KR20050021015A - Synchronizing optical scan and electrical addressing of a single-panel, scrolling color lcd system - Google Patents

Abstract

An electrical scan that applies data for one of the red, green, and blue colors of a liquid crystal display (LCD) to the pixels of each row of the display, and the optical scan of the panel with color stripes of that color is one color. Synchronized to ensure sufficient time for the switching of pixels from one value to another. Synchronizing the electrical and optical scans creates a better color rendition of the displayed image without any inter-color mixing drawbacks. An array or group of photosensors is laterally adjacent to the active portion of the panel, each array being covered by a filter that only passes light of one of the three colors (red, green, blue) used for the display. By providing an indication of the position of the leading and trailing edges of each color stripe at each moment, the color stripes provide an optical scan together with electrical signals from sensors providing the instantaneous velocity of each stripe. Scroll simultaneously on the active portion of the array and the sensors. The signals from the sensors are controlled to determine the order of the colors to which the rows of pixels are addressed and to provide data at each addressed position to maintain significant switching time despite changes in the relative speed of the three color stripes. To the circuit.

Description

SYNCHRONIZING OPTICAL SCAN AND ELECTRICAL ADDRESSING OF A SINGLE-PANEL, SCROLLING COLOR LCD SYSTEM}

BACKGROUND OF THE INVENTION The present invention generally relates to color liquid crystal displays (LCDs), which are sequentially scanned on a panel made up of a plurality of pixels arranged in rows of red, green and blue color stripes, and more specifically, optical scanning and electrical addressing. A method and apparatus for generating a better color rendition of a displayed image by synchronizing the scans without any disadvantages of inter-color mixing.

Single-panel color LCD systems often have signals corresponding to the color of the light that is projected to the row and optical scans made by successive scrolling of differently colored stripes of red, green, and blue on the pixels that make up the panel. Driven by a signal generated in response to an electrical scan indicative of the address of a row of pixels. Although rotary color wheels and other means are already used, optical scans are often created by a set of three scanning prisms. Although the prism is intended to rotate at a constant angular velocity, the stripes made on the surface of the panel do not necessarily move at a constant linear velocity. However, an electrical address scan signal is generated and moved through the rows of panels in a linear manner. This means that the leading edge of the color stripe where the data is provided by electrical scan and optical scan, ie electrical scan, is not separated by a time force sufficient for the pixel to switch in intensity, so that the inter This means that color mixing drawbacks can be created.

Typically, a given row of panels is addressed with data corresponding to one color, followed by scanning a panel with stripes of that color. Then, the same row with the first fixed offset is addressed with data corresponding to the second color, followed by scanning the panel with the stripe of the second color. Thereafter, the same row with the second fixed offset is addressed with the data corresponding to the third color, followed by scanning the panel with stripes of the third color. The next row is then addressed with data corresponding to the first color, and so on. In order to minimize the aforementioned distortions in the time interval between the electrical and optical scans and thereby reduce the color error resulting from the inter-color mixing disadvantages, two fixed offsets are measured as measured in the center of the panel. Corresponds to the size of the optical stripes (of row distance). Manual adjustment of the relative rotation phase of the three prisms, with a set of red, green, and blue test patterns, is done to visually minimize color errors. However, due to the potential mismatch in electrical and optical scans, i.e., the distortion of the time interval between the electrical address signal at a particular location on the panel and the projection of the leading edge of the color stripe at that location, the system can It is easy to receive.

1 shows the trailing edge of one color (red) stripe, the electrical addressing of the panel with data for the next color (green), and the green color stripe in prior art systems (i.e., systems not using the present invention). A graph showing a typical scan of panel position versus time of the leading edge of.

2 schematically shows an LCD panel with a preferred form of the appliance of the invention.

FIG. 3 is another view of the panel of FIG. 2, showing a colored stripe scrolled from top to bottom, and including a block diagram portion illustrating an implementation of the present invention;

4 is a graph of the same parameters as in FIG. 1 when implementing the present invention.

