JP2009100404A - Method for driving solid-state imaging element, and imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-state imaging element which can be driven at a high speed, while reducing the noise. <P>SOLUTION: A driving method is provided for the solid-state imaging element 10 having a semiconductor substrate 11, where there are provided a photoelectric conversion element 12; a plurality of VCCDs 13 for vertically transferring signal charges accumulated on the photoelectric conversion element 12; a line memory 18, provided at the end of each VCCD 13 and adapted to be driven independently from the VCCD 13 to be driven; and a HCCD 15 for transferring the signal charges transferred from the line memory 18 to the output end side. During the time the HCCD 15 horizontally transfers the signal charges, the VCCD 13 vertically transfers the signal charges and sweeps out the signal charges accumulated on the photoelectric conversion element 12 to the semiconductor substrate 11. At each pulse edge of drive pulses ΦV1-ΦV4 for driving the VCCDs 13 and sweep-out pulses ΦOFD for sweeping out the signal charge, the HCCD 15 temporarily stops its horizontal transfer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for driving a solid-state imaging device capable of high-speed driving.

  A CCD (Charge Coupled Devices) type imaging device includes a vertical charge transfer path (VCCD) and a horizontal charge transfer path (HCCD), as described in Patent Document 1 below, for example, and a semiconductor substrate. First, the signal charges read from the photodiodes (photoelectric conversion elements) arranged in a two-dimensional array on the surface are transferred to the vertical charge transfer path, and then transferred to the horizontal charge transfer path along the vertical charge transfer path. The signal charge is transferred along the horizontal charge transfer path to the charge detection unit and the output amplifier, and the output amplifier outputs a voltage value signal corresponding to each charge amount of the signal charge transferred to the charge detection unit. It has become.

  FIG. 3 is a timing chart showing the conventional transfer timing of signal charges. By applying vertical transfer pulses φV1, φV2, φV3, φV4 to the vertical charge transfer path, signal charges are transferred in the vertical direction, and horizontal transfer pulses φH1, φH2 are applied to the horizontal charge transfer path. Thus, the signal charges are transferred in the horizontal direction. In addition, by applying the sweep pulse φOFD to the semiconductor substrate, the signal charges accumulated in the photodiode during the transfer period are swept out to the semiconductor substrate.

  When the vertical transfer pulses φV1 to φV4 are applied to the vertical charge transfer path, the detected charges of the photodiodes in the horizontal horizontal row on the semiconductor substrate are transferred by one stage in the vertical direction, and the end of the vertical charge transfer path is It is stored in a buffer line memory (LM) provided between the horizontal charge transfer path. After the signal charge for one horizontal line in the horizontal direction is transferred by one stage in the vertical direction, when the sweep pulse φOFD is applied to the semiconductor substrate, the signal charge accumulated in the photodiode during the transfer period is swept to the semiconductor substrate. It is.

  When the drive pulse φLM is applied to the line memory, the signal charge on the line memory is transferred to the horizontal charge transfer path. Then, two-phase drive pulses φH1 and φH2 are applied to the horizontal charge transfer path, and after all of the signal charges on the horizontal charge transfer path are read by the output amplifier, the signal charge for the next row is transferred in the vertical direction. Is done.

  That is, in the related art, the horizontal charge transfer path is driven during the horizontal transfer period (output period), and the vertical charge transfer path and the line memory are Sweep drive is performed. This is because if the vertical transfer pulse φV1 to φV4 rise and fall timing overlaps the horizontal transfer period, or the sweep pulse φOFD pulse rise and fall timing overlaps the horizontal transfer period, noise will appear on the output side. This is because the influence appears.

JP 2000-350099 A

  As described above, in a conventional CCD-type imaging device, vertical transfer and signal charge sweep-out are performed in a period that does not overlap the horizontal transfer period, thereby avoiding mixing of noise. That is, the conventional CCD-type imaging device has a problem that the solid-state imaging device cannot be driven at high speed because vertical transfer and signal charge sweep-out cannot be performed during the horizontal transfer period.

  An object of the present invention is to provide a driving method of a solid-state imaging device that can be driven at high speed while avoiding noise.

