Abstract:
A color pixel array includes a plurality of micropixels. Each micropixel includes a photosensitive element and a filter element optically aligned with the photosensitive element such that incident light passes through the filter element prior to reaching the photosensitive element. The micropixels are organized into triangular macropixels that each includes multiple micropixels. A perimeter shape of each of the triangular macropixels forms a triangle. The triangular macropixels have a repeating pattern across the color pixel array.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation-in-part of U.S. patent application Ser. No. 12/755,125, filed on Apr. 6, 2010. 
     
    
     TECHNICAL FIELD 
       [0002]    This disclosure relates generally to image sensors, and in particular but not exclusively, relates to CMOS image sensors with non-rectangular photosensitive elements. 
       BACKGROUND INFORMATION 
       [0003]    Image sensors have become ubiquitous. They are widely used in digital still cameras, cellular phones, security cameras, as well as, medical, automobile, and other applications. The technology used to manufacture image sensors, and in particular, complementary metal-oxide-semiconductor (“CMOS”) image sensors (“CIS”), has continued to advance at great pace. For example, the demands of higher resolution and lower power consumption have encouraged the further miniaturization and integration of these image sensors. 
         [0004]    One field of application in which size and image quality is particularly important is medical applications (e.g., endoscopes). For medical applications the chip must typically be small while providing a high quality image. In order to achieve these characteristics, for a given chip size, the photosensitive apertures should be as large as possible, while peripheral circuitry should be as limited as possible. 
         [0005]    The pixel (picture element) fill factor denotes the fraction of the surface area of a pixel that is sensitive to light. Pixel pitch is the physical distance between adjacent pixels in an imaging device. Pixel fill factor has become smaller as pixel pitch has been reduced because the active circuit elements and metal interconnect consume an increasing proportion of the area in each pixel as the photosensitive regions are reduced in size. One way to address the loss of fill factor is to use a microscale lens (microlens) directly above each pixel to focus the light directly towards the photosensitive portion of the area within the pixel. Another way to address the loss of fill factor is to use backside illuminated (“BSI”) image sensors, which place the active pixel circuit elements and metal interconnects on a frontside of an image sensor die and the photosensitive element within the substrate facing a backside of an image sensor die. For BSI image sensors, the majority of photon absorption occurs near the backside silicon surface. However, a solution that provides larger individual pixel area on the same silicon area would improve BSI image sensors as well as frontside illuminated image sensors. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Non-limiting and non-exhaustive embodiments of the invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. 
           [0007]      FIG. 1  is a block diagram illustrating a backside illuminated imaging system. 
           [0008]      FIG. 2  is a circuit diagram illustrating pixel circuitry of two 4T pixels within a backside illuminated imaging system, in accordance with an embodiment of the invention. 
           [0009]      FIG. 3A  is a schematic representation of Bayer patterned macropixel blocks. 
           [0010]      FIG. 3B  is a schematic representation of triangular macropixel blocks each including three micropixels arranged on an X, Y grid, in accordance with a first embodiment of the invention. 
           [0011]      FIG. 4A  is a schematic representation of Bayer patterned macropixel blocks. 
           [0012]      FIG. 4B  is a schematic representation of triangular macropixel blocks each including three micropixels arranged on an X, Y grid, in accordance with a second embodiment of the invention. 
           [0013]      FIG. 5A  is a schematic representation of Bayer patterned macropixel blocks. 
           [0014]      FIG. 5B  is a schematic representation of triangular macropixel blocks each including three micropixels arranged on an X, Y grid, in accordance with a third embodiment of the invention. 
           [0015]      FIG. 6A  is a schematic representation of Bayer patterned macropixel blocks. 
           [0016]      FIG. 6B  is a schematic representation of triangular macropixel blocks each including three micropixels arranged on an X, Y, grid, in accordance with a fourth embodiment of the invention. 
           [0017]      FIG. 7  illustrates a conceptual schematic of the active circuits and metal interconnects for a frontside image sensor, in accordance with an embodiment of the invention. 
           [0018]      FIG. 8  illustrates a conceptual schematic of the active circuits and metal interconnects for a backside illuminated image sensor, in accordance with an embodiment of the invention. 
           [0019]      FIG. 9A  is a demonstrative simplified cross-sectional view of a frontside illuminated imaging pixel, in accordance with an embodiment of the invention. 
