Abstract:
A color picture solid-state pickup element comprising a solid-state image sensor and a colored matrix microfilter. The image sensor has photo elements arranged in a matrix. The horizontal lines are paired into scanning lines. The scanning lines alternate between two fields, one field being read after the other. The microfilter has rows of uniform colors, with a row covering one horizontal line. Every other row is of a first primary or complementary color. The remaining rows alternate between two other primary or complementary colors.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a color picture solid image-pickup element comprising: a solid image sensor including a photo-electric conversion section, a charge transfer section, and a transfer control section; and a matrix type microfilter having colored bits corresponding to picture elements and arranged on the photo-electric conversion section. 
     2. Background of the Invention 
     In general, the term &#34;solid image sensor&#34; and the term &#34;solid image-pickup element&#34; mean the same thing. However, for convenience in description, these terms will be defined as follows. The solid image sensor is used to detect only the brightness of a picture, i.e., it is used for monochromatic light. On the other hand, the solid image-pickup element is obtained by combining the solid image sensor with a microfilter, i.e., it is used for color pictures. 
     The above-described solid image-pickup element is well known in the art. The microfilter of the solid image-pickup element is in the form of a colored bit matrix. That is, the microfilter has colored bits of R (red), G(green), R, G, and so forth in first and second lines, fifth and sixth lines, and so forth in stated order, and has colored bits of G(green), B(blue), G, B, and so forth in third and fourth lines, seventh and eighth lines and so forth in the stated order. In the case of forming an interlacing type TV (television) picture field signal, the odd-numbered lines of the solid image-pickup element are successively read, and a 1H (one horizontal scanning period) delay line is used to obtain the signals of colors R, G and B from the picture.,signals of two lines. In this case, the luminance signal Y is formed by weighted-addition, and the color difference signals R-Y and B-Y can be formed in the same manner. 
     The above-described system is excellent. Although the color solid image-pickup element has substantially the same number of picture element as the monochromatic solid image sensor, the decrease in resolving power of the solid image-pickup element is minimized as it is designed for color pictures. 
     Owing to the recent improvement of the LSI manufacturing technique, more picture elements can be formed in one and the same chip. Therefore, if the number of picture elements are increased both in a horizontal direction and in a vertical direction and the above-described system is employed, then a color picture solid image-pickup element considerably high in resolving power can be obtained. It is apparent from a simple calculation that the color picture resolving power substantially equal to that of the monochromatic light solid image sensor can be obtained by increasing the number of picture elements by a factor of three (3). However, in a system in which, as in the case of TV pictures, the number of scanning lines is predetermined, it is difficult to increase the number of picture elements by three times. 
     Therefore, a variety of methods have been proposed in the art in which the number of picture elements is doubled both in a horizontal direction and in a vertical direction to obtain a resolving power equivalent to that of the monochromatic light solid image sensor. 
     One example of a solid image-pickup element in which the number of picture elements in a vertical direction is doubled according to the above-described system is known in the art. However, the solid image-pickup element is disadvantageous in that, since different colors are alternately arranged in each horizontal line of picture elements, the effective sampling frequency is decreased to half, and therefore the horizontal resolving power is insufficient. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of this invention is to provide a color picture solid image-pickup element whose resolving power is made substantially equal to that of the monochromatic light solid image sensor merely by doubling the number of picture elements in a vertical direction. 
     The foregoing object of this invention has been achieved as follows The number of scanning lines is doubled with two lines forming a scanning line Each scanning line is covered by a uniformly colored microfilter, with three primary or complementary colors covering different lines. A first color covers half the lines. Two additional colors each cover half of the remaining lines. The photocharge is transferred in parallel to two CCDs. One CCD always receives the first color signal. The other CCD alternates between the other two color signals on successive scanning lines. The CCDs are read in parallel and the color signals are combined both within a scanning line and between scanning lines of two field scanning. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing a first example of a color picture solid image-pickup element of this invention. 
     FIG. 2 is a block diagram showing peripheral circuits for obtaining NTSC TV signals from the output signals of the solid image-pickup element. 
     FIG. 3 is a diagram showing one example of a signal charge reading amplifier. 
     FIG. 4 is a block diagram showing a second example of the color picture solid image-pickup element. 
     FIG. 5 is a circuit diagram showing one example of a change-over switch in the solid image-pickup element shown in FIG. 4. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the first embodiment of the invention, the photoelectric conversion section has picture elements arranged in lines the number of which is twice as many as the number of scanning lines. In this case, the number of picture elements in a horizontal direction is the same as that of picture elements in the conventional case. The colored bits of the microfilter which correspond to the picture elements are arranged in such a manner that bits of the same color are arranged along a given line in the line direction. In the column direction a first one of the three primary colors or complementary colors, namely, G or W (white) appears every other line, and a second color R or Cy (cyan) and a third color B or Ye (yellow) of these primary or complementary colors occur alternately between the first colors. Furthermore, two horizontal charge transfer section are provided in such a manner that one of the horizontal charge transfer sections is used for the first color only, and the other is used alternately for the second and third colors. In addition, a 1H delay line is provided to obtain the three-primary-color signals for each scanning line. 
