JPH1172700A - Projection optical system and projector using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a projection optical system and a projector using it where the projected picture of an original picture displayed on a liquid crystal panel is projected on a screen surface by having high optical performance. SOLUTION: This system is constituted of a first group L1 having more negative lenses than positive lenses and a second group L2 having more positive lenses than negative lenses in order from a first conjugate point having a longer distance, and an off-axis principal ray crosses an optical axis between the first group L1 and the second group L2, and each component is set so as to be telecentric on the side of a second conjugate point. Then, the second group L2 possesses a negative meniscus lens whose convex surface is faced to the side of the second conjugate point and the positive lens whose both lens surfaces are formed into the convex surfaces in order from the side of the second conjugate point.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection optical system and a projection apparatus using the same, and enlarges and projects an original projected image displayed on an image modulation device such as a liquid crystal panel (liquid crystal display device) on a screen surface. It is suitable as a projection device such as a liquid crystal projector capable of appropriately setting the lens configuration of the projection optical system at the time and projecting with high optical performance while maintaining good telecentricity.

[0002]

2. Description of the Related Art Conventionally, various projection optical systems have been proposed in which a projection image such as a film image, a liquid crystal light valve, and a CRT is projected onto a predetermined surface, for example, a screen surface, and a projection apparatus using the same. Have been.

Various types of projection optical systems have been used. However, a projection optical system using a CRT, a liquid crystal panel or the like as a projection image original has a bright F-number of, for example, 1.5 or less. In order to secure a back focus of a predetermined length, a retro-focus type lens which is preceded by a lens unit having a negative refractive power is often used.

As a projection optical system for a CRT, for example, Japanese Patent Application Laid-Open No. 4-31910 proposes a projection lens for a three-tube CRT projection TV.

[0005]

Generally, in a projection optical system (projection lens) used for a projection apparatus using a CRT, a liquid crystal panel, or the like as a projection image original, when the distance (object distance) from the projection optical system to the screen changes. The negative lens is arranged near the image plane (CRT plane) in order to correct the curvature of field that occurs in the optical system. For this reason, the telecentricity is poor, and application to a projection optical system for a liquid crystal display device in which the contrast greatly changes due to a change in the incident angle of light has been difficult.

In particular, since a liquid crystal panel has a strong angle characteristic, it is necessary to reduce the incident angle of an off-axis light beam incident on the display surface in order to obtain a good projected image. For example, it is necessary to make the off-axis high speed incident on the display surface substantially perpendicularly. Further, many projection optical systems tend to have a small peripheral light amount, for example, the peripheral light amount is reduced to about 35%, and there is a disadvantage that the peripheral portion of the projected image is dark.

When a liquid crystal panel is used as a projection image original image in a projection apparatus, it is necessary to obtain a projection image in which a projection optical system used for the liquid crystal panel is bright, has a large amount of peripheral light, and can be constituted by an image side telecentric system. It is becoming.

However, if it is attempted to construct a projection optical system that satisfies each of the above conditions and reduces the occurrence of various aberrations and obtains good optical performance, the entire lens system becomes complicated.

For example, when an image side telecentric system is used, the number of lenses increases, and the entire lens system becomes complicated and large.

According to the present invention, a predetermined brightness (about an F number of about 1.5) can be easily obtained by appropriately setting the lens configuration, and the image side is excellent in that various telecentric aberrations are well corrected. It is an object of the present invention to provide a projection optical system that can provide optical performance and is suitable for, for example, a liquid crystal projector and a projection apparatus using the same.

[0011]

The projection optical system according to the present invention comprises: (1-1) a first lens unit having more negative lenses than a positive lens in order from the first conjugate point having a longer distance; The second lens group includes more positive lenses, and the off-axis principal ray is divided into the first lens group and the second lens group.
Each element is set so as to intersect with the group on the optical axis and to be telecentric on the second conjugate point side, and the second group has a meniscus having a convex surface facing the second conjugate point in order from the second conjugate point side. It is characterized in that it has a negative lens having a convex shape and a positive lens whose both lens surfaces are convex.

(1-2) A first group having more negative lenses than a positive lens and a second group having more positive lenses than negative lenses in order from the first conjugate point having a longer distance. The respective elements are set so that the principal ray intersects the first group and the second group along the optical axis and is telecentric on the second conjugate point side.
The group and the second group each have at least one plastic lens.

