JP2011075633A - Wide angle lens and projector device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high performance and compact wide angle lens having a small lens aperture, which enlarges and projects an image from a light valve for forming the image by changing a reflecting direction of light such as a DMD, to a screen or the other. <P>SOLUTION: The wide angle lens is constituted of: a first lens group having negative refractive power as a whole; a second lens group having positive refractive power as a whole; and a third lens group having positive refractive power as a whole in order from an enlargement side. The first lens group is constituted by arranging three lenses showing a lens having negative refractive power (hereinafter referred to as a negative lens) being a meniscus shape that is convex to the enlargement side, a negative lens, and a lens having positive refractive power (hereinafter referred to as a positive lens) in order from the enlargement side. The second lens group is constituted by arranging four lenses showing a junction system of a positive lens and a negative lens, a positive lens and a positive lens in order from the enlargement side. The third lens group is constituted by arranging one positive lens. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wide-angle lens with a small lens aperture for enlarging and projecting an image on a screen or the like, and a projector apparatus using the same.

  In recent years, DMD (digital micromirror device) displays images by arranging microscopic micromirrors (mirror elements) on a plane corresponding to pixels and mechanically controlling the angle of each mirror surface using micromachine technology. ) Has been put to practical use, and is characterized by a faster response speed and a brighter image than a liquid crystal panel that has been widely used in this field. It is rapidly spreading because it is suitable for realizing.

  When a DMD is used as a light valve in a projector device, a DMD-specific restriction occurs for a projection lens that is used simultaneously. The first restriction relates to the F value of the projection lens, which is considered to be the largest restriction in developing a small projector device. Currently, in the DMD, when the image is generated, the turning angle to represent ON and OFF of the micromirror is ± 12 °, which enables effective reflected light (effective light) and invalid reflected light (ineffective light). ). Therefore, in a projector apparatus using a DMD as a light valve, it is necessary to capture effective light and not to capture invalid light. From this condition, the F value of the projection lens can be derived, that is, F = 2. 4 Actually, there is a demand for capturing a light amount as much as possible, and therefore, a smaller F value is often required in consideration of a decrease in contrast in a range where there is no actual harm.

The second restriction relates to the arrangement with the light source system. Since the image circle of the projection lens is desired to be as small as possible for miniaturization, the arrangement of the light source system for inputting the projection light beam to the DMD is limited. In order to input effective light from the DMD to the projection lens, the light source system is installed in substantially the same direction (adjacent) as the projection lens. In addition, the projection lens and the light source system are used between the light valve side lens of the projection lens and the light valve (in general, the back focus), and the projection lens has a large back. In addition to providing a focus, it is necessary to design a small lens system on the light valve side in order to secure a light guide space from the light source. From the standpoint of optical design of the projection lens, this is a constraint that the pupil position on the light valve side is located near the rear of the projection lens. On the other hand, in order to improve the performance of the projection lens, it is necessary to combine a large number of lenses, and if a large number of lenses are arranged, the total length of the projection lens needs to be a certain length. If the total length of the lens is increased, the lens having the entrance pupil position on the rear side becomes a problem contrary to the size reduction in which the front lens diameter is naturally increased.

  In this way, although there are major restrictions on development, a projector device that employs DMD as a light valve is advantageous over other methods in terms of miniaturization, and is now convenient for presentations. Portable portable compact projectors have become widespread, centering on new data projectors. In addition, in order to make the device itself compact, it is natural that there is a strong demand for miniaturization of the projection lens used, and on the other hand, there is also a demand for multi-function, and correction of various aberrations. In addition to satisfying the specifications of the DMD used as a result of the image quality performance as a result of the above, the image circle has a large image circle in order to adopt a so-called shift configuration in which the center of the DMD and the optical axis of the projection lens are shifted. A lens with a large angle of view has been required. In the projection lens developed with such specifications, the aperture of the front lens group tends to be larger than desired, which greatly affects the thickness of the projector device. However, it is important to reduce the thickness of a projector device that is assumed to be portable, and it is the most important factor for projector devices that are often used with laptop personal computers. It can also be said. As means for solving this problem, there is an example of a compact design method for a projection lens as disclosed in Japanese Patent Application Laid-Open No. 2004-271668 (Patent Document 1).

