JP2996947B2 - Imaging device and imaging method - Google Patents

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]

The present invention is directed to a VCCD.
First and second images forming two unit pixels continuous in
Out of the element, the signal charge accumulation period for the first pixel
(T11) and shorter than the signal charge accumulation period (T11).
A second signal charge accumulation period (T21) is set, and the second image
For the element, the signal charge accumulation period (T12) and the signal
Signal charge accumulation period shorter than charge accumulation period (T12)
(T22) is set, and stored within each of the four storage periods.
The stored charges are stored in the VCCD in the signal charge storage period (T1).
1) the signal charge accumulation period (T12), the signal charge
Accumulation period (T21), the signal charge accumulation period (T22)
, And during the signal charge accumulation period (T21).
In the read charge and the signal charge accumulation period (T22),
The read charges are added, and the signal charges are accumulated in the signal charge accumulation period (T
11) and the signal charge accumulation period (T
12) the charge read out and the added charge
Is transferred independently in the VCCD, and the signal
The charge read during the load accumulation period (T11) and the signal
Load accumulation period (T21) and the signal charge accumulation period (T2
2) A method for driving a CCD, wherein
You.

Further, two unit images continuous in the direction of the VCCD are provided.
Out of the first and second pixels constituting the element,
The signal charge accumulation period (T11) and the signal
Signal charge accumulation period shorter than charge accumulation period (T11)
(T21) is set, and a signal is sent to the second pixel.
The charge storage period (T12) and the signal charge storage period (T1
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) and the signal charge accumulation.
A product period (T12), the signal charge accumulation period (T21),
The signals are read out in the order of the signal charge accumulation period (T22), and
The charge read during the signal charge accumulation period (T21)
The charge read during the signal charge accumulation period (T22) is added.
Calculated during the signal charge accumulation period (T11).
Charge and read out during the signal charge accumulation period (T12).
The three charges of the added charge and the added charge are represented by VC
Independently transferred within the CD, the signal charge accumulation period
(T11) Charge read out and signal charge accumulation period
(T21) and the signal charge accumulation period (T22) are aligned.
Having CCD driving means.
This is a solid-state imaging device.

[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; a unit pixel corresponds to 110; four transfer electrodes in the VCCD correspond to the unit cell, and a total of eight transfer electrodes corresponding to two consecutive unit pixels correspond to 101; φV1 transfer electrode, respectively.
102; φV2 transfer electrode, 103; φV3 transfer electrode, 1
04; φV4 transfer electrode, 105; φV5 transfer electrode, 10
6; φV6 transfer electrode, 107; φV7 transfer electrode, 10
8: An 8-phase transfer clock of the 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, two read gates are provided for one read electrode using a first layer of polysilicon, but the read electrode uses either the first or second layer of polysilicon. May be. Even when a conventional CCD is used, two pixels adjacent in the VCCD 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;
Even line pixels 227; get even line second signal charge; 207 by a signal incident during a period of 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 to the same accumulation period as 21 ; 208 from the signal incident during the period of T22 ; obtain the odd-numbered line second signal charge; read operation to the VCCD is 213; TAS21
It is performed at the timing of. Here, 202; V-Bla
During the nk period, 227 is performed to capture an image of a high-brightness region of the subject; T21 and 228; control of the accumulation time of T22 is performed in the entire 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, 212; the timing of TAS1 213; up timing TAS21, by aligning with 20 clock, 227; T21 and 228; T
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, 227; T21 and 228; the accumulation period T22 20
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 VOD-sweep period is increased or decreased by 229.

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 voltage V (T11), V (T12) during the accumulation period of T11 and T12 is true, the signal selection circuit 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.

[0015]

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

[0016]

## EQU2 ## Vsig ( T21 ) = a.V ( T21 )

[0017]

## EQU3 ## a = T11 / T21

[0018]

## EQU4 ## a = T12 / T22 The expansion of the incident light amount range according to the present embodiment will be described with reference to FIG.

The output signal charge amount obtained by the readout and transfer operation by mixing two pixels in the conventional CCD 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 according to 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; odd line pixels 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 the signal incident during the period of 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 into the accumulation period of T12, no color shift or luminance shift occurs.

[0023]

## EQU5 ## b = T12 / T11

[0024]

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, 412; the timing of TAS1 413; up timing TAS21, by aligning with 20 clock, 427; T21 and 428; T22
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 the 414; odd-line first signal charges shown in FIG. 7 is replaced with the storage period of 415; the even-line first signal charges. 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 line signal charge of the even-numbered line is 527; a signal charge obtained by a signal incident during the period of T21 , and 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.

[0027]

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 illustrating 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 an 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.

[Description of Signs ] 227, 427, 527; T21 228, 428, 528; T22

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-22670 (JP, A) JP-A-4-207581 (JP, A) JP-A-4-158684 (JP, A) JP-A-61- 158279 (JP, A) JP-A-60-254887 (JP, A) JP-A-63-250980 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 5/335

Claims (2)

(57) [Claims] 1. Two unit pixels continuous in the direction of VCCD
The first pixel of the first and second pixels constituting the first pixel;
The signal charge accumulation period (T11) and the signal charge
The signal charge accumulation period (T2) shorter than the accumulation period (T11)
1) is set, and a signal charge storage is performed for the second pixel.
The product period (T12) and the signal charge accumulation period (T12)
A shorter signal charge accumulation period (T22) is set,
Charge stored in each of the two storage periods is stored in the VCCD.
The signal charge accumulation period (T11), the signal charge accumulation period
(T12), the signal charge accumulation period (T21),
The signal is read out in the order of the signal charge accumulation period (T22),
The charge read out during the charge accumulation period (T21) and the signal
The charges read during the charge accumulation period (T22) are added,
The charge read during the signal charge accumulation period (T11) and
The charge read during the signal charge accumulation period (T12) and
The three charges of the added charges are stored in the VCCD.
Independently transferred and read during the signal charge accumulation period (T11).
The output charge, the signal charge accumulation period (T21), and the
The signal charge accumulation period (T22) is made uniform.
Driving method of CCD. 2. Unit pixels continuous in the direction of VCCD
The first pixel of the first and second pixels constituting the first pixel;
The signal charge accumulation period (T11) and the signal charge
The signal charge accumulation period (T2) shorter than the accumulation period (T11)
1) is set, and a signal charge storage is performed for the second pixel.
The product period (T12) and the signal charge accumulation period (T12)
A shorter signal charge accumulation period (T22) is set,
Charge stored in each of the two storage periods is stored in the VCCD.
The signal charge accumulation period (T11), the signal charge accumulation period
(T12), the signal charge accumulation period (T21),
The signal is read out in the order of the signal charge accumulation period (T22),
The charge read out during the charge accumulation period (T21) and the signal
The charges read during the charge accumulation period (T22) are added,
Charges read during the signal charge accumulation period (T11),
And the voltage read during the signal charge accumulation period (T12).
Load, and the three charges of the added charges are stored in the VCCD.
In the signal charge accumulation period (T1).
1) and the signal charge accumulation period (T2
1) and aligning the signal charge accumulation period (T22).
It is characterized by having CCD driving means.
Solid-state imaging apparatus.