JPH0474911B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention provides a single-chip color imaging device using an interline charge-coupled solid-state imaging device capable of simultaneously reading two lines, in which the ratio of the amount of smear to each color signal is constant. , relates to the structure and driving method of a solid-state imaging device that does not cause smear on the screen to be colored.

[Prior art]

The structure of a conventional interline charge-coupled solid-state imaging device capable of simultaneous two-line readout and its driving method will be explained with reference to FIGS. 1 and 2. The incident light is transmitted to a photoelectric conversion element group 102 consisting of photodiodes.
is converted into signal charge and accumulated. The accumulated signal charges are transferred to the vertical CCDs 111, 112, . . . 11N by applying a pulse 207 to the gate of the switch 125 during the vertical retrace period.
Thereafter, the vertical CCD is transferred two lines at a time in the direction of the arrow by a pulse 211 synchronized with the horizontal pulse of the television signal. (In pulse 211, a set of two pulses indicates that two lines of data are transferred) and horizontal direction.
By applying the pulse train 212 to the CCDs 121 and 122, two lines are simultaneously output as video signals from the output terminals 123 and 124 in one horizontal period. In addition, in the field following this, for interlace operation, only the first line is read out by pulse 219, and only one line is read out (pulse 219 consisting of one pulse indicates that only one line of data is transferred). ), and the subsequent horizontal period is pulses 221, 222.
As with the previous field, read out two lines at a time. This operation changes the combination of two lines read out at the same time, and interlaces the television signal. A single-chip color imaging device using the element shown in Figure 1 has a mosaic color filter placed above the photodiode of the element shown in Figure 1. Figure 3 shows an example using an RGB checkered filter. It is shown.
In the device shown in Fig. 3, the signals are read out in the first field using R ₁₁ , G ₁₂ , . . . R _IN and G ₂₁ , B ₂₂ ,
...Two lines of G _2N , R ₃₁ , G ₃₂ , ... R _3N and G ₄₁ ,
Signals are transferred and read for each set of two lines such as B ₄₂ , ...G _4N , ..., etc., and in the next field, G ₂₁ , B ₂₂ , ...G _2N and R ₃₁ , G ₃₂ ,
...2 lines of R _3N , G ₄₁ , B ₄₂ , ...G _4N and R ₅₁ ,
The interlacing operation is performed by changing the combination of two lines such as G52, . . . R _5N , and reading them out in different combinations.

By the way, in the device shown in Figure 1, the vertical structure near the photoelectric conversion element (photodiode) is constructed such that the CCD for transfer and the photodiode are adjacent to each other on the same plane as shown in Figure 4. Some of the charge generated on the substrate under the diode is vertically
It leaks into the CCD. Therefore, a smear occurs in which the influence of the strong light also appears on the signal output from the parts above and below the part that is not hit by the strong light. The amount of smear is determined as follows. That is, the transfer is performed in a short period of time during the horizontal blanking period, and the signal charge remains at a fixed position within the CCD in the vertical direction during the horizontal video period, which is the majority of the horizontal period. Charges mixed in from adjacent photodiodes during this horizontal video period form the main component of the smear. By the way, in the device shown in Fig. 3, for example, the signal charge accumulated in G _M1 becomes a pair with R _M-1,1 in the first field and moves in the vertical direction.
CCD111 is transferred. Then, as two lines are sequentially transferred in each horizontal period, the signal charge of G _M,1 is transferred to G _M-2,1 filter, ... G _4,1 filter, G _2,1 filter during horizontal video period. etc., always stays in a position adjacent to the photodiode with the G filter. Therefore, smear mainly due to green light ₁ 〓 ^M/2
g _2i,1 (where g _2i,1 is the amount of smear charge leaking from the photodiode portion where the G _2i,1 filter is located to the adjacent CCD portion during one horizontal period) is mixed and output. Similarly, the signal accumulated in P _M-1,1 is always R
Since it stops next to the photodiode with the filter, the smear mainly due to red light ₁ 〓 ^M/2 r _2j-1,1
(However, r _2j-1,1 is the amount of smear charge leaking from the photodiode portion where the R _2j-1,1 filter is located to the adjacent CCD portion during one horizontal period) mixed in and output. By the way, in the CCD 111 in the vertical direction, when the signal charge of G _M1 is transferred to the part below the part containing the signal charge of G _M1 , that is, the position adjacent to G _M-2,1 , the original There is already no signal charge at the CCD position adjacent to G _M1 , and smear charge g _M1 leaking from the photodiode of G _M1 accumulates. As the signal charge of G _M1 is transferred, this smear g _M1 is also transferred, so when the signal charge of G _M1 is read out from the output terminal 124, G ₂₁
A smear charge ₁ 〓 ^M/2 g _2i,1 is accumulated in the CCD adjacent to . Similarly, the CCD adjacent to G _i,1 has a smear charge _i0/2 〓 ^M/2 g _2i,1 , and the CCD adjacent to R _j0,1 has a smear charge _(i0+1)/2 〓 ^{M /2} r _2j-1,1 is accumulated.

