JP2014062953A - Super-wide-angle optical system and projection-type display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a super-wide-angle optical system that enlarges and projects an image from a light valve that changes a reflection direction of light to form an image such as a DMD on a screen or the like, and achieves a bright and hi-performance optical system, and a large screen despite the installation within an extremely close distance from a projection surface.SOLUTION: A super-wide-angle optical system is formed, in order from an enlargement side, of a first lens group having a negative refractive power as a whole, a second lens group having a negative refractive power as a whole, and a third lens group having a positive refractive power as a whole. The first lens group is formed, in order from the enlargement side, of a first a lens group having a negative refractive power as a whole, and a first b lens group having a negative refractive power as a whole; the second lens group is formed, from the enlargement side, of a second a lens group having a negative refractive power as a whole, and a second b lens group having a positive or a negative refractive power as a whole; and the third lens group is formed, from the enlargement side, of a third a lens group having a positive refractive power as a whole, and a third b lens group having a positive refractive power as a whole.

Description

  The present invention relates to an ultra-wide-angle optical system for short-distance projection, which is mainly used in a projection display apparatus that enlarges and projects an image from a light valve that forms an image by changing the reflection direction of light, such as DMD. .

  Projection-type display devices using DMD (Digital Micromirror Device) as a light valve have come to be widely used, but have projection ability at shorter distances, mainly for educational applications such as schools. There is a need for a projection display device. For example, when using a projection size of 80 inches, when projecting from a distance of about 3 m from the screen or wall, the person who explains will often see the light from the projection optical system beside the screen. Although it must be dazzling, even if the projection size is the same 80 inches, when it is projected from a short distance of about 50 cm, the light from the projection optical system is hardly seen. However, as far as the projection optical system is concerned, this is nothing but a super-wide-angle lens with a remarkably large field angle.

  When a DMD or the like is used as a light valve, there is a restriction on the angle of the light flux from each pixel to the projection optical system in order to realize an efficient projection type display device. In general, it is often expressed as a chief ray, but the ideal ray bundle is that the chief ray is emitted vertically from each pixel. (This may vary depending on the illumination method.) When the light bundle is emitted from the projection lens, the projection optical system gives an angle corresponding to the angle of view. It can be seen that the change in angle must be increased when passing through the projection optics. Therefore, off-axis aberrations such as distortion increase dramatically, the number of lenses increases for this correction, and the increase in the number of lenses increases the thickness of the optical system on the optical axis. This means that the diameter of the lens placed on the enlargement side will be increased, and the cost of the projection lens will increase due to factors such as the need to use a refractive surface such as an aspherical surface. Will be greatly increased. In addition, the projection optical system generally employs a mechanism in which a projection screen is projected above the optical axis when the optical axis is held horizontally. This can be realized by shifting the optical axis of the projection optical system and the center of the DMD and is called a so-called shift optical system. When the shift optical system is adopted, the size of the image circle required for the projection optical system is the distance between the radius of the optical axis and the angle at which it is arranged farthest from the optical axis of the DMD. Compared to an optical system such as a camera in which the optical axis coincides with the center of the image sensor, the optical system must be larger, which is a factor in increasing costs.

  As a super wide-angle lens for a projector, for example, Japanese Patent Application Laid-Open No. 2006-171127 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2006-171128 (Patent Document) having a total angle of view of about 130 ° and an F-number of about 4.0. 2), and Japanese Patent Laid-Open No. 5-34592 (Patent Document 3) having an entire field angle of about 100 ° and an F number of about 2.9.

JP 2006-171127 A JP 2006-171128 A Japanese Patent Laid-Open No. 5-34592

  In view of the circumstances described above, the present invention forms an image by changing the reflection direction of light such as DMD by effectively arranging two aspherical lenses made of resin as the optical element on the most enlarged side. It is suitable for the characteristics of light valves, and realizes an optical system that is bright, super wide-angle, and has high imaging performance in applications that enlarge and project images from light valves onto screens or other wall surfaces. It is an object to provide a high-quality projection display device capable of projecting a large screen even in a limited space.

The super wide-angle optical system according to the present invention has a first lens group having a negative refractive power as a whole, a second lens group having a weak positive or negative refractive power as a whole, and a positive refractive power as a whole in order from the magnification side. An ultra-wide-angle optical system configured by disposing a light valve such as a DMD after providing a large air space on the reduction side of the third lens group. An optical system that forms an image after a distance from the most reduction surface of the lens group, and satisfies the following conditional expression (1) with respect to the power of the first lens group, and is the most magnified side of the first lens group. The following conditional expressions (2) and (3) are satisfied with respect to the distance on the optical axis from the surface to the image plane and the effective diameter of the most magnified surface of the first lens group, and the second conditional expression (3) is satisfied. Regarding the distance on the optical axis from the most reduced surface of the lens group to the image plane, Characterized in that it satisfies the equation (4). (Claim 1)
(1) −0.48 ≦ f / f _I ≦ 0
(2) TL / f ≦ 36
(3) D _I1 / TL ≦ 0.72
(4) 6.2 ≦ b / f
However,
f : Total focal length of the entire optical system (focused on the projection surface at the design reference distance)
f _I : Composite focal length TL of the first lens group TL: Distance on the optical axis from the most magnified surface of the first lens group to the image plane (however, the fourth lens group and the cover glass part of the parallel plane are converted to air) distance)
D _I1 : Effective diameter b of the most magnified surface of the first lens group : Distance on the optical axis from the most reduced surface of the third lens group to the image plane (however, the fourth lens group and the cover glass portion of the parallel plane are air-converted distances)

