KR20070084858A - Display apparatus comprising spatial optical modulator and spatial optical modulator compensating method - Google Patents

Abstract

A display device including a light modulator and a light modulator compensation method are provided to allow a gray shown on a screen to indicate a uniform luminance all the time by measuring a change quantity of displacement according to the time of a micro-mirror and compensating a control voltage for the same input. A light modulator(720) outputs a modulation beam in which a luminance of an incident beam from a light source(710) is changed according to a provided control voltage. A scanner(730) projects the modulation beam on a certain position of a screen. A photodiode(750) measures a sampling luminance of the modulation beam outputted from the light modulator(720) to which a sampling voltage is supplied. A control circuit(770) provides the predetermined control voltage to the light modulator(720) to allow the modulation beam to have the luminance according to a reference table indicating relation between the luminance and the control voltage, recalculates the relation of the luminance for the control voltage of the light modulator(720) from the sampling voltage and the sampling luminance, and updates the reference table.

Description

Display apparatus comprising spatial modulator compensating method

1 is a perspective view of a micro mirror included in an optical modulator.

FIG. 2 is a plan view of an optical modulator including a plurality of micro mirrors shown in FIG. 1.

3 is a cross-sectional view taken along the line AA ′ of FIG. 2.

4 and 5 illustrate a case in which the displacement between the upper reflective layer and the lower reflective layer of the micromirror increases or decreases from the initially set displacement over time.

6 illustrates a method for finding approximated curves in accordance with one preferred embodiment of the present invention.

7 is a schematic configuration diagram of a display device for compensating an optical modulator according to an exemplary embodiment of the present invention.

8 is a flowchart of a method for compensating for a change in displacement of an optical modulator according to an exemplary embodiment of the present invention.

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

710: light source

720: optical modulator

730: Scanner

740: Light Directional Converter

750: photodiode

760: analog to digital converters

770: control circuit

780: screen

The present invention relates to an optical modulator, and more particularly, to a display apparatus and a compensation method including an optical modulator for compensating for a phenomenon in which the amount of displacement changes with time with respect to a constant input.

Recently, with the development of display technology, the demand for the implementation of large images is increasing day by day. Currently, most large image display devices (mainly projectors) use liquid crystals as optical switches. Compared with the CRT projectors of the past, it is small and inexpensive, and the optical system is simple and used. However, it is pointed out that a large amount of light loss occurs because light from the light source is transmitted through the liquid crystal plate to the screen. Therefore, a lighter image can be obtained by reducing light loss by utilizing a micromachine such as an optical modulator element using reflection.

Micromachines are extremely small machines that are difficult to discern with the naked eye. Also known as MEMS (Micro Electro Mechanical System), it can be called microelectromechanical system or device. It is mainly made by applying semiconductor manufacturing technology. It is applied to various information equipment parts such as magnetic and optical heads using micro-optics and limiting devices, and it is also applied to biomedical field and semiconductor manufacturing process using various micro fluid control technologies. Micromachines can be divided into micro-sensors that function as sensing elements, micro-actuators as driving devices, and miniature machines that serve as energy transfer devices.

MEMS is applied to the optical field as one of various application fields. MEMS technology enables the fabrication of optical components smaller than 1mm, enabling ultra-compact optical systems.

Micro-optical components such as optical modulator elements and micro lenses, which are miniature optical systems, have been adopted and applied to communication devices, displays, and recording devices due to advantages such as fast response speed, small loss, and ease of integration and digitization.

The Spatial Optical Modulator (SOM) used in a scanning display device, which is a kind of display, is composed of a driving integrated circuit and a plurality of micro mirrors. One or more micromirrors come together to represent one pixel of the projected image.

At this time, in order to express the light intensity of one pixel, the micromirror changes the amount of light of modulated light by changing its displacement in proportion to the driving voltage applied from the driving integrated circuit. Here, the driving integrated circuit generates a driving voltage having a specific relationship with respect to the input signal. In addition, the luminance of the modulated light has a specific nonlinear relationship with the driving voltage.

