JPS6089177A - Image pickup element - Google Patents

Abstract

PURPOSE:To obtain an image pickup element with high resolution from which blooming hardly takes place by providing a charge discharging section along the direction of row at a rate of one picture element per two rows in plural picture elements arranged in rows and columns. CONSTITUTION:The image pickup element consists of an image pickup section 1, a buffer section 2, a storage section 3, a shift register 4 of CCD structure as read means and an output amplifier 5, and the sections other than the image pickup section 1 are shut from light. The image pickup section 1 consists of plural line sensor 101-103 arranged horizontally and having a transfer function and an electric charge in a sensor is transferred to the left at the same time. Each line sensor is separated by a channel stop CS and overflow drains 112, 113 are arranged at a rate of one per two rows between the line sensors along the lengthwise direction. The drains 112, 113 are connected to an electrode VD and the CS including the drains has a potential barrier structure over which an excess electric charge flows to the drains. The electric charge in the register 4 is transferred vertically and downward at the transfer electrode 38.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an image sensor that can obtain a high-resolution video signal even though pluming occurs.

(Prior art) When a part of a charge transfer type solid-state image sensor such as a COD is irradiated with strong light, the generated charge overflows to the surrounding elements and destroys the image over a wide area on the screen. There is a phenomenon called pluming that causes Conventionally,
As a method used to suppress such pluming, in the frame transfer type COD, a method has been used in which an anti-pluming gate and an anti-pluming drain are provided to absorb overflowing charges.

Figure 1 (aL (b) shows such a frame transfer type C
FIG. 2 is a diagram showing the structure of a COD and the structure of a potential well in a conventional example in which an anti-pluming drain is provided at the border of each pixel in the horizontal direction in the OD.

In the figure, anti-pluming gates 212a-212C and anti-pluming drains 213a-213C are provided between pixels 211a-211d. 1st
In the diagram (b), the shaded area shows accumulated charges. When strong light is incident on this solid-state image sensor and a large amount of charge is generated, the charge flows into the anti-pluming drain sections 213a-213C over the anti-pluming gate sections 212a to 212C, and as a result, the charges are caused by pluming. Image disturbance is minimized.

However, in the conventional example shown in Figure 1, when the number of horizontal pixels is increased while keeping the screen thickness the same, the area occupied by the anti-plooming portion increases accordingly, which limits the number of pixels. It has the following drawbacks. However, there is still a drawback that the light incident on the anti-pluming gate section and the anti-pluming drain section cannot be used as an effective output, resulting in a decrease in light utilization efficiency and a decrease in sensitivity.

FIG. 2 shows a conventional example that has improved the above-mentioned drawbacks. FIG. 2 shows a method shown in, for example, Japanese Unexamined Patent Publication No. 54-24530, in which simple channel stop sections 114 and anti-pluming sections are alternately provided at the boundaries of pixels.

However, in this known example, although the drawbacks that existed in the conventional example shown in FIG. 1 are somewhat alleviated, new drawbacks also arise. One of them is that since the image detection positions are sampled at irregular intervals, moiré (folding of high-frequency components of the image into low-frequency components) occurs in the obtained luminance signal. The second drawback is that the R (red)-G (green)-B
When using a (blue) or R (red)-G (coat)-Cy (cyan) stripe type filter, the horizontal periodic structure becomes every 6 pixels, resulting in very low frequency components. For this reason, moiré occurs even in objects that do not have a fine structure, resulting in a decrease in the quality of the obtained image.

(Objective) An object of the present invention is to provide an image sensor capable of solving the above-mentioned drawbacks of the prior art.

A further object of the present invention is to provide an image sensor that does not cause pluming and has high resolution.

(Example) The present invention will be described in detail below based on Examples.

FIG. 3(a) is a diagram showing an example of the configuration of the image sensor 6 of the present invention,
FIG. 3(b) is a diagram of the electrode arrangement. In the figure, 1 is an imaging section, 2 is a part of a buffer as a means of buffering, 3 is an accumulation section, and 4
5 is a left register with a COD structure as a reading means, and 5 is an output amplifier. Everything other than the imaging section is shielded from light.

The imaging unit 1 consists of a plurality of line sensors 101 to 103 as transfer means arranged in the horizontal direction and having a transfer function. The charges within are simultaneously transferred to the left in the figure.

