US20120182450A1 - Solid state imaging device - Google Patents
Solid state imaging device Download PDFInfo
- Publication number
- US20120182450A1 US20120182450A1 US13/278,587 US201113278587A US2012182450A1 US 20120182450 A1 US20120182450 A1 US 20120182450A1 US 201113278587 A US201113278587 A US 201113278587A US 2012182450 A1 US2012182450 A1 US 2012182450A1
- Authority
- US
- United States
- Prior art keywords
- diode
- solid state
- imaging device
- state imaging
- period
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Images
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/70—SSIS architectures; Circuits associated therewith
- H04N25/71—Charge-coupled device [CCD] sensors; Charge-transfer registers specially adapted for CCD sensors
- H04N25/745—Circuitry for generating timing or clock signals
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
- H04N1/00976—Arrangements for regulating environment, e.g. removing static electricity
- H04N1/00978—Temperature control
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/60—Noise processing, e.g. detecting, correcting, reducing or removing noise
- H04N25/616—Noise processing, e.g. detecting, correcting, reducing or removing noise involving a correlated sampling function, e.g. correlated double sampling [CDS] or triple sampling
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/60—Noise processing, e.g. detecting, correcting, reducing or removing noise
- H04N25/67—Noise processing, e.g. detecting, correcting, reducing or removing noise applied to fixed-pattern noise, e.g. non-uniformity of response
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/70—SSIS architectures; Circuits associated therewith
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/70—SSIS architectures; Circuits associated therewith
- H04N25/71—Charge-coupled device [CCD] sensors; Charge-transfer registers specially adapted for CCD sensors
- H04N25/75—Circuitry for providing, modifying or processing image signals from the pixel array
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/60—Noise processing, e.g. detecting, correcting, reducing or removing noise
- H04N25/61—Noise processing, e.g. detecting, correcting, reducing or removing noise the noise originating only from the lens unit, e.g. flare, shading, vignetting or "cos4"
Definitions
- Embodiments described herein relate generally to a solid state imaging device.
- a temperature sensor is mounted in a solid state imaging device and an image signal is corrected based on the temperature of the solid state imaging device.
- an imaging element circuit and an A/D conversion circuit for an imaging element there is an imaging element circuit and an A/D conversion circuit for an imaging element, and in addition to the imaging element circuit, there are a diode used as a temperature sensor and an A/D conversion circuit for the temperature sensor.
- a circuit block related to temperature measurement is present independently of a signal processing circuit block for the imaging element, and correction is performed in a temperature correction circuit in a later stage by using stored temperature measurement data.
- FIG. 1 is a block diagram illustrating a schematic configuration of an image processing unit to which a solid state imaging device according to a first embodiment is applied;
- FIG. 2 is a block diagram illustrating a schematic configuration of the solid state imaging device according to the first embodiment
- FIG. 3 is a circuit diagram illustrating a configuration example of a pixel PC in FIG. 2 ;
- FIG. 4 is a circuit diagram illustrating a configuration example of a temperature sensor 8 in FIG. 2 ;
- FIG. 5 is a circuit diagram illustrating a configuration example of an image column CDS processing unit 3 - 1 in FIG. 2 ;
- FIG. 6 is a timing chart illustrating a temperature measurement operation of the solid state imaging device in FIG. 2 ;
- FIG. 7 is a diagram illustrating a relationship between a voltage difference value ⁇ Vt and temperature
- FIG. 8 is a block diagram illustrating an example of a method for transferring a pixel signal Sg and a temperature measurement value St of the solid state imaging device
- FIG. 9 is a timing chart illustrating a method for changing an analog gain when reading a pixel voltage Vs of a pixel PC of a solid state imaging device and when reading a diode voltage Vt of a temperature sensor 8 according to a second embodiment
- FIG. 10 is a block diagram illustrating a method for switching a current flowing through a temperature sensor 8 according to a third embodiment
- FIG. 11 is a block diagram illustrating a schematic configuration of a solid state imaging device according to a fourth embodiment.
- FIG. 12 is a block diagram illustrating a schematic configuration of a solid state imaging device according to a fifth embodiment.
- a solid state imaging device is provided with a pixel array unit, an image CDS processing unit, a temperature sensor, a temperature CDS processing unit, and a timing generator.
- the pixel array unit pixels which accumulate photoelectrically-converted charge are arranged in a matrix form.
- the image CDS processing unit outputs a pixel signal based on a difference between a pixel voltage read from the pixel during a reset period and a pixel voltage read from the pixel during a signal read period.
- the temperature sensor outputs a diode voltage when a diode current is changed.
- the temperature CDS processing unit outputs a temperature measurement value based on a difference of the diode voltage at the time when a diode current is changed.
- the timing generator controls the reset period, the signal read period, and the timing of changing the diode current of the temperature sensor.
- FIG. 1 is a block diagram illustrating a schematic configuration of an image processing unit to which a solid state imaging device according to a first embodiment is applied.
- FIG. 1 illustrates that a lens optical system 21 is provided in the previous stage of an image sensor 22 , and an image processing unit 24 is provided in the later stage of the image sensor 22 .
- a temperature sensor 23 which outputs a diode voltage when a diode current is changed, is mounted in the image sensor 22 .
- the image processing unit 24 is provided with a correction processing unit 25 which performs correction processing of a pixel signal Sg on the basis of a temperature measurement value St.
- a solid state imaging device as illustrated in FIG. 2 , 11 , or 12 can be used as the image sensor 22 .
- the pixel signal Sg When light enters the image sensor 22 through the lens optical system 21 , the pixel signal Sg according to an amount of the light is generated. At the same time, the temperature measurement value St is calculated on the basis of a difference of the diode voltage outputted from the temperature sensor 23 and transmitted to the image processing unit 24 .
- the correction processing unit 25 performs correction processing of the pixel signal Sg on the basis of the temperature measurement value St and image processing of the pixel signal Sg, on which the correction processing is performed.
- the correction processing of the pixel signal Sg can eliminate, for example, distortion of the pixel signal Sg due to variation of the refractive index and size of the lens optical system 21 caused by variation of temperature as well as fixed pattern noise and white spots due to dark current of a photodiode PD.
- Examples of the image processing of the pixel signal Sg include shading compensation, color separation interpolation processing, masking processing, ⁇ correction processing, color space conversion processing, brightness adjustment, contrast adjustment, color adjustment, and intensity adjustment.
- FIG. 2 is a block diagram illustrating a schematic configuration of the solid state imaging device according to the first embodiment.
- FIG. 2 illustrates that the solid state imaging device is provided with a pixel array unit 1 in which pixels PC that accumulate photoelectrically-converted charge are arranged in a matrix form in a row direction and a column direction, a vertical register 2 which scans the pixels PC to be read in a vertical direction, a temperature sensor 8 which outputs a diode voltage when a diode current is changed, a comparative voltage generation unit 7 which generates a comparative voltage to be a base of the diode current of the temperature sensor 8 , image column CDS processing units 3 - 1 which output a pixel signal Sg based on a difference between a pixel voltage Vs read from the pixel PC during a reset period and a pixel voltage Vs read from the pixel PC during a signal read period, a temperature column CDS processing unit 3 - 2 which outputs a temperature measurement value St based on a difference of the diode voltage when the diode current of the temperature sensor 8 is changed, a horizontal register 4 which scans the pixels PC
- the temperature sensor 8 and the pixel array unit 1 can be mounted on the same semiconductor chip.
- a ramp wave can be used as the reference voltage VF outputted from the reference voltage generation unit 6 .
- a band-gap reference circuit can be used as the comparative voltage generation unit 7 .
- horizontal control lines Hlin that control reading of the pixels PC are provided in the row direction and vertical signal lines Vlin that transfer signals read from the pixels PC are provided in the column direction.
- the pixels PC are scanned in the vertical direction by the vertical register 2 , so that the pixels PC in the row direction are selected and the pixel voltages Vs read from the pixels PC are transmitted to the image column CDS processing units 3 - 1 via the vertical signal lines Vlin.
- a source follower is formed between the load circuit 11 and the pixels PC when the signals are read from the pixels PC, so that the potentials of the vertical signal lines Vlin follow the pixel voltages Vs read from the pixels PC.
- each image column CDS processing unit 3 - 1 the pixel voltage Vs read from a pixel PC during the reset period and the pixel voltage Vs read from the pixel PC during the signal read period are sampled and a difference between them is calculated, so that a signal component of each pixel PC is digitalized by CDS and outputted as the pixel signal Sg through the sense amplifier 10 .