           [0020]      FIG. 9B  is a demonstrative simplified cross-sectional view of a backside illuminated imaging pixel, in accordance with an embodiment of the invention. 
           [0021]      FIG. 10  is a schematic representation of a triangular macropixel block including three micropixels with one of the micropixels having a clear filter, in accordance with an embodiment of the invention. 
           [0022]      FIG. 11  is a schematic representation of triangular macropixel blocks each including three micropixels with one of the micropixels of each macropixel block having a clear filter, in accordance with an embodiment of the invention. 
           [0023]      FIG. 12  is a schematic representation of triangular macropixel blocks each including three micropixels and having a repeating pattern that repeats every two triangular macropixel blocks, in accordance with an embodiment of the invention. 
           [0024]      FIG. 13  illustrates a conceptual schematic of the active circuits and metal interconnects for a frontside image sensor including triangular macropixels each having two micropixels, in accordance with an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    Embodiments of an apparatus for a backside illuminated (“BSI”) image sensor with a color filter array of non-rectangular elements are described herein. In the following description numerous specific details are set forth to provide a thorough understanding of the embodiments. One skilled in the relevant art will recognize, however, that the techniques described herein can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring certain aspects. 
         [0026]    Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
         [0027]      FIG. 1  illustrates an embodiment of a BSI image sensor  100  including a color pixel array  105 , readout circuitry  110 , function logic  115 , and control circuitry  120 . Color pixel array  105  is a two-dimensional (“2D”) array of imaging pixels (e.g., pixels P 1 , P 2  . . . , Pn) having X number of pixel columns (horizontal axis) and Y number of pixel rows (vertical axis). In one embodiment, each pixel is a complementary metal-oxide-semiconductor (“CMOS”) imaging pixel. Color pixel array  105  may be implemented as either a front side illuminated pixel array or a backside illuminated pixel array. As illustrated, each pixel is arranged into a row (e.g., rows R 1  to Ry) and a column (e.g., column C 1  to Cx) to acquire image data of a person, place, or object, which can then be used to render a 2D image of the person, place, or object. In one embodiment, color pixel array  105 , readout circuitry  105 , and control circuitry  120  are all integrated onto a single semiconductor die. 
         [0028]    After each pixel has acquired its image data or image charge, the image data is readout by readout circuitry  110  and transferred to function logic  115 . Readout circuitry  110  may include amplification circuitry, analog-to-digital (“ADC”) conversion circuitry, or otherwise. Function logic  115  may simply store the image data or even manipulate the image data by applying post image effects (e.g., crop, rotate, remove red eye, adjust brightness, adjust contrast, or otherwise). Control circuitry  120  is coupled to pixel array  105  to control operational characteristic of color pixel array  105 . For example, control circuitry  120  may generate a shutter signal for controlling an image acquisition window. 
         [0029]    Color pixel array  105  may also be referred to as a color filter array (“CFA”). The CFA may capture color image data using a number of techniques including additive filters and subtractive filters. Conventional color pixel array patterns are almost exclusively comprised of identical pixel elements, referred to as micropixels, each having a square shape and arranged in square X, Y patterns. Hexagonal and octagonal pixels have been proposed, but repeating pixel units, referred to as macropixels, are usually found in groups of four. The macropixels are formed of groups of micropixels having a repeating pattern within the array. In the vast majority of digital camera image sensors, the most popular CFA is the Bayer pattern. Using a checkerboard pattern with alternating rows of filters, the Bayer pattern has twice as many green pixels as red or blue pixels. They are arranged in alternating rows, of red pixels wedged between green pixels and of blue pixels wedged between green pixels. This takes advantage of the human eye&#39;s predilection to see green luminance as the strongest influence in defining sharpness. The Bayer pattern produces identical images regardless of how you hold the camera—landscape or portrait orientations. 
         [0030]    A macropixel that includes four micropixels arranged in an X, Y array is not flexible to arbitrarily adjust the proportion of colors within the macropixel. Each micropixel represents 25% of the total area, so colors are assigned in 25% increments. It may be useful to have more flexibility in the assignment of color proportions in order to optimize an image sensor for various applications, for example, the optimal human visual sensitivity may differ from a machine&#39;s optimal visual sensitivity. 
