1. A display, comprising:
a backlight configured to operate over a temperature range;
a first string of first light emitting diodes arranged within the backlight, wherein the first light emitting diodes have a first chromaticity at an equilibrium temperature of the backlight;
a second string of second light emitting diodes arranged within the backlight, wherein the second light emitting diodes have a second chromaticity at the equilibrium temperature of the backlight and wherein the second chromaticity is separated from the first chromaticity by a chromaticity difference greater than a maximum chromaticity shift of the first light emitting diodes over the temperature range;
one or more drivers configured to independently drive the first string and the second string at respective driving strengths to produce an emitted white point that corresponds to a target white point; and
a controller configured to detect temperature changes within the display and to adjust a ratio of the respective driving strengths to maintain correspondence to the target white point over the temperature range.
2. The display of claim 1, wherein the first light emitting diodes are selected from a first bin and wherein the second light emitting diodes are selected from a second bin.
3. The display of claim 1, wherein the first chromaticity, the second chromaticity, and the target white point lie on a line within the CIE 1976 uniform chromaticity scale diagram.
4. The display of claim 1, wherein the chromaticity difference and the maximum chromaticity shift are measured as \u0394u\u2032v\u2032 on a CIE 1976 uniform chromaticity scale diagram.
5. The display of claim 1, wherein the respective driving strengths are substantially equal at the equilibrium temperature of the backlight.
6. The display of claim 1, wherein the controller is configured to adjust a duty cycle ratio of the respective driving strengths to maintain correspondence to the target white point.
7. The display of claim 1, wherein the controller is configured to maintain a substantially constant luminosity over the temperature range.
8. The display of claim 1, comprising one or more sensors disposed in the backlight and configured to detect the temperature changes.
9. A display, comprising:
a backlight configured to operate over a temperature range;
a first string of first light emitting diodes arranged within the backlight, wherein the first light emitting diodes have a first range of chromaticities over the temperature range;
a second string of second light emitting diodes arranged within the backlight, wherein the second light emitting diodes have a second range of chromaticities over the temperature range;
a third string of third light emitting diodes arranged within the backlight, wherein the third light emitting diodes have a third range of chromaticities over the temperature range, and wherein the first range of chromaticities, the second range of chromaticities, and the third range of chromaticities are set apart from one another;
one or more drivers configured to independently drive the first string, the second string, and the third string at respective driving strengths to produce an emitted white point that corresponds to a target white point; and
a controller configured to detect temperature changes within the display and to adjust ratios of the respective driving strengths to maintain correspondence to the target white point over the temperature range.
10. The display of claim 9, wherein the first light emitting diodes are configured to emit red light, the second light emitting diodes are configured to emit blue light, and the third light emitting diodes are configured to emit green light.
11. The display of claim 9, wherein the first light emitting diodes, the second light emitting diodes, and the third light emitting diodes comprise white light emitting diodes.
12. The display of claim 9, wherein chromaticity differences between the first light emitting diodes, the second light emitting diodes, and the third light emitting diodes at an equilibrium temperature of the backlight each exceed maximum chromaticity shifts for each of the first light emitting diodes, the second light emitting diodes, and the third light emitting diodes.
13. The display of claim 12, wherein the chromaticity differences and the maximum chromaticity shifts are measured as \u0394u\u2032v\u2032 on a CIE 1976 uniform chromaticity scale diagram.
14. The display of claim 9, wherein the ratios between the respective driving strengths comprise approximately 1:1 ratios at an equilibrium temperature of the backlight.
15. A method of operating a backlight, the method comprising:
independently driving a first string of first light emitting diodes and a second string of second light emitting diodes at respective driving strengths to produce an emitted white point that corresponds to a target white point; and
adjusting a ratio of the respective driving strengths in response to temperature changes to maintain correspondence to the target white point over an operational temperature range of the backlight;
wherein a chromaticity difference between the first light emitting diodes and the second light emitting diodes at an equilibrium temperature of the backlight is greater than a maximum chromaticity shift of the first light emitting diodes over the operational temperature range.
16. The method of claim 15, wherein adjusting a ratio comprises adjusting a duty cycle ratio of the respective driving strengths.
17. The method of claim 15, wherein adjusting a ratio comprises maintaining a relatively constant luminosity of the backlight.
18. The method of claim 15, wherein the chromaticity difference is greater than a second maximum chromaticity shift of the second light emitting diodes over the operational temperature range.
19. The method of claim 15, comprising detecting temperature changes using one or more temperature sensors disposed within the backlight.
