1. Field
The following description relates to an apparatus and method for removing noise from input sound, and, more particularly, to an apparatus and method for removing noise from input sound using a digital sound acquisition apparatus including a microphone array.
2. Description of the Related Art
In a situation in which a sound source is recorded, or a sound signal is received through a mobile digital device, and so on, various noises and ambient sound are generally included in the sound. To overcome such conditions, a method of amplifying a particular sound source signal that a user wishes to acquire from among the various mixed sounds has been developed. As an alternative, a method of removing unnecessary noises from the various mixed sounds has also been developed. Recently, a desire for a technique for acquiring a target sound source signal more accurately, for example, to have a better quality of sound source signals for video call and voice recognition services, has increased.
In one general aspect, there is provided an apparatus to remove noise input from a rear direction, the apparatus including an acoustic signal input unit configured to include three or more microphones including a first microphone as a reference microphone, a second microphone disposed at a position asymmetrical to the first microphone, and a third microphone disposed at a position symmetrical to the first microphone, and an acoustic signal processing unit configured to remove rear noise using acoustic signals received from the first microphone, the second microphone, and the third microphone.
The acoustic signal processing unit may be further configured to include a frequency transformation unit configured to transform a first acoustic signal received by the first microphone, a second acoustic signal received by the second microphone, and a third acoustic signal received by the third microphone, respectively, into acoustic signals in a frequency domain, a phase compensation unit configured to compensate for a phase of the second acoustic signal with respect to sound waves input from the rear direction such that a first directivity direction in which a first phase difference between the first acoustic signal and the second acoustic signal is equal to or smaller than a first threshold value is approximate to a second directivity direction in which a second phase difference between the first acoustic signal and the third acoustic signal is equal to or smaller than a second threshold value, a first direction filter configured to form a first beam in such a direction that the first phase difference between the first acoustic signal and the second acoustic signal with the compensated phase is equal to or smaller than a predetermined threshold value, a second direction filter configured to form a second beam in such a direction that the second phase difference between the first acoustic signal and the third acoustic signal is equal to or smaller than the predetermined threshold value, and a beam processing unit configured to remove an acoustic signal input from the rear direction using the first beam and the second beam.
The symmetrical disposition of the microphones may cause a phase difference between acoustic signals with respect to sound waves input from the back in a perpendicular direction to the apparatus to be equal to or smaller than a certain threshold value and the asymmetrical disposition of the microphones causes a phase difference between the acoustic signals with respect to the sound waves input from the back in a perpendicular direction to the apparatus to be equal to or greater than the certain threshold value.
The phase compensation unit may be further configured to compensate for the phase of the second acoustic signal using a previously stored phase difference in order to make the first directivity direction approximate to the second directivity direction. The previously stored phase difference may be a phase difference between the first acoustic signal and the second acoustic signal with respect to the sound waves input from the back in the perpendicular direction to the apparatus.
The first direction filter may be further configured to form a first weight filter using components of a spectrogram in which a difference between the second acoustic signal with the compensated phase and the first acoustic signal is equal to or smaller than the predetermined threshold value, and apply the first weight filter to the first acoustic signal to obtain a first output signal.
The first direction filter may be further configured to assign a value of 1 to components of the spectrogram in which the phase difference between the first acoustic signal and the second acoustic signal is equal to or smaller than the predetermined threshold value, and assign a value of 0 to the remaining frequency components of the spectrogram to generate the first weight filter.
The second direction filter may be further configured to form a second weight filter using components of a spectrogram in which a phase difference between the third acoustic signal and the first acoustic signal is equal to or smaller than the predetermined threshold value, and apply the second weight filter to the first acoustic signal to obtain a second output signal.
The second direction filter may be further configured to assign a value of 1 to components of the spectrogram in which the phase difference between the first acoustic signal and the third acoustic signal is equal to or smaller than the predetermined threshold value, and assign a value of 0 to the remaining frequency components of the spectrogram to generate the second weight filter.
The beam processing unit may be further configured to form a beam processing filter using frequency components that allow a phase of the first output signal to be smaller than a predefined threshold value and allow a phase of the second output signal to be greater than the predefined threshold value, and apply the beam processing filter to the first acoustic signal to obtain an output signal from which rear noise is removed.
The beam processing unit may be further configured to assign a value of 1 to frequency components that allow the phase of the first output signal to be smaller than the predefined threshold value and allow the phase of the second output signal to be greater than the predefined threshold value, and assign a value of 0 to the remaining frequency components to generate the beam processing filter.