In the micromirror, the amount of change in displacement during initial manufacture and the amount of change in displacement with time are not constant with respect to a constant driving voltage. As a result, there is a problem that an error occurs when a user intends to generate modulated light having a desired brightness.

Since the optical modulator cannot compensate for the phenomenon that the amount of displacement changes with time for a certain input, the brightness may be reversed from the minimum or highest gray level value from the ideal brightness on the screen. This will seriously affect the image quality.

Accordingly, the present invention provides a display device and an optical modulator compensation method of measuring a change amount of displacement of a micromirror over time and compensating a control voltage with respect to the same input so that the gray level displayed on the screen always shows a constant luminance.

Other objects of the present invention will be readily understood through the following description.

In order to achieve the above object, according to an aspect of the present invention, a light source; An optical modulator (SOM) for outputting modulated light whose luminance of incident light from the light source is changed according to an applied control voltage; A scanner for projecting the modulated light to a predetermined position on a screen; A photo diode (PD) for measuring a sampling brightness of modulated light output from the optical modulator receiving a sampling voltage; And according to a reference table indicating a relationship between the brightness and the control voltage, the control voltage preset to have the brightness of the modulated light is applied to the optical modulator, and from the sampling voltage and the sampling brightness, A display device may be provided that includes a control circuit for recalculating the relationship of the luminance with respect to the control voltage to update the reference table.

Preferably, the apparatus further comprises a light direction converter for changing a direction of the portion of the modulated light directed to the scanner, wherein the photodiode may receive a portion of the modulated light whose direction is changed by the light direction converter.

The optical modulator may receive the sampling voltage at a blank time before an arbitrary frame image is output or the sampling voltage at the blank time after the output.

The optical modulator may include a plurality of micro mirrors, each of which is responsible for one pixel, and one micro mirror of the plurality of micro mirrors may receive the sampling voltage with respect to one frame image. In addition, the optical modulator may receive three or more sampling voltages for one pixel during the blank time.

In order to achieve the above objects, according to another aspect of the present invention, the luminance of incident light from a light source is changed in accordance with the control voltage set such that the modulated light has the luminance according to a reference table indicating a relationship between the luminance and the control voltage. A method of compensating physical deformation over time of an optical modulator for outputting the modulated light, the method comprising: (a) allowing a sampling voltage to be applied to the optical modulator; (b) measuring sampling luminance of modulated light output from the optical modulator according to the sampling voltage; And (c) calculating the relation of the luminance with respect to the control voltage of the optical modulator from the sampling voltage and the sampling luminance to update the reference table.

Preferably, step (c) may include repeating steps (a) to (b) three or more times for different sampling voltages.

In addition, the step (a) may apply the sampling voltage at the blank time before the arbitrary frame image is output or apply the sampling voltage at the blank time after the arbitrary frame image is output.

Here, in step (a), the sampling voltage for one pixel may be applied to one frame image.

And (d) changing the positions of the pixels to which the sampling voltage is applied for each successive frame image, and repeating steps (a) to (c).

Hereinafter, exemplary embodiments of a display apparatus and an optical modulator compensation method according to the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, when it is determined that the detailed description of the related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. Numbers (eg, first, second, etc.) used in the description of the present specification are merely identification symbols for sequentially distinguishing identical or similar entities.

1 is a perspective view of a micromirror included in an optical modulator, and FIG. 2 is a plan view of an optical modulator including a plurality of micromirrors shown in FIG. 1.

Referring to FIG. 1, the micromirror 10 includes a substrate 1, an insulating layer 2, a sacrificial layer 3, a ribbon structure 4, and a piezoelectric body 5. Assume that the wavelength of light is λ. Here, part of the sacrificial layer 3 is used to support the ribbon structure 4 without being etched.

