There are many application scenarios need adopt the scanning of image system to convert scanning object to a kind of electronic format, so that can analyze subsequently, print, send and file.Electronic format is an images of scanning object normally.A typical example of scanning of image system is exactly a scanner, and scanning object is exactly a piece of paper in a book or the one piece of article.By scanner, an image width of cloth electronics of this paper or numeral has just produced.
The scanning of image system generally comprises a sensory package, in order to objective optics convert an images to.In sensory package, in order to objective optics convert an images to key element be image sensor.Image sensor comprises a photodetector array, and these photodetectors can respond the light that shines on the image sensor.Each photodetector all can produce electronics (electric charge) signal of having represented from the light intensity of target reflection.Electronic signal from each photodetector is read, carry out digitizing by an analog quantity to the A/D converter of digital quantity then, to produce the digital signal or the image of target.
One of used image sensor is a kind of linear transducer in the scanning of image system, and it comprises three row's photodetectors, and is stacked respectively to align the optical filter of assorting with selectivity printing opacity with each photodetector on it.Figure 1A shows an exemplary linear image sensor 100, and it comprises three row's photodetectors 102,104,106.Each row front all is equipped with a kind of optical filter of the printing opacity to a certain specific spectral region sensitivity.For example, at row number stacked respectively red, green and blue optical filter on all photodetector in 102,104 and 106.Thereby when each photodetector in the image sensor 100 was exposed to a scanning object that is illuminated by the white illumination light source, image sensor 100 can produce three electronic signals simultaneously.
One of problem deserving of attention relevant with image sensor 100 is to need some auxiliary memory buffer unit and treating apparatus to re-assembly electronic signal, and each aligns the image pixel of assorting with accurate reproduction.Referring to Figure 1B, show the imaging model of a simplification, wherein, scanning object 110 scioptics 114 form image by color image sensor 112.Color image sensor 112 is similar to image sensor 100, has three row's photodetectors.Optical path shown in the figure shows that three row's photodetectors are owing to the physical separation between each row, and they do not align a sweep trace of assorting in scanning object 110 physically.In other words, three row's photodetectors seem not to be same sweep trace in scanning object 110, Here it is one typically align the problem of assorting.Interval between two row's photodetectors must keep, and reads electronic signal for the photodetector of sensing circuit from a row of adjoining.At last, an electronic signal array from each row's photodetector must be stored.The size of this array is proportional to the spacing distance D between two row's photodetectors.If the supposition distance D is 100 μ m (micron), and the height d=10 μ m of photodetector, and electronic signal is the data precision of 8 bits, then the memory capacity for a color pixel is estimated as:
8 (3D)/d=240 bits;
In fact, 8 * 11 inches the standard-sized paper that a color image sensor is designed for scanning rule is much, thereby, if the resolution of image sensor is 600dpi (per inch 600 points), this sensor one row will comprise 600 * 8=4800 photodetector.In other words, it is that the memory buffer unit of 240 * 4800=1.152Megabits (million bits) re-assemblies these electronic signals that a kind of capacity must be arranged exactly, aligns the color pixel signal of assorting with generation.In addition, in order to keep a rational sweep velocity, require memory buffer unit to have high performance usually.Thereby added considerable cost to image sensor.
Although existing many restrictions aspect the shortening spacing distance, there is the people constantly to make great efforts to make the distance at above-mentioned interval to reduce to minimum always.One of method that reduces the spacing distance between two row's photodetectors is the size that reduces each photodetector, so that corresponding each detector of each row can be more close relatively among three rows.But the problem that significantly reduces to bring visual sensitivity of photodetector size.
Though how to reduce since each row exist between photodetector physical separation caused aligns the problem of assorting, all can not eliminate the requirement that re-assemblies electronic signal with the memory buffer unit of assisting with the existing arrangement of the photodetector shown in Figure 1A.Thereby, being starved of a kind of color image sensor, it only needs the memory buffer unit of minimum and the color picture signal that treating apparatus just can be exported a kind of high-quality of satisfactory type.Along with the minimizing of memory buffer unit in this color image sensor, the cost of this color image sensor just can reduce significantly.
