JP2007105236A - Capsule type endoscope device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that when a fast-moving internal organ or the like is captured by a conventional capsule type endoscope device capturing an image using a rolling shutter type CMOS sensor, the capturing times of the captured image are different according to respective lines and the captured image is distorted. <P>SOLUTION: A global shutter type CMOS sensor 202 accumulates charges obtained by simultaneously exposing all the pixels of an internal site and photoelectrically converting them, transmits the charges to output transistors in all the pixels simultaneously, and then sequentially reads the output transistors of the respective pixels by defining the charges as changes in thresholds. Even if capturing the image of the fast-moving organ in the body, the captured image to be displayed is a precise image with no movement and distortion. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a capsule endoscope apparatus, and more particularly to a swallowable capsule endoscope apparatus that uses a global shutter type CMOS area sensor as an image pickup device to photograph a body lumen of a human being, an animal, or the like. .

  An endoscope for photographing the body lumen of a living organism such as a human being or an animal is a tube-type endoscope (for example, a patent) that inserts a thin insertion portion having a camera for photographing inside the body into the patient's body. And a capsule endoscope in which the camera system is entirely contained in a small capsule (for example, see Patent Document 2). In a capsule endoscope, there is a method of loading small internal batteries that must be driven independently in the body (for example, see Patent Document 3).

  On the other hand, a CCD (Charge Coupled Device) type imaging device (hereinafter simply referred to as a CCD) and a CMOS (Complementary Metal-Oxide Semiconductor) type imaging device (hereinafter referred to as a CMOS sensor) are known as solid-state imaging devices. However, the CMOS sensor can be driven at a lower voltage than the CCD, and can easily meet the demands for a large number of pixels and a high-speed reading, and is also used as an image sensor in the above-mentioned Patent Document 2. In recent years, the image quality of this CMOS sensor has been improved by miniaturization and improvement of process technology, and thus has attracted attention as an imaging device capable of obtaining a high-definition image with low power consumption.

  FIG. 6 shows a configuration diagram of an example of a capsule endoscope apparatus using a conventional CMOS sensor. A conventional capsule endoscope apparatus using the above CMOS sensor includes an extracorporeal apparatus shown in FIG. 6A and an in-vivo apparatus shown in FIG. The extracorporeal device shown in FIG. 6A includes an external antenna 110, an image processing device 111, and an output device 112. 6B is a capsule endoscope 101 in which a patient swallows the entire body and observes the inside of the body, and includes a CMOS sensor 102, a circuit unit 103, a power source 104, an antenna 105, a light emitting device 106, The light shielding layer 107 and the objective lens 108 are housed in an elliptical sphere transparent member 109.

  The light emitting device 106 includes a fluorescent tube or a light emitting diode (LED), and illuminates brightly so that a dark body can be photographed. The light showing the in-vivo image illuminated by the light emitting device 106 enters the CMOS sensor 102 through the transparent member 109 and the objective lens 108, where it is photoelectrically converted into an electrical signal (imaging signal). An electrical signal (imaging signal) from the CMOS sensor 102 is subjected to predetermined arithmetic processing, image compression processing, and the like in the circuit unit 103, and then the outside of the external device shown in FIG. It is transmitted to the antenna 110.

  The imaging signal received by the extracorporeal antenna 110 is subjected to predetermined image processing by the image processing device 111, and then sent to the output device 112 for display and the like, so that an external person can image the inside of the patient or the like. Can be seen as. In FIG. 6B, the CMOS sensor 102 and the circuit unit 103 are described separately, but here they are conceptually separated, and the CMOS sensor 102 and the circuit unit 103 are integrated into one chip. There are also. Further, since the capsule endoscope must be able to be driven independently in the body, a battery is used as the power source 104.

  Here, the CMOS sensor 102 will be described in more detail. This is a conventionally known rolling shutter type CMOS sensor (see, for example, Patent Document 4). FIG. 7 shows an equivalent circuit diagram of an example of the conventional CMOS sensor. In the CMOS sensor shown in the figure, for simplicity, the unit pixel 1 has a 2 × 2 pixel arrangement in which two horizontal pixels and two vertical pixels are arranged. The unit pixel 1 includes a photodiode (PD) 2 for photoelectrically converting a subject image, a signal charge amplification MOS field effect transistor (hereinafter referred to as MOSFET) 3, a charge transfer MOSFET 4, a reset MOSFET 5, and a selection. The power supply line 6 is connected to the drains of the MOSFETs 3 and 5, and the source of the amplification MOSFET 3 is connected to the drain of the selection MOSFET 7.

  The gate electrode of the amplification MOSFET 3 is in a floating diffusion (FD), and the charge of the photodiode 2 is transferred to the gate electrode (FD) of the amplification MOSFET 3 through the drain-source of the charge transfer MOSFET 4. The potential of the gate electrode (FD) of the amplification MOSFET 3 is reset by the reset MOSFET 5.

