US20150365643A1 - Method of color processing using a color and white filter array - Google Patents
Method of color processing using a color and white filter array Download PDFInfo
- Publication number
- US20150365643A1 US20150365643A1 US14/303,307 US201414303307A US2015365643A1 US 20150365643 A1 US20150365643 A1 US 20150365643A1 US 201414303307 A US201414303307 A US 201414303307A US 2015365643 A1 US2015365643 A1 US 2015365643A1
- Authority
- US
- United States
- Prior art keywords
- white
- signals
- interpolated
- color
- converted
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000000034 method Methods 0.000 title claims abstract description 24
- 238000012545 processing Methods 0.000 title claims abstract description 11
- 230000001131 transforming effect Effects 0.000 claims abstract 4
- 238000003708 edge detection Methods 0.000 claims description 10
- 238000001914 filtration Methods 0.000 claims description 3
- 230000010354 integration Effects 0.000 claims description 3
- 230000014509 gene expression Effects 0.000 description 12
- 238000010586 diagram Methods 0.000 description 6
- 238000012935 Averaging Methods 0.000 description 4
- 230000035945 sensitivity Effects 0.000 description 4
- 230000003044 adaptive effect Effects 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 230000006978 adaptation Effects 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N9/00—Details of colour television systems
- H04N9/64—Circuits for processing colour signals
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
- H01L27/146—Imager structures
- H01L27/14643—Photodiode arrays; MOS imagers
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/20—Filters
- G02B5/201—Filters in the form of arrays
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/20—Filters
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T3/00—Geometric image transformation in the plane of the image
- G06T3/40—Scaling the whole image or part thereof
- G06T3/4015—Demosaicing, e.g. colour filter array [CFA], Bayer pattern
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
- H01L27/146—Imager structures
- H01L27/14601—Structural or functional details thereof
- H01L27/1462—Coatings
- H01L27/14621—Colour filter arrangements
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
- H01L27/146—Imager structures
- H01L27/14665—Imagers using a photoconductor layer
- H01L27/14667—Colour imagers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
- H01L27/146—Imager structures
- H01L27/14683—Processes or apparatus peculiar to the manufacture or treatment of these devices or parts thereof
- H01L27/14685—Process for coatings or optical elements
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/10—Circuitry of solid-state image sensors [SSIS]; Control thereof for transforming different wavelengths into image signals
- H04N25/11—Arrangement of colour filter arrays [CFA]; Filter mosaics
- H04N25/13—Arrangement of colour filter arrays [CFA]; Filter mosaics characterised by the spectral characteristics of the filter elements
- H04N25/133—Arrangement of colour filter arrays [CFA]; Filter mosaics characterised by the spectral characteristics of the filter elements including elements passing panchromatic light, e.g. filters passing white light
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/10—Circuitry of solid-state image sensors [SSIS]; Control thereof for transforming different wavelengths into image signals
- H04N25/11—Arrangement of colour filter arrays [CFA]; Filter mosaics
- H04N25/13—Arrangement of colour filter arrays [CFA]; Filter mosaics characterised by the spectral characteristics of the filter elements
- H04N25/135—Arrangement of colour filter arrays [CFA]; Filter mosaics characterised by the spectral characteristics of the filter elements based on four or more different wavelength filter elements
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/14—Picture signal circuitry for video frequency region
- H04N5/142—Edging; Contouring
-
- H04N5/335—
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N2209/00—Details of colour television systems
- H04N2209/04—Picture signal generators
- H04N2209/041—Picture signal generators using solid-state devices
- H04N2209/042—Picture signal generators using solid-state devices having a single pick-up sensor
- H04N2209/045—Picture signal generators using solid-state devices having a single pick-up sensor using mosaic colour filter
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N2209/00—Details of colour television systems
- H04N2209/04—Picture signal generators
- H04N2209/041—Picture signal generators using solid-state devices
- H04N2209/042—Picture signal generators using solid-state devices having a single pick-up sensor
- H04N2209/045—Picture signal generators using solid-state devices having a single pick-up sensor using mosaic colour filter
- H04N2209/046—Colour interpolation to calculate the missing colour values
Definitions
- the present invention generally relates to a color and white filter array, and more particularly to a method of color processing using an RGBW filter array.
- a Bayer filter is a color filter array composed of red (R), green (G) and blue (B) color filters disposed on a grid of photo-sensors, and specifically configured with a pattern of 50% green, 25% red and 25% blue.
- the Bayer filter with the photo-sensors forms an image sensor that is commonly used in electronic devices such as digital cameras or camcorders.
- the image sensor with the Bayer filter generally suffers from low sensitivity and low signal noise ratio (SNR).
- SNR signal noise ratio
- a modified Bayer filter with transparent white (W) filter (commonly called RGBW filter array) is thus introduced to improve sensitivity and SNR.