         [0031]      FIG. 2  is a circuit diagram illustrating pixel circuitry blocks  200  of two four-transistor (“4T”) pixels within a BSI imaging array, in accordance with an embodiment of the invention. Pixel circuitry blocks  200  represent one possible pixel circuitry architecture for implementing each pixel within color pixel array  105  of  FIG. 1 . However, it should be appreciated that embodiments of the present invention are not limited to 4T pixel architectures; rather, one of ordinary skill in the art having the benefit of the instant disclosure will understand that the present teachings are also applicable to 3T designs, 5T designs, and various other pixel architectures. In  FIG. 2 , pixels Pa and Pb are arranged in two rows and one column. The illustrated embodiment of each pixel circuitry block  200  includes a photosensitive element PD, a transfer transistor T 1 , a reset transistor T 2 , a source-follower (“SF”) transistor T 3 , and a select transistor T 4 . During operation, transfer transistor T 1  receives a transfer signal TX, which transfers the charge accumulated in photosensitive element PD to a floating diffusion node FD. In one embodiment, floating diffusion node FD may be coupled to a storage capacitor for temporarily storing image charges. Reset transistor T 2  is coupled between a power rail VDD and the floating diffusion node FD to reset (e.g., discharge or charge the FD to a preset voltage) under control of a reset signal RST. The floating diffusion node FD is coupled to control the gate of SF transistor T 3 . SF transistor T 3  is coupled between the power rail VDD and select transistor T 4 . SF transistor T 3  operates as a source-follower providing a high impedance output from the pixel. Finally, select transistor T 4  selectively couples the output of pixel circuitry  200  to the readout column line under control of a select signal SEL. In one embodiment, the TX signal, the RST signal, and the SEL signal are generated by control circuitry  120 . 
         [0032]      FIG. 3A  illustrates a color pixel array  300  including micropixels organized into a Bayer pattern macropixel  310 . The Bayer pattern macropixels are located on a uniform X, Y grid within pixel array  105  and have a constant separation distance Ip or pitch. Separation distance Ip is determined by measuring the distance between two grid points, such as grid points  320 , each falling at a common reference point within adjacent macropixels. 
         [0033]    It should be noted that in backside illuminated (“BSI”) image sensors, the illumination of photosensitive element PD occurs without interference from any metal or dielectric layers that form, for example, the transistor components of the pixel circuitry and associated interconnects, allowing incident light a more direct path through to the photosensitive element. In a front side illuminated (“FSI”) image sensor, the photosensitive element is formed on the side of the semiconductor substrate closest to the polysilicon, dielectric, and metal layers such that care must be taken to ensure that the metal layers do not interfere with the light collection path. 
         [0034]    As mentioned above, with BSI image sensors, incident light has a more direct path through to photosensitive element PD, which may result in a larger photosensitive element when compared to a pixel cell occupying the same area in a FSI image sensor. For simplicity, only the color filter (which is placed between photosensitive element PD and the incident light, and allows incident light of a certain wavelength band through to photosensitive element PD) is illustrated in  FIGS. 3-6 .  FIGS. 7 and 8  illustrate greater details of the placement and orientations of the color filters, transfer transistors, and floating nodes. In  FIGS. 3-6 , the micropixels of individual macropixels are illustrated without any space separating adjacent micropixels; however, it should be appreciated that insulating material and/or isolating wells may be placed between adjacent micropixels within a given macropixel. 
         [0035]    A Bayer patterned macropixel is a repeating unit of a color filter array (CFA) for arranging red, green and blue color filters over an array of photosensitive elements. When a Bayer patterned sensor&#39;s charge is read out, the colors are recorded sequentially line by line. One line may be BGBGBG . . . , followed by a line of GRGRGR . . . , and so forth. This is known as sequential RGB. 
