KR100471458B1 - Lens for LCD Projection TV - Google Patents

Abstract

The present invention relates to a projection TV using a transmissive LCD (Liquid Crystal Device) for realizing a large screen, and in particular, the entire TV system by providing a lens system having a wide angle and a short focal length of a retrofocus type. The present invention relates to a lens for a liquid crystal projection TV that can realize a larger video screen while miniaturizing the size of the lens.

The present invention relates to a liquid crystal projection TV lens including a first lens group and a second lens group for enlarging and projecting a small size image displayed on an LCD panel on an image screen, wherein the first lens group is configured such that lateral aberration is corrected. A concave first lens, a convex second lens, a convex third lens, and a concave fourth lens are arranged in order from the image screen; The second lens group includes a convex fifth lens, a concave sixth lens, a convex seventh lens, a convex eighth lens, and a convex ninth from the first lens group so that longitudinal chromatic aberration is corrected. the first lens group and the focal length f ₁ is the second focal length by a combination of the focal length f ₂ of the lens group _{f 0, 20.0 <f 0 <} 24.0 the lens and configured to be arranged in the order, with, 1.10f ₂ <| f ₁ | <1.55f ₂ is simultaneously satisfied.

Description

Lens for liquid crystal projection TV

The present invention relates to a projection TV using a transmissive LCD (Liquid Crystal Device) for realizing a large screen, and in particular, the entire TV system by providing a lens system having a wide angle and a short focal length of a retrofocus type. The present invention relates to a lens for a liquid crystal projection TV that can realize a larger image screen while miniaturizing the size of the lens.

With the recent development of liquid crystal devices (LCDs), application fields using LCDs have been widely expanded to various electronic products and optical communication related products. In particular, CRT (Cathod Ray Tube) projection TVs are gradually expanding their projection TV systems using transmissive LCDs, due to performance and size limitations.

In general, in the liquid crystal projection TV, as shown in FIG. 1, image information is displayed on a liquid crystal element, that is, the LCD panel 3 by an electric signal, and the light source 1 is connected to the LCD panel 3 through an elliptical reflector 2. Permeate). The transmitted light passes through the lens system 4 located in front of the LCD panel 3, and the magnification is enlarged, and each aberration is corrected and reflected on the reflection mirror 5, and the screen (in the reflection mirror 5) 6) is projected and scattered.

Accordingly, in the liquid crystal projection TV, image information provided through a predetermined LCD panel 3 passes through the lens system 4 and appears on the large screen through the screen 6.

In particular, the lens system plays an important role in realizing a clearer picture and image while realizing a large screen in a projection TV.

U. S. Patent No. 5,218, 480 describes the lens for liquid crystal projection TV described above.

The US patent is composed of a plurality of lenses arranged from the screen as shown in Figure 2, the basic configuration is largely the first lens group (G ₁ ) having a negative refractive power and the second lens having a positive refractive power Divided into groups (G ₂ ). In FIG. 2, IS denotes an LCD panel as an image screen.

Here, the definition of the lens group G is defined as one or more lens elements that enable optical functions in the entire lens.

The first lens group G ₁ has a concave first lens L ₁ , a concave second lens L ₂ , and a concave third lens L from the screen 6 of FIG. 1. ₃ ) and the four lenses are arranged in this order in the order of the convex fourth lens L ₄ , and the chromatic aberration of magnification is corrected with negative refractive power as a whole.

The second lens group G ₂ is a convex fifth lens L ₅ , a concave sixth lens L ₆ , and a convex seventh lens from the first lens group G ₁ . (L ₇ ), the convex eighth lens (L ₈ ), the convex ninth lens (L ₉ ) in order five lenses are arranged in sequence, the function of correcting the axial chromatic aberration while having a positive refractive power as a whole Will be in charge.

In particular, at least one of the first lens group G ₁ and the second lens group G ₂ includes a lens element having an aspherical surface to correct aberration.

Here, the conventional liquid crystal projection TV requires a large volume of the cabinet to implement a large screen, but the current trend is required to further reduce the volume of the entire cabinet while realizing a large screen and clear image quality.

Therefore, one of the methods of reducing the volume of the cabinet is to reduce the total focal length (EFL) of the lens system. Of course, if the focal length EFL of the projection lens system is reduced in this way, the field angle of the lens is also increased.