The present invention is intended to overcome one or more problems or disadvantages associated with the related art.

The present invention provides a method of forming a delay of at least minimum duration between the electrical addressing of a panel position with the data for the next color stripe to be scrolled across the panel and the leading edge of the color stripe projected at the addressed position. ; Preferred mechanisms for implementing the method are also disclosed and form part of the present invention. A fixed delay is chosen to allow enough time for the pixel to switch from one color value to another, and will vary with the frame rate and liquid crystal response time of the system. For discussion of the present invention, the minimum duration of the delay is 2.5m. A fixed delay is achieved by three arrays of light sensors, where each light sensor with a filter is sensitive to one of the color stripes scrolling across the panel. The photosensor array is integrated into the display panel itself, for example in three, laterally adjacent, vertical regions along the right side of the panel.

As each horizontal color stripe scrolls vertically down the panel surface, the sensor array for each color indicates the row position of the leading and / or lagging edge of each color stripe at any instant in time. Will generate a signal. Signals from each sensor array are input to a control circuit that can adjust the position of the next electrically addressed row for each color. The control circuit is adapted to determine a selection for the row to be addressed next and a best choice for color data information based on the relative speed of the color stripe as scrolled across the panel. That is, rather than following a fixed sequence of row addressing for each color (i.e., row N is addressed as red data, then green data, then blue data, and row N + 1). Is addressed red, then green, then blue, row N + 2 is addressed red, and so on. The control circuit ensures at least a minimum time delay between addressing and scanning. In response to a change in the relative speed of scanning of the color stripes, addressing may be directed in a different order. By "synchronizing" the addressing and scanning function, the present invention creates a better color rendition of the displayed image without the disadvantages of inter-color mixing.

In the accompanying drawings, like reference numerals generally indicate corresponding parts.

Optical scanning of LCD panels with continuous color (red, green and blue) stripes is generated by a set of three scanning prisms. Although the prisms rotate at essentially constant angular velocity, the stripes produced on the surface of the panel do not necessarily move at a constant linear velocity. This means that the distance between stripes (from the trailing edge of one stripe to the next leading edge) can change as the stripes scroll across the surface of the panel while the stripe's relative speed varies. The electrical addressing of the rows of panels with data relating to the next color to be scanned is constant and proceeds at line speed, regardless of the speed of the color stripes. In order to effectively display an image on a panel, an electrical address is placed in the row at least at a minimum time prior to the color stripe projecting onto the row to allow enough time for pixels on the panel to switch from one color value to another. Should be applied.

In current addressing schemes for LCD panels, successive rows are fixed without synchronization between electrical addressing and optical scan and addressed with repeated sequence of color data. That is, the row is addressed as follows:

1. Address a row at position N with data corresponding to the red data for that row.

2. Specify the row address at position (N + offset ^? 1) with data corresponding to the green data for that row.

3. Row addressing at position (N + ^Δ 1 + ^Δ 2) with data corresponding to blue data for that row.

4. Specify the row address at position (N + 1) with data corresponding to the red data for that row.

5. Specify the row address at position (N + 1 + ^Δ 1) with data corresponding to the green data for that row.

6. Specify the row address at position (N + 1 + ^Δ 1 + ^Δ 2) with data corresponding to the blue data for that row. And in this way, the order of the colors can of course be other than RGB.

Indeed, optical scans of successive color stripes can be subtracted in time by different amounts because the relative speed of the scan across the surface of the panel is variable. This effect is shown in the graph of FIG. The solid line 10, which represents an address signal generated at a constant speed, is a straight line. The dotted lines 12, 14, which represent the trailing edge of the red color stripe (the end of red) and the leading edge of the green stripe (the start of green), respectively, are not linear because of the change in the speed of movement of each stripe. That is, line 12 indicates where the trailing edge of the red optical stripe is located on the panel, and line 14 indicates where the leading edge of the green optical stripe is located. Since the time period between the electrical addressing of the panel position and the optical scan of that position varies with the change in the speed of the optical scan, the time on which the pixel on the panel is available to switch from one color value to another The amount may be insufficient to avoid inter-color mixing. In the example of FIG. 1, a threshold switch time of 1.0 ms is shown; That is, the green electrical data is only 1 ms ahead of the leading edge of the green color stripe that illuminates that particular row. At another location on the panel, this can be a much longer time, causing the pixel to settle to the green data value before the green optical stripe arriving at that location.