JP 2004-271668 A

  However, according to the proposal of Patent Document 1, the effective diameter of the front lens when 0.7 inch DMD is used is 39 mm to 42 mm, and at least the thickness of the projector device cannot be 50 mm or less. When this thickness is actually carried with a notebook type personal computer or the like, the thickness is still unsatisfactory.

  In view of the above-described circumstances, the present invention is suitable for the characteristics of a light valve that forms an image by changing the reflection direction of light, such as DMD, and enlarges and projects an image from the light valve on a screen or other wall surface. Realizing a wide-angle lens with high imaging performance and a small lens diameter for applications, it is compact and bright, and is a thin projector device that is portable and has high image quality that can project a large screen even in a limited space such as a small conference room. The purpose is to provide.

The wide-angle lens of the present invention includes, in order from the magnification side, a first lens group having a negative refractive power as a whole and a second lens group having a positive refractive power as a whole. In order from the top, a lens having a negative meniscus shape having a negative refractive power (hereinafter referred to as a negative lens), a negative lens, and a lens having a positive refractive power (hereinafter referred to as a positive lens) are arranged in order. The second lens group includes four lenses, a positive lens and negative lens cementing system, a positive lens, and a positive lens, in order from the magnification side, and the third lens group includes one positive lens. A wide-angle lens configured as
The following conditional expression (1) is satisfied with respect to the combined focal length of the lens arranged closest to the magnifying side of the first lens group and the second lens arranged from the magnifying side:
The following conditional expression (2) is satisfied with respect to the combined focal length of the second lens group:
The following conditional expression (3) is satisfied with respect to the distance on the optical axis from the magnifying side surface of the lens arranged on the most magnifying side of the first lens group to the in-focus position:
The following conditional expression (4) is satisfied with respect to the positional relationship between the second lens group and the third lens group:
The following conditional expression (5) is satisfied with respect to the power of the lens arranged on the most magnifying side of the first lens group and the power of the lens arranged on the second lens from the magnifying side of the first lens group,
The following conditional expression (6) is satisfied with respect to the shape of the reduction side surface of the lens arranged closest to the magnification side of the first lens group and the shape of the reduction side surface of the lens arranged second from the magnification side of the first lens group. Satisfied,
The following conditional expression (7) is satisfied with respect to the dispersion characteristics of the glass material used for each lens constituting the first lens group,
The following conditional expression (8) is satisfied with respect to the shape of the enlargement side surface and the shape of the reduction side surface of the lens arranged closest to the reduction side of the first lens group,
The following conditional expression (9) is satisfied with respect to the power of the lens disposed on the second lens from the magnification side of the second lens group,
The following conditional expression (10) is satisfied with respect to the shape of the cemented surface of the cemented lens disposed on the magnification side of the second lens group,
The following conditional expression (11) is satisfied regarding the refractive index of the lens arranged closest to the magnification side of the second lens group and the refractive index of the lens arranged on the two surfaces from the magnification side of the second lens group. And
The following conditional expression (12) is satisfied with respect to the power of the lens disposed on the third lens from the magnification side in the second lens group and the power of the lens disposed on the most reduction side in the second lens group,
The following conditional expression (13) is satisfied with respect to the shape of the reduction side surface of the lens arranged on the most reduction side of the second lens group,
The following conditional expression (14) is satisfied regarding the dispersion characteristics of the glass material used for each lens constituting the second lens group. (Claim 1)
(1) -1.0 <f / f 1-2 <-0.4
(2) 0.3 <f / f II <0.6
(3) 5.0 <TL / f <9.0
_{(4) 5.0 <d II /} f <9.0
_{(5) 0.6 <f 2 /} f 1 <1.0
(6) −2.2 <r ₂ / r ₄ <−1.1
(7) 40 <(V ₁ + V ₂ ) / 2−V _{3
(8) -2.2 <r 5 /} r 6 <-1.1
(9) -1.5 <f / f 5 <-1.0
(10) -1.7 <f / r 8 <-1.1
(11) 0.2 <N ₅ −N _{4
(12) 0.7 <f 7 /} f 8 <1.3
(13) -1.0 <f / r 13 <-0.7
_{(14) 30 <(V 4} + V 6 + V 7) / 3 - V 5
f: Combined focal length of the entire lens system (focused on the magnifying side object distance of 700 mm from the most magnifying side of the first lens group)
f _1-2 : Composite focal length of the lens arranged closest to the magnification side of the first lens group and the second lens arranged from the magnification side of the first lens group f _II : Composite focal length of the second lens group TL: Distance on the optical axis from the magnifying side surface of the lens arranged closest to the magnifying side in the first lens group to the in-focus position (focusing state on the magnifying side object distance of 700 mm from the magnifying side of the first lens group)
d _II : Distance on the optical axis between the reduction side surface of the lens arranged closest to the reduction side in the second lens group and the enlargement side surface of the third lens group (magnification side object distance 700 mm from the most enlargement side surface of the first lens group) In focus)
f ₁ : Focal length of the lens arranged closest to the enlargement side in the first lens group f ₂ : Focal length r _{2 of the} lens arranged on the second lens from the enlargement side in the first lens group: Most in the first lens group The radius of curvature r ₄ of the reduction side of the lens arranged on the magnification side: the radius of curvature V ₁ of the reduction side of the lens arranged on the second lens from the magnification side in the first lens group: The radius of curvature closest to the magnification side of the first lens group Abbe number V _{2 of} the negative lens arranged: Abbe number r _{5 of the} negative lens arranged second from the magnification side in the first lens group: Enlarged side surface of the lens arranged closest to the reduction side in the first lens group Radius of curvature r ₆ : radius of curvature of the reduction side of the lens arranged closest to the reduction side in the first lens group f ₅ : focal length r _{8 of the} lens arranged on the second lens group from the enlargement side in the second lens group: In the second lens group, the lens arranged closest to the magnification side and the second lens from the magnification side Curvature radius f of the cemented surface of the lens _7: second focal length of the lens disposed from the enlargement side to the 3rd lens group f _8: focal length r ₁₃ of the lens disposed on the most reduction side in the second lens group : second radius of curvature of the contracting side surface of the arrangement the lens to the lens most reduction side group radius V _4: the Abbe number of the positive lens disposed closest to the magnifying side second lens unit V _5: enlarged side in the second lens group Abbe number V _{6 of the} negative lens arranged on the second lens from the first lens: Abbe number V _{7 of} positive lens arranged on the third lens from the magnifying side in the second lens group: arranged on the reduction surface side most in the second lens group Abbe number of positive lens

