JPS59201465A - Image pickup element - Google Patents

Abstract

PURPOSE:To contrive to improve the resolution and the color reproducibility by providing excess charge removing means arranged so as to split light receiving regions and an electric information adding means formed in each split region. CONSTITUTION:The light receiving regions 1a, 1b, 1d, 1e, 1g form picture elements as the photoelectric conversion element, respectively, and the light receiving regions 1c, 1c', and 1f, 1f' form picture elements respectively by a pair. The picture element consisting of these regions 1c and 1c' is split by anti-blooming formed of an anti-blooming drain D and a barrier B2. Therefore, the pitch between a channel stop CS and a barrier B1 which are the boundaries of each region can be put at an equal interval. Thereby, the center of gravity in the sensitivity of each picture element can be each brought to the center of the picture element, resulting in no generation of moire, etc. even in sampling. The aperture rate can be improved, and the horizontal resolution can be improved. The charges split by these regions 1c and 1c' are added by a transfer electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an image sensor, and particularly to an image sensor having an improved charge removal structure.

(Prior art) In a charge transfer type solid-state image sensor such as 00D, when some pixels are irradiated with strong light, the excess charge generated there overflows to the surrounding pixels. There is a phenomenon called blooming, which destroys the image over a wide area on the screen. Conventionally, in order to suppress such pre-flaming, for example, in the frame transfer type 00D, an anti-blooming section consisting of an anti-blooming gate and an anti-blooming gate and an anti-blooming gate and an anti-blooming gate and an anti-blooming gate and an anti-blooming gate and an anti-blooming gate and an anti-blooming gate and an anti-blooming gate and an anti-blooming gate and an anti-blooming gate and an anti-blooming gate and an anti-blooming gate and an anti-blooming unit and Figure 1 shows an example of the structure of a conventional COD imaging section in which an anti-blooming section is provided at the border of each pixel in the horizontal direction, and an example of the state of its potential well. be.

In the figure, anti-blooming barriers 2a, 2b, 2. Anti-pull consisting of c and anti-blooming drain 3a, 3b150
A mixing section is provided. In FIG. 1(1)), the shaded area shows the accumulated charge of each pixel. When strong light enters the pixels 1a to 1d and a large amount of charge is generated, the excess charge at that time crosses the anti-pluming barriers 2a to 2C and flows into the anti-pluming drain 3.
a to 3c, and as a result, image disturbance due to pluming is minimized.

However, in the conventional example shown in Figure 1, when the number of horizontal pixels is increased while keeping the size of the five screens the same, the area occupied by the anti-pluming section (2, 5) increases accordingly, so the number of pixels increases. It has the disadvantage of being limited.

In addition, if the light #-i incident on the anti-pluming part is not an effective output, it has the disadvantage that the light utilization efficiency decreases and the sensitivity decreases. An improved conventional example is shown in FIGS. 2 and 3.

FIG. 2 shows a method described in, for example, Japanese Unexamined Patent Publication No. 54-24550.
b-3b, 2d and -1 are provided alternately.

However, in the conventional tree f11, although the drawbacks that existed in the conventional example shown in FIG. 1 have been somewhat alleviated, new drawbacks also arise.

One of them is that since the sampling positions of pixels are irregularly spaced, a moiré phenomenon (a phenomenon in which high-frequency components of an image are folded back to low-frequency components) occurs in the obtained luminance signal. In other words, R (red) - G (green) - B (blue) or R (red) - (11) - 0y (cyan) stripe filters are said to be able to perform good color image detection in combination with frame transfer type COD. When using this method, the periodic structure in the horizontal direction is reduced to 6 pixels, resulting in image distortion of very low frequency components. Since the 6-pixel periodic structure has a very low frequency, moiré occurs even in subjects that do not have a detailed structure, and as a result, the quality of the obtained image deteriorates.

The CCD shown in FIG. 3 is a conventional example disclosed in Japanese Unexamined Patent Publication No. 55-F16789. In the figure, the anti-blooming barrier % 5 is the anti-blooming drain, 4' is the barrier, and a pair of anti-blooming parts (
2 and 3), six pixels IR, IB and 1G divided into a pair of barriers 4' are formed, and such a structure is periodically repeated in the horizontal direction. Pixel (IR, IB and I
G) are all equal in size (horizontal width W),
Pixel 1R has R (red), pixel 1B has B (blue), pixel 1
G is provided with a G (green) filter, respectively.

