# Patent

## Title
Solid-state image pickup apparatus and X-ray inspection system

## Abstract

A solid-state image pickup apparatus 1A includes a photodetecting section 10A and a signal readout section 20 etc. In the photodetecting section 10A, M×N pixel units P1,1 to PM,N are arrayed in M rows and N columns. When in a first imaging mode, a voltage value according to an amount of charges generated in a photodiode of each of the M×N pixel units in the photodetecting section 10A is output from the signal readout section 20. When in a second imaging mode, a voltage value according to an amount of charges generated in the photodiode of each pixel unit included in consecutive M1 rows in the photodetecting section 10A is output from the signal readout section 20. When in the second imaging mode than when in the first imaging mode, the readout pixel pitch in frame data is smaller, the frame rate is higher, and the gain being a ratio of an output voltage value to an input charge amount in the signal readout section 20 is greater.

## Background
This is a continuation application of copending application Ser. No. 12/989,129, having a §371 date of Aug. 29, 2011, which is a national stage filing based on PCT International Application No. PCT/JP2009/058006, filed on Apr. 22, 2009. The copending application Ser. No. 12/989,129 is incorporated by reference herein in its entirety.


TECHNICAL FIELD
The present invention relates to a solid-state image pickup apparatus and an X-ray inspection system.
BACKGROUND ART
Solid-state image pickup apparatuses using the CMOS technique are known, and among these, a passive pixel sensor (PPS) type solid-state image pickup apparatus is known. The PPS type solid-state image pickup apparatus includes a photodetecting section where PPS type pixel units including photodiodes for generating charges of amounts according to incident light intensities are two-dimensionally arrayed in M rows and N columns, accumulates, in a capacitor of an integrating circuit, charges generated in the photodiode in response to light incidence in each pixel unit, and outputs a voltage value according to the accumulated charge amount.
Generally, an output terminal of each of the M pixel units of each column is connected with an input terminal of an integrating circuit provided corresponding to the column via a readout wiring provided corresponding to the column. And, in sequence from the first row to the M-th row and row by row, charges generated in the photodiodes of the pixel units are input to a corresponding integrating circuit through a corresponding readout wiring, and a voltage value according to the charge amount is output from the integrating circuit.
The PPS type solid-state image pickup apparatus is used for various purposes, and used, for example, in combination with a scintillator section as an X-ray flat panel also for medical purposes and industrial purposes, and further specifically used also in an X-ray CT apparatus, a microfocus X-ray inspection system, etc. An X-ray inspection system disclosed in Patent Document 1 is a system that images X-rays output from an X-ray generator and transmitted through an inspection object by a solid-state image pickup apparatus to inspect the inspection object, and is capable of imaging X-rays transmitted through the inspection object by the solid-state image pickup apparatus in a plurality of types of imaging modes. These multiple types of imaging modes are mutually different in an imaging region in the photodetecting section.
CITATION LIST
Patent Literature
Patent Document 1: Pamphlet of International Publication No. WO2006/109808
SUMMARY OF INVENTION
Technical Problem
In Patent Document 1, there is a description to the effect of differentiating the imaging region in the photodetecting section of the solid-state image pickup apparatus depending on the imaging mode, but there is no disclosure of the configuration and operation of the solid-state image pickup apparatus. However, the inventor of the present invention has discovered that a problem exists that the solid-state image pickup apparatus cannot always operate favorably in any of the multiple types of imaging modes depending on the configuration and operation of the solid-state image pickup apparatus.
The present invention has been made in order to solve the above problem, and an object thereof is to provide a solid-state image pickup apparatus and an X-ray inspection system that can operate favorably in each of a plurality of types of imaging modes.
Solution to Problem
A solid-state image pickup apparatus according to the present invention comprises (1) a photodetecting section having M×N pixel units P1,1 to PM,N two-dimensionally arranged in M rows and N columns, each of the pixel units including a photodiode and a readout switch connected with the photodiode, the photodiode generating charges corresponding to an intensity of an incident light, (2) a readout wiring LO,n connected with a readout switch of each of the M pixel units P1,n to PM,n of an n-th column in the photodetecting section, for reading out charges generated in the photodiode of any pixel unit of the M pixel units P1,n to PM,n via the readout switch of the pixel unit, (3) a signal readout section connected with each of the readout wirings LO,1 to LO,N, for holding a voltage value according to an amount of charges input through the readout wiring LO,n, and sequentially outputting the held voltage values, and (4) a controlling section that controls an opening and closing operation of the readout switch of each of the M×N pixel units P1,1 to PM,N in the photodetecting section and controls an outputting operation of a voltage value in the signal readout section to make a voltage value according to an amount of charges generated in the photodiode of each of the M×N pixel units P1,1 to PM,N in the photodetecting section be output from the signal readout section. Further, the controlling section, (a) when in a first imaging mode, makes a voltage value according to an amount of charges generated in the photodiode of each of the M×N pixel units P1,1 to PM,N in the photodetecting section be output from the signal readout section, (b) when in a second imaging mode, makes a voltage value according to an amount of charges generated in the photodiode of each pixel unit Pm,n included in a specific range of consecutive M1 rows or N1 columns in the photodetecting section be output from the signal readout section, and (c) when in the second imaging mode than when in the first imaging mode, makes a readout pixel pitch in frame data based on a voltage value to be output from the signal readout section smaller, makes a frame rate being a number of frames of data to be output per unit time higher, and makes a gain being a ratio of an output voltage value to an input charge amount in the signal readout section greater. However, M and N are each an integer not less than 2, M1 is an integer less than M, N1 is an integer less than N, m is an integer not less than 1 and not more than M, and n is an integer not less than 1 and not more than N.
In the solid-state image pickup apparatus according to the present invention, under control by the controlling section, a charge generated in each pixel unit Pm,n in response to light incidence into the photodiode is, when a readout switch of the pixel unit is closed, input to the signal readout section through the readout switch and the readout wiring LO,n. In the signal readout section, a voltage value according to the input charge amount is output. This solid-state image pickup apparatus has a first imaging mode and a second imaging mode. Under control by the controlling section, when in the first imaging mode, a voltage value according to the amount of charges generated in the photodiode of each of the M×N pixel units P1,1 to PM,N in the photodetecting section is output from the signal readout section. On the other hand, when in the second imaging mode, a voltage value according to the amount of charges generated in the photodiode of each pixel unit Pm,n included in a specific range of consecutive M1 rows or N1 columns in the photodetecting section is output from the signal readout section. Further, when in the second imaging mode than when in the first imaging mode, the readout pixel pitch is made smaller, the frame rate is made higher, and the gain being a ratio of an output voltage value to an input charge amount in the signal readout section is made greater.
In the solid-state image pickup apparatus according to the present invention, the controlling section, when in the second imaging mode, preferably has as the specific range, a range of M1 rows counted in order from the row closest to the signal readout section out of the M rows in the photodetecting section, and makes a voltage value according to the amount of charges generated in the photodiode of each pixel unit Pm,n in the specific range be output from the signal readout section.
The solid-state image pickup apparatus according to the present invention preferably further includes, between the specific range in the photodetecting section and another range excluding the specific range, a disconnection switch provided on each readout wiring LO,n, and the controlling section preferably closes the disconnection switch when in the first imaging mode, and opens the disconnection switch when in the second imaging mode.
The solid-state image pickup apparatus according to the present invention preferably includes discharging means that discharges a junction capacitance section of the photodiode in each pixel unit Pm,n of another range excluding the specific range in the photodetecting section when in the second imaging mode.
The solid-state image pickup apparatus according to the present invention preferably further includes a scintillator section that is provided so as to cover the M×N pixel units P1,1to PM,N in the photodetecting section.
Moreover, an X-ray inspection system according to the present invention includes the solid-state image pickup apparatus according to the present invention described above and an X-ray generator, and images X-rays output from the X-ray generator and transmitted through an inspection object by the solid-state image pickup apparatus to inspect the inspection object. Moreover, it is preferable that the X-ray generator outputs X-rays at a predetermined divergence angle when in a first output mode, and outputs X-rays at a narrower divergence angle than the predetermined divergence angle when in a second output mode, and that the solid-state image pickup apparatus operates in the first imaging mode when the X-ray generator outputs X-rays in the first output mode, and the solid-state image pickup apparatus operates in the second imaging mode when the X-ray generator outputs X-rays in the second output mode.
Advantageous Effects of Invention
The solid-state image pickup apparatus according to the present invention can operate favorably in each of the multiple types of imaging modes.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view showing a configuration of a solid-state image pickup apparatus 1A according to a first embodiment.
FIG. 2 is a view showing a section of the solid-state image pickup apparatus 1A according to the first embodiment.
FIG. 3 is a circuit diagram of each of the pixel unit Pm,n , the integrating circuit Sn, and the holding circuit Hn of the solid-state image pickup apparatus 1A according to the first embodiment.
FIG. 4 is a timing chart for explaining operation of the solid-state image pickup apparatus 1A according to the first embodiment.
FIG. 5 is a timing chart for explaining operation of the solid-state image pickup apparatus 1A according to the first embodiment.
FIG. 6 is a timing chart for explaining operation of the solid-state image pickup apparatus 1A according to the first embodiment.
FIG. 7 is a view showing a configuration of a solid-state image pickup apparatus 1B according to a second embodiment.
FIG. 8 is a configuration diagram of an X-ray inspection system 100 according to the present embodiment.
FIG. 9 is a view showing a modification of the configuration of the solid-state image pickup apparatus 1A, 1B according to the present embodiment.