         [0036]      FIG. 3B  illustrates a portion of a color pixel array  350  including triangular macropixels  360  each including three micropixels, in accordance with an embodiment of the invention. The Bayer pattern color pixel array  105  illustrated in  FIG. 1  may be substituted or replaced by embodiments of color pixel array  350 . Each triangular macropixel  360  is partitioned to obtain three micropixels with an approximate fill ratio of red to green to blue micropixels of 1 to 2 to 1, respectively. Each triangular macropixel  360  includes two triangular micropixels and one quadrilateral (e.g., square, rectangle, rhombus, parallelogram, or even an irregular quadrilateral) micropixel. Duplicate triangular macropixels are arranged on a grid with uniform X and Y separation (e.g., adjacent macropixels are separated by a uniform distance Ip) as measured from common reference points (e.g., reference point  320 ). The total area of the three micropixels, which form a single triangular macropixel  360 , is approximately the same as that of Bayer patterned macropixel  310  in  FIG. 3A . In macropixel  360 , green color filters are allotted 50% of the total area of the macropixel, while red color filters and green color filters are each allotted 25% of the total area. This is substantially equivalent to the Bayer assignments, but with only one pixel assigned to green color filters. As seen in the patterning of macropixel  360  in color pixel array  350 , each red color filter (also referred to as a red micropixel) is adjacent to another red micropixel and adjacent to two green color filters (also referred to as green micropixels). Each blue color filter (also referred to as blue micropixels) is adjacent to another blue micropixel and two green micropixels, while each green micropixel is adjacent to two red micropixels and two blue micropixels. 
         [0037]    When referring to “adjacent” micropixels, this is intended to refer to those micropixels that share at least a portion of a parallel common side (even if that common side is in practice separated by a gap for isolation barriers/wells, pixel circuitry, etc), but is not intended to refer to micropixels that merely share a common vertex. Note, the phrase “common vertex” is also used broadly to include the overlapping vertices of two proximate/adjacent micropixels even though in practice their vertices may not actually overlap, but rather are offset due to gaps between adjacent/proximate micropixels. Micropixels that either share a common vertex or at least a portion of a parallel common side without an intervening micropixel are referred to herein as “proximate micropixels.” 
         [0038]    An advantage of triangular macropixel  360  compared to Bayer patterned macropixel  310  is that since there are only three micropixels in each triangular macropixel  360 , that means only three sets of non-photosensitive pixel circuitry elements (e.g., transfer transistor T 1 , reset transistor T 2 , etc. as illustrated in  FIG. 2 ) are included within each triangular macropixel  360 . In contrast, there are four sets of non-photosensitive pixel circuitry elements in Bayer pattern macropixel  310 . As a result, the fill factor of triangular macropixel  360  is greater than the fill factor of Bayer patterned macropixel  310 , since less area within each triangular macropixel  360  is devoted to non-photosensitive elements. The greater fill factor facilitates the use of larger photosensitive elements or photodiodes, which may result in an increase in the full well capacity (“FWC”) of the photodiode. FWC is the measure of the amount of charge which can be accumulated in a photosensitive element (e.g., PD in  FIG. 2 ) before saturation. 
         [0039]      FIG. 4A  illustrates the same Bayer patterned macropixel  310  for side-by-side comparison against another triangular macropixel  460  illustrated in adjacent  FIG. 4B .  FIG. 4B  illustrates a portion of a color pixel array  450  including triangular macropixels  460  each including three micropixels, in accordance with an embodiment of the invention. The Bayer pattern color pixel array  105  illustrated in  FIG. 1  may be substituted or replaced by embodiments of color pixel array  450 . Each macropixel  460  is partitioned into three micropixels with an approximate fill ratio of red to green to blue micropixels of 1 to 2 to 1, respectively. Triangular macropixels  460  are similar to triangular macropixels  360 , except that the layout of the red and blue micropixels is changed. In color pixel array  450 , each red micropixel of a given triangular macropixel  460  is adjacent to a blue micropixel from an adjacent triangular macropixel  460  and two green micropixels (one from within the given triangular macropixel  460  and one from yet another adjacent triangular macropixel  460 ). Each blue micropixel is adjacent to a red micropixel and two green micropixels, while each green micropixel is adjacent two red micropixels and two blue micropixels. 
         [0040]      FIG. 5A  illustrates the same Bayer patterned macropixel  310  for side-by-side comparison against another triangular macropixel  560  illustrated in adjacent  FIG. 5B .  FIG. 5B  illustrates a portion of a color pixel array  550  including triangular macropixels  560  each including three micropixels, in accordance with an embodiment of the invention. The Bayer pattern color pixel array  105  illustrated in  FIG. 1  may be substituted or replaced by embodiments of color pixel array  550 . 