  The solid-state imaging device driving method according to the present invention includes a photoelectric conversion element, a plurality of vertical charge transfer paths that transfer signal charges accumulated in the photoelectric conversion element in a vertical direction, and an end of each vertical charge transfer path. A signal charge temporary storage section that is driven independently of the driving of the vertical charge transfer path, and a horizontal charge transfer path that transfers the signal charge transferred from the signal charge temporary storage section to the output end side. A method of driving a solid-state imaging device including a semiconductor substrate, wherein a signal charge is vertically transferred by the vertical charge transfer path and a signal accumulated in the photoelectric conversion element during a horizontal transfer period of the signal charge by the horizontal charge transfer path. The horizontal charge transfer path at each pulse edge of the drive pulse for driving the vertical charge transfer path and the sweep pulse for sweeping the signal charge, while sweeping out charges to the semiconductor substrate To pause the horizontal transfer.

  In the solid-state imaging device driving method according to the present invention, the signal charge is transferred from the signal charge temporary storage unit to the horizontal charge during a horizontal blanking period that is provided between the horizontal transfer period and the next horizontal transfer period. Transfer to the transfer path.

  In the solid-state imaging device driving method according to the present invention, the temporary stop period is a period in which at least three horizontal stages of transfer are performed.

  An image pickup apparatus according to the present invention includes a photoelectric conversion element, a plurality of vertical charge transfer paths that transfer signal charges accumulated in the photoelectric conversion element in a vertical direction, and the vertical charges provided at an end of each vertical charge transfer path. A semiconductor substrate on which a signal charge temporary storage unit that is driven independently of the drive of the transfer path and a horizontal charge transfer path that transfers the signal charge transferred from the signal charge temporary storage unit to the output end side are formed; An image pickup apparatus having a solid-state image sensor, wherein a vertical transfer pulse for performing vertical transfer of signal charge through the vertical charge transfer path and accumulation in the photoelectric conversion element during a horizontal transfer period of signal charge through the horizontal charge transfer path The horizontal transfer in the horizontal charge transfer path is temporarily stopped at the time of the sweep pulse for sweeping out the signal charge to the semiconductor substrate and the pulse edge of the vertical transfer pulse and the sweep pulse. It generates a horizontal transfer pulse comprises a driving means for outputting to said solid state imaging device.

  In the imaging apparatus according to the aspect of the invention, the driving unit may output a driving pulse to the signal charge temporary storage unit in a horizontal blanking period provided between the period for performing the horizontal transfer and the period for performing the next horizontal transfer. The signal charge in the signal charge temporary storage unit is transferred to the horizontal charge transfer path.

  In the image pickup apparatus of the present invention, the driving means stops the change by stopping the change of the horizontal transfer pulse only during a period in which the transfer for at least three stages in the horizontal direction is performed.

  According to the present invention, horizontal transfer, vertical transfer, and signal charge sweeping can be simultaneously performed to shorten the horizontal blanking period, thereby enabling high-speed driving. In addition, since the horizontal transfer is temporarily stopped at the edge of the vertical transfer pulse and the sweep pulse, it is possible to avoid a situation in which noise is superimposed on the output signal.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic diagram of an imaging apparatus according to an embodiment of the present invention. The imaging apparatus according to the present embodiment includes a solid-state imaging device 10 and a drive unit 20 that outputs a driving timing pulse to the solid-state imaging device 10.

  The solid-state imaging device 10 includes a semiconductor substrate 11, a plurality of photodiodes (PD) 12 arrayed and formed on the semiconductor substrate 11 in a two-dimensional array (in the illustrated example, a square lattice), and the side of each photodiode row. And a readout gate 14 provided between each photodiode 12 and the vertical charge transfer path 13. In the illustrated example, four vertical transfer electrodes provided in the vertical charge transfer path 13 are provided per photodiode, and vertical transfer pulses φV1, φV2, φV3, and φV4 are applied to the four electrodes (4 Phase drive).

  Further, the solid-state imaging device 10 includes a horizontal charge transfer path (HCCD) 15 provided at the lower side of the semiconductor substrate 11, a charge detection unit 16 and an output amplifier 17 provided at the output part of the horizontal charge transfer path 15. Is provided.

  The horizontal charge transfer path 15 is provided with two horizontal transfer electrodes per vertical charge transfer path, and horizontal transfer pulses φH1 and φH2 are applied to the two electrodes, respectively (in the case of two-phase driving). It has become.

  In addition, the solid-state imaging device 10 is similar to the solid-state imaging device described in Patent Document 1 described above, and each vertical charge transfer path 13 is located at the boundary between the end of each vertical charge transfer path 13 and the horizontal charge transfer path 15. And a buffer line memory (signal charge temporary storage unit) 18 driven at a timing different from the drive timing of the vertical charge transfer path 13.

  Further, the solid-state imaging device 10 can apply an OFD voltage that determines the saturation charge amount of the photodiode 12 to the semiconductor substrate 11, and superimpose a high voltage sweep pulse φOFD on the OFD voltage, thereby causing the photodiode 12 to overlap. The accumulated signal charge can be swept out to the semiconductor substrate 11.