To minimize the inter-color mixing drawbacks, it is necessary to wait for the red optical stripe to pass over a particular row before electrically addressing the row with green data. If it is determined that a minimum delay of 2.5m between the electrical addressing and the optical scan is needed to allow full pixel switching time, the overlap of the trailing edge of the red color stripe and the electrical addressing at a specific location on the panel is It is clear at that location that the leading edge of the green stripe must be at least 2.5 m ahead. This ensures that the electrical address is addressed at linear speed, but between the trailing edge and the leading edge of the continuous stripe, while ensuring that the address is given at least 2.5 ms before the leading edge of the next color stripe despite the change in stripe speed. While it can be achieved by providing a much longer delay, the delay will not be acceptable in a color LCD system. Attempts have been made to minimize such errors by adjusting two fixed offsets ( ^Δ 1 and ^Δ 2 or higher) to correspond to the size of the optical stripe (at row distance) as measured at the center of the panel. Manual adjustment of the relative rotational phases of the three prisms was done to visually minimize color error with a set of red, green, and blue test patterns.

The present approach to this problem is illustrated in FIGS. 2 and 3. The active portion 16 comprises rows and columns of pixels of a conventional color LCD panel on which a visual display is formed. Vertical stripes 18, 20, 22 on the right side of active portion 16 represent a sensing portion of a panel consisting of three groups or arrays of photosensors, each of which is covered with a color filter. The filters are such that the filter in the stripe 18 passes only red light, the filter in the stripe 20 only green light, and the filter in the stripe 22 only blue light. Thus, as the color stripe scrolls across the surface of the panel comprising both the active portion 16 and the sensing portion, ie, the stripe 18, 20, 22, the light sensors in the stripe 18, 20, 22 are each red. Receive and generate signals only in response to green, green, and blue light. In the case of LCOS (liquid crystal on silicon) technology where display panels are made in standard silicon CMOS processes, incorporating such optical sensors into the display panel itself becomes very realistic. The stripes 18, 20, 22 are located side by side along the right side of the active portion 16 and have a combined width that is preferably less than half the width of the active portion 16. It is important to note that the sensitivity of the sensor to the amount of light it can capture is important, not the individual area.

3 shows a colored stripe scrolled downward on the panel surface. The complete red stripe 24 is visible in the figure from the leading edge 26 to the trailing edge 28. The leading edge 30 of the green stripe 32 is shown, but the trailing edge of this stripe has not yet reached the panel in the position shown. In the same way, the trailing edge 34 of the blue stripe 36 is shown. However, the leading edge has already passed through the bottom of the panel. The shaded area 38 represents the light sensor in the stripe 18 that generates a signal in response to an optical scan of the portion of the stripe 18 covered by the red stripe 24 and thus the depicted portion of the stripe. The dark areas 40, 42 represent portions of the stripe 20, 22, respectively, covered by the green and blue stripes 32, 36, respectively. Thus, each group of sensors will output a signal corresponding to the row position where the leading and trailing edges of each of the three color stripes are located at a distance from each other. The output signal from the photosensor in each vertical stripe is connected to the control circuit, represented by block 44. This circuit produces an output signal corresponding to the speed of movement of the color stripes across the surface of the display panel. These signals are provided to the electrical addressing block 46.

