JPH11331711A - Device and method for picking up image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent color slurrings on an image-pickup screen by independently transferring readout electric charges and making uniform a 1st pixel signal charge storage period (T 11) read charges, a signal charge storage period (T 21) shorter than T 11, and a signal charge storage period (T 22) shorter than a 2nd pixel signal charge storage period (T 12). SOLUTION: Incident light is photoelectrically converted by a one-unit pixel photoelectric conversion part and its charges are transferred to an HCCD and passed through a CDS and a clamp circuit, and a signal circuit makes a decision regarding signal saturation, a signal selecting circuit selects the output and a signal process circuit performs an arithmetic process to reproduce an image. The signal process circuit converts a T 21 (T 22) storage period signal voltage into Vsig (T 21). Since the pixel information is read out independently, the calculation Vsig'(T 11)=b.V(T 11) can be performed, taking in consideration the ratio (b=T 12/T 11) of the storage periods and the T 21 and T 22 signal charge storage periods which can be made uniform in the timing from TAS 1 to TAS 12 with the clocks.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device and a driving method thereof for expanding the handling range of incident light amount to a high illuminance side, and more particularly, to a fixed signal charge represented by a field or a frame of a video signal. By setting at least two signal charge accumulation periods for the period, and reproducing each signal charge in the signal charge accumulation period without using an external field memory or frame memory, the incident light amount handling range can be increased. The present invention relates to a solid-state imaging device characterized by being enlarged to the illuminance side and a driving method thereof.

[0002]

2. Description of the Related Art In the prior art, when extending the incident light amount handling range, at least two or more different accumulation periods are set in one frame or one field period. The first accumulation period T1 corresponding to the vertical scanning period and the second accumulation period T2 shorter than the first accumulation period are set during the vertical blank period, and the signal charges obtained during the first accumulation period are set. Q1 has a gain of 1, and the signal charge Q2 obtained during the second accumulation period is reproduced at a gain (T1 / T2) times. Here, when the signal charge Q1 has reached the saturated charge amount, by using the signal information of the signal charge Q2, as a result, an incident light amount handling range that is (T1 / T2) times as large as that of the related art is realized.

With respect to the above-described element driving method for expanding the incident light amount handling range, a proposal example in which an external frame memory is not required (Japanese Patent Laid-Open No. 63-250980).
There is. In the proposed example, three signal packets are created with a total of eight transfer electrodes, that is, four pixels in the current CCD configuration,
By using two packets of signal charges of two pixels mixed in the first accumulation period as two packets and one packets of signal charges of four pixels mixed in the second accumulation period, it is obtained in two accumulation periods divided in one field period TF. A method is described in which the received signal charges are continuously transferred by a vertical CCD.

[0004]

SUMMARY OF THE INVENTION
In order to add and mix the signal charges of the pixel mixture, it is necessary to read twice with a time shift of ΔT. Therefore, two different signals having different accumulation periods T2 and (T2 + ΔT) in the same packet. There will be charges. If the signal charges of the four pixels mixed by the two kinds of accumulation periods different from each other by the period ΔT are calculated without distinction by the gain (T1 / T2) times, the second accumulation period T2 is adjusted according to the amount of light of the subject. In such a case, inconveniences such as color shift and brightness shift occur.

An object of the present invention is to provide an imaging method that solves such a problem in consideration of the problems of the conventional imaging method.

[0006]

According to the present invention, a signal charge accumulation period (T11) is applied to the first pixel of the first and second pixels constituting two continuous unit pixels in the direction of the VCCD. ) And a signal charge accumulation period (T21) shorter than the signal charge accumulation period (T11). For the second pixel, a signal charge accumulation period (T12) and the signal charge accumulation period (T12) are set. A shorter signal charge accumulation period (T22) is set, and charges accumulated in each of the four accumulation periods are stored in the VCCD in the signal charge accumulation period (T1).
1) The signal charge accumulation period (T12), the signal charge accumulation period (T21), the signal charge accumulation period (T22)
, And the charge read during the signal charge accumulation period (T21) and the charge read during the signal charge accumulation period (T22) are added, and the signal charge accumulation period (T
11) and the signal charge accumulation period (T
The charge read out in 12) and the added charge are independently transferred in the VCCD, and the charge read out in the signal charge accumulation period (T11) and the signal charge accumulation period (T21). And the signal charge accumulation period (T2
This is a CCD driving method characterized in that the color shift is suppressed by aligning the method 2).

