CN85103453A - The improvement system of coring image representation signal - Google Patents
The improvement system of coring image representation signal Download PDFInfo
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Abstract
System can rely on following three measures reduce image in showing noise and unlikelyly cause tangible adverse consequences.These three measures are: (1) utilizes the spectrum analyzer (200) of a dead-beat, no alias, location conversion, octave bandwidth to obtain each sub-spectrum signal (I
1... I
N).(2) utilize the coring device (202-1 that disperses ... 202-N) with the one or more sub-spectrum signals that are decomposed of coring.(3) utilize one to have one or more dead-beats, no aliasing filter (204-1 ... synthesizer 204-N) (206) is represented signal (I so that draw an output image from whole sub-spectrum signals
R).
Description
The present invention relates to utilize the image processing system of coring technology,, for example be used for TV image signal to reduce the noise composition in the image representation signal.Particularly, the present invention is in the noise composition that reduces system and unconspicuous alias or other false spacing frequency composition introducing image representation signals.
Coring be a kind of everybody know, be used to reduce the technology of image representation signal noise composition.Coring is exactly that selectively the image representation signal that only allows absolute amplitude to surpass a certain set point passes through.Coring is a non-linear process, and it can be introduced in the image representation signal with the mutual spacing frequency composition of modulating by false harmonic wave originally.The power of these false spacing frequency compositions can increase with the increase of value.Therefore, the selection of coring value should be traded off between the two: value should be enough greatly to reduce the noise composition, and the while again can not be excessive, in order to avoid introduce too much false spacing frequency composition.
Observer for a displayed image, the influence that the noise composition of image representation signal is caused is depended on both: the relative size of the interval frequency spectrum of noise composition and signal composition in (1) displayed image, (2) are in the habit of experiencing people's vision system aspect the noise.
Known people's vision system is formed in the primary leading frequency of calculating luminousing image, and what lean on is that spacing frequency information is divided into many adjacent and overlapping separation band.Each bandwidth roughly is an octave, and the centre frequency of each frequency band and nearby frequency bands centre frequency roughly are the relations of twice.Studies show that have 7 frequency bands or " passage " to cross over the spacing frequency scope of the 0.5-6 circulation/degree of people's vision system approximately.Find further that again the spacing frequency processing that occurs in people's vision system is by sterically defined.Therefore the signal in each spacing frequency passage is that little subregion by image calculates.These subregions are overlapped, and the width of two circulations is roughly arranged on characteristic frequency.If, then can find as test pattern with-sinusoidal wave rastered picture, the contrast-sensitivity function of sinusoidal wave rastered picture tilts rapidly along with the raising of image spacing frequency.In other words, high spacing frequency needs high contrast (circulating 30/be about 20% when spending), and lower spacing frequency needs quite low contrast (circulating 3/be about 0.2% when spending).Know that people's vision system is observed the ability of the contrast variation of sinusoidal wave rastered picture (this image is on value), when lower spacing frequency, be better than the situation of higher spacing frequency.Particularly, people's average speciality is in order correctly to differentiate 75% of contrast variation, concerning the sinusoidal wave grating of one 3 circulation/degree, to need to change contrast 12%, and concerning the grating of one 30 circulation/degree, then need change contrast 30%.
Function based on people's vision system, obviously, higher signal to noise ratio (S/N) is easy to cover noise (promptly concerning the observer in the octave separation frequency band, noise is negligible), and for higher spacing frequency octave, this to cover effect just more remarkable, and this is because under higher spacing frequency, and people's vision system all descends aspect contrast sensitivity and changes in contrast sensitivity two to some extent.On the other hand, quite little high spacing frequency noise composition be added to one almost uniformly on the background (this background comprise direct current or very low tone every the video composition of frequency), be easy to by people's vision system observed.This point is very important, because the image of real world is on two orthogonal dimension, major part all has a frequency spectrum at interval, and this frequency spectrum contains a large amount of lower spacing frequency signal energies, have only the sub-fraction higher frequency signal energy, this will make any high spacing frequency noise become obvious especially.
Represent whole intervals frequency spectrum of signal if having only a coring device to be used for input imagery of coring, then selected value is too little probably and can not reduce tangible noise composition in the one or more octaves part of this interval frequency spectrum satisfactorily, and while other one or more octave parts in this interval frequency spectrum, it is too high that value can seem again, causes the false spacing frequency composition of excessive number to be introduced in the displayed image.
This problem can solve with following way.At first the frequency spectrum of input imagery being represented signal decomposes, and makes it to be included in several adjacent sub-spectral bands.Distinguish these frequency bands of coring one by one then, make the corresponding suitable value of each frequency band.At last these frequency bands by coring are synthesized a single output image and represent signal, and signal draws displayed image thus.
No. 4442454 patent that the present invention April 10 delivered with reference to U.S. Powell1984.
Image processing system of the present invention can make input imagery represent that any noise composition that occurs in the signal spectrum is reduced in output signal spectrum, and avoids representing to introduce in the signal spectrum tangible alias or other false spacing frequency compositions at output image.Therefore the present invention need not take into account the artifact that merits attention itself that handle to some extent in order to reduce noise.
The brief description of illustration
Two figures shown in Figure 1 are represented " brick wall " mode filter characteristic and a filter characteristic that tilts gradually respectively.
Fig. 2 is the functional block diagram of idealized realization of the present invention.
Fig. 2 a is depicted as the distortion of the frequency spectrum synthesizer among Fig. 2.
Fig. 3 a illustrates a Burt Pyramid spectrum analyzer, and its spectrum analyzer in specific implementation Fig. 2 is useful.
Fig. 3 b illustrates a Burt Pyramid synthesizer, is useful during its frequency spectrum synthesizer in specific implementation Fig. 2 a.
