JP2008085755A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily obtain an imaging apparatus capable of performing high-speed information transmission. <P>SOLUTION: The imaging apparatus is equipped with a rear-face incidence type solid-state imaging device, in which a plurality of pixel cells for image pickup are formed and an electrode for capacitive coupling for transmitting image information obtained by the pixel cells is formed and which inputs an image from an opposite side of a plane, formed with the electrode for capacitive coupling; a signal processing element, in which a signal processing circuit for performing signal processing on image information is formed and an electrode is formed for capacitive coupling for receiving image information, in corresponding to the position of the electrode for capacitive coupling in the solid-state imaging device; and a capacitive coupling transport means for performing signal transmission via a capacitor comprising the electrode for capacitive coupling in the solid-state imaging device and the electrode for capacitive coupling in the signal processing element. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image pickup apparatus, and more particularly to the technical field of a back-illuminated image pickup apparatus.

  2. Description of the Related Art Conventionally, as a semiconductor module provided with a MOS solid-state image sensor, a small MOS camera module in which a MOS solid-state image sensor (also referred to as a MOS image sensor chip) and a signal processing chip are stacked is known. This small MOS camera module is constructed by attaching a MOS image sensor chip on top of a signal processing chip and connecting the two chips by wire bonding, or forming a wiring that penetrates the substrate of the image sensor. There is something to do.

  However, since the MOS image sensor chip is usually several mm square, the number of wire bonds that can be formed for connection is about several tens. Due to the limitation of the number of wire bonds, the image information There was a limit to the transmission speed. On the other hand, forming a wiring penetrating through the substrate of the image sensor is not practical because it requires a high level of processing technology and leads to a decrease in yield and an increase in cost.

  From this point of view, in Patent Document 1, a back-illuminated MOS solid-state imaging device in which a micropad is formed, and a signal processing chip in which the micropad is formed corresponding to the position of the micropad An invention of connecting by bumps is disclosed. In the present invention, by using the back-illuminated MOS solid-state imaging device, the MOS solid-state imaging device having a high aperture ratio and the signal processing chip can be connected.

However, in the method of connecting by micro bumps, when the number of micro pads to be connected increases, the time and load required for connection increase, leading to an increase in cost and a decrease in yield.
JP 2006-49361 A

  The present invention has been made in view of the above situation, and in the case where a solid-state imaging element such as an image sensor and a signal processing element made of a signal processing chip or the like are formed on different chips or substrates, the cost increases. It is an object of the present invention to provide an image pickup apparatus having a configuration capable of transmitting information between a solid-state image pickup element and a signal processing element without causing a decrease in yield.

  In an image capturing apparatus according to an aspect of the present invention, a plurality of pixel cells for image capturing are formed, and electrodes for capacitive coupling for transmitting image information obtained by the pixel cells are formed. A back-illuminated solid-state imaging device that inputs an image from the opposite side of the surface on which the electrodes for capacitive coupling are formed, and a signal processing circuit for signal processing the image information are formed, and the capacitance of the solid-state imaging device A signal processing element on which an electrode for capacitive coupling for receiving image information corresponding to the position of the electrode for coupling is formed, an electrode for capacitive coupling in the solid-state imaging device, and the signal processing element And a capacitive coupling transmission means for transmitting a signal through a capacitor constituted by an electrode for capacitive coupling.

  In the present invention, a large amount of information is transmitted to the signal processing element at high speed by capacitively coupling a solid-state imaging element such as an image sensor and a signal processing element such as a signal processing chip to perform information transmission. Therefore, the cost of the image pickup device and the yield are not reduced.

[First Embodiment]
One embodiment of the present invention will be described below.

  FIG. 1 shows a configuration of an image capturing apparatus according to the present embodiment. FIG. 1A is a top view of the image pickup apparatus in the present embodiment, and FIG. 1B is a cross-sectional view taken along a broken line B1-B2. The image pickup apparatus in the present embodiment is composed of a back-illuminated solid-state image pickup element 11 and a signal processing element 12, and information transmission between the solid-state image pickup element 11 and the signal processing element 12 is formed on each of the electrodes. This is performed by a capacitor (capacitor) 15 constituted by 13 and 14.