- a diode voltage Vt read from the temperature sensor 8 is transmitted to the temperature column CDS processing unit 3 - 2 . Then, in the temperature column CDS processing unit 3 - 2 , the diode voltage Vt read before the diode current is changed and the diode voltage Vt read after the diode current is changed are sampled and a difference between them is calculated, so that a signal component of the temperature sensor 8 is digitalized by the CDS and outputted as the temperature measurement value St through the sense amplifier 10 .
- the temperature measurement value St is obtained from the difference of the diode voltage Vt before and after the diode current is changed, so that it is possible to eliminate temperature dependence of the current-voltage characteristics of the diode and improve accuracy of the temperature measurement.
- the temperature column CDS processing unit 3 - 2 may be integrated with the image column CDS processing units 3 - 1 .
- the image column CDS processing unit 3 - 1 can be switched between the pixels PC and the temperature sensor 8 .
- the image column CDS processing units 3 - 1 are switched to the pixels PC during an effective pixel period and the image column CDS processing units 3 - 1 are switched to the temperature sensor 8 during a vertical blanking period, so that it is possible to obtain the temperature measurement value St at least once in one frame period without causing a loss of the pixel signal Sg.
- the temperature sensor 8 may be used independently as a temperature measurement device.
- the temperature column CDS processing unit 3 - 2 may be mounted in the temperature measurement device along with the temperature sensor 8 .
- FIG. 3 is a circuit diagram illustrating a configuration example of the pixel PC in FIG. 2 .
- FIG. 3 illustrates that the pixel PC is provided with a photodiode PD, a row selection transistor Ta, an amplifier transistor Tb, a reset transistor Tc, and a read transistor Td.
- a floating diffusion FD is formed at a connection point of the amplifier transistor Tb, the reset transistor Tc, and the read transistor Td as a detection node.
- the source of the read transistor Td is connected to the photodiode PD and a read signal READ is inputted into the gate of the read transistor Td.
- the source of the reset transistor Tc is connected to the drain of the read transistor Td, a reset signal RESET is inputted into the gate of the reset transistor Tc, and the drain of the reset transistor Tc is connected to a power supply potential VDD.
- a row selection signal ADRES is inputted into the gate of the row selection transistor Ta and the drain of the row selection transistor Ta is connected to the power supply potential VDD.
- the source of the amplifier transistor Tb is connected to the vertical signal line Vlin, the gate of the amplifier transistor Tb is connected to the drain of the read transistor Td, and the drain of the amplifier transistor Tb is connected to the source of the row selection transistor Ta.
- the horizontal control lines Hlin in FIG. 2 can transmit the read signal READ, the reset signal RESET, and the row selection signal ADRES to the pixels PC for each row.
- FIG. 4 is a circuit diagram illustrating a configuration example of the temperature sensor 8 in FIG. 2 .
- the temperature sensor 8 is provided with a diode D and a current source G, and the current source G is connected to the diode D in series.
- the diode D for example, a bipolar transistor whose collector and base are connected to each other can be used.
- the current source G can switch between a current I 1 and a current I 2 and output one of them.
- the current I 2 can be larger than the current I 1 .
- the timing generator 5 in FIG. 2 can switch to the current I 1 during the reset period of the pixels PC and switch to the current I 2 during the signal read period of the pixels PC.
- the diode voltage Vt with respect to the diode current I 1 is measured from the current-voltage characteristics of the diode D. Temperature can be read from the diode voltage Vt by assuming that the diode voltage Vt is proportional to temperature.
- the diode current I 1 can be given by the following formula (1).
- I 1 Is *exp( qVt/kBT ) (1)
- Is is reverse current
- T temperature (temperature unit is Kelvin)
- Vt kBT/q ⁇ ln( I 1 /Is ) (2)
- T is 300K (27° C.)
- kBT/q is a constant of 0.0259 (V).
- V the temperature T can be obtained from the current-voltage characteristics, which are a relationship between Vt and I 1 of the formula (2).
- the reverse current Is has a temperature dependence
- the current-voltage characteristics of the diode D is technically nonlinear with respect to the temperature T.
- the temperature measurement value St is obtained from the difference of the diode voltage Vt when the diode current is switched from I 1 to I 2 , so that it is possible to eliminate the temperature dependence of the current-voltage characteristics of the diode and improve accuracy of the temperature measurement.
- FIG. 5 is a circuit diagram illustrating a configuration example of the image column CDS processing unit 3 - 1 in FIG. 2 .
- an image column ADC 3 a is provided with a capacitor C 1 , a comparator PA, a switch transistor Tcp, an inverter V, and an up/down counter UD for each column.
- the up/down counter UD is provided with a logical AND circuit N 1 .
- the vertical signal line Vlin is connected to the inverting input terminal of the comparator PA via the capacitor C 1 , and the reference voltage VF is inputted into the noninverting input terminal of the comparator PA.
- the switch transistor Tcp is connected between the inverting input terminal and output terminal of the comparator PA.
- the output terminal of the comparator PA is connected to one input terminal of the logical AND circuit N 1 , and a reference clock CKC is inputted into the other input terminal of the logical AND circuit N 1 .
- the row selection transistor Ta When the row selection signal ADRES is low level, the row selection transistor Ta is in an off state and does not perform a source follower operation, so that no signal is outputted to the vertical signal line Vlin. At this time, if the read signal READ and the reset signal RESET become high level, the read transistor Td turns on, and charge accumulated in the photodiode PD is discharged to the floating diffusion FD. Then, the charge is discharged to the power supply potential VDD through the reset transistor Tc.
- the row selection transistor Ta of the pixel PC turns on and the power supply potential VDD is applied to the drain of the amplifier transistor Tb, so that a source follower is formed by the amplifier transistor Tb and the load circuit 11 .
- the reset transistor Tc turns on, and excess charge generated in the floating diffusion FD by leakage current or the like is reset.
- a voltage according to a reset level of the floating diffusion FD is applied to the gate of the amplifier transistor Tb.
- a reset pulse Pcp is applied to the gate of the switch transistor Tcp while the pixel voltage Vs according to the reset level is outputted to the vertical signal line Vlin, an input voltage of the inverting input terminal of the comparator PA is clamped by the output voltage and an operating point is set. At this time, a difference between the pixel voltage Vs and the vertical signal line Vlin is held by the capacitor C 1 and the input voltage of the comparator PA is set to zero.
- the reference clock CKC is inputted into the other input terminal of the logical AND circuit N 1 .
- the output voltage Vcomp becomes high level. Therefore, the reference clock CKC passes through the logical AND circuit N 1 , and the reference clock CKCi having passed through the logical AND circuit N 1 is down-counted by the up/down counter UD.
- the reference clock CKC is cut off by the logical AND circuit N 1 , and down-counting is stopped in the up/down counter UD, so that the pixel voltage Vs at the reset level is digitalized.
- the read transistor Td turns on, the charge accumulated in the photodiode PD is transferred to the floating diffusion FD, and a voltage according to a signal level of the floating diffusion FD is applied to the gate of the amplifier transistor Tb.
- a ramp wave Vf 2 is provided as the reference voltage VF, and the pixel voltage Vs at the signal level and the ramp wave Vf 2 are compared.
- the output voltage of the comparator PA is inverted by the inverter V, and then inputted into one input terminal of the logical AND circuit N 1 as the output voltage Vcomp.
- the reference clock CKC passes through the logical AND circuit N 1 , and the reference clock CKCi having passed through the logical AND circuit N 1 is up-counted by the up/down counter UD.
- the output voltage of the comparator PA falls and the output voltage Vcomp becomes low level.
- the reference clock CKC is cut off by the logical AND circuit N 1 , and up-counting is stopped in the up/down counter UD, so that a difference between the pixel voltage Vs at the signal level and the pixel voltage Vs at the reset level is digitalized.
- the temperature column CDS processing unit 3 - 2 can be formed in the same manner as the image column CDS processing unit 3 - 1 in FIG. 5 .
- the diode voltage Vt when the diode current of the diode D in FIG. 4 is set to the current I 1 is inputted instead of the pixel voltage Vs at the reset level. Then, the diode voltage Vt when the diode current is set to the current I 1 is compared with the ramp wave Vf 1 . Further, the diode voltage Vt when the diode current of the diode D in FIG. 4 is set to the current I 2 is inputted instead of the pixel voltage Vs at the signal level. Then, the diode voltage Vt when the diode current is set to the current I 2 is compared with the ramp wave Vf 2 .
- FIG. 6 is a timing chart illustrating the temperature measurement operation of the solid state imaging device in FIG. 2 .
- a reset period, a signal read period, and a data transfer period are provided in one horizontal period.
- the diode current is set to I 1 in the reset period, and the diode current is set to I 2 in the signal read period.
