KR20090059630A - Light homogenization apparatus and display apparatus including it - Google Patents

Abstract

A light homogenization apparatus and a display apparatus including the same are provided to be applied to a portable device by improving space efficiency and energy efficiency. A light homogenization apparatus(120) includes a light source, a polarizing rotary device, and a birefringence device. The polarizing rotary device has two polarizing surfaces which are vertical each other. The polarizing rotary device outputs a light emitted from the light source as a linear polarization. The birefringence device is outputted as two refraction lights refracted into different two directions. Two refraction lights are homogenized in a predetermined position.

Description

Light homogenization apparatus and display apparatus including the same

The present invention relates to an illumination system, and more particularly, to a light equalization device included in an illumination system, which can increase the uniformity of an image by using a polarizer and a birefringent.

The one dimensional diffraction type optical modulator used in a scanning display device, which is a kind of display, is composed of a plurality of micro mirrors arranged in a line and outputs modulated light corresponding to a linear image. At this time, in order to express the light intensity of one pixel, the micromirror changes the amount of light of the modulated light by changing its displacement corresponding to the driving signal (for example, the driving voltage). Such modulated light is scanned on a screen by a scanner to realize a display screen of two or three dimensions.

At this time, the cross section of the laser beam used in the scanning display device is mostly ellipse. However, in order to display a uniform image, the cross section of the laser beam must be deformed to be closest to the form of the one-dimensional pixel array, that is, the form of the one-dimensional optical modulator array, and the intensity of the laser beam must be uniformly distributed. This is because, as described above, the light emitted from the light source is incident to the one-dimensional optical modulator and output as modulated light, and the display screen is formed using the modulated light. The distribution of the amount and intensity of light incident on each of the plurality of micromirrors constituting the optical modulator needs to be modified in the form of a one-dimensional pixel array to obtain an image with improved uniformity.

However, since the shape of the laser beam used as the actual light source is very different from that of the one-dimensional pixel array, the image formed through the scanning display device has to have a fringe pattern with the variation of the intensity between pixels. As a result, the brightness and the color of the image change for each pixel, and the quality of the image decreases.

Therefore, a technique for improving image quality by increasing image uniformity has been required. In the conventional technique for increasing uniformity of an image, there is a method of obtaining uniform light transmission using an aspherical lens. However, in order to increase the uniformity of the image through this method, the surface of the lens should be aspherical and exactly match the pre-calculated value, and the exact alignment of these is required. The slight deviation from the set position is because the uniformity of the image is reduced by generating a fringe pattern in the image formed by the display apparatus using the laser light source.

Accordingly, the present invention provides a light equalization device that increases the uniformity of an image by reducing a fringe pattern in an illumination system.

In addition, the present invention provides an optical equalization apparatus that can reduce laser speckle noise.

In addition, the present invention provides a light equalization device that is excellent in space efficiency and excellent in energy efficiency and applicable to a portable device.

According to an aspect of the present invention for achieving the above object, a light source; A polarization rotator having two polarization planes perpendicular to each other and outputting light incident from the light source as linear polarization; And a birefringent device in which the linearly polarized light is input and output as two refracted lights that are refracted in different directions, and the two refracted lights are synthesized at a predetermined position to be uniform light. have.

In this case, the polarization rotator is a liquid crystal polarization rotator, the linearly polarized light can be output by changing the photoactive characteristics corresponding to the applied voltage, the light intensity of the uniform light is twice the light intensity of one of the refractive light, The standard deviation of the uniform light may be characterized in that the square root of the standard deviation of the one refracted light.

In addition, the birefringent may be inclined by a predetermined angle with respect to the traveling direction of the light incident to the birefringent, the traveling speed of the plurality of refracted light is different, respectively, the plurality of refracted light is predetermined at the predetermined position And synthesized within a time interval.

According to another aspect of the invention, the light source; A polarization rotator having two polarization planes perpendicular to each other and outputting light incident from the light source as linear polarization; A birefringent unit configured to output a plurality of linearly polarized light inputs and to be refracted in two different directions, and to output the two linearly polarized light; A one-dimensional optical modulator for outputting the modulated light; And a scanner for sequentially scanning the modulated light on the display screen.