DESCRIPTION OF EMBODIMENTS
Hereinafter, a best mode for carrying out the present invention will be described in detail with reference to the accompanying drawings. Also, the same components will be denoted with the same reference numerals in the description of the drawings, and overlapping description will be omitted.
First, description will be given of a solid-state image pickup apparatus 1A according to a first embodiment. FIG. 1 is a view showing a configuration of the solid-state image pickup apparatus 1A according to the first embodiment. The solid-state image pickup apparatus 1A shown in this figure includes a photodetecting section 10A, a signal readout section 20, an A/D converting section 30, and a controlling section 40A. Moreover, in the case of use as one for X-ray detection, a scintillator section is provided so as to cover the photodetecting section 10A of the solid-state image pickup apparatus 1A.
For the photodetecting section 10A, M×N pixel units P1,1 to PM,N are two-dimensionally arrayed in M rows and N columns. A pixel unit Pm,n is located on the m-th row and the n-th column. The pixel units Pm,n are arrayed at a pitch of, for example, 100 μm. Here, M and N are each an integer not less than 2, m is an integer not less than 1 and not more than M, and n is an integer not less than 1 and not more than N. The pixel units Pm,n are pixel units of the PPS type, and have a common configuration.
In addition, the photodetecting section 10A may have, around the M×N pixel units P1,1 to PM,N two-dimensionally arrayed in M rows and N columns, pixel units including photodiodes. However, these surrounding pixel units, which are covered with a shielding portion that prevents incidence of X-rays into the signal readout section 20 and the like and where no light is made incident and no charge is generated, thus do not contribute to imaging. The photodetecting section 10A includes at least the M×N pixel units P1,1 to PM,N two-dimensionally arrayed in M rows and N columns as effective pixel units for imaging.
Each of the N pixel units Pm,1 to Pm,N of the m-th row is connected with the controlling section 40A by an m-th row selecting wiring LV,m. An output terminal of each of the M pixel units P1,n to PM,n of the n-th column is connected with an integrating circuit Sn of the signal readout section 20 by an n-th column readout wiring LO,n.
The signal readout section 20 includes N integrating circuits S1 to SN and the N holding circuits H1 to HN. The integrating circuits Sn have a common configuration. Moreover, the holding circuits Hn have a common configuration.
Each integrating circuit Sn has an input terminal connected with the readout wiring LO,n, accumulates charges input to this input terminal, and outputs a voltage value according to the accumulated charge amount from an output terminal to the holding circuit Hn. Each of the N integrating circuits S1 to SN is connected with the controlling section 40A by a reset wiring LR, and also connected with the controlling section 40A by a gain setting wiring LG.
Each holding circuit Hn has an input terminal connected with the output terminal of the integrating circuit Sn, holds a voltage value input to this input terminal, and outputs the held voltage value from an output terminal to a voltage outputting wiring Lout. Each of the N holding circuits H1 to HN is connected with the controlling section 40A by a holding wiring LH. Moreover, each holding circuit Hn is connected with the controlling section 40A by an n-th column selecting wiring LH,n.
The A/D converting section 30 is input with a voltage value output to the voltage outputting wiring Lout from each of the N holding circuits H1 to HN, and applies A/D converting to the input voltage value (analog value) to output a digital value according to the input voltage value.
The controlling section 40A outputs an m-th row selection control signal Vsel(m) to the m-th row selecting wiring LV,m to supply this m-th row selection control signal Vsel(m) to each of the N pixel units Pm,1 to Pm,N of the m-th row. M row selection control signals Vsel(1) to Vsel(M) sequentially take significant values. The controlling section 40A includes a shift register to sequentially output M row selection control signals Vsel(1) to Vsel(M) as significant values.
The controlling section 40A outputs an n-th column selection control signal Hsel(n) to the n-th column selecting wiring LH,n to supply this n-th column selection control signal Hsel(n) to the holding circuit Hn. N column selection control signals Hsel(1) to Hsel(N) also sequentially take significant values. The controlling section 40A includes a shift register to sequentially output N column selection control signals Hsel(1) to Hsel(N) as significant values.
Moreover, the controlling section 40A outputs a reset control signal Reset to the reset wiring LR to supply this reset control signal Reset to each of the N integrating circuits S1 to SN. The controlling section 40A outputs a gain setting signal Gain to the gain setting wiring LG to supply this gain setting signal Gain to each of the N integrating circuits S1 to SN. The controlling section 40A outputs a hold control signal Hold to the holding wiring LH to supply this hold control signal Hold to each of the N holding circuits H1 to HN. Further, the controlling section 40A also controls A/D converting in the A/D converting section 30, which is not shown.
The controlling section 40A, as in the above, controls an opening and closing operation of a readout switch SW1 in each of the M×N pixel units P1,1 to PM,N in the photodetecting section 10A, and controls a holding operation and an outputting operation of a voltage value in the signal readout section 20. Accordingly, the controlling section 40A makes a voltage value according to the amount of charges generated in the photodiode of each of the M×N pixel units P1,1 to PM,N in the photodetecting section 10A be repeatedly output as frame data from the signal readout section 20.
FIG. 2 is a view showing a section of the solid-state image pickup apparatus 1A according to the first embodiment. For the solid-state image pickup apparatus 1A, a semiconductor substrate 3 is adhered to a flat plate-like base member 2, and a scintillator section 4 is provided on the semiconductor substrate 3. On a main surface of the semiconductor substrate 3, the photodetecting section 10A where the pixel units Pm,n are arrayed, the signal readout section 20, the A/D converting section 30 (refer to FIG. 1), and the controlling section 40A (refer to FIG. 1) are formed and integrated, and a bonding pad 50 for signal input/output or power supply is formed. The scintillator section 4 is provided so as to cover the M×N pixel units P1,1 to PM,N in the photodetecting section 10A. The scintillator section 4 may be provided by vapor deposition on the semiconductor substrate 3. In addition, each of the signal readout section 20, the A/D converting section 30, and the controlling section 40A may be integrated not on the semiconductor substrate 3 on which the photodetecting section 10A is integrated, but on a semiconductor substrate separate from the semiconductor substrate 3.
FIG. 3 is a circuit diagram of each of the pixel unit Pm,n, the integrating circuit Sn, and the holding circuit Hn of the solid-state image pickup apparatus 1A according to the first embodiment. Here, a circuit diagram of the pixel unit Pm,n as a representative of the M×N pixel units P1,1 to PM,N is shown, a circuit diagram of the integrating circuit Sn as a representative of the N integrating circuits S1 to SN is shown, and a circuit diagram of the holding circuit Hn as a representative of the N holding circuits H1 to HN is shown. That is, circuit portions relating to the pixel unit Pm,n on the m-th row and the n-th column and the n-th column readout wiring LO,n are shown.
The pixel unit Pm,n includes a photodiode PD and a readout switch SW1. The anode terminal of the photodiode PD is grounded, and the cathode terminal of the photodiode PD is connected with the n-th column readout wiring LO,n via the readout switch SW1. The photodiode PD generates charge of an amount according to an incident light intensity, and accumulates the generated charge in a junction capacitance section of the photodiode itself. The readout switch SW1 is supplied with an m-th row selection control signal Vsel(m) passed through the m-th row selecting wiring LV,m from the controlling section 40A. The m-th row selection control signal Vsel(m) is a signal that instructs an opening and closing operation of the readout switch SW1 in each of the N pixel units Pm,1 to Pm,N of the m-th row in the photodetecting section 10A.
In this pixel unit Pm,n, when the m-th row selection control signal Vsel(m) is at low level, the readout switch SW1 opens, and charges generated in the photodiode PD are not output to the n-th column readout wiring LO,n but is accumulated in the junction capacitance section of the photodiode itself. On the other hand, when the m-th row selection control signal Vsel(m) is at high level, the readout switch SW1 closes, and the charge generated in the photodiode PD and accumulated in the junction capacitance section until then is output to the n-th column readout wiring LO,n through the readout switch SW1.
The n-th column readout wiring LO,n is connected with the readout switch SW1 in each of the M pixel units P1,n to PM,n of the n-th column in the photodetecting section 10A. The n-th column readout wiring LO,n reads out charges generated in the photodiode PD of any of the M pixel units P1,n to PM,n via the readout switch SW1 in this pixel unit, and transfers the charge to the integrating circuit Sn.
The integrating circuit Sn includes an amplifier A2, an integrating capacitor C21, an integrating capacitor C22, a discharge switch SW21, and a gain setting switch SW22. The integrating capacitor C21 and the discharge switch SW21 are connected in parallel to each other, and provided between an input terminal and an output terminal of the amplifier A2. Moreover, the integrating capacitor C22 and the gain setting switch SW22 are connected in series to each other, and provided between an input terminal and an output terminal of the amplifier A2, so that the gain setting switch SW22 is connected to the input terminal side of the amplifier A2. The input terminal of the amplifier A2 is connected with the n-th column readout wiring LO,n.