Further, of the first and second pixels constituting two unit pixels continuous in the direction of the VCCD, a signal charge accumulation period (T11) and a signal charge accumulation period (T11) are applied to the first pixel. A signal charge accumulation period (T21) shorter than T11) is set. For the second pixel, a signal charge accumulation period (T12) and the signal charge accumulation period (T1) are set.
A signal charge accumulation period (T22) shorter than 2) is set,
The charge accumulated in each of the four accumulation periods is referred to as VCC.
D indicates the signal charge accumulation period (T11), the signal charge accumulation period (T12), the signal charge accumulation period (T21),
The signal charges are read out in the order of the signal charge storage period (T22), and the charge read out during the signal charge storage period (T21) and the charge read out during the signal charge storage period (T22) are added to form the signal charge storage period. The charge read during the period (T11), the charge read during the signal charge accumulation period (T12), and the added charge are denoted by VC.
A CCD drive characterized in that the charges are transferred independently in a CD, and the charges read in the signal charge accumulation period (T11) are aligned with the signal charge accumulation period (T21) and the signal charge accumulation period (T22). This is a solid-state imaging device characterized by suppressing color misregistration by having means.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a solid-state imaging device used in an imaging method according to an embodiment of the present invention. 100; 110 for unit pixel; VCCD
, Four transfer electrodes correspond to each other. For a total of eight transfer electrodes corresponding to two consecutive unit pixels,
101; φV1 transfer electrode, 102; φV2 transfer electrode, 1
03; φV3 transfer electrode, 104; φV4 transfer electrode, 10
5; φV5 transfer electrode, 106; φV6 transfer electrode, 10
7; φV7 transfer electrode, 108; 8-phase transfer clock of φV8 transfer electrode is applied. A readout gate 109 is formed on the electrode to which 102; φV2 transfer electrode and 106; φV6 are applied. In FIG. 1, for one readout electrode using the first layer of polysilicon,
Although two read gates are provided, the read electrode may use either the first layer or the second layer of polysilicon. In addition, even when a conventional CCD is used, VC
Two pixels adjacent in the CD direction may be considered as one pixel at a time. In the example of driving the elements shown in FIG. 2 and subsequent figures, the description is based on the structure shown in FIG.

FIGS. 2, 3 and 4 show an embodiment of the present invention using the solid-state imaging device shown in FIG. FIG. 2 shows the timings of signal charge accumulation, readout, and transfer of 232; odd-line pixels and 233; even-line pixels in a normal TV frame 201; A-field and 203; B-field 232; 23
2; Odd line pixels and 233; Even line pixels are set in advance by a known vertical electronic shutter operation (VOD-s
(weep) to match the start timing of the accumulation period. 233; Even line pixel 224; Obtains even line first signal charge 205 by signal incident during period T11. Read operation to VCCD is 210; TAF
It is performed at the timing of 1. On the other hand, 232; an odd line pixel is 225;
06: The first signal charge of the odd-numbered line is obtained, and the read operation to the VCCD is performed at the timing of 211; TAF21. Further, in the 202; V-Blank period, 233;
The pixel of the even-numbered line obtains 207; second-line signal charge of the even-numbered line according to the signal input during the period of 227; T21. VC
The read operation to the CD is performed at the timing of 212; TAS1. On the other hand, 232; odd line pixel is 227; T
228 set in the same accumulation period as 21; 208 by the signal incident during the period of T22; the second signal charge of the odd-numbered line is obtained, and the reading operation to the VCCD is 213; TAS21.
It is performed at the timing of. Here, 202; V-Bla
During the nk period, the control of the accumulation time of 227; T21 and 228; T22, which is performed to image a high-luminance area of the subject, is performed in the total field period 226;
29: Performed by adjusting the VOD-sweep period. The same operation is performed for 203; B-FIELD, but as shown in FIG. 2, 214: the storage period of the odd-line first signal charges and 215; the storage period of the even-line first signal charges may be switched. .