- the temperature column CDS processing unit 3 - 2 in FIG. 2 the diode voltage Vt when the diode current is set to I 1 is sampled, and then the diode voltage Vt when the diode current is set to I 2 is sampled. Then, the temperature measurement value St is calculated on the basis of a difference between these diode voltages Vt, and the temperature measurement value St is outputted in the data transfer period via a data transfer bus in which the pixel signal Sg is outputted.
- the current I 2 when the current I 2 is changed to K times the current I 1 (K is a real number greater than or equal to 1), the current I 2 can be given by the following formula (3).
- a voltage difference value ⁇ Vt of the diode voltage Vt when the diode current is switched from I 1 to I 2 can be given by the following formula (4) from the formula (2).
- the voltage difference value ⁇ Vt is represented by a linear approximate equation of the temperature T, and a voltage change rate per degree is 0.18 mV/° C.
- FIG. 7 is a diagram illustrating a relationship between the voltage difference value ⁇ Vt and temperature.
- the temperature can be accurately measured from the current-voltage characteristics of the diode D, and if code values of temperature table are calculated in advance, temperature can be read from the temperature measurement value St. It is possible to perform difference processing of the diode voltage Vt within one horizontal period and output the temperature measurement value St, so that it is possible to surely perform temperature measurement once within one vertical period (also referred to as “one frame period”).
- FIG. 8 is a block diagram illustrating a method for transferring the pixel signal Sg and the temperature measurement value St of the solid state imaging device.
- a plurality of horizontal transfer buses BS for transferring the pixel signal Sg and the temperature measurement value St are provided in parallel in this solid state imaging device compared with the solid state imaging device in FIG. 2 .
- a case is shown in which four horizontal transfer buses BS are provided.
- Four pixel signals Sg and four temperature measurement values St can be transferred in parallel through the horizontal transfer buses BS.
- the number of the horizontal transfer buses BS is four, it is preferred that the sum of the number of the temperature column CDS processing units 3 - 2 and the number of the image column CDS processing units 3 - 1 is a multiple of four.
- a plurality of horizontal transfer buses BS are provided, so that it is possible to reduce the transfer time of the pixel signals Sg and the temperature measurement values St and speed up correction processing of the pixel signal Sg using the temperature measurement value St.
- FIG. 9 is a timing chart illustrating a method for changing an analog gain when reading the pixel voltage Vs of the pixel PC of the solid state imaging device and when reading the diode voltage Vt of the temperature sensor 8 according to a second embodiment.
- the voltage difference value ⁇ Vt is 0.053 (V) at 25° C., and it is smaller than the diode voltage Vt.
- the voltage change rate per degree is 0.18 mV/° C.
- the voltage change rate is 0.217° C. per LSB.
- the analog gain is set by an amount of incident light into the photodiode PD. For example, when the amount of incident light is great, the analog gain is reduced and the slopes of the ramp waves Vf 1 and Vf 2 increase.
- the temperature measurement processing is performed in a vertical blanking period in one vertical period, and the analog gain is increased when the temperature measurement processing is performed, and at the same time, the imaging process is performed in a remaining vertical blanking period and the effective pixel period in the vertical period, and the analog gain can be changed according to the amount of incident light when the imaging process is performed.
- the temperature column CDS processing unit 3 - 2 is integrated with the image column CDS processing units 3 - 1 , it is possible to appropriately adjust the level of the pixel signal Sg according to the amount of incident light as well as to improve accuracy of the temperature measurement based on the current-voltage characteristics of the diode D.
- the temperature measurement processing can be performed once in one horizontal period, so that, when a plurality of horizontal periods are included in one vertical blanking period, the temperature measurement processing can be performed multiple times in one vertical period.
- FIG. 10 is a block diagram illustrating a method for switching a current flowing through a temperature sensor 8 according to a third embodiment.
- the temperature sensor 8 is provided with a plurality of diodes D 1 to D 6 and a plurality of current sources G 1 to G 6 for setting diode currents of these diodes D 1 to D 6 respectively.
- a case is shown in which six diodes D 1 to D 6 and six current sources G 1 to G 6 are provided.
- the currents outputted from the current sources G 1 to G 6 can be set to I 1 , and the diode currents of the diodes D 1 to D 6 can be equal to each other.
- the diodes D 1 to D 6 are connected so that a diode voltage of one diode is received by the next-stage diode.
- the current sources G 1 to G 6 can be connected to the emitters of the bipolar transistors and the ground potential can be connected to the collectors of the bipolar transistors.
- the base of each bipolar transistor can be connected to the emitter of the next-stage bipolar transistor.
- the ground potential can be connected to the emitter of the last-stage bipolar transistor.
- the temperature sensor 8 is provided with a selector K 1 .
- the selector K 1 can switch between an emitter potential of the first-stage diode D 1 and an emitter potential of the last-stage diode D 6 on the basis of a switching signal SL 1 and output one of them.
- the emitter potential of the diode D 1 is the emitter potential of the diode D 6 when a current six times the current I 1 is passed through the diode D 6 . Therefore, when a current six times the current I 1 is defined as I 2 , it is possible to switch between the current I 1 and the current I 2 at the same timing as that in FIG. 5 by switching the selector K 1 . Therefore, it is possible to change the diode current of the temperature sensor 8 while the currents outputted from the current sources G 1 to G 6 are fixed to I 1 , so that the circuit configuration can be simplified compared with a case in which the current outputted from the current source G is changed.
- FIG. 11 is a block diagram illustrating a schematic configuration of a solid state imaging device according to a fourth embodiment.
- the solid state imaging device in FIG. 11 is formed by adding an amplifier 12 to the solid state imaging device in FIG. 2 .
- the amplifier 12 is inserted between the temperature sensor 8 and the temperature column CDS processing unit 3 - 2 .
- a PGA programmable gain amplifier
- the gain of the amplifier 12 may be used in conjunction with the analog gain of the image column CDS processing units 3 - 1 . Thereby, any analog gain can be used to perform the A/D conversion processing while the temperature is measured.
- FIG. 12 is a block diagram illustrating a schematic configuration of a solid state imaging device according to a fifth embodiment.
- the solid state imaging device in FIG. 12 is formed by adding a plurality of temperature sensors 8 and a selector K 2 to the solid state imaging device in FIG. 1 .
- the selector K 2 can switch between diode voltages of the plurality of temperature sensors 8 on the basis of a switching signal SL 2 and output one of them.
- the plurality of temperature sensors 8 are provided in the solid state imaging device, so that it is possible to improve accuracy of the temperature measurement even when the temperature varies in the solid state imaging device.
- the temperature sensor 8 can be disposed at a position near a disabled pixel at the beginning of one frame and a position near a disabled pixel at the end of one frame.
- the temperature sensor 8 can be switched between the temperature measurement during the vertical blanking period at the beginning of one frame and the temperature measurement during the vertical blanking period at the end of one frame. Thereby, it is possible to improve accuracy of image correction in a case such as shading occurs in the vertical direction depending on the temperature.
Abstract
According to one embodiment, a solid state imaging device includes an image CDS processing unit that outputs a pixel signal based on a difference between a pixel voltage read from a pixel during a reset period and a pixel voltage read from the pixel during a signal read period, a temperature sensor that outputs a diode voltage when a diode current is changed, a temperature CDS processing unit that outputs a temperature measurement value based on a difference of the diode voltage at the time when the diode current is changed, and a timing generator that controls the reset period, the signal read period, and timing of changing the diode current of the temperature sensor.
Description
- This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2011-008876, filed on Jan. 19, 2011; the entire contents of which are incorporated herein by reference.
- Embodiments described herein relate generally to a solid state imaging device.
- In a solid state imaging device, noise and defects in a captured image may become obvious as temperature increases, or distortion may occur in a captured image due to variation of temperature. Therefore, a temperature sensor is mounted in a solid state imaging device and an image signal is corrected based on the temperature of the solid state imaging device.
- Conventionally, there is an imaging element circuit and an A/D conversion circuit for an imaging element, and in addition to the imaging element circuit, there are a diode used as a temperature sensor and an A/D conversion circuit for the temperature sensor. Specifically, a circuit block related to temperature measurement is present independently of a signal processing circuit block for the imaging element, and correction is performed in a temperature correction circuit in a later stage by using stored temperature measurement data.
- When a diode is used as a temperature sensor, current-voltage characteristics of the diode cannot be represented by a linear approximate equation. In other words, current and voltage are not in a proportional relationship, so measurement accuracy is insufficient when using a method of obtaining temperature from the current-voltage characteristics of the diode.