  Conditional expression (1) is a condition relating to the power of the lens arranged in the first lens group. The combined power of the lens arranged on the most magnified side of the first lens group and the lens arranged on the second lens from the magnification side has a strong negative power, and an optical system for illuminating a light valve such as DMD is arranged. The purpose of this is to secure a space for the air gap between the second lens group and the third lens group. When the upper limit is exceeded, the negative power of the lenses arranged in the first lens group becomes small, and it becomes difficult to secure the air gap between the second lens group and the third lens group. Becomes larger and the positive power of the second lens group has to be strengthened, making it difficult to balance various aberrations.

  Conditional expression (2) is a condition relating to the power of the second lens group, and is a condition for balance between miniaturization and performance. If the upper limit of conditional expression (2) is exceeded, the positive power of the second lens group becomes strong, which is advantageous for downsizing, but it becomes difficult to correct aberrations. If the lower limit is exceeded, the positive power of the second lens group becomes weak. It becomes difficult to reduce the size.

  Conditional expression (3) is a condition of the distance on the optical axis from the magnifying side surface of the lens arranged closest to the magnifying side in the first lens group to the in-focus position. If the upper limit is exceeded, the distance from the magnifying side of the first lens group located on the most magnifying side to the in-focus position will increase, and the lens will have a large aperture, which will impair the reduction in size and diameter, and the lower limit. If it exceeds, it becomes difficult to balance various aberrations.

