KR100232604B1 - Zoom lens for lcd projector - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal projector for projecting image information onto a large screen, and in particular, it is possible to realize a large screen size while freely changing the size of the projection screen, and to improve the assemblability by securing surrounding space. The present invention relates to a zoom lens for a liquid crystal projector.

The present invention is a zoom lens for a liquid crystal projector comprising a first lens group, a movable second lens group and a third lens group, and a fourth lens group to enlarge and project an image having a predetermined size appearing on an LCD panel on a screen. The first lens group has a negative refractive power as a whole so as to be of the retro focus type, and the negative lens has a negative (+), (-), (-), and (+) angles from the screen to facilitate peripheral aberration correction. Lenses are arranged; The second lens group has a positive refractive power as a whole, is moved linearly to vary the size of the projection screen, and three lenses are arranged in (+), (-), and (+); The third lens group has a negative refractive power as a whole, is moved non-linearly to correct an amount of image movement, and two lenses are arranged in (+) and (-); The fourth lens group has a positive refractive power as a whole and four lenses are arranged in (-), (+), (+), and (+) to form an image.

Description

Zoom Lens for Liquid Crystal Projectors

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal projector for projecting image information onto a large screen, and in particular, it is possible to realize a large screen size while freely changing the size of the projection screen, and to improve the assemblability by securing surrounding space. The present invention relates to a zoom lens for a liquid crystal projector.

In general, a liquid crystal projector includes an LCD panel 10 that forms an image as shown in FIG. 1, a light source 11 positioned behind the LCD panel 10, and light from the light source 11. A concave reflection mirror 12 that reflects light to pass through the panel 10 and a zoom lens 13 that adjusts the magnification of the light passing through the LCD panel 10 to project an image onto the screen 20 It consists of.

The liquid crystal projector configured as described above allows the light transmitted through the LCD panel 10 to be projected through the zoom lens 13 so that the image is projected on the screen 20.

Light generated by the light source 11 is reflected by the reflecting mirror 12 to pass through the LCD panel 10 in which an image is formed. In this case, the light rays reflected by the reflection mirror 12 are transmitted through the front surface of the LCD panel 10 as linear light. Light passing through the LCD panel 10 is projected toward the screen 20 after being adjusted at an appropriate magnification while passing through the zoom lens 13. Thus, the same image as the LCD panel 10 is projected onto the screen 20.

However, since the quality of the image projected on the screen 20 is almost determined by the zoom lens 13, the importance of the zoom lens 13 in the LCD projector does not need to be reconsidered. Therefore, the zoom lens for the LCD projector uses different combination methods according to its use, and the kinds thereof are innumerable. Nevertheless, it is true that today's zoom lenses have some form of construction.

The above-mentioned conventional zoom lens for a liquid crystal projector is composed of a plurality of lens group combinations as shown in FIG. 2, and includes a first lens group G ₁ fixed from a large screen and a second movable lens. Group G ₂ and third lens group G ₃ , and a fixed fourth lens group G ₄ .

The first lens group G ₁ is a focusing unit for focusing, and a concave first lens L ₁ and a convex second lens L ₂ are bonded to each other to form a positive (+) whole. Has refractive power

In addition, the second lens group G ₂ is a variator part that varies the size of the projection screen by changing the focal length while moving back and forth linearly, and the concave third lens L ₃ and the concave type. The fourth lens L ₄ and the convex fifth lens L _{5 have} a negative refractive power as a whole.

In addition, the third lens group G ₃ is a non-linear conpensing unit for compensating image movement due to the movement of the second lens group G _2. The sixth lens L ₆ is convex. And the seventh convex lens L ₇ has a positive refractive power as a whole.

Lastly, the fourth lens group G ₄ is a concave type having a large back focal length so as to secure a space for arranging the color combining optical system as a master part for forming an image at the final image position. It consists of an eight lens L ₈ and a convex ninth lens L ₉ .

The zoom lens for a conventional liquid crystal projector configured as described above uses a fourth lens group G ₄ to have a large back focal length BFL to secure a peripheral space in which a prism, which is a color synthesis optical system, may be disposed. The concave eighth lens L ₈ and the convex ninth lens L ₉ have a characteristic that the rear main position is moved backward.

However, the conventional zoom lens for the liquid crystal projector constructed and operated as described above has a small angle of view, which limits the amount of information incident upon wide focusing, and also increases the overall focal length. The battlefield has a long problem.

