JPH06153083A - Solid state image pickup device and its driving method - Google Patents

Abstract

PURPOSE:To improve dynamic resolving power by reading a storing electric charge in an electric charge transfer column. CONSTITUTION:The combination of photodiodes which are electric charge-mixed is changed by two rows, the same kind of an electric load is read and transfer is executed. That is, concerning the photodiode under a green filter, G1+G2 is adopted and the electric charge of G2+G3 are mixture-transfered. In a same way, concerning an electric signal read from the photodiode under a blue filter or a red filter, the electric charge of B2+B3 and R2+and R3 are mixed. Thus, the electric signal of an interlacing system is obtained by deviating the electric charge to be mixed for the portion of the two rows. Since the storing electric charge of all the photodiodes are read in respective electric readings, electric charge storing time concerning the respective photodiodes becomes T and it takes half time compared with a still mode so that dynamic resolution force is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device,
In particular, it relates to a CCD transfer type solid-state imaging device.

[0002]

2. Description of the Related Art A large number of photodiodes are integrated on a semiconductor substrate to form a solid-state image pickup device. In the CCD transfer type solid-state image pickup device, a large number of photodiodes are arranged in a matrix, a vertical charge transfer path (VCCD) is arranged adjacent to each column of the photodiodes via transfer gates, and one is provided at the output end of the VCCD. Alternatively, two horizontal charge transfer paths (HCCD) are arranged.

Many solid-state image pickup devices include about 400,000 pixels, and for example, 500 rows of pixels are arranged vertically and 800 columns of pixels are arranged horizontally. The color solid-state image pickup device uses, for example, two CCD transfer type solid-state image pickup devices, one solid-state image pickup device is covered with a green (G) filter, and the other solid-state image pickup device is red (R) or blue (B). ) Is covered with a checkerboard pattern, and both solid-state imaging devices are illuminated with the same image. Such a two-plate color solid-state image pickup device has two
Not only is the structure complicated because a single semiconductor substrate is used, but also the optical system is complicated because the same image is projected onto the two solid-state imaging devices.

In recent years, with the progress of semiconductor integrated circuit devices,
The integration degree of the solid-state image pickup device is also improved. For example, a solid-state image pickup device having about 1000 vertical pixels and about 800 horizontal pixels has been developed. The present inventors have proposed a single-plate color solid-state image pickup device using such a solid-state image pickup device having about 800,000 pixels.

One 1000 photodiodes in the vertical direction
It is divided into two sets with row separation, one group is combined with a green G stripe filter, and the other group is arranged with an R / B point sequential filter so that two rows form one TV scanning line. By doing so, a high resolution color image similar to that of a two-plate type camera can be obtained with a single plate. By using this, the structure is simplified and the optical system is simplified.

As described above, in the solid-state image pickup device including the photodiodes of about 1000 rows in the vertical direction, the VCCD having two electrodes per one pixel row is usually used. Pixel 1
In the configuration of two electrodes per row, if the accumulated charges are read out from all the pixels at the same time, a normal driving method such as four-phase driving cannot be adopted.

According to the television (TV) scanning system,
A method is adopted in which an image of one frame is composed of two fields (A field and B field), and the image signal of the A field and the image signal of the B field are read alternately.

[0008]

In the solid-state image pickup device, not only still mode image pickup but also movie mode image pickup is required. According to a method in which one frame image is composed of A field and B field and the A field and B field are read alternately, it takes time to read two fields to read one frame image.

If the time required for one-time image reading is 1/60 second, for example, 1/30 second is required for one frame image reading. This means that the signal charge storage time for each pixel is about 1/30 second.

By the way, when a fast-moving image is picked up in the movie mode, as high a dynamic resolution as possible is desired.
If the signal storage time for each pixel is 1/30 second, it tends to lack dynamic resolution.

An object of the present invention is to provide a driving method of a single-plate solid-state image pickup device having high dynamic resolution.