The discharge switch SW21 is supplied with a reset control signal Reset through the reset wiring LR from the controlling section 40A (refer to FIG. 1). The reset control signal Reset is a signal that instructs an opening and closing operation of the discharge switch SW21 in each of the N integrating circuits S1 to SN. The gain setting switch SW22 is supplied with a gain setting signal Gain through the gain setting wiring LG from the controlling section 40A. The gain setting signal Gain is a signal that instructs an opening and closing operation of the gain setting switch SW22 in each of the N integrating circuits S1 to SN.
In this integrating circuit Sn, the integrating capacitors C21, C22 and the gain setting switch SW22 compose a feedback capacitance section where the capacitance value is variable. That is, when the gain setting signal Gain is at low level and the gain setting switch SW22 is open, the capacitance value of the feedback capacitance section is equal to a capacitance value of the integrating capacitor C21. On the other hand, when the gain setting signal Gain is at high level and the gain setting switch SW22 is closed, the capacitance value of the feedback capacitance section is equal to a sum of respective capacitance values of the integrating capacitors C21, C22. When the reset control signal Reset is at high level, the discharge switch SW21 closes, the feedback capacitance section is discharged, and a voltage value to be output from the integrating circuit Sn is initialized. On the other hand, when the reset control signal Reset is at low level, the discharge switch SW21 opens, a charge input to the input terminal is accumulated in the feedback capacitance section, and a voltage value according to the accumulated charge amount is output from the integrating circuit Sn.
The holding circuit Hn includes an input switch SW31, an output switch SW32, and a holding capacitor C3. One end of the holding capacitor C3 is grounded. The other end of the holding capacitor C3 is connected with the output terminal of the integrating circuit Sn via the input switch SW31, and connected with the voltage outputting wiring Lout via the output switch SW32. The input switch SW31 is supplied with a hold control signal Hold passed through the holding wiring LH from the controlling section 40A. The hold control signal Hold is a signal that instructs an opening and closing operation of the input switch SW31 in each of the N holding circuits H1 to HN. The output switch SW32 is supplied with an n-th column selection control signal Hsel(n) passed through the n-th column selecting wiring LH,n from the controlling section 40A. The n-th column selection control signal Hsel(n) is a signal that instructs an opening and closing operation of the output switch SW32 of the holding circuit Hn.
In this holding circuit Hn, when the hold control signal Hold switches from high level to low level, the input switch SW31 switches from a closed state to an open state, and a voltage value being input to the input terminal at this time is held in the holding capacitor C3. Moreover, when the n-th column selection control signal Hsel(n) is at high level, the output switch SW32 closes, and the voltage value held in the holding capacitor C3 is output to the voltage outputting wiring Lout.
The controlling section 40A shown in FIG. 1, when outputting a voltage value according to a received light intensity in each of the N pixel units Pm,1 to Pm,N of the m-th row in the photodetecting section 10A, instructs temporary closing and then opening of the discharge switch SW21 in each of the N integrating circuits S1 to SN by a reset control signal Reset, and then instructs closing of the readout switch SW1 in each of the N pixel units Pm,1 to Pm,N of the m-th row in the photodetecting section 100A for a predetermined period by an m-th row selection control signal Vsel(m). The controlling section 40A, in this predetermined period, instructs switching of the input switch SW31 in each of the N holding circuits H1 to HN from a closed state to an open state by a hold control signal Hold. Then, the controlling section 40A, after the predetermined period, instructs sequential closing of the output switches SW32 in the respective N holding circuits H1 to HN for a predetermined period by column selection control signals Hsel(1) to Hsel(N). The controlling section 40A performs such control as in the above for the respective rows in sequence.
The solid-state image pickup apparatus 1A according to the present embodiment particularly has a first imaging mode and a second imaging mode. The first imaging mode and the second imaging mode are mutually different in an imaging region in the photodetecting section 10A. The controlling section 40A, when in the first imaging mode, makes a voltage value according to the amount of charges generated in the photodiode PD of each of the M×N pixel units P1,1 to PM,N in the photodetecting section 10A be output from the signal readout section 20. Also, the controlling section 40A, when in the second imaging mode, makes a voltage value according to the amount of charges generated in the photodiode PD of each pixel unit Pm,n included in a specific range of consecutive M1 rows or N1 columns in the photodetecting section 10A be output from the signal readout section 20. In addition, M1 is an integer less than M, and N1 is an integer less than N.
The controlling section 40A, when in the second imaging mode, preferably has a range of consecutive M1 rows in the photodetecting section 10A as the specific range, and more preferably has, as the specific range, a range of M1 rows counted in order from the row closest to the signal readout section 20 out of the M rows in the photodetecting section 10A. That is, where the row closest to the signal readout section 20 in the photodetecting section 10A is the first row as shown in FIG. 1, the controlling section 40A, when in the second imaging mode, preferably has a range from the first row to the M1-th row in the photodetecting section 10A as the specific range, and makes a voltage value according to the amount of charges generated in the photodiode PD of each pixel unit Pm,n of this specific range (first row to M1-th row) be output from the signal readout section 20. This makes it highly likely, even with the n-th column readout wiring LO,n disconnected, to allow making a voltage value according to the amount of charges generated in the photodiode PD of each pixel unit Pm,n of the specific range be normally output from the signal readout section 20 when in the second imaging mode.
Moreover, the controlling section 40A, when in the second imaging mode than when in the first imaging mode, makes the readout pixel pitch in the frame data based on the voltage value to be output from the signal readout section 20 smaller, and the frame rate being the number of frames of data to be output per unit time higher, and the gain being a ratio of an output voltage value to an input charge amount in the signal readout section 20 greater.
For example, assuming that the solid-state image pickup apparatus 1A according to the present embodiment is used in the X-ray inspection system disclosed in Patent Document 1, and this X-ray inspection system is used for a dental application, the following applies. At this time, the first imaging mode corresponds to a CT mode described in Patent Document 1, and the second imaging mode corresponds to a panoramic mode or cephalographic mode described in Patent Document 1. When in the first imaging mode, the pixel pitch is 200 μm, and the frame rate (the number of frames (F) per 1 second (s)) is 30 F/s. On the other hand, when in the second imaging mode, the pixel pitch is 100 μm, and the frame rate is 300 F/s.
Thus, when in the second imaging mode than when in the first imaging mode, the pixel pitch is smaller, and the frame rate is higher. Therefore, when in the first imaging mode, it is necessary to perform binning readout in order to make the pixel pitch larger than when in the second imaging mode. Moreover, when in the second imaging mode than when in the first imaging mode, the amount of light that each pixel of each frame of data receives is smaller.
Then, the controlling section 40A differentiates the gain being a ratio of an output voltage value to an input charge amount in the signal readout section 20 between the first imaging mode and second imaging mode. That is, when each integrating circuit Sn is configured as shown in FIG. 3, the controlling section 40A, by controlling to open and close the gain setting switch SW22 by the gain setting signal Gain, appropriately sets the capacitance value of the feedback capacitance section of each integrating circuit Sn to differentiate the gain between the first imaging mode and second imaging mode.
More specifically, when in the first imaging mode, the controlling section 40A closes the gain setting switch SW22 to thereby make the capacitance value of the feedback capacitance section equal to a sum of the respective capacitance values of the integrating capacitor C21 and integrating capacitor C22. On the other hand, when in the second imaging mode, the controlling section 40A opens the gain setting switch SW22 to thereby make the capacitance value of the feedback capacitance section equal to the capacitance value of the integrating capacitor C21. In this way, when in the second imaging mode than when in the first imaging mode, the capacitance value of the feedback capacitance section of each integrating circuit Sn can be made smaller to make the gain larger. This allows, between the first imaging mode and second imaging mode, the respective pixel data to have mutually close values, and allows operating favorably in each imaging mode.
Next, operation of the solid-state image pickup apparatus 1A according to the first embodiment will be described. In the solid-state image pickup apparatus 1A according to the present embodiment, as a result of level changes of each of the M row selection control signals Vsel(1) to Vsel(M), the N column selection control signals Hsel(1) to Hsel(N), the reset control signal Reset, and the hold control signal Hold at predetermined timings under control by the controlling section 40A, light made incident on the photodetecting section 10A can be imaged to obtain frame data.
The operation of the solid-state image pickup apparatus 1A when in the first imaging mode is as follows. FIG. 4 is a timing chart for explaining operation of the solid-state image pickup apparatus 1A according to the first embodiment. Here, description will be given of the operation when in the first imaging mode for binning readout of 2 rows and 2 columns. That is, the readout pixel pitch in the frame data is set to two times the pitch of the pixel units. In each integrating circuit Sn, the gain setting switch SW22 is closed, the capacitance value of the feedback capacitance section is set to a large value, and the gain is set to a small value.
