JP5009726B2 - Projection lens and projection display device using the same - Google Patents

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 in particular, a so-called front type projection display apparatus. And a projection display apparatus using the same.

  In recent years, projection display devices using light valves such as liquid crystal display devices and DMD display devices have become widespread, and in particular, three light valves are used so as to correspond to RGB three primary color illumination lights. Therefore, it is widely used that each of these illumination lights is modulated, light modulated by individual light valves is combined by a prism or the like, and an image is displayed on a screen via a projection lens.

  The above-mentioned light valves are rapidly becoming smaller and higher definition, and coupled with the spread of personal computers, the demand for presentations using such projection display devices is also increasing. Therefore, there has been an increasing demand for higher performance, brighter and more compact projection display devices.

  In addition, in a projection display device that synthesizes and projects each modulated light from the three light valves by a color synthesis optical system, a long back focus for arranging a prism that performs color synthesis as a characteristic of the projection lens Is required. Furthermore, since the spectral characteristics change depending on the angle of incident light in the color synthesizing optical system, the projection lens needs to have a characteristic that the entrance pupil viewed from the reduction side is located far away, that is, telecentricity. Aberration correction corresponding to the resolution of the device is also required.

  As a projection lens satisfying such requirements, for example, a projection lens described in Patent Document 1 below is configured by seven elements in three groups, which can increase the back focus and make the reduction side telecentric. What makes it possible is known.

  However, the projection lens described in Patent Document 1 below is a rear type, and a space for inserting a light reflecting element is provided in the projection lens for the purpose of bending the optical path at a predetermined position in the apparatus cabinet. Since the basic design philosophy is different from the projection lens used in the front type projection display device, such as a configuration in which focus adjustment is not taken into consideration, this is the projection for the front type projection display device. It cannot be used as a reference when designing lenses.

  On the other hand, as a projection lens for a front type projection display device, like the projection lens described in the following Patent Document 2, it is composed of seven elements in three groups, and the first lens group on the most magnified side is an aspheric lens. Those configured to have are known.

Japanese Patent No. 3466002 JP 2000-305012 A

  However, the lens described in Patent Document 2 has a too long lens total length and is not considered to meet the demand for compactness. Further, the F number is 2.73 or 3.00, and it is not a lens that can project a bright image.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a compact projection lens that is bright and has high projection performance, and a projection display device using the projection lens.

The projection lens according to the present invention is
A first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power are disposed in order from the magnification side.
The first lens group consists of two lenses, a first lens composed of a negative lens in order from the magnification side, and a second lens composed of a negative aspheric lens whose both surfaces are aspheric surfaces. It consists only of a third lens consisting of a positive lens,
Furthermore, the following conditional expressions (1) , (2), and (4) are satisfied.
1.4 <DG23 / DG12 <5.0 (1)
0.3 <DG12 / f <1.3 (2)
1.5 <f2 / f <3.0 (4)
here,
DG12: distance between the first lens group and the second lens group DG23: distance between the second lens group and the third lens group
f: Focal length of the entire system
f2: Focal length of the second lens group
Although the numerical value of DG23 / DG12 in the conditional expression (1) changes with the movement of the second lens group, the projection lens according to the present invention has the conditional expression (1 over the entire movement range of the second lens group). ) Is satisfied.

Moreover, it is preferable that the following conditional expression (3) is satisfied.
2.8 <f ₂₃ /f<5.5 (3)
here,
f ₂₃ : combined focal length of the second lens group and the third lens group f: focal length of the entire system

  Further, it is preferable to perform focus adjustment by moving the second lens group in the optical axis direction.

  The third lens group is preferably composed of four lenses.

  The first lens is preferably made of a glass material, and the second lens is preferably made of a plastic material.

  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 optically modulated by the light valve and projected onto a screen by the projection lens.

  According to the projection lens of the present invention, it is possible to obtain a compact configuration that is bright and has high projection performance by including the above configuration.

  In particular, by configuring so as to satisfy the conditional expression (1), it is possible to improve the correction of off-axis aberrations (mainly distortion aberration, curvature of field), and the first lens group and the second lens group. By reducing the distance between the lens groups, the overall length of the lens system can be shortened and the optical system can be made compact.

  Further, the projection display device of the present invention is bright and has high projection performance by using the projection lens of the present invention, and the entire device can be made compact.

