KR20060015644A - Lcd display panel including segmented illumination scheme by scrolling illumination of the corresponding panel segments - Google Patents

Abstract

A step -wise scrolling of an LC display device is achieved using an array of modulatable/controllable light sources. The LC display is segmented, and each segment is addressed and subsequently illuminated simultaneously with each of the other segments. In addition to other benefits, this affords performance advantages, while substantially eliminating mechanically moving parts.

Description

LCD display panel comprising a segmented illumination structure by scrolling illumination of the corresponding panel segment.

Liquid crystal technology has been applied to projection displays for use in projection televisions, computer monitors, point-of-sale displays, and electronic films, to name just a few applications.

A more recent application of LC devices is reflective LC displays on silicon substrates, commonly called liquid crystal-on silicon (LCOS). Often, liquid crystals are twisted nematic liquid crystal (TNLC) devices. Reflective LC displays based on silicon often include an active matrix of complementary metal oxide semiconductor (CMOS) transistors / switches used to selectively rotate the axis of liquid crystal molecules.

In many LC display devices, the image is constructed on the display by first changing the orientation of the LC molecules in the LC device (panel) and then selectively illuminating the panel with light. This selective orientation of LC molecules is called addressing or 'preparing' the panel. To this end, the panel is prepared with a specific image and synchronized with the illumination by applying the appropriate voltage to the individual pixels. This process is often performed via Field Sequential Color Illumination (FSC), in which case each row of the LC device is ready for illumination sequentially. This process requires time to fully address each pixel, as well as any lag time for the last row to reach steady state prior to illumination.

After the pixels of each row of the LC are addressed (prepared), illumination occurs and this process is repeated to generate an image in the scrolling process. In many applications, illumination is performed using three primary colors, red (R), blue (B) and green (G). The illumination time for the full color frame time (ie, R, G & B) is called the duty cycle. As can be seen, it is useful to maximize the lighting duty cycle in order to provide the viewer with the appropriate brightness. Therefore, it is beneficial to minimize the sequential preparation time of the pixel rows of the panel and the lag time for the last row to reach steady state.

One known technique for increasing the illumination duty cycle involves the use of two transistor based memory elements per pixel. According to this known technique, each pixel comprises an operating transistor-capacitor pair that provides a crystal orientation for the current image and another pair that is charged to the appropriate voltage for the next image / FSC. By itself, when the next image is displayed, all the pixels are ready (addressed), not sequential, so there is no significant delay / latency.

While the mentioned method provides an improved duty cycle, it is often not practical. In particular, the requirements of smaller and less expensive panels cannot be realized if each pixel requires an extra device.

Therefore, what is needed is a method and apparatus of an illumination display using an LC device that improves the duty cycle and at least overcomes the deficiencies of known methods and apparatus.

According to an exemplary embodiment, a method of illuminating a display in an LCD comprises preparing a segment of an LC panel for illumination of at least one color of light illuminating the segment, and at least one other segment of the LC panel for the next illumination. Preparing virtually simultaneously. By way of example, each segment comprises at least two rows of pixels.

According to another exemplary embodiment, the LCD device comprises a first arrangement of separate light emitting devices that illuminate a first segment of a liquid crystal (LC) panel with light of a first color and a second of the LC panel with light of a second color. A second arrangement of separate light emitting devices illuminating the segments, and comprising at least one further arrangement of separate light emitting devices, each of said at least one further arrangement being each segment of the LC panel with a separate color of light; And each segment is illuminated only with light from at least one respective additional arrangement, each of the first, second, and each segment being illuminated simultaneously during the first particular time period.

The invention is best understood by the following detailed description when read in conjunction with the accompanying drawings. It is emphasized that several drawings are not necessarily drawn to scale. Indeed, the size may be arbitrarily increased or decreased for clarity of discussion.

1 is a schematic diagram of a cascading scrolling light emitting device color bar illumination device according to an exemplary embodiment.

2 is a perspective view of an arrangement of light emitting diodes (LEDs) each coupled to a collimation optical element in accordance with an exemplary embodiment.

3 is a conceptual diagram of an LC panel including N rows of pixels according to an exemplary embodiment.

4 is a graph of row drive voltage over time of first and Nth row pixels of an LC panel according to an exemplary embodiment.

5A and 5B are conceptual views of illumination time and illumination method of known full display addressing, and conceptual diagrams of sub-display (bar) addressing and illumination method of an exemplary embodiment.

