JPS6028435B2 - solid state imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid-state image device that converts optical information into electrical signals, and visually improves the vertical resolution of reproduced images through simple circuit processing without using analog delay lines. The purpose is to

Some devices that convert two-dimensional optical information into electrical signals include a combination of a photoelectric conversion cell and a charge transfer element such as a BBD or a CCD, or a combination of a photoelectric conversion cell and a MOS-FET.

A typical schematic diagram of such a solid-state imaging device is shown in FIG. 1A, and its operation will be explained with reference to FIGS. 1B and 2C and FIG. la, lb, ..., ln, 2a, 2 b, ......,
2n, ~na, nb, . ．． 、． ．． ．． Each of nn indicates a photoelectric conversion cell. Each photoelectric conversion cell is an element, such as a photodiode, that generates a photoelectric conversion signal corresponding to the intensity of light in the two-dimensional object light report, and each of the photoelectric conversion signals is shown in the figure. Charge transfer stage IT, 2T
、． ... are read into each of nT as indicated by arrows p (indicated by a solid line) and q (indicated by points) shown in the figure. The photoelectric conversion signal read into the charge transfer stage is transferred to the horizontal signal output line 4, and a time-series photoelectric conversion signal, that is, a video output signal is obtained from the output terminal 5 of the horizontal signal output line 4. The arrow p shown in the same figure shows the direction of signal charge transfer from the photoelectric conversion cell to the charge transfer stage in one field period of one TV signal, for example, the first field period, and the arrow q shows the direction of signal charge transfer from the photoelectric conversion cell to the charge transfer stage in one field period of one TV signal. It shows that in the period.

Any column of the photoelectric conversion cell columns, ma, mb,
For clarity of explanation, only mc, mf, mK and a charge transfer stage mT for transferring photoelectric conversion signals transferred from these photoelectric conversion cells are shown in FIG.

An arrow p indicated by a solid line in the figure indicates the transfer direction of signal charges in the first field period, and first, the signal charges obtained from the photoelectric conversion cells ma, mc, me, mK during the first field period are Along the vertical direction in the figure, every other charge is simultaneously transferred to the charge transfer stage mT in the flow shown by the arrow p, and in the next field period, that is, the second field period, the charge is transferred by the arrow q shown by the dotted line in the figure. With the flow of signal charges shown, the signal charges obtained from the remaining photoelectric conversion cells mb, md, mf are transferred to the transfer stage mT.

Here, the magnitudes of signal charges obtained from each photoelectric conversion cell ma, mc, me, mb obtained in the first field period are respectively a, c, e...x, Each photoelectric conversion cell mb obtained in the second field period
The magnitude of the signal charge obtained from , md, mf is expressed as b,
Let them be d and f. For ease of explanation, these first
The magnitude and order of the signal charges obtained in the field and the second field are determined by the time axis t of each field period.
are taken as the same and shown in IF and 2F, respectively. Figure 2 shows the signal magnitude a,
This shows that c, e, and x are reproduced on the scanning lines of the first field f, and similarly, b, d, and f are reproduced on the scanning lines of the second field itself.

The present invention has been made to further improve the resolution of the solid-state imaging device as described above, and proposes a solid-state imaging device that can obtain high resolution by using vertical interpolation signals.

Conventionally, to improve resolution using vertical interpolation signals, this was done by separately providing an analog delay line such as an ultrasonic glass delay line or a charge transfer element array and processing the circuit. Analog delay lines had problems in terms of electrical characteristics, cost, circuit processing complexity, and volume.
The present invention provides a compact and inexpensive solid-state imaging device that does not use such complicated circuits.

The present invention will be explained below based on examples together with the drawings.

The configuration of the present invention will be described based on FIGS. 3a, b, and d.

In the same figure a, Am, Bm,...Ym indicate photoelectric conversion cells, and a, b,..., y indicate the magnitude of signal charges obtained from these photoelectric conversion cells. , are transferred to the charge transfer element stage Tm in the direction of each arrow. Needless to say, the photoelectric conversion cell and the charge transfer stage shown here are only a part of the imaging surface of the solid-state imaging layer for the purpose of simplifying the explanation.

In the figure, G1 and G2 are a clock line for driving the charge transfer stage Tm, and a clock line for transferring signal charges from the photoelectric conversion cell to the charge transfer means Tm, respectively. Indicates a line that also serves as ? 1 and 2 are operated by applying, for example, a two-phase pulse voltage.

A description of the structure of the Sonobody imaging device that can commonly use the clock line of the charge transfer stage and the clock line for transferring signal charges is given in the Tokuwaki Sho 50-5, which was generally proposed by the present applicant.
Since it is detailed in the specification of No. 8827 (see Japanese Patent Publication No. 58-22898), it is omitted here.

The state of signal charge readout from the first field to the fourth field according to the timing of the two-phase pulse waveform is shown in FIG. 2B, geometrically corresponding to FIG.

The operation will be described together with drive pulse waveforms 1 and 2 shown in FIG. Although the transfer pulses ◇V,, and V2 are shown in a simplified manner in figure c, the waveform that is actually applied is the transfer pulse shown in figure d, which is an enlarged version of the dotted line in figure c. ing. In addition, each photoelectric conversion cell is
By applying a reset signal to the s line shown in FIG. 2 of No. 7 for each field, each field is reset and prepared for reading the next field. First, in the first field, that is, the first field period IF, the clock line? 1, the charge transfer pulse ◇V, and the photoelectric conversion cells Am, Cm, E
The aforementioned transfer pulse for transferring the signal charge obtained from m,...Ym to the charge transfer stage Tm', that is, reading it out? V, a read pulse R with a higher potential is applied, and a pulse signal is given that is superimposed with it during the field blanking period BI before the start of the first field scan IF, and on the other clock line 2, a transfer pulse ■ V2 only is applied. give.