(1-3) A first group having more negative lenses than positive lenses and a second group having more positive lenses than negative lenses in order from the first conjugate point having a longer distance. The respective elements are set so that the principal ray intersects the first group and the second group along the optical axis and is telecentric on the second conjugate point side.
The group and the second group each have at least one aspheric lens.

(1-4) A first group having more negative lenses than positive lenses and a second group having more positive lenses than negative lenses in order from the first conjugate point having a longer distance. The respective elements are set so that the principal ray intersects the first and second groups along the optical axis, and is telecentric on the second conjugate point side. It is characterized in that floating is performed by moving some or all of the lenses of the group.

[0015]

1 to 4 are lens sectional views of numerical examples 1 to 4 of a projection optical system (projection lens) according to the present invention. 5 and 6 are aberration diagrams at a magnification of 1/27 and 1/44 (d2 = 11.48) of Numerical Example 1 of the projection optical system according to the present invention, and FIGS. 7 and 8 are projection optical systems according to the present invention. 9 and 10 are aberration diagrams at a magnification of 1/27 and 1/44 (d2 = 13.42) of Numerical Example 2 of the system. FIGS. 9 and 10 show a magnification of 1/27 of Numerical Example 3 of the projection optical system of the present invention. , 1/44 (d8 = 8.33)
FIGS. 11 and 12 show magnifications of 1/27 and 1/44 (d6 = 9.10) of the numerical example 4 of the projection optical system according to the present invention.
It is an aberration figure at the time of 74).

First, the structural features of the projection optical system of the present invention will be described with reference to FIGS. L1 is a first unit, which is made up of a retrofocus type lens system. L2 is a second unit composed of a lens system having a positive refractive power. P is a glass block such as a cover glass of a liquid crystal panel. S
P is a stop, and CP is an intersection (stop position) where the off-axis principal ray intersects the optical axis La. SC denotes a screen, which is arranged on the side of the longer first conjugate point (hereinafter also referred to as “object side”). LC is a projection surface of a liquid crystal display element (liquid crystal panel) or the like, and is arranged on the second conjugate point side (hereinafter, also referred to as “image plane side”) with a shorter distance.

On the image plane side, for example, in the case of color liquid crystal projection, a liquid crystal display element which is an image to be projected, a light source,
Each element such as a filter is arranged, thereby constituting a projection device.

The projection optical system of this embodiment has an F number of 1.
With a large aperture ratio of 5, the projection angle of view is as wide as 81 degrees, and the image plane side is made of a telecentric system.

The projection lens according to the present invention is used to obtain a large projection image at a short projection distance (distance from the projection optical system to the screen S (object distance)) and to maintain good telecentricity (telecentricity). The first conjugate point side of the intersection (aperture) CP of the principal ray and the off-axis principal ray includes more negative lenses than the positive lens, and the second conjugate point side of the intersection CP has a more positive lens than a negative lens. It has a lens configuration that includes many. Therefore, when the off-axis light beam L2 is refracted by each lens, the number of prism components in the same direction increases.

For example, an off-axis light beam incident from above the first lens unit L1 from the first conjugate point side passes through a large number of lens portions corresponding to prism components having acute angles below. Because of this,
Many astigmatism and distortion occur. In order to correct various aberrations generated at this time, the second group is sequentially arranged from the second conjugate point side, and a meniscus-shaped negative lens G26 having a convex surface facing the second conjugate point side, and a positive lens having both lens surfaces convex. G2
5, the opposite aberration is generated.

Further, the lens surface of the second lens unit on the first conjugate point side of the positive lens G25 is made aspherical. Incident angle is increased. As described above, the two lenses G25 and G26 on the second conjugate point side of the second group allow the first lens G25 and G26 to move therefrom.
It corrects astigmatism, distortion, and the like generated by the lens disposed on the conjugate point side.

A negative meniscus lens G11 having a convex surface facing the first conjugate point is disposed on the first conjugate point side of the first lens unit. Then, the negative lens L11 is moved from the projection lens to the first
When the distance to the conjugate point (screen SC) (hereinafter, referred to as "object distance") changes, the entire lens system is extended to perform focusing, and for example, in FIGS. 1 and 2, the other lenses in the first unit L1 (G12-G15, G12-G
14) Floating is performed by moving relative to.

