KR20020042779A - Optical scanner - Google Patents

Abstract

PURPOSE: An optical scanner is provided to realize a normal image at a relative slow speed by alternatively changing a laser scanning direction in order to remove a feedback time. CONSTITUTION: Fixing members(4) are formed on an upper surface of a basic substrate(5) of an optical scanner. A mirror plate(1) is positioned above the basic substrate(5) and has a hardening surface for reflecting an incident rays. Shafts(2) are installed at both sides of the mirror plate(1) in order to ensure a rotational movement of the mirror plate(1) relative to the basic plate(5). Moving members(3) are attached to a lower portion of the mirror plate(1) with corresponding to the fixing members(4) of the basic substrate(5). The fixing members(4) and the fixing members(4) are provided between the mirror plate(1) and the basic substrate(5) at both sides of the shafts(2).

Description

Optical scanner

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanner that can be used for a laser projection apparatus and the like, and more particularly, to an optical scanner using a micro mirror capable of overcoming the driving limitation of scanning laser light onto a screen.

In order to realize an image on a screen, light must be scanned horizontally and light must be scanned vertically. In the case of a typical NTSC video signal, the horizontal scanning speed is 15.75 kHz and the vertical scanning speed is 60 Hz. That is, the moving picture is composed of 30 still images per second, and each still picture is composed of 525 horizontal scanning lines (see Fig. 4B). While the horizontal scan section draws 525 scan lines, the vertical scan section only needs to be scanned once from the top to the bottom of the screen. However, in order to scan the next line from the left to the right again, to return to the first left starting point 5 to 10 times faster than the horizontal scanning speed is no loss of light.

1 is a block diagram of an optical system of a laser projection apparatus to which a conventional optical scanner is applied. The light source 100 is a white light laser that generates white light. As a light source, a blue, green and red semiconductor laser may be used, or a wavelength converting solid state laser may be used. The optical separation unit 250 separates the laser beam of white light into monochromatic light of red, green, and blue. The optical splitter 250 includes two dichroic mirrors 670a and 680a and one high reflection mirror 690a. The dichroic mirrors 670a and 680a separate white light into red, green, and blue light, and the high reflection mirror 690a changes the light path of monochromatic light. The laser beam divided into red, green, and blue light is focused by an acousto-optic modulator (AOM) 610, 620, and 630 by focusing lenses 640a, 650a, and 660a, and optically modulated by an image signal. do. At the rear end of the optical modulator, collimating lenses 640b, 650b, and 660b for restoring the modulated laser beam to the parallel light form before the focusing lenses 640a, 650a, and 660a are positioned. Each of the blue, green, and red light modulated according to the image signal is combined by the integrated light unit 650 into one integrated beam. The light integrating portion 650 is composed of two dichroic mirrors 670b and 680b and one high reflection mirror 690b. The integrated beam is incident on the polygonal mirror 800 at an appropriate angle using the high reflection mirrors 710 and 720. The integrated beam is first incident to the polygonal mirror 800, which is a horizontal scanning unit, and then horizontally scanned. The horizontal scanning beam is focused on the mirror surface of the galvanometer 700 while passing through the relay lens systems 310 and 320 provided between the polygonal mirror 800 and the galvanometer 700. The laser beam collected at one point is again vertically scanned by the galvanometer 700. The image scanned by the polygonal mirror 800 and the galvanometer 700 is projected onto the front screen 900 by the reflector 850 installed on the top of the galvanometer.

In the conventional laser image projection apparatus configured as described above, a rotating polygon mirror 800 is used as a horizontal scan portion, which, as mentioned above, does not require a fast return time, but mechanically Since the rotation speed is not only limited to increase the scanning speed but also difficult to miniaturize, it is very disadvantageous when implementing a small laser TV. Therefore, a method of using a microscopic optical scanner using a micro-electro-mechanical system (MEMS) technology as a horizontal scanning unit has been proposed to realize a small laser TV. However, the general galvanometer driving method, which is not a rotary type, should return the return time about 5 to 10 times faster than one line scan time, and it is practically very difficult to manufacture a very small optical scanner capable of maintaining such a speed.

The present invention has been made to solve the above problems, by changing the scanning direction in a laser projection apparatus, etc. by eliminating the return time, the light using a micro-mirror to enable normal image reproduction even in a relatively slow operation The purpose is to provide a scanner.

1 is a schematic block diagram of a laser image projection apparatus having a conventional multi-sided projection optical system,

2 is a schematic block diagram of a laser image projection apparatus to which an optical scanner according to the present invention is applied;

3a and 3b are respectively a schematic perspective view of a micromirror disposed for horizontal scanning and vertical scanning in the optical scanner according to the present invention and a photograph taken of the actual micromirror produced,

4A and 4B are diagrams for explaining a conventional horizontal scanning method, respectively.

4A illustrates a horizontal scan signal;

4B is a diagram illustrating a scanning sequence according to the horizontal scan signal of FIG. 4A;

5A and 5B are views for explaining a horizontal scanning method according to the present invention, respectively.