Like this J1,? 2, the signal charges a, b,
They appear as c,...y (b in the same figure). next second
In the field period 2F, during the field blanking period B2 immediately before the start of the second field scanning period 2F, the read pulse R having the potential as described above for the 01 and 2 lines, and the respective transfer pulses JV, . A pulse signal that is superimposed with V2 is added.

During this period, the OV pulse is added in advance of the ◇V2 pulse. Then, the signal charges of each photoelectric conversion signal are immersed two by two, that is, the respective sum signals of the signal charges a and b, c and d, e and f, and g and x are sequentially generated as shown in 2F in b in the same figure. can get. Field blanking period B3 immediately before the start of the third field period F3
In some cases, when the above-mentioned read pulse R is superimposed on only 2 lines, the signal corresponding to each signal charge is generated as a part of the horizontal scanning signal obtained during this field period in 3F of the same figure (b). As shown, they appear as b, d, f, and x.

Furthermore, during the field blanking period B4 immediately before the start of the fourth field period 4F, the above-mentioned read pulse R is applied? It is superimposed on each of the clock lines 1 and 2, and is operated at the timing when the transfer pulse V2 pulse precedes the V pulse during the period in parentheses.

Each signal charge obtained at this time is a mixture of signal charges b and c, d and e, f and g, and x and y, as shown in 4F in Figure b, that is, a horizontal scanning signal. Obtained as a part. In this way, for example, a period of H/4 is shifted between video signals a and c, which are shifted by a period of days with respect to a scanning period t in the vertical direction of the TV screen, and a + b,
This makes it possible to insert video signals b and b+c. By repeating the operations from the first field to the fourth field as described above, a video output signal obtained by substantially 1:4 interlaced scanning is obtained.To reproduce this video output signal by 1:4 interlaced scanning, The receiver is of a different format from the conventional TV receiver, in other words, the scanning line is 1:2, with one field taking half the time of the conventional one field.
Instead, use a receiver with a ratio of 1:4.

For clarity of explanation, each of the signal charges a, b, c,...
. . . y is a signal charge corresponding to one point along the vertical direction in the two-dimensional optical information, that is, a signal corresponding to one pixel.

In other words, using these signal charges as a video signal,
When reproduced on a TV screen, a single vertical image on the screen is obtained. In reality, the combination of photoelectric conversion cells and charge transfer stages as shown in FIG.
...If y is expanded in the horizontal direction, a', b', c
', . . . y' can obviously be considered as horizontal scanning signals. An image obtained by reproducing the video output signal thus obtained on a TV screen is shown in FIG. 4 as a scanning line signal.

In the figure, the scanning signal f, shown by the solid line, is the first field, and the dotted line
〃 Rima No. 2〃 One-dot chain line〃 〃 Rima No. 3〃 Double-dot chain line〃 Rima No. 4〃 Indicates the position of the scanning line in each field period.

As mentioned above, in the second field period and the fourth field period, the signal output is obtained as the sum of the two photoelectric conversion signals, so the gain adjustment circuit adjusts the signal level to 1'2 only during these two periods. Guide the video output signal to.

Also, the signal output of the second field and the fourth field is
A TV receiver is used that displays a display between the signal output of one field and the signal output of the third field. If this is done, as shown in FIG. 4, the horizontal scanning line signal a'a' + b'2'b',b' + d' L ' `` appears and repeats with a cycle of f, to f4 until it reaches the bottom of the TV screen.

As can be seen from the figure, the original horizontal scanning signals are
Between each of c',...y', a' ten b'b'
+c'c'+d' - - - - - - - Horizontal scanning signals 2'2'2' (these signals are called interpolated signals) are obtained.

The higher the correlation between the two-dimensional optical information, that is, the vertical images in the subject, the more the visual effect is equivalent to a substantial increase in the vertical resolution of the reproduced image. Note that the present invention relates to a photoelectric conversion cell and a MOS-FET.
It can also be applied to a solid-state imaging device in combination with As explained above, in the solid-state imaging device of the present invention, the charge transfer means transfers the sum of signal charges of a plurality of photoelectric conversion cells in each column or each row. It is possible to obtain interpolated signals in the vertical or horizontal direction with a simple configuration, small size, and low cost without using an analog delay line, which is problematic in terms of problems.This interpolated signal can be used to improve image resolution. , which is of great practical value.

[Brief explanation of the drawing]

1A to 2C are configuration diagrams and operation explanatory diagrams of a conventional solid-state imaging device, and FIGS. 3A to 3D and FIG. 4 are configuration diagrams and operation explanatory diagrams of a solid-state imaging device of the present invention. . Am, Bm~Ym...Photoelectric conversion cell, Tm...
...Charge transfer stage, J1,02...Clock line,
R...Reading pulse, MAV,, JV2...Transfer pulse. Figure 1 Figure 2 Figure 4 Figure 3

Claims (1)

[Claims] 1 A plurality of photoelectric conversion cells arranged in a matrix and reset for each field, and a plurality of photoelectric conversion cells that transfer signal charges corresponding to the amount of light incident on each of the photoelectric conversion cells in the column direction or the row direction. charge transfer means; and means for obtaining, from the charge transfer means, a sum signal charge of a plurality of photoelectric conversion cells in each of the columns or in each row; A solid-state imaging device characterized in that both signal charges and direct read signal charges of a photoelectric conversion cell are used as video signals.