About in the detailed description of the present invention,, many concrete details have been introduced below in order to provide to thorough of the present invention.Yet,, it is evident that the present invention also can put into practice without these details for those skilled in the art.The description of this paper and illustrate that used means are the experienced or skilled personnel in present technique field and convey to the used common means of other skilled person in present technique field most effectively for the essence with their work.In other cases, some well-known methods, program, parts and circuit all are not described in detail, to avoid unnecessarily hiding looks of the present invention.
One width of cloth color image comprises the image of three kinds of intensity usually, and they derive from the exposure of a color body to three kinds of main color components respectively.One of universal method of three kinds of main color components exposures is to use a kind of image sensor, and it comprises a plurality of photodetectors, is superimposed with a kind of filtering apparatus of mosaic on it.This filtering apparatus comprises the optical filter of many selectivity printing opacities, and aligns with each photodetector and to assort, and has optionally first, second and the 3rd photodetector group thereby form, and they are respectively to redness, green and the blue region sensitivity of visible spectrum.Thereby, have only redness, green and blue three components can pass through these optical filters, thereby can obtain three images of intensity separately.
In general, the image of every kind of intensity, perhaps their digital version more precisely all is the array or the matrix of many pixels.If they are the accuracy representings with 8 bits, the value of these pixels is between 0 to 255 so.In other words, each the color pixel C in a width of cloth color image (i is a vector pixel j), and can be expressed as:
In the formula, (i be the coordinate of an image pixel j), and C is a color image.R, G and B then are respectively the images of three kinds of intensity among the color image C.Above-mentioned expression formula also shows: only three strength component R (i, j), G (i, j) and B (i j) assorts on time, and when promptly they all came in the comfortable color body same, a color pixel could be expressed effectively.
If each corresponding pixel of ordering corresponding to S in each in these three kinds of intensity images has identical value, be R (i, j)=G (i, j)=B (i, j), (i is j) within S in the formula, then that of ordering corresponding to S in this color body must be achromaticity, looks to be from secretly between the white.Otherwise, if each pixel of ordering corresponding to S in each in three kinds of intensity images has different values, promptly R (i, j) ≠ G (i, j) ≠ (i, j), then that of ordering corresponding to S on this color body looks it should is colored to B.For example, pure red, pure vector pixel green or ethereal blue be expressed as respectively C (i, j)=[255 0 0]
T, C (i, j)=[0 255 0]
TOr C (i, j)=[0 0 255]
TCan in a width of cloth color image, reproduce exactly in order to ensure color body, must carefully control a color imaging system, to produce the image of three kinds of intensity, guarantee that the color image that is generated after they combine can reproduce the shades of colour of this color body.
According to one embodiment of the present of invention, image sensor as herein described is a kind of linear array or linear transducer.This means that each this image sensor produces delegation's colour signal, the synthetic in proper order width of cloth color image that just produces of all these colour signals.Under the situation of not losing ubiquity, this image sensor produces the signal of three kinds of colors, and every kind of signal all comes from the exposure that filters through a kind of color.
Fig. 2 A shows a kind of exemplary arrangement 200 (image sensor) of each photodetector 202 of lining up two rows.Each photodetector of first row 204 is superimposed with the optical filter of alternative colors, second row's 206 the then topped optical filter with a kind of color of each photodetector.According to an embodiment who produces traditional redness (R), green (G) and blue (B) signal, in first row 204, colored optical filter alternately or be Red lightscreening plate, or be blue color filter, then be whole-colored green color filter at the second colored optical filter of arranging in 206.Thereby, image sensor 200 produces RGB (RGB) signal respectively from each photodetector, these photodetectors, 20 are labeled as G1, R2, G3, B4, G5, R6, G7, B8, G9, R10, G11, B12, G13, R14, G15, R16, G17, R18, G19 and B20 respectively.
More particularly, in first row 204 each photodetector alternately topped respectively with or be superimposed with a kind of light transmission filter mating plate (being referred to as redness or blue light detecting device herein) to " redness " or " blueness " spectral region sensitivity; In second row 206 each photodetector then by topped with or be superimposed with a kind of light transmission filter mating plate (being referred to as the green light detecting device herein) to " green " spectral region sensitivity.In the drawings, can be clear that, alternately insert the photodetector of a green between those red and blue photodetectors from the output of each detector.