In this case, the polarization rotator is a liquid crystal crystalline polarization rotator, the liquid crystal crystalline polarization rotator may be characterized in that the linearly polarized light is output by changing the photoactive characteristics corresponding to the applied voltage, the light intensity of the uniform light is the refractive The light intensity is twice the light intensity of one refracted light, and the standard deviation of the uniform light may be a square root of the standard deviation of the one refracted light.

In addition, the birefringent may be inclined by a predetermined angle with respect to the traveling direction of the light incident to the birefringent and the traveling speed of the plurality of refracted light is different, respectively,

The plurality of refractive lights may be synthesized within a predetermined time interval at the preset position.

In addition, the predetermined time interval may be less than the frame interval time when the modulated light is sequentially scanned on the screen to generate a two-dimensional image, the modulated light is sequentially scanned on the screen to generate a two-dimensional image and the period of the uniform light It may correspond to the size and number of micro mirrors arranged in the longitudinal direction in the one-dimensional optical modulator.

According to the light uniforming device according to the present invention, the uniformity of the image may be increased by reducing the fringe pattern.

In addition, the present invention can reduce laser speckle noise.

In addition, the present invention is excellent in space efficiency and excellent energy efficiency can be applied to a portable device.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all transformations, equivalents, and substitutes included in the spirit and scope of the present invention. In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. The term and / or includes a combination of a plurality of related items or any item of a plurality of related items.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art, and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

Although the light homogenizing device of the present invention and a display device including an optical modulator are mainly described, the light homogeneous device of the present invention can be used as an optical modulator as well as an apparatus using a one-dimensional scanning image without limitation.

Hereinafter, a display device including an optical uniform device according to an embodiment of the present invention will be described with reference to FIG. 1. 1 illustrates a display device according to an embodiment of the present invention.

Referring to FIG. 1, a display device according to an embodiment of the present invention includes a laser light source 110, a light equalizer 120, an optical modulator 130, an optical projector 140, and a scanner 150. It includes.

The laser light source 110 may be a semiconductor laser, a solid state laser, a gas laser, or a liquid laser, and is not limited to a specific laser.

The light passing through the laser light source 110 passes through the light equalization device 120 and enters the light modulator 130. In this case, when the light emitted from the laser light source 110 forms an image, the light equalization device 120 improves the uniformity of the image, which will be described later.

The optical modulator 130 is composed of a plurality of micro mirrors, and the micro mirrors are arranged in a line to form a line. That is, each micromirror corresponds to each pixel in the image displayed on the screen 160, and a plurality of micromirrors are arranged in a line to form the optical modulator 130. The structure of the optical modulator including upper and lower reflective layers for modulating light corresponding to one embodiment of the optical modulator will be described later with reference to FIG. 2.

Instead of inputting the point light into the micromirror of the pixel unit constituting the optical modulator 130, instead of time-dividing linear light into the linear light modulator 130, each micromirror modulates light and The optical modulator 130 composed of micro mirrors may output modulated linear light. Modulated light output from the entire optical modulator 130 finally represents one linear scanning line on the screen 160. When the linear scanning lines are sequentially scanned on the screen 160, a completed two-dimensional planar image may be formed.

The light modulated by the optical modulator 130 is input to the scanner 150 via the light projector 140, and the scanner 150 scans the linear light in a predetermined direction on the screen 160 to form a planar image. That is, the scanner 150 reflects the modulated linear light incident from the optical modulator 130 at a predetermined angle to project the screen 160 onto the screen 160. For example, when the linear light output from the vertical optical modulator 130 is scanned in the horizontal direction of the screen 160, a two-dimensional planar image is completed.

In this case, the predetermined angle is determined by a scanner control signal input from an image controller (not shown). The scanner control signal rotates the scanner 150 at an angle at which the modulated linear light can be projected at the position of the vertical scan line (or horizontal scan line) on the screen 160 corresponding to the image control signal in synchronization with the image control signal. That is, the scanner control signal includes information about a driving angle and a driving speed, and the scanner 150 is located at a specific position at a specific time according to the driving angle and the driving speed. The scanner 150 may be a polygon mirror, a rotating bar, a galvano mirror, or the like.