[0012]

According to the method for driving a solid-state image pickup device of the present invention, a large number of photoelectric conversion elements are formed in a matrix on a semiconductor substrate, and the number of elements in the column direction is 2 effective scanning lines of a television. In a solid-state imaging device having a doubled size, a method of driving a solid-state imaging device, in which accumulated charges are read out from each photoelectric conversion element to a charge transfer row formed adjacent to each photoelectric conversion element row to extract image information, ) Line and (4n +
3) The first read step of simultaneously reading the accumulated charges from the photoelectric conversion element of the row (n is 0 or a positive integer) and the read charges of the (4n + 1) th row and the (4n + 3) th row are mixed and the first type of (4n + 1) rows or (4n + 3) as charges
The first mixed arrangement step of arranging in rows, the second reading step of simultaneously reading accumulated charges from the photoelectric conversion elements of the (4n + 2) th row and the (4n + 4) th row, and the reading (4n + 2)
The charges of the rows and (4n + 4) rows are mixed in the empty pockets between the adjacent first type charge accumulating portions to form the second type of charges, which are arranged in the middle of the adjacent first type charges. It includes a two-mix placement step, and a step of performing the first read step, the first mix placement step, the second read step, and the second mix placement step by shifting two lines.

Preferably, in the solid-state image pickup device, green filters are arranged on every other row of photoelectric conversion elements, and red and blue filters are alternately arranged on every other column of the remaining photoelectric conversion elements. Including that.

[0014]

The number of signal charges becomes half of the number of photoelectric conversion elements by reading out the accumulated charges from every other row of photoelectric conversion elements and mixing them. If the accumulated charges are read out from the photoelectric conversion elements every other row, mixed and then arranged at a predetermined position, and the accumulated charges are read out from the remaining photoelectric conversion elements every other row and mixed, the accumulated charges from all pixels are read out, and 2 per line
The charge transfer path having only electrodes can be arranged in a transferable state.

Further, an image signal of the interlace system can be obtained by shifting the reading position by two lines and performing the same operation. Since the charges accumulated in all photoelectric conversion elements are read at the same time, 1 is set in the A and B fields.
Even if an image for a frame is formed, the charge storage time for each pixel is only the time required for scanning one field. Therefore, the dynamic resolution is improved.

By arranging a green filter in every other photoelectric conversion element and arranging red and blue filters in alternate rows for the remaining photoelectric conversion elements, pixel mixing can be performed in a state where each color is separated. it can.

[0017]

1 shows a single-plate type color solid-state image pickup device according to an embodiment of the present invention. FIG. 1A schematically shows a filter array arranged on a photodiode. As shown in the drawing, green filters G are arranged in stripes every other row, and blue filters B and red filters R are alternately arranged in the remaining rows.

Further, when viewed in the respective column directions, the green filters G and the blue filters B are alternately arranged for a certain column, and the green filters G and the red filters R are arranged for the adjacent columns.
Are arranged alternately. Therefore, two-color filters are arranged for each column.

In still mode imaging, two adjacent rows of photoelectric conversion elements form one television (TV) scanning line. Further, the A field and the B field are arranged alternately.

FIG. 1B is a plan view schematically showing the device structure of the solid-state image pickup device. For example, photodiodes PD forming 800,000 pixels are arranged in a matrix with 800 in the horizontal direction and 1000 in the vertical direction. A vertical charge transfer path VCCD for transferring charges is arranged adjacent to each column of the photodiodes PD.

Although not shown, each photodiode P
A transfer gate for controlling the transfer of accumulated charge is arranged between D and the adjacent VCCD. The colors of the filters arranged on the photodiodes PD are G, R, and B.
Indicated by.

In common with each vertical charge transfer path VCCD, two rows of horizontal charge transfer paths HCCD1 and HCCD2 are arranged on the lower side in the figure. A shift gate SG capable of controlling charge transfer is arranged between HCCD1 and HCCD2.

The VCCD includes two electrodes for each row of photodiodes, and a set of eight electrodes constitutes a drive signal φV1.
~ ΦV8 is applied. In addition, the horizontal charge transfer path HC
Two-phase drive signals φH1 and φH2 are applied to CD1 and HCCD2.
Is being applied. The drive signal φSG is applied to the shift gate SG. Each horizontal charge transfer path HCCD
1, an amplifier is connected to the output terminals of the HCCD2 and supplies outputs Vo1 and Vo2.