This figure shows, in order from the top, (a) the reset control signal Reset for instructing an opening and closing operation of the discharge switch SW21 in each of the N integrating circuits S1 to SN, (b) the first row selection control signal Vsel(1) and the second row selection control signal Vsel(2) for instructing an opening and closing operation of the readout switch SW1 in each of the pixel units P1,1 to P1,N and P2,1 to P2,N of the first and the second rows in the photodetecting section 100A, (c) the third row selection control signal Vsel(3) and the fourth row selection control signal Vsel(4) for instructing an opening and closing operation of the readout switch SW1 in each of the pixel units P3,1 to P3,N and P4,1 to P4,N of the third and the fourth rows in the photodetecting section 10A, and (d) the hold control signal Hold for instructing an opening and closing operation of the input switch SW31 in each of the N holding circuits H1 to HN.
Moreover, this figure further goes on to show, in order, (e) the first column selection control signal Hsel(1) for instructing an opening and closing operation of the output switch SW32 of the holding circuit H1, (f) the second column selection control signal Hsel(2) for instructing an opening and closing operation of the output switch SW32 of the holding circuit H2, (g) the third column selection control signal Hsel(3) for instructing an opening and closing operation of the output switch SW32 of the holding circuit H3, (h) the n-th column selection control signal Hsel(n) for instructing an opening and closing operation of the output switch SW32 of the holding circuit Hn, and (i) the N-th column selection control signal Hsel(N) for instructing an opening and closing operation of the output switch SW32 of the holding circuit HN.
Charges generated in the photodiode PD of each of the 2N pixel units P1,1 to P1,N and P2,1 to P2,N of the first and the second rows and accumulated in the junction capacitance section is read out as follows. Before the time t10, each of the M row selection control signals Vsel(1) to Vsel(M), the N column selection control signals Hsel(1) to Hsel(N), the reset control signal Reset, and the hold control signal Hold is at low level.
During a period from the time t10 to the time t11, the reset control signal Reset to be output from the controlling section 40A to the reset wiring LR becomes high level, and accordingly, in each of the N integrating circuits S1 to SN, the discharge switch SW21 closes, and the integrating capacitors C21, C22 are discharged. Moreover, during a period from the time t12 to the time t15 after the time t11, the first row selection control signal Vsel(1) to be output from the controlling section 40A to the first row selecting wiring LV,1 becomes high level, and accordingly, the readout switch SW1 in each of the N pixel units P1,1 to P1,N of the first row in the photodetecting section 10A closes. Moreover, during the same period (t12 to t15), the second row selection control signal Vsel(2) to be output from the controlling section 40A to the second row selecting wiring LV,2 becomes high level, and accordingly, the readout switch SW1 in each of the N pixel units P2,1 to P2,N of the second row in the photodetecting section 10A closes.
In the period (t12 to t15), during a period from the time t13 to the time t14, the hold control signal Hold to be output from the controlling section 40A to the holding wiring LH becomes high level, and accordingly, the input switch SW31 closes in each of the N holding circuits H1 to HN.
In this period (t12 to t15), the readout switch SW1 in each pixel unit P1,n, P2,n of the first and the second rows is closed, and the discharge switch SW21 of each integrating circuit Sn is open. Therefore, charges generated in the photodiode PD of the pixel unit P1,n and accumulated in the junction capacitance section until then are transferred to and accumulated in the integrating capacitors C21, C22 of the integrating circuit Sn through the readout switch SW1 of the pixel unit P1,n and the n-th column readout wiring LO,n. Moreover, simultaneously, charges generated in the photodiode PD of the pixel unit P2,n and accumulated in the junction capacitance section until then are also transferred to and accumulated in the integrating capacitors C21, C22 of the integrating circuit Sn through the readout switch SW1 of the pixel unit P2,n and the n-th column readout wiring LO,n. Then, a voltage value according to the amount of charges accumulated in the integrating capacitors C21, C22 of each integrating circuit Sn is output from the output terminal of the integrating circuit Sn.
At the time t14 in the period (t12 to t15), as a result of the hold control signal Hold switching from high level to low level, in each of the N holding circuits H1 to HN, the input switch SW31 switches from a closed state to an open state, and a voltage value being output from the output terminal of the integrating circuit Sn and being input to the input terminal of the holding circuit Hn at this time is held in the holding capacitor C3.
Then, after the period (t12 to t15), column selection control signals Hsel(1) to Hsel(N) to be output from the controlling section 40A to the column selecting wirings LH,1 to LH,N sequentially become high level for a predetermined period, and accordingly, the output switches SW32 in the N holding circuits H1 to HN sequentially close for the predetermined period, the voltage values held in the holding capacitors C3 of the holding circuits H, are sequentially output to the voltage outputting wiring Lout through the output switches SW32. The voltage value Vout to be output to the voltage outputting wiring Lout indicates a value of the received light intensities in the respective photodiodes PD of the 2N pixel units P1,1 to P1,N and P2,1 to P2,N of the first and the second rows being added in the column direction.
The voltage values sequentially output from the respective N holding circuits H1 to HN are input to the A/D converting section 30, and converted to digital values according to the input voltage values. Then, of the N digital values output from the A/D converting section 30, digital values corresponding to each of the first and the second columns are added, digital values corresponding to each of the third and the fourth columns are added, and the following digital values are continuously added two by two.
Subsequently, charges generated in the photodiode PD of each of the 2N pixel units P3,1 to P3,N and P4,1 to P4,N of the third and the fourth rows and accumulated in the junction capacitance section are read out as follows.
During a period from the time t20 to the time t21, the reset control signal Reset to be output from the controlling section 40A to the reset wiring LR becomes high level, and accordingly, in each of the N integrating circuits S1 to SN, the discharge switch SW21 closes, and the integrating capacitors C21, C22 are discharged. Moreover, during a period from the time t22 to the time t25 after the time t21, the third row selection control signal Vsel(3) to be output from the controlling section 40A to the third row selecting wiring LV,3 becomes high level, and accordingly, the readout switch SW1 in each of the N pixel units P311 to P3,N of the third row in the photodetecting section 10A closes. Moreover, during the same period (t12 to t15), the fourth row selection control signal Vsel(4) to be output from the controlling section 40A to the fourth row selecting wiring LV,4 becomes high level, and accordingly, the readout switch SW1 in each of the N pixel units P4,1 to P4,N of the fourth row in the photodetecting section 10A closes.
In this period (t22 to t25), during a period from the time t23 to the time t24, the hold control signal Hold to be output from the controlling section 40A to the holding wiring LH becomes high level, and accordingly, the input switch SW31 closes in each of the N holding circuits H1 to HN.
Then, after the period (t22 to t25), column selection control signals Hsel(1) to Hsel(N) to be output from the controlling section 40A to the column selecting wirings LH,1 to LH,N sequentially become high level for a predetermined period, and accordingly, the output switches SW32 in the respective N holding circuits H1 to HN sequentially close for the predetermined period. Thus, a voltage value Vout indicating a value of the received light intensities in the respective photodiodes PD of the 2N pixel units P3,1 to P3,N and P4,1 to P4,N of the third and the fourth rows being added in the column direction is output to the voltage outputting wiring Lout.
The voltage values sequentially output from the respective N holding circuits H1 to HN are input to the A/D converting section 30, and converted to digital values according to the input voltage values. Then, of the N digital values output from the A/D converting section 30, digital values corresponding to each of the first and the second columns are added, digital values corresponding to each of the third and the fourth columns are added, and the following digital values are continuously added two by two.
When in the first imaging mode, subsequent to the operation for the first and the second rows as in the above, and the subsequent operation for the third and the fourth rows, the same operation is performed for the fifth to the M-th rows, so that frame data indicating an image captured in one time of imaging is obtained. When the operation is completed for the M-th row, the same operation is again performed in a range from the first row to the M-th row, and frame data indicating a next image is obtained. By thus repeating the same operation with a predetermined period, voltage values Vout indicating a two-dimensional intensity distribution of an image of light received by the photodetecting section 10A are output to the voltage outputting wiring Lout, and the frame data is repeatedly obtained. Moreover, the readout pixel pitch in the frame data to be obtained at this time is two times the pitch of the pixel units.
On the other hand, the operation of the solid-state image pickup apparatus 1A when in the second imaging mode is as follows. FIG. 5 and FIG. 6 are timing charts for explaining operation of the solid-state image pickup apparatus 1A according to the first embodiment. No binning readout is performed in the second imaging mode. That is, the readout pixel pitch in the frame data is made equal to the pitch of the pixel units. In each integrating circuit Sn, the gain setting switch SW22 is open, the capacitance value of the feedback capacitance section is set to a small value, and the gain is set to a large value.