With this arrangement, it is possible to satisfactorily correct a variation in curvature of field caused by a large change in the height of the off-axis light beam from the optical axis in the lens on the first conjugate point side of the first lens unit L1 due to a change in the object distance. ing.

The floating of the present embodiment will be described in more detail. If the object distance becomes longer, the entire lens system approaches the second conjugate point, so that the light of the off-axis light flux on the lens surface of the first group on the first conjugate point side is obtained. The height from the axis is higher than when the object distance is short. Therefore, the curvature of field greatly varies.

Therefore, in the present embodiment, the entire lens system is extended and focused, and the negative lens G11 of the first group closest to the first conjugate point is connected to the negative lens G11 of the first group and other lenses in the first group. By using floating for moving in the direction of the optical axis so as to shorten the interval, a change in the height of the off-axis light flux of the negative lens G11 closest to the first conjugate point from the optical axis is reduced, and the field curvature is changed. Is kept small.

In the numerical examples 3 and 4 shown in FIGS. 3 and 4, floating is used in which the entire lens system is extended and focused in accordance with a change in the object distance, and the distance between the first unit L1 and the second unit L2 is changed. Thus, the fluctuation of the field curvature is corrected.

In this embodiment, the first lens unit has a negative lens G11 on the first conjugate point side and a positive lens G1 on the second conjugate point side.
5 so that the light flux between the first group and the second group is close to afocal. Thus, even if the distance between the first group and the second group slightly changes, the height of the on-axis light flux in the first group from the optical axis hardly changes, thereby reducing the variation in spherical aberration.

On the other hand, the height of the off-axis light beam from the optical axis in the first group changes greatly. At this time, by changing the distance between the first and second groups, the off-axis light in the first group is changed. The variation of the curvature of field is corrected by changing the place where the light beam passes.

As described above, the present embodiment employs the floating configuration in which a part of the projection lens is moved. That is,
The projection lens has a field curvature correction mechanism to correct variations in field curvature due to changes in object distance, and variations in optical performance due to manufacturing errors in plastic aspheric lenses manufactured by molding with a mold. doing.

Further, using a negative lens on the first conjugate point side of the first lens unit and an aspherical lens made of a plastic material in the second lens unit, astigmatism which largely occurs in the first lens unit of the retrofocus type, and The distortion is corrected.

In particular, the negative lens G on the first conjugate point side of the first lens unit
Numeral 11 denotes an aspherical lens made of a plastic material, and the positive lens G25 of the second group is an aspherical lens made of a plastic material to reduce the focus shift due to a change in the refractive index due to the temperature and humidity of the plastic.

For example, since the refractive index of a plastic lens such as PMMA decreases as the temperature rises, when the temperature rises, the focus position of the entire system moves in the direction of shortening the back focus by the negative lens G11 of the first group. Since the focus position of the entire system moves in the direction in which the back focus becomes longer by the two groups of positive lenses G25, the shift of the focus position as a whole is canceled out. The same effect can be obtained by using a plastic material for the first group positive lens and a plastic material for the second group negative lens.

In addition, plastic lenses can be manufactured at low cost by molding, and have the advantage of being lightweight. Further, the shape of the aspherical surface is a case where it is used on the first conjugate point side of the first group for correction of distortion, and when applied to a negative lens, the shape is such that negative power becomes weaker as the distance from the optical axis increases, When applied to a positive lens, it is preferable that the positive power increases as the distance from the optical axis increases.

When applied to the positive lens of the second group, the shape is such that the positive power decreases as the distance from the optical axis increases, and when applied to the negative lens, the shape where the negative power increases as the distance from the optical axis increases. preferable.

In the aspherical surface made of a plastic material included in the first and second groups, the declination when the most off-axis principal ray passes is set to 15 to reduce the sensitivity to the optical performance of the aspherical surface. It is preferable that the temperature be equal to or less than the temperature. In order to further reduce the sensitivity, it is preferable that the deviation angle of the off-axis chief ray on an aspherical surface made of a plastic material be 12 degrees or less.

As described above, by using the plastic lens at a position where the decentering of the most off-axis principal ray on the lens surface is small, the sensitivity on the plastic lens surface can be reduced and the aspherical lens made of a plastic material having low surface accuracy can be obtained. Even when used, high optical performance can be obtained.