- the conventional image sensor with RGBW filter array does not make effective use of the color and white information, and therefore cannot effectively improve sensitivity and SNR while preserving resolution and minimizing color artifacts.
- the embodiment may provide flexible sharpness control and/or low light auto-exposure adjustment.
- a color and white filter array is placed over pixels sensors of an image sensor, thereby generating converted color signals and converted white signals.
- the converted white signals are interpolated to generate interpolated white signals.
- White-chroma differences between the converted color signals and the converted white signals are interpolated to generate interpolated white-chroma difference signals.
- the interpolated white signal and the interpolated white-chroma difference signals are transformed into a color space, thereby generating transformed color signals.
- FIG. 1 schematically shows a Bayer filter
- FIG. 2 shows a block diagram illustrated of color processing according to one embodiment of the present invention
- FIG. 3 shows an exemplary array pattern of a portion of the RGBW array of FIG. 2 ;
- FIG. 4 exemplarily shows a portion of the RGBW array of FIG. 2 with a working window centered at a current center pixel;
- FIG. 5 illustrates a flow diagram of the white interpolation block of FIG. 2 according to one embodiment of the present invention
- FIG. 6 exemplarily shows a portion of the RGBW array of FIG. 2 with a current white center pixel
- FIG. 7 exemplarily shows a portion of the RGBW array of FIG. 2 with a current green center pixel
- FIG. 8 exemplarily shows a portion of the RGBW array of FIG. 2 with a current blue center pixel
- FIG. 9 illustrates a flow diagram of the white-chroma interpolation block of FIG. 2 according to one embodiment of the present invention.
- FIG. 2 shows a block diagram illustrated of color processing according to one embodiment of the present invention.
- the color processing may be performed by a processor such as a digital image processor.
- a color and white filter array (filter array hereinafter) 20 is used to filter light.
- the filter array 20 is composed of color filters, such as red (R) filters, green (G) filters and/or blue (B) filters, which filter light by wavelength range.
- the filter array 20 further includes white (W) filters that pass, or is transparent to, light in visible wavelength.
- a filter array 20 composed of red filter, green filters, blue filters and white filters is adopted, and the filter array 20 of the embodiment may sometimes be referred to as an RGBW array instead.
- FIG. 3 shows an exemplary array pattern (4 ⁇ 4 array is shown here) of a portion of the RGBW array 20 of FIG. 2 .
- the array pattern of the RGBW array 20 is configured of 50% white, 25% green, 12.5% red and 12.5% blue in a manner similar to a Bayer pattern as exemplified in FIG. 1 .
- the RGBW array 20 of the embodiment is generally placed over pixels sensors (or photo-sensors) of an image sensor, such as complementary metal-oxide-semiconductor (CMOS) image sensor, which converts an optical image captured by the RGBW array 20 into electrical signals.
- CMOS complementary metal-oxide-semiconductor
- the image sensor along with an associated circuitry 21 converts red light captured by the red filter into a red signal, converts green light captured by the green filter into a green signal, converts blue light captured by the blue filter into a blue signal, and converts white light captured by the white filter into a white signal.
- the circuitry 21 associated with the image sensor may include, for example, an amplifier 211 with gains and a bad-pixel corrector (BPC) 212 .
- the amplifier 211 and the BPC 212 may be implemented by conventional technique, details of which are omitted for brevity.
- FIG. 4 exemplarily shows a portion of the RGBW array 20 (5 ⁇ 5 array is shown) with a (e.g., 3 ⁇ 3) working window 41 centered at a current center pixel (P 13 in this example).
- FIG. 5 illustrates a flow diagram of the white interpolation block 22 of FIG. 2 according to one embodiment of the present invention.
- a filtered white (FW) signal for each pixel in the working window 41 may be generated by filtering, such as low-pass filtering, neighboring converted white signals according to the following exemplary expressions:
- a filtered white signal FW 7 at the pixel P 7 may be generated by averaging neighboring converted white signals, that is, W 2 , W 6 , W 8 and W 12 .
- a filtered white signal FW 8 at the pixel P 8 may be generated by taking weighted average of neighboring converted white signals (i.e., W 2 , W 4 , W 12 and W 14 ) with a weight of 1 ⁇ 8 and the converted white signal at the pixel P 8 itself with a (greater) weight of 0.5.
- edge-detection parameters are generated using the filtered white signals in the working window 41 according to the following exemplary expressions:
- a sum V_l of absolute values of pairs of adjacent pixels (e.g., a pair of P 12 and P 7 , and a pair of P 12 and P 17 ) along a vertically left direction may be generated to indicate the extent of detecting an edge along that direction (e.g., the less the value is, the more probably an edge exists).