  Upon receiving an instruction from an external CPU (not shown) (for example, a control CPU of a digital camera), the drive unit 20 receives vertical transfer pulses φV1 to φV4, horizontal transfer pulses φH1 and φH2, line memory drive pulse φLM, sweep pulse φOFD, and readout. A pulse or the like is generated and output to the solid-state image sensor 10.

  Although the terms “vertical” and “horizontal” have been described, this merely means “one direction” along the light receiving surface of the solid-state imaging device and “a direction substantially orthogonal to the one direction”.

  In the imaging apparatus having such a structure, each photodiode 12 accumulates a signal charge corresponding to the amount of incident light from the subject, and when a readout pulse is applied from the drive unit 20, the signal charge passes through the readout gate 14 and is transferred to the photodiode 12. To the adjacent vertical charge transfer path 13.

  When vertical transfer pulses φV 1 to φV 4 are applied to the vertical charge transfer path 13, the signal charge is transferred in the direction of the horizontal charge transfer path 15 and transferred to the end of each vertical charge transfer path 13. The signal charge is transferred to the line memory 18 and temporarily stored.

  When the drive pulse φLM is applied to the line memory 18, the signal charge on the line memory 18 is transferred to the horizontal charge transfer path 15. By controlling the line memory 18, pixel addition of signal charges in the horizontal direction can be performed.

  When the horizontal transfer pulses φH 1 and φH 2 are applied to the horizontal charge transfer path 15, the signal charge is transferred along the horizontal charge transfer path 15 in the direction of the charge detection unit 16. The pulse φH2 is an inverted pulse with respect to the pulse φH1, and the signal charge stored in the potential packet formed under one horizontal transfer electrode is adjacent when the pulses φH1 and φH2 are inverted. It is transferred into a potential packet formed under the horizontal transfer electrode. In other words, the horizontal transfer for one stage is performed, and when the pulses φH1 and φH2 are inverted next, the horizontal transfer for the next stage is performed.

  The signal charge is transferred in the horizontal direction, and a voltage value signal corresponding to the amount of signal charge entering the charge detection unit 16 is output from the output amplifier 17. After the signal charge is discarded, the next signal The operation (horizontal transfer period) in which the charge enters the charge detection unit 16 is repeated until the signal charge on the horizontal charge transfer path 15 disappears. A short horizontal blanking period is provided before the next horizontal transfer period starts.

  When the sweep pulse φOFD is applied to the semiconductor substrate 11, the signal charge accumulated in the photodiode 12 is swept out to the semiconductor substrate 11.

  FIG. 2 is a timing chart of each driving pulse for driving the solid-state imaging device 10 by the driving unit 20. In the present embodiment, horizontal transfer periods and horizontal blanking periods are alternately provided, as in the prior art shown in FIG.

  However, in this embodiment, the vertical transfer period is also distinguished from the horizontal transfer period, and vertical transfer is also performed during the horizontal transfer period. That is, the vertical charge transfer path 13 and the horizontal charge transfer path 15 operate simultaneously. The signal charge accumulated in the photodiode 12 is also swept out during the horizontal transfer period. Thereby, the solid-state image sensor 10 can be driven at high speed.

  However, if unlimited vertical transfer or signal charge sweep-out operation is performed during the horizontal transfer period, there is a risk that noise will appear on the output.

  Therefore, in this embodiment, the horizontal transfer is temporarily stopped for a predetermined short period at each of the rising timing and falling timing of the vertical transfer pulse and the sweep pulse. In order to reduce noise, it is necessary to temporarily stop at least one transfer in the horizontal transfer direction. Preferably, as shown in the figure, the transfer for three stages is temporarily stopped.

  FIG. 2 shows only the pulse falling portion of the vertical transfer pulse φV3, but when the vertical charge transfer path is driven in four phases, the rise and fall (pulse edges) of the pulses φV1 to φV4 are measured. There are eight places, and only these eight places are temporarily stopped during one horizontal transfer period. In the case of 8-phase driving, a total of 16 points are temporarily stopped. As a result, a situation in which noise rides on the output is avoided.

  Further, FIG. 2 shows only the pulse falling portion of the sweep pulse φOFD, but the pause is performed during one horizontal transfer period by the number of rising and falling edges of the sweep pulse φOFD. As a result, a situation in which noise rides on the output is avoided.

  Each time the horizontal transfer period ends, the horizontal charge transfer path 15 is stopped (horizontal blanking period), and the line memory 18 is driven during the horizontal transfer stop period, and the charge detection unit in the next horizontal transfer period. The signal charge transferred to 16 is transferred from the line memory 18 to the horizontal charge transfer path 15. In the present embodiment, since the operation performed during the horizontal blanking period is only driving the line memory 18, the horizontal blanking period can be shortened, and the solid-state imaging device 10 can be driven at high speed.

  Since the transfer pulses φH1 and φH2 of the horizontal charge transfer path 15 are high-speed pulses, 8 or 16 pauses associated with vertical transfer or multiple pauses associated with sweeping are performed during one horizontal transfer period. However, the delay time is only a moment and does not hinder speeding up.

  As described above, according to the present embodiment, since high-speed driving is possible, captured image data can be read at high speed even from a solid-state imaging device equipped with millions of pixels or more, and noise is superimposed. Therefore, high-quality captured image data can be read out.

It is a schematic diagram of the solid-state imaging device of the embodiment of the present invention. 2 is a drive timing chart of the imaging apparatus of FIG. 1. It is a drive timing chart of the conventional imaging device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Solid-state image sensor 11 Semiconductor substrate 12 Photodiode (photoelectric conversion element)
13 Vertical charge transfer path (VCCD)
14 Read gate 15 Horizontal charge transfer path (HCCD)
16 Charge detection unit 17 Output amplifier 18 Line memory (signal charge temporary storage unit)
20 Drive unit φV1 to φV4 Vertical transfer pulse φH1 and φH2 for four-phase drive Horizontal transfer pulse φLM for two-phase drive Line memory drive pulse

Claims (6)

A photoelectric conversion element, a plurality of vertical charge transfer paths that transfer signal charges accumulated in the photoelectric conversion element in the vertical direction, and provided at the end of each vertical charge transfer path, independent of driving of the vertical charge transfer paths A solid-state imaging device including a semiconductor substrate on which a signal charge temporary storage unit driven by a horizontal charge transfer path and a horizontal charge transfer path for transferring the signal charge transferred from the signal charge temporary storage unit to the output end side are formed. There,
During the horizontal transfer period of the signal charge by the horizontal charge transfer path, the signal charge is vertically transferred by the vertical charge transfer path and the signal charge accumulated in the photoelectric conversion element is swept out to the semiconductor substrate, and the vertical charge transfer is performed. A solid-state imaging device driving method for temporarily stopping horizontal transfer in the horizontal charge transfer path at each pulse edge of a drive pulse for driving a charge transfer path and a sweep pulse for sweeping out the signal charge. A method for driving a solid-state imaging device according to claim 1,
A solid-state imaging device driving method for transferring a signal charge from the signal charge temporary storage section to the horizontal charge transfer path in a horizontal blanking period provided between a period for performing the horizontal transfer and a period for performing the next horizontal transfer . A method for driving a solid-state imaging device according to claim 1 or 2,
A method for driving a solid-state imaging device, wherein the temporary stop period is a period in which at least three horizontal stages of transfer are performed. A photoelectric conversion element, a plurality of vertical charge transfer paths that transfer signal charges accumulated in the photoelectric conversion element in the vertical direction, and provided at an end of each vertical charge transfer path, independent of driving of the vertical charge transfer paths An image pickup apparatus having a solid-state image pickup device including a semiconductor substrate on which a signal charge temporary storage unit that is driven at a time and a horizontal charge transfer path that transfers a signal charge transferred from the signal charge temporary storage unit to the output end side are formed Because
During a horizontal transfer period of the signal charge by the horizontal charge transfer path, a vertical transfer pulse for performing a vertical transfer of the signal charge by the vertical charge transfer path, and sweeping of the signal charge accumulated in the photoelectric conversion element to the semiconductor substrate Driving to generate a sweep pulse for performing a horizontal transfer pulse and a horizontal transfer pulse for temporarily stopping horizontal transfer in the horizontal charge transfer path at each edge of the vertical transfer pulse and the sweep pulse, and outputting the generated pulse to the solid-state imaging device An imaging apparatus comprising means. The imaging apparatus according to claim 4,
The drive means outputs a drive pulse to the signal charge temporary storage unit during a horizontal blanking period provided between the period during which the horizontal transfer is performed and the period during which the next horizontal transfer is performed. An imaging device that transfers signal charges to the horizontal charge transfer path. The imaging apparatus according to claim 4 or 5, wherein
An image pickup apparatus in which the driving unit stops the change by stopping the change of the horizontal transfer pulse only during a period in which transfer of at least three stages in the horizontal direction is performed.

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