System and method for optimizing image resolution using pixelated imaging devices
A method of processing image data for display on a pixelated imaging device is disclosed. The method comprises: pre-compensation filtering an image input to produce pre-compensation filtered pixel values, the pre-compensation filter having a transfer function that approximates the function that equals one divided by a pixel transfer function; and displaying the pre-compensation filtered pixel values on the pixelated imaging device. In another disclosed method, the method further comprises: pre-compensation filtering an image input for each of a plurality of superposed pixelated imaging devices, at least two of which are unaligned, to produce multiple sets of pre-compensation filtered pixel values; and displaying the multiple pre-compensation filtered pixel values on the plurality of superposed pixelated imaging devices.
The present U.S. patent application is a divisional patent application of U.S. patent application Ser. No. 10/228,627 filed on Aug. 16, 2002, which is itself a continuation of U.S. patent application Ser. No. 09/775,884, filed Feb. 2, 2001 that claims the benefit of U.S. provisional patent application Ser. No. 60/179,762, filed Feb. 2, 2000. These related applications are incorporated herein by reference in their entirety.
FIELD OF THE INVENTIONThe invention generally relates to systems and methods for optimizing the resolution of graphical displays, and more particularly the invention relates to systems and methods for optimizing the resolution of pixelated displays.
BACKGROUND OF THE INVENTIONGraphical display engineers continue to minimize pixel hardware size. However, for any given minimum pixel size, there is an ongoing need to optimize display resolution.
SUMMARY OF THE INVENTIONIn one embodiment of the invention, a method of processing image data for display on a pixelated imaging device comprises: pre-compensation filtering an image input to produce pre-compensation filtered pixel values, the pre-compensation filter having a transfer function that approximates the function that equals one divided by a pixel transfer function; and displaying the pre-compensation filtered pixel values on the pixelated imaging device. In another embodiment of the invention, a method further comprises: pre-compensation filtering an image input for each of a plurality of superposed pixelated imaging devices, at least two of which are unaligned, to produce multiple sets of pre-compensation filtered pixel values; and displaying the multiple pre-compensation filtered pixel values on the plurality of superposed pixelated imaging devices.
In a further embodiment of the invention, a method further comprises: displaying the multiple pre-compensation filtered pixel values on six imagers, the six imagers being positioned into four phase families, the first and third phase families corresponding to separate green imagers, the second and fourth phase families corresponding to separate sets of aligned blue and red imagers.
Further related system and method embodiments are also disclosed.
BRIEF DESCRIPTION OF THE DRAWINGSThe foregoing description of various embodiments of the invention should be appreciated more fully from the following further description thereof with reference to the accompanying drawings wherein:
Individual pixel-like features 111 of the resulting combined display device 109 have a minimum dimension, S/4, that is one-quarter the minimum dimension, S, of the actual pixels of each separate imaging device 101-104. The pixel-like features 111 of the combined display device 109 thus have a square area that is one-sixteenth that of the actual pixels of each separate imaging device 101-104. The size reduction may be seen in
The unaligned superposition of
In
The below chart shows a comparison of three displays: in the “Aligned” array, three pixelated imagers are fully aligned, with no offset as shown in
In the above table, “Imager Visibility” is used to refer to the relative visibility of the imager as compared with the image when viewing the image of a close distance. As can be seen, unaligned imagers reduce the imager visibility, which is caused by the imagers' finite resolution and interpixel gaps; in general the reduction of imager visibility is proportional to the number of offsets used.
In step 221 of
By contrast, in step 225 of the embodiment of
In step 331 of
For example, a pixel could be modeled in one dimension as having a “boxcar” impulse response, equal to 1 at the pixel's spatial location and 0 elsewhere. A transfer function for such a pixel is given by:
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- for spatial frequency x. This transfer function is shown in the graph of
FIG. 4 , with frequency x on the x-axis in radians, and the pixel's transfer function on the y-axis.
- for spatial frequency x. This transfer function is shown in the graph of
Analogously, a pixel could be modeled in two dimensions as a square finite impulse response filter with unity coefficients inside the pixel's spatial location and zero coefficients elsewhere. A transfer function for such a pixel is given by:
H[u,V]=Sinc[u]*Sinc[V] {Eq. 2}
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- with Sinc as defined for Equation 1, and “*” denoting convolution.