FIGS. 3 and 4 show timings of reading and transferring. 210; 240 read out at the timing of TAF1; signal charges are transferred by one pixel in the VCCD;
At the timing of 211; TAF21, 241; signal charges are read. In FIG. 3, from the timing of 210; TAF1 to the timing of 211; TAF21, the operation is performed at 20 clocks. Thereafter, the timing from 212; TAS1 to the timing of 213; TAS21 is adjusted by 20 clocks, thereby obtaining 227; T21 and 228;
It is possible to make 22 accumulation periods uniform. In addition, 20
7; 242 corresponding to the second signal charge of the even-numbered line; after the signal charge is transferred by one pixel in the 20 clock period,
As shown in FIG. 3, at the timing of 212;
8; 243 corresponding to the odd-numbered line second signal charges; mixed by reading out the signal charges in a superimposed manner;
D is transferred by an eight-phase clock. In this example, the accumulation period of 227; T21 and 228;
Although the clock is used, it goes without saying that the number of clocks is not limited. Also, as mentioned earlier, 227; T
21 and 228; the accumulation period of T22 is controlled by increasing or decreasing the period from 211; TAF21 to 212; TAS1, and accordingly the 229; VOD-sweep period is increased or decreased.

FIG. 5 shows an embodiment of the present invention. FIG. 6 shows the effect of expanding the range of the incident light quantity handled. The incident light is photoelectrically converted at 300; one unit pixel photoelectric conversion unit, 301; two-pixel mixed signal charge at electronic shutter, 302; field signal charge 1, 303; field signal charge 2, respectively; 304; HCCD 1, 30
5; HCCD2, 306; transferred by HCCD3,
307; 30 after passing through the CDS & clamp circuit
9: The signal determination circuit determines the signal saturation, 308; the output of the signal is selected by the signal selection circuit, and 310: The signal processing circuit performs an arithmetic processing described later to reproduce the image signal.

Next, an example of an image reproduction processing method will be described.
In the following conditional expressions, VT indicates a voltage corresponding to the saturation charge of the device.

First, when the signal voltages V (T11) and V (T12) in the accumulation period of T11 and T12 satisfy the condition of (Equation 1), 308;
(T11), the signal of V (T12) is selected. If the condition of (Equation 1) is false, 308;
01: Select two pixel mixed signal charge at electronic shutter,
310: The signal processing circuit calculates T2
The signal voltage during the accumulation period of 1 (T22) is Vsig (T21)
Is converted to Here, a is defined as (Equation 3),
Other optimal values, for example, (Equation 4) may be used.

[0014]

Max (V (T11), V (T12)) <VT

[0015]

Vsig (T21) = a · V (T21)

[0016]

## EQU3 ## a = T11 / T21

[0017]

A = T12 / T22 The expansion of the incident light amount range according to the present embodiment will be described with reference to FIG.

In the conventional CCD, the output signal charge amount obtained by the reading and transferring operation by mixing two pixels is 3
20: conventionally shown as a two-pixel mixed type saturated charge amount.
224; T11 and 225; T in FIG. 2 (a)
Since the saturated charge amount of the signal charge during the accumulation period of No. 12 is a value corresponding to one transfer electrode in 100; one unit pixel shown in FIG. 1, about １ ／ of the conventional two-pixel mixed type saturated charge amount. However, when creating a luminance signal, 24
0; the signal charge and 241; the signal charge are added in an external circuit, so that the value eventually becomes about の of the conventional two-pixel mixed type saturated charge amount. This value is shown as 321; the saturated charge amount at the time of independent reading of all pixels.

Here, in the element and the driving method of the present embodiment, at the same time, 227; 207 during the accumulation period of T21;
In the accumulation period of T22, 208; the signal charges obtained by mixing the odd-numbered line second signal charges can be simultaneously and independently read out, and 322; the saturated charge amount can be obtained when two pixels of the electronic shutter are mixed. Here, 227; T2
1 and 228; the period of T22 is, for example, 1/50
Since it can be changed from 0 second to 1/2000 second, it is possible to obtain the effect represented by 325; variable in FIG. Therefore, 32
4: 32 which is larger than the conventional upper limit of the incident light amount
3: It is possible to achieve a wide range of handling incident light amount.