-
FIG. 1 is a block diagram illustrating a schematic configuration of an image processing unit to which a solid state imaging device according to a first embodiment is applied; -
FIG. 2 is a block diagram illustrating a schematic configuration of the solid state imaging device according to the first embodiment; -
FIG. 3 is a circuit diagram illustrating a configuration example of a pixel PC inFIG. 2 ; -
FIG. 4 is a circuit diagram illustrating a configuration example of atemperature sensor 8 inFIG. 2 ; -
FIG. 5 is a circuit diagram illustrating a configuration example of an image column CDS processing unit 3-1 inFIG. 2 ; -
FIG. 6 is a timing chart illustrating a temperature measurement operation of the solid state imaging device inFIG. 2 ; -
FIG. 7 is a diagram illustrating a relationship between a voltage difference value ΔVt and temperature; -
FIG. 8 is a block diagram illustrating an example of a method for transferring a pixel signal Sg and a temperature measurement value St of the solid state imaging device; -
FIG. 9 is a timing chart illustrating a method for changing an analog gain when reading a pixel voltage Vs of a pixel PC of a solid state imaging device and when reading a diode voltage Vt of atemperature sensor 8 according to a second embodiment; -
FIG. 10 is a block diagram illustrating a method for switching a current flowing through atemperature sensor 8 according to a third embodiment; -
FIG. 11 is a block diagram illustrating a schematic configuration of a solid state imaging device according to a fourth embodiment; and -
FIG. 12 is a block diagram illustrating a schematic configuration of a solid state imaging device according to a fifth embodiment. - A solid state imaging device according to one embodiment is provided with a pixel array unit, an image CDS processing unit, a temperature sensor, a temperature CDS processing unit, and a timing generator. In the pixel array unit, pixels which accumulate photoelectrically-converted charge are arranged in a matrix form. The image CDS processing unit outputs a pixel signal based on a difference between a pixel voltage read from the pixel during a reset period and a pixel voltage read from the pixel during a signal read period. The temperature sensor outputs a diode voltage when a diode current is changed. The temperature CDS processing unit outputs a temperature measurement value based on a difference of the diode voltage at the time when a diode current is changed. The timing generator controls the reset period, the signal read period, and the timing of changing the diode current of the temperature sensor.
- Hereinafter, exemplary embodiments of a temperature measurement device and a solid state imaging device will be explained below in detail with reference to the accompanying drawings. The present invention is not limited to the following embodiments.
-
FIG. 1 is a block diagram illustrating a schematic configuration of an image processing unit to which a solid state imaging device according to a first embodiment is applied. -
FIG. 1 illustrates that a lensoptical system 21 is provided in the previous stage of animage sensor 22, and animage processing unit 24 is provided in the later stage of theimage sensor 22. Atemperature sensor 23, which outputs a diode voltage when a diode current is changed, is mounted in theimage sensor 22. Theimage processing unit 24 is provided with acorrection processing unit 25 which performs correction processing of a pixel signal Sg on the basis of a temperature measurement value St. A solid state imaging device as illustrated inFIG. 2 , 11, or 12 can be used as theimage sensor 22. - When light enters the
image sensor 22 through the lensoptical system 21, the pixel signal Sg according to an amount of the light is generated. At the same time, the temperature measurement value St is calculated on the basis of a difference of the diode voltage outputted from thetemperature sensor 23 and transmitted to theimage processing unit 24. Thecorrection processing unit 25 performs correction processing of the pixel signal Sg on the basis of the temperature measurement value St and image processing of the pixel signal Sg, on which the correction processing is performed. - The correction processing of the pixel signal Sg can eliminate, for example, distortion of the pixel signal Sg due to variation of the refractive index and size of the lens
optical system 21 caused by variation of temperature as well as fixed pattern noise and white spots due to dark current of a photodiode PD. - Examples of the image processing of the pixel signal Sg include shading compensation, color separation interpolation processing, masking processing, γ correction processing, color space conversion processing, brightness adjustment, contrast adjustment, color adjustment, and intensity adjustment.
-
FIG. 2 is a block diagram illustrating a schematic configuration of the solid state imaging device according to the first embodiment. -
FIG. 2 illustrates that the solid state imaging device is provided with a pixel array unit 1 in which pixels PC that accumulate photoelectrically-converted charge are arranged in a matrix form in a row direction and a column direction, avertical register 2 which scans the pixels PC to be read in a vertical direction, atemperature sensor 8 which outputs a diode voltage when a diode current is changed, a comparative voltage generation unit 7 which generates a comparative voltage to be a base of the diode current of thetemperature sensor 8, image column CDS processing units 3-1 which output a pixel signal Sg based on a difference between a pixel voltage Vs read from the pixel PC during a reset period and a pixel voltage Vs read from the pixel PC during a signal read period, a temperature column CDS processing unit 3-2 which outputs a temperature measurement value St based on a difference of the diode voltage when the diode current of thetemperature sensor 8 is changed, ahorizontal register 4 which scans the pixels PC to be read and thetemperature sensor 8 in a horizontal direction, atiming generator 5 which controls the reset period of the pixels PC, the signal read period, and the timing of changing the diode current of thetemperature sensor 8, a referencevoltage generation unit 6 which outputs a reference voltage VF to the image column CDS processing units 3-1 and the temperature column CDS processing unit 3-2, adriver 9 which drives the image column CDS processing units 3-1 and the temperature column CDS processing unit 3-2, asense amplifier 10 which detects signals outputted from the image column CDS processing units 3-1 and the temperature column CDS processing unit 3-2, and aload circuit 11 which causes potentials of vertical signal lines Vlin to follow the signals read from the pixels PC. - The
temperature sensor 8 and the pixel array unit 1 can be mounted on the same semiconductor chip. A ramp wave can be used as the reference voltage VF outputted from the referencevoltage generation unit 6. A band-gap reference circuit can be used as the comparative voltage generation unit 7. - Here, in the pixel array unit 1, horizontal control lines Hlin that control reading of the pixels PC are provided in the row direction and vertical signal lines Vlin that transfer signals read from the pixels PC are provided in the column direction.
- The pixels PC are scanned in the vertical direction by the
vertical register 2, so that the pixels PC in the row direction are selected and the pixel voltages Vs read from the pixels PC are transmitted to the image column CDS processing units 3-1 via the vertical signal lines Vlin. Here, in theload circuit 11, a source follower is formed between theload circuit 11 and the pixels PC when the signals are read from the pixels PC, so that the potentials of the vertical signal lines Vlin follow the pixel voltages Vs read from the pixels PC. - In each image column CDS processing unit 3-1, the pixel voltage Vs read from a pixel PC during the reset period and the pixel voltage Vs read from the pixel PC during the signal read period are sampled and a difference between them is calculated, so that a signal component of each pixel PC is digitalized by CDS and outputted as the pixel signal Sg through the
sense amplifier 10. - On the other hand, a diode voltage Vt read from the
temperature sensor 8 is transmitted to the temperature column CDS processing unit 3-2. Then, in the temperature column CDS processing unit 3-2, the diode voltage Vt read before the diode current is changed and the diode voltage Vt read after the diode current is changed are sampled and a difference between them is calculated, so that a signal component of thetemperature sensor 8 is digitalized by the CDS and outputted as the temperature measurement value St through thesense amplifier 10. - Here, the temperature measurement value St is obtained from the difference of the diode voltage Vt before and after the diode current is changed, so that it is possible to eliminate temperature dependence of the current-voltage characteristics of the diode and improve accuracy of the temperature measurement.