  Conditional expression (4) is a condition regarding the positional relationship between the second lens group and the third lens group. As described above, the second space for arranging the optical system for illuminating the light valve such as DMD is the second. This is a condition that is secured in the air space between the lens group and the third lens group. If the upper limit is exceeded, aberration correction becomes difficult, and if the upper limit is exceeded, it becomes difficult to arrange an optical system for illumination.

  Conditional expression (5) is a condition regarding the power of the lens arranged closest to the magnification side in the first lens group and the power of the lens arranged second from the magnification side. As described above, increasing the negative power of the lens arranged on the enlargement side of the first lens group secures an air space between the second lens group and the third lens group and is effective for miniaturization. Although it is a feature of the retrofocus type, it is difficult to achieve downsizing while securing performance with one lens, and it is necessary to appropriately distribute negative power to the two lenses. If the upper limit is exceeded, the power of the lens arranged closest to the enlargement side of the first lens group becomes strong, making it difficult to correct coma, and if the lower limit is exceeded, correcting distortion is difficult.

  Conditional expression (6) is a condition regarding the shape of the reduction side surface of the lens arranged closest to the magnification side of the first lens group and the reduction side surface of the lens arranged second from the magnification side of the first lens group. This is a conditional expression for correcting distortion and coma in the entire lens system. While having strong power, the shape is generally concentric with respect to the light beam on the enlargement side, and the shape is basically suppressed from generating aberrations. Therefore, when the upper limit is exceeded, spherical aberration and coma aberration are undercorrected, and when the lower limit is exceeded, overcorrection is conversely performed.

  Conditional expression (7) is a condition regarding the dispersion characteristics of the glass material used for each lens arranged in the first lens group, and is a condition for correcting chromatic aberration in the first lens group. In order to correct the chromatic aberration, it is necessary that the power of each lens does not become excessive. For that purpose, the Abbe number satisfying conditional expression (7) is necessary. When the lower limit is exceeded, it becomes difficult to correct chromatic aberration.

  Conditional expression (8) is a condition relating to the shape of the enlargement side surface and the shape of the reduction side surface of the lens arranged closest to the reduction side of the first lens group, and is a condition for correcting spherical aberration, coma aberration, and distortion aberration. . If the upper limit is exceeded, the power on the reduction side becomes weaker than the power on the enlargement side, and if the lower limit is exceeded, the power on the enlargement side becomes weaker than the power on the reduction side, making it difficult to correct aberrations.

  Conditional expression (9) is a condition relating to the power of the second lens arranged from the magnification side of the second lens group, and is a condition for correcting the lateral chromatic aberration. The second lens group needs a strong positive power and is composed of three positive lenses and one negative lens. Since only the positive lens cannot correct the lateral chromatic aberration, it is necessary to dispose a negative lens having an appropriate power. If the upper limit is exceeded, the power of the negative lens becomes weak, and if the upper limit is exceeded, the power of the negative lens becomes strong, making it difficult to correct lateral chromatic aberration.

  Conditional expression (10) is a condition relating to the shape of the cemented surface of the cemented lens disposed on the magnification side of the second lens group, and is a condition relating to correction of lateral chromatic aberration and coma aberration. The positive lens arranged on the most magnifying side of the second lens group and the lens arranged on the second lens from the magnifying side of the second lens group are corrected for chromatic aberration of magnification and coma by using a cemented system. While having strong power, the shape is generally concentric with respect to the light beam on the enlargement side, and the shape is basically suppressed from generating aberrations. If the upper limit is exceeded, the surface power decreases, and if the lower limit is exceeded, the surface power increases, making it difficult to correct lateral chromatic aberration and coma.

  Conditional expression (11) is a condition regarding the refractive index of the lens arranged closest to the magnification side of the second lens group and the refractive index of the lens arranged second from the magnification side of the second lens group. This is a condition regarding correction. The cemented lens performs spherical aberration correction based on the difference in refractive index. If the lower limit is exceeded, the difference in refractive index decreases, making it difficult to correct spherical aberration.