First, a predetermined first voltage is applied to the piezoelectric body 5 of the micromirror 10 to form a ribbon structure 4 having an upper reflective layer 4a and an insulating layer 2 having a lower reflective layer 2a formed below the hole 4b. So that the spacing between The total path difference between the light reflected from the upper reflecting layer 4a and the light penetrating through the hole 4b and reflected from the lower reflecting layer 2a is equal to λ so that the 0th order diffracted light (ie, reflected light) has constructive interference, and ± The first order diffracted light has destructive interference.

In addition, a predetermined second voltage is applied to the piezoelectric body 5 so that the ribbon structure 4 moves toward the insulating layer 2 or vice versa by the pressure generated in the piezoelectric body 5. At this time, the interval between the ribbon structure 4 and the insulating layer 2 on which the lower reflective layer 2a is formed is λ / 4 or 3λ / 4. Therefore, the total path difference between the light reflected from the upper reflecting layer 4a and the light reflected from the lower reflecting layer 2a is equal to λ / 2, so that the zeroth order diffracted light has a destructive interference and the ± first order diffracted light has a constructive interference.

That is, in the case of using the 0th order diffracted light, the path difference of the diffracted light has a maximum luminance due to constructive interference when the path difference of the diffracted light is an even multiple of λ / 2, and a minimum luminance due to destructive interference when an odd multiple of λ / 2.

In the case of using ± 1st diffracted light, the diffraction light has a minimum luminance when the path difference is an even multiple of lambda / 2, and a maximum luminance due to constructive interference when an odd multiple of lambda / 2 is used.

If necessary, the micromirror 10 uses zero-order diffraction light or ± first-order diffraction light, and the principle of interference is as described above. Using the result of such interference, the micromirror 10 adjusts the distance between the ribbon structure 4 and the insulating layer 2 in accordance with the applied control voltage to adjust the amount of incident light so that the signal is loaded on the light and modulated light. You can print

The micro mirror 10 is in charge of any one of a plurality of pixels constituting the vertical scan line or the horizontal scan line to adjust the brightness.

Referring to FIG. 2, the optical modulator has a first pixel (pixel # 1), a second pixel (pixel # 2),. And n micromirrors 10-1, 10-2, ..., 10-n that are responsible for the nth pixel (pixel #n). The optical modulator is responsible for the image information of the one-dimensional image of the vertical scanning line or the horizontal scanning line (assuming that the vertical scanning line or the horizontal scanning line is composed of n pixels), and each micromirror 10-1, 10-2. , ..., 10-n) are in charge of any one of the n pixels constituting the vertical scan line or the horizontal scan line.

Hereinafter, the principle of light modulation will be described based on the first pixel (pixel # 1), but the same may be applied to other pixels.

In this embodiment, it is assumed that there are two holes 4b-1 formed in the ribbon structure 4. Due to the two holes 4b-1, three upper reflective layers 4a-1 are formed on the ribbon structure 4. Two lower reflective layers are formed in the insulating layer 2 corresponding to the two holes 4b-1. In addition, another lower reflective layer is formed on the insulating layer 2 corresponding to a portion of the gap between the first pixel (pixel # 1) and the second pixel (pixel # 2). Accordingly, the number of upper reflective layers 4a-1 and lower reflective layers per pixel is the same, and as described above with reference to FIG. 1, the luminance of modulated light is adjusted using zero-order diffraction light or ± first-order diffraction light. It is possible.

3 is a cross-sectional view taken along line AA ′ of FIG. 2. Assume that the 0th order diffracted light is used as the modulated light.

, λ는 입사광의 파장, n은 정수)이 되도록 하면 상쇄 간섭으로 인해 변조광은 최소 휘도(Black)를 나타낸다. Referring to FIG. 3, the upper reflective layer 4a-1 formed on the ribbon structure 4 of the micromirror corresponding to the first pixel pixel # 1 and the lower reflective layer 2a-1 formed on the insulating layer 2 are formed. ) Is the first interval (

,? is the wavelength of the incident light, n is an integer) and the modulated light shows the minimum luminance (Black) due to the destructive interference.