- Although, in the embodiment of
FIG. 2 , a method is described in which the temperature column CDS processing unit 3-2 is provided separately from the image column CDS processing units 3-1, the temperature column CDS processing unit 3-2 may be integrated with the image column CDS processing units 3-1. In this case, the image column CDS processing unit 3-1 can be switched between the pixels PC and thetemperature sensor 8. For example, the image column CDS processing units 3-1 are switched to the pixels PC during an effective pixel period and the image column CDS processing units 3-1 are switched to thetemperature sensor 8 during a vertical blanking period, so that it is possible to obtain the temperature measurement value St at least once in one frame period without causing a loss of the pixel signal Sg. - Although, in the embodiment of
FIG. 2 , a method is described in which thetemperature sensor 8 is mounted in the solid state imaging device, thetemperature sensor 8 may be used independently as a temperature measurement device. In this case, the temperature column CDS processing unit 3-2 may be mounted in the temperature measurement device along with thetemperature sensor 8. - Although, in the embodiment of
FIG. 2 , a method is described in which the pixel signal Sg and the temperature measurement value St are digitalized in the temperature column CDS processing unit 3-2 and the image column CDS processing units 3-1, it is possible to output the pixel signal Sg and the temperature measurement value St as analog signals without change and digitalize them outside the solid state imaging device as needed. -
FIG. 3 is a circuit diagram illustrating a configuration example of the pixel PC inFIG. 2 . -
FIG. 3 illustrates that the pixel PC is provided with a photodiode PD, a row selection transistor Ta, an amplifier transistor Tb, a reset transistor Tc, and a read transistor Td. A floating diffusion FD is formed at a connection point of the amplifier transistor Tb, the reset transistor Tc, and the read transistor Td as a detection node. - In the pixel PC, the source of the read transistor Td is connected to the photodiode PD and a read signal READ is inputted into the gate of the read transistor Td. The source of the reset transistor Tc is connected to the drain of the read transistor Td, a reset signal RESET is inputted into the gate of the reset transistor Tc, and the drain of the reset transistor Tc is connected to a power supply potential VDD. A row selection signal ADRES is inputted into the gate of the row selection transistor Ta and the drain of the row selection transistor Ta is connected to the power supply potential VDD. The source of the amplifier transistor Tb is connected to the vertical signal line Vlin, the gate of the amplifier transistor Tb is connected to the drain of the read transistor Td, and the drain of the amplifier transistor Tb is connected to the source of the row selection transistor Ta. The horizontal control lines Hlin in
FIG. 2 can transmit the read signal READ, the reset signal RESET, and the row selection signal ADRES to the pixels PC for each row. -
FIG. 4 is a circuit diagram illustrating a configuration example of thetemperature sensor 8 inFIG. 2 . - In
FIG. 4 , thetemperature sensor 8 is provided with a diode D and a current source G, and the current source G is connected to the diode D in series. As the diode D, for example, a bipolar transistor whose collector and base are connected to each other can be used. The current source G can switch between a current I1 and a current I2 and output one of them. The current I2 can be larger than the current I1. Thetiming generator 5 inFIG. 2 can switch to the current I1 during the reset period of the pixels PC and switch to the current I2 during the signal read period of the pixels PC. - Here, when the diode D is used as the
temperature sensor 8, the diode voltage Vt with respect to the diode current I1 is measured from the current-voltage characteristics of the diode D. Temperature can be read from the diode voltage Vt by assuming that the diode voltage Vt is proportional to temperature. - At this time, the diode current I1 can be given by the following formula (1).
-
I1=Is*exp(qVt/kBT) (1) - Here, Is is reverse current, T is temperature (temperature unit is Kelvin), kB is a Boltzmann constant (=8.62*10−5 eV/K), and q is an amount of charge (=1.602*10−19 Coulomb).
- When the formula (1) is expanded, the following formula (2) can be obtained.
-
Vt=kBT/q·ln(I1/Is) (2) - If T is 300K (27° C.), kBT/q is a constant of 0.0259 (V). In other words, if kB, q, and Is are constants, the temperature T can be obtained from the current-voltage characteristics, which are a relationship between Vt and I1 of the formula (2).
- However, strictly speaking, the reverse current Is has a temperature dependence, and the current-voltage characteristics of the diode D is technically nonlinear with respect to the temperature T. Here, the temperature measurement value St is obtained from the difference of the diode voltage Vt when the diode current is switched from I1 to I2, so that it is possible to eliminate the temperature dependence of the current-voltage characteristics of the diode and improve accuracy of the temperature measurement.
-
FIG. 5 is a circuit diagram illustrating a configuration example of the image column CDS processing unit 3-1 inFIG. 2 . - In
FIG. 5 , an image column ADC3 a is provided with a capacitor C1, a comparator PA, a switch transistor Tcp, an inverter V, and an up/down counter UD for each column. The up/down counter UD is provided with a logical AND circuit N1. - The vertical signal line Vlin is connected to the inverting input terminal of the comparator PA via the capacitor C1, and the reference voltage VF is inputted into the noninverting input terminal of the comparator PA. The switch transistor Tcp is connected between the inverting input terminal and output terminal of the comparator PA. The output terminal of the comparator PA is connected to one input terminal of the logical AND circuit N1, and a reference clock CKC is inputted into the other input terminal of the logical AND circuit N1.
- When the row selection signal ADRES is low level, the row selection transistor Ta is in an off state and does not perform a source follower operation, so that no signal is outputted to the vertical signal line Vlin. At this time, if the read signal READ and the reset signal RESET become high level, the read transistor Td turns on, and charge accumulated in the photodiode PD is discharged to the floating diffusion FD. Then, the charge is discharged to the power supply potential VDD through the reset transistor Tc.
- After the charge accumulated in the photodiode PD is discharged to the power supply potential VDD, when the read signal READ becomes low level, accumulation of effective signal charge is started in the photodiode PD.
- Next, when the row selection signal ADRES becomes high level, the row selection transistor Ta of the pixel PC turns on and the power supply potential VDD is applied to the drain of the amplifier transistor Tb, so that a source follower is formed by the amplifier transistor Tb and the
load circuit 11. - Next, when the reset signal RESET rises, the reset transistor Tc turns on, and excess charge generated in the floating diffusion FD by leakage current or the like is reset. A voltage according to a reset level of the floating diffusion FD is applied to the gate of the amplifier transistor Tb.
- If a reset pulse Pcp is applied to the gate of the switch transistor Tcp while the pixel voltage Vs according to the reset level is outputted to the vertical signal line Vlin, an input voltage of the inverting input terminal of the comparator PA is clamped by the output voltage and an operating point is set. At this time, a difference between the pixel voltage Vs and the vertical signal line Vlin is held by the capacitor C1 and the input voltage of the comparator PA is set to zero.
- After the switch transistor Tcp turns off, while the pixel voltage Vs at the reset level is inputted into the comparator PA via the capacitor C1, a ramp wave Vf1 is provided as the reference voltage VF, and the pixel voltage Vs at the reset level and the ramp wave Vf1 are compared. The output voltage of the comparator PA is inverted by the inverter V, and then inputted into one input terminal of the logical AND circuit N1 as an output voltage Vcomp.
- The reference clock CKC is inputted into the other input terminal of the logical AND circuit N1. When the pixel voltage Vs at the reset level is smaller than a level of the ramp wave Vf1, the output voltage Vcomp becomes high level. Therefore, the reference clock CKC passes through the logical AND circuit N1, and the reference clock CKCi having passed through the logical AND circuit N1 is down-counted by the up/down counter UD.
- When the pixel voltage Vs at the reset level corresponds to the level of the ramp wave Vf1, the output voltage of the comparator PA falls and the output voltage Vcomp becomes low level. Therefore, the reference clock CKC is cut off by the logical AND circuit N1, and down-counting is stopped in the up/down counter UD, so that the pixel voltage Vs at the reset level is digitalized.
- Next, when the read signal READ rises, the read transistor Td turns on, the charge accumulated in the photodiode PD is transferred to the floating diffusion FD, and a voltage according to a signal level of the floating diffusion FD is applied to the gate of the amplifier transistor Tb.
- While the pixel voltage Vs at the signal level is inputted into the comparator PA via the capacitor C1, a ramp wave Vf2 is provided as the reference voltage VF, and the pixel voltage Vs at the signal level and the ramp wave Vf2 are compared. The output voltage of the comparator PA is inverted by the inverter V, and then inputted into one input terminal of the logical AND circuit N1 as the output voltage Vcomp.
- When the pixel voltage Vs at the signal level is smaller than a level of the ramp wave Vf2, the output voltage Vcomp becomes high level. Therefore, the reference clock CKC passes through the logical AND circuit N1, and the reference clock CKCi having passed through the logical AND circuit N1 is up-counted by the up/down counter UD. When the pixel voltage Vs at the signal level corresponds to the level of the ramp wave Vf2, the output voltage of the comparator PA falls and the output voltage Vcomp becomes low level. Therefore, the reference clock CKC is cut off by the logical AND circuit N1, and up-counting is stopped in the up/down counter UD, so that a difference between the pixel voltage Vs at the signal level and the pixel voltage Vs at the reset level is digitalized.