In another general aspect, there is provided a method of removing noise, the method including receiving acoustic signals using an acoustic signal input unit configured to include a first microphone as a reference microphone, a second microphone disposed at a position symmetrical to the first microphone, and a third microphone disposed at a position asymmetrical to the first microphone, transforming a first acoustic signal received by the first microphone, a second acoustic signal received by the second microphone, and a third acoustic signal received by the third microphone, respectively, into acoustic signals in a frequency domain, compensating for a phase of the second acoustic signal with respect to sound waves input from a rear direction such that a first directivity direction in which a first phase difference between the first acoustic signal and the second acoustic signal is equal to or smaller than a first threshold value is approximate to a second directivity direction in which a second phase difference between the first acoustic signal and the third acoustic signal is equal to or smaller than a second threshold value, forming a first beam in such a direction that the first phase difference between the first acoustic signal and the second acoustic signal with the compensated phase is equal to or smaller than a predetermined threshold value, forming a second beam in such a direction that the second phase difference between the first acoustic signal and the third acoustic signal is equal to or smaller than the predetermined threshold value; and removing an acoustic signal input from the rear direction using the first beam and the second beam.
The symmetrical disposition of the microphones may cause a phase difference between acoustic signals with respect to sound waves input from the back in a perpendicular direction to the apparatus to be equal to or smaller than a certain threshold value and the asymmetrical disposition of the microphones causes a phase difference between the acoustic signals with respect to the sound waves input from the back in a perpendicular direction to the apparatus to be equal to or greater than the certain threshold value.
The compensating for the phase may include compensating for the phase of the second acoustic signal using a previously stored phase difference in order to make the first directivity direction approximate to the second directivity direction.
The previously stored phase difference may be a phase difference between the first acoustic signal and the second acoustic signal with respect to the sound waves input from the back in the perpendicular direction to the apparatus.
The forming of the first beam may include forming a first weight filter using components of a spectrogram in which a difference between the second acoustic signal with the compensated phase and the first acoustic signal is equal to or smaller than the predetermined threshold value, and applying the first weight filter to the first acoustic signal to obtain a first output signal.
The forming of the second beam may include forming a second weight filter using components of a spectrogram in which a phase difference between the third acoustic signal and the first acoustic signal is equal to or smaller than the predetermined threshold value, and applying the second weight filter to the first acoustic signal to obtain a second output signal.
The removing of the acoustic signal input from the rear direction may include forming a beam processing filter using frequency components that allow a phase of the first output signal to be smaller than a predefined threshold value and allow a phase of the second output signal to be greater than the predefined threshold value, and applying the beam processing filter to the first acoustic signal to obtain an output signal from which rear noise is removed.
The removing of the acoustic signal input from the rear direction may include assigning a value of 1 to frequency components that allow the phase of the first output signal to be smaller than the predefined threshold value and allow the phase of the second output signal to be greater than the predefined threshold value, and assigning a value of 0 to the remaining frequency components to generate the beam processing filter.
In another general aspect, there is provided an apparatus to remove rear noise, the apparatus including an acoustic signal input unit configured to comprise three or more microphones disposed on a surface which is linearly symmetrical and including one reference microphone, at least one microphone disposed at a position symmetrical to the reference microphone with respect to a line of symmetry of the linearly symmetrical surface, and at least one microphone disposed at a position which is not symmetrical to the reference microphone with respect to the line of symmetry, and an acoustic signal processing unit configured to remove the rear noise using acoustic signals input from the three or more microphones.
The acoustic signal input unit may be further configured to include a first microphone as the reference microphone, a second microphone disposed at a position which is not symmetrical to the first microphone with respect to the line of symmetry, and a third microphone disposed at a position symmetrical to the first microphone with respect to the line of symmetry.
The acoustic signal processing unit may be further configured to include a frequency transformation unit configured to transform a first acoustic signal received by the first microphone, a second acoustic signal received by the second microphone, and a third acoustic signal received by the third microphone, respectively, into acoustic signals in a frequency domain, a phase compensation unit configured to compensate for a phase of the second acoustic signal with respect to sound waves input from the rear direction such that a first directivity direction in which a first phase difference between the first acoustic signal and the second acoustic signal is equal to or smaller than a first threshold value is approximate to a second directivity direction in which a second phase difference between the first acoustic signal and the third acoustic signal is equal to or smaller than a second threshold value, a first direction filter configured to form a first beam in such a direction that the first phase difference between the first acoustic signal and the second acoustic signal with the compensated phase is equal to or smaller than a predetermined threshold value, a second direction filter configured to form a second beam in such a direction that the second phase difference between the first acoustic signal and the third acoustic signal is equal to or smaller than the predetermined threshold value, and a beam processing unit configured to remove an acoustic signal input from the rear direction using the first beam and the second beam.