Although not shown in FIG. 1, the laser light source 110, the optical modulator 130, the scanner 150, and the like described above may be controlled by the image controller. That is, the image controller may include a microprocessor and may be electrically connected to the elements inside the display to output a signal for controlling them. In addition, the image controller transmits a scanner control signal to the scanner to control the scanner scanning the one-dimensional image output from the optical modulator 130 from left to right, as described above. In addition, the image controller may control to change the position of each micro mirror constituting the optical modulator 130 to correspond to the image signal to generate a one-dimensional image having a desired brightness.

In the display device according to an embodiment of the present invention, the laser light source 110, the light equalization device 120, the optical modulator 130, the illumination system (Illumination system), the light projection unit 140, the scanner 150 and screen 160 are referred to as projection systems. Hereinafter, for convenience of understanding and explanation of the present invention, the illumination system and the projection system are used in the same meaning as described above.

Hereinafter, the structure of the optical modulator included in the display apparatus according to an exemplary embodiment of the present invention will be described with reference to FIGS. 2 to 3. 2 is a view showing the shape of the micro mirror constituting the optical modulator included in the display device according to an embodiment of the present invention.

The optical modulator 130 applied to the present invention is as follows. The light modulator 130 modulates the light in a manner that controls on / off of the light or in a manner that uses reflection / diffraction. The reflection / diffraction method may be divided into an electrostatic method and a piezoelectric method. Hereinafter, the piezoelectric method will be described. However, the same content may be applied to the electrostatic method.

The micromirrors included in the optical modulator of the open hole structure are shown in FIGS. 2 and 3. FIG. 2 is a three-dimensional perspective view of an optical modulator including a plurality of micro mirrors, and FIG. 3 is a plan view of the optical modulator including a plurality of micro mirrors shown in FIG. 2. In this embodiment, it is assumed that one micro mirror covers one pixel.

The optical modulator 130 has a plurality of micro mirrors 200-1, 200-2, ... 200-m (hereinafter referred to as 200) arranged in a row, each micro mirror 200 is a substrate 210, insulation Layer 220, sacrificial layer 230, ribbon structure 240, and piezoelectric material 250.

The insulating layer 220 is stacked on the substrate 210, and a sacrificial layer 230 exists to allow the ribbon structure 240 to be spaced apart from the insulating layer 220 at a predetermined interval. The ribbon structure 240 serves to modulate the signal by causing interference with the incident illumination light. The shape of the ribbon structure 240 may be provided with a plurality of open holes 240b in the center. Here, the open hole 240b is illustrated as having a long rectangular shape in the longitudinal direction of the micromirror 200, but various shapes such as a circular shape and an oval shape are possible, and also a long rectangular shape in the width direction of the micromirror 200. Multiple open holes of the type may be arranged in parallel.

As shown in FIG. 2, since the plurality of micro mirrors constituting the optical modulator 130 are arranged in a long line, the laser beam incident to the optical modulator 130 should be linearly deformed as described above. This will be described later with reference to Figure 4 for linearly transforming the light incident to the optical modulator 130 by using.

In addition, the piezoelectric material 250 includes the lower electrode 252, the piezoelectric layer 254, and the upper electrode 256. The piezoelectric material 250 may be contracted or expanded in a vertical or horizontal direction due to a voltage difference between the upper and lower electrodes. The ribbon structure 240 is controlled to move up and down. Here, the reflective layer 220a may be formed to correspond to the open hole 240b formed in the ribbon structure 240 or may be formed in the entire insulating layer 220.

For example, when the wavelength of light is λ, the distance between the upper reflective layer 240a formed on the ribbon structure 240 and the lower reflective layer 220a formed on the insulating layer 220 is (2 L) λ / 4 (L is a natural number. Is applied to the piezoelectric body 250. In this case, in the case of zero-order diffracted light, the total path difference between the light reflected from the upper reflective layer 240a and the light reflected from the lower reflective layer 220a is equal to λ, so that the modulated light produces the maximum luminance (that is, the maximum amount of light). Have Here, in the case of the + 1st and -1st diffracted light, the light has a minimum luminance (that is, a minimum amount of light) due to destructive interference.

