JP2008309988A - Projection lens and projection display apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a wide-angle projection lens having high projection performance while securing a long back focus, and also, capable of using an inexpensive light reflection mirror as an optical path bending component, and whose manufacturing cost is reduced. <P>SOLUTION: The projection lens is constituted by arraying a first lens group G<SB>1</SB>having negative refractive power and a second lens group G<SB>2</SB>having positive refractive power in order from an enlargement side, and the projection lens is nearly telecentric on a reduction side. The first lens group G<SB>1</SB>comprises at least five lenses in order from the enlargement side, that is, an aspheric lens L<SB>1</SB>, a negative meniscus lens L<SB>2</SB>with a convex surface facing the enlargement side, a negative lens L<SB>3</SB>with a concave surface facing the reduction side, a biconcave lens L<SB>4</SB>and a positive lens L<SB>5</SB>with a convex surface facing the enlargement side. Further, the projection lens satisfies three conditional expressions (1) to (3). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a projection lens for enlarging and projecting display information from a light valve such as a transmissive or reflective liquid crystal display element or DMD (digital micromirror device), and more particularly to a rear projection display device. The present invention relates to a suitable projection lens and a projection display device using the same.

  Conventionally, as a projection display device, a projection lens is disposed on the same side as a viewer with respect to a screen, and a front-type device that forms an image of light emitted from the projection lens on a reflective screen, a projection lens, There is known a rear-type device that is arranged so that a viewer sandwiches a screen and images light emitted from a projection lens on a transmissive screen.

  Among these, in a rear projection display device, for example, a rear projection TV, the light source to the screen are housed in a cabinet, and image information is projected from the projection lens disposed on the back toward the screen disposed on the front of the cabinet. A configuration for projecting light carrying the light is well known.

  In recent years, various projection lenses have been proposed for application to such cabinet-type projection display devices.

  Projection lenses are required to be able to project large sizes at short projection distances, and in particular for rear projection projectors, there is a strong demand for thinner devices. There is a demand for a projection lens that can achieve this.

  In addition, in an optical system using a plurality of light valves for colorization, etc., in order to arrange a synthesis unit that synthesizes light beams from each light valve, to separate illumination light and projection light, and further to heat A large back focus is required to alleviate problems.

  In response to such demands, lenses described in the following Patent Documents 1 to 4 are known as lenses having a relatively long back focus and an angle of view on the enlargement side exceeding 100 degrees.

JP 2003-015033 A JP 2004-326079 A USP 7123426 USP 7126767

  By the way, in the projection display device, particularly the rear projection type device, it is considered useful to insert a light reflecting element into the projection lens for the purpose of bending the optical path at a predetermined position in order to make the device compact. It is done.

  However, the above Patent Documents 3 and 4 do not have the concept of inserting a light reflecting element into the optical path. In addition, in the above-mentioned Patent Documents 1 and 2, as a light reflecting element to be inserted into the optical path, a prism with a long optical path length is used instead of a light reflecting mirror in order to compensate for a narrow space, which increases the manufacturing cost. There was a problem.

  The present invention has been made in view of such circumstances, and has a wide angle and high projection performance while ensuring a long back focus, and has a light reflection for bending an optical path in order to achieve a configuration suitable for downsizing. An object of the present invention is to provide a low-cost projection lens that can use an inexpensive light reflecting mirror as an element and correct various aberrations well, and a projection display device using such a projection lens.

The projection lens according to the present invention is
A projection lens in which a first lens group having a negative refractive power and a second lens group having a positive refractive power are arranged in order from the magnification side,
The distance between the first lens group and the second lens group is set to the maximum air distance in the projection lens, and the reduction side is configured to be substantially telecentric,
The first lens group includes, in order from the magnification side, a first lens composed of an aspheric lens, a second lens composed of a negative meniscus lens having a convex surface facing the magnification side, and a negative lens facing the concave surface toward the reduction side. 3 lenses, a fourth lens composed of a biconcave lens, and a fifth lens composed of a positive lens having a convex surface facing the enlargement side, and are composed of at least five lenses.
The following conditional expressions (1) to (3) are satisfied.
5.0 <Bf / f (1)
105 degrees <2ω (2)
20 <| f1 | / f (3)
here,
f: Total system focal length Bf: Air-equivalent back focus 2ω: Zoom-in angle of view f1: Focal length of the first lens

  In addition, it is preferable that the fourth lens and the fifth lens are cemented with each other.

