JP4058765B2 - Solid-state imaging device and driving method thereof - Google Patents

Description

  The present invention relates to a solid-state imaging device and a driving method thereof. More specifically, the present invention relates to a solid-state imaging device capable of discharging pixel signals of a specific sensor row of a plurality of sensor rows and a driving method thereof in a CCD linear sensor having a plurality of sensor rows as needed.

Horizontal transfer in which pixels consisting of photodiodes that store signal charges in an amount corresponding to the input light are arranged in a one-dimensional manner, and signal charges from these pixels are transferred to the output section using a charge transfer device (CCD) charge transfer method. The CCD linear sensor having a section is used in many fields such as copying, facsimile, OCR, pattern recognition, and various measurements, and in recent years, sensors capable of obtaining different resolutions have been developed as necessary.
Hereinafter, a conventional CCD linear sensor will be described with reference to the drawings.

FIG. 5 is a schematic diagram for explaining a conventional CCD linear sensor. The CCD linear sensor 101 shown here is a so-called staggered CCD linear sensor that can select and output resolutions of 2400 dpi and 1200 dpi.
In the following text, the length of one sensor in the direction of the sensor row indicated by the symbol w in the figure is described as one pitch.
A main sensor array 102 made up of a plurality of sensors that receives signal light, photoelectrically converts it and stores it as signal charges, and is provided in parallel in the column direction of the main sensor array to transfer the signal charges of the main sensor array to the output section side. One horizontal charge transfer unit 106, adjacent to the main sensor column and the first horizontal charge transfer unit, and from the first read gate 104 and the main sensor column for reading the signal charge of the main sensor column to the first horizontal charge transfer unit Sub-sensor array 103, which is arranged with a half-pitch shift and receives signal light, photoelectrically converts and accumulates as signal charges in the same direction as the main sensor array, and is arranged in parallel in the column direction of the sub-sensor array. A second horizontal charge transfer unit 107 that transfers the signal charges of the sub-sensor to the output unit side, adjacent to the sub-sensor array and the second horizontal charge transfer unit, The second read gate 105, the first horizontal charge transfer unit, and the second horizontal charge transfer unit that read the signal charges of the second horizontal charge transfer unit join together, and the first horizontal charge transfer unit and the second horizontal charge transfer unit If the third horizontal charge transfer unit 108 that transfers each signal charge transferred from the unit to the output unit and the staggered linear sensor can select a resolution of 2400 dpi and 1200 dpi, a signal with a resolution of 1200 dpi is output. An overflow drain 109, which is a transfer destination of signal charges taken in by the sub sensor array when outputting, is provided (for example, see Patent Document 1).

In the CCD linear sensor configured as described above, when an output signal having a resolution of 2400 dpi is obtained, an electrode (1) indicated by symbol A in FIG. 5 (hereinafter referred to as Hφ1) is indicated by symbol F in FIG. A drive pulse is given at the timing, and a drive pulse is given to the electrode (2) (hereinafter referred to as Hφ2) indicated by symbol B in FIG. 5 at a timing indicated by symbol G in FIG. ) (Hereinafter referred to as Hφ3) is given a drive pulse at the timing indicated by symbol H in FIG. 6, and the timing indicated by symbol I in FIG. 6 is applied to the electrode (4) (hereinafter referred to as Hφ4) indicated by symbol D in FIG. 5 is applied to the electrode indicated by symbol E in FIG. 5 (hereinafter referred to as Hφ5) at the timing indicated by symbol F in FIG. 6, and the electrode indicated by symbol K in FIG. 5 (hereinafter referred to as Hφ6). Timin as indicated by symbol G in FIG. In applying a driving pulse.
That is, the signal charges of the main sensor array received and photoelectrically converted by the main sensor array 102 are read to the first horizontal charge transfer unit 106 through the first readout gate 104, and the signal charges of the main sensor array are the first charge. Accumulated in the horizontal transfer unit 106. Therefore, by applying a drive pulse of 5 MHz to Hφ1 and Hφ2 of the first horizontal charge transfer unit at the timings indicated by the symbols F and G in FIG. 6, the signal charge of the main sensor row causes the first horizontal transfer unit 106 to pass through the first horizontal charge transfer unit 106. 3 is transferred in the direction of the horizontal transfer unit 108.
The signal charges of the sub sensor array 103 received and photoelectrically converted by the sub sensor array 103 are read to the second horizontal charge transfer section 107 through the second readout gate 105, and the signal charges of the sub sensor array 103 are read out from the second horizontal transfer section 107. Accumulated in. Therefore, by applying a drive pulse of 5 MHz to Hφ1 and Hφ2 of the second horizontal charge transfer unit at timings indicated by reference signs F and G in FIG. 3 is transferred in the direction of the horizontal transfer unit 108.
At this time, when a resolution of 2400 dpi is selected, a drive pulse is given to Hφ5 at a timing indicated by a symbol F in FIG. 6, and a drive pulse is given to Hφ6 at a timing indicated by a symbol G in FIG.
The signal charges of the main sensor array and the sub sensor array transferred by the first horizontal charge transfer section and the second horizontal charge transfer section are alternately transferred to the third horizontal transfer section 108, and the third horizontal charge transfer section 108 A transfer pulse of 10 MHz is given to the transfer units Hφ3 and Hφ4 at the timings indicated by the symbols H and I in FIG. 6 to transfer the signals to the output unit and output a signal having a resolution of 2400 dpi from the output unit.

When a resolution of 1200 dpi is selected, a drive pulse is applied to Hφ1 at a timing indicated by reference symbol F in FIG. 6, a drive pulse is applied to Hφ2 at a timing indicated by reference symbol G in FIG. 6, and Hφ3 is supplied with reference symbol F in FIG. A drive pulse is applied at a timing indicated by H, a drive pulse is applied to Hφ4 at a timing indicated by reference symbol G in FIG. 6, a drive pulse is applied to Hφ5 at a timing indicated by reference symbol J in FIG. 6, and Hφ6 is indicated by reference symbol G in FIG. A drive pulse is given at the timing shown.
By doing so, the signal charge transferred by the second horizontal charge transfer section is discharged from Hφ6 to the overflow drain.
In the third horizontal charge transfer unit, the signal charges of the main sensor transferred by the first horizontal charge transfer unit are output at 5 MHz by applying drive pulses to the Hφ3 and Hφ4 at the timings indicated by the symbols F and G in FIG. The signal is transferred in the direction, and a signal having a resolution of 1200 dpi is output from the output unit.
Here, the case where the signal charge is transferred in the direction of the output unit at 5 MHz when the resolution of 1200 dpi is selected has been described as an example. However, the resolution of 2400 dpi is also selected when the resolution of 1200 dpi is selected. As in the case of selection, transfer may be performed in the direction of the output unit at 10 MHz. In this case, although there is a merit that it is not necessary to perform switching according to the resolution, packets having signal charges and empty packets are alternately present.
Therefore, when driving pulses are applied to Hφ3 and Hφ4 at 5 MHz, specifically, Hφ3 has the same waveform as Hφ2, and Hφ4 has the same waveform as Hφ1.
By doing so, it is necessary to switch the driving timing, but there is no empty packet, and since the driving is performed at a low speed, a reduction in power consumption can be expected.

  Here, in the conventional CCD linear sensor, the resolution of the output signal is changed depending on whether the drive pulse applied to Hφ5 is at the timing indicated by the symbol F in FIG. 6 or the timing indicated by the symbol J in FIG. That is, when outputting a 1200 dpi signal, Hφ5 is fixed to a low level potential, and the resolution of the signal to be output is reduced by not transferring the charge read to the second horizontal charge transfer unit to the third horizontal charge transfer unit. Selected.

JP 2002-330359 A

However, even when a 1200 dpi signal is output, a drive pulse is applied to Hφ6 at the timing indicated by the symbol G in FIG. 6, that is, a high level potential and a low level potential are applied alternately. Even if Hφ5 is fixed at the low level potential, if the signal charge read to the second horizontal charge transfer unit is greater than or equal to a predetermined value, the transfer to the overflow drain is not performed within a predetermined time. There is a problem that the charge is not completely transferred to the overflow drain and the signal charge is transferred to the third horizontal charge transfer unit.
In particular, when the number of pixels of the solid-state imaging device is increased, high-speed charge transfer is required, and signal charge may be erroneously transferred to the third horizontal charge transfer unit when there is not enough time for charge transfer. It is thought to increase.