  Conditional expression (1) is a condition relating to the power of the first lens unit disposed on the most magnified side. In order to increase the angle of view while maintaining the back focus from the principle of retrofocus, it is better to apply negative power to the magnification side of the lens. Accordingly, it is effective for widening the angle to make the lens group on the enlargement side have negative power. However, in the optical system of the present invention, it is necessary to arrange positive power on the reduction side of the first lens group in order to secure the peripheral light amount. Therefore, the power of the first lens group is determined by the balance of these factors, and has negative power as a whole. If the upper limit is exceeded in conditional expression (1), the negative power will be insufficient and it will be difficult to increase the angle of view, and conversely if the lower limit is exceeded, the amount of peripheral light cannot be secured. Conditional expression (2) is a condition relating to the total length, that is, a condition for miniaturization. If the upper limit is exceeded, the total length becomes large, and thus the lens becomes large in diameter, and the feature of small size is lost. Conversely, when the lower limit is exceeded, it becomes difficult to balance various aberrations. Conditional expression (3) shows the range of the effective diameter of the front lens. If the range of conditional expression (3) is exceeded, along with the constraints from the specifications, the manufacturing cost will increase significantly, and as a product Lack of balance. Conditional expression (4) is a condition relating to an air interval set on the reduction side of the second lens group. Although this is a portion corresponding to a so-called back focus, it is a common space with the optical system for illuminating the light valve, so it is necessary to ensure this interval. Therefore, if the lower limit is exceeded, it becomes difficult to incorporate an illumination optical system.

The first lens group includes a 1a lens group having a negative refractive power as a whole and a 1b lens group having a negative refractive power as a whole in order from the magnification side, and the first a lens group and the first lens group. It is desirable that the following conditional expression (5) is satisfied with respect to the power of the 1b lens unit. (Claim 2)
(5) 0 ≦ f _Ia / f _Ib ≦ 1.50
However,
f _Ia : Composite focal length of the 1a lens group f _Ib : Composite focal length of the 1b lens group

  By satisfying this conditional expression, a negative power capable of ensuring a back focus can be applied to the first lens group without destroying the power balance of the entire lens system. That is, the conditional expression (5) represents the power ratio, and exceeding the upper limit means that the power of the first-a lens group is reduced in a balanced manner, and it is difficult to secure the back focus. It is also disadvantageous for widening the lens system. On the contrary, if the upper limit is exceeded, it is advantageous for widening the angle, but it is not possible to secure the target peripheral light amount for projector use.

The 1a lens group constituting the first lens group is configured by arranging a negative meniscus lens (hereinafter, negative lens) having a negative refractive power and a negative lens in order from the magnifying side. The 1b lens group includes a negative lens, a negative lens, a lens having a positive refractive power (hereinafter, positive lens), and a negative lens in order from the magnification side. Expression (6) is satisfied, the following conditional expression (7) is satisfied regarding the feature of the shape of the lens arranged closest to the magnification side in the 1a lens group, and the lens is arranged second from the magnification side in the 1a lens group. It is desirable that the following conditional expression (8) is satisfied with respect to the characteristics of the lens shape. (Claim 3)
(6) −0.18 ≦ f / f _Ia ≦ −0.12
(7) 2.2 ≦ r _I1 / r _I2 ≦ 7.2
(8) 1.8 ≦ r _I3 / r _I4 ≦ 5.2
However,
r _I1 : radius of curvature of the magnifying side of the lens arranged closest to the magnifying side in the 1a lens group r _I2 : radius of curvature r _I3 of the demagnifying side of the lens arranged _{maximally on} the 1a lens group: 1a lens Radius of curvature r _{I4 of} the lens disposed second from the magnification side in the lens group: radius of curvature of the reduction surface of the lens disposed second from the magnification side in the lens group 1a

  Conditional expression (6) is a condition relating to the power of the first-a lens group. The 1a lens group as a whole has negative power, and several negative power lenses are arranged on the magnifying side. This is closely related to the angle of view and back focus required for the optical system. Increasing the negative power of the lens realizes the required angle of view while ensuring the air gap between the second lens group and the cover glass CG, which is a component of the light valve such as the DMD. Although effective, if the upper limit of conditional expression (6) is exceeded, the negative power of the lens becomes strong and chromatic aberration and curvature of field occur, making it difficult to correct the aberration, and if the lower limit is exceeded, the negative power of the lens becomes weak. It becomes difficult to take a long space corresponding to the so-called back focus between the second lens group and the cover glass CG which is a component of the light valve such as DMD. Conditional expression (7) and conditional expression (8) both show the characteristics of the shape of the lens arranged closest to the magnification side and the lens arranged second from the magnification side in the 1a lens group. Although these lenses have a small power, they are configured for the purpose of strongly correcting distortion, but on the other hand, they have a shape that substantially suppresses the occurrence of aberrations by having a generally concentric shape. Therefore, if both conditional expressions exceed the upper limit, spherical aberration and coma aberration will be undercorrected, and if the lower limit is exceeded, overcorrection will occur.

