JP2880026B2 - CCD imaging device and driving method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging device, and more particularly to a CCD imaging device in which a large number of pixels are arranged in a matrix and image signals are transferred by a charge-coupled device (CCD).

[0002]

2. Description of the Related Art As a solid-state imaging device, a CCD transfer system is known, and is used in electronic cameras, copying machines, and other video equipment. A large number of photodiodes are vertically and horizontally arranged to form a pixel matrix. further,
A vertical charge transfer path (VCC) adjacent to each photodiode row
D), and a horizontal charge transfer path (HCCD) is formed adjacent to the end of each VCCD.

In an electronic still camera or the like using such a solid-state imaging device, there is a demand that all photodiodes (PDs) be exposed at the same time and signals be read independently. Simultaneously read out the charge accumulated in the photodiode,
In order to perform the transfer, three or more transfer pulses are usually required for one pixel or one row. In order to realize transfer pulses of three or more phases per pixel, the CCD needs three or more electrodes per pixel, which is disadvantageous in terms of miniaturization.

It is conceivable to form a well portion and a barrier portion under one electrode and perform two-phase driving. However, there is also a problem that a self-alignment cannot be used in a process for forming the well portion and the barrier portion. Occurs.

[0005] As a transfer method that does not have these disadvantages,
An accordion transfer method has been proposed (PHILI
PS TECHNICAL REVIEW VOL. 4
3, No. 1 / 2,1986, A. J. P. Theu
Wissen and C.I. H. L. Weijtens).

In the accordion transfer system, the number of electrodes is the same as that of an IT (interline transfer) CCD, FT (frame transfer) CCD, FIT (frame interline transfer) CCD, etc., with two electrodes per pixel or two rows, and all electrodes are used. Simultaneous readout of pixels is possible, and an electronic shutter for exposure at the same time using an electronic shutter for removing a substrate or the like is possible.

FIG. 7 shows an accordion transfer system.
FIG. 7A is a potential diagram showing how the potential under the electrode of the transfer path changes with time. FIG. 7B is a conceptual plan view showing how charges move by the accordion transfer method.

In FIG. 7A, the electrodes of the transfer path are classified into odd-numbered electrodes Od and even-numbered electrodes Ev.
A well or barrier of a charge transfer path is formed below each of these electrodes. The electron energy in the charge transfer path is schematically shown by a solid broken line. Height indicates electron energy.

First, the electron energy under the odd-numbered electrodes is reduced, a potential well is formed, and charges qa, qb, q
c is accumulated. If the potential barrier disposed between the potential wells is lowered in this state, charge mixing occurs.

Therefore, first, the electron energy below the rightmost even-numbered electrode is reduced, and the potential well is extended to two electrodes. Then, the electric charge qa is distributed on the right side by one electrode. Next, when the electron energy in the left portion of the potential well storing the charge qa is increased and the electron energy in the right potential barrier portion is decreased at the same time, the charge qa moves to the right by one electrode while being distributed over two electrodes.

Then, a potential barrier for two electrodes is formed between the charges qa and qb. Thereafter, the charge qa is sequentially transferred to the right by sequentially increasing the electron energy in the left portion of the charge qa and decreasing the electron energy in the right portion.

When a potential barrier corresponding to two electrodes is generated between the charges qa and qb, if the electron energy of the potential barrier on the right side of the charge qb is reduced at the next timing, the charge qb spreads over the two electrodes. Will be distributed.

At this time, a potential barrier for at least one electrode, usually two electrodes exists between the charges qa and qb.
No charge mixing occurs. In this manner, by transferring the electric charges accumulated in every other electrode to a double pitch and distributing them, electric charges can be transferred.

FIG. 7B schematically shows the distribution of charges transferred in this manner. In the figure, the horizontal axis indicates the passage of time, and the vertical axis indicates the electrodes of the transfer path. In the leftmost state, charges qa, qb,
qc and qd are accumulated. Of these charges, a potential well having a length of two electrodes and a potential barrier having a length of two electrodes are sequentially formed from the charges arranged on the lower side.
The charge is transferred downward while extending twice.