FIG. 5 shows the operation for each of the first and the second rows in the photodetecting section 10A. This figure shows, in order from the top, (a) the reset control signal Reset, (b) the first row selection control signal Vsel(1), (c) the second row selection control signal Vsel(2), (d) the hold control signal Hold, (e) the first column selection control signal Hsel(1), (f) the second column selection control signal Hsel(2), (g) the third column selection control signal Hsel(3), (h) the n-th column selection control signal Hsel(n), and (i) the N-th column selection control signal Hsel(N).
Charges generated in the photodiode PD of each of the N pixel units P1,1 to P1,N of the first row and accumulated in the junction capacitance section is read out as follows. Before the time t10, each of the M row selection control signals Vsel(1) to Vsel(M), the N column selection control signals Hsel(1) to Hsel(N), the reset control signal Reset, and the hold control signal Hold are at low level.
During a period from the time t10 to the time t11, the reset control signal Reset to be output from the controlling section 40A to the reset wiring LR becomes high level, and accordingly, in each of the N integrating circuits S1 to SN, the discharge switch SW21 closes, and the integrating capacitor C21 is discharged. Moreover, during a period from the time t12 to the time t15 after the time t11, the first row selection control signal Vsel(1) to be output from the controlling section 40A to the first row selecting wiring LV,1 becomes high level, and accordingly, the readout switch SW1 in each of the N pixel units P1,1 to P1,N of the first row in the photodetecting section 10A closes.
In this period (t12 to t15), during a period from the time t13 to the time t14, the hold control signal Hold to be output from the controlling section 40A to the holding wiring LH becomes high level, and accordingly, the input switch SW31 closes in each of the N holding circuits H1 to HN.
In the period (t12 to t15), the readout switch SW1 in each pixel unit P1,n of the first row is closed, and the discharge switch SW21 of each integrating circuit Sn is open, and therefore, charges generated in the photodiode PD of each pixel unit P1,n and accumulated in the junction capacitance section until then are transferred to and accumulated in the integrating capacitor C21 of the integrating circuit Sn through the readout switch SW1 of the pixel unit P1,n and the n-th column readout wiring LO,n. Then, a voltage value according to the amount of charges accumulated in the integrating capacitor C21 of each integrating circuit Sn is output from the output terminal of the integrating circuit Sn.
At the time t14 in the period (t12 to t15), as a result of the hold control signal Hold switching from high level to low level, in each of the N holding circuits H1 to HN, the input switch SW31 switches from a closed state to an open state, and a voltage value being output from the output terminal of the integrating circuit Sn and being input to the input terminal of the holding circuit Hn at this time is held in the holding capacitor C3.
Then, after the period (t12 to t15), column selection control signals Hsel(1) to Hsel(N) to be output from the controlling section 40A to the column selecting wirings LH,1 to LH,N sequentially become high level for a predetermined period, and accordingly, the output switches SW32 in the respective N holding circuits H1 to HN sequentially close for the predetermined period, and the voltage values held in the holding capacitors C3 of the holding circuits Hn are sequentially output to the voltage outputting wiring Lout through the output switches SW32. The voltage value Vout to be output to the voltage outputting wiring Lout indicates the received light intensity in the photodiode PD of each of the N pixel units P1,1 to P1,N of the first row.
Subsequently, a charge generated in the photodiode PD of each of the N pixel units P2,1 to P2,N of the second row and accumulated in the junction capacitance section is read out as follows.
During a period from the time t20 to the time t21, the reset control signal Reset to be output from the controlling section 40A to the reset wiring LR becomes high level, and accordingly, in each of the N integrating circuits S1 to SN, the discharge switch SW21 closes, and the integrating capacitor C21 is discharged. Moreover, during a period from the time t22 to the time t25 after the time t21, the second row selection control signal Vsel(2) to be output from the controlling section 40A to the second row selecting wiring LV,2 becomes high level, and accordingly, the readout switch SW1 in each of the N pixel units P2,1 to P2,N of the second row in the photodetecting section 10A closes.
In this period (t22 to t25), during a period from the time t23 to the time t24, the hold control signal Hold to be output from the controlling section 40A to the holding wiring LH becomes high level, and accordingly, the input switch SW31 closes in each of the N holding circuits H1 to HN.
Then, after the period (t22 to t25), column selection control signals Hsel(1) to Hsel(N) to be output from the controlling section 40A to the column selecting wirings LH,1 to LH,N sequentially become high level for a predetermined period, and accordingly, the output switches SW32 in the respective N holding circuits H1 to HN sequentially close for the predetermined period. Thus, a voltage value Vout indicating the received light intensity in the photodiode PD of each of the N pixel units P2,1 to P2,N of the second row is output to the voltage outputting wiring Lout.
When in the second imaging mode, subsequent to the operation for the first and the second rows as in the above, the same operation is performed for the third to the M1-th rows, so that frame data indicating an image captured in one time of imaging is obtained. When the operation is completed for the M1-th row, the same operation is again performed in a range from the first row to the M1-th row, and frame data indicating a next image is obtained. By thus repeating the same operation with a predetermined period, voltage values Vout indicating a two-dimensional intensity distribution of an image of light received by the photodetecting section 10A are output to the voltage outputting wiring Lout, and the frame data is repeatedly obtained.
When in the second imaging mode, output of a voltage value from the signal readout section 20 to the voltage outputting wiring Lout is not performed in terms of a range from the (M1+1)-th row to the M-th row. However, also in each pixel unit Pm,n of the range from the (M1+1)-th row to the M-th row, charges generated in response to light incidence into the photodiode PD are accumulated in the junction capacitance section of the photodiode PD, and exceed a saturation level of the junction capacitance section over time. If the amount of charges accumulated in the junction capacitance section of the photodiode PD exceeds the saturation level, a surplus of charges over the saturation level overflows to neighboring pixel units. If the neighboring pixel units belong to the M1-th row, voltage values to be output from the signal readout section 20 to the voltage outputting wiring Lout in terms of the neighboring pixel units are incorrect.
Therefore, it is favorable to provide discharging means for discharging the junction capacitance section of the photodiode PD in each pixel unit Pm,n of the range from the (M1+1)-th row to the M-th row when in the second imaging mode. The solid-state image pickup apparatus 1A according to the present embodiment performs, as such discharging means, the operation as shown in FIG. 6 when in the second imaging mode to transfer to the integrating circuit Sn the charges accumulated in the junction capacitance section of the photodiode PD in each pixel unit Pm,n of the range from the (M1+1)-th row to the M-th row, thereby discharging the junction capacitance section of the photodiode PD.
FIG. 6 shows the operation for each of the M1-th and the (M1+1)-th rows in the photodetecting section 10A. This figure shows, in order from the top, (a) the reset control signal Reset, (b) the M1-th row selection control signal Vsel(M1), (c) the (M1+1)-th row selection control signal Vsel(M1+1), (d) the hold control signal Hold, (e) the first column selection control signal Hsel(1), (f) the second column selection control signal Hsel(2), (g) the third column selection control signal Hsel(3), (h) the n-th column selection control signal Hsel(n), and (i) the N-th column selection control signal Hsel(N).
The operation for the M1-th row in the period from the time t40 to the time t30 shown in FIG. 6 is the same as the operation for the first row in the period from the time t10 to the time t20 shown in FIG. 5. However, during a period from the time t42 to the time t45, the M1-th row selection control signal Vsel(M1) to be output from the controlling section 40A to the M1-th row selecting wiring LV,M1 becomes high level, and accordingly, the readout switch SW1 in each of the N pixel units PM1,1 to PM1,N of the M1-th row in the photodetecting section 10A closes.
When the operation for the M1-th row is completed when in the second imaging mode, from the time t50 onward, the operation for the range from the (M1+1)-th row to the M-th row is performed. That is, from the time t50 onward, the reset control signal Reset to be output from the controlling section 40A to the reset wiring LR becomes high level, and accordingly, in each of the N integrating circuits S1 to SN, the discharge switch SW21 closes. Moreover, during a period from the time t50 onward where the discharge switch SW21 is closed, the (M1+1)-th row to the M-th row selection control signals Vsel(M1+1) to Vsel(M) become high level, and accordingly, the readout switch SW1 in each pixel unit Pm,n of the range from the (M1+1)-th row to the M-th row in the photodetecting section 10A closes.
Thus, as a result of the readout switch SW1 in each pixel unit Pm,n of the range from the (M1+1)-th row to the M-th row closing when in the second imaging mode, the charges accumulated in the junction capacitance section of the photodiode PD in the pixel unit are transferred to the integrating circuit Sn, and as a result of the discharge switch SW21 closing in each integrating circuit Sn, the integrating capacitor C21 of each integrating circuit Sn is always in a discharged state. In this way, the junction capacitance section of the photodiode PD in each pixel unit Pm,n of the range from the (M1+1)-th row to the M-th row can be discharged when in the second imaging mode.