Figure shown in Figure 4 is the baseband envelope line chart of 7 input multiplication constant core rights functions, and these 7 coefficients have numerical value separately.
Fig. 5 is the calcspar of the more excellent implementation method of coring device shown in Figure 2, and this device is suitable for vision signal of coring, and this signal is to be used for limiting a two-dimentional TV image that is scanned.
The description of more excellent implementation method
Outstanding feature of the present invention is, each spectrum analyzer and synthesizer only comprise and have the filter of slant filtering characteristic gradually.Centre frequency fc among Fig. 1 is two cut-off frequency f
lAnd f
hMean value.Concerning band pass filter, f
lGreater than 0, concerning low pass filter, f
lEqual 0.The problem of " brick wall " mode filter is, produces as out-of-band high-frequency impulse energy can cause vibration when excited by impact.This false signal can find out, because people's vision system is very responsive on the frequency background for low tone that high spacing frequency glitch is added to.
The filtering characteristic that the normalization of a band pass filter is tilted gradually is shown in figure 102, and its centre frequency is f
cBecause inclination is gradually, therefore there is not significantly to limit the bound frequency f of bandwidth
lAnd f
h, but attenuated input signal is located to a certain degree (for example half-power point place) as f
iAnd f
hBandwidth is exactly specified bound frequency f like this
hWith f
iPoor.Yet shown in the shadow region 104 of Fig. 1, use the spectrum analyzer of this filter, under a given sub-spectral bandwidth, will have the sub-fraction energy that contiguous sub-spectral bandwidth is caused interference.This situation can cause false spacing frequency in the image processing system that uses sampling and sub-sampled signal.And image processing system of the present invention reduces any alias effect with as described below.
The band pass filter that tilts gradually for shown in the figure 102 of Fig. 1 tilts to usually occur in centre frequency f
cHigh frequency limit and low frequency limit.Yet in fact have only the high frequency limit of centre frequency to tilt.The accurate shape of any specific characteristic of slant filtering gradually is a design problem.Image processing system of the present invention is used gradually, and the design criterion of slant filtering device will go through below.
Shown in Figure 2 is the functional block diagram of ideal scheme of the present invention.Among the figure, dead-beat, the conversion of no alias location, the spectrum analyzer 200 of octave bandwidth has an image representation signal I as input.In fact, input signal I can be a continuous analog signal, a sampled analog signal (for example CCD imager and signal converter are used) or sampled digital signal (for example deriving from analog to digital converter).In fact the image processing type that will discuss is almost always represented signal at sampling image, this processing is to be undertaken by the non real-time mode by the spectrum analyzer that utilizes digital computer, or undertaken by real-time or non real-time mode by the spectrum analyzer that utilizes physical hardware.Therefore, for convenience of explanation, input signal I is a sampled signal but not continuous signal.
As shown in Figure 2, image representation signal I is limited in the one dimension that is expressed image by a frequency spectrum at least, and the scope of this frequency spectrum is from highest frequency f
mTo 0.For not comprised, signal I is higher than f
mSpacing frequency, suppose that this signal is by a prefilter.For ease of explanation, putative signal I is a temporal vision signal, and this vision signal is from the two-dimentional TV image (although this is also nonessential) of a plain scan.In a word, analyzer 200 the interval spectral decomposition of input signal I is become N(N is integer greater than 1) the logical sub-frequency spectrum output signal L in individual phase adjacent band
0L
N-1With a sub-spectrum signal GN of remnants.L
0L
NBy the spacing frequency sequence arrangement that falls progressively, from f
mBeginning is up to zero.The bandwidth that each signal is composed every a frequency multiplication successively.GN comprises all spacing frequencies of the frequency spectrum of input signal I, and these frequencies are lower than all frequencies (the logical frequency spectrum of band that the logical sub-frequency spectrum of this band is minimum spacing frequency) that are included in the logical sub-frequency spectrum of (N-1) individual band.Particularly as shown in Figure 2, octave 1 has f
m/ 2 nominal bandwidth and 3f
m/ 4 centre frequency, octave 2 has f
m/ 4 bandwidth and 3f
m/ 8 centre frequency, the rest may be inferred.
Each coring device 202-1-202-N is corresponding to sub-frequency spectrum output signal L
oL
N-1With among the GN one.Coring device 202-1 ... each signal L of 202-N output
oL
N-1Add to corresponding each dead-beat of frequency spectrum synthesizer 206, no aliasing filter respectively with GN.Frequency spectrum synthesizer 206 also comprises an adder 208, is used for filter 204-1 ... the output addition of 204-N is represented signal I with the output image that obtains a reformulation
R
The image spacing frequency spectrum of 200 couples of input signal I of spectrum analyzer carries out linear transformation.Therefore, provide at spectrum analyzer 200 under the situation of location conversion of dead-beat, no alias, baseband slot frequency few in number will appear on each output of spectrum analyzer, appear at also few in the image spacing frequency spectrum of signal I.Therefore, the false spacing frequency composition of being introduced by spectrum analyzer 200 and not obvious.Yet, be operated in the coring device 202-1 of nonlinear state ... 202-N must introduce each output signal L with false spacing frequency composition
oL
N-1In the middle of GN.These false compositions are at interval made by the harmonic wave composition of sub-spectrum intervals frequency and mutual key that part forms, and this a little spectrum intervals frequency inputs to coring device 202-1 respectively ... 202-N.All harmonic wave compositions of any spacing frequency in the sub-frequency spectrum of octave bandwidth have the spacing frequency that is positioned on the sub-frequency spectrum of this octave bandwidth.
If the output of the coring device that sub-frequency spectrum input is operated to octave bandwidth is added on the filter with " brick wall " characteristic (seeing the figure 100 of Fig. 1), then the harmonic wave that is produced by coring device and all false spacing frequencies of mutual modulation composition filter filtered device.