FIG. 1C shows the charge reading in the still mode. In the still mode, the charges for the A field shown in FIG. 1A are read out, the accumulated charges read out from the photodiode PD under the green filter G are transferred to the horizontal charge transfer path HCCD1, and the blue filter (B) and the red filter are used. The signal charges read from the lower photodiode (R) are transferred to the horizontal charge transfer path HCCD2. In this way, the HCCD1 and HCCD2 simultaneously read out two charge signals for each column and transfer them in the horizontal direction.

After the charge reading of the A field is completed, the charge reading is performed from the photodiode of the B field which has not been read. After the charge of the B field is read, the charge of the A field is read again. If the time required to read charges in each field is T, the time required to read an image in one frame is 2T.

Considering the charge storage time for each pixel, the photodiode for the A field also has a B value.
The field photodiodes also have the same charge storage time of 2T. As described above, in the still mode imaging operation, the resolution is high, but the signal charge storage time for each pixel is as long as 2T.

FIG. 1D schematically shows the charge reading in the movie mode. In the movie mode, the charges stored in all the photodiodes are read out almost simultaneously. However, if the signals are completely read at the same time, charge mixing cannot be performed in a state where the respective colors are separated, so that the signal charges of the same color can be mixed by shifting the timing.

For example, first, every other row of green filters G
The accumulated charge is read out from the lower photodiode, and after mixing, it is placed at the position under one of the green filters. In this state, in each VCCD, one charge is arranged in the VCCD for every four rows of pixels. Subsequently, the accumulated charges are read out from the photodiodes PD of the remaining rows, and the two charges sandwiched between the green charges are mixed. Since the filters of the same color, that is, the blue filter and the red filter, are arranged for each column, the signal charges of the same color can be mixed. Therefore, a blue signal and a red signal that change alternately for each column can be obtained. In this way, since two signal charges are arranged per four rows of pixels, that is, per eight electrodes of the VCCD, these charges can be transferred in the VCCD at the same time. In this way, the accumulated charges of all the photodiodes can be read at the time T.

Next, the same charge is read out and transferred by changing the combination of photodiodes for mixing charges in two rows. That is, for the photodiode under the green filter, G
Instead of 1 + G2, the charges of G2 + G3 are mixed and transferred.
Similarly, regarding the charge signals read from the photodiodes under the blue filter and the red filter, the charges of B2 + B3 and R2 + R3 are mixed.

In this way, by shifting the charges to be mixed by two rows, an interlaced charge signal can be obtained. Since the accumulated charges of all the photodiodes are read in each charge reading, the charge accumulation time for each photodiode is T, which is half that in the still mode. Therefore, the dynamic resolution is improved.

The charge reading in the still mode and the charge reading in the movie mode will be described in more detail below with reference to FIGS. The still mode operation will be described with reference to FIG. FIG. 2A schematically shows the structure of the VCCD electrode. The electrodes of the VCCD have four rows of photodiodes as one unit, and two electrodes are arranged on each photodiode.
Therefore, eight electrodes are arranged as one set. Control signals φV1 to φV8 are applied to these eight electrodes.

The charge read from the photodiode PD is performed by the control signal φ applied to the odd-numbered electrodes of the VCCD.
It is controlled by V1, φV3, φV5, and φV7. φ
V1 and φV5 control the charge reading from the photodiode PD arranged under the green filter (G), and φV3 and φV7 are the red filter (R) and the blue filter (B).
It controls the charge readout from the lower photodiode PD.

Further, once the charges are read out, these 8
The electrodes of the book form one set, and by applying a voltage of a predetermined pattern, the read signal charges are transferred to the lower side of the VCCD. FIG. 2B schematically shows the charge reading in the still mode. In the A field, timing T1A
At, a read signal is applied to the electrode φV3, and charges are read from the photodiode PD under the blue filter (B) and the red filter (R) to VCCD.

After moving the read charges to below the electrodes φV4 and φV5, a read voltage is applied to the electrode φV1 to read the accumulated charges from the photodiode PD under the green filter (G) to VCCD.

In this way, the green signal charge (G) and the blue signal charge (B) or the red signal charge (R) are alternately read out to the VCCD. These signal charges are transferred downward through VCCD, and green signal charges (G) are transferred to HCCD1.
Red signal charge (R) and blue signal charge (B) are HCC
It is transferred to D2.