)이 되도록 하면 보강 간섭으로 인해 변조광은 최대 휘도(White)를 나타낸다. The interval between the upper reflective layer 4a-1 formed on the ribbon structure 4 and the lower reflective layer 2a-1 formed on the insulating layer 2 is equal to the second interval (

), The modulated light exhibits maximum luminance due to constructive interference.

To this end, the upper reflective layer 4a-1 on the ribbon structure 4 indicated by a solid line should have a change in displacement by l ₁ or L ₁ .

However, the ribbon structure 4 may be in a position indicated by a dotted line rather than an initial position indicated by a solid line even when voltage is not applied to the piezoelectric body 5 due to frequent vertical movements over time. In this case, the upper reflective layer 4a-1 on the ribbon structure 4 should have a change in displacement by l ₁ 'or L ₁ ' in order to display the minimum luminance black or the maximum luminance white.

) 또는 제2 간격(

)이 되도록 하기 위해서 실선으로 표시된 리본 구조물(4) 상의 상부 반사층(4a-2)은 ℓ₂ 또는 L₂ 만큼 변위의 변화가 있 어야 한다.In addition, in the case of the second pixel (pixel # 2) other than the first pixel (pixel # 1), the initial position indicated by the solid line may be different from the initial position of the first pixel (pixel # 1). In this case, the interval between the upper reflective layer 4a-2 and the lower reflective layer 2a-2 of the second pixel pixel # 2 is the first interval (

) Or second interval (

The top reflective layer 4a-2 on the ribbon structure 4, represented by the solid line, must have a change of displacement by ₁ or ₂ by.

However, even in the case of the second pixel (pixel # 2), even when no voltage is applied to the piezoelectric body 5 due to frequent vertical movements over time, the ribbon structure 4 is not in the initial position indicated by the solid line. It happens that you are in the marked position. In this case, the upper reflective layer 4a-2 on the ribbon structure 4 must have a change in displacement by L ₂ 'or L ₂ ' in order to indicate the minimum luminance Black or the maximum luminance White.

That is, it can be seen that the amount of change in displacement for displaying the minimum luminance Black or the maximum luminance white differs for each pixel, and thereafter, there is a difference in compensating the amount of displacement. Therefore, in the present invention, it is preferable to separately compensate for each pixel by measuring a compensation value required for each pixel.

4 and 5 illustrate a case where the displacement between the upper reflective layer 4a and the lower reflective layer 2a of the micromirror increases or decreases from the initially set displacement over time.

Referring to FIG. 4, the curve 400 of the voltage applied versus displacement 400 and the curve 410 of the displacement versus intensity set at the time of fabrication of the micromirror have a displacement when the control voltage is Vmin. Dmin 406, the luminance is Imin 402, and when the control voltage is Vmax, the displacement is Dmax 405 and the luminance is Imax 401.

That is, the control voltage is adjusted from Vmin to Vmax to change the displacement from Dmin 406 to Dmax 405 so that the luminance of the modulated light has Imin 402 which is the minimum luminance and Imax 401 which is the maximum luminance.

However, as shown in FIG. 3, when the position of the upper reflective layer 4a is different from the initial position as shown in FIG. 3, even if the control voltage is equally applied to Vmin to Vmax, a value intended for displacement and luminance is not output.

For example, as shown in the first pixel # 1 of FIG. 3, when the position of the upper reflective layer 4a approaches the lower reflective layer 2a as time passes, the control voltages Vmin to Vmax are applied. The target displacement is not reached and only the first displacement 436 to the second displacement 435 are reached. Therefore, in the case of the first displacement 436, modulated light having the first luminance 432 is output, and in the case of the second displacement 435, the modulated light having the second luminance 431 is output. That is, although the modulated light having the minimum luminance and / or the modulated light having the maximum luminance is output, the first luminance 432 and / or the second luminance (not the minimum luminance 402 and / or the maximum luminance 401) is output. And outputs modulated light having 431.