  That is, after the solid-state imaging element 11 and the signal processing element 12 are aligned with each other, the surfaces on which the electrodes 13 and 14 are formed are brought close to each other. Thus, a capacitor (capacitor) 15 formed of a parallel plate capacitor is formed by the capacitive coupling electrode 13 formed on the solid-state imaging element 11 and the capacitive coupling electrode 14 formed on the signal processing element 12. . Information is transmitted by changing the voltage of the electrode 13 formed on the solid-state imaging device 11 according to the information to be transmitted, thereby changing the potential of the electrode 14 formed on the signal processing device 12 due to capacitive coupling. This is done by detecting the change in potential at 14.

  Since the solid-state imaging device 11 is composed of a back-illuminated photoelectric conversion device, it is configured such that light enters from the surface opposite to the surface on which the electrode 13 is formed. Therefore, even if the electrode 13 in the solid-state imaging device 11 and the electrode 14 in the signal processing device 12 are brought close to each other, the light incident on the photoelectric conversion device in the solid-state imaging device 11 is not hindered, and the aperture ratio in the photoelectric conversion device is increased. It becomes possible to take widely. The signal processing element 12 includes an amplifier (not shown) for amplifying information received via capacitive coupling.

  As shown in FIG. 2, the number of capacitive coupling capacitors (capacitors) 15 formed by the electrodes 13 and 14 for transmitting information between the solid-state imaging device 11 and the signal processing device 12 is the number of pixels in the solid-state imaging device 11. By making the number equal to the number of cells 16, the information of all the pixels in the pixel cell 16 can be read out in a very short time, the time required for reading is shortened, and the information in the image cell 16 that has conventionally been required. The shutter that was used during the reading of the image becomes unnecessary. 2 conceptually shows the configuration of the present embodiment. Actually, the pixel cells 16 are two-dimensionally arranged, and all the pixel cells 16 have a capacity (capacitor) for transmitting information. 15 is provided. A signal transmitted to the signal processing element 12 via the capacitor (capacitor) 15 is received by a receiving circuit 17 including a sense amplifier and the like.

  Further, in the present embodiment, unlike the case of connecting by micro bumps, the solid-state imaging element 11 and the signal processing element 12 are destroyed by electrostatic breakdown because the metal surfaces that become the electrodes 13 and 14 are not exposed. Thus, the yield can be improved, and it is not necessary to form a protective element for countermeasures against electrostatic breakdown, so that miniaturization and high-speed signal transmission can be achieved.

  Next, the pixel cell 16 in the solid-state imaging device 11 will be described with reference to FIG. As shown in FIG. 3, the pixel cell 16 precharges the photoelectric conversion element PD that converts received light into an electrical signal, the transfer transistor T that transfers the signal to the floating diffusion FD, and the floating diffusion FD. And a buffer B for buffering the signal read to the floating diffusion FD. Since the solid-state imaging device 11 is composed of a plurality of pixel cells 16, a plurality of elements having this configuration are arranged.

  Although FIG. 3 shows the buffer B using an amplifier having a common source configuration, the pixel cell 16 having the configuration shown in FIG. 4 may be used. That is, as shown in FIG. 4A, a configuration using a source follower circuit as the buffer may be used. Moreover, as shown in FIG. 4B and FIG. 4C, a configuration not including the transfer transistor T may be used. Specifically, in the pixel cell 16 shown in FIG. 4A, the photoelectric conversion element PD is connected in series with the transfer transistor T and the precharge transistor P, and is output via the buffer B2 having a source follower configuration. It is a thing of the structure to be. In the pixel cell 16 shown in FIG. 4B, the photoelectric conversion element PD is connected in series with the precharge transistor P, and is output through a buffer B2 having a source follower configuration. Further, in the pixel cell 16 shown in FIG. 4C, the photoelectric conversion element PD is connected in series with the precharge transistor P, and is output via the buffer B having a common source configuration as in FIG. It is a thing of composition.

  Next, a method for transmitting information through capacitive coupling between the solid-state imaging device 11 and the signal processing device 12 will be described with reference to FIG. FIG. 5 is a configuration diagram of a transmission / reception unit in the solid-state imaging element 11 and the signal processing element 12.