- The temperature column CDS processing unit 3-2 can be formed in the same manner as the image column CDS processing unit 3-1 in
FIG. 5 . In this case, the diode voltage Vt when the diode current of the diode D inFIG. 4 is set to the current I1 is inputted instead of the pixel voltage Vs at the reset level. Then, the diode voltage Vt when the diode current is set to the current I1 is compared with the ramp wave Vf1. Further, the diode voltage Vt when the diode current of the diode D inFIG. 4 is set to the current I2 is inputted instead of the pixel voltage Vs at the signal level. Then, the diode voltage Vt when the diode current is set to the current I2 is compared with the ramp wave Vf2. -
FIG. 6 is a timing chart illustrating the temperature measurement operation of the solid state imaging device inFIG. 2 . - In
FIG. 6 , a reset period, a signal read period, and a data transfer period are provided in one horizontal period. The diode current is set to I1 in the reset period, and the diode current is set to I2 in the signal read period. In the temperature column CDS processing unit 3-2 inFIG. 2 , the diode voltage Vt when the diode current is set to I1 is sampled, and then the diode voltage Vt when the diode current is set to I2 is sampled. Then, the temperature measurement value St is calculated on the basis of a difference between these diode voltages Vt, and the temperature measurement value St is outputted in the data transfer period via a data transfer bus in which the pixel signal Sg is outputted. - Here, when the current I2 is changed to K times the current I1 (K is a real number greater than or equal to 1), the current I2 can be given by the following formula (3).
-
I2=I1*K (3) - A voltage difference value ΔVt of the diode voltage Vt when the diode current is switched from I1 to I2 can be given by the following formula (4) from the formula (2).
-
ΔVt=kBT/q·ln(I1/Is)−kBT/q·ln(I2/Is)=kBT/q·ln(I1/I2)=kBT/q·ln(I2*K/I2)=kBT/q·ln(K) (4) - When the voltage difference value ΔVt is obtained from the formula (4), the reverse current Is depending on temperature is cancelled, so that it is possible to eliminate the temperature dependence of the current-voltage characteristics of the diode D and improve accuracy of the temperature measurement.
- For example, when K is set to 8, as shown in the following formula (5), the voltage difference value ΔVt is represented by a linear approximate equation of the temperature T, and a voltage change rate per degree is 0.18 mV/° C.
-
ΔVt=kB/q·ln(K)·T=0.0259*ln(8)*(T/300)=0.0259* 2.079*(T/300)=0.00018*T(V) (5) -
FIG. 7 is a diagram illustrating a relationship between the voltage difference value ΔVt and temperature. - In
FIG. 7 , the voltage difference value ΔVt with respect to the temperature T in the formula (5) is graphed. As obvious from the formula (5), the relationship between the temperature T and the voltage difference value ΔVt is linear. - Therefore, the temperature can be accurately measured from the current-voltage characteristics of the diode D, and if code values of temperature table are calculated in advance, temperature can be read from the temperature measurement value St. It is possible to perform difference processing of the diode voltage Vt within one horizontal period and output the temperature measurement value St, so that it is possible to surely perform temperature measurement once within one vertical period (also referred to as “one frame period”).
-
FIG. 8 is a block diagram illustrating a method for transferring the pixel signal Sg and the temperature measurement value St of the solid state imaging device. - In
FIG. 8 , a plurality of horizontal transfer buses BS for transferring the pixel signal Sg and the temperature measurement value St are provided in parallel in this solid state imaging device compared with the solid state imaging device inFIG. 2 . In the example ofFIG. 8 , a case is shown in which four horizontal transfer buses BS are provided. Four pixel signals Sg and four temperature measurement values St can be transferred in parallel through the horizontal transfer buses BS. When the number of the horizontal transfer buses BS is four, it is preferred that the sum of the number of the temperature column CDS processing units 3-2 and the number of the image column CDS processing units 3-1 is a multiple of four. - Here, a plurality of horizontal transfer buses BS are provided, so that it is possible to reduce the transfer time of the pixel signals Sg and the temperature measurement values St and speed up correction processing of the pixel signal Sg using the temperature measurement value St.
-
FIG. 9 is a timing chart illustrating a method for changing an analog gain when reading the pixel voltage Vs of the pixel PC of the solid state imaging device and when reading the diode voltage Vt of thetemperature sensor 8 according to a second embodiment. - In
FIG. 9 , for example, the voltage difference value ΔVt is 0.053 (V) at 25° C., and it is smaller than the diode voltage Vt. The voltage change rate per degree is 0.18 mV/° C. To increase a voltage change rate per LSB when the voltage is digitalized, it is necessary to reduce the slopes of the ramp waves Vf1 and Vf2 and increase the analog gain. For example, when the output is 10-bit and the amplitude of the reference voltage VF is 40 mV, the voltage change rate per LSB is (40 mv)/((0.18 mv)*1023)=0.217° C./LSB. Thus, the voltage change rate is 0.217° C. per LSB. - On the other hand, in the image column CDS processing unit 3-1, the analog gain is set by an amount of incident light into the photodiode PD. For example, when the amount of incident light is great, the analog gain is reduced and the slopes of the ramp waves Vf1 and Vf2 increase.
- Therefore, to increase the voltage change rate when measuring temperature, it is necessary to differentiate the slopes of the ramp waves Vf1 and Vf2 when measuring temperature from those when performing imaging process. Therefore, when the temperature column CDS processing unit 3-2 is integrated with the image column CDS processing units 3-1, it is not possible to perform temperature measurement and imaging process in one horizontal period.
- Therefore, the temperature measurement processing is performed in a vertical blanking period in one vertical period, and the analog gain is increased when the temperature measurement processing is performed, and at the same time, the imaging process is performed in a remaining vertical blanking period and the effective pixel period in the vertical period, and the analog gain can be changed according to the amount of incident light when the imaging process is performed.
- Thereby, even when the temperature column CDS processing unit 3-2 is integrated with the image column CDS processing units 3-1, it is possible to appropriately adjust the level of the pixel signal Sg according to the amount of incident light as well as to improve accuracy of the temperature measurement based on the current-voltage characteristics of the diode D.
- Further, the temperature measurement processing can be performed once in one horizontal period, so that, when a plurality of horizontal periods are included in one vertical blanking period, the temperature measurement processing can be performed multiple times in one vertical period.
-
FIG. 10 is a block diagram illustrating a method for switching a current flowing through atemperature sensor 8 according to a third embodiment. - In
FIG. 10 , thetemperature sensor 8 is provided with a plurality of diodes D1 to D6 and a plurality of current sources G1 to G6 for setting diode currents of these diodes D1 to D6 respectively. In the example ofFIG. 10 , a case is shown in which six diodes D1 to D6 and six current sources G1 to G6 are provided. Here, the currents outputted from the current sources G1 to G6 can be set to I1, and the diode currents of the diodes D1 to D6 can be equal to each other. - The diodes D1 to D6 are connected so that a diode voltage of one diode is received by the next-stage diode. For example, when the diodes D1 to D6 are formed by bipolar transistors, the current sources G1 to G6 can be connected to the emitters of the bipolar transistors and the ground potential can be connected to the collectors of the bipolar transistors. The base of each bipolar transistor can be connected to the emitter of the next-stage bipolar transistor. However, the ground potential can be connected to the emitter of the last-stage bipolar transistor.
- The
temperature sensor 8 is provided with a selector K1. The selector K1 can switch between an emitter potential of the first-stage diode D1 and an emitter potential of the last-stage diode D6 on the basis of a switching signal SL1 and output one of them. - Here, the emitter potential of the diode D1 is the emitter potential of the diode D6 when a current six times the current I1 is passed through the diode D6. Therefore, when a current six times the current I1 is defined as I2, it is possible to switch between the current I1 and the current I2 at the same timing as that in
FIG. 5 by switching the selector K1. Therefore, it is possible to change the diode current of thetemperature sensor 8 while the currents outputted from the current sources G1 toG 6 are fixed to I1, so that the circuit configuration can be simplified compared with a case in which the current outputted from the current source G is changed. -
FIG. 11 is a block diagram illustrating a schematic configuration of a solid state imaging device according to a fourth embodiment. - The solid state imaging device in
FIG. 11 is formed by adding anamplifier 12 to the solid state imaging device inFIG. 2 . Here, theamplifier 12 is inserted between thetemperature sensor 8 and the temperature column CDS processing unit 3-2. - Here, the gain of the
amplifier 12 can be set in advance so that the voltage difference value ΔVt is substantially the same as the pixel voltage Vs during the reset period. For example, although ΔVt=0.054 (V) when the temperature is 25° C., the pixel voltage Vs during the reset period is about 1.0 V at normal temperature. Thus, the gain of theamplifier 12 can be set to about 16 times because 1.0/0.054≈18.51. - Thereby, to amplify the voltage difference value ΔVt, it is not necessary to increase the analog gain of the temperature column CDS processing unit 3-2 and also it is not necessary to change the slopes of the ramp waves Vf1 and Vf2 for the image column CDS processing units 3-1 and the temperature column CDS processing unit 3-2. Therefore, it is possible to perform the temperature measurement processing and the imaging process in one horizontal period, so that it is possible to output the temperature measurement value St for each horizontal period without causing a loss of the pixel signal Sg.