     In a second embodiment of the invention, the uniform arrangement of the colored bits of the microfilter in the horizontal direction is the same as that of the colored bits in the first embodiment. However, in the arrangement of the colored bits in the vertical direction, the color of one of two lines corresponding to an &#34;A&#34; field scanning line is the same as that of one of two lines corresponding to a &#34;B&#34; field scanning line. Furthermore, two horizontal charge transfer sections and a change-over switch are provided so as to restore the order of color signals for every field. For instance, in the microfilter, the colors G, B, B, G, G, R, R, G and so forth are assigned to the lines, respectively, in the stated order. If, as was described above, the picture elements of the first, second, fifth, sixth, . . . lines are for the &#34;A&#34; field, then in the scanning of the &#34;A&#34; field one of the horizontal CCDs outputs pictures signals of G(green) and the other alternately outputs picture signals of R(red) and B(blue) separately according to the scannings. Similarly, if the picture elements of the third, fourth, seventh, eighth, . . . lines are for the &#34;B&#34; field, then in the scanning of the &#34;B&#34; field, the one horizontal CCD alternately outputs picture signals of R and B separately according to the scanning and the other outputs pictures signals of G. This method is advantageous in that the microfilter can be set on the solid image sensor with relatively low accuracy not only in the horizontal direction but also in the vertical direction. 
     In the color picture solid image-pickup element according to the invention, a resolving power substantially equal to that of a conventional monochromatic light solid image sensor can be obtained merely by doubling the number of picture elements only in the vertical direction. Furthermore, in the solid image-pickup element of the invention, with respect to three colors such as R, G and B, the horizontal resolving power is uniform, and therefore the color Morie pattern scarcely occurs. In addition, the alignment of the solid image sensor with the microfilter in the horizontal direction is relatively loose, and therefore the color picture solid image-pickup element of the inventional can be manufactured readily because of this looseness. 
     Furthermore, in the solid image-pickup element of the invention, one color is assigned to two adjacent lines of the microfilter. Accordingly, not only the microfilter can be manufactured readily, but also the microfilter can be laid on the solid image sensor both in the horizontal direction and in the vertical direction with relatively low accuracy. 
     Preferred embodiments of this invention will be described with reference to the accompanying drawings. 
     FIG. 1 is a block diagram outlining a solid image-pickup element formed according to the invention. As shown in FIG. 1, picture elements 2 are arranged in matrix form on a substrate 1. A microfilter is placed on a photo-electric conversion section including the picture elements 2. In FIG. 1, reference characters R, G and B designate the color bits of the microfilter, namely red, green and blue. The picture elements in the lowermost two lines are for the first scanning line A 1  of the &#34;A&#34; field, those in the next two lines are for the first scanning line B 1  of the &#34;B&#34; field, those in the next two lines are for the second scanning line A 2  of the &#34;A&#34; field, those in the next two lines are for the second scanning line B 2  of the &#34;B&#34; field, and so forth. Signal charges are supplied through a vertical transfer section (not shown) successively two horizontal transfer sections 4 and 5 shown below the photo-conversion section in FIG. 1. In this operation, the &#34;A&#34; field signals and the &#34;B&#34; field signals are sorted out by a selection circuit 3. All A field lines are sequentially vertically transferred to the horizontal transfer sections 4 and 5 before the B field lines are so transferred. G signals are supplied to the horizontal transfer section 5 at all times. Depending on the field scanning lines, R signals and B signals are alternately applied to the horizontal transfer section 4. These picture signals supplied in parallel to the horizontal transfer sections 4 and 5 are outputted serially through amplifiers 6 and 7, respectively. 
     FIG. 2 shows the arrangement of peripheral circuits for forming NTSC TV signals by utilizing the output signals of the solid image-pickup element. The signal charges formed in the photo-electric conversion section 2 are shifted vertically adjacent to the picture elements 2 of the photo conversion section by a &#34;V&#34; driver 8 in the transfer control section. The signal charges thus shifted are supplied to the horizontal transfer sections 4 and 5 through the selection circuit 3 which is under the control of a distribution circuit 10. 
     As a result, the G signals of one scanning line are stored in the horizontal transfer section 5, while the R signals and the B signals are alternately stored in the horizontal transfer section 4 separately according to the scanning lines. These color signals are supplied through the above-described amplifiers 6 and 7 and a noise reducer circuit 14 to a signal processing circuit 15. In this operation, the signals in the horizontal transfer sections 4 and 5 are successively shifted by the &#34;H&#34; driver 9 in the transfer control section. 