  First, a predetermined voltage is applied to the transmission node Nt and the reception node Nr by the transmission timing signal E via the transmission precharge circuit 18 and the reception precharge circuit 19. Specifically, there is a method in which the transmission node Nt is the output voltage of the precharged pixel and Nr is the ground voltage, but the voltage to be applied corresponds to the characteristics of the pixel cell 16 and the characteristics of the transmission / reception circuit. These precharge voltages can be independently set to optimum values.

  Next, application of voltage at the transmission node Nt and the reception node Nr is stopped by the transmission timing signal E via the transmission precharge circuit 18 and the reception precharge circuit 19. As a result, a voltage corresponding to the amount of light received in the pixel cell 16 is transmitted to the transmission node Nt and applied to the electrode 13. This change in voltage at the electrode 13 is further transmitted as a change in potential to the capacitively coupled electrode 14, and the change in the potential of the electrode 14 also changes the potential at the reception node Nr. Information output from the pixel cell 16 of the element 11 is transmitted. In this embodiment, the signal used for transmission / reception may be an analog signal or a digital signal. When the signal is an analog signal, the potential at the electrode 14 connected to the reception node Nr changes according to the voltage value at the electrode 13 connected to the transmission node Nt. The quantity is communicated as an analog value.

  Next, a case where a plurality of pixel cells 16 in the present embodiment are arranged will be described.

  FIG. 6 shows a configuration diagram of the image pickup apparatus in the present embodiment. The image pickup apparatus according to the present embodiment includes a solid-state image pickup device 11 and a signal processing device 12, and the solid-state image pickup device 11 and the signal processing device 12 each have a plurality of electrodes 13 and 14 for capacitive coupling. The information is transmitted from the solid-state imaging device 11 to the signal processing device 12 through a plurality of capacitors (capacitors) 15 formed by the plurality of electrodes 13 and 14. The solid-state imaging device 11 is provided with a photoelectric conversion element group 56 including a plurality of photoelectric conversion elements 16 arranged two-dimensionally, and one transmission is provided corresponding to one of the photoelectric conversion elements 16. A circuit 20 is provided and connected to each photoelectric conversion element 16. A plurality of transmission circuits 20 form a transmission circuit group 60.

  Each transmission circuit 20 is connected to the electrodes 13 in the solid-state imaging device 11 in a one-to-one correspondence. Information is transmitted wirelessly to the electrode 14 in the signal processing element 12 capacitively coupled to the electrode 13 by capacitive coupling. In the signal processing element 12, one receiving circuit 17 is provided corresponding to one of the electrodes 14 and is connected to the electrode 14. A plurality of receiving circuits 17 constitute a receiving circuit group 57.

  In the present embodiment, information obtained by the pixel cell 16 can be quickly transmitted to the signal processing element 12.

  Note that the solid-state imaging device 11 may be configured not to form a control circuit. When the solid-state image sensor 11 is configured such that a control circuit is not formed, it is not necessary to form a control circuit when the solid-state image sensor 11 is manufactured. In the present embodiment, the solid-state image pickup element 11 and the signal processing element 12 are non-contacted and are connected by information transmission by capacitive coupling. Therefore, the solid-state image pickup element 11 has a predetermined area for this purpose. It is only necessary to form the electrodes.

[Second Embodiment]
Next, as a second embodiment, a method for transmitting information via capacitive coupling between the solid-state imaging device 11 and the signal processing device 12 will be described. In the present embodiment, information transmitted by capacitive coupling between the solid-state imaging device 11 and the signal processing device 12 is a digital signal.

  FIG. 7 is a configuration diagram for explaining information transmission in the solid-state imaging device 21 and the signal processing device 22 in the present embodiment. Specifically, the solid-state imaging device 21 is provided with a plurality of pixel cells 26, and one A / D converter 27 is provided corresponding to one pixel cell 26. The signal input to the A / D converter 27 is converted into a digital signal and then transmitted to the electrode 23 of the solid-state image sensor 21 via the inverter 28. This signal is wirelessly transmitted to the signal processing element 22 by capacitive coupling via a capacitor (capacitor) constituted by the electrode 23 of the solid-state imaging element 21 and the electrode 24 of the signal processing element 22.

  In the pixel cell 26 in the present embodiment, the photoelectric conversion element PD is connected in series with the precharge transistor P and the transfer transistor T, and the signal reset is input to the gate of the precharge transistor P. Has been. Information read out by the image cell 26 is input to the A / D converter 27 as an output signal Vs from the image cell 26.

