KR19980057953U - Focal Length Control System of Projection Display - Google Patents

Abstract

The present invention relates to a device for adjusting the focal length of a projection-type TV using a liquid-cooled CRT, a plurality of lenses located on the path of the light rays passing through the C-lens 54 fixed to the CRT (51) side The inner barrel 59 for connecting and fixing the 58 and the inner barrel 59 so that the inner barrel 59 can be linearly moved on a straight line connecting the inner barrel 59 and the C-lens 54. A case fixed to the outer barrel 60 is formed with a connection hole 1 formed so as to communicate with the outer barrel 60 to guide and the outer barrel 60 along the linear movement direction of the inner barrel 59. 2), a slider 3 linearly moved in parallel to the linear movement direction of the inner barrel 59 in the case 2 and connected to the inner barrel 59 through the connection hole 1, and a temperature; Thermal expansion and contraction means for expanding and contracting the slider 3 to generate a linear displacement in accordance with the change of The focal length adjusting device of the projection display device composed of an elastic member elastically supporting the lens compensates the focal length change of the projection lens unit due to heat generated from liquid-cooled CRT with the automatic focal length adjusting function according to the internal temperature of the projection TV. In this way, the optimum image can be projected on the screen 53 regardless of the operation start time of the projection TV.

Description

Focal Length Control System of Projection Display

The present invention relates to a device for adjusting a focal length of a projection lens used in a projection-type TV that enlarges a screen of a CRT (Cathode Ray Tube) and projects it on a screen. More specifically, a liquid refrigerant is used for heat generated from a CRT. The present invention relates to a device for automatically compensating that a focal length of a projection lens is changed by heat generated in the CRT in a projection-type TV employing a liquid-cooled CRT.

As shown in FIG. 1, a general projection TV includes a CRT 51 that generates a large screen, a projection lens unit 52 that enlarges an image of the CRT 51, and a projection lens unit 52. The projection lens unit 52 supports the C-lens 54 and the C-lens 54 whose position is fixed on the CRT 51 side again. And a coupler 56 in a state in which a refrigerant 55 that is in close contact with the screen of the CRT 51 and cools the heat generated by the CRT 51 is sealed, and the C-lens 54 and the screen 53. It is composed of a moving lens portion 57 which is positioned between and the position is variable so that the focal length can be changed.

Here, the moving lens unit 57 is an inner barrel 59 for integrally fixing and fixing a plurality of lenses 58 as shown in FIGS. 2A and 2B, and the inner barrel 59 is the C-lens. The outer diameter barrel 60 for guiding movement toward or near the 54 and the outer diameter barrel 60 to be fixed by adjusting the position of the inner diameter barrel 59 with respect to the outer diameter barrel 60. It consists of a butterfly nut 62 connected to the cam hole 61 and the inner barrel 59.

In the projection type TV configured as described above, the screen size of the CRT 51 is usually about 7 to 9 inches (Inch), and the screen 53 is about 40 to 120 inches (Inch) on the screen from the CRT 51. Since the projection is enlarged in size, the CRT 51 should provide a very bright screen in order to ensure the brightness of the screen formed on the screen 53 in a normal state or more while being enlarged and projected at a high magnification as described above.

Therefore, considering that the energy conversion efficiency of the CRT 51 is usually less than 10%, the CRT 51 inevitably generates a large amount of heat, thereby solving the heat generation problem of the CRT 51 as described above. To this end, the coupler 65 and the C-lens 54 in which the refrigerant 55 is sealed as shown in FIG. 1 are used.

In FIG. 3, an example of the coupler 65 and the C-lens 54 shown in FIG. 1 is shown in detail, and the coupler 65 and the C-lens 54 provided in contact with the screen of the CRT 51 are formed. A refrigerant is filled in the space, and one side of the coupler 65 includes an elastic expansion part 66 as a pressure regulating means for maintaining the internal pressure of the coupler 65 at a constant static pressure in consideration of thermal expansion of the refrigerant 55. Forming.

Here, the refrigerant 55 sealed by the C-lens 54 and the coupler 65 quickly absorbs the heat transferred from the CRT 51 screen to the conduction, thereby rapidly contributing to the convection circulating therein. A lens that transmits the heat from the 51 to another site to prevent overheating of the CRT 51 and simultaneously transmits the image provided from the CRT 51 together with the C-lens 54 as a transparent liquid. It is to play a role.

As described above, in the process of absorbing the heat generated from the CRT 51 and transferring it to the outside, the thermal expansion of the coolant 55 itself causes the density of the coolant 55 to change, and also the coolant 55. Since the C-lens 54 is also thermally expanded by the heat transmitted from the C-lens 54 and the refrigerant 55, the refractive index of the C-lens 54 and the coolant 55 change according to the temperature change of the CRT 51.

As the refractive index of the C-lens and the refrigerant is changed as described above, the overall focus of the projection lens unit is changed, so that the image formed on the screen can be accurately maintained by compensating the changed focus as described above. Proper required distance d between C-lens and the lens of the movable lens unit (hereinafter, the distance from the C-lens to the lens positioned at the shortest distance of the inner lens barrel of the movable lens unit is referred to as 'proper required distance d'). Should be adjusted.