On the other hand, in the next field, after the signal charge is again transferred from the photodiode group to the CCD in the vertical direction by pulse 217, one line of R ₁₁ , G ₁₂ , . . . R _1N is first transferred by pulses 219 and 220. Read only the signals of G ₂₁ , B ₂₂ , G _2N and R ₃₁ , G ₃₂ ,...
...2 lines of R _3N , G ₄₁ , B ₄₂ , ...G _4N and R ₅₁ ,
Transfer 2 lines at a time, such as 2 lines of G ₅₂ , ...R _5N . So in a new field, e.g.
The signal charge of G _M1 always stays at a position adjacent to the photodiode with the R filter, such as R _M-1,1 ...R ₃₁ , R ₁₁ , etc., and is on top of the smear of green light that remains after reading out the signal charge of the previous field. Furthermore, smear caused by red light is mixed into the output. Similarly, in general
The G _i0,1 signal is mixed with the smear charge _i0/2 〓 ^M/2 g _2i,1 + ₁ 〓 ^i0/2 r _2j-1,1 and output, and the R _j0,1 signal is output with the smear charge _{j0+ 1/2} 〓 ^M/2 r _2j-1,1 + ₁ 〓 ^j0-1/2 g _2i,1 is mixed and output.

Therefore, when the solid-state imaging device shown in FIG. 3 is driven by the driving method shown in FIG. 2, the smear not only differs depending on the color signal, but also the color of the smear changes in the vertical direction of the screen. Alternatively, since the amount of smear varies from field to field, the smear appears in a flickering manner, which significantly deteriorates the image quality.

[Purpose of the invention]

The present invention is a single-chip color imaging device that uses an interline charge-coupled solid-state imaging device that can read out two lines simultaneously.The present invention is a solid-state imaging device in which smear is constant and white in the vertical direction of the screen, and flicker does not occur, making smear less noticeable. The object of the present invention is to provide a device and a method for driving the device.

[Summary of the invention]

In order to achieve the above purpose, in this invention,
A transfer unit is provided between the vertical CCD and the horizontal CCD in FIG. 1 to perform a new interlacing operation. In other words, while the CCD in the vertical direction always transfers two lines at a time during one horizontal retrace period, the newly installed transfer section alternately transfers odd lines and even lines for each field. interlace operation. In this case, since the vertical CCD is always transferred two lines at a time, each color signal such as R signal charge, G signal charge, and B signal charge is always transferred adjacent to a photodiode with a filter of the same color during the horizontal video period. It stays in place and only smear from light of the same color is mixed in. Therefore, the ratio of the amount of smear to each color signal is constant, that is, the smear on the screen is white and difficult to stand out, but the smear does not flicker.
Deterioration in image quality due to smear can be reduced.

[Embodiments of the invention]

The present invention will be explained in detail below with reference to Examples.

FIGS. 5 and 6 are diagrams showing an embodiment of the structure of a solid-state imaging device and its operating method according to the present invention.
In FIG. 5, 126 is a newly installed transfer unit,
It consists of one line of CCDs that can be driven by drive signals φ _V3 and φ _V4 that are independent of the vertical CCD drive signals φ _V1 and φ _V2 .