  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 refractive power, a second lens group G ₂ having a positive refractive power, a third lens having a positive refractive power will be disposed between the group G _3, the reduction side is substantially telecentric. The first lens group G ₁ has a first lens L ₁ composed of a negative lens in order from the magnification side, both surfaces consist of two and the second lens L ₂ formed of a negative aspherical lens is aspherical, the second lens group _{G 2} is composed of only the third lens _{L 3,} which is a positive lens.

The third lens group _{G 3} is composed of four lenses _L 4 ~L ₇ as shown in FIG. 1, for example.

Further, an aperture stop 3 (a mask can be provided at another position) is disposed between the second lens group G ₂ and the third lens group G _3, and further, the second lens group G _2. If the interval between the third lens group G _3, are the largest adjacent lens distance (maximum air interval).

  In the projection lens of FIG. 1, a light beam that is incident from the right side of the paper and is given image information on the image display surface 1 of the light valve passes through a glass block (including various filters such as a low-pass filter and an infrared cut filter) 2. The light enters the projection lens, and is enlarged and projected by the projection lens in the left direction on the paper surface. 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.

  Specifically, the three primary color lights can be synthesized by disposing color synthesis means (glass block) such as a cross dichroic prism at the position of the glass block 2.

Further, it is preferable that the second lens group G ₂ is moved in the optical axis direction to perform focus adjustment.

By thus the second lens group G ₂ and the focus moving unit, when performing focus adjustment, the overall length of the lens system becomes possible to constant. Note that the third lens L ₃ constituting the second lens group G ₂ is formed of a spherical lens, and further, the third lens L ₃ is given power, which is more advantageous as a focus movement group. Can be.

The first lens L ₁ constituting the first lens group G ₁ is made of a glass material, while the second lens L ₂ constituting the first lens group G ₁ is made of a plastic material. Preferably it is.

In this way, since the first lens L ₁ which is exposed to the housing surface is formed by a glass material, less risk of being damaged, can be cleaned dirt easily first lens L ₁ of the surface.

In addition, the projection lens of the present embodiment satisfies the following conditional expressions (1) to (4).
1.4 <D _G23 / D _G12 <5.0 (1)
0.3 <D _G12 /f<1.3 (2)
2.8 <f ₂₃ /f<5.5 (3)
1.5 <f ₂ /f<3.0 (4)
here,
D _G12 : distance between the first lens group G ₁ and the second lens group G ₂ D _G23 : distance between the second lens group G ₂ and the third lens group G ₃ f: focal length of the entire system f ₂₃ : second synthesis of the lens group _{G 2} and _the third lens group _{G 3} a focal length f _2: focal length of the second lens group _{G 2}

  With the configuration described above, the projection lens of the present embodiment has a long back focus, is bright, has high projection performance, and can be made compact.

  These operational effects can be obtained by satisfying at least (1) among the above conditional expressions (1) to (4). Hereinafter, the significance of each of the conditional expressions (1) to (4) will be described. Will be described.

First, the conditional expression (1), it exceeds the upper limit, the first lens group G ₁ and only distance between the second lens group G ₂ becomes narrow when you try to ensure the angle of view required first lens group G ₁ Therefore, it becomes difficult to correct off-axis aberrations (mainly distortion aberration, curvature of field).

Meanwhile, below the lower limit, with the lens diameter of the second lens group G ₂ becomes large, the overall length of the lens system becomes too long, it is difficult to reduce the size of the optical system.

In addition, by replacing the conditional expression (1) with the following conditional expression (1 ′), it is possible to improve the correction of off-axis aberrations and to make the system more compact. It can be promoted more.
1.6 <D _G23 / D _G12 <4.0 (1 ′)

  Next, if the upper limit of conditional expression (2) is exceeded, the overall system will be enlarged, and the back focus will be too long, making it difficult to reduce the size of the lens system on the reduction side.

  On the other hand, below the lower limit, the back focus becomes too short, making it difficult to insert a color synthesis optical system or to correct aberrations of a bright lens.

It should be noted that by replacing the conditional expression (2) with the following conditional expression (2 ′), it is possible to further promote downsizing on the lens system reduction side, ensuring the back focus and brightening. Lens aberration correction can be made better.
0.5 <D _G12 /f<1.2 (2 ′)

  Next, in Conditional Expression (3), the balance of the entire system is lost both when the upper limit is exceeded and below the lower limit, so that an appropriate back focus is secured and various aberrations are corrected well. Difficult to do.

