance: ωw are as follows.

F = 14.7 mm, Fno = 1.71, ωw = 30.5 °
The data of Example 3 is shown in Table 9.

"Aspherical data"
Table 10 shows the aspheric data.

`` Lens group interval ''
Table 11 shows the distance between the lens groups.

"Condition Parameter Values"
Table 12 shows parameter values of the conditions (1) to (5).

  FIG. 9 is an aberration diagram of Example 3 similar to FIG.

  The upper part of FIG. 9 shows the aberration in the state where the projection distance is 1800 mm (medium distance), the middle part is the projection distance: 1117 mm (near distance), and the lower part is the projection distance: 4083 mm (far distance).

  That is, the projection lens of Example 3 can focus on an arbitrary projection distance between these short distances and long distances.

Example 4
The projection zoom lens of Example 4 is shown in FIG.

  The movement of the lens group when the projection distance changes from a short distance to a long distance is shown by a broken line in FIG.

  At the time of focusing, the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed, and the first lens group G2 and the fourth lens group G4 move to the reduction side in the optical axis direction.

  In Example 4, the focal lengths of the entire system: F and F numbers, and the half angle of view at a short distance: ωw are as follows.

F = 13.9 mm, Fno = 1.71, ωw = 32.0 °
The data of Example 4 is shown in Table 13.

"Aspherical data"
Table 14 shows the aspheric data.

`` Lens group interval ''
Table 15 shows the lens group spacing.

"Condition Parameter Values"
Table 16 shows parameter values of the conditions (1) to (5).

  FIG. 12 shows aberration diagrams of Example 4 according to FIG.

  The upper part of FIG. 12 shows the aberration in the state where the projection distance is 1700 mm (medium distance), the middle part is the projection distance: 1054 mm (near distance), and the lower part is the projection distance: 3842 mm (far distance).

  That is, the projection lens of Example 4 can focus on an arbitrary projection distance between these short distances and long distances.

"Example 5"
The projection zoom lens of Example 5 is shown in FIG.

  The movement of the lens group when the projection distance changes from a short distance to a long distance is shown by a broken line in FIG.

  At the time of focusing, the first lens group G1, the second lens group G2, and the fifth lens group G5 are fixed, and the third lens group G3 and the fourth lens group G4 are “in opposite directions” in the optical axis direction. Moving.

  As shown in the figure, the third lens group G3 and the fourth lens group G4 initially move away from each other and then move closer to each other when focusing from a short distance to a long distance.

  In Example 5, the focal lengths of the entire system: F and F numbers, and the half angle of view at a short distance: ωw are as follows.

F = 13.9 mm, Fno = 1.71, ωw = 32.0 °
The data of Example 5 is shown in Table 17.

"Aspherical data"
Table 18 shows the aspheric data.

`` Lens group interval ''
Table 19 shows the lens group intervals.

"Parameter values for each condition"
Table 20 shows parameter values of the conditions (1) to (6).

  FIG. 15 is an aberration diagram of Example 5 similar to FIG.

  The upper part of FIG. 15 shows the aberration in the state where the projection distance is 1700 mm (medium distance), the middle part is the projection distance: 1048 mm (near distance), and the lower part is the projection distance: 3684 mm (far distance).

  That is, the projection lens of Example 5 can focus on an arbitrary projection distance between these short distances and long distances.

  As shown in each aberration diagram, in the projection lenses of the respective examples, various aberrations are corrected at a high level, and spherical aberration, astigmatism, curvature of field, lateral chromatic aberration, and distortion are sufficiently corrected.

  As shown in Examples 1 to 5, in focusing, the first lens group and the fifth lens group are fixed, and the focusing is divided into a “fixed group and a moving group”, so that the weight of the lens can be reduced. There is an effect of suppressing the occurrence of eccentricity.

  In addition, as shown in FIGS. 3, 6, 9, 12, and 15, “aberration fluctuation during focusing” can be made sufficiently small.

  Further, in all of Examples 1 to 5, the F number is 1.71, which is extremely bright.

