JP2013076792A - Projection optical system and projection type display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection optical system that magnifies and project an image from a DMD onto a screen, is bright, has a small lens aperture, is low in cost and optimum for a projection display device of small type.SOLUTION: The projection optical system comprises: in order from a magnifying side; a first optical system with one mirror face; and a second optical system comprising, in order from the magnifying side, a first lens group having negative or positive refractive power as a whole and a second lens group having positive refractive power as a whole. The first lens group comprises, in order from the magnifying side, a 1a-th lens group having negative refractive power as a whole and a 1b-th lens group having positive refractive power as a whole. The second lens group comprises: a 2a-th lens group having negative or positive refractive power as a whole and a 2b-th lens group having positive refractive power as a whole. The 1a-th lens group comprises negative, negative, positive, and negative lenses, and the 1b-th lens group comprises one or two positive lenses. The 2a-th lens group comprises a negative lens, one or two positive lenses, and a negative lens, and the 2b-th lens group comprises one positive lens or comprises a positive or negative lens and a positive lens arranged after the positive or negative lens.

Description

  The present invention mainly relates to a projection optical system that enlarges and projects an image from a light valve that forms an image by changing the reflection direction of light, such as DMD, onto a screen or the like.

  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 light is projected from a short distance of about 1 m, the light from the projection optical system is hardly seen. However, in terms of the projection optical system, this is nothing but increasing the angle of view.

  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 when it is intended to realize a projection display device with efficient brightness. 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. When the light bundle is emitted from the projection lens, an angle corresponding to the angle of view is given by the projection optical system. Therefore, the projection optical system having a larger angle of view has a larger angle when the light bundle passes through the projection optical system. It turns out that the change must be increased. 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 this shift optical system is adopted, the size of the image circle required for the projection optical system is that the radius is the distance from the optical axis to the corner arranged farthest from the optical axis of the DMD. Compared to an optical system such as a normal camera in which the optical axis and the center of the image sensor coincide with each other, the optical system must be larger, which is a factor in increasing costs.

  In this way, in a projection optical system with a large angle of view, particularly in an optical system that is entirely composed of lenses, the refraction of a negative lens that is disposed on the most magnified side and in most cases has a convex shape on the magnified side. The surface is aspherical. The objective is to efficiently correct off-axis aberrations such as this increased distortion, but for that purpose, the glass with the highest correction capability is required despite the need for a large effective diameter. Spherical lenses cannot be used because of their high cost, and the actual situation is that they are composed of aspherical lenses made of a resin material. However, a lens made of a resin material has a demerit such that a change in optical characteristics due to a change in temperature and humidity is large, and the power applied to the lens cannot be increased in adopting the lens. Therefore, although depending on the specifications, a single aspherical lens cannot secure a good aberration correction capability, and there are many that use a plurality of aspherical lenses.

  On the other hand, there is one that uses a reflective surface to shorten the projection distance. Many are employed as rear projection display devices, such as those disclosed in Japanese Patent Application Laid-Open No. 2006-235516 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2008-250296 (Patent Document 2). In the projection optical system, an aspherical reflecting surface (concave mirror) is arranged on the magnification side of the lens system, and in addition, an intermediate image is formed in the space between the lens system and the reflecting surface, so that the reflecting surface is completely covered. This enables a compact optical system. Forming an intermediate image is not a problem when it is inside the device as in the rear type, but it is assumed that when the front type is adopted, the part to be imaged is external. As it is dangerous, it must be avoided. The projection optical system disclosed in Japanese Patent Application Laid-Open No. 2010-217887 (Patent Document 3) is used for a front type, and has at least one aspherical reflecting surface (convex mirror) on the enlargement side of the lens system. This is a method of obtaining a projected image without forming an intermediate image by disposing an aspherical lens made of a resin material having a large effective diameter. As for the projection optical system disclosed in Japanese Patent Application Laid-Open No. 2004-226997 (Patent Document 4), an optical system configured to project an image similar to the present invention onto a screen without forming an intermediate image is disclosed. It is an optical system for a transmission type light valve, and has a problem such as a short back focus, and cannot be used for a DMD which is a reflection type light valve as in the present invention, or even if it is not possible. The spherical lens is used, and it becomes a product having disadvantages such as being expensive or becoming large.

JP 2006-235516 A JP 2008-250296 A JP 2010-217887 A JP 2004-226997 A

  On the other hand, there is one that uses a reflective surface to shorten the projection distance. Many are employed as rear projection display devices, such as those disclosed in Japanese Patent Application Laid-Open No. 2006-235516 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2008-250296 (Patent Document 2). In the projection optical system, an aspherical reflecting surface (concave mirror) is arranged on the magnification side of the lens system, and in addition, an intermediate image is formed in the space between the lens system and the reflecting surface, so that the reflecting surface is completely covered. This enables a compact optical system. Forming an intermediate image is not a problem when it is inside the device as in the rear type, but it is assumed that when the front type is adopted, the part to be imaged is external. As it is dangerous, it must be avoided. The projection optical system disclosed in Japanese Patent Application Laid-Open No. 2010-217887 (Patent Document 3) is used for a front type, and has at least one aspherical reflecting surface (convex mirror) on the enlargement side of the lens system. This is a method of obtaining a projected image without forming an intermediate image by disposing an aspherical lens made of a resin material having a large effective diameter. As for the projection optical system disclosed in Japanese Patent Application Laid-Open No. 2004-226997 (Patent Document 4), an optical system configured to project an image similar to the present invention onto a screen without forming an intermediate image is disclosed. It is an optical system for a transmission type light valve, and has a problem such as a short back focus, and cannot be used for a DMD which is a reflection type light valve as in the present invention, or even if it is not possible. The spherical lens is used, and it becomes a product having disadvantages such as being expensive or becoming large.