In another general aspect, there is provided a method of removing rear noise, the method including receiving signals from first, second, and third microphones on a shared surface, the second microphone being asymmetrical on the surface relative to the first microphone, and the third microphone being symmetrical on the surface relative to the first microphone, compensating a phase of a signal received by the second microphone according to a phase difference with the first microphone, and removing portions of the signals of which the phase difference between the first and second microphone is approximately the same as a phase difference between the first and third microphone.
The phase of the signal received by the second microphone may be compensated with respect to sound waves input from a rear perpendicular direction such that the phase difference between the first microphone and the second microphone is equal to or smaller than a first threshold value.
The symmetrical disposition of the microphones may cause a phase difference between the signals with respect to sound waves input from a rear perpendicular direction to be equal to or smaller than a certain threshold value, and the asymmetrical disposition of the microphones causes a phase difference between the signals with respect to the sound waves input from the rear perpendicular direction to be equal to or greater than the certain threshold value.
In another general aspect, there is provided a device including an apparatus to remove noise, the apparatus including first, second, and third microphones provided on a shared surface to receive signals, the second microphone being asymmetrical on the surface relative to the first microphone, and the third microphone being symmetrical on the surface relative to the first microphone, and a controller to compensate a phase of a signal received by the second microphone according to a phase difference with the first microphone, and to remove portions of the signals of which the phase difference between the first and second microphone is approximately the same as a phase difference between the first and third microphone.
The phase of the signal received by the second microphone may be compensated with respect to sound waves input from a rear perpendicular direction such that a phase difference between the first microphone and the second microphone is equal to or smaller than a first threshold value.
Other features and aspects will be apparent from the following detailed description, the drawings, and the claims.
Throughout the drawings and the detailed description, unless otherwise described, the same drawing reference numerals will be understood to refer to the same elements, features, and structures. The relative size and depiction of these elements may be exaggerated for clarity, illustration, and convenience.
The following description is provided to assist the reader in gaining a comprehensive understanding of the methods, apparatuses, and/or systems described herein. Accordingly, various changes, modifications, and equivalents of the methods, apparatuses, and/or systems described herein will be suggested to those of ordinary skill in the art. Also, descriptions of well-known functions and constructions may be omitted for increased clarity and conciseness.
As indicated in the example illustrated in
The apparatus 100 may be implemented in various electronic devices such as, for example, and as a non-exhaustive illustration only, a personal computer, a laptop computer, a mobile phone, a personal digital assistant (PDA), a portable/personal multimedia player (PMP), an MP3 player, a game controller, a TV input device, a portable game console, a digital camera, a global positioning system (GPS) navigation, and the like.
The acoustic signal input unit 210 may include a microphone array having three or more microphones. In the apparatus 100, a first microphone 112 may be provided as a reference microphone, and two or more additional microphones may be provided that are either symmetrical or asymmetrical to the first microphone 112. In more detail, a microphone that is asymmetrical to the first microphone 112 outputs a sound signal with a phase that is asymmetrical to a phase of a sound signal output from the first microphone 112, and a microphone that is symmetrical to the first microphone 112 outputs a sound signal with a phase that is symmetrical to the phase of the sound signal output from the first microphone 112. A symmetrically placed microphone will be symmetrical to the reference microphone relative to a line on a linearly symmetrical surface provided with the microphones that divides the surface into two symmetric halves. Also, as described later, it may not be necessary to have a perfectly symmetrical surface in order to have symmetrically provided microphones.
In the example illustrated in
In a case in which the microphones are located at positions symmetrical to each other, a phase difference between acoustic signals with respect to sound waves input in a perpendicular direction to the apparatus 100 from the rear of the apparatus 100 may be smaller than a certain threshold value. If the microphones are located at positions perfectly symmetrical to each other, the phase difference between the acoustic signals input to the microphones from among the sound waves input in a perpendicular direction to the apparatus 100 from the rear of a surface on which the microphones are located may be 0. However, in practice, in consideration of manufacturing errors, even in a case in which the phase difference is close to 0, the microphones may be considered to be located at positions symmetrical to each other. In a case in which the microphones are regarded as being located at positions asymmetrical to each other, it indicates that the microphones are not located at positions symmetrical to each other. That is, if the microphones are located at positions asymmetrical to each other, a phase difference between acoustic signals input to the microphones with respect to sound waves input in a perpendicular direction to the back may be greater than the certain threshold value.