By replacing the conditional expression (3) with satisfying the following conditional expression (3 ′), it becomes easier to secure an appropriate back focus and correct various aberrations. can do.
3.0 <f ₂₃ /f<5.2 (3 ′)

Further, in the conditional expression (4), the When the value exceeds the upper limit, the amount of movement of the second lens group G ₂ is too large at the time of focus adjustment, the overall length of the lens is too long. Meanwhile, below the lower limit, the second lens group G ₂ of the power becomes too strong to correct aberration becomes difficult.

Instead of the conditional expression (4), by configuring so as to satisfy the following conditional expression (4 '), making the movement amount of the second lens group G ₂ at the time of focus adjustment with smaller ones Thus, the overall lens length can be further shortened, and aberration correction can be further improved.
1.8 <f ₂ /f<2.8 (4 ′)

Further, the projection lens of this embodiment, the second lens L ₂ of the second lens group G _2, and a bi-aspherical lens, thereby, while reducing the number of lenses can be improved resolution.

  In the above-described patent document 2, anomalous dispersion glass is used as the glass material of the lens in the third lens group in order to reduce the chromatic aberration of magnification. Invite up. In this embodiment, since various aberrations are made good without using such anomalous dispersion glass, it is possible to reduce the manufacturing cost.

  Next, an embodiment of a projection display device according to the present invention will be described. FIG. 7 is a configuration diagram showing an example of a main part (illumination optical system 10) of the projection display apparatus according to an embodiment of the present invention.

  As shown in FIG. 7, 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 composition, 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). Then, the light is modulated and projected onto the screen by the projection lens.

  Since this projection display apparatus uses the projection lens according to the present invention, it is possible to obtain a large high-resolution screen in which chromatic aberration is well corrected.

  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>
As shown in FIG. 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, a second lens group G ₂ having a positive refractive power, positive It will have and a third lens group G ₃ having a refractive power, the reduction side is substantially telecentric. The first lens group G ₁ includes, in order from the magnification side, a first lens L ₁ composed of a negative meniscus lens having a concave surface facing the reduction side, and a second lens L ₂ composed of a negative aspheric lens whose both surfaces are aspheric surfaces. consists of two, a second lens group G ₂ is composed of only the third lens L ₃ which is a biconvex lens. The third lens group _{G 3} includes the fourth lens _{L 4} is a biconvex lens, a fifth lens _{L 5} which is a biconcave lens, a sixth lens _{L 6} and the seventh lens _{L 7} having a biconvex lens, from is configured, the fourth lens L ₄ and the fifth lens L ₅ are bonded to each other.

Aspherical shape of the surfaces of the second lens L ₂ is defined by the aspheric equation shown below.

  The projection lens according to Example 1 is configured to satisfy the conditional expressions (1) to (4) (and the conditional expressions (1 ′) to (4 ′)).

  FIG. 1 also shows an image display surface 1, a glass block 2, and an aperture stop 3 of the light valve.

The radius of curvature R of each lens surface of the projection lens according to Example 1 (normalized with a focal length of 1.00: the same in the following examples), the center thickness of each lens, and the air space between each lens (hereinafter referred to as the following) D (referred to as “axis upper surface distance”) D (normalized with a focal length of 1.00: the same in the following examples), the refractive index N _e of each lens at the e-line, and the Abbe number ν at the e-line of each lens The value of _e 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 middle part of Table 1 shows the values of the constants K, A _{3 to} A ₁₆ corresponding to the respective aspheric surfaces, and the lower part of Table 1 shows that the magnification on the enlargement side is 125.3 and 310.4. in each case, (the distance between the second lens group G ₂ and the third lens group G ₃₎ variable interval 1 (the first lens group G ₁ and the second spacing between the lens group G ₂₎ and the variable interval 2 is shown ing.

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

<Example 2>
The configuration of the projection lens according to Example 2 is as shown in FIG. 2, and in order from the magnification side, the first lens group G ₁ having negative refractive power and the second lens group G ₂ having positive refractive power. When made with and a third lens group G ₃ having a positive refractive power, the reduction side is substantially telecentric, but in that is similar to the projection lens according to example 1, mainly, the The fourth lens L ₄ and the fifth lens L ₅ constituting the three lens group G ₃ are different from each other in that they are constituted by a single lens. Incidentally, in terms of the lens configurations of the first lens group G ₁ and second lens group G _2, it is substantially the same as the projection lens according to Example 1.