In field B, timing T1
At B, a read voltage is applied to the electrode φV7, and the accumulated charge is read from the photodiode PD under the blue filter (B) and the red filter (R) to the VCCD. After the read charge is transferred to the electrodes φV8 and φV1, a read voltage is applied to the electrode φV5 to read the stored charge from the photodiode PD under the green filter (G) to the VCCD.

In this way, similarly for the B field, the green signal charge (G) and the blue signal charge (B) or the red signal charge (R) are alternately read out, the VCCD is transferred downward, and the HCCD1 and HCCD2 are transferred. Transfer to.

FIG. 3 shows a timing chart of control signals applied to the VCCD and the HCCD in the still mode. 3A shows a control signal for the A field, and FIG. 3B shows a control signal for the B field. The same control signal is applied to the electrodes φV2 and φV6, and the same control signal is also applied to φV4 and φV8.

The control signal takes three levels H, M, and L, and the level of H reads out charges from the photodiode PD to VCCD. The potential of M forms a potential well in the VCCD and the potential of L forms a potential barrier in the VCCD.

In the reading of the A field, the control signal φV3 becomes the level H at the timing T1A, and as shown in FIG. 2B, the photodiodes PD to VC under the blue filter (B) and the red filter (R) are connected.
The electric charge is read out to the CD. At this time, the control signal φV4 is also at the M level, and the read charge signal is distributed under the electrode φV4. At the next timing, the control signal φV3
Becomes M level, and the electrode φV5 also becomes M level.
The read charges are substantially evenly distributed under the electrodes φV3, φV4, and φV5.

At the next timing T2A, the control signal φV1 becomes H level, and the accumulated charge is read from the lower photodiode PD to the VCCD. That is, FIG.
As shown in (B), the green signal under the green filter (G) is read out to the VCCD. At this time, since the control signal φV3 changes to the L level, the already read blue signal (B) and red signal (R) are distributed under the electrodes φV4 and φV5.

As described above, after the charge in the A field is read out, two signal charges are HC in each VCCD.
Transfer to CD1 and HCCD2, signal for driving HCCD φH
1 to φH4 transfers in the horizontal direction in the HCCD.
By this operation, parallel / serial conversion is performed.
In the B field shown in FIG. 3B, the control signal φV7 becomes H level at the timing T1B, and as shown in FIG. 2B, the photodiode PD under the blue filter (B) and the red filter (R) changes to VCCD. Read the accumulated charge. Further, at timing T2B, the control signal φV5 becomes H level, and the signal charge is read out from the photodiode under the green filter (G) to the VCCD. VC
The charge transfer in the CD and the HCCD is the same as in the A field.

Next, the operation of the movie mode will be described with reference to FIGS. 4 and 5. FIG. 4 is a schematic diagram showing, as an example, a column including a green filter (G) and a red filter (R), and reading out and transferring charges in the column over time. FIG. 5 is a timing chart of control signals for causing the operation shown in FIG.
In both figures, t indicates timing.

At timing t1, the control signals φV3 and φV7 become H level as shown in FIG. 5, and the photodiodes under the red filters (R) arranged every other row as shown in FIG. read out.

At subsequent timings t2 to t7,
The read red charges are grouped in pairs of two, and the charges are mixed and arranged at the position where the even-numbered charges were arranged at the timing t1.

At the next timing t8, the control signals φV1 and φV5 become H level, and the green filter (G)
The accumulated charge is VC from the photodiode PD arranged below.
Read to CD. In this state, for example, the charge G
3 and G4, the already mixed red charge R1 +
Two green charges G3 and G4 are read between R2 and R3 + R4.

At successive timings t9 to t12, two adjacent green charges G1 + G2, G3 + G4,
G5 + G6. ． ． Are mixed with each other and arranged at equal intervals together with the red charges. In this way, the green charges and the red charges are alternately arranged at equal intervals.

At the subsequent timings t13 to t26, the charge distribution is extended to the left side in the figure, the right side is contracted, and this operation is repeated to transfer the charge to the left side in the figure by the shakuri insect method. In each horizontal scanning period, two charges are transferred from each VCCD to HCCD1 and HCCD2 to form one TV scanning line. In the case of the NTSC system, the charges from all the photodiodes PD are read out every about 1/60 second, and an image for one field is formed.