In addition, in the case of the microphones being located on the same surface, if the surface is linearly symmetrical in a geometric view, the symmetrical and the asymmetrical dispositions of the microphones may be defined as described below.
A linearly symmetrical figure may be a figure that has a half with the same dimensions as the other half when it is folded with respect to a line (or axis) of symmetry. Homologous sides of the linearly symmetrical figure have the same length, homologous angles also have the same value, and a line between homologous points of the figure is bisected by the line (or axis) of symmetry and perpendicularly meets the axis of symmetry. The linearly symmetrical figure may be, for example, rectangular, pentagonal, hexagonal, and the like.
A symmetrical disposition is a disposition in which microphones are located at positions symmetrical to a position of a single reference microphone with respect to a line of symmetry on a linearly symmetrical surface. An asymmetrical disposition is a disposition in which microphones are located at positions which are not symmetrical to a position of a single reference microphone with respect to a line of symmetry on a linearly symmetrical surface. The position of the reference microphone may be defined arbitrarily.
Even in a case in which a surface on which a microphone array is located is not perfectly linearly symmetrical, once imaginary lines extended from both edge microphones of the microphone array to the surface are identical with each other in length, the microphone array can be considered as symmetrical or asymmetrical as described above, and thus the present invention is applicable to such microphone array.
Hereinafter, a surface on which the microphones 112, 114, and 116 are located is referred to as a “surface A” for convenience of explanation.
The first microphone 112 may be a reference microphone MR. The second microphone 114 may be a microphone MU1 which is paired with the first microphone 112 in an asymmetrical disposition. An acoustic signal received through the first microphone 112 may be referred to as a first acoustic signal, and an acoustic signal received through the second microphone 114 may be referred to as a second acoustic signal. With respect to sound waves input in a perpendicular direction to the rear of surface A, a phase difference between the first acoustic sound and a second acoustic sound may be equal to or greater than a previously defined certain threshold value. One or more asymmetrical microphones may be provided. The certain threshold value may be previously defined as any value close to 0.
The third microphone 116 may be a microphone MS1 which is paired with the first microphone 112 in a symmetrical disposition. In a case in which an acoustic signal received through the third microphone 116 is referred to as a third acoustic signal, a phase difference between the first acoustic signal and the third acoustic signal with respect to the sound waves input in a perpendicular direction to the rear of surface A may be equal to or smaller than the certain threshold value. One or more symmetrical microphones, in addition to the reference microphone, may be provided.
The acoustic signal processing unit 270 may be configured to remove rear noise using the acoustic signals received from the three microphones 112, 114, and 116.
The frequency transformation unit 220 may transform the acoustic signals input through the acoustic signal input unit 210 into acoustic signals in a frequency domain. For example, the frequency transformation unit 220 may transform an acoustic signal in a time domain into an acoustic signal in a frequency domain using a discrete Fourier transform (DFT) or fast Fourier transform (FFT). The frequency transformation unit 220 may divide a temporally input acoustic signal into frames, and transform the acoustic signal into an acoustic signal in a frequency domain on a frame-by-frame basis. The unit of frame may be determined according to sampling frequency, a type of an application, and the like.
The frequency transformation unit 220 may include a first frequency transformation unit 222 which transforms the first acoustic signal into an acoustic signal in a frequency domain, a second frequency transformation unit 224 which transforms the second acoustic signal into an acoustic signal in a frequency domain, and a third frequency transformation unit 226 which transforms the third acoustic signal into an acoustic signal in a frequency domain. Hereinafter, transformation from a temporally input acoustic signal into an acoustic signal in a frequency domain will be referred to as a “spectrogram.”