- a sum H_t of absolute values of pairs of adjacent pixels (e.g., a pair of P 8 and P 7 , and a pair of P 8 and P 9 ) along a horizontally top direction may be generated to indicate the extent of detecting an edge along that direction.
- edge detection is performed based on the edge-detection parameters generated from step 222 .
- one of three edge-detection decisions is determined: an edge detected, no edge detected, and an in-between.
- an interpolated white signal e.g., W 13
- the current center pixel e.g., P 13 in the example
- Steps 223 and 224 A-C may be carried out according to the following exemplary expressions, where ev_thL and ev_thH are threshold values:
- the interpolated white signal is generated by averaging neighboring converted white signals (e.g., W 8 and W 18 ) along the edge.
- the interpolated white signal is generated by averaging neighboring converted white signals (e.g., W 12 and W 14 ) along the edge.
- the interpolated white signal is generated by averaging all neighboring converted white signals (e.g., W 8 , W 18 , W 12 and W 14 ).
- the interpolated white signal is a weighted sum of the interpolated white signal with an edge detected, and the interpolated white signal without an edge detected.
- sharpness enhancement 23 may be further performed on the interpolated white signal. Specifically, scaled differences between the interpolated signal of the current white center pixel (e.g., P 13 in FIG. 4 ) and the converted white signals of neighboring pixels (e.g., P 8 , P 12 , P 14 and P 18 ) may be added back to the current white center pixel to generate a weighted average value with enhanced sharpness. Other conventional technique may be adopted to perform sharpness enhancement 23 on the interpolated white signal.
- the converted color signals e.g., red, green and/or blue signals
- white signals are subjected to an interpolation 24 of white-chroma (or white-color) difference (e.g., W-R, W-G, W-B).
- the white-chroma interpolation 24 may be performed in one of four manners depending on what the current center pixel is: a white pixel (as exemplified in FIG. 6 ), a green pixel (as exemplified in FIG. 7 ), a blue pixel (as exemplified in FIG. 8 ) and a red pixel.
- FIG. 9 illustrates a flow diagram of the white-chroma interpolation block 24 of FIG. 2 according to one embodiment of the present invention.
- a white-red difference set dWR_set 10 composed of differences respectively between the converted white signals and neighboring converted red signals is obtained
- a white-green difference set dWG_set 16 composed of differences respectively between the converted white signals and neighboring converted green signals is obtained
- a white-blue difference set dWB_set 10 composed of differences respectively between the converted white signals and neighboring converted blue signals is obtained.
- Obtaining the white-chroma difference sets in step 241 may be carried out according to the following exemplary expressions:
- the white-chroma difference set is analyzed to determine its data distribution.
- a ratio of (maximum value minus minimum value) to (maximum value plus minimum value) of the white-chroma difference set is used to determine data distribution. If the ratio is greater than a threshold value th, indicating that the white-chroma difference set is not normally distributed, a median of the white-chroma difference set is preferably used as an interpolated white-chroma difference signal (step 243 ), otherwise, a mean of the white-chroma difference set is used as an interpolated white-chroma difference signal (step 244 ).
- Steps 242 - 244 may be carried out according to the following exemplary expressions:
- the interpolation 24 of white-chroma difference with a green current center pixel may be carried out according to the following exemplary expressions. It is noted that W, G, R or B in the following expressions may represent the filtered signal if it is not available directly from the RGBW array 20 .
- the interpolation 24 of white-chroma difference with a blue current center pixel may be carried out according to the following exemplary expressions. It is noted that W, G, R or B in the following expressions may represent the filtered signal if it is not available directly from the RGBW array 20 .
- the interpolation 24 of white-chroma difference with a red current center pixel may be carried out in a manner similar to the interpolation with a blue current center pixel, and details of which are thus omitted for brevity.
- the interpolated white signal from the block 22 (or enhanced one from the block 23 ) and the interpolated white-chroma difference signals from the block 24 are transformed into a color space (e.g., RGB space), therefore generating transformed color signals.
- a transformed red signal may be generated by subtracting the interpolated white-red difference signal from the interpolated white signal
- a transformed green signal may be generated by subtracting the interpolated white-green difference signal from the interpolated white signal
- a transformed blue signal may be generated by subtracting the interpolated white-blue difference signal from the interpolated white signal, according to the following exemplary expressions. It is noted that W in the following expressions represent the interpolated white signal.
- the transformed color signals may be generated taking into consideration low light (i.e., less than normal lighting) auto-exposure adjustment.
- auto-exposure may generally be determined by integration time (INTG), analog gain (AG) and digital gain (DG) obtained from the circuitry 21 .
- a parameter ⁇ which acts as weighting on the interpolated white signal, is introduced here for brightness adaptation under different lighting conditions.