In addition, a second voltage such that a distance between the upper reflective layer 240a formed on the ribbon structure 240 and the lower reflective layer 220a formed on the insulating layer 220 is (2L + 1) λ / 4 (L is a natural number) It is applied to the piezoelectric body 250. In this case, in the case of the zero-order diffracted light, the total path difference between the light reflected from the upper reflecting layer 240a and the light reflected from the lower reflecting layer 220a is equal to (2L + 1) λ / 2, so that it interferes with each other so that the modulated light has a minimum luminance. (Ie, minimum light quantity). Here, in the case of + 1st and -1st diffraction light, the light has the maximum luminance (that is, the maximum amount of light) by constructive interference.

As a result of this interference, the micromirror can adjust the amount of diffracted light to carry a signal for one pixel on the light. In the above, the case where the space | interval between the ribbon structure 240 and the insulating layer 220 is (2L) (lambda) / 4 or (2L + 1) (lambda) / 4 was demonstrated. However, by adjusting the distance between the ribbon structure 240 and the insulating layer 220, it is possible to control the luminance of the light interfered by the incident illumination light is diffracted, reflected. The 0th order diffracted light, the + nth order diffracted light, the -nth order diffracted light (n is a natural number), and the like correspond to modulated light.

The optical modulator 130 includes a first pixel (pixel # 1), a second pixel (pixel # 2),. , M micromirrors 200-1, 200-2,..., 200-m respectively responsible for the m-th pixel (pixel #m). The optical modulator 130 is responsible for image information on a linear image of a vertical line (here, the vertical line is assumed to be composed of m pixels), and each micro mirror 200-1, 200-2,. m represents one pixel of the m pixels constituting the vertical line. Thus, the light reflected and / or diffracted at each micromirror is then projected by the scanner 150 to a screen in two or three dimensional images.

As illustrated in FIGS. 2 and 3, an open-hole structure is provided so that one micro-mirror is responsible for one pixel. However, a plurality of micro-mirrors are provided for one pixel. You may be in charge. Alternatively, an open hole is not provided in the micromirror, and a path difference of reflected light according to the height difference between the odd mirror and the even mirror among the plurality of micromirrors may be used. In addition, those skilled in the art will understand that various types of light modulator can be applied to the present invention.

Hereinafter, a structure of an illumination system of a display device including a light equalization device according to an embodiment of the present invention will be described with reference to FIGS. 4A and 4B. 4A and 4B are structural diagrams illustrating a structure of an illumination system including a light equalization device according to an embodiment of the present invention.

4A and 4B, the illumination system 400 according to an embodiment of the present invention includes a light source 410, a collimator 420, a beam shaper 430, a polarization rotator 440, And a power source 450, a birefringent 460, and an optical modulator 470.

Light is emitted from the light source 410. In this case, the light source may be a semiconductor laser, a solid state laser, a gas laser, or a liquid laser as described above, and is not limited to a specific laser.

The light emitted from the light source 410 proceeds in parallel through the collimator 420. The collimator 420 serves to adjust the degree of divergence of the light emitted from the laser. In particular, when the light source 410 is a semiconductor laser, the degree of light is emitted is large, it is necessary to parallel or focus the light emitted in order to control the degree of divergence.

Referring to FIG. 4A, light emitted in parallel past the collimator 420 in the display device according to the exemplary embodiment of the present invention is changed into a linear shape light after passing through the beam former 430. It is incident to the optical modulator 470. The beam former 430 changes the shape of the light incident to the optical modulator 470 to improve uniformity of the completed image together with the polarization rotator 440 and the birefringent 460.

Light linearly changed past the beam former 430 is incident to the polarization rotator 440. Light passing through the polarization rotator 440 is output as linearly polarized light. At this time, the polarization rotator 440 has two polarization planes perpendicular to each other.

Referring to FIG. 4B, unlike the display device illustrated in FIG. 4A, the beam former 430 may be disposed between the polarization rotator 440 and the birefringent 460. As such, the beam former 430 serves to change the point light into a linear shape light regardless of its position. That is, the beam former 430 converts the point light into linear light before being incident to the birefringence, and its position is either between the polarization rotator 440 and the collimator 420 or between the polarization rotator 440 and the birefringer 450. It can be either one.