Further, in the first lens group constituting the first lens group, the following conditional expression (9) is satisfied with respect to the size of the gap on the reduction side of the lens disposed second from the magnification side in the first lens group, and the first lens group The following conditional expression (10) is satisfied with respect to the power of the positive lens arranged third from the enlargement side in the 1b lens group constituting the lens, and the following conditional expression (9) is satisfied with respect to the lens shape characteristics of the lens. It is desirable that (Claim 4)
(9) 2.8 ≦ d _I4 / f ≦ 4.0
(10) 0.13 ≦ f / f _I5 ≦ 0.37
(11) | r _I10 / r _I9 | ≦ 1.5 (because the absolute value is r _I10 ≦ 0)
However,
d _I4 : A gap f _I5 on the reduction side of the lens arranged second from the magnification side in the 1a lens group, f _I5 : Focal length r _{I9 of the} positive lens arranged third from the magnification side in the 1b lens group, 1b Curvature radius r _{I10 of} the positive side lens arranged third from the magnification side in the lens group: Curvature radius of the reduction side surface of the positive lens arranged third from the magnification side in the 1b lens group

  In the first lens group, the lens arranged closest to the reduction side and the lens arranged second from the magnification side are preferably aspherical lenses made of a plastic material in terms of cost. However, if a plastic material is used, the change with respect to temperature and humidity becomes large, and it is impossible to give large power to these lenses. Therefore, by reducing the distance from the next negative power lens, it is possible to cope with the design with respect to low power. However, in this case, the shape of the lens arranged second from the enlargement side is particularly good. , It will deviate from the concentric shape, and the balance of aberration will be lost. Conditional expression (9) indicates a geometric condition for achieving this balance. When the lower limit of conditional expression (9) is exceeded, the aberration balance of the two lenses on the enlargement side is lost. Conversely, if the upper limit is exceeded, the negative power of the two lenses on the enlargement side will be insufficient. Conditional expression (10) relates to the condition of power applied to the positive lens arranged third from the magnification side in the 1b lens group. In order to increase the angle of view while keeping the aperture diameter of the magnifying side lens small and to secure the peripheral light amount, it is necessary to largely bend the direction of the principal ray with respect to the periphery of the screen, and the whole has a large negative power. Even in the first lens group, a large positive power is required on the reduction side. The lens plays this role. When the lower limit of conditional expression (10) is exceeded, the power becomes small, and the amount of peripheral light cannot be secured while maintaining the required angle of view. Conversely, if the upper limit is exceeded, the power balance with the other lens groups is lost, and various aberrations increase. The following conditional expression (11) relates to the lens shape of the lens. The light beam incident on the last lens under the influence of the strong negative power on the enlargement side is a strong divergent light beam, and in order to converge this moderately and reduce the occurrence of aberration as the first lens group, conditional expression (11) The restriction indicated by is required. If the upper limit is exceeded, spherical and coma aberrations are excessively corrected on the enlarged side surface of the lens, and good performance cannot be obtained.

The second lens group includes a 2a lens group having a negative refractive power as a whole and a second b lens group having a positive or negative refractive power as a whole in order from the magnification side. It is desirable that the following conditional expression (12) is satisfied with respect to power. (Claim 5)
(12) −0.18 ≦ f / f _IIa ≦ −0.06
However,
f _IIa : Composite focal length of the 2a lens group

  In the second lens group, the power of the constituent elements is large, but the power as a group is not so great. This is also the case with the second lens group, but the power as a group is not so great in both the 2a lens group and the 2b lens group. This is because the positive power and the negative power composing each other are antagonistic. However, it is considered that the high power of the element improves the Petzval sum. Among them, it is desirable that the power of the 2a lens group disposed on the enlargement side in the second lens group is set within the range of the conditional expression (12), which exceeds the lower limit, that is, the negative power of the 2a lens group is Increasing the size requires that the positive power on the reduction side also be increased, which deteriorates the aberration and makes it impossible to maintain good performance. On the contrary, exceeding the upper limit lowers the retrofocus degree of the entire lens system, making it impossible to secure the back focus according to the specification.

The 2a lens group constituting the second lens group is configured by arranging a positive lens and a negative lens in order from the magnification side, and the 2b lens group constituting the second lens group is composed of the magnification side. Are arranged in order from the positive lens and the negative lens, and satisfy the following conditional expression (13) with respect to the power of the lens arranged closest to the magnifying side of the 2a lens group, and arranged second from the magnifying side. It is desirable that the following conditional expression (14) is satisfied with respect to the power of the lens. (Claim 6)
(13) 0.09 ≦ f / f _II1 ≦ 0.3
(14) −0.4 ≦ f / f _II2 ≦ −0.26
However,
f _II1 : Focal length of the lens arranged closest to the magnification side in the 2a lens group f _II2 : Focal length of the lens arranged second from the magnification side in the 2a lens group

  The positive lens arranged in the 2a lens group is given a large positive power for maintaining the peripheral light amount. On the other hand, the second lens is a negative power lens, but the Petzval sum is kept appropriate by applying power. Therefore, in order to maintain the amount of peripheral light and at the same time maintain good flatness of the image surface, the power of these lenses must be set to a relatively large state, but this also causes deterioration of the aberration. Therefore, we will balance these. Conditional expression (13) expresses these conditions regarding the magnifying side lens. If the lower limit is exceeded, neither the peripheral light amount nor the flatness of the image plane can be secured, but if the upper limit is exceeded, the aberrations deteriorate. . Conditional expression (14) is a condition for the lens on the reduction side. If the upper limit is exceeded, the power is insufficient, so that the flatness of the image surface is impaired. Will be worsened.

The third lens group includes a 3a lens group having positive or negative refractive power as a whole and a 3b lens group having positive refractive power as a whole in order from the magnification side. It is desirable that the following conditional expression (15) is satisfied with respect to the power of: (Claim 7)
(15) 0 ≦ f / _fIIIb ≦ 0.42
However,
_fIIIb : Composite focal length of the 3b lens group

  Conditional expression (15) is a range for appropriately setting the positive power range of the third lens group. The arrangement of the 3b lens group on the most reduction side of the lens system directly relates to the setting of the so-called back focus on the reduction side. In order to maintain the balance of the aberrations, it is not preferable to give an excessive positive power. Therefore, the positive power of the third lens group is determined by the balance of these conditions. Therefore, if the lower limit of conditional expression (15) is exceeded, the amount of positive power is small and it is difficult to ensure back focus. On the other hand, if the upper limit is exceeded, the power becomes excessive and the aberration cannot be maintained properly.