In order to reduce the occurrence of various aberrations,
The first group includes at least two meniscus negative lenses each having a convex surface facing the object side in order from the first conjugate point side, and a positive lens having a convex surface having strong refractive power facing the first conjugate point side. I have.

The second group includes a meniscus-shaped positive lens having a convex surface facing the second conjugate point, a cemented lens in which a negative lens having both concave surfaces and a positive lens having both convex surfaces are joined, Two positive lenses having a convex lens surface and a meniscus negative lens having a convex surface facing the second conjugate point are provided. Of these, the meniscus negative lens in the first group favorably corrects distortion.

As described above, by specifying the lens configuration, spherical aberration, coma, axial and chromatic aberration of magnification, and the like are satisfactorily corrected.

In particular, as a lens configuration of the first group, in the numerical example 1 of FIG. 1, there are three meniscus negative lenses with the convex surface facing the first conjugate point side, negative lenses with both lens surfaces concave, and both lenses. The surface is composed of five positive lenses having a convex surface.

In the numerical examples 2 and 3 shown in FIGS. 2 and 3, a negative meniscus lens having a convex surface facing the first conjugate point is used.
First, both lenses are composed of four lenses, a negative lens having a concave surface and both lens surfaces having a positive lens having a convex surface.

In numerical embodiment 4 of FIG. 4, two negative meniscus lenses having convex surfaces facing the first conjugate point and three positive meniscus lenses having convex surfaces facing the first conjugate point are used. It consists of a lens.

Next, numerical examples of the present invention will be described. In the numerical examples, ri is the radius of curvature of the i-th lens surface in order from the object side, di is the i-th lens thickness and air gap in order from the object side, and ni and νi are the i-th lens in order from the object side. Are the refractive index and Abbe number of the glass. Table 1 shows the relationship between the above-mentioned conditional expressions and various numerical values in the numerical examples.
It is shown in FIG. The aspherical shape has an X axis in the optical axis direction, a Y axis in a direction perpendicular to the optical axis, R represents a paraxial radius of curvature, A, B, C, D, E,
When F and G are each aspheric coefficients

[0044]

(Equation 1) This is represented by “D-0X” means “× 10 ^−X ”.

[0045]

[Outside 1]

[0046]

[Outside 2]

[0047]

[Outside 3]

[0048]

[Outside 4]

[0049]

[Outside 5]

[0050]

According to the present invention, as described above, a predetermined brightness (about F number 1.5) can be easily obtained by appropriately setting the lens configuration, and various telecentric images can be obtained. For example, it is possible to achieve a projection optical system suitable for a liquid crystal projector and a projection apparatus using the same, which can provide good optical performance in which aberration is well corrected.

In particular, according to the present invention, a single-panel liquid crystal having a small number of lenses, a bright F-number of about 1.5, good telecentricity, a rich peripheral light quantity of 50 to 60%, and good optical performance. A projection optical system for a projector can be realized. Further, by appropriately using an aspherical lens made of a plastic material, a configuration in which the manufacturing cost is low and the focus shift due to temperature is small is realized. Further, deterioration of optical performance due to a projection distance or a manufacturing error can be corrected by moving a part of the lens, so that good optical performance can be maintained.

The projection optical system according to the present invention has a projection angle of view of 80.
Since it is wide enough, it is particularly suitable as a projection optical system for rear projection televisions.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lens according to a numerical example 1 of the present invention.

FIG. 2 is a sectional view of a lens according to a numerical example 2 of the present invention.

FIG. 3 is a sectional view of a lens according to a numerical example 3 of the present invention.

FIG. 4 is a sectional view of a lens according to a numerical example 4 of the present invention.

FIG. 5 is an aberration diagram (1/2 magnification) of Numerical Example 1 of the present invention;
7)

FIG. 6 is an aberration diagram (magnification １ ／) of Numerical Example 1 of the present invention;
4) d2 = 11.48

FIG. 7 is an aberration diagram (1/2 magnification) of Numerical Example 2 of the present invention.
7)

FIG. 8 is an aberration diagram (magnification 1/4) of Numerical Example 2 of the present invention.
4) d2 = 13.42

FIG. 9 is an aberration diagram (1/2 magnification) of Numerical Example 3 of the present invention.
7)

FIG. 10 is an aberration diagram of a numerical example 3 of the present invention (magnification: １ ／);
4) d8 = 8.33

FIG. 11 is an aberration diagram (1/2 magnification) of Numerical Example 4 of the present invention.
7)