  However, in the proposal of Patent Document 1, according to the embodiment of the present invention, two aspherical lenses are used. If cost and productivity are taken into consideration, a design that is effective for providing products is provided. It is not a means. Also, in the proposal of Patent Document 4, this is because a wide-angle, high zoom ratio, and bright optical system is demanded as a zoom lens for photographing, but the zoom in the same technical field designed on the assumption that the zoom cam is used. It is not better than the lens. When considering the cost in the range including the optical system and the lens frame mechanism that holds it and realizes focusing and zooming, it is advantageous to use an optically corrected zoom lens that does not require an expensive zoom cam as a mechanism part. is there. However, the adoption to the thin projection apparatus cannot achieve the angle of view and the F value in the example of Patent Document 2, cannot achieve the angle of view in the example of Patent Document 3, and cannot achieve the F value in the example of Patent Document 4. . Further, through each of the above examples, the projection lens cannot be adopted unless the resolution is higher.

  In view of the circumstances described above, 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, by disposing an aspherical reflecting mirror as the most enlarged optical element. Realizes a compact, single-focus lens that is bright, wide-angle, and has high imaging performance without using an aspheric lens in applications that enlarge and project images from light valves onto a screen or other wall surface. An object of the present invention is to provide a projection display device that can project a large screen even in a limited space such as a conference room and has high image quality and is inexpensive.

The projection optical system in the present invention is composed of a first optical system and a second optical system in order from the enlargement side, the first optical system is composed of one mirror surface, and the second optical system is A first lens group having a negative or positive refractive power as a whole and a second lens group having a positive refractive power as a whole in order from the magnification side, and the mirror surface constituting the first optical system is rotationally symmetric The lens constituting the second optical system is composed of only a spherical lens, and the rotationally symmetric axis of the mirror surface coincides with the optical axis of the second optical system. The power of the first lens group satisfies the following conditional expression (1), and the effective diameter of the most enlarged surface of the first lens group satisfies the following conditional expression (2), The distance on the optical axis from the mirror surface to the most magnified surface of the first lens group. The following conditional expression (3) is satisfied, the following conditional expression (4) is satisfied with respect to the distance on the optical axis from the most magnified surface of the first lens group to the image plane, and the second lens group is the most The following conditional expression (5) is satisfied with respect to the distance on the optical axis from the reduction side surface to the image plane. (Claim 1)
(1) −0.22 ≦ f / f _I ≦ 0.25
(2) 0.97 ≦ h _I1 / h _im ≦ 1.20
(3) ML / f ≦ 10
(4) GL / f ≦ 15
(5) 3.0 ≦ b / f
However,
f: Composite focal length of the entire optical system (focusing on the projection surface at the design reference distance)
f _I : _Combined focal length h _{I1 of} the first lens group: Radius of effective diameter of the most magnified side surface of the first lens group h _im : Radius of the image circle ML: From the mirror surface to the most magnified side surface of the first lens group Distance GL on the optical axis of the first lens group: Distance on the optical axis from the most magnified surface of the first lens group to the image plane (however, the third lens group and the cover glass portion of the parallel plane are air-converted distances)
b : Distance on the optical axis from the most reduced surface of the second lens group to the image plane (however, the third 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 a large 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 the whole is a negative or positive weak group power. 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) relates to the relationship between the effective diameter of the most enlarged side surface of the first lens group and the size of the image circle diameter. Conditional expression (2) shows the optimum range for downsizing of the effective diameter on the most enlarged side of the first lens group. When the effective diameter is increased, the effective light beam for obtaining the projection image reflected by the mirror is blocked, and therefore, the mirror shown in the following conditional expression (3) and the surface on the most magnified side of the first lens group. Therefore, not only the change in the size of the effective diameter but also the size of the projection apparatus is greatly affected. If the design exceeds the lower limit of conditional expression (2), the amount of light in the surrounding area will be insufficient, and if the value becomes smaller, the angle of view with respect to the specification cannot be maintained. On the other hand, when the upper limit is exceeded, miniaturization becomes difficult as described above.
The following conditional expression (3) shows the limitation on the distance from the mirror to the most magnified surface of the first lens group. Realizing the distance between the mirror and the most magnified surface of the first lens group with a small value as in the conditional expression (3) is important for realizing the compactness of the entire apparatus, and the smaller the value, the more compact. Although the performance is improved, as described above, it is often determined indirectly in conjunction with the content of conditional expression (2). If the usage method exceeds the upper limit, the optical system becomes large and a compact projection device cannot be supplied.
Conditional expression (4) is a condition relating to the entire length of the second optical system, 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 (5) is a condition regarding the 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 first lens group having a negative refractive power as a whole and a first lens group having a positive refractive power as a whole in order from the magnification side, and the first lens group is a magnification lens. A lens having a negative meniscus shape (hereinafter referred to as a negative lens), a negative lens, a lens having a positive refractive power (hereinafter referred to as a positive lens), and a negative lens in order from the side to a convex meniscus shape, It is desirable that the 1b lens group is configured by arranging one or two positive lenses, and the following conditional expression (6) is satisfied with respect to the power of the first a lens group and the first b lens group. (Claim 2)
(6) −4.50 ≦ f _Ia / f _Ib ≦ −0.32
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, negative power necessary for the focusing operation can be applied to the first lens group without destroying the power balance of the entire optical system. That is, the conditional expression (9) represents the power ratio. Exceeding the upper limit means that the power of the first lens group is reduced in a balanced manner, and the amount of movement in the focusing operation is increased. Aberration variation also increases. 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.