         [0041]    Triangular macropixel  560  is partitioned into three micropixels with an approximate fill ratio of red to green to blue micropixels of 1 to 1 to 1, respectively. This 1 to 1 to 1 ratio results in three four-sided polygon micropixels (e.g., one square, rhombus, or rectangular quadrilateral and two irregular shaped quadrilaterals), as opposed to two triangular and one quadrilateral micropixels, as illustrated in the embodiments of  FIGS. 3B and 4B . The patterning of triangular macropixel  560  is similar to the patterning for triangular macropixel  360 , except that each red polygon micropixel and each blue polygon micropixel is adjacent to five other polygon micropixels and each green polygon micropixel is adjacent to four other polygon micropixels. 
         [0042]      FIG. 6A  illustrates the same Bayer patterned macropixel  310  for side-by-side comparison against another triangular macropixel  660  illustrated in adjacent  FIG. 6B .  FIG. 6B  illustrates a portion of a color pixel array  650  including triangular macropixels  660  each including three micropixels, in accordance with an embodiment of the invention. The Bayer pattern color pixel array  105  illustrated in  FIG. 1  may be substituted or replaced by embodiments of color pixel array  650 . 
         [0043]    Triangular macropixel  660  is partitioned into three micropixels with an approximate fill ratio of red to green to blue micropixels of 26 to 37 to 37, respectively. This partitioning ratio results in one triangular micropixel (with 26% of the total area of the macropixel) and two four-sided polygon or quadrilateral micropixels (each with 37% of the total area of the macropixel), as illustrated in  FIG. 6B . Similar to triangular macropixels  360 , each triangular macropixel  660  are arranged on a grid with uniform X and Y separation having uniform pitch Ip as measured from a common reference point within each adjacent macropixel. 
         [0044]    Although the triangular macropixels  360 ,  460 ,  560 , and  660  each have a triangular shape, their layout along with their uniform pitch in the X and Y axis provides rotational symmetry. In other words, whether or not the pixel array is rotated by 90 degrees for a portrait or landscape orientation, vertical and horizontal lines drawn through the middle of the pixel array are lines of symmetry. Furthermore, despite the triangular shape of macropixels  360 ,  460 ,  560 , and  660 , orthogonal X, Y addressing can still be used by control circuitry  120  or readout circuitry  110  to address individual macropixels. 
         [0045]      FIG. 7  is a plan view illustrating the active circuit and metal interconnects for an FSI image sensor  700  implemented using triangular macropixels, in accordance with an embodiment of the invention. Each triangular macropixel  710  may be implemented using any of the above described triangular macropixel layouts (e.g., triangular macropixels  360 ,  460 ,  560 , or  660 ). Triangular macropixel  710  includes three micropixels separated by shallow trench isolations (“STIs”) or isolation wells  720 . Transfer gate  730  is located at one corner of each micropixel, with one portion of floating node  740  occupying the apex of each micropixel that is adjacent to transfer gate  730 . As illustrated in  FIG. 7 , each floating node  740  may be shared between two proximate micropixels. For example, floating node (or floating diffusion FD)  740 A is shared by two adjacent micropixels on the left from different macropixels, floating node  740 B is shared by two adjacent micropixels on the right from different macropixels and floating node  740 C is shared by two proximate micropixels in the middle top and middle bottom from two different macropixels. 
         [0046]    As previously mentioned, the photosensitive elements of a macropixel in a FSI image sensor are typically not covered by polysilicon or metal interconnects. As such, metal interconnects  750  and  760  are placed around triangular macropixels  710  and their respective color filters so that incident light has a direct path through the color filters to their respective photosensitive elements below. Metal interconnects  750  and  760  may carry control signals (as seen in  FIG. 2 ) such as transfer signal TX, reset signal RST, power rail VDD, address signals or other signals which may be generated by control circuitry  120  or readout circuitry  110  in  FIG. 1 . 
         [0047]      FIG. 8  is a plan view illustrating the active circuit and metal interconnects for a BSI image sensor  800  implemented using triangular macropixels, in accordance with an embodiment of the invention. Each triangular macropixel  810  may be implemented using any of the above described triangular macropixel layouts (e.g., triangular macropixels  360 ,  460 ,  560 , or  660 ). Triangular macropixel  810  includes three micropixels, separated by STIs or isolation wells  820 . A transfer gate  830  is located at one corner of each micropixel, with one portion of a floating node  840  occupying the apex of each micropixel that is adjacent to transfer gate  830 . As illustrated in  FIG. 8 , floating node  840  may be shared between two proximate micropixels. In the illustrated embodiment, two micropixels share floating node  840 ; however, in alternative embodiments any number between one and six micropixels may share a single floating node  840 . For example, if all six micropixels surrounding a single centralized floating node, then a six-share pixel read out may be implemented. In this six-share pixel read out embodiment, micropixels  871  thru  876  could share one central floating node. In contrast, with Bayer patterned macropixel  310  illustrated in  FIG. 3A , at most four micropixels could share a single floating node. 