Accordingly, when assembling the transmissive TV, the moving lens unit is in a state in which the temperature of the refrigerant 55 as described above is thermally balanced with the heat transmitted from the CRT 51 and becomes a constant steady state temperature. The proper focusing distance d, which is a relative distance to the C-lens 54 of (57), is adjusted to properly focus the projection lens unit 52 to ensure a stable focus setting state of the transmissive TV.

That is, in the state where the temperature of the refrigerant 55 is sufficiently increased so that there is no further change, the inner barrel is formed by using the cam hole 61 and the butterfly nut 62 of the outer barrel 60 shown in FIG. Move (59) to fix the proper demand distance (d).

However, when looking at the temperature change of the refrigerant 55, as shown in FIG. 5, since the steady state is achieved only after 5 hours after the TV is turned on, the temperature of the refrigerant is constant as described above. When the focal length of the projection lens unit 52 is adjusted in the state of T ₀ ), the viewer has a problem that the optimized screen can be viewed only after 5 hours after the TV is turned on.

Accordingly, an object of the present invention is to provide a focal length control device of a projection display device that automatically compensates for a change in focal length according to a change in temperature of a refrigerant to ensure an optimized image quality at all times.

1 is a block diagram showing a projection-type TV lens system employing a general liquid-cooled CRT,

FIG. 2 illustrates the moving lens unit of FIG. 1.

2a is a perspective view,

Figure 2b is a cross-sectional view taken along the line A-A of Figure 2a,

3 is a detailed view of the coupler and C-lens of FIG. 1;

4 is a view illustrating a focusing state of a C-lens and a moving lens unit;

5 is a graph illustrating a state in which a temperature of a refrigerant changes from an operation start point of a projection TV;

6 shows a focal length adjusting device of a projection display device according to the present invention,

6a is a plan view,

6b is an exploded perspective view;

6c is a cross-sectional view,

FIG. 7 shows the bimetal of FIG. 6;

8 is a view showing another embodiment of the thermal stretching means.

Explanation of symbols for the main parts of the drawings

1: connecting hole 2: case

3: Slider 4: Butterfly Bolt

5: bimetal 6: coil spring

7: metal wire in the form of a single spiral 8: metal wire in the form of a double spiral

The focal length adjusting device of the projection display device according to the present invention for achieving the above object is a C-lens fixed to the CRT side, and a plurality of lenses located on the path of the light rays passing through the C-lens A projection lens portion of a projection display device comprising an inner barrel for fixing and connecting an outer barrel for guiding the inner barrel so that the inner barrel can be linearly moved on a straight line connecting the inner barrel and the C-lens;

A connection hole is formed along the linear movement direction of the inner barrel so as to communicate with the outer barrel. The case is fixed to the outer barrel, and is linearly moved in parallel to the linear movement direction of the inner barrel. It characterized in that it comprises a slider connected to the inner barrel through, the elastic means for stretching in accordance with the change in temperature to generate a linear displacement on the slider, and an elastic member for elastically supporting the slider to the thermal stretching means.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention.

6 is a view illustrating a focal length adjusting device of a projection display device according to the present invention, FIG. 6A is a plan view, FIG. 6B is an exploded perspective view, and FIG. 6C is an assembled sectional view showing an assembled state of an outer barrel and an inner barrel. .

That is, the inner barrel 59 connecting and fixing the plurality of lenses 58 positioned on the path of the light beam passing through the C-lens 54 fixed to the CRT 51 side, and the inner barrel 59 and The outer barrel 60 for guiding the inner barrel 59 so that the inner barrel 59 can be linearly moved on a straight line connecting the C-lens 54 and along the linear movement direction of the inner barrel 59. A connection hole 1 is formed to communicate with the outer barrel 60, and the case 2 fixed to the outer barrel 60 and the linear movement direction of the inner barrel 59 in the case 2. A linear movement in parallel with the slider (3) connected to the inner barrel (59) through the connection hole (1), and a thermal expansion and contraction means for stretching in response to a change in temperature to generate a linear displacement in the slider (3); And an elastic member that elastically supports the slider 3 to the thermal expansion and contraction means.

Here, the case (1) is to be fixed to the outer diameter tube (60) with a butterfly bolt (4), the heat-expandable means are two metal plates of different thermal expansion coefficients are bonded to the two metal plates in accordance with the temperature change The bi-metal 5 was formed so that the curvature was changed, so that the change in curvature could generate a linear displacement of the slider 3.

That is, the curvature change of the bimetal 5 is expressed in the following manner in a free state,

ρ = t {3 (1 + m) ² + (1 + mn) [m ² + 1 / (mn)]} / 6 {(α _A -α _B ) (T ₂ -T ₁ ) (1 + m) ² }

Where ρ: curvature,

t: overall thickness,

n: modulus of elasticity E _B / E _A ,

m: thickness ratio t _B / t _A ,

T ₂ -T ₁ : temperature change,

α: coefficient of linear expansion

Since the curvature of the bimetal 5 changes as the temperature changes, the displacement S generated between both ends and the center of the bimetal 5 by changing the shape of the bimetal 5 as shown in FIG. 7. Is to be provided at the linear displacement of the slider (3).