  Conditional expression (12) is a condition relating to the power of the lens disposed on the third lens from the magnification side in the second lens group and the power of the lens disposed on the most reduction side in the second lens group, and correction of spherical aberration. And conditions for correction of coma aberration. It is necessary to arrange a strong positive power lens on the reduction side of the second lens group to guide the divergent ray bundle exiting the first lens group to a converged state, but with one positive lens, aberration correction Therefore, it is necessary to divide the power into two positive lenses. If the upper limit is exceeded, the power of the lens arranged on the most reduction side of the third lens group becomes strong, and the under spherical aberration becomes large. If the upper limit is exceeded, the lens arranged on the most reduction side of the third lens group The power of the lens becomes weak, the over-spherical aberration increases, the occurrence of coma around the periphery becomes significant, and correction of the aberration becomes difficult.

  Conditional expression (13) is a condition relating to the shape of the reduction side surface of the lens arranged closest to the reduction side of the second lens group, and is a condition for finely correcting spherical aberration and coma aberration in the entire lens system. While having strong power, it has a concentric shape with respect to the light beam on the magnification side, and a shape that fundamentally suppresses the occurrence of aberrations, so that it cannot be corrected with three lenses from the magnification side of the second lens group. The remaining spherical aberration and coma are corrected. If the upper limit is exceeded, spherical aberration and coma aberration will be undercorrected, and if the lower limit is exceeded, overcorrection will occur.

  Conditional expression (14) is a condition for correcting chromatic aberration in the second lens group. In order to correct axial chromatic aberration and lateral chromatic aberration, it is necessary that the power of each lens does not become excessive. For this purpose, the Abbe numbers of the positive lens and the negative lens that satisfy the conditional expression (14) are required. It becomes a condition. When the lower limit is exceeded, it becomes difficult to correct chromatic aberration.

  In addition, it is preferable that at least one of the enlargement side surface and the reduction side surface of the lens disposed on the most enlargement side of the first lens group has an aspherical shape. (Claim 2)

  As described above, increasing the negative power of the lens arranged closest to the enlargement side in the first lens group ensures an air space between the second lens group and the third lens group, and is effective for miniaturization. However, since it is difficult to correct various aberrations including curvature of field with a spherical shape, either one or both of the enlargement side and the reduction side of the lens disposed on the most enlargement side of the first lens group is arranged. By using an aspherical shape, various aberrations including curvature of field can be corrected.

  Further, the magnifying side surface of the third lens arranged from the magnifying side of the second lens group is aspherical than the surface power of the paraxial radius of curvature as the distance in the direction perpendicular to the optical axis increases. Preferably, the reduction side surface has an aspherical shape in which the surface power changes from positive power to negative power as the distance in the direction perpendicular to the optical axis increases. (Claim 3)

  The second lens group has a strong positive power for guiding the divergent light beam emitted from the first lens group to a focused state, and various aberrations such as spherical aberration are generated. The lens constituting the second lens group corrects various aberrations as a constitution of four lenses of a positive lens, a negative lens, a positive lens, and a positive lens from the magnifying surface side, but the positive power of the second lens group is Because the lens is strong, aberration correction is insufficient, and the large-aperture ratio of the entire lens system is secured by making the enlargement side and reduction side of the third lens arranged from the enlargement side of the second lens group aspherical. This makes it possible to reduce the diameter of the entire lens system and correct spherical aberration and the like.

  Further, it is preferable to perform focusing by moving the second lens group. (Claim 4)

  When projection is performed while changing the magnification-side object distance, focusing is required. As a focusing method, a method of moving the first lens group, a method of moving the second lens group, a second lens group to a second lens group are used. It is also possible to take a method of moving the lens group as a unit, or a method of moving the lenses arranged from the first lens group to the second lens group into groups different from the present invention. However, when the enlargement-side object distance is set to a wide range from about 300 mm to about 3000 mm, the performance when the enlargement-side object distance is changed may be deteriorated depending on the focusing method, and the second lens group is moved. It is possible to reduce the performance change when the enlargement-side object distance is changed.

  Thus, by mounting the wide-angle lens according to the present invention on the projector device, the entire device can be reduced in size (claim 5), and a thin projector device that is convenient for carrying can be provided.