As another example, as shown in the second pixel (pixel # 2) of FIG. 3, when the position of the upper reflective layer 4a moves away from the lower reflective layer 2a with time, a control voltage of Vmin to Vmax is applied. Also, the target displacement is not reached and only reaches the third displacement 426 to the fourth displacement 425. As a result, the modulated light having the third luminance 422 is output in the case of the third displacement 426 and the modulated light having the fourth luminance 421 in the case of the fourth displacement 425. That is, although the modulated light having the minimum luminance and / or the modulated light having the maximum luminance is output, the third luminance 422 and / or the fourth luminance (not the minimum luminance 402 and / or the maximum luminance 401) are output. And modulated light having 421.

Thus, the curve of displacement vs. luminance 410 with time does not change, and the variation of displacement is compensated because the curve of control voltage vs. displacement 400 changes to the displacement increasing curve 420 or the displacement decreasing curve 430. Just do it.

When centering on the minimum luminance Imin 402, when it corresponds to the third luminance 422 which is the luminance when the displacement corresponds to the third displacement 426 and the first displacement 436 where the displacement is reduced. It is difficult to determine whether the first luminance 432, which is the luminance of R, is larger than the minimum luminance Imin 402 so that the displacement increases or decreases.

Further, even when the maximum luminance Imax 401 is centered, the fourth luminance 421 which is the luminance when the displacement corresponds to the fourth displacement 425 is increased, and the second displacement 435 where the displacement is reduced. It is difficult to determine whether the displacement increases or decreases since the second luminance 431, which is the luminance at that time, becomes smaller than the maximum luminance Imax 401.

Accordingly, as shown in FIG. 5, the intermediate displacement Dmid 407 and the intermediate control voltage Vmid corresponding to the intermediate luminance Imid 403, which are about the middle of the minimum luminance Imin and the maximum luminance Imax, are obtained. Decide

When the intermediate control voltage Vmid is applied, the displacement increasing curve 420 has a fifth displacement 427, and the fifth luminance 423 is displayed. According to the sixth displacement 437, the sixth luminance 433 is displayed. Since the fifth luminance 423 has a large value and the sixth luminance 433 has a small value when compared to the intermediate luminance Imid 403, the upper reflecting layer 4a and the lower reflecting layer 4b of the micromirror currently applicable. It is possible to obtain information on the interval between the gaps, that is, whether the displacement increases or decreases. On the basis of this, it is possible to determine the compensation direction such as reducing or increasing the displacement.

Alternatively, any three or more control voltages among control voltages Vmin to Vmax are selected to search for corresponding displacements and luminances, respectively. Displacement and luminance according to three or more control voltages are also searched by three or more. By using this, it is possible to find the maximum and minimum points from the approximated curve about the relationship between the luminance and the control voltage. This is because the curve of displacement vs. brightness 410 has a similar shape to the cubic curve (see FIG. 5), so that it is possible to approximate the curve of curve vs. 410 from three or more points.

6 is a diagram illustrating a method for finding an approximated curve according to a preferred embodiment of the present invention.

Referring to FIG. 6, one frame image includes a main screen 620 for outputting image information to be displayed to a user, and a first or second screen at both ends of the main screen 620 before and after output of the main screen 620. A blank time area 610 or 630. A predetermined luminance value is output in the first or second blank time region 610 or 630, and the luminance at that time is measured by a photodiode.

The control circuit applies a control voltage corresponding to the luminance to be displayed on the screen to the optical modulator to output the modulated light modulating the incident light. Therefore, the relationship between the specific luminance and the control voltage to be applied to the optical modulator in order to output it is in the form of a lookup table (LUT). The reference table is a table for quick calculation of the relationship between the displacement according to the control voltage and the luminance according to the displacement as shown in FIG. 3 or 4.