Further, the following conditional expression (7) is satisfied with respect to the power of the lens disposed closest to the magnifying side in the first lens group, and the following conditional expression (8) is satisfied with respect to the characteristics of the shape of the reduction side surface of the lens, It is desirable that the following conditional expression (9) is satisfied with respect to the power of the lens arranged closest to the reduction side, and further, the following conditional expression (10) is satisfied with respect to the lens shape characteristics of the lens. (Claim 3)
(7) −0.62 ≦ f / f _I1 ≦ −0.25
(8) 0.75 ≦ f / r _I2 ≦ 0.96
(9) 0.23 ≦ f / f _I6 ≦ 0.42
(10) | r _I12 / r _I11 | ≦ 3.50 (because the absolute value is r _I12 ≦ 0)
However,
f _I1 : Focal length r _{I2 of} the lens arranged closest to the enlargement side in the first lens group: Curvature radius f _I6 of the reduction side surface of the lens arranged closest to the enlargement side in the first lens group: Most in the first lens group Focal length r _{I11 of} the lens arranged on the reduction side: radius of curvature r _I12 of the enlargement side surface of the lens arranged closest to the reduction side in the first lens group: reduction of the lens arranged closest to the reduction side in the first lens group Side radius of curvature

Conditional expression (7) is a condition relating to the power of the lens arranged closest to the enlargement side of the first lens group. Although the first lens group as a whole has a weak power close to negative or afocal, a large negative power lens is arranged on the magnification side, and a lens arranged on the most magnification side also has a large negative power. doing. This is closely related to the angle of view required for the optical system and the back focus. In the optical system according to the present invention, the negative power of the lens arranged closest to the enlargement side of the first lens group is increased. Is effective in achieving 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, and is effective for reducing the size. If the upper limit of the lens 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. If the lower limit is exceeded, the negative power of the lens becomes weak and the second lens group and a light valve such as a DMD. It is difficult to take a long space corresponding to the so-called back focus, the air gap from the cover glass CG, which is a component.
Conditional expression (8) is a conditional expression for correcting distortion and coma aberration of the present optical system. This relates to the shape of the lens on the reduction side of the lens arranged closest to the magnifying side of the first lens group, and is basically concentric with the beam bundle on the magnifying side while having strong power. It has a shape that suppresses the occurrence of 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 (9) relates to the condition of power applied to the positive lens arranged closest to the reduction side of the first 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, which has a large negative power as a whole. Even in the first lens group, a large positive power is required on the reduction side. The lens plays this role. If the lower limit of conditional expression (9) 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 (10) 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. In order to converge this appropriately and reduce the occurrence of aberration as the first lens group, conditional expression (10) 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 or positive refractive power as a whole and a second b lens group having a positive refractive power as a whole in order from the magnification side. The negative lens, one or two positive lenses, and a negative lens are arranged in order from the enlargement side, and the second b lens group is constituted by arranging at least one positive lens, or an enlargement It is desirable that a positive lens is disposed after a positive or negative lens is disposed on the side, and the following conditional expression (11) is satisfied with respect to the power of the second a lens group and the second b lens group. (Claim 4)
(11) −7.36 ≦ f _IIa / f _IIb ≦ 11.1
However,
f _IIa : Composite focal length of the 2a lens group f _IIb : Composite focal length of the 2b lens group

  Conditional expression (11) indicates the power distribution on the enlargement side and the reduction side in the second lens group having a positive refractive power as a whole. While the projection optical system according to the present invention has power suitable as the second lens group, in order to realize good telecentricity as a projection lens, a large positive power must be input on the reduction side. The 2a lens group is preferably a lens system having negative or weak positive power. Therefore, if the upper limit is exceeded, the reduction-side positive power will be insufficient, and the telecentricity cannot be kept good.On the other hand, if the lower limit is exceeded, the power balance of the entire lens system will deteriorate and the projection performance will be corrected satisfactorily. It becomes difficult to do.

Further, the following conditional expression (12) is satisfied with respect to the power of the second lens group, and the following conditional expression (13) is satisfied with respect to the shape of the lens arranged on the most enlargement side in the second lens group. Is desirable. (Claim 5)
(12) 0.20 ≦ f / f _II ≦ 0.35
(13) −0.15 ≦ f / r _II1 ≦ 0.40
However,
f _II : Composite focal length of the second lens group r _II1 : Radius of curvature of the enlargement side surface of the lens arranged closest to the enlargement side in the second lens group