At this time, in terms of the range from the (M1+1)-th row to the M-th row, the row selection control signals Vsel(M1+1) to Vsel(M) may sequentially become high level, but a plurality of row selection control signals of the row selection control signals Vsel(M1+1) to Vsel(M) may simultaneously become high level, and all of the row selection control signals Vsel(M1+1) to Vsel(M) may simultaneously become high level. Thus, in terms of the range from the (M1+1)-th row to the M-th row, as a result of a plurality or all of the row selection control signals simultaneously becoming high level, the junction capacitance section of the photodiode PD in each pixel unit Pm,n can be discharged in a shorter time.
Meanwhile, as another imaging mode for outputting data of a smaller number of pixel units than in the first imaging mode from the signal readout section 20, a voltage value according to the amount of charges generated in the photodiode PD of each pixel unit Pm,n included in consecutive N1 columns in the photodetecting section 10A may be output from the signal readout section 20. Here, N1 is an integer less than N. However, in the imaging mode for thus outputting data of each pixel unit Pm,n of the N1 columns from the signal readout section 20, it is necessary to output the M row selection control signals Vsel(1) to Vsel(M) from the controlling section 40A in order to obtain one frame of data. In contrast thereto, the solid-state image pickup apparatus 1A according to the present embodiment, for which, it suffices, when in the second imaging mode for outputting data of each pixel unit Pm,n of the M1 rows from the signal readout section 20, to output M1 row selection control signals Vsel(1) to Vsel(M1) from the controlling section 40A in order to obtain one frame of data, can thus perform a high-speed operation.
In addition, in the timing charts shown in FIG. 4 to FIG. 6 described thus far, each integrating circuit Sn is initialized after readout of a voltage value from each holding circuit Hn is completed. However, if after an output voltage value of each integrating circuit Sn is held by the holding circuit Hn, the reset control signal Reset may be made high level to initialize each integrating circuit Sn during a period of reading out a voltage value from each holding circuit Hn. This allows a higher-speed operation.
Next, description will be given of a solid-state image pickup apparatus 1B according to a second embodiment. FIG. 7 is a view showing a configuration of the solid-state image pickup apparatus 1B according to the second embodiment. The solid-state image pickup apparatus 1B shown in this figure includes a photodetecting section 10B, a signal readout section 20, an A/D converting section 30, and a controlling section 40B. Moreover, in the case of use as one for X-ray detection, a scintillator section is provided so as to cover the photodetecting section 10B of the solid-state image pickup apparatus 1B.
As compared with the configuration of the solid-state image pickup apparatus 1A according to the first embodiment shown in FIG. 1, the solid-state image pickup apparatus 1B according to the second embodiment shown in FIG. 7 is different in that a disconnection switch SW1n and a discharge switch SW2n are provided on each n-th column readout wiring LO,n, and is different in including a controlling section 40B in place of the controlling section 40A.
Each disconnection switch SW1n is provided, on the readout wiring LO,n, between the M1-th row and the (M1+1)-th row in the photodetecting section 10B. That is, when the disconnection switch SW1n is closed, each pixel unit Pm,n in a range from the first row to the M-th row is connected via the readout wiring LO,n with the signal readout section 20. On the other hand, when the disconnection switch SW1n is open, each pixel unit Pm,n in a range from the first row to the M1-th row is connected via the readout wiring LO,n with the signal readout section 20, but each pixel unit Pm,n in a range from the (M1+1)-th row to the M-th row is disconnected from the signal readout section 20. Each disconnection switch SW1n is connected via a disconnection wiring LD1 with the controlling section 40B, and supplied with a disconnection control signal Disconnect passed through the disconnection wiring LD1 from the controlling section 40B. The disconnection control signal Disconnect is a signal for instructing an opening and closing operation of each disconnection switch SW1n.
Each discharge switch SW2n is provided, on the readout wiring LO,n, at a side further distant from the signal readout section 20 than the position where the disconnection switch SW1n is provided. One end of the discharge switch SW2n is connected, via the readout wiring LO,n, with each pixel unit Pm,n in the range from the (M1+1)-th row to the M-th row. The other end of the discharge switch SW2n is grounded. Each discharge switch SW2n is connected via a discharge wiring LD2 with the controlling section 40B, and supplied with a discharge control signal Discharge passed through the discharge wiring LD2 from the controlling section 40B. The discharge control signal Discharge is a signal for instructing an opening and closing operation of each discharge switch SW2n.
The controlling section 40B, in the same manner as the controlling section 40A in the first embodiment, outputs an m-th row selection control signal Vsel(m) to the m-th row selecting wiring LV,m, outputs an n-th column selection control signal Hsel(n) to the n-th column selecting wiring LH,n, outputs a discharge control signal Reset to the discharge wiring LR, outputs a gain setting signal Gain to the gain setting wiring LG, and outputs a hold control signal Hold to the holding wiring LH.
In addition, the controlling section 40B outputs a disconnection control signal Disconnect to the disconnection wiring LD1 to supply this disconnection control signal Disconnect to each of the N disconnection switches SW11 to SW1N. Moreover, the controlling section 40B outputs a discharge control signal Discharge to the discharge wiring LD2 to supply this discharge control signal Discharge to each of the N discharge switches SW21 to SW2N.
The solid-state image pickup apparatus 1B according to the second embodiment also has a first imaging mode and a second imaging mode. The first imaging mode and the second imaging mode are mutually different in an imaging region in the photodetecting section 10B. The controlling section 40B, when in the first imaging mode, makes a voltage value according to the amount of charges generated in the photodiode PD of each of the M×N pixel units P1,1 to PM,N in the photodetecting section 10B be output from the signal readout section 20. Also, the controlling section 40B, when in the second imaging mode, makes a voltage value according to the amount of charges generated in the photodiode PD of each pixel unit Pm,n of the range from the first row to the M1-th row in the photodetecting section 10B be output from the signal readout section 20.
Moreover, the controlling section 40B, when in the second imaging mode than when in the first imaging mode, makes the readout pixel pitch in the frame data based on the voltage value to be output from the signal readout section 20 smaller, and the frame rate being the number of frames of data to be output per unit time higher, and the gain being a ratio of an output voltage value to an input charge amount in the signal readout section 20 greater.
In the solid-state image pickup apparatus 1B according to the second embodiment, when in the first imaging mode, the disconnection control signal Disconnect to be supplied to each disconnection switch SW1n through the disconnection wiring LD1 from the controlling section 40B becomes high level, and each disconnection switch SW1n closes. Moreover, the discharge control signal Discharge to be supplied to each discharge switch SW2n through the discharge wiring LD2 from the controlling section 40B becomes low level, and each discharge switch SW2n opens. In this state, each pixel unit Pm,n in the range from the first row to the M-th row is connected via the readout wiring LO,n with the signal readout section 20. Then, the same operation as in the case of the first embodiment is performed, whereby a voltage value according to the amount of charges generated in the photodiode PD of each of the M×N pixel units P1,1 to PM,N in the photodetecting section 10B is output from the signal readout section 20.
On the other hand, in the solid-state image pickup apparatus 1B according to the second embodiment, when in the second imaging mode, the disconnection control signal Disconnect to be supplied to each disconnection switch SW1n through the disconnection wiring LD1 from the controlling section 40B becomes low level, and each disconnection switch SW1n opens. Moreover, the discharge control signal Discharge to be supplied to each discharge switch SW2n through the discharge wiring LD2 from the controlling section 40B becomes high level, and each discharge switch SW2n closes. In this state, each pixel unit Pm,n in the range from the first row to the M1-th row is connected via the readout wiring LO,n with the signal readout section 20, but each pixel unit Pm,n in the range from the (M1+1)-th row to the M-th row is disconnected from the signal readout section 20 and grounded.
Moreover, when in the second imaging mode, in terms of the range from the first row to the M1-th row, the same operation as in the case of the first embodiment is performed, whereby a voltage value according to the amount of charges generated in the photodiode PD of each pixel unit Pm,n is output from the signal readout section 20. On the other hand, in terms of the range from the (M1+1)-th row to the M-th row, the row selection control signals Vsel(M1+1) to Vsel(M) become high level, and accordingly, the cathode terminal of the photodiode PD of each pixel unit Pm,n is grounded via the readout switch SW1 and the discharge switch SW2n, and thus the junction capacitance section of the photodiode PD of each pixel unit Pm,n is discharged. That is, in this case, each discharge switch SW2n acts as discharging means for discharging the junction capacitance section of the photodiode PD in each pixel unit Pm,n of the range from the (M1+1)-th row to the M-th row when in the second imaging mode.