That is, the charge during the transfer is 2
A potential barrier for two electrodes is formed between the charges during the transfer and distributed between the electrodes. In this way, it is possible to transfer the charges accumulated every other electrode while preventing charge mixing. In the rightmost state where the transfer is completed, the electric charges qa, qb, qc, and qd are distributed again every other electrode.

Since the appearance of the potential well and the potential barrier at the time of transfer is similar to the case where the accordion of the musical instrument is gradually widened and then closed again, this charge transfer method is an accordion transfer method. Called. In this method, one signal can be transferred per row with two electrodes per photodiode row.

The present applicant has proposed a domino type transfer system for performing similar charge transfer in a solid-state imaging device including a photodiode matrix, a vertical charge transfer path, and a horizontal charge transfer path. However, instead of the frame transfer, the vertical charge transfer path V
The charges read to the CCD are transferred to the horizontal charge transfer path HCCD while being stretched to twice the length.

In brief, it corresponds to the driving method of the upper half of FIG. 7B. Drive signal is also interline type C
Data is transferred by four-phase driving similar to CD. Also in this method, one signal can be transferred per photodiode row.

As described above, when the image signal is transferred while the interval between the image signals is widened, it takes time to widen the charge distribution. The time at which the image signal stops on the transfer path differs greatly depending on where it is located on the transfer path. Also, the transfer time is naturally different. A dark current is generated in the transfer path. Therefore, a larger dark current is added to image information that stays in the transfer path for a long time.

In order to correct such a dark current component, C
A light-shielding portion called optical black (OB) is formed in the CD imaging device. If the same dark current is generated in an area for extracting image information and an OB for extracting a dark current component, the dark current component can be calibrated by comparing the two.

FIG. 8 is a diagram for explaining the function of such an OB section. FIG. 8A shows a case where the OB unit performs an ideal function. The same dark current is generated in the area and the OB. Although the baseline corresponding to the black level is raised by the dark current, the lifting of the OB part is the same as that of the OB part because the lifting of the OB part is the same as the lifting of the OB part. The components can be calibrated, and only true image information can be extracted.

FIG. 8B is a graph in which the baseline of the image information extracted in this manner is viewed in one field. A true image signal obtained by subtracting the signal of the OB part from the image signal detected in the area part is kept at a constant value during the vertical scanning period V.

However, the pixel structure in the area part is slightly different from the pixel structure in the OB part. In the OB part, the photodiode is covered with an aluminum film. For this reason, OB
The capacitance of the portion is larger than the capacitance of the area portion, and a difference occurs in the accumulated dark current component.

FIG. 8C is a graph showing the baseline of the image signal actually obtained. The baseline of the OB section is lower than the baseline of the area section. For this reason, the image signal base line in the area and the OB
An OB step occurs between the base lines of the sections.

When the signal of the OB section is subtracted from the image signal,
A signal in which an OB step is added to a true image signal is obtained.
The OB step increases as the time during which the image signal stays in the vertical charge transfer path increases.

FIG. 8D is a graph showing a change in the baseline of the image signal in one field. The image signal read at the beginning of the vertical scanning period V has almost no OB level difference because it stays in the vertical transfer path for a short time. On the other hand, the image signal read at the end of the vertical scanning period has a large OB step because it stays in the vertical charge transfer path for a long time. Since the OB step gradually increases with the passage of time, the baseline of the image signal has a shape as indicated by a broken line.

[0027]

As described above,
In a CCD imaging device, even if an OB section is provided, an OB step occurs, and the black level of an image signal changes.

An object of the present invention is to provide a C circuit capable of maintaining a constant black level even when the time in the charge transfer path changes.
An object of the present invention is to provide a CD imaging device.