  Conditional expression (12) is a condition relating to the group power required for the second lens group. The 2a lens group disposed on the enlargement side of the second lens group has a weak negative power, and the 2b lens group disposed on the reduction side has a strong positive power. As a result of combining the powers, the second lens group has a positive power. As a whole lens system, the optical system having a wide angle of view and a large back focus must be a retrofocus type, and this is why the second lens group has a strong positive power. On the other hand, the fact that the 2a lens group has a weak negative power is a result of the relatively fine specifications of the lens system. For example, in the case where the specification of the peripheral light amount is relaxed, it is possible to reduce the positive power of the 2b lens group, and as a result, the 2a lens group has a positive power to balance the whole. Is likely to give better results. In any case, it is preferable that the power distribution as the second lens group is based on conditional expression (12). If the upper limit of conditional expression (12) is exceeded, the power will be excessive and the amount of various aberrations will increase, making it impossible to maintain good performance. If the lower limit is exceeded, the back focus according to the specification cannot be secured. Further, when focusing on spherical aberration, since it is close to the intersection of the off-axis principal ray and the optical axis, the conditional expression (13) is satisfied, so that a substantially afocal luminous flux from the first lens group is balanced with spherical aberration and the like. It becomes possible to transmit to subsequent lens groups, and when the upper limit is exceeded, the generated spherical aberration is too under, and when it exceeds the lower limit, the spherical aberration cannot be corrected in a well-balanced manner.

Further, the following conditional expression (14) is satisfied with respect to the shape of the lens arranged closest to the reduction side in the 2a lens group, and a positive lens constituting the 2a lens group and a negative lens constituting the 2a lens group The following conditional expression (15) is satisfied with respect to the dispersion characteristics of the lens, and the following conditions are respectively satisfied with respect to the characteristics of the refractive index of the lens arranged closest to the reduction side and the lens arranged adjacent to the magnification side of the lens in the 2a lens group: It is desirable that the expression (16) is satisfied. (Claim 6)
(14) −1.00 ≦ f / r _II5 ≦ −0.75
(15) 15 ≦ v _IIaP −v _{IIaN
(16) 0.26 ≦ n II4 -n} II4S ≦ 0.40
However,
r _II5: the 2a lens curvature of the magnifying side surface of the lens which is disposed closest to the reduction side in the group radius v _IIAP: average Abbe number of the positive lens constituting the first 2a lens group v _IIaN: configuring the first 2a lens group mean value of Abbe numbers of the negative lens n _II4: the 2a lens refractive index at the d-line of the lens element which is disposed closest to the reduction side in the group n _II4S: d of the lens element which is disposed second from the reduction side at the 2a lens group Refractive index for the line

  In the 2a lens group, the off-axis principal ray intersects with the optical axis in the vicinity and the ray height of the on-axis marginal ray is high, so that the spherical aberration and its color difference are greatly affected. Conditional expression (14) to conditional expression (16) are constraints on the relationship between the shape condition, the dispersion characteristic, and the refractive index, respectively. If the lower limit is exceeded, excessive spherical aberration will be generated too much, and if the upper limit is exceeded, under spherical aberration will be generated too much. In either case, the spherical aberration cannot be corrected satisfactorily for the entire lens system. Conditional expression (15) is similarly a condition for limiting the chromatic difference of spherical aberration. If the lower limit of conditional expression (15) is exceeded, a good correction state of chromatic difference of spherical aberration and axial chromatic aberration is obtained. It cannot be realized. Regarding spherical aberration, it is important to satisfy not only the conditional expression (14) but also the conditional expression (16). The local radius of the bonded surface is reduced, and the refractive index difference between the glass materials before and after this surface. As in the conditional expression (14), it is important to control the spherical aberration correction capability on this surface. When the lower limit of conditional expression (16) is exceeded, sufficient spherical aberration correction capability cannot be obtained. Conversely, when the upper limit is exceeded, there is spherical aberration correction capability, but aberration occurs in other off-axis rays. Will result in poor overall performance balance.

Further, it is desirable that the following conditional expression (17) is satisfied with respect to the shape of the lens arranged closest to the reduction side in the second lens group. (Claim 7)
(17) −0.65 ≦ f / r _II10 ≦ _−0.30
However,
r _II10 : radius of curvature of the reduction side surface of the lens arranged closest to the reduction side in the second lens group

  Conditional expression (17) relates to the shape of the surface arranged closest to the reduction side in the second 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 projection optical system in the projection display apparatus according to the present invention, the entire apparatus can be reduced in size with high luminance, and the cost can be kept low. (Claim 8) Furthermore, it is possible to provide a compact projection display device that is more convenient to carry by making the mirror portion movable (not shown) when not in use, for example, during storage or carrying. It becomes possible. (Claim 9)

  According to the present invention, a projection optical system capable of projecting a large screen even at a short distance suitable for the characteristics of a light valve such as a DMD, having a high imaging performance, compact and advantageous in terms of cost can be realized. Thus, a large screen can be projected even at a short distance, and a compact and high-quality projection display device can be provided at low cost.

