JPS5990464A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To prevent the generation of smear by providing two switch elements in series for row and column selection between each photosensitive picture element and a signal charge read line and giving sequentially a signal charge on the read line to an output line. CONSTITUTION:When one column selecting line 201 is driven by a vertical register 19, MOS switches 13 for column selection are all turned on. A row selecting line 18 is driven sequentially from the left by a horizontal register 17 and MOS switches 12 for row selection are turned on sequentially from the left. Since switches 13 are all turned on in this case in advance, the stored signal charge of a photodiode PD11 for one column's share is read sequentially on a read line 141 and outputted seuqnetially from a terminal 16. Similarly, the signal charge of each column is outputted sequentially. When a strong incident light is given to the PD11(1,1), a part of excess charge flows to the read line 141 via the switches 12(1,1),13(1,1) and superimposed on all the output signal charge to prevent the generation of smear.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a solid-state imaging device such as a solid-state area image sensor used in a video camera, for example.

[Technical background of the invention]

FIG. 1 is a circuit diagram of a conventional solid-state area image sensor that uses photodiodes as photosensitive pixels and MOS switches as means for selecting signal charges accumulated in these photodiodes. In the figure, a plurality of photodiodes 7(1,1) to '(i,j) are arranged in a matrix in the row and column directions (where i is the number of arrays for one row, and j is the number of arrays for one column. When light is incident on each of the photodiodes 1 (1, 1) to J (i, j), a signal charge corresponding to the incident light is generated in each of the photodiodes 1 (1, 1) to J (i, j). Accumulated. Photodiode 1 (1°1) ~ J (i, j)
The signal charges accumulated in each column select line 3. are sequentially and selectively driven by the output of the vertical register 2. ~
MOS switch 4 (1
, 1) to 4(i, j) to each of the plurality of vertical signal lines 5.
~5j, respectively. Each of these vertical signal lines 5
The signal charges read out to MOS switches 1 to 5j are sequentially and selectively driven by the output of the horizontal register 6,
~7j to the horizontal output line 8. As a result, from the output terminal 9 provided on the horizontal output line 8, the photodiodes 1(1,1) to 1<t,j)
The signal charges accumulated in i rows are sequentially output column by column.

[Problems with background technology]

As shown in Fig. 1, a MOS is used as the signal charge selection means.
In a solid-state area image sensor using a switch, for example, when there is strong incident light on the photodiode 7 (1, 1), excess charge is generated here and a part of it is transferred to the vertical signal line 5I.
flows into. Vertical signal line5. Since the charge flowing into the signal line 5 is accumulated in advance in this signal line 5°, one row of photodiodes 7(1,1) to 1(i,1 ), a part of the excess charge generated in the photodiode Z(1,1) is also read out in addition to each accumulated signal charge. For this reason, when a conventional solid-state area image sensor is used to image an object whose part is particularly bright, there is a drawback that a white band-like image defect called a smear appears above and below the doma bright spot on the playback screen.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and an object thereof is to provide a solid-state imaging device that can prevent the occurrence of smear.

[Summary of the invention]

According to this invention, a plurality of signal charge readout lines are provided, and two MOS switches for row selection and column selection are provided between each photodiode and the corresponding signal charge readout line, and the By commonly connecting each of a plurality of signal charge readout lines to the signal charge output line, when excess charge is generated in one photodiode, a part of it is transferred to the two MOS switches and the signal charge readout line. A solid-state imaging device is provided in which a portion of the excess charge is applied to an output line and superimposed on signal charges from all photodiodes, thereby preventing the occurrence of smear.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 2, a plurality of photodiodes 11 (1°1) to 17 (i, j) are arranged in a matrix in the row and column directions. These photodiodes I J (1,
1) to I Z (i, j) are MOS switches 1.2 (1, 1) to 12 <i, j> for row selection and MOS switches I J (1, 1) to I for column selection, respectively. J (i, j
) are connected in series to a plurality of signal readout lines 14.
．． ~141, each column is combined with a corresponding one. Further, the plurality of signal readout lines 14. ~141 are commonly connected to the signal charge output line 15, and this output line 15
An output terminal 16 is provided at the terminal.

The above row selection MOS switches f2(1,1) to 72(
i, j) are selected by a plurality of row selection lines 18° to 18j sequentially and selectively driven by the output of the horizontal register 17.
Each row is controlled by a switch. In addition, the column selection MOS switches 13(1,1) to 1.9(i
j) are a plurality of column selection lines 20 . ~2J, the switches are controlled for each row.

In a solid-state area image sensor having such a configuration, photodiodes 11 (1, 1) to 77 (i, j)
The signal charges accumulated in each are read out as follows. First, one column selection line 201 is driven by the vertical register 19. Then, in FIG. 2, one row of photodiodes 77 (1, 1) arranged at the top
11(1,j) is connected to column selection MOS switch 13. ~13'' are all turned on. Next, the plurality of row selection lines 181 to 18j are sequentially driven by the horizontal register 17 from the left side to the right side in the figure.