[0029]

According to the present invention, there is provided a CCD image pickup apparatus for outputting a plurality of vertical charge transfer paths for transferring charge signals and charge signals transferred from the plurality of vertical charge transfer paths. Horizontal charge transfer paths, each of which is coupled to the vertical charge transfer path, and a plurality of rows of photodiodes in the area for capturing an image signal, and a plurality of rows between the photodiodes in the area and the horizontal charge transfer paths. An imaging chip including a lower OB portion photodiode, each of which is arranged so as to be coupled to the vertical charge transfer path and is shielded from light, but has the same electrostatic characteristics as the photodiode in the area portion; By performing an extrapolation operation based on signals from the photodiodes in a plurality of rows in the OB section,
A circuit for estimating and calculating a dark current component of image information in the area.

[0030]

Since the photodiodes in the lower OB section have the same electrostatic characteristics as the photodiodes in the area section, a dark current equivalent to that in the area section is generated in the lower OB section. If the dark current component of the area is estimated and calculated based on the dark current component, highly accurate dark current information can be obtained.

By inputting the subject image to the CCD image pickup means and subtracting the estimated and calculated dark current component from the image information of the area obtained by driving the vertical transfer path, highly accurate image information can be obtained. .

In the image information thus obtained, the black level can be maintained at a constant value even when the OB level changes.

[0033]

FIG. 1 is a block diagram showing a configuration of a CCD image pickup apparatus according to an embodiment of the present invention. Light from the subject is collected by the lens 1 and passes through
The image is projected on the CD imaging chip 3. CCD imaging chip 3
A semiconductor imaging circuit including a matrix of photodiodes, a vertical charge transfer path, a horizontal charge transfer path, and the like is incorporated therein. The driver circuit 4 supplies a driving signal for driving the CCD to the CCD imaging chip 3.

The image signal from the CCD image pickup chip 3 is subjected to processing such as detection of a difference in the signal level of the OB section in a signal processing circuit 5, and is converted into a digital signal via an A / D converter 6 to become an image signal. Input to the processing circuit 8.

An input terminal 10 of the image signal processing circuit 8 is connected to a movable contact of a changeover switch 12, and a fixed contact of the changeover switch 12 is connected to a black level detection operation circuit 11 and a subtractor 13.

The black level detection operation circuit 11 extrapolates and calculates a shading component in the entire screen based on the lower OB signal supplied at the beginning of the vertical scanning period to generate a black level signal. The output signal of the black level detection operation circuit 11 is connected to a subtractor 13, and the subtractor 13 performs a process of subtracting the black level signal from the image signal.

The output signal of the subtractor 13 is supplied to a numerical processor 14 and subjected to processing such as data compression, and then supplied to the recording unit 9 from an output terminal. The recording unit 9 is composed of, for example, a memory card.

Switches S1, S
2, a switch circuit 17 including S3 is provided. For example, the switch S1 is a first contact switch of the release switch, and the switch S2 is a second contact switch of the release switch.
This is a contact switch, and the switch S3 is a power switch.

When the switch button on the camera is pressed, the power switch S3 is turned on first, and then the first contact switch S1 and the second contact switch S2 are turned on. The CCD imaging device is also provided with a system control circuit 18 for controlling the entire system. When the power switch S3 is turned on, the CCD image pickup device is energized and becomes ready for image pickup. When the first contact switch S1 is turned on, the mode is set to the automatic exposure and the automatic distance measurement, and the motor M1,
By driving M2, the focal length of the lens 1 and the proper aperture of the iris 2 are selected. Further, selection of a shutter speed is also performed.

The CCD imaging chip 3 performs accordion transfer (domino transfer) as described with reference to FIG. 7 in the vertical charge transfer path. Therefore, the stay time of the image signal read from the photodiode to the vertical charge transfer path changes depending on the position in the vertical charge transfer path.

An image signal that stays in the vertical charge transfer path for a relatively long time receives a relatively large dark current. The corresponding dark current component is calculated by the black level detection calculation circuit 11.
By subtracting the black level signal from the image signal by the subtractor 13, an image signal from which the dark current component has been removed can be obtained.

FIG. 2 shows the configuration of the CCD image pickup chip.
FIG. 2A shows a plan configuration of the CCD imaging chip 3.
The CCD imaging chip 3 has an area 2 on which an image is projected.
1 and an OB section 22 covered with a light shielding film.
In the area, a large number of photodiodes PD arranged in a matrix, a vertical charge transfer path VCCD formed along each column of the photodiodes, a transfer gate TG for controlling charge transfer from the photodiodes to the VCCD, and the like are formed. ing.