The phase compensation unit 230 may compensate for a phase difference between the first acoustic signal transformed into an acoustic signal in a frequency domain and the second acoustic signal transformed into an acoustic signal in a frequency domain with respect to the sound waves input in a perpendicular direction to the rear of surface surface A. The compensation for the phase difference may include compensation for a phase which allows the phase difference to be equal to or smaller than a threshold value. That is, with respect to the sound waves incoming from the back, or from behind the surface upon which the microphones are provided, the phase compensation unit 230 may compensate for a phase of the second acoustic signal such that a first directivity direction in which a first phase difference between the first acoustic signal and the second acoustic signal is equal to or smaller than a first threshold value can be close to a second directivity direction in which a second phase difference between the first acoustic signal and the third acoustic signal is equal to or smaller than a second threshold value. The second threshold value may be the certain threshold value to satisfy the symmetrical deposition of the microphones. The first threshold value may be greater than the second threshold value.
The phase compensation unit 230 may compensate for the phase of the second acoustic signal using a previously stored phase difference value in order to make the first directivity direction close to the second directivity direction. The previously stored phase difference value may be a phase difference between the first acoustic signal and the second acoustic signal with respect to sound waves input in a perpendicular direction to the back of the apparatus 100.
The first direction filter 240 and the second direction filter 250 may be configured to filter an acoustic signal input in a particular direction. The particular direction may be an arbitrary direction, and once the direction is defined, a phase difference between microphones may be set according to the direction. However, in the example described herein, the particular direction may be a direction in which there is no phase difference between acoustic signals received by the microphones, or the phase difference is equal to or smaller than a predetermined threshold value that is close to 0.
The first direction filter 240 may form a first beam in a direction in which a phase difference between the first acoustic signal and the second acoustic signal with a compensated phase is equal to or smaller than the predetermined threshold value. The first direction filter 240 may form a first weight filter (not illustrated) using components of a spectrogram in which a phase difference between the first acoustic signal and the second acoustic signal with the compensated phase is equal to or smaller than the predetermined threshold value, and may obtain a first output signal by applying the first weight filter to the first acoustic signal. The first direction filter 240 may assign a value of 1 to components of the spectrogram in which a phase difference between the first acoustic signal and the second acoustic signal is equal to or smaller than the predetermined threshold value, and may assign a value of 0 to the remaining components of the spectrogram to generate the first weight filter.
The second direction filter 250 may form a second beam in a direction in which a phase difference between the first acoustic signal and the third acoustic signal is equal to or smaller than the predetermined threshold value. The second direction filter 260 may form a second weight filter (not illustrated) using components of a spectrogram in which the phase difference between the third acoustic signal and the first acoustic signal is equal to or smaller than the predetermined threshold value, and may obtain a second output signal by applying the second weight filter to the first acoustic signal. The second direction filter 260 may assign a value of 1 to components of the spectrogram in which the phase difference between the first acoustic signal and the third acoustic signal is equal to or smaller than the predetermined threshold value, and may assign a value of 0 to the remaining components of the spectrogram to generate the second weight filter.
The beam processing unit 260 may use the first beam and the second beam to remove a rear acoustic signal input to the apparatus 100. The beam processing unit 260 may remove a beam received from the back of the apparatus 100 using a beam from an asymmetrical microphone and a beam with a compensated phase from a symmetrical microphone. The beam processing unit 260 may form a beam processing filter (930 in an example illustrated in
Although the apparatus 100 is described as including three microphones in the example illustrated in
Referring to the example illustrated in
As indicated in the example illustrated in
Although the sound waves are generally incident to the microphones in various directions, for convenience of explanation, only two propagation paths of the sound waves are considered in the example illustrated in
Referring to the example illustrated in
(d+r1+r2)·sinθ′+t+r1=t·cosθ′+r2 (1)
Equation 1 may be rearranged, in terms of t·cosθ′, as follows: t·cosθ′=(d+r1+r2)·sinθ′+t+r1−r2. r2. Since (t·cosθ′)2+(t·sinθ′)2=t2, if t·cosθ′=(d+r1+r2)·sinθ′+t+r1−r2 is substituted to (t·cosθ′)2+(t·sinθ′)2=t2, θ′ can be obtained.
In this example, d denotes a distance between the reference microphone MR and the asymmetrical microphone MU1, r1 denotes a distance from the left side of the apparatus 100 to the reference microphone MR, and r2 denotes a distance from the right side of the apparatus 100 to the asymmetrical microphone MU1. t denotes a thickness of the side of the apparatus 100. θ′ denotes an angle, relative to a direction perpendicular to the front surface of the acoustic signal input unit 210, at which a phase of the acoustic signal input to the reference microphone MR becomes the same as a phase of the acoustic signal input to the asymmetrical microphone MU1.