         [0048]    The illumination of a photosensitive element of a BSI image sensor occurs without interference from any frontside metal interconnects or dielectric layers, therefore there are fewer restrictions on the placement of metal interconnects  850  and  860 . Metal interconnects  850  and  860  need not routed around the perimeter of macropixels including their color filters. Metal interconnects  850  and  860  may carry control signals (as seen in  FIG. 2 ) such as transfer signal TX, reset signal RST, power rail VDD, address signals or other signals which may be generated by control circuitry  120  or readout circuitry  110  in  FIG. 1 . 
         [0049]      FIGS. 9A and 9B  are demonstrative simplified cross-sectional views of an FSI imaging pixel  905  and a BSI imaging pixel  910 , respectively, in accordance with embodiments of the invention. The color filters in either FSI imaging pixel  905  or BSI imaging pixel  910  may be patterned using any triangular macropixel layouts described above. As illustrated in  FIG. 9A , the color filter of FSI imaging pixel  905  is disposed above the metal stack on the frontside of the die, while the color filter of BSI imaging pixel  910  is disposed below the EPI layer/substrate on the backside of the die opposite the metal stack used for routing signals (e.g., metal interconnects  850  and  860  illustrated in  FIG. 8 ). 
         [0050]    The triangular macropixels described above are illustrated as including three primary color micropixels, such as for example, red, green, and blue, or cyan, yellow, and magenta. However, it should be appreciated that in various other embodiments, each triangular macropixel may include just two micropixels or more than three micropixels (e.g., four or more micropixels of various colors). In addition to primary colors, the micropixels may include clear micropixels (i.e., micropixels with clear filter elements) that pass white light and/or infrared light. Alternatively, the clear filter element may be an infrared filter that blocks infrared light and passes visible spectrum light or that passes infrared light and blocks visible spectrum light. 
         [0051]      FIG. 10  is a schematic representation of a triangular macropixel block  1000  including three micropixels with one of the micropixels having a clear filter element, in accordance with an embodiment of the invention. The illustrated embodiment of triangular macropixel block  1000  includes a clear filter element  1005  and two primary color filter elements  1010  and  1015 . In one embodiment, the single macropixel block  1000  may repeat across color pixel array  100 . A color pixel array pattern, such as the Bayer pattern color pixel array  105  illustrated in  FIG. 1 , may be substituted or replaced by a repeating pattern of macropixel blocks  1000 . It should be appreciated that the “repeating pattern” of macropixel blocks  1000  includes alternating minor image repetitions of macropixel block  1000 . In other words, it is macropixel block  1000  that is repeated, though it may be alternately rotated, flipped, or mirrored in a repeating manner. In order to produce a full color image, image data for three primary colors is typically used. Full color image data may be extracted from a macropixel block  1000 , since micropixel  1010  provides the image data for the first primary color (P 1 ), micropixel  1015  provides the image data for the second primary color (P 2 ), and the third primary color (P 3 ) can be determined via P 3 =C/W−P 1 −P 2 . Thus, micropixel  1005  includes a clear filter element that passes white light. 
         [0052]      FIG. 11  is a schematic representation of triangular macropixel blocks  1101 ,  1102 , and  1103  each including three micropixels with one of the micropixels of each macropixel block having a clear filter element, in accordance with an embodiment of the invention. The illustrated embodiment of triangular macropixel  1101  includes a clear filter element  1105  and two primary color filter elements  1110  and  1115 . The illustrated embodiment of triangular macropixel  1102  includes a clear filter element  1120  and two primary color filter elements  1125  and  1130 . The illustrated embodiment of triangular macropixel  1103  includes a clear filter element  1135  and two primary color filter elements  1140  and  1145 . 