It is an optical system block diagram of the 1st Example of the projection optical system by this invention. FIG. 6 is a diagram illustrating all aberrations of the projection optical system according to the first example. It is an optical system block diagram of 2nd Example of the projection optical system by this invention. It is an aberration diagram of the projection optical system of the second example. It is an optical system block diagram of 3rd Example of the projection optical system by this invention. It is an aberration diagram of the projection optical system of the third example. It is an optical system block diagram of 4th Example of the projection optical system by this invention. It is an aberration diagram of the projection optical system of the fourth example. It is an optical system block diagram of 5th Example of the projection optical system by this invention. FIG. 10 is a diagram illustrating all aberrations of the projection optical system according to the fifth example. It is an optical system block diagram of 6th Example of the projection optical system by this invention. It is an aberration diagram of the projection optical system of the sixth example. It is an optical system block diagram of the 7th Example of the projection optical system by this invention. It is an aberration diagram of the projection optical system of the seventh example. It is an optical system block diagram of the 8th Example of the projection optical system by this invention. It is an aberration diagram of the projection optical system of the eighth example. It is an optical system block diagram of the 9th Example of the projection optical system by this invention. It is an aberration diagram of the projection optical system of the ninth example. It is an optical system block diagram of 10th Example of the projection optical system by this invention. It is an aberration diagram of the projection optical system of the tenth example. It is an optical system block diagram of 11th Example of the projection optical system by this invention. It is an aberration diagram of the projection optical system of the eleventh example. It is an optical system block diagram of 12th Example of the projection optical system by this invention. It is an aberration diagram of the projection optical system of the twelfth example. It is an optical system block diagram of 13th Example of the projection optical system by this invention. It is an aberration diagram of the projection optical system of the 13th example. It is an optical system block diagram of 14th Example of the projection optical system by this invention. It is an aberration diagram of the projection optical system of the 14th example. It is an optical system block diagram of 15th Example of the projection optical system by this invention. It is various aberration diagrams of the projection optical system of the fifteenth example. It is an optical system block diagram of the 16th Example of the projection optical system by this invention. It is an aberration diagram of the projection optical system of the 16th example. It is an optical system block diagram of the 17th Example of the projection optical system by this invention. It is an aberration diagram of the projection optical system of the seventeenth example.

  Hereinafter, the present invention will be described with respect to specific numerical examples. The projection optical systems of the following first to fifteenth examples are composed of a first optical system (optical system name PG1 in each drawing) and a second optical system (optical system name PG2) in order from the enlargement side. The first optical system PG1 is composed of one mirror surface (surface number 001), and the second optical system PG2 is a first lens group having negative or positive refractive power as a whole in order from the magnification side. (Lens group name LG1) and a second lens group (lens group name LG2) having a positive refractive power as a whole, and the first lens group LG1 has a negative refractive power as a whole in order from the magnification side. 1a lens group (lens group name LG1a) and 1b lens group (lens group name LG1b) having positive refractive power as a whole, and the second lens group LG2 is generally negative or positive in order from the magnification side. Second with refractive power The lens group (lens group name LG2a) and a 2b lens group (lens group name LG2b) having a positive refractive power as a whole, the first a lens group LG1a has a meniscus shape that is convex from the magnifying side to the magnifying side. Negative lens (the lens name is L11, the surface number of the enlargement side is 101, the surface number of the reduction side is 102), the negative lens (the lens name is L12, the surface number of the enlargement side is 103, and the surface number of the reduction side is 104), a positive lens (the lens name is L13, the surface number of the enlargement side is 105, and the surface number of the reduction side is 106) and a negative lens (the lens name is L14, the surface number of the enlargement side is 107, the reduction side) The first b lens group LG1b is composed of one or two positive lenses (in the case of a single lens, the lens name is L16, the surface number of the enlarged side surface). 111, the surface number of the reduction side is 112, and in the case of two lenses, the lens name of the enlargement side lens is L15, and the surface number of the enlargement side is 109 (however, in the case of a joint surface with the lens on the enlargement side) The surface number is 108), the surface number of the reduction side surface is 110, the lens name of the reduction side lens is L16, the surface number of the enlargement side surface is 111, and the surface number of the reduction side surface is 112). The second-a lens group LG2a includes, in order from the enlargement side, a negative lens (the lens name is L21, the enlargement side surface number is 201, and the reduction side surface number is 202), one or two positive lenses (one sheet In this case, the lens name is L22, the surface number of the enlargement side is 202 for joining, the surface number of the reduction side is 205, and in the case of two lenses, the lens name of the enlargement side lens is L22, and the surface number of the enlargement side is for joining 202, reduction The surface number of the side surface is 203, the lens name of the reduction side lens is L23, the surface number of the enlargement side surface is 204, the surface number of the reduction side surface is 205, and a negative lens (the lens name is L24, and the surface number of the enlargement side surface is The second b lens group LG2b is composed of a single positive lens (lens name is L26, the surface number of the enlarged side surface is 209, and is reduced). Or a positive or negative lens on the enlargement side (L25 is the lens name, 207 is the enlargement side surface number, and 208 is the reduction side number). , The positive lens (the lens name is L26, the surface number of the enlarged side is 209 (however, the surface number is 208 when the surface is a cemented surface with the lens on the enlarged side), and the surface number of the reduced side is 210. ) A large air gap is provided on the reduction side of the second lens group LG2, and then the third lens group (lens group name LG3) is connected to the positive lens (lens name) in relation to the illumination optical system. L31, the surface number of the enlarged side surface is 301, and the surface number of the reduced side surface is 302). Subsequently, there is a slight gap between the reduced side of the third lens group LG3 and the light valve surface. A cover glass CG (C01 for the enlarged side surface and C02 for the reduced side surface), which is a component of a light valve such as a DMD, which is arranged with a proper air gap, is arranged.

[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 is the focal length of the entire projection optical system, F _no is the F number, 2ω is the total angle of view (unit: degree) of the projection optical system, and d _p is the 001 plane and the enlarged side of the plane Represents the design reference distance to the projection surface, h _I1 represents the radius of the effective diameter on the 101 surface, and h _im represents the radius of the image circle. 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.