Yet for above-mentioned reasons, this filter with " brick wall " characteristic is easy to introduce the false spacing frequency vibration composition that causes excited by impact.For fear of introducing this composition, this band pass filter should have the filtering characteristic (shown in the figure among Fig. 1 102) of inclination gradually and the nominal bandwidth of an octave.At this moment the spacing frequency composition that a spot of harmonic wave and mutual modulation cause will can all not suppressed, and this is owing to exist the outer part of band (shown in the dash area among Fig. 1 104) of filtering characteristic.Yet, will go through below, the caused false spacing frequency composition of the characteristic of Qing Xieing can rely on special Design of Filter to be eliminated (promptly can not discovering basically) on displayed image gradually.
Each filter 204-1 of spectrum analyzer (206) ... 204(N-1) can be band pass filter or low pass filter.If band pass filter, then each filter all has a centre frequency and the bandwidth corresponding to octave spectrum.If low pass filter, then each filter all has one from zero bandwidth to specified upper cut off frequency, and this bandwidth is identical with the bandwidth of the respective band pass filters with same octave spectrum.
Filter 204-N with remaining sub-frequency spectrum is a low pass filter, the lower limiting frequency of the sub-frequency spectrum of its specified upper cut off frequency as many as (n-1) individual octave.
If low pass (but not band is logical) filter is as octave filter 204-1 ... 204-(N-1), then the false spacing frequency composition of low strap difference frequency (beat frequency) of nucleating course can't suppress.Yet the mutual modulation signal of this beat frequency will be low level, thereby appear in the displayed image and just to be difficult for being discovered by people's vision system.This be since the real world image in the higher level signal composition be positioned at the image spacing frequency spectrum low tone every the frequency part, thereby form a kind of masking effect.Moreover in real system, low pass filter is than the suitable dead-beat of the easier realization of band pass filter, the slope characteristic gradually of no alias.
In Fig. 2,, also nonessential for purposes of the invention like this although the sub-frequency spectrum output signal of each of analyzer 200 all has an independent coring device.All required is exactly that at least one sub-frequency spectrum output signal has independent coring device.Yet, if coring device 202-2 ... among the 202-N any one has that this is the highest interval frequency spectrum by being lower than octave 1() the frequency spectrum formed of spacing frequency, then this device must have the respective filter of a frequency spectrum synthesizer 206, so that remove at least in the frequency band because the false spacing frequency composition that is caused is handled in nonlinear coring.But under the situation of octave 1 sub-frequency spectrum, often occupy the filter 204-1 of frequency spectrum synthesizer 206.This is because most of image shows that the spacing frequency of being differentiated can not be higher than the highest spacing frequency f of octave 1 sub-frequency spectrum
mBecause synthesized output signal I
RIn, the arbitrary false spacing frequency composition of a last frequency band all can not be differentiated in image shows, thereby concerning this special circumstances, does not need the composition of filtering frequency band on this.
Whether need to comprise the filter of an independent dead-beat, no alias in the frequency spectrum synthesizer 206, make it to link, can select arbitrarily with the sub-frequency spectrum output of any one omission coring.Yet adder 208 is with whole N band pass filter and the signal plus frequency spectrum of remnants.And still save filtering no matter always in the signal that any one sub-frequency spectrum of spectrum analyzer 200 is exported, save coring.
Now referring to Fig. 2 a, the figure shows out a frequency spectrum synthesizer 206a who changes picture, the frequency spectrum synthesizer 206 of its available Fig. 2 is replaced.Synthesizer 206a has used a plurality of low pass filter 210-2 ... 210-N and half adder 212-1 ... 212-(N-1).The specified upper cut off frequency of low pass filter 210-2 equals image representation signal I(, and this is the upper cut off frequency of frequency multiplication 2 sub-frequency spectrums) the largest interval frequency f of image spacing frequency spectrum
mPartly.Similarly, low pass filter 210-3 ... the specified upper cut off frequency of each equals the upper cut off frequency of the octave spectrum that links with this filter 210-(N-1).The specified upper cut off frequency of low pass filter 210-N equals the lower limiting frequency of (N-1) individual octave spectrum.
In Fig. 2 a, filter and the half adder arranged by reverse order close mutually by the series connection form, and the result is that (the residue signal G ' of coring is N) successively one by one by each series connection low pass filter filtering for minimum interval spectrum signal.Shown in Fig. 2 a, the next signal L ' of minimum interval spectrum signal
N-1With the output signal of filter 210-N by half adder 212-(N-1) carry out addition, then successively by each low pass filter filtering.Similarly, the sub-spectrum signal L ' of the spacing frequency octave of coring (N-2) ... each signal among the L ' 2 is all successively by all filter filterings of frequency spectrum synthesizer 206a, shown in Fig. 2 a.At last, the output of filter 210-2 is through the sub-spectrum signal L of the highest spacing frequency octave of half adder 212-1 and coring
oAddition is represented signal I to obtain an output image that reconstitutes
RIn Fig. 2 a, suppose that visual demonstration can not differentiate input imagery frequency spectrum largest interval frequency f
mOn spacing frequency, therefore do not need to provide a low pass filter for the output of half adder 212-1.
According to the discussion of Fig. 2 and 2a as can be known, essence of the present invention is that spectrum analyzer 200 is no longer exported sub-spectrum signal except that residue signal, and this will have a nominal bandwidth less than an octave.Yet in the logical sub-frequency spectrum letter of the band that principle of the present invention is used for analyzing, each all has the spacing frequency bandwidth less than an octave.
