Abstract:
A color linear CCD for a pickup apparatus comprises a photodiode array including a blue-sensing photodiode array formed between a red-sensing photodiode array and a green-sensing photodiode array. A storage area is located beside of the red-sensing photodiode array for storing the signal charges produced by the red-sensing and blue-sensing photodiode arrays. A first HCCD shift register area is located beside of the green-sensing photodiode array for moving the signal charges produced by the green-sensing photodiode array. A second HCCD shift register area is formed beside of the storage area for alternately receiving the signal charges produced by the red-sensing and blue-sensing photodiode arrays. In another embodiment the red-sensing photodiode array is placed between the blue and green sensing photodiode arrays.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a color linear charge coupled device (CCD) for a pickup apparatus, and more particularly to a color linear device CCD and driving method suitable for improving color resolution and simplifying a corresponding structure by reducing distances between adjacent pixels. 
     2. Discussion of the Related Art 
     The conventional color linear CCD shown in FIG. 1 is formed of three linear CCD sets of red, green and blue, which are the three primary colors of light. 
     Each CCD set includes a photodiode array (1, 2 or 3), a pair of transfer gates 5, one on either side of the photodiode array (1, 2 or 3), horizontal CCD (hereinafter simply referred to as HCCD) shift registers 4 positioned at the outer side of the transfer gates 5, a floating diffusion region (hereinafter referred to as FD) 7 placed on one side of the device and a sensing amplifier 8 connected to FD 7. 
     Signal charges photoelectrically converted in the photodiodes of photodiode arrays 1, 2 and 3 are transferred to HCCD shift registers 4 when transfer gates 5 are turned or. The photodiodes are divided in an odd/even order for transfer to HCCD shift registers 4 disposed on transfer gates 5 in a zigzag mode. 
     The photodiode signal charges are moved successively in one direction by clock signals applied to the HCCD shift register 4. The output gate (OG) 6 transfers signal charges from the HCCD shift register 4 to the FD 7 and sensing amplifier 8. The three linear CCDs of red R, green G and blue B are identically constructed except for the color filters. Respective sensing amplifiers 8 provide the signals of red R, green G and blue B. 
     The conventional color linear CCD described above requires two HCCDs, one FD, and a sensing amplifier for each photodiode array, resulting in a structure for extracting the three colors of red R, green G and blue B that is much more complicated than a black and white linear CCD. Furthermore, two HCCDs 4 are disposed in the space between red R and green G photodiode arrays and between green G and blue B photodiode arrays, so that the distance between the photodiode arrays becomes wide, thus degrading color separation in the vertical direction. 
     SUMMARY OF THE INVENTION 
     The present invention is provided to solve the above-described problems of the conventional color linear CCD. 
     Accordingly, it is an object of the present invention to provide a color linear device CCD and driving method suitable for improving color resolution and simplifying the structure of the device by reducing distances between adjacent pixels. 
     Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
     To achieve the above object of the present invention, there is provided a color linear CCD image device including a photodiode array having of a blue-sensing photo diode array formed between a red-sensing photodiode array and a green-sensing photodiode array, each of the photodiode arrays producing signal charges by photoelectric conversion. A storage area is positioned on a side of the red-sensing photodiode array opposite the blue-sensing photodiode array and stores the signal charges produced by the red-sensing and blue-sensing photodiode arrays. A first HCCD shift register area is positioned near a side of the green-sensing photodiode array opposite the blue-sensing photodiode array and accepts the signal charge produced by the green-sensing photodiode array. A second HCCD shift register area is formed beside said storage area and alternately accepts the signal charges produced by the red-sensing and the blue-sensing photodiode arrays. 