  The A / D converter 27 is constituted by a differential amplifier circuit, and a bias voltage of Vbias1 [V] is applied to both gates of the transistors Ts1 and Ts2 constituting the differential amplifier circuit. A bias voltage of Vbias2 [V] is applied to the gate of the transistor Tr5 constituting the differential amplifier circuit. A voltage of VREF [V], which is a threshold value of the A / D converter 27, is applied to the gate of the transistor Tr4. In this state, by inputting the output signal Vs from the image cell 26 to the gate of the transistor Tr3 constituting the differential amplifier circuit, a digital signal is output as the output of the differential amplifier circuit.

  Thus, the signal output from the A / D converter 27 is transmitted to the electrode 23 in the solid-state imaging device 21 through the inverter 28, and the potential at the electrode 23 is changed. Since capacitive coupling is formed by the electrode 23 in the solid-state imaging element 21 and the electrode 24 in the signal processing element 22, the potential of the electrode 24 also varies as the potential varies in the electrode 23. Information is transmitted to the signal processing element 22 as a digital signal by detecting a change in potential at the electrode 24 in the receiving circuit 29. The P-type transistor PT constituting the receiving circuit 29 is connected so that / Reset, which is an inverted signal of the input signal Reset of the precharge transistor P in the pixel cell 26, is input.

  Since the signal transmitted in the capacitor (capacitor) composed of the electrode 23 and the electrode 24 is a digital signal, it is possible to communicate noise-resistant information, increase the transmission speed, and reduce the area of the electrodes 23 and 24. There is an effect of improving the image quality by the transmitted image information.

  Next, the case where a plurality of pixel cells 26 are arranged in the present embodiment will be described.

  FIG. 8 shows a configuration diagram of the image pickup apparatus in the present embodiment. The image pickup apparatus according to the present embodiment includes a solid-state image pickup element 21 and a signal processing element 22, and the solid-state image pickup element 21 and the signal processing element 22 have a plurality of electrodes 23 and 24 for capacitive coupling, respectively. The information is transmitted from the solid-state imaging element 21 to the signal processing element 22 via a plurality of capacitors (capacitors) 25 formed by the plurality of electrodes 23 and 24. The solid-state imaging device 21 is provided with a photoelectric conversion element group 46 composed of a plurality of photoelectric conversion elements 26 arranged in a two-dimensional shape, and one A corresponds to one of the photoelectric conversion elements 26. / D converter 27 is provided and connected to each photoelectric conversion element 26. The plurality of A / D converters 27 form an A / D converter group 47. Corresponding to one of the A / D converters 27, one transmission circuit 28 is provided and connected to each A / D converter 27. Each transmission circuit 28 forms a transmission circuit group 48. Each transmission circuit 28 is connected to the electrodes 23 in the solid-state imaging device 21 in a one-to-one correspondence, and a capacitance (capacitor) 25 is configured by the electrodes 23 and the electrodes 24. Information transmission is wirelessly transmitted to the electrode 24 in the signal processing element 22 capacitively coupled to the electrode 23 as a signal due to voltage fluctuation in capacitive coupling. In the signal processing element 22, one receiving circuit 29 is provided corresponding to one of the electrodes 24 and is connected to the electrode 24. The plurality of receiving circuits 29 form a receiving circuit group 49.