When in the second imaging mode, in terms of the range from the (M1+1)-th row to the M-th row, the row selection control signals Vsel(M1+1) to Vsel(M) may sequentially become high level, but a plurality of row selection control signals of the row selection control signals Vsel(M1+1) to Vsel(M) may simultaneously become high level, and all of the row selection control signals Vsel(M1+1) to Vsel(M) may simultaneously become high level. Thus, in terms of the range from the (M1+1)-th row to the M-th row, as a result of a plurality or all of the row selection control signals simultaneously becoming high level, the junction capacitance section of the photodiode PD in each pixel unit Pm,n can be discharged in a shorter time.
Moreover, when in the second imaging mode, the period for which a voltage value according to the amount of charges generated in the photodiode PD of each pixel unit Pm,n is output from the signal readout section 20 in terms of the range from the first row to the M1-th row, and the period for which the junction capacitance section of the photodiode PD in each pixel unit Pm,n is discharged in terms of the range from the (M1+1)-th row to the M-th row may be partially overlapped with each other. In such a case, a higher-speed operation is possible.
Moreover, as a result of the disconnection wiring LD1 being opened when in the second imaging mode, the n-th column readout wiring LO,n to be connected to the signal readout section 20 is shortened, and thus noise can be reduced.
Next, description will be given of an embodiment of an X-ray inspection system including the solid-state image pickup apparatus according to the above embodiment. FIG. 8 is a configuration diagram of the X-ray inspection system 100 according to the present embodiment. The X-ray inspection system 100 according to the present embodiment includes the solid-state image pickup apparatus and an X-ray generator, and images X-rays output from the X-ray generator and transmitted through an inspection object by the solid-state image pickup apparatus to inspect the inspection object.
In the X-ray inspection system 100 shown in this figure, the X-ray generator 106 generates X-rays toward a subject (inspection object). The radiation field of X-rays generated from the X-ray generator 106 is controlled by a primary slit plate 106b. The X-ray generator 106 has an X-ray tube built therein, and by adjusting conditions of the X-ray tube, such as a tube voltage, a tube current, and energization time, the X-ray dose to the subject is controlled. An X-ray image sensor 107 has a built-in CMOS solid-state image pickup apparatus having a plurality of pixel units arrayed two-dimensionally, and detects an X-ray image transmitted through the subject. In front of the X-ray image sensor 107, a secondary slit plate 107a that limits an X-ray incident region is provided.
A swing arm 104 holds the X-ray generator 106 and the X-ray image sensor 107 so as to be opposed, and swings these around the subject in panoramic tomography. Moreover, in the case of linear tomography, a sliding mechanism 113 for linearly displacing the X-ray image sensor 107 with respect to the subject is provided. The swing arm 104 is driven by an arm motor 110 that forms a rotary table, and a rotation angle thereof is detected by an angle sensor 112. Moreover, the arm motor 110 is mounted on a movable portion of an XY table 114, and the center of rotation is arbitrarily adjusted in a horizontal plane.
Image signals output from the X-ray image sensor 107 are converted to, for example, 10-bit (=1024 level) digital data by an A/D converter 120, and once taken in a CPU (central processing unit) 121, and thereafter stored in a frame memory 122. From the image data stored in the frame memory 122, a tomographic image along any tomographic plane is reproduced by a predetermined arithmetic processing. The reproduced tomographic image is output to a video memory 124, and converted to analog signals by a D/A converter 125, and then displayed by an image display section 126 such as a CRT (cathode ray tube), and provided for various diagnoses.
The CPU 121 is connected with a work memory 123 required for signal processing, and further connected with an operation panel 119 having a panel switch, an X-ray irradiation switch, etc. Moreover, the CPU 121 is connected to a motor drive circuit 111 that drives the arm motor 110, slit control circuits 115, 116 that control the opening range of the primary slit plate 106b and the secondary slit plate 107a, an X-ray control circuit 118 that controls the X-ray generator 106, respectively, and further outputs a clock signal to drive the X-ray image sensor 107.
The X-ray control circuit 118 is capable of feedback-controlling the X-ray dose to the subject based on signals imaged by the X-ray image sensor 107.
In the X-ray inspection system 100 configured as above, the solid-state image pickup apparatus 1A or 1B according to the present embodiment is used as the X-ray image sensor 107.
The X-ray generator 106 can, as a result of the opening range of the slit plate 16b being controlled, output X-rays at a predetermined divergence angle when in a first output mode, and output X-rays at a narrower divergence angle than the predetermined divergence angle when in a second output mode. When the X-ray generator 106 outputs X-rays in the first output mode, the X-ray image sensor 107 being a solid-state image pickup apparatus operates in the first imaging mode. On the other hand, when the X-ray generator 106 outputs X-rays in the second output mode, the X-ray image sensor 107 being a solid-state image pickup apparatus operates in the second imaging mode.
Here, for example, the first output mode and the first imaging mode correspond to the CT mode described in Patent Document 1, and the second output mode and the second imaging mode correspond to the panoramic mode or cephalographic mode described in Patent Document 1. The solid-state image pickup apparatus 1A, 1B is disposed so that the longitudinal direction of an imaging region (the first row to the M1-th row) in the photodetecting section 10A, 10B when in the second imaging mode is vertical to a swing plane.
The X-ray inspection system 100 according to the present embodiment includes the solid-state image pickup apparatus 1A or 1B according to the present embodiment, and can thus favorably operate in each imaging mode.
In addition, assuming that the X-ray inspection system 100 including the solid-state image pickup apparatus 1A, 1B is used for a dental application, it is preferable that the number of rows M is larger than the number of columns N in the photodetecting section 10A, 10B of the solid-state image pickup apparatus 1A, 1B. This is attributed to the following reasons. That is, in the first imaging mode corresponding to the CT mode, a size of a light receiving range to be used for imaging in the photodetecting section 10A, 10B of, for example, 8 cm or more×12 cm or more is required. Moreover, in the second imaging mode corresponding to the panoramic mode, a size of a specific range to be used for imaging in the photodetecting section 10A, 10B of, for example, 15 cm or more×7 mm or more is required. In consideration of satisfying the requirements regarding the size as in the above and most efficiently preparing a single integrated solid-state image pickup apparatus 1A, 1B from a circular silicon wafer, the photodetecting section 10A, 10B cannot help but have a rectangular shape long in one direction. Therefore, on the assumption that the photodetecting section 10A, 10B cannot help but have a rectangular shape, the number of columns N is set larger than the number of rows M to reduce the number M of selection control signals to be output from the controlling section 40A, 40B. Moreover, it is preferable to separate the N holding circuits H1 to HN in the signal readout section 20 into a plurality of sets, provide A/D converting sections individually for the sets, and make these A/D converting sections operate in parallel. This allows realizing a high-speed readout of pixel data.
For example, as shown in FIG. 9, the N integrating circuits S1 to SN and the N holding circuits H1 to HN are separated into four sets, where integrating circuits S1 to Si and holding circuits H1 to Hi are provided as the first set, integrating circuits Si+1 to Sj and holding circuits Hi+1 to Hj are provided as the second set, integrating circuits Sj+1 to Sk and holding circuits Hj+1 to Hk are provided as the third set, and integrating circuits Sk+1 to SN and holding circuits Hk+1 to HN are provided as the fourth set. Here, “1<i<j<k<N.” Voltage values sequentially output from the first set of respective holding circuits H1 to Hi are converted to digital values by an A/D converting section 31, voltage values sequentially output from the second set of respective holding circuits Hi+1 to Hj are converted to digital values by an A/D converting section 32, voltage values sequentially output from the third set of respective holding circuits Hj+1 to Hk are converted to digital values by an A/D converting section 33, and voltage values sequentially output from the fourth set of respective holding circuits Hk+1 to HN are converted to digital values by an A/D converting section 34. Moreover, A/D converting in the respective four A/D converting sections 31 to 34 are performed in parallel. This allows realizing a high-speed readout of pixel data.
Moreover, in consideration of, for example, binning readout of 2 rows and 2 columns, it is also preferable to provide holding circuits corresponding to odd-numbered columns out of the N holding circuits H1 to HN as the first set, and holding circuits corresponding to even-numbered columns, as the second set, provide A/D converting sections individually for these first and second sets, respectively, and make these two A/D converting sections operate in parallel. In this case, voltage values are simultaneously output from the holding circuit corresponding to an odd-numbered column and a holding circuit corresponding to an even-numbered column neighboring the odd-numbered column, and these two voltage values are simultaneously A/D converted into digital values. Then, in the case of binning, these two digital values are added. This also allows realizing a high-speed readout of pixel data.
INDUSTRIAL APPLICABILITY
The present invention can be applied to a solid-state image pickup apparatus and an X-ray inspection system.
REFERENCE SIGNS LIST
1A, 1B Solid-state image pickup apparatus

