JPH04373275A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To attain the high speed reading-out of signal charge accumulated in respective photosensors in an image pickup area without hurting the driving operation of horizontal transfer. CONSTITUTION:Four mutually adjacent photosensors 11-14 among the respective photosensors in the image pickup 4 make set to be a unit cell. Signal charge in one image pickup period is made to certainly accumulat in one of the four photosensors 11-14 by successively reading-out signal charge accumulated in the four photosensors 11-14 so that no scene is remain to be image-picked up.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a solid-state imaging device.
In particular, the present invention relates to a solid-state imaging device capable of high-speed readout of signal charges accumulated in each photosensor in an imaging region.

0002

[Technical Background] As an example of a solid-state imaging device, FIG. 6 shows the configuration of a CCD solid-state imaging device using an interline transfer method.
Shown below. In the figure, a plurality of photosensors 1 are arranged two-dimensionally in pixel units and perform photoelectric conversion, a readout gate 2 reads out signal charges accumulated in these photosensors 1, and a readout gate 2 is used to read out signal charges accumulated in these photosensors 1. An imaging region 4 is constituted by a plurality of vertical CCDs (vertical transfer units) 3 that vertically transfer signal charges read out in each vertical column.

[0003] The signal charge read out to the vertical CCD 3 is
During a part of the horizontal blanking period, portions corresponding to one scanning line are transferred to the horizontal CCD (horizontal transfer unit) 5. This one
The signal charges for the scanning lines are sequentially transferred in the horizontal direction by the horizontal CCD 5 and outputted as electrical signals through the output section 6.

On the other hand, this type of CCD solid-state imaging device has
By sweeping out the signal charges accumulated in each photosensor 1 in the imaging area 4 to the semiconductor substrate at a predetermined timing,
Some photosensors have a so-called electronic shutter function that allows the accumulation time (exposure time) of signal charges in the photosensor 1 to be controlled.

[0005]

2. Description of the Related Art FIG. 7 shows an example of the timing of a conventional electronic shutter in a CCD solid-state imaging device having an electronic shutter function. In the figure, normally 1/6
A signal charge is accumulated for an arbitrary period of 0 seconds, for example, 1/240 second, and this signal charge is read out to the vertical CCD 3 by a readout pulse, and during the remaining period, the signal charge accumulated in the photosensor 1 is electronically transferred. It is swept away onto a semiconductor substrate etc. by the shutter pulse.

[0006] For this reason, with the timing of a normal electronic shutter, only the image information corresponding to the signal charge accumulated over 1/240 seconds is reproduced as an image. For example, when photographing the moment of impact of a golf swing, However, if that moment is a signal charge sweep-off period, the scene at that moment will not be photographed, resulting in what is called a missed scene.

One possible method for capturing such high-speed phenomena using a CCD solid-state imaging device is to change the timing of reading out signal charges accumulated in each photosensor 1. That is, as shown in the timing chart of FIG. 7, signal charges are normally read out once every 1/60 seconds, but for example, signal charges are read out once every 1/60 seconds.
This is a method of reading signal charges once every 240 seconds.

[0008]

[Problem to be Solved by the Invention] However, as shown in the timing chart of FIG. 8, when the readout timing (readout pulse frequency) is changed to four times the normal speed, there is no missed scene, but other timings For example, it is necessary to change the driving frequency of the vertical CCD 3 and horizontal CCD 5 to four times the normal frequency. In particular, horizontal CCD5
Taking a 380,000-pixel NTSC CCD solid-state imaging device as an example, the driving frequency is normally about 15 MHz, which is four times as high as 6.
0 MHz, making it almost impossible to drive horizontal transfer.

The present invention has been made in view of the above-mentioned points, and enables high-speed readout of signal charges accumulated in each photosensor in the imaging area without adversely affecting the driving operation of horizontal transfer. The purpose is to provide a solid-state imaging device.