In this conventional example, for example, when a three-color E-G-B stripe filter is used, it is possible to obtain a good color image. However, this conventional example also has the following drawbacks. That is, when the area component of the bright north (Y) signal is synthesized with the output from the solid-state image sensor/device, a complex signal processing circuit is required. As shown in the above publication, in order to synthesize the high-frequency components of the luminance signal, (1) means for separating and sampling the output corresponding to each color filter;

(2) Means for amplifying the separated output to the required signal level.

(3) Means for resampling each color signal with a necessary phase shift fr4.

As a result, the signal processing circuit becomes complicated. In addition, in this structure, the sampling positions of pixels are irregularly spaced, and the resolution is determined by the largest interval, resulting in a decrease in resolution.
When the sampling interval is equal as in the solid-state image sensor shown in the figure, R-G-H stripe filters are combined so that the output signal from each pixel is read out equally for a white (achromatic) object. Sleeves if set,
As described in the Journal of the Society of Television Engineers, Vol. 33, No. 7, pages 516-522, the high-frequency components of the luminance signal can be extracted by simply inputting the signal obtained from a single-K, solid-state image sensor to a high-pass filter. It is known that it is possible to obtain

(Objective) The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide an improved image pickup device that is simple in structure and capable of obtaining high resolution and high quality images. This is its main purpose.

Furthermore, another object of the present invention is to provide an image sensor with a wide dynamic range of color reproducibility.

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

FIGS. 4(a) to 4(C) are diagrams showing configuration examples of the image sensor of the present invention, and here, an example of a frame transfer type 00D will be explained.

The m structure shown in FIG. 4(a) is the structure of the frame and the light receiving part of the transfer type COD, and in the figure, 1a, 1b, and 1c.

1c', 1d, 1e, 1f, 1f', 1g .
each form a pixel as a photoelectric conversion element. or,
1c, 1c' and 1f, 1f' each form a pair of pixels. aS is a channel stop that prohibits the movement of charge between the receiving regions. Figure 4(b) is shown in Figure 4(b).
It is a potential profile of the cross section of a). B is a potential barrier, and charges overflowing the light-receiving region can move to the adjacent light-receiving region via this barrier. DFi Anti Bloomin again! )''v-in, and an anti-blooming portion serving as an excess charge removing means is formed by the anti-blooming drain and a barrier B2 provided so as to surround this drain.

This is a diagram showing an example of a color filter that is pasted on the front surface of the light-receiving part of the image sensor or formed in the manufacturing process of the image sensor. channel stop aS and barrier B1
Place it according to the pitch of

In this example, an anti-pluming section is provided for every three pixels, but this is to improve the aperture ratio when a stripe filter is used, and an anti-pluming section is provided for every two pixels when a mosaic filter is used. It is desirable to provide a blooming section.

As shown in this embodiment, in the present invention, the light receiving areas 1a, 1
The pixels consisting of c and ' are divided by anti-pluming sections as means for removing excess charge.

Therefore, it is easy to make the pitches of the channel stops aS and barriers B, which are the boundaries of each pixel, equal intervals. As a result, the center of gravity of each pixel's sensitivity can be brought to the center of the pixel as shown in FIG.

Furthermore, since the proportion of the anti-blooming section in the entire light receiving section can be reduced, the aperture ratio can be increased and the horizontal resolution can be improved.

Furthermore, as shown in Fig. 4 (tc), when light with a strong red spectral component is incident, the charge of the pixel corresponding to the color filter RIC is saturated, and when it further overflows, this charge is transferred to the region 1c of the pixel corresponding to G, Infiltrate 1F. Further R
When the charges corresponding to overflow, regions 1c and 1f
The charges also overflow and flow into the drain D, where they are removed.

In this case, no matter how strong the spectral components are, they are all removed by the removal means, so blooming is prevented.

If only N and P are strong and G and B spectral components are not so strong, the signal components of pixels 1a, 1a, and 1g corresponding to 1A region IC', 1f' of pixels corresponding to GK and B are not saturated. Therefore, the G and B color signals can be obtained as valid signals, and as a result, information remains that only the FCRO color signal is strong.

In other words, if the overall brightness level is too high, it has the effect of faithfully reproducing the information of a subject with a high degree of color.In addition, this effect can be achieved by adding an anti-blooming section to each pixel. On the other hand, when filters with the same color spectral characteristics are arranged, K is particularly large.