The 3a lens group constituting the third lens group is configured by arranging a positive lens, a negative lens, a positive lens, and a negative lens in order from the magnification side, and is a positive lens constituting the 3a lens group. It is desirable that the following conditional expression (16) is satisfied with respect to the dispersion characteristics, and the following conditional expression (17) is satisfied with respect to the characteristics of the refractive index. (Claim 8)
(16) 48 ≦ _vIIIaP
(17) _nIIIaP ≦ 1.6
However,
v _IIIaP : average value of Abbe number of positive lens constituting the 3a lens group n _IIbP : average value of refractive index of positive lens constituting the 3a lens group

  Conditional expression (16) and conditional expression (17) both indicate an appropriate range for chromatic aberration correction in the 3a lens group. In other words, both types cannot exceed the limit value, and the chromatic aberration of the entire lens system cannot be properly designed.

The 3b lens group constituting the third lens group includes a positive lens, a negative lens, a positive lens, and a positive lens arranged in order from the magnification side, and a positive lens constituting the third b lens group; The following conditional expression (18) is satisfied with respect to the dispersion characteristics of the negative lens, and the following conditional expression (19) is satisfied with respect to the characteristics of the refractive index of the positive lens, and the lens arranged closest to the reduction side in the third lens group It is desirable that the following conditional expression (20) is satisfied with respect to the shape of (Claim 9)
(18) 26 ≦ v _IIIbP −v _IIIbN
(19) _nIIIbP ≦ 1.60
(20) −0.33 ≦ f / _rIII13 ≦ −0.24
However,
v _IIIbP: average Abbe number of the positive lens constituting the 3b-th lens group v _IIIbN: average Abbe number of the negative lens constituting the 3b-th lens group n _IIIbP: refraction of the positive lens constituting the 3b-th lens group Average value r _III13 : radius of curvature of the reduction side surface of the lens arranged closest to the reduction side in the third lens group

  Conditional expression (18) shows a preferable state of the chromatic aberration balance of the third lens group in order to maintain a good chromatic aberration balance of the entire lens system. It is important to configure the chromatic aberration of the third lens group having strong positive power in the range of the conditional expression (18) because it greatly affects the chromatic aberration correction of the entire lens system. If the range of the conditional expression is exceeded, the chromatic aberration of the entire lens system cannot be designed properly. Further, regarding chromatic aberration correction, it is possible to substantially select a glass material by setting the refractive index of the positive lens within the range of conditional expression (19). That is, in order to increase the Abbe number of the positive lens, the refractive index must be set substantially within the range of the conditional expression (19). If the upper limit is exceeded, chromatic aberration correction must be insufficient. Absent. Conditional expression (20) relates to the shape of the surface arranged closest to the reduction side in the third lens group. Since this surface is essentially located on the most reduction side in the entire lens system, it has a great influence on various characteristics relating to off-axis light flux. In particular, in order to secure a large amount of peripheral light while maintaining good telecentricity in the vicinity of the focal plane, it is necessary to select an appropriate radius of curvature. If the upper limit is exceeded, the surface power is too small and the peripheral light is secured. It becomes difficult to do. Conversely, when the lower limit is exceeded, it becomes difficult to control telecentricity, and the power as a lens tends to increase, leading to deterioration of various aberrations.

  As described above, by mounting the super wide-angle optical system of the present invention on the projection display device, the entire device can be miniaturized with high brightness, and the cost can be kept low. (Claim 10)

  According to the present invention, it is possible to project a large screen even at a short distance suitable for the characteristics of a light valve such as DMD, and to realize a projection optical system with high imaging performance. By using this, a large screen can be projected even at a short distance. Can be projected, and a projection display device with high image quality can be provided.

It is an optical system block diagram of the 1st Example of the short distance projection optical system by this invention. FIG. 6 is a diagram illustrating various aberrations of the short-distance projection optical system according to the first example. It is an optical system block diagram of 2nd Example of the short distance projection optical system by this invention. It is an aberration diagram of the short-distance projection optical system of the second example. It is an optical system block diagram of 3rd Example of the short-distance projection optical system by this invention. FIG. 11 is a diagram illustrating all aberrations of the short-distance projection optical system according to the third example. It is an optical system block diagram of 4th Example of the short distance projection optical system by this invention. It is an aberration diagram of the short-distance projection optical system of the fourth example. It is an optical system block diagram of 5th Example of the short distance projection optical system by this invention. FIG. 10 is a diagram illustrating all aberrations of the short-distance projection optical system according to the fifth example. It is an optical system block diagram of 6th Example of the short-distance projection optical system by this invention. It is an aberration diagram of the short-distance projection optical system of the sixth example. It is an optical system block diagram of 7th Example of the short distance projection optical system by this invention. FIG. 10 is a diagram illustrating all aberrations of the short-distance projection optical system according to the seventh example. It is an optical system block diagram of 8th Example of the short-distance projection optical system by this invention. It is an aberration diagram of the short-distance projection optical system of the eighth example. It is an optical system block diagram of 9th Example of the short-distance projection optical system by this invention. FIG. 10 is a diagram illustrating all aberrations of the short-distance projection optical system according to the ninth example.