FIGS. 7, 8, and 9 show VOD-sweep.
An embodiment in which p is not used will be described. FIG. 7 shows a normal TV frame 401; A-Field and 403;
432 in B-FIELD; odd line pixel and 43
3: Even line pixels, each showing signal charge accumulation, readout, and transfer timing.

In this case, 432; an odd line pixel and 43
3: The start timing of the accumulation period of the even-numbered line pixels is different from each other. 433; The even-line pixel obtains 405; even-line first signal charge according to the signal incident during the period 424; T11. Read operation to VCCD is 410; T
It is performed at the timing of AF1. On the other hand, 432; the odd line pixel is 425; the first signal charge of the odd line 406 is obtained by the signal incident during the period of T12, and the reading operation to the VCCD is performed at the timing of 411; TAF21.
Further, 402; 43 in the V-Blank period.
3: Even-line pixels 427; 407; Even-line second signal charge is obtained by a signal incident during period T21.
The read operation to the VCCD is performed at the timing of 412; TAS1. On the other hand, 432;
7; 428 set to the same accumulation period as T21; T2
408; the second signal charge of the odd-numbered line is obtained by the signal incident during the period 2, and the read operation to the VCCD is 413;
This is performed at the timing of TAS21. Here, 424; T1
1 and 425; the periods of T12 are different from each other,
01; A-Field and 403; 427 having the same accumulation time because they differ in B-Field; T21 and 42
8: When the period of T22 is controlled, there is a possibility that a color shift and a brightness shift occur between four fields. However, in the present invention, since the pixel information is read out independently, an operation (Equation 6) in which the ratio of the accumulation period (Equation 5) is considered is possible. Therefore, by using the value Vsig '(T11) converted to the accumulation period of T12, no color shift or luminance shift occurs.

[0022]

## EQU5 ## b = T12 / T11

[0023]

Vsig ′ (T11) = b · V (T11) FIGS. 8 and 9 show timings of reading and transferring. 410; 44 read at the timing of TAF1
0: The signal charge is transferred by one pixel in the VCCD, and 41
1; At the timing of TAF21, 441; signal charges are read. In FIG. 3, from the timing of 410; TAF1 to the timing of 411; TAF21, the operation is performed at 20 clocks. Thereafter, the timings from 412; TAS1 to 413; TAS21 are aligned by 20 clocks, whereby 427; T21 and 428;
Can be made uniform. Further, 407;
442 corresponding to the second signal charge of the even-numbered line; after the signal charge is transferred by one pixel in the 20 clock period,
412; TAS21 timing 408;
443 corresponding to the odd-numbered second signal charge; mixed by reading the signal charge in a superimposed manner, and thereafter transferred within the VCCD by an eight-phase clock. In this example,
427; T21 and 428; the accumulation period of T22 is set to 20 clocks, but it goes without saying that the number of clocks is not limited.

FIG. 10 shows a case in which the storage period of 414; the first signal charge of the odd-numbered line and the storage period of 415; the first signal charge of the even-numbered line shown in FIG. Where 5
05; the first signal charge of the even-numbered line is a signal charge obtained by a signal incident during the period of 524;
Reading to the CD is performed at the timing of 510; TAF1. 506; odd signal first signal charge is 525; T
The signal charge obtained by the signal incident during the period 12 is read out to the VCCD at the timing of 511; TAF2. 507; the second signal charge of the even-numbered line is a signal charge obtained by a signal incident during the period of 527; T21, and the readout to the VCCD is 512;
This is performed at the timing of AS1. 508; odd line second
The signal charge is a signal charge obtained by a signal incident during the period of 528; T22.
513: Performed at the timing of TAS2.

In the present invention, 524; T11, 525;
Since the 12 periods can be set to the same length,
Conversion of (Equation 6) is unnecessary.

[0026]

As described above, according to the present invention, it is possible to extend the incident light amount handling range to the high illuminance side without using an external field memory or frame memory.

[Brief description of the drawings]

FIG. 1 is a diagram showing a solid-state imaging device used in an embodiment of an imaging method according to the present invention.