According to an embodiment of the present invention, the polarization rotator 440 may be a liquid crystal polarization rotator. In the case of the liquid crystal polarization rotator, the photoactive characteristic changes according to the applied voltage, and linear polarization perpendicular to each other is output according to the change of the photoactive characteristic. That is, a voltage is applied from the power source 450 to the liquid crystal crystal polarization rotator, and the photoactive characteristic of the liquid crystal crystal polarization rotator is changed corresponding to the value of the applied voltage. Then, linearly polarized light corresponding to the photoactive characteristic is output.

The linearly polarized light output from the polarization rotator 440 is incident to the birefringent 460. The linearly polarized light incident on the birefringent 460 is refracted to correspond to the plane of polarization of the linearly polarized light. In this case, the light that passes through the birefringent 460 is referred to as refractive light, and for the convenience of understanding and explanation of the present invention, the refractive light is clearly used in the same meaning as described above.

The linearly polarized light is incident on the birefringent 460 and then birefringed and output as two refracted lights. The birefringence refers to a phenomenon in which light incident on a certain kind of material splits into two refracted lights having different directions. This is a phenomenon that occurs because the speed of linearly polarized light incident on the birefringent 460 varies depending on the polarization direction.

Referring to FIGS. 4A and 4B, the light passing through the birefringent 460 is divided into two refractive lights 461 and 462 to proceed. At this time, the optical axis of the birefringent 460 is parallel to any one of the two polarization planes of linearly polarized light. Thus, the other polarization plane that is not parallel to the optical axis is perpendicular to the optical axis. The two refracted lights 461 and 462 that are birefringent have a phase difference. The phase difference approximately coincides with the half period of the fringe pattern of the image.

In this case, the birefringent 460 is inclined by a predetermined angle with respect to the traveling direction of the light incident on the birefringent 460. That is, it is rotated by a predetermined angle with respect to the optical axis of the optical modulator 470. As such, the birefringent unit 460 is inclined by a predetermined angle with respect to the traveling direction of the incident light, and the light incident into the birefringent unit 460 is separated into two refractive lights.

These two refractive lights 461 and 462 are combined at a predetermined position to form uniform light. Hereinafter, for the convenience of explanation and understanding of the present invention, uniform light is used in the same meaning as described above. The intensity of the uniform light is equal to the sum of the light intensities of the two refracted lights, that is, twice the light intensity of one refracted light. This is because the two refracted lights only have a phase difference and the same intensity. In this case, the relationship between the uniform light and the refractive light will be described below with reference to FIGS. 6 to 7.

As described above, the traveling speeds of the refracted light passing through the birefringent 460 are different from each other, and the two birefringent proceeding light are synthesized at predetermined positions within a predetermined time interval to form uniform light. The light equalization apparatus according to the embodiment of the present invention may include the birefringent 460 and the polarization rotator 440 as described above.

The uniform light incident on the light modulator 470 is then modulated to form an image on the screen. At this time, the period of the uniform light corresponds to the size and number of micro mirrors arranged in the longitudinal direction of the light modulator 470. The uniform light incident on the optical modulator 470 is output as modulated light, and then the modulated light is sequentially scanned on the screen to generate a two-dimensional image.

In this case, the predetermined time interval at which the refracted light is synthesized is equal to or less than the frame interval time when the output modulated light is sequentially scanned on the screen to generate the 2D image. This is because the refractive light is synthesized within the time for forming one frame to form uniform light so that uniform light forms a frame, thereby obtaining an image with improved uniformity.

Hereinafter, a structure of an illumination system including a light equalization device according to another embodiment of the present invention will be described with reference to FIG. 5. 5 is a structural diagram showing a structure of an illumination system including a light equalization device according to another embodiment of the present invention. Illumination system according to another embodiment of the present invention is similar to the configuration of the illumination system according to an embodiment of the present invention described in Figures 4a and 4b. Therefore, hereinafter, redundant description will be omitted for the convenience of explanation and understanding of the present invention.

Referring to Figure 5, the illumination system 500 according to another embodiment of the present invention is a light source (511, 512, 513), a collimator (Collimator, 521, 522, 523), a cubic beam splitter (Cubic Beam Splitter, 531) 532, a beam shaper 430, a polarization rotator 440, a power source 450, a light equalizer 460, and a light modulator 470.