If the control voltage is applied according to the reference table set at the time of manufacture of the optical modulator due to the above-described problems such as the initial position of the ribbon structure 4 of the micromirror 10 of the optical modulator changes over time. The desired brightness will not be output. Therefore, in the first or second blank time region 610 or 630, the reference table is updated by measuring the luminance according to the control voltage at regular intervals. The control voltage applied in the first or second blank time region 610 or 630 for updating the reference table is called a sampling voltage, and the luminance measured from the modulated light is called a sampling luminance.

It is possible to output one frame image for the first blank time region 610 and the second blank time region 620 and measure the sampling luminance according to the sampling voltage at the same time or only one. In the present embodiment shown in FIG. 6, the sampling luminance according to the sampling voltage is measured for all pixels of the vertical scanning line, or the sampling luminance according to the sampling voltage is measured for only one or more specific pixels. It is also possible to measure the sampling luminance according to the sampling voltage applied to the plurality of pixels by performing spatial division or time division such as A1 and A2 in the first or second blank time region 610 or 630.

It is preferable to apply three or more sampling voltages to each pixel to measure corresponding sampling luminances, respectively. As shown in FIG. 3 or FIG. 4, the curve of the luminance according to the displacement has a form similar to that of the cubic curve, and thus it is easy to obtain an approximated curve when three or more values are known. The control voltages corresponding to the maximum and minimum values of the luminance and the maximum and minimum values of the luminance are respectively retrieved from the approximated curve, and the reference table is updated based on these values. That is, the relationship between the control voltage and the luminance is reset in the reference table to set the control voltage at which the current maximum luminance is output to the maximum voltage and to set and maintain the control voltage at which the minimum luminance is output to the minimum voltage.

Hereinafter, a display apparatus and a method for compensating for a change in displacement of an optical modulator with time as described above will be described.

7 is a schematic configuration diagram of a display device for compensating an optical modulator according to an exemplary embodiment of the present invention.

Referring to FIG. 7, the display device includes a light source 710, an optical modulator 720, a scanner 730, a photodiode 750, and a control circuit 770. The optical direction converter 740 or the analog / digital converter 760 may further include.

The light source 710 irradiates light to project the image onto the screen 880. The light source 710 may radiate white light, or may radiate any one of three primary colors of red, green, and blue light. Preferably the light source 710 may be a laser, LED or laser diode. When irradiating white light, a color separation unit (not shown) may be provided to separate white light into red light, green light, and blue light according to a predetermined condition.

An illumination optical system (not shown) is provided between the light source 710 and the light modulator 720 to reflect the direction of the light projected from the light source 710 at a predetermined angle so that the light can be concentrated in the light modulator 720. . When color separation is performed by a color separator (not shown), a function of concentrating the light may be added.

The optical modulator 720 modulates the light irradiated from the light source 710 according to a control signal (for example, a control voltage) received from the control circuit 770 to generate modulated light that is diffracted light. The optical modulator 720 controls the luminance to be output in correspondence with any one of the vertical scan lines of the image to be displayed or the luminance to be output in correspondence with any one of the horizontal scan lines. The optical modulator 720 includes a plurality of micro mirrors as described above.

A plurality of micromirrors 10-1, 10-2,..., And 10-n, which are responsible for one pixel, are gathered together (n is a natural number) to form an optical modulator 720 (see FIG. 2). The optical modulator 720 includes a plurality of micromirrors 10-1, 10-2, ..., 10-n, which are diffracted light, that is, modulated light having various signal sizes with respect to a constant incident light by the above-described interference principle. As a device capable of generating a signal to light, the device responsible for the vertical scanning line which is a one-dimensional image as described above is collectively referred to. Hereinafter, the optical modulator 720 will be described as being in charge of a vertical scanning line composed of n pixels (n is a natural number), that is, a one-dimensional image, but may also be in charge of a horizontal scanning line.