Burt pyramid spectrum analyzer and Burt pyramid frequency spectrum synthesizer are suitable to especially spectrum analyzer 200 and frequency spectrum synthesizer 206a among the present invention, and reason has two at least.The first, the characteristic that this Burt pyramid allows filter to have to tilt gradually but not " brick wall " characteristic, thus be suitable for as frequency analyzer and frequency spectrum synthesizer.The second, in optimal case of the present invention, Burt pyramid spectrum analyzer produces the logical sub-frequency spectrum output signal of specified octave bandwidth band and the sub-frequency spectrum output signal of remnants.
Burt pyramid analyzer is to the input signal G of sampling
OAnalyze.In the following explanation of relevant Burt pyramid, suppose G
OThe form of (being equivalent to the image representation input signal I among Fig. 2) is the conventional vision signal (for example TSC-system vision signal) of the determined interval of continuous sweep bidimensional TV image frequency spectrum, this video letter at first through filtering in advance to remove any the highest given spacing frequency f that is higher than
mThe spacing frequency composition, then at least two times of f
mSample frequency under be sampled.
Burt pyramid analyzer is shown in the function diagram of Fig. 3 a in real time.Fig. 3 a shows that analyzer contains one by identical substantially sampled signal transmitting stage 300-1,300-2 ... the streamline that 300-N formed.Each level work is by digital dock CL
1, CL
2CL
NOn the determined sample frequency.Be added to clock frequency on any one-level and all be lower than the clock frequency value of its prime.For purposes of the invention, 300-2 ... the clock frequency value of each of 300-N grade all is half of its previous stage clock frequency value.
Shown in Fig. 3 a, the 300-1 level contains convolution filtering device and attenuating device 302, deferred mount 304, substracting unit 306 and expansion and interpolation filtering device 308.One with clock CL
1The input traffic of the digital sample values Go that samples of frequency be added into by convolution filtering device and attenuating device 302, to obtain one with clock CL
2The digital sample values G that samples of frequency
1Output stream.The convolution filtering utensil has lowpass function, can be with G
1The visual fibrillar center of each of representative frequency is reduced to half of centre frequency of the respective dimension of Go representative.Simultaneously, attenuating device reduces half with the sampling density of each dimension.
Each digital sample values of Go is added on the substracting unit 306 by deferred mount 304 as first input.Simultaneously, G
1The sampled value of reduction density add to expansion and interpolation filter 308, it has improved G
1The sampling density of sampled value, and turn back to G
0Sampled value.Then, interpolation G
1Density after the expansion of sampled value adds to substracting unit 306 as second input.The existence of deferred mount 304 has guaranteed G corresponding mutually on interval location
0And G
1Each sampled value is added in first and second inputs of substracting unit 306, and coincide mutually in time.Define the highest spacing frequency in each dimension of scanned picture from the output stream of the continuous sampling value Lo of substracting unit 306.
300-2 ... 300-N structure at different levels is identical with the 300-1 level basically.Yet, 300-2 ... during 300-N was at different levels, the higher level of each sequence number was handled than the signal of low tone every frequency, and this signals sampling density is lower than the sampling density of its previous stage.Particularly, continuous sampling value L
1Output stream represented in each image dimension the next octave of the highest octave of frequency at interval, therefore shown in Fig. 3 a, the signal that decomposes through Burt pyramid is by each octave sampled data stream L
0L
N-1(derive from 300-1 respectively ... the substracting unit that 300-N is at different levels) and a low frequency residue signal G
N(deriving from the convolution filtering device of 300-N level and the output of attenuating device) formed.Fig. 3 b shown one with Fig. 2 b in the corresponding Burt pyramid of synthesizer 206a synthesizer, be used for the output signal I that obtains to reformulate
RThis is by utilizing coring sampled data stream L '
oL '
N-1The time-delay mechanism 310-0 that operates ... 310-(N-1), and expansion and interpolation filter 312-1 ... 312-N and adder 314-0 ... 314-(N-1) finish.As mentioned above, serve as reasons two times of represented each image spacing dimension of expansion and interpolation filter 312-N of the sampling density that the remaining sampled data stream GN of least density has are then via adder 314-(N-1) and the sampled data stream L of a demonstration
N-1Addition.This process is carried out repeatedly by continuous synthetic level, has drawn the output signal L that reconfigures
R, bidimensional image is shown due to high sampling density.
Each convolution filtering device and interpolation filter that Burt pyramid is used all are low pass filters, and they must satisfy following two conditions.The first, each this filter uses a symmetrical core weighting function that comprises three multiplication constants at least.The second, each multiplication constant of core rights function must play a part identical, in other words, must provide identical total power to each node that is positioned at next higher level to each node of a preset level.To the requirement of the filtering characteristic aspect that actual dead-beat, no alias, location change is provided, as of the presently claimed invention, to the Burt pyramid analyzer that uses for the present invention and the convolution and the used core rights function of interpolation low-pass filter of synthesizer additional restrictions has been proposed again.Just consider these conditions now.
Because the operand of each grade of the Burt pyramid analyzer shown in Fig. 3 a all is the input signal of sampling, therefore will consider that sort signal not only comprises the Base Band part, and comprise the repeating part that each contains a lower sideband and upper sideband.In addition, in order to prevent alias, sample frequency should be at least and adds to the Burt Pyramid analyzer sampled input signal Base Band at different levels twice of the highest frequency of frequency spectrum at interval.
Utilize mathematical analysis to express, concerning Base Band, the 300-1 of Burt Pyramid spectrum analyzer ... each grade during 300-N is at different levels all is similar to the device of a dead-beat, no alias, location conversion, when following relation is set up, can be used to obtain the signal L that decomposes through Burt Pyramid
0L
N-1In have of corresponding octave bandwidth.These relations are:
1. (f in the formula within spacing frequency scope 0≤f≤fh/4
hSpecified upper cut off frequency for the sub-spectrum signal of each octave), the product of the normalization transmission characteristic of every grade convolution filtering device and interpolation filter is 1.Particularly, every grade convolution filtering device and any one in the interpolation filter, the transmission characteristic in this scope all are 1.