Next, in step 332 of
{Pre-compensation filter transfer function}={1/pixel transfer function} {Eq. 3}
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- although other relations that give similar results will be apparent to those of ordinary skill in the art.
Next, in step 333 of
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- with G being a gain factor that could be set, for example, to equal 4.
Using the analogous two-dimensional example given above, an example of a two-dimensional gain-limited and clipped pre-compensation filter transfer
-
- with G being a gain factor that could be set, for example, to equal 4.
Next, in step 334 of
Next, in step 335 of
Next, in step 336 of
In this fashion a pre-compensation filter of the embodiment of
In an alternative version of the embodiment of
Whereas the embodiment of
Steps 338-340 of
In step 342, the individual coefficients calculated in step 341 are used to calculate an entire pre-compensation finite impulse response filter, for each spatially phase-shifted pixelated imaging device. Arrow 343 indicates that individual coefficients are calculated, in step 341, until the coefficients for all pre-compensation filters are filled. For example, four filter arrays would be filled with coefficients, to create four pre-compensation filters for the unaligned imagers of the embodiment of
In step 344, each pre-compensation filter is used to transform image input data for its corresponding phase-shifted pixelated imaging device. In step 345, a superposed, pre-compensation filtered image is displayed.
The embodiment of
The embodiment of
In another embodiment according to the invention, a perception-based representation of the image—such as a YUV or HIS representation, for example, instead of an RGB representation—is processed by its own reconstruction filter. The output of the filter yields the appropriate perception-based pixel value for each element of each grid; this is then converted to the appropriate color value for each element of each grid.
While the embodiments described above have been discussed in terms of image projection on pixelated displays, similar methods may be used for image sensing and recording, in accordance with an embodiment of the invention.
Multiple unaligned sensors may be set up, in an analogous fashion to the multiple displays of
For color applications, each imager may operate in one color frequency band. For example, a set of six unaligned color sensors may be implemented in a similar fashion to that described for
In addition, however, the separate viewpoint provided by each sensor may be considered as a single 2D-filtered view of an infinite number of possible image signals, that provides constraints on the image to be displayed. A displayed image is then calculated by determining the lowest energy signal that satisfies the constraints established by the signals from the various separate sensors. That is, the energy
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- is minimized for proposed signals S[m,n] that satisfy the boundary conditions established by sensor image signals S1[m,n] . . . Sk[m,n], for k imagers. The proposed signal S[m,n] that provides the minimum energy value is then used as the sensed signal for display.
In another embodiment, a color camera is implemented by dividing the visible spectrum for each physical sensor using a diachroic prism. In one example, six imagers are used, with a prism dividing the image into six color frequency ranges. Information from each color frequency range is then supplied to a displaced imager. The lowest energy luminance and color difference signals are then solved. These signals satisfy the constraints generated by the six imager signals and their known 2D frequency response and phasing. In addition to the frequency response and phasing of each imager, the sagital and tangential frequency response of the optics at that light frequency may be included in calculations, to correct for the Modular Transfer Function (MTF) of the optics. The contribution of each of the six color bands is then weighted for human perception of luminance and of the Cb and Cr signals.
In another embodiment, a playback device is implemented. The playback device filters and interpolates the original signal to provide the correct transfer function and signal value at the location of each pixel on each imager. If more than one imager is used for each color component, the component image energy may be divided and weighted for perception among the imagers. If each color component is divided into separate color frequencies, the image energy may be divided among those components and weighted by perception.
Another embodiment comprises a recording device. To record the signal, there are two approaches. One is to record each imager's information as a separate component. This preserves all of the information. The other alternative is to record a combined high-frequency luminance signal and two combined color difference signals. If three to six imagers are used, good results can be obtained by recording a luminance signal with twice the resolution in both dimensions as the two color difference signals.
In a polarized light embodiment, multiple imagers are operated with two classes of polarized light. Separate eye views are supplied to imagers, so that a single projection device gives a three-dimensional appearance to the projected image.
An embodiment of the invention also provides a technique for manufacturing imagers for use with the embodiments described above. In accordance with this embodiment, if color component imagers are assembled with little concern to their precise orientation, or response, spot response sensors (for projection), or calibrated spot generators (in the case of a camera), allow inspection at the geometric extremes of the image. This inspection, combined with a hyperaccuity-based signal processing approach, determine exact placement phase, scale, rotation and tilt of each manufactured display. If tilt is not required, two sensors suffice.