The OB section is arranged below the area section 21,
It includes an OBb portion 22b that is shielded from light by an insulator, such as a filter or a light-shielding plate, and an OBa portion 22a that is disposed to the right of the area portion 21 and that is shielded from light by a metal such as aluminum. As described later, the OBa section 22 on the right side of the area section 21
a is not always necessary.

FIG. 2B is a sectional view showing the structure of the pixel in the OBa section. Substrate 31 formed of n-type Si
A p-type well 32 is arranged on the substrate. p-type well 3
2 has an n-type region 33 forming a photodiode PD and n ⁻ forming a vertical charge transfer path (VCCD).
Region 34, photodiode and vertical charge transfer path VCCD
And ap ⁺ -type region 35 forming a transfer gate (TG) is formed. The p ⁺ type region 36 is formed around a pair of a photodiode and a vertical charge transfer path, and performs electrical isolation.

An insulating film 37 made of SiO ₂ or the like is arranged on the surface of the semiconductor substrate. In the insulating film 37, a polycrystalline silicon gate 38 for controlling the potential of the transfer gate TG and the vertical charge transfer path VCCD is arranged. The surface of the insulating layer 37 is covered with a light-shielding layer 39 of aluminum or the like.
Covered with. Therefore, light incident on the photodiode PD is blocked.

In the pixels in the area 21, an opening is formed in the aluminum light shielding layer 39 on the photodiode PD. Therefore, the incident light is introduced into the photodiode PD. The photodiode PD detects the intensity of the incident light,
Image information can be obtained by transferring the photoelectrically converted charge to the vertical charge transfer path VCCD via the transfer gate TG and extracting a charge signal through the vertical charge transfer path VCCD.

FIG. 2C is a sectional view showing the pixel structure of the OBb portion. The configuration in the semiconductor substrate and the configuration in the insulating layer 37 are the same as the configuration of the pixels in the area. However, on the aluminum light shielding layer 39 in which the opening is formed,
A light shielding material 40 formed of an insulating material such as a filter or a light shielding plate is arranged.

Accordingly, although the photodiode PD is formed in the semiconductor substrate, no light is incident on the photodiode PD. However, the light shielding material 40 does not affect the electrostatic characteristics of the pixel. When the pixels in the OBb section are driven in the same manner as the pixels in the area section, the charge signal read out by the vertical charge transfer path VCCD is only a dark current component.

Here, the configuration of the area section and the configurations of the OBa section and the OBb section will be compared. In the OBa section, the aluminum light shielding layer 39 exists on the photodiode PD. This difference in configuration results in a difference in parasitic capacitance in the pixel. Therefore, the amount of dark current induced in the vertical charge transfer path VCCD is affected. In the OBb part, the aluminum light shielding layer 39 does not exist on the photodiode PD as in the area part. However, a light shielding material 40 made of an insulator or the like which does not affect the electrostatic characteristics is disposed thereon. Therefore, there is no incident light in the OBb part, and the same dark current as in the area part can be detected.

FIG. 3 is a diagram for explaining an OB step. In the CCD imaging chip, as shown in FIG. 2A, a large number of photodiodes PD are arranged in a matrix in the area 21. A vertical charge transfer path VCCD is arranged adjacent to each column of the photodiodes PD, and is connected to the photodiodes PD by a transfer gate TG.

From the photodiode PD to the vertical charge transfer path V
The charge signal read to the CCD is transferred to the vertical charge transfer path VC.
CDs are sequentially transferred downward. At this time, the image information corresponding to the photodiode PD arranged below the area 21 and the image information corresponding to the photodiode PD arranged above the area 21 are separated by the vertical charge transfer path VCC.
The time to stay at D is very different.

For example, assuming that one horizontal scanning period is 1H, the time during which the image information read from the photodiode PD arranged in the lowermost row stops in the vertical charge transfer path VCCD is 1H, and is read out to the horizontal charge transfer path. The time until it is 1H.