The values of the curvature radius R of each lens surface of the projection lens according to Example 2, the axial top surface distance D of each lens, the refractive index N _e of each lens at the e line and the Abbe number ν _e of each lens at the e line are 2 is shown in the upper part. The middle part of Table 2 shows the values of the constants K, A _{3 to} A ₁₆ corresponding to each aspheric surface, and the lower part of Table 2 shows the magnifications of 125.3 and 310.8, respectively. when, variable interval 1 (the distance between the first lens group G ₁ and the second lens group G ₂₎ and the variable interval 2 is shown (second distance between the lens group G ₂ and the third lens group G ₃₎ is Yes.

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

<Example 3>
The configuration of the projection lens according to Example 3 is as shown in FIG. 3. 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. When made with and a third lens group G ₃ having a positive refractive power, the reduction side is substantially telecentric, but in that is similar to the projection lens according to example 1, mainly, the The third lens group G _{3 is different} in that the fourth lens L ₄ is a biconcave lens while the fifth lens L ₅ is a biconvex lens. Incidentally, in terms of the lens configurations of the first lens group G ₁ and second lens group G _2, it is substantially the same as the projection lens according to Example 1.

The values of the radius of curvature R of each lens surface of the projection lens according to Example 3, the axial top surface distance D of each lens, the refractive index N _e of each lens at the e-line and the Abbe number ν _e of each lens at the e-line are 3 is shown in the upper part. The middle part of Table 3 shows the values of the constants K, A _{3 to} A ₁₆ corresponding to each aspheric surface, and the lower part of Table 3 shows the magnifications of 125.3 and 310.9. when, variable interval 1 (the distance between the first lens group G ₁ and the second lens group G ₂₎ and the variable interval 2 is shown (second distance between the lens group G ₂ and the third lens group G ₃₎ is Yes.

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

  4 to 6 are aberration diagrams showing various aberrations (spherical aberration, astigmatism, distortion, and lateral chromatic aberration) of the projection lenses according to Examples 1 to 3. FIG. In these aberration diagrams, ω represents a half field angle, spherical aberration diagrams show aberration curves of e-line, F-line, and C-line, and lateral chromatic aberration aberration diagrams show F-line (dotted line: Aberration curves of C-line (two-dot chain line: same below) are shown. As shown in FIGS. 4 to 6, the projection lenses according to Examples 1 to 3 have a F number of 1.70 and a bright projection lens in which each aberration including distortion and lateral chromatic aberration is corrected well.

  The projection lens according to the present invention is not limited to the above-described embodiment, and various modifications can be made. For example, the radius of curvature 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.

The figure showing the structure of the projection lens which concerns on Example 1 of this invention. 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 principal part of the projection type display apparatus of this invention

Explanation of symbols

1 image display surface 2 glass block 3 aperture stop 10 illumination optics 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, _{G 3} lenses group L ₁ ~L ₇ lens R ₁ to R of curvature such as ₁₆ lens surface radius D ₁ to D ₁₆ lens spacing (lens thickness)
X optical axis

Claims (6)

A first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power are disposed in order from the magnification side.
The first lens group includes, in order from the magnification side, two lenses, a first lens made of a negative lens and a second lens made of a negative aspheric lens whose both surfaces are aspheric surfaces. , Consisting only of a third lens consisting of a positive lens,
Furthermore, the projection lens characterized by satisfying the following conditional expressions (1) , (2), and (4) .
1.4 <DG23 / DG12 <5.0 (1)
0.3 <DG12 / f <1.3 (2)
1.5 <f2 / f <3.0 (4)
here,
DG12: distance between the first lens group and the second lens group DG23: distance between the second lens group and the third lens group
f: Focal length of the entire system
f2: Focal length of the second lens group The projection lens according to claim 1, wherein the following conditional expression (3) is satisfied.
2.8 <f23 / f <5.5 (3)
here,
f23: combined focal length of the second lens group and the third lens group f: focal length of the entire system The projection lens according to claim 1, wherein focus adjustment is performed by moving the second lens group in an optical axis direction. The projection lens according to any one of claims 1 to 3, wherein the third lens group includes four lenses. The first lens is made of a glass material,
The projection lens according to claim 1, wherein the second lens is made of a plastic material. 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 any one of claims 1 to 5 , 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.

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