The optical modulator 720 may include a driving integrated circuit generating a driving voltage of each pixel according to luminance information to be output from each pixel constituting the vertical scanning line included in the control signal, and a light according to the driving voltage generated from the driving integrated circuit. Is composed of a plurality of micromirrors 10-1, 10-2, ..., 10-n for generating modulated light, the diffracted light of which the light intensity is modulated using the interference or diffraction principle.

The plurality of micro mirrors 10-1, 10-2, ..., 10-n is preferably equal to the number of pixels constituting the vertical scanning line. The modulated light is light in which image information (ie, luminance information of each pixel) of the vertical scanning line to be projected on the screen 780 is reflected later. Here, the modulated light may be zero-order diffraction light or ± first-order diffraction light.

The relay optical system (not shown) allows the modulated light generated by the optical modulator 720 to be transmitted to the scanner 730. One or more lenses may be included, and modulated magnification may be adjusted to suit the size of the optical modulator 720 and the size of the scanner 730 to transmit modulated light as necessary.

The scanner 730 reflects the modulated light incident from the light modulator 720 at a predetermined angle and projects it onto the screen 780. At this time, the predetermined angle is determined by the scanner control signal received from the control circuit 770. The scanner control signal rotates the scanner 730 at an angle at which the modulated light can be projected at the position of the vertical scan line on the screen 780 corresponding to the control signal in synchronization with the control signal.

The scanner 730 may be a galvanometer scanner or a polygon mirror scanner. The galvano scanner has a rectangular plank shape and a mirror is attached to one side. It rotates from side to side within a predetermined angle range about an axis, and in the present invention, the image is projected on the screen 780 by changing the angle of reflection of the incident light when rotating in either the left or right direction or left and right directions. Polygon mirror scanners have the shape of a polygonal column with mirrors attached to the sides of the polygonal column. A mirror attached to each side and rotating in one direction about an axis changes an angle of reflection of light incident by the rotation to project an image on the screen 780.

Projection optics (not shown) cause the modulated light reflected by the scanner 730 to be projected onto the screen 780. Projection lens (not shown).

The photo diode 750 measures sampling luminance from modulated light output from the optical modulator 720 according to the sampling voltage. Since the sampling voltage is set to be applied to the optical modulator 720 in the first or second blank time region 610 or 630 as shown in FIG. 6, the photodiode 750 may be configured as a first or second blank time region (see FIG. 6). Only operating at 610 or 630 is advantageous for power consumption.

The display device may further include a light direction converter 740 to incident modulated light to the photodiode 750. The light direction converter 740 separates or partially reflects a portion of the modulated light from the light modulator 720 to the scanner 730 to be incident to the photodiode 750. The light direction converter 740 may be a beam splitter or partial reflect optics. That is, about 99% of the modulated light passes through the scanner 730, and about 1% of the modulated light is directed to the photodiode 750.

The sampling luminance measured by the photodiode 750 is an analog signal, and the bar display device may further include an analog / digital converter 760 for converting the analog signal into a digital signal. It is advantageous for power consumption that the analog-to-digital converter 760 operate only in the first or second blank time region 610 or 630 as with the photodiode 750.

The control circuit 770 has a reference table indicating the relationship between the control voltage applied to the optical modulator 720 and the luminance, and the predetermined control voltage is applied to the optical modulator 720 so that the desired luminance is output according to the reference table. do. Three or more sampling voltages are applied to the optical modulator 720 in the first or second blank time region 610 or 630, thereby receiving the sampling luminance measured by the photodiode 750. Then, the approximated curve is searched according to the relationship between the sampling voltage and the sampling luminance, the luminance and control voltage representing the maximum point of the approximated curve, the luminance and control voltage representing the minimum point are found, and the already stored reference table is updated.