On the other hand, the image information read out from the photodiode PD arranged in the uppermost row to the vertical charge transfer path VCCD is stopped for 500H before the transfer starts when the number of rows is 1,000, and 500H for the transfer. Need time. Therefore, the entire time until reading is 1000H
Becomes

As described above, the stop time and the read time greatly change depending on the vertical position.
As shown in (A) and (B), the OB level difference greatly changes depending on from which position in the area the image information is read. FIG. 3A shows a case where only dark current is read in a light-shielded state, and FIG. 3B shows a state where image signals and dark current are read in an open state.

In FIGS. 3A and 3B, the base line of the image information increases as the vertical position increases, and the OB step increases. When such image information is displayed as it is, the screen is displayed so as to gradually become brighter as it goes down.

By the way, in this embodiment, FIG.
As shown in (A), an OBb portion 22b having the same electrostatic characteristics as the pixels in the area portion is formed below the area portion 22. Since the OBb portion 22b is shielded from light by the light shielding material 40, only a dark current is generated in the OBb portion 22b. This dark current has the same characteristics as the dark current in the area, as shown in FIG.

Even when light enters the area,
As shown in FIG. 3B, only the dark current component is generated in the OBb portion, and the dark current in the OBb portion and the dark current in the area portion have the same characteristics.

Therefore, as shown in FIG.
The OB step that increases for each line can be obtained by detecting the dark current of the section. In this way, by detecting and extrapolating the OB step, the OB step in the entire area 21 can be estimated.

The black level detection operation circuit 11 shown in FIG.
This circuit is located below the area, detects a dark current in the OBb section having the same electrostatic characteristics as the pixels in the area, detects the dark current in the area by an estimation operation, and generates a black level signal. The image signal detected from the area is subtracted from the black level signal in the arithmetic unit 13 and an image signal in which the OB step is eliminated is supplied.

Since the subtractor 13 subtracts the black level information from the image information, the OBa at the right end of each horizontal scanning line is used.
The black level information of a copy is not always necessary. Therefore, the OBa section 22 on the right side of the area section 21 shown in FIG.
a may be omitted.

If the OBa section 22a is omitted, there is no OB step in the image signal for one horizontal scanning line.
It is not always necessary to provide an OB portion disposed at the end of each horizontal scanning line, but a change in a baseline of image information due to a dark current component is referred to as an OB step in this specification.

FIG. 4 shows a CCD according to another embodiment of the present invention.
FIG. 3 is a diagram illustrating an imaging device. FIG.
2 shows a planar configuration of a CD imaging chip. In this configuration,
The point where the OBa section 22a exists on the right side of the area section 21 is as follows.
The configuration is the same as that of FIG. 2A, but the OBb portions 22 b having the same electrostatic characteristics as the pixels in the area portion are arranged above and below the area portion 21.

Therefore, as shown in FIG. 4B, the output from the CCD image pickup chip in the light-shielded state is output to the OBb section disposed below the area section, the area section, and the OBb section disposed above the area section. And the electrostatic properties are equal. Therefore, the generated dark currents have the same characteristics.

As described above, since the OB portions having the same electrostatic characteristics as the area portion are arranged before and after the area portion, the OB level difference in these areas is detected and interpolated to detect the OB level difference in the area portion. An estimation operation can be performed.

In the case of this embodiment, since the OB level difference in the area cannot be calculated until all the pixel signals have been read out, the image signal processing circuit 8 shown in FIG.
As shown in (1), an image information memory 19 is further connected. The black level detection calculation circuit 11 detects the shading components of the OBb portion at the beginning and end of the image output, estimates the black level in the entire area portion, and outputs it.
The black level signal is subtracted from the image information once stored in the image information memory 19 by the subtractor 13, and only the image information whose shading component is calibrated is output.

As described above, in any of the above-described embodiments, the black level detection calculation circuit 11 properly estimates and calculates the shading component (black level) in the area, and the subtractor 13 subtracts the shading component from the image signal. As a result, only the true image information is stored in the numerical processor 1
4 given.