That is, since the angle of view of the zoom lens is limited to the maximum angle of view at the time of wide focusing, the size of the screen that can be formed within a certain distance is small, and the focal length of the first lens group G ₁ is long, so This lengthening makes mechanical assembly adjustment difficult, and also makes it difficult to compact the liquid crystal projector.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and by newly distributing the refractive powers of each group from the first lens group to the fourth lens group, the lens zooms to a larger size while having a larger postfocal distance. The present invention provides a zoom lens for a liquid crystal projector to improve performance and assemblability.

1 is a schematic configuration diagram showing a general liquid crystal projector;

2 is a side configuration diagram of a zoom lens for a conventional liquid crystal projector,

(a) is a wide angle state (Wide) state diagram, (b) is a telephoto state (Tele) state diagram,

3 is a side configuration diagram of a zoom lens for a liquid crystal projector according to the present invention;

(a) is a wide-angle end (Wide) state diagram, (b) is a telephoto end (Tele) state diagram.

<Explanation of symbols for the main parts of the drawings>

G ₁ , G ₂ , G ₃ , G ₄ : 1st, 2, 3, 4 lens group

L ₁ to L ₁₃ : First lens to 13th lens

S ₁ to S ₂₄ : First lens surface to thirteenth lens surface

STOP: Aperture DG: Dummy Glass

A zoom lens for a liquid crystal projector according to the present invention for realizing the above object includes a first lens group, a second movable lens group, and a movable second lens group for enlarging and projecting an image of a predetermined size appearing on an LCD panel; In a zoom lens for a liquid crystal projector comprising a third lens group and a fourth lens group, the first lens group has a negative refractive power as a whole so as to be a retro focus type, and the peripheral aberration correction is easily performed from the screen. A convex first lens, a concave second lens, a concave third lens, and a convex fourth lens; The second lens group has a positive refractive power as a whole, and is linearly moved to vary the size of the projection screen, from the first lens group a convex fifth lens, a concave sixth lens, Arranged in a convex seventh lens order; The third lens group has a negative refractive power as a whole, and is moved non-linearly to correct an amount of image shift, and is arranged in the order of the convex eighth lens and the concave ninth lens from the second lens group. ; The fourth lens group has a positive refractive power as a whole and a concave tenth lens, a convex eleventh lens, a convex twelfth lens, and a convex type from the third lens group to form an image surface. The thirteenth lens is characterized in that arranged in order.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

The zoom lens for a liquid crystal projector according to the present invention includes a first lens group G ₁ having a negative refractive power as a whole from a screen to be enlarged and projected as shown in FIG. A second lens group G ₂ having positive refractive power, a third lens group G ₃ moving non-linearly and having a negative refractive power as a whole, and a positive refractive power as a whole the fourth consists of a lens group (G _4).

Here, an aperture stop is positioned between the first lens group G ₁ and the second lens group G ₂ to minimize distortion of the distortion projection screen.

A prism that is a color synthesizing optical system is positioned behind the fourth lens group G ₄ , and a dummy glass DG is positioned behind the fourth lens group G ₄ , and a rear side of the dummy glass DG is positioned on an LCD panel that provides image information. The light reflected from the light source transmits the information of the LCD panel to each lens group.

In detail, each lens group described above has the negative refractive power of the first lens group G ₁ to be of the retro focus type in order to secure a sufficiently large postfocal distance, and the aberration of the peripheral portion in the enlarged projection. The convex first lens L ₁ , the concave second lens L ₂ , the concave third lens L ₃ , and the convex fourth lens L ₄ from the screen for easy correction. Are arranged in order).

The second lens group G ₂ is linearly moved to vary the size of the projection screen by a variator unit having a positive refractive power as a whole, from the first lens group G ₁ . The convex fifth lens L ₅ , the concave sixth lens L ₆ , and the convex seventh lens L ₇ are arranged in this order.

In addition, the third lens group G ₃ is moved to a non-linear in order to correct an amount of image movement by a compensator unit having negative refractive power as a whole, and is convex from the second lens group G ₂ . The eighth lens L ₈ and the concave ninth lens L ₉ are arranged in this order.

Finally, the fourth lens group G ₄ has a positive refractive power as a whole, and the concave tenth lens L ₁₀ and the convex shape are formed from the third lens group G ₃ to form an image on an image surface. The eleventh lens L ₁₁ , the convex twelfth lens L ₁₂ , and the convex thirteenth lens L ₁₃ are arranged in this order.