- the transformed color signals in the embodiment, may be generated according to the following exemplary expressions:
- the parameter ⁇ In normal lighting, the parameter ⁇ is equal to 0. As lighting goes down, INTG, AG and DG mentioned above all moves toward maximum. The parameter ⁇ starts to increase from 0 to 1 so that the brightness is boosted.
- an auto-exposure target is AE target
- a current mean brightness value is Y mean
- a current mean white value is W mean
- the parameter ⁇ may be obtained as:
Abstract
Description
- 1. Field of the Invention
- The present invention generally relates to a color and white filter array, and more particularly to a method of color processing using an RGBW filter array.
- 2. Description of Related Art
- A Bayer filter, as depicted in
FIG. 1 , is a color filter array composed of red (R), green (G) and blue (B) color filters disposed on a grid of photo-sensors, and specifically configured with a pattern of 50% green, 25% red and 25% blue. The Bayer filter with the photo-sensors forms an image sensor that is commonly used in electronic devices such as digital cameras or camcorders. - As each composing color filter of the Bayer filter passes only one color, information of other colors at each pixel position need be calculated by interpolation. The image sensor with the Bayer filter generally suffers from low sensitivity and low signal noise ratio (SNR). A modified Bayer filter with transparent white (W) filter (commonly called RGBW filter array) is thus introduced to improve sensitivity and SNR. The conventional image sensor with RGBW filter array, however, does not make effective use of the color and white information, and therefore cannot effectively improve sensitivity and SNR while preserving resolution and minimizing color artifacts.
- A need has thus arisen to propose a novel scheme of processing the color and white information obtained from the RGBW filter array in order to overcome the disadvantages mentioned above.
- In view of the foregoing, it is an object of the embodiment of the present invention to provide a method of color processing using a color and white filter array that performs pixel adaptive edge-sensing interpolation of white signal, and effectively utilizes white and white-chroma difference for color space transformation, therefore substantially improving sensitivity and signal noise ratio while preserving resolution and minimizing color artifacts. Moreover, the embodiment may provide flexible sharpness control and/or low light auto-exposure adjustment.
- According to one embodiment, a color and white filter array is placed over pixels sensors of an image sensor, thereby generating converted color signals and converted white signals. The converted white signals are interpolated to generate interpolated white signals. White-chroma differences between the converted color signals and the converted white signals are interpolated to generate interpolated white-chroma difference signals. The interpolated white signal and the interpolated white-chroma difference signals are transformed into a color space, thereby generating transformed color signals.
-
FIG. 1 schematically shows a Bayer filter; -
FIG. 2 shows a block diagram illustrated of color processing according to one embodiment of the present invention; -
FIG. 3 shows an exemplary array pattern of a portion of the RGBW array ofFIG. 2 ; -
FIG. 4 exemplarily shows a portion of the RGBW array ofFIG. 2 with a working window centered at a current center pixel; -
FIG. 5 illustrates a flow diagram of the white interpolation block ofFIG. 2 according to one embodiment of the present invention; -
FIG. 6 exemplarily shows a portion of the RGBW array ofFIG. 2 with a current white center pixel; -
FIG. 7 exemplarily shows a portion of the RGBW array ofFIG. 2 with a current green center pixel; -
FIG. 8 exemplarily shows a portion of the RGBW array ofFIG. 2 with a current blue center pixel; and -
FIG. 9 illustrates a flow diagram of the white-chroma interpolation block ofFIG. 2 according to one embodiment of the present invention. -
FIG. 2 shows a block diagram illustrated of color processing according to one embodiment of the present invention. In the embodiment, the color processing may be performed by a processor such as a digital image processor. - According to the embodiment, a color and white filter array (filter array hereinafter) 20 is used to filter light. Specifically, the
filter array 20 is composed of color filters, such as red (R) filters, green (G) filters and/or blue (B) filters, which filter light by wavelength range. Thefilter array 20 further includes white (W) filters that pass, or is transparent to, light in visible wavelength. In the embodiment, afilter array 20 composed of red filter, green filters, blue filters and white filters is adopted, and thefilter array 20 of the embodiment may sometimes be referred to as an RGBW array instead. -