Here, the slider 3 is elastically supported by the coil spring 6, which is an elastic member, on the bimetal 5 side, so that even when the displacement generated in the bimetal 5 changes in a direction of decreasing, the bimetal 5 The state of contact with (5) is maintained.

In addition, the bimetal 5 should change the position of the inner barrel 59 precisely according to the change in the internal temperature of the projection TV, so that the proper demand distance d can be set, so that the internal temperature of the projection TV shown in FIG. 4 changes. The bimetal 5 should be designed after the appropriate request distance d from the C-lens 54 to the lens 58 installed at the shortest distance of the inner barrel 59 is determined by experiment.

That is, it is assumed that a change in the internal temperature of the projection-type TV occurs at 20 ° C. to 60 ° C. as in the case of Table 1 below in a general case (outside air temperature 20 ° C.). The change amount 0.11 mm is such that the displacement S generated at both ends and the central portion of the bimetal 5 is generated.

TABLE 1

TV internal temperature (ΔT) Proper required distance (d) 20 ° C (0 ° C) 0 mm 60 ° C (40 ° C) 0.11 mm

Referring to the operation of the present invention configured as described above are as follows.

The internal temperature of the projection-type TV is changed by the heat generated in the CRT 51 and the heat generated in the circuit part, and generally starts at 20 ° C. and then changes to about 60 ° C. after turning on the first TV as described above at room temperature (20 ° C.). In this case, the amount of change in the proper request distance d from the C-lens 54 of the projection lens unit to the lens 58 at the shortest distance position of the inner barrel 59 is 0.11 mm in the temperature range.

Therefore, in order to always project the optimal image on the screen 53 despite the temperature change as described above, the proper request distance d should be automatically changed according to the temperature change, which is bimetal (the thermal stretching means). 5) is performed by automatically changing the position of the inner barrel 59 through the slider 3 by forming an appropriate displacement (S = about 0.11 mm) according to the change of the internal temperature of the TV.

That is, after the TV is turned on, the CRT 51 generates heat, and when the proper demand distance d is changed due to a change in refractive index according to the density change of the refrigerant 55 and the C-lens 54 receiving the heat. The bimetal 5 is thermally expanded by the heat generated by the CRT 51 and the heat generated by the circuit unit (not shown) to overcome the elastic force of the coil spring 6 acting on the slider 3 and to the slider 3. A linear displacement is generated, and the linear displacement of the slider 3 as described above means a linear displacement of the lens 58 fixed to the inner barrel 59, so that the proper required distance d is changed to an appropriate state.

Of course, when the TV is turned off, the internal temperature of the TV decreases and the displacement generated due to the temperature of the bimetal 5 decreases, while the inner barrel 59 and the slider 3 are in situ by the coil spring 6. The next time you turn on the TV, you can achieve the proper focal length depending on the temperature at that time.

In addition, as a thermal expansion and contraction means for generating a linear displacement on the slider (3) in accordance with the temperature change, in addition to the bimetal (5) described above, as shown in FIG. 8, as shown in FIG. It is composed of a spiral metal wire (7), or composed of a double helix-shaped metal wire (8) to change the length between the two ends of the metal wire in accordance with the temperature change, the change of the relative angle between the two ends of the metal wire caused by the temperature change or the change of the length Can be applied to the linear movement of the slider (3).

Therefore, the focal length adjusting device according to the present invention compensates the focal length change of the projection lens unit due to heat generated by liquid-cooled CRT with the automatic focal length adjusting function according to the change of the internal temperature of the projection-type TV. You can get the effect of always being able to project the best image onto the screen.

Claims (4)

An inner barrel connecting and fixing the C-lens fixed to the CRT side, a plurality of lenses positioned on the path of the light rays passing through the C-lens, and the inner barrel being straight on a straight line connecting the inner barrel and the C-lens. A projection lens portion of a projection display device including an outer barrel for guiding the inner barrel so as to be movable; A connection hole is formed along the linear movement direction of the inner barrel so as to communicate with the outer barrel. The case is fixed to the outer barrel, and is linearly moved in parallel to the linear movement direction of the inner barrel. A projection type comprising: a slider connected to the inner barrel through; a thermal stretching means for stretching in response to a change in temperature to generate a linear displacement on the slider; and an elastic member for elastically supporting the slider on the thermal stretching means. Focal length adjusting device. The method of claim 1, The thermal expansion and contracting means is a focal length adjusting device of a projection display device, characterized in that the two metal plates having different thermal expansion coefficients are bonded to each other so that the curvature of the two metal plates is changed according to temperature change. . The method of claim 1, The thermal stretching means is a focal length control device of a projection display device, characterized in that consisting of a single spiral-shaped metal wire to change the relative angle between both ends of the metal wire in accordance with the temperature change. The method of claim 1, The thermal stretching means is a focal length control device of a projection display device, characterized in that the length of the two ends of the metal wire to change the length of the metal wire in the form of a double spiral.