KR100248010B1 - Projecting lens unit for projector - Google Patents

Abstract

Projector lens unit for projectors, which is employed in a projector having a light source and a display element for selectively generating an image for each pixel of the light emitted from the light source, and enlarges and projects the light incident at an angle to the optical axis via the display element. Is disclosed.

This disclosed apparatus comprises: a first lens group disposed sequentially from the display element side, having a positive power to focus an incident image, and arranged so that light incident from the display element side is transmitted through one side from its center; A negative power to diverge and enlarge the focused image, the optical axis of which is disposed coaxially with the optical axis of the first lens group, and having at least one aspherical lens to correct distortion aberration; And a second lens group in which light passing through the group is divergently transmitted and transmitted around the optical axis. The aperture is positioned between the first lens group and the second lens group, and between the first and second lens groups. And a mirror or prism capable of bending the optical path.

Description

Projection lens unit for projector

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection lens unit for a projector for expanding and projecting a generated image on a screen. More particularly, the present invention relates to a projection lens unit for a projector having an improved structure to improve aberration characteristics and to reduce the occupied space of a lens. .

In general, a projector includes a lamp for generating and irradiating light using halogen, xenon, and the like, a transmissive / reflective display device for generating an image by selectively transmitting or reflecting light emitted from the lamp, and displaying an image on a screen. And a projection lens unit for magnifying and projecting. As the display device, a liquid crystal display device (LCD) or a movable mirror device (DMD) may be employed.

The projection lens unit should be designed in consideration of optical performance such as angle of view and aberration in the vertical and horizontal directions, and occupied space in the projector.

In view of this, the present applicant has proposed a projection lens unit through Korean Patent Application No. 1858 filed on January 24, 1996 (name of the invention: wide-angle liquid crystal projection lens system, inventor: Kim Dong-ha).

The proposed projection lens unit includes a prism for switching the angle of the optical axis, and by arranging the optical axis by 90 ° or more, the space occupied in the projector can be reduced and the angle of view can be obtained.

However, since each lens group has a circular structure, there is a limit to reducing the space occupied.

In addition, two 'reflective project devices' proposed by the applicant [(Korean Patent Application No. 130525, filing date; April 9, 1997, Inventor; Choi Soon-Cheol), 1997 Korean Patent Application No. 132222 , April 10, 1997, inventor; Choi, Soon-Chul)], a critical angle prism is used to convert the traveling path of the light by inclining and reflecting the light to the reflective liquid crystal display, that is, the ferroelectric display device. Accordingly, when a projection lens unit having a well-known general structure is adopted, the light reflected from the ferroelectric display element is obliquely progressed with respect to the optical axis of the projection lens unit, and the contrast and aberration characteristics of the image formed on the screen are deteriorated. There is this.

Accordingly, the present invention has been made in view of the above problems, and by using only about half of the lens group, the space occupied by the optical system can be reduced, and the traveling path of light incident at an angle to the incident optical axis can be corrected. It is an object of the present invention to provide a projection lens unit for a projector having an improved structure.

1 is a schematic view showing an optical arrangement of a projection lens unit for a projector according to an embodiment of the present invention.

2 is a schematic view showing an optical arrangement of a projection lens unit for a projector according to another embodiment of the present invention.

3 is an aberration diagram of a tangential plane of the projection lens unit for the projector shown in FIG. 1; FIG.

4 is an aberration diagram of a sagittal plane of the projection lens unit for the projector shown in FIG. 1; FIG.

Fig. 5 is an astigmatism diagram of the projection lens unit for the projector shown in Fig. 1;

6 is a distortion aberration diagram of the projection lens unit for the projector shown in FIG. 1;

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

Ⅰ ... 1st lens group Ⅱ ... 2nd lens group

STOP ... Aperture M ... Reflector

1 ... optical axis 3 ... first optical member

5 ... second optical member 7 ... third optical member

In order to achieve the above object, the present invention is adopted in a projector having a light source and a display element for selectively generating an image for each pixel of the light irradiated from the light source, and obliquely with respect to the optical axis via the display element. A projection lens unit for a projector for expanding and projecting incident light, the projection lens unit being arranged sequentially from the display element side, having positive power to focus the incident image, and having a central axis of the lens inclined with respect to the incident optical axis A first lens group configured to transmit light incident from the display element toward one side from its center; A negative power to diverge and enlarge the focused image, the optical axis of which is disposed coaxially with the optical axis of the first lens group, and having at least one aspherical lens to correct distortion aberration; And a second lens group in which light passing through one lens group is divergently transmitted and transmitted around the optical axis.