0010

[Means for Solving the Problems] A solid-state imaging device according to the present invention includes a plurality of photosensors that are two-dimensionally arranged in pixel units and performs photoelectric conversion, and a plurality of photosensors that read out signal charges accumulated in these photosensors. The imaging area includes a readout gate and a vertical transfer section that vertically transfers signal charges read out from the photosensor by these readout gates, and a readout pulse is supplied to the plurality of readout gates at a predetermined timing. N (N>2) mutually adjacent photosensors among the plurality of photosensors are used as unit cells, and the drive circuit reads out the signal charges. The configuration is such that the corresponding readout gates are read out and driven so as to sequentially read out the signal charges accumulated in the gates.

[0011]

[Operation] In the solid-state imaging device according to the present invention, by sequentially reading out the signal charges accumulated in the N photosensors forming a unit cell, the signal charges for a certain imaging period are always accumulated in one of the photosensors. Therefore, there is no missed shot of the scene, and even if the readout timing is set to, for example, four times the normal speed, the drive frequency of the horizontal CCD can be doubled and the frequency of the readout pulse can remain the same as before.

0012

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram showing one embodiment of the present invention. In the figure, a plurality of photosensors 1 are two-dimensionally arranged in pixel units, a readout gate 2 for signal charges accumulated in these photosensors 1, and a plurality of vertical lines arranged for each vertical column of photosensors 1. An imaging area 4 is constituted by the CCD 3.

In the imaging area 4, a unit cell is formed by forming a group of, for example, four photosensors adjacent to each other. Also, two vertical Cs adjacent to each other
The output end portions of CD3k and 3k+1 are integrated. That is, the number of vertical CCDs 3 is reduced to half in the lower part of the imaging area 4.

For example, a single horizontal CCD 5 is disposed on the output side of the imaging area 4, and an FDA (Floating Diffusion A) is arranged at the final end of the horizontal CCD 5.
An output section 6 consisting of a mplifier, etc. is connected thereto. This output section 6 detects the transferred signal charge, converts it into an electrical signal, and outputs it as a television signal.

The readout pulse φRP of the readout gate 2 in the imaging region 4, the four-phase drive pulses φV1 to φV4 of the vertical CCD 3, the electronic shutter pulse φSP applied to the semiconductor substrate (not shown), and the two of the horizontal CCDs 5
A timing generator 7 is provided that generates various timing signals such as phase drive pulses φH1 and φH2. These various timing signals are sent to the CCD driver 8.
The voltage is applied to the imaging area 4, the semiconductor substrate, and the horizontal CCD 5 through the respective channels.

Next, a high-speed readout operation of the signal charges accumulated in each photosensor 1 in the imaging area 4 will be explained with reference to the operation explanatory diagram of FIG. 2 and the timing chart of FIG. 3. For convenience of explanation, 4 cells forming a unit cell
The photosensors 1 are tentatively given subscripts 1 to 4 and hereinafter referred to as photosensors 11 to 14.

After the first 1/240 seconds after signal charges start to be accumulated in each photosensor 1 in the imaging region 4, the signal charges of the first photosensor 11 are read out by applying a read pulse φRP. At this time, the signal charges of the other 2nd to 4th photosensors 12 to 14 are swept away onto the semiconductor substrate by applying the electronic shutter pulse φSP.

After the next 1/240 second, the signal charge of the second photosensor 12 is read out, and the signal charges of the other photosensors 11, 13, and 14 are also swept away. A similar operation is performed sequentially for the third photosensor 13 and the fourth photosensor 14. By repeating the above operations, a high-speed readout operation of the signal charges accumulated in each photosensor 1 in the imaging area 4 is performed.

According to such a high-speed readout operation, as is particularly clear from FIG. 3, immediately after reading out the signal charges of a certain photosensor, the signal charges of all the photosensors are swept away by the electronic shutter operation. Since signal charges during a certain shooting period are always stored in one of the photosensors 11 to 14, even when shooting the moment of impact of a golf swing, for example, the scene at that moment No more missed shots.