Next, FIG. 5 is a plan view showing the 'rFL pole arrangement of such an image sensor.

Although the figure shows an example of KL pole arrangement using a one-phase drive system, it is not limited to this.

In the figure, the φxB frame is the transfer electrode of the light receiving section of the transfer type D, and is commonly connected.

Further, φ8 is the transfer m pole of the storage section of the frame transfer type CCD, and is also commonly connected.

Further, VK is a virtual electrode portion in which a potential of a predetermined level is fixedly formed in advance by ion implantation or the like.

In addition, a step-like potential inclined downward in the figure is formed under each transfer electrode and each virtual electrode.The step-like potential under the transfer electrode changes up and down depending on the voltage level applied to the electrode. Therefore, when the potential under the transfer electrode is increased, the charge under the transfer electrode moves to the potential well under the virtual electrode adjacent to the lower part of the figure1, and when the potential under the transfer electrode is lowered, the charge under the transfer electrode moves to the potential well below the virtual electrode. The existing charge moves to the potential well below the transfer electrode adjacent to the lower part of the figure.

Therefore, by applying an alternating pulse of a predetermined level to the transfer power transmitter, the electric current wL that was initially under the transfer electrode or the virtual electrode of the light receiving section is sequentially moved downward in the figure. still,
Regarding COD of this more phase drive method, for example, IT
It is described in detail in EtP 4.229.752 etc.

In this embodiment, the anti-pluming section is provided extending in the column direction within a predetermined pixel in the light receiving section, and its terminal end reaches near the boundary between the light receiving section and the accumulation section.

Therefore, for example, virtual electrode area A7. A, When the same alternating voltage is applied to the transfer electrodes φ and φ8, the lower electrode moves to the Vl area A and + A4 under the virtual electrode in the bottom row of the light receiving section, respectively.
After that 1, for example, if the substrate is a P-type semiconductor, the transfer electrode φ
By applying a relatively high level signal to region 8, a lightning charge of 3+A4 is added to region S1 below transfer electrode φ6. In this case, the addition is performed under the transfer electrode in the first row of the storage section, and this transfer electrode in the first row functions as the adding W means according to the present invention, but this is the terminal end of the anti-blooming section. Needless to say, it varies depending on where the extension is extended.

Therefore, the addition means may be a transfer electrode or a virtual electrode in a lower row within the light receiving section.

That is, the addition means of the present invention is a frame transfer type CO.
In case of D, any electrode near the boundary between the light receiving section and the storage section may be used.

(Effects) As explained above, according to the present invention, the sampling pitch of each pixel can be set at equal intervals, and the resolution is improved.

Furthermore, even if charges from another pixel overflow into one light-receiving region of the pixels divided by the removing means, charge information in the other light-receiving region is unlikely to be lost, resulting in excellent color reproducibility.

[Brief explanation of the drawing]

Fig. 1 fa) (b) is a diagram showing the first example of a conventional image sensor, in which (a) is a schematic plan view, (1)) is a potential diagram, and Fig. 2 (a) (t → conventional 2 is a diagram showing a second example of the image sensor, in which (a) is a plan view, (b) is a potential diagram,
FIG. 3(al(t)) is a diagram showing a third example of a conventional image sensor, in which (a) is a plan view, (b) is a potential diagram,
Figure 4 (!L) (b) and (c) are diagrams showing an embodiment of the image sensor according to the present invention, in which (a) is an H plan view, (b) is a potential diagram, and (c) is a diagram regarding color reproducibility. Diagram to explain, @5
The figure is a diagram showing an example of the electrode configuration of the fourth illustrated element. 1 a, 1b (1c, 1c, 1d11e, (1f, 1
f'l, 1g-, pixel B, . . . . Anti-blooming barrier and anti-blooming drain O8 forming the anti-blooming section; channel stop B, . . . barrier.

Claims (2)

[Claims] (1) A plurality of light converting elements each having a light receiving area and arranged in a matrix, and an excess light converting element provided within the light receiving area of a predetermined light %f converting element and arranged so as to divide the light receiving area. An image sensor having a removing means for removing electric charges, and an adding means for adding electrical information formed in each area in the light receiving area divided by the removing means. (2) The imager according to claim (1), further comprising a color filter that allows light having the same spectral characteristics to enter the photoelectric conversion element provided with the removing means.