  The present invention was devised in view of the above points, and when transferring only the charges accumulated in the first sensor array to the output unit, the signal charges accumulated in other sensor arrays are erroneously output. It is an object of the present invention to provide a solid-state imaging device that can be prevented from being transferred to a unit and a driving method thereof.

  In order to achieve the above object, a solid-state imaging device according to the present invention includes a first sensor array, and a first horizontal charge transfer unit for transferring signal charges accumulated in the first sensor array. A second sensor array arranged in parallel with the first sensor array, a second horizontal charge transfer unit for transferring signal charges accumulated in the second sensor array, and the second horizontal An overflow drain unit that is arranged in parallel with the charge transfer unit and selectively discharges the signal charge of the second horizontal charge transfer unit, and the first horizontal charge transfer unit and the second horizontal charge transfer unit are each A first electrode and a second electrode; and the second horizontal charge transfer section includes a third electrode adjacent to the overflow drain section and a third electrode adjacent to the signal charge transfer direction of the third electrode. In the solid-state imaging device having four electrodes, the signal of the second horizontal charge transfer unit is When discharging a charge to the overflow drain portion, a circuit for applying a constant potential to the third electrode is provided, and the fourth electrode has a potential lower than that applied to the third electrode. A circuit for applying a constant potential was provided.

Here, when discharging the signal charge of the second horizontal charge transfer section to the overflow drain section, a circuit for applying a constant potential to the third electrode is provided, and the fourth electrode is applied to the third electrode. By providing a circuit that applies a constant potential that is lower than the potential to be applied, the signal charge of the second horizontal charge transfer portion is discharged between the third electrode and the fourth electrode when discharged to the overflow drain portion. In addition, the potential difference is maintained while the signal charge of the second horizontal charge transfer section is discharged to the overflow drain section.
That is, the potential of the third electrode that discharges the signal charge to the overflow drain part is kept at a high level, so that the potential difference with the fourth electrode becomes a barrier to the output part side for the signal charge, It is possible to suppress erroneous transfer of the signal charge of the second horizontal charge transfer unit to the output unit side.

  In order to achieve the above object, the solid-state imaging device driving method according to the present invention includes a first sensor array and a first sensor for transferring signal charges accumulated in the first sensor array. A horizontal charge transfer section; a second sensor array arranged in parallel with the first sensor array; a second horizontal charge transfer section for transferring signal charges accumulated in the second sensor array; An overflow drain portion that is arranged in parallel with the second horizontal charge transfer portion and selectively discharges signal charges of the second horizontal charge transfer portion; the first horizontal charge transfer portion and the second horizontal charge transfer portion A third horizontal charge transfer unit to which signal charges are transferred, and each of the first horizontal charge transfer unit and the second horizontal charge transfer unit includes a first electrode and a second electrode, Further, the second horizontal charge transfer section includes a third electrode adjacent to the overflow drain section. In the driving method of the solid-state imaging device having the fourth electrode adjacent in the signal charge transfer direction of the third electrode, when discharging the signal charge of the second horizontal charge transfer unit to the overflow drain unit, A constant potential is applied to the third electrode, and a constant potential that is lower than the potential applied to the third electrode is applied to the fourth electrode.

  Here, when the signal charge of the second horizontal charge transfer section is discharged to the overflow drain section, a constant potential is applied to the third electrode, and the fourth electrode is applied with the potential applied to the third electrode. By applying a constant potential which is also a low potential, there is a potential difference between the third electrode and the fourth electrode when the signal charge of the second horizontal charge transfer portion is discharged to the overflow drain portion, and While the signal charge of the second horizontal charge transfer unit is being discharged to the overflow drain part, this potential difference relationship is maintained.

