MULTIPLE-LINEAR-ARRAY MEMS DISPLAY CHIPS
Single-chip, multiple-linear-array MEMS form the basis for high-resolution, high-frame-rate video displays.
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The disclosure is generally related to linear-array MEMS (micro-electromechanical systems) display chips.
BACKGROUNDLinear arrays of miniature light modulators form the basis for a broad family of MEMS-based video displays. These displays form line images that are swept back and forth to “paint” two-dimensional scenes.
In
Array 115 imparts phase information onto a narrow strip of light. Optical system 125 then converts the phase information into amplitude variations to form a line image. Scan mirror 130 scans a line image 135 across a screen such as screen 140 shown in
Optical system 125 may take different forms which are complementary to different methods of encoding phase information with array 115. Some examples of such optical systems are presented in U.S. Pat. No. 7,054,051 (“Differential interferometric light modulator and image display device”), U.S. Pat. No. 7,286,277 (“Polarization light modulator”) and U.S. Pat. No. 7,940,448 (“Display system”).
One of the properties of MEMS light modulators which enables their use in linear array display systems like that of
Consider, for example, a “4K” video display having 4096 columns by 2160 rows of pixels. If the display operates at 196 frames per second, and is reconfigured to display red, green and blue information sequentially on a column by column basis, then the amount of time that the linear array remains in any particular configuration is only a few hundred nanoseconds.
As resolution requirements become even greater and the desired number of frames of video information per second also increases, the time available to reconfigure a linear array for each new column (i.e. each new line image) becomes a limiting factor. Of course, in the example above, one could turn the display chip on its side and use an array with 4096 elements to generate 2160 columns, but that strategy requires a display chip twice as long, using up valuable wafer real estate.
Hence, what are needed are linear-array MEMS display chips that can provide high-resolution, high-frame rate video.
Multiple-linear-array MEMS display chips, and methods for operating them, are described below. Chips that have more than one linear array light modulator offer a way to build single-chip, high-resolution display systems. Multiple linear arrays on a single chip also lead to better optical power handling, higher display brightness and wider color gamut.
Double-linear-array chips may be used to improve resolution in monochrome or full color displays. Along-array offsets between two arrays may be used to improve resolution in monochrome displays, for example. When three-color illumination is used, one array modulates one of the three colors, while the second array modulates the other two colors. Humans have better visual acuity at, and are more sensitive to, green than red or blue. Hence a double-linear-array chip may use one array to modulate green and the other array to modulate red and blue.
A triple-linear-array chip provides one array for each of three illumination colors while a quadruple-linear-array chip may be illuminated by four colors for a wider color gamut, higher brightness, or both. Single-level wiring schemes for double-, triple-, and quadruple-linear-array chips mean that only layout, rather than process flow, changes are required to transition from single- to multiple-linear-array chip production.
Displays based on linear-array light modulators produce line images. The line images are scanned to produce what appears to human observers to be two-dimensional images with rows and columns of pixels. As a line image is scanned from one column position to the next, the linear array light modulator changes configuration to create the new column of pixels.
When line images from two or more linear-array light modulators are scanned by a single scan mirror, the line images are separated in the resulting apparent two-dimensional image. A signal delay may be applied to column data for different colors to compensate for the spatial separation of arrays on a multi-array chip. Similarly, when one array modulates two colors, the delay between the time that the array is configured for the first and second colors leads to a separation of the corresponding line images. Separating illumination light on the linear array can compensate for this effect so that columns of each color are lined up in a two-dimensional image.
Various methods for operating multiple-linear-array display chips offer tradeoffs among resolution and available column time, among other parameters. In some cases two arrays are used to modulate three colors, for example. One way to have a single array modulate both red and blue information is to have the line image from that array alternate between red and blue columns. This omits half of the red and blue information from displayed images, but surprisingly the omission may not be particularly noticeable.
These and other aspects of multiple-linear-array MEMS display chips are now discussed in greater detail.
In
Multiple-linear-arrays 215 impart phase information onto narrow strips of light. Optical system 225 then converts the phase information into amplitude variations to form line images. Scan mirror 230 scans line images, e.g. 235, 236, across a screen such as screen 240 shown in
Optical system 225 may take different forms which are complementary to different methods of encoding phase information with arrays 215. Some examples of such optical systems are presented in U.S. Pat. No. 7,054,051 (“Differential interferometric light modulator and image display device”), U.S. Pat. No. 7,286,277 (“Polarization light modulator”) and U.S. Pat. No. 7,940,448 (“Display system”).