  Hereinafter, the present invention will be described with respect to specific numerical examples. In the super wide-angle optical systems of the following first to ninth embodiments, in order from the magnification side, the first lens group (lens group name LG1) having a negative refractive power as a whole, and having a negative refractive power as a whole The first lens group LG1 is composed of a second lens group (lens group name LG2) and a third lens group (lens group name LG3) having a positive refractive power as a whole, and the first lens group LG1 is negatively refracted in order from the enlargement side. 1a lens group having a power (lens group name LG1a) and 1b lens group having a negative refractive power as a whole (lens group name LG1b), and the second lens group LG2 is entirely in order from the magnification side. The second lens group (lens group name LG2a) having a negative refractive power and the second b lens group (lens group name LG2b) having a positive or negative refractive power as a whole are configured, and the third lens group LG3 is enlarged. From the side 3a lens group (lens group name LG3a) having positive or negative refractive power as a whole, and 3b lens group (lens group name LG3b) having positive refractive power as a whole, and the first a lens group LG1a Is a negative meniscus lens (lens name is L11, the surface number of the enlargement side is 101, and the surface number of the reduction side is 102) and a negative lens (lens name is L12, enlargement) The surface number of the side surface is 103 and the surface number of the reduction side surface is 104. The first b lens group LG1b is a negative lens in order from the enlargement side (lens name is L13, and the surface number of the enlargement side surface is 105). , The surface number of the reduction side is 106), the negative lens (the lens name is L14, the surface number of the enlargement side is 107, and the surface number of the reduction side is 108), the positive lens (the lens name is 15. The surface number of the enlarged side surface is 109, the surface number of the reduced side surface is 110, and a negative lens (the lens name is L16, the surface number of the enlarged side surface is 111 (however, in the case of a cemented surface, the 110 and 111 surfaces are the same) Surface), and the surface number of the reduction side surface is 112), and the second a lens group LG2a is a positive lens (lens name is L21, surface number of the expansion side surface is 201, and reduction side surface in order from the enlargement side) And the negative lens (the lens name is L22, the surface number of the enlarged side surface is 203 (in the case of the cemented surface, the 202 and 203 surfaces are the same surface), and the surface number of the reduced side surface is 204. ), And the second b lens group LG2b includes, in order from the enlargement side, a positive lens (lens name L23, enlargement side surface number 205, reduction side surface number 206) and negative lens ( Len The lens number LG24a is a positive lens (lens name) in order from the magnification side. L31, the surface number of the enlarged side surface is 301 and the surface number of the reduced side surface is 302), the negative lens (the lens name is L32, the surface number of the enlarged side surface is 303, and the surface number of the reduced side surface is 304), positive Lens (L33 is the lens name, 304 is the surface number of the enlarged side for bonding, and 305 is the surface number of the reducing side) and a negative lens (the lens name is L34, the surface number of the expanding side is 305 for bonding, the reducing side surface) The third lens group LG3b has a positive lens in order from the enlargement side (lens name is L35, the enlargement side surface number is 307, and the reduction side surface number is 30). Negative lens (the lens name is L36, the surface number of the enlargement side is 309, the surface number of the reduction side is 310), the positive lens (the lens name is L37, and the surface number of the enlargement side is 310 for bonding, The third lens group LG3 includes a reduction lens surface number 311) and a positive lens (lens name L38, enlargement side surface number 312 and reduction side surface number 313). On the reduction side, a large air space is provided, and then, in relation to the illumination optical system, the fourth lens group (lens group name LG4), the positive lens (lens name is L41, the surface number of the enlarged side surface is 401, and the reduction is performed. The surface number of the side surface is 402), and a DMD or the like that is arranged with a slight air gap between the reduction side of the fourth lens group LG4 and the light valve surface is subsequently provided. Light valve (An expanded side C01, the C02 reduction side) cover glass CG is formed parts arranged constituted.

[Example 1]
Table 1 shows numerical examples of the first embodiment of the projection optical system according to the present invention. FIG. 1 is a diagram showing the lens configuration, and FIG. 2 is a diagram showing various aberrations thereof.
In the upper part of the table, f represents the focal length of the short-distance projection optical system, F _no represents the F number, 2ω represents the total angle of view (unit: degrees) of the short-distance projection optical system, and d _p represents the 101 plane and the corresponding plane. This represents the distance to the projection surface on the enlargement side, and h _I1 represents the radius of the effective diameter on the 101 surface. In the lower row, r is a radius of curvature, d is a lens thickness or a lens interval, _nd is a refractive index with respect to the d line, and ν _d is an Abbe number of the d line. CA1, CA2, and CA3 in the spherical aberration diagrams in the various aberration diagrams are aberration curves at wavelengths of CA1 = 550 nm, CA2 = 450 nm, and CA3 = 620 nm, respectively. In the astigmatism diagram, S indicates sagittal and M indicates meridional. Unless otherwise specified throughout, the wavelength used for calculation of various values is CA1 = 550.0 nm, and the unit of length is mm.

[Example 2]
Table 2 shows numerical examples of the second embodiment of the projection optical system of the present invention. FIG. 3 is a diagram showing the lens configuration, and FIG. 4 is a diagram showing various aberrations thereof.

[Example 3]
Table 3 shows numerical examples of the third embodiment of the projection optical system according to the present invention. FIG. 5 is a diagram showing the lens configuration, and FIG. 6 is a diagram showing various aberrations.

[Example 4]
Table 4 shows numerical examples of the fourth embodiment of the projection optical system according to the present invention. FIG. 7 is a diagram showing the lens configuration, and FIG. 8 is a diagram showing various aberrations.

[Example 5]
Table 5 shows numerical examples of the fifth embodiment of the projection optical system according to the present invention. FIG. 9 is a lens configuration diagram, and FIG. 10 is a diagram showing various aberrations.

[Example 6]
Table 6 shows numerical examples of the sixth embodiment of the projection optical system according to the present invention. FIG. 11 is a diagram showing the lens configuration, and FIG. 12 is a diagram showing various aberrations.