The device shown in FIG. 5 is driven as follows. That is, in FIG. 6, the first field is driven from the photodiode 102 in the vertical direction by the pulse 207 in the same manner as in FIG.
12...Transfer the signal charge to 11N. vertical
The CCD transfers two lines every horizontal retrace period using the pulse 211 in FIG. On the other hand, the newly installed transfer unit 126 in FIG. 5 transfers three lines during this time (a set of three pulses 311 in FIG. 6 indicates the transfer of these three lines).
Two lines of signals transferred from the vertical CCD are transferred to the horizontal CCDs 121 and 122.
Therefore, there is no signal charge in the transfer section 126. Thereafter, the horizontal CCD is driven by the pulse 212 in FIG. 6, and signal charges for two lines are output as video signals. In the next field, the signal charge is transferred to the CCD in the vertical direction by pulse 217, and as in the previous field, two lines are transferred therein every horizontal retrace period. On the other hand, the newly provided transfer section 126 in FIG. 5 is different from the previous field.
Two lines of data are transferred during this time by the pulse 321 in FIG. When transferred in this way, in the first horizontal period, only the signal charges on the first line are read out through the CCD 122 in the horizontal direction in FIG. 5, and the signal charges on the second line are left in the transfer section 126. Then, in the next horizontal period, the signal charges of the second line left in the transfer section 126 are transferred to the horizontal CCD 121, and the newly transferred signal charges of the third line are transferred to the CCD 122 of the horizontal direction. The signal charge on the line moves into the transfer section 126. Thereafter, the signal charges on the second and third lines are simultaneously read out by the pulse 222 in FIG. By performing similar operations thereafter, it is possible to simultaneously read two lines in a combination different from that of the first field.

In other words, in the device shown in Fig. 5, even if interlace operation is performed, the vertical CCD always transfers two lines of the same combination, and each color signal charge is adjacent to a photodiode with a filter of the same color during the horizontal image period. Stops at the desired position. Therefore, each color signal contains only smear caused by light of the same color as itself, and the smear is uniform in the vertical direction of the screen and is white, making it inconspicuous. Furthermore, since the amount of smear does not vary in a flicker-like manner from field to field, deterioration in image quality due to smear can be reduced.

In the present embodiment shown in FIG. 5, a transfer section consisting of one line of CCD is added to the device shown in FIG. Also good. In addition, the number of lines transferred to the transfer section during the horizontal retrace period is determined by the number of lines provided in the transfer section.
A similar effect can be obtained by alternately repeating the number of even lines and odd lines, which are smaller than the number of CCD lines and (horizontal retrace period)/(transfer time for one line), for each field.

〔Effect of the invention〕

As explained above, by using the solid-state imaging device and its driving method according to the present invention, the smear can be made into an inconspicuous white smear that is uniform in the vertical direction of the screen, and the interline charge-coupled solid-state imaging system can read out two lines simultaneously. Deterioration in image quality due to smear in a single-chip color imaging device using the element can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the structure of a conventional interline charge-coupled solid-state image sensor capable of simultaneous two-line readout, Fig. 2 is a waveform diagram for explaining the operation of Fig. 1, and Fig. 3 is the same as Fig. 1. 4 is a partial sectional view for explaining the cause of smear generation, and FIG. 5 is a diagram showing the structure of an embodiment of the solid-state imaging device according to the present invention. FIG. 6 is a waveform diagram for explaining the operation of the embodiment shown in FIG. 102...Photoelectric conversion element group, 111-11N...
...Vertical CCD, 121,122...Horizontal direction
CCD, 123, 124...output terminal, 126...
...transfer department.

Claims (1)

[Claims] 1. A plurality of photoelectric conversion elements arranged two-dimensionally, a plurality of first charge transfer elements that vertically transfer signal charges accumulated in each photoelectric conversion element, and a plurality of first charge transfer elements that vertically transfer signal charges accumulated in the respective photoelectric conversion elements, and signal charge to 1
In a solid-state imaging device that includes a second charge transfer element that reads out horizontally in a horizontal period and has a structure that allows two lines of signal charges to be read out simultaneously, a charge transfer element is provided between the first charge transfer element and the second charge transfer element. is provided with a third charge transfer element that can be driven independently, and the first charge transfer element transfers the same number of lines in each field period, while the third charge transfer element transfers an even number of lines in two consecutive fields. A solid-state imaging device characterized by alternately transferring odd-numbered lines.