Line images 235, 236 from arrays 215 appear separated on screen 240 by an amount labeled “δ×” in the figure. At any given time line images 235 and 236 represent different columns of a two-dimensional image that appears on screen 240. Therefore image data corresponding to a single column of a two-dimensional image is sent to different linear arrays in a multi-array system at different times.
In
In
Arrays A1 and A2 are offset from each other, in the direction of the longest array dimension, by an amount Δx equal to one-half the ribbon pitch, p/2. Arrays A3 and A4 are offset by one ribbon pitch, p. Along-array offsets such as those depicted in
In
Triple- and quadruple-linear-array chips may include single layer wiring schemes which permit their fabrication using processes designed for single linear arrays. Only layout, rather than process flow, changes are required. As an example,
In
In
Double-, triple- or quadruple-linear-arrays of MEMS light modulators may thus be fabricated on a single chip using processes developed for single linear array chips. Arrays on a single chip are spaced apart from each other in the y direction (see
Arrays on a single chip may also be offset from each other in the x direction (see
A single chip with multiple-linear-arrays per chip may be used as part of a high-resolution monochrome or color display. Choices related to how each array of a multiple-linear-array chip is used affect the available column time for each array. The available column time is the length of time during which a linear array of MEMS modulators is configured for one column of image data. After one column time, the MEMS linear array is reconfigured for the next column of image data.
As an example, if the number of columns to be shown in a two-dimensional image is multiplied by X, then the available column time is divided by X. Showing an image with twice as many columns leaves half the time available to display each one, all other things being equal. Thus MEMS arrays must work faster to display images having more columns of image pixels. More rows of image pixels may be obtained by using linear arrays containing more modulator elements.
If the number of frames of image data shown per second is multiplied by Y, then the available column time is divided by Y. Frames are still images that form a video when shown in rapid succession. Image data, such as the location of objects in an image, may change from frame to frame.
Available column time is reduced by scanner duty factor. A scan mirror, such as 230 in
Available column time is reduced by a factor of three when a single linear array is used to modulate red, green and blue light sequentially for each column in a color display when compared to modulating only one color for a monochrome display. Using two, three or four linear arrays to modulate different colors is a way to increase the available column time. Multiple-linear-arrays per chip can make a single-chip, high-resolution, color video display feasible given limits on the amount of time required to reconfigure MEMS light modulator elements.
In
In the timing scheme of
During column time 1, the other array of the double-array chip is configured with line image data “R1” which represents the red component of one column of a two-dimensional video image. The “red/blue” array is illuminated with red light during this time. During column time 2, the red/blue array is configured with line image data “B2” which represents the blue component of the next column of the two-dimensional video image.
In the timing scheme of
In
The drop and interlacing timing schemes of
Pixel width adjustments may be made by changing the focus of illumination light on a linear array of light modulators. Lenses 210 and 211 in
Row interlacing may be achieved by slightly tilting a scan mirror (e.g. mirror 230 in
In the timing scheme of
The separation between arrays A1 and A2 is W, while the separation between the red and blue stripes of light is Y. If the delay between red and blue line images in a red/blue sequential timing scheme is a certain number of pixels, then the spacing Y between red and blue illumination stripes on array A2 can be adjusted by the same number of pixels to superimpose red and blue line images. The red/blue delay and corresponding spacing Y, may be less than one pixel size.
Array A2 may be thought of as two arrays separated by Y with each array available only half the time. Red/blue sequential timing with a double-linear-array chip increases the available column time by about 40% compared to using one array for red, blue and green sequential column color. Given a fixed MEMS modulator reconfiguration time, this increase in available column time can be used to increase the number of columns in a video image, the frame rate, or both.
MEMS light modulator chips having multiple linear arrays of light modulators offer a way to produce high-resolution, high-frame rate video from a single-chip display system. Various timing schemes may be used to display three colors using two linear arrays. Similar methods may be used to display four colors using three linear arrays, for example. The specific methods used depend on color and resolution requirements of each potential application.
Although many of the examples above are presented in terms of one array in a double-array chip handling green while the other handles red and blue, different colors may be assigned to different arrays. Multiple-linear-array chips may also be used to improve resolution of monochrome displays.
The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the principles defined herein may be applied to other embodiments without departing from the scope of the disclosure. Thus, the disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A light modulator chip comprising:
- two linear arrays of micro-electromechanical light modulator elements integrated on the chip, the arrays parallel to each other and separated from one another in a direction perpendicular to the longest array dimension.
2. The chip of claim 1 where movable elements in each array are addressed by a single layer of wiring that provides direct connection to each element.
3. The chip of claim 1 where the arrays are offset from one another in a direction parallel to the longest array dimension.