  When the selection MOSFET 7 is turned on, the source of the amplification MOSFET 3 is conducted to the pixel output line 8 through the drain and source of the selection MOSFET 7. The pixel output line 8 is connected to the drain of the constant current supply MOSFET 9. The constant current supply MOSFET 9 acts as a load of the source follower circuit of the amplification MOSFET 3. The constant current supply MOSFET 9 is controlled by the gate potential of the gate potential supply line 13.

  The reset control line 10, the charge transfer control line 11, and the pixel selection control line 12 are connected to the gate electrodes of the reset MOSFET 5, the charge transfer MOSFET 4, and the selection MOSFET 7, respectively. It is supplied from the pulse supply terminals 15, 14, 16 through the drains and sources of the MOSFETs 19, 20, 21.

  The vertical shift register 17 is a circuit for selecting a 2 × 2 pixel row for row sequential scanning, and the vertical shift register output lines 18-1 and 18-2 are connected to the gate electrodes of the MOSFETs 19, 20, and 21 in each row. It is connected and determines which row of pixels is controlled by the pulse supplied to the terminals of the pulse supply terminals 15, 14, 16.

  The read block 22 is connected to a capacitor 23 for holding a reset signal output, a capacitor 24 for holding an optical signal output, switching MOSFETs 25 and 26 for selecting which one to hold, and horizontal output lines 27 and 28. Switch MOSFETs 29 and 30. The switching MOSFETs 25 and 26 are switching-controlled by pulses supplied from the terminals 37 and 38 to the gate electrodes.

  The horizontal shift register 34 is a horizontal shift register output line 35-connected to the gates of the MOSFETs 29 and 30 for switching which column of the 2 × 2 pixels is to be output to the horizontal output lines 27 and 28. 1 and the output potential to 35-2. In addition, a potential for resetting the horizontal output lines 27 and 28 is supplied from the terminal 33, and the reset timing is performed by switching the switching MOSFETs 31 and 32 with a pulse supplied from the terminal 36. The horizontal output lines 27 and 28 are connected to the input terminal of the differential amplifier 39. The differential amplifier 39 takes the difference between the reset signal output and the optical signal output, and outputs the difference signal from the amplifier output terminal 40 to the outside of the sensor.

  Next, the operation of the conventional CMOS sensor shown in FIG. 7 will be described with reference to the timing chart of FIG. Note that all the MOSFETs in FIG. 7 are N-type, and therefore, the MOSFET is turned on when the gate potential is high (High) and turned off when the gate is low (Low).

  First, as shown in FIG. 8D, the potential of the vertical shift register output line 18-1 becomes High at time t1, thereby selecting the pixel 1 in the first row. Subsequently, as shown in FIG. 8C, the input pulse of the pulse supply terminal 16 becomes High at time t2 (> t1), and thereby the selection MOSFET 7 of the pixel 1 in the first row is turned on. The source of the amplification MOSFET 3 of the pixel 1 in the first row is connected to the constant current supply MOSFET 9 through the drain / source of the selection MOSFET 7 and the pixel output line 8 to form a source follower circuit.

  In this state, first, a high-level pulse is supplied to the pulse supply terminal 15 as shown in FIG. 8B, and the gate electrode of the amplification MOSFET 3 passes through the drain and source of the reset MOSFET 5 of the pixel 1 in the first row. (FD) is reset. Thereafter, at time t3 (> t2), the input pulse of the pulse supply terminal 37 becomes High as shown in FIG. 8I, the switching MOSFET 25 is turned on, and the source of the pixel 1 in the first row is stored in the capacitor 23. The reset signal output output from the follower circuit is held.

  Next, when a high pulse is applied to the pulse supply terminal 14 at time t4 (> t3) as shown in FIG. 8A, the charge transfer MOSFET 4 in the pixel 1 in the first row is turned on, and one row The charges accumulated in the photodiode 2 in the pixel 1 of the eye are transferred to the gate electrode (FD) of the amplification MOSFET 3 through the drain / source of the charge transfer MOSFET 4. At time t5 (> t4), when a high pulse is applied to the pulse supply terminal 38 as shown in FIG. 8J, the light output from the source follower circuit of the pixel 1 in the first row to the capacitor 24. The signal output is retained. Subsequently, since the input pulse of the pulse supply terminal 16 becomes Low at time t6 (> t5) as shown in FIG. 8C, the selection MOSFET 7 in the pixel 1 in the first row is turned off. There is no output from pixel 1 in the row.

  During this time, the input signal at the terminal 36 is High as shown in FIG. 8H, and the horizontal output lines 27 and 28 are in the reset state. However, at time t6, the input signal at the terminal 36 becomes Low as shown in FIG. 8 (H), and when the High pulse shown in FIG. 8 (F) is applied to the horizontal shift register output line 35-1 in this state. Since the switching MOSFETs 29 and 30 in the first column are turned on, the signals of the capacitors 23 and 24 in the first column are output to the horizontal output lines 27 and 28 through the switching MOSFETs 29 and 30 in the first column, respectively. And supplied to the differential amplifier 39. The differential amplifier 39 calculates the difference between each signal of the capacitors 23 and 24 in the first column, that is, the reset signal output and the optical signal output, and removes the optical signal from which the noise caused by the threshold variation of the amplification MOSFET 3 is removed. Output from the output terminal 40.