  According to the present invention, a compact wide-angle lens with high imaging performance suitable for the characteristics of a light valve such as a DMD can be realized, and a small, thin, bright and high-quality projector can be provided.

It is a lens block diagram of 1st Example of the wide angle lens by this invention. FIG. 6 is a diagram illustrating all aberrations of the lens of the first example. It is a lens block diagram of 2nd Example of the wide angle lens by this invention. FIG. 6 is a diagram illustrating various aberrations of the lens of the second example. It is a lens block diagram of 3rd Example of the wide angle lens by this invention. FIG. 10 is a diagram illustrating all aberrations of the lens of the third example. It is a lens block diagram of 4th Example of the wide angle lens by this invention. FIG. 10 is a diagram illustrating various aberrations of the lens of the fourth example. It is a lens block diagram of 5th Example of the wide angle lens by this invention. FIG. 10 is a diagram illustrating all aberrations of the lens of the fifth example.

  Hereinafter, the present invention will be described with respect to specific numerical examples. In the following wide angle lenses of the first to fifth embodiments, in order from the magnifying side, a first lens group (lens group name LG1) having a negative refractive power as a whole and a second lens having a positive refractive power as a whole The first lens group LG1 is composed of a group (lens group name LG2) and a third lens group (lens group name LG3) having a positive refractive power as a whole. The first lens group LG1 has a meniscus shape that is convex on the enlargement side in order from the enlargement side. Negative lens (lens name is L11, enlargement side name is 101, reduction side name is 102), negative lens (lens name L12, enlargement side 103, reduction side 104), positive lens (lens name L13, enlargement) The second lens group LG2 includes a positive lens (lens name L21, enlargement side surface 201, reduction-side cemented surface 202) and negative lens in order from the enlargement side. (Lens name L22, enlargement side joining surface 202, reduction side surface 203), positive lens (lens name L23, enlargement side surface 204, reduction side surface 205) and positive lens (lens name L24, enlargement side 206, reduction side surface 207) ), And the third lens group LG3 is configured by arranging one positive lens (lens name L31, enlargement side surface 301, reduction side surface 302), and subsequently reduction of the third lens group LG3. A cover glass CG (enlarged side C01, reduced side C02), which is a component of a light valve such as DMD, is arranged with a slight air gap between the side and the light valve surface. ing. In the first example, the second example, and the third example, there are two diaphragms (aperture name ST1, surface name S01, aperture name ST2, and surface name S02) between the first lens group and the second lens group. In the fourth and fifth embodiments, one stop (aperture name ST1, surface name S01) is arranged between the first lens group and the second lens group. It is configured.

As is well known, the aspherical surface used in each embodiment has an aspherical formula when taking the Z axis in the optical axis direction and the Y axis in the direction orthogonal to the optical axis:
Z = (Y ² / r) / [1 + √ {1- (1 + K) (Y / r) ² }]
+ A4 · Y ⁴ + A6 · Y ⁶ + A8 · Y ⁸ + A10 · Y ¹⁰ + A12 · Y ¹²
Is a curved surface obtained by rotating the curve given by around the optical axis, giving a paraxial radius of curvature: r, a conic constant: K, and higher-order aspherical coefficients: A4, A6, A8, A10, A12. Define In the notation of the conic constant and the higher-order aspheric coefficient in the table, “E and the number following it” represent “power of 10”. For example, “E-4” means 10 ⁻⁴ , and this numerical value may be multiplied by the immediately preceding numerical value.

Table 1 shows numerical examples of the first embodiment of the wide-angle lens of the present invention. FIG. 1 is a lens configuration diagram, and FIG. In the tables and drawings, f represents the focal length of the entire wide-angle lens system, F _no represents the F number, and 2ω represents the total angle of view of the wide-angle lens. In addition, r is a radius of curvature, d is a lens thickness or a lens interval, n _d is a refractive index with respect to the d line, and ν _d is an Abbe number of the d line (however, the numerical value that changes due to the focusing operation in the table is 101 plane) In the in-focus state where the object distance from the center is 700 mm). CA1, CA2, and CA3 in the spherical aberration diagrams in the various aberration diagrams are aberration curves at wavelengths of CA1 = 550.0 nm, CA2 = 450.0 nm, and CA3 = 620.0 nm, respectively. In the astigmatism diagram, S indicates sagittal and M indicates meridional. In addition, unless otherwise specified throughout, the wavelength used for calculation of various values is CA1 = 550.0 nm.