2. at spacing frequency scope f
hWithin≤f≤3fh/4, the product of every grade the convolution filtering device and the normalization transmission characteristic of interpolation filter is decayed gradually.Particularly, every grade convolution filtering device and any one in the interpolation filter all have the characteristic of decay gradually in this scope.
3. at spacing frequency scope 3f
h/ 4≤f≤f
hWithin, the product of every grade the convolution filtering device and the normalization transmission characteristic of interpolation filter is zero.Particularly, every grade convolution filtering device and any one in the interpolation filter, the transmission characteristic in this scope all are zero.
Have only the convolution filtering device of the 300-N level of Burt pyramid analyzer to be used to produce remaining sub-spectrum signal G
NTherefore, concerning the 300-N level, must make the convolution filtering device really meet above-mentioned condition 1,2 and 3.In addition, each interpolation filter of the synthesizer of Burt pyramid shown in Fig. 3 b also should meet these three conditions (wherein, concerning synthesizer, f
hBe the adder output signal upper cut off frequency, this adder is immediately following after the interpolation filter shown in Fig. 3 b).
The actual convolution and the design of interpolation filter not only must meet above-mentioned three conditions, and must meet the restrictive condition of above-mentioned symmetry and even distribution core rights function.This Burt Pyramid sampled signal convolution of core rights function or the interpolation filter of utilizing can not satisfy above-mentioned condition 1 and 3.Just equal two times the situation (this is the minimum sample frequency that prevents that alias is required) of the specified upper cut off frequency of an octave for sample frequency, can design a sampled signal Burt Pyramid convolution or an interpolation filter with core rights function of 5 multiplication constants, it can satisfy above-mentioned condition 1 or 2, but can not the both satisfy.In order to design the Burt pyramid convolution or an interpolation filter that can satisfy all above-mentioned three conditions, need have the sampled signal filter of the core rights function of 7 multiplication constants at least.Particularly, be the specified upper cut off frequency f of filter input signal frequency spectrum just for what have minimum no alias value
hThe sample frequency of twice, when the value of variable P for-when 0.052(sees that Fig. 4 a), Base Band filtering characteristic shown in Figure 4 (it meets all above-mentioned three conditions) is by 7 shown in Fig. 4 a multiplication functions, symmetry and equally distributed filter kernel weight function limits.
For situation about being discussed (being that sample frequency is the situation with specified minimum no alias), the core rights function of 7 multiplication constants can provide real location conversion, because this function is only operated quite local image region.(it is normally enough little for the core rights function of 9 multiplication constants, provide real location conversion with the no alias sample frequency of specified minimum for it as before) be desirable, because it is next compared with the core rights function of 7 multiplication constants at the vpg connection of the sloping portion gradually that limits the Base Band filtering characteristic, can provide good tuning capability.
Yet, produce the no alias value of specified minimum in order to make sample frequency, when the quantity of the multiplication constant of filter kernel weight function greater than 9 the time, filter transform tends to not have locate mode day by day, and this is undesirable.On the other hand, if filter signal is over-sampling (being the twice that sample frequency substantially exceeds the specified upper cut off frequency of filter input signal frequency spectrum), then the quantity of multiplication constant must increase in the core rights function, so that the same filter characteristic with same location degree to be provided.For example, if the sample frequency shown in Fig. 4 and the 4a is 4 times of f
1H, then the core rights function that tool is identical with the envelope of core rights function shown in Fig. 4 a will be made of (in other words, an interpolate value will be inserted between any a pair of adjacent multiplication constant shown in Fig. 4 a) 13 to 15 multiplication constants.
Because coring is a non-linear process, and introduce artifact, the coring outside therefore need not wishing is to remove the noise that appears in the coring device input signal.In addition, coring value should remain on to be enough to remove on the minimum level of this noise.Fig. 5 is coring device 202-1 ... the calcspar of the desirable scheme of 202-N, these coring devices are used to represent to scan standard (for example NTSC) vision signal of two-dimentional TV image.Known in TV, this TV signal comprises continuous interlaced field, and each scanning field partly is made up of effective scanning field part and vertical blanking.Transitive graph image information during effective field is at black-out intervals transitive graph image information not.The noise that black-out intervals occurred of each scanning field can be used as the tolerance of the noise of next valid period.
As shown in Figure 5, the value of coring device 202-K(K is 1 ... N) contain switch 500, only the vertical blanking part at each just applies control signal with this switch connection.Therefore in the whole valid period of each, switch 500 is all opened a way.The L that links with coring device 202-K
K-1This sub-frequency spectrum input signal is added to switch 500 and nonlinear amplifier 502.Therefore, has only L
K-1The switch 500 that is closed of noise section be sent to rectifier 504(because at vertical blanking period, signal only comprises noise).Noise section through rectifier 504 rectifications is sent to integrator 506, and its time constant is t
Kt
KEnough big, with extend by rectification at the noise component that vertical blanking period took place, make it to cover fully the live part of next.Therefore, integrator 506 one of generation have adjustable value ε
kDirect current signal use for the live part of a field.The noise level of the blanking part of this direct current signal and previous field is proportional.The signal that this is adjustable adds to nonlinear amplifier 502 as a control signal.In addition, in order to be total signal gain of each coring prosthetics different value, the gain of the nonlinear amplifier of each coring device can be regulated by gain controlling respectively.Particularly, ε on duty
kWhen big, the coring output signal L ' of nonlinear amplifier 502
K-1Relative power just can be less than input signal L
K-1Relative power.Therefore, the purpose of gain-adjusted compensation is, makes sub-spectrum signal (the output L ' of nonlinear amplifier 500 for example of each independent coring
K-1) offer synthesizer output signal I
RPower and corresponding L
K-1The power that sub-spectrum signal offers the input signal I of spectrum analyzer keeps equating.