  In recent years, DMDs used for light valves have been intended to increase the peristaltic angle of micromirrors, and correspondingly large-diameter projection lenses have been demanded. This is in line with this trend.

  Finally, Table 21 shows the “peripheral light quantity ratio” of each example. In all the examples, the peripheral light amount (image height: Y ′ = 1) is approximately 80%, which indicates that the peripheral light amount ratio of the present invention is high.

The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments described above, and the invention described in the claims unless otherwise specified in the above description. Various modifications and changes are possible within the scope of the above.
Since the projection lens of the present invention has a lens diameter that forms a real image, it can be used not only for an image display device but also for a digital camera, a video camera, a silver salt camera, a surveillance camera, and the like.

  The effects described in the embodiments of the present invention are merely a list of suitable effects resulting from the invention, and the effects of the present invention are not limited to those described in the embodiments.

G1 first lens group
G2 second lens group
G3 Third lens group
G4 4th lens group
G5 5th lens group
Stop Aperture stop
1 Image display device (projector)
2 Lighting system 3 Image display element (light valve)
4 Projection optical system (projection lens)
5 Projected surface (screen)

Japanese Patent No. 4265649 Japanese Patent No. 4305506 Japanese Patent No. 4355861

Claims (7)

An image displayed on the image display element is projected onto a projection surface to be enlarged and displayed, and a projection lens that can be focused according to a projection distance,
From the enlargement side toward the image display element side, positive or negative first lens group having a refractive power close to 0, second lens group having a negative refractive power, third lens group having a positive refractive power, and positive refraction A fourth lens group having a power, a fifth lens group having a positive refractive power, and an aperture stop in the fifth lens group;
During focusing, the first lens group and the fifth lens group are fixed, and two or more of the second to fourth lens groups move,
When the effective lens diameter of the lens having the largest effective lens system in the i-th lens group (i = 1 to 5) is defined as MDi, these are magnitude relationships:
MD5 <MD2 <MD3 <MD4 <MD1
Projection lens that satisfies the requirements. The projection lens according to claim 1,
Focal length of the entire system: F, focal length of the first lens group: f1, focal length of the second lens group: f2, focal length of the third lens group: f3, focal length of the fourth lens group: f4, fifth The focal length of the lens group: f5 is the condition:
(1) -0.02 <F / f1 <0.25
(2) −2.5 <f2 / F <−0.5
(3) 5.5 <f3 / F <7.5
(4) 5.5 <f4 / F <7.5
(5) 1.9 <f5 / F <3.9
Projection lens that satisfies the requirements. The projection lens according to claim 1 or 2,
A projection lens in which all the lenses constituting the first lens group are made of a glass material having a d-line refractive index: nd of 1.9 or more. The projection lens according to any one of claims 1 to 3,
A projection lens in which the third lens group is fixed and the second lens group and the fourth lens group move in the same direction during focusing. The projection lens according to any one of claims 1 to 3,
During focusing, the second lens group is fixed, the third lens group and the fourth lens group move in opposite directions, and the combined focal length f12 of the first lens group and the second lens group is a condition:
(6) −2.5 <f12 / F <−0.5
Projection lens that satisfies the requirements. A light source;
An image display element for displaying an image to be projected;
An illumination optical system that illuminates the image display element with light emitted from the light source;
A projection optical system that is irradiated with the illumination optical system and receives a projection light beam modulated by an image displayed on the image display element, and projects an enlarged image of the image on a projection surface;
An image display device using the projection lens according to claim 1 as the projection optical system. A light source;
An image display element for displaying an image to be projected;
An illumination optical system that illuminates the image display element with light emitted from the light source;
A projection optical system that is irradiated with the illumination optical system and receives a projection light beam modulated by an image displayed on the image display element, and projects an enlarged image of the image on a projection surface;
An optical path separating unit that is disposed between the projection optical system and the image display element and separates a part of the light from the projection surface;
An image sensor that receives the light separated by the optical path separating means and reads an image on the projection surface, and
An image display device using the projection lens according to claim 1 as the projection optical system.

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