20. A method of manufacturing a backlight, the method comprising:
arranging a first string of first light emitting diodes within a backlight, wherein the first light emitting diodes have a first chromaticity at an equilibrium temperature of the backlight;
arranging a second string of second light emitting diodes with respect to the first string of first light emitting diodes to produce a target white point over an operational temperature range of the backlight, wherein the second light emitting diodes have a second chromaticity at the equilibrium temperature of the backlight, and wherein the second chromaticity is separated from the first chromaticity by a chromaticity difference greater than a maximum chromaticity shift of the first light emitting diodes over the operational temperature range of the backlight;
configuring one or more drivers configured to independently drive the first string and the second string at respective driving strengths to produce an emitted white point that corresponds to the target white point; and
configuring a controller to adjust a ratio of the respective driving strengths in response to temperature changes to maintain correspondence to the target white point over the operational temperature range.
21. The method of claim 20, comprising configuring the controller to scale the respective driving strengths to maintain a constant luminosity of the backlight over the operational temperature range.
22. The method of claim 20, comprising selecting the first light emitting diodes and the second light emitting diodes so that light from the first light emitting diodes and the second light emitting diodes mixes to produce the target white point when the first light emitting diodes and the second light emitting diodes are driven at substantially equal driving strengths at an equilibrium temperature of the backlight.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A system for computing a location of an acoustic source, comprising:
an array of microphones for receiving acoustic signals generated by the acoustic source;
a memory configured to store phase-delay look-up tables based upon a plurality of candidate source locations and a spatial configuration of the array of microphones; and
a processor for computing the location of the acoustic source by processing the received acoustic signals using the phase-delay look-up tables.
2. The system of claim 1, further comprising at least one AD converter for digitizing the received acoustic signals.
3. The system of claim 1, further comprising a data segmenter for segmenting digitized received acoustic signals into a plurality of blocks.
4. The system of claim 1, further comprising an overlap-add filter bank for performing a discrete Fast Fourier Transform (FFT).
5. A system for computing a location of an acoustic source, the system comprising:
a microphone array including a plurality of microphones configured to receive acoustic signals generated by the acoustic source;
at least one analog to digital converter configured to generate a plurality of digital signals corresponding to the acoustic signals received by the plurality of microphones;
at least one data segmenter configured to divide each digital signal into a plurality of blocks;
at least one filter bank configured to perform a transformation on each of the plurality of blocks from the time domain to the frequency domain, thereby creating a plurality of transformed blocks, each transformed block comprising a plurality of complex coefficients and each complex coefficient being associated with a frequency bin; and
a processor configured to compute the location of the acoustic source from the transformed blocks by computing a total signal energy received from each of a plurality of candidate source locations and selecting as the location of the acoustic source one of the plurality of candidate source locations having a highest total signal energy.
6. The system of claim 5 wherein the plurality of candidate source locations are located along a circle having as its center the microphone array.
7. The system of claim 5 wherein computing a total signal energy received from each of a plurality of candidate source locations comprises:
multiplying the complex coefficients of each transformed block by a predetermined phase delay corresponding to a candidate source location, wherein the predetermined phase delay is stored in a look-up table stored in a memory operatively coupled to the processor; and
summing the complex coefficients to compute a signal energy for each frequency bin;
normalizing the signal energy for each frequency bin; and
summing the normalized signal energies for each candidate source location.
8. The system of claim 7 wherein summing the normalized signal energies for each candidate source location comprises omitting from the sum very low and very high frequency bins.
9. The system of claim 7 wherein computing a total signal energy received from each of a plurality of candidate source locations further comprises, for each of the transformed blocks, setting the coefficients to zero in each block where the maximum energy is less than a threshold energy.
10. The system of claim 9 wherein the threshold energy is predefined and stored in a memory.
11. The system of claim 10 wherein the threshold energy is computed using the plurality of microphone signals during periods of silence.
12. The system of claim 5 wherein the plurality of microphones is two microphones.
13. The system of claim 5 wherein the plurality of microphones is three microphones.
14. The system of claim 5 wherein the plurality of microphones is more than three microphones.
15. The system of claim 5 wherein the plurality of microphones is sixteen microphones.
16. The system of claim 5 wherein the microphone array is a two-dimensional array.
17. The system of claim 5 wherein the microphone array is a three-dimensional array.
18. The system of claim 5 wherein the processor is configured to refine the computed location of the acoustic source by computing a total signal energy received from each of a plurality of refined candidate source locations and selecting as the refined location of the acoustic source one of the plurality of refined candidate source locations having a highest total signal energy.
19. The system of claim 18 wherein the plurality of microphones is two microphones.
20. The system of claim 18 wherein the plurality of microphones is three microphones.
21. The system of claim 18 wherein the plurality of microphones is more than three microphones.
22. The system of claim 18 wherein the plurality of microphones is sixteen microphones.
23. The system of claim 18 wherein the microphone array is a two-dimensional array.
24. The system of claim 18 wherein the microphone array is a three-dimensional array.
25. The system of claim 18 wherein the refined candidate source locations are centered about the first selected candidate source location.