Although the charge reading and transfer of the column including the green filter G and the red filter R has been described, the green filter G and the blue filter B are arranged on the adjacent columns. Regarding the operation of these columns, red in the above description may be read as blue.

In the next one field, the charges from all the photodiodes PD are read out again, and the combination of charge mixing is shifted by two rows to form interlaced signal charges.

When the number of pixels in one screen is large as in the HDTV system, it takes time to read and transfer the signal charges from all the pixels independently, so that the moving resolution in the movie mode is lowered. Resulting in. In such a case, the dynamic resolving power can be improved by reading out the charges from all the photodiodes and transferring the charges by utilizing the charge mixing as in the above-described embodiment.

The present invention has been described above with reference to the embodiments.
The present invention is not limited to these. For example,
It will be apparent to those skilled in the art that various changes, improvements, combinations and the like can be made.

[0053]

As described above, according to the present invention,
In the movie mode, it is possible to shorten the signal charge accumulation time for each pixel and improve the dynamic resolution.

[Brief description of drawings]

FIG. 1 shows a single-plate color solid-state image pickup device according to an embodiment of the present invention. 1A is a schematic plan view showing a filter array, FIG. 1B is a schematic plan view showing a device structure, FIG.
(C), (D) is a conceptual diagram for demonstrating a still mode and a Movi mode, respectively.

FIG. 2 is a diagram illustrating a still mode. FIG. 2A is a schematic plan view showing the electrode structure on the VCCD, and FIG. 2B is a conceptual diagram showing the charge reading in the still mode.

FIG. 3 is a timing chart of control signals in a still mode.

FIG. 4 is a conceptual diagram showing charge reading and transfer in a movie mode.

FIG. 5 is a timing chart of control signals in a movie mode.

[Explanation of symbols]

 G green filter B blue filter R red filter PD photodiode VCCD vertical charge transfer path HCCD horizontal charge transfer path φV control signal

Claims (3)

[Claims] 1. A solid-state imaging device comprising a plurality of photoelectric conversion elements formed in a matrix on a semiconductor substrate and having two times the number of elements in the column direction of a television effective scanning line. A method for driving a solid-state imaging device, wherein accumulated charge is read out to a charge transfer column formed adjacent to a conversion element column to extract image information, which comprises a (4n + 1) th row and a (4n + 3) th row (n is 0 or a positive value). First read-out step of simultaneously reading the accumulated charges from the photoelectric conversion element of (4 n + 1) rows and the read-out charges of (4n + 1) rows and (4n + 3) rows to obtain (4n + 1) rows or (4n + 1) rows as the first type of charges.
+3) row, a first mixed placement step, a second readout step of simultaneously reading accumulated charges from the photoelectric conversion elements of the (4n + 2) th row and the (4n + 4) th row, and (4n + 2) row and (4n + 4) read A second mixing and arranging step of mixing the row charges into an empty pocket between the adjacent first type charge accumulating portions to form the second type charges, and arranging the charges in the middle of the adjacent first type charges; A method for driving a solid-state imaging device, comprising: the first read-out step, the first mixed placement step, the second read-out step, and the step of shifting the second mixed placement step by two lines. 2. In the solid-state imaging device, green filters are arranged on every other row of photoelectric conversion elements, and red and blue filters are alternately arranged on every other column of the remaining photoelectric conversion elements. The method for driving the solid-state imaging device according to claim 1. 3. A semiconductor substrate, a plurality of photoelectric conversion elements formed on the semiconductor substrate and arranged in a matrix, and each row formed on the semiconductor substrate adjacent to each column of the photoelectric conversion elements. A charge transfer path means having two electrodes per drive; a drive circuit capable of driving the electrodes in units of eight and reading out and accumulating charges accumulated in the photoelectric conversion elements in every other row; A pair of green filters arranged on the other photoelectric conversion elements and arranged side by side in the row direction, and a blue filter and a red filter alternately arranged on every other column on the remaining photoelectric conversion elements. Solid-state imaging device.