However, the conventional liquid crystal projection TV lens configured as described above generally has a long focal length because the focal length (EFL) of the entire lens is in the range of 40 to 110 mm, thereby realizing miniaturization of the optical length and the entire projection TV system. There is a difficult issue.

In other words, when the entire lens has a long focal length, wider realization of the wider lens is limited, and thus, it becomes difficult to reduce the volume of the entire TV system because the length of the lens array becomes longer.

In addition, the conventional liquid crystal projection TV lens also has a problem that the manufacturing cost increases because at least one group of lenses includes a lens element having an aspherical surface.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the liquid crystal projection is designed to achieve stable large screens and to miniaturize the entire TV system by maintaining a stable performance at a wide angle and having a short focal length. To provide a lens for the TV.

The liquid crystal projection TV lens of the present invention for achieving the above-mentioned problems is a liquid crystal projection TV lens composed of a first lens group and a second lens group for enlarging and projecting an image of a predetermined size appearing on an LCD panel on a video screen. Wherein the first lens group is arranged in the order of a concave first lens, a convex second lens, a convex third lens, and a concave fourth lens from the image screen so that lateral aberration is corrected; The second lens group includes a convex fifth lens, a concave sixth lens, a convex seventh lens, a convex eighth lens, and a convex ninth from the first lens group so that longitudinal chromatic aberration is corrected. Characterized in that arranged in the order of the lens.

In addition, the present invention for realizing the above object is a lens for a liquid crystal projection TV comprising a first lens group and a second lens group for expanding and projecting an image of a predetermined size appearing on the LCD panel on the video screen, the first The lens group is arranged in the order of the concave first lens, the convex second lens, and the concave third lens from the image screen so that the lateral aberration is corrected; The second lens group includes a convex fourth lens, a concave fifth lens, a concave sixth lens, a convex seventh lens, and a convex eighth from the first lens group so that longitudinal chromatic aberration is corrected. The lens is arranged in the order of the convex ninth lens.

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

3 to 5, the lens for the liquid crystal projection TV according to the present invention has an overall focal length (EFL) to enlarge and project an image of a predetermined size appearing on the LCD panel IS onto an image screen. The back focal length (BFL) has a relatively larger retrofocus format, and is composed of a first lens group G ₁ and a second lens group G ₂ .

In particular, as shown in FIG. 3 and FIG. 4, the first lens group G ₁ includes a concave first lens from the image screen such that horizontal color aberration is corrected. L ₁ ), the convex second lens L ₂ , the convex third lens L ₃ , and the concave fourth lens L ₄ are arranged in the order of the second lens group G _2. ) Is a convex fifth lens L ₅ , a concave sixth lens L ₆ , and a convex seventh lens (L ₅ ) from the first lens group G ₁ so that longitudinal color aberration (Longitudial Color) is corrected. L ₇ ), the convex eighth lens L ₈ , and the convex ninth lens L ₉ .

In another embodiment of the present invention, as shown in FIG. 4, the third lens L ₃ and the fourth lens L _{4 of} the first lens group G ₁ do not have an air space therebetween. It can be configured as.

Meanwhile, another exemplary embodiment of the present invention illustrated in FIG. 5 includes a concave first lens L ₁ and a convex second lens from the image screen such that the first lens group G ₁ is corrected for lateral chromatic aberration. L ₂ and the concave third lens L ₃ , and the second lens group G ₂ is convex from the first lens group G ₁ so that the longitudinal chromatic aberration is corrected. L ₄ ), the concave fifth lens L ₅ , the concave sixth lens L ₆ , the convex seventh lens L ₇ , the convex eighth lens L ₈ , And the convex ninth lens L ₉ is arranged in order.

According to the present invention configured as described above, the focal length of the first lens group G ₁ is f ₁ , the focal length of the second lens group G ₂ is f ₂ , and the focal length of the entire lens is f _0. Assuming that, the following equation 20.0 <f ₀ <24.0 with, 1.10f ₂ <| is configured such that in the <range satisfying simultaneously 1.55f ₂ | f _1.

In addition, a stop is inserted between the first lens group G ₁ and the second lens group G ₂ of the present invention to minimize distortion on the image screen, and the second lens group G ₂ ) and a dummy glass (DG) for compensating for an optical path difference by a prism for color synthesis is placed between the LCD panel IS.