Result according to such arrangement is that the delegation's signal that obtains from image sensor 200 samplings is sequenced, and is uniformity, and this point can be found out easily by 210 among Fig. 2 B.Concerning versicolor photodetector, the green light detecting device is by 212 arranged in patterns that repeat, to red light detecting device and blue light detecting device then respectively by 214 and 216 arranged in patterns that repeat that repeat.Particularly importantly, this arrangement has reduced significantly in order to recombinate from the quantity of the required memory buffer unit of the electronic signal of these photodetectors.Fig. 2 C shows the comparison of a simplification between two row's photodetectors of three traditional row's photodetectors and present embodiment.Suppose that the physical clearance between two row's photodetectors is just caused by the height of each photodetector.Thereby an image sensor 220 that has three traditional row's photodetectors only just can be exported a colour signal after three scanning is all finished.In other words, image sensor 220 must provide memory buffer unit to store signal from each photodetector of the first two times scanning, and when scanning beginning for the third time output signal.More particularly, for to scan line 222 imagings in the scanning target, after scanning for the first time, must store from the signal of blue light detecting device.In scanning for the second time, when scan line 222, each redness and blue light detecting device are not considered, and only investigate the green light detecting device.Thereby, must store from the signal of each green light detecting device.When beginning scanning for the third time, from each signal of each red light detecting device with in scanning for the first time from each signal of each blue light detecting device and in scanning for the second time each signal from each green light detecting device be combined to.Consider to scan whole target and produce to align the colour signal of assorting, must have the triplex row memory buffer unit available.And, only need delegation's memory buffer unit to store each signal from preceding one scan for image sensor 230.Because in second row, all can supply with the usefulness that output aligns the colour signal of assorting to each RGB (RGB) signal of scan line 222.Though Fig. 2 C shows the comparison of a simplification, be appreciated that for the skilled artisan in the art the remarkable minimizing aspect memory buffer unit needs is the arrangement that has benefited from this uniqueness of disclosed each photodetector in the present embodiment.
For each vector pixel (colour signal) is described, Fig. 2 D shows a color pixel and how is formed by the arrangement of this uniqueness and do not bring pixel to align the problem of assorting in the horizontal direction, and should combine understanding with Fig. 2 A and Fig. 2 B.10 exemplary color pixels that the image sensor 200 by Fig. 2 A is produced have been listed in the table 240.Row 242 has listed 10 pixel: P1, P2 ... P10.Row 244,246 and 248 shows in each color pixel green, redness and the blue component of each respectively.
More particularly, represented the one-component of a color pixel from the signal of each green light detecting device, corresponding signal red from each and the blue light detecting device then becomes in two adjacent color pixels a component jointly accordingly.For example, colour phasor pixel P1 respectively has a green component from two different green light detecting devices with P2, but shares same redness and same blue signal from same redness and same blue light detecting device.So, the horizontal clearance between two color pixels is reduced to minimum and does not cause the loss of picture resolution.
Should be pointed out that about foregoing description of the present invention is red realize to use, green and blue light detecting device.The skilled artisan in the art is appreciated that top explanation also is same being suitable for when primary colors that uses other or complementary colors optical filter.For example, magenta, yellow and blue-green are exactly one group of common alternative complementary colors, and they can be used for producing color image.In addition, a cover green light detecting device being assigned into alternately with red and blue light detecting device is not to implement requirement of the present invention therebetween.Yet in practice, this is an implementing method preferably, because human vision system is more responsive to each color in the green area of chromatic spectrum.
Fig. 3 A shows another exemplary image sensor 300, and it comprises and is arranged in each single photodetector 302.As shown in FIG., every a photodetector alternately and topped respectively with or be superimposed with a light transmission filter mating plate to " green " spectral region sensitivity, every the another one photodetector then alternately and topped respectively with or be superimposed with a light transmission filter mating plate to " redness " or " blueness " spectral region sensitivity.These color pixels are formed by the colorama detecting device of being advised as Fig. 2 D.One of the advantage that adopts the photodetector of this single arrangement be cancelled to reorganization from the required memory buffer unit of the electronic signal of each photodetector.These signals can be read very easily now and not need to recombinate.