  Table 2 shows numerical examples of the second embodiment of the wide-angle lens of the present invention. FIG. 3 is a diagram showing the lens configuration, and FIG. 4 is a diagram showing various aberrations thereof.

  Table 3 shows numerical examples of the third embodiment of the wide-angle lens of the present invention. FIG. 5 is a diagram showing the lens configuration, and FIG. 6 is a diagram showing various aberrations.

  Table 4 shows numerical examples of the fourth embodiment of the wide-angle lens of the present invention. FIG. 7 is a diagram showing the lens configuration, and FIG. 8 is a diagram showing various aberrations.

  Table 5 shows numerical examples of the fifth embodiment of the wide-angle lens of the present invention. FIG. 9 is a lens configuration diagram, and FIG. 10 is a diagram showing various aberrations.

  Next, Table 6 collectively shows values corresponding to the conditional expressions (1) to (14) regarding the first to fifth embodiments. As is clear from Table 6, the numerical values related to the first to fifth embodiments satisfy the conditional expressions (1) to (14) and are clear from the aberration diagrams in the respective embodiments. Thus, each aberration is corrected well.

Claims (5)

The first lens group having a negative refractive power as a whole, the second lens group having a positive refractive power as a whole, and the third lens group having a positive refractive power as a whole in order from the magnification side, The lens group includes, in order from the magnifying side, a lens having a negative meniscus shape having a negative refractive power (hereinafter, negative lens), a negative lens, and a lens having positive refracting power (hereinafter, positive lens). The second lens group is configured by arranging four lenses of a positive lens and a negative lens, a positive lens, and a positive lens in order from the magnification side, and the third lens group includes: A wide-angle lens constructed with a single positive lens,
The following conditional expression (1) is satisfied with respect to the combined focal length of the lens arranged closest to the magnifying side of the first lens group and the second lens arranged from the magnifying side:
The following conditional expression (2) is satisfied with respect to the combined focal length of the second lens group:
The following conditional expression (3) is satisfied with respect to the distance on the optical axis from the magnifying side surface of the lens arranged on the most magnifying side of the first lens group to the in-focus position:
The following conditional expression (4) is satisfied with respect to the positional relationship between the second lens group and the third lens group:
The following conditional expression (5) is satisfied with respect to the power of the lens arranged on the most magnifying side of the first lens group and the power of the lens arranged on the second lens from the magnifying side of the first lens group,
The following conditional expression (6) is satisfied with respect to the shape of the reduction side surface of the lens arranged closest to the magnification side of the first lens group and the shape of the reduction side surface of the lens arranged second from the magnification side of the first lens group. Satisfied,
The following conditional expression (7) is satisfied with respect to the dispersion characteristics of the glass material used for each lens constituting the first lens group,
The following conditional expression (8) is satisfied with respect to the shape of the enlargement side surface and the shape of the reduction side surface of the lens arranged closest to the reduction side of the first lens group,
The following conditional expression (9) is satisfied with respect to the power of the lens disposed on the second lens from the magnification side of the second lens group,
The following conditional expression (10) is satisfied with respect to the shape of the cemented surface of the cemented lens disposed on the magnification side of the second lens group,
The following conditional expression (11) is satisfied regarding the refractive index of the lens arranged closest to the magnification side of the second lens group and the refractive index of the lens arranged on the two surfaces from the magnification side of the second lens group. And
The following conditional expression (12) is satisfied with respect to the power of the lens disposed on the third lens from the magnification side in the second lens group and the power of the lens disposed on the most reduction side in the second lens group,