    10A, 10B Photodetecting section
    20 Signal readout section
    30 A/D converting section
    40A, 40B Controlling section
    P1,1 to PM,N Pixel unit
    PD Photodiode
    SW1 Readout switch
    SW11 to SW1N Disconnection switch
    SW21 to SW2N Discharge switch
    S1 to SN Integrating circuit
    C21, C22 Integrating capacitor
    SW21 Discharge switch
    A2 Amplifier
    H1 to HN Holding circuit
    C3 Holding capacitor
    SW31 Input switch
    SW32 Output switch
    LV,m m-th row selecting wiring
    LH,n n-th column selecting wiring
    LO,n n-th column readout wiring
    LR Reset wiring
    LG Gain setting wiring
    LH Holding wiring
    Lout Voltage outputting wiring

## Claims

1. An X-ray inspection system used for a dental application, comprising:
a solid-state image pickup apparatus; and
an X-ray generator,
wherein the X-ray output from the X-ray generator transmits through an inspection object to form an X-ray image, and the X-ray image is picked up by the solid-state image pickup apparatus to inspect the inspection object,
where M and N are each an integer not less than 2, M1 is an integer less than M, N1 is an integer less than N, m is an integer not less than 1 and not more than M, and n is an integer not less than 1 and not more than N,
wherein the solid-state image pickup apparatus comprises:
a photodetecting section where M×N pixel units Pl,1 to PM,N, each including a photodiode that generates a charge of an amount according to an incident light intensity and a readout switch connected with the photodiode, are two-dimensionally arrayed in M rows and N columns,
a readout wiring LO,n connected with a readout switch of each of the M pixel units P1,n to PM,n of an n-th column in the photodetecting section, for reading out a signal caused by charges generated in the photodiode of any pixel unit of the M pixel units P1,n to PM,n via the readout switch of the pixel unit;
a signal readout section including N holding circuits H1 to HN, each of the holding circuits being connected with each of the readout wirings LO,1 to LO,N, for holding a voltage value caused by the signal from the readout wiring LO,n, and sequentially outputting the held voltage values; and
a controlling section that controls an opening and closing operation of the readout switch of each of the M×N pixel units P1,1 to PM,N in the photodetecting section and controls an outputting operation of a voltage value in the signal readout section to make a voltage value according to an amount of charge generated in the photodiode of each of the M×N pixel units P1,1 to PM,N in the photodetecting section be output from the signal readout section, wherein
the controlling section
when in a first imaging mode, makes a voltage value according to an amount of charge generated in the photodiode of each of the M×N pixel units P1,1 to PM,N in the photodetecting section be output from the signal readout section, and
when in a second imaging mode, makes a voltage value according to an amount of charge generated in the photodiode of each pixel unit Pm,n included in a specific range of consecutive M1 rows in the photodetecting section be output from the signal readout section,
wherein
the solid-state image pickup apparatus and the X-ray generator are rotatable around the inspection object while facing each other, or
the image pickup apparatus is linearly movable with respect to the inspection object,
wherein a direction of the rotation movement or a direction of the linear movement is perpendicular to a longitudinal direction of the specific range in the photodetecting section in the second imaging mode.

2. The X-ray inspection system according to claim 1, wherein the controlling section, when in the second imaging mode, has as the specific range, a range of M1 rows counted in order from the row closest to the signal readout section out of the M rows in the photodetecting section, and makes a voltage value according to the amount of charge generated in the photodiode of each pixel unit Pm,n in the specific range be output from the signal readout section.

3. The X-ray inspection system according to claim 2, further comprising, between the specific range in the photodetecting section and another range excluding the specific range, a disconnection switch provided on each readout wiring LO,n, wherein
the controlling section closes the disconnection switch when in the first imaging mode, and opens the disconnection switch when in the second imaging mode.

4. The X-ray inspection system according to claim 1, including discharging means that discharges a junction capacitance section of the photodiode in each pixel unit Pm,n of another range excluding the specific range in the photodetecting section when in the second imaging mode.

5. The X-ray inspection system according to claim 1, further comprising a scintillator section that is provided so as to cover the M×N pixel units P1,1 to PM,N in the photodetecting section.

6. An X-ray inspection system used for a dental application, comprising
a solid-state image pickup apparatus; and
an X-ray generator,
wherein the X-ray output from the X-ray generator transmits through an inspection object to form an X-ray image, and the X-ray image is picked up by the solid-state image pickup apparatus to inspect the inspection object,
where M and N are each an integer not less than 2, M1 is an integer less than M, N1 is an integer less than N, m is an integer not less than 1 and not more than M, and n is an integer not less than 1 and not more than N,
wherein the solid-state image pickup apparatus comprises:
a photodetecting section where M×N pixel units P1,1 to PM,N each including a photodiode that generates a charge of an amount according to an incident light intensity and a readout switch connected with the photodiode are two-dimensionally arrayed in M rows and N columns;
a readout wiring LO,n, connected with a readout switch of each of the M pixel units P1,n, to PM,n of an n-th column in the photodetecting secion, for reading out a signal caused by charges generated in the photodiode of any pixel unit of the M pixel units P1,n to PM,n via the readout switch of the pixel unit;
a signal readout section including N holding circuits H1 to HN, each of the holding circuits being connected with each of the readout wirings L0,1, to L0,N, for holding a voltage value caused by the signal from the readout wiring LOn, and sequentially outputting the held voltage values; and
a controlling section that controls an opening and closing operation of the readout switch of each of the M×N pixel units P1,1 to PM,N in the photodetecting section and controls an outputting operation of a voltage value in the signal readout section to make a voltage value according to an amount of charge generated in the photodiode of each of the M×N pixel units P1,1 to PM,N in the photodetecting section be output from the signal readout section,
wherein
the controlling section
when in a first imaging mode, makes a voltage value according to an amount of charge generated in the photodiode of the photodetecting section be output from the signal readout section, and
when in a second imaging mode, makes a voltage value according to an amount of charge generated in the photodiode of each pixel unit Pm,i included in a specific range of consecutive M1 rows in the photodetecting section be output from the signal readout section,
wherein
the solid-state image pickup apparatus and the X-ray generator are retatable around the inspection object while facing each other, or
the image pickup apparatus is linearly movable with respect to the inspection object,
wherein a direction of the rotation movement ofr a direction of the linear movement is perpendicular to a longitudinal direction of the specific range in the photodetecting section in the second imaging mode.

7. The X-ray inspection system according to claim 6, wherein the controlling section, when in the second imaging mode, has as the specific range, a range of M1 rows counted in order from the row closest to the signal readout section out of the M rows in the photodetecting section, and makes a voltage value according to the amount of charge generated in the photodiode of each pixel unit Pm,n in the specific range be output from the signal readout section.

8. The X-ray inspection system according to claim 7, further comprising, between the specific range in the photodetecting section and another range excluding the specific range, a disconnection switch provided on each readout wiring LO,n, wherein
the controlling section closes the disconnection switch when in the first imaging mode, and opens the disconnection switch when in the second imaging mode.

9. The X-ray inspection system according to claim 6, including discharging means that discharges a junction capacitance section of the photodiode in each pixel unit Pm,n of another range excluding the specific range in the photodetecting section when in the second imaging mode.

10. The X-ray inspection system according to claim 6, further comprising a scintillator section that is provided so as to cover the M×N pixel units P1,1 to PM,N in the photodetecting section.