Light is emitted to the light sources 511, 512, and 513. The biggest difference between the structure of the illumination system according to one embodiment of the invention shown in FIGS. 4A and 4B and the structure of the illumination system according to another embodiment of the invention shown in FIG. 5 is that there are three light sources. to be.

The light sources 511, 512, and 513 are composed of a red light source 511, a green light source 512, and a blue light source 513. In this case, the light output from the three light sources 511, 512, and 513 is linearly polarized, and the polarization planes of the output light are perpendicular or parallel to each other.

The light output from the light sources 511, 512, and 513 passes through collimators 521, 522, and 523 arranged for each light source so that light rays travel in parallel with each other. Light output from the three light sources passing through the collimators 521, 522, and 523 in parallel with each other is combined into one light by a cubic beam splitter 531 and 532. That is, the light output from the tricolor light source is combined by the cubic beam splitters 531 and 532 into one light.

The light merged into one by the cubic beam splitters 531 and 532 is changed by the beam shaper 430 to change the shape of the light incident to the light modulator 470 by the beam shaper 430. The light whose shape is changed by the beam former 430 passes the polarization rotator 440 and the birefringent 460 to form uniform light. The uniform light is then incident on the light modulator 470 to form an image. In this case, as shown in FIG. 5, the beam shaper 430 may be disposed between the cubic beam splitters 531 and 532 and the polarization rotator 440, but as described above with reference to FIG. 4B, the polarization rotator 440 and the birefringent ( It is clear that 460 may be arranged between.

Through the above process, the uniformity of the image formed on the screen later is improved. At this time, since the process of forming the uniform light passing through the polarization rotator 440 and the birefringent 460, as described above with reference to Figure 4 will be omitted for avoiding the overlapping of the understanding and description of the invention. .

Hereinafter, a method of generating uniform light of the light equalization device according to an embodiment of the present invention will be described with reference to FIGS. 6A to 7B. 6A and 6B are graphs showing a relationship between refractive light and uniform light having a regular fringe pattern according to an embodiment of the present invention. 7A and 7B are graphs showing a relationship between refractive light and uniform light having an irregular fringe pattern according to an embodiment of the present invention.

First, referring to FIG. 6A, a graph 610 showing the light intensity of one refractive light according to an embodiment of the present invention is shown. Looking at the graph 610 representing the light intensity of one refractive light output from the light source and past the polarization rotator, it can be seen that the intensity changes regularly with a certain period.

Referring to FIG. 6B, two refractive lights 611 and 612 passing through a birefringent are shown in accordance with one embodiment of the present invention. As described above, the linearly polarized light output through the polarization rotator is incident on the birefringent and the birefringent refractive light has a phase difference of about half a period of the fringe pattern as a result of birefringence. This can be easily seen by looking at the graphs 611 and 612 showing the light intensity of the refracted light of FIG. 6B.

The two refracted lights 611 and 612 outputted through the birefringent are combined into one uniform light 620 at a predetermined position. At this time, a graph 620 showing the light intensity of uniform light is shown in FIG. 6B. Looking at the graph 620 showing the light intensity of the uniform light, it can be easily seen that the light intensity uniformity is improved compared to the graphs 611 and 612 showing the light intensity of the refracted light.

In this case, the average light intensity of the uniform light is equal to twice the light intensity of one of the two refracted lights, and the standard deviation of the uniform light has a square root of the standard deviation of one of the refracted lights. That is, since the standard deviation of uniform light is the same as the square root of the standard deviation of one of the refracted light, the value of the standard deviation of the light intensity of the uniform light decreases. This is equivalent to saying that the uniformity of the image increases. Accordingly, the two light beams refracted through the linear polarizer and the birefringent are combined into one uniform light, thereby increasing the light intensity and the light uniformity.

This can be equally explained even when one refractive light has an irregular fringe pattern. Therefore, redundant description will be omitted for the convenience of explanation and understanding of the invention.

Referring to FIG. 7A, there is shown a graph 710 showing the light intensity of the refracted light after the birefringence. Looking at the graph 710 showing the light intensity of one refractive light output from the light source and passed through the polarization rotator and the birefringent, it can be seen that the intensity is not constant, and the period of change of the intensity is also not constant.