     In another embodiment a red-sensing photodiode array is formed between a blue-sensing photodiode array and a green-sensing photodiode array, each of the photodiode arrays producing signal charges by photoelectric conversion. A storage area is placed on a side of the blue-sensing photodiode array opposite the red-sensing photodiode array and stores the signal charges produced by the red-sensing and blue-sensing photodiode arrays. A first HCCD shift register area is spaced apart from one side of the green-sensing photodiode array to transfer signal charges produced by the green-sensing photodiode array. A second HCCD shift register area is formed to one side of the storage area for alternately transferring the signal charges produced by the red-sensing and blue-sensing photodiode arrays. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of this specification illustrate embodiments of the invention and, together with the description, serve to explain the objects, advantages and principles of the invention. In the drawings, 
     FIG. 1 is a view showing a construction of a conventional color linear CCD image device; 
     FIG. 2a is a view showing a construction of a color linear CCD image device according to the present invention; 
     FIG. 2b shows a section view of the color linear CCD image device shown in FIG. 2a; 
     FIG. 2c shows a plane layout of the color linear CCD image device shown in FIG. 2a; 
     FIG. 3 shows another construction of a color linear CCD image device; 
     FIGS. 4(a) and 4(b) show a potential profile of the color linear CCD image device according to the present invention; 
     FIG. 5 shows the operational timing chart of the color linear CCD image device according to the present invention; 
     FIG. 6 shows the potential wells associated with the color linear CCD image device shown in FIG. 2a; and 
     FIG. 7 is a view showing a construction of a color linear CCD image device according to a second embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in FIGS. 2a, 2b, 2c, and 3, a blue-sensing photodiode array 22 is formed between a red-sensing photodiode array 21 and a green-sensing photodiode array 23. The photodiode arrays produce a signal charge by photoelectric conversion. A storage area 24 is provided adjacent an upper side of the red-sensing photodiode array 21 and sequentially receives the signal charges produced by the red-sensing photodiode array 21 and the blue-sensing photodiode array 22 in an upward direction, and stores the signal charges produced by the blue-sensing photodiode array 22 while extracting the signal charge produced by the red-sensing photodiode array 21. A first HCCD shift register 26 area is separately formed adjacent a lower side of the green-sensing photodiode array 23 and receives the signal charge produced by the green-sensing photodiode array 23 in a downward direction. A second HCCD shift register 27 area is formed to one side of storage area 24 and alternately receives the signal charges produced by the red-sensing and blue-sensing photodiode arrays 21 and 22. A transfer gate 25, provided in an isolation region of the green-sensing photodiode array 23 and the first HCCD shift register 26 area, transfers the signal charges produced by the green-sensing photodiode array 23 to the first HCCD shift register 26 area. 
     A plurality of poly gates 1 and 2, seen in FIGS. 2b and 2c, are formed between the red-sensing photodiode array 21 and the storage area 24 for transferring the signal charges in one direction based on a 3-phase clock signals generated by clock generator 300 or a 4-phase clock. Channel stop layers CST 33 (FIGS. 2b, 2c, and 3) are formed between isolation regions of photodiode arrays 21, 22 and 23 and include photodiode cells for isolating the signal charges. Preferably there are no channel stop regions between the blue and red photodiode arrays. As shown in FIG. 2b, a barrier layer is formed between the blue photodiode array and the red photodiode array when the clock signal φR 1  is applied to the poly gate 2 nearest the blue, otherwise the movement from blue to red shown in FIG. 4a as A4-A8 would not occur. An output gate 32 and an FD 30 are placed at one side of the first HCCD shift register 26, and an output gate 31 and an FD 29 are placed at one side of the second HCCD shift register 27. Sensing amplifiers 28a and 28b are connected to the FDs for sensing the signal charges. FIG. 2b shows metal light shielding layer 34 beside the green and red layers. 
     The potential of the blue-sensing photodiode array 22 area is set at a lower potential than that of the red-sensing photodiode array 21 area by adjusting the impurity density of implanted ions. FIG. 6 is a view of the potential wells associated with the respective colors. As shown, the potential well associated with the blue-sensing photodiode array is at a lower potential than the potential well associated with the red-sensing photodiode array. 
