JP3008578B2 - Solid-state imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device,
In particular, the present invention relates to a solid-state imaging device suitable for use in a video camera or the like.

[0002]

2. Description of the Related Art As an example of a solid-state imaging device, a schematic configuration of, for example, an interline transfer type CCD solid-state imaging device is shown in FIG. In the figure, a plurality of photosensors 51 which are two-dimensionally arranged in pixel units and accumulate signal charges according to the amount of incident light, and which are arranged for each vertical column of these photosensors 51 and have one vertical blanking period The imaging area 54 is constituted by a vertical transfer CCD 53 that vertically transfers the signal charges read instantaneously via the read gate section 52 in the section.

In the imaging area 54, for example, a photodiode is used as the photo sensor 51. The signal charges transferred to the vertical transfer CCD 53 are sequentially transferred to the horizontal transfer CCD 55 by a portion corresponding to one scanning line during a part of the horizontal blanking period. The signal charges for one scanning line are sequentially transferred in the horizontal direction by the horizontal transfer CCD 55. At the last end of the horizontal transfer CCD 55, an output section 56 composed of, for example, a floating diffusion amplifier for detecting the transferred signal charge and converting it into an electric signal is arranged.

[0004]

As described above, the CC
In the D solid-state imaging device, signal charges (electrons) generated by the photo sensor 51 are vertically and horizontally transferred in a semiconductor crystal in a bucket brigade manner, and finally, the amount of charges transferred by the output unit 56 is converted into a voltage. It is configured to convert to a signal.

That is, in order to obtain an image pickup output, a signal must be transmitted by transferring electric charges from the photosensor 1 to the output section 56.
Since there is a limit to the transfer speed of the electric charge in 3, 55, if an attempt is made to increase the transfer speed, more signal charges will be lost in the middle. Therefore, it has been difficult to significantly increase the transfer speed of signal charges with the conventional structure.

The transfer direction in the horizontal transfer CCD 55 is generally one direction, but a solid-state imaging device capable of transferring in both directions is known (for example, Japanese Patent Application Laid-Open No. 64-23686).
No. 7).

SUMMARY OF THE INVENTION It is an object of the present invention to provide a solid-state imaging device capable of greatly increasing the transfer speed of signal charges.

[0008]

According to the present invention, there is provided a solid-state imaging device in which a light receiving surface is divided into at least two in a vertical transfer direction , and an incident light is converted into signal charges in units of pixels and stored, and Of the light receiving surface by adding the signal charges read out for each vertical column of pixels for every two pixels
Vertical transfer in the opposite direction from
The transfer part corresponding to the minute is independent of the transfer electrode of the other transfer part
A vertical transfer unit having a transfer electrode that is driven and driven, a horizontal transfer unit that transfers the signal charge received from the vertical transfer unit in the horizontal direction, and driving and transferring each of the vertical transfer unit and the horizontal transfer unit. for transfer of the division direction of the region has a configuration in which a driving means for transferring driving reverse to the signal charges to the boundary divided portion.

[0009]

In the solid-state imaging device according to the present invention, at least
Also in the vertical transfer direction , the signal charges in the imaging area where the light receiving surface is divided into two are read out to the vertical transfer unit for each pixel. this
When the signal charges read to the vertical transfer unit are every two pixels
So-called field readout is added (mixed) to
Done. Also, the transfer corresponding to the divided part of the vertical transfer unit
The transfer electrodes in some parts are independent of the others, and
The signal charge at the center of the optical surface is upward in one field
In the other field, transfer downward
By driving, the signal charge at the center of the light receiving surface
Two-pixel addition is always performed in the field. This addition
The signal charges are transferred by the vertical transfer unit and the horizontal transfer unit independent in the division direction . Here, for example, the imaging area
Consider the case of four divisions in the vertical and horizontal transfer directions
If that, since the length of the path from each pixel to the output unit is 1/4, it is possible to shorten the time required for the transfer of the image signals to 1/4.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration block diagram showing one embodiment of a solid-state imaging device according to the present invention. In the figure, a plurality of photosensors 1 that convert incident light into signal charges in pixel units and accumulate them are two-dimensionally arranged to form an imaging region 2, and the light receiving surfaces of the imaging region 2 In the direction (vertical transfer direction) and in the left-right direction (horizontal transfer direction), each is divided into two, and equally divided into a total of four regions I to IV.

In the image pickup area 2, a plurality of vertical transfer CCDs 3 for vertically transferring signal charges read from a plurality of photosensors 1 are arranged for each vertical column of pixels. The vertical transfer CCD 3 is divided into two parts by an area dividing part in the vertical transfer direction. Then, the signal charges read out from the photosensor 1, the vertical transfer CCD3U the upper region _L, 3U _R in the upward direction of the figure, the vertical transfer CCD3D _L of the lower region, 3D _R charge respectively downward in FIG. It is driven by the vertical CCD driver 4 to transfer.