[Example 7]
Table 7 shows numerical examples of the seventh embodiment of the projection optical system according to the present invention. FIG. 13 is a lens configuration diagram thereof, and FIG. 14 is a diagram showing various aberrations thereof.

[Example 8]
Table 8 shows numerical examples of the eighth embodiment of the projection optical system according to the present invention. FIG. 15 is a lens configuration diagram, and FIG. 16 is a diagram showing various aberrations.

[Example 9]
Table 9 shows numerical examples of the ninth embodiment of the projection optical system according to the present invention. FIG. 17 is a lens configuration diagram, and FIG.

  Next, Table 10 collectively shows values corresponding to the conditional expressions (1) to (20) regarding the first to ninth embodiments.

  As is clear from Table 10, the numerical values for the first to ninth embodiments satisfy the conditional expressions (1) to (20) and the aberrations in the respective embodiments. As is apparent from the figure, each aberration is corrected well.

The invention described in the scope of claims at the beginning of the filing of the present application will be appended.
[Claim 1]
In order from the magnification side, the first lens group having a negative refractive power as a whole, a second lens group having a weak positive or negative refractive power as a whole, and a third lens group having a positive refractive power as a whole, An ultra-wide-angle optical system configured by disposing a light valve such as a DMD after providing a large air gap on the reduction side of the third lens group, from the most reduction side surface of the third lens group An optical system that forms an image after passing through a distance, satisfies the following conditional expression (1) with respect to the power of the first lens group, and is on the optical axis from the most magnified surface of the first lens group to the image plane. And the following conditional expression (2) and the following conditional expression (3) are satisfied with respect to the distance and the effective diameter of the most magnified surface of the first lens group, and from the most demagnifying surface of the second lens group: The following conditional expression (4) is satisfied with respect to the distance on the optical axis to the image plane: Super-wide-angle optical system for a butterfly.
(1) −0.48 ≦ f / f _I ≦ 0
(2) TL / f ≦ 36
(3) D _I1 / TL ≦ 0.72
(4) 6.2 ≦ b / f
However,
f : Total focal length of the entire optical system (focused on the projection surface at the design reference distance)
f _I : Composite focal length TL of the first lens group TL: Distance on the optical axis from the most magnified surface of the first lens group to the image plane (however, the fourth lens group and the cover glass part of the parallel plane are converted to air) distance)
D _I1 : Effective diameter b of the most magnified surface of the first lens group : Distance on the optical axis from the most reduced surface of the third lens group to the image plane (however, the fourth lens group and the cover glass portion of the parallel plane are air-converted distances)
[Claim 2]
2. The super wide-angle optical system according to claim 1, wherein the first lens group includes a first lens group having a negative refractive power as a whole and a first lens group having a negative refractive power as a whole in order from the magnification side. In addition, the following conditional expression (5) is satisfied with respect to the powers of the first-a lens group and the first-b lens group.
(5) 0 ≦ f _Ia / f _Ib ≦ 1.50
However,
f _Ia : Composite focal length of the 1a lens group f _Ib : Composite focal length of the 1b lens group [Claim 3]
2. The super wide-angle optical system according to claim 1, wherein the first lens group constituting the first lens group is a lens having a negative meniscus shape that is convex toward the enlargement side in order from the enlargement side (hereinafter, negative lens). ) And a negative lens, and the 1b lens group includes a negative lens, a negative lens, a lens having a positive refractive power (hereinafter positive lens) and a negative lens in order from the magnification side, The following conditional expression (6) is satisfied with respect to the power possessed by the 1a lens group, and the following conditional expression (7) is satisfied with respect to the characteristic of the shape of the lens arranged at the most enlargement side in the 1a lens group, and the 1a lens group The following conditional expression (8) is satisfied with respect to the characteristics of the shape of the lens arranged second from the enlargement side in FIG.
(6) −0.18 ≦ f / f _Ia ≦ −0.12
(7) 2.2 ≦ r _I1 / r _I2 ≦ 7.2
(8) 1.8 ≦ r _I3 / r _I4 ≦ 5.2
However,
r _I1 : radius of curvature of the magnifying side of the lens arranged closest to the magnifying side in the 1a lens group r _I2 : radius of curvature r _I3 of the demagnifying side of the lens arranged _{maximally on} the 1a lens group: 1a lens Radius of curvature r _{I4 of} the lens disposed second from the magnification side in the group: Curvature radius of the reduction surface of the lens disposed second from the magnification side in the 1a lens group [Claim 4]