5A illustrates a horizontal scan signal,

5B is a diagram illustrating a scanning sequence according to the horizontal scan signal of FIG. 5A.

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

10. Light source 25. Optical splitter

61, 62, 63. Acousto-optic modulate (AOM)

64a, 65a, 66a. Focusing lenses 64b, 65b, 66b. Collimating lens

65. Light integrating portion 67a, 68a. Dichroic mirror

69a. Highly Reflective Mirrors 64a, 65a, 66a. Focusing lens

61, 62, 63. Acousto-optic modulate (AOM)

64b, 65b, 66b. Collimating Lens 65. Light Integration

70. Mirror for vertical injection 71, 72. High reflection mirror

80. Mirror for horizontal injection 85. Reflector

90. Screen

100. Light source 250. Optical separation unit

310, 320. Relay lens system

610, 620, 630. Acousto-optic modulate (AOM)

640a, 650a, 660a. Focusing lenses 640b, 650b, 660b. Collimating lens

650. Light Integrating Units 670a and 680a. Dichroic mirror

690a. Highly Reflective Mirrors 640a, 650a, 660a. Focusing lens

610, 620, 630. Acousto-optic modulate (AOM)

640b, 650b, 660b. Collimating Lens 650. Light Integration

700. Galvanometer 710, 720. Highly reflective mirror

800. polygonal mirror 850. reflector

900. Screen 1000. Optical Scanner

In order to achieve the above object, the optical scanner according to the present invention is:

A base substrate;

A fixed comb teeth formed on an upper surface of the base substrate;

A mirror plate disposed above the bay substrate and having a mirror surface reflecting incident light;

Shafts provided at both sides of the mirror plate to ensure rotational movement of the mirror plate with respect to the base substrate;

It is characterized in that the moving comb attached to the lower portion of the mirror plate corresponding to the fixed comb of the base substrate.

According to the present invention, the fixed comb and the corresponding moving comb are preferably provided on both sides of the axis.

Hereinafter, an embodiment of an optical scanner using a micromirror according to the present invention, a laser image projection apparatus to which the optical scanner of the present invention can be applied, and a driving method thereof will be described in detail with reference to the accompanying drawings.

The optical scanner using the micromirror according to the present invention is characterized in that a normal image can be realized with a relatively slow optical scanner by eliminating the return time by alternately changing the scanning direction of the horizontal scan line. To this end, the video signals drawn in the opposite direction are stored in the buffer memory and then output in the opposite direction so that normal images are reproduced. Looking at the configuration of the present invention in detail as follows.

2 is a block diagram of an optical system of a laser projection apparatus to which an optical scanner using a micromirror according to the present invention is applied. In the figure, the light source 10 is a white light laser that generates white light. As a light source, a blue, green and red semiconductor laser may be used, or a wavelength conversion solid state laser may be used. The optical separation unit 25 separates the laser beam of white light into monochromatic light of red, green, and blue. The optical splitter 25 has two dichroic mirrors 67a and 68a and one high reflection mirror 69a. The dichroic mirrors 67a and 68a separate white light into red, green and blue light, and the high reflection mirror 69a changes the optical path of monochromatic light. Laser beams separated into red, green, and blue light are focused by an acousto-optic modulator (AOM) 61, 62, and 63 by focusing lenses 64a, 65a, and 66, and optically modulated by an image signal. do. At the rear end of the optical modulator, collimating lenses 64b, 65b, and 66b for restoring the modulated laser beam to the form of parallel light before entering the focusing lenses 64a, 65a and 66a are located. Each of the blue, green, and red light modulated according to the video signal is combined in the integrated beam 65 into one integrated beam. The light integrating portion 65 is composed of two dichroic mirrors 67b and 68b and one high reflection mirror 69b. The integrated beam uses high reflection mirrors 71 and 72 to be incident on the horizontal scanning micromirror 80 of the light scanner 1000 according to the present invention at an appropriate angle. The integrated beam first enters the horizontal scanning micromirror 80 of the light scanner 1000 and is scanned horizontally. The horizontally scanned beam is again focused on the mirror surface of the vertically-injected micromirror 70 of the light scanner 1000 and vertically scanned. The image scanned by the horizontal scanning micromirror 80 and the vertical scanning micromirror 70 is projected onto the front screen 90 by the reflector 85 disposed on the top of the vertical scanning micromirror.

As such, the optical scanner 1000 of the present invention having the horizontal scanning micromirror 80, the vertical scanning micromirror 70, and the reflecting mirror 85 uses a micro-electro-mechanical systems (MEMS) technique. Produced in a very small size. In the optical scanner 1000, the vertical injection micromirror 70 and the horizontal injection micromirror 80 are manufactured using MEMS technology to have a structure as shown in FIGS. 3A and 3B, respectively.