  Next, when a High pulse is applied to the terminal 36 at time t7 (> t6) shown in FIG. 8H, the horizontal output lines 27 and 28 are reset again, and then the horizontal shift register output line 35-2 is connected to FIG. As shown in (G), a high pulse is applied at time t8 (> t7) and the switching MOSFETs 29 and 30 in the second column are turned on, so that each signal of the capacitors 23 and 24 in the second column is 2 The signals are output to the horizontal output lines 27 and 28 through the switching MOSFETs 29 and 30 in the columns and supplied to the differential amplifier 39, and the signals in the second column are output from the differential amplifier 39 to the output terminal 40 in the same manner as in the first column. Is done.

  After that, at time t9 (> t8) shown in FIG. 8D, the potential of the vertical shift register output line 18-1 becomes Low, and the processing for the first row is completed. Next, at time t10 (> t9), as shown in FIG. 8E, the potential of the vertical shift register output line 18-2 becomes High, and processing similar to that in the first row is performed to read out all pixels. Ends.

  Therefore, in the case of this CMOS sensor, the timing of photoelectric conversion by the photodiodes 2 in the first and second rows is different. Such an imaging method is called a rolling shutter or a focal plane.

JP 2000-10027 A JP 2003-260025 A JP 2003-38424 A JP 2003-17677 A

  In a conventional capsule endoscope apparatus using such a rolling shutter type CMOS sensor 102 as an image pickup element, for simplicity, description will be made with a conceptual diagram shown in FIG. 9A of pixels P11 to P24 in 2 rows and 4 columns. Then, the pixels P11 to P14 in a certain row are sequentially read from the left to the right (solid arrow I). When one row is read, the head returns to the beginning of the next row (broken arrow II), and then the next Repeat the operation of reading the line from left to right again (solid arrow III). Therefore, since the exposure process is performed for the first time when each pixel is selected, the signal acquisition times do not coincide with each other when all the pixels are read. When all the pixels of the CMOS sensor have been read, one picture has been read.

  For example, as shown in FIG. 9B, when a rectangle 150 that moves from the left to the right of the screen is photographed, when the conventional rolling shutter type CMOS sensor 102 is photographed, the photographed images have different photographing times in each row. In addition, if the rectangle to be photographed moves while reading the pixels as described above, the image is photographed as a parallelogram image 151 distorted by the movement of the rectangle 150 as shown in FIG. 9C. The

  Therefore, when the capsule endoscope moves violently in the body, or when the movement of an extremely fast moving organ or the like is photographed in the body, image distortion depending on the readout method generated in FIG. 9C described above. Will occur. For this reason, it has been difficult for conventional capsule endoscope apparatuses to capture an image of an object that moves at high speed, or a case where the image sensor itself moves.

  The present invention has been made in view of the above points, and the captured image is not distorted even when the capsule endoscope moves violently in the body or when the movement of an extremely fast moving organ or the like is imaged. An object of the present invention is to provide a capsule endoscope apparatus.

  In order to achieve the above object, a capsule endoscope apparatus of the present invention includes an illuminating unit that illuminates a body lumen of a living organism such as a human being or an animal, and an imaging element that reads a portion illuminated by the illuminating unit as an image. A swallowable capsule endoscope in which an objective optical system that forms an image on the imaging surface of the imaging device and a transmission unit that transmits an imaging signal output from the imaging device to the outside are incorporated in a transparent member And receiving means for receiving the imaging signal transmitted by the transmitting means, signal processing means for processing the imaging signal received by the receiving means as a video signal, and output means for outputting the video signal from the signal processing means In a capsule endoscope apparatus having an external device outside the capsule endoscope, a global shutter type CMOS sensor is used as an imaging element. In the present invention, since the global shutter type CMOS sensor is used as the image sensor, an image captured at the same time can be displayed even on a moving subject.

  In order to achieve the above object, according to the present invention, the global shutter type CMOS sensor is provided at a position of the substrate corresponding to the ring-shaped gate electrode on the substrate and the central opening of the ring-shaped gate electrode. A signal output transistor comprising a source region and a source vicinity region provided on the substrate so as to surround the source region and not reach the outer periphery of the ring-shaped gate electrode, and a photodiode for converting light into electric charge and storing it And a plurality of charge transfer means for transferring the charge accumulated in the photodiode to the source vicinity region. The transfer means in each pixel transfers the charge accumulated in the photodiode. All the pixels are transferred to the corresponding source neighborhood area in the same pixel at the same time, and the signal output transistor uses the amount of input charge as the change in threshold value. Output.

In order to achieve the above object, the present invention provides a global shutter type CMOS sensor, wherein the global shutter type CMOS sensor is a light having a ring-shaped gate electrode (45) on a first conductivity type substrate. A solid-state imaging device in which a plurality of pixels including a signal output transistor and a photodiode are two-dimensionally arranged,
Each of the pixels includes a second conductivity type well region provided on the surface of the substrate, a photoelectric conversion region of the first conductivity type photodiode provided in the well region, and a well region other than the photoelectric conversion region. A ring-shaped gate electrode provided with an insulating film on the top, a transfer gate electrode provided with an insulating film on the well region between the ring-shaped gate electrode on the insulating film and the photoelectric conversion region, and a well High-concentration second conductivity type drain that is electrically integrated with the well region and is provided in at least a part of the surface of the region excluding the region corresponding to the ring-shaped gate electrode and the transfer gate electrode A source region of a second conductivity type provided at a position in the well region corresponding to the central opening of the ring-shaped gate electrode, and a well region surrounding the source region and not reaching the drain region. And having a first conductivity type source region near provided in.

  According to the present invention, since a global shutter type CMOS sensor is used, an image captured at the same time can be displayed even on a moving subject. Therefore, when the capsule endoscope moves violently in the body, Even in the state where the movement of a fast-moving organ or the like is imaged, accurate in-vivo imaging can be performed without causing image deformation or distortion depending on the readout method.

  Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a configuration diagram of an embodiment of a capsule endoscope apparatus according to the present invention. In the figure, the same components as those in FIG. 6 are denoted by the same reference numerals, and the description thereof is omitted. The capsule endoscope apparatus according to the present embodiment includes an extracorporeal apparatus shown in FIG. 1A and an in-vivo apparatus shown in FIG. 1B. The extracorporeal apparatus shown in FIG. The image processing device 111 and the output device 112 are the same as the conventional extracorporeal device.

  A capsule endoscope apparatus according to the present embodiment is an in-vivo apparatus shown in FIG. 1B. A capsule endoscope 201 that swallows the entire patient and observes the inside of the body is a global shutter type as a CMOS sensor. This is characterized in that the CMOS sensor 202 is housed in an elliptical sphere transparent member 109.

  As a result, the light emitted from the light emitting device 106 passes through the transparent member 109 and is reflected inside the body, and the reflected light enters the global shutter type CMOS sensor 202 through the transparent member 109 and the objective lens 108, where After the photoelectric conversion at the same time in the pixels, the signals obtained by the photoelectric conversion are sequentially read out from each pixel and input to the circuit unit 103, and then output from the circuit unit 103 in the same manner as in the past. A video signal is transmitted from the antenna 105 to the external antenna 110.

Next, the configuration of the global shutter type CMOS sensor 202 will be described in more detail. 2A and 2B are configuration diagrams of an embodiment of the global shutter type CMOS sensor 202, where FIG. 2A is a plan view, and FIG. 2B is a longitudinal section taken along line XX ′ in FIG. The figure is shown. As shown in FIGS. 2A and 2B, in the CMOS sensor 202 of the present embodiment, a p ⁻ type epitaxial layer 42 is grown on a p ⁺ type substrate 41, and an n well is formed on the surface of the epitaxial layer 42. There are 43. On the n-well 43, a gate electrode 45 having a ring shape as a first gate electrode is formed with a gate oxide film 44 interposed therebetween.

An n ⁺ -type source region 46 is formed on the surface of the n-well 43 corresponding to the center portion of the ring-shaped gate electrode 45, a source vicinity p-type region 47 is formed adjacent to the source region 46, and An n ⁺ -type drain region 48 is formed at a position spaced outside the source region 46 and the p-type region 47 near the source. In addition, there is a buried p ⁻ type region 49 in the n well 43 below the drain region 48. The buried p ⁻ type region 49 and the n well 43 constitute the buried photodiode 50 shown in FIG.

  Between the embedded photodiode 50 and the ring-shaped gate electrode 45, there is a transfer gate electrode 51 which is a second gate electrode. The drain region 48, the ring-shaped gate electrode 45, the source region 46, and the transfer gate electrode 51 include a drain electrode wiring 52, a ring-shaped gate electrode wiring 53, a source electrode wiring (output line) 54, and a transfer gate electrode, which are metal wirings, respectively. A wiring 55 is connected. Further, as shown in FIG. 2B, a light shielding film 56 is formed above each of the above components, and an opening 57 is formed at a position corresponding to the embedded photodiode 50 in the light shielding film 56. Has been. The light shielding film 56 is formed of a metal or an organic film. The light reaches the embedded photodiode 50 through the opening 57 and is photoelectrically converted.

  Next, the pixel structure of the CMOS sensor and the structure of the entire image sensor will be described with reference to FIG. In the figure, first, pixels are arranged in a pixel spread area 61 in m rows and n columns. In FIG. 3, one pixel 62 of s rows and t columns among these m rows and n columns pixels is represented by an equivalent circuit. The pixel 62 includes a ring-shaped gate MOSFET 63, a photodiode 64, and a transfer gate MOSFET 65. The drain of the ring-shaped gate MOSFET 63 is the n-side terminal of the photodiode 64 and the drain electrode wiring 66 (corresponding to 52 in FIG. 2). , The source of the transfer gate MOSFET 65 is connected to the p-side terminal of the photodiode 64, and the drain is connected to the back gate of the ring-shaped gate MOSFET 63.

In FIG. 2B, the ring-shaped gate MOSFET 63 has a p-type region 47 near the source directly below the ring-shaped gate electrode 45 as a gate region, and an n ⁺ -type source region 46 and an n ⁺ -type drain region 48. An n-channel MOSFET. In FIG. 2B, the transfer gate MOSFET 65 has an n well 43 just below the transfer gate electrode 51 as a gate region, a p ⁻ type region 49 embedded with a photodiode 50 as a source region, and a p-type region 47 near the source. A p-channel MOSFET serving as a drain.

  In FIG. 3, in order to read a signal for one frame from each pixel of m rows and n columns, there is a circuit 67 for generating a frame start signal for giving a signal to start reading. The frame start signal may be given from outside the image sensor. This frame start signal is supplied to the vertical shift register 68. The vertical shift register 68 outputs a signal indicating which row of pixels is read out from each pixel of m rows and n columns.

  The pixels in each row are connected to a control circuit that controls the potentials of the ring-shaped gate electrode, transfer gate electrode, and drain electrode, and these control circuits are supplied with the output signal of the vertical register 68. For example, the ring-shaped gate electrode of each pixel in the s-th row is connected to the ring-shaped gate potential control circuit 70 via the ring-shaped gate electrode wiring 69 (corresponding to 53 in FIG. 2), and the transfer gate electrode of each pixel is Are connected to the transfer gate potential control circuit 72 via the transfer gate electrode wiring 71 (corresponding to 55 in FIG. 2), and the drain electrode of each pixel is drained via the drain electrode wiring 66 (corresponding to 52 in FIG. 2). It is connected to the potential control circuit 73. Each control circuit 70, 72, 73 is supplied with an output signal from the vertical shift register 68.

  Since the ring-shaped gate electrode is controlled for each row, wiring is performed in the horizontal direction. However, since the transfer gate electrode is controlled simultaneously for all pixels, the wiring direction is not limited and the vertical direction may be used. Here, it is expressed as wiring in the horizontal direction. The drain potential control circuit 73 controls all the pixels at the same time, but may be controlled for each row. Therefore, the drain potential control circuit 73 is represented by being connected to both the frame start signal and the vertical register 68.

  The source electrode of the ring-shaped gate MOSFET 63 of the pixel 62 is branched into two via a source electrode wiring 74 (corresponding to 54 in FIG. 2), one of which is supplied to a source potential control circuit 75 that controls the source electrode potential via a switch SW1. The other is connected to the signal readout circuit 76 via the switch SW2. When reading the signal, the switch SW1 is turned off and the switch SW2 is turned on. When the source potential is controlled, the switch SW1 is turned on and the switch SW2 is turned off. Since the signal is output in the vertical direction, the wiring direction of the source electrode is set to be vertical.

  The signal readout circuit 76 is configured as follows. The output of the pixel 62 is performed from the source of the ring-shaped gate MOSFET 63, and a load, for example, a current source 77 is connected to the output line 74. Therefore, it is a source follower circuit. One end of each of the capacitor C1 and the capacitor C2 is connected to the current source 77 via the switch sc1 and the switch sc2. One end of each of the capacitors C1 and C2 whose other ends are grounded is connected to the inverting input terminal and the non-inverting input terminal of the differential amplifier 78, and the potential difference between the capacitors C1 and C2 is output from the differential amplifier 78. It is like that.

  Such a signal readout circuit 76 is called a CDS circuit (correlated double sampling circuit), and various circuits other than the method described here have been proposed, and the circuit is not limited to this circuit. The signal output from the signal readout circuit 76 is output via the output switch swt. The output switches swt in the same column are subjected to switching control by a signal output from the horizontal shift register 79.

Next, a method for driving the CMOS sensor shown in FIG. 3 will be described with reference to the timing chart of FIG. First, in the period shown in FIG. 4A, light is incident on the embedded photodiode (50 in FIG. 2A, 64 in FIG. 3, etc.), and an electron / hole pair is generated due to the photoelectric conversion effect. Holes accumulate in the buried p ^- type region 49 of the diode. At this time, the potential of the transfer gate electrode 51 is the same as the drain potential Vdd, and the transfer gate MOSFET 65 is off. These accumulations are performed at the same time as the previous frame read operation is being performed.

  In the subsequent period shown in FIG. 4 (2), when the reading of the previous frame is completed, a new frame start signal is transmitted as shown in FIG. First, all the pixels are performed simultaneously from the photodiode (50 in FIG. 2A, 64 in FIG. 3) to the p-type region (47 in FIG. 2) near the source of the ring-shaped gate electrode (45 in FIG. 2). It is to transfer the hole. Therefore, as shown in FIG. 4B, the transfer gate control signal output from the transfer gate potential control circuit 72 falls from Vdd to Low2, the potential of the transfer gate electrode (41 in FIG. 2) becomes Low2, and the transfer gate MOSFET 65 Turns on.

  At this time, the potential of the ring-shaped gate electrode wiring 69 controlled by the ring-shaped gate potential control circuit 70 changes from Low to Low1 as shown in FIG. 4C, but Low2 is larger than Low1. Low1 may be the same as Low. Most simply, Low1 = Low = 0 (V) is set.

  On the other hand, the source potential of all the pixels including the source potential supplied from the source potential control circuit 75 to the source of the ring-shaped gate MOSFET 63 from the source electrode wiring 74 through the switch SW1 is as shown in FIG. The potential is set to S1. S1> Low1, which keeps the ring-shaped gate MOSFET 63 off and prevents current from flowing. As a result, charges (holes) accumulated in the photodiodes of all the pixels are transferred all at once under the ring-shaped gate electrodes of the corresponding pixels.

  In the region below the ring-shaped gate electrode 45 shown in FIG. 2 (B), the p-type region 47 near the source has the lowest potential, so the holes accumulated in the photodiode reach the p-type region 47 near the source. Accumulated in. As a result of the accumulation of holes, the potential of the p-type region 47 near the source rises.

Subsequently, in the period shown in FIG. 4 (3), as shown in FIG. 4 (B), the transfer gate electrode becomes Vdd again, and the transfer gate MOSFET 65 is turned off. As a result, in the photodiode (50 in FIG. 2A, 64 in FIG. 3, etc.), electron-hole pairs are generated again due to the photoelectric conversion effect, and holes start to accumulate in the buried p ⁻ -type region 49 of the photodiode. This accumulation operation is continued until the next charge transfer.

  On the other hand, since the read operation is performed in units of rows, the potential of the ring-shaped gate electrode is low as shown in FIG. 4C in the period (3) in which the first to (s−1) th rows are read. In this state, a standby state is entered with holes accumulated in the p-type region 47 near the source. The source potential can take various values depending on the value of the signal from the pixel while the signal is read from another row. The ring-shaped gate electrode potential can take various values for each row, but is set to Low in the s-th row, and the ring-shaped gate MOSFET 63 is in an off state.

  In the subsequent period shown in FIGS. 4 (4) to (6), pixel signal readout is performed. This signal readout operation will be described representatively for the pixel 62 in the s-th row and the t-th column. First, in the state where holes are accumulated in the p-type region 47 near the source, the vertical shift register 68 shown in FIG. In the period (4) in which the output signal is at a low level as shown in FIG. 5H, the ring-shaped gate electrode 45 is controlled by the control signal output from the ring-shaped gate potential control circuit 70 to the ring-shaped gate electrode wiring 69. Is raised from Low to Vg1, as shown in FIG.

Here, the potential Vg1 is between the potentials Low, Low1, and Vdd described above.
Low ≦ Low1 ≦ Vg1 ≦ Vdd (where Low <Vdd)
Is an electric potential that holds the inequality. In the period (4), the switch SW1 is turned off as shown in FIG. 4I, the switch SW2 is turned on as shown in FIG. 4J, and the switch sc1 is turned on as shown in FIG. The switch sc2 is turned off as shown in FIG.

  As a result, the source follower circuit connected to the source of the ring-shaped gate MOSFET 63 works, and the source potential of the ring-shaped gate MOSFET 63 is S2 (= Vg1-Vth1) in the period (4) as shown in FIG. Become. Here, Vth1 is a threshold voltage of the ring-shaped gate MOSFET 63 in a state in which there is a hole in the back gate (p-type region 47 near the source). The source potential S2 is stored in the capacitor C1 through the switch sc1 that is turned on.

  In the subsequent period shown in FIG. 4 (5), the potential of the ring-shaped gate electrode 45 is set as shown in FIG. 4 (K) by the control signal output from the ring-shaped gate potential control circuit 70 to the ring-shaped gate electrode wiring 69. At the same time as raising to High1, the switch SW1 is turned on and the switch SW2 is turned off as shown in FIGS. 1I and 1J, and the source potential output from the source potential control circuit 75 is shown in FIG. Raise to Highs as shown. Here, High1 and Highs> Low1.

  The values of the potentials High1 and Highs may be the same or different, but High1 and Highs ≦ Vdd are desirable for simplicity of design. In a simple setting, High1 = Highs = Vdd. Further, it is desirable to set the potential so that the ring-shaped gate MOSFET 63 is turned on and no current flows. As a result, the potential of the p-type region 47 near the source rises, and holes are discharged to the epitaxial layer 42 beyond the barrier of the n-well 43 (reset).

  In the subsequent period shown in FIG. 4 (6), the same signal readout state as in the period (4) is set again. However, unlike the period (4), as shown in FIGS. 4M and 4N, the switch sc1 is turned off and the switch sc2 is turned on. The ring-shaped gate electrode is set to Vg1 which is the same as that in the period (4) as shown in FIG. However, in this period (6), holes are discharged to the substrate in the immediately preceding period (5), and no holes are present in the p-type region 47 near the source. Therefore, the source potential of the ring-shaped gate MOSFET 63 is as shown in FIG. L), the period (6) is S0 (= Vg1-Vth0). Here, Vth0 is the threshold voltage of the ring-shaped gate MOSFET 63 in a state where there is no hole in the back gate (p-type region 47 near the source).

  The source potential S0 is stored in the capacitor C2 through the switch sc2 that is turned on. The differential amplifier 78 outputs the potential difference between the capacitors C1 and C2. That is, the differential amplifier 78 outputs (Vth0−Vth1). This output value (Vth0-Vth1) is a change in threshold value due to hole charge. Thereafter, among the pulses shown in FIG. 4F output from the horizontal shift register 79, the output switch swt in FIG. 3 is turned on based on the output pulse in the t-th column shown in FIG. During the ON period, as schematically shown by hatching in FIG. 4 (P), the threshold value change due to the Hall charge from the differential amplifier 78 is output to the outside of the sensor as the output signal Vout of the pixel 62.

  Subsequently, in the period indicated by (7) in FIG. 4, the potential of the ring-shaped gate electrode 45 is set to low again as shown in FIG. It waits until the signal processing of the next row is completed (until the readout of pixels of the s + 1 row to the nth row is completed). During these readout periods, the photodiode 64 is accumulating holes due to the photoelectric conversion effect. Thereafter, the process returns to the period (1) and repeats from the hole transfer. As a result, the output signal shown in FIG. 4G is read from each pixel. When signals are read from all pixels, the next frame is started again.

  2A and 2B, the ring-shaped gate MOSFET 63 having the ring-shaped gate electrode 45 is an amplifying MOSFET, and as shown in FIG. It is a kind of CMOS sensor in the sense that it has an amplifying MOSFET. In this CMOS sensor, the charge (hole) accumulated in the photodiode is transferred to the p-type region 47 in the vicinity of the source under the ring-shaped gate electrode of the corresponding pixel at the same time. Is realized.

  Note that the potential supply of the source electrode wiring 74 at the time of resetting in the period (5) of FIG. That is, in the period (5), both the switches SW1 and SW2 are turned off, and the source electrode wiring 74 is floated. Here, when the potential of the ring-shaped gate electrode wiring 69 is High1, the ring-shaped gate MOSFET 63 is turned on, current is supplied from the drain to the source electrode, and the source electrode potential rises. As a result, the potential of the p-type region 47 in the vicinity of the source is raised, and holes are discharged to the p-type epitaxial layer 42 beyond the barrier of the n-well 43 (reset). The source electrode potential when the holes are completely discharged becomes High1-Vth0. This method can reduce the number of transistors that supply Highs in the source potential control circuit 75, and as a result, the chip area can be reduced.

  Note that the circuit configuration of the pixel 62 in FIG. 3 is simplified. Strictly speaking, the circuit of the pixel 62 is provided with a switch linked to each potential of the ring-shaped gate electrode wiring 69 and the transfer gate electrode wiring 71 between the source of the transfer gate MOSFET 65 and the back gate of the ring-shaped gate MOSFET 63. It is a configuration. This switch is turned on when there is a relationship of Low1 ≦ Low2 between the potential Low1 of the ring-shaped gate electrode wiring 69 and the potential Low2 of the transfer gate electrode wiring 71, and when there is a relationship of Low1> Low2. Turns off.

  By providing this switch, the substrate potential under the ring-shaped gate electrode 45 (potential Low1) is higher than the substrate potential under the transfer gate electrode 61 (potential Low2), and the ring-shaped gate electrode 45 (potential). The phenomenon that the substrate potential under Low 1) functions as a barrier and the holes cannot reach the p-type region 47 near the source can be expressed in a circuit form. However, at the time of transfer, the above condition of Low1 ≦ Low2 is always satisfied by the potential control circuits 70, 72, etc., and therefore this switch is omitted in FIG.

  Next, the operation of the capsule endoscope apparatus of the present embodiment using the global shutter type CMOS sensor 202 having the above configuration and operation will be described. The global shutter type CMOS sensor 202 of this embodiment is reflected in the body, and the reflected light enters the global shutter type CMOS sensor 202 through the transparent member 109 and the objective lens 108 of FIG. As described above, the exposure is performed in the same one frame period without shifting the timing for each line. This corresponds to the period (1) in FIG.

  After exposure for a certain period, the charges of all the pixels are simultaneously transferred to a predetermined region of each pixel (the back gate of the ring-shaped gate MOSFET 63 in FIG. 3) by the transfer gate (transfer gate MOSFET 65 in FIG. 3) in the global shutter CMOS sensor 202. (Near source p-type region 47 in FIG. 2B). This corresponds to the period (2) in FIG. Thereafter, signals from each pixel are sequentially read out by the readout circuit within the readout period. This corresponds to the periods (3) to (7) in FIG.