Further, it is preferable that the fifth lens satisfies the following conditional expressions (4) and (5).
2.5 <f5 / f <25.0 (4)
45> νd5 (5)
here,
f5: focal length of the fifth lens νd5: Abbe number of the fifth lens

Moreover, it is preferable that the following conditional expressions (6) and (7) are satisfied.
6.0 <d / f (6)
7.0 <F2 / f (7)
here,
d: the maximum air gap (the largest of the adjacent lens gaps)
F2: focal length of the second lens group

  Further, it is preferable that a reflection mirror is inserted between adjacent lenses to bend the optical path.

  In addition, it is preferable to correct the image plane curve accompanying the change in the projection distance by moving the first lens in the optical axis direction.

  Further, it is preferable that the image plane position correction accompanying the change in the projection distance is performed by changing an air interval between the first lens group and the second lens group.

  Furthermore, a projection display device according to the present invention includes a light source, a light valve, an illumination optical unit that guides a light beam from the light source to the light valve, and the projection lens according to the present invention. The light beam is modulated by the light valve and projected onto the screen by the projection lens.

  Since the projection lens of the present invention has the above-described configuration, it can have a wide angle and high projection performance while ensuring a long back focus. In addition, when a light reflecting element for bending an optical path is used in order to achieve a configuration suitable for downsizing, the light reflecting element can be configured with an inexpensive light reflecting mirror, and the manufacturing cost can be reduced.

  In addition, since it is configured to satisfy the conditional expression (3), the power of the first lens having a large diameter and an aspheric surface located closest to the enlargement side of the first lens group is regulated to be small. As this first lens, it is possible to use an inexpensive material that is easily affected by a temperature change, for example, a lens made of plastic, so that the manufacturing cost can be reduced.

  Further, the projection display device of the present invention uses the projection lens of the present invention, so that it is possible to widen the angle while ensuring a long back focus and to reduce the manufacturing cost.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a projection lens according to the present invention, and is a lens configuration diagram of Example 1 to be described later. This lens will be described below as a representative of this embodiment. In the figure, X represents the optical axis.

Projection lens of this embodiment, in order from the magnification side, a first lens group G ₁ having a negative refracting power and is the second lens group G ₂ and the sequence having a positive refractive power, a substantially telecentric reduction side It is said that. Further, above the first lens group G _1, in the most reduction side, two cemented lens of two lenses are bonded L _4, L ₅ are arranged. Further, the second lens group _{G 2,} an aperture stop 3 (the possible features a mask), two three-element cemented lens _{L 8 ~L 10, L 12 ~L} 14 is arranged, the first between the lens group G ₁ and the second lens group G _2, are the largest adjacent lens distance (maximum air interval).

The three-piece cemented lenses L _{8 to} L ₁₀ are obtained by sandwiching the ninth lens L ₉ made of a negative lens between the eighth lens L ₈ and the tenth lens L _{10 made} of a positive lens, and the three-piece cemented lens L _{12 to} L ₁₄ sandwich the thirteenth lens L ₁₃ made of a negative lens between the twelfth lens L ₁₂ and the fourteenth lens L _{14 made} of a positive lens.

  In the projection lens of FIG. 1, a light beam incident from the right side of the paper and given image information on the image display surface 1 of the light valve is incident on the projection lens via the cover glass 2, and the left side of the paper surface by the projection lens. Is enlarged and projected. Although only one image display surface 1 is shown in FIG. 1 for ease of viewing, in the projection display device, a light beam from a light source is separated into three primary color lights by a color separation optical system. Some light valves are provided with three light valves so that a full-color image can be displayed. By arranging color synthesizing means (glass block) such as a cross dichroic prism at the position of the cover glass 2, the three primary color lights can be synthesized.