There may be no phase difference between an acoustic signal SR received by the reference microphone MR and an acoustic signal SU1 received by the asymmetrical microphone MU1 with respect to the sound waves input at an angle of θ′ as indicated in the example illustrated in
In the example illustrated in
Referring to the example illustrated in
In the example illustrated in
To compensate for a phase, as represented by Equation 2 below, a phase difference between an acoustic signal received by the reference microphone MR and an acoustic signal received by the asymmetrical microphone MU1 in a rear perpendicular direction may be subtracted from a phase difference between the acoustic signal received by the reference microphone MR and the acoustic signal received by the asymmetrical microphone MU1. As shown in the fourth line in Equation 4, a phase (∠SU1|θ=α) of the acoustic signal of the asymmetrical microphone MU1 is added to a phase difference (∠SR|θ=0−∠SU1|θ=0) between the phase of the acoustic signal of the reference microphone MR and the phase of the acoustic signal of the asymmetrical microphone MU1 with respect to the acoustic signal input in a rear perpendicular direction.
ΔΦθ=0=∠SR|θ=0−∠SU1|θ=0
ΔΦθ=α=∠SR|θ=α−∠SU1|θ=α−ΔΦθ=0
=∠SR|θ=α−∠SU1|θ=α−(∠SR|θ=0−∠SU1|θ=0)
=∠SR|θ=α−[∠SU1|θ=α+(∠SR|θ=0−∠SU1|θ=0)]
That is, as described with reference to
The first direction filter 240 may form a first beam in a direction in which a phase difference between the first acoustic signal and the second acoustic signal with a compensated phase is equal to or smaller than the predetermined threshold value. To this end, the first direction filter 240 may form a first weight filter using components of a spectrogram in which the phase difference between the first acoustic signal and the second acoustic signal with the compensated phase is equal to or smaller than the predetermined threshold value.
Reference numeral 710 denotes phase information of the first acoustic signal which is converted into an acoustic signal in a frequency domain by the first frequency conversion unit 222 on a time frame-by-time frame basis according to time flow. That is, 710 denotes a phase ΦR in a time-frequency domain of the first acoustic signal SR.
Reference numeral 720 denotes a phase ΦU1 in a time-frequency domain of the second acoustic signal SU1 with the compensated phase. The first direction filter 240 may assign a value of 1 to components of the spectrogram in which a phase difference between the phase ΦR in a time-frequency domain of the first acoustic signal and the phase ΦU1 in a time-frequency domain of the second acoustic signal SU1 with the compensated phase is equal to or smaller than the predetermined threshold value, and assign a value of 0 to the remaining components of the spectrogram to generate a first weight filter 730. The first weight filter 730 may be applied to the first acoustic signal SR to obtain a first output signal. Although it is described that the first weight filter 730 is applied to the first acoustic signal SR to generate the first output signal in this example, the application of the first weight filter 730 to the second acoustic signal SU1 may produce the same result.
The second direction filter 250 may perform operations in the same manner as the first direction filter illustrated in
In the example illustrated in
In the example illustrated in
Referring to the examples illustrated in
The beam processing unit 260 may form a beam processing filter using a frequency component which allows the phase Φt, fsym 910 of the first output signal to be smaller than the predefined threshold value, and allows the phase Φt, fasym 920 of the second output signal to be greater than the predefined threshold value.
The beam processing unit 260 may assign a value of 1 to a weight ωt, f for the frequency component which allows the phase Φt, fsym 910 of the first output signal to be smaller than the predefined threshold value and allows the phase Φt, fasym 920 of the second output signal to be greater than the predefined threshold value, and may assign a value of 0 to a weight ωt, f for the remaining frequency components so as to generate the beam processing filter 930. This may be represented as Equation 3 below.
Here, δ denotes the predefined threshold value, and may be determined experimentally.
As indicated in the example illustrated in
A number of examples have been described above. Nevertheless, it will be understood that various modifications may be made. For example, suitable results may be achieved if the described techniques are performed in a different order and/or if components in a described system, architecture, device, or circuit are combined in a different manner and/or replaced or supplemented by other components or their equivalents. Accordingly, other implementations are within the scope of the following claims.
Number | Date | Country | Kind |
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10-2010-0025913 | Mar 2010 | KR | national |
This application claims the benefit under 35 U.S.C. §119(a) of Korean Patent Application No. 10-2010-0025913, filed on Mar. 23, 2010, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference for all purposes.