3A is a view schematically showing the structure of an optical scanner according to the present invention. As shown, the optical scanner according to the present invention is characterized in that the micromirrors 70, 80 are mirror mirrors 1 having mirror surfaces, an axis 2 for ensuring the rotational movement of the mirror plate 1, and the shafts ( 2) the upper structure having movable combs 3 attached to the lower side of the mirror plate 1, and the lower part having the fixed comb 4 and the substrate 5 to which the fixed comb 5 is attached. The structure has a combined structure. Thus, the direction of the mirror surface 1 is finely converted by the electrostatic force between the fixed comb 4 and the moving comb 3 engaged therewith. FIG. 3B is a photograph of an actual fabricated state of the micro mirror in which the reflection direction is finely converted.

The core content of the present invention is to propose a laser TV by ultimately reducing the size of the system by applying the optical scanner of the present invention that can be manufactured in such a small size to a laser image projection apparatus. In other words, the high-precision laser TV can be realized by replacing the conventional optical mirror, the polygonal mirror and the galvanometer, with a very small optical scanner having two micro mirrors, and applying a driving method suitable for high-speed image signal processing.

Such a driving method is well illustrated in FIGS. 5A and 5B, which are as follows when compared with a conventional driving method using an optical scanner shown in FIGS. 4A and 4B.

4A and 5A show a conventional horizontal scan signal and a horizontal scan signal of the present invention, respectively, and FIGS. 4B and 5B show scanning directions of a laser beam scanned according to the conventional horizontal scan signal and the horizontal scan signal of the present invention, respectively. Is shown on the screen. The comparison is as follows.

Conventionally, as shown in FIG. 4A, according to the solid line portion of the horizontal scan signal, as shown in FIG. 4B, a line from left to right is scanned along the line indicated by the solid line, and again, the horizontal scan signal of FIG. 4A. According to the dotted line of FIG. 4B, the left side returns to the left at a speed of about 5 to 10 times faster than the scanning speed. The image was implemented by sequentially repeating the horizontal scanning from the left to the right and the horizontal return from the right to the left. Therefore, in the conventional driving method, it is necessary to gradually increase the horizontal scanning speed to realize a high resolution image, but there is a limit in actually improving the scanning speed of the optical scanner.

In contrast, in the laser image projection apparatus according to the present invention, the horizontal scanning micromirror proposed to downsize the polygonal mirror, which is a conventional horizontal scanning unit, is operated by the horizontal scanning signal as shown in FIG. 5A. This horizontal scan signal has no signal for return as indicated by the solid line. Therefore, it is characterized by the fact that the horizontal scanning is performed even at the moment of return. Therefore, as shown in FIG. 5B, when scanning once from left to right according to the horizontal scanning signal of FIG. 5A, horizontal scanning is performed while returning from right to left. The entire image is realized while repeating the horizontal scanning from the left to the right and the horizontal scanning from the right to the left. Therefore, such a driving method can realize the image sufficiently even if the speed of the micromirror is not faster than the existing one by using the scan time even the return time that is previously lost. That is, when the scanning method as shown in FIG. 5B is applied to the ultra-small optical scanner, a fast return time is not required, and thus the normal high resolution image can be realized beyond the driving limit of the optical scanner. In this case, since the image scanned from the right to the left becomes opposite to the input video signal, the transmitted video signal is stored in the buffer memory and outputted in reverse so that the normal image is reproduced. As described above, in the present invention, the driving method that does not require the post-scanning return time is applied to the ultra-small optical scanner so that the image realization is not hindered even when driving at a relatively slow speed.

As described above, in the optical scanner using the micromirror according to the present invention, a mirror plate is provided on the upper surface of the base substrate, and fixed comb teeth and moving comb teeth are formed on the upper surface of the substrate and the remarks of the mirror plate, thereby making the mirror full size. The area occupied by the plate can be maximized, and the size of the plate can be miniaturized.

Such a light mirror using a micromirror can be used as a substitute for a galvanometer for horizontal injection and a rotating multifaceted mirror. In addition, the laser image projection device to which the optical scanner of the present invention is applied comprises an optical scanner using a micromirror in which the micromirror is replaced with a horizontal scanning rotary multi-facet mirror and a vertical injection galvanometer, and the horizontal scanning is returned. After going from left to right without scanning time, scanning is performed while returning from right to left, which drastically improves the driving speed compared to the conventional driving method that requires a return speed that is 5 to 10 times faster than the horizontal scanning speed. As a result, the driving limitation of the optical scanner can be overcome when high resolution image is realized. In addition, it is possible to prevent damage to the optical scanner according to the present invention by driving the symmetrical form can improve the reliability of the optical scanner.

Claims (2)

A base substrate; A fixed comb teeth formed on an upper surface of the base substrate; A mirror plate disposed above the bay substrate and having a mirror surface reflecting incident light; Shafts provided at both sides of the mirror plate to ensure rotational movement of the mirror plate with respect to the base substrate; And a moving comb attached to a lower portion of the mirror plate to correspond to a fixed comb of the base substrate. The method of claim 1, The fixed comb and the corresponding moving comb are provided on both sides of the axis around the optical scanner.