Further, the vertical transfer CCD3U _L, 3U _R and 3D _L, the horizontal transfer CCD5 for transferring signal charges received from the 3D _R in the horizontal direction is disposed above and below the imaging area 2, these horizontal transfer CCD5 the horizontal transfer direction Are divided into two parts by the area dividing part in. Then, the horizontal transfer CCD5L _U, 5L _D of the left area to the left of the figure, the horizontal transfer CCD5R _D, 5R _U in the right area is driven by the horizontal CCD driver 6 so as to charge transfer respectively in the right direction in FIG. You.

[0013] The vertical transfer CCD3U _L, 3U _R and 3
D _L , 3D _R are driven, for example, in four phases, and the horizontal transfer CCD 5
L _U, 5L _D and 5R _D, 5R _U is driven for example, 2-phase. A timing generator 7 is provided for timing control such as these transfer driving. The timing generator 7 outputs vertical transfer clocks φ _V1 to _V4 for vertical four-phase driving and horizontal two-phase transfer driving. Various timing signals such as horizontal transfer clocks φ _H1 and φ _H2 are generated.

[0014] Four horizontal transfer CCD5L _D provided corresponding to each divided region I~IV imaging region 2, 5R
_D, and the output ends of the 5R _U, 5L _U, the output unit 8 _{1-8 4} comprising, for example, the floating diffusion is converted into a voltage signal is provided by detecting a signal charge transferred. Each output signal of the output unit 8 _{1-8 4} S
/ H (sample / hold) & A / D (analog / digital) conversion circuit 9.

The S / H & A / D conversion circuit 9 performs a process of shaping the waveform of each output signal, removing unnecessary noise (sample & hold), and then converting the output signal into a digital signal. Each digitized output signal is written to the semiconductor memory 10 and temporarily stored.

The four output signals stored in the semiconductor memory 10 are read out so that the vertical and horizontal positional relationship (temporal positional relationship as an output signal) of each pixel information on the imaging area 2 is correct. And the D / A converter 11
Is converted into an analog signal and is derived as a video signal. Each control of the S / H & A / D conversion circuit 9, the semiconductor memory 10, and the D / A converter 11 is performed by the timing controller 12.

Although the output signal read from the semiconductor memory 10 has been converted into an analog signal, it can be derived and recorded as a digital signal when recording it on a VTR or the like.

Next, the concept of the transfer operation in the solid-state imaging device according to the present invention having the above-described configuration will be described. First, the vertical transfer will be described. In the imaging region 2, since it is necessary to transfer signal charges upward in the upper region from the center of the light receiving surface and downward in the lower region, two pixels which are normally performed are used. When the mixed readout method (field readout) is adopted, if charge transfer is controlled by an electrode arrangement as shown in FIG.
In each stage, signals for two pixels are transferred, and a complete two-pixel mixed signal is obtained.

On the other hand, in the odd-numbered field, pixel mixing is not performed for two pixels at the center of the light-receiving surface (the portion marked with * in the figure), and the pixels are vertically separated. Note that a constant voltage is applied to the upper and lower split electrodes at the center of the light receiving surface,
This prevents signal charges from being mixed above and below the divided electrodes.

A two-pixel mixed signal can also be obtained by externally adding separately output image information for one pixel. However, considering that there is a possibility that image quality degradation occurs in a horizontal line shape when the addition accuracy is insufficient, and that it is necessary to secure time for performing addition, etc., even if the light receiving surface is divided, It is preferable that a two-pixel mixed output can be derived.

[0021] Accordingly, the vertical transfer CCD3U _L, 3U _R and 3D _L, the 3D _R, add one independent drive electrodes,
The arrangement of the electrodes near the center of the light receiving surface is changed as shown in FIG. 3 with respect to FIG. 2, and the driving of the added center electrode is made independent from the other four electrodes, so that the signal charge at the center of the light receiving surface is reduced. Driving is performed so that data is transferred upward in one field and downward in the other field. According to this transfer drive, a two-pixel mixed output can be always derived for each of the even and odd fields.

Further, as the drive signal which is required when taking this transfer method, the vertical transfer CCD3U _L, 3U _R
And 3D _L and 3D _R which are used as standard for the transfer drive
A single-phase vertical transfer clock φ _V5 dedicated to the central distribution drive electrode is added to the phase vertical transfer clocks φ _V1 to _{V 4} to provide a total of five phases of vertical transfer clocks.

The fifth phase vertical transfer clock φ _V5
Can be the same as the first phase in the even field and the same as the third phase in the odd field. Therefore, it is possible to use a switching circuit or the like to also share the vertical transfer clock.