The work of nonlinear amplifier 502 is amplification input signal L only
K-1In, absolute level surpasses that part of existing adjustable value.Therefore, even when the absolute level of input signal has surpassed existing adjustable value, the part of also having only the quilt of the input signal of exceedance to prune just can be passed through nonlinear amplifier 502, and to coring device L
K-1Output signal power is provided.Another kind method is that the absolute level of input signal and adjustable value are compared.If input signal absolute value exceedance, then input signal will be all by arriving L '
K-1Output, otherwise will can pass through without any signal.The advantage of this method is that quite a large amount of input signal powers are retained in the output signal power.Yet in the past, a shortcoming of this method is that this method is easy to produce a high alias artifact that is called " spark " in displayed image, and this image is got by this coring device.Yet an image processing system that combines with principle of the present invention can suppress " spark ", thereby makes this method more practical.
Claims (23)
1, an image processing system (Fig. 2) comprising:
(A) spectrum analyzer (200) is used for handling the image representation signal (I) of an input, and this signal is defined as visual one dimension at least by the frequency spectrum of being made up of many spacing frequencies.The scope of these spacing frequencies from highest frequency Fm to zero.Above-mentioned analyzer carries out following separation with the frequency spectrum of above-mentioned input signal in proper order by the spacing frequency that falls progressively:
(a) begin to be separated into the output signal (L that one group of single or multiple phases adjacent band leads to sub-frequency spectrum from Fm
oL
N-1), each sub-frequency spectrum output signal has a nominal bandwidth, and its width is not more than an octave in the above-mentioned scope.
(b) begin to be separated into the output signal (GN) of a sub-frequency spectrum of remnants from Fm, it comprises all spacing frequencies of above-mentioned input signal spectrum, and this frequency spectrum is arranged under those frequency spectrums that are included in the logical sub-frequency spectrum output signal of minimum spacing frequency band.
(B) device (202-1 etc.) is used for the logical sub-frequency spectrum output signal of at least one above-mentioned band of conversion.
(C) a frequency spectrum synthesizer (206), it links by above-mentioned converting means and analyzer.Also contain an adder (208), it undertakes all the sub-spectrum signal from analyzer, to produce whole sub-spectrum signal (L
o' ... L
N-1' and G
N') and, represent signal (I thereby form an output image
R);
For appear at first in input and image representation signal spectrum output the noise composition and will be not any tangible alias disturb or other false spacing frequency compositions introducing output images are represented in the frequency spectrum of signal, must accomplish:
Spectrum analyzer (200) is the spectrum analyzer of a real dead-beat, no alias, location conversion;
By leading to sub-band output signal (I to band of major general
1oI
1N-1) carry out coring, make chromacoder (202-1 ... 202-N) the signal of generation conversion;
In order to remove the pseudofrequency composition that those belong to frequency band veritably at least, synthesizer must be by the dead-beat that links of the frequency spectrum of each coring signal, the filter (204-1 of no alias at least respectively ... 204-N) form; And
Summing unit is to following the two summation: (a) by in those sub-spectrum signals of coring and filtering any one and (b) represent any one not only sub-spectrum signal of coring but also non-filtered not in the process of signal obtaining output image.
2, in first system that claim limited, output image represents that signal will be used for an image is presented on the display unit, and the lack of resolution of this display unit is higher than the spacing frequency of F with demonstration,
The highest spacing frequency octave output signal from spectrum analyzer is attached to adder and need connect any synthesizer Shanghai wave apparatus by coring device.
3, in first or second system that claim limited, each synthetic filtering device (204-2 etc.) comprises a low pass filter, and this filter has the frequency characteristic that descends gradually at a nominal cut-off frequency place.This cut-off frequency equals the last spacing frequency of sub-frequency spectrum, and the promptly sub-therewith frequency spectrum of filter combines.
4, the 3rd system that claim limited (Fig. 2 a) in, synthesizer (comprise at least two low pass filters (210-2 for example, 210-3), they are together in series and adder (212-2) links, this adder is included in the adder.
First filter (210-3) and sub-frequency signal (L '
N-1) lower frequency in links, second filter and sub-spectrum signal (L '
1) in a upper frequency link.
A lower frequency in the sub-spectrum signal is added on first low pass filter via 212 as input signal.
The output of first low pass filter adds to adder (212-2) as first input signal.
A upper frequency in the sub-spectrum signal (L '
1) add to adder as second input signal.
The output of adder is added on second low pass filter (210-2) as an input signal.
Therefore a lower frequency in the sub-spectrum signal carries out filtering by first and second low pass filters of series connection.
5, in the 4th system that claim limited, a lower frequency and the sub-spectrum signal that higher frequency is coring in the sub-spectrum signal.
6, in the 5th system that claim limited, a lower frequency and a higher frequency in the sub-spectrum signal are in adjacent sub-frequency spectrum.
7, in first image processing system that claim limited, input imagery represents that signal is the vision signal of a presentation image.This image is at least in the enterprising line scanning of one dimension, and with at least two times of F
mSample frequency sample.Above-mentioned spectrum analyzer (Fig. 3
a) be a BURT PYRAMID spectrum analyzer, its one-level (300-1) is used for obtaining a highest frequency (L in the sub-frequency spectrum output signal
o), this one-level comprises: (1) convolution filtering one attenuating device, it bears the vision signal (G of sampling
o), so that under half sample frequency of vision signal, obtain first filtered output signal (G
l).(2) expansion one interpolation filtering device (308), it have first through output signal of filtering as an input signal so that with the same sample frequency of vision signal under obtain second output signal through filtering.(3) substracting unit (304) is used for deducting second sampled level value through the output signal of filtering from the corresponding sampled level value of vision signal, thereby tries to achieve the highest frequency (L in the sub-frequency spectrum output signal
o), make output signal from substracting unit.Each convolution filtering one attenuating device in each grade and expansion one interpolation device present a kind of filtering spacing frequency characteristic that meets symmetry, equally distributed core rights function.