  As a result, as shown in FIG. 5A, even when a subject (part in the body) 150 that moves from left to right is imaged on the screen, for example, the captured image is an image exposed at the same time. A captured image as indicated by 160 in FIG. (B) is obtained, and image distortion different from the image of the subject 150 does not occur. Therefore, according to the present embodiment, even when the capsule endoscope moves vigorously in the body, or even when the movement of an extremely fast moving organ or the like is photographed in the body, the photographed image is accurate without distortion or deformation. Images can be obtained.

It is a block diagram of one embodiment of a capsule endoscope apparatus of the present invention. FIG. 2 is a plan view of an element structure for one pixel of the global shutter type CMOS sensor of FIG. 1 and a cross-sectional view taken along line X-X ′. It is the figure which showed the whole structure of the global shutter type | mold CMOS sensor used by this invention with the electrical equivalent circuit. 3 is a timing chart for explaining the operation of the CMOS sensor of FIG. 2. It is a figure which shows an example of the to-be-photographed object image and its picked-up image by this invention. It is a block diagram of an example of the conventional capsule type endoscope apparatus. It is an equivalent circuit diagram of an example of a rolling shutter type CMOS sensor. 8 is a timing chart for explaining the operation of FIG. It is a figure which shows an example of the reading method by the conventional capsule type endoscope apparatus, a to-be-photographed object image, and its picked-up image.

Explanation of symbols

43 n well 45 ring-shaped gate electrode 46 n ⁺ type source region 47 near source p type region 48 n ⁺ type drain region 49 buried p ⁻ type region 50, 64 photodiode 51 transfer gate electrode 52, 66 drain electrode wiring 53, 69 Ring-shaped gate electrode wiring 54, 74 Source electrode wiring (output line)
55, 71 Transfer gate electrode wiring 61 Pixel covering area 62 Pixel 63 Ring-shaped gate MOSFET
65 Transfer gate MOSFET
DESCRIPTION OF SYMBOLS 103 Circuit part 104 Power supply 105 Antenna 106 Light-emitting device 107 Light-shielding layer 108 Objective lens 109 Transparent member 110 External antenna 111 Image processing device 112 Output device 201 Capsule type endoscope (internal device)
202 Global shutter type CMOS sensor

Claims (3)

Illuminating means for illuminating a body lumen of a living organism such as a human being or an animal, an imaging element for reading a part illuminated by the illuminating means as an image, and an objective optical system for forming an image on the imaging surface of the imaging element The transmission means for transmitting the imaging signal output from the imaging element to the outside has a swallowable capsule endoscope built in the transparent member,
A receiving means for receiving the imaging signal transmitted by the transmitting means, a signal processing means for processing the imaging signal received by the receiving means as a video signal, and an output for outputting the video signal from the signal processing means In a capsule endoscope apparatus having a means as an extracorporeal device outside the capsule endoscope,
A capsule endoscope apparatus using a global shutter type CMOS sensor as the image sensor. The global shutter CMOS sensor is
A ring-shaped gate electrode on the substrate; a source region provided at a position of the substrate corresponding to a central opening of the ring-shaped gate electrode; and surrounding the source region and reaching an outer periphery of the ring-shaped gate electrode A signal output transistor comprising a source vicinity region provided on the substrate so as not to
A photodiode that converts light into charge and stores it;
A plurality of two-dimensionally arranged pixels including charge transfer means for transferring the charge accumulated in the photodiode to the source vicinity region;
The transfer means in each pixel transfers all the charges accumulated in the photodiode to the corresponding source vicinity region in the same pixel all at once, and the signal output transistor 2. The capsule endoscope apparatus according to claim 1, wherein the quantity is output as a change in threshold value. The global shutter type CMOS sensor is a solid-state imaging device in which a plurality of pixels including an optical signal output transistor having a ring-shaped gate electrode and a photodiode are two-dimensionally arranged on a first conductive type substrate,
Each of the pixels
A well region of a second conductivity type provided on the surface of the substrate;
A photoelectric conversion region of the photodiode of the first conductivity type provided in the well region;
The ring-shaped gate electrode provided on the well region other than the photoelectric conversion region with an insulating film interposed therebetween;
Between the ring-shaped gate electrode on the insulating film and the photoelectric conversion region, a transfer gate electrode provided on the well region with the insulating film interposed therebetween,
A high concentration second electrically integrated with the well region provided in at least a part of the surface of the well region excluding the region corresponding to the ring-shaped gate electrode and the transfer gate electrode. A drain region of a conductivity type of
A source region of a second conductivity type provided at a position in the well region corresponding to the central opening of the ring-shaped gate electrode;
2. A capsule-type endoscope according to claim 1, further comprising: a first-conductivity-type source vicinity region provided in the well region so as to surround the source region and not to reach the drain region. Mirror device.

Images