Then, - the photodiodes 11 (1, 1
) to 11(1,j) for row selection
Switches 72(1,1) to 12(1,j) are turned on sequentially starting from the one on the left side in the figure. At this time, since all the MOS switches 13 (1, 1) to 73 (Lj) are turned on in advance, the photodiodes 71 (1, 1) to
The signal charge stored in advance in the signal readout line 14. are read out sequentially. After this, the signal readout line 14. The signal charges read out are sequentially output from the output terminal 16 via the signal charge output line 15. Photodiodes 27 (1, 1) to 1 for the above one row
After reading the signal charge from the column selection line 20. (1, j), the next column selection line 20. is driven, and after that, the row selection lines 181 to 18j are sequentially driven to select the photodiodes IJ(2,1) to 1 in the second column from the top in the figure.
11(2,j) is applied to the output line 15 via the signal readout line 142, and is sequentially outputted from the output terminal 16. Similarly, below,
Signal charges accumulated in advance in the photodiodes arranged in each column are read out to each signal readout line 14, and are sequentially outputted from an output terminal 16 via an output line 15.

Next, in such a sensor, a case will be described in which, for example, there is strong incident light on the photodiode 77 (1, 1). At this time, the photodiode I J (1, 1
) A part of the excess charge generated in the two MOS switches J
2(1,1), 1.9(1,1) via the signal readout line 14. flows into. Here, the signal readout line 14
．． is connected to the signal charge output line 15 through which the signal charges read out from all the photodiodes 11 are passed, so a part of the excess charge flowing from the photodiode IJ (1, 1) is transferred to the output terminal It is superimposed on all signal charges sequentially output from 16.

Therefore, it is possible to prevent smear from occurring in the row including the photodiode 11 (1, 1). In addition, no matter where the photodiode 11 is located with strong incident light, a portion of the excess charge generated there will be transferred to one of the MOs.
Since the signal charges flow into one of the signal charge readout lines 14 via the S switches 12 and 13, no smear occurs in any row.

FIG. 3 is a circuit diagram of another embodiment of the present invention, which is further improved from that of FIG. 2. That is, in the embodiment circuit of FIG. 2, a plurality of signal charge readout lines 14. ~ 14j are directly connected to the signal charge output line 15, the capacitance seen from the output terminal 16 is large, and as a result, the signal output from the output terminal 16 can be obtained by detecting the charge. Signal S/N
The ratio will be poor. Therefore, in the embodiment circuit shown in FIG. 3, in order to reduce the capacitance seen from the output terminal 16 and increase the S/N of the detection signal, each of the plurality of signal charge readout lines 14, to 14j and the Between the signal charge output line 15 and the column selection lines 201 to 20I, there are provided MOS switches 21 to 21 whose gates receive signals from each of the column selection lines 201 to 20I.
1 is connected to the signal charge output line 15 through each of the MO8 switches 2 to 211 controlled by the output of the vertical register 19, instead of being directly connected to the line 15. It is.

In such a configuration, when signal charges are sequentially output from the output terminal 16, the capacitance seen from the output terminal 16 is at most 1.
This is the sum of the capacitances in each of the signal charge readout lines 14 and the signal charge output lines 15, and this value can be made smaller than that in FIG. Therefore, the S/N ratio of the detection signal can be increased more than in the case of FIG.

Further, in this embodiment circuit, when excess charge is generated in one photodiode 11, a part of it flows into the signal charge readout line 14 of the corresponding column. However, at the same time as the column selection MOS switch 13 is turned on, the MOS switch 21 of that column is also turned on, and most of the excess charge is transferred to the column selection MOS switch 13 and the signal charge is transferred from the photodiode 11. Since the light flows into the output line 15 and is further output from the output terminal 16 before being read out, there is no risk of smearing occurring in the left and right directions of bright spots on the playback screen. That is, for example,
The frequency at which the horizontal register 17 drives the row selection line 18 is 7.16 MHz, and the frequency at which the vertical register 19 drives the column selection line 20 is 7.16 MHz.
The frequency at which the MOS switch 21 is driven is set to 15.7 KHz, and each MOS switch 21 in this embodiment
5 compared to the MOS switch 7 in the conventional circuit shown in the figure.
It will continue to be turned on for a period 00 times longer, and most of the excess charge will be output from the output terminal 16 during this period.

Note that although this invention is limited to the above embodiments, 20... Column selection line, 21... MOS switch.

Needless to say, various modifications are possible.

〔Effect of the invention〕

As explained above, according to the present invention, two switch elements for row selection and column selection are provided in series between each photosensitive pixel and the corresponding signal charge readout line, and the signal charges are Since the signal charges on the readout line are sequentially applied to the signal charge output line, a solid-state imaging device that can prevent the occurrence of smear can be provided.

[Brief Description of the Drawings] Fig. 1 is a circuit diagram of a conventional solid-state area image sensor, Fig. 2 is a circuit diagram of an embodiment of the present invention, and Fig. 3 is a circuit diagram of another embodiment of the invention. FIG. 11...Photodiode, 12...M for row selection
OS switch, 13...MOS switch for column selection,
14... Signal charge readout line, 15... Signal charge output line, 16... Output terminal, 17... Horizontal register,
18... Row selection line, 19... Vertical register, 2

Claims (2)

[Claims] (1) A photosensitive section consisting of photosensitive pixels arranged in the row and column directions that generate and accumulate signal charges in response to incident light, a plurality of signal charge readout lines, and each of the photosensitive pixels and corresponding thereto. two switch elements each for row selection and column selection, which are provided in series between the signal charge readout line, and a row drive for selectively driving the row selection switch elements for each row. column driving means for selectively driving the column selection switch element for each column;
A solid-state imaging device comprising: a signal charge output line to which signal charges on the plurality of signal charge readout lines are sequentially applied. (2) Each of the plurality of signal charge readout lines is coupled to the signal charge output line via each switch element controlled by the column selection means.
The solid-state imaging device described in .