FIG. 3 shows an exemplary array pattern (4×4 array is shown here) of a portion of theRGBW array 20 ofFIG. 2 . The array pattern of theRGBW array 20 is configured of 50% white, 25% green, 12.5% red and 12.5% blue in a manner similar to a Bayer pattern as exemplified inFIG. 1 . - The
RGBW array 20 of the embodiment is generally placed over pixels sensors (or photo-sensors) of an image sensor, such as complementary metal-oxide-semiconductor (CMOS) image sensor, which converts an optical image captured by theRGBW array 20 into electrical signals. Specifically, the image sensor along with an associatedcircuitry 21 converts red light captured by the red filter into a red signal, converts green light captured by the green filter into a green signal, converts blue light captured by the blue filter into a blue signal, and converts white light captured by the white filter into a white signal. - The
circuitry 21 associated with the image sensor may include, for example, anamplifier 211 with gains and a bad-pixel corrector (BPC) 212. Theamplifier 211 and the BPC 212 may be implemented by conventional technique, details of which are omitted for brevity. - In the embodiment, as shown in
FIG. 2 , the converted white signals are then subjected to aninterpolation 22, particularly an adaptive edge-sensing interpolation.FIG. 4 exemplarily shows a portion of the RGBW array 20 (5×5 array is shown) with a (e.g., 3×3)working window 41 centered at a current center pixel (P13 in this example). -
FIG. 5 illustrates a flow diagram of thewhite interpolation block 22 ofFIG. 2 according to one embodiment of the present invention. Instep 221, a filtered white (FW) signal for each pixel in theworking window 41 may be generated by filtering, such as low-pass filtering, neighboring converted white signals according to the following exemplary expressions: -
- FW7=(W2+W6+W8+W12)/4;
- FW8=0.5*W8+(W2+W4+W12+W14)/8;
- FW9=(W4+W8+W10+W14)/4;
- FW12=0.5*W12+(W6+W8+W16+W18)/8;
- FW13=(W8+W12+W14+W18)/4;
- FW14=0.5*W14+(W8+W10+W18+W20)/8;
- FW17=(W12+W16+W18+W22)/4;
- FW18=0.5*W18+(W12+W14+W22+W24)/8;
- FW19=(W14+W18+W20+W24)/4
- For example, a filtered white signal FW7 at the pixel P7 may be generated by averaging neighboring converted white signals, that is, W2, W6, W8 and W12. Similarly, for example, a filtered white signal FW8 at the pixel P8 may be generated by taking weighted average of neighboring converted white signals (i.e., W2, W4, W12 and W14) with a weight of ⅛ and the converted white signal at the pixel P8 itself with a (greater) weight of 0.5.
- Subsequently, in
step 222, edge-detection parameters are generated using the filtered white signals in theworking window 41 according to the following exemplary expressions: -
- V_l=abs(FW12−FW7)+abs(FW12−FW17);
- V_c=abs(FW13−FW8)+abs(FW13−FW18);
- V_r=abs(FW14−FW9)+abs(FW14−FW19);
- V_con=V_l<FW12*Eth&&V_c<FW13*Eth&&V_r<FW14*Eth;
- H_t=abs(FW8−FW7)+abs(FW8−FW9);
- H_c=abs(FW13−FW12)+abs(FW13−FW14);
- H_b=abs(FW18−FW17)+abs(FW18−FW19);
- H_con=H_t<FW8*Eth&&H_c<FW13*Eth&&H_b<FW18*Eth;
- EV=V_l+V_c+V_r+H_t+H_c+H_b
- For example, a sum V_l of absolute values of pairs of adjacent pixels (e.g., a pair of P12 and P7, and a pair of P12 and P17) along a vertically left direction may be generated to indicate the extent of detecting an edge along that direction (e.g., the less the value is, the more probably an edge exists). Similarly, for example, a sum H_t of absolute values of pairs of adjacent pixels (e.g., a pair of P8 and P7, and a pair of P8 and P9) along a horizontally top direction may be generated to indicate the extent of detecting an edge along that direction.
- Afterwards, in
step 223, edge detection is performed based on the edge-detection parameters generated fromstep 222. In the embodiment, one of three edge-detection decisions is determined: an edge detected, no edge detected, and an in-between. Finally, instep window 41 in accordant with the determined edge-detection decision.Steps -
- Summarily speaking, in case a vertical edge has been detected, the interpolated white signal is generated by averaging neighboring converted white signals (e.g., W8 and W18) along the edge. In case a horizontal edge has been detected, the interpolated white signal is generated by averaging neighboring converted white signals (e.g., W12 and W14) along the edge. In case no edge has been detected, the interpolated white signal is generated by averaging all neighboring converted white signals (e.g., W8, W18, W12 and W14). In case an in-between has been detected, the interpolated white signal is a weighted sum of the interpolated white signal with an edge detected, and the interpolated white signal without an edge detected.