The signals from the photosensors in the stripes 18, 20, 22 tell the control circuit 44 the instantaneous position and velocity of the color stripe. The function of the control circuit 44 is to determine the best choice as to which row should be addressed next and which color data information to use to maintain addressing for at least a predetermined time interval (2.5 ms) before color stripes. It is to process these signals. That is, if the input signal to the control circuit 44 indicates that the red color stripe moves faster than the green and blue stripes, this instructs the addressing block 46 to address the corresponding row faster with the red color data. Should be. In practice, since the control circuitry functions to synchronize the two scans, electrical addressing corresponds to the optical scan in time.

In the example of a red stripe that advances faster than a green and blue stripe at a specific location on the panel, electrical addressing results in one or more consecutive rows of data for the red color before addressing the row located for irradiation of the green and blue stripe. Will be guided by control circuitry 44 to address. In this case, the sequence of row addressing may be as follows:

1. Addressing a row at position N with data corresponding to the red data for that row

2. Addressing a row at position (N + 1) with data corresponding to the red data for that row

3. Addressing a row at position (N + ^Δ 1) with data corresponding to the green data for that row

4. Address the row at position (N + ^Δ 1 + ^△ 2) with data corresponding to the blue data for that row

5. Address the row at position (N + 2) with data corresponding to the red data for that row

6. Address the row at position (N + 3) with data corresponding to the red data for that row

7. Address the row at position (N + 1 + ^Δ 1) with data corresponding to the green data for that row

8. Addressing of the row at position (N + 1 + ^Δ 1 + ^Δ 2) with data corresponding to the blue data for the row, and so on.

4 provides a graph of the scanning of the trailing edge 48 and leading edge 50 of the red and green stripes, respectively, and the electrical addressing of the rows with green color data in an implementation of the present invention. The graph corresponds to the graph of the same parameters of FIG. 1. However, instead of a straight (bold) addressing line 52, which exhibits a constant velocity as in FIG. 1, this is essentially parallel to the dashed line 50, which represents the leading edge of the green color stripe. This means that addressing of the rows with green color data remains prior to irradiation of the green stripe, for example by at least a critical switching time of 2.5 ms.

The addressing order will change in response to changes in the position, color, and speed of the stripe on the panel. The present invention ensures that the data for a row is addressed in a manner synchronized with an optical scan on the panel, while providing the critical switching time required for the pixel to change from one color value to another. This allows for a more uniform pixel switching time at all locations on the panel. In addition, the use of photosensors to determine the position of the stripes at all times eliminates the need to manually adjust the prism. This is advantageous because any change in the system due to movement of the optical machine, or mechanical wear or slip of the prism motor will be compensated by synchronized electrical addressing, thus avoiding any color error in the displayed image.

Other aspects and features of the invention may be obtained by reference to the drawings, the disclosure, and the appended claims.

As described above, the present invention can be applied to methods and apparatus for producing better color rendition of displayed images without synchronizing optical scans and electrical addressing scans without any inter-color mixing disadvantages.

Claims (19)

A method of driving a single-panel, scrolling color liquid crystal display comprising an array of pixels arranged in a plurality of rows, wherein the plurality of different colored stripes are trained in a continuous stripe of spaced apart relations to provide an optical scan and Scrolled continuously in a predetermined direction across the surface of the panel with a leading edge, the leading edge of each of the stripes leading to an electrical addressing scan indicating addressing of discrete locations on the panel with data for a subsequent one of the colors. A method for driving a single-panel scrolling color liquid crystal display, a) providing an electrical signal (12, 14) to the leading and trailing edges of each said stripe present on said panel corresponding to a continuous indication of a position on said panel; And b) generating the electrical addressing scan at a time preceding a leading interval of the leading edge of the subsequent color stripe, the predetermined interval being from one color value to another value of the individual pixels of the display. Generating an electrical addressing scan sufficient to allow for a complete switching time. The method of claim 1, wherein the electrical signal is generated by light sensors. 3. The apparatus of claim 2, wherein the photosensors are arranged in a plurality of groups corresponding to the number of the plurality of different colors, each group responsive to each of the colors. Way. 4. The unit of claim 3, wherein the panel is divided into a first portion 16 containing the pixels and forming an active display and a second portion 18, 20, 22 comprising a group of photosensors. A method of driving a scrolling color liquid crystal display of a panel. 5. The method of claim 4, wherein the panel is made in a standard silicon CMOS process with the pixels and the photosensor integrated in the panel. A method of driving a single-panel, color LCD to improve color rendition of the displayed image without the disadvantages of inter-color mixing. The electrical addressing of the rows of pixels constituting the panel with data for a predetermined color and the optical scan of the panel with light stripes of a predetermined color are synchronized (44, 46), so that the electrical addressing And providing a predetermined time delay between the optical scans of the rows of cells of the single-panel color LCD. The method of claim 6, wherein the synchronizing step comprises a continuous monitoring step 44, 46 of at least one of the velocity and position of the light stripe 18, 20, 22 for each of the colors. Panel, how to drive color LCD. 8. The single-panel color LCD of claim 7, wherein the speed and / or position monitoring step is performed by light sensors passed by the optical scan with the light stripes 18, 20, 22. How to drive. 8. The single-panel, color LCD of claim 7, wherein the step of synchronizing further comprises controlling the position of the electrical addressing and the color data sequence in response to the light stripe speeds (18, 20, 22). How to drive it. 8. The method of claim 7, wherein the predetermined time delay is established above a minimum critical switching time of the pixels from one color value to another. An apparatus for controlling the timing of an electrical addressing signal provided to a row of pixels of a panel for successive optical scans by a plurality of different colored light stripes scrolling across an LCD panel surface. a) a plurality of groups of optical sensors 18, 20, 22 corresponding to the plurality of different colors numerically, each group producing an electrical signal in response to the projection of the corresponding one of the colors; And the groups are positioned to receive the optical scan as the optical scan scrolls across the panel, whereby the electrical signals are at least one indication of the speed and position of the optical scans. A plurality of groups of 18, 20, 22); b) a control circuit 44 in which the electrical signals are provided as an input signal, the control circuit generating a control signal corresponding to the speed and / or positions of each of the optical scans indicated by the input signals. (44); And c) addressing circuit 46 adapted to generate electrical scans each directed to a particular one of the rows with color data for one of the colors in response to the control signals, the order and data of addressing of the rows. The selection of the color to which is provided is selected by the control circuit to maintain a threshold switching time between the electrical scan and the optical scan for providing color data for one of the colors, the switching time Is an addressing circuit (46), sufficient to cause the pixel to change from one value to another value. 12. The method of claim 11, wherein each of said groups of photosensors 18, 20, 22 are covered by a filter that passes only light of one of said plurality of colors. Device for. 13. Apparatus according to claim 12, wherein said photosensors (18, 20, 22) are integrated on the surface of said LCD panel. 14. The apparatus of claim 13, wherein the number of the plurality of colors is three, ie red, green and blue. 15. The apparatus of claim 14, wherein the group of photosensors are arranged in a side by side relationship in a stripe extending along one or both side edges of the panel. As a color LCD panel, a) an active portion comprising a plurality of horizontal rows of individual pixels, each active in response to an electrical scan conveying data for one of the plurality of colors and an optical scan scrolled in a vertical direction with the action of the pixel part; And, b) one side of the active portion numerically corresponding to the plurality of colors, to receive the optical scan simultaneously with the active portion, and to generate an electrical signal in response to the projection of the optical scan And a sensing portion comprising a plurality of arrays of photosensors (18, 20, 22) laterally adjacent to the color LCD panel. 17. The color LCD panel of claim 16, wherein the number of the plurality of colors and arrays is three. 18. The color LCD panel of claim 17, further comprising three color filters, one located in a covering relationship for each of the arrays, wherein each of the filters passes light through each one of the colors. . 19. The color LCD panel of claim 18, wherein the pixels and photosensors are integrated on the panel and the panel is made with standard CMOS process technology.