- A PGA (programmable gain amplifier) may be used as the
amplifier 12, and the gain of theamplifier 12 may be used in conjunction with the analog gain of the image column CDS processing units 3-1. Thereby, any analog gain can be used to perform the A/D conversion processing while the temperature is measured. -
FIG. 12 is a block diagram illustrating a schematic configuration of a solid state imaging device according to a fifth embodiment. - The solid state imaging device in
FIG. 12 is formed by adding a plurality oftemperature sensors 8 and a selector K2 to the solid state imaging device inFIG. 1 . The selector K2 can switch between diode voltages of the plurality oftemperature sensors 8 on the basis of a switching signal SL2 and output one of them. - Here, the plurality of
temperature sensors 8 are provided in the solid state imaging device, so that it is possible to improve accuracy of the temperature measurement even when the temperature varies in the solid state imaging device. - For example, the
temperature sensor 8 can be disposed at a position near a disabled pixel at the beginning of one frame and a position near a disabled pixel at the end of one frame. Thetemperature sensor 8 can be switched between the temperature measurement during the vertical blanking period at the beginning of one frame and the temperature measurement during the vertical blanking period at the end of one frame. Thereby, it is possible to improve accuracy of image correction in a case such as shading occurs in the vertical direction depending on the temperature. - While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
Claims (20)
1. A solid state imaging device comprising:
a pixel array unit in which pixels that accumulate photoelectrically-converted charge are arranged in a matrix form;
an image CDS processing unit configured to output a pixel signal based on a difference between a pixel voltage read from one of the pixels during a reset period and a pixel voltage read from the one of the pixels during a signal read period;
a temperature sensor configured to output a diode voltage when a diode current is changed;
a temperature CDS processing unit configured to output a temperature measurement value based on a difference of the diode voltage at the time when the diode current is changed; and
a timing generator configured to control the reset period, the signal read period, and timing of changing the diode current of the temperature sensor.
2. The solid state imaging device according to claim 1 , wherein the diode current is changed for each horizontal period.
3. The solid state imaging device according to claim 1 , wherein the timing generator changes the diode current of the temperature sensor at the same timing as when changing a period from the reset period to the signal read period.
4. The solid state imaging device according to claim 1 , wherein the image CDS processing unit and the temperature CDS processing unit are integrated with each other.
5. The solid state imaging device according to claim 1 , wherein the image CDS processing unit and the temperature CDS processing unit have the same configuration.
6. The solid state imaging device according to claim 1 , wherein
the image CDS processing unit has an image ADC circuit configured to digitalize the pixel signal by performing a first count operation based on a pixel voltage read during the reset period and performing a second count operation based on a pixel voltage read during the signal read period, and
the temperature CDS processing unit has an temperature ADC circuit configured to digitalize the temperature measurement value by performing a first count operation based on a diode voltage outputted before the diode current is changed and performing a second count operation based on a diode voltage outputted after the diode current is changed.
7. The solid state imaging device according to claim 1 , wherein an operation of the temperature CDS processing unit is performed during a vertical blanking period.
8. The solid state imaging device according to claim 1 further comprising: an amplifier configured to be inserted between the temperature sensor and the temperature CDS processing unit and amplify the diode voltage.
9. The solid state imaging device according to claim 8 , wherein a gain of the amplifier is used in conjunction with an analog gain of the image CDS processing unit.
10. The solid state imaging device according to claim 1 , wherein
the temperature sensor is provided with a plurality of diodes whose diode currents are equal to each other and which are connected so that a diode voltage of one diode is received by a next-stage diode, and
the diode current when the diode voltage is outputted is changed by switching a diode from which the diode voltage is extracted.
11. The solid state imaging device according to claim 1 , wherein the temperature sensor includes
a diode, and
a current source configured to be connected to the diode in series and be able to switch a current provided to the diode.
12. The solid state imaging device according to claim 1 , wherein the pixel includes
a photodiode configured to perform photoelectric conversion,
a read transistor configured to transfer a signal from the photodiode to a floating diffusion on the basis of a read signal,
a reset transistor configured to reset a signal accumulated in the floating diffusion on the basis of a reset signal, and
an amplifier transistor configured to detect a potential of the floating diffusion.
13. The solid state imaging device according to claim 1 , wherein the image CDS processing unit is provided for each column.
14. The solid state imaging device according to claim 1 , wherein the image CDS processing unit includes
a comparator configured to compare a signal level read from the pixel with a reference voltage, and
a counter configured to perform a count operation on the basis of a result of comparison between the signal level and the reference voltage.
15. The solid state imaging device according to claim 1 , further comprising:
a vertical register configured to scan the pixels in a vertical direction, and
a horizontal register configured to scan the pixels and the temperature sensor in a horizontal direction.
16. The solid state imaging device according to claim 1 , wherein
a reset period, a signal read period, and a data transfer period are provided in one horizontal period, and
the diode current is set to a first value in the reset period, the diode current is set to a second value in the signal read period, and a temperature measurement value is outputted in the data transfer period via a data transfer bus in which a pixel signal is outputted.
17. The solid state imaging device according to claim 16 , wherein a plurality of the data transfer buses are provided in parallel.
18. The solid state imaging device according to claim 1 , wherein temperature measurement processing is performed in a first vertical blanking period in one vertical period, and imaging process is performed in a remaining second vertical blanking period and an effective pixel period in the vertical period.
19. The solid state imaging device according to claim 18 , wherein an analog gain of the temperature measurement processing is set higher than that of the imaging process and the analog gain of the imaging process is controlled according to an amount of incident light.
20. The solid state imaging device according to claim 1 , wherein a plurality of the temperature sensors are provided.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US14/530,899 US9154718B2 (en) | 2011-01-19 | 2014-11-03 | Solid state imaging device |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2011-008876 | 2011-01-19 | ||
JP2011008876A JP2012151664A (en) | 2011-01-19 | 2011-01-19 | Solid-state imaging apparatus |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US14/530,899 Division US9154718B2 (en) | 2011-01-19 | 2014-11-03 | Solid state imaging device |
Publications (1)
Publication Number | Publication Date |
---|---|
US20120182450A1 true US20120182450A1 (en) | 2012-07-19 |
Family
ID=46490514
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US13/278,587 Abandoned US20120182450A1 (en) | 2011-01-19 | 2011-10-21 | Solid state imaging device |
US14/530,899 Active US9154718B2 (en) | 2011-01-19 | 2014-11-03 | Solid state imaging device |
Family Applications After (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US14/530,899 Active US9154718B2 (en) | 2011-01-19 | 2014-11-03 | Solid state imaging device |
Country Status (2)
Country | Link |
---|---|
US (2) | US20120182450A1 (en) |
JP (1) | JP2012151664A (en) |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9521345B2 (en) | 2013-12-05 | 2016-12-13 | Samsung Electronics Co., Ltd. | Data transmission circuit, image sensor including the same |
KR20170132029A (en) * | 2016-05-23 | 2017-12-01 | 삼성전자주식회사 | Image sensor chip capable of feedback voltage and temparature information, and image processing system having the same |
CN107578026A (en) * | 2017-09-15 | 2018-01-12 | 京东方科技集团股份有限公司 | Fingerprint detection circuit, the detection method of fingerprint detection circuit and fingerprint sensor |
US20180184031A1 (en) * | 2016-12-28 | 2018-06-28 | Canon Kabushiki Kaisha | Solid state imaging device |