- Referring back to
FIG. 2 ,sharpness enhancement 23 may be further performed on the interpolated white signal. Specifically, scaled differences between the interpolated signal of the current white center pixel (e.g., P13 inFIG. 4 ) and the converted white signals of neighboring pixels (e.g., P8, P12, P14 and P18) may be added back to the current white center pixel to generate a weighted average value with enhanced sharpness. Other conventional technique may be adopted to performsharpness enhancement 23 on the interpolated white signal. - Still referring to
FIG. 2 , the converted color signals (e.g., red, green and/or blue signals) and white signals are subjected to aninterpolation 24 of white-chroma (or white-color) difference (e.g., W-R, W-G, W-B). The white-chroma interpolation 24 may be performed in one of four manners depending on what the current center pixel is: a white pixel (as exemplified inFIG. 6 ), a green pixel (as exemplified inFIG. 7 ), a blue pixel (as exemplified inFIG. 8 ) and a red pixel. - Take the current white center pixel demonstrated in
FIG. 6 as an example,FIG. 9 illustrates a flow diagram of the white-chroma interpolation block 24 ofFIG. 2 according to one embodiment of the present invention. Instep 241, a white-red difference set dWR_set10 composed of differences respectively between the converted white signals and neighboring converted red signals is obtained, a white-green difference set dWG_set16 composed of differences respectively between the converted white signals and neighboring converted green signals is obtained, and a white-blue difference set dWB_set10 composed of differences respectively between the converted white signals and neighboring converted blue signals is obtained. Obtaining the white-chroma difference sets instep 241 may be carried out according to the following exemplary expressions: -
- at P13:
- dWR_set10=[W13−R14;W9−R14;W15−R14;W19−R14;W7−R2;W1−R2;W3−R2;W17−R22;W21−R22;W23−R22];
- dWG_set16=[W3−G8;W7−G8;W13−G8;W9−G8;W13−G18;W17−G18;W19−G18;W23−G18;
- W7−G6;W11−G6;W11−G16;W17−G16;W19−G20;W15−G20;W15−G10;W9−G10];
- dWB_set10=[W7−B12;W11−B12;W17−B12;W13−B12;W3−B4;W5−B4;W9−B4;W19−B24;W23−B24;W25−B24]
- Subsequently, in
step 242, the white-chroma difference set is analyzed to determine its data distribution. In the embodiment, a ratio of (maximum value minus minimum value) to (maximum value plus minimum value) of the white-chroma difference set is used to determine data distribution. If the ratio is greater than a threshold value th, indicating that the white-chroma difference set is not normally distributed, a median of the white-chroma difference set is preferably used as an interpolated white-chroma difference signal (step 243), otherwise, a mean of the white-chroma difference set is used as an interpolated white-chroma difference signal (step 244). Steps 242-244 may be carried out according to the following exemplary expressions: -
- dWR=median(dWR_set10); if
- (max(dWR_set10)−min(dWR_set10))/(max(dWR_set10)+min(dWR_set10))>th;
- Else dWR=mean(dWR_set10);
- dWG=median(dWG_set16); if
- (max(dWG_set16)−min(dWG_set16))/(max(dWG_set16)+min(dWG_set16))>th;
- Else dWG=mean(dWG_set16);
- dWB=median(dWB_set10); if
- (max(dWB_set10)−min(dWB_set10))/(max(dWB_set10)+min(dWB_set10))>th;
- Else dWB=mean(dWB_set10)
- The
interpolation 24 of white-chroma difference with a green current center pixel (FIG. 7 ) may be carried out according to the following exemplary expressions. It is noted that W, G, R or B in the following expressions may represent the filtered signal if it is not available directly from theRGBW array 20. -
- at P13:
- dWR_set8=[W13−R14;W9−R14;W15−R14;W19−R14;W7−R2;W1−R2;W3−R2;W17−R22;W21−R22;
- W23−R22];
- dWG_set16=[W3−G8;W7−G8;W13−G8;W9−G8;W13−G18;W17−G18;W19−G18;W23−G18;
- W7−G6;W11−G6;W11−G16;W17−G16;W19−G20;W15−G20;W15−G10;W9−G10];
- dWB_set8=[W7−B12;W11−B12;W17−B12;W13−B12;W3−B4;W5−B4;W9−B4;W19−B24;W23−B24;
- W25−B24];
- dWR=median(dWR_set8); if