Incidentally, FIG. 2, between the first lens group G ₁ and second lens group G ₂ of the projection lens 1, and the plate-like light reflecting mirror 4 as an optical path deflecting means for deflecting the optical path is disposed The structure of the case is shown. Incidentally, in the first lens group G ₁ and the second lens group G _2, when a large adjacent lens distance (large air gap) is provided, the light-reflecting mirror 4 of the plate-like and disposed in the gap May be.

Moreover, the following conditional expressions (1) to (7) are satisfied.
5.0 <Bf / f (1)
105 degrees <2ω (2)
20 <| f1 | / f (3)
2.5 <f5 / f <25.0 (4)
45> νd5 (5)
6.0 <d / f (6)
7.0 <F2 / f (7)
here,
f: Total system focal length Bf: Air-converted back focus (the distance from the final lens surface on the reduction side to the image display surface, and the cover glass or glass block interposed between them is air-converted)
2ω: Magnification-side angle of view f1: Focal length of the first lens f5: Focal length of the fifth lens νd5: Abbe number of the fifth lens d: The maximum air spacing (the largest of the adjacent lens spacings) )
F2: focal length of the second lens group

  With the configuration as described above, the projection lens of the present embodiment can have high projection performance at a wide angle while ensuring a long back focus. Moreover, an inexpensive light reflecting mirror can be employed as the light reflecting element for bending the optical path. Furthermore, chromatic aberration can be corrected satisfactorily by satisfying various aberrations, particularly conditional expressions (4) and (5). Since each of the above-mentioned constituent elements is set so as to be related to each other, these operational effects can be obtained by satisfying at least all of (1) to (3) among the above conditional expressions. The significance of each of the conditional expressions (1) to (7) will be described.

  Conditional expression (1) indicates the lower limit of the value of the back focus Bf with respect to the focal length f of the entire system. Below this lower limit, the required back focus cannot be secured.

Note that, by replacing the conditional expression (1) with the following conditional expression (1 ′), the necessary back focus can be ensured more reliably.
6.5 <Bf / f (1 ′)

  Conditional expression (2) represents the lower limit of the angle of view on the enlargement side. If the lower limit is not reached, the light reflecting mirror for bending the optical path cannot be inserted or the lens back becomes too short.

Condition (3) is, relative to the total focal length, prescribes the lower limit of the value of the ratio of the absolute value of the first lens focal length of L _1. When equal to or less than the lower limit value, only the first lens L ₁ of the power becomes strong, it becomes difficult to a plastic lens, the manufacturing cost is increased. Further, by using an aspheric surface at a position away from the aperture stop 3, fluctuations such as field curvature and distortion can be reduced.

Condition (4) is provided to define with respect to the focal length f5 of the first lens group positive lens G _1, the range of the ratio of the values of the focal length f of the entire system. If out of this range, chromatic aberration correction becomes difficult.

Condition (5) is obtained by defining the lower limit of the Abbe number νd5 positive lens of the first lens group G _1. If the lower limit is not reached, chromatic aberration correction becomes difficult.

  Conditional expression (6) defines the lower limit of the ratio of the focal length f of the entire system to the maximum air gap d. When the lower limit is not reached, it becomes impossible to insert a light reflecting mirror for bending the optical path between the lenses, or the lens back becomes too short.

The conditional expression (7), to the focal length F2 of the second lens group G _2, a definition of the lower limit of the ratio of the values of the focal length f of the entire system. If the lower limit is not reached, the light reflecting mirror for bending the optical path cannot be inserted between the lenses, or the lens back becomes too short.

In the projection lens of the present embodiment, the two-lens cemented lenses L ₄ and L ₅ are disposed in the first lens group G ₁ , and the two three-lens cemented lenses L ₈ to L ₅ are disposed in the second lens group G _2. By arranging L ₁₀ and L _{12 to} L ₁₄ , it is possible to make the entire system compact while satisfactorily correcting chromatic aberration (particularly high-order chromatic aberration). In particular, two pairs of positive during the second lens group _{G 2,} negative, by providing a positive cemented triplet _{L 8 ~L 10, L 12 ~L} 14, is possible to satisfactorily reduce the secondary chromatic aberration it can.