Do not comprise image spacing frequency in the vision signal greater than F.Each convolution filtering-attenuating device and expansion-interpolation filtering device contains seven multiplication constants at least, and it is a given spacing frequency rate characteristic that their value should make the product of each filter spacing frequency characteristic of convolution and interpolation filter.(a) from zero to F
mIn/4 the spacing frequency scope, this characteristic is a uniformity, (b) from F
m/ 4 to 3F
m/ 4 to 3F
mIn/4 the spacing frequency scope, this characteristic tilts gradually, (c) from 3F
m/ 4 to F
mThe spacing frequency scope in, this characteristic is zero.
8, in the 7th image processing system that claim limited, each convolution filtering-attenuating device and expansion-interpolation filtering device presents given spacing frequency characteristic.
9, in the 8th image processing system that claim limited, (A) BURT PYRAMID analyzer comprises N level (300-1 ... 300-N), wherein N is the integer greater than 1, and (300-1) this one-level is the first order in the N level, at different levelsly all draws a logical sub-frequency spectrum output signal (L of band
10, L
11, or the like).Second to each level of (N-1) level, (1) convolution filtering attenuating device bears from first output signal through filtering of previous stage (for example 300-1) convolution filtering attenuating device (G for example
1), so that under the frequency partly of this signal sampling frequency, draw first output signal through filtering.(2) expansion interpolation filtering device is used as its input signal with this output signal, so that draw second output signal through filtering under the sample frequency of above-mentioned output signal.(3) the used device of each sampled value that deducts the second filtering output signal from the corresponding sampling of the first filtering output signal of prime can draw the logical sub-frequency spectrum output signal of an octave band corresponding to this grade.(B) from second to (N-1) level each convolution filtering device and interpolation filter present a kind of meet the symmetry and the filter spacing frequency characteristic of equally distributed core rights function.Each above-mentioned filter contains 7 multiplication constants with different value at least so that the spacing frequency characteristic of each filter in the one-level can Enough: (a) from zero to F
mBe uniformity in/4 the scope, F wherein
mSpecified upper frequency for the spacing frequency of prime first filtering output signal spectrum.(b) from F
m/ 4 to 3F
mTilt gradually in/4 the spacing frequency scope.(C) from 3F
mBe zero in/4 to F the spacing frequency scope.
10, in the 9th image processing system that claim limited, the remaining sub-frequency spectrum output signal (G of analyzer
N) be the first filtering output signal of N level.
11, in the 10th image processing system that claim limited, synthesizer is a BURT PYRAMID synthesizer, it comprises: expand interpolation filtering device (312-1 for the N of Pai Lieing in order ... 312-N) and adder (314-0 ... 314-(N-1)), correspond respectively to certain one-level of N level BURD PYRAMID synthesizer.Expansion interpolation filtering device and adder is together in series by reverse order and mutually lotus root close, the output of each filter is first input of an adder, and the output of adder is the input of the filter before it, remaining sub-spectrum signal (G '
N) adding to filter as input signal, the logical sub-frequency signal of the band of each grade in the analyzer N level adds to corresponding adder as second input signal, and the output of analyzer first order adder has just constituted output image and represents signal.Each interpolation filter present a kind of meet the symmetry and the filter spacing frequency characteristic of equally distributed core rights function.Each interpolation filter contains seven multiplication constants with different value at least so that the spacing frequency characteristic of each grade interpolation filter is necessary: (a) from zero to F
mBe uniformity in/4 the scope, F wherein
mBe the specified upper frequency of the prime first filtering output signal, (b) from E
m/ 4 to 3F
mTilting gradually in/4 the scope, (C) is zero in the scope from 3F/4 to F.
12, in the 11st image processing system that claim limited, input imagery represents that signal is the vision signal of a two-dimensional image of expression, and this image is scanned on two dimension.
13, in the 1st image processing system that claim limited, input imagery represents that signal is the vision signal of a two-dimensional image of expression, and this image is scanned on two dimension.
14, in the 13rd image processing system that claim limited, vision signal is a television raster scan video signal of being made up of the scanning field that recurs, each scanning field comprises efficient image part of a blanking part heel, and each coring device (Fig. 5) comprising:
First device is made up of switching device (500) and time constant device (506), is used for drawing an adjustable value control signal (ε
K).During the efficient image part of each scanning field, this signal has certain value.This value is the function of the noise level of sub-frequency spectrum output signal, and during scanning field blanking part, this output signal adds to coring device as an input signal.
Second device (502), it is controlled by above-mentioned control signal.During each scanning field, if input to coring device signal (L '
K-1) surpass the value of control signal, this device just by obtain in the coring device output signal (L '
K-1).
15, an image processing system (Fig. 2) is used for handling an input imagery and represents signal (I), in the one dimension at least of the image spectrum that is expressed, from highest frequency F in zero scope, the image representation signal limiting spacing frequency, the economic spectrum analysis of this image representation signal is from F
mBeginning, the phase adjacent band that extends to one group of single or multiple separation by the spacing frequency that falls progressively in proper order leads to sub-spectrum signal (L, L
1Deng).In these signals any has the nominal bandwidth that is not more than an octave in the said frequencies scope.Sub-spectrum signal (the G of remnants
N) comprised all the following spacing frequencies in the image representation signal spectrum, promptly those are lower than the frequency that is included in the logical spectrum signal of minimum spacing frequency band.Described system comprises: be used for the device (201-1 etc.) of at least one sub-spectrum signal of conversion, a frequency spectrum synthesizer (206) that receives sub-spectrum signal by this converting means.This synthesizer also comprises an adder, is used for bearing the sub-spectrum signal that all receive, so that produce whole sub-spectrum signal sums, thereby forms an image representation output signal (I
R).