- (max(dWR_set8)−min(dWR_set8))/(max(dWR_set8)+min(dWR_set8))>th;
- Else dWR=mean(dWR_set8);
- dWG=median(dWG_set16); if
- (max(dWG_set16)−min(dWG_set16))/(max(dWG_set16)+min(dWG_set16))>th;
- Else dWG=mean(dWG_set16);
- dWB=median(dWB_set8); if
- (max(dWB_set8)−min(dWB_set8))/(max(dWB_set8)+min(dWB_set8))>th;
- Else dWB=mean(dWB_set8)
- The
interpolation 24 of white-chroma difference with a blue current center pixel (FIG. 8 ) may be carried out according to the following exemplary expressions. It is noted that W, G, R or B in the following expressions may represent the filtered signal if it is not available directly from theRGBW array 20. -
- at P13:
- dWR_set12=[W2−R3;W4−R3;W8−R3;W6−R11;W16−R11;W12−R11;W18−R23;W22−R23;W24−R23;W10−R15;W14−R15;W20−R15];
- dWG_set16=[W2−G7;W6−G7;W8−G7;W12−G7;W4−G9;W8−G9;W10−G9;W14−G9;
- W12−G17;W16−G17;W18−G17;W22−G17;W18−G19;W14−G19;W20−G19;W24−G19],
- dWB_set12=[W8−B13;W12−B13;W14−B13;W18−B13;W2−B1;W6−B1;W4−B5;W10−B5;W16−B21;
- W22−B21;W20−B25;W24−B25];
- dWR=median(dWR_set12); if
- (max(dWR_set12)−min(dWR_set12))/(max(dWR_set12)+min(dWR_set12))>th;
- Else dWR=mean(dWR_set12);
- dWG=median(dWG_set16); if
- (max(dWG_set16)−min(dWG_set16))/(max(dWG_set16)+min(dWG_set16))>th;
- Else dWG=mean(dWG_set16);
- dWB=median(dWB_set12); if
- (max(dWB_set12)−min(dWB_set12))/(max(dWB_set12)+min(dWB_set12))>th;
- Else dWB=mean(dWB_set12)
- The
interpolation 24 of white-chroma difference with a red current center pixel may be carried out in a manner similar to the interpolation with a blue current center pixel, and details of which are thus omitted for brevity. - Referring back to
FIG. 2 , the interpolated white signal from the block 22 (or enhanced one from the block 23) and the interpolated white-chroma difference signals from theblock 24 are transformed into a color space (e.g., RGB space), therefore generating transformed color signals. Specifically, in the embodiment, a transformed red signal may be generated by subtracting the interpolated white-red difference signal from the interpolated white signal, a transformed green signal may be generated by subtracting the interpolated white-green difference signal from the interpolated white signal, and a transformed blue signal may be generated by subtracting the interpolated white-blue difference signal from the interpolated white signal, according to the following exemplary expressions. It is noted that W in the following expressions represent the interpolated white signal. -
- {circumflex over (R)}=W−dWR;
- Ĝ=W−dWG;
- {circumflex over (B)}=W−dWB;
- In an alternative embodiment, the transformed color signals may be generated taking into consideration low light (i.e., less than normal lighting) auto-exposure adjustment. Specifically, auto-exposure may generally be determined by integration time (INTG), analog gain (AG) and digital gain (DG) obtained from the
circuitry 21. A parameter α, which acts as weighting on the interpolated white signal, is introduced here for brightness adaptation under different lighting conditions. The transformed color signals, in the embodiment, may be generated according to the following exemplary expressions: -
- {circumflex over (R)}=W−(1−α)*dWR=α*W+(1−α)*R;
- Ĝ=W−(1−α)*dWG=α*W+(1−α)*G;
- {circumflex over (B)}=W−(1−α)*dWB=α*W+(1−α)*B;
- In normal lighting, the parameter α is equal to 0. As lighting goes down, INTG, AG and DG mentioned above all moves toward maximum. The parameter α starts to increase from 0 to 1 so that the brightness is boosted. Suppose an auto-exposure target is AEtarget, a current mean brightness value is Ymean, a current mean white value is Wmean, then the parameter α may be obtained as:
-
- Although specific embodiments have been illustrated and described, it will be appreciated by those skilled in the art that various modifications may be made without departing from the scope of the present invention, which is intended to be limited solely by the appended claims.