In addition, each line sensor in this embodiment has a structure in which a plurality of pixels having a photoelectric conversion function are arranged in the row direction.
Therefore, the imaging unit maps these pixels in rows and columns.
The structure is arranged in a square arrangement. In this embodiment, each pixel itself constitutes a transfer means, but the pixel and the transfer means may be constructed separately. In the figure, the pixels are arranged in a matrix of 4 rows and 6 columns.

Each line sensor is also isolated by a channel stop C8. Further, an overwrite 70 and drains 112 and 113 are provided between the line sensors at a rate of one for every two rows of the line sensor consisting of a plurality of pixels. Each over-train is arranged along the longitudinal direction of the line center.

Further, each overflow drain 112 and 113 are both connected to the drain power supply VDK.

In addition, the channel stop sandwiching the over 070-drain has a potential barrier structure that allows excess charge to flow out to the drain.

The buffer part 2 consists of the same number of linear CCDs 104 to 107 for time axis conversion as the imaging part 1, and each linear CCD
In this embodiment, each D has a capacity of 3 bits. Further, the charges of each line-shaped COD in the buffer part 2 are horizontally transferred to the transfer electrodes 31 to 33 one pit at a time to the left in the figure.

The storage section 3 has the same number of horizontally arranged linear C as the imaging section 1.
It consists of CDs 108 to 111, and the electrodes of each line-shaped COD are horizontally transferred to the left in the figure by transfer electrodes 34 to 37, respectively.

38 is a transfer electrode for vertically transferring the charges in the shift register 4 downward in the figure.

In this embodiment, an example of a single-phase drive type COD structure is shown.

In addition, when a high-level voltage is applied to each transfer electrode, the potential level in the substrate becomes relatively low below the electrodes when viewed from the electrons, forming a well and collecting charges under each electrode. has been done.

Also, when the voltage applied to the transfer electrodes is set to a low level, a potential well is formed relative to the area not covered by the adjacent left or lower adjacent electrode of each transfer electrode, and the transfer up to that point is The structure is such that the charge collected under the electrode is transferred to the left or downward.

Also, φ1 to φ. denotes a clock signal applied to electrodes 30-38, respectively.

A color separation filter CF having, for example, vertical striped color filters as shown in FIG. 4 is disposed on the surface of the imaging section l.

This color separation filter is B (blue), G (green), and R (red).
It has a structure in which striped color filters are repeatedly arranged in this order in the horizontal direction at a period of three. In addition to such a striped color separation filter having a repeating pattern in the horizontal direction, a mosaic color separation filter having a repeating pattern of color filters in the vertical direction may also be used.

FIG. 5 is a diagram showing an example of the configuration of an imaging device using the imaging device of the present invention. Light from a subject passes through an imaging optical system 7, an infrared cut filter 8, and a color separation filter CF to the imaging device 6. is imaged. A clock generator 11 generates various clock pulses φ1 to φ as shown in FIG. The output of the clock generator 11 is appropriately amplified by the driver 10 and then supplied to the image sensor 6. This clock generator 11 and driver 1
0 forms the drive means. As a result, a dot-sequential color signal is outputted from the image pickup device 6, which will be described later. This dot-sequential color signal increases the duty ratio by the sample and hold circuit 12 to facilitate subsequent sample bolding for each color.

13 to 15 are sample/hold circuits for performing the above-mentioned sample/bold for each color, which samples the dot-sequential color signal at a period corresponding to the color line reversal period of the color filter and at a phase for each dark color. Do the following.

16 to 19 are LPFs, and LPF 16 is, for example, 3.
Has a cutoff of about MHz, LPF 17 to 19
has, for example, around 500 KHz (7) and a +17 toe-off. 20 to 23 are process circuits, each with an LP
Black level clamp, γ
Perform various corrections such as correction, white clip l APC, etc.

24 is a matrix circuit, which includes process circuits 20 to 23;
For example, from the Y, B, G, and H signals obtained through
, R-Y, l3-Y luminance signals and color difference signals are formed.

The 25ij encoder uses the luminance signal and color difference signal to form a standard television signal such as an NTSC signal. 25 is a recording device for recording this standard television signal.Next, using FIG. 6, an example of how the driver 10° clock generator 11 shown in FIG. explain.