[Example 10]
Table 10 shows numerical examples of the tenth embodiment of the projection optical system according to the present invention. FIG. 19 is a lens configuration diagram, and FIG. 20 is a diagram showing various aberrations.

[Example 11]
Table 11 shows numerical examples of the eleventh embodiment of the projection optical system according to the present invention. FIG. 21 is a lens configuration diagram, and FIG. 22 is a diagram showing various aberrations.

[Example 12]
Table 12 shows numerical examples of the twelfth embodiment of the projection optical system according to the present invention. FIG. 23 is a lens configuration diagram, and FIG.

[Example 13]
Table 13 shows numerical examples of the thirteenth embodiment of the projection optical system according to the present invention. FIG. 25 is a diagram showing the lens configuration, and FIG. 26 is a diagram showing various aberrations thereof.

[Example 14]
Table 14 shows numerical examples of the fourteenth embodiment of the projection optical system according to the present invention. FIG. 27 is a lens configuration diagram, and FIG. 28 is a diagram showing various aberrations.

[Example 15]
Numerical examples are shown in Table 15 for the fifteenth embodiment of the projection optical system of the present invention. FIG. 29 is a diagram showing the lens configuration, and FIG. 30 is a diagram showing various aberrations thereof.

[Example 16]
Table 16 shows numerical examples of the sixteenth embodiment of the projection optical system according to the present invention. FIG. 31 is a diagram showing the lens configuration, and FIG. 32 is a diagram showing various aberrations thereof.

[Example 17]
Table 17 shows numerical examples of the seventeenth embodiment of the projection optical system according to the present invention. FIG. 33 is a diagram showing the lens configuration, and FIG. 34 is a diagram showing various aberrations.

Next, Table 18 collectively shows values corresponding to the conditional expressions (1) to (17) regarding the first to seventeenth embodiments.

  As is clear from Table 18, the numerical values related to the first to seventeenth examples satisfy the conditional expressions (1) to (17) and the aberrations in the respective examples. 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.
According to a first aspect of the present invention, in the projection optical system, the first optical system and the second optical system are configured in order from the enlargement side, and the first optical system is configured by a single mirror surface, The second optical system includes a first lens group having a negative or positive refractive power as a whole and a second lens group having a positive refractive power as a whole in order from the magnification side, and constitutes the first optical system. The mirror surface has a rotationally symmetric aspherical shape, and the lens constituting the second optical system is composed only of a spherical lens, and the rotationally symmetric axis of the mirror surface and the light of the second optical system. It coincides with the axis, satisfies the following conditional expression (1) regarding the power of the first lens group, and the size of the effective diameter of the most enlarged surface of the first lens group is the following conditional expression (2) And light from the mirror surface to the most magnified surface of the first lens group. The following conditional expression (3) is satisfied with respect to the upper distance, and the following conditional expression (4) is satisfied with respect to the distance on the optical axis from the most magnification side surface of the first lens group to the image plane, and the second lens The following conditional expression (5) is satisfied with respect to the distance on the optical axis from the most reduction side surface of the group to the image surface.
(1) −0.22 ≦ f / f _I ≦ 0.25
(2) 0.97 ≦ h _I1 / h _im ≦ 1.20
(3) ML / f ≦ 10
(4) GL / f ≦ 15
(5) 3.0 ≦ b / f
However,
f: Composite focal length of the entire optical system (focusing on the projection surface at the design reference distance)
f _I : _Combined focal length h _{I1 of} the first lens group: Radius of effective diameter of the most magnified side surface of the first lens group h _im : Radius of the image circle ML: From the mirror surface to the most magnified side surface of the first lens group Distance GL on the optical axis of the first lens group: Distance on the optical axis from the most magnified surface of the first lens group to the image plane (however, the third lens group and the cover glass portion of the parallel plane are air-converted distances)
b : Distance on the optical axis from the most reduced surface of the second lens group to the image plane (however, the third lens group and the cover glass portion of the parallel plane are air-converted distances)

According to a second aspect of the present invention, in the projection optical system according to the first aspect, the first lens group has a first a lens group having a negative refractive power as a whole in order from the magnification side and a positive refractive power as a whole. The first 1a lens group has a negative meniscus lens having a negative refractive power (hereinafter referred to as a negative lens), a negative lens, and a positive refractive power in order from the magnifying side to the magnifying side. A lens (hereinafter, positive lens) and a negative lens are arranged, and the 1b lens group is constituted by arranging one or two positive lenses, and the power of the 1a lens group and the 1b lens group The following conditional expression (6) is satisfied.
(6) −4.50 ≦ f _Ia / f _Ib ≦ −0.32
However,
f _Ia : Composite focal length of the 1a lens group f _Ib : Composite focal length of the 1b lens group