FIG. 12 is an aberration diagram of a numerical example 4 of the present invention (magnification: １ ／);
4) d6 = 9.74

[Explanation of symbols]

 L1 First group L2 Second group SC screen LC liquid crystal panel SP stop CP Intersection S Sagittal image plane M Meridional image plane d d line c c line FF line

Claims (17)

[Claims] 1. A first group having more negative lenses than a positive lens and a second group having more positive lenses than a negative lens in order from a first conjugate point having a longer distance. The first
Each element is set so that the group and the second group intersect on the optical axis and are telecentric on the second conjugate point side, and the second group has a convex surface on the second conjugate point side in order from the second conjugate point side. A projection optical system comprising a meniscus-shaped negative lens directed toward and a positive lens whose both lens surfaces are convex. 2. A first group having more negative lenses than a positive lens and a second group having more positive lenses than a negative lens in order from the first conjugate point having a longer distance. The first
Each element is set so that the group and the second group intersect at the optical axis and are telecentric on the second conjugate point side. Each of the first and second groups has at least one plastic lens. A projection optical system. 3. A first group having more negative lenses than a positive lens and a second group having more positive lenses than a negative lens in order from the first conjugate point having a longer distance. The first
Each element is set so that the group and the second group intersect on the optical axis and are telecentric on the second conjugate point side. Each of the first and second groups has at least one aspheric lens. A projection optical system. 4. A first group having more negative lenses than positive lenses and a second group having more positive lenses than negative lenses in order from the first conjugate point having a longer distance. The first
Each element is set so that the group intersects with the second group on the optical axis, and is telecentric on the second conjugate point side. The entire system is moved to perform focusing, and some lenses of the first group are moved. Alternatively, a projection optical system wherein all lenses are moved to perform floating. 5. The projection optical system according to claim 1, wherein each of said first group and said second group has at least one aspheric lens. 6. The projection optical system according to claim 1, wherein each of the first group and the second group has at least one plastic lens. 7. The projection optical system according to claim 2, wherein the refractive powers of the plastic lenses provided in the first group and the second group have opposite signs. 8. The projection of claim 7, wherein the plastic lenses in the first group have a negative refractive power and the plastic lenses in the second group have a positive refractive power. Optical system. 9. The lens surface of the first group of plastic lenses and the lens surface of the second group of plastic lenses have a tilt angle of 15 degrees or less when the most off-axis ray passes. Item 6. The projection optical system according to Item 2, 6, 7, or 8. 10. The lens surface of the first group of aspherical lenses and the lens surface of the second group of aspherical lenses have an inclination angle of 15 degrees or less when the most off-axis ray passes. The projection optical system according to claim 3, 5, 6, 7, or 8. 11. The optical system according to claim 1, wherein focusing is performed by moving the entire system, and floating is performed by moving at least a part of the lenses of the first group. The projection optical system according to any one of the above. 12. A meniscus-shaped negative lens 11 having a convex surface facing the first conjugate point is disposed on the first conjugate point side of the first group, and the negative lens 11 is moved to perform floating. 12. The method according to claim 4, wherein
Projection optics. 13. The projection optical system according to claim 12, wherein when the object distance becomes longer, the negative lens 11 is moved toward the second conjugate point to perform floating. 14. The aspheric lens in the first group is a negative lens whose negative refractive power becomes weaker as the distance from the optical axis increases, or a positive lens whose positive refractive power increases as the distance from the optical axis increases. Wherein the aspheric lens in the second group is a positive lens having a shape in which the positive refractive power becomes weaker as the distance from the optical axis increases, or a negative lens having a shape in which the negative refractive power increases as the distance from the optical axis increases. Claim 3 or 5
Projection optics. 15. The projection optical system according to claim 4, wherein when the object distance becomes longer, the first lens unit is moved toward the first conjugate point to perform floating. 16. The first lens unit includes, in order from the first conjugate point side, a negative meniscus lens having a convex surface facing the first conjugate point side.
A positive lens having a convex surface facing the first conjugate point, and the second group is a cemented lens of a negative lens and a positive lens having a cemented lens surface convex toward the first conjugate point; And a positive lens.
6. The projection optical system according to claim 5. 17. A projection apparatus, wherein a projection image is projected onto a predetermined surface using the projection optical system according to claim 1. Description: