JPH03196676A - Driving method of charge transfer device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method of driving a charge transfer element used in a solid-state imaging device or the like, and particularly to a method of driving a charge transfer element that can improve transfer efficiency.

“Prior art” Charge transfer devices (CCDs), typically charge-coupled devices (CCDs)
Examples of TD) include solid-state imaging devices such as the one-dimensional image sensor shown in Figure 2, the two-dimensional image sensor shown in Figure 3, and the serial-parallel-serial (SP) shown in Figure 4.
S) type delay line, etc.

In these devices, in any case, charges No. 48 of the plurality of vertical transfer sections 3 are transferred to the horizontal transfer section 4, and then transferred within the horizontal transfer section 4, and then outputted from the signal charge detection section 5.
It is read out as a number.

In FIGS. 2 and 3, 1 is a photoelectric conversion section (shown as a shaded area), and 2 is a transfer gate.

A driving method for transferring the No. 43 1i load from the vertical transfer section 3 to the horizontal transfer section 4 will be explained with reference to FIG.

In the following, a case will be explained in which a CCD is used as each transfer section 3.4, and the vertical transfer section 3 is 4-phase drive and the horizontal transfer section 4 is 2-phase drive. The same holds true for the number of phases.

FIG. 5 shows a timing diagram for the conventional drive system.

Further, FIG. 6 shows a schematic diagram of the charge transfer region from the vertical transfer section 3 to the horizontal transfer section 4.

Kokote, transfer electrode GVI, GV2. GV3. GV
4. Gl and GD3 have transfer links φ shown in FIG.
vl.

φV2. φV3. φV4. φH1 and φH2 are applied.

Further, in FIG. 6, the hatching portions provided in the areas of the transfer electrodes GHI and GD3 are barrier areas for directing the transfer.

5, the signal charge accumulated in the area under the transfer electrodes GVI, GVZ constituting the final bit of the vertical transfer section 3 at time t1 in FIG. 5 is transferred to the transfer electrode GV3. The data is transferred to the corresponding transfer unit 1firG of the horizontal transfer unit 4 directly below the old one via the channel area of the GV4.

At the next timing, the signal charges accumulated in the transfer electrode GH1 are transferred in the horizontal direction after time tlo, and 48
The signal charge detection section 5 carries the signal to the signal charge detection section 5.

In such horizontal transfer, as shown in FIG.
The period T2 during which the transfer electrode Gl, which is the beginning of horizontal transfer, is transferred to GHl2 is longer than the period T1 during which the transfer electrode Gl is transferred to GHl2.
It's getting much shorter.

``Problems to be Solved by the Invention'' By the way, FIG. 7 is a diagram showing a more detailed example of FIG. 6.

In FIG. 7, the region surrounded by the dashed line is the active region, which forms the transfer channel of the CCD. Further, the broken line indicates the lower electrode of each transfer electrode, and the solid line indicates the upper electrode, and in the horizontal transfer section 4, a potential barrier for directing the transfer has been formed in the channel region under the upper (+!1) electrode.

In addition, each transfer electrode GVI, GV2. GV3. GV
4. GHl, Gl (21: is the clock φ in FIG.
Vl, φv2゜φV3. φV4. φold and φH2 are applied.

As is clear from FIG. 7, when the two-phase driving force type is adopted, the vertical transfer channel formed below the vertical transfer section 3i' joins the horizontal transfer channel formed directly below the horizontal transfer section 4. The channel width WO of the region must necessarily be smaller than the channel width W1 of the lower electrode to which the transfer torque φ is applied.

In the case of the conventional drive timing shown in FIG. , period TI, which is a relatively long period of time, transmission deterioration due to small channel congestion WO is unlikely to occur.

However, the period T2 during which transfer 1 is transferred from below the lower N pole for the old pole G to below the lower electrode of the next transfer electrode GH2 is 1 transfer when reading from the horizontal transfer section 4 to the No. 48 charge detection section 5. Since it is the same as the per-stage period T3, it is much shorter than the period T1.

Therefore, if the channel congestion WO is narrow and its length LO is larger than the channel congestion WO, immediately after horizontal transfer,
This causes a phenomenon in which some signal charges in the WOXLO region are left behind.

The amount of remaining charge tends to vary among the vertical transfer channels, and if the amount of remaining charge varies, for example, in the case of the two-dimensional image sensor shown in FIG. 3, a vertical striped pattern is generated and the image is degraded.

Therefore, the present invention solves these problems and proposes a driving method that prevents charges from being left behind in the horizontal transfer section.

"Means for Solving the Problems" In order to solve the above-mentioned problems, the present invention includes a plurality of vertical transfer sections, a horizontal transfer section that horizontally transfers No. 48 charge from the vertical transfer sections, and a plurality of vertical transfer sections. 4g from horizontal transfer section
In a charge transfer element consisting of a signal charge detection section that converts a signal charge into a voltage or current signal and outputs it, the signal charge is transferred from the final stage accumulation region of the vertical transfer section to the accumulation region of the horizontal transfer section that intersects with the vertical transfer section. Both the period during which data is transferred from the storage area to the storage area at the next stage in the horizontal transfer section are set to be longer than the period for each subsequent horizontal transfer stage. It is characterized by:

"Function" The period during which charge No. 48 is transferred from the last stage accumulation region in the vertical transfer section 3 to the accumulation region of the horizontal transfer section 4 that intersects with the vertical transfer section 3, and the period during which charge No. 48 is transferred from the accumulation region in the next stage in the horizontal transfer section 4. The period during which the data is transferred to the storage area is set to be longer, for example, twice or more, than the period per one transfer stage during which the data is transferred in the horizontal direction thereafter.

Then, since the transfer period from the horizontal transfer area having a narrow and long storage area in contact with the vertical transfer section 3 to the next horizontal transfer area is set to be sufficiently long, even if there is a narrow transfer area (LOXWO), Charges within this region can be reliably transferred to the next stage transfer region. Therefore, no charges transferred and accumulated in this narrow transfer region are left behind.

"Example" Next, an example of a method for driving a charge transfer element according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is an example of a timing diagram showing a method for driving a charge transfer device according to the present invention.

In this invention as well, the structure of the charge transfer element is as shown in FIG. 2, 3, or 4, and more specifically, the structure of the transfer electrode and the transfer channel as shown in FIG. being done. Therefore, the charge transfer region from the vertical transfer section 3 to the horizontal transfer section 4 is the same as in FIGS. 6 and 7.

In FIG. 1, the final bit transfer electrodes GV1. The signal charges accumulated in the GV2 region are transferred to the transfer electrodes C1V3.
The signal is transferred directly below the old transfer electrode G of the horizontal transfer section 4 via the GV4 area.

Next, the signal charge accumulated in the transfer electrode GHI is transferred to the time tlO
Thereafter, the signal is completely transferred in the horizontal direction and is then transported to the signal charge detection section 5.

In this invention, as shown in FIG. 1, the period T2 in which signal charges are carried from the transfer electrode G old, which is the beginning of horizontal transfer, to GH2, is transferred from the transfer electrode 'R' GV4 to G old, which is the last of the immediately preceding vertical transfer. The transfer timings of the horizontal transfer locks φold and φN2 applied to the horizontal transfer unit 4 are set to be approximately the same as the transfer period T1.

This period T2 is sufficiently longer than the period T3 per one transfer stage during which the signal charge is transferred in the direction of the signal charge detection unit 5, as will be described later, and is selected to be more than twice as long in this example.

Therefore, one electrode constituting the transfer electrode G old (transfer electrode G from the bottom, to which the transfer lock φ old is applied) one electrode (transfer lock φH2 is applied) forming the transfer electrode G old. During the period T2 in which signal charges are first transferred horizontally downward (lower electrode), one electrode (transfer lock φH1 is applied) forming the transfer electrode G'H1 from below the immediately previous transfer electrode GV4 region. (lower electrode) is as long as the period T1 during which the data is transferred downward.

As a result, a
The signal charges accumulated in the narrow and long transfer region WOXLO can also be completely transferred directly under the transfer electrode of the next stage.

"Effects of the Invention" As described above, according to the method for driving a charge transfer element according to the present invention, when signal charges from a plurality of vertical transfer sections are transferred to a horizontal transfer section, each step is divided into two stages. Both are designed so that a sufficient transfer period can be maintained.

As a result, even in the case of transfer that involves changing the direction of signal charges,
The transfer process is performed smoothly, and even if there is charge left behind, there will be no variation in the amount of leftover charge for each vertical transfer section.

Therefore, when the present invention is applied to, for example, a two-dimensional image sensor, the occurrence of vertical stripes in a reproduced image can be reduced or eliminated, so that the present invention has a feature that the image quality can be significantly improved.

[Brief explanation of drawings]

FIG. 1 is a timing diagram showing an example of a method for driving a charge transfer device according to the present invention, FIG. 2 is a configuration diagram of a line sensor using a charge transfer device, FIG. 3 is a configuration diagram of a two-dimensional sensor, and FIG. Figure 4 is a block diagram of the delay line, Figure 5 is a timing diagram of the driving method used for these, and Figure 6 is a diagram of the area from the vertical transfer section to the horizontal transfer section of the charge transfer element to which the present invention is applied. The schematic diagram, FIG. 7, is a plan pattern diagram shown in detail as an example of FIG. 6.・Photoelectric conversion section ・Transfer gate ・Vertical transfer section ・Horizontal transfer section ・Signal charge detection section

Claims (1)

[Claims] (1) A plurality of vertical transfer units, a horizontal transfer unit that horizontally transfers signal charges from the vertical transfer units, and a signal charge detection unit that converts the signal charges from the horizontal transfer units into voltage or current signals and outputs the signals. In a charge transfer element consisting of a charge transfer element, there is a period in which signal charges are transferred from a final stage storage region in the vertical transfer part to a storage region in a horizontal transfer part that intersects with the vertical transfer part, and a period in which signal charges are transferred from the storage region to the next stage in the horizontal transfer part. A method for driving a charge transfer element, characterized in that a period during which charge is transferred to an accumulation region is set to be longer than a period per transfer stage during which charge is transferred in the horizontal direction thereafter.