Claims (21)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US14/303,307 US9219896B1 (en) | 2014-06-12 | 2014-06-12 | Method of color processing using a color and white filter array |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US14/303,307 US9219896B1 (en) | 2014-06-12 | 2014-06-12 | Method of color processing using a color and white filter array |
Publications (2)
Publication Number | Publication Date |
---|---|
US20150365643A1 true US20150365643A1 (en) | 2015-12-17 |
US9219896B1 US9219896B1 (en) | 2015-12-22 |
Family
ID=54837249
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US14/303,307 Expired - Fee Related US9219896B1 (en) | 2014-06-12 | 2014-06-12 | Method of color processing using a color and white filter array |
Country Status (1)
Country | Link |
---|---|
US (1) | US9219896B1 (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20150194127A1 (en) * | 2014-01-06 | 2015-07-09 | Fibar Group sp. z o.o. | Rgbw controller |
US20160196474A1 (en) * | 2014-12-10 | 2016-07-07 | Denso Corporation | Image processing apparatus and lane partition line recognition system including the same |
CN106447597A (en) * | 2016-11-02 | 2017-02-22 | 上海航天控制技术研究所 | High-resolution image accelerated processing method based on parallel pipeline mechanism |
CN109348204A (en) * | 2018-10-30 | 2019-02-15 | 德淮半导体有限公司 | Imaging sensor and the method for generating image |
CN112104847A (en) * | 2020-09-17 | 2020-12-18 | 北京理工大学 | SONY-RGBW array color reconstruction method based on residual error and high-frequency replacement |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2010288150A (en) * | 2009-06-12 | 2010-12-24 | Toshiba Corp | Solid-state imaging device |
JP5724185B2 (en) * | 2010-03-04 | 2015-05-27 | ソニー株式会社 | Image processing apparatus, image processing method, and program |
JP2011239252A (en) * | 2010-05-12 | 2011-11-24 | Panasonic Corp | Imaging device |
-
2014
- 2014-06-12 US US14/303,307 patent/US9219896B1/en not_active Expired - Fee Related
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20150194127A1 (en) * | 2014-01-06 | 2015-07-09 | Fibar Group sp. z o.o. | Rgbw controller |
US9693427B2 (en) * | 2014-01-06 | 2017-06-27 | Fibar Group S.A. | RGBW controller |
US20160196474A1 (en) * | 2014-12-10 | 2016-07-07 | Denso Corporation | Image processing apparatus and lane partition line recognition system including the same |
US9727794B2 (en) * | 2014-12-10 | 2017-08-08 | Denso Corporation | Image processing apparatus and lane partition line recognition system including the same |
CN106447597A (en) * | 2016-11-02 | 2017-02-22 | 上海航天控制技术研究所 | High-resolution image accelerated processing method based on parallel pipeline mechanism |
CN109348204A (en) * | 2018-10-30 | 2019-02-15 | 德淮半导体有限公司 | Imaging sensor and the method for generating image |
CN112104847A (en) * | 2020-09-17 | 2020-12-18 | 北京理工大学 | SONY-RGBW array color reconstruction method based on residual error and high-frequency replacement |
Also Published As
Publication number | Publication date |
---|---|
US9219896B1 (en) | 2015-12-22 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US8948506B2 (en) | Image processing device, image processing method, and program | |
US7668391B2 (en) | Image signal processor and image signal processing method | |
KR102170410B1 (en) | Device for acquiring bimodal images | |
US9219896B1 (en) | Method of color processing using a color and white filter array | |
KR100809687B1 (en) | Image processing apparatus and method for reducing noise in image signal | |
EP3093819B1 (en) | Imaging apparatus, imaging system, and signal processing method | |
US8744206B2 (en) | Image processing apparatus, image processing method, and program | |
US9253459B2 (en) | Image processing apparatus and image processing method, and program | |
US20150042848A1 (en) | Image processing apparatus, image processing method, and electronic apparatus | |
JP4346634B2 (en) | Target detection device | |
US20160254300A1 (en) | Sensor for dual-aperture camera | |
KR100587143B1 (en) | Method for edge detection of image signal | |
EP2348482B1 (en) | Image processing device and image processing method | |
US20130077858A1 (en) | Image processing module and image processing method | |
US10694118B2 (en) | Signal processing apparatus, imaging apparatus, and signal processing method | |
CN113068011B (en) | Image sensor, image processing method and system | |
US8767101B2 (en) | Image processing apparatus and system | |
US9401006B2 (en) | Image processing apparatus, image processing method, and storage medium | |
KR102366254B1 (en) | Image processing apparatus and method | |
KR20180118432A (en) | Image Processing Apparatus and Method for Improving Sensitivity | |
US20130077860A1 (en) | Image signal processor and method for image enhancement | |
KR101874538B1 (en) | Method and Apparatus for Processing Image to Simultaneously Enhance Contrast and Saturation of Image | |
JP4990240B2 (en) | Image processing apparatus and image processing program | |
US8995766B1 (en) | Image processing method and image processing device | |
US9357193B2 (en) | Method and apparatus for compensating for color imbalance in image data |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: HIMAX IMAGING LIMITED, TAIWAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:SHI, MIAOHONG;REEL/FRAME:033145/0576 Effective date: 20140522 |
|
STCF | Information on status: patent grant |
Free format text: PATENTED CASE |
|
FEPP | Fee payment procedure |
Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY |
|
MAFP | Maintenance fee payment |
Free format text: PAYMENT OF MAINTENANCE FEE, 4TH YEAR, LARGE ENTITY (ORIGINAL EVENT CODE: M1551); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY Year of fee payment: 4 |
|
FEPP | Fee payment procedure |
Free format text: MAINTENANCE FEE REMINDER MAILED (ORIGINAL EVENT CODE: REM.); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY |
|
LAPS | Lapse for failure to pay maintenance fees |
Free format text: PATENT EXPIRED FOR FAILURE TO PAY MAINTENANCE FEES (ORIGINAL EVENT CODE: EXP.); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY |
|
STCH | Information on status: patent discontinuation |
Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362 |
|
FP | Lapsed due to failure to pay maintenance fee |
Effective date: 20231222 |