In addition, an aperture stop is disposed at a position deviating from the optical axis between the first lens group and the second lens group, and a mirror or a prism for bending an optical path is provided between the lens groups.

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

Referring to FIG. 1, a projection lens unit for a projector according to an exemplary embodiment of the present invention is an apparatus that is adopted in a projector having a light source and a display element to enlarge and project light incident at an angle to an optical axis via the display element. The first lens group I and the second lens group II are sequentially arranged from the display element (image surface in FIG. 1).

Here, the projection lens unit is a device for irradiating an image from the first lens group (I) to the second lens group (II). However, in the lens design, the second lens group (II) is irradiated with light to pass through the first lens group (I) and then to form an image on the image surface on which the display element is located. Therefore, in consideration of the lens design, FIG. 1 is arranged in the order of the second lens group (II) and the first lens group (I) from the left of the drawing.

The first lens group I has a positive power to focus incident light. For this purpose, the first lens group I is composed of four convex lenses L6, L9, L11 and L12, two concave lenses L7 and L10 and one aspherical lens L8. It is composed. The first lens group I is generated in the display element to correct the modulation of light incident at an angle to the optical axis 5 in accordance with the optical arrangement of the display elements as described above, and the third optical member 7, The light incident through the second optical member 5 and the first optical member 3 is disposed so as to pass through either side of the optical axis 1.

Therefore, since the first lens group I is approximately half unused around the optical axis 1, it is preferable to have a semi-cylindrical structure in which unused portions are cut out. In this case, the space occupied by the first lens group I normally located in the projector can be reduced.

The second lens group II has a negative power to diverge and enlarge the focused image. The second lens group (II) includes one convex lens (L5), one concave lens (L3), one meniscus lens (L4), and two sheets in consideration of the wide angle of view and aberration characteristics. It consists of aspherical lenses L1 and L2, the optical axis of which is coaxial with the optical axis of the first lens group I. Here, the light transmitted through the first lens group I is transmitted through the entire second lens group II.

An aperture stop may be provided between the first lens group I and the second lens group II at a position off the optical axis to block light having an abnormal path due to aberration.

As described above, embodiments of curvature radius, lens thickness, and distance between lenses, refractive index, and dispersion for each lens forming the first lens group I and the second lens group II are shown in Tables 1 and 2. Indicated.

Here, each of the lens 1 (L1), the lens 2 (L2), and the lens 8 (L8) is an aspherical lens, and follows the aspherical equation represented by Equation (1).

Where Z is a value representing the sag from the lens vertex at a position h apart from the optical axis of each lens group, c is the curvature (inverse of the radius of curvature) of the lens at the optical axis, and k is a conic constant , Constants A, B, C and D each represent the aspherical coefficient of each lens.

The conic constant is different for each lens, and FIG. 1 shows a case in which a value of 0.000 is set as the conic constant for accurate design of the lens.

Lens Bending Radius (mm) Lens (optical member) thickness and distance between lenses (mm) Refractive index Dispersion L1 R1 = -156.001 (aspherical surface 1) D1 = 5.500 1.492 57.1 R2 = 45.170 (aspheric surface 2) D2 = 9.556 L2 R3 = 110.088 (aspherical 3) D3 = 5.500 1.492 57.1 R4 = 88.419 (Aspherical 4) D4 = 17.333 L3 R5 = -155.010 D5 = 4.000 1.620 60.3 R6 = 55.323 D6 = 6.734 L4 R7 = 190.024 D7 = 4.000 1.620 60.3 L5 R8 = 52.354 D8 = 14.378 1.805 25.5 R9 = -304.031 D9 = 104.515 STOP ∞ D10 = 8.635 L6 R11 = 127.538 D11 = 10.256 1.487 70.4 L7 R12 =-50.410 D12 = 3.500 1.805 40.7 R13 = 242.605 D13 = 1.754 L8 R14 = 173.386 (aspheric 5) D14 = 7.821 1.492 57.1 R15 = 85.233 (Aspherical surface 6) D15 = 0.100 L9 R16 = ∞ D16 = 6.703 1.603 60.7 L10 R17 = -103.411 D17 = 5.000 1.755 27.5 L11 R18 = 193.170 D18 = 15.876 1.603 60.7 R19 = 56.917 D19 = 0.100 L12 R20 = 98.248 D20 = 13.740 1.658 50.9 R21 = -109.062 D21 = 4.000 First optical member R22 = ∞ D22 = 30.980 1.517 64.2 R23 = ∞ D23 = 0.510 Second optical member R24 = ∞ D24 = 28.310 1.517 64.2 R25 = ∞ D25 = 1.235 Third optical member R26 = ∞ D26 = 2.212 1.523 63.0 R27 = ∞ D27 = 0.001