Further, the projection lens of this embodiment, between the first lens group G ₁ and the second lens group G _2, i.e. in the maximum air gap, the expansion of the lens group disposed on the reduction side than the air gap The side focal position is configured to exist.

Further, the projection lens of this embodiment, the first lens group G ₁ and in the second lens group G _2, respectively and to arrange at least one aspherical surface, thereby, while reducing the number of lenses Resolution can be improved.

Further, the projection lens of the present embodiment is configured so that the most magnification side lens and any lens in the second lens group G ₂ in the first lens group G ₁ is an aspherical lens, the correction of the field curvature due to the projection distance change, and the most magnification side lens in the first lens group G ₁ as carried out by moving in the optical axis direction. Furthermore, the image plane position correcting due to the change of the projection distance, and to perform by varying the air gap between the first lens group G ₁ and the second lens group G _2.

  Next, an embodiment of a projection display device according to the present invention will be described. FIG. 8 is a longitudinal sectional view of a projection display device according to an embodiment of the present invention, and FIG. 9 is a configuration diagram showing an example of the illumination optical system 10 shown in FIG.

  The projection display device shown in FIG. 8 is a rear projection display device that particularly exhibits the above-described effects of the projection lens, and guides the light source, the light valve, and the light flux from the light source to the light valve. An illumination optical unit (both included in the illustrated illumination optical system 10) and the projection lens are provided in the cabinet 8, and a light beam from a light source is optically modulated by a light valve to carry a light beam carrying image information. The projection lens and the rear mirror 6 are configured to project onto the rear surface of the screen 7 disposed at a predetermined distance. The viewer views the image enlarged and projected on the screen 7 from the front side (left side of the paper) of the screen 7.

  As shown in FIG. 9, the illumination optical system 10 includes transmissive liquid crystal panels 11a to 11c as light valves, dichroic mirrors 12 and 13 for color separation, a cross dichroic prism 14 for color synthesis, and a condenser. Lenses 16a to 16c and total reflection mirrors 18a to 18c are provided. Although the illustration of the front stage of the dichroic mirror 12 is omitted, the white light from the light source passes through the illumination optical unit and the liquid crystal panels 11a to 11c respectively correspond to the three color light beams (G light, B light, and R light). And is optically modulated and projected onto the screen 7 by the projection lens shown in FIG.

Since this projection type display apparatus uses the projection lens according to the present invention, it is possible to obtain a large screen with high resolution in which chromatic aberration is well corrected. Further, by disposing the mirror 4 for deflecting the optical path between the first lens group G ₁ of the projection lens and the second lens group G _2, which is configured to bend the optical path acute, low profile It is possible to make it thinner and thinner. Further, since the mirror 4 is used as an element for deflecting the optical path, it is advantageous in terms of cost compared to the case of deflecting light using a prism. Instead of the prism capable of shortening the physical path length, it became possible to use a plate-shaped light reflecting mirror 4, between the first lens group G ₁ and the second lens group G ₂ This is because the spatial distance or the distance between the lenses in each of the lens groups G ₁ and G ₂ can be greatly increased.

  Specific examples of the projection lens according to the present invention will be described below. In addition, in each Example, the same code | symbol is attached | subjected about the member which makes mutually the same effect.

<Example 1>
1, the projection lens according to Example 1, in order from the magnification side, a first lens group G ₁ having a negative refractive power, positive second lens group G ₂ and the sequence having a refractive power As a result, the reduction side is substantially telecentric. Incidentally, FIG. 2, between the first lens group G ₁ and second lens group G ₂ of the projection lens 1, configuration in which a light reflecting mirror 4 as an optical path deflecting means for deflecting the optical path is disposed Is shown.

The first lens group G ₁ includes, in order from the magnification side, a first lens L _{1 made of} an aspheric lens having a small refractive power, and a second lens L ₂ and a third lens made of a negative meniscus lens having a concave surface facing the reduction side. and L _3, the fourth lens L ₄ and the fifth lens L ₅ 2 cemented lens formed by cementing a consisting of a positive meniscus lens having a convex surface facing the magnification side is formed by array of a biconcave lens.