The following conditional expression (13) is satisfied with respect to the shape of the reduction side surface of the lens arranged on the most reduction side of the second lens group,
A wide-angle lens satisfying the following conditional expression (14) with respect to dispersion characteristics of a glass material used for each lens constituting the second lens group.
(1) -1.0 <f / f 1-2 <-0.4
(2) 0.3 <f / f II <0.6
(3) 5.0 <TL / f <9.0
_{(4) 5.0 <d II /} f <9.0
_{(5) 0.6 <f 2 /} f 1 <1.0
(6) −2.2 <r ₂ / r ₄ <−1.1
(7) 40 <(V ₁ + V ₂ ) / 2−V _{3
(8) -2.2 <r 5 /} r 6 <-1.1
(9) -1.5 <f / f 5 <-1.0
(10) -1.7 <f / r 8 <-1.1
(11) 0.2 <N ₅ −N ₄
(12) 0.7 <f ₇ / f ₈ <1.3
(13) -1.0 <f / r 13 <-0.7
_{(14) 30 <(V 4} + V 6 + V 7) / 3 - V 5
f : Combined focal length of the entire lens system (focused on the magnifying side object distance of 700 mm from the most magnifying side of the first lens group)
f _1-2 : Composite focal length of the lens arranged closest to the magnification side of the first lens group and the second lens arranged from the magnification side of the first lens group f _II : Composite focal length of the second lens group TL: Distance on the optical axis from the magnifying side surface of the lens arranged closest to the magnifying side in the first lens group to the in-focus position (focusing state on the magnifying side object distance of 700 mm from the magnifying side of the first lens group)
d _II : Distance on the optical axis between the reduction side surface of the lens arranged closest to the reduction side in the second lens group and the enlargement side surface of the third lens group (magnification side object distance 700 mm from the most enlargement side surface of the first lens group) In focus)
f ₁ : Focal length of the lens arranged closest to the enlargement side in the first lens group f ₂ : Focal length r _{2 of the} lens arranged on the second lens from the enlargement side in the first lens group: Most in the first lens group The radius of curvature r ₄ of the reduction side of the lens arranged on the magnification side: the radius of curvature V ₁ of the reduction side of the lens arranged on the second lens from the magnification side in the first lens group: The radius of curvature closest to the magnification side of the first lens group Abbe number V _{2 of} the negative lens arranged: Abbe number r _{5 of the} negative lens arranged second from the magnification side in the first lens group: Enlarged side surface of the lens arranged closest to the reduction side in the first lens group Radius of curvature r ₆ : radius of curvature of the reduction side of the lens arranged closest to the reduction side in the first lens group f ₅ : focal length r _{8 of the} lens arranged on the second lens group from the enlargement side in the second lens group: In the second lens group, the lens arranged closest to the magnification side and the second lens from the magnification side Curvature radius f of the cemented surface of the lens _7: second focal length of the lens disposed from the enlargement side to the 3rd lens group f _8: focal length r ₁₃ of the lens disposed on the most reduction side in the second lens group : second radius of curvature of the contracting side surface of the arrangement the lens to the lens most reduction side group radius V _4: the Abbe number of the positive lens disposed closest to the magnifying side second lens unit V _5: enlarged side in the second lens group Abbe number V _{6 of the} negative lens arranged on the second lens from the first lens: Abbe number V _{7 of} positive lens arranged on the third lens from the magnifying side in the second lens group: arranged on the reduction surface side most in the second lens group Abbe number of positive lens   2. The wide-angle lens according to claim 1, wherein at least one of the enlargement side surface and the reduction side surface of the lens arranged closest to the enlargement side of the first lens group has an aspherical shape.   The magnification side surface of the third lens element arranged from the magnification side of the third lens group has an aspheric surface power that is greater than the surface power of the paraxial radius of curvature as the distance in the direction perpendicular to the optical axis increases. The reduced side surface is an aspherical shape whose surface power changes from positive power to negative power as the distance in the direction perpendicular to the optical axis increases. Item 2. The wide-angle lens according to Item 1.   4. The wide-angle lens according to claim 1, wherein focusing is performed by moving the second lens group. 5.   A projector device, comprising the wide-angle lens according to any one of claims 1 to 4.

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