In addition, the control circuit 770 receives an image signal corresponding to one frame and controls the optical modulator 720 and the scanner 730 according to the image signal. The control circuit 770 transmits the luminance information of each pixel constituting the frame to the optical modulator 720, so that the vertical scan line is properly projected on the screen 780 in accordance with the control signal transmitted to the optical modulator 720. 730 to adjust the rotation angle. In the present invention, when the plurality of vertical scan lines corresponding to one frame are all the same, the scanner 730 may be rotated at a predetermined angular velocity.

8 is a flowchart of a method of compensating for a change in displacement of an optical modulator according to an exemplary embodiment of the present invention.

In step S810, the control circuit 770 causes the driving integrated circuit to apply the sampling voltage to the optical modulator 720 through the control signal. Preferably, the sampling voltage is three or more, and is applied to the micromirror of the light changing device 720 that is responsible for the pixel in the first or second blank time region 610 or 630.

In operation S820, the photodiode 750 measures the sampling luminance of the modulated light output from the optical modulator 720 according to the sampling voltage.

In step S830, the control circuit 770 recalculates the relationship of the luminance with respect to the control voltage of the current optical modulator 720 from the sampling voltage and the corresponding sampling luminance, and updates the reference table.

As described above, the display device and the optical modulator compensation method according to the present invention measure the amount of change of the displacement of the micromirror over time to compensate for the control voltage for the same input so that the gradation displayed on the screen always shows a constant luminance.

In addition, a constant image quality is always output.

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.

Claims (12)

Light source; An optical modulator for outputting modulated light whose luminance is changed from incident light from the light source in accordance with an applied control voltage; A scanner for projecting the modulated light to a predetermined position on a screen; A photodiode measuring a sampling brightness of modulated light output from the optical modulator receiving a sampling voltage; And According to a reference table showing a relationship between the brightness and the control voltage, the control voltage preset to have the brightness of the modulated light is applied to the optical modulator, and the sampling voltage and the sampling brightness of the light modulator A control circuit for updating the reference table by recalculating the relationship of the luminance to the control voltage Display device comprising a. The method of claim 1, Further comprising a light direction converter for changing the direction of the portion of the modulated light directed to the scanner, And the photodiode receives a portion of the modulated light whose direction is changed by the optical direction converter. The method of claim 1, And the optical modulator receives the sampling voltage at a blank time before an arbitrary frame image is output. The method of claim 1, And the optical modulator receives the sampling voltage at a blank time after an arbitrary frame image is output. The method according to claim 3 or 4, The optical modulator is composed of a plurality of micro mirrors each responsible for one pixel, And one micro mirror from among the plurality of micro mirrors receives the sampling voltage with respect to one frame image. The method of claim 5, And the optical modulator receives three or more sampling voltages for one pixel during the blank time. According to a reference table showing the relationship between the luminance and the control voltage, the physical deformation of the optical modulator for outputting the modulated light that changes the luminance of the incident light from the light source in accordance with the control voltage set to have the luminance is obtained. In the compensation method, (a) causing a sampling voltage to be applied to the optical modulator; (b) measuring sampling luminance of modulated light output from the optical modulator according to the sampling voltage; And (c) updating the reference table by calculating a relationship of the luminance with respect to the control voltage of the optical modulator from the sampling voltage and the sampling luminance; Optical modulator compensation method comprising a. The method of claim 7, wherein The step (c) comprises repeating the steps (a) to (b) three or more times for different sampling voltages. The method of claim 7, wherein The step (a) is an optical modulator compensation method for applying the sampling voltage at a blank time before any frame image is output. The method of claim 7, wherein The step (a) is the optical modulator compensation method for applying the sampling voltage at the blank time after the arbitrary frame image is output. The method of claim 9 or 10, The step (a) is applied to the optical modulator compensation method for applying the sampling voltage for one pixel to one frame image. The method of claim 11, and (d) repeating the steps (a) to (c) by changing the position of the pixel applying the sampling voltage for each successive frame image.

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