     The potential well of green-sensing photodiode array 23 area is set lower than that of the first HCCD shift register 26 area by adjusting the ion impurity density. 
     An image sensing operation of the color linear CCD image device will be described below. 
     FIGS. 4(a) and 4(b) show a potential profile of the color linear CCD image device according to the present invention, and FIG. 5 shows the operational timing chart of the color linear CCD image device according to the present invention. 
     Signal charges produced by respective photodiode arrays 21, 22 and 23 by photoelectric conversion are extracted in the direction of the first and second HCCD shift registers 26 and 27. The red R and blue B signal charges are vertically moved by clock pulses φR 1 , φR 2 , φR 3 , φR 4 , Vφ 1 , Vφ 2  and Vφ 3  applied to poly gates 1 and 2. Thus, the red and blue signal charges are respectively transferred to the second HCCD shift register 27 area, and the signal charges are read out by the FD 29 to sensing amplifier 28a. 
     Here, the signal charge transfer toward storage area 24 is performed such that a potential well region is varied to be moved between A 1  -A 19  and B 1  -B 6  by clock pulses φR 1 , φR 2 , φR 3 , φR 4 , Vφ 1 , Vφ 2  and Vφ 3  during a blanking period of fixing the clock of the first and second HCCD shift registers 26 and 27. Clock pulses φR 1  and Vφ 3  are identical for the cases of A 1  -A 2 , A 4  -A 5 , A 12  -A 14 , A 18  -B 1 , and B 5  -B 6 . Clock pulses φR 2  and Vφ 1  are identical for the cases of A 1  -A 7 , A 10 , A 12  -A 13 , A 17  -A 19 , and B 4  -B 6 . Clock pulses φR 4  and Vφ 3  are identical for cases A 1  -A 14 , A 18  -B 1 , and B 5  -B 6 . The clock pulses for the remaining cases are different. 
     The signal charges produced by the green-sensing photodiode array 23 are transferred to the first HCCD shift register 26 area by the clock pulse applied to transfer gate 25. 
     The reason for placing the blue-sensing photodiode array 22 in between the green and red-sensing photodiodes is described below. 
     Since the green signal charge output by the green-sensing photodiode array 23 corresponds to a lumina signal, it should be separately extracted. The luminance signal which represents the brightest signal is green. Therefore, it is provided at the lower end of the overall device region. 
     The wavelength of the blue light is short, and is absorbed by a polysilicon layer because of its property of absorbing light of a short wavelength, thereby lowering the sensitivity of the blue-sensing photodiode array 22. 
     Forming the blue-sensing photodiode array 22 as the center photodiode array is advantageous because the vertical movement of the signal charges from the blue-sensing photodiode array 22 to the second HCCD shift register 27 is carried out very rapidly, while the polysilicon layer inhibits the red signal component from mixing with the blue signal component, thus improving color separation. 
     In another embodiment of the color linear CCD image device shown in FIG. 7, the red-sensing photodiode array 21 is placed at the center of the overall device region, flanked by the green-sensing photodiode array 23 on one side and the blue-sensing photodiode array 22 on the other side. The order in which the layers are formed is red, green and then blue. The other features of the color linear CCD image device of this embodiment is the same as discussed above with respect to the first embodiment. 
     A DC bias is applied to a polysilicon gate that is preferably formed above the area of the red-sensing photodiode array 21, so that the potential of the green-sensing photodiode array 23 area is lower than that of the red-sensing photodiode array 21 area, resulting in a potential step between the two arrays. 
     In the above described color linear CCD image device and driving method, the distance between respective photodiode arrays 21, 22 and 23 is reduced to enhance color resolution, and fewer transfer gates, FDs and sensing amplifiers are required to simplify the structure of the device. 
     Moreover, absorption characteristics of polysilicon degrades short wavelength light component and thus the polysilicon layer is preferably also not formed above the blue-sensing photodiode array. 
     The foregoing description of preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents.