JP2007088750A - Ccd solid-state imaging element and drive method thereof, and digital camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a CCD solid-state imaging element or the like capable of realizing a shutter of ultrahigh speed such as 1/10000 second or the like. <P>SOLUTION: The CCD solid-state imaging element provided with a plurality of pohotodiodes PDs formed on the surface of a semiconductor substrate in an array form and with vertical transfer path VCCDs for receiving light receiving electric charges of each photodiode PD via each transfer gate TG and for transferring the electric charges, includes a drive means that makes the electronic shutter "open" by discarding even unnecessary electric charges to the semiconductor substrate (Fig. 4(b)) when the light receiving electric charges of the photodiodes PDs are discarded to the semiconductor substrate and makes the electronic shutter "close" at a point of time when a potential barrier of the transfer gates TG is temporarily decreased and the light receiving electric charges stored in the photodiodes PDs after the electronic shutter is made "open" are read by the vertical transmission paths via the transfer gates (Fig. 4(e)). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a CCD (Charge Coupled Device) type solid-state imaging device, and more particularly to a CCD type solid-state imaging device capable of realizing an ultrafast shutter such as [1/10000] seconds, a driving method thereof, and a digital camera. About.

  For example, when a still image is captured by a digital camera equipped with an IT (intertransfer) -CCD type solid-state imaging device, the aperture opening amount and the shutter speed are determined in order to obtain a required exposure amount. The shutter speed is the time from the shutter “open” to the shutter “closed”, but in a digital camera using an IT-CCD solid-state image sensor, the residual charge of the photodiode mounted on the solid-state image sensor is emptied by the overflow drain function. The time when the electronic shutter is set to “open”, and the time when the mechanical shutter is closed and the photodiode is shielded from light is set to “close”.

  In addition, there exists the following patent document 1 as a thing relevant to a prior art.

Japanese Patent Publication No. 2-25313

  In a camera that determines the time when the shutter is closed by a mechanical shutter, the shutter speed is often restricted depending on the operation speed of the mechanical shutter, and a shutter speed of [1/2000] seconds can be realized. It is difficult to realize a very high speed shutter such as [10000] seconds.

  An object of the present invention is to provide a CCD solid-state imaging device capable of realizing an ultra-high-speed shutter, a driving method thereof, and a digital camera.

  A CCD type solid-state imaging device of the present invention is a CCD type comprising a plurality of photodiodes formed in an array on the surface of a semiconductor substrate, and a vertical transfer path for receiving and transferring the received light charges of each photodiode via a transfer gate. In the solid-state imaging device, when the received light charge of the photodiode is discarded to the semiconductor substrate side, unnecessary electric charges on the vertical transfer path are also discarded to the semiconductor substrate side to make the electronic shutter “open”, and the potential barrier of the transfer gate And a driving means for closing the electronic shutter when the received light charge accumulated in the photodiode after the potential shutter is opened is read to the vertical transfer path through the transfer gate. And

  The CCD type solid-state imaging device of the present invention is an inter-transfer type CCD, and once the received light charges read to the vertical transfer path are transferred, the received charges in every other potential well on the vertical transfer path are once matched. After the transfer, the received charge remaining in the vertical transfer path is transferred to the phototransistor. After the transfer, the received charge returned to the phototransistor is read to the vertical transfer path and the received charge is transferred to the vertical transfer path. It is characterized by transferring by.

  A method for driving a CCD solid-state imaging device according to the present invention includes a plurality of photodiodes formed in an array on the surface of a semiconductor substrate, and a vertical transfer path for receiving and transferring received light charges of each photodiode via a transfer gate. In the driving method of the CCD type solid-state imaging device provided, when the received light charge of the photodiode is discarded to the semiconductor substrate side, the unnecessary charge on the vertical transfer path is also discarded to the semiconductor substrate side to make the electronic shutter `` open '', The electronic shutter is “closed” when the potential barrier of the transfer gate is temporarily lowered and the light-receiving charge accumulated in the photodiode after the potential shutter is opened is read to the vertical transfer path through the transfer gate. It is characterized by.

  The driving method of the CCD type solid-state imaging device of the present invention is an inter-transfer type CCD, and before transferring the received light charges read to the vertical transfer path, the received light charges in every other potential well on the vertical transfer path. Is transferred back to the corresponding phototransistor and then the received light charge remaining on the vertical transfer path is transferred.After the transfer, the received light charge returned to the phototransistor is read to the vertical transfer path and the received charge is transferred to the phototransistor. The transfer is performed using a vertical transfer path.

  A digital camera according to the present invention is equipped with any one of the CCD solid-state imaging devices described above.

  The digital camera according to the present invention includes a mechanical shutter that is “closed” after the electronic shutter is “closed”.

  According to the present invention, it is possible to realize an ultrafast shutter such as [1/10000] seconds.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram of a digital still camera according to an embodiment of the present invention. This digital still camera includes a photographing lens 10, an IT-CCD type solid-state imaging device 11, a mechanical shutter 12 provided between them, a diaphragm (not shown), an infrared cut filter 13, and an optical low-pass filter 14. Is provided.

  The CPU 15 that controls the entire digital still camera controls the light emitting unit 16 and the light receiving unit 17 for flash, and also controls the lens driving unit 18 to adjust the position of the photographing lens 10 to the focus position, thereby opening the aperture. And the closing time point of the mechanical shutter is controlled via the shutter drive unit 19.

  Further, the CPU 15 drives and controls the CCD solid-state image pickup device 11 as will be described in detail later through an image pickup device driving unit 20 manufactured on the chip on which the solid-state image pickup device 11 is formed, and images the image through the photographing lens 10. The subject image is output as a color signal. In addition, a user instruction signal is input to the CPU 15 through the operation unit 21, and the CPU 15 performs various controls according to the instruction.

  The electric control system of the digital still camera converts the analog signal processing unit 22 connected to the output of the solid-state imaging device 11 and the RGB image signal (color signal) output from the analog signal processing unit 22 into a digital signal. And an A / D conversion circuit 23, which are controlled by the CPU 15.

  Furthermore, the electric control system of the digital still camera includes a memory control unit 25 connected to the main memory 24, a digital signal processing unit 26 that performs image processing, and compresses the captured image into a JPEG image and decompresses the compressed image. Mounted on the back side of the camera, the compression / decompression processing unit 27, the integration unit 28 for integrating the photometric data and adjusting the white balance gain, the external memory control unit 30 to which the removable recording medium 29 is connected. And a display control unit 32 to which the liquid crystal display unit 31 is connected. These are connected to each other by a control bus 33 and a data bus 34, and are controlled by a command from the CPU 15.

  FIG. 2 is a schematic view of the surface of the CCD solid-state imaging device 11 shown in FIG. A large number of photodiodes (PD) 41 are arranged in a square lattice pattern on the light-receiving surface of the semiconductor substrate of the solid-state imaging device 11. The right side of each photodiode row receives the light received by the photodiodes 41 in the vertical direction. A vertical transfer path (VCCD) 42 for transferring is formed, and a horizontal transfer path 43 for receiving the photocharge transferred by each vertical transfer path 42 and transferring it in the horizontal direction is formed at the lower side of the solid-state imaging device 11. Yes.

  An image signal corresponding to the received light charges transferred through the horizontal transfer path 43 is output from the amplifier 44 provided at the output stage of the horizontal transfer path 43 to the analog signal processing unit 22 in FIG.

  FIG. 3 is an enlarged schematic view of one row of the photodiodes and vertical transfer paths of the solid-state imaging device 11 shown in FIG. The vertical transfer path 42 includes a buried channel formed on the surface portion of the semiconductor substrate and transfer electrodes V1, V2, V3, V4, V1,... Arranged in a line on the buried channel.

  In the illustrated example, two transfer electrodes are provided for one photodiode, and each photodiode and odd-numbered transfer electrodes V1, V3, V1,... Are referred to as transfer gates (hereinafter referred to as TG). ) 45, and as will be described later, the received charge is transferred between the photodiode 41 and the vertical transfer path 42 via the transfer gate 45.

  FIG. 4 is a diagram for explaining the operation of the solid-state imaging device 11 using the potential shape at the position of the IV-IV line in FIG. Before the digital still camera shown in FIG. 1 captures a still image, the mechanical shutter 12 is in an “open” state, and an unnecessary charge 51 is generated in the photodiode 41 as shown in FIG. is doing. Further, unnecessary charges 52 remain in the vertical transfer path 42 covered with a light shielding film (not shown).

  When the user presses the release button of the digital still camera, the CPU 15 outputs a command to the image sensor driving unit 20 and discards unnecessary charges 51 and 52 on the back side of the semiconductor substrate as shown in FIG. That is, a voltage for raising the potential well of the vertical transfer path is applied to the transfer electrode, a voltage for lowering the barrier height of the TG 45 is applied to the TG 45, and an overflow drain control voltage is further applied.

  Unnecessary charges are discarded by applying these voltages in an instant. The photodiode starts exposure from the electronic shutter “open” at the moment when the potential shape returns to its original state (FIG. 4C), and during the exposure period (FIG. 4). 4 (d)), the received light charge corresponding to the exposure amount is accumulated in the photodiode.

  Next, the shutter is closed, but in this embodiment, as shown in FIG. 4E, the CPU 15 instructs the image sensor driving unit 20 to control the voltage applied to the TG, and at the TG position. The shutter is closed by moving the accumulated charge of the photodiode to the vertical transfer path by lowering the potential barrier for a moment and then returning the potential barrier of the TG to the original state (FIG. 4 (f)).

  After returning the potential barrier of the TG, the CPU 15 controls the mechanical shutter drive unit 19 to close the mechanical shutter 12 and block the incident light to the photodiode.

  The state of FIG. 4F is shown as “f state” in FIG. That is, in the vertical transfer path 42, potential wells are formed under the odd-numbered transfer electrodes V1, V3, V1,..., And the light-receiving charges of the photodiodes (PD1 to PD5) have moved into each potential well. It has become.