FIG. 5 shows a CC having a configuration as shown in FIGS.
9 is a flowchart illustrating an imaging routine when actually performing imaging using the D imaging apparatus. When the power is turned on in step A1, the process proceeds to step A2, where the first contact switch S
It is determined whether 1 is on. When the first contact switch S1 is not turned on, step A2 is repeated according to the arrow of NO.

When the first contact switch S1 is ON, the operation proceeds to step A3 according to the arrow YES to start domino driving of the vertical charge transfer path VCCD, and transfer the charge of the vertical charge transfer path VCCD to the horizontal charge transfer path HCCD. Transfer to

Next, the process proceeds to step A4, in which an automatic exposure and an automatic distance measuring (AE / AF) operation are started as a preparation stage for image pickup. Next, the process proceeds to step A5, where it is determined whether the AE / AF operation has been completed. If the AE / AF operation has not been completed, the process returns to step A4 according to a NO arrow.

When the AE / AF operation is completed, YE
The process proceeds to step A6 according to the arrow of S, and it is determined whether the second contact switch S2 is turned on. When the second contact switch S2 is not turned on, the process returns to step A4 according to a NO arrow.

If the second contact switch S2 is on,
According to the arrow of YES, the process proceeds to step A7, and the main imaging is performed. When the main imaging is performed, the dark current component of the OBb portion is first output from the CCD imaging chip, and then the pixel signal component of the area portion is output.

In step A8, a signal output from the CCD image pickup chip is read out, and O
The dark current component in the Bb portion is detected, and the dark current component in the entire area is calculated by extrapolation. Thus, the inclination of the OB step in the area is given.

Subsequently, in step A9, the OB level difference data is subtracted from the image signal to obtain an image signal from which the dark current component has been removed for each row. In step A10, the image signal from which the OB steps thus obtained are eliminated is recorded in the recording unit. Recording can be either magnetic recording or digital storage. Thus, the imaging routine is completed.

FIG. 6 is a flowchart showing an imaging routine according to another embodiment of the present invention shown in FIG. In step B1, the power is turned on. Next, step B
At 2, it is determined whether the first contact switch S1 has been turned on. When the first contact switch S1 is not turned on, NO
Step B2 is repeated according to the arrow.

When the first contact switch S1 is on, the flow advances to step B3 according to the arrow YES to start domino driving. Subsequently, in step B4, automatic exposure and automatic distance measurement (AE / AF) are started as a preparation process for imaging.

Next, at step B5, it is determined whether or not the AE / AF operation has been completed. If not completed, the process returns to step B4 according to the arrow of NO. If the AE / AF operation has been completed, the process proceeds to step B6 according to the YES arrow,
It is determined whether the second contact switch S2 has been turned on.

If the second contact switch S2 is not turned on, the process returns to step B4 according to a NO arrow. When the second contact switch S2 is ON, the process proceeds to step B7 according to the arrow of YES to perform the main imaging. Image information including a dark current component is obtained by the main imaging.

Next, in step B8, the image signals from all the pixels are read out, and the level information of the OBb portion which has been read out first is stored in the black level detection operation circuit 11 shown in FIG.
To memory.

Subsequently, in step B9, the data of the area is stored in the image information memory 19 shown in FIG. Next, in step B10, the level difference data of the OBb section supplied last is supplied to the black level detection arithmetic circuit 1
The OB step in the area is estimated and calculated by combining the OB step in the area 1 with the OB step information below the area previously stored in the black level detection calculation circuit.

In this way, O in the entire area
After obtaining the B level difference information, in step B11, the subtractor 13 subtracts the OB level supplied from the black level detection operation circuit 11 from the image information supplied from the image information memory 19, and only the true image information is obtained. obtain.

In this manner, image information from which the shading component has been deleted in line units can be obtained. This image information is recorded in the recording unit in step B12. In this way, image information from which dark current has been removed is obtained, and the imaging routine is completed.