Referring to FIG. 7B, two refractive lights 711 and 712 passing through the birefringent are shown. The two refractive lights 711 and 712 have a phase difference of about half a period of the fringe pattern with each other, and they are combined into one uniform light 720 as described above. Looking at the graph 720 showing the light intensity of the uniform light, it can be easily seen that the light intensity uniformity is improved compared to the graphs 711 and 712 showing the light intensity of the refracted light.

In this case, the average light intensity of the uniform light is equal to twice the light intensity of one refracted light as described above, and the standard deviation of the uniform light has a value of the square root of the standard deviation of one refracted light among the two refracted lights.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art to which the present invention pertains without departing from the spirit and scope of the present invention as set forth in the claims below It will be appreciated that modifications and variations can be made.

1 is a view showing a display device according to an embodiment of the present invention.

2 is a view showing the shape of the micro mirror constituting the optical modulator included in the display device according to an embodiment of the present invention.

3 is a plan view of an optical modulator including a plurality of micromirrors shown in FIG.

4A and 4B are structural diagrams illustrating a structure of an illumination system including a light equalization device according to an embodiment of the present invention.

5 is a structural diagram showing a structure of an illumination system including a light equalization device according to another embodiment of the present invention.

6A and 6B are graphs showing a relationship between refractive light and uniform light having a regular fringe pattern according to an embodiment of the present invention.

7A and 7B are graphs showing a relationship between refractive light and uniform light having an irregular fringe pattern according to an embodiment of the present invention.

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

310: light source

320: collimator

330: beam former

340: polarization rotator

360: birefringence

Claims (13)

Light source; A polarization rotator having two polarization planes perpendicular to each other and outputting light incident from the light source as linear polarization; And It includes a birefringent which is input as the linear polarized light is output as two refracted light proceeds to be refracted in different directions, And the two refracted lights are combined at a predetermined position to be uniform light. The method of claim 1, The polarization rotator is a liquid crystal crystalline polarization rotator, And the liquid crystal polarization rotator outputs the linearly polarized light by changing a photoactive characteristic corresponding to an applied voltage. The method of claim 1, Wherein the light intensity of the uniformed light is twice the light intensity of one of the refracted light, and the standard deviation of the uniformed light is a square root of the standard deviation of the one refracted light. The method of claim 1, And the birefringent device is inclined by a predetermined angle with respect to a traveling direction of light incident to the birefringent device. The method of claim 1, The traveling speeds of the plurality of refractive lights are different from each other, And the plurality of refractive lights are synthesized within a predetermined time interval at the predetermined position. Light source; A polarization rotator having two polarization planes perpendicular to each other and outputting light incident from the light source as linear polarization; A birefringent outputting the plurality of linearly polarized light and outputting the two refracted lights which are refracted in different directions and proceed; A one-dimensional optical modulator disposed at a position at which the two refracted lights are combined to become uniform light, and outputting modulated light in which the uniform light is incident and modulated; And And a scanner for sequentially scanning the modulated light on a display screen. The method of claim 6, The polarization rotator is a liquid crystal crystalline polarization rotator, And the liquid crystal crystal polarization rotator outputs the linearly polarized light by changing a photoactive characteristic corresponding to an applied voltage. The method of claim 6, Wherein the light intensity of the uniformed light is twice the light intensity of one of the refracted light, and the standard deviation of the uniformed light is a square root of the standard deviation of the one refracted light. The method of claim 6, The birefringent display device, characterized in that inclined by a predetermined angle with respect to the traveling direction of the light incident to the birefringent. The method of claim 6, The traveling speeds of the two refractive lights are different from each other, And the two refractive lights are synthesized within a predetermined time interval at the predetermined position. The method of claim 10, The predetermined time interval is less than the frame interval time when the modulated light is sequentially scanned on the screen to generate a two-dimensional image. The method of claim 6, The modulated light is sequentially scanned on the screen to generate a two-dimensional image. The method of claim 6, And the period of the uniform light corresponds to the size and number of micro mirrors arranged in the longitudinal direction in the one-dimensional optical modulator.

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