Aspheric coefficients for the respective aspherical lenses are shown in Table 2.

Aspheric modulus A B C D Aspheric surface 1

-

Aspheric surface 2 -

-

-

Aspheric surface 3

-

-

Aspheric surface 4

-

-

Aspheric surface 5

-

-

Aspheric surface 6

-

-

In order to facilitate the optical arrangement between the first lens group I and the second lens group II, the first lens group I and the second lens group II are disposed relatively sufficiently separated from each other in the optical arrangement between the lenses constituting the lens groups.

In this case, as shown in FIG. 2, a reflector M which is disposed on an optical path between the first lens group I and the second lens group II to reflect an incident image and converts the traveling path. ) May be further provided to facilitate the optical arrangement.

3 to 6 are aberration diagrams showing aberration characteristics of the projection lens unit for the projector shown in FIG.

3A to 3C each show aberrations in a tangential direction for light having different wavelengths. That is, the aberration 11 for light having a wavelength of 460.0 nm, the aberration 12 for light having a wavelength of 550.0 nm, and the aberration 13 for light having a thickness of 640.0 nm are shown for the 1.00 top surface, the 0.69 top surface, and the 0.00 top surface, respectively. .

4A to 4C show aberrations in the SAGITTAL direction for light having different wavelengths, respectively. That is, the aberration 11 for light having a wavelength of 460.0 nm, the aberration 12 for light having a wavelength of 550.0 nm, and the aberration 13 for light having a thickness of 640.0 nm are shown for the 1.00 top surface, the 0.69 top surface, and the 0.00 top surface, respectively. .

FIG. 5 is an aberration diagram showing astigmatism, and shows tangential field curvature (T) 14 and sagittal field curvature (S) 11 at the height of water according to the focal point.

6 is an aberration diagram illustrating distortion 16.

As described above, the projection lens unit for a projector according to the embodiment of the present invention configured to improve the contrast characteristics and aberration characteristics by allowing the image incident at an angle to the first lens group I to be projected normally on the screen.

In addition, by using only one portion of the first lens group I around its optical axis, the unused portion can be removed to reduce the space occupied in the projector.

Claims (4)

Projector lens for a projector which is employed in a projector having a light source and a display element arranged at an angle with respect to the optical axis of the light irradiated from the light source to generate an image, and enlarges and projects the light incident at an angle to the optical axis via the display element. In the unit, Disposed sequentially from the display element, A first lens group having a positive power to focus the incident image, the central axis of the lens being inclined with respect to the incident optical axis so that the light incident from the display element side is transmitted from one side of the center toward the other; A negative power to diverge and enlarge the focused image, the optical axis of which is disposed coaxially with the optical axis of the first lens group, and having at least one aspherical lens to correct distortion aberration; And a second lens group configured to diverge and transmit the light passing through the first lens group over the optical axis in its entirety. The projection lens unit for a projector according to claim 1, wherein each of the first lens groups has a semi-cylindrical structure in which about half of the first lens group is cut in the center of the optical axis. The method according to claim 1 or 2, A projection lens unit for a projector, characterized in that it further comprises an aperture disposed at a position off the optical axis on the optical path between the first lens group and the second lens group. The method according to claim 1 or 2, And a reflecting mirror arranged on an optical path between the first lens group and the second lens group to reflect an incident image and convert a traveling path thereof.

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