라하고, 상기 제 1 렌즈군(G₁)의 초점 거리를

, 상기 제 2 렌즈군(G₂)의 초점 거리를

, 상기 제 3 렌즈군(G₃)의 초점 거리를

, 상기 제 4 렌즈군(G₄)의 초점 거리를

라 하면,In particular, the present invention measures the overall focal length of the wide-angle end of the zoom lens for the liquid crystal projector.

The focal length of the first lens group G ₁

, The focal length of the second lens group G ₂

, The focal length of the third lens group G ₃

And focal length of the fourth lens group G ₄ .

Say,

와,

Wow,

와,

Wow,

와,

Wow,

를 만족시키도록 구성되어 있다.And,

It is configured to satisfy.

Table 1 below shows data in a wide-angle end state of the zoom lens of the liquid crystal projector of the present invention, and Table 2 shows the zoom (Z00m) position of the zoom lens according to the present invention.

In the following table, 'incident light 1' is the refractive index of each medium at a wavelength of 546.0 nm with green light, 'incident light 2' is the refractive index of each medium at a wavelength of 610.0 nm with red light, Incident light 3 'is a blue light and represents the refractive index of each medium at a wavelength of 480.0 nm. In addition, in each table, "dispersion" means the difference between "incident light 3" and "incident light 2".

TABLE 1

TABLE 2

Here, the method of reading the data of Table 1 and Table 2 is as follows.

Table 1 In the first and the back (S ₂₎ of curvature of the first lens (L ₁₎ in the lens unit (G ₁₎ is -0.002326, a thickness of 8.500, and the outer diameter is 29.50. The refractive index of the material of the first lens L ₁ is 1.71616 of incident light 1 (green light), 1.71155 of incident light 2 (red light), 1.72295 of incident light 3 (blue light), and the dispersion of the incident light 3 to incident light 2. Is 0.01140.

In Table 2, Table 1 shows the data of the wide-angle end state of the zoom lens, and thus the distance and focal length comparison values of the tele-state of the zoom lens at each A, B, and C point of Table 1 are shown. Indicates.

The zoom lens for the liquid crystal projector of the present invention constructed and shown as described above is configured as a RetroFocus type in which the postfocal length BFL is larger than the total focal length EFL, thereby providing a sufficient postfocal distance. The larger angle of view allows a larger screen to be projected, and the overall length of the zoom lens group is reduced, making it easier to assemble and adjust the projector.

The zoom lens for a liquid crystal projector according to the present invention constructed and acting as described above newly distributes the refractive power of each group from the first lens group to the fourth lens group, thereby having a larger postfocal distance and having a larger rear focus distance. Since the projector is configured to be enlarged to a size, it is possible to realize a high-quality image while realizing a large screen, and to improve assembly performance by securing a peripheral space of the LCD panel.

Claims (3)

A zoom lens for a liquid crystal projector comprising a first lens group, a movable second lens group and a third lens group, and a fourth lens group to enlarge and project an image of a predetermined size appearing on an LCD panel on a screen, The first lens group has a negative refractive power as a whole to be of the retro focus type, and a convex first lens, a concave second lens, and a concave third from the screen to facilitate peripheral aberration correction. The lenses and the convex fourth lens in order; The second lens group has a positive refractive power as a whole, and is linearly moved to vary the size of the projection screen, from the first lens group a convex fifth lens, a concave sixth lens, Arranged in a convex seventh lens order; The third lens group has a negative refractive power as a whole, and is moved non-linearly to correct an amount of image shift, and is arranged in the order of the convex eighth lens and the concave ninth lens from the second lens group. ; The fourth lens group has a positive refractive power as a whole and a concave tenth lens, a convex eleventh lens, a convex twelfth lens, and a convex type from the third lens group to form an image on an image surface. A zoom lens for a liquid crystal projector, characterized in that arranged in order of the thirteenth lens. The method of claim 1, The overall focal length of the wide-angle end of the zoom lens for the liquid crystal projector

The focal length of the first lens group

, The focal length of the second lens group

, The focal length of the third lens group

, The focal length of the fourth lens group

Say,

Wow,

Wow,

Wow, And,

Zoom lens for a liquid crystal projector, characterized in that to satisfy the. The method of claim 1, A zoom lens for a liquid crystal projector according to claim 1, wherein an aperture stop is positioned between the first lens group and the second lens group.

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