  According to the solid-state imaging device and the driving method thereof of the present invention, when only the signal charges accumulated in the first sensor array are transferred to the output unit, the signal charges accumulated in other sensor arrays are erroneously transferred to the output unit. It can be suppressed.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings, so that the present invention can be understood. In the following description, as with the conventional CCD linear sensor described above, a CCD linear sensor having a main sensor array and a sub sensor array and capable of outputting signals with resolutions of 2400 dpi and 1200 dpi will be described as an example. Note that the output resolution is not limited to 2400 dpi and 1200 dpi. Further, if there are a plurality of horizontal charge transfer units, the third horizontal charge transfer unit is not necessarily present.

  FIG. 1 is a schematic diagram for explaining a CCD linear sensor which is an example of a solid-state imaging device to which the present invention is applied. The CCD linear sensor 1 shown here can output signals of 2400 dpi and 1200 dpi in the same manner as the conventional CCD linear sensor described above. The main sensor array 2, the sub sensor array 3 arranged with a half-pitch shift from the main sensor array, the main A first readout gate 4 provided adjacent to the sensor row for reading out the electric charge taken in by the main sensor row, a second readout gate 5 provided adjacent to the sub sensor row for reading out the electric charge taken in by the sub sensor row, and a first readout gate The first horizontal charge transfer unit 6 that transfers the charge read by the first read gate provided adjacent to the output unit, and the charge read by the second read gate provided adjacent to the second read gate The second horizontal charge transfer unit 7, the first horizontal charge transfer unit, and the second horizontal charge A third horizontal charge transfer unit 8 for transferring signal charges transferred from the first horizontal charge transfer unit and the second horizontal charge transfer unit to the output unit side and a signal having a resolution of 1200 dpi; In this case, an overflow drain 9 is provided for discharging charges taken in by the sub sensor array.

FIG. 2 is a schematic diagram for explaining an example of a switch circuit (1) that is built in a CCD linear sensor, which is an example of a solid-state imaging device to which the present invention is applied, and that outputs a driving pulse to be applied to Hφ5 indicated by symbol e in FIG. The switch circuit (1) shown here has a switch (1) 10 and a switch (2) 11, and the switch (1) is in an ON state and an input signal to the switch circuit (1) is switched to the switch circuit ( 1), the switch (2) is in an ON state, and is kept at a constant low level (hereinafter referred to as L level) voltage, for example, a ground level regardless of the input signal to the switch circuit (1). The signal is arranged at a position where the signal can be output from the switch circuit (1).
Here, when the switch circuit control pulse applied to the switch circuit (1) is at the L level, the switch (1) is on and the switch (2) is off, and the signal input to the switch circuit (1) remains unchanged. The switch circuit (1) is configured to be able to output. When the switch circuit control pulse applied to the switch circuit (1) is at a high level (hereinafter referred to as H level), the switch (1) is turned off and the switch (2) is turned on. The ground level signal can be output from the switch circuit (1).
2 indicates a signal input to the switch circuit (1), and reference numeral y1 in FIG. 2 indicates a signal output from the switch circuit (1).

FIG. 3 illustrates an example of a switch circuit (2) that is built in a CCD linear sensor, which is an example of a solid-state imaging device to which the present invention is applied, and that outputs a drive pulse applied to Hφ6 indicated by a symbol t in FIG. The switch circuit (2) shown here has a switch (3) 12 and a switch (4) 13, and the switch (3) is switched on to switch the input signal to the switch circuit (2). Arranged at a position where the circuit (2) can output, the switch (4) is in the ON state, and a constant H level voltage, for example, a voltage of 5V, for example, is applied regardless of the input signal to the switch circuit (2). Can be applied.
Here, when the switch circuit control pulse applied to the switch circuit (2) is at the L level, the switch (3) is on and the switch (4) is off, and the signal input to the switch circuit (2) remains unchanged. The switch circuit (2) can be output. When the switch circuit control pulse applied to the switch circuit (2) is at the H level, the switch (3) is turned off and the switch (4) is turned on. For example, a voltage of 5 V is set as the H level voltage. ) Can be applied.
In FIG. 3, symbol x2 indicates a signal input to the switch circuit (2), and symbol y2 in FIG. 3 indicates a signal output from the switch circuit (2).