In Fig. 6, VS is the vertical scanning period of the standard television signal.
VBLK is a vertical blanking period, and by supplying a high-speed clock pulse φ1 during the blanking period vBLK, the clock generator 11 discharges the charges previously accumulated in the imaging unit 1 as shown in FIG. The data is horizontally transferred to the left and temporarily stored in the storage unit 3 via the buffer part 2. As described above, this horizontal transfer is performed for one bit each time the voltage applied to each electrode is once set to high level and then lowered to low level.

Therefore, in the case of an imaging section having pixels of 6 horizontal bits x 4 vertical bits as shown in Figure 3, the buffer section has 3 bits, so φ, and if a 9-bit clock pulse is supplied, 1
Transfer of one screen is achieved.

In addition, in this embodiment, when the clock generator 11 temporarily transfers the charges in the υ imaging unit 1 to the storage unit 3, the clock generator 11 transfers the charges in the υ imaging unit 1 to the storage unit 3 at times t, ~t3 and t4 during the period VBLKO for horizontal transfer.
The transfer operation is stopped between ~ts and ts~t0.In addition, in this embodiment, the transfer operation is performed at a period corresponding to the horizontal color line reversal period of the color separation filter C8, that is, every 3 bits. is stopped intermittently.

Therefore, for example, the signal corresponding to R (red) accumulated at ■ in Fig. 1 is sequentially transferred to the position →■→■−dimension■, and then stopped for a relatively long period at the position ■. Ru.

After that, it is transferred again to the →■→■→■ position, and then →■
→■→The data are sequentially transferred to the O position. In this way, even during horizontal transfer, the time the charges stay at the same color filter position becomes relatively long, and the time the charges stay at the different color filter positions becomes relatively short, so the charges differ during the transfer period. Charges corresponding to different colors formed when passing under a color filter are reduced. Therefore, color reproducibility can be improved even if color mixing occurs during transfer in an image pickup device that includes a color line repeating pattern with a predetermined period in a direction perpendicular to the transfer direction of each line sensor of the image pickup section.

Further, in this embodiment, a buffer unit 2 is provided, and the time axis is converted so that the pulse φ, which includes the intermittent transfer stop state, is gradually converted into a pulse with a shorter stop period using predetermined delayed pulses φ2 to φ4. Therefore, the storage section 3 can receive charges from the imaging section 1 using relatively low frequency pulses φ, .about.φ. Therefore, since the storage section drives each line-shaped COD independently, the structure becomes complicated and the transfer efficiency may drop slightly, but by providing this buffer section 2, the storage section becomes more complicated. There is no need to drive the unit at high speed, and transfer efficiency can be maintained. The charges accumulated in the accumulation section 3 at a relatively low speed during the period VBLK in this way are then stored at time L? A pulse φ is supplied during one horizontal period of ~ts, and a pulse φ is supplied. The first row is read by supplying , and then from time t8 to . . 1
Pulse φ in the horizontal period. By supplying pulses φ and φ, the second row is read out, and in the same manner, one screen worth of signals formed by the imaging unit l are sequentially read out one line at a time. Note that the pulse φ is always supplied at high speed. As shown in this embodiment, in the present invention, an overflow drain as a charge discharge section is provided in the imaging section 1 in the horizontal direction, and the charges in the imaging section are horizontally transferred. Does not affect horizontal resolution at all.

Furthermore, since it does not adversely affect the pixel pitch, there is little possibility of moiré occurring.

Furthermore, since one charge discharge section is provided for every two rows of pixels, the reduction in the effective light receiving area can be kept relatively small.

It is also effective in improving yield. Note that there is no problem with the resolution in the vertical direction because it is limited by the number of horizontal scanning lines in the standard TV system.

Next, FIG. 7(a) is a diagram showing a second embodiment of an imaging device using the imaging device of the present invention, and FIG. 7(b) is a timing chart thereof. The structure is simplified by omitting the buffer section in the image sensor.

In the drawings, the same reference numerals as in FIGS. 3 to 6 indicate the same elements.