In each of the imaging routines shown in FIGS. 5 and 6, the image information including the dark current component obtained in the main imaging is obtained by correcting the OB step since the dark current component is subtracted thereafter. . O with the same electrostatic characteristics as the area
The portion B may be provided on only one of the area portions or on both the upper and lower sides. When it is provided on one side, the structure is simplified, and when it is provided on both sides, the accuracy is high.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example,
It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0084]

As described above, according to the present invention,
Image information in which the OB level difference has been corrected can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a CCD imaging device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a CCD imaging chip used in the configuration of FIG. 1; FIG. 2A is a plan view illustrating a plan configuration, and FIGS. 2B and 2C are cross-sectional views illustrating a configuration of a pixel in an OBa portion and an OBb portion.

FIG. 3 is a graph for explaining an image signal.

FIG. 4 is a diagram for explaining another embodiment of the present invention. FIG. 4A is a plan view of a CCD imaging chip, and FIG.
4B is a graph of an output signal, and FIG. 4C is a partial block diagram of an image signal processing circuit.

FIG. 5 is a flowchart showing an imaging routine according to the embodiment shown in FIGS. 2 and 3;

FIG. 6 is a flowchart showing an imaging routine according to another embodiment shown in FIG.

FIG. 7 is a conceptual diagram for explaining an accordion transfer method.

FIG. 8 is a conceptual diagram for explaining a function of an OB unit.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 lens 2 iris 3 CCD imaging chip 4 driver circuit 5 signal processing circuit 6 A / D converter 8 image signal processing circuit 9 recording unit 10 input terminal 11 black level detection calculation circuit 12 changeover switch 13 subtractor 14 numerical calculation processor 17 switch Reference Signs List 18 system control unit 21 area part 22 OB part 31 n-type substrate 32 p-type well 33 n-type area (photodiode) 34 n ^- type area (VCCD) 39 light shielding layer 40 light shielding material

Claims (4)

(57) [Claims] 1. A plurality of vertical charge transfer paths (VCCD) for transferring charge signals, and a horizontal charge transfer path (HCCD) for collectively outputting charge signals transferred from the plurality of vertical charge transfer paths. , Each of which is coupled to the vertical charge transfer path and has a photodiode (P) in an area for picking up an image signal.
D), and a plurality of rows between the photodiodes in the area and the horizontal charge transfer paths, each of which is arranged so as to be coupled to the vertical charge transfer path and is shielded from light, but equivalent to the photodiodes in the area. An imaging chip including a photodiode in a lower OB portion having the following electrostatic characteristics: and a dark current of image information in the area portion by performing an extrapolation operation based on signals from the photodiodes in a plurality of rows in the lower OB portion. And a circuit (11) for estimating and calculating components. 2. A plurality of vertical charge transfer paths (VCCD) for transferring charge signals, and a horizontal charge transfer path (HCCD) for collectively outputting charge signals transferred from the plurality of vertical charge transfer paths. , Each of which is coupled to the vertical charge transfer path and has a photodiode (P
D), between the photodiode in the area and the horizontal charge transfer path,
Each of the photodiodes is disposed so as to be coupled to the vertical charge transfer path and is shielded from light, but has a lower OB part photodiode having the same electrostatic characteristics as the photodiode in the area part. And an imaging chip including an upper OB part photodiode, which is arranged on the side, is coupled to the vertical charge transfer path, is shielded from light, but has the same electrostatic characteristics as the photodiode in the area part, and reads out from the area part. An image information memory (19) for storing the image information obtained by the interpolation and an interpolation operation based on the signals from the photodiodes of the lower OB section and the upper OB section, thereby estimating the dark current component of the image information in the area section. Circuit to do (11)
CCD imaging device having: 3. A step of extrapolating a dark current component read from the photodiode in the lower OB section and subtracting a dark current component in the area section using the CCD image pickup device according to claim 1, Calculating a dark current component obtained by the extrapolation operation from the read image information. 4. A CCD imaging device according to claim 2,
Calculating the dark current component of the area by interpolating the dark current components read from the photodiodes of the lower OB section and the upper OB section; and calculating the interpolation calculation from the image information read from the photodiodes of the area section. Subtracting a dark current component.