Fig. 3 B shows the embodiment of a single photodetector, these photodetectors be make leg-of-mutton.Should be noted that leg-of-mutton definition is to comprise all similar leg-of-mutton shapes here, such as rounded triangle.As shown in the figure, all (up) triangle photodetectors, such as G1, G3, G5, G7, G9, G11, G13, G15, G17 and G19 all topped with or be superimposed with a optical filter (being referred to as the green light detecting device herein), and all inverted triangle photodetectors to " green " spectral region sensitivity, such as R2, B4, R6, B8, R10, B12, R14, B16, R18 and B20 then alternately and topped respectively with or be superimposed with a optical filter to " redness " or " blueness " spectral region sensitivity.Because such result who arranges, the physical separation between two photodetectors in the horizontal direction is reduced to minimum.
In many application, a color image sensor commonly used scans an achromatic object or is exactly a black and white object simply, such as the one page in the textbook, and produces a width of cloth black and white (grey or monochrome) image.This is the image that a width of cloth only reflects brightness.Photodetector in order to ensure each color can be to producing the signal of equal response from the reflection of this black and white scanning object, and one group of weighting coefficient as described below is used to the response of balance from the different spectrum of each color detector:
KG
1.967KR
5.360KB in the formula, K is an adjustment factor, is set at 1 usually.In other words, can directly be plotted on the gray image that is produced, then be plotted to the gray image that is produced from the signal of red and blue light detecting device and get on by interpolation suitably from the signal of green light detecting device.So, this image sensor has been turned over some inherently for the resolution of black and white scanning object, as shown in Figure 4, is wherein correspondingly handled from the individual signals of each photodetector.In the certain embodiments as shown in FIG., K is set to 1, thereby r=1.967 and b=5.360.The gray scale image that is produced has the double resolution that resembles the resolution that a traditional color image sensor can produce.
See also Fig. 5 A now, wherein show a circuit diagram 500 of having simplified, this circuit is used to read the signal that each photodetector produced in the image sensor 502.Image sensor 502 can be equivalent to the image sensor 200 among Fig. 2 A, or 300 and 310 among Fig. 3 A and Fig. 3 B.Multicircuit switch 504 comprises many diode switches 508, each in the switch 508 all with photodetector in one link to each other.Diode switch 508 is controlled by a switching signal collective.After each photodetector is exposed to a scanning object that has illuminated, a not shown control signal makes each photodetector no longer gather photon, produce charge signal to each holding capacitor (not shown), and, switch 508 orders are open-minded therebetween.Sequentially read out to amplifier 511 then from the electronic signal in each holding capacitor of each photodetector.This readout realizes that by shift register 510 shift register 510 comprises and the same number of storage unit of photodetector usually.For example, a pulsed D i is fed to shift register 510, and Di moves to another by clock pulse signal CLK from a storage unit.When a storage unit received Di, a continuous switch in the diode switch 508 was switched on (i.e. " conducting "), and a corresponding electronic signal is just therefrom read in corresponding holding capacitor.Along with passing through of Di, the electronic signal in each holding capacitor is just sequentially shifted out, and carries out digitizing by an A/D (analog quantity/digital quantity) converter 512 subsequently.Fig. 5 B shows a time clock signal 520, from wherein can obtaining many control signals, and S1, S2, S3 and S4 are some exemplary control signals (through the Di of displacement), they can connect the switch of 4 orders.Be shown in Fig. 5 B from the digital signal 530 of A/D converter 512.
The present invention is done quite detailed explanation above, and had singularity to a certain degree.The those of skill in the art in present technique field should be appreciated that what each embodiment of being disclosed was just undertaken by some examples, and the many variations in the permutation and combination of part is possible in addition, and do not break away from the spirit and scope of claim of the present invention.For example, the preferable shape of photodetector is a triangle, and the those of skill in the art in present technique field can think that the photodetector of other shape also can design like this, so that each colorama detecting device can replace arrangement adjacent to each other, makes to align the problem of assorting and reduce to minimum.Thereby scope of the present invention is to limit by appended claim rather than by each embodiment described above.