39 is a driver for driving the image sensor, 40 is a clock generator, and 39 and 40 form p driving means. As shown in FIG. 5(a), in this embodiment, the buffer section 2 is omitted, so the structure is much simpler.
Yield can be improved. Further, 112 and 113 are overflow drains serving as charge discharging sections, which are provided in the horizontal direction and are connected to two rows of a plurality of pixels of the imaging section 1.
One for each. Also, drain 1
14 to 117 are all connected to the drain power supply VD. Also in this embodiment, the filter CF shown in the second diagram is arranged on the imaging section 1.

Next, the operation of the clock generator 40 of this embodiment will be explained using the timing chart shown in FIG. 7(b).

During the period vBLK from time t12 to time t16, the charges of each line sensor in the imaging section 1 are horizontally transferred to the corresponding line-shaped COD of the storage section 3 by six pulses φ1 to φ. At this time, in this embodiment, time 1, 3 to 7, 4, time t
Since the transfer is intermittently stopped between t15 and t16, color mixing is less likely to occur as in the first embodiment. Moreover, in this embodiment, fewer pulses are required for horizontal transfer, and the pulses for driving the buffer section 2 are also omitted, so the configuration of the clock generator circuit 40 is simplified. Incidentally, since the charge of the imaging unit 1 has been accumulated in the storage unit 3 by time t16, the time tl? During the vertical scanning period of .about.till, the clock generator circuit 4o is supplied with signals .phi. and .phi.8 in order to perform reading similar to the embodiment shown in FIG. Also, pulse φ.

(not shown) is constantly supplied as a high-speed pulse.

Next, FIG. 8 is a diagram showing a third embodiment of the image sensor of the present invention, and this embodiment is shown in FIG. 3(a), (b) or FIG. 7(a).
This is a modification of the electrode configuration of the imaging unit 1 in this embodiment. In this embodiment, the imaging unit has a configuration in which a plurality of horizontal line sensors are arranged in the vertical direction.
The structure is the same as that shown in FIG. 7(a), but the first feature is that each horizontal line sensor is reversely driven by an independent transfer electrode. That is, 114 to 117 are horizontal line sensors, respectively, 118 to 121 are electrodes for horizontal transfer of the line sensors 114 to 117, and voltages independent of each other are supplied to each electrode 118 to 121. Also, the shaded area C8 at the bottom left of the figure is a channel stop.

The 14 structure shown in the figure is a virtual electrode as shown in Japanese Unexamined Patent Publication No. 11394/1983.
The explanation has been made based on a single-phase drive method using a single-phase drive system (VB and VW), and VB and VW are virtual electrode portions each having a predetermined fixed potential level. The potential level seen from the electron is higher in VB than in vW. Also, CB and CW are variable potential regions each having a predetermined potential level, but this variable potential region is located under the transfer electrode and is at a low level of the potential applied to this electrode. The potential level increases or decreases depending on the current level. Even in that case, the potential level seen from the electron is CB
CW is more expensive. In a state where a high level voltage is applied to the transfer electrode, the potential of the CB region is lower than that of the VW region. Furthermore, when a low-level voltage is applied to the transfer electrode, the potential of the VB region is lower than that of the CW region. Therefore, when a low level is first applied to each transfer electrode, the charge is collected in the VW region of each cell, and when a low level is applied to the transfer electrode, the charge in each cell is transferred to the CW region on the left side of the figure. Then, when the voltage to the electrode is set to low level again, the VW area of the left cell (l1l) is transferred.

In this embodiment, as described above, while the voltage applied to the transfer electrode is at a low level or when it is changed from a high level to a low level, any of the charges collected in the VW region that exceeds the potential level of the VB region The charge flows into overflow drains 112 and 113, which serve as charge discharge sections, and is discharged. Pluming is therefore completely resolved.

Furthermore, in this embodiment, since each pixel in adjacent pixel rows is shifted horizontally by a false pixel amount, resolution can be improved.

Next, FIG. 9 is a diagram showing a fourth embodiment of the image sensor of the present invention, in which the imaging section 1 of FIG. 3(a), (b) or FIG. 7(a) is shown.
This is a modification of the electrode configuration. This embodiment is also similar to the third embodiment in that the imaging section has a plurality of horizontal line sensors arranged in the vertical direction, and each horizontal line sensor is driven by an electrically independent transfer electrode.

This embodiment is characterized in that a charge recombination electrode is provided as a charge discharge portion in every two rows of a plurality of pixels.