In addition, all the lenses of the first lens unit (G ₁₎ and the second lens group (G ₂₎ of the present invention is composed of a spherical lens.

When the embodiment of the present invention configured as described above is shown in a table as follows.

Here, Table 1 is according to FIG. 3, and Table 2 is according to FIG.

In the following table, 'incident light 1' is the green light and the refractive index of each medium at a wavelength of 546.0 nm, and 'incident light 2' is the red light and the refractive index of each medium at a wavelength of 610.0 nm. , '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 the "incident light 3" and the "incident light 2".

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

For example, referring to Table 1, the curvature of the back surface S ₂ of the first lens L ₁ in the first lens group G ₁ is 0.026312, the thickness is 2.000, and the outer diameter is 25.32. The refractive index of the material of the first lens L ₁ is 1.59143 for incident light 1 (green light), 1.58807 for incident light 2 (red light), 1.59635 for incident light 3 (blue light), and the dispersion showing the difference between incident light 2 and incident light 3. This is 0.00828.

TABLE 1

TABLE 2

The lens for a liquid crystal projection TV of the present invention as described above allows the first lens group G ₁ to realize lateral chromatic aberration correction even in a wide-angle region, and the second lens group G ₂ is responsible for correcting the longitudinal color aberration. At the same time, a stop is positioned between the first lens group G ₁ and the second lens group G ₂ to minimize distortion on the screen.

In addition, since both the first lens group G ₁ and the second lens group G ₂ use only spherical lenses but are divided by using convex lens elements and appropriate air spacing so as to have excellent performance for each field, aberration correction is easy. At the same time, it has a short focal length.

Accordingly, the present invention can reduce the size of the cabinet of the liquid crystal projection TV system by combining all lenses into spherical lenses so as to have a wide angle and a short focal length while reducing costs.

The lens for a liquid crystal projection TV according to the present invention constructed and acting as described above is of a retrofocus type, which is stable to maintain performance at a wide angle and at the same time has a short focal length, thereby realizing a larger screen. In addition, there is an advantage that can be miniaturized the entire TV system.

1 is a schematic diagram showing the internal structure of a typical liquid crystal projection TV;

2 is a configuration diagram of a lens for a conventional liquid crystal projection TV;

3 is a block diagram showing an embodiment of a lens for a liquid crystal projection TV according to the present invention;

4 and 5 illustrate another embodiment of the present invention.

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

G ₁ : first lens group G ₂ : second lens group

L ₁ to L ₉ : First lens to ninth lens

S ₁ to S ₁₈ : Each lens surface DG: Dummy glass

IS: LCD Panel

Claims (7)

A first lens group in which a plurality of lenses are arranged to correct lateral aberration from a video screen, and a second lens group in which a plurality of lenses are arranged to correct longitudinal chromatic aberration are arranged in order; The focal length f ₀ combining the focal length f ₁ of the first lens group and the focal length f ₂ of the second lens group is 20.0 <f ₀ <24.0 and 1.10f ₂ <| f ₁ | <1.55f ₂ . A lens for a liquid crystal projection TV, characterized in that it is within the range to satisfy at the same time. The method of claim 1, The first lens group is arranged from the image screen in order of a concave first lens, a convex second lens, a convex third lens, and a concave fourth lens; The second lens group is arranged in order from the first lens group in order of a convex fifth lens, a concave sixth lens, a convex seventh lens, a convex eighth lens, and a convex ninth lens. Lens for liquid crystal projection TV, characterized in that configured. The method of claim 2, And a stop is inserted between the first lens group and the second lens group to minimize distortion on the image screen. The method of claim 2, And all the lenses of the first lens group and the second lens group are composed of spherical lenses. The method of claim 2, And the third lens and the fourth lens of the first lens group are made of a bonded lens having no air space therebetween. The method of claim 2, And a dummy glass (Dummy Glass) is disposed between the second lens group and the LCD panel to compensate the optical path difference of the prism for color synthesis. The method of claim 1, The first lens group is arranged in the order of a concave first lens, a convex second lens, and a concave third lens from the image screen; The second lens group includes a convex fourth lens, a concave fifth lens, a concave sixth lens, a convex seventh lens, a convex eighth lens, and a convex type from the first lens group. A lens for a liquid crystal projection TV, characterized in that arranged in order of the ninth lens.