  Next, another aspect in the present embodiment will be described. Specifically, as shown in FIG. 9, by multiplexing the information to be transmitted, the number of the electrodes 23 in the solid-state image sensor 21 and the electrodes 24 in the signal processing element 22, the transmission circuit, and the reception circuit can be reduced. It becomes possible. That is, the solid-state imaging device 21 is provided with a photoelectric conversion element group 46 including a plurality of photoelectric conversion elements 26 arranged two-dimensionally, and corresponds to one of the photoelectric conversion elements 26, An A / D converter 27 is provided and is connected to each photoelectric conversion element 26. The plurality of A / D converters 27 form an A / D converter group 47. The output of each A / D converter 27 is connected to the multiplexer 33. Information converted into one signal by the multiplexer 33 is transmitted to the transmission circuit 34. The transmission circuit 34 is connected to the electrodes 23 in the solid-state imaging device 21 in a one-to-one correspondence, and a capacitance (capacitor) 25 is configured by the electrodes 23 and the electrodes 24. Information transmission is wirelessly transmitted to the electrode 24 in the signal processing element 22 capacitively coupled to the electrode 23 as a signal due to voltage fluctuation in capacitive coupling. The signal processing element 22 is provided with a receiving circuit 35 connected to the electrodes 24 on a one-to-one basis. With this configuration, the number of transmitting elements 34 in the solid-state imaging device 21 and the number of receiving elements 35 in the signal processing element 22 can be greatly reduced, thereby reducing the size of the solid-state imaging element 21 and the signal processing element 22, and consequently. It is possible to reduce the size of the configured image pickup apparatus. In FIG. 9, one capacitor (capacitor) 25 composed of the electrode 23 and the electrode 24 has been described. However, even if there are a plurality of capacitors, the same effect can be obtained if the number is smaller than the number of image cells 26.

  Furthermore, another aspect in the present embodiment will be described based on FIG. Specifically, by multiplexing the information to be transmitted, the number of A / D converters as well as the electrode 23 in the solid-state image sensor 21 and the electrode 24 in the signal processing element 22, the transmission circuit, and the reception circuit are reduced. Is possible. That is, the solid-state imaging device 21 is provided with a photoelectric conversion element group 46 composed of a plurality of photoelectric conversion elements 26 arranged in a two-dimensional shape, and the output of each photoelectric conversion element 26 is connected to the multiplexer 36. ing. Information converted into one signal by the multiplexer 36 is transmitted to the transmission circuit 34 through the A / D converter 37. The A / D converter 37 and the transmission circuit 34 are connected in a one-to-one correspondence, and the transmission circuit 34 and the electrodes 23 in the solid-state imaging device 21 are connected in a one-to-one correspondence. A capacitance (capacitor) 25 is constituted by the electrode 23 and the electrode 24. Information transmission is wirelessly transmitted to the electrode 24 in the signal processing element 22 capacitively coupled to the electrode 23 as a signal due to voltage fluctuation in capacitive coupling. The signal processing element 22 is provided with a receiving circuit 35 connected to the electrodes 24 on a one-to-one basis. With this configuration, the number of A / D converters 37, transmission elements 34, and reception elements 35 in the signal processing element 22 in the solid-state imaging element 21 can be significantly reduced, and the solid-state imaging element 21 and the signal processing element 22 can be reduced. And miniaturization of the image pickup apparatus. In FIG. 10, one capacitor (capacitor) 25 composed of the electrode 23 and the electrode 24 has been described. However, even if there are a plurality of capacitors (capacitors) 25, the same effect can be obtained if the number is smaller than the number of image cells 26.

[Third Embodiment]
The third embodiment is a method for transmitting grayscale data of a pixel cell when a 1-bit A / D converter is used in the second embodiment in which information transmitted by capacitive coupling is a digital signal. It is.

  Specifically, the image processing element 22 measures the time “1” from the time when the precharge stop signal is received from the solid-state imaging device 21, measures the time, and based on the time, It is used as gradation information.

  This embodiment will be described based on the flowcharts of FIGS.

  First, in step 12 (S12), the photoelectric conversion element PD is precharged. Specifically, the photoelectric conversion element PD in the solid-state imaging element 21 is precharged. At this time, a signal of “0” is transmitted from the solid-state imaging element 21 to the signal processing element 22 via the A / D converter 27, the inverter 28, the electrode 23 and the electrode 24 constituting the capacitor (capacitor) 25. The A / D converter 27 is applied with a threshold voltage VREF [V].

  Next, in step 14 (S14), the precharge of the photoelectric conversion element PD is stopped. At this time, this information is transmitted from the solid-state imaging device 21 to the signal processing device 22 through a line different from the capacitive coupling in the capacitor 25. Based on this signal, the operation of a timer (not shown) in the signal processing element 22 is started.

  Next, in step 16 (S 16), a signal “1” is transmitted from the solid-state imaging device 21. Specifically, in step 12, a signal “0” is transmitted from the solid-state imaging device 21 to the signal processing element 22 via the electrode 23 and the electrode 24 each including a capacitor (capacitor) 25. The signal “1” is output from the A / D converter 27 at the moment when the signal input to the A / D converter 27 output from 26 falls below VREF [V]. This signal is transmitted to the signal processing element 22 through the inverter 28, the electrode 23 and the electrode 24 constituting the capacitor (capacitor) 25.

  Next, in step 18 (S 18), the signal processing element 22 receives the signal “1”, thereby stopping the operation of a timer (not shown) in the signal processing element 22. The time from the end time of charging to the reception of the signal “1” is calculated.

  Based on this time, the gradation information in the pixel cell 26 is transmitted as data. Thus, even when a 1-bit A / D converter is used, data can be transmitted in an analog manner, and gradation information in the pixel cell 26 can be transmitted to the signal processing element 22 as data. it can.

[Fourth Embodiment]
The fourth embodiment is a method for optimizing the value of VREF, which is the threshold voltage in the A / D converter in the third embodiment.

  Next, in the pixel cell 26, when the time until the voltage falls below VREF [V] is not appropriate, that is, when the time until the voltage falls below VREF [V] is short or long, or below VREF [V]. This is a method of optimizing the value of VREF when there is a pixel with a short period of time or when there is a pixel with a long time.

  Specifically, referring to FIG. 12, first, in step 22 (S22), the photoelectric conversion element PD is precharged.

  Next, in step 24 (S24), the photoelectric conversion element PD receives light.

  Next, in step 26 (S26), the time t until it falls below VREF [V] is measured by the signal input to the A / D converter 27 output from the pixel cell 26, and the time t is VREF [V]. It is determined whether or not it is longer than a predetermined time t1 until it falls below. If it is determined in step 26 that the value of the time t is longer than the time t1 until it falls below the predetermined VREF [V], the process proceeds to step 28 (S28).

  In step 28, after increasing the value of VREF, the routine proceeds to step 22.

  On the other hand, if it is determined in step 26 that the value of the time t is not longer than the time t1 until it falls below the predetermined VREF [V], the process proceeds to step 30 (S30).

  In step 30, it is determined whether or not the time t is shorter than a predetermined time t2 until the time t falls below VREF [V]. If it is determined in step 30 that the value of the time t is shorter than the time t2 until it falls below the predetermined VREF [V], the process proceeds to step 32 (S32).

  In step 32, after the value of VREF is lowered, the process proceeds to step 22.

  On the other hand, if it is determined in step 30 that the value of time t is not shorter than the time t2 until it falls below the predetermined VREF [V], the process proceeds to step 34 (S34).

  In step 34, the value of VREF is determined and the process ends. Specifically, the value of VREF is set so that the time t is in the range of t1 <t <t2.

  By this method, a sufficient dynamic range of the pixel cell 26 can be ensured. Note that, in the image imaging apparatus according to the present embodiment, the imaging and reading of the image in the photoelectric conversion element PD are performed at a higher speed than in an image imaging apparatus such as a normal image sensor. It can be performed in a short time.

  If the time until VREF [V] falls is very long and does not fall within the predetermined time, information in the pixel cell 26 is obtained by changing the value of VREF after a certain time has elapsed. Is possible.

  Further, in the step of increasing the VREF value in step 28 and the step of decreasing the VREF value in step 32 in the present embodiment, a predetermined VREF value is obtained by controlling the voltage generated by the voltage generation circuit. It can be. In the present embodiment, more specifically, when the voltage value that is the value of VREF is changed stepwise, as shown in FIG. 13, a plurality of voltage generation circuits 1 (61) and voltage generation circuits 2 are used. (62), a voltage generation circuit 3 (63), a voltage generation circuit 4 (64), and a voltage generation circuit 5 (65) are provided, and different voltages VREF1 [V], VREF2 [V], VREF3 [ There is a method of generating V], VREF4 [V], VREF5 [V] and applying the voltage selected by the selector 66 as VREF [V].

  Further, as shown in FIG. 14, a voltage of VREF [V] generated by the voltage generation circuit 72 is applied to a cell 71 including a photoelectric conversion element PD and an AD converter corresponding to one of the pixel cells, and VREF After the value of [V] is converted into a digital value by the A / D converter 73, the value is transmitted from the solid-state imaging device 21 to the signal processing device, and the value of VREF [V] is confirmed in the signal processing circuit based on this value. Is also possible.