In the following detailed description, in order to provide a thorough understanding of the present invention, for purposes of explanation and not limitation, exemplary embodiments are disclosed that disclose specific details. However, having the benefit of this disclosure, it will be apparent to those skilled in the art that the present invention may be practiced in other embodiments that depart from the specific details disclosed herein. In addition, descriptions of well-known devices, methods, and materials may be omitted so as not to obscure the description of the present invention.

According to at least one exemplary embodiment, stepped scrolling of the LC display device is achieved using an arrangement of adjustable / controllable light sources. This provides the performance advantages described below and virtually eliminates mechanically moving parts.

1 shows an exemplary embodiment of an illumination device 100 for generating an image on a display (not shown) using an LC device 101, which is illustratively an LCOS device. The device 100 comprises an array of light emitting elements 102, 103, 104 which provide red light, blue light and green light, respectively. The light emitting device is illustratively a light emitting diode (LED) having an emission wavelength in each of the colors mentioned. These LEDs can be one of various types. Alternatively, other types of separate addressable light emitting devices can be used at this capacity. These include known light sources such as incandescent bulbs, organic light emitting diodes (OLEDs) and laser diodes, provided they meet certain requirements such as addressability, tunability, response time and lumen output. It is not limited to. As such, devices that meet these requirements can be used.

In this exemplary embodiment, each array of LEDs is coupled to an optical collimator 105, and each optical collimator 105 is coupled to a respective optical integrator 105. The output of the optical integrator 105 is the input of the dichroic coupler 106, which combines the light of the individual colors (wavelengths) into the output color. These devices are useful for providing a more uniform light source for the LC device 101.

The light output of the dichroic coupler 106 is imaged to the LC device 101 by the lens 107 and the polarizing beam splitter (PBS) 108. PBS 108, as is well known, provides polarization selectivity with light selectivity in the dark state, thereby providing contrast in the image. Light reflected from the PBS 108 is incident on the LC device 101 and then selectively enters the projection optics 109. In addition, the uniformity of illumination can be detected using a detector disposed at 110, and a feedback loop to the LED array can provide correction and adjustment as needed.

2 shows an LED arrangement 201 in accordance with an exemplary embodiment. The LED arrangement 201 is an arrangement for one of the primary colors and can be any of the arrangements 102, 103, 104 of FIG. 1, depending on the output wavelength of the LEDs of the arrangement 201. Each LED array 201 may be disposed on a circuit board or in a similar connection manner that enables selective addressing of individual LEDs in the array 201. This is somewhat advantageous in that one or more three primary colors allow illuminating the LC device in a sequential / scrolling manner in accordance with the exemplary embodiments described herein.

The collimating optical element 202 is illustratively a composite parabolic reflector, which usefully preserves the etendue of light. The light is uniform using an integrator such as slab light guide 203. Various light from the array (eg, array 102, 103, 104) is combined using dichroic coupler 204 or similar elements.

It is noted that each glass section of the slab light guide 203 guides light from the corresponding row of LEDs. The glass row sections are separated by a suitable adhesive, fluid or other suitable material (not shown) having a refractive index that supports the total internal reflection (TIR) 205 in the light guide 203. The light is therefore guided from a particular row of LED array 201 to the corresponding exit row of the lighting unit. This substantially beneficially prevents optical cross-talk between rows.

The LEDs in array 201 are selectively addressable by a current source driver, such as a field effect transistor (FET) circuit current supply or similar device mounted on the interconnect. They are particularly useful for performing stepped scrolling with sequential illumination. It is noted that the LED arrangement can be coupled to the video signal to emphasize a constant image. For example, bright or dark areas can be made on the display to improve contrast.

It is also noted that the various elements used to implement the embodiments shown in FIGS. 1 and 2 are merely illustrative. Indeed, other devices and devices may be used to provide an array of addressable discrete optical sources for cascading scrolling color bar illumination according to a typical embodiment.

According to a typical embodiment, stepped scrolling of the image is realized by sequentially illuminating segments of the LC device 101. By way of example, each segment comprises at least two rows of pixels. These and other embodiments will be described in more detail soon.

3 shows a display area 300 of an LC device, such as the LC device 101 of a typical embodiment. The display area 300 includes N rows of pixels 301, each row having M pixels, and N and M are both two or more. According to a typical embodiment, the arrangement of M × N pixels is divided into L segments, which form the entire LC device. The total number of rows in each segment is equal to N / L.

According to an exemplary embodiment, this display area 300 is divided into three bars (segments), each bar having 240 (720/3) rows. The device may be implemented as a high definition TV (HDTV) with a total resolution of 1280 (M columns) x 720 (N rows). This is merely exemplary, and many other displays may benefit from this exemplary embodiment. Finally, it is noted that the individual pixels of the segment can be addressed / prepared row by row, top to bottom, column by column, or addressed in groups of rows and columns simultaneously. In the extreme, the entire segment can be addressed at the same time.

As mentioned above, the pixels are prepared / addressed by selectively applying a constant voltage to direct the liquid crystal molecules in a constant direction, such that light crosses the LC device. An image is formed by adjusting the polarization of light across the pixel array, which pixel array is subsequently selectively separated by the PBS. According to a typical embodiment, the entire display area 300 of the LC panel adjusts the light incident on that area according to the desired input video information for the color impinging on its various parts. The light thus adjusted is reflected from the display, and once all L-segments are scrolled from beginning to end, the image is complete.

According to an exemplary embodiment, all three colors are incident on the display area 300, in which case each color is incident on N / 3 of the row. That is, each color is incident on a segment that is 1/83 of the entire area of the display area 300. In the next illumination, each segment is illuminated by a different color that provides the desired stepped scrolling. This process is repeated over and over. Finally, it is noted that the use of three colors is merely exemplary, and that additional colors or other combinations of colors may be used, resulting in further segmentation. For example, if four colors are used, each color will be incident on N / 4 rows (four segments).

Once the video signal is applied to the entire segment, light from the LED array is incident on the segment of display 300 and each portion of the entire image is projected onto the display. Addressing of the display 300 is performed by simultaneous addressing of each segment (ie, in parallel), followed by simultaneous illumination of each segment.

Thus, as can be seen, unlike the entire display illumination technique described above, a typical embodiment provides segmented preparation and illumination that increases the illumination time of each row of pixels, thereby improving display brightness. In other words, rather than waiting for alignment with the video signal of every pixel of the LC device, a typical method and apparatus is only delayed by the address time and LC response time of the sub display (segment). This increases the lighting duty cycle, increasing the display brightness.

4 shows another advantageous embodiment of the exemplary embodiment. The first curve 401 shows the row drive voltage versus time for the pixels in row 1, and the second curve 402 shows the Nth row drive voltage of the pixels. Since voltages are sequentially applied, the initial application of the Nth row driving voltage is delayed. To ensure more uniform illumination, the row drive voltage of the Nth row pixel may be greater than the row drive voltage of the first row pixel to compensate for the finite line address and reaction rate of the liquid crystal. This produces the same area under the curve, thus creating the same field flux for the row pixels, giving a more uniform projected image of the entire segment of the row. It is noted that this technique can be applied to each segment. In this case, the last row is N / 3, and this process is repeated in the next segment, in which case the applied voltage of the N / 3th row of the segment is greater than the first row of the segment.

The splitting of the LC device provides the ability to illuminate each L-segment at the same time and is limited only by the address time and LC response time of the segment. This is in stark contrast to the known full field technique, which requires delaying the illumination until the entire LC device is ready and the delay for the last row reaches a steady state. As can be seen, the segmentation technique of the exemplary embodiment allows for longer duty cycles and greater illumination time.

5A and 5B show a comparison of known global display addressing and illumination, and show split display illumination and addressing in an exemplary embodiment, respectively.

In FIG. 5A, the LC device 501 requires all rows to be properly oriented and in a steady state, so the total illumination time is

Given by I _t = T (Color) -T (LC) -LAT × N,

Where I _t is the illumination time, T (Color) is the color frame time, T (LC) is the LC response time, LAT is the line address time, and N is the number of rows.

In contrast, the segmented LC display 502 addresses and illuminates each segment 503, 504, 505 in parallel as described above. In such a device, the total lighting time I _t is

It is given by I _t = T (Color) -T (LC) -LAT × N / 3.

Thus, the total illumination time is increased. As such, the display addressing time is reduced by this embodiment.

As a quantitative example, considering a device with a display update frequency of 100 Hz, the color update is three times 100 Hz, i.e. 300 Hz or a color frame time of 3.3 Hz. Given an address line time T (LAT) of 1 ms and a liquid crystal response time of 1 ms, the LED illumination times for the two cases of FIGS. 5A and 5B in 1024 row devices are 1.3 ms and 2.0 ms, respectively. Clearly, the illumination time of the device of the exemplary embodiment is at least 50% greater than the known device of FIG. 5A. It is also shown graphically as curves 506 and 507 in FIGS. 5A and 5B, respectively. Clearly, the illumination time of the embodiment of FIG. 5B is significantly greater than the illumination time of the known technique in FIG. 5A.

Stepped scrolling in a typical embodiment is also shown in FIG. 5B. Each segment 503-505 is simultaneously subjected to first illumination with its respective first color. Then in the next illumination, each segment is again illuminated with its respective second color at the same time. This process is repeated to effect scrolling, in contrast to known techniques in which the entire display is illuminated in a first color at a single time and then in turn a different color.

The present invention has been described and therefore it will be apparent to one skilled in the art that the present invention may be equally modified in many ways with the benefit of the present disclosure. Such modifications are not to be regarded as a departure from the spirit and scope of the present invention, and such modifications which will become apparent to those skilled in the art are intended to be included within the scope of the following claims and their legal equivalents.

As described above, the present invention is applicable to the fields of projection televisions, computer monitors, sales advertisement displays, projection displays for use in electronic movies, and the like.

Claims (16)

As a method of illuminating a display on an LCD, Preparing at least two segments of the LC panel substantially simultaneously for illumination; And Illuminating each segment substantially simultaneously with light of a different color, wherein each segment comprises at least two rows of pixels Including a display in the LCD. The method of claim 1, wherein the at least two segments comprise three segments. The method of claim 1, wherein the process is repeated over and over, each time the color of light illuminating each segment changes. The method of claim 2, wherein the first of the three segments is illuminated with red light, the second of the three segments is illuminated with blue light, and the third of the three segments is illuminated with green light. , How to illuminate the display on the LCD. The method of claim 4, wherein the process is repeated over and over again, the color illuminating the first, second and third segments is different from the last illumination. The method of claim 1, wherein the number of segments is equal to the number of light colors illuminating the display. The method of claim 1, wherein the illumination time for each segment is I _t = T (Color) -T (LC) -LAT × N / C Where I _t is the illumination time, T (Color) is the color frame time, T (LC) is the LC response time, LAT is the line address time, C is the number of colors illuminating the LC device, and N is the number of rows. , How to illuminate the display on the LCD. 2. The method of claim 1, wherein the method comprises applying a voltage to the pixel elements in the first row, the voltage being less than the voltage applied to the pixel elements of the last row of each of the at least two segments. How to. As an LCD device, A first arrangement of separate light emitting devices illuminating a first segment of a liquid crystal (LC) panel with light of a first color; A second arrangement of separate light emitting devices illuminating a second segment of the liquid crystal (LC) panel with light of a second color; And At least one further arrangement of separate light emitting devices, each of said at least one further arrangement illuminating each segment of said LC panel with light of a different color, each segment from said at least one further arrangement Only illuminated with light, wherein the first, second and each segment is simultaneously illuminated during a first specific time period. 10. The LCD device according to claim 9, wherein said at least one further arrangement is a third arrangement, which illuminates a third segment simultaneously with the first and second arrangements with light of a third color. 10. The method of claim 9, wherein after the first specific time period, each of the first, second and the at least one additional arrangement are each different from the illuminated segment during the first specific time period, during the second specific time period. Illuminating different segments of the LCD device. 12. The method of claim 11, wherein after the second specific time period, each of the first, second and the at least one further arrangement is different from the illuminated segment during the second specific time period, respectively, during the third specific time period. Illuminating different segments of the LCD device. 13. The LCD device according to claim 12, wherein scrolling by each arrangement from one segment to another is continued, and simultaneous illumination is performed after each scrolling step. 10. The method of claim 9, wherein prior to illuminating the first, second and at least one additional segment, each segment is simultaneously prepared for illumination with a voltage selectively applied to each of the plurality of pixels of the segment. LCD device. 10. The LCD device of claim 9, wherein each array is selectively addressable to emit light of a particular color that is different from the color of light from the other array. The LCD device according to claim 10, wherein the first color is red, the second color is green, and the third color is blue.

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