Next, horizontal transfer will be described with reference to FIG.
As shown in FIG.
_U, 5R _U and 5L _D, as 5R _D, a CCD having a symmetrical structure. In the horizontal transfer CCD 5, generally, signal charges are transferred by transfer driving using two-phase horizontal transfer clocks φ _H1 and φ _H2 , so that a step near the center under each drive electrode is formed by ion implantation. I have. In addition, a high barrier is formed at the boundary portion divided into right and left by implanting high-concentration ions.

This horizontally symmetrical horizontal transfer CCD 5L
_U , 5R _U and 5L _D , 5R _D are used to transfer and drive by two-phase horizontal transfer clocks φ _H1 and φ _H2 ,
Vertical transfer CCD3U _L, 3U _R and 3D _L, the signal charges transferred from the 3D _R is distributed to the left and right are transferred in opposite directions, it will be derived as the signal output of the four systems.

As described above, the light receiving surface of the imaging area 2 is set to 4
Divided, its four independent vertical transfer signal charges in the region I~IV CCD3U _L, 3U _R and 3D _L, 3D
_R, as well as the horizontal transfer CCD5L _U, 5R _U and 5L _D,
By transferring the 5R _D, as compared with the imaging region 2 sequentially as shown in FIG. 5 to be transferred in the vertical and horizontal directions constituting each signal charge as a single region, the path from each pixel to the output unit Becomes 1/4, so that the transfer of the signal charge can be completed in 1/4 time.

In the above embodiment, the light receiving surface of the imaging area 2 is divided into four parts. However, the light receiving surface is divided into two parts in at least one of the vertical direction (vertical transfer direction) and the horizontal direction (horizontal transfer direction). In this case, the path from each pixel to the output unit is halved and the transfer time is halved as compared with the configuration shown in FIG.

[0028]

As described above, according to the present invention,
Set the light receiving surface of the imaging area to at least 2 in the vertical transfer direction .
By dividing and transferring the signal charges in each region by independent vertical transfer units and horizontal transfer units in the division direction, when the length of the path from each pixel to the output unit is four, for example, 1 Therefore, the time required to transfer the image signal can be reduced to 1/4, and the transfer speed can be greatly increased. Therefore, by using the solid-state imaging device according to the present invention as an imaging device such as a video camera , four-times high-speed shooting is possible in the case of four divisions. In particular, a solid-state imaging device of the field readout type
Transfer part corresponding to the divided part of the vertical transfer part
Is provided with a transfer electrode independent of
The electrode charges the signal charge at the center of the light receiving surface in one field.
Forward up, down in the other field
The signal charge at the center of the light receiving surface.
Even two pixels can always be added in even and odd fields
Will be.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram showing an embodiment of a solid-state imaging device according to the present invention.

FIG. 2 is a conceptual diagram (part 1) for explaining the operation of charge transfer in the vertical direction.

FIG. 3 is a conceptual diagram (part 2) for explaining the operation of charge transfer in the vertical direction.

FIG. 4 is a conceptual diagram for explaining an operation of charge transfer in a horizontal direction.

FIG. 5 is a configuration diagram of an interline transfer type CCD solid-state imaging device.

[Explanation of symbols]

1 photosensor second imaging region _{3U L, 3U R, 3D L} , 3D R vertical transfer _{CCD 5L U, 5R U, 5L} D, 5R D horizontal transfer CCD 7 timing generator 8 _{1-8 4} output unit 9 S / H & A / D Conversion circuit 10 Semiconductor memory 12 Timing controller

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-102983 (JP, A) JP-A-47-32727 (JP, A) JP-A-63-310283 (JP, A) JP-A-1- 302974 (JP, A) JP-A-3-224371 (JP, A) JP-A-1-175074 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 5/30-5 / 335

Claims (1)

(57) [Claims] 1. An imaging area in which a light receiving surface is divided into at least two parts in a vertical transfer direction , an incident light is converted into signal charges in pixel units and stored, and a signal read from the imaging area for each vertical column of pixels is provided. The electric charge is added for every two pixels, and the charge is inverted at the divided portion of the light receiving surface.
In the vertical direction, and in the divided part of the light receiving surface.
Independent to the transfer electrode of the other transfer part to the corresponding transfer part
A vertical transfer unit having a transfer electrode to be driven; a horizontal transfer unit configured to transfer a signal charge received from the vertical transfer unit in a horizontal direction; and driving and transferring each of the vertical transfer unit and the horizontal transfer unit; the solid-state imaging device being characterized in that a driving means for transferring driving reverse to the signal charges to the boundary dividing portion to the transfer portion of the dividing direction of the image pickup area.