FIG. 2 is an explanatory diagram of a first driving method according to the embodiment of the present invention;

FIG. 3 is a diagram showing an A field according to the first driving embodiment of the embodiment of the present invention;

FIG. 4 is a diagram showing a B field according to the first driving embodiment of the embodiment of the present invention;

FIG. 5 is a diagram illustrating an example of a first solid-state imaging device according to an embodiment of the present invention;

FIG. 6 is an explanatory diagram of an effect of the first embodiment of the present invention.

FIG. 7 is an explanatory view of a second method of the present invention.

FIG. 8 shows an A field according to the second embodiment of the present invention.

FIG. 9 shows a B field according to the second embodiment of the present invention.

FIG. 10 is an explanatory diagram of a method according to a third embodiment of the present invention.

[Explanation of symbols]

100; 1 unit pixel 101; φV1 transfer electrode 102; φV2 transfer electrode 103; φV3 transfer electrode 104; φV4 transfer electrode 105; φV5 transfer electrode 106; φV6 transfer electrode 107; φV7 transfer electrode 108; φV8 transfer electrode 109; readout gate 110 VCCD 201, 401, 501; A-FIELD 202, 204, 402, 404, 502, 504;
-Blank 203, 403, 503; B-FIELD 205, 215, 405, 415, 505, 514; First line signal charges 206, 214, 406, 414, 506, 515 of even lines; First line signal charges 207, 217 of odd lines , 407, 417, 507, 516; even-numbered line second signal charges 208, 218, 408, 416, 508, 517; odd-numbered line second signal charges 209, 218, 409, 418, 509, 518;
TAF1 211, 411, 511; TAF21 212, 412, 512; TAS1 213, 413, 513; TAS21 219, 419, 519; TBF1 220, 420, 520; TBF21 221, 421, 521 TBS1 222, 422, 522; TBS21 223, 229; VOD-sweep 224, 424, 524; T11 225, 425, 525; T12 226, 426, 526; TF 227, 427, 527; T22 232; odd line pixel 233; even line pixel 240, 241, 242, 243, 250, 251, 2
52, 253; signal charge 300; one-pixel photoelectric conversion unit 301; two-pixel mixed signal charge at electronic shutter 302; field signal charge 1 303; field signal charge 2 304; HCCD1 305; HCCD2 306; HCCD3 307; 308; signal selection circuit 309; signal judgment circuit 310; signal processing circuit 320; conventional two-pixel mixed type saturated charge amount 321; all-pixel independent readout saturated charge amount 322; electronic shutter two-pixel mixed charge amount 323; Light intensity expansion range 324; Conventional handling incident light intensity upper limit 325; Variable

Claims (2)

[Claims] 1. A signal charge accumulation period (T11) and a signal charge accumulation period (T11) for a first pixel among first and second pixels constituting two unit pixels continuous in a VCCD direction. The signal charge accumulation period (T2) shorter than T11)
1) is set, and for the second pixel, a signal charge accumulation period (T12) and a signal charge accumulation period (T22) shorter than the signal charge accumulation period (T12) are set.
The charges accumulated in each of the two accumulation periods are stored in the VCCD in the signal charge accumulation period (T11), the signal charge accumulation period (T12), the signal charge accumulation period (T21), and the signal charge accumulation period (T22). The charges are read out in order, and the charges read in the signal charge accumulation period (T11), the signal charge accumulation period (T21), and the signal charge accumulation period (T2).
2. A method for driving a CCD, wherein the color shift is suppressed by aligning the method 2). 2. A signal charge accumulation period (T11) and a signal charge accumulation period (T11) for the first pixel of the first and second pixels constituting two unit pixels continuous in the direction of the VCCD. The signal charge accumulation period (T2) shorter than T11)
1) is set, and for the second pixel, a signal charge accumulation period (T12) and a signal charge accumulation period (T22) shorter than the signal charge accumulation period (T12) are set.
The charges accumulated in each of the two accumulation periods are stored in the VCCD in the signal charge accumulation period (T11), the signal charge accumulation period (T12), the signal charge accumulation period (T21), and the signal charge accumulation period (T22). The charges are read out in order, and the charges read in the signal charge accumulation period (T11), the signal charge accumulation period (T21), and the signal charge accumulation period (T2).
2) A solid-state imaging device having a CCD driving means characterized in that the color shift is suppressed by aligning 2).