According to a third aspect of the present invention, in the projection optical system according to the first aspect, the following conditional expression (7) is satisfied with respect to the power of the lens arranged closest to the enlargement side in the first lens group, and the reduction of the lens: The following conditional expression (8) is satisfied with respect to the characteristics of the shape of the side surface, the following conditional expression (9) is satisfied with respect to the power of the lens arranged closest to the reduction side, and the following conditional expression ( 10) is satisfied.
(7) −0.62 ≦ f / f _I1 ≦ −0.25
(8) 0.75 ≦ f / r _I2 ≦ 0.96
(9) 0.23 ≦ f / f _I6 ≦ 0.42
(10) | r _I12 / r _I11 | ≦ 3.50 (because the absolute value is r _I12 ≦ 0)
However,
f _I1 : Focal length r _{I2 of} the lens arranged closest to the enlargement side in the first lens group: Curvature radius f _I6 of the reduction side surface of the lens arranged closest to the enlargement side in the first lens group: Most in the first lens group Focal length r _{I11 of} the lens arranged on the reduction side: radius of curvature r _I12 of the enlargement side surface of the lens arranged closest to the reduction side in the first lens group: reduction of the lens arranged closest to the reduction side in the first lens group Side radius of curvature

According to a fourth aspect of the present invention, in the projection optical system according to the first aspect, the second lens group includes a second a lens group having negative or positive refractive power as a whole in order from the magnification side and positive refraction as a whole. 2b lens group having power, the 2a lens group is configured by arranging a negative lens, one or two positive lenses and a negative lens in order from the magnification side, and the second b lens group is A single positive lens is arranged, or a positive lens is arranged after a positive or negative lens is arranged on the magnifying side, and the power of the second a lens group and the second b lens group is described below. Conditional expression (11) is satisfied.
(11) −7.36 ≦ f _IIa / f _IIb ≦ 11.1
However,
f _IIa : Composite focal length of the 2a lens group f _IIb : Composite focal length of the 2b lens group

According to a fifth aspect of the present invention, in the projection optical system according to the first aspect, the following conditional expression (12) is satisfied with respect to the power of the second lens group, and the second lens group is disposed on the most enlarged side. The following conditional expression (13) is satisfied with respect to the shape of the lens.
(12) 0.20 ≦ f / f _II ≦ 0.35
(13) −0.15 ≦ f / r _II1 ≦ 0.40
However,
f _II : Composite focal length of the second lens group r _II1 : Radius of curvature of the enlargement side surface of the lens arranged closest to the enlargement side in the second lens group

According to a sixth aspect of the present invention, in the projection optical system according to the fourth aspect, the following conditional expression (14) is satisfied with respect to the shape of the lens arranged closest to the reduction side in the second a lens group, and the second a lens: The following conditional expression (15) is satisfied with respect to the dispersion characteristics of the positive lens constituting the group and the negative lens constituting the 2a lens group, and the lens disposed closest to the reduction side in the 2a lens group and the lens It is characterized in that the following conditional expression (16) is satisfied with respect to the characteristics of the refractive index of the lens disposed adjacent to the enlargement side.
(14) −1.00 ≦ f / r _II5 ≦ −0.75
(15) 15 ≦ v _IIaP −v _{IIaN
(16) 0.26 ≦ n II4 -n} II4S ≦ 0.40
However,
r _II5: the 2a lens curvature of the magnifying side surface of the lens which is disposed closest to the reduction side in the group radius v _IIAP: average Abbe number of the positive lens constituting the first 2a lens group v _IIaN: configuring the first 2a lens group mean value of Abbe numbers of the negative lens n _II4: the 2a lens refractive index at the d-line of the lens element which is disposed closest to the reduction side in the group n _II4S: d of the lens element which is disposed second from the reduction side at the 2a lens group Refractive index for the line

A seventh aspect of the present invention is the projection optical system according to the first aspect, wherein the following conditional expression (17) is satisfied with respect to the shape of the lens arranged closest to the reduction side in the second lens group. And
(17) −0.65 ≦ f / r _II10 ≦ _−0.30
However,
r _II10 : radius of curvature of the reduction side surface of the lens arranged closest to the reduction side in the second lens group

  According to an eighth aspect of the present invention, in the projection display device, the projection optical system according to at least one of the first to seventh aspects is mounted.

  According to a ninth aspect of the present invention, in the projection display device according to the eighth aspect, the aspherical symmetry axis of the mirror surface of the first optical system and the optical axis of the second optical system are in use. It is characterized by not matching except.

Claims (9)