In the figure, the same reference numerals as in FIG. 7 indicate the same elements. Further, a hatched area C8 in the upper right corner of the figure indicates a channel stop, hatched areas 118 to 121 in the lower right corner indicate transfer electrodes of each horizontal line sensor, and AB indicates a charge recombination electrode. The charge under the VW area of each line sensor enters under each electrode AB.
There is provided an area A B W configured to contain the area A B W .

In each region ABW, the potential level inside the substrate changes as shown in FIG. 10 depending on the voltage applied to the electrode AB. That is, FIG. 10 is a diagram showing the state of the voltage of this electrode AB and the potential inside the semiconductor substrate in the thickness direction of the semiconductor substrate 306.・The well is not shallow,
Excess carriers recombine with majority carriers at the interface with the insulating layer 305.

On the other hand, at a low level electrode voltage -1, an accumulation state occurs and majority carriers gather around the interface.
The majority carrier is supplied from the channel stop C8, for example, from the channel stop C8.

Therefore, for example, by applying the voltage -1 to the electrodes 118 to 121 to form a barrier and collecting the charges in the VW area, by alternately applying the voltages -V1 and V to the electrodes ABK, the electrode P, Minority carriers accumulated below are limited to a predetermined amount or less.

In this example, a charge recombination electrode is used as a charge discharge part, and since this electrode is provided between every two rows of pixels, it affects the transfer efficiency of the line sensor. There's nothing wrong.

Also, it does not affect horizontal resolution.

Further, as in the third embodiment, since the position of each pixel is shifted in the horizontal direction by a target pixel for each horizontal line, the resolution can be further improved.

In addition, in order to perform charge recombination, an area large enough to serve as the recombination region is required, but in this embodiment, the recombination region ABW is provided in the space between the horizontal line sensors, so that sufficient recombination can be achieved. You can gain efficiency. Also, it can be easily made adjacent to the VW area. Moreover, in this embodiment, since the recombination region is provided in an adjacent portion where the VW region does not overlap, the charge recombination electrode can be manufactured by the same manufacturing process as the transfer electrode, which is useful for improving the yield.

(Effects) As explained above, the image sensor of the present invention includes a plurality of pixels arranged in rows and columns, a charge discharge part arranged along the row direction at a ratio of one for every two rows, Since it is configured to have a transfer means for horizontally transferring the charge of each pixel and a readout means for reading out the charge via the transfer means, there is no need to sacrifice horizontal resolution as in conventional image pickup devices. Pluming can be prevented.

Furthermore, since the pitch of pixels in the horizontal direction can be made constant, moiré is less likely to occur.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are diagrams showing a first example of a conventional image sensor, in which (a) is a schematic plan view, (b) is a button/circle diagram, and FIGS. 2(a), ( b) is a diagram showing a second example of a conventional image sensor, in which (a) is a plan view, (b) is a potential diagram, and FIG. 3 (a) is a configuration of the first embodiment of the image sensor of the present invention. FIG. 3(b) is a diagram showing its electrodes, FIG. 4 is a diagram showing an example of a color separation filter, and FIG. 5 is a first embodiment of an imaging device using the imaging device shown in FIG. 3. FIG. 6 is a timing chart of the imaging device shown in FIG. 5, and FIG. 7(a)
Figure 7 shows a second embodiment of the tH quadrant element of the present invention.
b) is a drive timing chart thereof, FIG. 8 is a diagram of the third embodiment of the image element 1#i of the present invention, and FIG. 9 is a diagram of the fourth embodiment f of the same.
FIG. 1j and FIG. 10 are diagrams for explaining the charge recombination characteristics of the embodiment shown in FIG. 100-103...Line sensor as a transfer means,
1゛・Imaging unit, CF・”・Color separation filter, 10
39...driver, 11.40 is a clock generator, and 10, 11.39, and 40 constitute driving means, respectively. 3...Storage section, 4...Readout section s
112+ 113...+-- as a charge discharge part
Nokuichi flow drain, AB...Charge recombination electrode 0 as a charge discharge part

Claims (1)

[Claims] a plurality of pixels arranged in rows and columns; a charge discharge section arranged along the row direction at a ratio of one for every two rows;
An image pickup device comprising a transfer means for horizontally transferring the charge of each pixel, and a readout means for reading out the charge via the transfer means.