         [0053]    Triangular macropixels  1101 ,  1102 , and  1103  may repeat as a group of three in a repeating pattern  1100  across color pixel array  100 . A color pixel array pattern, such as the Bayer pattern color pixel array  105  illustrated in  FIG. 1 , may be substituted or replaced by repeating pattern  1100 . Again, it is noted that the repeating pattern  1100  may be alternately mirrored, flipped, or rotated as it is repeated along the pixel array. As illustrated, each macropixel  1101 ,  1102 , and  1103  may include a clear filter element and two primary color filter elements. In the illustrated embodiment, the combination of primary color filters may be different for each macropixel  1101 ,  1102 , and  1103  within repeating pattern  1100 . 
         [0054]      FIG. 12  is a schematic representation of triangular macropixel blocks  1201  and  1202  each including three micropixels and having a repeating pattern  1200  that repeats every two triangular macropixel blocks, in accordance with an embodiment of the invention. The illustrated embodiment of triangular macropixel  1201  includes three color filter elements  1205 ,  1210 , and  1215 . The illustrated embodiment of triangular macropixel  1202  includes three color filter elements  1220 ,  1225 , and  1230 . 
         [0055]    Triangular macropixels  1201  and  1202  repeat as a group of two in repeating pattern  1200  across color pixel array  100 . A color pixel array pattern, such as the Bayer pattern color pixel array  105  illustrated in  FIG. 1 , may be substituted or replaced by repeating pattern  1200 . Again, it is noted that the repeating pattern  1200  may be alternately mirrored, flipped, or rotated as it is repeated along the pixel array, though not necessary since the repeating pattern include two triangular macropixels that align without mirroring, flipping, or rotating. The assignment of color filter elements or clear filter elements to micropixels  1205  to  1230  is arbitrary. For example, in one embodiment, repeating pattern  1200  may include primary color filter elements P 1 , P 2 , and P 3  and three filter elements C/W. In another embodiment, repeating pattern  1200  may include two primary color filter elements P 1 , one primary color filter element P 2 , one primary color filter element P 3 , and two clear filter elements C/W. In yet another embodiment, repeating pattern  1200  may include two primary color filter elements P 1 , two primary color filter element P 2 , and two clear filter elements C/W. In yet another embodiment, repeating pattern  1200  may include two primary color filter elements P 1 , two primary color filter elements P 2 , and two primary color filter elements P 3  with no clear filter elements C/W. In embodiments that only include two different primary color filter types (e.g., P 1  and P 2 ), the third primary color P 3  may be calculated via P 3 =C/W−P 1 −P 2 , as discussed above. Of course, other embodiments, may include various partial or complete combinations of filter elements P 1 , P 2 , P 3 , and C/W assigned to the various micropixels  1205 - 1230  within repeating pattern  1200 . 
         [0056]      FIG. 13  illustrates a conceptual schematic of the active circuits and metal interconnects for a frontside image sensor  1300  including triangular macropixels  1305  each having two micropixels  1310  and  1315  or  1320  and  1325 , in accordance with an embodiment of the invention. Image sensor  1300  is similar to image sensor  700 , but only includes two micropixels  1310  and  1315  (or  1320  and  1325 ) per triangular macropixel  1305 . In one embodiment, to achieve a full color display, triangular macropixel  1305  may repeat as a group of two in a repeating pattern across color pixel array  100 . A color pixel array pattern, such as the Bayer pattern color pixel array  105  illustrated in  FIG. 1 , may be substituted or replaced by a repeating pattern of two macropixels  1305 . In one embodiment, the repeating pattern includes a first triangular macropixel that includes micropixels having primary colors P 1  and P 2  and a second triangular macropixel that includes micropixels having a primary color P 3  and a clear filter (C/W). As mentioned above, primary colors P 1 , P 2 , and P 3  represent three different color filter element types (e.g., red, green, and blue or cyan, yellow, and magenta, etc.). 
         [0057]    It should be noted that the above description assumes implementation of image sensors using red, green and blue photosensitive elements. Those skilled in the art having benefit of the instant disclosure will appreciate that the description is also applicable to other primary or complementary color filters. For example, magenta, yellow and cyan are a set of common alternative complementary colors that can be used to produce color images. In addition, having a set of green photosensitive elements interleaved or interspersed with alternating red and blue photosensitive elements is also not necessary, though such configurations are common since the human vision system is more sensitive to colors in the green band than other colors in the visual spectrum. The color filters may also include a clear color filter for passing white light or an infrared filter for filtering infrared light. 
         [0058]    The above description of illustrated embodiments of the invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. 
         [0059]    These modifications can be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.