On the other hand, the second lens group G ₂ includes a sixth lens L ₆ made of a biconvex lens, the aperture stop 3, a seventh lens L ₇ of a negative meniscus lens having a convex surface directed toward the reduction side, a biconcave lens the 9 lens and the eighth lens L ₈ and 3 cemented lens formed by interposing the tenth lens L ₁₀ and L ₉ is a positive lens, an eleventh lens L ₁₁ made of a small aspherical lens having refractive power, a biconcave lens a cemented triplet consisting sandwiching twelfth lens _{L 12} and a fourteenth lens _{L 14} made a thirteenth lens _{L 13} of a positive lens, and a fifteenth lens _{L 15} which is a biconvex lens are arrayed.

The shape of each aspherical surface is defined by the following aspherical surface formula. In the first lens L ₁ and the eleventh lens L ₁₁ having an aspheric surface, an effect can be obtained even if either one of the surfaces is an aspheric surface, but a lens in which both surfaces are aspherical surfaces. It is more preferable that

  Although the projection lens according to Example 1 is configured to satisfy the conditional expressions (1) to (7), the lower limit value of the conditional expression (1) is set to a more preferable numerical value. Further, the above-described conditional expression (1 ′) is satisfied.

  FIG. 1 shows an image display surface 1 and a cover glass 2 of the light valve.

Projection lens according to Example 1, between the first lens group G ₁ and second lens group G _2, and a mirror 4 for deflecting the optical path have disposed possible air gap, shown in FIG. 2 Thus, the mirror 4 can be arranged. The projection lens is configured to be telecentric on the reduction side.

The radius of curvature R of each lens surface of the projection lens according to Example 1 (standardized with a focal length of 1; the same in the following examples), the center thickness of each lens, and the air space between each lens (hereinafter “axis”) D) (referred to as “upper surface distance”) D (normalized with a focal length of 1; the same in the following examples), the refractive index N _d of each lens at the d-line and the Abbe number ν _d of each lens at the d-line. It is shown in the upper part of Table 1. In Table 1 and the following table, the surface number numbers indicate the order from the enlargement side, and the surface marked with * on the right side of the surface number is an aspheric surface. In Example 1 and Examples 2 and 3 below, the curvature radius R of these aspheric surfaces is shown as the value of the curvature radius R on the optical axis X in each table, but in the corresponding lens configuration diagram. In order to make the drawing easy to see, there are some leader lines that are not necessarily drawn from the intersection with the optical axis X.

The lower part of Table 1 shows the values of the constants K, A _{3 to} A ₁₂ corresponding to the aspheric surfaces. The lower part of Table 1 shows the projection distance (enlarged side conjugate position to lens first surface). Are shown).

  In Example 1, values corresponding to the conditional expressions (1) to (7) are as shown in Table 4 described later, and all of the conditional expressions (1) to (7) are satisfied (conditional expression (1 ') Is also satisfied).

<Example 2>
The configuration of the projection lens according to Example 2 is as shown in FIG. 3, and in order from the magnification side, the first lens group G ₁ having a negative refractive power and the second lens group G ₂ having a positive refractive power. DOO is being arranged, the reduction side is substantially telecentric, in terms that it is similar to the projection lens according to example 1, during the first lens group G ₁ and the second lens group G _2, The difference is that a mask 3a and an aperture stop 3b are provided. Also, in terms of the lens configurations of the first lens group G _1, it is similar to the projection lens according to Example 1.

On the other hand, the second lens group G ₂ includes, in order from the magnification side, a sixth lens L ₆ of a positive meniscus lens having a concave surface directed toward the reduction side, consisting of a seventh lens L ₇ and a positive lens formed of a negative lens 8 and two cemented lens formed by cementing a lens L _8, a reduction-side surface of the eighth lens L ₈ proximity, a ninth lens L _9, which opposing comprising, consisting small aspheric lens refractive power, both and 3 cemented lens formed by interposing the tenth lens _{L 10} and the twelfth lens _{L 12} made the eleventh lens _{L 11} formed from concave positive lens, a thirteenth lens _{L 13} which is a biconvex lens are arrayed.