WO2018128816A1 (en) * | 2017-01-04 | 2018-07-12 | Semiconductor Components Industries, Llc | Methods and apparatus for a power management unit |
US10212369B2 (en) | 2017-01-25 | 2019-02-19 | Seiko Epson Corporation | Solid-state imaging apparatus and electronic device |
WO2019151065A1 (en) * | 2018-01-31 | 2019-08-08 | Sony Semiconductor Solutions Corporation | Imaging device and calibration method |
US10863132B2 (en) | 2016-11-18 | 2020-12-08 | Olympus Corporation | Solid-state image pickup device and image pickup apparatus |
US11361691B2 (en) * | 2020-07-27 | 2022-06-14 | Chongqing Hkc Optoelectronics Technotogy Co., Ltd. | Drive circuit and display device |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9652692B1 (en) * | 2016-09-26 | 2017-05-16 | Cognex Corporation | Machine vision system for capturing a digital image of a sparsely illuminated scene |
JP6800682B2 (en) | 2016-09-30 | 2020-12-16 | キヤノン株式会社 | Imaging equipment, imaging systems and mobiles |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5045928A (en) * | 1988-04-21 | 1991-09-03 | Canon Kabushiki Kaisha | White balance control with choice of control dependent on brightness |
US20030107661A1 (en) * | 2001-07-20 | 2003-06-12 | Pahr Per Olaf | Double sampling active pixel sensor with double sampling temperature sensor |
US20050270413A1 (en) * | 2004-06-08 | 2005-12-08 | Matsushita Electric Industrial Co., Ltd. | Adjustment of illumination light quantity for moving picture in moving picture image pickup device |
US20090009635A1 (en) * | 2007-05-11 | 2009-01-08 | Sony Corporation | Solid-state imaging device and imaging apparatus |
US7648271B2 (en) * | 2007-04-23 | 2010-01-19 | Texas Instruments Incorporated | Systems and methods for temperature measurement using n-factor coefficient correction |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR100630707B1 (en) * | 2004-10-22 | 2006-10-02 | 삼성전자주식회사 | Image device correctable defects having temperature-dependency and method for correcting defect using the same |
JP2007329655A (en) | 2006-06-07 | 2007-12-20 | Konica Minolta Holdings Inc | Imaging apparatus |
JP5028075B2 (en) | 2006-12-04 | 2012-09-19 | キヤノン株式会社 | Imaging apparatus and imaging method |
JP2008236158A (en) | 2007-03-19 | 2008-10-02 | Olympus Imaging Corp | Imaging module |
-
2011
- 2011-01-19 JP JP2011008876A patent/JP2012151664A/en active Pending
- 2011-10-21 US US13/278,587 patent/US20120182450A1/en not_active Abandoned
-
2014
- 2014-11-03 US US14/530,899 patent/US9154718B2/en active Active
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5045928A (en) * | 1988-04-21 | 1991-09-03 | Canon Kabushiki Kaisha | White balance control with choice of control dependent on brightness |
US20030107661A1 (en) * | 2001-07-20 | 2003-06-12 | Pahr Per Olaf | Double sampling active pixel sensor with double sampling temperature sensor |
US20050270413A1 (en) * | 2004-06-08 | 2005-12-08 | Matsushita Electric Industrial Co., Ltd. | Adjustment of illumination light quantity for moving picture in moving picture image pickup device |
US7648271B2 (en) * | 2007-04-23 | 2010-01-19 | Texas Instruments Incorporated | Systems and methods for temperature measurement using n-factor coefficient correction |
US20090009635A1 (en) * | 2007-05-11 | 2009-01-08 | Sony Corporation | Solid-state imaging device and imaging apparatus |
Cited By (21)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9521345B2 (en) | 2013-12-05 | 2016-12-13 | Samsung Electronics Co., Ltd. | Data transmission circuit, image sensor including the same |
KR20170132029A (en) * | 2016-05-23 | 2017-12-01 | 삼성전자주식회사 | Image sensor chip capable of feedback voltage and temparature information, and image processing system having the same |
KR102563926B1 (en) * | 2016-05-23 | 2023-08-04 | 삼성전자 주식회사 | Image sensor chip capable of feedback voltage and temparature information, and image processing system having the same |
US11509850B2 (en) * | 2016-05-23 | 2022-11-22 | Samsung Electronics Co., Ltd. | Image sensor chip that feeds back voltage and temperature information, and an image processing system having the same |
US10827144B2 (en) * | 2016-05-23 | 2020-11-03 | Samsung Electronics Co., Ltd. | Image sensor chip that feeds back voltage and temperature information, and an image processing system having the same |
US20200053306A1 (en) * | 2016-05-23 | 2020-02-13 | Samsung Electronics Co., Ltd. | Image sensor chip that feeds back voltage and temperature information, and an image processing system having the same |
US10863132B2 (en) | 2016-11-18 | 2020-12-08 | Olympus Corporation | Solid-state image pickup device and image pickup apparatus |
US20180184031A1 (en) * | 2016-12-28 | 2018-06-28 | Canon Kabushiki Kaisha | Solid state imaging device |
CN108259789A (en) * | 2016-12-28 | 2018-07-06 | 佳能株式会社 | Solid-state imaging apparatus |
US10531033B2 (en) * | 2016-12-28 | 2020-01-07 | Canon Kabushiki Kaisha | Solid state imaging device |
CN110169049A (en) * | 2017-01-04 | 2019-08-23 | 半导体元件工业有限责任公司 | Method and apparatus for Power Management Unit |
US20190138080A1 (en) * | 2017-01-04 | 2019-05-09 | Semiconductor Components Industries, Llc | Methods and apparatus for a power management unit |
US10824220B2 (en) * | 2017-01-04 | 2020-11-03 | Semiconductor Components Industries, Llc | Methods and apparatus for a power management unit |
US10209761B2 (en) * | 2017-01-04 | 2019-02-19 | Semiconductor Components Industries, Llc | Methods and apparatus for a power management unit |
WO2018128816A1 (en) * | 2017-01-04 | 2018-07-12 | Semiconductor Components Industries, Llc | Methods and apparatus for a power management unit |
US10212369B2 (en) | 2017-01-25 | 2019-02-19 | Seiko Epson Corporation | Solid-state imaging apparatus and electronic device |
CN107578026B (en) * | 2017-09-15 | 2020-11-27 | 京东方科技集团股份有限公司 | Fingerprint detection circuit, detection method of fingerprint detection circuit and fingerprint sensor |
CN107578026A (en) * | 2017-09-15 | 2018-01-12 | 京东方科技集团股份有限公司 | Fingerprint detection circuit, the detection method of fingerprint detection circuit and fingerprint sensor |
WO2019151065A1 (en) * | 2018-01-31 | 2019-08-08 | Sony Semiconductor Solutions Corporation | Imaging device and calibration method |
US11686630B2 (en) | 2018-01-31 | 2023-06-27 | Sony Semiconductor Solutions Corporation | Imaging device and calibration method |
US11361691B2 (en) * | 2020-07-27 | 2022-06-14 | Chongqing Hkc Optoelectronics Technotogy Co., Ltd. | Drive circuit and display device |
Also Published As
Publication number | Publication date |
---|---|
US20150049227A1 (en) | 2015-02-19 |
JP2012151664A (en) | 2012-08-09 |
US9154718B2 (en) | 2015-10-06 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US9154718B2 (en) | Solid state imaging device | |
US8908066B2 (en) | Solid state imaging device | |
US7755686B2 (en) | Physical quantity distribution detecting apparatus and imaging apparatus | |
US7715661B2 (en) | Solid-state image pickup device, method of driving solid-state image pickup device and imaging apparatus | |
US9307173B2 (en) | Signal processing circuit, solid-state imaging device, and camera system | |
US8174422B2 (en) | Power-supply-noise cancelling circuit and solid-state imaging device | |
US8264580B2 (en) | Solid state imaging device, signal processing method of solid-state imaging device and imaging apparatus capable of removing vertical smears | |
US8823850B2 (en) | Image processing system with on-chip test mode for column ADCs | |
US20110221931A1 (en) | Temperature information output apparatus, imaging apparatus, method of outputting temperature information | |
US11863896B2 (en) | Image sensor and photodetector with transistor diode-connected via a resistance element | |
US8803993B2 (en) | Solid-state imaging device and camera system with a reset-level variation correction function | |
US20060001476A1 (en) | Current stabilization circuit, current stabilization method, and solid-state imaging apparatus | |
US20150138413A1 (en) | Ad conversion circuit and solid-state imaging device | |
JP2012199913A (en) | Signal reception section test circuit, imaging apparatus, signal reception section test method and test method of imaging apparatus | |
US11025853B2 (en) | Comparator circuit, solid-state imaging apparatus, and electronic device | |
US10212369B2 (en) | Solid-state imaging apparatus and electronic device | |
US20130234004A1 (en) | Imaging device | |
US20120199723A1 (en) | Solid-state imaging device | |
US20150189203A1 (en) | Solid state imaging device and method of driving solid state imaging device | |
US11575868B2 (en) | Photoelectric conversion apparatus, method of driving photoelectric conversion apparatus, photoelectric conversion system, and moving body | |
US20100073539A1 (en) | Solid-state imaging device | |
US10277854B2 (en) | Image capturing apparatus, control method therefor, and storage medium | |
JP2014192542A (en) | Imaging apparatus, semiconductor integrated circuit device, and a/d conversion method |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: KABUSHIKI KAISHA TOSHIBA, JAPAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:SATO, MAKI;HIZU, KAZUKI;AMANO, TETSUYA;AND OTHERS;REEL/FRAME:027101/0059 Effective date: 20111011 |
|
STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |