Patent Application
20070091429
This application claims the benefit of Korean Patent Application No. 2005-96769 filed with the Korea Industrial Property Office on Oct. 14, 2005, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a tilting device and an operation method thereof.
2. Description of the Related Art
An image projection device using Digital Light Processing (DLP), in which the mosaic phenomenon in pixels, a problem in regular Liquid Crystal Display (LCD) imaging devices, is eliminated to improve the ability to reproduce original colors, is used widely in theaters, conference rooms, and projection TV's, etc. The image projection device can be divided into a Front Projection device and a Rear Projection device according to the projection method.
The Front Projection device adopts the method of projecting image signals from the front, and is generally used in theaters, conference rooms, etc. On the other hand, the Rear Projection device adopts the method of projecting image signals from the rear of the screen. The Rear Projection device is commonly used in the form of projection TV's. In particular, Rear Projection devices are used more often than Front Projection devices, because of its ability to display a relatively bright image even in a bright environment.
As shown in
On the DMD 99 are formed numerous micro-mirrors (not shown), which are minute in size and are associated with a pixel structure on a silicon wafer, and these micro-mirrors convert the path of the incident light on/off by individually undergoing a highly rapid tilting motion according to the digital information provided to the DMD 99 by a controller. The pixels controlled individually by the DMD 99 are magnified through a projection lens 98 so that a large display picture is formed on the screen S.
As described above, since conventional image projection devices form a large display simply through the magnified projection of the small original picture, there is the problem that the picture quality is degraded due to the grid pattern formed between each pixel P, as seen in
The invention provides a tilting device and an operation method thereof which provides a smooth and natural display by periodically tilting light reflected from a DMD in constant time intervals and reflecting it to a screen.
The invention provides a tilting device and an operation method thereof which may reduce the number of pixels for a DMD.
Additional aspects and advantages of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the general inventive concept.
An aspect of the invention provides a tilting device comprising: a mirror positioned on a light path which periodically tilts light, a mirror holder joined to the mirror which vibrates with the mirror, a holder support part supporting the mirror holder to allow vibration, and a driving part which provides driving power to the mirror holder, wherein the driving part forms a predetermined angle with the mirror holder and causes vibration about the intersecting first axis and second axis.
Embodiments of the tilting device according to the invention may include the following features. For instance, the first axis and the second axis may form an angle of about 90°.
The driving part may comprise a first driving part positioned on the second axis and a second driving part positioned on the first axis, with the first driving part causing the mirror holder to vibrate about the first axis and the second driving part causing the mirror holder to vibrate about the second axis.
The first driving part and the second driving part may each have a coil joined to the reverse side of the mirror holder and a magnet surrounding the perimeter of the coil, and the coils may each be positioned on the first axis and the second axis.
The first driving part and the second driving part may further comprise yokes which are in contact with the magnets and which surround the perimeter of the coils. Also, the first driving part and the second driving part may further comprise cores which are in contact with the magnets and and of which a portion is positioned inside the coils.
Damping forces may be applied on the reverse side of the mirror holder at positions symmetrical to the coils with respect to the first axis and the second axis.
Dampers may be mounted on the reverse side of the mirror holder which are symmetrical to the coils with respect to the first axis and the second axis and on which damping forces are applied, the holder support part may comprise insertion grooves which hold the dampers and through which fluid is inserted, and damping of the dampers may be effected by means of a fluid. Such a fluid may be selected from a group consisting of grease, glycerin, UV-setting silicon, castor oil, SAE 30 oil, SAE 10W-30 oil, and SAE 10W oil.
The holder support part may support the mirror holder to allow vibration by means of a connection element. The connection element may be formed as a single body with the mirror holder and the holder support part. Also, the mirror holder and the holder support part may be formed with polyphenylene sulfide. The connection element may too be formed with polyphenylene sulfide.
The mirror holder may have a shape of a cross. The tilting device may further comprise a base holder, which secures the holder support part and has a housing groove that houses a portion of the driving part.
The holder support part may have a penetration hole adjoining the housing groove, and a portion of the coil may be positioned through the penetration hole, and inside the housing groove.
The mirror may be supported by the mirror holder via a securing element. Also, the mirror may be elastically supported by an elastic element positioned between the mirror holder and the mirror.
The mirror holder may have a securing protrusion on one side, and the elastic element may have a securing hole through which the securing protrusion may be inserted. The elastic element may be a flat spring.
Another aspect of the invention provides an operation method for a tilting device comprising: sending periodically a first signal to a first driving part in constant time intervals, and sending periodically a second signal to a second driving part in constant time intervals, wherein portions of the first signal and the second signal overlap.
Embodiments of the operation method for a tilting device according to the invention may include the following features.
For example, the first signal and the second signal may have the same magnitude. The first signal and the second signal may be pulse waves. The first signal and the second signal may have a T1 section during which signals are inputted and a T2 section during which signals are not inputted. The T1 section and the T2 section may have the same time duration. The overlap section during which the first signal and the second signal overlap may be approximately a half of the section during which the first signal or the second signal is sent. During the overlap section, the color wheel motor may undergo N rotations, or 1 rotation to be specific.
A further aspect of the invention provides a light engine module comprising: a digital micro-mirror chip disposed so that corners of micro-mirrors are adjacent, and a color wheel positioned between a light source and the digital micro-mirror chip, which separates the light emitted from the light source, wherein pixels generated by the micro-mirrors are tilted by a tilting device.
These and/or other aspects and advantages of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures.
As seen in
The mirror 60 is located on the light path and periodically tilts the light. The reverse side of the mirror 60 is elastically in contact with the contacting part 55 of the elastic element 50 (see
The first axis X1 and the second axis X2 may pass the center of gravity of the mirror 60 and may intersect at a predetermined angle, for instance approximately 90 degrees. The first axis X1 and the second axis X2, as shown in FIGS. 6 to 7, may pass the centers of gravity of the mirror holder 30 and the holder support part 20, respectively, which will further be discussed below.
The elastic element 50 is mounted on the upper side of the mirror holder 30 and elastically supports the reverse side of the mirror 60. The elastic element 50 has securing holes 57 on a diagonal line of its body 51, and into each securing hole 57 is inserted a securing protrusion 37 positioned on the upper side of the mirror holder 30. This prevents the detachment of the elastic element 50.
A sloped part 53 having a certain inclination angle and protruded upward is positioned on each side of the body 51 of the elastic element 50, and a contacting part 55 parallel to the body 51 is formed at the end of the sloped part 53. When the mirror 60 is secured to the mirror holder 30 by the securing element 40, the sloped parts 53 bend to a certain degree and elastically apply pressure to the mirror 60. The contacting parts 55 are in contact with the reverse side of the mirror 60, as seen in
As illustrated in
The mirror holder 30 comprises securing ledges in contact with the four sides of the mirror 60, respectively, mirror securing parts 33 protruding from the securing ledges and having fastening holes 34, and dampers 35 positioned on the reverse side of the mirror holder 30.
The securing ledges are protruded upward from one side of the mirror holder 30 and are in contact with the four sides of the mirror 60, respectively. The distance between securing ledges positioned on the first axis X1 and the second axis X2 may be equal to the parallel sides of the mirror 60, respectively. Obviously, the length of the securing ledge may be varied as needed.
The mirror securing part 33 is formed at the securing ledge and has a fastening hole 34 that joins with the securing element 40. The securing element 40 is mounted on the upper side of the mirror securing part 33 and secured with screws. The securing element 40 positioned on the mirror securing part 33 is in contact with the upper side of the mirror 60 and secures the mirror 60 to the mirror holder 30. The mirror securing parts 33 may be positioned on the first axis X1 and the second axis X2, respectively.
As illustrated in
On the reverse side of the mirror holder 30, a first coil 71′ and a second coil 71 may be positioned on the second axis X2 and the first axis X1, respectively. Also, the first coil 71′ and the second coil 71 may be positioned to be symmetrical to the dampers with respect to the first axis X1 and the second axis X2, respectively. The first coil 71′ and the second coil 71 cause the mirror holder 30 and the mirror 60 to vibrate about the first axis X1 and the second axis X2, which will further be discussed below.
As illustrated in
The penetration holes 21 are formed on the first axis X1 and the second axis X2, which pass the center of gravity of the holder support part 20, at positions eccentric to the center of gravity. The positions of the penetration holes 21 correspond with the positions of the first coil 71′ and the second coil 71 attached to the reverse side of the mirror holder 30 seen in
The fluid insertion grooves 23 are positioned to be symmetrical to the penetration holes 21 with respect to the first axis X1 and the second axis X2. As shown in
Any viscous fluid 90 may be used that can provide damping force on the dampers 35. A fluid that does not easily evaporate or leak is preferable. Examples of viscous fluid include grease, glycerin, UV-setting liquid silicon, castor oil, SAE 30 oil, SAE 10W-30 oil, and SAE 10W oil, etc.
For grease, a consistency of about 265 to 475 is preferable (as specified by the National Lubricating Grease Institute). For the base oil, silicon oil or PAO, etc. is preferable, of which the change in consistency is not great under high temperatures. For the thickener, lithium, silica gel, or PTFE (polytetrafluoroethylene, commonly known as “Teflon”), etc. may be used.
UV-setting silicon has a very high viscosity of 87,000 mPas (error range ±10,000) and is very stable, as there is virtually no change in viscosity in the temperature range of −40 to 80° C. Also, excellent damping may be effected with only a small amount.
Since the viscosity coefficient μ is 1.494 (kg/ms) at 20° C. for glycerin and μ≈1 for castor oil, sufficient damping forces may be transferred to the dampers 35.
Also, since SAE 30 oil, for which μ=0.43, SAE 10W-30 oil, for which μ=0.17, and SAE 10W oil, for which μ=0.1, have much higher viscosity coefficients compared to water (μ=0.001), damping forces may efficiently be transferred to the dampers 35.
The holder support part 20 comprises fastening holes 25 formed on the first axis X1 and the second axis X2, respectively. The positions of the fastening holes 25 correspond with the positions of the fastening holes 13 on the base holder 10 (see
As illustrated in
The housing groove 11 is a groove formed in the center of the base holder 10, of which the driving part (not shown) is positioned in the interior. That is, the core 73 is mounted in the housing groove 11, and the magnet 75 and yoke 77 are positioned at the upper part of the core 73, as is shown in
As illustrated in
As illustrated in
The coil 71 is a wound coil joined to the reverse side of the mirror holder 30 and creates an electric field when an electric signal is sent. As in
The magnet 75 is positioned on the core 73 and surrounds the coil 71. The magnet 75 magnetizes the yoke 77 and the core 73 and generates a magnetic field that passes through the coil 71.
The core 73 is magnetized by the magnet 75, and a portion is positioned inside the coil 71, as shown in
Joining relationships within the tilting device will be discussed below with reference to
After the core 73, the magnet 75 and the yoke 77 are sequentially positioned in the housing groove 11 of the base holder 10, the core 73 is joined to the housing groove 11 by means of adhesives or screws, etc. Here, the first driving part 70 of the first axis X1 and the second driving part 70′ of the second axis X2 are both equally positioned in the housing groove 11.
The coil 71 is joined to the reverse side of the mirror holder 30 and is passed through the penetration hole 21 of the holder support part 20 to be positioned between the core 73 and the magnet 75 and yoke 77. When the mirror holder 30, the holder support part 20, and the connection element 80 are formed as a single body, the coil 71 is passed through the penetration hole 21 of the holder support part 20 and attached to the reverse side of the mirror holder 30. A suitable amount of viscous fluid is injected into the fastening hole 25.
The securing protrusion 37 of the mirror holder 30 is inserted in the securing hole 57 of the elastic element 50 and secured, after which the mirror 60 is positioned on the contacting part 55 of the elastic element 50. Then, the securing element 40 is screwed to the mirror securing part 33 of the mirror holder 30 so that the securing element 40 is in contact with the mirror 60 elastically supported by the elastic element 50.
After the holder support part 20, to which the mirror holder 30 is joined, is positioned on the base holder 10, the holder support part 20 is secured to the base holder 10 by applying screws at each fastening hole 13, 25. Also, a suitable amount of fluid 90 is injected into the fluid insertion groove 23 of the holder support part 20.
The operation of a tilting device according to an embodiment of the invention will be discussed below with reference to FIGS. 10 to 12.
Referring to
When the first signal S1 is inputted, the mirror holder 30 and the mirror 60 vibrate about the first axis X1 due to the interaction between the first coil 71′ (see
Here, the first signal S1 and the second signal S2 have an overlap section S in which the signals overlap for a time period of T1/2, and during this overlapping period, the mirror holder 30 and the mirror 60 vibrate about the first axis X1 and the second axis X2 both. Therefore, the pixel formed on the screen appears on the third position P3 due to the overlapping of the second position P2 and the fourth position P4. Also, If neither the first signal S1 nor the second signal S2 are inputted to the first coil 71′ and the second coil 71, the pixel returns to its original position. Thus, the pixel is positioned sequentially at the first position P1, the second position P2, the third position P3, and the fourth position P4. If the first signal S1 and the second signal S2 are identical, T1 and T2 are identical, and the overlap section S is a half of the T1 section, the times during which the pixel stays at the first position P1, the second position P2, the third position P3, and the fourth position P4 are equal. The resulting pixels on the entire screen are as shown in
As illustrated in
As mentioned above, the times during which a pixel stays at the first position P1, the second position P2, the third position P3, and the fourth position P4 may all be equal, which are equal to the time during which a color wheel (not shown) undergoes N revolutions. This is because the color wheel must undergo at least 1 revolution to separate white light from a light source (not shown) into natural colors.
As illustrated in
While the spirit of the invention has been described with reference to particular embodiments, it is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the invention.
According to the invention, a tilting device and an operation method thereof may be provided which provides a smooth and natural display by periodically tilting light reflected from a DMD in constant time intervals and reflecting it to a screen.
The invention may also provide a tilting device and an operation method thereof which may reduce the number of pixels for a DMD.
Although a few embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-96769 | Oct 2005 | KR | national |