In the super wide-angle optical system according to claim 1, the following conditional expression (9) is satisfied with respect to the size of the gap on the reduction side of the lens disposed second from the enlargement side in the 1a lens group constituting the first lens group. And the following conditional expression (10) is satisfied with respect to the power of the positive lens arranged third from the magnification side in the 1b lens group constituting the first lens group, and the lens shape characteristics of the lens The following conditional expression (9) is satisfied.
(9) 2.8 ≦ d _I4 / f ≦ 4.0
(10) 0.13 ≦ f / f _I5 ≦ 0.37
(11) | r _I10 / r _I9 | ≦ 1.5 (because the absolute value is r _I10 ≦ 0)
However,
d _I4 : A gap f _I5 on the reduction side of the lens arranged second from the magnification side in the 1a lens group, f _I5 : Focal length r _{I9 of the} positive lens arranged third from the magnification side in the 1b lens group, 1b The radius of curvature r _I10 of the magnification side of the positive lens arranged third from the magnification side in the lens group: The radius of curvature of the reduction side of the positive lens arranged third from the magnification side in the 1b lens group [Claim 5]
2. The super wide-angle optical system according to claim 1, wherein the second lens group includes a second a lens group having a negative refractive power as a whole and a second b lens group having a positive or negative refractive power as a whole in order from the magnification side. And the following conditional expression (12) is satisfied with respect to the power of the second-a lens group.
(12) −0.18 ≦ f / f _IIa ≦ −0.06
However,
f _IIa : Composite focal length of the 2a lens group [Claim 6]
2. The super wide-angle optical system according to claim 1, wherein the second a lens group configuring the second lens group includes a positive lens and a negative lens in order from the magnification side, and configures the second lens group. The second b lens group includes a positive lens and a negative lens in order from the magnifying side, and satisfies the following conditional expression (13) with respect to the power of the lens arranged closest to the magnifying side of the second a lens group. The following conditional expression (14) is satisfied with respect to the power of the lens arranged second from the enlargement side.
(13) 0.09 ≦ f / f _II1 ≦ 0.3
(14) −0.4 ≦ f / f _II2 ≦ −0.26
However,
f _II1 : Focal length of the lens arranged closest to the magnification side in the 2a lens group f _II2 : Focal length of the lens arranged second from the magnification side in the 2a lens group [Claim 7]
2. The super wide-angle optical system according to claim 1, wherein the third lens group includes a third lens group having positive or negative refractive power as a whole and a third lens group having positive refractive power as a whole in order from the magnification side. The third lens group satisfies the following conditional expression (15) regarding the power of the third lens group.
(15) 0 ≦ f / _fIIIb ≦ 0.42
However,
f _IIIb : Composite focal length of the third lens group [Claim 8]
The super wide-angle optical system according to claim 1, wherein the third lens group constituting the third lens group is configured by sequentially arranging a positive lens, a negative lens, a positive lens, and a negative lens from the magnification side, The following conditional expression (16) is satisfied with respect to the dispersion characteristics of the positive lens constituting the 3a lens group, and the following conditional expression (17) is satisfied with respect to the characteristics of the refractive index.
(16) 48 ≦ _vIIIaP
(17) _nIIIaP ≦ 1.6
However,
_vIIIaP : average value of Abbe number of positive lens constituting the 3a lens group _nIIbP : average value of refractive index of positive lens constituting the 3a lens group [claim 9]
The super wide-angle optical system according to claim 1, wherein the third lens group constituting the third lens group is configured by sequentially arranging a positive lens, a negative lens, a positive lens, and a positive lens from the magnification side, The following conditional expression (18) is satisfied with respect to the dispersion characteristics of the positive lens and the negative lens constituting the third lens group, and the following conditional expression (19) is satisfied with respect to the refractive index characteristics of the positive lens, and the third lens: The following conditional expression (20) is satisfied with respect to the shape of the lens arranged closest to the reduction side in the group.
(18) 26 ≦ v _IIIbP −v _IIIbN
(19) _nIIIbP ≦ 1.60
(20) −0.33 ≦ f / _rIII13 ≦ −0.24
However,
v _IIIbP: average Abbe number of the positive lens constituting the 3b-th lens group v _IIIbN: average Abbe number of the negative lens constituting the 3b-th lens group n _IIIbP: refraction of the positive lens constituting the 3b-th lens group Average ratio r _III13 : radius of curvature of the reduction side surface of the lens arranged closest to the reduction side in the third lens group [claim 10]
A projection type display device comprising the super-wide-angle optical system according to any one of claims 1 to 8.