The values of the curvature radius R of each lens surface of the projection lens according to Example 2, the axial distance D between each lens, the refractive index N _d of each lens at the d-line and the Abbe number ν _d at the d-line of each lens are 2 is shown in the upper part. The lower part of Table 2 shows the values of the constants K, A _{3 to} A ₁₂ corresponding to the respective aspheric surfaces, and the lower part of Table 2 shows the projection distance (enlarged side conjugate position to lens first surface). Are shown).

The values of the curvature radius R of each lens surface of the projection lens according to Example 2, the axial distance D between each lens, the refractive index N _d of each lens at the d-line and the Abbe number ν _d at the d-line of each lens are 2 is shown in the upper part. The lower part of Table 2 shows the values of the constants K, A _{3 to} A ₁₂ corresponding to the respective aspheric surfaces, and the lower part of Table 2 shows the projection distance (enlarged side conjugate position to lens first surface). Are shown).

  In Example 2, values corresponding to the conditional expressions (1) to (7) are as shown in Table 4 described later, and all of the conditional expressions (1) to (7) are satisfied (conditional expression (1 ′)). Is also satisfied).

<Example 3>
The configuration of the projection lens according to Example 3 is as shown in FIG. 4. In order from the enlargement side, the first lens group G ₁ having a negative refractive power and the second lens group G ₂ having a positive refractive power. DOO is being arranged, the reduction side is substantially telecentric, in terms that it is similar to the projection lens according to example 1, during the first lens group G ₁ and the second lens group G _2, The difference is that a mask 3a and an aperture stop 3b are provided.

The first lens group G ₁ includes, in order from the magnification side, a first lens L _{1 made of} an aspheric lens having a small refractive power, and a second lens L ₂ and a third lens made of a negative meniscus lens having a concave surface facing the reduction side. and L _3, the fourth lens L ₄ and the fifth lens L ₅ 2 cemented lens formed by cementing a of a positive meniscus lens having a convex surface facing the magnification side which is a biconcave lens, a sixth lens L having a biconvex lens ₆ is arranged.

On the other hand, the second lens group G ₂ includes, eighth lens becomes seventh lens L ₇ made of small meniscus lens having a power having a convex surface facing the reduction side, a ninth lens L _9, which is a biconcave lens of a positive lens L ₈ and a cemented triplet consisting sandwiching the tenth lens L _10, the eleventh lens L ₁₁ made of a small aspherical lens having refractive power, second lens becomes a thirteenth lens L ₁₃ which is a biconcave lens of a positive lens L and 3 cemented lens formed by interposing at ₁₂ and 14 the lens _{L 14,} a fifteenth lens _{L 15} which is a biconvex lens are arrayed.

The values of the radius of curvature R of each lens surface of the projection lens according to Example 3, the axial distance D between each lens, the refractive index N _d of each lens at the d-line, and the Abbe number ν _d of each lens at the d-line are 3 is shown in the upper part. The lower part of Table 3 shows the values of the constants K and A _{3 to} A ₁₂ corresponding to the respective aspheric surfaces, and the lower part of Table 3 shows the projection distance (enlarged side conjugate position to lens first surface). Are shown).

  In Example 3, values corresponding to the conditional expressions (1) to (7) are as shown in Table 4 to be described later, and all of the conditional expressions (1) to (7) are satisfied (conditional expression (1 ′)). Is also satisfied).

  FIGS. 5 to 7 are aberration diagrams illustrating various aberrations (spherical aberration, astigmatism, distortion, and lateral chromatic aberration) of the projection lenses according to Examples 1 to 3. FIGS. In these aberration diagrams, ω represents a half angle of view, the aberration diagram of spherical aberration shows aberration curves of d-line, F-line and C-line, and the aberration diagram of magnification chromatic aberration shows F-line and C-line with respect to d-line. The aberration curve is shown. As shown in FIGS. 5 to 7, in the projection lenses according to Examples 1 to 3, each aberration including distortion and lateral chromatic aberration was corrected well, and the half angle of view was 58.3 degrees (conditional expression (2 in Table 4)). ), F number 2.40, and a wide-angle and bright projection lens. In addition, a sufficient back focus (see each numerical value corresponding to the conditional expression (1)), and an inter-lens air space sufficient to insert the light reflecting mirror (respective numerical values corresponding to the conditional expression (6)). Reference) is secured.