In this way, the image is transferred to the horizontal CCD 5,
Further, the signal charge transferred to the output section 6 is transferred to the output section 6.
When observed, the image shown in Figure 4 is obtained. Furthermore, Figure 4
In Figure 2, the numbers ■ to ■ in the diagram representing signal charges are
corresponds to each signal charge of photosensors 11 to 14 in , and when the rows of signal charges ■ to ■ are divided as shown in the figure, each group (I to IV in the figure) is 1/2
It consists of images taken every 40 seconds.

[0021] That is, the output signal derived from the output section 6 is a sequence of image information taken every 1/240 seconds, in other words, 240 pictures (images) are taken per second. It turns out. In order to convert this signal back to a normal NTSC television signal, signal conversion processing may be performed using a frame memory or the like. However, since the number of pixels on one screen is 1/4 of the normal number, signal processing such as interpolation between pixels is required.

In the above embodiment, in the imaging area 4, two adjacent vertical CCDs 3k and 3k+1
The output end portion of the vertical CCD 3 is integrated, and the number of vertical CCDs 3 is reduced by half. If all charges are transferred to the horizontal CCD 5 before being read out to the vertical CCD 3, the vertical CCD
Since the CD 3 becomes empty and there is no mixing of signal charges between pixels, there is no problem even if the two vertical CCDs 3 are integrated in the middle.

If this is pushed further, an embodiment as shown in FIG. 5 can be considered. This embodiment has a structure in which one vertical CCD 3 is arranged for two vertical columns of photosensors 1. Regardless of the structure of either embodiment, the effective number of photosensors in the horizontal direction is halved, so a normal configuration in which one vertical CCD 3 is arranged for each vertical row of photosensors 1 is used for high-speed readout operation. This means that the horizontal transfer frequency can be halved compared to when doing so.

Furthermore, in the above embodiment, a case has been described in which four adjacent photosensors are grouped to form a unit cell and the high-speed readout speed is set to 4 times the speed. The speed is not limited to this, and the speed may be N times higher than twice the speed, and the number N of photosensors forming a unit cell is determined in accordance with the speed.

[0025]

[Effects of the Invention] As explained above, according to the present invention,
N (N>
2) By using a configuration in which N photosensors are used as unit cells and the signal charges accumulated in N photosensors are sequentially read out, the signal charges for a certain shooting period are always accumulated in one of the photosensors. Therefore, there is no missed shot of the scene, and even if the readout timing is set to, for example, four times the normal speed (N=4), the driving frequency of the horizontal CCD can be doubled, and the frequency of the readout pulse can remain the same as before.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a high-speed read operation.

FIG. 3 is a timing chart during high-speed read operation.

FIG. 4 is an image diagram of an output signal.

FIG. 5 is a configuration diagram showing another embodiment of the present invention.

FIG. 6 is a configuration diagram of an example of an interline transfer type CCD solid-state imaging device.

FIG. 7 is a timing chart during normal operation using a conventional electronic shutter.

FIG. 8 is a timing chart during a conventional high-speed read operation.

[Explanation of symbols]

1 Photo sensor 3 Vertical CCD 4 Imaging area 5 Horizontal CCD 7 Timing generator 8 CCD driver

Claims (1)

[Claims] 1. A plurality of photosensors that are two-dimensionally arranged in pixel units to perform photoelectric conversion, a plurality of readout gates that read out signal charges accumulated in these photosensors, and a plurality of readout gates that read out signal charges accumulated in these photosensors; an imaging region including a vertical transfer section that vertically transfers read signal charges; and a drive circuit that supplies read pulses at predetermined timing to the plurality of read gates to drive readout of signal charges. N (N
>2) A solid-state, wherein the number of photosensors is a unit cell, and the drive circuit performs readout driving of the corresponding readout gate so as to sequentially read out the signal charges accumulated in the N photosensors. Imaging device.