  However, in the “f state” of FIG. 5, it is not possible to transfer each received light charge to the horizontal transfer path (HCCD). This is because there is only one transfer electrode provided between the potential wells in which each received charge is placed.

  Therefore, in order to enable transfer to the horizontal transfer path, in the present embodiment, the light-receiving charge that has been moved below the transfer electrode V3 is returned to the corresponding photodiode (PD2, PD4).

  However, since there is a possibility that electric charge is accumulated in the photodiode between the shutter “closed” by the TG control and the mechanical shutter closed, the overflow drain control is performed as shown in FIG. Unnecessary charges of the diode are discarded on the semiconductor substrate side.

  After that, the TG potential barrier of the photodiodes (PD2, PD4) is lowered and the voltage applied to the transfer electrode V3 is controlled to raise the potential well. As shown in FIG. Return the received charge to the photodiode side. As a result, as shown in the “h state” in FIG. 5, the received light charge remaining on the vertical transfer path can be transferred to the horizontal transfer path.

  After the transfer of the received charge to the horizontal transfer path is completed, the received charge returned to the photodiode side in FIG. 4H is returned to the vertical transfer path (“i state” in FIG. 5), and the horizontal transfer is performed. Transfer to the road.

  As described above, in the digital still camera equipped with the solid-state imaging device according to the present embodiment, both the shutter “open” and the shutter “closed” are constituted by the electronic shutter, and therefore, an ultrafast shutter of [1/10000] seconds. But it will be possible.

  In the above-described embodiment, the IT-CCD type solid-state image pickup device has been described as an example. However, the present invention can also be applied to a CCD type solid-state image pickup device having a progressive transfer readable vertical transfer path. In this case, needless to say, it is not necessary to return the received light charges read out to the vertical transfer path to the photodiode.

  Since the solid-state imaging device according to the present invention can realize an ultra-high-speed shutter, it is useful when applied to a digital camera capable of high-speed shooting.

1 is a configuration diagram of a digital still camera according to an embodiment of the present invention. It is a surface schematic diagram of the solid-state image sensor shown in FIG. It is a schematic diagram for 1 row of the solid-state image sensor shown in FIG. It is explanatory drawing which shows the drive procedure of the solid-state image sensor shown in FIG. It is drive explanatory drawing of the solid-state image sensor shown in FIG.

Explanation of symbols

11 Solid-state image sensor 12 Mechanical shutter 15 CPU
20 Image sensor drive unit 41 Photodiode (PD)
42 Vertical transfer path (VCCD)
43 Horizontal transfer path (HCCD)
45 Transfer gate (TG)

Claims (6)

  In a CCD type solid-state imaging device comprising a plurality of photodiodes formed in an array on the surface of a semiconductor substrate, and a vertical transfer path for receiving and transferring the received light charges of each photodiode through a transfer gate, the light reception of the photodiode When the electric charge is discarded to the semiconductor substrate side, unnecessary electric charges on the vertical transfer path are also discarded to the semiconductor substrate side to make the electronic shutter “open”, and the potential barrier of the transfer gate is temporarily lowered to make the electric potential shutter “open”. A CCD type solid-state image pickup device comprising: a driving unit that closes the electronic shutter when the received charge accumulated in the photodiode is read out to the vertical transfer path through the transfer gate.   This is an inter-transfer type CCD, and before transferring the received light charges read to the vertical transfer path, the received charge in every other potential well on the vertical transfer path is once returned to the corresponding phototransistor and then transferred to the vertical transfer path. The received light charge remaining in the path is transferred, and after the transfer, the received charge returned to the phototransistor is read out to the vertical transfer path and transferred to the vertical transfer path. The CCD solid-state imaging device according to 1.   In the method for driving a CCD type solid-state imaging device, comprising: a plurality of photodiodes formed in an array on the surface of a semiconductor substrate; and a vertical transfer path for receiving and transferring light received by each photodiode through a transfer gate. When the received light charge of the diode is discarded to the semiconductor substrate side, unnecessary electric charges on the vertical transfer path are also discarded to the semiconductor substrate side to set the electronic shutter to “open”, and the potential barrier of the transfer gate is temporarily lowered to reduce the potential shutter. A method of driving a CCD type solid-state imaging device, characterized in that the electronic shutter is closed when the received light charge accumulated in the photodiode after “opening” is read to the vertical transfer path through the transfer gate.   This is an inter-transfer type CCD, and before transferring the received light charges read to the vertical transfer path, the received charge in every other potential well on the vertical transfer path is once returned to the corresponding phototransistor and then transferred to the vertical transfer path. The received light charge remaining in the path is transferred, and after the transfer, the received charge returned to the phototransistor is read out to the vertical transfer path and transferred to the vertical transfer path. 3. The CCD solid-state imaging device according to 3.   A digital camera comprising the CCD solid-state imaging device according to claim 1 or 2 mounted thereon.   6. The digital camera according to claim 5, further comprising a mechanical shutter that is closed after the electronic shutter is closed.

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