  The projection lens according to the present invention is not limited to the above-described embodiments, and various modifications can be made. For example, the curvature radius R and the lens interval (or lens thickness) D of each lens can be changed as appropriate. Is possible.

  Further, the projection display device of the present invention is not limited to the above-described configuration, and various device configurations including the projection lens of the present invention are possible. As the light valve, for example, a transmissive or reflective liquid crystal display element, or a micro mirror element in which a large number of micro mirrors capable of changing the inclination are formed on a substantially flat surface (for example, manufactured by Texas Instruments). Digital micromirror device) can be used. Also, as the illumination optical system, an appropriate configuration corresponding to the type of light valve can be adopted.

FIG. 3 is a diagram illustrating the configuration of a projection lens according to Example 1 of the invention. 1 is a diagram illustrating a configuration in the case where a mirror for deflecting an optical path is provided in the projection lens according to FIG. The figure showing the structure of the projection lens which concerns on Example 2 of this invention. The figure showing the structure of the projection lens which concerns on Example 3 of this invention. Various aberration diagrams of the projection lens according to Example 1 Various aberration diagrams of the projection lens according to Example 2 Various aberration diagrams of the projection lens according to Example 3 The figure showing schematic structure of the projection type display apparatus of this invention The figure showing the composition of the illumination optical system of a projection type display device

Explanation of symbols

1 Image display surface 2 Cover glass (glass block)
3a mask 3,3b aperture stop 4 mirror 6 back mirror 7 screen 8 cabinet 10 an illumination optical system 11a~11c transmissive liquid crystal panel 12, 13 dichroic mirror 14 cross dichroic prism 16a~16c condenser lens 18a~18c total reflection mirror G _1, G ₂
Lens group L ₁ ~L ₁₅ lens R ₁ to R of curvature such as ₂₉ lens surface radius D ₁ to D ₂₈ lens spacing (lens thickness)
X optical axis

Claims (8)

A projection lens in which a first lens group having a negative refractive power and a second lens group having a positive refractive power are arranged in order from the magnification side,
The distance between the first lens group and the second lens group is set to the maximum air distance in the projection lens, and the reduction side is configured to be substantially telecentric,
The first lens group includes, in order from the magnification side, a first lens composed of an aspheric lens, a second lens composed of a negative meniscus lens having a convex surface facing the magnification side, and a negative lens facing the concave surface toward the reduction side. 3 lenses, a fourth lens composed of a biconcave lens, and a fifth lens composed of a positive lens having a convex surface facing the enlargement side, and are composed of at least five lenses.
A projection lens satisfying the following conditional expressions (1) to (3):
5.0 <Bf / f (1)
105 degrees <2ω (2)
20 <| f1 | / f (3)
here,
f: Total system focal length Bf: Air-equivalent back focus 2ω: Zoom-in angle of view f1: Focal length of the first lens   The projection lens according to claim 1, wherein the fourth lens and the fifth lens are cemented with each other. The projection lens according to claim 1, wherein the fifth lens satisfies the following conditional expressions (4) and (5).
here,
2.5 <f5 / f <25.0 (4)
45> νd5 (5)
here,
f5: focal length of the fifth lens νd5: Abbe number of the fifth lens The projection lens according to claim 1, wherein the following conditional expressions (6) and (7) are satisfied.
6.0 <d / f (6)
7.0 <F2 / f (7)
here,
d: the maximum air gap (the largest of the adjacent lens gaps)
F2: focal length of the second lens group   The projection lens according to claim 1, wherein a reflection mirror is inserted between adjacent lenses to bend the optical path.   6. The projection lens according to claim 1, wherein the correction of an image plane curve accompanying a change in projection distance is performed by moving the first lens in the optical axis direction.   The image plane position correction associated with a change in the projection distance is performed by changing an air space between the first lens group and the second lens group. Projection lens. A light source, a light valve, an illumination optical unit that guides a light beam from the light source to the light valve, and a projection lens according to claim 1, wherein the light beam from the light source is converted into the light A projection display device, wherein light is modulated by a bulb and projected onto a screen by the projection lens.

Images