A first optical system and a second optical system are formed in order from the enlargement side, the first optical system is constituted by a single mirror surface, and the second optical system is negative or negative in order from the enlargement side. The first lens group having a positive refractive power and the second lens group having a positive refractive power as a whole, the mirror surface constituting the first optical system has a rotationally symmetric aspheric shape, The lens constituting the second optical system is composed of only a spherical lens, the rotationally symmetric axis of the mirror surface coincides with the optical axis of the second optical system, and the first lens group The following conditional expression (1) is satisfied with respect to the power of the first lens group, the effective diameter of the most enlargement side surface of the first lens group satisfies the following conditional expression (2), and the mirror surface and the first lens group The following conditional expression (3) is satisfied with respect to the distance on the optical axis to the most enlarged surface of The following conditional expression (4) is satisfied regarding the distance on the optical axis from the most magnified side surface of the first lens group to the image plane, and the optical axis from the most reduced side surface of the second lens group to the image plane is satisfied. A projection optical system satisfying the following conditional expression (5) with respect to the upper distance:
(1) −0.22 ≦ f / f _I ≦ 0.25
(2) 0.97 ≦ h _I1 / h _im ≦ 1.20
(3) ML / f ≦ 10
(4) GL / f ≦ 15
(5) 3.0 ≦ b / f
However,
f: Composite focal length of the entire optical system (focusing on the projection surface at the design reference distance)
f _I : _Combined focal length h _{I1 of} the first lens group: Radius of effective diameter of the most magnified side surface of the first lens group h _im : Radius of the image circle ML: From the mirror surface to the most magnified side surface of the first lens group Distance GL on the optical axis of the first lens group: Distance on the optical axis from the most magnified surface of the first lens group to the image plane (however, the third lens group and the cover glass portion of the parallel plane are air-converted distances)
b : Distance on the optical axis from the most reduced surface of the second lens group to the image plane (however, the third lens group and the cover glass portion of the parallel plane are air-converted distances) The first lens group includes a 1a lens group having a negative refractive power as a whole and a 1b lens group having a positive refractive power as a whole in order from the magnification side. A lens having a negative meniscus shape (hereinafter referred to as a negative lens), a negative lens, a lens having a positive refractive power (hereinafter referred to as a positive lens), and a negative lens, which are sequentially convex on the enlargement side, are arranged. The lens group is configured by arranging one or two positive lenses, and satisfies the following conditional expression (6) with respect to the power of the first a lens group and the first b lens group. The projection optical system according to 1.
(6) −4.50 ≦ f _Ia / f _Ib ≦ −0.32
However,
f _Ia : Composite focal length of the 1a lens group f _Ib : Composite focal length of the 1b lens group In the first lens group, the following conditional expression (7) is satisfied with respect to the power of the lens arranged closest to the enlargement side, and the following conditional expression (8) is satisfied with respect to the characteristics of the shape of the reduction side surface of the lens. 2. The projection according to claim 1, wherein the following conditional expression (9) is satisfied with respect to the power of the lens disposed on the lens, and further, the following conditional expression (10) is satisfied with respect to the lens shape characteristics of the lens. Optical system.
(7) −0.62 ≦ f / f _I1 ≦ −0.25
(8) 0.75 ≦ f / r _I2 ≦ 0.96
(9) 0.23 ≦ f / f _I6 ≦ 0.42
(10) | r _I12 / r _I11 | ≦ 3.50 (because the absolute value is r _I12 ≦ 0)
However,
f _I1 : Focal length r _{I2 of} the lens arranged closest to the enlargement side in the first lens group: Curvature radius f _I6 of the reduction side surface of the lens arranged closest to the enlargement side in the first lens group: Most in the first lens group Focal length r _{I11 of} the lens arranged on the reduction side: radius of curvature r _I12 of the enlargement side surface of the lens arranged closest to the reduction side in the first lens group: reduction of the lens arranged closest to the reduction side in the first lens group Side radius of curvature The second lens group includes a 2a lens group having a negative or positive refractive power as a whole and a second b lens group having a positive refractive power as a whole in order from the magnification side. A negative lens, one or two positive lenses, and a negative lens are arranged in order from the side, and the second b lens group is configured by arranging one positive lens or is positive on the enlargement side. Alternatively, a negative lens is disposed and then a positive lens is disposed, and the following conditional expression (11) is satisfied with respect to the power of the second a lens group and the second b lens group: The projection optical system described.
(11) −7.36 ≦ f _IIa / f _IIb ≦ 11.1
However,
f _IIa : Composite focal length of the 2a lens group f _IIb : Composite focal length of the 2b lens group The following conditional expression (12) is satisfied with respect to the power of the second lens group, and the following conditional expression (13) is satisfied with respect to the shape of the lens disposed on the most enlarged side in the second lens group. The projection optical system according to claim 1.
(12) 0.20 ≦ f / f _II ≦ 0.35
(13) −0.15 ≦ f / r _II1 ≦ 0.40
However,
f _II : Composite focal length of the second lens group r _II1 : Radius of curvature of the enlargement side surface of the lens arranged closest to the enlargement side in the second lens group The following conditional expression (14) is satisfied with respect to the shape of the lens arranged closest to the reduction side in the 2a lens group, and dispersion of the positive lens that constitutes the 2a lens group and the negative lens that constitutes the 2a lens group Regarding the characteristics, the following conditional expression (15) is satisfied, and regarding the characteristics of the refractive index of the lens arranged closest to the reduction side and the lens arranged adjacent to the enlargement side of the lens in the 2a lens group, The projection optical system according to claim 4, wherein 16) is satisfied.
(14) −1.00 ≦ f / r _II5 ≦ −0.75
(15) 15 ≦ v _IIaP −v _{IIaN
(16) 0.26 ≦ n II4 -n} II4S ≦ 0.40
However,
r _II5: the 2a lens curvature of the magnifying side surface of the lens which is disposed closest to the reduction side in the group radius v _IIAP: average Abbe number of the positive lens constituting the first 2a lens group v _IIaN: configuring the first 2a lens group mean value of Abbe numbers of the negative lens n _II4: the 2a lens refractive index at the d-line of the lens element which is disposed closest to the reduction side in the group n _II4S: d of the lens element which is disposed second from the reduction side at the 2a lens group Refractive index for the line The projection optical system according to claim 1, wherein the following conditional expression (17) is satisfied with respect to a shape of a lens arranged closest to the reduction side in the second lens group.
(17) −0.65 ≦ f / r _II10 ≦ _−0.30
However,
r _II10 : radius of curvature of the reduction side surface of the lens arranged closest to the reduction side in the second lens group   A projection display device, comprising the projection optical system according to claim 1.   9. The projection type display device according to claim 8, wherein an axis of symmetry of the aspherical surface of the mirror surface of the first optical system and an optical axis of the second optical system do not coincide except when in use.

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