     In the signal processing circuit 15, AGC (automatic gain control), γ-value correction, and white balance control are carried out. The G signal, and the R or B signal outputted by the signal processing circuit 15 are supplied to a 1H delay line 16, where they meet the B or R signal of the preceding scanning line. Therefore, the complete R, G and B signals are provided by the 1H delay line 16. The R, G and B signals are supplied to a matrix circuit 17, where the γ-value correction is carried out and they are converted into color difference signals Y H , R-Y, and B-Y. These color difference signals are applied to an encoder 18, where they are added to a timing signal and a synchronizing signal to form an NTSC TV signal. 
     Furthermore, as shown in FIG. 2, a synchronizing signal generator 11 and a timing signal generator 12 are provided. The synchronizing signal generator 11 operates to add the synchronizing signal to the picture signal with the aid of the encoder 18 and to supply the synchronizing signal, as a reference value, to the white balance control circuit 13. The timing signal generator 12 operates to add the timing signal to the picture signal with the aid of the encoder 18 and to supply the timing signal to the signal processing circuit 15, the 1H delay line 16, and the transfer control section 8 and 9. 
     FIG. 3 shows one example of the amplifier 7 adapted to read the signal charges out of the horizontal transfer section 5. It goes without saying that the amplifier 6 is similar in construction to the amplifier 7. In the example, the charge transfer section 5 is of the CCD type, and therefore the first stage of the amplifier 7 is a conventional floating diffusion amplifier. As shown in FIG. 3, a floating diffusion 19 is arranged between output gates 20 and 21. The floating diffusion 19 is adapted to convert the signal charge into a voltage, which is amplified by an ordinary transistor amplifier 22. 
     In the above-described embodiment, the microfilter of the primary colors R, G and B are employed. However, it is obvious to those skilled in the art that the technical concept of the invention is applicable to the case where the complementary colors Cy, W and Ye are employed. 
     In the above-described embodiment, the microfilter can be laid on the image sensor with relatively low accuracy in the horizontal direction, but the microfilter must be laid on the image sensor with considerably high accuracy in the vertical direction. However, this problem can be solved by the following embodiment of the invention. 
     FIG. 4 shows a microfilter 31. In FIG. 4, reference characters R, G and B designates the colors of the elements of the microfilter 31. FIG. 4 shows only eight (8) color lines; however, it should be noted that the color lines are followed by color lines arranged in the same order. 
     A photo-electric conversion circuit (not shown) and a vertical charge transfer section (not shown) are arranged below the microfilter 31. The elements of the photoelectric conversion section confront the color regions R, G and B of the filter 31, respectively, similarly to the embodiment of FIG. 2. 
     The charge signals of two color lines are read into horizontal CCDs 32 and 33, respectively, during every horizontal scanning line period (about 63.5 microseconds in the embodiment). And during the period, these signals are, in a parallel mode, read out of the CDDs 32 and 33. In FIG. 4, reference characters A and B on the left-hand side of the microfilter 31 designate the &#34;A&#34; and &#34;B&#34; fields, respectively. For instance during the &#34;A&#34; field period, the R signals and the B signals are alternately and separately written into the horizontal CCD 32 according to the scanning lines. On the other hand, the G signals are all written into the horizontal CCD 33. In the embodiment, the signals stored in the horizontal CCDs 32 and 33 are outputted through floating diffusion amplifiers (FDA) 34 and 35, respectively 
     Similarly, during the &#34;B&#34; field period, the G signals are written in the horizontal CCD 32, while the R signals and the B signals are alternately read into the CCD 33 separately according to the scanning lines 
     The floating diffusion amplifiers 34 and 35 adapted to read the signals out of the CCDs 32 and 33 respectively are connected to a change-over switch 36. The change-over switch 36 is switched once every A or B field, so that the G signal is provided at one output terminal 37, and the R signal and the B signal are alternately provided at the other output terminal 38 separately according to the scanning line The output terminal 38 is connected to another change-over switch, similar to half of the switch 36. The change-over switch is changed once every scanning line, so that the R signal and the B signal can be separately delivered out. That is, all of the R, B and G signals are separately delivered out. 
     In the above-described second embodiment, the three primary colors R, G, and B are employed However, it goes without saying that the technical concept of the invention is applicable to the case where the combination of the colors W, Cy and Ye, the combination of the colors W, R and B or the combination of G, Cy and Ye is employed. That is any combination of colors can be employed if all the colors can be reproduced by addition and subtraction of the color signals or conversion into complementary colors. 
     As is apparent from the above description, in the color picture solid image-pickup element according to the invention, merely by doubling the number of picture elements only in the vertical direction, the resolving power is made substantially equal to that of the monochromatic light solid image sensor. Furthermore, in the solid image-pickup element, three colors such as R, G, and B are uniformly arranged in the horizontal direction. Therefore, the color Morie pattern scarcely occurs, and the alignment of the micro-filter with the solid image sensor may be low in accuracy.