4. The chip of claim 1 where the light modulator elements are reflective micro-electromechanical ribbons comprising silicon nitride.
5. The system of claim 1 further comprising:
- a third linear array of micro-electromechanical light modulator elements integrated on the chip, the third array parallel to the other two and separated from the other two in a direction perpendicular to the longest array dimension.
6. The system of claim 5 further comprising:
- a fourth linear array of micro-electromechanical light modulator elements integrated on the chip, the fourth array parallel to the other three and separated from the other three in a direction perpendicular to the longest array dimension.
7. A display system comprising:
- a first light source that illuminates a single-chip, multiple-linear-array, micro-electromechanical light modulator;
- an optical system that converts light modulated by the multiple-linear-array light modulator into multiple line images; and,
- a scan mechanism that scans the multiple line images simultaneously to form a two-dimensional image.
8. The system of claim 7, where the multiple-linear-array, micro-electromechanical light modulator comprises two, and only two, linear arrays of micro-electromechanical light modulator elements integrated on the chip.
9. The system of claim 7, where the multiple-linear-array, micro-electromechanical light modulator comprises three, and only three, linear arrays of micro-electromechanical light modulator elements integrated on the chip.
10. The system of claim 7, where the multiple-linear-array, micro-electromechanical light modulator comprises four, and only four, linear arrays of micro-electromechanical light modulator elements integrated on the chip.
11. The system of claim 7 further comprising a second light source that illuminates the multiple-linear-array light modulator.
12. The system of claim 11 where the first light source is focused to a first thin strip of light that illuminates a first array of the multiple-linear-array light modulator and the second light source is focused to a second thin strip of light that illuminates a second array of the multiple-linear-array light modulator.
13. The system of claim 12 where the first and second thin strips of light have different widths.
14. The system of claim 11 further comprising a third light source that illuminates the multiple-linear-array light modulator.
15. The system of claim 14 where the first light source is focused to a first thin strip of light that illuminates a first array of the multiple-linear-array light modulator, the second light source is focused to a second thin strip of light that illuminates a second array of the multiple-linear-array light modulator and the third light source is focused to a third thin strip of light that illuminates the second array of the multiple-linear-array light modulator.
16. The system of claim 15 where the second and third thin strips of light are separated from one another on the second array.
17. A method of displaying a video image having columns of pixels comprising:
- providing a display based on a single-chip, multiple-linear-array, micro-electromechanical light modulator; and,
- (a) configuring a first linear array of the single-chip modulator to modulate a first color component of a first column of the video image;
- (b) configuring a second linear array of the single-chip modulator to modulate a second color component of the first column of the video image;
- (c) configuring the first linear array of the single-chip modulator to modulate the first color component of a second column of the video image;
- (d) configuring the second linear array of the single-chip modulator to modulate a third color component of the second column of the video image; and,
- (e) for successive columns after the second, alternately configuring the second linear array of the single-chip modulator to modulate the second and third color components on a column by column basis.
18. A method of displaying a video image having columns of pixels comprising:
- providing a display based on a single-chip, multiple-linear-array, micro-electromechanical light modulator; and,
- for each frame of video data:
- (a) configuring a first linear array of the single-chip modulator to modulate a first color component of a first column of the video image;
- (b) configuring a second linear array of the single-chip modulator to modulate a second color component of the first column of the video image;
- (c) configuring the first linear array of the single-chip modulator to modulate the first color component of a second column of the video image;
- (d) configuring the second linear array of the single-chip modulator to modulate a third color component of the second column of the video image;
- (e) for successive columns after the second, alternately configuring the second linear array of the single-chip modulator to modulate the second and third color components on a column by column basis; and,
- (f) repeating steps (a) through (e) with the roles of the second and third color components reversed.
19. A method of displaying a video image having columns of pixels comprising:
- providing a display based on a single-chip, multiple-linear-array, micro-electromechanical light modulator; and,
- for each column of video data:
- (a) configuring a first linear array of the single-chip modulator to modulate a first color component of the column of the video image during a column time;
- (b) configuring a second linear array of the single-chip modulator to modulate a second color component of the column of the video image during a first part of the column time; and,
- (c) configuring the second linear array of the single-chip modulator to modulate a third color component of the column of the video image during a second part of the column time.
Type: Application
Filed: Nov 8, 2011
Publication Date: May 9, 2013
Applicant: Alces Technology, Inc. (Jackson, WY)
Inventors: David M. Bloom (Jackson, WY), Matthew A. Leone (Jackson, WY)
Application Number: 13/291,867
International Classification: G02B 26/00 (20060101);