In order to reduce any noise composition that appears at first in the input signal spectrum, and in output signal spectrum too much alias or the false spacing frequency composition of unlikely introducing, necessary:
Chromacoder (202-1 ... 202-N) rely on sub-spectrum signal (I of coring at least
10I
1N-1) produce figure signal.
The frequency spectrum synthesizer is by dead-beat, no alias filter (204-1 ... 204-N) form.These devices link with the frequency spectrum of each coring signal at least, and the frequency of this signal is lower than the highest frequency of output signal spectrum, so that remove the pseudofrequency that those are positioned at frequency band at least.
Adder is with all spectrum signal additions, and these signals comprise: (a) by any signal in the spectrum signal of coring with not by any signal in the spectrum signal of coring and filtering; (b) any both not coring in obtaining the output signal process, also unfiltered sub-spectrum signal.
16, in the 15th system that claim limited, output pattern represents that signal will be used to show an image on a display device, and the lack of resolution of this equipment is to show any F of being higher than
mSpacing frequency.
The highest spacing frequency octave output signal of above-mentioned frequency spectrum is coupled to adder by coring device is not had any synthesizer filter.
17, it is characterized in that in the 15th system that claim limited: each above-mentioned composite filter contains one by one the low pass filter that tilts, its normal cutoff frequency equal time frequency spectrum upper spacing frequency, this filter is to connect separately.
18, in the 17th system that claim limited.Synthesizer contain at least two low pass filters that are together in series by adder (212-2) (210-2 for example, 210-3).This adder is included in the adder.
First filter (210-3) separately with the sub-spectrum signal of a lower frequency (L '
N-1) link, second filter (210-2) separately with the sub-spectrum signal of a upper frequency (L '
1) link.The sub-spectrum signal (via 212N-1) of this lower frequency is as the input signal of first low pass filter.The output of first low pass filter is as first input of adder (212-2).The sub-spectrum signal of this upper frequency is as second input of adder, and the output of adder is as the input of second low pass filter (210-2).Therefore the sub-spectrum signal of this lower frequency has been subjected to the filtering of the first and second two series filters.
19, in the 18th system that claim limited, two sub-spectrum signals low and upper frequency all are the sub-spectrum signals of coring.
20, in the 19th system that claim limited, two sub-spectrum signals low and upper frequency are adjacent sub-frequency spectrums.
21, in the 15th image processing system that claim limited, the image representation signal through spectrum analysis is certain visual vision signal of expression, and this image is subjected to one-dimensional scanning at least.Vision signal does not comprise greater than F
mThe image spacing frequency, and be equivalent to twice F
mSample frequency under be sampled.One group of logical sub-spectrum signal of band is made up of N the logical sub-spectrum signal of band, wherein N is the integer greater than 1, synthesizer is a BURT PYRAMID synthesizer, and it contains N the expansion interpolation filtering device (312-1 that arranges in order ... 312-N) and adder (314-0 ... 314(N-1)).These filters and adder are together in series by reverse order and mutual lotus root is closed, and the output of each filter is as the input of an adder, and the output of this adder is used as the input of previous filter again.Remaining sub-spectrum signal (G '
N) as the input of N filter, each in N logical sub-spectrum signal of band is used as second of corresponding adder and imports, and represents signal and constituted output image with the output of the corresponding adder of the analyzer first order.Each interpolation filter presents and accords with symmetry and the filtering spacing frequency characteristic of equally distributed core rights function.
Each interpolation filter comprises 7 multiplication constants with different value at least, make the spacing frequency characteristic of each grade interpolation filter necessary: (a) from zero being uniformity in the F/4 scope, wherein F is the specified upper frequency of interval frequency spectrum of the first filtering output signal of previous stage; (b) from F
m/ 4 to 3F
mTilt gradually in/4 the scope; (c) from 3F
m/ 4 to F
mScope in be zero.
22, in the 21st image processing system that claim limited, input imagery represents that signal is the vision signal of an expression two-dimensional image, and this image has been subjected to the scanning of bidimensional.
23, in the 15th image processing system that claim limited, input imagery represents that signal is the vision signal of an expression two-dimensional image, and this image has been subjected to the scanning of bidimensional.
24, in the 23rd image processing system that claim limited, vision signal is the vision signal of a television raster scanning, and this signal is made up of the scanning place that recurs, and each scanning field contains a blanking part, effective video part of heel.
Each coring device (Fig. 5) comprising:
First device is made up of switching device (500) and time constant device (506), is used for obtaining a control signal (ε
k), this signal has a value during the effective video part, and this value is the function of sub-frequency spectrum noise in output signal level.Have only during the blanking part of scanning field, this output signal just is used as the input of coring device.
Second device (502), it is controlled by control signal, during each scanning field, if input to the signal (L of coring device
K-1) level surpasses the control signal value of this moment, this device can draw an output (L '
K-1).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN85103453.5A CN1003413B (en) | 1985-04-30 | 1985-04-30 | Improved system for coring an image-representing signal |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN85103453.5A CN1003413B (en) | 1985-04-30 | 1985-04-30 | Improved system for coring an image-representing signal |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN85103453A true CN85103453A (en) | 1986-10-29 |
| CN1003413B CN1003413B (en) | 1989-02-22 |
Family
ID=4793199
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN85103453.5A Expired CN1003413B (en) | 1985-04-30 | 1985-04-30 | Improved system for coring an image-representing signal |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN1003413B (en) |
-
1985
- 1985-04-30 CN CN85103453.5A patent/CN1003413B/en not_active Expired
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| Publication number | Publication date |
|---|---|
| CN1003413B (en) | 1989-02-22 |
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