26. The system of claim 18 wherein computing a total signal energy received from each of a plurality of candidate source locations comprises:
multiplying the complex coefficients of each transformed block by a predetermined phase delay corresponding to a candidate source location, wherein the predetermined phase delay is stored in a look-up table stored in a memory operatively coupled to the processor; and
summing the complex coefficients to compute a signal energy for each frequency bin;
normalizing the signal energy for each frequency bin; and
summing the normalized signal energies for each candidate source location.
27. The system of claim 26 wherein summing the normalized signal energies for each candidate source location comprises omitting from the sum very low and very high frequency bins.
28. The system of claim 18 wherein the refined candidate source locations are predetermined candidate source locations stored in a memory.
29. The system of claim 28 wherein the refined candidate source locations are located along a plurality of concentric rings.
30. The system of claim 29 wherein computing a total signal energy received from each of a plurality of candidate source locations further comprises, for each of the transformed blocks, setting the coefficients to zero in each block where the maximum energy is less than a threshold energy.
31. The system of claim 30 wherein the threshold energy is predefined and stored in a memory.
32. The system of claim 31 wherein the threshold energy is computed using the plurality of microphone signals during periods of silence.
33. A method for computing the location of an acoustic source, the method comprising:
receiving a plurality of analog signals from a microphone array comprising a plurality of microphones;
digitizing each of the received plurality of analog signals;
segmenting each digitized signal into a plurality of blocks;
transforming each of the plurality of blocks from the time domain to the frequency domain;
computing from the transformed blocks a total signal energy received from each of a plurality of candidate source locations; and
selecting as the location of the acoustic source the candidate source location highest total signal energy.
34. The method of claim 33 wherein the plurality of candidate source locations are located along a circle having as its center the microphone array.
35. The method of claim 33 wherein computing from the transformed blocks a total signal energy received from each of a plurality of candidate source locations comprises:
multiplying complex coefficients of each transformed block by a predetermined phase delay corresponding to a candidate source location; and
summing the multiplied coefficients to compute a signal energy.
36. The method of claim 33 wherein computing a total signal energy received from each of a plurality of candidate source locations comprises:
multiplying the complex coefficients of each transformed block by a predetermined phase delay corresponding to a candidate source location; and
summing the multiplied coefficients to compute a signal energy for each of a plurality of frequency bins;
normalizing the signal energy for each frequency bin; and
summing the normalized signal energies for each candidate source location.
37. The method of claim 36 wherein summing the normalized signal energies for each candidate source location comprises omitting from the sum very low and very high frequency bins.
38. The method of claim 36 further comprising, for each of the transformed blocks, setting the coefficients to zero in each block where the maximum energy is less than a threshold energy.
39. The method of claim 38 wherein the threshold energy is predefined and stored in a memory.
40. The method of claim 39 wherein the threshold energy is computed using the plurality of microphone signals during periods of silence.
41. The method of claim 33 further comprising:
refining the selected location of the acoustic source by computing from the transformed blocks a total signal energy received from each of a plurality of refined candidate source locations; and
selecting as the refined location of the acoustic source one of the plurality of refined candidate source locations having a highest total signal energy.
42. The method of claim 41 wherein the refined candidate source locations are centered about the first selected candidate source location.
43. The method of claim 41 wherein computing from the transformed blocks a total signal energy received from each of a plurality of candidate source locations comprises:
multiplying complex coefficients of each transformed block by a predetermined phase delay corresponding to a candidate source location; and
summing the multiplied coefficients to compute a signal energy.
44. The method of claim 41 wherein the refined candidate source locations are predetermined candidate source locations stored in a memory.
45. The method of claim 44 wherein the refined candidate source locations are located along a plurality of concentric rings.
46. The method of claim 41 wherein computing a total signal energy received from each of a plurality of candidate source locations comprises:
multiplying the complex coefficients of each transformed block by a predetermined phase delay corresponding to a candidate source location; and
summing the multiplied coefficients to compute a signal energy for each of a plurality of frequency bins;
normalizing the signal energy for each frequency bin; and
summing the normalized signal energies for each candidate source location.
47. The method of claim 46 wherein summing the normalized signal energies for each candidate source location comprises omitting from the sum very low and very high frequency bins.
48. The method of claim 46 further comprising, for each of the transformed blocks, setting the coefficients to zero in each block where the maximum energy is less than a threshold energy.
49. The method of claim 48 wherein the threshold energy is predefined and stored in a memory.
50. The method of claim 49 wherein the threshold energy is computed using the plurality of microphone signals during periods of silence.