In the CCD linear sensor with the built-in switch circuit (1) and switch circuit (2) as described above, a drive pulse is applied to Hφ1 indicated by symbol a in FIG. 1 at the timing indicated by symbol f in FIG. A drive pulse is given to the Hφ2 indicated by the middle symbol b at the timing indicated by the symbol g in FIG. 4, and a drive pulse is given to the Hφ3 indicated by the symbol c in FIG. 1 at the timing indicated by the symbol h in FIG. A driving pulse is applied to Hφ4 indicated by d at the timing indicated by symbol i in FIG.
Further, the drive pulse at the timing indicated by the symbol f in FIG. 4 is given as the input x1 to the switch circuit (1), and the drive pulse at the timing indicated by the symbol g in FIG. 4 is given as the input x2 to the switch circuit (2).

When a signal having a resolution of 2400 dpi is obtained by the CCD linear sensor to which the drive pulse is applied as described above, an L level switch circuit control pulse is applied to the switch circuit (1) and the switch circuit (2).
That is, by applying an L level switch circuit control pulse to the switch circuit (1), the drive pulse at the timing indicated by the symbol f in FIG. 4 input to the switch circuit (1) is output from the switch circuit (1), and Hφ5 4 is supplied with a drive pulse at the timing indicated by reference numeral f in FIG. 4 and is supplied to the switch circuit (2) by applying a switch circuit control pulse of an L level signal to the switch circuit (2). A timing drive pulse is output from the switch circuit (2), and a signal having a resolution of 2400 dpi is output from the CCD linear sensor by applying a drive pulse having a timing indicated by symbol g in FIG.

Further, when obtaining a signal having a resolution of 1200 dpi, an H level switch circuit control pulse is applied to the switch circuit (1) and the switch circuit (2).
That is, the ground level potential is output from the switch circuit (1), the ground level potential is applied to Hφ5, the potential of 5V is output from the switch circuit (2), and the potential of 5V is applied to Hφ6. To a signal having a resolution of 1200 dpi.

Here, in the CCD linear sensor which is an example of the solid-state imaging device to which the present invention is applied, the switch circuit (1) and the switch circuit (2) are built in, and a switch circuit control pulse is given to these switch circuits. Although the timing of the drive pulse given to Hφ5 and Hφ6 is controlled, the switch circuit (1) and the switch circuit (2) are not necessarily built in the CCD linear sensor, and the timing of the drive pulse given to Hφ5 and Hφ6 May be controlled outside the CCD linear sensor.
However, it is necessary to provide another chip for controlling the timing of drive pulses applied to Hφ5 and Hφ6 outside the CCD linear sensor, and it is inconvenient in terms of manufacturing cost, installation space, etc. in a device incorporating the CCD linear sensor. In order to be considered, it is preferable that the switch circuit (1) and the switch circuit (2) are built in the CCD linear sensor.

  In the CCD linear sensor as an example of the solid-state imaging device to which the present invention is applied, the first horizontal charge transfer unit and the second horizontal charge transfer unit transfer charges at 5 MHz, whereas the third horizontal charge transfer. The unit is configured to transfer charges at 10 MHz. When outputting a signal having a resolution of 2400 dpi, the charges transferred by the first horizontal charge transfer unit and the second horizontal charge transfer unit are transferred to the third horizontal charge transfer unit. If the first horizontal charge transfer unit and the second horizontal charge transfer unit transfer charges at 5 MHz in order to add and transfer at the charge transfer unit, the third horizontal charge transfer unit needs to transfer charges at 10 MHz. However, when outputting a signal with a resolution of 1200 dpi, the third horizontal charge transfer unit does not necessarily have a charge because the third horizontal charge transfer unit transfers only the charge transferred by the first horizontal charge transfer unit. Not necessary to transfer at 0 MHz, it may be a charge similar to the first horizontal charge transfer part transfers at 5 MHz.

In the CCD linear sensor which is an example of the solid-state imaging device to which the present invention is applied, when the output of the sub sensor array is transferred to the overflow drain, Hφ5 is fixed to the ground potential and the potential of Hφ6 is fixed to 5V. Therefore, it is possible to prevent the output of the sub sensor array from being erroneously transferred to the output unit side.
That is, as compared with the conventional CCD linear sensor in which the driving pulse applied to Hφ6 repeats H level and L level, there is a potential difference between Hφ5 and Hφ6, and Hφ6 that discharges the signal charge to the overflow drain remains at high level. By being constant, the potential difference with Hφ5 becomes a barrier to the output unit side for the signal charge, and it is possible to prevent the output of the second sensor array from being erroneously transferred to the output unit side.