In one embodiment, such sensors can be used in manufacturing to set placement parameters. In another embodiment, such sensors are used in the product to automatically optimize response for component grid placement. In this embodiment, the sensors can also be used for automatic color correction and white balance for the current environment. The process and the feedback hardware required can be generalized to compensate for manufacturing tolerance, operational, or calibration requirements. In the most general case, automatic compensation requires a full image sensor for a projector, or a reference image generator for a camera. In this case, flat field, black field, linearity, color shift, geometric distortion, and modulated transfer function can all be compensated for.
Some embodiments of the invention may be implemented, at least in part, in any conventional computer programming language comprising computer program code. For example, preferred embodiments may be implemented, at least in part, in a procedural programming language (e.g., “C”) or an object oriented programming language (e.g., “C++”). Alternative embodiments of the invention may be implemented, at least in part, as preprogrammed hardware elements (e.g., application specific integrated circuits, FPGAs, and digital signal processors), or other related components.
The present invention may be embodied in other specific forms without departing from the true scope of the invention. The described embodiments are to be considered in all respects only as illustrative and not restrictive.
Claims
1. A method of displaying an image, the method comprising:
- feeding a plurality of image input data sets to a time-multiplexing optical display device, each image input data set comprising pixel values, the image input data sets corresponding to at least two superposed unaligned display data sets;
- using the time-multiplexing optical display device at a first time to display a pixel value corresponding to a first display data set of the at least two superposed unaligned display data sets; and
- using the time-multiplexing optical display device at a second time to display a pixel value corresponding to a second display data set of the at least two superposed unaligned display data sets.
2. A method according to claim 1, wherein the time-multiplexing optical display device moves its optics between the first time and the second time.
3. A method according to claim 2, the method further comprising:
- using the time-multiplexing optical display device to display pixel values corresponding to six display data sets, the six display data sets being positioned in four spatial phase families, the first and third spatial phase families each corresponding to a separate display data set composed of green chrominance values, the second and fourth spatial phase families each corresponding to a pair of aligned display data sets, each pair having a display data set composed of blue chrominance values and a display data set composed of red chrominance values.
4. A method according to claim 3, wherein the four spatial phase families are diagonally offset from each other by one-quarter of a diagonal pixel dimension of the display data sets.
5. A method according to claim 2, the method further comprising:
- using the time-multiplexing optical display device to display pixel values corresponding to three display data sets, the three display data sets being positioned in two spatial phase families, the first spatial phase family corresponding to a display data set composed of green chrominance values, the second spatial phase family corresponding to a display data set composed of blue chrominance values and to an aligned display data set composed of red chrominance values.
6. A method according to claim 5, wherein the two spatial phase families are diagonally offset from each other by one-half of a diagonal pixel dimension of the display data sets.
7. A method according to claim 2, the method further comprising:
- pre-compensation filtering each of the plurality of image input data sets to produce pre-compensation filtered pixel values, the pre-compensation filtering being performed with a filter having a transfer function that equals the result of gain-limiting and clipping a function that equals one divided by a pixel transfer function.
8. A method according to claim 7, wherein the pre-compensation filter transfer function is clipped at a frequency that does not exceed the Nyquist frequency of the display data sets.
9. A method according to claim 7, wherein the pre-compensation filter transfer function is clipped at a frequency that exceeds the Nyquist frequency of the display data sets.
10. A method according to claim 7, wherein the method comprises:
- pre-compensation filtering image input data sets that are in a perception-based format to yield a filtered perception-based pixel value for each pixel of each image input data set; and
- converting each filtered perception-based pixel value to a corresponding color value, for each pixel of each image input data set.
11. A method according to claim 7, wherein the step of pre-compensation filtering comprises filtering each of the image input data sets with a pre-compensation filter having a transfer function that equals the result of gain-limiting and clipping a function equal to: H [ u, V ] = 1 { Sinc [ u ] * Sinc [ V ] } where a function Sinc[x] is defined as: Sinc [ x ] = { 1, x = 0 sin [ x ] x, x ≠ 0 and “*” denotes convolution, and u,V are spatial frequency variables.
12. A method according to claim 2, wherein the at least two superposed unaligned display data sets are square pixel arrays, spatially phase-shifted from each other by equal amounts in the horizontal and vertical directions.