Claims (10)

In order from the magnification side, the first lens group having a negative refractive power as a whole, a second lens group having a weak positive or negative refractive power as a whole, and a third lens group having a positive refractive power as a whole, An ultra-wide-angle optical system configured by disposing a light valve such as a DMD after providing a large air gap on the reduction side of the third lens group, from the most reduction side surface of the third lens group An optical system that forms an image after passing through a distance, satisfies the following conditional expression (1) with respect to the power of the first lens group, and is on the optical axis from the most magnified surface of the first lens group to the image plane. And the following conditional expression (2) and the following conditional expression (3) are satisfied with respect to the distance and the effective diameter of the most magnified surface of the first lens group, and from the most demagnifying surface of the second lens group: The following conditional expression (4) is satisfied with respect to the distance on the optical axis to the image plane: Super-wide-angle optical system for a butterfly.
(1) −0.48 ≦ f / f _I ≦ 0
(2) TL / f ≦ 36
(3) D _I1 / TL ≦ 0.72
(4) 6.2 ≦ b / f
However,
f : Total focal length of the entire optical system (focused on the projection surface at the design reference distance)
f _I : Composite focal length TL of the first lens group TL: Distance on the optical axis from the most magnified surface of the first lens group to the image plane (however, the fourth lens group and the cover glass part of the parallel plane are converted to air) distance)
D _I1 : Effective diameter b of the most magnified surface of the first lens group : Distance on the optical axis from the most reduced surface of the third lens group to the image plane (however, the fourth lens group and the cover glass portion of the parallel plane are air-converted distances) 2. The super wide-angle optical system according to claim 1, wherein the first lens group includes a first lens group having a negative refractive power as a whole and a first lens group having a negative refractive power as a whole in order from the magnification side. In addition, the following conditional expression (5) is satisfied with respect to the powers of the first-a lens group and the first-b lens group.
(5) 0 ≦ f _Ia / f _Ib ≦ 1.50
However,
f _Ia : Composite focal length of the 1a lens group f _Ib : Composite focal length of the 1b lens group 2. The super wide-angle optical system according to claim 1, wherein the first lens group constituting the first lens group is a lens having a negative meniscus shape that is convex toward the enlargement side in order from the enlargement side (hereinafter, negative lens). ) And a negative lens, and the 1b lens group includes a negative lens, a negative lens, a lens having a positive refractive power (hereinafter positive lens) and a negative lens in order from the magnification side, The following conditional expression (6) is satisfied with respect to the power possessed by the 1a lens group, and the following conditional expression (7) is satisfied with respect to the characteristic of the shape of the lens arranged at the most enlargement side in the 1a lens group, and the 1a lens group The following conditional expression (8) is satisfied with respect to the characteristics of the shape of the lens arranged second from the enlargement side in FIG.
(6) −0.18 ≦ f / f _Ia ≦ −0.12
(7) 2.2 ≦ r _I1 / r _I2 ≦ 7.2
(8) 1.8 ≦ r _I3 / r _I4 ≦ 5.2
However,
r _I1 : radius of curvature of the magnifying side of the lens arranged closest to the magnifying side in the 1a lens group r _I2 : radius of curvature r _I3 of the demagnifying side of the lens arranged _{maximally on} the 1a lens group: 1a lens Radius of curvature r _{I4 of} the lens disposed second from the magnification side in the lens group: radius of curvature of the reduction surface of the lens disposed second from the magnification side in the lens group 1a In the super wide-angle optical system according to claim 1, the following conditional expression (9) is satisfied with respect to the size of the gap on the reduction side of the lens disposed second from the enlargement side in the 1a lens group constituting the first lens group. And the following conditional expression (10) is satisfied with respect to the power of the positive lens arranged third from the magnification side in the 1b lens group constituting the first lens group, and the lens shape characteristics of the lens The following conditional expression (9) is satisfied.
(9) 2.8 ≦ d _I4 / f ≦ 4.0
(10) 0.13 ≦ f / f _I5 ≦ 0.37
(11) | r _I10 / r _I9 | ≦ 1.5 (because the absolute value is r _I10 ≦ 0)
However,
d _I4 : A gap f _I5 on the reduction side of the lens arranged second from the magnification side in the 1a lens group, f _I5 : Focal length r _{I9 of the} positive lens arranged third from the magnification side in the 1b lens group, 1b Curvature radius r _{I10 of} the positive side lens arranged third from the magnification side in the lens group: Curvature radius of the reduction side surface of the positive lens arranged third from the magnification side in the 1b lens group 2. The super wide-angle optical system according to claim 1, wherein the second lens group includes a second a lens group having a negative refractive power as a whole and a second b lens group having a positive or negative refractive power as a whole in order from the magnification side. And the following conditional expression (12) is satisfied with respect to the power of the second-a lens group.
(12) −0.18 ≦ f / f _IIa ≦ −0.06
However,
f _IIa : Composite focal length of the 2a lens group 2. The super wide-angle optical system according to claim 1, wherein the second a lens group configuring the second lens group includes a positive lens and a negative lens in order from the magnification side, and configures the second lens group. The second b lens group includes a positive lens and a negative lens in order from the magnifying side, and satisfies the following conditional expression (13) with respect to the power of the lens arranged closest to the magnifying side of the second a lens group. The following conditional expression (14) is satisfied with respect to the power of the lens arranged second from the enlargement side.
(13) 0.09 ≦ f / f _II1 ≦ 0.3
(14) −0.4 ≦ f / f _II2 ≦ −0.26
However,
f _II1 : Focal length of the lens arranged closest to the magnification side in the 2a lens group f _II2 : Focal length of the lens arranged second from the magnification side in the 2a lens group 2. The super wide-angle optical system according to claim 1, wherein the third lens group includes a third lens group having positive or negative refractive power as a whole and a third lens group having positive refractive power as a whole in order from the magnification side. The third lens group satisfies the following conditional expression (15) regarding the power of the third lens group.
(15) 0 ≦ f / _fIIIb ≦ 0.42
However,
_fIIIb : Composite focal length of the 3b lens group The super wide-angle optical system according to claim 1, wherein the third lens group constituting the third lens group is configured by sequentially arranging a positive lens, a negative lens, a positive lens, and a negative lens from the magnification side, The following conditional expression (16) is satisfied with respect to the dispersion characteristics of the positive lens constituting the 3a lens group, and the following conditional expression (17) is satisfied with respect to the characteristics of the refractive index.
(16) 48 ≦ _vIIIaP
(17) _nIIIaP ≦ 1.6
However,
v _IIIaP : average value of Abbe number of positive lens constituting the 3a lens group n _IIbP : average value of refractive index of positive lens constituting the 3a lens group The super wide-angle optical system according to claim 1, wherein the third lens group constituting the third lens group is configured by sequentially arranging a positive lens, a negative lens, a positive lens, and a positive lens from the magnification side, The following conditional expression (18) is satisfied with respect to the dispersion characteristics of the positive lens and the negative lens constituting the third lens group, and the following conditional expression (19) is satisfied with respect to the refractive index characteristics of the positive lens, and the third lens: The following conditional expression (20) is satisfied with respect to the shape of the lens arranged closest to the reduction side in the group.
(18) 26 ≦ v _IIIbP −v _IIIbN
(19) _nIIIbP ≦ 1.60
(20) −0.33 ≦ f / _rIII13 ≦ −0.24
However,
v _IIIbP: average Abbe number of the positive lens constituting the 3b-th lens group v _IIIbN: average Abbe number of the negative lens constituting the 3b-th lens group n _IIIbP: refraction of the positive lens constituting the 3b-th lens group Average value r _III13 : radius of curvature of the reduction side surface of the lens arranged closest to the reduction side in the third lens group   A projection type display device comprising the super-wide-angle optical system according to any one of claims 1 to 8.

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