  In addition, a 1-bit A / D converter is used, and the photoelectric conversion element PD is precharged by VREF [V] which is the threshold voltage of the A / D converter. Immediately after starting, the threshold voltage in the A / D converter is changed, and the output of the photoelectric conversion element PD is read out to the signal processing element. Thereafter, after a predetermined time has elapsed, the threshold voltage in the A / D converter is changed again, and the output of the photoelectric conversion element PD is read out to the signal processing element. By using the difference between the two read output values, CDS (Correlated Double Sampling) can be realized and noise can be eliminated, so that a good image can be obtained. In addition, when the output difference due to the two readings from the photoelectric conversion element is smaller than a predetermined value, the measurement accuracy is improved by setting the interval between the two readings to be long and performing the measurement again. Can do. Similarly, when the output difference between the two readings from the photoelectric conversion element is larger than a predetermined value, the measurement accuracy is improved by setting the interval between the two readings to be short and performing the measurement again. be able to.

  As described above, when the interval of the readout time is changed, when it is made longer, a time twice as long as the interval measured immediately before is set. By setting the value to a power of 2 and repeating this operation, the number of times to reach a predetermined voltage can be shortened. Similarly, when shortening, the time of 1/2 of the interval measured immediately before is set, and when further shortening is required, the value is 1/4 times that becomes 1/2, By setting this to a power value and repeating this operation, the number of times to reach a predetermined voltage can be made relatively short.

  Further, by changing the VREF value depending on whether or not the image requires high accuracy, efficient image acquisition can be performed. Specifically, in the case of an image that requires high accuracy, the change in VREF is moderated, and in the case of an image that does not require high accuracy, the change in VREF is made abrupt. This makes it possible to acquire images quickly. In this case, the dynamic range can be made wider by changing the value of VREF exponentially.

  Although the present invention has been described in detail above in the embodiments, the present invention is not limited to the above-described embodiments and aspects, and can take other forms.

Overview of the image pickup apparatus in the first embodiment 1 is a configuration diagram of an image pickup apparatus according to a first embodiment. Circuit diagram of a pixel cell used in the first embodiment Circuit diagram of another pixel cell used in the first embodiment Explanatory drawing of the transmission / reception part of the imaging device in 1st Embodiment 1 is a configuration diagram of an image pickup apparatus according to a first embodiment. Explanatory drawing of the imaging device in 2nd Embodiment The block diagram of the image pick-up device in a 2nd embodiment The block diagram of another image pick-up device in a 2nd embodiment The block diagram of another image pick-up device in a 2nd embodiment Flowchart in the third embodiment Flowchart in the fourth embodiment Configuration diagram for setting the value of VREF in the fourth embodiment Configuration diagram for transmitting the value of VREF to the signal processing element in the fourth embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Solid-state image sensor, 12 ... Signal processing element, 13, 14 ... Electrode for capacitive coupling, 15 ... Capacitance (capacitor), 16 ... Pixel cell, 17 ... Reception circuit

Claims (5)

A surface on which a plurality of pixel cells for image capturing are formed, electrodes for capacitive coupling for transmitting image information obtained by the pixel cells are formed, and electrodes for the capacitive coupling are formed A back-illuminated solid-state image sensor that inputs an image from the opposite of
A signal in which a signal processing circuit is formed for signal processing the image information, and an electrode for capacitive coupling for receiving image information corresponding to a position of the electrode for capacitive coupling of the solid-state imaging device is formed. A processing element;
Capacitive coupling transmission means for transmitting a signal through a capacitor constituted by an electrode for capacitive coupling in the solid-state imaging device and an electrode for capacitive coupling in the signal processing device;
An image pickup apparatus comprising:   The image capturing apparatus according to claim 1, wherein one capacitor in the capacitive coupling transmission unit is provided corresponding to one of the pixel cells.   The image capturing apparatus according to claim 1, wherein the signal transmitted by the capacitive coupling unit is a digital signal.   The image capturing apparatus according to claim 1, wherein the image information signals acquired in the plurality of pixel cells are multiplexed and transmitted.   The image pickup apparatus according to claim 1, wherein a circuit for control is not formed in the solid-state image pickup device.

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