13. A method of image sensing, the method comprising:
- sensing light from the image with a set of superposed pixelated imaging devices, at least two of which are unaligned.
14. A method according to claim 13, the method further comprising:
- splitting light from the image into components using a beam splitter; and
- directing each component for reception by one of the superposed pixelated imaging devices.
15. A method according to claim 14, the method further comprising:
- splitting the light into components using a diachroic prism, each component corresponding to a separate color frequency band.
16. A method according to claim 15, the method further comprising:
- directing each separate color component for reception by a different one of the superposed pixelated imaging devices.
17. A method according to claim 16, the method further comprising:
- splitting the light from the image into six color frequency ranges.
18. A method according to claim 16, the method further comprising:
- processing the received components by solving for a lowest energy signal, for a whole sensed image, that satisfies constraints provided by color component values received by each of the superposed pixelated imaging devices.
19. A method according to claim 18, the method further comprising:
- solving for a lowest energy luminance and color difference signal.
20. A method according to claim 16, the method further comprising:
- processing received color component values from each superposed pixelated imaging device by adjusting for the sagittal and tangential frequency response of each device at its associated color frequency.
21. A method according to claim 16, the method further comprising:
- processing received color component values by weighting each color component based on human perception of luminance, Cb, and Cr signals.
22. A method according to claim 16, the method further comprising:
- processing received color components to adjust for the two-dimensional frequency response and spatial phase of the superposed imaging device by which it was received.
23. A method of image sensing, the method comprising:
- sensing light from the image with a time-multiplexing pixelated imaging device, at a first time and a first location;
- moving the time-multiplexing device to a second location such that its pixelated sensors are spatially phase-shifted from, and superposed with, the spatial location they occupied when the time-multiplexing device was at the first location; and
- sensing light from the image with the time-multiplexing pixelated imaging device at a second time, at the second location.
24. A method according to claim 23, the method further comprising:
- splitting light from the image into components using a beam-splitter; and
- directing the components for separate reception by the time-multiplexing imaging device at different locations, including at least the first and second locations.
25. A method according to claim 24, the method further comprising:
- processing the received components by solving for a lowest energy signal, for a whole sensed image, that satisfies constraints provided by color component values received by the time-multiplexing imaging device at each of the different locations.
26. A method according to claim 24, the method further comprising:
- processing received color component values by weighting each color component based on human perception of luminance, Cb, and Cr signals.
27. A method of recording a motion picture image, the method comprising:
- splitting light from the image into components using a beam splitter;
- directing each component for reception by one of a set of superposed pixelated imaging devices, at least two of which are unaligned; and
- separately recording a component value received by each superposed pixelated imaging device.
28. A method of recording a motion picture image, the method comprising:
- splitting light from the image into components using a beam splitter;
- directing each component for reception by one of a set of superposed pixelated imaging devices, at least two of which are unaligned;
- recording a luminance signal combining component values received by the superposed pixelated imaging devices; and
- recording two color difference signals combining component values received by the superposed pixelated imaging devices.
29. A method according to claim 28, the method further comprising:
- recording the luminance signal with a resolution that is twice a resolution, in both dimensions, of the color difference signals.
30. A method according to claim 29, the method further comprising:
- recording signals obtained by three superposed pixelated imaging devices.
31. A method according to claim 29, the method further comprising:
- recording signals obtained by six superposed pixelated imaging devices.
32. A method of playing back a recorded motion picture image, the method comprising:
- filtering and interpolating the recorded image; and
- displaying the filtered and interpolated image on a set of superposed pixelated imaging devices, at least two of which are unaligned.
33. A method according to claim 32, the method further comprising:
- dividing the recorded image's energy amongst the superposed pixelated imaging devices, the division being weighted amongst the imaging devices in accordance with human color perception.
34. A method of playing back a recorded motion picture image, the method comprising:
- filtering and interpolating the recorded image; and
- displaying the filtered and interpolated image using a time-multiplexing imaging device, the time-multiplexing device moving between at least two display positions to create a set of superposed pixelated displays, at least two of the displays being unaligned.
35. A method according to claim 34, the method further comprising:
- dividing the recorded image's energy amongst the superposed pixelated displays, the division being weighted amongst the displays in accordance with human color perception.
Type: Application
Filed: May 25, 2005
Publication Date: Sep 29, 2005
Inventor: Kenbe Goertzen (Topeka, KS)
Application Number: 11/137,050