  In addition, the CCD linear sensor that is the position of the solid-state imaging device to which the present invention is applied has a built-in switch circuit that controls the timing of the driving pulse applied to Hφ5 and Hφ6. Since switching to a voltage (for example, a DC voltage such as a ground level voltage applied to Hφ5) is performed within the CCD linear sensor chip, a general-purpose timing generator can be used simply by inputting a command signal for switching from outside the chip, In a device incorporating a CCD linear sensor, the cost can be reduced and the usability can be improved.

It is a schematic diagram for demonstrating the CCD linear sensor which is an example of the solid-state image sensor to which this invention is applied. It is a figure for demonstrating the switch circuit (1) which outputs the drive pulse given to Hphi5 shown with the code | symbol e in FIG. It is a figure for demonstrating the switch circuit (2) which outputs the drive pulse given to Hphi6 shown with the code | symbol t in FIG. It is a figure for demonstrating the operation timing of each drive pulse given to the CCD linear sensor which is an example of the solid-state image sensor to which this invention is applied. It is a schematic diagram for demonstrating the conventional CCD linear sensor. It is a figure for demonstrating the operation timing of each drive pulse given to the conventional CCD linear sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 CCD linear sensor 2 Main sensor row | line | column 3 Sub sensor row | line | column 4 1st read-out gate 5 2nd read-out gate 6 1st horizontal charge transfer part 7 2nd horizontal charge transfer part 8 3rd horizontal charge transfer part 9 Overflow drain 10 Switch (1)
11 Switch (2)
12 switches (3)
13 switches (4)

Claims (4)

A first sensor row; a first horizontal charge transfer portion for transferring signal charges accumulated in the first sensor row; and a second sensor row arranged in parallel with the first sensor row. , A second horizontal charge transfer unit for transferring the signal charge accumulated in the second sensor array, and a signal charge of the second horizontal charge transfer unit, which is provided in parallel with the second horizontal charge transfer unit And an overflow drain part for selectively discharging,
The first horizontal charge transfer unit and the second horizontal charge transfer unit each have a first electrode and a second electrode, and the second horizontal charge transfer unit is adjacent to the overflow drain unit. In a solid-state imaging device having a third electrode and a fourth electrode adjacent to the third electrode in the signal charge transfer direction,
A circuit for applying a constant potential to the third electrode when discharging the signal charge of the second horizontal charge transfer section to the overflow drain section;
A solid-state imaging device, wherein a circuit that applies a constant potential that is lower than a potential applied to the third electrode is provided to the fourth electrode. The solid-state imaging device according to claim 1, further comprising a third horizontal charge transfer unit to which signal charges are transferred from the first horizontal charge transfer unit and the second horizontal charge transfer unit. 3. The solid-state imaging device according to claim 1, wherein the sensor rows of the first sensor row and the second sensor row are arranged with a predetermined shift relative to each other. A first sensor row; a first horizontal charge transfer portion for transferring signal charges accumulated in the first sensor row; and a second sensor row arranged in parallel with the first sensor row. , A second horizontal charge transfer unit for transferring the signal charge accumulated in the second sensor array, and a signal charge of the second horizontal charge transfer unit, which is provided in parallel with the second horizontal charge transfer unit An overflow drain portion for selectively discharging the first horizontal charge transfer portion, and a third horizontal charge transfer portion to which signal charges are transferred from the first horizontal charge transfer portion and the second horizontal charge transfer portion,
The first horizontal charge transfer unit and the second horizontal charge transfer unit each have a first electrode and a second electrode, and the second horizontal charge transfer unit is adjacent to the overflow drain unit. In a driving method of a solid-state imaging device having a third electrode and a fourth electrode adjacent to the third electrode in the signal charge transfer direction,
When discharging the signal charge of the second horizontal charge transfer portion to the overflow drain portion, a constant potential is applied to the third electrode,
A solid-state imaging element driving method, wherein a constant potential that is lower than a potential applied to the third electrode is applied to the fourth electrode.

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